Biomedical subjects
Publications and source records attributed to R A Lazzarini.
Ribosomes are observed intimately associated with nucleocapsids of vesicular, stomatitis virus, especially those that line structures that are either cytoplasmic vesicles or invaginations of the plasma membrane.
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Two separate protein factors that markedly stimulate DNA-dependent RNA polymerase have been partially purified from ribosome-free extracts of E. coli Q13 cells. These proteins appear to differ from sigma, M, H, psi, and the factor described by Mahadik and Srinivasan. The stimulation by either factor requires the presence of the sigma protein. Using RNA-DNA hybridization competition analyses, we also demonstrate that neither of the new factors preferentially stimulates the synthesis of ribosomal RNA. The purification, properties, and mechanism of action of these new factors are examined.
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The effect of chloramphenicol on the synthesis and accumulation of ribonucleic acid (RNA) in Bacillus subtilis was studied. In the presence of chloramphenicol, transfer RNA and ribosomal RNA were synthesized as rapidly 2 to 3 hr after challenge as they were just prior to the addition of the antibiotic. However, under the same conditions, net RNA accumulation ceased after only 30 to 45 min. The failure to accumulate RNA after this time resulted from a rapid degradation of ribosomal RNA synthesized in the presence of chloramphenicol and a slow degradation of mature ribosomes. Since transfer RNA was not appreciably degraded, the ratio of transfer RNA to total RNA increased during the challenge.
The presence of the altered lysine transfer ribonucleic acid (tRNA) in Bacillus subtilis spores is strongly dependent on the medium on which the cells were sporulated. Cells sporulated on synthetic media or dilute complex media contain little or none of the new component, whereas those sporulated on concentrated complex media accumulate the altered tRNA. The accumulation begins during the fifth or sixth stage of sporulation, the formation of the tunic, and the appearance of refractility, respectively. Mutants blocked early in sporulation differ in their ability to accumulate the altered tRNA when cultured on the same complex medium. Of the four mutants examined, one failed to accumulate any of the RNA, whereas a second contained the full complement characteristic of spores. The third and fourth mutant contained small amounts of the material. It is tentatively concluded that the accumulation of the altered lysine tRNA is not obligate to sporulation but is an epiphenomenon of the process.
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In multiple sclerosis, a demyelinating disease of young adults, there is a paucity of myelin repair in the central nervous system (CNS) which is necessary for the restoration of fast saltatory conduction in axons. Consequently, this relapsing disease often causes marked disability. In similar diseases of small rodents, however, remyelination can be quite extensive, as in the demyelinating disease caused by the A59 strain of mouse hepatitis virus (MHV-A59), a coronavirus of mice. To investigate when and where oligodendrocytes are first triggered to repair CNS myelin in such disease, we have used a complementary DNA probe specific for one major myelin protein gene, myelin basic protein (MBP), which hybridizes with the four forms of MBP messenger RNA in rodents. Using Northern blot and in situ hybridization techniques, we previously found that MBP mRNA is first detected at about 5 days after birth, peaks at 18 days and progressively decreases to 25% of the peak levels in the adult. We now report that in spinal cord sections of adult animals with active demyelination and inflammatory cells, in situ hybridization reveals a dramatic increase in probe binding to MBP-specific mRNA at 2-3 weeks after virus inoculation and before remyelination can be detected by morphological methods. This increase of MBP-specific mRNA is found at the edge of the demyelinating area and extends into surrounding areas of normal-appearing white matter. Thus, in situ hybridization with myelin-specific probes appears to be a useful method for detecting the timing, intensity and location of myelin protein gene reactivation preceding remyelination. This method could be used to elucidate whether such a reactivation occurs in multiple sclerosis brain tissue. Our results suggest that in mice, glial cells react to a demyelinating process with widespread MBP mRNA synthesis which may be triggered by a diffusible factor released in the demyelinated areas.
Transgenic mice of line M beta P3 express bacterial beta-galactosidase in oligodendrocytes but not other cells of the CNS. The marker enzyme, demonstrated histochemically or by immunostaining in oligodendrocyte cell bodies and along myelin internodes, appears at the time of myelination and persists thereafter; in transplantation experiments, the marker may serve to indicate both the source of particular cells and their state of differentiation. The subventricular zone of the lateral ventricle, grafted from transgenic to wild-type perinatal recipient mice, yields histochemically labeled oligodendrocytes in surrounding host tissue. When grafts are placed in cerebral cortex near callosal radiations, graft-derived oligodendrocytes are found in cerebral cortex and subcortical white matter as far as 1.5 mm from the site of implant but not in nearby caudoputamen. This study is the first to document differentiation of transplant-derived oligodendrocytes in normal developing CNS. Our results are consistent with the well-established notion that oligodendrocyte progenitors migrate during normal development and suggest that such migration might be guided or restricted by mechanisms yet to be identified.