bluuebunny/crossref_metadata_2025 huggingface dataset:
In the eye (D‐Pro2, D‐Trp7,9)‐SP is a substance P agonist, which modifies the responses to substance P, prostaglandin E1 and antidromic trigeminal nerve stimulation
Authors: MANDAHL AGNETA , BILL ANDERS
Published: December 2008

A substance P analogue, (D‐Pro2, D‐Trp7,9)‐SP, has been described to have SP antagonistic and SP agonistic effects in different tissues. We have investigated the effects of (D‐Pro2, D‐Trp7,9)‐SP on the sphincter pupillae muscle, the blood aqueous barrier (BAB) and the intraocular pressure (IOP) in the albino rabbit eye. We also investigated the modifying effects of (D‐Pro2, D‐Trp7,9)‐SP on miosis, BAB damage and IOP rise caused by SP, prostaglandin E1 (PGE1), capsaicin and on the miosis caused by electrical intracranial antidromic trigeminal nerve stimulation (NV stim). Endogenous PG synthesis was inhibited by systemic indomethacin i. v., cholinergic influence on the pupil size was inhibited with biperiden, i. v., adrenergic nerve influence by cervical sympathectomy just prior to the expts. Tubocurarine chloride was used to cause relaxation of striated muscles in the expts with NV stim. We found 100 μg (D‐Pro2, D‐Trp7,9)‐SP to cause miosis, breakdown of the BAB with heavy leakage of Evans blue into the ciliary processes and aqueous humor, and a rise in IOP. At 10 μg (D‐Pro2, D‐Trp7,9)‐SP caused slight miosis and did not inhibit the miosis caused by SP or capsaicin, but caused a significant reduction of the miotic response caused by PGE1 and NV stim. The rise in protein concentration in the aqueous humor caused by SP or PGE1 was slightly but significantly lower after pretreatment with (D‐Pro2, D‐Trp7,9)‐SP. Thus (D‐Pro2, D‐Trp7,9)‐SP was found to act as a SP agonist on the sphincter pupillae muscle, on the BAB and IOP. However, (D‐Pro2, D‐Trp7,9)‐SP seemed to have some SP antagonistic effects on mechanisms that require sensory nerve conduction e. g. miosis caused by PGE1 and NV stim. The antagonistic mechanism is not clear. The SP analogue may have an unspecific membrane stabilizing effect or a toxic effect or block SP receptors on the sensory nerve fibers. Such effects of (D‐Pro2, D‐Trp7,9)‐SP may explain also why the rise in protein concentration in the aqueous humor caused by SP and PGE1 was lower in eyes pretreated with (D‐Pro2, D‐Trp7,9)‐SP.
Morphology, distribution, and specificity of olfactory receptor cells in salmonid fishes
Authors: THOMMESEN GEORG
Published: December 2008

Electrophysiological and anatomical investigations of the olfactory epithelium of three salmonid species have been coordinated. Different corridors in the olfactory rosettes were examined by recording of the electro‐olfactogram (EOG) using two recording electrodes simultaneously against one common indifferent electrode. Biopsies comprising the two lamellae bounding each of the examined corridors were examined by scanning electron microscopy (SEM). The electrophysiological results confirm a higher relative density of bile salt‐receptors in the peripheral parts of all the corridors, and a higher relative density of amino acid‐receptors in central parts. The SEM micrographs show that ciliated receptor cells are more numerous than microvillous ones. The density of ciliated receptor cells increases towards the peripheral margin of each lamella. The density of microvillous receptor cells increases towards the central margin. The correspondence between the electrophysiological and the anatomical observations support the hypothesis that the ciliated receptor cells are those specific to bile salt‐like substances, the microvillous those specific to amino acids.
Morphology of the brachial biceps muscle and elbow flexion in man
Authors: NYGAARD E. , HOUSTON M. , SUZUKI Y. , JØRGENSEN K. , SALTIN B.
Published: December 2008

This study was undertaken to determine whether skeletal muscle fibre characteristics could be demonstrated to be of significance for muscle function in voluntary contraction in man. 4 male and 4 female adult subjects were studied. During elbow flexion force and velocity was measured at the hand with the forearm in a 100° position. A motor‐driven heavy flywheel guaranteed a constant velocity of movement at the time of measurement. Force was registered by a straingauge dynamometer, and velocity by two sets of photocells. Cross‐sectional area of the brachial biceps muscle was determinded by computerized tomography scanning. Muscle fibre composition and fibre cross‐sectional areas were assessed histochemically on needle biopsy samples obtained superficially from the brachial biceps muscle, the more superficial of the two large elbow flexor muscles. At contraction velocities from 2 to 7 radians per second (rad/s) a close relationship existed between the relative force output and the relative area of fast‐twitch fibers (p<0.01). Maximal voluntary isometric contraction force averaged 189 N (120 to 309 N), and showed a close relationship with total cross‐sectional area of the brachial biceps muscle. The specific tension (maximal isometric tension) of the muscle averaged 33 N/cm2 with no demonstrable difference between subjects of widely different fibre compositions, suggesting that maximal tetanic tension is similar in fast‐ and slow‐twitch fibres in man.
Kinetics of the TEA and 4‐AP sensitive K+ current in the slowly adapting lobster stretch receptor neurone
Authors: GESTRELIUS S. , GRAMPP W.
Published: December 2008

