bluuebunny/crossref_metadata_2025 huggingface dataset:
Action of Ophiostoma piceae proteinase and lipase on wood nutrients
Authors: Abraham Linda , Hoffman Brad , Gao Yong , Breuil Colette
Published: April 2011

Fungi excrete a variety of extracellular enzymes capable of breaking down complex nutrient sources into products that can be directly metabolized by the fungi. An extracellular proteinase and lipase produced by the sap-staining fungus, Ophiostoma piceae, have been purified and the specificities of these enzymes for a variety of substrates have been determined. In this work, we show that these enzymes were able to hydrolyze natural substrates isolated directly from wood. Key words: Ophiostoma piceae, triglycerides lipase, proteinase, carbohydrates, proteins.
Relationships between net nitrogen mineralization, properties of the forest floor and mineral soil, and wood production in Pinus radiata plantations
Authors: Carlyle J Clive , Nambiar EK Sadanandan
Published: April 2011

We examined the relationship between net nitrogen (N) mineralization (subsequently termed N mineralization) in the forest floor and mineral soil (00.15 m) of 20 Pinus radiata D. Don plantations ranging in age from 23 to 59 years, how mineralization was influenced by soil properties, and its relationship to wood production. Forest floor properties had a narrower relative range than the same set of mineral soil properties. Total N in the litter layer was 5.09.5 g·kg1 compared with 0.232.53 g·kg1 in mineral soil. Laboratory rates of net N mineralization ranged between 1.1 and 9.7 mg·kg1·day1 in forest floor and between 0.02 and 0.53 mg·kg1·day1 in mineral soil. The range in litter lignin (35.348.0%) was especially narrow, despite the large range in stand productivity. Nitrogen mineralized in the forest floor was not correlated with any of the measured forest floor or mineral soil properties. Nitrogen mineralized per unit mineral soil N (ksn) was negatively correlated with the mineral soil N to organic phosphorus ratio (N/Po) (r2 = 0.82). In mineral soil a relationship combining N/Po and total N concentration explained 90% of the variation in N mineralized. Nitrogen mineralized in the forest floor was correlated with that mineralized in the mineral soil when expressed per unit C or N (r2 = 0.54 or 0.57, respectively). Thus, the quality of organic matter in the forest floor partly reflected the quality of organic matter in the mineral soil with respect to N mineralization. Mineralization in mineral soil dominated the net N available to the stand. For sandy soils, wood production (m3·ha1·year1) was correlated with N mineralized in the forest floor + mineral soil (r2 = 0.71). In P. radiata stands growing in southern Australia, rates of wood production per unit N mineralized and per unit rainfall appear to be substantially higher than those of a wide range of natural and planted stands in North America.
Local Differentiation of Populations of Rocky Mountain Douglas-fir
Authors: Rehfeldt G. E.
Published: April 2011

Half-sib families representing 12 populations of Rocky Mountain Douglas-fir (Pseudotsugamenziesii var. glauca) were compared to assess local differentiation of populations in northern Idaho. Populations were separated by 0.5–17 km and represented north and south aspects at three elevations (950, 1125, and 1300 m) in each of two drainages. Tests of 2-year-old families growing in two contrasting environments revealed (1) substantial differentiation that was not associated with the aspect, elevation, or drainage from which populations originated, (2) variation among families within populations, and (3) relatively large components of variance for families in date of bud set, number of branches, and seedling height.
Effect of Applied Abscisic Acid and Silicone on Water Relations and Photosynthesis of Woody Plants
Authors: Davies W. J. , Kozlowski T. T.
Published: April 2011

Fraxinusamericana and Pinusresinosa seedlings were treated with 7.5% silicone or 10−4 M ABA. Plants were watered on the day following treatment and then subjected to a soil drying cycle. At frequent intervals after the compounds were applied, transpiration, net photosynthesis, leaf water potential, and soil moisture percentage were determined for treated and control plants. Transpiration and photosynthesis of control plants decreased as the soil dried. Silicone was more effective than ABA in reducing water loss of both species, and was much more effective on Pinus than on Fraxinus. Although silicone had a very positive effect on the water potential of Pinus, photosynthesis of treated plants was greatly reduced with rates of treated plants never exceeding those of control plants. As the drying cycle progressed rates of photosynthesis were higher in ABA-treated Pinus plants than in controls. ABA also significantly increased plant water potential and soil moisture percentage. In Fraxinus, as the drying cycle progressed, both ABA- and silicone-treated plants had lower water stresses than untreated plants. Rates of photosynthesis were higher than in untreated plants. The data indicated that film-forming antitranspirants may be unsuitable for use with some gymnosperms, and that compounds which very significantly decrease transpiration are not necessarily useful and practical in the long term.
The effect of environmental factors on wood characteristics. 3. The influence of climate and site on young Pinusradiata material
Authors: Nicholls J. W. P. , Wright J. P.
Published: April 2011

Three trees from each of six clones of Pinusradiata, replicated at five sites in Victoria and growing under similar silvicultural schedules, were sampled. Edaphic and climatic factors varied markedly between sites and featured in the interpretation of the data. From each tree, a series of wood samples formed by cambia of the same ages provided material for densitometric analysis. Within a growing season, defined by temperature thresholds, potential growth days were determined on the basis of favourable water deficits. The number of potential growth days in a growing season correlated with ring width and the number of such days in autumn correlated with the formation of late wood. Ring width was negatively correlated with minimum and average density. No relationship between environmental factors and maximum and minimum density could be determined.
Fertilization of a pole-sized maple stand: 10-year results
Authors: Stone Douglas M.
Published: April 2011

