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S Pande

Publications and source records attributed to S Pande.

At least 37 records · Page 2Linked to original sources
PubMed1996

Determination of proteins secreted by growing rat decidual cells in vitro.

Proteins secreted by rat decidual cells while growing in culture medium were monitored on gel electrophoresis. It was done by assuming that outgrowing cells in vitro mimic differentiated endometrial stromal tissue in vivo following attachment of embryo. The decidual cells were obtained from implantation swellings of day 10 pregnant rats, maintained in serum free medium and the cell dependent protein profile was analysed after 48 hr on single dimensional polyacrylamide gel electrophoresis (SDS-PAGE). The proteins identified were in molecular weight range of 29, 43 and 66 kDa respectively. The result indicated involvement of the differentiated stromal cells in secreting these low molecular weight proteins.

Animals↗
PubMed1995

Surface morphology of hamster (Mesocricetus auratus) decidual cells in vitro.

Cell surface morphology of hamster decidual cells isolated from day 8 implantation swellings was studied, using both phase-contrast and scanning electron microscopy. Two kinds of cells, fibroblastic and epithelioid, were identified in cultures examined by phase-contrast microscopy. Fibroblastic cells were spindle-shaped, having pointed or blunt terminals on one end and bifid or webbed projections at the other end. Epithelioid cells, on the other hand, were flat and discoid, having a distinctively ruffled plasma membrane. Further, the plasma membrane of epithelioid cells formed rope-like or flange-like processes. The significance of such adaptations is discussed.

Animals↗
PubMed1995

Pulling the ribosome out of frame by +1 at a programmed frameshift site by cognate binding of aminoacyl-tRNA.

Programmed translational frameshifts efficiently alter a translational reading frame by shifting the reading frame during translation. A +1 frameshift has two simultaneous requirements: a translational pause which occurs when either an inefficiently recognized sense or termination codon occupies the A site, and the presence of a special peptidyl-tRNA occupying the P site during the pause. The special nature of the peptidyl-tRNA reflects its ability to slip +1 on the mRNA or to facilitate binding of an incoming aminoacyl-tRNA out of frame in the A site. This second mechanism suggested that in some cases the first +1 frame tRNA could have an active role in frameshifting. We found that overproducing this tRNA can drive frameshifting, surprisingly regardless of whether frameshifting occurs by peptidyl-tRNA slippage or out-of-frame binding of aminoacyl-tRNA. This finding suggests that in both cases, the shift in reading frame occurs coincident with formation of a cognate codon-anticodon interaction in the shifted frame.

Anticodon↗
PubMed1995

Peptidyl-tRNAs promote translational frameshifting.

Programmed translational frameshifting is a ubiquitous, though rare, mechanism of gene expression in prokaryotes and eukaryotes. Research on many such sites has led to a general understanding that frameshifting depends on slippage of one or two ribosome-bound tRNAs on the mRNA. We recently found an example of an efficient frameshift in the Ty3 retrotransposon of the yeast Saccharomyces cerevisiae which occurs without tRNA slippage. Frameshifting appears to occur by misplacement of aminoacyl-tRNA in the ribosomal A site. Most of the eight tRNAs which induce measurable amounts of +1 frameshifting are predicted to slip only very poorly. In fact, frameshifting by tRNA slippage appears an unusual event in yeast, and where it occurs depends on peptidyl-tRNAs which employ two-out-of-three decoding. In addition, frameshifting either by slippage or by aminoacyl-tRNA misplacement depends on adequate availability of the first +1 frame tRNA. We present two models to explain how the tRNA which reads the shifted frame codon could promote +1 translational frameshifting.

Base Sequence↗
PubMed1993

A rare tRNA-Arg(CCU) that regulates Ty1 element ribosomal frameshifting is essential for Ty1 retrotransposition in Saccharomyces cerevisiae.

