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Biomedical subjects

S Nayak

Publications and source records attributed to S Nayak.

At least 19 recordsLinked to original sources
PubMed2025

Polygenic Associations between Motor Behaviour, Neuromotor Traits, and Active Music Engagement in Four Cohorts.

Phenotypic investigations have shown that actively engaging with music, i.e., playing a musical instrument or singing may be protective of motor decline in aging. For example, music training associated with enhanced sensorimotor skills accompanied by changes in brain structure and function. Although it is possible that the benefits of active music engagement "transfer" to benefits in the motor domain, it is also possible that the genetic architecture of motor behaviour and the motor system structure may influence active music engagement. This study investigated whether polygenic scores (PGS) for five behavioural motor traits, 12 neuromotor structural brain traits, and seven rates of change in brain structure traits trained from existing discovery genome-wide association studies (GWAS) predict active music engagement outcomes in four independent cohorts of unrelated individuals of European ancestry: the Canadian Longitudinal Study on Aging (CLSA; N=22,198), Wisconsin Longitudinal Study (WLS; N=4,605), Vanderbilt's BioVU Repository (BioVU; N=6,150), and Vanderbilt's Online Musicality study (OM; N=1,559). Results were meta-analyzed for each PGS main effect across outcomes and cohorts, revealing that PGS for a faster walking pace was associated with higher amounts of active music engagement. Within CLSA, a higher PGS for walking pace was associated with greater odds of engaging with music. Findings suggest a shared genetic architecture between motor function and active music engagement. Future intervention-based research should consider the genetic underpinnings of motor behavior when evaluating the effects of music engagement on motor function across the lifespan.

BioVU↗
PubMed2006

Development of alternative support system for viable count of cyanobacteria by most probable number method.

A technique was developed to evaluate alternative support systems to test tubes used in the standard most probable number technique, for simultaneous isolation and enumeration of cyanobacteria. Five different support systems were tested for their suitability in terms of accuracy, sensitivity, economics and ease of handling. PCR plates with 96 wells and carrying capacity of 300 microL per well were found to be most sensitive, besides being cost- and time-effective. This technique can also be useful for isolation of cyanobacteria, due to immobilization of colonies in the gel matrix and storage of samples at room temperature, without loss of viability for 5-6 weeks. This technique can help to process large sample size with ease--both for enumeration and isolation and can be extended for enumeration of other microorganisms from diverse sources.

Colony Count, Microbial↗
PubMed2006

Anaesthesia-related maternal mortality.

Complications of anaesthesia leading to death in young pregnant women might be prevented if more experienced personnel could be entrusted with the job. The contribution of anaesthesia to maternal mortality in the United Kingdom is 1.7 per million pregnancies with almost similar incidence from United States. The commonest single factor responsible for anaesthesia-related death is difficult or failed intubation. A pregnant woman with a potentially difficult airway should receive aspiration prophylaxis (mechanical or pharmacological) as soon as operative delivery is anticipated. Anaesthetists should make a plan that comes into effect as soon as failure to view the larynx or to intubate the trachea becomes evident. Unsuspected difficult airway can be managed if the skill of the anaesthetists is of high standard. Pulmonary aspiration is one cause of death in obstetric anaesthesia. Regurgitation and vomiting prevention can minimise pulmonary aspiration. In regional anaesthesia, local anaesthetics toxicity is another cause of concern. This should be tackled with some safe local anaesthetics. Preventing a high spinal or epidural block involves ways to detect inadvertent injection of local anaesthetic into the cerebrospinal fluid. Postoperative care after anaesthesia in obstetric cases is very important.

Anesthesia, Conduction↗
PubMed2004

The value of Bilicheck as a screening tool for neonatal jaundice in term and near-term babies.

AIMS: To determine the accuracy of Bilicheck in assessing serum bilirubin. To evaluate the effectiveness of Bilicheck as a screening device in a population of jaundiced term and near-term babies. METHODS: Prospective evaluation of paired Bilicheck measurements and serum bilirubin in 300 babies. RESULTS: There was a strong correlation between Bilicheck and serum bilirubin. The mean difference between Bilicheck and serum bilirubin was -10.7 micromol/l, but the 95% limits of agreement were wide at -80 micromol/l to +60 micromol/l. Bilicheck identified significant jaundice (serum bilirubin above 250 micromol/l) with a sensitivity (95% confidence interval) of 91% (88% to 94%) and specificity of 66% (60% to 71%). The area under the receiver operator characteristic curve was 0.85. There were five false negatives, all of whom had a serum bilirubin below 300 micromol/l. If Bilicheck had been used as a screening device, there would have been a 55% decrease in blood samples taken in these babies. CONCLUSION: Bilicheck cannot be used to measure serum bilirubin in term and near-term babies with jaundice, but is an effective screening method, which can be used to safely reduce the number of blood tests in these babies.

