Epithelial downgrowth following clear cornea phacoemulsification in a buphthalmic eye.
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Adult↗
Biomedical subjects
S Srinivasan
Publications and source records attributed to S Srinivasan.
Features of the metabolic syndrome after childhood craniopharyngioma.
Obesity and multiple pituitary hormone deficiency are common complications after surgery for childhood craniopharyngioma. We hypothesized that post craniopharyngioma surgery, children are at high risk for the metabolic syndrome, including insulin resistance due to excess weight gain and GH deficiency. This study characterized body composition (anthropometry and dual energy x-ray absorptiometry) and metabolic outcomes in 15 children (10 males and 5 females; age, 12.2 yr; range, 7.2-18.5 yr) after surgical removal of craniopharyngioma. In 9 subjects, outcomes were compared with those of healthy age-, sex-, body mass index-, and pubertal stage-matched controls. Insulin sensitivity was measured by 40-min iv glucose tolerance test. Seventy-three percent of subjects were overweight or obese. Sixty-six percent had normal growth velocity without GH treatment. Subjects had increased abdominal adiposity (P = 0.008) compared with controls. However, there was no significant difference in total body fat. Subjects had higher fasting triglycerides (P = 0.02) and lower high density lipoprotein cholesterol to total cholesterol ratio (P = 0.015). Insulin sensitivity was equally reduced for subjects and controls (P = 0.86). After craniopharyngioma removal, patients had more features of the metabolic syndrome compared with controls. This could be a result of hypothalamic damage causing obesity and GH deficiency. Further studies exploring predictors of the metabolic syndrome after craniopharyngioma surgery are required.
Abdomen↗
Tilt table testing in the diagnostic evaluation of presyncope and syncope: a case-series report.
Tilt table testing has long been used as a standard tool in the diagnostic evaluation of syncope. However, differences of opinion exist with regard to its utility in the evaluation of patients with only presyncopal attacks. We present the results of drug-free, 70-degree head-up tilt table tests (maximum duration of 45 minutes), conducted between May 2002 and May 2003 in the Department of Physiology at JIPMER. This series consisted of both male and female patients (age 6-79 yr) with presyncope (n = 43), unexplained syncope (n = 43) and asymptomatic healthy volunteers without a history of syncope (n = 14). 28 out of 43 patients with unexplained syncope had a history of recurrent syncope while the remaining 15 had only 1 episode. 2 out of 43 patients (4.6%) with a history of only presyncopal attacks had a positive test (induction of intense presyncope and/or syncope accompanied by hypotension and/or a relative bradycardia). 21 out of 43 patients (49%) with a history of syncope had a positive test. 7 had vasodepressor syncope due to hypotension, 6 had cardioinhibitory syncope characterized by asystole and 10 had a mixed form of the vasovagal syndrome characterized by hypotension as well as bradycardia. 18 out of 28 patients (64%) with recurrent unexplained syncope had a positive test. All fourteen healthy volunteers had a negative test. We conclude that tilt table testing is useful in the diagnostic evaluation of patients with unexplained syncope, especially those with recurrent syncope, but not in the evaluation of patients with presyncope alone.
Adolescent↗
A zero-crossing strain estimator for elastography.
A novel zero-crossing tracking strain estimator (ZCT) has been developed for elastography. This technique is based on tracking the zero-crossings between the pre- and postcompression A-lines, and does not require global or adaptive A-line stretching. For multicompression elastography, ZCT can be implemented as a tracking scheme, where a temporal track of the zero-crossings between successive radiofrequency (RF) A-lines is obtained, or as an averaging scheme, where a cumulation of the interframe strains is performed, to yield high elastographic signal-to-noise ratio (SNR). Other advantages of the scheme include fast processing and its potential to be implemented in hardware. The limitations of the technique are the need for small compression steps due to lack of robustness when large compression steps (> 3% applied compression) are used. Simulations and experiments were performed to illustrate its utility as an alternative strain-estimation technique. This technique provides lower SNR but higher contrast-to-noise ratio (CNR) than the conventional strain-estimation techniques in elastography.