Translation of the yeast retrotransposon Ty1 TYA1(gag)-TYB1(pol) gene occurs by a +1 ribosomal frameshifting event at the sequence CUU AGG C. Because overexpression of a low abundance tRNA-Arg(CCU) encoded by the HSX1 gene resulted in a reduction in Ty1 frameshifting, it was suggested that a translational pause at the AGG-Arg codon is required for optimum frameshifting. The present work shows that the absence of tRNA-Arg(CCU) affects Ty1 transposition, translational frameshifting, and accumulation of mature TYB1 proteins. Transposition of genetically tagged Ty1 elements decreases at least 50-fold and translational frameshifting increases 3-17-fold in cells lacking tRNA-Arg(CCU). Accumulation of Ty1-integrase and Ty1-reverse transcriptase/ribonuclease H is defective in an hsx1 mutant. The defect in Ty1 transposition is complemented by the wild-type HSX1 gene or a mutant tRNA-Arg(UCU) gene containing a C for T substitution in the first position of the anticodon. Overexpression of TYA1 stimulates Ty1 transposition 50-fold above wild-type levels when the level of transposition is compared in isogenic hsx1 and HSX1 strains. Thus, the HSX1 gene determines the ratio of the TYA1 to TYA1-TYB1 precursors required for protein processing or stability, and keeps expression of TYB1 a rate-limiting step in the retrotransposition cycle.

Base Sequence↗
PubMed1993

Reverse single radial immunodiffusion for estimation of titre of anti IgG antibody.

Reverse Single Radial Immunodiffusion (SRID) for estimating titre of anti IgG antisera is reported. Unlike the conventional radial immunodiffusion, the antigen (IgG) is held immobile in the gel while the antibody (Anti IgG) diffuses radially from the well (7 microliters) and the diameter of the resulting immuneprecipitates after immunodiffusion at 4 degrees C for 24 hr, represents a linear correlation with the antibody titre. The procedure was standardised by an extensive trial and error employing different concentrations of human IgG in the gel (60-240 micrograms) against varying dilutions of the standard antibody (titre: 3.8 mg/ml). The best results were obtained at 80 micrograms of IgG in the gel. The locally raised rabbit anti IgG antisera displayed a distinctive titre pattern under optimised conditions. Technical reproducibility, high-sensitivity threshold (0.25 mg/ml), simultaneous visual scrutiny of several antibody batches at a glance and ability to assess the shelf life of the stored antisera are its distinct assets.

Antibodies, Anti-Idiotypic↗
PubMed1992

Evidence that a 1.6 kilobase region of Neurospora mtDNA was derived by insertion of part of the LaBelle mitochondrial plasmid.

The LaBelle mitochondrial plasmid hybridizes to a small region of the mtDNA of different Neurospora species. Here, we show that the region of homology encompasses 1385 bp of plasmid sequence and 1649 bp of mtDNA sequence. Several findings--that the region of homology is not found in the mtDNAs of other organisms, that it includes the C-terminus of the ORF encoding the plasmid DNA polymerase, and that the ORF sequence in the mtDNA is interrupted by insertions--suggest that the region was part of the plasmid that integrated into mtDNA prior to the divergence of Neurospora species. Since the LaBelle plasmid has been found in only one Neurospora strain, we infer that the plasmid was lost subsequently from most strains. The LaBelle plasmid is transcribed by the host Neurospora mitochondrial RNA polymerase and the major promoter is located upstream of the long ORF, within the region of homology to mtDNA. A promoter used for the transcription of the mitochondrial small rRNA is found at a corresponding position in Neurospora mtDNA and may have been acquired via integration of the plasmid sequence. Our results provide evidence that an autonomous infectious element may contribute to sequences that functionally constitute an organism's mtDNA.

Base Sequence↗
PubMed1991

Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. I. Purification and physical properties.

Compared to other tRNAs all known histidine tRNAs have the unique feature of possessing an additional nucleotide at their 5' end. It is usually a guanosine residue but not in bacteriophage T5 tRNA which carries an additional uridine. The additional nucleotide is not encoded in eukaryotic histidine tRNA genes but is added in a post-transcriptional modification reaction (Cooley, L., Appel, B., and Söll, D. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 6475-6479) by histidine tRNA guanylyltransferase (tRNAHis guanylyltransferase). Here we report the purification of this enzyme from Saccharomyces cerevisiae and the determination of some of its physical properties. Six different steps including Polymin P precipitation, chromatography on DEAE-cellulose, phosphocellulose, heparin-agarose, ATP-agarose, and gel filtration on Superose 12 were employed for the purification of the guanylyltransferase from an S-100 extract. A Stokes radius of 46.5 +/- 0.5 A and a sedimentation coefficient (S20,w) of 7.8 +/- 0.2 were determined by gel filtration and rate zonal sedimentation, respectively. A relative molecular weight (Mr) of approximately 120,000 was calculated for the purified native enzyme. The Mr of the denatured protein is approximately 58,000 as demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicate a homodimeric (alpha 2) structure for the enzyme. Among all acceptor RNAs in unfractionated tRNA only tRNAHis is a substrate for the purified guanylyltransferase. The reaction requires ATP, a guanosine substrate, and a divalent metal ion. Treatment of guanylyltransferase with 5,5'-dithiobis(2-nitrobenzoic)-acid abolishes activity; this suggests the importance of sulfhydryl groups for enzymatic activity. The enzyme shows discrimination among different histidine tRNA species; tRNA from plant and prokaryotes are better substrates than mammalian and insect tRNAs.

