Biomedical subjects

R Ramanathan

Publications and source records attributed to R Ramanathan.

At least 55 records · Page 3Linked to original sources

PubMed1998

Differential regulation of IL-8 by IL-1beta and TNFalpha in hyaline membrane disease.

Mechanisms that regulate cytokine-mediated inflammation in the lungs of preterm infants, including factors which regulate production of the chemokine IL-8, remain poorly defined. Sequential bronchoalveolar lavage samples were obtained from preterm newborns with hyaline membrane disease over a 28-day period. Bronchoalveolar lavage cell cytokine relationships were evaluated and the differential regulation of IL-8 by IL-1beta and TNFalpha was studied in a short-term culture system. In vivo, IL-8 and IL-1beta protein levels correlated closely with each other and with macrophage counts. In cell culture, exogenous anti-IL-1beta antibody led to a 40% maximum inhibition (approximately) of IL-8 production by lipopolysaccharide stimulated lung inflammatory cells. Comparable amounts of exogenous anti-TNFalpha antibodies achieved a 15% maximum inhibition (approximately) of IL-8 production. Anti-IL-1beta and anti-TNFalpha antibodies in combination did not inhibit IL-8 production beyond that achieved by anti-IL-1beta antibody alone. These results, in preterm newborns, support the concept of lung inflammation mediated in part by a macrophage, IL-1beta, and IL-8 cell cytokine pathway. The results also suggest that factors other than IL-1beta and TNFalpha regulate IL-8 expression in the lungs of preterm infants.

Antibodies, Blocking↗

PubMed1998

Relief of urinary tract obstruction in tuberculosis to improve renal function. Analysis of predictive factors.

OBJECTIVE: To assess the effect of the relief of obstruction on the ultimate function of the affected renal unit in urinary tuberculosis, and to identify predictors of functional recoverability. PATIENTS AND METHODS: Of a total of 82 patients with urinary tuberculosis presenting over 7 years, 38 with evidence of upper tract obstruction were analysed. All patients were assessed with pre-operative excretory urography, urinary mycobacterial cultures and serum chemistry. Patients with subnormally functioning kidneys were assessed with baseline renal scans. Preliminary intervention in the form of JJ stenting or percutaneous nephrostomy (PCN) was carried out in patients with reasonable renal function. Function was reassessed after 4 weeks to detect evidence of improvement and factors which could affect the outcome were determined. RESULTS: Thirty-eight patients had documented upper tract obstruction, of whom six had bilateral obstruction (total of 44 renal units). Ten renal units were not functioning at presentation, with a mean (SD) glomerular filtration rate (GFR) of 3.0 (5.73) mL/min, and no preliminary intervention was performed. In the remaining 34, preliminary intervention was carried out before definitive surgery (JJ stenting in 14, PCN in 15 and PCN followed by antegrade JJ stenting in five); 21 of these renal units were salvaged but 13 were lost despite overcoming the obstruction. Three of the 13 units deteriorated from having acceptable pre-treatment GFRs to becoming non-functional. Good renal cortical thickness, a low grade of renal involvement (Semb 1 or 2), the presence of more distal disease in the form of ureteric stricture and a GFR of > 15 mL/min were good predictors of renal recovery after diversion. CONCLUSIONS: The loss of some renal units seems inevitable in patients with urinary tuberculosis, despite advances in chemotherapy. Having pre-operative predictors of renal recovery may ensure optimal patient selection, thereby reducing the number of procedures and economic burden on the patient who does not require intervention.

Adult↗

PubMed1998

Aneurysm of the ductus arteriosus: a congenital lesion.

