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Biomedical subjects

M Archer

Publications and source records attributed to M Archer.

At least 37 records · Page 2Linked to original sources
PubMed1990

DNA/DNA hybridization studies of the carnivorous marsupials. I: The intergeneric relationships of bandicoots (Marsupialia: Perameloidea).

A complete suite of comparisons among six bandicoot species and one outgroup marsupial was generated using the hydroxyapatite chromatography method of DNA/DNA hybridization; heterologous comparisons were also made with three other bandicoot taxa. Matrices of delta Tm's, delta modes, and delta T50Hs were generated and corrected for nonreciprocity, homoplasy, and, in the case of delta Tm's, normalized percent hybridization; these matrices were analyzed using the FITCH algorithm in Felsenstein's PHYLIP (version 3.1). Uncorrected and nonreciprocity-corrected matrices were also jackknifed and analyzed with FITCH to test for consistency. Finally, sample scores for delta Tm, delta mode, and delta T50H matrices were bootstrapped and then subjected to phylogenetic analysis. These manipulations were carried out, in part, to address criticisms of the statistics used to summarize DNA/DNA hybridization (especially T50H) and the method itself. However, with the exception of an unresolved trichotomy among the two Echymipera species and Peroryctes longicauda, all trees showed the same branchpoints. Except in the case of the tree generated from reciprocal-corrected delta Tm data, nodes were stable under jackknifing; and, again excepting the above-mentioned trichotomy, all nodes were supported by 95% or more of the bootstrapped trees. These results suggest that, despite arguments to the contrary, all three summary statistics can be valid for DNA/DNA hybridization data. Of taxonomic interest is the placement of Echymipera spp. and Peroryctes longicauda together and separate from the more distant Peroryctes raffrayanus; the genus Peroryctes is thus at least paraphyletic. The trees further grouped Echymipera-plus-Peroryctes as the sister group of Isoodon-plus-Perameles. Limited hybridizations with Macrotis lagotis suggest that its current position as representative of an entirely distinct family of perameloids is correct.

Animals↗
PubMed1988

Enamel of Yalkaparidon coheni: representative of a distinctive order of tertiary zalambdodont marsupials.

The enamel of an incisor and a premolar of Yalkaparidon coheni was examined by scanning electron microscopy in fractured and in sectioned, polished surfaces. The enamel of both teeth demonstrated: complete, ovoid and horse-shoe shaped prisms in a Pattern 2 arrangement; a simple parallel prism course; and, enamel tubules in abundance in the premolar but restricted to the innermost enamel in the incisor. Overall, the enamel ultrastructure supports the marsupial affiliation proposed for Yalkaparidon coheni but does not unambiguously ally it with any other order of marsupials. The observation of a significant ultrastructural difference between the anterior and posterior teeth of a marsupial emphasizes the need to sample both if available. In pursuing this, we report here also the lack of tubules in the anterior teeth of the extant Tarsipes rostratus. This together with a similar absence of typical marsupial tubules from the incisor of the extinct Yalkaparidon coheni, would suggest that the wombat is not the only surviving marsupial to have experimented so extensively with this particular structural feature. It is likely that further study will demonstrate an unexpected and relative lack of tubules in the incisor enamel of other fossil Australian marsupials.

Animals↗
PubMed1987

Marsupial and monotreme enamel structure.

We present some recent developments in our understanding of two basic questions: the origin, extent, nature and course of marsupial enamel tubules; and the characterisation of monotreme enamel, more particularly, the prismatic nature of platypus enamel. Methods used included SEM of methacrylate casts of marsupial enamel tubules, worn and cut surfaces of whole marsupial teeth, developing and erupted platypus teeth, and a well-developed molar of the newly discovered Miocene ornithorhynchid Obdurodon sp., and tandem scanning reflected light microscopy of intact marsupial teeth. We conclude that there are significant species differences with respect to prism shape, row formation and tubule disposition in marsupials and, moreover, that these features change in a consistent way through the thickness of the enamel. Consideration of enamel prism course in incisor and molar enamel of Macropus eugenii, together with the tubule casts, enables us to conclude that there is a fundamental relationship of tubule to prism in the body of marsupial enamel. This and previously reported data put beyond dispute the essential relationship of the marsupial tubule to the formative ameloblast. The enamel of Ornithorhynchus anatinus is shown to be prismatic only in part, with well-formed regular prisms not being a primary structural feature. The enamel of the fossil monotreme is prismatic and tubular and displays large areas of Pattern 2 prism packing. Monotreme enamel has been interpreted as representing a structural stage intermediate between that of known multituberculates and extant tribosphenid mammals.

