The effects of long-term elevated ozone concentrations on the growth and photosynthesis of Sphagnum recurvum and Polytrichum commune

Although ozone is generally accepted to be an important phytotoxic air pollutant, little is known of its effects on natural and semi-natural vegetation. In this study two bryophyte species, Sphagnum recurvum P. Beauv. and Polytrichum commune Hedw., were exposed to long-term chronic ozone concentrations, i.e. 70-80 ppb (nl 1^-1 ), for 6-9 wk in summer conditions (mean 15°C) and in winter conditions (mean 6.4°C) in open-top chambers (OTC), in the field, and at 15°C and 5°C in controlled-environment chambers, under laboratory conditions. Fumigation with ozone caused a significant reduction in the growth of treated plants in comparison with that of control plants. However, there were differences between species. S. recurvum was more affected than P. commune. In the controlled-environment chambers growth of S. recurvum was reduced under both winter and summer conditions by 21 and 15%, respectively. In the OTCs, S. recurvum growth was reduced (by 17%) only under summer conditions. P. commune growth was only significantly reduced following ozone exposure in the OTCs under winter conditions. Here the growth reduction was by 22%. Net CO₂ assimilation of the two species was also significantly reduced by ozone exposure but only in the OTCs under winter conditions. Net CO₂ assimilation of S. recurvum and P. commune was reduced by 60 and 80%, respectively. The ratio of variable to maximal fluorescence (F_v /F_m ratio) was the least affected of the parameters measured. Only for P. commune fumigated in the OTCs under winter conditions was the F_v /F_m ratio significantly reduced (by 4.4%). Bryophytes, by the very nature of their morphology and physiology are, perhaps, more likely to be susceptible to ozone pollution than higher plants; these results are discussed in relation to their possible ecological significance.

Pigeons do not complete partly occluded figures

One of the most common obstacles to object perception is the fact that objects often occlude parts of themselves and parts of other objects. Perceptual completion has been studied extensively in humans, and researchers have shown that humans do complete partly occluded objects. In an effort to understand more about the mechanisms underlying completion, recent research has extended the study of perceptual completion to other mammalian species. Monkeys and mice also seem to complete two-dimensional representations of partly occluded objects. The present study addresses the question of whether this capacity generalizes to a nonmammalian species, the pigeon (Columba livia). The results point to a limit of the generalizability of perceptual completion: pigeons do not complete partly occluded figures.

Photolysis of the novel inotropes EMD 57033 and EMD 57439: evidence that Ca2+ sensitization and phosphodiesterase inhibition depend upon the same enantiomeric site

1. We studied the effects of flash photolysis on the novel enantiomeric cardiac inotropes EMD 57033 (a calcium sensitizer) and EMD 57439 (a phosphodiesterase III inhibitor) in rat isolated ventricular trabeculae. 2. In skinned trabeculae, EMD 57439 had no effect on force production, consistent with lack of an active cyclic AMP system in this preparation. In contrast, EMD 57033 potentiated force at partial and maximal activation. A single flash of near u.v. light given at partial activation (30-70%) reduced force potentiation by 52.4 +/- 5.2%. No effect was produced by flashes in the presence of EMD 57439 or in the absence of either drug. 3. The time course of relaxation induced by EMD 57033 photolysis was indistinguishable from that obtained on deactivating the muscle by rapidly lowering Ca2+ using photolysis of the caged chelator of calcium, diazo-2. 4. In intact, twitching trabeculae, EMD 57033 increased diastolic and peak force and slowed relaxation. These effects were simultaneously reduced by a light flash. In these muscles EMD 57439 reduced force, without affecting the twitch time course. These effects were also reduced by a light flash. 5. The u.v. absorbance spectra of EMD 57033 and EMD 57439 were identical. After photolysis optical density decreased substantially and the peak shifted from 320 nm to 280 nm. 6. The proton n.m.r. spectra of these compounds were identical. The main change post-photolysis was a decrease in the proton signal associated with the enantiomeric carbon atom. 7. This novel manipulation of the molecular structure of EMD 57033 and EMD 57439 within an experiment thus provides direct evidence linking calcium sensitization to a particular molecular structure. The three main effects of the sensitizer on the twitch were simultaneously abolished and may be mechanistically linked. Flash photolysis may be a useful tool for further investigations of the actions of these compounds. In particular, flash photolysis of the sensitizer represents a novel method of rapidly deactivating cardiac muscle.

