Decreased conformational stability of the sarcoplasmic reticulum Ca-ATPase in aged skeletal muscle

Sarcoplasmic reticulum (SR) membranes purified from young adult (4-6 months) and aged (26-28 months) Fischer 344 male rat skeletal muscle were compared with respect to the functional and structural properties of the Ca-ATPase and its associated lipids. While we find no age-related alterations in (1) expression levels of Ca-ATPase protein, and (2) calcium transport and ATPase activities, the Ca-ATPase isolated from aged muscle exhibits more rapid inactivation during mild (37 degrees C) heat treatment relative to that from young muscle. Saturation-transfer EPR measurements of maleimide spin-labeled Ca-ATPase and parallel measurements of fatty acyl chain dynamics demonstrate that, accompanying heat inactivation, the Ca-ATPase from aged skeletal muscle more readily undergoes self-association to form inactive oligomeric species without initial age-related differences in association state of the protein. Neither age nor heat inactivation results in differences in acyl chain dynamics of the bilayer including those lipids at the lipid-protein interface. Initial rates of tryptic digestion associated with the Ca-ATPase in SR isolated from aged muscle are 16(+/- 2)% higher relative to that from young muscle. indicating more solvent exposure of a portion of the cytoplasmic domain. During heat inactivation these structural differences are amplified as a result of immediate and rapid further unfolding of the Ca-ATPase isolated from aged muscle relative to the delayed unfolding of the Ca-ATPase isolated from young muscle. Thus age-related alterations in the solvent exposure of cytoplasmic peptides of the Ca-ATPase are likely to be critical to the loss of conformational and functional stability.     

Hearing loss from combined exposures among petroleum refinery workers

Seventy-three consecutive cases of childhood acute lymphoblastic leukemia (ALL) diagnosed and managed in Queen Mary Hospital over a 10-year period from 1985 to 1994 were retrospectively analysed for their presenting features and treatment outcome. The 48 boys and 25 girls ranged in age from 0.4 to 14.2 years (median: 4.3 years). Bone and joint pain was a relatively common presenting feature besides fever, hepatosplenomegaly and lymphadenopathy. Immunophenotyping of blast cells showed: 51 B-cell precursor ALL, one B-ALL, 10 T-ALL and three myeloid-antigen positive ALL. Eight cases were unclassified since immunophenotyping had not been performed. Out of the 73 patients, treatment outcome was analysed in 20 cases treated with UKALL-VIII regimen and 28 cases treated with either the UKALL-XI regimen or the Hong Kong Children Cancer Study Group (HKCCSG) protocol which was modelled upon UKALL-XI. Although complete remission rates were similar between the two groups, patients treated with the former regimen that was less intensified suffered more relapses than the latter (56 per cent versus 21 per cent, P = 0.04). There were, however, no significant differences both in event-free survival (38.2 +/- 11.2 per cent versus 71.3 +/- 9.3 per cent, P = 0.12) and overall survival (70.0 +/- 10.2 per cent versus 79.6 +/- 8.3 per cent, P = 0.41) between the two groups at 3 years by long-rank test. With the use of risk-directed therapy and improved supportive care, two-thirds of our patients are able to enjoy long-term event-free survival.     

Detection of intrauterine illicit drug exposure by newborn drug testing. National Academy of Clinical Biochemistry

Identification of intrauterine drug-exposed newborns with toxicological screening may have benefits including close follow-up of the infant by both medical and social services. Applying specific written guidelines to select newborns for drug testing decreases bias and protects the physicians and hospitals involved. All drugs reported as positive should be confirmed by an appropriate second test. Urine and meconium testing are the best current options for identifying drug-exposed neonates. Urine testing sensitivity is low because of problems encountered in urine collections and the high thresholds used in current urine assays. The disadvantage to meconium testing is the increased labor and time required to work with this material. Testing of newborn hair is unlikely to be widely used until technically less demanding assays become available. Testing of amniotic fluid or gastric lavage is still in the developmental stages. Adopting lower urine assay thresholds for newborn samples would increase sensitivity and would be an appropriate modification of current methodologies.     

Laryngeal survey in glyphosate intoxication: a pathophysiological investigation

Respiratory aspiration is a serious potential complication of glyphosate-surfactant herbicide intoxication. From October 1, 1992 to June 30, 1996, we performed laryngeal evaluations in 53 cases to investigate the possible pathophysiological mechanism of glyphosate intoxication. There were 36 cases with significant laryngeal injury. The blood WBC count were significantly higher and the hospital stays were significantly longer in patients with laryngeal injury, when compared with patients with no laryngeal injury (Student t-test, P < 0.005). Laryngeal injury was strongly correlated with aspiration pneumonitis (mean 2 = 4.449, P < 0.05). We concluded that laryngeal injury may be the major cause of aspiration that leads to some degree of morbidity and mortality, following concentrated glyphosate-surfactant herbicide intoxication. Laryngeal survey may be indicated in cases of glyphosate-surfactant intoxication, to evaluate the severity of mucosal injury, and to apply adequate supportive management as early as possible to prevent from aspiration complications and even mortality.     

