bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Progesterone and of Insulin Administration on Regional Adipose Tissue Cellularity in the Rat
Authors: Krotkiewski Marcin , Björntorp Per
Published: December 2008

Female rats were given progesterone in a high and a low dose or insulin by injection. Both hormones caused hyperinsulinemia and an elevated body weight, explainable by increased fat tissue weight, which in turn was due to an increased fat cell size. There was a regional specificity of these effects for both procedures. It was therefore concluded that adipose tissue does not react as a homogenous tissue to different stimuli. Although not definitely conclusive because of difference in the degree of hyperinsulinemia the results also indicate that the effects of insulin are primarily exerted on the small fat cells of the subcutaneous region while progesterone increased the size of the larger parametrial fat cells.
Effects of pressure on fast axoplasmic flow. An in vitro study in the vagus nerve of rabbits
Authors: Hahnenberger Rudolph W.
Published: December 2008

By using a radially directed stream of fluid it is possible to compress a section of a nerve in vitro by known pressures without interrupting the supply of oxygen and nutrients to the nerve. Motor neurons of the vagus nerves of rabbits labelled with SH‐leucine were used at room temperature. When a nerve was subjected to 20 mmHg pressure fast axoplasmic flow was not altered, but at 30 mmHg there was a slight but consistent inhibition, which was even more marked at 60 mmHg and still more at 90 mmHg. The pressure induced block of axoplasmic flow was reversible when 60 mmHg pressure was applied for as long as 4 h, when the nerves were compressed for 15 h there was reversibilkty in only 5 out of 8 cases.
On the capacity of the β‐oxidation of palmitate and palmitoyl‐esters in rat liver mitochondria
Authors: Farstad Mikael , Berge Rolf
Published: December 2008

The β‐oxidation of palmitate, palmitoyl‐CoA and palmitoyl‐L‐carnitine proceeded at a high rate in isolated rat liver mitochondria. At high concentrations (100 nmol/mg protein) the oxidation of palmitate and palmi‐toyl‐CoA was only partly carnitine dependent. All substrates were most rapidly oxidized in the presence of oxaloacetate and state 3 conditions. Succinate inhibited β‐oxidation especially in state 4 conditions. β‐Oxidation was faster in hypotonic than in isotonic medium both in state 3 and state 4 conditions. Hyper‐tonicity inhibited β‐oxidation. The initial formation of palmitoyl‐CoA from palmitate, CoA and ATP was faster than the oxidation of palmitate under identical conditions. The presence of bovine serum albumin inhibited the β‐oxidation, especially with palmitoyl‐CoA or free palmitate as the substrates. Mitochondria contain a palmitoyl‐CoA hydrolase which may influence the available intramitochondrial palmitoyl‐CoA. The present results demonstrate no single rate limiting step in the β‐oxidation in vitro. Both the NADH/ NAD ratio, competition for the respiratory chain, the level of ADP, binding of palmitoyl‐CoA to extramitochondrial protein, and possibly intramitochondrial hydrolysis of palmitoyl‐CoA all seem to influence the rate of β‐oxidation in vitro. It is suggested that in vivo the most important factor is the availability of acyl‐CoA to the outer carnitine palmitoyl‐transferase of the mitochondria.
Left atrial pressure in normotensive and spontaneously hypertensive rats
Authors: NORESSON EDDY , RICKSTEN SVEN‐ERIK , THORÉN PETER
Published: December 2008

The left atrial pressure in adult spontaneously hypertensive rats (SHR) of the Okamoto strain and normotensive control rat (NCR) was measured via chronically implanted catheters. In SHR left atrial pressure in end‐expiration was more than twice as high (10.3±0.4 mmHg) as in NCR (4.6±0.3 mmHg). There was no difference in the intrapleural pressure between the two groups of rats, therefore the enhanced left atrial pressure in SHR represents a real rise in the diastolic filling pressure of its left ventricle. This is considered to be the most important compensation for the earlier reported rightward shift of the Frank‐Starling curve in SHR (Hallbäck, Isaksson & Noresson 1975, Noresson et al. 1979a). Without this compensation the stroke volume would have been drastically reduced for the hypertrophied heart.
The effect of different diets and of insulin on the hormonal response to prolonged exercise
Authors: GALBO H. , HOLST J. J. , CHRISTENSEN N. J.
Published: December 2008

The importance of carbohydrate availability during exercise for metabolism and plasma hormone levels was studied. Seven healthy men ran on a treadmill at 70% of individual maximal oxygen uptake having eaten a diet low (F) or high (CH) in carbohydrate through 4 days. At exhaustion the subjects were encouraged to continue to run while glucose infusion increased plasma glucose to preexercise levels. Forearm venous blood, biopsies from vastus muscle and expiratory gas were analyzed. Time to exhaustion was longer in CH‐(106±5 min (S.E.)) than in F‐expts. (64±6). During exercise, overall carbohydrate combustion rate, muscular glycogen depletion and glucose and lactate concentrations, carbohydrate metabolites in plasma, and estimated rate of hepatic glucose production were higher, fat metabolites lower, and the decrease in plasma glucose slower in CH‐than in F‐expts. Plasma norepinephrine increased and insulin decreased similarly in CH‐and F‐expts., whereas the increase in glucagon, epinephrine, growth hormone and Cortisol was enhanced in F‐expts. Glucose infusion eliminated hypoglycemic symptoms but did not substantially increase performance time. During the infusion epinephrine decreased markedly and glucagon even to preexercise levels. Infusion of insulin (to 436% of preexercise concentration) in addition to glucose in F‐expts. did not change the plasma levels of the other hormones more than infusion of glucose only but reduced fat metabolites in plasma. At exhaustion muscular glycogen depletion was slow, and the glucose gradient between plasma and sarcoplasma as well as the muscular glucose 6‐phosphate concentration had decreased. Conclusions: The preceding diet modifies the energy depots, the state of which (as regards size, receptors and enzymes) is of prime importance for metabolism during prolonged exercise. Plentiful carbohydrate stores favor both glucose oxidation and lactate production. During exercise norepinephrine increases and insulin decreases independent of plasma glucose changes whereas receptors sensitive to glucose privation but not to acute changes in insulin levels enhance the exercise‐induced secretion of glucagon, epinephrine, growth hormone and Cortisol. Abolition of cerebral hypoglycemia does not inevitably incrase performance time, because elimination of the hypoglycemia may not abolish muscular energy lack.
Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles
Authors: BERGH U. , EKBLOM B.
Published: December 2008

