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D D Williams

Publications and source records attributed to D D Williams.

At least 19 recordsLinked to original sources
PubMed1995

Factors regulating cryIVB expression in the cyanobacterium--Synechococcus PCC 7942.

The expression of the larvicidal Bacillus thuringiensis subsp. israelensis cryIVB gene in cyanobacteria has been suggested to be an effective means of controlling mosquito populations. Using a variety of cryIVB constructs, in this study we have examined the effect of Synechococcus PCC 7942 culture age on intracellular toxin levels and have attempted to determine the mechanisms by which cryIVB gene expression is regulated. The data suggest that specific degradation of the cryIVB mRNA limits toxin production; however, the addition of cyanobacterial 3' untranslated DNA sequences to the cryIVB gene did not improve mRNA stability or toxin levels. An analysis of the cryIVB sequence and comparison of codon usage patterns with highly expressed cyanobacterial genes suggest that inefficient translation and intragenic ribosomal binding sites impede protein synthesis and result in rapid turnover of the toxin mRNA.

Bacillus thuringiensis↗
PubMed1994

Immunologic markers in a longitudinal study of aging in pigtailed macaques (Macaca nemestrina).

Blood lymphocyte subsets, serum immunoglobulins (Ig), response of lymphocytes to mitogens, and natural killer (NK) cell activity were evaluated as potential biomarkers for primate aging. All were evaluated in a cross-sectional study of 60 pigtailed macaques (Macaca nemestrina) ranging from 2 to 32 years of age. Lymphocyte responses to mitogens were lower in older animals than in most younger ones. NK cell activity showed no clear relation to age cohort. In a longitudinal study of lymphocyte subsets and immunoglobulins, class I restricted T cells (CD8+bri) of the memory (CD18+bri) subtype increased with age, whereas those of the naive (CD18+dull) subtype decreased with age in females. A class II restricted T-cell subset (CD4+CD45RA-), which includes memory T cells, increased with age in females. Serum IgA increased. These results support the utility of memory and naive subsets of CD8+ T cells, CD4+ T cells, and serum IgA as biomarkers for longitudinal studies. Total lymphocytes, total T cells, CD4+ T cells, and CD8+ T cells may also be useful in this species.

Aging↗
PubMed1993

Effect of promoter modification on mosquitocidal cryIVB gene expression in Synechococcus sp. strain PCC 7942.

The impact of promoter modification on the expression of the mosquitocidal Bacillus thuringiensis subsp. israelensis cryIVB gene when used to transform the cyanobacterium Synechococcus sp. strain PCC 7942 has been examined. Maximal transcript and protein abundances were achieved by the addition of the lacZ promoter upstream of the cryIVB sequence. Replacement of the endogenous corresponding Bacillus sequences with the Synechococcus petF1 promoter, ribosome binding site, and initiation codon also resulted in increased expression of the cryIVB gene relative to the expression obtained with the Bacillus promoter alone but decreased expression relative to the expression achieved with the tandem array of the Bacillus and lacZ promoters. Synechococcus cells carrying plasmids in which the expression of the cryIVB gene was regulated by either the lacZ or the petF1 promoter were readily consumed by first-instar Culex restuans larvae and proved to be toxic for these organisms.

Bacillus thuringiensis↗
PubMed1991

High school counselors' perception of baccalaureate degree nursing career choices.

A sample of 100 high school counselors in a southeastern state was surveyed to explore their perceptions of baccalaureate degree nursing as a career choice and the type and availability of resources used in counseling students toward careers in nursing. With a response rate of 31 percent, the findings indicate that counselors need more up-to-date, specific information about the requirements and scope of professional nursing practice.

Adolescent↗
PubMed1990

Fingernail growth rate as a biomarker of aging in the pigtailed macaque (Macaca nemestrina).

