bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Incorporation of Cholesterol into the Nervous System of the Newly Hatched Chick
Authors: Svanberg Olof 
Published: December 2008

AbstractThe deposition of cholesterol in the myelin of the central nervous system has been compared with that in the myelin of the peripheral nervous system. C14‐4‐cholesterol was injected into the yolk sacs of newly hatched chicks and whole body autoradiography was performed according to Ullberg (1954, 1958). No radioactivity was found in the central nervous system, except in the pineal gland, during the 9 days of the investigation. However, the peripheral nerves were heavily marked. The results indicate the existence of a “blood‐brain barrier” which excludes cholesterol. Most of the cholesterol of the myelin in the brain and the spinal cord is accordingly synthesized in situ, while in peripheral nerves it is derived from the blood.
Plasma Skimming in the Intestinal Tract
Authors: Jodal Mats , Lundgren Ove 
Published: December 2008

AbstractThe “tissue hematocrit” of the different wall layers of the small and large bowel of the cat was studied in three different experimental conditions, i.e. during “resting” blood flow of the denervated intestine, during vasodilatation induced by isopropylnoradrenaline and during nervous vasoconstriction. The “tissue hematocrit” was estimated from the distribution of 51Cr‐labelled red cells and 125I‐labelled human serum albumin. It was demonstrated that the “tissue hematocrit” of the mucosa of the small intestine only amounted to 50–60 per cent of the arterial hematocrit while the “muscularis hematocrit” was 90 per cent of the arterial. Similar results were obtained in the three different experimental situations. The low mucosal “tissue hematocrit” could neither be explained by an extravascular accumulation of 125I‐labelled albumin nor by different degrees of axial streaming of erythrocytes in the different wall layers. The observations are therefore taken to indicate the presence of a plasma skimming in the small intestine of the cat. In the colon the “tissue hematocrit” of the mucosa was only slightly lower than that of the submucosa, the muscularis or the arterial blood indicating that no or only a slight plasma skimming occurs in this organ.
Blood Flow through Limb Muscles during Heavy Rhythmic Exercise
Authors: Folkow B. , Gaskell P. , Waaler B. A. 
Published: December 2008

AbstractThe effect of rhythmically performed muscle contractions on blood flow through muscles was investigated in the calf of cat. During a series of contractions, which had led to maximal dilatation of the resistance vessels, a considerable lowering of the pressure in a small vein from the contracting muscles could be demonstrated between contractions, despite the huge inflow. An optimal effect was obtained when the muscle nerve was stimulated with a short (200–300 msec) impulse train once per sec, a pattern mimicking that during running. Rhythmic contractions of this type led to a characteristic blood flow pattern through the muscles. Arterial inflow to the muscle vascular bed occurred only in between contractions, whereas nearly all the venous outflow from the muscles occurred during the contractions.The venous pressure reduction occurring between contractions implies a gain in effective perfusion pressure and a corresponding augmentation in blood flow through the muscles. Such an effect was found to be considerable in dependent limbs. Here average blood flow through the rhythmically contracting calf muscles could be as great as, or even greater than, the “free” flow in the immediate post‐exercise period. This effect of the “muscle pump” may be of great importance also in the dependent limbs of man.
Distribution of Choline Acetyltransferase in the Hearts of Mammals
Authors: Ekström Jörgen 
Published: December 2008

AbstractCholine acetyltransferase activity was estimated in hearts of dogs, cats, rabbits and rats. The ventricles, which form about 90 per cent of the fresh weight of the hearts, are responsible for about two thirds of the total enzyme activity of the heart in dogs, cats and rats, and in rabbits for about half the total activity of the heart. The concentration of the enzyme is higher in the atria than in the ventricles. In dogs the apex of the ventricles showed the same enzyme concentration as the basal parts; in cats and rabbits it was somewhat lower in the apex than in the base. The findings are discussed in relation to the controversial question of a parasympathetic innervation of the mammalian heart ventricles.
Background of Increased Flow Resistance and Vascular Reactivity in Spontaneously Hypertensive Rats
Authors: Folkow Björn , Hallbäck Margareta , Lundgren Yen , Weiss Lilian 
Published: December 2008

