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Biomedical subjects

D G Anderson

Publications and source records attributed to D G Anderson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Chi-activated RecBCD enzyme possesses 5'-->3' nucleolytic activity, but RecBC enzyme does not: evidence suggesting that the alteration induced by Chi is not simply ejection of the RecD subunit.

BACKGROUND: Homologous recombination in Escherichia coli is initiated by the RecBCD enzyme, and is stimulated by DNA elements known as Chi (chi) sites. The RecBCD enzyme is both a helicase and a nuclease. Recognition of chi causes both attenuation of the 3'-->5' exonuclease activity of the RecBCD enzyme, and activation of an exonuclease activity with 5'-->3' polarity, while leaving the helicase activity unaffected. A variety of evidence suggests that chi-recognition by RecBCD enzyme is accompanied by ejection of the RecD subunit. RESULTS: Through examination of RecBCD exonuclease activity under a variety of conditions, we have shown that recognition of chi by the RecBCD enzyme results in a net reduction of nuclease activity. In addition, the exact location of the first cleavage event elicited by chi-activation of the 5'-->3' nuclease is dependent upon the concentration of free magnesium ions. Finally, we have demonstrated that purified RecBC enzyme (i.e. without the RecD subunit) possesses no significant exonuclease activity under conditions where the chi-modified RecBCD enzyme is an active 5'-->3' exonuclease. CONCLUSIONS: We have shown that, despite the activation of a 5'-->3' exonuclease, recognition of chi by the RecBCD enzyme results in a net preservation of DNA. This new chi-activated nucleolytic action shows surprising variability in the exact location of its initial cleavage. We have demonstrated that purified RecBC enzyme is not an exact analogue of the chi-activated RecBCD enzyme, suggesting that the biochemical basis of chi-activation is not simply ejection of the RecD subunit.

DNA↗
PubMed1997

Three medical schools' responses to the HIV/AIDS epidemic and the effect on students' knowledge and attitudes.

PURPOSE: To assess the relative importance of factors influentail by the prevalence of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), such as didactic and clinical training, and the number of HIV-infected individuals known personally, on students' HIV-related knowledge and attitudes. METHOD: A survey was undertaken of the classes of 1991 and 1994 at the University of Colorado School of Medicine, the University of New Mexico School of Medicine, and the University of South Dakota School of Medicine. The questionnaire contained 40 knowledge questions, 20 attitude questions, and demographic questions. The students reported estimates of HIV-related didactic hours and clinical encounters experienced during their training, as well as the number of HIV-infected individuals known personally. Data analysis employed two-way analysis of variance (ANOVA) and Pearson correlation coefficients. RESULTS: In 1991 the response rates were 73% from Colorado, 54% from New Mexico, and 50% from South Dakota; in 1994 the rates were 80%, 63%, and 60%, respectively. Training programs were similar between schools and over time, varying only in the amounts of didactic information offered. The 1994 students scored significantly better than did 1991 students on knowledge, overall attitude, fear of infection, and willingness to treat HIV-infected patients; these variables were significantly correlated with the numbers of HIV-infected individuals known personally by the students. Didactic training hours were not significantly correlated with any study variable, and clinical experiences were correlated only with increased knowledge. CONCLUSION: Differences in HIV/AIDS prevalences did not affect the schools' training programs, but indirectly affected the students' knowledge and attitudes, which were related to the numbers of HIV-infected individuals known personally by the students. The authors recommend that medical schools increase students' opportunities for meaningful personal contact with HIV-infected individuals.

Academic Medical Centers↗
PubMed1996

Homeless women's perceptions about their families of origin.

The purpose of this study was to examine descriptively the families of origin of women who are, or who had been, homeless. The research was done using a descriptive qualitative research design; specifically, intensive interviewing. A feminist framework guided the research process. Lofland and Lofland's (1984) conceptualization of units of social settings was used as the basis for analysis of the data. The sample consisted of 20 women who had been homeless. Twelve of the women were interviewed individually. Six of those 12 women and an additional 8 women were later interviewed as part of two focus groups. Themes within each social unit included: meanings--homelesness, home, family of origin, lack of connectedness, and being without; practices--male privilege, transiency, and abuse issues; episodes--loss of family and being homeless; roles--traditional female-male, scapegoating, and little adult; and relationships--mother/daughter, father/daughter, and sibling. Within the mother/daughter relationships, the dominant themes were betrayal, devaluation of self, enmeshment, emotional void, longing for, emotional cutoff, and destructive coalitions. The themes from the father/daughter relationships social unit were abuse issues, differential treatment, idealized father figure, and banished daughter. Criteria for transferability and adequacy were used to determine scientific rigor.

