bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of blood pressure manipulations on shivering thermogenesis in the pigeon
Authors: HOHTOLA E. , SAARELA S. , HISSA R.
Published: December 2008

The effects of blood pressure (BP) manipulations on shivering thennogenesis were studied in conscious pigeons. A rise in BP induced by noradrenaline (NA) or equipotent doses of angiotensin II (Ang 11) effectively suppressed shivering at +12°C and partly abolished the cold‐induced vasoconstriction in the feet. The inhibition commenced when the rise in BP reached +40 nunHg, and a fall in body temperature followed these responses. Comparison of the trajectories in the BP‐shivering plane revealed that the inhibition of shivering by Ang II could be completely explained by changes in BP, whereas NA had also another, more prolonged inhibitory action independent of baroreceptor activity. A similar dose‐dependence for effects on BP and shivering could be established with both drugs. An acute reduction of BP by sodium nitroprusside had also a very potent inhibitory effect on shivering. In hypotensive pigeons elevation of BP with NA initially enhanced shivering, but when BP was raised beyond normal levels shivering was again suppressed. We conclude that both a ripe and a fall in BP can inhibit shivering in the pigeon, and that normal levels of BP facilitate shivering. NA inhibits shivering by more than one mechanism, but the initial effect is mediated through a baroreflexive action. The interactions of thermoregulatory and cardiovascular mechanisms suggest an integrated control of body temperature and circulation, which should be considered in experimental approaches to these homeostatic systems.
Regional blood flow during reactive hyperemia in canine myocardium as determined by local washout of Xenon‐133
Authors: HAUNSØ STIG , AMTORP OLE
Published: December 2008

The mechanisms regulating vascular tone in the myocardium were studied in open‐chest anesthetized dogs by occlusions of the left anterior descending coronary artery (LAD) for 3 to 600 s. Cumulative excess blood flow (flow in excess of control flow), and repayment of flow debt (cumulative excess blood flow divided by blood flow deficit) were calculated using local injections of Xenon‐133 for blood flow measurements. Release of vascular occlusion following 3 s of ischemia was not associated with any measurable hyperemia. Cumulative excess blood flow increased with increasing duration of ischemia from 5 to 600 s, but the increment in excess flow per unit extention of the occlusion time showed a considerable decline. Blood flow in excess exceeded blood flow debt incurred during the occlusion of 10 s duration of 161%; with prolongation of ischemia to 600 s repayment of flow debt declined markedly to about 10%. Oxygen lack in the tissue elicited by perfusion of LAD—for 10 s with constant perfusion rate—with deoxygenated blood produced a fall in peripheral coronary resistance of about 40% which closely corresponds to the fall in resistance observed after a period of LAD occlusion of similar duration. The results lead to the conclusion that ‘vasodilator’ metabolites formed in the tissue during periods of arterial occlusion are of prime importance for the fall in the tone of the vascular smooth muscle cell occurring in the post‐occlusion period. The findings argue against a myogenic component in this response.
Adjustments of hepatic and small intestine blood flow on selective vasoconstrictor fibre stimulation
Authors: FASTH S. , HULTÉN L. , NORDGREN S.
Published: December 2008

FASTH, S., HULTÉN, L. & NORDGREN, S.: Adjustments of hepatic and small intestinal blood flow on selective vasoconstrictor fibre stimulation. Acta Physiol Scand 1980, 110:343–350. Received 16 Jan. 1980. ISSN 0001–6772. Department of Surgery II, Sahlgrenska sjukhuset, University of Goteborg, Sweden.

The mutual changes in hepatic and small intestinal blood flow on selective nervous stimulation of the periarterial vasoconstriction fibres, were studied in anaesthetized cats. Occlusion of the hepatic artery did not change portal blood flow, whereas occlusion of superior mesenteric blood flow caused a significant increase in hepatic arterial flow. Stimulation of the hepatic sympathetic nervous supply caused a phasic blood flow response with a marked transient peak flow reduction of hepatic arterial blood flow. The magnitude of the peak response varied with the frequency of the stimulation. Despite continuous stimulation the first phase went over into a second phase of less pronounced vasoconstriction. This “steady state” blood flow, was maintained at about 20% below the control level, irrespective of stimulation frequency. Corresponding in time with the peak vasoconstriction there was a transient increase of portal pressure. Sympathetic nerve stimulation increased portal pressure even on occlusion of the hepatic artery. Stimulation of the mesenteric sympathetic nerves evoked the characteristic transient peak vasoconstrictor response consisting of two phases, a brief intense peak resistance response followed by a second phase of less pronounced but generally well maintained constriction. Simultaneously a slight reduction of portal pressure and hepatic arterial vascular resistance was regularly seen. In contrast to the observations in the hepatic arterial circuit the magnitude of this “steady state” blood flow in the small intestine was dependent on the rate of the stimulation, however. On simultaneous stimulation of the hepatic and mesenteric sympathetic nerves the hemodynamic responses were largely the same as when these nerves were stimulated separately. The portal pressure affecting mean capillary pressure in the intestine differed, however. Small and variable pressure changes were followed by rapid return towards control and during steady state it did not differ from the prestimulatory level.