AbstractThe hindquarters of a spontaneously hypertensive rat (SHR) and a matched normotensive control rat (NCR) were perfused at a constant rate of flow with oxygenated plasma substitute in 15 paired experiments. As is the case in the entire systemic vascular bed (Folkowet al.1969), flow resistance was raised even during maximal dilatation in SHR (p<0.001), almost in proportion to their raised blood pressure. Graded noradrenaline (NA) infusions showed identical NA “thresholds”, while SHR displayed a steeper curve, relating log NA dose to resistance response (p<0.001) and a greater maximal contractile strength of the resistance vessels (p<0.001). These characteristics of the resistance curves for SHR and NCR were compared with those mathematically deduced for two hypothetical vessels, identical except for the presence in one of them of a 30 per cent increase of its media thickness encroaching upon its lumen even at complete relaxation. In all essential points the relationships between the two sets of curves were the same while no other type of vascular change, structural or functional, could alone reproduce all the characteristics of the SHR curve. The results therefore suggest the presence of an increased contractile wall mass in the systemic resistance vessels of SHR encroaching upon their lumina even during maximal dilatation. Without necessitating any increased smooth muscle activity the haemodynamic effects of the proposed structural change can largely alone account for the raised resistance and increased vascular “reactivity” in SHR.
Potentiation by Various Smooth Muscle Stimulants of an Isolated Sympathetic Nerve‐Seminal Vesicle Preparation from the Guinea‐Pig1
Authors: Sjöstrand Nils O. , Swedin Göran 
Published: December 2008

AbstractThe contractions of the seminal vesicle in response to hypogastric nerve stimulation or coaxial stimulation were recorded with a balloon inserted in the lumen of the seminal vesicle.Adrenaline (A), noradrenaline (NA), acetylcholine (Ach), histamine (Hi), serotonin (5‐HT), barium chloride and high concentrations of angiotensin were found to potentiate the motor response of the seminal vesicle to sympathetic nerve stimulation. This potentiation occurred with concentrations 10–100 times smaller than those giving a direct contraction of the organ. Prostaglandins (PGE1, PGE2 and PGF2a) in low concentrations (1–10 ng/ml) exerted no effect or caused a slight decrease in the response to sympathetic nerve stimulation, while higher concentrations (100 ng–1 μg/ml) enhanced the response to nerve stimulation. This effect was pronounced with PGE1, but rather weak with the other prostaglandins. Oxytocin, vasopressin and felypressin were without effect on the seminal vesicle preparation. It is concluded that the seminal vesicle responds to smooth muscle stimulants in a similar way as the vas deferens.
Single Unit Analysis of Mechanoreceptor Activity from the Human Glabrous Skin
Authors: Knibestöl M. , Vallbo Å. B. 
Published: December 2008

AbstractSingle unit impulses were recorded from the median and the ulnar nerves in waking human subjects with percutaneously inserted tungsten electrodes. 61 mechanoreceptor units in the glabrous skin were analysed with regard to the characteristics of their receptive fields and the basic physiological properties of their endings. 4 different types of receptors could be distinguished. This distinction was based mainly upon the adaptation and the receptive field characteristics although other differences were also observed. The fields had very sharp borders for the majority of the slowly as well as the rapidly adapting units. The field sizes varied considerably: between 10 mm2 and 600 mm2. For a minority of the receptors, slowly as well as rapidly adapting ones, the receptive fields were constituted of a center of high sensitivity and a wide surrounding area of lower sensitivity without distinct borders. The four types of receptors encountered in the present study have striking similarities with four different types of mechano‐receptors which have been described in sub‐human primates, namely the type I and type II slowly adapting, intradermal receptor, according to Iggo's terminology, an intradermal rapidly adapting receptor and the Pacinian corpuscle which is located in the subcutaneous tissues. Roughly 75% of the units were slowly adapting. This is a much larger proportion than found in the monkey. Further, it was shown how the recording method offers the opportunity to analyse the perceptive responses as well as the neurophysiological responses in first order neurons to mechanical stimuli.
The Circadian Fluctuations of the Amount of Free Phosphate and of the Activity of Acid Phosphatase in the Kidneys of Mice and the Effect of UV Radiation upon this Rhythm
Authors: Lindahl Per Eric , Surowiak Jósef 
Published: December 2008