A 48-year-old stand of Acersaccharum Marsh. and A. rubrum L. in northeastern Wisconsin, U.S.A., was fertilized with 168 kg/ha (150 lb/acre) of elemental N, P, N + P, or N + P + K in May 1966. Trees were stratified by crown class and initial diameter. Ten-year diameter and basal area growth were evaluated by analysis of covariance with initial plot basal area (IBA) as the covariate and by stepwise multiple regression in hierarchal models. Both diameter and basal area growth were influenced greatly by initial diameter and stand density. IBA accounted for 65% of the variation in diameter growth and 49% of the variation in basal area growth.Fertilization decreased diameter growth and increased mortality of suppressed trees. Pole-sized maples in intermediate and codominant crown positions tended to respond to fertilization with N and N + P but the differences were not statistically significant. Dominant trees grew more than did intermediates or codominants, but fertilization response could not be evaluated. Treatment effects were confounded by widely varied stand and site conditions. Results illustrate conditions likely to be encountered in fertilizing northern hardwoods on an operational scale.
A regional approach to litter dynamics in Southern Appalachian forests
Authors: Sharpe D. M. , Cromack Jr. K. , Johnson W. C. , Ausmus B. S.
Published: April 2011

Foliage litterfall, Ol litter mass, and its Mg, P, and K content were estimated for six forest types in the Southern Appalachian region using 252 forest survey plots of the USDA Forest Service. General allometric equations were used to compute foliage litterfall, and average species foliage elemental concentrations were used for litterfall elemental content. Exponential decay rate constants (k) of foliage mass and elements were estimated from foliage lignin concentrations. The procedure was tested with measured litterfall and Ol litter at Coweeta Hydrologic Laboratory and selected Forest Service plots in Macon County, North Carolina. Litterfall and Ol litter mass were accurately computed. Elemental content of litterfall and Mg and K mineralization rates were overestimated; P mineralization rate was underestimated. First-year immobilization of Ca may render the exponential decay model invalid for Ca.
Effects of temperature, drought, and gibberellin A4/7, and timing of treatment, on flowering in potted Piceaengelmannii and Piceaglauca grafts
Authors: Ross Stephen D.
Published: April 2011

Four experiments conducted over 2 years on potted 4- to 7-year-old Piceaengelmannii and 3-year-old Piceaglauca grafts compared the effectiveness of different temperature, drought, and gibberellin A4/7 treatment regimes for promotion of flowering. With the exception of one study in which trees were not properly preconditioned, heat treatment within a polyethylene–covered house (polyhouse) promoted profuse female and male flowering in previously root-pruned P. engelmannii grafts. The optimal daytime temperature of 22–25 °C in the polyhouse was well below the 30 °C temperature for Piceaabies suggested in the literature. Timing of heat treatment was critical. Few trees produced seed or pollen cones if moved indoors before the new shoots were at least 80% elongated, with 85–95% elongation being optimal. Drought also promoted flowering but only if applied outdoors while shoots were actively elongating. Response to these cultural practices was further enhanced by spray applications of gibberellin A4/7 during the rapid growth phase. Younger P. glauca grafts that were not root-pruned or sprayed with gibberellin A4/7 failed to respond to early drought and late heat treatments, but did so the following year when these adjunct treatments were given. Response of P. engelmannii grafts to retreatment indicates that alternate-year induction, with a year's rest for cone maturation and vegetative replenishment of shoots turned reproductive, is practical and will result in sustained abundant cone production in potted trees.
Frost hardiness of commercial Eucalyptus species at different elevations
Authors: Hallam P. M. , Reid J. B. , Beadle C. L.
Published: April 2011

Six Eucalyptus species, E. regnans F. Muell., E. delegatensis R.T. Bak., E. globulus Labill., E. nitens (Deane & Maid.) Maid., E. pauciflora Sieb. ex Spreng, and E. grandis Hill ex Maid., were sampled for determination of frost hardiness in March (late summer) and August (late winter) 1985 from trial plantings at four elevations in southern Tasmania. In March, there was a statistically significant difference between sites, but not between species or provenances. In August, significant differences between species, and for E. delegatensis between provenances, had developed. The species ranked in order of increasing frost hardiness as follows: E. regnans < E. grandis < E. globules = E. delegatensis (Maydena provenance) < E. pauciflora < E. nitens < E. delegatensis (Guildford provenance). Greatest frost hardiness was developed at the 60-m site (elevation), followed by (in decreasing order) the 650-m site, the 440-m site, and the 240- m site. This order corresponded to the minimum temperatures experienced at the sites. Conversely, greatest growth occurred at the 60-and 240-m sites followed by the 440-m site and then the 650-m site, corresponding to decreasing maximum temperatures. It is argued that good growth and productivity are possible on quite frost prone sites, provided suitable provenances are selected for planting.
The role of mechanized harvesting in the development of bluestain in pine
Authors: Uzunovic' Adnan , Webber Joan F , Peace Andy J , Dickinson David J
Published: April 2011

