Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica.

The meltwater streams of the McMurdo Dry Valleys are hot spots of biological diversity in the climate-sensitive polar desert landscape. Microbial mats, largely comprised of cyanobacteria, dominate the streams which flow for a brief window of time (~10 weeks) over the austral summer. These communities, critical to nutrient and carbon cycling, display previously uncharacterized patterns of rapid destabilization and recovery upon exposure to variable and physiologically detrimental conditions. Here, we characterize changes in biodiversity, transcriptional responses and activity of microbial mats in response to hydrological disturbance over spatiotemporal gradients. While diverse metabolic strategies persist between marginal mats and main channel mats, data collected from 4 time points during the austral summer revealed a homogenization of the mat communities during the mid-season peak meltwater flow, directly influencing the biogeochemical roles of this stream ecosystem. Gene expression pattern analyses identified strong functional sensitivities of nitrogen-fixing marginal mats to changes in hydrological activities. Stress response markers detailed the environmental challenges of each microhabitat and the molecular mechanisms underpinning survival in a polar desert ecosystem at the forefront of climate change. At mid and end points in the flow cycle, mobile genetic elements were upregulated across all mat types indicating high degrees of genome evolvability and transcriptional synchronies. Additionally, we identified novel antifreeze activity in the stream microbial mats indicating the presence of ice-binding proteins (IBPs). Cumulatively, these data provide a new view of active intra-stream diversity, biotic interactions and alterations in ecosystem function over a high-flow hydrological regime.

Nitrogen and Iron Availability Drive Metabolic Remodeling and Natural Selection of Diverse Phytoplankton during Experimental Upwelling.

Nearly half of carbon fixation and primary production originates from marine phytoplankton, and much of it occurs in episodic blooms in upwelling regimes. Here, we simulated blooms limited by nitrogen and iron by incubating Monterey Bay surface waters with subnutricline waters and inorganic nutrients and measured the whole-community transcriptomic response during mid- and late-bloom conditions. Cell counts revealed that centric and pennate diatoms (largely Pseudo-nitzschia and Chaetoceros spp.) were the major blooming taxa, but dinoflagellates, prasinophytes, and prymnesiophytes also increased. Viral mRNA significantly increased in late bloom and likely played a role in the bloom's demise. We observed conserved shifts in the genetic similarity of phytoplankton populations to cultivated strains, indicating adaptive population-level changes in community composition. Additionally, the density of single nucleotide variants (SNVs) declined in late-bloom samples for most taxa, indicating a loss of intraspecific diversity as a result of competition and a selective sweep of adaptive alleles. We noted differences between mid- and late-bloom metabolism and differential regulation of light-harvesting complexes (LHCs) under nutrient stress. While most LHCs are diminished under nutrient stress, we showed that diverse taxa upregulated specialized, energy-dissipating LHCs in low iron. We also suggest the relative expression of NRT2 compared to the expression of GSII as a marker of cellular nitrogen status and the relative expression of iron starvation-induced protein genes (ISIP1, ISIP2, and ISIP3) compared to the expression of the thiamine biosynthesis gene (thiC) as a marker of iron status in natural diatom communities. IMPORTANCE Iron and nitrogen are the nutrients that most commonly limit phytoplankton growth in the world's oceans. The utilization of these resources by phytoplankton sets the biomass available to marine systems and is of particular interest in high-nutrient, low-chlorophyll (HNLC) coastal fisheries. Previous research has described the biogeography of phytoplankton in HNLC regions and the transcriptional responses of representative taxa to nutrient limitation. However, the differential transcriptional responses of whole phytoplankton communities to iron and nitrogen limitation has not been previously described, nor has the selective pressure that these competitive bloom environments exert on major players. In addition to describing changes in the physiology of diverse phytoplankton, we suggest practical indicators of cellular nitrogen and iron status for future monitoring.

Diel transcriptional response of a California Current plankton microbiome to light, low iron, and enduring viral infection.

