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Biomedical subjects

S Ramanathan

Publications and source records attributed to S Ramanathan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effect of epidural analgesia with ambulation on labor duration.

BACKGROUND: Ambulatory epidural analgesia (AEA) is a popular choice for labor analgesia because ambulation reportedly increases maternal comfort, increases the intensity of uterine contractions, avoids inferior vena cava compression, facilitates fetal head descent, and relaxes the pelvic musculature, all of which can shorten labor. However, the preponderance of evidence suggests that ambulation during labor is not associated with these benefits. The purpose of this study is to determine whether ambulation with AEA decreases labor duration from the time of epidural insertion to complete cervical dilatation. METHODS: In this prospective, randomized study, 160 nulliparous women with AFA were randomly assigned to one of two groups: AEA with ambulation and AEA without ambulation. AEA blocks were initiated with 15-20 ml ropivacaine (0.07%) plus 100 microg fentanyl, followed by a continuous infusion of 0.07% ropivacaine plus 2 microg/ml fentanyl at 15-20 ml/h. Maternal measured variables included ambulation time, time from epidural insertion to complete dilatation, stage II duration, pain Visual Analogue Scale scores, and mode of delivery. APGAR scores were recorded at 1 and 5 min. Results are expressed as mean +/- SD or median and analyzed using the t test, chi-square, or the Mann-Whitney test at P < or = 0.05. RESULTS: The ambulatory group walked 25.0 +/- 23.3 min, sat upright 40.3 +/- 29.7 min, or both. Time from epidural insertion to complete dilatation was 240.9 +/- 146.1 min in the ambulatory group and 211.9 +/- 133.9 min in the nonambulatory group (P = 0.206). CONCLUSION: Ambulatory epidural analgesia with walking or sitting does not shorten labor duration from the time of epidural insertion to complete cervical dilatation.

Adult↗
PubMed2001

Bioavailability and preliminary clinical efficacy of intrarectal artesunate in Ghanaian children with moderate malaria.

We report the first detailed pharmacokinetic assessment of intrarectal (i.r.) artesunate (ARS) in African children. Artesunate was given intravenously (i.v.; 2.4 mg/kg of body weight) and i.r. (10 or 20 mg/kg formulated as 50- or 200-mg suppositories [Rectocaps]) in a crossover study design to 34 Ghanaian children with moderate falciparum malaria. The median relative bioavailability of dihydroartemisinin (DHA), the active antimalarial metabolite of ARS, was higher in the low-dose i.r. group (10 mg/kg) than in the high-dose i.r. group (20 mg/kg) (58 versus 23%; P = 0.018). There was wide interpatient variation in the area under the concentration-time curve after i.r. ARS administration (up to 9-fold in the high-dose group and 20-fold in the low-dose group). i.r. administered ARS was more rapidly absorbed in the low-dose group than the high-dose group (median [range] absorption half-lives, 0.7 h [0.3 to 1.24 h] versus 1.1 h [0.6 to 2.7 h] [P = 0.023]. i.r. administered ARS was eliminated with a median (range) half-life of 0.8 h (0.4 to 2.7 h) (low-dose group and 0.9 h (0.1 to 2.5 h) (high-dose group) (P = 1). The fractional clearances of DHA were 3.9, 2.6, and 1.5 liters/kg/h for the 20-mg/kg, 10-mg/kg and i.v. groups, respectively (P = 0.001 and P = 0.06 for the high-and low-dose i.r. groups compared with the i.v. groups, respectively). The median volumes of distribution for DHA were 1.5 liters kg (20 mg/kg, i.r. group), 1.8 liters/kg (10 mg/kg, i.r. group), and 0.6 liters/kg (i.v. group) (P < 0.05 for both i.r. groups compared with the i.v. group). Parasite clearance kinetics were comparable in all treatment groups. i.r. administered ARS may be a useful alternative to parenterally administered ARS in the management of moderate childhood malaria and should be studied further.

Administration, Rectal↗
PubMed2000

Chlorocatechol detection based on a clc operon/reporter gene system.

