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Biomedical subjects

R A Anderson

Publications and source records attributed to R A Anderson.

At least 19 recordsLinked to original sources
PubMed1992

Cell cycle-dependent localization of casein kinase I to mitotic spindles.

Casein kinase I (CKI) is a class of protein kinases ubiquitous to all eukaryotic cells. Recently, cDNA clones encoding several bovine CKI isoforms have been sequenced that show high sequence identity to the HRR25 gene product of the budding yeast Saccharomyces cerevisiae; HRR25 is required for normal cellular growth, nuclear segregation, DNA repair, and meiosis. We have raised polyclonal antibodies to a human erythroid 34-kDa CKI and have sequenced a portion of this kinase. The amino acid sequence identifies the CKI as the alpha-CKI isoform, which is 62% identical to the HRR25 protein kinase. By use of immunofluorescence, the alpha-CKI has been localized to vesicular cytosolic structures and to the centrosome in interphase cells. As cells progress into mitosis, centrospheric staining increases and, in mitosis, alpha-CKI associates with kinetochore fibers. This localization suggests that alpha-CKI, like HRR25, plays a role in the segregation of chromosomes during mitosis and may be cell cycle-regulated both in humans and in yeast.

Amino Acid Sequence↗
PubMed1992

Genetic markers associated with high density lipoprotein cholesterol levels in a biracial population sample.

An explanation for the consistently documented finding of higher levels of high density lipoprotein-cholesterol in black men relative to white men was sought by comparing the frequency of restriction fragment length polymorphism markers present in blacks and in whites at the gene loci coding for the two major apolipoprotein constituents of high density lipoprotein, apolipoproteins AI and AII. The measurements were made in population-based samples of 45 to 54-year-old black (n = 190) and white (n = 370) subjects from the Minnesota Heart Survey for whom lipoprotein levels were available. The mean high density lipoprotein-cholesterol level for black men in the sample (47 +/- 1.5 mg/dl) was higher (P less than 0.05) than that for white men (42 +/- 0.9 mg/dl), while levels in women were not different between races. While the SacI and MspI markers at the apolipoprotein AI-CIII-AIV gene locus showed similar frequencies in blacks compared to whites, the degree of the linkage disequilibrium previously noted between these markers in white subjects was altered in blacks and the minor allele of the PstI marker at this locus was virtually absent in the black subjects (P less than 0.005 vs whites). For black men, there were significant associations of the M2 allele and the S2M2 haplotype at the apolipoprotein AI locus with lower high density lipoprotein-cholesterol levels. The results are consistent with the hypothesis that DNA sequence variations in the vicinity of the apolipoprotein AI-CIII-AIV gene locus are associated with the difference in high density lipoprotein-cholesterol levels between blacks and whites.

Adult↗
PubMed1992

Evaluation of the co-mutagenicity of ethanol and delta 9-tetrahydrocannabinol with Trenimon.

