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The article discusses the effectiveness of selection in producing laboratory stocks that are genetically uniform to be resistant to dental caries. The author details methods to avoid breeding that is somewhat selective because of small sample numbers as well as ways to ensure that random mating produces genetic equilibrium.

, , 551-558. Chlorphentermine hydrochloride (`Lucofen') is a sympathomimetic agent which is used in the treatment of obesity at a dosage of 25 mg thrice daily. When this drug, which is available on the British market, was administered intraperitoneally to rats in a dosage of 50 mg per kg body weight for 50 days, they all developed striking pathological changes in the lungs. Numerous large cells with foamy cytoplasm appeared in the alveolar spaces. Groups of them clumped together and disintegrated to pack the alveoli with granular eosinophilic material. The identification of these cells proved to be difficult even by electron microscopy, and this ultrastructural study is described separately in the following paper. During our acute experiments the rats did not develop right ventricular hypertrophy or hypertensive pulmonary vascular disease. [ABSTRACT FROM PUBLISHER]

The aim of the present investigation was to determine whether or not repeated administration of estrogen and progesterone induces an increased gingival exudation in dogs. Five female mongrel dogs constituted the experimental material. Six months prior to the start of the hormone experiments and during the experimental period the animals were given a soft gingivitis-inducing diet. During the "hormone-periods" each dog was given 1 mg estrogen every second day, and 25 mg progesterone every day. The hormones were injected intramuscularly in one of the dogs hind legs. The degree of gingival exudation was assessed by the method described by Brill (1959) and Egelberg (1964). The results of the investigation clearly show that, in dogs with a manifest chronic gingivitis, the administration of estrogen and progesterone causes a rise in the amount of exudates obtainable on filter paper strips inserted into the gingival crevice. The termination of the hormone supply resulted in a marked and rapid decrease in exudation. This increase and decrease of the amount of gingival fluid in relation to the increase and decrease of the estrogen and progesterone level indicate that these female sex hormones affect the permeability of the dento-gingival vessels. [ABSTRACT FROM AUTHOR]

It is estimated that an unknown, yet possibly large, number of patients would benefit from transplantation of the heart and both lungs if technically, physiologically, and immunologically feasible. In this paper we attempt to explore the main non-immunological areas in which we feel that cardiopulmonary transplantation requires further evaluation. A technique is described by which the heart and lungs, as one unit, can be removed from a donor animal, and viability of these organs can be maintained for several hours by autoperfusion (circulation being through the coronary and pulmonary vessels) with positive pressure ventilation via the trachea. This simple heart-lung preparation preserves the organs concerned for sufficient time to allow preparation of the recipient, transport of the donor organs, and tissue typing to be carried out. Our technique of implanting these donor organs into the recipient is also described. We have carried out this operation on approximately 100 dogs and have been impressed by the good cardiac function obtained, but spontaneous respiratory function has been either absent or inadequate to sustain life for more than a few hours. It would appear that dogs cannot tolerate bilateral pulmonary denervation, and our findings are discussed in the light of other work on this subject. Work on primates suggests that man would be able to undergo this procedure successfully. The organizational and ethical problems involved in cardiac and cardiopulmonary transplantation are briefly discussed. [ABSTRACT FROM PUBLISHER]

This article presents the theoretical bases of convulsive therapy in relation to animal experimentation. Before turning to the experiments to be described on animal behavior, it is necessary to consider some of the alternative and often-conflicting theories advanced to account for the changes produced in patients as a result of convulsive therapy. Various workers have advanced two sets of theoretical constructs. One is generically labeled as psychogenic and has received most impulsion from the speculations of the psychoanalytic schools. The other, with which this paper will occupy itself, seeks an organic, biochemical, and physiological etiology. More recent theories have emphasized the role of metabolic processes in the causation of improvement and psychological change. Researcher F. Georgi finds that sugar metabolism, produced slowly in hypoglycemia and rapidly under electrical and metrazol therapy, is an evidence of an alteration in the membrane tissue of neural cellular matter. Researcher L. Von Angyal believes that the reduction of sugar content in the brain during hypoglycemia causes a compensatory increase in metabolism in malfunctioning cells, thereby producing changes in specific behavior patterns as well as general improvement in the patient.

