Unsupervised Online Paired Associates Learning Task from the Cambridge Neuropsychological Test Automated Battery (CANTAB®) in the Brain Health Registry

BACKGROUND

Unsupervised online cognitive assessments have demonstrated promise as an efficient and scalable approach for evaluating cognition in aging, and Alzheimer's disease and related dementias.

OBJECTIVES

The aim of this study was to evaluate the feasibility, usability, and construct validity of the Paired Associates Learning task from the Cambridge Neuropsychological Test Automated Battery® in adults enrolled in the Brain Health Registry.

DESIGN, SETTING, PARTICIPANTS, MEASUREMENTS

The Paired Associates Learning task was administered to Brain Health Registry participants in a remote, unsupervised, online setting. In this cross-sectional analysis, we 1) evaluated construct validity by analyzing associations between Paired Associates Learning performance and additional participant registry data, including demographics, self- and study partner-reported subjective cognitive change (Everyday Cognition scale), self-reported memory concern, and depressive symptom severity (Patient Health Questionnaire-9) using multivariable linear regression models; 2) determined the predictive value of Paired Associates Learning and other registry variables for identifying participants who self-report Mild Cognitive Impairment by employing multivariable binomial logistic regressions and calculating the area under the receiver operator curve; 3) investigated feasibility by looking at task completion rates and statistically comparing characteristics of task completers and non-completers; and 4) evaluated usability in terms of participant requests for support from BHR related to the assessment.

RESULTS

In terms of construct validity, in participants who took the Paired Associates Learning for the first time (N=14,528), worse performance was associated with being older, being male, lower educational attainment, higher levels of self- and study partner-reported decline, more self-reported memory concerns, greater depressive symptom severity, and self-report of Mild Cognitive Impairment. Paired Associates Learning performance and Brain Health Registry variables together identified those with self-reported Mild Cognitive Impairment with moderate accuracy (areas under the curve: 0.66-0.68). In terms of feasibility, in a sub-sample of 29,176 participants who had the opportunity to complete Paired Associates Learning for the first time in the registry, 14,417 started the task. 11,647 (80.9% of those who started) completed the task. Compared to those who did not complete the task at their first opportunity, those who completed were older, had more years of education, more likely to self-identify as White, less likely to self-identify as Latino, less likely to have a subjective memory concern, and more likely to report a family history of Alzheimer's disease. In terms of usability, out of 8,395 received requests for support from BHR staff via email, 4.4% (n=374) were related to PAL. Of those, 82% were related to technical difficulties.

CONCLUSIONS

Our findings support moderate feasibility, good usability, and construct validity of cross-sectional Paired Associates Learning in an unsupervised online registry, but also highlight the need to make the assessment more inclusive and accessible to individuals from ethnoculturally and socioeconomically diverse communities. A future, improved version could be a scalable, efficient method to assess cognition in many different settings, including clinical trials, observational studies, healthcare, and public health.

Evidence for N- and C-terminal processing of a plant defense-related enzyme: Primary structure of tobacco prepro-beta-1,3-glucanase

Tobacco glucan endo-1,3-beta-glucosidase (beta-1,3-glucanase; 1,3-beta-D-glucan glucanohydrolase; EC 3.2.1.39) exhibits complex hormonal and developmental regulation and is induced when plants are infected with pathogens. We determined the primary structure of this enzyme from the nucleotide sequence of five partial cDNA clones and the amino acid sequence of five peptides covering a total of 70 residues. beta-1,3-Glucanase is produced as a 359-residue preproenzyme with an N-terminal hydrophobic signal peptide of 21 residues and a C-terminal extension of 22 residues containing a putative N-glycosylation site. The results of pulse-chase experiments with tunicamycin provide evidence that the first step in processing is loss of the signal peptide and addition of an oligosaccharide side chain. The glycosylated intermediate is further processed with the loss of the oligosaccharide side chain and C-terminal extension to give the mature enzyme. Heterogeneity in the sequences of cDNA clones and of mature protein and in Southern blot analysis of restriction endonuclease fragments indicates that tobacco beta-1,3-glucanase is encoded by a small gene family. Two or three members of this family appear to have their evolutionary origin in each of the progenitors of tobacco, Nicotiana sylvestris and Nicotiana tomentosiformis.

RAD51 loss of function abolishes gene targeting and de-represses illegitimate integration in the moss Physcomitrella patens

Gene targeting (GT) is a major tool for basic and applied research during which the transforming DNA, which shares sequence homology with a chromosomal target, integrates at the corresponding locus by homologous recombination (HR). In eukaryotes, GT recruits enzymes from the HR-mediated double strand break repair pathway. Different mechanisms of HR have been described which depend on the Rad52 epistasis group of genes, but which specific mechanism is used by the cell for GT remains unclear. In Saccharomyces cerevisiae, the RAD52 protein is essential for GT, and the RAD51 protein plays a minor role. In filamentous fungi and animal cells, however, GT depends on RAD51 and is weakly affected by suppression of RAD52. Genetic evidence also indicates that the non-homologous end-joining pathway of DSB repair has a negative impact on GT efficiencies, but how the balance between these two pathways is controlled is poorly understood. Here, we have examined the role of RAD51 in the only plant that exhibits high GT frequencies, the model bryophyte Physcomitrella patens. Our results show that the two RAD51 proteins have partially redundant functions in the maintenance of genome integrity and resistance to ionizing radiation. Furthermore, we demonstrate that loss of function of the two RAD51 proteins completely abolishes GT and strongly increases illegitimate integration rates in this moss. These findings demonstrate for the first time in plant the critical role of RAD51 in controlling the balance between targeted and random integration events observed upon transgenesis, and confirm that P. patens is a particularly interesting tool for studying GT in higher eukaryotes.

Fear conditioning in frontotemporal lobar degeneration and Alzheimer's disease

Emotional blunting and abnormal processing of rewards and punishments represent early features of frontotemporal lobar degeneration (FTLD). Better understanding of the physiological underpinnings of these emotional changes can be facilitated by the use of classical psychology approaches. Fear conditioning (FC) is an extensively used paradigm for studying emotional processing that has rarely been applied to the study of dementia. We studied FC in controls (n = 25), Alzheimer's disease (n = 25) and FTLD (n = 25). A neutral stimulus (coloured square on a computer screen) was repeatedly paired with a 1 s burst of 100 db white noise. Change in skin conductance response to the neutral stimulus was used to measure conditioning. Physiological-anatomical correlations were examined using voxel-based morphometry (VBM). Both patient groups showed impaired acquisition of conditioned responses. However, the basis for this deficit appeared to differ between groups. In Alzheimer's disease, impaired FC occurred despite normal electrodermal responses to the aversive stimulus. In contrast, FTLD patients showed reduced skin conductance responses to the aversive stimulus, which contributed significantly to their FC deficit. VBM identified correlations with physiological reactivity in the amygdala, anterior cingulate cortex, orbitofrontal cortex and insula. These data indicate that Alzheimer's disease and FTLD both show abnormalities in emotional learning, but they suggest that in FTLD this is associated with a deficit in basic electrodermal response to aversive stimuli, consistent with the emotional blunting described with this disorder. Deficits in responses to aversive stimuli could contribute to both the behavioural and cognitive features of FTLD and Alzheimer's disease. Further study of FC in humans and animal models of dementia could provide a valuable window into these symptoms.