This investigation was supported by grants from the Swedish Medical Research Council (No. 17X‐3117), from the Faculty of Medicine, University of Goteborg, The Swedish Society of Medical Sciences, from Goteborgs Likaresallskap and Assar Gabrielsson's Fund.
The effect of glucagon, dibutyrylic cyclic AMP and insulin on bile production in the intact rat and the perfused rat liver
Authors: THOMSEN OLE ØSTERGAARD , LARSEN JENS ANKER
Published: December 2008

The effect of glucagon, dibutyrylic cyclic AMP (DBcAMP) and insulin on bile flow and composition was studied in fasting, Nembutal anesthetized intact rats and perfused rat livers. In intact rats the infusion of glucagon (0.5 μg · kg b. w‐1· min‐1) resulted in a parallel increase in bile flow and 14C‐erythritol clearance of approx. 20%. The biliary excretion rate of electrolytes increased, whereas the net ductular fluid transport and the excretion rate of bile acids remained unchanged. Thus glucagon choleresis in intact rats appears to be due to a stimulation of the bile acid independent fraction of canalicular bile production. A similar effect was seen when DBcAMP (0.5 μmol · kg b. w.‐1· min‐1) and insulin (1 U · kg b. w.‐1) was given. In the perfused liver glucagon or DBcAMP also increased bile flow. However, bile acid excretion rate also increased and the rise in bile flow was proportional to the rate of taurocholate administration. This effect may be due to uneven distribution of perfusate flow. Insulin was totally without effect on bile production in the perfusion experiments. It is concluded that the choleretic effect of glucagon and insulin is dependent on unknown factors which may be related to extrahepatic actions of the hormones.
Opening of the blood‐brain barrier by acute elevation of intracarotid pressure
Authors: HARDEBO J. E. , NILSSON B.
Published: December 2008

A method for local opening of the blood‐brain barrier in the territory of one internal carotid artery in the rat is described. A local hypertensive insult is induced by rapid infusion of blood into the internal carotid via the external carotid. The hemodynamic changes caused by the infusion, in particular relation to the threshold and extent of barrier opening, are analyzed. This mode of hypertensive barrier opening may be advantageous to those in which the insult is induced systemically, especially when studying the cerebrovascular effects of neurotransmitter catecholamines, since all the latter methods interfere with adrenergic mechanisms. Further, unilateral intracarotid infusion may allow the territory of the contralateral middle cerebral artery to be used as internal control.
Anaphylactic shock in monkeys passively sensitized with human reaginic serum
Authors: SMEDEGÅRD G. , REVENÄS B. , LUNDBERG C. , ARFORS K.‐E.
Published: December 2008

Mechanisms inducing a low cardiac output (CO) state in IgE‐mediated (cytotropic) anaphylactic shock in anesthetized Macaca irus monkeys were studied. 7 monkeys were sensitized by 2 i. v. injections of a human reaginic serum containing a high concentration of IgE antibodies against dog albumin. Anaphylactic shock was elicited 48 h after the last sensitization dose, by an i. v. injection of dog albumin. The severe anaphylactic shock which developed was characterized by an initial phase consisting of increased CO (+16%, mean value, 1 min after challenge), pulmonary hypertension and systemic vasodilatation followed by a phase consisting of decreased CO (‐67%), a fall in mean arterial pressure from 113 to 45 mmHg, decreases in left and right arterial pressures (‐5.3 and ‐3.2 mmHg, respectively) and increases in pulmonary vascular (+364%) and total peripheral (+30%) resistances. These changes were recorded 5 min after challenge and the values then remained essentially unaltered during the rest of the 30‐min observation period. Pulmonary vascular resistance was only increased by 140% at the end of that period. Myocardial blood flow was maintained during shock at the expense of flow to other organs. However, initially there was a redistribution of blood flow withing the left ventricular myocardium, resulting in a relative decrease in subendocardial flow. This finding was not related either to occasional S‐T changes in the electrocardiograms or to the level of decreased CO. The oxygen supply to the myocardium was reduced in shock but the reduction was always smaller than the corresponding decrease in heart work. Two additional monkeys sensitized with an IgE fraction from the human serum showed a smaller amount of specific IgE in their serum prior to challenge than the other monkeys. The response to challenge was milder, but resembled the initial vasodilatory reaction in monkeys sensitized with serum. These data on cytotropic anaphylaxis in the monkey show that the main cause of decreased CO and thus of the shock state is a decreased venous return, primarily due to peripheral blood pooling and, to a smaller extent, extravasation of plasma. No appreciable involvement of the heart in the induction of shock was detected.
Depletion of substance P‐like immunoreactivity in the cat dental pulp by antidromic nerve stimulation
Authors: GAZELIUS BERTIL , BRODIN ERNST , OLGART LEIF
Published: December 2008

Tissue levels of substance P‐like immunoreactivity (SPLI) were determined by radioimmunoassay in incubated cat dental pulps with and without previous electrical stimulation of the inferior alveolar nerve (I.A.N.). The ability of the dental pulp to degrade substance P (SP) was also studied. The pulpal SPLI levels in teeth incubated at 37°C for up to 240 min immediately after removal from the jaws did not differ from those in contralateral unincubated teeth. Following I.A.N, stimulation (3–45 min at 10 V, 15 Hz and 5 ms) and subsequent incubation (30 min 37°C) of the teeth the SPLI levels in ipsilateral pulps were significantly lower (45% reduction) than those in contralateral unstimulated controls. Incubation of homogenized pulp tissue at 37°C with synthetic bovine SP or 125I‐Tyr8‐SP led to rapid inactivation of SP, whereas similar incubation of whole blood with 125I‐Tyr8‐SP had little effect. Endogenous SPLI levels were also rapidly reduced (50% reduction within 3 min) in incubated pulp homogenates. Incubation at a lower temperature (22°C) resulted in a somewhat reduced rate of degradation and incubation with boiled homogenates failed to inactivate SP. The results indicate that the pulp contains enzymes capable of destroying SP and that within the nerve terminals SP is stored in such a way that it is protected against degradation. The data obtained also provide further evidence for a nerve evoked release of SP.
On the adrenergic system of ganoid fish: the Florida spotted gar,Lepisosteus platyrhincus(Holostei)
Authors: NILSSON STEFAN
Published: December 2008

