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Biomedical subjects

J Ramcharan

Publications and source records attributed to J Ramcharan.

12 recordsLinked to original sources
PubMed2004

Systemic lupus erythematosus in Trinidadian children.

Thirty-three children with a diagnosis of systemic lupus erythematosus (SLE) were studied. At diagnosis, 29 of them (88%) were aged between 10 and 17 years and the other four (12%) between 5 and 9 years. The majority were girls (28, 82%) and the male:female ratio was 1:6.6. Children of East Indian and mixed racial origin formed the largest groups (37 and 39%, respectively) and mortality was higher in these two groups. The most common symptoms at diagnosis were: fever for > 1 week (75.8%), musculoskeletal symptoms (arthralgia, arthritis and myalgia (69.7%) and renal involvement (63.6%). Malar and discoid rashes were common, 39 and 37%, respectively. Central nervous system involvement at presentation was a rare but important cause of mortality. The mortality rate during follow-up was high at 39.3% and the commonest cause of death was renal failure. Childhood SLE is uncommon in Trinidad and Tobago. Diagnosis is often delayed because of the protean and non-specific manifestations. This study reports a higher prevalence, a more severe course and greater mortality in children of East Indian and mixed descent than in children of African origin. It also shows that the symptomatology at first presentation is consistent with other studies and should be recognised early. Early diagnosis and prompt and appropriate management are essential in order to reduce the high mortality still associated with SLE.

Adolescent↗
PubMed2001

Localization of GAR transformylase in Escherichia coli and mammalian cells.

Enzymes of the de novo purine biosynthetic pathway may form a multienzyme complex to facilitate substrate flux through the ten serial steps constituting the pathway. One likely strategy for complex formation is the use of a structural scaffold such as the cytoskeletal network or subcellular membrane of the cell to mediate protein-protein interactions. To ascertain whether this strategy pertains to the de novo purine enzymes, the localization pattern of the third purine enzyme, glycinamide ribonucleotide transformylase (GAR Tfase) was monitored in live Escherichia coli and mammalian cells. Genes encoding human as well as E. coli GAR Tfase fused with green fluorescent protein (GFP) were introduced into their respective cells with regulated expression of proteins and localization patterns monitored by using confocal fluorescence microscopy. In both instances images showed proteins to be diffused throughout the cytoplasm. Thus, GAR Tfase is not localized to an existing cellular architecture, so this device is probably not used to concentrate the members of the pathway. However, discrete clusters of the pathway may still exist throughout the cytoplasm.

Animals↗
PubMed2001

Crystal structure of a bifunctional transformylase and cyclohydrolase enzyme in purine biosynthesis.

ATIC, the product of the purH gene, is a 64 kDa bifunctional enzyme that possesses the final two activities in de novo purine biosynthesis, AICAR transformylase and IMP cyclohydrolase. The crystal structure of avian ATIC has been determined to 1.75 A resolution by the MAD method using a Se-methionine modified enzyme. ATIC forms an intertwined dimer with an extensive interface of approximately 5,000 A(2) per monomer. Each monomer is composed of two novel, separate functional domains. The N-terminal domain (up to residue 199) is responsible for the IMPCH activity, whereas the AICAR Tfase activity resides in the C-terminal domain (200-593). The active sites of the IMPCH and AICAR Tfase domains are approximately 50 A apart, with no structural evidence of a tunnel connecting the two active sites. The crystal structure of ATIC provides a framework to probe both catalytic mechanisms and to design specific inhibitors for use in cancer chemotherapy and inflammation.

Animals↗
PubMed2001

Ataxia Telangiectasia. A case report.

The case of an eight year old girl with Ataxia Telangiectasia (AT) is described. She presented at seven years of age with gait problems and was found to have the neurological, dermatological and immunological features characteristic of AT along with a history of frequent sino-pulmonary infections. This report highlights the refractory nature of the disease, the difficulties in medical management, and the problems posed by late diagnosis which can compromise patient care. This is a rare inherited form of ataxia which has not been previously reported in West Indian literature.

Ataxia Telangiectasia↗
PubMed1998

Two Afro-Trinidadian siblings with end-stage renal disease.

The case histories of two Afro-Trinidadian brothers aged 8 and 11 years who developed end-stage renal disease (ESRD) are presented. Neither had had cause in the past to seek medical attention for any renal-related illness. At presentation both had anaemia, growth failure and other clinical and laboratory evidence of ESRD. Kidney histology in one child was consistent with familial juvenile nephronophthisis (NPH). This is a common cause of ESRD in children in other countries but it has not been recognized previously in Trinidadian and other West Indian children, and should be considered as a possible aetiology in West Indian children presenting with renal failure.

Anemia↗
PubMed1997

10-Formyl-5,8,10-trideazafolic acid (10-formyl-TDAF): a potent inhibitor of glycinamide ribonucleotide transformylase.

The synthesis of 10-formyl-5,8,10-trideazafolic acid (3) as a potential inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) is reported. The target compound was prepared by a convergent synthesis utilizing the alkylation of hydrazone 5 with benzylic bromide 6 to construct the core heterocycle 7. The aldehyde 3 and related agents were evaluated as inhibitors of purN GAR Tfase and avian AICAR Tfase. Compound 3 exhibited potent inhibition of GAR Tfase with a Ki of 0.26 +/- 0.05 microM. In contrast, 3 exhibited more moderate inhibition of aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase), with Ki of 7.6 +/- 1.5 microM.

Cell Division↗
PubMed1997

Functionalized analogues of 5,8,10-trideazafolate: development of an enzyme-assembled tight binding inhibitor of GAR Tfase and a potential irreversible inhibitor of AICAR Tfase.

A set of inhibitors 3 and 4 of GAR and AICAR Tfase based on the TDAF core which contain an sp2 C-10 carbon atom replacing N-10 of the natural cofactor are detailed. Both possess electrophilic olefins and the potential of trapping the reacting amine of the substrates GAR and AICAR by a Michael addition at the enzyme active site to provide an enzyme-assembled tight binding inhibitor. While these agents did not display such characteristics and served as simple competitive inhibitors of GAR Tfase and AICAR Tfase, inhibitor 15 prepared in the conversion of 3 to 4 may provide an enzyme-assembled tight binding inhibitor of GAR Tfase upon reaction with the substrate GAR and may inactivate AICAR Tfase by virtue of alkylation of an active site residue.

Cell Division↗
PubMed1997

Abenzyl 10-formyl-trideazafolic acid (abenzyl 10-formyl-TDAF): an effective inhibitor of glycinamide ribonucleotide transformylase.

The synthesis of N-[7-(2-amino-3,4-dihydro-4-oxo-quinazolin-6-yl) -6-formyl-1-oxo-heptyl]-L-glutamic acid (2, abenzyl 10-formyl-5,8,10-trideazafolic acid) as a potential enzyme-assembled tight binding inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) or aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) is reported. The inhibitor was prepared by a convergent synthesis utilizing the sequential alkylations of acetaldehyde dimethylhydrazone with 6 and 8. The agent exhibited effective inhibition of GAR Tfase (Ki = 4.5 +/- 0.3 microM) and more modest inhibition of AICAR Tfase (Ki = 42 +/- 11 microM).

Cell Division↗