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Biomedical subjects

J Ambati

Publications and source records attributed to J Ambati.

13 recordsLinked to original sources
PubMed2001

Do urinary levels of vascular endothelial growth factor predict proliferative retinopathy?

PURPOSE: Vascular endothelial growth factor (VEGF) is elevated in the vitreous of patients with proliferative retinopathies (PR). Angiogenic factors like VEGF are elevated in the urine of subjects with cancers, including those distant from the genitourinary tract. We hypothesized that local increases in VEGF in the vitreous would be reflected in the urine of subjects with PR. METHODS: Urine samples were collected from adults with absent, mild, or severe (requiring laser photocoagulation) PR. VEGF was measured by enzyme linked immunosorbent assay. RESULTS: Of 42 subjects, 16 had no PR and 26 had PR (8 mild, 18 severe). Thirty subjects had diabetes mellitus; 24 of these had PR. Subjects with PR were older than controls. Subjects with PR tended to have higher urinary VEGF (median 123 pg/ml Cr, range 3--1738) than controls without PR (median 93 pg/ml Cr, range 2--200) (p = 0.08). None of 16 controls, but 11/15 subjects with PR had >200 mg VEGF/mg Cr (p = 0.003), yielding high specificity (100%), but poor sensitivity (42%) of elevated urinary VEGF for PR. Urinary VEGF was also modestly correlated with urinary protein excretion (r(2 ) = 0.23). Correction of VEGF values for urinary protein abrogated any correlation with PR. CONCLUSIONS: Urinary levels of VEGF are associated with PR, but this relationship may be caused by concurrent renal diseases that result in proteinuria and/or renal VEGF production. The insensitivity of the association may preclude its use in screening to avoid eye examinations.

Diabetic Retinopathy↗
PubMed2000

Periorbital and orbital cellulitis before and after the advent of Haemophilus influenzae type B vaccination.

OBJECTIVE: To evaluate the effect of the introduction of the Haemophilus influenzae B (Hib) vaccine (introduced first in 1985, then extended in 1990 to children at least 2 months of age) on the epidemiologic features of periorbital and orbital cellulitis. DESIGN: Retrospective, comparative case series. PARTICIPANTS: Three hundred fifteen pediatric inpatients. METHODS: Children at Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary with discharge diagnosis of periorbital or orbital cellulitis from 1980 through 1998 were reviewed. MAIN OUTCOME MEASURES: Case rate, culture-positive isolates, and associated conditions. RESULTS: A total of 297 cases of periorbital cellulitis and 18 cases of orbital cellulitis were reviewed. Before 1990, there were 27 cases of Hib-related cellulitis (11.7% of total in that period), whereas after 1990, there were only three (3.5% of total; P = 0.028). The number of cases per year was significantly lower after 1990 (21.2 +/- 10.4 vs. 8.7 +/- 3.9; P = 0.008), as were the number of positive culture isolates (for any organism) after 1990 (76 [33. 0%] vs. 9 [10.6%]; P < 0.001). The medical conditions most commonly associated with periorbital cellulitis were sinusitis (44 [14.5%]) and upper respiratory infections (73 [26.6%]). All cases of orbital cellulitis were associated with sinusitis. CONCLUSIONS: The introduction of the Hib vaccine coincided with a sharp decline not only in the number of periorbital and orbital cellulitis cases related to H. influenzae, but also in the annual case rate. These data are consistent with a facilitative role for H. influenzae in the development of cellulitis secondary to other pathogens. They also may support restriction of the spectrum of antibiotics used to manage these conditions.

Cellulitis↗
PubMed2000

Postoperative complications of scleral buckling surgery.

The postoperative course of scleral buckling surgery can witness a host of untoward events, which may undo the anatomical success of retinal reattachment. Diligent preoperative identification of all retinal breaks and meticulous intraoperative technique will enhance the likelihood of a tranquil postoperative course.

Humans↗
PubMed2000

Diffusion of high molecular weight compounds through sclera.

