Peripheral nervous system functions of workers exposed to n-hexane at a low level

In order to assess the effects on the peripheral nervous system of n-hexane at a low level, an epidemiological study using a questionnaire, neurological examinations, and neurophysiological studies was carried out on two age-matched groups; one, consisting of 14 exposed workers and the other, of 14 control workers. The 8 h time weighted average of n-hexane concentration in the exposure environment was 58 +/- 41 (mean +/- SD) ppm. In the individual worker, no obvious signs could be found indicating damage to the nervous system that were referable to the n-hexane exposure. On the other hand, when the subjects were taken in groups, the results obtained from the exposed group showed a minor partiality for functional impairment of the peripheral nervous system in many test items. In particular, statistically significant differences between the two groups were detected in the following items: (1) inquiries by questionnaire for persistent or transient symptoms regarding muscle weaknesses and dyesthesia of limbs; (2) the jump test on one foot; (3) the tuning fork test for vibration sensation on the radial processes; (4) the maximal velocity and the residual latency of motor nerve conduction of the posterior tibial nerve. In conclusion, it is not likely that at exposure levels less than the current threshold limit value of 100 ppm proposed by ACGIH, n-hexane may induce clinically overt polyneurophathy. However, there is no gainsaying the possibility that in the exposed workers as a whole, small cumulative effects in the peripheral nervous system may be brought about by long-term n-hexane exposure less than 100 ppm.

Does activation of cyclic AMP dependent phosphorylation induced by beta-adrenergic agent control the tone of vascular muscle?

1. The relaxing action of the beta-adrenergic agent, isoprenaline, on the porcine coronary artery was investigated in relation to the cyclic AMP level, the endogenous binding of cyclic AMP to the regulatory unit of cyclic AMP dependent protein kinase or the phosphorylation as a result of activation of protein kinase of the muscle homogenate in Krebs solution and excess [K]o solution. These relations were also compared with those of the rat cardiac muscle, in which isoprenaline showed a positive inotropic action. 2. Excess [K]o decreased the cyclic AMP level in proportion to the amplitude of K-induced contracture in the porcine coronary artery. Isoprenaline increased the cyclic AMP level in Krebs solution, while it had no effect in excess [K]o. 3. In the porcine coronary artery, the particulate fraction possessed only 5% of the total cyclic AMP dependent protein kinase, while in the rat cardiac muscle, the particulate fraction was 25% of the total protein kinase. 4. The cyclic AMP dependent protein kinase in the particulate fraction of the porcine coronary artery was already saturated with the endogenous cyclic AMP. However, the binding of cyclic AMP to the protein kinase in the particulate fraction in the cardiac muscle and in the cytosol fraction of both tissues were increased in accordance with the cyclic AMP level. In the coronary artery, the protein kinase in the cytosol fraction was bound to a greater extent with cyclic AMP than was measured in the rat cardiac muscle. 5. In the rat cardiac muscle, isoprenaline enhanced the phosphorylation, detected by autoradiography of SDS gel electrophoresis in individual fractions of phosphorylated protein, while little enhancement was observed in the porcine coronary artery. 6. These observations led to the conclusion that in the porcine coronary artery, beta-adrenergic agent increases the levels of cyclic AMP but does not increase the phosphorylation. If the phosphorylation catalysed by cyclic AMP dependent protein kinase was utilized for Ca mobilization in the cell, the change in the cyclic AMP level would probably not have a causal relation to the muscle tone. This conclusion, however, may not be applicable in the case of the cardiac muscle.