The mutagenic potential of chronic treatments of male CF-1 mice with ethanol and delta 9-tetrahydrocannibinol (THC), and their comutagenic potential with a known mutagenic agent, Trenimon, were examined. This was accomplished by measuring the frequency of dominant lethal mutations arising from mating of treated males with nontreated females. Adult male mice were treated with 5% (v/v) ethanol as part of a liquid diet (28% ethanol-derived calories) for five weeks; 10 mg/kg body weight (p.o.) THC every two days for five weeks; a single injection of Trenimon (0.125 mg/kg, i.p.) on day 28 of diet treatment; and all combinations of treatments. The control group was pair-fed a liquid diet in which isocaloric sucrose replaced ethanol; these males were also given sesame oil (vehicle for THC) and saline (vehicle for Trenimon) on the same schedule as that for the treated males. Neither body weights nor hematocrits were adversely affected by any treatment. Both ethanol and Trenimon treatments resulted in a small (8-9%; p less than 0.05) decrease in testicular weight. The effect of combined treatment with ethanol and Trenimon was roughly additive. Treatment with THC had no effect on testicular weight. Seminal vesicle weights were not affected by any treatment. Treatments were without significant effect on fertility, as measured by the frequency of males producing pregnancies. Ethanol and Trenimon treatments produced approximately 3- and 7-fold increases, respectively in the frequencies of preimplantational loss over that seen for the control group (7.3%), resulting in significant ethanol and Trenimon effects (p less than 0.001). No interactive effects of ethanol and Trenimon treatments were noted. Frequencies of dead fetuses per pregnancy in the ethanol- and Trenimon-treated groups were increased approximately 2.5- and 4-fold, respectively, over the control value of approximately 16%. However, the effect of combined treatments was not greater than that due to Trenimon alone, resulting in Trenimon and ethanol effects (p less than 0.001) and ethanol-Trenimon interaction (p less than 0.001). The calculated mutation index resulting from each treatment yielded significant (p less than 0.001) ethanol- and Trenimon-induced effects. In contrast to effects of ethanol and Trenimon treatments, THC, given alone, or in combination with ethanol and/or Trenimon, had no effect on either preimplantational loss, fetal mortality or the resulting mutation index. The data suggest that chronic ethanol treatment, at levels resulting in minimal fertility impairment, increases the frequency of dominant lethal mutations. In contrast, chronic treatment with THC, as administered in the present study, appears to be without effect.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of Variance↗
PubMed1992

Heterozygosity for the "DN allele" (G533-greater than A) of the beta-hexosaminidase alpha subunit gene identified by direct DNA sequencing in a family with the B1 variant of GM2-gangliosidosis.

A new patient having clinical, pathologic and biochemical features of the exceedingly rate B1 variant of GM2-gangliosidosis is described. This patient, of northern European (non-Ashkenazi) ancestry, is the first affected child of this ethnic background available for molecular genetic analysis; thus, she represented an opportunity to identify a new mutation associated with this phenotype or, conversely, to further characterize the DN allele of the hexosaminidase alpha gene (G533-greater than A) as a more widely distributed mutation not previously observed in this gene pool. As a means of rapid analysis, we report a strategy for PCR amplification and direct DNA sequencing of exon 5 of the hexosaminidase alpha gene, the most frequent site of mutations in this condition. With this technique, the father of the affected child was determined to be heterozygous for the DN allele, while the mother was found to have only the normal sequence in this region. This observation further extends the known geographic and ethnic distribution of this mutation, and suggests the likelihood that the DN allele has been derived by multiple independent mutational events.

Alleles↗
PubMed1992

Efficacy of chromium supplementation in athletes: emphasis on anabolism.

As the biologically active component of glucose tolerance factor (GTF), the essential trace mineral chromium is now being marked to athletes. GTF potentiates insulin activity and is responsible for normal insulin function. Thus, insulin's effects on carbohydrate, fat, and protein metabolism are dependent upon the maintenance of adequate chromium stores. Due to excessive chromium loss and marginal chromium intake, athletes may have an increased requirement for chromium. Therefore, in some circumstances the dietary supplementation of a chromium compound may be efficacious. The restoration and maintenance of chromium stores via supplementation would promote optimal insulin efficiency, necessary for high-level athletic performance. However, potential anabolic effects of enhanced insulin function would likely be marginal, and reports of short-term anabolic increases from the supplementation of an organic chromium compound need to be confirmed.

Animals↗
PubMed1992

Insulin activity: stimulatory effects of cinnamon and brewer's yeast as influenced by albumin.