Family-specific approaches to the analysis of case-control family data

Case-control studies augmented by the values of responses and covariates from family members allow investigators to study the association between the response and genetics and environment by relating differences in the response directly to within-family differences in covariates. However, existing approaches for case-control family data parameterize covariate effects in terms of the marginal probability of response, the same effects that one estimates from standard case-control studies. This article focuses on the estimation of family-specific covariate effects and develops efficient methods to fit family-specific models such as binary mixed-effects models. We also extend the approach to cover any setting where one has a fully specified model for the vector of responses in a family. We illustrate our approach using data from a case-control family study of brain cancer and consider the use of weighted and conditional likelihood methods as alternatives.

A comparison of lorazepam, diazepam, and placebo for the treatment of out-of-hospital status epilepticus

BACKGROUND

It is uncertain whether the administration of benzodiazepines by paramedics is an effective and safe treatment for out-of-hospital status epilepticus.

METHODS

We conducted a randomized, double-blind trial to evaluate intravenous benzodiazepines administered by paramedics for the treatment of out-of-hospital status epilepticus. Adults with prolonged (lasting five minutes or more) or repetitive generalized convulsive seizures received intravenous diazepam (5 mg), lorazepam (2 mg), or placebo. An identical second injection was given if needed.

RESULTS

Of the 205 patients enrolled, 66 received lorazepam, 68 received diazepam, and 71 received placebo. Status epilepticus had been terminated on arrival at the emergency department in more patients treated with lorazepam (59.1 percent) or diazepam (42.6 percent) than patients given placebo (21.1 percent) (P=0.001). After adjustment for covariates, the odds ratio for termination of status epilepticus by the time of arrival in the lorazepam group as compared with the placebo group was 4.8 (95 percent confidence interval, 1.9 to 13.0). The odds ratio was 1.9 (95 percent confidence interval, 0.8 to 4.4) in the lorazepam group as compared with the diazepam group and 2.3 (95 percent confidence interval, 1.0 to 5.9) in the diazepam group as compared with the placebo group. The rates of respiratory or circulatory complications (indicated by bag valve-mask ventilation or an attempt at intubation, hypotension, or cardiac dysrhythmia) after the study treatment was administered were 10.6 percent for the lorazepam group, 10.3 percent for the diazepam group, and 22.5 percent for the placebo group (P=0.08).

CONCLUSIONS

Benzodiazepines are safe and effective when administered by paramedics for out-of-hospital status epilepticus in adults. Lorazepam is likely to be a better therapy than diazepam.

Assessing change with longitudinal and clustered binary data

Investigators often gather repeated measures on study subjects to directly measure how a subject's response changes with changes in explanatory variables. This paper focuses on several statistical issues related to assessing change with longitudinal and clustered binary data. Many popular approaches for analyzing repeated binary outcomes measure cross-sectional or between-subject, rather than within-subject, effects of covariates. The class of models known as cluster specific measures within-subject effects of covariates on responses but are subject to additional statistical complications. It is useful to decompose covariates into between- and within-cluster components. This paper describes several approaches that yield consistent estimates of the within-subject covariate effects of interest. Example data from three studies illustrate the results.

Regeneration of a lytic central vacuole and of neutral peripheral vacuoles can be visualized by green fluorescent proteins targeted to either type of vacuoles

Protein trafficking to two different types of vacuoles was investigated in tobacco (Nicotiana tabacum cv SR1) mesophyll protoplasts using two different vacuolar green fluorescent proteins (GFPs). One GFP is targeted to a pH-neutral vacuole by the C-terminal vacuolar sorting determinant of tobacco chitinase A, whereas the other GFP is targeted to an acidic lytic vacuole by the N-terminal propeptide of barley aleurain, which contains a sequence-specific vacuolar sorting determinant. The trafficking and final accumulation in the central vacuole (CV) or in smaller peripheral vacuoles differed for the two reporter proteins, depending on the cell type. Within 2 d, evacuolated (mini-) protoplasts regenerate a large CV. Expression of the two vacuolar GFPs in miniprotoplasts indicated that the newly formed CV was a lytic vacuole, whereas neutral vacuoles always remained peripheral. Only later, once the regeneration of the CV was completed, the content of peripheral storage vacuoles could be seen to appear in the CV of a third of the cells, apparently by heterotypic fusion.

The internal propeptide of the ricin precursor carries a sequence-specific determinant for vacuolar sorting

Ricin is a heterodimeric toxin that accumulates in the storage vacuoles of castor bean (Ricinus communis) endosperm. Proricin is synthesized as a single polypeptide precursor comprising the catalytic A chain and the Gal-binding B chain joined by a 12-amino acid linker propeptide. Upon arrival in the vacuole, the linker is removed. Here, we replicate these events in transfected tobacco (Nicotiana tabacum) leaf protoplasts. We show that the internal linker propeptide is responsible for vacuolar sorting and is sufficient to redirect the ricin heterodimer to the vacuole when fused to the A or the B chain. This internal peptide can also target two different secretory protein reporters to the vacuole. Moreover, mutation of the isoleucine residue within an NPIR-like motif of the propeptide affects vacuolar sorting in proricin and in the reconstituted A-B heterodimer. This is the first reported example of a sequence-specific vacuolar sorting signal located within an internal propeptide.

Demonstration in yeast of the function of BP-80, a putative plant vacuolar sorting receptor

BP-80, later renamed VSR(PS-1), is a putative receptor involved in sorting proteins such as proaleurain to the lytic vacuole, with its N-terminal domain recognizing the vacuolar sorting determinant. Although all VSR(PS-1) characteristics and in vitro binding properties described so far favored its receptor function, this function remained to be demonstrated. Here, we used green fluorescent protein (GFP) as a reporter in a yeast mutant strain defective for its own vacuolar receptor, Vps10p. By expressing VSR(PS-1) together with GFP fused to the vacuolar sorting determinant of petunia proaleurain, we were able to efficiently redirect the reporter to the yeast vacuole. VSR(PS-1) is ineffective on GFP either alone or when fused with another type of plant vacuolar sorting determinant from a chitinase. The plant VSR(PS-1) therefore interacts specifically with the proaleurain vacuolar sorting determinant in vivo, and this interaction leads to the transport of the reporter protein through the yeast secretory pathway to the vacuole. This finding demonstrates VSR(PS-1) receptor function but also emphasizes the differences in the spectrum of ligands between Vps10p and its plant equivalent.

Living arrangements affect dietary quality for U.S. adults aged 50 years and older: NHANES III 1988-1994

The number and proportion of older U.S. adults who live alone have increased dramatically in the past three decades, and there is concern that these individuals may have particularly poor dietary quality. We examined the association of four living arrangements (living with a spouse only, with a spouse plus someone else, with someone other than a spouse or living alone) with dietary quality (the number of low nutrients out of a possible 15, with low defined as <67% of the recommended dietary allowance) among 6525 U.S. adults aged 50-64 y and those >/=65 y in the third National Health and Nutrition Examination Survey (NHANES III 1988-1994). Among non-Hispanic Caucasian adults, those who lived with a spouse only had better dietary quality, with significant differences ranging from 0.8 to 1.5 fewer low nutrients compared with those with other living arrangements. Effects of living arrangements on dietary quality were also seen among non-Hispanic African-Americans, Mexican-Americans, and those of "other" races, but differences were significant only for African-American men aged >65 y living with a spouse plus others (1.6 additional low nutrients compared with those living with a spouse only). Energy intake was strongly associated with dietary quality, but did not account for the associations between living arrangements and dietary quality. Although middle-aged and older adults with living arrangements other than living with a spouse only (including those living alone) tended to have poorer dietary quality, the effects varied substantially across age, gender and ethnic categories.

