Our laboratory has identified plasma membrane oestrogen receptors on a GH3/B6 rat pituitary tumour cell line and several sublines which produce rapid (within minutes), non-genomic responses to oestrogens. Oestrogen receptors have been identified by their binding to nine different antibodies (Abs) which together recognize at least seven epitopes on the oestrogen receptor-α. GH3/B6/F10 cells, a membrane oestrogen receptor-enriched subline, elevate intracellular calcium levels in response to 10 nM oestradiol. Prolactin release in these cells is triggered by both 1 pM and 1 nM oestradiol and diethylstilbestrol (DES). A membrane oestrogen receptor-α immunocyto-chemical signal rapidly disappears (at 3 min) and reappears (at 12-15 min) when 1 nM oestradiol, 10 nM diethylstilbestrol, or 10 nM nonylphenol is applied to the cells. This suggests that both oestrogens and xenoestrogens can utilize this alternative pathway for oestrogenic action. Xenoestrogens, which have so far shown weak effects in genomic assay systems, should now be retested for activity in eliciting membrane-initiated oestrogenic responses.

It is not resolved whether the anionic channel involved in volume regulation after cell swelling comprises one or more subunits. Moreover, it remains to be determined which of the different proteins cloned so far, for which an involvement in cell volume regulation has been postulated, is the ideal candidate. In this review, we consider the role of the ICln protein, cloned from MDCK cells, in cell volume regulation.

We have functionally expressed and identified a monocarboxylate transporter (MCT1) from rat jejunal enterocyte and we provide evidence for its basolateral localization. Poly(A)+ RNA isolated from rat jejunum was injected into Xenopus laevis oocytes and expression of a proton-lactate symporter was investigated by means of L-[14C]lactate uptake. The existence of an endogenous capacity for L-lactate transport was demonstrated; when, however, oocytes were injected with jejunal mRNA, an expressed L-lactate uptake was seen which differed from the endogenous transporter since it was significantly pH dependent. After sucrose density gradient fractionation, the highest expression of the pH-dependent lactate uptake was detected with the mRNA size fraction of about 2-3 kb in length. The substrate specificity, stereoselectivity and sensitivity to pCMBS (an organomercurial thiol reagent that modifies cysteine residues) of the expressed transport were in good agreement with results previously obtained using isolated jejunal basolateral membranes. Using the reverse transcriptase-polymerase chain reaction, the presence of mRNA coding for the MCT1 isoform was demonstrated in jejunal enterocytes. These data, together with previous results, suggest that MCT1 is a major route for lactate efflux across the basolateral membrane of rat jejunum; this is in contrast to current opinion which restricts the presence of MCT1 to the apical membrane of the whole small intestine.

We studied the effects of an external acute 10 min application of cytoskeletal interfering agents on cardiac L-type calcium current (ICa,L). We found that colchicine, taxol and cytochalasin D had no direct effect on the L-type calcium channel as indicated by the absence of effect on voltage-dependent parameters. Phalloidin induced a shift in the I-V curve which renders it difficult to use in excitation-contraction coupling studies. Microfilaments of actin did not seem to regulate cardiac ICa,L as indicated by the lack of effect of cytochalasin D on ICa,L amplitude and inactivation kinetics. On the contrary, microtubules seem to be involved in the calcium-dependent inactivation of ICa,L. This involvement might be direct, i.e. a physical link between the microtubules and some part of the channel protein, or it could be indirect, i.e. the calcium chelating properties and physical obstacle of microtubules in the space between the sarcolemma and the SR.

The effects of streptozotocin (STZ) diabetes and the antihyperglycaemic agent metformin on the contractile characteristics of the limb skeletal muscles and on erythrocyte volume were examined in rats. After 8 weeks of diabetes, the tetanic tension of the extensor digitorum longus (EDL) muscle decreased and the half-relaxation time of the soleus muscle increased. Endurance decreased in both muscles. Metformin treatment of the diabetic rats did not prevent the development of these contractile changes. Diabetes induced depolarisation in the EDL and soleus muscles. Following exposure to insulin, both muscles repolarised. Metformin treatment of control rats induced depolarisation in the EDL and soleus muscles, but in the depolarised EDL and soleus muscles of the diabetic rats metformin treatment caused no further depolarisation. The muscles of metformin-treated control and diabetic rats hyperpolarised in the presence of insulin. Diabetes caused an increase in the volume of the blood erythrocytes. This was prevented by metformin treatment.

