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Biomedical subjects

R Chandran

Publications and source records attributed to R Chandran.

At least 19 recordsLinked to original sources
PubMed2003

EMG frequency content changes with increasing force and during fatigue in the quadriceps femoris muscle of men and women.

The purpose of this study was to determine the effect of gender on changes in electromyographic (EMG) signal characteristics of the quadriceps muscles with increasing force and with fatigue. A total of fourteen healthy adults (seven men, seven women) participated in the study. Subjects had to perform isometric ramp contractions in knee extension with the force gradually increasing from 0 to 100% of the maximal voluntary contraction (MVC) in a 6-s period. Subjects then performed a fatigue task, consisting of a sustained maximum isometric knee extension contraction held until force decreased below 50% of the pre-fatigue MVC. Subjects also performed a single ramp contraction immediately after the fatigue task. The Root Mean Square (RMS) amplitude, mean power frequency (MPF) and median frequency (MF) of EMG signals obtained from the vastus lateralis, vastus medialis and rectus femoris were calculated at nine different force levels from the ramp contractions (10, 20, 30, 40, 50, 60, 70, 80 and 90% MVC), as well as every 5 s during the fatigue task. The main results were a more pronounced increase in EMG RMS amplitude for the three muscles and in MPF for the VL muscle with force in men compared with women. No significant effect of gender was found with regards to fatigue. These observations most likely reflect a moderately greater type II fiber content and/or area in the VL muscle of men compared to that of women.

Adult↗
PubMed2003

Role of probiotics on the environment of shrimp pond.

Recent disease outbreak in shrimp farming caused mainly by bacteria, virus, fungi or a combination of these etiologic agents is attributed to disturbance in the environment of pond. To combat this, different antibiotics and chemicals are being used which are reported to be not environment friendly. Of late, a new and unique biotechnological product called "Probiotics " is being used widely by all the shrimp farmers worldwide, which is found to be more effective and environmentally safe also. In the present study 2 probiotics were used in a small 0.7 ha shrimp farm near Pattukottai in Tamil Nadu State for one culture period for the management of pond environment and also the gut ecology of Penaeus monodon. The environmental parameters analysed were within the acceptable limits. It was evident from the results that the production was better in the experimental pond where the probiotics were used. The biological parameters such as the average body weight, FCR and total harvest achieved were better in the experimental pond than the control pond, all due to congenial environment, which obtained in the former mainly due to the use of probiotics.

Animals↗
PubMed2003

Toxicity of leaf extract of yellow oleander Thevetia nerifolia on Tilapia.

The usefulness of leaf extract as an ideal source of 'piscicide' in shrimp farming is described Leaf toxins are safe, eco-friendly and biodegradable. The fish Tilapia, Oreochromis mossambicus was exposed to the extract and the percentage of mortality at the end of 24,48, 72 and 96 hrs was recorded. The respective toxic range of aqueous, alcohol and acetone extracts of 24 hr LC50 and 96 hr LC50 values were found to be respectively 1118.79-330.30, 699.24-129.02 and 749.95-347.23 mg dry extract/litre for Oreochromis mossambicus. The LC50 values observed in different time periods in the fish exposed to aqueous extract were relatively high compared to the values obtained in acetone and alcohol extracts. Use of leaf extract, as piscicide in aquaculture farms is considered advantageous when viewed against the backdrop of using persistent chemicals.

Animals↗
PubMed2002

Major review: the clinical spectrum of pediatric myasthenia gravis: blepharoptosis, ophthalmoplegia and strabismus. A report of 14 cases.

