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Biomedical subjects

G Chari

Publications and source records attributed to G Chari.

At least 19 recordsLinked to original sources
PubMed2005

Characterization of serine/cysteine protease inhibitor alpha1-antitripsin from meconium-instilled rabbit lungs.

We have recently purified from meconium-instilled rabbit lungs a novel serine proteinase inhibitor, with an apparent molecular mass of 50 kDa, which we assign to be alpha1-antitripsin. We hypothesize that serpin may attenuate pulmonary inflammation and improve surfactant function after meconium aspiration. Alpha1-antitripsin is a member of the proteinase inhibitor (serpin) superfamily and inhibitor of neutrophil elastase, and it can be identified as a member of the family by its amino acid sequence due to the high degree of conserved residues. Alpha1-antitripsin is synthesized by epithelial cells, macrophages, monocytes, and neutrophils. Deficiency in alpha1-antitripsin leads to exposure of lungs to uncontrolled proteolytic attack from neutrophil elastase or other damaging factors culminating in lung destruction and cell apoptosis. We hypothesize that accumulation of alpha1-antitripsin in the lungs serves as a predisposed protection against meconium-induced lung injury. In this paper, we show how this knowledge can lead to the development of novel therapeutic approaches for treatment of MAS.

Animals↗
PubMed2001

Cocaine permeability and metabolism in colonic T-84 epithelial cell line.

We studied the uptake, transport and metabolism of cocaine in human intestine using the colonic T-84 monolayers as a model. T-84 cells were grown in DMEM/Ham's F-12 medium containing 6% newborn calf serum at 37 degrees C on 1.0 microm collagen inserts. The cells develop into a polarized monolayer with the apical surface facing the upper chamber and the basolateral surface facing the lower. The monolayers develop a transepithelial resistance of > or = 600 ohms cm2 in 7 days. Varying concentrations of cocaine HCI was added in a serum free medium to the luminal side only, and after 30 min and 60 min samples from the luminal and serosal aspect were removed for analysis. Cocaine and its metabolites were measured by GC/MS. Cocaine transport across T-84 monolayers increased linearly with increasing concentration of cocaine, with no significant difference between 30 min and 60 min of exposure. Transepithelial resistance did not change even at 800 ng of cocaine suggesting no effect on monolayer viability. The metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME) but not norcocaine were detected in both luminal and serosal side. The concentrations of BE and EME in the luminal side were significantly higher than in the serosal. Combined recovery of cocaine, BE and EME from luminal and serosal sides were 52 - 80% of total added cocaine. While fresh medium did not metabolize cocaine, media previously exposed to the monolayer (cell-free medium) caused a significant breakdown into BE and EME, suggesting that esterases may be released into the medium. These results indicate transfer of cocaine across this model of intestinal epithelial cell line is by simple diffusion and is concentration dependent. These studies imply that cocaine in swallowed amniotic fluid can be absorbed by the fetal gastrointestinal tract.

Cell Line↗
PubMed1999

Current issues in depression in Parkinson's disease.

Depression affects 40%-50% of Parkinson's disease (PD) patients. The authors, by use of a Mednet and manual search of pertinent literature, summarize current issues in the treatment of depression in PD. Open-label studies suggest that antidepressants may be effective for treating depression in PD. Although case reports indicate that selective serotonin reuptake inhibitors (SSRIs) can potentially worsen the motor symptoms of PD, this effect has not been confirmed in the small number of open-label studies that have been performed to date. The occurrence of the serotonin syndrome resulting from a combination of selegiline and an SSRI appears to be rare. Double-blind prospective studies are needed to evaluate the safety and efficacy of antidepressants in PD and their effect on motor function.

Aged↗
PubMed1998

Opioid-induced analgesia in neonatal dogs: pharmacodynamic differences between morphine and fentanyl.

Whether the analgesic effects of opioids change as a neonate matures is not well understood. To address this issue, we determined the pharmacokinetics and pharmacodynamics of analgesic effects of morphine and fentanyl in 35 dogs aged 1 to 34 days. Opioids were infused to produce analgesia, response times to a noxious thermal stimulus were measured and plasma opioid concentrations were determined. An effect compartment pharmacodynamic model was fit to the values for time to response to determine the rate constant for equilibration (Keo) between plasma and effect-site (Ce) concentrations and analgesic effect (increase in time to response to a noxious stimulus) above baseline per microgram/ml of Ce (delta). A time-to-event data analysis (modeled with a Weibull function) was used to account for censored time to response values. For both opioids, values for Keo did not vary with age. Values for delta decreased with age (i.e., decreasing sensitivity with increasing age), and the magnitude of the change during the first month of life was similar for the two opioids. In the context of our previous study concerning ventilatory depressant effects of these opioids (that sensitivity to morphine, but not to fentanyl, decreased markedly during the first month of life), these results in dogs suggest that fentanyl has greater utility than morphine in neonates during spontaneous ventilation.