Do triglycerides provide meaningful information about heart disease risk?

BACKGROUND

Prior research suggests that adding triglyceride determinations to measurements of total cholesterol and cholesterol subfractions may improve the prediction of coronary heart disease (CHD).

OBJECTIVE

To determine the additional value of measuring triglyceride levels, in addition to cholesterol levels and subfractions, for predicting CHD.

STUDY DESIGN

A set of secondary analyses of previously reported studies.

METHODS

We performed secondary analyses of data from the Multiple Risk Factor Intervention Trial, the Lipid Research Clinics Coronary Primary Prevention Trial, and the Lipid Research Clinics Prevalence and Mortality Follow-Up Study. Predictor variables included the levels of fasting triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and fasting blood glucose; age; blood pressure; cigarette smoking; body mass index; and postmenopausal estrogen use. Analytic methods included Cox proportional hazards models, calculation of stratified crude incidence rates, and measurement of the area under the receiver operating characteristic curve.

MAIN OUTCOME MEASURES

Outcome variables were fatal and nonfatal myocardial infarctions.

RESULTS

With few exceptions, no significant interactions between cholesterol subfractions and triglyceride levels were found and receiver operating characteristic curve analyses revealed that triglyceride measurements did not improve discrimination between those subjects who did and did not suffer CHD events. In men, categorical analyses employing both triglyceride and cholesterol levels were similar to those using cholesterol categories alone. In the one study of women, those subjects with both a high-risk cholesterol profile and high triglyceride levels were more likely to have a CHD event, though this finding was based on fewer subjects and CHD events.

CONCLUSION

These data suggest that, in men, measurement of serum triglyceride levels does not provide clinically meaningful information about CHD risk beyond that obtainable by measurement of serum cholesterol subfractions alone.

Persistent stress as a predictor of genital herpes recurrence

BACKGROUND

Results of several studies suggest that psychological stress and negative mood can trigger genital herpes recurrences, but results are inconsistent.

OBJECTIVE

To determine whether short-term or persistent psychological stress or specific negative moods are predictive of genital herpes recurrences in women.

METHODS

A prospective cohort study followed up participants for 6 months using weekly assessments of stress and mood, monthly assessments of life change events, and diary reports of genital herpes recurrences confirmed by medical examination when feasible. The community sample consisted of 58 women, aged 20 to 44 years, with a 1- to 10-year history of visible genital herpes recurrence and at least 1 recurrence in the previous 6 months.

RESULTS

Persistent stress predicted recurrence in the subsequent week (odds ratio, 1.08 per unit increase in stress; 95% confidence interval, 1.01-1.15; P=.03). After adjusting for recurrence in the previous week, the more weekly persistent stress reported, the greater the likelihood of recurrence the following week. Also, an increased recurrence rate occurred after the month during which participants experienced their highest levels of anxiety (P =.03). There were no significant associations between recurrence and short-term stress, life events, depressive mood, anger, or phase of menstrual cycle.

CONCLUSIONS

Persistent stressors and highest level of anxiety predicted genital herpes recurrence, whereas transient mood states, short-term stressors, and life change events did not. Women with herpes can be reassured that short-term stressful life experiences and dysphoric mood states do not put them at risk for increased outbreaks of recurrent genital herpes.

Effect of receptive oral sex and smoking on the incidence of hairy leukoplakia in HIV-positive gay men

We sought to determine whether hairy leukoplakia (HL), an Epstein-Barr virus-related oral lesion, is associated with receptive oral sex activity and cigarette smoking among HIV-positive gay men. Oral examinations were conducted every 6 months among San Francisco Men's Health Study participants over a 6-year period. We fitted time-to-lesion regression models to compare the incidence of HL among men who had mouth-to-penis contact with various numbers of partners, while controlling for cigarette smoking and CD4 count. The 6-year incidence of HL was 32% among 291 HIV-positive men. We found no significant increase in the hazard of developing HL for each additional insertive-oral-sex male partner in the past 6 months (relative hazard = 1.01; 95% confidence interval [CI], 0.99, 1.02), and a similar lack of association when number of sex partners was categorized. However, the hazard of developing HL doubled with any 300-unit decrease in CD4 count (95% CI, 1.4, 2.7), or if men smoked > or =20 cigarettes/day compared with nonsmokers (95% CI, 1.2, 3.9). This finding, which may suggest one effect that smoking produces on the oral mucosa's local immune response, merits further investigation.

Differential immune system changes with acute and persistent stress for optimists vs pessimists

This study investigated whether acute and persistent stressors and life change events were followed by changes in immune status, and whether dispositional optimism moderated these relationships. Thirty-nine healthy women ages 18-45 were followed prospectively for 3 months, with weekly assessment of acute and persistent stressors and monthly assessment of life events and immune parameters (NK cell cytotoxicity, and CD4 and CD8 T cell subsets). The study used an autoregressive linear model to examine how weekly appraised acute and persistent stress levels were associated with immune parameters in the subsequent week. Analyses revealed that the immune outcomes were differentially affected by acute and persistent stressors. Further, the association between acute stress and subsequent immune parameters was buffered by an optimistic perspective. However, when stress persisted at high levels, optimists showed more subsequent immune decrements than pessimists.

Dental care access and use among HIV-infected women

OBJECTIVES

This study sought to identify predictors of dental care use in HIV-infected women.

METHODS

In a cross-sectional survey of HIV-infected women enrolled in the northern California site of the Women's Interagency HIV Study, dental care use and unmet need were assessed in relation to selected variables.

RESULTS

Among 213 respondents, who were predominantly Black and younger than 45 years, 43% had not seen a dentist and 53% (among dentate women) reported no dental cleaning in more than a year (although 67% had dental insurance coverage, mainly state Medicaid). Nine percent were edentulous. Among nonusers of dental care, 78% reported that they wanted care but failed to get it. Barriers included fear of and discomfort with dentists, not getting around to making an appointment, and not knowing which dentist to visit. Multivariate analysis showed that lack of past-year dental care was associated mainly with unemployment, a perception of poor oral health, and edentulism.

CONCLUSIONS

HIV-positive women appear to be underusing dental care services. Fear and lack of information regarding available resources, in addition to unemployment and perception of poor oral health, may be important barriers.

Subcellular localization and in vivo identification of the putative movement protein of olive latent virus 2

The gene encoding the 36.5 kDa ('36K') nonstructural protein located on RNA3 of olive latent virus 2 (OLV-2) was cloned, expressed with the Escherichia coli pGEX-2T system and the purified protein used to raise a polyclonal antiserum. Immunoblot analysis of OLV-2-infected Nicotiana benthamiana plants showed that the 36K protein accumulated in the early stages of infection and was associated with a subcellular fraction enriched in cytoplasmic membranes. In infected cells there were tubular structures, some containing virus-like particles, scattered in the cytoplasm or protruding from or penetrating the cell wall at the plasmodesmata. Immunogold labelling localized the 36K protein in the plasmodesmata of OLV-2-infected cells and showed it to be associated with virus-containing tubules. Leaf trichome cells of N. tabacum plants, transformed with a 36K-green fluorescent protein (GFP) fusion construct, revealed localized fluorescence in the cell walls, possibly due to association of the fusion protein with plasmodesmata. When the same 36K-GFP fusion protein was expressed in N. tabacum protoplasts, long tubular fluorescent structures protruded from the protoplast surface, suggesting that the 36K protein is responsible for tubule induction. The conclusion is drawn that this protein is likely to be the OLV-2 movement protein, mediating cell-to-cell virus movement, and that movement is by a tubule-guided mechanism.

