bluuebunny/crossref_metadata_2025 huggingface dataset:
The function of baroreceptor C fibres in the rabbit's aortic nerve
Authors: Aars Harald , Myhre Lisbeth , Haswell Bruce A.
Published: December 2008

The participation of aortic nerve C fibres in the baroreflex was investigated by recording changes in renal nerve activity in response to acute increases in arterial pressure, in two experimental situations: with the A and C fibres of the left aortic nerve intact, and with the A fibres temporarily blocked by a hyperpolarizing current (anodal block). Pressure was increased by manual inflation of an intra‐aortic balloon, and interference from other baroreceptor areas was avoided by carotid occlusion and sectioning of the right aortic nerve. Rises in mean arterial pressure exceeding 20 mmHg, to levels above 110 mmHg, were needed to trigger sympathetic inhibition via C fibres. A rise of 45 mmHg caused 50% reduction in sympathetic activity, equal to that obtained by stimulation of aortic nerve C fibres at about 3 Hz. In contrast, a rise of 20–30 mmHg evoked more than 60% reduction in sympathetic activity when the A fibres were operative. Judged by these studies of peak reflex responses to brief pressure rises, baroreceptors with C fibres in the aortic nerve have a much higher threshold to pressure than their myelinated counterparts; the C fibres contribute to the baroreflex inhibition of sympathetic discharge only when pressure is increased well above normal resting levels.

Preliminary presentations of this paper were given in June 1976 at the 7th European Congress of Cardiology, Amsterdam, The Netherlands, and at the 8th Nordic Hypertension Meeting, Marstrand, Sweden (Aars, Myhre and Haswell 1976).
Tissue osmolality in intestinal villi during luminal perfusion with isotonic electrolyte solutions
Authors: Jodal Mats , Hallbäck Dan‐Axel , Lundgren Ove
Published: December 2008

A cryoscopic technique has been developed that makes it possible to determine tissue osmolality in the core of the intestinal villi. During absorption from an isotonic electrolyte solution containing glucose an osmolality gradient was demonstrated from tip to base of the villi in both the jejunum and the ileum. The tissue osmolality at the villous tips was measured to 1 000–1 200 mOsm/kg H2O while the osmolality at the villous bases was approximately isotonic with plasma. Increasing intestinal blood flow by i.a. administration of a vasodilator drug, or making the intestine ischemic by clamping the intestinal vascular supply while supplying the mucosa with oxygen, markedly decreased tissue osmolality. Substituting all sodium ions with choline in the luminal perfusate abolished almost completely the tissue hyperosmolality and the intestine became a secretory organ. These observations are consistent with the view that the observed villous tissue hyperosmolality was created by a countercurrent multiplication of sodium chloride. The physiological implications of this mechanism is discussed and it is, among other things, proposed that the hyperosmolar region represents the hyperosmotic compartment necessary for explaining intestinal water absorption.
An “on‐line” colorimetric method for repeated, rapid determinations of capillary diffusion capacity
Authors: Rippe Bengt , Stage Lars
Published: December 2008

The single injection indicator diffusion method for estimation of capillary diffusion capacity (Crone 1963) has been developed to provide directly visualized, continuous colorimetric recordings of the venous time‐concentration curves by means of a two‐colour densitometer system. Cardio‐Green, bound to albumin, is used as the non‐permeant (“reference”) tracer and Cr‐EDTA as the permeant one. The artificially perfused hindquarter muscle vascular bed of rats is used. Highly reproducible curve recordings can be obtained every fourth minute. Accidental disturbances of the recordings are readily detected. Thus, compared to the fractional venous sampling technique, the present technique has the great advantage of allowing immediately controlled and frequently repeated determinations of capillary diffusion capacity. It is therefore easily used together with measurements of filtration‐absorption events, e.g. for frequent quantitative comparisons of capillary diffusion and filtration capacities over a wide range of induced changes in perfused capillary surface area and/or capillary permeability. The main limitation is that the employed permeant tracer necessitates the use of erythrocyte‐free perfusates.
Short‐latency ventilatory responses to sudden withdrawal of hypoxia at normal and raised body temperature in man
Authors: Jensen J. Ingemann , Vejby‐Christensen H. , Petersen E. Strange
Published: December 2008

Approximately isopnoeic conditions (VE=40 1/min) were achieved by the inhalation of asphyxial gas mixtures (PA1O2 60 torr, PA1CO2 40–45 torr) in normothermia and after a rise in rectal temperature of 1.6°C had been induced by a heated flying suit. Arterial chemoreceptor drive was transiently reduced by either isocapnic removal of hypoxia (type (1) tests: two breaths of CO2 in O2) or simultaneous withdrawal of both hypercapnia and hypoxia (type (2) tests: two breaths of O2). 8–13 tests of each type were performed at both temperature conditions in 6 expts. on 4 healthy human subjects. Expired volume, total breath duration and inspiralory time were recorded, and minute ventilation and expiratory time subsequently computed breath by breath. In hyperthermia the steady‐state ventilation of 40 1/min (at a relatively higher respiratory frequency and a correspondingly lower tidal volume) was achieved at a PA1CO2 which was 5 torr lower than in normothermia. Ventilation decreased significantly in all tests. Tested with a 3‐way analysis of variance significant differences between the ventilatory responses at the two temperature conditions, and between the two test types were found. The rate of change of ventilation was greater in hyperthermia than in normothermia, and also greater in type (2) tests than in type (1) tests. Since isopnoeic conditions existed prior to the tests, this implies that the arterial chemoreceptor contribution to the total ventilatory drive is increased in hyperthermia. In type (2) tests a significant lengthening of expiratory time was observed in the first test breath. This finding confirms the effect in man of changes in airway PCO2 on lung stretch receptor discharge.
The mechanism of histamine release induced by the ionophore X537A from isolated rat mast cells: 1. Significance of Monovalent Cations, Calcium, Metabolic Energy and Temperature
Authors: Kazimierczak W. , S. A. Patkar  , Diamant B.
Published: December 2008

