Biomedical subjects
Publications and source records attributed to J Thornton.
Nuclear magnetic resonance spectroscopy has been used to examine the conformations of cobalamins in solution. The perturbation of the resonances in the n.m.r. spectra by lanthanide probes provided particularly valuable information. Except for minor details the conformations are the same as those in the crystalline state. The temperature dependence of the conformation has been reassessed.
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Two hundred forty-six patients admitted to the Trauma Unit of Cook County Hospital with penetrating neck wounds have been reviewed. A policy of mandatory neck exploration combined with a systematic approach to resuscitation and a diagnostic evaluation including neck and chest X-rays, endoscopy, and arteriography has been employed. The study has revealed a high incidence of negative neck explorations (63%) but minimal morbidity (less than 1%), no mortality, and a brief duration of hospitalization in the negative exploration group. Patients with positive explorations had an 8% morbidity and a 9% mortality rate. In addition, 13 of the patients with positive explorations had clinically negative wounds which might have been overlooked if selective management had been utilized in this series. We conclude that a policy of mandatory neck exploration is justified and advisable for patients sustaining penetrating neck injuries.
Immunologically competent mouse spleen cells were exposed to negative pi mesons in the entrance plateau or at the peak of the dose distribution at a maximum dosage of 5 rads/min. or to 60Co gamma rays at 4.96 rads/min. Survival curves from cells irradiated in vitro but incubated in vivo yielded RBE values of 2.15 for the peak and 1.84 for the entrance plateau at a surviving fraction of 0.1. The dose-rate dependence of antibody-forming spleen cells for both 60Co gamma rays and the lot-LET components of the pion beam is discussed. The authors suggest that these RBE values constitute an upper limit for normal mammalian cells exposed to pions and tha the RBE with clinically useful dose rates may be significantly lower than those reported here.
Mouse bone marrow cells exposed in vitro to graded doses of negative pi mesons at 3.5-6.0 rads/min. gave Do values of 160 rads in the plateau (0.6 and 12.0 cm), and 130 rads in the peak (16.5 and 18.4 cm). Survival curve shoulders were narrow, with Dq values of 25 and 15 rads for plateau and peak positions. Gamma rays from 60Co at 4.5 rads/min. produced a curve with wider shoulder but steeper slope such that the RBE was essentially 1 for single doses between 100-400 rads.
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A polygraph assessment of medicated psychiatric patients suggests anticholinergic effects are the primary cause of a diminished gag reflex. Sex differences indicate that females are relatively protected.
Four unfit thoroughbred horses were exercised on a treadmill twice, 5 weeks apart. Exercise consisted of stepwise increments in treadmill speed up to a maximum of 12 m s-1 and then maintained at this speed until the horses were fatigued. Two of the horses were administered phenylbutazone (4.4 mg kg-1) intravenously immediately before the first exercise period and the other two horses immediately before the second exercise period. Clinical observation revealed stiffness of gait and palpable soreness over the lumbar-sacral region in the horses 24 h after the exercise concluded. Mean plasma aspartate aminotransferase and creatine kinase activities and urinary creatinine clearance did not change as a result of exercise. The mean urinary excretion and clearance of hydroxyproline significantly increased in the 24 h following exercise (P < 0.001). A concurrent increase in the urinary excretion of malondialdehyde also occurred (P < 0.001). Prior administration of phenylbutazone did not affect hydroxyproline or malondialdehyde excretion or clearance, nor did it appear to reduce the severity of soreness after exercise. The results indicate that lipid peroxidation and the excretion and clearance of hydroxyproline increase when unfit thoroughbreds are strenuously exercised on a treadmill.
The alpha-helix defined in 1951 by Pauling et al. on the basis of model building and X-ray fibre diffraction data has 3.65 residues per turn (n) achieved with planar peptides, torsion angles of phi = -48 degrees and psi = -57 degrees and hydrogen bonds which are close to linear. Although X-ray analyses of proteins have confirmed the general correctness of the model for the helix, recent high resolution (1.7-1.0 A) diffraction studies have shown that the parameters described by Pauling et al. and later by Perutz and Arnott and Wonacott are not a good description of the alpha-helices in globular proteins, where the mean values of phi, psi are usually close to -63 degrees, -42 degrees. Here we show that these values arise as a mean of two significantly different classes in amphipathic helices depending on whether the peptide carbonyl oxygen is hydrogen bonded to a solvent or polar side-chain atom. The hydrogen bonds made by the hydrophilic carbonyls to the NH groups within helices are longer and less linear than those involving hydrophobic carbonyls. We also show that these effects are associated with a significant curvature of helices in globular proteins. For example, the alpha-helix in avian pancreatic peptide (aPP) has a radius of curvature of approximately 70 A. These results are of significance in the packing of helices in fibrous and globular proteins, in the calculation of their dipole moments, solvent accessibilities and internal energies, and in the theoretical estimation of spectroscopic properties such as circular dichroism and Raman scattering.
