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Biomedical subjects

A K Bansal

Publications and source records attributed to A K Bansal.

At least 19 recordsLinked to original sources
PubMed2005

Stabilization against hyperthermal denaturation through increased CG content can explain the discrepancy between whole genome and 16S rRNA analyses.

Based largely upon analysis of ribosomal RNA, a third domain of life, called archaea, had been proposed in addition to bacteria and eukaryotes. However, quantitative analysis of 73 whole genomes shows only a two-domain division of life: into eukaryotes and prokaryotes. Thousands of orthologous genes in archaea and bacteria show an essentially unimodal distribution of sequence identities. Thus, whole genome analyses indicate that archaea are a phylum of bacteria rather than a separate domain of life. In contrast, archaeal rRNA and that of hyperthermophilic bacteria differ from the rRNA of mesophilic bacteria. Thus, there is a bimodal distribution of rRNA sequence identities which differ by 12%. This discrepancy in rRNA and gene content based analyses of whole genomes is likely due to a 15% elevated C:G content of the rRNA of archaea and hyperthermophilic bacteria. The elevated C:G content is consistent with stabilization against thermal denaturation caused by additional hydrogen bonding (3 bonds) in C:G pairs compared to A:U pairs (2 bonds). Based upon this premise, there is no reliable way to correct rRNA for such differences in base composition and it is not possible to quantitatively compare hyperthermophiles with mesophiles by the rRNA method. Furthermore, quantitative study of whole genomes shows that the extent of change in both bacterial and archaeal genes, including rRNA, has reached a limit. Thus, direct sequence comparisons work with closely related genomes, but it is not possible to differentiate the most divergent prokaryotic species, which are currently designated as separate phyla. We believe that the differences in characteristics of archaeal species is based primarily upon selection of genes and pathways compatible with the extreme environmental lifestyle, i.e., hyperthermophily.

Animals↗
PubMed2005

Outcome of pterygium surgery: analysis over 14 years.

AIM: To report the outcome of pterygium surgery performed at a tertiary eye care centre in South India. METHODS: Retrospective analysis of medical records of 920 patients (989 eyes) with primary and recurrent pterygia operated between January 1988 and December 2001. The demographic variables, surgical technique (bare sclera, primary closure, amniotic membrane transplantation (AMT), conjunctival autograft (CAG), conjunctival-limbal autograft (CLAG), or surgical adjuvants), recurrences and postoperative complications were analysed. RESULTS: A total of 496 (53.9%) were male and 69 (7.5%) had bilateral pterygia. Bare sclera technique was performed in 267 (27.0%) eyes, primary conjunctival closure in 32 (3.2%), AMG in 123 (12.4%), CAG in 429 (43.4%), and CLAG in 70 (7.1%). Adjuvant mitomycin C was used in 44 (4.4%) cases. The mean duration of follow-up was 8.9+/-17.0 and 5.9+/-8.8 months for unilateral primary and recurrent pterygia, respectively. The overall recurrence rate was 178 (18.0%). Following primary and recurrent unilateral pterygium excision respectively, recurrences were noted in 46 (19.4%) and 1 (33.3%) eyes after bare sclera technique, five (16.7%) and 0 after primary closure, 28 (26.7%) and 0 with AMG, 42 (12.2%) and five (31.3%) with CAG, and nine (17.3%) and two (40%) with CLAG. Recurrences were significantly more in males with primary (23.3 vs 10.7%, P<0.0001) and recurrent (26.7 vs 0%, P=0.034) pterygia, and in those below 40 years (25.2 vs 14.8%, P=0.003). CONCLUSION: CAG appears to be an effective modality for primary and recurrent pterygia. Males and patients below 40 years face greater risk of recurrence. Bare sclera technique has an unacceptably high recurrence. Prospective studies comparing CAG, CLAG, and AMG for primary and recurrent pterygia are needed.

Adolescent↗
PubMed2005

Modulation of N-nitrosodiethylamine (NDEA) induced oxidative stress by vitamin E in rat erythrocytes.

