Biomedical subjects

K Brock

Publications and source records attributed to K Brock.

24 records · Page 2Linked to original sources

PubMed1987

Pathologic effects of ESWL on canine renal tissue.

The introduction of extracorporeal shock wave lithotripsy (ESWL) has provided an avenue for dealing with many urinary stones noninvasively. The margin of safety for the kidney during shock wave administration is largely undefined. A pilot study was performed where six kidneys in five female mongrel dogs were shocked. Group A kidneys were given 1,776, 4,500, 6,000, or 8,000 shocks, respectively, at 18-24 kV. Group B kidneys received 1,600 and 8,000 shocks (18-24 kV). The number of shocks per electrode ranged from 500 to 4,538 and averaged 2,490. The dogs were sacrificed forty-eight to seventy-two hours (Group A) or twenty-eight to thirty-two days (Group B) post-treatment. Modest damage (hematoma and/or interstitial hemorrhage) was noted in all kidneys. Evidence of permanent change (fibrosis) was noted in both Group B kidneys. Complete necrosis of the kidney was not seen after administration of 8,000 shocks. These preliminary data indicate that lithotripsy can, in some circumstances, produce renal damage in the canine model.

Animals↗

PubMed1986

Evaluation of the effect of agar on the results obtained in the L5178Y mouse lymphoma assay.

The L5178Y TK+/- mouse lymphoma assay is widely used in mutagenicity testing. Trifluorothymidine-resistant (TFTr) mutants are quantitated following growth in agar-supplemented cloning medium. In an attempt to evaluate the effect of agar on plating efficiency, we have tested several lots of Difco Noble agar (cat. No. 0142-01-8; normally used in this assay) and compared it with Baltimore Biological Laboratory (BBL) agar (cat No. 11849). We find that BBL agar gives a higher and less variable plating efficiency than any of the Noble lots tested. Colonies plated in BBL agar tend to appear significantly earlier on the plates than those cloned in Noble agar. The absolute mutant number and the induced mutant frequency quantitated from a treated culture is generally higher in BBL compared to Noble agar. To determine if this higher frequency is due to increased mutant recovery rather than "sneak through" of nonmutant cells, we isolated 97 mutants from treated cultures (44 large colonies and 53 small colonies) and 69 mutants from untreated cultures (24 large colonies and 45 small colonies) and tested them for TFT resistance. All but one (a large colony from an untreated culture) were found to be TFTr, indicating that the mutant frequency is due to an increased mutant recovery. The spontaneous mutant frequency was quantitated for 122 untreated cultures. Showing little variation within and between experiments, the spontaneous mutant frequency yielded a mean of 57.7, with a standard deviation of 14.4. Under our laboratory conditions, BBL agar gave reliable results, and we prefer it for use in cloning L5178Y mouse lymphoma cells.

Agar↗

PubMed1986

The penetration of mammalian skin by cercariae of Trichobilharzia sp. (Trematoda: Schistosomatidae) from South Africa.

The ability of the cercariae of Trichobilharzia sp., the commonest avian schistosome in South Africa, to cause dermatitis in man is confirmed, and their progress through and resultant histopathology in rodent skin are documented. These cercariae reach the subcutaneous tissue within one hour after exposure, and some migrate to the lungs. Between 46 and 97 h later, those stranded in the skin have died, while those in the epidermis are extruded by 97 h. There were haematological changes in the peripheral blood and a rapid rise and fall in the mitotic rate of the basal epithelium of the epidermis.

Animals↗

PubMed1984

Normal sister chromatid exchange levels in hospital sterilization employees exposed to ethylene oxide.

This study was undertaken to determine whether a specific group of hospital workers exposed to ethylene oxide (ETO) in sterilizing areas showed evidence of increased levels of sister chromatid exchange (SCE) formation. SCE frequencies were determined for 14 sterilizer workers and 14 matched controls. Time-weighted average (TWA) and peak ambient levels of ETO were measured in the sterilizing areas. Results indicated that all sterilizer workers were exposed to less than 5 parts per million TWA of ETO and that there were no statistically significant differences in SCE levels between sterilizer workers and controls. Smoking habits did appear to be associated with increased SCE levels. In this particular hospital setting no evidence of genetic effects stemming from employees' exposure to low levels of ETO was found.

Adult↗

PubMed1982

Comparative genotoxicity studies of ethyl carbamate and related chemicals: further support for vinyl carbamate as a proximate carcinogenic metabolite.

In vivo and/or in vitro mammalian cell systems were used to evaluate sister chromatid exchange (SCE) induction and gene mutagenesis effects following exposure to ethyl carbamate (urethane), vinyl carbamate, ethyl N-hydroxycarbamate, and 2-hydroxyethyl carbamate. Although ethyl carbamate caused dose-dependent increases in SCE when injected into mice, it was ineffective for inducing SCE and gene mutation (6-thio-guanine resistance) in Chinese hamster V-79 cells cultured with or without the addition of S9 enzyme mix during treatment. Chemical-specific patterns of genotoxicity were evident for the known or suspect metabolites under test: only vinyl carbamate consistently (in vivo and in vitro) revealed strong activity for the genetic endpoints. SCE induction levels of 5-8 times baseline were observed after animal or cell culture exposures to vinyl carbamate. Doses required to produce this effect in V-79 cells in the presence of S9 mix were approximately 100 times lower than those needed when S9 was absent. The extensive gene mutagenesis (approaching 600 mutants/10(6) survivors) noted was completely dependent upon the presence of S9 mix. These observations are consistent with current theory holding that vinyl carbamate is a metabolic intermediate of ethyl carbamate, and is converted to the ultimately reactive species (presumably, vinyl carbamate epoxide) which is responsible for ethyl carbamate carcinogenesis.

Animals↗

PubMedDate not supplied

Aging but not arousal influences the effect of environmental noise on the span of attention.

In young samples environmental noise acts to reduce attention to low salience events. We asked whether noise would affect old individuals similarly. Furthermore, both aging and noise effects on performance have been attributed to changes in physiological arousal. Therefore, we also asked whether performance changes with noise and aging were necessarily associated with changes in physiological arousal. Young, middle-aged and older individuals (total N = 50) performed a dual task in the presence or absence of 90 dBA white noise. In noise relative to quiet, young and middle-aged but not older participants responded to low salience events less accurately. Neither self-report nor cardiovascular change unequivocally supported the view that general arousal induced the performance changes associated with noise or aging. Cardiovascular changes were controlled by engagement in the task, not by the presence or absence of noise. Age-related changes in preparation for infrequent events were related to vascular change. Alternatives to general arousal explanations were considered.

Adolescent↗