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Biomedical subjects

S Deb

Publications and source records attributed to S Deb.

At least 19 recordsLinked to original sources
PubMed2001

The human oncoprotein MDM2 uses distinct strategies to inhibit transcriptional activation mediated by the wild-type p53 and its tumor-derived mutants.

Human MDM2 (hMDM2) inhibits transcriptional activation mediated by wild-type p53 and its tumor-derived mutants. We present evidence to show that hMDM2 interacts with the tumor-derived mutants of p53 and inhibits transcriptional activation of the human c-myc promoter mediated by the tumor-derived mutants of p53 through two domains. These two domains of hMDM2 are able to function independent of each other. Interaction with either of the domains is sufficient for inhibition of mutant p53-mediated transactivation. One of these domains is the same as the wild-type p53 interaction domain of hMDM2, whereas a second domain is situated within amino acid 190 and 276 residues and is specific for mutant p53. hMDM2 does not inhibit transcriptional activation mediated by the transcriptional activator VP16, suggesting that the inhibition is not mediated by inactivation of a general transcription factor. The transactivation and the oligomerization domains of mutant p53 are dispensable for its interaction with hMDM2. Thus, both hMDM2 and p53 recognize each other through unique domains. These observations suggest that forms of hMDM2 incapable of interacting with the wild-type p53, and are often expressed in transformed cells, would inhibit mutant p53-mediated transactivation and antagonize the tumorigenic function of mutant p53. This inhibitory function of hMDM2 may account for infrequent co-occurrence of p53 mutation and hMDM2 overexpression in cancer cells. Our results also suggest distinct mechanisms for wild-type and mutant p53-mediated transcriptional activation.

Biomarkers, Tumor↗
PubMed2001

Differential modulation of cellular and viral promoters by p73 and p53.

p73 has been shown to transcriptionally activate genes positively responsive to wild-type p53. In order to undertake a comparative study of functions of p53 and p73 we have cloned the cDNA of p73 from MCF-7 cells. Adenovirus onco-protein E1A inhibits the transactivation by p73; a deletion mutant of E1A incapable of interacting with p300 and CREB-binding protein (CBP) fails to disrupt the transactivation. Furthermore, CBP increases the transactivation mediated by p73 suggesting that CBP may function as a co-activator and E1A inhibits p73-mediated transactivation by sequestering p300 or CBP. We show that p73 can transcriptionally inhibit a number of cellular and viral promoters. However, wild-type p53, p73 alpha and p73 beta differ in their ability to inhibit transcriptional activity of different promoters. While wild-type p53 inhibits the promoters of the human cytomegalovirus (CMV) immediate-early gene, the long terminal repeat of human immunodeficiency virus type 1 (HIV LTR), human cyclin A (cyc A) gene, and insulin-like growth factor receptor I (IGF-I-R), p73 alpha only inhibits the HIV LTR and cyc A promoters significantly; and p73 beta inhibits the CMV, HIV LTR and cyc A promoters. A mutant of p73 alpha having amino acid substitutions at positions 268 and 300 on the presumptive DNA-binding domain fails to transactivate the p21 promoter but represses the CMV and the HIV LTR promoter quite efficiently showing that the mechanisms of transactivation and repression by p73 are different. Interestingly, p73 alpha transactivates the IGF-I-R promoter, which is inhibited by wild-type p53; p73 beta has no significant effect on this promoter. This is a unique situation where p73 alpha differs from p73 beta as well as p53.

Adenovirus E1A Proteins↗
PubMed2000

Regional and age-related expression of gelatinases in the brains of young and old rats after treatment with kainic acid.

Due to the possible detrimental impact of local inflammatory responses in neurodegenerative disease, it was of interest to measure the expression of extracellular matrix-degrading enzymes, a group of proteases that are induced during an inflammatory response, in the brains of old and young animals in a model of neuronal death. Doses of kainic acid were administered that resulted in comparable hippocampal pyramidal neuron loss in young and old F344/BN hybrid rats, even though each age group received widely differing doses. Two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, were differentially induced with respect to time after kainic acid in sensitive brain regions in both young and old rats. However, the elevation of MMP-9 in the temporal lobe 12 h after injection in old rats was significantly greater than that observed in young animals. These results suggest that early and late induction of MMPs may play a role in neuronal death and repair mechanisms, respectively, and that inflammatory mechanisms in the central nervous system (CNS) of old rats are exaggerated compared to young rats.

