Biomedical subjects
Publications and source records attributed to D Paton.
Blood samples were taken from 121 sows and gilts on 7 commercial piggeries located around Lusaka (Zambia). The samples tested negative for antibodies to Aujeszky's disease, transmissible gastroenteritis (TGE), swine influenza, hog cholera and brucellosis. Seventy-eight pigs from 5 farms had positive titres to porcine parvovirus. Eighteen sera showed positive titres to Leptospira celledoni.
The use of a lymphocyte transformation test (LTT) to confirm allergic contact dermatitis from thiurams has been investigated. The responses of peripheral blood mononuclear cells (PBMC) from thiuram-sensitive and non-sensitive individuals following culture with dimethylcarbamoyl-protein (human serum albumin; HSA) and dimethylthiocarbamoyl-HSA conjugates has been compared. Only PBMC from those patients who were patch-test-positive with thiuram-mix and sensitized to tetramethylthiuram monosulphide (TMTM) or TMTM and tetramethylthiuram disulphide (TMTD) exhibited significant proliferative responses to these conjugates. Thiuram-patch-test-negative patients and control donors with no history of allergic contact dermatitis failed to mount a significant response to any concentration of either conjugate. Two of the thiuram-sensitive patients were also nickel-patch-test-positive, and PBMC isolated from these donors, but not from nickel-patch-test-negative patients, proved positive in a nickel LTT. The data reveal that relevant hapten-protein conjugates are capable of provoking specific human lymphocyte proliferative responses in vitro, and that, using this technique, the LTT can, in principle, be used for the investigation and/or diagnosis of skin sensitization to lipophilic contact allergens.
The first Clinical Symposia on glaucoma (Volume 28, Number 2), by Drs. Paton and Craig, was published in 1976 and updated in 1981. The impact of this disease on public health and the advances in diagnosis and treatment have prompted this revision. The text has been completely rewritten by Drs. Danyluk and Paton and is illustrated with all new plates by Dr. Craig.
The increasing cost of American health care necessitates major adjustments in the systems for providing that care. Computerization has the potential for facilitating efficient, affordable, and high-quality care while maintaining a fee-for-service system. The development of model delivery systems for health care should receive research funding from private and government sources. For ophthalmology, a paradigm for technology-dependent specialties, mechanisms to streamline eye care are being explored via a nonprofit foundation.
In the lung of Rana perezi no differences as a function of age have been found for any of the five major antioxidant enzymes, reduced (GSH), oxidized (GSSG) or glutathione ratio (GSSG/GSH), oxygen consumption (VO2) and for in vivo or in vitro stimulated tissue peroxidation. This frog shows a moderate rate of oxygen consumption and a life span substantially longer than that of rats and mice. Chronic (2.5 months) catalase depletion in the lung did not affect survival or any additional antioxidant enzyme, GSH, GSSG or in vivo and in vitro lung peroxidation in any age group. Only the GSSG/GSH ratio and the VO2 were elevated in catalase depleted old but not young frogs. After comparison of these results with those obtained in other animal species by other authors we suggest the possibility that decreases in antioxidant capacity in old age be restricted to species with high basal metabolic rates. Nevertheless, scavenging of oxygen radicals can not be 100% effective in any species. Thus, aging can still be due to the continuous presence of small concentrations of O2 radicals in the tissues throughout the life span in animals with either high or low metabolic rates.
1-Chloromethylpyrene (1-CMP) has been evaluated as a model mutagen and toxin related to the ultimate electrophiles derived from benzo[a]pyrene and 1-nitropyrene. It was mutagenic to Salmonella (greater than 100 pg/plate) and exceptionally reactive to DNA when assessed by the 32P-postlabelling technique. 1-CMP was inactive in a mouse bone micronucleus assay when administered by gavage, probably due to hydrolysis, whose kinetics have been studied (t1/2 approximately 23 min at 37 degrees C). However, as expected, it was a potent skin toxin as determined by its activity as a mitogen to mouse skin and its contact allergenicity, as determined using the local lymph node proliferative assay. It is concluded that 1-CMP will probably be a potent human skin carcinogen and contact allergen.
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The presenting features of 250 consecutive patients who underwent a ventilation/perfusion lung scan for suspected pulmonary embolus (PE) were analysed. Ninety-six patients had lung scans highly suggestive of PE, with one or more unmatched segmental perfusion defects (scan positive), 86 had low probability scans (scan negative) and 68 an indeterminate scan. Scan positive patients were more likely to have a PaO2 of less than 10.7 kPa, an elevated P(A-a)O2 and an abnormal chest X-ray compared with scan negative patients but these measurements were of poor specificity. Furthermore, scan-positive patients had a higher incidence of lung disease. Localized chest wall tenderness was more common in scan-positive patients, occurring in 9% of patients, but there were no other significant differences in individual symptoms, signs or electrocardiographic findings between scan-positive and scan-negative patients. The diagnosis of PE should not be made on clinical grounds alone and all patients suspected of having a PE should at least undergo isotope lung scanning.
Twenty patients who had taken overdoses of paracetamol were treated with acetylcysteine between 12 and 24 hours after the incident. Although 19 patients had plasma paracetamol concentrations greater than those associated with a 90% risk of moderate to severe liver damage, this complication occurred in only seven (35%) individuals. No patient developed hepatic encephalopathy or acute renal failure and all recovered without sequelae. We conclude that acetylcysteine administration up to 24 hours following paracetamol overdose is not dangerous and may prevent further liver damage.
The rat liver carcinogen methapyrilene is shown to be a selective mutagen to strain TA1535 of Salmonella typhimurium when tested in the absence of S9 mix and using the standard plate-incorporation assay protocol. The activity observed was weak but was reproducible for a range of samples on many occasions of test and was not due to impurities. These data contrast with six earlier reports of the inactivity of this chemical in the Salmonella mutation assay.
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A structure--activity study is described in which four new derivatives of the potent bacterial mutagen 5-dimethylaminophenylazoindazole (5I) have been evaluated for mutagenicity to Salmonella. As expected, monodemethylation of the -NMe2 group of 5I increased its mutagenic potency while replacement of the -NMe2 with a cyclic amine reduced it. However, replacement of the aromatic indazole -NH group (of 5I) by an -NMe group (yielding NMe5I) dramatically attenuated mutagenic potency, a reduction which was both unexpected and not reversed in the monomethyl analogue (NMeMA5I). In competition experiments NMe5I had an inhibitory effect on the mutagenic potency of 5I itself and on that of the nonazo mutagen 2-acetylaminofluorene 2AAF. The results illustrate some of the problems associated with evaluating mixtures for mutagenicity and of assuming simple structure--activity relationships in the absence of relevant experimental data.
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A retrospective study of patients who underwent keratoplasty for keratoconus was done in 100 consecutive cases, of which 50 were penetrating keratoplasty procedures, and 50 were lamellar keratoplasty procedures. Each case was done by the same surgeon in both series. Criteria for patient selection were essentially the same. Postoperative care differed primarily in the time before suture removal, being an average of ten months in the penetrating keratoplasty group and three months in the lamellar keratoplasty group. Of those patients who underwent penetrating keratoplasty, the mean best-corrected visual acuity was 6/6 (20/20-) and the average corneal astigmatism was + 5.00 diopters. Of those patients who received lamellar keratoplasty, the mean best-corrected visual acuity was 6/9 (20/30-), and the average corneal astigmatism was +3.25 diopters. The most frequent complications of both techniques were wound separations that responded well to resuturing.
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