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Biomedical subjects

S Sen

Publications and source records attributed to S Sen.

At least 91 records · Page 5Linked to original sources
PubMed2001

Adverse events following vaccination in premature infants.

UNLABELLED: The aims of this study were to study the frequency, severity and types of adverse reactions following DPT/Hib (diphtheria and tetanus toxoids and pertussis/Haemophilus influenzae type B conjugate) immunization in very preterm infants and to identify possible risk factors. Case notes of 45 preterm babies vaccinated in the neonatal intensive care unit between January 1993 and December 1998 were studied retrospectively. Birthweight, gestational age, duration of ventilation, oxygen dependency, timing of vaccination, weight, corrected gestation at vaccination and apparent adverse effects were noted. Apparent adverse events were noted in 17 of 45 (37.8%) babies: 9 (20%) had major events, i.e. apnoea, bradycardia or desaturations, and 8 (17.8%) had minor events, i.e. increased oxygen requirements, temperature instability, poor handling and feed intolerance. Babies with major events were significantly younger (p < 0.05), had a lower postmenstrual age (p < 0.05) and weighed less (p < 0.05) at the time of vaccination compared with babies without major events. No differences in the mean birthweight, gestational age, duration of ventilation or oxygen dependency were found between the two groups. Age at vaccination of 70 days or less was significantly associated with increased risk (p < 0.01). Of 27 babies vaccinated at 70 days or less, 9 (33.3%) developed major events compared with none when vaccinated over 70 d. CONCLUSION: Vaccine-related cardiorespiratory events are relatively common in preterm babies. Problems were much more common if vaccine is administered at or before 70 d. These babies should therefore be monitored postvaccination. Further prospective studies are needed to clarify whether delaying vaccination offers protection against these adverse events.

Apnea↗
PubMed2001

How can we standardize peritoneal thickness measurements in experimental studies in rats?

OBJECTIVE: The various methods of measuring peritoneal thickness in experimental studies in rats have yielded conflicting results. Also, no standard method exists to assess histologic findings in peritoneal morphology. We therefore undertook the present study to create a reproducible and standard method for assessing rat peritoneal histology in experimental studies. METHODS: Parietal peritoneal samples from 61 Wistar albino rats were used in the study. Excepting the skin, the whole abdominal wall from each rat was cut two-dimensionally (longitudinally and horizontally), fixed in formalin, and processed routinely for light microscopy. Slides were divided into two groups according to the direction of the inner abdominal muscle fibers in the sections. Longitudinal and horizontal sections of abdominal muscle were evaluated. For every section, one histopathology image was captured from a light microscope to an IBM-compatible computer. Peritoneal thickness (mean of the maximum and the minimum) and submesothelial area (SMA) were drawn on the image. A computer program then automatically performed measurements. Two different measurement methods were compared, based on the same sections. RESULTS: The mean peritoneal thickness was 91 +/- 8 microm in the longitudinal sections and 75 +/- 7 microm in the horizontal sections (p < 0.05). Measurements of the SMA were found to be 47,762 +/- 4,374 microm2 for the longitudinal sections and 40,389 +/- 3,631 microm2 for the horizontal sections (p < 0.05). In both types of sections, a positive correlation (96% for longitudinal and 90% for horizontal) was found between the SMA and the peritoneal thickness (p < 0.01). The SMA measurements correlated significantly with functional properties [ratio of the dialysate concentration of glucose initially and after a 1-hour dwell (D1/D0 glucose), ultrafiltration, and protein loss; p < 0.01]. CONCLUSION: Peritoneal thickness can be measured as a mean of the minimum and maximum values. That measurement strongly correlates with submesothelial area. Both types of sections can be used, but the horizontal and longitudinal sections show systematic differences. All samples in a study should be taken using the same section pattern, either longitudinal or horizontal.

Animals↗
PubMed2000

Crossing of identical solitary waves in a chain of elastic beads.

We consider a chain of elastic beads subjected to vanishingly weak loading conditions, i.e., the beads are barely in contact. The grains repel upon contact via the Hertz-type potential, Vinfinitydelta(n), n>2, where delta> or =0, delta being the grain-grain overlap. Our dynamical simulations build on several earlier studies by Nesterenko, Coste, and Sen and co-workers that have shown that an impulse propagates as a solitary wave of fixed spatial extent (dependent only upon n) through a chain of Hertzian beads and demonstrate, to our knowledge for the first time, that colliding solitary waves in the chain spawn a well-defined hierarchy of multiple secondary solitary waves, which is approximately 0.5% of the energy of the original solitary waves. Our findings have interesting parallels with earlier observations by Rosenau and colleagues [P. Rosenau and J. M. Hyman, Phys. Rev. Lett. 70, 564 (1993); P. Rosenau, ibid. 73, 1737 (1994); Phys. Lett. A 211, 265 (1996)] regarding colliding compactons. To the best of our knowledge, there is no formal theory that describes the dynamics associated with the formation of secondary solitary waves. Calculations suggest that the formation of secondary solitary waves may be a fundamental property of certain discrete systems.

