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Biomedical subjects

D L Stevens

Publications and source records attributed to D L Stevens.

At least 163 records · Page 9Linked to original sources
PubMed1978

Pulmonary carcinogenesis in rats given implants of cigarette smoke condensate in beeswax pellets.

Lungs of inbred OM/NCR and outbred Sprague-Dawley rats were given implants, through a thoracotomy, of pellets of cigarette smoke condensate (CSC) suspended in a beeswax-tricaprylin vehicle. The pellets slowly released material into the surrounding parenchyma, which resulted in a dose-related increased incidence of lung cancer, predominantly invasive and metastasizing epidermoid carcinoma. A 42% prevalence of pulmonary carcinoma was present in the highest dosage group, which received 67 mg CSC, exposing approximately 1.65 cm2 bronchiolar epithelium. Squamous metaplasia associated with the implanted site preceded the appearance of the carcinomas and was more severe, with the larger pellets having more concentrated CSC. No difference was observed in incidence of pulmonary carcinomas with the use of CSC containing high or low concentrations of nicotine. The potential value of this bioassay system were discussed.

Animals↗
PubMed1978

Clinical and pathological effects of cigarette smoke exposure in beagle dogs.

To compare the clinical and pathological effects of high and low nicotine cigarette smoke 12 young adult male beagles were separated into four equal groups and exposed to smoke from high (4.6 mg) or low (1.4 mg) nicotine cigarettes, administered in six or 12 cigarettes per day. Two control groups, sham-exposed and nontracheostomized, consisted of three dogs each. The dogs were exposed seven days per week for five months. Tracheobronchitis developed in smoke-exposed dogs; gross lesions were generally confined to the lungs and tracheobronchial lymph nodes. Histopathological changes were found in all smoke-exposed dogs, with slightly more severe or extensive lesions in the dogs exposed to 12 cigarettes per day. The incidence and severity of rhinitis, turbinate basal epithelial cell hyperplasia, and squamous metaplasia were increased among dogs in the high nicotine cigarette groups.

Animals↗
PubMed1977

Haemophilus influenzae pneumonia in adults.

Thirty cases of Haemophilus influenzae pneumonia with clinical and laboratory features have previously been recorded in adults. During the past three years, we have examined 18 patients in whom this diagnosis was established by transtracheal aspirate or blood culture. Our study suggests that H influenzae, both typable and nontypable strains, is a more frequent cause of pneumonia in adults than previously appreciated. We found no clinical values that distinguished H influenzae pneumonia from other bacterial pneumonias. A properly performed Gram's stain of a transtracheal aspirate specimen is classical in its appearance and facilitates instritution of appropriate initial treatment. The emergence of both typable and nontypable organisms resistant to ampicillin makes it important that organisms be isolated from reliable samples for sensitivity testing. With appropriate therapy, the prognosis for patients with H influenzae pneumonia appears to be good.

Adolescent↗
PubMed1973

Cryptogenic drop attacks: an affliction of women.

A drop attack was defined as falling without warning, not apparently due to any malfunction of the legs, not induced by change of posture or movement of the head, and not accompanied by vertigo or other cephalic sensation. All 33 patients attending a neurological clinic with a primary complaint fulfilling these criteria were women, and a further seven examples were found by questioning 200 consecutive patients at a gynaecological clinic. No affected male was found.In all but one patient, falls occurred only when walking. They were not due to wearing high-heeled shoes. The average age at onset was 44.5 years and in younger women onset was often during pregnancy. The accepted causes of drop attacks were not found with certainty in any of these patients. The sex incidence and the circumstances of the falls suggest that the cause may lie in differences between the two sexes in the mechanism of walking rather than in any central disturbance. Drop attacks in women commonly occur as an isolated symptom for many years, and although distressing have no serious prognostic implications.

Accidents↗
PubMed1970

Impotence in farm workers using toxic chemicals.

