PACAP deficiency sensitizes nigrostriatal dopaminergic neurons to paraquat-induced damage and modulates central and peripheral inflammatory activation in mice.

Exposure to the pesticide paraquat (PQ) increases the risk of Parkinson's disease (PD), and its effect may be modulated by genetic or other environmental factors. The neuropeptide PACAP (pituitary adenylyl cyclase-activating polypeptide, Adcyap1) has been shown to enhance tyrosine hydroxylase (TH) and VMAT2 expression, protect dopaminergic (DA) neurons against the neurotoxin 6-hydroxydopamine, regulate neuronal mitochondria, and inhibit inflammation. Decreased expression of PACAP may thus interact with environmental factors such as PQ to increase the risk of PD. To mimic a low level environmental exposure to PQ, wild type (WT) and PACAP knockout (KO) mice were given a single [10 mg/kg] dose of PQ, a regimen that did not induce the loss of TH expression or DA neurons in WT mice. This treatment selectively reduced the number of TH-positive cell bodies in the substantia nigra pars compacta (SNpc) selectively in PACAP KO mice. Because inflammation is also a risk factor for PD, we performed a quantitative analysis of SNpc Iba⁺ microglia. As expected, PQ increased the number of larger microglial profiles, indicative of activation, in WT mice. Strikingly, microglial activation was already evident in PACAP KO mice in the basal state. PQ caused no further activation in these mice, although tumor necrosis factor-α gene expression was enhanced. In the periphery, PQ had no effects on the abundance of proinflammatory Th1 or Th17 cells in WT mice, but increased the numbers of anti-inflammatory regulatory T cells (Tregs). PACAP KO mice, in contrast, had elevated numbers of Th17 cells after PQ, and the induction of Tregs was impaired. The results indicate that endogenous PACAP acts to maintain the integrity of DA neurons during exposure to PQ, an action that may be linked to its ability to regulate microglia and/or other immune cells.

Chromosomal alterations in breast cancer revealed by multicolour fluorescence in situ hybridization.

The aim of this study was to characterise cytogenetically, breast cancer cell lines and primary tumours to identify chromosomal regions of interest in breast cancer. Multicolour fluorescence in situ hybridization (MFISH) and comparative genomic hybridization (CGH) were used to karyotype five established breast cancer cell lines and two short-term primary tumour cultures. Chromosome 8 was identified as a frequent target for aberrations in all cell lines and one primary culture by MFISH and CGH. CGH identified frequent gains of 1q (all samples) and 14q (all cell lines) and deletion of 22q (all samples). MFISH revealed a t(9;17) translocation in both primary tumours and the T47D cell line. MFISH analysis of the cell lines revealed a significant number of translocations previously unidentified in other studies using similar techniques, highlighting the necessity of utilising data from both primary cultures and established cell lines when investigating complex cytogenetic aberrations using MFISH and CGH.

Mercuric chloride: toxicity and apoptosis in a human oligodendroglial cell line MO3.13.

A human-human oligodendroglial cell line MO3.13 was chosen in this study to model the loss of oligodendrocytes that occurs during episodes of multiple sclerosis. The influence of mercuric chloride (HgCl(2)) upon cell viability specifically the mode of cell death, whether by an active apoptotic mechanism or passive necrosis was determined by morphological and biochemical analysis. Mitochondrial dehydrogenase activity MTT assay showed that HgCl(2) had toxic effects on MO3.13 cells at levels of (5-25 microM) with approximately 50% cell death observed at 58 microM. Death of cells was dependent on both time and concentrations of HgCl(2). Differentiated MO3.13 cells exposed to low concentrations (25 microM) of HgCl(2) exhibited features of apoptotic cell death, including cell shrinkage and chromatin condensation. High doses of HgCl(2) (>100 microM) induced death with characteristics of necrosis. Biochemical analysis showed that HgCl(2) activated the caspase family of proteases. This was measured directly by cleavage of fluorescent substrates and by immunoblotting assay of caspase substrate proteins; alpha-fodrin, lamin B and poly (ADP-ribose) polymerase (PARP). These results indicate that HgCl(2) is toxic at low concentrations for oligodendroglial cells and that the MO3.13 cell line dies in an apoptotic manner when exposed to low concentrations of HgCl(2). However, blood mercury concentrations in vivo in a normal population with amalgam restorations are lower by a factor of some 500 times than those causing toxicity in vitro suggesting a good safety margin in respect of environmental uptake.