The article presents a study that examines carious lesions in cotton rat molars. The author examines the effects of the type of cage and bedding that laboratory animals live in on the initiation and development of lesions. Data concerning the relation of diet to tooth decay and possible correlations between wire cages and dental caries is provided.

SUMMARY Experiments using animal litters as experimental units usually require a weighted analysis to allow for variation in litter size. This paper describes methods of assessing appropriate weights for fully randomized and for randomized block experiments. [ABSTRACT FROM AUTHOR]

The article presents a paper that reviews the psychological theories of electroconvulsive therapy (ECT). It considered the theoretical approaches towards explaining the effects of electroconvulsive shock (ECS) on animals. As the work of ECS with animals has been more empirical than corresponding work with human beings, it has led to more consistent findings and a sounder basis of theorizing. Hence, theories drawn from animal research may be able to give useful leads for explaining the effects of ECT on human beings. The main conclusion arising out of this reviews is that the researchers have come very little way towards explaining the effects of ECT. It is further suggested that help in the solution of the problem may be obtained from utilizing the results of experimentation on animals.

The article offers information on neuroanatomical hypotheses. According to a researcher, stimulation is a basic inclination inherent in all living tissues towards the expression of its characteristic activity. It is also a derivative tendency in the early life history of the animal wherein it is subjected to perform random movements to various kinds of external stimulation and to the gratification of internal needs. This concept, which was developed by extensive experimentation with rats, posits that supplementation is still useful in understanding the notion of deprivation.

The article cites several animal experimentation. A researcher has discovered that albino rats which had been taken as pets were less timid and less apprehensive as opposed to those who had received infrequent handling. These animals were also known to survive thyroidectomy. Another researcher also identified that albino rats who had experienced gentle handling, stroking, and caressing or tactile simulation via strokes of a brush gained more body weight than did the nonstimulated ones. It is identified that the severity of stimulation largely contributes to this fact.

Correlations were computed between defecation and ambulation scores from the open-field test, body weight, and the basal defecation level as measured over a 5-day period in the animals' home cages for male and female hooded rats. The pattern of correlations indicates a sex difference in the ‘meaning’ of open-field defecation which appears to be a valid emotionality index only in females. In males the score correlates positively with body weight and basal defecation level. But the sex difference in the level of open-field defecation obtained probably represents a genuine sex difference in responsiveness to the test situation, since it persists even when the scores are corrected to take account of underlying basal differences in the amount of faeces available as inferred from the home-cage defecation scores. The results are discussed in terms of the validity of the defecation index and discrepancies in the literature on emotionality. [ABSTRACT FROM AUTHOR]

The author discusses the questions concerning relative doses of strontium (Sr)-90 in experimental animals and man. He pointed out that leveling trend in infant mortality is cannot be due to a natural minimum having been reached, not only as congenital malformations account the infant deaths. On the other hand, main argument links to the amounts of Sr-90 used in animal experiments. Furthermore, he describes the clues of unforeseen action of Sr-90, first was peak of infant mortality do not occur immediately after a nuclear test, and the other came from the work of Walter A. Muller, in which he measured the actual dose to the gonads of male mice following the injection of Sr-90.

We have determined unidirectional influxes by measuring rate of uptake between 0.5 and 1.0 min of incubation in 5 mm galactose.H-inulin was used to correct for galactose in residual mucosal solution. Influx was greatly depressed by removing Na from or adding 10 m phlorizin to the incubation medium. Influx was also greatly depressed by making the mucosal solution anaerobic during a 10-min preincubation period. The same severe inhibition of galactose influx by mucosal anaerobiosis also occurrend under conditions in which the epithelial cells did not gain Na. After taking into account the effect of the mucosal unstirred water layer, influxes could be normalized to a concentration of 1.0 mm at the membrane surface. It was estimated that at 1.0 mm the phlorizin-sensitive component of galactose influx was reduced 93% by 10 min of mucosal anaerobiosis. Unidirectional effluxes were estimated by subtracting steady-state downhill mucosal-to-serosal flux from influx. The ease of efflux was apparently augmented 2.8-fold by mucosal anaerobiosis. After 10 min of mucosal anaerobiosis, there was no longer any directional preference for movement of galactose across the brush border and there was no uphill transport, in spite of the persistence of a large Na gradient. These results provide strong evidence against the theory that ion gradients provide the major source of energy for directional preference and uphill transport. [ABSTRACT FROM AUTHOR]