Analgesia↗
PubMed1997

Bile flow and composition in preterm, term and infant baboons.

UNLABELLED: We studied the maturational changes in bile composition, bile flow and choleretic effects of sodium taurocholate and secretin in preterm (160 +/- 2 days, n = 4, group I), term (184 +/- 2 days, n = 4, group II), 7-day postnatal age (n = 5, group III) and 60-day-old (n = 5, group IV) baboons. The canalicular bile flow was determined by 14C-erythritol clearance. RESULTS: Gall bladder volume increased from group I to group III (0.08 +/- 0.06 to 1.06 +/- 0.93 ml). Bile flow increased significantly from group I to IV (0.13 +/- 0.05 to 0.34 +/- 0.07 microliter/min/g liver weight, p < 0.05). This was associated with significant increases in total bile acid excretion (16 +/- 3.6 to 31 +/- 2.5 mEq/l, p < 0.05). The composition of bile also showed maturational changes with increasing postnatal age. Sodium taurocholate and secretin increased the bile flow significantly in all groups. CONCLUSION: Data from these studies clearly demonstrate that the bile flow and bile acid excretion is immature in preterm and term baboons when compared to 7- and 60-day-old baboons. The present studies also suggest that baboons can be used as a model to study the postnatal maturation of hepatic excretory function.

Animals↗
PubMed1996

Progressive deterioration of intellect and motor function occurring several decades after cranial irradiation. A new facet in the clinical spectrum of radiation encephalopathy.

OBJECTIVE: To report the cases of 2 patients who developed the features of radiation encephalopathy 33 and 28 years after cranial irradiation. DESIGN: Case reports; clinical data were available for 2 years in each instance. CONCLUSION: Latent intervals approaching 2 decades have been reported in cases of radiation necrosis following cranial irradiation, but a similar or greater delay before the onset of radiation encephalopathy has not been described previously. This report indicates that a diagnosis of radiation encephalopathy must be considered when any individual who has received cranial irradiation presents with deterioration in intellectual or motor function, whatever the interval.

Adult↗
PubMed1996

Nonverbal visual attention, but not recognition memory of learning, processes are impaired in motor neurone disease.

Pathology outside the motor system is being increasingly recognised in motor neurone disease (MND) and up to 3% of patients may have overt dementia of frontal lobe type; it is not clear whether milder cognitive disturbance is a more frequent feature of the disease. Standard neuropsychological testing can be difficult in MND and we therefore used the microcomputer-controlled Cambridge Neuropsychological Test Automated Battery (CANTAB), which allows accurate assessment in the presence of motor and bulbar dysfunction. The results of subtests evaluating nonverbal visual attention, recognition memory and learning from a large (n = 50) group of patients with MND compared to normal (n = 27) and neurological disease (n = 23) control groups are presented in this report. The MND group showed significant impairment in a focal attention (visual search) task, but no deficits in memory or learning. Inspection of the visual search data showed that up to a quarter of the MND patients scored two or more standard deviations below the mean control score. It is suggested that this reflects pathology in fronto-striatal circuitry.

Attention↗
PubMed1995

Renal actions of endothelin-1 in newborn piglets: dose-effect relation and the effects of receptor antagonist (BQ-123) and cyclooxygenase inhibitor (indomethacin).