Solitary astrocytoma of the retina in a child

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Nevi and migration within the United States and Canada: a population-based cross-sectional study

A survey to ascertain factors associated with benign melanocytic nevi or moles was conducted among randomly-selected White adults (aged 18 to 50 years) in Washington State (United States). Participants of the telephone interview in 1990-91 were questioned about lifetime places of residence and constitutional factors. Subjects counted raised nevi on their arms at the end of the survey. Logistic regression was used to examine the risk for two or more nevi compared with no nevi. Individuals who resided in warmer areas and lower latitudes than Washington State were at higher risk of having multiple nevi. This association held for residence at birth, during childhood, adolescence, and over lifetime: an odds ratio (OR) of 2.3 (95 percent confidence interval = 1.2-4.3) for lifetime average daily maximum temperature of > or = 64 degrees F compared with 58.9 degrees F, and similar ORs of 2.1 for adolescence and 1.8 for childhood. These associations remained significant after adjusting for potential confounding effects of constitutional factors and for childhood sunburns as a potential mechanism. Risk of multiple nevi was reduced for both early age at migration and longer duration of stay in Washington. These data are consistent with the importance of childhood and adolescent sun exposure in the etiology of nevi, but also suggest an effect of lifetime sun exposure.

Innervation of the liver: morphology and function

Although it has been known for many years that the liver receives a nerve supply, it is only with the advent of immunohistochemistry that this innervation has been analysed in depth. It is now appreciated not only that many different nerve types are present, but also that there are significant differences between species, especially in the degree of parenchymal innervation. This has stimulated more detailed investigation of the innervation of the human liver in both health and disease. At the same time, functional studies have been underlining the important roles that these nerves play in processes as diverse as osmoreception and liver regeneration. This article briefly reviews current understanding of the morphology and functions of the hepatic nerve supply.

Constitutional factors and sun exposure in relation to nevi: a population-based cross-sectional study

A survey of benign melanocytic nevi (moles), suspected precursors or markers for melanoma, was conducted in Washington State among 717 randomly selected 18- to 50-year-old white adults who participated in a telephone interview in 1990-1991. Participants were questioned about constitutional factors, time spent in the sun, and severe sunburns over three time periods and were asked to count the raised nevi on both their arms. Logistic regression was used to examine the risk for 2+ nevi compared with none. An odds ratio (OR) of 2.0 (95% confidence interval (CI) 1.3-3.1) was seen for current freckling. Skin color, tendency to burn, and inability to tan were important risk factors but were not independent of each other. Individuals with a history of severe sunburns had an increased risk of nevi: OR = 1.9 (95% CI 0.9-3.9) for 3+ severe sunburns compared with none in the last 5 years; OR = 2.0 (95% CI 1.2-3.1) for 4+ severe teenage sunburns; and OR = 3.1 (95% CI 1.7-5.3) for 4+ severe childhood sunburns. Furthermore, childhood sunburns were related to nevi independently of sun sensitivity and teenage and recent sunburns: OR = 2.0 (95% CI 1.0-4.0) for 4+ severe sunburns. These data suggest that childhood sunburns are important in the etiology of nevi. This study supports prior studies of the relation between melanoma and early sun exposure.

Growth responses of Polytrichum commune and Hylocomium splendens to simulated environmental change in the sub-arctic

Total moss cover and the growth responses of the two dominant bryophytes within a sub-arctic heath ecosystem, Polytrichum commune Hedw, and Hylocomium splendens (Hedw.) Br. Eur., were investigated in response to simulated environmental change. Temperature, water supply and nutrients (NPK fertilizer) were increased in a factorial field study in Swedish Lapland. After 3 yr of treatment, total moss caver on fertilized plots was found to be less than 50% of that on unfertilized plots. H. splendens made a smaller contribution to total cover, and also had fewer shoots on the fertilizer treated plots. The relative contribution of P. commune to the bryophyte community was greater on the fertilized plots, although total shoot numbers of P. commune were not greater. There was, however, a larger number of dead shoots of P. commune on the fertilized plots. Total moss cover, relative contribution to moss cover by P. commune and H. splendens, and the numbers of shoots of these two species, were unresponsive to both the temperature and water treatments. The growth of the current year's segment of H. splendens was retarded by both the fertilizer and temperature treatments. Furthermore, the dry weight of the physiologically active shoot was found to be significantly altered by all three treatments. The current year's growth of P. commune showed increases in d. wt and morphological parameters in response to the fertilizer treatment. There were also interactive effects of both the fertilizer and temperature treatments with the water treatment on the current year's stem length increment.

