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Biomedical subjects

G Mehta

Publications and source records attributed to G Mehta.

At least 19 recordsLinked to original sources
PubMed2004

Bone mineral status in immigrant Indo-Asian women.

BACKGROUND: Indo-Asian immigrants are known to be at high risk of metabolic bone disease, but the prevalence of osteoporosis in this population is unknown. AIM: To compare the bone mineral at the lumbar spine and femoral neck of Indo-Asian immigrant women with that of age-matched Caucasian women. DESIGN: Retrospective analysis. METHODS: Women of Indo-Asian origin referred for bone density scans in the last five years were identified. The skeletal status of each was compared with an age-matched Caucasian control for bone mineral content (BMC), bone mineral density (BMD) and bone mineral apparent density (BMAD) at the lumbar spine and femoral neck, and hip axis length was measured. RESULTS: At the lumbar spine, Indo-Asians had a significantly lower BMD than Caucasians (0.834 vs. 0.913, p = 0.008), but there was no significant difference when BMAD values were calculated (0.123 vs. 0.122). At the femoral neck, there was no difference in BMD (0.728 vs. 0.712, p = 0.5), and BMAD values were significantly higher among Indo-Asians than Caucasians (0.393 vs. 0.319, p = 0.022). Hip axis length was significantly shorter among Indo-Asian women (10.3 vs. 10.7, p = 0.009). DISCUSSION: Although Indo-Asian women appear to have lower spinal BMD than Caucasians, these differences disappear when BMAD values are calculated. While BMD is an areal density, not taking into account the 'depth' of the bone, BMAD is an estimation of volumetric density. Hence lower BMD values in Asians may be a size-related artefact. Longitudinal studies may be required to evaluate the use of BMD as a marker for fracture risk in this population.

Aged↗
PubMed2004

Aminoglycoside resistance in enterococci isolated from paediatric septicaemia in a tertiary care hospital in north India.

BACKGROUND & OBJECTIVES: Enterococci are important nosocomial agents and serious infections caused by them are often treated with a combination of cell wall inhibitor and aminoglycoside. However, the presence of high level aminoglycoside resistance in these isolates makes this treatment combination ineffective. The prevalence of such isolates in a tertiary care set up has important diagnostic and therapeutic implications. The present study was carried out to find out the occurrence of high level aminoglycoside resistant isolates of enterococci in paediatric septicaemia cases in a tertiary care set up in north India. METHODS: Blood of paediatric cases with a clinical diagnosis of septicaemia was cultured to isolate and identify enterococci. Agar screen method was used to detect high level streptomycin and gentamicin resistance in these isolates. Vancomycin susceptibility of these isolates were determined as per the National Committee for Clinical Laboratory Standards (NCCLS) recommendations. RESULTS: Fifty one enterococcal strains were isolated from 21 neonates, nine infants and 21 children with a clinical diagnosis of septicaemia. Sixty eight per cent of these isolates had high level gentamicin resistance and forty three per cent had high level streptomycin resistance. All the isolates with high level streptomycin resistance also had high level gentamicin resistance. More than ninety five per cent of these isolates were sensitive to vancomycin. INTERPRETATION & CONCLUSION: The occurrence of high level gentamicin and high level streptomycin resistance in enterococcal isolates in our set up was high. This would require routine testing of the enterococcal isolates for high level aminoglycoside resistance. Alternative treatment regimes need to be sought, besides prudent use of antibiotics.

Aminoglycosides↗
PubMed2003

An outbreak of candidemia due to Candida tropicalis in a neonatal intensive care unit.

An outbreak of candidemia due to Candida tropicalis involving 16 neonates (gestational age 28-36 weeks) is reported. All infants had received hyperalimentation and at least one course of antibiotics. The commonest clinical manifestations included episodes of acute respiratory distress and lack of response to antibacterial antibiotic therapy. Candida tropicalis was recovered from blood in all the 16 infants and urine cultures were positive in 14 infants. Environmental sampling yielded C. tropicalis from one each of the blankets and mattresses used for neonates. Four of five urinary tract isolates and both environmental isolates genotyped by arbitrarily primed-PCR with several random primers were shown to belong to the same genotype.

Antifungal Agents↗
PubMed2002

Intrauterine exposure to a maternal low protein diet reduces adult bone mass and alters growth plate morphology in rats.

Epidemiological studies suggest that poor growth during fetal life and infancy is associated with decreased bone mass in adulthood. However, theses observations have not, to date, been corroborated in animal models. To address this issue we evaluated the influence of maternal protein restriction on bone mass and growth plate morphology among the adult offspring, using a rat model. Maternal protein restriction resulted in a reduction in bone area and BMC, but not BMD, among the offspring in late adulthood. The widened epiphyseal growth plate in the protein-restricted offspring is compatible with the programming of cartilage and bone growth by maternal nutrition in early life.

