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Biomedical subjects

S Shah

Publications and source records attributed to S Shah.

At least 271 records · Page 15Linked to original sources
PubMed1996

The expression of MEF2 genes is implicated in CNS neuronal differentiation.

The myocyte enhancer factor-2 (MEF2) proteins are transcription factors required for muscle differentiation. In the present study we examined MEF2 expression in developing cerebellar granule neurons. In the developing postnatal cerebellum, RNA blot analysis revealed that MEF2A and MEF2D RNA levels increase after birth. The majority of this increase occurs around postnatal day 9 reaching a peak at postnatal day 15-18 which is maintained in adults. This time course of expression coincides with the expression of GABA(A) receptor alpha6 subunit RNA, a marker for the differentiation of the mature cerebellar granule neurons. We further observed, using the polyclonal antibody generated against an MEF2A peptide, that MEF2 protein expression occurs primarily in the internal granule cell layer of the developing cerebellum. Thus, MEF2 expression increases as granule neurons differentiate and mature. Experiments also indicated that MEF2 expression not only occurs in the cerebellum but also in other regions of the CNS. In adult mice, expression of RNA for the MEF2 isoforms A, C and D occurs throughout the CNS. MEF2A and D expression occurs at highest levels in the olfactory bulb, hippocampus and cerebellum. The expression of MEF2C differs with low levels of expression in the cerebellum and hindbrain. Using the MEF2A polyclonal antibody, we observed a similar adult pattern of expression for the MEF2 protein with high level of expression in the olfactory bulb, cortex, hippocampus, thalamus and cerebellum. These observations suggest that MEF2 molecules may be an important factor involved in CNS neuron differentiation similar to their role in muscle differentiation.

Amino Acid Sequence↗
PubMed1996

In vitro rejoining of double-strand breaks in cellular DNA by factors present in extracts of HeLa cells.

We described previously a cell-free assay, that could be employed to study the rejoining of radiation-induced DNA double-strand breaks (dsb) in agarose embedded nuclei by activities present in an extract prepared from exponentially growing HeLa cells. Here, we extend the study and present an in vitro assay for rejoining of radiation-induced DNA dsb that employs 'naked' DNA prepared from agarose-embedded cells as a substrate and extract of HeLa cells as an enzyme source. There is no detectable residual protein on substrate DNA after extensive lysis with ionic detergents and treatment with proteases, as determined by SDS-PAGE and silver staining. We demonstrate that rejoining of dsb is absolutely dependent on cell extract and that, under optimal reaction conditions, it proceeds to an extent and with kinetics similar to those observed in intact cells. Dsb rejoining in this assay requires Mg 2+ and is inhibited by high concentrations of either K+ or Na+. This assay complements the nuclei assay for DNA dsb repair previously developed, and may be preferable to the latter in the purification of factors involved in DNA dsb repair, as it employs as substrate DNA deprived of proteins.

Adenosine Triphosphate↗
PubMed1996

Activity of glycylcyclines CL 329998 and CL 331002 against minocycline-resistant and other strains of methicillin-resistant Staphylococcus aureus.

Two glycylcyclines have been tested against 191 strains of methicillin-resistant Staphylococcus aureus, 72 of which were resistant to minocycline, isolated from many parts of the world. MICs of CL 329998 ranged from 0.06 to 4 mg/L, with MIC50 and MIC90 0.5 and 2 mg/L, respectively. CL 331002 was slightly less potent, having an MIC range 0.12-16 mg/L and MIC50 and MIC90 values of 1 and 4 mg/L, respectively.

Americas↗
PubMed1996

Determining approximate estimates of inheritance parameters from sib-pair IBD proportions.

The use of IBD proportions from a large set of affected sib-pair data to estimate some or all of the main parameters describing the inheritance of a disease susceptibility gene is here considered. We assume there is no recombination present and neglect ascertainment bias, and assume that there are four distinct parental haplotypes present in each family.

Genetic Diseases, Inborn↗
PubMed1996

Anomalous but helpful findings from the BBL Crystal ID kit with Haemophilus spp.

Fourteen strains of Haemophilus (12 H. influenzae, 1 H. parainfluenzae and 1 H. aphrophilus) were processed in BBL Crystal ID Enteric/Nonfermenter, API 20E and API 20NE kits, to determine whether the BBL kit misidentifies, as API kits may do, Haemophilus spp. as Pasteurella spp. The 13 H. influenzae and H. parainfluenzae strains produced uninterpretable colour reactions in the Crystal kit, thus signalling that an inappropriate species had been tested. On the other hand, the API kits (especially 20NE) often confidently "identified' Haemophilus spp. as Pasteurella spp., giving no warning that this was a misidentification.