The influence of muscle temperature (Tm) on maximal muscle strength, power output, jumping, and sprinting performance was evaluated in four male subjects. In one of the subjects the electromyogram (EMG) was recorded from M. vastus lateralis, M. biceps femoris, and M. semitendinosus. Tm ranged from 30.0°C to 39°. Maximal dynamic strength, power output, jumping, and sprinting performance were positively related to Tm. The changes were in the same order of magnitude for all these parameters (4–6%× C‐1) Maximal isometric strength decreased by 2%× C‐1 with decreasing Tm. The force‐velocity relationship was shifted to the left at subnormal Tm. Thus in short term exercises, such as jumping and sprinting, performance is reduced at low Tm and enhanced at Tm above normal, primarily as a result of a variation in maximal dynamic strength.
Partition of 125I‐iodoantipyrine among erythrocytes, plasma, and renal cortex in the dog
Authors: CLAUSEN G. , HOPE A. , AUKLAND K.
Published: December 2008

The tissue/blood partition coefficient, Λtb, defined as the amount of blood having the same tracer content as one unit of tissue at diffusion equilibrium, was determined for 125I‐iodoantipyrine (I‐Ap) and tritiated water (THO) in the dog kidney cortex. Measurements were made after in vivo equilibration for 75 to 300 s and with liver circulation excluded. In 18 kidneys, Λtb for I‐Ap averaged 1.38 (S.D. 0.13) w/w (weight/weight), without significant correlation to hematocrit (range: 23–43) or to urine pH (range 5.5–8.6). The Λtb for THO averaged 0.97 (S.D. 0.06) v/w (volume/weight), close to the relative water contents. Erythrocyte/plasma partition for I‐Ap was 0.82 w/w, compared to a water partition of 0.72. Thus, at diffusion equilibrium the apparent I‐Ap concentration in renal cortical and red cell water exceeds that of plasma water by 14 and 60%, respectively. It follows that I‐Ap cannot be used as a general indicator for total tissue water content. When used for measurement of local blood flow and modum Kety, Λtb must be determined for each tissue and species.
A comparative study on the uptake and subsequent decarboxylation of monoamine precursors in cerebral microvessels
Authors: HARDEBO J. E. , FALCK B. , OWMAN CH.
Published: December 2008

The endothelial cells and pericytes of brain microvessels (capillaries and small veins) are equipped with an enzymatic barrier, impeding the passage of circulating amino acids, such as amine precursors, into the brain. The properties of this mechanism was studied in brain slices and isolated microvessels from various species including man and also fetal material, following incubation in dihydroxyphenylalanine (DOPA), 5‐hydroxytryptophan (5‐HTP) and dihydroxyphenylserine (DOPS). A stereospecific, energy‐dependent uptake leading to accumulation in the brain microvessel walls was found in all species studied; this process was found to exist already prenatally. The capacity of decarboxylation, the second step in the trapping mechanism at the blood‐brain interphase, showed considerable species variation. The enzyme was present also in fetal brain microvessels. Inhibition experiments provided support for the presence of monoamine oxidase, but absence of catechol‐O‐methyl transferase, in the microvessel walls.
The vagal control of the feline pyloric sphincter
Authors: EDIN R. , AHLMAN H. , KEWENTER J.
Published: December 2008

In acute experiments on cats in chloralose anesthesia the effects of efferent and afferent electrical stimulation of the cervical vagi on an applied constant flow of saline through the feline pylorus was studied. The motor activity of the stomach was recorded simultaneously with a volume recording technique. Efferent cervical vagal stimulation caused a decrease in the transpyloric flow and an increased gastric motor activity. In a few animals the decreased transsphincteric flow was preceded by a short period of increased flow. When the transpyloric flow was reduced by splanchnic nerve stimulation or a noradrenaline infusion, vagal nerve stimulation induced an increased flow through the pylorus indicating the presence of relaxatory fibres to the pylorus within the vagi. Electrical stimulation of the central end of the ipsilateral vagal nerve in the neck, with the contralateral vagal nerve left intact, resulted in a decreased transpyloric flow and relaxation of the stomach. This response could be induced with or without intact splanchnic nerves, and disappeared when the intact contralateral vagus was cut. It is concluded that the vagi mediate both excitatory and inhibitory fibres to the pyloric sphincter in the cat. A vago‐vagal excitatory reflex to the pylorus can be elicited by afferent vagal nerve stimulation together with a vago‐vagal relaxatory response of the stomach.
Effects of cholera toxin on villous tissue osmolality and fluid and electrolyte transport in the small intestine of the cat
Authors: HALLBÄCK DAN‐AXEL , JODAL MATS , LUNDGREN OVE
Published: December 2008

