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Biomedical subjects

J H Hamilton

Publications and source records attributed to J H Hamilton.

16 recordsLinked to original sources
PubMed2006

Discovery of 109Xe and 105Te: superallowed alpha decay near doubly magic 100Sn.

Two new alpha emitters 109Xe and 105Te were identified through the observation of the 109Xe --> 105Te --> 101Sn alpha-decay chain. The 109Xe nuclei were produced in the fusion-evaporation reaction 54Fe(58Ni,3n)109Xe and studied using the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. Two transitions at Ealpha = 4062 +/- 7 keV and Ealpha = 3918 +/- 9 keV were interpreted as the l = 2 and l = 0 transitions from the 7/2+ ground state in 109Xe (T1/2 = 13 +/- 2 ms) to the 5/2+ ground state and a 7/2+ excited state, located at 150 +/- 13 keV in 105Te. The observation of the subsequent decay of 105Te marks the discovery of the lightest known alpha-decaying nucleus. The measured transition energy Ealpha = 4703 +/- 5 keV and half-life T1/2 = 620 +/- 70 ns were used to determine the reduced alpha-decay width delta2. The ratio delta105Te(2)/delta213Po(2) of approximately 3 indicates a superallowed character of the alpha emission from 105Te.

Journal Article↗
PubMed2003

Fine structure in proton emission from 145Tm discovered with digital signal processing.

Fine structure in proton emission from the 3.1(3) mus activity of 145Tm was discovered by using a novel technique of digital processing of overlapping recoil implantation and decay signals. Proton transitions to the ground state of 144Er and to its first excited 2(+) state at 0.33(1) MeV with a branching ratio I(p)(2(+))=9.6+/-1.5% were observed. The structure of the 145Tm wave function and the emission process were analyzed by using particle-core vibration coupling models.

Journal Article↗
PubMed2000

Phase transitions above the Yrast line in 154Dy.

Spectra of the E2 quasicontinuum gamma rays feeding different spin regions of the 154Dy yrast line have been extracted. These are compared with corresponding theoretical spectra obtained by numerical simulations based on temperature-dependent Hartree-Fock theory, with thermal shape fluctuations. In this manner, different regions of the spin-energy plane can be examined. The results support the predictions of a smeared-out phase transition at high spin above the yrast line.

Journal Article↗
PubMed1998

Influence of race and dietary salt on the antihypertensive efficacy of an angiotensin-converting enzyme inhibitor or a calcium channel antagonist in salt-sensitive hypertensives.

Dietary salt restriction is a recommended adjunct with antihypertensive therapy. There may be racial differences in blood pressure response to salt restriction while on antihypertensive therapy. We performed a multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trial (black, n=96; Hispanic, n=63; white, n=232). Participants were initially preselected for stage I to III hypertension and then further selected for salt sensitivity (> or = 5 mm Hg increase in diastolic blood pressure after 3 weeks of low salt [< or = 88 mmol/d Na+] and high salt [>190 mmol/d Na+] diet). We compared the antihypertensive effect of an angiotensin-converting enzyme inhibitor (enalapril 5 or 20 mg BID) or a calcium channel antagonist (isradipine 5 or 10 mg BID) during alternating periods of high and low salt intake. The main outcome measure was blood pressure change and absolute blood pressure level achieved with therapy. During the high salt diet (314.7+/-107.5 mmol/d urinary Na+) there was greater downward change in blood pressure with both enalapril and isradipine compared with the low salt diet (90.1+/-50.8 mmol/d Na+); however, the absolute blood pressure achieved in all races was consistently lower on a low salt diet for both agents. Black, white, and Hispanic isradipine-treated salt-sensitive hypertensives demonstrated a smaller difference between high and low salt diets (black, -3.6/-1.6 mmHg; white, -6.2/-3.9 mmHg; Hispanic, -8.1/-5.3 mm Hg) than did enalapril-treated patients (black, -9.0/-5.3 mm Hg; white, -11.8/-7.0 mm Hg; Hispanic, -11.1/-5.6 mm Hg). On the low salt diet, blacks, whites, and Hispanics had similar blood pressure control with enalapril and isradipine. On the high salt diet, blacks had better blood pressure control with isradipine than with enalapril, whereas there was no difference in the blood pressure control in whites and Hispanics treated with either drug. Dietary salt reduction helps reduce blood pressure in salt-sensitive hypertensive blacks, whites, and Hispanics treated with enalapril or isradipine. These data demonstrate that controlling for salt sensitivity diminishes race-related differences in antihypertensive activity.

