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Biomedical subjects

J E Hunter

Publications and source records attributed to J E Hunter.

At least 55 records · Page 3Linked to original sources
PubMed1992

Apramycin resistance plasmids in Escherichia coli: possible transfer to Salmonella typhimurium in calves.

An outbreak of salmonellosis in calves was monitored for persistence of Salmonella typhimurium excretion in faeces and the effect of treatment with apramycin. Prior to treatment apramycin-resistant Escherichia coli were present but all S. typhimurium isolates were sensitive. Following the treatment of six calves with apramycin, apramycin-resistant S. typhimurium were isolated from two treated calves and one untreated calf. Plasmid profiles of E. coli and S. typhimurium were compared and plasmids conferring resistance to apramycin and several other antibiotics were transferred by conjugation in vitro from calf E. coli and S. typhimurium isolates to E. coli K-12 and from E. coli to S. typhimurium. The plasmids conjugated with high frequency in vitro from E. coli to S. typhimurium, and hybridized to a DNA probe specific for the gene encoding aminoglycoside acetyltransferase 3-IV (AAC(3)-IV) which confers resistance to apramycin, gentamicin, netilmicin and tobramycin.

Animals↗
PubMed1992

Fertilization and embryonic development of human oocytes after cooling.

Injury to living cells resulting from rapid cooling to temperatures at or near 0 degrees C has long been recognized, and the phenomenon, which is termed 'cold shock', has been known to occur in some mammalian gametes. Although human embryos have been successfully stored at low temperatures, cryopreservation of the human oocyte is proving to be more difficult. Whether or not this lack of success is a direct result of cellular injury brought about by 'cold shock' is the purpose of the current investigation. Human oocytes were cooled, in the absence of cryoprotectants, at two different cooling rates (-3 degrees C/min and -1000+ degrees C/min) to a temperature of 0 degrees C and rewarmed prior to insemination. In both cases fertilization after cooling was similar to the rates achieved in a routine in-vitro fertilization and embryo transfer procedure. After cooling at -3 degrees C/min, the rate of fertilization was 19/22 (86%) and after cooling at -1000+ degrees C/min, 9/9 (100%), with non-cooled control rates of 62/87 (71%) and 35/50 (70%) respectively. Fertilized oocytes from both groups were successfully cultured for a further 24 h before termination of the experiment.

Cryopreservation↗
PubMed1991

Reassessment of trans fatty acid availability in the US diet.

This report updates our 1984 estimate of the amount of trans fatty acids available for consumption in the US diet, namely 7.6 g.person-1.d-1, for 1989. Compared with 1984 data, we found essentially no change in 1989 for the per capita availability of trans fatty acids from total food service fats and oils. The 1989 value we obtained for industrial fats and oils is somewhat higher than the value we reported for 1984, in part because more complete data were available for 1989. In contrast, however, since 1984 the per capita availability of trans fatty acids from household salad and cooking oils, household shortenings, and all margarines and spreads (retail, food service, and industrial) has decreased. Overall, our reassessed (1989) value for total trans fatty acid availability is 8.1 g.person-1.d-1, which is similar to our original estimate. This total may increase slightly (approximately 0.3 g.person-1.d-1) as a result of the recent switch by many establishments from the use of tallow to partially hydrogenated vegetable oils for frying.

Dairy Products↗
PubMed1991

Fertilization and development of the human oocyte following exposure to cryoprotectants, low temperatures and cryopreservation: a comparison of two techniques.

Both glycerol and dimethyl sulphoxide (DMSO) equilibration prior to cryopreservation produced adequate rates of survival and development to the hatching blastocyst stage for mouse oocytes using the two chosen cooling and warming regimes. Successful fertilization of human oocytes and further development of the embryos produced, was achieved following equilibration with DMSO at 0 degrees C. Although fertilization of fresh human ova previously exposed to glycerol was recorded, all oocytes with two pronuclei failed to continue to undergo cell division by 48 h in culture. Following cryopreservation, human oocytes were successfully inseminated after equilibration with both glycerol and DMSO. However, cell division to the 2-cell stage was recorded in only one oocyte which had undergone exposure to DMSO, freezing and thawing. No cell divisions were recorded after glycerol cryopreservation, or even after simple exposure to glycerol. Therefore it appears that DMSO and slow cooling may be the best protocol, although further evaluation will be necessary.

Animals↗
PubMed1990

n-3 fatty acids from vegetable oils.

Principal food sources of the n-3 fatty acid alpha-linolenic acid are salad and cooking oil, salad dressing, shortening, margarine, and food-service fat and oil products made from canola oil or soybean oil. Using food production data provided by US trade associations and by Statistics Canada, I estimated the per capita availability of alpha-linolenic acid from vegetable-oil products in the United States to be approximately 1.2 g/d and in Canada, approximately 2 g/d. The higher alpha-linolenic acid availability in Canada is largely accounted for by widespread use of canola oil there. Considering also contributions to dietary alpha-linolenic acid of other foods such as nuts, dairy products, and vegetables, it would appear that total intake of alpha-linolenic acid in US and Canadian diets adequately exceeds the reported nutritional requirement. Emerging research has suggested possible health benefits associated with modest increases in dietary alpha-linolenic acid, including reduced blood-clotting tendency and reduced blood pressure.

