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Biomedical subjects

J H van den Berg

Publications and source records attributed to J H van den Berg.

12 recordsLinked to original sources
PubMed2006

Future opportunities in preventing cisplatin induced ototoxicity.

Cisplatin is one of the most commonly used cytotoxic agents. Ototoxicity is an important and dose-limiting side-effect of cisplatin therapy. It is believed that cisplatin suppresses the formation of endogenous anti-oxidants that normally prevent the inner ear against reactive oxygen species (ROS). These ROS affect the outer hair cells (OHCs) in the organ of Corti. Results from clinical trials with amifostine, an anti-oxidant with possible otoprotective action during cisplatin therapy, were disappointing. A variety of agents with chemoprotective action against cisplatin-induced ototoxicity were successfully tested in animal models. It is important to translate these promising results from animal models into clinical practice. The possible routes of administration are systemic and transtympanic. An important condition when using such an agent systemically is that the compound may not affect the anti-tumor effect of cisplatin. The critical step at transtympanic administration is the diffusion of the compound through the round window membrane (RWM). This diffusion depends on the characteristics of the medication as on the properties of the RWM. Positive results of an otoprotector in clinical practice may increase the effectiveness of cisplatin therapy and can improve the quality of life for a large group of patients.

Adrenocorticotropic Hormone↗
PubMed2000

Effects of oral exposure to polychlorinated biphenyls (PCBs) on the development and metamorphosis of two amphibian species (Xenopus laevis and Rana temporaria).

This study examined the effects of polychlorinated biphenyls (PCBs) on development of families of amphibians using the African clawed frog (Xenopus laevis) and the European common frog (Rana temporaria). Amphibians were orally exposed to the technical PCB-mixture Clophen A50 or to the non-ortho-3,3',4,4',5-CB congener (PCB 126) either for a 10-day period or until metamorphosis. Occurrence and rate of malformations, mortality, period until metamorphosis and thyroid hormone levels were measured. Mortality increased in a dose-dependent manner, as did the rates of malformation. Time until metamorphic transformation was prolonged and the weight of froglets was increased. Although not statistically significant, thyroid hormone levels were also lowered. PHAHs such as PCBs may affect important aspects of amphibian fitness and may influence amphibian reproductive success.

Administration, Oral↗
PubMed1998

On-site screening for syphilis at an antenatal clinic.

OBJECTIVE: To determine the validity, predictive value and accuracy of the rapid plasma reagin card test performed on site to diagnose active syphilis in pregnant women so that immediate treatment can be offered to prevent congenital syphilis. DESIGN: Open, descriptive study. SETTING: Antenatal clinic, Mamelodi Hospital, Pretoria. PATIENTS: Four hundred and seventy-four pregnant women attending the antenatal clinic for the first time were entered into the study. METHODS: A rapid plasma reagin test was performed on site with no specialised equipment and the results were compared with those of the reference laboratory. RESULTS: In the event of rapid plasma reagin titres of 1:8 and higher, indicative of active syphilis, the on-site rapid plasma reagin test had a sensitivity of 90.5%. The test had a sensitivity of 100% if the rapid plasma reagin titres were 1:16 and higher. CONCLUSION: The on-site rapid plasma reagin test identified all women with rapid plasma reagin titres higher than 1:8. This implies that all women whose fetuses were in danger of acquiring congenital syphilis were identified at the clinic and could be treated immediately.

Female↗
PubMed1996

Carcinogenicity study of outdoor airborne particulate matter in newborn male NMRI mice.

An organic extract of airborne particulate matter (APM) was tested for carcinogenicity at two dose levels in the newborn mouse bioassay. The samples used were taken under specific polluted conditions. The doses tested corresponded with 0.75 and 1.5 times the amount of air man inhales during lifetime. Benzo(a)pyrene, which was used as a positive control, significantly increased the lung tumor incidence. No evidence was found for a carcinogenic activity of the organic extract of APM. Considering the high dose of APM applied in this animal model and the much lower actual cumulative dose to which man is exposed to in many areas, the conclusion can be drawn that exposure to APM alone probably does not represent an important cancer risk for man.

Adenoma↗
PubMed1991

The toxicity of tetrachlorobenzyltoluenes (Ugilec 141) and polychlorobiphenyls (Aroclor 1254 and PCB-77) compared in Ah-responsive and Ah-nonresponsive mice.

The toxicity of the PCB substitute Ugilec 141, a mixture of tetrachlorobenzyltoluenes (TCBTs), is compared with the toxicity of a commercial mixture of polychlorobiphenyls (Aroclor 1254) and with the model toxic PCB-congener 3,3',4,4',-tetrachlorobiphenyl (PCB-77) as a positive control. Alterations in liver weight, hepatic cytochrome P450 content and EROD and PROD activity, plasma thyroxin and retinol level, hepatic retinoid level and liver and thyroid pathology, have been studied in Ah-responsive and Ah-nonresponsive mice. Ugilec 141 proved to induce similar toxicological changes, qualitatively and quantitatively, to Aroclor 1254. Therefore Ugilec may pose a similar environmental and health risk as PCBs. The criteria for acceptance of new substances, like Ugilec 141, on the European market are discussed.

Journal Article↗
PubMed1980

The determination of cortisol in human plasma: evaluation and comparison of seven assays.

In a comparative study, seven different methods for the determination of cortisol in human plasma were evaluated, using routine patient samples. Four of these methods used radioactive steroids (125I- or 3H-labelled) and in three no radioactivity was needed. For the statistical evaluation a direct 3H-radioimmunoassay was arbitrarily taken as the independent variable. It was found that all other methods correlated well with this assay. However, the simplest method, the fluorimetric, cannot be recommended mainly because of its non-specific fluorescence and troublesome interference from some widely-used drugs. Of the methods evaluated a radioimmunoassay is recommended. For laboratories having no equipment for measurements of radioactivity, the more elaborate and time-consuming fluorometric method of Clark may represent a good alternative.

Binding, Competitive↗
PubMed1977

A quantitative assay of cortisol in human plasma by high performance liquid chromatography using a selective chemically bonded stationary phase.

The extraction and subsequent liquid chromatographic analysis of human plasma samples for cortisol is described. Extraction and chromatography are optimized, resulting in a recovery for cortisol of 96% and a detection limit of 1 microgram cortisol in 100 ml plasma. The application of two chemically modified silicas has been evaluated. The specificity of the method was tested by field desorption - mass spectrometry experiments.

Chromatography, High Pressure Liquid↗