EMD 57033 enhances arrhythmias associated with increased wall-stress in the working rat heart

1. EMD 57033 produces a positive inotropic effect by increasing the sensitivity of cardiac muscle myofilaments to calcium. Since the elevation in intracellular calcium produced by conventional inotropic compounds is thought to be arrhythmogenic, it is hoped that compounds such as EMD 57033 may increase cardiac output without exacerbating arrhythmias in patients with cardiac failure. This is the first study to examine whether EMD 57033 influences the susceptibility of the heart to ventricular arrhythmias. 2. We used the isolated working rat heart to investigate the effect of EMD 57033 on wall-stress-induced ventricular arrhythmia. Arrhythmias were induced by increases in ventricular afterload, and the effect of 2 mumol/l EMD 57033 on ventricular arrhythmias was investigated. The effect of 2 mumol/l EMD 57033 on contractility and arrhythmias was also assessed in the presence of different levels of perfusate calcium. 3. EMD 57033 was positively inotropic in the working rat heart, but it also produced a reversible increase in wall-stress-induced ventricular arrhythmia. The incidence of both ventricular ectopics and complex arrhythmias such as ventricular tachycardia were significantly increased by EMD 57033. Arrhythmias increased progressively as the level of perfusate calcium was raised within the physiological range. 4. The mechanism by which EMD 57033 increases wall-stress-induced arrhythmia is unclear, but it seems unlikely to be directly due to elevation of intracellular calcium. Further studies of the arrhythmogenic profile of this novel compound are required in a variety of models to assess its suitability and safety as a potentially therapeutic compound in heart failure.

Application of dual internal standards for precise sizing of polymerase chain reaction products using capillary electrophoresis

Capillary electrophoresis (CE) is an analytical technique which provides rapid, high resolution analysis of amplified DNA fragments produced by the polymerase chain reaction (PCR). In this study, two internal standards are used as size markers to bracket und precisely size PCR products. The technique is applied to typing PCR products from the short tandem repeat locus HUMTH01. HUMTH01 consists of five to seven major alleles in the size range of 179-203 bp, with each allele four bp apart. Using this genetic marker, a population containing 97 individuals was examined with both polyacrylamide gel electrophoresis and CE. Identical genotypes were obtained with both techniques demonstrating the reliability of CE in DNA typing applications. The DNA analysis took place in sets of 10 with a calibration of the CE being performed between each set of samples. For the 97 samples examined, the pooled standard deviation was 0.3 bp. The observed genotype frequencies determined from the sample set did not deviate significantly from Hardy-Weinberg expectations. From these CE results, we conclude that HUMTH01 PCR products can be accurately and precisely sized by capillary electrophoresis using the method described.

Lysine 182 of endothelin B receptor modulates agonist selectivity and antagonist affinity: evidence for the overlap of peptide and non-peptide ligand binding sites

The potent vasoactive peptide hormone endothelin (ET) binds to receptors which belong to the G-protein coupled receptor family. The availability of non-peptide antagonists for ET receptors allows investigation of the relationship among the binding sites for peptide and non-peptide ligands. In this study, a lysine residue, conserved within transmembrane domain 3 (TM3) of the ETA and ETB receptor subtypes, is implicated in agonist and antagonist binding by its analogous position within TM3 to a binding site aspartate residue conserved within bioactive amine receptors. Replacement of this lysine within hETB by arginine, alanine, methionine, aspartate, or glutamate results in hETB variants with unaltered affinities for agonist peptide ET-1 but which have affinities for peptide agonists ET-2, ET-3, sarafotoxin 6C, and TRL 1736 which are between 1-3 orders of magnitude lower than their corresponding wild-type hETB values. Significantly, the affinities of non-peptide antagonists, (+/-)-SB 209670 and its analogs as well as Ro 46-2005, are abrogated. The results suggest that an interaction of K182 of hETB with the indan 2-carboxyl of (+/-)-SB 209670 may contribute to the high-affinity binding of the diarylindan antagonists. The results indicate that TM3 of hETB is a region of overlap among the binding sites of non-peptide antagonists and the affected peptide agonists.

Duodenal leiomyosarcoma presenting with iron deficiency anemia

Failed iron therapy warrants investigation to rule out disorders of iron absorption or intestinal blood loss. The authors report the third case of duodenal leiomyosarcoma in childhood, which presented with iron deficiency anemia. Endoscopy failed to elicit the cause of this problem. Wide surgical resection, sparing the pancreas, was possible.