The objective of this study was to evaluate the clinical, radiological, and echocardiographic findings in 11 neonates with aneurysm of ductus arteriosus presented in our institutions between 1993 and 1996, and to postulate a new theory for the pathogenesis of this lesion. Medical records, radiographic studies, and echocardiograms were reviewed. All infants underwent follow-up echocardiograms every 2 to 3 days until the aneurysm spontaneously resolved or surgery was performed. The infants were predominantly term males; six had evidence of fetal distress, two were diagnosed prenatally by fetal echocardiogram, chest X ray evidenced mediastinal mass in six patients. The first echocardiogram showed structurally normal heart with an aneurysmal patent ductus arteriosus. In eight patients the aneurysm completely resolved by 5 to 10 days. One infant underwent surgical resection of the aneurysm after observation for 11 days with no change in size. Thrombosis of the aneurysm was noted in two patients; both underwent surgery. Increasing reports of ductal aneurysms in infants may reflect the availability of high-resolution echocardiography and more frequent use of echocardiography in the neonatal intensive care unit. Spontaneous resolution occurred in the majority of cases as in previous reports. We postulate that, at least in some cases, aneurysm of the ductus arteriosus is a congenital lesion that may represent poststenotic dilation of the ductus due to turbulent flow through a stenotic segment at its pulmonary artery end during fetal life. The presence of aneurysm of the ductus arteriosus should be excluded in selected cases of fetal distress, by fetal echocardiography.

Aortic Aneurysm, Thoracic↗

PubMed1998

A new transformation-deficient mutant of Haemophilus influenzae Rd with normal DNA uptake.

Haemophilus influenzae Rd is a gram-negative natural transformer. A mutant strain, RJ248, that has normal DNA uptake and translocation but whose transformation frequency is 300 times lower than that of wild-type H. influenzae and whose phage recombination is 8 times lower was isolated. The affected gene, comM, is induced during competence development in wild-type H. influenzae but not in RJ248.

DNA Transposable Elements↗

PubMed1998

Arthroscopy under local anaesthesia.

We studied 95 patients who underwent knee Arthroscopy under local anaesthesia between JANUARY 1995 till 1997. Materials used were 1% Xylocaine and 0.25% Bupivacaine of 20 mls each combined with midazolam 2 mg and IV pethidine 30 mgm for sedation. The patients were attached to monitors (pulse Oxymeter, ECG and BP and pulse recorders) and blood less field was created using a tornquet. The procedures lasted about 45 minutes. 90 out of 95 patients completed the procedures successfully without any complications. 2 developed respiratory embarrassments and were intubated and ventilated. 3 procedures abandoned and converted to general anaesthesia. The range of procedures done include meniscectomy, meniscal repair, synovial biopsy, debridement for osteoarthrosis, shaving of osteophytes, drilling of cartilage and bones and removal of loose bodies. This study is to show that knee arthroscopy under LA is a safe alternative in hospitals where GA time is limited.

Adult↗

PubMed1997

Monitoring recombinant protein drugs: a study of insulin by H/D exchange and electrospray ionization mass spectrometry.

The increasing emergence of new protein- and peptide-based drugs makes necessary the development of rapid and sensitive methods to check consistency between and within batches of biotechnology pharmaceuticals to ensure product quality. We evaluated electrospray ionization mass spectrometry in combination with H/D isotopic exchange as a potential tool, taking as examples for this case study the four insulins used for treating insulin-dependent diabetes. Two (bovine and porcine) are produced naturally, and two are produced by recombinant biotechnology techniques [recombinant human (r-human) and its human insulin analog (LysPro)]. The extent of H/D exchange at a given time was measured with less than 2 micrograms (< 350 pmol) of sample and was sufficient for discriminating among the different insulins. After 60 min, bovine, porcine, r-human, and LysPro insulins exchanged on average 25, 28, 30, and 38 amide protons, respectively. After prolonged incubation with D2O for 24 h, bovine and porcine insulins exchanged 31 protons, whereas r-human and LysPro insulins exchanged 34 and 43 amide protons, respectively. The differences in H/D exchange are protein signatures that relate to differences in conformation and folding. The extent of exchange distinguishes among the insulin types and assures the consistency of batch preparations for a given insulin.

Animals↗

PubMed1997

Molecular origin of cancer: catechol estrogen-3,4-quinones as endogenous tumor initiators.