A sensitive and selective sensing system for chlorocatechols (3-chlorocatechol and 4-chlorocatechol) was developed based on Pseudomonas putida bacteria harboring the plasmid pSMM50R-B'. In this plasmid, the regulatory protein of the clc operon, ClcR, controls the expression of the reporter enzyme beta-galactosidase. When bacteria containing components of the clc operon are grown in the presence of chlorocatechols, ClcR activates the clcA promoter, which is located upstream from the beta-galactosidase gene. Thus, the concentration of chlorocatechols can be related to the production of beta-galactosidase in the bacteria. The concentration of beta-galactosidase expressed in the bacteria was determined by measuring the chemiluminescence signal emitted with the use of a 1,2-dioxetane substrate. ClcR has a high specificity for chlorocatechols and provides the sensing system with high selectivity. This was demonstrated by evaluating several structurally related organic compounds as potential interfering agents. Both 3-chlorocatechol and 4-chlorocatechol can be detected with this sensing system at concentrations as low as 8 x 10(-10) and 2 x 10(-9) M, respectively, using a 2-h induction period. In the case of 3-chlorocatechol, a highly selective sensing system was developed that can detect this species at concentrations as low as 6 x 10(-8) M after a 5-min induction period; the presence of 4-chlorocatechol at concentrations as high as 2 x 10(-4) M did not interfere with this system.

Arabidopsis Proteins↗
PubMed2000

Improved bowel function after gynecological surgery with epidural bupivacaine-fentanyl than bupivacaine-morphine infusion.

PURPOSE: To compare postoperative gastrointestinal recovery between continuous epidural bupivacaine-fentanyl and bupivacaine-morphine. METHODS: In a blinded, randomized, prospective trial, 60 women undergoing surgery for gynecologic cancer were studied. Anesthesia was provided by a combined general/epidural (L2-3 catheter) technique without epidural opioids. Postoperative epidural analgesia was by continuous infusion of bupivacaine 0.1% with either morphine 0.05 mg x ml(-1) (BM) or fentanyl 5 microg x ml(-1) (BF). Visual Analogue Scale (VAS) scores for pain at rest and during movement, and the return of bowel function were collected for three days and the duration of hospitalization were noted. RESULTS: On POD-1, 18.5% of patients in the BM group had emesis compared with none in the BF group (P = 0.038) and fewer patients in the BM group tolerated clear oral fluids (11.1% BM vs 40.6% BF, P = 0.025). These differences became insignificant on POD-2 and 3. Median pain scores were comparable at rest and ranged from 10-20 in the BM group vs 0-20 in the BF group over the three days. Similarly, median pain scores with movement respectively ranged from 20-25 and 20-30 in the BF and BM groups. The mean duration of hospitalization was longer in the BM group (5.7 +/- 2.4) vs BF (4.5 +/- 1.2 days), P = 0.017. CONCLUSION: Epidural BM and BF provided equally effective postoperative analgesia at rest and during movement. Compared with BM, epidural BF is associated with less emesis and an increased ability to tolerate oral fluids on POD-1 and an overall shorter hospital stay.

Adult↗
PubMed2000

Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125%-- fentanyl infusions for epidural labour analgesia.

PURPOSE: To compare analgesic efficacies of ropivacaine-fentanyl and bupivacaine-fentanyl infusions for labour epidural analgesia. METHODS: In this double- blind, randomized study 100, term, nulliparous women were enrolled. Lumbar epidural analgesia (LEA) was started at cervical dilatation < 5 cm using either bupivacaine 0.25% followed by bupivacaine 0.125% + 2 microg x ml(-1) fentanyl infusion (n=50) or ropivacaine 0.2% followed by ropivacaine 0.1% + 2 microg x ml(-1) fentanyl infusion (n=50). Every hour maternal vital signs, visual analog scale (VAS) pain score, sensory levels, and motor block (Bromage score) were assessed. Data were expressed as mean +/-1 SD and analyzed using Chi -Squared and Mann-Whitney U tests at <0.05. RESULTS: The onset times were 10.62+/-4.9 and 11.3+/-4.7 min for the bupivacaine and ropivacaine groups respectively (P = NS). The median VAS scores were not different between the groups at any of the evaluation periods. However, at least 80% of patients in the ropivacaine group had no demonstrable motor block after the first hour compared with only 55% of patients given bupivacaine (P =0.01). CONCLUSIONS: Both bupivacaine and ropivacaine produce satisfactory labour analgesia. However, ropivacaine infusion is associated with less motor block throughout the first stage of labour and at 10 cm dilatation.

Adult↗
PubMed2000

Engineering aspects of enzymatic signal transduction: photoreceptors in the retina.

Identifying the basic module of enzymatic amplification as an irreversible cycle of messenger activation/deactivation by a "push-pull" pair of opposing enzymes, we analyze it in terms of gain, bandwidth, noise, and power consumption. The enzymatic signal transduction cascade is viewed as an information channel, the design of which is governed by the statistical properties of the input and the noise and dynamic range constraints of the output. With the example of vertebrate phototransduction cascade we demonstrate that all of the relevant engineering parameters are controlled by enzyme concentrations and, from functional considerations, derive bounds on the required protein numbers. Conversely, the ability of enzymatic networks to change their response characteristics by varying only the abundance of different enzymes illustrates how functional diversity may be built from nearly conserved molecular components.

