摘要:

Most experiments on dental nerves have been made using dentine recording technique and it seems that only the fast conducting myelinated pulpal nerve fibres can be recorded with this technique. However, histological studies have revealed that even 80% of intradental fibres in the cat are unmyelinated. In the present work we studied activation of intradental nerve fibres with monopolar electrical stimulation of the intact mandibular canine tooth crown of the cat. The purpose was to determine the proportion of responding intradental A‐and C‐fibres dissected from the inferior alveolar nerve. In 17 anesthetized cats 350 pulp nerve fibre units were identified and recorded. Conduction time (based on the shortest latency), distance between the stimulation and the recording sites and threshold current for each fibre unit were determined. The mean conduction velocity for all pulp nerve fibres was 9.2 m/s (SD=9.8). The number of C‐fibres (conduction velocity ≤2.0 m/s) was 122 (34.9%) and the number of A‐fibres was 228 (65.1 %). The mean conduction velocities of C‐ and A‐fibres were 1.0 m/s (SD=0.4) and 13.4 m/s (SD=9.4), repectively. The mean threshold current was 22.8 μA (SD=20.1) for the whole group, 40.4 μA (SD=20.7) for C‐fibres and 13.5 μA (SD=11.8) for A‐fibres. Although the function of pulpal C‐fibres is poorly known, it has been suggested that they have a distinct role in mediation of sensations from tooth, particularly in inflammatory processes. Using nerve dissection technique the activity of a considerable part of intradental C‐fibres can be recorded and it seems to be the only available method to study the func

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07132.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The role of α‐ and β‐adrenergic receptor stimulation for the effect of epinephrine on muscle glycogenolysis, glucose‐ and oxygen uptake and muscle performance was studied in the perfused rat hindquarter at rest and during electrical stimulation (60 contractions/min). Adrenergic stimulation was obtained by epinephrine in a physiological concentration (2.4 × 10‐8M) and α‐ and β‐adrenergic blockade by 10‐5M phentolamine and propranolol, respectively. Epinephrine enhanced net glycogenolysis during contractions most markedly in slow‐twitch red fibers. In these fibers the effect was mediated by α‐ as well as by β‐adrenergic stimulation, the latter involving production of cAMP, phosphorylase activation and synthase inactivation. In contrast, in fast‐twitch fibers only β‐adrenergic mechanisms were involved in the glycogenolytic effect of epinephrine. Moreover, inactivation of synthase was less in these fibers. Epinephrine also increased the net release of lactate from the hindquarter, an effect abolished by combined α‐ and β‐adrenergic blockade but by neither α‐ nor β‐adrenergic blockade alone. Epinephrine increased uptake of oxygen and glucose by stimulation of α‐adrenergic receptors and had a positive inotropic effect during contractions which was abolished by α‐ as well as by β‐adrenergic blockade. The results indicate that epinephrine has profound effects on contracting muscle, and that these effects are elicited through different comb

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07133.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effects of experimentally induced hyperosmolality has been studied in rats. Renal vascular pedicle ligation was performed on all animals to prevent renal clearance of the infused solute, xylose, and allow accurate ECF space determinations with51Cr EDTA. Small volume hyperosmolar xylose infusions caused parallel elevation of the osmolality of thoracic duct lymph and arterial plasma. A positive correlation was obtained between lymph osmolality and flow alterations. The maximal osmolality elevation of 22 mosmxkg‐1H2O was associated with an intracellular fluid mobilisation which was equal to 7.1% of the ECF space. The infused and mobilised fluid volumes were distributed unequally between the intra and extra vascular compartments of the EC

