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Biomedical subjects

J Kim

Publications and source records attributed to J Kim.

At least 739 records · Page 41Linked to original sources

Uveitis in the southeastern United States.

PURPOSE: Previous epidemiologic studies of uveitis have focused on predominantly Caucasian populations, and none have been based in the Southeast. We analyzed the epidemiology of uveitis among a referral population with a high percentage of African Americans in the United States. METHODS: We evaluated demographic data from 385 consecutive patients referred to the Duke Uveitis Clinic. RESULTS: Of the 385 patients, 120 (31%) were African American and 258 (67%) Caucasian; 237 (62%) were female and 148 (38%) male. The most common diagnoses among the 385 patients were idiopathic panuveitis (64 patients [17%]), idiopathic anterior uveitis (47 patients [12%]), pars planitis (46 patients [12%]), sarcoidosis (44 patients [11%]), and toxoplasmosis (39 patients [10%]). These diagnoses were also the most common among the 120 African American patients: 33 patients (28%) had idiopathic panuveitis, 30 (25%) had sarcoidosis, 10 (8%) had idiopathic anterior uveitis, 8 (7%) had toxoplasmosis, and 6 (5%) had pars planitis. Among the 258 Caucasian patients, the most common diagnoses were pars planitis (39 patients [15%]), idiopathic anterior uveitis (37 patients [14%]), toxoplasmosis (30 patients [12%]), idiopathic panuveitis (28 patients [11%]), and multifocal choroiditis and panuveitis (MCP) (17 patients [7%]). Categorizing diagnoses of all 385 patients by anatomic location, panuveitis was most frequent (148 patients [38%]), followed by anterior uveitis (97 patients [25%]), posterior uveitis (93 patients [24%]), and intermediate uveitis (47 patients [12%]). CONCLUSIONS: The higher frequency of sarcoidosis and idiopathic panuveitis than previously reported is related to our larger African American population base. The racial composition of the Southeast does not, however, account for differences such as our higher percentage of MCP; it is possible that other genetic or environmental factors play a role in this region.

Adolescent↗

Genetic analysis of default mating behavior in Saccharomyces cerevisiae.

Haploid Saccharomyces cerevisiae cells find each other during conjugation by orienting their growth toward each other along pheromone gradients (chemotropism). However, when their receptors are saturated for pheromone binding, yeast cells must select a mate by executing a default pathway in which they choose a mating partner at random. We previously demonstrated that this default pathway requires the SPA2 gene. In this report we show that the default mating pathway also requires the AXL1, FUS1, FUS2, FUS3, PEA2, RVS161, and BNI1 genes. These genes, including SPA2, are also important for efficient cell fusion during chemotropic mating. Cells containing null mutations in these genes display defects in cell fusion that subtly affect mating efficiency. In addition, we found that the defect in default mating caused by mutations in SPA2 is partially suppressed by multiple copies of two genes, FUS2 and MFA2. These findings uncover a molecular relationship between default mating and cell fusion. Moreover, because axl1 mutants secrete reduced levels of a-factor and are defective at both cell fusion and default mating, these results reveal an important role for a-factor in cell fusion and default mating. We suggest that default mating places a more stringent requirement on some aspects of cell fusion than does chemotropic mating.

DNA-Binding Proteins↗

Candidate biomarkers of aging: age-sensitive indices of immune and muscle function covary in genetically heterogeneous mice.

A longitudinal experiment was designed to test the hypothesis that individual mice differ in their aging rate and to validate candidate biomarkers proposed to measure the rate of aging. Mice were bred as the genetically heterogeneous progeny of a cross between CB6F1 mothers and C3D2F1 fathers. Half of the mice were fed ad libitum (AL group), and the other half were subjected to 60% calorie restriction (CR group). Each mouse was tested at about 9 months of age using age-sensitive tests of immune status, and then again at about 12 months of age using age-sensitive tests of muscle function. The data were then analyzed using the method of partial least squares to determine the combinations of test weights that maximize the covariance of the weighted sum of immune measures with the weighted sum of muscle function measures. Both AL and CR mice exhibited a statistically significant relation between the immune status tests and the muscle function tests. Maximal covariance was obtained with a set of weighting coefficients consistent with our working hypothesis: mice with high levels of CD4 memory T cells (which increase with age) also had relatively low levels of muscle strength and endurance. Low strength was associated with low CD8 cells in the AL mice, with high numbers of CD8 memory cells in the CR mice and with low CD3 cells in both diet groups. The partial least squares method generates composite indices of immune status and muscle function that can be evaluated as biomarkers of aging rate in these mice. Further work will be needed to assess whether these tests predict either longevity or the trajectory of change in other age-sensitive molecular and physiological traits.

