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Biomedical subjects

M L Field

Publications and source records attributed to M L Field.

15 recordsLinked to original sources
PubMed1998

Targeted intervention research studies on sexually transmitted diseases (STD): methodology, selected findings and implications for STD service delivery and communications.

OBJECTIVE: To report the findings of qualitative studies designed for use in improving sexually transmitted disease (STD) programs. The studies explore illness conceptions and treatment behaviors for STD in five African countries. These targeted intervention research (TIR) studies were performed on clinic-based and community-based samples in representative communities and utilized a variety of qualitative research methods (e.g. in-depth and key informant interviews, focus group discussions). FINDINGS: Study findings revealed that community members' explanations of symptoms, classification of illnesses, and perceptions of whether symptoms are pathological or serious influence individual health-care-seeking behaviors. Data also showed that local terms for STD are often disparaging and do not fit into biomedical designations. STD patient care-seeking frequently reflects an ordered, albeit loosely constructed, process of elimination in pursuit of symptom relief, wherein alternative treatments are tried and proven effective or abandoned. CONCLUSIONS: The TIR studies highlight the importance of community-specific strategies aimed at increasing prompt care seeking at qualified biomedical facilities. Information from study data should lead programs to sensitize health professionals to community understanding about STD and to design services and communication programs that are meaningful and appropriate to local contexts.

Developing Countries↗
PubMed1996

Intracellular [Ca2+] staircase in the isovolumic pressure--frequency relationship of Langendorff-perfused rat heart.

Fluorescence and 31P magnetic resonance spectroscopy have been used to monitor simultaneously, the [Ca2+]i staircase and high energy phosphate metabolism in isolated Langendorff-perfused rat heart paced at 2, 4 and 6 Hz. In order to investigate further the relationship between high energy phosphate metabolism and the calcium staircase we perturbed the intracellular phosphocreatine (PCr)/creatine concentration with dietary beta-guanidinopropionic acid (beta-GPA). We have observed that: (a) At 2 Hz stimulation, the ventricular -Ca2+-i-dependent fluorescence decay is biexponential and continues to decay throughout the interstimulus interval; (b) at 4 Hz and 6 Hz, the [Ca2+]i decay is monoexponential; (c) end-diastolic [Ca2+]i is elevated at higher stimulation frequencies; (d) net [Ca2+]i flux per cycle is reduced at higher stimulation frequencies and is therefore correlated inversely with stimulation frequency and end-diastolic [Ca2+]i; (e) "heart rate * [Ca2+]i flux product" which is a measure of the work done in cycling calcium, is directly proportional to stimulation frequency; (f) the hysteresis between peak ventricular isovolumic pressure and peak fluorescence is decreased at higher stimulation frequencies; (g) no correlation was detected between the PCr/ATP ratio and stimulation frequency; (h) despite a 60% decrease in the myocardial PCr/ATP ratio after beta-GPA feeding, rat heart is able to maintain the end-diastolic [Ca2+]i-dependent fluorescence, and therefore the [Ca2+]i staircase relationship, similar to that of normal rat heart. In conclusion, using a physiological stimulation range and substrate supply we have observed a negative staircase of both [Ca2+]i and isovolumic pressure in whole heart which is not hypoxic. We propose that the inability of the sarcoplasmic reticulum to sequester sufficient cytosolic calcium at high stimulation frequencies leads to an elevation in end-diastolic [Ca2+]i, decreased net calcium flux per cycle resulting in a negative [Ca2+]i staircase and thus a negative isovolumic pressure-frequency relationship. We did not detect any correlation between steady-state high energy phosphate metabolism and stimulation frequency.

Adenosine Triphosphate↗
PubMed1994

Intracellular Ca2+ transients in isolated perfused rat heart: measurement using the fluorescent indicator Fura-2/AM.

We have investigated the nature of Fura-2/AM loading into isolated perfused rat heart and the temporal and kinetic relationship between left ventricular [Ca2+]i dependent fluorescence and isovolumic pressure. The contribution of hydrolysed mitochondrial matrix Fura-2 fluorescence to that measured from the surface of the heart was estimated to be 43.9 +/- 5.5% by the addition of 100 microM Mn2+ to the perfusate. Maximum endothelial Fura-2 fluorescence ratio, estimated by the addition of 3 microM bradykinin to the perfusate, was found to constitute 33.6 +/- 2.7% of the maximum myocardial Fura-2 fluorescence ratio. Approximately 11.2% of the 340 nm surface fluorescence was insensitive to 20 mM Mn2+ in the presence of ionomycin (3 microM) and therefore indicates the degree of partial hydrolysis of Fura-2/AM. Thus, depending on the contribution of endothelial Fura-2 fluorescence at a physiological endothelial calcium concentration, cytosolic fluorescence may comprise between 11-45% of the total cellular fluorescence at 340 nm. Net tissue interference of the Fura-2 fluorescence ratio by NADH emission and myoglobin absorption remained unaltered, providing the oxygenation state of the tissue was unaltered throughout the experiment. The [Ca2+]i dependent fluorescence decay from peak systole was best fitted to a biexponential decay with fast and slow rate constants of 18.08 +/- 1.97 s-1 and 0.23 +/- 0.02 s-1, respectively. In addition, a phase shift was observed between temporal and kinetic measurements of the left ventricular isovolumic pressure and calcium dependent fluorescence traces during a contraction-relaxation cycle. We conclude that despite imperfect Fura-2/AM loading, the temporal and kinetic characteristics of intracellular [Ca2+] transients in normal isolated perfused rat heart are similar to those reported in more controlled preparations such as isolated myocytes and cardiac trabeculae.