Adult↗
PubMed1995

Kawasaki disease associated with streptococcal infection within a family.

OBJECTIVE: To describe the illness occurring in four members of a family, which had clinical and laboratory features of Kawasaki disease and streptococcal infection. METHODOLOGY: A retrospective report of three siblings and an adult male living in one household. The children had serology, blood counts, cultures and echocardiography performed and were treated with antibiotics and gammaglobulin infusions. RESULTS: The patients developed clinical, and exhibited laboratory, features suggesting streptococcal infection and 4/5 criteria suggesting the diagnosis of Kawasaki disease. All made a good clinical recovery but the youngest developed a coronary artery aneurysm. CONCLUSIONS: It may be difficult to distinguish streptococcal infection and Kawasaki disease. It is possible that some cases of Kawasaki disease are precipitated by streptococcal infection.

Adult↗
PubMed1993

Morphologic basis for loss of regulated insulin secretion by isolated rat pancreatic islets.

Laboratories engaged in secretory studies of rat pancreatic islets often encounter high baseline insulin secretion with poor secretory response to secretagogues, such as glucose. The specific morphologic abnormalities that accompany this unregulated release have not been described. We isolated islets comparing two approaches. Both used stationary digestion with collagenase. In method I, we distended the biliary duct extracorporeally with collagenase and minced the pancreas after a 28 min digestion (37 degrees C). In method II, we distended the pancreas intracorporeally and digested for 40 min without mincing. Both methods utilized a similar collagenase concentration (2 micrograms/ml in Hank's balanced salt solution (HBSS). Both methods yielded over 300 islets/rat. Islets from both methods appeared intact, when viewed under the dissecting microscope. We found that adequate secretion from incubated islets was evoked with method I, i.e., low basal insulin levels at low glucose (3.3 mM), tripling at 11.0 mM glucose, and nearly quadrupling in response to higher glucose (16.7 mM). In contrast, method II was characterized by high basal levels without response to higher glucose. Ultramicroscopic examination of islet B cells in method I revealed normal cytological features, while B cells in method II showed marked degranulation, profiles of swollen endoplasmic reticulum, and swollen mitochondria. Morphometric analysis of B cells confirmed quantitatively a decrease in secretory granule density and mitochondrial enlargement in method II compared to method I. Anatomic changes, largely confined to the B cells of islets may account for functional alterations of responses. Defects cannot be predicted from gross appearance of islets.

Animals↗
PubMed1990

Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation.

Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Physiological de novo thyroid hormone formation in primary culture of porcine thyroid follicles: adenosine 3',5'-monophosphate alone is sufficient for thyroid hormone formation.

We describe a method of culturing intact porcine thyroid follicles for physiological de novo thyroid hormone formation; the roles of cAMP and protein kinase-C in thyroid hormone formation were also studied. Thyroid follicles were obtained by digesting minced porcine thyroid tissue with 0.04% collagenase and cultured in Coon's Modified Ham's F-12 medium supplemented with 0.5% calf serum, 0.5 mU/ml TSH, other standard hormones, and 3 antibiotics (6H medium). On the fourth day of culture, 6000-8000 follicles/well were plated in 12-well culture dishes. On the sixth day, thyroid hormone formation was carried out by incubating thyroid follicles with 0.5 microM KI in the presence of 6H medium for 2 days in a 5% CO2-95% air incubator at 37 C. To examine the effects of cAMP and protein kinase-C on de novo thyroid hormone formation, follicles were incubated with KI in the presence of 1-2.5 mM (Bu)2cAMP, 10 microM forskolin, 2 microM prostaglandin E2 (PGE2), or 0.5-1 microM 12-O-tetradecanoylphorbol-13-acetate in TSH-free medium for 2 days. The amount of newly formed thyroid hormone was measured by RIA of T3 content in the Pronase digest of thyroid follicular cells. Thyroid follicles cultured in 6H medium had normal polarity of the membrane, determined by electron microscope, and thyroid cAMP was responsive to the alteration of TSH. In this culture system cAMP alone was sufficient to form thyroid hormone. 12-O-Tetradecanoylphorbol-13-acetate, a protein kinase-C stimulator, disrupted thyroid follicles and inhibited cAMP-mediated thyroid hormone formation. The integrity of follicular structure was also required for thyroid hormone formation in this culture system. This study introduces perhaps the most physiological culture system for de novo thyroid hormone formation. Our data provide direct evidence that thyroid hormone formation is linked to cAMP and that the protein kinase-C system acts as an inhibitor of thyroid hormone formation.

