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Biomedical subjects

R F Meyer

Publications and source records attributed to R F Meyer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Genetic relatedness of the caliciviruses: San Miguel sea lion and vesicular exanthema of swine viruses constitute a single genotype within the Caliciviridae.

The San Miguel sea lion viruses (SMSV) and vesicular exanthema of swine viruses (VESV) are related morphologically and antigenically, but little has been done to determine their genotypic relationship to each other and to other caliciviruses. To examine this relationship, reverse transcriptase PCRs were performed by using oligonucleotide primer sets designed to amplify portions of the 2C RNA helicase-like and RNA-dependent RNA polymerase regions with total cellular RNA purified from virus-infected cell cultures as a template. The 2C RNA helicase primers directed the amplification of this region from eight SMSV serotypes, five VESV serotypes, and four related viruses. The RNA polymerase primer sets amplified products from all these viruses except one. Phylogenetic comparison of the caliciviruses demonstrated that SMSV, VESV, and four related viruses are closely related while being distinct from feline calicivirus, the human caliciviruses (small, round-structured viruses), and rabbit hemorrhagic disease virus and that they should be classified as a single genotype within the Caliciviridae.

Amino Acid Sequence↗
PubMed1995

NaK-ATPase pump sites in cultured bovine corneal endothelium of varying cell density at confluence.

PURPOSE: The driving force for ion and water flow necessary for efficient deturgesence of the corneal stroma resides in the ouabain-sensitive sodium (Na) pump of corneal endothelial cells. Using a cell culture model of corneal endothelial cell hypertrophy, the authors examined the expression of Na pumps at the cell surface to see how this central element of the endothelial pump changed as corneal endothelial cell density decreased to a level associated with corneal decompensation in vivo. METHODS: 3H-ouabain binding to NaK-ATPase at saturating conditions was used to quantitate the number of Na pump sites on cultured bovine corneal endothelial cells as the confluent density decreased from approximately 2750 cells/mm2 to approximately 275 cells/mm2. RESULTS: The mean number of Na pump sites per cell at confluence (1.92 +/- 0.07 x 10(6)) did not change as the cell density decreased 2.7-fold from 2763 cells/mm2 to 1000 cells/mm2. However, pump site expression doubled to approximately 4 x 10(6) sites/cell as the cell density decreased from 1000 cells/mm2 to 275 cells/mm2. Despite the incremental increase in Na pump site expression that occurred as the cells hypertrophied below a density of 1000/mm2 to achieve confluence, this increase was insufficient to prevent a decrease in Na pump site density of the intact monolayer, expressed as pump sites/mm2. CONCLUSION: The confluent cell density of cultured bovine corneal endothelial cells can be varied from that found in the normal native cornea to that associated with corneal decompensation. In confluent cultures with cell densities ranging from 2750 cells/mm2 to 1000 cells/mm2, the number of pump sites per cell remains relatively unchanged. Below cell densities of 1000 cells/mm2, the number of pump sites per cell progressively increases. The increased Na pump site abundance in markedly hypertrophied endothelial cells cannot adequately compensate for the progressive reduction in the number of transporting cells per unit area within the intact monolayer. Even when considered with the decrease in the size of the paracellular ion conductive pathway that is a consequence of progressive endothelial hypertrophy, the overall pumping capacity of the intact endothelial monolayer declines.

Animals↗
PubMed1994

Analysis of sites of foot and mouth disease virus persistence in carrier cattle via the polymerase chain reaction.

This study was undertaken in order to explore possible sites of foot-and-mouth disease virus (FMDV) persistence during the carrier state. Tissue samples taken from experimentally infected animals at different times post-infection (p.i.) were examined by conventional viral isolation and the polymerase chain reaction (PCR) technique. The analysis of samples from several organs taken from 17 bovines between 3 and 270 days p.i. allowed the following conclusions: 1) Virus present in oesophageal-pharyngeal fluids (OPF) during the carrier state originates in the pharynx as shown by the detection of antisense FMDV RNA by PCR, 2) PCR is more sensitive than standard virus isolation techniques and may be used for the rapid detection of FMDV in specimens obtained during the acute stage of FMD and for identification of persistently infected cattle.