Sorting of proteins to vacuoles in plant cells

An individual plant cell may contain at least two functionally and structurally distinct types of vacuoles: protein storage vacuoles and lytic vacuoles. Presumably a cell that stores proteins in vacuoles must maintain these separate compartments to prevent exposure of the storage proteins to an acidified environment with active hydrolytic enzymes where they would be degraded. Thus, the organization of the secretory pathway in plant cells, which includes the vacuoles, has a fascinating complexity not anticipated from the extensive genetic and biochemical studies of the secretory pathway in yeast. Plant cells must generate the membranes to form two separate types of tonoplast, maintain them as separate organelles, and direct soluble proteins from the secretory flow specifically to one or the other via separate vesicular pathways. Individual soluble and membrane proteins must be recognized and sorted into one or the other pathway by distinct, specific mechanisms. Here we review the emerging picture of how separate plant vacuoles are organized structurally and how proteins are recognized and sorted to each type.

Specific accumulation of GFP in a non-acidic vacuolar compartment via a C-terminal propeptide-mediated sorting pathway

The green fluorescent protein (GFP) from Aequorea victoria can be detected in living plant cells after transient transformation of protoplasts. Expression of the GFP can be used to monitor protein trafficking in a mixed cell population and also to study the different function and importance of organelles in different cell types. We developed a vacuolar form of GFP that was obtained by replacing the C-terminal endoplasmic reticulum (ER)-retention motif of mGFP5-ER by the vacuolar targeting peptide of tobacco chitinase A. The vacuolar GFP was transported and accumulated in the vacuole as expected. However, we found two patterns of GFP accumulation after prolonged incubation (18-24 h) depending on the cell type. Most chloroplast-rich protoplasts had a fluorescent large central vacuole. In contrast, most chloroplast-poor protoplasts accumulated the GFP in one smaller vacuole but not in the large central vacuole, which was visible under a light microscope in the same cell. This differential accumulation reflected the existence of two different vacuolar compartments as described recently by immunolocalization of several vacuolar markers. We were able to characterize the vacuolar compartment to which GFP is specifically targeted as non-acidic, since it did not accumulate neutral red while acidic vacuoles did not accumulate GFP.

Between- and within-cluster covariate effects in the analysis of clustered data

Standard methods for the regression analysis of clustered data postulate models relating covariates to the response without regard to between- and within-cluster covariate effects. Implicit in these analyses is the assumption that these effects are identical. Example data show that this is frequently not the case and that analyses that ignore differential between- and within-cluster covariate effects can be misleading. Consideration of between- and within-cluster effects also helps to explain observed and theoretical differences between mixture model analyses and those based on conditional likelihood methods. In particular, we show that conditional likelihood methods estimate purely within-cluster covariate effects, whereas mixture model approaches estimate a weighted average of between- and within-cluster covariate effects.

Variation among rheumatologists in clinical outcomes and frequency of office visits for rheumatoid arthritis

OBJECTIVE

To estimate the variation among rheumatologists in clinical outcomes and frequency of office visits for patients with rheumatoid arthritis (RA), after accounting for patient demographic and clinical characteristics and treatments prescribed.

METHODS

Multiple regression analysis using random effects for rheumatologists and adjustments for patient characteristics and treatments received, based on data derived from a panel study of persons with RA.

RESULTS

During the years 1984-1993, rheumatologists accounted for a moderate amount of the total variation in clinical outcomes and nearly one-third of the total variation in frequency of office visits. For example, in 1993 rheumatologist associated variation in 4 clinical outcomes ranged from 16 to 25%, while the variation in office visit frequency attributable to rheumatologists stood at 46% of the total variation. However, rheumatologist associated variation in clinical outcomes was not statistically significant in any year, while variation in office visits was highly significant in all years (p < or = 0.0001). Although there was an increase in the percentage of variation attributable to rheumatologists for all outcomes examined across the years of this study, the time trend reached statistical significance only for frequency of office visits (2.4% per year; p = 0.0135) and functional status (1.6% per year; p = 0.0034).

CONCLUSION

The magnitude and strength of rheumatologist associated variation in frequency of office visits, without comparable strength in the variation in clinical outcomes, may suggest inefficiencies in the use of resources for the care of persons with RA. Further work is needed to directly examine the relationship between health outcomes and resource utilization.

Living arrangements, changes in living arrangements, and survival among community dwelling older adults

OBJECTIVES

This study examines whether living arrangements and changes in living arrangements are associated with survival among older community-dwelling adults, and whether differences in health status account for observed differences in survival.

METHODS

The sample consisted of 5085 persons aged 70 years or older who had participated in the Longitudinal Study of Aging in 1984 and 1986. Proportional hazards models were used to examine associations of survival time through 1990 with living arrangements in 1984 and with changes in living arrangements from 1984 to 1986.

RESULTS

Women who lived with someone other than a spouse at baseline or who changed from living with a spouse to living with someone other than a spouse were at greater risk of dying than women in other living arrangements, independent of health status or functioning. Among men, survival time was not generally associated with baseline living arrangements.

CONCLUSIONS

Older adults who live alone or who change from living with someone to living alone do not have an increased mortality risk. However, living with or changing to living with someone other than a spouse may be associated with increased mortality risk.

Expression of beta-1,3-glucanase and chitinase in healthy, stem-rust-affected and elicitor-treated near-isogenic wheat lines showing Sr5-or Sr24-specified race-specific rust resistance

Pathogenesis-related expression of the two antifungal hydrolases beta-1,3-glucanase (EC 3.2.1.39) and chitinase (EC 3.2.1.14) was studied in wheat (Triticum aestivum L.) as part of the defence response to stem rust (Puccinia graminis f.sp. tritici, Pgt), mediated by the semi-dominantly acting resistance genes Sr5 and Sr24. Complete resistance (infection type 0), mediated by the Sr5 gene in cultivar Pre-Sr5, closely correlates with the hypersensitive response of penetrated cells at early stage of the interaction, when the first haustorium is formed. In contrast, cultivar Pre-Sr24 shows intermediate resistance (infection type 2-3) which is not directly linked to cell death. In both cases, the plant response included a rapid increase in beta-1,3-glucanase activity between 24 and 48 h after inoculation. One main extracellular 30-kDa isform of beta-1,3-glucanase was present in both lines, as shown by polyacrylamide-gel electrophoresis. Two additional minor isoforms (32 and 23 kDa) were detected only in Pre-Sr24, and only at later time points. Increased enzme activity and the appearance of new isoforms in the resistance lines was preceded by accumulation of mRNAs encoding beta-1,3-glucanase and chitinases. However, there were no changes in chitinase activity or isoforms. A high constitutive level of chitinase activity was observed in all wheat genotypes. Serological studies indicated the presence of a class II chitinase of 26 kDa. Accumulation of beta-1,3-glucanase and chitinase transcripts was detected before the pathogen penetrated the leaves through stomata and approximately 16 h before the typical hypersensitive response was observed, indicating that signal(s) for defense gene activation were recognised by the host plant long before a tight contact between the pathogen and a host cell is established. A glycoprotein (Pgt elicitor) derived from hyphal walls, strongly induced beta-1,3-glucanase. We discuss the possible role of the elicitor in the early signalling mediating Sr5- and Sr24-specified resistance in wheat.

