bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECTS OF RAPID HEMODIALYSIS ON BRAIN TISSUES AND CEREBROSPINAL FLUID OF DOGS
Authors: Pappius Hanna M. , Oh J. H. , Dossetor J. B.
Published: April 2011

The effects of hemodialysis on cerebral tissue and cerebrospinal fluid constituents and on intracranial pressure were investigated in dogs. It was shown that the potassium content of the cerebral cortical gray matter is decreased in uremic brain. In uremic animals the urea concentration of cerebral tissues was found to be in equilibrium with that of plasma whereas the urea concentration of cerebrospinal fluid was significantly lower. Hemodialysis for 60 minutes with a Kolff twin-coil artificial kidney rapidly decreased the urea concentration in the plasma and caused a considerable but slower decrease in the urea content of cerebral tissues. The urea level in cerebrospinal fluid was only slightly altered. Consequently, a significant transient difference developed between the urea concentrations in brain and plasma. The difference between the concentration of urea in cerebrospinal fluid and plasma was always more pronounced and of longer duration after hemodialysis. Swelling of cortical gray matter was demonstrated in 50% of dialyzed uremic animals and of white matter in 75%. A rapid rise in cerebrospinal fluid pressure occurred during dialysis in all cases. Similar effects were observed when a concentration gradient for sodium between plasma and the central nervous system was produced in normal animals by dialysis against a hyposmotic, low-sodium bath fluid. It was concluded that, in experimental uremia, hemodialysis results in increased cerebrospinal fluid pressure owing to an osmotically induced increase in cerebrospinal fluid volume and, to a variable extent, to osmotically induced cerebral tissue swelling. Osmotically induced cerebral swelling was shown to be a different phenomenon from cerebral edema associated with trauma.
THE INFLUENCE OF SEX AND AGE IN ALBINO RATS GIVEN A DAILY ORAL DOSE OF CAFFEINE AT A HIGH DOSE LEVEL
Authors: Peters Josef M. , Boyd Eldon M.
Published: April 2011

Caffeine was given daily for 14 days in an oral dose of 185 mg/kg to male and female albino rats in groups of increasing body weight. The sensitivity of rats to the lethal effects of caffeine increased with increase in age. Psychotoxic (auto-mutilation plus hemorrhage) deaths were most common in young rats, and hypokinetic–convulsive deaths in older animals. In survivors, the incidence of glycosuria and hydration of the kidneys was greater, and dehydration of the adrenal glands and gonads less, in older than in younger rats. Sublethal signs of toxicity in male survivors were greater than in female survivors. Anorexia and loss of body weight were greater in male than in female survivors, diuresis was less evident, loss of muscle weight was greater, and the relative gain in weight of the adrenal glands and gastrointestinal tract were greater. In brief, caffeine was found to be more toxic in older than in younger rata and in males than in females.
METHIONINE TOXICITY IN RATS EXPOSED TO COLD
Authors: Beaton J. R.
Published: April 2011

Male rats of the Wistar strain were fed a control diet (20% casein) and the same diet to which 3% DL-methionine was added, at environmental temperatures of 24 and 7 °C. Effects of methionine feeding at 24 °C were hypophagia, reduced body weight gain, increased kidney weight, decreased liver weight, deposition of iron in the spleen, and paleness of the eyes; there was no effect upon liver fat concentration. At 7 °C, food (and hence methionine) intake was markedly increased in rats fed the methionine-supplemented diet; the accentuation of effects of methionine feeding in these animals might be attributable to the increased intake of this amino acid. In addition, a condition resembling severe frostbite of the ears and paws was observed in these animals. From the results of this experiment it is apparent that the catabolic effect of cold exposure does not eliminate the deleterious effect of excess dietary methionine.
STUDIES ON TOLERANCE AND IONIC ANTAGONISM FOR CADMIUM OR MERCURY
Authors: Gabbiani G. , Baic D. , Déziel C.
Published: April 2011

In the rat the parenteral administration of cadmium chloride induces selective hemorrhagic lesions in sensory ganglia; these heal within 15 days, after which time the animals become tolerant to a second injection of the compound. Ganglionic lesions caused by cadmium chloride are also inhibited by pretreatment with cobaltous chloride; the inhibition is maximal when the prophylactic agent is administered 17 hours before cadmium chloride. Cobaltous chloride also protects, although to a lesser extent, against the kidney lesions induced by mercuric chloride. Finally, when the animals have been protected by cobaltous chloride against a first dose of cadmium chloride, they develop ganglionic lesions following the administration 15 days later of a second dose of the latter compound.
STUDIES ON FACTORS INFLUENCING THE ACUTE TOXICITY OF MALATHION AND MALAOXON IN RATS
Authors: Brodeur Jules , DuBois K. P.
Published: April 2011

A study was undertaken to investigate the mechanisms responsible for the higher susceptibility of immature rats to the organophosphate insecticide malathion. In vitro measurements of the activity of malathionase in the tissues of rats, at various time intervals after birth, indicated that the livers of immature rats detoxify the insecticide at a much slower rate than do the livers of adult animals. Evidence was obtained which showed that prolonged administration of testosterone causes a significant increase of the enzymatic activity in the livers of castrated young male rats and adult female rats. On the other hand, castration interferes with the maintenance of normal levels of malathionase in adult males and partially prevents the development of the activity in weanlings. Estradiol decreases the enzymatic activity in adult males. It appears, therefore, that the age difference in the susceptibility of rats to malathion might be due, to a large extent, to a slower rate of inactivation of the insecticide by the livers of immature animals. The results obtained also indicate that the sex hormones play an important role in the development and maintenance of normal levels of the enzyme system involved in the degradation of malathion in the livers of rats.
RELEASE OF BOUND SODIUM IN SINGLE MUSCLE FIBERS
Authors: Hinke J. A. M. , McLaughlin S. G. A.
Published: April 2011

