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Biomedical subjects

N Shankar

Publications and source records attributed to N Shankar.

At least 19 recordsLinked to original sources
PubMed2003

Pathogenic enterococci: new developments in the 21st century.

Enterococci, traditionally viewed as Gram-positive commensal bacteria inhabiting the alimentary canals of humans and animals, are now acknowledged to be organisms capable of causing life-threatening infections in humans, especially in the nosocomial environment. The existence of enterococci in such a dual role is facilitated, at least in part, by its intrinsic and acquired resistance to virtually all antibiotics currently in use. Beginning with the initial identification of a 'streptococci of fecal origin' in the late 19th century, enterococci have been studied for over a century now. A number of comprehensive reviews during this time have addressed various aspects of enterococci, including classification, biology, virulence, antibiotic resistance and so on. This review specifically addresses the important advances in the field of enterococcal research that have occurred since the beginning of the 21st century. Most notable among these developments have been the insights into enterococcal genomes and pathogenicity.

Adhesins, Bacterial↗
PubMed2003

Training teachers of day care centres for primary ear care.

The feasibility of training teachers of day care centres for children (balwadi teachers) to recognize and manage common ear problems was studied so that they could provide primary care for ear related morbidity in the community. A training module was designed, piloted on grass root level workers and used to train 19 balwadi teachers. Their knowledge, skills and technique of examination was assessed following training. Pathways for referral were established between the balwadis, secondary and tertiary hospitals. The knowledge score of the balwadi teachers increased from a mean of 28.4% to 86%; they scored an average of 75% in an assessment of their examination technique. Their sensitivity in identifying overall ear related morbidity was 75%, and 96% in identifying children with ear discharge, specifically. Age, education and experience did not affect the outcome of their training. While it may be premature to comment on the impact of the training, periodic supervision, close monitoring and review sessions would sharpen the skills of the balwadi teachers and improve their efficiency.

Adult↗
PubMed2003

Effect of iron on growth in iron deficient anemic school going children.

Iron deficiency anemia (IDA) in children has been associated with retardation in growth and the cognitive development. In the ongoing study on the effects of IDA in school going children, the effects on anthropometric parameters such as height (Ht), Weight (Wt), head circumference (HC), body mass index (BMI) and the mid arm circumference (MAC) were studied along with the hematological parameters such as hemoglobin (Hb), hematocrit (Hct), MCV, MCH, serum iron (SI), total iron binding capacity (TIBC) and % saturation. The pre-supplementation values of all these parameters were taken in anemic and control groups of girls and boys. After deworming all the children with albendazole (400 mg), the anemic group was put on iron supplementation (Ferrous iron 3-4 mg/kg body weight/day) along with vitamin C (100 mg OD) and the control children were given vitamin C (100 mg OD), for 90 days. Pre-supplementation values of IDA children were significantly lower for MAC and HC in girls and for Ht and MAC in boys, when compared to the control group. After the therapy both the groups of girls showed improvement in the hematological parameters though it was greater in the anemic girls. Ht and Wt of both groups also improved significantly but the anemic girls showed increase in BMI also. Both the control and anemic boys showed gain in weight. Post therapy, improvement in hematological parameters for both the anemic girls and boys were greater than their respective control groups. The MAC value for anemic girls were in the control range but those of anemic boys remained lesser than the control boys. So, it can be concluded from the present study that the IDA children lagged behind the control children in terms of anthropometric parameters and they benefited relatively more in terms of anthropometric improvement and hematological improvement after iron supplementation.

Anemia, Iron-Deficiency↗
PubMed2003

Effects of iron therapy on cognition in anemic school going boys.

The present study was conducted on 18 anemic and 34 control subjects (mean age 9.26 +/- 0.26 years) to observe the effect of anemia on cognition and to see effect of 3 months of iron therapy on it. Anemia was defined on the basis of hematological values and peripheral smear examinations. Cognitive data consisted of the recording of the P300 wave of Auditory Event Related Potentials (AERP), Ravens Progressive Matrices Test (RPMT), and Digit Span Attention Test (DSAT) under standard test conditions. RPMT scores were then converted to the intelligence quotient (IQ) scores for comparison. Both anemic and control boys were dewormed after recording pretreatment values and then anemic boys were given iron therapy for 3 months, after which the recordings were taken again. Pretreatment, anemic boys showed significantly lower hematological values, delayed P300 latency, and lower RPMT scores as compared to controls. Post therapy the hematological profile of anemic boys though significantly improved as compared to the pretreatment values, was still significantly lower than that of control boys. The P300 latency values of anemic boys showed improvement but were still significantly delayed than the control group. RPMT values and derived IQ scores of anemic boys were similar to control boys after therapy suggesting that though the 3 months iron therapy regime resulted in improvement in psychometric cognitive tests in anemic boys, the basic P300 defects persisted. This suggests that the P300 component of AERP in anemic children is relatively refractory to 3 months of iron therapy.