Phytoplankton and associated microbial communities provide organic carbon to oceanic food webs and drive ecosystem dynamics. However, capturing those dynamics is challenging. Here, an in situ, semi-Lagrangian, robotic sampler profiled pelagic microbes at 4 h intervals over ~2.6 days in North Pacific high-nutrient, low-chlorophyll waters. We report on the community structure and transcriptional dynamics of microbes in an operationally large size class (>5 µm) predominantly populated by dinoflagellates, ciliates, haptophytes, pelagophytes, diatoms, cyanobacteria (chiefly Synechococcus), prasinophytes (chiefly Ostreococcus), fungi, archaea, and proteobacteria. Apart from fungi and archaea, all groups exhibited 24-h periodicity in some transcripts, but larger portions of the transcriptome oscillated in phototrophs. Periodic photosynthesis-related transcripts exhibited a temporal cascade across the morning hours, conserved across diverse phototrophic lineages. Pronounced silica:nitrate drawdown, a high flavodoxin to ferredoxin transcript ratio, and elevated expression of other Fe-stress markers indicated Fe-limitation. Fe-stress markers peaked during a photoperiodically adaptive time window that could modulate phytoplankton response to seasonal Fe-limitation. Remarkably, we observed viruses that infect the majority of abundant taxa, often with total transcriptional activity synchronized with putative hosts. Taken together, these data reveal a microbial plankton community that is shaped by recycled production and tightly controlled by Fe-limitation and viral activity.

Hypoglycaemia-induced changes in regional brain volume and memory function.

BACKGROUND: Hypoglycaemic events can be a serious complication of insulin therapy in Type 1 diabetes mellitus. Severe hypoglycaemic exposure can lead to episodic memory impairments, including anterograde amnesia. However, relatively little is known regarding the long-term impact of severe hypoglycaemia on brain structure in Type 1 diabetes mellitus. The goals of the present study were to gain a greater understanding of the long-term effects of severe hypoglycaemia exposure on brain structure and the neural correlates of memory impairments in Type 1 diabetes mellitus. CASE REPORT: Regional grey and white matter volume and total white matter lesion volume were quantified in an individual with long-standing hypoglycaemia-induced anterograde amnesia and compared with age- and gender-matched healthy controls. Our patient has significant reductions in grey matter volume in the hippocampus, thalamus and pallidum, and significant reductions in white matter volume in the splenium, isthmus of the cingulate and cerebellum. He also has a significantly larger total white matter lesion volume than controls. CONCLUSION: This case study highlights the potential of hypoglycaemia for permanent deleterious effects on brain structure and memory function. Our results suggest that subcortical grey matter, periventricular white matter and posterior white matter may be most susceptible to injury from hypoglycaemia exposure, and that structural damage to the hippocampus and isthmus of the cingulate may play a central role in hypoglycaemia-induced memory impairments.

Patterns and predictors of treatment seeking after onset of a substance use disorder.

BACKGROUND: We studied survey respondents aged 18 through 54 years to determine consistent predictors of treatment seeking after onset of a DSM-III-R substance use disorder. METHODS: Survey populations included a regional sample in Ontario (n = 6261), a national sample in the United States (n = 5388), and local samples in Fresno, Calif (n = 2874) and Mexico City, Mexico (n = 1734). The analysis examined the effects of demographics, symptoms, and types of substances on treatment seeking. RESULTS: Between 50% (Ontario) and 85% (Fresno) of people with substance use disorders seek treatment but the time lag between onset and treatment seeking averages a decade or more. Consistent predictors of treatment seeking include: (1) late onset of disorder (odds ratio [OR], 3.8; 95% confidence interval [CI], 2.6-5.6 for late [> or =30 years] vs early [1-15 years] age at first symptom of disorder); (2) recency of cohort (OR, 3.4; 95% CI, 2.3-5.0 for most recent [aged 15-24 years at interview] vs earliest [aged > or =45 years] cohorts); (3) 4 specific dependence symptoms (using larger amounts than intended, unsuccessful attempts to cut down use, tolerance, and withdrawal symptoms), with ORs ranging between 1.6 (95% CI, 1.3-2.0) and 2.7 (95% CI, 2.1-3.6) for people with vs without these symptoms; and (4) use vs nonuse of cocaine (OR, 2.1; 95% CI, 1.6-2.7) and heroin (OR, 2.6; 95% CI, 1.1-6.0). CONCLUSIONS: Although most people with substance use disorders eventually seek treatment, treatment seeking often occurs a decade or more after the onset of symptoms of disorder. While treatment seeking has increased in recent years, it is not clear whether this is because of increased access, increased demand, increased societal pressures, or other factors.