Nitrosamines, such as N-nitrosodiethylamine (NDEA), induced oxidative stress due to the generation of reactive oxygen species, which are capable of initiating peroxidative damage to the cell. The present study was designed to establish whether pre-treatment with vitamin E (40 mg/kg body wt, intraperitoneally (ip), twice a week for 4 weeks) to NDEA induced rats provides protection against oxidative stress caused by NDEA. A single necrogenic dose of NDEA (200 mg/kg body wt) was administered intraperitoneally (ip) to the rats with or without vitamin E pre-treatment and the animals were sacrificed on Day 7, 14 or 21 after NDEA administration. Lipid peroxidation (LPO) and the activities of antioxidant enzymes were determined in erythrocytes as indices of oxidative damage. The result showed elevated levels of LPO in erythrocytes with NDEA treatment, however, vitamin E pre-treated rats administered NDEA showed decreased LPO (Day 14 and 21). Superoxide dismutase (SOD) enzyme activity and the glutathione (GSH) content increased with NDEA treatment and remained high in vitamin E pre-treated group. Catalase (CAT), glutathione reductase (GSH-R) and glutathione-S-transferase (GST) enzyme activities declined with NDEA treatment; however, vitamin E pre-treated rats administered NDEA, showed elevation in the enzyme activities. Glutathione peroxidase (GSH-Px) activity increased in erythrocytes in vitamin E pre-treated rats administered NDEA, while Se-GSH-Px activity was not affected significantly. This study demonstrates that the pre-treatment with vitamin E prior to the administration of NDEA was effective in counteracting and modulating oxidative stress in rat erythrocytes in a time-dependent manner.

Alkylating Agents↗
PubMed2005

Ternary amorphous composites of celecoxib, poly(vinyl pyrrolidone) and meglumine with enhanced solubility.

The present study highlights the development of ternary amorphous composites to enhance the solubility of a poorly soluble crystalline drug, celecoxib (CEL). These systems comprised of an 'amorphous drug,' and its 'stabilizer' and 'solubilizer.' The ternary amorphous system of CEL, poly(vinyl pyrrolidone) (PVP) and meglumine (MEG) (7:2:1 w/w) enhanced CEL solubility by approximately equal to 10.2-fold over that for the crystalline drug, and maintained the thermodynamic stability of the amorphous drug. However, MEG alone was unable to stabilize the amorphous CEL against thermally-induced crystallization, and so gave no solubility advantage. The PVP-MEG combination provided a 'synergistic' enhancement of CEL solubility, as compared to their use alone in the amorphous systems. Phase-solubility studies provided greater insight into molecular mechanisms underlying stability and solubility of these amorphous systems. MEG exhibited phase-specific interaction with CEL molecules, when stabilized by PVP in the amorphous state. The higher solubility of CEL from ternary amorphous systems was also thermodynamically favored, as analyzed by van't Hoff plots. A possible molecular level interaction of MEG with PVP-stabilized amorphous CEL seems to be responsible for the solubility advantage of the CEL-PVP-MEG ternary amorphous system.

Calorimetry, Differential Scanning↗
PubMed2004

Pellucid marginal corneal degeneration.

