bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blood‐to‐tissue transport of albumin in rat fibrosarcomas at two different implantation sites
Authors: HARALDSSON B. , REGNÉR L. , WEISS L. , JANSSON I. , Hultborn R. 
Published: December 2008

Albumin clearance and blood flow were measured in normal tissues and in fibrosarcomas by means of a multiple tracer method in intact male rats. Sarcomas implanted in testes had higher albumin clearances than the same tumours implanted in skeletal muscle, 59 and 26 μl min‐1 per 100 g, respectively. Albumin extraction (defined as the ratio of albumin clearance to plasma flow) was found to be 1 times 10–4–14 times 10–4 in normal tissues. Fibrosarcomas in muscle showed high extractions (24 times 10–4), especially in the central portions (96 times 10–4), where the extraction was similar to that in tumours implanted in the testes (111 times 10–4).The high albumin extraction in poorly perfused central parts of the muscle‐implanted tumours and in the similarly insufficiently perfused testicular sarcomas is probably due to an increased endothelial permeability of the exchange vessels and not to an increased capillary exchange surface area compared with the better‐perfused peripheral parts of the muscle‐implanted tumours. The latter tissue also had a high albumin clearance, however, in the range of that of maximally dilated skeletal muscle vasculature, possibly reflecting a large functional capillary surface area.
Responses to antidromic trigeminal nerve stimulation, substance P, NKA, CGRP and capsaicin in the rat eye
Authors: ANDERSSON SVEN E. 
Published: December 2008

In the rat eye, intracameral injections of substance P in doses of 10–30 pmol caused a maximal long‐lasting miosis and a leakage of plasma proteins into the aqueous humor, indicating a breakdown of the blood‐aqueous barrier. Neurokinin A seemed equipotent to SP, but calcitonin‐gene‐related peptide (CGRP) (17 pmol) caused neither moisis nor protein leakage into the aqueous humor. The same result was obtained when CGRP was administered intravenously. Intracameral injection of capsaicin caused only a transient moisis which could not be repeated with further injections, even though the pupillary sphincter was still able to react to exogenous SP.Antidromic electrical stimulation of the trigeminal nerve caused plasma extravasation in the skin and a breakdown of the blood‐aqueous barrier with an increased protein content in the aqueous humor. The stimulation did not affect the pupil size. The results indicate that in rat eyes SP and NKA are miotics, but the amounts that can be released from sensory nerve endings are too small to cause persistent miosis. These peptides are more likely to play a role in the neurogenic breakdown of the blood‐aqueous barrier. CGRP at the same dose affects neither the pupillary sphincter muscle nor the barrier.
Fatigue during dynamic muscle contractions in male sprinters and marathon runners: relationships between performance, electromyographic activity, muscle cross‐sectional area and morphology
Authors: LORENTZON R. , JOHANSSON C. , SJÖSTRÖM M. , FAGERLUND M. , FUGL‐MEYER A. R. 
Published: December 2008

Knee extensor fatigue and endurance during repeated maximum isokinetic manoeuvres were studied in five sprinters and five marathon runners, all males. Fatigue and endurance were expressed in terms of output (contractional work, CW) and input (integrated electromyograms, iEMG), and was related to muscle fibre composition of m. vastus lateralis and to cross‐sectional area (CSA) of m. quadriceps.The initially performed contractional work was positively related to the calculated absolute type II fibre area of m. vastus lateralis, but not to the cross‐sectional area of m. quadriceps. During the first 25 contractions, sprinters fatigued, with a slope of decline in contractional work that was correlated to the absolute type II fibre area, also after correction of performed work for CSA of m. quadriceps. As the electromyographic activity decreased less than the contractional work, a drastic fall in the CW/iEMG ratio was found in the sprinter group. Three out of five sprinters could perform less than 50 knee extensions, due to subjective discomfort in tested thighs. In contrast, all marathon runners could, after a minor similar decline in electromyographic activity and contractional work during the first part of the experiment, maintain a steady‐state endurance level of CW and iEMG throughout the test (200 knee extensions). In conclusion, fatigue during isokinetic maximal knee extensions is closely related to the muscle structure of m. vastus lateralis.
Measurements of macula densa cell volume changes in isolated and perfused rabbit cortical thick ascending limb. I. Isosmotic and anisosmotic cell volume changes
Authors: GONZÁLEZ E. , SALOMONSSON M. , MÜLLER‐SUUR C. , PERSSON A. E. G. 
Published: December 2008

