摘要:

AbstractThe effects on the isolated human umbilical artery (HUA) of the recently isolated endoperoxide intermediates in prostaglandin (PG) biosynthesis, PGG2and PGH2, were studied. Both endoperoxides were potent contractors of the artery strips, the threshold concentrations being 3 (1–4) ng/ml for PGG2and 1 (1–2) ng/ml for PGH2, as compared with 200 (40–400) ng/ml for PGE2. The hemiacetal derivative of 8‐(1‐hydroxy‐3‐oxopropyl)‐9,12L‐dihydroxy‐5,10‐heptadecadienoic acid (thromboxane B2), a metabolite of PGG2, appeared in the bath medium indicating PG and thromboxane generation in the isolated HUA. The formation of thromboxane B2was inhibited by indomethacin (8–40 μg/ml) and by eicosa‐5,8,11,14‐tetraynoic acid (ETA) (25 μg/ml). ETA also inhibited the contractile responses to both endoperoxides. The results support the view that local generation of PGs might be involved in th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10183.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractA method for isolating gastric glands from the corpus of the rabbit gastric mucosa is presented. The stomach of an anesthetized rabbit was perfused with saline under high pressure through the aorta, taken out and emptied. The mucosa was stripped off, minced into small pieces and transferred to a 1 mg/ml collagenase solution. After 90 min at 37°C, a large number of isolated gastric glands and cells were separated free. By a simple washing procedure the glands were freed from cell contamination and collagenase. The gastric glands were viable, as demonstrated by dye exclusion technique, oxygen consumption and electrolyte content. For identification of the glandular cells both common staining techniques and electron microscopy were used. Four types of cells were identified, viz. parietal cells, zymogen cells, mucous neck cells and some endocrine cells. The intracellular morphology of the glandular cells did not differ significantly from that seen in intact gastric mucosa. The glands could be stimulated with histamine, in a dose‐response manner, as revealed by the increase in oxygen consumption (ED‐50 equal 3 × 10‐6M). This isolated gastric gland preparation may serve as a useful tool for new approaches in gastric phy

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10184.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractLipolysis and cyclic AMP accumulation were studied in isolated rat fat cells at normal (7.4) and decreased (7.0, 6.6) pH. Acidosis inhibited lipolysis and cyclic AMP accumulation due to NA non‐competetively. Maximal lipolysis (3 μM NA) was inhibited by 25% at pH 7.0 and by 61 % at pH 6.6. Cyclic AMP accumulation 5 min after 3 μM NA was inhibited by 57% at pH 7.0 and by 83% at pH 6.6. Between 10 and 60 minutes of incubation NA‐stimulated lipolysis was linear at pH 7.4, whereas a progressively increasing inhibition was seen at lower pH. The FFA production was inhibited to the same degree as glycerol production by acidosis. The fraction of FFA associated with the cells was the same at all pHs. Thus, we have no evidence that acidosis inhibits lipolysis via accumulation of FFA intracellularly. NA‐induced accumulation of3H‐cAMP from3H‐ATP, endogenously formed by prelabelling the cells with3H‐adenine, was inhibited by acidosis both in the presence and absence of theophylline in the incubation medium (by 48 and 44% respectively at pH 7.0 and by 74 and 68 % at pH 6.6). Cyclic nucleotide phosphodiesterase in homogenates of fat cells was inhibited by decreasing the pH, whether measured at high or low substrate concentrations. Basal adenylyl cyclase activity in a cell membrane fraction from fat cells was affected to a minor degree, while NA‐stimulated activity was inhibited by decreased pH. The response to 3 μM NA at pH 6.6 was inhibited by 43% relative to control. The results show that acidosis inhibits NA‐induced cyclic AMP accumulation by interfering with the formation, rather than the inactivation of the nucleotide. Since NA‐induced lipolysis is a cyclic AMP‐mediated process it is suggested that at least part of the antilipolytic effect of acidosis is due to inhibition o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10185.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractNA‐stimulated lipolysis and cAMP formation in isolated rat fat cells is inhibited by acidosis. In the present report we have examined the quantitative relationship between lipolysis and cAMP formation at normal and reduced pH and the possible involvement of adenosine, an endogenous inhibitor of cAMP formation. Adenosine antagonized cAMP accumulation and to a considerably lower degree lipolysis, effects potentiated by acidosis. Theophylline, an antagonist of adenosine effects, stimulated lipolysis and cAMP‐accumulation, and potentiated responses to NA. Adenosine deaminase (ADA) had theophylline‐like effects. Acidosis inhibited lipolysis and cAMP accumulation induced by ADA and theophylline to a larger extent than those induced by NA. It is suggested that adenosine modulates fat cell cAMP production and may contribute to the antilipolytic effect of acidosis. There was a curvilinear relationship between cAMP elevation and glycerol production in fat cell suspensions, which was different at pH 7.4 and at pH 6.6. The amount of cAMP needed for half‐maximal activation of lipolysis increased from 1.3 (pH 7.4) to 3.1 pMol × 10‐5cells (pH 6.6). The maximal glycerol production was reduced from 1 300 to 900 nMol × 10‐5cells. The antilipolytic effect of acidosis is apparently due partly to an inhibition of cAMP formation and partly to inhibition of subsequent step(s) in the activa