OBJECTIVE: To report the clinical features and outcome of patients with pellucid marginal corneal degeneration (PMCD). DESIGN: Retrospective noncomparative case series. METHODS: Retrospective chart review of 116 eyes of 58 patients with PMCD seen between 1990 and 2002 at the Cornea Service at L.V. Prasad Eye Institute, Hyderabad, India. The diagnosis of PMCD was based on the presence of corneal thinning with ectasia of the normal cornea above or below the area of thinning with no evidence of scarring, vascularization, or lipid deposition and typical topographic features whenever topography was performed. A detailed history including the age of presentation, onset of symptoms, systemic diseases, atopy, and relevant family history was reviewed. The visual acuity (VA) at presentation; the location, extent, and degree of thinning; presence of concurrent keratoconus and keratoglobus; and complications, if any, were noted. The mode of visual rehabilitation; surgical procedure, if any; and the final VA achieved were analyzed. MAIN OUTCOME MEASURES: Clinical features, associations, complications, and outcome of treatment. RESULTS: There were 45 males (77.6%) and 13 females (22.4%). All cases were bilateral. In one eye, no clinical features of PMCD were seen, but the diagnosis was made based on topographic features of typical PMCD. The age of the patients ranged from 8 to 66 years, with a mean of 34.0+/-14.8. One patient (1.7%) had associated vernal keratoconjunctivitis (VKC), 1 (1.7%) had Marfan's syndrome, and 1 (1.7%) had ocular hypertension. The degree of astigmatism was <5.0 diopters (D) in 19 eyes (19.2%), 5 to 10 D in 36 (36.4%), 10 to 15 D in 23 (23.2%), 15 to 20 D in 15 (15.2%), and >20 D in 6 (6.1%). Typical inferior PMCD was seen in 99 eyes (85.3%), and superior PMCD was seen in 17 (14.7%). The thinning was commonly seen between the 5-o'clock and 7-o'clock positions. In 12 eyes (10.3%), PMCD was associated with keratoconus, and in 15 eyes (12.9%), keratoglobus was associated. Seven eyes (6.0%) had hydrops. Visual acuity improved in 52 eyes (55.3%) with correction, in 40 eyes (42.6%) it remained the same as that of the initial presentation, and in 2 eyes (2.1%) it worsened relative to the initial presentation. Forty-one eyes (35.3%) received spectacles, and 31 eyes (26.7%) were fitted with rigid gas-permeable contact lenses. Five eyes (4.3%) underwent surgery. Lamellar keratoplasty was performed in 3 eyes, and a crescentic lamellar graft was done in 2 eyes. Visual acuity improved in 4 eyes after surgery with a follow-up of 2 to 37 months. The final astigmatism in the operated eyes at the last follow-up ranged from 4 to 11 D. CONCLUSIONS: Pellucid marginal corneal degeneration was seen predominantly in males in this series, and was not strongly associated with VKC. Keratoconus was seen in approximately 10% of the eyes, and keratoglobus in approximately 13%. Superior PMCD was seen in approximately 15% of the eyes. In our study, patients presented with severe astigmatism, and hydrops was a common complication. The majority of patients were treated with spectacles or contact lens. Surgery for PMCD-lamellar keratoplasty and crescentic lamellar keratoplasty, if indicated-usually results in significant residual astigmatism.

Adolescent↗
PubMed2004

Superior pellucid marginal corneal degeneration.

PURPOSE: To report the clinical features and topographic findings of superior pellucid marginal corneal degeneration (PMCD). METHODS: Retrospective chart review of 15 eyes of eight patients of superior PMCD. Detailed history, visual acuity at presentation, degree of astigmatism, slit-lamp examination findings, topographic features, and Orbscan findings were noted where available. Improvement in visual acuity with spectacles or contact lens correction, surgical procedure if any, and final visual acuity were analysed. RESULTS: In all, six patients were males and two were females. All cases except one were bilateral. The patients ranged in age from 18 to 48 years. All cases had isolated superior PMCD. One patient was a diagnosed case of vernal keratoconjunctivitis. The visual acuity at presentation ranged from hand motions to 20/25. The degree of thinning varied from 30 to 90%. The extent of thinning was commonly seen between the 10 and 2 o'clock positions. Ectasia was seen below the site of thinning in all the cases of superior PMCD. Topographic features including vertical corridor of reduced power, against-the-rule astigmatism and superior loop cylinder were seen in 10 eyes. Orbscan was carried out in two eyes of one patient and revealed an area of increased elevation in relation to the best-fit sphere superiorly corresponding to the area of ectasia in both the eyes. The visual acuity improved with rigid gas-permeable contact lens in six eyes and the final visual acuity ranged from 20/400 to 20/30. Two eyes were subjected to surgical intervention (peripheral annular graft=1 and lamellar graft=1). CONCLUSIONS: PMCD can occur superiorly. It should be considered in the differential diagnosis of superior ectatic disorders. The topographic findings, of reduced power in the vertical meridian and superior loop cylinder, are typical of superior pellucid marginal degeneration. Visual rehabilitation is usually possible with contact lenses, with surgical management required in selected cases.

Adolescent↗
PubMed2004

In vitro-in vivo characterization of release modifying agents for parenteral sustained-release ketorolac formulation.