Animals↗
Trade-offs between the axial resolution and the signal-to-noise ratio in elastography.
Elastography involves tracking the ultrasonic A-mode signals before and after mechanical compression of tissue to form a computed image of the local strains undergone by various tissue components. The quality of the strain estimates in elastography is typically quantified using factors such as the elastographic SNR (SNR(e)), contrast-to-noise ratio (CNR(e)), and the spatial resolution. These quality factors depend on the mechanical parameters (such as the applied strain and the boundary conditions), the acoustic parameters (such as the sonographic SNR, the center frequency, and the bandwidth), and the signal-processing parameters (such as the window length and the window separation). Theoretical developments in elastography have established functional relationships between the SNR(e) and CNR(e) and these parameters. Similarly, simulations have established empirical relationships between the axial resolution and the acoustic and signal-processing parameters. We find that a trade-off exists between the achievable SNR(e) (CNR(e)) and the axial resolution in elastography and that the trade-off occurs only with respect to the signal-processing parameters. Theoretical work on the spatial resolution accompanied with simulations and experiments were used to confirm such an observation. The trade-off between the SNR(e) (CNR(e)) and the resolution was found to be nonlinear, with large improvements in the SNR(e) being possible at the expense of small reductions in the axial resolution. All the quality factors improve with the acoustic parameters, which suggests the preferred use of transducers with high absolute bandwidths and center frequencies.
Acoustics↗
Primary squamous cell carcinoma of the lacrimal gland.
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Aged↗
Japanese encephalitis in and around Pondicherry, South India: a clinical appraisal and prognostic indicators for the outcome.
Japanese encephalitis (JE) is numerically one of the most important causes of viral encephalitis worldwide, with an estimated 50,000 cases and 15,000 deaths annually. About one-third of patients die and half of the survivors have severe neuropsychiatric sequelae. Three hundred patients clinically suspected of JE were tested in the present study. Laboratory confirmation of JE was on the basis of detection of antigen or presence of JE-specific IgM antibody and/or neutralizing antibody in a single CSF sample. The risk factors that were associated with fatal outcome were determined. Japanese encephalitis infection was confirmed in 70.7 per cent (212/300) of the patients. All patients were from rural areas and with low socioeconomic background. Prominent clinical findings were: fever in 100 per cent (212/212) patients, altered sensorium in 87.73 per cent (186/212), convulsion in 85.84 per cent (182/212), headache in 50 per cent (106/212), and vomiting in 47.64 per cent (101/212). The final clinical outcome was available for only 68.39 per cent (145/212) of patients, as children were taken home against medical advice. Of these, 35.86 per cent (52) died while 63.44 per cent (92) of patients survived. Correlations of investigative findings with the final outcome revealed that absence of virus-specific IgM and neutralizing antibodies in CSF were associated with fatal outcome. In patients diagnosed with Japanese encephalitis the presence of a virus-specific immune response is associated with a favourable outcome and an important parameter in recovery from illness.
Antigens, Viral↗
Hyperinsulinism and overgrowth without obesity.
We report a 5 year old girl with postnatal overgrowth (height velocity >97th centile), hyperinsulinaemia, and increased insulin-like growth factor 1 for age, without evidence of bioactive or immunoreactive growth hormone excess or pituitary abnormality. Although her overgrowth may be a result of hyperinsulinism, her serum contains a factor (neither insulin nor IGF-1) which is able to stimulate the proliferation of lymphocyte precursors, and this could also account for the overgrowth. Over the course of two years observation she has developed acanthosis nigricans and diabetes mellitus.
Acromegaly↗
Role of splenectomy in chronic idiopathic thrombocytopenic purpura.