The kinetics of the TEA and 4‐AP sensitive K+ current (Ik) in the slowly adapting lobster stretch receptor neurone were investigated in sub‐and near‐threshold voltage regions using electrophysiological and pharmacological techniques. In dynamic conditions Ik was found to display both fast and slow reactions. These were attributed to a Hodgkin‐Huxley type of K activation, and a slow type of K inactivation, respectively. The slow K inactivation could be shown to be unrelated to K+ flux dependent changes in intra‐and pericellular K+ concentrations. Its stationary voltage dependence was however shifted in a depolarizing direction by increasing, and in hyperpolarizing direction by decreasing the extracellular Ca++ concentration. In view of these findings, and of its kinetic properties, the slow K inactivation was classified as a genuine channel gating process. The process of K activation was too fast for a dynamic analysis with the recording technique available. An estimate of its stationary voltage dependence could however be obtained in a voltage range from about ‐100 to about ‐40 mV. The experimental observations were utilized in the formulation of a mathematical model describing the kinetic behaviour of Ik in the present preparation based on constant field and state transition theories.
Peripheral control of the cat's step cycle
Authors: ANDERSSON OLOF , GRILLNER STEN
Published: December 2008

Acute low spinal and curarized cats injected with noradrenergic agonists i.v. can elicit an efferent burst pattern which can be recorded in muscle nerve filaments and can be referred to as “fictive locomotion”. This study investigates the effect that feedback, arising from movements in the hip joint, can exert on the central network generating fictive locomotion. The central network is uncoupled from generating any active movements by curarization. The motor pattern could be entrained by applying sinusoidal hip movements, even when a very extensive denervation of the leg had been performed leaving only some of the muscles around the hip and the hip joint innervated. During flexion movements, efferents to different flexor muscles became active and during movements in the reverse direction (extension), efferents to extensors were active. With an increasing movement frequency the onsets of both flexor and extensor bursts were delayed in the movement cycle. The duration of the extensor bursts varied markedly with the movement cycle, whereas pure flexors changed less in burst duration. The frequency range within which the efferent burst activity was entrained in a strict 1:1 relation to the movement varied between 5 to 70% above and below the resting burst period. In preparations with a narrow 1:1 range, a “relative coordination” was encountered outside this range. The flexor burst duration was in these cases dependent on where in the hip movement cycle the bursts appeared.
Plasma renin activity and plasma aldosterone concentration in pregnant and lactating goats in different sodium states
Authors: BENLAMLIH S. , KARLBERG B. E.
Published: December 2008

Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were compared in 8 goats (5 delivering twins = TP, 3 delivering one kid = SP) during pregnancy, lactation, and anestrus during sodium replete and sodium deplete conditions. Sodium depletion was provoked by intravenous infusions of furosemide (10 mg followed by 0.2 mg/min for 3 h) causing huge natriuresis and kaliuresis. The drinking response was not sufficient to compensate for the renal water loss. The plasma Na concentration had fallen by 1–2 mmol/1 the day after the infusion and the plasma K concentration fell during the infusion by 0.4 to 0.6 mmol/1 and remained low the day after the infusion. Total plasma protein increased by 7 g/1 (pregnancy and lactation) and by 11 g/1 (anestrus) and the hematocrit by about 2% during the infusions. PRA and PAC differed markedly in SP goats vs TP goats and during pregnancy vs lactation and anestrus. In sodium replete pregnant TP goats, PRA was higher than during lactation or anestrus and in these animals, furosemide caused a large elevation of PRA, which remained elevated also the day after the infusion. The mean PAC was elevated in sodium replete pregnant TP goats and furosemide infusions induced further increases in mean PAC values. However, the individual differences were large, and only 3 of the 5 TP goats were responsible for these effects. PRA of sodium replete SP goats were not elevated during pregnancy and the response in PRA to furosemide was similar during pregnancy, lactation and anestrus. Basal PAC of the SP goats was of the same order during pregnancy, lactation and anestrus. 2 TP and 2 SP goats were subjected to a load of hypertonic NaCl, and they excreted the extra Na as efficiently during pregnancy as during anestrus. During the NaCl infusions the goats drank double the amount during pregancy as compared to their consumption during anestrus. PAC fell in all animals but after the NaCl infusions the PAC returned to initial values or above within 2 h in the TP goats but not in the SP goats. Glomerular filtration rate was found to be higher in two TP goats with elevated basic PAC than in two TP goats with low basal PAC values. The role of the renin‐angiotensin‐aldosterone system during pregnancy is discussed in relation to the arterial pressure, to the levels of progesterone and estrogen, and to the water intake in pregnant goats. The inconsistent correlation between PRA and PAC indicates a possible hyperreactivity of the adrenal cortex in some pregnant TP goats.
Mechanisms of leukotriene‐induced contractions of guinea pig airways: Leukotriene C4 has a potent direct action whereas leukotriene B4 acts indirectly
Authors: DAHLÉN SVEN‐ERIK , HEDQVIST PER , WESTLUND PÄR , GRANSTRÖM ELISABETH , HAMMARSTRÖM SVEN , LINDGREN JAN ÅKE , RÅDMARK OLOF
Published: December 2008

