Search PubMed⌕ Search

Biomedical subjects

C Kidson

Publications and source records attributed to C Kidson.

At least 91 records · Page 5Linked to original sources
PubMed1986

Sensitivity to ultraviolet radiation in a dominantly inherited form of xeroderma pigmentosum.

An Australian family is described in which a mild form of xeroderma pigmentosum (XP) is inherited as an autosomal dominant trait. Studies of lymphoblastoid cells and fibroblasts from affected persons demonstrated cellular sensitivity to ultraviolet (UV) light as judged by diminished clonogenicity and higher frequencies of UV induced chromosome aberrations compared to normal controls. After UV irradiation of dominant XP cells, replicative DNA synthesis was depressed to a greater extent than normal and the level of UV induced DNA repair synthesis was lower than that in normal cells. The level of sister chromatid exchanges and the numbers of 6-thioguanine resistant mutants induced by UV irradiation were equal to those found in normal controls. Although two subjects in the family had skin cancers, this dominant form of XP is not apparently associated with high risk, or large numbers, of skin cancers in affected persons.

Adult↗
PubMed1986

Synapse formation and induction of acetylcholine receptors by spinal neurones in cocultures with sympathetic ganglion and muscle cells.

Coculture of chick embryonic sympathetic neurones with spinal cord explants induced an age-dependent increase in the acetylcholine receptor numbers of the ganglion cells. These acetylcholine receptors did not appear to be necessary for the initial formation of spinal cord-ganglion synapses since their blockade with the alpha-bungarotoxin-horseradish peroxidase complex did not prevent synapse formation in culture. The presence of acetylcholine receptors appears to be sufficient for synapse formation since inappropriate motoneurone-ganglion synapses could form and were stable.

Animals↗
PubMed1985

A specific S-antigen of Plasmodium falciparum is expressed in a proportion of primary isolates in Brazil, Thailand and Papua New Guinea.

The expression by Plasmodium falciparum of a specific S-antigen has been examined in primary isolates in different regions of the world using a monoclonal antibody that recognizes an epitope within a known repeated amino acid sequence. The epitope was expressed by a small proportion of primary isolates in each of Brazil, Thailand and Papua New Guinea, demonstrating that this S-antigen gene is widespread. The data are consistent with the possibility that the occurrence of P. falciparum strains expressing a particular S-antigen is periodic, related to the duration of immunity against that antigen in a given human population.

Adult↗
PubMed1985

Two apparently nonrepeated epitopes on gametes of Plasmodium falciparum are targets of transmission-blocking antibodies.

One-site and two-site immunoradiometric assays have been developed against an antigen on gametocytes of Plasmodium falciparum, using monoclonal antibodies (Mabs) which block transmission of the parasites to mosquitoes. Three such Mabs have been studied, each of which immunoprecipitates a complex of three gamete surface proteins of apparent Mr 260,000, 59,000, and 53,000 from Triton X-100 extracts of the parasites. The assays showed that the Mabs recognized one or the other of two distinct, nonrepeated epitopes on the target antigen(s). In the one-site assay certain combinations of two Mabs interacted at appropriate concentrations to enhance binding of the Mabs to the antigen. The same combinations of Mabs synergize to suppress infectivity of gametocytes to mosquitoes.

Animals↗
PubMed1985

Complementation analysis of ataxia-telangiectasia.

In a number of laboratories genetic analysis of ataxia-telangiectasia (AT) has been performed by studying the expression of the AT phenotype in fused somatic cells or mixtures of cell-free extracts from different patients. Complementation of the defective response to ionizing radiation was observed frequently, considering four different parameters for radiosensitivity in AT. The combined results from studies on cultured fibroblasts or lymphoblastoid cells from 17 unrelated families revealed the presence of at least four and possibly nine complementation groups. These findings suggest that there is an extensive genetic heterogeneity in AT. More extensive studies are needed for an integration of these data and to provide a set of genetically characterized cell strains for future research of the AT genetic defect.

Ataxia Telangiectasia↗
PubMed1984

Wilms' tumour: association with cellular sensitivity to mitomycin C in patients and first-degree relatives.

To investigate whether predisposition to Wilms' tumour is associated with a particular defect in the handling of DNA damage, cell-lines from families in which the tumour had occurred were tested for sensitivity to a variety of DNA-damaging agents. Lymphoblastoid lines from both Wilms' tumour patients and their first-degree relatives showed increased sensitivity to the cross-linking agent, mitomycin C, but normal sensitivity to ultraviolet (UV) and gamma irradiation. Thus sensitivity to mitomycin C damage can be associated with the Wilms'-tumour-susceptible genotype and could be a genetic factor responsible for the modification of expression of this genotype.

Adult↗
PubMed1984

Gene dosage and complementation analysis of ataxia telangiectasia lymphoblastoid cell lines assayed by induced chromosome aberrations.

An approach of general applicability to mammalian radiosensitive mutants has been used in the analysis of gene dosage and complementation in ataxia telangiectasia (A-T). Thymidine residues in DNA of one parental lymphoblastoid cell line were substituted with bromodeoxyuridine before fusion with a second parental cell line, to allow differential staining of the two sets of chromosomes. Following gamma-irradiation, induced chromosome aberrations were scored in diploid and homokaryon cells from each parental line as well as in heterokaryons. Four complementation groups were ascertained among 7 A-T cell lines. Analysis of heterokaryons formed between appropriate combinations of normal, A-T homozygote and A-T heterozygote cells, gave a quantitative measure of gene dosage and demonstrated increasing radiosensitivity with increasing numbers of A-T alleles.

Ataxia Telangiectasia↗
PubMed1984

In vitro translation of Plasmodium falciparum proteins.

RNA was prepared from cultured Plasmodium falciparum using ribonucleoside-vanadyl ribonuclease inhibitors and assayed in a rabbit reticulocyte, cell-free lysate translation system. Discrete proteins, ranging from less than 10,000 to greater than 200,000 daltons, were synthesized. Some of these proteins were precipitated by immune serum and were similar to those metabolically synthesized. Purified poly [A] mRNA was also translated and differences between the fractions which either bind or pass through a poly [U] Sepharose column are described.

Animals↗
PubMed1984

Decreased membrane deformability in Melanesian ovalocytes from Papua New Guinea.

We examined the ability of Melanesian ovalocytes from Papua New Guinea to be deformed in order to probe the resistance of these cells to invasion by several species of malaria parasite. We found ovalocytes were refractile to drug-induced endocytosis, that they formed abnormal rouleaux, showed reduced deformability when aspirated into 0.6-micron diameter pores in polycarbonate sieves, and failed to crenate when mounted under a glass coverslip. No substantial differences were found between normocytes and ovalocytes in their initial rate of filtration through 4.5-micron pore polycarbonate sieves, their membrane fluidity as measured by the rate of depolarization of fluorescent probes or the rate of extraction of cytoskeletal proteins in low ionic strength buffers. We conclude that the resistance of ovalocytes to undergo localized deformation might be significant in explaining the resistance of these cells to invasion by malarial merozoites.

Chlorpromazine↗
PubMed1984

A high molecular weight antigen in Plasmodium falciparum recognized by inhibitory monoclonal antibodies.

Inhibitory monoclonal antibodies which bind to some isolates of Plasmodium falciparum from Papua New Guinea, but not from other areas, bound to a 220 kD antigen. By immunofluorescence microscopy this antigen was shown to be located both within the schizont cytoplasm and also within the schizont infected erythrocyte, but external to the schizont itself. Even at antibody concentrations which caused greater than 70% inhibition of parasite multiplication, accumulation of schizont stages or aggregates of merozoites were not seen, consistent with inhibition occurring at a point after the release of merozoites. While this suggests that the antigen may be present on merozoites, the quantity was below the limit of detection. It is suggested that the large amount of antigen released by rupturing schizonts may be a mechanism used by the parasite to evade immunological attack.

Animals↗
PubMed1984

Cellular radiosensitivity: expression of an MS susceptibility gene?

As a group, of 40 MS patients exhibited significantly more cellular sensitivity to ionizing (gamma) radiation than 30 age- and sex-matched controls (p less than 0.0001), as measured by radiation-induced chromosome aberrations. Studies of phytohemagglutinin-stimulated T lymphocytes, B lymphoblastoid cell lines, and fibroblasts indicated that the cellular radiosensitivity was a general property of the cells of an individual. Patterns of cellular radiosensitivity among the unaffected first-degree relatives of some MS patients suggested autosomal dominant inheritance. Cellular radiosensitivity may be due to mutations of DNA-processing that predispose to MS.

Chromosome Aberrations↗
PubMed1983

A rapid assay for DNA repair synthesis using neutral and alkaline sodium iodide gradients.

