Molecular analysis of mutation in the human gene for hypoxanthine phosphoribosyltransferase.
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Amino Acid Sequence↗
Biomedical subjects
S Marcus
Publications and source records attributed to S Marcus.
Missense mutations and evolutionary conserved amino acids at the human hypoxanthine phosphoribosyl-transferase locus.
Molecular characterization of in vivo mutation at the human hypoxanthine phosphoribosyltransferase (hprt) locus has revealed a broad spectrum of mutation, both with regard to germ-line mutation in Lesch-Nyhan and gout patients, and somatic mutation in 6-thioguanine resistant T-lymphocytes from healthy individuals. The pattern of missense mutation shows a non-random distribution with a preferential location to codons for amino acids which are identical in human and the two parasites Schistosoma mansoni and Plasmodium falciparum. Although these 'evolutionary conserved' amino acids account for only 32% of the amino acids in the human hprt protein, they are involved in 76% of the missense mutations at the hprt locus in human T-lymphocytes, 67% in Lesch-Nyhan patients (with severe hprt-deficiency), but only 43% in gout patients (with partial hprt deficiency). This observation supports the notion that evolutionary conserved amino acids constitute functionally important sites in the hprt enzyme, and missense mutations affecting these amino acids will often lead to complete loss of enzyme activity. Substitutions of 'non-conserved' amino acids cause less severe hprt-deficiency (as seen in the gout patients), or may even escape clinical diagnosis. These considerations are important for the understanding of structure-activity relationships in the hprt protein, possible differences between hprt mutational spectra in germ-line and somatic cells, and the mutational spectra induced by specific exogeneous mutagens.
Amino Acid Sequence↗
Ethnic heterogeneity and cystic fibrosis transmembrane regulator (CFTR) mutation frequencies in Chicago-area CF families.
The identification of a common mutation, delta F508, in the CFTR gene allowed, for the first time, the detection of cystic fibrosis (CF) carriers in the general population. Further genetic studies revealed > 100 additional disease-causing mutations in this gene, few of which occur on > 1% of CF chromosomes in any ethnic group. Prior to establishing counseling guidelines and carrier risk assessments, we sought to establish the frequencies of the CFTR mutations that are present in CF families living in the Chicago area, a region notable for its ethnic heterogeneity. Our sample included 283 unrelated CF carriers, with the following ethnic composition: 78% non-Ashkenazi Caucasians, 5% Ashkenazi, 9% African-American, 3% Mexican, 0.3% Native American, and 5% mixed ancestry. When a panel of 10 mutations (delta F508, delta I507, G542X, G551D, R553X, S549N, R1162X, W1282X, N1303K, and 1717-1G-->A) was used, detection rates ranged from 75% in non-Ashkenazi Caucasians to 40% in African-Americans. These data suggest that the goal of screening for 90%-95% of CF mutations may be unrealistic in this and other, similar U.S. populations.
Base Sequence↗
[Communicating literary aspects by non-literary means: references to the unconscious in William Wordsworth].
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Freudian Theory↗
Smoking initiation in the United States: a role for worksite and college smoking bans.
Data from four National Health Interview Surveys were combined, and a birth-cohort analysis was undertaken to determine the age when regular smoking is initiated. By the age of 25 years, most smokers have already become regular smokers. Among men, the proportion of each birth cohort who become regular smokers has declined at a rate of about 1.0% for each year of birth since 1945. There has been no identifiable decline in successive birth cohorts of women. For those born in the most recent birth cohorts, there was no sex difference in the proportion who became regular smokers. The proportion of smokers beginning to smoke during the secondary-school years (less than or equal to 18 years of age) has increased steadily, especially among people with a high-school education or less. However, in the latest birth cohort (1960-1962), over 18% of ever smokers with at least a high-school education did not start to smoke regularly until their young-adult years (19-24 years of age). If the effect of tobacco-education programs in the schools is to postpone the uptake of regular smoking, it is important to have tobacco policies in place in other areas of society that will maintain non-smoking behavior through the young-adult years. Accordingly, the banning of smoking in colleges, universities, and worksites, as well as in secondary schools, may significantly decrease the proportion of young people who eventually become regular smokers.
