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Biomedical subjects

S Wray

Publications and source records attributed to S Wray.

At least 145 records · Page 8Linked to original sources
PubMed1988

Smooth muscle intracellular pH: measurement, regulation, and function.

Smooth muscle performs many functions that are essential for the normal working of the human body. Changes in pH are thought to affect many aspects of smooth muscle. Despite this, until recently little was known about either intracellular pH (pHi) values or pHi regulation in smooth muscle. Recent work measuring pHi with either microelectrodes or nuclear magnetic resonance spectroscopy is now providing some of this much needed information for smooth muscles. From these studies, it can be concluded tentatively that pHi is the same in different smooth muscles, approximately 7.06 (37 degrees C). This value is very close to those obtained in cardiac and skeletal muscle. It is clear that H+ is not in equilibrium across the smooth muscle membrane; i.e., pHi is regulated. Preliminary results in smooth muscle suggest that certain aspects of this regulation are different from that described for other muscle types. Changes in pHi have been found to produce marked effects on contraction in smooth muscle. Of particular interest is the fact that, unlike striated muscles, some smooth muscles can product more force during an intracellular acidification.

Blood Vessels↗
PubMed1987

The effects of membrane potential on active and passive sodium transport in Xenopus oocytes.

1. The effects of membrane potential on the Na+-K+ pump were studied by measuring membrane current and 22Na+ efflux in voltage-clamped Xenopus oocytes. The effects of inhibiting the Na+-K+ pump with strophanthidin were examined. 2. Strophanthidin produced an inward shift of membrane current which reversed on removal of the drug. In control oocytes the magnitude of this current was not significantly affected by changing membrane potential over the range -20 to -160 mV. 3. In another series of experiments the intracellular Na+ concentration ([Na+]i) was elevated either by overnight Na+-K+ pump inhibition (strophanthidin or exposure to K+-free solutions) or by loading with nystatin. This Na+-loading increased the magnitude of the strophanthidin-sensitive current. The ratio of strophanthidin-sensitive 22Na+ efflux:strophanthidin-sensitive current was consistent with that expected from a 3Na+-2K+ exchange. 4. When [Na+]i was elevated the strophanthidin-sensitive current was sensitive to changes of membrane potential. Hyperpolarization from -20 to -80 mV decreased the current to 60% of control. It is suggested that the current is not sensitive to membrane potential at normal [Na+]i because the over-all reaction is rate limited by the availability of intracellular Na+. 5. The application of strophanthidin decreased the rate of 22Na+ efflux. Both the strophanthidin-insensitive and the strophanthidin-sensitive components of efflux were sensitive to changes of membrane potential. The strophanthidin-insensitive component was not greatly affected by hyperpolarization from -40 to -160 mV but was increased by depolarization to +40 mV. 6. In Na+-loaded oocytes, the strophanthidin-sensitive component of 22Na+ efflux was inhibited by hyperpolarization negative from -40 mV. Hyperpolarization from -40 to -160 mV decreased the efflux by 54 +/- 5%. Over the limited range of potentials for which a comparison could be made, the effects on 22Na+ efflux were somewhat less than on the electrogenic Na+-K+ pump current. On average there was no significant effect of depolarizing from 0 to +40 mV. However, in some experiments a clear inhibition of the efflux was observed. If the oocytes were not Na+ loaded there was no significant effect of membrane potential on the strophanthidin-sensitive Na+ efflux. 7. These results show that the effects of membrane potential on the net reaction of the Na+-K+ pump (as measured by the electrogenic current) result partly from an inhibition of the forward mode of operation. However, there is also evidence to suggest a contribution from stimulation of the reverse reaction.

Animals↗
PubMed1987

A phosphorus nuclear magnetic resonance study of metabolites and intracellular pH in rabbit vascular smooth muscle.

