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Biomedical subjects

A Walker

Publications and source records attributed to A Walker.

At least 253 records · Page 14Linked to original sources
PubMed1988

Effect of prolonged subclinical infection with Trichostrongylus colubriformis on the performance and nitrogen metabolism of growing lambs.

Ten 5-month-old lambs, reared free of parasites and prepared with abomasal and ileal cannulas, were paired and given rations of pelleted dried grass by means of continuous feeders. From 7 months of age one of each pair was dosed daily with 2500 Trichostrongylus colubriformis larvae for 34 weeks. An untreated animal served as a pair-fed control to each infected lamb. During 5 experimental periods (pre-infection, and Weeks 6-8, 12-14, 18-20 and 29-34 of dosing) measurements were made of the amounts of N leaving the small intestine, the digestibility of 35[S]-labelled microbial protein in the small intestine, and the amounts of plasma protein leaking into the digestive tract. The infection caused a growth check (P less than 0.05) from Week 6 to approximately Week 13 of dosing. This resulted from inappetence, but also from a disruption in the N digestion and metabolism of the lambs. There was a marked eosinophilia at this time. Measurements of ileal flow rates during Weeks 6 and 12 indicated that significantly more N flowed to the terminal ileum of infected lambs during this period (Week 6, 3.1 g N day-1 P less than 0.05; Week 12, 5.0 g N day-1 P less than 0.001). Plasma N leakage into the intestine during Weeks 8 and 14 was higher in infected lambs (1.2 g N day-1 P less than 0.01 and 0.9 g N day-1 P less than 0.05, respectively) but the digestibility of 35[S]-labelled microbial protein was depressed below that of the controls during the later part of this period, i.e. during Week 13. Continued larval challenge beyond this point caused a less severe nutritional penalty. Voluntary feed intake increased and the animals started to gain weight. The amount of extra N flowing to the terminal ileum of infected lambs was less at Week 18 of dosing (3.5 g N day-1 P less than 0.01) than it had been at Week 12. Similarly, extra plasma N leakage into the tract of infected lambs was less during Week 20 (0.26 g N day-1) than during Week 14. There was however, still a detectable reduction in the coefficient of digestibility of 35S microbial protein in infected lambs during Week 19. By Weeks 29-34 the only detectable difference between the infected and control lambs was in their eosinophil counts.

Animals↗
PubMed1988

Total lung capacity measured by body plethysmography and by the helium dilution method. A comparative study in different patient groups.

The helium dilution method is known to underestimate the total lung capacity (TLC) in patients with poorly or non-ventilated areas in the lungs. The standard plethysmographic method has been reported to overestimate TLC in patients with severe airway obstruction. To determine the magnitude of the difference between the two methods, a comparison was made in different patient groups. In a group of patients with normal lung function tests (n = 20) there was a small but significant average difference in TLC between plethysmography and the helium dilution method, the larger values being obtained with the latter. In patient groups with moderately obstructed airways (n = 23), severely obstructed airways (n = 20), or emphysema (n = 19), there were no significant average differences, although in two patients in the emphysema group the plethysmographic values were considerably larger than those obtained by helium dilution. We conclude that the gas dilution methods and plethysmography with a pressure-compensated volume displacement plethysmograph gave estimates of TLC which agreed even in patients with airway obstruction or emphysema, except in patients with very severe lung disease.

Emphysema↗
PubMed1987

DNA deletions in mild and severe Becker muscular dystrophy.

The DNA of 33 patients diagnosed as suffering from Becker muscular dystrophy (BMD) has been probed with cloned DNA sequences from Xp21, known to reveal DNA deletions in patients suffering from the more severe Duchenne muscular dystrophy (DMD). Two BMD cases showed clear deletions. A third case gave aberrant band sizes, which further analysis showed to be caused by a small deletion. This suggests that deletions in DXS164 occur approximately as frequently in BMD as they do in DMD. Of the two cases showing large deletions, one is at the severe end of the Becker clinical spectrum, whilst the other is a classical Becker-type dystrophy. The fact that loci defined by probes commonly deleted in classical DMD patients are also deleted in BMD patients of varying severity is strong additional evidence that these disorders are allelic, and further justifies the use of probes with defined linkage relationships to DMD also being used for counselling in BMD families.

Adolescent↗
PubMed1987

Attitudes towards donor insemination--a post-Warnock survey.

In a multi-centred study, a total of 799 patients, donors and health-care professionals concerned with artificial insemination with donor semen (AID) responded to a questionnaire regarding their attitudes towards current provision of AID services and proposed legislation. There was little support for any fundamental change in the way in which AID is practised, at least in those centres. The anonymous status of the donor met with universal agreement. Although there was some support for the communication of non-identifying details to the recipient couple, where they wanted them, there was no support for any legislation which might give the AID child a right of access to details of the donor. The greatest divergence of opinion was over the question of who should have access to AID treatment and whether or not screening procedures should be applied to prospective parents. Most respondents felt that the closed and confidential relationship between the clinic and the other parties involved should not automatically be extended to general practitioners or any national bodies. In respect of specific recommendations of the Warnock Committee, there was support for changes which might legitimize or assist the present system, but not for any which might be restrictive.

