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Biomedical subjects

D H Roberts

Publications and source records attributed to D H Roberts.

At least 55 records · Page 3Linked to original sources
PubMed1991

Antihypertensive treatment in concomitant peripheral vascular disease: current experience and the potential of carvedilol.

The relative importance of hypertension as a risk factor for peripheral vascular disease is of the same order as coronary artery disease. The design of drug studies in occlusive vascular disease presents several problems. First, investigations must be placebo-controlled and crossover in design. Second, since these patients are very much at risk from other vascular occlusions, length of treatment phase is critical. Third, drug doses are also critical--probably best chosen by titration to similar antihypertensive effect. Fourth, patients must be trained in treadmill procedure. Fifth, measurements of limb blood flow must be accompanied where possible by "functional" assessment, e.g., claudication distance. With respect to the specific problem of low perfusion pressure distal to the blockage of peripheral vasculature, resting blood flow may remain normal, implying compensatory reduction in tone of arteriolar resistance vessels. Thus, regional circulation distal to blockage is sensitive to changes in perfusion pressure. There is the risk of "steal" with vasodilator agents; however, conflict exists in the literature over effects of beta-blockers in this situation. In view of its peripheral hemodynamic profile, the theoretical possibilities with the beta-blocker/vasodilator carvedilol in patients with hypertension and peripheral vascular disease seem extremely rewarding, but remain to be borne out in practice.

Adrenergic beta-Antagonists↗
PubMed1990

First degree atrioventricular block associated with right atrial myxoma.

First degree atrioventricular block occurred in a 68 year old man with a large right atrial myxoma. This conduction abnormality resolved within three months of successful surgical removal of the tumour. It is suggested that mechanical compression by the myxoma on either the underlying conduction tissue or the interventricular septum is likely to have caused this phenomenon.

Aged↗
PubMed1989

Comparison of the agar gel immunodiffusion test and ELISA in the detection of bovine leukosis virus antibody in cattle persistently infected with bovine virus diarrhoea virus.

When six cattle persistently infected with bovine virus diarrhoea virus (BVDV) were inoculated with lymphocytes infected with bovine leukosis virus (BLV), a depressed antibody response to BLV was observed by ELISA which was due to a decrease in IgG1 synthesis. The ELISA was more sensitive and more reliable than the agar gel immunodiffusion (AGID) test in detecting BLV infection in cattle persistently infected with BVDV. Decreased antibody responses were manifested in the AGID test by negative, inconclusive or weakly positive reactions: only two of the six cattle developed antibodies that generated positive AGID reactions.

Animals↗
PubMed1988

Response of cattle persistently infected with bovine virus diarrhoea virus to bovine leukosis virus.

Six cattle persistently infected with bovine virus diarrhoea virus (BVDV) and seronegative, and two control, virus negative seropositive cattle were inoculated with lymphocytes infected with bovine leukosis virus (BLV). The two controls produced a normal immune response to BLV, developing antibodies at four and five weeks after inoculation. Two of the six cattle persistently infected with BVDV developed a strong antibody response by six weeks after inoculation with BLV. Four developed a depressed response to BLV, characterised in three by a 'hooking' reaction in the immunodiffusion test which persisted in successive bleedings but was interspersed occasionally by a weak positive reaction. In one of these animals, a series of 'hooking' reactions was followed by a number of negative results. The fourth animal remained serologically negative until 16 weeks after inoculation when a 'hooking' reaction was observed followed by a series of negative results. BLV was isolated from all the cattle persistently infected with BVDV at 42 or 58 weeks after inoculation regardless of whether the serum samples gave negative, 'hooking', weak positive or positive reactions in the immunodiffusion test. BLV was consistently isolated from the nasal secretions of a steer which was BVDV negative but seropositive. The possibility of decreased immune responsiveness to BLV in animals persistently infected with BVDV should be considered when formulating regulations governing the testing of animals for freedom from BLV.

Animals↗
PubMed1987

Placebo-controlled comparison of captopril, atenolol, labetalol, and pindolol in hypertension complicated by intermittent claudication.

In a six month placebo-controlled cross-over trial twenty patients with hypertension and peripheral arterial disease were randomised to captopril 25 mg twice daily, atenolol 100 mg once daily, labetalol 200 mg twice daily, or pindolol 10 mg twice daily for one month. Although all treatments were equally effective at lowering blood pressure, pain-free and maximum walking distances on a treadmill were decreased by atenolol, labetalol, and pindolol, but not by captopril. Post-exercise calf blood flow availability was impaired by atenolol, labetalol, and pindolol, but not by captopril. Despite ancillary characteristics of cardioselectivity, intrinsic sympathomimetic activity, or combination with alpha-blockade, beta-blockers seem to impair the lower limb circulation in such patients, whereas captopril seems to preserve it, possibly by maintaining the collateral blood supply.

Atenolol↗
PubMed1987

Outbreaks of classical swine influenza in pigs in England in 1986.

