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Biomedical subjects

A R Vasavada

Publications and source records attributed to A R Vasavada.

At least 19 recordsLinked to original sources
PubMed2005

Cassini Imaging Science: initial results on Saturn's atmosphere.

The Cassini Imaging Science Subsystem (ISS) began observing Saturn in early February 2004. From analysis of cloud motions through early October 2004, we report vertical wind shear in Saturn's equatorial jet and a maximum wind speed of approximately 375 meters per second, a value that differs from both Hubble Space Telescope and Voyager values. We also report a particularly active narrow southern mid-latitude region in which dark ovals are observed both to merge with each other and to arise from the eruptions of large, bright storms. Bright storm eruptions are correlated with Saturn's electrostatic discharges, which are thought to originate from lightning.

Atmosphere↗
PubMed2005

Cassini Imaging Science: initial results on Phoebe and Iapetus.

The Cassini Imaging Science Subsystem acquired high-resolution imaging data on the outer Saturnian moon, Phoebe, during Cassini's close flyby on 11 June 2004 and on Iapetus during a flyby on 31 December 2004. Phoebe has a heavily cratered and ancient surface, shows evidence of ice near the surface, has distinct layering of different materials, and has a mean density that is indicative of an ice-rock mixture. Iapetus's dark leading side (Cassini Regio) is ancient, heavily cratered terrain bisected by an equatorial ridge system that reaches 20 kilometers relief. Local albedo variations within and bordering Cassini Regio suggest mass wasting of ballistically deposited material, the origin of which remains unknown.

Extraterrestrial Environment↗
PubMed2005

Cassini Imaging Science: initial results on Saturn's rings and small satellites.

Images acquired of Saturn's rings and small moons by the Cassini Imaging Science Subsystem (ISS) during the first 9 months of Cassini operations at Saturn have produced many new findings. These include new saturnian moons; refined orbits of new and previously known moons; narrow diffuse rings in the F-ring region and embedded in gaps within the main rings; exceptionally fine-scale ring structure in moderate- to high-optical depth regions; new estimates for the masses of ring-region moons, as well as ring particle properties in the Cassini division, derived from the analysis of linear density waves; ring particle albedos in select ring regions; and never-before-seen phenomena within the rings.

Journal Article↗
PubMed2004

Epidemiology based etiological study of pediatric cataract in western India.

BACKGROUND: Cataract is responsible for about 10% blindness among children in India. Etiology of cataract is not well defined especially for childhood cataracts and epidemiological data for Indian population is not available in details. AIM: This study was performed to survey the causes of childhood cataracts and to identify the preventable factors in four western states of India. SETTINGS AND DESIGN: The present study is a hospital-based, prospective study on 172 consecutive pediatric cataract patients. MATERIAL AND METHODS: Type of cataract was determined using slit-lamp bio-microscopy or operation microscope after mild general anesthesia especially on very young babies. Other anomalies of eye were determined using appropriate ophthalmic instruments. Parents of the patients were interviewed in their native language using a standardized questionnaire. Biochemical and microbiological tests such as for rubella, reducing sugar and blood glucose were also performed. RESULTS: Out of 172 children, 88.4% had non-traumatic cataract and 11.6% had traumatic cataracts. Among non-traumatic cataracts, 7.2% were hereditary, 4.6% were due to congenital rubella syndrome, 15.1% were secondary and 73.0% were undetermined. In the group of undetermined cases, during pregnancy 67% of the mother had history of illness, and 22% had taken medications during pregnancy. CONCLUSIONS: Our study shows that nearly 12% of non-traumatic cataract is due to potentially preventable causes. Health education of women to childbearing age and school children can decrease incidence of pediatric cataracts.

Adolescent↗
PubMed2003

Sequential effects of ultraviolet radiation on the histomorphology, cell density and antioxidative status of the lens epithelium--an in vivo study.