Histamine release induced by X537A from isolated rat mast cells was dependent on the presence of sodium or potassium but not on calcium in the incubation medium. The rate of release was faster in potassium than in sodium, but the final release was the same after prolonged incubation. Extracellular calcium as well as metabolic inhibitors depressed the rate of release induced by X537A. Pretreatment of mast cells with either EDTA or the ionophore A23187 in the absence of extracellular calcium did not influence subsequent release induced by X537A. The findings of release at 45°C and lack of release at 0°C distinguish the mechanism of action of X537A from calcium‐and energy‐dependent releasing agents like compound 48/80 and A23187 on the one hand and the simple lytic action of decylamine on the other.
Insulin‐stimulated bile formation in cats
Authors: Jens Anker Larsen  , Christensen Kent Dencker
Published: December 2008

The effects of insulin on bile flow and composition were examined in fasting, chloralose‐anesthetized cats. Insulin in doses from 0.01 to 2.00 U/kg increased bile flow and biliary erythritol clearance without any detectable change in the difference between them; thus insulin presumably had no effect on ductular fluid transport. Continuous infusion of insulin (0.8 U/kg + 0.05 U/kg/min or 0.05 Uykg + 0.002 U/kg/min) increased biliary erythritol clearance by 22%. The increase was caused by a rise in the bile acid‐independent fraction of bile production and accompanied by a parallel increase in the rates of biliary excretion of Na+and Cl‐. When ouabain, 80 μg/kg, was injected intraportally during insulin infusion the erythritol clearance, bile flow and the rates of biliary excretion of Na+ and Cl‐ were lowered towards but not to their pre‐ insulin levels. The effects of insulin on these parameters were unchanged after atropin or gastrectomy and 2‐Deoxy‐D‐Glucose was without effect on bile production. The results indicate that administration of insulin affects bile formation by stimulating the active transport of sodium across the canalicular membrane.
Circulatory and metabolic effects in the brain induced by amphetamine sulphate
Authors: Berntman Leif , Carlsson Christer , Magnus Hägerdal  , Siesjö Bo K.
Published: December 2008

Cerebral circulatory and metabolic effects of amphetamine sulphate (0.25–25 mg·kg‐1i.v. or 5–10 mg·kg‐1i.p.) were studied in anesthetized, paralyzed and artificially ventilated rats. Cerebral blood flow (CBF) was measured with a modification of the Kety and Schmidt (1948) technique, and oxygen consumption (CMRo2) was calculated from CBF and arteriovenous differences in oxygen content. Regional CBF was evaluated from the uptake of 14C‐ethanol. Cortical metabolites were analysed following freezing of tissue in situ. Amphetamine administration gave rise to a marked increase in CBF that was doubled following 0.25 mg·kg‐1 and increased 4‐fold following 15 mg·kg‐1. However, such excessive increases in flow were confined to frontoparietal cortical regions, while other cortical or subcortical areas showed more moderate hyperemia. The increase in CBF was unrelated to changes in arterial Pco2, blood pressure, or tissue lactate content. CMRo2 increased by 30% to 95% depending on dose and rat strain used. At all doses employed, amphetamine gave rise to glycogenolysis in cerebral cortex but, in animals studied within the first 30 min after 5 mg‐kg‐1, or less, the only other changes were increases in glucose‐6‐phosphate and α‐ketoglutarate concentrations. When the dose was increased to 15 mg·kg‐1, there were moderate increases in lactate concentration and lactate/pyruvate ratio. Sixty min after 5 mg·kg‐1 there were increases in tissue concentrations of pyruvate, citric acid cycle intermediates and alanine, as well.
Urinary cyclic AMP and vasopressin excretion in rat strains selected for their alcohol intake
Authors: Jaakko Linkola  , Fyhrquist Frej
Published: December 2008

Urinary excretion of adenosine 3′,5′‐cyclic monophosphate (cAMP) and immunoreactive arginine vasopressin (AVP) were investigated after water loading and following ethanol loading in two rat strains selected for their voluntary ethanol intake. After ethanol loading ethanol preferring (AA) rats excreted more cAMP but less AVP than water preferring (ANA) rats. The results suggest that the strain difference in cAMP excretion is of renal origin and is not due to vasopressin or parathormone. Differences in the sympathetic nervous activity may be responsible for the difference in cAMP excretion.
Polyamines and nucleic acids in the mouse kidney induced to growth by testosterone propionate
Authors: Henningsson Stig , Persson Lo , Rosengren Elsa
Published: December 2008

