Biomedical subjects

L E Smith

Publications and source records attributed to L E Smith.

At least 37 records · Page 2Linked to original sources

PubMed1998

Targeted breakage of paracentromeric heterochromatin induces chromosomal instability.

Current models suggest that genomic instability is crucial in the accumulation of the multiple alterations required for tumorigenesis. However, the nature of the initial damage responsible for the origin of genomic instability remains poorly understood. In this investigation we demonstrate that the nucleotide analog 2,6-diaminopurine (DAP) can be used to induce highly focused damage to the large blocks of paracentromeric heterochromatin on chromosomes 1, 9 and 16. A large fraction of cells exposed to DAP exhibit undercondensation of alpha and classical heterochromatin which persists into metaphase. Subsequent chromosome breakage was observed for one of the target chromosomes by preferential exclusion of chromosome 16 fragments into micronuclei (P < 0.0001). The specificity of DAP-induced chromosomal breakage enabled us to utilize it as a reagent to demonstrate that paracentromeric heterochromatin is a sensitive target for the induction of persistent genomic instability. We observed a 100-fold increase in mutagenesis affecting a chromosome 16 marker (APRT) compared with marker loci on chromosomes 17 (TK) or X (HPRT). We previously reported that APRT- mutants were recovered at a high rate upon selection in DAP in a process involving recombinationally mediated loss of heterozygosity that extends from the telomere to the boundary region of the paracentromeric heterochromatin. Karyotypic analysis of DAP-resistant APRT- mutant clones demonstrated extensive genomic instability, particularly evidence of multiple and sequential events affecting chromosome 16. These data suggest that the heterochromatic breakage observed cytogenetically immediately following DAP exposure is also responsible for the initiation of persistent genomic instability.

2-Aminopurine↗

PubMed1998

Fractionated premotor, motor, and ankle dorsiflexion reaction times in hemiplegia.

Ten hemiplegic subjects completed 20 rapid dorsiflexions of their afflicted and nonafflicted limbs. Electrodes were attached to the tibialis anterior and the gastrocnemius muscles and electromyograms were recorded for their premotor time, motor time, and simple reaction time during ankle dorsiflexion and plantar flexion of their lower limbs. The fractionated components of reaction time, namely, premotor time and motor time, of both legs were statistically compared. It was found that the premotor time of the subject's stroke-affected limb was significantly slower than the premotor time of the nonaffected limb (control), with no differences between their associated mean motor times. These results supported the hypothesis that a stroke has a deleterious affect upon the central, premotor time processing centers and has no disruptive influence upon the peripheral motor time. Comparing the fractionated components of reaction time (premotor time and motor time), with simple reaction time, the former provided a more sensitive and valid method to detect possible injurious side effects of a stroke upon the brain's neuromotor transmission centers and subcenters, and their peripheral, stimulus, response network.

Adult↗

PubMed1997

Essential role of growth hormone in ischemia-induced retinal neovascularization.

Retinal neovascularization is the major cause of untreatable blindness. The role of growth hormone (GH) in ischemia-associated retinal neovascularization was studied in transgenic mice expressing a GH antagonist gene and in normal mice given an inhibitor of GH secretion (MK678). Retinal neovascularization was inhibited in these mice in inverse proportion to serum levels of GH and a downstream effector, insulin-like growth factor-I (IGF-I). Inhibition was reversed with exogenous IGF-I administration. GH inhibition did not diminish hypoxia-stimulated retinal vascular endothelial growth factor (VEGF) or VEGF receptor expression. These data suggest that systemic inhibition of GH or IGF-I, or both, may have therapeutic potential in preventing some forms of retinopathy.

Animals↗

PubMed1997

Isolation of an APRT heterozygote from TK6 human lymphoblasts: predominance of multi-locus loss of heterozygosity among spontaneous APRT-mutants.