One of the prerequisites for a parenteral preparation is that the excipients incorporated are biocompatible and biodegradable. In the present study hydrophilic and hydrophobic excipients were investigated for developing an intramuscular sustained-release formulation of ketorolac. Kollidon 17 PF, Peceol (glyceryl monooleate), and castor oil were chosen as the potential release-retarding agents, each with a distinct mechanism of action. They were evaluated by in vitro drug-release profiles and in vivo pharmacodynamic and pharmacokinetic study in mice. Cumulative drug release was determined for standard and test formulations in modified Franz diffusion cell. Pharmacodynamic parameter, T = 70% response of peak analgesic response, was used to compare the performance of test formulations. Based on pharmacodynamic/pharmacokinetic correlation in the animal studies, Css(max) and Css(min) of 51.39 and 30.0 microg/mL, respectively, were determined and considered as performance markers for pharmacokinetic evaluation of test formulations. The study suggested that the sustained-release capability of glyceryl monooleate was maximum followed by that of castor oil and Kollidon 17 PF, when compared to conventional ketorolac tromethamine formulation. It was inferred that water soluble excipient, though, showed release retarding property in vitro but could not maintain it in the in vivo environment. Glyceryl monooloeate-based formulation produced the most favorable drug blood concentration vs. time profile.

Animals↗
PubMed2002

Birth weight patterns in rural undernourished pregnant women.

OBJECTIVE: To study the birth weight pattern in chronic as well as currently undernourished pregnant women. DESIGN: Prospective study of rural pregnant women by following eligible women. SETTING: Two adjoining blocks of rural Varanasi. METHOD: 3700 pregnant women from rural areas of Varanasi for whom data for anthropometry, hemoglobin, dietary intake, birth weight, fundal height and abdominal girth at 16 +/- 2, 28 +/- 2 and 36 +/- 2 weeks of gestation were recorded. Outcome measure was birth weight pattern of newborns. RESULTS: Of the births, 7.2% were < 2250 g and 27.4% < 2500 g. The weekly birth weight increments in gestation 36-42 weeks were 5-53 g, only. The fundal height did not increase during 35-39 weeks of gestation (lower by 5 cm as compared to normal). Nutrition supplement in the third trimester significantly increased fundal height and abdominal girth. Fundal height below 24.5 cm at 28 weeks of gestation (1368 women) was associated with higher low birth weight deliveries. CONCLUSION: Birth weight and fundal height increments during later pregnancy are low in undernourished pregnant women. Fundal height < 24.5 cm at 28 weeks of gestation identified women with higher risk for lowbirth weight infants. The prevalence of low birth weight was 27.4% and of prematurity was 6.6%.

Adult↗
PubMed2001

Oxidative damage induced by the injection of HIV-1 Tat protein in the rat striatum.

Oxidative stress has been hypothesized to play a role in the pathogenesis of different neurodegenerative disorders, including HIV-related dementia. Tat, a nonstructural protein of HIV, is implicated in potentiation of neuronal apoptosis by mechanisms involving the disruption of calcium homeostasis and oxidative stress. The injection of Tat caused an increase of protein carbonyl formation in the rat striatum. Increased oxidative modification of proteins occurred early after Tat injection and preceded Tat-mediated astrogliosis. Immunostaining of brain sections demonstrated that an area of prominent protein carbonyl immunoreactivity surrounded an injection site in the striatum of Tat-injected rats. Intense protein carbonyl immunoreactivity was localized in cell bodies. Our study suggests that increased protein oxidation may be an important part of the mechanism of Tat neurotoxicity.

Animals↗
PubMed2001

Bilateral infectious keratitis after laser in situ keratomileusis: a case report and review of the literature.

OBJECTIVE: To report a case of bilateral infectious keratitis after simultaneous bilateral laser in situ keratomileusis (LASIK) and to explore appropriate preventive, diagnostic, and therapeutic measures. DESIGN: Interventional case report and literature review. INTERVENTION: A 22-year-old woman had bilateral corneal infiltrates after simultaneous bilateral LASIK. The same set of instruments was used for surgery on both eyes. Corneal scrapings from the edge of the infiltrate and underneath the flap were taken for microscopic examination and inoculation on culture media. Treatment consisted of irrigation of stromal bed with amikacin sulphate (2.5%) solution along with half hourly instillation of amikacin (2.5%) and cefazolin (5%) eye drops. MAIN OUTCOME MEASURES: Causative organism and response to medical treatment. RESULTS: Culture revealed a significant growth of Mycobacterium chelonae from the corneal scrapings of both eyes. There was progressive thinning of corneal stroma in the right eye requiring cyanoacrylate tissue adhesive application. The left eye showed progressive worsening after initial response and required penetrating keratoplasty. CONCLUSIONS: The risk of bilateral sight-threatening complications must be kept in mind when contemplating bilateral simultaneous LASIK. Nontuberculous mycobacteria should be considered as an etiologic agent in cases of infectious keratitis occurring after LASIK. Microbiology work-up of a specimen collected directly from the site of lesion can help in early diagnosis and institution of appropriate therapy.