Neurones located in cervical segments (C6/C7) of the spinal cord were investigated electrophysiologically in cats deeply anaesthetized with α-chloralose. Extracellular recordings of antidromic action potentials were performed in order to establish whether long descending propriospinal neurones projecting to sacral segments could have collateral axonal branches ascending to supraspinal centres. The effects of stimulation of the lateral reticular nucleus (LRN) and the inferior cerebellar peduncle (restiform body, RB), as well as the thirteenth thoracic (Th13) and sacral (S1/S2) segments of the spinal cord were tested in 93 cells. Two main groups of cells were identified: 54 % of the total sample were classified as purely propriospinal and 46 % as bidirectional neurones. Various patterns of projections, as well as the ipsi-, contra- or bilateral courses of axons in the lateral funiculi of the spinal cord, enabled several types of neurones to be distinguished within the above groups. Comparison between particular types showed no significant difference with respect to location in the grey matter (predominantly Rexed's laminae VII-VIII) and the conduction velocities of descending axons. However, the mean axonal conduction velocities of branches ascending to LRN and/or RB were significantly lower in comparison to those measured for spinal collaterals. The hypothetical function of the neurones examined is discussed. Since the same information can be conveyed simultaneously by these branching neurones to lower spinal segments and supraspinal centres, an integrative role in the system of motor control is suggested.

Chromogranin A (CgA) is a member of a family of highly acidic proteins, chromogranins, which are co-stored in the adrenergic neurons and paraneurons and co-released with adrenaline and noradrenaline (NAd) in response to adequate stimulation. The present study provides novel evidence that CgA-like immunoreactivity (IR) is stored in the exocrine cells in the granular convoluted tubule, and is secreted into saliva by stimulation with NAd and acetylcholine (ACh) in the isolated and perfused rat submandibular gland. NAd at 1 µM produced maximum secretion of CgA-like IR (<< 0·9 mM) and a marked increase in salivary flow. Further increases in NAd concentration (10 or 100 μM) yielded concentration-dependent decreases in both responses. ACh at 1 μM produced maximum salivary flow and a slight elevation of CgA-like IR secretion (6 μM); 100 μM ACh decreased the salivary flow but increased the CgA-like IR secretion (0·6 mM). Electron microscopic examination showed vigorous compound exocytosis of secretory granules in the cells of the granular convoluted tubule when the submandibular gland was stimulated with 1 μM NAd. These results provide an experimental basis for the view that the salivary CgA-like IR secretion may be a sensitive and quantitative index of the activity of the sympathetic nervous system innervating the gland.

The effects of longitudinal stretch on vasoreactivity were assessed in isolated, pressurised arteries from the rat mesentery, rat mid-cerebral and human subcutaneous vascular beds. A stretch-dependent increase in reactivity was observed only in rat third order mesenteric arteries. Longitudinal stretch >> 20 % (force equal to 0·23 ± 0·04 mN) optimises vasoconstrictor responses to noradrenaline and phenylephrine in rat third order mesenteric arteries. Stretch did not affect the vasoconstriction response to depolarisation by 30 mM K+ PSS in any of the arteries studied. Similarly, stretch had no affect on pressure-dependent myogenic responses in rat mid-cerebral arteries. Endothelium-independent and endothelium-dependent mechanisms of vasorelaxation were unaffected by stretch in rat third order mesenteric arteries. Likewise, stretch did not affect vasoreactivity in rat mid-cerebral and human subcutaneous resistance arteries. Our results show that longitudinal stretch in isobaric-mounted rat third order mesenteric arteries is an important methodological consideration. Considering our results, we recommend that isobaric-mounted rat third order mesenteric arteries are stretched >> 20 % to provide optimal experimental conditions for pharmacological studies.