Journal Article↗
PubMed2000

RecA realigns suboptimally paired frames of DNA repeats through a process that requires ATP hydrolysis.

Microsatellite repeats such as mono-, di-, and trinucleotides are highly abundant and viable targets for homologous recombination in the genome. However, if recombination ensues in such repetitive regions, they are intrinsically prone to frame misalignments during pairing and might eventually give rise to genetic instabilities. Suboptimally paired frames lead to an abrogation of branch migration at the junctions of mixed sequences and repeats, due to a heterologous register. If so, can recombination machinery rectify such misalignments in order to avoid subsequent arrest in branch migration? We analyzed Escherichia coli RecA, the universal prototype of a recombinase, for its pairing abilities across repeats. We used a complementary pairing assay to test whether RecA can mediate realignments of stochastically paired suboptimal frames to a maximally aligned register. Here, we demonstrate that RecA-single stranded DNA filament indeed facilitates such a realignment, probably by sliding the paired strands across mono- and di- as well as trinucleotide repeats. These realignments apparently have no net directional bias. Such a putative "motor" function of RecA seems to be ATP hydrolysis-dependent.

Adenosine Triphosphate↗
PubMed2000

Acute onset of decreased vision and hearing traced to hemodialysis treatment with aged dialyzers.

CONTEXT: A recent event in which 7 patients at 1 hospital developed decreased vision and hearing, conjunctivitis, headache, and other severe neurologic symptoms 7 to 24 hours after hemodialysis drew attention to the issue of the long-term integrity of dialysis machines and materials. OBJECTIVE: To determine the cause of the adverse reactions that occurred during this event. DESIGN, PATIENTS, AND SETTING: Retrospective cohort study of all 9 patients who received hemodialysis at hospital A on September 18, 1996, the day of the outbreak. A case-patient was defined as any hospital A patient with acute onset of decreased vision and hearing and conjunctivitis after dialysis on that day. Non-case-patients were all others who underwent dialysis at hospital A on that day but did not develop adverse reactions. In an attempt to reproduce the conditions of the event, cellulose acetate dialysis membranes of various ages were retrieved from other sources and tested for physical and chemical degradation, and degradation products were identified, characterized, and injected intravenously into rabbits. MAIN OUTCOME MEASURES: Clinical signs and symptoms, time to resolution of symptoms, mortality, and dialyzer type and age, for case- vs non-case-patients. RESULTS: Seven of the 9 patients met the case definition. In addition to diminished vision and hearing, conjunctivitis, and headache, some case-patients had blood leak alarm activation (n=6), confusion/lethargy (n=5), corneal opacification (n=4), cardiac arrest (n=2), or other neurologic signs and symptoms. One case-patient died during hospitalization after the event; 5 of 7 case-patients died within 13 months. Resolution of signs and symptoms varied but persisted more than 3 years or until death in 3 of the 6 patients who survived hospitalization. All case-patients but no non-case-patients were exposed to 11.5-year-old cellulose acetate dialyzers (all of these dialyzers were discarded by the hospital before our investigation). Laboratory investigation of field-retrieved 0- to 13.6-year-old dialyzers of similar type indicated significant chemical degradation in the older membranes. In vivo injection of extracts of membrane degradation products produced iritis and hemorrhages in rabbits' eyes. CONCLUSIONS: Severe patient injury was associated with exposure to aged cellulose acetate membranes of dialyzers, allowing cellulose acetate degradation products to enter the blood. Clinicians should be aware that aged cellulose acetate membranes may cause severe adverse reactions.

Acute Disease↗
PubMed2000

Protective effect of oral L-arginine administration on gentamicin-induced renal failure in rats.