Animals↗
PubMed1994

Genetic variation of foot-and-mouth disease virus from field outbreaks to laboratory isolation.

Foot-and-mouth disease virus (FMDV), by nature of its RNA genome, possesses a high rate of mutation during replication. This results in extensive genetic polymorphism of virus populations in nature. The emergence of FMDV variants during replication has been reported. Genetic changes in the viral capsid protein (VP1) gene can result in amino acid changes affecting the immunodominant epitopes of FMDV. The genetic heterogeneity of FMDV in the field and the antigenic variants observed after cell culture isolation has been investigated by PCR sequencing and reactivity with monoclonal antibodies. These methods were applied to viruses causing two different outbreaks of FMD before and after replication in cell culture and in the animal host. The VP1 region of the genome was amplified by PCR and sequenced to reveal variant sequences identified after passage and to determine their presence in the original field tissue. In one case, reactivity with monoclonal antibodies was lost after passage as a result of an amino acid change in the subpopulation. These findings suggest that host cells can select specific virus genetic and antigenic subpopulations during virus isolation and propagation.

Amino Acid Sequence↗
PubMed1994

Interleukin-10 inhibition of HLA-DR expression in human herpes stromal keratitis.

PURPOSE: Human herpes stromal keratitis (HSK) is an important cause of visual loss and morbidity. The presentation of corneal and/or viral antigens is thought to activate T lymphocytes, resulting in aberrant cell-mediated immune responses that are central to the pathogenesis of HSK. Aberrant cellular expression of HLA-DR and intercellular adhesion molecule-1 (ICAM-1), both of which are necessary for optimal antigen-induced T-lymphocyte responses, is present in lesions of HSK, but little is known concerning endogenous cytokines that may inhibit HLA-DR or ICAM-I expression in human disease. In this study, the authors investigated the effects of interleukin-10 (IL-10) on HLA-DR and ICAM-1 expression in human HSK. METHODS: Penetrating keratoplasty specimens removed from 5 patients with HSK were divided to provide adjacent sections that were incubated with control medium or the same medium containing IL-10 (100 U/ml) for 48 hours. Immunoperoxidase staining was performed on each control and IL-10-treated corneal specimen to determine HLA-DR and ICAM-1 antigen expression. RESULTS: Interleukin-10 treatment resulted in profound reduction in immunoreactive HLA-DR, but not ICAM-1, in corneal cells and infiltrating leukocytes of all five HSK specimens. CONCLUSIONS: This study suggests that HLA-DR antigens may be selectively inhibited by cytokines released during inflammation in HSK. These results are the first to demonstrate cytokine suppression of HLA-DR in a human disease. Pharmacologic doses of IL-10 may inhibit HLA-DR-dependent immune responses that underlie a variety of destructive ocular inflammatory diseases.

Adult↗
PubMed1994

Presence of African horse sickness virus in equine tissues, as determined by in situ hybridization.

In a retrospective study, a negative-sense digoxigenin-labeled RNA probe, corresponding to the gene encoding nonstructural protein-1 of African horse sickness virus (AHSV) serotype 4, was applied to formalin-fixed, paraffin-embedded tissue taken from horses in the terminal stages of infection with AHSV. Fifteen infected ponies and one noninfected control were studied. Ponies exhibited a range of clinical signs and lesions. Thirteen ponies were infected with serotype 4, one with serotype 1, and one with serotype 2. Ponies were monitored clinically and euthanatized when severely clinically ill. The following tissues were available for study by in situ hybridization and histopathology: lung, heart, spleen, neck muscle, and supraorbital fat. Histologically, the most striking changes were pulmonary edema and, in some, acute myocardial necrosis. In situ hybridization revealed virus distributed widely in sections of lung and heart examined, with relatively less in spleen, neck muscle, or supraorbital fat. Virus was localized to target cells with morphologic features compatible with endothelium in all organs except spleen, where it was found in both endotheliumlike cells and large mononuclear cells.