Falck‐Hillarp fluorescent histochemistry, analyses of catecholamine content in different organs and experiments with drug effects on isolated strip preparations were used to study the adrenergic system of the Florida spotted gar,Lepisosteus platyrhincus.The study reveals a well developed system of adrenergic nerve terminals, especially in blood vessels and in the wall of the sinus venosus and atrium. The lung (swimbladder) receives an excitatory cholinergic nerve supply which controls both smooth and striated muscle in the trabeculae of the lung. No conclusive evidence for an adrenergic inhibitory innervation of the lung was obtained. Chromaffin cells line the walls of the posterior cardinal veins, similar to the situation in the teleosts, and the dominating catecholamine in the chromaffin tissue and in the blood plasma is adrenaline. The concentration of adrenaline in the blood plasma is high enough to affect the contraction force of the heart, and circulating adrenaline may thus contribute to the adrenergic control of the heart in this species.
Lactate concentrations after short, maximal exercise at various glycogen levels
Authors: JACOBS IRA
Published: December 2008

The present study was designed to evaluate the effects of changes in glycogen concentrations on lactate accumulation in human skeletal muscle during a 1 min maximal muscle fatigue test (MFT). All subjects first performed the MFT during a control experiment. Four subjects then performed the MFT again 1 h after prolonged exercise. Seven other subjects performed the MFT again after a 3 day carbohydrate (CHO) poor diet and again after 4 additional days of a CHO rich diet. The m. vastus lateralis was biopsied prior to (for glycogen determinations) and immediately after (for lactate determinations) each performance of the MFT. High but similar lactate concentrations were observed (22.3 mmol × kg‐1 w. w.) with normal and supernormal glycogen leves. Lactate was significantly reduced following both the prolonged exercise (to 7.0 mmol × kg‐1 w. w.) and the CHO poor diet (to 16.8 mmol × kg‐1 w. w.). Alterations in muscle strength and fatigue patterns were also observed after the dietary manipulations but they were neither commensurate with the changes in metabolite concentrations nor statistically significant.
Regional differences in skin blood flow as measured by radioactive microspheres
Authors: LUNDBERG CLAES , SMEDEGÅRD GÖRAN
Published: December 2008

Regional skin blood flows in the trunk were measured by means of radioactive labeled microspheres in anesthetized rats and monkeys. Mean arterial pressure, heart rate, cardiac output and arterial pH, pO2 and pCO2 were registrated and body and ambient air temperature were kept constant for the duration of the experiments. The blood flows were determined on a total of 6 skin samples, 2 samples each from the thoracic, lumbar and sacral regions. The reproducibility of the microsphere technique for measurements of skin blood flow was evaluated in the rats by two separate microsphere injections which were given with a 10 min interval. The coefficient of variation varied with the region from 10.3 to 22.7%. In both species the skin blood flows in the thoracic regions were significantly higher than in the lumbar and sacral regions (P<0.05). The skin blood flows in the thoracic region of the rat ranged from 39–45 ml min‐1· 100 g‐1 in the lumbar region from 32–33 and in the sacral region from 29–30. In the monkeys the corresponding values for the different regions were: thoracic: 7–9, lumbar: 5–7 and sacral: 4–7 ml· min‐1· 100 g‐1, respectively. Our results support the use of radioactive microspheres for skin blood flow measurements, and demonstrate the existence of regional differences in the skin blood flow of the trunk. We suggest that this may be an important consideration during the development, and interpretation of data from experimental models in which skin blood flow is important.
Influence of mannitol‐induced reduction in CSF Na on nervous and endocrine mechanisms involved in the control of fluid balance
Authors: LEKSELL L. G. , CONGIU M. , DENTON D. A. , FEI D. T. W. , McKINLEY M. J. , TARJAN E. , WEISINGER R. S.
Published: December 2008

Infusions (20 μl/min) of isotonic (0.27 M) and hypertonic (0.7 M) mannitol dissolved in Na‐free artificial CSF were made for 1 h. into the lateral cerebral ventricle (IVT) of conscious water‐replete sheep. The IVT infusion of both 0.27 M and 0.7 M mannitol induced a water‐diuresis. Samples of CSF were collected prior to, and 5, 35, 65 and 125 min after the end of the infusion. These consistently showed a reduction in CSF [Na], while CSF osmolality remained unchanged after 0.27 M mannitol, and was considerably increased after 0.7 M mannitol. In the 44 h dehydrated sheep IVT infusion of 0.7 mannitol in Na‐free artificial CSF was made for 6 h. The water deprivation as such caused a marked increase in plasma and CSF [Na] and osmolality. The 6 h IVT infusion of hypertonic mannitol further increased the CSF osmolality, while CSF [Na] decreased and reached a value below the normal for water‐replete animals. The infusion also induced a fall in plasma ADH resulting in a water‐diuresis, and extinguished the thirst of the dehydrated sheep. Furthermore, the infusion markedly reduced renal sodium excretion without causing any substantial change in blood aldosterone, in spite of the fact that there was a conspicuous increase in plasma renin concentration. The study supports the view that sodium sensitive receptors close to the cerebral ventricular system participate in the regulation of ADH secretion, water intake, renin release, and renal sodium excretion.
Interstitial fluid volume, colloid osmotic and hydrostatic pressures in rat skeletal muscle. Effect of hypoproteinemia
Authors: REED ROLF K.
Published: December 2008

