Biomedical subjects

A K Tyagi

Publications and source records attributed to A K Tyagi.

At least 19 recordsLinked to original sources

PubMed2005

Structural characterization, expression analysis and evolution of the red/far-red sensing photoreceptor gene, phytochrome C (PHYC), localized on the 'B' genome of hexaploid wheat (Triticum aestivum L.).

Phytochromes are a family of red/far-red light perceiving photoreceptors. The monocot phytochrome family is represented by three members, PHYA, PHYB and PHYC. We have isolated and characterized the first PHY gene member (TaPHYC) from common wheat, Triticum aestivum var. CPAN1676. It codes for a species of the photoreceptor, phyC, which is known to be light-stable in all plants analyzed so far. A sequence of 7.2 kb has been determined, which includes 3.42 kb of coding region. This is the second full-length PHYC gene sequenced from a monocot (first was from rice). TaPHYC gene shares structural similarities with the rice PHYC containing four exons and three introns in the coding region. The 5' UTR is 1.0-kb-long and harbors an upstream open reading frame (URF) encoding 28 aa. Southern blot analysis of TaPHYC indicates that it represents single locus in the wheat genome, although the possibility of additional loci cannot be completely ruled out. Chromosomal localization using nullisomic-tetrasomic lines of Triticum aestivum var. Chinese Spring places TaPHYC on chromosome 4B. PHYC represents a constitutively expressed gene in all the organs tested and under light/dark conditions. However, PHYC was found to be developmentally regulated showing maximal expression in 3-day-old dark-grown seedlings, which declined thereafter. In silico analysis has also been done to compare TaPHYC gene with the partial sequences known from other wheat species and cultivars. The presence of a topoisomerase gene immediately downstream of the PHYC gene, both in rice and wheat genomes, presents yet another example of synteny in cereals and its possible significance has been discussed.

Amino Acid Sequence↗

PubMed2005

Effectiveness of emergency argon laser retinopexy performed by trainee doctors.

OBJECTIVE: To report the outcomes following treatment of retinal tears with argon laser photocoagulation by trainee doctors as an emergency procedure. METHODS: Retrospective, case note analysis of 100 consecutive patients treated between August 2000 and December 2002 at a tertiary referral hospital. RESULTS: The case notes of 100 consecutive patients (41 male, 59 female) with a mean age of 57.5 years were reviewed. Out of these 90 were symptomatic. The follow-up period ranged from 1 week to 8 months. All patients had argon laser retinopexy in the Emergency department. The on-call Registrar performed the procedure on 94 patients, and Senior House Officers performed the other six. A total of 98 procedures were performed on the slit lamp and two by laser indirect ophthalmoscope. In all, 24 patients needed further treatment with either indirect laser, cryotherapy, or surgery. At the last follow-up, all the patients had anatomically attached retinas. CONCLUSION: A significant proportion of patients (24%) undergoing laser retinopexy in the emergency department needed further treatment. The relative inexperience in using the indirect laser, together with its unavailability in the Emergency department, may be the contributory factors. There seems to be scope for supervised training in using the laser indirect ophthalmoscope for the trainees in the Ophthalmic Emergency department.

Adult↗

PubMed2005

Does vitreoretinal surgery under local anaesthesia result in missed fellow eye pathology?

PURPOSE: There has been a significant increase in the number of vitreoretinal procedures being performed under local anaesthesia over the past few years. This trend is expected to continue. This study was performed to investigate whether by undertaking retinal detachment surgery under local anaesthesia fellow eye examination was compromised. DESIGN: This was a prospective, consecutive, blind, observational study. METHODS SETTING: This study was performed at a tertiary referral vitreoretinal unit in a teaching hospital. STUDY POPULATION: In all, 108 consecutive patients undergoing retinal detachment surgery under general anaesthesia were included. OBSERVATION PROCEDURES: Patients were examined independently by different retinal surgeons pre- and intraoperatively. MAIN OUTCOME MEASURES: The findings of the two examiners were compared and differences were analysed. RESULTS: There were 108 patients in this study, 57 of these were males and 51 females. The mean age was 59.01 years (range 16-91). Of these 108 eyes, 48/108 (49.08%) the preoperative examination was regarded as unsatisfactory by the examiner. Over 34% of eyes had fellow eye pathology when examined preoperatively but there were nine (8.33%) eyes in which additional lesions were found intraoperatively. CONCLUSION: General anaesthesia should be considered for patients in whom preoperative fellow eye examination is unsatisfactory.

Adolescent↗

PubMed2005

Increased expression of Mycobacterium tuberculosis 19 kDa lipoprotein obliterates the protective efficacy of BCG by polarizing host immune responses to the Th2 subtype.

