High dose-rate dependence of early skin reaction in mouse

Early skin reactions in the legs of mice were studied as a function of average and instantaneous dose rate. A dose-rate dependence of the reaction score was found at instantaneous dose rates higher than 10(7) rad/min, regardless of the average dose rate. The skin reaction was greatest at an instantaneous dose rate of around 10(8) rad/min. The 95 per cent significance of the instantaneous dose-rate dependence was confirmed by the Mann-Whitney rank-order test (U-test).

Effects of concanavalin A on 5-hydroxytryptamine uptake by rabbit blood platelets and on their ultrastructure

1. Effects of concanavalin A (Con A) and other lectins on 5-hydroxytryptamine (5-HT) uptake by rabbit blood platelets and on their ultrastructure were studied. 2. Uptake of [3H]-5-HT by platelets was decreased by application of Con A, E-PHA (lectin from Phaseolus vulgaris) and lentil-PHA (lectin from Lens culinaris), but not by wheat germ agglutinin (WGA). Con A induced specific changes in the ultrastructure of platelets, causing (i) a change in external appearance from a discoid to an irregularly spherical shape, (ii) re-arrangement of the canalicular system and formation of a concentric structure. These effects of Con A on platelets were antagonized by pretreatment with alpha-methyl-D-mannoside (alpha-MM), a specific inhibitor of Con A binding to glycoprotein. 3. The inhibition of 5-HT uptake by Con A was antagonized by colchicine, vinblastine and sodium nitroprusside (SNP), but not by cytochalasin B. 4. Theophylline, papaverine and dibutyryl cyclic adenosine 3',5'-monophosphate (db cyclic AMP) antagonized the effect of Con A on 5-HT uptake, but dibutyryl cyclic guanosine 3',5'-monophosphate had no effect. Theophylline and db cyclic AMP did not influence the effect of Con A on the ultrastructure of platelets. 5. It is suggested that binding of Con A to specific receptor glycoproteins can inhibit the 5-HT uptake system of platelets. Microtubules, contractile protein and the membrane adenylate cyclase system of platelets may also be regulatory factors in this mechanism.

Action of guanethidine on rabbit atrial membranes

1 Intracellular potentials were recorded in driven left atria from reserpine-treated rabbits. Guanethidine 2 X 10(-5) M slightly increased Vmax and shortened the total duration (TD) of the action potential (AP) without causing hyperpolarization. For the first 30 min after 4 X 10(-4) M, Vmax increased without hyperpolarization and AP height increased slightly. Thereafter, Vmax and height decreased with a slight and gradual depolarization. This depolarization was irreversible. TD was increased after 15 minutes. Guanethidine 2 X 10(-3) M initially decreased Vmax and height before causing depolarization. 2. Pretreatment with tetrodotoxin (TTX) 1.6 X 10(-7) M prevented or reversed the initial increases in Vmax, height and TD induced by guanethidine (4 X 10(-4) M). 3 TTX 3.1 to 6.2 X 10(-6) M, added 15 or 30 min after guanethidine 4 X 10(-4) M, delayed or prevented depolarization by guanethidine. 4 Ouabain 10(-5) M incubated for 20 and 90 min greatly inhibited Na+, K+-adenosine triphosphatase and K+-phosphatase activities; guanethidine was without effect. 5 Guanethidine probably increases resting sodium permeability after the promotion of increases in sodium permeability during the AP. High doses of the drug decrease sodium permeability during the AP.

Selective staining of hepatitis B surface antigen in thick epoxy sections of liver

Hepatitis B surface antigen (HBsAg) in epoxy-embedded liver tissues can be stained by aldehyde-fuchsin stain. Sections are oxidized in KMnO4 acidified with H2SO4, then bleached in NaHSO3, both at 70 C. Heating for oxidation and bleaching are absolutely necessary. Diluted aldehyde-fuchsin stain adjusted to pH 1.5 to 1.8 with NaOH is used for staining. HBsAg is specifically stained purple. Other components such as mitochondria and bile pigments are also strained, but are easily distinguished from HBsAg. This staining method is advantageous for the identification of HBsAg-positive cells for electron microscopic observation.

A new guanidine derivative: dissociation of the adrenergic neuron blocking activity from local anesthetic activity

Effects of 4-7-exo-methylene-hexahydroisoindoline-ethyl-guanidine hemisulfate (No. 865-123), a new guanidine derivative, on adrenergic neurons and its local anesthetic activity were investigated in comparison with guanethidine. Both derivatives produced in a dose-dependent manner a progressive irreversible reduction of positive chronotropic and contractile responses to postganglionic sympathetic nerve stimulation in isolated rabbit atria. The time course of the reduction by No. 865-123 was somewhat slower. In dogs administered both agents, the pressor response to carotid occlusion was reduced and that to exogenous noradrenaline was potentiated with a slight decrease in blood pressure. Noradrenaline stores in the heart and spleen of rats were also depleted to a similar extent. In the guinea pig weal method, guanethidine acted as a potent local anesthetic with a slow onset and a prolonged action as compared to procaine. No. 865-123 revealed no more anesthetic activity than did saline. It is unlikely that the local anesthetic activity of the guanidine derivatives contributes to the adrenergic neuron blocking activity.