The activities of sodium, potassium, and hydrogen in the myoplasm of single muscle fibers from the giant barnacle were measured by cation-sensitive microelectrodes as the temperature of the bathing solution was increased from 7 to 40 °C. An irreversible shortening occurred in all fibers between 37 and 40 °C. When the fibers shortened in a sodium-free Ringer solution, the mean activity of sodium increased by 130%, the mean activity of potassium remained relatively constant, and the pH decreased from 7.17 to 6.77. The results have been interpreted as meaning that at 37–40 °C there was a disruption of the myofilaments and a release of associated sodium ions.
SITES AT WHICH FORMALIN AND CAPSAICIN ACT TO STIMULATE CORTICOTROPIN SECRETION
Authors: Makara G. B. , Stark E. , Mihály K.
Published: April 2011

The sites at which injected Formalin and capsaicin act to stimulate ACTH secretion, as concluded from changes in the plasma corticosterone level, were studied in male Wistar rats. Formalin injected into an area deafferentated by denervation or spinal cord transection failed to raise the plasma corticosterone level, showing that it acted locally and that the nervous impulses it produced travelled to the hypothalamus through ascending pathways in the spinal cord. Capsaicin proved to be a potent stressor agent, and it produced a rise in the corticosterone level even when injected into a denervated area. This shows that chemonociceptor excitation at the site of injection is only one of several factors responsible for the stimulation of ACTH secretion by capsaicin. Pretreatment with capsaicin "desensitizing" the chemonociceptors in the skin and the mucous membranes merely inhibited, but did not suppress, the rise in the corticosterone level produced by a subsequent injection of capsaicin; it had no effect on the "nociceptive response" and the rise in the corticosterone level elicited by Formalin.
ON THE RELATIONSHIP BETWEEN DRUG-INDUCED CHANGES IN BRAIN AMINES AND BODY TEMPERATURE
Authors: Ingenito Alphonse J. , Bonnycastle Desmond D.
Published: April 2011

To test the previously reported theory that changes in brain amine levels caused by drugs would lead to disturbances in body temperature regulation, the levels of 5-hydroxytryptamine and noradrenaline in the whole brain of male albino rats were determined after the animals were treated with drugs and then exposed to room temperature or elevated temperatures of 37 or 40 °C. Control experiments with untreated animals were run in parallel. The drugs used were reserpine, α-methyl-m-tyrosine (MMT), 4-chloro-N-methyl-amphetamine, 3,4-dihydroxyphenyl-L-alanine (dopa), 5-hydroxy-DL-tryptophan (5-HTP), chlorpromazine, and 2,4-dinitrophenol. The results indicated that amine levels of the brain could be increased or decreased pharmacologically without a significant interference in body temperature regulation, and also that certain drugs which interfered with body temperature regulation did so without any effect on whole-brain amine levels. It was concluded that, in the rat, there were no clear-cut relationships between whole-brain 5-hydroxytryptamine or noradrenaline levels and the ability to regulate body temperature.
THE EFFECT OF EXPOSURE TO HEAT AND COLD UPON RAT BRAIN CATECHOLAMINE AND 5-HYDROXYTRYPTAMINE LEVELS
Authors: Ingenito Alphonse J. , Bonnycastle Desmond D.
Published: April 2011

A study was made of the possible relationship between the amine levels (dopa, dopamine, noradrenaline, and 5-hydroxytryptamine (5-HT)) of whole brain and of the hypothalamus and the body temperature of the male albino rat. Acute exposure to a warm environment (34 °C and 40 °C) and acute exposure to cold (20 °C and 3 °C) produced no significant changes in amine levels in spite of a hyperthermia of 3 °C and a hypothermia of 0.7 °C. A maintained hypothermia of about 1.5 °C occurred in the rats exposed to cold over a 30-day period, but only late in the exposure period were significant changes in dopamine and noradrenaline observed.
STUDIES ON THE MECHANISM OF PHENOBARBITAL-INDUCED PROTECTION AGAINST MALATHION AND EPN
Authors: Brodeur Jules
Published: April 2011

The administration of phenobarbital, at a dose of 50 mg/kg per day, increased the resistance of adult female rats to the toxic effects of malathion and EPN, as measured by an increase in the LD50and a decrease in the in vivo anticholinesterase activity of the thiophosphates. Maximum protection against EPN occurred after a pretreatment period of 2 days with phenobarbital whereas maximum protection against malathion was achieved after five successive daily administrations of phenobarbital. The administration of phenobarbital also resulted in a rise in the liver ali-esterase activity as evidenced by an increased ability of liver homogenates to hydrolyze methyl butyrate. Administration of tri-o-cresyl phosphate (TOCP), an ali-esterase inhibitor, at a dose of 100 mg/kg, abolished the protective effect of phenobarbital against malathion but did not change the effect against EPN. It is concluded that the induction of liver ali-esterases plays a major role in the protection afforded by phenobarbital against malathion, but that ali-esterases have little to do regarding the protection against EPN.
Removal of angiotensins from the systemic circulation
Authors: Biron Pierre , Meyer Philippe , Panisset Jean-Claude
Published: April 2011

