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Biomedical subjects

S Gunasekaran

Publications and source records attributed to S Gunasekaran.

At least 37 records · Page 2Linked to original sources
PubMed2002

Reduction of immunogenicity by cyclophosphamide pretreatment and culture on xenograft survival of monkey pancreatic islets transplanted into rats.

INTRODUCTION: Islet cell transplantation offers a new approach for the treatment of diabetes. Before transplantation, immunomodulation procedures are conducted to reduce the immunogenicity of the pancreatic islets. AIM: To study the effect of cyclophosphamide pretreatment and culture on the xenograft survival of monkey pancreatic islets. METHODOLOGY: Islets were isolated from normal monkeys and transplanted under the renal capsule of the rats. The grafts were removed 7 days after transplantation and processed for histologic study to examine graft survival. Islets from normal monkeys without cyclosporine treatment were destroyed in 7 days. These islets required cyclosporine (30 mg/kg) to prevent rejection. In the second group, the donor monkeys were treated with cyclophosphamide (60 mg/kg body weight) -4 and -2 days before harvesting of the islets. On day 0, the islets were isolated and cultured in RPMI-1640 medium for 7 days in 95% air and 5% CO2. After culture, the islets were transplanted into the rats. The grafts were removed and processed for histologic study to examine graft survival. RESULTS: The pretreated and cultured islets required 15 mg/kg cyclosporine to prevent rejection. Half of the usual dose of cyclosporine is enough to prevent rejection if the donor monkeys were pretreated and the islets cultured. CONCLUSION: This study shows that donor pretreatment and culture reduces immunogenicity of the xenotransplanted primate islets into rats.

Animals↗
PubMed2002

Cytogenetic, fluorescent in situ hybridization & reverse transcriptase-polymerase chain reaction analysis in acute promyelocytic leukaemia patients.

BACKGROUND & OBJECTIVES: The presence of t(15;17) or PML-RAR alpha fusion transcript is the diagnostic hallmark of patients with acute promyelocytic leukaemia (APL). Cytogenetic (CG), fluorescent in situ hybridization (FISH) and reverse transcriptase-polymerase chain reaction (RT-PCR) are mainly the techniques used for detecting this abnormality. The objective of this study was to compare and assess the role of CG, FISH and RT-PCR in the diagnosis of APL. METHODS: CG, FISH and RT-PCR analysis were performed in 29 patients with APL (28 M3, 1 M3v; 27 studied at diagnosis and 2 at relapse). RESULTS: Karotypes obtained in 25 patients revealed t(15;17) in 21 normal karyotype in 3 and trisomy 8 in 1 patient. In 26 patients FISH was positive for PML-RAR alpha fusion in both interphase (IP) and metaphase, two were negative and one patient had no cells for FISH analysis. IP FISH confirmed the fusion of PML-RAR alpha in all patients with t(15;17) detected by CG. RT-PCR was positive in the 22 patients analyzed (7 patients did not have RT-PCR). PCR was positive in the 3 patients with cytogenetically normal karyotypes and in one patient when karyotyping was a failure. CG detected 21 (72.4%) patients with t(15;17) of which additional chromosomal abnormalities were detected in 20 per cent of patients with successful karyotype. INTERPRETATION & CONCLUSION: FISH and RT-PCR were useful in detecting PML-RAR alpha fusion in cytogenetically normal patients and those in when karyotyping was a failure and can be used in routine analysis for rapid confirmation of t(15;17) in patients with acute myeloid leukaemia.

Adolescent↗
PubMed2001

Effect of heat treatments on the meltability of cheeses.

The effect of heat treatments on the meltability of cheese was investigated. Cheddar cheeses of different composition and low-moisture, part-skim Mozzarella cheese were studied at 1, 3, 6, and 12 wk of aging. Cheese samples were heated to 60 degrees C and held for 0, 10, and 20 min before allowing the melted cheese to flow. Mean meltabilities, over all ages, of both Cheddar and Mozzarella cheeses decreased significantly as holding time increased. Meltability of young cheese was scarcely affected by the holding time, in sharp contrast to that of the old cheese where increasing the holding time greatly reduced meltability.

Cheese↗
PubMed2001

Nuclear magnetic resonance study of water mobility in pasta filata and non-pasta filata mozzarella.

Changes in molecular mobility of water in pasta filata and non-pasta filata Mozzarella cheeses were investigated during the first 10 d of storage using nuclear magnetic resonance (NMR) relaxation techniques. Water in pasta filata Mozzarella was classified into two fractions by spin-spin relaxation times, T21 and T22, and corresponding proton intensities, A1 and A2, representing low and high molecular mobility, respectively. Increase in A1 (and decrease in A2) suggested that, there was a redistribution of water from more- to less-mobile fraction (from T22 to T21 fraction) during the first 10 d of storage. The NMR data did not indicate the two-state behavior of water molecules in non-pasta filata Mozzarella. However, the T2 values of non-pasta filata Mozzarella were comparable to the T21 values of pasta filata Mozzarella indicating that the molecular mobility of water in non-pasta filata Mozzarella is comparable to that of the less mobile water fraction in pasta filata Mozzarella. Generally, T2 and T1 values of pasta filata and non-pasta filata Mozzarella cheeses increased during the 10-d storage. This is believed to be due to structural changes in the protein matrix.

