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Biomedical subjects

M A Taylor

Publications and source records attributed to M A Taylor.

At least 145 records · Page 8Linked to original sources
PubMed1990

Efficacy of ivermectin against benzimidazole-resistant nematodes of sheep.

Two trials involving a total of 36 Dorset horn lambs were conducted to assess the anthelmintic efficacy of ivermectin against experimental infections of benzimidazole-resistant strains of Haemonchus contortus and Ostertagia circumcincta. Two resistant strains of each of the two species were used and in each trial the lambs were allocated to three groups. One group was given 200 micrograms ivermectin/kg bodyweight orally, the second group was given 5 mg oxfendazole/kg bodyweight orally and the third group remained untreated as controls. Fourteen days after treatment the lambs were necropsied. Ivermectin was found to be more than 99 per cent to 100 per cent effective against all four benzimidazole-resistant strains, whereas oxfendazole was 78.6 per cent and 83.8 per cent effective against the H contortus strains, and 25.6 per cent and 39.8 per cent effective against the O circumcincta strains.

Animals↗
PubMed1990

A larval development test for the detection of anthelmintic resistance in nematodes of sheep.

First stage larvae of a number of species of parasitic nematodes of sheep have been shown to develop to third stage larvae in the presence of a defined medium consisting of Earle's balanced salt solution and yeast extract. A larval development test, based on this culture technique, was used as a screen for detecting the presence of anthelmintic resistance in nematodes of sheep. It was found to be sensitive and simple to use and also appeared capable of detecting resistance to any of the main anthelmintic groups. Available anthelmintic sensitive and resistant strains of Haemonchus contortus and Ostertagia circumcincta showed differences in development when incubated in the presence of either thiabendazole, levamisole and ivermectin. These differences were expressed as the minimum inhibitory concentration required to prevent larval development over the incubation period.

Animals↗
PubMed1989

Anthelmintic drug resistance in the UK.

The term 'anthelmintic drug resistance' describes the heritable ability of some nematode parasites to survive treatment with anthelmintic drugs at the recommended therapeutic dose levels. Genes for resistance appear to be present in many of the important pathogenic nematodes of ruminants and horses. Under intensive management systems, where heavy reliance is placed on anthelmintic drugs for worm control, the selection of resistant genotypes may result in increased reports of the drugs failing to control the nematode populations against which they are aimed. Anthelmintic resistance has been reported from many parts of the world, and in some countries multiple drug-resistant strains have emerged. In the UK, recent investigations indicate an increasing level of resistance to benzimidazoles among nematodes of sheep and horses. The incidence, diagnosis, epidemiology and implications of anthelmintic resistance are discussed.

Animals↗
PubMed1989

Comparison of two early season anthelmintic programmes on a commercial beef farm.

Two early season suppressive anthelmintic programmes, ivermectin given three, eight and 13 weeks after turn out and a morantel sustained release bolus administered at turn out, were compared on a commercial farm. The morantel treated cattle grew significantly faster than the ivermectin treated group during the period of treatment, on average at 0.80 kg/day compared with 0.71 kg/day (P less than 0.01). In the second half of the grazing season (13 to 25 weeks after turn out) the ivermectin treated group grew faster than the morantel treated group although the difference was not statistically significant. Over the entire grazing season there was no significant difference in average growth rate between the morantel treated group which grew at 0.80 kg/day and the ivermectin treated group which grew at 0.77 kg/day. These results were related to pasture larval counts, faecal egg counts and plasma pepsinogen levels throughout the grazing period. It was concluded that the morantel sustained release bolus allowed growing cattle to reach their production potential during the period of treatment. However, its efficacy in maintaining production throughout the grazing season was reduced by the 90 day treatment period which failed to give the level of control of gastrointestinal nematode parasites achieved by the 105 day period of treatment in the ivermectin programme.

Animals↗
PubMed1989

Atrial natriuretic factor in essential hypertension.

We measured circulating levels of immunoreactive atrial natriuretic factor (ANF) in 10 patients with untreated, uncomplicated mild to moderate essential hypertension and in 15 normotensive controls. ANF concentrations were significantly higher in the hypertensive group than in the control group (38.4 +/- 6.9 pg/ml versus 18.3 +/- 1.8 pg/ml, p less than 0.02). A positive correlation between ANF levels and systolic, diastolic and mean blood pressure was noted in the total study population (p less than 0.008, r = 0.52; p less than 0.005, r = 0.55; p less than 0.02, r = 0.46, respectively). Thus, plasma ANF concentrations are elevated in essential hypertension and may result from increased intraarterial pressure.