The leukotrienes (LT's) are a group of arachidonic acid derivatives implicated as mediators of allergic bronchoconstriction and acute inflammation. Tracheal spirals and strips of lung parenchyma from guinea pigs were used under non‐flow conditions to characterize the contractions caused by LTA4, LTB4 and LTC4. Cumulative administrations of leukotrienes desensitized the lung strip, whereas non‐cumulative dose‐response relationships for the leukotrienes and histamine were reasonably parallel. Half maximal contractions of the lung strips were obtained at a final bath concentration of 1 nM for LTC4 and 300 nM for LTA4 or LTB4, as compared with 6000 nM for histamine. In the trachea, LTC4 was approximately 100 times more potent than LTA4 and histamine. Leukotrienes B4 and C4, but not acetylcholine or histamine, elicited release of the bronchoconstrictive thromboxane A2 from the lung under non‐flow conditions. Indomethacin blocked the contractile response to LTB4, whereas the contractile effect of LTC4 remained unaltered. The β‐adrenoceptor agonist isoproterenol and the LTC4 antagonist FPL 55712 attenuated the contraction, but not the release of thromboxane A2, induced by LTC4. Changing to a perifusion technique rendered the lung strips less sensitive to the direct action of LTC4, and released thromboxane A2 now contributed significantly to the contractile response. In addition, the perifusion experiments indicated that LTB4 released histamine as well. We conclude that the chemoattractant LTB4 is an indirectly acting bronchoconstrictor, whereas the slow reacting substance LTC4 contracts the airway muscle by a predominantly direct mechanism. The exquisite bronchoconstrictive activity of LTC4 may be unrelated to its ability to induce formation of thromboxane A2.
Time characteristics and potential dependence of early and late adaptation in the crustacean stretch receptor
Authors: SWERUP C. , RYDQVIST B. , OTTOSON D.
Published: December 2008

The receptor potential of the crustacean stretch receptor evoked by a ramp and hold stretch is depolarizing and consists of an initial peak followed by a static phase. The receptor current, defined as the stretch induced current change is inward and has a similar appearance. The adaptive fall of the receptor potential and receptor current occurs in two phases which can be separated by their different time characteristics. Using intracellular recordings including potential clamp an attempt has been made to fit experimental values of the adaptive fall of the potential and current response to a double exponential function. Ramp and hold stretches with a rise time of about 7–15 ms were used. The time constants were determined with the cell clamped or polarized to different holding potentials. It was found that the adaptive fall for both potential and current could be fitted reasonably well by double exponential functions with an initial fast phase and a second slow phase. For the potential response the time constant of the early adaptive fall, τ1, varied with holding potential, having a minimum of approximately 3 ms at about ‐50 mV.τ1 for the current response showed a similar variation with holding potential, although less pronounced than for the potential response. The minimum value was about 5 ms. The time constant, τ2, of the late phase of adaptation both for the current and potential response was about 500 ms and did not vary in a systematic way with holding potential. The results are consistent with the idea that the first phase of adaptation is related to ionic mechanisms in the membrane of the receptor neuron while the second phase might be caused by mechanical factors
Influence of low muscle temperature on muscle metabolism during intense dynamic exercise
Authors: BLOMSTRAND E. , BERGH U. , ESSÉN‐GUSTAVSSON B. , EKBLOM B.
Published: December 2008

Eight males performed intense leg cycle exercise at a constant rate of work averaging 350 W, according to three different protocols: 1) “Cold exhaustive” exercise (initial muscle temperature (Tm)=29°C), 2) “Warmnon‐exhaustive” exercise (initialTm=34°C)forthe same period of time as in 1), and 3) “Warm exhaustive” exercise (initial Tm=34°C). In five subjects the concentration of various muscle metabolites was determined before and immediately, 1 min, and 5 min after exercise. Blood lactate concentration was determined before and repeatedly after exercise. At low Tm maximal work time was considerably shorter for all subjects compared to normal Tm, 1.3 and 2.1 min, respectively. Comparing conditions 1) and 2) oxygen deficit and the decrease in ATP and CP content were the same in the two experiments. There was a significantly higher concentration of glucose‐6‐phosphate 17.6±10.1 and 8.0±6.2 mmol·kg dw‐1, respectively, and a tendency to higher lactate concentration 60±36 and 33±14 mmol·kg dw‐1, respectively, immediately after exercise in the “cold exhaustive exercise”. Peak blood lactate concentration appeared significantly later after “cold exhaustive” exercise indicating a slower elimination rate of lactate from the muscle compared to “warm non‐exhaustive” exercise. The reduction in performance observed at low Tm may partially be explained by an increased accumulation rate of lactate in four of five subjects.
Interaction between propranolol and electron donors in altering the calcium ion‐dependent potassium ion‐permeability of the human red blood cell membrane
Authors: SKULSKII I. A. , MANNINEN V.
Published: December 2008

Both propranolol and the electron donors ascorbate plus phenazine methosulfate increase the K+‐permeability of the red blood cell membrane. The present investigation examined whether these effects were additive. Contrary to expectations, propranolol added after electron donors sharply inhibited the K+ (86Rb) efflux induced by such donors, without forming new K+ channels analogous to those induced by propranolol in intact red blood cells. The inhibitory effect of propranolol may be due to generalized disturbances of membrane structures necessary for the functioning of the K+ channels organized in the presence of reducing agents. In contrast, the electron donors added after propranolol caused a further stimulation of the 86Rb loss from the propranolol‐treated red cells. The combined effect of these drugs therefore depends on the order of their addition. The possible mechanism of their interaction is briefly discussed.
Skeletal muscle morphology, metabolism and function in smokers and non‐smokers. A study on smoking‐discordant monozygous twins
Authors: LARSSON LARS , ÖRLANDER JAN
Published: December 2008