Animals↗
PubMed1988

Electron microscope study of the association between hypothalamic blood vessels and oxytocin-like immunoreactive neurons.

An association between oxytocin-like immunoreactive neurons and hypothalamic blood vessels has been observed with the light microscope. Recently, it has been demonstrated that oxytocin stimulates vascular smooth muscle contraction in vitro. A hypothesis has thus been proposed that oxytocin may play a role in modulating blood flow in certain brain regions. In a study on the golden-mantled ground squirrel (Spermophilus lateralis) we noted the association at the light microscope level between oxytocin-like immunoreactive neurons and blood vessels in preoptic and paraventricular nuclei of the hypothalamus. To determine if these neurons were associated with hypothalamic capillaries, transverse 30 micron immunostained hypothalamic sections were prepared for thin sectioning and observation by transmission electron microscopy. Oxytocin-like immunoreactive neurons were observed to lie within 77 nm of the edge of the lumen of capillary blood vessels. One neuronal cell body was observed approximately 380 nm from the edge of a capillary lumen and what appears to be an output region of a neuron was observed to terminate on the basement membrane of a capillary blood vessel.

Animals↗
PubMed1988

Escherichia coli F41 adhesin: genetic organization, nucleotide sequence, and homology with the K88 determinant.

The genetic organization of the polypeptides required for the biosynthesis of the F41 adhesin of enterotoxigenic Escherichia coli strains was investigated. Maxicell analysis demonstrated that a recombinant plasmid which mediated mannose-resistant hemagglutination and F41 antigen production encoded four polypeptides of 29, 30, 32, and 86 kilodaltons. The 29-kilodalton protein was identified as the F41 antigen, and the nucleotide sequence of the gene was determined. Extensive homology was observed between the region encoding the putative signal sequences of the F41 and K88 antigens and in the region immediately upstream of the antigen genes. The nucleotide sequence homology between F41 and K88 determinants was further investigated by Southern blot hybridization. A K88 probe hybridized at high stringency to all fragments shown to be essential for F41 production except for fragments internal to the F41 antigen gene.

Adhesins, Escherichia coli↗
PubMed1986

Validation of an in vivo developmental toxicity screen in the mouse.

A test system for identifying toxicity, including potential teratogenicity has been developed that is based on growth and viability of embryonic, fetal, and postnatal mice (J Toxicol Environ Health 10:541-550, 1982). To test the utility of this assay, a series of 55 compounds was administered to timed-pregnant ICR/SIM mice during organogenesis. The test compounds included known teratogens, known nonteratogens, and equivocal teratogens. They represented a wide variety of classes including pesticides, organic solvents, metals, steroids, nutrients, food additives, antimetabolites, alkylating agents, and pharmaceutical agents. A single dose level, at or near the level producing overt maternal toxicity in preliminary range-finding studies, was administered by gavage on gestation days 8 through 12. Females were allowed to deliver; litter size and weight on the day of birth and 2 days postpartum were recorded, and stillborns were examined. Dams that had not given birth by gestation days 21 or 22 were killed and their uteri were examined. The results confirmed a strong correlation between reported teratogenic activity and embryo/fetal viability, and/or postnatal growth and viability. The results indicate that this test system is an effective, cost-efficient means of prioritizing compounds for more detailed teratogenicity testing.

Animals↗
PubMed1986

Blood glucose monitoring by children at home: a comparison of methods.

The accuracy of measurements of blood glucose performed at home by the index children and/or parents was compared using the Boehringer Mannheim reagent strips, Ames Visidex-2 strips, an Ames Glucometer and a Boehringer Mannheim Reflolux reflectance meter. Capillary plasma samples, collected simultaneously, were later analysed by a Beckman glucose oxidase analyser. The coefficient of correlation between the self-monitored results (SMR) and the laboratory-analysed results (LAR) ranged from 0.59 to 0.92, the composite being 0.74. The mean difference between the SMR and the LAR was 1.0 mmol/l. The occurrence of potential errors of management due to incorrect SMR results was determined. On four occasions, the SMR was greater than 6 mmol/l when the LAR was less than 3 mmol/l, and on 36 occasions a discrepancy greater than 50% occurred between the two values, without resulting hypoglycaemia.

Adolescent↗
PubMed1985

Comparison of the radiosensitivity of interleukin-2 production between species, between tissues, and between young and old individuals.

