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Biomedical subjects

C R Engel

Publications and source records attributed to C R Engel.

At least 19 recordsLinked to original sources
PubMed2005

Genetic entities and mating system in hermaphroditic Fucus spiralis and its close dioecious relative F. vesiculosus (Fucaceae, Phaeophyceae).

To date, molecular markers have not settled the question of the specific status of the closely related, but phylogenetically unresolved, brown seaweeds, hermaphroditic Fucus spiralis and dioecious Fucus vesiculosus, nor their propensity for natural hybridization. To test the degree of species integrity and to assess effect of the mating system on the population genetic structure, 288 individuals coming from parapatric (discontinuous) and sympatric (contiguous) spatial configurations at two sites were genotyped with five microsatellite loci. Using a Bayesian admixture analysis, our results show that F. spiralis and F. vesiculosus comprise clearly distinct genetic entities (clusters) generally characterized by cosexual and unisexual individuals, respectively. Genetic diversity within each entity suggests that F. spiralis reproduces primarily through selfing while F. vesiculosus is characterized by an endogamous breeding regime. Nevertheless, aberrant sexual phenotypes were observed in each cluster, no diagnostic alleles were revealed and 10% of study individuals were intermediate between the two genetic entities. This pattern can be explained by recent divergence of two taxa with retention of ancestral polymorphism or asymmetrical, introgressive hybridization. However, given (i) coincident monomorphism at three loci in spiralis clusters and (ii) that significantly more intermediates were observed in sympatric stations than in parapatric stations, we argue that interspecific gene flow has occurred after divergence of the two taxa. Finally, we show that whether recently separated or recently introgressive, the divergent breeding systems probably contribute to species integrity in these two taxa.

Bayes Theorem↗
PubMed2004

White matter lesions, cognition, and recurrent hemorrhage in lobar intracerebral hemorrhage.

BACKGROUND: Accumulating evidence suggests that white matter lesions are associated with vascular cognitive impairment. The authors investigated the relationships between white matter lesions, cognitive impairment, and risk of recurrent hemorrhage in a prospectively identified cohort of patients with lobar intracerebral hemorrhage (ICH). METHODS: The authors collected clinical and genetic information on 182 consecutive patients age > or = 55 who had CT scan at admission for lobar ICH. White matter disease was graded on CT in all subjects and on MRI in a subset of 82 patients. All scans were interpreted blinded to clinical information. Survivors were followed for recurrent ICH by telephone interview. RESULTS: White matter damage was common (present on CT in 77%) and severe (advanced CT grade in 32%). White matter damage was correlated with the total number of hemorrhages on gradient-echo MRI and with risk of recurrent ICH. Subjects with cognitive impairment prior to their index ICH were more likely to have severe white matter damage on CT (OR 3.6, 95% CI 1.6 to 8.1, p = 0.003) and more likely to have advanced periventricular hyperintensities on MRI. The relationships between white matter damage and cognitive impairment were similar in the subset of 88 subjects meeting criteria for probable or definite cerebral amyloid angiopathy and remained independent after adjustment for age, cortical atrophy, and APOE genotype. CONCLUSIONS: White matter damage in lobar ICH is common and is associated with cognitive impairment. These data support the possibility that an underlying vasculopathy in lobar ICH patients, possibly cerebral amyloid angiopathy, can cause clinically important vascular dysfunction.

Cerebral Amyloid Angiopathy↗
PubMed2004

Mating system and gene flow in the red seaweed Gracilaria gracilis: effect of haploid-diploid life history and intertidal rocky shore landscape on fine-scale genetic structure.

The impact of haploid-diploidy and the intertidal landscape on a fine-scale genetic structure was explored in a red seaweed Gracilaria gracilis. The pattern of genetic structure was compared in haploid and diploid stages at a microgeographic scale (< 5 km): a total of 280 haploid and 296 diploid individuals located in six discrete, scattered rock pools were genotyped using seven microsatellite loci. Contrary to the theoretical expectation of predominantly endogamous mating systems in haploid-diploid organisms, G. gracilis showed a clearly allogamous mating system. Although within-population allele frequencies were similar between haploids and diploids, genetic differentiation among haploids was more than twice that of diploids, suggesting that there may be a lag between migration and (local) breeding due to the long generation times in G. gracilis. Weak, but significant, population differentiation was detected in both haploids and diploids and varied with landscape features, and not with geographic distance. Using an assignment test, we establish that effective migration rates varied according to height on the shore. In this intertidal species, biased spore dispersal may occur during the transport of spores and gametes at low tide when small streams flow from high- to lower-shore pools. The longevity of both haploid and diploid free-living stages and the long generation times typical of G. gracilis populations may promote the observed pattern of high genetic diversity within populations relative to that among populations.

Diploidy↗
PubMed1987

Reduced sodium concentration and increased sodium-potassium pump activity of erythrocytes in human hypertension.

Erythrocyte Nai, Nai/Ki and ouabain-sensitive and ouabain-insensitive 86Rb uptake (K transport) were measured in whole blood of 16 normotensive and 19 hypertensive white male subjects, within seconds or minutes after withdrawal of blood. Erythrocyte Nai and Nai/Ki were reduced (p less than 0.05), and ouabain-sensitive 86Rb uptake was increased (p less than 0.01) in hypertensive subjects. In a separate group of hypertensive white male subjects, an inverse correlation was found between erythrocyte Nai/Ki and ouabain-binding sites per erythrocyte (r = 0.85, p less than 0.01, n = 9). The abnormalities of erythrocyte cation fluxes in hypertensive subjects are similar to those induced by aldosterone in vascular smooth muscle cells and by glucocorticoid administration in the erythrocytes of human subjects, suggesting similarities in pathogenesis.