In vivo progressive effects of UV irradiation on the lens epithelium were studied using various histomorphological and biochemical parameters. Fifteen day old rat pups were exposed to 600 mW/m2 of radiation, including UV-A and UV-B, 12 h daily for 90, 120, 150 and 180 days. Biochemical parameters such as protein-bound and non-protein-bound sulfhydryl groups in both soluble and insoluble fractions and enzymes, which play an important role in combating the oxidative stress, were studied. Decreased cell density of lens epithelial cells (LEC) was observed in all three zones along with the decrease in the levels of soluble sulfhydryls (S-SH), glutathione reductase (GR), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT). On the other hand, an increase in insoluble sulfhydryls was observed. Because of the decrease in S-SH and GR activities, the LEC became vulnerable to oxidative stress. Decreased activities of SOD, GPx and CAT suggest elevated oxidative stress. This effect of UV radiation may lead to cell death that may be responsible for the observed decrease in the cell density in all three zones of the lens epithelium.

Animals↗
PubMed2001

Acute transient bilateral diabetic posterior subcapsular cataracts(1).

A 62-year-old man in whom diabetes was recently detected presented with visually significant, bilateral posterior subcapsular cataracts within days of initiating antihyperglycemic therapy. With efficient control and a stable serum glucose level, the cataracts started regressing. Except for a few scattered opacities, the patient was left with essentially clear lenses. Visual acuity of counting fingers at 2 ft in the right eye and 20/63 in the left eye improved to 20/20 in both eyes within 5 weeks.

Acute Disease↗
PubMed2001

Necessity of vitrectomy when optic capture is performed in children older than 5 years.

PURPOSE: To determine whether anterior vitrectomy is necessary when optic capture is performed in children between 5 and 12 years old with congenital cataract. SETTING: Iladevi Cataract and IOL Research Center, Ahmedabad, India. METHODS: This prospective randomized controlled study comprised 41 eyes of 25 children whose mean age was 83.57 months (range 60 to 144 months). Intraocular lens (IOL) implantation with optic capture through a primary posterior continuous curvilinear capsulorhexis was performed in all the eyes. The IOL haptics were bag fixated. Patients were randomly assigned to 1 of 2 groups. Vitrectomy was performed in 1 group (n = 21 eyes) and not performed in the other group (n = 20 eyes). The mean follow-up was 21.04 months. A Student t test and chi-square test were used for statistical analysis. RESULTS: All eyes in the vitrectomy group and 30% in the no-vitrectomy group had a clear visual axis at the last follow-up (P <.001) The visual axis was obscured as a result of anterior vitreous fibrosis in 70% of eyes in the no-vitrectomy group. High-contrast visual acuity was not significantly different between groups (P =.28). Low-contrast sensitivity was significantly better in the vitrectomy group (P =.02). Eighteen eyes (85.7%) in the vitrectomy group and 16 eyes (80%) in the no-vitrectomy group developed deposits on the IOL (P =.62). The deposits were present at the last follow-up in 4 eyes (19.0%) in the vitrectomy group and in 6 eyes (30.0%) in the no-vitrectomy group (P =.85). Three eyes (14.3%) in the vitrectomy group and 8 eyes (40.0%) in the no-vitrectomy group developed synechias (P =.06). CONCLUSION: The results suggest that anterior vitrectomy is necessary with optic capture in children with congenital cataract who are between 5 and 12 years old.

Capsulorhexis↗
PubMed2001

Phacoemulsification of brunescent and black cataracts.

PURPOSE: To evaluate the efficacy and safety of a step-by-step, chop in situ, lateral separation technique to remove brunescent and black cataracts. SETTING: Iladevi Cataract and IOL Research Center, Ahmedabad, India. METHODS: In this prospective study conducted between May 1997 and June 1998, 167 consecutive eyes were divided into 2 groups: Group 1, brunescent cataract (n = 123), and Group 2, black cataract (n = 44). Preoperative assessment included axial length (AL), slitlamp examination, corneal pachymetry, tonometry, and specular microscopy. During phacoemulsification performed by a single surgeon, a step-by-step, chop in situ, lateral separation technique was used to divide the nucleus. Intraoperatively, hydroxypropyl methylcellulose 2% was used and irrigation was by balanced salt solution (BSS). Postoperatively, all eyes were assessed at 1, 7, 30, 90, 180, and 360 days. The results were evaluated using regression analysis, the chi-square test, and the Student t test. RESULTS: The mean follow-up was 14.4 months (range 6 to 35 months) in Group 1 and 13.0 months (range 6 to 32 months) in Group 2. The AL was significantly greater in Group 2 (P =.02). Corticapsular adhesions were present in 17.82% in Group 1 and 31.82% in Group 2. The mean cumulative dissipated energy was 2.03 and 3.12, respectively (P =.0005). Wound site thermal injury occurred in 16 eyes (13.01%) in Group 1 and 4 eyes (9.09%) in Group 2. No serious intraoperative or postoperative complications were noted. One day postoperatively, the mean rise in intraocular pressure was 1.76 mm Hg in Group 1 and 4.15 mm Hg in Group 2 (P =.012), and transient corneal edema was present in 24.40% and 34.10%, respectively. At 1 month, the endothelial cell loss was 10.06% in Group 1 and 9.22% in Group 2. CONCLUSION: The step-by-step, chop in situ, lateral separation technique was effective and did not produce serious complications such as zonulysis or posterior capsule rupture. However, the incidence of wound site thermal injury and endothelial cell loss was greater than after emulsification of standard cataracts.