Daily injections of testosterone propionate to castrated mice resulted in a striking increase in kidney weight. Renal putrescine rose sharply and the amounts of spermidine and spermine were also increased. The activity of ornithine decarboxylase was enhanced to values of more than 1 000 times the control level within a few days of testosterone substitution. A moderate and temporary increase in the activity of the putrescine‐activated S‐adenosyl‐L‐methionine decarboxylase was observed. Testosterone injections produced a large increase of renal RNA but only a minor change in DNA. It is apparent that in mice distinct alterations in polyamine metabolism occur during the development of renal hypertrophy induced by testosterone administration.
Time course of light induced changes in pilocarpine sensitivity of rat iris
Authors: Claesson Heléan , Báaráany Ernst
Published: December 2008

Pigmented rats were kept under different light regimens for 1–20 days. Supramaximal light was used. The response of the iris sphincter in enucleated eyes with their cornea intact was tested in vitro. Pilocarpine at 6 × 10‐5M was used as a standard stimulus. In agreement with previous authors there was a marked difference between constant light treated (subsensitive) eyes and dark treated (supersensitive) ones. Animals pretreated to reach maximal sub‐ and supersensitivity and then shifted to the opposite regimen, showed that reversal was a gradual process starting within a few hours. Full reversal had not been reached at 72 h. The two curves of sensitivity vs time intersected around 24 h. The time constants of the two curves were approximately equal. Light regimens using intermittent light shifting every 1, 3, 6 or 12 h gave intermediate results.
Inhibition of vasopressin‐release during developing hypernatremia and plasma hyperosmolality: An effect of intracerebroventricular glycerol
Authors: Olsson K. , Fyhrquist F. , Larsson B. , Eriksson L.
Published: December 2008

In non‐hydrated goats prolonged (3 h, 0.02 ml/min) intracerebroventricular (IVT) infusion of 0.35 M glycerol depressed the plasma vasopressin level during the entire infusion period which resulted in a conspicuous water diuresis outlasting the infusion by about 20 min. Since no compensatory drinking occurred during this sustained water diuresis it gradually induced pronounced dehydration (loss of > 1 liter of total body water causing 5% increase in plasma [Na+] and osmolality). The same degree of dehydration was in other experiments induced by water deprivation. It then caused a 5‐fold increase in plasma vasopressin level.

Corresponding IVT infusions of 0.35 M d‐glucose depressed plasma vasopressin level only during the first half of the 3 h infusion period. Consequently, the resulting water diuresis was transient and subsided before the glucose infusion was finished.

Plasma renin activity increased during the IVT glycerol infusion and during water deprivation, but was largely unaffected by IVT glucose. Both IVT glycerol and glucose decreased renal sodium excretion.

The possibility is discussed that the pronounced ability of IVT glycerol to depress the vasopressin release and thirst is not only due to dilution induced reduction of CSF [Na+], but also to an influence of glycerol on choroidal and/or transependymal Na+‐transporting mechanisms.
Tension and cycb'c GMP changes in potassium depolarized rabbit colon muscle
Authors: Andersson Rolf G. G. , Djáurv Lars
Published: December 2008

Potassium depolarization of rabbit colon muscle elicited a contraction consisting of 2 distinct phases, an initial rapid phasic contraction and a tonic contracture. The tonic contraction was, in contrast to the phasic contraction, dependent on the extracellular calcium for its development. There was a correlation between the tension development and the increase of the cyclic GMP level in the K+‐depolarized muscle. Experimental conditions which abolished the tonic contracture,vizglucose omission and treatment with Ca2+‐antagonists (verapamil, SKF 525A) also inhibited the cyclic GMP response. The changes of the cyclic GMP levels were Ca2+‐dependent. K+‐ions also changed the cyclic AMP content an effect which was atropine sensitive. From the experimental data obtained in this investigation we suggest that the co‐variation of the tension and the cyclic GMP level in the depolarized colon muscle might depend on oscillations in a common intracellular factor, probably Ca2+.
The effect of secretin on bile production, splanchnohepatic hemodynamics and liver function in cats
Authors: Larsen Jens Anker , Krarup Niels
Published: December 2008

The effect of secretin on bile flow, biliary clearance of 14C‐erythritol and bile composition was studied in fasting, chloralose anesthetized cats. Secretin (2 U · kg‐1·h‐1) increased bile flow by 85% and increased the rates of excretion of Na+, Cl‐ and HCO‐3. Bile flow increased from values below to values above the erythritol clearance, which did not change significantly. It is therefore concluded that secretin altered ductular transfer of fluid from a net reabsorption to a net secretion of a bicarbonate rich fluid. Secretin did not affect the sphlanchno‐hepatic hemodynamics or the overall function of the liver and Indomethacin did not significantly alter the response to secretin.
Sympathetic control of metabolic and hormonal responses to exercise in rats
Authors: Galbo H. , Richter E. A. , Christensen N. J. , Holst J. J.
Published: December 2008

