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Biomedical subjects

A Negi

Publications and source records attributed to A Negi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Noradrenaline receptor-mediated potentiation of caffeine-induced Ca( 2+)-activated K(+) currents in bovine ciliary muscle cells.

PURPOSE: Adrenoceptor-mediated modulation of a caffeine (CAF)-induced [Ca(2+)](i) elevation and resulting Ca(2+)-activated K(+) current (I(CAF)) in bovine ciliary muscle (CM) cells were investigated. METHODS: The nystatin-perforated patch clamp technique for the measurement of membrane currents and a microscope based fura-2 fluorescence imaging of [Ca(2+)](i) were applied to CM cells freshly dissociated with collagenase and identified with smooth muscle-specific alpha-isoactin. RESULTS: Under voltage-clamped conditions, noradrenaline (NA) potentiated I(CAF) in a NA concentration-dependent manner without producing current responses to NA when NA was applied alone. NA-induced potentiation of I(CAF) occurred within 20 sec after the application of NA, while the NA-potentiated I(CAF) gradually recovered to the control level within 30 min after removal of NA. Despite the little current response to NA applied alone, NA elicited a [Ca(2+)](i) elevation in a manner similar to that induced by CAF although the NA-induced [Ca(2+ )](i) elevation was smaller than the CAF-induced [Ca(2+ )](i) elevation. In contrast to the significant potentiation of I(CAF) with NA, NA produced little potentiation of the CAF-induced [Ca(2+)](i) elevation. The NA-induced potentiation of I( CAF) was antagonized by an alpha(1) adrenoceptor antagonist, prazosin. Neither clonidine nor isoproterenol had an effect on I(CAF), suggesting that alpha(2) and beta adrenoceptor are not involved in the response to NA. CONCLUSIONS: These results suggest that NA potentiates I( CAF) via alpha(1) adrenoceptor activation and that the NA-induced potentiation occurs at Ca(2+)-activated K(+) channels but not CAF-induced Ca(2+) releasing sites.

Adrenergic alpha-Antagonists↗
PubMed2001

[Three ocular sarcoidosis patients examined by indocyanine green angiography].

PURPOSE: To assess the findings of indocyanine green angiography(IA) in patients with ocular sarcoidosis. SUBJECTS AND METHODS: Three active ocular sarcoidosis patients with various retinochoroidal findings diagnosed by biopsy or systemic examination. Two patients were diagnosed pathologically and one patient was diagnosed clinically. IA & fluorescein angiography(FA) were performed before and after treatment with systemic steroid administration. RESULTS: IA revealed hyperfluorescence surrounding the presumed granulomatous lesions. This hyperfluorescence disappeared immediately after the treatment. FA showed hyperfluorescence continuing even after therapy. CONCLUSIONS: It is purposed that the ring-form hyperfluorescence in IA is due to accelerated vascular permeability in the active sarcoid granuloma. IA, which vividly reflects activity of sarcoid lesions, is an important tool for clinical evaluation of ocular sarcoidosis.

Aged↗
PubMed2001

Profile of glaucoma in a major eye hospital in north India.

PURPOSE: To study the clinical profile and distribution of various subtypes of glaucoma in a referral practice in North India. METHOD: A retrospective analysis was done of 2425 patients who attended the glaucoma clinic in a tertiary eye-care centre for five years from January 1995 to December 1999. A detailed history was obtained and a thorough examination was performed, including gonioscopy, disc assessment, applanation tonometry and automated perimetry. Diurnal variation of IOP and provocative tests for glaucoma were done where applicable. RESULT: Primary angle closure glaucoma (PACG) was the most common glaucoma subtype. The primary open angle glaucoma (POAG) to the PACG ratio was 37:63. Chronic angle closure glaucoma (CACG) was the most common PACG subtype. The majority of CACG cases were relatively asymptomatic. Male dominance was seen for POAG, juvenile open angle glaucoma (JOAG), CACG, normal tension glaucoma (NTG) and secondary glaucomas. Female dominance was seen for ocular hypertension (OHT), acute or intermittent ACG and developmental glaucomas. The mean age in years at presentation was POAG:60.54 years (males 61.54 years, females 59.01 years) and PACG: 55.13 years (males 57.25 years, females 53.60). The three common secondary glaucomas were: glaucoma secondary to adherent leucoma, aphakic and pseudophakic glaucomas and traumatic glaucomas. Advanced glaucoma was detected in 42 to 53% of patients and bilateral blindness in 8 to 14% of patients in various subtypes. CONCLUSION: Compared to Caucasians, glaucoma patients in North India seem to present nearly a decade earlier and the disease is more advanced at presentation. While PACG is the most commonly encountered glaucoma, NTG and exfoliative glaucoma are relatively rare.

