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S Ramanathan

Publications and source records attributed to S Ramanathan.

At least 55 records · Page 3Linked to original sources
PubMed1998

Rural palliative care volunteer education and support program.

The present paper looks at the challenges of palliative care delivery in rural and remote areas and proposes the establishment, education and coordination of a network of palliative care volunteers to assist in the delivery of non-clinical services. The development of a rural palliative care volunteer education and support training package is documented, together with details of the trailing of the package and its evaluation. Possible benefits of the program and some key issues to be considered when establishing a volunteer network are raised.

Attitude of Health Personnel↗
PubMed1998

What is glaucoma?

Explore the source record for details and available documents.

Glaucoma↗
PubMed1998

Excessive production of nitric oxide by macrophages from DP-BB rats is secondary to the T-lymphopenic state of these animals.

Activated macrophages are the first mononuclear cells to migrate to the pancreas of DP-BB rats at the initiation of insulitis. These cells produce an excess of NO, which has been implicated as a mediator of both beta-cell damage and inhibition of T-cell proliferation in this rat strain. Genetic studies have shown that the impaired proliferative response of T-cells segregates with one of the diabetes-susceptibility genes of the DP-BB rat, lyp, which is responsible for a peripheral T-lymphopenia. This observation suggests that the dysregulated expression of inducible NO synthase (iNOS) is under the control of lyp itself or a gene in linkage disequilibrium with lyp. Using two models of hemopoietic chimeras--DP-BB rats reconstituted with isocongenic T-cells and irradiated (WF x DP-BB)F1 animals reconstituted with bone marrow of both parental strains--we demonstrated that the production of NO by DP-BB macrophages is normal when these cells originate from a non-T-lymphopenic environment. Consequently, these macrophages no longer inhibit the stimulation of DNA synthesis in activated T-cells. Macrophages of young WF rats were found to produce high levels of NO, which inhibited T-cell proliferation in vitro. This observation strongly suggests that upregulation of NO synthesis in DP-BB macrophages represents the abnormal persistence of a phenomenon restricted to the first few weeks of life in non-diabetes-prone rats. Taken together, these results demonstrate that the elevated production of NO by DP-BB macrophages results from the lyp mutation and represents a crucial mechanism through which T-lymphopenia contributes to the development of diabetes.

Animals↗
PubMed1997

Interaction of immobilized avidin with an aequorin-biotin conjugate: an aequorin-linked assay for biotin.

Biotinylated recombinant aequorin was used in the development of a heterogeneous bioluminescence binding assay for biotin. This assay is based on a competition between a biotinylated aequorin conjugate and biotin for the binding sites of avidin immobilized on solid particles. Dose-response curves were obtained that relate solid-phase aequorin activity to the concentration of biotin. Under certain experimental conditions these curves were biphasic; i.e., as the biotin concentration increased, the solid-phase aequorin activity first increased reaching a maximum and then decreased at higher biotin concentrations. This "hook" effect was observed with four different types of immobilization supports. The effect was more pronounced when low concentrations of aequorin-biotin conjugate were used, and diminished at a high conjugate concentration. This behavior indicates a possible positive cooperativity in the interaction between the immobilized avidin and biotin. Scatchard plot analysis was also consistent with a positive cooperativity mechanism. By using the ascending portion of the dose-response curve, the detection limit of the assay for biotin was 1 x 10(-15) M (100 zmol of biotin in the sample).

Aequorin↗
PubMed1997

Pooled normal human polyspecific IgM contains neutralizing anti-idiotypes to IgG autoantibodies of autoimmune patients and protects from experimental autoimmune disease.