Animals↗
PubMed2000

Uniport soft-tip, open-ended catheters versus multiport firm-tipped close-ended catheters for epidural labor analgesia: a quality assurance study.

STUDY OBJECTIVE: To compare a multiport, firm-tipped, close-ended, epidural catheter (Portex catheter) with a uniport, open-ended, soft-tipped, wire-reinforced catheter (Arrow catheter) in obstetric patients. STUDY DESIGN: Prospective data collection for intradepartmental quality assurance. SETTING: Obstetric unit in a tertiary care maternity hospital. PATIENTS: 2612 patients requesting labor analgesia. INTERVENTIONS: The Arrow catheter was used in 1,352 women and the Portex catheter in 1,260 women. MEASUREMENTS AND MAIN RESULTS: The incidence of unsatisfactory block were 3.3% and 4.4% with the Arrow and Portex catheters, respectively (p = 0.2). The catheter perforated the dura matter in 0.4% of cases with both catheters. The incidence of epidural venipuncture was 1.1% with the Arrow catheter and 5.7% with the Portex catheter (p = 0.0001). Paresthesias occurred in 6% of cases with the Arrow catheter and 11. 2 % of cases with the Portex catheter (p = 0.0001). Epidural catheter reinsertion was required in fewer patients in the Arrow group than in the Portex group (4.8% vs. 7.1%; p = 0.01). CONCLUSIONS: In obstetric patients, the softer uniport Arrow catheter produces paresthesias and venipunctures less frequently than the firm multiport Portex catheter.

Adult↗
PubMed2000

Postdural puncture headache: a randomized comparison of five spinal needles in obstetric patients.

This prospective, blinded, randomized study compares the incidence of postdural puncture headache (PDPH) and the epidural blood patch (EBP) rate for five spinal needles when used in obstetric patients. One thousand two women undergoing elective cesarean delivery under spinal anesthesia were recruited. We used two cutting needles: 26-gauge Atraucan and 25-gauge Quincke, and three pencil-point needles: 24-gauge Gertie Marx (GM), 24-gauge Sprotte, and 25-gauge Whitacre. The needle for each weekday was chosen randomly. Cutting needles were inserted parallel to the dural fibers. The incidences of PDPH were, respectively, 5%, 8.7%, 4%, 2.8%, and 3.1% for Atraucan, Quincke, GM, Sprotte, and Whitacre needles (P = 0.04, chi(2) analysis), and the corresponding EBP rates in those with PDPH were 55%, 66%, 12.5%, 0%, and 0% (P = 0.000). The Quincke needle had a more frequent PDPH rate than the Sprotte or the Whitacre needle (P = 0.02) and a more frequent EBP rate than the GM, Sprotte, or the Whitacre needle (P = 0.01). The Atraucan needle had a more frequent EBP rate than the Sprotte or Whitacre needle (P = 0.05). Neither the PDPH rate nor the EBP rates differed among the pencil-point needles. The cost of EBP must be taken into consideration when choosing a spinal needle. We conclude that pencil-point spinal needles should be used for subarachnoid anesthesia in obstetric patients.

Adult↗
PubMed1999

T cell reconstitution of BB/W rats after the initiation of insulitis precipitates the onset of diabetes.

One of the diabetes susceptibility genes of the BB/W (Biobreeding/Worcester) rat maps to the lyp locus on chromosome 4. The BB/W lyp allele is responsible for a severe peripheral T lymphopenia. Correction of this lymphopenia by transfer of normal, histocompatible T cells prevents diabetes, providing T cell reconstitution is initiated before insulitis. We have analyzed this time-dependent regulation of the diabetogenic process by normal T cells. We demonstrate that T cell reconstitution after the initiation of insulitis precipitates the onset of diabetes through the recruitment of donor T cells to the autoimmune process. This inability of normal T cells to regulate primed diabetogenic BB/W T cells and their own autoreactive potential were observed when normal T cells outnumbered pathogenic T cells by approximately 1000-fold. Analysis of donor-derived T cells recovered from BB/W rats that were reconstituted before insulitis, and hence protected from diabetes, demonstrates that early T cell reconstitution of BB/W rats does not result in a long term physical or functional depletion of islet cell-specific T cell precursors among donor cells or in the expansion of T cells that can regulate the activation and expansion of diabetogenic T cells.

ADP Ribose Transferases↗
PubMed1999

Green fluorescent protein in the design of a living biosensing system for L-arabinose.

