Performance of induction module cavity ring-down spectroscopy (IM-CRDS) for measuring δ18 O and δ2 H values of soil, stem, and leaf waters.

RATIONALE: Induction module cavity ring-down spectroscopy (IM-CRDS) has been proposed as a rapid and cost-effective alternative to cryogenic vacuum distillation (CVD) and isotope ratio mass spectrometry (IRMS) for the measurement of δ18 O and δ2 H values in matrix-bound waters. In the current study, we characterized the performance of IM-CRDS relative to CVD and IRMS and investigated the mechanisms responsible for differences between the methods. METHODS: We collected a set of 75 soil, stem, and leaf water samples, and measured the δ18 O and δ2 H values of each sample with four techniques: CVD and IRMS, CVD and CRDS, CVD and IM-CRDS, and IM-CRDS alone. We then calculated the isotopic errors for each of the three CRDS methods relative to CVD and IRMS, and analyzed the relationships among these errors and suites of diagnostic spectral parameters that are indicative of organic contamination. RESULTS: The IM-CRDS technique accurately assessed the δ18 O and δ2 H values of pure waters, but exhibited progressively increasing errors for soil waters, stem waters, and leaf waters. For soils, the errors were attributable to subsampling of isotopically heterogeneous source material, whereas for stems and leaves, they were attributable to spectral interference. Unexpectedly, the magnitude of spectral interference was higher for the solid samples analyzed directly via IM-CRDS than for those originally extracted via CVD and then analyzed by IM-CRDS. CONCLUSIONS: There are many types of matrix-bound water samples for which IM-CRDS measurements include significant errors from spectral interference. As a result, spectral analysis and validation should be incorporated into IM-CRDS post-processing procedures. In the future, IM-CRDS performance could be improved through: (i) identification of the compounds that cause spectral interference, and either (ii) modification of the combustion step to completely oxidize these compounds to CO2 , and/or (iii) incorporation of corrections for these compounds into the spectral fitting models used by the CRDS analyzers. Copyright © 2016 John Wiley & Sons, Ltd.

Comprehensive overexpression analysis of cyclic-di-GMP signalling proteins in the phytopathogen Pectobacterium atrosepticum reveals diverse effects on motility and virulence phenotypes.

Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a ubiquitous bacterial signalling molecule produced by diguanylate cyclases of the GGDEF-domain family. Elevated c-di-GMP levels or increased GGDEF protein expression is frequently associated with the onset of sessility and biofilm formation in numerous bacterial species. Conversely, phosphodiesterase-dependent diminution of c-di-GMP levels by EAL- and HD-GYP-domain proteins is often accompanied by increased motility and virulence. In this study, we individually overexpressed 23 predicted GGDEF, EAL or HD-GYP-domain proteins encoded by the phytopathogen Pectobacterium atrosepticum strain SCRI1043. MS-based detection of c-di-GMP and 5'-phosphoguanylyl-(3'-5')-guanosine in these strains revealed that overexpression of most genes promoted modest 1-10-fold changes in cellular levels of c-di-GMP, with the exception of the GGDEF-domain proteins ECA0659 and ECA3374, which induced 1290- and 7660-fold increases, respectively. Overexpression of most EAL domain proteins increased motility, while overexpression of most GGDEF domain proteins reduced motility and increased poly-ß-1,6-N-acetyl-glucosamine-dependent flocculation. In contrast to domain-based predictions, overexpression of the EAL protein ECA3549 or the HD-GYP protein ECA3548 increased c-di-GMP concentrations and reduced motility. Most overexpression constructs altered the levels of secreted cellulases, pectinases and proteases, confirming c-di-GMP regulation of virulence in Pe. atrosepticum. However, there was no apparent correlation between virulence-factor induction and the domain class expressed or cellular c-di-GMP levels, suggesting that regulation was in response to specific effectors within the network, rather than total c-di-GMP concentration. Finally, we demonstrated that the cellular localization patterns vary considerably for GGDEF/EAL/HD-GYP proteins, indicating it is a likely factor restricting specific interactions within the c-di-GMP network.

Green leaf volatiles and oxygenated metabolite emission bursts from mesquite branches following light-dark transitions.

Green leaf volatiles (GLVs) are a diverse group of fatty acid-derived compounds emitted by all plants and are involved in a wide variety of developmental and stress-related biological functions. Recently, GLV emission bursts from leaves were reported following light-dark transitions and hypothesized to be related to the stress response while acetaldehyde bursts were hypothesized to be due to the 'pyruvate overflow' mechanism. In this study, branch emissions of GLVs and a group of oxygenated metabolites (acetaldehyde, ethanol, acetic acid, and acetone) derived from the pyruvate dehydrogenase (PDH) bypass pathway were quantified from mesquite plants following light-dark transitions using a coupled GC-MS, PTR-MS, and photosynthesis system. Within the first minute after darkening following a light period, large emission bursts of both C(5) and C(6) GLVs dominated by (Z)-3-hexen-1-yl acetate together with the PDH bypass metabolites are reported for the first time. We found that branches exposed to CO(2)-free air lacked significant GLV and PDH bypass bursts while O(2)-free atmospheres eliminated the GLV burst but stimulated the PDH bypass burst. A positive relationship was observed between photosynthetic activity prior to darkening and the magnitude of the GLV and PDH bursts. Photosynthesis under (13)CO(2) resulted in bursts with extensive labeling of acetaldehyde, ethanol, and the acetate but not the C(6)-alcohol moiety of (Z)-3-hexen-1-yl acetate. Our observations are consistent with (1) the "pyruvate overflow" mechanism with a fast turnover time (<1 h) as part of the PDH bypass pathway, which may contribute to the acetyl-CoA used for the acetate moiety of (Z)-3-hexen-1-yl acetate, and (2) a pool of fatty acids with a slow turnover time (>3 h) responsible for the C(6) alcohol moiety of (Z)-3-hexen-1-yl acetate via the 13-lipoxygenase pathway. We conclude that our non-invasive method may provide a new valuable in vivo tool for studies of acetyl-CoA and fatty acid metabolism in plants at a variety of spatial scales.

Mercury distribution across 14 U.S. Forests. Part I: spatial patterns of concentrations in biomass, litter, and soils.

Results from a systematic investigation of mercury (Hg) concentrations across 14 forest sites in the United States show highest concentrations in litter layers, strongly enriched in Hg compared to aboveground tissues and indicative of substantial postdepositional sorption of Hg. Soil Hg concentrations were lower than in litter, with highest concentrations in surface soils. Aboveground tissues showed no detectable spatial patterns, likely due to 17 different tree species present across sites. Litter and soil Hg concentrations positively correlated with carbon (C), latitude, precipitation, and clay (in soil), which together explained up to 94% of concentration variability. We observed strong latitudinal increases in Hg in soils and litter, in contrast to inverse latitudinal gradients of atmospheric deposition measures. Soil and litter Hg concentrations were closely linked to C contents, consistent with well-known associations between organic matter and Hg, and we propose that C also shapes distribution of Hg in forests at continental scales. The consistent link between C and Hg distribution may reflect a long-term legacy whereby old, C-rich soil and litter layers sequester atmospheric Hg depositions over long time periods. Based on a multiregression model, we present a distribution map of Hg concentrations in surface soils of the United States.

Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks.

The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO(2) uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO(2) uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle-climate models.

Short communication: Validation of in vitro fertility genes in a Holstein bull population.

Previously, we constructed an in vitro fertilization system for the identification of genes affecting fertility traits in dairy cattle. The efficiency of this system has been demonstrated by the identification of several genes affecting fertilization rate and early embryonic survival. However, to employ these genetic markers in marker- and gene-assisted selection programs, there is a need to validate in vitro results in phenotypic data sets collected in vivo. Thus, the objective of this study was to validate, in a population of Holstein bulls, the fertility trait genes we previously identified in an in vitro system. Estimated relative conception rate (ERCR) data from 222 Holstein bulls were obtained from 5 different artificial insemination companies in the United States. Bulls were genotyped for the genes FGF2, POU1F1, PRL, PRLR, GH, GHR, STAT5A, OPN, and UTMP, and the data were analyzed for association with ERCR using a mixed effects sire model. A stepwise model selection procedure revealed evidence of association with ERCR for FGF2 and STAT5A polymorphisms. The in vivo validation suggests that these genes can be used in gene-assisted selection programs for reproductive performance in dairy cattle. The genotypes found to be associated with low bull fertility in this study have been reported to be associated with high milk composition in previous studies. These findings provide molecular evidence for the antagonistic relationship between milk production and fertility observed for many years in different breeds of dairy cattle.

Obesity and weight gain in relation to depression: findings from the Stirling County Study.

