Biomedical subjects

M Subramaniam

Publications and source records attributed to M Subramaniam.

At least 37 records · Page 2Linked to original sources

PubMed1998

Impact of distal aortic and visceral perfusion on liver function during thoracoabdominal and descending thoracic aortic repair.

PURPOSE: We examined the impact of distal aortic and visceral perfusion on liver function during thoracoabdominal and descending thoracic aortic repair. METHODS: Between January 1991 and July 1996, 367 patients underwent thoracoabdominal and descending thoracic aortic repair. Baseline and postoperative total bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, fibrinogen, prothrombin time (PT), and partial thromboplastin time (PTT) were measured for 286 patients. We examined the impact of distal aortic and direct visceral perfusion on liver function-related clinical laboratory values. Univariate and multivariate statistical methods for categorical and continuous variables were used. RESULTS: In categorical analysis, type II thoracoabdominal aortic aneurysm, history of hepatitis, and emergency presentation had a statistically significant multivariate association with abnormal laboratory values. In continuous-distributed multivariate data analysis, type II thoracoabdominal aortic aneurysm and visceral perfusion were statistically significant predictors of postoperative alkaline phosphatase, PT, and PTT. Type II aneurysms increased postoperative liver function-related laboratory values significantly above other aneurysm types (alkaline phosphatase, +114 IU, p < 0.0001; PT, +1.99 seconds, p < 0.02; PTT, +6.7 seconds, p < 0.03). Visceral perfusion was associated with a concomitant decrease (alkaline phosphatase, -101.2 IU, p < 0.0001; PT, -1.8 seconds, p < 0.07; PTT, -5.6 seconds, p < 0.02). CONCLUSIONS: Visceral perfusion negates the rise in postoperative liver function-related clinical laboratory values associated with type II thoracoabdominal aortic aneurysm repair.

Alkaline Phosphatase↗

PubMed1998

Estrogen regulation of a transforming growth factor-beta inducible early gene that inhibits deoxyribonucleic acid synthesis in human osteoblasts.

This laboratory reported the identification and characterization of a unique three zinc finger, transcription factor-like, transforming growth factor-beta inducible early gene (TIEG) (see Ref. 35). TIEG expression has been shown to be tissue- and cell type specific, enhanced by specific growth factors, and to decrease with advancing stages of breast cancer. Recent studies involving TIEG overexpression in pancreatic carcinoma cells indicate that TIEG expression inhibits DNA synthesis, similar to a tumor suppressor-like gene, and plays a role in apoptosis (see Ref. 37). This paper describes the rapid, but transient, induction of TIEG steady-state messenger RNA (mRNA) levels by 17beta-estradiol (E2) in estrogen receptor (ER)-positive, human fetal osteoblastic (hFOB/ER) cells. This rapid induction is shown to be ER- and steroid dose-dependent but protein synthesis independent. An antagonism between E2 and PTH, which occurs in skeletal metabolism, is shown to concur rapidly with TIEG mRNA expression. Scanning confocal microscopy (using polarized, laser-based immunofluorescence) shows that TIEG protein is localized in the nucleus of hFOB/ER cells, with the levels rapidly increasing after E2 treatment. The rapid E2-induced increase in TIEG expression is followed by an E2-induced inhibition of DNA synthesis in the hFOB/ER cells. Antiestrogens block not only the induction of TIEG mRNA levels but also the inhibition of cell proliferation. Lastly, hFOB cells, stably transfected with a TIEG expression vector, display markedly reduced DNA synthesis/cell proliferation, compared with nontransfected cells. These results support the finding that TIEG is an early responding regulatory gene for E2 in human osteoblast cells that inhibits DNA synthesis. It is speculated that TIEG may play a role in the signaling pathway for E2 in inhibiting cell proliferation.

Cell Division↗

PubMed1998

Religious--sociocultural psychotherapy in patients with anxiety and depression.

