Search PubMed⌕ Search

Biomedical subjects

M Smith

Publications and source records attributed to M Smith.

At least 811 records · Page 45Linked to original sources
PubMed1991

Amino acid substitutions at tryptophan-51 of cytochrome c peroxidase: effects on coordination, species preference for cytochrome c, and electron transfer.

Amino acid replacements of an aromatic residue, Trp-51, which is in contact with the heme of yeast cytochrome c peroxidase have a number of significant effects on the kinetics and coordination state of the enzyme. Six mutants at this site (W51F, W51M, W51T, W51C, W51A, and W51G) were examined. Optical and EPR spectra show that each of these mutations introduces a shift from the 5-coordinate to 6-coordinate form, and slightly increases the asymmetry of the heme ligand field. Conversion from a 6-coordinate high-spin form at pH 5 to a 6-coordinate low-spin form at pH 7 is observed for several of the variants (W51F, W51T, and W51A), while W51G and W51C appear as predominantly low-spin species between pH 5 and 7. Addition of 50% glycerol prevents the facile conversion to the low-spin conformation for W51F, W51T, and W51A, and only W51F can be stabilized in a 5-coordinate configuration by glycerol. For the oxidation of cytochrome c by H2O2, three of the variants (W51F, W51M, and W51T) exhibit values of kcat(app) that are greater than for the wild-type enzyme, while the other mutations give decreased rates of enzyme turnover. Unlike the wild-type enzyme, which functions more efficiently with cytochrome c from yeast than with the horse heart protein, the mutant W51F does not show a preference for substrate from its native organism. The three mutants which exhibit increased values of kcat(app) show a pH optimum at 6.8 compared with that of 5.25 for the wild-type enzyme when measured with horse heart cytochrome c. This shift in pH optimum is not observed with yeast cytochrome c. Construction of single and multiple mutations at Trp-51, Ile-53, and Gly-152 shows that these kinetic properties are not due to natural amino acid variations observed at these sites. Pre-steady-state kinetics show that the bimolecular rate constant for the fast phase of the reaction of the enzyme with H2O2 is only slightly decreased from 3.03 (0.09) X 10(7) to 2.2 (0.1) X 10(7) M-1 s-1 for W51F and to 1.5 (0.1) X 10(7) M-1 s-1 for W51A. The slow phase of the reaction (4.9 s-1) which contributes approximately 30% to the amplitude of the change for the wild-type enzyme is not observed for W51F or W51A.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1991

Domain structure and interaction within the pentafunctional arom polypeptide.

The AROM locus of Aspergillus nidulans specifies a pentafunctional polypeptide catalysing five consecutive steps leading to the production of 5-enolpyruvylshikimate 3-phosphate in the shikimate pathway. Aided by oligonucleotide-mediated site-directed mutagenesis, the whole AROM locus and various overlapping subfragments from within it have been fused to the powerful hybrid trc promoter in the Escherichia coli plasmid pKK233-2. Expression of these subfragments in appropriate aro mutants of E. coli has (a) allowed the delineation of functional domains within the arom polypeptide, (b) shown that the arom polypeptide falls in two independently folding and functioning regions, the N-terminal half specifying 3-dehydroquinate (DHQ) synthase and EPSP synthase and the C-terminus specifying shikimate kinase, biosynthetic 3-dehydroquinase (DHQase) and shikimate dehydrogenase, and (c) strongly suggested an interaction between the DHQ synthase and EPSP synthase domains to stabilise the EPSP synthase activity. In addition an isoenzyme of biosynthetic DHQase, catabolic DHQase, encoded by the QUTE gene of A. nidulans has been transcribed from the trc promoter and upon isopropyl-thio-beta-D-galactoside induction produces up to 20% of the total soluble cell protein.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1991

The efficiency of intestinal calcium absorption is increased in late pregnancy but not in established lactation.

The fractional absorption of calcium (FA-Ca) was measured using a dual non-radioactive Ca isotope technique in 26 control women, 49 women in the last trimester (36 weeks) of pregnancy and 31 of these women in established (20 weeks) lactation. The ratio of the two non-radioactive Ca isotopes was measured, by high precision thermal ionisation mass spectrometry, in urine 12-24 hours after administration and was used to calculate FA-Ca. This is the first study to clearly show that FA-Ca is significantly elevated in late pregnancy but not in established lactation, when compared with control women.

Calcium↗
PubMed1991

An exploration of family and individual profiles following father-daughter incest.