Differences in skeletal muscle characteristics between smokers and non‐smokers have been demonstrated in a previous study (Örlander, J. et al. 1979, Acta Physiol Scand 107: 39–46). In order to decide whether these differences had a genetical background, six pairs of smoking‐discordant monozygous twins were studied with respect to muscle (vastus lateralis) morphology, metabolism and function. The percentage type I fibres was lower in the smokers, who also had smaller diameters of this fibre type. Cytochrome oxidase activity was decreased in the smokers. No differences were seen for other enzymes of energy metabolism, capillary density, isometric or dynamic strength, or short‐term muscular endurance. The non‐smokers tended to be more physically active. In four ex‐smoker/non‐smoker pairs, no significant differences were found for the investigated parameters. It was concluded, that the difference in fibre type distribution is not due to a hereditary predisposition to take up smoking. Furthermore, the small difference in physical activity level is an unlikely cause. Thus, smoking per se appears to be the most plausible explanation for the difference in fibre type distribution and associated muscle characteristics. No definitive conclusion regarding the reversibility of the smoking‐related differences can be drawn from the present results.
Renal excretion of prostaglandin metabolites, arginine vasopressin, and sodium during endotoxin and endogenous pyrogen induced fever in the goat
Authors: JÓNASSON H. , BASU S. , ANDERSSON B. , KINDAHL H.
Published: December 2008

Responses to intravenous injections of an endotoxin (E. coli‐lipopolysaccharide, 1 μg/kg b.wt.) and endogenous pyrogen were studied in euhydrated and hyperhydrated goats. The biphasic febrile response to the endotoxin was associated with a pronounced increase in the renal excretion of measured prostaglandin (PG) metabolites (11‐ketotetranor PGF metabolites). This increase was time‐correlated with the elevation of the rectal temperature, and (in hyperhydrated animals) with an inhibition of the water diuresis and an increase in renal excretion of arginine vasopressin (AVP). Other effects of the endotoxin were an immediate depression of renal Na and K excretion followed by the development of pronounced natriuresis, and a reduction of plasma Fe and Zn concentrations. The appearance of the febrile reactions (peripheral vasoconstriction and shivering) was accompanied by miosis. The maximum elevation of the rectal temperature was significantly greater during euhydration than during hyperhydration. Also endogenous pyrogen elicited miosis concomitant with febrile reactions, and an elevation of the renal excretion of PG metabolites which was closely correlated in time with the monophasic febrile response, and (during hyperhydration) with temporary inhibition of the water diuresis and an increase in the renal AVP excretion. However, the responses were much weaker than the corresponding endotoxin effects. No appreciable changes in renal excretion of Na and K were observed in response to the endogenous pyrogen. It is concluded that the observed effects on renal cation excretion were manifestations of direct endotoxin influences on kidney function. The possibilities are discussed that the observed stimulation of the AVP release might have been secondary to increased PG liberation, and that the miosis was the manifestation of direct pyrogen stimulation of cerebral pupillomotor neurons. The close temporal correlation between the PG response and the elevation of the rectal temperature could be regarded as further indirect support of the idea that some component of the PG system acts as CNS mediator in the fever mechanism.
Hypertonic KCI, NaCI and capsaicin intracamerally causes release of substance P‐like immunoreactive material into the aqueous humor in rabbits
Authors: MANDAHL AGNETA , BRODIN ERNST , BILL ANDERS
Published: December 2008

We have investigated release of substance P‐like immunoreactivity (SPLI) into the anterior chamber of the rabbit eye evoked by stimuli which cause non‐cholinergic miosis. In a recent study such miosis was reported to be blocked by the substance P analogue (D‐Arg1 D‐Pro2 D‐Trp7,9 Leu11)‐SP. Mechanical intracranial antidromic trigeminal nerve stimulation caused marked SPLI release presumably from primary sensory nerve endings in the anterior part of the eye. Intermittent stimulation for 20 min was not more effective than stimulation for 10 min. Intracameral injection of either 20 μl 4.65 M KCl, 20 μl 4.65 M NaCl or 100 μg capsaicin also caused SPLI release. Intracameral injection of 70 μl 150 mM KCl, 28 μg prostaglandin E1 or 200 μg of compound 48/80 did not cause detectable SPLI release.
Induced development of proximal tubular NaKATPase, basolateral cell membranes and fluid reabsorption
Authors: APERIA ANITA , LARSSON LARS
Published: December 2008

We have previously demonstrated that adrenal corticoid hormones (ACH) induce NaKATPase activity in immature proximal tubular (PT) cells in rats. We have now determined the effect of betamethasone (beta) and aldosterone (aldo) on the size of PT basal and lateral cell membranes (BLM), PT fluid reabsorption (J v (a)) measured in vivo with the split drop technique and PT NaKATPase activity in 20‐day‐old (young) and 40‐day‐old (adult) rats. Serum levels of ACH were the same in young and in adult rats, but adrenalectomy caused a significantly larger fall in NaKATPase activity in young than in adult rats. BLM surface area (μm2/μm‐3 cell volume), J v (a) and NaKATPase were significantly lower in young than in adult rats. Three‐day treatment with high doses of beta (60 μg· 100 g‐1 or aldo (40 μg· 100 g‐1) significantly increased BLM surface area, J v (a) and NaKATPase activity in young but not in adult rats. Three days after adrenalectomy, J v (a) was significantly depressed in adult rats. There was a significant correlation between the ACH‐dependent changes in NaKATPase activity and J v (a). Short‐term treatment (2–3 hours) with high doses of ACH did not significantly increase NaKATPase activity and J v (a) in young rats.
Characteristics of dopamine and GABA transport in primary cultures of astroglial cells
Authors: HANSSON ELISABETH , ISACSSON HELENA , SELLSTRÖM ÅKE
Published: December 2008

