bluuebunny/crossref_metadata_2025_split huggingface dataset:
Skeletal Muscle Fiber Splitting Induced by Weight‐Lifting Exercise in Cats
Authors: Gonyea W. , Ericson G. C. , Bonde‐Petersen F. 
Published: December 2008

AbstractAdult skeletal muscle hypertrophy induced by exercise has been thought to be exclusively related to an increase in cross‐section area of individual muscle fibers and not to an increase in the number of muscle fibers. Recent experiments using surgical intervention to cause muscle overload have induced an increase in fiber numbers; however, the muscle also exhibited pathological alterations. The purpose of this study was to determine if an exercise regimen also induced hyperplasia. Cats were trained to lift weights with their right forelimb to receive a food reward. After 19–46 weeks of training, the flexor carpi radialis muscle (FCR) was removed and prepared for histochemical examination. The total number of muscle fibers of the right exercised FCR increased significantly (19.3%) when compared with that of the unexercised left FCR (p < 0.05). This increase was found to be due to muscle fiber splitting.
Influence of Acetate on the Metabolism of β‐Hydroxybutyrate in the Perfused Hind‐Quarter of the Rat
Authors: Karlsson N. , Fellenius E. , Kiessling K.‐H. 
Published: December 2008

AbstractThe effect of acetate, at concentrations normally found during ethanol combustion in intact animals and man in vivo, on the uptake and oxidation of β‐hydroxybutyrate by the perfused rat hind‐quarter was studied. The addition of acetate did not significantly affect the total uptake of β‐hydroxybutyrate, but caused a 40 % decrease in the oxidation of β‐hydroxybutyrate to CO2. The oxidation of 14CO2‐hydroxybutyrate to 14CO2 accounted for about 10 % of the total oxygen consumption by the perfused muscle in the absence of acetate. In the presence of acetate this figure was reduced to about 5 %. The addition of β‐hydroxybutyrate did not significantly affect the metabolic fate of 14C‐acetate. It is concluded that acetate is preferred as oxidative substrate to β‐hydroxybutyrate. The inhibited oxidation of β‐hydroxybutyrate by acetate did not affect the concentration ratio between β‐hydroxybutyrate and acetoacetate in the medium at the end of the perfusion, indicating that the ability of the muscle tissue to restore an increased redoxlevel, “exported” from the liver during ethanol combustion to extrahepatic tissues, was not impaired by acetate.
Flow and Composition of Leg Lymph in Normal Men during Venous Stasis, Muscular Activity and Local Hyperthermia
Authors: Olszewski W. , Engeset A. , Icger P. M. , Sokolowski J. , Theodorsen L. 
Published: December 2008

AbstractChanges in normal human leg lymph protein concentration, output, and lymph flow/lymph protein concentration relationship, as well as lactate dehydrogenase and alkaline phosphatase activity were followed during procedures known to increase capillary filtration as venous stasis, muscular exercise and warming of tissues. Lymph flow increased by 83% during two hour ergometer cycling, and by 117% during two hour warm water foot bath. During a two hour period of venous stasis lymph flow dropped by 50%. There was an increase in lymph flow during the rest period following all three types of experiment, most pronounced after foot warming. An inverse relationship between the lymph flow rate and lymph protein concentration was found. Lymph enzymes followed the same pattern of changes as total protein.
Influence of Acetate on the Metabolism of Palmitate in the Perfused Hind‐Quarter of the Rat
Authors: Karlsson N. , Fellenius E. , Kiessling K.‐H. 
Published: December 2008

AbstractThe metabolism of l‐14C‐palmitate and its metabolic interaction with U‐14C‐acetate were studied in the perfused hind‐quarter of the rat. 9% of l‐14C‐palmitate taken up was oxidized to 14CO2 accounting for 7% of total oxygen consumption by the perfused tissue. Most label from l‐14C‐palmitate was found in the lipid fraction of the muscle tissue. In spite of a 40% inhibition of palmitate oxidation, acetate only caused minor changes in the overall metabolism of palmitate. U‐14C‐acetate was mainly oxidized to 14CO2 and the oxygen consumption due to oxidation of acetate accounted for 20–30% of the total oxygen uptake. Minor amounts of 14C‐acetate were found in muscle lipids. The addition of palmitate did not alter the metabolism of acetate. It is concluded that the presence of palmitate did not affect 14C‐acetate metabolism, while the presence of acetate inhibited 14C‐palmitate oxidation. The possible sites of interaction are discussed. The found interaction will probably not contribute to any major extent to the disturbed lipid metabolism found in animals and man during ethanol intake. No major changes in the tissue content of high‐energy phosphate compounds were found in the presence of palmitate or acetate or both.
Contractile Responses to Noradrenaline: Varying Dependence on External Calcium of Consecutive Vascular Segments of Perfused Rat Hindquarters
Authors: Sutter Morley C. , Hallback Margareta , Jones John V. , Folkow Björn 
Published: December 2008

