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Biomedical subjects

S Deb

Publications and source records attributed to S Deb.

At least 55 records · Page 3Linked to original sources
PubMed1998

Spectroscopic study of Y210C lambda-repressor: implications for cooperative interaction.

A non-cooperative mutant of lambda-repressor, Y210C, has been purified and characterized. The mutant protein does not show any evidence of cooperative interaction as judged by difference near-UV circular dichroism spectra of DNA. The mutant protein also shows much weaker self-assembly as revealed by fluorescence anisotropy measurement. The far-UV circular dichroism spectrum of the protein shows a modest but significant reduction in the 220 nm range, suggesting a structural change. The Lehrer plot of acrylamide quenching of Y210C repressor at a predominantly dimeric concentration (0.5 microM) is almost identical with that of the wild-type protein at the same concentration. Transmission of operator-induced conformational change is also preserved in the mutant protein. Like that of the wild-type protein, cysteines of the mutant protein are unreactive to sulfhydryl reagents under native conditions. Most importantly, C210 is unreactive to sulfhydryl reagents under native conditions. This fact, coupled with the structural change observed in the far-UV CD spectra, suggests that C210 is located at the interior of the protein and exerts its effect indirectly on cooperative contact probably through destabilization of a reverse turn, of which it is an important part.

Bacteriophage lambda↗
PubMed1998

Neuropsychiatric sequelae one year after a minor head injury.

OBJECTIVE: To assess neuropsychiatric sequelae 1 year after minor head injury in a cross sectional study using home interviews with patients and their relatives at 1 year after head injury. METHODS: The study cohort included 148 adults who were admitted to hospital after a minor head injury between 1 July 1994 and 30 June 1995 and showed clinical or radiological evidence of brain injury. Main outcome measures used in the study were the Glasgow outcome scale, Edinburgh rehabilitation status scale, Barthel index, clinical interview schedule-revised, mini mental state examination, and assessment of symptoms of postconcussional syndrome. RESULTS: At one year follow up, four (2.9%) patients had a severe disability, 35 (25.5%) had a moderate disability, and 95 (69.3%) had no disability according to the Glasgow outcome scale. A slightly higher proportion (33.3%, n=45) showed disability according to the Edinburgh rehabilitation status scale. Thirty one patients (23.1%) scored <24 in the mini mental state examination. These were mostly patients over the age of 65. Twenty three patients (17.2%) were diagnosed as psychiatric cases according to the clinical interview schedule-revised scale. Seventy four (55.2%) patients showed one of the symptoms of postconcussional syndrome. The most commonly shown neurobehavioural problems were irritability (30%), sleep disturbance (29%), and impatience (27%). CONCLUSION: One year after a minor head injury, a substantial proportion of patients showed neuropsychiatric sequelae.

Adolescent↗
PubMed1998

Self-injurious behaviour as part of genetic syndromes.

BACKGROUND: The purpose of this paper is to review the association between genetic syndromes and self-injurious behaviour. METHOD: The information available from the literature on the subject of self-injurious behaviours and genetic syndromes was collated and presented with a critical appraisal. RESULTS: Self-injurious behaviours are associated with some genetic syndromes. However, the causal relationship between the genetic syndromes and the self-injurious behaviour remains far from clear. CONCLUSIONS: Although self-injurious behaviour has been shown to be the part of a broader phenotype in many genetic disorders, the specificity and sensitivity of these behaviours in this context remain unclear.

Brain Damage, Chronic↗
PubMed1998

Neuroimaging in autism.

BACKGROUND: Childhood autism is a developmental disorder with distinctive clinical features and characteristic cognitive deficits. Neuroimaging techniques have been extensively used in the study of autism and related disorders. METHOD: Recent important literature reported on structural and functional neuroimaging in autism was reviewed and discussed in the context of other neurobiological research findings. RESULTS: Various abnormalities of brain structure and function have been proposed, but no focal defect has been reliably demonstrated. Important findings, so far, include increased brain volume, structural abnormality in frontal lobe and corpus callosum in a proportion of autistic individuals. Functional neuroimaging findings emphasised the imbalance in inter-regional and inter-hemispheric brain metabolism and blood flow as well as abnormality in the anterior cingulate gyrus. CONCLUSION: The research to date has been hindered by methodological difficulties. However, hypothesis-driven research, particularly involving activation studies and neurotransmitter/neuroreceptor activities, using functional neuroimaging will be very useful in unravelling the enigma associated with this intriguing and distressing condition.

Autistic Disorder↗
PubMed1998

Differential expression of the estrogen receptors alpha and beta in the rat corpus luteum of pregnancy: regulation by prolactin and placental lactogens.