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07134.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Prostaglandin E2(PGE2) increased the blood pressure, heart rate and body temperature, when administered at the doses of 0.001–10 μg into the lateral cerebral ventricle (i. c. v.) of the urethane‐anesthetised rat. The highest dose of 10 μg/rat induced a strong initial hypotensive effect. Intravenously (i. v.), PGE2at the doses of 0.01–10 μg/rat caused a biphasic blood pressure response with dose‐related initial decreases followed by slight increases in blood pressure. The heart rate and body temperature were slightly increased by i. v. administrations of PGE2. The highest i. v. dose of 10 μg/rat initially decreased also the heart rate. Central pretreatment with indomethacin (1 mg/rat i. c. v.) partly antagonised all of the recorded central effects of PGE2, while sodium meclofenamate (1 mg/rat i. c. v.) abolished the hypertensive response to i. c. v. administered PGE2but failed to significantly affect the PGE2‐induced rises of heart rate and body temperature. The results support the previous suggestions that PGE2may participate in the central cardiovascular and thermoregulatory control. The results also suggest that indomethacin and sodium meclofenamate antagonize the effects of exogenous prostaglandins. Since sodium meclofenamate, unlike indomethacin, affected preferentially the hypertensive response to centrally administered PGE2, there may be differences in the sites and/or modes of action betwee

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07135.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Extracellular fluid volumes have been determined in fed and 24–30 h starved rats, before and after 60 min of hemorrhagic hypotension at 70 mmHg. Bilateral renal vascular ligation was carried out to prevent clearance of the isotope tracer used,51Cr EDTA. The time taken for a bolus of the tracer to distribute itself in its space, was determined in fed and starved animals after the standard period of hypotension. This was found to be 37 min for fed animals, and 50 min for those which had been starved. When the isotope ECF space was compared before and after hemorrhage in fed animals, it was unchanged, despite an estimated blood volume loss of 39%. The isotope ECF space was reduced 5.5% after hemorrhage in animals which had been starved. It is concluded that fed rats mobilised intracellular fluid to the interstitium in hemorrhage, whereas, starved animals did not. This finding of variable fluid homeostasis is ascribed to the different nutritional status of the animals investigated, and has considerable implication

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07136.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The rat kidney autoregulates its blood flow (RBF) when renal arterial blood pressure (RAP) is lowered, but less efficiently than does the dog kidney. We wanted to investigate to what extent acute unilateral elevation of ureteral pressure (UP) in the Sprague‐Dawley rat would interfere with the renal vasodilatory responses elicited by RAP reduction and by intraarterial infusion of acetylcholine (Ach). RBF was significantly better autoregulated before than during UP elevation to 43 mmHg (p<0.001), as measured electromagnetically in an extracorporal flow circuit. However, RBF decreased within the autoregulatory pressure range: Closely similar RBF reductions, 3–4% per 10 mmHg, were obtained both by increasing UP and by decreasing RAP by 10 to 50 mmHg. These RBF reduction did not involve active renal vasoconstriction since maximal dilation by i. a. Ach infusion (∽1.0 μg/min) increased RBF significantly more before and after than during UP elevation (p<0.01). The proportional responses to changes in intra and extra‐vascular pressures therefore suggest that a mechanism controlled by transmural pressure is responsible for RBF autoregulation. UP increase had no effect on contralateral RBF. The effect of UP elevation on intrarenal blood flow distribution, as determined by zonal uptake rates of the diffusible tracer125I‐iodoantipyrine, was studied in a second group of rats at an UP averaging 32 mmHg. Fractional zonal blood flow decreased in outer third (p<0.05) and increased in inner third of the cortex and outer half of the outer medullap<0.05). This redistribution was not detected if cortex was divided in h

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07137.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

To examine whether the right ventricle responds differently to blood volume expansion and selective right ventricular volume loading, segment lengths in the interventricular septum and the free walls of both ventricles and right ventricular septal‐to‐free‐wall‐ distance were measured by an ultrasonic technique in open‐chest dogs. Blood volume expansion increased segment lengths at all recording sites in proportion to stroke volume, Selective right ventricular volume loading induced by opening a shunt between the pulmonary artery and the superior vena cava increased right ventricular stroke volume by 40–80%; end‐diastolic segment length and myocardial shortening increased in the septum and free wall of the right ventricle whereas left ventricular stroke volume and segment length decreased. Comparison of data obtained before and after opening of the shunt indicated that changes in myocardial dynamics of the right ventricle and septum accounted for approximately 30% of the increase in right ventricular stroke volume. However, both end‐diastolic dimension and systolic shortening of the right ventricular septal‐to‐free‐wall distance were larger during right ventricular volume loading than during blood volume expansion. Thus, most of the increase in stroke volume during selective right ventricular volume loading is caused by a change in the configuration o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07138.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Single spontaneously beating myocardial cells were prepared by mechanical or enzymatical isolation. Using a TV camera and videotape recorder, beating parameters were characterized in different buffer solutions in regard to temperature and integrity of sarcolemma, which was tested by ability of cells to exclude a vital stain, Evans blue. The mechanically disaggregated cells were totally permeable to this stain, but about 60% of the enzymatically isolated myocytes were able to exclude the stain. The myocytes prepared in the presence of calcium were most tolerant to physiological concentration of calcium. Contractions were mainly of phasic type where the velocity of contraction wave was very slow (50–330 μm/s). The velocity was not correlated to the beat rate. Temperature dependence of the velocity was positively correlated with the integrity of sarcolemma. Beat rate was inversely related to the integrity of sarcolemma being slowest in calcium tolerant enzymatically isolated cells. Beat rate of calcium sensitive myocytes was higher but unstable and the temperature dependence of the rate was steeply reduced and even reversed during the incubation. Some calcium tolerant myocytes generated occasionally an electric type of contraction which came in bursts and was characterized by synchronous sarcomere shortening without any contraction wa