Mycobacterium tuberculosis can not only neutralize immune effector functions, but also has the ability to modulate host-signalling cascades involved in the development of these responses. The 19 kDa antigen (Rv3763), a lipoprotein of M. tuberculosis, elicits high levels of interleukin (IL)-12 from macrophages in addition to its powerful immunomodulatory properties, leading to suppression of antigen-presentation signalling cascades. The present study was aimed at analysing the effect of overexpression of this antigen on the immunostimulatory properties of M. bovis Bacille Calmette-Guerin (BCG). We have constructed a recombinant BCG strain (rBCG19N) producing higher levels of the 19 kDa antigen in both the cytoplasmic (approximately eightfold) and extracellular (approximately fivefold) fractions as compared to the wildtype BCG. Immunization of mice with rBCG19N elicited high levels of interferon-gamma (IFN-gamma) and relatively low levels of IL-10 against the purified 19 kDa antigen. However, in response to total BCG sonicate, mice immunized with rBCG19N produced significantly high levels of IL-10 with relatively very low levels of IFN-gamma. This polarization of the host immune responses towards T-helper 2 subtype resulted in complete abrogation of the protective efficacy of BCG, when rBCG19N was used as a live vaccine against M. tuberculosis challenge in guinea pigs.

Animals↗

PubMed2004

Surgical treatment and outcome of patients with giant retinal tears.

OBJECTIVE: To report the management and outcome in retinal detachments associated with giant retinal tears (GRTs). METHODS: Retrospective, case note analysis of patients treated between November 1991 and June 2002 at a tertiary referral hospital. RESULTS: The case notes of 29 patients (24 males, 5 females) with a follow-up ranging from five months to 7 years were reviewed. In all, 25 eyes had retinal detachments with macular involvement and 10 patients had myopia more than 6 D. All patients underwent vitrectomy. A total of 23 patients had heavy liquid and 16 had scleral explants; 28 patients had silicone oil and one had C3F8 tamponade. Intraoperative complications included lens trauma and iatrogenic GRT. Six eyes had recurrent retinal detachment and needed multiple surgical procedures. At the last follow-up, 25 patients had anatomically attached retinas. In all, 18 fellow eyes were treated prophylactically. Three patients had total retinal detachment and marked PVR. The visual acuity improved in 20 eyes. CONCLUSION: GRTs are more common in patients with high myopia. With newer techniques of surgical treatment of GRTs, the anatomical and visual outcomes are more favourable.

Adolescent↗

PubMed2003

Studies on the immunogenic potential of plant-expressed cholera toxin B subunit.

Nicotiana tabacum var. Samsun was transformed via Agrobacterium-mediated transformation with a gene encoding the cholera toxin B subunit (CTB) of Vibrio cholerae, modified to contain a sequence coding for an endoplasmic reticulum retention signal (SEKDEL), under the control of the cauliflower mosaic virus 35S promoter. Total protein from the transgenic leaf tissue was isolated and an aliquot containing 5 microg recombinant CTB was injected intradermally into Balb/c (H2K(d)) mice. CTB-specific serum IgG was detected in animals that had been administered plant-expressed or native purified CTB. A T-cell proliferation study using splenocytes and cytokine estimations in supernatants generated by in vitro stimulation of macrophages isolated from the immuno-primed animals was carried out. Inhibition of proliferation of T lymphocytes was observed in splenic T lymphocytes isolated from animals injected with either native or plant-expressed CTB. Macrophages isolated from mice immunised with native or plant-expressed CTB showed enhanced secretion of interleukin-10 but secretion of lipopolysaccharide-induced interleukin-12 and tumor necrosis factor alpha was inhibited. These studies suggest that plant-expressed protein behaved like native CTB with regards to effects on T-cell proliferation and cytokine levels, indicating the suitability of plant expression systems for the production of bacterial antigens, which could be used as edible vaccine. The transgene was found to be inherited in the progeny and was expressed to yield a pentameric form of CTB as evident by its interaction with G(M1) ganglioside.

Animals↗

PubMed2003

Modulation of host immune responses by overexpression of immunodominant antigens of Mycobacterium tuberculosis in bacille Calmette-Guérin.