Substance use during pregnancy in the state of California, USA.

Most analyses of prenatal substance use focus on individual level correlates and ignore community level variables and the effect of the dependency of respondents within communities. This analysis uses multilevel logistic regression models to more accurately assess the correlates of perinatal substance use in California. Statistical results indicate that a significant portion of substance use can be attributed to neighborhood heterogeneity, and that traditional models of substance use may inaccurately attribute this variation to individual level regression coefficients. Substantive results indicate that levels of neighborhood public assistance had an independent, significant effect on the prevalence of all substances tested for except alcohol. Black women had higher predicted prevalence risks for alcohol and cocaine while White women had higher predicted risks for tobacco, marijuana and amphetamines. Racial contrasts were non-significant for the overall illicit drug category and opiates, after controlling for neighborhood public assistance. Finally, individual level variables, with the exception of age, were not moderated by levels of neighborhood public assistance.

Help seeking for mental health problems among Mexican Americans.

This study uses data from a household survey (Mexican American Prevalence and Services Study; MAPSS) of 3,000 respondents in Fresno County, California, to 1) contrast use across multiple sectors of care among immigrant and U.S. born Mexican Americans with recent psychiatric disorders, 2) contrast multiple provider utilization patterns, and 3) identify specific factors associated with the use of mental health specialty and general medical sectors. Immigrants and U.S. born disproportionately used the general medical sector for treating mental health problems. The U.S. born were more likely to use family physicians and counselors than were immigrants, and neither relied heavily upon informal network providers to treat psychiatric disorders. A comparison of patterns showed that most people with a recent disorder used a combination of providers. The logistic regression analyses showed that knowing where to find a provider increased the likelihood of specialty mental health use by an odds ratio (O.R.) of 4.68. Private insurance increased use of mental health providers, O.R. = 3.76. Public insurance availability did not increase mental health provider use, suggesting that other factors were linked to use of mental health specialty care. Public insurance did increase medical sector care for psychiatric problems, O.R. = 2.57. Poor self-rated mental health status was primarily associated with use of physicians by U.S. born (O.R. = 5.39). Severe mental health impairment increased use of both general medical (O.R. = 5.54) and specialty mental health (O.R. = 5.1) providers. These results point out that eligibility for public insurance is a necessary but not sufficient status to increase mental health sector care among immigrants, and education and more effective referral from other sectors are needed to encourage use of these services.

Perceived discrimination and depression among Mexican-origin adults in California.

We contend that perceived discrimination has an independent effect on depression outcomes among adults of Mexican origin. Using a sample of 3,012 Mexican-origin respondents in Fresno, California in 1995/96 (ages 18-59) we investigate the direct and moderating connections between perceived discrimination, acculturative stress, and mental health (CES-D). We also investigate the social patterning of perceived discrimination. While more highly acculturated immigrant respondents were more likely to experience discrimination than their less acculturated counterparts, more highly acculturated U.S. born respondents were less likely to experience discrimination. Discrimination was directly related to depression, but this effect was moderated through nativity/country of residence, English-language acculturation, sex, and country of education variables. Moderate levels of legal status acculturative stress were especially depressive for native-born U.S. residents.

Effects of time in the United States and Indian ethnicity on DSM-III-R psychiatric disorders among Mexican Americans in California.

The study examines the effects of time in the United States and Indian ethnicity on prevalence of 12 DSM-III-R psychiatric disorders among Mexican Americans in California. In Fresno County, primarily an agricultural area, 3012 participants of Mexican origin (18 to 59 years) were selected under a cluster sampling design and interviewed using a version of the World Health Organization's Composite International Diagnostic Instrument (WHO-CIDI). Lifetime prevalence of any psychiatric disorder was 46.4% for Indians and 32.9% for non-Indians. Alcohol dependence was the most prevalent disorder (Indians = 17.4%, non-Indians = 10.7%). Indians had significantly higher risk of affective disorders (adjusted OR = 2.9) and drug abuse/dependence (adjusted OR = 2.6) compared with non-Indians. Time in the United States was associated with higher risk of lifetime affective disorders and drug abuse/dependence. This effect was more pronounced among Indians. Mexican immigrants are ethnically heterogenous and Indians appear to be more vulnerable to negative effects of exposure to U.S. society.

