[Effects of atrial natriuretic polypeptide on arterial pressure and renal sympathetic nerve activity in anesthetized rats]

The effects of atriopeptin III (AP III) on the arterial pressure (AP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were investigated in anesthetized rats. The results were as follows: (1) In intact rats (n = 12), following intravenous injection of AP III (50 micrograms/kg), systolic arterial pressure (SAP) decreased by 23.0 +/- 1.66 mmHg (M +/- SE, P less than 0.001), HR decreased by 9 +/- 3.5 beats/min (P less than 0.05), and RSNA decreased by 4.89 +/- 2.95% (P greater than 0.05). After vagotomy, the decrease in SAP following iv. AP III showed no significant difference with that of intact rats. HR showed no change, while there was a small increase in RSNA (P greater than 0.05); (2) In the intact vagi but sinoaortic denervated rats (n = 7), intravenous AP III decreased SAP by 27.4 +/- 3.25 mmHg (P less than 0.001), HR by 13 +/- 3.1 beats/min (P less than 0.01), and RSNA by 11.67 +/- 1.95% (P less than 0.001). After vagotomy, the decrease in SAP following i.v. AP III was attenuated, HR showed no significant change, but there was a small but significant increase in RSNA (P less than 0.05); (3) Following intravenous injection of nitroprusside, SAP decreased significantly. Such a hypotensive effect was associated with an increase in RSNA in either the intact or the vagotomized rats. The results indicate that (1) the hypotensive effect of AP III was mediated partly by vagi; (2) in the sinoaortic denervated rats AP III could reflexly inhibit RSNA by activation of vagal afferent fibers.

[Effects of atrial natriuretic factor on regional blood flow in anesthetized rabbit]

The regional blood flow changes induced by intravenous injection of atriopeptin III (AP III) and the effects of intra-arterial injection of AP III on regional vascular resistance were investigated in 42 anesthetized rabbits. The results were as follows: (1) In anesthetized rabbits (n = 8), intravenous injection of AP III (30 micrograms/kg) resulted in a decrease in mean arterial pressure by 11.0 +/- 1.5 mmHg (M +/- SE, P less than 0.01), while the heart rate showed no change. (2) By using the isotopic biomicrosphere method, it was revealed that AP III increased the blood flow in renal cortex (P less than 0.05) and decreased the blood flow in renal medulla. However, the blood flow in brain, heart, intestine, and hindlimb muscle remained unchanged. (3) With the constant autoperfusion method, renal intra-arterial administration of AP III (0.8 micrograms/kg) decreased the mean renal perfusing pressure by 21.2 +/- 3.3 mmHg (n = 9, P less than 0.001). By injecting AP III into the femoral artery, the mean perfusing pressure of hindlimb lowered by 7.8 +/- 1.1 mmHg (n = 7, P less than 0.001). No change occurred in the perfusing pressure of mesenteric vascular bed following intraarterial injection of AP III. The results showed that AP III dilated the renal artery and thereby increased the renal blood flow. The vasodilating effect of AP III appeared to be more prominent in renal vascular bed than that in the other vascular beds. The increase in renal blood flow induced by AP III may be one of the mechanisms diuretic and natriuretic actions.

First report of an epidemic of diarrhoea in human neonates involving the new rotavirus and biological characteristics of the epidemic virus strain (KMB/R85)

An outbreak of diarrhoea in neonates occurred at the nurseries of the Department of Obstetrics of Zhao Tong Regional Hospital, Yunnan Province, from the middle of August to the end of November, 1985. Fifty-one percent of children were affected 2-8 days after birth. The clinical symptoms were mild; patients mainly had diarrhoea and did not vomit. Rotaviruses were detected in 66.7% by RNA PAGE and in 72.7% by EM. The virus strain designated as KMB/R85 had a typical morphology, which was indistinguishable from that of infantile rotaviruses by EM. The viral RNA genome was composed of 11 segments. The buoyant density in CsCl was 1.377 g/cm3. The KMB/R85 strain possessed a hemagglutinin for rhesus monkey erythrocytes. By ELISA, IEM, and HAI, it was found that KMB/R85 strain did not possess the common group antigen shared by group A rotaviruses and was antigenically similar to the Chinese adult diarrhoea rotavirus (serogroup B).