The extraction of α-angiotensin and its aminopeptidase-resiistant analogue β-angiotensin by the pulmonary, hepatoportal, femoral, and renal vascular beds was studied in normal anesthetized dogs and rats by comparing the systemic pressor responses to infusions into the afferent and efferent vessel of each organ. The extraction percentage of both peptides by the pulmonary circulation was negligible whereas it averaged 70% for α-angiotensin and 63% for the β-analogue in the other three systemic vascular beds studied. It is concluded that the main process responsible for the clearing of angiotensin from the systemic circulation is not the activity of circulating angiotensinases but rather occurs in the tissues.
The location of chloride in single striated muscle fibers of the giant barnacle
Authors: Gayton D. C. , Hinke J. A. M.
Published: April 2011

Chloride-sensitive Ag–AgCl microelectrodes were inserted into single striated muscle fibers of the giant barnacle, Balanus nubilus, to measure the activity of Cl− in the myoplasm, (aCl)i. Chemical analysis was also carried out to determine the total concentration of Cl− in the fiber, [Cl]i. In two sets of experiments, (aCl)i was 28.8 and 22.4 mM while [Cl]i was 75.1 and 66.8 mmoles/kg fiber water respectively. The transmembrane Cl− potential, calculated from the aCl measurements in the myoplasm and the bath, was slightly less than the membrane potential. To locate the large fraction of fiber Cl− that is not free in the myoplasm, Cl− washout studies were done in constant [K]o[Cl]o product Ringer solutions in which [Cl]o was reduced to 50% and 25% of the normal concentration. Fibers which were soaked in these solutions for 30 min showed no change in (aCl)i but a large drop in [Cl]i. From the extent of this drop, it was calculated that these muscle fibers have an extracellular space of about 5% of fiber volume. Electron microscopic studies indicate that this space is comprised of large clefts and smaller tubules which penetrate deeply into the fiber.
Alcohol, diet, and experimental hepatic injury
Authors: Hartroft W. Stanley , Porta Eduardo A.
Published: April 2011

The concept of the prevention of fatty livers and cirrhosis by lipotropic factors and protein led to the notion that the latter might also be capable of affording protection against similar liver damage frequently seen in alcoholic man. The relevant literature, which had been published before the first investigations in this area were undertaken in Professor Best's department in 1949, is briefly cited. Developments in this field then utilized three approaches: experiments in which alcohol when administered in the drinking water supplied 27% of calories (Best), experiments with a completely fluid diet which supplied 36% of calories as alcohol (Lieber), and experiments in which an ethanol–sucrose mixture (Porta) in place of drinking water supplied 40–60% of calories as alcohol, with the remainder provided by semisynthetic diets. Most of the results obtained from these investigations did not support the concept of a direct hepatotoxic action of alcohol. Finally, evidence is presented that alcohol did not prevent regression of established cirrhosis in rats if they were treated by a "super diet" which contained abundant lipotropes and protein. Mallory bodies (alcoholic hyaline) formed in liver cells of alcohol-fed rats if basal diets were inadequate; the same structures appeared in rats fed certain other inadequate diets even without alcohol, and their development was prevented in rats consuming large amounts of alcohol if the basal diets were suitably fortified. The mitochondrial nature of these bodies was demonstrated. It is concluded that even large intakes of alcohol for weeks or months by rats do not injure their livers if the accompanying diet is suitably designed.
Use of a digital balance for the bioassay of acetylcholine
Authors: Jasper Herbert , Koyama Ikuko
Published: April 2011

A method is described for the bioassay of acetylcholine (ACh) using a standard digital balance to which a strip of eserinized frog rectus abdominus muscle is attached directly in a 0.6-ml perfusing bath. Dose–tension curves were linear between about 10 and 100 ng of ACh with 10–15 mg increment in tension per nanogram of ACh in the bath. With 60 s allowed for contraction, samples can be tested each 4 min, with good reproducibility for 6–8 h.
Components of Glucose Transport in the Host–Parasite System, Hymenolepis diminuta (Cestoda) and the Rat Intestine
Authors: Podesta R. B. , Mettrick D. F.
Published: April 2011

Glucose and fluid transport by the rat intestine and by the tapeworm Hymenolepis diminuta has been studied in vivo, using closed loops of the entire small intestine. The effect of pH, glucose concentration, and the presence of sodium on solute and solvent absorption has been determined in both host and parasite. The effect of the worms on intestinal absorption by the rat has also been evaluated. Three components of the glucose transport system, namely active transport, diffusion, and solvent drag, were determined by means of a model transport equation.Saturation kinetics for glucose absorption did not occur and the absence of sodium in the luminal fluid, while not affecting glucose absorption, markedly reduced fluid absorption by both the intestine and the worms. Lowering the pH of luminal fluids significantly reduced glucose transport by the intestine but increased absorption of fluid and glucose by H. diminuta. Irrespective of pH, fluid and glucose absorption were significantly reduced in the parasitized intestine.Active transport of glucose by normal or parasitized intestine and by H. diminuta was unaffected by the concentration of glucose in the lumen, or by changes in pH. The solvent drag and diffusion components of glucose transport were reduced by increasing the hydrogen ion concentration in uninfected and parasitized intestines. The solvent drag component of glucose absorption by the tapeworms was increased with increasing hydrogen ion concentration.The results are discussed in terms of the current hypotheses on the mechanism of glucose transport, sodium dependency, and the effect of hydrogen ions on transport mechanisms.
Factors Related to the Dive Reflex in Harbor Seals: Respiration, Immersion Bradycardia, and Lability of the Heart Rate
Authors: Dykes Robert W.
Published: April 2011