A method to measure time‐dependent volume changes in macula densa (MD) cells is described. Cell volume is calculated from cell height measurements for which an image‐splitting eyepiece is used. This paper presents the results of experiments designed to investigate the behaviour of the macula densa cells in anisosmotic media, to evaluate the cell volume response to sudden decreases in luminal or peritubular osmolarity and to examine the effect of different luminal NaCl concentrations on the steady‐state isosmotic cell volume and on the regulatory volume response to anisosmotic media. The result showed that induced alteration in macula densa cell volume did not change macula densa surface area, but only cell height. The mean control cell height was 13.3 μm ± 0.4. When MD cells were exposed to a luminal osmolarity of 180 mosM (control 300 mosM) they swelled only to 1.19 ± 0.02 of the control value and with furosemide present to 1.13 ± 0.02 or with low NaCl to 1.13 ± 0.01. While after 5 min of exposure values were 1.15 ± 0.03, 0.99 ± 0.02 and 1.02 ± 0.02, respectively. Addition of furosemide (10‐1 M) to the luminal perfusate (300 mosM) resulted in a rapid decrease in cell height to 0.8 ± 0.02 in relation to control. When furosemide was removed cell volume was restituted (0.98 ± 0.03). When luminal perfusate was replaced by mannitol and (12 mM Na+, 7 mM CI‐) cell volume decreased to 0.83 ± 0.02 of the control value.The results of this study are in accordance with the view that the macula densa cells have a furosemide‐sensitive NaCl absorption system (cation and chloride co‐transport) across the apical membrane. The basolateral cell membrane have very rapid regulatory mechanisms which maintain the cell volume during reductions in basolateral osmolarity. The transport properties of the macula densa cells are not affected by maximal and supramaximal doses of vasopressin. These findings offer more direct support to the hypothesis that the initiation of the tubuloglomerular feedback response involve furosemide‐inhibitable uptake of sodium and chloride ions into the macula densa cells ‐ where the ions would, subsequently, be absorbed and accumulated inside the juxtaglomerular interstitium.
Sympathetic vascular control of the pig nasal mucosa (2): reserpine‐resistant, non‐adrenergic nervous responses in relation to neuropeptide Y and ATP
Authors: LACROIX J. S. , STJÄRNE P. , ÄNGGÅRD A. , LUNDBERG J. M. 
Published: December 2008