OBJECTIVE: This study concerns the question of whether obese subjects in a community sample experience depression in a different way from the nonobese, especially whether they overeat to the point of gaining weight during periods of depression. DESIGN: A representative sample of adults was interviewed regarding depression and obesity. SUBJECTS: The sample consisted of 1396 subjects whose interviews were studied regarding relationships between obesity and depression and among whom 114 had experienced a major depressive episode at some point in their lives and provided information about the symptoms experienced during the worst or only episode of major depression. MEASUREMENTS: The Diagnostic Interview Schedule (DIS) was used to identify major depressive episodes. Information was also derived from the section on Depression and Anxiety (DPAX) of the Stirling Study Schedule. Obesity was calculated as a body mass index >30. Logistic regressions were employed to assess relationships, controlling for age and gender, by means of odds ratios and 95% confidence intervals. RESULTS: In the sample as a whole, obesity was not related to depression although it was associated with the symptom of hopelessness. Among those who had ever experienced a major depressive episode, obese persons were 5 times more likely than the nonobese to overeat leading to weight gain during a period of depression (P<0.002). These obese subjects, compared to the nonobese, also experienced longer episodes of depression, a larger number of episodes, and were more preoccupied with death during such episodes. CONCLUSIONS: Depression among obese subjects in a community sample tends to be more severe than among the nonobese. Gaining weight while depressed is an important marker of that severity. Further research is needed to understand and possibly prevent the associations, sequences and outcomes among depression, obesity, weight gain and other adversities.

Effects of signal transducer and activator of transcription (STAT) genes STAT1 and STAT3 genotypic combinations on fertilization and embryonic survival rates in Holstein cattle.

Infertility is a major cause of dairy cow culling and economic loss. Signal transducer and activator of transcription (STAT) proteins are transcription factors that play an important role in fertility and early embryonic development, among many other functions. Previous studies have reported the association of several genes from the JAK/STAT signaling pathway with fertility traits in cattle. The STAT1 and STAT3 genes are members of this pathway and are known to interact with each other by forming a heterodimer complex that enters the nucleus and controls expression of specific genes. Thus, the objective of this study was to investigate the effects of the interactions between polymorphisms in these genes on fertilization and early embryonic survival rates using an in vitro fertilization system. A total of 7,519 oocytes, collected from 445 ovaries, were exposed to sperm and a total of 5,075 embryos were produced. Fertilization rate was calculated as the number of cleaved embryos at 48 h post-fertilization out of the total number of oocytes exposed to sperm. Early embryonic survival rate of embryos was calculated as the number of blastocysts on d 7 of development out of the total number of embryos cultured. Effects of ovary genotypes on fertilization and early embryonic survival rates were evaluated. Single-SNP analysis revealed a statistically significant association between SNP25402 in STAT3 and fertilization rate. Oocytes produced from ovaries with AA genotype showed a 0.701 fertilization rate versus 0.666 and 0.663 for oocytes produced from AC and CC ovaries, respectively. The interaction between STAT3 SNP (SNP19069/SNP25402) was highly significant for survival rate but not for fertilization rate. Also, the interaction between STAT1 SNP and SNP19069 was highly significant for survival rate. Genotype combinations found to promote fertilization and embryonic survival could be incorporated into breeding programs aimed at improving fertility performance in dairy cattle.

Single gene and gene interaction effects on fertilization and embryonic survival rates in cattle.

Decrease in fertility and conception rates is a major cause of economic loss and cow culling in dairy herds. Conception rate is the product of fertilization rate and embryonic survival rate. Identification of genetic factors that cause the death of embryos is the first step in eliminating this problem from the population and thereby increasing reproductive efficiency. A candidate pathway approach was used to identify candidate genes affecting fertilization and embryo survival rates using an in vitro fertilization experimental system. A total of 7,413 in vitro fertilizations were performed using oocytes from 504 ovaries and semen samples from 10 different bulls. Fertilization rate was calculated as the number of cleaved embryos 48 h postfertilization out of the total number of oocytes exposed to sperm. Survival rate of embryos was calculated as the number of blastocysts on d 7 of development out of the number of total embryos cultured. All ovaries were genotyped for 8 genes in the POU1F1 signaling pathway. Single-gene analysis revealed significant associations of GHR, PRLR, STAT5A, and UTMP with survival rate and of POU1F1, GHR, STAT5A, and OPN with fertilization rate. To further characterize the contribution of the entire integrated POU1F1 pathway to fertilization and early embryonic survival, a model selection procedure was applied. Comparisons among the different models showed that interactions between adjacent genes in the pathway revealed a significant contribution to the variation in fertility traits compared with other models that analyzed only bull information or only genes without interactions. Moreover, some genes that were not significant in the single-gene analysis showed significant effects in the interaction analysis. Thus, we propose that single genes as well as an entire pathway can be used in selection programs to improve reproduction performance in dairy cattle.