The importance of the sympatho‐adrenal system for the pancreatic hormonal response to exercise and, furthermore, the role of glucagon and catecholamines for the hepatic glycogen depletion during exercise were studied. Rats were either surgically adrenomedullectomized and chemically sympathectomized with 6‐hydroxydopamine or shamtreated. Two weeks later the rats had either rabbit‐antiglucagon serum or normal rabbit serum injected. Subsequently the rats either rested or swam with a tail weight for 75 min. Immediately afterwards cardiac blood was drawn and liver and muscle tissue collected. In control rats in spite of an increase in blood glucose concentrations during exercise plasma insulin concentrations were unchanged, while glucagon concentrations increased. In sympathectomized rats, compared to control rats, glucagon concentrations increased less, and insulin concentrations were higher, although glucose concentrations were lower during exercise. Sympathectomy completely abolished the exercise‐induced decrease in liver and muscle glycogen concentrations, whereas neither glycogen depletion nor plasma catecholamine concentrations were influenced by the administration of glucagon antibodies. These findings indicate that the sympatho‐adrenal system enhances glucagon secretion as well as muscular and hepatic glycogen depletion but inhibits insulin secretion in exercising rats. The increase in glucagon concentrations, however, does not enhance hepatic glycogen depletion at the work load used.
Influence of indomethacin and of prostaglandin E1 on total and regional blood flow in man
Authors: Nowak Jacek , Wennmalm ÅRke
Published: December 2008

The central and regional circulatory effects in man of the prostaglandin synthetase inhibitor indomethacin and of prostaglandin E1 (PGE1) were studied. Systemic blood pressure, cardiac output, and renal and splanchnic blood flow were measured at rest, following infusion of indomethacin (50 mg i.v.), and during infusion of PGE1 (4–8 μg X min‐1 i.v.) after the administration of indomethacin. An increase in the total systemic resistance (+ 20%), as well as in the renal (+ 30%) and splanchnic (+ 16%) vascular resistances developed rapidly following the administration of indomethacin. Infusion of PGE1 completely restored the resistance in the renal and splanchnic regions, and in addition markedly increased the blood flow in non‐visceral tissues. We suggest that the circulatory effects by indomethacin are elicited via the drug's inhibitory effect on prostaglandin synthetase in the vessel walls, and that vasodilating products of PG synthetase affect the regional blood flow distribution in man.
Measurement of cerebral blood flow in the fetal lamb with a note on the flow‐distribution
Authors: Blomstrand Svante , Karlsson Kirsten , Kjellmer Ingemar
Published: December 2008

The cerebral blood flow was measured in the acutely exteriorized fetal lamb by 133Xenon washout and microsphere distribution techniques. The measurements were performed at different blood gas levels. Regional cerebral blood flow was calculated from the microsphere distribution for five different parts of the brain. This gave estimates for blood flow in both the grey and white matter of the hemispheres, which were in close agreement with the cerebral blood flow estimated by the 133Xe washout technique. The microsphere distribution shows that the fetal cerebral hemisphere has a low blood flow compared to the basal parts of the brain, and that this difference is increased during hypoxia and hypercarbia.
Histochemical and biochemical changes in human skeletal muscle with age in sedentary males, age 22–65 years
Authors: Larsson Lars , Sjödin Bertil , Karlsson Jan
Published: December 2008

Biopsies for histochemical and biochemical analyses were taken from the vastus lateralis muscle of 55 untrained, healthy male subjects from 22 to 65 years of age. Fibre type distribution changed towards a decrease in the percentage of type II fibres, both in type IIA and type IIB fibres, whereas type IIB/IIA fibre ratio and type IIC percentage did not change with increasing age. It was found that the type IIB/flA fibre ratio was inversely related to type I fibres, i.e. subjects rich in type I fibres had a relatively smaller proportion of type IIB fibres. Fibre area determinations revealed a selective decrease in type II fibre area. Consequently, the type II/I fibre area ratio and relative type II fibre area decreased. No changes in the specific activities of Mg2+ stimulated ATPase and myokinase were observed, while the activity of lactate dehydrogenase (LDH) was higher in the youngest groups than in the oldest. LDH isozyme pattern shifted towards a decrease in percentage distribution of the muscle specific isozymes and a corresponding decrease in muscle specific activity while the activity of the heart specific isozymes did not change.
Isometric strength performance and muscle fibre type distribution in man
Authors: Tesch Per , Karlsson Jan
Published: December 2008

Maximal isometric one‐leg strength (MIS) was determined in 31 physical education students displaying a wide range in muscle fibre type distribution (21–79% fast twitch (FT) muscle fibres) in their vastus lateralis muscles. A linear positive correlation was found between MIS and the relative distribution of FT fibres (p < 0.001). This should mean that not only muscle mass involved but also the quality of muscle will be decisive for the ability to develop high isometric strength.
Reinnervation of partially denervated rat soleus muscle
Authors: Thompson Wesley
Published: December 2008