Normal human serum contains IgM antibodies that regulate the natural autoantibody activity of IgG in autologous serum. In the present study, we show that pooled normal human IgM (IVIgM) purified from plasma of more than 2,500 healthy donors and processed in a similar fashion to that of therapeutic preparations of pooled normal human IgG (IVIg) suppresses activity of IgG autoantibodies purified from the serum of patients with autoimmune diseases in vitro. The inhibitory effect of IVIgM was greater or equivalent to that of IVIg on a molar basis. We show that IVIgM contains anti-idiotypic antibodies directed against idiotypic determinants of autoantibodies, in particular by showing that Sepharose-bound IVIgM selectively retained F(ab')2 fragments of IgG autoantibodies. The infusion of (Lewis x Brown-Norway) F1 rats with IVIgM protected the animals against experimental autoimmune uveitis induced by immunization with the soluble retinal S antigen, as evidenced by clinical scoring and histopathological analysis. The present findings provide a rationale for considering pooled IgM for immunomodulation of autoimmune disease.

Animals↗
PubMed1997

Sensing antimonite and arsenite at the subattomole level with genetically engineered bioluminescent bacteria.

A highly sensitive and selective optical sensing system for antimonite has been developed using genetically engineered bacteria. The basis of this system is the ability of certain bacteria to survive in environments that are contaminated with antimonite, arsenite, and arsenate. The survival is conferred to the bacteria by the ars operon, which consists of five genes that code for three structural proteins, ArsA, ArsB, and ArsC, and two regulatory proteins, ArsD and ArsR. ArsA, ArsB, and ArsC form a protein pump system that extrudes antimonite, arsenite, and arsenate once these anions reach the cytoplasm of the bacterium. A method was developed for monitoring antimonite and arsenite by using a single plasmid that incorporates the regulatory gene of the extrusion system, arsR, and the genes of bacterial luciferase, luxA and luxB. In the designed plasmid, ArsR regulates the expression of bacterial luciferase in a manner that is dependent on the concentration of antimonite and arsenite in the sample. Thus, the bioluminescence emitted by luciferase can be related to the concentration of antimonite and arsenite in the sample. Concentrations for antimonite and arsenite in the order of 10(-5) M, which corresponds to subattomole levels, can be detected. This bacterial-based sensing system is highly selective for antimonite and arsenite.

Adenosine Triphosphatases↗
PubMed1997

Genetically engineered bacteria: electrochemical sensing systems for antimonite and arsenite.

A bacterial sensing system that responds selectively to antimonite and arsenite has been investigated. The bacteria used in these studies have been genetically engineered to produce the enzyme beta-galactosidase in response to these ions. This is accomplished by using a plasmid that incorporates the gene for beta-galactosidase (reporter gene) under the control of the promoter of the ars operon. This plasmid also encodes for the ArsR protein, a regulatory protein of the ars operon, which, in the absence of antimonite or arsenite, restricts the expression of beta-galactosidase. In the presence of antimonite or arsenite the ArsR protein is released from the operator/ promoter region of the ars operon and beta-galactosidase is expressed. The activity of this enzyme was monitored electrochemically using p-aminophenyl beta-D-galactopyranoside as the substrate. The bacterial sensing system responds selectively to arsenite and antimonite (and to a lesser extent arsenate) and shows no significant response to phosphate, sulfate, nitrate, and carbonate.

Antimony↗
PubMed1997

Labour analgesia with intrathecal fentanyl decreases maternal stress.