Bilirubin↗
PubMed2002

Congenital reducible atlantoaxial dislocation: classification and surgical considerations.

BACKGROUND: Reducible atlanto-axial dislocation (AAD) may cause severe motor and respiratory compromise due to recurrent spinal cord and/or brain stem impingement. To the best of the authors' knowledge, this is the first study concentrating on the classification, the protocol of the surgical management and the outcome of congenital, reducible AAD. METHODS: 109 patients with congenital, reducible AAD underwent posterior stabilization. Their preoperative disability was graded as: I (n=11, 10.09%) no functional disability (a history of minor trauma led to quadriparesis that subsequently improved); II (n=31, 28.44%) independent for activities of daily living with minor disability; III (n=42, 38.53%) partially dependent on others for their daily needs; and, IV (n=25, 22.93%) totally dependent. They were classified into 4 groups depending upon their association with: a normal odontoid and posterior arch of atlas (n=27); a dysplastic odontoid and normal posterior arch (n=25); an assimilated posterior arch (n=49); and, Arnold Chiari malformation type I (n=8). Nine patients with a dysplastic odontoid had a "hypermobile" AAD with an unrestricted backward and forward movement of the axis relative to the atlas in flexion as well as in extension of the neck, respectively. The surgical procedures included Brooks' (n=12) or modified Brooks' C1-2 fusion (n=39); Goel's C1-2 fusion (3); Ransford's contoured rod fusion (n=7); Jain's occipitocervical fusion (n=47); and, transoral decompression and Jain's occipitocervical fusion (n=1). There were 6 peri-operative mortalities in the series. FINDINGS: At follow-up (ranging from 3 months to 6 years; n=86), 64 patients had shown improvement by one grade or more; 8 patients, who had a history of transient quadriparesis but were without neurological deficits at presentation, remained in grade I; 11 had achieved stabilization of neurological functions; while 3 had deteriorated despite adequate radiological reduction of AAD and fusion of the construct. A follow-up of 6 months or more was available in 79 of these 86 patients, in whom a dynamic intrathecal CT scan showed a good osseous union. INTERPRETATION: The patients with congenital reducible AAD, depending on their surgical management, may be classified into four groups. Some patients with a dysplastic odontoid have a "hypermobile" AAD and require special care during intubation, positioning and stabilization. An assimilated posterior arch is often associated with asymmetrical lateral occipito-C1-C2 joint synostosis rendering transarticular screw placement difficult. The various causes of failure of constructs are discussed.

Adolescent↗
PubMed2002

Bending properties of carbon nanotubes encapsulating solid nanowires.

Using empirical potentials and atomistic simulations, we model three-point bend tests of single-walled carbon nanotubes encapsulating metal nanowires. The presence of a metal nanowire inside the nanotube greatly suppresses the tube-buckling instability. Increasing tube diameter leads to an increase in the bending strength; however, in contrast to hollow tubes, there is no decrease in the maximum deflection before buckling. Analysis of the principal bending vibrational mode shows a lowering of the frequency, associated with increased tube inertia. Remarkably, metal-filled tubes exhibit strong damping of oscillations whereas unfilled single-walled and multiwalled tubes show no damping. Our studies demonstrate the benefits of filling tubes with solids to modify bending strength and flexibility, suggesting applications for nanotube-based elements in micromechanical devices or nanoprobes.

Computer Simulation↗
PubMed2001

The Phe-X-Glu DNA binding motif of MutS. The role of hydrogen bonding in mismatch recognition.

The crystal structures of MutS protein from Thermus aquaticus and Escherichia coli in a complex with a mismatch-containing DNA duplex reveal that the Glu residue in a conserved Phe-X-Glu motif participates in a hydrogen-bonded contact with either an unpaired thymidine or the thymidine of a G-T base-base mismatch. Here, the role of hydrogen bonding in mismatch recognition by MutS is assessed. The relative affinities of MutS for DNA duplexes containing nonpolar shape mimics of A and T, 4-methylbenzimidazole (Z), and difluorotoluene (F), respectively, that lack hydrogen bonding donors and acceptors, are determined in gel mobility shift assays. The results provide support for an induced fit mode of mismatch binding in which duplexes destabilized by mismatches are preferred substrates for kinking by MutS. Hydrogen bonding between the O epsilon 2 group of Glu and the mismatched base contributes only marginally to mismatch recognition and is significantly less important than the aromatic ring stack with the conserved Phe residue. A MutS protein in which Ala is substituted for Glu(38) is shown to be defective for mismatch repair in vivo. DNA binding studies reveal a novel role for the conserved Glu residue in the establishment of mismatch discrimination by MutS.

Adenosine Triphosphatases↗
PubMed2001

Interaction of Escherichia coli MutS and MutL at a DNA mismatch.

