Biomedical subjects

S Rajaraman

Publications and source records attributed to S Rajaraman.

At least 91 records · Page 5Linked to original sources

PubMed1992

Allopurinol-induced nephrotoxicity: protection by the antioxidant, butylated hydroxytoluene.

The present study was conducted to provide morphological evidence for allopurinol-induced nephrotoxicity in rats and its prevention by the antioxidant butylated hydroxytoluene (BHT). The kidneys of male Sprague Dawley rats fed a diet containing 0.3% allopurinol for 25 days exhibited a marked increase in the weight (2.5 times) as compared to the controls (without allopurinol). Upon microscopic examination, extensive tubulo-interstitial injury leading to structural damage was observed. Feeding BHT (0.4%) along with 0.3% allopurinol brought about a remarkable amelioration of the nephrotoxicity. The results indicate that usage of BHT along with the antiurecemic drug, allopurinol, may be helpful in improving the allopurinol-induced nephrotoxicity observed in some gout patients.

Allopurinol↗

PubMed1991

High-affinity binding sites for bombesin on mouse colonic mucosal membranes.

Bombesin (BBS) has specific biological effects on colonic mucosal cells, but the presence of BBS receptors on colonic mucosa have not been described to-date. In the present study we examined the mouse colonic mucosal membranes for the presence of specific binding sites for BBS/gastrin releasing peptides (GRP), and characterized the binding kinetics and molecular weight of the specific binding proteins. The radiolabeled ligand (125I-Tyr4-BBS), in the absence or presence of a 1000-fold excess of BBS, was used to establish the optimal binding assay conditions of time, pH and temperature for measuring the maximum number of specific binding sites for BBS related peptides. Under the optimal binding assay conditions, BBS displaced the binding of 125I-Tyr4-BBS in a dose-related manner. A single class of high-affinity binding sites (Kd = 0.23 +/- 0.02 nM) for BBS were measured, with a binding capacity of 27.3 +/- 4.6 fmoles/mg membrane protein. The binding sites were specific for binding BBS/GRP related peptides, since all structurally related peptides inhibited the binding of 125I-Tyr4-BBS in a dose-dependent manner, while structurally unrelated peptides did not compete for the 125I-Tyr4-BBS binding sites. The relative binding affinity (RBA) of BBS/GRP related peptides was determined to be in the order of GRP (14-27) = GRP (18-27) greater than GRP (1-27) greater than neuromedin B greater than BBS. The BBS-receptor antagonists, [Leu13-psi-(CH2NH) Leu14]-BBS (LL-BBS) and D-Phe6, BN(6-13) propylamide (D-Phe6, BN(6-13)-PA), inhibited the specific binding of 125I-Tyr4-BBS to colonic mucosal membranes in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Expression of cholecystokinin forms by medullary thyroid cancer.

We have studied the production and release of cholecystokinin (CCK) forms by rat medullary thyroid cancer (MTC) in vivo. MTC cells were inoculated s.c. into 8 Wag-Rij rats. One month later, after i.v. injection of calcium plasma levels of CCK, calcitonin and tissue contents of gastrin and calcitonin were determined by radioimmunoassay (RIA), immunocytochemistry, and high-pressure liquid chromatography (HPLC). The tumors were passed 4 times to 8 rats in 1-month intervals fasting levels of CCK in control rats were unaffected by calcium stimulation, and in tumor-bearing rats, plasma CCK was elevated in 3 out of 4 passages, falling to normal levels at the end of passage 4. Hypercalcemia had no effect on plasma levels of CCK in tumor-bearing rats, but did stimulate the release of calcitonin in both control and some tumor-bearing rats in later passages. CCK-8 sulfate was found in all 4 tumor passages but not CCK-33/39. We conclude that rat MTC synthesizes and releases CCK-8, but unlike calcitonin, release of CCK appears unresponsive to calcium stimulation.

Animals↗

PubMed1991

Characterization of secretory component in amniotic fluid. Identification of new forms of secretory IgA.