Adult↗
PubMed1989

Some effects of Ledermix paste and Pulpdent paste on mouse fibroblasts and on bacteria in vitro.

Dilutions of Ledermix paste, Pulpdent paste and a mixture of equal parts by weight of Ledermix paste and Pulpdent paste were added to in vitro cultures of mouse fibroblasts or bacteria for 24 h, and various cell functions were then examined: mitosis in and survival of fibroblasts, and survival of Lactobacillus casei or Streptococcus mutans. Ledermix was found to reversibly inhibit mitosis while present in the concentrations range 10(-3) to 10(-6) mg/ml. Mixing with Pulpdent did not modify this antimitotic effect. Ledermix killed mouse fibroblasts at 10(-3) mg/ml and above, while Pulpdent killed at 1 mg/ml and above. The toxic effect of Ledermix was slightly inhibited by mixing it with Pulpdent. Ledermix killed S. mutans at about the same concentration at which it killed the mammalian cells, but required a one thousand-fold greater concentration to kill L. casei. Pulpdent killed both L. casei and S. mutans at approximately one-fifth of the concentration at which it killed the mammalian cells. Pulpdent slightly potentiated the antibacterial effect of Ledermix. The pH of Pulpdent was reduced by approximately 0.3 units by mixing with Ledermix. The present data showed that the 50:50 mix of Ledermix and Pulpdent retained the properties examined that are thought to be of therapeutic benefit, while not increasing the toxicity of the component parts to mammalian cells.

Animals↗
PubMed1989

Platelet calcium and quenched-flow aggregation kinetics in essential hypertension.

Abnormal platelet function may contribute to the complications of essential hypertension. We have studied the kinetics of platelet aggregation induced by adenosine diphosphate (ADP) or epinephrine, plasma beta-thromboglobulin, and basal, cytosolic, and free calcium, as correlates of platelet function. Fifteen untreated patients with essential hypertension and without detectable atherosclerosis, 18-40 years old, were compared with 30 matched normotensive control subjects. Maximal rates of platelet aggregation (Vmax) with ADP and epinephrine were significantly higher in patients than in control subjects (p less than 0.03), as assessed by quenched-flow aggregometry. However, significance was lost when Vmax was corrected for the platelet count. Paradoxically, the activation constants (Ka) for ADP were higher in patients than in control subjects (p less than 0.03). With ADP as the inducing agent, onset time (t) or lag period before aggregation begins was longer in patients than in control subjects (p less than 0.02). beta-thromboglobulin levels, an index of in vivo platelet activation, were not significantly different between the two groups (p = 0.13). The mean platelet cytosolic free calcium concentration was higher in patients (213 +/- 19 nM) than in control subjects (172 +/- 14 nM), but this difference was not statistically significant (p = 0.07). However, there was a close correlation between the free calcium level and systolic, diastolic, and mean blood pressure (p less than 0.003, p less than 0.04, p less than 0.004, respectively). No difference in platelet volume between the two groups was found. Our data suggest that platelets in the early stages of essential hypertension display an overall increased aggregation potential but a diminished sensitivity to ADP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1989

The diagnostic implications of formal thought disorder in mania and schizophrenia: a reassessment.

The authors compared nine manic patients exhibiting formal thought disorders (tangentiality, neologisms, drivelling, private use of words, and paraphasias) with 102 manic patients without these thought disorders and with 31 schizophrenic patients. Manic patients with formal thought disorders tended to have more "schizophrenic" symptoms than did manic patients without formal thought disorders, but both groups improved significantly more during the index episode than did the schizophrenic patients. Although the prevalence of flight of ideas was high in mania, narrowly defined formal thought disorder was rare, suggesting that precise definition and description of thought disorders would be helpful in distinguishing mania from schizophrenia.

Adult↗
PubMed1989

Effectiveness of lithium in schizophrenia: do we really have an answer?

The authors review all double-blind studies assessing the efficacy of lithium treatment in schizophrenia. They conclude that active affective symptoms, previous affective episodes, and a family history of affective disorder may predict a favorable response to lithium. However, methodological problems in past studies (e.g., small samples, lack of strict diagnostic criteria) suggest that further clinical trials are warranted.

Chronic Disease↗
PubMed1989

Diagnosis of affective disorders and schizophrenia in the U.S.: a 1984 survey of psychiatrists and graduating residents.