Short communication: Effects of the progesterone receptor variants on fertility traits in cattle.

The progesterone receptor (PGR) gene is a key factor in the initiation and maintenance of pregnancy and in embryo development. Currently, it is unknown what variants of the PGR gene are related to fertility traits in cattle. Identification of such variants would allow the implementation of marker-assisted selection in breeding schemes. The objective of this study was to investigate the association of single nucleotide polymorphisms (SNP) of PGR with fertility traits in Holstein dairy cattle. An in vitro fertilization system was used to maximize the efficiency of the identification of genetic factors affecting fertility. This in vitro fertilization system would allow the assessment of fertilization and embryonic survival rates independently of influences from the uterine environment. A total of 5,566 fertilization attempts were performed, and a total of 3,679 embryos were produced using oocytes from 324 Holstein cows and semen from 10 Holstein bulls. Sequencing of pooled DNA samples from ovaries revealed an SNP (G/C) in intron 3 of PGR. A generalized linear model was used to analyze the association of this SNP with fertilization and embryonic survival rates for each ovary. Oocytes obtained from CC ovaries showed a 61% fertilization rate, compared with 68 and 69% for GC and GG ovaries, respectively. The survival rate of embryos produced from GG ovaries was 5 and 6% higher than that of GC and CC ovaries . These results indicate that the PGR SNP could be used in marker-assisted selection breeding programs in Holstein dairy cattle.

Mutations in the STAT5A gene are associated with embryonic survival and milk composition in cattle.

The objective of this study was to investigate the association of the signal transducer and activator of transcription 5A (STAT5A) gene with fertilization rate, embryonic survival, and milk production and composition in cattle. The STAT proteins are transcription factors that are specifically activated to regulate gene transcription when cells encounter cytokines and growth factors. The STAT5A gene is a member of the interferon-tau (IFN-tau) and placental lactogen (PL) signaling pathway, which is involved in both milk production and initiation of pregnancy. Using the DNA-pooling sequencing approach, a total of 12 single nucleotide polymorphisms (SNP) were identified, 1 exonic and 11 intronic. For the study of association of these SNP with embryonic survival, 1,551 embryos were produced in vitro from 160 cows and 3 sires. Significant associations with embryonic survival were found for 7, 5, and 2 SNP for embryos produced from sires 1, 2, and 3 respectively. The association of fertilization rate with STAT5A polymorphisms was evaluated in more than 2,300 oocytes. Significant associations were found for 6, 2, and 2 SNP for sires 1, 2, and 3 respectively. For sire 1, 5 SNP showed significant associations with both embryonic survival and fertilization rate compared with 1 SNP for sires 2 and 3. To determine if embryonic losses had occurred before the blastocyst stage, 145 of the surviving embryos were harvested at d 7 of development and genotyped for the single exonic SNP12195. A significant segregation distortion was observed between oocytes produced from 2 sires carrying the same genotype. Thus, it is most likely that STAT5A is associated with 2 mechanisms of embryo death. One is a prefertilization mechanism involving sperm factors that cause low fertilization rate. The second is a postfertilization mechanism that causes incompatibility between the male pronucleus and the oocyte, which in turn leads to death of the embryo before the blastocyst stage. Association testing of SNP12195 (exon 8) and SNP14217 (intron 9) with milk composition revealed that allele G of SNP12195 was associated with a decrease in both protein and fat percentages. However, SNP14217 in intron 9 showed no significant association with milk production or health traits. The G allele of SNP12195 was also associated with low embryonic survival, making this SNP an attractive candidate for progeny testing programs in dairy cattle.

Atmospheric deposition, CO2, and change in the land carbon sink.

Concentrations of atmospheric carbon dioxide (CO2) have continued to increase whereas atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades. Using time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models, we found that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011. Statistical models indicated that increasing atmospheric CO2 was the most important factor driving the increasing strength of carbon sinks in these forests. We also found that the reduction of sulphur deposition in Europe and the USA lead to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. Our findings support the hypothesis of a general CO2-fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions. Our results show the need to include the effects of changing atmospheric composition, beyond CO2, to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling.