Cheese↗
PubMed2000

A viscoelasticity index for cheese meltability evaluation.

A device especially designed for uniaxial creep test was used in this study. Cheddar cheeses of different fat content were used. To study the linear viscoelastic response of the cheese, temperature of 40 degrees C and stress of 1119.5 Pa were chosen. Tests were carried out at cheese ages of 1, 3, 6, and 12 wk after production date. A six-element Kelvin model was used to model the creep data. Instantaneous slope of the creep curve was defined as the viscoelasticity index. The results showed that the viscoelasticity index based on viscoelastic parameters could be used for predicting cheese meltability. From the analysis of variance test, it was evident that that the viscoelasticity index can be used to distinguish the meltability of Cheddar cheeses of different ages and fat levels.

Cheese↗
PubMed1999

Distal external iliac lymph nodes in early cervical cancer.

OBJECTIVE: To evaluate the utility of the deep circumflex iliac vein as a landmark for the caudal limit of external iliac lymphadenectomy for early cervical cancer. METHODS: During dissection of the distal (caudal), anterior (ventral) aspect of the external iliac vessels in conjunction with radical hysterectomy for carcinoma of the cervix, a careful search was made for the deep circumflex iliac vein. Lymph nodes immediately above this vein were sent as adjacent and lymph nodes caudal to the vein were sent as distal. The distance from the vein to the femoral canal was measured. RESULTS: Seventy-one women were studied over 40 months. Fifty-five had squamous cell carcinoma, 15 had adenocarcinoma, and one had adenosquamous carcinoma. The mean distance from the deep circumflex iliac vein to the femoral canal was 16 mm. Sixty-three patients had dissections distal to identified deep circumflex iliac veins and 49 (77%) of these had distal lymph nodes removed. The median number of pelvic lymph nodes removed was 24 (range nine to 68), and the median number of distal lymph nodes removed was 1.0 from each side. Lymph node metastases were found in 13 women (18%). One subject with multiple macroscopically positive nodes had a single positive distal lymph node. Thus, a small number of distal lymph nodes were found in most women with early invasive cervical cancer, and 8% of those with positive nodes had involvement of this nodal group. CONCLUSION: The deep circumflex iliac vein was an appropriate landmark for the caudal limit of external iliac lymphadenectomy.

Adult↗
PubMed1999

Acute renal failure from multiple myeloma precipitated by ACE inhibitors.

Renal failure in multiple myeloma can be precipitated during hemodynamic perturbances of renal blood flow, as seen secondary to volume depletion, radiocontrast dye, and nonsteroidal anti-inflammatory agents. We report two cases of acute renal failure that developed suddenly after initiation of angiotensin-converting enzyme (ACE) inhibitor, both with biopsy-proven cast nephropathy. ACE inhibitors may contribute to the intratubular light chain cast formation and acute "myeloma kidney" in susceptible patients.

Acute Kidney Injury↗
PubMed1999

Evaluation of radioiodination of meta-iodobenzylguanidine (MIBG) catalysed by in situ generated Cu(I) and directly added Cu(II).

A reliable method of labelling MIBG with 131I is reported. Radioiodination involved nucleophilic exchange reaction (160 degrees C, 30 min) catalysed by directly added Cu(II) or by Cu(I) generated in situ by addition of Na2S2O5 to CuSO4. An additional step of purification of the radiolabelled MIBG by anion exchange chromatography is recommended. The radiochemical (RC) yield was over 90%, while the typical RC purity of 131I-MIBG was not less than 98%. Higher labelling yield was achieved with Cu(I) than when using Cu(II), and with 125I (commercial product) than with 131I obtained by wet radiochemical processing method in-house. The purity and stability of MIBG-131I was confirmed by biodistribution studies in monkeys with 0.03% and 0.8% uptake in adrenals and myocardium, respectively. It is concluded that Cu(I) or Cu(II) catalysed radioiodination method is well suited for production of MIBG-131I.

3-Iodobenzylguanidine↗
PubMed1999

Evaluation of uroprotective efficacy of amifostine against cyclophosphamide induced hemorrhagic cystitis.