Based on their immunodominant nature and ability to induce appropriate immune responses in the host, several antigens of Mycobacterium tuberculosis have shown promise of protection. However, most of the candidate vaccines developed by employing various strategies have afforded protection that is at best comparable with bacillus Calmette-Guérin (BCG) in animal models. Due to the inherent ability of BCG to prime cellular responses in the host, it has become an attractive vehicle for development of a vaccine against intracellular infections. In this study, we have cloned the genes of three immunodominant antigens of M. tuberculosis viz. the ESAT6 (Rv3875), the 19 kDa lipoprotein (Rv3763) and the 38 kDa antigen (Pst homolog) (Rv0934) in pSD5 under the transcriptional control of Trrn, a strong mycobacterial promoter, and expressed them in BCG. The19 kDa antigen and the 38 kDa antigen were expressed at levels that were approximately five and eightfolds higher in the cytosols of recombinant BCG strains rBCG19T and rBCG38T, respectively, as compared with their corresponding levels in M. bovis BCG. Both these antigens were also secreted into the extracellular medium at enhanced levels (19 kDa antigen fourfold and 38 kDa antigen twofold) by rBCG strains in comparison with the wild type BCG. ESAT6 antigen, which is absent in M. bovis BCG, was also expressed at a very high level in the cytosol of the rBCG strain (rBCGE6T). Evaluation of immune responses induced by these three rBCG strains in mice shows a markedly different pattern. The rBCG strain overexpressing the 38 kDa antigen exhibited a predominant T helper 1 (Th1) response with high levels of interferon-gamma (IFN-gamma) production, whereas overexpression of the 19 kDa antigen resulted in completely polarized Th2 responses against the BCG sonicate. The rBCG-expressing ESAT6 antigen induced a mixed Th1/Th2 response. Our observations suggest that the 38 kDa antigen may hold excellent promise in the rBCG approach for the development of a vaccine against tuberculosis.

Animals↗

PubMed2003

Raman scattering investigations of nanocrystalline thorium oxide.

Raman scattering investigations are carried out on nanocrystalline thorium oxide powders. Shift and broadening of the Raman peak associated with F2g phonons are observed for the nanocrystalline samples as compared with those of the bulk. The peak shift and broadening are found to increase further as the particle size decreases. A quantitative analysis of the Raman line shape is carried out with a Gaussian confinement model, and the estimated size is found to be consistent with that obtained from X-ray diffraction and transmission electron microscopy.

Crystallization↗

PubMed2003

Blood gases, hematology, and renal blood flow during prolonged mountain sojourns at 3500 and 5800 m.

BACKGROUND: This study mainly focused on renal blood flow, hematological parameters, blood gases, and blood pH, which are affected on exposure to moderate (3500 m) and extreme altitudes (5800 m) in sea level residents. HYPOTHESIS: Acute and prolonged exposure to high or extreme altitude may cause pathophysiological changes in kidney and renal plasma/blood flow, leading to retention of fluids in the tissues. Combined with the decreased availability of oxygen to the tissues, these may be responsible for high altitude maladies. METHOD: Fifteen male sea level (SL) volunteers, 22-25 yr old, were studied for blood gases, blood viscosity, hematocrit, hemoglobin concentration, and effective renal blood/plasma flow at Delhi (260 m), 3500 m (60 d stay), 5800 m (70 d stay), and 7 d after return to SL. RESULTS: Compared with SL, a significant increase from 7.34 to 7.43 (p < 0.01) in blood pH was observed at 3500 m that remained significantly increased at 5800 m. PO2 was about 39% less at 5800 m than at SL. PCO2 reduced significantly from 42.07 to 28.05 mm Hg on return from 5800 m to SL. The blood viscosity increased significantly (38%) at 5800 m and decreased significantly by 38% (p < 0.01) after return to SL. The effective renal plasma flow reduced significantly (p < 0.01) from 615.6 at SL to 381.5 ml x min(-1) x 1.73 m(-2) at 5800 m. CONCLUSION: The study suggests a crucial role of renal function in the acclimatization process; renal function also appears to be one factor by which the body protects itself against severe hypoxia.

Acclimatization↗

PubMed2003

Tuberculous osteitis of clivus.

Tuberculous osteitis of clivus is rare. Its diagnosis is difficult because of the rarity of the site and the non-specific nature of the disease. Management consists of confirmation of diagnosis by biopsy and chemotherapy with anti-tubercular drugs. Meningitis may complicate the clinical course, increase morbidity and mortality.

Adult↗

PubMed2002

Transgenics of an elite indica rice variety Pusa Basmati 1 harbouring the codA gene are highly tolerant to salt stress.