1. 31P nuclear magnetic resonance (n.m.r.) spectroscopy was used to investigate metabolites, intracellular pH (pHi) and the effects of pHi on tone in rabbit blood vessels. The vessels were bathed in mammalian Ringer solution and maintained at 20 degrees C while inside the spectrometer. 2. Vascular spectra showed relatively low phosphocreatine (PCr) concentrations compared to skeletal muscle. The [PCr]/[ATP] ratio was only 1.32 +/- 0.09 (n = 7). There was also a prominent phosphomonoester (PME) peak. Similar features have been reported for other smooth muscles examined by 31P n.m.r. 3. The [PCr] was higher and the inorganic phosphate (Pi) concentration lower than values deduced from chemical analysis of arterial extracts. However, the [PCr] value fell within the range obtained for other smooth muscles when studied by 31P n.m.r. 4. Measurement of pHi under control conditions (external pH 7.25) gave a mean value of 7.19 +/- 0.03 at 20 degrees C (n = 5). Metabolic inhibition brought about by 0.5 mM-cyanide and 0.2 mM-fluoride did not significantly alter pHi. At higher inhibitor concentrations (3 and 1 mM respectively) there was a significant acidosis. 5. The effects of NH4Cl upon pH were investigated in metabolically inhibited preparations. During 10 min applications of 30 mM-NH4Cl (isosmotically substituted for NaCl) the pHi rose; during subsequent NH4Cl removal it fell below control values. In the least inhibited tissues the total pHi excursion between NH4Cl applications and removals was 0.5 unit. 6. Rabbit ear vessels have been found to increase vascular tone during manoeuvres which were expected to decrease pHi. From the direct measurement of pHi reported in this study, it is concluded that the vascular tone changes brought about by NH4Cl application and withdrawal may be attributed to the alteration of pHi.

Adenosine Triphosphate↗
PubMed1987

Effect of neonatal gonadectomy on the postnatal development of LHRH cell subtypes in male and female rats.

The total number of LHRH cells and the distribution of LHRH cell morphological subtypes (classified as smooth or irregular LHRH cells) was investigated in adult male and female rats that received neonatal gonadectomies using light- and electron-microscopic immunocytochemistry. An identical number of immunoreactive LHRH cells (about 1,200) was observed in both treated and control animals. Both LHRH cell subtypes were present in treated animals, and the total number of each LHRH cell subtype and their distributions were similar to that seen in the control animals. At the EM level, LHRH cell subtypes from gonadectomized animals had similar morphological characteristics as have been described for normal adult rats. Synapses were present on both smooth and irregular LHRH cells of treated animals. These data indicate that the removal of gonadal steroids shortly after birth does not alter the overall LHRH cell number and distribution, nor the development of characteristic LHRH cell morphologies.

Animals↗
PubMed1987

Cerebral monitoring in newborn infants by magnetic resonance and near infrared spectroscopy.

Phosphorus magnetic resonance spectroscopy (MRS) and near infrared spectroscopy (NIRS) have been used to study the brains of normal newborn infants and infants with cerebral disorders admitted to a neonatal intensive care unit. MRS, which involves transporting the infant to the spectrometer, allows measurement of mobile phosphorus compounds such as adenosine triphosphate and phosphocreatine in brain tissue, and has been performed on over 160 babies. NIRS gives cotside information about cerebral oxygenation and haemodynamics and has recently been introduced. These techniques, especially when used together, show promise of providing important information about the mechanisms and prognostic significance of hypoxic-ischaemic damage to the brain--the most important cause of permanent neurodevelopmental disabilities in infants who require intensive care.

Brain↗
PubMed1986

Catecholamine innervation of LH-RH neurons: a developmental study.

Catecholamine innervation of luteinizing hormone-releasing hormone (LH-RH) cell subtypes in rats was investigated over development using double label, light microscopic immunocytochemistry. Similar results were observed in both sexes. The number of catecholamine-apposed sLH-RH cells remained constant, while the number of catecholamine-apposed iLH-RH cells increased as a function of age. These results suggest that LH-RH cell subtypes are differentially innervated and support the hypothesis that the development of iLH-RH cells represent newly innervated surfaces which are related to changes in the processing of incoming information relevant to reproductive maturation.

Aging↗
PubMed1986

Quantification of cerebral oxygenation and haemodynamics in sick newborn infants by near infrared spectrophotometry.

