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Biomedical subjects

F Jackson

Publications and source records attributed to F Jackson.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Anthelmintic resistance--the state of play.

There is evidence that the incidence of anthelmintic resistance is increasing in livestock in countries throughout the world including the United Kingdom. Early detection of emerging drug resistance is important since reversion to susceptibility appears not to occur in highly selected homozygous strains. Because the current in vivo and in vitro assays, which generally determine the degree of disruption of normal physiological function of different parasite stages, are relatively insensitive, effort is being made to develop more direct genetic and biochemical diagnostic assays. Studies on the selection and genetics of resistance suggest that resistance is normally polygenic and arises from within the normal phenotypic range and that there are three phases in the selection process. An initial susceptible phase is followed by an intermediate one in which heterozygous resistant individuals are common within the population and finally homozygous resistant individuals predominate within the population. For these reasons low efficacy treatments, which enable the survival of heterozygous resistant individuals, and suppressive regimes, which only allow homozygous resistant individuals to survive, increase the rate of development of drug resistance. Strategies to delay the onset of resistance and control resistant strains usually incorporate minimal chemoprophylaxis, seek to maximize drug efficacy, and if possible include a 'slow' drug rotation and seek to limit host parasite contact by manipulation of the grazing environment. Although multi-species mathematical models of anthelmintic resistance appear to offer a means of assessing the long term impact of these and other control strategies, current models are limited by a lack of detailed biological knowledge. In particular, more information on the status and numbers of alleles associated with resistance to specific drugs, their frequencies within populations of different species and the fitness of resistant and susceptible populations is required. Anthelmintic resistance provides an example of the adaptability of metazoan parasites under intensive selection and suggests that sustainable control strategies will require an integrated approach in which both chemotherapy and immunotherapy, together with environmental management are used to control nematodoses.

Animal Diseases↗
PubMedDate not supplied

Plasma profiles of albendazole metabolites after administration of netobimin and albendazole in sheep: effects of parasitism and age.

Netobimin and albendazole were administered to 3-month-old lambs with moderate infections of Nematodirus battus and to comparable parasite-naive lambs. Albendazole sulphoxide and albendazole sulphone concentrations were determined in the plasma of all lambs at frequent intervals after treatment. Both anthelmintic preparations were 100% effective in reducing nematode faecal egg output in the lambs. There were no significant differences in the concentrations of the sulphoxide or sulphone metabolites in parasitized compared with non-parasitized lambs given the same parent anthelmintic. The parasite-naive lambs were subsequently weaned and maintained indoors in conditions designed to preclude nematode parasite infection until they were 9 months old. Netobimin and albendazole were administered again and the plasma profiles of the albendazole sulphoxide and albendazole sulphone metabolites determined. There were no significant differences in the plasma distribution of these metabolites with age of the lambs. The area under the plasma concentration time curve, mean resident time and apparent half-life of the albendazole sulphoxide metabolite was determined following administration of each parent drug and the clearance of the metabolite/systemic availability of parent drug was determined as a marker of the amount of drug available for metabolism. There were no significant differences in pharmacokinetic variables between parasitized and non-parasitized animals nor with the age of the animals.

Aging↗
PubMedDate not supplied

Comparative field evaluation of divided-dosing and reduced feed intake upon treatment efficacy against resistant isolates of Teladorsagia circumcincta in sheep and goats.

The effects of modifying drug administration and food intake upon the efficacy of fenbendazole against resistant isolates of Teladorsagia (Ostertagia) circumcincta were investigated using naturally infected sheep and goats. Administration of the manufacturer's recommended dose (MRD) as two 2.5 mg kg(-1) bodyweight doses divided by a 12-hour interval resulted in an apparent increase in efficacy of over 28 per cent compared with conventionally treated sheep. Withholding feed for 24 hours before treatment at the MRD resulted in respective increases of 39.7 per cent (P<0.05) and 25.2 per cent compared with conventionally treated sheep and goats. A combination of food withdrawal and divided dosing did not further increase treatment efficacy in goats. It is suggested that withholding feed, divided-dosing or combining these methods may extend the useful life of the broad spectrum class of anthelmintics.

Animals↗
PubMedDate not supplied

Comparative aspects of plasma antioxidant status in sheep and goats, and the influence of experimental abomasal nematode infection.