Amniotic fluid (AmF) contains low levels of IgA of fetal origin. Western blot analysis revealed that the major forms of IgA in human AmF contain secretory component (SC), but ranged in size between 170 and 200 kDa, unlike the 380-kDa size typical of previously described secretory (s)IgA. Preliminary characterization of these novel forms of sIgA suggests they may arise by reduction of selected disulfide bonds, rather than proteolytic cleavage, of 380-kDa sIgA. This study also shows that AmF contains SC in its free form. Free SC measured by ELISA in 30 AmF samples increased with gestational age of the fetus from 26 to 40 wk postconception. Late in gestation, the concentrations of free SC levels reached those of other external secretions. Both the fetal urogenital system and the amniotic membrane appear to contribute to both the free SC and sIgA in AmF. This report presents the initial description of a new form of sIgA and provides evidence that the AmF may be an early expression of the mucosal immune system in the developing fetus.

Amniotic Fluid↗

PubMed1991

Differential effects of sodium butyrate and hexamethylene bisacetamide on growth and secretion of cultured human endocrine tumor cells.

Advanced gastrointestinal endocrine tumors respond poorly to conventional chemotherapy. In this study we examined the effects of two agents that promote cellular differentiation, sodium butyrate and hexamethylene bisacetamide, on the in vitro growth and secretory responses of a human pancreatic carcinoid (BON) and human gastrinoma (PT-2 and PT-SM) cell lines that have been established in our laboratory. We found that both sodium butyrate and hexamethylene bisacetamide strongly inhibited growth of BON, PT-2, and PT-SM cells. With continuous exposure of BON cells to sodium butyrate (2 mmol/L), the doubling time was prolonged, from 60 hours in controls to 156 hours, and saturation density was reduced to 28% that of controls. Hexamethylene bisacetamide (4 mmol/L) reduced saturation density to 37% that of controls in BON cells and prolonged the doubling time, from 60 hours to 103 hours. Antiproliferative effects of similar magnitudes were observed in the gastrinoma cell lines. In contrast, differential effects were produced on amine biosynthesis in BON cells; sodium butyrate stimulated levels of 5-hydroxytryptamine in the cells, whereas hexamethylene bisacetamide caused a profound dose-dependent inhibition of amine biosynthesis. The significant antiproliferative activity of sodium butyrate and hexamethylene bisacetamide and the inhibitory effects of hexamethylene bisacetamide on amine biosynthesis warrant evaluation of these agents or analogues for treatment of metastatic carcinoid and gastrinoma.

5-Hydroxytryptophan↗

PubMed1991

Pancreatic regeneration after partial pancreatectomy.

The ability of the pancreas to regenerate and the effects of trophic hormones on regeneration of the pancreas after partial pancreatectomy are not completely understood. We investigated the effects of the trypsin inhibitor FOY-305 (an agent that stimulates endogenous cholecystokinin) on pancreatic regeneration after partial pancreatectomy in rats. FOY-305 or water was administered for either 13 days or 27 days by gavage feeding, after sham operation or partial pancreatectomy (n = 6 to 8 animals per group). FOY-305 stimulated hypertrophy of the pancreatic remnant at 13 days; prolonged treatment for 27 days produced both hypertrophy and hyperplasia. The magnitude of pancreatic growth after FOY-305 administration was significantly greater at 27 days in the pancreatic remnant than growth of the equivalent pancreatic segment (duodenal and parabiliary) in sham-operated rats treated with FOY-305. Our results suggest that endogenous cholecystokinin released by FOY-305 stimulates regeneration after partial pancreatectomy. The pancreatic remnant is more sensitive to trophic stimulation in comparison to the normal pancreas. FOY-305 may be a useful agent in the treatment of pancreatic insufficiency after extensive subtotal pancreatectomy or chronic pancreatitis.

Animals↗

PubMed1991

Interferon-gamma modulates terminal differentiation and the expression of desquamin in cultured keratinocytes.

Interferon (IFN)-gamma has been shown to modulate cell differentiation and the expression of cell surface molecules of cultured human keratinocytes; it also induces cell shedding. We have previously described the properties of desquamin, a cell surface adhesion molecule from the stratum corneum. We report here on the impact of IFN-gamma on the expression of desquamin. We document the related morphological changes in terminal differentiation. We cultured human keratinocytes in three different culture systems: in serum-free medium at low Ca2+ (0.1 mM), at high Ca2+ (1.5 mM), and at high Ca2+ with 10% serum. IFN-gamma (100 U/ml) was added to each culture system after overnight incubation. In all cases, IFN-gamma induced an altered phenotype, as shown by phase contrast and electron microscopy. We exposed cultured cells to antibodies to the desquamins (glycoproteins from the stratum corneum). Immunoflurescent localization and Western blotting showed that the desquamins were expressed only under culture conditions where both serum and IFN-gamma were present. The induction of desquamin expression by IFN-gamma coupled with an increase in cell shedding, suggests that we have developed a suitable culture system for the study of desquamation in vitro.