Acetates↗
PubMed2000

Proximate humid and dry regions in Jupiter's atmosphere indicate complex local meteorology.

Models of Jupiter's formation and structure predict that its atmosphere is enriched in oxygen, relative to the Sun, and that consequently water clouds should be present globally near the 5-bar pressure level. Past attempts to confirm these predictions have led to contradictory results; in particular, the Galileo probe revealed a very dry atmosphere at the entry site, with no significant clouds at depths exceeding the 2-bar level. Although the entry site was known to be relatively cloud-free, the contrast between the observed local dryness and the expected global wetness was surprising. Here we analyse near-infrared (around 5 microm) observations of Jupiter, a spectral region that can reveal the water vapour abundance and vertical cloud structure in the troposphere. We find that humid and extremely dry regions exist in close proximity, and that some humid regions are spatially correlated with bright convective clouds extending from the deep water clouds to the visible atmosphere.

Atmosphere↗
PubMed2000

Induction of cataracts of varying degrees of hardness in human eyes obtained postmortem for cataract surgeon training.

PURPOSE: To report a method of inducing nuclear cataracts of varying degree of hardness using intralenticular injection of the Karnovsky solution. METHODS: Twelve postmortem human eyes were prepared according to the Miyake-Apple posterior video technique. After performing capsulorhexis and hydrodissection/delineation, 0.2 ml of the Karnovsky solution was injected into the lens nucleus of the eyes. Manual extracapular cataract extraction techniques and various two-handed phacoemulsification maneuvers were then practiced at various time intervals after the injection. RESULTS: Uniform nuclear cataracts with varying degrees of hardness were successfully induced in all globes. The optimum dose of the Karnovsky solution and time for induction of nuclear hardness of grade 3 (ideal for practicing two-handed phacoemulsification maneuvers) were 0.2 ml and 15 minutes, respectively. CONCLUSION: The Karnovsky solution can be successfully used for the induction of hard, uniform nuclear cataracts for learning/practicing extracapular cataract extraction and phacoemulsification.

Cataract↗
PubMed2000

Role of optic capture in congenital cataract and intraocular lens surgery in children.

PURPOSE: To evaluate the role of optic capture in eyes having cataract extraction, anterior vitrectomy, and intraocular lens (IOL) implantation for congenital cataract. SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHODS: This prospective study comprised 40 eyes of 28 children, whose mean age was 26.08 months (range 4 to 55 months). Primary posterior continuous curvilinear capsulorhexis, anterior vitrectomy, and IOL implantation were performed in all eyes. Eyes were randomly assigned to 1 of 2 groups of 20 each: in 1 group, optic capture would be used and in the other, the noncapture technique. Permanent optic capture was achieved in 14 eyes, and 26 eyes had no optic capture. Mean follow-up was 16.53 months (range 5 to 24 months). A Student t test and chi-square test were used for statistical analyses. RESULTS: All eyes in both groups maintained a clear visual axis. One eye in the optic-capture group developed a membrane in front of the IOL that required a secondary procedure. Posterior synechia formation was significantly greater in the optic-capture group (P =.04), as were deposits on the IOL optic (P =.0086). Although all eyes in both groups maintained a clinically centered IOL, geometric decentration was more common in the no-capture group (P =.0000). CONCLUSION: Optic capture resulted in better IOL centration but predisposed the eye to an increased uveal inflammatory response.