Pathophysiological significance of coronary collaterals for preservation of the myocardium during coronary occlusion and reperfusion in anaesthetised dogs

The significance of pre-existing coronary collaterals for preservation of the myocardium during coronary occlusion and reperfusion was studied in anaesthetised open-chest dogs. The extent of myocardial ischaemic damage was assessed by the accumulation of calcium in the central zone of the ischaemic area and the size of myocardial infarct by the p-nitroblue tetrazolium staining method. Myocardial creatine kinase release was considered as an index reflecting both the extent of ischaemic myocardial damage and the size of the infarct. Reperfusion with the arterial blood of a main branch of the left coronary artery following the 60 min occlusion aggravated the ischaemic myocardial damage, as evidenced by exaggerated cardiac irregularity, myocardial calcium accumulation, and creatine kinase release. The myocardial calcium content and the logarithm of the creatine kinase release during reperfusion were linearly related to the infarct size. These parameters of myocardial damage were inversely related to the retrograde blood flow through the peripheral end of the occluded artery or the ratio of the retrograde-to-orthograde flow, indicating that the pre-existing collaterals influence preservation of the ischaemic myocardium. Thus, it is suggested that the collateral flow available during an ischaemic episode determines the viability of the myocardial cells during ischaemia, and in turn during reperfusion.

Coronary vasospastic action of thromboxane A2 in isolated, working guinea pig hearts

The effects of thromboxane A2 (TXA2) on isolated, working guinea pig heart and left ventricular papillary muscle preparations were investigated. TXA2 was generated by the enzymatic conversion of prostaglandin H2 (PGH2) with indomethacin-treated horse platelet microsomes (IPM). TXA2 caused dose-dependently a considerable decrease in the coronary flow, left ventricular systolic pressure and left ventricular dp/dt in the perfused heart, while the similar effects of PGH2 were transient and weaker than those of TXA2. These effects of TXA2 disappeared after the TXA2-generating system was left standing at 37 degree C for 3 min. When IPM in the TXA2-generating system was pretreated with a TXA2 synthetase inhibitor, L-8027, the enhanced cardiac responses induced by the mixture of IPM and PGH2 disappeared. TXA2 had no direct effect on the contractile force of the papillary muscle. These results suggest that TXA2 has a specific coronary vasopastic action without a direct inotropic effect.

Involvement of an acidic protein in regulation of smooth muscle contraction by the tropomyosin-leiotonin system

An acidic Ca-binding protein of about 18,000 dalton, different from both modulator protein and troponin C, was found to be involved in the regulatory mechanism of smooth muscle contraction by the tropomyosin-leiotonin system.

Prognostic and therapeutic values of peritoneal cytology in gastric cancer

Exfoliative cytology of peritoneal lavage was performed at the time of laparotomy for 458 patients with gastric cancer. Positive cytologic specimens were obtained from 28 per cent of all cases and from 16 per cent of patients with curative surgery. Peritoneal cytology has revealed itself to be a good predictor of prognosis and an indicator for adjuvant therapies. In the group treated with curative surgery, the five year survival rate was 86 per cent for patients with intact serosa and negative cytologic specimens, and 52 per cent for patients with involved serosa and negative cytology. None of the patients who had involved serosa and positive cytologic specimens survived more than five years. A slight benefit of adjuvant chemotherapy was observed in the patients who had curative surgery with negative cytology. Long term immunochemotherapy, including repeated intraperitoneal administration of mitomycin-C, improved the lifespan of patients with non-curative surgery.

Neutral proteases in the guinea-pig lymphocytes

Partial purification of neutral proteolytic enzymes in guinea-pig lymphocytes yielded 2 enzymes. Both enzymes were heat-labile and inhibited by thiol reagents. The molecular weights were more than 200,000 and 150,000-200,000, and optimal pH around 9 and 8, respectively.

Reconstruction of the superior vena cava in a patient with a thymoma

Surgical treatment was attempted in a 71-year-old man who had superior vena caval syndrome caused by incomplete obstruction of the superior vena cava with a thymoma. Using a temporary internal shunt, the superior vena cava was almost entirely resected together with the tumor and reconstructed by autogenous venous grafts. Patency of the reconstructed vein was proved by angiography one year after the operation. He has been asymptomatic for 15 months after surgery.