Aging↗

Phylogenetic reconstruction of vertebrate Hox cluster duplications.

In vertebrates and the cephalochordate, amphioxus, the closest vertebrate relative, Hox genes are linked in a single cluster. Accompanying the emergence of higher vertebrates, the Hox gene cluster duplicated in either a single step or multiple steps, resulting in the four-cluster state present in teleosts and tetrapods. Mammalian Hox clusters (designated A, B, C, and D) extend over 100 kb and are located on four different chromosomes. Reconstructing the history of the duplications and its relation to vertebrate evolution has been problematic due to the lack of alignable sequence information. In this study, the problem was approached by conducting a statistical analysis of sequences from the fibrillar-type collagens (I, II, III, and IV), genes closely linked to each Hox cluster which likely share the same duplication history as the Hox genes. We find statistical support for the hypothesis that the cluster duplication occurred as multiple distinct events and that the four-cluster situation arose by a three-step sequential process.

Animals↗

Magnetic resonance imaging of children without sedation: preparation with simulation.

OBJECTIVE: It was hypothesized that a scanner simulator that replicates the magnetic resonance imaging (MRI) environment could be used to prepare pediatric subjects for successful completion of a diagnostic-quality MRI examination without pharmacological sedation. METHOD: Sixteen healthy children, 6 to 17 years of age, were matched for age and sex with 16 psychotropic medication-naive children with obsessive-compulsive disorder. Distress was measured throughout simulation and scanning procedures using heart rate and a self-report distress scale. Ten healthy children, 6 to 17 years of age, also underwent the same actual MRI scanning procedure but did not undergo the simulation scanning procedure. RESULTS: Significant decreases in heart rate and self-reported distress level were observed in all subjects during the simulator session that were maintained to the end of the actual scanner experience. All subjects successfully completed MRI examinations without chemical restraint. Subjects who were not trained in the simulator had higher heart rates and self-reported distress levels in the actual scanner than did simulation-trained subjects. CONCLUSIONS: Simulation without pharmacological sedation successfully prepared pediatric subjects in this pilot study for high-quality MRI studies. Subject preparation may be an alternative procedure to sedation for routine MRI examination in healthy and anxious children 6 years of age and older.

Adolescent↗

Detection of Aspergillus ribosomal RNA using biotinylated oligonucleotide probes.

Aspergillosis continues to be a devastating disease entity that results in significant mortality in immunosuppressed patients. Rapid diagnosis is often required to initiate appropriate therapy. Although the histopathologist may be able to visualize fungal organisms in tissue specimens, the histology of Aspergillus species may overlap with a variety of fungi, so diagnosis often relies on fungal cultures that can take weeks to complete. Recently, an in situ hybridization assay targeting Aspergillus 5S ribosomal RNA (rRNA) was reported. This assay proved to be useful when fungal cultures were negative or not performed but when fungi compatible with Aspergillus species were identified in tissue sections. That study was performed to compare the probe described in the previous study (5S-1 probe) with two other probes specific for Aspergillus. Two customly designed 21- and 23-base oligonucleotide probes complementary to 5S (5S-2 probe) and 18S (18S-1 probe) rRNA of Aspergillus were synthesized and labeled with multiple biotin moieties at the 3' termini. By GenBank analysis, the sequence of the 18S-1 probe was shown to have 90% to 100% homology to Aspergillus fumigatus group, Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Aspergillus parasiticus, Aspergillus tamarii, and Aspergillus glaucus group; the 5S-2 probe was homologous to Aspergillus flavus, Aspergillus niger, Aspergillus nidulans, Aspergillus awamori, and Aspergillus wentii. In situ hybridization was performed on 43 cases of Aspergillus infection including 41 localized aspergillomas in the lung, brain, sinonasal tract, and ear, and 2 cases of invasive aspergillosis involving pleura and soft tissue of the scapular region. The results were compared with those obtained using a previously reported 5S-1 probe. In situ hybridization was positive in 38, 38, and 40 cases with the 5S-1, 5S-2, and 18S-1 probes, respectively. The 18S-1 probe was most useful because of a wider detection spectrum. In situ hybridization for Aspergillus rRNA provides a useful means for rapidly and accurately identifying Aspergillus in tissues and may be useful if fungal organisms suggestive of Aspergillus species are present but if cultures are negative or have not been performed.