Long-term administration of NG-nitro-L-arginine methyl ester (L-NAME) induces development of hypertension and hypertrophy of the left ventricle in rats. The aim of the present study was to demonstrate the effect of chronic L-NAME treatment on DNA and RNA concentration, and protein synthesis in the rat heart, aorta, brain and kidney and to determine the effect of angiotensin converting enzyme (ACE) inhibitor captopril on these potential alterations. Four groups of rats were investigated: control, L-NAME (40 mg kg-1 day-1), captopril (100 mg kg-1 day-1), and L-NAME (40 mg kg-1 day-1) + captopril (100 mg kg-1 day-1). NO synthase activity in the heart, aorta, brain and kidney was found to be decreased in the L-NAME group. In the group of rats treated with L-NAME + captopril, captopril did not affect NO synthase inhibition. Captopril, however, completely prevented development of hypertension and left ventricular hypertrophy in this group. In the L-NAME group, DNA and RNA concentrations, as well as [14C]leucine incorporation, were significantly increased in all the tissues investigated. In the L-NAME + captopril group, captopril completely prevented the enhancement of DNA and RNA concentrations and [14C]leucine incorporation in all tissues compared to the L-NAME group. Moreover, a significant decrease in RNA concentration and [14C]leucine incorporation below control values was found in the captopril group as well as the L-NAME + captopril group in all the tissues investigated. We conclude that captopril prevented the development of hypertension and increase in nucleic acid concentration and protein synthesis in the heart, aorta, brain and kidney in rats treated with L-NAME + captopril. However, this protective effect of captopril was not associated with increased NO synthase activity in this model of hypertension.

The role of nitric oxide (NO) in mediating pancreatic endocrine responses to moderate hypoglycaemia has been investigated in conscious unrestrained calves. The synthesis of endogenous NO was inhibited by the administration of N-nitro-L-arginine methyl ester (L-NAME; 100 mg kg-1 I.A.), while sodium nitroprusside was infused continuously (2-4 μg min-1 kg-1 I.V.) to mimic the tonic production of NO. This effectively abolished the rise in plasma pancreatic polypeptide (PP) concentration during moderate hypoglycaemia (0·7 nmol kg-1 insulin I.V.) and significantly reduced the response to more intense hypoglycaemia (2·0 nmol kg-1 insulin I.V.). In contrast, the glucagon response was not significantly affected in either group, although consistently higher plasma glucagon values were obtained in response to the higher dose of insulin following the administration of L-NAME. It is concluded that, in the absence of L-NAME, production of NO contributes to the PP response, but not the glucagon response to hypoglycaemia in this species under physiological conditions.

We investigated the influence of ambient temperature on the thermoregulatory response to hypoxia in developing lambs before (at 4 and 14 days of age) and after (17 and 30 days of age) carotid body denervation (CBD). Lambs were studied during non-rapid eye movement sleep at thermoneutral (23-15°C) and cool (10-5°C) ambient temperatures, during normoxia and acute hypoxia (inspired oxygen content of 13 %). Measurements of oxygen consumption, arterial partial pressures of O2 and CO2, colonic temperature, incidence of shivering and plasma concentrations of thyroid hormones, cortisol, insulin and glucose were made under each condition. Oxygen consumption was higher at cool compared with thermoneutral ambient temperatures and decreased during hypoxia during cooling at all stages. At 4 days of age, only one lamb shivered during cooling in normoxia, but 4 out of 12 lambs shivered during hypoxia and colonic temperature fell, significantly, by 0·2°C. At 14 days, 8 out of 12 lambs shivered during cooling, of which 6 continued to shiver during hypoxia but colonic temperature did not change significantly. Plasma triiodothyronine concentrations increased on cooling at 4 and 14 days, an affect that was inhibited by hypoxia at 4, but not 14 days of age. At 17 days of age, i.e. post-CBD, plasma thyroid hormone concentrations and oxygen consumption were lower during cold exposure compared with intact lambs at 14 days of age. In CBD lambs, imposing further hypoxia resulted in colonic temperature falling 0·6°C during cooling, with only 2 out of 10 lambs shivering. Plasma glucose and insulin, but not cortisol, concentrations decreased during hypoxia, irrespective of age or CBD. It is concluded that hypoxia has an important influence on metabolism and thermoregulation, which is modulated by age and environmental conditions. Compromised carotid body function, in lambs older than 2 weeks of age, can result in severe hypoxia and thermoregulatory dysfunction even with modest environmental cooling.