Age Factors↗
PubMed2000

DNA sequence dependent and independent conformational changes in multipartite operator recognition by lambda-repressor.

Binding of regulatory proteins to multipartite DNA binding sites often occurs with protein-protein interaction, resulting in cooperative binding. The operators of bacteriophage lambda have several pairs of repressor binding sites (O(R)1-O(R)2, O(R)2-O(R)3, O(L)1-O(L)2, and O(L)2-O(L)3) separated by a variable number of base pairs, and thus, bacteriophage lambda is a model system for studying multipartite operator recognition by DNA-binding proteins. Near-UV circular dichroism spectra show that the DNA is distorted in O(R)1-O(R)2 and O(L)2-O(L)3 but much less so in O(R)2-O(R)3. Upon titration of lambda-repressor with single-operator sites O(R)1, O(R)2, and O(R)3, it was observed that the tryptophan fluorescence quenches to different degrees, suggesting different conformations of the protein in the three DNA-protein complexes. Acrylamide quenching of tryptophan fluorescence of lambda-repressor bound to these single operators also shows different Stern-Volmer constants, supporting the above conclusions. Titration of lambda-repressor with oligonucleotides containing pairs of operator sites also causes different degrees of fluorescence quenching. In particular, fluorescence quenching induced by O(R)1-O(R)2 binding is less than the quenching induced by either of the single operators alone, suggesting additional conformational changes upon establishment of protein-protein contact. Stern-Volmer constants obtained from acrylamide quenching of tryptophan fluorescence of lambda-repressor bound cooperatively to pairs of operator sites are different from those of the single-operator-site-bound repressors. For example, O(R)2-O(R)3-bound repressor has significantly higher acrylamide quenchable components than either of the O(R)2- or O(R)3-bound proteins, again suggesting additional conformational changes upon establishment of protein-protein contact. We conclude that the strategy of recognition of multipartite operator by lambda-repressor is complex and varied, involving conformational changes in both DNA and protein that are determined by the separation of the binding sites as well as the nucleic acid sequence.

Acrylamide↗
PubMed2000

p73 transcriptional activity increases upon cooperation between its spliced forms.

The p53 homologue p73 efficiently activates p53-responsive genes. The well documented over-expression of p73 spliced forms in a wide variety of tumor types promoted us to elucidate the mechanisms underlying p73-mediated transcription. Using the luciferase reporter gene driven by Mdm2-minimal promoter in p53 null cells, we demonstrate that the weak transcriptional activity mediated by p73alpha was increased by the mutant form p73beta292, which by itself is transcriptionally inactive. Similarly, cooperation between p73beta and an inactive form of p73alpha increased p73beta-mediated transcriptional activities. Conversely, p73beta elicited a silencing effect on a gain of function mutant, p53(281), which by itself mediated efficient transactivation of the MDR promoter. Neither anisomycin nor actinomycin D altered p73-mediated transcriptional activities, whereas sorbitol profoundly inhibited them through a rapid proteasome-dependent degradation of p73. Our observations point to plausible scenarios in which p73, through cooperation between p73 spliced forms and suppression of gain of function mutant p53 may elicit changes in the transcription of p53 target genes that play key roles in cell growth and death.

Animals↗
PubMed2000

A study of energetics of cooperative interaction using a mutant lambda-repressor.

A lambda-repressor mutant, S228N, which is defective in tetramer formation in the free state but retains full cooperativity, was studied in detail. Isolated single operator-bound S228N repressor shows association properties similar to those of the wild-type repressor. Fluorescence anisotropy studies with dansyl chloride-labeled repressor show a dimer-monomer dissociation constant of around 10(-5) M. The structure of the mutant repressor was studied by circular dichroism, acrylamide quenching and sulfhydryl reactivity at protein concentrations of < or =10(-6) M, where it is predominantly monomeric. The results suggest no significant perturbations in the structure of the S228N mutant repressor from that of the wild-type repressor. Urea denaturation studies also indicate no significant change in the stability of the repressor. The results were used to calculate energetics of loop formation in the cooperative binding process.

DNA-Binding Proteins↗
PubMed2000

Lactated ringer's solution and hetastarch but not plasma resuscitation after rat hemorrhagic shock is associated with immediate lung apoptosis by the up-regulation of the Bax protein.