We investigated the effects of orally supplemented L-arginine, the substrate of nitric oxide (NO) and N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide-synthase inhibitor in gentamicin-induced renal failure. Rats were given gentamicin (100 mg/kg/day s.c.), gentamicin and L-arginine (2 g/l, drinking water), gentamicin and L-NAME (100 mg/l, drinking water) or gentamicin plus L-arginine and L-NAME. After 8 days, the gentamicin group developed marked renal failure, characterized by a significantly decreased creatinine clearance and increased blood creatinine, fractional excretion of sodium, fractional excretion of lithium, urine gamma glutamyl transferase, systolic blood pressure and daily urine volume when compared to controls. Renal histological analysis confirmed tubular necrosis. L-arginine administration caused normalization of these parameters, whereas L-NAME led to aggravation of the failure. Concomitant administration of L-NAME and L-arginine to gentamicin-treated rats caused no significant changes when compared to the rats receiving gentamicin alone. We conclude that L-arginine supplementation has beneficial effects in gentamicin-induced renal failure in rats and that these effects are reversed by the NO-synthase inhibitor, L-NAME.

Administration, Oral↗
PubMed2000

ATP-hydrolysis-dependent conformational switch modulates the stability of MutS-mismatch complexes.

The mismatch repair pathway in Escherichia coli has been extensively studied in vitro as well as in vivo. The molecular mechanisms by which nucleotide cofactors regulate the whole process constitute an area of active debate. Here we demonstrate that nucleotide (ADP or ATP) binding to MutS mediates a switch in protein conformation. However, in MutS that is DNA bound, this switch ensues only with ATP and not with ADP and is similar, irrespective of whether it is bound to a homo- or a heteroduplex. The results envisage a minimal model of three confor-mational states of MutS as reflected in: (i) a specific and highly stable MutS-mismatch complex in the absence of a nucleotide; (ii) a specific but less stable complex in the presence of ATP hydrolysis; and (iii) an irreversibly dissociated complex in the presence of ATP binding (ATPgammaS). Such transitions are of relevance to the protein's function in vivo where it has to first recognize a mismatch, followed by a search for hemimethylated sites.

Adenosine Triphosphatases↗
PubMed2000

Gott time machines, BTZ black hole formation, and choptuik scaling

We study the formation of Banados-Teitelboim-Zanelli black holes by the collision of point particles. It is shown that the Gott time machine, originally constructed for the case of vanishing cosmological constant, provides a precise mechanism for black hole formation. As a result, one obtains an exact analytic understanding of the Choptuik scaling.

Journal Article↗
PubMed2000

Hepatopulmonary syndrome in inferior vena cava obstruction responding to cavoplasty.

Reports show that hepatopulmonary syndrome mostly occurs in the setting of advanced hepatic dysfunction, with the associated vasoactive substance imbalance believed to be responsible for its pathogenesis. However, hepatopulmonary syndrome has also been reported in cases of mild hepatic dysfunction or noncirrhotic portal hypertension, indicating that portal hypertension also plays a part in the pathogenesis. Liver transplantation remains the only therapeutic option of proven benefit. We describe 2 cases of hepatopulmonary syndrome in the setting of inferior vena cava (suprahepatic) obstruction, but with minimal hepatic dysfunction. After balloon cavoplasty, 1 patient showed, in addition to improvement of the features of hepatic outflow obstruction, significant reduction of dyspnea, cyanosis, and hypoxemia with arterial blood gas normalization within 2 weeks and intrapulmonary shunt reversal within 8 weeks. This implies that hemodynamic alterations (such as portal hypertension) independently contribute to the pathogenesis of hepatopulmonary syndrome in at least some of the cases. Therapies aimed at correcting these abnormal hemodynamics may be important in the treatment of this condition, especially when the hepatic functional status by itself does not warrant a liver transplant.

Adult↗
PubMed2000

Effect of dothiepin on gastric ulceration mediated by lipid derived eicosanoids.

Dothiepin, a tricyclic antidepressant, significantly inhibited the development of gastric ulcers induced by alcohol, aspirin, indomethacin and Shay's pyloric ligation. Antisecretory studies in pyloric ligated rats revealed that the drug at a dose of 100 mg/kg significantly reduced total acidity, gastric output and protein content. In another set of experiments, dothiepin significantly reduced gastric output, total acidity and protein content in pyloric ligated rats which received 50% alcohol (v/v) 30 minutes after the administration of dothiepin.

Animals↗
PubMed2000

Endogenous monoamine oxidase inhibitory activity and HPA activation in the pig.

