Biomedical subjects
Publications and source records attributed to A D Steele.
Pterygium is known to cause corneal topographic changes that can result in decreased visual acuity. We present a case of recurrent pterygium causing blurred vision and diplopia, and document the corneal topographic changes, showing astigmatism of 15 diopters induced by lateral gaze, prior to surgical excision.
The sequences of the gene encoding VP7 (the major outer capsid protein) from one bovine and three human rotavirus strains were determined because of their unusual VP7 specificities. Two of the human strains (PA 169 and PA 151) had VP7 serotype 6 specificity whereas the two other strains, recovered from a child (HAL 1166) and a calf (678) belonged to VP7 serotype 8. The serotype 8 strains exhibited a high degree of sequence conservation when compared with each other and with other serotype 8 strains previously sequenced. The serotype 6 human strains shared a greater degree of sequence similarity with previously reported serotype 6 bovine strains than with other rotavirus serotypes; however the degree of sequence similarity among PA 169, PA 151 and the bovine strains was lower than had been previously reported for strains belonging to the same serotype. The demonstration of rotavirus serotypes that are shared between human and animal species supports the concept that interspecies transmission occurs and may play a role in rotavirus evolution.
Five cytopathic rotavirus strains were isolated in MA104 cells from stool specimens of kids with diarrhoea. Pre-treatment of the virus with trypsin and incorporation of low levels of trypsin in the maintenance medium were important for the successful cultivation of the strains in these cells. The isolates were shown to be group A rotaviruses by antigenic reactivity with a group A monoclonal antibody. This was confirmed by the migration patterns of the viral RNA genome during polyacrylamide gel electrophoresis, which also confirmed that all five strains had an identical RNA electropherotype. Analysis with monoclonal antibodies to the subgroup-specific VP6 antigen showed that these strains carried the subgroup I epitope.
Rotavirus particles were detected in the stools of 8 out of 12 Saanen kids with either diarrhoea or an increased rectal temperature. No other pathogenic organisms could be recovered from these kids. This is believed to be the first report of rotavirus infection in goats in southern Africa.
Faecal specimens from 1- to 7-week-old piglets (n = 251) with acute diarrhoeal illness were examined by direct negative staining electron microscopy for the presence of viral agents. Rotaviruses were observed in almost 40% of cases while adenoviruses and astroviruses were also observed in 3 specimens each. The majority of the rotaviruses reacted with a commercial Group A rotavirus ELISA although in 11 specimens they did not react with the Group A antigen and could represent atypical rotaviruses. This is the first report of adenoviruses and astroviruses in diarrhoeal faecal specimens from pigs in South Africa.
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Antibodies to human immunodeficiency virus 1 (HIV-1) and human T lymphotropic virus type 1 (HTLV-I) have been identified in various population groups living in southern and central Africa. Sera from 291 !Kung Bushmen in Bushmanland, Namibia were examined for the presence of antibodies to HIV-1 and HIV-2 and to HTLV-I. Initial screening for HIV-1/2 by two enzyme-linked immunosorbent assays (ELISAs) revealed evidence of past exposure in four individuals. However, no HIV-1/2 infection could be confirmed by a particle agglutination assay, a recombinant ELISA, or by Western blot for HIV-1 and HIV-2. Indeterminate Western blot profiles (with a p55 for each and either a p25 or p18 band) existed for all four HIV-1-reactive sera. Eight sera were reactive in the HTLV-I ELISA, although only five were positive on a second ELISA. Only three of the five HTLV-I-reactive sera could be confirmed by Western blot.
We evaluated the performance of six commercially available immunoassays for their ability to detect rotaviruses in stool specimens. Four of the assays were enzyme-linked immunosorbent assays (ELISA), including two rapid enzyme immunoassays (Testpack, Abbott Laboratories, Chicago and Pinpoint, Cambridge Biomedical, UK), and the remaining two were latex agglutination tests. A total of 100 specimens from children with gastroenteritis were tested with the commercial immunoassays and compared with electron microscopy (EM) and polyacrylamide gel electrophoresis (PAGE) as reference tests for the detection of rotavirus. Discordant results were further evaluated by a standard blocking ELISA. The rapid EIAs were found to be highly sensitive (100% for the Testpack and 97% for the Pinpoint) and more sensitive than the other immunoassays tested. High specificity was also recorded with both rapid EIAs (96% and 100% for Testpack and Pinpoint, respectively). The rapid EIA tests were easy to perform, required no specialized equipment, and could yield a result in less than 15 min. The results show that each of the commercial assays evaluated could accurately detect rotavirus in the stools of children with gastroenteritis, although the suitability of choice of assay will ultimately depend upon the requirements of the individual laboratory.
Corneal splinting is an old and well established surgical technique and modern straight needles allow for atraumatic and accurate placement, providing an alternative to suture-fixation scleral ring support. We have routinely used two straight, 150-micrometer diameter, 16-millimeter length suture needles passed through clear cornea, to act as anterior segment splint supports during anterior segment surgery in which the cornea would otherwise collapse. The needles enter through the clear corneal periphery, pass across the anterior chamber, and exit through clear cornea in a criss-cross configuration. This splint technique is quick and easy to perform and is an alternative or addition to suture-fixation scleral ring support.
