bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen competition using 15N between early successional plants and planted white spruce seedlings
Authors: Staples Thomas E , Van Rees Ken CJ , Kessel Chris van
Published: April 2011

The ability of noncrop plants to compete with white spruce (Picea glauca (Moench) Voss) seedlings for applied fertilizer N is not well understood. Therefore, the objective of this study was to examine the efficacy of fertilizer N uptake using 15N by planted white spruce seedlings and understory vegetation. Double 15N-labeled NH4NO3 was broadcast in 1-m2plots for control, disc-trenched, and disc-trenched + manual brushing treatments. The fate of applied 15N in white spruce and noncrop plants was determined at the end of the first two growing seasons. The major competitors for fertilizer 15N were Populus tremuloides Michx. and grasses during the first growing season, and Populus tremuloides, Epilobium angustifolium L., and Achillea millefolium L. during the second growing season. Disc-trenching plus manual brushing significantly increased the fertilizer use efficiency of white spruce seedlings by limiting competition; however, <1% of the applied fertilizer 15N was utilized by the spruce seedlings after two growing seasons. The ability of competing vegetation to absorb broadcast fertilizer N suggests that alternative fertilizer types and placements be investigated to increase N uptake by white spruce seedlings planted in the boreal mixedwood forest.
Diversity and productivity of hypogeous fungal sporocarps in a variably thinned Douglas-fir forest
Authors: Colgan III Wes , Carey Andrew B , Trappe James M , Molina Randy , Thysell David
Published: April 2011

Although ecosystem management techniques are designed to enhance species diversity in managed forests, no comprehensive study has been conducted to evaluate effects of such techniques on diversity and productivity of hypogeous fungi (truffles). During this study, truffles were collected in a 55- to 65-year-old Douglas-fir forest from March 1993 through December 1995 at approximately 6-week intervals. Half of the stands served as controls, half were assigned a variable density thinning (VDT) treatment. A VDT stand comprised a mosaic of patches thinned to different densities of standing live trees. To further evaluate the effect of harvesting impacts, this mosaic was divided into two thinning categories, lightly thinned and heavily thinned areas. Truffle standing crop varied greatly but generally was highest in spring with a smaller peak in the fall. At least some sporocarps were found year round, with winter having the lowest biomass and species richness. Overall standing crop biomass (over all seasons) was significantly lower in VDT stands compared with control stands. The abundance of Gautieria and Hysterangium species was lower in thinned stands, while Melanogaster species diversity and productivity were highest in these stands.
The contribution of coarse woody debris to carbon, nitrogen, and phosphorus cycles in three Rocky Mountain coniferous forests
Authors: Laiho Raija , Prescott Cindy E
Published: April 2011

The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) - Engelmann spruce (Picea engelmannii Parry ex Engelm.) in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured for 14 years. Litter input was measured during 10 years for coarse woody debris, 1 year for ground vegetation, and 5 years for other aboveground litter types. Release of C, N and P from decomposing litter were simulated for a period of 40 years. After 14 years, log segments of pine, spruce, and fir had lost on average 71, 38, and 40%, respectively, of their dry mass. The N content of the pine logs increased, spruce changed little, and fir lost N. Phosphorus accumulated in all logs. The greatest imports of N and P occurred at the pine sites and fir sites, respectively, where these nutrients were the least available, indicating that wood decay organisms may compete with vegetation for limiting nutrients in these forests. Coarse woody debris comprised 3-24% of aboveground litter and contributed less than 5% of the N and P released. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests.
The effect of silviculture on genetic gain in growth of Pinus radiata at one-third rotation
Authors: Carson S D , Kimberley M O , Hayes J D , Carson M J
Published: April 2011

A trial planted on six sites representing five growth modelling regions and a range of site qualities in New Zealand was used to examine the interaction of silviculture and genetic improvement in Pinus radiata D. Don. Four seed lots with differing genetic potential for growth were grown under four stocking treatments from 100 to 600 stems/ha, all with a thinning ratio of 5:2. In addition, two treatments were planted at 500 stems/ha, one pruned and one unpruned. Among sites, differences were large for mean top height (8.1-13.9 m), basal area (7.9-21.5 m2/ha), and volume (25-108 m3/ha) at 8 years from planting. Differences among silvicultural treatments were large for basal area (with a range of 4.3-18.8 m2/ha over sites) and volume (17-86 m3/ha) and smaller but statistically significant for mean top height (10.1-11.6 m). Differences among seed lots were statistically significant for all traits but larger for basal area (12.1-13.6 m2/ha) and volume (51-59 m3/ha) than for height (10.7-11.1 m). Genetically different seed lots performed similarly relative to each other over the range of sites and silvicultural treatment, with a slight trend for greater differences among seed lots in the faster growing silvicultural treatments. However, differences in tree growth were many times greater among sites and silvicultural treatment than among genetically different seed lots.
Light extinction coefficients specific to the understory vegetation of the southern boreal forest, Quebec
Authors: Aubin Isabelle , Beaudet Marilou , Messier Christian
Published: April 2011