Rate of fingernail growth (FNG) of the middle digit of the right hand was assessed in 46 healthy pigtailed macaques at approximately 6-month intervals for 4 to 6 years. Mean FNG for 24 females, ranging in mean age at measurement from 7 to 24 years, was 104 mu/day; the mean for 22 males, ranging from 7 to 20 years, was 111 mu/day. Longitudinal analysis showed that FNG declined in animals of both sexes and that the rate of decline (-4.8 mu/day/year) did not differ between them, i.e., the mean regression coefficients (beta) of the two sexes were significantly different from zero and not significantly different from each other. Results of cross-sectional analysis differed from those of longitudinal analysis in that the mean FNG appeared to be more rapid in males than in females, particularly in the older animals. Inter- and intra-individual variability in FNG did not increase with age. FNG appears to be an excellent functional marker of the rate of aging because the direction of change is essentially decremental, a significant degree of change can be detected in a few years, and the rate of change is relatively constant across the adult lifespan. In addition, measurement of FNG is innocuous, quantitative, inexpensive, and simple.

Aging↗
PubMed1990

Constructing an instrument to measure the rate of aging in female pigtailed macaques (Macaca nemestrina).

To develop a battery of innocuous tests measuring individual differences in the rate of biological aging, longitudinal data were gathered on 28 biochemical, physiological, and morphological characteristics of 40 adult female pigtailed macaques. The change in each variable over time, i.e., the beta coefficient of linear regression, was calculated for each animal, and a matrix of correlations among the variables was constructed. Eight variables correlated well with the first principal component of the matrix. These variables (rate of fingernail growth, blood lymphocytes, mean corpuscular hemoglobin, immunoglobulin A, and serum sodium, chloride, total protein, and creatinine) represented the best subset of the potential biomarkers analyzed to produce an index covering a range of morphologic and functional systems that change with age. A similar set representing a wider range of systems and measured over a larger fraction of the life span should provide a valid index of an individual's rate of biological aging.

Aging↗
PubMed1987

Cross-sectional evaluation of potential biological markers of aging in pigtailed macaques: effects of age, sex, and diet.

The objective of our research was to establish a useful battery of innocuous tests suitable for detecting individual differences in biological aging rate in pigtailed macaques. Data were gathered from more than 60 animals of three age groups (8 to 9, 12 to 17, and 18 to 28 years olds) fed two diets differing in lipid, cholesterol, complex carbohydrate, refined sugar, and sodium chloride content. Candidate variables for an aging battery were identified in a cross-sectional analysis by performing a three-way analysis of variance (ANOVA) for the effects of age, sex, and diet on each of 72 variables. Twenty-eight variables were found to be influenced by age. By examining patterns of differences among means, 20 variables were identified that show promise of being useful, including, for example, rectal body temperature, blood albumin, immunoglobulin A, fingernail growth rate, bone thickness, and blood calcium. The set of variables used to estimate biological aging might not be identical for all age-sex classes.

Aging↗
PubMed1986

Aging and dietary influences on plasma lipoproteins and apolipoproteins in nonhuman primates.

Nineteen young (3 to 4-years-old), 25 adult (8 to 14-years-old), and 22 aged (18 years and older) pig-tailed macaques (Macaca nemestrina) were fed a semipurified control diet stringent in fat, cholesterol, refined sugar, and sodium for six months. Each group was almost equally divided by sex. Thereafter, half of each age group was fed a test diet high in fat (41% of calories), cholesterol (865 mg/kg), sodium, and refined sugar, while the rest consumed the control diet. After three years of dietary treatment, plasma and blood volumes were determined and fasting blood samples were collected for lipoprotein analysis. The protein content of very low density lipoproteins (VLDL) was increased in the test animals as compared to the controls. In general, low density lipoprotein (LDL) cholesterol, protein, and apolipoprotein B-100 values were markedly elevated by the test diet. However, these elevations were mainly confined to the young and adult groups, with little or no increases observed in the old group. The test diet also induced small but significant increases in high density lipoprotein (HDL) cholesterol, protein, and apolipoprotein A-I values. In addition, HDL cholesterol and protein values were higher in young females than males, whereas this trend was not observed in adults.

Aging↗
PubMed1985

Projections of medial terminal accessory optic nucleus, ventral tegmental nuclei, and substantia nigra of rabbit and rat as studied by retrograde axonal transport of horseradish peroxidase.