New apparatus was made whereby indices of cerebral oxygenation and haemodynamics in sick newborn infants could be quantified by near infrared (NIR) spectrophotometry and displayed instantaneously at the cotside. The indices included oxygenated haemoglobin, reduced haemoglobin, oxidised cytochrome aa3, and total haemoglobin concentration: cerebral blood volume, mixed cerebral venous saturation, and changes in cerebral blood flow were then derived. Striking changes were observed in response to alterations in arterial oxygen saturation and carbon dioxide tension and to tilting of the infant. Abnormal responses were detected in cerebral oedema following birth asphyxia, patent ductus arteriosus, and cystic encephalomalacia. NIR spectrophotometry provides valuable quantitative data at the cotside for the management of sick infants and for exploring the pathophysiology of damage to the brain.

Blood Volume↗
PubMed1986

A developmental study of the quantitative distribution of LHRH neurons within the central nervous system of postnatal male and female rats.

The quantitative distribution of LHRH neurons within the central nervous system of male and female rats during postnatal development was investigated with light microscopic immunocytochemistry. Approximately 1,300 immunoreactive LHRH cells were found within the forebrain at all ages. The topographic distribution of LHRH neurons was adultlike in the earliest neonatal stage examined (2 days postnatal) and remained similar throughout development. Two LHRH cell subtypes, smooth LHRH cells and LHRH cells with spinelike processes (irregular LHRH cells), were found throughout the entire extent of the LHRH neuronal field in both sexes. A sex difference in the number of LHRH cells anterior to the organum vasculosum lamina terminalis/preoptic area (a 20% greater number in this region in females) was observed. This sex difference was present throughout development and was not limited to one specific LHRH cell subtype. These data are consistent with the hypothesis that the LHRH system is established early in postnatal development, and that the signal for reproductive maturation is related to the development of synaptic inputs to the LHRH cells.

Animals↗
PubMed1986

Direct in vivo measurement of absolute metabolite concentrations using 31P nuclear magnetic resonance spectroscopy.

Whilst in vivo NMR spectroscopy provides much useful biochemical information, a limitation to such studies has been the difficulty in quantitating the results to obtain absolute metabolite concentrations. We report here a simple direct method to obtain absolute metabolite concentrations when using in vivo NMR with radiofrequency surface coils. The method has been validated for nucleoside triphosphates in two tissues; rat brain and skeletal muscle. The results obtained are in close agreement with nucleoside triphosphate concentrations obtained using other methods. Precautions for the accurate application of the method are discussed. This method can be applied to other metabolites, coils and NMR nuclei.

Animals↗
PubMed1986

Postnatal morphological changes in rat LHRH neurons correlated with sexual maturation.

The postnatal development of the luteinizing hormone-releasing hormone (LHRH) system in male and female rats was investigated using light microscopic immunocytochemistry. An identical number of immunoreactive LHRH cells (about 1,300) was observed for males and females throughout development. Two LHRH cell types, based on morphological appearance, were present in both sexes: smooth LHRH cells and LHRH cells with spine-like processes (irregular LHRH cells). In both sexes, the number of smooth LHRH cells decreases and the number of irregular LHRH cells increases during postnatal life, stabilizing shortly after puberty. We propose that smooth LHRH cells transform into irregular LHRH cells during the development of reproductive maturation.

Animals↗
PubMed1985

Changes in brain phosphorus metabolites during the post-natal development of the rat.