African Horse Sickness↗
PubMed1994

Identification of African horse sickness virus in cell culture using a digoxigenin-labeled RNA probe.

A digoxigenin-labeled RNA probe was synthesized from a plasmid containing a portion of the African horse sickness virus (AHSV) serotype 4 genome segment coding for nonstructural protein 1. In an in situ hybridization procedure, this probe hybridized successfully to Vero cells infected with each of the 9 serotypes of AHSV. There was no hybridization with noninfected cell cultures or cell cultures infected with bluetongue virus.

African Horse Sickness Virus↗
PubMed1993

Predictive factors for endothelial cell loss after penetrating keratoplasty.

To assess the influence of donor age, donor endothelial cell density, recipient age, and diagnosis on loss of endothelial cell density after penetrating keratoplasty, we evaluated endothelial cell density data from specular endothelial images collected during the follow-up penetrating keratoplasty surgeries performed from 1980 through 1985 at one center. Univariate and multivariate analyses of information from 265 grafts showed consistent and statistically significant associations between 1-year postoperative loss of endothelial cell density and donor age, donor endothelial cell density, and recipient age. Corneas obtained from older donors, corneas with higher donor endothelial cell density, and corneas transplanted to older recipients demonstrated greater percentage of loss of endothelial cell density 1 year after surgery. These three factors accounted for 17% of the total variance in percentage of loss of endothelial cell density 1 year after surgery.

Adolescent↗
PubMed1993

The detection of foot-and-mouth disease virus in oesophageal-pharyngeal samples by a polymerase chain reaction technique.

A polymerase chain reaction (PCR) technique was used to detect the presence of foot-and-mouth disease virus (FMDV) in oesophageal-pharyngeal(OP) samples from experimentally infected steers. Ten-fold dilutions of OP samples were also diluted, inoculated onto lamb kidney cell cultures, and incubated overnight. The cultures that did not show overt cytopathogenic effects (CPE) of FMDV infection were frozen and thawed; both the fluid and the cell pellet were tested by the PCR technique. The PCR detected FMDV in the fluids of 57% of the cell cultures inoculated with 2-20 tissue culture infective doses-50% (TCID50) and of 33% of cell cultures inoculated with the 0.4-2 TCID50. The PCR detected FMDV in cell pellets of all cell cultures inoculated with 20 TCID50, of 71% of cell cultures inoculated with 2-20 TCID50 and of 50% of cell cultures inoculated with 0.2-2 TCID50. A diagnostic scheme using PCR and cell culture that would provide rapid and sensitive detection of FMDV in OP samples is proposed.

Animals↗
PubMed1993

Use of a digoxigenin-labeled RNA probe to detect all 24 serotypes of bluetongue virus in cell culture.

A digoxigenin-labeled RNA probe, corresponding to the section of the bluetongue virus (BTV) serotype 17 genome coding for nonstructural protein-1 (NS1), was applied to noninfected cell cultures and cell cultures infected with 24 different serotypes of BTV, 2 serotypes of epizootic hemorrhagic disease virus, and African horse sickness virus type 4. The probe hybridized to all cell cultures infected with the various BTV serotypes but did not hybridize to noninfected cell cultures or cell cultures infected with any of the other orbiviruses.

Animals↗
PubMed1992

A randomized, prospective, double-masked clinical trial of Optisol vs DexSol corneal storage media.

We compared Optisol and DexSol, two chondroitin-sulfate-based media for corneal storage at 4 degrees C, by transplanting 31 donor cornea pairs (one cornea stored in Optisol and its mate in DexSol for 20 to 134 hours) into 31 pairs of recipients (62 patients). All grafts were clear 1 year after transplantation except for one primary donor failure (Optisol group). Optisol-stored corneas were significantly thinner than DexSol-stored corneas after cardinal suture placement (0.64 mm vs 0.76 mm) and at the end of surgery (0.69 mm vs 0.78 mm); at all points afterward through 1 year the two groups did not differ. The activity of two lysosomal enzymes released into the media during storage, alpha-mannosidase and alpha-glucosidase, was lower in the Optisol group. Epithelial status and all endothelial morphometric parameters, except the figure coefficient at 1 year, did not differ between the two groups before surgery and 3, 6, and 12 months after surgery. Mean endothelial cell loss at 1 year was 15% for the Optisol group and 21% for the DexSol group (P = .22). Thus, Optisol-stored corneas were thinner during surgery than DexSol-stored corneas and there was less lysosomal enzyme activity in the Optisol medium after tissue storage. There were no significant differences in postoperative clinical or endothelial morphometric parameters, however.