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07139.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Histamine induced changes in microvascular permeability to macromolecules were studied in two models, the hamster cheek pouch and the canine forelimb preparation. Fluoresceinlabelled dextran FITC‐dextran. Mw=70000 and 150000 was used as tracer of permeability increases. Studies in the hamster showed that morphological changes as indicated by intravital microscopy of FITC‐dextran leakage at postcapillary venules were accompanied by an increased concentration of FITC‐dextran in the superfusion solution for the cheek pouch. Following histamine challenge during 4 min the cheek pouch microcirculation was normalized 30 min later both with regard to number of leakage sites and the concentration of FITC‐dextran in the superfusion solution. Pretreatment of the cheek pouch with terbutaline (3.6 × 10‐6M) for 1 h resulted in total inhibition of both morphologically and fluorometrically recorded changes from continuous histamine superfusion. When terbutaline and histamine were given at the same time, there was a significant inhibition of the histamine induced increase in the number of leakage sites to 10% of the pre‐terbutaline response. The fluorometrically detected efflux of FITC‐dextran was 65% of the preterbutaline value. The dynamics of interendothelial cell gap formation and closure was also studied in the dog. Intra‐arterial infusions of histamine into forelimbs perfused at a constant pump controlled flow rate produced decreases in perfusion pressure, increases in lymph flow, lymph protein concentration, total protein transport and weight. FITC‐dextran was given as an i. v. injection 30 min before and 0, 30 and 60 min after the start of a 90 min arterial infusion of histamine into the brachial artery of the forelimb. Lymph (CL) and plasma (Cp) concentrations of FITC‐dextran were determined and CL/Cp‐ratios showed that the permeability increasing effect lasted less than 30 min although histamine was given for further 60 min. The results of both hamster and forelimb experiments suggest that leakage sites or interendothelial cell gaps in postcapillary venules are closed within 30 min from the first exposure to histamine, probably within 15 min and that there is little indication of any remaining increase in macromolecular permeability via any other route (vesicular) fol

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07140.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

We have investigated the extent to which the properties of small arteries from the hindquarters of spontaneously hypertensive rats (SHRs) are consistent with the characteristics of perfused SHR hindquarter preparations (for which the relaxed vascular resistance, the reactivity and the sensitivity are reported to be increased). We have therefore compared the in vitro morphological and pharmacological properties of a femoral resistance vessel (i. d. ca 200 μm) and of the tail artery (i. d. ca 600 μm) from SHRs with those from control Wistar‐Kyoto rats (WKYs). When relaxed, for any given wall tension, the internal circumference of the SHR resistance vessels was reduced, but that of the SHR tail artery was normal. When activated with 10 μM noradrenaline, the SHR resistance vessels had an increased calcium sensitivity, but the calcium sensitivity of the SHR tail arteries was normal. However, the maximum response of both types of SHR vessels was such that the vessels would have been able to contract against increased transmural pressure. The noradrenaline sensitivity of the SHR resistance vessels was normal but the SHR tail arteries had a decreased sensitivity. The results suggest that the femoral resistance vessel is in general a better model for the hindquarter vasculature than the tail ar

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07141.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY