Biomedical subjects
Publications and source records attributed to M J Anderson.
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Fully automated methods have been developed for the determination of thyroxine and triiodothyronine levels, antibodies to thyroglobulin and the assessment of thyroid hormone binding proteins in serum, using a continuous flow radioimmunoassay system. In addition the feasibility of a partially automated assay for thyrotrophin levels has been demonstrated. These employ Auto Analyzer modules and antibodies covalently linked to a magnetisable solid phase support. Separation of bound and free antigen is achieved by applying an external magnetic field. The system currently operates at a rate of 30 samples/h and requires only 10 minutes incubation since it is not necessary to reach equilibrium. The results are similar to those obtained by conventional manual techniques, however the precision is improved and operator error eliminated.
Responding to reports that diarrhea and pseudomenbranous colitis occurred relatively frequently among patients who received clindamycin, we initiated a program of surveillance in clindamycin-treated patients, including direct examination of the colon mucosa for inflammation or pseudomembranes and a patient follow-up by a nurse-epidemiologist. Observation of 145 patients having 161 consecutive clindamycin treatment episodes determined that unexplained diarrhea (two or more stools per day) occurred in 30 patients (21%), and more severe diarrhea (five or more stools per day) occurred in 12 patients (8%). Colitis was not identified at all. The absence of pseudomembranes was confirmed by direct examination of colon mucosa in 114 patients. Development of disabling diarrhea or colitis in association with clindamycin therapy is not a universal phenomenon.
The presence in the spleens of unsensitized CBA mice of cells that are spontaneously cytotoxic for Sendai virus-infected L cells was confirmed. This innate cytotoxic activity to virus-infected cells was shown to exhibit some H-2 restriction. Partial identity of only the D end of the H-2 gene complex between the target and effector cells was required to produce cytolysis. Attempts to characterize the kind of cell active in this system indicated that neither the theta antigen nor the surface immunoglobulin markers were present. Furthermore, the cells appeared to have no adherent or phagocytic properties. The relationship between the effector cells responsible for innate cytotoxicity to virus-infected cells and the natural killer (NK) cells spontaneously cytotoxic for certain tumor cells is discussed.
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Denervated skeletal muscle fibers of mice develop discrete patches of high acetylcholine receptor density. The patches vary in size from less than 1 micrometer up to 30 micrometers, depending on the muscle and the period of denervation. Within the patches the acetylcholine receptor density is some 20 times greater than elsewhere along the muscle fiber and probably approaches that in the subsynaptic membrane.
Fifty-three patients were treated for pedunculated adenomatous polyps that contained foci of invasive cancer confined to the stroma. This entity is a stage of malignant involvement intermediate between in situ carcinoma and frank infiltrative cancer that invades the muscularis mucosae. Metastases to regional lymphatics were not observed. Local removal of such lesions without regional lymphadenectomy is adequate treatment.
1. Myotomal muscle cells from embryos of Xenopus laevis were cultured as a monolayer either alone or together with neural tube cells from the same embryos. 2. Spontaneous twitching and contractions evoked by electrical stimulation of neural perikarya were observed only in nerve-contacted muscle cells, and could be abolished by curare or alpha-bungarotoxin. 3. Within 2 days in culture muscle cells not contacted by nerve developed one or more discrete patches of acetylcholine (ACh) receptors as revealed by staining with fluorescent conjugates of alpha-bungarotoxin. Similar patches were also seen when staining was carried out after paraformaldehyde fixation, suggesting that they were not induced by the dyetoxin conjugate. 4. Radioautography after labelling with [125I]alpha-bungarotoxin revealed patches with grain densities approximately twenty-five-old greater than over the remainder of the cell. 5. Fluorescent stain on innervated cells was restricted to the path of nerve-muscle contact and sometimes extended for greater lengths than the largest patches seen on non-contacted muscle cells. 6. Similar long bands of stain associated with nerve--muscle contacts were observed when cultures were grown in high concentrations of curare and carbachol which prevented spontaneous twitching. They were also seen in cultures in which the addition of neural tube cells was delayed for 2-3 days. 7. It is concluded that innervation caused receptors to accumulate at sites of nerve-muscle contact and that this process can operate independently of muscle activity.