Changes in brain phosphorus metabolites during the post-natal development of the rat and in neonatal and adult guinea-pigs have been studied in vivo using 31P nuclear magnetic resonance spectroscopy (n.m.r.s.). The brain spectra showed clear differences with age, particularly during the first 3 weeks post-partum. The spectra from 4-day-old rats resembled those of new-born human infants. We suggest that the differences between human and animal brains seen in previously published spectra arise because of an age difference rather than a species difference. The phosphocreatine (PCr) to nucleoside triphosphate (NTP) ratio increased from around 1.0 in 3-day-old rats to 1.8 in adult animals. The adult ratio is larger than that previously reported from in vitro chemical analyses. An unknown compound in the phosphomonoester (PME) region of the spectra predominated in young animals, but decreased in concentration relative to NTP with age and reached adult values by around 2 weeks post-partum. Neonatal guinea-pigs, which are much more developed at birth than the rat, had a significantly greater PCr/NTP ratio than the neonatal rat, but their brain spectra also contained the large PME peak. The intracellular pH of cerebral tissue was estimated to be 7.21 +/- 0.02 and did not show any change with age. The changes we find in the phosphorus compounds in the brain may be of importance in post-natal development, and the possible functional significance of these results is discussed.

Adenosine Triphosphate↗
PubMed1985

The effects of pregnancy and parturition on phosphorus metabolites in rat uterus studied by 31P nuclear magnetic resonance.

Concentrations of phosphorus metabolites and intracellular pH have been measured in non-pregnant, late-pregnant and post-partum rat uterus using 31P nuclear magnetic resonance (31P n.m.r.). Intact uterine tissue was superfused with oxygenated de-Jalon solution at 4, 20 or 37 degrees C while inside the n.m.r. spectrometer. The phosphocreatine concentration [PCr], was higher and the inorganic phosphate concentration [Pi], lower than values determined by chemical analysis of extracts from both pregnant and non-pregnant rat uterus. [PCr] was 1.4-fold greater in late-pregnant than in non-pregnant rat uterus. Following parturition, large changes were observed in [PCr], [Pi] and in an unidentified metabolite in the phosphomonoester (PME) region of the n.m.r. spectrum. The time course of the recovery of these metabolites to prepregnant values was determined. The [PCr] remained below the non-pregnant value for at least 1 week post-partum and the [Pi] was elevated, compared to the non-pregnant value, during this period. More rapid changes were seen in the [PME], which doubled on day 0 post-partum but almost returned to its non-pregnant value on day 1 post-partum. No significant difference was observed between intracellular pH values in late-pregnant and non-pregnant rat uterus; however, there was a large acid shift following parturition. Intracellular pH depended upon the temperature at which the tissue was maintained. The effect of muscular work during parturition was investigated by comparing Caesarian-sectioned uteri with uteri which had undergone normal parturition. Uteri examined 1 day after Caesarian operation showed no differences in metabolite levels from normal, 1 day post-partum uteri. We conclude that concentrations of phosphorus metabolites depend upon the physiological state of the uterus. We suggest that the changes following parturition are not a consequence of the mechanical work performed by the uterus, but must be caused by some other event associated with parturition such as hormonal changes.

Animals↗
PubMed1985

Activation of nuclear chromatin in stretch-dependent growth of tissues.

The growth of connective tissue cells can be controlled both by mechanical extension and by diffusion gradients. We have used nuclear fluorescence with acridine orange (AO) as a measure of nuclear activation, to study growth control in vivo in rat mesometrium and mouse spine. Frozen sections of spinal muscle taken from animals after two h exercise, revealed nuclear activation in peripheral cells. The number of active muscle nuclei decreased drastically with age. During mesometrial growth in pregnancy, AO fluorescence showed that activated cell nuclei occurred mainly near the capillaries. The width of the zone of activated nuclei was within 20 microns from the capillary walls. AO appears to be a sensitive stain for tracing gradients of growth in intact connective tissue.

Acridine Orange↗
PubMed1984

Distribution of neurotensin-immunoreactivity within baroreceptive portions of the nucleus of the tractus solitarius and the dorsal vagal nucleus of the rat.