PURPOSE: To determine the in vitro permeability of the sclera to high molecular weight compounds and the relationship between scleral permeability and molecular size. METHODS: Fresh rabbit sclera was mounted in a two-chamber diffusion apparatus, and its permeability to sodium fluorescein, fluorescein isothiocyanate (FITC)-conjugated bovine serum albumin, FITC-IgG, and FITC dextrans ranging in molecular weight from 4 to 150 kDa was determined by fluorescence spectrophotometry. Electron microscopy was used to assess the impact of the experimental design on scleral ultrastructural integrity. The effect of the diffusion apparatus on scleral hydration was examined. Rabbit scleral permeability was compared with previously reported data for human and bovine sclera. RESULTS: Scleral permeability decreased with increasing molecular weight and molecular radius, consistent with previous human and bovine data. Molecular radius was a better predictor of scleral permeability than molecular weight. The sclera was more permeable to globular proteins than to linear dextrans of similar molecular weight. The experimental apparatus did not alter scleral ultrastructure. Permeability of rabbit sclera was similar to human sclera but greater than bovine sclera. CONCLUSIONS: Large molecules, such as IgG, diffuse across sclera in a manner consistent with porous diffusion through a fiber matrix. Transscleral delivery of immunoglobulins and other large compounds to the choroid and retina may be feasible.

Animals↗
PubMed2000

Transscleral delivery of bioactive protein to the choroid and retina.

PURPOSE: To investigate the feasibility of transscleral drug delivery to the choroid and retina. METHODS: An osmotic pump was used to deliver IgG across the sclera of pigmented rabbits, and levels were measured in the choroid, retina, vitreous humor, aqueous humor, orbit, and plasma over 28 days. This method was then used to deliver an anti-intercellular adhesion molecule-1 (ICAM-1) monoclonal antibody (mAb), and its effect on inhibiting vascular endothelial growth factor (VEGF)-induced leukostasis in the choroid and retina was determined by measuring tissue myeloperoxidase (MPO) activity. RESULTS: Levels of retinal and choroidal IgG were significantly higher than baseline at all points up to 28 days (P < or = 0.01). IgG levels in the orbit, vitreous humor, aqueous humor, and plasma were negligible (P > 0.05). MPO activity in the choroid of eyes treated with anti-ICAM-1 mAb was 80% less (P = 0.01) than in eyes receiving an equal rate of delivery of an isotype control antibody. Inhibition of MPO activity in the retina was 70% (P = 0.01). The plasma concentration of anti-ICAM-1 mAb was 31,000-fold less than the concentration in the osmotic pump. CONCLUSIONS: Minimally invasive transscleral delivery can be used to deliver therapeutic levels of bioactive drugs to the choroid and retina with negligible systemic absorption. This method of ocular drug delivery may be used in the treatment of a variety of chorioretinal disorders.

Animals↗
PubMed1999

Anterior uveitis associated with intravenous cidofovir use in patients with cytomegalovirus retinitis.

AIM: Intravenous cidofovir is used to treat cytomegalovirus (CMV) retinitis, and has been reported to cause anterior uveitis. Relations were sought between this complication and patient characteristics that might help predict its occurrence. METHODS: 17 patients with AIDS and CMV retinitis who were treated with intravenous cidofovir were identified, and the following data collected in a retrospective chart review: demographic characteristics, duration of CMV retinitis, retinal lesion characteristics, dose and duration of cidofovir therapy, tests of renal function, CD4+ T lymphocyte counts, visual acuity, intraocular pressure, iris colour, history of diabetes mellitus, and use of concomitant medications. Case-control analyses were performed to determine risk factors for developing cidofovir associated uveitis. RESULTS: Anterior uveitis characterised by pain, ciliary injection, and decreased visual acuity occurred in 10 patients (59%). Median interval to development of uveitis was 11 doses of cidofovir. Symptoms developed 4.4 (SD 2.5) days (median 3.5) after an infusion of cidofovir. Patients who developed uveitis had a significantly greater rise in CD4+ T lymphocyte count while receiving cidofovir (68.4 (75.7) x10(6)/l versus 5.0 (0.6) x10(6)/l, (p = 0.04)). By stepwise linear regression, this factor accounted for 33% (p = 0.03) of the effect of developing uveitis. Mean follow up time, intraocular pressure decline during cidofovir therapy, serum creatinine and urine protein concentrations, and rates of protease inhibitor use were not significantly different between patients who developed uveitis and those who did not. Uveitis responded to topical corticosteroids and cycloplegia. CONCLUSION: Anterior uveitis in patients receiving intravenous cidofovir therapy may be related to improving immune function. The uveitis responds to treatment and may not preclude continuation of cidofovir.