Analysis of monosaccharides is typically performed using analytical systems that involve a separation step followed by a detection step. The separation step is usually necessary because of the high degree of structural similarity between different monosaccharides. A novel sensing system for monosaccharides is described here in which living bacteria were designed to detect a model monosaccharide, L-arabinose, without the need for a separation step. In such sensing systems, analytes are detected by employing the selective recognition properties found in certain bacterial proteins. These systems are designed so that a reporter protein is expressed by the bacteria in response to the analyte. The concentration of the analyte can be related to the signal generated by the reporter protein. In the sensing system described here, the green fluorescent protein (GFP) was used as the reporter protein. L-Arabinose concentrations can be determined by monitoring the fluorescence emitted by the bacteria at 509 nm after excitation of GFP at 395 nm. The system can detect L-arabinose at concentrations as low as 5 x 10(-7) M and is selective over D-arabinose, the stereoisomer of the analyte, as well as over a variety of pentose and hexose sugars.

AraC Transcription Factor↗
PubMed1999

ST-segment depression and myocardial contractility during cesarean section under spinal anesthesia.

PURPOSE: To evaluate myocardial contractility during ST segment depression in healthy parturients during Cesarean section (CS). METHODS: Forty-seven consecutive term parturients undergoing elective CS under spinal anesthesia were studied. The ST segment was recorded continuously on leads II and V5 using a Holter monitor. Myocardial performance was evaluated by measuring cardiac index (CI), heart rate (HR), pre-ejection period (PEP), ventricular ejection time (VET), systolic time ratio (STR, PEP/VET), and ejection fraction (EF) with an impedance cardiograph. RESULTS: Fourteen patients (30%) developed ST segment depression within 15 min after delivery and the remaining 33 (70%) did not (controls). Seven patients developed a 1 mm change, five patients a 2 mm change and the remaining two a 3 mm change in the ST segment. Compared with pre-anesthesia values, the mean HR increased from 103 +/- 10 to 116 +/- 10 (ISD) bpm (P = 0.001), CI from 4.7 +/- 0.7 to 5.6 +/- 1.7 L.min-1 (P = 0.01), EF from 0.58 +/- 0.08 to 0.66 +/- 0.05 (P = 0.01) and STR decreased from 0.26 +/- 0.06 to 0.2 +/- 0.04 (P = 0.01) during ST segment depression. At this time, CI, HR and EF were greater and STR smaller than values obtained 15 min after delivery in the control subjects. CONCLUSION: ST-segment depression occurring during CS is associated with a hyperkinetic myocardial contractile state.

Adolescent↗
PubMed1999

Post partum creatine phosphokinase and its muscle-brain isoenzyme elevation and transient Q-wave in a patient with idiopathic hypertrophic subaortic stenosis.

A primigravida with idiopathic hypertrophic subaortic stenosis, New York Heart Association Classification III, developed acute chest pain with significant ST segment depression together with a new Q-wave in chest lead V6 on the electrocardiograph following delivery under lumbar epidural analgesia. An intrapartum myocardial infarct was suspected because serial creatine phosphokinase and its muscle-brain isoenzyme levels were elevated in the postpartum period. However, the ST segment and the Q-wave changes returned to baseline within 4 h, thus eliminating the possibility of acute myocardial infarction. The uterus and placenta release creatine phosphokinase and its muscle-brain isoenzyme substantially during normal vaginal delivery, thus mimicking acute myocardial infarction. Consequently, the elevations of creatine phosphokinase and its muscle-brain fraction alone are not diagnostic of myocardial infarction in the postpartum period. The diagnosis of myocardial infarction must be based on the clinical picture, serial electrocardiogram recording and determination of lactate dehydrogenase and aspartate amino transferase.

Journal Article↗
PubMed1999

Kinetics of T cell turnover following thymectomy.

We develop a mathematical formula that provides the number of cells in an isolated population that have divided k times in n days (O< or =k< or =n). This differential cell division formula is applied to the kinetics of peripheral T cells in the diabetes-prone BB rat following thymectomy. These rats received daily intraperitoneal injections of the DNA precursor, bromodeoxyuridine (BrdUrd), over a period of 12-13 days. As the cells divided, they incorporated BrdUrd progressively into their DNA molecules, and the differential formula provides a close prediction of the fraction of BrdUrd-positive T cells present each day during this 'pulse' phase. No further BrdUrd was administered after 13 days, and the diminishing fraction of BrdUrd-positive cells was recorded for several more weeks. The differential cell division formula was capable of describing the rather complex form of the retention curve as BrdUrd-tagged DNA molecules passed to progeny cells during this 'chase' phase. We believe that this simple formula may be found generally useful in describing cell kinetic data in mitotically active cells.