Effect of transfer of one or two in vitro-produced embryos and post-transfer administration of gonadotropin releasing hormone on pregnancy rates of heat-stressed dairy cattle.

Pregnancy rates following transfer of an in vitro-produced (IVP) embryo are often lower than those obtained following transfer of an embryo produced by superovulation. The purpose of the current pair of experiments was to examine two strategies for increasing pregnancy rates in heat stressed, dairy recipients receiving an IVP embryo. One method was to transfer two embryos into the uterine horn ipsilateral to the CL, whereas the other method involved injection of GnRH at Day 11 after the anticipated day of ovulation. In Experiment 1, 32 virgin crossbred heifers and 26 lactating crossbred cows were prepared for timed embryo transfer by being subjected to a timed ovulation protocol. Those having a palpable CL were randomly selected to receive one (n = 31 recipients) or two (n = 27 recipients) embryos on Day 7 after anticipated ovulation. At Day 64 of gestation, the pregnancy rate tended to be higher (P = 0.07) for cows than for heifers. Heifers that received one embryo tended to have a higher pregnancy rate than those that received two embryos (41% versus 20%, respectively) while there was no difference in pregnancy rate for cows that received one or two embryos (57% versus 50%, respectively). Pregnancy loss between Day 64 and 127 only occurred for cows that received two embryos (pregnancy rate at Day 127=17%). Between Day 127 and term, one animal (a cow with a single embryo) lost its pregnancy. There was no difference in pregnancy rates at Day 127 or calving rates between cows and heifers, but females that received two embryos had lower Day-127 pregnancy rates and calving rates than females that received one embryo (P < 0.03). Of the females receiving two embryos that calved, 2 of 5 gave birth to twins. For Experiment 2, 87 multiparous, late lactation, nonpregnant Holstein cows were synchronized for timed embryo transfer as in Experiment 1. Cows received a single embryo in the uterine horn ipsilateral to the ovary containing the CL and received either 100 microg GnRH or vehicle at Day 11 after anticipated ovulation (i.e. 4 days after embryo transfer). There was no difference in pregnancy rate for cows that received the GnRH or vehicle treatment (18% versus 17%, respectively). In conclusion, neither unilateral transfer of two embryos nor administration of GnRH at Day 11 after anticipated ovulation improved pregnancy rates of dairy cattle exposed to heat stress.

Cancer mortality and morbidity among rubber workers.

Mortality and morbidity from cancer among a cohort of 13,570 white male rubber workers were examined. Each man worked for at least 5 years at the Akron, Ohio, plant of the B. F. Goodrich Company. The potential period of follow-up was from January 1, 1940 to June 30, 1976. Departmental work histories were based primarily on records maintained by Local no. 5, United Rubber Workers. The occurrence of cancer was measured by death certificates and by a survey of Akron-area hospital tumor registries from 1964 to 1974. Two types of analyses were made: 1) an external comparison of mortality rates of rubber workers versus rates of U.S. white males, and 2) an internal comparison of cancer morbidity rates among persons who were employed in various work areas of the plant. Excess cases of specific cancers (observed/expected numbers) among workers in specific work areas included: stomach and intestine: rubber making (30/14.4); lung: tire curing (31/14.1), fuel cells and/or deicers (46/29.1); bladder: chemical plant (6/2.4), and tire building (16/10.7); skin cancer: tire assembly (12/1.9); brain cancer: tire assembly (8/2.0); lymphatic cancer: tire building (8/3.2); and leukemia: calendering (8/2.2), tire curing (8/2.6), tire building (12/7.5), elevators (4/1.4), tubes (4/1.6), and rubber fabrics (4/1.1). Agents that may be responsible for these excesses were considered.

Cancer mortality in women after repeated fluoroscopic examinations of the chest.