Regulation of abscisic acid-induced stomatal closure and anion channels by guard cell AAPK kinase.

Abscisic acid (ABA) stimulates stomatal closure and thus supports water conservation by plants during drought. Mass spectrometry-generated peptide sequence information was used to clone a Vicia faba complementary DNA, AAPK, encoding a guard cell-specific ABA-activated serine-threonine protein kinase (AAPK). Expression in transformed guard cells of AAPK altered by one amino acid (lysine 43 to alanine 43) renders stomata insensitive to ABA-induced closure by eliminating ABA activation of plasma membrane anion channels. This information should allow cell-specific, targeted biotechnological manipulation of crop water status.

Arginine decarboxylase (polyamine synthesis) mutants of Arabidopsis thaliana exhibit altered root growth.

Putrescine and polyamines are produced by two alternative pathways in plants. One pathway starts with the enzyme arginine decarboxylase; the other with ornithine decarboxylase. The authors developed an in vivo screening strategy to identify mutants with low levels of arginine decarboxylase activity. The screen requires both a primary screen of the M2 generation and a secondary screen of the M3 generation. The method used was to screen 15,000 EMS-mutagenized M2 seedlings for low levels of arginine decarboxylase (ADC) activity and identified seven mutants that fall into two complementation groups. These mutants have from 20% to 50% of wild-type enzyme activity. Morphological alterations common among the mutants include increased levels of lateral root branching. The authors obtained a double mutant combining the alleles with the lowest activities from the two complementation groups; this has lower ADC enzyme activity and putrescine levels than either of the single mutants. The double mutant has highly kinked roots that form a tight cluster; it also has narrower leaves, sepals, and petals than either single mutant or wild-type, and delayed flowering. These results suggest there may be more than one ADC gene in Arabidopsis, and that ADC and polyamine levels play roles in root meristem function and in lateral growth of leaf-homolog organs.

Black south African adolescents' attitudes about studying.

Black South African high school students (N = 523) were questioned about their attitudes and motivation towards studying. Analysis indicated that the students expressed negative attitudes toward studying and were concerned about failing. 34% indicated a lack of interest in most school subject matter.

Occupational aspirations of black South African adolescents.

The present study provides a description of the occupational aspirations of 216 black high school students in a special program by the amount of training required (status) and Holland's 1973 typology as well as by gender, age, socioeconomic status, knowledge of self, and occupational knowledge. Analysis indicates that most adolescents aspire to Social and Investigative occupations, and occupations with a high status. Most of this select sample displayed low self- and occupational knowledge. Aspirations appear unrealistic in terms of trends within the labor market, but might be more realistic with effective and relevant guidance programs in schools.

Regulation of Arabidopsis thaliana (L.) Heynh Arginine decarboxylase by potassium deficiency stress.

Arginine decarboxylase (ARGdc) is the first enzyme in one of the two pathways to putrescine in plants. ARGdc enzyme activity has been shown to be induced by many environmental factors, including potassium deficiency stress. We investigated the mechanism for induction of ARGdc activity during potassium deficiency stress in Arabidopsis thaliana (L.) Heynh. We show that A. thaliana responds to potassium deficiency stress by increasing ARGdc activity by up to 10-fold over unstressed plants with a corresponding increase in putrescine levels of up to 20-fold. Spermidine and spermine levels do not increase proportionately. Northern analysis showed no increase in ARGdc mRNA levels correlated with the increase in ARGdc enzyme activity. Western analysis revealed that there was no difference between ARGdc protein levels in stressed plants compared with controls. The increase in ARGdc enzyme activity due to potassium deficiency stress does not appear to involve changes in mRNA or protein abundance.

