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Biomedical subjects

A Segall

Publications and source records attributed to A Segall.

At least 19 recordsLinked to original sources
PubMed2001

Perceived control in relation to socioeconomic and behavioral resources for health.

Perceived control is a personality characteristic that contributes to well-being, but few studies have attempted to integrate the functions of perceived control with those of other determinants of health. This research tested two hypotheses about the functions of perceived control: (a) individual differences in perceived control would account for socioeconomic differences in self-rated health status; (b) performance of health-related behaviors would account for the health benefits of perceived control. Using data from adult, nonproxy respondents in the National Population Health Survey of Canada (1995; n = 11, 110), confirmatory factor analysis supported a measurement model of self-rated health status composed of two correlated factors: physical health (i.e., chronic conditions. restricted activities, self-rated general health, physical functional capacity) and mental health (i.e., distress, depression). Structural equation modeling supported the first hypothesis, but not the second, regarding perceived control as a determinant of self-rated physical and mental health. Health-related behaviors partially mediated age differences in self-rated health, but different behaviors functioned in this way for men than for women. The findings suggest that psychological process, that of perceiving control over life events, underlies social inequality in health. Health-related behaviors appear not to serve as the primary mechanism through which perceived control influences health.

Adolescent↗
PubMed2001

Dissolution test for silymarin tablets and capsules.

Silybine (SBN), isosilybine (ISBN), silycristine (SCN), silydianine (SDN), and taxifoline (TXF) are the main active flavonoids commonly found in the dried fruits of Silybum marianum, Gaertner (Compositae). Concentrations of these compounds, except TXF, are usually expressed together as silymarin content. This paper describes a simple dissolution test developed to estimate silymarin (Sl) in pharmaceutical formulations. Five commercial products were tested using this new method (including tablets, sugar tablets, and capsules): two from Argentina, one from Brazil, one from Spain, and one from Italy. Results demonstrated that, provided the dosage form disintegrates, amounts dissolved range from 50 to 90% of the labeled value. Products were analyzed by high performance liquid chromatography (HPLC) and UV spectrophotometry.

Antioxidants↗
PubMed2000

Dissection of bacteriophage lambda site-specific recombination using synthetic peptide combinatorial libraries.

A wide variety of tools have been used to dissect biochemical pathways, inhibitors being chief among them. Combinatorial approaches have made the search for inhibitors much more efficient. We have applied such an approach to identify hexapeptides which inhibit different steps in a site-specific recombination reaction mediated by the bacteriophage lambda integrase protein. Integrase's mechanism is still incompletely understood, in large part because several pathway intermediates remain hard to isolate. Integrase-catalyzed recombination is very efficient, but if blocked, it is highly reversible to substrates; this combination makes some intermediates exceedingly transient. We have used synthetic peptide combinatorial libraries to screen for hexapeptides that affect the recombination pathway at different stages, and have identified two families of peptides: one probably blocks DNA cleavage, the other may stabilize the Holliday junction intermediates. These peptides do not resemble parts of integrase or any of the other helper functions in the pathway. The deconvolution of hexapeptide libraries based both on inhibition of an enzymatic reaction as well as on accumulation of reaction intermediates is a novel approach to finding useful tools for dissecting a biochemical pathway.

Alanine↗
PubMed2000

A stability-indicating HPLC method to determine cyproterone acetate in tablet formulations.

A simple and accurate liquid chromatographic method was developed to estimate cyproterone acetate (CA) in pharmaceuticals. The drug was chromatographed on a reversed-phase C18 column. Eluents were monitored at a wavelength of 254 nm utilizing a mixture (60:40) of acetonitrile and water. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method was statistically validated for linearity, accuracy, precision, and selectivity. Due to its simplicity and accuracy, we believe that the method can be used for routine quality control analysis. No specific sample preparation is required except for the use of a column guard and a suitable prefilter attached to the syringe.

Androgen Antagonists↗
PubMed1999

The geometry of a synaptic intermediate in a pathway of bacteriophage lambda site-specific recombination.

Bacteriophage lambda uses site-specific recombination to move its DNA into and out of the Escherichia coli genome. The recombination event is mediated by the phage-encoded integrase (Int) at short DNA sequences known as attachment ( att ) sites. Int catalyzes recombination via at least four distinct pathways, distinguishable by their requirements for accessory proteins and by the sequence of their substrates. The simplest recombination reaction catalyzed by Int does not require any accessory proteins and takes place between two attL sites. This reaction proceeds through an intermediate known as the straight-L bimolecular complex (SL-BMC), a stable complex which contains two attL sites synapsed by Int. We have investigated the orientation of the two substrates in the SL-BMC with respect to each other using two independent direct methods, a ligation assay and visualization by atomic force microscopy (AFM). Both show that the two DNA substrates in the complex are arranged in a tetrahedral or nearly square planar alignment skewed towards parallel. The DNA molecules in the complex are bent.

Attachment Sites, Microbiological↗
PubMed1999

Development and validation of a reversed-phase liquid chromatographic method for analysis of estradiol valerate and medroxyprogesterone acetate in a tablet formulation.

A simple and accurate liquid chromatographic method was developed for estimation of estradiol valerate and medroxyprogesterone acetate in pharmaceuticals. Drugs were chromatographed on a reverse phase C18 column, using a mixture (30:70) of ammonium nitrate buffer and acetonitrile and eluants monitored at a wavelength of 280 nm. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method was statistically validated for its linearity, accuracy, precision and selectivity. Due to its simplicity and accuracy, the authors believe that the method may be used for routine quality control analysis. It does not require any specific sample preparation except the use of a column guard before the analytical column and suitable prefilter attached to the syringe prior to injection.