AIDS-Related Opportunistic Infections↗
PubMed1998

Ice incubation step allows adherence of archival histological specimens on gelatin-coated slides for TUNEL staining.

Gelatin-coated slides provide poor tissue adherence during histological procedures which require 37 degreesC incubations, such as terminal deoxynucleotidyl transferase nick-end labelling (TUNEL) analysis. We encountered this difficulty during attempts to analyze archival ocular tissue sections which had been previously sectioned and mounted on gelatin-coated slides. The solution to this problem turned out to be relatively straightforward: Immediately after the 37 degreesC terminal deoxynucleotide transferase step, we incubated the slides on ice for 30 min before continuing with the remainder of the protocol. This ice-incubation step re-solidified the melted gelatin, which allowed for continued adherence of the tissue specimen for further manipulations. This modified TUNEL staining protocol has been used successfully to analyze 14 archival specimens thus far, which would have been nearly impossible to accomplish otherwise. We believe that this ice re-solidification step for gelatin-coated slides has broad applications for procedures which require 37 degreesC incubations, including TUNEL staining, as well as other in situ hybridization and immunohistochemistry protocols.

Apoptosis↗
PubMed1997

Elevated gamma-aminobutyric acid, glutamate, and vascular endothelial growth factor levels in the vitreous of patients with proliferative diabetic retinopathy.

OBJECTIVE: To examine the relative levels of gamma-aminobutyric acid (GABA), glutamate, and vascular endothelial growth factor (VEGF) in the vitreous of nondiabetic and diabetic patients. METHODS: Undiluted vitreous samples were obtained from 22 patients with proliferative diabetic retinopathy (PDR) and 28 patients without diabetes who underwent pars plana vitrectomy. Simultaneous venous blood samples also were obtained. Amino acid concentrations were determined using sensitive high-performance liquid chromatography, and VEGF levels by quantitative enzyme-linked immunosorbent assay. Hemoglobin concentrations in the blood and vitreous were determined using spectrophotometry. RESULTS: The level of GABA in the vitreous of patients with PDR, 29.4 +/- 7.8 mumol/L, was significantly higher than in controls (18.4 +/- 5.5 mumol/L) (P = .004). The vitreous concentration of glutamate was higher in patients with PDR (24.7 +/- 14.0 mumol/L) compared with controls (9.1 +/- 5.1 mumol/L) (P < .001). Vitreous VEGF level was significantly higher in patients with PDR (1759 +/- 1721 pg/mL) compared with controls (27 +/- 65 pg/mL) (P < .001). There were moderately strong correlations between GABA and VEGF levels (r = 0.68) and glutamate and VEGF levels (r = 0.43). Elevated GABA, glutamate, and VEGF levels also correlated strongly with the presence of PDR. Correcting for possible introduction of these molecules by vitreous hemorrhage did not significantly alter these findings. CONCLUSIONS: Levels of glutamate potentially toxic to retinal ganglion cells are found in the vitreous of patients with PDR. Elevated vitreous GABA may reflect amacrine cell dysfunction and underlie electroretinographic oscillatory potential abnormalities seen in diabetic retinopathy. The correlations of glutamate and GABA levels with an elevated VEGF level provide biochemical support for ischemia-induced neovascularization in patients with PDR. These findings present opportunities for novel therapeutic modalities in the treatment of PDR.

Chromatography, High Pressure Liquid↗
PubMed1997

Dynamics of knowledge and attitudes about AIDS among the educated in southern India.

AIDS awareness and attitudes among an educated segment of the Indian population were assessed. The study population was a total of 433 students and faculty in colleges and universities, and research & technical staff of the Public Health Service. While most knew that sexual intercourse (96%) & injection drug use (85%) could transmit HIV, and that shaking hands (95%) & mosquitoes (86%) could not, 63% did not know that breastfeeding was a mode of transmission and 71% falsely believed that they could acquire HIV by donating blood. The only variable to correlate positively with knowledge was education. Knowledge about true and false modes of transmission constituted three distinct dimensions as determined by factor analysis. An overwhelming majority (90%) harboured at least one hostile view towards persons with AIDS. Knowledge and education independently correlated with decreased hostility. There was great concern about the impact of the disease: 85% believed that AIDS is a very serious problem in India and 93% favoured increased government spending on AIDS education. These results display high levels of knowledge (with some gaps), and widespread support for increased action.

Adolescent↗