Evaluation of the clastogenicity of water treated with sodium hypochiorite or monochioramine using a micronucleus test in newt larvae (Pleurodeles waltl)

We have previously described a micronucleus test using erythrocytesfrom larvae of the urodele amphibian Pleurodeles waltl (pleurodele).The test is based on a comparison of the levels of micronucleatederythrocytes in blood smears from larvae reared in water containinga clastogen, with the levels from larvae reared in purifiedwater. We have employed this test to evaluate mutagenic activityof chlorinated or monochloraminated water devoid of all organicmatter. (i) The level of micronuclei in erythrocytes was comparedbetween a group of larvae reared for 12 days in chlorinatedreconstituted ultrapure water treated with sodium hypochlorite,and a control group reared in just the reconstituted water.Sodium hypochlorite was added when both the food and mediumwere changed each day. Chlorine levels of 0.125 and 0.25 p.p.m.led to significant elevations of micronuclei. (ii) The possibilityof indirect effects of chlorine through chemical interactionswith the food were also investigated, using the following scheme:larvae were left for 3 h in chlorinated reconstituted ultrapurewater and then placed in non-chlorinated water. Food was onlyintroduced when they were transferred to the non-chlorinatedwater. This procedure was repeated for 12 consecutive days.Control larvae were reared in non-chlorinated water throughoutthis period. In this case results were also positive when thelarvae were exposed for only 3 h to the chlorine (0.2 p.p.m.for 12 days) in the absence of food. (iii) This was the sameas experiment 1 except that the water was chlorinated with monochloramineinstead of sodium hypochlorite. The level of micronuclei increasedwith increasing concentration of monochloramine (0.05, 0.1 and0.15 p.p.m.) although only the 0.15 p.p.m. concentration gavea statistically significant response. The results indicate thatfree chlorine and monochloramine are responsible for the clastogeneffect in newt larvae.     

Relationship between the gas composition of the middle ear and the venous blood at steady state

Concomitant continuous measurements of the steady-state gas composition of the middle ear and of the venous blood were recorded by mass spectrometry in four guinea pigs. The following mean values were obtained for the partial pressures of middle ear gases; nitrogen + argon, 606.4 mm Hg; oxygen, 46.2 mm Hg; and carbon dioxide, 60.2 mm Hg. The corresponding values for the venous blood were as follows: Nitrogen + argon, 563.4 mm Hg; oxygen, 38.0 mm Hg; and carbon dioxide, 61.4 mm Hg. The similarity of the steady-state gas composition of the middle ear to that of the venous blood suggests that the partial pressures of the gases in the middle ear are controlled by interchange with gases present in the blood.     

Equivalent intrinsic blur in spatial vision

We used Gaussian blurred stimuli to explore the effect of blur on three tasks: (i) 2-line “resolution”; (ii) line detection; and (iii) spatial interval discrimination, in both central and peripheral vision. The results of our experiments can be summarized as follows.

(i) 2-Line “resolution”: thresholds for pairs of unblurred, low contrast, stimuli are approx. 0.5min arc in the fovea. When the stimulus blur is small, it has little effect upon 2-line “resolution”; however, when the stimulus blur, σ, exceeds 0.5 min, thresholds are degraded. We operationally define this transition point as the equivalent intrinsic blur or B_i. When the standard deviation of the stimulus blur, σ, is greater than B_i, then the “ resolution” threshold is approximately equal to σ. Both the unblurred “resolution” threshold, and the equivalent intrinsic blur, B_i, vary with eccentricity in a manner consistent with the variation of cone separation within the central 10 deg. When the stimulus blur exceeds the equivalent intrinsic blur, “resolution” in the periphery is the same as in the fovea.

(ii) Line detection: when the standard deviation of the stimulus blur, σ, is less than B_i, then the line detection threshold is approximately inversely proportional to σ (it is≈ T_dB_i/gs) i.e. it obeys Ricco's law. When the standard deviation of the stimulus blur, σ, is greater than B_i, then the “resolution” threshold is approximately equal to σ and the detection threshold is approximately a fixed contrast (to be referred to as T_d).

According to (i) and (ii), the equivalent intrinsic blur, B_i, plays a dual role in determining both the “resolution” threshold and the detection threshold, B_i corresponds to the “Ricco's diameter” for spatial summation in a detection task, and it also corresponds to the “resolution” threshold for thin lines. This connection between detection and “resolution” is somewhat surprising.

