Search PubMed⌕ Search

Biomedical subjects

A Basu

Publications and source records attributed to A Basu.

At least 145 records · Page 8Linked to original sources
PubMed1995

IPEB transcription factor regulating the intracisternal A particle gene during F9 cell differentiation is expressed at sites of lymphoid development.

The murine intracisternal A particle (IAP) proviral elements are expressed at low levels in undifferentiated F9 embryonal carcinoma cells but are highly expressed when F9 cells are induced to differentiate into parietal endoderm-like cells. IAP elements are also expressed in parietal endoderm-like PYS-2 cells. We previously identified an IAP proximal enhancer (IPE) element that mediates a F9 differentiation-specific enhancer activity. We also identified a 60 kDa IPE binding (IPEB) protein whose activity is high in PYS-2 cells, where IAP is expressed, but very low in F9 cells. Transcription of IAP elements has also been shown in the adult mouse thymus and in activated splenic B cells. We have now shown by DNA affinity chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and band-shift analysis that the 60 kDa IPEB is expressed in adult T lymphocytes and in resting as well as lipopolysaccharide activated splenic B cells but not in adult liver cells, suggesting an important role for IPEB in IAP transcription in vivo. In addition, we find IPEB expressed in the fetal mouse at sites of lymphoid development, such as the liver, spleen, and thymus, suggesting it may play an important role in gene expression during lymphoid development. In support of this, we find IPEB in the human T cell tumor lines, Jurkat and Molt 13, as well as the Daudi B cell line and in the normal calf thymus and in the thymus and spleen of the chicken and rat.

Animals↗
PubMed1995

Views on the sustenance of resistant Mycobacterium tuberculosis in the environment.

Microbial resistance to conventional as well as newly introduced drugs is a hallmark feature of several infectious diseases, notably tuberculosis. It is hypothesized that the greater the selective pressure exerted by increasingly potent drugs, the more rapidly is an organism able to adapt to a drug-containing environment. The roles of drug-containing environments, and the immunological status of the host and bacterial molecular mechanisms of development of drug resistance to Mycobacterium tuberculosis have been examined and examples cited for implementation of modified drug regimens in tuberculosis-control programmes. The views expressed, albeit restricted to Mycobacterium tuberculosis, encourage consideration of drug regimens on a disease evolution basis as well as understanding of the natural rules that govern development and sustenance of drug resistance in the microbial world.

Antitubercular Agents↗
PubMed1995

Lunar soil evolution processes and Apollo 16 core 60013/60014.

Soils of the 62-cm deep Apollo 16 double drive tube 60013/14 are mature at the top and submature at the bottom. Modal analyses of 5529 grains from the 90-150 micrometers and the 500-1000 micrometers fractions from 12 levels of the core show that, in general, agglutinate abundance increases somewhat monotonically to the top and mimics the Is/FeO profile. There is a general decrease in the modal abundance of monomineralic fragments towards the top, suggesting that agglutinates were formed in part at the expense of monomineralic grains, especially feldspars, which are by far the most abundant mineral in these soils. In detail, the top 27 cm of the core differs from the bottom 21 cm, and the middle 14 cm is intermediate in its properties. In the upper segment, variations in the abundances of feldspars correspond with those of feldspathic fragmental breccias and cataclastic anorthosites; in the bottom segment, a similar but weak correspondence between feldspars and crystalline matrix breccias is observed. Mixing of the comminuted products of these three rock types likely produced the bulk of the core material. Many single feldspars in all size fractions are remarkably fresh, show no damage from shock, and are similar in appearance to the large feldspars in anorthosites and feldspathic fragmental breccias, which we consider to be the primary sources of single feldspars in this core. Major (Na, Al, Si, K, Ca) and minor (Fe, Ba) element analyses of 198 single feldspar grains indicate the presence of only one population of feldspars, which is consistent with our interpretation of feldspar provenance. Classification of 890 monomineralic feldspar, olivine, pyroxene, and glass spherules on the basis of the presence or absence of thin brownish coating--related to reworking at the surface--shows that coated grains are much more abundant in the top segment than in the bottom segment. A comparison with the mixing and maturation model (McKay et al., 1977) of soils in the core 60009/10, some 60 m away from 60013/14, shows that mixtures of an immature, nearly pure plagioclase soil (dominant in 60009/10) and another immature, crystalline breccia-rich soil (dominant in 60013/14) may have matured through in situ reworking to produce the soils under investigation. We conclude that the soils in this core are products of mixing along soil evolution Path 2 of McKay et al. (1974). Superimposed on that soil column is the reworking of the upper part, which has evolved more recently along Path 1. This core thus represents a consanguineous column of the lunar regolith with an upper reworked segment.