Diagnostic Errors↗
PubMed1996

PRK in patients with a keratoconic topography picture. The concept of a physiological 'displaced apex syndrome'.

AIMS/BACKGROUND: Keratoconus is generally held to be an absolute contraindication for photorefractive keratectomy (PRK). Corneas with inferior steepening on corneal topography are widely thought to have subclinical keratoconus. We were not convinced that this is always the case, as there seems to be a group of patients with a stable inferior steepening pattern on topography who show no other characteristics of clinical keratoconus. We thus decided to offer PRK to some of these patients under strictly defined criteria. METHOD: Four myopic patients with a topography pattern of inferior steepening were submitted to PRK. They were selected on the basis of being aged over 35, with a stable refraction, no slit-lamp signs of keratoconus, and a corrected vision of not less than 6/7 (0.9) with a spherical spectacle correction. They gave fully informed consent that this was an experimental procedure. RESULTS: The refractive results at 6 months after operation were within the range one would expect for PRK on corneas with a regular 'bow-tie' topography and similar level of myopia. No unusual problems were encountered. CONCLUSION: We feel that the corneal topography pattern of inferior steepening is not always a contraindication for PRK. The concept of a physiological 'displaced apex syndrome' is discussed and illustrated by corneal topography in different positions of gaze.

Adult↗
PubMed1996

Topical analgesia for superficial corneal injuries.

OBJECTIVE: To assess the analgesic effects of a topical non-steroidal anti-inflammatory agent, flurbiprofen 0.03%, during healing after superficial corneal injuries. METHODS: 401 patients treated for corneal abrasion in a five month period were randomly allocated to one of four treatment groups: polyvinyl alcohol alone (control), homatropine 2%, flurbiprofen 0.03%, or homatropine 2% followed by flurbiprofen 0.03%. Treatments were given for 48 h. Ocular pain was recorded on a visual analogue scale by the patients over the first 24 h, and use of oral analgesics was also recorded. Usable responses were received from 224 patients (55.8%). RESULTS: Patients treated with flurbiprofen had significantly lower pain scores for the 24 h duration of the study than controls (P < 0.05). CONCLUSIONS: Flurbiprofen eye drops provide more effective pain relief than traditional treatments for superficial corneal injuries.

Administration, Topical↗
PubMed1996

Once daily subcutaneous growth hormone-releasing hormone therapy accelerates growth in growth hormone-deficient children during the first year of therapy. Geref International Study Group.

The efficacy and safety of 1 yr of GH-releasing hormone [GHRH-(1-29)] therapy in GH-deficient children were determined. One hundred and ten previously untreated prepubertal GH-deficient children were treated for up to 1 yr in a multicenter, open label study with 30 micrograms/kg GHRH-(1-29)/day, sc, given at bedtime. Eighty-six of the 110 patients were eligible for efficacy analysis. The main outcome measures, monitored every 3-6 months, were linear growth enhancement (height velocity), bone age progression, and safety measures including clinical chemistry. The mean height velocity for the group increased from 4.1 +/- 0.9 cm/yr at baseline to 8.0 +/- 1.5 and 7.2 +/- 1.3 cm/yr after 6 and 12 months of therapy, respectively. At 6 months, 74% of the children were considered to have a good response to GHRH. The ratio of the change in bone age to height age was not significantly different from unity at 12 months (1.04 +/- 0.58; P = 0.63). No adverse changes in general biochemical or hormonal analyses were noted. No change in fasting glucose concentration or excessive generation of insulin-like growth factor I occurred, and overall GHRH was well tolerated. We conclude that GHRH administered as a once daily dose of 30 micrograms/kg GHRH.(1-29), s.c., was effective in increasing height velocity in GH-deficient children.

Adolescent↗
PubMed1996

A comparative study of the awareness and attitude of HIV/AIDS among students living in India and migrants to the United States.

The goal of the current study was to collect preliminary data regarding HIV/AIDS awareness among Indian students who are residing in India and those who have migrated to the United States. A questionnaire was distributed to thirty-four college students in the United States and thirty-eight college students who are residing in India, between ages 18-26 years. 74% of the Indian group and 53% of the USA group felt that their knowledge of this disease is not adequate. 3% felt that this disease is completely curable. Only 13% of the Indian group and 23% of the USA group thought that tuberculosis is linked to HIV infection. Both groups felt that the newspapers and magazines are good sources of information. The majority of the Indian (71%) and USA (50%) groups felt that HIV/AIDS education should begin in high school. 90% of the Indian group and 79% of the USA group felt that people in India do not have adequate knowledge about AIDS. The majority felt that the high-risk population should be screened and there should be more governmental support.