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10186.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractA neurogenic β‐adrenergic vasodilatation in skeletal muscle has been indicated by some recent investigations. The present study describes the extent to which this neurogenic β‐dilator mechanism contributes to the integrated vascular response in consecutive sections of the muscle vascular bed during sympathetic nerve activation. This was done by studying the vascular reactions to graded sympathetic stimulation (1–16 Hz) before and after β‐adrenoceptor blockade, β‐blockade did not influence significantly the sympathetically induced changes of total muscle vascular resistance or capacitance. Vascular tone in the “micro‐vessels” during stimulation was, however, clearly more pronounced in the β‐blocked than in the non‐blocked region, as revealed by segmental resistance analysis and by determination of precapillary sphincter tone (CFC). In addition, β‐blockade markedly reduced the net transcapillary absorption of extravascular fluid evoked by nerve activation. This effect could be ascribed to the mentioned influence on the precapillary sphincters, leading to a decrease of the number of capillaries available for transcapillary exchange, and to a limitation of the nerve induced fall of capillary hydrostatic pressure. The described effects of β‐blockade were observed at all rates of sympathetic stimulation. — The conclusion was reached that the β‐adrenergic dilator component of the sympathetic vascular response in skeletal muscle significantly modifies the α‐adrenergic constriction in the micro‐vessels. It is suggested that, in the intact organism, this neurogenic β‐dilator mechanism is primarily aim

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10187.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractInterneurones identified as mediating the disynaptic reciprocal Ia inhibition of motoneurones (referred to as “Ia inhibitory interneurones”) were recorded in the lumbar spinal cord of the cat. It was revealed that the Ia inhibitory interneurones themselves receive disynaptic Ia inhibition. The muscles from which this inhibition is evoked are strictly antagonistic to those supplying their Ia excitation. Similar to the Ia inhibition in motoneurones the Ia inhibition in the Ia inhibitory interneurones is decreased when preceded by an antidromic stimulation of ventral roots. Furthermore, transmission of Ia inhibition to the Ia inhibitory interneurones is facilitated from ipsilateral and contralateral primary afferents as well as several supraspinal pathways analogous to earlier findings for the Ia inhibition of motoneurones. The pattern and control of the Ia inhibition of motoneurones and of Ia inhibitory interneurones display so striking similarities that it is suggested that identical interneurones are responsible. The conclusion thus emerges that “opposite” Ia inhibitory interneurones (i.e.interneurones monosynaptically connected to antagonistic muscles) are mutually inhibiting each other. The functional significance of this organization is di

