Design and evaluation of nonpeptide fibrinogen gamma-chain based GPIIb/IIIa antagonists.

Two series of nonpeptide turn mimetics were designed by analysis of the solution NMR structure of the 385-411 sequence of the gamma-chain of fibrinogen. These compounds, based on the KQAGD (Lys-Gln-Ala-Gly-Asp, 406-410) sequence, were synthesized and studied in vitro. The most interesting compound from our study, RWJ 50042 (25), exhibits potent inhibition of fibrinogen binding to GPIIb/IIIa (IC50 = 0.009 microM), as well as thrombin- or collagen-induced platelet aggregation (IC50 = 0.76, 0.14 microM). Since the 400-411 sequence is required for gamma-chain bioactivity and is a unique recognition sequence among ligands for integrins, vis-a-vis other RGD (Arg-Gly-Asp)-presenting proteins, these turn mimetics may represent a new, selective approach to antagonism of the fibrinogen receptor.

Pericardial pressure attenuates release of atriopeptin in volume-expanded dogs.

The role of the pericardium in the release of atriopeptin (AP) was examined, utilizing two separate protocols, in alpha-chloralose-anesthetized dogs. Protocol I consisted of an experimental group (9 dogs), in which the pericardium was incised to allow instrumentation and reapproximated, and a control group (6 dogs), in which the pericardium was left undisturbed. In the experimental group, mean right atrial pressure (Pra) was elevated from a control value of 1.8 +/- 0.9 mmHg (mean +/- SD) to 8.3 +/- 0.8 mmHg for 40 min by volume expansion with isoncotic, lactated Ringer solution. After this period of volume expansion, the pericardium was removed while holding Pra at 8 mmHg. During volume expansion, arterial blood samples for AP analysis were taken at 5, 10, 15, 20, 30, and 40 min, pre- and postpericardiectomy. A similar protocol was followed in the control group. At a Pra of 8 mmHg prepericardiectomy, the plasma AP concentration was 76 +/- 17 pM/l and 74 +/- 38 pM/l in the experimental and control groups, respectively. However, after pericardiectomy, AP levels increased significantly in both the experimental group (136 +/- 41 pM/l; P less than 0.001) and the control group (107 +/- 53 pM/l; P less than 0.025). In protocol II (6 dogs), the pericardium was removed before volume expansion, and Pra was elevated by 2- to 3-mmHg increments and maintained for periods of 13 min at each pressure. AP concentration did not increase until Pra reached 3-4 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure and serum calcium responses to altered sodium intake in high renin hypertension.

Subjects with high renin hypertension tend to be sodium-resistant showing paradoxical blood pressure responses to alterations in sodium intake. Of twenty-five subjects with high renin essential hypertension (ten females, 15 males, mean age 30 years), 14 were noted to have a decrease in mean arterial blood pressure (MAP) when sodium intake was increased from 10 to 100 mmol/d. The percentage response of plasma renin activity was greater in these patients than in those with an increase in MAP (-55.4 +/- 5.4 v -33.6 +/- 6.9, P = .018). Overall, the response of MAP was directly correlated to the percentage response of plasma renin activity (r = .549, P = .005), and inversely related to the change in serum calcium concentration (corrected for changes in serum albumin) (r = -.547, P = .005). No intercorrelation between the changes in plasma renin activity and serum calcium concentration was detected. The blood pressure response to increased sodium intake in high renin hypertension would appear to be divergent and related not only to the suppression of plasma renin activity, but also to changes in circulating calcium.

Flupenthixol and fluvoxamine in mild to moderate depression: a comparison in general practice.

Seventy-two depressed patients attending general practices were randomly allocated to treatment with either flupenthixol dihydrochloride (1 to 2 mg/day) or fluvoxamine maleate (100 to 200 mg/day) to assess efficacy and side-effects over a 4-week period. Clinical assessments were carried out before medication (Day 1) and on Days 8, 15 and 29 of treatment using the Hamilton Rating Scale for Depression, Clinical Global Impressions (CGI) and a patient self-assessment visual analogue scale for depression. Unwanted symptoms were also recorded. Reduction in mean total scores on the Hamilton scale at each assessment and therapeutic effect improvement on the CGI were greater for patients treated with flupenthixol (p less than 0.05). Reduction in unwanted symptoms was progressive in both groups, but more pronounced in patients receiving flupenthixol. Twice as many new symptoms arose in the fluvoxamine group compared to the flupenthixol group. Four patients were withdrawn in the fluvoxamine group due to untoward drug effects compared with none in the flupenthixol group.