Colloid osmotic pressures in plasma (COPp) and interstitial fluid (COPp), interstitial fluid pressure (P1) as well as interstitial fluid volume (IFV) was measured in rat skeletal muscle during development of hypoproteinemia. The hypoproteinemia was induced with intraperitoneal injections of aminonucleoside puromucin causing a renal lesion similar to that in human nephrotic syndrome with renal loss of plasma protein and subsequent fall in COPp. When COPp fell from control values (about 20 mmHg) to about 10 mmHg, the fall was accompanied by an identical fall in COPp (in mmHg) while P1 did not change. Provided the pre‐to postcapillary resistance ratio was unchanged, the pressure imbalance in the Starling forces (net nitration pressure) was similar to the control situation at this stage of the hypoproteinemia. With further fall in COPp, the absolute fall in COPp was less,—leading to increased net filtration pressure, and finally edema appeared. In presence of edema, P1 rose from average control values of—0.20 mmHg to an average of +1.5 mmHg. Interstitial fluid volume in hypoproteinemic rats without edema was similar to that of controls (about 0.30 ml/g dry tissue), and increased to 3 to 4 times this value in the presence of edema. Comparing the fall in COPp to IFV in the nephrotic rats without edema show that the fall in COPp must have been brought about by a lymphatic washout of interstitial proteins since IFV was similar to the controls when COPp had fallen to 4 that of control.
Distribution of coronary blood flow across the canine left ventricular free wall during reactive hyperemia
Authors: HAUNSØ STIG
Published: December 2008

In a group of open‐chest anesthetized dogs, reactive hyperemia (RH) in epi‐and endocardial layers of the myocardium was quantitated by measurements of cumulative excess blood flow (CEBF) in the hyperemic period following occlusions of the left anterior descending coronary artery (LAD) for 10 to 120 s. Blood flow measurements were obtained by means of the local Xe‐133 washout technique. When ischemia was extended from 10 to 45 s, CEBF increased significantly and uniformly in both layers; with further extension of the ischemia to 60, 90 and 120 s, the increment in CEBF was significantly greater in the endocardial than in the epicardial layer (29, 57 and 64% greater, respectively). In accordance with the concept that CEBF is mainly controlled by metabolic factors, this result supports the hypothesis that the capacity for formation of vasodilatory “metabolites” is greater in the subendocardial tissue. Left ventricular wall was homogeneously perfused in the pre‐occlusive period and during maximal vasodilatation of the coronary bed. In another group of dogs, maximal vasodilation and abolishment of local autoregulation was ascertained by 30 s of occlusion of LAD. When diastole in the post‐occlusion period was shortened by 33%, i. e. from about 37.5 s · min‐1to about 25.5 s · min‐1by artificial pacing at 250 min‐1, endocardial maximum blood flow amounted to only 43% of that of the corresponding epicardial region, which apparently was not affected by the increased heart rate.
GIP‐like immunoreactivity in glucagon cells Interactions between GIP and glucagon on insulin release
Authors: AHRÉN BO , HÅKANSON ROLF , LUNDQUIST INGMAR , SJÖLUND KRISTINA , SUNDLER FRANK
Published: December 2008

In the present study the cellular and subcellular distribution of immunoreactive glucagon and GIP (gastric inhibitory polypeptide) were studied in the mouse. Furthermore, the effects of pure GIP and glucagon on basal and stimulated insulin secretion were investigated. Immunohistochemistry revealed that immunoreactive GIP occurred in the pancreatic glucagon cells and in endocrine cells, also displaying glucagon immunoreactivity, scattered along the small and large intestines. Electron immunocytochemistry revealed that the GIP‐like material and glucagon coexisted in the secretory granules of the pancreatic glucagon cells. Pure porcine GIP and glucagon both stimulated basal insulin release. When equipotent doses of the peptides were given together, the two peptides antagonized each other's effect. Both peptides potentiated glucose‐and carbachol‐induced insulin release. When equipotent doses of the two peptides were given together prior to the administration of each of these secretagogues their effects on insulin release were additive.
Hormonal and neurogenic adrenergic control of the fluid transfer from skeletal muscle to blood during hemorrhage
Authors: HILLMAN JAHN , LUNDVALL JAN
Published: December 2008

During hemorrhage net transcapillary absorption of interstitial fluid from skeletal muscle into the intravascular space compensates effectively for the blood loss. This absorption of fluid is mainly linked to decrease of the capillary hydrostatic pressure (Pc), as caused by reflex adrenergic re‐adjustment of the ratio of pre‐to postcapillary resistance (ra/rv). The present study demonstrates the existence of both a neurogenic and a humoral component in the adrenergic control of the fluid transfer from skeletal muscle to blood. In the early period of bleeding (<5 min) reflex activation of the vasomotor fibres contributed significantly to the fluid absorption. The subsequent, main part of the fluid gain from the extra‐to the intravascular space was due to the action of the blood‐borne catecholamines. Both the neurogenic and the hormonal control of the fluid absorption process was mainly linked to β‐adrenergic inhibition of vascular smooth muscle tone. This control was effected via two mechanisms, viz. by a relatively larger β‐adrenergic dilatation of post‐than precapillary resistance vessels, leading to adjustment of ra/rv and thereby to decrease of Pc, and via β‐adrenergic dilatation of ‘precapillary sphincters’ leading to increased capillary surface area available for fluid exchange.
Brain uptake of mannitol and sucrose after cerebral ischemia: Effect of hyperglycemia
Authors: SIEMKOWICZ EUGENIUSZ
Published: December 2008