The effects of cholera toxin on tissue osmolality and on net transport rates of water, sodium, chloride and potassium as well as on unidirectional fluxes of water and sodium were studied in vivo. In all experiments the toxin caused a net secretion of water, sodium, chloride and potassium. The unidirectional sodium transport from tissue to lumen was increased while the flux in the opposite direction was reduced 180 min after cholera toxin instillation. Cholera toxin produced only a small reduction in the villous tissue hyperosmolality, created by the intestinal countercurrent exchanger. This reduction was far too small to explain the observed net secretion of fluid and solutes induced by the cholera toxin. Other mechanisms underlying the cholera secretion are discussed.
The effect of divalent and trivalent cations on the sodium permeability of myelinated nerve fibres of Xenopus laevis
Authors: BRISMAR T.
Published: December 2008

The effect of external Ca, Mg, Sr, Ba and La concentration was studied in potential clamp experiments on single myelinated nerve fibres of the frog (Xenopus laevis). An increase in cationic concentration caused a positive shift of the Na permeability (PNa) curve along the potential axis, a decrease in max. PNa and a decrease in the slope of the PNa curve. The effectiveness of Mg, Sr and Ba was similar and about 0.6 compared to that of Ca, whereas La was about 80 times more effective than Ca.
Role of heating in non‐invasive blood pressure measurements in rats
Authors: BORG E. , VIBERG A.
Published: December 2008

The “tail‐cuff technique for indirect blood pressure measurements was standardized, with respect to heating, in experiments on 47 adult Sprague‐Dawley rats. The direct, intra‐arterial, and the indirect blood pressures were simultaneously obtained. Pulse volume was recorded from the tail by a non‐invasive technique, and was controlled by gradual application of heat. It was found that pulse volume and body temperature were poorly related. A stable relation existed, however, between the error in the indirect blood pressure recordings and the pulse volume. The error was minimized, provided that the heating was adjusted to induce a pulse volume of at least 25% of the maximum obtainable value. It was suggested that the validity of the indirect blood pressure recording could be improved, if heat application was regulated on the basis of observations of pulse volume in the tail instead of ambient temperature or body temperature. Errors due to excessive vasoconstriction, or discomfort due to overheating could thereby be minimized.
Beta‐adrenergic dilator interaction with the constrictor response in resistance vessels of skeletal muscle during hemorrhage
Authors: HILLMAN JAHN , LUNDVALL JAN
Published: December 2008

A marked β‐adrenergic dilator interaction with the vasoconstrictor response in skeletal muscle during hemorrhage is described. The dilator influence corresponded to some 40% of the constrictor response both at mild and moderate as well as at large bleeding. In absolute resistance units, the β‐adrenergic dilator influence averaged no less than 14 mmHg/(mlXmin‐1 X 100 g‐1) at large bleeding (hemorrhagic hypotension of 50 mmHg). Comparison of the hemorrhage induced resistance effects in the autoperfused innervated muscle, in the autoperfused denervated muscle, and in the innervated muscle cross‐circulated from a donor animal, showed that the β‐adrenergic dilator influence more or less completely was caused by blood‐borne catecholamines, in all likelihood by adrenaline, which is known to be secreted in large amounts during hemorrhage. The described β‐adrenergic dilator mechanism may serve to maintain nutritional blood flow by counteracting the constrictor response. It deserves consideration also from the point of view that it obviously has to be taken into account for proper evaluation of other vascular control mechanisms brought into action in hemorrhage.
Sulphonylurea (Glibenclamide) enhances somatostatin and inhibits glucagon release induced by arginine
Authors: EFENDIĆ S. , ENZMANN F. , NYLÉN A. , UVNÄS‐WALLENSTEN K. , LUFT R.
Published: December 2008

Arginine significantly stimulated the release of insulin, glucagon and somatostatin from the isolated perfused rat pancreas. A Sulphonylurea, glibenclamide, markedly enhanced the effect of arginine on somatostatin release and inhibited its effect on glucagon release. Insulin release was not modulated by addition of glibenclamide. These findings support the idea of a paracrine interaction of islets hormones.
Sensitization of the rat parotid gland to secretagogues following either parasympathetic denervation or sympathetic denervation or decentralization
Authors: EKSTRÖM JÖRGEN
Published: December 2008

The sensitivity of the rat parotid gland to chemical agents was examined 2–3 weeks after either parasympathetic denervation or sympathetic denervation or decentralization. The parasympathetically denervated gland was markedly sensitized towards methacholine; a nonspecific supersensitivity mainly mediated via α‐adrenoceptors was also demonstrated. The sympathetically denervated gland had developed a supersensitivity which was both of the pre‐and the postjunctional type; it was predominantly of the former type to noradrena‐line and adrenaline, and entirely so to phenylephrine; it was of the latter type to isoprene‐line, and also to methacholine. The sympathetically decentralized gland was mainly sensitized towards noradrenaline, adrenaline and isoprenaline. The postjunctional super‐sensitivity developed towards the sympathomimetic drugs after sympathetic decentralization was of about the same magnitude as that observed after sympathetic denervation; this type of supersensitivity was mainly mediated via β‐adrenoceptors.
The locomotion of the low spinal cat I. Coordination within a hindlimb
Authors: FORSSBERG H. , GRILLNER S. , HALBERTSMA J.
Published: December 2008

