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Biomedical subjects

P Venugopalan

Publications and source records attributed to P Venugopalan.

At least 19 recordsLinked to original sources
PubMed2006

Pattern of chronic diarrhoea in children: a prospective analysis of causes, clinical features and outcome.

OBJECTIVES: To determine the pattern of chronic diarrhoea in children in Oman. STUDY DESIGN: This is a prospective study carried out over a 7 year period at the Sultan Qaboos University Hospital, Muscat, Oman. SUBJECTS: Sixty two children (37 M:25 F), aged 3 months to 13 years who presented with chronic diarrhoea, defined as diarrhoea persisting for more than 4 weeks, were studied. RESULTS: Principal identifiable causes in the study population include post-gastroenteritis syndrome in 50% of cases, enteric infections and infestations in 27%, and coeliac disease in 13%. On presentation 63% were malnourished, 27% were anaemic while 39% were dehydrated. The median duration of hospital admission was 50 days. Majority of the patients responded to conservative therapy with correction of dehydration, and careful nutritional supplementation, in addition to specific therapy where necessary. Mortality was low (1.5%) resulting from immunodeficiency and gram-negative septicaemia. CONCLUSION: Chronic diarrhoea remains an important cause of morbidity especially malnutrition in children and early and adequate nutritional rehabilitation plays a pivotal role in the management.

Adolescent↗
PubMed2005

Acardia syndrome coexisting with gastroschisis in the co-twin.

Acardia syndrome is a rare complication affecting monozygotic twins, wherein one twin fails to develop brain and thoracic structures, while the co-twin most often develops normally. In this report we present an acardiac anencephalic monozygotic twin with an omphalocoele and a co-twin with severe intrauterine growth retardation and gastroschisis. The presence of gastroschisis in the co-twin of an acardiac foetus is rare. The embryologic basis of the twin reversed arterial perfusion (TRAP) sequence is outlined and the observed anomalies in the co-twin traced to a similar pathophysiology.

Abnormalities, Multiple↗
PubMed2004

Experience with NTBC therapy in hereditary tyrosinaemia type I: an alternative to liver transplantation.

We present the clinical data of five infants with type I (hepato-renal) tyrosinaemia on NTBC therapy. All presented initially at the local hospital in the 1st year of life with progressive abdominal distension owing to hepato-splenomegaly and with radiological evidence of liver cirrhosis, except for one child who was diagnosed during screening because of an affected sibling. Age at commencement of NTBC therapy ranged from 6 to 30 months. All infants showed remarkable improvement within 2-6 months of starting NTBC treatment, except one who died 2 months after commencement of therapy from uncontrolled liver failure, severe coagulopathy and Streptococcus pneumoniae septicaemia. NTBC treatment along with a phenylalanine- and tyrosine-restricted diet has effectively reversed most clinical manifestations of this disease. To date, none of our patients has developed hepatic carcinoma and NTBC was well tolerated without side-effects. NTBC is costly but life-saving and is an obvious alternative to more hazardous liver transplantation.

Child, Preschool↗
PubMed2003

Origin of 1,3-induction in the addition of alkyl lithium to imines bearing an N-stereogenic center.

The origin of diastereoselectivity in the addition of alkyl lithium to chiral Schiff bases has been investigated experimentally and theoretically and the formation of the major diastereomer can be explained from the energy minimized structure of the Schiff base in which the phenyl group has been found to orient in such a manner that it posed lesser steric hindrance to the incoming nucleophile as compared to the alkyl group.

Journal Article↗
PubMed2003

Ansa versus spiro substitution of cyclophosphazenes: is fluorination essential for ansa to spiro transformation of cyclophosphazenes?