This study was conducted in six different forest types in Abitibi, Que., (i) to identify the factors that most influence understory light transmission in the southern boreal forest and (ii) to develop light extinction coefficients (k), which could be used to simulate light transmission in the understory. Light availability and understory vegetation (cover, composition, vertical distribution, and leaf area index) were characterized within three strata (0.05-5 m) in a total of 180 quadrats. Calculated k values were based on measured light availability and leaf area index. These values varied among forest types, strata, understory vegetation types, and cover in the upper stratum. The highest k values were generally associated with a dense stratum of Acer spicatum Lam. We developed five sets of k values based on the factors that most affected light transmission. Measured transmission (Tm) was compared with transmission predicted (Tp) from each set of k values. Light transmission predicted using a single k value (mean k = 0.54) underestimated Tm. More accurate predictions were obtained when we used the other four sets of k values. Our results indicate that, in the southern boreal forest, the understory vegetation can be quite heterogeneous and patterns of light transmission cannot be accurately simulated using a unique k value. However, the various sets of k values developed in this study could be used in prediction models of forest dynamics to obtain relatively good predictions of understory light extinction in forest types similar to the ones studied here.
Coarse woody debris in the southeastern Canadian boreal forest: composition and load variations in relation to stand replacement
Authors: Hély C , Bergeron Y , Flannigan M D
Published: April 2011

Quantities and structural characteristics of coarse woody debris (CWD) (logs and snags) were examined in relation to stand age and composition in the Canadian mixedwood boreal forest. Forty-eight stands originating after fire (from 32 to 236 years) were sampled on mesic clay deposits. The point-centered quadrant method was used to record canopy composition and structure (living trees and snags). The line-intersect method was used to sample logs of all diameters. Total log load, mean snag density, and volume per stand were similar to other boreal stands. Linear and nonlinear regressions showed that time since fire and canopy composition were significant descriptors for log load changes, whereas time since fire was the only significant factor for snag changes. Coarse woody debris accumulation models through time since fire were different from the U-shaped model because the first initial decrease from residual pre-disturbance debris was missing, the involved species had rapid decay rates with no long-term accumulation, and the succession occurred from species replacement through time.
Effects of renin on aldosterone secretion in the rat
Authors: Masson Georges M. C. , Travis Randall H.
Published: April 2011

A single subcutaneous injection of 40 units of renin to uninephrectomized rats about triples aldosterone secretion. Chronic injections of renin cause hypertension and a stimulation of the zona glomerulosa, whether the animals are given tap water or 1% saline to drink. On the 12th day aldosterone secretion is about four times the normal rate. The appearance of the zona glomerulosa is like that after sodium deficiency, with cellular hypertrophy and watery vacuoles.
Dose–response changes in organ weights and water contents following rectal administration of toxic doses of acetylsalicylic acid
Authors: Coldwell Blake B. , Boyd Eldon M.
Published: April 2011

Most of the significant changes in the mean weight and water content of 18 organs of albino rats at 18 h after the rectal administration of an LD50 of acetylsalicylic acid were found to be dose-dependent. Variations in the dose of drug and in the interval after drug administration selected for measurements were factors which affected the relation between mean changes and close–response correlations. Most mean changes in organ weights and water contents in an acute drug toxicity study will probably be dose–dependent. A dose–response correlation of changes in organ weights and water contents is not necessarily indicated in routine acute toxicity studies on new drugs. Gastric ulcers were found in albino rats 18 h after the rectal administration of 0.8 g of acetylsalicylic acid per kg; and over. It is concluded that measurement of organ weights and water contents in representative groups of animals at death and at intervals in survivors of specified doses of the drug under study will provide probably as much information as the more expensive dose–response studies.
Mechanical properties of semipermeable microcapsules
Authors: Jay A. W. L. , Edwards M. A.
Published: April 2011

A study has been made of the mechanical properties of the membrane of semipermeable nylon microcapsules containing erythrocyte hemolysate. The use of a "cell elastimeter" and the application of Laplace's Law have shown that the nylon membrane has very high resistance to stretching, but only negligible resistance to bending. The membrane tension in undeformed microcapsules has been determined to be 1840 dynes/cm and observed to increase with deformation, indicating elastic properties in the membrane. At a tension of 2520 dynes/cm, resistance to stretching is sharply reduced. The results indicate that the internal pressure varies directly as the reciprocal of microcapsule radius, and an extrapolation of these results, assuming that the relation holds for very small capsules, yields an internal pressure of 4.3 × 106 dynes/cm2 for a microcapsule of erythrocyte diameter. Any stretch in the nylon membrane has been shown to be almost irreversible. The diameter of the smallest pipette through which a spherical microcapsule can pass without suffering irreversible change has been found to be no smaller than 90% of the microcapsule diameter, and the pressure required is of the order of 105 dynes/cm2.
Thrombin and acetylated thrombin in the activation of fibrinolysis
Authors: Landaburu Ricardo H. , Giavedoni Elda , Santillán Rina
Published: April 2011

Thrombin that has been acetylated on its free amino group loses its fibrinogen-clotting properties, but when injected intravenously produces a fibrinolytic syndrome. The lytic results compare very closely to those obtained with thrombin administration, but acetylated thrombin does not produce fibrin deposition. In spite of the difference a common mechanism is suggested.
Plasma tocopherol levels in normal adults
Authors: Desai I. D.
Published: April 2011