The TK6 human B lymphoblastoid cell line contains two easily and widely used selectable markers: the X-linked, hemizygous hprt locus, and the heterozygous tk locus on chromosome 17q. In this study, rare APRT heterozygotes were directly isolated from the TK6 population by clonal selection in cell culture medium supplemented with 5 micrograms/ml of 8-azaadenine. One of nine isolated heterozygotes, AZH1, was characterized extensively. APRT- mutants can be recovered from AZH1 at a mutation rate of 1.5 x 10(-7), similar to rates previously determined for the selection of TK- and HPRT- mutants from TK6. A unique sequence alteration was identified in the non-functional aprt allele at position 1930. A G:C to A:T transition at this site alters the canonical AG splice acceptor dinucleotide in exon 3, and also results in the destruction of a Stul recognition sequence. This polymorphism was used to analyze loss of heterozygosity in a set of 32 spontaneous APRT- mutants by restriction analysis following PCR amplification. Analysis of flanking microsatellite dinucleotide polymorphisms demonstrated that LOH occurring in spontaneous APRT- mutants is nearly always a multi-locus event extending at least 7.5 cM along chromosome 16q. This pattern of LOH among APRT- mutants differs from extensive LOH in spontaneous, normal-growth TK- mutants derived from TK6 cells (p < 0.0001), and suggests that cis-acting factors may be equally important in shaping the mutational spectrum as trans-acting factors such as cellular apoptotic capacity.

Adenine↗

PubMed1997

Probes for narcotic receptor mediated phenomena. 23. Synthesis, opioid receptor binding, and bioassay of the highly selective delta agonist (+)-4-[(alpha R)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]- N,N-diethylbenzamide (SNC 80) and related novel nonpeptide delta opioid receptor ligands.

The highly selective delta (delta) opioid receptor agonist SNC 80 [(+)-4- [(alpha R)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N ,N- diethylbenzamide, (+)-21] and novel optically pure derivatives were synthesized from the enantiomers of 1-allyl-trans-2,5-dimethylpiperazine (2). The piperazine (+/-)-2 was synthesized, and its enantiomers were obtained on a multigram scale in > 99% optical purity by optical resolution of the racemate with the camphoric acids. The absolute configuration of (+)-2 was determined to be 2S,5R by X-ray analysis of the salt with (+)-camphoric acid. Since the chirality of the starting material was known, and the relative configuration of compounds (-)-21, (-)-22, and (+)-23 were obtained by single-crystal X-ray analysis, the assignment of the absolute stereochemistry of the entire series could be made. Radioreceptor binding studies in rat brain preparations showed that methyl ethers (+)-21 (SNC 80) and (-)-25 exhibited strong selectivity for rat delta receptors with low nanomolar affinity to delta receptors and only micromolar affinity for rat mu (mu) opioid receptors. Compounds (-)-21, (-)-22, and (-)-23 showed micromolar affinities for delta opioid receptors. The unsubstituted derivative (+)-22 and the fluorinated derivative (-)-27 showed > 2659- and > 2105-fold delta/mu binding selectivity, respectively. The latter derivatives are the most selective ligands described in the new series. Studies with some of the compounds described in the isolated mouse vas deferens and guinea pig ileum bioassays revealed that all were agonists with different degrees of selectivity for the delta opioid receptor. These data show that (+)-21 and (+)-22 are potent delta receptor agonists and suggest that these compounds will be valuable tools for further study of the delta opioid receptor at the molecular level, including its function and role in analgesia and drug abuse.

Animals↗

PubMed1997

Symptomatic improvement and reduced hospitalization for patients attending a cardiomyopathy clinic.

BACKGROUND: The major costs associated with the management of congestive heart failure (CHF) are inpatient costs. Outcome studies are therefore important to establish whether intensive outpatient care for heart failure can reduce these costs while at the same time improving outcomes in this disabling disorder. HYPOTHESIS: Care delivered in a cardiomyopathy clinic might result in objective improvement in cardiac function and symptoms while reducing hospital admissions and emergency department visits. METHODS: The outcomes of 21 patients treated for 6 months in a cardiomyopathy clinic are evaluated. New patients referred to the clinic with ejection fraction (EF) < 0.45 were enrolled. The Minnesota Living with Heart Failure questionnaire was completed at initial and final visits. All patients underwent baseline and final echocardiogram, radionuclide left ventriculogram, and cardiopulmonary exercise testing. Patients were followed by a nurse practitioner and a cardiologist with maximization of standard treatment. Congestive heart failure-related hospitalizations and clinic and emergency room visits for both 6-month periods before and during the study were determined. RESULTS: There was significant (p < 0.05) improvement in these parameters: Heart failure score increased 23 points; New York Heart Association class decreased from 2.6 to 2.2; EF increased from 0.24 to 0.36; diastolic and systolic left ventricular dimensions decreased from 65 to 59 mm and from 57 to 50 mm, respectively. The number of clinic visits increased 5-fold, whereas there were 86% (14 to 2, p = 0.017) and 100% (8 to 0, p = 0.002) reductions in the number of CHF hospitalizations and emergency visits. There was one death during follow-up. CONCLUSION: Managing patients in a cardiomyopathy clinic may result in a better quality of life, with both symptomatic improvement and decreased hospitalizations.