Adult↗
PubMed1992

Secondary localized amyloidosis in interstitial keratitis. Clinicopathologic findings.

Cases of secondary localized corneal amyloidosis have been described in various corneal and ocular inflammations but are believed to occur uncommonly. The authors examined histopathologic specimens from 33 consecutive patients with interstitial keratitis who underwent penetrating keratoplasty for visual rehabilitation. In 11 cases (33%), multiple fusiform deposits of amyloid were identified and confirmed in middle and deep corneal stroma using histochemical staining. Characteristic electron microscopic findings were present in two cases. These results indicate that secondary localized corneal amyloidosis occurs frequently in interstitial keratitis and displays a distinct pattern of deposition.

Aged↗
PubMed1992

A pathogenesis study of foot-and-mouth disease in cattle, using in situ hybridization.

Eight calves were exposed in an aerosol chamber to nebulized foot-and-mouth disease virus. Two control animals were exposed in a similar manner to cell culture media only. Animals were euthanized at intervals and various tissues examined by in situ hybridization using a biotinylated RNA probe corresponding to a portion of the viral gene coding for the polymerase enzyme. By this technique large amounts of viral nucleic acid were found in coronary band, interdigital cleft and tongue as early as six hours postexposure, indicating a very rapid delivery from the portal of entry to the predilection sites for lesion development. This occurred well before the onset of viremia which by virus isolation was not detectable until 30 hours postexposure. The in situ hybridization signal in these tissues decreased in intensity and extent with time to focally positive areas, occasionally surrounding a vesicle. Other epidermal sites not normally thought of as sites for foot-and-mouth lesion development, such as carpus and eyelid, also had some viral nucleic acid detectable at various time intervals. In the lung by in situ hybridization, alveolar septa had viral nucleic acid early in infection (6-18 h postexposure) while later (36-96 h postexposure), the in situ hybridization signal was prominent in alveolar macrophages.

Animals↗
PubMed1991

The effect of allograft rejection after penetrating keratoplasty on central endothelial cell density.

We identified all patients who had undergone penetrating keratoplasty for keratoconus and were being observed longitudinally (N = 174). During the follow-up period, 57 of 174 patients (33%) showed evidence of an allograft rejection episode, which occurred at an average of eight months after the operation. We analyzed specular photographs of the corneal endothelium, taken before and after the first allograft rejection episode. A significant decrease in endothelial cell density was observed (11.8%, P less than .0001). As a control, we analyzed all available specular photographs from patients with keratoconus who showed no evidence of allograft rejection after penetrating keratoplasty. The observed endothelial cell density decrease (11.8%) in patients with keratoconus undergoing allograft rejection exceeded that found in the control subjects (6.8%) during a comparable time period (P = .06). Severe allograft rejection episodes resulted in a decrease in endothelial cell density that exceeded expected loss significantly (14.8% compared with 6.9%, P = .01), whereas mild allograft rejection episodes were not associated with a loss in endothelial cell density exceeding that expected (1.8% compared with 6.5%, P = .34).

Endothelium, Corneal↗
PubMed1991

Implantation of Kelman-style, open-loop anterior chamber lenses during keratoplasty for aphakic and pseudophakic bullous keratopathy. A comparison with iris-sutured posterior chamber lenses.