AbstractTo study the dependency of vascular smooth muscle contractions, produced by noradrenaline, on the concentration of extracellular calcium, experiments were performed on adult male Wistar rats. The hemodynamic characteristics of the isolated, perfused hindquarters were investigated from maximal dilatation up to maximal, noradrenaline‐induced constriction under constant flow conditions. Pressor responses to noradrenaline in the consecutive segments of the vascular bed (“proximal” and “distal” precapillary resistance vessels and postcapillary resistance vessels) were determined at low (0.2 mM) and at normal (1.5‐2.0 mM) Ca++ concentrations in the perfusate. Dependence on external calcium is much greater peripherally. The smallest pre‐ and postcapillary resistance vessels are the most dependent while the larger, “proximal” precapillary resistance vessels are the least dependent on the availability of external calcium. The results illustrate the considerable differentiation of smooth muscle, depencling on its location along the vascular circuit. They further indicate that it is likely that the hemodynamically so important microvessels are highly dependent on extrinsic Ca++ sources not only concerning their involvement of remote adrenergic control, but also in their maintenance of normally pronounced “myogenic” tone.
Rate‐dependent Myogenic Response of Vascular Smooth Muscle during Imposed Changes in Length and Force
Authors: Sigurdsson Stefan B. , Johansson Börje , Mellander Stefan 
Published: December 2008

AbstractA recent study of electrical and mechanical responses to stretch in isolated vascular smooth muscle revealed a clear‐cut and graded influence of the rate of change in length, dL/dt (Johansson and Mellander, 1975). This myogenic “dynamic” response at high rates of stretch was much more pronounced than the “static” response to constant, increased (+ 40%) length. In this previous study the mechanical responses were recorded as active force. In view of the fact that myogenic reactions in vivo must be associated with changes in vessel caliber, it was considered of interest to investigate the responses to stretch also in smooth muscle undergoing active shortening. In the present study, as in the one referred to above, electrical and mechanical activity in the isolated rat portal vein was studied by the sucrose gap method. However, in the present experiments the mechanical responses were recorded not only as active force but also as active shortening, making possible a comparison of the myogenic responses under these two types of smooth muscle contraction. Dynamic passive stretch was found to be associated with marked increases in spike discharge and mechanical activity under both these experimental conditions and the quantitative relation between spike discharge and rate of passive stretch (or shortening) was similar. Thus, active shortening of the smooth muscle did not interfere with the ability of the vessel to respond myogenically to passive stretch. A further analysis of the results suggested that, for the preparations as a whole, the dynamic excitatory response was more closely related to the rate of change of passive force, dP/dt, than to dL/dt.
Cardiovascular Control in the Milan Strain of Spontaneously Hypertensive Rat (MHS) at “Rest” and during Acute Mental “Stress”
Authors: Hallbäck Margareta , Jones John V. , Bianchi Giuseppe , Folkow Björn 
Published: December 2008

AbstractThe cardiovascular responses to acute mental “stress” were compared in the Milan strain of spontaneously hypertensive rats (MHS) and in normotensive control rats (NR). Blood pressure and heart rate were followed in pairs of awake MHS and NR, while defence reactions were provoked by alerting stimuli (noise, vibration). No differences were noted between the two groups in response to “stress” although resting heart rate in MHS was lower than in NR. Administration of atropine or propranolol to MHS and NR showed the MHS to have a higher resting vagal tone and lower sympathetic tone than the NR. Subsequent (at least two weeks later) hemodynamic investigation, under nembutal anesthesia, showed no difference in cardiac output between MHS and NR but a higher stroke volume, presumably related to the lower heart rate in MHS. Thus, total peripheral resistance was increased in MHS as was the ratio left ventricular weight/body weight, and in good proportion to the blood pressure rise. Thus MHS differ substantially in both their responses to “stress” and also hemodynamically from the Okamoto strain of spontaneously hypertensive rat (SHR), being the so far most studied and best known model of essential hypertension in man. In MHS the hypertension is more of a systolic type and is of primarily renal origin. As such, MHS provide another model for investigating the polygenic nature of hypertension in man.
Effects of Carbachol and Calcium on the Cyclic Guanosine‐3‘,5’‐Monophosphate (Cyclic GMP) Metabolism in Intestinal Smooth Muscle
Authors: Nilsson Karin B. , Andersson Rolf G. G. 
Published: December 2008

