Predictors of perceived stigmatization in patients with psoriasis.

BACKGROUND: The physical appearance of psoriasis can be cosmetically disfiguring, resulting in a substantial social burden for patients. An important aspect of this burden is the experience of stigmatization. While stigmatization is known to be disabling and stressful for patients, little is known about its correlates, and effective interventions are lacking. OBJECTIVES: To examine predictor variables for perceived stigmatization in psoriasis. METHODS: Questionnaires were administered to 514 patients with psoriasis in a cross-sectional study. Zero-order correlation and multiple-regression analyses were conducted including sociodemographic, disease-related, personality, illness cognitions and social support predictor variables. RESULTS: Stigmatization was experienced by 73% of patients to some degree, and correlated with all five categories of predictor variables. In multiple-regression analyses, stigmatization was associated with higher impact on daily life; lower education; higher disease visibility, severity and duration; higher levels of social inhibition; having a type D personality; and not having a partner. CONCLUSIONS: The results indicate that perceived stigmatization is common in psoriasis, and can be predicted by sociodemographic, disease-related and personality variables. These predictor variables provide indications of which patients are especially vulnerable regarding perceived stigmatization, which might be used in treatment.

Zebrafish chromosome banding.

Banding techniques were carried out on metaphase chromosomes of zebrafish (Danio rerio) embryos. The karyotypes with the longest chromosomes consist of 12 metacentrics, 26 submetacentrics, and 12 subtelocentrics (2n = 50). All centromeres are C-band positive. Eight chromosomes have a pericentric C-band in each arm and 22 chromosomes have one in the longest arm. Two chromosomes have a slightly heterochromatic long arm and five chromosomes have an Ag-NOR at the terminal end of the long arm. Other banding patterns and sex chromosomes could not be revealed.

Sister chromatid exchanges in cultured immature embryos of wheat species and regenerants.

Immature embryos of Triticum aestivum (ten cultivars and lines), T. durum, T. dicoccum and T. monococcum were cultured in vitro on MS medium supplemented with 1 or 2 mg/l of 2,4-D and 20 or 30 g/l of sucrose for 3 days and processed to score sister chromatid exchanges (SCEs) per chromosome. Media components affect DNA replication from the start of the culture. The SCE frequencies were dependent on the genotype and were not correlated with the degree of ploidy. They increased after doubling of the concentration of 2,4-D and/or sucrose, except in one cultivar of T. aestivum. The mean numbers were lower than observed in root meristems of T. aestivum (two cultivars) and T. dicoccum. Immature embryos of regenerants of T. aestivum (one cultivar) and T. durum demonstrated variable SCE frequencies, which may have been caused by mutations in the parental cell cultures. In the T. aestivum embryos the lowest frequencies were found in regenerants obtained from explants with the highest frequencies.

Microsporogenesis in three tetraploid somatic hybrids of potato and their di(ha)ploid fusion partners.

The microsporogenesis of three somatic hybrids of potato, i.e. one tetraploid Solanum tuberosum (+) S. phureja, one tetraploid and one hypertetraploid S. tuberosum (+) desynaptic mutant, has been examined and compared with the microsporogenesis of the di(ha) ploid fusion partners. The somatic hybrids had a first meiotic division with uni-, bi-, and multivalents like that of tetraploid potatoes, illustrating introgression and dominance over desynapsis. Abnormal spindle orientations at second meiotic division, sporad types with reduced and unreduced cells and viable pollen occurred at various frequencies. Pollen fertility could not be predicted on the basis of pollen fertility of the fusion partners. Pollen sterility was partially due to abnormal chromosome numbers. Only the tetraploid S. tuberosum (+) desynaptic mutant produced normal amounts of viable seeds.

A cytogenetic and phenotypic characterization of somatic hybrid plants obtained after fusion of two different dihaploid clones of potato (Solatium tuberosum L.).

Somatic hybrid plants of various ploidy levels obtained after chemical fusion between two dihaploid clones of potato Solanum tuberosum L. have been analysed by cytological, morphological and molecular methods. The hybrid nature of tetraploid and hexaploid plants and the genome dosage in hexaploid hybrids were confirmed by Giemsa C-banding. Tetraploid and hexaploid hybrids showed numerical as well as structural chromosome mutations. The latter occurred mainly in the nuclear organizing chromosome. The tetraploid hybrids were more vigorous than the dihaploid parents as demonstrated by an increase in height, enlargement of leaves, increase in the number of internodes, restored potential for flowering and increased tuber yield. The grouping of tetraploid somatic hybrids into various classes on the basis of leaf morphology revealed that plants with a full chromosome complement were more uniform than aneuploids. Many hexaploid somatic hybrids were also more vigorous than the dihaploid parents and could be grouped into two different classes on the basis of floral colour and tuber characteristics, the differences being due to their different dosage of parental genomes. Most of the tetraploid somatic hybrids showed pollen development halted at the tetrad stage as one of the parental clones contained a S. Stoloniferum cytoplasm. However, one tetraploid plant produced pollen grains with high viability. The chloroplast genome in the hybrid plants was determined by RFLP analysis. All of the hybrids had a cpDNA pattern identical to one parent, which contained either S. Tuberosum or S. Stoloniferum cpDNA. A slight preference for S. Tuberosum plastids were observed in hybrid plants. No correlation between pollen development and plastid type could be detected.

Nucleolar organizer function in developing potato calli.

The number of transcriptionally active nucleolar organizer regions (NORs) of one monohaploid, one dihaploid and two tetraploids of Solanum tuberosum and one diploid S. phureja was established by the silver staining of metaphases in root meristems and in in vitro-cultured leaf explants. The maximum number of active NORs per cell was one per haploid set of chromosomes. One or more NORs could be inactive in cells of the tetraploid meristems and in non-polyploidized and polyploidized cells of the dihaploid and tetraploid explants. Inactivation was determined by genotype and tissue and could remain constant during in vitro culture.

Flow cytometric and karyological analysis of polysomaty and polyploidization during callus formation from leaf segments of various potato genotypes.

Flow cytometry and karyological analysis were used to study polysomaty and polyploidization during the first 15 days of callus formation in leaf segments from shoot cultures and greenhouse-grown plants of various lines and genotypes of Solanum tuberosum and S. phureja. The greenhouse-grown plants showed a higher degree of polysomaty (77% and 49% of polyploidized nuclei) than the shoot cultures (< 3%). During the in vitro culture period, polyploidization occurred through endoreduplication. Segments of the five shoot cultures showed up to 87%, 53%, 59%, 45% and 56% polyploidization, respectively; the DNA content of corresponding interphase nuclei amounted to 8C, 16C, 16C, 16C and 8C, and the chromosome numbers to 96. Segments from the two greenhouse-grown genotypes showed up to 87% and 84% polyploidization; the DNA content amounted to 32C and 16C, and the chromosome numbers to 192 and 96. The number of reduplication cycles was species-dependent; the degree of polyploidization was dependent on the initial ploidy level of the genotypes. Cell proliferation did not take place at a constant rate. The maximum frequencies of metaphases (52-171 per segment) occurred after 1 week of culture and were correlated with the ploidy level of the genotypes. Cells were triggered to mitosis rather than to endoreduplication. Cell cycles with normal monochromosomes could be shorter than 1 day, and those with diplochromosomes lasted at least 1 day. Polysomaty, degree of polyploidization and abnormal nuclear processes are discussed in relation to the origin of genetic instability early in culture.

Chromosome elimination and mutation in tetraploid somatic hybrids ofSolanum tuberosum andSolanum phureja.

The hybridity of eleven somatic hybrids between a diploidS. tuberosum and a diploidS. phureja clone could be verified because the parent karyotypes differed in their C-banding patterns. The hybrids were hypotetraploid and some carried structurally rearranged chromosomes and/or minute centric fragments. The nucleolar chromosomes ofS. phureja were eliminated preferentially. The function of the remaining nucleolar organizer regions was not suppressed. Nuclear DNA content was correlated with the hypotetraploid chromosome numbers.