AIM OF THE STUDY: To evaluate the usefulness of splenectomy and factors which predict long term remission in chronic idiopathic thrombocytopenic purpura (ITP). METHODS: We reviewed the data of 364 patients diagnosed as chronic ITP between January 1983 to December 1996 of whom 71 patients underwent splenectomy. The patients were followed up for an average period of 58 months and the short and long term response to splenectomy were analyzed at the end of one month and 60 months, respectively. RESULTS: At the end of one month after splenectomy, 82% had complete response, 7% partial response and 11% had no response. At the end of 60 months, 42% maintained complete response, 7% partial response, 34% had no response and 17% were lost to follow up. The results were statistically evaluated by using non-parametric test (Chi-square test) to age, sex, platelet count prior to treatment, initial response to steroids, time interval between diagnosis and splenectomy and post-operative platelet count. Of these factors only preoperative response to steroids (p value = 0.018303) and postoperative platelet count (p value = 0.013536) were found to be significant, statistically to predict long term remission. Age, sex, initial platelet count and time interval between diagnosis and splenectomy didn't seem to be statistically significant. CONCLUSION: This study suggests, that patients with an initial complete response to steroids and a post-operative platelet count > 300 x 10(9)/L at the time of discharge were associated with a long term remission. Splenectomy in ITP is a safe procedure with minimal morbidity and mortality and gives a good long term remission in steroid- failure patients with chronic ITP.
Adolescent↗
Blinded rechecking of sputum smears for acid-fast bacilli to ensure the quality and usefulness of restaining smears to assess false-positive errors.
SETTING: Microscopy Centres, Velliyur Tuberculosis Unit, Tiruvallur District, Tamil Nadu, India. PROCEDURES: Twelve microscopy centre laboratory technicians examined 41978 direct sputum smears for acid-fast bacilli. Senior Tuberculosis Laboratory Supervisors (STLS) checked all positive smears (4696) and 10% of negative smears (4776) in an unblinded fashion as per Revised National Tuberculosis Control Programme (RNTCP) guidelines. Ten per cent of the positive and negative slides and another 10% of unchecked negative slides were selected systematically for blinded rereading at the Tuberculosis Research Centre (TRC); 422 slides were reread without and with restaining. RESULTS: Unblinded checking by STLS of the smears read by the laboratory technicians yielded 95 to 100% agreement. Blinded rereading at the TRC revealed that false-negative errors were greater among the laboratory technicians (2-7%) than the STLS (0-3%). Restaining and blinded rereading of slides reduced false-positive errors from 27% to 7%. CONCLUSIONS: Blinded rereading at the reference centre facilitates assessment of laboratory technicians and STLS. Restaining before rereading the smears was found to be useful for precise estimation of false-positive errors.
Coloring Agents↗
Pitfalls in the diagnosis of pulmonary primary complex.
The phenomenon of overdiagnosis of pulmonary primary complex (PPC) results in unnecessary and prolonged treatment with antituberculous drugs, which are often hepatotoxic. To overcome the pitfalls in the diagnosis of PPC, the author has described, in detail, the reasons for overdiagnosis and the nature of mistakes in arriving at the diagnosis.
Contact Tracing↗
Growth pattern of low birth weight babies in the first year of life.