The possible occurrence of non‐adrenergic mechanisms in the sympathetic vascular control of the nasal mucosa was studiedin vivousing reserpine‐treated pigs (1 mg kg‐1, i.v., 24 h earlier) in combination with pharmacological blockade of alpha‐adrenoceptors by local phenoxybenzamine (1 mg kg‐1, i.a.) infusion. The nasal mucosal depletion (99%) of the content of noradrenaline (NA) in reserpinized animals was not influenced by preganglionic denervation while the depletion (44%) of neuropeptide Y (NPY) was prevented. Upon stimulation with single shocks, 25% of the arterial blood flow reduction and 47 % of the nasal mucosal volume reduction (reflecting contraction of venous sinusoids) were still present after reserpine as compared with controls. In reserpinized animals, the vascular responses were slow developing and long‐lasting, and about 60% remained at 0.59 Hz and more than 80% at 6.9 Hz. The vascular effects after reserpine were, however, subjected to fatigue, which may explain why phenoxybenzamine treatment still reduced the functional effects in the absence of NA. Local intra‐arterial injections of NA, NPY and the metabolically stable adenosine‐5′‐triphospate analogue alpha, beta‐methylene ATP (mATP) caused reduction in both arterial blood flow and nasal mucosal volume. The C‐terminal fragment of NPY (NPY 13–36) also induced nasal vasoconstriction although with a fivefold lower potency than NPY 1–36. Adenosine‐5′‐triphosphate caused a biphasic vascular effect with vasodilatatory actions at low doses and a short‐lasting vasoconstriction followed by vasodilatation at very high doses (100‐fold higher than the threshold response to mATP). In contrast to the response to NA, the long‐lasting vascular effects of NPY and mATP were resistant to phenoxybenzamine treatment.In conclusion, although NA is likely to mediate most of the sympathetic vascular responses to low‐frequency stimulation in the pig nasal mucosa, a large resistance and capacitance vessel component upon high‐frequency stimulation seems to be non‐adrenergic and mimicked by NPY rather than ATP.
Effects of adrenaline on excitation‐induced stimulation of the sodium‐potassium pump in rat skeletal muscle
Authors: EVERTS M. E. , RETTERSTØL K. , CLAUSEN T. 
Published: December 2008

Experiments were performed on isolated rat soleus and extensor digitorum longus (EDL) muscles of 4–week‐old rats. In the soleus, direct electrical stimulation for 10 min induced a frequency‐dependent increase in the ouabain‐suppressible 86Rb+ uptake, which was maximal (+110%) at a frequency of 2 Hz. In the EDL this frequency only induced a 31% increase. A supramaximal concentration of adrenaline (10μmol l‐1) stimulated ouabain‐suppressible 86Rb+ uptake by 80% and 27% in soleus and EDL, respectively. The combined effect of stimulation at 2 Hz and adrenaline was not significantly larger than each of the interventions alone in either of the muscles. The fractional loss of 22Na+ from soleus muscle was increased by around 50% by the exposure to adrenaline, electrical stimulation at 2 Hz or a combination of both. The effect of electrical stimulation on 22Na+ efflux was not prevented by addition of propranolol (I or 10μmol 1–1).The results indicate that the stimulation of active Na+‐K+ transport induced by adrenaline or electrical stimulation is much more pronounced in soleus (slow‐twitch) muscle than in EDL (fast‐twitch) muscle. Since it has been suggested that an accumulation of K+ ions in the extracellular space may play a role in the development of fatigue (Bigland‐Ritchie 1984), our findings might be related to the fact that slow‐twitch muscles have a much higher resistance to fatigue than fast‐twitch muscles (Burke et al. 1971).
Myelin basic protein present in the acid extracts of rat hypothalami releases insulin and glucagon from isolated rat pancreatic islets
Authors: LEPPÄLUOTO J. , ZEYTIN F. , UENO N. , YING S.‐Y. , LING N. , GUILLEMIN R. 
Published: December 2008

The insulinotropic and glucagon‐releasing activity of acid extracts of rat hypothalami were tested in two bioassay systems using short‐time incubation of isolated rat pancreatic islets and a rat insulinoma (RIN) cell line. Release of insulin and glucagon into the incubation medium was measured by radioimmunoassay. The major insulin‐releasing and glucagon‐releasing activity eluted in a broad zone in Sephacryl S‐zoo gel filtration in 30% acetic acid corresponding to the molecular weights between approximately 10 and 40 kD. The highest activity was eluted in a zone corresponding to 14 kD and was purified to homogeneity by means of two steps of reversed—phase HPLC. Amino acid analysis and SDS polyacrylamide gel electrophoresis indicated that the biologically active material was the rat small (myelin) basic protein characterized previously by Dunkley & Carnegie (1974). The purified rat hypothalamic material showed insulinotropic and glucagon‐releasing activity indistinguishable from that of purified porcine myelin basic protein, and lost its insulinotropic activity when incubated with anti‐myelin basic protein immunosorbent.We conclude that the major insulin‐releasing and glucagon‐releasing activity in acid extracts of the high‐molecular‐weight fractions of rat hypothalami is myelin basic protein.
Distribution of recurrent inhibition within a motor nucleus. II. Amount of recurrent inhibition in motoneurones to fast and slow units
Authors: HULTBORN H. , KATZ R. , MACKEL R. 
Published: December 2008