A study of plasma tocopherol levels of 379 normal adult human subjects residing in metropolitan Vancouver and in the nearby rural community of Chilliwack was conducted. The plasma tocopherol values ranged from 0.38 to 2.28 mg/100 ml and averaged 0.97 ± 0.29 mg/100 ml. No significant differences were found between men and women and between city and rural populations. However, statistically significant differences were observed between tocopherol values of various age groups studied. It was also recognized that on an average, plasma tocopherol levels of university students were significantly lower than those found for the rest of the population. About 5.9% of the university students and 1.1% of the other subjects had tocopherol values below the generally accepted deficiency level of 0.5 mg/100 ml.
Thyroid parameters and metabolic adaptation to cold in rats fed a low-bulk thyroxine-free diet
Authors: Héroux O.
Published: April 2011

Rats fed a purified low-bulk thyroxine-free diet (T4-F) showed an increased sensitivity to noradrenaline similar to that in rats fed Master laboratory cubes. They also showed hypertrophy of the heart, liver, kidney, and adrenals, and reduced growth of the soleus and gastrocnemius muscles. However, thyroid weight and resting metabolic rate remained normal in cold-acclimated T4F-fed rats whereas both parameters increased in cold-acclimated rats fed Master laboratory cubes. These observations are taken as evidence that thyroid hypertrophy and increased resting metabolic rate are diet-dependent and unnecessary for metabolic adaptation to cold. The responsible factor or factors in the diet remain to be determined.
Changes in regional blood flows induced by dopamine and by isoproterenol during experimental hemorrhagic shock
Authors: Gifford R. M. , MacCannell K. L. , McNay J. L. , Haas J. A.
Published: April 2011

Although there is little experimental evidence that the heart is functionally deranged early in hemorrhagic shock, it appeared possible that desirable hemodynamic responses could be obtained with agents which would increase cardiac output without further compromising the peripheral circulation. Dopamine and isoproterenol exert a prominent positive inotropic effect on the heart. The amines differ in their action on peripheral blood vessels: isoproterenol produces β-adrenergic vasodilatation; dopamine lacks this action but does produce selective renal vasodilatation. In the experiments reported here, the hemodynamic response to intravenous infusion of these amines was examined in dogs subjected to hemorrhagic shock. In the doses selected (0.06 μg/kg per minute of isoproterenol and 6.0 μg/kg per minute of dopamine) both agents increased thoracic and abdominal aortic blood flow. "Splanchnic" and renal blood flows were increased by both amines, although the increments were statistically significant only in the case of dopamine. The cardiac output, as measured by the Fick principle, was increased only by isoproterenol.
Problems associated with selenium deficiency in beef calves
Authors: Hidiroglou M. , Carson R. B. , Brossard G. A.
Published: April 2011

Tissue selenium levels were low in calves born from cows receiving various forages, all low in selenium, but varying in tocopherol content and fatty acid composition. Blood and liver selenium contents were closely related to the age of the calves and decreased during the course of the experiment. The incidence of nutritional muscular dystrophy (NMD) was related to the maternal diet. No clinical NMD was noted in calves born from dams fed oat silage, a diet low in selenium and polyunsaturated fatty acids but adequate in tocopherol. The etiological mechanisms preceding the onset of NMD in the calves are discussed. It is suggested that the myopathy-promoting effect was chiefly associated with the degree of saturation of fatty acids and the tocopherol content of the diet.
Effect of norepinephrine and uncoupling agents on brown adipose tissue
Authors: Horwitz Barbara A. , Herd Paul A. , Smith Robert Emrie
Published: April 2011

Examination of the in vivo effect of 2,4-dinitrophenol (DNP) on the brown adipose tissue of cold-exposed rats, as well as the in vitro response of this tissue to DNP and dicumarol, indicates that brown fat does possess a functional electron transport coupled phosphorylating system. Moreover, the fact that a norepinephrine-induced thermogenic response (in vivo) can be elicited from the brown fat after DNP administration implies that the effect of norepinephrine (NE) is not primarily due either to a physiological uncoupling by fatty acids, the level of which is increased by NE, or to stimulation of an ATP-ase system. Alternatively, our data suggest that under basal conditions (i.e. when the animal is not stimulated by cold stress or NE), the heat production (oxygen consumption) of the brown fat is limited by the availability of substrate rather than ADP. It is thus proposed that the thermogenic effect of NE results from the stimulation of lipolysis and an attendant increase of substrate available for oxidation.
Oxidative phosphorylation, adenine nucleotides, and phosphofructokinase in the livers of rats receiving thrombogenic diets
Authors: Simard-Duquesne Nicole
Published: April 2011