OBJECTIVE: The growth pattern of low birth weight (LBW) babies was studied prospectively in our hospital from September 1995 to august 1996. METHOD: Every baby <1.5 kg birth weight (B.Wt), every 2nd baby between 1.5 to 2 kg, every 6th baby between 2 to 2.5 kg and 120 term appropriate for gestation (AGA) babies ( as controls) were included in the study. Severe birth asphyxia, multiple gestation, major malformations or severe birth trauma formed exclusion criteria. Weight, length and head circumference were measured in all babies at birth and at 2 monthly intervals till 1 year of age. All babies completing 1 year follow-up were included for final analysis. Growth distance curves were constructed separately for each parameter for the six categories based on birth weight (Groups I-VI) and on gestational age (Divisions A-F). Comparison was made between the LBW babies and the controls for growth pattern among the babies who completed 1 year follow up (total of 220 babies). RESULT: The growth pattern for weight and length showed good catch up growth in babies >1.25 kg B.Wt. and >30 weeks gestation, reaching almost the same level as controls by 1 year of age. Babies with B.Wt <1.25 kg and <30 weeks gestation showed late and poor catch up growth, with considerable lag persisting at 1 year of age. Head circumference increased rapidly in all babies, with maximal growth rate initially followed by a steady decline. All babies showed catch up growth, although those <1.25 kg and <30 weeks gestation still lagged behind even at 1 year. CONCLUSION: It was seen that the smallest and least mature babies had late and poor catch up growth. Recognition of the factors influencing catch up growth and adequate measures to improve growth (like attention to feeding practices) may improve the overall outcome of these babies.
Anthropometry↗
Estimating the elastographic signal-to-noise ratio using correlation coefficients.
In conventional elastography, strain is estimated from the gradient of the displacement (time-delay) estimates. The displacement estimates involve estimating the peak location of the cross-correlation function between matching pre- and post-compression A-lines. Bias errors in estimating the peak location of the cross-correlation function, amplified by the gradient operation on the displacement estimates (needed for the computation of the strain), could result in values of elastographic signal-to-noise ratio (SNR(e)) that exceed the theoretical upper bounds, thereby hindering a consistent interpretation of this parameter. These algorithmic errors have not been accounted for by the theory. We propose the use of the measured correlation coefficients in the theoretical SNR(e) expressions to estimate the SNR(e), rather than computing them directly from the elastograms. This methodology results in values of SNR(e) that are lower than the theoretical upper bounds, thereby avoiding the problems associated with computing SNR(e) directly from the elastograms. Using simulated models of uniformly elastic phantoms, a proof of principle of such an SNR(e) measure is shown.
Algorithms↗
Japanese viral encephalitis.
One of the leading causes of acute encephalopathy in children in the tropics is Japanese encephalitis (JE). Transmitted by the culex mosquito, this neurotropic virus predominately affects the thalamus, anterior horns of the spinal cord, cerebral cortex, and cerebellum. It mainly affects children <15 years and is mostly asymptomatic. The occasional symptomatic child typically presents with a neurological syndrome characterised by altered sensorium, seizures, and features of intracranial hypertension. Aetiological diagnosis is based on virus isolation or demonstration of virus specific antigen or antibodies in the cerebrospinal fluid/blood. Though no antiviral drug is available against JE, effective supportive management can improve the outcome. Control of JE involves efficient vector control and appropriate use of vaccines.
Adolescent↗
Infective endocarditis: report of a prospective study in an Indian hospital.
Forty-six patients who fulfilled the Duke's clinical diagnostic criteria for infective endocarditis (IE) were evaluated. Thirty-five (76%) patients were below 40 years of age with rheumatic heart disease being the most common underlying heart lesion affecting 26 (56%). An obvious predisposing cardiac lesion could not be ascertained in 22%. Blood culture positivity was 44% with streptococcus heading the list. The incidence of the staphylococcal (25%) and gram negative bacillary endocarditis (15%) were found to be increasing. Streptococci were susceptible to penicillin with minimum bactericidal concentration: minimum inhibitory concentration within acceptable limits. However, the appearance of methicillin resistant staphylococcus aureus and high level gentamicin resistant enterococcus as aetiological agents of infective endocarditis were found to add to the complexity of the problem. With the emergence of drug-resistant organisms as causative agents of IE, whenever medical therapy is the primary method of treatment of this condition, the selection of antibiotics should depend upon extensive in vitro testing and in vivo monitoring of clinical efficacy.
Adolescent↗
Analysis of an adaptive strain estimation technique in elastography.
