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Biomedical subjects

D Hogan

Publications and source records attributed to D Hogan.

53 records · Page 3Linked to original sources
PubMed1992

Recombination between genes encoding major outer surface proteins A and B of Borrelia burgdorferi.

Borrelia burgdorferi causes Lyme disease, a multisystem illness that can persist in humans for many years. We describe recombination between homologous genes encoding the major outer surface proteins (Osps) A and B of B. burgdorferi which both deletes osp gene sequences and creates chimaeric gene fusions. Recombinant osp genes occur in multiple strains and encode unique proteins that lack some characteristic Osp epitopes. Antigenic variation in Osp through recombination may be relevant to the persistence of B. burgdorferi in an infected host, and has important implications for the utility of OspA and OspB as diagnostic or vaccine candidates for Lyme disease. We also describe Osp variation arising from nonsense mutations and sequence divergence, which may also represent significant sources of Osp polymorphism.

Amino Acid Sequence↗
PubMed1991

Working group recommendations: research on content and efficacy of geriatric evaluation and management interventions.

Methods of conducting comprehensive geriatric evaluation and management (GEM) are proliferating in a variety of clinical settings. However, rigorous evaluations of efficacy for this new approach to care of older patients have demonstrated a favorable impact on patient outcome in only a few studies. All of these have been controlled single site studies, and replication is needed. If replication studies show similar results, further studies should be undertaken to define the minimum necessary intervention to achieve the desired outcome. Controlled trials are needed to determine if consultative geriatric evaluation and/or primary patient management is effective. Further innovative work is needed in model development for geriatric assessment and management in outpatient settings. Finally, studies of geriatric evaluation and management in other environments, such as home care or the nursing home, are recommended.

Forecasting↗
PubMed1991

Polymerase chain reaction analyses identify two distinct classes of Borrelia burgdorferi.

We sequenced homologous chromosomal loci from several North American and European isolates of the Lyme disease spirochete Borrelia burgdorferi, as well as from the relapsing fever spirochete Borrelia hermsii. Inter- and intraspecies sequence comparisons permitted the design of B. burgdorferi-specific polymerase chain reaction primers that detected all strains tested (n = 31) from diverse geographical and biological origins. Polymerase chain reaction "typing" with other unique sets of primers subdivided B. burgdorferi isolates into two groups: all North American isolates and a few European isolates made up one group, while the majority of the European and Asian isolates made up the second group. This classification may have a clinical correlate reflected in differences between "typical" Lyme borreliosis in North America and Europe.

Animals↗
PubMed1989

Human immunodeficiency virus infection and porphyria cutanea tarda.

A recent report documents three homosexual men with porphyria cutanea tarda associated with acquired immune deficiency syndrome (AIDS). We report two brothers with hemophilia and human immunodeficiency virus (HIV) exposure who developed porphyria cutanea tarda. These brothers are heterosexual, have familial porphyria cutanea tarda, and developed overt familial porphyria cutanea tarda in their early twenties. One brother's symptoms were provoked by attending an ultraviolet A suntanning parlor. Our two patients, unlike the previously reported three patients, have not developed AIDS, though one patient has evidence of defective cell-mediated immunity. Three of the five cases of porphyria cutanea tarda associated with HIV infection involved familial porphyria cutanea tarda. It now may be advisable to order HIV serology tests in patients who have porphyria cutanea tarda. We recommend that HIV-positive individuals avoid ultraviolet A radiation because of its immunosuppressive effects in persons already at risk of immunosuppression. Such exposure is further contraindicated in those individuals with porphyria cutanea tarda.

Adult↗
PubMed1988

Bone histomorphometry, bone mass, and related parameters in alcoholic males.

Bone mass and related metabolic variables were studied in 50 males known to be, or to have been, regular alcohol abusers. Subjects were divided into those who were still drinking and those who had abstained for at least 3 months, and the former further subdivided into moderate and heavy drinkers. Twenty-five had at least two atraumatic spinal crush fractures. In 25 cases, bone histomorphometry was carried out. Lumbar bone mineral density and iliac crest bone volume were significantly lower in spinal crush fracture cases. Parathyroid hormone, testosterone, and urinary cortisol measurements showed no difference between groups. Alkaline phosphatase and 24-hour urine hydroxyproline were higher in osteoporotics than in nonosteoporotics. On bone histomorphometry, there were essentially no differences between those with and those without fractures in terms of bone formation and resorption parameters. Drinkers showed lower osteoid seam width and fraction of osteoid covered by osteoblasts, as well as fewer osteoblasts per 10 cm of bone surface than abstainers. Mineralization lag time was prolonged, and mineralization rate per day was lower in the drinkers. Osteon formation time was prolonged in the drinkers. On the resorption side, only the osteon resorption time was significantly different in the drinkers, being prolonged. The heavy drinkers, but not the moderate drinkers, had a significantly reduced surface extent of lacunae. We conclude that alcohol consumption has clear detrimental effects on bone formation with less pronounced suppressive effects on bone resorption. In no biochemical or hormonal measurement, however, with the exception of hydroxyproline excretion and plasma alkaline phosphatase, could those who had osteoporosis be distinguished from those who did not.

Alcoholism↗
PubMed1982

Effects of iron and ascorbic acid on acid phosphatases of the enamel organ of rat molars.

Protein extracts from 6- to 11-day-old rat enamel organs were applied to columns of carboxymethyl-52 cellulose. Protein eluted from the columns was assayed for acid phosphatase activity with substrates para-nitrophenylphosphate (p-NPP), beta-glycerolphosphate (beta-GP), ATP and phosphocasein. A weakly-bound peak of activity (A) emerged first which was insensitive to stimulation by iron and ascorbic acid. This enzyme hydrolysed only the phosphomonoester substrates (p-NPP and beta-GP). A strongly bound peak of activity (B) emerged later and was completely separated from the first activity. It hydrolysed all substrates except beta-GP, and was stimulated at least 10-fold by 0.1 mM ferrous ion (Fe2+) in the presence of a strong reducing agent (1.0 mM ascorbic acid). Both substances were more effective as stimulators when used together than they were when each was used separately. Dependency on these co-factors for the development of full activity increased with purification, especially when phosphocasein was substrate. The results were similar for each age of rat used. These properties of enzyme B are parallel with those of the acid phosphoprotein phosphatases of liver and spleen, and the tartrate-resistant acid phosphatase of rat bone. We conclude that enzyme B requires iron and a reducing agent for full activity and has properties that distinguishes it from the classical acid phosphatases (E.C. 3.1.3.2.).

Acid Phosphatase↗
PubMedDate not supplied

Postpartum amenorrhoea in Ethiopia: the role of weaning, child death, and socioeconomic factors.

Using data from the 1990 National Family and Fertility Survey (NFFS) and employing discrete-time hazards models, we examine the effect of weaning, child death, and socioeconomic factors on postpartum amenorrhoea in Ethiopia. The results show that 91 in every 100 mothers breastfed their child for at least 6 months. The median duration of breastfeeding stands at 18 months, and amenorrhoea lasts for a median duration of 12 months. Significant variations in breastfeeding and amenorrhoea duration are also observed among the different categories of breastfeeding women. The median duration of breastfeeding for lactating women is 24 months, 6 months for those who weaned, and 2 months for those whose child died. The median duration of postpartum amenorrhoea is 14 months for breastfeeding women, 12 months for those who weaned, and 6 months for those whose child died. Discrete-time hazard models reveal that child death has the strongest effect on the resumption of menses. Net of other factors, the risk of returning to menses increased 3 times for mothers whose child died. The effect of child death, however, decreases over time. Weaning also has a significant positive effect; and, like child death, its effect diminishes as time passes. The study further shows significant differences in the risk of returning to postpartum menses by socioeconomic characteristics of the women, even though they are breastfeeding.

Adolescent↗