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Biomedical subjects

T J Moore

Publications and source records attributed to T J Moore.

At least 37 records · Page 2Linked to original sources
PubMed1998

Biomechanical analysis of hindfoot fixation using an intramedullary rod.

To measure the stiffness of the hindfoot when fixed with an intramedullary rod placed in a retrograde manner, two biomechanical experiments were carried out on five matched pairs of cadaveric below knee specimens. Experiment 1: In the right leg of each pair, an intramedullary rod was placed in a retrograde fashion through the calcaneus, talus, and into the tibial intramedullary canal. Biomechanical testing was done to determine hindfoot stiffness, with and without distal and proximal transverse interlocking screws. The uninstrumented left leg of each pair was tested as a control. Experiment 2: A series of similar biomechanical experiments were done on the same specimens to determine the effect on hindfoot stiffness of an intramedullary rod with one distal screw as compared with a method of tibiotalocalcaneal fixation using three cross-cannulated screws. The results show that an intramedullary rod placed in a retrograde manner stiffens the hindfoot and the placement of interlocking screws enhances that effect (Experiment 1). The intramedullary rod with one distal screw inserted provides more stiffness to the hindfoot than does three cross-cannulated screws (Experiment 2).

Aged↗
PubMed1997

A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group.

BACKGROUND: It is known that obesity, sodium intake, and alcohol consumption factors influence blood pressure. In this clinical trial, Dietary Approaches to Stop Hypertension, we assessed the effects of dietary patterns on blood pressure. METHODS: We enrolled 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80 to 95 mm Hg. For three weeks, the subjects were fed a control diet that was low in fruits, vegetables, and dairy products, with a fat content typical of the average diet in the United States. They were then randomly assigned to receive for eight weeks the control diet, a diet rich in fruits and vegetables, or a "combination" diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat. Sodium intake and body weight were maintained at constant levels. RESULTS: At base line, the mean (+/-SD) systolic and diastolic blood pressures were 131.3+/-10.8 mm Hg and 84.7+/-4.7 mm Hg, respectively. The combination diet reduced systolic and diastolic blood pressure by 5.5 and 3.0 mm Hg more, respectively, than the control diet (P<0.001 for each); the fruits-and-vegetables diet reduced systolic blood pressure by 2.8 mm Hg more (P<0.001) and diastolic blood pressure by 1.1 mm Hg more than the control diet (P=0.07). Among the 133 subjects with hypertension (systolic pressure, > or =140 mm Hg; diastolic pressure, > or =90 mm Hg; or both), the combination diet reduced systolic and diastolic blood pressure by 11.4 and 5.5 mm Hg more, respectively, than the control diet (P<0.001 for each); among the 326 subjects without hypertension, the corresponding reductions were 3.5 mm Hg (P<0.001) and 2.1 mm Hg (P=0.003). CONCLUSIONS: A diet rich in fruits, vegetables, and low-fat dairy foods and with reduced saturated and total fat can substantially lower blood pressure. This diet offers an additional nutritional approach to preventing and treating hypertension.

Adult↗
PubMed1996

Salt sensitivity of hypertension and responses to angiotensin converting enzyme inhibition with benazepril.

Salt intake, and the sensitivity of blood pressure (BP) to excessive salt intake is thought to contribute to the pathogenesis of essential hypertension in some patients. This study was designed to ascertain whether salt sensitivity of BP is a determinant of BP and renal vascular responsiveness to angiotensin converting enzyme (ACE) inhibition. In 24 patients with essential hypertension, ranging in age from 30 to 68 years, renin status, renal hemodynamics, and sensitivity of BP to steady state changes in salt intake were assessed. Twenty-four hour ambulatory BP monitoring (ABPM) was employed to measure baseline BP and BP response to 4 weeks' treatment with benazepril at 20 or 40 mg/day. Benazepril induced a highly-significant reduction in BP (P < .001) and increase in renal plasma flow (530 +/- 17 to 580 +/- 19 mL/min/1.73 m2; P < .001). Systolic BP fell from 143 +/- 2 to 129 +/- 2 mm Hg (P < .001), and diastolic BP fell from 91 +/- 1.6 to 80 +/- 2 mm Hg (P < .001). The magnitude of the BP and renal vascular response to ACE inhibition was not influenced by the sensitivity of BP to salt intake. In a multivariate analysis neither body mass index nor age influenced the BP response to ACE inhibition or the relationships between salt intake and a BP response to ACE inhibition. We conclude that the factors that influence sensitivity of BP to salt intake do not influence the systemic or renal hemodynamic response to ACE inhibition.

Adult↗
PubMed1995

Enzymatically amplified voltammetric sensor for microliter sample volumes of salicylate.

A new voltammetric sensing strategy for salicylate employing two enzymes and applicable to microliter sample volumes is demonstrated. The method involves the use of the enzyme salicylate hydroxylase to convert salicylate to catechol, which is oxidized at a carbon electrode. The product of this oxidation reaction, o-quinone, is then reduced by a second enzyme, glucose oxidase, to regenerate catechol. Reoxidation of catechol results in a signal that is amplified due to repeated cycling of catechol molecules between the oxidized and reduced states. This chemistry is implemented in two configurations. (i) A paper disk into which both enzymes have been absorbed is mounted on a coplanar three-electrode assembly for aqueous experiments. Determination of salicylate in a nonprescription dermatological product is demonstrated. (ii) A small solution volume confined directly on the coplanar electrodes is used for determination of salicylate in whole blood. The advantages of the use of two enzymes and of monitoring steady-state catalytic currents are discussed.

Electrochemistry↗
PubMed1995

Evaluation of mucosal damage of surfactants in rat jejunum and colon.

Surfactants are one of the most frequently used adjuvants in oral pharmaceutical preparations, used primarily as solubilizers, stabilizers, emulsifiers, and wetting agents. However, surfactants can disrupt normal membrane structure. In this study, lactate dehydrogenase (LDH) and mucus were evaluated as potential markers of intestinal damage in a single-pass in situ perfusion model in the rat. The release of LDH and mucus into the intestinal lumen of the rat following perfusion of the nonionic surfactants Tween 80 and Triton X-100 was determined. The release rate of LDH increased in the order saline < Tween 80 < Triton X-100 in both jejunum and colon. LDH release rate was approximately three times lower in the colon than in the jejunum, but relative effects of nonionic surfactants were comparable between regions. In addition, the rate of LDH release in the jejunum increased with decreasing perfusion rates for both saline and Tween groups and with increasing Tween 80 concentrations. At each flow rate studied, mucus release rate was greater in the presence of Tween 80 and Triton X-100 than saline, but there was no significant difference between the effect of Tween 80 and Triton X-100 on mucus release rate. When perfusion of Triton X-100 was followed by saline, rates of both mucus and LDH release returned to baseline values, suggesting damage is reversible. Histological damage agreed with trends observed in LDH and mucus release rates. This model allows for early evaluation of intestinal damage due to both excipients and active ingredients and simultaneous measurement of drug absorption.

Animals↗
PubMed1995

Retrograde intramedullary nailing for ankle arthrodesis.

This is a retrospective study of retrograde intramedullary rodding for ankle arthrodesis in 19 ankles in 16 patients. The preoperative diagnosis of 16 patients was diabetic neuropathic arthropathy in seven patients, rheumatoid arthritis in three patients, post traumatic arthrosis in three patients, paraplegia with fixed equinovarus of the foot in two patients, and avascular necrosis of the talus in one patient. Retrograde intramedullary rodding for ankle arthrodesis was done as a salvage procedure in each patient. Fourteen of the 19 ankles had radiographic evidence of solid arthrodesis. In the four patients with five ankles with pseudarthrosis, no case was clinically significant. There was one deep infection and one broken rod. Thirteen of the 16 patients are ambulatory, and nine required either an ankle-foot orthosis or shoe modification. The standard method of ankle fusion using crossed cancellous screws is the procedure of choice because it preserves the subtalar joint. Retrograde intramedullary rodding for ankle arthrodesis should be considered for patients with significant posttraumatic arthrosis and bone loss following distal tibial plafond fractures, concomitant subtalar arthrosis, severe osteopenia, such as in patients with rheumatoid arthritis, or neuropathic arthropathy.

Adolescent↗
PubMed1995

Dietary factors and blood pressure regulation.

This article reviews the potential effects of dietary constituents and manipulations on blood pressure. Dietary approaches with documented efficacy are discussed, as are the effects of other nutritional factors, which, after study, demonstrate no proven change on blood pressure. The effects of dietary ions (micronutrients) and of individual dietary macronutrients also are reviewed. The article concludes by examining the evidence for effects of weight loss, alcohol restriction, and vegetarian diets and offers for future research.

Blood Pressure↗
PubMed1994

Age and the renal blood supply: renal vascular responses to angiotensin converting enzyme inhibition in healthy humans.

OBJECTIVE: To assess the relation between age, sodium intake, renal blood flow (RBF) and the renal vascular response to an angiotensin converting enzyme (ACE) inhibitor, captopril. DESIGN: Blood flow studies were performed before and during the acute response to an oral 25-mg dose of captopril, selected to induce a maximal response, after 5 to 7 days on a metabolic ward, sufficient time to have achieved external balance on a fixed low-salt (10 mE/day) or high salt (200 mEq/day) diet. Blood flow was measured as radioxenon transit through the kidney. SETTING: The study was performed on a metabolic ward, the Clinical Research Center, and in the Cardiovascular Radiology Laboratories of the Brigham and Women's Hospital in Boston. PARTICIPANTS: The participants, all community dwellers, were potential kidney donors, in a renal transplant program. They were thought to be sufficiently healthy to consider donation of a kidney. The age range was 18 to 69 years. RESULTS: Renal blood flow showed the anticipated decline with increasing age, whether the subjects were on a restricted or a liberal salt intake. Captopril induced an acute increase in RBF, averaging 88 +/- 7 mL/100 g/min in subjects on a high-salt diet, but no influence of age was identified on the renal vasodilator response on either diet. Increasing age did not limit the renal vasodilator response, although subjects beyond the sixth decade were not studied. CONCLUSIONS: The limited renal vascular response to vasodilators we had documented in earlier studies does not extend to ACE inhibitors. Although ACE inhibitors lack the pharmacological specificity required to prove a role for angiotensin II (Ang II), the data are compatible with a contribution of Ang II to the maintenance of renal vascular tone that does not change with increasing age, at least to 70 years of age.

Adolescent↗
PubMed1994

Responses to converting enzyme and renin inhibition. Role of angiotensin II in humans.

We compared the renal vascular responses to angiotensin converting enzyme inhibition and renin inhibition to assess the influence of angiotensin II (Ang II). We examined the renal and endocrine responses to the renin inhibitor enalkiren, to captopril, and to placebo in nine healthy and nine hypertensive men on a 10-mmol sodium diet. Ang II was infused to assess effects of the agents on renal and adrenal responsiveness to Ang II. Plasma Ang II concentration was suppressed similarly with enalkiren and captopril--an identical level of blockade was achieved. Although renal plasma flow was stable during placebo, a substantial rise was seen with both enalkiren (+133 +/- 26 mL/min per 1.73 m2) and captopril (+99.4 +/- 22.6). There was remarkable intrasubject concordance between the renal plasma flow responses to renin inhibition and converting enzyme inhibition (r = .90, P < .004). The vasodilator response to both agents correlated inversely with the fall in renal plasma flow induced by Ang II alone (r = -.66, P < .05). Both agents significantly enhanced the renal vascular response to Ang II (P = .01), and, furthermore, the renal vasodilator response to captopril predicted the potentiation of the renal plasma flow response to Ang II after either agent (enalkiren: r = .91, P < .001; captopril: r = .56, P < .05). Concordance of the maximal renal plasma flow response to the two agents appeared in the hypertensive men as well. Our results indicate that the acute renal response to captopril largely reflects a reduction in Ang II formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Regulation of aldosterone secretion in hypertensive blacks.

Hypertension in blacks is common, often severe, and largely unexplained. Recent studies have suggested that aldosterone secretion in blacks may be reduced, whereas older data demonstrate no racial differences in aldosterone excretion. We performed this study to examine adrenal responsiveness in black hypertensive patients under controlled metabolic conditions. Thirty-one black hypertensive patients and 7 black normotensive subjects were studied on intakes of 10 mmol/d sodium and 100 mmol/d potassium, with the renin-angiotensin-aldosterone system further stimulated by upright posture or infusion of angiotensin II (Ang II). Forty-six hypertensive and 14 normotensive whites underwent the same protocol as a comparison group. Hypertensive blacks and whites had similar mean basal plasma aldosterone levels on a low salt diet, lower in both groups than in normotensive subjects. In the black patients, however, plasma aldosterone responses were significantly lower than responses in white hypertensive patients when further stimulated by either posture (1451 +/- 216 versus 2571 +/- 225 pmol/L [52.3 +/- 7.8 versus 92.7 +/- 8.1 ng/dL], P < .002) or Ang II infusion (843 +/- 122 versus 1617 +/- 189 pmol/L [30.4 +/- 4.4 versus 58.3 +/- 6.8 ng/dL], P < .001). Renin status did not account for the difference. Basal and stimulated plasma aldosterone concentrations, on the other hand, were similar in normotensive white and black subjects. Blunted adrenal responses to upright posture and Ang II infusion are common among black hypertensive patients. These abnormalities may be part of a larger constellation of abnormalities in blacks, reflecting perhaps a greater, more frequent underlying disturbance in salt handling than in whites.

Adrenocorticotropic Hormone↗
PubMed1994

The effect of losartan on potassium-stimulated aldosterone secretion in vitro.

Potassium (K+) and angiotensin-II (Ang-II) are two distinct secretagogues for aldosterone release. However, a local adrenal renin-angiotensin system is present, and several studies suggest a complex interaction between K+ and locally produced Ang-II. First, superfusing zona glomerulosa (ZG) cells with K+ stimulates the secretion of both Ang-II and aldosterone. Second, K(+)-stimulated aldosterone secretion can be reduced in the presence of angiotensin-converting enzyme inhibitors. Because angiotensin-converting enzyme inhibitors are not specific inhibitors of the adrenal renin-angiotensin system, we further tested the hypothesis that locally produced Ang-II participates in K(+)-stimulated aldosterone release from rat ZG cells by using a specific Ang-II antagonist. Although type 1 (AT1) and type 2 (AT2) Ang-II receptors are present in ZG cells, only AT1 antagonist has been shown to mediate Ang-II-induced aldosterone secretion. Losartan, a specific AT1 antagonist, was used in this study. In the presence of losartan (10 microM for 9 mM K+ and 100 microM for 5 mM K+), the average aldosterone secretion during 2 h of superfusion with 9 mM K+ and 5 mM K+ was 70.1 +/- 5.4% (n = 5) and 58.5 +/- 2.2% (n = 3), respectively, of that in its absence. Losartan did not alter the amount of Ang-II secreted. The inhibitory effect of losartan lasted longer than 60 min after it was terminated. In summary, our results support the hypothesis that locally produced Ang-II contributes to the aldosterone secretory response to K+ stimulation at both physiological and supraphysiological levels.

Aldosterone↗
PubMed1993

Functional outcome following surgical excision of heterotopic ossification in patients with traumatic brain injury.

Increased osteogenesis, both in fracture healing and heterotopically, occurs in a significant percentage of patients with traumatic brain injury. Periarticular heterotopic ossification, especially in the hip and elbow joint, can cause functional loss of motion in patients with traumatic brain injury and interfere with activities of daily living. Seventeen patients with traumatic brain injury had periarticular heterotopic ossification resected in 20 joints (13 hips and seven elbows). Each joint was ankylosed prior to surgical resection (Brooker IV). In the immediate postoperative period, the average arc of motion was 85 degrees in the hips and 65 degrees in the elbows. At the final follow-up observation (average, 23 months), 17 of the 20 heterotopic ossification resected joints had maintained functional range of motion. Three joints in two patients reankylosed. Two additional patients had significant complications. In summary, surgical excision of periarticular heterotopic ossification in patients with traumatic brain injury can give satisfactory results, provided appropriate preoperative selection is done.

Adolescent↗
PubMed1993

Rapid modulation of renal and adrenal responsiveness to angiotensin II.

Reciprocal changes in adrenal and vascular responsiveness to angiotensin II (Ang II) are part of the normal adaptation to shifts in salt intake. When dietary salt intake is abruptly reduced from high to low, enhancement in aldosterone secretion requires several days to develop. Once established it is not known how quickly the enhancement is reversed with salt repletion. We investigated the time course and relative contributions of salt, volume expansion, or both to this process by studying 15 normotensive subjects; 5 were studied during both high-salt and low-salt balance, and 10 were studied only in low-salt balance. For rapid volume expansion to reverse low-salt balance, 5 subjects received in random order an infusion of normal saline or dextran. The adrenal glomerulosa and renal vascular responses to Ang II were assessed after each volume expansion maneuver. Saline and dextran infusions suppressed plasma renin activity and aldosterone equally, although dextran acted more slowly. Both also increased renal perfusion and renal vascular and pressor responses to Ang II, which in 3 to 7 hours became identical to responses seen during high-salt intake ("modulation"). Saline infusion also blunted adrenal responsiveness to Ang II during that same interval. Despite suppression of the renin-angiotensin system by dextran infusion, aldosterone responsiveness to Ang II remained enhanced. These observations suggest that the renal and vascular responses to Ang II are modulated rapidly by the effects of volume expansion per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1992

Antibacterial activity of dental implant metals.

This study was conducted to investigate the specific in vitro antibacterial effect of seven dental implant metals on oral bacteria which have often been identified in failing implants. The metals chosen for evaluation were titanium, chromium, cobalt, aluminum, iron, gold, and vanadium. These metals were selected because they are contained in many commonly used dental implants. The bacteria selected for this study included isolates of Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella melaniogenica, Actinobacillus actinomycetemcomitans, Actinomyces naeslundii, and Actinomyces viscosus. Sets of tubes containing either supplemented trypticase soy broth, brain-heart infusion-yeast extract, or brain-heart infusion-yeast extract with 5 percent defibrinated rabbit blood were aseptically prepared with doubling dilutions of the seven metals starting at an initial concentration of 500 micrograms/ml and terminating at 0 microgram/ml. Cultures of each organism were inoculated into each set of broth tubes containing all concentrations of metals. Tubes were incubated either anaerobically or in an atmosphere of 5 percent carbon dioxide for 48 hours at 35 degrees C and then assayed for ATP content which was proportional to the viable cellular biomass. The results showed that, although being bacteria and concentration dependent, all seven metals suppressed the growth of each organism. The rank order of antibacterial activity expressed by dental implant metals was gold > titanium > cobalt > vanadium > aluminum > chromium > iron.

Actinomyces↗
PubMed1992

Increased platelet angiotensin II receptor number in pregnancy-induced hypertension.

Women with pregnancy-induced hypertension (PIH) are characterized by relatively greater blood pressure sensitivity to exogenous angiotensin II (Ang II) than normotensive pregnant women. Evidence suggests that this is due to an alteration in Ang II receptor sites. However, the question of whether this represents an increase in receptor number or affinity remains unanswered. To answer this question Ang II receptors on platelets from normotensive women during each trimester of pregnancy and the postpartum period were studied and compared with platelet Ang II binding in third trimester women with PIH and in postpartum women who had had a recent pregnancy complicated by PIH. We also measured plasma renin activity, Ang II, and aldosterone in blood samples from these women and sodium and creatinine in 24-hour urine collections. Normotensive pregnant women had significantly less platelet Ang II binding than nonpregnant, postpartum women (0.85 +/- 0.19 versus 2.87 +/- 0.83%, p = 0.003), reflecting a reduction in receptor number but not affinity. This probably reflects the significant increase in Ang II during pregnancy. Urinary sodium excretion was equivalent and could not explain these changes. Comparisons of third trimester women with PIH against those without PIH documented a significantly higher Ang II binding in the women with PIH (2.23 +/- 0.42 versus 0.85 +/- 0.19%) that was caused by an increase in receptor number (6.0 +/- 1.3 versus 3.0 +/- 0.8 fmol Ang II per 5.6 x 10(8) platelets, p = 0.047) but similar Ang II binding affinity. This reflected significantly lower Ang II levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Non-modulation as an intermediate phenotype in essential hypertension.

Non-modulation is a trait characterized by abnormal angiotensin-mediated control of aldosterone release and the renal blood supply. To determine whether non-modulation defines a specific subgroup of the hypertensive population and its utility as an intermediate phenotype, we have studied the distribution of this quantitative trait, whether its features are reproducible on repeated testing, and whether there is concordance of its multiple features. Essential hypertensive patients (224) and normotensive subjects (119) received an infusion of angiotensin II (Ang II) at 3 ng.kg-1.min-1 for 30-45 minutes. p-Aminohippurate (PAH) clearance was assessed as an index of renal plasma flow while the subjects were on a 200 meq sodium diet; plasma aldosterone levels were measured while the subjects were on a 10 meq sodium diet. In 54 subjects, diuretic-induced volume depletion superimposed on a low salt diet was substituted for the Ang II infusion. The results of each study were submitted to maximum likelihood analysis to assess bimodality. In response to both diuretic-induced volume depletion (p < 0.000023) and Ang II infusion (p < 0.0009), aldosterone responses were bimodally distributed in the essential hypertensive but not in the normotensive subjects, suggesting that this trait identifies a discrete subgroup. In the 59 subjects who had both an adrenal and renal study, 50 (85%) were concordant. Finally, in 27 subjects studied two to six times over a span of 1-60 months, the intraclass correlations of the adrenal, PAH, or both responses were highly significant (p values between 0.001 and 0.00007), indicating high reproducibility of results on repeated testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