The effect of 10 min cerebral ischemia on blood‐brain barrier permeability to mannitol and sucrose was evaluated in normo‐and hyperglycemic rats. In the period immediately after ischemia (1–4 min) the PS (permeability‐surface area product) for mannitol was 159%± 75 of control (0.17 ± 0.02 ml/100g min) in the normoglycemic rats (plasma glucose 8mM) and 204%± 30 of control (0.09 ± 0.02ml/100g min) in the hyperglycemic rats (plasma glucose 28mM). Two hours after ischemia, PS for mannitol returned to the control levels in the normoglycemic rats and remained elevated in the hyperglycemic animals. The mannitol/sucrose ratios—2.3 ± 0.4 in normoglycemic rats and 2.6 p± 0.I in hyperglycemic rats—remained unchanged after ischemia. As there was no significant difference in the effects of ischemia on normo‐and hyperglycemic rats, it was concluded that the deleterious effect of hyperglycemia on clinical recovery after cerebral ischemia in rats (Siemkowicz & Hansen 1978) is not related to enhancement of BBB damage.
Some factors of significance for respiratory gas exchange in muscle tissue A mathematical analysis of a capillary model
Authors: MILD KJELL HANSSON , LINDERHOLM HÅKAN
Published: December 2008

Morphological dimensions of the Krogh cylinder capillary model were calculated by mathematical simulation of respiratory gas exchange and blood flow in muscle tissue, using experimentally determined values for oxygen consumption (n'O2), blood flow (Q′), a‐V O2 difference (a‐v O2D) and pressure difference over the capillary (ΔP), for resting and exercise conditions up to maximum performance. In the resting state a capillary radius, r., of 3.5 (3–5) μm a capillary density (CD) of 35 (30–90) capillaries/mm2 and a capillary length (L) of 900(400–1000) μm can satisfy experimentally determined values of the physiological variables. During muscular activity a maintained r1 and L with an increased CD allows higher n'O2. An increase in capillaries to about 600/mm2 can allow an n'O2 uptake 30 times the resting value (maximum performance). This increase cannot be achieved by an increase only in the r1. A shift to the right in the O2Hb dissociation curve during exercise has only a small effect on the O2 delivering capacity of the model, as has an increase in the diffusion constant for O2 in tissue. It is remarkable how limited a range of morphological dimensions, particularly of r1, is compatible with the known range of values for n'O2, Q′, a‐v O2D and ΔP, at rest and particularly during maximum performance of the muscle.
The effect of deep hypothermia on the secretion of thyroid hormones and cortisol and oxygen consumption in guinea‐pigs
Authors: LEPPÄLUOTO JUHANI , HUTTUNEN PIRKKO , HIRVONEN JORMA
Published: December 2008

Adult guinea‐pigs were exposed to cold (‐20°C) to the point of deep hypothermia, and the heart rate (HR), rectal temperature (Tr), oxygen consumption (VO2), serum concentrations of proteins, thyroid hormones (by T3 and T4 radioimmunoassays) and cortisol (by fluorometry) were determined and compared with those obtained from sham‐exposed animals (22°C). VO2 and HR rose to a maximum in 1 h in the cold, but then declined in parallel to Tr for 2–3 h. The cold‐exposed animals became unconscious after 2 h and developed cardiac failure in 4h. At this time serum proteins and T3 concentrations were similar in the cold and sham‐exposed animals. Serum T4 was significantly higher (P < 0.01) in the cold‐exposed animals than in the sham‐exposed animals (45.0 ± 4.2 nmol/1 vs. 28 ± 1.4 nmol/1). Similarly, the cortisol levels were higher in the cold‐exposed animals (1.34 ± 0.11 μmol/1 vs. 0.26±0.03 μmol/1). Severe cold exposure for 4 h resulted in simultaneous activation of the thyroid gland and adrenal cortex preceded by an increase in oxygen consumption and a decrease in rectal temperature.
Characteristics of the axonal transport of vasoactive intestinal polypeptide (VIP) in nerves of the cat
Authors: LUNDBERG J. M. , FAHRENKRUG J. , BRIMIJOIN S.
Published: December 2008

The axonal transport of vasoactive intestinal polypeptide (VIP) was examined in anesthetized cats. The distally directed (anterograde) flux of peptide was found to be about 35 fmol/h in the sciatic nerve. A smaller retrograde flux (8.5 fmol/h) was also detected. In ulnar, radial and sciatic nerves, the average velocity of transport was calculated to be 2.5 mm/h in the anterograde and 0.6 mm/h in the retrograde direction. Clearance experiments indicated that the amounts of peptide available for transport in these two phases were 28% and 15% of the total, respectively. Estimates of true velocity based on these figures are 9 mm/h for anterograde transport and 4 mm/h for retrograde transport. Local injections of vinblastine were found to induce marked local increases in VIP‐immunoreactivity, indicating that microtubules play a role in peptide transport. Subcellular distribution experiments showed that most of the transported VIP was associated with a particulate fraction, possibly corresponding to large vesicles. Only one molecular form of VIP‐immunoreactivity was detected by gel permeation chromatography and no evidence was obtained for cleavage of VIP precursors in the axon. Comparison of axonal flux of peptide with the apparent content of VIP in terminal regions indicated that the turnover time for this peptide is 5 days or longer in the periphery. The results are consistent with the view that peripheral neurons are dependent upon rapid axonal transport for the supply of VIP to their terminals.
A servo‐controlled roller pump for constant flow or constant pressure blood perfusion under normal pulsatile or non‐pulsatile conditions
Authors: BORGSTRÖM PER , CLEMENTZ LARS‐ÅKE , GRÄNDE PER‐OLOF
Published: December 2008