OBJECTIVE: To show the effectiveness of incorporating religious-sociocultural components in the management of patients with generalised anxiety disorders and major depression who have strong religious and cultural backgrounds as compared with a normal psychotherapeutic approach. METHODS: One hundred and three cases of anxiety and 100 cases of depression with strong religious and cultural backgrounds were randomly assigned to the study or control groups. Both groups received standard treatment for their respective illnesses. The study group was given additional religious-sociocultural psychotherapy. They were followed for 6 months and were assessed in a double-blind fashion using the Hamilton Anxiety Rating Scale or the Hamilton Depression Rating Scale. RESULTS: Patients receiving additional religious-sociocultural psychotherapy responded significantly faster than those who received standard treatment. However, the difference became non-significant at the end of 6 months. CONCLUSIONS: Incorporating a religious and sociocultural component in the treatment program rapidly improved anxiety and depressive symptoms in patients with strong religious and cultural backgrounds. The present study demonstrates a need for more sensitivity to religious-sociocultural issues in the field of mental health.

Anxiety Disorders↗

PubMed1997

A DNA-binding element for a steroid receptor-binding factor is flanked by dual nuclear matrix DNA attachment sites in the c-myc gene promoter.

The receptor-binding factor (RBF) for the avian oviduct progesterone (Pg) receptor (PR) has previously been shown to be a unique 10-kDa nuclear matrix protein that generates high affinity PR-binding sites on avian DNA. This paper describes the use of Southwestern blot and DNA gel shift analyses with RBF protein to identify a minimal 54-base pair RBF-binding element in the matrix-associated region (MAR) of the Pg-regulated c-myc gene promoter. This element contains a 5'-GC-rich domain and a 3'-AT-rich domain, the latter of which has a homopurine/homopyrimidine structure. The gel shift assays required the generation of an RBF-maltose fusion protein (RBF-MBP), which specifically binds this element and is supershifted when the anti-RBF polyclonal antibody is added. Computer analysis of the full-length amino acid sequence for RBF predicts a DNA-binding motif involving a beta-sheet structure at the N-terminal domain. Southern blot analyses using nuclear matrix DNA suggests that there are dual MAR sites in the c-myc promoter, which flank an intervening domain containing the RBF element. The co-transfection of this MAR sequence, containing the RBF element and cloned into a luciferase reporter vector, together with an RBF expression vector construct, into steroid treated human MCF-7 cells, results in a decrease of the c-myc promoter activity relative to control transfections containing only the parent vector of the RBF expression construct. These data suggest that a unique chromatin/nuclear matrix structure, composed of the RBF-DNA element complex which is flanked by nuclear matrix attachment sites, serves to bind the PR and repress the c-myc promoter.

Animals↗

PubMed1997

Overexpression of the TGFbeta-regulated zinc finger encoding gene, TIEG, induces apoptosis in pancreatic epithelial cells.

Members of the TGFbeta family of peptides exert antiproliferative effects and induce apoptosis in epithelial cell populations. In the exocrine pancreas, these peptides not only regulate normal cell growth, but alterations in these pathways have been associated with neoplastic transformation. Therefore, the identification of molecules that regulate exocrine pancreatic cell proliferation and apoptotic cell death in response to TGFbeta peptides is necessary for a better understanding of normal morphogenesis as well as carcinogenesis of the pancreas. In this study, we have characterized the expression and function in exocrine pancreatic epithelial cells of the TGFbeta-inducible early gene (TIEG), a Krüppel-like zinc finger transcription factor encoding gene previously isolated from mesodermally derived osteoblastic cells. We demonstrate that this gene is expressed in both acinar and ductular epithelial cell populations from the exocrine pancreas. In addition, we show that the expression of TIEG is regulated by TGFbeta1 as an early response gene in pancreatic epithelial cell lines. Moreover, overexpression of TIEG in the TGFbeta-sensitive epithelial cell line PANC1 is sufficient to induce apoptosis. Together, these results support a role for TIEG in linking TGFbeta-mediated signaling cascades to the regulation of pancreatic epithelial cell growth.

Adult↗

PubMed1997

Role of endothelial selectins in wound repair.

P- and E-selectins are adhesion molecules expressed on activated endothelium and platelets at sites of vascular injury and inflammation. The selectins are important for leukocyte recruitment. Because little is known about the role of selectins in wound healing, we studied cutaneous wound repair of full-thickness excisional skin wounds in mice lacking P-selectin, E-selectin, or both of these selectins. The absence of either selectin alone had no notable effect on healing, and the only deficit observed was a delay in early neutrophil extravasation in the P-selectin-deficient mice. Mice deficient in both P- and E-selectins had markedly reduced recruitment of inflammatory cells and impaired closure of the wounds. Wound sections, studied up to 3 days after wounding, showed significant impairment of neutrophil influx. Macrophage numbers were also reduced in the double mutants at 3 and 7 days after wounding as compared with wild-type mice. Additionally, a wider epithelial gap in the wounds of the P- and E-selectin-double-deficient mice 3 days after wounding indicated delayed keratinocyte migration. These results demonstrate an important combined role for P- and E-selectins in processes leading to wound healing.