Anemia↗
PubMed2001

Role of Enterococcus faecalis surface protein Esp in the pathogenesis of ascending urinary tract infection.

Enterococcus faecalis bacteria isolated from patients with bacteremia, endocarditis, and urinary tract infections more frequently express the surface protein Esp than do fecal isolates. To assess the role of Esp in colonization and persistence of E. faecalis in an animal model of ascending urinary tract infection, we compared an Esp(+) strain of E. faecalis to its isogenic Esp-deficient mutant. Groups of CBA/J mice were challenged transurethrally with 10(8) CFU of either the parent or mutant strain, and bacteria in the urine, bladder, and kidneys were enumerated 5 days postinfection. Significantly higher numbers of bacteria were recovered from the bladder and urine of mice challenged with the parent strain than from the bladder and urine of mice challenged with the mutant. Colonization of the kidney, however, was not significantly different between the parent and mutant strains. Histopathological evaluations of kidney and bladder tissue done at 5 days postinfection did not show marked histopathological changes consistent with inflammation, mucosal hyperplasia, or apoptosis, and there was no observable difference between the mice challenged with the parent and those challenged with the mutant. We conclude that, while Esp does not influence histopathological changes associated with acute urinary tract infections, it contributes to colonization and persistence of E. faecalis at this site.

Animals↗
PubMed2001

Noise pollution: a study of noise levels in the operation theatres of a general hospital during various surgical procedures.

Noise, defined as any unwanted or undesirable sound, is a known environmental pollutant and health hazard. Sound levels during the entire surgical procedures were measured in the operation theatres (OTs) of a general hospital in Delhi, using a sound level meter, B & K 2209, on the dB(A) scale. The sound levels were found to be higher as compared to the recommended international standands. The noise was contributed mainly by doors, trolleys, equipment and alarms and the incessant conversation among the operation theatre (OT) staff. It is well documented that noise is stressful eliciting changes in the autonomic nervous system, impairing mental faculties and producing masking that could affect the staff and the conscious patient alike, leading to decreased work performance and increased anxiety respectively. Better acoustic designing and maintenance of equipment together with an increased awareness of the OT staff towards this vital factor of work environment may effectively reduce the noise pollution in OTs.

Humans↗
PubMed2001

Conformational study of peptides containing dehydrophenylalanine: helical structures without hydrogen bond.

The conformational behaviour of deltaZPhe has been investigated in the model dipeptide Ac-deltaZPhe-NHMe and in the model tripeptides Ac-X-deltaZPhe-NHMe with X=Gly,Ala,Val,Leu,Abu,Aib and Phe and is found to be quite different. In the model tripeptides with X=Ala,Val,Leu,Abu,Phe the most stable structure corresponds to phi1=-30 degrees, psi1=120 degrees and phi2=psi2=30 degrees. This structure is stabilized by the hydrogen bond formation between C=O of acetyl group and the NH of the amide group, resulting in the formation of a 10-membered ring but not a 3(10) helical structure. In the peptides Ac-Aib-deltaZPhe-NHMe and Ac-(Aib-deltaZPhe)3-NHMe, the helical conformers with phi = +/-30 degrees, psi = +/-60 degrees for Aib residue and phi=psi= +/-30 degrees for deltaZPhe are predicted to be most stable. The computational studies for the positional preferences of deltaZPhe residue in the peptide containing one deltaZPhe and nine Ala residues reveal the formation of a 3(10) helical structure in all the cases with terminal preferences for deltaZPhe. The conformational behaviour of Ac-(deltaZPhe)n-NHMe with n< or =4 is predicted to be very labile. With n > 4, degenerate conformational states with phi,psi values of 0 degrees +/- 90 degrees adopt helical structures which are stabilized by carbonyl-carbonyl interactions and the N-H-pi interactions between the amino group of every deltaZPhe residue with one C-C edge of its own phenyl ring. The results are in agreement with the experimental finding that screw sense of helix for peptides containing deltaZPhe residues is ambiguous in solution. The helical structures stabilized by hydrogen bond formation are found to be at least 3kCalmol(-1) less stable. Conformational studies have also been carried out for the peptide Ac-(deltaEPhe)6-NHMe and the peptide Ac-deltaAla-(deltaZPhe)6-NHMe containing deltaAla residue at the N-terminal. The N-H-pi interactions are absent in peptide Ac-(deltaEPhe)6-NHMe.