Attitude↗
PubMed1987

The application of linkage analysis to genetic counselling in families with Duchenne or Becker muscular dystrophy.

A total of 278 families of probands with Duchenne or Becker muscular dystrophy has been ascertained and offered genetic counselling. Linkage studies have been performed in these families using polymorphic DNA markers identifying loci linked to Duchenne and Becker muscular dystrophy. The clinical features of the probands are discussed: there was marked intrafamilial resemblance in the severity of the disease. We estimate that a complete study of potential carriers in these families would require analysis of samples from approximately 1400 subjects. The results of linkage studies tended to move women's carrier risk estimates (based on CK and pedigree data) towards the extremes of the risk categories, providing a more definitive risk estimate for 81% of the women who were previously in the middle range of carrier risk probabilities. About 70% of the families had only one affected member. Linkage analysis altered carrier risk estimates in 95% of sisters and aunts of index cases, but only affected estimates of the mother's carrier risks in about 11% of isolated cases. Even where linkage studies were not helpful in elucidating carrier risks, information could usually be obtained for use in prenatal diagnosis if required. We have assessed the attitudes to pregnancy and prenatal diagnosis of women at risk of being carriers of Duchenne or Becker muscular dystrophy and report 17 pregnancies in these women.

Amniocentesis↗
PubMed1987

A serum-free medium for culturing lactogen dependent and autonomous NB2 node lymphoma cells.

A serum-free, hormone-free medium (SF2) was designed for the Nb2 rat lymphoma bioassay for lactogens as batches of horse serum (HS), which were commonly used, were found to be inconsistent in their suitability and to contain factors modulating the PRL-induced growth response of clone Nb2-11C. In a 3-day incubation with less than 500 pg/ml human GH (hGH), SF2 was better than the traditional medium in supporting Nb2-11C growth, although the comparative efficiency of SF2 decreased at higher hGH levels. Known growth factors (epidermal growth factor, fibroblast growth factor, platelet derived-growth factor, recombinant somatomedin-C, multiplication-stimulating activity) and insulin had no consistent effect on the cell growth in SF2 either in the presence or absence of hGH. Corticosterone (12.4-150 nM) was toxic to the Nb2-11C cells. SF2 could support the growth of Nb2-11C cells for at least 30 passages in the presence of 5 ng/ml hGH, and that of 2 spontaneously proliferating cell lines (Nb2-SP and Nb2-HSP) for the same length of time in the absence of lactogen. However, in all cases the growth rate in SF2 was lower than that seen in the presence of 10% HS. Long-term culture of Nb2-SP and Nb2-HSP cells in SF2 led to an increase of the growth rate with time. There was a change in the responsiveness of Nb2-SP cells to lactogens after long-term culture in SF2 which was only apparent in the presence of HS. After 10 passages in SF2, Nb2-11C cells showed no apparent changes in lactogen-induced growth response, cell phenotype, cell size, or binding capacity for [125I]hGH.

Animals↗
PubMed1987

Identification of amiloride-sensitive Na+/H+ exchange in rat NB2 node lymphoma cells. Stimulation by 12-O-tetradecanoyl-phorbol-13-acetate.

Stimulation of mitogenesis in rat Nb2 node lymphoma cells by human (h) PRL was inhibited by inhibitors of Na+/H+ exchange (viz. amiloride and its analogs) and inhibitors of protein kinases (isoquinolinesulfonamide derivatives). The most potent were ethylisopropylamiloride (EP-Am) (IC50, 13 microM) and H-7, selective for protein kinase C (IC50, 23 microM), suggesting the possible involvement of Na+/H+ exchange and protein kinase C in mediating Nb2 cell mitogenesis. In the presence of hPRL, the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA), known to activate the Na+/H+ antiporter as well as protein kinase C in other cell systems, enhanced the hPRL-stimulated Nb2 cell mitogenesis. TPA alone caused a dose- and time-dependent stimulation of H+ efflux in stationary cultures of Nb2 cells but had no effect on cell growth. From 25-100 nM TPA, the increase in the rate of H+ efflux was detectable by 3 min, reached a maximum by 15 min, and was sustained 30 min after the addition of TPA. The TPA-stimulated H+ efflux was dependent on extracellular Na+ and was almost completely inhibited after a 10 min preincubation with 25 microM EP-Am. TPA also increased the intracellular pH (pHi) of stationary cultures of Nb2 cells from 7.29 +/- 0.02 (n = 8) to a maximum of 7.45 +/- 0.03 (n = 10). The most rapid and greatest response was observed with 40 nM TPA which gave a detectable increase in pHi within 1 min and reached a maximum alkalinization by 6 min. Higher concentrations of TPA had no additional effect. The nontumor promoter phorbol 12,13,20-triacetate (PTA), either alone or in the presence of hPRL, had no effect on Nb2 cell proliferation or on H+ efflux or pHi in Hb2 cells. The TPA-induced increase in pHi was Na+-dependent and was inhibited by EP-Am and H-7. A preincubation with EP-Am (25 microM) for 5-10 min abolished the TPA-induced increase in pHi whereas prolonged incubation with H-7 (50 microM) for up to 3 h was required to decrease the stimulatory effect of TPA by approximately 50%. Although activation of the Na+/H+ exchange system is clearly an early consequence of the action of TPA on Nb2 cells, the failure of TPA to stimulate Nb2 cell proliferation suggests that stimulation of Na+/H+ exchange and protein kinase C activity are not sufficient to generate a mitogenic response in these cells.