The normal heart rate of young breathing harbor seals, 130.1 beats/min (S.E.M. = 22, n = 33), decreases by 50% during periods of spontaneous apnea in air and by 69% during 2 min of forced apnea in air. Apneic bradycardia develops five times more slowly than bradycardia observed during immersion. During forced apnea the heart rate drops to 31% of the value observed during periods of breathing in 200 s while during immersion the heart rate drops to this value only after 20 s. Since the bradycardia during apnea has a slower time course, apnea alone cannot account for the bradycardia observed during immersion.In quietly resting seals, the apneustic breathing pattern consisted of periods of breathing (duration of 10–115 s) interrupted by apneic pauses (duration of 19–104 s). During the breathing periods successive breaths tended to be smaller so that at the end of a breathing period the mean amplitude of a respiratory movement was only 57% of the mean amplitude of the first inspiration. Tracheostomy altered the breathing pattern and lowered the mean heart rate during breathing to 43% of the rate observed in intact animals. Under controlled conditions immersion bradycardia was highly reproducible and showed no signs of conditioning to the experimental regime. Data from 56 immersions on three animals illustrated minor individual differences in the time course of the immersion bradycardia and provided the basis for an estimate of the average time course of immersion bradycardia in young harbor seals.
Bile Flow and Composition During Bile Acid Depletion and Administration
Authors: Klaassen Curtis D.
Published: April 2011

Relatively similar concentrations of the inorganic ions were detected in rat, rabbit, and dog bile; however, dog bile had a higher concentration of protein, cholesterol, phospholipid phosphorous, and percentage solids than rat bile, and rabbit bile had the lowest concentration. The biliary excretion of bile acids was altered in each species by: (1) interruption of the enterohepatic circulation; (2) rapid administration of an exogenous load of bile acids; and (3) constant infusion of an exogenous load of bile acids. Bile acid and phospholipid phosphorous concentration and percentage solids increased after bile acid administration in all three species; however, species differences in bilirubin concentration were observed and a marked decrease was detected in rabbit and dog bile but it markedly increased in rat bile. When the enterohepatic circulation was interrupted in the dog and rat, the bile acid concentration markedly decreased with only minor changes in bile flow. This not only supports the theory that there is a bile salt independent fraction of bile formation, but also demonstrates that canalicular bile formation can be maintained at relatively normal rates with almost no excretion of bile acids. Marked discrepancy between bile acid excretion and bile flow was observed in the rat after bile acid administration, in that a marked increase in bile acid excretion was observed but little or no increase in flow. When bile flow was plotted against bile acid excretion for the three species, the slope of the line was less during bile acid administration than during depletion, indicating that the bile acids are accompanied by less water during bile acid administration than during depletion. Variation in the bile flow intercept with zero bile acid excretion (thought to represent the bile salt-independent fraction) was relatively large, which is probably due in part to alteration in the production of the bile salt independent fraction when bile acid secretion is altered. It appears that both the choleretic property of bile acids varies during various rates of bile acid excretion and the bile salt-independent fraction is not constant. Therefore, calculation of the bile salt independent fraction as previously performed should be interpreted with extreme caution. Thus, it appears difficult to determine the quantitative importance of bile acid excretion in bile formation.
An Artifact in Measurement of Ionized Calcium Concentration from a Heparin Preservative, Benzyl Alcohol
Authors: Klassen Gerald A. , Davidova Eva
Published: April 2011

The previously reported decrease in plasma ionized calcium concentration associated with the presence of heparin has been shown to result largely from the presence of the preservative benzyl alcohol and only partially from heparin. Methanol, ethanol, or benzene did not have an effect on measured serum ionized calcium concentration.
Active Bronchial Anaphylaxis in the Rat
Authors: Stotland L. M. , Share N. N.
Published: April 2011

Sprague–Dawley female rats were immunized with egg albumin (EA) in aluminum hydroxide gel (AHG) and with or without Bacillus pertussis vaccine (BPV). Fourteen days later, the animals were anesthetized and challenged with EA intravenously. The resultant increase in tracheal pressure was recorded as an index of anaphylactic bronchoconstriction. Ventilation with tracheal pressures of 6 cm H2O (588 N/m2) allowed maximal development of bronchoconstrictor responses to specific antigen challenge that were similar in both pithed and pentobarbital-anesthetized preparations. Forced reinflation of the lungs did not affect the magnitude of the response but did facilitate its recovery. Serum titers evaluated by 3-h and 72-h passive cutaneous anaphylactic reactions indicated that reaginic antibodies were primarily involved, although other immunoglobulins may have played a contributory role. Antigen dose-responses were similar for both the EA-AHG and EA-AHG-BPV immunized groups of animals despite lower reaginic serum titers for the former group. Thus, an immediate-type bronchial anaphylactic response mediated primarily by reaginic antibodies can be elicited in rats and quantitatively assessed. The potential immunologic similarity of these animals to human allergic asthma suggests their utility for further investigation.
Metabolism of Δ1-Tetrahydrocannabinol by Rats Tolerant to Cannabis
Authors: Siemens A. J. , Kalant H.
Published: April 2011