Serum samples from pig herds in Great Britain have been examined for antibodies to influenza virus since 1968. Antibodies to H3N2 virus strains have been found since 1968 and the serological data presented here suggests that H3N2 virus strains continue to persist in the pig population. An outbreak of acute respiratory disease occurred in a 400-sow unit. The outbreak was characterised by coughing, anorexia, fever, inappetence and loss of condition. The gilts and weaners were affected and the morbidity approached 100 per cent. An influenza A virus designated A/Swine/Weybridge/117316/86 (H1N1) was isolated from the herd and 28 paired serum samples from the affected animals showed increases in the haemagglutination inhibition titres to this isolate. Haemagglutinin and neuraminidase characterisation indicated that the virus is similar to H1N1 viruses isolated recently from pigs in Europe. A total of 91 herds experiencing respiratory disease were investigated, of which 42 gave positive reactions in the haemagglutination inhibition test. Antibodies to A/Port Chalmers/1/73 (H3N2) were also detected in some of the herds but it is not known whether this strain plays any role in the current respiratory disease problems in pigs.

Animals↗
PubMed1987

Indirect measurement of skin blood flow and transcutaneous oxygen tension in patients with peripheral vascular disease.

The transcutaneous oxygen monitor was used in the vascular laboratory to give an objective measurement of the severity of arteriosclerotic disease in patients presenting with intermittent claudication. With the electrode operating at 44 degrees C on the leg, patients and normal volunteers performed treadmill exercises. It was observed that the resulting electrode heat consumption correlated closely with the degree of exercise. Claudicants, however, showed smaller changes than the normal group, the relationship forming an index of the severity of the disease.

Adult↗
PubMed1987

Haemodynamic effects of atenolol, labetalol, pindolol and captopril: a comparison in hypertensive patients with special reference to changes in limb blood flow, heart rate and left ventricular function.

1 To compare the haemodynamic effects of secondary characteristics of beta-adrenoceptor blockers with an angiotensin converting enzyme inhibitor forty patients with previously untreated mild to moderate hypertension were prescribed either atenolol 50-100 mg day-1, labetalol 200-800 mg day-1, pindolol 10-30 mg day-1 or captopril 25-100 mg day-1 and observed for 6 months. 2 Over this period: (a) All four drugs produced similar reductions in blood pressure at rest (P less than or equal to 0.01) and after exercise (P less than or equal to 0.01). (b) All four drugs significantly decreased resting forearm (P less than or equal to 0.01) and calf blood flow (P less than or equal to 0.01). They all also caused a significant reduction in the increased calf blood flow following exercise (P less than or equal to 0.01). (c) No drug produced a change in resting forearm vascular resistance, while resting calf vascular resistance was decreased by captopril and pindolol, unaltered by labetalol and increased by atenolol. Post-exercise calf vascular resistance was increased by atenolol, labetalol and pindolol but unaltered by captopril. (d) Although all four drugs produced a fall in resting heart rate this was significantly greater for atenolol and labetalol (P less than or equal to 0.01). All four treatments however significantly reduced the increase in heart rate following exercise (P less than or equal to 0.01). (e) No drug produced any significant change in resting and post-exercise stroke volume/ejection fraction. 3 It is concluded that despite differing modes of action all four drugs reduce limb blood flow. This primarily appears to be a consequence of reduced perfusion pressure associated with limited autoregulation of skeletal muscle circulation. The reduction in arterial vascular resistance produced by captopril and pindolol is inconsistent and does not appear of major benefit in preserving limb blood flow. The reduction in perfusion with the agents studied may in part be related to a fall in cardiac output associated with decreased heart rate. This suggests that captopril may exert antisympathetic activity when used as an antihypertensive agent.

Adrenergic beta-Antagonists↗
PubMed1986

To compare the incubation period following intratracheal and subcutaneous inoculation of bovine leukosis virus infected lymphocytes and to study their clearance from the circulation.

The migration of fluorescein isothiocyanate labelled lymphocytes through the tracheobronchial mucosa has been studied in cattle. Following intratracheal inoculation of labelled non-infected autologous lymphocytes and bovine leukosis virus (BLV) infected heterologous (presumed allogeneic) lymphocytes, the labelled lymphocytes appeared in the blood circulation between 4 and 7 days post inoculation. Following intravenous inoculation of labelled autologous lymphocytes, the cells could be detected in the circulation for 10 days post inoculation whereas BLV infected and non-infected heterologous lymphocytes could be detected for only 2 days. The migration of BLV-infected heterologous lymphocytes through the tracheobronchial mucosa caused a delay in the appearance of labelled lymphocytes in the circulation and a corresponding delay in the appearance of BLV antibodies. Comparison was made of the effect of two different routes of inoculation, subcutaneous and intratracheal on the incubation period as indicated by the detection of antibody. Subcutaneous inoculation of 1 X 10(4), 5 X 10(3), 1 X 10(3) of lymphocytes from a BLV infected cow caused seroconversion whereas 5 X 10(2) cells did not. Intratracheal inoculation of 5 X 10(3) cells caused sero-conversion. One animal did not develop BLV antibody until 30 weeks after inoculation although BLV could be isolated from the blood at 24 and 26 weeks post inoculation.

Animals↗