Aspergillosis↗

The human homolog of a mouse-imprinted gene, Peg3, maps to a zinc finger gene-rich region of human chromosome 19q13.4.

Peg3 (paternally expressed gene 3) is the first imprinted gene detected in the proximal region of mouse chromosome 7. Because imprinting is a trait that is generally conserved among mammals, and imprinted domains generally encompass several adjacent genes, expression patterns and chromosomal environment of the human counterpart of Peg3 are of special interest. In this study we have localized human PEG3 approximately 2 Mb proximal of the telomere of chromosome 19q, within a region known to carry large numbers of tandemly clustered Krüppel-type zinc finger-containing (ZNF) genes. Peg3 also encodes a Krüppel-type ZNF protein but one that is distinguished from other ZNF gene products by the fact that it carries two novel proline-rich motifs. Comparison between mouse Peg3 and partial human PEG3 gene sequences revealed a high level of conservation between the two species, despite the fact that one of the two proline-rich repeats is absent from the human gene. Our data demonstrate that the human gene is expressed at highest levels in ovary and placenta; mouse Peg3, by contrast, is transcribed at highest levels in the adult brain. These comparative mapping, sequencing, and expression data provide the first clues to the potential activities of PEG3, and generate new tools to aid in the analysis of structure and function of a potentially new imprinted domain located in human chromosome 19q13.4 and mouse chromosome 7.

Age Factors↗

Volumetric object reconstruction using the 3D-MRF model-based segmentation.

A number of segmentation algorithms have been developed, but those algorithms are not effective on volume reconstruction because they are limited to operating only on two-dimensional (2-D) images. In this paper, we propose the volumetric object reconstruction method using the three-dimensional Markov random field (3D-MRF) model-based segmentation. The 3D-MRF model is known to be one of efficient ways to model spatial contextual information. The method is compared with the 2-D region growing scheme under three types of interpolation. The results show that the proposed method is better in the aspect of image quality than other methods.

Algorithms↗

Colonic absorption of antiepileptic agents.

PURPOSE: To evaluate a canine intestinal accessport model to study colonic absorption of drugs. The antiepileptic drugs phenytoin and gabapentin were chosen to study absorption of a lipophilic and hydrophilic compound, respectively. METHODS: Drug plasma level-time plots were generated subsequent to small intestinal and colonic drug administration of both drugs. The poorly water-soluble phenytoin was administered in two doses to evaluate the impact of dissolution rate limits on colonic absorption. Maximal plasma concentration (Cmax) and area under the plasma level-time curve (AUC) were used to assess the relative contribution of colonic absorption to plasma levels. RESULTS: Whereas colonic gabapentin AUC and Cmax were only 0.25 and 0.15 of those seen after small intestinal administration, colonic phenytoin AUC and Cmax were one half and equivalent to, respectively, those observed for small intestinal administration. Furthermore, colonic administration of a higher phenytoin dose showed secondary maxima and continued increases in drug plasma levels with time. CONCLUSIONS: Colonic gabapentin absorption is poor compared with upper intestinal absorption, consistent with membrane transport rate limits to the absorption of this hydrophilic AED. Peak phenytoin plasma levels from colonic and small intestinal administration are comparable, indicating membrane transport does not limit absorption of this lipophilic agent. Continued plasma-level increases from higher phenytoin doses are consistent with dissolution-rate control of drug absorption in the colon. We suggest that colonic absorption provides a greater potential for toxicity from phenytoin overdose as a function of continued drug dissolution than for gabapentin overdose.

Acetates↗

Liver and gastrointestinal first-pass effects of azosemide in rats.