AbstractThe activity of acid phosphatase and the content of Pi1 were estimated in kidney homogenates from male and female mice. The determinations were repeated at 6‐hr intervals during the day, starting at noon, using control animals and animals previously subjected to a high dose of UV radiation. Marked changes in the activity of this enzyme were found during the course of the day, indicating the existence of a circadian rhythm. This phenomenon is observed both in males and in females and exhibits similar features in both sexes. The content of Pi in the kidney homogenate varies in an analogous manner. UV irradiation produced significant changes both in the enzyme activity and in the content of inorganic phosphate. In irradiated animals the new maxima in the activity of acid phosphatase were generally accompanied by maxima in the amount of Pi. It is supposed that the end products of the reactions in the skin formed under the influence of UV radiation and associated with the degradation of phospholipids are the main factors responsible for the observed changes in the kidney.
Effect of Prostaglandin E1on Fat Mobilizing Lipolysis in Rat Adipose Tissue in Relation to the Nutritional Condition
Authors: Carlson Lars A. , Micheli Horace 
Published: December 2008

AbstractThe effect of prostaglandin E1(PGE1) on fat mobilizing lipolysis in rat adipose tissue was studied in relation to the nutritional condition by following the release of glycerol during incubation in vitro. In fed tissues PGE1at concentration of 0.01, 0.1, 1 and 10 μg/ml incubation medium significantly lowered the lipolysis to 64, 41, 48 and 68% of the basal rate (average of 6 expts.). The lipolytic rate was significantly higher with 10 than with 0.1 μg/ml of PGE1. The corresponding figures in adipose tissue from fasted rats were 90, 91, 86 and 95% respectively (average of 7 expts.). These average decreases were not statistically significant. Refeeding fasted rats with glucose one hour before the study restored the sensitivity of adipose tissue to the antilipolytic effect of PGE1. In rat fat the nutritional condition is thus of importance for the appearance of the antilipolytic effect of PGE1. The possible role of the tissue sensitivity to PGE1in regulating fat mobilizing lipolysis during fasting was discussed.
Effects of Some Adrenergic Neuron Blockers, Related Quaternary Ammonium Compounds and Guanidine Derivatives on Degenerating Adrenergic Nerves in the Conscious Rat
Authors: Lundberg Dag 
Published: December 2008

AbstractAdrenergic neuron blockers, related quarternary ammonium compounds and guanidine derivatives, and some other drugs have been tested on a degenerating nerve‐effector system in the rat periorbital smooth muscle. The main attention was paid to their influence on the degeneration contraction. The quaternary ammonium compounds structurally related to bretylium and xylocholine, with few exceptions, distinctly delayed the onset of the degeneration contraction. The guanidine derivatives known to be related to bretylium and xylocholine pharmacologically caused almost no delay. The simple compound phenyltrimethylammonium (PTMA) was chosen for further studies. It was found to possess actions on the degenerating system similar to those of bretylium. The PTMA‐induced delay was efficiently reduced by desmethylimipramine, but not at all by anticholinergic drugs.Conclusions: — Guanidine derivatives are much less efficient delayers than related quaternary ammonium compounds. The main structural features essential for delaying activity are found in PTMA. There does not seem to be any correlation between the neuron‐blocking or the sympathomimetic activity and the delaying effect of the drugs. The processes responsible for the onset of the normal degeneration contraction and those effecting the drug‐induced delay do not appear to involve any cholinergic sites.
The Effect of Periarterial Nerve Stimulation on the Jejunal and Ileal Motility in Cat
Authors: Kewenter J. , Pahlin P.‐E. , Storm B. 
Published: December 2008

AbstractThe effect of nervous stimulation of the periarterial nerve trunks along the superior mesenteric artery on the jejunal and ileal motility was investigated. With the same physiological frequencies it was possible to induce excitatory as well as inhibitory motor responses by changing the voltage and/or pulse duration. Guanethidine abolished the inhibitory responses in the jejunum and the ileum. It was concluded that the periarterial nerves contain two different sets of nerve fibres mediating excitatory and inhibitory impulses to the small intestine.
Correlation between the Rise Time of Miniature End‐Plate Potential and the Distance of the Recording Microelectrode from the Myoneural Junction
Authors: Nickels J. 
Published: December 2008

