Exposure to hazardous substances and male reproductive health: a research framework.

The discovery in the mid-1970s that occupational exposures to pesticides could diminish or destroy the fertility of workers sparked concern about the effects of hazardous substances on male reproductive health. More recently, there is evidence that sperm quantity and quality may have declined worldwide, that the incidence of testicular cancer has progressively increased in many countries, and that other disorders of the male reproductive tract such as hypospadias and cryptorchidism may have also increased. There is growing concern that occupational factors and environmental chemical exposures, including in utero and childhood exposures to compounds with estrogenic activity, may be correlated with these observed changes in male reproductive health and fertility. We review the evidence and methodologies that have contributed to our current understanding of environmental effects on male reproductive health and fertility and discuss the methodologic issues which confront investigators in this area. One of the greatest challenges confronting researchers in this area is assessing and comparing results from existing studies. We elaborate recommendations for future research. Researchers in the field of male reproductive health should continue working to prioritize hazardous substances; elucidate the magnitude of male reproductive health effects, particularly in the areas of testicular cancer, hypospadias, and cryptorchidism; develop biomarkers of exposure to reproductive toxins and of reproductive health effects for research and clinical use; foster collaborative interdisciplinary research; and recognize the importance of standardized laboratory methods and sample archiving.

A thermodynamic and mutational analysis of an RNA purine loop as a protein binding site.

The thermal stability and protein binding of a 36 nucleotide RNA hairpin containing an internal loop were studied under various solution conditions. Yeast ribosomal protein L32 binds to its transcript and small RNAs which reproduce the L32 transcript's secondary structure have been examined. Replacement of the internal loop with canonical base pairs did not affect the salt dependence of the melting temperature suggesting that both molecules adopt a linear shape. Several electrostatic contacts are formed on binding to a ribosomal fusion protein, but Mg+2 is not required for binding. The RNA protein complex is stable up to 50 degrees C. Two internal loop deletion mutants have similar thermodynamic stabilities and chemical and enzymatic reactivities, but fail to bind the fusion protein. However, several of the internal loop bases of the deletion mutants are moderately reactive to chemical agents whereas the wild type loop sequence displayed a mixed pattern of protection and hyperreactivity.

Validation of risk factors for the nursing diagnosis decreased intracranial adaptive capacity.

Mitchell has proposed a series of factors that may aid in the identification of individual patients with intracranial hypertension at risk for decreased intracranial adaptive capacity. The etiology of decreased intracranial adaptive capacity is failure of normal intracranial compensatory mechanisms. The defining characteristic of this nursing diagnosis is repeated disproportionate increase in intracranial pressure (ICP) that can occur in response to a variety of noxious and nonnoxious stimuli. The purpose of this study was to determine predictive validity of two risk factors (wide amplitude of ICP tracing and increased level of ICP at rest) for the phenomenon of decreased intracranial adaptive capacity. Data were derived from secondary analysis of 30 recordings from a sample of eight children who had ICP monitoring as part of their medical treatment. Results indicated that wide amplitude of ICP tracing or wide amplitude plus increased level of ICP at rest (specificity and positive predictive value were each 100%) with suctioning and turning was more likely to be associated with a disproportionate increase in ICP than when an increased level of ICP at rest alone was the only risk factor (specificity = 25% and positive predictive value = 67% with suctioning and specificity and positive predictive value each = 40% with turning). It was also concluded that, despite high positive predictive values, the combination of risk factors was sufficient but not solely necessary for a disproportionate increase in ICP (false negative predictive value for wide amplitude was 65% with suctioning and false negative predictive value for increased level of ICP was 83% with suctioning and 43% with turning).(ABSTRACT TRUNCATED AT 250 WORDS)