Environmental factors in the etiology of rhabdomyosarcoma in childhood

In a case-control study of childhood rhabdomyosarcoma (RMS), families of 33 cases and 99 controls were interviewed. A relative risk (RR) of 3.9 was found associated with fathers' (but not mothers') cigarette smoking (P = 0.003). Cases had had fewer immunizations than controls, particularly smallpox vaccination (RR = 0.2; P = 0.001), and conversely had more preventable infections. An RR of 3.2 (P = 0.03) was found associated with exposure to chemicals and and RR of 3.7 (P = 0.004) was found associated with diets that included organ meats. Mothers of cases were more likely to be over age 30 years at subject's birth, to have used antibiotics preceding or during pregnancy, and to have had an overdue and/or assisted delivery. Other findings suggest that low socioeconomic status is associated with an increased risk of RMS. These aggregate findings imply that environmental factors may play an important role in the etiology of childhood RMS.

Chronic exposure to inhaled anesthetics increases cholesterol content in Acholeplasma laidlawii

Acholeplasma laidlawii cells were grown in cholesterol-enriched medium and exposed continuously to either air (control), 4.0 vol.% halothane in air at 1 atm pressure (4% atm halothane), or 80% cyclopropane in oxygen for 24 h at 37 degrees C. Cells grown in the presence of 4% atm halothane or 80% cyclopropane had approximately twice as much membrane cholesterol content/mg protein as the control cells. Cells grown in an anesthetic environment also tended to have a higher membrane cholesterol/phospholipid molar ratio compared to control cells. Membranes isolated from halothane-exposed cells grown in a cholesterol-enriched medium were more ordered at 37 degrees C (measurements were made with no anesthetic present) than membranes from control cells grown in an identically enriched medium. This difference in membrane physical state between control and anesthetic-exposed cells decreased as the temperature decreased, and disappeared at approx. 23 degrees C. Continuous exposure of A. laidlawii to 4% atm halothane or 80% cyclopropane for 24 h did not markedly affect membrane fatty acid composition, either in cells grown on an unsupplemented medium or in cells grown in a medium enriched in myristic, palmitic or stearic acids. These results further support the hypothesis that an increased membrane cholesterol content may play a role in the tolerance or dependence that develops after chronic exposure to anesthetic agents.

Effects of prostaglandins and thromboxane A2 on the coronary circulation of adult dogs and puppies

Intracoronary injections of prostaglandin endoperoxide (PGH2), prostacyclin (PGI2) and thromboxane A2 (TXA2) were given to adult dogs and puppies three months or younger. Both PGH2 and PGI2 caused dose-related coronary vasodilation in the adult as well as in the puppy dogs; and PGH2 was about twice as potent as PGI2. The threshold dose of PGH2 for coronary vasodilation, 0.01-0.02 microgram, was the same for the adult and puppy dogs although control coronary blood flow of the adult dog was 3-10 times higher. In the pupply, maximal coronary vasodilation was effected with high doses (1.0 microgram or more) of PGI2, but not with PGH2. TXA2 prepared from PGH2 up to 1.0 microgram, had no effects on the coronary circulation of the adult dog. In contrast, both the vasocon-stricting and platelet aggregating actions of TXA2 were demonstrated in the puppy. Mechanisms for the observed age-dependent differences of the canine coronary circulation to PGH2 quantitatively, and to TXA2 qualitatively, remain to be determined.

Mortality of pesticide applicators

Information has been obtained on a cohort of professional pesticide applicators which will be followed prospectively. The cohort consists of 16,126 males employed for three months or more between 1967 and 1976 by any of three nationwide pest control companies. Deaths which occurred between 1967 and 1976 were reported by the Social Security Administration as a result of a search of its records. Overall, 311 deaths were ascertained, giving a standardized mortality ration (SMR) of 84. SMRs were over 100 for three causes of death--cancer of the lung (115), cancer of the skin (173) and cancer of the bladder (277). The confidence intervals of two of these ratios include 100, and the observed numbers therefore do not differ significantly from those expected. For bladder cancer the excess is on the border of statistical significance (p less than 0.05). The excess of deaths from lung cancer was not seen for applicators classified as termite control operators, a group more likely to be exposed to chlordane and heptachlor. There were significantly low SMRs for cancer of the digestive organs (46) and for other diseases of the digestive (55) and respiratory (29) systems. Deaths from cerebrovascular disease were also less than expected, though not significantly so.

Mortality of workers employed in the manufacture of chlordane and heptachlor

A retrospective mortality study has been carried out on workers employed in the manufacture of chlordane and heptachlor between 1946 and 1976. The study group was comprised of 1403 white males who worked for more than three months at either of the two plants in the United States now producing these compounds. Information on deaths among terminated employees was obtained from the Social Security Administration and supplemented by information collected by another investigator by individual follow-up. There were 113 deaths observed in the group, compared to 157 expected, giving a standardized mortality ratio (SMR) of 72. There was no overall excess of deaths from cancer, even among workers followed twenty or more years after entry into the occupation. There was one death from liver cancer. An excess of deaths from lung cancer (12 observed, 9.0 expected) was not statistically significant and was not distributed by duration of exposure or of latency in any pattern suggesting an etiologic role for chlordane-heptachlor exposure. Although diseases of the circulatory system as a whole showed fewer deaths than expected (SMR 83), there was a statistically significant excess of deaths from cerebrovascular disease (17 observed, 9.3 expected). This excess was not related to duration of exposure or latency and occurred exclusively after termination of employment.