Aluminum Silicates↗
PubMed1995

Identification of a stable RNA encoded by the H-strand of the mouse mitochondrial D-loop region and a conserved sequence motif immediately upstream of its polyadenylation site.

By using a combination of Northern blot hybridization with strand-specific DNA probes, S1 nuclease protection, and sequencing of oligo-dT-primed cDNA clones, we have identified a 0.8 kb poly(A)-containing RNA encoded by the H-strand of the mouse mitochondrial D-loop region. The 5' end of the RNA maps to nucleotide 15417, a region complementary to the start of tRNA(Pro) gene and the 3' polyadenylated end maps to nucleotide 16295 of the genome, immediately upstream of tRNA(Phe) gene. The H-strand D-loop region encoded transcripts of similar size are also detected in other vertebrate systems. In the mouse, rat, and human systems, the 3' ends of the D-loop encoded RNA are preceded by conserved sequences AAUAAA, AAUUAA, or AACUAA, that resemble the polyadenylation signal. The steady-state level of the RNA is generally low in dividing or in vitro cultured cells, and markedly higher in differentiated tissues like liver, kidney, heart, and brain. Furthermore, an over 10-fold increase in the level of this RNA is observed during the induced differentiation of C2C12 mouse myoblast cells into myotubes. These results suggest that the D-loop H-strand encoded RNA may have yet unknown biological functions. A 20 base pair DNA sequence from the 3' terminal region containing the conserved sequence motif binds to a protein from the mitochondrial extracts in a sequence-specific manner. The binding specificity of this protein is distinctly different from the previously characterized H-strand DNA termination sequence in the D-loop or the H-strand transcription terminator immediately downstream of the 16S rRNA gene. Thus, we have characterized a novel poly(A)-containing RNA encoded by the H-strand of the mitochondrial D-loop region and also identified the putative ultimate termination site for the H-strand transcription.

Adenine↗
PubMed1995

A novel transcriptional initiator activity of the GABP factor binding ets sequence repeat from the murine cytochrome c oxidase Vb gene.

The murine cytochrome c oxidase (COX) subunit Vb mRNA contains heterogeneous 5' ends mapping to +1, +6, +12, +17-22, +24-29, and +32-35 positions of the gene. We have previously shown that initiation of RNA at the +1 position of the promoter depends upon a YY-1 (NF-E1) binding initiator motif. In this article we show that the GABP factor binding duplicated ets motif, GTTCCCGGAAG, at +16 to +26 position functions as an independent initiator for transcription of RNAs mapping to the +18-19 and +23-26 regions. The initiation region ets sequence repeat (ets-ets sequence) can drive the transcription of the CAT reporter gene. The upstream ets site of the ets-ets sequence exhibits a low affinity for binding to purified GABP factors, whereas the downstream site exhibits high affinity. S1 analyses of RNA from transfected COS cells demonstrate that the initiation region ets-ets sequence can accurately initiate transcription at the +18-19 and +24-25 regions. Transcriptional initiation at these two positions, but not at +1, +12, and +31-32 positions, show a selective dependence for intact downstream ets site and GABP alpha and beta factors as tested in an in vitro reconstituted system. The activities of both COX IV and COX Vb single site ets initiators are induced in vivo by coexpression with GABP alpha and beta cDNAs. These results provide evidence that the 5' heterogeneity of the COX Vb mRNA is largely due to independent transcription initiators at multiple initiator motifs that bind to various transcription factors.

3T3 Cells↗
PubMed1994

Cloning of a human cDNA encoding a putative nucleotide-binding protein related to Escherichia coli MinD.