Absorptiometry, Photon↗
PubMed2001

Oxa bowls: synthesis and C-H...O mediated solid state structure of pentaoxa-[5]-peristylane.

We have conceptualized [n]-oxa-[n]-peristylanes as a new family of "oxa bowls" having a crownlike shape and potential C(nv)() symmetry. Recognizing their equivalence to the corresponding [n]-formyl-[n]-cycloalkanes, we have conceived of a general synthetic strategy in which "intramolecular cascade acetalizations" constitute the pivotal step. As our first synthetic effort, we describe the synthesis of pentaoxa-[5]-peristylane 3b from the readily available Diels-Alder adduct 10 of 5,5-dimethoxy-tetrachlorocyclopentadiene and maleic anhydride. The norbornyl framework of 10 serves as the rigid structural matrix to build the stereochemical features and latent aldehyde functionalities as in 9 through a series of functional group adjustments. Ozonation of 9 furnished 3b in a one-step transformation in which five tetrahydrofuran rings were generated. While 3b exhibited C(5v) symmetry in solution, its symmetry in the solid state was observed to be C(s) by X-ray crystallography. In the solid state, 3b is endowed with a multicolumnar architecture, whose distinctive features include C-H...O interactions involving the less acidic cyclopentane hydrogens. Indeed, all the 10 CH moieties and 5 oxygen atoms (through both the lone pairs) of 3b (C(10)H(10)O(5)) are involved in short C-H...O contacts (strong and soft) and its crystal structure indicates marked proclivity toward maximal hydrogen bonding.

Journal Article↗
PubMed2001

Oxa bowls: studies toward hexaoxa-[6]-peristylane. Synthesis of a seco-derivative of hexaoxa-[6]-peristylane.

When the concept of equivalency of all-cis-[n]-formyl-[n]-cycloalkanes with [n]-oxa-[n]-peristylanes was followed, an approach to the "oxa bowl" hexaoxa-[6]-peristylane 4a was delineated. This required an access to all-cis-cyclohexane-hexacarbaldehyde 5, which could be subjected to a 6-fold intramolecular acetalization cascade. A readily available Diels-Alder adduct of cyclooctatetraene and maleic anhydride was chosen as the starting material and was elaborated to the endo, endo-tetraene 6 in which all the six aldehyde functionalities are present in a latent form with cis orientation in a locked cyclohexane ring. Although ozonolysis of 6 has so far led only to intractable products, the novelty and brevity of our approach have been demonstrated through the intramolecular acetalizations through ozonolysis in 7 and 15, leading to oxa bowls 9 (seco-hexaoxaperistylane) and 16, respectively. The formation of 9 and 16 requires the generation of five tetrahydrofuran and four oxacyclic rings, respectively, in a single-pot operation.

Journal Article↗
PubMed2001

Intramolecular C-H insertion reactions of (eta(5)-cyclopentadienyl)dicarbonyliron carbene complexes: scope of the reactions and application to the synthesis of (+/-)-sterpurene and (+/-)-pentalenene.

(eta(5)-Cyclopentadienyl)dicarbonyliron carbene complexes, [(eta(5)-C(5)H(5))(CO)(2)Fe=CHR](+)BF(4)(-), are generated as reactive intermediates from thioether derivatives, (eta(5)-C(5)H(5))(CO)(2)FeCH(R)SPh, by S-alkylation with trimethyloxonium tetrafluoroborate and loss of thioanisole. The carbene complexes undergo intramolecular C-H insertion into appropriately situated side chains to form cyclopentane derivatives. The reaction has been developed into a general procedure employing cycloalkanones as scaffolds bearing the iron carbene moieties and the side chains at C(2) and C(3), respectively. The products of the intramolecular insertion reactions are substituted bicyclo[n.3.0]alkanones. The scope and limitations of the reaction are described. The reaction is applied to a total synthesis of sterpurene and to a formal synthesis of pentalenene. Overall, this approach to cyclopentane annulation complements the related metal-catalyzed insertion reactions of diazocarbonyl compounds, which are also believed to occur via metal carbene complexes.

Cyclopentanes↗
PubMed2001

Intraoperative glove perforation--single versus double gloving in protection against skin contamination.

Surgeons have the highest risk of contact with patients' blood and body fluids, and breaches in gloving material may expose operating room staff to risk of infections. This prospective randomised study was done to assess the effectiveness of the practice of double gloving compared with single gloving in decreasing finger contamination during surgery. In 66 consecutive surgical procedures studied, preoperative skin abrasions were detected on the hands of 17.4% of the surgeons. In the double gloving pattern, 32 glove perforations were observed, of which 22 were in the outer glove and 10 in the inner glove. Only four outer glove perforations had matching inner glove perforations, thus indicating that in 82% of cases when the outer glove is perforated the inner glove will protect the surgeon's hand from contamination. The presence of visible skin contamination was also higher in perforation with the single gloving pattern (42.1%) than with the double gloving pattern (22.7%). An overwhelming majority of glove perforations (83.3%) went unnoticed. Double gloving was accepted by the majority of surgeons, especially with repeated use. It is recommended that double gloves are used routinely in all surgical procedures in view of the significantly higher protection it provides.

