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Biomedical subjects

R L Atkinson

Publications and source records attributed to R L Atkinson.

At least 55 records · Page 3Linked to original sources
PubMed1995

Dietary fat and adiposity: a dose-response relationship in adult male rats fed isocalorically.

This study examined the effects of increasing levels of dietary fat fed isocalorically on body weight, body composition, and adipose distribution. Adult male rats were weight matched into four groups. One group that was fed a low-fat diet (12%) served as reference controls. The other three groups were fed diets of 24, 36, or 48% fat in amounts to equal the energy intake of the control group. After 6 wk, body weights of the four groups were not significantly different. Intrascapular brown fat did not differ between groups. Total body fat and adipose depot weights, however, increased in proportion to the level of fat in the diet. Total body fat and retroperitoneal and mesenteric depot weights of the 48% fat group were greater than controls (P < 0.05). Mesenteric fat in this group was also significantly increased over all other groups (P < 0.05). These results show that high-fat diets fed to adult animals cause increased body fat in the absence of significant changes in body weight and that mesenteric fat is increased disproportionately.

Adipose Tissue↗
PubMed1995

Increased adipose tissue expression of tumor necrosis factor-alpha in human obesity and insulin resistance.

Obesity is frequently associated with insulin resistance and abnormal glucose homeostasis. Recent studies in animal models have indicated that TNF-alpha plays an important role in mediating the insulin resistance of obesity through its overexpression in fat tissue. However, the mechanisms linking obesity to insulin resistance and diabetes in humans remain largely unknown. In this study we examined the expression pattern of TNF-alpha mRNA in adipose tissues from 18 control and 19 obese premenopausal women by Northern blot analysis. TNF-alpha protein concentrations in plasma and in conditioned medium of explanted adipose tissue were measured by ELISA. Furthermore, the effects of weight reduction by dietary treatment of obesity on the adipose expression of TNF-alpha mRNA were also analyzed in nine premenopausal obese women, before and after a controlled weight-reduction program. These studies demonstrated that obese individuals express 2.5-fold more TNF-alpha mRNA in fat tissue relative to the lean controls (P < 0.001). Similar increases were also observed in adipose production of TNF-alpha protein but circulating TNF-alpha levels were extremely low or undetectable. A strong positive correlation was observed between TNF-alpha mRNA expression levels in fat tissue and the level of hyperinsulinemia (P < 0.001), an indirect measure of insulin resistance. Finally, body weight reduction in obese subjects which resulted in improved insulin sensitivity was also associated with a decrease in TNF-alpha mRNA expression (45%, P < 0.001) in fat tissue. These results suggest a role for the abnormal regulation of this cytokine in the pathogenesis of obesity-related insulin resistance.

Adipose Tissue↗
PubMed1995

Intravascular ultrasound imaging of coarctation of the aorta: animal and human studies.

Although the use of balloon dilation for treatment of native and recurrent coarctation of the aorta (coA) has become widespread, the optimal balloon size and postdilation vessel wall changes remain undetermined. Intravascular ultrasound (IVUS) imaging has emerged as a an important adjunct in the treatment and follow-up of patients with coronary artery and peripheral vascular lesions, and has been used for evaluation in a limited number of patients with CoA. We used a combination of balloon dilation/ultrasound imaging catheter in animals with experimentally-induced CoA. We used a combination balloon dilation/ultrasound imaging catheter in animals with experimentally-induced CoA . This technique provided real-time data regarding aortic wall morphology and luminal diameter during balloon angioplasty of the CoA. In humans, we used IVUS to study CoA before and after both transcatheter and surgical therapy. IVUS was more sensitive than angiography in the detection of intimal tears post-balloon dilation and in the evaluation of vessel wall changes and remodelling observed at follow-up after relief of CoA. IVUS may provide valuable information regarding vascular wall changes that predict aneurysm format ion, restenosis, or a successful result after balloon dilation.

Animals↗
PubMed1994

Higher calorie content preserves myocardial electrical activity during very-low-calorie dieting.

