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Biomedical subjects

G L Blackburn

Publications and source records attributed to G L Blackburn.

At least 19 recordsLinked to original sources
PubMed1996

n-3 fatty acids decrease colonic epithelial cell proliferation in high-risk bowel mucosa.

The n-3 fatty acids (C20:5, eicosapentaenoic acid; c22:6, docosahexaenoic acid) may be important in the development, growth, and metastasis of colon cancer, a leading cause of death in North America. Patients who have had a bowel neoplasm have a high risk of developing a second neoplasm, and this risk is associated with a high percentage of cells correspond to the S phase of bromodeoxyuridine (BrdUrd) labeling in mucosal epithelial cells. To determine the effect of n-3 fatty acid supplementation on DNA synthesis of rectal mucosa, patients with stage 1 or stage 2 colon carcinoma or adenomatous polyps were randomized to consume either 9 g/d n-3 fatty acid capsules or 9 g/d placebo capsules. Plasma phospholipid fatty acid analysis and proctoscopic mucosal biopsies were performed at baseline, 3, and 6 mon. Colonic crypts were isolated from the mucosa, disassociated with enzymes, and incubated with BrdUrd, and %S phase was measured by flow cytometry. The plasma phospholipid n-6/n-3 ratio was determined by gas chromatography. Supplement compliance was assessed by plasma phospholipid n-6/n-3 ratio. Mean capsule consumption in these two group was 82%. Prior to supplementation, there were no significant differences in the %S phase and the plasma n-6/n-3 ratio between these groups. Patients whose colonic epithelial cells indicated hyperproliferation at baseline showed a strongly positive correlation to the %S phase of BrdUrd uptake and the n-6/n-3 ratio. There was no significant change after n-3 treatment in patients with low baseline. Those in the placebo group showed no significant difference in n-6/n-3 ratio, although there was an increase in the %S phase of BrdUrd uptake at 6 mon. The n-3 group did not have significant side effects, and polyps were not found after completing 12 mon of n-3 fatty acid supplementation. This study suggests that n-3 fatty acid may be a useful chemopreventive agent in some patients as reflected in a plasma biomarker of colon tumor growth and metastasis. A low plasma phospholipid n-6/n-3 fatty acid ratio may serve as a nutritional marker that is associated with colonic epithelial cell hyperproliferation in the n-3-supplemented group as compared with the placebo group. Characteristics of mucosal proliferation at baseline may be a crucial factor for the effect of n-3 fatty acid supplementation.

Cell Division↗
PubMed1996

Monitoring dietary change in a low-fat diet intervention study: advantages of using 24-hour dietary recalls vs food records.

OBJECTIVE: The purpose of the study was to evaluate two methods of dietary assessment for monitoring change in fat intake in a low-fat diet intervention study. DESIGN: The two dietary assessment methods were a 4-day food record (4DFR) and an unannounced 24-hour dietary recall conducted by telephone interview (referred to as a telephone recall [TR]). Subjects were assigned randomly to either a low-fat diet intervention group or a control group that received no counseling about fat intake. Dietary data were collected at baseline, 6 months, and 12 months. SUBJECTS: Two hundred ninety postmenopausal women with localized breast cancer were recruited at seven clinical centers in the United States. STATISTICAL ANALYSIS: Analysis of variance was used to test for significant differences in mean fat and energy intakes. RESULTS: Three sources of error were identified: (a) an instrument effect, suggesting underreporting at baseline of approximately 8% in mean energy intake and 11% in mean fat intake in the TR group compared with the 4DFR group (P = .0001); (b) a repeated measures effect observed for the 4DFR, suggesting underreporting of approximately 7% for energy intake and 14% for fat intake in the control group at 6 and 12 months compared with baseline values (P < .001); and (c) an adherence effect (or compliance bias), suggesting greater compliance to the low-fat intervention diet when subjects were keeping food records than when estimates were based on the unannounced TR. Compared with the TR, the 4DFR overestimated the extent of fat reduction in the low-fat diet intervention group by 41% (P = .08) and 25% (P = .62) at 6 and 12 months, respectively. APPLICATION: Multiple days of unannounced 24-hour recalls may be preferable to multiple-day food records for monitoring dietary change in diet intervention studies.

Aged↗
PubMed1996

Nutrition Societies Presidents' Forum: future challenges and opportunities for nutrition societies in the 21st century.