Ionophoric material isolated by tryptic digestion of (Na+K)-ATPase containing electroplax membranes shows fluctuating discrete current levels in oxidized cholesterol membranes with conductance amplitudes ranging from 10 to 10 mhos, suggesting pore formation. The rate of pore formation is dependent on the imposed voltage. If the voltage is maintained for a short time (5 to 10 sec), pore formation is reversible, whereas permanent pores are formed when the voltage is maintained for more than 10 sec. At pH=7 the permeability ratio for sodium versus chloride is 5 and for potassium versus sodium, 1.7. The permeability of the ionophoric material is dependent on pH. At pH=6 a conversion takes place from more cation-permeable to more anionpermeable pores, suggesting that histidine plays a role in the permeation mechanism. A model is proposed to account for the observed ionophoric properties. [ABSTRACT FROM AUTHOR]

The cation selectivity and its relation to the inward-going rectification of the immature egg cell membrane of a starfish, Nordora punctiformis, were studied and the following results were obtained. (1) When the external saline contains usual ion species the cell membrane at rest is predominantly permeable to K ions. The K chord conductance g depends on the electrochemical potential of K ions, Δ V=V−E and the external K concentration [K] by $$(\Delta V_h \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } - 15mV,\upsilon \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ \doteq } 7mV)$$ . (2) The permeability sequence of monovalent cations and the permeability ratios P/P of the cell membrane at rest obtained with membrane tpotential measurements are, T1 (1.5)>K(1.0)>Rb(0.3 to 0.4)>NH(0.03 to 0.04)>Na, Cs. (3) Current-voltage relations obtained when the external solution contains Rb, Cs or T1 in addition to K show: (a) Rb and Cs decrease the K conductance and the rate of decrease becomes greater with an increasing hyperpolarization, thereby the inward-going rectification is reduced; (b) the membrane conductance shows an 'anomalous mole fraction dependence' in Tl-K media, i.e., the conductance becomes minimum at a certain mole fraction; and (c) the current-voltage relation often shows a transitiontype behavior suggesting that the membrane undergoes metastable states during an ncrease of hyperpolarization. [ABSTRACT FROM AUTHOR]

The turnover numbers of the ionophores valinomycin, the macrolide actins, enniatin B and dicyclohexyl 18-crown-6 for translocation of cations through the mitochondrial membrane have been compared quantitatively. The rank order of decreasing maximum turnover number for K transport calculated on the basis of the ionophore concentration within the membrane is trinactin>dinactin∼monactin∼ valinomycin>nonactin>18-crown-6>enniatin B. The strength of binding of the ionophores to the mitochondria has the following rank order: valinomycin>macrolide actins>enniatin B>18-crown-6. A rough proportionality was observed between the transport rate of K, Rb, Cs or Na with a given ionophore and the heterogeneous complexation constant of the corresponding ionophore-cation pair in two-phase extraction experiments. However, the proportionality constants between transport and the heterogeneous complexation constant differ between the ionophores. These comparisons indicate that valinomycin and enniatin B transport cations about 10 times slower than would be expected from their two-phase complexation behavior, using the complexation and transport reactions of the macrolide actins as a basis for comparison. Transport with 18-crown-6 was about 1,000 times slower than predicted. These observations are discussed in terms of partitioning of the ionophores between various regions of the mitochondrial membrane. The data are discussed in terms of a carrier model involving hydrophilic complexes on the membrane surface in addition to hydrophobic complexes which cross the membrane. [ABSTRACT FROM AUTHOR]