Fluorinated ansa substituted cyclophosphazenes endo-FcCH(2)P(S)(CH(2)O)(2)[P(F)N](2)(F(2)PN) [Fc = ferrocenyl] (1) and exo-FcCH(2)P(S)(CH(2)O)(2)[P(F)N](2)(F(2)PN) (2) readily transform to the spirocyclic compound [FcCH(2)P(S)(CH(2)O)(2)PN](F(2)PN)(2) (3) not only in the presence of CsF but also with non-fluorinated bases such as Cs(2)CO(3), K(2)CO(3), KOBu(t), Et(3)N, DABCO, DBN, and DBU. The analogous tetrachloro ansa compound exo-FcCH(2)P(S)(CH(2)O)(2)[P(Cl)N](2)(Cl(2)PN) (5), however, did not transform to the chlorinated spiro compound (6) in the presence of these bases. With excess of CsF, P-Cl bonds of 5 were found to undergo fluorination leading to the formation of 2, which transformed to spirocyclic compound 3. Time dependent (31)P NMR spectroscopy was used to monitor this transformation. Crystal structure studies on the ansa substituted compounds 4 and 5 have shown weak bonding interactions involving C-H...Cl, C-H...O, and C-H...S interactions.

Journal Article↗
PubMed2003

Conformational control and photoenolization of pyridine-3-carboxaldehydes in the solid state: stabilization of photoenols via hydrogen bonding and electronic control.

We have investigated the solid-state photobehavior of a broad set of pyridine-3-carboxaldehydes 1-5. The introduction of a heteroatom into mesitaldehydes as in aldehydes 1 raises the question of conformational preference in the solid state. The preferred conformations have been unequivocally established from X-ray crystal structure analyses of two of the aldehydes, 1c and 2c; it is shown that intramolecular hydrogen bonding could be utilized to achieve conformational control. In contrast to mesitaldehydes, which undergo efficient photocyclization to benzocyclobutenols in the solid state, the heteroatom analogues 1b and 1c exhibit a perceptible color change (from colorless to pale yellow for 1b and yellow-orange for 1c) upon UV irradiation; the color attributed to (E)-enols is persistent for several hours. Continued irradiation leads to an intractable polymeric material. The AM1 calculations, which have been reliably applied to the thermal cyclization of xylylenols to benzocyclobutenols, reveal that the (E)-enols of 1 are more stable than those of the mesitaldehydes relative to their corresponding benzocyclobutenols. The stabilization is interpreted as arising from the possibility of engaging the heteroatom in resonance delocalization. That the contribution from such a role of the nitrogen atom is so pronounced is elegantly demonstrated by forming the fluoroborate salts; 1a-HBF(4) and 1b-HBF(4) readily exhibit highly red-shifted absorption upon exposure to UV radiation as a result of stabilization of the photoenols. Notably, such a remarkable stabilization via electronic control of the photoenols is unprecedented. All of the 2-methoxy- and 2-chloro-substituted aldehydes 2-5 exhibit photochromism. Ab initio calculations show that the methoxy group in aldehydes 2 and 3 stabilizes the (E)-enols via O[bond]H...O hydrogen bonding as compared to those of 1 by 5-6 kcal/mol relative to their corresponding benzocyclobutenols. Thus, the presence of methoxy and halo groups at position 2 serves not only to direct the formyl oxygen toward the methyl group for H-abstraction but also to stabilize the (E)-enols.

Journal Article↗
PubMed2003

Unusual reaction of chloramine-T with araldoximes.

Reaction of araldoximes with 4 equiv of chloramine-T in refluxing methanol produces N-(p-tolyl)-N-(p-tosyl)benzamides via addition of 2 equiv of chloramine-T to the intermediate nitrile oxide followed by extrusion of sulfur dioxide.

Journal Article↗
PubMed2003

Solid-state diphotocyclization of iso- and terephthalaldehydes via dihalogen substitution.