(iii) Spatial interval discrimination: thresholds are proportional to the separation of the lines (i.e. Weber's law). At the optimal separation, the thresholds represent a “hyperacuity” (i.e. they are smaller than the “resolution” threshold). For unblurred lines, the optimal separation is approximately 2–3 times the “resolution” limit at all eccentricities, so the optimal separation varies with eccentricity at the same rate as the equivalent intrinsic blur, B_i. However, the optimal spatial interval threshold falls off with eccentricity about 3–4 times more rapidly, consistent with the rate of decline of other position acuity tasks. For Gaussian blurred lines, over a wide range of separations and eccentricities, spatial interval discrimination thresholds begin to rise when the stimulus blur exceeds between about⅓ and ½ the separation of the lines. The strong elevation of the optimal spatial interval discrimination threshold in the periphery cannot be predicted on the basis of detectability of the lines, “resolution”, or on the basis of the equivalent intrinsic blur. We hypothesize that the increased spatial interval discrimination thresholds are a consequence of position uncertainty, perhaps due to sparse spatial sampling in the periphery.

Diverging trends in breast cancer mortality within Switzerland

Background: Substantial regional heterogeneity in the provisionof cancer prevention and management services results from thedecentralised Swiss healthcare system. Materials and methods: Breast cancer mortality trends between1980 and 2002 were compared in two French- and in two German-speakingfemale populations of Switzerland, aged 55–74 years, characterisedby different access to, and use of, mammography screening. Results: Since the early 1990s, a 30% fall was observed in theFrench-speaking regions of Vaud and Geneva, where mammographyscreening is widespread, with no decline in the German-speakingareas of Basel and Zurich. Conclusion: Modification in breast cancer diagnosis and managementin selected regions of Switzerland is urgently needed. Key words: breast cancer, mortality, Switzerland, treatment, mammography screening     

Effects of new smoking regulations

The introduction of a comprehensive smoke-free law in all indoorworkplaces (including bars and restaurants) is supported bya large majority of the population. In Italy, where such legislationwas     

Incidence of invasive cervical cancer in the Swiss canton of Vaud, and a note on screening.

Age adjusted incidence rates (World standard) from invasive cervical cancer in the Swiss canton of Vaud decreased from 17.7/100,000 in 1968-70 to 9.9/100,000 in 1983-85. The decline was substantial in younger middle age, but no appreciable trend was observed in women over 70. This is consistent with available interview based information on the pattern of cervical screening in the Swiss population. Although there was no organised screening programme in Switzerland, over 80% of women aged 20-44 and 65% of those aged 45-64 reported one or more screening smears over the previous 3 years, compared to only 22% of women aged 65 or over. In the last calendar period, there was an apparent increase in the incidence of invasive cervical cancer (from 2.5 to 6.1/100,000) in women aged 25-29. Although based on small absolute numbers, this is in agreement with incidence and mortality data from other countries, and may therefore confirm a change in risk factor exposure in younger women.     

Effect of acidic and basic isoferritins on in vitro growth of human granulocyte-monocyte progenitors

Acidic isoferritins have been previously found to be highly potent inhibitors of hematopoietic progenitors at concentrations of 10(-16) to 10(-18) mol/L, and it has been suggested that acidic isoferritin inhibitory activity plays a role in the regulation of normal hematopoiesis and also in the pathogenesis of leukemia. To characterize the ferritin species that affect the in vitro growth of human colony- forming unit-granulocyte-macrophage (CFU-GM), we tested different preparations of basic (L-subunit-rich) and acidic (H-subunit-rich) isoferritins. Three preparations of human liver (basic) ferritin did not show any effects on CFU-GM growth at concentrations up to 10(-9) mol/L, irrespective of the degree of glycosylation. Acidic isoferritins were purified both from HeLa cells and human heart. HeLa cell ferritin did not affect in vitro colony formation. One of two preparations of human heart ferritin, containing 5% glycosylated ferritin, showed a mean inhibition of 26% +/- 8% of the control at 10(-9) mol/L (P less than .02), whereas the other preparation, which contained no glycosylated ferritin, did not show any effect of CFU-GM growth. A preparation enriched for glycosylated acidic isoferritins from human heart was found to produce a mean inhibition of 32% +/- 11% of the control at 10(-9) mol/L (P less than .01), whereas another one was ineffective. A significant part of the inhibitory activity was removed by preincubation with the monoclonal antibody 2A4 directed against human heart ferritin. The present findings indicate that basic isoferritins, ie, the predominant ferritin type in human blood, have no effect on the growth of human CFU-GM, and this is in keeping with indirect clinical evidence. Inhibition of colony formation may be obtained by some preparations of acidic isoferritins that are rich in H subunits and bind to concanavalin A. The mechanism(s) responsible for this are not clear, but the effective concentrations are higher than those found in human blood both under normal conditions and in leukemia. At present, the physiologic significance of the observed inhibitory activity is uncertain.     

Cytomegalovirus mononucleosis in children and adults: differences in clinical presentation

In 2 previously healthy groups of 14 children and 17 adults with cytomegalovirus mononucleosis, significant clinical differences were observed. Cervical lymphadenopathy, hepatomegaly and lymphocytosis (greater than 5000/microliter) were more common in children and protracted fever more common in adults. Exudative tonsillitis indistinguishable from infectious mononucleosis was sometimes seen in children but never in adults.