The operation of a seven-compartment model is described with respect to flows of Na within and across this system, simulating published results obtained on frog skin. The seven compartments represent: one outside and one inside solution compartment; the subcorneal space; the first reacting cell layer (1. RCL); the remaining cell compartment; the non-, or slowly exchangeable Na compartment; the extracellular space. Assuming reasonable volumes for the epidermal compartments and further chosing, by trial and error, appropriate rate constants, a set of seven simultaneous linear differential equations was solved by the application of the Continuous System Modeling Program (CSMP), using an IBM 1130 computer. Initial conditions for influx, backflux and net flux were taken which correspond to [Na]; [Na]=115 mm. Print-out data were obtained at 0.5-min intervals for 30 min, when steady states were obtained in 13 models studied, varying certain k's thus simulating actions of chemical agents (hormones; drugs). Simulation was achieved with regard to rate of influx, backflux and net flux, steady-state time (30 min), and electrical potentials. In addition, this approach gave detailed information on Na pool sizes and their variations with changes in k's. These results are compared to published data on frog skin and good agreement between operation of skin epidermis and model was found. [ABSTRACT FROM AUTHOR]

There are no studies that define the optimum intensity or time to begin exercising reinnervating muscle. Through overwork of reinnervating muscle, accomplished by synergistic tenotomy, we developed a working hypothesis. This hypothesis was tested on a physiological model. In the present study, the sciatic nerve of five groups of rats was crushed. One group served as the control and the remaining animals were exercised by swimming with weights attached to their tails for one or two hours each day (early reinnervation group) or four weeks (late reinnervating group) after crush denervation. The evaluation of muscle weights, fibre types, and protein concentration indicate that intense swimming (two hours every day) does not enhance the repair of reinnervation muscle. An evaluation of total proteins suggests that a high workload may be hazardous in the early phase of reinnervation. This study tends to confirm the hypothesis that when there are too few contractile units, as presumably is the case in early reinnervation, exercise inhibits the reinnervation process. [ABSTRACT FROM AUTHOR]

Focuses on the use of animal models for the generalization of clinical results to become directly applicable to the human system. Significance of dimensional analysis in physiology in minimizing the number of animal experiments required and permit the application of results to other cases by simple calculations; Involvement of mathematical technique for finding those combinations or groupings of variables in the analysis; Application of engineering modeling techniques to physiologic problems.

Cortical blood flow and epidural intracranial pressure have been measured in the two supratentorial compartments of the intracranial space in experimental baboons during the acute expansion of a parieto-occipital epidural balloon. Differential pressures between the two halves of the supratentorial space have been found, and these have been associated with evidence that flow has fallen more quickly in the hemisphere most compressed. The evidence points to a more rapid exhaustion of the autoregulatory capacity in the hemisphere subjected to greater compression, a fall in perfusion pressure to below critical autoregulatory levels occurring slightly before that in the opposite hemisphere, and the establishment of a differential flow pattern for a short time during a critical phase of compression. The displacements induced by inflation of the parieto-occipital balloon have been described. [ABSTRACT FROM AUTHOR]

An in vivo study of skeletal muscle paralysis induced by intravenous barium chloride has been made in curarized and non-curarized rats. The influence of potassium and calcium chlorides, propranolol, ouabain, and prior adrenalectomy on the paralysis has also been studied. Paralysis is found to be due to a direct effect on skeletal muscle, and to correlate well with the development of hypokalaemia. Possible mechanisms of action of barium are discussed, and attention is drawn to the similarity between barium poisoning and hypokalaemic familial periodic paralysis. [ABSTRACT FROM AUTHOR]

A study has been made into the effects of blood pressure on the spinal cord blood flow. Under conditions of normoxia and normocarbia a well-functioning autoregulation was present between 150-60 mmHg. Below 60 mmHg the flow decreased with reductions in pressure. In individual dogs, autoregulation was sometimes present to 40 mmHg. Under conditions of hypoxia or hypercarbia, autoregulation was absent or severely impaired. The results are discussed in relation to the cerebral circulation and to some aspects of experimental cord disease. [ABSTRACT FROM AUTHOR]

