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W J Nelson

Publications and source records attributed to W J Nelson.

At least 163 records · Page 9Linked to original sources
PubMed1982

Discrimination of slow growth from non-survival among small colonies of diploid Syrian hamster cells after chromosome damage induced by a range of x-ray doses.

Synchronous samples of cultured diploid Syrian hamster cells (BHK 21 C13/A3) were obtained by mitotic selection, transferred to an observation chamber and given a single X-ray dose in the range 0.2 to 3.8 Gy. Each cell's radiation response was followed by visual observations of its progress alive through post-radiation mitosis (M1), and subsequently of its clonogenicity, by methods already published (Grote et al. 1981 a, b; Joshi et al. 1982a). Our recent paper about the same cell samples (Joshi et al. 1982b) showed that the probability of reaching M1 is nearly unity in controls and over the whole dose range (mean greater than 0.99). The present paper describes the clonogenicity of each sample, based on five daily cell counts at the site of each initial cell. The frequency of viable colonies falls from 98 per cent for unirradiated cells to 8 per cent in the 3.8 Gy sample, but the proportion of these which grow slowly rises from 3 to more than 70 per cent. There was substantial overlap in cell numbers reached by larger abortive colonies and smaller slow-growth colonies, and many of the later had not reached 50 cells at the last count at 5 1/2 days. Impaired colony growth (slow growth or stop growth) was strongly correlated with chromosome fragment loss detected as micronuclei in the daughter cells of M1.

Animals↗
PubMed1982

Effect of the ionic environment on the incorporation of the intermediate-sized filament protein vimentin into residual cell structures upon treatment of Ehrlich ascites tumour cells with triton X-100. II. Ultrastructural analysis.

Ehrlich ascites tumour cells were extracted in buffers containing Triton X-100 and mono-di- and polyvalent cations and then analysed by phase-contrast and electron microscopy. The results of this ultrastructural analysis confirm those of the biochemical analysis in the accompanying paper that the stability of intermediate-sized filaments is dependent on the ionic environment. Furthermore, the organization of filaments in long parallel arrays is dependent on the presence of divalent cations and can be inhibited, to some extent, by the presence of monovalent cations. The stability of other detergent-resistant structures, the boundary lamina, microfilaments, microtubules, centrioles, polyribosomes and the nuclear cortex, is also affected by the ionic environment but to a lesser extent.

Animals↗
PubMed1982

Polyribosomes are not associated with vimentin-type intermediate filaments in Ehrlich ascites tumor cells.

Polyribosomes were isolated from Mg2-stabilized, Triton X-100-resistant residual cell structures and from a postmitochondrial supernatant of hypotonically swollen and homogenized Ehrlich ascites tumor cells and analysed for their vimentin contents by polyacrylamide gradient slab gel electrophoresis. Whereas polyribosomes from detergent-resistant cell residues were accompanied by a small amount of vimentin on sucrose gradients, polyribosomes isolated from a hypotonic, postmitochondrial supernatant were free of vimentin. Since the presence of vimentin in cell residue-derived polyribosomes might be interpreted as the result of unspecific adsorption or cosedimentation of vimentin filament fragments, both due to the presence of high Mg2 concentration during cell extraction, the results suggest that there is no direct and stable interaction of polyribosomes with vimentin-type intermediate filaments in suspension-grown Ehrlich ascites tumor cells. This is in accordance with the electron microscopic observation that cytoplasmic regions rich in intermediate filaments are virtually devoid of polyribosomes. When the extraction of the same cells with Triton X-100 was carried out at low ionic strength and in the presence of small amounts of Ca2, residual cell structures were completely destabilized and clean nuclei without any attached cytoplasmic material were obtained. This is due to the degradation of the vimentin-type filaments by the Ca2-activated thiol proteinase highly specific for vimentin.

Animals↗
PubMed1981

Properties of Ca2+-activated protease specific for the intermediate-sized filament protein vimentin in Ehrlich-ascites-tumour cells.

A Ca2+-activated neutral protease is described which, when tested against various native proteins, appears to be specific for vimentin, the 58,000-Mr subunit protein of intermediate-sized (7--11 nm) filaments in Ehrlich-ascites-tumour cells. The protein subunits of other classes of intermediate-sized filaments have been tested; neurofilament protein and glial fibrillary acidic protein are not degraded, however skeletin, the subunit protein of intermediate-sized filaments in smooth muscle, is degraded. The protease is found associated with the detergent-resistant cytoskeleton of Ehrlich-ascites-tumour cells; proteins, other than vimentin, present in this structure are not degraded. The protease is activated by Ca2+ and Sr2+ but not by other divalent cations tested: the Ca2+ concentration required for activation is 10 microM. The pH optimum is between pH 7.5 and 8.0, and the KCl concentration required for optimal activity is 100 mM. The protease is inhibited by 1-chloro-3-tosylamido-7-amino-L-2-heptanone hydrochloride and L-1-tosylamido-2-phenylethyl chloromethyl ketone but not by soybean trypsin inhibitor; inhibition by phenylmethylsulphonyl fluoride is moderate. The high substrate specificity of the protease suggests it may play a role in vimentin intermediate-sized filament protein turnover in Ehrlich-ascites-tumour cells.

Animals↗
PubMed1981

Comparison of Ehrlich ascites tumour and mouse liver cells by analytical subcellular fractionation combined with a sensitive computational method for data analysis.