Estradiol, together with PRL and placental lactogens, regulates steroidogenesis and cell hypertrophy in the rat corpus luteum of pregnancy. Although binding experiments have demonstrated the presence of estrogen-binding sites, no evidence exists as to whether the rat corpus luteum of pregnancy expresses the estrogen receptor (ER) genes. In this investigation, we have analyzed the expression of the two ER genes (ER alpha and ER beta) (by RT-PCR and in situ hybridization) in the rat corpus luteum, studied their developmental changes throughout pregnancy, and investigated the regulation of ER alpha and ER beta messenger RNA (mRNA) expression by PRL and placental lactogens. The RT-PCR studies showed that both ER mRNA species (ER alpha and ER beta) are coexpressed in the rat corpus luteum during pregnancy. Whereas ER alpha mRNA increased from early pregnancy, reached a maximum at midpregnancy, and had a remarkable decline before parturition; ER beta mRNA remained constant throughout pregnancy, with a significant decline at parturition. Examination of ER alpha and ER beta mRNA expression at the cellular level, by in situ hybridization, showed ER alpha expressed in both follicles and corpus luteum, with maximal expression at midpregnancy. In parallel with the RT-PCR studies, ER beta mRNA was similarly expressed throughout pregnancy in the corpus luteum, but it was less abundant when compared with small and growing follicles. Western blot analysis revealed two ER immunoreactive proteins in the nuclear fraction obtained from pregnant rat corpus luteum: a 67-kDa moiety, highly expressed at midpregnancy but barely detectable in early and late gestation; and a 61-kDa form that remained developmentally unchanged. Hypophysectomy, performed early in pregnancy, induced a sharp decline in ER alpha mRNA expression but a less-marked reduction in ER beta mRNA levels. PRL treatment reverted the inhibition induced by hypophysectomy in both receptor subtypes. When primary luteinized cells were used to test the effect of PRL, rat placental lactogen I, and rat placental lactogen II on the expression of ER alpha and ER beta mRNA, all these lactogenic hormones stimulated both ER mRNA species in a dose-dependent manner. The regulation of ER mRNA expression was further evaluated in a luteal cell line, termed GG-CL, which apparently expresses only the ER beta mRNA species. Culture of the GG-CL cells, in the presence of PRL, resulted in a dose-related up-regulation of ER beta mRNA expression. In addition, PRL treatment enhanced the binding activity of GG-CL cell nuclear proteins to a classical estrogen response element. Furthermore, in these cells, estradiol treatment induced a dose-dependent up-regulation of the mRNA encoding protein kinase C delta isoform, a well-known estrogen target gene in the corpus luteum of the pregnant rat.

Animals↗
PubMed1998

Polymers in dentistry.

There is a wide choice of materials available for restorative dentistry covering a range of requirements. Fundamental knowledge about the properties of the polymers in use in dentistry is an advantage as it provides information relevant to clinical practice. Dentistry, perhaps, has the unique distinction of using the widest variety of materials, ranging from polymers, metal and metal alloys, ceramics, inorganic salts and composite materials. In the present paper, polymers and polymer composites used directly or indirectly for restorations, prostheses or for production of appliances in dentistry is discussed.

Biomechanical Phenomena↗
PubMed1998

Congenital bronchoesophageal fistula in an adult.

We present a rare case of a congenital bronchoesophageal fistula in a 54-year-old woman with a history of poor feeding tolerance since infancy and repeated pulmonary infections. She initially presented with epigastric and right upper quadrant abdominal pain. Her workup included a barium esophagogram that revealed a fistula between her midesophagus and a left lower lobe segmental bronchus. The fistula was divided, a left lower lobe superior segmentectomy was performed, and an intercostal muscle was placed over the esophageal closure. The patient noted an immediate decrease of postprandial coughing. Congenital respiratory esophageal fistulas that are not associated with esophageal atresia may persist into adulthood before they become clinically apparent. The diagnosis should be considered in certain individuals with suggestive symptomatology and unexplained respiratory pathology.

Bronchial Fistula↗
PubMed1998

Clinical significance of pituitary apoplexy.