Daily treatment of rats with phenobarbital, 75 mg/kg, for 5 days resulted in an induction of the metabolism of 14C-Δ1-transterahydrocannabinol (THC) in vitro and in vivo. Although the Km and Vmax for THC metabolism by liver preparations in vitro were not altered, the rate of formation of highly polar THC metabolites was significantly increased and the final concentration of 7-hydroxy-Δ1-THC was decreased. Phenobarbital also significantly increased the rate of biliary excretion of THC and its metabolites and their disappearance from the blood and tissues.In one experiment, rats receiving a marihuana extract daily (providing THC, 5–10 mg/kg) failed to gain body weight during the first week of treatment, but then became tolerant to this effect. But neither the rate of THC metabolism in vitro nor the pattern of metabolites formed was influenced in the tolerant animals compared to controls. In another experiment, rats were shown to become tolerant on chronic treatment with marihuana extract, as indicated by a reduction in marihuana-induced enhancement of ethanol sleeping time. The biliary excretion, disappearance from the blood, and residual tissue levels of THC and its metabolites were not altered in the tolerant animals compared to pair-fed and ad libitum-fed controls. Therefore the mechanism of tolerance development to cannabis in the rat is more likely of CNS than of metabolic origin.
Effects of Morphine and Meperidine on Action Potential Production in Frog's Skeletal Muscle Fibers
Authors: Frank G. B. , Buttar H. S.
Published: April 2011

Morphine (3.3 × 10−4–33 × 10−4 M) and meperidine (8.8 × 10−5–35 × 10−5 M) inhibited action potential production in frog's skeletal muscle fibers. Over these concentration ranges, neither the resting membrane potentials nor the resting membrane electric properties of the fibers appeared to be modified. Both drugs depressed excitability and the rising phase of the action potential by inhibiting the specific increase in sodium conductance which normally follows an adequate stimulus. Both drugs also seemed to inhibit the secondary rise in potassium conductance which normally occurs during an action potential, causing a prolongation of the action potential duration.
A Prolonged After-Effect of Intense Synaptic Activity on Acetylcholine in a Sympathetic Ganglion
Authors: Bourdois P. S. , McCandless D. L. , MacIntosh F. C.
Published: April 2011

The finding was confirmed that there is a "rebound" increase of stored acetylcholine (ACh) in cat superior cervical ganglia conditioned by prolonged preganglionic stimulation at a frequency high enough to cause initial depletion of the store. Ganglia removed immediately after 60 min of continuous or interrupted stimulation at 50 Hz, with chloralose as anesthetic, contained about 30% more ACh than their unconditioned controls; the rebound rose to about 60% after 15 min of rest and then subsided with an apparent half-time of about 2 h. Tests with hemicholinium, combined with hexamethonium or tubocurarine, showed that rebound ACh was located pre-synaptically and could be released by nerve impulses; but conditioned ganglia perfused with an eserine-containing medium did not release more ACh than their unconditioned controls, except in circumstances in which the mobilization of ACh from a reserve store appeared to be the rate-limiting process for release. The appearance of rebound ACh during and after conditioning stimulation was suppressed by hexamethonium and by tubocurarine, neither of which has much effect on ACh turnover in ganglia excited at lower frequencies, but not by atropine, noradrenaline, or phenoxybenzamine. The formation of rebound ACh is thus contingent on the postsynaptic nicotinic response to released ACh, and may represent an augmentation of the transmitter store in structures remote from the release sites.
Mechanical Properties of Human Mitral Valve Chordae Tendineae: Variation with Size and Strain Rate
Authors: Lim Koon O. , Boughner Derek R.
Published: April 2011

A knowledge of the mechanical properties of valve tissue is a necessary prerequisite for a better understanding of valvular behavior and the design of prosthetic heart valves. Elastic response of chordae tendineae under strain rates of 0.05 cm min−1(6.25% min−1) to 12.7 cm min−1 (1600% min−1) were obtained by the application of an uniaxial tensile stress using an Instron machine. The chordae exhibited viscoelastic properties in that extensibility decreased with increasing strain rates. The approximate maximum physiological strain rate of the chordae was estimated from echocardiographic traces at the instant of valve closure, and a high value of 29 (S.D. = 9) cm s−1 (2000% s−1) was found. The breaking strain and stress were found to have values of 21.4 ± 0.5% and 3.1 ± 0.1 × 108 dyn cm−2 respectively, and were independent of strain rates (1 dyn = 10−5 N). These values are typical of collagen fibers. The final modulus, before the proportional limit, was found to be about 109 dyn cm−2, which is again typical of collagen fibers. In addition, smaller chordae exhibited less extensibility than the larger chordae. This behavior could be due to structural and functional differences and allows the more centrally inserted chordae to maintain an even valve surface during valve closure.
Effects of the Diethyl and Dimethyl Esters of Glutamic Acid on Morphine Anti-nociception in the Rat
Authors: Wong C. , Yarbrough G. G.
Published: April 2011

The effects of pretreatments with various doses of glutamic acid diethyl or dimethyl esters on morphine-induced anti-nociception in the hot-plate and tail-flick tests on rats were examined. While neither substance alone altered control reaction times, they both antagonized the effects of morphine, suggesting the possible involvement of glutamate receptors in narcotic ";analgesia". However, several aspects of the data inveigh against the significance of the findings with regard to narcotic mechanisms.
Kinetics of the Red Cell Washout from Coronary Vessels of Isolated Feline Hearts
Authors: Song S. H.
Published: April 2011