A technique of block surface-staining and serial cinematography was modified to review serial sections of normal and dystrophic muscle from the Bar Harbor 129 Re strain of mice as a preliminary study of fibre splitting in dystrophic muscle. Using this technique, muscle fibres were reconstructed for up to 1·5 mm of their length without difficulty. Split fibres were identified only when the actual separation of fibres was observed. Splitting was seen to be a significant cause of the variations in fibre diameter and was at times responsible for the formation of groups of small atrophic fibres which resembled those seen in denervation atrophy. Complex multiple splitting and recombination of daughter and parent fibres was also observed and reconstructed to scale. These results may have considerable significance for the interpretation of physiological data on both human and murine dystrophic muscle. [ABSTRACT FROM AUTHOR]

The article discusses the study showing the ways of using animals in psychotherapy in the U.S. Members and Fellows of the American Psychological Association were sent with a questionnaire that includes queries about the use of animals in psychotherapy. Results show that 64% of the total sample returned the questionnaire and of these 21% reported that they use animals or animal content in psychotherapy. Moreover, it was determined that most of the respondents use animals to cultivate or model the positive nature of interpersonal relationships. The respondents also cited the dog and cat as the most frequently used animals.

The role played by transmembrane K gradients in providing an energy input for Na-dependent monosaccharide transport systems was evaluated with the use of isolated intestinal epithelial cells. Experimentally imposing a K gradient in a sense reversed from normal did not lead to extrusion of sugar from cells which had been pre-equilibrated withC-3-OMG, even in situations where a reversed Na gradient was also imposed. Furthermore, cells preloaded with K have no better ability to accumulate 3-OMG than do cells depleted of K, when the two populations are compared under identical incubation conditions. Fluxes of K associated with the sugar carrier could not be detected in terms of suspected sensitivity to agents which immobilize the sugar carrier. In addition, fluxes of sugar in response to imposed K gradients were not demonstrable in cells de-energized by preincubation with DNP, no matter in which direction the K gradient was imposed. Finally, the severe inhibitory effects of K on Na-dependent sugar transport by the cells disappears in de-energized cells, despite the fact that Na-dependent carrier-mediated sugar entry still occurs. All of these facts are difficult to reconcile with a significant role for cellular K gradients in supporting active sugar transport as envisioned by the ion gradient hypothesis. We have suggested instead a fundamental Na-dependent energy transductive event which depends on ATP, and which can generate a membrane-bound energized intermediate which serves to support a variety of active transport events. An analogy is drawn between this concept for animal cell plasma membranes and the better documented phosphotransferase system for sugar transport described for certain microorganisms. [ABSTRACT FROM AUTHOR]

The concept that interaction between sodium-dependent transport systems represents competition for energy inherent in the transmembrane sodium gradient was examined with the use of isolated intestinal epithelial cells. The isolated cells exhibit transport interactions which are more significant in magnitude than those which have been described for intact tissue preparations. Accumulation of 1 mm valine is inhibited 60% by 10 mm 3-OMG. Conversely, uptake of 1 mm 3-OMG is inhibited only 20% by 10 mm valine. These data suggest that 3-OMG must discharge the cellular Na gradient more effectively than valine, if Na gradient dissipation can be taken as a basis for the inhibitory interaction. However, entry of 10 mm 3-OMG is significantly slower than the entry of 10 mm valine. Even if appropriate corrections are made for passive substrate entry and for differences in Na/substrate entry stoichiometry, it appears that valine should be somewhat more effective than 3-OMG in discharging the Na gradient. In light of these facts, it seems unlikely that the mechanistic basis for interaction between sugar and amino acid transport systems can be related to concomitant co-entry of Na. It is suggested that the interaction results instead from competition for energized intermediates generated at limited rates by basic energy transduction events associated with the cell membrane which serve in support of a variety of active transport systems. [ABSTRACT FROM AUTHOR]