Animals↗
PubMed1998

Antigen activation rescues recent thymic emigrants from programmed cell death in the BB rat.

One of the diabetes susceptibility genes of the BB rat is a mutation at the lyp locus that decreases the thymic output of T cells and the life span of most recent thymic emigrants (RTE). Consequently, there is a 10-fold reduction in the number of CD4+ and CD8+ T cells in secondary lymphoid organs. Results presented in this work demonstrate that the BB rat lyp mutation is associated with an accelerated apoptotic death in vitro of mature CD4+ 8- and CD4- 8+ thymocytes and peripheral T cells. The stability of the pool of recirculating T cells (PRL) of BB rats over time results from a > 10-fold increase in the mitotic activity of T cells as assessed in vivo by bromodeoxyuridine incorporation. This increased mitotic activity is not observed when BB T cells develop in the context of a normal sized PRL. MHC haploidentical WF and BB rats differ at minor histocompatibility loci. Intravenous injection of (WF x BB)F1 T cells into euthymic BB rats led to the rejection of donor T cells within 3 wk by unprimed recipients and within 1 wk by primed recipients. This secondary immune response was unaffected by postpriming thymectomy. F1 T cells were not rejected, but rather expanded after their injection into thymectomized BB rats that had been primed as early as 48 h after thymectomy. These results strongly suggest that the BB rat PRL is devoid of long-lived naive T cells and that rescue of recent thymic emigrants from programmed cell death is initiated by Ags, exclusively.

Animals↗
PubMed1998

Advantages and limitations of day surgery in children in a developing country.

Day surgery (DS) especially in children, has been widely accepted by surgeons, and the benefits to the patients, parents, and hospital have been well-established. It has become particularly popular among working parents and is accepted by hospital administrators. Proper case selection, preoperative assessment, and proper parent counselling, choice of anaesthesia, postoperative analgesia, and follow-up advice are essential for a successful outcome. This paper records our experience with 465 infants and children who underwent DS at Government Stanley Hospital and two semi-charitable trust hospitals in Madras during the years 1985-1986. The overall acceptance of the programme was excellent, with minimal complications and a fallout rate of 9.6%. The advantages of DS in our environment are discussed.

Ambulatory Surgical Procedures↗
PubMed1998

Incomplete hypospadiac urethral duplication with posterior urethral valves.

Urethral duplication (UD) is an uncommon malformation. Obstruction rarely occurs in hypospadiac UD. We describe two children with incomplete hypospadiac UD in association with posterior urethral valves, a combination not previously recognised. The embryonic significance of this anomaly is discussed. Keywords Urethral duplication. Hypospadias. Posterior urethral valve. Megalourethra

Child↗
PubMed1998

An intravenous fluid bolus is not necessary before administration of intrathecal fentanyl for labor analgesia.

STUDY OBJECTIVE: To determine if an intravenous (i.v.) fluid bolus is necessary to prevent any possible hemodynamic sequelae after administration of intrathecal fentanyl in laboring parturients. DESIGN: Prospective, randomized study. SETTING: Labor suite of a women's tertiary care hospital. PATIENTS: 30 ASA physical status I and II parturients in active labor requesting labor analgesia. INTERVENTIONS: Patients were randomly divided into two groups of 15. One group received no i.v. fluid prior to the administration of 25 micrograms of intrathecal fentanyl, and the other group received 500 ml of lactated Ringer's solution before the block. MEASUREMENTS AND MAIN RESULTS: Blood pressures [systolic (SBP), diastolic (DBP), mean (MAP)], heart rate (HR), cardiac index (CI; using impedance cardiography), and visual analog scores were measured before the block, after fluids, and then every 5 minutes for 45 minutes after the block. Prenatal baseline blood pressures before the onset of labor were obtained from the obstetrician's office records. Results were analyzed using analysis of variance. All patients reported good pain relief. No patient from either group required treatment for hypotension. In the no fluid group, SBP and MAP decreased 10% and 14%, respectively (p = 0.05), following intrathecal fentanyl administration compared with preblock values obtained during labor but not when compared with prelabor prenatal values. In the fluid group, no significant changes occurred in SBP after intrathecal fentanyl but MAP decreased approximately 12% only in comparison to preblock values. No significant changes were noted in CI in either group. Fluid infusion itself caused an increase in HR and CI of approximately 12% and 9.4%, respectively. CONCLUSION: Intrathecal fentanyl produces only minimal hemodynamic changes with or without prior fluid administration.

Adult↗