Cancer is a disease that begins with mutation of critical genes: oncogenes and tumor suppressor genes. Our research on carcinogenic aromatic hydrocarbons indicates that depurinating hydrocarbon-DNA adducts generate oncogenic mutations found in mouse skin papillomas (Proc. Natl. Acad. Sci. USA 92:10422, 1995). These mutations arise by mis-replication of unrepaired apurinic sites derived from the loss of depurinating adducts. This relationship led us to postulate that oxidation of the carcinogenic 4-hydroxy catechol estrogens (CE) of estrone (E1) and estradiol (E2) to catechol estrogen-3,4-quinones (CE-3, 4-Q) results in electrophilic intermediates that covalently bind to DNA to form depurinating adducts. The resultant apurinic sites in critical genes can generate mutations that may initiate various human cancers. The noncarcinogenic 2-hydroxy CE are oxidized to CE-2,3-Q and form only stable DNA adducts. As reported here, the CE-3,4-Q were bound to DNA in vitro to form the depurinating adduct 4-OHE1(E2)-1(alpha,beta)-N7Gua at 59-213 micromol/mol DNA-phosphate whereas the level of stable adducts was 0.1 micromol/mol DNA-phosphate. In female Sprague-Dawley rats treated by intramammillary injection of E2-3,4-Q (200 nmol) at four mammary glands, the mammary tissue contained 2.3 micromol 4-OHE2-1(alpha, beta)-N7Gua/molDNA-phosphate. When 4-OHE1(E2) were activated by horseradish peroxidase, lactoperoxidase, or cytochrome P450, 87-440 micromol of 4-OHE1(E2)-1(alpha, beta)-N7Gua was formed. After treatment with 4-OHE2, rat mammary tissue contained 1.4 micromol of adduct/mol DNA-phosphate. In each case, the level of stable adducts was negligible. These results, complemented by other data, strongly support the hypothesis that CE-3,4-Q are endogenous tumor initiators.

Animals↗

PubMed1997

Functional and pharmacokinetic properties of antibody-avidin fusion proteins.

In an attempt to produce broadly useful targeting agents, genetic engineering and expression techniques have been used to produce Ab-avidin fusion proteins. Chicken avidin has been fused to mouse-human chimeric IgG3 at the end of C(H)1 (C(H)1-Av), immediately after the hinge (H-Av), and at the end of C(H)3 (C(H)3-Av). Fusion heavy chains of the expected molecular mass were expressed, assembled with a co-expressed light chain, and secreted. The resulting molecules continued to bind Ag. They also bound biotinylated human serum albumin; C(H)3-Av had reduced affinity (K(A) = 5.13 x 10(9) M(-1)) compared with the tetrameric avidin (K(A) = 1 x 10(15) M(-1)), but greater affinity than monomeric avidin (K(A) = 1 x 10(7) M(-1)). Importantly, the avidin-IgG fusion proteins had a longer serum t1/2 in rats than avidin. The favorable pharmacokinetic parameters suggest that these avidin fusion proteins can be used effectively to deliver biotinylated ligands such as drugs and peptides to locales expressing any Ag recognized by the associated Ab.

Animals↗

PubMed1997

The characterization, molecular cloning, and expression of a novel hematopoietic cell antigen from CD34+ human bone marrow cells.

The adhesion molecule BEN/SC1/DM-GRASP (BEN) is a marker in the developing chicken nervous system that is also expressed on the surface of embryonic and adult hematopoietic cells such as immature thymocytes, myeloid progenitors, and erythroid progenitors. F84.1 and KG-CAM, two monoclonal antibodies to rat neuronal glycoproteins with similarity to BEN, cross-react with an antigen on rat hematopoietic progenitors, but F84.1 only also recognizes human blood cell progenitors. We have defined the antigen recognized by F84.1 as the hematopoietic cell antigen (HCA). HCA expression was detected on 40% to 70% of CD34+ fetal and adult bone marrow cells and mobilized peripheral blood cells. Precursor cell activity for long-term in vitro bone marrow cell culture was confined to the subset of CD34+ cells that coexpress HCA. HCA is expressed by the most primitive subsets of CD34+ cells, including all rhodamine 123(lo), Thy-1+, and CD38(-/lo) CD34+ adult bone marrow cells. HCA was also detected on myeloid progenitors but not on early B-cell progenitors. We also describe here the cloning and characterization of cDNAs encoding two variants of the human HCA antigen (huHCA-1 and huHCA-2) and of a cDNA clone encoding rat HCA (raHCA). The deduced amino acid sequences of huHCA and raHCA are homologous to that of chicken BEN. Recombinant proteins produced from either human or rat HCA cDNAs were recognized by F84.1, whereas rat HCA but not human HCA was recognized by antirat KG-CAM. Expression of either form of huHCA in CHO cells conferred homophilic adhesion that could be competed with soluble recombinant huHCA-Fc. The molecular cloning of HCA and the availability of recombinant HCA should permit further evaluation of its role in human and rodent hematopoiesis.