Transgenic lines of indica rice were generated by Agrobacterium-mediated transformation with the choline oxidase ( codA) gene from Arthrobacter globiformis. Choline oxidase catalyses conversion of choline to glycine betaine. Glycine betaine is known to provide tolerance against a variety of stresses. Molecular analyses of seven independent transgenic lines as performed by Southern, Northern and Western hybridization revealed integration and expression of the transgene as well as inheritance in the progeny plants. A good correlation was observed between levels of mRNA and protein accumulation, and a significant amount of choline oxidase product, i.e. glycine betaine, accumulated in R0 as well as R1 plants. Mendelian as well as non-Mendelian segregation patterns were obtained in the progeny plants. Challenge studies performed with R1 plants by exposure to salt stress (0.15 M NaCl) for 1 week, followed by a recovery period, revealed that in some cases more than 50% of the transgenic plants could survive salt stress and set seed whereas wild-type plants failed to recover.

Betaine↗

PubMed2002

Spectrally resolved luminescence of undoped and Dy3+ doped Na2SO4.

Structural phase transitions influence the luminescence characteristics by modifying the spectra, sensitivity and luminescence efficiency in each phase. This has implications for dosimetric materials both for sensitivity and reproducibility. Previous work with dosemeter materials has not documented effects of different phases on thermoluminescence but Na2SO4 exists in several phases in the temperature range of interest for thermoluminescence dosimetry. Therefore spectrally resolved TL and radiothermoluminescence analyses of undoped and Dy3+ doped Na2SO4 have been performed. Dramatic differences between TL of slow cooled and quenched Na2SO4:Dy are explained in terms of the initial phase of the samples at room temperature. For undoped material the effect of phase conversions during heating shift the wavelengths of the emission bands. A model of Dy in small precipitate phases is considered.

Dysprosium↗

PubMed2001

OsIAA1, an Aux/IAA cDNA from rice, and changes in its expression as influenced by auxin and light.

The Aux/IAA class of genes are rapidly induced by exogenous auxins and have been characterized extensively from many dicot species like Arabidopsis, Glycine max and Pisum sativum. We report here the isolation and characterization of rice (Oryza sativa L. subsp. Indica) OsIAA1 cDNA as a monocot member of the Aux/IAA gene family. The predicted amino acid sequence of OsIAA1 corresponds to a protein of ca. 26 kDa, which harbors all four characteristic domains known to be conserved in Aux/IAA proteins. The conservation of these Aux/IAA genes indicates that auxins have essentially a similar mode of action in monocots and dicots. Northern blot analysis revealed that the OsIAA1 transcript levels decrease in the excised coleoptile segments on auxin starvation, and the level is restored when auxin is supplemented; the increase in OsIAA1 transcript level was apparent within 15 to 30 min of auxin application. Auxin-induced OsIAA1 expression appears to be correlated with the elongation of excised coleoptile segments. In light-grown rice seedlings, OsIAA1 is preferentially expressed in roots and basal segment of the seedling, whereas in the etiolated rice seedlings, the OsIAA1 transcripts are most abundant in the coleoptile. A comparative analysis in light- and dark-grown seedling tissues indicates that the OsIAA1 transcript levels decrease on illumination.

Amino Acid Sequence↗

PubMed2001

Isolation and molecular characterization of the COP1 gene homolog from rice, Oryza sativa L. subsp. Indica var. Pusa Basmati 1.

The COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) gene has been identified earlier from dicot species namely Arabidopsis, tomato and pea. The protein encoded by this gene acts as a molecular switch that negatively regulates the transition from the skotomorphogenic to the photomorphogenic mode of plant development. We have isolated and characterized the COP1 homolog from a monocot species, i.e. rice (var. Pusa Basmati 1). All the functional domains (Zn-binding RING finger motif, coiled-coil region, WD-40 repeats, cytoplasmic/nuclear localization sequences and protein-protein interaction domains) that are known in the COP1 proteins from dicots are conserved in COP1 from rice as well. The transcript levels of COP1 vary in various tissues of the rice plant. These variations were found to be development-dependent and do not solely depend on the light conditions.

Amino Acid Sequence↗

PubMed2001

Argemone mexicana poisoning: autopsy findings of two cases.

Epidemic dropsy, a disease due to Argemone mexicana poisoning, is characterized by pathological accumulation of diluted lymph in body tissues and cavities. Recently, the largest epidemic of the disease in India affected Delhi and its neighboring states during the months of August-September 1998. Over 3000 persons fell ill, and more than 65 died in the state of Delhi alone. Two cases belonging to the same family died, out of the large number of cases admitted in this tertiary care teaching hospital situated in eastern part of Delhi. Autopsy findings of these two cases are presented and discussed here along with the review of toxicity due to this poisoning.

Autopsy↗

PubMed2001

Management of spontaneous cerebellar hematomas: a prospective treatment protocol.

