The effect of lead incorporation on the elemental composition of earthworm (Annelida,Oligochaeta) chloragosome granules

Summary The elemental compositions of chloragosome granules in the earthworm Lumbricus rubellus living in non-polluted (Dinas Powys) and heavily Pb-polluted (Wemyss) soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. High Pb concentrations were found in chloragosomes of Wemyss animals; Pb was not detected in chloragosomes of Dinas Powys animals. Partial correlation and regression analysis indicated that the in vivo accumulation of Pb by chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Pb is bound by P-containing ligand(s) in the chloragosome matrix. The sequestration of Pb by chloragosomes results in the detoxification of the metal by accumulative immobilization.     

Induction of human B cell differentiation by Fc region activators. II. Stimulation of IL-6 production

Fc region fragments derived from the enzymatic cleavage of human IgG have been shown to induce human peripheral blood-derived B cells to differentiate into Ig secreting cells (ISC). The synthetic peptide p23, corresponding to residues 335 to 357 in the Fc region of human IgG1, represents a region of the molecule responsible for stimulation of ISC formation. Fc region-induced ISC formation requires at least two signals; one supplied by Fc region activators and one supplied by a T cell-derived factor(s). In this report we show that the coculture of human PBMC with pFc' or p23, results in the release of factor(s) that resemble IL-6 in its pattern of biologic activity. This conclusion is based on the observations that supernatants from Fc region-stimulated PBMC cultures contained increased levels of elements that scored as positive in two assays for IL-6: the B9.9 hybridoma growth and the CESS cell differentiation assays. Moreover, RNA from Fc region-stimulation PBMC contained increased levels of IL-6 cDNA-hybridizable elements. Finally, it was observed that rabbit anti-IL-6 inhibited the ability of supernatants derived from Fc region-stimulated PBMC cultures to induce B9.9 cell proliferation as well as p23-induced ISC formation in intact PBMC cultures. Fc region fragments induce both monocytes and T cells to produce IL-6. Taken together, these results indicate that IL-6 is produced in Fc region-stimulated PBMC cultures and is involved in B cell activation by these activators.     

The molecular basis for Duchenne versus Becker muscular dystrophy: Correlation of severity with type of deletion

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.     

CAP 37, a 37 kD human neutrophil granule cationic protein shares homology with inflammatory proteinases

We have previously shown that a major granule-associated cationic protein CAP 37 (Mr = 37 kD) derived from human PMN is a monocyte-specific chemoattractant. The N-terminal amino acid sequence of this novel chemotactic protein shares significant homology with a number of inflammatory molecules with protease activity including elastase and cathepsin G. However, a critical substitution of a serine for a histidine at position 41, results in its lack of serine protease activity.     

Negative modulation of Epstein-Barr virus episomes by a human B-cell growth factor.

To study the effect of T-cell-derived BCGF-12kD on human B-cell autocrine growth-associated functions, we cultured Epstein Barr virus (EBV)-transformed normal B cells (LCL 72285) and Burkitt's lymphoma cells (Raji) in the presence or absence of BCGF-12kD. When cultured in media supplemented only with fetal calf serum, the LCL and Raji cell lines maintained relatively high levels of episomes. Although a similar level of proliferation could be maintained under defined culture conditions in media supplemented with BCGF-12kD, these conditions resulted in a time-dependent reduction of EBV sequences, as detected with EBV nuclear antigen (EBNA-1 and EBNA-2) gene probes. These results suggest that stimulation with T-cell-derived BCGF-12kD can alter a regulatory step which may be involved in the EBV transformation of B cells.     

