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Biomedical subjects

F D Shaw

Publications and source records attributed to F D Shaw.

At least 19 recordsLinked to original sources
PubMed1990

The role of the vertebral arteries in maintaining spontaneous electrocortical activity after electrical stunning and slaughter in calves.

This paper examines the role of the vertebral arteries of calves in determining the time to loss of spontaneous electrocortical activity after slaughter by a throat-cut severing the soft tissues of the neck ventral to the spinal column. Four calves with the vertebral arteries ligated took 43 +/- 1.3 s to lose cortical activity after the throat was cut. Four similar animals with intact vertebral arteries and the rostral end of the common carotid arteries clamped immediately after slaughter, to ensure that vertebral blood passed to the brain, took 51 +/-25 s to lose cortical activity. It was concluded that factors other than blood flow from the vertebral arteries contribute to the prolonged time to loss of electrocortical activity after slaughter that has been observed in some calves.

Journal Article↗
PubMed1988

Localization of vasopressin mRNA-containing neurones in the hypothalamus of the monkey.

Neuronal perikarya containing vasopressin mRNA were detected in cryostat sections of cynomolgus monkey brains by using an in situ hybridization technique. The neurones were observed in hypothalamic regions (supraoptic nucleus, paraventricular nucleus, suprachiasmatic nucleus and accessory supraoptic nucleus). These findings are in agreement with previous reports using immunohistochemical methods.

Animals↗
PubMed1987

Ultrastructural characterisation of vasopressinergic terminals in the lateral septum of murine brains by use of monoclonal anti-neurophysins.

Synapses in the lateral septum of the murine brain have been investigated by ultrastructural immunocytochemistry, using monoclonal anti-neurophysins in both immunoperoxidase and immunogold techniques. In the region shown by light microscopy to be rich in vasopressinergic innervation, synaptic boutons containing approximately 30 nm clear vesicles and occasional approximately 100 nm dense-cored granules (granules) were stained by pre-embedding immunoperoxidase procedures with antisera to vasopressin-neurophysin, but not oxytocin-neurophysin; reaction product was diffusely distributed in the terminals. Terminals were symmetrical, and both axosomatic and axodendritic in type. Postembedding immunogold procedures by use of anti-vasopressin-neurophysin labeled only the approximately 100 nm diameter granules in the terminals. Sodium meta-periodate treatment 'bleached' immunoreactive granules, indicating the presence of a carbohydrate residue. The quantum of peptide packaged in the granules appears to be smaller than that in magnocellular neurones; nevertheless, the results indicate that, as in the magnocellular neurosecretory system, vasopressin and its neurophysin are packaged exclusively in granules, and that vasopressin in the septum is likely to be derived from a precursor comprising vasopressin, vasopressin-neurophysin and a glycosylated residue.

Animals↗
PubMed1987

Legging orthosis for venous and lymphatic insufficiency.

Presented are the description and advantages of a unique compression device in the form of a legging for the treatment of venous and lymphatic insufficiency. It consists of a number of pliable, unyielding, adjustable compression bands, from the knee to the instep. The bands are easily closed, tightened, and opened, which is particularly useful for the physically handicapped patient for whom the commonly prescribed elastic stocking is inappropriate because of the difficulty in putting it on and removing it. The effectiveness of the legging is enhanced by its nonelasticity, as has been long proven by the Unna boot, and its ability to maintain an unreduced compression level throughout its lifetime, regardless of edema changes.

Equipment Design↗
PubMed1985

Triacylglycerol lipase activities of cultured rat L6 myoblasts.

The utilization of exogenous triacylglycerol by fusing and non-fusing rat L6 myoblasts grown in culture was investigated. Although small quantities of triacylglycerol were accumulated by both cell lines during an incubation of 2 h, no evidence could be found for the presence of lipoprotein lipase, either in the cells or released into the medium. Cell homogenate studies confirmed the absence of lipoprotein lipase but revealed the presence of an acid lipase having a pH optimum at 4.6. Acid lipase activity was mainly associated with a 15 000 g pellet and was capable of hydrolysing triolein at maximum velocity in the millimolar range. Unlike lipoprotein lipase, acid lipase was strongly inhibited by serum and preliminary investigations suggest that the inhibitory component of serum is located amongst the higher density lipoproteins. It is likely that the acid lipase is of lysosomal origin and is responsible for the hydrolysis of internalized triacylglycerol for subsequent utilization by the cell.

Acid Phosphatase↗
PubMed1984

The relationship between calcium uptake and hormone release in the isolated neurohypophysis. A reassessment.

The release of peptide hormones and uptake of radiolabelled calcium were measured in isolated rat neurohypophyses incubated in vitro. Neuropeptide release was provoked either by depolarising the tissue with raised extracellular potassium, or by application of biphasic electrical stimulus pulses. Potassium stimulation increased uptake of radiolabelled calcium, but electrical stimulation caused no measurable change, suggesting that non-neuronal elements unresponsive to electrical stimulation were responsible for the uptake. This possibility is supported by the results of 2 further series of experiments, in which the neurohypophyses were manipulated in vivo before incubation in vitro. First, the experimental animals were given a 2% solution of sodium chloride in place of drinking water for 3 days, to deplete the neuropeptide content of the incubated tissue. After such treatment, potassium-stimulated neuropeptide release was greatly reduced, but calcium uptake was increased relative to that of normal tissue. Secondly, the pituitary stalk was lesioned electrolytically 14 days before the incubation, thus completely eliminating the neural elements of the neurohypophysis. Potassium stimulation then released no neuropeptide, but calcium uptake increased as in normal tissue. It thus appears that calcium uptake does not always closely parallel neuropeptide release, in contrast with previous results, and that depolarisation of the non-neuronal elements is responsible for the measurable uptake of calcium. The results do not contradict existing concepts of the central role of calcium influx in stimulus-secretion coupling in neurohypophyseal terminals, but serve to emphasise the need for care in the interpretation of calcium uptake data in tissues which are not homogeneous. The neurohypophyseal glial cells (pituicytes) are a likely site for the calcium uptake caused by potassium depolarisation.