Adult↗
PubMed1998

N-3 fatty acid deficiency in the rat pineal gland: effects on phospholipid molecular species composition and endogenous levels of melatonin and lipoxygenase products.

N-3 essential fatty acid deficiency affects a number of biological and physiological processes. In this study, we investigated the effect of n-3 essential fatty acid status on two key pineal biochemical functions, melatonin production and lipoxygenation, using pineal glands from rats given an n-3-adequate or n-3-deficient diet. The pineal total lipid profile and phospholipid molecular species distribution altered by n-3 deficiency were evaluated in parallel. In pineal glands from n-3-deficient rats, an 87% reduction of 22:6n-3 (docosahexaenoic acid) was observed, and this decrease was accompanied by increases in 22:4n-6 (docosatetraenoic acid, 3-fold), 22:5n-6 (docosapentaenoic acid, 12-fold), and 20:4n-6 (arachidonic acid, 48%). The significant decrease of 22:6n-3 containing species in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) was also evident. These decreases in 22:6n-3 containing PL species were compensated by substantial accumulations of 22:4n-6 or 22:5n-6 and slight increases in 20:4n-6 containing PL species in PC and PE. In PS, however, the accumulation of n-6 species was not adequate to compensate for the loss of 22:6n-3 species. N-3 deficiency significantly reduced non-esterified 20:4n-6 and 22:6n-3 levels in pineals (25% and 65%, respectively). Concomitantly, the endogenous 12-HETE level decreased by 35% in deficient pineals. In contrast, n-3 deficiency led to a more than 60% increase in the daytime pineal melatonin level. In conclusion, n-3 fatty acid deficiency not only has profound effects on pineal lipid profiles but also on pineal biochemical activities. These results suggest that n-3 fatty acids may play a critical role in regulating pineal function.

Animals↗
PubMed1994

One year experience of elderly hypertensive patients with isradipine therapy.

This is the first report of long-term use (one year) of isradipine, a new dihydropyridine calcium channel blocker, in the treatment of elderly patients with essential hypertension. Patients completing a three month, double-blind, multicentre study comparing isradipine to hydrochlorothiazide (HCTZ) were eligible to enroll in this open-label, continuation study. At initial baseline, patients were at least 60 years of age and had DBP from 95 mmHg to 120 mmHg. Patients were titrated when necessary every two weeks with isradipine, 5 mg to 15 mg once daily or 2.5 mg to 10 mg twice daily, to maintain sitting DBP < or = 90 mmHg. HCTZ, 12.5 mg to 50 mg once daily, could be added for better BP control. A total of 136 patients completed the one year, open-label phase. One hundred and fourteen patients (84%) received isradipine as monotherapy (mean dose, 9.7 mg/day); 22 received concomitant HCTZ therapy at one year. Reduction in DBP was significant and similar among all age groups and races (mean change of -19 mmHg). Reduction in SBP was similar among all age groups. Ninety-four per cent of those receiving isradipine monotherapy achieved BP control during the last four months of treatment. Twenty-six patients (16%) withdrew from the study: 11 (7%) had adverse reactions (one with headache, two with pedal oedema, eight with other problems); 11 (7%) had nondrug-related problems; and in four (2%), the drugs were ineffective. Based on these observations, isradipine is a well-tolerated, safe and effective agent for long-term BP control in elderly patients with essential hypertension.