The supramolecular nonbonded C-H...X interactions between formyl hydrogens and ortho-halogen atoms (Br/Cl) have been exploited to achieve conformational control in the solid state of dimethyl-substituted iso- and terephthaladehydes (1-3) for unprecedented diphotocyclization. It is shown that the dihalogen substitution also contributes to the stability of the benzocyclobutenols relative to their precursor photoenols, so that the solid-state photolysis of dialdehydes 2b, 2c, and 3b leads to diphotocyclization to afford respectable yields of bis-benzocyclobutenols.

Journal Article↗
PubMed2003

A child with supraventricular tachycardia and convulsions.

We present an 11-year-old girl, referred for management of episodes of supraventricular tachycardia followed by generalised tonic-clonic convulsions. The episodes did not respond to digoxin and propranolol, but subsided after initiation of carbamazepine therapy. Seizures following supraventricular tachycardia are uncommon in older children. The differential diagnosis and pathophysiology of arrhythmia-related seizures are discussed.

Anticonvulsants↗
PubMed2003

Kawasaki disease resistant to immunoglobulin G therapy.

We describe a 3-year-old boy with Kawasaki disease who, despite therapy with two doses of intravenous immunoglobulin G and high-dose aspirin, developed myocarditis in the 1st week of illness and coronary artery aneurysms in the 2nd week. He required a short course of systemic corticosteroids for remission of the illness. The myocarditis subsided and coronary aneurysms remained static and uncomplicated during 6 weeks of follow-up. The diagnosis and recent trends in management of this not uncommon vasculitic disorder are outlined.

Adrenal Cortex Hormones↗
PubMed2003

Spectrum of congenital heart defects associated with Down Syndrome in high consanguineous Omani population.

OBJECTIVE: To identify the pattern of congenital heart defects (CHD) in children with Down Syndrome (DS) in an Omani population, and compare it with CHD in children without DS and with historical cohorts from populations with low prevalence of consanguinity. SETTING: Open-access Paediatric Echocardiography Clinic at Sultan Qaboos University Hospital, Muscat, Oman. DESIGN: Prospective study. METHODS: All children with DS referred to the Clinic from 1995-1998 formed the subjects (Group I). Children without DS or other known associations of CHD seen at the clinic during the same period served as controls (Group II). Two-dimensional echo-Doppler studies were performed on both groups and the results compared. RESULTS: CHD were detected in 54/90 (60%) children in Group I, compared to 698/2122 (32.9%) in Group II (P<0.001). The common CHD in Group I included secundum atrial septal defect (ASD; 18/54), atrioventricular septal defect (AVSD; 15/54) and ventricular septal defect (VSD; 14/54), and in Group II included ASD (175/698), VSD (175/698), patent ductus arteriosus (123/698), pulmonary stenosis (PS; 76/698) and AVSD (35/698). AVSD was more common (P <0.001) and PS less common (P = 0.03) in Group I. Aortic stenosis, coarctation of aorta, transposition of great arteries and complex heart diseases were not detected. Compared to several studies from populations with low prevalence of consanguineous marriages, our study showed a higher frequency of CHD in DS (P <0.05). CONCLUSION: A high frequency of CHD was documented in DS-children from a population with widely prevalent consanguinity. AVSD was most frequent in DS. An interesting observation was the relative rarity of some CHD in the DS population studied.

Child↗
PubMed2002

Helical self-assembly of substituted benzoic acids: influence of weaker X...X and C-H...X interactions.

The X-ray crystal packing analyses of the sterically encumbered halogen-substituted benzene carboxylic acids 1-4 reveal a novel and unprecedented crystal packing in that the association of the carboxyl groups through O-H...O bonds results in the generation of a helix along the 41-screw axis. Such an organization of the acids is shown convincingly to be a result of the close packing, which exploits the weaker X...X and C-H...X interactions in conjunction with the stronger O-H...O hydrogen bonds. In contrast, the chloro- and bromo-substituted durene carboxylic acids 6 and 7 exhibit a pattern that is akin to tape/ribbon involving the centrosymmetric-dimer motif and X...X short intermolecular interactions. The structural investigations demonstrate the ability of the weaker interactions in modifying the supposedly "robust" centrosymmetric-dimer motif of the carboxyl groups in a decisive manner.