Amiloride↗
PubMed1987

Enlarging the caring capacity of the community: informal support networks and the welfare state.

In common with most modern industrial societies, Great Britain is facing the unique late 20th century phenomenon of rapidly increasing numbers of people, especially very elderly people, requiring health and social care. The response in Britain has been to search for ways to enlarge the caring capacity of the "community" and, thereby, reduce the demands on public health and social services. Similar policy responses have been developed in other capitalist societies such as Canada, France, and the United States. Although a policy of "community care"--the provision of state services in people's own homes--was followed by governments of both major British political parties over the postwar period, under the right wing neo-monetarist regime of the present Thatcher administration the locus of policy has shifted toward encouraging greater reliance on the informal support networks of kin, friends, and neighbors. The reasons for this sea-change are explored and the assumptions that these networks are "natural" and necessarily the proper matrix of care are examined critically. This analysis draws on the results of recent research which indicates that informal support networks have significant limitations and that a policy based on withdrawing public services in the hope that these networks will fill the growing care gap is likely to be counterproductive. In conclusion, the author indicates the areas where further research is required to provide a sound basis for policy.

Aged↗
PubMed1987

Sweet survival.

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Female↗
PubMed1987

Improved accuracy of cholinesterase phenotyping after participation in a proficiency survey.

We report results of an investigation into the proficiency of cholinesterase (EC 3.1.1.8) phenotying, assessed in 13 laboratories between 1983 and 1986. Thirty-two specimens of serum were distributed for analysis: two, each in duplicate, from the eight genotypes that can be recognized by differential enzyme inhibitor numbers. The accuracy of genotype ascription was markedly improved over that observed in an earlier study in which 12 of these laboratories took part, although the proportion of clinically significant errors did not change. Consequently, although participation in a proficiency testing program can lead to a considerable enhancement of performance, we still recommend the use of reference centers for detailed cholinesterase studies.

Cholinesterases↗
PubMed1986

A linkage study of Emery-Dreifuss muscular dystrophy.

We have searched for linkage between polymorphic loci defined by DNA markers on the X chromosome and X-linked Emery-Dreifuss muscular dystrophy (EDMD). There are high recombination rates between EDMD and the Xp loci known to be linked to Becker and Duchenne muscular dystrophy. There is a suggestion of linkage between EDMD and the loci DXS52 and DXS15, defined by probes St14 and DX13 respectively, located at Xq28. Z for DXS15 = 1.14 at theta = 0.15. This is in agreement with the previously reported linkage between a disorder strongly resembling EDMD and colour-blindness (Thomas et al. 1972), suggesting that there is a second locus on the X chromosome concerned with muscle integrity.

Adolescent↗
PubMed1986

Reduction in periventricular haemorrhage in preterm infants.

Our previous cerebral ultrasound study of antecedents of periventricular haemorrhage in infants weighing 1250 g or less at birth suggested that neonatal events that caused increased or fluctuating cerebral blood flow lead to periventricular haemorrhage. As the risk period for this type of haemorrhage was the first four days of life strict guidelines were introduced to avoid the previously identified neonatal risk factors. No attempt was made to modify obstetric practice. Over the next two years, although the obstetric risk profile, the frequency and severity of hyaline membrane disease, and the gestation, birth weight, and sex distributions of a similar cohort of infants did not change, the incidence of periventricular haemorrhage decreased significantly from 60% to 36%. Significant antecedents of haemorrhage similar to those found in the previous study included severe bruising, low arterial:fractional inspiratory oxygen ratio and low packed cell volume on admission, hyaline membrane disease, hypercarbia, and hypoxaemia. Assisted ventilation, pneumothorax, treatment with tubocurarine, and hypotension were no longer significant risk factors for periventricular haemorrhage. A multivariate discriminant analysis correctly predicted haemorrhage in 86% of the study group when bruising, hypercarbia, hypoxaemia, hyaline membrane disease, and low gestation were considered. These results suggest that changes in neonatal practices can reduce the incidence of periventricular haemorrhage and that drug studies indicating similar reduction in haemorrhage need to be evaluated carefully to ensure that placebo and treated groups are in fact comparable.

Birth Injuries↗