Primary astroglial cultures were grown from newborn rat cerebral hemispheres. Cultures, aged 7 and 14 days, were analysed with respect to their capacity to accumulate radioactive GABA and dopamine. Concentrative high‐affinity uptake, showing Na4‐dependence was observed for GABA where Kmand Vmaxwere not significantly altered with age of the culture. No Na+‐dependent high‐affinity transport of dopamine was observed. The addition of 0.1 mM dibutyryl‐cyclic‐3′‐5′‐adenosinemonophosphate (dB‐cAMP) after removal of fetal calf‐serum reduced the Vmaxas well as the Kmof3H‐GABA uptake. The ionic dependence of3H‐GABA and3H‐dopamine was not significantly altered following this treatment. The results are difficult to interpret in terms of a potentiated differentiation of the cells.
Kinetic aspects of human platelet monoamine oxidase thermolability
Authors: WAHLUND L.‐O. , SÄÄF J. , ROSS S. B. , WETTERBERG L. , SMEDBY Y.
Published: December 2008

Monoamine oxidase in platelets collected on two different occasions, from twelve apparently healthy subjects, were studied. The influence of human platelet poor plasma (PPP) on MAO thermolability and variation in enzyme activity over time was investigated. A 30–70% reduction of the activity was observed after heat treatment at 52°C for 30 min. Activity of MAO was determined before (C) and after heat treatment (H). No significant differences between the H/C ratios on the two occasions were observed for either Vo, Vmax or Km with or without 10% PPP added to the incubates. A temporal increase of the kinetic parameters was observed. The magnitude of this increase was smaller for vo than for apparent Km and Vmax. Platelet MAO activity regulation by human PPP is discussed.
Modes of thermal protection in newborn muskoxen (Ovibos moschatus)
Authors: BLIX A.S. , GRAV H.J. , MARKUSSEN K.A. , WHITE R.G.
Published: December 2008

The muskoxen (Ovibos moschatus), a native of Greenland and the Canadian North West Territories, give birth in late April, and the newborn calves are known to tolerate an ambient temperature (Ta) of ‐35°C.At birth the calves weigh about 8 kg, increasing in weight with 0.6 kg. day‐1 for the first 30 days. With a deep body temperature (DBT) of 39.5°C (range 37.7–41.3°C) the newborn calves are consequently able to maintain a thermogradient of at least 70°C between body core and the environment. The calves use primarily two modes of thermal protection: High metabolic heat production and prime fur insulation. Metabolic rate was about 3.5 W.kg‐1 at thermoneutrality in calves aged from 8 h to 7 days. Lower critical temperature at this age was about ‐7°C and a drop in Ta to ‐30°C increased metabolism to about 5.3 W.kg‐1.Upper critical temperature at age 4–7 days is as low as 20°C, while it in calves aged only 18–24 h appears to be even lower. The calves possess great amounts of brown adipose tissue (BAT) at birth. Mitochondria from the BAT deposits were isolated and found to be in an extremely loose‐coupled state with a great capacity for thermogenesis. Skeletal muscle contained very few mitochondria and is hardly employed in aerobic non‐shivering thermogenesis. Calves shiver visibly while drying just after birth, but are normally not seen shivering thereafter. The conductance value for the dry pelt of newborn calves averaged 3.2 W.m‐2.°C‐1 (n=4).Wetting of the pelt with ice‐water at a Ta of 3°C increased conductance to 8.8 W.m‐2.°C‐1.The conductance of the pelt was also influenced by wind, being 10 W.m‐2.C‐1 at a windspeed of 10 m. sec‐1.The legs of the newborn calves are heavily furred and countercurrent circulation is not present, subcutaneous temperature just above the hooves being +29.8°C at Ta of ‐24°C as compared to 37.5°C on the back. The newborn calves could cope with a Ta of ‐30°C without apparent problems under experimental conditions, but they suffered hypothermia when exposed to a Ta of ‐33°C in combination with wind of 10 m. sec‐1.At birth these calves are, however, able to walk, albeit with difficulty, with a DBT of 31°C.Wetting of the intact newborn calf with ice‐water at a Ta of +6°C was tolerated, but the calves will most certainly succumb to the unlikely event of wetting of the pelt combined with strong winds.
Trunk movements in human locomotion
Authors: THORSTENSSON ALF , NILSSON JOHNNY , CARLSON HANS , ZOMLEFER MICHAEL R.
Published: December 2008

Trunk movements in the frontal and sagittal planes were studied in 10 healthy males (18–35 yrs) during normal walking (1.0–2.5 m/s) and running (2.0–6.0 m/s) on a treadmill. Movements were recorded with a Selspot optoelectronic system. Directions, amplitudes and phase relationships to the stride cycle (defined by the leg movements) were analyzed for both linear and angular displacements. During one stride cycle the trunk displayed two oscillations in the vertical (mean net amplitude 2.5–9.5 cm) and horizontal, forward—backward directions (mean net amplitude 0.5–3 cm) and one oscillation in the lateral, side to side direction (mean net amplitude 2–6 cm). The magnitude and timing of the various oscillations varied in a different way with speed and mode of progression. Differences in amplitudes and timing of the movements at separate levels along the spine gave rise to angular oscillations with a similar periodicity as the linear displacements in both planes studied. The net angular trunk tilting in the frontal plane increased with speed from 3–10°. The net forward‐backward trunk inclination showed a small increase with speed up to 5° in fast running. The mean forward inclination of the trunk increased from 6° to about 13° with speed. Peak inclination to one side occurred during the support phase of the leg on the same side. Peak forward inclination was reached at the initiation of the support phase in walking, whereas in running the peak inclination was in the opposite direction at this point. The adaptations of trunk movements to speed and mode of progression could be related to changing mechanical conditions and different demands on equilibrium control due to e.g. changes in support phase duration and leg movements.
Determinants of pulmonary blood volume. Effects of acute changes in pulmonary vascular pressures and flow
Authors: THORVALDSON JØRGEN , ILEBEKK ARNFINN , LERAAND SEVERIN , KIIL FREDRIK
Published: December 2008