Previously we have shown that an increase in endogenous monoamine oxidase A inhibitory activity (MAO-AI), measured in human saliva, both precedes and predicts psychological stress-induced activation of the hypothalamic pituitary adrenal (HPA) axis, as determined by the cortisol response. We now report the relationship between endogenous MAO-AI and the cortisol response in the plasma of prepubertal pigs (n=5 or 6) under two experimental paradigms of HPA activation. In the first condition, pigs were physically restrained (snaring) for 15 minutes. Blood samples were taken from indwelling catheters at intervals before and after snaring (a sampling period of about 1 hour), and at the same time intervals on a separate day to provide baseline measures. Both cortisol concentration and percentage MAO-AI were determined in each plasma sample. There was a pronounced cortisol response on the snaring day (cortisol peaked 30 minutes after the start of the snaring). There was also a significant MAO-AI response to snaring which peaked 15 minutes after the start of the stress challenge. In the second experimental paradigm, bacterial endotoxin (LPS: 20microg/pig) was used to induce HPA activation and plasma cortisol and MAO-AI were determined. This time, however, the cortisol response was not preceded by any change in MAO-AI. We conclude that generation of MAO-AI, which is associated with HPA activation induced by psychological stress, is not a component of the pathways involved in immunological stimulation of the HPA axis.

Animals↗
PubMed2000

Ten-fold augmentation of endothelial uptake of vascular endothelial growth factor with ultrasound after systemic administration.

OBJECTIVES: In this study, the feasibility of delivering and enhancing the uptake of vascular endothelial growth factor (VEGF) into the intact endothelium by using ultrasound (US) facilitation was determined. BACKGROUND: A limitation of tissue-targeted drug delivery is the need for direct arterial cannulation. We postulate a mechanism by which agents injected intravenously may be targeted to a tissue using US and ultrasonic contrast agents. METHODS: We used a rat model to test the ability of US and an ultrasonic contrast agent perflurocarbon exposed sonicated dextrose albumin (PESDA) to increase uptake of VEGF in the myocardium. Continuous wave Doppler US (0.6 W/cm2 at 1 MHz for 15 min) was applied to the chest wall overlying the myocardium during intravenous injection with either VEGF (100 microg/kg) alone or a combination of VEGF and PESDA (0.1%). Control rats had VEGF infused without US or PESDA. The VEGF uptake was measured quantitatively in the heart, lung, liver and kidneys by enzyme-linked immunosorbent assay (ng/g of tissue) and morphologically by fluorescence microscopy. RESULTS: There was an eight-fold increase in VEGF uptake in the heart by US alone (16.86 +/- 1.56 vs. 2.11 +/- 0.953 ng/g of tissue, p < 0.0001) and a 13-fold increase with US + PESDA (26.78 +/- 2.88 vs. 2.11 +/- 0.953 ng/g of tissue, p < 0.0001) compared with control rats. Fluorescence microscopy revealed deposition of VEGF in the endothelium of small intramyocardial arterioles. CONCLUSIONS: These results show a marked increase in endothelial VEGF uptake with US and US + PESDA. Thus, US may be used to augment endothelial VEGF uptake 10-fold to 13-fold.

Animals↗
PubMed2000

Clinical and haemodynamic aspects of hepatopulmonary syndrome in Indian patients with cirrhosis.

BACKGROUND: Hepatopulmonary syndrome consists of the triad of hepatic dysfunction and/or portal hypertension, intrapulmonary vascular dilatation and hypoxaemia, in the absence of detectable primary cardiopulmonary diseases. In the present study, we examined the frequency of hepatopulmonary syndrome among Indian patients with cirrhosis, and studied clinical predictors and pulmonary haemodynamic alterations. METHODS: Forty-five patients with cirrhosis and no cardiopulmonary diseases were investigated by air-contrast echocardiography. Where patients were positive, arterial blood gas analysis was carried out. Positive contrast echocardiography with PO2 < 70 mmHg confirmed the diagnosis of hepatopulmonary syndrome. Three cases with the syndrome and 24 without were assessed for haemodynamic status by hepatic and pulmonary catheterization. RESULTS: Four of 45 cases of cirrhosis (8.9%) had positive contrast echocardiographies, including three (6.7%) with hepatopulmonary syndrome and one 'subclinical' case (positive contrast echocardiography without hypoxaemia). Under haemodynamic study, the mean pulmonary arterial and pulmonary capillary wedge pressures appeared to be lower among those patients with hepatopulmonary syndrome. CONCLUSIONS: In this small study, the frequency of hepatopulmonary syndrome was relatively low (6.7%). Cyanosis was the only reliable clinical indicator, and there was no clear relationship with the severity of cirrhosis by Child's grading.

Adolescent↗
PubMed2000

Upper sternal cleft associated with unusual symptoms.

We report a rare case of upper sternal cleft in a 20-year-old adult with associated unusual symptoms such as dysphagia, restricted lingual movements and a voice problem. The strap muscles causing unusual symptoms were divided from their abnormal insertion site on the lower edge of the cleft. Direct complete closure without compromising the cardiac function was achieved in this patient.

Adult↗