During a 5-month period in 1983 and 1984, the authors surveyed a random sample of U.S. psychiatrists and all psychiatric residents graduating in 1984, with response rates of 56.1% and 51.9% respectively. They report the diagnostic classifications and subtypes used by the clinicians as well as the clinical features required by the clinicians to diagnose affective disorders and schizophrenia. When diagnosing schizophrenia, the graduating residents differed from their senior colleagues by giving more importance to the course of illness, duration of symptoms, and exclusion of affective disorder. These findings are discussed in light of past surveys and the development of new diagnostic systems.

Adult↗
PubMed1989

Tissue and biliary glutathione disulfide in the perfused vitamin E-deficient rat liver.

Vitamin E and glutathione protect against oxidative damage in vivo. In this study the relationship between these two defenses has been examined in the isolated perfused rat liver. The activities of glutathione reductase and glutathione S-transferase were unaffected by vitamin E deficiency, while glutathione peroxidase activity was decreased slightly. The glutathione redox status of vitamin E-deficient and control livers was assessed. GSSG was slightly higher in vitamin E-deficient livers (70 +/- 5 nmol GSH equivalents/g liver) than in controls (56 +/- 3 nmol GSH equivalents/g liver) under basal conditions. However, biliary GSSG release was 41% lower in vitamin E-deficient livers (0.46 +/- 0.08 nmol GSH equivalents/g liver.min) than in controls (0.78 +/- 0.23 nmol GSH equivalents/g liver.min). Inhibition of GSSG reduction by BCNU raised liver and biliary GSSG by a similar amount in vitamin E-deficient and control livers. Thus biliary GSSG efflux, a frequently used index of oxidant stress, is not increased in vitamin E-deficient perfused livers compared with control. Therefore, in the perfused rat liver model, no evidence was obtained that vitamin E deficiency activates the hepatic glutathione system.

Animals↗
PubMed1988

Field observations on the control of ovine parasitic gastroenteritis in south-east England.

Three worm control strategies, on a commercial farm in south east England, were monitored parasitologically for a grazing season. Three peaks of larval infection in June, late August and late October/early November occurred on paddocks grazed by dosed ewes and lambs on a new ley (preventive strategy). Lambs dosed and moved on to a hay aftermath in July (evasive strategy), had a mean egg count of 2090 by late August, attributable to infection with Haemonchus contortus. Three weekly drenching of lambs (suppressive strategy), suppressed faecal egg counts until September when the treatment interval was extended due to other on-farm commitments. In addition to these observations, autoinfection, with Haemonchus contortus, was seen to occur in lambs grazing summer turnips. An in vitro egg hatch assay, and critical efficacy trial, confirmed the presence of a benzimidazole resistant strain of Haemonchus contortus on this farm. The implications of these findings are discussed.

Animals↗
PubMed1988

Reiterated DNA sequences defining genomic diversity within the species Mycoplasma hyorhinis.

Genomic restriction fragments isolated from Mycoplasma hyorhinis and Mycoplasma hyopneumoniae were shown by DNA hybridization and nucleotide sequence analyses to contain sequences common to these two species, as well as another porcine-derived mycoplasma, Mycoplasma flocculare. Intraspecies hybridization experiments using these fragments as probes indicated that the sequence is highly redundant in several strains of M. hyorhinis, but that there is diversity in the sizes of restriction fragments detected among these strains. In contrast, repetition of the sequence was limited in M. hyopneumoniae and M. flocculare, and no homologies to this repeated element were apparent in mycoplasma species isolated from animal hosts other than the swine. The reiterated sequence may reflect intraspecies genomic diversification in M. hyorhinis and its selective presence in otherwise unrelated species raises the possibility that it has been horizontally transmitted between these organisms.

Bacteriophages↗
PubMed1988

Elevation of cathepsin L levels in the synovial lining of rabbits with antigen-induced arthritis.

The activity and distribution of the collagenolytic lysosomal enzyme, cathepsin L, has been assessed in the synovial lining of the rabbit during the initiation and development of chronic (antigen-induced) arthritis. Biochemical assay of homogenates of synovial lining revealed a marked increase in the activity of lysosomal enzymes, including cathepsin L, between 1 and 5 days following initiation of arthritis. Elevated levels of these enzymes were still present at 4 weeks duration of arthritis. Using a monospecific antibody to cathepsin L. enzyme was immunolocated only in synovial lining cells in normal joints. In arthritic joints the enzyme was found in synovial lining cells, synovial fibroblasts and in infiltrating macrophages. Measurement, by scanning and integrating microdensitometry, of the peroxidase-reaction product in synovial lining cells revealed an increased content of cathepsin L in these cells in the diseased tissues.

Acetylglucosaminidase↗