A retrospective analysis of 280 cases of pituitary adenoma operated on over a period of 10 years from 1985-94 revealed 15 cases (5.3%) presenting with apoplexy, though there were 48 cases in which haemorrhage in pituitary adenoma was confirmed at operation. In the apoplectic group all but one had abrupt onset of severe headache. Seven of these 15 patients had diminution of vision and ocular motility defects were detected in 5 patients. There were 5 patients of amenorrhoea/galactorrhoea syndrome and 2 had acromegalic features. In the remaining 8 patients retrospective analysis failed to reveal any conclusive evidence of pituitary dysfunction. Trans-sphenoidal surgery was performed in 9 cases and the rest had transcranial surgery. Visual acuity loss improved in most of the affected patients, residual ocular motility defects were mild. Urgent trans-sphenoidal surgery to decompress the expanding mass seems to be the preferred mode of surgery.

Adenoma↗
PubMed1997

Effect of crosslinking agents on acrylic bone cements based on poly(methylmethacrylate).

Three different crosslinking agents were added to the monomer content of the bone cement formulation based on poly(methylmethacrylate), PMMA, in various concentrations, and their effects on the curing parameters and mechanical properties were determined. The different crosslinking agents were dimethacrylates containing a range of chain lengths and degrees of flexibility. For the parent formulation of the bone cement, PMMA powder was used, and the properties and kinetics of curing were compared for the same system with and without crosslinking agents. It was found that at low concentrations of crosslinking agents, the mechanical properties were superior but steadily decreased with increasing concentrations. Poly(ethyleneglycoldimethacrylate), EGDMA(400), even when used at very low concentrations, produced a steady improvement in the mechanical properties and could be used in cement formulations with a view to reducing creep and improving mechanical properties.

Acrylates↗
PubMed1997

A novel method for the purification of recombinant subunit I of the Dolichos biflorus seed lectin.

Lectins are carbohydrate-binding proteins that are ubiquitous in nature. Their ability to specifically bind carbohydrates has been used as a means of purification mainly through affinity chromatography techniques. Plant lectins are one of the most thoroughly studied class of lectins, however, details of their in situ function remains elusive. Recent advances in recombinant DNA techniques have been used in several laboratories to study the function of these lectins by heterologous overexpression. The larger subunit of the Dolichos biflorus seed lectin was described by Chao et al. in 1994 and purification through affinity chromatography techniques was described. Here we report on a new method for the purification of this recombinant protein with techniques that are not dependent on the ability of the lectin to bind sugars. This method may have uses in the purification of mutant proteins that may not bind carbohydrates. Characterization of the purified protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy shows that the lectin is over 99% pure with a molecular weight of 27,090 +/- 16.17 Da, and hemagglutination assays confirm that the lectin retains its biological activity.

Chromatography, Affinity↗
PubMed1997

A comparison of obstetric and neonatal complications between children with autistic disorder and their siblings.

Sixty-one children had a diagnosis of autistic disorder according to the DSM3-R criteria in a population based study of mentally retarded children between the ages of 5 and 19 years in the Aberdeen city area of Scotland. Obstetric case records were traced for 36 out of these 61 autistic children. The obstetric case records of siblings of 30 of these autistic children were also traced. Modified versions of Prechtl's obstetric optimality scale along with that of Parnas were used to score pre-, peri- and neonatal obstetric complications in the autistic group and their normal sibling controls. A Spearman's correlation coefficient test between the scores of the Childhood Autism Rating Scale (CARS) and the Obstetric and Neonatal Complication (ONC) scores of all autistic children did not reveal any significant correlation. However, among the 20 severe autistic children, Spearman's test showed significant correlation between the scores of CARS and some ONC scores. Overall, no statistically significant difference between the autistic children and their siblings in the scores of obstetric optimality was detected by using the Wilcoxon test.

Adolescent↗
PubMed1997

Structural neuroimaging in learning disability.

BACKGROUND: Neuroimaging has proven useful in confirming diagnoses of certain neuropsychiatric conditions, but neuroimaging studies in learning disability are at an early stage. METHOD: A review of recent structural neuroimaging research in relation to learning disability was carried out. RESULTS: Brain abnormalities can be detected in cases of idiopathic and non-idiopathic learning disability, but their significance is not clear due to discrepancies in study findings and the small cohorts involved. CONCLUSION: Although the role of structural neuroimaging in the assessment of people with learning disability is not clear, new magnetic resonance imaging technology holds great promise for future research.

Autistic Disorder↗
PubMed1996

Placental lactogen-I variant utilizes the prolactin receptor signaling pathway.