With the use of chopped guinea-pig lung, previously perfused with Tyrode's solution, the rate and extent of uptake of antibody λ globulin has been measured using “131”I-labelled rabbit antibody. The reversibility of uptake was studied by soaking the tissue in Tyrode's solution or in a solution of unlabelled λ globulin. Uptake and wash-off of antibody resembled a process of reversible adsorption, and occurred both at low temperatures and when dead tissue was used. Wash-off of labelled antibody was more rapid in the presence of added normal rabbit λ globulin than in its absence. Simultaneous measurements were made of the degree of sensitization, defined as the ability of the tissue to release histamine on subsequent contact with antigen for a standard period of time at 37°. It was found that a plateau level of sensitization had been reached in a few minutes, when only a small fraction of the total antibody eventually taken up had been adsorbed. Under the conditions of our experiments, it was not possible to wash off the antibody sufficiently to de-sensitize the tissue. Evidence was obtained that antigen was most effective in releasing histamine when added over a broad but definite range of antigen excess. By pre-incubation of the labelled antibody with lung tissue, or by ‘screening’ in a living guinea pig, it was shown to be unlikely that sensitization was due to taking up by the lung of a specific readily adsorbed fraction of antibody. When the antibody preparation was separated by chromatography into physico-chemically distinct fractions, there were quantitative differences, but all were taken up and caused sensitization of the tissue. The mechanism of sensitization of guinea-pig lung by rabbit antibody is discussed, and is considered to be one of reversible adsorption of λ globulin at unidentified sites. [ABSTRACT FROM AUTHOR]

The methods successfully used to induce immunological tolerance in mice to a variety of antigens were applied to studies on mycobacterial antigens (whole tubercle bacilli). Mice were injected with approximately 5 × 105 living attenuated (BCG) or heat-killed virulent (H37Rv) tubercle bacilli on the 15th, 16th or 17th day of foetal life. Acid-fast bacilli were found in the lungs, spleens and livers of these mice after birth. Such mice subsequently developed normally and were not more susceptible to BCG than mice primarily infected in adult life. The immunological state of the mice exposed to mycobacteria in utero was determined by challenging 5 to 6 weeks after birth with either virulent or attenuated tubercle bacilli. These tests showed that an intra-embryonic injection of mycobacteria resulted in protective immunity and not tolerance. Furthermore, the mice also showed delayed-type hypersensitivity to mycobacteria. These results are discussed in relation to the ability of other antigens to induce immunological tolerance in mice and to the response of other animal species to mycobacteria. [ABSTRACT FROM AUTHOR]

A state of acquired immunological tolerance to bovine gamma globulin (BGG) has been observed in CBA mice injected with 10 mg. BGG within 12 hours of birth. Tolerance was demonstrated by a lack of immune elimination of 131I labelled BGG (BGG-131I) after prior challenge with Freund's adjuvant containing BGG. The degree of tolerance was found to diminish when the time between the tolerance injection and the challenge injection with adjuvant was increased. Mice were found to be tolerant 4 months after injection of 10 mg. BGG at birth but other similarly treated mice were found to be partially immune when challenged 6 months after the tolerance injection. This diminution of tolerance could be prevented by injections of antigen into adult mice whilst they were still tolerant. Precipitin and haemagglutination tests showed that antibody to BGG was present in mice shown to be tolerant to BGG by the antigen-elimination technique. The Ouchterlony double-diffusion technique showed that the mice were tolerant to one fraction of BGG but immune to at least one other fraction. The tolerated fraction of BGG was identified by means' of starch-gel electrophoresis. [ABSTRACT FROM AUTHOR]