A novel human cDNA encoding a putative nucleotide-binding protein (NBP) was obtained by screening a human SHSY5Y neuroblastoma library. The deduced protein contains 320 amino acids (aa) with a M(r) of 34,540. NBP displays sequence similarity with the product of the minD gene from Escherichia coli. MinD is involved in the proper placement of the division septum, and has ATPase activity. NBP and MinD contain consensus nucleotide (nt)-binding domains. The NBP mRNA is approx. 1500 nt in length and is expressed in several human cell lines and in all rat tissues examined, with the highest levels in lung and testis.

Adenosine Triphosphatases↗
PubMed1994

Comparison of effects of growth factors and protein kinase C activators on cellular sensitivity to cis-diamminedichloroplatinum(II).

The anti-proliferative activity of the DNA-interactive anti-cancer agent cis-diamminedichloroplatinum(II) (cDDP) can be modulated by intracellular signaling systems. We have investigated the effects of growth factors on the sensitivity of human cervical carcinoma (HeLa) cells to cDDP. A 24-hr pretreatment of HeLa cells with 10 ng/ml epidermal growth factor (EGF) or transforming growth factor-alpha increased the anti-proliferative activity of cDDP by 2- to 4-fold. A similar pretreatment of HeLa cells with EGF did not alter cellular sensitivity to doxorubicin or vincristine. A brief exposure (15 min) to growth factors was not sufficient for cDDP sensitization. EGF caused a modest and transient increase in cellular diacylglycerol, the endogenous activator of protein kinase C. Bryostatin I, a partial agonist of protein kinase C, antagonized phorbol ester-mediated cDDP sensitization but had no effect on EGF-mediated sensitization to cDDP. Both EGF and phorbol 12,13-dibutyrate (PDBu) enhanced the rate of [195mPt]cDDP uptake but had no effect on the rate of [195mPt]cDDP efflux in HeLa cells. Bryostatin I reversed the increase in [195mPt]cDDP content by PDBu but failed to block EGF-induced increase in [195mPt]cDDP accumulation. Therefore, although the mechanism of cDDP sensitization by both EGF and phorbol ester appears to involve enhanced drug uptake, they may utilize distinct signal transduction pathways.

Bryostatins↗
PubMed1994

Kinetics of ligand binding of cytochrome oxidases: a comparative study.

The plethora of microbial oxidases revealed by photochemical action spectra (Chance, B. (1989)) Biochim. Biophys. Acta 1000, 345-347) has led to detailed identification, purification and overproduction in many species, to the point where kinetic comparison of properties seems to allow structure/function deductions. This work compares the carbon monoxide recombination of five types of oxidases obtained from various organisms. The results are plotted in an Arrhenius-type plot and suggest that the carbon monoxide ligation is a sensitive indicator of the heme environment specific for an oxidase expressed under a given oxygen concentration. This survey of the carbon monoxide recombination kinetics of naturally occurring cytochrome oxidases in whole cells shows evidence for structural control of the reaction kinetics.

Animals↗
PubMed1994

Characterization of cluster 13: the epithelial/carcinoma antigen recognized by MAb RS7.

Cluster 13 was defined by 2 independently derived murine monoclonal antibodies (MAbs), RS7 (IgG1) and MR54 (IgG2a), which were raised against human squamous-cell carcinoma of the lung and a human ovarian-carcinoma cell line, respectively. Immunologic and biochemical evidence demonstrated that RS7 and MR54, as well as 2 additional MAbs, MR6 (IgG2a) and MR23 (IgG1), generated in the same fusion as MR54, recognize the same antigen, a 46- to 48-kDa glycoprotein. Evaluation of the expression of antigen on the surface of tumor cell lines, Western blotting analyses, competitive binding studies, and double-determinant ELISA assays, support this conclusion. Two distinct epitopes are defined by these MAbs. In order to further characterize this antigen, amino-acid-sequence analyses were performed on peptides derived from antigen purified by affinity chromatography with MAb RS7. The sequence data obtained from 2 peptides, which were independently generated by CNBr cleavage and trypsin digestion respectively indicated identity to GA733-1. The GA733-1 genomic DNA sequence predicted a type-1 membrane protein of 35 kDa, with 4 potential N-linked glycosylation sites. The GA733-1 protein product has not been identified previously, and MAbs to this tumor-associated antigen were not previously known.