Animals↗
PubMed1986

A description of the molar enamel of a middle Miocene monotreme (Obdurodon, Ornithorhynchidae).

The dentine and enamel of a newly discovered well-formed tooth of a Tertiary monotreme, Obdurodon sp., was examined for ultrastructural information relevant to the phylogenetic interpretation of monotremes. Obdurodon sp. presents a unique combination of mammalian structural features in the fractured enamel surfaces examined: tubules in great number; prisms of small diameter; a substantial and coherent inter-prismatic component and, in the middle third enamel, inter-row sheet; a simple non-decussating prism course; a predominantly pattern 1 prism packing in the innermost enamel; and a predominantly pattern 2 prism packing in the middle third enamel; and non-prismatic outer enamel. Although the particular combination of structural characteristics suggests that monotremes represent a possibly unique and relatively plesiomorphic group of mammals, many of the features are very similar to those seen in multituberculates. If multituberculates and monotremes are monophyletic, it would help to explain what has otherwise been a puzzling zoogeographic pattern in the distribution of each group.

Animals↗
PubMed1985

Cutaneous pythiosis in beef calves.

Six Brahman and Brahman-cross calves less than or equal to 9 months old were examined because of ulcerative swellings of the fetlocks (5 calves) or numerous focal ulcerated cutaneous lesions (1 calf). Biopsies revealed focal cutaneous granulomas around regular, thick-walled branching hyphae, 4 to 9 micron in diameter. In all cases, portions of the hyphae were surrounded by granular encrustations, which ultrastructurally were composed of amorphous material comparable to antigen-antibody complexes. The protist Pythium sp was isolated from 2 calves.

Animals↗
PubMed1985

What use is generic prescribing?

The dispensing of generic preparations at four dispensing chemist shops was investigated by means of a questionnaire. Certain generic prescriptions result in the dispensing of proprietary products despite the existence of generic preparations, and the pharmacist may be reimbursed for the cost of the proprietary drug which has been dispensed. Not all generic prescriptions result in the dispensing of cheaper drugs because of the methods of payment to chemists. If doctors write more generic prescriptions there will ultimately be more dispensing of generic products. Even in the case of drugs still under patent, prescribing by generic name should be encouraged. The savings achieved by generic prescribing are to some extent at the cost of the dispensing chemists. The method and scale of payments for dispensing requires urgent review.

Costs and Cost Analysis↗
PubMed1984

Postirradiation malignant fibrous histiocytoma arising in juvenile nasopharyngeal angiofibroma and producing alpha-1-antitrypsin.

A fatal nasopharyngeal malignant fibrous histiocytoma developed in a young male after irradiation of juvenile nasopharyngeal angiofibroma diagnosed 5 years earlier. The sarcoma extended from the nasopharynx into the floor of the pituitary fossa and into both parasellar regions. There was no clinical evidence of any distant spread. Many of the malignant cells contained cytoplasmic granular and globular PAS-positive inclusions shown to be alpha-1-antitrypsin immunohistochemically. Ultrastructurally, this probably corresponded to electron-dense material with distinctive patterns and which had accumulated within distended ergastoplasmic cisternae of the neoplastic cells. Three previously reported case of postirradiation sarcomas arising in nasopharyngeal angiofibroma were said to be fibrosarcomas and none produced alpha-1-antitrypsin.

Adult↗
PubMed1983

Necropsy study of the olfactory portal of entry in herpes simplex encephalitis.

Two fatal cases of sporadic herpes simplex virus (HSV) encephalitis were seen and diagnosed at the Sir Charles Gairdner Hospital, Perth, between 1979 and 1981. Necropsy studies were directed to the possible portal of entry of HSV into the central nervous system. Viruses were present in the left olfactory nerve in one patient. No viruses were found in the Gasserian ganglia of either patient. The finding of HSV within an olfactory nerve provides further evidence of an olfactory portal of entry to the central nervous system in sporadic human HSV encephalitis.

Aged↗
PubMed1982

Shunt nephritis.