Aged↗

PubMed1997

Histopathology and vascular endothelial growth factor in untreated and diode laser-treated retinopathy of prematurity.

OBJECTIVES: We had the unique opportunity to compare the eyes of a premature infant with stage 3 retinopathy of prematurity (ROP) in both eyes after the condition was treated by diode laser photocoagulation in one eye only. After the infant's death, we investigated the extent of structural damage incurred with the diode laser and examined the effect of treatment on vascular endothelial growth factor (VEGF) expression. METHODS: The eyes were fixed and embedded in paraffin. Adjacent 6 microns sections were either stained for histopathologic analysis or used for in situ hybridization. VEGF messenger RNA (mRNA) was detected by using radiolabeled antisense riboprobes. RESULTS: In the treated eye, histopathologic results demonstrated the clinically evident dose-response effect, with sparing of inner retinal elements with mild laser burns and full-thickness retinal cell disruption with severe burns. Scleral and ciliary nerve effects were absent. VEGF mRNA was localized primarily in the ganglion cell layer but was also found in the inner nuclear layer. In the untreated eye, an increase in VEGF mRNA was detected at the peripheral edge of the vascularized retina anterior to the ridge. In the laser-treated eye, VEGF mRNA expression was dramatically upregulated in the ganglion cell layer in areas adjacent to laser burns. CONCLUSIONS: VEGF mRNA was found to be elevated in the peripheral, avascular retina of the untreated eye, consistent with the hypothesis that retinal hypoxia stimulates VEGF expression. In the treated eye with recurrent ROP, VEGF mRNA was not detected in the photocoagulated areas of retina but was increased between laser scars. This finding confirms the results of prior animal studies and validates the use of these models.

Adult↗

PubMed1997

Directed mutagenesis of the Trypanosoma cruzi trans-sialidase enzyme identifies two domains involved in its sialyltransferase activity.

Of the increasing number of sialidases found to be made by microorganisms, the trypanosome trans-sialidase is unique in its added ability to efficiently carry out a sialyltransferase reaction using preformed glycoconjugates. The enzyme is predicted to have a multidomain structure, with one domain containing sequence and expected structural features found in bacterial sialidases. The trans-sialidase is very similar in overall sequence to another trypanosome enzyme that has only sialidase activity. Hybrid expression constructs containing pieces of these trypanosome trans-sialidase and sialidase genes were used to determine which regions of trans-sialidase are required for sialyltransferase activity. Two domains were found to influence the enzymatic activity: the N-terminal catalytic domain, and a downstream domain that resembles an Fn3-like module.

Amino Acid Sequence↗

PubMed1997

Vascular endothelial growth factor-induced retinal permeability is mediated by protein kinase C in vivo and suppressed by an orally effective beta-isoform-selective inhibitor.

Increased vascular permeability and excessive neovascularization are the hallmarks of endothelial dysfunction, which can lead to diabetic macular edema and proliferative diabetic retinopathy in the eye. Vascular endothelial growth factor (VEGF) is an important mediator of ocular neovascularization and a known vasopermeability factor in nonocular tissues. In these studies, we demonstrate that intravitreal injection of VEGF rapidly activates protein kinase C (PKC) in the retina at concentrations observed clinically, inducing membrane translocation of PKC isoforms alpha, betaII, and delta and >threefold increases in retinal vasopermeability in vivo. The effect of VEGF on retinal vascular permeability appears to be mediated predominantly by the beta-isoform of PKC with >95% inhibition of VEGF-induced permeability by intravitreal or oral administration of a PKC beta-isoform-selective inhibitor that did not inhibit histamine-mediated effects. These studies represent the first direct demonstration that VEGF can increase intraocular vascular permeability through activation of PKC in vivo and suggest that oral pharmacological therapies involving PKC beta-isoform-selective inhibitors may prove efficacious for the treatment of VEGF-associated ocular disorders such as diabetic retinopathy.

Animals↗

PubMed1996

Oligodeoxynucleotides inhibit retinal neovascularization in a murine model of proliferative retinopathy.