Factor analysis of the Career Decision Scale on South African high school students.

A factor analytic study of the Career Decision Scale-High School version of Hartman and Hartman on 312 white South African adolescents from Grades 11 and 12 was undertaken. A simple two-factor structure emerged which accounted for 47.36% of the total variance in the scores. These results support the use of the version as a differential measure of career indecision and indicate that the number and structure of factors can change across populations. The implications of these results for research in South Africa are considered.

Androgen deprivation induces phenotypic and functional changes in the thymus of adult male mice.

The functional immunological consequences of thymic regeneration after castration were studied in adult male C57Bl/6 mice. Phenotypic profiles of thymocytes present in the enlarged thymuses of castrate animals demonstrated a significant decrease in the proportion of thymocytes positive for the suppressor/cytotoxic phenotype (CD4-CD8+; P = 0.005). Thymic enlargement in castrate animals was accompanied by increased capacity of thymocytes to incorporate thymidine in response to Concanavalin A in vitro. Spleens from castrate mice also were enlarged, and in vitro generation of functional suppressor cells by splenocytes from castrate animals was decreased. Testosterone replacement resulted in thymic regression, with a shift toward expression of mature thymocyte phenotypes, a decrease in the double-positive phenotype (CD4+CD8+), and a relative predominance of the CD4-CD8+ suppressor/cytotoxic phenotype over the CD4+CD8- helper phenotype. Unstimulated thymidine incorporation by thymocytes from androgen-treated animals was decreased compared to controls (P = 0.050). Spleen size was not altered by androgen administration. These findings suggest that in the adult animal, changes in androgen status effect alterations in thymocyte phenotypic profiles and thymocyte function, with removal of androgens shifting the T cell balance toward the CD4 helper subset and administration of androgens changing the balance toward CD8 suppressor/cytotoxic T cell predominance.

Studies of immunological function in mice with defective androgen action. Distinction between alterations in immune function due to hormonal insensitivity and alterations due to other genetic factors.

The presence of androgen receptors in thymocytes and the well-described effects of exogenous androgens on thymus size suggest a role for androgenic hormones in thymocyte growth and maturation. Testicular feminization (Tfm/Y) mice which bear a heritable defect in the androgen receptor protein were studied to investigate how androgens might influence immune phenotype and function. These mice were compared to two types of controls; their Tabby/Y normal male littermates and male mice of the C57 Bl/6 strain from which the Tabby and Tfm mice were derived. Thymuses and spleens from Tfm/Y mice were larger than both types of controls. Phenotypic differences in thymocyte and splenocyte subpopulations identified by the T-cell markers CD3, CD4 and CD8 suggested that T-cell maturation was altered in the androgen-resistant animal. However, both Ta/Y and Tfm/Y were found to be high producers of interleukin-4 (IL-4) by both spleen and thymus cells, while cells from the C57 mice produced predominantly IL-2. These findings suggest that some immunological features of the Tfm/Y mouse may be related to its defect in androgen action, but that high levels of IL-4 production are probably related to other genetic changes in the C57 background.

The influence of curing time and environment on the fracture properties of bone cement.

Fracture of bone cement at the bone-cement interface is considered to be of significance in the aseptic loosening of orthopaedic implants. The characterisation of the fracture properties of bone cement is influenced by the time and environment in which it is cured. Cement samples stored in air and water at 21 and 37 degrees C for 7 and 21 days were tested using the 'Chevron' test to determine the work of fracture. It was found that the storage temperature and environment had important influences on the fracture resistance of bone cement. In a physiological environment cement appears to take longer to attain a fracture resistance equivalent to that of cement stored at room temperature.