Cinnamon and Brewer's yeast extracts have been shown to potentiate the action of insulin in isolated adipocytes. In this study, isolated rat epididymal adipocytes were used to evaluate the influence of bovine serum albumin on insulin activity as affected by cinnamon and Brewer's yeast extracts. Albumin at 0.01-0.1% decreased the insulin stimulatory effects of cinnamon from 11.8- to 5.3-fold and 2% albumin decreased this effect to near control levels. Conversely, the insulin-enhancing properties of Brewer's yeast remained low in the presence of less than 0.25% albumin but subsequently increased 2.8-, 4.8- and 5.6-fold in the presence of 0.25, 0.50 and 1.0% albumin, respectively. In the absence of added insulin, increased activity of the insulin-stimulated utilization of glucose by both extracts was observed but only Brewer's yeast extract displayed additive effects when tested at higher insulin levels. Due to the inhibitory and enhancing effects of albumin on the insulin activity of cinnamon and Brewer's yeast, respectively, it is suggested that the effects of albumin be assessed when evaluating the insulin-enhancing effects of other substances using isolated adipocytes.

Adipose Tissue↗
PubMed1992

The effects of exogenous testosterone on sexuality and mood of normal men.

The effects of supraphysiological levels of testosterone, used for male contraception, on sexual behavior and mood were studied in a single-blind, placebo-controlled manner in a group of 31 normal men. After 4 weeks of baseline observations, the men were randomized into two groups: one group received 200 mg testosterone enanthate (TE) weekly by im injection for 8 weeks (Testosterone Only group), the other received placebo injections once weekly for the first 4 weeks followed by TE 200 mg weekly for the following 4 weeks (Placebo/Testosterone group). The testosterone administration increased trough plasma testosterone levels by 80%, compatible with peak testosterone levels 400-500% above baseline. Various aspects of sexuality were assessed using sexuality experience scales (SES) questionnaires at the end of each 4-week period while sexual activity and mood states were recorded by daily dairies and self-rating scales. In both groups there was a significant increase in scores in the Psychosexual Stimulation Scale of the SES (i.e. SES 2) following testosterone administration, but not with placebo. There were no changes in SES 3, which measures aspects of sexual interaction with the partner. In both groups there were no changes in frequency of sexual intercourse, masturbation, or penile erection on waking nor in any of the moods reported. The Placebo/Testosterone group showed an increase in self-reported interest in sex during testosterone treatment but not with placebo. The SES 2 results suggest that sexual awareness and arousability can be increased by supraphysiological levels of testosterone. However, these changes are not reflected in modifications of overt sexual behavior, which in eugonadal men may be more determined by sexual relationship factors. This contrasts with hypogonadal men, in whom testosterone replacement clearly stimulates sexual behavior. There was no evidence to suggest an alteration in any of the mood states studied, in particular those associated with increased aggression. We conclude that supraphysiological levels of testosterone maintained for up to 2 months can promote some aspects of sexual arousability without stimulating sexual activity in eugonadal men within stable heterosexual relationships. Raising testosterone does not increase self-reported ratings of aggressive feelings.

Adult↗
PubMed1991

Cloning and expression of cDNA encoding human lysosomal acid lipase/cholesteryl ester hydrolase. Similarities to gastric and lingual lipases.

Molecular cloning of a full-length cDNA for human lysosomal acid lipase/cholesteryl ester hydrolase (EC 3.1.1.13) reveals that it is structurally related to previously described enteric acid lipases, but lacks significant homology with any characterized neutral lipases. The lysosomal enzyme catalyzes the deacylation of triacylglyceryl and cholesteryl ester core lipids of endocytosed low density lipoproteins; this activity is deficient in patients with Wolman disease and cholesteryl ester storage disease. Its amino acid sequence, as deduced from the 2.6-kilobase cDNA nucleotide sequence, is 58 and 57% identical to those of human gastric lipase and rat lingual lipase, respectively, both of which are involved in the preduodenal breakdown of ingested triglycerides. Notable differences in the primary structure of the lysosomal lipase that may account for discrete catalytic and transport properties include the presence of 3 new cysteine residues, in addition to the 3 that are conserved in this lipase gene family, and of two additional potential N-linked glycosylation sites. Transfection of the cDNA into Cos-1 cells resulted in the expression of acid lipase activity with the substrate range of the native enzyme at a level that was greater than 40 times the endogenous activity.