Twenty seven isolated feline hearts were perfused with cell-free oxygenated Ringer–Locke solutions. The concentration of red blood cells in samples of venous outflow collected from the coronary sinuses was determined by means of a Celloscope counter. Cellular concentrations decreased gradually as the perfusion time increased, and from 109 to 105 cells per millilitre after 300 ml perfusion. When the ventricular lumens were filled with residual blood (group I, 15 cats), several red cell peaks were superimposed on the smooth exponential decay curve of red cell washout. It is suggested that the peaks were caused by ejection of red cells from the ventricular lumens into communicating branches between the ventricular lumens and coronary capillaries. In cases of blood-emptied hearts (group II, 12 cats) these peaks did not occur, and mathematical analysis showed that summing three exponential functions could approximate the whole washout curve of red cells. This suggests that the coronary circulation may be described by three red cell compartments. The functional implication of this analysis for the microcirculation in the coronary vessels was discussed.
The Effects of Δ9-Tetrahydrocannabinol on Action Potentials in the Mollusc Aplysia
Authors: Acosta-Urquidi Juan , Chase Ronald
Published: April 2011

The effects of Δ9-tetrahydrocannabinol (Δ9-THC) on action potentials were examined during intrasomatic recordings from the isolated buccal and parieto–visceral ganglia of Aplysia californica. When added to the saline solution bathing the preparation, the compound (in concentrations 10−4–10−5 M) caused a reduction in spike overshoot (15–20% of total amplitude) and increased the lability of responses to electrical stimulation. The somatic membrane appeared to be more affected than the axonal membrane. Diffusion barriers in the ganglion probably account for the high degree of variability in drug response, such that both of the characteristic changes were observed in only about 30% of the tests. This is the first report to describe effects of Δ9-THC on invertebrate neurones. The results indicate that Δ9-THC causes a depression in nerve cell excitability, and these data are consistent with reported effects of THC compounds in mammals.
Rate of Incorporation of CO2 Carbon into Glucose and Other Body Constituents in Vivo
Authors: Shipley R. A. , Gibbons A. P.
Published: April 2011

Specific activity curves of respired CO2 and of body glucose after intravenous NaH14CO3 as tracer and, in separate experiments, after [U-14C]glucose as tracer were employed to assess rate of interchange of carbon between HCO3 and glucose, and to calculate other rates of input and output for each of these substances. Solution for six rates attending the model was by integrals rather than by curve analysis. Fasting caused a twofold increase in rate of transport of CO2 carbon to glucose. Whereas in fed animals this rate was only 7% of the forward flow from glucose to CO2, it rose to 31% during fasting. Glucose carbon derived from CO2 rose from 3.7 to 20%. As expected, the rates of entry of new glucose to blood, and the conversion rate of glucose to products in body depots and to CO2 were reduced by fasting, whereas, the non-glucose input to CO2 was increased. Fasting was attended by a 20-fold increase in rate of conversion of CO2-derived carbon to hepatic glycogen and a fourfold increase to non-hepatic glycogen. Protein exceeded all whole-body depots for rate of acceptance of such carbon, and total lipids received an appreciable amount, but fasting caused no overall increase for either.
Temperature-Induced Changes in Metabolism and Body Weight of Cattle (Bos taurus)
Authors: Young B. A.
Published: April 2011

The metabolic and body weight changes in two non-pregnant beef cows were studied during prolonged exposure to warm (20 ± 3 °C, relative humidity 50–70%) and cold (−10 ± 2 or −25 ± 4 °C) temperatures. Other factors including daily food intake were held constant throughout each 8-week exposure. During cold exposures, metabolic rate, blood hematocrit, and plasma concentrations of glucose and free fatty acid were elevated and respiratory frequencies and skin temperatures decreased. Resting metabolic rates measured at 20 °C, i.e., without the direct influence of cold, were 83.4–95.3 litres O2 per hour when the cows were cold acclimated, at either −10 or −25 °C, and 30–40% greater than when the cows were warm acclimated. The resting metabolic response and the concomitant reduction in intensity of shivering is indicative of metabolic acclimation to cold in these animals of greater than 500 kg body weight.As well as the expected changes in body weight with changes in energy metabolism there were losses in weight (13–24 kg) during the first 3 days of each cold exposure. Weight gains occurred when the cold stress was abruptly removed. These short term weight changes were associated with changes in water intake and apparent shifts in body fluid content.
54Mn Uptake by the Ovaries and Reproductive Tract of Cycling and Anestrous Ewes
Authors: Hidiroglou M.
Published: April 2011

The uptake of 54Mn by the ovaries and reproductive tract of cycling and anestrous ewes has been investigated following intravenous injection of a single dose of S4Mn Cl2 and sacrifice of the ewes 6 h later. The uptake of 54Mn was greater in the Graafian follicle and the corpus luteum (CL) of the cycle than in the other components of the ovary. An increased uptake of radioactivity was recorded in the CL of the 11th day of the cycle when compared with that of the 4th day. The uptake of 54Mn was lower in the corpus albicans and follicles. A low uptake of radio manganese was found also in the various tissues of the reproductive tract. These findings indicate that manganese may play a role in the normal functioning of ovarian activity in the ewe.
Incorporation of Thymidine and Iododeoxyuridine into the DNA of Mouse Tissues
Authors: Myers D. K. , Feinendegen L. E.
Published: April 2011