Norepinephrine and calcium responses to altered sodium intake in modulating and non-modulating high-renin hypertension.

Sodium sensitivity in subjects with high-renin hypertension has been associated with non-modulation of cardiovascular and biochemical responses to alteration in sodium intake. Using the percentage suppression of plasma renin activity in response to an increase in dietary sodium intake, high-renin hypertensive subjects were categorized in two groups. In association with the increase in sodium intake, modulators showed greater than 58% suppression of plasma renin activity, and significant reductions in mean arterial pressure, plasma aldosterone, norepinephrine and serum calcium concentration. Non-modulators had no significant change in plasma renin activity, mean arterial blood pressure, plasma aldosterone, norepinephrine or serum calcium concentration. The blood pressure response to an increase in dietary sodium intake may be a composite of responses of the renin-angiotensin-aldosterone axis, the adrenergic nervous system and calcium regulatory system.

Excessive growth of cultured beta cells from an adult patient with beta cell hyperplasia.

We have studied a 25-year-old female with frequent, severe hypoglycemic episodes. Concurrent with low serum glucose levels, the concentrations of C-peptide and insulin were markedly elevated. Tests for sulfonylurea hypoglycemic agents were negative. Special tests did not disclose any neoplasm. Biopsy of the pancreatic tail revealed islet cell hyperplasia and adenomatosis. About two-thirds of the pancreas was resected, resulting in correction of all metabolic abnormalities. Specific fluorescein-labeled anti-insulin antibodies revealed staining in 60-80% of the cultured cells isolated from the patient's pancreas, while electron microscopy disclosed insulin storage granules in about 80%. By comparison, for each of these findings, the range for cells from normal pancreases was 30-50%. In contrast to these control cells, cells from the patient grew about 2 and 2.6 times more rapidly during the first two cell cycles, and the growth persisted through four cycles. The greater and more enduring growth of the patient's cells in culture must have been at least partly independent of circulating factors. Paracrine/autocrine principles from the beta cells or other islet cells may have been responsible.

Studies of thyroxine binding to plasma proteins in health and disease.

Thyroxine binding protein characteristics were defined in 6 normal subjects, 4 with thyroxine binding globulin (TBG) deficiency, 3 with TBG increase, one with hyperthyroxinemic dysalbuminemia, 7 with severe non-thyroidal illness, and 3 with chronic renal failure. Free thyroxine was measured by Sephadex partition in plasma to which increasing thyroxine concentrations were added. Deconvolution of the resultant titration data was performed by computer modelling. Abnormalities of thyroxine binding capacities or of binding affinities occur in non-thyroidal illness, chronic renal failure, and sporadically. The patient with hyperthyroxinemic dysalbuminemia had increased thyroxine binding affinity to thyroxine binding prealbumin as well as to albumin. "Free-T4 assays" or estimates of Free-T4 by calculation from total thyroxine and measures of protein binding such as T3-uptake must be expected to be perturbed by these binding protein abnormalities unless such interferences are explicitly demonstrated to be absent.

Lung angiotensin converting enzyme activity in chronically hypoxic rats.

A study was carried out to test the hypothesis that the reduced lung angiotensin converting enzyme (ACE) activity which occurs in chronic hypoxia is related to the development of pulmonary hypertension rather than to hypoxia per se. Right ventricular mean systolic pressure (Prvs, mm Hg) and ACE activity (nmol/mg protein/min) in lung tissue homogenates were measured in seven groups of four rats placed in a hypobaric chamber (380 mm Hg; 51 kPa) for two to 24 days. Identical measurements were made on 11 groups of four rats, which were placed in the chamber for 24 days and then allowed to recover in room air for one to 153 days. After two days of hypoxia the mean Prvs (25.5 (SD 3.7] and the mean lung ACE activity (56 (4.6] did not differ significantly from control values. Exposure to hypoxia for four to 24 days caused a progressive increase in mean Prvs to 44.4 (5.9) and a progressive reduction in mean lung ACE activity to 34 (4.0). During recovery lung ACE activity increased and Prvs decreased, so that normal values were achieved by 15 and 56 days respectively. Decreased lung ACE activity may be related to haemodynamic factors associated with pulmonary hypertension rather than to hypoxia.

Pulmonary hypertension induced in rats by monocrotaline and chronic hypoxia is reduced by p-chlorophenylalanine.