Among 1,047 women fluoroscopically examined in average of 102 times during pneumothorax therapy for tuberculosis and followed up to 45 years (average = 27 yr), no increase in the total number of cancer deaths occurred when these women were compared to 717 women who received other treatments [relative risk (RR) = 0.8]. However, elevated risks of mortality from stomach cancer (RR = 2.3), rectal cancer (RR = 3.8), breast cancer (RR = 1.2), lung cancer (RR = 1.8), and leukemia (RR = 1.2) were observed, but none was statistically significant and all were based on very small numbers of deaths. These increases were balanced by decreases of genital cancer (RR = 0.2), pancreatic cancer (RR = 0.9), lymphoma (RR = 0.6), and all other cancers (RR = 0.1). Average cumulative absorbed doses were 110 rads for the lungs, 33 rads for the trunk, 13 rads for the active bone marrow, and 7 rads for the stomach. The following upper levels of excess risk could be excluded with 95% confidence: 3.5 deaths/10(6) woman-year (WY)-rad for lung cancer, 4.8 deaths/10(6) WY-rad for lymphoma, and 12 deaths/10(6) WY-rad for leukemia. These findings indicated that the carcinogenic effect of multiple low-dose X-ray exposures was not greater than that currently assumed.

Cancer mortality after multiple fluoroscopic examinations of the chest.

Total cancer deaths were not increased among 2,074 women and 1,277 men who were fluoroscopically examined an average of 73 and 91 times, respectively, during lung-collapse therapy for tuberculosis (TB). Patients who did not receive this form of therapy (2,141 women and 1,418 men) and general population rates were used for comparison. All subjects were discharged alive from eight TB sanatoria in Massachusetts between 1930 and 1954; the average follow-up was 23 years. Deaths due to breast cancer were not increased among exposed females [standardized mortality ratio (SMR) = 1.0, n = 24], and SMRs greater than 2.1 could be excluded with 95% confidence. In contrast to other series, our inability to detect a breast cancer excess was likely due to lower breast doses (66 rad) and higher average ages at exposure (28 yr) and thus lower sensitivity. A deficit of lung cancer among exposed males and females was observed (SMR = 0.8, n = 26), even though increased risks have been observed among other populations exposed to similar dose levels. The estimated average lung dose was 91 rad, and SMRs greater than 1.2 for lung cancer could be excluded with 95% confidence. Overall, this study indicates that the radiation hazard of multiple low-dose exposures experienced over many years is not greater than currently accepted estimates for breast and lung cancer. For lung cancer the radiogenic risk may be less than predicted from high-dose, single-exposure studies.

Biochemistry and physiology of foliar isoprene production.

Leaves of some plants emit isoprene, a volatile hydrocarbon. This is formed by a novel chloroplastic isoprenoid biosynthetic pathway, the 1-deoxy-D-xylulose-5-phosphate pathway. The thermoprotection hypothesis suggests that isoprene protects thylakoids from damage at high temperatures. In this article, we discuss the most recent discoveries about the metabolic pathway underlying isoprene biosynthesis, explore the experimental evidence surrounding thermoprotection and advance some alternative hypotheses about the adaptive role that isoprene biosynthesis might play.

Cancer mortality in women with thyroid disease.

A retrospective follow-up study of 7338 women with either nontoxic nodular goiter, thyroid adenoma, hyperthyroidism, hypothyroidism, Hashimoto's thyroiditis, or no thyroid disease was conducted. All women patients at the Massachusetts General Hospital Thyroid Clinic who were seen between 1925 and 1974 and who were treated for a minimum of 1 year were traced. A total of 2231 women (30.4%) were dead and 2012 women (27.4%) were alive as of December 31, 1978. Partial follow-up information was available for the remaining 3095 women (42.2%). The average length of follow-up was 15.2 years. When losses to follow-up were withdrawn at the time of their loss, the standardized mortality ratios (SMR) for all causes of death were 1.2 [95% confidence interval (CI), 1.1-1.3] for women with nontoxic nodular goiter, 1.2 (95% CI 1.0-1.3) for those with thyroid adenoma, 1.4 (95% CI 1.3-1.5) for women with hyperthyroidism, 1.5 (95% CI 1.3-1.7) for hypothyroid women, 1.2 (95% CI 0.9-1.5) for those with Hashimoto's thyroiditis, and 1.5 (95% CI 1.4-1.6) for those without thyroid disease. For deaths from all cancers, the standardized mortality ratios were 1.5 (95% CI 1.2-1.8) for women with nontoxic nodular goiter, 1.5 (95% CI 1.1-1.9) for those with thyroid adenoma, 1.2 (95% CI 1.0-1.4) for women with hyperthyroidism, 1.0 (95% CI 0.7-1.4) for the hypothyroid women, 1.2 (95% CI 0.7-2.1) for those with Hashimoto's thyroiditis, and 1.3 (95% CI 1.0-1.5) for those women without thyroid disease. When specific cancer sites were studied, excess numbers of deaths were observed from breast cancer in women with nontoxic nodular goiter (SMR = 1.6, 95% CI 1.0-2.6) and from lymphatic and hematopoietic cancer in women with nontoxic nodular goiter (SMR = 2.4, 95% CI 1.2-4.3) and thyroid adenoma (SMR = 2.7, 95% CI 1.1-5.2). An increase in thyroid cancer risk was observed in women with thyroid adenoma (SMR = 11.7, 95% CI 1.3-42.1) but was based on only two deaths. In hyperthyroid women, statistically significant increases in the number of deaths were observed from pancreatic cancer (SMR = 2.6, 95% CI 1.4-4.3) and respiratory cancer (SMR = 2.2, 95% CI 1.3-3.5), but not breast cancer (SMR = 1.3, 95% CI 0.8-1.8). When the data were stratified by the time between the onset of thyroid symptoms and death, a nonsignificant excess number of cancer deaths was observed in hyperthyroid women who died 20 or more years after their symptoms began.(ABSTRACT TRUNCATED AT 400 WORDS)