BACKGROUND: We previously demonstrated that the type of resuscitation fluid used in hemorrhagic shock affects apoptosis. Unlike crystalloid, whole blood seems to attenuate programmed cell death. The purpose of this study was to determine whether the acellular components of whole blood (plasma, albumin) attenuated apoptosis and to determine whether this process involved the Bax protein pathway. METHODS: Rats were hemorrhaged 27.5 mL/kg, kept in hypovolemic shock for 75 minutes, then resuscitated over 1 hour (n = 44). Control animals underwent anesthesia only (sham, n = 7). Treatment animals were bled then randomly assigned to the following resuscitation groups: no resuscitation (n = 6), whole blood (n = 6), plasma (n = 6), 5% human albumin (n = 6), 6% hetastarch (n = 7), and lactated Ringer's solution (LR, n = 6). Hetastarch was used to control for any colloid effect. LR was used as positive control. Immediately after resuscitation, the lung was collected and evaluated for apoptosis by using two methods. TUNEL stain was used to determine general DNA damage, and Bax protein was used to specifically determine intrinsic pathway involvement. RESULTS: LR and hetastarch treatment resulted in significantly increased apoptosis in the lung as determined by both TUNEL and Bax expression (p < 0.05). Plasma infusion resulted in significantly less apoptosis than LR and hetastarch resuscitation. Multiple cell types (epithelium, endothelium, smooth muscle, monocytes) underwent apoptosis in the lung as demonstrated by the TUNEL stain, whereas Bax expression was limited to cells residing in the perivascular and peribronchial spaces. CONCLUSION: Apoptosis after volume resuscitation of hemorrhagic shock can be affected by the type of resuscitation fluid used. Manufactured fluids such as lactated Ringer's solution and 6% hetastarch resuscitation resulted in the highest degree of lung apoptosis. The plasma component of whole blood resulted in the least apoptosis. The process of apoptosis after hemorrhagic shock resuscitation involves the Bax protein.

Animals↗
PubMed2000

APOE epsilon 4 influences the manifestation of Alzheimer's disease in adults with Down's syndrome.

BACKGROUND: Recent studies of the relationship between the apolipoprotein E (APOE) gene and Alzheimer's disease in adults with Down's syndrome have revealed inconsistent results. AIMS: To assess the role of the APOE gene in the manifestation of Alzheimer's disease in adults with Down's syndrome. METHOD: We studied the APOE genotypes of 24 adults with dementia and 33 non-demented adults with Down's syndrome over 35 years of age, and an additional group of 164 non-learning disabled adults. We also carried out a meta-analysis of all previously published studies of association between APOE and Down's syndrome, incorporating the current data. RESULTS: We observed a non-significant excess of APOE epsilon 4 and a reduction of epsilon 2 in adults with dementia compared with non-demented adults with Down's syndrome in our sample. However, meta-analysis showed a significantly higher frequency of epsilon 4 in adults with dementia compared with non-demented adults with Down's syndrome (odds ratio = 2.02, 95% CI 1.33-3.07, P = 0.001), but no significant reduction in the frequency of epsilon 2. CONCLUSIONS: The APOE epsilon 4 allele acts as a risk factor for the age-specific manifestation of Alzheimer's disease in people with Down's syndrome.

Adult↗
PubMed2000

Estrogen receptors alpha and beta in rat decidua cells: cell-specific expression and differential regulation by steroid hormones and prolactin.