Adolescent↗
PubMed2000

Acidic electrolysed water in the disinfection of the ocular surface.

Acidic electrolysed water (AEW) is a colorless solution prepared by the electrolysis of sodium chloride solution, which has potent anti-microbial activity against a wide variety of bacteria, fungi and virus. In this study, the safety and efficacy of an isotonic AEW solution (iAEW) was investigated both in vitro and in vivo using denuded corneas of guinea pigs. Povidone iodine (0.01-1.0%) was used as control. Exposure of P. aeruginosa to iAEW for 5 sec caused total inhibition of bacterial growth in vitro. Comparable results were obtained with 1% povidone iodine, while more dilute solutions required longer exposure times for similar effects. Cytotoxicity of iAEW on corneal epithelial cells in vitro was significantly less compared to 1% povidone iodine (P<0.05), while minimal damage was observed in vivo by irrigation of the cornea with either iAEW or 1% povidone iodine. Treatment of P. aeruginosa with iAEW (15 sec) significantly inhibited the onset of corneal infection in guinea pigs. iAEW may offer an effective and safe method for disinfection of the ocular surface.

Disinfectants↗
PubMed2000

Expression of Sonic hedgehog and retinal opsin genes in experimentally-induced myopic chick eyes.

The purpose of this study was to evaluate changes in the expression of different genes in chick retinal tissues after induction of experimental myopia and to evaluate the roles of these genes in the regulation of postnatal eye growth and myopia. Form-deprivation using occlusive goggles and hyperopic defocus by negative spectacle lenses were used to induce myopia in hatched chicks. Expression levels of Sonic hedgehog, its receptor complex, and other retinal cell genes were evaluated by semi-quantitative reverse transcription-polymerase chain reaction. Levels of Sonic hedgehog protein were further evaluated by Western blot analysis. The induction of myopia caused significant increase in expression of Sonic hedgehog mRNA and protein and increased expression of blue and red opsin mRNA. In contrast, the expression of mRNA for Sonic hedgehog receptor complex (Patched-Smoothened), rhodopsin, vimentin, green opsin, violet opsin, and HPC-1 were unaffected by the induction of myopia. The increase in expression of Sonic hedgehog in chick retinas in experimentally-induced myopia suggests involvement in the retina control of postnatal eye growth. Furthermore, Sonic hedgehog may influence the expression of blue and red opsins under myopic conditions.

Animals↗
PubMed2000

The process of closure of experimental retinal holes in rabbit eyes.

BACKGROUND: To investigate the healing process of retinal holes, including the identification of the cell types which play an important role in the process, we created experimental retinal holes with minimal damage to retinal pigment epithelium (RPE) in rabbit eyes. METHODS: Pars plana vitrectomy was performed in the rabbit eye. A dome-shaped retinal detachment (bleb; diameter 1.5 mm) was made by injecting balanced salt solution into the subretinal space, followed by making a retinal hole (diameter 0.5 mm) in the center of the bleb with a silicone-tipped extrusion needle. In one group of rabbits, fluid-air exchange was performed and sulfur hexafluoride gas was injected into the vitreous cavity postoperatively. In another group, gas tamponade was not performed. The operated eyes were examined ophthalmoscopically and enucleated at 1, 4, 7, 14, 30, and 90 days after surgery. Tissues were prepared in 5-microm sections for hematoxylin-eosin staining and immunohistochemistry with antibodies to cytokeratin 18 and glial fibrillary acidic protein (GFAP) and examined by light microscopy. RESULTS: In the gas-injected eyes, the retinal holes were ophthalmoscopically closed by 7 days after the surgery. Microscopic examination revealed that the sensory retina around the retinal hole was reattached, and the area of retinal defect was covered with cells which were positive for cytokeratin 18 and GFAP by 7 days after the surgery. In the eyes without gas tamponade, the retinal holes did not close during the observation period. CONCLUSIONS: These findings suggest that early attachment between the sensory retina and RPE could be essential for closure of a retinal hole, where glial and RPE cells might play an important role. This model seems to be useful to investigate the process of closure of retinal holes.