Kittens were subjected to a complete transection of the spinal cord (Th 10–12) 1–2 weeks after birth. A few days after the operation they could perform alternating limb movements and somewhat later walking movements with their hindlimbs on a treadmill. The stepcycle of the hindlimbs could be divided into a flexion phase (F) and a first (E1), second (E2) and third (E3) extension phase. The duration of the support phase decreased markedly with treadmill velocity while the swing phase decreased to a much smaller extent. The pattern of electromyographical activity in hip, knee, ankle and toe muscles during treadmill locomotion was very similar to that of the intact cat. This related to both the timing and the general shape of locomotor bursts. The extensor muscles were thus activated well before the placement of the foot and able to produce enough force to support the body. The propulsive thrust in each step was, however, decreased and the animals showed more severe deficits particularly in their equilibrium control. It is concluded, however, that neural networks in the spinal cord (with its peripheral inflow intact but without supraspinal influences) have the capacity to generate a specific and detailed locomotor pattern.
The locomotion of the low spinal cat. II. Interlimb coordination
Authors: FORSSBERG H. , GRILLNER S. , HALBERTSMA J. , ROSSIGNOL S.
Published: December 2008

The interaction of the two hindlimbs were investigated by an analysis of the muscular activity and the movements in 14 chronic spinal kittens during treadmill locomotion (i.e. in kittens subjected to a transection of the spinal cord (Th10–12) one or two weeks after birth). At low speed the limbs were alternating (walk or trot). At higher they were activated more simultaneous, as during gallop. The two limbs could walk at different velocities, as during walking in a circle, when the two belts of the treadmill were driven at different speeds. The duration of the support phases was mainly influenced by the speed of the belt on which the limb was walking. The limbs could still maintain a common rhythm up to a two or three fold speed difference, as the flexion or the first extension phase of the limb walking on the “fast” belt was prolonged and the flexion phase of the “slow limb” was shortened. At extreme speed differences the limb on the “fast belt” performed 2, 3 and even 4 steps during one stepcycle of the “slow limb”. The placement of the feet was found to maintain the most stable relationship during alternating gaits at different speed differences. It is concluded that all phases of the step cycle are modifiable and that there are several mechanisms coordinating the limbs within the spinal cord.
Muscarinic autoreceptor regulates acetylcholine release in rat hippocampus: in vitro evidence
Authors: NORDSTRÖM Ö. , BARTFAI T.
Published: December 2008

Release of 3H‐ACh from isolated nerve endings of rat hippocampus was evoked by incubation in Krebs‐Ringer's buffer containing 25 or 35 mM potassium. The release was Ca2+‐dependent and could be inhibited by Mg2+ (20 mM). The muscarinic antagonist, atropine (10‐10–10‐6 M), enhanced 3H‐ACh‐release. The muscarinic agonist, carbachol (10‐5–10‐3 M) inhibited 3H‐ACh release via interaction with muscarinic receptors: this effect could be blocked by atropine (10‐6 M). The presence of the feed‐back regulation of 3H‐ACh release in a cell‐free preparation provides further evidence that the presynaptic regulation is exerted by muscarinic autoreceptors localized on the cholinergic nerve ending itself. The feed back inhibition of the 3H‐ACh release does not require the presence of intact neurons or neuronal loops as tetrodotoxin (2.5. 10‐6 M) does not affect the above results.
Effect of isotonic volume expansion on glomerular filtration rate and renal hemodynamics in the developing rat kidney
Authors: ELINDER G. , APERIA A. , HERIN P. , KÄLLSKOG Ö.
Published: December 2008

Young rats (20–24 days) and adult rats (4–5 days) were studied during hydropenia and volume expansion with regard to glomerular filtration rate (GFR) and the determinants of GFR. During hydropenia, GFR and renal blood flow (RBF) were significantly lower in younger than in adult rats both in absolute terms and when related to bodyweight. Equivalent degrees of volume expansion (6% of b. wt.) resulted in a much more pronounced increase in GFR and RBF in younger than in older rats. This suggests that the high renal vascular resistance in hydropenic young rats is primarily due to vasoconstriction. The relationship between the filtration rate of superficial nephrons and the total GFR was the same in hydropenic and volume expanded rats in both age groups. The tubular stop flow pressure, the calculated hydrostatic glomerular capillary pressure and ultrafiltration pressure in the afferent part of the glomerular capillaries was slightly lower in hydropenic young rats than in hydropenic adult rats. The pressures did not rise after volume expansion. It is concluded that the marked increase in GFR in volume expanded young rats is mainly due to increased renal plasma flow.
Vasomotor effects of facial nerve stimulation: noncholinergic vasodilation in the eye
Authors: STJERNSCHANTZ JOHAN , BILL ANDERS
Published: December 2008

