An observation of thromboxane A2 in arterial blood after cholesterol feeding in rabbits

Agents responsible for the entry of cholesterol-bearing lipoproteins into the arterial wall represent local risk factors in atherogenesis. In an attempt to identify these agents, we inserted a catheter into the ascending aorta of rabbits and 5 ml of arterial blood sample was withdrawn. The contraction of the aortic strip of rabbit against Piper and Vane's antagonists with application of this sample was observed. Samples obtained after feeding of 1 Gm/Kg of cholesterol and after an intravenous administration of thromboxan A2 (TXA2) contracted the aortic strip. Samples from non-treated rabbits or those obtained after intravenous administration of 10 microgram of epinephrine or norepinephrine did not contract the strip. Previous administration of 20 mg/Kg of indomethacin decreased the contraction developed after feeding of 1 Gm/Kg of cholesterol. It was suggested that TXA2 might be released into the arterial blood by the ingestion of cholesterol and might be one of the agents repsonsible for the entry of lipoproteins.

Glucose tolerance in spontaneously hypertensive rats

In order to clarify the relationship between essential hypertension and glucose metabolism, and to approach the pathophysiology or the etiology of essential hypertension, we examined glucose tolerance test (GTT) using spontaneously hypertensive rats (SHR) as models. SHR, namely stroke-prone SHR (SHRSP) and stroke-resistant SHR (SHRSR) always had higher serum glucose levels at each GTT phase than normotensive control Wistar-Kyoto rats. They also tended to show higher levels in the young even at 5 weeks of age rather than in the adult. These results indicate that hyperglycemic tendency or lower glucose tolerance may be a characteristic of spontaneous hypertension and may be related to the mechanism of hypertension.

Hemolytic pattern of erythrocytes in the newborn measured by the coil planet centrifuge system and its relationship to neonatal jaundice

Dynamic osmotic fragility of erythrocytes in cord blood and its changes during the neonatal period were studied by means of a coil planet centrifuge system. The starting-point for hemolysis in the newborn become similar to that of adult blood after approximately a week, while the shift of the end-point to the adult range required one month or more. The percentage of fragile cord blood cells with a hemolysis starting-point above 110 m osmol and the maximum bilirubin level during neonatal period were examined. A high percentage of fragile cells was associated with high bilirubin levels, and when fragile cells comprised more than 7.0% of the total cord blood erythrocytes, the bilirubin level tended to rise above 15 mg/dl.

Atherogenic mechanisms: enhancement of regression of atheromatous lesions by phthalazinol

Atherosclerosis was produced in rabbits by feeding 1% cholesterol pellets for 15 weeks to 35 male rabbits divided into two equal groups--the placebo control and phthalazinol group--with a comparable serum cholesterol level. The phthalazinol group was given 20 mg/kg of the compound daily. 13 rabbits of both groups were on 15 weeks of the treatment and the remaining 22 rabbits were treated for 30 weeks. The treated group exhibited a statistically significant increased removal of cholesterol from atherosclerotic aortas and improvement in pathological changes. This enhancing effect was more marked in the animals treated for 30 weeks. Such evidence indicates that there are substances capable of enhancing the removal of cholesterol from atheromatous lesions. In light of the pharmacological properties of phthalazinol, the possible role of thromboxane A2 released from platelets adhered and aggregated on atheromatous plaques, in the progression of atherosclerosis is worthy of continued investigation.

Experimental ischemic heart disease induced by thromboxane A2 in rabbits

How an acute ischemic attack is induced in a patient with coronary atherosclerosis is unknown and we carried out studies using thromboxane A2 (TXA2) to determine if acute myocardial ischemia and necrosis could be induced in rabbits. TXA2 was perfused through the coronary artery for 5 seconds by means of a Swan-Ganz catheter through the right common carotid artery. Significant serial changes of ST-T on ECG and hypotension were observed from 1 minute to more than 1 day after the perfusion in all 22 rabbits. The TXA2 that was composed of both aggregated platelets and prostaglandin H2 induced the same response, and such was dose dependent. The inactivated TXA2 was without effect. Seventeen of the experimental rabbits were autopsied. Histological studies of the hearts showed focal myocardial ischemia and necrosis in all rabbits except one autopsided 10 minutes after the perfusion. TXA2 is apparently capable of inducing acute myocardial ischemia and necrosis.

Effect of isometric handgrip on systolic time intervals in patients with ischemic heart disease and cyclic amp phosphodiesterase inhibitor pretreatment

The effect of cAMP phosphodiesterase inhibitor EG626 on the left ventricular function was studied in 23 patients with ischemic heart disease at rest and during the IHG test. Administration of a single dose of the substance produced changes in STIs indicating an increase in cardiac output and a possible enhancement of myocardial contractility during the IHG test. EG626 may have a beneficial effect on impaired left ventricular function in patients with ischemic heart disease.

