High-protein Weight-loss Diets: Are They Safe and Do They Work? A Review of the Experimental and Epidemiologic Data

Recommendations for increased consumption of protein are among the most common approaches of popular or fad diets. This review summarizes the effects of dietary protein on satiety, energy intake, thermogenesis, and weight loss, as well as its effect on a variety of health outcomes in adults. In short-term studies, dietary protein modulates energy intake via the sensation of satiety and increases total energy expenditure by increasing the thermic effect of feeding. Whereas these effects did not contribute to weight and fat loss in those studies in which energy intake was fixed, one ad libitum study does suggest that a high-protein diet results in a greater decrease in energy intake, and therefore greater weight and fat loss. In terms of safety, there is little long-term information on the health effects of high-protein diets. From the available data, however, it is evident that the consumption of protein greater than two to three times the U.S. Recommended Daily Allowance contributes to urinary calcium loss and may, in the long term, predispose to bone loss. Caution with these diets is recommended in those individuals who may be predisposed to nephrolithiasis or kidney disease, and particularly in those with diabetes mellitus.     

Tissue expression of the tumour associated antigen CA242 in benign and malignant pancreatic lesions. A comparison with CA 50 and CA 19-9

The expression of a novel tumour associated antigen CA 242, defined by the monoclonal antibody C 242, was studied by immunoperoxidase staining in formalin-fixed, paraffin-embedded tissue sections from normal pancreata, pancreata with pancreatitis and benign and malignant pancreatic neoplasms. The antigenic determinant of the C 242 antibody is a sialylated carbohydrate structure, related but chemically different from tumour marker antigens CA 19-9 and CA 50. Thirty-eight of 41 (93%) well to moderately differentiated ductal adenocarcinomas of the pancreas and all cystadenocarcinomas were positive for CA 242. The staining was most intense in the apical border of the cells, and in the intraluminal mucus. Only two out of seven poorly differentiated adenocarcinomas stained, and the number of positive cells was smaller than in well differentiated carcinomas. Only occasional cells were stained in one out of five anaplastic carcinomas. Part of large ducts were positive in 91% (21/23) specimens of chronic pancreatitis. In acute pancreatitis small terminal ducts, centro-acinar cells and some large ducts stained for CA 242. In normal pancreas only a few small terminal ducts were CA 242 positive. Carcinomas always stained more strongly for CA 242 than normal pancreatic tissue adjacent to the carcinoma. The results of CA 242 are compared with those of tumour marker antigens CA 50 and CA 19-9. Serum CA 242 levels were determined in 23 of the patients with pancreatic cancer using a fluoroimmunoassay. Fifteen (65%) patients had an elevated value. There was no clear-cut correlation between the serum levels and the immunohistochemical expression of the CA 242 antigen. The expression of CA 242 in pancreatic tissue resembles that of CA 50 and is similar to CA 19-9. The antigen is expressed in serum of many patients with pancreatic cancer and, therefore, is a potential candidate for a serum tumour marker.     

Prognostic value of various staging and grading systems in proximal colon cancer.

OBJECTIVE: To compare the ability of various methods of staging and grading to predict survival in proximal colon cancer. DESIGN: Retrospective study. SETTING: University hospital, Finland. SUBJECTS: 153 patients with primary proximal colon cancer. MAIN OUTCOME MEASURES: Staging by four classification systems, grading by two grading systems, and survival analysis based on Kaplan-Meier survival curves. RESULTS: In all staging systems the survival curves of different stages differed significantly from each other. The modified Dukes' classification was still the best predictor of survival. Grade of tumours had no significant effect on long term survival, but short term survival was affected adversely by the presence of anaplastic tissue. Tumours with no mucin had a worse prognosis than those that produced mucin. All staging methods were superior to either of the histological grading systems tested as prognosticators. Tumour depth correlated with the operator's clinical impression of radicality of operation, and also predicted survival. CONCLUSION: The clinicopathological modified Dukes' staging system was the most powerful prognosticator in proximal colonic cancer and its use in clinical practice should continue. Even a small amount of anaplastic tissue (> or = 5%) had an adverse effect on short term survival.     

The prevalence of airways hyperresponsiveness in members of an exercise training facility.

