Exposure to p-phenylendiamine in hairdressing parlours

Summary The purpose of this study is to verify and assess, in working conditions, the respiratory exposure to PPD of hairdressing parlour personnel. Several air samples collected in a hairdressing parlour during the time required for 8 applications of dyeing products containing PPD 2.52% have been analyzed. Tests are also carried out by extracting air immediately above the bowls containing the dyeing products, both at room temperature and at 37°C. PPD was assessed by means of HPLC. Only air sampled directly on bowls at 37°C has shown a level of 1 g, corresponding to an environmental release of PPD equivalent to 8 applications of dyeing products. On the basis of these experimental data, the PPD concentration in the air according to the parlour volume and to the supposed air exchanges has been calculated. Our results show a substantial insignificance of the concentration of PPD released in the environmental air during normal operations of hair dyeing: authors are of the opinion that hairdressers can't be truly considered as a PPD-asthmatic risk category like other workers exposed to PPD dust dispersed in the air of their working environment.     

The role of air temperature in determining dormancy release and flowering ofCorylus avellana L.

Summary 7 years of airborne pollen monitoring in Perugia (central Italy) were used to determine the temperature requirements to break dormancy and to resume growth and bloom ofCorylus avellana L.,Corylus needs 1000 chill-units to complete its dormancy and this value, in the Perugian area, is met by the end of December or the first days of January. MoreoverCorylus trees require 220 growth degree hours before they are able to flower. If air temperature is high, this value can be achieved in only 10 days, but if the temperature remains too low, the heat accumulation can require up to 35 days. With these parameters it is possible to build a model to predict the date of the beginning ofCorylus avellana pollen season.     

Prevention by N-acetylcysteine of benzo[a]pyrene clastogenicity and DNA adducts in rats

The daily i.t. administration of benzo[a]pyrene (BP) to Sprague-Dawley rats, for 3 consecutive days, did not cause any toxicity or clastogenicity in bone marrow cells, as evaluated by monitoring the ratio of polychromatic to normochromatic erythrocytes and the frequency of micronucleated polychromatic erythrocytes. However, BP produced a considerable enhancement of binucleated and micronucleated pulmonary alveolar macrophages, as well as a significant increase in polymorphonucleates recovered by bronchoalveolar lavage. These effects were prevented by administering the thiol N-acetylcysteine (NAC) by gavage 5 h before each BP instillation. In addition, the i.t. treatment with BP resulted in the formation of BP diolepoxide (BPDE)-DNA adducts in lungs and liver, as assessed by synchronous fluorescence spectrophotometry, with fluorescence peaks of similar magnitude in the 2 tissues. Pretreatment with NAC by gavage completely prevented BPDE adducts to liver DNA and significantly decreased those to lung DNA.     

Costs to host defence and the persistence of parasitic cuckoos.

Raising genetically unrelated young is maladaptive, yet brood parasitism is widespread in birds. In several systems, hosts can evolve near-perfect defences against the parasite (discrimination and rejection of unlike eggs), making it difficult to understand how the parasite continues to exist. This study demonstrates costs to host defences (e.g. rejection of one's own eggs) such that once the parasite goes extinct on a particular host species, defence mechanisms are selectively disadvantageous. The consequent loss of host defences, and potential for re-exploitation of the host by the parasite, can explain the continued persistence of avian brood parasites. The results provide one general explanation for coexistence of parasites and their hosts.     

Effects of prolonged sodium restriction on the morphology and function of rat adrenocortical autotransplants