During 1989 stool specimens from hospitalised children with gastroenteritis at Ga-Rankuwa Hospital in South Africa were examined for the presence of rotaviruses. Overall 16% of the children were positive for rotavirus. However, 43% of the rotavirus positive patients were infected in the hospital. Further characterisation of the rotavirus strains was performed by electrophoresis of the RNA genome and hybridisation analysis of the VP7 and VP4 genes present. The strains associated with nosocomial infection were similar to those strains acquired in the community. The majority of the strains, both community- or hospital-acquired, were associated with a serotype 1 strain with a long electrophoretype and bearing the Wa-like VP4 gene. Three minor rotavirus strains with a long electrophoretype were also observed to be circulating bearing serotype 1 or 4 VP7 genes and the Wa-like VP4 gene. Interestingly, a serotype 4 strain bearing the M37-like VP4 gene was identified to occur almost exclusively in neonates although the gene was associated with diarrhoea in these cases. Two strains with differing short RNA electrophoretypes were also observed, members of which hybridised to VP7 serotype 2 and VP4 DS-1 type probes.
A prospective study of excimer laser photorefractive keratectomy was performed with the aim of correcting a range of myopic errors between -1.00 and -10.00 dioptres. Corneal healing was monitored through the first post-operative year by serial assessments of refraction, contrast sensitivity, corneal haze, pachymetry and keratometry. Eighty-one patients were recruited for the study. At 12 months 81% were within +/- 1.00 dioptre of desired emmetropia and with unaided vision of 6/12. Contrast sensitivity was found by Pelli-Robson assessment to be reduced throughout the 12 months and regression analysis predicted recovery by 2 years. At 12 months, however, only 15% of patients were found to have lost a single line of best corrected Snellen acuity. Predictability of results was found to be greatest for initial errors less than -4.00 dioptres. No serious complications were observed during the follow-up period, but refraction had not stabilised in all cases and patients remain under review.
In a retrospective survey of 117 operations for primary or recurrent pterygium, conjunctival autografting was compared with both excision without conjunctival closure ('bare sclera excision') and excision with complete conjunctival closure. The probability of corneal recurrence at 36 months after surgery was determined by survival curve analysis. In previously unoperated cases conjunctival autografting (n = 15) resulted in a 14% probability of recurrence, compared with 70% for bare sclera excision (n = 50) and 69% for excision with complete conjunctival closure (n = 20). In previously operated cases conjunctival autografting (n = 17) resulted in a 7% probability of recurrence, compared with 82% for bare sclera excision (n = 15). Hazard ratio analysis confirmed the statistical significance of these results at the 95% confidence level. Conjunctival autografting was more likely to produce an improvement in visual acuity than other forms of surgery.
Large numbers of patients are being treated for myopia, hyperopia, and astigmatism using the excimer laser. For many patients who are treated for myopia and hyperopia, the procedure is elective and these treatments remain investigational. The use of other lasers for refractive surgery is at an earlier stage, with human trials commencing for infrared lasers. Animal studies are being performed for pulsed picosecond and solid-state ultraviolet lasers. The indications for refractive treatment should be clearly defined, although the results of laser application remain the subject of investigation. Complications of laser application to the cornea occur in the immediate, short-term, and long-term posttreatment period. A continual improvement in refractive results along with a reduction in complications remains the goal of laser refractive research.
Rotavirus-positive specimens were recovered from 143 Afrikander calves on two farms in the northeastern Cape of South Africa during late 1988 and 1989. The rotavirus strains were analyzed by polyacrylamide gel electrophoresis of the RNA genome, and four rotavirus RNA electrophoretypes, each with a long profile, were identified. A distinct RNA profile was identified on the farms during 1988, but by early 1989, two patterns existed, one unique to each farm. Over the next 8 months a new electrophoretic pattern emerged on one farm, whereas the pattern on the other farm remained unchanged. The rotavirus subgroup I antigen was detected in all specimens examined with subgroup-specific monoclonal antibodies. Non-group A rotaviruses were not identified by RNA genome analysis of 82 specimens from calves with diarrhea negative for group A rotaviruses by an enzyme-linked immunosorbent assay.
The rotavirus VP4 protein elicits the production of neutralizing antibodies and is known to play a role in inducing resistance to disease. At least five human rotavirus VP4 gene alleles have been described on the basis of antigenic polymorphism and/or nucleotide sequence differences. In the present study, we developed cDNA probes directed at the hyperdivergent region of the VP4 gene of the five described human rotavirus VP4 alleles (Wa, DS1, M37, AU228, and 69M) and used them in hybridization assays with human rotavirus strains from Latin America and Europe to determine the distribution of the VP4 gene alleles in nature. The Wa-like allele was detected most frequently, occurring in 57% of the 402 rotavirus strains tested, and the DS1-like allele was the next most common, occurring in 14% of the strains tested. The M37- and AU228-like alleles were detected in only 4 and 3% of the rotavirus strains tested, respectively, whereas the 69M-like VP4 gene allele was not detected. Several rotavirus strains from Europe did not react with any of the VP4 gene probes, although they did hybridize to a probe generated from a representative strain from the group. These data indicate the global distribution of various VP4 gene alleles and raise the possibility that other, unrecognized human VP4 alleles exist in nature because almost one-fourth of the strains could not be classified into any of the established VP4 groups.
The relative frequencies of the Wa (corresponding to serotype P1A), DS-1(P1B), M37(P2), and AU-1(P3) alleles of the VP4 gene from rotaviruses collected from the stools of individuals in Japan between 1982 and 1991 were determined to be 83.1, 15.6, 0, and 1.3%, respectively, by a polymerase chain reaction-based typing assay.
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