Animals↗

PubMed1996

Defects in hemostasis in P-selectin-deficient mice.

Recently, our laboratory showed that platelets, like leukocytes, roll on activated endothelium expressing P-selectin, thus suggesting a role for P-selectin in hemostasis (Frenette et at, Proc Natl Acad Sci USA 92:7450, 1995). We report here that the P-selectin--deficient mice show a 40% prolongation of the bleeding time on amputation of the tip of the tail. Moreover, defective hemostasis was observed in a local Shwartzman-like reaction induced by skin injections of lipopolysaccharide followed by tumor necrosis factor-alpha in the P-selectin--deficient mice. The hemorrhagic lesions, quantitated both macroscopically and microscopically, were twofold larger in the P-selectin--deficient mice. This was also confirmed by measuring the radioactivity in the skin using chromium-labeled red blood cells. Therefore, it is evident that P-selectin plays a role in hemostasis as suggested by its support of platelet rolling.

Animals↗

PubMed1996

A nuclear matrix acceptor site for the progesterone receptor in the avian c-myc gene promoter.

It has been the goal of this project to determine the location, composition, and biological function of the nuclear acceptor sites (i.e., the nuclear binding sites) for the avian oviduct progesterone (Pg) receptor (PR). Many laboratories have demonstrated a native-(in vivo) like cell-free binding of steroid receptor complexes to specific acceptor sites in nuclei/chromatin in a variety of target tissue systems. These sites appear to involve protein-DNA complexes and some of these have been shown to reside in the nuclear matrix, including the chromatin acceptor sites for the avian oviduct PR. We have purified a nuclear matrix "acceptor protein" for the avian PR. termed receptor binding factor-1 (RBF-1), based on its ability to generate specific, high-affinity PR binding on avian genomic DNA. This 10 kD nuclear matrix protein was found to be unique with minimal homology to a couple of other proteins. Using immunohistochemical techniques and antibodies against the purified RBF-1, the RBF-1 was localized to the nuclei of many avian and rat tissues. Co-localizations of RBF-1 and PR in select cell types in the avian oviduct and rat reproductive organs were also reported. A tissue specificity was found with regard to RBF-1 concentrations. The full length cDNA to RBF-1 has been isolated and used to identify a 0.7 kb mRNA whose levels in various avian tissues reflect the protein levels. Genomic sequences of RBF-1 have been isolated and characterized. Preliminary studies indicate that the over-expression of the RBF in human MCF-7 cells results in an inhibition of the c-myc gene promoter activity which is further inhibited by steroid hormone treatments of the cells. Past studies in our laboratory demonstrated that the c-myc mRNA steady state levels are rapidly (approximately 15 min) reduced by Pg and glucocorticoids in the avian oviduct. Further, partially purified fractions of RBF-1 were shown to generate specific PR binding sites only on the genomic DNAs of certain animal species and on the c-myc gene, but not ovalbumin gene. Using Southwestern blot analyses, the purified RBF-1 was shown to bind specifically to sequences in the 5' end of c-myc, c-jun proto-oncogenes but not to genomic sequences of the ovalbumin gene. A specific DNA binding element in the promoter region of the c-myc proto-oncogene has been identified as AT-rich domain of homopurine/pyrimidine stretches flanked by GC-rich sequences. Southern blot analyses using 200 bp matrix DNA fragments protected by the nuclear matrix structure indicate that the matrix is attached on either side of the RBF-1 binding element. A model is described for a nuclear matrix acceptor site attached to the c-myc promoter which may mediate the Pg-induced down-regulation of the c-myc gene expression.

Animals↗

PubMed1995

Identification of a novel TGF-beta-regulated gene encoding a putative zinc finger protein in human osteoblasts.