The effect of facial nerve stimulation on ocular blood flow was studied in rabbits. The intracranial part of the facial nerve was stimulated electrically and the regional blood flow was measured with labelled microspheres. Effects on the intraocular pressure were determined in a separate series of experiments. Stimulation increased choroidal blood flow by about 200%. The blood flow of the iris and the ciliary processes also increased. The blood flow of the eyelids and the nictitating membrane increased by approximately 1000%, and the blood flow of Harder's gland increased by about 200%. The blood flow of the tongue and the submandibular gland also increased. The increase in the uveal blood flow could not be abolished by a cholinergic or ganglionic blockade. Ganglionic blockade abolished most of the increase in the blood flow of the eyelids, nictitating membrane and Harder's gland; the cholinergic blockade seemed less effective. The intraocular pressure increased with a mean value of 6 mmHg during optimal (20–30 Hz) stimulation. The increase could not be prevented by cholinergic blockade. Much of the increase in uveal blood flow seemed to be caused by stimulation of unconventional nerves. It is suggested that these nerves may be peptidergic using VIP as a transmitter and lacking a hexamethonium sensitive synapse between the site of stimulation and the eye. Their nature—afferent or efferent—remains unknown. A great part of the increase in blood flow of the eyelids, nictitating membrane and Harder's gland seemed to be due to other mechanisms involving nerves with a peripheral synapse.
Functional and metabolic effects of terbutaline and propranolol in fast‐ and slow‐contracting skeletal muscle in vitro
Authors: FELLENIUS ERIK , HEDBERG ROLAND , HOLMBERG EVA , WALDECK BERTIL
Published: December 2008

The soleus, a slow‐contracting, and the extensor digitorum longus (EDL), a fast‐contracting skeletal muscle from guinea‐pig were prepared for isometric recording of sub‐tetanic contractions in vitro. The contents of adenosine‐triphosphate (ATP) and creatinephosphate (CP) together with their metabolites and the contents of lactate, pyruvate and cyclic adenosine‐monophosphate (c‐AMP) in the muscles were determined. It was found that the energy and redox state of the isolated soleus and EDL muscles is very stable and does not significantly differ from the normal state in vivo. Moreover, there were no consistent changes in these variables after treatment with terbutaline (a β2‐adrenoceptor agonist) or propranolol or both. Thus, effects on energy metabolism do not seem to cause the changes in muscle contraction, characteristic for β‐adrenoceptor stimulation. On the other hand, the functional effects were accompanied by elevation of the c‐AMP level of the muscles.
The effect of polycythemia on blood flow in working and non‐working skeletal muscle
Authors: GUSTAFSSON L. , APPELGREN L. , MYRVOLD H. E.
Published: December 2008

The effect of acutely induced polycythemia on blood flow and viscosity in the vasodilated vascular bed of working and non‐working skeletal muscle was studied. In 12 mongrel dogs anesthetized with thiopental sodium the calf muscle of one hind limb was isolated. Vasodilation was induced either by sciatic stimulation setting the muscle at maximal work or by i.a. infusion of papaverine. Blood flow was measured at different perfusion pressures before and after infusion of 300 ml packed homologous red cells. Blood viscosity in vitro was determined in a coneplate viscometer. Apparent viscosity in vivo was analyzed by comparing pressure‐flow relationships for blood and a reference solution. Polycythemia decreased blood flow by 35% in the non‐working muscle but less than 10% in the working muscle at comparable perfusion pressures. Blood viscosity in vitro increased by 35% at low shear rates. Apparent viscosity in vivo increased by 35% in the non‐working muscle but less than 10% in the working muscle. The flow impairment induced by polycythemia was far more pronounced in the non‐working skeletal muscle indicating a flow facilitation by the rhythmic muscle contractions. Erythrocyte flow in fact increased in the working muscle after induced polycythemia while decreased in the non‐working muscle.
Human renal cytoplasmic carbonic anhydrase Tissue levels and kinetic properties under near physiological conditions
Authors: WISTRAND PER J.
Published: December 2008

The cytoplasmic form of human renal carbonic anhydrase, CA‐C (carbonate dehydratase, EC 4.2.1.1), purified by affinity chromatography, was characterized kinetically at 37°C in 25 mM N‐methyl imidazole buffer, 1=0.15, pH 7.1, using a pH‐indicator stopped‐flow technique. Under these conditions the rate constants for the uncatalyzed hydration of CO2 and dehydration of H2CO3 were 0.12 s‐M1 and 0.60‐s‐1, respectively. The kinetic parameters for CA‐C were found to be: Hydration reaction, Km=11.8 mM, V/[E]0=10.6 × 105 · s‐1, dehydration reaction, Km=70 mM, V/[E]0=5×105· s‐1. In the hydration reaction CA‐C was non‐competitively inhibited by acetazolamide, Ki= 16 nM, sulfanilamide, Ki=8 μM, and chlorothiazide, Kil μM. The levels of immunoassayable CA‐C in cortex, medulla and papilla of perfused donor kidneys were 1.3, 1.0 and 0.6 mg enzyme protein/g tissue protein respectively which corresponded well with the levels measured catalytically. The erythrocyte form, HCA‐B, was also detected immunochemically (˜0.1 mg/g protein) but is thought to be a contaminant. Calculations indicated that the uncatalyzed hydration of CO2 in the tubular cells can support 17 or 0.7% of the rate of urine acidification, dependent on whether the cellular alkaline pH‐disequilibrium during acid secretion is 0.1 or 0.01 pH units, respectively. CA‐C accelerates the hydration rate 6800‐fold which enables the cell to sustain high rates of proton generation, while maintaining near CO2‐equilibrium and maximal buffering capacity. Even at an assumed pH‐disequilibrium of only 0.01 pH‐unit, CA‐C is present in 50‐fold excess of apparent physiological needs. When the enzyme is inhibited the rate of the uncatalyzed reaction increases, which partly overcomes the effect of inhibition.
Pulmonary O2 transfer during pulsatile and non‐pulsatile perfusion
Authors: HAUGE ANTON , NICOLAYSEN GUNNAR
Published: December 2008