To examine the effects of pulmonary vascular pressures and flow on pulmonary blood volume (PBV), experiments were performed at constant heart rate and zone 3 conditions (mean left atrial pressure (LAP) above airway pressure) in six anesthetized, open‐chest dogs. PBV was calculated as the product of electromagnetic aortic flow and pulmonary mean transit time for ascorbate, obtained without blood withdrawal by polarographic recording of aortic ascorbate changes. In three series of experiments LAP was raised similarly in three steps, from 4.5 to 14.8 mmHg: by mitral constriction which reduced pulmonary blood flow, by blood volume expansion which more than doubled pulmonary blood flow, or by a combination of the two procedures which kept pulmonary blood flow constant. In all three series, LAP and mean pulmonary arterial pressure (PAP) rose in proportion, but PBV was better correlated to PAP (r=0.87±0.02) than to LAP (r=0.66±0.09). These experiments suggest that PAP is the most important factor in determining PBV under zone 3 conditions, whether PAP is raised by increasing pulmonary blood flow or by mitral constriction.
Histochemical study of the distribution of carbonic anhydrase in the cat brain
Authors: RIDDERSTRÅLE YVONNE , HANSON MARK
Published: December 2008

The distribution of carbonic anhydrase (CA) in cerebrum, cerebellum and medulla oblongata of the cat brain has been examined by a histochemical method. Neuron cell bodies and dendrites are stained in some locations. Many axons are distinctly stained and different intensities of staining can be seen even in adjacent axons. One of the most intensely stained structures is the capillary endothelium and stained capillaries are found in all parts examined. Glial cells are intensely stained in agreement with biochemical and earlier histochemical works. Myelin sheaths are never stained, possibly due to enzyme loss during embedding. The localization of the enzyme shows regional differences. In this respect, the medulla oblongata has been examined in more detail. A small area close to the ventral surface, medial to the roots of the hypoglossal nerve, is characterized by a high CA staining of the neuropil. The cell membrane of some large neurones and the capillary endothelium in this area were also stained. With regard to position and CA content, this area corresponds well to the characteristics of the medullary chemosensitive area as defined by previous experimental studies.
Electrical resistance of arterioles and venules in the hamster cheek pouch
Authors: OLESEN SØREN‐PETER
Published: December 2008

The electrical resistance of the vascular endothelium was determined on single microvessels in the hamster cheek pouch in order to obtain information about this variable in a mammalian preparation. So far, the technique has only been applied to frog microvessels. The technique consists of injection of current into the vascular lumen via a microelectrode and recording of the ensuing intravascular potential distribution by a second microelectrode. Cable theory was used for the analysis. The average diameter of the vessels under study was 41 μm for arterioles and 28 μm for venules. The average resistance of the vessel wall at 37oC was 19 ωcm2 and 3.3 ωcm2, respectively. For the venules this is somewhat lower than what has been recorded on muscle capillaries (Olesen & Crone 1983) in the frog at room temperature, whilst the values on arterioles are rather similar. The calculated sodium permeabilities, PNa+, were for arterioles 4 ± 10‐5 cm. s‐1 and for venules 23 × 10‐5 cms‐1. The high permeability values for arterioles and venules indicate that the vascular exchange function may not be limited to capillaries only.
Time‐dependent heterogeneity of filtration rate in the autoreguiating rat kidney
Authors: SJÖQUIST MATS , GÖRANSSON ANN
Published: December 2008

Experiments were performed to study the regulation of the single‐nephron glomerular filtration rate (SNGFR) in superficial and juxtamedullary nephrons, as the left kidney of Sprague Dawley rats was submitted to a reduced arterial pressure of 70 mmHg by means of an aortic clamp. The SNGFR at different cortical levels was measured 0.5, 1, 5, 20 or 45 min after the reduction, in order to ascertain whether the effects of the regulatory mechanisms are modified with time. A Hanssen technique was used, which allows one determination of filtration rates per animal. At a renal arterial pressure (RAP) of 100 mmHg (= control animals) the SNGFR amounted to 20±1.2 and 23± 0.8 nlmin‐1–g‐1 kidney weight in the outer and inner cortical (OC, IC) nephrons. When RAP was further reduced to 70 mmHg, the autoregulation of SNGFR, determined after 0.5 min, was highly efficient for both OC and IC nephrons (19 ± 2.0, 23 ± 2.6). A prolonged reduction in RAP caused a gradual decline in SNGFR. The filtration rate measured after 5 min was 15 ±1.4 for OC and 20 ± 1.8 for IC nephrons. The decline was most pronounced for OC nephrons, which led to a fractional redistribution in favour of IC nephrons. Thus, SNGFRIC/SNGFRoc was 1.16± 0.065 when RAP was 100 mmHg and 1.41 ± 0.126 after 5 min with an RAP of 70 mmHg. It is well documented that suprarenal aortic occlusion is a powerful stimulus for the release of renin. This was manifested as an increase in the arterial pressure proximal to the aortic clamp. The fractional redistribution to IC nephrons and the loss of autoregulation, when the renal hypotension was sustained, may be an expression of the intrarenal mechanisms attempting to restore RAP. It is likely that the renin/angiotensin system is involved in these processes.
Distribution of fibre sizes in human skeletal muscle. An enzyme histochemical study in m tibialis anterior
Authors: HENRIKSSON‐LARSÉN K. , FRIDEN J. , WRETLING M‐L.
Published: December 2008