Adult↗
The fragile X mutation does not have any major effect on the expression of the hypoxanthine phosphoribosyltransferase (HPRT) locus in human fibroblasts.
The possible influence of the fragile X mutation at Xq27 on the expression of the neighbouring gene (at Xq26) for hypoxanthine phosphoribosyl transferase (HPRT) was studied by determination of the levels of HPRT-RNA and HPRT enzyme activity in fibroblast cell cultures from 7 fragile X patients. These levels were lower (although not statistically significantly lower) than in normal fibroblast cultures. Hence, these data do not support the notion of a major effect of the fragile X mutation on the expression of the HPRT gene.
Cells, Cultured↗
Hand impairment assessment: some suggestions.
A critical review is made of hand impairment assessment from an occupational therapy and ergonomics perspective. This article concludes that a concerted move be made towards a standardisation of hand function assessment. Also, to make meaningful quantitative statements concerning performance of arthritic people, comparison with 'fit' elderly cohorts is necessary. There is a great need for normative data on strength and joint range from elderly people. Finally, an innovative application of motion-time-measurement is proposed as a potential avenue for future hand function assessment of elderly and disabled people.
Journal Article↗
Choroidal blood flow in diabetic retinopathy.
The ocular hemodynamics in diabetic patients with increasingly severe retinopathy have been evaluated using a non-invasive computerized methodology. In a group of 19 healthy volunteers the mean ophthalmic arterial pressure and the ocular pulsatile blood flow were 83 +/- 2.4 mmHg and 648 +/- 42 microliters min-1 respectively. Nine diabetics with no apparent retinopathy had ophthalmic pressures and pulsatile blood flows similar to those in the control subjects. In 11 diabetic patients with background retinopathy the mean pulsatile blood flow was 471 +/- 70 microliters min-1. Thirteen diabetics with proliferative retinopathy had a pulsatile blood flow of 210 +/- 37 microliters min-1 and abnormally low ophthalmic arterial pressures. The results provide evidence that the choroidal blood flow decreases with the severity of the retinopathy in diabetes due to increased vascular resistance and a decreased ocular perfusion pressure.
Adult↗
Raynaud's syndrome. Using a range of therapies to help patients.
Raynaud's syndrome is a common medical problem. Approach to diagnosis must involve a search for underlying causes. Treatment includes avoidance of precipitating factors, biofeedback, and possibly pharmacologic therapy, after careful consideration of risks.
Humans↗
Degradation of a-factor by a Saccharomyces cerevisiae alpha-mating-type-specific endopeptidase: evidence for a role in recovery of cells from G1 arrest.
Mating response between opposite mating types of Saccharomyces cerevisiae is dependent upon alpha factor, a tridecapeptide, and a-factor, an isoprenylated, methyl esterified dodecapeptide whose interaction with the alpha target cell has not been characterized. We report on the first biochemical and physiological evidence of an alpha-mating-type-specific a-factor-degrading activity. Radioiodinated a-factor was used to identify the a-factor-degrading activity, which is cell associated, endoproteolytic, and not required for response to pheromone. a-factor degradation was not energy dependent, nor did it require pheromone internalization or interaction with its receptor. Phenylmethylsulfonyl fluoride and tosyl-L-arginyl-methyl ester inhibited degradation of a-factor and increased the time required by alpha cells to recover from a-factor-induced growth arrest and morphological alteration, providing evidence that a-factor degradation plays a role in the recovery of alpha cells from the pheromone response.
Amino Acid Sequence↗
Significance of C-terminal cysteine modifications to the biological activity of the Saccharomyces cerevisiae a-factor mating pheromone.
We have undertaken total synthesis of the Saccharomyces cerevisiae a-factor (NH2-YIIKGVFWDPAC[S-farnesyl]-COOCH3) and several Cys-12 analogs to determine the significance of S-farnesylation and carboxy-terminal methyl esterification to the biological activity of this lipopeptide mating pheromone. Replacement of either the farnesyl group or the carboxy-terminal methyl ester by a hydrogen atom resulted in marked reduction but not total loss of bioactivity as measured by a variety of assays. Moreover, both the farnesyl and methyl ester groups could be replaced by other substituents to produce biologically active analogs. The bioactivity of a-factor decreased as the number of prenyl units on the cysteine sulfur decreased from three to one, and an a-factor analog having the S-farnesyl group replaced by an S-hexadecanyl group was more active than an S-methyl a-factor analog. Thus, with two types of modifications, a-factor activity increased as the S-alkyl group became bulkier and more hydrophobic. MATa cells having deletions of the a-factor structural genes (mfal1 mfa2 mutants) were capable of mating with either sst2 or wild-type MAT alpha cells in the presence of exogenous a-factor, indicating that it is not absolutely essential for MATa cells to actively produce a-factor in order to mate. Various a-factor analogs were found to partially restore mating to these strains as well, and their relative activities in the mating restoration assay were similar to their activities in the other assays used in this study. Mating was not restored by addition of exogenous a-factor to a cross of a wild-type MAT alpha strain and a MATaste6 mutant, indicating a role of the STE6 gene product in mating in addition to its secretion of a-factor.
Amino Acid Sequence↗
Soft plastic bread packaging: lead content and reuse by families.
The presence of lead in labels painted on soft plastic bread packaging was evaluated. Lead was detected on the outside of 17 of 18 soft plastic bread bags that were analyzed, with an average of 26 +/- 6 mg per bag with lead. Of 106 families questioned, 16 percent of respondents reported turning the bags inside out before reusing for food storage, thus putting food in contact with the lead paint. We estimate that a weak acid, such as vinegar, could readily leach 100 micrograms of lead from a painted plastic bag within 10 minutes. Further, lead and other metals painted on food packaging of any type becomes part of the municipal waste stream subject to incineration and to land-filling. The use of lead in packaging presents an unnecessary risk to public health.
Bread↗
Eosinophilia, lead poisoning and Toxacaris canis infection in children.
This report identifies Toxacaris canis infestation as a frequent cause of eosinophilia in both lead-poisoned and nonlead-poisoned children. An overall prevalence of 23% was recorded. Literature reveals a vast difference in regional prevalence of T canis infestations and emphasizes the need for the practitioner to be aware of the community in which he/she practices. Because of the adverse neuropsychological effects from T canis infestations, doctors in areas where there is a high prevalence of the disease should consider screening for infestations and conducting psychological testing of infested children.
Animals↗
Total in vitro maturation of the Saccharomyces cerevisiae a-factor lipopeptide mating pheromone.
The a-factor mating pheromone, produced by Saccharomyces cerevisiae a haploid cells, is post-translationally modified in a manner analogous to that of the ras proto-oncogene product. A consensus C-terminal amino acid sequence, -CAAX (C is cysteine, A is aliphatic amino acid, and X is any amino acid), is the target of these modifications, which include isoprenylation (essential for Ras function), proteolysis of the -AAX sequence, and carboxy methyl esterification. Recently, the RAM/DPR1 gene product was shown to be a component of the activity responsible for isoprenylation of both Ras and a-factor. In this report, we present an in vitro assay which not only detects a-factor isoprenylation, but also proteolysis and carboxy methyl esterification, and directly demonstrates, biochemically, the order of these processing events. This a-factor maturation assay may prove useful for screening agents which block any of the steps involved in the post-translational modification of the a-factor and Ras -CAAX sequences. Such agents would be potential anti-Ras-related cancer therapeutic drugs.
Amino Acid Sequence↗
Beta-interferon therapy in patients with poor-prognosis Kaposi sarcoma related to the acquired immunodeficiency syndrome (AIDS). A phase II trial with preliminary evidence of antiviral activity and low incidence of opportunistic infections.