The importance of the perfusion pattern for the oxygen transfer has been examined in isolated rabbit lungs perfused with plasma at constant volume inflow. The lungs were ventilated with constant tidal volume and constant end‐expiratory pressure. Following a standardized rise in F1,0,2 the rate of rise in pulmonary venous PO2, (ΔPO2/Δt) was measured during alternately pulsatile and non‐pulsatile perfusion in normal lungs and in lungs made edematous by elevation of left atrial pressure. In normal lungs there was no difference in ΔPO2/Δt when the two modes of perfusion were compared. In edematous lungs ΔPO2/Δt was statistically higher during pulsatile perfusion, indicating a beneficial effect of flow‐ and pressure pulsations, e.g. a better distribution of V/Q ratios throughout the lungs. In a separate series of expts. the advancement of a high O2 front through the airways was measured, and the two perfusion patterns compared. Since no difference was found, we suggest that the phenomenon of “cardiogenic gas mixing” in the airways in vivo is a result of a direct action of the heart on the lungs rather than arterial pulsations.
Effects of phasic and tonic activation on contraction dynamics in smooth muscle
Authors: UVELIUS BENGT , HELLSTRAND PER
Published: December 2008

Responses to isotonic quick releases of rabbit urinary bladder strips and rat portal veins activated by AC‐stimulation and K+‐high medium were studied. The AC stimulation was adjusted to give the same tension as the K+contractures. Releases were performed at peak of the contractions (which was attained after 1.5–4.5 s AC‐stimulation or 2–3 min in K+‐high solution). The length response consisted of 3 parts: (1) elastic recoil, (2) isotonic transient, (3) steady shortening. Shortening velocity was determined at 100 ms after the release, as phase (2) had subsided by then. Characteristics of the initial elastic response was virtually unaffected by the mode of stimulation for both preparations. Vmax was significantly higher for the AC‐stimulations than for the K+‐contractures (bladder: 0.37 l/s vs. 0.26 l/s, portal vein: 0.46 l/s vs. 0.33 l/s). By means of computer analysis a fast exponential shortening component comprising the larger part of phase (2) could be separated from the subsequent slower shortening (see further in Hellstrand & Johansson 1979). In each preparation the amplitude of this exponential was the same for both modes of activation. The time constant was, however, smaller for the AC‐stimulated preparations. Our results thus indicate that in response to a sudden decrease in force the initial elastic recoil is the same whereas the rate of transition to steady shortening, and the steady shortening velocity itself, are lower for preparations activated by K+‐high medium compared to AC‐stimulation.
Effects of carbachol on isoprenaline evoked amylase release from the rabbit parotid gland in vitro
Authors: ASKING BENGT , GJÖRSTRUP PER
Published: December 2008

Amylase secretion from dispersed lobules of the parotid gland of the rabbit was studied in response to isoprenaline (10‐8–10‐8M) and to carbachol (10‐8–10‐5M). The effects of each agent were investigated alone and in combination at certain concentrations. Isoprenaline produced a dose‐related amylase secretion with an average maximum of 688 units/100 mg, at 10‐5M. The amylase secretion produced by submaximal concentrations of isoprenaline could be further increased by carbachol, already in low concentrations (10‐8–10‐7M), that were subthreshold for amylase secretion. This potentiating effect was seen not only as a larger secretion but also as a greater depletion of amylase from the tissue. In contrast to what is known from experiments in vivo, carbachol in a high concentration (10‐5M), by activating muscarinic receptors only, released amylase to the same extent as that released by isoprenaline. This concentration of carbachol regularly decreased the amylase secretion evoked by isoprenaline, and may be regarded as unphysiologically high. The increase in isoprenaline evoked amylase secretion, brought about by carbachol in lower concentrations, may be due to an improved transport of amylase, because of secretion of fluid, but could also be caused by augmentation of the β‐adrenoceptor mediated effects.
Measurement of myometrial blood flow in rabbits by washout of Xenon‐133 after atraumatic local labelling
Authors: OTTESEN BENT
Published: December 2008

In vivo experiments were performed on the uterine tissue of non‐pregnant estradiol treated rabbit anesthetized with sodium pentobarbitone. The average blood flow calculated from the washout of Xenon‐133 after atraumatic labelling from the uterine surface was 25.4 ml‐min‐1‐(100 g)‐1 (range 7.4–66.6), and after local injection of the tracer in isotonic saline directly into the myometrium 24.4 ml‐min‐1‐(100 g)‐1(range 8.7–45.3). During the experiments a monoexponential washout curve was found for the whole washout process both after atraumatic labelling and when the injected volume was 5μl. No trauma of injection was observed using this injection volume. The results support the applicability of a monocompartmental model for the washout of inert gas from the myometrium. Thus myometrial blood flow can be calculated from the Xenon‐133 washout rate at any time interval during the washout process.
Transient vasopressin release and thirst in response to prolonged intracerebroventricular infusions of hypertonic mannitol in saline
Authors: McKINLEY M. J. , OLSSON K. , FYHRQUIST F. , LILJEKVIST E.
Published: December 2008