The Chair introduced "Pasteur's Quadrant" as a potentially useful paradigm for modern science. Developed by Princeton's Donald E Stokes, the quadrant is two-by-two matrix that classifies knowledge as fundamental and/or applied. The Chair also noted the effect of competitive pressures, and the necessity for cooperation among nutrition societies. The Presidents of The American Society for Nutritional Sciences (ASNS), The American Society for Clinical Nutrition (ASCN), The American Society for Parenteral and Enteral Nutrition (ASPEN), and the Chair of the Institute of Food Technologist's (IFT) Nutrition Division presented their views on how societies can prepare to meet their members' upcoming needs. The Director of the Center for Food and Nutrition Policy discussed the future role of nutrition societies and how they might interact with various interest groups. The Forum, which included an opportunity for audience participation, took place soon after the February 1996 release of "Meeting the Challenge: A Research Agenda for America's Health, Safety, and Food." Published by the Executive Office of the President's Office of Science and Technology Policy, the report highlights the importance of nutrition to our nation's health.

Humans↗
PubMed1995

Weight cycling.

Explore the source record for details and available documents.

Humans↗
PubMed1995

Developing strategies for intervention/prevention trials of individuals at risk of hereditary colon cancer.

Environmental causes are thought to be the etiology of most colorectal cancers (sporadic colorectal cancer). However, about 10% of the cases result from one of two well-defined forms of hereditary colorectal cancer: hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis. The development of intervention/prevention strategies for patients with newly diagnosed colon cancer and their families at high risk for hereditary colon cancer was framed in the questions: "Who is the target?" and "How to identify those at high risk"? There is agreement that genetic analysis for hereditary colorectal cancer holds tremendous promise but that it requires the development of highly structured protocols to ensure that genetic testing is a positive experience for patients at high risk. Appropriate strategies to identify high-risk patients would include recruiting minority (ethnic, racial, and socioeconomic) populations into these studies. Implementation of the protocol would begin with primary-care physicians working with cancer prevention centers in a network to achieve informed consent, to obtain bank-blood samples for genotyping, and to provide the social support and genetic counseling necessary to achieve the goal of a positive experience in cancer prevention. Initial studies would be directed at the known hereditary colorectal cancer groups, including familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer.

Adenomatous Polyposis Coli↗
PubMed1994

Does the amount of endurance exercise in combination with weight training and a very-low-energy diet affect resting metabolic rate and body composition?

Effects of large (LA; 400 min/wk) and moderate (MA; 200 min/wk) amounts of endurance exercise in combination with weight training (3 d/wk) were compared with the effects of no exercise (C) in 23 obese females after a 12-wk, 3360-kJ/d very-low-energy diet (VLED). The LA group lost 6.5 kg more weight, mainly as fat (6.4 kg), than the C group (P < 0.05). No measurable differences were found among groups for decreases in resting metabolic rate (-729 to -1233 kJ/d; NS) or fat-free mass (-2.9 to -3.9 kg; NS). No improvements in aerobic capacity were achieved with the addition of exercise to a VLED (-0.079 to -0.037 L/min; NS). Strength indexes were improved (+16 to +5 kg; P < 0.05) or maintained with exercise (-3 kg; NS) whereas a loss (-9.3 kg; P < 0.05) or maintenance (+4.5 kg; NS) was found for VLED alone. Large amounts of endurance exercise in combination with weight training added to a VLED appear to improve weight and fat loss compared with a VLED alone.

Adipose Tissue↗
PubMed1993

Comparison of medically supervised and unsupervised approaches to weight loss and control.

The rising incidence of obesity in the United States has given physicians an increased role in its treatment. Although unsupervised programs can produce significant weight losses, the lack of medical supervision increases the potential for health problems. As with other lifestyle changes (for example, smoking cessation and blood pressure control), even minimal physician involvement may enhance outcome. In published clinical trials, the absence of contact with health professionals among control group participants may account in part for their poor success at weight loss or for their weight gain. Smaller trials examining the value of physician advice and encouragement among dieting patients have shown promising results. Physicians should monitor the health of obese and overweight patients during and after weight loss as is appropriate for the patient, depending on caloric levels, rate of weight loss, weight-loss goals, and intercurrent health events. Medical supervision is necessary for patients on very-low-calorie diets, for severely obese patients (body mass index > 35), and for patients with other health problems.

Clinical Trials as Topic↗
PubMed1993

Thermogenesis secondary to transdermal water loss causes growth retardation in essential fatty acid-deficient rats.