AbstractIn a submaximal concentration carbachol contracted the rabbit colon muscle and increased the cyclic GMP level. The cyclic AMP level was reduced. In a Ca++‐depleted muscle carbachol reduced the cyclic GMP level while the effect on the cyclic AMP content of the muscle was unchanged. Carbachol had no effect on the guanylate cyclase activity of the “plasma membrane fraction” (the 35–45% fraction). In the homogenate and the microsomal fractions Ca++ had no effect on the guanylate activity while it stimulated the enzyme in a soluble fraction. In the “plasma membrane fraction” cyclic GMP released Ca++ from the preloaded fraction and inhibited the Ca++ accumulation. These effects were not found in the vesicular microsomal fraction (the 35% fraction). In both fractions, however, cyclic GMP counteracted the stimulating effect of cyclic AMP. These results indicate that cyclic AMP and cyclic GMP may have antagonistic roles on the Ca++ metabolism in the colon muscle. It is suggested that cyclic GMP may act as some kind of positive feedback mechanism which may have a modulating effect on the release of Ca++ from one pool to another in rabbit colon.
The Effect of Oxygen on Peripheral Airways
Authors: Nielsen Tage Mors , Pedersen Ole Find 
Published: December 2008

AbstractIn ten normal young subjects four alveolar O2‐concentration levels ranging from about 7 % to 95 % were obtained by breathing different concentrations of oxygen in nitrogen at a constant alveolar CO2‐con‐centration of about 5%. Maximum expiratory flows at 60% TLC were measured at each level and corrected for the influence of the expired gas density on flow. The corrected maximum flows were not significantly different, which is taken as evidence of no effect of oxygen on tone of peripheral bronchi.
Spatial Distribution of the EOG in the Rat; a Variation with Odour Quality
Authors: Thommesen G. , Doving K. B. 
Published: December 2008

AbstractThe spatial distribution of olfactory receptors in the rat has been studied by simultaneous recordings of the electroolfactograms (EOGs) from areas of the olfactory mucosa. The potentials were recorded from the dorsal surface of the cribriform plate, leaving the mucosa and the nasal cavities intact. The ratio between the peak amplitude of the EOG potentials served as a measure of the relative sensitivity of one area against the other. The results obtained by stimulating with 31 substances at 38 positions demonstrate a non‐homogeneous distribution of different receptors. Each substance gives a spatial pattern of response efficiency. The response distributions are mapped on the cribriform plate for the different odours.
Changes in ATP and Cyclic Nucleotide Levels during Sympathetic Nerve Stimulation in Canine Subcutaneous Adipose Tissue in situ
Authors: Fredholm Bertil B. , Belfrage Erik , Blaschke Eleonora 
Published: December 2008

AbstractSubcutaneous adipose tissue in fed, female dogs was isolated. Biopsies of the tissue (30–150 mg) were taken and rapidly frozen in liquid nitrogen before, during and after nerve stimulation (3–4 Hz). In unstimulated adipose tissue the levels of ATP1were 74 ± 7 nmol/g, of cyclic AMP 90 ± 12 pmol/g and of cyclic GMP 18 ± 3 pmol/g (mean + S.E.). During sympathetic nerve stimulation the levels of ATP and cyclic GMP fell by 30 and 50% respectively (p < 0.01), while the cyclic AMP content increased by 50 % (p < 0.05). After nerve stimulation there was a marked increase in glycerol release, and the levels of all three nucleotides returned to control. The fall in ATP during nerve stimulation was essentially eliminated by prior adrenergic a‐receptor blockade. It is concluded that 1) sympathetic nerve stimulation induces a rapid, reversible fall in tissue ATP content, which may be related to hypoxia secondary to the vasoconstriction, and 2) lipolytic responses to sympathetic nerve stimulationin vivoare preceeded by small increases in the tissue cyclic AMP level, and a 3‐fold increase in the cyclic AMP/cyclic GMP ratio.
Renal Na‐K‐ATPase Activity during Saline Infusion in the Rabbit
Authors: Sejersted Ole M. 
Published: December 2008