Diseases characterized by retinal neovascularization are among the principal causes of visual loss worldwide. The hypoxia-stimulated expression of vascular endothelial growth factor (VEGF) has been implicated in the proliferation of new blood vessels. We have investigated the use of antisense phosphorothioate oligodeoxynucleotides against murine VEGF to inhibit retinal neovascularization and VEGF synthesis in a murine model of proliferative retinopathy. Intravitreal injections of two different antisense phosphorothioate oligodeoxynucleotides prior to the onset of proliferative retinopathy reduced new blood vessel growth a mean of 25 and 31% compared with controls. This inhibition was dependent on the concentration of antisense phosphorothioate oligodeoxynucleotides and resulted in a 40-66% reduction in the level of VEGF protein, as determined by Western blot analysis. Control (sense, nonspecific) phosphorothioate oligodeoxynucleotides did not cause a significant reduction in retinal neovascularization or VEGF protein levels. These data further establish a fundamental role for VEGF expression in ischemia-induced proliferative retinopathies and a potential therapeutic use for antisense phosphorothioate oligodeoxynucleotides.

Animals↗

PubMed1996

Regulation of vascular endothelial growth factor by oxygen in a model of retinopathy of prematurity.

OBJECTIVES: To investigate the role of vascular endothelial growth factor (VEGF) in the pathogenesis of the first phase of retinopathy of prematurity (ROP) and to examine the mechanism by which supplemental oxygen therapy might inhibit neovascularization in the second phase of ROP. METHODS: A novel combination of fluorescein-dextran perfusion and colorimetric whole-retina in situ hybridization was used to evaluate the expression of VEGF messenger RNA in relationship to the location of blood vessels in retinas from neonatal mice that were exposed to hyperoxia. Northern blot and immunoblot analyses were used to quantify the changes in VEGF messenger RNA and protein expression caused by hyperoxia. The ability of VEGF to prevent hyperoxia-induced vaso-obliteration was evaluated by injecting exogenous VEGF into the vitreous cavity prior to oxygen exposure. RESULTS: Vascular endothelial growth factor messenger RNA was produced in a reticular pattern just anterior to the developing blood vessels in normal retina on postnatal day 7. The expression of VEGF in the peripheral retina was down-regulated by hyperoxia in conjunction with the arrest of growth and the loss of some of the developing vasculature. Total VEGF messenger RNA and protein levels in retinas from animals on postnatal day 7 were decreased 55% and 85%, respectively, after 6 hours in 75% oxygen. Vaso-obliteration was inhibited 57% by pretreatment of animals with exogenous VEGF. In animals with retinal ischemia secondary to loss of vasculature, treatment with supplemental oxygen therapy decreased stimulated retinal VEGF levels by approximately 70%. CONCLUSIONS: Down-regulation of VEGF expression by hyperoxia may be partly responsible for the vaso-obliteration and cessation of normal retinal blood vessel growth observed in premature infants in whom ROP develops. Hyperoxia also has the potential to be used therapeutically to down-regulate VEGF expression in hypoxic retina in the hope of limiting the neovascular complications of ROP. Based on these findings about the regulation of VEGF expression in the retina, an explanation of the pathogenesis of ROP is proposed.

Animals↗

PubMed1996

Transanal endoscopic microsurgery. Initial registry results.

UNLABELLED: Transanal endoscopic microsurgery (TEM) was first used on a regular basis in the United States in 1990. Because there is a sole source of instrumentation, the surgeons who use this equipment are known to us. Thus, this earliest registry is a compilation of data based on most patients who underwent TEM in the United States from 1990 to 1994. METHOD: One hundred fifty-three cases were voluntarily registered by six surgeons. Pathology included 54 carcinomas, 82 adenomas, and 17 other entities. Most resections were full thickness. Fifty percent of cases were out of reach of standard instruments. Complication rate, hospital stay, and blood loss were recorded. Technical difficulties at time of surgery (9 percent), early complications (15 percent), and late complications (5 percent) have been tabulated. RESULTS: Recurrence rates for carcinoma were 10 percent for T1, 40 percent for T2, and 66 percent for T3 stages. Failures were treated by abdominoperineal resection or low anterior resection. Adenomas recurred in 11 percent, but these recurrences were small and easily treatable. CONCLUSION: TEM has a low complication rate. By carefully selecting small, superficial cancers and adenomas, TEM results in superior outcome over other approaches to the mid and upper rectum.

