Biomedical subjects

J M Neuhaus

Publications and source records attributed to J M Neuhaus.

At least 19 recordsLinked to original sources

PubMed1992

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.

Amino Acid Sequence↗

PubMed1992

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.

Clinical Trials as Topic↗

PubMed1992

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.

Acetate-CoA Ligase↗

PubMed1992

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.

Blotting, Northern↗

PubMed1992

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.

Amino Acid Sequence↗

PubMed1992

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.

Base Sequence↗

PubMed1992

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.

Acquired Immunodeficiency Syndrome↗

PubMed1992

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.

Age Factors↗

PubMed1992

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.

Age Factors↗

PubMed1991

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.

Amino Acid Sequence↗

PubMed1991

High-level expression of a tobacco chitinase gene in Nicotiana sylvestris. Susceptibility of transgenic plants to Cercospora nicotianae infection.

Endochitinases (E.C.3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen.

Base Sequence↗

PubMed1991

A consequence of omitted covariates when estimating odds ratios.

In the epidemiologic literature, one finds three criteria for confounding, which we will call the classical (marginal), operational (change-in-estimate) and conditional criteria. We define mavericks to be covariates that satisfy the operational criterion, but not the classical criterion. We present what is known about the problems of mavericks for estimating odds ratios and clarify the interpretation of odds ratios. Key results are: (1) omitting mavericks biases odds ratios towards 1; (2) omitting mavericks cannot artificially introduce an effect in contrast to omitting classical confounders; (3) the operational criterion for confounding corresponds to the conditional criterion when estimating odds ratios, but for relative risks, there are no mavericks (i.e. the classical and operational criterion correspond); and (4) the interpretation of odds ratios obtained from standard methods is that of comparing proportions, not of individual risk.

Confounding Factors, Epidemiologic↗

PubMed1991

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.

Adult↗

PubMed1991

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.

Azure Stains↗

PubMed1991

Knee osteoarthritis and physical functioning: evidence from the NHANES I Epidemiologic Followup Study.

Although osteoarthritis (OA) is common among adults, little is known about its long-term impact on physical function. Therefore, in a cohort of 2,884 adults aged 45 years or older, [National Health and Nutrition Examination Survey I (NHANES I 1971-1975)] we examined the association of baseline radiographic knee OA and difficulty in physical functioning 10 years later (NHANES I Followup Study 1982-1984). In sex specific analyses, after controlling for age, race and length of followup, persons with radiographic knee OA were more likely than persons without knee OA to report difficulty with physical functioning, particularly for activities involving mobility, transfer and instrumental activities of daily living. However, the association of knee OA with physical functioning was influenced by the radiographic grade of OA and knee pain at NHANES I, suggesting that disease severity and pain are important in anticipating difficulties with physical functioning in persons with knee OA.

Adult↗

PubMed1990

Obesity and osteoarthritis of the knee: evidence from the National Health and Nutrition Examination Survey (NHANES I).

The importance of systemic/metabolic factors in the association of obesity with radiographic knee osteoarthritis (OA) was examined for 3,905 adults aged 45 to 74 from the United States National Health and Nutrition Examination Survey, 1971 to 1975 (NHANES I). Obesity was associated with both bilateral and unilateral OA, but more strongly with bilateral OA. Obesity was also associated with both symptomatic and nonsymptomatic knee OA. Controlling for age, sex, serum cholesterol, serum uric acid, diabetes, body fat distribution, bone density, and blood pressure did not significantly reduce the association between obesity and knee OA. Findings from these data are not supportive of a metabolic link between obesity and knee OA.

Adult↗

PubMed1990

Body fat distribution and osteoarthritis.

The association of body fat distribution with single and combined site osteoarthritis was investigated using data from the US Health Examination Survey I, 1960-1962 (HES I) and the first National Health and Nutrition Examination Survey I, 1971-1975 (NHANES I). The study included 1,636 adults aged 35-79 years from HES I with hands and feet radiographs and four anthropometric fat distribution measures--subscapular and triceps skinfolds, waist girth, and seat breadth--and 3,885 adults aged 45-74 from NHANES I with knee radiographs and subscapular and triceps skinfold measures. Sex-specific data, adjusted for age, race, and body mass index, were analyzed using polychotomous logistic regression. There was a positive association of body mass index with knee osteoarthritis and with combined hands and feet osteoarthritis. A peripheral body girth pattern was associated with combined site osteoarthritis of the hands and feet; however, there was no consistent pattern of association of body fat distribution with knee osteoarthritis nor with osteoarthritis of the hands or feet only. These findings suggest that the central body fat pattern observed in previous studies to be associated with cardiovascular and gallbladder disease, and with diabetes, is not associated with osteoarthritis of the hands, feet, or knees.

Adipose Tissue↗

PubMed1990

The effect of retrospective sampling on binary regression models for clustered data.

Recently a great deal of attention has been given to binary regression models for clustered or correlated observations. The data of interest are of the form of a binary dependent or response variable, together with independent variables X1,...., Xk, where sets of observations are grouped together into clusters. A number of models and methods of analysis have been suggested to study such data. Many of these are extensions in some way of the familiar logistic regression model for binary data that are not grouped (i.e., each cluster is of size 1). In general, the analyses of these clustered data models proceed by assuming that the observed clusters are a simple random sample of clusters selected from a population of clusters. In this paper, we consider the application of these procedures to the case where the clusters are selected randomly in a manner that depends on the pattern of responses in the cluster. For example, we show that ignoring the retrospective nature of the sample design, by fitting standard logistic regression models for clustered binary data, may result in misleading estimates of the effects of covariates and the precision of estimated regression coefficients.

Cluster Analysis↗