AbstractA new marking method which permits accurate positioning of the microelectrode tip in the muscle cell and subsequent histochemical staining of the myoneural junction was used to study the correlation between the rise time of miniature end‐plate potentials and the distance of the recording microelectrode from the myoneural junction. The muscle examined was the m.tibialis anterior of the rat. The recording was performed in vivo. A positive correlation was established between the distance and the rise time and the correlation coefficient was +0.94. The mean rise time of the miniature end‐plate potentials in different muscle cells ranged from 0.27 to 0.70 msec., while the distance of the recording microelectrode varied between 0 and 552 μ measured from the midpoint of the motor end‐plate. The rise time was distinctly shorter than is usually reported in the literature.
The Role of Vagal Cardiac Nerves and Arterial Baroreceptors in the Circulatory Adjustments to Hemorrhage in the Cat
Authors: ÖBerg B. , White S. 
Published: December 2008

AbstractThe relative importance of arterial baroreceptors and receptors with afferent fibres in the cardiac nerves, respectively, in producing compensatory circulatory adjustments in moderate hemorrhage was analyzed in chloralose‐anesthetized cats. — The effects of standardized hemorrhage on blood pressure, heart rate and renal and skeletal muscle blood flows were observed before and after section of respective receptor afferents. Both groups of receptors, when operating in the absence of the other, were capable of producing tachycardia and vasoconstriction during a blood loss, but the pattern of response, elicited via the two sets of afferents, differed. Compensation via cardiac nerve afferents thus implied a particularly strong engagement of vasomotor neurons, controlling the heart and the renal vessels, while the arterial baroreceptor adjustments seemed to involve a more uniform exitation of all vasomotor centre neurons. Very rapid hemorrhages often produced a pronounced bradycardia, resembling that seen in the “vaso‐vagal” syncope in man. This response was found to be mediated through a vago‐vagal reflex arch, and probably constitutes a protective mechanism, causing a break on the heart in situations of extremely poor diastolic filling.
The Response of RNA Synthesis to Mitotic Regulation in the Erythron
Authors: Kivilaakso E. 
Published: December 2008

AbstractMitotic homeostasis in the erythron appears to be controlled by a humoral feedback mechanism consisting of a tissue‐specific mitotic inhibitor, the erythrocytic chalone, and a tissue‐specific mitotic stimulator. The present report is an account of the way in which these two regulatory factors affect RNA synthesis in normal rat bone marrow cells in vitro. The responses were measured in terms of 3H‐uridine incorporation into the target cells. The primary action of the erythrocytic chalone on 3H‐uridine incorporation was manifested as a rapid and strong inhibition. The initial inhibition was reversible and was followed, after a few hours' incubation, by an increased rate of 3H‐uridine incorporation, which ultimately led to complete compensation of the inhibition. The tissue specificity of these findings was demonstrated indirectly by means of polycythemic target bone marrow, on which the erythrocytic chalone had only a negligible effect. The effect of the mitotic stimulator on 3H‐uridine incorporation in the cells was invariably a stimulation, which showed a slight tendency to increase with incubation time. The results demonstrate that the effects of the mitotic regulatory factors are not restricted to DNA metabolism alone but can also be elicited within other metabolic processes in the cell.
Reduction in Pulmonary Blood Volume after a Blood Loss
Authors: Aarseth Petter 
Published: December 2008

AbstractThere is little information about the possible role of the pulmonary vascular bed as a variable blood depot. An evaluation of the degree of blood mobilization from this vascular compartment after a blood loss has therefore been attempted. Rats were given labelled erythrocytes and albumin, and immediately after a standardized blood loss the circulation was arrested by immersing the animals in liquid nitrogen. The lungs and tissue samples from liver and skeletal muscles were removed, and their blood contents evaluated. Values found in the tissues of the bled animals were compared with those from a group of non‐bled control animals. In a group of animals bled 12% of their total blood volume the mean pulmonary blood volume was reduced by 25%, while the muscle and liver blood contents were reduced by about 10% only. This difference was even more pronounced in a group of animals bled 24% of their total blood volume. The reduction in pulmonary blood volume was in the former group equal to 27% of the lost blood. This was more than the amount of blood contributed from the whole mass of skeletal muscle. In the bled animals the weight of the lung tissue proper was considerably reduced, indicating that there had been a reduction also in lung tissue water.
A Double Isotope Method for Determination of the Miscible Inorganic Sulfate Pool of the Mouse Applied to in vivo Studies of Sulfate Incorporation into Costal Cartilage
Authors: Herbai Georg 
Published: December 2008