Amino Acid Sequence↗
PubMed1991

Purification and reconstitution of phosphatidylinositol 4-kinase from human erythrocytes.

A membrane-bound phosphatidylinositol 4-kinase (PtdIns kinase) has been purified to apparent homogeneity from human erythrocytes. Enzyme activity was solubilized from urea-KCl-stripped, inside-out membrane vesicles by 3% Triton X-100. Purification to apparent homogeneity was accomplished by cation-exchange chromatography on phosphocellulose, followed by heparin-acrylamide chromatography. This resulted in a nearly 3900-fold purification of PtdIns kinase activity to a specific activity of 44 nmol min-1 mg-1. The purified enzyme has an Mr of 59,000 on silver-stained SDS-PAGE; however, many preparations also contain 54 kDa and 50 kDa proteins which are related to the 59 kDa protein and have PtdIns kinase activity. Kinetic analysis of the PtdIns kinase indicate apparent Km values of 40 and 35 microM for phosphatidylinositol and ATP, respectively. The purified enzyme has been reconstituted into phospholipid liposomes and shown to phosphorylate phosphatidylinositol.

Electrophoresis, Polyacrylamide Gel↗
PubMed1991

Phosphorylation of protein 4.1 on tyrosine-418 modulates its function in vitro.

Protein 4.1 was initially characterized as a protein that regulates cytoskeletal assembly in erythrocytes. However, recent studies have shown that protein 4.1 is ubiquitous in mammalian cells. Here, we show that protein 4.1 is phosphorylated on tyrosine by the epidermal growth factor receptor (EGFR) tyrosine kinase. The phosphorylation site has been localized to the 8-kDa domain, which has one tyrosine, tyrosine-418. The 8-kDa region is required for the assembly of the spectrin/actin complex, and phosphorylation by EGFR reduced the ability of protein 4.1 to promote the assembly of the spectrin/actin/protein 4.1 ternary complex. Immunoblotting with anti-phosphotyrosine antibodies showed that purified protein 4.1 contained phosphorylated tyrosine, and this increased upon phosphorylation by EGFR. This suggests that tyrosine phosphorylation of protein 4.1 occurs in vivo and may be functionally significant. The tyrosine phosphorylation site is in the center of a sequence motif that is expressed by a differentiation-specific splicing mechanism.

Actins↗
PubMed1991

Casein kinase I is regulated by phosphatidylinositol 4,5-bisphosphate in native membranes.

Casein kinase I activity is present in cells as a cytosolic and a membrane-bound enzyme. Previously, the erythroid membrane-bound casein kinase I was shown to associate with purified integral membrane proteins; this association and protein kinase activity was regulated by phosphatidylinositol 4,5-bisphosphate (PIP2) (Bazenet, C.E., Brockman, J.L., Lewis, D., Chan, C., and Anderson, R.A. (1990) J. Biol. Chem. 265, 7369-7376). Here we show that both the membrane-bound and the cytosolic casein kinase interact with native membranes and that this interaction is regulated by the membrane content of PIP2. On native membranes, casein kinase I activity is potently inhibited by small increases (10-20%) in the membrane content of either exogenously added or intrinsic PIP2. However, the majority of the intrinsic content of PIP2 in isolated membranes does not inhibit casein kinase, suggesting that this PIP2 is not accessible. Regulation of the casein kinases on membranes is sensitive to detergents and to chymotrypsin treatment of membranes.

Animals↗
PubMed1991

Effects of carbohydrate loading and underwater exercise on circulating cortisol, insulin and urinary losses of chromium and zinc.