AbstractDuring saline infusion, sodium reabsorption (RNa) in the diluting segment (thick ascending limb of Henle's loop) increases acutely. The mechanism for this higher pumping rate of outer medullary Na‐K‐ATPase is unknown. Following left‐sided nephrectomy, immediate i.v. infusion of hypertonic saline increased RNain the remaining whole right kidney by 28 ± 14% (p < 0.05). Na‐K‐ATPase activity in outer medulla was raised by (A) 23 + 4% above the left kidney (p < 0.05), whereas cortical activity was unchanged. The mechanism for this increase in Na‐K‐ATPase activity was explored. The catalytic rate per enzyme did not differ in the two kidneys and equalled 5 340 min‐1. The increase was therefore due to higher tissue concentration of active enzyme. The response was fully developed during continuous infusion within 20 min, and of equal magnitude whether protein synthesis had been inhibited by cycloheximide (Δ= 23 ± 7%) or stimulated by unilateral nephrectomy 6 days earlier combined with saline infusion for 2 h (Δ= 34+ 10 %). Thus, during hypertonic saline infusion, the increased RNain the outer medulla was partly accounted for by the activation of latent Na‐K‐ATPase. High delivery of sodium to the diluting segment for more than 20 min during hypertrophy caused no further activity change.
Slow Action of Ca on Myelinated Nerve Fibres of Xenopus laevis
Authors: Brismar Tom 
Published: December 2008

AbstractSingle myelinated nerve fibres were isolated and the nodal currents were recorded with potential clamp technique. Rapid solution changes were performed by use of a recording chamber so shaped that it had a minimal dead space. A volume ten times larger than the dead space flowed past the node within about 20 ms. The half‐time of the change in Na current (INa) amplitude associated with changes between solutions of different [Na]:s was 100–150 ms, whereas the half‐time of the change in INa associated with changes between solutions of different [Ca]:s was 200–300 ms. The external [Ca] affects INa through its action on the Na permeability properties of the nodal membrane. The difference in rate of effect between changes in [Na] and [Ca] was also noticeable when simultaneous changes were performed. These findings are discussed with regard to the properties of the nodal gap.
Quantitative Evaluation of the Blood‐Brain Barrier Capacity to Form Dopamine from Circulating L‐DOPA
Authors: Hardebo J. E. , Edvinsson L. , Owman Ch. , Rosengren E. 
Published: December 2008

AbstractThe ability of the blood‐brain barrier to form dopamine from increasing doses of systemically administered L‐DOPA has been studied in rats by a combination of chemical determination of dopamine, and histo‐chemical and cytofluorometric measurements of L‐DOPA and dopamine. The break‐through of L‐DOPA from the circulation into the brain parenchyma via the enzymatic blood‐brain barrier was estimated by comparing the amount of newly formed dopamine in the caudate nucleus‐putamen and in the cerebellum. The capillaries were found to efficiently trap L‐DOPA in their walls, and an upper limit was reached (at an administered i.p. dose of 100 mg/kg of L‐DOPA). It could be estimated that approximately 3 % of the total dose of L‐DOPA given was decarboxylated by the blood‐brain barrier. The possible influence by the regional differences in perfusion of the two regions seen after administration of L‐DOPA was ruled out in measurements of local cerebral blood flow using the14C‐ethanol technique.
Evidence for a Rate‐Sensitive Regulatory Mechanism in Myogenic Microvascular Control
Authors: Grände Per‐Olof , Lundvall Jan , Mellander Stefan 
Published: December 2008

AbstractTo reveal a possible rate‐sensitive component in the myogenic control, changes of total and segmental vascular resistances in sympathectomized skeletal muscle in response to alteration of vascular transmural pressure (extravascular pressure) by 40 mmHg were compared when the pressure change was applied at two distinctly different rates (15 and 120 s). The papaverine‐dilated vascular bed showed an entirely passive behaviour, whereas the normal, myogenically reactive vascular bed responded with active constriction upon transmural pressure increase and active dilation upon pressure decrease. These responses were especially pronounced in the microvessels where a clearcut two‐component effector response was observed. The magnitude of the initial component was distinctly correlated to the rate at which the transmural pressure stimulus was applied, whereas the later steady state component during the static pressure change was rate‐independent. At the high rate of pressure increase, the initial rate‐dependent microvascular constrictor response was some ten times larger than the steady state response. These observations indicate the existence of a rate‐sensitive as well as a static component in the myogenic response to changed transmural pressure, an interpretation strongly supported by a previous analogous study on isolated single‐unit vascular smooth muscle (Johansson and Mellander 1975). It is concluded that the microvessels in skeletal muscle are highly responsive to myogenic stimuli and that emphasis should be placed on the dynamic rather than the static characteristics of the stimulus. Such rate‐sensitivity in myogenic control would seem to facilitate prompt and proper vascular adjustments, for instance in myogenic autoregulation.
Characteristics of Aortic Baroreceptor C‐Fibres in the Rabbit
Authors: Thoren Peter , Jones John V. 
Published: December 2008