We have studied the role of 5-hydroxytryptamine (5-HT) in monocrotaline pulmonary hypertension and chronic hypoxic pulmonary hypertension in rats using p-chlorophenylalanine (PCPA) which inhibits 5-HT synthesis. We measured right ventricular mean systolic pressure (Prvs), right ventricular hypertrophy, medial thickness of muscular pulmonary arteries, and muscularization of pulmonary arterioles 17 days after a single dose of monocrotaline (60 mg/kg) and after 26 days of chronic hypobaric hypoxia (380 mm Hg). In monocrotaline pulmonary hypertension, pretreatment with PCPA (500 mg/kg) was associated with significant reductions (p less than 0.05) in Prvs (29%), right ventricular hypertrophy (33%), and medial thickness of muscular pulmonary arteries (14%). In chronic hypoxic pulmonary hypertension, pretreatment with PCPA was associated with significant reductions in Prvs (20%), right ventricular hypertrophy (28%), medial thickness of muscular pulmonary arteries (14%), and muscularization of pulmonary arterioles (47%). 5-HT may play a role in the development of monocrotaline pulmonary hypertension and chronic hypoxic pulmonary hypertension in rats.

Limitations of the oral calcium loading test in the management of the recurrent calcareous renal stone former.

Twenty-two patients with idiopathic hypercalciuria were evaluated using an oral calcium loading test and compared with 20 normal controls. Following a 12-hour overnight fast, all subjects collected a two-hour urine sample after which they received 1 g elemental calcium as galacto-gluconate in milk. Two further two-hour urine collections were obtained consecutively following the oral calcium load. In the fasting state, 4 (18%) of the 22 patients had urinary calcium excretion (UCaE) above normal, but none had elevated iPTH or urinary cAMP values. After calcium loading, only 10 (45%) of the 22 patients had delta UCaE greater than controls (delta = difference in UCaE between third and first urine samples). We conclude that despite demonstrable differences between the mean values of patient and control groups with respect to the UCaE following calcium loading, the large overlap of values negates the clinical usefulness of such procedures in the routine management of individual patients. The definition of renal leak hypercalciuria based on a high fasting UCaE alone remains of uncertain significance.

Failure to show decrease in small pulmonary blood vessels in rats with experimental pulmonary hypertension.

We induced chronic pulmonary hypertension in one group of rats by exposing them to chronic hypobaric hypoxia (380 mm Hg for three weeks) and in another group by administering a single subcutaneous dose of monocrotaline (60 mg/kg body weight). Both groups of rats showed increase of the right ventricular mean systolic blood pressure and right ventricular hypertrophy. We measured the surface area of histological sections of the left or right lungs and counted all small blood vessels with an external diameter of less than 50 microns and with a definite elastic coat lying distal to respiratory bronchioles. In the 10 rats with chronic hypoxic pulmonary hypertension the mean total number of small pulmonary blood vessels was 428.8 +/- 96.9 (SD) compared with 337.8 +/- 91.9 in 10 untreated control rats. The number of small pulmonary blood vessels per mm2 of lung tissue was 4.0 +/- 1.3 in the chronically hypoxic rats compared with 3.8 +/- 1.2 in the controls. The mean total number of small pulmonary blood vessels in nine rats with monocrotaline-induced pulmonary hypertension was 396.8 +/- 61.7 compared with 384 +/- 55.4 in three control rats. The number of small pulmonary blood vessels per mm2 lung tissue was 3.3 +/- 0.6 in the rats treated with monocrotaline compared with 3.6 +/- 0.6 in the control group. We conclude that the number of small pulmonary blood vessels is not reduced in rats with pulmonary hypertension induced by chronic hypoxia or monocrotaline.

Lung angiotensin converting enzyme activity in rats with pulmonary hypertension.

