The effects of biosynthetic methionyl human growth hormone (met-hGH) on body composition and endogenous secretion of insulin-like growth factor I (IGF-I) were studied in obese women ranging between 138 and 226% of ideal body weight. Following double-blind procedures, 12 subjects were assigned at random to either treatment with met-hGH (n = 6, 0.08 mg/kg desirable body weight) or placebo (n = 6, bacteriostatic water diluent). Treatments were delivered intramuscularly three times per week for a period of 27–28 days. Subjects were instructed to follow a weight-maintaining diet and their pre- and posttreatment kilocaloric intake was monitored for verification. The baseline peak serum GH response to L-dopa/arginine stimulation for the study population as a whole, was in the hyposecretory range (9.6 ± 1.9 ng/ml), accompanied by a low level of circulating IGF-I (0.56 ± 0.09 U/ml). Hydrodensitometry revealed that the met-hGH-treated subjects had a significant reduction in body fat, while an observed mean increase in fat-free mass (FFM) approached significance. The percent change in body fat was unrelated to pretreatment levels of body fat, total body weight, or initial endogenous GH status. Changes in circulating IGF-I were similar to those for FFM, with increases approaching significance. There were no significant changes in body composition or IGF-I in the placebo-treated subjects. No significant differences were observed in the self-reported dietary intake of kilocalories during the experimental period between the two groups. We conclude that exogenous GH reduces body fat in obese women in the apparent absence of significant kilocaloric restriction. The effect appears to be unrelated to endogenous GH secretion or body composition.
Tropospheric lifetimes and ozone-depletion potentials (ODPs) are estimated for all 53 possible one-and twocarbon hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs). The relationships among C-H bond strength, activation energy for removal of H by OH, tropospheric lifetime, and ODP are examined. Algorithms are developed that are easy to apply and accurate enough for initial screening purposes. On the basis of extant theory and our analysis, the controlling variables for determining HCFC tropospheric lifetimes include number of hydrogen atoms, molecular weight, number of carbons, number of chlorine atoms a and ß to hydrogen, and number of fluorine atoms ß to hydrogen. The formula presented predicts lifetimes for molecules with atmospheric lifetimes below 30 years with a root mean square (rms) error of a factor of 2.4. An algorithm is also presented to calculate ODP based on tropospheric lifetime; the overall rms error for calculating ODP from the structure is a factor of 2.5. In many cases, ODPs of chlorine-containing compounds are predicted to be below 0.001. These estimates also aid in making tentative choices among alternative HFCs and HCFCs based on environmental considerations.
Halon fire extinguishing agents are used throughout the world to protect valuable electronics, oil and gas production operations, military systems, as well as a number of other critical facilities. Unfortunately, halons deplete stratospheric ozone, causing destruction at 3 to 16 times the rate of CFC-11 (a common refrigerant). As a consequence, the production of halons was prohibited on December 31, 1993 by an international treaty, the Montreal Protocol. This ban on halon production resulted in a search for replacement chemicals for firefighting and explosion protection applications. Replacements must satisfy the following three criteria in order to be successful candidates: effectiveness, cleanliness, and environmental acceptability (low ozone depletion and global warming potentials). It is also necessary that a replacement agent be as non-toxic as possible relative to possible exposures and generate minimal toxic and corrosive decomposition products during the suppression event. Herein, the toxicological aspects of halon replacements are discussed. The specific toxic endpoints of concern for halocarbon candidates, as well as the kinds of toxicity testing required for halon replacements, will be addressed. The paper will also provide a summary of the toxicological properties for the most promising near term halon replacements. Associated decomposition product formation will be briefly discussed. Toxicity ConsiderationsConsiderations of the short-and long-term health hazards of exposure are of key importance when deciding which compounds hold potential for use in explosion and fire protection. Human and animal research indicates several principal adverse health effects caused by halocarbons. They can stimulate or suppress the central nervous system (CNS) to produce symptoms ranging from lethargy and unconsciousness to convulsions and tremors (7). Halocarbons can cause cardiac arrhythmias and can 1
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