Adolescent↗
PubMed1995

The pleckstrin homology domain of phospholipase C-delta 1 binds with high affinity to phosphatidylinositol 4,5-bisphosphate in bilayer membranes.

The pleckstrin homology (PH) domain of phospholipase C-delta 1 (PLC-delta 1) binds to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) in phospholipid membranes with an affinity (Ka approximately 10(6) M-1) and specificity comparable to those of the native enzyme. PLC-delta 1 and its PH domain also bind inositol 1,4,5-trisphosphate, the polar head group of PI(4,5)P2, with comparable affinity and approximately 1:1 stoichiometry. A peptide corresponding to amino acids 30-43 of the PLC-delta 1 PH domain contains several basic residues predicted to bind PI(4,5)P2, but binds weakly and with little specificity for PI(4,5)P2; hence the tertiary structure of the isolated PH domain is required for high affinity PI(4,5)P2 binding. Our PI-(4,5)P2 binding results support the hypothesis that the intact PH domain, serving as a specific tether, directs PLC-delta 1 to membranes enriched in PI(4,5)P2 and permits the active site, located elsewhere in the protein, to hydrolyze multiple substrate molecules before this enzyme dissociates from the membrane surface.

Amino Acid Sequence↗
PubMed1995

Catalytic strategy of citrate synthase: subunit interactions revealed as a consequence of a single amino acid change in the oxaloacetate binding site.

The active site of pig heart citrate synthase contains a histidine residue (H320) which interacts with the carbonyl oxygen of oxaloacetate and is implicated in substrate activation through carbonyl bond polarization, a major catalytic strategy of the enzyme. We report here the effects on the catalytic mechanism of changing this important residue to glycine. H320G shows modest impairment in substrate Michaelis constants [(7-16)-fold] and a large decrease in catalysis (600-fold). For the native enzyme, the chemical intermediate, citryl-CoA, is both hydrolyzed and converted back to reactants, oxaloacetate and acetyl-CoA. In the mutant, citryl-CoA is only hydrolyzed, indicating a major defect in the condensation reaction. As monitored by the carbonyl carbon's chemical shift, the extent of oxaloacetate carbonyl polarization is decreased in all binary and ternary complexes. As indicated by the lack of rapid H320G--oxaloacetate catalysis of the exchange of the methyl protons of acetyl-CoA or the pro-S-methylene proton of propionyl-CoA, the activation of acetyl-CoA is also faulty. Reflecting this defect in acetyl-CoA activation, the carboxyl chemical shift of H320G-bound carboxymethyl-CoA (a transition-state analog of the neutral enol intermediate) fails to decrease on formation of the H3020G-oxaloacetate-carboxymethyl-CoA ternary complex. Progress curves and steady-state data with H320G using citryl-CoA as substrate show unusual properties: substrate inhibition and accelerating progress curves. Either one of two models with subunit cooperativity [Monod, J., Wyman, J., & Changeux, J.-P. (1965) J. Mol. Biol. 12, 88; Koshland, D. E., Jr., Nemethy, G., & Filmer, D. (1966) Biochemistry 5, 365] quantitatively accounts for both the initial velocity data and the individual progress curves. The concentrations of all enzyme forms and complexes are assumed to rapidly reach their equilibrium values compared to the rate of substrate turnover. The native enzyme also behaves according to models for subunit cooperativity with citryl-CoA as substrate. However, the rates of formation/dissociation and reaction of complexes are kinetically significant. Comparisons of the values of kinetic constants between the native and mutants enzymes lead us to conclude that the mutant less readily undergoes a conformation change required for efficient activation of substrates.

Acetyl Coenzyme A↗
PubMed1995

Two Drosophila genes that encode the alph and beta subunits of the brain soluble guanylyl cyclase.