Adenoma↗

PubMed1996

Excellent outcome using selective criteria for rectocele repair.

PURPOSE: The aim of this study was to review our experience with patients with rectoceles using very selective criteria for operative repair and to critically review our surgical results. METHODS: This is a review of patients selected for rectocele repair between 1989 and 1994. RESULTS: Two hundred seventy-nine patients were evaluated for pelvic outlet symptoms in our clinic. Defecography was performed in 180 patients; rectocele was seen in 143 patients (79 percent; 135 females and 8 males). On physical examination, 132 patients had a palpable rectocele (73 percent). Rectocele repair was recommended for 35 patients (13 percent); 33 (32 females and 1 male) underwent this procedure. Mean age was 55 (range, 16-78) years. Although many patients complained of constipation, incontinence and pelvic pain, in these 33 patients criteria for repair included the sensation of a vaginal mass or bulge that required digital support and/or rectal digitizing for evacuation (58 percent), retention of barium in the rectocele on defecography (55 percent), or a very large rectocele with internal anterior rectal wall prolapse (6 percent). A hysterectomy had been performed previously in 47 percent of women repaired. Rectocele repair was performed by a standard transanal approach in 31 patients and transabdominally in 2 patients. Hospital stay averaged 3.7 (range, 1-8) days. Few postoperative complications occurred; urinary retention was the most common (18 percent). All patients were followed postoperatively, and 26 patients (79 percent) answered a standardized questionnaire. Mean follow-up was 31 (range, 5-64) months. Eighty percent of patients questioned who initially complained of a vaginal mass or bulge reported complete resolution (significant improvement by the sign test, P < 0.5). Subjectively, 92 percent of patients questioned reported improvement in their preoperative symptoms and satisfaction with the operation. CONCLUSION: Rectoceles are frequently identified during defecography, which is performed for pelvic floor complaints, yet are often asymptomatic. In contrast to other recent reports of rectocele repair, our data indicate that careful selection of patients using specific criteria may result in very good clinical results.

Constipation↗

PubMed1996

Isolation and expression of an open reading frame encoding sialidase from Trypanosoma rangeli.

Several protozoan parasites of human have been found to express enzymes capable of releasing terminal sialic acid residues from host glycans. These include enzymes similar in activity to bacterial and viral sialidases, as well as a novel type of enzyme, trans-sialidase, which can transfer sialic acid from one carbohydrate chain to another. Here we report the isolation of a gene and a gene fragment from the kinetoplastid Trypanosoma rangeli which encode products related in sequence to the trans-sialidase enzyme of T. cruzi. The gene fragment ORF is nearly identical to that of the complete gene, which encodes an enzymatically inactive protein. When the ORF of the gene fragment is fused to fragments from related genes, it encodes a product with sialidase activity. Both predicted T. rangeli protein products also have other potential structural features found in bacterial sialidases and in members of a previously described Trypanosoma trans-sialidase superfamily.

Amino Acid Sequence↗

PubMed1996

Prevention of postoperative abdominal adhesions by a sodium hyaluronate-based bioresorbable membrane: a prospective, randomized, double-blind multicenter study.

BACKGROUND: Postoperative abdominal adhesions are associated with numerous complications, including small bowel obstruction, difficult and dangerous reoperations, and infertility. A sodium hyaluronate and carboxymethylcellulose bioresorbable membrane (HA membrane) was developed to reduce formation of postoperative adhesions. The objectives of our prospective study were to assess the incidence of adhesions that recurred after a standardized major abdominal operation using direct laparoscopic peritoneal imaging and to determine the safety and effectiveness of HA membrane in preventing postoperative adhesions. STUDY DESIGN: Eleven centers enrolled 183 patients with ulcerative colitis or familial polyposis who were scheduled for colectomy and ileal pouch-anal anastomosis with diverting-loop ileostomy. Before abdominal closure, patients were randomly assigned to receive or not receive HA membrane placed under the midline incision. At ileostomy closure eight to 12 weeks later, laparoscopy was used to evaluate the incidence, extent, and severity of adhesion formation to the midline incision. RESULTS: Data were analyzed for 175 assessable patients. While only five (6 percent) of 90 control patients had no adhesions, 43 (51 percent) of 85 patients receiving HA membrane were free of adhesions (p < 0.00000000001). The mean percent of the incision length involved was 63 percent in the control group, significantly greater than the 23 percent observed in patients who received HA membrane (p < 0.001). Dense adhesions were observed in 52 (58 percent) of the 90 control patients, but in only 13 (15 percent) of the 85 receiving HA membrane (P < 0.0001). Comparison of the incidence of specific adverse events between the groups did not identify a difference (P > 0.05). CONCLUSIONS: This study represents the first controlled, prospective evaluation of postoperative abdominal adhesion formation and prevention after general abdominal surgery using standardized, direct peritoneal visualization. In this study, HA membrane was safe and significantly reduced the incidence, extent, and severity of postoperative abdominal adhesions.

