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Biomedical subjects

P Sengupta

Publications and source records attributed to P Sengupta.

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

Cell fate specification and differentiation in the nervous system of Caenorhabditis elegans.

Neuronal cell fates are specified by a hierarchy of events mediated by cell-intrinsic determinants and cell-cell interactions. The determination of cell fate can be subdivided into three general steps. First, cell fate is restricted by the cell's position in the animal. For example, neurons are specified along the anterior-posterior body axis through the action of the Hox genes lin-39, mab-5, and egl-5. Second, a decision is made to generate a particular cell type, such as the progenitor of a neurogenic lineage as opposed to that of an epidermal lineage. Among the genes that influence this decision is the proneural gene lin-32. Third, characteristics of a particular cell type are specified. For example, in a neurogenic lineage, a decision may be made to generate a specific neuron type such as a sensory or motor neuron. Genes that affect neuronal fate can act in different ways to influence the development of different types of neurons.

Animals↗
PubMed1995

Structure of the O-specific side chain of the Escherichia coli O128 lipopolysaccharide.

The O-specific polysaccharide isolated from Escherichia coli O128 lipopolysaccharide contains D-galactose, L-fucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratios 2:1:2. The primary structure of the O-specific polysaccharide from E. coli was established by compositional analysis, methylation analysis, together with 1H and 13C NMR spectroscopy including two-dimensional shift-correlated and one-dimensional NOE spectroscopy. The polysaccharide moiety was found to consist of a tetrasaccharide backbone containing D-galactose and 2-acetamido-2-deoxy-D-galactose, with L-fucose as a side chain in a branched pentasaccharide repeating unit having the following structure: [formula: see text]

Carbohydrate Conformation↗
PubMed1995

A novel DNA/protein complex interacts with the insulin-like growth factor binding protein-1 (IGFBP-1) insulin response sequence and is required for maximal effects of insulin and glucocorticoids on promoter function.

Glucocorticoids stimulate and insulin inhibits hepatic production of IGFBP-1 at the level of gene transcription. We previously identified contiguous insulin and glucocorticoid response sequences in the proximal rat IGFBP-1 promoter. This insulin response sequence (IRS) is palindromic (CAAAACAAACTTATTTTG) and each half resembles an IRS in the phosphoenolpyruvate carboxykinase (PEPCK) gene. We have reported that both the IGFBP-1 and PEPCK IRSs bind hepatocyte nuclear factor-3 (HNF-3) proteins [1]. We now report that IRSs from the IGFBP-1 and PEPCK, as well as an IRS which also binds HNF-3 in the rat tyrosine aminotransferase (TAT) gene, also interact with another DNA/protein complex in gel shift studies. Further, methylation interferences studies, gel shift and transient transfection studies with site-specific mutations identified a single base in the first half of the IRS that is critical both for interactions with proteins in this complex, and for maximal effects of insulin and glucocorticoids, on promoter function. Of note, a 250-fold excess of an oligo containing a C/EBP binding site (but not other AT-rich sequences) inhibits the formation of this complex in gel shift assays. Nevertheless, interactions with this C/EBP site are negligible at lower titers (< or = 100-fold excess), and antibodies against known C/EBP proteins do not react with this complex. Similarly, preincubation with CHOP, a truncated member of the C/EBP family which contains a beta-leucine zipper domain, does not prevent or alter the mobility of this novel DNA/protein complex, indicating that components of this complex do not form heterodimers with beta-ZIP proteins. We conclude that HNF-3 proteins and this novel C/EBP-related DNA/protein complex may play an important role in mediating interactions between glucocorticoids and insulin in the regulation of IGFBP-1 and perhaps multiple hepatic genes.

Animals↗
PubMed1995

Properties of mitochondrial DNA polymerase in mitochondrial DNA synthesis in yeast.

Mitochondrial DNA polymerase from Saccharomyces cerevisiae, purified 3500 fold, was separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis into three polypeptides. The major 150 kDa polypeptide was probably the catalytic subunit of the mitochondrial (mt) DNA polymerase and the other two polypeptides could be either proteolytic cleavage products of the polymerase, other subunits of the enzyme or protein contaminants. The mtDNA polymerase preferred an A+T-rich DNA template and did not require any RNA primer for DNA synthesis, at least under in vitro reaction conditions. It showed higher processivity on a double-stranded linear DNA template than on a single-stranded circular DNA template, and was capable of synthesizing at least about 1200 nucleotide primer-extended products without any major pause on a double-stranded DNA template.

Base Sequence↗
PubMed1994

The C. elegans gene odr-7 encodes an olfactory-specific member of the nuclear receptor superfamily.

Olfactory discrimination is achieved through the action of olfactory neurons with diverse chemical specificities. In C. elegans, at least ten different types of chemosensory neurons respond to different chemicals. The odr-7 gene is required for the function of one pair of chemosensory neurons called AWA neurons. odr-7 null mutants fail to respond to all odorants detected by the AWA neurons, while a missense mutation in odr-7 causes a specific defect in one odorant response. odr-7 encodes a protein with similarity to the DNA-binding domain of the nuclear receptor genes; it is expressed predominantly in the AWA neurons. odr-7 may regulate the expression of olfactory signaling molecules that define a single type of olfactory neuron.

