Biomedical subjects
Publications and source records attributed to N Malik.
We report a case of pancreatic endometriosis that presented as a renal mass. The patient had a history of recurrent left loin pain and pathological examination revealed pancreatic endometriosis, with huge cyst formation around the kidney. The clinicopathological features and the possible pathogenesis are discussed.
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Occurrence of renovascular hypertension and its etiology is described in this work as seen in north India. Out of 2395 young hypertensives admitted for evaluation during the years 1978-1983, 91 patients (3.8%) were found to be having renovascular hypertension. In all patients suspected diagnosis of RVH was confirmed by the angiography of aorta and main vessels. Idiopathic aortoarteritis, diagnosed in 54 patients (59.4%) was the commonest cause of renovascular hypertension. In this group renal arterial involvement was found to be bilateral in 26 patients. Twenty-eight patients had isolated renal artery stenosis of unknown etiology. Six had fibromuscular dysplasia, 2 had polyarteritis and one had renal artery aneurysm. Twenty-three patients underwent surgery which included autotransplantation, arterial by-pass and nephrectomy with improved blood pressure control in 15. It is concluded that aortoarteritis seems to be the major cause of renovascular hypertension in the young in this part of the world.
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The chromatin-associated enzyme poly(ADP-Rib) polymerase catalyzes the posttranslational modifications of histones. Antibody to poly(adenosine diphosphate ribose) [poly(ADP-Rib)] has been coupled to Sepharose, and the resulting immunoadsorbant was used to fractionate, specifically, oligonucleosomes derived from cells pulse labeled for the acetylation modifications of chromatin by incubation with [3H]acetate followed by treatment with sodium butyrate. Generally, about 50% of the histone H3 and H4 mass becomes acetylated under these conditions. Pulse-labeled acetylated regions of chromatin were selectively retained by the anti-poly(ADP-Rib)-Sepharose column due to the presence of endogenous poly(ADP-Rib) components. The data suggest that certain histone molecules might be mutally poly(ADP-ribosylated) and acetylated, and this phenomenon was further explored at the protein level in the accompanying paper [Wong, M., & Smulson, M. (1984) Biochemistry (following paper in this issue)].
The possibility that chromatin domains containing acetylated histones are proximal to domains containing chromosomal high mobility group protein 17 (HMG-17) has been investigated. Oligonucleosomes containing [3H]acetate-labeled histones have been immunofractionated on anti-HMG-17 IgG-Sepharose columns. Ninety-one per cent of the 3H counts present in the oligonucleosomes specifically bound to the anti-HMG-17 column. Extraction of HMG-17 from chromatin by treatment with 0.4 M NaCl abolished the specific binding of acetylated chromatin to the Sepharose columns. Autoradiographic analysis of polyacrylamide gels of the bound fraction revealed that it contained all the major acetylated histone species. We conclude that acetylated histones are present on or near nucleosomes containing protein HMG-17.
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Antibody to poly(ADP-ribose) has been covalently coupled to Sepharose and utilized to isolate selectively oligonucleosomes undergoing the poly(ADP-ribosyl)ation reaction from the bulk of chromatin. Approximately 12% of the unfractionated oligonucleosomes were bound to the immunoaffinity column and these represented essentially 100% of the original poly(ADP-ribosyl)ated nucleosomal species in the unfractionated chromatin. Poly(ADP-ribosyl)ated chromatin was not bound by preimmune IgG columns. KSCN eluted the modified nucleosomes in the form of nucleoprotein complexes. The eluted chromatin components were shown to contain poly(ADP-ribosyl)ated histones as well as automodified poly(ADP-ribose) polymerase. By using [3H]lysine- and [3H]arginine-labeled chromatin, it was shown that the poly-(ADP-ribosyl)ated histones, attached to stretches of oligonucleosomes bound to the column, had a 6-fold enrichment of the modification compared to histones of the unfractionated chromatin. This indicated that non-poly(ADP-ribosyl)ated nucleosomes, connected and proximal to the modified regions, were copurified by this procedure. This allowed characterization of the oligonucleosomal DNA around poly(ADP-ribosyl)ated chromatin domains to be compared with the unbound bulk chromatin. The data indicated that immunofractionated poly(ADP-ribosyl)ated oligonucleosomal DNA contained significant amounts of internal single-strand breaks compared with bulk chromatin. The bound nucleo-protein complexes were found to be enzymatically active for poly(ADP-ribose) polymerase after elution from the antibody column. In contrast, the unbound nucleosomes, representing 90% of the unfractionated chromatin, were totally inactive in the poly(ADP-ribosyl)ation reaction.
Up to 550 ppm (550 micrograms/ml) of nisin in combination with 60 ppm (60 micrograms/ml) of nitrite failed to prevent outgrowth of Clostridium botulinum spores in pork slurries adjusted to pH 5.8. Reducing the pH enhanced nisin activity. Proteolytic and nonproteolytic type B spores were equally resistant to nisin.
The host nuclear enzyme poly(ADP-ribose) polymerase has been shown to be associated with the replicative intermediate and mature forms of polyoma virus minichromosomes. Minichromosome-associated histones H2A and H2B as well as several nonhistone proteins were poly ADP-ribosylated by endogenous poly(ADP-ribose) polymerase. In addition, minichromosome fractions catalyzed the formation in vitro of dimers of endogenous histone H1 linked by poly(ADP-ribose). Poly ADP-ribosylated polyoma virus minichromosome chromatin labeled in vivo with [3H]thymidine could be retained and eluted from anti-poly(ADP-ribose) immunoglobulin G-Sepharose. Pulse-labeled replicative intermediate minichromosomes were retained better on the antibody columns than were mature minichromosomes labeled for 2.5 h. The possible role of poly ADP-ribosylation of viral nucleosomes during polyoma replication or transcription is discussed.