The TGF-beta family of growth factors has been extensively studied and found to play major roles in bone physiology and disease. A novel, TGF-beta-inducible early gene (TIEG) in normal human fetal osteoblasts (hFOB) has been identified using differential-display PCR. Using this differentially expressed cDNA fragment of TIEG to screen a hOB cDNA library, a near full-length cDNA for this gene was isolated. Northern analyses indicated that the steady-state levels of the 3.5 kb TIEG mRNA increased within 30 min of TGF-beta treatment of human osteoblasts and reached a maximum of 10-fold above control levels at 120 min post-treatment. This regulation was independent of new protein synthesis. Computer sequence analyses indicates that TIEG mRNA encodes for a 480 amino-acid protein. The TIEG protein contains three zinc finger motifs, several proline-rich src homology-3 (SH3) binding domains at the C-terminal end, and is homologous in this region to the zinc finger-containing transcription factor family of genes. A growth factor/cytokine-specific induction of TIEG has been shown. TIEG expression in hFOB cells was highly induced by TGF-beta and bone morphogenetic protein-2 (BMP-2), with a moderate induction by epidermal growth factor (EGF), but no induction by other growth factors/cytokines was observed. In addition to osteoblastic cells, high levels of TIEG expression were detected in skeletal muscle tissue, while low or no detectable levels were found in brain, lung, liver or kidney. Because TIEG is an early induced putative transcription factor gene, and shows a growth factor induction and tissue specificity, its protein product might play an important role as a signalling molecule in osteoblastic cells.

Base Sequence↗

PubMed1995

Blood cell dynamics in P-selectin-deficient mice.

P-selectin is expressed on the surfaces of activated platelets and endothelium where it mediates binding to leukocytes. P-selectin-deficient mice were shown to exhibit peripheral neutrophilia (Mayadas et al: Cell 74:541, 1993). We now show that this is not caused by changes in bone marrow precursors nor by a lack of neutrophil margination. Both P-selectin-positive and -negative animals displayed similar increases in peripheral blood neutrophil numbers after injection of epinephrine. However, clearance of 51Chromium-labeled neutrophils is delayed in mice deficient for P-selectin, indicating that the neutrophilia is at least in part the result of delayed removal. We detected no obvious alterations in lymphocyte differentiation, distribution, or adhesion to high endothelial venules in peripheral lymph nodes. Through intravital microscopy, we examined the impact of P-selectin deficiency on leukocyte/endothelial interaction beyond the initial stages of inflammation. Four hours after the administration of an inflammatory irritant, leukocyte rolling was observed even in the absence of P-selectin. There were significantly fewer rolling cells relative to wild-type mice, and their velocity was reduced. Moreover, in the peritonitis model, the number of peritoneal macrophages in wild-type mice increased threefold at 48 hours, whereas the macrophages in the mutant mice remained near baseline levels. Thus, whereas P-selectin is known to be involved in early stages of an inflammatory response, our results indicate that it is additionally responsible for leukocyte rolling and macrophage recruitment in more prolonged tissue injury.

Animals↗

PubMed1995

Reduced recruitment of inflammatory cells in a contact hypersensitivity response in P-selectin-deficient mice.

The inflammatory response at sites of contact hypersensitivity induced by oxazolone was examined in the ears of P-selectin-deficient and wild-type mice. Accumulation of CD4+ T lymphocytes, monocytes, and neutrophils was reduced significantly in the mutant mice, as well as mast cell degranulation. In contrast, there was no significant difference in vascular permeability or edema between the two genotypes. The results demonstrate a role for P-selectin in recruitment of CD4+ T lymphocytes and show that P-selectin plays a role in long-term inflammation as well as in acute responses.

Animals↗

PubMed1995

TGF-beta regulation of nuclear proto-oncogenes and TGF-beta gene expression in normal human osteoblast-like cells.