Calibration↗
PubMed1997

The effectiveness of a hospital-based program to promote exclusive breast-feeding among low-income women in Brazil.

OBJECTIVES: This study examined the effectiveness of a hospital program to promote exclusive breast-feeding in Santos, Brazil. METHODS: In a prospective design, women who delivered at a hospital with an active breast-feeding promotion program (n = 236) were compared with women who delivered at a nearby control hospital (n = 206). RESULTS: The two groups had similar demographic characteristics and previous breast-feeding histories. Exposure to breast-feeding activities, assessed by maternal recall prior to discharge, was universally high at the program hospital and universally low at the control hospital. Multivariate survival analysis showed that exclusive breast-feeding lasted 53 days longer among women who delivered at the program hospital. CONCLUSIONS: Hospital-based breast-feeding promotion programs may be effective in extending the duration of exclusive breast-feeding.

Adult↗
PubMed1996

Seniors' attributions for task performance difficulties: implications for feelings of task efficacy.

Some seniors face difficulties carrying out simple everyday tasks such as opening containers and turning doorknobs. This study began with the premise that seniors' appraisals about such difficulties may have consequences for feelings of task efficacy (e.g., feelings of control and optimism). Attributions to poor product design (an external/environmental factor) and to limitations (an internal/personal factor) were considered in addition to joint attributions to both factors. After controlling for health and gender, type of attribution for task difficulties was found to relate to feelings of task efficacy. Overall, the results suggest that seniors may be advantaged by viewing their performance difficulties as a consequence of poor product design. Compared to their counterparts, these individuals reported the highest levels of control, ability to cope, optimism, and beliefs about overcoming problems. Individuals who made joint attributions reported feeling most helpless and unable to cope with the present problems.

Activities of Daily Living↗
PubMed1994

Construction of chromosomal rearrangements in Salmonella by transduction: inversions of non-permissive segments are not lethal.

Homologous sequences placed in inverse order at particular separated sites in the bacterial chromosome (termed "permissive") can recombine to form an inversion of the intervening chromosome segment. When the same repeated sequences flank other chromosome segments ("non-permissive"), recombination occurs but the expected inversion rearrangement is not found among the products. The failure to recover inversions of non-permissive chromosomal segments could be due to lethal effects of the final rearrangement. Alternatively, local chromosomal features might pose barriers to reciprocal exchanges between sequences at particular sites and could thereby prevent formation of inversions of the region between such sites. To distinguish between these two possibilities, we have constructed inversions of two non-permissive intervals by means of phage P22-mediated transduction crosses. These crosses generate inversions by simultaneous incorporation of two transduced fragments, each with a sequence that forms one join-point of the final inversion. We constructed inversions of the non-permissive intervals trp ('34) to his ('42) and his ('42) to cysA ('50). Strains with the constructed inversions are viable and grow normally. These results show that our previous failure to detect formation of these inversions by recombination between chromosomal sequences was not due to lethal effects of the final rearrangement. We infer that the "non-permissive" character of some chromosomal segments reflects the inability of the recombination system to perform the needed exchanges between inverse order sequences at particular sites. Apparently these mechanistic problems were circumvented by the transductional method used here to direct inversion formation.

Chromosome Inversion↗
PubMed1994

Antimicrobial activity of 5,6-dihydrobenzo-[a]-carbazoles.

A new series of 5,6-dihydrobenzo[a]carbazoles was synthesized, some showing good antibacterial activity. The presence of a dialkylamino ethyl chain on the 2-, 3- or 4-O-substituent seems to be critical for such activity.

Anti-Infective Agents↗
PubMed1991

Gender differences in health related behaviour: some unanswered questions.

To date, no single explanation has accounted for discrepancies between male and female morbidity rates and health care utilization patterns. The sociomedical approach to sex/gender differences in health related behaviour has generated a variety of hypotheses. However, despite extensive study, many unanswered questions remain. The findings of this study fall short of offering conclusive evidence as to the causes of variations in morbidity and health services use between women and men. However, an effort is made to identify the salience of social role and related social status characteristics (e.g. labour force participation) in accounting for variation in health, illness and sick role behaviour. This paper utilizes data from the 1983 Winnipeg Area Study. Findings of this study raise questions about the adequacy of current concepts and measures for studying sex/gender differences in health related behaviour. The study concludes with a critical discussion of conceptual, methodological and theoretical issues which must be considered in our efforts to advance our understanding of why women experience greater longevity, but experience greater morbidity and make more extensive use of health services.

Adult↗
PubMed1990

A community survey of self-medication activities.

The objectives of this research were to explore lay medication activities as an aspect of self-managed health care in the Canadian context and to identify the sociodemographic and sociomedical characteristics of those who engage in self-medication. Interview data were collected in 1983 from a random cross-sectional sample of 524 adult residents living in Winnipeg, Canada. Respondents were questioned about the types of medicines they keep in their home (both prescribed and nonprescribed), self-treated symptomatic conditions; recent medication activities, the use of prescribed medicine in self-treated illness episodes, and the use of home remedies. This study contributes to a growing body of international evidence that has demonstrated that self-medication is a vital part of daily self-care behavior. For the most part, the results are comparable to those reported by previous British and U.S. studies of self-medication. Winnipeg residents were found to be active self-care providers who engage in a variety of self-medication practices. The study also illustrates the fact that the altered use of prescribed drugs (particularly by those with higher levels of formal education) is an important aspect of self-medication behavior. These findings have clear implications for health care practitioners.

Cross-Sectional Studies↗