Equipment Failure↗
PubMed2001

Comparison of endoscopic brush cytology with biopsy for detection of Helicobacter pylori in patients with gastroduodenal diseases.

Upper GI endoscopy was performed in 50 adult patients attending the gastroenterology OPD with gastroduodenal diseases. Gastric antral mucosal brushings were taken for cytological evaluation and urea broth test followed by antral biopsy. The slides prepared were stained with Wright Giemsa (WG), Hema toxylin & Eosin (H&E) and Papanicolaou (Pap). Brush Cytology Smears were compared with biopsy sections for detection of Helicobacter pylori and the staining techniques were evaluated to see which stain was easiest to perform and interpret on routine basis. H&E stained sections were examined for histomorphological parameters associated with H. pylori infection. Brush cytology was rapid and simple with observed sensitivity of 90% and specificity of 100%. On evaluating the various stains, M.B. and W.G. were found to the rapid and easy to perform and the bacteria stood out very well against the background. Of the histomorphological parameters studied, presence of actively and lymphoid aggregates and absence of intestinal metaplasia correlated positively with the presence of the bacteria. Cytological brushing urea broth test was not very sensitive (55.2%) and specific (51%) for detection of the bacteria.

Adult↗
PubMed2000

Oxa bowls: synthesis of new tetraoxa-cages and their C-H.O-mediated solid-state architecture

We have envisioned a new family of oxa-bowls, and a general approach to these entities has been proposed through polycyclic frameworks having two converging olefinic double bonds. Ozonolysis of such molecules was envisaged to give all-cis-tetraaldehyde functionality, which could undergo intramolecular cascade acetalization to oxa-bowls having C(2)(v )()symmetry. Homohypostrophene 16a and its functionalized derivative 16b and hypostrophene 17 on ozonolysis furnished the oxa-cages 22a, 22b, and 23, respectively. Single-crystal X-ray analysis of 22a and 23 showed an interesting network of C-H.O interactions mainly involving the nonacidic cycloalkane hydrogen atoms. The molecule 22a exhibits an interesting tapelike C-H.O hydrogen bonding motif in its crystal structure. On the other hand, the molecule 23 revealed an undulated ribbonlike C-H. O motif. The "chain of rings" pattern of C-H.O interactions in 23 has been observed for the first time in the solid-state structure of oxa-bowls.

Journal Article↗
PubMed2000

Role of Heteroatoms in Diastereofacial Control in Cycloaddition to a Dissymmetric Cyclohexa-1,3-diene Moiety in a Polycyclic Framework. Remarkable Stereodirecting Influence of Distal Protective Groups.

Diels-Alder cycloaddition to several derivatives of a facially dissymmetric diene, the hexacyclo[7.5.1.0.(1,6)0.(6,13)0.(8,12)0(10,14)]pentadeca-2,4-diene-7,15-dione 4a, with a variety of dienophiles such as singlet oxygen, N-phenyltriazolinedione, dimethyl acetylenedicarboxylate, maleic anhydride, and N-methylmaleimide has been studied. The stereochemistry of the resulting adducts has been unambiguously secured by (1)H and (13)C NMR spectral data, chemical correlations, and X-ray crystal structure determination. While a variety of dienophiles undergo [4 + 2]-cycloadditions with 4a predominantly from the carbonyl face, protection of the carbonyl groups in 4a as simple mono- or bis-acetals 4b-e or thioacetals 9a,b leads to complete reversal in selectivity, favoring addition from the cyclobutane face, with heterodienophiles and acetylenic dienophiles. The reversal in selectivity observed in mono- and bis-acetals 4b-e has been attributed to unfavorable electrostatic interaction between the oxygen atom and the incoming dienophile. Whereas, in the case of thioacetals 9a,b, apart from unfavorable electrostatic interactions, Cieplak-type hyperconjugative interactions have to be given due consideration in order to account for the observed selectivities. Our studies highlight the role of simple protective groups (acetals in the present case) in modulating diastereoselection during [4 + 2]-cycloadditions.

Journal Article↗
PubMed2000

Stereoelectronic control in Diels-Alder reaction of dissymmetric 1, 3-dienes.

The Diels-Alder reaction is a widely employed protocol in which four stereogenic centers are generated in a predictable manner with olefin geometry, adjoining chiral center, and transition-state topology serving as the main controlling elements. However, when the Diels-Alder partners are in a dissymmetric environment, pi-face selection is determined through the interplay of steric, orbital, and electrostatic factors whose relative importance is a subject of intense debate. Several new systems have been crafted to probe the mechanistic nuances of the pi-face selection. The available data have enabled us to qualitatively define a hierarchy of various stereoelectronic effects that would aid predictability of the stereochemical outcome.

Cyclopentanes↗