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Child, Preschool↗
PubMed1980

Grassland management for horses.

The pasture needs for horses as compared to those for farm livestock are reviewed. The differing preferences of various types of grasses and other plants, and the patterns of grazing seen on"horse-sick" pastures, are discussed. Suggestions for practical management include frequent collection and removal of droppings, the use of grazing by cattle, adequate rest from horses and the application of cattle manure. Methods for controlling weeds and renovating horse-sick paddocks are discussed and compared to ploughing up. Finally, the place of fertilisers is considered for use on pastures for horses.

Animal Feed↗
PubMed1980

The Anti-Coronary Club: 1957 to 1972.

The Diet and Coronary Heart Disease Study Project, known as the Anti-Coronary Club, was established by the New York City Department of Health, Bureau of Nutrition in June 1957. The major goals were: 1) to develop an acceptable experimental diet capable of reducing serum cholesterol in ambulatory middle-aged men; and 2) to test the hypothesis that a reduction in serum cholesterol is associated with a modified diet and a reduced incidence of coronary heart disease development. The Prudent Diet was developed to provide a way of eating consistent with the American dietary pattern, avoiding an excess of empty calories, saturated fat, and food cholesterol. It provides a favorable balance of nutrients, limits total fat content and makes possible a more desirable ratio of PUFA to saturated fats. Based on the data, it seems reasonable to attribute the lower coronary heart disease incidence rates in the active experimental group of both age categories studied (40 to 49 and 50 to 59) directly to the reduction in serum cholesterol levels, with weight reduction as a beneficial accomplishment. Dietary intervention with the Prudent Diet was instrumental in achieving the lower coronary heart disease incidence rates that demonstrated the efficacy of the Prudent Diet as a sensible diet.

Adult↗
PubMed1977

Suspension of non-viable fungal spores as a standard for platelet counting.

In the search among biological particles for a standard for counting human platelets, a strain of Absidia corymbifera was found to have spores that resembled platelets. After fixing in formalin and autoclaving the spores had a similar mean cell volume to that of human platelets. A suspension of these killed spores was tested in 100 laboratories and gave consistent results as a standard for human platelet counting. The Absidia corymbifera standard can be used in electronic counting methods but not in sedimentation methods, as the spores will be removed by centrifugation.

Blood Cell Count↗
PubMed1976

Gastric cancer in Colombia. I. Cancer risk and suspect environmental agents.

A case control study of patients discharged from hospitals revealed fourfold differences in geographic variation in stomach cancer risk within the Department of Narino (Colombia). Data from gastroscopic surveys of population groups, samples of water supplies, and urine and saliva in Narino also indicated a generally positive correlation among the following parameters: 1) gastric cancer risk, 2) prevalence of chronic atrophic gastritis and intestinal metaplasia, 3) nitrate content of well waters, and 4) nitrate excretion by the population. Urinary excretion reflected the ingestion of nitrates, and this implied a higher average intake of nitrates in the populations at high risk for stomach cancer. The Narino data could be construed as presumptive epidemiologic evidence for the role of nitrate availability in the etiology of stomach cancer.

Carcinogens, Environmental↗
PubMed1975

A model for gastric cancer epidemiology.

It is postulated that one major subtype of gastric carcinoma ("intestinal type") is the end- result of a series of mutations and cell transformation begun in the first decade of life. The mutagen could be a nitroso compound synthesised in the upper gastrointestinal tract by the action of nitrite (i.e., from food or saliva) on naturally occurring nitrogen compounds. Under normal conditions these nitroso compounds do not reach the gastric epithelial cell, presumably because their synthesis is inhibited by antioxidants present in food or because of their inability to pass the mucous barrier. The barrier may be overcome by abrasives or irritants such as hard grains, food with high sodium-chloride concentration, or surfactants. Once the first mutation occurs, the glandular gastric epithelium is gradually changed to intestinal-type epithelium, the mucous barrier altered, and the pH elevated. Under these conditions, bacteria proliferate in the gastric cavity and facilitate the conversion of nitrates to nitrites, thereby increasing the nitrite pool and the probability of formation of mutagenic-carcinogenic nitroso compounds. This process of gastric atrophy and intestinal metaplasia goes on for 30 to 50 years until some of the individuals affected have the final mutation or cell transformation which allows the cell to become autonomous and invade other tissues.

Carcinogens↗