Immuno-conglutinin has been stimulated in rabbits after infection with Listeria monocytogenes, Salmonella typhi-murium and other bacterial species. Infection of rabbits with Western Equine Encephalomyelitis, Hammon Reeves, Murray Valley Encephalitis and Aedes trivittatus viruses also stimulated the production of this substance. The most marked immuno-conglutinin response followed infection of rabbits with Trypanosma brucei. Rickettsia burneti infection in guinea pigs produced a biphasic immunoconglutinin response, the first phase being coincident with the rise of antibodies to the Phase II antigen and the second phase with the retarded rise of antibodies to the Phase I antigen. In mice also, the immuno-conglutinin level was raised following infection with Escherichia coli, Salmonella typhi-murium and other bacterial species. [ABSTRACT FROM AUTHOR]

The article examines the effect of Bordetella pertussis vaccine on the development of experimental thyroiditis in rats immunized by the intra-lymph node route or into a hind footpad. Pertussis vaccine has been shown to have an enhancing effect on the development of experimental autoallergic diseases in laboratory animals. The results indicate that moderate to severe thyroiditis may be established within 8 days with the production of circulating thyroglobulin antibody but not thyroid complement fixing antibody.

A method of partial left heart bypass is described. A non-pulsatile atraumatic pump capable of handling 2 to 4 litres of blood a minute has been developed and tested. It lends itself to easy adjustment to meet changes in left atrial and systemic pressures and can function for many hours without adjustment. Partial left heart bypass for 24 hours was carried out on sheep. No damage to the blood resulted from its use and air embolism was completely excluded. Initial difficulties associated with 24 hours' anaesthesia were solved by maintaining the animal erect in a cage. In the last series of experiments only one out of 11 sheep had an unexplained death that could have been associated with bypass. The equipment appears to be suitable for clinical trial. [ABSTRACT FROM PUBLISHER]

The pyrrolizidine alkaloid, fulvine, is now accepted as a major cause of veno-occlusive disease of the liver in the West Indies, where it is ingested as a decoction of the plant in bush tea. Fulvine is similar in chemical structure to monocrotaline, which is known to cause pulmonary hypertension in rats. Thirty young female rats were given a single dose of fulvine either by intraperitoneal injection (50 mg/kg body weight) or by stomach tube (80 mg/kg body weight). Eleven of these rats died of acute haemorrhagic centrilobular necrosis of the liver, and two of pneumonia, within 23 days of receiving fulvine. These 13 showed no evidence of hypertensive pulmonary vascular disease. The remaining 17 rats (which survived from 24 to 37 days) developed hypertensive pulmonary vascular disease with right ventricular hypertrophy together with medial thickening of the pulmonary trunk and muscular pulmonary arteries. The pulmonary arterioles showed hypertensive changes and some contained thrombi. In four animals an acute necrotizing arteritis also occurred. We have shown that fulvine resembles monocrotaline in its ability to produce pulmonary hypertension in rats. We suggest that, in any patient presenting with unexplained pulmonary hypertension, a careful enquiry should be made to elicit the possibility of recent ingestion of drugs or plant extracts that may have caused a rise in the pulmonary arterial pressure. [ABSTRACT FROM PUBLISHER]

Trimetaphan (Arfonad), which acts as a histamine-releasing agent in dogs, was observed to increase the shunt of blood through the lungs. Although external examination of the lungs showed no appreciable collapse, more detailed examination of lungs fixed by perfusion showed that the shunt could be explained on the basis of alveolar collapse and there was no need to postulate the opening of anatomical shunts. Histamine-releasing agents or histamine produced rapid, shallow breathing, which persisted after inflation of the lungs sufficient to restore the elastic and non-elastic resistance of the lungs to normal. It seems possible that the rapid, shallow breathing is due to sensitization of vagal nerve endings by the histamine or by some other substance released from the mast cells. [ABSTRACT FROM PUBLISHER]

This article focuses on various researches on infrahuman animals to the understanding of electric convulsive shock phenomena. The fundamental scientist in this area of research sees several advantages in using certain species of infrahuman subjects. Such subjects are available in large, relatively homogeneous research samples. It is recognized that some of these very advantages may prove to be disadvantageous when attempts are made to apply the principles discovered in animal research to the understanding of human behavior. Cross-population generalizations are always precarious. The researcher using groups of human subjects suffering from mental disorders has also found this to be true, for he does not have an adequate sample for generalizing to the normal characteristics of the "convulsive mechanism." The "convulsive mechanism" is being found to exhibit the general characteristics of other neuromuscular systems evidencing threshold phenomena, all-or-none relationships, and subject to variations, which are functions of the general physiological state of the organism at the time of stimulation. Widespread physiological changes of a reversible nature have been observed to accompany the convulsion, their durations varying from very short periods, as in the case of acute cerebral anoxia, to days, as in the case of general activity and weight changes.