In the conscious goat infusions of 0.4 M mannitol in 0.15 M NaCl into the lateral cerebral ventricle (40 or 100 min, 0.02 ml/min) caused slight, transient vasopressin release and temporary thirst, whereas infusions of pure, hypertonic (0.7 M) mannitol did not elicit thirst and inhibited the basic vasopressin release in the nonhydrated animal. In contrast, infusions of equiosmolal (0.35 M) NaCl induced persistent thirst and pronounced elevation of the plasma vasopressin concentration throughout the infusion period. The cerebrospinal fluid (CSF) osmolality was raised by the same order of magnitude (=13%) after the mannitol/NaCl and the hypertonic NaCl infusions. The CSF Na4 concentration was elevated by >10% at 5 min after the hypertonic NaCl infusions, but it was reduced by approximately 10% at 5 min after the mannitol/NaCl infusions. There was no appreciable difference in the CSF K+ concentration after the infusions. The results are discussed with regard to the possible importance of CSF Na+ concentration as opposed to strict osmotic factors for the excitation of receptors involved in the control of water balance.
Early effects of cervical sympathetic stimulation on cerebral, ocular and cochlear blood flow
Authors: BEAUSANG‐LINDER MARIANNE , HULTCRANTZ ELISABETH
Published: December 2008

Autoregulatory mechanisms may be expected to modify effects of vasomotor nerve stimulation in many tissues. Attempts were made to reveal a distinct early, but transient effect of cervical sympathetic stimulation on cerebral, retinal and cochlear blood flow. The labelled microsphere method was used to determine regional blood flow during electrical stimulation of the cervical sympathetic chain for 15–25 s and 5 min. At a frequency of 6 Hz there was a 5% reduction in cerebral flow at 15–25 s and 7% at 5 min. In the choroid plexus the mean reduction was 22% at 15–25 s but decreased to 10% after 5 min. In the cerebellum, optic nerve and retina, sympathetic stimulation had no appreciable effect on the blood flow. In the cochlea and iris, the blood flow reductions were 25 and 32%, respectively, on both occasions. In the choroid, vasoconstriction increased with time, whereas in the masseter muscle there was a decrease. Thus in the present experiments no indication was found of an autoregulatory escape phenomenon in the brain, the eye or the cochlea. Some escape was noted in the masseter muscle.
Transfer properties of the slowly adapting stretch receptor of the crayfish abdomen
Authors: SYDNES GUNNAR , WALLØE LARS
Published: December 2008

The slowly adapting stretch receptor in the abdomen of freshwater crayfish (Astacus fluviatilis) was investigated to determine its properties under dynamic conditions. An in situ preparation was used; the necessary dissection did not involve the receptor organ or its immediate surroundings. Sinusoidal variations in the angle of flexion in the joint to which the receptor organ was connected, were generated by a feed‐back controlled stretcher. Nerve spikes recorded from the axon of the receptor neurone and information about angle of flexion in the joint obtained by position transducers, were fed into a computer. Fourier transforms were performed on both input and output data to determine the amplitude of the 0. and I. harmonic together with the phase of the 1. harmonic. The receptor organ was investigated for linearity up to 1.5 degrees input amplitude, and proved to be surprisingly linear within this range. In addition, the transfer function of the receptor organ was determined by stimulating it with small‐amplitude sinusoidals with different frequencies. With a steady flexion of 35–40° in the joint, the gain of the receptor organ increased 5–6 times when the modulation frequency of the input signal was increased from 0.1 to 5 cycles/s. A maximum in gain was constantly found at about 5 cycles/s, with a rapid fall towards 0 when the modulation frequency was increased further. A change in phase lead from positive (leading output) to negative with change in sign about 1 cycle/s was also found. These results resemble the results found by investigators of isolated preparations. A “hold” property is probably a part of the overall property of the receptor organ together with an element of Maxwell type. An element of the form h(s)=ksn with n=0.45 is also a part of the transfer function of the receptor organ, although the physiological parallel to this element is uncertain.
The pulmonary vasoconstrictor response to hypoxia. The hypoxia‐sensitive site studied with a volatile inhibitor
Authors: BJERTNÆS LARS J. , HAUGE ANTON , TORGRIMSEN TORGRIM
Published: December 2008

Recent investigations have revealed that a number of inhalation anesthetics, including halothane, inhibit the pulmonary vasoconstrictor response to hypoxia without affecting other vasoconstrictor stimuli. Various injectable anesthetics do not show this effect. This discrepancy could be due either to different pharmacological properties or to the different routes of administration. There is no general agreement on whether the response to hypoxia is elicited mainly by airway hypoxia or by blood hypoxemia, i. e. where within the lungs hypoxia acts. This work is an attempt to localize the hypoxia‐sensitive site employing halothane. We have studied the reduction of standardized vasoconstrictor responses to hypoxia during administration of halothane via: (1) the airways, (2) the pulmonary artery and (3) the pulmonary veins (backward perfusion). Our experimental model has been two pairs of series‐perfused hyperventilated isolated rat lungs. An equimolar concentration of halothane most effectively inhibits the response when presented to the alveoli, less when presented to the arterial‐ and least when presented to the venous segments of the pulmonary vasculature. We suggest that the response to hypoxia is inhibited by halothane at some extravascular site on the arterial side of the pulmonary vasculature, functionally closer to the alveoli than to the responding vessels. A model which combines all the data into an unifying concept has been presented.
Compensatory increase of responses to nerve stimulation of the partially denervated rat urinary bladder
Authors: EKSTRÖM JÖRGEN , ELMÉR MATS
Published: December 2008

The rat urinary bladder was deprived of half of its innervation by removing the pelvic ganglion on one side. The motor responses of such a partially denervated bladder to stimulation of the pelvic nerve on the other side were examined I week, 1 month and 2 months postoperatively. On all three occasions the increase in pressure of the operated bladder was larger than that of the control bladder; the enlargement was most marked 2 months after operation. The responses were further enlarged by esenne, and markedly reduced by atropine. The present results combined with those of previous investigations, showing a rapid recovery in the activity of the acetylcholine forming enzyme from a reduced level and a transient supersensitivity to chemical stimuli after unilateral removal of the pelvic ganglion. suggest that the enlarged responses to nerve stimulation 1 week postoperatively are mainly due to sensitization, while those observed at the later stages are due to collateral sprouting from the cholinergic nerve fibres of the intact pelvic nerve.
Neuronal VIP in salivary glands: Distribution and release
Authors: UDDMAN ROLF , FAHRENKRUG JAN , MALM LARS , ALUMETS JAN , HÅKANSON ROLF , SUNDLER FRANK
Published: December 2008