Amino Acid Sequence↗
PubMed1994

A three-dimensional representation of an athletic female knee joint using magnetic resonance imaging.

Intense interest in knee joint mechanics has resulted in the development of numerous models to predict forces acting at the knee. However, few models have accounted for the unique geometric characteristics of the knee joint's articular surfaces when predicting the mechanical response of the joint. The purpose of this study was to stimulate accurately the complex geometric characteristics of the tibiofemoral joint for input into a finite element model representing the knee joint of athletic females. The right knee of an athletic female with no history of knee joint trauma was imaged using a 0.5 T magnetic resonance imaging (MRI) unit. Twelve cross-sectional slices of the knee were scanned in each of three orthogonal planes (coronal, sagittal and axial) at slice intervals of 6 mm, 7 m, and 8 mm respectively. A scan plan (two coronal images and an axial image) was also generated to enable calculation of the orthogonal scans with respect to one another. Select anatomical reference points representing cancellous and compact bone, major ligament attachment areas, and articular cartilage of the distal femur and proximal tibia were digitized from the processed shadowgraphs. The processed digitized data were input into a computer graphics program which was the pre- and post-processing software for the finite element analysis package. Contours of the cancellous and compact bone of the tibial and femoral condyles were generated using beta and cubic spline curves. Bezier quadratic and cubic polynomials were used to reconstruct the tibial and femoral shafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Engineering of the human-immunodeficiency-virus-type-1 (HIV-1) reverse transcriptase gene to prevent dimerization of the expressed chimaeric protein: purification and characterization of a monomeric HIV-1 reverse transcriptase.

We report here a human-immunodeficiency-virus-type-1 (HIV-1) recombinant reverse transcriptase (RT) engineered to contain a 26-amino-acid linker insertion from the tether domain of feline leukaemia virus (FLV) RT. The chimaeric protein was expressed in Escherichia coli and migrated on SDS/PAGE as a 68 kDa band. A monomeric form of the chimaeric HIV-1 RT has been prepared by the coordinated applications of immobilized-metal-affinity chromatography and gel filtration on Superose 12 columns. The monomeric nature of this chimaeric HIV-I RT was further characterized by cross-linking studies using disuccinimidyl suberate. The RNA-dependent DNA polymerase activity of the monomeric chimaeric HIV-1 RT was 35% that of the heterodimeric (p66/p51) HIV-1 RT. These results support our recent studies on the monomeric polymerase domain (p51 RT) which exhibited an RNA-dependent DNA polymerase activity equal to 33% of that of the p66/p51 heterodimeric HIV-1 RT (Evans, Kezdy, Tarpley and Sharma [1993] Biotechnol. Appl. Biochem. 17, 91-102). The inability of the monomeric chimaeric HIV-1 RT to display polymerase activity like that of the heterodimeric HIV-1 RT is attributed to a decrease in the processive rate of DNA synthesis (75%) and DNA binding (65%). However, the monomeric chimaeric HIV-1 RT (p68) exhibited RNAase H activity like that of the heterodimeric form (p66/p51) of HIV-1 RT. These results suggest that the linker insertion from FLV RT does not interfere with the RNAase H activity associated with the monomeric HIV-1 RT.

Amino Acid Sequence↗
PubMed1993

Sulphydryl groups in the template-primer-binding domain of murine leukaemia virus reverse transcriptase. Identification and functional analysis of cysteine-90.