BACKGROUND: Myasthenia gravis is infrequently encountered in pediatric ophthalmology practice. The purpose of this study is to evaluate the clinical spectrum of this condition in children and to identify factors that may aid the clinician in its diagnosis and management. SUBJECTS AND METHODS: A retrospective chart review was performed on all pediatric patients presenting with myasthenia gravis to the Departments of Pediatric Ophthalmology and Neuro- ophthalmology at the Texas Children's Hospital from 1989-1999. Information regarding mode of presentation, myasthenic classification, ocular and systemic involvement, diagnostic investigations, therapy and outcome was collected and evaluated. RESULTS: Fourteen patients were included in the study whose ages ranged from 1-17 years at presentation. One patient had congenital myasthenia gravis and 13 had juvenile myasthenia gravis. Thirteen of 14 (93%) patients presented with ocular findings; two of whom had associated systemic disease at presentation. Six of 14 (43%) patients had systemic involvement during the course of their illness, of whom three (21%) had respiratory compromise requiring assisted ventilation. Thirteen of 14 (93%) patients received pyridostigmine as first line treatment. Ten of 14 (71%) patients had a favorable response. A favorable response was defined as improvement in the extraocular motility to within 10 prism diopters of orthotropia with resolution of the blepharoptosis. Three of 14 patients (21%) received a combination of pyridostigmine and steroids, all of whom had a favorable response. Seven of 14 patients (50%) underwent thymectomy; all had a favorable response. Two of 14 patients (14%) required both blepharoptosis and strabismus surgery. CONCLUSION: Pediatric myasthenia gravis may present initially to the ophthalmologist and should be considered in any pediatric patients with blepharoptosis and an ocular motility disturbance. Prompt diagnosis may be associated with significant reduction in morbidity. A favorable response to medical and surgery therapy was noted in most of our patients.

Adolescent↗
PubMed2001

Should we prescribe antibiotics for acute bronchitis?

OBJECTIVES: People with acute bronchitis may show little evidence of bacterial infection. If effective, antibiotics could shorten the course of the disease. However, if they are not effective, the risk of antibiotic resistance may be increased. The objective of this review was to assess the effects of antibiotic treatment in patients with a clinical diagnosis of acute bronchitis. SEARCH STRATEGY: The authors searched MEDLINE, Embase, reference lists of articles, personal collections up to 1996 and Sci-search from 1989 to 1996. SELECTION CRITERIA: Randomized trials comparing any antibiotic therapy with placebo in acute bronchitis. DATA COLLECTION AND ANALYSIS: At least two reviewers extracted data and assessed trial quality. PRIMARY RESULTS: The results of eight trials involving 750 patients from eight years of age to 65 and older and including smokers and nonsmokers were included. The quality of the trials was variable. A variety of outcome measures was assessed. In many cases, only outcomes that showed a statistically significant difference between groups were reported. Overall, patients taking antibiotics had slightly better outcomes than those taking placebo. They were less likely to report feeling unwell at a follow-up visit (odds ratio, 0.42; 95 percent confidence interval [CI] 0.22 to 0.82), to show no improvement on physician assessment (odds ratio, 0.43; CI, 0.23 to 0.79) or to have abnormal lung findings (odds ratio, 0.33; CI, 0.13 to 0.86), and had a more rapid return to work or usual activities (weighted mean difference, 0.7 days earlier; CI, 0.2 to 1.3). Antibiotic-treated patients reported significantly more adverse effects (odds ratio, 1.64; CI, 1.05 to 2.57), such as nausea, vomiting, headache, skin rash or vaginitis. REVIEWERS' CONCLUSIONS: Antibiotics appear to have a modest beneficial effect in the treatment of acute bronchitis, with a correspondingly small risk of adverse effects. The benefits of antibiotics may be overestimated in this analysis because of the tendency of published reports to include complete data only on outcomes found to be statistically significant.

Acute Disease↗
PubMed1998

Elevation of serum tumor marker CA 15.3 levels as the first manifestation of metastatic breast cancer to the cavernous sinus.