The maximal recurrent inhibition was studied by intracellular recording from 43 triceps surae motoneurones (tentatively type‐identified by the biophysical properties of the neurones) and from 67 medial gastrocnemius motoneurones (type‐identified by the muscle unit properties; fast fatiguing, FF; fatigue resistant, FR and slow, S). Maximal homonymous recurrent IPSP (RIPSP) and input resistance (Rn) were measured at ‘resting’ membrane potential and close to firing threshold. The ‘synaptic current’ at the peak of the RIPSP was estimated (RIPSP/Rn).At ‘resting’ membrane potential the RIPSPs increased in the order FF < FR < S (0.9, 1.4, and 2.5 mV, respectively). This order was preserved when the ‘current’ (RIPSP/Rn) rather than voltage was considered, although the overall range was much reduced. When investigated close to firing threshold there were no significant differences in synaptic ‘current’. This apparent paradox may be explained by systematic differences in firing threshold between motor unit types; it increased in the order S < FR < FF (4.6, 8.9 and 13.5 mV, respectively).
Sympathetic vascular control of the pig nasal mucosa (III): co‐release of noradrenaline and neuropeptide Y
Authors: LACROIX J. S. , STJÄRNE P. , ÄNGGÄRD A. , LUNDBERG J. M. 
Published: December 2008

The overflows of noradrenaline (NA) and neuropeptide Y like immunoreactivity (NPYLI) and vascular responses upon sympathetic nerve stimulation were analysed in the nasal mucosa of pentobarbital anaesthetized pigs. In controls, a frequency‐dependent increase in NA overflow was observed whereas detectable release of NPY‐LI occurred only at 6.9 Hz. Parallel decreases in blood flow in the sphenopalatine artery and vein and in nasal mucosa volume (reflecting blood volume in the venous sinusoids) were observed. The laser Doppler flowmeter signal (reflecting superficial blood flow) increased upon low and decreased upon high frequency stimulation. Twenty‐four hours after reserpine pretreatment and preganglionic decentralization, the NA overflow was abolished while a frequency‐dependent release of NPY‐LI occurred. Forty, 60 and 80% of the vasoconstrictor responses then remained upon stimulation with a single impulse, 0.59 and 6.9 Hz, respectively. Both the vasoconstriction and NPY‐LI overflow, however, were subjected to fatigue upon repeated stimulation. In reserpinized animals release of NPY‐LI and vasoconstrictor responses were larger upon stimulation with irregular bursts at 0.59 Hz compared to effects seen at stimulation with continuous impulses. Pre‐treatment with the a‐adrenoceptor antagonist phenoxybenzamine or the monoamine reuptake inhibitor, desipramine, enhanced NA overflow by 2–3 and 1.5 times at 0.59 and 6.9 Hz, respectively. Phenoxybenzamine significantly reduced the nerve‐evoked vascular responses while the release of NPY‐LI at 6.9 Hz was increased. Desipramine increased the functional responses but reduced the NPY‐LI overflow. During tachyphylaxis to the vasoconstrictor effects of the stable adenosine 5′‐triphosphate (ATP) analogue α‐β‐methylene ATP (mATP) in controls, the vasoconstrictor responses as well as the NA and NPY‐LI overflow to nerve stimulation were unmodified. In reserpinized animals, however, the vascular responses and the overflow of NPY‐LI were reduced after mATP tachyphylaxis.These data show that both NA and NPY are released upon sympathetic nerve stimulation in the nasal mucosa in vivo and this release seems to be regulated via prejunctional a‐adrenoceptors. The lack of effect of mATP tachyphylaxis under control conditions makes it less likely that ATP serves as a major mediator of the large nonadrenergic vasoconstrictor component.
Functional and biochemical analyses of isolated rat hearts in renal and reversed renal hypertension
Authors: FRIBERG P. , RUPP H. , NORDLANDER M. 
Published: December 2008

