Search PubMed⌕ Search

Biomedical subjects

M Misra

Publications and source records attributed to M Misra.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Configuration of subunits within crystals of Na, K-ATPase maintained in the frozen-hydrated state.

Two-dimensional crystalline sheets of Na, K-ATPase were studied in the vitrified, frozen-hydrated state by electron microscopy and image processing. The technique of correlation averaging was used to determine the projected structure. The projection map shows asymmetry between the pair of "alpha beta" protomers comprising a dimer of Na, K-ATPase molecules. The two protomers differ in overall density as well as in shape. One protomer has an oblong shape, whereas the other with higher density has a head and a hook region. Such an asymmetry has not been reported by other laboratories. This asymmetry may either be due to the coexistence of two different conformations of the enzyme in the dimeric form or due to the simultaneous existence of two molecular species of Na, K-ATPase.

Animals↗
PubMedDate not supplied

Nickel(II)-mediated oxidative DNA base damage in renal and hepatic chromatin of pregnant rats and their fetuses. Possible relevance to carcinogenesis.

DNA base damage was studied in renal and hepatic chromatin of nickel(II)-injected pregnant female F344/NCr rats and their fetuses under conditions leading to initiation of sodium barbital-promotable renal tumors, but not liver tumors, in the male offspring. Pregnant rats were given a total of 90 or 180 mumol of nickel(II) acetate/kg body wt in a single ip dose on day 17 or in 2 or 4 ip doses between days 12 and 18 of gestation. Control rats received 180 mumol of sodium acetate/kg body wt. The animals were killed 24 or 48 h after the last injection. Chromatin was isolated from livers and kidneys from both adults and fetuses and analyzed by gas chromatography/mass spectrometry with selected ion monitoring. Eleven products derived from the purine and pyrimidine bases in DNA bases were identified and quantified. These were the following: 5-hydroxy-5-methylhydantoin, 5-hydroxyhydantoin, 5-(hydroxymethyl)uracil, cytosine glycol, thymine glycol, 5,6-dihydroxycystosine, 4,6-diamino-5-formamidopyrimidine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyadenine, 2-hydroxyadenine, and 8-hydroxyguanine (8-OH-Gua). Nickel(II) exposure increased the content of these products, especially those derived from purines, in both renal and hepatic chromatin of pregnant rats. The major difference between these two organs was the content of 8-OH-Gua, which increased greatly in the kidney but remained unchanged in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Enhancement by L-histidine of nickel(II)-induced DNA-protein cross-linking and oxidative DNA base damage in the rat kidney.

Formation of DNA-protein cross-links and oxidatively damaged DNA bases was investigated with the use of alkaline elution and gas chromatography/mass spectrometry techniques in the nuclei from kidneys of rats 3 and 18 h after a single iv injection of the NiII(His)2 complex (NiHis), nickel(II) acetate (NiAcet), or L-histidine (His). Administration of 20 mumol of NiHis/kg body wt caused the formation of DNA-protein cross-links and significantly increased levels of oxidatively damaged DNA bases, including 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua; 3.5-fold vs the control value) 3 h postinjection and 8-oxoguanine (2.6-fold), cytosine glycol (2.5-fold), 8-oxoadenine (2-fold), and FapyGua (1.9-fold) 18 h postinjection. Injection of 20 mumol of NiAcet/kg body wt enhanced the cross-linking to a lesser extent than NiHis and did not significantly increase the amounts of modified DNA bases over the control levels. Forty micromoles of His per kilogram body wt alone caused a marked DNA-protein cross-linking effect and increased the amount of 4,6-diamino-5-formamidopyrimidine (2-fold vs the control) 3 h, but not 18 h, after treatment. The DNA base derivatives found were typical products of hydroxyl radical (.OH) attack on DNA. Formation of the cross-links may also be attributed to .OH, although other mechanisms, e.g., formation of ternary complexes of Ni(II), cannot be excluded. The present in vivo study confirms the conclusion of our former in vitro experiments that His enhances Ni(II)-mediated oxidative damage to DNA and chromatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The influence of light wavelength on reproductive photorefractoriness in migratory blackheaded bunting (Emberiza melanocephala).

There are two effects of long day length on reproductive responses in birds, one is the photoinduction of gonadal growth and maturation and the other is the induction of gonadal regression and photorefractoriness. Although it is likely that the same photoreceptors are involved in the photoinduction of gonadal growth and the onset and maintenance of photorefractoriness. and so the influence of wavelength should be similar, this has not been investigated. Therefore, we investigated the influence of light wavelength on reproductive photorefractoriness in the migratory male blackheaded bunting held under long photoperiods. In mid May, when photoperiod was approximately 14L:10D (14 hours light:10 hours darkness), eight groups of sexually mature birds were moved indoors on an artificial photoperiod of 14L:10D (L - 450 lux. D - 0 lux). Then after 3 weeks, for six groups, a 4-h light period in the morning (zt 0-4; zt 0 [zeitgeber time 0] refers to the beginning of lights-on period) or in the evening (zt 10-14) was substituted with green (428 nm), red (654 nm) or white light at 16 +/- 2 lux intensity. Of the remaining two groups, one was maintained on 14L: 10D and the other transferred to 10L:14D: these served as controls. At the end of 4 weeks, all birds were found to have undergone testicular regression, irrespective of LD cycle they were exposed to. When these gonadally regressed birds were subjected to 16L:8D for another 4 weeks, to test their responsiveness to the stimulatory effects of long day lengths, only those exposed to 10L:14D and 14L:10D with a 4-h green light period showed testicular regrowth. On the other hand, birds exposed to 14L:10D with a 4-h white or red light period remained fully regressed, similar to 14L:10D controls. Except for some individual difference, there was no difference in response between the groups that received a 4-h light period in the morning and that received it in the evening. These results suggest that the wavelengths of light influence induction of buntings from the photosensitive state into the photorefractory state. Whereas the short light wavelengths facilitated recovery from the photorefractoriness, the long light wavelengths were more effective in maintaining the photorefractoriness.

Animals↗
PubMedDate not supplied

An unusual orbito-cranial foreign body.

The rarity of orbito-cranial gun shot injury in both war and civilian practice has been reported. In a large series of 351 missile head injuries in the Vietnam war, orbital penetration was noted in 0.6% cases only. Review of literature shows that orbital injury was ipsilateral to the cerebral injury in most reported cases. We have previously reported a rare case of left parieto-occipital lobe injury due to gun shot wound of the contralateral (right) orbit. The case reported here sustained a bullet injury to the left frontal bone but the missile was located below the contralateral (right) optic canal. The rarity of the case prompted this report.

Adult↗
PubMedDate not supplied

Orbital reconstruction in fibrous dysplasia--a case report.

A case of orbitofrontal fibrous dysplasia with optic canal involvement is reported. Surgical excision of the mass with unroofing of the optic canal followed by orbito-cranian reconstruction by methyl methacrylate gave excellent results.

Adult↗