Aged↗
PubMed1992

A comparison of the safety of therapeutically equivalent doses of isradipine and diltiazem for treatment of essential hypertension.

We compared the safety of a new dihydropyridine calcium entry blocker, isradipine, with an equipotent dose of diltiazem in 174 mild hypertensives (diastolic blood pressure [DBP] 95 to 105 mm Hg). After appropriate washout and placebo periods, patients were randomly assigned to receive either 1.25 mg isradipine twice daily (Group I) or 40 mg diltiazem thrice daily (Group D). If DBP remained above 90 mm Hg, doses were increased to a maximum of 5 mg isradipine twice daily or 120 mg diltiazem thrice daily. Active therapy was given for a total of 12 weeks. Only 18 patients (nine from each group) did not complete the protocol. The patients were well-matched at baseline with a mean BP of 149/100 mm Hg for those who were randomized to isradipine and completed the protocol and 153/99 mm Hg for the diltiazem group. The responses to each drug were excellent with 72% of the isradipine patients and 73% of the diltiazem group having DBP less than 90 mm Hg at the completion of the study. Of the 156 patients who completed the protocol, only 18 patients (ten in Group I and eight in Group D) failed to respond. Both drugs were well-tolerated. No adverse reactions were reported by 68 percent of the patients in Group I and 65% of those in Group D. The most common side effect was headache (9.0% in Group I and 7.8% in Group D) followed by fatigue (5.2% in Group I and 3.9% in Group D). Age and race did not predict response to either agent but men responded slightly better to diltiazem than women. We conclude that isradipine and diltiazem are equally well tolerated and can be used successfully as a monotherapy to treat hypertension in a wide variety of patients.

Adult↗
PubMed1986

Ventilation in intact and glossopharyngeal nerve sectioned anaesthetized rats exposed to oxygen at high pressure.

The cause of the initial hyperventilation, which occurs on exposure to O2 at high pressure (o.h.p.), has been investigated by measuring tidal volume (VT), frequency of breathing (f) and hence ventilation (VE) in thirty-six barbiturate-anaesthetized rats, with or without their glossopharyngeal (IX) nerves sectioned, during 30-60 min of exposure to o.h.p. at 4, 6 or 8 atm absolute. In intact rats the rates of rise of VT, f and VE with time during exposure to o.h.p. were smallest at 4 and greatest at 8 atm absolute. In IX-sectioned rats the rates of rise of VT at 4, 6 and 8 atm absolute and of f at 4 atm absolute were similar to those of intact rats. At 6 atm absolute and even more so at 8 atm absolute, however, f decreased. Hence the slope of VE in IX-sectioned compared with intact rats was similar at 4 atm absolute but smaller at 6 and 8 atm absolute. In fact at 8 atm absolute VE remained constant in IX-sectioned rats. Since the slope of VE versus time in intact rats was steeper the greater the pressure and since the removal of carotid bodies in IX-sectioned rats reduced the VE slope at 6 and 8 atm absolute, the stimulus to the hyperventilation induced by o.h.p. cannot be an accumulation of CO2 in the brain resulting from the lack of O2 desaturation of haemoglobin. This theory would predict that VE should be identical at all pressures above 3.5 atm absolute. The findings in the IX-sectioned rats indicate a major contribution of the carotid bodies to the f increase in o.h.p. They may be stimulated by a histotoxic hypoxia induced by early O2 poisoning. Since the VT increase on exposure to o.h.p. was both large and fairly similar in intact and IX-sectioned rats, it is suggested that a large part of the VT increase was caused by stimulation of the central chemoreceptors by lactic acidosis induced by an o.h.p.-induced histotoxic hypoxia of the brain.

Anesthesia, General↗
PubMed1984

Improvement in depressed cardiac function in hypertensive patients during pindolol treatment.