The present study evaluates cardiac function, plasma renin activity (PRA) and left ventricular (I.V) myosin isoenzymes in untreated two‐kidney, one‐clip Goldblatt hypertensive rats (2K1C) and in 2K1C treated with felodipine and metoprolol. Normotensive rats (NCR) and another group of 2K1C, in which the renal artery constriction was removed (UC‐2K1C), were also investigated. Cardiac performance was assessed by means of a working heart perfusion device, allowing also for measurements of myocardial oxygen consumption.Following antihypertensive therapy and unclipping, blood pressure became close to normotensive levels. PRA remained equally elevated in treated and untreated 2K1C, but became practically normalized after unclipping. Relative LV weight in 2K1C increased 74% above that in NCR but in treated 2K1C increased by only 20%. In UC‐2K1C LV hypertrophy became reversed, LV weight/body being about the same as in treated 2K1C. In treated 2K1C, coronary resistance at maximal dilatation was significantly reduced, implying prevention of hypertensive, structural coronary vascular changes, and optimal LV function was improved markedly in the lower range of perfusion pressures compared with untreated 2K1C. When, however, the hearts were challenged at a high pumping resistance (perfusion pressure), I.V function was similar in untreated and treated 2K1C. Myocardial oxygen consumption for given levels of stroke work was significantly lower in treated than in untreated 2K1C. The myosin isoenzyme pattern in the LV of 2K1C was shifted, with significantly higher amounts of VM‐3 than in NCR. This shift was normalized by antihypertensive therapy or by unclipping.In conclusion, antihypertensive therapy with felodipine and metoprolol prevents the development of coronary vascular and left ventricular hypertrophy in 2K1C. This may contribute to enhance cardiac performance at low aortic pressure. The lack of improvement in optimal cardiac performance (at high aortic pressure) implies that the hypertensive stateper se, rather than extent of pressure elevation, cardiac hypertrophy, or changes of LV isoenzymes, determines the reduced cardiac function in renal hypertensive rats (Friberg & Nordborg 1986).
Mechanoreceptive units in the human infra‐orbital nerve
Authors: NORDIN M. , HAGBARTH K.‐E. 
Published: December 2008

Eighty‐four low‐threshold mechanoreceptive afferents innervating facial hairy skin or the red zone of the lip were recorded with micro‐electrodes from the human infra‐orbital nerve. Based on their responses to skin indentations, the units were classified as slowly or fast‐adapting, with small or large receptive fields. The responses to hair movement, skin stretching and contraction of facial muscles were also studied.Both hairy skin and the red zone were innervated by slowly and by fast‐adapting units. The innervation density was found to be highest at the corner of the mouth and on the upper lip. Slowly adapting units with small fields in hairy skin were most common and included units responding to sustained hair displacement. These units are suggested to have two types of end‐organs, either pilo‐Ruffini endings or Merkel cell‐neurite complexes. The slowly adapting units with large fields were spontaneously active stretch receptors and may have corresponded to Ruffini corpuscles, although the possibility of other, intramuscular, receptors could not be ruled out. Only one afferent possibly innervated a Pacinian corpuscle.Most mechanoreceptors were also activated by skin stretching or contraction of facial muscles. Many of the slowly adapting units with small fields responded to the onset and release of stretch, whereas their discharge in response to sustained stretching adapted more or less completely. Spontaneously active units had the most sustained stretch response. It is concluded that several types of cutaneous mechanoreceptors can operate as sensitive proprioceptors of importance for facial kinaesthesia and motor control.
Transmural distribution of left ventricular glucose uptake in spontaneously hypertensive rats during rest and exercise
Authors: LEIPÄLÄ J. A. , VIRTANEN P. , RUSKOAHO H. J. , HASSINEN I. E. , TAKALA T. E. S. 
Published: December 2008