Diets of varying thrombogenic potencies were fed to rats for a period of 6 weeks. The thrombogenic potency of these diets was determined by the extent of the hepatic infarcts (consequent upon thrombosis in the hepatic vein) which occurred within 24 h after the injection of S. typhosa endotoxin. Those groups of rats receiving the low thrombogenic diets were more suitable as controls for the animals on the high thrombogenic diets than were normal rats fed standard laboratory chow. The thrombogenic potency of the diets was inversely related to the ratio of [AMP][ATP]/[ADP]2 found in the liver. A decrease in this ratio should favor platelet aggregation, and the results are thus in accord with the hypotheses implicating adenine nucleotides in thrombogenesis. The thrombogenic potency of the diets was directly related to the activity of liver phosphofructokinase. This increase in activity is probably linked to the disturbed adenine nucleotide metabolism. Oxidative phosphorylation mechanisms were investigated as possible causes for the changes in adenine nucleotides, but no important alteration in these reactions could be demonstrated. The exact mechanism by which the thrombogenic diets alter the adenine nucleotide ratio and the phosphofructokinase activity remains to be elucidated.Des rats ont été nourris pendant 6 semaines avec des régimes de forces thrombogènes variées. Cette capacité thrombogène est évaluée d'après la sévérité des infarcti hépatiques (provoqués par un thrombus dans la veine hépatique) que l'on trouve en dedans de 24 h après l'injection d'endotoxine de S. typhosa. Les groupes de rats sur régimes thrombogènes à force faible constituent de meilleurs groupes témoins que ne le sont des animaux, recevant un régime usuel. La force thrombogène de ces régimes est en relation inverse avec le rapport [AMP][ATP]/[ADP]2 que l'on trouve dans le foie. Un abaissement de ce rapport devrait favoriser l'agrégation des plaquettes sanguines; les résultats obtenus supportent les hypothèses selon lesquelles les nucléotides d'adénine sont impliqués dans la thrombogénèse. L'activité de la phosphofructokinase est augmentée en relation directe avec la force thrombogène des régimes. Cette augmentation est probablement liée au métabolisme anormal des nucleotides d'adénine. Aucun changement n'a pu être décelé dans les mécanismes de phosphorylation oxydative, qui pourraient provoquer des altérations dans le métabolisme des nucléotides d'adénine. Le mécanisme exact par lequel les régimes thrombogènes agissent au niveau des nucléotides d'adénine et de la phosphofructokinase est inexpliqué.
Interaction between deoxycorticosterone treatment, fluid intake, sodium consumption, blood pressure, and organ changes in rats drinking water, saline, or sucrose solution
Authors: Hall C. E. , Hall O.
Published: April 2011

Intact control and DOCA-treated rats were allowed to drink distilled water, a 1% NaCl solution, or a 5% sucrose solution. Fluid intake, blood pressure changes, and organoleptic responses were evaluated. Control rats drank more sucrose solution than saline and more saline than water. Hormone treatment slightly increased water intake and greatly augmented saline consumption, but invariably depressed that of sucrose solution even though a considerable polydipsia remained in effect. Hypertension and cardiorenal enlargement characterized all groups given DOCA. Both were substantially more severe in those also given excess salt, and only in that group were cardiovascular–renal lesions grossly visible.
Norepinephrine and renin content in arterial tissue from different vascular beds
Authors: Genest J. , Simard S. , Rosenthal J. , Boucher R.
Published: April 2011

Norepinephrine and renin contents in arterial tissues from different vascular territories in mongrel dogs were measured simultaneously. A significantly greater concentration of these two substances was found in the branches of the superior and inferior mesenteric arteries in contrast to arterial tissue taken from the aorta and from carotid, renal, femoral, and hind limb arteries of similar diameter. Norepinephrine and renin were undetectable in the rectus abdominis artery. There was no significant difference in the norepinephrine content of branches of mesenteric vein when compared with similar branches of mesenteric artery.
Preparation of highly active enterogastrone
Authors: Brown J. C. , Pederson R. A. , Jorpes E. , Mutt V.
Published: April 2011

By using a 10% pure preparation of cholecystokinin–pancreozymin (CCK–PZ) a fraction was obtained which was inhibitory for H+ secretion, pepsin secretion, and motor activity in antral and fundic pouches. This material possessed no significant CCK–PZ activity or secretin-like activity.
Protection of L-cells by thiols against the toxicity of sulfur mustard
Authors: Walker I. G. , Smith J. F.
Published: April 2011

The lethal effect of sulfur mustard on L-cells was reduced by pretreating the cells with dithiothreitol (DTT), aminoethylisothiuronium bromide, mercaptoethylamine, and some alkyl derivatives of this compound. The disulfides of these agents were without protective activity. The protective mechanism by which DTT operated involved a simple inactivation of the sulfur mustard. This deduction was based on the finding that alkylation by mustard of cellular DNA, RNA, and protein was reduced by DTT treatment in parallel with the reduction in toxicity of the mustard. DTT at a tolerated dose of 100 mg/kg provided scant protection to mice against the nitrogen mustard HN2.
Calcitonin content of ultimobranchial body tissue in chicks, pullets, and laying hens
Authors: Wittermann Ernst R. , Cherian A. George , Radde Ingeborg C.
Published: April 2011