This paper presents the results of a range of psychometric assessments which attempted to identify family and individual variables associated with father-daughter incest. Psychometric self-report measures were used to examine differences between families in which incest had been confirmed and a matched comparison group. Significant differences between the members of the incest and the comparison groups included behavioral and self-esteem problems in the daughters and differences in the familial environments of the two groups. Daughters who had been sexually abused reported lower levels of self-esteem about their intellectual and school status. Mothers in the incest group reported that their daughters had more conduct problems than the comparison mothers. The incest families were generally reported to be higher in conflict and organization and lower in cohesion, expressiveness, and active recreation. No differences between groups were found for levels of marital adjustment, self-esteem in mothers, or overall level of psychopathology in the perpetrators.

Adaptation, Psychological↗
PubMed1991

Safety of immediate treadmill testing in selected emergency department patients with chest pain: a preliminary report.

To determine the feasibility and safety of an immediate, symptom-limited, treadmill test on selected emergency department (ED) patients, a convenience sample of 28 patients underwent an exercise treadmill test (ETT) within the first several hours after hospital arrival using the modified Bruce protocol. Patients were included in the study if they presented with otherwise unexplained chest pain consistent with (but not characteristic for) angina pectoris and had a normal electrocardiogram. A negative ETT was seen in 23 of 28 patients, and five of 28 patients had a positive ETT. No patients had serial enzyme or electrocardiogram evolution suggestive of myocardial ischemia, and all patients with a negative ETT were discharged after a full inpatient evaluation designed to rule out unstable coronary disease. At a mean follow-up period of 6.1 months there has been no cardiac morbidity or mortality in the patients with negative ETTs. It was concluded that early ETTS of selected ED patients with chest pain is safe, and an exercise test administered during the ED visit which is negative can preclude unnecessary hospitalization.

Adult↗
PubMed1991

Errors in reporting cervical screening among public health clinic patients.

This study examines women's knowledge of whether or not they had a cervical smear as part of their examination in a public health clinic for sexually transmitted diseases. Usable interviews were completed with a cluster sample of 318 women. Approximately 56% of the women were not able to correctly report if they had a cervical smear; and 90% of the erroneous responses consisted of reporting a cervical smear when none actually was done. Young women and single women were more likely to report incorrectly. Overall, the results suggest considerable error in overreporting cervical screening in this population.

Adult↗
PubMed1991

A comparison of epidural diamorphine with intramuscular papaveretum following caesarean section.

Following caesarean section carried out under epidural blockade using local anaesthetic only, 40 consenting women were randomly allocated to receive either epidural diamorphine 2.5-5 mg in 10 ml physiological saline and intramuscular saline or epidural saline and intramuscular papaveretum 10-20 mg, dosage depending on weight, when the pain returned. When analgesia was next requested the alternative treatment was given. A visual analogue pain score was recorded before and 15, 30, 60, 120, 180 and 240 min after the first treatment. Respirations were counted and symptoms noted. On the following day the mother was asked whether she preferred the first or the second treatment. Both treatments produced a reduction in pain score but analgesia was significantly better with epidural diamorphine and the duration of action (8.5 +/- 5.2 h) was significantly longer than that following intramuscular papaveretum (4.1 +/- 2.3 h, P < 0.01). Two mothers who received epidural diamorphine initially required no further analgesia. No difference in respiratory rate was noted but side-effects were more frequent with epidural diamorphine. Despite this more women preferred this treatment. Because of enhanced mobility provided by good analgesia epidural diamorphine is worth offering to women following caesarean section.

Journal Article↗
PubMed1991

Vaginosonographic measurement of endometrial thickness in the evaluation of amenorrhea.

The progestin-induced withdrawal bleeding test has often been used in patients with amenorrhea to assess endogenous estrogen (E) production. The endometrial thickness measured by vaginal ultrasonography with a 5 MHz transducer is also dependent on E stimulation of the endometrium. In this study, 70 consecutive patients were evaluated with both the progestin-induced withdrawal bleeding test and a measurement of the endometrial thickness by vaginosonography. An endometrial thickness of 1.5 mm or less was selected to predict absence of bleeding after a progesterone (P) challenge test. This resulted in a sensitivity of 94% with a 95% confidence interval (CI) of 0.70 to 1.00 and a specificity of 93% with a 95% CI of 0.82 and 0.98. The positive and negative predictive values were 79% and 98%, respectively. This study shows that the endometrial thickness measured by vaginosonography can predict the results of the P challenge test in patients with amenorrhea.