Hydrogen Bonding↗
PubMed2000

An acoustic/thermal model for self-heating in PMN sonar projectors

Dielectric hysteresis and a strong material temperature dependence uniquely couple the acoustic output and temperature of a sonar projector driven by electrostrictive Pb(Mg1/3, Nb2/3)O3 (PMN). Both the source level and the source of self-heating, i.e., dielectric hysteresis, dramatically decrease as the PMN driver heats. The final temperature delineates outstanding PMN transducers from mediocre PMN transducers, so accurate acoustic performance prediction requires accurate transducer temperature prediction. This study examined this self-heating phenomenon by combining an electro-acoustics model for a PMN flextensional transducer with a thermal finite element model. The sonar model calculated the source level and heat generation rate for the PMN driver as a function of temperature. This computed source level varied 12 dB over a 75 degrees C temperature range solely due to the temperature dependent ceramic. The heat transfer model used the computed heat rate to predict the transducer's transient thermal response. The results clearly demonstrate that the transducer reached a steady-state equilibrium temperature, where the heat generated by the PMN driver balanced the heat dissipated. While the transducer model predicted a significant temperature rise, the corresponding acoustic output still surpassed the output of an equivalent Pb(Zr,Ti)O3 (PZT) transducer by 8 dB. Good agreement with experiments made on a PMN flextensional transducer validated the model.

Journal Article↗
PubMed2000

Brainstem auditory evoked potential responses in iron-deficient anemic children.

Iron deficiency is a major health problem in developing countries manifesting not only as overt anemia but also involving the CNS resulting in cognitive and behavioral deficits. Iron is an important nutrient and essential element involved in myelin formation and neurotransmitter synthesis and thus contributes to normal neurological activity. Hypomyelination has been reported in iron deficient states with possible neural conduction defects. The brainstem auditory evoked potential response is used extensively to identify lesions associated with various demyelinating diseases and hence has been used in the present study to observe the effect of iron deficiency on sensory brain function. A trend of increased absolute and interpeak latencies and reduced amplitudes of the waves leading to a definite linear correlation between the severity of anemia and the degree of neurophysiological deficit suggests a subclinical involvement of the auditory pathway in the brainstem of iron deficient children.

Adolescent↗
PubMed1999

Behavioural parameters in hypertensives on atenolol therapy.

Behavioural responses which included psychological tests and cold pressor test as a stress test were studied in 20 mild to moderate hypertensives of both sexes, excluding smokers, alcoholics, secondary hypertensives and patients of chronic obstructive pulmonary diseases. Subjects were put on 2 weeks of placebo washout period followed by 6 weeks of treatment with atenolol. Following treatment with atenolol they showed no significant alteration in the scores of psychological tests which included Weschler adult intelligence scale for orientation, while showing significant depression in the rise of heart rate, systolic blood pressure and diastolic blood pressure following cold pressor test. On further analysis, the results showed that hypertensives on placebo had lower scores of memory and attention test as compared to normotensive controls. Besides this, hypertensives on placebo had higher rise of heart rate and systolic blood pressure as compared to normotensive controls after cold pressor test.

Adrenergic beta-Antagonists↗
PubMed1999

Analgesic effect of environmental noise: a possible stress response in rats.

Environmental noise is a known stress, which induces alterations of various physiological responses in individuals exposed to it. Stress has been shown to cause changes in the perception of various sensations including pain and stress-induced analgesia has been observed following exposure to a diverse set of stimuli. To examine the algesic behavior of rats exposed to loud environmental noise, for long duration, we used an environment simulating chamber and conducted the tail flick test for the assessment of pain. The rats were divided into groups and subjected to loud noise for test sessions lasting 1 h, 2 h or 3 h in trials of 5 consecutive days. The noise was of two kinds--a continuous shrill noise (pure tone 92 dB & 98 dB) and an intermittent heavy artillery noise (white noise 102 dB). 15 min before and after each test session, tail flick latencies (TFL) were recorded at 5 min interval. The TFL recorded were normalised to an Index of Analgesia (IA) and the readings statistically analyzed using the F test (ANOVA), the significance being obtained by Tukey's test (at 5% level). The results revealed a significant increase in the TFL and the IA (P < 0.0001) in all the test groups demonstrating a significant analgesic response in rats subjected to noise stress. The analgesia was maximum immediately after noise exposure and declined with time. It was found to be directly related to the duration of exposure, the intensity and the characteristics of the noise with loud intermittent (white) noise and longer duration of exposure producing more analgesia.

Analgesia↗
PubMed1998

A study of pulmonary profile of hypertensive patients--comparison of atenolol vs amlodipine.

