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R Peek

Publications and source records attributed to R Peek.

35 records · Page 2Linked to original sources
PubMed1998

Cytomegalovirus glycoprotein B genotyping in ocular fluids and blood of AIDS patients with cytomegalovirus retinitis.

PURPOSE: To determine the frequency of cytomegalovirus glycoprotein B (gB) genotypes in clinical samples of ocular fluids of patients with acquired immune deficiency syndrome (AIDS) who have cytomegalovirus retinitis and to compare these with the cytomegalovirus gB genotype in paired peripheral blood leukocytes. METHODS: Glycoprotein B genotypes of cytomegalovirus genomic DNA were determined in 29 ocular and 9 paired blood samples of 27 patients, by polymerase chain reaction amplification followed by restriction fragment length polymorphism analysis. RESULTS: In the 29 ocular samples, 30 gB genotypes were determined: Glycoprotein B1 was found in 8 samples (27%), gB2 in 9 samples (30%), gB3 in 6 samples (20%), and gB4 in 3 samples (10%). In one sample, a mixed genotype was observed. In addition to these previously characterized gB genotypes, a new gB variant was observed in the ocular fluid of four patients. Partial sequence analysis revealed that this new gB genotype is closely related to gB3, and it was therefore named gB3'. In the blood samples, only gB1, gB2, and gB3 genotypes were observed. In the nine paired samples of ocular fluid and blood, four showed a difference in gB genotype between these compartments. CONCLUSIONS: The distribution of cytomegalovirus glycoprotein B genotypes gB1-gB4 in ocular fluids of patients with AIDS who have cytomegalovirus retinitis was determined in this study. The predominance of gB2, as described by others, was not confirmed. The glycoprotein B genotype in the eye can be different from the genotype found in the blood of the same patient. A new gB variant, gB3', was found in the ocular samples of 4 of 27 patients, but not in the blood samples tested.

AIDS-Related Opportunistic Infections↗
PubMed1998

Molecular cloning of a new angiopoietinlike factor from the human cornea.

PURPOSE: To isolate tissue-specific gene products that contribute to corneal integrity. METHODS: A cDNA library was constructed and differentially hybridized. Cornea-specific clones were purified and further characterized. RESULTS: In this study cornea-specific gene products were isolated by differential cDNA hybridization. In addition to known cornea-specific gene products, a transcript was isolated coding for a protein homologous to the angiopoietins, a recently described family of (anti)angiogenic factors. Subsequently, the full cDNA was sequenced, and the identified open reading frame was named cornea-derived transcript 6 (CDT6). Similar to the angiopoietins, CDT6 contains a hydrophobic NH2-terminal sequence, a coiled-coil domain, and a COOH-terminal fibrinogenlike domain. Expression of CDT6 could be detected only in the cornea and not in several other adult human tissues. Within the cornea, expression of CDT6 is confined to the stromal layer. CONCLUSIONS: The human cornea shows high-level expression of a gene product homologous to the (anti)angiogenic factors, the angiopoietins. This homology, together with stromal-specific expression, suggests that this factor may contribute to the avascularity of the human cornea.

Amino Acid Sequence↗
PubMed1998

Müller cell-specific autoantibodies in a patient with progressive loss of vision.

PURPOSE: To study the specificity of circulating retinal autoantibodies in a patient with progressive loss of vision resembling cancer-associated retinopathy in the absence of systemic malignancy. METHODS: Patient's serum was tested for the presence of antiretinal antibodies by Western blot analysis, and immunohistochemical analysis was performed on cryosections of rat retina and on cultured rat retinal Müller cells. RESULTS: Western blot analysis revealed that the serum contained a high titer of autoantibodies against a 35-kDa retinal antigen. A protein of similar molecular weight and antigenicity has been found to be present in protein extracts of bovine, rat, and fish retina. Immunohistochemical analysis suggested that the autoantibodies did not localize to retinal neural cells, as reported for several other putative autoimmune retinal disorders, but rather to the retinal Müller cells. This cell type-specificity could be confirmed using purified cultured retinal Müller cells. CONCLUSIONS: These results suggest that an autoimmune response directed against the retinal Müller cells, in the absence of overt systemic malignancy, may lead to a slow-developing visual deterioration.