Dependence estimation for marginal models of multivariate survival data

We have previously (Segal and Neuhaus, 1993) devised methods for obtaining marginal regression coefficients and associated variance estimates for multivariate survival data, using a synthesis of the Poisson regression formulation for univariate censored survival analysis and generalized estimating equations (GEE's). The method is parametric in that a baseline survival distribution is specified. Analogous semiparametric models, with unspecified baseline survival, have also been developed (Wei, Lin and Weissfeld, 1989; Lin, 1994). Common to both these approaches is the provision of robust variances for the regression parameters. However, none of this work has addressed the more difficult area of dependence estimation. While GEE approaches ostensibly provide such estimates, we show that there are problems adopting these with multivariate survival data. Further, we demonstrate that these problems can affect estimation of the regression coefficients themselves. An alternate, ad hoc approach to dependence estimation, based on design effects, is proposed and evaluated via simulation and illustrative examples.

Human immunodeficiency virus-related oral manifestations and gender. A longitudinal analysis. The University of California, San Francisco Oral AIDS Center Epidemiology Collaborative Group

BACKGROUND

Because human immunodeficiency virus (HIV) infection affects an increasing number of women in the United States, we investigated the role played by gender in the occurrence of HIV-related oral conditions.

METHODS

As part of a 4-year prospective study of 3 epidemiological cohorts, oral and physical examinations (including blood tests) were performed on HIV-infected men (n = 200) and women (n = 218) at 6-month intervals. Our outcome variables included oral conditions commonly associated with HIV infection: hairy leukoplakia, candidiasis, ulcers, warts, non-Hodgkin lymphoma, Kaposi sarcoma, and parotid enlargement.

RESULTS

Only hairy leukoplakia, candidiasis, and ulcers were observed. The occurrence of hairy leukoplakia and candidiasis was higher in men (22% and 24%, respectively) than in women (9% and 13%, respectively) during the study period. A regression model for longitudinal data (generalized estimating equation) disclosed that the odds of having hairy leukoplakia were 2.5 times higher for men than for women, after controlling for CD4+ cell count, race, and injecting drug use (95% confidence interval, 1.34-4.76; P = .003). Length of follow-up did not confound this association. A weaker association was found between the occurrence of oral candidiasis and gender (adjusted odds ratio, 1.85; 95% confidence interval, 1.0-3.43; P = .05).

CONCLUSIONS

In this sample of HIV-infected adults, we found that men were significantly more likely to have hairy leukoplakia than were women. The hairy leukoplakia-gender association merits further investigation, because it may be related to a gender difference in the mode of expression of Epstein-Barr virus.

Plant chitinases use two different hydrolytic mechanisms

Bacterial, fungal, animal, and some plant chitinases form family 18 of glycosyl hydrolases. Most plant chitinases form the family 19. While some chitinases also have lysozyme activity, animal lysozymes belong to different families. For glycosyl hydrolases, two reaction mechanisms are possible, leading to either retention or inversion of the anomeric configuration. We analyzed by HPLC the stereochemical outcome of the hydrolysis catalyzed by cucumber and bean chitinases, belonging to families 18 and 19, respectively. Cucumber chitinase used the retaining mechanism as known for bacterial chitinases and hen egg white lysozyme for which the mechanism has been determined. In contrast, bean chitinase catalyzed the hydrolysis of chitooligosaccharides with overall inversion of anomeric configuration.

Serum fatty acids and the risk of coronary heart disease

To examine the relation between serum fatty acids and coronary heart disease (CHD), the authors conducted a nested case-control study of 94 men with incident CHD and 94 men without incident CHD who were enrolled in the Usual Care group of the Multiple Risk Factor Intervention Trial between December 1973 and February 1976. After confirming the stability of the stored serum samples, the authors measured serum fatty acid levels by gas-liquid chromatography and examined their association with CHD. In all multivariate models, levels of the cholesterol ester saturated fatty acid palmitic acid (16:0) were directly associated with CHD risk (standardized odds ratio = 1.68; 95% confidence interval 1.10-2.55 in the model that adjusted for total plasma cholesterol level). Levels of the phospholipid omega-3 fatty acid docosapentaenoic acid (22:5) were inversely associated with CHD risk in the two multivariate models that controlled for the effects of total plasma cholesterol level or high density lipoprotein cholesterol to total plasma cholesterol ratio (standardized odds ratio = 0.58; 95% confidence interval 0.38-0.89 in the first model that controlled for total plasma cholesterol level). In contrast to the first two multivariate models, levels of the docosahexaenoic acid (22:6) were inversely associated with CHD risk in a third multivariate model that controlled for the effects of high density lipoprotein cholesterol to low density lipoprotein cholesterol ratio (standardized odds ratio = 0.57; 95% confidence interval 0.36-0.90). These findings are consistent with other evidence indicating that saturated fatty acids are directly correlated with CHD and that omega-3 polyunsaturated fatty acids are inversely correlated with CHD. Because these associations were present after adjustment for blood lipid levels, other mechanisms, such as a direct effect on blood clotting, may be involved.

Long-term physical functioning in persons with knee osteoarthritis from NHANES. I: Effects of comorbid medical conditions

This study examined the effects of comorbid medical conditions (heart disease, pulmonary disease, hypertension and obesity) on the association of radiographic knee osteoarthritis (OA) with long-term difficulty in physical function. Data are from the National Health and Nutrition Examination Survey, 1971-1975 (NHANES I), a prospective epidemiologic cohort study, and the NHANES Epidemiologic Follow-up Study, 1982-1984 (NHEFS) and included 4059 persons who were 45-74 years old and participated in the detailed examination component of NHANES I. Knee OA was ascertained by anterior-posterior bilateral radiographs of the knee and self-report of knee pain, heart and pulmonary disease by self report of disease or symptoms, and hypertension and obesity by blood pressure and weight measurements. The presence of symptomatic knee OA at NHANES I was associated with reported difficulty at NHEFS 1982-84 in functions which used the lower extremity (ambulation and transfer). The presence of coexistent chronic conditions, particularly heart disease, pulmonary disease and obesity, increased the likelihood of subsequent disability. These findings suggest that knee OA is associated with long-term physical disability, and that the presence of coexistent chronic disease may increase the amount of long-term disability from knee OA.

Health behaviors and survival among middle-aged and older men and women in the NHANES I Epidemiologic Follow-up Study

BACKGROUND

Since the 1960s there has been a decline in mortality rates for older U.S. adults, suggesting the importance of examining the role of prevention and health promotion in improving the health and survival of older adults. Epidemiologic studies of age and gender differences in the impact of health behaviors on survival for older U.S. adults are needed to provide information for intervention and health promotion efforts for older Americans.

METHODS

We examined whether health behavior risk factors (smoking, drinking, physical activity, and body weight) for mortality vary by age and gender among 6,109 adults 45-74 years old in the National Health and Nutrition Examination Survey 1971-1975 (NHANES I) who were traced during the 1982-1984 NHANES I Follow-up Survey.