Antibodies, Monoclonal↗

PubMed1991

Establishment and characterization of a human carcinoid in nude mice and effect of various agents on tumor growth.

The authors have established a long-term tissue culture cell line (BON) derived from a metastatic human carcinoid tumor of the pancreas. The cells have been in continuous passage for 46 months. Tissue culture cells produce tumors in a dose-dependent fashion after SC inoculation of cell suspensions in athymic nude mice. BON tumors, grown in nude mice, are histologically identical to the original tumor; they possess gastrin and somatostatin receptors, synthesize serotonin and chromogranin A, and have a doubling time of approximately 13 days. The antiproliferative effects of the long-acting somatostatin analogue, SMS 201-995 (300 micrograms/kg, t.i.d.), and 2% alpha-difluoromethylornithine on BON xenografts in nude mice were examined. Tumor size was significantly decreased by day 14 of treatment with either agent and at all points of analysis thereafter until the animals were killed (day 33). In addition, tumor weight, DNA, RNA, and protein contents were significantly decreased in treated mice compared with controls. Establishment of this human carcinoid xenograft line, BON, provides an excellent model to study further the biological behavior of carcinoid tumors and the in vivo effect of chemotherapeutic agents on tumor growth.

Animals↗

PubMed1991

Grafting of leg ulcers with undifferentiated keratinocytes.

A procedure for transplanting cultured human keratinocytes has been developed and used successfully to treat patients with persistent leg ulcers. Shave excisions of donor skin of 1 cm2 or less were expanded in culture in 1 week to cover wounds as large as 90 cm2. The uniqueness of this system is the use of a biochemically modified surgical dressing that permits the transplantation of undifferentiated cells. Several hours after inoculation, trypsinized single cells become attached to the dressing and are ready for grafting. Seven of eight persistent stasis ulcers completely reepithelialized after application of the modified surgical dressing with undifferentiated keratinocytes.

Bandages↗

PubMed1991

Studies on the mechanism of urotoxic effects of N,N'-dimethylaminopropionitrile in rats and mice. 1. Biochemical and morphologic characterization of the injury and its relationship to metabolism.

N,N'-Dimethylaminopropionitrile (DMAPN), a major component of the NIAX catalyst ESN, is known to cause urinary bladder dysfunction in exposed workers. In order to investigate the mechanism of DMAPN toxicity, we carried out time-course (0-72 h) and dose-response (175-700 mg/kg) studies on the effects of DMAPN in rats and mice. Treated animals exhibited several signs of toxicity including loss of body weight, reduced water consumption, and bladder urine retention, as well as bladder injury. DMAPN-induced bladder injury was characterized by distended bladders with marked diffuse submucosal and subserosal edema, petechial hemorrhage, and multifocal perivascular inflammatory infiltrates. The qualitative and quantitative analysis of urine indicated hypoosmolality, aciduria, hematuria, proteinuria, and oliguria. Elevated levels of creatinine and urea levels in plasma were indicative of renal dysfunction. Within hours following DMAPN administration, the animals exhibited a significant increase in urinary retention that resolved between 60 and 72 h. Rats excreted about 44% of the administered DMAPN dose unchanged in the urine, while mice excreted only about 6% of the dose. Commercially available DMAPN metabolites, administered by gavage, produced toxic effects less adverse than DMAPN. The biochemical effects of DMAPN included depletion of glutathione and increased lipid peroxidation in target organs, including urinary bladder and kidney. These studies indicate that there are species differences in DMAPN toxicity. The differences may be due to differences in the formation of reactive metabolic intermediates of DMAPN.

Aminopropionitrile↗

PubMed1991

Expression of neurotensin messenger RNA in a human carcinoid tumor.