Adult↗

PubMed1997

Intestinal fatty acid binding protein: a specific residue in one turn appears to stabilize the native structure and be responsible for slow refolding.

The intestinal fatty acid binding protein is one of a class of proteins that are primarily beta-sheet and contain a large interior cavity into which ligands bind. A highly conserved region of the protein exists between two adjacent antiparallel strands (denoted as D and E in the structure) that are not within hydrogen bonding distance. A series of single, double, and triple mutations have been constructed in the turn between these two strands. In the wild-type protein, this region has the sequence Leu 64/Gly 65/Val 66. Replacing Leu 64 with either Ala or Gly decreases the stability and the midpoint of the denaturation curve somewhat, whereas mutations at Gly 65 affect the stability slightly, but the protein folds at a rate similar to wild-type and binds oleate. Val 66 appears not to play an important role in maintaining stability. All double or triple mutations that include mutation of Leu 64 result in a large and almost identical loss of stability from the wild-type. As an example of the triple mutants, we investigated the properties of the Leu 64 Ser/Gly 65 Ala/Val 66 Asn mutant. As measured by the change in intrinsic fluorescence, this mutant (and similar triple mutants lacking leucine at position 64) folds much more rapidly than wild-type. The mutant, and others that lack Leu 64, have far-UV CD spectra similar to wild-type, but a different near-UV CD spectrum. The folded form of the protein binds oleate, although less tightly than wild-type. Hydrogen/deuterium exchange studies using electrospray mass spectrometry indicate many more rapidly exchangeable amide protons in the Leu 64 Ser/Gly 65 Ala/Val 66 Asn mutant. We propose that there is a loss of defined structure in the region of the protein near the turn defined by the D and E strands and that the interaction of Leu 64 with other hydrophobic residues located nearby may be responsible for (1) the slow step in the refolding process and (2) the final stabilization of the structure. We suggest the possibility that this region of the protein may be involved in both an early and late step in refolding.

Carrier Proteins↗

PubMed1997

Mitrofanoff principle for continent urinary diversion.

In 1980 Mitrofanoff described a method to achieve continent urinary diversion by surgically closing the bladder neck and creating a continent catheterizable stoma from the appendix which had been implanted in a nonrefluxing manner into the bladder or from a nonrefluxing distal ureter. The Mitrofanoff principle (MP) serves well as a continence mechanism for either the native bladder or intestinal reservoirs. We review 17 patients, including 10 children, who were treated with the MP and received a continent catheterizable channel. For the MP, appendix was used in 16 patients and ureter in 1. The continuity between the urinary reservoir and urethra was maintained wherever possible. Bladder neck suspension was preferred to bladder neck closure in incontinent females and boys. Complications and their management have been discussed at length. Stable renal functions, ease of catheterization and urinary continence were achieved in 93.8% of the patients.

Adolescent↗

PubMed1997

A method for preserving saliva samples at ambient temperatures.

To facilitate biochemical and biopharmaceutical studies when cold storage is unavailable, we assessed the stability of saliva samples containing preservatives stored at room temperature over a 1-year period. Two preservative mixtures were evaluated: sodium benzoate and citric acid (P1), and ethyl and propyl paraben (P2). Saliva samples were spiked with acetaminophen (APAP) or antipyrine (AP) and stored in preservative-coated vials and examined for concentrations of APAP, AP, melatonin, and cortisol at regular intervals as a function of preservative type and storage duration. Samples were stored at room temperature or at -20 degrees C (positive control) and analyzed periodically for APAP and AP by high-performance liquid chromatography and for melatonin and cortisol by radioimmunoassay. The effectiveness of the preservatives was determined by calculating the value of samples stored at room temperature in terms of percent of control (-20 degrees C) values. P1 effectively maintained the stability of APAP (100%) and AP (100%) for 360 days at room temperature; concentrations in samples at room temperature on day 360 were comparable to those on day 01. P1 also effectively maintained melatonin (100%) and cortisol (95%) concentrations for 180 days at room temperature. P2 preserved AP and cortisol in saliva for 60 days, but APAP for only 14 days.

