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Biomedical subjects

G D Foster

Publications and source records attributed to G D Foster.

At least 19 recordsLinked to original sources
PubMed1995

The potential exploitation of plant viral translational enhancers in biotechnology for increased gene expression.

The regulation of gene expression is extremely important for all organisms, not least for viruses that require a maximum rate of production of viral proteins to allow rapid multiplication and spread. Single-stranded positive-sense RNA viruses contain specific nucleotide sequences that can be used to elevate the expression of vital gene products to required high levels. Among plant viruses, translational enhancement has been documented widely, especially over the past few years. Reported candidates include one of the best known and most intensely researched virus, tobacco mosaic virus, members of the potyvirus group, and even a small satellite RNA of tobacco necrosis virus. Enhancement values range from 2-100-fold with different viruses, different reporter genes, and in different systems. Research indicates that an absence of secondary structure alone does not explain translational enhancement and despite attempts to determine the mechanism by which this enhancement occurs very little conclusions can be made as yet. Whatever the mechanism, the presence of these sequences upstream from an open reading frame results in an elevated level of protein production and may feature as important tools for biotechnology in the future.

Base Sequence↗
PubMed1995

The energy cost of walking before and after significant weight loss.

The purpose of this study was to determine whether significant weight loss reduced the energy cost of activity more than that expected based on decreased body weight. Standing energy expenditure was measured and subtracted from the total energy cost of walking to determine ambulatory energy expenditure (AEE). The energy cost of walking was determined in 11 obese women at baseline, week 9 [after 8 wk of a 1758-3349 kJ.d-1 diet], and week 22 (after 2 wk of weight stability). AEE accounted for 80% of the energy cost of walking. Body weight was the principal determinant of AEE, but the relationship was not 1:1. Subjects reduced body weight by 13% at week 9 and 21% at week 22. Analyses which controlled for the relationship between AEE and weight at baseline, showed no change in AEE at week 9. By contrast, at week 22, AEE was reduced more than expected based on a lower body weight. These findings suggest that after significant weight loss, reduced-obese persons will expend less energy for the same activity, even after accounting for the decrease in body weight. These data also suggest that weight-based estimates of exercise energy expenditure may be inappropriate after significant weight loss.

Adult↗
PubMed1994

Analysis of a translational enhancer upstream from the coat protein open reading frame of potato virus S.

Evidence has suggested that the subgenomic RNA of the carlavirus potato virus S is an efficient message for the coat protein, even though evidence suggests it is uncapped at its 5' terminus. We have investigated the effect of the upstream region of the coat protein gene of potato virus S on the level of reporter gene expression in vitro. The region of 101 nucleotides upstream of the coat protein, designated VTE (viral translational enhancer) was found to increase levels of translation in comparison to a synthetic leader when linked to the beta-glucuronidase (GUS) reporter gene in vitro in rabbit reticulocyte and wheat germ lysate. VTE was also able to increase translation of the reporter gene luciferase (LUC) in vitro above the levels obtained for both a synthetic leader and a leader obtained from a plant gene isolated from Arabidopsis thaliana. The level of enhancement was evident with both capped and uncapped transcripts. When the VTE sequence was deleted to 20 nucleotides of the upstream region, thus removing the nucleotide block homologous among carlaviruses, the ability to enhance levels of translation was removed. In vitro translation studies indicated that the translational enhancement activity of VTE was at least partially cap independent. Translation of VTE linked to reporter genes in the presence of cap analogue was relatively unaffected whereas synthetic leader and a plant leader constructs were both more sensitive. In vitro competition analysis revealed that when short RNA transcripts representing the 101 nucleotides of VTE were added in trans to functional VTE leader LUC constructs there was a marked decrease in the level of translation when compared with a synthetic leader added in trans. These results suggest that the upstream region of the coat protein ORF of potato virus S promotes translation in a cap-independent manner that may involve the binding of proteins and/or ribosomes to the 101 nucleotides of the VTE sequence.