The influence of mechanized harvesting on the development of bluestain was assessed by comparing pine logs felled and trimmed with a chainsaw with those felled by a commercial harvesting machine. Corsican pine (Pinus nigra var maritima (Ait.) Melville) grown in the United Kingdom was cut in June and August, and the logs were assessed for bluestain 3, 6, 9, and 12 weeks after felling. Mechanically harvested logs were in two groups: maximum damage (mean amount of bark loss ~35% of total cover) and minimum damage (~12% mean bark loss). However, all mechanically harvested logs were much more susceptible to attack by bluestain fungi than chainsaw-processed logs, which typically had <1% bark loss. Mechanically harvested logs had bluestain on ~10% of the surface area of sample discs compared with <1% in the chainsaw-harvested logs. Little bluestain developed if bark loss was <10%. The most extensive stainers were Ceratocystis coerulescens (Münch) Bakshi and Leptographium wingfieldii Morelet; other frequent bluestain fungi included Ophiostoma piceae (Münch) H. & P. Sydow, Sphaeropsis sapinea (Fr.) Dyko & Sutton, and a Graphium species. Bluestain bark beetle vectors were excluded from the logs, but other arthropods apparently acted as vectors. Using data from the study, a model was devised to predict of stain development following a known amount of bark damage.
Efficacy of climate transfer functions: introduction of Eurasian populations of Larix into Alberta
Authors: Rehfeldt Gerald E , Tchebakova Nadja M , Barnhardt Leonard K
Published: April 2011

Growth and survival of eight populations of Larix sukaczewii Dylis and one of both Larix sibirica Ledeb. and Larix gmelinii (Rupr.) Rupr. were used to assess the effectiveness of climate transfer functions for predicting the 13-year performance of Eurasian provenances introduced to Alberta. Quadratic regression models showed that transfer distances for five climate variables (mean annual temperature, degree-days <0°C, mean temperature in the coldest month, ratio of the mean annual temperature to mean annual precipitation, and the summer-winter temperature range) were particularly effective in predicting height and survival. Optimal transfer distances did not differ significantly from zero, and as a result, the best growth and survival in Alberta should be obtained by matching the provenance climate to that of the planting site for the five variables. Verification of the climate transfer functions with independent data from Russian provenance tests were strongly supportive. The results demonstrate the effectiveness of climate transfer functions for describing the response of plant populations to the environment and thereby have practical implications in reforestation.
In vitro germination of western larch pollen
Authors: Dumont-BéBoux Nicole , Anholt Bradley R , Aderkas Patrick von
Published: April 2011

We have been able to successfully germinate western larch (Larix occidentalis Nutt.) pollen in vitro. Pollen was rehydrated at 100% RH for 16 h before being sprinkled on semisolid and liquid media. The basic medium contained Brewbaker and Kwack minerals diluted 1:10 and was supplemented with polyethylene glycol 4000 and three different concentrations of sucrose. The flavonol quercetin was also included in half of the media. More pollen grains survived on liquid media, but semisolid media gave superior germination results. Two to 9% of the grains produced tubes. Quercetin had no major effect on germination, viability, or tube length.
Factors in the reduced food intake of rats fed a low-protein diet
Authors: Beaton J. R. , Feleki V. , Stevenson J. A. F.
Published: April 2011

Male rats of the Wistar strain were fed either a control (20% casein) or a low-protein (5% casein) diet. Following the intraperitoneal injection of glucose solution it was observed from the blood glucose curve that low-protein fed rats had a delayed or impaired utilization of this carbohydrate. Resting oxygen consumption was not significantly different, and after glucose injection the slight increase in both groups was not significant. On refeeding after fasting, the colonic temperature of low-protein fed rats rose to a greater extent than did that of controls. Administration of protamine zinc insulin (PZI) decreased colonic temperature during fasting particularly in low-protein fed animals, and also during refeeding following a brief fasting period. From the results of these several experiments, it would appear that low-protein fed rats may have (a) an impairment in utilization of carbohydrate, and (b) a defect in immediate energy dissipation or an increased rate of energy production from ingested food. These two abnormalities may contribute to the reduced food intake of such animals. The association of a greater increase in colonic temperature on feeding and the hypophagia of rats fed a low-protein diet, as well as the hypothermic effect of PZI associated with an increase in food intake are suggestive of a thermostatic control of food intake in addition to a glucostatic control.
Release of tritiated noradrenaline from perfused rat hearts by sympathomimetic amines
Authors: Nash C. W. , Wolff S. A. , Ferguson B. A.
Published: April 2011

The hypothesis that the limiting factor controlling the noradrenaline-releasing activity of a sympathomimetic amine is the ability of the nerve ending to take up the amine, i.e. the affinity of the amine for the postulated amine carrier in the sympathetic nerve ending, was tested on perfused rat hearts labelled with tritiated noradrenaline (NA). Experiments were done to determine whether cocaine and desmethylimipramine (DMI) would block the releasing action of sympathomimetic amines (SMA) and to determine whether the ranking order of the releasing activity of a series of SMA corresponds to the order of affinity for the amine carrier as reported by Iversen. The releasing activity of NA was found to be a saturable process, reaching a maximum rate estimated to be 2.6% of the amount present in the heart per minute. In addition, cocaine and DMI competitively blocked the releasing activity of infused NA, adrenaline, and dopamine, but this inhibition could be overcome by increasing the dose of the SMA. The ranking order of releasing activity of this series of amines was l-noradrenaline, dopamine, l-adrenaline, p-tyramine, d-noradrenaline, d-adrenaline, l-isoproterenol, phenylethylamine, d-isoproterenol, which was approximately the same as their order of affinity for the amine carrier. Our results indicate that uptake by a membrane carrier is probably the limiting factor in the releasing activity of SMA which are catechols and have a β-OH group. However, those amines studied which do not have these structural properties, i.e. dopamine, tyramine, and phenylethylamine, are further limited in their releasing activity, possibly owing to a less rapid exchange at the binding site on the storage granule.
Effects of adrenaline on plasma calcium, phosphate, and blood glucose in the dog
Authors: Shim Sun Shik , Copp D. Harold , Patterson Frank P.
Published: April 2011