The clinical and specular microscopic results of 40 cases (39 patients) of penetrating keratoplasty during which a Kelman-style anterior chamber intraocular lens was implanted were reviewed retrospectively. Thirty-one pseudophakic eyes received an intraocular lens exchange and nine aphakic eyes received a secondary intraocular lens. Postoperative follow-up averaged 24.5 months (range, 3 to 51 months). At 1, 2, and 3 years after keratoplasty, 39.3%, 63.2%, and 63.6% of eyes, respectively, had visual acuities of 20/40 or better. Ninety-five percent of the grafts remained clear. Causes of poor postoperative visual acuity included cystoid macular edema (32.5%), new glaucoma (22.5%), and age-related macular degeneration (10.0%). Other causes were endothelial rejection leading to graft failure, corneal ulceration, and retinal detachment. Corneal endothelial cell loss by specular microscopy was 11.5% at 1 years, 21.3% at 2 years, and 25.0% at 3 years. These results were compared with cell loss associated with iris-sutured posterior chamber lenses in penetrating keratoplasty. Visual outcomes and complication rates were similar between these two methods; however, the endothelial attrition at 1 and 2 years for the sutured posterior chamber lens was greater than that of the Kelman anterior chamber lens.

Adult↗
PubMed1991

A preliminary study of the pathogenesis of foot-and-mouth disease virus using in situ hybridization.

Five adult guinea pigs were inoculated intraepithelially in the right hindfoot pad with foot-and-mouth disease virus. Animals were euthanatized with carbon dioxide at 4, 10, 24, 48, and 72 hours post-inoculation. Generalized disease developed in the guinea pigs, as evidenced by depression and inappetance by 24 hours post-inoculation and by the formation of vesicles in the noninoculated hindfoot pad by 48 hours post-inoculation. By in situ hybridization, using a 500 base pair biotinylated RNA probe, viral nucleic acid was detected in the noninoculated fore- and hindfoot pads as early as 10 hours post-inoculation, well before any pathologic changes associated with foot-and-mouth disease virus infection were detected. These tissues remained consistently positive for the presence of viral nucleic acid up to the end of the experiment. At this time, in the forefoot pad, even though virus had first been detected with certainty in that tissue 62 hours previously, there was still no microscopic evidence of foot-and-mouth disease virus-induced damage in the histologic section. Similarly, tongue tissue was positive by in situ hybridization at 4, 48, and 72 hours post-inoculation, yet there was never any microscopic evidence of degeneration or vesicle formation. From this preliminary study, it appears that, in the guinea pig, the virus is widely disseminated to foot pads and tongue, with epidermal lesions resulting only in selected areas.

Animals↗
PubMed1990

Proteoglycan biosynthesis by human corneas from patients with types 1 and 2 macular corneal dystrophy.

Corneal buttons were obtained from patients with types 1 and 2 macular corneal dystrophy (MCD) and from control patients with Fuchs' dystrophy or keratoconus. Buttons were incubated for 20 h in the presence of [3H]glucosamine or [2-3H]mannose. Radiolabeled proteoglycans and lactosaminoglycan-glycoproteins (L-GPs) were purified using chromatography on Q-Sepharose, Superose 6, and octyl-Sepharose. They were identified using chondroitinase ABC, keratanase or endo-beta-galactosidase digestion, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis or Superose 6 chromatography. This study confirms previous reports that type 1 MCD corneas synthesize a normal dermatan sulfate-proteoglycan (DS-PG) and an abnormal keratan sulfate-proteoglycan (KS-PG). The data indicate that typ 1 MCD corneas synthesize L-GP instead of KS-PG. This L-GP has a core protein of similar hydrophobicity (elution from octyl-Sepharose) and nearly similar mass (42 kDa) as the core protein of the KS-PG. It has identical glycoconjugates as those of the KS-PG except that they lack sulfate. Thus, type 1 MCD fails to synthesize keratan sulfate as a result of a defect in a sulfotransferase specific for sulfating lactosaminoglycans. Further, proteoglycans synthesized by a cornea from a patient with type 2 MCD were studied. This cornea synthesized a normal ratio of KS-PG to DS-PG although net synthesis of proteoglycans was approximately 30% below normal. The KS-PG appeared normal whereas the DS-PG had dermatan sulfate chains that were approximately 40% shorter than normal.

Cells, Cultured↗