A comparison of the cardiovascular effects of sodium nitroprusside and trimethaphan

In dogs anesthetized with pentobarbital-chloralose, cardiac output and blood flows of four regional vascular beds (superior mesenteric, left renal, left circumflex coronary and left femoral) were continuously monitered with electromagnetic flowmeters. Arterial blood pressure and heart rate were also measured. Hypotension was induced with intravenous infusions of sodium nitroprusside and trimethaphan for 5-16 min to produce comparable reductions of mean arterial pressure (32 mm Hg or 26 per cent with nitroprusside and 37 mm Hg or 31 per cent with trimethaphan). Cardiac output also decreased, but to a lesser extent (11.5 per cent with nitroprusside and 12.5 per cent with trimethaphan). Thus, total peripheral resistance was consistently decreased. Nitroprusside caused slight tachycardia, while trimethaphan produced bradycardia. Both drugs decreased mesenteric blood flow and increased mesenteric vascular resistance. Renal blood flow was maintained or increased with nitroprusside; thus, renal vascular resistance decreased; with trimethaphan, renal blood flow decreased and renal vascular resistance did not change. Both nitroprusside and trimethaphan reduced coronary blood flow; the reduction was more pronounced with the latter. Nitroprusside affected femoral blood flow minimally, with a slight reduction of femoral vascular resistance. In contrast, trimethaphan increased femoral blood flow and markedly decreased femoral vascular resistance. Redistribution of cardiac output favoring the dilated skin and muscle vascular beds appears to be an important undesirable effect of trimethaphan.

Determination of mycelial steroids with the aid of polyene antibiotics. II. Quantitative determination of the mycelial steroids of Mucor hiemalis

UV absorption spectrum of polyene antibiotics was dramatically altered in the presence of steroids. The introduction of a steroid to an aqueous solution of polyene antibiotics resulted in a change in the ratio of absorbance of peak 3 (with shorter wavelength) to peak 1 (with longer wavelength), E3/E1. Interactions between 28 steroids and 4 polyene antibiotics were studied and the results revealed that the structures of steroids essential for the optimal interaction with polyene antibiotics were C-17 side chain, substitution C-3 hydroxyl group, intact steroid nucleus and aromatic A-ring. The ratio of E3/E1 was used for the determination of steroids in mycelium of Mucor hiemalis and the result was in good agreement with that obtained from gas chromatograph. The (-) strain had a greater change in the ratio of absorbance, E3/E1, than that of the (+) strain. The ratio of absorbance, E3/E1, decreased in the following order: the (-) strain, the (-) strain with the addition of the filtrate of (+) strains, the mated strains, the (+) with the addition of the filtrate of (-) strain and the (+) strain.

Creatine phosphokinase release as a measure of tourniquet effect on skeletal muscle

In anesthetized dogs, a pneumatic tourniquet was applied to a hind limb for one, two, or three hours. Resultant ischemic damage to skeletal muscle was assessed by creatine phosphokinase (CPK) levels in the femoral venous blood of the experimental limb after the tourniquet was released. The CPK levels did not rise after release of one-hour occlusion in three experiments. The elevation of CPK values was demonstrated after occlusion for two hours in three of four experiments, and after occlusion of three hours in all four experiments. When a three-hour occlusion was interrupted for 15 minutes after each hour in three experiments, elevation of CPK levels was minimal or absent. Thus, skeletal muscle injury, as measured by the level of venous CPK elevation, becomes apparent after two to three hours of occlusion and can be prevented by short periods of recirculation.

Experimental coronary arterial occlusion and release. Effects on enzymes, electrocardiograms, myocardial contractility and reactive hyperemia

After less than 1 hour of coronary arterial occlusion, the myocardium suffers irreversible changes as revealed by electron microscopy. Yet, the earliest clinical laboratory indexes of myocardial infarction--elevated serum enzyme levels and significant Q waves on the electrocardiogram--are not detected until at least 6 hours after coronary occlusion. To study the early period after coronary occlusion in the dog, occlusion of the left anterior descending coronary artery for 1 to 3 hours was followed by release, and coronary sinus and venous enzyme levels, the electrocardiogram and myocardial contractility from the infarcted area, and reactive hyperemia were monitored. Coronary sinus enzyme levels rose within 15 minutes after release of occlusion in half of the experiments with 1 to 1 1/2 hours and in all of those with 2 to 3 hours of occlusion, and this rise preceded the rise in venous levels by only 10 to 20 minutes. Significant Q waves appeared 15 to 30 minutes after release of occlusion as the serum enzymes were increasing. Thus, clinically, the delayed appearance of increased serum enzymes and significant electrocardiographic Q waves is probably largely due to a lack of circulation in the infarcted area rather than to prolonged survival time. Also, the venous enzyme level reflects the coronary sinus level minutes later. The presence of viable myocardium in the infarcted area was suggested by elevation of the S-T segment upon reclamping, and by residual myocardial contractility and retained capacity for reactive hyperemia. These findings occurred in some experiments even in the presence of a significant Q wave.