Biomedical subjects
Publications and source records attributed to A Ho.
Conjunctival hyperaemia was assessed in noncontact lens wearers using a photographic reference scale. The study was carried out on a sample of 252 females and 227 males within the age range of 1 to 89 years. The results show increasing levels of hyperaemia with age and higher levels of hyperaemia in males than in females. The differences in hyperaemia level for age and sex, however, were small and were insignificant clinically.
Peripheral focusing of light by the anterior eye may provide a unifying concept to explain the location and etiology of sun-related eye conditions (ophthalmohelioses). Using a bovine eye model, along with computer-assisted ray-tracing techniques to model limbal focusing, we demonstrated a correlation between the locations of the foci of scattered incident light (resulting in a 20-fold concentration of light at the limbus) and the usual locations of pterygium and cortical cataract. These findings suggest the need for improved ocular protective devices, particularly ones that provide lateral protection of the eye against the increased ultraviolet insolation resulting from thinning of the ozone layer.
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A new geometrical method of determining the location of the image of an optical component is described. This method does not require rays to be drawn. It can be applied to refractive and reflective components as well as multi-component systems.
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Feeding and drinking were recorded in male ob/ob mice and lean mice fed pelleted Purina Lab Chow No. 5001 with water to drink. The circadian patterns of eating and drinking of obese mice differed from those of lean mice, in both the proportional temporal distributions of feeding and of drinking behavior across the 24-hour day and in the absolute amounts consumed hourly. The pattern of increased food consumption by the obese mice was different than that underlying increased water consumption. When meal parameters were analyzed in terms of 'complete meals' of both feeding and drinking (the end of a meal defined as at least 12 consecutive minutes with no ingestion), obese and lean mice had the same number of meals and their periodicity was similar, but meal size was much greater in the obese mice. In the dark, both obese and lean mice showed strong postprandial correlations of meal size with time from the start of a meal to start of the next meal.
Drinking behavior of the isogenic mouse strain C57BL/6J was analyzed into nongenetic components: stochastic fluctuations, responses to fluctuations in the current environment, and persistent differences between individual animals. The latter accounted for the major part of the variance. The variance was neither increased by differences in diet during the postweaning rapid growth period (prior to assay for drinking choice) nor diminished by uniformity of treatment during this period, suggesting that significant differentiation had occurred prior to weaning. The large variance between animals could be explained by assuming that the genetic role in consumption of alcohol by C57BL mice is permissive--a relative insensitivity to the aversive orosensory and pharmacological effects of 10% alcohol--rather than a specific drug-seeking predisposition.
Individual differences in the amount of alcohol consumed in a choice situation are found in highly inbred C57BL/6J mice. The extent to which environmental stress can modify alcohol preference was studied by coupling acute episodes of poisoning with restricted fluid availability, and recovery with free choice of drinking fluids. Addition of actinomycin D, a mycotoxin, to ordinary chow during 2-day periods produced acute episodes of nonlethal food poisoning from which the mice recovered rapidly. Consumption of a 10% alcohol solution and of water was recorded for several weeks before poisoning and for several weeks after the last episode. By varying drinking fluids available to the mice during the episodes of poisoning, long-lasting changes in alcohol preference were produced. When 10% alcohol was the sole drinking fluid available during poisoning, preference for the alcohol solution was abolished. When water was the sole fluid during poisoning, alcohol preference was increased above the already high levels established in the baseline and above a control group that was restricted to water during the treatment periods but was not poisoned. This increased alcohol preference was due to a nearly complete suppression of water intake in the posttreatment period; there was no significant increase in amount of alcohol consumed. The greatest individual differences in subsequent alcohol preference were found in the group of mice which continued to have free choice of alcohol and water during episodes of poisoning. The variety of responses to the same treatment show how environmental influences outside the experimenter's control may account for the variability found in voluntary alcohol consumption among genetically homogeneous mice.
We report the skeletal abnormalities in a 4 1/2-year-old boy with acrogeria, a progeroid syndrome of premature aging of the skin without the involvement of internal organs seen in Hutchinson-Gilford progeria syndrome. Acro-osteolysis of the distal phalanges, delayed cranial suture closure with wormian bones, linear lucent defects of the metaphyses, and antegonial notching of the mandible are the predominant skeletal features of the disorder. The skeletal features described in 21 other reported cases of acrogeria are summarized.
Leukemic cells of a 19 year old patient with prolymphocytic leukemia of T-cell type (T-PLL) were characterized by surface markers and immunologic functions. Phenotypic analysis using a large panel of monoclonal antibodies corresponding to the clusters (CD) of differentiation antigens established on the Leukocyte Typing Workshops I and II revealed a unique T-cell phenotype not yet reported in the literature: CD1 (T6)-, CD2 (T11)+, CD3 (T3)+, CD4 (T4)-, CD5 (T1)-, CD6 (T411)+, CD7 (Leu9)+, CD8 (T811)-, CD10 (J5)-, CD11 (M22)+, CD12 (M67)-, CD13 (My7)-, CD14 (Mo2)-, CD16 (Vep13, 3G8, Leu11)+, CD18 (MHM23)+, CD19 (B4)-, CD20 (B1)-, CD25 (TAC)-, MHC-class II (HLA-DR, HLA-DQ)-, NKH1A+, Leu7-. Despite the expression of surface structures associated with natural killer (NK) function (CD16, CD18, NKH 1 A) the T-PLL cells were inactive in NK assays in vitro. Low in vitro ADCC activity was detectable. This unusual T-PLL phenotype might help to identify a new distinct T-cell differentiation stage.