Placenta lactogen-I variant (PL-Iv) is a member of a family of proteins expressed by the rat placenta with characteristics similar to prolactin (PRL). In this report, we present the molecular cloning, chromosomal localization, and heterologous expression of PL-Iv. Nucleotide sequence analysis of the PL-Iv cDNA clone predicted a precursor protein of 223 amino acids, including a 28-amino acid signal sequence. The PL-Iv gene was localized to chromosome 17 of the rat genome, which also carries other members of the PRL gene family. PL-Iv heterologously expressed in Chinese Hamster ovary (CHO) cells exhibited similar immunoreactive and electrophoretic characteristics with PL-Iv produced by the rat placenta. N-terminal sequencing verified the identity and purity of the recombinant PL-Iv species and the site of cleavage of the signal peptide from the mature secreted PL-Iv species. Recombinant PL-Iv was shown to bind to ovarian and liver PRL receptors, stimulate the proliferation of Nb2 lymphoma cells, and activate Jak2. Each of these actions is consistent with PL-Iv utilizing the PRL receptor signal transduction pathway.

Animals↗
PubMed1996

Effect of cross-linking agents on the dynamic mechanical properties of hydrogel blends of poly(acrylic acid)-poly(vinyl alcohol-vinyl acetate).

A range of hydrogels were prepared by blending aqueous solutions of poly(vinyl alcohol-vinyl acetate) with poly(acrylic acid) in various proportions. The effects of two cross-linking agents (glyoxal and glutaraldehyde) and subsequent thermal treatment on the properties of the blends are discussed. Dynamic mechanical analysis (DMA) of the xerogels indicated complete miscibility of the various blends which was evident from the appearance of a single glass transition temperature (Tg) in the presence of either glyoxal or glutaraldehyde at all thermal treatments studied. A 50/50% wt/wt blend was found to have the highest storage modulus and was thus selected for further study. Hydrogels prepared with glutaraldehyde without subsequent thermal treatment exhibited higher storage modulus values than those prepared using glyoxal when tested isothermally at 20 degrees C in a water bath. A further increase in the storage modulus was observed when these hydrogels were thermally treated at 120 or 150 degrees C. In a non-isothermal study on the cross-linked hydrogels, no variation in storage modulus was observed. Broad peaks were observed in tan delta plots, these peaks shifting towards higher frequencies as the degree of cross-linking increased in the hydrogel.

Acrylates↗
PubMed1996

Increased production of matrix metalloproteinases in enriched astrocyte and mixed hippocampal cultures treated with beta-amyloid peptides.

Growing evidence supports the notion of a functional relationship between the presence of the beta-amyloid (A beta) peptide and the production of inflammatory mediators in and around neuritic plaques of Alzheimer's disease. Tissue remodeling enzymes that are critical in peripheral inflammatory responses are the matrix metalloproteinases (MMPs), enzymes produced by neurons and glia. Thus, it was of interest to determine whether A beta may alter the expression of MMPs in glial and neuronal cultures. It was demonstrated that A beta (1-40) is a potent stimulator of MMP-9 and MMP-2 activity in addition to inducing the expression of a lower molecular weight, unidentified gelatinase activity in mixed hippocampal and astrocyte cultures. Shorter fragments of A beta were less effective in stimulating the production of these enzymes. The lower molecular weight activity was observed only in response to A beta, and not after treatment with various cytokines. In addition, both cultures express MMP-3 (stromelysin-1) in response to A beta peptides. These results suggest that MMPs may play a role in the development or progression of neuritic plaques, i.e., abnormal neurite outgrowth.

Amyloid beta-Peptides↗
PubMed1996

Transcriptional activation of the human epidermal growth factor receptor promoter by human p53.

The human epidermal growth factor receptor (EGFR) promoter is activated by both wild-type and tumor-derived mutant p53. In this communication, we demonstrate that EGFR promoter sequence requirements for transactivation by wild-type and mutant p53 are different. Transient-expression assays with EGFR promoter deletions identified a wild-type human p53 response element, 5'-AGCTAGACGTCCGGGCAGCCCCCGGCG -3', from positions --265 to --239. Electrophoretic mobility shift analysis and DNase I footprinting assays indicated that wild-type p53 binds sequence specifically to the response element. Using circularly permuted DNA fragments containing the p53-binding site, we show that wild-type p53 binding induces DNA bending at this site. We further show that the EGFR promoter is also activated by tumor-derived p53 mutants p53-143A, p53-175H, p53-248W, p53-273H, and p53-281G. However, the transactivation by mutant p53 does not require the wild-type p53-binding site. The minimal EGFR promoter from positions --104 to --20 which does not contain the wild-type p53-binding site is transactivated by the p53 mutants but not by the wild-type protein, showing a difference in the mechanism of transactivation by wild-type and mutant p53. Transactivation of the EGFR promoter by p53 may represent a novel mechanism of cell growth regulation.

Amino Acid Sequence↗