We have studied serum and lung tissue angiotensin converting enzyme (ACE) activity in female Wistar rats with pulmonary hypertension induced by two different methods. Chronic pulmonary hypertension was produced in one group of 10 rats (CH) by confinement in a hypobaric chamber (380 mmHg) for three weeks, and in another group fo 10 rats (M) by a single subcutaneous injection of monocrotaline (60 mg/kg body weight). In these two groups of tests rats and in 20 untreated controls (C), we evaluated right ventricular mean systolic blood pressure (Prvs mmHg), right ventricular hypertrophy, and serum ACE (n mol/ml/min). In lung tissue homogenate, we measured the specific activity of ACE (n mol/mg protein/min), alkaline phosphatase (AP) (IU/mg protein) and lactic dehydrogenase (LDH) (IU/mg protein). The Prvs in groups, C, CH, and M was 25 +/- 7 SD, 41 +/- 7, and 51 +/- 5, respectively. The ratio of right ot left ventricular weight (RV/(LV + S)%) in groups, C, CH, and M was 29 +/- 4, 52 +/- 5, and 56 +/- 7, respectively. The lung tissue ACE in groups C, CH, and M was 85 +/- 11, 65 +/- 20, and 22 +/- 5, respectively. In groups CH, and M the Prvs and RV/(LV + S)% were significantly elevated above control values while lung ACE was significant decreased (p less than 0.05). There was a significant inverse relationship between lung ACE on one hand, and Prvs (r = - 0.73) and RV/(LV + S)% (r = - 0.71) on the other hand. Serum ACE and lung AP were unchanged. In group M there was a slight but significant reduction in lung LDH. Chronic pulmonary hypertension, irrespective of its method of production, is associated with decreased lung ACE. The reduction in lung ACE is inversely proportional to the severity of pulmonary hypertension and right ventricular hypertrophy.

Angiotensin converting enzyme activity and evolution of pulmonary vascular disease in rats with monocrotaline pulmonary hypertension.

We have investigated the role of angiotensin converting enzyme (ACE) in the development of pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular disease in rats given a single subcutaneous injection of the pyrrolizidine alkaloid monocrotaline. Thirty-six young female Wistar rats were divided into a test group of 27 animals and a control group of nine animals. Each test rat was given a single subcutaneous injection of monocrotaline (60 mg/kg body weight). On the first, third, fifth, seventh, tenth, twelfth, fourteenth, seventeenth, and twenty-second days after the injection of monocrotaline the mean right ventricular systolic blood pressure was measured in one control and three test rats. The animals were then killed and we measured the specific activity of ACE in serum and lung homogenate. We also evaluated muscularisation of pulmonary arterioles, medial hypertrophy of muscular pulmonary arteries, and right ventricular hypertrophy. The sequence of changes was as follows: muscularisation of pulmonary arterioles and medial hypertrophy of muscular pulmonary arteries were apparent seven days after administration of monocrotaline; pulmonary hypertension and reduced lung ACE activity occurred after 10 days; right ventricular hypertrophy was detected after 12 days. Serum ACE activity was unchanged. It is concluded that the reduction in lung ACE activity is a result rather than a cause of the pulmonary hypertension. This reduction in lung ACE activity may be a protective mechanism designed to limit the elevation of the pulmonary arterial pressure.

Effect of intermittent normoxia on muscularization of pulmonary arterioles induced by chronic hypoxia in rats.

We studied the effect of continuous and intermittent normoxia for 6 and 20 wk on the muscularization of pulmonary arterioles in rats with chronic hypoxic hypertension. After 4 wk in a hypobaric chamber (380 mm Hg) the proportion of small pulmonary blood vessels with 2 elastic laminae (PVTEL) was 21.57 +/- 14.86% (SD) (n = 10) compared with 3.66 +/- 1.86% in 10 untreated control animals. Recovery using continuous normoxia and intermittent normoxia 16 h/day for 6 wk caused a reduction in PVTEL to 8.45 +/- 4.09% (n = 6) and 7.16 +/- 6.96% (n = 6), respectively. Right ventricular hypertrophy (RVH) was reversed by recovery using continuous normoxia for 6 wk but was unaffected by intermittent normoxia (16 h/day). Intermittent normoxia 8 h/day for 6 wk did not reduce the PVTEL or RVH. Continuous normoxia for 20 wk reversed the muscularization of small pulmonary vessels (PVTEL, 3.86 +/- 3.57%; n = 4) and RVH. Intermittent normoxia (16 h/day) for 20 wk significantly diminished the PVTEL to 7.39 +/- 3.73% (n = 5) but did not reduce RVH. Prolonged continuous normoxia slowly reversed the pulmonary hypertension, RVH, pulmonary vascular lesions, and polycythemia induced by chronic hypoxia. Intermittent normoxia (16 h/day) diminished the pulmonary vascular lesions but not the pulmonary hypertension, RVH, and polycythemia. Intermittent normoxia (8 h/day) was ineffective.

Mast cell stabilizing compound FPL 55618 reduces right ventricular hypertrophy and lung mast cell hyperplasia in chronically hypoxic rats.

Rats treated with chronic hypobaric hypoxia (21 days, 380 Torr) and mast cell stabilizing compound FPL 55618 had significantly less right ventricular hypertrophy and lung mast cell hyperplasia than rats subjected to chronic hypoxia alone. Right ventricular blood pressure was not reduced.