Aged↗
PubMed1996

Interaction of the La (SS-B) autoantigen with small ribosomal subunits.

The La (SS-B) autoantigen is an evolutionarily conserved 47-kDa protein which binds to nascent RNA polymerase III transcripts and to a number of viral leader RNAs. The La protein plays a direct role in the termination of RNA polymerase III transcription and recent findings have suggested an additional role in several aspects of translation of (viral) messenger RNAs. Here, we show that La in the cytoplasm is associated with a subset of small ribosomal subunits, possibly by direct association with 18S ribosomal RNA. This association is likely to be related to the putative role of this protein in translation regulation.

3T3 Cells↗
PubMed1994

Epitope specificity determines the ability of anti-Ro52 autoantibodies to precipitate Ro ribonucleoprotein particles.

Ro ribonucleoprotein particles (Ro RNPs) are evolutionarily conserved cytoplasmic complexes of unknown function. They are composed of several proteins and a small, RNA polymerase III-transcribed Ro or Y RNA. Abs directed against the protein moiety of Ro RNPs are often found in sera of patients suffering from certain autoimmune disorders. The association of one of the Ro proteins, a protein of 52 kDa (Ro52), with Ro RNPs is still questionable. In this study, we have used anti-Ro52 Abs isolated from autoimmune sera to locate the antigenic determinants of Ro52 and to analyze the correlation between regions of Ro52 recognized by these Abs and their ability to immunoprecipitate Ro RNPs. The results indicate that the autoimmune response against Ro52 is heterogeneous and that the exclusive recognition of certain epitopes does not result in immunoprecipitation of Ro RNPs.

Antibodies, Antinuclear↗
PubMed1994

Adenovirus infection induces loss of HLA class I and CD3 antigens, but does not induce cell surface presentation of the La (SS-B) autoantigen.

Antibodies to the RNA polymerase III transcription termination factor La are frequently found in the serum of patients with various autoimmune diseases. The mechanisms by which autoimmune responses are evoked remain largely obscure, but the presentation of autoantigens on the cell surface during stress conditions has been reported as a possible factor. In this study we analysed the effects of adenovirus infection on the binding of anti-La antibodies to the surface of several human cell lines and on the levels of the membrane-expressed glycoproteins HLA class I, CD44 and the CD3 complex. In addition, we studied the relative amount and the intracellular distribution of the La protein as well as its association with the major species of non-coding virus-associated (VAI) RNA. While immunofluorescence patterns revealed a redistribution and possibly cell surface expression of the La protein during infection, this could not be confirmed by other techniques. In contrast, surface levels of HLA class I proteins and CD3 complex were severely affected. The data suggest that the subcellular distribution of the La protein is not detectably influenced by adenovirus infection.

Adenovirus Infections, Human↗
PubMed1993

Subcellular distribution of Ro ribonucleoprotein complexes and their constituents.

Ro ribonucleoprotein particles (Ro RNPs) are complexes of several proteins with a small RNA polymerase III-transcribed Ro RNA. Despite their relative abundance and evolutionary conservation no function has as yet been ascribed to these complexes. Also their subcellular distribution is still largely unknown as immunofluorescence studies concerning their localization have produced conflicting data. We have used cell enucleation to fractionate cells into cytoplasmic and nuclear fractions. Analysis of these fractions revealed an exclusively cytoplasmic localization for the Ro RNPs. The majority of the Ro RNAs are shown to be stably associated with all three known Ro RNP proteins. Although no Ro RNAs could be detected in the nuclear fraction, the Ro RNP-specific proteins were abundantly present. These nuclear non-Ro RNA-associated proteins are shown to be capable of binding Ro RNAs.

3T3 Cells↗
PubMed1992

Activation and repression sequences determine the lens-specific expression of the rat gamma D-crystallin gene.