Neurotensin (NT), a distal gut peptide, has important regulatory and trophic effects throughout the gut; however the intracellular mechanisms that regulate the gene expression and release of human NT are not known. The purpose of this endeavor was to study a functioning human pancreatic carcinoid cell line (called BON) in vitro that expresses the NT gene, and to study the effect of the cyclic adenosine monophosphate (cAMP) signal-transduction pathway on the expression and release of human NT. RNA was prepared from BON cell line (which has been established in this laboratory); the RNA was analyzed for NT mRNA expression by Northern hybridization with a complementary DNA probe. RNA blot analysis demonstrated that the NT gene is expressed in BON and is transcribed to two mRNAs of 1.0- and 1.5-kb sizes. In the second part of this study, BON cells were treated with either forskolin (FSK), which increases intracellular levels of cAMP, or with serotonin (5-HT), which reduces cAMP in BON cells. Forskolin produced a dose-dependent increase in NT peptide release and, furthermore, FSK (10(-6) mol/L) rapidly increased NT mRNA abundance 1 hour after addition; conversely, 5-HT (10(-5) mol/L) decreased NT mRNA at 1 hour. Neurotensin mRNA levels returned to control values by 3 hours after either FSK or 5-HT, which suggests that the transcript half-life for NT is relatively short. These findings show that the expression and peptide release of human NT is mediated, in part, by the cAMP signal-transduction pathway. Our human carcinoid cell line will provide a useful model to study the in vitro regulation of NT gene expression and peptide release.

Animals↗

PubMed1991

Sensitivity of desquamin to proteolytic degradation.

The stratum corneum is both a desquamating and degradative tissue; cell contacts become weaker in the outer lamellae and a variety of proteolytic and glycolytic enzymes cleave many macromolecules into free amino acids and saccharides. We have reported on a 40-kilodalton glycoprotein from human stratum corneum; because of its unique lectin-like properties, we believe that it plays a major role in desquamation and have named it desquamin. If desquamin is to function as a lectin during desquamation, it must survive enzymatic degradation in the outer stratum corneum. Accordingly, we treated this glycoprotein with a number of proteinases and found that desquamin is resistant in vitro to most of the types of proteinases that have been reported in the stratum corneum as well as several others that have not been identified as present in the tissue. In the stratum corneum, the lipids of the intercorneal mortar shield the glycoproteins; hence, desquamin is even less likely to be susceptible to endogenous proteolysis in vivo than in vitro.

Blotting, Western↗

PubMed1991

Effects of parathyroid hormonal peptides on the gut.

Our previous studies have shown PTH to be an effective relaxant of smooth muscle throughout the mammalian tract. Recently, we found PTHrP to be equally as potent and effective on the gut as PTH, and we hypothesized that PTHrP, rather than PTH, might be the natural ligand for the gut receptors which mediate GI smooth muscle relaxation. To approach this question, we asked whether rat GI tissue expresses mRNA for PTHrP. Using selective reverse transcription and PCR we have found PTHrP mRNA in smooth muscle throughout the rat GI tract and in gastric and colonic mucosa as well. Our findings support the idea that PTHrP can be produced by GI tissues and that it may function there as an autocrine or paracrine factor. One of its actions may involve regulation of GI muscle tone.

Animals↗

PubMed1991

Expression of the parathyroid hormone-related peptide gene in rat tissues.

We have demonstrated that parathyroid hormone-related peptide (PTHrP) mRNA is expressed ubiquitously in normal tissues of the rat, including organs previously considered to be transcriptionally silent. We reverse transcribed PTHrP and PTH mRNA and amplified the resultant cDNA using the polymerase chain reaction. The level of transcriptional activity of PTHrP was highly variable in different tissues, suggesting tissue-specific regulation. Significant PTHrP gene activity in the nonlactating mammary gland of the pregnant rat suggests that PTHrP may be involved in mammary differentiation. PTHrP gene expression was detected throughout the gastrointestinal tract and in cardiovascular tissues, suggesting that it might act as an autocrine and/or paracrine regulatory factor and may be the natural ligand for the receptors discovered originally in these tissues using PTH analogs. In contrast, PTH gene activity is restricted to the parathyroids, under physiologic conditions.

Animals↗

PubMed1990

Spontaneous induction of malignancy in mouse cells by a human small cell lung cancer implanted in nude mice.

This report provides evidence for spontaneous transfer of human tumor DNA in vivo to mouse cells by a human small cell lung cancer implanted in nude mice. The transformation of the mouse cells was characterized by the presence of neurosecretory granules, which are hallmarks of small cell lung cancer. The carcinogenicity of the human xenografted tumor DNA was confirmed by transfecting NIH3T3 cells in vitro, suggesting that the human tumor DNA may have been the cause of the transformation of the mouse cells in vivo. The spontaneous induction of malignancy in mouse cells in vivo by human tumor DNA may be a factor of potential importance in tumor cell heterogeneity and propagation of the malignant state for some tumors. The observations support the thesis that some human cancer cells can transform normal cells to become malignant in vivo.