Biocompatible Materials↗
PubMed2000

Is pseudophakic astigmatism a desirable goal?

PURPOSE: To determine whether pseudophakic astigmatism is a desirable goal, and if so, which one is better: against-the-rule (ATR) or with-the-rule (WTR). METHOD: Eyes were included only if they had an uncorrected vision > or = 6/18 and N/18. Three groups, of 40 patients each were evaluated: group 1, pseudophakes with neutral astigmatism; group 2, with ATR and group 3, with WTR astigmatism Unaided distance and near visual acuity was recorded. Statistical analysis was performed using the chi-square test for independence. RESULTS: Unaided distance vision of > or = 6/7.5 was achieved in 19 eyes (47.5%) of group 1 (neutral), 12 eyes (30%) in group 2 (ATR), and 5 eyes (12.5%) in group 3 (WTR) (p = 0.0133, significant). Unaided near vision of > or = N/9 was achieved in 17 eyes (42.5%) in group 1 (neutral), 34 eyes (85%) in group 2 (ATR), and 10 eyes (25%) in group 3 (WTR) (P < 0.001, significant). Group 1 (neutral) fared the best for unaided distance visual acuity. Group 2 (ATR) was better than in group 3 (WTR) for distant vision. Group 2 (ATR) fared the best for unaided near vision. CONCLUSION: ATR astigmatism could be a desirable goal after cataract extraction in selected populations because the largest proportion of these cases achieved good unaided near vision with acceptable distant vision.

Astigmatism↗
PubMed1999

Posterior capsule striae.

PURPOSE: To find the incidence, contributing factors, outcomes, and clinical impact of intraoperative posterior capsule striae. SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHODS: In a prospective study, 100 consecutive eyes had phacoemulsification and intraocular lens (IOL) (AcrySof MA30BA) implantation. The presence of striae was noted at the end of the operation, and factors contributing to their development were identified. Follow-up was done at regular intervals, and the clinical impact of striae on patients' vision was evaluated. RESULTS: Striae were observed in 56 eyes (Group 1) but were absent in 44 (Group 2). Mean age in Group 1 was 65.96 years +/- 9.15 (SD) and in Group 2, 59.20 +/- 10.36 years (P = .0012). Mean axial lengths were 23.47 +/- 1.63 and 24.12 +/- 1.49 mm, respectively (P = .0419). Average lens thickness was greater in Group 1 (4.50 +/- 0.43 mm) than in Group 2 (4.13 +/- 0.41 mm) (P = .0001). The sex of patient, capsulorhexis size and centration, grade of cataract hardness, scleral rigidity, and IOL centration were not found to contribute to striae development. The striae disappeared by 5 months postoperatively and did not show a positive Maddox rod phenomenon. CONCLUSION: Intraoperative striae observed in many patients were associated with relatively older age, greater lens thickness, and shorter axial length. The striae eventually disappeared and had no effect on vision.

Cataract Extraction↗
PubMed1999

Flash heating on the early Earth.

It has been suggested that very large impact events (approximately 500 km diameter impactors) sterilized the surface of the young Earth by producing enough rock vapor to boil the oceans. Here, we consider surface heating due to smaller impactors, and demonstrate that surface temperatures conductive to organic synthesis resulted. In particular, we focus on the synthesis of thermal peptides. Previously, laboratory experiments have demonstrated that dry heating a mixture of amino acids containing excess Asp, Glu, or Lys to temperatures approximately 170 degrees C for approximately 2 hours yields polypeptides. It has been argued that such temperature conditions would not have been available on the early Earth. Here we demonstrate, by analogy with the K/T impact, that the requisite temperatures are achieved on sand surfaces during the atmospheric reentry of fine ejecta particles produced by impacts of bolides approximately 10-20 km in diameter, assuming approximately 1-100 PAL CO2. Impactors of this size struck the Earth with a frequency of approximately 1 per 10(4)-10(5) y at 4.2 Ga. Smaller bolides produced negligible global surface heating, whereas bolides > 30 km in diameter yielded solid surface temperatures > 1000 K, high enough to pyrolyze amino acids and other organic compounds. Thus, peptide formation would have occurred globally for a relatively narrow range of bolide sizes.

Amino Acids↗