Animals↗
PubMed2000

Susac syndrome.

PURPOSE: To report the first Japanese case of the Susac syndrome characterized by microangiopathy of the brain, retina, and cochlea. METHODS: Case report. A 36-year-old Japanese man underwent extensive clinical and laboratory examination for encephalopathy, bilateral recurrent branch retinal arterial occlusion, and hearing loss. RESULTS: This case was initially diagnosed as acute disseminated encephalomyelitis. Despite exhaustive clinical and laboratory examination of the patient, no evidence of a known systemic disease was found. The bilateral recurrent branch retinal arterial occlusions were widely disseminated. Remission occurred 1 year after symptom onset. This patient demonstrated all of the clinical features associated with the Susac syndrome. CONCLUSION: Susac syndrome has been considered rare, but it is probably more common than previously thought and seems to occur in any race. This disorder usually occurs in young women, but it can affect men.

Adult↗
PubMed2000

Effect of infusion air pressure on visual field defects after macular hole surgery.

PURPOSE: A defect in the visual field is one of the serious complications of macular hole surgery. We investigated the relationship between the occurrence of visual field defect and the location of infusion cannula and air pressure during fluid-air exchange. METHODS: We studied 100 eyes from 90 patients with macular holes. All patients underwent preoperative and postoperative visual field testing. Vitreous surgery was performed in a standard three-port fashion, with surgically induced posterior vitreous detachment, fluid-air exchange, and sulfur hexafluoride gas injection. We analyzed differences in surgical methods in three groups. In group A, the infusion cannula was placed inferotemporally, and the air pressure was set at 50 mm Hg. In group B, the infusion cannula was placed inferonasally, and the air pressure was set at 50 mm Hg. In group C, the infusion cannula was placed inferotemporally, and the air pressure was set at 30 mm Hg. RESULTS: Eighteen eyes (18%) showed visual field defects after vitrectomy. The defect was always located contralateral to the infusion cannula. There was no statistically significant difference in the incidence of visual field defects in groups A and B. Decreased air pressure reduced the occurrence of visual field defects significantly (24% in group A versus 4% in group C, P = .011). CONCLUSIONS: The location of the visual field defect correlated with the location of the infusion cannula. The incidence of this visual field defect was influenced strongly by the infusion air pressure. The visual field defect may be caused by the mechanical damage of air infusion.

Aged↗
PubMed2000

Posterior capsule tear with plate-haptic silicone intraocular lens dislocation.

We report a case of posterior capsule rupture and posterior dislocation of an intraocular lens (IOL) caused by the tip of a silicone plate-haptic lens. The dislocation occurred during IOL implantation after uneventful phacoemulsification in a patient with a small pupil. Discussed are the possible reasons for the complication and measures to prevent it.

Aged↗
PubMed2000

New perimetric threshold test algorithm with dynamic strategy and tendency oriented perimetry (TOP) in glaucomatous eyes.