Ten dogs were anesthetized with pentobarbital, and after a control period of at least 1 h, during which three blood samples were taken, adrenaline (2–4 μg/kg per min) was infused intravenously for 1 h. Blood samples were taken at 15- or 30-min intervals during the infusion and for 2 h thereafter. These were analyzed for calcium, inorganic phosphate, and glucose. The plasma calcium level did not change significantly during or following the infusion; however, the plasma glucose rose and the plasma phosphate fell during adrenaline administration. The glucose level returned to normal within 2 h of termination of the infusion; in some dogs the plasma phosphate also returned to the control level, whereas in others it remained depressed at this time.
Body temperature of chicks in response to lysine deficiency
Authors: Pastro K. R. , March B. E. , Biely J.
Published: April 2011

Body temperatures were compared in chicks fed diets adequate and deficient in lysine. Temperatures were measured with thermistor probes implanted in the pectoralis major muscle. In three separate experiments lysine-deficient diets were fed for 18 h, 30 h, or 2 weeks before measuring temperatures. Temperatures were consistently higher in the birds fed the lysine-deficient diet.
Action of pyridine-2-aldoxime methochloride (PAM) on the rectus abdominis muscle of the frog
Authors: Goyer G. Robert
Published: April 2011

The neuromuscular action of pyridine-2-aldoxime methochloride (PAM) was evaluated in vitro on the frog rectus abdominis muscle. Dose-response curves were obtained from eserinized and non-eserinized preparations, with acetylcholine and succinylcholine as the agonists. It was possible to demonstrate the dualistic activity of PAM, i.e. a facilitating and a depressing effect. From the present study it can be concluded that the facilitation observed with the lower concentrations is closely related to the anticholinesterasic activity of PAM, whereas the depressing effect seen when higher concentrations are used can be associated with a noncompetitive mechanism of inhibition.
Serotonin and other vasoactive agents in experimental decompression sickness
Authors: Clark M. L. , Philp R. B. , Gowdey C. W.
Published: April 2011

A number of vasoactive agents were screened for their effects on the incidence and severity of decompression sickness in rats by a standardized bends-inducing procedure involving compression, decompression, and exercise at altitude. None of the substances in the dosage schedules used altered the incidence of bends, but serotonin markedly increased the severity. This result is interesting in view of recent observations from this laboratory on the role of platelets in decompression sickness.
Some factors influencing the toxicity of thrombolytic enzymes (Brinase)
Authors: Freedman Harvey J. , Roschlau Walter H. E.
Published: April 2011

A heterogenous dog population was subjected to standardized systemic administration of the fibrinolytic enzyme Brinase. The extent of toxicity (hypocoagulable blood, hypotension, hemoconcentration) depended primarily on the degree and speed of inhibitor neutralization and the eventual appearance of free proteolysis. Administration of an "optimal" (i.e. thrombolytic yet not proteolytic) dosage elicited occasional unexpected hypotensive responses owing to variations in body condition of individual dogs and variations in the rate and duration of drug infusion.
Unchanged sensitivity to noradrenaline in isolated tissues from cold-acclimated rats
Authors: Himms-Hagen Jean , Mazurkiewicz-Kwilecki I. M.
Published: April 2011

Acclimation of rats to cold did not alter either the sensitivity to noradrenaline or the size of the maximum response to noradrenaline of three isolated tissue preparations (chronotropic response of isolated atria; inotropic response of left atrium; contractile response of vas deferens). It is concluded that a change in the response of the heart to exogenous noradrenaline is an unlikely explanation for the modified cardiovascular responses to noradrenaline known to occur in intact cold-acclimated rats.
The Sympathetic Nervous System in Short-Term Adaptation to Cold
Authors: LeBlanc J. , Roberge C. , Vallière J. , Oakson G.
Published: April 2011

Rats were adapted to cold by 10-min exposure to −20 °C every hour during daytime for a total of 27 exposures over a period of 3 days. The significant delayed hypothermia observed in these adapted animals when exposed to severe cold (−16 °C) for 4 h was concomitant with only a 15% increase in oxygen consumption over control animals. While some protection against severe cold was observed in rats given 27 injections of 1 μg thyroxine over a 3-day period, the same treatment with 30 μg noradrenaline (NA)/100 g body weight had opposite effects. Urinary NA was increased during the second and third day of adaptation and the excretion during the 4-h test at −16 °C was significantly greater in the adapted than in the control group. No significant changes in adrenaline (A) excretion were observed during the adaptation period. However during the 4-h test at −16 °C, A excretion was four times greater in the control than in the adapted animals. These results could indicate emotional adjustments in animals adapted by intermittent exposures to severe cold (IS adaptation). It might be suggested that adaptation by continuous exposure to moderate cold (CM adaptation) and IS adaptation are both related to catecholamine secretion: in the case of CM adaptation an increased sensitivity to NA would prevail, whereas in IS adaptation a decreased A secretion could be a factor of some importance.
Inhibition of Hypothalamic Obesity in the Mouse with Diethylstilbestrol
Authors: Montemurro D. G.
Published: April 2011