Transforming growth factor-beta (TGF-beta) is present in high levels in bone and plays an important role in osteoblast growth and differentiation. In order to dissect the molecular mechanisms of action of TGF-beta on osteoblasts, the effects of TGF-beta on the steady state mRNA levels of c-fos, c-jun, and jun-B proto-oncogenes on normal human osteoblast-like cells (hOB) and a transformed human osteoblast cell line (MG-63) were measured. Treatment of hOBs with 2 ng/ml of TGF-beta 1 resulted in a rapid increase in c-fos mRNA levels as early as 15 min post-treatment. A maximum (10-fold) increase was observed at 30 min after TGF-beta treatment followed by a decrease to control values. Similar responses were measured whether the cells were rapidly proliferating or quiescent. TGF-beta 1 induced jun-B mRNA levels more gradually with steady increase initially observed at 30 min and a maximum induction measured at 2 h post-TGF-beta treatment. In contrast, TGF-beta treatment caused a time dependent decrease in the c-jun mRNA levels, an opposite pattern to that of jun-B mRNA. Treatment of hOBs with TGF-beta 1 in the presence of actinomycin-D abolished TGF-beta 1 induction of c-fos mRNA, suggesting that TGF-beta action is mediated via transcription. In the presence of cycloheximide, TGF-beta causes super-induction of c-fos mRNA at 30 min, indicating that the c-fos expression by TGF-beta is independent of new protein synthesis. Further, transfection of 3 kb upstream region of jun-B promoter linked to a CAT reporter gene into ROS 17/2.8 cells was sufficient to be regulated by TGF-beta 1. Interestingly, TGF-beta treatment also increased the mRNA levels of TGF-beta 1 itself at 4 h post TGF-beta treatment, with a maximum increase observed at 14 h of treatment. TGF-beta 1 treatment for 30 min were sufficient to cause a delayed increase in TGF-beta protein secretion within 24 h. These data support that TGF-beta has major effects on hOB cell proto-oncogene expression and that the nuclear proto-oncogenes respond as rapid, early genes in a cascade model of hormone action.

Animals↗

PubMed1995

Nuclear matrix acceptor binding sites for steroid hormone receptors: a candidate nuclear matrix acceptor protein.

Steroid/nuclear-hormone receptors are ligand-activated transcription factors that have been localized to the nuclear matrix. The classic model of hormone action suggests that, following activation, these receptors bind to specific "steroid response elements" on the DNA, then interact with other factors in the transcription initiation complex. However, evidence demonstrates the existence of specific chromatin proteins that act as accessory factors by facilitating the binding of the steroid receptors to the DNA. One such protein, the "receptor binding factor (RBF)-1", has been purified and shown to confer specific, high-affinity binding of the progesterone receptor to the DNA. Interestingly, the RBF-1 is localized to the nuclear matrix. Further, the RBF-1 binds specifically to a sequence of the c-myc proto-oncogene that has the appearance of a nuclear matrix attached region (MAR). These results, and other findings reviewed here, suggest that the nuclear matrix is involved intimately in steroid hormone-regulated gene expression.

Animals↗

PubMed1995

Effect of high-frequency interrupted noise exposures on evoked-potential thresholds, distortion-product otoacoustic emissions, and outer hair cell loss.

The effect of high-frequency interrupted noise exposures on evoked potential (EP) thresholds, distortion-product otoacoustic emissions (DPOAEs), and status of the outer hair cells was studied with the aim of understanding the correspondence among the three measures. Animal subjects were exposed to an octave band noise centered at 4 kHz at 85 dB SPL for 6 hr/day for 10 days. EP and DPOAE recordings were made before the exposure and on days 1, 2, 4, 6, 8, and 10 of exposure. A final set of measurements were made 5 days after the last exposure, following which the animals were sacrificed and their cochleas were examined using scanning electron microscopy. Both EPs and DPOAEs showed a worsening of auditory function after the first exposure and then showed a progressive recovery toward baseline. However, there was no consistent relationship between changes in EP thresholds and changes in DPOAEs nor were there any systematic changes in outer hair cells that corresponded with the changes in DPOAEs. Furthermore, EP thresholds often revealed considerable deficits in function while DPOAEs were normal.

Acoustic Stimulation↗

PubMed1995

Effects of noise exposure, race, and years of service on hearing in U.S. Army soldiers.