Athletes have a high prevalence (11-50%) of exercise-induced asthma, which may be caused by the hyperventilation accompanying repetitive bouts of strenuous exercise. We hypothesized that recreational exercisers would display a similar trend. Eucapnic voluntary hyperventilation (EVH) bronchoprovocation (breathing 21% O2, 5% CO2, and 74% N2 at 60% of MVV for 5 minutes) was performed to determine the prevalence of airways hyperresponsiveness (AHR) in adults (n=212, 146 males, mean +/- standard deviation, age 32 +/- 10 years) who exercised regularly (10 +/- 10 years, 31 +/- 28% of their lives): none had a previous diagnosis of asthma. AHR was defined by at least a 10%, 20%, or 25% decline in FEV1, FEF(25-75), or PEFR, respectively, by spirometry at 1, 5, 10, and 15 minutes post-EVH. Forty-one of 212 (19%) tested positive for AHR: 20 of 41 (49%) were positive by FEV1, 28 of 41 (68%) by FEF(25-75), and 27 of 41 (66%) by PEFR. Comparing responders with nonresponders: pre-EVH lung function was equivalent, except for FEV1, which was reduced (p<0.05) in responders (96 +/- 13 vs. 102 +/- 12% predicted). Mean maximal negative deflections for responders were: for FEV1, -17 +/- 7%; FEF(25-75), -31 +/- 10%; PEFR, -38 +/- 11%. Ranges of decline for responders were: FEV1, -10 to -33%; FEF(25-75), -20 to -59%; PEFR, -25- to -70%. We conclude that in these regular exercisers, the prevalence of AHR is high and comparable with some athletic populations.     

Sensitivity of a ribosomal RNA gene probe for identification of life stages of Anopheles arabiensis and An. gambiae (Diptera: Culicidae) using three storage methods.

Individual larvae, pupae, female adults, and adult body parts of Anopheles arabiensis Patton and An. gambiae Giles were stored for 1 mo either in isopropanol at room temperature, over a desiccant at room temperature, or at -70 degrees C. DNA was extracted, digested with EcoR1 restriction enzyme, subjected to electrophoresis in agarose gel, transferred to filters, then hybridized to a 32P-labeled rDNA probe. There was no difference among storage treatments in the proportion of correctly identified samples. First instars were not identifiable. Pupae and female adults were more likely to be identified than earlier life history stages. Nonetheless, the probe identified greater than 75% of second instars, 94% of third instars, and 74% of fourth instars. There were no differences between the species in the proportion of identifiable samples for any life history stage.     

Unmyelinated cutaneous afferent neurons activate two types of excitatory amino acid receptor in the spinal cord of Xenopus laevis embryos

The trunk and tail skin of Xenopus laevis embryos near the time of hatching is innervated by the mechanoreceptive free nerve endings of Rohon-Beard neurons, a homogeneous class of cutaneous primary afferent fibers. Rohon-Beard neurons have cell bodies and axons in the dorsal spinal cord, where they monosynaptically excite a population of dorsolaterally situated interneurons (Clarke and Roberts, 1984). EPSPs can be recorded in these dorsolateral interneurons following electrical stimulation of the unmyelinated neurites of Rohon-Beard neurons in the skin. The EPSPs are dual component, consisting of separate fast and slow potentials that are usually evoked synchronously and that closely resemble those described previously in Xenopus and lamprey motoneurons (Dale and Roberts, 1985; Dale and Grillner, 1986). The excitation of dorsolateral interneurons by Rohon-Beard neurons is reduced by the bath application of excitatory amino acid antagonists. Kynurenic acid suppresses both the fast and slow components of the EPSPs, while both (+/-)-2-amino-5-phosphonovaleric acid (APV) and 1 mM magnesium reduce the slow component but have little or no effect on the peak amplitude of the EPSPs. These data suggest that Rohon-Beard neurons release an excitatory amino acid neurotransmitter, which acts simultaneously at both N-methyl-D-aspartate (NMDA) and non-NMDA receptor types. This is the first direct demonstration of dual-component excitatory amino acid-mediated synaptic transmission from cutaneous primary afferent neurons in the vertebrate spinal cord. The bath application of the agonists NMDA, kainate, or quisqualate in salines containing 1 microM TTX depolarized the interneurons and reduced their input resistance, which suggests that the interneurons possess all 3 types of excitatory amino acid receptor. Kynurenic acid strongly inhibits responses to NMDA and kainate, but is relatively less effective against the larger responses of quisqualate in this system.