STUDY OBJECTIVE: To study the efficacy of high doses of beta-ser-interferon (recombinant human 17-serine beta-interferon) in patients with human immunodeficiency virus (HIV) infection and Kaposi sarcoma. DESIGN: A nonrandomized, controlled trial of two high-dose regimens of beta-ser-interferon administered until tumor progression, toxicity, or an acquired immunodeficiency syndrome (AIDS)-defining opportunistic infection occurred. SETTING: An AIDS treatment clinic at a tertiary care center. PATIENTS: A sequential sample of 39 patients with biopsy-proven, AIDS-related Kaposi sarcoma were enrolled during a 2-year period. Thirty-eight patients were evaluable for response. Most patients (35 of 38) had one or more of the following clinical or laboratory predictors for a poor response to interferon therapy: HIV p24 antigenemia, low CD4 cell numbers, elevated beta 2-microglobulin levels, previous opportunistic infections, or previous systemic chemotherapy. INTERVENTIONS: Beta-ser-interferon was self-administered subcutaneously at home 5 days per week. The first 21 patients used 90 million IU/d, and the remainder used 180 million IU/d. MEASUREMENTS AND MAIN RESULTS: Six patients (16%) had a major clinical response, and 15 (39%) had stable disease for prolonged periods. Toxicities were minimal; the major toxicity was a skin reaction at the injection site. The HIV p24 antigen level declined more than 50% in 8 of the 19 patients with initial values greater than 50 pg/mL. Antiretroviral activity and antitumor activity were seen only in patients with normal initial beta 2-microglobulin levels. Minimal changes were seen in CD4 and CD8 cell numbers. Only 1 patient had an opportunistic infection while on study, but five other patients developed infections after treatment was discontinued for an incidence of six opportunistic infections in 285 patient-observation months. CONCLUSIONS: The high doses of interferon did not improve the major response rate in patients with poor-prognosis, AIDS-related Kaposi sarcoma. There was, however, a suggestion of antiviral activity in patients with normal beta 2-microglobulin levels and a decrease in the expected incidence of opportunistic infections.
Acquired Immunodeficiency Syndrome↗
Synthesis of biologically active analogs of the dodecapeptide a-factor mating pheromone of Saccharomyces cerevisiae.
A number of dodecapeptides with the sequence YIIKGVFWDPAC were synthesized using solid phase peptide synthesis. The purity of the crude cleavage product was found to be directly related to the cysteine protecting group and the conditions employed for cleavage of the peptide from the resin. When 4-methyl-benzyl cysteine was used, complete deprotection was only achieved with low-high HF conditions at temperatures of 10 degrees-25 degrees, whereas milder conditions could be used for dodecapeptides containing ethyl cysteine or acetamidomethyl cysteine. In several syntheses the biological activity of the crude cleavage product greatly exceeded the biological activity of a purified major peptide component. The high activity found in the crude cleavage peptide was probably due to minor peptide side products in which the cysteine sulfur was alkylated by hydrophobic species during HF treatment. Two dodecapeptides, YIIKGVFWDPAC and YIIKGFWDPAC(Ethyl), had significant a-factor activity against MAT alpha strains of Saccharomyces cerevisiae. These peptides represent the first synthetic analogs with a-factor activity.
Amino Acid Sequence↗
Molecular analysis of mutation at the human hprt locus.
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Animals↗
Intestinal colonization with Clostridium difficile in infants up to 18 months of age.
The faecal colonization with Clostridium difficile was investigated among 343 infants during their first 18 months of life. Rectal swabs were taken at the ages of 6 days, 6 weeks, 6 months, 11 months and 18 months. About 25% of the children were colonized with Clostridium difficile between 6 days and 6 months of age. The colonization rate decreased to 3% at 18 months of age. The rate of strains producing cytotoxin was low in infants less than 6 months of age, but at that age about half of the strains isolated were toxin-producing. Breast-fed children were significantly less often colonized with Clostridium difficile than were bottle-fed infants, both at 6 weeks of age (21% versus 47%, p less than 0.05) and at 6 months of age (19% versus 39%, p less than 0.001). Colonization with Clostridium difficile at 6 months of age was associated with a greater frequency of diarrhoeal disease between 6 and 11 months of age (27% versus 16%, p less than 0.05). This association was even more pronounced when the bacteria persisted at 11 months of age (54%, p less than 0.01). Antibiotic therapy could not be demonstrated to influence colonization with Clostridium difficile at any age.
Age Factors↗