Summary Regenerated adrenocortical nodules were obtained by implanting fragments of the capsular tissue of excised adrenal glands into the musculus gracilis of rats (Belloni et al. 1990). Five months after the operation, operated rats showed a normal basal blood level of corticosterone, but a very low concentration of circulating aldosterone associated with a slightly increased plasma renin activity (PRA). Regenerated nodules were well encapsulated and some septa extended into the parenchyma from the connective-tissue capsule. The majority of parenchymal cells were similar to those of the zonae fasciculata and reticularis of the normal adrenal gland, while zona glomerulosa-like cells were exclusively located around septa (juxta-septal zone; JZ). In vitro studies demonstrated that nodules were functioning as far as glucocorticoid production was concerned, while mineralocorticoid yield was very low. Prolonged sodium restriction significantly increased PRA and plasma aldosterone concentration, and provoked a marked hypertrophy of JZ, which was due to increases in both the number and average volume of JZ cells. Accordingly, the in vitro basal production of aldosterone and other 18-hydroxylated steroids was notably enhanced. The plasma level of corticosterone, as well as zona fasciculata/reticularis-like cells and in vitro production of glucocorticoids by regenerated nodules were not affected. These findings, indicating that autotransplanted adrenocortical nodules respond to a prolonged sodium restriction similar to the normal adrenal glands, suggest that the relative deficit in mineralocorticoid production is not due to an intrinsic defect of the zona glomerulosa-like JZ, but is probably caused by the impairment of its adequate stimulation under basal conditions. The hypothesis is advanced that the lack of splanchnic nerve supply and chromaffin medullary tissue in regenerated nodules may be the cause of such an impairment.     

pKa values of the 8 alpha-imidazole substituents in selected flavoenzymes containing 8 alpha-histidylflavins

Difference absorption spectroscopy as a function of pH is described as a probe to determine the pKa values of the 8 alpha-imidazole substituent in flavoenzymes containing 8 alpha-histidylflavin coenzymes. Reversible absorption difference spectra are observed in the pH range 5.5 to 8.5 when synthetic 8 alpha-imidazolyl-FMN is bound to the apoflavodoxins from Azotobacter vinelandii and from Clostridium pasterianum. The observed spectral perturbations of these two flavodoxin complexes follow a single proton ionization dependence with respective pKa values of 6.7 and 6.8. No pH-induced spectral perturbations were observed when 8 alpha-(N-CH3)-imidazolium FMN was bound to either flavodoxin. Similar approaches are described to determine the 8 alpha-imidazolyl pKa values of the 8 alpha-histidyl-FAD coenzyme of the cholesterol oxidases from Schizophyllum commune and from Gleocystidium chrysocreas. Previous work has shown the former enzyme contains an 8 alpha-N1-histidyl-FAD (W. C. Kenney et al. (1979) J. Biol. Chem. 254, 4689-4690) while experiments reported here show the latter enzyme also contains one 8 alpha-N1-histidyl-FAD per mole of enzyme. The pKa value for the 8 alpha-imidazole substituent on the flavin of S. commune cholesterol oxidase is 5.4 while that determined for the G. chrysocreas enzyme is 6.2. These results demonstrate that the pKa of the 8 alpha-imidazole substituent can be determined in enzymes containing an 8 alpha-histidylflavin, provided that the enzyme is stable in the pH range required to observe ionization. Furthermore it is shown this the pKa value can differ even on comparison of enzymes from different sources that catalyze the same reaction.     

The complete amino acid sequences of cytosolic and mitochondrial aspartate aminotransferases from horse heart,and inferences on evolution of the isoenzymes

Summary We report here the complete amino acid sequences of the cytosolic and mitochondrial aspartate aminotransferases from horse heart. The two sequences can be aligned so that 48.1% of the amino acid residues are identical. The sequences have been compared with those of the cytosolic isoenzymes from pig and chicken, the mitochondrial isoenzymes from pig, chicken, rat, and human, and the enzyme fromEscherichia coli. The results suggest that the mammalian cytosolic and mitochondrial isoenzymes have evolved at equal and constant rates whereas the isoenzymes from chicken may have evolved somewhat more slowly. Based on the rate of evolution of the mammalian isoenzymes, the geneduplication event that gave rise to cytosolic and mitochondrial aspartate aminotransferases is estimated to have occurred at least 10⁹ years ago. The cytosolic and mitochondrial isoenzymes are equally related to the enzyme fromE. coli; the prokaryotic and eukaryotic enzymes diverged from one another at least 1.3×10⁹ years ago.