Mice made hyperphagic and obese by electrolytic destruction in the region of the ventro-medial hypothalamic nuclei are supersensitive to the anorexigenic effects of diethylstilbestrol. A dramatic body weight loss was observed in such mice, but not in those with lesions in the anterior or posterior hypothalamus, nor in sham-operated control mice.
Vasomotion and Contraction in the Perfused Mesenteric–Portal Vein: Effect of Drugs and Altered Perfusion Pressure
Authors: Rhodes H. James , Sutter M. C.
Published: April 2011

Isolated rabbit anterior mesenteric–portal veins (A.M.V.) which possess vasomotion were perfused with Kreb's solution in an apparatus designed so that intraluminal pressure and longitudinal tension could be measured simultaneously. The rate of vasomotion increased as perfusion pressure was increased from 0 to approximately 5 or 6 mm Hg. The amplitude of these spontaneous contractions increased to a maximum at a perfusion pressure of approximately 6 mm Hg and then decreased as perfusion pressure was raised further. Noradrenaline (10−7 g/ml) increased the longitudinal tension, but slightly decreased intraluminal pressure. Isopropylnoradrenaline (10−7 g/ml) had little effect on intraluminal pressure but decreased the amplitude of spontaneous contractions. It is suggested that the effect of perfusion pressure on the frequency and amplitude of vasomotion in the A.M.V. is related to autoregulation and that this perfused preparation may be a useful model for study of the rheology and responses to drugs of the splanchnic circulation.
Amino Acid Imbalance and Diet Preference in the Hypothalamic–Hyperphagic Rat
Authors: Arakawa S. M. , Standal B. R. , Beaton J. R.
Published: April 2011

Diet selection by control and hypothalamic–hyperphagic rats was recorded to examine the hypothesis that the plasma amino acid pattern may act as a satiety signal with respect to the decreased food intake associated with amino acid unbalanced diets. Rats were offered choices between: (a) protein-free and imbalanced diets; (b) imbalanced and corrected diets; (c) corrected and basal diets. Although selection by control and operated rats differed with respect to choice a, selection behaviors were comparable for choices b and c. Plasma amino acid patterns were similar in control and operated rats indicating that the same potential satiety signal was present in both groups. Since the "satiety center" was ablated in operated rats, it would seem that if plasma amino acid patterns serve as a satiety signal, this signal must act in some manner other than on the ventromedial area of the hypothalamus.
Effect of Trimethadione on the Self-Stimulation Phenomenon
Authors: St-Laurent J.
Published: April 2011

The effects of the anticonvulsant drug trimethadione on the self-stimulation (S.S.) phenomenon are studied on rats. S.S. is elicited via electrodes implanted in the posterior medial forebrain bundle (M.F.B.). Following administration of trimethadione (325 mg/kg i.p.) a tendency toward improvement of S.S. is found; this trend is not statistically significant. The fact that no change of S.S. is observed in the areas of the posterior M.F.B. where seizures rarely occur is discussed in the light that the high rates of S.S. obtained from these areas might be related to the absence of disruptive epileptiform activity. It is concluded that the high rates of S.S. usually obtained from the posterior areas of the M.F.B. may be due to properties such as the involvement of these areas in high-drive behavior and facilitation of motor activity.
The Influence of Rate of Filling on Apparent Venous Distensibility in Man
Authors: Hollenberg Norman K. , Boréus Lars O.
Published: April 2011

The influence of the rate of filling on the relation between venous volume and transmural pressure in the human extremity was investigated with two techniques, venous occlusion plethysmography (leg) and infusion into an isolated venous segment (forearm). Both methods revealed a quantitatively important rate-related component in the response of veins to distension; the venous volume was lower at a given transmural pressure when filling was rapid. This component can serve as a local buffering mechanism, minimizing volume changes after sudden changes in postcapillary pressure such as occur with changes of posture or blood flow. Since blood flow and apparent venous distensibility are interrelated, flow changes must be taken into account in the interpretation of studies in which venous distensibility curves determined by plethysmography are used as an index of venous tone.It has also been demonstrated that the limb supported above heart level contains a minimal volume of blood which is not altered by external pressures up to 40 mm Hg.
Interaction of Diphenylhydantoin-4-14C with Subcellular Fractions of Rat Brain
Authors: Wilensky A. J. , Lowden J. A.
Published: April 2011

The mode and site of action of diphenylhydantoin (DPH) in the brain are unknown. We studied the binding of DPH to subcellular fractions of the brain of male Wistar rats, which previously had been injected with DPH-4-14C and killed at intervals. At most times the distribution of the radioactivity among the fractions was similar to that observed when the drug was added after homogenization. However, 12 h after injection there was increased concentration in a heavy microsomal fraction which contains mainly small nerve endings. Measurement of radioactivity in submitochondrial fractions indicated that redistribution was occurring during fractionation. Subcellular fractions from brains of uninjected rats were dialyzed against solutions containing DPH-4-14C and various electrolytes. DPH tends to bind to fractions containing plasma membranes. The degree of binding was decreased by the presence of Ca2+ in the dialysis solution while Mg2+ had no effect. When both ions were present at concentrations of 12.1 mM Mg2+ and 1.4 mM Ca2+, binding was the same as when ions were not present. The data suggest that DPH interacts with plasma membranes by electrostatic forces and that this interaction is altered by Ca2+.
Hypoactivity as a Possible Contributing Cause of Obesity in the Weanling Rat Ventromedial Syndrome
Authors: Bernardis Lee L.
Published: April 2011