PURPOSE: To investigate the time-wise reliability and efficiency of two new perimetric test algorithms, two computerised static threshold perimetry strategies, namely dynamic strategy (DS) and tendency oriented perimetry (TOP), were compared with the standard full-threshold strategy (normal strategy, NS). METHODS: We examined 41 eyes of 41 normal individuals without any ocular disease and 36 eyes of 36 glaucomatous patients, with the NS (4-to-2 dB), DS and TOP using an Octopus 1-2-3 perimeter. We analysed test time, stimulus time and the two global indices, mean sensitivity (MS) and loss variance (LV). Program 32X was used as test grid pattern. RESULTS: The mean test time for the NS was reduced by 52% with the DS and by 78% with the TOP strategy. Concerning the global indices, the MS value did not differ among the three strategies in the control or glaucoma group. However, the LV value was lower in the TOP strategy compared with the other two strategies in the glaucoma group. This suggested that the TOP strategy underestimated local glaucomatous visual field defects. The ability to detect early-stage glaucoma with the DS and TOP was inferior to that with the NS. CONCLUSIONS: The DS was more efficient than the TOP strategy for the detection of early glaucomatous defects, whereas the TOP strategy required less testing time. The TOP strategy may be an appropriate approach for patients in whom time-consuming perimetry is not possible, or in whom the visual field defect is already advanced.

Adult↗
PubMed2000

Expression and localization of enzymes of arginine metabolism in the rat eye.

PURPOSE: Production of NO may be regulated by argininosuccinate synthetase and argininosuccinate lyase which recycle citrulline to arginine, and by arginase which hydrolyzes arginine to urea and ornithine. Expression of these and related enzymes in rat eye was studied. METHODS: mRNAs for the enzymes were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). Localization of the enzyme proteins and mRNAs was analyzed by immunohistochemistry and in situ hybridization, respectively. RESULTS: In RT-PCR analysis, arginase II (nonhepatic type) mRNA was detected in retina and weakly in cornea, whereas arginase I (hepatic type) mRNA was not detected in any area. mRNAs for argininosuccinate synthetase, argininosuccinate lyase, ornithine aminotransferase and ornithine decarboxylase were present in all areas. In immunohistochemical analysis, arginase II was stained in cornea, epithelium of iris and ciliary process, inner part of neural retina and retinal pigment epithelium. Immunostaining of ornithine aminotransferase resembled that of arginase II. In in situ hybridization, arginase II and ornithine aminotransferase mRNAs were located much as seen with the enzyme proteins. CONCLUSIONS: These results indicate that arginine recycling activity from citrulline is present widely in ocular tissues, whereas expression of arginase II differs among the tissues. We suggest that NO production may be regulated by these enzymes in the cells where NO synthase is colocalized. Colocalization of arginase II and ornithine aminotransferase suggests a role for arginase II in collagen synthesis in the eye.

Animals↗
PubMed2000

Retinal damage by air infusion during vitrectomy in rabbit eyes.

PURPOSE: Visual field defects after vitrectomy can be seen after any surgery involving fluid-air exchange. To elucidate the effect during surgery of the infused air on the retina, the present study investigated the changes in the morphology of the rabbit retina induced by air infusion and the changes resulting from varying amounts of infused air pressure. METHODS: Eighteen eyes of 18 rabbits were used. A standard three-port vitrectomy with artificial posterior vitreous detachment followed by fluid-air exchange was performed in 12 eyes. During the fluid-air exchange, humidified air was infused with an air pressure of 25 or 40 mm Hg for 30 seconds. As a control, vitrectomy without fluid-air exchange was performed in six eyes. The eyes were enucleated and fixed immediately. Specimens were processed and examined by light and scanning electron microscopy (SEM). RESULTS: With SEM, sharply demarcated retinal lesions were observed at the opposite side from the infusion cannula in all eyes in which a fluid-air exchange was performed. At the lesion, the internal limiting membrane was often detached, and the underlying nerve fiber layer was exposed. Light microscopy revealed that the inner retina was most affected, with concomitant swelling of the inner plexiform layer and the inner granular layer. In addition, the retina was often focally detached with adhesion of some retinal pigment epithelial cells to the photoreceptor cells. Increased infused air pressure was accompanied by a significant increase in the area of retinal damage. In contrast, no morphologic change was observed in the control eyes. CONCLUSIONS: Air infusion during vitrectomy can cause mechanical retinal damage in the rabbit retina. The mechanical damage may result in a visual field defect after vitrectomy.

