Blood flow acceleration in the carotid and brachial arteries of healthy volunteers: respective contributions of cardiac performance and local resistance

Summary— The influence of local resistance and cardiac performance on peripheral blood acceleration was investigated in 14 healthy male volunteers. Steady and pulsatile flow was studied in the brachial and in the common carotid arteries, ie, two territories that exhibit marked differences in resistive characteristics. Instantaneous blood velocity (V), mean blood velocity (V_m) and artery diameter (D) were evaluated at rest by an ultrasonic range-gated pulsed Doppler flowmeter using a double transducer probe, thus allowing the calculation of mean blood flow (Q). Mean local resistance (R) was obtained by dividing the mean arterial pressure by Q. The peak value of the local acceleration of the blood was obtained by computer-assisted calculation of the first derivative of instantaneous blood velocity (G_max = +dV/dt_max). Peak aortic blood acceleration (GAo) was simultaneously measured from the suprasternal notch using a pulsed Doppler velocity meter. In the brachial and the common carotid arteries, G_max was of a similar magnitude (551 ±30 and 555 ± 44 cm/s², respectively) despite major differences in the respective D, V_m, Q and R values. In neither artery was there a relationship between G_max and either resting Q or R. At the brachial artery level, G_max was positively related to GAo ( r = 0.79, P = 0.0008). At the common carotid artery level, there was a weak, although non significant relationship between G_max and GAo ( P = 0.08). Our results indicate that the local acceleration of peripheral blood flow in the brachial artery is related rather to upstream central impulse than to downstream hemodynamics, and suggest some regional differences in the hemodynamic determinants of the local acceleration of peripheral blood flow.     

Antitumour imidazotetrazines XXVIII 3-methyladenine DNA glycosylase activity in cell lines sensitive and resistant to temozolomide.

The ability of extracts of a range of cell lines to release methylated bases from a DNA substrate, which had been modified with [3H]dimethyl sulphate, has been compared in cell lines with differing sensitivity to the cytotoxic drug, temozolomide. High performance liquid chromatography profiles of the bases released by these extracts showed that the activity was specific for 3-methyladenine. There was little variation in the level of 3-methyladenine-DNA glycosylase between the different cell lines despite a 40-fold difference in sensitivity to temozolomide and no correlation with the level of O6-alkylguanine-DNA alkyltransferase.     

Weight loss in a murine cachexia model is not associated with the cytokines tumour necrosis factor-alpha or interleukin-6.

Daily administration of an escalating dose of tumour necrosis factor-alpha (TNF-alpha) to female NMRI mice caused a progressive loss of body weight representing 12% of the original weight over a 6-day period. Weight loss was associated with a decreased food intake and pair-fed controls exhibited a weight loss of similar magnitude to that caused by TNF-alpha. However, weight loss in animals bearing a murine adenocarcinoma (MAC16) occurred without a change in energy intake and thus differed from that produced by TNF-alpha. Anti-TNF-alpha monoclonal antibodies at levels capable of protecting mice against lethal endotoxaemia were ineffective in reversing weight loss in animals bearing the MAC16 tumour and had no effect on the increase in tumour volume. Circulating levels of interleukin-6 were not elevated in animals bearing the MAC16 tumour and with a weight loss between 1.8 and 5.4 g. These results suggest that these cytokines are not involved in the cachexia produced by this murine tumour.     

Effect of polyunsaturated fatty acids on the growth of murine colon adenocarcinomas in vitro and in vivo.

The effect of the polyunsaturated fatty acids (PUFAs) linoleic acid (LA) and arachidonic acid (AA) on the growth of two murine colon adenocarcinoma cell lines (MAC26 and MAC13) has been determined both in vitro and in vivo. When the serum concentrations in the medium became growth limiting, low concentrations (18-33 microM) of both PUFAs were growth stimulatory to both cell lines, while higher concentrations were growth inhibitory. Growth stimulation by AA in both cell lines, and by LA in MAC13, was effectively inhibited by both the cyclo-oxygenase and lipoxygenase inhibitor indomethacin, and the lipoxygenase inhibitor BWA4C in a dose-dependent manner. The most effective inhibition was exerted by BWA4C, suggesting metabolism of both PUFAs through the lipoxygenase pathway for growth stimulation. In vivo studies using the MAC26 tumour showed a significant stimulation of tumour growth when LA was administered orally at concentrations higher than 0.4 g kg-1 day-1. Higher concentrations did not produce a further increase in tumour growth rate. This suggests that there is a threshold dose for growth stimulation by LA which, together with that in the diet, amounted to 3.8% of the total caloric intake. The increase in tumour volume induced by LA arose from a reduction in the potential doubling time from 41 to 28 h and was effectively reversed by indomethacin (5 mg kg-1). These results suggest that PUFAs may play an important role in tumour growth and may offer a potential target for the development of chemotherapeutic agents.     

Early diagnosis of acute postoperative renal transplant rejection by indium-111-labeled platelet scintigraphy

A prospective evaluation of 111In-labeled platelet scintigraphy (IPS) for the early diagnosis of acute postoperative renal transplant rejection (TR) was undertaken. The results of IPS were compared with in vitro biochemical tests, the clinical finding of graft tenderness, and combined [99mTc]DTPA and [131I]orthoiodohippurate scintigraphy. With a sensitivity of 0.93 and a specificity of 0.95, IPS provided otherwise unavailable diagnostic information. Furthermore, postoperative IPS was a good predictor of long-term allograft survival.     

Segmental intestinal muscular thinning: a possible cause of intestinal obstruction in the newborn

Intestinal obstruction proximal to a transition zone without an interposed physical barrier usually indicates Hirschsprung disease. The authors report one case of focal small bowel muscular thinning just distal to a transition zone that produced clinical and radiographic findings that simulated long-segment Hirschsprung disease in a 2-day-old infant.