We investigated the effect of calorie and protein content of very-low-calorie diets for weight loss upon myocardial electrical activity. Patients were followed on very low calorie diets for up to 20 weeks. Study No. 1 had 16 obese patients (4 men and 12 women). Study No. 2 had 113 obese women. Both study groups were consecutive samples with patients who had BMI > 30. In Study No. 1 patients were given 400 kcal/d with 50 gm of protein and 45 gm of carbohydrates over 12 weeks. In Study No. 2 patients were given either Metabolic Nutrition Program (MNP) which contained 600 kcal/d with 70 gm protein and 70 gm carbohydrates, or Optifast-70 which contained 420 kcal/d with 70 gm protein and 32 gm carbohydrates, for up to 20 weeks. Electrocardiograms were obtained at baseline and during the third month in Study No. 1, and monthly in Study No. 2. The sum of the voltage in leads I+II+III and the length of the QT interval were derived from the electrocardiograms. In Study No. 1 the QRS voltage decreased from 2.77 +/- .18 mv to 2.45 +/- .17 mv (p < .02). Patients lost 18.1 kg +/- 4 kg and the QT interval remained unchanged. In Study No. 2 at 20 weeks the QRS voltage decreased on Optifast-70 (p < .001) in comparison to MNP, in which the QRS voltage remained unchanged. Patients on Optifast-70 lost 17.5 +/- .53 kg, patients on MNP lost 18.5 +/- .66 kg and the QT interval in both groups remained unchanged. The formula diets tested of less than 600 kcal/d were associated with a decrease in electrocardiographic voltage.

Adult↗
PubMed1994

Maxillofacial biomodelling.

The authors report the clinical applications of biomodelling with the stereolithography apparatus, a computer-controlled manufacturing technique that builds anatomically accurate skeletal models from sectional radiological data. Reference to several individual cases demonstrates how pre-operative 3-D modelling can refine the accuracy of diagnostic information, facilitate preoperative planning and surgical technique, and reduce operating time.

Acrylic Resins↗
PubMed1994

Report on the NIH Workshop on Pharmacologic Treatment of Obesity.

A National Institutes of Health workshop on pharmacologic treatment of obesity concluded that pharmacologic agents may be effective in reducing body weight over an extended period of time. Drugs should be used as only one component of a comprehensive weight-reduction program, and additional research is needed on the long-term efficacy and safety of drugs for obesity, and especially for combinations of drugs. Improvement in comorbidities and risk factors of obesity should be used along with weight reduction as an outcome measure in clinical trials. Industry, professional societies, and governmental agencies should work together to explore the potential for drugs for obesity and to reassess the regulatory and administrative controls on the use of currently available drugs for obesity and on the approval process for future drugs.

Animals↗
PubMed1994

Treatment of trigeminal neuralgia by posterior fossa microvascular decompression.

A series of 109 cases of microvascular decompression for intractable trigeminal neuralgia was reviewed. Operations were performed by a single surgeon and cases were reviewed independently by the one author. The failure rate in this study was 17.6%. A further 6.5% of cases endured brief recurrences not requiring treatment. Two-thirds of significant recurrences occurred within the initial 12 months. Long-term complications were experienced in 7.4% of cases. There was one postoperative mortality occurring in a patient with a large fibroblastic meningioma invading the brain stem. The classic Jannetta approach was modified following the first 32 cases allowing the cerebellum to be depressed inferiorly with a subsequent decline in the rate of loss of hearing from 12.5 to 3.7%. In over 70% of cases an aberrant superior cerebellar artery was found compressing the fifth cranial nerve. Patients had dental work performed in an attempt to control the pain prior to operation in 44% of cases.

Adult↗
PubMed1994

Insulin sensitivity of adipocytes from inbred mouse strains resistant or sensitive to diet-induced obesity.