We report rising tumor marker levels of CA 15.3 as the presenting manifestation of metastatic breast cancer to the cavernous sinus and orbit. A 39-year-old woman with a history of breast cancer developed increasing levels of tumor marker CA15.3. Ten months later, she developed vision loss in the right eye, diplopia, and right-sided ptosis. A magnetic resonance scan of the head showed a mass involving the right cavernous sinus and superior orbital fissure. Biopsy of the lesion showed metastatic breast cancer. She was treated with surgery and radiotherapy and did well. Ophthalmologists should be aware of the significance of increasing levels of tumor markers, such as CA 15.3, in patients with a history of breast cancer and new neuroophthalmologic signs or symptoms.

Adenocarcinoma↗
PubMed1997

The effect of nifedipine and methyldopa on maternal cerebral circulation.

OBJECTIVE: To study how the treatment of severe gestational hypertension affects maternal middle cerebral artery velocimetry. DESIGN: Prospective, clinical, descriptive study. SETTING: John Radcliffe Maternity Hospital, Oxford, England. PARTICIPANTS: Pregnant and puerperal women who required acute or chronic antihypertensive treatment with nifedipine (n = 46) or methyldopa (n = 26), respectively. METHODS: Transcranial Doppler ultrasound examinations of maternal middle cerebral arteries were performed before and 45 min after nifedipine; and before and 48 hours after the onset of methyldopa therapy. Blood pressure and heart rate were also recorded. MAIN OUTCOME MEASURES: Clinical and transcranial Doppler changes induced by the antihypertensive medication. RESULTS: Blood pressure and middle cerebral artery velocities decreased significantly following both short- and long-acting antihypertensive therapy. Nifedipine-induced changes were more pronounced and uniform than those found after methyldopa (16.7% and 6.4% decrease in middle cerebral artery mean velocity, respectively). The middle cerebral artery mean velocity decrease was independent of changes in the blood pressure or heart rate. CONCLUSIONS: Maternal cerebral haemodynamics are influenced by antihypertensive treatment. The reduction of middle cerebral artery flow velocities following administration of nifedipine and methyldopa may suggest that cerebral vasodilatation is occurring, which is consistent with the concept that cerebral vasospasm is present in women with pre-eclampsia. The cerebral vasodilatation could result from a direct effect of the medication on the arteries in question.

Antihypertensive Agents↗
PubMed1997

Maternal middle cerebral artery velocimetry in normal pregnancy and postpartum.

OBJECTIVE: To study changes throughout gestation and the puerperium of middle cerebral artery flow velocity waveforms obtained by transcranial Doppler ultrasound. DESIGN: Prospective, observational study. SETTING: John Radcliffe Maternity Hospital, Oxford, UK. PARTICIPANTS AND METHODS: Middle cerebral artery velocities were measured by transcranial Doppler ultrasound in 25 nonpregnant women, 22 women longitudinally followed throughout pregnancy and 21 women serially studied from delivery until the late puerperium. MAIN OUTCOME MEASURES: Transcranial Doppler changes in pregnancy and the puerperium. RESULTS: The transcranial Doppler ultrasound measurements showed good reproducibility. Signals from one middle cerebral artery could not be obtained in 4.6% of the examinations, but otherwise readings were similar on both sides. Women in the second half of pregnancy had lower middle cerebral artery mean velocities than nonpregnant women. Velocities decreased with advancing gestation but increased in the immediate puerperium to levels comparable to those found in nonpregnant women. CONCLUSIONS: Transcranial Doppler ultrasound is a noninvasive technique suitable for studying maternal cerebral haemodynamics in pregnancy and postpartum. Middle cerebral artery mean velocity decreased with advancing gestation and increased to nonpregnant values in the immediate puerperium. These physiological changes need to be considered when comparing data with measurements taken in abnormal pregnancy states.

Adult↗
PubMed1996

Histopathology of the substantia nigra in Alzheimer's disease.