Adult↗
PubMed2001

Amniotic membrane transplantation in the management of shield ulcers of vernal keratoconjunctivitis.

PURPOSE: To report our experience with amniotic membrane transplantation in the management of severe shield ulcers. DESIGN: Retrospective, interventional, noncomparative case series. PARTICIPANTS: Four patients (seven eyes) with grade 2 (ulcer with opaque base) and grade 3 (plaquelike lesions) shield ulcers not responding to steroid therapy with or without surgical debridement. INTERVENTION: Amniotic membrane transplantation with stromal side down was performed after meticulous debridement of the ulcer. MAIN OUTCOME MEASURES: Healing of the ulcer with no epithelial defect. RESULTS: The ulcers healed with disintegration or retraction of the membrane in all patients within 2 weeks. CONCLUSIONS: Amniotic membrane transplantation in combination with debridement is an effective surgical modality in the management of severe shield ulcers. Further studies are warranted to confirm the efficacy of amniotic membrane transplantation in the management of shield ulcer and its correct position in the treatment algorithm.

Adolescent↗
PubMed2001

Laser refractive surgery: technological advance and tissue response.

Photorefractive keratectomy (PRK) and laser assisted in situ keratomileusis (LASIK), using an excimer laser, are the currently popular techniques of correcting refractive errors. Since these techniques work by selective ablation of corneal stroma, the tissue healing response plays a great role in the ultimate outcome of surgery. Also, various methods of wound healing modulation can be used to achieve better results. While these procedures do lead to a decrease in dioptric power and increase in unaided visual acuity, higher visual functions like contrast sensitivity can sometimes be compromised after the surgery.

Corneal Injuries↗
PubMed2001

Activity profile of glycolamide ester prodrugs of ibuprofen.

Glycolamide esters of ibuprofen (I), namely, unsubstituted (II), N,N dimethyl (III), and N,N diethyl (IV), were synthesized and studied for different physicochemical, pharmacological, and toxicological properties. They were comparable with I in respect of anti-inflammatory and analgesic activity but did not exhibit reduction in the ulcerogenicity on oral administration. However, all three exhibited significantly better topical activity in carrageenan-induced rat paw edema assay. In the same assay, they provided significant protection against inflammation when applied at a site remote to the inflammation site.

Administration, Oral↗
PubMed2001

Impression cytology-proven corneal stem cell deficiency in patients after surgeries involving the limbus.

PURPOSE: To report three cases of limbal stem cell deficiency (confirmed by impression cytology) that followed multiple pterygium surgeries and therapeutic penetrating keratoplasty. METHODS: The first case, after multiple pterygium surgeries, presented with corneal scarring and thickened epithelium with vascularization sparing the central cornea in the right eye and involving the entire cornea in the left eye. The second case presented with superficial scarring and extensive vascularization after failed therapeutic graft performed for a large perforated corneal ulcer. The third case was a clear graft performed for a progressing fungal ulcer with signs of conjunctivalization inferotemporally. Limbal stem cell deficiency was clinically suspected in all of these cases. RESULTS: Goblet cells with mucin globules were found on the corneal surface by impression cytology in all three cases. CONCLUSIONS: We report three cases of limbal stem cell deficiency (proven by impression cytology) that followed multiple pterygium surgeries and therapeutic penetrating keratoplasty. Surgical insult to the limbus is the predisposing factor for stem cell damage in these cases. Involvement of the limbus by infection and use of intensive medications are probable contributing factors for stem cell damage in cases of therapeutic penetrating keratoplasty.

Adult↗
PubMed2001

Ipsilateral rotational autokeratoplasty: an alternative to penetrating keratoplasty in nonprogressive central corneal scars.