Estradiol is known to play an important role in the growth and differentiation of rat uterine stromal cells into decidual cells. In particular, this hormone with progesterone is necessary for blastocyst implantation and subsequent decidualization in the rat. Although binding experiments have demonstrated the presence of estrogen-binding sites, no evidence exists as to whether the rat decidua expresses both isoforms of the estrogen receptor (ER), alpha and beta. In this investigation, we analyzed the expression of decidual ERalpha and ERbeta, studied their regulation by PRL and steroid hormones and examined the ability of decidual ERp to transduce the estradiol signal to the progesterone receptor. Immunocytochemistry, RT-PCR, and Northern blot analysis showed that both ER species are coexpressed in the decidua during pseudopregnancy. Interestingly, these genes were preferentially found in a cell population localized in the antimesometrial site of the uterus where blastocyst implantation takes place. Using decidual cells in primary culture obtained from pseudopregnant rats and a decidua-derived cell line (GG-AD), we show a differential regulation of ERalpha and ERbeta by PRL and ovarian steroid hormones. Whereas PRL, estradiol, and progesterone all increased ERbeta messenger RNA (mRNA) expression in a dose-dependent manner, only PRL up-regulated the mRNA levels of ERa. Estradiol had no effect on ERalpha expression, whereas progesterone markedly decreased its mRNA levels. Interestingly, progesterone, which up-regulates the ability of PRL to signal to a PRL-regulated gene in mammary-gland derived cells, prevented PRL stimulation of decidual ERalpha and had no synergistic effect on ERbeta expression. The use of GG-AD cells, which express only ERbeta, allowed us to demonstrate that this receptor subtype is functional and transduces estradiol signal to the progesterone receptor. In summary, the results of this investigation have revealed that ERbeta is expressed in addition to ERalpha in the rat decidua, and that the expression of both ERs are cell specific and differentially regulated by PRL and steroids. One salient finding of this investigation is that progesterone down-regulates ERalpha, but concomitantly increases the expression of a functional ERbeta that mediates estradiol up-regulation of the decidual progesterone receptor.

Aging↗
PubMed2000

Comparison of titanium vascular closure staples with suture repair of the thoracic aorta in swine.

OBJECTIVE: Devices that reduce technical difficulty and anastigmatic time when repairing large vessels such as the thoracic aorta would be beneficial. The aim of this study was to determine if titanium vascular closure staples (3 mm) could be safely and quickly applied in the repair of large vessels such as the thoracic aorta. DESIGN: Through a left thoracotomy in 10 female swine (110 to 130 lb), an interposition graft (14 to 16 mm textile) was placed into the aorta distal to the left subclavian artery. Animals were randomized at the time of repair to either running sutures (n = 5; 6-0 polypropylene) or vascular closure staples (n = 5; 3 mm). The anastomosis was evaluated after 2 months with aortograms, and the aorta was harvested to evaluate healing. RESULTS: The clamp times (mean +/- SD) were 30.8 +/- 8.2 min for suture repair and 24.8 +/- 5.1 min for vascular closure staple repair (p = 0.2). Anastomosis times were 20. 0 +/- 6.2 min for the suture group and 16.4 +/- 6.4 min for the vascular closure staple group (p = 0.4). Arch aortograms at 2 months revealed no significant difference in luminal narrowing between the two groups. Gross and microscopic examination revealed no thrombosis, well-healed wounds with a continuous intimal layer, and no differences in intimal thickness or inflammation between the two groups. CONCLUSION: Vascular closure staples were equivalent to sutures in terms of durability, graft patency, and wound healing at 2 months. Vascular closure staples may offer the trauma surgeon a quick and easy alternative when repairing large vessels such as the thoracic aorta.

Anastomosis, Surgical↗
PubMed1999

Genotoxic effect of arecoline given either by the peritoneal or oral route in murine bone marrow cells and the influence of N-acetylcysteine.

The carcinogenic potentiality of the major alkaloid of betel nut, arecoline (ARC), is well established. This study was undertaken to determine the differences in genotoxic effects of ARC when given by two different routes (oral administration (OA) and intraperitoneal injection (IP)) in mouse bone marrow cells (BMC) since ARC carcinogenicity was observed only when ARC was given orally. The data indicate that ARC-OA induced a higher frequency of cancers, a greater delay in the cell cycle and greater sister chromatid exchanges than ARC-IP. The presence of N-acetyl cysteine along with ARC-OA significantly reduced the effect of ARC.

Acetylcysteine↗
PubMed1999

Activated isoforms of MMP-2 are induced in U87 human glioma cells in response to beta-amyloid peptide.