Histopathologic examination of the pars compacta of the substantia nigra of 17 patients with Alzheimer's disease showed Lewy bodies in six, neurofibrillary tangles in another six and only histologic changes that did not differ from age-matched controls in five patients. Four of the six patients with nigral Lewy bodies showed severe loss of neural cell bodies, reactive astrocytosis, gliosis and neuromelanin in macrophages and in the neuropile. By contrast, the loss of neuronal cell bodies in our patients without nigral Lewy bodies regardless of whether or not they also had nigral neurofibrillary tangles was no greater than what we observed in our age-matched controls. Quantitative cell counts confirmed our histopathologic estimates of neuronal loss. Our study and the findings of others show that the substantia nigra is often abnormal in Alzheimer's disease and that the abnormalities are rarely severe without nigral Lewy bodies.

Aged↗
PubMed1993

Fetal cerebral Doppler in the recognition of fetal compromise.

OBJECTIVE: To establish reference ranges for the human fetal middle cerebral artery pulsatility index (MCA PI) for the local obstetric population, and to compare computerised antenatal fetal heart rate (FHR) analysis with the MCA PI as indicators of fetal compromise. DESIGN: Prospective data collection for selected patients. SETTING: High risk pregnancy unit of a teaching hospital. SUBJECTS: Group 1 consisted of 18 healthy women with uncomplicated singleton pregnancies. Group 2 consisted of 27 women admitted to the high risk pregnancy unit over a 9 month period with intrauterine growth retardation and other related problems; all these women were delivered by prelabour caesarean section. INTERVENTION: Serial Duplex sonography to determine fetal MCA PI in Groups 1 and 2. Serial FHR analysis using computerised numerical techniques in Group 2 only. MAIN OUTCOME MEASURES: Serial MCA PI values from 24 to 39 completed weeks of gestation in Group 1. Comparison of serial MCA PI values with FHR analysis in relation to fetal outcome in Group 2. RESULTS: In Group 1 the MCA PI diminished significantly as gestation advanced from 1.73 (SD 0.25) at 24 weeks to 1.38 (SD 0.26) at 39 weeks (P < 0.01). In Group 2 eleven babies were hypoxaemic at delivery: all had low MCA PI values while only nine had an abnormal FHR prior to delivery. CONCLUSION: In normal pregnancy, there is a fall in the fetal MCA PI with advancing gestation which probably reflects a decreasing vascular resistance to fetal cerebral blood flow. Hypoxaemia at delivery appeared to be better recognised by the fetal MCA flow velocity waveform than the FHR analysis. This increased sensitivity, however, was achieved at the expense of a reduced specificity. Larger studies are needed to confirm the findings of this preliminary investigation.

Adult↗
PubMed1992

Spontaneous resolution of pre-eclampsia-related thrombocytopenia.

OBJECTIVE: To observe the spontaneous resolution of pre-eclampsia-related thrombocytopenia. DESIGN: A retrospective study. SETTING: High Risk Pregnancy Unit, John Radcliffe Maternity Hospital, Oxford. SUBJECTS: Thirty women with pre-eclampsia complicated by the HELLP/ELLP syndrome who did not receive any specific treatment for their thrombocytopenia. INTERVENTION: Serial platelet counts throughout labour and the puerperium until the platelet counts returned to levels above 100 x 10(9)/l. MAIN OUTCOME MEASURES: Time taken from delivery and platelet nadir for platelet counts to return to levels above 100 x 10(9)/l. The rate of recovery from the platelet nadir was measured by the slope of the serial platelet counts plotted against time. RESULTS: The mean time until platelet count exceeded 100 x 10(9)/l was 67 h (SD 25) after delivery and 44 h (SD 17) from the platelet nadir. All women had counts above 100 x 10(9)/l by 111 h after delivery, and by 88 h after the platelet nadir. Although the time to recovery appeared to depend on the degree of thrombocytopenia, the rate of resolution did not. CONCLUSION: These data can be used as a guide by clinicians as to the expected time course for postpartum resolution of pre-eclampsia-related thrombocytopenia.

Adolescent↗