To assess changes in left ventricular function during antihypertensive treatment using pindolol, a beta-adrenocepter blocking drug with potent intrinsic sympathomimetic activity, serial echocardiographic measurements were obtained in 70 hypertensive patients before and during 15 weeks of treatment with pindolol. For analysis, the patients were separated into three groups on the basis of their baseline left ventricular fractional shortening (Group I, 35 patients with normal fractional shortening of 28 percent or more; Group II, 16 patients with abnormal fractional shortening of 21 to 27 percent; and Group III, 19 patients with markedly abnormal fractional shortening of 20 percent or less). More than half of the patients in Group I and Group II had decreases in mean blood pressure of 10 percent or more in response to pindolol, but only one fourth of Group III patients had similar responses (p less than 0.05). Patients with normal pretreatment fractional shortening had a mild decrease in fractional shortening during pindolol treatment, whereas patients with either abnormal or markedly abnormal fractional shortening had an increase in fractional shortening. This increase in fractional shortening suggests the possibility that the partial agonist or intrinsic sympathomimetic activity of pindolol may play a role in preserving left ventricular function in patients with borderline or impaired function.

Adult↗
PubMed1983

Intrinsic sympathomimetic activity of pindolol. Evidence for interaction with pretreatment sympathetic tone.

Eighty-six hypertensive patients were treated with pindolol, a beta-adrenergic blocking drug with intrinsic sympathomimetic activity. To evaluate the interactions between beta-blockade, intrinsic sympathomimetic activity, and the level of pretreatment sympathetic activity, blood pressure, heart rate, and forced expiratory volume in one second (FEV1) were examined before and during a 15-week treatment program. The response of patients with a relatively higher pretreatment sympathetic tone reflected by a resting heart rate equal to or greater than 80 beats per minute (Group I) was compared with the response of patients with a lower pretreatment heart rate (less than 80 beats per minute) (Group II). Decreases in mean blood pressure were similar in the two groups. In patients in Group I, the net effect of pindolol was a modest decrease in heart rate and FEV1, supporting the concept that when sympathetic tone is relatively high, the beta-blocking effect is dominant. In contrast, patients in Group II showed little change in heart rate or FEV1 during pindolol treatment, reflecting a balance between the intrinsic sympathomimetic activity and beta-blocking effects of pindolol. Thus, the intrinsic sympathomimetic activity of pindolol is physiologically evident, and relative impact is dependent on the pretreatment level of sympathetic tone.

Clinical Trials as Topic↗
PubMed1982

Pindolol and systolic time intervals in patients with hypertension.

Two studies of systolic time intervals (STIs) in patients with mild to moderate hypertension (HBP) revealed that no mean change in systolic intervals occurred with pindolol therapy, although some patients had significant alterations in their STIs. Pindolol responders with normal pretreatment preejection period to left ventricular ejection time (PEP/LVET) ratios had a significant increase in this ratio following pindolol therapy, whereas those with abnormal pretreatment PEP/LVET ratios had improvement in this ratio on administration of the drug. Patients on propranolol showed no change in PEP/LVET ratio. Propranolol administration slowed heart rate and lengthened Q-S2, S1-S2, and LVET, however, without altering the Q-S2 and LVET index, indicating that the changes were caused by the effect of propranolol on the heart rate alone. Chlorthalidone in high doses significantly reduced the Q-S2 index and the S1-S2 index, indicating that these changes were not caused by alteration of the heart rate. The second study suggests that STIs may provide a predictive clue for clinical response to pindolol. Patients with normal cardiac function (group I) are more likely to respond to pindolol than are those with abnormal cardiac function (group II). Directionally opposite changes in STIs in the two subgroups suggest different mechanisms for changing cardiac function. Pindolol's dual role as a beta-blocking agent with intrinsic sympathomimetic activity is proposed as a possible explanation, beta-blocking effects predominating in group I and sympathomimetic activity balancing the beta effect in group II.

Adult↗
PubMed1981

[New developments in the area of education of the hearing impaired].