Four out of five members of a team of farmworkers who had been using various herbicides and pesticides in intensive agriculture became impotent. Sexual function recovered after further contact with the chemicals was stopped and hormone therapy had been given, though in one case this took about a year. We have not been able to incriminate one particular substance, but with the circumstantial evidence and the lack of any other obvious cause it seems likely that the impotence was due to the toxic effects of one or more of the chemicals being used.

Adult↗
PubMed1970

Alterations in lumbar cerebrospinal fluid protein during air encephalography.

A significant fall occurred in the protein content of successive specimens of lumbar cerebrospinal fluid (C.S.F.) withdrawn during the course of air encephalography in 57% of cases. No correlation was found between the fall in the protein concentration and the total volume of air injected or the total volume of C.S.F. withdrawn, but the size of the fall was greater when the initial lumbar C.S.F. protein concentration was raised. The importance of taking specimens for routine laboratory analysis before the injection of any air is emphasized.

Adolescent↗
PubMed1968

Origin of cyanide in cultures of a psychrophilic basidiomycete.

An unidentified psychrophilic basidiomycete used valine and isoleucine as precursors to hydrocyanic acid (HCN). As probable intermediates in the pathway from valine and isoleucine two cyanogenic glucosides, linamarin and lotaustralin, were demonstrated in fungus cultures. The fungus contained two beta-glucosidases and an oxynitrilase which, acting together, were capable of releasing cyanide from both linamarin and lotaustralin. The two beta-glucosidases were purified and compared as to pH optimum, Michaelis constant, energy of activation, thermal stability, and substrate specificity. The products of methyl ethyl ketone cyanohydrin and acetone cyanohydrin dissociation by the oxynitrilase were demonstrated to be HCN together with methyl ethyl ketone and acetone, respectively. The oxynitrilase attacked aliphatic hydroxynitriles, but showed no activity on aromatic hydroxynitriles.

Amino Acids↗
PubMedDate not supplied

Synergistic interaction of cefotaxime and its metabolite desacetylcefotaxime demonstrated by drug-impregnated disks.

Because no simple in vitro test for cefotaxime (CTX) and desacetylcefotaxime (dCTX) synergy exists, and, because no disk susceptibility data is available for dCTX, we investigated the potential of antibiotic impregnated disks as a test for positive in vitro interaction. Results of this study indicate that all strains of Staphylococcus aureus tested demonstrated additive interactions using disks that contained 30 micrograms of dCTX. In contrast, it was necessary to use much smaller concentrations of each cephalosporin to demonstrate additive effects against Gram-negative bacteria. Zones of inhibition were greater for disks containing the combination compared to either CTX or dCTX alone, among all the Gram-negative genera tested; however, these differences were statistically significant only for Klebsiella pneumoniae and Escherichia coli (P less than 0.05). These results demonstrate that disk susceptibility testing is reliable for the CTX metabolite, dCTX, and suggests that this technique using disks impregnated with CTX and dCTX singly and in combination is a simple method with which to evaluate positive antimicrobial interactions in the clinical laboratory.

Cefotaxime↗
PubMedDate not supplied

Direct effects of purified staphylococcal toxic shock syndrome toxin 1 on myocardial function of isolated rabbit atria.

Toxic shock syndrome is associated with reversible cardiomyopathy. The cardiac dysfunction may be mediated by toxic shock syndrome toxin 1 (TSST-1), an exotoxin generated by Staphylococcus aureus. However, the effects of purified TSST-1 on cardiac function are unknown. In a study of the toxin's effect on myocardial function, TSST-1 (200 ng/mL) was added to muscle baths containing isolated rabbit atria. TSST-1 caused time-dependent inhibition of developed force (systolic function) but did not alter resting force (an index of muscle stiffness or cardiac compliance). These data show that TSST-1 can directly inhibit myocardial function, but the significance of this effect in patients with toxic shock syndrome remains to be determined.

Animals↗