Journal Article↗
PubMed2002

Spread of heart diseases seen in an open-access paediatric echocardiography clinic.

All patients <13 years of age referred to the open-access paediatric echocardiography clinic at the Sultan Qaboos University Hospital, Muscat, Oman, during the five years from 1994 to 1998 were analysed. Among the 2633 patients studied, 1543 (58.6%) were normal, 845 (32.1%) had congenital heart disease, and 245 (9.3%) had acquired heart disease. The major congenital heart diseases identified were secundum atrial septal defect (22.5%), ventricular septal defect (22.5%), patent ductus arteriosus (15.7%), mitral valve prolapse (10.7%), pulmonary stenosis (9.7%) and atrioventricular septal defect (4.5%). Fifty-eight percent of the congenital heart diseases were identified in the first year of life. Among the acquired heart diseases, rheumatic heart disease (30.2%) and cardiac involvement secondary to haemoglobinopathies (16.7%), dilated cardiomyopathy (16.3%) and hypertrophic cardiomyopathy (12.7%) were significant. Although the presence of specific cardiac symptoms was associated with a high yield of abnormalities, such disorders were also discovered in a significant number of children with isolated cardiac murmur. The referral source did not influence significantly the frequency of heart diseases diagnosed in this study. Open-access echocardiography is important in early detection of heart disease in the paediatric population.

Cardiology Service, Hospital↗
PubMed2002

Cardiac involvement in infantile Sandhoff disease.

An 18-month-old boy with enzyme assay-confirmed infantile Sandhoff disease (MIM 268800) is reported. Besides the classical neurological features, this patient exhibited severe mitral regurgitation secondary to mitral valve prolapse and mild aortic regurgitation from aortic valve prolapse. He also had asymmetric hypertrophy of the interventricular septum without left ventricular outflow tract obstruction.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2002

Pattern of inborn errors of metabolism in an Omani population of the Arabian Peninsula.

We analysed all patients < 18 years of age diagnosed with inborn errors of metabolism (IEM) in the Metabolic Division, Sultan Qaboos University Hospital, Muscat, Oman from June 1998 to December 2000. A total of 82 patients from 76 families were studied, of whom 33 (40%) were aged < 1 week at presentation. Disorders identified included different lysosomal storage disorders (22), organic acidurias (9), carbohydrate metabolic disorders (9), congenital lactic acidosis (9), urea cycle disorders (8), amino acidopathies (8), fatty acid oxidation defects (7/82) and various other miscellaneous disorders (10). Tandem mass spectrometry helped in the diagnosis of 26 (32%) cases. Parental consanguinity was twice as frequent in the study patients as in the general population. Duration of follow-up ranged from 1 to 30 months (median 15) during which time 46/56 (82%) patients with disorders amenable to specific dietary and drug therapy available in Oman were free from frequent exacerbation. Our study shows the relevance of identifying patients with IEM in Oman and the need to establish screening for the conditions identified and provide effective management protocols.

Adolescent↗
PubMed2002

pH-sensitive liposomes: mechanism of triggered release to drug and gene delivery prospects.

A growing amount of literature describes the development and applications of novel targeting and/or release triggering schemes to improve the therapeutic index of drugs encapsulated within liposomes. The composition of liposomal systems can be modified to facilitate site specific release in response to environmental conditions, namely at the gross anatomical level, at the cellular or sub-cellular level. They are designed in order to release their contents in response to acidic pH within the endosomal system while remaining stable in plasma thus improving the cytoplasmic delivery of various polar materials and macromolecules such as anti-tumor drugs, toxins, proteins and DNA. This review covers various aspect of research on pH-sensitive liposomes.

Animals↗