Developments for the language- and hearing-impaired include intensive diagnostic and prognostic evaluation by a professional team. Possibilities are presented to the parents and child, with whom the final decision of educational placement rests. Further growth in language and speech education is ascribed to advanced scientific equipment and increasing knowledge, e.g. of the brain. Home units and an after care section also supply increased differentiation.

Adolescent↗
PubMed1981

Human synovial fibroblast plasminogen activator. Modulation of enzyme activity by antiinflammatory steroids.

Human synovial fibroblasts in culture have been shown to have low plasminogen activator (PA) activity; however, conditioned medium from concanavalin A-stimulated peripheral blood mononuclear cells (c-MCCM) stimulates the cellular levels of this protease. The present study shows that low concentrations of a series of antiinflammatory steroids inhibit the PA activities of both unstimulated and c-MCCM-stimulated fibroblasts. Dexamethasone, the corticosteroid studied in greatest detail, suppresses both the extracellular and cell-associated enzyme activities; this inhibition is rapid, reversible, and is not due to the inhibition of cellular RNA, protein, or DNA synthesis. PA has been invoked as possibly being generally important for the processes of cell migration, tissue remodeling, and inflammation. These in vitro observations suggest that physiologic and/or pharmacologic control of the PA levels in synovial fibroblasts might also be achieved in vivo by the interacting effects of mutually antagonistic agents, namely, a product from stimulated mononuclear cells and glucocorticoids.

Anti-Inflammatory Agents↗
PubMed1979

Effect of adrenal suppression with dexamethasone in essential hypertension.

The 24-h integrated plasma concentration of aldosterone (IC-ALDO), PRA (IC-PRA), and cortisol (IC-F) were measured in 34 male patients with uncomplicated mild essential hypertension and 15 matched normal controls using a portable 24-h continuous nonthrombogenic blood withdrawal system. The hypertensive were subsequently given 0.5 mg dexamethasone three times per day, resulting in suppression of their urinary excretion of 17-hydroxycorticosteroids and free cortisol. The diastolic blood pressure of the hypertensives fell during adrenal suppression from 104 +/- 5 to 96 +/- 8 mm Hg (mean +/- 1 SD; P less than 0.0001). The systolic pressure fell from 150 +/- 16 to 148 +/- 17 (P greater than 0.01). Baseline values for IC-F, IC-ALDO, and IC-PRA were similar in hypertensive subjects and normal controls. After treatment with dexamethasone for 8 weeks, IC-F in the hypertensives decreased from 7.8 +/- 2.1 to 0.7 +/- 0.6 microgram/dl (P less than 0.0001). There was no associated change in IC-ALDO or IC-PRA. Thus, the fall in diastolic blood pressure in response to dexamethasone was associated with suppression of IC-F, without demonstrable changes in other endocrine or biochemical factors measured.

Adrenal Glands↗
PubMedDate not supplied

Hypertension in elderly persons.

OBJECTIVE: To provide an overview of the prevalence of hypertension in the elderly population and discuss the advantages and disadvantages of various classes of antihypertensive drugs. METHODS: We review the published clinical trials on treatment of elderly patients with hypertension and describe adverse reactions that are frequently associated with antihypertensive therapy. RESULTS: On the basis of the standard for control of hypertension established by the National Health and Nutrition Examination Survey for 1988-1991 (140/90 mm Hg), almost 75% of all African-Americans and 50% of all whites 60 to 74 years of age have hypertension. If modifications in lifestyle (such as weight reduction and increase in exercise) do not normalize blood pressure levels, drug therapy is warranted. Meta-analyses of major trials of treatment of hypertension have revealed significant reductions in cardiovascular-related mortality and stroke, and available data indicate that prudent use of antihypertensive agents is associated with an acceptable degree of toxicity. Low-dose thiazide diuretics and b-blockers remain the agents of choice. CONCLUSION: Several trials have substantiated the effectiveness of treatment of hypertension in elderly subjects. Drug therapy should be initiated at low doses, and careful follow-up should monitor for adverse effects.

Journal Article↗