Elimination of Solanum phureja nucleolar chromosomes in S. tuberosum + S. phureja somatic hybrids.

The karyotype of the dihaploid SVP1 line of S. tuberosum (2n=2x=24) showed two nucleolar chromosomes with differently sized satellites. The diploid SVP5 line (2n=2x=24) and tetraploid regenerants of S. phureja had larger but similar satellites. Somatic hybrids between the diploid lines of these potato species with genome combinations 4 tub + 2 ph (plants 1-3), 2 tub + 4 ph (plants 4-7) and 4 tub + 4 ph (plant 8) had lost 2 phureja nucleolar chromosomes if 4 phureja genomes were present. One phureja nucleolar chromosome of plants 1-3 and both of plants 5 and 7 had rearranged satellites. Elimination of the two nucleolar chromosomes occurred preferentially, was under genetic control, and probably took place during early callus development. NOR activity resulting in rear-rangements between NORs may have caused the elimination.

Karyotype variation in aminoethylcysteine resistant cell and callus cultures and regenerated plants of a dihaploid potato (Solanum tuberosum).

Karyotypic studies on cell suspensions and calli of an S-(2-aminoethyl)cysteine resistant cell line of the interdihaploid potato H(2)578 (2n=24) revealed a high degree of variation in the number of chromosomes (33-217) and dicentric chromosomes (0-8). The suspensions also exhibited megachromosomes and fused chromosomes. Differential staining showed that in suspensions dicentrics survived mitotic cycles mainly by parallel separation of the chromatids during anaphase and hardly by the breakage-fusion-bridge cycle. Two phenotypes of plantlets regenerated, each with 34 or 35 chromosomes with gross structural mutations and with the triploid amount of DNA. Chromosomal variation was related to the degree of tissue organization.

Variability of DNA content and karyotype in cell cultures of an interdihaploid Solanum tuberosum.

Karyological and DNA cytophotometric observations were carried out to follow nuclear events in cell cultures of an interdihaploid potato, genotype H(2)578, 2n=2x=24. The percentage of polyploid cells increased in leaf calluses, but decreased and then remained at a constant level when these cells were cultured in suspension. These suspension cultures did not survive, maybe because they did not become tetraploid. Another suspension culture proliferated with hypotetraploid cells only. Unlike the DNA contents of their interphase nuclei, the karyotypes varied considerably because of numerical and structural chromosome mutations.

Behaviour of chromosomes in potato leaf tissue cultured in vitro as studied by BrdC-Giemsa labelling.

Cells of leaf explants of a monohaploid potato (Solanum tuberosum) were stimulated to mitosis on a medium with 5-bromodeoxycytidine during a period of 7 days. The cells cycled with mono- or diplochromosomes which showed differential staining of the sister chromatids and sister chromatid exchanges by the fluorescent plus Giemsa technique after two rounds of BrdC incorporation. Through the staining pattern the course of the first three cell cycles could be traced and the duration of the cycles estimated. Polyploidisation was enhanced by selective stimulation of polyploid cells and by endoreduplication of G2-phase cells. The percentage of polyploid mitoses increased from 10 to 70.

Experiments on blocking and unblocking of first meiotic metaphase in eggs of the parthenogenetic stick insect Carausius morosus Br. (Phasmida, Insecta).

The eggs of the parthenogenetic stick insect Carausius morosus, which remain arrested in first meiotic metaphase until oviposition, must be activated in order to develop. The activating agent is oxygen from the air, which enters the egg cell through the micropyle. An exposure shorter than one minute is sufficient to release the blockage. In non-activated (micropyle-less) eggs the first metaphase chromsomes either degenerate or change into an interphase nucleus. This nucleus polyploidizes by endoreduplication, and then either degenerates or multiplies by amitosis. Similarly more generations of nuclei may arise resulting in a chaotic development. These nuclei survive better in the anterior region of the egg. The question of whether the cytoplasmic factors which control nuclear behaviour, also operate in eggs of C. morosus is discussed.