AbstractThe characteristics of 40 C‐fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between 0.5‐1.8 m/s (0.91±0.05, mean ± S.E.). The activation threshold for all the fibres lay between 70–140 mmHg. 32 medullated fibres from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C‐fibres occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C‐fibres. The mean activity at 100 mmHg was, for the C‐fibres 5.0 Hz and for the medullated fibres 34 Hz. At 130 mmHg the activity in the C‐fibres was 13 Hz and in the medullated fibres 68 Hz. Thus C‐fibres from the aortic baroreceptor regions are activated at higher pressures than the medullated fibres and have lower discharge frequencies. Noradrenaline did not influence the pressure response curves of the C‐fibres. It is concluded that the arterial baroreceptor C‐fibres may exert a weak tonic influence on the vasomotor centre at normal pressures but are likely to be of greater importance when the arterial pressure rises acutely.
Contractility, Muscle Mass and Agonist Sensitivity of Isolated Portal Veins from Normo‐ and Hypertensive Rats
Authors: Sutter Morley C. , Ljung Bengt 
Published: December 2008

AbstractProperties of the longitudinal smooth muscle of portal veins from normotensive Wistar rats, adult (NCR) and young (NCRy); spontaneously hypertensive Okamoto rats, adult (SHR) and young (SHRy); and adult Wistar rats with renal hypertension (RHR) were studied in vitro and histologically. Some aortic strips from SHR and SHRywere compared with controls. In response to noradrenaline (NA) and acetylcholine (ACh) greater maximum force was developed by veins from all hypertensive groups than by those from control rats. Cross‐sectional area of the longitudinal muscle of veins from SHR but not SHR nor RHR was greater than control. Maximum stress in response to agonists was greater in both SHR and RHR than NCR. EDso‐values for NA and ACh were lower in portal veins from SHR than NCR but not from RHR nor SHRycompared to controls. Denervation did not abolish any of the differences between SHR and NCR. Aortic strips from SHR developed less maximum force to NA and ED50was greater than those from NCR.i.e.opposite to the findings in portal veins. Low levels of external Ca2‐reveal altered calcium handling in veins from SHR compared to controls.It is concluded that portal veins from hypertensive rats are functionally different from those of normotensive rats and differ in SHR compared to RHR. It is suggested that the altered functional properties of portal vein, but not of aorta, in several respects resemble those of arterial resistance vessels. The implications of these findings are discussed in terms of mechanisms of hypertension in these animal models.
Effect of Atropine and Methiamide on Vagally Induced Gastric Acid Secretion and Gastrin Release in Anesthetized Cats
Authors: Uvnäs‐Wallensten Kerstin , Andersson Harriet 
Published: December 2008

AbstractGastrin release and HC1 secretion was induced by electrical vagal stimulation in anesthetized cats. Both atropine (0.1‐0.3 mg/kg) and methiamide (4–20 mg/kg) inhibited the HC1 secretion (by˜60 and˜80%). On the other hand, neither atropine (0.2‐2 mg/kg) nor methiamide (20 mg/kg) inhibited the vagally induced gastrin release. Possible explanations of the atropine resistance of the vagal gastrin release mechanism are discussed.
Effect of Hypercapnia and Hypocapnia on Tryptophan and Tyrosine Hydroxylation in Rat Brain
Authors: Carlsson A. , Holmin T. , Lindqvist M. , Siesjo B. K. 
Published: December 2008

AbstractThe effects of induced hypo‐ and hypercapnia upon the rate of hydroxylation of tryptophan and tyrosine in the rat brain were studied by measuring the accumulation of 5‐HTP and DOPA following administration of the aromatic L‐aminoacid decarboxylase inhibitor 3‐hydroxybenzylhydrazine HC1 (NSD 1015). The results suggest that the hydroxylation of tryptophan varies directly with the tissue Po2‐ On the other hand, the hydroxylation of tyrosine did not show a simple relationship to Po2 but appeared to be influenced by pH changes.