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10188.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe redox substrates—lactate, malate, α‐glycerophosphate, dihydroxy acetonephosphate and pyruvate—have been determined in liver and muscle tissue from young salmon. The redox quotients have also been calculated. The freeze clamping technique was used and reliable samples of fish muscle for the determination of lactate were obtained with the aid of a pair of pliers with a gear mechanism. It was established that the lactate content in the body muscle is in close agreement with that in the blood from rested salmon parr. The concentrations of redox substrates are in good agreement with those found in mammalian tissue. The determination of the content of glycogen in fish muscle is discussed in the light of the results obtained in this

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10189.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe voluntary recruitment order of anterior tibial motor units was studied in electromyographic recordings using both low and high impedance electrodes. It was shown in previous papers, that the recruitment order in sustained voluntary contraction is normally stable and that motor units with low thresholds discharge at low, regular frequencies and that motor units with high thresholds discharge at higher and more irregular frequencies. In this paper the consequences for the discharge properties of reduced afferent inflow in sustained voluntary contraction were studied, using partial ischemic or lidocain blockades of the muscle nerve and local cooling of the muscle belly. 1. The recruitment order of certain low and certain high frequency units was reversed. 2. The muscle tension and sense of effort necessary for tonic firing were increased for certain low frequency units but decreased for certain high frequency units. 3. On severe reduction of the afferent inflow, the differences in discharge pattern between low and high frequency units were decreased. It is concluded that the recruitment of low frequency units before high frequency units in sustained voluntary contraction is partly due to proprioceptive afferent activity favouring low frequency units and disfavouring high frequency units. It is also concluded that the afferent inflow is involved in restricting certain units to low frequency discharge and others to high frequency discharge.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10190.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractConvergence of vestibulospinal and segmental effects onto spinal interneurones which project to the ventral spino‐cerebellar tract (VSCT) neurones has been studied by intracellular recording in VSCT cells. The disynaptic Ia IPSPs evoked in a group of VSCT neurones from the quadriceps nerve are monosynaptically facilitated by the vestibulospinal tract while there was no facilitation of Ia IPSP evoked from a flexor nerve. These results support the view that Ia inhibition to VSCT cells and motoneurones is mediated by common interneurones. The disynaptic inhibition evoked in other VSCT cells from the vestibulospinal tract is facilitated by volleys in the contralateral flexor reflex afferents (FRA) or bilaterally from the FRA. It is postulated that these actions are mediated by collaterals of the interneurones responsible for the analogous effects in motoneurones. Findings are reported suggesting that the monosynaptic vestibulospinal EPSP in VSCT cells in most cases is collateral to the excitatory input to the last order interneurones of reflex pathways from the FRA to motoneurones and only exceptionally to the corresponding input to Ia inhibitory interneurones. In many VSCT cells the vestibulospinal tract evoked disynaptic EPSPs which are facilitated from the FRA; the functional significance of this actions is uncertain. The results are consistent with the hypothesis that VSCT neurones signal information on interneuronal transmission to motoneurone

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10191.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractStimulation of the contralateral red nucleus evoked monosynaptic EPSPs in 14 of 82 ventral spinocerebellar tract neurones. In some of these cells the monosynaptic EPSP was followed by a disynaptic IPSP. The remaining cell population received di‐ or polysynaptic PSPs from the rubrospinal tract, either EPSPs or IPSPs or both. Convergence of the rubrospinal tract onto interneurones of the segmental pathways projecting to VSCT cells was demonstrated. Rubrospinal volleys facilitated disynaptic Ia IPSPs evoked in VSCT neurones from both flexors and extensors, as well as disynaptic Ib IPSPs. Facilitation of the Ia interneurones was disynaptic whereas facilitation of Ib interneurones was monosynaptic. Disynaptic rubrospinal EPSPs and IPSPs were facilitated by volleys in ipsi‐ as well as in contralateral cutaneous and high threshold muscle afferents. The complex pattern of projections from the rubrospinal tract onto VSCT neurones and the related reflex pathways gives further support to the hypothesis that these tract cells convey information on transmission through interneurones of the spinal segmental mechani

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10192.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY