Biomedical subjects

D C Hatton

Publications and source records attributed to D C Hatton.

At least 37 records · Page 2Linked to original sources

PubMed1997

Dietary calcium decreases blood pressure without decreasing renal vascular resistance or altering the response to NO blockade.

Many vasoactive elements are involved in the elevation of blood pressure in spontaneously hypertensive rats (SHR). Elevated dietary calcium has been observed to reduce blood pressure in SHR. This study investigates interactions among dietary calcium, renal vascular resistance (RVR), elevation of blood pressure and effects of norepinephrine and nitric oxide synthesis. We completed a series of experiments on two groups each (fed low, 0.1% and high, 2.0% dietary calcium, respectively) of 9-week-old Wistar Kyoto (WKY), 9-week-old and 6-week-old SHR. Although 9-week-old SHR had elevated baseline blood pressure compared to 9-week-old WKY and also compared to 6 week-old SHR, there was no corresponding elevation in baseline RVR. All SHR fed high calcium diets had lower blood pressure compared to low calcium diets, and there was no corresponding reduction in RVR. WKY controls' blood pressure and RVR were unaffected by dietary calcium levels. In all hypertensive rats the blood pressure and renal vascular resistance were elevated by N(G)-nitro-L-arginine methylester (L-NAME), but the dietary differences were sustained. Blood pressure of WKY was unaffected by the low dose of L-NAME. The increase in RVR to L-NAME was greater in SHR than in controls. The renal vascular response to norepinephrine was related to diet in older SHR, but smaller and unrelated to diet in younger SHR. Following L-NAME, WKY had greater responses to norepinephrine than 9-week-old SHR. We conclude that noradrenergic vasoconstriction is enhanced in the adult SHR, especially in the absence of high calcium diet. Alterations in NO synthesis may effect the norepinephrine response.

Age Factors↗

PubMed1997

Dietary compliance and cardiovascular risk reduction with a prepared meal plan compared with a self-selected diet.

Noncompliance with therapeutic diets remains a major obstacle to achieving improvements in cardiovascular disease (CVD) morbidity and mortality. This study compared dietary compliance and CVD risk factor response to two dietary interventions designed to treat hypertension, dyslipidemia, and diabetes mellitus. In a multicenter trial, 560 adults were randomly assigned to either a self-selected, mixed-food plan (n = 277), or a nutrient-fortified prepared meal plan (n = 283); each was designed to provide 15-20% of energy from fat, 55-60% from carbohydrate, and 15-20% from protein. Nutrient intake was estimated from 3-d food records collected biweekly throughout the 10-wk intervention. Compliance was determined by evaluating the participants' ability to meet specific criteria for energy intake [+/-420 kJ (100 kcal) from the midpoint of the prescribed energy range], fat intake (< 20%, < 25%, or < 30% of energy from total fat), and the National Cholesterol Education Program/American Heart Association Step 1 and 2 diet recommendations. Compliance with energy, fat, and Step 1 and 2 criteria was better in participants who followed the prepared meal plan than in those who followed the self-selected diet (P < 0.0001). Compliant participants in both groups achieved greater reductions in body weight, systolic and diastolic blood pressure, and total and low-density-lipoprotein cholesterol than noncompliant participants (P < 0.05). In general, better endpoint responses were observed with lower fat intakes regardless of group assignment. The prepared meal plan is a simple and effective strategy for meeting the many nutrient recommendations for CVD risk reduction and improving dietary compliance and CVD endpoints.

Adult↗

PubMed1997

Managing health problems among homeless women with children in a transitional shelter.

PURPOSE: To describe health problems among homeless women with children living in a transitional shelter, analyze how they managed various ailments and when and how they sought care. DESIGN: Qualitative using grounded theory and dimensional analysis. SAMPLE: During 1992 and 1993, data were gathered from a convenience sample of 13 Latina, 11 White, and 6 African American women (n = 30) who lived in a transitional shelter in California, USA. METHODS: In-depth, semi-structured interviews. FINDINGS: Despite many supportive services in transitional shelter, respondents had difficulty managing health problems. Typically, a woman reported she managed a health problem by overcoming it alone. CONCLUSIONS: The pattern of overcoming it alone existed years before transitional shelter life, and, in many instances, persisted during shelter years. CLINICAL IMPLICATIONS: Clinical nursing interventions that address shame, fear, lack of information, and eligibility for services could improve health outcomes among women and children living in transitional shelters.

Adaptation, Psychological↗

PubMed1997

Chronic ANG II infusion and reflex control of norepinephrine and corticosterone in conscious rabbits.

The hypothesis that long-term increases in angiotensin II (ANG II) produce pressure-independent resetting of baroreflex control of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis was tested in rabbits by determining the effect of chronic ANG II infusion on reflex relationships between mean arterial pressure (MAP) and plasma concentrations of norepinephrine (NE) and corticosterone (CS). After 2 wk, ANG II increased MAP from 61 +/- 1 to 99 +/- 2 mmHg (P < 0.05) without altering heart rate or plasma NE concentration, but increased CS from 9.8 +/- 1.3 to 29.5 +/- 13.7 ng/ml (P < 0.05). Heart rate, NE, and CS baroreflex curves were all reset to a higher pressure level (P < 0.05) after 24 h, 1 wk, and 2 wk of ANG II. Forty minutes after stopping ANG II on the same days, MAP decreased, and curves were shifted back toward control (P < 0.05), indicating that ANG II was required for the resetting. Two findings suggest that the resetting action ofANG II is distinct from the pressor effect. First, although stopping ANG II reversed the hypertension as it reversed the resetting, reversal of the hypertension instead by prolonged infusion of nitroprusside along with ANG II did not have the same effect. Second, NE and heart rate baroreflex curves returned toward preinfusion positions after stopping ANG II (P < 0.05), even when the hypertension was nearly maintained by phenylephrine infusion. In conclusion, chronic increases in ANG II may have a global baroreflex resetting effect by a mechanism that is in part independent of the hypertension.

Angiotensin II↗

PubMed1997

Cardiovascular response to stress: baroreflex resetting and hemodynamics.

Borderline hypertensive rats (BHR) were used to test the hypothesis that baroreflex resetting prevents a fall in blood pressure (BP) when cardiac output (CO) is reduced during air-jet stress. Eight-week-old BHR were instrumented with flow probes around the ascending aorta for measuring CO, femoral and jugular catheters were inserted for measurement of arterial pressure and infusion of drugs, and sinoaortic baroreceptors were either denervated (SAD) or left intact. Alternating bolus injections of phenylephrine and sodium nitroprusside were given at baseline and during air-jet stress to assess the baroreflex. Air-jet stress immediately shifted the midpoint of the baroreflex curve for heart rate (HR) to a higher BP levels. When metoprolol was administered during air-jet stress, HR was reduced and CO reverted to prestress levels, but the stress-induced pressor response was not changed. In SAD BHR, air-jet stress caused an elevation of BP that was not different from intact rats. Administration of metoprolol to SAD rats during air-jet stress resulted in a further elevation rather than a reduction in BP. We conclude that the sinoaortic cardiac baroreflex is reset during air-jet stress and that it integrates reflex changes in BP during stress. The arterial baroreflex is not, however, necessary for the initiation or maintenance of the pressor response during stress, nor does it prevent a fall in BP when CO is compromised during stress.

Animals↗

PubMed1996

Improved quality of life in patients with generalized cardiovascular metabolic disease on a prepared diet.

Current dietary recommendation for cardiovascular disease risk reduction and recommended dietary allowances (RDAs) were used to develop a nutritionally complete prepackaged prepared meal plan specifically designed to reduce the risk of cardiovascular disease. In the current study we tested patient acceptance of the diet as defined by measures of quality of life. In a randomized, parallel-design, multicenter clinical trial, 77 persons with hypertension, diabetes mellitus, dyslipidemia, or a combination of two or more of these conditions were recruited and randomly assigned to either a prepared meal plan (n = 39) or a comparable self-selected diet (n = 38) for 10 wk. The prepared meal plan met both the RDAs for all essential micronutrients and the dietary recommendations of national health organizations for macronutrients, cholesterol, sodium, and fiber. The prescribed self-selected diet was matched for macronutrients. Quality of life, as measured by a battery of instruments, was the major endpoint. Individuals consuming the prepared meal plan had significant improvements in mental health (P < 0.01), general perceived health (P < 0.005), daily activities (P < 0.05), work performance (P < 0.005), affect (P < 0.01), and nutritional health perceptions (P < 0.001), and reductions in nutrition hassles based on a standardized questionnaire (P < 0.001). The self-selected-diet group had significant improvements in nutritional health perceptions (P < 0.001) and affect (P < 0.001). There were significant improvements in weight (P < 0.001), blood pressure (P < 0.001), cholesterol (P < 0.002), low-density lipoproteins (P < 0.001), glucose (P < 0.014), and glycated hemoglobin (Hb A(1c) (P < 0.004) that were comparable in both groups. In summary, this study shows that a nutritionally complete diet, whether prepackaged or self-selected, improves multiple risk factors for cardiovascular disease. The prepackaged prepared meal plan had the added benefit of a greater improvement in quality of life.

Blood Glucose↗

PubMed1996

Dietary salt and hypertension.

Sodium restriction is the most commonly used lifestyle modification for control of hypertension. Nevertheless, there is no consensus on the relative importance of salt in the development of hypertension, nor is the physiological mechanism(s) responsible for salt-induced elevations of blood pressure clearly understood. This review focuses on new research developments in this area.

Animals↗

PubMed1995

Mechanisms of calcium's effects on blood pressure.

Manipulations of dietary calcium have been repeatedly shown to alter blood pressure in animal models of human essential hypertension. Supplemental dietary calcium lowers blood pressure, whereas restricted calcium diets tend to elevate blood pressure. The mechanisms responsible have not been identified, but numerous possibilities have been proposed. Many of the proposals have attempted to relate dietary calcium to calcium metabolism in vascular smooth muscle and altered vascular tone. Other proposals have focused on neural, hormonal, and renal effects of dietary calcium. In this article, mechanisms through which elevations in extracellular calcium levels might influence intracellular calcium levels are explored. Also examined are the potential roles of calcium regulating hormones, sympathetic nervous system, and electrolyte interactions in modifying blood pressure.

Animals↗

PubMed1995

Captopril and stress-induced hypertension in the borderline hypertensive rat.

OBJECTIVE: Daily exposure to air-jet stress (AJS) causes sustained elevations of blood pressure in borderline hypertensive rats (BHR). It is known that the renin-angiotensin system is activated during episodes of behavioral stress, and the purpose of this study was to assess the involvement of renin-angiotensin system in the development of stress-induced hypertension in the BHR. DESIGN: Four groups of 8- and 9-week-old rats were studied: they received, respectively, oral captopril and AJS; oral captopril without AJS; AJS without captopril; and neither AJS nor captopril. METHODS: After 10 days of AJS and captopril conditions, femoral and jugular catheters were implanted for the measurement of mean arterial pressure and pressor responses to norepinephrine and tyramine. Blood samples were collected for the measurement of norepinephrine and plasma renin activity. RESULTS: Ten days of AJS caused a significant elevation of blood pressure in BHR exposed to AJS without receiving captopril but not in those animals given captopril concurrently with AJS. Circulating norepinephrine and blood pressure responses to exogenous norepinephrine and tyramine were similar across the four groups. Plasma renin activity was highest in BHR given captopril, and was significantly elevated during an acute episode of AJS. CONCLUSIONS: The renin-angiotensin system may be important in the development of stress-induced hypertension in the BHR.

Animals↗

PubMed1994

Dietary calcium and blood pressure in experimental models of hypertension. A review.

More than 80 studies have reported lowered blood pressure after dietary calcium enrichment in experimental models of hypertension. The evidence presented here suggests that dietary calcium may act concurrently through a number of physiological mechanisms to influence blood pressure. The importance of any given mechanism may vary depending on the experimental model under consideration. Supplemental dietary calcium is associated with reduced membrane permeability, increased Ca(2+)-ATPase and Na,K-ATPase, and reduced intracellular calcium. These results suggest that supplemental calcium may limit calcium influx into the cell and improve the ability of the VSMC to extrude calcium. This could be a direct effect of calcium on the VSMC or an indirect effect mediated hormonally. The calcium-regulating hormones have all been found to have vasoactive properties and therefore may influence blood pressure. Furthermore, CGRP and the proposed parathyroid hypertensive factor are both vasoactive substances that are responsive to dietary calcium. Therefore, diet-induced variations in calcium-regulating hormones may influence blood pressure. Modulation of the sympathetic nervous system is another important way that dietary calcium can influence blood pressure. There is evidence of altered norepinephrine levels in the hypothalamus as a consequence of manipulations of dietary calcium as well as changes in central sympathetic nervous system outflow. Dietary calcium has also been shown to specifically modify alpha 1-adrenergic receptor activity in the periphery. In some experimental models of hypertension, dietary calcium may alter blood pressure by changing the metabolism of other electrolytes. For example, the ability of calcium to prevent sodium chloride-induced elevations in blood pressure may be attributed to natriuresis. However, natriuresis does not account for all of the interactive effects of calcium and sodium chloride on blood pressure. Sodium chloride-induced hypertension may be due in part to calcium wasting and subsequent elevation of calcium-regulating hormones. Chloride is an important mediator of this effect because it appears that sodium does not cause calcium wasting when it is not combined with chloride. More attention to the central nervous system effects of dietary calcium is needed. Not only can calcium itself influence neural function, but many of the calcium-regulating hormones appear to affect the central nervous system. The influence of calcium and calcium-regulating hormones on central nervous system activity may have important implications for blood pressure regulation and also may extend to other aspects of physiology and behavior.

Animals↗

PubMed1994

Health perceptions among older urban American Indians.

There is a dearth of empirically based accounts dealing with health from the perspective of older American Indians. Some have even referred to these individuals as a "forgotten population." The purpose of the present investigation was to explore the phenomenon of health among urbanized members of this vulnerable population. More specifically, the study focused on how these individuals perceived their health and how they managed their health problems. Using the grounded theory method, discoveries indicated that these older adults constructed their ideas of health by observing signs of illness, incorporating the ideas of others, and evaluating getting around. Moreover, their health ideas often reflected a biomedical perspective. The data analysis also revealed factors in the historical and contemporary context that had salient consequences for these individuals' health beliefs and practices. Research implications include future studies of the complex factors that have consequences for health beliefs and practices, as well as a critical examination of the underlying social conditions that relate to health among these older American Indians.

Age Factors↗

PubMed1994

1,25(OH)2 vitamin D3-induced alterations in vascular reactivity in the spontaneously hypertensive rat.

Recent studies showed that 1,25(OH)2 vitamin D3 stimulates calcium uptake in vascular smooth muscle cells resulting in increased vascular reactivity. Despite reliable effects on vascular tissue, daily injections of 1,25(OH)2 vitamin D3 have not consistently altered basal blood pressure. In the current study, 1,25(OH)2 vitamin D3 was examined for vascular reactivity in vitro as well as blood pressure reactivity in vivo. 1,25(OH)2 vitamin D3 was either injected as a daily subcutaneous dose of 48 ng/kg or placed in an osmotic minipump that was implanted subcutaneously and delivered at a rate of 2/ng/kg/hr (48 ng/kg/d). Blood pressure reactivity to bolus injections of norepinephrine (NE) and angiotensin II (AII) was tested after 1, 6, and 7 days of 1,25(OH)2 vitamin D3 treatment. On the seventh day, the animals were killed and rings from the aorta and mesenteric artery were placed in a muscle bath for measurement of vascular reactivity to NE and potassium chloride. Vessels from animals injected with 1,25(OH)2 vitamin D3 had significantly greater responses to NE (p < 0.001) and potassium chloride (p < 0.001) than those from minipump or control animals. There was no significant difference in baseline BP across treatment conditions or any reliable difference in blood pressure reactivity to NE or AII. The data showed that 1,25(OH)2 vitamin D3 can enhance vascular reactivity without altering baseline blood pressure or blood pressure reactivity. Moreover, intermittent administration of calcitriol may enhance vascular reactivity to norepinephrine and potassium chloride to a greater extent than the same dose of calcitriol given as a continuous infusion.

Animals↗

PubMed1993

Stress-induced hypertension in the borderline hypertensive rat: stimulus duration.

Blood pressure and circulating catecholamines were evaluated in borderline hypertensive rats (BHR) that were exposed to daily sessions of either short (20 min) or long (120 min) duration air-jet stimulation. Indirect measures of systolic blood pressure indicated that within 2 weeks both experimental groups developed stress-induced hypertension in comparison to home cage controls. Animals exposed to 120 min stress sessions had significantly higher systolic blood pressure relative to the 20 min group. However, direct measures of blood pressure taken after 5 weeks of daily stress did not reveal any differences between the stress groups. Daily measurements indicated that acute changes in blood pressure during stress were modest and transient, suggesting little contribution to the chronic elevation in blood pressure observed as a consequence of stress. Circulating catecholamines were significantly increased by the stressor. Epinephrine returned to baseline within 60 min, although norepinephrine remained elevated throughout the 120 min session. The results indicate that increasing the duration of daily air jet stimulation did not impact the development of stress-induced hypertension over the 5-week measurement period.

Animals↗

PubMed1993

Dietary calcium modulates blood pressure through alpha 1-adrenergic receptors.

To investigate the role of adrenergic receptor activity in dietary calcium-induced alterations in blood pressure, weanling spontaneously hypertensive rats (SHR) were placed on either high-calcium (2.0%) or low-calcium (0.1%) diets for 1-2 wk. Baseline blood pressure was higher and pressor responses to exogenous norepinephrine (NE) were greater in the SHR on low-calcium diets than high-calcium diets. There was no difference between diet groups in circulating NE or in the pressor response to angiotensin II. The difference in basal blood pressure was eliminated by the alpha 1-adrenergic receptor blockers phentolamine and prazosin but was not altered by alpha 2-, beta 1-, or beta 2-adrenergic receptor blockade (idazoxan, metoprolol, and butoxamine, respectively). Furthermore, hypotension produced by either calcitonin gene-related peptide, captopril, or nitroprusside failed to eliminate the diet-induced difference in blood pressure. The results suggest the possibility that diet-induced differences in alpha 1-adrenergic activity may be responsible, in part, for variations in blood pressure on different calcium diets.

Adrenergic Agonists↗

PubMed1993

Information transmission in bilingual, bicultural contexts: a field study of community health nurses and interpreters.

The purpose of this article is to present the findings made in a field study of nurses and interpreters who were working in a county health department. Informed by the qualitative research method of grounded theory, analysis of 37 semistructured interviews revealed three types of interactions among nurses, interpreters, and clients. In these situations, the interpreter worked as a voice box, an excluder, or a collaborator. Collaborative interactions allowed both interpreters and community health nurses to establish the most effective rapport with clients. Rapport, in turn, facilitated client assessment and the planning and delivery of nursing services. Implications for community health nursing practice include providing opportunities for interpreters to establish a rapport with clients. Research implications include the development of strategies that promote collaboration between community health nurses and interpreters. Theoretically, such strategies would enhance client outcomes.