Calcitonin concentrations were determined by bioassay in hydrochloric extracts of ultimobranchial bodies of chickens aged 3 weeks, 3 months, and 9 months. The results were compared with those obtained with two standard preparations (MRC "Thyroid Calcitonin Research Standard A" and a porcine thyroid house standard). Nine-month-old, hypercalcemic hens showed similar concentrations of calcitonin in their ultimobranchial bodies when compared with the two younger age groups of chickens which had been normocalcemic. The maximal hypocalcemic response was 25%. The degree of hypophosphatemia produced by injection of ultimobranchial extracts from the three age groups was also similar, the maximal response being a 35% decrease from original levels. The concentration of calcitonin in ultimobranchial tissue, when expressed in milliunits per milligram fresh gland (125–180 mU/mg) was comparable to values found by other investigators. It is concluded that the hypercalcemia of egg-laying does not lead to a measurable depletion of calcitonin from ultimobranchial bodies.
Effect of atropine and DMAE (a hemicholinium derivative) on contractile responses of the guinea pig ileum
Authors: Goldenberg Marvin M.
Published: April 2011

A close structural analogue of hemicholinium, α,α′-bis(dimethylammoniumacetaldehyde diethylacetal)-p,p′-diacetylbiphenyl bromide (DMAE), was reported to antagonize responses to ganglionic stimulants more than responses to preganglionic nerve stimulation in the cat or dog and to possess activity both similar to and different from cocaine. The present study was concerned with the effect of DMAE and atropine on the response of the isolated guinea pig ileum to ganglionic stimulants and to transmural stimulation. Nicotine and DMPP, ganglionic stimulants, caused initial spike-like contraction, which was blocked by atropine, followed by a slow sustained contraction, which was atropine-resistant but was inhibited by DMAE. Cocaine and morphine, unlike DMAE, did not elicit a differential antagonism of the biphasic effects of the ganglionic stimulants. Contractions evoked by transmural stimulation were, however, augmented by DMAE but reduced by cocaine and atropine. DMAE could induce contractions of the ileum, by means of intrinsic excitation of the cholinergic neuronal elements and not by a direct action on cholinergic smooth muscle receptors. In conclusion, ganglionic stimulants have revealed in the guinea pig ileum an atropine-resistant noncholinergic neuronal pathway which was sensitive to DMAE blockade. Furthermore, actions of DMAE and cocaine on contractions caused by ganglionic stimulants and transmural stimulation were found to be nonparallel.
Procaine-induced contraction in vein and its modification by drugs
Authors: Sanders H. D.
Published: April 2011

Procaine (or lidocaine) contracted whole segments of the rhythmically contracting anterior mesenteric vein (AMV) of the cat and rat in vitro. Autonomic blocking drugs, antihistamines, and antiserotonin agents were ineffective in reducing either the spontaneous activity of the vein or the procaine-induced contraction. Only those agents which abolished the spontaneous activity of the AMV prevented the procaine-induced contraction. It is suggested that conditions which permit action potential production in the AMV may be required for procaine-induced contractions to occur.
Metabolic control mechanisms in mammalian systems. IV. Androgenic induction of hexokinase and glucose-6-phosphate dehydrogenase in rat seminal vesicles
Authors: Singhal Radhey L. , Ling George M.
Published: April 2011

The hormonal control of hexokinase and glucose-6-phosphate dehydrogenase activities was investigated in seminal vesicles of the orchidectomized rat. Whereas castration produced marked decreases in the activities of these vesicular enzymes, administration of testosterone propionate (100 μg/100 g) to castrated rats for 3 days increased hexokinase to 462% and glucose-6-phosphate dehydrogenase to 843% of the control values. Time-course studies revealed that after a single injection of testosterone (5 mg/100 g), the activities of both hexokinase and glucose-6-phosphate dehydrogenase were elevated significantly at 16 h and increased further during the 48-h period. The observed enzyme increases were inhibited by the administration of 17β-estradiol to testosterone-treated rats, although this estrogen by itself exerted no significant effect. Actinomycin, cycloheximide, and ethionine effectively prevented the androgen-induced increases in vesicular enzyme activities observed 24 h after hormone injection. The data presented suggest that the increases in vesicular hexokinase and glucose-6-phosphate dehydrogenase activities induced by testosterone propionate represent new enzyme production involving stimulation of the synthesis of certain RNA species.
Experimental production of hemorrhagic shock in the rat
Authors: Steinman Ralph , Denstedt Orville F.
Published: April 2011

Hypotensive shock was produced in albino rats by removal of blood and maintenance of the blood pressure at 30 or 40 mm Hg until the spontaneous 'take-back' of blood reached a definite proportion (usually 40%) of the maximum blood loss. The rest of the blood was then infused. Controlled removal and infusion of the blood were accomplished by means of a special apparatus, which is described. While the degree and duration of hypotension are the most critical conditions in determining the severity of shock and the probability of survival, other conditions such as a high environmental temperature, a fasted state, and lack of previous exercise also lessen the capacity of the rat to withstand the stress of hypotension. The standardized method for the production of hypovolemic shock in the rat is useful in quantitative evaluation of the influence of various physical and chemical agents in the production and treatment of shock.
Effect of calcitonin on the domestic fowl
Authors: Kraintz Leon , Intscher K.
Published: April 2011