Since considerable first-pass effects of azosemide have been reported after oral administration of the drug to rats and man, first-pass effects of azosemide were evaluated after intravenous, intraportal and oral administration, and intraduodenal instillation of the drug, to rats. The total body clearances of azosemide after intravenous (5 mg kg-1) and intraportal (5 and 10 mg kg-1) administration of the drug to rats were considerably smaller than the cardiac output of rats suggesting that the lung or heart first-pass effect (or both) of azosemide after oral administration of the drug to rats was negligible. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) after intraportal administration (5 mg kg-1) of the drug was significantly lower than that after intravenous administration (5 mg kg-1) of the drug (1000 vs 1270 micrograms min mL-1) suggesting that the liver first-pass effect of azosemide was approximately 20% in rats. The AUC from time 0 to 8 h (AUC0-8 h) after oral administration (5 mg kg-1) of the drug was considerably smaller than that after intraportal administration (5 mg kg-1) of the drug (27.1 vs 1580 micrograms min mL-1) suggesting that there are considerable gastrointestinal first-pass effects of azosemide after oral administration of azosemide to rats. Although the AUC0-8 h after oral administration (5 mg kg-1) of azosemide was approximately 15% lower than that after intraduodenal instillation (5 mg kg-1) of the drug (27.1 vs 32.0 micrograms min mL-1), the difference was not significant, suggesting that the gastric first-pass effect of azosemide was not considerable in rats. Azosemide was stable in human gastric juices and pH solutions ranging from 2 to 13. Almost complete absorption of azosemide from whole gastrointestinal tract was observed after oral administration of the drug to rats. The above data indicated that most of the orally administered azosemide disappeared (mainly due to metabolism) following intestinal first-pass in rats.

Administration, Oral↗

Population dynamics of polychlorinated biphenyl-dechlorinating microorganisms in contaminated sediments.

The growth dynamics of polychlorinated biphenyl (PCB)-dechlorinating microorganisms were determined for the first time, along with those of sulfate reducers and methanogens, by using the most-probable-number technique. The time course of Aroclor 1248 dechlorination mirrored the growth of dechlorinators; dechlorination ensued when the dechlorinating population increased by 2 orders of magnitude from 2.5 x 10(sup5) to 4.6 x 10(sup7) cells g of sediment(sup-1), at a specific growth rate of 6.7 day(sup-1) between 2 and 6 weeks. During this period, PCB-dechlorinating microorganisms dechlorinated Aroclor 1248 at a rate of 3.9 x 10(sup-8) mol of Cl g of sediment(sup-1) day(sup-1), reducing the average number of Cl molecules per biphenyl from 3.9 to 2.8. The growth yield was 4.2 x 10(sup13) cells mol of Cl dechlorinated(sup-1). Once dechlorination reached a plateau, after 6 weeks, the number of dechlorinators began to decrease. On the other hand, dechlorinators inoculated into PCB-free sediments decreased over time from their initial level, suggesting that PCBs are required for their selective enrichment. The numbers of sulfate reducers and methanogens increased in both PCB-free and contaminated sediments, showing little difference between them. The maximum population size of sulfate reducers was about an order of magnitude higher than that of dechlorinators, whereas that of methanogens was slightly less. Unlike those of dechlorinators, however, numbers of both sulfate reducers and methanogens remained high even when dechlorination ceased. The results of this study imply that PCB concentrations may have to exceed a certain threshold to maintain the growth of PCB dechlorinators.

Journal Article↗

Promiscuous use of CC and CXC chemokine receptors in cell-to-cell fusion mediated by a human immunodeficiency virus type 2 envelope protein.

The CC chemokine receptors CCR5, CCR2, and CCR3 and the CXC chemokine receptor CXCR4 have been implicated as CD4-associated cofactors in the entry of primary and cell line-adapted human immunodeficiency virus type 1 (HIV-1) strains. CXCR4 is also a receptor for T-cell-line-adapted, CD4-independent strains of HIV-2. With the exception of this latter example, little has been reported on the entry cofactors used by HIV-2 strains. Here we show that a CD4-dependent, T-cell-line-adapted HIV-2 strain uses CXCR4 and, to a lesser extent, CCR3 for fusion with and infectious entry into cells. In a cell-to-cell fusion assay, the envelope protein of this virus can utilize a wider repertoire of chemokine receptors to induce fusion. These include CCR1, CCR2, CCR3, CCR4, CCR5, CXCR2, and CXCR4. Kinetic analysis indicated that cell lines expressing the receptors that support infection, CXCR4 and CCR3, form syncytia more rapidly than do cell lines expressing the other receptors. Nevertheless, although less efficient, fusion with CXCR2 expressing cells was specific, since it was inhibited by antibodies against CXCR2. The extensive use of chemokine receptors in cell-to-cell fusion has implications for understanding the molecular basis of CD4-chemokine receptor-induced lentivirus fusion and may have relevance for syncytium formation and the direct cell-to-cell transfer of virus in vivo.