This paper describes the design of a servo‐controlled precision roller pump applicable for constant blood flow or constant blood pressure perfusion in research on the peripheral circulation. The pump, and its feed‐back control, can simulate normal cardiac induced autoperfusion by reproducing the arterial pulse pressure configuration with high fidelity. Its design is such as to minimize damage of the red blood cells and consequent release of vasoactive substances, a problem encountered with most conventional pumps. The present pump principle may also find a use in heart‐lung machines and dialysis equipment and can be used as a precision infusion pump.
Myocardial metabolism in relation to electrocardiographic changes and cardiac function during graded hypoxia in the fetal lamb
Authors: HÖKEGÅRD K. ‐H. , ERIKSSON B. O. , KJELLMER I. , MAGNO R. , ROSÉN K. G.
Published: December 2008

Previous studies from this laboratory have demonstrated early and progressive alterations in the ST‐T period of the fetal and neonatal electrocardiogram in relation to asphyxia. The aims of the present study were to investigate the metabolic background of these hypoxic ECG changes by means of serial myocardial biopsies in fetal lambs, relating these changes to the hypoxic depletion of glycogen, ATP and creatinephosphate stores in the heart and to the altered myocardial performance as measured by heart rate, mean arterial blood pressure, combined cardiac output and max. dP/dt. The experiments were performed on 21 fetal lambs, acutely exteriorized and subjected to graded hypoxia. During hypoxia there was a significant relationship between the degree of changes in the ST‐T period according to a scoring system and the depletion of myocardial glycogen and ATP, a highly significant correlation between the rate of myocardial glycogenolysis and the rate of increase in T wave amplitude, and a parallelism between the amount of glycogen available and fetal cardiovascular function. The myocardium was capable of regenerating its glycogen stores under conditions of adequate oxygenation and in the absence of acidosis and hypoglycaemia.
Peripheral control of the cat's step cycle I. Phase dependent effects of ramp‐movements of the hip during “fictive locomotion”
Authors: ANDERSSON OLOF , GRILLNER STEN
Published: December 2008

Acute spinal and curarized cats can generate “fictive locomotor activity” after an i.v. injection of Nialamid followed by 4‐AP and L‐DOPA. The efferent burst activity to flexors and extensors can be recorded in peripheral nerve filaments. Ramp‐formed movements were applied in the hip at constant angular velocity in different phases of the spontaneous efferent burst activity. The cycle duration was markedly influenced. A flexion or an extension ramp applied in the early part of the “step‐cycle” (during flexor activity) will prolong the cycle duration, but in the later part of the cycle instead a marked shortening effect will occur. The transition from a prolongation to a shortening is very steep for the extension‐ramps, with a subsequent gradual increase from a shortening to a lengthening of the cycle. This type of phase response curve expresses a potent peripheral modulatory effect on the central pattern generator. A ramp movement (flexion or extension) applied in the beginning of the flexor burst will reinforce the flexor activity. In the end of the flexor burst instead there is a directional sensitivity with positive feedback, resulting in an excitation of the flexor activity for flexion ramps, but a depression of the flexor activity for extension‐ramps. Extension‐ramps also show a position dependent effect which enhances the response in the flexors for more extended hip positions.
Oxygen consumption in rabbit Langendorff hearts perfused with a saline medium
Authors: EDLUND ANDERS , WENNMALM ÅKE
Published: December 2008

Isolated rabbit hearts were perfused according to Langendorff at a temperature of 38°C and a pressure of 5.9 kPa with gassed Tyrode solution. Gas mixtures containing 5 % CO2 and 15, 20, 30, 60, or 95% O2 in N2 were used to saturate the perfusion medium. In some cases lactate (50 or 500 μM) was present in the medium perfusing the heart. Coronary flow (CF), oxygen pressure in the perfusion medium and in the cardiac effluent and lactate in the effluent were analysed in all experiments. The oxygen uptake in the hearts perfused with a medium equilibrated at atmospheric pressure with 95% O2 and 5% CO2 (oxygen pressure˜87 kPa, oxygen content 19 ml × 1‐1), averaged 3 mix 100 g w.w. ‐1× min‐1. Reduction of the oxygen pressure in the perfusion medium resulted in an increase in CF and in the fractional extraction of oxygen from the medium, making it possible to maintain the heart's oxygen uptake (V̇o2) down to an oxygen pressure in the perfusion medium of about 24 kPa (oxygen content˜5 ml × 1‐1, the perfusion medium equilibrated with 20% O2 and 5%CO2 in N2). Myocardial lactate production was low during perfusion at pO2˜ 87 kPa but increased rapidly when the oxygen pressure was lowered. The addition of lactate (500 /°M) to the perfusion medium at pO2˜ 87 kP induced a fractional uptake of about 20%. It is concluded that the V̇o2 observed during perfusion at pO2˜ 87 kPa mainly reflects aerobic myocardial metabolism in this preparation. This assumption is based on the facts that coronary flow and fractional oxygen extraction are submaximal and that a considerable uptake of lactate occurs concurrently with a very limited production. However, even moderate reduction of the oxygen pressure in the perfusion medium (to ˜ 61 kPa) is followed by a significant increase in lactate production, indicating that myocardial oxygenation is inefficient.
Cardiac effects of splanchnic and non‐splanchnic blood volume redistribution during aortic occlusions in dogs
Authors: STOKLAND OLAV , MOLAUG MÅLFRID , THORVALDSON JØRGEN , ILEBEKK ARNFINN , KIIL FREDRIK
Published: December 2008