Treatment of murine leukaemia virus reverse transcriptase with benzophenone 4-maleimide inactivates DNA polymerase activity, but has no effect on the RNAase H function. Kinetic measurements indicated that benzophenone 4-maleimide is a competitive inhibitor with respect to template-primer binding, but is non-competitive with respect to dNTP binding. Enzyme modified with benzophenone 4-maleimide cannot bind template-primer or primer alone, as judged by u.v.-mediated cross-linking of radiolabelled substrates. Of the eight cysteine residues in murine leukaemia virus reverse transcriptase, only two were modified by benzophenone 4-maleimide, which were identified as Cys-90 and Cys-310 by comparative tryptic-peptide mapping and amino acid composition analysis. Inclusion of template-primer or primer alone in the modification mixture protected only Cys-90 from modification by benzophenone 4-maleimide. To investigate the role of Cys-90 in detail, we converted it to alanine by site-directed mutagenesis. The mutant enzyme, however, exhibited no loss either of DNA polymerase or of RNAase H activity. These results indicate that Cys-90 is located in a domain of murine leukaemia virus reverse transcriptase that binds template-primer, but may not have a direct role in the enzymic function of the enzyme. Ala-90 mutant murine leukaemia virus reverse transcriptase is at least 10-fold more susceptible to heat inactivation than is the wild-type enzyme, which suggests that Cys-90 in murine leukaemia virus reverse transcriptase may play a role in maintaining structural integrity.

Base Sequence↗
PubMed1993

Specificity and properties of MAb RS7-3G11 and the antigen defined by this pancarcinoma monoclonal antibody.

The murine monoclonal antibody (MAb) RS7-3G11 is an IgG1 with pancarcinoma reactivity, which has been raised against human squamous-cell carcinoma of the lung. Immunoperoxidase staining of frozen tissue sections demonstrated that the antigen defined by RS7-3G11 is present in tumors of the lung, stomach, bladder, breast, ovary, uterus and prostate. The rate and extent of internalization of RS7-3G11 into Calu-3, an adenocarcinoma of the lung cell line, was investigated using unconjugated MAb, followed by fluorescence labelling, and by binding 125I-RS7-3G11 followed by acid removal of surface-bound antibody. Rapid internalization of MAb RS7-3G11 into target cells was observed. Antibody internalization was noted at 30 min, and by 2 hr virtually all MAb RS7-3G11 was internal. Although MAb RS7-3G11 was raised against non-small-cell carcinoma of the lung, ME-180, a cervical-carcinoma cell line, expresses higher quantities of the antigen than the lung-carcinoma cell lines. Due to the higher antigen density in ME-180 cells, this line was used for immunoprecipitation studies and antigen purification. Immunoprecipitation studies using the ME-180 cervical-carcinoma cell line metabolically labeled with [3H]leucine or [3H]glucosamine demonstrated that the antigen defined by RS7-3G11 is a glycoprotein of M(r) 46 kDa. Deglycosylation by treatment with endoglycosidase-F resulted in a protein with a M(r) of 35 kDa. RS7-3G11-antigen was purified from ME-180 tissue-culture cells using affinity-column chromatography. By SDS-PAGE it was seen that the antigen was highly purified. The major band appeared at M(r) of 45 to 48 kDa. This result is in agreement with the immunoprecipitation studies. The broad band observed in the SDS-PAGE is typical of many glycoproteins, and suggests heterogeneity of glycosylation. Chemical and enzymatic treatments of the antigen, followed by Western blot analyses, suggest that the RS7-3G11 antigenic determinant is composed of a conformation-dependent peptide.

Animals↗
PubMed1993

Renal corticosterone 6 beta-hydroxylase in the spontaneously hypertensive rat.

Excess 6 beta-OH-corticosterone production by family 3A cytochromes P-450 may play a role in genesis of hypertension in the spontaneously hypertensive rat (SHR), by producing a renal defect in Na+ excretion. Renal cytochromes P-450 may be a causal factor in this genetic model. Since family 3A P-450 is present in rat kidney (collecting duct), the renal family 3A catalytic (6 beta-OHase) and immunoreactive activities were compared in SHR and normotensive control (Wistar-Kyoto; WKY) rats. Corticosterone 6 beta-hydroxylation is markedly higher in SHR than in WKY renal microsomal preparations. Western blot analysis with antibodies to rat and rabbit liver family 3A isoforms demonstrated related proteins. Densitometry revealed greater relative intensity of staining in SHR compared to WKY with both antibodies. Both antibodies inhibited corticosterone 6 beta-hydroxylation by SHR renal microsomes. Increased renal 6 beta-OH-corticosterone production by increased renal family 3A cytochromes P-450 may play a role in the blood pressure elevation in SHR.

Animals↗