PURPOSE: Lumbar epidural analgesia (LEA) decreases maternal stress as measured by maternal circulating plasma catecholamine concentrations. Intrathecal fentanyl (ITF) provides effective labour analgesia but its effect on maternal epinephrine (Epi) and norepinephrine (NE) concentrations is not known. This study assesses whether ITF reduces maternal stress in the same manner as conventional LEA. METHODS: Twenty-four healthy women in active labour received either 25 micrograms ITF (n = 12) or epidural lidocaine 1.5% (n = 12) for analgesia. Venous blood samples were collected before anaesthesia and at five minute intervals for 30 min following anaesthesia for the measurement of plasma Epi and NE by high performance liquid chromatography. Maternal blood pressure (BP), heart rate (HR), visual analog scores (VAS) to pain and pruritus were recorded at the same time. RESULTS: Both ITF and LEA decreased pain VAS scores, maternal BP, and plasma Epi concentrations with only minimal effects on plasma NE concentrations. Intrathecal fentanyl (ITF) and LEA reduced plasma epi to a similar extent, with ITF reducing the levels slightly faster than LEA. Intrathecal fentanyl(ITF) and LEA reduced plasma Epi concentrations by 52% and 51%, respectively (P value < 0.01). CONCLUSION: We conclude that ITF is as effective as LEA in producing pain relief in the labouring patient. Intrathecal Fentanyl (ITF) is also capable of reducing maternal plasma epinephrine concentration, thus avoiding the possibly deleterious side effects of excess amounts of this catecholamine during labour.

Adult↗
PubMed1997

Bacterial biosensors for monitoring toxic metals.

Biosensors utilize biological components to provide selectivity for monitoring compounds of environmental, clinical and industrial importance. A number of biosensors based on bacteria have recently been developed for monitoring toxic metals in the environment. The advantages and disadvantages of these types of biosensors are discussed.

Bacterial Proteins↗
PubMed1997

2-Chloroprocaine antagonism of epidural morphine analgesia.

BACKGROUND: 2-Chloroprocaine (2-CP) used for lumbar epidural anesthesia (LEA) reportedly decreases the efficacy of epidural morphine (EM) administered for post-cesarean section (CS) analgesia. The amount of supplemental i.v. morphine self-administered by the patient via the patient-controlled analgesia device (PCA) is used to study the interaction between EM and 2-CP. METHODS: Forty-two patients scheduled for elective CS were randomly divided into 3 equal groups, and received 2-CP, 2-CP + epinephrine (Epi, 5 micrograms.ml-1) or 2% lidocaine (Lido) with Epi for LEA. All patients received 5 mg EM and i.v. PCA morphine for postoperative pain. Cumulative amount of i.v. morphine used in the first 24 hours as well as the amount of the drug used during each 2-h period were noted. Nonparametric analysis of variance and Chi-squared analysis were used for statistical comparisons. RESULTS: The mean cumulative 24-h i.v. PCA morphine requirement in the 2-CP, 2-CP+Epi and Lido+Epi groups respectively was 20.5 +/- 24, 33.1.5 +/- 27 and 4.07 +/- (mean +/- SD). The Lido + Epi group used significantly less morphine (P = 0.01) compared to either of the 2-CP groups with no significant difference between the 2-CP groups. The maximum i.v. PCA morphine use occurred in the first 4 hours following surgery in all three groups. CONCLUSION: Analgesic efficacy of EM is decreased when 2-CP is used for LEA compared to when Lido + Epi is used.

Adult↗
PubMed1996

Recombinant IL-4 aggravates experimental autoimmune uveoretinitis in rats.

IL-4 is the critical regulatory cytokine that preferentially promotes a Th2 type of immune response. In certain models of organ-specific autoimmune diseases in which Th1 cells are implicated in the disease process, treatment with IL-4 has been shown to confer protection by deviating the immune response toward a Th2 type. In this study, we addressed the role of IL-4 in experimental autoimmune uveoretinitis, a prototypic Th1-dependent disease induced in susceptible animals following immunization with soluble retinal Ag. Interestingly, treatment of Lewis rats with IL-4 exacerbated experimental autoimmune uveoretinitis, and simultaneous treatment with neutralizing anti-IL-4 Abs attenuated this increase in the severity of the disease. Ex vivo analysis of cytokines produced in response to the immunizing Ag showed an enhancement in the levels of IFN-gamma, TNF-alpha, and nitric oxide following IL-4 treatment. In vitro, IL-4 augmented the production of IFN-gamma by Con A-stimulated splenocytes in a dose-dependent manner. At low concentrations of IL-4, IFN-gamma production was enhanced, while at higher concentrations this production was inhibited. The specificity of the induction of IFN-gamma by IL-4 was confirmed by neutralizing the activity of IL-4 with anti-IL-4. Taken together, the results herein reported demonstrate that IL-4 can induce the production of IFN-gamma and of inflammatory cytokines under certain conditions, and indicate that IL-4 can exert a dose-dependent differential effect on the induction of immune responses and on autoimmunity.