Adult↗
PubMed1991

The prevalence, risks, and management of Chlamydia trachomatis infections in fertile and infertile patients from the high socioeconomic bracket of the South African population.

OBJECTIVE: The main objective of the study was to evaluate the prevalence of Chlamydia trachomatis endocervicitis in an infertile population. DESIGN: Forty consecutive patients were enrolled in the study group and 41 in the control group. SETTING: The study was undertaken in the Department of Obstetrics and Gynaecology of the University of the Orange Free State, Bloemfontein, Republic of South Africa. PATIENTS: Infertile white females, visiting an infertility clinic in an academic hospital and fertile white female patients visiting an antenatal clinic. INTERVENTIONS: Endocervical swabs were taken, and monoclonal direct immunofluorescence for C. Trachomatis were done on each. MAIN OUTCOME MEASURES: A difference was expected between the prevalence of C. trachomatis infection in the fertile and infertile population. RESULTS: In the study group, 14(35.9%) positive, 25(64.1%) negative, and 1 fallout were obtained. In the control group, 3 patients (7.32%) tested positive. CONCLUSION: Although no correlation was found between C. trachomatis infection of the female genital tract and the clinical history, it showed a significant correlation with infertility. This justifies routine screening tests and antibiotic treatment of positive infertile couples. Analysis of cost-effectiveness showed that empirical treatment of new infertile couples is justified in some populations.

Chlamydia Infections↗
PubMed1991

A modeling framework for AIDS/HIV nonacute care services.

This paper describes the conceptual structure underlying the microcomputer-based modeling system developed by Mathematica Policy Research, Inc. The modeling system was developed to assist communities in planning nonacute care services for symptomatic human immunodeficiency virus (HIV)-infected persons. The modeling system is based on the assumptions that (1) the characteristics of the HIV epidemic and the availability of nonacute care service vary across communities and (2) combinations of nonacute care services can be appropriately substituted for one another and for hospital-based nonacute care to meet the varying medical and social needs of symptomatic HIV-infected persons.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Pharmacologic interventions after an LD50 cocaine insult in a chronically instrumented rat model: are beta-blockers contraindicated?

STUDY PURPOSE: To evaluate drug management of acute cocaine toxicity in a new animal model. The study null hypothesis was that no drug would affect outcome compared with a placebo control. MODEL: Chronically instrumented, conscious, unrestrained rats subjected to an LD50 dose (1.4 mg/100 g body wt) of IV cocaine. METHODS: Rapid injection of IV cocaine by IV vascular access port followed by injection of therapeutic study drugs. Outcome (survival vs death) with drug treatment was compared with a placebo group. PHARMACOLOGIC INTERVENTIONS: Normal saline placebo (0.2 mL/100 g), diazepam (0.5 mg/100 g), chlorpromazine (0.2 mg/100 g), propranolol (1.0 mg/100 g), labetalol (3.0 mg/100 g), or verapamil (0.1 mg/100 g) was given. There were ten rats in each treatment group. Allocation to treatment groups was nonrandomized. STATISTICAL METHODS: Fisher's exact test. RESULTS: IV injection of cocaine was followed by tonic-clonic seizure activity in all treatment groups. No study drug significantly improved survival compared with the placebo group. However, no animal treated with propranolol survived (P less than .05 vs saline control), and only one of ten animals treated with labetalol survived (P = .14 vs placebo group). CONCLUSION: In this conscious animal model subjected to an LD50 IV cocaine insult, chlorpromazine and diazepam, previously shown to be of value in other animal models, had no effect on survival. Verapamil also did not affect outcome. Outcome was adversely affected by treatment with beta-blocking agents.

Adrenergic beta-Antagonists↗
PubMed1991

The continuity of babble and speech in children with specific expressive language delay.

A natural language sample of babble and words was obtained for 37 two-year-olds with severe specific expressive language delay. Variables derived from this sample were used to predict individual differences in expressive language scores 5 months later. The rate of word use was positively related to language outcome, whereas rate of vowel babble was negatively related to outcome. Together, these two variables accounted for 41% of the variance in language outcome test scores. The addition of one nonlinguistic variable, a measure of behavior problems, allowed the prediction equation to account for over 50% of the variance in expressive language outcome. The single strongest correlate of language outcome was the proportion of consonantal to vowel babble. The degree of social responsiveness of babble and the length of babble were not related to later language scores. These findings indicate that for children with specific expressive language delay, vowel babble competes with expressive language, consonantal babble facilitates expressive language, and the length and social responsiveness of babble are independent of expressive language. The continuity between babble and speech is multidimensional and multidirectional.