RESULTS

For middle-aged men (45-54 years old) and for older men (65-74 years old), both smoking and nonrecreational physical activity were predictors of survival time. Additionally, for older men, drinking and low body mass index were associated with shorter survival time. Among women, there was less consistency of associations across age groups. As with men, nonrecreational physical activity and low body mass index were associated with shorter survival among older women.

CONCLUSIONS

These findings suggest that health behaviors are associated with survival in older adults as well as in middle-aged adults, although the specific behavioral risk factors may vary by age and gender.

Mutation analysis of the C-terminal vacuolar targeting peptide of tobacco chitinase: low specificity of the sorting system, and gradual transition between intracellular retention and secretion into the extracellular space

The C-terminal propeptide of tobacco (Nicotiana tabacum) chitinase A has been shown to be necessary and sufficient for targeting of chitinases to the plant vacuole. The sequence specificity of this vacuolar targeting peptide (VTP) has now been analysed using transient expression of chitinases in Nicotiana plumbaginifolia protoplasts. An extracellular cucumber chitinase, previously used as a secreted reporter protein in transgenic tobacco, was also secreted into the incubation medium by the transiently transformed protoplasts. Addition of six to seven amino acids at the C-terminus to generate the VTP of tobacco chitinase A were sufficient to cause retention of most of the cucumber chitinase within the protoplasts. The chitinase A itself, as well as a mutant lacking the N-terminal chitin-binding domain, were retained to 80% in the protoplasts when low concentrations of the plasmid were used in the transient expression system. At high concentrations of plasmid, causing high levels of transiently expressed chitinase, retention was reduced, indicating saturation of the sorting system. Deletion of the C-terminal methionine did not affect the intracellular location, but deletion of even a single internal amino acid of the VTP caused predominantly secretion of tobacco chitinase A. In contrast, exchanges of amino acids in the VTP as well as substitution of the VTP with random sequences had intermediary effects that covered the whole range from retention to secretion. The results suggest that the sorting system responsible for the diversion of secretory proteins to the vacuole has a low specificity for the sequence of C-terminal targeting peptides, and that sequence changes in the VTP allow a gradual transition from vacuolar retention to secretion.

Estimation efficiency and tests of covariate effects with clustered binary data

Several approaches have been proposed to analyze clustered binary data, which arise in fields such as teratology and ophthalmology. These methods include mixed-effects and quasi-likelihood approaches, as well as models that use cluster responses as covariates. The three approaches measure different effects of covariates on binary responses, but simple approximations relate the magnitudes of their parameters. In this article, we present approximations to relate the standard errors of model parameters and Wald tests for covariate effects obtained from the different approaches. These approximations show that Wald tests involving cluster-level covariates will be approximately equivalent using the different approaches. However, approaches that model intracluster correlation, such as the mixed-effects model, provide more powerful tests of within-cluster covariates than those that do not model the correlation. Simulations and example data illustrate these findings.

Physiological compensation in antisense transformants: specific induction of an "ersatz" glucan endo-1,3-beta-glucosidase in plants infected with necrotizing viruses

Plant class I glucan endo-1,3-beta-glucosidases (beta-1,3-glucanase; 1,3-beta-D-glucan glucanohydrolase, EC 3.2.1.39) have been implicated in development and defense against pathogen attack. Nevertheless, beta-1,3-glucanase deficiencies generated by antisense transformation of Nicotiana sylvestris and tobacco have little biological effect. We report here that another beta-1,3-glucanase activity is induced in these deficient mutants after infection with necrotizing viruses. Induction of class I beta-1,3-glucanase was markedly inhibited in leaves of N. sylvestris and tobacco antisense transformants infected with tobacco necrosis virus and tobacco mosaic virus, respectively. A serologically distinct beta-1,3-glucanase activity was present in the infected antisense transformants but was absent in both healthy and infected control plants and in antisense transformants treated with the stress hormone ethylene. Immunoblot analyses, localization studies, and measurements of antibody specificity indicate that this compensatory beta-1,3-glucanase activity is an intracellular enzyme different from known tobacco beta-1,3-glucanases. Therefore, plants can compensate for a deficiency in enzyme activity by producing a functionally equivalent replacement--i.e., "ersatz"--protein or proteins. The fact that compensation for beta-1,3-glucanase activity occurs in response to infection argues strongly for an important role of these enzymes in pathogenesis.

The N-terminal cysteine-rich domain of tobacco class I chitinase is essential for chitin binding but not for catalytic or antifungal activity

The vacuolar chitinases of class I possess an N-terminal cysteine-rich domain homologous to hevein and chitin-binding lectins such as wheat germ agglutinin and Urtica dioica lectin. To investigate the significance of this domain for the biochemical and functional characteristics of chitinase, chimeric genes encoding the basic chitinase A of tobacco (Nicotiana tabacum) with and without this domain were constructed and constitutively expressed in transgenic Nicotiana sylvestris. The chitinases were subsequently isolated and purified to homogeneity from the transgenic plants. Chromatography on colloidal chitin revealed that only the form with the N-terminal domain, and not the one without it, had chitin-binding properties, demonstrating directly that the domain is a chitin-binding domain (CBD). Under standard assay conditions with radioactive colloidal chitin, both forms of chitinase had approximately the same catalytic activity. However, kinetic analysis demonstrated that the enzyme without CBD had a considerably lower apparent affinity for its substrate. The pH and temperature optima of the two chitinases were similar, but the form with the CBD had an approximately 3-fold higher activation energy and retained a higher activity at low pH values. Both chitinases were capable of inhibiting growth of Trichoderma viride, although the form with the CBD was about three times more effective than the one without it. Thus, the CBD is not necessary for catalytic or antifungal activity of chitinase.

Design effects for binary regression models fitted to dependent data

Dependent data, such as arise with cluster sampling, typically yield variances of parameter estimates which are larger than would be provided by a simple random sample of the same size. This variance inflation factor is called the design effect of the estimator. Design effects have been derived for cluster sampling designs using simple estimators such as means and proportions, and also for linear regression coefficient estimators. In this paper, we show that a method to derive design effects for linear regression estimators extends to generalized linear models for binary responses. In particular, some simple expressions for design effects in the linear regression model provide accurate approximations for binary regression models such as those based on the logistic, probit and complementary log-log links. We corroborate our findings with two examples and some simulation studies.

Robust inference for multivariate survival data

Multivariate survival data arise when an individual records multiple survival events or when individuals recording single survival events are grouped into clusters. In this paper we propose a new method for the analysis of multivariate survival data. The technique is a synthesis of the Poisson regression formulation for univariate censored survival analysis and the generalized estimating equation approach for obtaining valid variance estimates for generalized linear models in the presence of clustering. When the survival data are clustered, combining the methods provides not only valid estimates for the variances of regression parameters but also estimates of the dependence between survival times. The approach entails specifying parametric models for the marginal hazards and a dependence structure, but does not require specification of the joint multivariate survival distribution. Properties of the methodology are investigated by simulation and through an illustrative example.