Comparative effects of strophanthidin in tilapia and human heart tissues

Production of growth factors may provide a mechanism for disease evolution in some leukemias. Interleukin-1 is a plelotropic cytokine with the ability to synergize with other growth factors as well as to stimulate their production and release. Autocrine and/or paracrine secretion of interleukin-1 has been implicated in the pathogenesis of both chronic and acute myelogenous leukemia. Recently, a series of both specific and nonspecific IL-1 inhibitory molecules have been identified. These include IL-1 receptor antagonist, soluble IL-1 receptors, IL-1-converting enzyme inhibitor, IL-4, IL-10 and IL-1-antisense. Early experiments demonstrating the ability of some of these molecules to inhibit acute and chronic myelogenous leukemia growth suggest that clinical trials of these compounds may provide a novel management approach in these malignancies. Here we review the potential biologic and therapeutic role of IL-1 and its inhibitors in the myeloid leukemias.     

Role of metabolism in ethyl carbamate-induced suppression of antibody response to sheep erythrocytes in female Balb/C mice

A possible role of metabolism by cytochrome P450 (P450) in ethyl carbamate-induced suppression of the antibody response to a T-cell-dependent antigen, sheep erythrocytes (SRBCs), was investigated in female Balb/C mice. When mice were treated with ethyl carbamate intraperitoneally for 14 consecutive days at 25, 50, 100, 200 and 400 mg/kg, the antibody response was significantly suppressed from 200 mg/kg. These doses also caused a decrease in thymus weight. An acute dosing of ethyl carbamate at 1 g/kg also caused not only a significant suppression of the antibody response, but also a decrease in thymus weight. The antibody response was most likely to be the IgM antibody response, which was demonstrated in a haemagglutination study. When mice were pretreated with phenobarbital (80 mg/kg) for 3 days to induce P450 enzymes, followed by administration of ethyl carbamate intraperitoneally for 7 consecutive days, the antibody response was more suppressed than in saline-pretreated controls. Moreover, a study using aminoacetonitrile, a P450 inhibitor, showed that the antibody response suppressed by ethyl carbamate was completely recovered by the inhibitor. The present results suggest that metabolism of ethyl carbamate by P450 may be the critical pathway to produce metabolites capable of suppressing the antibody response.     

Mutational spectrum induced by chromium(III) in shuttle vectors replicated in human cells: relationship to Cr(III)-DNA interactions

Trivalent chromium (Cr(III)), the ultimate species of chromium (VI) intracellular reduction, can associate with DNA forming Cr(III) monoadducts and DNA-DNA cross-links. However, the mutational specificity of Cr(III) has not been determined partly because Cr(III) has difficulty entering cells. In this study, we have characterized the types of Cr(III)-induced DNA lesions in two buffer systems and the mutational spectrum of Cr(III)-treated shuttle vectors replicated in human 293 cells. Plasmids were treated with Cr(III) in buffers consisting of either 10 mM potassium phosphate, pH 7.5 (designated as KP), or 0.2 mM Tris-HCl and 20 microM EDTA, pH 7.4 (designated as TE/50). The amounts of Cr(III) bound to DNA increased as Cr(III) concentration increased in both buffers; these Cr(III)-DNA associations were stable in both buffers during a 24-h dialysis. The electrophoretic mobility of supercoiled DNA was markedly retarded in samples treated with Cr(III) in TE/50 but not KP buffer, suggesting that Cr(III)-mediated DNA-DNA cross-links were generated in TE/50 but did not form in KP. Polymerase-stop assay showed that DNA polymerases were mostly blocked at the 3' adjacent bases of guanines on templates treated with Cr(III) in TE/50 but were not observed on those treated in KP. The signals of Cr(III)-mediated cross-links generated in TE/50 buffers were reduced when they were dialyzed against KP buffers. Similarly, Cr(III)-DNA monoadducts formed in KP were converted to primer-template cross-links by dialysis against TE/50. The mutation frequency of Cr(III) in the supF gene of pSP189 or pZ189 shuttle vectors replicated in human cells increased as Cr(III) concentration increased in both buffers. DNA sequencing analysis showed that single-base substitutions (61-68%), two-base substitutions (3-5%), and deletions (21-34%) were induced in similar frequencies in plasmids treated with Cr(III) in either TE/ 50 or KP. The Cr(III)-induced base-substitution hot spots are different from those occurring spontaneously. Cr(III) enhances G.C base substitutions, particularly G.C-->C.G transversions, at 5'GA, 5'CG, and 5'AG sites. Base-substitution hot spots did not correlate with strong polymerase-stop sites, suggesting that base substitutions are derived from Cr(III) monoadducts, not from DNA-DNA cross-links.