Abstract In vivo sulfate incorporation into tissues of small animals, as a metabolic research tool, has been previously handicapped since convenient micromethods for sulfate determination were lacking. A double isotope method for determination of the inorganic sulfate pool applicable to very small animals is presented and evaluated. It is based on a principle which makes blood samples unnecessary. Phenol injected i.v. is converted to phenyl sulfate in the viscera and the circulating inorganic sulfate pool of the animal participates in this reaction. 3H‐phenol and 35S‐sulfate mixed with suitable amounts of carrier are given to the animals and the tagged phenyl sulfate formed is isolated from the urine by thin‐layer radio‐chromatography. Its 3H/35S ratio together with the specific activities of the injection mixture yield all necessary values for calculation of the size of the sulfate pool. Simultaneously the incorporated amount of sulfate into a defined portion of costal cartilage is measured after correction for the individual sulfate pool values.In 20 g N.M.R.I. mice the total miscible sulfate pools were about 300–400 μg SO4/mouse and the sulfate incorporation during the 30 min experimental period reached 200–400 nanogram SO4 per 5 pairs of cartilaginous ribs including their osteochondral junctions. The size of the sulfate pool increased with increasing body wegiht at different ages both in N.M.R.I. and in obese‐hyperglycemic mice. The sulfate incorporation rates showed markedly different values in different mouse strains investigated at similar ages.
Synchronization of Activity in Afferent Nerve Branches within the Frog's Muscle Spindle
Authors: Ottoson D. , Shepherd G. M. 
Published: December 2008

AbstractThe mechanisms underlying the generation of activity in the afferent nerve branches within the muscle spindle have been studied in isolated frog spindles. Repetitive stimulation at given frequencies and strengths caused a disintegration of the synchronous activity of the spindle as revealed by a decomposition of the impulse into small abortive spikes of different amplitudes. The breakdown of synchronous activity was preceded by a stage during which the impulse appeared gradually later but then remained steady at a given delay. The isolated receptor potential exhibited a latency shift closely similar to that of the impulse response under repetitive stimulation. Treatment of the spindle with tetrodotoxin at critical concentrations caused a decomposition of the impulse similar to that with repetitive stimulation. It could be shown in these spindles that synchronization of the activity within the spindle is related to the amount of depolarization of the sensory endings. The mechanisms for generation of activity in the spindle are discussed in relation to the structural organization of the branches of the afferent fibre. It is concluded that the anatomical and functional properties of the spindle provide the basis for a synchronization of the activity of its different parts during the response to an applied stretch.
Regional Differences in the Incorporation Rates of 3H‐Acetate and 35S‐Sulfate into Chondroitin Sulfate of Mouse Costal Cartilage in Vitro
Authors: Herbai Georg , Lindahl Ulf 
Published: December 2008

AbstractThe rates of incorporation of 3H‐acetate and 35S‐sulfate into chondroitin sulfate of mouse costal cartilage were studied by an in vitro‐incubation technique. Cartilage specimens from two different regions of costal cartilage prepared from growing mice, were incubated for varying periods of time. Chondroitin sulfate was isolated, after proteolytic digestion of the tissues, by repeated precipitation with cetylpyridinium chloride. The average incorporation rates, which were followed during 24 hrs, showed a marked decrease after 2 hrs of incubation and then remeained essentially constant. During the entire incubation period much more exogenous sulfate than acetate was incorporated into the segments. Considerably more exogenous sulfate and acetate were incorporated into the lateral segments of the cartilage, including the osteochondral junctions, than into the medial segments. It is concluded that chondroitin sulfate is synthetized at a higher rate in the vicinity of the osteochondral junction than in other portions of mouse costal cartilage.