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Biomedical subjects

S R Shaw

Publications and source records attributed to S R Shaw.

At least 37 records · Page 2Linked to original sources
PubMed1989

Do local analgesics injected at the time of third molar removal under general anaesthesia reduce significantly post operative analgesic requirements? A double-blind controlled trial.

A prospective, controlled, randomised, double-blind trial suggested that: 1. The use of bupivacaine 0.5% plain and prilocaine 3% with felypressin 0.03 i.u./ml. as peroperative local analgesics reduce postoperative pain scores recorded on the first postoperative morning (P less than 0.05). 2. Bupivacaine 0.5% plain reduces postoperative opiate requirements (P less than 0.025). 3. Patients do not find peroperative bilateral inferior alveolar and lingual nerve blocks with buccal infiltrations significantly unpleasant. Thus peri-operative bupivacaine 0.5% is a valuable adjunct to third molar removal under general anaesthesia.

Adolescent↗
PubMed1989

Evolutionary remodeling in a visual system through extensive changes in the synaptic connectivity of homologous neurons.

The cellular mechanisms by which nervous systems evolve to match evolutionary changes occurring in the rest of the body remain largely unexplored. In a distal visual neuropil of a previously unexamined ancient dipteran family, Stratiomyidae, homologues of all of the periodic neurons known already from more recent Diptera can be recognized, occupying the same locations within the unit structure. This points to extreme developmental stasis for more than 200 million years, conserving both cell identity and position. The arborizations that some neurons make also have remained conservative, but others show marked differences between families in both size and branching patterns. At the electron-microscopical level, extensive differences in synaptic connectivity are found, some sufficient to radically redefine the systems roles of particular neurons. The findings bear out an earlier prediction that changes in the connectivity matrix linking conserved neurons may have been a major factor in implementing evolutionary change in the nervous system.

Animals↗
PubMed1988

Effects of a 1-wk spaceflight on morphological and mechanical properties of growing bone.

The morphological and mechanical responses of tibia and humerus were assessed in growing male rats after a 1-wk spaceflight aboard NASA Spacelab 3. In contrast to flights of longer duration, changes in middiaphysial cross-sectional morphology were minimal. Inhibition of longitudinal growth was not found in the tibia but was apparent in the humerus. The normal age-related increase in tibial middiaphysial density was not observed in the flight animals. Three-point bending tests indicated that a 1-wk spaceflight impeded the maturation of bone strength and stiffness, with the effects more pronounced in the tibia than in the humerus. Material property alterations in bone thus overshadowed morphological factors in determining the bone's mechanical response. It is likely that deprivation of normal weight-bearing loads was a major factor contributing to the observed changes, but endocrine and other local factors must also be considered.

Animals↗
PubMed1987

Mechanical, morphological and biochemical adaptations of bone and muscle to hindlimb suspension and exercise.

The influences of weightbearing forces on the structural remodeling, matrix biochemistry, and mechanical characteristics of the rat tibia and femur and surrounding musculature were examined by means of a hindlimb suspension protocol and highly intensive treadmill running. Female, young adult, Sprague-Dawley rats were designated as either normal control, sedentary suspended, or exercise suspended rats. For 4 weeks, sedentary suspended rats were deprived of hindlimb-to-ground contact forces, while the exercise suspended rats experienced hindlimb ground reaction forces only during daily intensive treadmill training sessions. The suspension produced generalized atrophy of hindlimb skeletal muscles, with greater atrophy occurring in predominantly slow-twitch extensors and adductors, as compared with the mixed fiber-type extensors and flexors. Region-specific cortical thinning and endosteal resorption in tibial and femoral diaphyses occurred in conjunction with decrements in bone mechanical properties. Tibial and femoral regional remodeling was related to both the absence of cyclic bending strains due to normal weightbearing forces and the decrease in forces applied to bone by antigravity muscles. To a moderate extent, the superimposed strenuous running counteracted muscular atrophy during the suspension, particularly in the predominantly slow-twitch extensor and adductor muscles. The exercise did not, however, mitigate changes in bone mechanical properties and cross-sectional morphologies, and in some cases exacerbated the changes. Suspension with or without exercise did not alter the normal concentrations of collagen, phosphorus, and calcium in either tibia or femur.

Animals↗
PubMed1986

Anti-adhesive coating for glass microelectrodes.