Mice were injected intravenously with a solution containing tritiated thymidine (TdR) and iodine-labelled iododeoxyuridine (IUdR). The ratio of 3H/125I activities was measured in the acid-soluble fraction and in the DNA of several tissues at various times from 0.08 to 24 h after injection. There did not appear to be any discrimination in favor of TdR in the acid-soluble fraction of the tissues. The amount of TdR incorporated into the DNA was four to five times greater than the amount of IUdR incorporated; moreover, this value remained relatively constant throughout the period of DNA synthesis under the conditions used.Although IUdR was destroyed more rapidly than TdR in the body, particularly at high concentrations of both precursors, this factor did not account for the major portion of the discrimination observed with tracer amounts of the two DNA precursors. Discrimination in favor of TdR as a precursor for DNA must, therefore, occur at some stage in the utilization of intracellular precursor.
Endocrine Effects of Chronic Administration of Psychoactive Drugs to Prepubertal Male Rats. II. LSD
Authors: Collu Robert , Letarte Jacques , Lebœuf Gilles , Ducharme Jacques R.
Published: April 2011

The endocrine effects of chronic D-lysergic acid diethylamide (LSD) administration to prepubertal animals were studied by injecting intraperitoneally three times a week for a month either 100 μg or 500 μg of the psychoactive drug per kilogram or the vehicle to groups of Sprague–Dawley male rats starting at 21 days of age. Animals injected with either dosage of LSD had smaller body weights than controls and tail length was significantly reduced in the high dosage group, plasma levels of growth hormone (GH) were decreased in the high dosage group, and pituitary levels in the low dosage group. Plasma levels and pituitary concentrations of luteinizing hormone and follicle stimulating hormone were not significantly modified by the drug. The low dosage of LSD decreased the brain levels of noradrenaline and increased those of dopamine, while the high dosage decreased those of 5-hydroxyindoleacetic acid. These data suggest that LSD, when administered chronically to developing animals, can inhibit body growth probably by altering the secretion of GH through modifications of its neuroendocrine control.
Effects of Cortisol on Serially Propogated Fibroblast Cell Cultures Derived from the Rabbit Fetal Lung and Skin
Authors: Smith Barry T. , Giroud C. J. P.
Published: April 2011

Cortisol affects the growth of serially propogated, fibroblast cell cultures derived from the rabbit fetal lung in a manner which is dependent upon the gestational age of the material used: early in gestation (20 days), the hormone (10−7–10−5 M) stimulates [6-3H]thymidine incorporation into DNA, while in late gestation (28 days), cortisol (10−7 and 10−6 M) inhibits this process. Cultures derived from the rabbit fetal skin are inhibited by cortisol (10−5 M) at both gestational ages. Fibroblasts derived from lung, but not from skin, efficiently convert cortisone to cortisol and this activity increases with advancing gestation. Cortisol does not affect the incorporation of [3H]choline into lecithin by confluent cultures of any of the fibroblast types studied.
Monolayer Cultures of Dispersed Cells from Bovine Anterior Pituitary: Responses to Synthetic Hypophysiotropic Peptides
Authors: Queen G. , Vivian S. , LaBella F.
Published: April 2011

Cells were dispersed from bovine anterior pituitary glands, by digestion with collagenase, and cultured. After 4 days the cell monolayers were incubated with fresh medium containing synthetic hypophysiotropic peptides for 2, 6, or 20 h, and hormone released into the medium was estimated by radioimmunoassay. After 2 h, thyroid releasing hormone (TRH) stimulated the release of thyroid-stimulating hormone (TSH) up to eightfold, and of prolactin (PRL) and follicle-stimulating hormone (FSH) about twofold at a minimal effective concentration of 1 ng/ml; enhanced growth hormone (GH) release was not apparent until 20 h, and release of luteinizing hormone (LH) and adrenocorticotrophic hormone (ACTH) was unaffected. Luteinizing hormone releasing hormone (LH-RH) enhanced release of LH maximally (three- to fourfold) during a 2 h incubation and was effective at 0.1 ng/ml; FSH release was significantly enhanced by about 50% above control level. Growth hormone release inhibiting hormone (GH-RIH) (somatostatin) showed significant effects only in the 20 h incubation; GH release was inhibited by 50% and release of PRL was slightly, but significantly, enhanced. Pituitary cell monolayers apparently permit maximal expression of releasing activities inherent in the hypothalamic hormones.
Effects of Potassium Chloride and Smooth Muscle Relaxants on Tension and Cyclic Nucleotide Levels in Rat Myometrium
Authors: Diamond Jack , Holmes Thomas G.
Published: April 2011