Cloning and disruption of a gene required for growth on acetate but not on ethanol: the acetyl-coenzyme A synthetase gene of Saccharomyces cerevisiae

A DNA fragment of Saccharomyces cerevisiae with high homology to the acetyl-coenzyme A (acetyl-CoA) synthetase genes of Aspergillus nidulans and Neurospora crassa has been cloned, sequenced and mapped to chromosome I. It contains an open reading frame of 2139 nucleotides, encoding a predicted gene product of 79.2 kDa. In contrast to its ascomycete homologs, there are no introns in the coding sequence. The first ATG codon of the open reading frame is in an unusual context for a translational start site, while the next ATG, 24 codons downstream, is in a more conventional context. Possible implications of two alternative translational start sites for the cellular localization of the enzyme are discussed. A stable mutant of this gene, obtained by the gene disruption technique, had the same low basal activity of acetyl-CoA synthetase as wild-type cells when grown on glucose but completely lacked the strong increase in activity upon entering the stationary phase, providing direct proof that the gene encodes an inducible acetyl-CoA synthetase (ACS1) of yeast. As expected, the mutant was unable to grow on acetate as sole carbon source. Nevertheless, it showed normal induction of isocitrate lyase on acetate media, indicating that activity of acetyl-CoA synthetase is dispensable for induction of the glyoxylate cycle in S. cerevisiae. Surprisingly, disruption of the ACS1 gene did not affect growth on media containing ethanol as the sole carbon source, demonstrating that there are alternative pathways leading to acetyl-CoA under these conditions.

Posttranslational processing of a new class of hydroxyproline-containing proteins. Prolyl hydroxylation and C-terminal cleavage of tobacco (Nicotiana tabacum) vacuolar chitinase

The fungicidal class I chitinases (EC 3.2.1.14) are believed to be important in defending plants against microbial pathogens. The vacuolar isoforms of tobacco (Nicotiana tabacum), chitinases A and B, are the first examples of a new type of hydroxyproline-containing protein with intracellular location, enzymic activity, and a small number of hydroxyprolyl residues restricted to a single, short peptide sequence. We have investigated the posttranslational processing and intracellular transport of transgene-encoded chitinase A in callus cultures of Nicotiana tabacum L. cv Havana 425 and leaves of Nicotiana sylvestris Spegazzini and Comes. Pulse-chase experiments and cell fractionation show that chitinase A is processed in two distinct steps. In the first step, the nascent protein undergoes an increase in apparent M(r) of approximately 1500 detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Experiments with the inhibitor of prolyl hydroxylation, alpha,alpha'-dipyridyl, and pulse-chase labeling of cells expressing recombinant forms of chitinase A indicate that the anomalous increase in M(r) is due to hydroxylation of prolyl residues. This step occurs in the endomembrane system before sorting for secretion and vacuolar transport and does not appear to be required for correct targeting of chitinase A to the vacuole. The second step is a proteolytic cleavage. Sequencing of tryptic peptides of the mature proteins indicates that during processing essentially all molecules of chitinase A and B lose a C-terminal heptapeptide, which has been shown to be a vacuolar targeting signal. This appears to occur primarily in the endomembrane system late in intracellular transport. A model for the posttranslational modification of chitinase A is proposed.

Correlates of knee pain among US adults with and without radiographic knee osteoarthritis

We examined the associations of sociodemographic variables, health behaviors, health status and psychological well being with radiographic knee osteoarthritis (OA) and self-reported knee pain for 4056 US adults aged 45-74 years. Among persons with or without knee OA known correlates of radiographic knee OA (age, sex, race, obesity) were generally not associated with knee pain. Radiographic severity, psychological well being and health status were associated with knee pain, both among persons with and without radiographic knee OA, suggesting that nonradiographic correlates of self-reported knee pain are independent of whether a person has radiographic knee OA.

Statistical methods for longitudinal and clustered designs with binary responses

Dependent binary response data arise frequently in practice due to repeated measurements in longitudinal studies or to subsampling primary sampling units as in fields such as teratology and ophthalmology. Several classes of approaches have recently been proposed to analyse such repeated binary outcome data. The different classes of approaches measure different effects of covariates on binary responses and address different statistical questions. This article compares the different classes of approaches in terms of parameter interpretation and magnitude, standard errors of model parameters and Wald tests for covariate effects. The results help to clarify the substantive questions which data analysts can address with each approach, as well as why the covariate effects measured by different approaches may be different. Finally, I will provide guidelines to the advantages and disadvantages of alternative approaches for analysing dependent binary responses. Simulations and example data illustrate these findings.

Regulated inactivation of homologous gene expression in transgenic Nicotiana sylvestris plants containing a defense-related tobacco chitinase gene

The class I chitinases are vacuolar proteins implicated in the defense of plants against pathogens. Leaves of transgenic Nicotiana sylvestris plants homozygous for a chimeric tobacco (Nicotiana tabacum) chitinase gene with Cauliflower Mosaic Virus (CaMV) 35S RNA expression signals usually accumulate high levels of chitinase relative to comparable leaves of non-transformed plants. Unexpectedly, some transgenic plants accumulated lower levels of chitinase than nontransformed plants. We call this phenomenon silencing. The incidence of silencing depends on the early rearing conditions of the plants. When grown to maturity in a greenhouse, approximately 25% of plants raised as seedlings in closed culture vessels were of the silent type; none of the plants raised from seed in a greenhouse showed this phenotype. Silencing is also developmentally regulated. Plants showed three patterns of chitinase expression: uniformly high levels of expression in different leaves, uniformly low levels of expression in different leaves, and position-dependent silencing in which expression was uniform within individual leaves but varied in different leaves on the same plant. Heritability of the silent phenotype was examined in plants homozygous for the transgene. Some direct descendants exhibited a high-silent-high sequence of activity phenotypes in successive sexual generations, which cannot be explained by simple Mendelian inheritance. Taken together, the results indicate that silencing results from stable but potentially reversible states of gene expression that are not meiotically transmitted. Gene-specific measurements of chitinase and chitinase mRNA showed that silencing results from co-suppression, i.e. the inactivation of both host and transgene expression in trans. The silent state was not correlated with cytosine methylation of the transgene at the five restriction sites investigated.

The function of vacuolar beta-1,3-glucanase investigated by antisense transformation. Susceptibility of transgenic Nicotiana sylvestris plants to Cercospora nicotianae infection

Vacuolar class I beta-1,3-glucanases (EC 3.2.1.39) are believed to be important in the induced defense reaction of plants to fungal infection. We used antisense transformation to test this hypothesis and to identify other possible physiological functions of this enzyme. Nicotiana sylvestris plants were transformed with antisense constructions containing the region from position 27 to 608 of the coding sequence of the basic, vacuolar beta-1,3-glucanase gene GLA of tobacco regulated by cauliflower mosaic virus 35S RNA expression signals. Plants homozygous for this transgene showed a marked, ca. 20-fold reduction in the constitutive expression of class I beta-1,3-glucanase antigen in their leaves. RNA blot analysis indicated that the antisense plants expressed low levels of the sense transcript of the host beta-1,3-glucanase gene and the antisense transcript of the transgene. Immune blot analysis of plant extracts indicated that only expression of the N. sylvestris homologue of class I tobacco beta-1,3-glucanase and not the acidic, class II isoforms of the enzyme was blocked in the antisense plants. Class I isoforms of beta-1,3-glucanase and chitinase were coordinately induced in leaves of untransformed and empty-vector-transformed N. sylvestris plants treated with ethylene or infected with the fungal leaf pathogen Cercospora nicotianae. In antisense plants, chitinase but not beta-1,3-glucanase was induced under these conditions indicating that antisense transformation effectively blocks constitutive as well as induced expression of class I beta-1,3-glucanase. Under greenhouse conditions, antisense plants developed normally and were fertile. The plants did not exhibit increased susceptibility to C. nicotianae infection. These results suggest that expression of the beta-1,3-glucanase isoform blocked by antisense transformation is not necessary for 'housekeeping' functions of N. sylvestris nor defense against the fungal pathogen tested.