The reinnervation of partially denervated rat soleus muscles by their interrupted, regenerating motor axons has been examined in adult white rats. If reinnervation occurred after the remaining, intact motor axons had sprouted to their full, maximal extent, then the regenerating axons formed synapses preferentially with denervated muscle fibers and not with fibers innervated by sprouts. The sprouted motor units retained their size as if no reinnervation had occurred. On the other hand, if reinnervation occurred early during the sprouting process, the sprouting motor units were never able to attain their maximal size. Further, some muscle fibers became innervated by both sprouted and regenerating axons. These “hyperinnervated” fibers lost their dual innervation within a few weeks. The sprouted axons seemed to be the nerve fibers preferentially eliminated from these hyperinnervated fibers, since during the loss of hyperinnervation the sprouted motor units decreased in size while the motor units formed by the regenerating axons did not change in size. It is proposed that the occurrence of hyperinnervation is influenced by the amount of time sprouting axons have to consolidate their synapses with muscle fibers. Further, it is proposed that on muscle fibers which can become hyperinnervated, the sprouted motor neurons are at a disadvantage in the competition for maintenance because of their larger unit sizes.
Delayed drinking in response to electrical and thermal stimulation of the medial forebrain
Authors: Rundgren Mats
Published: December 2008

Water intake in response to electrical and thermal stimulation of the medial forebrain was studied in the goat. When the frontal wall of the third cerebral ventricle was included in a field of bipolar electrical stimulation a dipsogenic response was obtained after discontinuation of the stimulation. Release of antidiuretic hormone (ADH) was apparently also elicited. The water intake was roughly proportional to the amount of current which had been applied during the stimulation period. Water consumption in response to stimulation attenuated the dipsogenic effect of subsequent stimulation, as did also pre‐stimulatory hydration by stomach tube. A 2 C elevation of he temperature of parts of the preoptic/anterior hypothalamic region for 40 min periods induced cumulative drinking starting after 2.5 to 18 min. There were great interindividual differences in the amount of water consumed in response to the thermal stimulation, possibly due to variations in thermo‐couple electrode placement. The dipsogenic effect of forebrain warming was inhibited by pre‐hydration, and by lowering of the environmental temperature. The delayed thirst responses are discussed in relation to stimulus‐bound drinking previously observed in the same and other species. It appears possible that the delayed drinking was a manifestation of artificially induced excitation of juxtaventricular “thirst” receptors.
Effects of sodium salicylate on plasma insulin concentration and fatty acid turnover in dogs
Authors: Vik‐Mo By Harald , Hove Knut , Mjøs Ole D.
Published: December 2008

The effects of intravenous sodium salicylate administration on plasma concentrations of insulin, free fatty acids (FFA) and glucose were studied in intact, anaesthetized dogs both during basal and isoprenaline stimulated lipolysis. In both situations sodium salicylate reduced the plasma concentrations of insulin. The reduction was associated with decreased plasma FFA concentrations and FFA turnover rate, while plasma glucose concentrations remained unaltered. The reduced plasma insulin concentrations effected by sodium salicylate is most likely secondary to the concomitant fall in plasma FFA concentrations due to inhibition of FFA mobilization from adipose tissue.
Regional changes in structural and functional integrity of myometrial adrenergic nerves in pregnant guinea‐pig, and their relationship to the localization of the conceptus
Authors: Thorbert By G. , Alm P. , Owman Ch. , Sjöberg N.‐O. , Sporrong B.
Published: December 2008

Pregnancy is accompanied by a reduction in uterine noradrenaline, and the study was undertaken to investigate associated structural and functional integrity of the sympathetic nerves in the organ. The formaldehyde‐induced fluorescence of adrenergic nerves was studied in different uterine regions before and after in vitro incubation or injection with α‐methyl‐noradrenaline in pregnant and puerperal guinea‐pig uterus at 6 time periods, from early pregnancy (about 20 days post coitum) to 3 months post partum. The changes were related to the position of the fetuses, which were often present in only one of the two uterine horns. There was a drastic loss of fluorescent adrenergic nerves in myometrial tissue from horns distended by fetuses. Attemps to restore this fluorescence by incubation or injection with α‐methyl‐noradrenaline were essentially ineffective. Tissues from uterine regions outside (and not distended by) fetuses (in the case of early pregnancy), from horns devoid of fetuses (in the case of unilateral pregnancy), and from the cervix also lost their noradrenaline‐fluorescent nerves, but this occurred at a much later stage of pregnancy. After treatment with α‐methyl‐noradrenaline, a fluorescent plexus of sympathetic nerves could be restored to a considerable extent in these latter tissues. In puerperal animals the horn that had been devoid of fetuses regained its endogenous fluorescence much faster, and ihe uptake of α‐methyl‐noradrenaline was more efficient, than in the horn which had contained fetuses. In this latter horn clear signs of restoration of endogenous adrenergic fluorescence and a clear uptake capacity was not found until 3 months after delivery. In the tubal end of the uterus, the reduction in the number of fluorescent nerves was only insignificant, and the region thus clearly differed from the rest of the uterus. It is concluded that (1) there are clear regional differences with regard to the disappearance of the noradrenaline transmitter in the uterus, (2) this disappearance in early pregnancy is related to the position of the conceptus, and (3) the changes involve de‐and regenerative phenomena as well as alterations in transmitter levels of intact neurons.
The postnatal development of the inferior oblique muscle of the cat: I. Isometric twitch and tetanic properties
Authors: Lennerstrand Gunnar , Hanson Jerker
Published: December 2008