Potent convulsant actions of the adenosine receptor antagonist, xanthine amine congener (XAC)

The convulsant properties of xanthine amine congener (XAC, 8-(4-(2-aminoethyl)-aminocarboxylmethyloxy)phenyl-1,3-dipropylxant hine) are compared to those of caffeine. Male Swiss albino mice were infused with convulsants through a lateral tail vein. Convulsion thresholds (i.e. the amount of convulsants required to elicit convulsions) of 39.8 +/- 2.0 mg/kg (n = 10) and 109.8 +/- 2.3 mg/kg (n = 10) were calculated for XAC and caffeine respectively. Pretreatment of animals with the adenosine receptor agonists 2-chloroadenosine, N6-cyclohexyladenosine or 5'-N-ethylcarboxamido-adenosine (1 mg/kg, i.p., 20 minutes prior to infusion) significantly decreased the seizure threshold of both XAC and caffeine. The adenosine uptake blockers, 6-nitrobenzylthioinosine or dipyridamole (0.25 mg/kg, i.p., 20 minutes prior to infusion) did not significantly affect the seizure threshold to either XAC or caffeine. The benzodiazepine agonist diazepam (5 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to both XAC (p less than 0.05) and caffeine (p less than 0.01), whereas the benzodiazepine antagonist Ro 15-1788 (10 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to caffeine (p less than 0.01), but not XAC. The results suggest that actions at benzodiazepine receptors may be a tenable hypothesis to explain the convulsant actions of caffeine, but not those of XAC.     

Genetic analysis of 24 French families with multiple endocrine neoplasia type 2A.

The gene for multiple endocrine neoplasia type 2A (MEN2A) has been mapped to the pericentromeric region of chromosome 10 by linkage analysis. Thirty-four families with multiple cases of medullary carcinoma of the thyroid (MTC), including 24 families with origins in France, have been typed with nine polymorphic markers spanning the centromere of chromosome 10. No recombination was observed between the MEN2A locus and either of the four loci D10Z1 (lod score 12.79), D10S102 (lod score 6.38), D10S94 (lod score 7.76), and D10S34 (lod score 5.94). There was no evidence for genetic linkage heterogeneity in the panel of 34 families. Haplotypes were constructed for a total of 11 polymorphisms in the MEN2A region, for mutation-bearing chromosomes in 24 French families and for 100 spouse controls. One haplotype was present in four MEN2A families but was not observed in any control (P less than .01). Two additional families share a core segment of this haplotype near the MEN2A gene. It is likely that these six families have a common affected ancestor. Because the incidence of pheochromocytoma among carriers varies from 0% to 74% within these six families, it is probable that additional factors modify the expression of the MEN2A gene.     

Intramolecular electron transfer in cytochrome c oxidase: a cascade of equilibria.

Intramolecular electron redistribution in cytochrome c oxidase after photolysis of the partially reduced CO-bound enzyme was followed at a number of different wavelengths by absorption spectroscopy. Spectra were constructed for the first two phases of this process. The first phase (tau = 3 microseconds) has a spectrum essentially identical to the difference between the Fea and Fea3 reduced-minus-oxidized spectra, indicating a 1:1 stoichiometry between the amount of Fea3 oxidized and Fea reduced. It is not necessary to invoke reduction or oxidation of other redox carriers in this phase. The second phase (tau = 35 microseconds) spectrum appears to be a linear combination of the Fea3 and Fea reduced-minus-oxidized difference spectra, reflecting the oxidation of four parts of Fea3 for every part of Fea oxidized. This process can be described in terms of transfer to CuA of electrons from the Fea3<==>Fea equilibrium system established in the first phase. The relative contributions of Fea3 and Fea in the second phase allow us to calculate the equilibrium constant for Fea3<==>Fea electron exchange, which yields a delta Em of 36 mV for the two centers (Fea3 more positive). Together with the apparent rate constant for the fast phase, this equilibrium constant yields, in turn, the forward (kf) and reverse (kr) rates for electron transfer from Fea to Fea3 as follows: kf = 2.4 x 10(5) s-1 and kr = 6 x 10(4) s-1. kf is much faster than any observed step in the reaction of the reduced enzyme with O2. Thus, the catalytic mechanism of O2 reduction to water is not rate-limited by electron transfer from Fea to the binuclear Fea3/Cu(B) site.