Lifetime prevalence of and risk factors for psychiatric disorders among Mexican migrant farmworkers in California.

OBJECTIVES: In this study, the prevalence of and risk factors for 12 psychiatric disorders were examined by sex and ethnicity (Indian vs non-Indian) among Mexican migrant farm-workers working in Fresno County, California. METHODS: Subjects aged 18 through 59 years were selected under a cluster sampling design (n = 1001). A modified version of the Composite International Diagnostic Interview was used for case ascertainment. The effects of sociodemographic and acculturation factors on lifetime psychiatric disorders were tested. RESULTS: Lifetime rates of any psychiatric disorder were as follows: men, 26.7% (SE = 1.9); women, 16.8% (SE = 1.7); Indians, 26.0% (SE = 4.5); non-Indians, 20.1% (SE = 1.3). Total lifetime rates were as follows: affective disorders, 5.7%; anxiety disorders, 12.5%; any substance abuse or dependence, 8.7%; antisocial personality, 0.2%. Lifetime prevalence of any psychiatric disorder was lower for migrants than for Mexican Americans and for the US population as a whole. High acculturation and primary US residence increased the likelihood of lifetime psychiatric disorders. CONCLUSIONS: The results underscore the risk posed by cultural adjustment problems, the potential for progressive deterioration of this population's mental health, and the need for culturally appropriate mental health services.

Effects of health-related physical education on academic achievement: project SPARK.

The effects of a 2-year health-related school physical education program on standardized academic achievement scores was assessed in 759 children who completed Metropolitan Achievement Tests before and after the program. Schools were randomly assigned to condition: (a) Specialists taught the Sports, Play, and Active Recreation for Kids curriculum; (b) classroom teachers were trained to implement the curriculum; and (c) controls continued their usual programs. The Trained Teacher condition was superior to Control on Language, Reading, and Basic Battery. The Specialist condition was superior to Control on Reading, but inferior on Language. Despite devoting twice as many minutes per week to physical education as Controls, the health-related physical education program did not interfere with academic achievement. Health-related physical education may have favorable effects on students' academic achievement.

Gaps in service utilization by Mexican Americans with mental health problems.

OBJECTIVE: The purpose of this study was to ascertain the degree of underutilization of services for mental health problems among urban and rural Mexican American adults. METHOD: A probability sample (N = 3,012) was used to represent the Mexican American population of Fresno County, California, and face-to-face interviews were conducted with the use of the Composite International Diagnostic Interview. Bivariate and multivariate analyses were used to analyze the data on diagnosis and service utilization. RESULTS: Among the respondents with DSM-III-R-defined disorders, only about one-fourth had used a single service or a combination of services in the past 12 months, and Mexican immigrants had a utilization rate which was only two-fifths of that of Mexican Americans born in the United States. Overall use of mental health care providers by persons with diagnosed mental disorders was 8.8%, use of providers in the general medical sector was 18.4%, use of other professionals was 12.7%, and use of informal providers was only 3.1%. According to logistic regression analyses, factors associated with utilization of mental health services included female sex, higher educational attainment, unemployment, and comorbidity. CONCLUSIONS: Immigrants are unlikely to use mental health services, even when they have a recent disorder, but may use general practitioners, which raises questions about the appropriateness, accessibility, and cost-effectiveness of mental health care for this population. Several competing hypotheses about the reasons for low utilization of services need to be examined in future research.

Comorbidity of substance use disorders with mood and anxiety disorders: results of the International Consortium in Psychiatric Epidemiology.