The postnatal development of the inferior oblique muscle in the cat has been studied with physiological and histochemical teckniques. This paper describes the changes with age in isometric twitch and tetanic response characteristics. The twitch amplitude increased and the twitch contraction time (ct) and half‐relaxation time (hrt) decreased almost linearly from birth to adulthood. The relation between the strength of nerve stimulation and twitch ct and hrt changed during development with a threshold slow response appearing at 10 weeks. Twitch responses in cats 6 weeks of age or older were of longer duration than in younger cats, in spite of the longer ct and hrt in young cats. Fusion frequency of the tetanic response reached a constant level in muscles 6 weeks or older. The maximum rate of tension rise remained the same from birth to 6 weeks of age and later increased markedly up to 20 weeks of age. The contracture induced by succinylcholine was the same in muscles of all ages. These data were related to previous findings on the postnatal development of fast and slow muscles and motor units in the hindlimb of the cat. A differentiation of the development of fast and slow eye muscle fibres is suggested. Slow fibres seemed to have completed their maturation at about ten weeks of age, while the development of fast fibre properties continued, probably up to the adult stage.
Maintenance of lactose secretion during acute insulin deficiency in lactating goats
Authors: Hove Knut
Published: December 2008

Induction of alloxan diabetes in 5 lactating goats resulted in reduced milk yields in 3 of the animals, while the yield was unchanged in two. After treatment of the diabetic goats with insulin for 4–5 days–the last 24 h intravenously–lactose secretion returned to the control values before alloxan administration provided that normoglycemia developed. In 2 experiments infusion of a large dose of insulin caused hypoglycemia and a 20–30 per cent reduction in lactose secretion rates. In the course of 1 h after withdrawal of the insulin infusion, patent signs of insulin deficiency developed as evidenced by steadily increasing plasma glucose concentrations. Nevertheless, lactose secretion continued at the same rate as during insulin infusion for the 4 h studied after discontinuation of the insulin infusion. In the goats where lactose secretion was reduced due to insulin‐induced hypoglycemia, lactose secretion returned to control values when following discontinuation of insulin infusion the plasma glucose concentrations increased into normal and diabetic ranges. It is concluded that during insulin deficiency of short term duration, mammary lactose secretion was maintained at a normal rate. Since lactose is the major product of mammary glucose utilization, it is suggested that glucose uptake in the mammary gland was not reduced by short term insulin deficiency.
Morphology and contraction properties of cat lumbar back muscles
Authors: Carlson Hans
Published: December 2008

The gross morphology, innervation pattern and contraction properties of lumbar back muscles in the cat were investigated. The medially located multifidi and interspinales are formed by short bundles interconnecting adjacent vertebrae. Laterally located bundles composing longissimus and iliocostalis are attached to the spinous processes by a fascial layer and to the pelvic bone by a well developed intermuscular septum. Different spinal segments innervate the various sections along the muscles in such a way that the myotomes composing a muscle belly seem to be arranged after one another, in a row. The contraction time of a maximal isometric twitch is 34 ms for multifidi and interspinales and 29 ms for longissimus and iliocostalis. No large segmental variations of contraction times were found. The time course of twitch responses and a study of reflex contractions in middle and lower sections of lateral muscles indicate the presence also of a slowly contracting portion located to the longissimus. The initial muscle length is more decisive for the twitch amplitude of medial than of lateral muscles. In medial muscles summation of individual twitches starts at a stimulus frequency of 10–15 Hz and apparent fusion occurs at about 50 Hz. For lateral muscles corresponding values are 15–20 Hz and about 70 Hz. The contractile tension declines markedly in all muscles during a 10 min period of stimulation at 5 Hz.
Skeletal muscle fibre types, enzyme activities and physical performance in young males and females
Authors: Komi P. V. , Karlsson J.
Published: December 2008

Differences in skeletal muscle characteristics, metabolic profiles and functional performance between males and females were investigated using young (15–24 yrs) male and female twins as subjects. The comparison included such variables as anthropometry, muscle strength, mechanical power, maximum oxygen uptake, electrical activation of muscle, muscle fibre composition (m. vastus lateralis), and activities of several skeletal muscle enzymes. The results disclosed the following primary differences between males and females: In the various functional tests the performance of females was from 61.1 to 84.6% of that in males; distribution of slow twitch fibres in m. vastus lateralis of the females (49.1 ± 7.7%) was lower (p<.05) than that of the males (55.9 ± 11.9); activities of enzymes Ca2+ stimulated ATPase, CPK, phosphorylase and LDH ± were higher (p <.05‐.01) in the males, whereas the distribution pattern of LDH‐1 isozyme was higher (p <05) in the females. A pronounced difference between the two groups was an almost 100% longer rise time of isometric force in females. It is concluded that the males as compared to the females demonstrate higher aerobic and strength performance capacity, more efficient neuromotoric output during contraction, more slow twitch muscle fibres and more pronounced contractile and glycolytic profiles in the skeletal muscles.
Differentiation between pre‐ and postjunctional α‐receptors in guinea pig ileum and rabbit aorta
Authors: Wikberg Jarl
Published: December 2008