Over the last two decades the U.S. Army has instituted a comprehensive hearing conservation program (HCP) to reduce the prevalence of hearing loss in soldiers and civilian employees. As a component of this program, hearing threshold levels (HTLs) are stored in a central computerized Army-wide hearing conservation data registry. The aim of this study was to analyze the hearing threshold data to compare the hearing loss among soldiers representing different (1) race groups, (2) noise exposure groups, and (3) duration of military service. HTLs were age-corrected using data base B values from ISO 1999 (1990). As may be expected, soldiers exposed to high noise levels had significantly poorer hearing than the group of soldiers with limited noise exposure. On the average, results indicated a significant difference in HTLs among the race groups with black soldiers having the most sensitive hearing and white soldiers having the poorest. Also, subjects with greater durations of military service had the least sensitive hearing. Finally, race and years of service factors were found to interact in their effect on HTL. The findings are discussed in terms of implications of race differences, normative data, and effectiveness of the U.S. Army HCP.

Adolescent↗

PubMed1994

Anatomical effects of impact noise.

Four groups of binaural chinchillas were exposed to impact noise (B-duration = 200 ms) ranging from 119 dB to 137 dB peak equivalent SPL at repetition rates of 1/s or 4/s. The duration of exposure was adjusted so that each exposure consisted of equal acoustic energy. Animals were then sacrificed immediately, 24 h or 30 days after the exposure and their cochleas subjected to scanning electron microscopy. For exposures of 119 dB or greater, there appeared to be direct mechanical damage, including large clefts between the third row of outer hair cells and Deiters' cells and fracture of tight cell junctions at the reticular lamina. There was also a progressive increase in cochlear damage over the 30 days of recovery. The patterns of cochlear pathology are compared with hearing losses and cochleograms of chinchillas previously subjected to similar exposures and with results of studies using higher level impulse noise. The results are discussed in terms of 'critical level' for impact and impulse noise.

Acoustic Stimulation↗

PubMed1994

The ubiquitous nature of the progesterone receptor binding factor-1 (RBF-1) in avian tissues.

The avian oviduct receptor binding factor-1 (RBF-1) is a 10 kDa nuclear matrix protein that was originally identified through its ability to effect high affinity interaction of activated progesterone receptor (PR) with chromatin. In the present study, the RBF-1 is shown to not be restricted to reproductive tissues (e.g., oviduct) but present in all avian tissues examined by Western blot analysis with a monoclonal antibody prepared against purified RBF-1. The heart and pancreas had the highest and lowest RBF-1 levels, respectively; the concentration ranging by approximately 50-fold in these tissues. The 10 kDa size of the RBF-1 detected in all tissues suggests no significant tissue-specific differences in the protein. This was consistent with the finding that purified hepatic and oviductal RBF-1 have identical amino-terminal sequence. Using a recently isolated cDNA to RBF-1, the levels of RBF-1 mRNA were found to correlate well with the ubiquitous presence of the protein as well as tissue-specific differences in concentration. The presence of RBF-1 in non-progesterone responsive tissues suggests the possibility that RBF-1 may not be specifically involved in PR-DNA interactions but may play a more diverse role, possibly involving other steroid receptors such as the glucocorticoid receptor.

Amino Acid Sequence↗

PubMed1994

The effect of 'conditioning' exposures on hearing loss from impulse noise.

Research has shown that prior noise exposures or 'conditioning' can moderate the amount of permanent threshold shift (PTS) from subsequent high intensity noise exposures. The aim of this experiment was to study the effect of 'conditioning' on subsequent exposure to high intensity impulse noise. The subjects were seven experimental and 14 control monaural chinchillas. Evoked potential (EVP) thresholds were measured before and after the noise exposures. Experimental animals received 10 days of exposure to an octave band noise (OBN) centered at 0.5 kHz OBN at 95 dB SPL (6 h on/18 h off) and allowed to recover for 5 days. The subjects were then exposed to an impulse noise at 150 dB SPL. The temporal spacing of the impulses consisted of a series of 50 pairs of impulses presented 50 ms apart with 1000 ms between the onset of each pair. The total duration of exposure was approximately 1 min. Control animals received only the impulse noise exposure. PTS was measured after 4 weeks. The threshold shift (TS) patterns during the 'conditioning' phase were consistent with previous research, with the greatest amount of TS occurring on the second day and decreasing with continued exposures. Four weeks after recovery from the impulse noise, the experimental animals showed significantly less PTS than the control animals. In addition, histological examination revealed significantly less hair cell loss in the experimental than in the control subjects. The results are discussed in the context of previous studies on 'toughening' and on the effects of impulse noise.

Acoustic Stimulation↗