We evaluated insulin sensitivity in epididymal adipocytes from two mouse strains shown to be either sensitive (AKR/J, n = 14) or resistant (SWR/J, n = 12) to the development of obesity when fed a high-fat diet. Half of each strain was fed a chow (CH) diet (12% fat), and half received a sweetened condensed milk (CM) diet (33% fat). After 1 wk, epididymal adipose depots were removed and digested with collagenase, and glucose transport was measured with labeled 2-deoxyglucose. Plasma glucose and insulin were slightly higher in AKR/J than SWR/J mice (glucose: 139.7 vs. 118.8 mg/dl, P < 0.06; insulin: 3.45 vs. 2.99 ng/ml, P < 0.04). One week of high-fat feeding increased adipose depot mass and carcass lipid in both strains to approximately the same extent. Adipocytes from AKR/J mice had greater insulin-stimulated glucose transport compared with SWR/J mice at both submaximal and maximal insulin levels (P < 0.0001). Short-term feeding of the high-fat diet increased AKR/J adipocyte insulin sensitivity but decreased the sensitivity of SWR/J adipocytes to insulin. The differences in adipocyte insulin sensitivity between strains were not explained by differences in adipocyte cell size. Access to the high-fat CM diet for 12 wk increased total dissected adipose depot size by 209% in the AKR/J mice and 82% in the SWR/J mice. These data clearly demonstrate that the two strains differ in adipocyte insulin sensitivity as well as sensitivity to dietary obesity. Increased adipocyte insulin sensitivity could contribute to a predisposition to increase adipose tissue lipid stores with diets high in fat content.

Adipocytes↗
PubMed1994

Evaluating success of weight loss programs, with an application to fluoxetine weight reduction clinical trial data.

We modified criteria for judging successful obesity treatment proposed by Atkinson to provide objective criteria for successful benefit from weight reduction programs with respect to data from a clinical trial. The criteria include assessments of changes in both weight-related factors (e.g. excess weight, excess body fat) and obesity-related risk factors (e.g. hypertension, hyperglycemia, hyperlipemia). To demonstrate the use of this methodology, we applied the criteria in an analysis of eight randomized, double-blind controlled trials comparing fluoxetine (n = 522) with placebo (n = 504) for weight loss. The results suggest these criteria can be useful for evaluating a treatment program or for comparing treatments from clinical trials.

Adolescent↗
PubMed1993

Proposed standards for judging the success of the treatment of obesity.

The purpose of this report is to propose standards for the successful treatment of obesity. This process is somewhat arbitrary because obesity is a multifactorial disease and because standards need revision as diagnostic and treatment techniques improve. Weight loss, the classic standard of success, does not account for individual variability. Reduction in other measures of body size, such as body mass index, percentage of excess weight, and body fat, may be preferable. Improvement in known complications of obesity (diabetes mellitus, hypertension, hyperlipoproteinemia, sleep apnea, and psychosocial problems) are equally valid measures of success. Because obesity is a chronic disease, maintenance of weight loss is included as a standard of success. Response to obesity treatment varies, and thus criteria to define minimal, intermediate, and full success for each variable are necessary.

Adipose Tissue↗
PubMed1993

Dietary fat affects weight loss and adiposity during energy restriction in rats.

This study examined the effect of dietary fat during food restriction on weight loss, body composition, and adipose tissue lipoprotein lipase activity (ATLPL). Rats previously fed a high-fat diet were divided into four groups. One group served as baseline controls. The other three groups were fed diets of 12%, 28%, or 45% fat, restricted (R) in amounts to equal 75% of their previous ad libitum energy intake. After 10 wk, body weight loss and reduction of adiposity were significantly less in the 45%-R group compared with the 12%-R group (weight P < 0.05; adiposity P < 0.01). Rats fed restricted amounts of the high-fat diet (45%-R group) retained adiposity equivalent to baseline control rats. ATLPL activity was increased in the 45%-R group compared with baseline control rats. Further studies are needed in humans, but these results suggest that body composition will not be normalized with reduction of energy intake unless dietary fat is also reduced.

Adipose Tissue↗
PubMed1993

Obesity. Workshop III. AHA Prevention Conference III. Behavior change and compliance: keys to improving cardiovascular health.