A simple procedure is described for coating the tips of glass micropipette electrodes with a durable thin film of a commercially available anti-adhesive agent (Antispread). This lowers the surface tension of the electrode glass, and helps reduce damage and distortion to tissue, by preventing the microelectrode from sticking permanently to cell membranes. In controlled trials, the coating actually increased the probability that nearby cells could be recorded from successively by about 30%. Electrode resistance increased only very slightly (on average by 8%) as a result of the coating. Coated electrodes yielded excellent long-term penetrations of small visual cells, and in addition allowed these to be dye-filled in the normal way. The coating may have applications in all situations where prevention of wetting by tissue is desirable.

Animals↗
PubMed1986

Evolutionary progression at synaptic connections made by identified homologous neurones.

A comparative ultrastructural study of photoreceptor synapses formed upon homologous postsynaptic neurones in insects has been made by using serial-section electron microscopy in representative Diptera from a monophyletic series of 14 families. At all of the synaptic contacts there is a presynaptic dense bar, surmounted in phylogenetically more recent families by a presynaptic platform. Opposite the bar lies a pair of postsynaptic elements that invariably originate one each from two unique monopolar neurones L1 and L2. Both elements contain increasingly elaborate cisternae in more recent flies. Within the phylogenetic series, the postsynaptic ensemble itself changes from the original dyad to a tetradic configuration in more recent Muscomorpha by the addition of two new postsynaptic elements from an amacrine cell. This transition occurs once only in the series, which, gauged by the fossil record, covers divergences from the stem line extending back greater than 200 million years.

Animals↗
PubMed1986

Heterogeneous mechanical response of rat knee menisci to thermomechanical stress.

Thermodilatometric, dynamic thermomechanical, and light-microscopic analyses were done on the anterior and posterior regions of the rat knee menisci to correlate regional differences in morphology and extracellular matrix composition with regional mechanical behavior. Following the administration of a general anesthetic, menisci were excised from 12 young female Sprague-Dawley rats. During thermodilatometric and thermomechanical testing, tissue temperature was increased at a constant rate of 3.5 degrees C/min from 30 to 100 degrees C. Light microscopy revealed regional differences in cell density and proteoglycan content. The anterior horn was significantly heavier (greater than 87%) and thicker (greater than 60%) than the posterior region. During thermal analyses, both the anterior and posterior horns decreased in tissue thickness as the temperature increased from 30 to 73 degrees C. After 73 degrees C, however, the posterior horn expanded significantly, whereas the anterior remained in a comparatively contracted state. The rates of linear contraction and expansion of the posterior horn were seven times those of the anterior horn, and the stiffness of the anterior horn was significantly greater than the posterior horn.

Analysis of Variance↗
PubMed1984

Asymmetric distribution of gap junctions amongst identified photoreceptor axons of Lucilia cuprina (Diptera).

The relative number of gap junctions within the ring of axon terminals of identified adult photoreceptors has been counted, in the lamina cartridges of Lucilia cuprina. Terminals are similar in size, but some pairs of terminals make up to four times as many junctions with each other as do other pairs; the frequency of connection varies markedly along the length of the cartridge. Junctions across the cartridge occasionally occur out of the normal sequence, frequently in the upper cartridge between one pair of axons. The distributions suggest that mechanical factors transmitted down from the upper cartridge are responsible for the non-uniformities. There may be indiscriminate competition between terminals at some stage of development for a fixed quota of junctions, the groupings of which have to reach a minimum size to remain viable. Amongst the neurones of the cartridge, great specificity is shown in which cells form gap junctions: only receptors R1-6 are involved, making junctions only with each other. Within this class R1-6, however, there is no evidence from the distribution of gap junctions for unique cell labelling, that distinguishes one photoreceptor from another. Connections appear to form indiscriminately, on the basis of proximity. This same generalization holds true for a particular class of chemical feedback synapse. The identity of tight-junction-like structures on the photoreceptor axon membrane is also discussed.

Animals↗
PubMed1982

Survey of lameness in British dairy cattle.