MutS and MutL are both required to activate downstream events in DNA mismatch repair. We examined the rate of dissociation of MutS from a mismatch using linear heteroduplex DNAs or heteroduplexes blocked at one or both ends by four-way DNA junctions in the presence and absence of MutL. In the presence of ATP, dissociation of MutS from linear heteroduplexes or heteroduplexes blocked at only one end occurs within 15 s. When both duplex ends are blocked, MutS remains associated with the DNA in complexes with half-lives of 30 min. DNase I footprinting of MutS complexes is consistent with migration of MutS throughout the DNA duplex region. When MutL is present, it associates with MutS and prevents ATP-dependent migration away from the mismatch in a manner that is dependent on the length of the heteroduplex. The rate and extent of mismatch-provoked cleavage at hemimethylated GATC sites by MutH in the presence of MutS, MutL, and ATP are the same whether the mismatch and GATC sites are in cis or in trans. These results suggest that a MutS-MutL complex in the vicinity of a mismatch is involved in activating MutH.

Adenosine Triphosphatases↗
PubMed2001

ADP-dependent DNA strand exchange by the mutant [P67G/E68A] RecA protein.

We have prepared a mutant RecA protein in which proline 67 and glutamic acid 68 in the NTP binding site were replaced by a glycine and alanine residue, respectively. The [P67G/E68A]RecA protein catalyzes the single-stranded DNA-dependent hydrolysis of ATP and is able to promote the standard ATP-dependent three-strand exchange reaction between a circular bacteriophage phiX174 (phiX) single-stranded DNA molecule and a homologous linear phiX double-stranded (ds) DNA molecule (5.4 kilobase pairs). The strand exchange activity differs from that of the wild type RecA protein, however, in that it is (i) completely inhibited by an ATP regeneration system, and (ii) strongly stimulated by the addition of high concentrations of ADP to the reaction solution. These results indicate that the strand exchange activity of the [P67G/E68A]RecA protein is dependent on the presence of both ATP and ADP. The ADP dependence of the reaction is reduced or eliminated when (i) a shorter linear phiX dsDNA fragment (1.1 kilobase pairs) is substituted for the full-length linear phiX dsDNA substrate, or (ii) the Mg(2+) concentration is reduced to a level just sufficient to complex the ATP present in the reaction solution. These results indicate that it is the branch migration phase (and not the initial pairing step) of the [P67G/E68A]RecA protein-promoted strand exchange reaction that is dependent on ADP. It is likely that the [P67G/E68A]RecA mutation has revealed a requirement for ADP that also exists (but is not as readily apparent) in the strand exchange reaction of the wild type RecA protein.

Adenosine Diphosphate↗
PubMed2001

Ocular oscillations induced by shifts of the direction and depth of visual fixation.

Shifts of the point of fixation between two targets aligned on one eye that are located near and far (Müller paradigm) stimulates a combined saccadic-vergence movement. In normal subjects, this test paradigm often induces saccadic oscillations of about 0.3 degrees at 20 to 30 Hz. We measured eye movements using the magnetic search coil technique in 2 patients recovering from viral opsoclonus-myoclonus syndrome, comparing saccadic-vergence responses to the Müller paradigm with conjugate saccades between distant targets. Both patients exhibited intermittent conjugate ocular oscillations of about 4 to 5 degrees amplitude at about 10 Hz. Combined saccadic-vergence movements induced these oscillations twice as often as did conjugate saccades. One patient also exhibited disjunctive ocular oscillations at 10 Hz while sustaining fixation on the near target. The Müller paradigm provides a useful clinical and experimental technique for inducing saccadic oscillations. The probable mechanism is that pontine omnipause neurons, which normally gate saccades, are inhibited during the sustained vergence movement that follows the saccadic component of the response to the Müller paradigm.

Adult↗
PubMed2001

Spinal subarachnoid hemorrhage complicating oral anticoagulant therapy.

Spinal subarachnoid hemorrhage (SAH) is rare clinical entity possible owing to the diluting and fibrinolytic effects of cerebrospinal fluid (CSF). When it occurs, it is most commonly encountered in the thoracic segment of the subarachnoid space. We present a case of a 50-year-old man who sustained spinal SAH in the cervical and thoracic segments related to anticoagulant therapy. He progressed to significant neurological deficit since he was inoperable, an observation that supports the need for decompression surgery. We should be aware of potential hematomyelia should a patient on anticoagulant therapy develop neurological symptoms localized to the spinal cord. When available, magnetic resonance (MR) imaging is the modality of choice to diagnose and follow-up spinal SAH.

Anticoagulants↗
PubMed2001

Segmental anatomy of the temporal bone.