The workshop provided the opportunity to discuss issues and develop and integrate ideas. The following recommendations for public policies, education programs, and high-priority research initiatives were developed: Recommendations for Public Policies: Focus on prevention by requiring school programs to emphasize appropriate diet, physical activity, and general health guidance to promote cardiovascular health and prevent disease through federal funding. Provide better access to exercise (city planning, work-site interventions). Influence food availability and accessibility. Influence reimbursement policies for effective early intervention and prevention strategies for obesity. Reevaluate policies for use of drugs in the treatment of obesity. Recommendations for Education Programs: Sponsor scientific workshop to: Define the most appropriate weight standards for prevention and treatment. Identify who should lose weight and why, when, and how. Promote the fact that obesity is an important health risk factor, even at moderate levels, and that excess visceral fat is particularly hazardous. Target health care professionals, consumers, and the media for education about: Nature of obesity as a heterogeneous syndrome. Recommendations for diet, exercise, behavioral interventions, drugs, and surgery. Recognition of special needs of populations of different ethnicity, gender, age, etc. State-of-the-art treatment and treatment programs. High-Priority Research Initiatives: Build better bridges between basic research and treatment/prevention practices. Acknowledge that obesity is a heterogeneous syndrome that may best be characterized as different obesities. Research on defining subtypes. Implications for etiology and treatment. Better characterization of genotypes and phenotypes. Study the effects of weight loss, weight gain,and weight cycling on medical and psychosocial outcomes and mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Combination of very-low-calorie diet and behavior modification in the treatment of obesity.

Very-low-calorie diets (VLCDs) cause rapid weight loss. However, weight regain is rapid upon discontinuing the VLCD unless lifestyle is altered. The addition of a behavioral-modification (BMOD) program improves the long-term outcome. The major components of a BMOD program to alter lifestyle are education about nutrition and eating habits with alteration of amount and patterns of eating, institution of an aerobic activity program designed to increase energy expenditure, training in self-awareness and assertiveness, and training in coping techniques for long-term alteration of lifestyle. By retrospective chart review, we evaluated two VLCD programs at the same institution. One program gave 12 wk of BMOD before a 12-wk course of VLCD (Program 1), then scheduled individual visits regularly thereafter. The other program used simultaneous VLCD and BMOD in a 26-wk treatment course (Program 2), consisting of 2 wk of stabilization on 5020 kJ/d (1200 kcal/d), 12 wk of VLCD, and 12 wk of transition to a low-calorie solid food diet. Follow-up was obtained at 1 y in both groups. Maximum weight loss was similar, but subjects in Program 2 regained about one-third of the lost weight versus approximately 10% in Program 2. A third program of preceding BMOD followed by a low-calorie diet (Program 3) gave similar weight maintenance at 1 y as Program 1. Prospective studies are needed to determine if BMOD simultaneously with or preceding VLCD promotes better long-term weight maintenance. These data confirm the benefits of long-term follow-up for maintaining weight loss.

Adult↗
PubMed1992

Dietary obesity in nine inbred mouse strains.

The effect of 7 wk consumption of a diet containing 32.6% of kilocalories as fat [condensed milk (CM) diet] on body composition and energy intake was evaluated in nine strains of inbred mice (AKR/J, C57L/J, A/J, C3H/HeJ, DBA/2J, C57BL/6J, SJL/J, I/STN, and SWR/J). Control animals were fed a high-carbohydrate diet containing 11.6% of energy as fat (Purina Rodent Chow diet). Relative to Chow diet controls, the CM diet significantly increased carcass lipid content in six strains (AKR/J, C57L/J, A/J, C3H/HeJ, DBA/2J, and C57BL/6J), but had no or a marginal effect on adiposity in three strains of mice (SJL/J, I/STN, and SWR/J). The obesity produced by the CM diet in six strains was not due to hyperphagia. Only one of six (AKR/J) of the strains that increased adiposity on the CM diet consumed more energy than controls during the 7 wk of the experiment. The identification of inbred mouse strains that are sensitive to dietary obesity, vs. others that are resistant, provides a useful tool to pursue the metabolic and genetic basis of this trait in the mouse.

Animal Feed↗
PubMed1992

Adrenocorticotropic hormone-secreting pituitary tumor associated with pregnancy: case report.

A patient with an adrenocorticotropic hormone-secreting pituitary adenoma diagnosed at the same time as pregnancy is reported. Treatment was by transsphenoidal tumor resection, which has only been described once previously in such a case. Treatment rationale is discussed, and transsphenoidal tumor resection is recommended as the therapy of choice.

Adrenocorticotropic Hormone↗