Effect of nitrogen supply on frost hardiness in Calluna vulgaris (L.) Hull

Frost hardiness in Calluna vulgaris (L.) Hull, which had received ammonium nitrate applications in the field for 30 months, was assessed using scores of visible injury and measurements of the rate of total electrolyte leakage from excised shoots following controlled freezing treatments in the laboratory. There was good overall correlation between the two methods (Spearman correlation coefficient 0.77), but leakage measurements were more sensitive than injury scores to the effects of nitrogen. Visible injury was not significantly altered by nitrogen supply (Kruskal-Wallis non-parametric test). Ion leakage was analyzed in different ways, using either calculations of the first-order rate coefficients or expressions of relative conductivity. These analyses produced similar results with respect to the effect of frost and nitrogen. Shoots of nitrogen-fertilized (40, 80 and 120 kg ha^-1 yr^-1 ) C. vulgaris sampled in October 1991 showed significantly (P < 0.05) less leakage after overnight frosts of -15 and -20 °C than did the water-treated controls. In October the temperature which killed 50% of the shoots (LT₅₀ ), derived from the leakage data, was raised by at least 4 °C by the highest nitrogen treatments compared with the control plants. Frost treatments to pot-grown C. vulgaris in November produced similar visible injury to attached and excised shoots from the same plants, both being significantly less damaged by a -18 °C frost after a 7-month exposure to an NaNO₃ mist solution (1.0 mM, pH 4.5) than were water-misted controls. Ammonium-mist treatments also marginally reduced frost injury, but the effects were not statistically significant. These results demonstrate that frost hardiness of C. vulgaris in the field can be assessed rapidly and accurately in the laboratory by analysis of electrolyte leakage from excised shoots.

Endochondral pseudocyst of the auricle

Endochondral pseudocyst of the auricle is an uncommon, though distinctive clinicopathological entity occurring mainly in young men. An additional case is reported and the differential diagnosis and pathogenesis discussed. It is suggested that lymphatic dilatation of normally present tissue planes could be the most likely causative mechanism. Minor trauma to susceptible ears also seems to be a requirement for development of this condition.

Effects of acidosis and hypoxia on the response of isolated ferret cardiac muscle to inotropic agents

OBJECTIVE

The aim was to study the effects of acidosis and hypoxia on the response of cardiac muscle to inotropic agents which (a) act predominantly by increasing intracellular [Ca2+] (raising extracellular [Ca2+], noradrenaline, isoprenaline) and (b) act partly (phenylephrine) or predominantly (EMD 57033) by increasing myofilament calcium sensitivity.

METHODS

The experiments were performed on isometrically contracting, isolated ferret papillary muscles (n = 45). For each intervention dose-response curves were performed in control solution (pH 7.35), in hypercapnic acidosis (pH 6.85), and in hypoxia (produced by replacing O2 with N2 in the superfusing solution). In some experiments, the photoprotein aequorin was microinjected into superficial cells of the preparation in order to measure intracellular [Ca2+] as well as force.

RESULTS

The results were broadly similar for both classes of inotropic agent. Acidosis caused a shift of the pCa-tension curve to the right (desensitisation of the myofilaments to calcium), but had no significant effect on maximum force. A sufficient inotropic stimulus supplied by either class of inotropic agent could completely reverse the negative inotropic effects of acidosis. The main difference between the two inotropic mechanisms was that the enhanced force produced by calcium sensitisers was associated with a reduction in calcium transient amplitude, while the other inotropes increased the amplitude. The main effect of hypoxia was to decrease maximum force. All the inotropes tested were relatively ineffective in reversing the force depression due to hypoxia.

CONCLUSIONS

The negative inotropic effects of acidosis can be reversed by a sufficiently large inotropic stimulus. Since calcium transient amplitude is already increased in acidosis, the results suggest that calcium sensitisers are likely to be less arrhythmogenic in this situation. The relative ineffectiveness of the inotropes in hypoxia indicates that the main mechanisms causing reduced force in this situation lie downstream of the mechanisms of action of the inotropic agents tested.

Isolated xanthogranuloma of the limbus in an adult

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Tyr-129 is important to the peptide ligand affinity and selectivity of human endothelin type A receptor

Molecular modeling and protein engineering techniques have been used to study residues within G-protein-coupled receptors that are potentially important to ligand binding and selectivity. In this study, Tyr-129 located in transmembrane domain 2 of the human endothelin (ET) type A receptor A (hETA) was targeted on the basis of differences between the hETA and type B receptor (hETB) sequences and the position of the residue on ET receptor models built using the coordinates of bacteriorhodopsin. Replacement of Tyr-129 of hETA by alanine, glutamine, asparagine, histidine, lysine, serine, or phenylalanine results in receptor variants with enhanced ET-3 and sarafotoxin 6C affinities but with unchanged ET-1 and ET-2 affinities. Except for Tyr-129-->Phe hETA, these hETA variants have two to three orders of magnitude lower binding affinity for the ETA-selective antagonist BQ123. Replacement of His-150, the residue in hETB that is analogous in sequence to Tyr-129 of hETA, by either tyrosine or alanine does not affect the affinity of peptide ligands. These results indicate that although transmembrane domain 2 is important in ligand selectivity for hETA, it does not play a significant role in the lack of ligand selectivity shown by hETB. Chimeric receptors have been constructed that further support these conclusions and indicate that at least two hETA regions contribute to ligand selectivity. Additionally, the data support an overlap in the binding site in hETA of agonists ET-3 and sarafotoxin 6C with that of the antagonist BQ123.