Amino Acid Sequence↗
PubMed1994

Modulation of Fc and C3b receptor activity of mouse peritoneal macrophages elicited by preformed immune complexes.

A study was undertaken to reveal the role of Fc and C3b receptor of mouse peritoneal macrophages (MPM) in the uptake of radiolabelled immune complexes. Large latticed preformed complexes consisting of human serum albumin (HSA)-anti HSA at equivalence (IC-Eq) and with antibody excess (IC-Ab) were observed to be avidly taken up by resident macrophages unlike small size complexes with antigen excess (IC-Ag). Macrophages elicited by thioglycollate (Tg) showed higher IC-binding capacity while IC-elicited MPM showed reduction in the same when compared to the resident cells. However, complement coated complexes were significantly taken up by these IC-elicited macrophages. Uptake studies were further extended to determine the expression of Fc and C3b receptor activity in MPM when elicited with preformed IC. Tg-elicited MPM were observed to bind greater number of IgG-coated erythrocytes (E-IgG) than resident MPM whereas IC-elicited MPM bound E-IgG poorly. When Fc receptors were blocked by in vitro IC treatment, poor binding of complement coated E-IgG [E(IgG)C] was recorded in resident MPM. The present complement medicated rosetting data tends to show enhanced expression of C3b receptors on IC-elicited macrophages.

Animals↗
PubMed1993

The cellular and genetic basis of olfactory responses in Caenorhabditis elegans.

The small soil nematode Caenorhabditis elegans has only 302 neurons in its entire nervous system, so it is possible to analyse the functions of individual neurons in the animal's behaviour. We are using behavioural, cellular and genetic analyses of chemotactic responses to find out how olfactory behaviour patterns are generated and regulated. Single chemosensory neurons in C. elegans can recognize several different attractive odorants that are distinguished by the animal. Distinct sets of chemosensory neurons detect high and low concentrations of a single odorant. Odorant responses adapt after prolonged exposure to an odorant; this adaptation is odorant specific and reversible. Mutants with defects in odorant responses have been identified. Some genes appear to be necessary for the development or function of particular kinds of sensory neurons. Other genes have effects that suggest that they participate in odorant reception or signal transduction.

Adaptation, Physiological↗
PubMed1993

Prediction of malnutrition by the ratio of the head circumference to the chest circumference.

This study was carried out in West Bengal, amongst 127 rural children aged 1-5 years. It was found that the ratio of the head circumference to the chest circumference (H:C ratio) was valuable in predicting malnutrition. An increase in the ratio occurred 2-3 months before a drop in weight was noted; a decrease in the ratio was followed 2-3 months later by a gain in weight. Hence, it is felt that this method can be used in field work to forestall malnutrition.

Child Development↗
PubMed1991

MAT alpha 1 can mediate gene activation by a-mating factor.

In the yeast Saccharomyces cerevisiae, expression of alpha-specific genes is governed by the MAT alpha 1 and MCM1 gene products. MAT alpha 1 and MCM1 bind cooperatively to PQ elements upstream of alpha-specific genes. The PQ element not only directs alpha-specific expression but can also direct gene induction in response to treatment with a-mating pheromone. We have used gene fusions to investigate whether induction conferred by the PQ box is mediated through either MAT alpha 1 or MCM1, or a combination of both. When MCM1 is fused to the DNA-binding domain of the bacterial repressor LexA, this fusion protein is capable of trans-activating a lacZ reporter gene driven by a LexA operator. However, the transcriptional activity of the MCM1-LexA fusion is not further enhanced by treatment of cells with a-factor. A MAT alpha 1-LexA fusion protein is also capable of trans-activation through a LexA operator. Moreover, the activity of the MAT alpha 1-LexA fusion protein can be further induced by treatment with a-factor. When progressive deletions are made from the amino terminus of MAT alpha 1 in the fusion protein, the basal level of trans-activation progressively decreases, but the inducibility of the fusion protein increases. MAT alpha 1-LexA fusion proteins, which have greater than or equal to 57 amino acids deleted from the amino terminus of MAT alpha 1 are not capable of trans-activation. In addition, the activity of the MAT alpha 1-LexA fusion protein is dependent on the functions of the STE7, STE11, and STE12 genes that encode components of the pheromone response pathway.

Amino Acid Sequence↗
PubMed1990

The PRE and PQ box are functionally distinct yeast pheromone response elements.