Two groups of drugs commonly used for the treatment of hypertension are atenolol and amlodipine. These drugs are reported to have conflicting changes on pulmonary responses. In order to study the effect of hypertension and antihypertensive treatment on pulmonary responses, 40 patients with essential hypertension having diastolic blood pressure between 90-114 mmHg on three consecutive weekly visits were taken. Pulmonary responses were tested at the end of 2 weeks of placebo washout period and then at the end of 6 weeks of treatment with either atenolol or amodipine. Using a computerized autospiror along with the weekly recordings of heart rate and blood pressure, the various pulmonary and cardiac parameters were taken. Analysis of the result showed that atenolol treatment resulted in significant decline of forced vital capacity (FVC), % forced vital capacity (%FVC), and forced expiratory volume in first second (FEV1) whereas amlodipine did not show any significant change on pulmonary parameters.

Amlodipine↗
PubMed1997

Ontogeny of taste sense.

Developmental changes in the taste receptors and CNS, in physiological and behavioural patterns in fetus and postnatal animals constitute the ontogeny of taste. Tongue epithelial cells are modified into taste buds only with innervation and are seen to degenerate on denervation. On removal of a portion of the tongue, with its taste buds, the central projections of gustation also atrophy, indicating an interdependence of taste receptors and central areas for their development. Gradual transitions in electrical responses to taste stimuli are shown from fetal to adult stage. While responses to ammonium chloride are marked in early fetus, with advancements in age responses to a wide variety of chemicals are shown. Again, early in the development, fibers responsive to chloride are predominant while at a later stage fibers responsive to sodium increase in number. Behaviourally, human fetus and neonatal mammals showed increased swallowing movements on sweet taste and decreased movements on bitter taste which is somewhat at variance with electrophysiological evidence and reflects on the multimodal involvement of taste cell functional and behavioural dynamics with age.

Animals↗
PubMed1996

Electroacupuncture, morphine and clonidine: a comparative study of analgesic effects.

This is a comparative study of the analgesic effects of the modified traditional method of analgesia, electroacupuncture (EA), a standard analgesic drug, morphine, a potential analgesic drug, clonidine and the combination of EA + morphine and EA + clonidine. In each case, the index of analgesia (IA) was determined by recording the tail flick latency (TFL) in 60 rats divided into 6 groups of 10 rats each. Group I rats served as control group while Group II-VI were subjected to EA for 20 min (at Zusanli and Kunlun points), morphine (5 mg/kg bw i.p.), clonidine (150 micrograms/kg bw i.p.), EA + morphine and EA + clonidine respectively. TFLs were recorded after the procedure and at 10 min intervals for 150 min or til the TFL returned to¿ the baseline. The IA, analyzed using the Kruskal-Wallis test and its significance determined by multiple comparison test (at 5% level), was found to be significantly different, at various time intervals, in the 6 groups studied.

Analgesics↗
PubMed1993

Urinary bladder serosal chemoreceptor induced cardio-respiratory responses: possible pathway.

There is limited experimental information about pain originating from the urinary bladder. In the present study application of 3-5 ml of 1% ammonium oxalate, 1% potassium chloride, 100m M citric acid, IM ammonium chloride, 1% oxalic acid, 0.5% sodium hydroxide, or 2 micrograms/ml bradykinin, to the serosal surface of the urinary bladder in anaesthetized dogs, resulted in an increase in heart rate, rise of both systolic and diastolic blood pressures and increase in respiratory rate and depth. These facilitatory cardio-respiratory responses were coupled with powerful contractions of the urinary bladder wall. By contrast, mucosal application of the chemicals did not bring about any significant change. The cardio-respiratory responses obtained were completely abolished on serosal application of procaine (1%), section of the hypogastric nerves or by spinalectomy at T8. Bilateral cervical vagotomy and pelvic nerve section did not modify the responses. However, the blood pressure responses were abolished by the administration of tolazoline hydrochloride, indicating a major role of sympathetics in this nociceptive reflex.

Animals↗
PubMed1991

An analysis of alpha/beta TCR V gene expression in the human thymus.

We have previously analysed alpha/beta T cell receptor (TCR) V gene usage in CD4+ and CD8+ subpopulations from human peripheral blood lymphocytes (PBL) and umbilical cord blood, and described a biased usage of some of the TCR V beta genes towards the CD4+ subpopulation. In this report, the TCR V gene usage in single positive (SP) CD4+ or CD8+ human thymocytes was analysed. Three previously described mAb with a biased usage in PBL and umbilical cord blood also had a skewed reactivity towards the CD4+ subpopulation in SP human thymocytes. Thus, in all 12 cases V beta 5.1 and V beta 6.7, and in 11/12 cases V beta 12 were preferentially used in the CD4+CD8-, compared to the CD4-CD8+ thymic subpopulation. Altogether, these results suggest a selection process in the thymus, supposedly through the positive influence of MHC class II determinants, to be responsible for this non-random, skewed TCR V gene usage.

Antibodies, Monoclonal↗