Adjuvants, Immunologic↗
PubMed1996

Future directions for resuscitation research. III. External cardiopulmonary resuscitation advanced life support.

This discussion about advanced cardiac life support (ACLS) reflects disappointment with the over 50% of out-of-hospital cardiopulmonary resuscitation (CPR) attempts that fail to achieve restoration of spontaneous circulation (ROSC). Hospital discharge rates are equally poor for in-hospital CPR attempts outside special care units. Early bystander CPR and early defibrillation (manual, semi-automatic or automatic) are the most effective methods for achieving ROSC from ventricular fibrillation (VF). Automated external defibrillation (AED), which is effective in the hands of first responders in the out-of-hospital setting, should also be used and evaluated in hospitals, inside and outside of special care units. The first countershock is most important. Biphasic waveforms seem to have advantages over monophasic ones. Tracheal intubation has obvious efficacy when the airway is threatened. Scientific documentation of specific types, doses, and timing of drug treatments (epinephrine, bicarbonate, lidocaine, bretylium) are weak. Clinical trials have failed so far to document anything statistically but a breakthrough effect. Interactions between catecholamines and buffers need further exploration. A major cause of unsuccessful attempts at ROSC is the underlying disease, which present ACLS guidelines do not consider adequately. Early thrombolysis and early coronary revascularization procedures should also be considered for selected victims of sudden cardiac death. Emergency cardiopulmonary bypass (CPB) could be a breakthrough measure, but cannot be initiated rapidly enough in the field due to technical limitations. Open-chest CPR by ambulance physicians deserves further trials. In searches for causes of VF, neurocardiology gives clues for new directions. Fibrillation and defibrillation thresholds are influenced by the peripheral sympathetic and parasympathetic nervous systems and impulses from the frontal cerebral cortex. CPR for cardiac arrest of the mother in advanced pregnancy requires modifications and outcome data. Until more recognizable critical factors for ROSC are identified, titrated sequencing of ACLS measures, based on physiologic rationale and sound judgement, rather than rigid standards, gives the best chance for achieving survival with good cerebral function.

Animals↗
PubMed1996

Immunological profiles of leprosy patients and healthy family contacts toward M. leprae antigens.

In this study, we measured simultaneously the in vitro and in vivo T lymphocyte reactivities and the antibody responses of leprosy patients and healthy family contacts (HFC) toward Mycobacterium leprae antigens. The in vitro lymphoproliferative response of the HFC to leprosin A was comparable to that of tuberculoid leprosy patients. However, their skin-test reactivity to Dharmendra lepromin was considerably higher compared to the in vitro response to leprosin A. A significant number of HFC failed to respond to M. leprae antigens, both in vitro and in vivo, and the unresponsiveness to either test was not related to the type of leprosy patients in the household. A marginal correlation was observed between the skin-test reactivity of HFC and the age of the individuals. Even though a significant proportion of HFC showed positive anti-PGL-I IgM levels, none showed a positive titer in the serum antibody competition test toward the M. leprae-specific epitope My2. A positive anti-PGL-I IgM response together with a negative lepromin skin-test reactivity showed a clear downward trend from the lepromatous pole toward the tuberculoid pole. A small number of HFC, all contacts of lepromatous patients, were lepromin skin-test negative with positive anti-PGL-I IgM levels, but the majority among them showed T-cell reactivity to mycobacterial antigens in vitro. These results are discussed in relation to immunological correlates of the susceptibility to M. leprae infection.