Animals↗
PubMed1984

Facilitation of vasopressin release from the neurohypophysis by application of electrical stimuli in bursts. Relevant stimulation parameters.

The physiological significance of the 'bursting' pattern of firing exhibited by activated vasopressin-secreting neurones was investigated by delivering bursts of electrical stimuli to isolated rat neurohypophyses incubated in vitro and by determining vasopressin release. The stimuli were delivered in bursts at three different average frequencies (2.5, 5.0, and 7.5 Hz). For each average frequency, stimuli were delivered at a constant 10 Hz, and the durations of the burst and silence periods were altered, so that the stimulator was switched on for 25, 50 or 75% of the total time. The burst duration varied from 2.5 to 30 s. The vasopressin release generally increased with the average frequency of stimulation, but varied widely for different burst durations. The vasopressin release per stimulus pulse was found to correlate extremely well (r2 = 0.91) with burst durations of up to 20 s, regardless of the average frequency. If it is assumed that complete recovery from the effects of each burst of stimuli took place during the intervening silence periods, it can be shown that vasopressin release per burst increased as the square of burst duration. By analogy with other neurosecretory systems, facilitation of calcium entry during the bursts may be responsible.

Animals↗
PubMed1980

Calcium localization in the rat neurohypophysis.

Neurosecretory nerve endings in the rat neurohypophysis release their hormones by exocytosis subsequent to an influx of calcium from the external medium. The nerve endings are characterized by the presence of neurosecretory granules, mitochondria, occasional vacuoles, and a population of microvesicles similar in appearance to spherical synaptic vesicles. The function of the microvesicles has, for a long time, been uncertain. In view of evidence that coated microvesicles isolated from cerebral cortex are capable of ATP-dependent calcium accumulation, a method has now been developed for the visualization of calcium in the neurohypophysis at the ultrastructural level. With this technique, calcium precipitates are consistently seen in the microvesicles, mitochondria and glial cell (pituicyte) nuclei. In addition, the pituicyte cytoplasm and perivascular space show a diffuse precipitate which can be removed by washing the tissue prior to fixation. The function of the microvesicles might therefore be to sequester calcium within the nerve endings.

Animals↗
PubMed1980

The immunological approach to pregnancy diagnosis: a review.

The developing embryo/fetus bears antigens which are foreign to the mother and it could be expected that immune rejection of the conceptus would occur. One of the reasons why the fetus is not rejected is because a depression of the maternal immune response takes place during pregnancy. Serum from pregnant animals of several species has been shown to contain a factor, early pregnancy factor (EPF), which is immunosuppressive. EPF has been detected as early as six hours after mating and its detection could aid diagnosis of early pregnancy in all species.

Animals↗
PubMed1980

Effect of electrical stimulation post mortem of bovine muscle on the binding of glycolytic enzymes. Functional and structural implications.

The extent of binding of glycolytic enzymes to the particulate fraction of homogenates was measured in bovine psoas muscle before and after electrical stimulation. In association with an accelerated glycolytic rate on stimulation, there was a significant increase in the binding of certain glycolytic enzymes, the most notable of which were phosphofructokinase, aldolase, glyceraldehyde 3-phosphate dehydrogenase and pyruvate kinase. From the known association of glycolytic enzymes with the I-band of muscle it is proposed that electrical stimulation of anaerobic muscle increases enzyme binding to actin filaments. Calculations of the extent of enzyme binding suggest that significant amounts of enzyme protein, particularly aldolase and glyceraldehyde 3-phosphate dehydrogenase, are associated with the actin filaments. The results also imply that kinetic parameters derived from considerations of the enzyme activity in the soluble state may not have direct application to the situation in the muscle fibre, particularly during accelerated glycolysis.

Animals↗
PubMed1979

A test for early pregnancy in sheep.

The rosette inhibition test has been used to detect an early pregnancy factor (EPF) in the serum of ewes. EPF was shown to be to be present within 72 h of mating and was still detectable after one month of gestation and in some cases after four months' gestation. The detection of EPF could be of value in the diagnosis of pregnancy in the ewe during the first month of gestation.

Animals↗
PubMed1978

Bruising in cattle transported over long distances.

The relative susceptibility of cattle of different sexes to bruising was examined in five trials. In each trial there were three groups of cattle--bullocks, cows and mixed (bullocks and cows). The weight of bruised tissue trimmed from the carcases of the cows was significantly greater than that trimmed from the carcases of bullocks. The amount of bruising in cows, but not in bullocks, increased with increase in duration of journey. There was no evidence to suggest that differences in carcase weight or temperament, or "riding" of cows in oestrus were major contributing factors to the different levels of bruising.

Animals↗