A modification to the method for estimation of repair DNA synthesis in cultured mammalian cells using density labeling which reduces the time and labor involved is described. Centrifugation times are reduced by using high-molecular-weight DNA which is loaded onto the top of a preformed sodium iodide gradient. Cerenkov counting is used to locate the region of the gradient containing light DNA for rebanding and likewise to identify appropriate fractions from alkaline gradients for acid precipitation for scintillation counting. The procedures give results indistinguishable from cesium chloride equilibrium gradients in a shorter time, with less effort, and at a lower cost.

Centrifugation, Density Gradient↗
PubMed1983

Responses of Huntington's disease and ataxia telangiectasia lymphoblastoid cells to bleomycin.

Ionizing radiation sensitive, mutant human lymphoblastoid cell lines derived from patients with Huntington's disease (HD), or ataxia telangiectasia (AT) both showed cross sensitivity to bleomycin, as assayed by reduced cell viability and increased frequency of chromosome aberrations compared to normal controls. In contrast to AT cells which failed to show inhibition of DNA synthesis after exposure to ionizing radiation, or bleomycin treatment, the sensitive cells from HD patients had depressed rates of DNA synthesis after damage with these agents, similar to that seen in normal cells. In terms of progression through the cell cycle bleomycin damaged AT cells moved from G1 into S and from S to G2 + M at almost the same rate as untreated cells. Bleomycin treated HD cells showed a large proportion of cells blocked in G1, cells were slowed down in S, the rate of entry to G2 + M was reduced and only 5% of cycling cells reached G2. Progress through the cell cycle in normal cells exposed to bleomycin showed a partial block in G1 and the rate of entry to G2 + M was reduced. These differences in response of normal, AT and HD cells to ionizing radiation and bleomycin treatment indicates that the defect underlying the sensitivity is different in HD cells from that in AT cells.

Ataxia Telangiectasia↗
PubMed1983

The synthesis and fate of stage-specific proteins in Plasmodium falciparum cultures.

Cultured ring, trophozoite and schizont stages of Plasmodium falciparum were metabolically labeled with [35S]methionine. After labeling, cultures were incubated for varying times in the presence of non-radioactive methionine. Triton-soluble proteins from different stages of growth were analysed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Most proteins were synthesized by every stage of growth and remained unchanged throughout the cycle through to the ring stage following merozoite invasion of erythrocytes. At least 15 proteins, most of high molecular weight, were synthesized solely or predominantly by schizonts. Eight proteins (approx. 177, 170, 158, 87, 83, 47, 41 and 24 kDa) appeared in schizonts but not merozoites. Eight proteins (approx. 240, 203, 106, 80, 35, 19, 15 and 14 kDa) appeared in merozoites, but not in rings following merozoite invasion. Some proteins appeared to be modified after synthesis.

Amino Acids↗
PubMed1983

Effects of ultraviolet irradiation on the cell cycle in normal and UV-sensitive cell lines with reference to the nature of the defect in xeroderma pigmentosum variant.

Analysis of the distribution of cells through the phases of the cell cycle by DNA flow cytofluorimetry has been utilized to investigate the effects of ultraviolet (UV) irradiation on cell-cycle progression in normal and UV-sensitive lymphoblastoid cell lines. In time-course studies only slight perturbation of DNA distribution was seen in normal cells, or UV-sensitive familial melanoma (FM) lines in the 48 h following irradiation. Xeroderma pigmentosum (XPA) excision-deficient cells showed a large increase in the proportion of cells in S phase 16-40 h post-irradiation. XP variant (XPV) cells were blocked in G1 and S phases with the complete absence of cells with G2 DNA content 16-28 h after irradiation. By 48 h post-irradiation the DNA distribution of XPA and XPV cells had returned to that of an unirradiated control. When colcemid was added to the cultures immediately after irradiation to prevent mitotic cells dividing and re-entering the cell cycle, progression through the first cycle after irradiation was followed. UV irradiation did not affect the rate of movement of cells out of G1 into S phase in normal, FM or XPA cells. The proportion of cells in S phase was increased in UV-irradiated cultures in these cell types and the number of cells entering the G2 + M compartment was reduced. In UV-irradiated cultures of XPV cells a large proportion of cells was blocked in G1. The rate of accumulation of cells with G2 DNA content was equal to that of the control until 4 h post-irradiation, thereafter falling below the control. Thus XPV cells in S phase at the time of irradiation complete DNA synthesis to reach G2 DNA content. However, cells irradiated in G1 are blocked from entry into S. These results suggest that there is a defect in XPV cells that affects a step prior to the onset of DNA replication.

Cell Cycle↗