Animals↗
PubMed1994

In vivo characterisation of a translational enhancer upstream from the coat protein open reading frame of potato virus S.

The 101 nucleotide region upstream from the ATG of the potato virus S (PVS) coat protein gene was isolated and the effect of this region on the translation of a downstream open reading frame analysed in vivo. Translation was monitored using the reporter genes B-glucuronidase (GUS) and luciferase (LUC). Translational enhancement was assayed transiently using DNA microprojectile bombardment into both leaf and pollen tissue and also by polyethylene glycol mediated transfection of tobacco protoplasts. In both cases the presence of this region resulted in a 2-3 fold increase in translation when compared to reporter expression with synthetic leader and authentic plant leader constructs. Tobacco plants stability transformed with this PVS 101 nucleotide region and downstream GUS gene gave 4 times the level of translation over synthetic leader GUS control plants.

Base Sequence↗
PubMed1994

One-year behavioral treatment of obesity: comparison of moderate and severe caloric restriction and the effects of weight maintenance therapy.

This study compared the weight losses of 49 obese women randomly assigned to a 52-week behavioral program combined with either moderate or severe caloric restriction. Subjects in the balanced deficit diet (BDD) condition were prescribed a 1,200-kcal/day diet throughout treatment, and those in the very-low-calorie diet (VLCD) condition were given a 420-kcal/day liquid diet for 16 weeks and a 1,200-kcal/day diet thereafter. The VLCD subjects lost significantly more weight than the BDD subjects at all periods through Week 26, at which time mean losses were 21.45 and 11.86 kg, respectively. VLCD subjects, however, regained weight during the next 26 weeks of weekly therapy and during a 26-week weight maintenance program that provided biweekly meetings. Mean weight losses at the end of the maintenance program were 10.94 and 12.18 kg, respectively. Reports of binge eating declined in both groups, and no relationship was observed between binge eating and weight loss or attrition.

Adult↗
PubMed1994

Decline in delayed-type hypersensitivity response in obese women following weight reduction.

The effect of weight loss on immuno function was evaluated in 14 middle-aged obese women. Cutaneous delayed-type hypersensitivity to five recall antigens was measured before a weight loss of 21 kg and again after weight had been stabilized. Weight loss was associated with a decrease in both number and magnitude of delayed-type hypersensitivity responses. The number of positive skin tests decreased from 3.1 +/- 0.2 to 2.4 +/- 0.3 per subject, and the mean cutaneous induration size decreased by 38%. The decrease in induration size was positively correlated with the decrease in body mass index (r = 0.63), weight (r = 0.59), and fat mass (r = 0.52). These preliminary findings suggest that large weight losses may result in decreased expression of immune function.

Adult↗
PubMed1993

Nucleotide sequence of the 7 K gene of Helenium virus S.

The sequence of 380 nucleotides upstream of the start codon of the open reading frame (ORF) of the coat protein of the carlavirus Helenium virus (HelVS) was determined from cloned cDNA. This portion of the viral RNA contained one complete ORF encoding a protein of 7 K which had homology with similar sized proteins from other members of the carla- and potexvirus groups. Sequence data was also obtained beyond the start codon of the 7 K ORF into what was presumed to be the 12 K protein gene of the previously identified triple gene block of carla- and potexviruses. Significant sequence similarity of 46.3% and 41.6% was evident at the amino acid level with the equivalent regions of the 12 K proteins of potato virus S, Andean strain (PVSA) and potato virus M (PVM), respectively, with 25.4% similarity detected with the equivalent region of potato virus X (PVX).

Amino Acid Sequence↗
PubMed1992

The 3'-nucleotide sequence of an ordinary strain of potato virus S.