This article reports the results of a cross-national investigation of patterns of comorbidity between substance use and psychiatric disorders in six studies participating in the International Consortium in Psychiatric Epidemiology. In general, there was a strong association between mood and anxiety disorders as well as conduct and antisocial personality disorder with substance disorders at all sites. The results also suggest that there is a continuum in the magnitude of comorbidity as a function of the spectrum of substance use category (use, problems, dependence), as well as a direct relationship between the number of comorbid disorders and increasing levels of severity of substance use disorders (which was particularly pronounced for drugs). Finally, whereas there was no specific temporal pattern of onset for mood disorders in relation to substance disorders, the onset of anxiety disorders was more likely to precede that of substance disorders in all countries. These results illustrate the contribution of cross-national data to understanding the patterns and risk factors for psychopathology and substance use disorders.

Lifetime prevalence of DSM-III-R psychiatric disorders among urban and rural Mexican Americans in California.

BACKGROUND: The Mexican American Prevalence and Services Survey presents lifetime prevalence rates for 12 DSM-III-R psychiatric disorders in a sample of 3012 adults of Mexican origin by place of residence and nativity, and compares these results with those of population surveys conducted in the United States and Mexico. METHODS: The stratified random sample included non-institutionalized persons aged 18 to 59 years of Mexican origin, who were residents of Fresno County, California. Psychiatric disorders were assessed using a modified version of the World Health Organization Composite International Diagnostic Interview in face-to-face interviews. RESULTS: Mexican immigrants had lifetime rates similar to those of Mexican citizens, while rates for Mexican Americans were similar to those of the national population of the United States. This difference is attributable to a prevalence rate for any disorder among immigrants of 24.9%, compared with 48.1% among US-born respondents. A higher prevalence for any disorder was reported in urban (35.7%) compared with town (32.1%) or rural (29.8%) areas. Multivariate analyses showed an adjusted effect of country of birth, but not of urban residence. CONCLUSIONS: Despite very low education and income levels, Mexican Americans had lower rates of lifetime psychiatric disorders compared with rates reported for the US population by the National Comorbidity Survey. Psychiatric morbidity among Mexican Americans is primarily influenced by cultural variance rather than socioeconomic status or urban vs rural residence.

Children's television viewing, body fat, and physical fitness.

PURPOSE: The study examines the relationship between children's television (TV) viewing and physical fitness. DESIGN: Cross-sectional data from questionnaires and objective measures were analyzed. SETTING: Data were collected during the fall of 1990 from public elementary school students in a suburban California city. SUBJECTS: Approximately 98% of eligible students participated. Of these, 10% were dropped due to missing data, yielding a final sample of 284 girls and 304 boys. MEASURES: Children reported their amount of TV viewing on a typical summer day; parents reported their child's TV viewing on a typical weekday during the school year. Cardiovascular fitness was the 1-mile run/walk. Body fat was both the child's body mass index (BMI) and skinfolds. Additional measures included muscular strength/endurance and flexibility. RESULTS: Mile run/walk times were associated with both parental (eta 2 = .051 and .031 for boys and girls, respectively) and child reports (eta 2 = .020 and .028) of the child's amount of TV viewing. Parental reports, but not child reports, of the child's TV viewing were related to BMI (eta 2 = .041 and .058) and skinfolds (eta 2 = .050 and .029). Neither measure of children's TV viewing was related to muscular strength/endurance or flexibility. CONCLUSIONS: Children's TV viewing seems to be weakly and inconsistently related to various components of physical fitness. However, given the tracking of cardiovascular disease risk factors from childhood into adulthood and the high proportion of children who watch television, these relationships are worthy of further study.

Illicit drug use among Mexicans and Mexican Americans in California: the effects of gender and acculturation.