We have examined the distribution of neurotensin immunoreactivity within subnuclear regions of the nucleus of the tractus solitarius (NTS) and the dorsal motor nucleus of the vagus nerve (DVN) in the rat. In order to determine which regions of the NTS were involved in the regulation of baroreceptor reflexes, we mapped the central distribution of the aortic branch of the vagus nerve using transganglionic transport of horseradish peroxidase. Comparison of the pattern of aortic nerve innervation with that of the distribution of neurotensin-immunoreactive cells and fibers shows the dorsomedial nucleus of the NTS both to be the primary site of aortic baroreceptor termination and to contain the highest concentration of neurotensin-immunoreactive elements within the NTS. Neurotensin-immunoreactive fibers are also present in medial regions of the NTS adjacent to the area postrema where they may be involved in the modulation of vagal gastric afferents. Double-label experiments, in which, on the same tissue sections, neurotensin immunohistochemistry was combined with retrograde horseradish peroxidase labeling of DVN neurons, reveal a topographic innervation of vagal preganglionic motoneurons by neurotensin-immunoreactive fibers. The heaviest innervation is of lateral portions of the DVN and adjacent ventral portions of the NTS at the level of the obex, an area which may contain cardiac motoneurons. In this region neurotensin-immunoreactive fibers can be observed in close proximity to retrogradely labeled cells. The concentration of neurotensin elements in a region of the NTS which is involved in the control of baroreceptor reflexes provides a morphological basis for the cardiovascular effects produced by central administration of the peptide. Additional control may be exerted at the level of the motoneuron, as evidenced by apparent neurotensin fiber innervation of presumptive cardiac preganglionic neurons. Similarly, the distribution of neurotensin fibers suggests that the peptide may be acting in gastric regulatory areas of the NTS or on vagal secretomotor neurons to regulate gastric acid secretion.

Afferent Pathways↗
PubMed1983

The effect of pregnancy and lactation on the mesometrium of the rat.

Weight and collagen content of the mesometrium, that part of the reproductive tract which lies between the uterus and the body wall, were measured in the rat, throughout pregnancy and post-partum. Both the weight and the collagen content increased significantly during pregnancy and decreased rapidly after parturition, the collagen content halving in around four days. The changes were almost entirely in the part of the mesometrium between the main longitudinal blood vessels and the uterus. At any given stage of pregnancy, the larger the uterus, the larger were both the weight and collagen content of the mesometrium. In rats pregnant in only one uterine horn the mesometrium associated with the barren horn showed no changes in weight or collagen content during pregnancy. Removal of fetuses from one uterine horn reversed the growth of the mesometrium associated with that horn, but not the growth of the mesometrium associated with the other (pregnant) horn. Cutting the attachment to the body wall prevented mesometrial growth during pregnancy although the tissue remained attached to the uterus, with its blood supply and the metrial gland intact. These data suggest that mesometrial growth in pregnancy is stimulated by stretch associated with the pregnant uterine horn.

Animals↗
PubMed1982

Chiasmal syndrome caused by arteriovenous malformations.

Only four cases of chaismal syndromes caused by arteriovenous malformations (AVMs) have been reported. We have examined two patients with chiasmal dysfunction caused by an AVM. In one patient, the AVM was suspected only after angiography. However, the presence of an angioma of the lip might have been a clue to the diagnosis. In the other patient, seizures and pulsating proptosis led to the correct diagnosis before angiography was performed. This patient also had episodes of transient bilateral blindness, presumably caused by postictal states or by periodic shunting with ischemia (chiasmal steal).

Adult↗
PubMed1982

The role of mechanical and hormonal stimuli on uterine involution in the rat.

1. Distension of part of the uterus of the rat after parturition by an inert material ('Silgel') prevented involution, as measured by change in collagen content and weight in the distended part. The other parts of the uterus, those emptied at parturition, involuted at the normal rate. 2. Removal of the distending material four days after parturition was followed by involution (measured in the same way) in this part of the uterus. 3. Removal of all fetal material from one horn before the end of pregnancy (at day 19) was followed by involution, but at a slower rate than after normal term. Bilateral ovariectomy at the same time as removal of fetuses increased the rate of this involution, but it was still slower than at normal term. 4. Ovariectomy alone on day 19 had no effect on subsequent changes in the uterus; weight and collagen content then followed the normal course to term. 5. It is concluded that mechanical factors associated with the presence of material within the uterine cavity play a preponderant role in maintaining the uterine wall, though hormonal factors can affect its reaction to a lesser extent.

Animals↗