Acquired Immunodeficiency Syndrome↗

Mutational analysis of the hepatitis C virus RNA helicase.

The carboxyl-terminal three-fourths of the hepatitis C virus (HCV) NS3 protein has been shown to possess an RNA helicase activity, typical of members of the DEAD box family of RNA helicases. In addition, the NS3 protein contains four amino acid motifs conserved in DEAD box proteins. In order to inspect the roles of individual amino acid residues in the four conserved motifs (AXXXXGKS, DECH, TAT, and QRRGRTGR) of the NS3 protein, mutational analysis was used in this study. Thirteen mutant proteins were constructed, and their biochemical activities were examined. Lys1235 in the AXXXXGKS motif was important for basal nucleoside triphosphatase (NTPase) activity in the absence of polynucleotide cofactor. A serine in the X position of the DEXH motif disrupted the NTPase and RNA helicase activities. Alanine substitution at His1318 of the DEXH motif made the protein possess high NTPase activity. In addition, we now report inhibition of NTPase activity of NS3 by polynucleotide cofactor. Gln1486 was indispensable for the enzyme activity, and this residue represents a distinguishing feature between DEAD box and DEXH proteins. There are four Arg residues in the QRRGRTGR motif of the HCV NS3 protein, and the second, Arg1488, was important for RNA binding and enzyme activity, even though it is less well conserved than other Arg residues. Arg1490 and Arg1493 were essential for the enzymatic activity. As the various enzymatic activities were altered by mutation, the enzyme characteristics were also changed.

Adenosine Triphosphatases↗

Differential regulation of neurogenesis by the two Xenopus GATA-1 genes.

Previously, we have shown that the ventralizing factor bone morphogenetic protein 4 (BMP-4) can inhibit Xenopus neurogenesis. The erythroid transcription factor GATA-1 functions downstream of the BMP-4 signaling pathway and mediates BMP-4-induced erythropoiesis. We have found that similar to BMP-4, GATA-1b inhibits neuralization of Xenopus animal cap (AC) cells. The neural inhibition is not seen with GATA-1a, although both GATA-1a and GATA-1b RNAs are translated at the same efficiency and induce globin expression equally in AC cells. GATA-1b RNA injection into AC cells neither induces expression of Xbra (a general mesoderm marker) nor affects expression of XK81 (epidermal keratin) or BMP-4 and Xvent-1 (two ventral markers). These data suggest that GATA-1b retains the epidermal fate of the AC. Intact GATA-1b protein is required for both inhibition of neurogenesis and induction of globin expression. Our findings indicate that GATA-1b can function in ectoderm to specifically regulate neural inducing mechanisms, apparently related to the expression of chordin, a neuralizing gene. Furthermore, tadpole stage embryos injected with GATA-1b are devoid of all dorsoanterior structures including neural tissue. This report provides evidence that the two transcription factors, derived from a recent genome duplication, share a common biological activity (stimulation of erythropoiesis) while also exhibiting a distinct function (inhibition of neurogenesis).

Animals↗

Prebending the estrogen response element destabilizes binding of the estrogen receptor DNA binding domain.