Case-control study of malignant melanoma in Washington State. I. Constitutional factors and sun exposure

Constitutional factors and sun exposure were examined among 256 cases of melanoma and 273 controls in three counties of western Washington State. Cases were individuals diagnosed with melanoma at ages 25-65 years during 1984-1987 who were identified from a Seattle-Puget Sound cancer registry. Population controls were identified through random digit dialing and were randomly selected, stratified by age, sex, and county. Participants completed a telephone interview with questions on demographic, sun exposure, and constitutional factors. Risk factors for melanoma were examined through the use of logistic regression, controlling for age, sex, and educational level, and data on each exposure variable were tested for the significance of trends across levels of exposure. The constitutional factor most strongly associated with melanoma risk was sun sensitivity, measured as either reaction to chronic sun exposure (for no tan vs. deep tan, odds ratio (OR) = 9.0, 95% confidence interval (CI) 3.8-21.1; p < 0.001 for trend across four categories) or reaction to acute sun exposure (for severe burn vs. tan, OR = 5.7, 95% CI 2.6-12.6; p < 0.001 for trend across four categories). The number of raised nevi counted on both arms by subjects was also associated with increasing risk (for > or = 10 nevi vs. none, OR = 5.7, 95% CI 2.2-14.6; p for trend < 0.001). Sun exposure in adulthood and occupational sun exposure were not related to melanoma risk. The effect of sun exposure in childhood on melanoma risk was modified by tanning ability. Poor tanners showed no effect of sun exposure at ages 2-10 years or ages 11-20 years. In contrast, people who reported a deep or moderate tan in reaction to chronic sun exposure appeared to be protected from melanoma with increasing sun exposure at ages 2-10 years (for upper third vs. lower third, OR = 0.3, 95% CI 0.2-0.6; p for trend < 0.001), with identical results for exposure at ages 11-20 years. The finding that childhood sun exposure is protective only among those able to tan supports the hypothesis that developing a tan during childhood may reduce the risk of melanoma by offering protection from the effects of sunlight exposure.

Case-control study of malignant melanoma in Washington State. II. Diet, alcohol, and obesity

Intakes of vitamin A, dietary antioxidants, and other dietary components were examined for their relation to the risk of malignant melanoma among 234 cases and 248 controls in three counties of western Washington State. Cases were drawn from persons diagnosed with melanoma between 1984 and 1987 and identified through a Seattle-Puget Sound cancer registry. Population controls were identified through random digit dialing and were randomly selected, stratified by age, sex, and county. Subjects completed a telephone interview and a mailed food frequency questionnaire asking for information on diet, demographic factors, and factors known to be associated with melanoma. Subjects were asked to estimate their food intake 7 years prior to diagnosis for cases and during a comparable time period for controls. Among data on 16 nutrients calculated from reported food intake, one significant finding emerged: Vitamin E obtained from food was inversely related to risk of melanoma (for highest quartile vs. lowest quartile, age-, education-, and energy intake-adjusted odds ratio (OR) = 0.34, 95% confidence interval (CI) 0.16-0.72; p for trend = 0.01). When intake of nutrients from food plus vitamin and mineral supplements was considered, zinc from food and supplements was associated with a decreased risk of melanoma (for highest quartile vs. lowest quartile, adjusted OR = 0.46, 95% CI 0.24-0.91; p for trend = 0.01). There was no evidence that vitamin A, preformed retinol, or carotenoids were associated with a decreased risk of melanoma or that alcohol or polyunsaturated fats were associated with an increased risk. Body mass index (weight (kg)/height (m)2) was significantly related to melanoma risk; cases were more obese than controls (for highest quartile vs. lowest quartile, age-, sex-, and education-adjusted OR = 1.90, 95% CI 1.10-3.27; p for trend = 0.02). These results provide limited support for the hypothesis that antioxidants such as vitamin E or cofactors in protection from oxidative damage such as zinc may be protective for melanoma, and they suggest that obesity should be measured in future studies of melanoma.