The sequence of 1346 nucleotides of the 3'-terminal region of an ordinary strain of potato virus S was determined from cloned cDNA. This portion of the viral RNA contains two major open reading frames (ORFs), encoding the coat protein of M(r)33K and a protein of M(r)11K 3' to the coat protein, both of which showed high homology, 93% and 79%, respectively, with the equivalent proteins of the Andean strain. A major block of amino acids that differ between the ordinary and Andean strains was present in both the coat protein and the 11K. These blocks may be responsible for the substantial differences between the ordinary and Andean strains at the symptom and aphid transmissibility levels.

Amino Acid Sequence↗
PubMed1992

Translation of potato virus S RNA in vitro: evidence of protein processing.

RNA from potato virus S (PVS), a member of the carlavirus group, was translated in vitro in rabbit reticulocyte lysate. Time-course experiments revealed the largest product of Mr 190 kD, decreasing in intensity after 60-min incubations, correlating with the accumulation of a 150-kD peptide. This apparent processing could be blocked by the addition of the amino-acid analogues p-fluorophenylalanine and L-canavanine for phenylalanine and arginine, respectively. L-canavanine also appeared to specifically reduce the quantity of PVS (34 kD) coat protein, concomitant with the synthesis of a 36-kD peptide. Sucrose gradient-fractionated genomic RNA directed the synthesis of predominantly 190-kD peptides that appeared not to be processed in the absence of small molecular weight (subgenomic) RNA products.

Alphavirus↗
PubMed1992

Early-onset repeated dieting reduces food intake and body weight but not adiposity in dietary-obese female rats.

As dieting behavior and attempts at weight loss are becoming increasingly common in adolescent girls, we wished to determine whether early-onset repeated dieting influenced the development of obesity and its metabolic correlates. Female rats were fed a high-fat diet and subjected to six cycles of dieting and regain, beginning in the peripubertal period. Although dieted rats weighted less than nondieted high-fat fed controls at the completion of the sixth cycle, body composition analysis revealed that the two groups were equally obese. Cumulative caloric intake was less in dieted rats, suggesting that the pattern of consumption promoted by dieting helped to establish the obesity. Resting metabolic rate did not differ between the two groups. These data suggest that although early-onset repeated dieting may result in reduced body weight, the eventual level of adiposity may be unknowingly elevated, potentially leading to long-term health risks.

Adipose Tissue↗
PubMed1992

Response of obese binge eaters to treatment by behavior therapy combined with very low calorie diet.

This study examined attrition and weight loss in 235 female obese binge eaters, episodic overeaters, and nonbingers treated by a 26-week program of behavior modification and very low calorie diet. No significant differences were observed among conditions in the number of Ss who completed treatment. Episodic overeaters, however, were more likely than Ss in the other 2 conditions to drop out during the last 7 weeks of treatment, when Ss resumed consumption of a conventional diet. End-of-treatment weight losses for the 3 conditions, which did not differ significantly, averaged 21.5, 19.4, and 21.7 kg, respectively. No significant differences were observed among conditions in weight regain (which averaged 8.8 kg) in the year following treatment, although small sample sizes prevented an adequate evaluation.

Adult↗
PubMed1992

A controlled comparison of three very-low-calorie diets: effects on weight, body composition, and symptoms.

To determine the optimal energy intake of very-low-calorie diets (VLCDs), 76 obese women were randomly assigned, in a double-blind fashion, to one of three liquid-formula diets: 1758 kJ/d (420 kcal/d), 2763 kJ/d (660 kcal/d), or 3349 kJ/d (800 kcal/d). Weight, body composition, symptoms, mood, and acceptability of the diet were assessed throughout the 6-mo study. There were no significant differences in weight losses or changes in body composition among the three dietary conditions at the end of treatment, nor were there significant differences among conditions in acceptability of the diet, symptoms, or mood. These results suggest that there is no clinical advantage to using VLCDs that provide less than 3349 kJ/d (800 kcal/d).

Adult↗
PubMed1992

Relationship of dieting history to resting metabolic rate, body composition, eating behavior, and subsequent weight loss.