More of us suffer from hearing loss than from visual impairment, coronary artery disease, and cancer combined. Auditory dysfunction is detected in less than one third of newborns afflicted and is underdiagnosed in the elderly. Despite biomedical and technological advances, our understanding of vestibular dysfunction has grown little. Forming part of the lateral and inferior surfaces of the skull, the temporal bone contains the organs of hearing and balance. Diagnosis of diseases in these important regions requires adequate clinical information and a thorough knowledge of normal temporal bone anatomy to recognize abnormal findings when present. This article dissects the temporal bone into segments, describes the relevant radiologic anatomy of each, and discusses the imaging appropriate to specific concerns.

Anatomy, Cross-Sectional↗
PubMed2001

Reduced levels of rat lens antioxidant vitamins upon in vitro UVB irradiation.

Ultraviolet (UV) radiation is one of the major risk factors of cataractogenesis. UV radiation induced damage to the eye lens is believed to be mediated through reactive oxygen species. Antioxidant defense systems, enzymatic and non-enzymatic, resist this damage. In the present study, the levels of rat lens endogenous antioxidants, L-ascorbic acid, alpha-tocopherol and beta-carotene, have been determined by HPLC upon in vitro UVB irradiation. UVB irradiation for 24 h (300 nm; 100 µW/cm(2)) of three months old rat lens suspended in RPMI medium, leads to 69-89% decrease in endogenous levels of these antioxidants. The addition of ascorbic acid (2 mM), alpha-tocopherol (2.5 µM) or beta-carotene (10 µM), separately to the medium during irradiation significantly prevented the decrease in their endogenous levels, thereby suggesting a protective role for these antioxidant micronutrients against photodamage to the eye lens.

Journal Article↗
PubMed2001

Quantification and validation of enzyme immunoassay for urinary aflatoxin B1-N7-guanine adduct for biological monitoring of aflatoxins.

The aflatoxin B1-N7-guanine (AFB1-N7-guanine) adduct has been established as one of the relevant biomarkers of dietary aflatoxin (AFB1) exposure. Measurement of this adduct is potentially a useful dosimeter in molecular epidemiological studies. This paper reports the application and evaluation of a sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of urinary AFB1-N7-guanine adduct in high risk populations exposed to dietary aflatoxin. Earlier, we had reported a simple and rapid indirect ELISA method for AFB1-N7-guanine adduct in the urine and liver tissues using polyclonal antibodies specific to AFB1-N7-guanine adduct. The method was evaluated using a rodent model (Fischer 344), exposed to 1 mg kg-1 body mass of AFB1 and human urine samples obtained from a maize eating population, environmentally exposed to AFB1 through their diet. The levels of AFB1-N7-guanine adduct in rat and human urine ranged from 6.42 to 20.16 micrograms mg-1 creatinine and from 9.30 to 13.43 ng mg-1 creatinine, respectively. The level of AFB1 in the diet as estimated by ELISA ranged from 1000 to 3600 ng d-1. The interesting observation in these studies is that the females (in both rodents and human subjects) are more efficient than males at excreting the adduct. Total adduct (DNA bound adduct and guanine adduct excreted in urine) was found to be similar in male and female rats. However, 63% of the total adduct was accounted for in urine of female rats, whereas male rats excreted 47% of the total adduct in their urine. The present method may find wide application as a biochemical tool in molecular epidemiological studies with respect to human exposure to dietary aflatoxins.

Aflatoxin B1↗
PubMed2001

Is acupuncture effective in treating chronic pain after spinal cord injury?

OBJECTIVES: To evaluate the efficacy of acupuncture as a treatment for chronic pain and secondary symptoms after spinal cord injury (SCI) and to identify disease-specific variables associated with response to treatment. DESIGN: A within-subjects design consisting of a 7(1/2)-week no-acupuncture baseline period followed by a 7(1/2)-week treatment period and a follow-up assessment 3 months posttreatment. SETTING: Medical rehabilitation research center. PARTICIPANTS: Twenty-two people with SCI who experienced moderate to severe pain of at least 6 months' duration. INTERVENTION: A course of 15 acupuncture treatments was administered over a 7(1/2)-week period. MAIN OUTCOME MEASURES: Numeric Rating Scale of pain intensity; ratings of interference with activity, individualized symptom rating, Center for Epidemiologic Studies-Depression Scale; Speilberger State Trait Anxiety Inventory, and General Well-Being Schedule. RESULTS: Ten patients (46%) showed improvement in pain intensity and pain sequelae after treatment. However, 6 patients (27%) reported an increase in pain that was still present 3 months after treatment. CONCLUSIONS: About 50% of the study sample reported substantial pain relief after acupuncture treatment, suggesting that acupuncture may provide pain relief for at least a subgroup of individuals with SCI. Future research is needed to determine what part of this effect is because of acupuncture versus nonspecific effects such as placebo effects and regression to the mean.

Acupuncture Therapy↗