The plasma calcium response of intact and acute partially parathyroidectomized cockerels (Gallus domesticus) to the intravenous infusion of porcine thyroid calcitonin, avian ultimobranchial calcitonin, and chicken thyroid extract was determined. No hypocalcemic response was obtained in the intact cockerels with any of the agents tested. However, marked hypocalcemic responses were obtained in the partially parathyroidectomized cockerels following administration of porcine thyroid calcitonin or avian ultimobranchial calcitonin at the same dose levels (300 MRC milliunits/kg). No hypocalcemic activity was obtained with chicken thyroid extract. It is possible to speculate, from these results, that calcitonin from the ultimobranchial gland is involved in the maintenance of plasma calcium homeostasis in the chicken.
Lethal factor released from submandibular grafts in mice
Authors: Hoshino K. , Lin C. D.
Published: April 2011

The present series of experiments clearly demonstrates the existence of the lethal factor in the submandibular gland of male BALB/c mice. This lethal factor was released from the submandibular gland of male mice when the glands were transplanted autologously into submandibular-sialoadenectomized male mice or isologously into normal intact adult male or female mice. Neither the sublingual nor the parotid grafts demonstrated the same effect. The lethal effect was not observed in the experiments with submandibular grafts obtained from immature male or mature female mice. As a host, the female mouse was found to be more susceptible to the lethal factor. There was a linear relationship between the strength of the lethal factor and the number of submandibular grafts used. The site of production of the lethal factor is unknown. It was extremely unusual to see the death of host mice which merely received a normal organ other than the submandibular gland.
Investigations on the effects of hyperbaric oxygen on enzyme activity
Authors: Bégin-Heick Nicole , Hochstein P. , Hill Gale B.
Published: April 2011

The ability of hyperbaric oxygen to produce lasting effects on enzyme activities was investigated. Mice were subjected to hyperbaric oxygen until they suffered sustained convulsions. The enzyme activities were then determined in brain and liver tissue. The results presented indicate that under these conditions of in vivo exposure and in vitro assay, hyperbaric oxygen does not affect permanently the activities of the enzymes which were examined.
The effect of facial cold stimulation on airway conductance in healthy man
Authors: Josenhans W. T. , Melville G. N. , Ulmer W. T.
Published: April 2011

The effect on airway conductance (Gaw) and functional residual capacity (FRC) of stimulation of cold receptors in facial skin was studied in 12 healthy young subjects, with a body plethysmograph. Mean Gaw decreased significantly, from 0.44 to 0.38 liter s−1 cm−1 H2O, in 10 subjects. FRC was only slightly affected, probably because the experiment was too brief to allow air-trapping. It is concluded that the Gaw decrease during exposure to cold results from bronchoconstriction due to (a) stimulation of trigeminal nerve cold receptors and to (b) pharyngeal and glottal airway resistance increase resulting from frequent involuntary 'dry' swallowing.
The effect of fluoride ingestion on the response of the rat to parathormone and calcitonin
Authors: Kraintz Leon
Published: April 2011

Long-term ingestion of 100 p.p.m. of fluoride as NaF in the drinking water of the intact growing rat resulted in a slight but significant decrease of fasting plasma calcium concentration when compared with that in controls given distilled water. The plasma calcium response of both groups of rats to administered calcitonin was similar. The effect of parathormone on the plasma calcium response of thyroparathyroidectomized rats given NaF or distilled water showed a similar degree of hypercalcemia. Intact rats receiving fluoride or distilled water, given the same amount of parathormone, exhibited only a slight elevation of plasma calcium which was similar in both groups. It is concluded that the long-term ingestion of fluoride probably does not alter the response of the growing rat to endogenous or exogenous parathormone or calcitonin.
A study of gastric secretion induced by close arterial infusions of histamine in the dog
Authors: Stavraky G. W. , Knill J. R. , Currie R. B.
Published: April 2011

The effects of close arterial infusions of progressively increasing quantities of histamine into different regions of a denervated total stomach pouch were compared with the effects of infusions of histamine into the splenic vein in dogs under chloralose–urethane anesthesia. Infusions of 0.5 mg/h and 2.0 mg/h of histamine into the left gastric artery (lesser curvature of the stomach) were more effective than were the infusions of the same solutions into the gastrosplenic artery (greater curvature) as shown by the shorter latency to the appearance of free HCl and by a greater volume of secretion and total acid output per square centimeter of mucosa. Infusions of excessive quantities of histamine (32.0 mg/h) resulted in a reversible inhibition of HCl output as observed on the lesser curvature. The peptic activity of the gastric juice was low and decreased progressively with increasing amounts of infused histamine. Systemic blood histamine concentrations did not change during infusions of 0.5 mg/h or 2.0 mg/h of histamine into the gastric arteries or splenic vein; infusions of larger amounts of histamine (8.0 mg/h and 32.0 mg/h) resulted in a penetration of histamine into the general circulation and in systemic effects. These effects appeared earlier and with smaller quantities of histamine when the latter was infused into the portal vein close to the liver than when administered into the splenic vein as judged by the appearance of free hydrochloric acid in the gastric contents.
Regression of cardiac hypertrophies of various origin
Authors: Beznak Margaret , Korecky B. , Thomas Gwynneth
Published: April 2011