In a study reported recently, the effects of long-term extended wear of soft contact lenses on the human cornea were found to include epithelial thinning, a reduction in epithelial oxygen uptake, induction of epithelial microcysts, stromal thinning, and an increase in endothelial polymegathism. A multiple regression analysis was performed on data from this study to identify lens or patient characteristics associated with these effects. Although generalization to the population of conclusions based on associations identified using a small sample should be treated with caution, results from this analysis suggest that lens-induced effects on the cornea may be minimized by fitting lenses that are thinner and more mobile, and by encouraging more frequent lens removal and replacement. Patients with thinner corneas and with high endothelial cell density and low polymegathism before commencing lens wear tended to show fewer effects from extended lens wear.
Hypertrophic osteoarthropathy (HO) is a specific clinicoradiologic entity, the most common cause of which is the presence of pulmonary lesions. Eight cases of aortic graft infection and aortoenteric fistulae in association with HO have been recognized. A case of an infected axillary-axillary graft presenting as unilateral HO of the upper limb is reported, and its unusual features are used to postulate a mechanism underlying HO.
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A dry eye history questionnaire was completed by 500 patients who presented for the correction of refractive errors (normals), and 68 patients with previously diagnosed sicca syndrome. Subsamples of females over 45 years were extracted for comparison, and discriminant analysis yielded correct classification for 62 of 63 sicca subjects and 36 of 37 normals, representing 98% sensitivity and 97% specificity. An equivocal classification that warranted supplementary diagnostic procedures was indicated for 5% of subjects. The results indicated that the use of the questionnaire will obviate the need for supplementary ocular sicca examination procedures for the majority of patients presenting for an ocular examination.
Articular cartilage contains at least 2 proteoglycans (PGs) which aggregate with hyaluronate: one larger, richer in chondroitin sulphate (CSRPG); the other smaller, relatively richer in keratan sulphate (KSRPG). With maturation the ratio of CSRPG/KSRPG decreases. In order to test the hypothesis that osteoarthritic cartilage contains an increased amount of proteoglycans characteristic of immature cartilage, experimental osteoarthritis (OA) was induced in 11 dogs by transection of the anterior cruciate ligament. Proteoglycan populations were assessed by composite agarose polyacrylamide gel electrophoresis (CAPAGE). The OA cartilage had more proteoglycan and an increased proportion of the slower migrating band on CAPAGE, which corresponds to the CSRPG, supporting the hypothesis that OA cartilage contains an increased amount of proteoglycans characteristic of immature cartilage.
A dry eye questionnaire was completed by 500 patients who presented for the correction of refractive error. A sample of non-contact lens wearers was extracted (N = 177) and responses were compared between males and females, and between three subgroups according to age. Females responded at a significantly higher rate in regard to 4 of 24 questionnaire segments. Differences according to age were found for 5 of 24 questionnaire segments. Except for the question concerning arthritis, increased prevalence of dry eye findings in over-45-year-old females was not found in this normal population. These results, combined with those reported previously, validate the use of the questionnaire as a screening instrument that will enable ocular sicca cases to be identified.
Test charts with three different contrast levels were used to measure acuity of six subjects at distance and near. Reduction in measured acuity as a result of refractive defocus was shown to be independent of contrast level. Reduction in measured acuity with diffusive blur was greater on the medium and low contrast charts than on the high contrast chart. We advocate the use of charts with two different contrast levels to help differentiate between causes of visual degradation.
Although many ultrasonic pachometers are commercially available, little has been reported about their performance. We outline a technique for evaluating the accuracy of ultrasonic pachometers by simulating corneal thickness measurements using hydrogel contact lenses. On-eye contact lens thickness is determined using ultrasonic and optical pachometry. Absolute lens thickness is determined using a thickness gauge. Comparisons are made between measurements from the ultrasonic pachometer and measurements from the thickness gauge and optical pachometer. We used this technique to evaluate the performance of the Vida-55 ultrasonic pachometer. This technique was also used to determine the ultrasonic velocity for cat corneal tissue and two hydrogel lens materials. We determined the velocity of ultrasound in cat corneal tissue to be 1590 m/s at 33 degrees C. The velocity of ultrasound in hydroxyethyl methacrylate (HEMA) was 1740 +/- 24 m/s and 1700 +/- 40 m/s in Snoflex 50. We found the Vida-55 pachometer measured corneal thickness accurately when the appropriate ultrasound velocity was used (SEM = 6 microns).