Effect of chloride on nitrite-induced methaemoglobinemia in Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill).

We evaluated the effects of chloride concentration on the clinical pathology in juvenile Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), following semi-static exposures to 1 mg L(-1) nitrite for 96 h. In spring water naturally low in chloride (5 mg L(-1)), plasma nitrite concentrated to more than 40× environmental levels resulting in a severe methaemoglobinemia characterized by torpid behaviour, 30-fold increase in methaemoglobin fraction, anaemia, leucopenia and hyperkalaemia. Loss of intracellular water and potassium to extracellular space may have resulted in hyperkalaemia and haemodilution. Fish survived nitrite exposure, but 60% of torpid fish died following capture and tissue sampling. Fish acclimated to 10-fold higher chloride content (55 mg L(-1)) did not concentrate nitrite in the plasma above environmental levels or develop methaemoglobinemia, but did exhibit similar haematology and plasma chemistry changes. Plasma nitrite returned to preexposure levels by 14 days following nitrite exposures, but severity of clinical pathology changes persisted or increased, suggesting that Atlantic sturgeon have reduced capacity to recover from methaemoglobinemia. Fish that survive methaemoglobinemia may be susceptible to mortality from the cumulative effects of intoxication, handling and other stresses for two or more weeks following nitrite remediation. Chloride buffering in aquaculture systems reduces the toxic effects of nitrite accumulation.

Induction of DNA crosslinks and DNA strand lesions by cyclophosphamide after activation by cytochrome P450 2B1.

Cyclophosphamide requires metabolic activation by cytochrome P450 to exert its genotoxic effects. Therefore in vitro studies on its mechanism of action have been limited to the use of self-activating derivatives of cyclophosphamide or to hepatocytes as an activating system. In this study we used a cell line of Chinese hamster lung fibroblasts (V79 cells), genetically engineered to express active cytochrome P450 2B1 as the sole observable cytochrome P450 (SD1 cells). An increase in DNA strand lesions (SL: DNA single-strand breaks and alkali labile sites) was observed between 0.5 and 1.5 mM cyclophosphamide (24 h incubation) which could be classified as alkali labile sites using a modified alkaline elution assay. Compared to cyclophosphamide, its active metabolite 4-hydroperoxycyclophosphamide (4-OOH-CY) was about 250-fold more effective in induction of SL. Equimolar concentrations of phosphoramide mustard (50 microM), the ultimate DNA binding metabolite of cyclophosphamide, caused only about 50% of SL compared to 4-OOH-CY. A minimum of 12 h of incubation of SD1 cells was needed for cyclophosphamide (1 mM) until SL were detectable, compared to only 2 h for 4-OOH-CY and 1.5 h for phosphoramide mustard (50 microM). DNA crosslinks were observable after shorter incubation periods than single-strand breaks (6 h for cyclophosphamide and 1 h for 4-OOH-CY and phosphoramide mustard) and were no longer detectable at incubation periods of more than 20 h. Treatment of SD1 cells with ionizing radiation only, cyclophosphamide only, and radiation plus cyclophosphamide showed that SL induced by cyclophosphamide were not repaired during incubation with fresh culture medium (24 h). However, an efficient repair of SL caused by ionizing radiation was observed and was not inhibited by cyclophosphamide. These observations give strong evidence that different types of SL were induced by cyclophosphamide and radiation. SD1 cells were able to repair the special kind of SL induced by radiation but not the SL caused by cyclophosphamide.

The production of anti-H-Y monoclonal antibodies: their potential use in a sex test for bovine embryos.

In an attempt to improve the accuracy of sexing bovine embryos, new anti-H-Y monoclonal antibodies were produced and selected, using an extended screening procedure. In addition to the commonly used screening of soluble H-Y antigen sources, such as testis supernatant and Daudi supernatant, the binding specificity to cell surface H-Y antigen was tested also. A radioimmunoassay (RIA) employing male and, as a control, female bovine lymphocytes, and enzyme-linked immunosorbent assays (ELISAs) on solubilized membrane fractions resulted in the selection of a number of clones producing monoclonal antibody (mAb) with male-enhanced binding. Four of the anti-H-Y mAb were assessed for binding to Day 7 or 8 bovine embryos. The accuracy of sexing bovine embryos ranged from 58% to 71%. Two of the four antibodies did not react with presumed soluble H-Y antigen-containing sources in an ELISA. These results raise doubts about the suitability of the presumed soluble H-Y antigen sources, Daudi, TM4 and testis supernatant, to be used in screening tests for anti-H-Y antibodies.