Weanling rats, with electrolytic lesions primarily destroying the ventromedial hypothalamic nuclei (V.M.N.) and sparing the median eminence, have in the past been shown to be growth-retarded, to have reduced pituitary and plasma growth hormone levels, to be obese despite normal body weight gains, and to show normophagia, normoglycemia, hyperinsulinemia, hypertriglyceridemia, and hypercholesterolemia. In the present study, the spontaneous running activity of such animals, as measured in rotating drum type activity cages, was normal during the first 24 h after the operation, became suggestively reduced during the 1st week, and was significantly reduced 2 weeks after the hypothalamic operation. Food intake was normal throughout the experiment but the V.M.N. lesioned animals weighed less than the controls despite a higher obesity index. It is concluded that hypoactivity may be a contributing factor in the development of the normophagic–normoglycemic–hyperinsulinemic obesity that characterizes the weanling rat ventromedial syndrome.
Sequestration and Possible Maturation of Reticulocytes in the Normal Spleen
Authors: Song S. H. , Groom A. C.
Published: April 2011

The presence, in the feline spleen, of a slowly exchanging red cell 'compartment' ([Formula: see text] 54 min) has been demonstrated previously. These red cells adhere to reticulum cells and sinus walls in the red pulp and have been shown to be larger in cellular volume and lighter in cellular density than the rest. This suggested that they might be younger cells and we have reported briefly that they contain a high proportion of reticulocytes. Using supravital stains we have measured the percentage of reticulocytes in the outflow from isolated spleens of cats and dogs, perfused with oxygenated Ringer solution. Reticulocyte counts increased from 0.4% to 99% as the perfusion progressed. The results show that the slow compartment consists entirely of reticulocytes. The ratio of reticulocytes to rubricytes in the spleen was found to be 75:1. Therefore the reticulocytes were not produced in the spleen but were accumulated from the circulating blood. The total number of reticulocytes so stored is 1.2 × 1010 cells, equivalent to 1.5 times the daily production in the whole animal. From these data we conclude that reticulocytes released from the bone marrow under physiological conditions are sequestered and matured in the spleen.
Influence of Ethacrynic Acid on Muscle Surface Enzymes and of Ethacrynic Acid and Ouabain on Na, K, and H2O in Frog Muscle
Authors: Riordan J. R. , Manery J. F. , Dryden E. E. , Still T. S.
Published: April 2011

Isolated frog muscles were exposed to concentrations of ethacrynic acid (2,3-dichloro-4-(2-methylene-butyryl)phenoxyaceticacid)ranging from 10−8 to 10−2 M. The diuretic (EA) at a concentration (10−3 M) which is sufficient to markedly inhibit net Na and K movements had no effect on three muscle surface enzymes (ATPase, adenylate kinase, 5′-AMP deaminase). The minimum concentration of EA required for inhibition of Na and K movement lies within the narrow range of 0.2 × 10−3 M to 10−3 M. The degree of inhibition increased with EA concentration up to 10−2 M. Concentrations of 0.2 × 10−3 M caused some contracture of the muscles as well. EA causes an increased K loss over that caused by ouabain alone both in the presence and absence of external Na. Na concentrations are not affected. Ouabain causes increased K loss over that caused by EA alone both in the presence and absence of external Na. Frog muscle has a component of K movement (about 35% of the total concentration) dependent upon external Na. This component is distinct from the ouabain-inhibited component and equal to the EA-inhibited component. The results are consistent with inhibition of the active transport of Na and K by EA as well as by ouabain and suggest that in the presence of Ca, EA also increases the passive permeability of the muscle membrane to K.
The Actions of Polymyxin B and Histamine on Ganglionic Transmission
Authors: Brezenoff H. E. , Gertner S. B.
Published: April 2011

The ganglionic effects of histamine and the histamine-liberating agent polymyxin B were studied in the cat. Nictitating membrane contractions and postganglionic action potentials were used to monitor the actions of these drugs on the superior cervical ganglion. Close arterial injections of low doses of histamine (1 μg) directly stimulated the ganglion while considerably higher doses (above 300 μg) caused a block of transmission. The two effects were due to separate and independent mechanisms. In contrast, administration of polymyxin B (100–500 μg) only caused ganglion block.The effects of histamine on the ganglion were prevented by chlorpheniramine while those of polymyxin B were potentiated by this antihistamine. The results of this study indicate that the ganglion blocking effects of polymyxin B are not mediated by released ganglionic histamine.
Failure of Human Growth Hormone and Human Placental Lactogen to Affect Glucose Consumption by Human Erythrocytes and Leucocytes In Vitro
Authors: Tanser Catherine L. , Leeuw Nannie K. M. de
Published: April 2011