Dietary Fats, Unsaturated↗
PubMed1986

Hepatic damage in the rat following administration of thyroxine or triiodothyronine, assessed by measurement of plasma glutathione S-transferase YaYa concentrations.

A specific radioimmunoassay (RIA) has been developed that has sufficient sensitivity to allow measurement of the changes in plasma and tissue glutathione S-transferase (GST) YaYa concentrations which occur following thyroid hormone administration in the rat. Using the RIA it was demonstrated that the only tissues that had significant amounts of GST YaYa were liver, small gut and kidney. Administration of triiodothyronine (T3) or thyroxine (T4) resulted in increases in plasma GST YaYa concentration and in animals given high doses of T4 plasma alanine aminotransferase activity was also elevated. Thyroid hormone administration produced a significant fall in the hepatic content of GST YaYa and in total GST activity, as assessed using 1-chloro-2,4-dinitrobenzene as substrate. It is concluded that the elevated plasma GST YaYa concentrations observed following administration of thyroid hormones result from hepatic damage, not from induction of hepatic synthesis of the enzyme.

Animals↗
PubMed1986

Isomeric fatty acids in the US diet: levels and health perspectives.

Data on market size, market share, and compositional changes of various products made from partially hydrogenated fats and oils were used to estimate current, previous, and predicted levels of trans fatty acids in the US diet. Recent literature and various perceptions of the toxicological, physiological, and nutritional effects of trans fatty acids were reviewed. Trans acid availability has changed little during the last 15-20 yr and currently is estimated to be approximately 7.6 g X person-1 X day-1. Modest decreases in total fat intake, including trans fatty acid intake, may occur in the future if consumers adopt certain dietary recommendations. We believe that concerns about possible relationships of trans fatty acids to development of atherosclerotic disease or cancer are not supported by reliable data. Numerous literature accounts support the conclusion that trans fatty acids do not pose any harm to humans or animals consuming a balanced diet containing adequate linoleic acid.

Animals↗
PubMed1985

Isomeric fatty acids and tumorigenesis: a commentary on recent work.

This article critically reviews the existing, although limited, literature concerning trans fatty acids and tumorigenesis. Neither epidemiological nor experimental studies published to date have demonstrated any valid association between trans fatty acid ingestion and tumorigenesis. A recent study showed that under controlled conditions, a fat with a high content of trans fatty acids did not promote the development of mammary tumors induced in rats by 7,12-dimethylbenz[a]anthracene to any greater extent than did a comparable fat with a high content of cis fatty acids. In addition, in this study a high trans fat was less tumor promoting than was a blend of fats that simulated the dietary fat composition of the United States and had a lower level of trans fatty acids. Another study using comparable cis and trans fats demonstrated that the high trans fat did not affect the growth and metastasis of implanted mammary tumors in mice relative to the high cis fat. Also, two recent studies reported no significant difference in the development of induced colon tumors in rats fed diets high in cis or trans fatty acids. The results of these and other studies are consistent with the conclusion that trans fatty acids are not uniquely related to tumor development.

Animals↗
PubMed1982

Retinal white without pressure: review and relative incidence.

Examination of 1000 consecutive patients revealed that lattice degeneration, retinal white without pressure, and retinoschisis were present more frequently in black than in white patients. The association between these conditions and rhegmatogenous retinal detachments is confirmed. Periodic reexaminations should be done at approximately 6- to 12-month intervals.

Black People↗
PubMed1981

Iron availability and absorption in rats fed sodium phytate.

Effects of dietary sodium phytate on iron availability and absorption in rats were assessed in two experiments. In the first experiment, iron-deficient rats were switched to diets containing variable levels of added sodium phytate and variable levels of iron as ferrous sulfate. Iron availability was evaluated by measuring hemoglobin regeneration after 2 weeks of feeding these diets. In the second experiment, both iron-adequate and iron-deficient rats were force-fed a slurry containing an iron-deficient diet, 59Fe and sodium phytate. Iron absorption was assessed by measuring the percentage of the 59Fe dose retained by the rats after 9 days. The results of the first experiment indicated that levels of dietary phytate up to 4% of the diet do not impair hemoglobin regeneration by anemic rats. The results of the second experiment indicated that sodium phytate does not affect iron absorption differently in iron-adequate rats compared to iron-deficient rats. It is suggested that conflicting results in the literature on effects of phytate on iron absorption may be explained by differences in experimental conditions or by the presence in the diet of some inhibitory component besides phytate, possibly dietary fiber.

Absorption↗