Communication↗

PubMed1992

Chronic alcohol consumption lowers blood pressure but enhances vascular contractility in Wistar rats.

OBJECTIVE: To determine the effect of chronic alcohol consumption upon blood pressure, blood pressure reactivity and vascular contractility in Wistar rats. DESIGN: Wistar rats were fed a liquid diet containing 36% ethanol; control rats were pair fed. METHODS: Rats were maintained on diets for 18 weeks. Indirect systolic blood pressure was measured weekly. Catheters were implanted for assessment of direct arterial pressure and blood pressure reactivity to norepinephrine, angiotensin II and ethanol injections. In a subgroup of rats, contractility of isolated mesenteric resistance vessels was measured. RESULTS: In comparison with simultaneously pair-fed controls, ethanol-treated rats developed significantly lower blood pressure within 3 weeks of exposure to alcohol; this continued throughout the study. Despite the reduction in blood pressure, in vitro assessment of vascular contractility in mesenteric resistance vessels indicated that ethanol consumption significantly enhanced vascular contractility to norepinephrine and attenuated the vasodepressive effects of ethanol. Measurement of blood pressure reactivity to infused pressor agents showed no difference between controls and ethanol-treated rats in response to norepinephrine but a significantly attenuated pressor response to angiotensin II was observed in ethanol-treated rats. CONCLUSIONS: The blood pressure results contrast with reports of elevated blood pressure in Wistar rats given ethanol in drinking water. This disparity may be due to nutritional factors. Increased vascular contractility combined with hypotension suggests that cardiovascular regulatory systems offset the direct effects of ethanol upon the vasculature. This view is reinforced by the lack of difference between groups in blood pressure reactivity to norepinephrine. The attenuated angiotensin II responses in the ethanol-treated rats suggests altered levels of circulating angiotensin II in this group.

Alcoholism↗

PubMed1992

Information transmission in bilingual, bicultural contexts.

The purpose of this article is to present the discoveries made in a field study which explored the nature of translators' work in community health settings. Informed by the grounded theory method, I did participant observation and had multiple conversations of varying length with translators, clients, health-care providers, and other ancillary staff. The findings suggest that the seemingly simple work of translating is, instead, quite complex. Translators are, more accurately, interpreters who appraise tasks, clients, providers, and/or information, and they hold considerable power. This article includes a consideration of the study's relevance for community health nursing practice and implications for further research.

Communication↗

PubMed1991

Hypotension during vasopressin receptor blockade: role of V2 receptors and sympathetic nervous system.

This study investigated possible mechanisms for the hypotension produced by nitroprusside infusion in conscious dogs pretreated with a V1 vasopressin antagonist. The hypothesis that an action of vasopressin at V2-like receptors contributes to the hypotension was tested by comparing the effects of a V1 antagonist to the effects of a combined V1/V2 antagonist. Nitroprusside infusion produced dose-dependent decreases in arterial and atrial pressures. Larger decreases in pressures were produced in animals pretreated with either antagonist; however, the decreases in V1/V2-blocked dogs were not less than the decreases in V1-blocked dogs. These data suggest that V2-like actions of vasopressin do not contribute to the hypotensive effects of V1 blockade. A second hypothesis was that the greater hypotension was due to activation of a cardiac reflex to cause withdrawal of sympathetic tone, a decrease in peripheral resistance, and adrenal activation. Measurement of cardiac output revealed that the larger decreases in arterial pressure were due to larger decreases in total peripheral resistance. The hypotension was also associated with decreases in heart rate, unchanging plasma norepinephrine concentration, and increases in epinephrine concentration. These data are consistent with the hypothesis that the fall in pressure observed in dogs pretreated with a V1 antagonist is secondary to a decrease in peripheral resistance that is due at least in part to withdrawal of sympathetic tone.

Angiotensin II↗