Enlargement of the heart was produced in rats by four methods: (a) unilateral nephrectomy with DOC pellet implantation and salt loading, (b) experimental hyperthyroidism, (c) experimental aortic coarctation, and (d) nutritional anemia. All enlargements proved to be reversible if the provoking stimulus was removed. In hearts enlarged by anemia up to 80–100%, the extra protein and RNA synthesized during the process of accelerated growth of the heart disappeared as the size of the heart reverted to normal. In this way, the concentration of these two macromolecules remained the same, in spite of the changes in the size of the heart. On the other hand, a large part of the new DNA was not removed during regression.
Rates of formation and oxidation of lactic acid in dogs at rest and during moderate exercise
Authors: Depocas Florent , Minaire Yves , Chatonnet Joseph
Published: April 2011

The rates of formation and oxidation of plasma lactic acid were measured in dogs, either resting quietly or running at 6 km/h on the level, by priming and continuous infusion with uniformly labelled 14C-lactic acid. During running at rates of oxygen consumption almost 5 times the resting value, corresponding to approximately 30% of the maximal effort, the rates of lactic acid formation and disposal were always greater than at rest and doubled on the average. Average plasma lactic acid concentrations during running were greater, equal, or lower than at rest in different dogs. The energy released by formation of the extra lactic acid from glucose during running represented, energetically, less than 0.5% of the extra energy cost of running. Seventy-four percent of the lactate formed was promptly converted to CO2, and about 12% of the respiratory carbon was derived from lactic acid in the running dogs. About 10% of the plasma glucose was derived from lactic acid during both rest and activity. At similar plasma lactate concentrations, running dogs had greater rates of formation of lactic acid than resting animals.
Blood lipids in experimental cardiac necrosis
Authors: Solymoss B. , Varga S. , Classen H. G.
Published: April 2011

Infarctoid necroses were observed in combination with elevated serum free fatty acids, triglycerides, cholesterol, and total lipids in the Electrolyte-Steroid-Cardiopathy with Necrosis (ESCN) when the latter was aggravated by the oral administration of corn oil. Although treatment with amiloride, a potassium-sparing agent, inhibited the development of cardiac lesions, it did not normalize the blood lipids. It is concluded that, in the ESCN, lipids have a cardiotoxic effect only in conjunction with electrolyte disturbances.
Incorporation of radioactive label from pyrimidines into liver lipids
Authors: Myers D. K. , Ram S.
Published: April 2011

After injection of tritiated thymidine into rats, the lipid fraction of the liver contained three times more tritium than did the nucleic acid fraction. Similar results were obtained with labelled thymine, uracil, and cytosine. The results emphasize the importance of exhaustive lipid extraction in autoradiographic studies of nucleic acid synthesis.
Evidence for a renal-dependent factor in the control of muramidase (lysozyme) formation
Authors: Keeler R.
Published: April 2011

After bilateral nephrectomy the total body muramidase in the rat increases by about 50% in 6 h. Since there was no evidence to suggest that this increase was the result of failure to remove or inactivate muramidase, experiments were performed to measure the rate of muramidase formation in the bone marrow of normal and nephrectomized rats. The enzyme production was measured as the product of the plasma flow and the arterio–venous difference. Results showed that 6 h after bilateral nephrectomy there was a 14-fold increase in muramidase production. It is suggested that renal tissue may normally exert an inhibitory influence upon muramidase formation.
Effects of high temperature and acute diuresis on glucose-6-phosphate dehydrogenase activity of macula densa and plasma renin activity in rats
Authors: Rojo-Ortega J. M. , Rosenthal J. , Boucher R. , Genest J.
Published: April 2011

Experiments performed in rats exposed to heat and to acute diuresis revealed: (a) a positive influence of the environmental temperature on plasma renin activity; (b) a dissociation between plasma renin activity and the glucose-6-phosphate dehydrogenase activity of the macula densa following furosemide administration; and (c) the absence of any significant changes in juxtaglomerular cell granularity despite a very significant increase in plasma renin activity.
Inhibition of prostaglandin effects by ouabain in the canine vascular tissue
Authors: Kadar D. , Sunahara F. A.
Published: April 2011

The effects of prostaglandins on the isolated mesenteric vein and artery of the dog were investigated. Prostaglandin E1 (PGE1) inhibited spontaneous contractions of the tissue whereas prostaglandin F1α (PGF1α) and prostaglandin F2α (PGF2α) stimulated them. The effects of prostaglandins were not influenced by pretreatment with atropine, phenoxybenzamine, propranolol, or tetrodotoxin. The norepinephrine-induced contractions were inhibited by PGE1 and enhanced by PGF1α and PGF2α Both these contrasting effects were enhanced in a low concentration of K+ (1.2 mM) and diminished when the media contained K+ in high concentration (23.2 mM). Pretreatment of the tissue with ouabain in sufficiently high concentration (1.5 × 10−5 M) produced an initial contracture followed by relaxation. PGE1 and PGF1α had no effect on the ouabain-treated tissue but PGF2α still induced dose-dependent contractions. In the ouabain-treated tissue the effects of PGE1 and PGF1α on the norepinephrine-induced contraction were also absent. From these experiments it is concluded that the transport enzyme (Na+ + K+)-dependent ATPase is necessary for PGE1 and PGF1α to elicit their action on vascular tissue. The PGF2α effect is probably mediated by an enzyme which is not sensitive to ouabain.
Amino and urea nitrogen levels in lambs receiving different nitrogen sources and injections of lysine and methionine
Authors: Ely D. G. , Little C. O. , Mitchell Jr. G. E.
Published: April 2011