Electric stimulation of proximal and terminal guinea pig ileum induced contractions which were mediated by stimulation of cholinergic neurons. After blocking β‐receptors, prejunctional α‐receptors mediating inhibition could be studied in these neurons. In proximal ileum the order of potencies of the following agonists was: clonidine (8)* < epinephrine (3) < oxymetazoline (2)< norepinephrine (1)< phenylephrine (0.02). The intrinsic activities of clonidine and phenylephrine were not maximal. In electrically stimulated terminal ileum practically identical results were obtained on the prejunctional α‐receptor except that phenylephrine was ineffective; the drug instead acted as a competitive blocker against norepinephrine. After blocking cholinergic receptors with atropine, excitatory α‐receptors located postjunctionally in the smooth muscle cells of terminal ileum could be studied. Under these conditions the order of potencies of the agonists was: oxymetazoline (40)< epinephrine (7) < phenylephrine (4)<norepinephrine (1)< clonidine (0.2). In contracting postjunctional α‐receptors in rabbit aorta the order of potencies was: oxymetazoline (5) < norepinephrine (1) < epinephrine (0.7) < phenylephrine (0.2) > clonidine (0.04). On the postjunctional α‐receptor in terminal guinea pig ileum phentolamine was 55 fold more effective in blocking the response of norepinephrine than it was on blocking the response on the prejunctional receptor of the same preparation. Phenoxybenzamine (4 times 10‐8M) was ineffective on the prejunctional α‐receptor of the cholinergic neuron, while it blocked the postjunctional α‐receptor of smooth muscle in guinea pig terminal ileum noncompetitively. It is suggested that the differences in the activities of clonidine and phenylephrine between prejunctional α‐receptors located to cholinergic neurons and postjunctional α‐receptors located to smooth muscle cells was due to a pharmacological difference between the receptors. The results obtained with the blockers support this suggestion.
Autoradiography on erythrokinesis and multihemoglobins in juvenile Salmo salar L. at various respiratory gas regimes
Authors: Härdig Jan , Olsson LarsÅke , Höglund Lars B.
Published: December 2008

The kinetics of erylhropoiesis in 5 6 month old Salmo salar L. was correlated to 4 combinations of environmental PO2 and pH/PCO2. Given single doses of 55Fe at the start of continuous flow bioassays, the incorporation was examined in circulating red blood cells (RBC) by autoradiography on blood smears. The proportions of immature, labelled immature and labelled mature erythrocytes were calculated on samples taken at intervals up to 52 days. Compared to control fish kept at a PO2 corresponding to 90% air saturation and pH PCO2 at 7.6/8 pH units/mmHg, oxygen depletion to 50% air saturation stimulated the proliferation of RBC stem cells and enhanced RBC maturation. Ceteris paribus, sustained hypercapnia at a PCO2 in the respiratory water raised to 23 mmHg (pH 7.1–7.2), stimulated proliferation but did not affect the output of mature RBC. Simultaneously lowered PO2 and raised PCO2 to the levels mentioned above obviously stressed the fish, as the effect of lowered PO2per se was not manifested. Radioactivity was traced to all clecdophorelically separable protein fractions from RBC hemolysates. The relevance of blood physiological criteria for probing the fitness or well being of fish in environmental respiratory stress conditions has been discussed.
Effects of isoprenaline and cooling on histamine induced changes of capillary permeability in the rat hindquarter vascular bed
Authors: Rippe Bengt , Grega George J.
Published: December 2008

Histamine infused intra‐arterially into artificially perfused, maximally dilated rat hindquarters markedly increased fluid filtration and CFC but had essentially no effect on the diffusion capacity to small molecules. Isoprenaline largely prevented the increase in fluid filtration and CFC if infused prior to the start of the histamine infusion and, if infused after the start of the histamine infusion, promptly reduced fluid filtration and CFC to near control levels. Additionally, it was noted that severe cooling of the perfusate also largely prevented the marked increase in fluid filtration and CFC by histamine. This antagonism of histamine induced increases in macromolecular permeability represents a direct action of isoprenaline on the microvascular membrane which effectively counteracts that of histamine. The data also suggest that the large pores created by histamine are different from the large pore through which macromolecules normally transverse the microvascular membrane, and that catecholamines may exert a regulatory function in the control of microvascular permeability to macromolecules in pathophysiological states associated with massive histamine release.
Antilipolytic effect of adenosine in isolated perifused fat cells
Authors: Hjemdahl Paul , Sollevi Alf
Published: December 2008

Adenosine markedly inhibits cyclic AMP accumulation in isolated fat cells, whereas inhibitory effects of adenosine on lipolysis have been difficult to demonstrate. The present study has been performed on isolated “perifused” fat cells where continuous monitoring of the lipolytic rate is possible and where modulating substances, such as adenosine, are not allowed to accumulate. Adenosine deaminase was ineffective as a lipolytic agent in perifused fat cells, suggesting no important background activity of adenosine in this system. Micromolar concentrations of adenosine inhibited lipolysis induced by noradrenaline (0.3‐1 μM) and theophylline (1 mM). Theophylline was an effective lipolytic agent also in perifused fat cells suggesting that antagonism of adenosine is not the major mode of action of this drug on fat cells.
Bronchial and cardiovascular actions of prostaglandin endoperoxides and an endoperoxide analogue
Authors: Hedqvist Per , Strandberg Kjell , Hamberg Mats
Published: December 2008