Translocation of blood from the lower body dilates the left ventricle during occlusion of the descending thoracic aorta and by increased activation of the Frank‐Starling mechanism, stroke volume is maintained despite raised aortic blood pressure. The contributions from the splanchnic and non‐splanchnic blood volumes to the left ventricular dilation were examined by ultrasonic measurements of myocardial chord length (MCL) in atropinized open‐chest dogs. End‐diastolic MCL rose by 2.5±0.9% during abdominal suprarenal aortic occlusion, draining blood from the non‐splanchnic region, and by 7.4±1.7% during thoracic aortic occlusion draining blood from both splanchnic and non‐splanchnic regions. Systolic left ventricular pressure rose by 16±3 mmHg and 76±12 mmHg, respectively. End‐diastolic MCL rose by 6.0±1.2% during combined thoracic aortic and abdominal infrahepatic vena cava occlusion draining blood solely from the splanchnic region and further by 2.5±0.8% by blood drained from the non‐splanchnic region after release of the vena cava occlusion. Similar results were obtained using a shunt permitting selective drainage first from the non‐splanchnic region during thoracic aortic occlusion. Blood translocation from the non‐splanchnic region maintains cardiac output during abdominal aortic occlusion. During occlusion of the thoracic aorta, drainage from the splanchnic region accounts for about 70% of the increase in end‐diastolic MCL.
Effects of 4‐aminopyridine on contractile response and action potential of rabbit papillary muscle
Authors: WOLLMER PER , WOHLFART BJÖRN , KHAN A. RAUF
Published: December 2008

The effects of 4‐aminopyridine (4‐AP) were studied on isolated papillary muscles from the heart of reserpinized rabbits (at 37°C). The preparations were paced to contract at 0.67 Hz under isometric conditions and the muscle length was adjusted to 95 % of the length for optimum force production. Simultaneous recordings of isometric force and membrane potentials were performed. 4‐AP (50 μM) increased peak force by approximately 20% of the control and prolonged the action potential by 20%. Higher concentrations of 4‐AP (800 μ.M) resulted in further increments of force and action potential duration (60 and 70% of controls, respectively). Prolongation of the action potential and potentiation of the isometric force was still present one hour after withdrawal of the drug from the perfusate. The results are consistent with the view that 4‐AP prolongs the action potential by inhibiting the late repolarizing potassium current. It is suggested that the calcium uptake by the ventricular cell during the prolonged action potential is increased and that this leads to the positive inotropic effect.
Responses of single arterioles in vivo in cat skeletal muscle to change in arterial pressure applied at different rates
Authors: BORGSTRÖM PER , GRÄNDE PER‐OLOF , LINDBOM LENNART
Published: December 2008

The concept of a rate‐dependent, dynamic as well as a static component in the myogenic control has been suggested in some previous in vitro and whole organ investigations. The present study is an attempt to reveal a dynamic component in the myogenic response directly on single arterioles by a vital microscopic technique. The study was made on the autonomically blocked vascular bed of cat tenuissimus muscle and performed by analysing the arteriolar diameter changes to an arterial pressure increase and decrease when applied at two different rates. The results demonstrate a transient, dynamic constrictor response upon the phasic increase in pressure and a transient, dynamic dilator response upon the phasic decrease in pressure, the magnitudes of which being related to the rate of the pressure change. The static response developing during the steady‐state phase of constant increased pressure was also shown. The dynamic responses were confined to arterioles smaller than about 20 μm while the steady‐state response was present in larger arterioles as well. Even if the metabolic control system partly could be responsible for the obtained responses, arguments are given that the described reactions are mainly myogenic in nature.
Synaptic triggering of epileptiform discharges in CA1 pyramidal cells in vitro
Authors: GJERSTAD L. , ANDERSEN P. , LANGMOEN I. A. , LUNDERVOLD A. , HABLITZ J.
Published: December 2008

Intra‐ and extracellular recordings were made in the transverse hippocampal slice in vitro to study the requirements for the triggering of epileptiform discharges of CA1 cells. Spontaneous and induced epileptiform discharges were produced by adding small amounts of sodium benzyl penicillin. Recorded intracellularly, the epileptiform activity consisted of a burst of action potentials superimposed on a depolarizing wave. Extracellular recordings demonstrated a marked synchronization. The epileptiform activity of the CA1 cells appeared without changes in the passive membrane properties or in the spike generating mechanism. Spontaneous epileptiform discharges of the CA1 cells depended upon a synaptic activation from the CA3 region. Stimulation of afferent fibres evoked an early and a late burst response in the CA1 cells. The long latency burst was caused by a re‐excitation from the CA3 region. The early burst response seems to be an intrinsic property of the CA1 cells and may be induced by synaptic activation of either apical or basal dendrites. The findings suggest that synaptic depolarization is necessary for the generation of epileptiform discharges of the CA1 cells.
Nervous control of pancreatic endocrine secretion in pigs IV. The effect of somatostatin on the insulin and glucagon responses to electrical vagal stimulation and to intraarterial acetylcholine
Authors: HOLST JENS J. , GRØNHOLT RIKKE , DE MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN
Published: December 2008