Air↗
PubMed1999

Expression of citrulline-nitric oxide cycle in lipopolysaccharide and cytokine-stimulated rat astroglioma C6 cells.

Nitric oxide (NO) is involved in many physiological and pathological processes in the brain. NO is synthesized from arginine by nitric oxide synthase (NOS), with citrulline generated as a by-product of the reaction. Thus, citrulline can by recycled to arginine by argininosuccinate synthetase (AS) and argininosuccinate lyase (AL) via the citrulline-NO cycle. Rat astroglioma C6 cells were treated with bacterial lipopolysaccharide (LPS), interferon-gamma (IFNgamma) and tumor necrosis factor-alpha, and the expression of the enzymes of the citrulline-NO cycle was investigated by RNA blot and immunoblot analyses. NO production from arginine and citrulline was also assessed. iNOS mRNA and protein were induced 6-12 h after stimulation with LPS and cytokines and decreased at 24 h. AS mRNA increased up to 12 h and decreased at 24 h. AS protein increased gradually up to 48 h. On the other hand, AL mRNA remained unchanged by stimulation. NO production from arginine was enhanced by the treatment with LPS and cytokines. NO production was also observed when arginine was replaced by citrulline. These results indicate that NO production is enhanced in LPS- and cytokine-stimulated C6 cells due to induction of iNOS and that the citrulline-arginine recycling is important for NO production.

Animals↗
PubMed1999

Unusual self-association properties of transthyretin Y114C related to familial amyloidotic polyneuropathy: effects on detection and quantification.

We performed biochemical and immunological examinations of heterozygotic carriers of the transthyretin (TTR) mutant Y114C associated with familial amyloidotic polyneuropathy (FAP). The total serum TTR levels in Y114C TTR carriers were extremely low when analyzed by single radial immunodiffusion (SRID), whereas by indirect enzyme-linked immunosorbent assay (ELISA) procedure, their total TTR concentrations were increased. Recombinant homozygotic Y114C TTR showed no immunoreactivity towards a TTR antibody when analyzed by SRID, whereas by the ELISA procedure presented the same degree of reactivity as that of normal TTR or isolated serum heterozygotic Y114C TTR. These results indicate that immunodifusion based techniques cannot properly determine TTR serum levels in Y114C carriers. Analyses of serum TTR of the Y114C TTR carriers by electrospray ionization mass spectrometry (ESI-MS) with the orifice corn voltage at 60 V revealed a small peak of the free Y114C TTR in addition to large TTR peaks of normal TTR. The levels of the free mutant TTR increased with the orifice corn voltage at 90 V. In contrast, increase in orifice voltage from 60 to 90 V produced a reduction in the level of normal TTR. The results suggest a different pattern of association between monomers in Y114C relative to normal TTR.

Adult↗
PubMed1999

Vitreous surgery for traumatic macular holes.

PURPOSE: To review the anatomic and visual outcomes of a series of patients with traumatic macular holes who underwent vitreous surgery without adjunctive therapy. METHODS: We performed a retrospective chart review of 23 patients who underwent vitrectomy, fluid-gas exchange, and sulfur hexafluoride gas tamponade for traumatic macular holes. Anatomic success rate and final visual improvement after the surgery were studied. RESULTS: Medical records of 23 patients (23 eyes) who underwent this procedure were reviewed. Closure of the macular hole was achieved in 16 (70%) eyes with one surgery and in 22 (96%) of the 23 eyes with two surgeries. The mean best-corrected preoperative visual acuity was 20/160, and postoperative visual acuity was 20/60 with a mean (+/- standard deviation) follow-up of 23+/-13 months (range 3-56 months). Fourteen (61 %) of the 23 eyes achieved a best-corrected postoperative visual acuity of 20/60 or better, and 11 (48%) of the 23 eyes achieved 20/40 or better. Twenty (87%) of the 23 eyes achieved at least two lines of visual improvement. CONCLUSIONS: Vitreous surgery without adjunctive therapy for traumatic macular holes can lead to anatomic success and visual acuity improvement in most eyes.

Adolescent↗