L-Arginine transport by the fetal side of human placenta was investigated through the characterization of L-[3H]arginine uptake in isolated perfused cotyledon. Competitive inhibition experiments suggest the presence of at least two transport systems: a Na+-independent, pH-insensitive system inhibitable by cationic amino acids, similar to system y+, and a Na+-dependent system which recognizes both cationic and neutral amino acids only in the presence of Na+, i.e. a Bo,+-like system. The kinetic analysis of L-arginine uptake in the presence of Na+ revealed that the process is mediated by saturable components: a high-affinity system (Km = 167 ± 18·0 μM; Vmax = 0·174 ± 0·012 μmol min-1) and a low-affinity carrier (Km = 980 ± 112 μM; Vmax = 1·60 ± 0·12 μmol min-1). In the absence of Na+, L-arginine uptake was fitted by one model with a Michaelis-Menten constant of 200 ± 24·8 μM. These results suggest that the high-affinity component corresponds to the Na+-independent system y+, whilst the low-affinity system may represent the activity of the Na+-dependent Bo,+ transporter. Kinetic studies in placentae taken from aspirin-treated pregnancies showed that L-arginine is transported with a significantly higher affinity (Km = 42·5 ± 5·7 μM), but with a lower capacity (Vmax = 0·064 ± 0·003 μmol min-1) than in the non-treated group. The latter finding suggests that aspirin would facilitate the uptake of the NO precursor only at very low arginine concentrations.

The purpose of the present study was to investigate the effect of temperature on the rates of isometric force development and relaxation in electrically activated fresh and fatigued human adductor pollicis muscle. Following immersion of the lower arm for 20 min in water baths of four different temperatures, muscle temperatures were approximately 37, 31, 25 and 22°C. Maximal isometric force was reduced by 16·8 ± 1·5 % at 22°C. The stimulation frequency-force and -rate of force development relationships were shifted to the left at lower temperatures. Q10 values for the maximal rates of force development and relaxation, and the times for 100 to 50 % and 50 to 25 % force relaxation, were about 2·0 between 37 and 25°C and about 3·8 between 25 and 22°C. However, the time for 50 to 25 % force relaxation had a relatively high Q10 value between 25 and 22°C (6·9) and this parameter also appeared to be more sensitive to fatigue compared to the other indices of relaxation. Nevertheless, the effect of fatigue on all parameters decreased with cooling over the entire (37-22°C) temperature range.

Synchronisation of motor unit discharges is commonly seen in hand muscles of normal man but is absent following neurologically complete spinal cord injury and reduced after stroke. These findings support the notion that some corticospinal inputs to motoneurones are shared and contribute to the observed synchrony of discharge. In this study we have examined motor unit discharge in hand muscles below the level of an incomplete spinal cord injury in an attempt to relate strength of synchrony to the integrity of the corticospinal tract. Eight patients with incomplete spinal cord injury (neurological level C3-C7) and eight control subjects took part in the study. The patients had sustained injury 14-191 weeks prior to the recordings and had since regained good motor function in their hands. Two concentric needle electrodes were inserted into the first dorsal interosseus muscle which subjects were instructed to contract weakly so that potentials from individual motor units could be reliably identified on both recordings. Synchrony was detected by constructing cross-correlograms between the discharges of pairs of individual motor units. The amount of synchronous firing was determined from the magnitude of any peak in the cross-correlogram, as the probability above chance (XP) of one motor unit firing with respect to the other and vice versa. The degree of synchrony was lower (P < 0·05) in the patient group (mean XP 0·06) than in the control group (mean XP 0·09). The incidence of significant synchrony was lower in the patient group (41·8 %) than in the control group (92·9 %). The mean (± S.E.M.) frequency of motor unit discharge was slightly lower (P < 0·05) in patients (9·7 ± 0·4 impulses s-1) than controls (10·8 ± 0·5 impulses s-1). The mean width of synchrony peaks was narrower (P < 0·05) in patients (11·4 ± 1·1 ms) than controls (13·2 ± 0·6 ms). We conclude that the weaker synchrony of motor unit discharge in incomplete spinal cord injury may reflect permanent damage to some corticospinal axons.

This book is designed to meet the needs of advanced undergraduates and graduate students from a range of disciplines including neurobiology, psychology and speech sciences. The description of the book as a new analysis and synthesis is inappropriate as the book covers established areas. Basic physiological mechanisms of sound representation and psychological aspects of hearing are discussed with the emphasis on the latter. The book is therefore in a niche that includes physiological texts such as those by Pickles, and the well-established psychoacoustic texts by Moore.