Antibodies, Bacterial↗
PubMed1995

A re-evaluation of the ability of thiopental to identify cerebrospinal fluid in epidural catheter aspirate.

STUDY OBJECTIVE: Sodium thiopental has been used to determine whether fluid aspirated from an epidural catheter is previously injected local anesthetic or cerebrospinal fluid (CSF). The purpose of this study was to test the efficacy of this test in distinguishing opioids from CSF. DESIGN: in vitro study. SETTING: Laboratory of a university hospital. MEASUREMENTS AND MAIN RESULTS: Three in vitro studies were performed. The first study tested for precipitation when thiopental was mixed with several commonly used epidural medications. Then, thiopental was mixed in combinations of opioids with local anesthetics to see if the opioid might prevent the precipitation of the local anesthetics. Finally, lidocaine was serially diluted and precipitation with thiopental was assessed. It was found that certain concentrations of opioids as well as normal saline do not precipitate with thiopental. In addition, the ratio of opioids to local anesthetic of 10:1 prevented precipitation when thiopental was added. Local anesthetics combined with cerebrospinal fluid in a 1:10 ratio produced a precipitate on mixing with thiopental. CONCLUSIONS: Use of thiopental to differentiate opioids from cerebrospinal fluid is unreliable. In addition, in some simulated situations, opioids may mask the presence of local anesthetic.

Anesthesia, Epidural↗
PubMed1994

Determination of the antifilarial drug UMF-078 and its metabolites UMF-060 and flubendazole in whole blood using high-performance liquid chromatography.

A rapid and selective high-performance liquid chromatographic (HPLC) method for the simultaneous determination of the antifilarial drug UMF-078 (I) and its metabolites UMF-060 (II) and flubendazole (III) is described. After a simple extraction from whole blood, the compounds were determined by HPLC using a C18 Inertsil ODS-2 reversed-phase column with methanol-0.05M ammonium acetate (pH 4.0) as the mobile phase and ultraviolet detection at 291 nm. The average recoveries of I, II and III over the concentration range 20-500 ng ml-1 were 69.9 +/- 4.7, 85.6 +/- 4.4 and 85.1 +/- 6.0%, respectively. The minimum detectable concentrations in whole blood for I, II and III were 10, 7 and 7 ng ml-1, respectively. This method was found to be suitable for pharmacokinetic studies.

Animals↗
PubMed1994

The effect of lumbar epidural and general anesthesia on plasma catecholamines and hemodynamics during abdominal aortic aneurysm repair.

Twenty-four patients undergoing abdominal aortic aneurysm (AAA) repair were studied to compare the effects of lumbar epidural anesthesia (LEA) and general anesthesia (GA) on plasma catecholamine levels and hemodynamics before and during infrarenal aortic cross-clamping. Patients received either a high dose of opioid anesthetic (GA group, n = 12), or lumbar epidural anesthesia to T4 sensory level with a light general anesthetic (LEA group, n = 12). Systemic vascular resistance (SVR) and norepinephrine (NE) and epinephrine (E) levels were measured before anesthetic induction (before epidural activation in the LEA group, and before general anesthesia induction in the GA group), 15 min before cross-clamping, and 1,5, and 10 min after cross-clamping. There was a large (P < 0.05) increase in NE and E in the GA group by 15 min before aortic cross-clamping, but NE and E levels in the LEA group did not increase. The GA group had significantly higher levels of NE and E than the LEA group 15 min before cross-clamping and also after clamping. NE levels in the LEA group increased after cross-clamping, and NE levels in the GA group remained constant. E levels remained stable in both groups after cross-clamping. After clamping, SVR increased in both groups, but the increase occurred after 1 min in the GA group and took 5 min to become significant in the LEA group. There was no significant correlation between changes in NE or E and changes in SVR in either group. This study shows that epidural anesthesia to T4 prevents NE and E increases in response to abdominal surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Epidural↗