The effect of human growth hormone (HGH) and human placental lactogen (HPL) on glucose consumption by erythrocytes and leucocytes in vitro was investigated. Glucose consumption was measured by determining glucose utilization during 3 h incubation at 37 °C, using the glucose oxidase method.HGH and HPL showed no effect on glucose consumption by erythrocytes, and HPL showed no effect on glucose consumption by leucocytes in vitro. Our results do not confirm previous reports of an inhibitory effect of HGH on glucose consumption by erythrocytes in vitro.
Immunohistochemical Localization of Prolactin in the Pituitary Gland of the Pigeon, Columba livia
Authors: McKeown B. A.
Published: April 2011

Specific antibodies to ovine prolactin were produced in rabbits. The antisera were conjugated to fluorescein isothiocyanate and "purified" by column chromatography. Antibodies, thus labelled, were applied to fresh-frozen sections of pigeon pituitary glands. Fluorescence was observed in specific cells of the cephalic lobe. After staining, these cells were identified as the erythrosinophilic eta cells.
The Mechanism of Acute Neuromuscular Weakness Induced by Chloroquine
Authors: Vartanian G. A. , Chinyanga H. M.
Published: April 2011

Chloroquine caused muscle weakness in neuromuscular preparations of both frog and cat in doses as low as those used in clinical practice. Studies of end-plate and action potentials in the muscle fibers and action potentials in single nerve fibers showed that the muscle weakness induced by chloroquine resulted from depression of the excitability of the electrically excitable membranes of the axon and muscle fiber. This led to the decrease of action potentials of the axon resulting in the reduction of transmitter output at the end plate and decreased firing index, as well as to the decrease in the amplitude of action potential of the muscle fiber itself. It was inferred that the mechanism of action of chloroquine was similar to that of local anesthetics.
Espace extracellulaire, perméabilité à l'inuline et accumulation de L-alanine dans l'intestin isolé de Grenouille
Authors: Noüe Joël de la , Gagnon André
Published: April 2011

In order to calculate the intracellular concentration of accumulated L-alanine, the extracellular space (inulin-14C) of frog intestine was measured. To check the validity of the technique, frog liver and gastrocnemius were used too. By scraping proximal portions of intestine, the inulin space was found to be similar (around 20% of total tissue water) in both the muscle layer and the mucosa. The mucosal epithelium is an imperfect barrier to inulin while the serosa is very permeable. These results suggest that the interstitial solute concentration is best approximated by equating it to that of the serosal solution. The in vitro inulin space, compared to the in vivo one, increases with time, as does the cellular hydration. The data obtained from measurements of extracellular space and from L-alanine uptake show that the intracellular amino acid is in a free state.
Effect of Starvation on Gonadotropin Secretion in Intact and Castrated Male Rats
Authors: Howland B. E. , Skinner K. R.
Published: April 2011

The effect of starvation on serum and pituitary concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was studied in intact and in castrated 4-month-old male rats. In intact rats, starvation for 7 days resulted in lower serum FSH (P < 0.05) and LH (P < 0.01) levels than in fed controls. Body, pituitary, and ventral prostate weights were also lower (P < 0.01) in rats starved for 7 days than in controls. The starvation-induced reductions in the serum levels of FSH and LH occurred within 48 and 24 h, respectively, after food was withheld. Rats subjected to starvation for 7 days immediately following castration showed higher (P < 0.05) pituitary concentrations of both FSH and LH than fed castrates. The serum levels of FSH and LH were equally high in both groups of castrates.The results suggest that starvation results in a rapid inhibition of gonadotropin secretion and the inhibition is dependent on an intact negative-feedback system.
A New Instrument for Sampling of Biological Liquid
Authors: Strasberg S. M. , Kooiman C. J. , Lomas B. , Johnson E. B. , Scott W. G. , Ord J. , Green P. H.
Published: April 2011

A new instrument for automatic continuous sampling of bile has been developed. Bile produced by an animal is externally diverted into a reservoir. A detection device permits evacuation of the reservoir into separate chambers, so that a preset continuous sample of total flow is diverted for collection, while the remainder is returned to the animal. The system is closed to air. Biliary tract pressure may be regulated, and bile flow calculated. The apparatus has been found to be very reliable and accurate in over 1 year of use. This instrument is adaptable to sampling other biological liquids.
Androgen-Induced Enhancement of Vascular Reactivity
Authors: Greenberg Stanley , George W. R. , Kadowitz P. J. , Wilson W. R.
Published: April 2011

Impairment of testosterone metabolism or excretion has been found in some patients with essential hypertension (Nowacynski et al. Can. J. Biochem. (1968), 46, 1031–1038). The effects of testosterone (10 mg/kg, intramuscular (i.m.)), methyltestosterone (10 mg/kg, i.m.), and vehicle on heart rate, arterial pressure, and responses of perfused canine hindpaws to intra-arterial norepinephrine (0.1–3.0 μg), tyramine (50 and 200 μg), angiotensin (0.1, 0.3, and 1.0 μg), and nitroglycerin (10 and 100 μg) were studied in three groups of dogs (five per group), 5 days after single doses of androgen or vehicle. Plasma and tibial artery electrolytes were also measured. After testosterone, heart rate (157 ± 5 beats/min) was higher than in control dogs after vehicle (132 ± 6 beats/min). Mean arterial pressure was similar in the two groups. Methyltestosterone-treated dogs had a significantly greater heart rate (160 ± 8 beats/min) than vehicle-treated animals. However, mean arterial pressures were similar in the two groups. A second series of dogs that received propranolol (1 mg/kg) 30 min before evaluation of heart rate showed no significant differences in heart rate among the treatment groups. Mean arterial pressures were similar in the three experimental groups. Pressor responses (expressed as the percentage change in perfusion pressure from the base line) to norepinephrine and tyramine were significantly enhanced after testosterone treatment. Pressor responses to angiotensin- and nitroglycerin-induced vasodilatation were unchanged after testosterone treatment when compared with vehicle controls. Pressor responses to tyramine, but not to norepinephrine, were also enhanced after methyltestosterone when compared with control responses after vehicle. Responses to angiotensin and nitroglycerin were similar in the two groups of animals. Plasma and tibial artery electrolytes were not different in the three experimental groups. These data suggest that single doses of androgen sensitized these animals to exogenously administered and endogenously released catecholamines. The effects were not mediated by sodium retention or altered plasma or tissue calcium concentrations.
The Effect of Ovarian Hormones on the Contractility of the Rabbit Oviductal Isthmus
Authors: Higgs G. W. , Moawad A. H.
Published: April 2011

