G2 phase cell cycle disturbance as a manifestation of genetic cell damage

The predominant cell cycle change induced by X-rays and clastogens in peripheral blood mononuclear cells is the accumulation of cells in the G2 phase of the cell cycle. We show that this accumulation consists of cells that are either delayed or arrested within the G2 phase. Since both X-rays and DNA crosslinking chemicals are known to damage DNA, the G2 phase inhibition caused by these agents is thought to be one of the primary manifestations of (unrepaired) DNA damage. This interpretation is supported by two additional findings. (1) Older individuals have elevated baseline levels of mononuclear blood cells that are delayed and/or arrested in the G2 phase of the cell cycle. This coincides with the increased chromosomal breakage rates reported for older individuals. (2) Irrespective of their age, individuals with inherited genetic instability syndromes (such as Fanconi anemia and Bloom syndrome) exhibit elevated G2 phase cell fractions. We show that the method used to detect such induced or spontaneous cell cycle changes, viz. BrdU-Hoechst flow cytometry, is a rapid and highly sensitive technique for the assessment of genetic cell damage.Dedicated to Professor Ulrich Wolf on the occasion of his 60th birthday     

Clinical ethics and nursing: "yes" to caring, but "no" to a female ethics of care

According to a contemporary school of thought there is a specific female approach to ethics which is based not on abstract "male" ethical principles or rules, but on "care". Nurses have taken a keen interest in these female approaches to ethics. Drawing on the views expounded by Carol Gilligan and Nel Noddings, nurses claim that a female "ethics of care" better captures their moral experiences than a traditional male "ethics of justice". This paper argues that "care" is best understood in a dispositional sense, that is, as sensitivity and responsiveness to the particularities of a situation and the needs of "concrete" others. While "care", in this sense, is necessary for ethics, it is not sufficient. Ethics needs "justice" as well as "care". If women and nurses excessively devalue principles and norms, they will be left without the theoretical tools to condemn some actions or practices, and to defend others. They will, like generations of nurses before them, be condemned to silence.     

Effect of male accessory glands autoaggression on androgenic cytosolic and nuclear receptors of rat prostate.

The effect of immunization against male accessory gland (MAG) homogenates over androgenic cytosolic and nuclear receptors of rat prostate was studied. In the MAG-immunized rats the Bmax of cytosolic receptors was significantly increased (120.3 +/- 44.3 vs 47.7 +/- 24.9 fmol/mg protein, p less than 0.01, mean +/- SD). In contrast, the Bmax of nuclear receptors in the MAG-immunized rats showed no significant difference as regarded controls (kidney immunized rats) when expressed as fmol/100 micrograms DNA (196.1 +/- 84.8 vs 148.3 +/- 88.9) but it show to slight differences (p less than 0.1) when data were reported as percent of weight of tissue (2,189 +/- 918.6 vs 1,303 +/- 611.2 fmol/g wet issue). Results (mean +/- SD) on binding affinity of cytosolic receptors showed no significant differences in MAG-immunized rats as compared with controls (Kd: 1.98 +/- 0.66 vs 1.92 +/- 0.20 nM). Likewise, only a slight difference between both groups was attained for Kds of nuclear receptors (2.34 +/- 0.28 vs 1.80 +/- 0.62 nM, p less than 0.2). On the other hand, 5 alpha 1-dihydrotestosterone (DHT) values obtained in prostate homogenates were significantly decreased in MAG-immunized rats as compared with controls (17.4 +/- 2.0 vs 7.1 +/- 0.9 ng/g tissue, mean +/- SD, p less than 0.01). However, testosterone (T) levels in gland tissue showed no significant differences between both groups (2.4 +/- 0.5 vs 2.6 +/- 0.3 ng/g tissue) with an increase in the T: DHT ratio from 0.14 to 0.37.(ABSTRACT TRUNCATED AT 250 WORDS)     

The involvement of phytochrome in controlling chlorophyll and 5-aminolevulinate formation in a gymnosperm seedling (Pinus sylvestris)

Chlorophyll a (Chl a) accumulation in the cotyledons of Scots pine seedlings (Pinus sylvestris L.) is much higher in the light than in darkness where it ceases 6 days after germination. When these darkgrown seedlings are treated with continuous white light (3,500 lx) a 3 h lag phase appears before Chl a accumulation is resumed. The lag phase can be eliminated by pretreating the seedlings with 7 h of weak red light (0.14 Wm^-2) or with 14 red light pulses separated by relatively short dark periods (<100 min). The effect of 15s red light pulses can be fully reversed by 1 min far-red light pulses. This reversibility is lost within 2 min. In addition, the amount of Chl a formed within 27 h of continuous red light is considerably reduced by the simultaneous application of far-red (RG 9) light. It is concluded that phytochrome (P_fr) is required not only for the elimination of the lagphase but also to maintain a high rate of Chl a accumulation in continuous light. Since accumulation of 5-aminolevulinate (ALA) responds in the same manner as Chl a accumulation to a red light pretreatment it is further concluded that ALA formation is the point where phytochrome regulates Chl biosynthesis in continuous light. No correlation has been found between ALA and Chl a formation in darkness. This indicates that in a darkgrown pine seedling ALA formation is not rate limiting for Chl a accumulation.Abbreviations Chl chlorophyll(ide) - PChl protochlorophyll(ide) - ALA 5-aminolevulinate - P_r the red absorbing form of phytochrome - P_fr the far-red absorbing form of phytochrome - P_tot total phytochrome ([P_r]+[P_fr])