OBJECTIVE: To identify easily applicable guidelines for the surgical and conservative management of spontaneous cerebellar hematomas. METHODS: A treatment protocol was developed and prospectively applied for the management of 50 consecutive cases of cerebellar hematomas. The appearance of the fourth ventricle, adjacent to the hematoma, on computed tomographic scans was divided into three grades (normal, compressed, or completely effaced). The degree of fourth ventricular compression was correlated with the size and volume of the hematoma and the presenting Glasgow Coma Scale (GCS) score. The hematoma was surgically evacuated for all patients with Grade III compression and for patients with Grade II compression when the GCS score deteriorated in the absence of untreated hydrocephalus. Patients with Grade I or II compression were initially treated with only ventricular drainage in the presence of hydrocephalus and clinical deterioration. RESULTS: The degree of fourth ventricular compression was classified as Grade I in 6 cases, Grade II in 26, and Grade III in 18. The degree of fourth ventricular compression was significantly correlated with the volume of the hematoma (r(s) = 0.67, P < 0.0001), hydrocephalus (r(s) = 0.44, P = 0.001), the preoperative GCS score (r(s) = 0.43, P = 0.001), the maximal diameter of the hematoma (r(s) = 0.43, P = 0.001), and a midline location of the hematoma (chi(2) = 6.84, P < 0.009). Acute deterioration in GCS scores occurred for 6 (43%) of 14 patients with Grade III ventricular compression who were conscious at presentation. Thirteen patients with Grade I or II ventricular compression and stable GCS scores of more than 13 were treated conservatively. Nine patients were treated with ventricular drainage only, and 28 underwent posterior fossa craniectomy and evacuation of the hematoma with ventricular drainage. The mortality rate at 3 months was 40%. None of the patients with Grade III fourth ventricular compression and GCS scores of less than 8 at the time of treatment experienced good outcomes. Overall, 15 (60%) of 25 patients with hematomas with maximal diameters of more than 3 cm and Grade I or II compression did not require clot evacuation. CONCLUSION: Conscious patients with Grade III fourth ventricular compression should undergo urgent clot evacuation before deterioration. Surgical evacuation of the clot may not be required for large hematomas (>3 cm) if the fourth ventricle is not totally obliterated at the level of the clot.

Adolescent↗

PubMed2000

Recombinant BCG approach for development of vaccines: cloning and expression of immunodominant antigens of M. tuberculosis.

In spite of major advances in our understanding of the biology and immunology of tuberculosis, the incidence of the disease has not reduced in most parts of the world. In an attempt to improve the protective efficacy of Mycobacterium bovis bacille Calmette-Guérin (BCG), we have developed a generic vector system, pSD5, for expression of genes at varying levels in mycobacteria. In this study, we have cloned and overexpressed three immunodominant secretory antigens of M. tuberculosis, 85A, 85B and 85C, belonging to the antigen 85 complex. All the genes were cloned under the control of a battery of mycobacterial promoters of varying strength. The expression was analysed in the fast-growing strain M. smegmatis and the slow-growing vaccine strain M. bovis BCG. The recombinant BCG constructs were able to express the antigens at high levels and the majority of the expressed antigens was secreted into the medium. These results show that by using this strategy the recombinant BCG approach can be successfully used for the development of candidate vaccines against infections associated with mycobacteria as well as other pathogens.

Antigens, Bacterial↗

PubMed2000

Referral delay and ocular surgical outcome in Terson syndrome.

BACKGROUND: In Terson syndrome, vitreous hemorrhage can result from intracranial hypertension associated with intracranial bleeding. The vitreous hemorrhage can cause a considerable visual handicap. The aim of this study was to determine the outcome of surgery in patients with Terson syndrome and any delay in referral to an ophthalmologist. METHODS: Retrospective case review of 25 eyes of 17 patients undergoing vitrectomy for Terson syndrome. Delay in presentation to an ophthalmologist, intraoperative and postoperative complications, and the final visual acuity were noted. RESULTS: The mean interval between visual symptoms and referral to an ophthalmologist was 5.2 months for the nine unilateral cases and 4.9 months for the eight bilateral cases. Intraoperative complications included retinal break (2) and retinal dialysis (3). Late complications included epiretinal membrane (4), ghost cell glaucoma (1), and cataract (8). Twenty-two of the 25 eyes achieved a final visual acuity of 20/30 or better. CONCLUSION: Vitrectomy for vitreous hemorrhage in Terson syndrome is a safe and effective procedure, offering a rapid and prolonged improvement in vision. There is good reason to consider early vitrectomy, particularly when the hemorrhage is bilateral and dense.

Adult↗