Binding Sites↗
PubMed1986

Steroids and related products. LIII. The synthesis of 11-oxa steroids. V. The synthesis of 17-ethynyl-11-oxatestosterone.

The synthesis of 17-ethynyl-11-oxatestosterone, both from 11-oxa-5 alpha-pregnane-3,20-dione and, via a 3,17-dioxygenated 9-oxo 9,12-seco 11-nor 5 alpha-androstane-12-oic ester, from 3 beta-acetoxy-17-hydroxy-5 alpha-pregnan-12-one--two products available from hecogenin--is reported. The new hormone analogue shows significant progestational activity in the Clauberg test and relatively weak activity in a post-coital antifertility assay.

Progesterone Congeners↗
PubMed1983

An in vivo study of the radioprotective effect of diethyldithiocarbamate (DDC).

We have recently shown that diethyldithiocarbamate (DDC) protects plateau-phase cultures of mammalian cells from radiation. Experiments in vivo have extended our knowledge of the radioprotective properties of DDC and show that the LD50/30 in mice is increased from 780 rad to approximately 1400 rad when non-toxic concentrations of DDC are present prior to the irradiation. When DDC is present during irradiation, the pattern of death of the mice is similar to that seen in the absence of the drug and is quite different from that seen in animals dying of a gastrointestinal syndrome (LD50/7 congruent to 1700 rad). To confirm that the LD50/30 data represent bone marrow protection by DDC, we performed bone marrow CFUS assays with and without the presence of DDC, at the time of in vivo irradiation. The DO of the CFUS is increased from 80 rad in the control animals to 120 rad in the animals that have been pretreated with DDC. In experiments using 35S-labelled DDC, the tissue distribution of the drug in tumor-bearing mice indicates a preferential uptake of DDC in kidney, lung and bone marrow compared to tumor tissue. Based on data from both in vitro and in vivo studies, we believe that DDC shows promise as a radioprotective agent and should be considered for clinical trials.

Animals↗
PubMed1979

Steroids and related products. XLVI. The regiospecific alpha-hydroxymethylation of saturated carbonyl compounds via preformed enolate ions. An improved synthesis of 17-hdyroxymethyl 20-keto steroids.

As demonstrated for pregnenolone, saturated ketones are conveniently alpha-hydroxymethylated by their transformation into a lithium enolate and by the reaction of the latter with formaldehydr. The 17-hydroxymethylpregnenolone prepared by this method in very good yield was readily converted to 17-hydroxymethylprogesterone; either by selective acetylation in position 17(1) and subsequent Jones oxidation, followed by hydrolysis, or by conversion to the 4,5-dibromo 3-ketone - by bis(tri-n-butyltin)oxide-bromine oxidation or by dibromination and oxidation with N-bromoacetamde - and debromination with zinc and acetic acid.

Chemical Phenomena↗
PubMed1977

Steroids and related products. XLIII. The synthesis of 17-hydroxymethylprogesterone.

The synthesis of the first 17-hydroxymethyl analogue of a steroid hormone of the progesterone-corticoid group, 17-hydroxymethylprogesterone, is described. The starting material for its preparation was 3alpha,12alpha-diacetoxy-5beta-pregnan-20-one and the 17-hydroxymethyl structure was developed by functionalization of the 17-methyl group of a 17alpha-methyl etio ester by a Barton reaction. Neither 17-hydroxymethylprogesterone nor its acetate shows appreciable progestational activity in the Clauberg-McPhail assay.

Methods↗
PubMed1976

Steroids and related products. XLII. (1) The synthesis of 11-oxa steroids. IV. (2) The synthesis of 17,21-dihydroxy-11-oxa-4-pregene-3,20-dione, an 11-oxa analogue of the 17-hydroxylated glucocorticoids.

The synthesis, from 11-oxa-5alpha-pregnane-3,20-dione, available from hecogenin, of 17,21-dihydroxy-11-oxa-4-pregnene-3,20-dione, the first 11-oxa analogue of corticoid hormones, is described. The acetate of its 1-dehydro derivative, 17-hydroxy-21-acetoxy-1,4-pregnadiene-3,20-dione, analogous in structure to the acetates of prednisone and prednisolone, is an intermediate in the synthesis.

Magnetic Resonance Spectroscopy↗
PubMed1975

Steroids and related products. XLI. (1) the synthesis of 11-oxa steroids. III. (2) 17-acetoxy-11-oxaprogesterone (3).

The synthesis of 17-acetoxy-11-oxaprogesterone, the 11-oxa analogue of the orally active progestational and anti-fertility agent 17-acetoxyprogesterone, is described. An intermediate in the synthesis of 11-oxaprogesterone, 11-oxa-5alpha-pregnane-3,20-dione, available from hecogenin, was used as starting material and the 17-hydroxy function was introduced by a modified Barton oxidation. The new hormone analogue shows only extremely weak progestational activity in the oral Clauberg assay.

Contraceptives, Oral↗