The effects of carbohydrate loading on relative stress responses of eight male subjects performing intermittent leg exercise at 80% maximum oxygen consumption during headout immersion in 25 degrees C water were tested. Carbohydrate loading increased the number of work cycles completed, with less physical stress compared with that completed following the control diet period. Pre-exercise serum cortisol values were similar on both diets prior to exercise but following exercise control values were greater (1152, 94 vs 858, 77 nmol l-1; mean, SEM). Chromium losses, which have been shown to correlate with stress, were lower during the carbohydrate loading period, 8.6, 1.3 vs 12.4, 2.0 ng h-1, and were correlated with post-exercise serum cortisol. Urinary zinc losses were also lower during carbohydrate loading, while urinary losses of potassium, magnesium and calcium remained constant. Insulin values decreased similarly following exercise in both groups and were not altered by carbohydrate loading. These data demonstrate that carbohydrate loading increases immersion exercise output with less stress as determined by serum cortisol and urinary chromium losses.

Adult↗
PubMed1991

Supplemental-chromium effects on glucose, insulin, glucagon, and urinary chromium losses in subjects consuming controlled low-chromium diets.

The effects of low-chromium diets containing chromium in the lowest quartile of normal intake on glucose tolerance and related variables in 11 females and 6 male subjects were evaluated. Subjects with glucose concentration greater than 5.56 mmol/L but less than 11.1 mmol/L 90 min after an oral-glucose challenge were designated as the hyperglycemic group and the remainder, the control group. Glucose tolerance and circulating insulin and glucagon of the hyperglycemic group all improved during chromium supplementation (200 micrograms/d) whereas those of the control group were unchanged. Glucose and insulin concentrations 60 min after the oral-glucose challenge and the sum of the 0-90 min and 0-240 min glucose values were all significantly lower after chromium supplementation in the hyperglycemic group. These data demonstrate that consumption of diets in the lowest 25% of normal chromium intake lead to detrimental effects on glucose tolerance, insulin, and glucagon in subjects with mildly impaired glucose tolerance.

Adult↗
PubMed1991

Human sperm capacitation and the acrosome reaction.

A model is presented that describes the mechanism of human sperm capacitation and the acrosome reaction. The processes of capacitation and the acrosome reaction are proposed to function in control of the activation/release of acrosomal enzyme(s) involved in sperm penetration through the zona pellucida. During capacitation, the sperm head membranes are biochemically modified, allowing the acrosome reaction to take place when the spermatozoon approaches or reaches the zona pellucida, resulting in the localized activation and release of the appropriate enzyme(s). Further, capacitation is presented as a continuing process that occurs during sperm transport through the female genital tract and is physiologically not completed until the spermatozoon reaches the oocyte (unless the spermatozoa are kept at a particular genital tract site for prolonged periods). The biochemical alterations that occur during capacitation are discussed. It is suggested that extensive modifications in the lipid bilayer structure, e.g. in the cholesterol or phospholipid content, are not part of capacitation because such changes would prematurely destabilize the membranes. Rather, such changes occur during the acrosome reaction. It is also proposed that the human sperm acrosome reaction has many similarities to the somatic cell exocytotic events which occur during the regulated pathway of secretion. One or more oocyte stimuli result in the activation of protein kinases, likely (but not necessarily) via activation of G-protein coupled receptors on the sperm plasma membrane and the formation of second messengers. The kinases phosphorylate and activate proteins, continuing the biochemical cascade that ultimately results in the acrosome reaction. The role of other enzyme systems such as those involved in ion transport, proteolysis, phospholipid metabolism (including that of arachidonic acid) and other metabolic events, is discussed. Calcium ion influx as initiator of the acrosome reaction is reconsidered. The proposed model also takes into consideration the structural events of membrane fusion.

Acrosome↗
PubMed1991

Hospitals as interpretation systems.

In this study of 162 hospitals, it was found that the chief executive officer's (CEO's) interpretation of strategic issues is related to the existing hospital strategy and the hospital's information processing structure. Strategy was related to interpretation in terms of the extent to which a given strategic issue was perceived as controllable or uncontrollable. Structure was related to the extent to which an issue was defined as positive or negative, was labeled as controllable or uncontrollable, and was perceived as leading to a gain or a loss. Together, strategy and structure accounted for a significant part of the variance in CEO interpretations of strategic events. The theoretical and managerial implications of these findings are discussed.

Decision Making, Organizational↗