A comparative study on the use of bovine and murine monoclonal antibodies for passive immunization in cattle.

In the present experiments the efficacy of murine and bovine monoclonal antibodies for passive immunization in cattle was compared. The in vivo immunoneutralization of pregnant mare serum gonadotrophin (PMSG) by murine and bovine antibodies after repeated administration was chosen as a model for this study. Results indicate that repeated injections of murine monoclonal antibodies against PMSG (mMCA) alone did not, or only to a small extent, elicit an anti-mouse immune response. The simultaneous administration of mMCA and PMSG resulted in relatively high levels of anti-mouse antibodies after the second injection, leading to a decrease in neutralizing activity of mMCA. The results suggest that the neutralizing activity of mMCA is inhibited more by anti-idiotypic than by anti-isotypic antibodies against mMCA. In vivo, the bovine monoclonal antibody against PMSG (bMCA) only partially neutralizes PMSG. After repeated administration of bMCA, either alone or in combination with PMSG, no anti-bMCA antibodies could be detected in our assay system. In addition, no change in plasma levels of bMCA and PMSG compared with levels after the first injection was observed. Although it has to be confirmed by further experiments whether our findings can be generalized, the present results suggest that for repeated passive immunization in cattle homologous antibodies are to be preferred above heterologous antibodies.

Satisfaction with medical care: replications and theoretic reevaluation.

Satisfaction with medical care is frequently measured in health services research but for many different reasons. The widening conceptualizations and uses of satisfaction reported make comparisons between studies difficult. Questions regarding the structure and dimensionality of satisfaction remain. The relation of satisfaction with utilization still requires theoretic and empiric clarification. This article reports on several surveys containing measures of satisfaction conducted in a research program in community pediatrics. Using multidimensional scaling techniques, the stability of the structure of satisfaction and patients' preferences for care is examined across several samples. The different structures that emerged seem to reflect unique patient experience. Several multivariate approaches were applied to study the relation between satisfaction and utilization. A regulatory self-equilibrating model was offered. Satisfaction is seen as a multifaceted concept related to short-term and long-term processes. Specific models are required to link satisfaction to the various health and illness behaviors.

Satisfaction with medical care: its measurement and relation to utilization.

Both the conceptualization and the measurement of satisfaction have been of major concern in medical care research. Some scholars used satisfaction as a determinant of utilization, others as a consequence of utilization. Measures of satisfaction are largely content oriented. Reliabilities are reported, but validity is usually assumed (face validity) or assessed through correlations with a criterion variable like "wish to change providers." Using multidimensional scaling techniques, this study identifies several components in the construct "satisfaction" and relates them to the utilization of services. A general satisfaction measure provides us with an assessment of physicians and the medical care delivered, a specific satisfaction measure assesses past experience with the regular source of the care. Both of these can be divided into a positive and negative subcluster. Regressions were computed predicting satisfaction from utilization, and utilization from satisfaction, each time controlling in a preceding step for sociodemographic factors. The relationships varied strongly by provider; as a rule, a larger proportion of the variance could be explained analyzing for one provider at a time than for all providers combined. Analyzing one provider at a time showed that satisfaction substantially increased the proportion of explained variance in utilization in hierarchical regression, but utilization did not increase the explained variance in satisfaction.

The two dimensions in satisfaction with dental care.

Satisfaction with health services is an aspect of quality of care that is of special importance for captive clients like low-income clinic users. Several methodologies have been reported, but validation has been difficult. This study compares two older scaling techniques with a new, nonmetric method to detect underlying dimensions. Unlike previous research, the typical satisfaction scale was found to be two-dimensional, with one dimension measuring latent hostility or resentment, and the other measuring general glorification of the health professional. The two components do not form polar opoosites of one attitude dimension. Latent hostility seems to be more related to personal experiences with providers than is general glorification.