Acetaminophen↗

PubMed1996

Alcohol inhibits cell-cell adhesion mediated by human L1.

Mental retardation, hydrocephalus, and agenesis of the corpus callosum are observed both in fetal alcohol syndrome (FAS) and in children with mutations in the gene for the cell adhesion molecule L1. We studied the effects of ethanol on cell-cell adhesion in mouse fibroblasts transfected with human L1. L1-transfected fibroblasts exhibited increased cell-cell adhesion compared with wild-type or vector-transfected controls. Ethanol potently and completely inhibited L1-mediated adhesion both in transfected L cells and NIH/3T3 cells. Half-maximal inhibition was observed at 7 mM ethanol, a concentration achieved in blood and brain after ingesting one alcoholic beverage. In contrast, ethanol did not inhibit the adhesion of fibroblasts transfected with vector alone or with N-CAM-140. L1-mediated cell-cell adhesion was inhibited with increasing potency by n-propanol and n-butanol, but was not inhibited at all by n-alcohols of 5 to 8 carbons, acetaldehyde, or acetate, suggesting that ethanol interacts directly with a small hydrophobic pocket within L1. Phenylalanine, teratogenic anticonvulsants, and high concentrations of glucose did not inhibit L1-mediated cell-cell adhesion. Ethanol also inhibited potently the heterotypic adhesion of rat cerebellar granule cells to a monolayer of L1-transfected NIH/3T3 cells, but had no effect on their adhesion to N-CAM-140 or vector-transfected NIH/3T3 cells. Because L1 plays a role in both neural development and learning, ethanol inhibition of L1-mediated cell-cell interactions could contribute to FAS and ethanol-associated memory disorders.

3T3 Cells↗

PubMed1996

Spontaneous perforation of the ureter: endourological management with renal preservation.

Spontaneous perforation of the ureter proximal to an obstruction has not been well described in the literature. We present a rare case of spontaneous perforation of the ureter, proximal to a radiolucent upper ureteric stone, in a 58-year-old diabetic female, causing a large infected urinoma and septicaemia in a solitary functioning kidney. The diagnosis was confirmed by computer tomography scan. We managed the case successfully by endourology only. The case emphasizes the importance of the differential diagnosis in a diabetic patient with obstructive uropathy.

Female↗

PubMed1996

Paclitaxel and carboplatin in metastatic non-small cell lung cancer: preliminary results of a phase I study.

Given their known activity against non-small cell lung cancer, paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) and carboplatin were combined in this phase I study of patients with metastatic disease to determine the maximum tolerated dose and the dose-limiting toxicity of the combination. The initial dose of paclitaxel was fixed at 135 mg/m2 given as a 24-hour infusion with carboplatin administered in escalating doses in cohorts using Calvert's formula-dose (mg) = target AUC x (GFR + 25), where AUC is area under the concentration-time curve and GFR is glomerular filtration rate-based on target AUCs of 5, 7, 9, or 11 mg/mL.min. Dose escalations were based on cycle 1 toxicities. Filgrastim was not administered with the first cycle until two or more patients developed grade 4 or febrile neutropenia at the preceding dose level. Dose-limiting toxicity occurred in two patients at level 2 (cycle 1), and filgrastim was administered thereafter for the next four dose levels. Grade 4 thrombocytopenia was seen at level 4; thus, the carboplatin dose was de-escalated thereafter, and the paclitaxel dose escalated. Rare nonhematologic toxicities include fatigue, diarrhea, and nausea and vomiting. Among the first 30 patients, one had a complete response and 14 had partial responses, for an overall response rate of 50%. The combination of paclitaxel and carboplatin is active in non-small cell lung cancer, and the recommended phase II dose without filgrastim support is paclitaxel 175 mg/m2 via a 24-hour infusion with the carboplatin dose targeted to achieve an AUC of 7 mg/ mL.min.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1995

Protection of plasmid pBR322 DNA by flavonoids against single-stranded breaks induced by singlet molecular oxygen.