Enhancement of platelet sensitivity to ADP-aggregation by isometric exercise in arteriosclerosis patients and its prevention

A new method for assessment of platelet sensitivity to ADP-aggregation was devised. Its reproducibility and the correlations between the values obtained by this method, the optical density (O. D.) method, and the screen filtration pressure (SFP) method were assessed. In summary, this method may be said to have three main points: 1. It can be performed without centrifugation, avoiding mechanical stress to platelets, using only 0.8 ml. of blood and inexpensive equipment. 2. It may reflect different aspects of platelet function from the O. D. method and the SFP method, despite the positve significant correlations between the values obtained by these three methods. 3. It was proved to be highly reproducible and is thought to be useful clinically. By using this method, the effect of sustained isometric exercise by handgripping on platelet aggregability was assessed in coronary sclerotic and cerebral arteriosclerotic patients on placebo and EG-626, a newly synthesized cyclic AMP phosphodiesterase inhibitor. On placebo, an enhancement platelet sensitivity was observed after isometric exercise in coronary and cerebral arteriosclerotic patients but not in healthy control subjects. The enhancement was prevented by pretreatment of EG-626, administered orally 1.5 hours prior to exercise.

Ischemic carotid endothelium. Transmission electron microscopic studies

The endothelium of monkey and rabbit common carotid arteries subjected to ischemia was examined by transmission electron microscopy (TEM). The right carotid artery of 24 rhesus monkeys was occluded by proximal and distal placement of removable surgical clips for periods ranging from five minutes to four hours. A single clip was used to occlude the right carotid artery of 15 rabbits for periods ranging from 5 to 30 minutes. With TEM, numerous blebs, intracytoplasmic vacuoles, membranous whorls, and pseudopodia were found in the endothelium of arterial segments subjected to ischemia by double or single clipping for as little as five minutes. Following occlusion of one hour or longer, disruption of interendothelial junctions was also noted. These TEM findings were compared with earlier TEM studies of the response of endothelium to other injurious stimuli and with previous scanning electron microscopic studies in which the same ischemic models were utilized.

Prenatal diagnosis of osteogenesis imperfecta congenita by means of fetography

By means of fetography, prenatal diagnosis of osteogenesis imperfecta congenita was performed on two pregnant women in the 34th week of gestation with familial histories of the disease. In 1 of the 2 cases, the fetogram revealed abnormal twisting of the torso, shortening, and severe angulation deformities of the extremities with callus formation and parchmentlike skull despite clear-cut outline of the scalp. On the basis of these findings, the fetus was diagnosed as osteogenesis imperfecta congenita and subsequently confirmed. Thus, the excellent fetal resolving power of fetography permitted successful prenatal diagnosis of the disease far more easily and precisely than plain roentgenography.

Hyperreactive arterial endothelial cells: a clue for the treatment of atherosclerosis

Arterial endothelial cells, which are capable of phagocytizing carbon particles of the same size as beta- and pre-beta-lipoprotein, were found only in endothelial cells of arterial segments susceptible to atheromatous changes in susceptible animal species, and the distribution closely corresponded to the susceptibility. The distribution of such endothelial cells is dense in large arteries, in the openings to their branches, especially in downstream portions, of rabbits, hens, and cocks; however, the distribution is relatively scanty in arteries of rhesus monkeys and is very scanty in dogs. Carbon particles were also rare in the suckling rabbit and tended to increase with age. They were not found in Wistar rats but were found in spontaneously hypertensive rats, which showed a characteristically diffuse distribution, even in relatively small arteries. The carbon particles, phagocytized, were released to the subendothelial space but were difficult to pass through the internal elastic lamina and tended to stagnate there for more than one month. The authors therefore call these cells hyperreactive endothelial cells. Various vasoactive substances, such as angiotensin II, histamine, and serotonin, significantly enhanced the phagocytic activities of arotic endothelial cells in rabbits; epinephrine and norepinephrine also slightly enhanced these activities. Various smooth muscle relaxants, such as ATP, pyridinol carbamate (ATP synthesis-enhancing substance), cycli-AMP, dibutyryl cycli-AMP, phthalazinol (cyclic-AMP phosphodiesterase inhibitor), iproveratril (calcium entry-inhibiting substance), colchicine, and vinblastine, with their different modes of action, commonly inhibited phagocytic activities, a finding that suggests a significant role for contractile protein in the permeability problem of atherogenesis. The atheromatous lesions of cholesterol-fed rabbits exhibited a striking increase in hyperreactive endothelial cells, accompanied by a marked rise in the activity of low-Km cyclic-AMP phosphodiesterase activity in atheromatous lesions and adjacent muscular layers, especially in rabbits with rapidly progressing atheroma.

Treatment of senile dementia and cerebellar disorders with phthalazinol. Cyclic AMP-increasing agent, phthalazinol, in therapeutic trials in hitherto incurable morbid conditions (I)

Three patients suffering from presenile dementia and two patients suffering from senile dementia were treated with phthalazinol. A limited but definite improvement in attentiveness, vocabulary reception and psychologic attainment and also a limited but definite improvement in range of motion, gait and endurance were noted shortly after the treatment with phthalazinol and the progression of their dementia seemed to be temporarily retarded by phthalazinol. Seven patients suffering from parenchymatous cerebellar degeneration (late cortico-cerebellar atrophy) and four patients suffering from olivopontocerebellar atrophy were treated with phthalazinol. A relatively rapid, limited and sustained improvement of cerebellar functions, including those of speaking, writing and walking, was noted in almost all patients. Also, rigidity, akinetic tendency and abnormal posture seen in olivopontocerebellar atrophy fairly well responded to the treatment. Dysphagia, disturbance of micturition, and hypersecretion of saliva have also rapidly and completely disappeared in all cases. The cases with a long history responded relatively poorly, but the cases with a relatively short history responded quite strikingly to the therapy. No side effects were noted.