Prior studies using rat primary hippocampal cultures indicated induction of matrix metalloproteinases (MMPs) in response to beta-amyloid (A beta). Hence, it was of interest to determine whether MMP activity in a human cell line is influenced by A beta. A beta, but not interleukin-1beta (IL-1beta) or lipopolysaccharide (LPS), stimulated an active form of MMP-2 in human U87 glioblastoma cells, as well as increased the expression of the well-known activator of MMP-2, membrane-type (MT)-MMP. Activation experiments carried out with amino phenyl mercuric acetate (APMA), immunoprecipitation, as well as immunoblotting, suggest that the lower molecular weight, gelatin-degrading activity was an activated form of MMP-2. Furthermore, it was demonstrated that a synthetic furin convertase inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethylketone, decreased the production of A beta-induced active MMP-2 in U87 cells. The induction of MMP-3 by cytokines, but not by A beta, suggests that the effect of A beta on MMP-2 is selective. Although A beta stimulated tissue inhibitor of metalloproteinase-1 (TIMP-1), there was no obvious effect of A beta on TIMP-2 production in U87 cells. These results demonstrate that A beta induces an active form of MMP-2 likely by increasing the expression of MT-MMP in a human glioblastoma cell line. Active MMP-2 may degrade A beta or act on ECM components critical in neuronal survival mechanisms and possibly play a role in Alzheimer's disease (AD) neuropathology.

Amyloid beta-Peptides↗
PubMed1999

Water absorption characteristics and cytotoxic and biological evaluation of bone cements formulated with a novel activator.

A novel activator, N,N,Dimethylamino 4-benzyl laurate (DML) was used in the curing of acrylic bone cements, based on poly(methylmethacrylate). The water absorption characteristics were studied, and the behavior was found to be similar to commercial bone cements. The net amount of solubles were also in the same range as obtained for commercial cements cured with conventional activators. Biocompatibility tests were conducted on the neat activator (DML) and cured cements. The present study indicated that there were no toxic effects; furthermore, osteoblast-like cells were seen to proliferate and differentiate more readily on DML containing cements. The analysis of the effect of leachables from cements into the media showed continued cell proliferation and cell viability.

Bone Cements↗
PubMed1999

Comparison of rating scales for the diagnosis of dementia in adults with Down's syndrome.

Making a diagnosis of dementia, particularly in its early stages, in a person with intellectual disability can be difficult Some neuropsychological tests which were originally devised for the diagnosis of dementia in the non-intellectually disabled population have been modified for use in people with intellectual disability. Observer-rated scales have also been used for making a diagnosis of dementia in people with intellectual disability. Within the context of a genetic study, the rates of diagnosis of dementia according to different criteria, namely the clinician's diagnosis (ICD-10), the Dementia Questionnaire for Persons with Mental Retardation (DMR), the Dementia Scale for Down Syndrome (DSDS) and the Mini Mental State Examination (MMSE), were compared among 62 adults with Down's syndrome (26 demented and 36 non-demented adults according to the clinician's diagnosis). A comparison between the clinician's diagnosis and the diagnosis according to DMR criteria showed specificity and sensitivity at the 0.92 level for both categories. Similarly, a comparison between the clinician's diagnosis and the diagnosis according to the DSDS criteria showed a specificity of 0.89 and a sensitivity of 0.85. A good positive correlation was also shown between the scores of the DSDS and the DMR (Pearson's r = +0.868, P < 0.001). A similar positive correlation was found between the overall DSDS score and the scores in the main subcategories of the DMR. An MMSE could be performed in only 34 (55%) out of the 62 subjects with Down's syndrome. Out of the 30 subjects who had an MMSE score of less than 24 (the usual cut-off for the diagnosis of possible dementia), 23 (77%) did not have a diagnosis of dementia according to any criteria. It seems that the observer-rated scales, rather than the direct neuropsychological tests, are more useful for the diagnosis of dementia in people with an intellectual disability.

Adult↗
PubMed1999

ICD-10 codes detect only a proportion of all head injury admissions.

Despite criticism, the codes covering traumatic brain injury under the International Classification of Diseases have been widely used for sample collection in the epidemiological studies of head injury. Data have been collected from an Accident and Emergency department's (A&E's) case register on all head injury admissions to hospitals from a defined geographic area between 1 April 1996 and 31 March 1997, and compared with the list collected from the heath authority's central database by using the ICD-10 codes. Thirty seven per cent of the names in the A&E register appeared in the ICD-10 list, and 41% of the names in the ICD-10 list appeared in the list collected from the A&E department. The incidence of reported head injury was found to be three times higher among the 0-15 years age group compared with the 16-64 years age group (3.3% compared with 1% of the population). Among the 16-64 years age group, the peak rates of admission to hospital were in the months of February and August. Approximately 14% of all the head injury admissions stayed in hospital for more than 72 hours, another 14% stayed between 48 and 72 hours, and the rest (72%) stayed for less than 48 hours.

Adolescent↗