Although the effects of endothelin-1 (ET-1) on intact or perfused adult kidney are well understood, its effects in the fetus and the newborn have not been well studied. We examined the effects of infusions of 25, 50, and 100 ng/kg of ET-1 per minute on mean blood pressure (MBP), cardiac index (CI), renal blood flow (RBF), glomerular filtration rate (GFR), and urine volume (UV) in 7- to 10-day-old piglets (n = 24). In addition, the effects of pretreatment with a receptor antagonist (BQ-123) and with a cyclooxygenase inhibitor (indomethacin) were studied in 12 separate piglets. ET-1 produced a dose- and level-dependent decrease in CI (60%), RBF (50% to 75%), GFR (66% to 80%) and MBP 15% to 17%. These changes returned to 75% to 80% of baseline 60 minutes after discontinuation of ET-1. Low-dose infusion (25 ng/kg) did not result in any changes in systemic or renal hemodynamics. Plasma half-life of ET-1 in piglets was 2.1 +/- 0.4 minutes. Pretreatment with the specific ETA receptor antagonist BQ-123 completely blocked the ET-1-induced systemic and renal hemodynamic changes. Indomethacin blocked the ET-1-induced rise in MBP but failed to block any renal changes. In fact, indomethacin accentuated the changes induced by ET-1, especially the changes in RBF, RVR, and GFR. Studies of receptor binding in the renal cortex and medulla showed that, in the cortex, the Ki value for ET-1 was 6.32 +/- 1.57, and for ET-3 it was 20.05 +/- 4.38 (p < 0.05); in the medulla, the Ki values were similar for both ET-1 and ET-3. These results indicate that in piglets the renal vascular bed is highly sensitive to ET-1, and its effects are predominantly mediated through ETA receptors.

Animals↗
PubMed1994

Identification of a novel exon 4 SOD1 mutation in a sporadic amyotrophic lateral sclerosis patient.

We have been screening a cohort of 46 sporadic and 10 familial amyotrophic lateral sclerosis patients for mutations in the superoxide dismutase gene (SOD1) using a combination of SSCP and direct PCR sequencing. A novel missense mutation (Asp101Asn) has been detected in one sporadic patient and a previously reported mutation has been found in two familial cases.

Amyotrophic Lateral Sclerosis↗
PubMed1993

High-performance liquid chromatographic determination of morphine and its metabolites in plasma using diode-array detection.

An isocratic high-performance liquid chromatographic method has been developed for the determination of morphine, codeine, normorphine, morphine 3-glucuronide and morphine 6-glucuronide in plasma using a diol column and diode-array detection. Samples were extracted using solid-phase extraction with recoveries in excess of 90%. The limit of determination was 1 ng/ml for morphine, codeine and morphine 3-glucuronide, and 10 ng/ml for normorphine and morphine 6-glucuronide. Inter- and intra-day precision were better than 10%.

Chromatography, High Pressure Liquid↗
PubMed1993

Dexamethasone treatment suppresses collagen synthesis in infants with bronchopulmonary dysplasia.

Collagen is an essential component of connective tissue and is present in the pulmonary interstitium. Collagen deposition is known to increase in many acquired chronic diseases, including bronchopulmonary dysplasia (BPD). Urinary excretion of hydroxyproline has been used as a specific index of collagen synthesis. Many studies have demonstrated that dexamethasone therapy is associated with respiratory improvement in infants with BDP but the mechanism of this effect is not well understood. We postulated that in infants with BDP who receive dexamethasone, suppression of collagen synthesis may cause respiratory improvement. Therefore, we studied the effect of dexamethasone on respiratory status and urinary excretion of hydroxyproline in 14 ventilator-dependent infants with BDP. Infants received 0.5 mg/kg/day dexamethasone, tapered by half every 3 days to complete a 12 day course. Eleven of the 14 infants were extubated at a mean +/- SD of 8.7 +/- 4.9 days after starting dexamethasone. Mean urinary hydroxyproline/creatinine ratios at 3, 6, 9, and 12 days of dexamethasone therapy were significantly lower than the mean pretreatment value, but after discontinuation rapidly rose toward baseline values. Decreased urinary excretion of hydroxyproline indicates that dexamethasone suppressed collagen synthesis in these infants. We speculate that suppression of collagen synthesis reduced pulmonary inflammation and fibrosis, resulting in respiratory improvement.

Bronchopulmonary Dysplasia↗
PubMed1992

Ontogeny of endothelin and its receptors in rat brain.

The ontogeny of endothelin (ET) system in rats was studied in preterm (18 days of gestation), term (21 days of gestation) and 1 week post term rats. Brains were dissected out and (1) processed for the estimation of endogenous ET-1 by RIA and (2) membranes were prepared for radioreceptor binding. Receptor characteristics, affinity (Kd) and density (Bmax) were determined using [125I] ET-1 and [125I] SRT 6b (which is structurally similar to ET) and cold ET-1 or SRT 6b as displacer. ET levels were found to be 25.66 +/- 3.18 pg/g protein in preterm, 47.37 +/- 5.31 pg/g protein in term and 48.30 +/- 1.90 pg/g protein in post term rats. ET levels were significantly lower in preterm as compared to term and post term rats. Preterm, term and post term rats showed single high affinity binding site for both [125I] ET-1 and [125I] SRT 6b. The Kd values for [125I] ET-1 and [125I] SRT 6b binding were similar in preterm, term and post term rats. The Bmax values of both [125I] ET-1 and [125I] SRT 6b binding were found to be similar in preterm and term rats while they were significantly higher in post term rats. In adult (4 month old) rats the Kd values were similar to neonatal rats while the Bmax values were significantly lower than the post term neonatal rats. It is concluded that ET and its receptors are developmentally regulated and there is a possibility that endogenous ET is involved in the regulation of ET receptor density.