Manifestations of essential fatty acid (EFA) deficiency in rats include growth retardation and increased transdermal water loss. The extra metabolic energy requirement could be caused by greater evaporative water loss from the skin surface. To test this hypothesis, 38 weanling rats were randomly assigned to one of two environments, control (CE) at 20 degrees C and 40% humidity or warm/humid (WHE) at 30 degrees C and 90% humidity. Half of the 20 CE rats were fed an EFA-adequate diet and the other 10 an EFA-deficient diet; the 18 WHE rats were also equally partitioned to the two diets. CE and WHE animals were independently group-fed to maintain equal energy intakes within each environment. Weight gain at 90 days was lower for CE EFA-deficient rats than for CE EFA-adequate rats (P < .0001). Growth rates in the WHE to 140 days did not differ. Mean weights at 90 days were as follows: CE EFA-adequate, 196 g; CE EFA-deficient, 148 g; WHE EFA-adequate, 148 g; WHE EFA-deficient, 135 g. In both CE and WHE animals, the triene/tetraene ratio of both serum and liver phospholipids (PL) was 100-fold greater for EFA-deficient versus EFA-adequate diets. PL fatty acids of liver in CE and WHE EFA-deficient rats contained 2.09 and 1.92 micrograms of 20:3 omega 9 per micrograms phosphorus (Pi), respectively, compared with 0.03 and 0.02 microgram 20:3 omega 9/micrograms Pi in CE and WHE EFA-adequate rats. These results indicate equivalent degrees of EFA deficiency in the two environments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Rapid incorporation of fish or olive oil fatty acids into rat hepatic sinusoidal cell phospholipids after continuous enteral feeding during endotoxemia.

Therapeutic modalities that downregulate macrophage and endothelial production of eicosanoid mediators by displacing membrane arachidonic acid (20:4 omega 6) may benefit patients at increased risk of septic complications. The objective of this study in rats was to assess the incorporation of fish or olive oil fatty acids into hepatic Kupffer and endothelial (K&E) cell phospholipids after 4 d of continuous enteral feeding during endotoxemia. Either endotoxin (ETX) (0.5-1 mg-1.day-1) or vehicle was infused intravenously during the last 72 h. Dietary fish and olive oil fatty acids were rapidly incorporated into both K&E and plasma phospholipids irrespective of ETX cotreatment. Rats infused with the fish oil-enriched diet had a significantly lower relative percent of both K&E linoleic acid (18:2 omega 6) and 20:4 omega 6, whereas rats infused with the olive oil-enriched diet only had a lower relative percent of 18:2 omega 6 compared with control rats receiving corn oil. Provision of specific dietary lipids by continuous enteral infusion may prove efficacious for the rapid modulation of hepatic sinusoidal cell membrane fatty acids under either normal or endotoxemic conditions.

Animals↗
PubMed1993

Adherence to a dietary fat intake reduction program in postmenopausal women receiving therapy for early breast cancer. The Women's Intervention Nutrition Study.

PURPOSE: To evaluate the feasibility of integrating a program based on dietary fat intake reduction into adjuvant treatment strategies for postmenopausal women receiving therapy for early breast cancer. PATIENTS AND METHODS: Two hundred ninety postmenopausal women with localized (stage I to IIIa) breast cancer receiving conventional systemic therapy provided informed consent and were randomized in a multicenter trial to either a dietary intervention group receiving a program of individualized instruction for reducing total fat intake or a dietary control group with minimal dietary counseling. RESULTS: Significantly reduced (P < .001) fat intake (in terms of percent calories derived from fat) was observed in the intervention group versus the control group at 3 months (20.3% +/- 2.4% v 31.5% +/- 2.6%, mean +/- SD, respectively) and maintained throughout 24 months of observation. The 50% reduction in daily fat-gram intake (from 66 +/- 23 to 33 +/- 14 g, P < .001) seen at 6 months was associated with reduced saturated fat, monounsaturated fat, polyunsaturated fat, and linoleic acid (P < .001). Significantly lower body weight was also seen in intervention compared with control patients at all observation periods, resulting in a 3.3-kg weight difference 18 months after randomization (P < .001). CONCLUSION: Substantial and sustained dietary fat reduction with associated weight change can be achieved at relatively low cost within the context of conventional multimodality clinical management of postmenopausal women with localized breast cancer. This result supports the feasibility of conducting a full-scale evaluation of the influence of dietary fat intake reduction on the clinical outcome of breast cancer patients.

Aged↗