The role of amifostine in the prevention of cyclophosphamide-induced hemorrhagic cystitis (HC) was evaluated in the rat model. Urinary bladders from control rats that received no drugs (group I) were compared with those from rats receiving cyclophosphamide alone at a dose of 150 mg/kg (group II), and two other groups receiving amifostine at 100 mg/kg (group III) and 200 mg/kg (group IV), 15 min prior to cyclophosphamide. Bladders were assessed macroscopically and histologically at 24 h and after 7 days. All the animals that received cyclophosphamide alone developed severe HC. On the basis of the scores of macroscopic and histologic changes, animals that received amifostine showed excellent uroprotection. Only 2/6 rats in group III and 1/6 rats in group IV developed mild HC at 24 h. None of the rats in either of these groups showed any evidence of HC at 7 days. It is concluded that amifostine protects the urothelium against cyclophosphamide-induced HC.

Amifostine↗
PubMed1999

Optimization of culture conditions for the preservation of monkey pancreatic islets in culture.

Culturing of islets is essential for various purposes before transplantation. It is necessary to establish optimal culture conditions for each animal species for their preservation in culture. In this study, attempts were made to preserve the Indian bonnet monkey islets in culture. The islets were isolated from monkey pancreas by the collagenase digestion method. They were separated from acinar cells by dextran density-gradient centrifugation. They were preserved in a humidified atmosphere of 5% carbon dioxide and 95% air for 7 days. The culture medium used was RPMI-1640. Various optimal conditions such as volume of the culture medium used, number of islets in one culture dish, concentration of glucose in culture medium, and fetal calf serum percentage were tested for their better preservation in culture. After the culture period, they were tested for their insulin secretory capacity by exposing them to various secretagogues. Histologic appearance of the cultured islets also was examined. Both insulin secretory characteristics and histologic structure were found to be normal.

Animals↗
PubMed1997

Xenographic transplantation of monkey pancreatic islets into rats.

Islets of Langerhans were isolated from the monkey pancreatic by collagenase digestion method. Freshly isolated monkey pancreatic islets were transplanted under the renal capsule of normal rats. Treated group of rats received Cyclosporine A injections and the control group of rats did not receive any drug. In Cyclosporine A treated rats the monkey islets were not destroyed. They maintained their normal structural integrity with occasional neutrophils surrounding the islets. In the untreated rats dense infiltration of neutrophils destroyed the islets in three days. On the seventh day dense infiltration of lymphocytes was seen. Granulomas composed of epitheloid cells and occasional multinucleated Langerhans type giant cells were seen on the fourteenth day.

Animals↗
PubMed1997

Intravenous glucose tolerance test in Macaca radiata radiata.

A reliable method for performing sensitive intravenous glucose tolerance tests in monkeys has been standardized. This helps in assessment of beta cell function. A normal curve for glucose disposal is constructed. A high variability in insulin levels is also documented.

Animals↗
PubMed1997

Antifungal activity of conjugated styryl ketones.

The susceptibility of Aspergillus fumigatus to a series of alpha, beta-unsaturated styryl ketones known to be thiol-alkylators was examined, and the results were compared with those obtained for Candida albicans. Among 13 compounds used in our study, one (designated NC1110) inhibited the growth of A. fumigatus completely at low concentrations (minimum inhibitory concentration = 32 microM). Structure-activity analysis of these compounds indicated that the electron attracting property as well as the overall hydrophobicity of the compounds are important parameters for their antifungal activity. These preliminary results suggest that further modification of these molecules to enhance their hydrophobicity and the electron attracting property may result in more active compounds with improved antifungal activity.

Antifungal Agents↗
PubMed1996

Changes in glutathione metabolic enzymes during yeast-to-mycelium conversion of Candida albicans.

Candida albicans is a dimorphic yeast capable of producing alternate morphological forms (yeast or mycelium) in response to environmental changes. The intracellular level of glutathione, which helps to maintain the redox potential of the cell, is decreased significantly during the thermal induction of yeast-to-mycelium conversion. The reason for the decline of glutathione in the mycelial form is not understood. We have, therefore, investigated the levels of glutathione reductase, glutathione S-transferase, gamma-glutamyltranspeptidase, and glutathione peroxidase, four key enzymes involved in glutathione metabolism, in the yeast and mycelial forms. Yeast cells of C. albicans 3153A were induced in Lee's medium (pH 6.5) at 37 degrees C for 3 h to produce germ tubes. Cell lysates were prepared from yeast and mycelial cells, and glutathione reductase, glutathione S-transferase, gamma-glutamyltranspeptidase, and glutathione peroxidase were assayed spectrophotometrically. There was a 640% increase of the level of gamma-glutamyltranspeptidase in the germ tubes as compared with the yeast cells. No other significant alteration of the levels of enzymes was noted. This increased activity of gamma-glutamyltranspeptidase, which cleaves the glutamic acid residue of glutathione (Glu-Cys-Gly) appears to be, at least in part, responsible for the rapid decrease of the intracellular glutathione in C. albicans during the yeast-to-mycelium conversion.

Amino Acid Sequence↗