Animals↗
PubMed1992

Morphine metabolism in acutely ill preterm newborn infants.

To examine the manner in which morphine is metabolized in acutely ill premature infants, we measured the levels of morphine, morphine-3- and -6-glucuronides, and codeine in timed urine specimens and paired plasma specimens at 4 hours and 24 hours after a single dose of morphine in 16 preterm infants (less than 32 weeks of gestational age). A large amount of unmetabolized morphine was found in the urine in 13 (81.2%) of the 16 infants at 4 hours; in 12 of them, morphine was excreted even at 24 hours. Urinary morphine levels varied greatly; the coefficient of variation was 130% at 4 hours and 118% at 24 hours. Codeine was not found in any of the infants. In 10 (62.5%) of the 16 infants, at least one metabolite was found in either plasma or urine. Plasma and urinary levels of morphine conjugates also varied greatly among these 10 infants (coefficient of variation: 109% to 317%). All six infants (37.5%) who had no metabolites excreted large amounts of unmetabolized morphine in the urine for up to 24 hours. Birth weight, gestational age, postnatal age, systemic blood pressure, and other clinical or physiologic variables did not differ significantly between the 10 infants who had morphine conjugates and the six who did not. We conclude that (1) nearly two thirds of acutely ill preterm infants born at less than 32 weeks of gestational age conjugate morphine; (2) irrespective of their ability to produce morphine conjugates, preterm infants excrete large amounts of morphine unmetabolized, as late as 24 hours after a single dose; (3) morphine handling patterns are highly variable among premature infants, and no obvious factors account for the variability; and (4) such variability in morphine handling in general, and the production of the highly potent morphine-6-glucuronide in particular, could explain the variance in morphine pharmacokinetic measures and in the clinical responses to morphine during the newborn period.

Chromatography, High Pressure Liquid↗
PubMed1991

High-performance liquid chromatographic determination of morphine, morphine-3-glucuronide, morphine-6-glucuronide and codeine in biological samples using multi-wavelength forward optical detection.

An isocratic high-performance liquid chromatographic method has been developed for the determination of morphine, morphine-3-glucuronide, morphine-6-glucuronide and codeine in plasma, urine and cerebrospinal fluid. The use of an efficient solid-phase extraction procedure together with a forward optical scanning detector allows a detection limit of 500 pg/ml. The method was evaluated by examination of biological samples taken from newborn infants following the intravenous administration of morphine sulfate.

Chromatography, High Pressure Liquid↗
PubMed1991

Analgesic and hyperthermic effects of intravenously administered morphine in the rat are related to its serum levels.

The analgesic response, colonic temperature changes and the pharmacokinetic parameters of i.v. administered morphine sulfate (2.5, 5.0 and 10.0 mg/kg) through indwelling cannulas in the jugular vein were determined in male Sprague-Dawley rats. The analgesic and hyperthermic responses were determined before and at 30-min intervals for a period of 360 min after the morphine injection and were expressed as area under the time-response curve. Blood samples were collected periodically for a period of 24 h. Serum was separated and was used for the estimation of morphine by the highly sensitive radioimmunoassay. The pharmacokinetic parameters, half life, the terminal elimination rate constant, the mean residence time, the apparent volume of distribution at steady state and the total clearance were determined by using noncompartmental analysis. The area under the serum concentration-time curve from time zero to infinity was related to the dose of morphine. The other parameters were the same for all the doses of morphine, except the serum levels of morphine extrapolated to zero time which increase gradually with the dose. Dose-dependent analgesic and hyperthermic responses were related to the area under the serum concentration-time curve. It is concluded that the dose-dependent pharmacological effects of morphine were related to the area under the serum concentration-time curve from time zero to infinity for serum levels of morphine but not to the other pharmacokinetic parameters.

Analgesia↗