Adenosine Triphosphate↗
PubMed1991

Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. II. Catalytic mechanism.

Yeast histidine tRNA guanylyltransferase (TGT) catalyzes in the presence of ATP the addition of GTP to the 5' end of eukaryotic cytoplasmic tRNAHis species. A study of the enzyme mechanism with purified protein showed that during the first step ATP is cleaved to AMP and PPi creating adenylylated TGT. In a second step the activated enzyme forms a stable complex with its cognate tRNA substrate. The 5'-phosphate of the tRNA is adenylylated by nucleotide transfer from the adenylylated guanylyltransferase to form A(5')pp(5')N at the 5'-end of the tRNA. Finally, the 3'-hydroxyl of GTP adds to the activated 5' terminus of the tRNA with the release of AMP. This mechanism of tRNAHis guanylyltransferase is very similar to that of RNA ligases. dATP can substitute for ATP in this reaction. Since among several guanosine compounds active in this reaction GTP is most efficiently added we believe that it is the natural substrate of TGT.

Adenine↗
PubMed1989

The mitochondrial plasmid from Neurospora intermedia strain Labelle-1b contains a long open reading frame with blocks of amino acids characteristic of reverse transcriptases and related proteins.

We have determined the DNA sequence of the 4070 base pair mitochondrial plasmid from the Labelle-1b strain of Neurospora intermedia. Analysis of the sequence revealed that the plasmid contains a long open reading frame (ORF) that could encode a protein of up to 1151 amino acids. Codon usage in the long ORF shows no clear relationship to Neurospora mitochondrial genes, nuclear genes, nor to the ORF of a different Neurospora mitochondrial plasmid. The long ORF contains regions of similarity to yeast mitochondrial RNA polymerase as well as blocks of amino acids that are characteristic of reverse transcriptases and the ORFs of certain group II mtDNA introns (Michel and Lang, (1985) Nature 316,641). The plasmid gives rise to specific transcripts, some of which may be unit length, and which carry the information for expression of the long ORF. The genetic organization and content of the plasmid suggest that it is related to mobile genetic elements.

Amino Acid Sequence↗
PubMed1988

Fundamental considerations in pacing of the diaphragm for chronic ventilatory insufficiency: a multi-center study.

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results from the Center group yielded information on the early experience with diaphragm pacing important to its future application.

Diaphragm↗
PubMed1985

Pediatric Hodgkin's disease in India.

Twenty-one percent of all Hodgkin's disease in India was seen in the pediatric age groups at the Tata Memorial Hospital (Bombay, India). From 1975 to 1982, 151 cases of children were reviewed. The youngest presentation was at 3 years in three patients, with a marked male: female ratio of 5.5:1. Twenty-six patients were previously treated before referral while the remaining 125 cases were investigated and treated according to the prevalent protocols in 1975 to 1978 and 1979 to 1982. Clinical staging revealed 54% of patients in stages I and II with symptoms in 20%, and 46% of patients in stages III and IV with symptoms in 67%. Staging laparotomy was performed in 27 patients, with a total changes of staging in 17 children (63%). The mixed cell types (46%) and lymphocytic predominant types (31%) were the most common histologic presentations. Nine percent nodular sclerosis and 9% lymphocytic-depleted varieties were also observed. Five percent of all cases were not classifiable. Minimum adequate treatment was completed in 87 cases. Comparisons were made between the treatments administered to 40 patients during the initial period 1975 to 1978 when individualized treatment was administered, and the later 47 patients during the 1979 to 1982 period, when chemotherapy was the mainstay of treatment with involved field radiation.

Actuarial Analysis↗