Significant occupational exposure to polychlorinated biphenyls (PCBs) may occur in the manufacturing of capacitors and transformers, in which PCBs are used as electrical insulators. Reports of adverse health effects resulting from PCB exposure have come primarily from an incident resulting from the accidental ingestion of contaminated rice oil in Japan in 1968 ("yusho"). Dermatological findings were prominent features and included pigmentation disturbances and chloracne. To evaluate the dermatological effects of long-term occupational exposure to PCBs, a cross-sectional clinical survey was conducted of 326 capacitor manufacturing workers. A high prevalence (37%) of dermatological abnormalities was found, but typical PCB-associated signs, such as chloracne, were less frequent than among patients with "yusho," despite high concentrations of plasma PCB. As association between dermatological signs and plasma levels of higher homologues of PCBs was suggested, but contaminants which have been reported to be present in commercial PCB mixtures (polychlorinated dibenzofurans) should be considered an etiologic factor or co-factor in the development of "PCB-associated" dermatological findings.
BACKGROUND: Ambulation, balance, and lower extremity bone mass and strength are all partially dependent on lower limb skeletal muscle mass. At present, both research and clinical methods of evaluating lower limb skeletal muscle mass as a component of nutrition assessment are limited. One potential simple and inexpensive method is lower extremity bioimpedance analysis (BIA). The present study had two objectives: to examine the determinants of lower limb resistance, with the underlying hypothesis that fluid-containing muscle is the main electrical conductor of the lower limbs; and to establish if a correlation of equivalent magnitude and similar covariates is observed when height squared (H2) is used instead of lower limb length squared (L2) in multiple regression models relating resistance to independent variables. METHODS: Lower limb resistance was measured using a contact-electrode BIA system, and lower limb fat and skeletal muscle were estimated by dual-energy x-ray absorptiometry in healthy adults. A physical BIA model was developed in the form of a regression equation with path-length (as L2 and H2)-adjusted resistance as dependent variables and lower limb skeletal muscle, fat, age, and gender as potential independent variables. RESULTS: There were 94 subjects, 34 men and 60 women, with a mean (-/+SD) age of 41.5+/-17.8 years. Strong associations were observed between L2/resistance and lower limb skeletal muscle, although for both men and women, age entered into the model as a significant covariate (total R2, men = .79 and women = .72; both p < .001). Similar models were observed with H2/resistance as dependent variable. Additional analyses showed a significantly lower resistance in lower limb skeletal muscle and height-matched old vs young subjects. CONCLUSIONS: Strong associations exist between measured lower limb resistance and lower limb muscle mass, adjusting for electrical path length either by L2 or H2. These observations suggest the potential of predicting skeletal muscle using BIA-measured lower limb resistance adjusted for stature. Age is also an independent variable in lower limb resistance-skeletal muscle associations, suggesting the need to establish underlying mechanisms of age-related resistance effects and to consider subject age when developing BIA prediction models.
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A retrospective investigation of squash-related injuries incurred at a private and a public club in New York was undertaken to gain insight into the incidence and nature of such injuries. Telephone interviews were conducted with 200 randomly selected individuals to obtain their entire injury history. Sixty-nine of the 155 squash players contacted sustained injuries during their participation. Some had multiple injuries. This resulted in an overall injury rate of 44.5%. Strains and sprains accounted for over one-third of the injuries. Nearly one-half of the injuries involved the lower extremity, with the ankle and lower leg being injured most often. Forty-seven percent of the injuries seen were considered disabling because the patients were out of action for more than two weeks after injury. Players over the age of 40 are at increased risk for injury, as are newcomers to the game. Increased injury rates were also associated with an increased frequency of play among females. Only rarely will an injured squash player become permanently impaired.
Since World War II, synthetic chemical pollutants have accumulated in the environment and food webs on a global basis, have damaged wildlife populations, and may pose large-scale hazards to human health. Despite the global nature of this problem, the vast majority of environmental regulations focus on preventing local risks using risk assessment of individual compounds, discharge permits, and control and disposal technologies. The current approach has failed to prevent global contamination and environmental damage because it underestimates the scale, complexity, and diversity of the hazards of chemical pollution. Fundamental shifts in the mode of chemical assessment and policy are required; a new framework should focus on chemical classes rather than individual substances, convert industrial processes to prevent the production and use of persistent and/or bioaccumulative substances, and shift the default state of pollution policy in the face of uncertainty from permission to restriction.
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A unique, deep-seated, benign, glandular peripheral nerve sheath tumor (PNST) of the cerebellopontine angle is described. The tumor arose from the seventh and eighth cranial nerve complex in a 15-year-old boy without neurofibromatosis. Histologically, benign glands were embedded in a bland spindle cell stroma. The epithelial cells were immunoreactive for CAM 5.2, and focally for chromogranin. The spindle cells were positive for S100P. The benign glandular PNST unassociated with neurofibromatosis is a controversial entity. The superficial location of most reported cases has made it difficult to exclude entrapped adnexae as a source for the glands. This tumor was separate from the internal auditory meatus on MRI scan, the most likely source of entrapped glands at this site. This case is the first report of a deep-seated, benign, glandular peripheral nerve sheath tumor. It suggests that glandular differentiation in PNSTs, while unusual, is not synonymous with neurofibromatosis or malignancy.