Rat lens nuclear extracts contain a factor that binds to position -57 to -46 of the rat gamma D-crystallin promoter region. This factor protects the sequence 5'-CTGCCAACGCAG-3' in a footprint analysis. Binding to this region is crucial for maximal promoter activity in rat lens cells, but this sequence was unable to act as an enhancer when cloned in front of a heterologous promoter. A region directly upstream from this activating sequence, between position -85 to -67, acts as a strong silencer of promoter activity in non-lens cells. This silencing effect is mediated by trans-acting factor(s). Our data provide evidence for two regulatory elements in rat gamma D-crystallin gene expression, an activating sequence active in lens cells and a silencing sequence active only in non-lens cells. The factor that binds to the activating sequence could be detected only in lens cells and may be a determinant of the lens-specific expression of the gamma-crystallin genes.

Animals↗
PubMed1992

Rise and fall of crystallin gene messenger levels during fibroblast growth factor induced terminal differentiation of lens cells.

Explanted rat lens epithelial cells differentiate synchronously in vitro to lens fiber cells in the presence of basic fibroblast growth factor (bFGF). We have monitored the expression of the three rat crystallin gene families, the alpha-, beta-, and gamma-crystallin genes, during this process. The expression of these gene families is sequentially activated, first the alpha-crystallin genes at Day 1, then the beta-crystallin genes at Day 3, and finally the gamma-crystallin genes at Day 8. The steady state levels of alpha- and beta-crystallin mRNA are not affected by incubation with actinomycin D, suggesting that these mRNAs are stable. Nevertheless, all crystallin mRNAs disappear from the differentiated explants between Days 10 and 11, a process signaled by bFGF. At this time a novel abundant mRNA appears. Cloning and sequencing showed that this mRNA encoded aldose reductase. Our results suggest a novel model for the regulation of crystallin synthesis during lens cell differentiation: a gene pulse delivers a certain amount of stable mRNA, this mRNA is removed at a later stage of differentiation by a stage-specific breakdown mechanism. Each of these regulatory steps requires a signal from bFGF.

Age Factors↗
PubMed1991

DNA methylation as a regulatory mechanism in rat gamma-crystallin gene expression.

We have investigated the methylation state of the rat gamma-crystallin genes in DNA from lens cells at different developmental stages as well as from kidney and heart cells. A clear correlation between the extent of demethylation of the promoter and 5' gene regions and the expression of these genes was observed. No change in the methylation state of the far upstream or 3' regions of the genes was seen. The demethylation of the promoter region was shown to occur during the differentiation from the lens epithelial to the lens fiber cell. The effect of cytosine methylation on gamma-crystallin promoter activity was tested by measuring gamma-crystallin promoter/chloramphenicol acetyltransferase fusion gene expression after in vitro primed repair synthesis of the promoter region in the presence of either dCTP or 5mdCTP. The hemimethylated promoter was no longer capable of promoting high CAT activity after introduction into lens-like cells. Taken together, our data suggest that DNA demethylation may be the determining step in the developmental stage-specific expression of the rat gamma-crystallin genes.

Animals↗
PubMed1990

Tissue- and species-specific promoter elements of rat gamma-crystallin genes.

The 5' flanking regions of the six rat gamma-crystallin genes (gamma A-gamma F) are all capable of conferring lens-specific expression to the bacterial chloramphenicol acetyl transferase (CAT) reporter gene in either transdifferentiating chicken neural retina cells or mouse lens epithelial cells. Deletion mapping of the most active gamma-crystallin promoter region, the gamma D region, showed that at least three elements are required for maximal expression in mouse lens epithelial cells: element(s) located between -200 and -106, a conserved CG rich region around position -75, and a CG stretch around -15. The region between -200 and -106 was dispensable in transdifferentiating chicken neural retina cells, which instead required the region between -106 and -78. The maximal activity of the gamma E and gamma F promoters was also dependent upon the integrity of the conserved CG region located around -75. A synthetic oligonucleotide containing this sequence was capable of lens-specific enhancement of the activity of the tk promoter in transdifferentiating chicken neural retina cells but not in mouse lens epithelial cells. Our results further show that this region may contain a silencer element, active in non-lens tissues, as well.

Animals↗
PubMed1979

Protection of the eyes against damage by light activated psoralen.