PURPOSE: To report the outcome of ipsilateral rotational autokeratoplasty performed for nonprogressive central corneal opacities. METHODS: Medical records of 27 patients who underwent ipsilateral rotational autokeratoplasty between June 1995 and December 1998 were retrospectively reviewed. The etiology of corneal opacity, preoperative visual acuity, and size of the trephine used was noted. Any intraoperative and early and late postoperative complications were noted in all patients. The final outcome, visual acuity, and astigmatism at final correction were analyzed. RESULTS: The main etiology of corneal opacity was trauma (44.4%), followed by resolved keratitis (29.6%). The size of the graft ranged from 6.5 to 9 mm. Fifteen patients underwent autokeratoplasty alone; additional procedures were combined in the remaining 12. Wound leak was the most common postoperative complication, which was seen in seven patients. The mean follow-up was 12.11 months (SD = 11.95 months). Five patients (18.5%) were lost to follow-up. Of the remaining 22, 19 (86.36%) had clear grafts and 3 (13.6%) had failed grafts. The mean astigmatism at final correction was 4.25 diopters cylinder (SD = 2.72). Final visual acuity of 20/80 or better was obtained in 13 cases (59.09%). CONCLUSIONS: Contrary to common belief, ipsilateral rotational autokeratoplasty is a safe and effective surgical procedure. It can be considered as an alternative procedure to penetrating keratoplasty in a scenario in which tissue scarcity exists, as well as in cases that have a high risk of developing immunologic allograft rejection. Further prospective studies with preoperative specular microscopy and postoperative corneal topography will provide greater insight into the usefulness of this procedure.

Adolescent↗
PubMed2001

Anterior stromal puncture in bullous keratopathy: a clinicopathologic study.

PURPOSE: We report our experience of anterior stromal puncture (ASP) in symptomatic chronic corneal edema patients awaiting penetrating keratoplasty (PK) and hypothesize the mechanism of action of ASP in bullous keratopathy (BK). METHODS: We reviewed the medical records of 28 patients with BK who underwent ASP between November 1996 and September 1999 with at least 1 month of follow-up. In all these patients, approximately 200 punctures were given with a bent 26-gauge needle sparing the peripheral cornea. Patients were examined on days 1 and 7, 1 month, and every 3 months after the procedure. The symptoms, corneal findings, and visual acuity of the patients at last follow-up were noted and compared with the preprocedure findings. For 11 patients who underwent PK, histopathologic study of corneal buttons was performed and a clinicopathologic correlation was attempted. RESULTS: Of the 28 patients, there were 15 men and 13 women with a mean age of 61.1 years. The clinical diagnosis was pseudophakic BK in 11 (39.3%), aphakic BK in 11 (39.3%), Fuchs' dystrophy in 4 (14.3%), failed graft in 1 (3.6%), and chronic corneal edema of unknown etiology in 1 (3.6%). The follow-up ranged from 1 to 33 months with a mean of 9.5 +/- 7.5 months. Symptomatic relief was noted in all. Twenty patients (71.4%) had complete relief, whereas eight patients (28.6%) experienced mild symptoms such as tearing and occasional pain. Visual acuity improved in 7 patients (25%), decreased in 12 (42.8%), and remained the same in 9 (32.4%). Objective evidence of scarring after ASP was noted in all patients. Complete regression of epithelial bullae and epithelial edema was found in 10 (35.7%) and partial regression in 18 (62.25%) patients. There was no progression or appearance of new blood vessels except in one patient (3.6%). Histologically, puncture marks and superficial stromal scarring were noted in all corneal buttons. Adhesion of epithelium with varying degrees of subepithelial fibrosis was seen in six, whereas in the remaining five buttons, there was complete denudation of the epithelium. Vascularization was seen in five and inflammation in two buttons. Clinicopathologic correlation revealed that symptomatic patients had persistent edema and loose adhesion of the epithelium to the stroma, resulting in detachment. CONCLUSIONS: ASP is a simple, safe, and cost-effective outpatient procedure for symptomatic relief in patients with BK. The possibility of decreased visual acuity after the procedure should be explained to all patients. Although ASP promoted subepithelial fibrosis in all cases, its subsequent adhesion is variable and probably has clinical relevance. Further studies could be directed toward identifying specific mediators that promote epithelial-stromal interaction and firm anchoring of epithelium to the underlying stroma.

Adult↗