A simple method of analytical subcellular fractionation, combined with a sensitive computational method for data analysis and presentation, has been used to reinvestigate the distribution and relative amounts of several enzymes in the cytoplasmic and plasma membranes of two different cell types: one is a neoplastic, transformed cell type (Ehrlich ascites tumour cells), the other an untransformed, highly differentiated cell type (liver hepatocytes plus Kupffer and endothelial cells). In general the distribution of the enzymes in particular membranes is similar in the two cell types, however the relative amounts differ. Ehrlich ascites tumour cells have a higher specific activity of galactosyltransferase and ouabain-sensitive (Na,K)ATPase, while liver cells have higher glucose-6-phosphatase, 5'-nucleotidase and succinate dehydrogenase activity. These differences appear to be correlated with morphological and, in some cases, functional differences between the two cell types.

5'-Nucleotidase↗
PubMed1981

Fractionation of the detergent-resistant filamentous network of Ehrlich ascites tumour cells.

Previous investigations of the filamentous network in eukaryotic cells have been based on observations by electron and fluorescence microscopy. In order to examined, in more detail, the interconnection of the various components of th filamentous network, we have treated Ehrlich ascites tumour cells with Triton X-100 in the presence of Mg++, disassembled the detergent-resistant, residual cell structure with Tris-EDTA and subjected the postnuclear supernatant to sucrose density gradient equilibrium centrifugation. Using this technique we are able to demonstrate 1) the association of the major part of intermediate-sized filament protein (vimentin) with unfolded ribosomal subunits, 2) the nearly identical sedimentation behavior of the boundary lamina and actin, and a minor part of the intermediate-sized filament protein respectively, and 3) the association of a Ca++-dependent protease specific for vimentin intermediate-sized filament protein with the Triton X-100 resistant, residual cell structure. Furthermore, we are able to confirm, by labelling intact Ehrlich ascites tumour cells with [3H] concanavalin A and recovering radioactivity in the lighter sucrose gradient fractions, that the detergent-resistant boundary lamina is derived from the plasma membrane. The presence of coated vesicles in Triton X-100-treated cells as well as of coated pits in the derived membrane point at the same origin of the boundary lamina. The results of the fractionation study are correlated with structures observed by electron microscopy of ultrathin sections of the intact filamentous network.

Actins↗
PubMed1981

Occurrence in various mammalian cells and tissues of the Ca 2+ activated protease specific for the intermediate-sized filament proteins vimentin and desmin.

Several mammalian cell lines propagated in suspension and monolayer culture and some normal and cancerous tissues from rat, hamster and cat were screened for the presence of the Ca 2+ activated protease specific for the intermediate-sized filament protein vimentin. Gel permeation chromatography on Sephacryl S-300 of postnuclear supernatants, and sucrose density gradient centrifugation of extracts from Triton X-100-resistant residual cell structures revealed the presence of the enzyme in all cells and tissues tested. Its apparent molecular weight amounted to 100 000. Except in the cases of a spontaneous rat lung tumour and a rat hepatocellular carcinoma induced by diethylnitrosamine, most of the enzyme was released into the postnuclear supernatant during cell or tissue extraction, indicating that it is of cytoplasmic origin. There was no correlation between the enzyme level and the vimentin content of cells and tissues. Rat and hamster liver as well as cat kidney, in which vimentin has not been detected by polyacrylamide gel electrophoresis, were relatively rich in the Ca 2+ activated protease. The experimental results point at the widespread, if not general, occurrence of the enzyme in mammalian cells.

Animals↗
PubMed1980

Recovery and enhancement of reflex reaction time after nitrous oxide analgesia.

The findings of this study substantiate the assumption that psychomotor impairment is rapidly reversed following the administration of nitrous oxide. The concern of clinicians is to determine the optimum oxygenation period after administration of N2O and to show whether there is a need for prolonged observation before the patient can be released. Generally, under short-term conditions such as are used in conjunction with outpatient dental treatment, the patient should be largely recovered after a five-minute exposure to 100% oxygen at the conclusion of the appointment. However, further benefit apparently is gained from a somewhat longer time of recuperation before engaging in any activity requiring extracting psychomotor skills. The results of this study indicate that 15 minutes is an appropriate delay after relatively short exposure to N2O. It cannot be determined from this study whether longer-term exposure, such as the periods involved in complicated restorative procedures, would require longer recovery periods for certain individuals.

Adult↗
PubMed1979

The distribution of spontaneous chromosome aberrations in BHK21/C13 fibroblasts.

Previous investigations of spontaneous aberrations in mammalian cells have been carried out on large heterogeneous samples of individuals, each of whom had had a different exposure to exogenous clastogens. In the present analysis using Syrian Hamster cells, a large number of metaphases were analysed from one sample of control cells. In this way all cells were exposed to the same doses of any unknown clastogens. The overall distribution of spontaneous breaks was found to be nonrandom. Breaks involved in different types of aberration had a nonrandom distribution, which was specific for each type. (e.g. terminal deletion and rearrangement).

Animals↗
PubMed1978

Comprehensive self-medication program for epileptic patients.

The establishment and operation of a comprehensive self-medication program for hospitalized epileptic patients are described. The patients in the program are required to meet established behavioral criteria during each of four stages of self-medication before progressing to the next stage. The patient has increasing responsibility in each successive phase of the program. The areas of patient involvement for the pharmacist are: (1) obtaining a medication history, (2) teaching patients about seizure medications, (3) conducting patient consultations during the self-medication program and (4) counseling the patient at discharge.

Counseling↗