Two trials were conducted to study changes in plasma urea and amino nitrogen of lambs fed different nitrogen sources. In the first trial, zein, zein and urea, or urea were fed as the only dietary nitrogen sources. Nitrogen balance data indicated the superiority of the zein–urea ration. Plasma amino acid concentrations were lower at 4 h after feeding than just before feeding. The concentration of total plasma amino acids was greatest when zein was fed and least when the zein–urea ration was fed. Lysine injections into the systemic blood caused a steady decline in total amino acid concentration up to 60 min after injection when zein was fed. Increases in total concentrations were noted after injection when urea had been fed. Intermediate values resulted in lambs fed the zein–urea ration. Lysine appeared to be the limiting amino acid required for maximum tissue protein synthesis when zein was fed. In the second trial, zein, purified soy protein, urea plus sulfur, and urea without sulfur were fed. Plasma collected from lambs fed zein contained less urea nitrogen at every collection period than those fed the other three nitrogen sources. Urea nitrogen decreased from time of feeding to 4 h after feeding zein and soy but increased after feeding both urea rations. Plasma amino nitrogen decreased from time of feeding to 4 h after feeding all rations. Neither urea nitrogen nor amino nitrogen was affected by intravenous amino acid injections.
Criteria for differentiation of brown and white fat in the rat
Authors: Daniel H. , Derry D. M.
Published: April 2011

By using a modified method of Falck, the distribution of nerves containing catecholamines in brown and white fat was studied. The brown fat cells had sympathetic nerve fibers with synaptic varicosities running between all cells. White fat had no sympathetic innervation of the parenchymal cells. Both tissues contained a dense network of fibers around the arterial blood vessels.
The renal action of angiotensin in rats after expansion of plasma volume or of extracellular fluid
Authors: Regoli D.
Published: April 2011

Expansions of extracellular space or of plasma volume were produced in rats by infusing Ringer's solution or bovine albumin 6% in Ringer's solution. Urinary volume (V), glomerular filtration rate (GFR), and the fraction of sodium escaping tubular reabsorption (TRFNa+) were measured in the two series of animals during the first 40 min of infusion: an analogous increase of V and TRFNa+ was observed in the two groups. On the contrary, when the infusion was continued for 100 min, V, TRFNa+, and GFR of animals receiving isooncotic solution were markedly depressed. Val-5-angiotensin II-amide (0.25 μg/kg per min) was natriuretic in animals whose extracellular fluid volume had been expanded with an isotonic infusion, whereas most of the animals receiving isooncotic solutions did not respond to the octapeptide. The fraction V of bovine albumin used in the present study was devoid of a pressor effect and did not show any angiotensinase activity. The results are consistent with the hypothesis that the decrease of plasma oncotic pressure is an important factor facilitating the natriuretic effect of angiotensin.
The role of protein–polysaccharides in hydration of the arterial wall
Authors: Palatý Vladimír , Gustafson Brigid K. , Friedman Sydney M.
Published: April 2011

There is a statistically significant positive correlation between the total water content of the arterial wall and the concentration of sodium bound to negatively charged groups of the protein–polysaccharide gel. The fraction of water associated with the protein–polysaccharide gel is located almost exclusively in the inulin space, and is significantly increased in hypertension. The size of this fraction can be reduced by exchanging sodium—the main counterion under physiological conditions—for a divalent ion. There is no difference between calcium and magnesium in this regard. The configuration of the gel, which is given primarily by the relative concentration of the charged groups and the valency of the counterion, determines the size of the inulin space.
The effect of incubation on the weight of guinea pig cardiac muscle preparations
Authors: MacLeod Don P.
Published: April 2011

Guinea pig atria and ventricular strips were found to lose weight during incubation in vitro. This weight loss is not measurably changed by incubation under anoxic conditions, at 20 °C, or in the presence of ouabain. The percent water of the preparations remained constant during weight loss. Various changes in sodium and potassium occurred in the two preparations and in the same preparation under different environmental conditions but did not correlate with the weight loss. The results demonstrated weight loss of equal parts water and solid from cardiac muscle during incubation in vitro with no serious alteration in cation concentrations. The loss is not altered by metabolic depression, suggesting a physical process.
The effect of oxyphenbutazone (Tandearil) on the seromucoid-bound carbohydrates of rats with formalin- and turpentine-induced inflammation
Authors: Macbeth R. A. , Belur N. V. , Bell G. D. , Barron C.
Published: April 2011

The seromucoid response, as determined by the estimation of seromucoid protein and seromucoid-bound hexoses, hexosamines, N-acetylneuraminic acid, and fucose, was studied in rats following the creation of an aseptic intramuscular inflammatory focus with either formalin or turpentine. Both irritants caused an intense local inflammatory reaction but the use of formalin was associated with an unacceptable level of mortality and morbidity. Turpentine resulted in a brisk seromucoid response, as judged by all parameters mentioned, whereas formalin caused no significant seromucoid response. Oxyphenbutazone did not significantly affect the local inflammatory response or the seromucoid response to either of these irritants under the conditions of the experiment.