This paper provides, for the first time, comparative data on the plasma antioxidant status of two ruminant species, namely sheep and goats. In addition, the influence of experimental infection with Teladorsagia circumcincta on antioxidant status in the same two species is compared and contrasted. In general terms, antioxidant status was significantly higher in uninfected kids than in lambs. Differences in protein sulphydryl groups and vitamin E concentrations were particularly noteworthy; trends were similar, however, for albumin, vitamin A and total antioxidant capacity (TAC). Parasitological results, based on worm burden, faecal egg counts and peripheral blood eosinophil numbers, confirmed that goat kids were more susceptible than lambs to experimental T. circumcincta infection. "Trickle infection" had a variable impact on both total and individual antioxidant status; particularly during the early weeks, the trend was for reduced values in lambs and increased values in kids, as compared with uninfected controls. Subsequent challenge infection was associated with a transient decrease in TAC and albumin in trickle-infected animals of both species, and in appropriate control animals. The observed differences in plasma antioxidant capacity between sheep and goats may have important implications in terms of the comparative resilience of sheep and goats to parasite infection.

Abomasum↗
PubMedDate not supplied

Continuous core temperature monitoring of search and rescue divers during extreme conditions.

OBJECTIVES: To study the feasibility of continuously monitoring core temperatures of search and rescue divers, to compare core temperature gradients occurring during warm and cold diving events, and to identify conditions under which divers are subjected to extreme temperatures. METHODS: Between June 1994 and March 1995, emergency medical technicians (EMTs) from two midwestern dive teams volunteered to ingest an encapsulated temperature sensor developed for the National Aeronautics and Space Administration. The capsule monitored continuous core temperatures and transmitted the data to a recorder worn under the divers' dry suits. RESULTS: Twenty male EMTs, mean age 34 years and mean body weight 184 pounds, were monitored during training. Nine dives were ice dives, with ice thickness averaging 9 inches, and mean ambient temperatures of 33 degrees F. Eleven dives were warm-water dives; average water temperature was 70 degrees F and mean ambient temperature was 74 degrees F. The average time spent in the dry suit was 95 minutes, and the mean total bottom time was 15 minutes. The ice divers showed a mean increase in core temperature of 1.0 degrees C, while the warm-water divers showed a mean increase of 1.2 degrees C. Divers experiencing the most extreme fluctuations were those in the role of safety diver, regardless of the season. Divers reported more subjective discomfort during ice dives than during warm-water dives. CONCLUSIONS: Continuous monitoring of body temperature during the duration of dive operations is possible, but labor-intensive. Safety measures to protect divers from extreme core temperature fluctuations should focus on the safety diver as well as the active diver.

Adult↗
PubMedDate not supplied

Effects on experimental acute lung injury 24 hours after exogenous surfactant instillation.

Subcutaneous injection of N-nitroso-N-methylurethane (NNNMU) produces an acute lung injury mimicking the adult respiratory distress syndrome. NNNMU-injured rats treated with intratracheal Survanta, 100 mg phospholipid/kg body weight, air, or normal saline were observed for 24 h. Twenty-four hours after treatment survival among Survanta-treated rats was significantly greater than for air- and saline-treated rats (9/15 vs. 2/15 and 3/15, respectively). The alveolar-to-arterial O2 gradient was lower in Survanta-treated than in either air- or saline-treated rats during the 24-h period. Analysis of bronchoalveolar lavage fluid revealed a higher phospholipid: protein ratio (1.73 +/- 0.31 Survanta-treated, 0.20 +/- 0.05 air control, and 0.41 +/- 0.17 saline control) and a more normal phospholipid composition among treated than control rats. Minimum dynamic surface tension was significantly lower among treated rats (10.9 +/- 2.9 dyn/cm) than air and saline control rats (36.0 +/- 0.6 and 35.8 +/- 1.0 dyn/com, respectively). In vitro mixing of surfactant with pulmonary edema proteins significantly raised the minimum surface tension of surfactant from a group of Survanta-treated, NNNMU-injured rats (8.7 +/- 3.5 dyn/cm before and 32.0 +/- 0.5 dyn/cm after mixing). Intratracheal Survanta shows a beneficial effect on physiologic parameters and biochemical and functional characteristics of alveolar surfactant for 24 h in rats with NNNMU-induced acute lung injury.

Animals↗
PubMedDate not supplied

Alabama's hospital legacy. Interview by Rosemary Blackmon.

Jackson, Carraway, and Flowers--three men who truly personify medicine in the state of Alabama. ALAHA public relations director Rosemary Blackmon recently spoke with each of them about the past and future of healthcare.

Alabama↗