1. Theree-day-old cultures of myotomal muscle, obtained from embryos of Xenopus laevis, were stained with fluorescent conjugates of alpha-bungarotoxin and maintained in native toxin in order to ensure that ACh receptors subsequently inserted into the sarcolemma would not be stained. Neural tube cells were then added to the cultures. 2. When cultures were exmained 1-3 days later fluorescent stain was found to be associated with sites of nerve-muscle contact. In some cases the stain along the path of contact extended for greater distances than the patches of stain seen on non-contacted muscle cells. 3. The development of new areas of fluorescent stain at sites of nerve-muscle contact was confirmed by making successive observations on the same muscle cells over a period of a day. 4. Similar experiments on muscle cells not contacted by nerve revealed the formation of new receptor patches, usually in areas of cell growth. 5. The majority of fluorescent pathes on non-contacted muscle cells did not undergo changes in size or shape over the course of 1-2 days. However some examples of enlargement, shrinkage and disappearance were observed. 6. On the basis of these findings it is concluded that ACh receptors aggregate within the sarcolemma, spontaneously as well as in response to innervation. In the latter case extrajunctional receptors accumulate at the site of nerve contact thereby contributing to the development of high receptor density in the subneural muscle membrane. This process of receptors redistribution occurs in the absence of synaptic or contractile activity. 7. Possible mechanisms involved in the redistribution of ACh receptors are discussed in relation to those which appear to modulate ligand-induced changes in the distribution of lectin and immunoglobulin receptors.
The development of a cell-mediated immune response to Sendai virus infection in mice was examined by the use of a 51Cr release assay of cytotoxicity. A low level of "background cytotoxicity" to Sendai virus-infected L cells was found in the spleens of uninfected CBA mice. Spleen cells from Sendai-infected mice showed an elevated level of cytotoxicity against these target cells for a period of 5 weeks, commencing 4 days after infection of the mice. A more transient response was observed in the spleens of mice infected with a serologically distinct virus, the Kunz strain of influenza. This cross-reacting, cell-mediated immune response was intermediate between that observed in unsensitized and Sendai-sensitized spleen cells. The relevance of these cell-mediated immune responses to respiratory tract virus infections is discussed.
That dairy cows housed in confinement might benefit if they were exercised during the dry period prompted development of a facility for exercising dairy cows. Two methhods of the exerciser, which consist of a circular lane and a driving mechanism powered by a variable speed electric motor, are described. A speed of 3.5 k, per h provides a steady but comfortable pace for pregnant dairy cows and heifers. Many animals refused to go at speeds greater than 5.5 km per h.
An alternative to transcolonic polypectomy, transabdominally directed, transanal colonoscopic polypectomy, for patients who require polyp removal but in whose cases standard colonoscopic approach has failed is presented. The early results are excellent, and the method also can be applied to other patients who have colonic polyps who undergo procedures such as hysterectomy and cholecystectomy.
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Digestion was studied with three groups of four sheep each fed alfalfa hay. Treatments were whey only, whey plus water, and water only. Digestibilities of dry matter for the three rations were 71.3, 69.7, and 62.9%. Digestibilities of whey solids calculated by difference was 86.9% for whey only and 81.6% for whey plus water. Twelve sheep were in three trials to determine the intake of whey, water, and hay consumption. They were assigned to whey only, whey plus water, and water only. Hay, whey, and water consumption was 1.89, 8.73, and 0; 1.88, 7.62, and 1.21; and 2.05, 0, and 6.07 kg per animal daily. Three mature fistulated wether sheep were fed 6 liters of liquid whey daily. Three mature fistulated wether sheep uere fed 6 liters of liquid whey daily, and three similar sheep were fed water only. Rumen liquor samples were taken for analysis of volatile fatty acids at 0, 3, and 6 h after whey feeding on each of three alternate days. Alfalfa hay (1.2 kg/animal daily) was fed after the 6-h sampling. Molar percentage of acetic and valeric acids were lower and for butyric acid was higher for sheep fed whey. Propionic acid, acetate:propionate ratio, and total concentration were not affected significantly by whey feeding. Acetic acid decreased from 0 to 3 h, then partly returned to the prefeeding level at 6 h. The reverse was true for butyric acid. Valeric acid and total concentration of volatile fatty acids decreased from 0 to 6 h. Effects of day were unexplained.
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1. alpha-Bungarotoxin was labelled with fluorescent dyes and used as a stain for visualizing the distribution of acetylcholine receptors in vertebrate skeletal muscle fibres.2. Dye-toxin conjugates had the same pharmacological properties as native toxin, but their potencies were lower.3. Fluorescent staining was examined in teased muscle fibres. The stain was found to be confined to the neuromuscular junction and associated with the subsynaptic membrane.4. Staining intensity was reduced by curare and even more so by carbachol, but not by atropine or neostigmine. Pre-treatment of muscles with unlabelled alpha-bungarotoxin entirely prevented staining.5. The staining at amphibian neuromuscular junctions was characterized by a pattern of intense transverse bands occurring at intervals of approximately 0.5-1 mum, with fluorescence of lower intensity between them. Fluorescent staining was not detected on adjacent, extrasynaptic, muscle membrane. In side views the staining appeared as a fine line with small protuberances occurring at the same intervals as the intense bands seen face-on. These results indicate that acetylcholine receptors are associated with the entire subsynaptic membrane, including the membrane of the junctional folds and that their density changes abruptly at the border between synaptic and extrasynaptic muscle membrane.
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