During 1977 a survey was undertaken by practising veterinary surgeons of the incidence of different lesions causing lameness in dairy cattle. Forty-eight veterinary practices participated and they treated 7526 cases of lameness in 1821 herds. The average incidence of lameness among all cows was 5.5 per cent and the annual incidence among practices ranged from 1.8 to 11.8 per cent. Most lesions (88.3 per cent) occurred in the feet; the commonest were foul of the foot (16.7 per cent), white line abscess (15.6 per cent), sole ulcer (13.6 per cent), punctured sole and pus (10.4 per cent) and underrun heel (8.7 per cent). These proportions varied in different parts of the country. Eighty-four per cent of foot lesions occurred in the hind feet and of these lesions 85 per cent occurred in the outer claw; 42 per cent of foot lesions occurred in abnormally shaped claws. The remaining 11.7 per cent of lesions occurred in the legs and trunk, 76 per cent of which occurred in the hindlimb. Trauma was the main cause of leg lesions, which occurred most frequently in the joints and ligaments.

Animals↗
PubMed1980

Net hepatic and splanchnic metabolism of lactate, pyruvate and propionate in dairy cows in vivo in relation to lactation and nutrient supply.

1. Circulating concentrations of glucose, propionate, lactate and pyruvate, and net exchange of these compounds across the liver and gut, were measured in lactating and non-lactating dairy cows (a) in the normal fed state, (b) before, during and after intravenous infusion of an aqueous solution of glucose, propionate or lactate (lactating cows only) in fed animals, and (c) before and during 6 days of food deprivation. 2. In the normal fed state, gut output of propionate, hepatic output of glucose and hepatic uptake of lactate were all higher in the lactating group. There was a net uptake of pyruvate across the liver in the lactating cows and a net output in the non-lactating cows. In the lactating cows there was a net uptake of lactate and pyruvate by the splanchnic bed (i.e. gut and liver combined). 3. In the lactating cows, the glucose and propionate infusions had the following effects: decrease in net hepatic uptake of lactate; a switch in pyruvate exchange across the liver from uptake to output; suppression of uptake of lactate and pyruvate by the splanchnic bed; increase in the magnitude of the liver (propionate uptake)/(glucose output) ratio. Lactate infusion did not affect hepatic propionate uptake. 4. Food deprivation increased hepatic extraction of lactate and pyruvate and decreased the liver (propionate uptake)/(glucose output) ratio in both groups. 5. It is concluded that mechanisms exist to ensure an inverse relationship between the availability to the cow of glucose or propionate and utilization by the splanchnic bed of endogenously derived lactate and pyruvate.

Animals↗
PubMed1980

The isolation and characterization of human and bovine strains of Babesia divergens from Drumnadrochit, Scotland.

Strains of Babesia divergens of human and bovine origin were isolated from the same locality in Scotland. A morphometric comparison was then made between Babesia divergens parasites in blood smears made from groups of 3 splenectomized calves reacting to the inoculation of these strains. The various forms taken by the parasites of each strain were seen to be divisible into 7 categories and representatives of each category were found for each strain. More amoeboid forms were found in blood smears from calves infected with the strain of bovine origin but otherwise the frequencies of occurrence of different forms coincided. The dimensions of 3 forms of the parasites of each strain were compared and the parasites of human origin were found to be significantly larger. The reactions of the groups of calves to inoculation of the 2 strains of B. divergens were seen to be very similar, although inoculation of the bovine strain had a slightly greater effect on the animals' haematology as indicated by an an increase in erythrocyte mean corpuscular volume.

Animals↗
PubMed1979

The effects of subcutaneous injections of sodium selenate on blood composition and milk yield in dairy cows.

Three groups of four lactating cows received a subcutaneous injection of 0 . 05, 0 . 10 and 0 . 15 mg Se/kg body weighty respectively administered as sodium selenate. A fourth group was injected with saline. In all the cows injected with sodium selenate, the concentration of Se in blood increased rapidly and was significantly higher than in control cows for two days in the group receiving the lowest dose and for 182 days (the duration of the experiment) in the two other groups. The activity of glutathione peroxidase in blood increased slowly in all cows injected with sodium selenate and was significantly greater than in control cows after 15, 22 and 29 days respectively, and remained significantly greater for 63, 91 and 182 days respectively. In a second experiment a single subcutaneous injection of 0 . 15 mg Se/kg body weight had no effect on the mean milk yield of 37 animals (19 . 1 kg/day) compared with the milk yield of a similar group of control animals (19 . 1 kg/day) during 70 days. The concentration of Se in milk was significantly higher on the first (168 microgram/litre) and second (69 microgram/litre) day after injection than in control animals (mean 26 microgram/litre).

Animals↗