The article presents information on the research performed on the two forms of Glossobalanus marginatus Meek and Protoglossus, collected from the west coast of Sweden. In the present area these animals live in comparatively deep water and are necessarily collected by means of dredging. Owing to the fact all the specimens collected are, unfortunately more or less incomplete, the hind parts of their fragile trunk regions being crushed or torn off by the too rough treatment. Consequently, the present author has not been able to examine the parts of the nervous system proximal to the liver region.

The article presents the author's views on conducting the study. The author is thankful to Ivar Johansson, director of the Institute of Animal Breeding, Royal Agriculture College of Sweden. During the author's visit to the institute Johansson suggested him the problem which has formed the subject of these studies and gave him the opportunity of commencing the experimental work. Author expressed his gratitude to Johansson for his frequent discussions and his continued interest throughout the course of the work.

The spinal cord blood flow has been measured in anaesthetized dogs using an inert radioactive gas ((133)Xenon) clearance technique. The (133)Xe was placed in the cord by direct injection. This study has demonstrated that the flows obtained from the white matter are reproducible and that there is little variation in blood flow in the white matter between different thoracolumbar segments in the same dog. No difference was found in blood flow between dogs anaesthetized with halothane, trichlorethylene, or pentobarbitone. [ABSTRACT FROM AUTHOR]

A small pneumatic cuff inflated around the knee was used to produce tourniquet paralysis in baboons. A cuff pressure of 1,000 mm Hg maintained for one to three hours produced paralysis of distal muscles lasting up to three months. Nerve conduction studies showed that most of the motor fibres to the abductor hallucis muscle were blocked at the level of the cuff and that they conducted impulses normally in their distal parts. There was a significant correlation between the duration of compression and that of the subsequent conduction block. When tested two to three weeks after the tourniquet, the amplitude of the response of m. abductor hallucis to nerve stimulation distal to the cuff was usually slightly reduced compared with the precompression figure. This was assumed to mean that a small proportion of the motor fibres had undergone Wallerian degeneration as a result of compression. Maximal motor conduction velocity was reduced in recovering nerves. It was also reduced when a cuff pressure of 500 mm Hg was used, which was insufficient to produce persistent conduction block. In such cases a reduced velocity without evidence of block could be demonstrated 24 hours after compression. Ascending nerve action potentials were recorded from the sciatic nerve in the thigh, with stimulation at the ankle. Before compression the fastest afferent fibres had a significantly higher velocity than the fastest motor fibres in the same nerve trunk. Results after compression suggested that the high-velocity afferent fibres had a susceptibililty to the procedure similar to that of the fastest motor fibres. [ABSTRACT FROM AUTHOR]

Conduction in the lateral popliteal nerve of the baboon was studied during the course of Wallerian degeneration. Six nerves were examined. In each case the muscle response to nerve stimulation and the ascending nerve action potential were recorded daily until the nerve became inexcitable. The muscle response to nerve stimulation disappeared after four to five days, but ascending nerve action potentials could be recorded for a further two to three days. There was no change in maximal motor conduction velocity or in distal latency until the muscle response to nerve stimulation was severely reduced in amplitude. At this stage there was a consistent increase in distal latency, sometimes associated with a mild reduction in maximal motor velocity in the leg. There was no change in the velocity of ascending nerve action potentials. Histological studies confirmed the presence of degeneration in the terminal parts of the intramuscular nerve fibres at a time when the proximal parts of the same fibres were relatively normal. [ABSTRACT FROM AUTHOR]