We identified two Drosophila genes (dgc alpha 1 and dgc beta 1) that encode the soluble guanylyl cyclase alpha and beta subunits, respectively. The putative Dgc alpha 1 protein is 76 kDa, has 35% amino acid identity with previously isolated alpha subunits, and was immunolocalized to the adult retina, to the optic lobes, and throughout the brain neuropil. The Dgc beta 1 protein is 86 kDa and exhibits 59% amino acid identity with the rat beta 1 protein. However, the Dgc beta 1 protein has an additional 118 amino acids inserted near the amino terminus, which makes it significantly larger than the rat beta 1. The Dgc beta 1 protein was immunolocalized to the optic lobes and throughout the brain neuropil, with no detectable expression in the retina. The Dgc alpha 1 and Dgc beta 1 cDNAs were stably transfected into human kidney 293 cells. Expression of the individual subunits and mixing of the individually expressed subunits failed to generate significant guanylyl cyclase activity. Only coexpression of the subunits resulted in significant guanylyl cyclase activity. Our results indicate that Dgc alpha 1 and Dgc beta 1 are soluble guanylyl cyclase alpha and beta subunits that are capable of forming a functional guanylyl cyclase heterodimer.

Amino Acid Sequence↗
PubMed1995

Organization, sequence and regulation of expression of the murine Hoxa-7 gene.

The genomic sequence of Hoxa-7 (encoding the HOXa-7 homeobox protein), including the coding region (0.7 kb), flanked by a 5'-upstream region (2.8 kb), a 3'-downstream region (1 kb) and interrupted by an intron (995 bp), was determined. Northern blot analysis indicated the transcript size of Hoxa-7 to be 2.1-2.4 kb. Reverse transcription-PCR and primer extension analysis established the 5'-boundary of the mRNA to be in the region 1166 nt upstream from the start codon. Transient transfection of various Hoxa-7::cat constructs in NIH 3T3 cells was used to characterize the transcriptional activity of the 5'-flanking region of the gene. Constructs containing 544, 274 and 71 bp of the region upstream from the transcription start point (tsp) exhibited 78, 203 and 407%, respectively, of the activity shown by a control construct containing 739 bp of the upstream region. These data suggested the presence of negative regulatory elements in the region from 544 to 71 bp upstream from the tsp.

3T3 Cells↗
PubMed1995

1H, 13C and 15N NMR assignments and solution secondary structure of rat Apo-S100 beta.

The 1H, 13C and 15N NMR assignments of the backbone and side-chain resonances of rat S100 beta were made at pH 6.5 and 37 degrees C using heteronuclear multidimensional NMR spectroscopy. Analysis of the NOE correlations, together with amide exchange rate and 1H alpha, 13C alpha and 13C beta chemical shift data, provided extensive secondary structural information. Thus, the secondary structure of S100 beta was determined to comprise four helices (Leu3-Ser18, helix I; Lys29-Leu40, helix II; Gln50-Glu62, helix III; and Phe70-Ala83, helix IV), four loops (Gly19-His25, loop I; Ser41-Glu49, loop II; Asp63-Gly66, loop III; and Cys84-Glu91, loop IV) and two beta-strands (Lys26-Lys28, beta-strand I and Glu67-Asp69, beta-strand II). The beta-strands were found to align in an antiparallel manner to form a very small beta-sheet. This secondary structure is consistent with predictions that S100 beta contains two 'helix-loop-helix' Ca(2+)-binding motifs known as EF-hands. The alignment of the beta-sheet, which brings the two EF-hand domains of S100 beta into close proximity, is similar to that of several other Ca(2+)-ion-binding proteins.

Amino Acid Sequence↗
PubMed1995

The epidemiology of stroke and transient ischaemia in Brisbane, Australia.

This study presents the crude and age-adjusted annual incidence rates and diagnostic classifications of acute strokes and identified transient ischaemia cases in persons 25 years and over in an urban population slightly over one million. Ot the total of 2676 hospital admissions 1244 were stroke patients (the other 89 were unsubstantiated, 144 were resident outside the incidence area, 555 were asymptomatic lesions and 644 were TIA admissions); 139 patients were in chronic care facilities; 134 were managed in their own homes by their medical practitioners, with 84 certified community and 455 medical practitioners' reported deaths giving a total of 2056 strokes. Including the TIAs treated at home and admissions to hospitals there were 1877 TIAs (population at risk 660,598). The overall age-adjusted incidence rate for stroke was 1.22 or 40 percent of the crude rate per 1000 persons at risk, while the overall TIA age-adjusted rate was 1.20 or 43 percent. Aetiological classifications revealed thrombosis 0.46, embolism 0.09, intracerebral haemorrhage 0.19, subaracnoid 0.14, and acute but ill-defined events were 0.34 per 1000 persons. Early mortality was 32 percent with a significant winter peak with incidence unrelated to mean ambient temperature.

Adult↗