The transmural distribution of glucose uptake was studied in the left ventricle of 6‐month‐old male Wistar–Kyoto (WKY) and spontaneously hypertensive rats (SHR) during rest and swimming (20 min) using the 2‐deoxyglucose method. The baseline mean arterial pressure was 128 ± 8 (n= 8) in the WKY and 188 ± 22 mmHg (n= 8) in the SHR (P < 0.001). This pressure remained constant in the resting groups, whereas the product of mean arterial pressure and heart rate was initially 45×103± 3 times 103 and 63×103± 4×103 mmHg beats min‐1 in the swimming WKY and SHR and increased by 34–48×103 mmHg beats min‐1 during the swimming period. Total glucose uptake was 3.9 ± 1.2 μ mol min‐1 g‐1 protein in the resting WKY rats and 1.4 ± 0.4, μ mol min‐1 g‐1 protein (P < 0.001) in the swimming ones, the corresponding values for the resting and swimming SHR being 4.8 ± 1.4 μ mol min‐1 g‐1 protein and 3.2 ± 1.2 μmol min‐1 g‐1 protein (P < 0.01). Glucose uptake was 30% greater in the subendocardium (ENDO) of the resting WKY than in the subepicardium (EPI) (P < 0.01), but this gradient disappeared during swimming. Glucose uptake in the resting SHR was greatest in the middle layer of the ventricular wall, with no difference between ENDO and EPI, whereas during swimming the glucose uptake was distributed evenly across the left ventricular wall.The blood lactate/pyruvate ratio increased only transitorily during the first minutes in the swimming SHR, while their plasma free fatty acid concentration was 1.2–1.3 mm initially and decreased by 32% (P < 0.01). The data show that both hypertension and acute exercise alter the transmural distribution of glucose uptake. Swimming caused a decrease in total left ventricular glucose uptake in both the WKY and SHR, which cannot be explained solely by an altered supply of competitive myocardial fuels.
Involvement of D1 dopamine receptors in the control of TSH secretion in the male rat
Authors: ANDERSSON K. 
Published: December 2008

The effects of SCH 23390 (D1 dopamine receptor antagonist), SK&F 38393 (D1 dopamine receptor agonist), raclopride and remoxipride (D2 dopamine receptor antagonists) and ketanserin (5‐hydroxytryptamine 2 receptor antagonist) on TSH serum levels (radioimmunoassay) and on brain catecholamine levels (Falck‐Hillarp methodology in combination with quantitative histofluorimetry) were studied.SCH 23390 produced a dose‐dependent increase in serum TSH levels in the lower dose range (0.01–0.03 mg kg‐1, i.p.) administered 30 min before decapitation and in the higher dose range (1.0–3.0 mg kg‐1) when given 2 h before decapitation. Following 30 min of treatment with the high doses of SCH 23390, reductions in serum TSH levels were found. The changes observed following SCH 23390 treatment occurred without affecting catecholamine levels in the median eminence and the peri‐ and paraventricular hypothalamic regions. Raclopride (0.1–10 mg kg‐1, i.p.), remoxipride (1.0 mg kg‐1, i.p.) or ketanserin (0.3 mg kg‐1, i.p.) changed neither serum TSH levels nor brain catecholamine levels. SK&F 38393 (1.0–10 mg kg‐1, i.p.) produced an increase in serum TSH levels.The results suggest the existence of inhibitory and facilitatory mechanisms regulating TSH secretion mediated via D1 dopamine receptors.