Nerves containing vasoactive intestinal peptide (VIP) were observed in salivary glands of rat, cat and man. VIP nerves were numerous in the cat while they were moderate in number in rat and man. The measured concentrations of immunoassayable VIP were in agreement with the immunohistochemical findings. Electrical stimulation of the feline chorda lingual nerve, which stimulates salivary secretion and local blood flow, resulted in a marked elevation of VIP in the venous effluent from the submandibular gland. VIP was not measurable in saliva. Gel permeation chromatography of extracts from cat submandibular gland and from venous plasma collected before and during nervous stimulation revealed one immunoreactive peak with an elution position identical to that of highly purified porcine VIP. The finding of neuronal VIP in salivary glands, its release upon nerve stimulation and its known effect on local blood flow support the view that VIP is a neurotransmitter in the salivary glands.
Distension of pulmonary vein—left atrial junction: Heart rate responses in conscious and anesthetized dogs
Authors: NEVALAINEN T. O. , HAKUMÄKI M. O. K. , HYÖDYNMAA S. J. , NÄRHI M. V. O. , SARAJAS H. S. S.
Published: December 2008

The cardiac chronotropic effects of distension of pulmonary vein‐left atrial junction were investigated in conscious dogs and in dogs anesthetized with intravenous alpha‐chloralose (100 mg/kg) or pentobarbital (30 mg/kg). All the experiments were made on trained, chronically instrumented, closed chest animals held in horizontal position. Inflation of a single small balloon in the junction elicited a tachycardic response both in conscious and chloralose‐anesthetized dogs, while in pentobarbital anesthesia no change in heart rate was found. Contrary to reports of other investigators, no transient bradycardia was found, nor any correlation between predistension heart rate and the increase in heart rate due to the distension. It is suggested that the choice of anesthetic can be done only after its modifying effect on the parameter studied is known. Only the use of trained, chronically instrumented and conscious dogs will reveal this effect.
Temporal dissociation between the negative inotropism and the increase in cyclic GMP level induced by choline esters in spontaneously beating rat atria preparations1
Authors: METSÄ‐KETELÄ T. , KUOSA R. , VAPAATALO H.
Published: December 2008

The effects of acetylcholine and carbacholine on cyclic GMP levels and contraction amplitude were investigated simultaneously in spontaneously beating rat atria preparations. Both drugs at the concentrations of 5times10‐‐7M or higher produced a very rapid decline of amplitude. However, the cyclic GMP level was not elevated earlier than 5 s later, when the amplitude was already reduced to 50% of the initial value. Concentrations of acetylcholine below 5times 10‐‐7M were not able to affect the cyclic GMP level, although they reduced the contractility significantly. Acetylcholine had no effect on the cyclic AMP level. The data demonstrate that cyclic GMP does not mediate the negative inotropic effect of choline esters in rat atria preparations.
Villous tissue osmolality, water and electrolyte transport in the cat small intestine at varying luminal osmolalities
Authors: HALLBÄCK DAN‐AXEL , JODAL MATS , LUNDGREN OVE
Published: December 2008

Villous tissue osmolality and net transport for water, sodium, potassium and chloride were determined in the feline small intestine when exposing the mucosa to solutions with different mannitol concentrations (0, 100, 315 and 600 mmol/l). Tissue osmolality at the villous tip varied with luminal osmolality. At the villous base, on the other hand, tissue osmolality remained around the plasma osmolality regardless of the osniolality of the luminal fluid. Transport rates for water were affected in the way predicted from the lumen to tissue osmolality difference. A net flux from tissue to lumen was always recorded for the studied electrolytes. The hydraulic conductivity (Lp) of the intestinal epithelium with dilated intercellular spaces was estimated from the present results to be around 30times10–12 cm xs‐1xPa‐1. When the intercellular spaces were collapsed Lp was estimated to be 15times10–12 cmxs‐1xPa‐l.
Lipoprotein lipase of human postheparin plasma and adipose tissue in relation to physical training
Authors: MARNIEMI JUKKA , PELTONEN PEKKA , VUORI ILKKA , HIETANEN EINO
Published: December 2008

Adipose tissue lipoprotein lipase and postheparin plasma triglyceride lipase activities were measured in 28 men differing in their physical training activity. They were divided into 4 subclasses based on their training intensity. The two most active classes (17 subjects) having regular heavy exercise at least 4 times a week were considered as the actively training group, and the other two (11 subjects) classes not training regularly as the control group. In postheparin plasma, the lipoprotein lipase activities were not different between the two groups, whereas training subjects had significantly (P<0.02) lower hepatic lipase activities. Adipose tissue lipoprotein lipase activity was in the training group at about 70% higher level on an average than in the controls (P<0.10). A significant positive correlation (r=0.38, P<0.05) was obtained between the adipose tissue lipoprotein lipase activity and the level of physical activity. Our data suggest that even moderate inter‐group differences in the physical training activity are reflected as measurable alterations in the adipose tissue lipoprotein lipase activity in man.