Binding of many eukaryotic transcription regulatory proteins to their DNA recognition sequences results in conformational changes in DNA. To test the effect of altering DNA topology by prebending a transcription factor binding site, we examined the interaction of the estrogen receptor (ER) DNA binding domain (DBD) with prebent estrogen response elements (EREs). When the ERE in minicircle DNA was prebent toward the major groove, which is in the same direction as the ER-induced DNA bend, there was no significant effect on ER DBD binding relative to the linear counterparts. However, when the ERE was bent toward the minor groove, in a direction that opposes the ER-induced DNA bend, there was a four- to eightfold reduction in ER DBD binding. Since reduced binding was also observed with the ERE in nicked circles, the reduction in binding was not due to torsional force induced by binding of ER DBD to the prebent ERE in covalently closed minicircles. To determine the mechanism responsible for reduced binding to the prebent ERE, we examined the effect of prebending the ERE on the association and dissociation of the ER DBD. Binding of the ER DBD to ERE-containing minicircles was rapid when the EREs were prebent toward either the major or minor groove of the DNA (k(on) of 9.9 x 10(6) to 1.7 x 10(7) M(-1) s(-1)). Prebending the ERE toward the minor groove resulted in an increase in k(off) of four- to fivefold. Increased dissociation of the ER DBD from the ERE is, therefore, the major factor responsible for reduced binding of the ER DBD to an ERE prebent toward the minor groove. These data provide the first direct demonstration that the interaction of a eukaryotic transcription factor with its recognition sequence can be strongly influenced by altering DNA topology through prebending the DNA.

Animals↗

Chicken GnRH II-like peptides and a GnRH receptor selective for chicken GnRH II in amphibian sympathetic ganglia.

Amphibia, like most vertebrate species, have two forms of GnRH, namely [Arg8]GnRH (mammalian GnRH) and [His5,Trp7,Tyr8] GnRH (chicken GnRH II). The differential distribution of the two peptides in the amphibian brain suggests that they may play different roles. Mammalian GnRH, which is found predominantly in the hypothalamus, is most likely the prime regulator of gonadotropin release, while chicken GnRH II, which occurs predominantly in the midbrain and hindbrain, may play a neuromodulatory role. In amphibian sympathetic ganglia, GnRH has been demonstrated to be a neurotransmitter where its release from the presynaptic nerve terminals reversibly inhibits M current, a time- and voltage-dependent potassium current. The occurrence of GnRH in sympathetic ganglia extracts from two amphibian species was investigated. Chicken GnRH II-like immunoreactivity was detected in extracts of bullfrog (Rana catesbeiana) and platanna (Xenopus laevis) sympathetic ganglia after high performance liquid chromatography. Under the chromatographic conditions used, a second unknown peptide co-eluted with synthetic mammalian GnRH, but showed no cross-reactivity with specific mammalian GnRH antisera. To test the possibility of the presence of a chicken GnRH II receptor in sympathetic ganglion neurones, competition binding of membranes extracted from the sympathetic ganglia of the two amphibian species was investigated with 125I-labelled GnRH agonists. The binding of 125-I-[His5,D-Arg6,Trp7,Tyr8]GnRH (a chicken GnRH II agonist) to membranes from the sympathetic ganglia of both amphibian species was specific and had a higher affinity than chicken GnRH II, mammalian GnRH and a mammalian GnRH agonist [D-Ala6,NMe-Leu7,Pro9-NHEt]GnRH. These findings suggest that endogenous chicken GnRH II may play a role in synaptic transmission in the sympathetic ganglia via a receptor specific for chicken GnRH II.

Amphibians↗

Visualization and flow of platelets and leukocytes in vivo in rat retinal and choroidal vessels.

PURPOSE: To directly visualize the flow of leukocytes in choroidal vessels and the flow of platelets in retinal vessels in a rat without incision by fluorescein leukocyte angiography (FLA) using a scanning laser ophthalmoscope (SLO). METHODS: Blood was withdrawn from a tail vein of a Sprague-Dawley rat with a tuberculin syringe traced with sodium heparin and mixed with sodium fluorescein. The fluorescent plasma layer was diluted with saline solution, centrifuged and then the overlying plasma discarded. The remaining cell suspension was diluted with saline to create the original hematocrit, then infused into the vein of the same rat while performing fluorescein angiography with an SLO. The angiographic image was recorded on a videotape using time-lapsed photography. RESULTS: Fluorescent platelets were detected and the flow within the retinal vessels traced over time. Fluorescent leukocytes in the choroidal vessels were also detected and the flow of a leukocyte was traced and its relative velocities were plotted against the time sequence. The relative size and fluorescence intensities of the platelets and leukocytes in the angiographic image corresponded well with the smear of the blood preparation. CONCLUSIONS: FLA using an SLO can be used to detect the flow of platelets in the retinal vessels and the flow of leukocytes in the choroidal vessels in the experimental rat eye model.

Animals↗