The aim of the study was to determine the fibre size distribution within the human m tibialis anterior. Ten‐micron thick cross‐sections of the whole muscle were enzyme histochemically stained for myofibrillar ATPase at pH 9.4. The cross‐sectional area of 100 fibres with low (type 1) ATPase and high (type 2) ATPase activity was measured in three different regions (superficial, central and deep). Both the type 1 and type 2 fibres were found to be larger in the deep region than in the central or superficial regions. The variation in fibre size could not be explained by the cryofixation or cryo‐embedding techniques used. The data suggest that muscle adaptation to physical demands may not only occur by means of variation in types and number of muscle fibres, but also by variation in fibre size over the muscle cross‐section.
Effect of oestrogen and progesterone on the blood flow in the lower urinary tract of the rabbit
Authors: BATRA S. , BJELLIN L. , IOSIF S. , MARTENSSON L. , SJÖGREN C.
Published: December 2008

The effects of oestrogen and of oestrogen combined with progesterone were examined on the fractional distribution of cardiac output (blood flow) in the genitourinary tissues of the female rabbit. Oestradiol treatment significantly increased blood perfusion in the uterus, vagina and urethra but caused no change in the perfusion of the urinary bladder or the kidneys. The wet weight of the uterus and vagina increased significantly and in the urethra there was a tendency to weight gain following oestradiol treatment. Progesterone treatment following oestrogen appeared to reduce the effect of oestrogen on both perfusion and weight gain.
Erythrocyte 2,3‐diphosphoglycerate, Po2 50% and available O2 in rabbits with bleeding anaemia superimposed on the early post‐natal fall in haemoglobin
Authors: HOLTER P. H. , REFSUM H. E.
Published: December 2008

Erythrocyte 2,3‐diphosphoglycerate (2,3‐DPG), Po250%, whole blood haemoglobin (Hb), haematocrit (Hct) and available O2 were determined in two matched groups of suckling rabbits from the 17th to the 34th day after birth. One group was subjected to repeated bleeding, amounting to 1.0–1.5% of the body weight, on day 17, 19, 22 and 25, while the other served as control. The bleeding group had markedly lower Hb and Hct than the control group, which showed the ordinary post‐natal fall in Hb. There were, however, no differences between 2,3‐DPG and Po250% in the two groups. The changes were essentially the same as observed previously in animals in which the post‐natal anaemia was avoided by iron‐treatment. Thus, these and previously reported data show that the post‐natal rise in 2,3‐DPG and Po250% within wide limits is uninfluenced by marked variations in Hb, even severe bleeding anaemia, and support the assumption that the post‐natal rise in 2,3‐DPG and Po250% is dominated by processes related to the growth and maturation of the animals.
Changes in leg movements and muscle activity with speed of locomotion and mode of progression in humans
Authors: NILSSON JOHNNY , THORSTENSSON ALF , HALBERTSMA JÑ
Published: December 2008

Knowledge of adaptations to changes in speed and mode of progression (walking‐running) in human locomotion is important for an understanding of underlying neural control mechanisms and allows a comparison with more detailed animal studies. Leg movements and muscle activity patterns were studied in ten healthy males (19–29 yr) during level walking (0.4‐3.0 m‐s‐1) and running (1.0–9.0 m‐s‐1) on a motor‐driven treadmill. Movements were recorded in the sagittal plane with a Selspot optoelectronic system. Recordings of EMG were made from seven different muscles of one leg by means of surface electrodes. Durations, amplitudes and relative phase relationships of angular displacements and EMG activity were analysed in relation to different phases of the stride cycle (defined by the leg movements). The durations of the entire stride cycle and of the support phase were found to decrease curvilinearly with velocity. Swing and support phase durations were linearly related to cycle duration in walking, and curvilinearly related in running. The characteristic occurrence of double support phases in walking was also seen in very slow running. Support length increased with speed up to about i,2 m both in walking and running, but was longer in walking at the same velocity. Increases in net angular displacements were largest for hip movements and for knee flexion‐extension during the swing phase in running. With increasing velocity a clear shift in relative rectus femoris activity occurred from knee extension to hip flexion. Gastrocnemius lateralis (LG) was co‐activated with the other leg extensors prior to foot contact in running, whereas in walking LG was not turned on until later in the support phase. The ankle flexor tibialis anterior had its main peak of activity after touch‐down in walking and before touch‐down in running. The same basic structure of the stride cycle as in other animals suggests similarities in the underlying neural control. Human speed adaptation is distinguished primarily by an increase in both frequency and amplitude of leg movements and by a possibility of changing between a walking and a running type of movement pattern.
Studies on the integrated extrinsic nervous control of rectal motility in the cat
Authors: HEDLUND H. , FASTH S. , HULTÉN L. , NORDGREN S.
Published: December 2008