We studied the effect of a primed i.v. infusion of somatostatin (0.5 μg×min–1×kg–1 on the glucose dependent insulin and glucagon responses to electrical stimulation of the vagus nerves or to i.a. acetylcholine in anesthetized pigs. Somatostatin completely abolished the insulin and glucagon responses to ongoing vagal stimulation; after 70 min somatostatin infusion the response to reiterated stimulation was profoundly inhibited. After termination of the somatostatin infusion, a considerable rebound secretion of insulin and glucagon was noted. By contrast, the endocrine response to acetylcholine persisted in spite of the somatostatin administration. Blood glucose increased slightly during somatostatin infusion. The results suggest that somatostatin inhibits the responses to vagal stimulation by interference with the neural transmission to the pancreatic islets rather than by inhibition of the islet cells themselves; acetylcholine may be involved in this neural transmission (acting on nicotinic receptors.
Compliance of the interstitial space in rats I. Studies on hindlimb skeletal muscle
Authors: REED R.K. , WIIG H.
Published: December 2008

Interstitial compliance, defined as the ratio between changes in interstitial fluid volume (ΔIFV) and interstitial fluid pressure (ΔIFP), was determined for rat skeletal muscle. IFV was measured as the extravascular distribution space for 51Cr‐EDTA, while sharpened micropipettes connected to a servo‐controlled counterpressure system were used to measure IFP. The experimental protocol was designed to bring about acute (2–4 h) and chronic (24–28h) tissue over‐ and dehydration. During dehydration, the average compliance was 0.056 ml/g dry weight · mmHg, corresponding to 1.40 ml/100 g wet tissue mmHg, and was not significantly different in acute and chronic experiments. In hydration (acute and chronic), compliance increased several‐fold when IFV increased. Even at greatly increased IFV, IFP did not rise more than 1 to 1.5 mmHg above control level. Since control IFV amounts to 10 ml/100 g wet tissue, IFV will decrease by 14% when IFP falls by 1 mmHg from this control level. Provided unchanged interstitial protein mass the dehydration will cause interstitial fluid colloid osmotic pressure to increase by somewhat more than 1 mmHg—from a control level of 9 mmHg. Furthermore, since IFP was not increased by more than 1 to 1.5 mmHg during hydration, an increase in IFP plays a minor role in edema‐prevention compared to dilution and/or washout of interstitial proteins.
Compliance of the interstitial space in rats II. Studies on skin
Authors: WIIG H. , REED R. K.
Published: December 2008

Interstitial compliance, defined as the ratio between changes in interstitial fluid volume (ΔIFV) and interstitial fluid pressure (ΔIFP), has been measured for rat skin. IFP has been measured with sharpened glass capillaries connected to a servocontrolled counterpressure system, while IFV has been determined as the extravascular distribution space for 51Cr‐EDTA. The measurements were performed at hydration and dehydration of various duration. Compliance was 0.162 ml/g dry tissue per mmHg in dehydration, corresponding to 5.4 ml/100 g wet tissue per mmHg. The volume‐pressure curve was similar at 2–4 and 24–28 h of dehydration. Up to 20% increase in IFV compliance was similar to that in dehydration, but thereafter increased severalfold upon further increase in IFV. Even at sixfold increase in IFV, IFP did not rise by more than I to 2 mmHg. Control IFV in skin amounts to 40 ml/100 g wet tissue and IFV will therefore change by 14% when IFP changes by 1 mmHg from the control level. This change in IFV will cause interstitial fluid colloid osmotic pressure to increase or decrease by somewhat more than 1 mmHg in dehydration or hydration respectively from a normal control level of about 9 mmHg. With further increase in IFV secondary to increased capillary filtration, the interstitial edmaprevention will depend on washout and/or dilution of interstitial proteins since IFP did not increase by more than 1 to 2 mmHg.
Acid soluble and insoluble glycogen in human skeletal muscle
Authors: JANSSON E.
Published: December 2008

Quantitative biochemical analysis of glycogen was performed with and without perchloric acid pretreatment on biopsy specimens of varying glycogen content, obtained at rest and immediately after exercise after different diets. If analysis was carried out after perchloric acid pretreatment, as is commonly done, lower values were obtained than without such pretreatment. This could be explained by the existence of glycogen in forms of greater and lesser solubility. Evidence for this was obtained by quantitative analysis of glycogen in the perchloric acid extract. The acid soluble form in the extract constituted a greater fraction of total glycogen at supra‐normal than at low concentrations. This might also explain why supra‐normal levels of glycogen cannot be detected by histochemical methods. The existence of soluble and insoluble glycogen may also be of physiological importance, e.g. by interacting differently with enzymes of glycogen metabolism.
Monosynaptic transmission during epileptiform activity induced by penicillin in hippocampal slices in vitro
Authors: GJERSTAD L. , LANGMOEN I. A. , ANDERSEN P.
Published: December 2008

Synaptic transmission was studied in the CA1 region of transverse hippocampal slices in vitro before and after the addition of the epileptogenic agent sodium benzyl penicillin. The presynaptic fibre volley and the field potential associated with the intracellular EPSP, ‘field EPSP’, were recorded from the layer of the activated synapses. Addition of penicillin did not change either response. The rising phase of the intracellularly recorded EPSP did not change. However, the peak amplitude and, particularly, the duration of the EPSP both increased. The prolongation of the EPSP may be of importance for the triggering of epileptiform bursts.