Ten minutes after KCl-depolarization of rat myometrial strips, at which time the muscles were in a state of sustained contracture, tissue levels of adenosine 3′,5′-cyclic monophosphate (cyclic AMP) were increased by approximately 40% over relaxed controls, and levels of guanosine 3′,5′-cyclic monophosphate (cyclic GMP) were decreased by 40%. At this point both nitroglycerin (4 × 10−4 M) and papaverine (2 × 10−5 M) were capable of relaxing the depolarized muscles without significantly increasing cyclic AMP levels. Isoproterenol, in concentrations from 5 × 10−9 M to 10−6 M, relaxed the depolarized muscles and significantly increased tissue levels of cyclic AMP. However, the magnitudes of the cyclic AMP increases seen after the lower concentrations of isoproterenol were small relative to the increases observed during KCl-contracture alone. For example, the 40% elevation of cyclic AMP seen 10 min after KCl-depolarization did not cause the muscles to relax, whereas 5 × 10−9 M isoproterenol caused relaxation with an increase in cyclic AMP levels of only 16% over depolarized controls. It was concluded that changes in total tissue levels of cyclic AMP were not responsible for the uterine relaxation caused by nitroglycerin, papaverine or isoproterenol in these experiments. Cyclic GMP levels in the depolarized muscles were not significantly changed by isoproterenol or papaverine but were increased approximately 80% by nitroglycerin.The above results are not consistent with the previously suggested roles for cyclic GMP and cyclic AMP as mediators of smooth muscle contraction and relaxation, respectively.
Effect of Cocaine and Other Drugs on Sensitivity of the Estrogen-dominated Isthmus of Rabbit Oviduct to Noradrenaline
Authors: Johns A. , Paton D. M.
Published: April 2011

The influence of the adrenergic innervation on the magnitude of responses of the isthmus of rabbit oviduct to (–)-noradrenaline was examined. Tissues were obtained from estrogen-dominated animals, and isometric contractions of longitudinal and circular muscle layers separately recorded. Longitudinal muscle was significantly more sensitive to (–)-noradrenaline. Cocaine potentiated responses of both circular and longitudinal muscle to (–)-noradrenaline, circular muscle being more potentiated. Similar results were obtained with desipramine. Tissues obtained from 6-hydroxydopamine pretreated animals did not respond to tyramine, and longitudinal and circular muscles were equisensitive to (–)-noradrenaline. Cocaine did not potentiate responses to (–)-noradrenaline in such tissues. Responses to (–)-noradrenaline were not altered by propranolol, hydrocortisone, or oxytetracycline. It was concluded that responses resulted from a predominant effect on α-receptors. The magnitude of responses to (–)-noradrenaline was mainly influenced by neuronal uptake of amine. Indirect evidence was obtained for a greater degree of adrenergic innervation to the circular muscle layer of the isthmus, in keeping with histological studies.
The Effect of Somatostatin on Release and Insulinotropic Action of Gastric Inhibitory Polypeptide
Authors: Pederson Raymond A. , Dryburgh Jill R. , Brown John C.
Published: April 2011

Studies were carried out in conscious dogs in which the effect of intravenous somatostatin on immunoreactive gastric inhibitory polypeptide (IR-GIP) release was investigated. In addition, the inhibitory action of somatostatin on the insulin response to pure porcine GIP was assessed. Intravenous administration of somatostatin resulted in a delayed IR-GIP and immunoreactive insulin (IRI) response to oral glucose. Somatostatin also delayed the IR-GIP response to the ingestion of fat. In both types of experiments, initial depression of IRI levels was followed by a sharp rise in IRI release. Intravenous infusion of somatostatin produced 80% inhibition of the IRI response to pure porcine GIP. It was concluded that somatostatin inhibits the physiological release of IR-GIP and the insulinotropic action of exogenous porcine GIP.
Effects of alterations in maternal thyroid metabolism on embryonic thyroid development in the chick
Authors: March B. E. , Leung Peter
Published: April 2011

The cause of embryonic thyroidal enlargement in the progeny of chickens fed goitrogenic rapeseed meal (RSM) has been investigated. It has been found that eggs from birds fed RSM are low in iodine. The low concentration of iodine in the eggs of the goitrous birds is apparently due to diversion of a large proportion of the circulating iodine into the thyroid glands with the result that the amounts reaching the developing ova are reduced.
Adrenergic neuron blocking action of dehydrocorydaline isolated from Corydalis bulbosa
Authors: Kurahashi Kazuyoshi , Fujiwara Motohatsu
Published: April 2011

Dehydrocorydaline, an active principle of Corydalis bulbosa alkaloids, in concentrations of 10−5M to 5 × 10−5M inhibited relaxation and the concomitant release of [3H]-noradrenaline caused by 10−4M nicotine and electrical perivascular nerve stimulation in the taenia caecum of guinea pig. The same inhibitory effects were observed on contraction and release of [3H]noradrenaline in the sympathetic nerve – pulmonary artery preparation of rabbit. On the other hand, neither relaxation nor contraction caused by exogenously applied noradrenaline was affected. These results suggest that the inhibitory action of dehydrocorydaline on the relaxation or contraction, produced by nicotine and electrical nerve stimulation, is due to blockade of noradrenaline release from the adrenergic nerve terminals in both the taenia caecum and pulmonary artery. Participation of the adrenergic neuron blocking action of dehydrocorydaline in preventing experimental ulceration is discussed.
Motor and sensory fibres of neck muscle nerves in the cat
Authors: Richmond F. J. R. , Anstee G. C. B. , Sherwin E. A. , Abrahams V. C.
Published: April 2011

The numbers and sizes of nerve fibres to the dorsal neck muscles, splenius, complexus and biventer cervicis have been examined in the cat. The total number of fibres is unusually high as is the content of sensory fibres (estimated as the loss of fibres after ganglionectomy). The fibre spectra of these sensory nerves has an unusually large number of fibres in the group II and III range (3–7 μm) and differs markedly in this way from other muscle nerves. The motor fibres contain a high proportion (64–99%) in the gamma fibre size range. Large motor fibres are absent in the nerves to biventer cervicis (a slow muscle). The ratio of unmyelinated to myelinated fibres in neck muscle nerves is similar to that in hind legs at about 2.5:1.