The radiosensitivity of interleukin-2 (IL-2) production was assessed of (a) peripheral blood mononuclear cells (PBMC) of young humans, dogs, and mice (C57BL/6); (b) PBMC and splenic cells of young mice; and (c) PBMC of young and old humans and the splenic cells of young and old mice. The results indicate that (a) large differences in radiosensitivity exist between the PBMC of humans, dogs, and mice (e.g., the radiation doses which resulted in 37% remaining IL-2 activity (D37) of human, dog, and mouse PBMC were 3771, greater than 10,000, and 1398 rads, respectively); (b) only a small difference exists between the PBMC and splenic cells of mice; and (c) no difference exists between the PBMC of young and old humans and between splenic cells of young and old mice. Topological abnormalities, as judged by scanning electron microscopic analysis, could not be detected in dog PBMC after their exposure to 1800 rads, but could be detected in mouse PBMC after their exposure to 400 rads.

Adult↗
PubMed1985

Gorgosterol biosynthesis: localization of squalene formation in the zooxanthellar component of various gorgonians.

Four species of gorgonians: three related pseudoplexaurids Pseudoplexaura porosa, P. flagellosa and P. wagenaari; and the unrelated Pseudopterogorgia americana, are sources of zooxanthellae capable, in purified broken cell preparations, of converting [14C]labeled farnesyl pyrophosphate into squalene. More extensive studies with P. porosa and P. americana zooxanthellae preparations characterize the conversion as enzymatic and demonstrate farnesyl pyrophosphate and reduced pyridine nucleotide as substrates. NADPH and NADH are essentially equivalent. Anaerobic conditions are not required. Despite numerous attempts zooxanthellae formation of sterols, including gorgosterol, from radioactive substrates was unsuccessful. By enzyme studies, we can show only the conversion of mevalonate into squalene as a zooxanthellae capability.

Animals↗
PubMed1984

In Vivo Cloning of lac Genes in Streptococcus lactis ML3.

The isolation and characterization of a Streptococcus lactis ML3 strain which possessed a recombinant lactose plasmid is described. The recombination events generating this plasmid occurred in vivo in a recombination-deficient strain and appeared to be mediated by transposition events. Restriction mapping revealed that the recombinant plasmid, pDA0307, contained a region of the lactose plasmid, pSK08, linked to another resident plasmid, pSK07. Copy number determinations indicated that the lac genes were present at approximately 20 copies per cell in pDA0307, whereas the lac genes are normally present at approximately 10 copies per cell in pSK08. The strain containing pDA0307 displayed a 21 to 54% increase in the expression of the Lac enzyme phospho-beta-d-galactosidase. However, the strain containing pDA0307 both grew and produced lactic acid in milk at rates identical to that of a strain containing pSK08. This result suggests that lac gene dosage of plasmid-linked lac genes was not limiting the rate at which these derivatives of S. lactis ML3 fermented milk.

Journal Article↗
PubMed1984

Genetic and physical characterization of recombinant plasmids associated with cell aggregation and high-frequency conjugal transfer in Streptococcus lactis ML3.

Restriction mapping was employed to characterize the 104-kilobase (kb) cointegrate lactose plasmids from 15 independent transconjugants derived from Streptococcus lactis ML3 as well as the 55-kb lactose plasmid ( pSK08 ) and a previously uncharacterized 48.4-kb plasmid ( pRS01 ) from S. lactis ML3. The data revealed that the 104-kb plasmids were cointegrates of pSK08 and pRS01 and were structurally distinct. The replicon fusion event occurred within adjacent 13.8- or 7.3-kb PvuII fragments of pSK08 and interrupted apparently random regions of pRS01 . Correlation of the transconjugants' clumping and conjugal transfer capabilities with the interrupted region of pRS01 identified pRS01 regions coding for these properties. In the 104-kb plasmids, the pRS01 region was present in both orientations with respect to the pSK08 region. The replicon fusion occurred in recombination-deficient (Rec-) strains and appeared to introduce a 0.8 to 1.0-kb segment of DNA within the junction fragments. The degeneration of the cointegrate plasmids was monitored by examining the lactose plasmids from nonclumping derivatives of clumping transconjugants. These plasmids displayed either precise or imprecise excision of pRS01 sequences or had dramatically reduced copy numbers. Both alterations occurred by rec-independent mechanisms. Alterations of a transconjugant 's clumping phenotype also occurred by rec-independent inversion of a 4.3-kb KpnI-PvuII fragment within the pRS01 sequences of the cointegrate plasmid.

Base Sequence↗