Animals↗
PubMed1994

Alterations in the myocardial creatine kinase system during chronic anaemic hypoxia.

OBJECTIVE: The aim was to use a model of chronic anaemia in the rat, in which there is an increase in cardiac mitochondrial creatine kinase activity (mito-CK) per mitochondrion, to test the hypothesis that creatine stimulated respiration in saponin skinned fibres is correlated with mito-CK activity. In order to discuss the altered regulation of mitochondrial respiratory rate in the context of other metabolic alterations, steady state metabolite concentrations and maximum extracted activities of regulatory enzymes in glycolysis were also investigated. METHODS: Weanling male Wistar Albino rats were randomly distributed into two experimental groups. One group received a powdered diet deficient in iron (5-7 mg iron.kg-1) while the second group was placed on a standard laboratory chow diet (109 mg iron.kg-1) for 4-8 weeks. RESULTS: Total cardiac creatine kinase activity was unchanged in anaemic rats; however, a 25% increase in nascent or functional mito-CK activity per mitochondrion was detected [0.969(SEM 0.005), control group and 1.203(0.040), anaemic group, p < 0.001]. The sensitivity of creatine (40 mM creatine, VCr) and ADP (0.1 mM ADP, V0.1) stimulated respiration, as a percentage of maximum respiratory rate (2.0 mM ADP, V2.0), was increased by 48% and 52% respectively in the anaemic skinned cardiac fibres. An increase in basal respiration with glutamate and malate as substrates was detected in the anaemic group compared to the control group, at 6.77(0.74) v 4.58(0.35) ng O.min-1 x mg-1 dry weight (p < 0.025). Cytosolic ATP was decreased in isolated perfused hearts from anaemic animals, at 35.18(3.11) mumol.g-1 dry weight in control hearts versus 23.66(1.42) in anaemic hearts (p < 0.01). A significant increase in myocardial glycolytic capacity was detected in anaemic cardiac tissue, as evidenced by a 20% increase in phosphofructokinase activity (p < 0.01). Phosphorylase activity was unaltered in anaemic hearts, indicating that the increased glucose requirement originated from exogenous sources. Lactate dehydrogenase (LDH) was increased by 30% in anaemic hearts (p < 0.001). The LDH isozyme profile was shifted in favour of lactate and NAD+ production, thus supporting anaerobic glycolysis. CONCLUSIONS: In support of the phosphocreatine circuit model, the increased mito-CK per mitochondrion in the anaemic skinned fibre preparation was associated with an increase in creatine stimulated respiration. In addition, the sensitivity of mitochondrial respiratory rate to ADP and the maximum glycolytic capacity were increased in anaemic fibres. Although the net effect of these changes in metabolic capacity and regulation on in vivo high energy phosphate flux is unknown, it is likely that they are adaptive alterations that compensate for the lower steady state cytosolic nucleotide concentration.

Adenosine Diphosphate↗
PubMed1988

Effectiveness of teaching breast self examination during office visits.

In a randomized clinical trial a comparison was made of two BSE teaching interventions delivered by primary providers during office visits in a group nursing faculty practice. Patients who reported no regular BSE (n = 121) received either individualized teaching focused on reducing perceived barriers and reinforcing benefits of BSE, or routine teaching limited to usual instruction in BSE technique. Patients reporting frequent/monthly BSE during the past year were comparison subjects (n = 81). Self-reported data on BSE behavior were obtained in questionnaires administered before the interventions and via telephone interviews three months after the visit. Analysis using chi square showed that, contrary to expectation, individualized and routine teaching were equally effective: 61.4% of the individually taught and 63.5% of the routinely taught reported frequent or monthly practice at followup. Both groups were significantly more confident in technique and ability to detect change in the breast. The previously non-practicing women remained significantly less likely than comparison subjects to be performing BSE monthly at followup. The perceived benefit of BSE giving peace of mind predicted non-practicers most likely to change.

Adult↗
PubMed1985

Low-renin hypertension in young infants.

Plasma renin activity (PRA) in neonates is significantly higher than in older infants and children and may increase as a result of numerous physiologic or therapeutic factors. For these reasons, the measurement of PRA is not usually helpful in establishing the cause of hypertension in neonates. In conditions that suppress renin release, however, measurement of PRA can be most useful. Herein, we describe two infants (ages 4 and 5 months, respectively) with sustained hypertension and low PRA secondary to dexamethasone-suppressible hyperaldosteronism. Low PRA was essential in establishing this diagnosis in both patients. Dexamethasone-suppressible hyperaldosteronism should be considered in hypertensive infants who have normal genitalia and low PRA.

Dexamethasone↗