Saccharomyces cerevisiae mating pheromones function by binding to cell surface receptors and activating signal transduction processes which regulate gene expression. In this report, we have analyzed the minimum sequence requirements for conferring both a and alpha mating pheromone inducibilities onto a heterologous promoter. Here we show that the repetitive pheromone response element (PRE) which binds to STE12 protein is sufficient to confer pheromone responsiveness only when present in multiple copies. Moreover, by itself, it is preferentially responsive to alpha factor in a cells. In contrast, a single copy of the PQ box of the STE3 upstream activation sequence (UAS) is sufficient to confer a-factor responsiveness in alpha cells. The PQ box binds both MCM1 and MAT alpha 1 in a cooperative manner, and neither the P nor Q site alone is sufficient to confer a-factor responsiveness. In a cells, however, even multiple copies of the PQ box fail to confer alpha-factor responsiveness. Therefore, the PRE and the PQ box are functionally distinct pheromone-responsive elements with opposite cell type specificities. Moreover, these results indicate that the MCM1 protein functions in a signal transduction pathway in a manner analogous to that of its mammalian homolog, the serum response factor, which regulates the expression of the c-fos proto-oncogene in mammals.

Base Sequence↗
PubMed1989

Prevention of postdural puncture headache after spinal anaesthesia for extracorporeal shockwave lithotripsy. An assessment of prophylactic epidural blood patching.

The prevention of postdural puncture headache after spinal anaesthesia for extracorporeal shockwave lithotripsy was investigated by a controlled clinical trial which compared epidural injection of 10 ml of autologous blood with 10 ml of normal saline immediately after intrathecal injection of local anaesthetic. The incidence of postdural puncture headache was 8.3% in the group that received blood compared with 45% in the group that received saline, a significant reduction (p less than 0.01). The incidences of backache and lower limb paraesthesiae were similar in both groups. No serious complications were reported.

Adult↗
PubMed1988

Nitrous oxide and day-case laparoscopy: effects on nausea, vomiting and return to normal activity.

Patients admitted for day-case laparoscopy were assigned randomly to receive nitrous oxide-oxygen or oxygen, with enflurane, during a standard anaesthetic technique. Postoperative morbidity, in particular nausea and vomiting, and ability to resume normal activity were assessed over the ensuing 48 h. Supplementary administration of propofol during the operative procedure was required significantly more often (P less than 0.05) in the absence of nitrous oxide. There was no significant difference in the incidence of vomiting before discharge when nitrous oxide was omitted. The incidence and severity of nausea over the 48 h following operation was similar in both groups. There was no difference in analgesic or anti-emetic requirements before discharge and the time taken to resume normal activity was similar. It is concluded that nitrous oxide may be avoided readily in day-case laparoscopy without affecting postoperative morbidity or time taken to return to "street fitness" and normal activity.

Adolescent↗
PubMed1988

The human c-fos serum response factor and the yeast factors GRM/PRTF have related DNA-binding specificities.

One of the elements that mediates growth factor and serum inducibility of the human c-fos gene is a region of dyad symmetry that lies between nucleotides -320 and -299 of the human gene. A mammalian protein specifically binds to this sequence element and has been termed the serum response factor (SRF). Gel-shift analysis and competition experiments demonstrate that there is a factor in the yeast Saccharomyces cerevisiae that binds specifically to the human c-fos SRE. The methylation interference pattern of the yeast factor is identical to that of the mammalian SRF. Regulatory elements of cell-type-specific genes in yeast have homologies to the c-fos SRE and complete for binding of both the mammalian and yeast factors to the SRE. Antisera to the gene product of the MCM1 locus react with the yeast SRE-binding factor. These data suggest that this yeast protein is closely related or identical to the factors [general regulator of mating type (GRM) and pheromone/receptor transcription factor (PRTF)] that are required for the regulation of cell-type-specific genes in yeast.

Cloning, Molecular↗
PubMed1987

Post-operative morbidity associated with the use of atracurium and vecuronium in day-case laparoscopy.

Patients were randomly allocated to receive either vecuronium or atracurium as the sole muscle relaxant for day-case gynaecological laparoscopy to determine if either agent was superior with respect to post-operative morbidity during the 48 h after operation. Intubating conditions and cardiovascular stability were similar in both groups. Post-operative morbidity prior to discharge was also similar except for a significantly higher incidence of abdominal pain in the vecuronium group. There was no statistical difference in specific morbidity during the 48 h after laparoscopy, but a greater number of patients in the vecuronium group was able to resume normal activity 24 h after laparoscopy. Both agents are very suitable for day-case laparoscopies and other short surgical procedures.

Ambulatory Surgical Procedures↗
PubMed1986

Morbidity after day case laparoscopy. A comparison of two techniques of tracheal anaesthesia.

A comparison was made of postoperative morbidity following two anaesthetic techniques for day case laparoscopies. One group of patients was allowed to breathe spontaneously after intubation under suxamethonium. The second group received atracurium and their lungs were mechanically ventilated. Patients in the controlled ventilation group experienced significantly less severe sore throats and muscle pain in the first 24 hours postoperatively than the patients who breathed spontaneously. Both techniques proved to be safe and are suitable for day case laparoscopy. The safety of patients is discussed in relation to the choice of anaesthetic technique used.

Adult↗