It is current practice to order eye protection while patients are under treatment with psoralen. There is considerable variation in the protection against long wave light provided by different sunglasses, therefore, it is necessary to write a specific prescription for sunglasses for these patients. We have found Noir Model 102 or 109 with side flaps or the Rayban dark green glass to be the most effective.

Eye Injuries↗
PubMed1978

Raynaud's disease: reduced hand blood flows with normal blood viscosity.

Hand blood flows and the blood and plasma viscosities were measured in patients with Raynaud's disease in an attempt to identify the mechanism of the episodic vascular insufficiency. Using venous occlusion plethysmography the following observations were made: (1) the hand blood flows were significantly less than in normals at 32 degrees, 27 degrees and 20 degrees C; (2) the percentage decrease in flow with cooling was greater in normals and (3) cooling of one hand from 32 degrees to 27 degrees C caused an abnormal decrease in flow through the contralateral hand. Using a rotational viscometer the blood and plasma viscosities were found to be normal at both high and low shear rates. The percentage increase in the blood viscosity with cooling from 35 degrees to 25 degrees was also normal. These studies demonstrate an increased constrictive response of the cutaneous vasculature of the hand to both local and reflex stimulation, and exclude a rheological abnormality, under conditions similar to those of the present study.

Adolescent↗
PubMed1977

Blood hyperviscosity with reduced skin blood flow in scleroderma.

The vascular complications of scleroderma have previously been attributed to the progressive obliteration of small vessels. Our study was carried out to determine whether abnormalities of blood viscosity occur in this disease, thereby contributing to the ischaemic process. Blood viscosity was measured in 20 patients using a rotational viscometer. At a high rate of shear, blood hyperviscosity was found in 35% of the patients and at a low rate of shear, in 70%. In addition there was a significant increase in the plasma viscosity which implicates changes in plasma proteins (fibrinogen, immunoglobulins) as causing the hyperviscosity. Measurement of the hand blood flow by venous occlusion plethysmography showed reduced flow at 32 degrees , 27 degrees , and 20 degrees C. A unique finding was a delayed recovery of the blood flow after cooling. These observations suggest that the increased resistance to blood flow in skin affected by scleroderma may be caused by an interaction between the occlusive vascular lesion and blood hyperviscosity. In addition, blood flow patterns and hyperviscosity could help distinguish scleroderma from primary Raynaud's disease.

Blood Viscosity↗
PubMedDate not supplied

Cytokines in aqueous humour and serum before and after corneal transplantation and during rejection.

Cytokine profiles in aqueous humour were studied in relation to corneal disease and subsequent corneal graft survival or rejection. Cytokine levels in samples obtained from eyes with clear grafts (n = 59) were all within the normal range. At the time of penetrating keratoplasty (n = 146), intraocular levels of IL-6 were increased in 38% (50/131), most markedly in eyes with previous allograft failure or herpetic stromal keratitis. The level of IL-10 was increased in 1 eye (n = 144) and of IL-4 and IFN-gamma in none. During rejection (n = 10), the levels of IL-6 in aqueous humour were increased in 75% (3/4), of IL-10 in 50% (3/6), of IL-4 in none (0/4) and of IFN-gamma in 40% (2/5). In conclusion, the levels of total protein and IL-6 were increased prior to penetrating keratoplasty in eyes with previous inflammation. These results could however not predict the final outcome of the graft. Increased intraocular levels of IL-6, IL-10 and IFN-gamma were observed during rejection.

Adult↗
PubMedDate not supplied

The SS-A/SS-B autoantigenic complex: localization and assembly.

The subcellular distribution of Ro ribonucleoprotein particles (Ro RNPs) and their constituents was determined using mammalian tissue culture cells and Xenopus laevis oocytes. Cell fractionation revealed that Ro RNPs are restricted to the cytoplasm, while the Ro RNP-specific proteins were also present in the nucleus. Transport studies indicated that the protein components of Ro RNPs are actively imported into the nucleus while the RNA component accumulates in the cytoplasm. These results suggest a model for the assembly of Ro RNPs.

Animals↗