The effect of sympathetic nervous activity on rectal motility induced by pelvic nerve stimulation (PNS) was studied in anaesthetized cats. Division of the sympathetic lumbar colonic and hypogastric nerves or alpha‐adrenoreceptor blockade, both of which reduced rectal tone, also reversed a predominantly relaxatory pelvic nerve response into a pure contraction. Contractions to pelvic nerve stimulation were reduced by simultaneous lumbar colonic nerve stimulation. This lumbar colonic nerve‐induced inhibition was augmented by alpha‐adrenoceptor blockade and abolished by beta‐blockade. Close intra‐arterial injection of a beta‐adrenergic agonist reduced contractions to PNS, while an alpha‐adrenergic agonist had no effect. Stimulation of the hypogastric nerves enhanced rectal contractions to simultaneous PNS. The apparent similarity with the arrangement of extrinsic nervous control of the internal anal sphincter suggests that the rectum is functionally involved in continence mechanisms.
Changes in transcapillary exchange induced by perfusion fixation with glutaraldehyde, followed by measurements of capillary filtration coefficient, diffusion capacity and albumin clearance
Authors: HARALDSSON BÖRJE , JOHANSSON BENGT R.
Published: December 2008

The isolated, maximally vasodilated rat hindquarter preparation was used to determine how fixation of the vascular bed (glutaraldehyde, 2.5% in 0.05 M Na‐cacodylate with dextran 40 g.l‐1) affected transcapillary filtration and diffusion events, as well as macromolecular transfer, measured as transport of water (CFC), of small solutes (PS) and of 125I‐albumin. Vascular conductance to flow was decreased by 52% after fixation. The three capillary permeability‐surface area parameters were reduced almost equally to 50% of control after fixation, i.e. the relative flux rates of water, small and large molecules were similar in the living and in the fixed vascular bed. As this fall in transendothelial exchange was larger than the calculated degree of wall shrinkage of the resistance vessels, it could not be ascribed simply to a uniform shrinkage which also involved the capillaries. Rather, the fixation appears to have induced closure of entire capillaries. As a consequence, the surface area for exchange is reduced, with no apparent changes in membrane ‘permselectivity’.
No correlation between membrane potential and increased cytosolic free Ca2+ concentration, 86Rb+ influx or subsequent [3H]‐thymidine incorporation in neoplastic human B cells stimulated with antibodies to surface immunoglobulin
Authors: HEIKKILÄ REINO , IVERSEN JENS‐GUSTAV , GODAL TORE
Published: December 2008

We have followed the changes in the membrane potential of neoplastic B cells after addition of antibodies to cell specific surface immunoglobulin heavy chains (anti‐Ig). Two methods were used, both based on the distribution of lipophilic fluorescent indicators: the anionic bis(1,3‐diethylthiobarbiturate)‐trimethine oxonol (fluorescence measurement made on whole cell suspensions) and the cationic 3,3‐dihexyloxacarbocyanine iodide (diOC6‐(3)) (using flow cytofluorimetric analysis). By the latter method, the resting membrane potential was calculated to range from ‐40 to ‐63 mV. The stimulatory effect of anti‐Ig was investigated on two B cell populations. In one, which may be stimulated in this way to [3H]‐thymidine incorporation, the membrane potential was apparently unchanged, at least during the first hour of stimulation. In the other population, anti‐Ig induced a rapid depolarization (oxonol method), but these cells did not, on the other hand, respond with [3H]‐thymidine incorporation. The nature of this depolarization was further investigated. Both Na+ and K+ permeabilities appeared increased, while Ca2+ influx did not contribute to the change in membrane potential. Nor did depolarization itself change free cytosolic Ca+ concentration, [Ca2+]i, as estimated by the quin‐2 method. Furthermore, anti‐Ig stimulation increased [Ca2+]i in these cells, even when depolarization was abolished by lowering the extracellular Na+ concentration. Thus, in cells where depolarization could be demonstrated, it was linked neither to early changes in [Ca2+]i nor to late [3H]‐thymidine incorporation. In contrast, such effects of anti‐Ig stimulation were observed in other cells without any significant early change in the membrane potential.
Mechanical output and iEMG of isokinetic plantar flexion in 40–64‐year‐old subjects
Authors: GERDLE BJÖRN , FUGL‐MEYER AXEL R.
Published: December 2008

Peak torque (PT), contractional work (CW) and mean power of isokinetic plantar flexions were measured in unselected, clinically healthy subjects, randomly chosen from the official census lists of Umeå, in three age groups: 40–44, 50–54 and 60–64 years. Simultaneous recordings of integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. PT and CW decreased exponentially with increasing velocity of angular motion and at 60°. s‐1 (r2= 0.79 and 0.63, respectively) were adequately determined by crural circumference, age and sex. The muscular output declined with increasing age. Both output and iEMG showed an approximate 3:2 male: female ratio. Therefore, the ratio CW/iEMG was age, but not sex‐dependent at any given velocity of angular motion. Independently of this age, the iEMGs were inversely proportional to velocity of angular motion, while iEMG/manoeuvre time was constant indicating that torque/velocity and work/velocity exponential relationships are mainly determined by muscular properties. Based on the literature it is suggested that the dependence of the measured parameters on age and sex is determined by muscular properties, rather than by the central nervous system. Moreover, the CW/iEMG ratio appears to provide a comprehensive picture of excitation and mechanical output of the muscle group studied and may therefore be a useful measure.