Adenomatous Polyposis Coli↗

PubMed1995

Suppression of retinal neovascularization in vivo by inhibition of vascular endothelial growth factor (VEGF) using soluble VEGF-receptor chimeric proteins.

The majority of severe visual loss in the United States results from complications associated with retinal neovascularization in patients with ischemic ocular diseases such as diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. Intraocular expression of the angiogenic protein vascular endothelial growth factor (VEGF) is closely correlated with neovascularization in these human disorders and with ischemia-induced retinal neovascularization in mice. In this study, we evaluated whether in vivo inhibition of VEGF action could suppress retinal neovascularization in a murine model of ischemic retinopathy. VEGF-neutralizing chimeric proteins were constructed by joining the extracellular domain of either human (Flt) or mouse (Flk) high-affinity VEGF receptors with IgG. Control chimeric proteins that did not bind VEGF were also used. VEGF-receptor chimeric proteins eliminated in vitro retinal endothelial cell growth stimulation by either VEGF (P < 0.006) or hypoxic conditioned medium (P < 0.005) without affecting growth under nonstimulated conditions. Control proteins had no effect. To assess in vivo response, animals with bilateral retinal ischemia received intravitreal injections of VEGF antagonist in one eye and control protein in the contralateral eye. Retinal neovascularization was quantitated histologically by a masked protocol. Retinal neovascularization in the eye injected with human Flt or murine Flk chimeric protein was reduced in 100% (25/25; P < 0.0001) and 95% (21/22; P < 0.0001) 0.0001) of animals, respectively, compared to the control treated eye. This response was evident after only a single intravitreal injection and was dose dependent with suppression of neovascularization noted after total delivery of 200 ng of protein (P < 0.002). Reduction of histologically evident neovascular nuclei per 6-microns section averaged 47% +/- 4% (P < 0.001) and 37% +/- 2% (P < 0.001) for Flt and Flk chimeric proteins with maximal inhibitory effects of 77% and 66%, respectively. No retinal toxicity was observed by light microscopy. These data demonstrate VEGF's causal role in retinal angiogenesis and prove the potential of VEGF inhibition as a specific therapy for ischemic retinal disease.

Animals↗

PubMed1995

Enamel hypoplasia, bilateral cataracts, and aqueductal stenosis: a new syndrome?

We report on a 12-year-old girl who presented with generalized enamel hypoplasia, cataracts, and enlargement of the cerebral ventricles secondary to aqueductal stenosis. Previously described syndromes of enamel defects with or without cataracts were excluded on the basis of clinical criteria and appearance of the dentition. Metabolic conditions which could have caused cataracts were excluded clinically and by biochemical tests. The combination of signs in this patient may represent a new syndrome.

Abnormalities, Multiple↗

PubMed1995

Vascular endothelial growth factor/vascular permeability factor expression in a mouse model of retinal neovascularization.

Neovascular diseases of the retina are a major cause of blindness worldwide. Hypoxia is thought to be a common precursor to neovascularization in many retinal diseases, but the factors involved in the hypoxic neovascular response have not been fully identified. To investigate the role of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) in retinal neovascularization, the expression of VEGF/VPF mRNA and protein were studied in a mouse model of proliferative retinopathy. RNA (Northern) blot analysis revealed that retinal VEGF/VPF mRNA expression increased 3-fold between 6 and 12 hr of relative retinal hypoxia and remained elevated during the development of neovascularization. In situ hybridization localized VEGF/VPF mRNA to cells bodies in the inner nuclear layer of the retina. Immunohistochemical confocal microscopy demonstrated that VEGF/VPF protein levels increase with a time course similar to that of the mRNA. The cells in the inner nuclear layer of the retina that produce VEGF/VPF were identified morphologically as Müller cells. These data suggest that VEGF/VPF expression in the retina plays a central role in the development of retinal ischemia-induced ocular neovascularization.

Animals↗