Elastography is based on the estimation of strain due to tissue compression or expansion. Conventional elastography involves computing strain as the gradient of the displacement (time-delay) estimates between gated pre- and postcompression signals. Uniform temporal stretching of the postcompression signals has been used to reduce the echo-signal decorrelation noise. However, a uniform stretch of the entire postcompression signal is not optimal in the presence of strain contrast in the tissue and could result in loss of contrast in the elastogram. This has prompted the use of local adaptive stretching techniques. Several adaptive strain estimation techniques using wavelets, local stretching and iterative strain estimation have been proposed. Yet, a quantitative analysis of the improvement in quality of the strain estimates overconventional strain estimation techniques has not been reported. We propose a two-stage adaptive strain estimation technique and perform a quantitative comparison with the conventional strain estimation techniques in elastography. In this technique, initial displacement and strain estimates using global stretching are computed, filtered and then used to locally shift and stretch the postcompression signal. This is followed by a correlation of the shifted and stretched postcompression signal with the precompression signal to estimate the local displacements and hence the local strains. As proof of principle, this adaptive stretching technique was tested using simulated and experimental data.
Elasticity↗
Elastographic imaging using staggered strain estimates.
Conventional techniques in elastography estimate strain as the gradient of the displacement estimates obtained through crosscorrelation of pre- and postcompression rf A-lines. In these techniques, the displacements are estimated over overlapping windows and the strains are estimated as the gradient of the displacement estimates over adjacent windows. The large amount ofnoise at high window overlaps may result in poor quality elastograms, thus restricting the applicability of conventional strain estimation techniques to low window overlaps, which, in turn, results in a small number of pixels in the image. To overcome this restriction, we propose a multistep strain estimation technique. It computes the first elastogram using nonoverlapped windows. In the next step, the data windows are shifted by a small distance (small fraction of window size) and another elastogram is produced. This is repeated until the cumulative shift equals/exceeds the window size and all the elastograms are staggered to produce the final elastogram. Simulations and experiments were performed using this technique to demonstrate significant improvement in the elastographic signal-to-noise ratio (SNRe) and the contrast-to-noise ratio (CNRe) at high window overlaps over conventional strain estimation techniques, without noticeable loss of spatial resolution. This technique might be suitable for reducing the algorithmic noise in the elastograms at high window overlaps.
Computer Simulation↗
Bicyclic nucleoside inhibitors of varicella-zoster virus: effect of terminal aryl substitution in the side-chain.
We have previously reported the discovery and preliminary structure-activity relationships of a new class of inhibitors of varicella-zoster virus (VZV). These novel furanopyrimidine nucleosides bear unusual bicyclic base moieties and exhibit complete specificity for VZV. Limited in vitro cytotoxicity has been detected and the bicyclic nucleosides are now well established as a new family of potent antivirals. Our initial studies revealed an absolute requirement of a long alkyl side-chain, with an optimal chain length of C8-C10, for antiviral activity. Following further studies, we recently reported a significant enhancement of both antiviral potency and selectivity by the inclusion of a phenyl group within the alkyl side-chain of these compounds. The new lead p-alkylphenyl analogues displayed EC50 values below 1 nM versus VZV and selectivity index values >1000000. We herein report the synthesis and characterization of a further series of alkylaryl analogues bearing terminal phenyl groups with varying n-alkyl side-chain lengths. Synthesis of the target bicyclic systems involved the Pd-catalysed coupling of terminal acetylenes with 5-iodo-2'-deoxyuridine to give intermediate 5-alkynyl nucleosides which were then cyclized in the presence of copper (I) iodide. The current compounds display excellent selectivity for VZV with no detectable in vitro cytotoxicity but despite being chemically isomeric with the previous lead p-alkylphenyl analogues, the compounds reported herein exhibit only moderate antiviral activities. A possible correlation between antiviral activity and conformational freedom of the side-chain is discussed.
Antiviral Agents↗