Animals↗

PubMed1990

Effect of somatostatin and tamoxifen on the growth of human pancreatic cancers in nude mice.

We studied the effects of SMS 201-995 (SMS), a somatostatin analog, and tamoxifen, an antagonist of estrogenic actions, on the growth of human pancreatic cancers (SKI and PGER) in vivo. Male nude mice were inoculated with either SKI or PGER by passage of tumor chunks (3 mm2) to the scapular region. Mice from each tumor group were randomly allocated to one of four treatment groups: group 1, control group; group 2, SMS (100 micrograms/kg t.i.d.); group 3, tamoxifen (10 mg/kg three times a week); and group 4, SMS (100 micrograms/kg t.i.d.) + tamoxifen (10 mg/kg three times a week). The somatostatin analog, SMS, given alone or as a combined regimen with tamoxifen, significantly reduced (a) the rate of growth of SKI, and (b) DNA, RNA, and protein content of the tumors. On the other hand, in the case of PGER tumors, none of the treatment regimens significantly influenced the growth of PGER in vivo. Despite showing no significant effects during the study, PGER tumors in mice receiving tamoxifen alone had significantly lower total DNA, RNA, and protein contents compared to control tumors; this was reversed on combined treatment with SMS. None of the growth parameters of PGER was effected by SMS alone. We conclude that, in the case of SKI, SMS with or without tamoxifen was effective as a growth inhibitory agent, whereas in the case of PGER, tamoxifen alone was effective. This finding suggests that independent pathways mediate the growth-inhibitory effects of tamoxifen and SMS, and that different pancreatic cancers may respond to the two agents differently, some with inhibition, some not.

Animals↗

PubMed1990

Reduced cholecystokinin mediates the inhibition of pancreatic growth induced by bile salts.

The effects of luminal bile salts on plasma levels of cholecystokinin (CCK) and growth of the pancreas in mice were studied. Nonfasting levels of plasma CCK in control mice were 8.1 +/- 1.5 pM. Feeding mice a 0.5% (wt/wt) sodium taurocholate-supplemented diet for 1 wk significantly lowered nonfasting levels of plasma CCK to 4.1 +/- 0.5 pM and decreased the total contents of pancreatic DNA by 22%, RNA by 25%, and protein by 24%. All of the inhibitory effects of taurocholate on pancreatic growth were completely reversed by the simultaneous administration of CCK-8 (3 micrograms/kg, 3 times daily). In contrast, intraluminal neutralization of endogenous bile salts by feeding a 4% (wt/wt) cholestyramine-supplemented diet for 1 wk significantly elevated nonfasting levels of plasma CCK to 14.7 +/- 1.5 pM and increased the total contents of pancreatic DNA by 34%, RNA by 40%, and protein by 35%. All of the stimulatory actions of cholestyramine on pancreatic growth were completely abolished by the administration of the highly potent and specific CCK-receptor antagonist L364,718 (1 mg/kg, twice daily). These findings, therefore, indicate that bile salts appear to play a physiological role in pancreatic growth by regulation of plasma levels of CCK.

Animals↗

PubMed1990

Manipulation of macrophage migration inhibition/stimulation responses by adjuvants and interleukins.

C57 B1/6 mice were immunized with bovine serum albumin (BSA) and Freund's complete and incomplete adjuvants in various concentrations. Spleen cells from these animals were subsequently stimulated with concanavalin A (Con A), purified protein derivative or BSA, and lymphokine responses were measured in one-stage migration assays. Con A consistently produced macrophage migration inhibition factor (MIF) responses in nonimmunized animals and those immunized with complete adjuvant. This was switched to migration stimulation factor (MStF) responses by prior immunization with incomplete adjuvant. Immunization with complete adjuvant and with BSA alone was followed by MIF responses to antigenic stimulation whereas incomplete adjuvant promoted MStF responses. The MStF responses to both mitogenic and antigenic stimulation were inhibited by the addition of affinity purified interleukin-1 to the spleen cells. Interleukin-1 also inhibited MStF responses and potentiated MIF responses to Con A stimulation by human mononuclear cells whereas interleukin-2 did not influence these responses.

Animals↗