Flavonoids, the dominant colouring pigments of plants, as well as the related polyphenol tannic acid significantly inhibit single-strand breaks in plasmid pBR322 DNA induced by singlet molecular oxygen ((1)O2). This reactive species of oxygen was generated in an aqueous buffer system by the thermal dissociation of the endoperoxide of 3,3'-(1,4-naphthylene)dipropionate. Among the antioxidants examined, myricetin showed the highest protective ability, followed by tannic acid, (+)catechin, rutin, fisetin, luteolin and apigenin, when the inhibitory abilities were compared at 90 min after incubation. The protective abilities of these compounds were both time and concentration dependent. At equimolar concentrations (100 microM) the antioxidant effect of myricetin was better than that of other known antioxidants such as lipoate, alpha-tocopherol and beta-carotene. Data, when analysed in relation to the structures of various compounds, showed a rough correlation with protective abilities. Owing to the abundance of these compounds in our normal diet, they may play significant roles in preventing oxidative damage resulting from potentially deleterious (1)O2.

Antioxidants↗

PubMed1995

Pharmacokinetics of paclitaxel and carboplatin in combination.

We studied the pharmacokinetics of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) and carboplatin administered in combination to 21 patients with advanced non-small cell lung cancer. Paclitaxel was administered as a 24-hour intravenous infusion at doses of 135 to 200 mg/m2. Carboplatin, dosed to a target area under the concentration-time curve of 5, 7, 9, or 11 mg/mL.min, was administered as a 20-minute infusion immediately following paclitaxel. Neither the paclitaxel concentrations at the end of the infusion nor the terminal elimination of paclitaxel, as assessed by the duration of time that plasma paclitaxel concentrations were 0.05 mumol/L or greater, were different compared with historical data of paclitaxel as a single agent. Thus, we concluded that carboplatin had no perceived effect on the pharmacokinetics of paclitaxel in this schedule. The observed areas under the concentration-time curves for carboplatin were consistently 10% to 15% less than the target values. Although this may indicate a possible interaction between paclitaxel and carboplatin, it also may have been a result of inadequate assessment of glomerular filtration rate, which was used to determine the carboplatin dose.

Adult↗

PubMed1994

Use of a physiologically based model to predict systemic uptake and respiratory elimination of perchloroethylene.

The pharmacokinetics of inhaled perchloroethylene (PCE) were studied in male Sprague-Dawley rats to characterize the pulmonary absorption and elimination of the volatile organic chemical (VOC). The direct measurements of the time course of PCE in the blood and breath were used to evaluate the ability of a physiologically based pharmacokinetic (PBPK) model to predict systemic uptake and elimination of PCE. Fifty or 500 ppm PCE was inhaled for 2 hr through a miniaturized one-way breathing valve by unanesthetized male Sprague-Dawley rats of 325-375 g. Serial samples of the inhaled and exhaled breath streams, as well as arterial blood, were collected during and following PCE inhalation and analyzed by headspace gas chromatography. PCE-exhaled breath concentrations increased rapidly to near steady state (i.e., within 20 min) and were directly proportional to the inhaled concentration. Uptake of PCE into the blood was also rapid, but blood levels continued to increase progressively over the course of the 2-hr exposure at both exposure levels. Cumulative uptake, or total absorbed dose, was not proportional to the exposure level. A PBPK model was developed from in vivo parameters determined from tissue concentration-time data in a companion ia study (Dallas et al., 1994, Toxicol. Appl. Pharmacol. 128, 50-59). PCE concentrations in the blood and exhaled breath during and following PCE inhalation were well predicted by the PBPK model. Despite species differences in blood:air and lung:air partition coefficients, the model was used to account for similar levels of PCE and other VOCs in the expired air of rats and humans. The model also accurately simulated percentage uptake and cumulative uptake of PCE over time. The model's ability to predict systemically absorbed doses of PCE under a variety of exposure scenarios should be useful in assessment of risks in occupational and environmental settings.

Absorption↗