Effects of PGG2, PGH2 and the endoperoxide analogue, EPA, on bronchial and vascular smooth muscle were studied in vivo and in vitro. In the cat PGG2, PGH2 and particularly EPA proved potent stimulators of airway resistance, and they were all significantly more active than PGF2α. They also increased pulmonary vascular resistance but EPA alone was more active than PGF2α. In guinea pigs EPA was 90–190 times more active than PGF2α in increasing tracheal insufflation pressure. Human bronchi contracted in response to PGG2, PGH2 and EPA. PGG2 and PGH2 were equiactive with PGF2α and EPA was more than 500 times as potent. PGG2 and PGH2 lowered systemic arterial blood pressure and increased heart rate in cats. They were as active or more active than PGE2. EPA, on the other hand, resembled PGF2α in producing biphasic changes of blood pressure and heart rate or decrease of blood pressure and bradycardia in guinea pig and cat. The results obtained in this study indicate that PGG2, PGH2 and EPA are potent stimulators of bronchial and pulmonary vascular smooth muscle. The data are also consistent with the view that a significant proportion of effects resulting from prostaglandin generation in the lung is due to prostaglandin endoperoxides rather than primary prostaglandins.
The influence of supraspinal impulse activity on the intra‐axonal transport of acetylcholine, choline acetyltransferase and acetylcholinesterase in rat motor neurons
Authors: Dahlström Annica , Heiwall Per‐Olof , Bööj Serney , Dahllöf Ann‐Gret
Published: December 2008

The effect of supraspinal impulse activity upon the intra‐axonal transport of acetylcholine (ACh), AChesterase (AChE) and cholineacetyltransferase (CAT) in rat sciatic nerve has been studied. A decreased impulse activity was obtained by spinal cord transsection (SCT) in the thoracic region 18 h, 6 days or 20 days before killing the rats. An increased neuronal activity was obtained by exercising the rats in a commercial rodent treadmill a couple of hours per day for 14 days. The amounts of substances which had accumulated in the sciatic nerve segments relative to a nerve crush performed 12 or 18 h. earlier were used to calculate the intra‐axonal transport. The amounts of proximo‐distally transported ACh decreased markedly with time after the SCT, while the proximo‐distal transport of AChE‐activity increased. Physical exercise appeared to increase ACh‐transport. Thus, input to motor pericarya from supraspinal centres may regulate intra‐axonal transport from the cell body of motor neurons into their axons.
Effect of intralobular substitution of Na+ and Cl‐ ions on the operation of the tubuloglomerular feedback
Authors: Müller‐Suur R. , Gutsche H.‐U.
Published: December 2008

Henle's loops of surface nephrons in rat kidneys were perfused orthogradely with various solutions of different compositions, while the stop‐flow pressure (SFP) was monitored in the early proximal tubulus as a measure of the tubuloglomerular feedback response. Modified Ringer solution or iso‐osmotic solutions of NaCl, KC1, LiCl, RbCl, choline‐Cl, and Na‐acetate used to perfuse Henle's loop led to significant SFP decrease indicating an intact operation of a tubuloglomerular feedback mechanism. Increased rates with isoosmotic solutions of sodium sulphate, potassium sulphate and mannitol did not yield SFP alterations. In order to estimate intratubular sodium and chloride concentration at the macula densa during Ringer‐, LiCl‐, choline‐Cl‐, and Na‐acetate perfusion, early distal tubular fluids were collected at low and high perfusion rates, corresponding to an absent or a maximal feedback response. Analysis was performed by microflame photometry and microchloride titration. The results showed that there does not exist a common threshold for the early distal sodium or chloride concentration at which the feedback starts to operate. We conclude that the intraluminal signal at the macula densa, initiating a tubuloglomerular feedback response is not necessarily coupled to a single ion species. Either an unspecific ion transfer or more passive events of ionic interaction with the macula densa cells might operate as the initiating step in the feedback loop.
Localization of kallikrein and its relation to other trypsin‐like esterases in the rat pancreas. A comparison with the submandibular gland
Authors: ØRstavik Torill B. , Glenner G. G.
Published: December 2008

Kallikrein was located by the direct immunofluorescence technique to the granule‐containing luminal portion of pancreatic acinar cells. For the demonstration of the intracellular distribution of pancreas kallikrein, in vivo fixation of the gland was necessary. No kallikrein was found in the duct cells or in the islets of Langerhans. Quantitation by single radial immunodiffusion showed that the concentration of kallikrein in the pancreas was 132 ± 51 μg/g wet weight, i.e. 1/91 that of the rat submandibular gland. Bz‐Arg‐OEt‐esterases were in |the pancreas found as pro‐enzyme but as active enzyme in the submandibular gland. Trypsin‐like esterases, hydrolyzing σ‐amino caproic acid naphtol‐AS‐D‐ HBr (ACA), were found in the active form in both submandibular gland and pancreatic homogenates. The submandibular gland contained per g wet weight 6 times as much ACA‐esterase activity as the pancreas. In the submandibular gland, kallikrein and ACA‐esterase activity were found together in practically all granular tubular cells. Thus, the granular tubular cell contains kallikrein as well as other trypsin‐like enzymes like the ACA‐esterase, and is in this way comparable to the pancreatic acinar cell. An extraglandular function of kallikrein is suggested for the pancreas in contrast to other kallikrein‐containing exocrine organs.
Muscle fatigue and its relation to lactate accumulation and LDH activity in man
Authors: Tesch Per , Sjödin Bertil , Thorstensson Alf , Karlsson Jan
Published: December 2008

The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M‐LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.