Cancer mortality in a radiation-exposed cohort of Massachusetts tuberculosis patients.

The mortality experience of 13,385 tuberculosis patients treated between 1925 and 1954 in Massachusetts was determined through August 1986. Among 6,285 patients examined by X-ray fluoroscopy an average of 77 times during lung collapse therapy and followed for up to 50 yr (average = 25 yr), no increase in the total number of cancer deaths occurred [standardized mortality ratio (SMR) = 1.05, n = 424]. In contrast, the 7,100 patients treated by other means were at significant risk of dying from cancer (SMR = 1.3), especially of sites linked to cigarette smoking and alcohol use. Among the irradiated patients, estimates of mean radiation doses to the breast, lung, esophagus, and active bone marrow were 0.75, 0.84, 0.80, and 0.09 Gy, respectively. Cancers of the breast (SMR = 1.4, n = 62) and esophagus (SMR = 2.1, n = 14) were significantly increased. The risk of esophageal cancer, however, decreased with time since exposure. Lung cancer (SMR = 0.8, n = 69) and leukemia (SMR = 1.2, n = 17) were not elevated. Despite a wide range of doses to the lung, reaching over 8 Gy, there was no evidence of a dose response. Lung cancer risk also did not vary by time since exposure or age at exposure. Adjustment for smoking and the amount of lung tissue at risk did not appreciably modify these findings. These data suggest that frequent exposures to low doses of radiation over a period of several years increase the occurrence of cancer of the breast. When compared with studies of atomic bomb survivors, however, the fractionated exposures experienced by this cohort appear less effective in causing lung cancer than single exposures of the same total dose.

Breast cancer after multiple chest fluoroscopies: second follow-up of Massachusetts women with tuberculosis.

A second follow-up was conducted of 1742 women with tuberculosis who were treated in one of two sanatoria in Massachusetts between 1930 and 1956. One hospital treated only children under the age of 17. Patient follow-up was extended from 1975 through 1980, and an additional 18 breast cancers were identified from hospital records, death certificates, and responses to a mailed questionnaire. Vital status was established for 97% of the subjects. Among 1044 women who were examined an average of 101 times with X-ray fluoroscopies during lung collapse therapy, 55 breast cancers were observed in contrast to 35.8 expected, based on incidence rates from the general population. No excess was found for 698 women treated by other means (19 observed versus 22.8 expected). Excess breast cancer risk did not appear until 15 years after initial exposure and was present at the end of 50 years of observation. Risk appeared to decrease with increasing age at exposure. Estimates of radiation dose to the breast for individuals (mean = 96 rad) were based on the most current information for the numbers of fluoroscopies, reconstruction of exposure conditions, and absorbed dose calculations. The relation between dose and breast cancer risk was consistent with linearity up to 400 rads (4 Gy). For 10-year survivors, the absolute excess risk was 5.5/1 million woman-year-rad, the excess relative risk per rad was 0.73%, and the relative risk at 100 rad was 1.7. These data indicate that a woman's lifetime risk of breast cancer is influenced by events occurring in early reproductive life, that low-dose fractionated exposures are as effective as single exposures of the same total dose in inducing breast cancer, and that risk of radiogenic breast cancer persists for many years, and perhaps for life.