Projections of the medial terminal nucleus (MTN) of the accessory optic system, the ventral tegmental area of Tsai, and the substantia nigra of the rabbit and the rat have been studied by the method of retrograde axonal transport of horseradish peroxidase. The data show that MTN projections are remarkably similar in the rabbit and rat. The MTN projects heavily to the ipsilateral nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system and to a portion of the contralateral ventral tegmental area of Tsai that we have termed the visual tegmental relay zone (VTRZ). Further, the MTN sends projections to the ipsilateral mesencephalic (deep mesencephalic nucleus, pars medialis) and pontine (nucleus reticularis pontis oralis) reticular formations; the contralateral dorsolateral division of the basal pontine complex; the superior and lateral vestibular nuclei (contralateral in rat; bilateral in rabbit); and the ipsi- and contralateral interstitial nucleus of Cajal, nucleus of Darkschewitsch, and supraoculomotor-periaqueductal gray. The findings also indicate that the MTN has a small bilateral, but mainly ipsilateral, projection to the dorsal cap, its ventrolateral outgrowth, and the B division of the inferior olivary complex. This study further reveals that ventral tegmental nuclei (n. parabrachialis pigmentosus and n. paranigralis) and subdivisions of the substantia nigra (pars compacta and pars reticulata) project to many brain stem targets of the MTN. Thus, the VTRZ projections are similar to those of the MTN in both distribution and density except that the VTRZ projection to the inferior olive is substantially stronger. The nucleus parabrachialis pigmentosus sends a small contralateral projection to the VTRZ and a moderate-sized bilateral projection to the supraoculomotor-periaqueductal gray. The nucleus paranigralis sends a moderate number of axons to the ipsilateral deep mesencephalic nucleus, pars medialis, and the nucleus reticularis pontis oralis and provides a strong bilateral projection to the supraoculomotor-periaqueductal gray. The pars compacta of the substantia nigra provides a sparse input to the ipsilateral deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and to the contralateral VTRZ and sends a moderate number of axons, bilaterally, to the supraoculomotor-periaqueductal gray. The pars reticulata of the substantia nigra sends an ipsiateral projection of moderate size to the intermediate and deep layers of the superior colliculus, sparse ipsilateral projections to the deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and a sparse bilateral projection to

Animals↗
PubMed1984

Aging.

Explore the source record for details and available documents.

Aging↗
PubMed1981

Hypothalamic control of endocrine thermogenesis.

Hypothalamic and ruminal cooling raised serum thyrotropin (TSH), adrenocorticotropin (ACTH), norepinephrine (NE), and glucose in conscious goats in 20 degree C ambient temperature. Cooling of the preoptic anterior hypothalamus (POAH) for 2 h initially evoked shivering and vasoconstriction, leading to 1.5 degree C rise in rectal temperature (Tr). Pituitary-thyroid activation by POAH cooling was shown by peak rises in TSH of 60% at 40 min, in triiodothyronine (T3) of 54% at 80 min, and in thyroxine (T4) of 40% at 140 min. At 60 min, ACTH and NE peaked at 57 and 65%, respectively. TSH, ACTH, and NE declined during the 2nd h of POAH cooling as Tr plateaued; when POAH cooling was stopped, these hormones fell below basal level as vasodilation and panting restored Tr to normal. In contrast to the core hyperthermia evoked by POAH cooling, ruminal intubation with O degree C water (1 liter/10 kg) led to general hypothermia, Tpoah and Tr falling 1.6 degree C at 40 min. Pituitary-thyroid responses were less but ACTH and NE more, compared with POAH cooling. TSH peaked at 37% at 20 min, T3 at 55% at 60 min, and T4 at 18% at 200 min. ACTH peaked at 250% at 30 min and NE at 120% at 20 min. Thermosensitive neurons in the POAH seem to mediate more sensitive and complete control over TSH than over ACTH, or NE release, whereas extrahypothalamic core thermosensitivity (e.g., brain stem, spinal cord, abdomen) may influence ACTH and NE more than TSH release.

Adrenocorticotropic Hormone↗