This study examined the relationship of dieting history to resting metabolic rate, body composition, and subsequent weight loss in 50 obese women. A preliminary study showed that the women were able to report with satisfactory reliability the number of diets in which they had engaged (mean = 4.9 +/- 0.5), as well as the total weight loss resulting from these diets (mean = 55.9 +/- 6.0 kg). We found no evidence that weight cycling, as measured by either of these variables, was associated at baseline with a reduced resting metabolic rate or an increased percentage of body fat. Nor did we find that weight cycling was associated with smaller weight losses in a prospective trial in which subjects were treated by very-low-calorie diet and behavior therapy. The clinical implications of these findings are discussed, as are the methodological problems encountered in conducting research on this topic.

Adipose Tissue↗
PubMed1992

Clinical correlates of short- and long-term weight loss.

This study was designed to identify psychological, behavioral, and physiological correlates of short- and long-term weight loss. Measures of psychological functioning, body composition, fat cell size and number, and attendance were evaluated in 76 obese women for their relationship to weight loss at the end of treatment and at a 1-y follow-up evaluation. Losing more weight during the first month of treatment and attending a higher percentage of treatment sessions were strongly associated with greater weight loss at the end of treatment and at 1-y follow-up. In addition, patients with the highest initial weights lost the most weight both at the end of treatment and at 1-y follow-up. Easily obtained measures are as successful in predicting weight loss as are more expensive and complicated measures.

Adipose Tissue↗
PubMed1992

Expression of Helenium virus S coat protein in Escherichia coli, in vitro in rabbit reticulocyte lysate and transgenic tobacco.

The coat protein open reading frame (ORF) sequence of Helenium virus S (HelVS) was cloned and expressed in E. coli, rabbit reticulocyte and transgenic tobacco. In E. coli the size of the protein was identical to that obtained for the coat protein from purified virus particles and less than that predicted for the fusion protein. This may be due to ribosome binding at a potential ribosome binding site present on the viral sequence, approximately 45 nucleotides upstream from the initiating methionine of the coat protein ORF. This region of HelVS, equivalent to the 1.5 kb subgenomic RNA, also produced high levels of protein when transcribed and translated in vitro. When introduced into Nicotiana tabacum by leaf disk transformation via Agrobacterium tumefaciens, high levels of stable coat protein were detected which were identical in molecular weight to that of HelVS coat protein and constituted approximately 0.1-0.5% of the total extracted protein.

Animals↗
PubMed1992

A multicenter evaluation of a proprietary weight reduction program for the treatment of marked obesity.

BACKGROUND: Congressional hearings initiated in March 1990 revealed that America's $10 billion a year weight loss industry is subject to minimal regulation by federal agencies. Consumers are forced to rely on advertisements and testimonials when selecting treatment because no proprietary program has provided a prospective assessment of its short- and long-term results of treatment. This report describes such an assessment. METHODS: A total of 517 obese patients (407 women and 110 men) participated in a proprietary program that included 12 weeks of treatment by very-low-calorie diet within a 26-week program of life-style modification. Patients were treated in two cohorts (6 months apart) according to a standardized protocol implemented at 18 hospital-based clinics across the nation. RESULTS: Fifty-six percent of women and 54% of men completed treatment, at which time their weight losses (mean +/- SEM) were 22.0 +/- 0.6 and 32.1 +/- 1.4 kg, respectively. Weight losses of women and men who discontinued treatment averaged 14.3 +/- 0.7 and 20.0 +/- 1.6 kg, respectively. Weight loss was associated with significant improvements in blood pressure and total serum cholesterol levels. A 1-year follow-up evaluation of 74% of patients in the second cohort who completed treatment revealed that they maintained 15.3 +/- 1.2 of their 24.8 +/- 1.0-kg end-of-treatment weight loss; 59% of patients maintained a loss of 10 kg or more. CONCLUSION: We hope that this report will lead to the systematic evaluation of other proprietary weight loss programs and to the publication of findings that will permit consumers to make informed treatment decisions.

Adult↗