The focus of our laboratory has been to ascertain how the poly(ADP-ribosyl)ation reaction influences the structure and biological function of nucleosomal chromatin. Antibody to poly(ADP-ribose (ADP-Rib] was coupled to Sepharose to prepare an immunoaffinity column. The following new information concerning poly(ADP-Rib) and chromatin was obtained with this column: 1) those limiting domains of nucleosomal chromatin undergoing the modification (circa 10%) could be isolated in the "bound" fraction, 2) antibody-bound nucleosomes contained all the poly ADP-ribosylated acceptors and polymerase activity of the bulk chromatin, 3) bound nucleosomes contain significant numbers of internal DNA strand breaks, and [3H]-thymidine (TdR) repair incorporation from in vivo "DNA repair label," compared to the unbound, bulk of the chromatin, 4) the presence of actively transcribed genes in "bound" nucleosomes is being investigated, 5) the acetylation modification of histones occurs in the same domains of chromatin as does poly(ADP-ribosyl)ation, and 6) poly ADP-ribosylated histone H1 can be selectively purified by the immunoaffinity method. These same histone H1 molecules appear to be equally accessible to the histone kinase, phosphorylation modification. In addition, new information has been obtained concerning histone H1 cross-linking by poly(ADP-ribosyl)ation, and on polymerase binding sites to chromatin. We have reconstituted histone H1-depleted chromatin with intact H1 and peptide domains of H1, and subsequently studied H1-poly(ADP-Rib)-complex synthesis. The data indicate that elongation of poly(ADP-Rib) proceeds on the amino terminal region of this histone. By utilizing the new techniques of DNA technology, huge advances in our understanding of the programmed structure of the eukaryotic genome have been accomplished in a relatively short time. To complement this explosion of information, it is important to ascertain how these recently appreciated properties of eukaryotic DNA are packaged within extended and condensed domains of chromatin. The research to be discussed is directed, in part, at this latter topic. We have initiated a program aimed at furthering our comprehension of chromatin structure by studying one specific, enzymatically active chromosomal protein.
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To facilitate investigations on the organization of poly (ADP-Rib) polymerase in chromatin, and to elucidate its biological function, polymerase purified from HeLa nuclei was used to elicit antibodies in mice. The anti-polymerase sera was found to be specific by multiple criteria. The association of polymerase with oligonucleosomes of differing chain size was determined by the specific binding of polymerase antibody (and as control, anti-histone H3) to nitrocellulose transfers of native electrophoretic gels of these particles. By this technique, polymerase appears to be associated with a select subclass of nucleosomes. Further resolution of the polymerase binding sites within nucleosome classes was achieved with the antibody by two-dimensional native polyacrylamide gel electrophoresis and nitrocellulose transfer.
The chromatin-associated enzyme poly(ADP-Rib) polymerase causes an NAD-dependent crosslinking of modified oligonucleosomes, as demonstrated by electrophoretic and sedimentation analysis [Butt, T. R. and Smulson, M. (1980) Biochemistry, 19, 5235-5242]. It was speculated that poly(ADP-ribosyl)ation of histone H1 and subsequent formation through crosslinking to an H1 dimer may be an important component of this phenomenon. To study this process, a method of complexing histone H1 to chromatin was required that promoted the restoration of accurate poly(ADP-ribosyl)ation of this histone. Previously we have established that two histone H1 molecules are crosslinked by a chain of poly(ADP-Rib) 15 or 16 units in length. In the current study, we made use of the ability of oligonucleosomes, reconstituted with H1, to carry out the synthesis of the poly(ADP-Rib)-H1 complex in order to monitor the accuracy of reconstitution. It appears that a specific distance and juxtaposition of adjacent H1 molecules along the polynucleosome fiber is required for the enzymatic synthesis of this modified histone complex. We established that a controlled trypsin digestion of oligonucleosomes removed H1 histone with minimal perturbation of other nuclear proteins associated with chromatin. In addition, poly(ADP-Rib) polymerase was partially removed from chromatin by this procedure. Subsequently, methods utilizing gradient salt dialysis have been employed to reconstitute both the polymerase and histone H1 to the depleted oligonucleosomes. The reassociation of H1 (and polymerase) to specific binding sites within oligonucleosomes was accomplished by the above procedures. Poly(ADP-Rib)--H1-dimer synthesis was not observed in depleted oligonucleosomes, but this capacity was found to be partially restored in the reconstituted chromatin. Similarly, the ability of NAD to promote crosslinking of nucleosomes was restored in the reconstituted samples. These results provide a basis for further studies on how the poly(ADP-ribosyl)ation of histones alters the structure of chromatin.
Two methods for the direct isolation of spontaneous ssd mutants of Escherichia coli K-12 strains are described; (i) by growth with L-serine as the carbon source, and (ii) by low-level kanamycin resistance. A newly isolated mutant had the same phenotype as the mutant described previously, including inefficient use of the glucose, inability to growth with succinate, altered transport characteristics, and altered resistance to certain growth effectors. Succinate-utilizing derivatives which appear to be intragenic are characterized in detail. The relation between the mutants isolated here and mutants which are thought to have impairment in a system of coupling respiratory energy to active transport (ecfB mutants) is discussed.
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