Vacuolar chitinases of tobacco: a new class of hydroxyproline-containing proteins

The fungicidal type I chitinases contribute to the defense response of plants against pathogens. Two tobacco chitinases represent a different class of hydroxyproline-containing proteins. Hydroxyproline-rich proteins are predominantly extracellular, structural glycoproteins proteins that lack enzymatic activity and contain many hydroxyproline residues. In contrast, type I chitinases are vacuolar enzymes. They are not glycosylated and contain a small number of hydroxyproline residues restricted to a single, short peptide sequence.

The structure and regulation of homeologous tobacco endochitinase genes of Nicotiana sylvestris and N. tomentosiformis origin

The fungicidal class I chitinases are believed to be important in the induced defense response of plants. We isolated and partially characterized genomic clones representing two members, CHN14 and CHN50, of the gene subfamily encoding these enzymes in Nicotiana tabacum L. cv. Havana 425. The coding sequences of genes CHN14, CHN50, and CHN48, which was cloned earlier, are identical at 79-95% of the positions. Tobacco is an amphidiploid species derived from ancestors most closely related to the present-day species N. sylvestris and N. tomentosiformis. Southern analysis of genomic DNA, comparison of deduced amino acid sequences, and partial sequencing of the purified enzymes suggest that the gene pairs CHN48/CHN50 and CHN14/CHN14' are homeologues. Gene CHN48, which encodes chitinase A (Mr ca. 34 kDa), and gene CHN14 are derived from N. tomentosiformis; whereas gene CHN50, which encodes chitinase B (Mr ca. 32 kDa), and gene CHN14' are derived from N. sylvestris. Class I chitinases are induced in leaves of plants treated with ethylene or infected with the fungal pathogen Cercospora nicotianae and in cultured cells transferred to medium without added auxin and cytokinin. RNase protection assays show that under these conditions transcripts encoded by the homeologues CHN48 and CHN50 account for greater than 90% of the total chitinase mRNA. The less abundant transcript, CHN48, consistently showed a greater degree of induction than CHN50. Expression of the homeologues CHN14 and CHN14' represented less than 10% of the total chitinase mRNA. They showed a pattern of hormonal regulation similar to CHN48 and CHN50, but transcripts of these genes were not detected in leaves infected with C. nicotianae. Therefore the two sets of homeologues are regulated in the same way by hormones and respond differently to infection by a pathogen.

Living arrangements and survival among middle-aged and older adults in the NHANES I epidemiologic follow-up study

BACKGROUND

There is concern about but little information on how living alone affects the health and survival of older adults.

METHODS

We examined the association between living arrangements (living alone, with a spouse, or with someone other than a spouse) and survival among 7651 adults, aged 45 to 74 years in the National Health and Nutrition Examination Survey (NHANES I) (1971-1975) and traced at the NHANES I Follow-up Study (1982-1984), to see whether certain sociodemographic factors (race, education, income, and employment), health behaviors (alcohol, smoking, physical activity, and obesity), or chronic medical conditions were influential in the association.

RESULTS

We found a stronger association of living arrangements with survival for men than for women, and for middle-aged men than for older men. For men, those living alone and those living with someone other than a spouse were equally disadvantaged in terms of survival. Income, race, employment, and physical activity influenced the association of living arrangements and survival, but their impact varied by age, gender, and living arrangement.

CONCLUSION

Living arrangements had a weak impact on survival among men, but had no effect among women.

An annotated bibliography of methods for analysing correlated categorical data

This paper provides an annotated bibliography of over 100 articles concerning methods for analysing correlated categorical response data. Most of the papers listed here concern categorical regression models and estimation, with particular emphasis on binary responses. The papers are classified by several characteristics which group them according to common themes. The bibliography serves as a reference of methods for analysts of correlated categorical data, as well as for persons interested in methodologic work in this active area of statistical research.

A short C-terminal sequence is necessary and sufficient for the targeting of chitinases to the plant vacuole

Tobacco contains different isoforms of chitinase (EC 3.2.1.14), a hydrolase thought to be involved in the defense against pathogens. Deduced amino acid sequences for putatively vacuolar, basic chitinases differ from the homologous extracellular, acidic isoforms by the presence of a C-terminal extension. To examine the role of this C-terminal extension in protein sorting, Nicotiana silvestris plants were stably transformed with chimeric genes coding for tobacco basic chitinase A with and without the seven C-terminal amino acids. In plants expressing unmodified chitinase A, the enzyme activity was low in the intercellular wash fluid but high in protoplasts and isolated vacuoles. In contrast, in plants expressing mutant chitinase lacking the C terminus, the activity was high in the intercellular wash fluid but low in protoplasts. N. silvestris plants were also transformed with similar constructions coding for a structurally unrelated, extracellular cucumber chitinase. In plants expressing unmodified cucumber chitinase, its activity was present in the intercellular wash fluid and absent from protoplasts. In plants expressing cucumber chitinase with the C-terminal extension from tobacco chitinase A, activity was low in intercellular wash fluids but high in protoplasts and vacuoles. These results demonstrate that the C-terminal extension of tobacco chitinase A is necessary and sufficient for the vacuolar localization of chitinases and, therefore, that it comprises a targeting signal for plant vacuoles.

Age and sex differences in variation of nutrient intakes among U.S. adults

Studies assessing associations of diet with health frequently use multi-day dietary records to estimate usual dietary intakes. We examined variation in intakes of 13 nutrients for 13,388 U.S. adults using 3 days of dietary data from the 1977-1978 Nationwide Food Consumption Survey. Ratios of within-person variability to between-person variability in intakes were large and would result in attenuated linear regression estimates of diet-health associations. For many nutrients, the magnitude of the attenuation decreased with age for both sexes but particularly for men, implying that fewer days of dietary intake per person would correctly assess diet-health associations among older adults than have been suggested for younger adults.

Characterization by image cytometry of duct epithelial proliferative disease of the breast

To develop a morphometric model of premalignant breast epithelium, we evaluated 120 lesions classified as nonproliferative disease (n = 20), hyperplasia (n = 20), moderate hyperplasia (n = 20), atypical hyperplasia (n = 20), carcinoma in situ (n = 20), and carcinoma (n = 20) in tissue from surgical biopsy or mastectomy. Atypical hyperplasia, a component of duct epithelial proliferative disease, has frequently been described in breasts with carcinoma. Atypical hyperplasia is generally viewed as premalignant or as a marker of increased risk for breast cancer. Measurements of nuclei in breast lesions were obtained with the Leitz TAS Plus on 4-microns sections stained for DNA with the Azure A Feulgen reaction. Nuclei of duct epithelial lesions had morphometric features that displayed changes from nonproliferative disease to carcinoma. The morphometric data from each lesion were compared among the six disease groups. Means of nuclear area, perimeter, maximum and minimum diameter, and large dark and large light intranuclear areas increased with higher degrees of proliferative abnormality. When the six groups of lesions were compared using the means of the first four nuclear features, atypical hyperplasia was significantly different (P less than 0.05) from carcinoma and non-proliferative lesions, but not from hyperplasia, moderate hyperplasia, or carcinoma in situ. These findings suggest that objective morphometric descriptors for characterizing significant proliferative lesions can be established using image cytometry. The progressive increases also suggest that proliferative breast disease is a continuum that includes premalignant lesions.