In order to investigate the phenomenon of "tubal locking" of ova, the in vitro contractility of circular rings from the rabbit oviductal isthmus was examined in different hormonal states. Both alpha and beta adrenergic receptors were found to be present in this preparation with predominance of the alpha receptors when the tissues were from either estrogen- or progesterone-dominant animals.Progesterone treatment of estrogen-primed, immature females influenced the dose–response curve of the circular oviductal muscle to norepinephrine, significantly shifting it to the right, in comparison with tissues from animals that had been treated with estrogen only. There was less of a shift when dose–response relations were determined for phenylephrine after beta receptor blocked with propranolol, suggesting that progesterone enhanced the responses of beta compared with alpha receptors. However, there was still a small difference between responses of estrogen- and progesterone-dominated tissue, at least at low concentrations. Since beta receptor activity had been effectively eliminated, this tendency suggests that progesterone's effect on the response to norepinephrine is not completely due to a modification in beta receptor activity.The spontaneous contractility of tissues from estrogen-treated animals was characterized by a series of rapid spike-like contractions with fairly consistent shape and frequency. Additional treatment with progesterone modified the pattern to an irregular one. Moreover, the total spontaneous activity of muscle from estrogen-dominant animals (as measured by the area under the contractility curve) was significantly reduced, and the rate of tension increase was considerably slower than that from animals with progesterone as the dominant hormone. This indicated a form of antagonism to estrogen by progesterone not involving adrenergic receptors.Maximal excitation of the strips with nonspecific agents or adrenergic agonists resulted in significantly less activity in tissues from progesterone-treated animals. The mechanism of action of progesterone to produce this effect probably involves a step or steps in the excitation–contraction process beyond the adrenergic receptors.
Clotting Factor Deficiencies in Rats Fed a Modified Iodine-Deficient Diet
Authors: Jobin Michel , Jobin François
Published: April 2011

Fatal hemorrhages were found to occur in rats after 3–4 weeks of feeding a commercial iodine-deficient (Remington) diet corrected for iodine deficiency. Hematological investigation revealed a markedly prolonged one-stage prothrombin time in these rats, and reduced circulating levels of two vitamin-dependent clotting factors, factors VII and X. Cold exposure (5 °C) afforded partial protection to the Remington-fed rats: decreased incidence of deaths and partial correction of the clotting time. Complete correction or prevention of the clotting defects was obtained with the administration of vitamin K1, suggesting either an insufficient supply or an inadequate absorption of vitamin K in the Remington-fed rats.
Normal glutamic decarboxylase activity in rat striatum and retina following administration of L-DOPA
Authors: Tunnicliff G. , Butterworth R. F. , Tsukada Y. , Barbeau A.
Published: April 2011

Recent reports of the in vivo action of L-dihydroxyphenylalanine (L-DOPA) on glutamic acid decarboxylase (GAD) activity are contradictory. This investigation was undertaken to clarify the situation. Both acute (100 mg/kg and 1 g/kg) and chronic (1 g/kg) administration of L-DOPA to rats failed to produce any alteration in the activity of striatal or retinal GAD activity. These results are discussed in the light of a report relating L-DOPA therapy to modification of GAD activity in Parkinson's disease.
The effect of pH on rabbit atrial response to histamine
Authors: Hughes M. J. , Coret I. A.
Published: April 2011

The chronotropic response of isolated rabbit atria in normal Tyrode's medium increases monotonically with increasing doses of histamine (9 × 10−7–9 × 10−4 M). Plots of the inverse of response against the inverse of concentration were linear; and from these plots were derived values for the theoretical maximum response at 'infinite' dose and for the histamine concentration required to evoke a half maximum response. Alteration of pH by changing [HCO3−] at constant pCO2, [Na+] and osmolality did not appreciably affect the response to histamine in the range pH 7.0–7.6. However, at pH below 7.0 the magnitude of histamine response was reduced at all concentrations of histamine tested. In the pH range 7.0–7.6, additions of NaHCO3 at constant pCO2 increased the spontaneous rate of rabbit atria (in the absence of histamine); however, there was little effect of changing pH (in this range) by altering [HCO3−] at constant pCO2 when [Na+] and osmolality were kept constant. Immersion in solutions at pH's less than 7.0 led to decline in spontaneous rate and force of contraction. It is probable that depression of adenyl cyclase activity rather than a specific change in ionization of histamine receptor is responsible for a decreased response to histamine at pH 6.9.