Child Language↗
PubMed1991

Family history in developmental expressive language delay.

Familial aggregation of language deficits has been demonstrated in previous studies. However, researchers have typically failed to differentiate subgroups of language-impaired children. The present study used questionnaire data to assess the family history of speech, language, and school problems in a group of young children with developmental expressive language delay (ELD) and in a sample of normally developing children. In contrast to previous studies of language and speech problems, no strong familial component of ELD was found. Further, family history was not predictive of later language development in ELD children. These findings argue against genetic and familial causes of ELD and attest to the importance of differentiating subtypes of early language problems.

Chi-Square Distribution↗
PubMed1991

Mental health services of the rural elderly outreach program.

This paper describes an elderly outreach program (EOP) designed to identify and provide mental health services to the rural elderly. The project integrates a variety of health, mental health, and human service agencies in the planning and delivery of services. Five referral sources are identified and described as well as the assessment, treatment, and referral process. Outcomes are discussed in terms of: characteristics of persons served, ability of the project to identify and deliver mental health services, treatment effectiveness, and cost effectiveness of the project. The EOP seems to have prevented an increase in need for mental health care among Iowans that might have occurred in the program's absence.

Aged↗
PubMed1991

Implementation of mass media community health education: the Forsyth County Cervical Cancer Prevention Project.

The Forsyth County Cervical Cancer Prevention Project (FCP) is a community-based health education project funded by the National Cancer Institute. The target population includes around 25 000 black women age 18 and older who reside in Forsyth County, North Carolina. The overall goal of the program is to prevent mortality from cervical cancer by promoting Pap smears and return for follow-up care when needed. Based on the principles of social marketing, a plan to reach the target population with mass media educational messages through electronic and print channels was developed. Guided by marketing objectives, the target population was divided into relatively discrete segments. The segments included church attenders, patients in waiting rooms of public and selected health providers, female students at local colleges, shoppers, viewers of radio and television, newspaper readers, and business owners and managers. Introduction of the program was based on strategies developed for reaching the target population in each segment with television, radio and print mass media messages. Qualitative assessment of the mass media developed by the program indicated that all forms of communication helped to increase awareness of the program.

Adolescent↗
PubMed1991

Analysis of the invariant Phe82 residue of yeast iso-1-cytochrome c by site-directed mutagenesis using a phagemid yeast shuttle vector.

A phagemid (pING4) carrying the yeast iso-1-cytochrome c gene was constructed which bears all the elements necessary for replication in yeast and bacteria and may be converted into a single-stranded form of DNA for site-directed mutagenesis and nucleotide sequencing. The recombinant vector was used to create a complete set of 19 amino acid changes at position 82, a phylogenetically conserved phenylalanine residue in mitochondrial cytochrome c. All the different forms of cytochrome c were functional in vivo, based upon their ability to support respiration when the mutant proteins were expressed in a yeast strain (otherwise devoid of cytochrome c) grown on non-fermentable carbon sources, with only the strain containing the Cys82 variant having a substantially decreased growth rate. These results are interpreted in terms of the available structural and functional information previously reported on a subset of cytochrome c proteins with mutations at position 82.

Amino Acid Sequence↗
PubMed1991

Expression in Escherichia coli of a synthetic gene coding for horse heart myoglobin.

A gene for expression of horse heart myoglobin in Escherichia coli has been constructed in one step from long synthetic oligonucleotides. The synthetic gene contains an efficient translation initiation signal and used codons that are commonly found in E. coli. Unique restriction sites are placed throughout the gene. It has been inserted in a phagemid vector and is expressed from the lac promoter in E. coli at high efficiency, the soluble heme protein representing approximately 10% of soluble protein. Two versions of horse heart myoglobin were produced with aspartic acid or asparagine at residue 122. Comparison of chromatographic mobilities of these two proteins with authentic horse heart myoglobin identified aspartic acid as the correct residue 122. The availability of this gene, which is designed to facilitate oligonucleotide mutagenesis or cassette mutagenesis, will allow systematic structure-function analysis of horse heart myoglobin.

Amino Acid Sequence↗