AIMS: To examine the effects of gender and acculturation on illicit drug use among the Mexican-origin population in California. DESIGN: The 3012 subjects between 18 and 59 years of age were selected under a stratified, multi-stage cluster sampling method. SETTING: Fresno County in California is primarily agricultural, with only one metropolitan area. Over 30% of the total population of 764,800, are Hispanics, of Mexican origin. MEASUREMENTS: A modified version of the World Health Organization's Composite International Diagnostic Instrument (WHO-CIDI) was used to ascertain drug use. Respondents were considered drug users if they had ever used marijuana, cocaine, hallucinogens, heroin or inhalants. Acculturation was measured with a Likert scale, assessing English vs. Spanish language preference. Other covariates of interest were nativity and place of residence. FINDINGS: Men had higher rates of use than women for every drug (men = 46.3%, women = 23.2%). Urban rates were higher than rural rates, for both women (urban = 32.8% vs. rural = 16.6%) and men (urban = 57.0% vs. rural = 36.8%). In logistic regression models, men were more likely than women to have ever used illicit drugs or inhalants (adjusted OR = 4.8), cocaine (adjusted OR = 5.3) or marijuana (OR = 4.3). However, the combined effect of United States nativity and acculturation, on drug use, was greater among women (adjusted OR = 29.3) than among men (adjusted OR = 7.4). The effect of acculturation was stronger among urban, than among town or rural residents. CONCLUSIONS: Acculturation and United States nativity are risk factors for illicit drug use among Mexican origin men and women. However, women have increased vulnerability compared with men. Findings reinforce the need for culturally based public health interventions.

The effects of a 2-year physical education program (SPARK) on physical activity and fitness in elementary school students. Sports, Play and Active Recreation for Kids.

OBJECTIVES: This study evaluated a health-related physical education program for fourth- and fifth-grade students designed to increase physical activity during physical education classes and outside of school. METHODS: Seven schools were assigned to three conditions in a quasi-experimental design. Health-related physical education was taught by physical education specialists or trained classroom teachers. Students from these classes were compared with those in control classes. Analyses were conducted on 955 students with complete data. RESULTS: Students spent more minutes per week being physically active in specialist-led (40 min) and teacher-led (33 min) physical education classes than in control classes (18 min; P < .001). After 2 years, girls in the specialist-led condition were superior to girls in the control condition on abdominal strength and endurance (P < .001) and cardiorespiratory endurance (P < .001). There were no effects on physical activity outside of school. CONCLUSIONS: A health-related physical education curriculum can provide students with substantially more physical activity during physical education classes. Improved physical education classes can potentially benefit 97% of elementary school students.

Effects of age on perinatal substance abuse among whites and African Americans.

This descriptive study assessed age effects on perinatal use of alcohol, marijuana, and cocaine among African-American and white women. Data were derived from the California Perinatal Exposure Study, relying on a statistical probability sample n = 29,494) of women who underwent anonymous urine toxicology screening in birthing hospitals. The central hypothesis was that there would be no difference in age effects on drug use among white and African-American women. Marital status and payment source were used as risk factors in order to create detailed age-risk profiles for both racial-ethnic groups. Logistic regression analyses were used and findings indicated that cocaine use peaked in early adulthood for whites and in mid-adulthood for African-Americans who had higher prevalence levels with the same or fewer risk factors as whites. Over one third of African-American women in their mid-thirties who were not married and who had publicly assisted births tested positive for cocaine. In contrast, high risk whites had higher marijuana prevalence levels than African-American women, and prevalence increased with age. Alcohol prevalence increased with age for African-American and white women who were publicly assisted, but decreased with age for all others. Findings for alcohol and marijuana generally followed the same risk-adjusted patterns for African American and white women but with different prevalence levels; however, cocaine use had a unique pattern with higher prevalence among African-American women in mid-adulthood regardless of risk level.

Perinatal drug use among immigrant and native-born Latinas.

Perinatal drug exposures pose a significant health hazard for women and imperil normal fetal and neonatal development. Little is known about patterns of drug exposure among pregnant immigrant and native-born Latinas in the United States. We present multivariate risk factor analyses for alcohol and illicit drug use from the California Perinatal Substance Exposure Study using a statistical probability sample (N = 11,002) of Latinas who were tested anonymously using urine toxicology screening techniques. Alcohol use during pregnancy was pervasive among both immigrant and United States-born Latinas (7%) with little variation on risk factors. Illicit drug use was found primarily in a high risk group of United States-born Latinas between 25 and 34 years of age who received no prenatal care (prevalence 50%, odds ratio of 185). Increased general awareness of perinatal alcohol risk by medical providers and public health practitioners serving this population is needed. The potential isolation of United States-born Latinas who are at risk using illicit drugs during pregnancy requires effective communication and outreach.