Comparison of the roles of neurohormones in the regulation of blood distribution from the hearts of American and Japanese lobsters

The decapod cardiovascular system consists of a single ventricle that pumps blood into seven arteries; previous work has shown that the outflow distribution patterns of intact animals are variable. In the present study, flow recordings were made from pairs of arteries in semi-isolated hearts whilst different cardioactive hormones were infused into the heart. Each hormone (5-hydroxytryptamine, octopamine, dopamine, proctolin and F1) changed the outflow pattern, heart rate and ventricular pressure in a unique way. The probable sites of hormone action are the cardioarterial valves located at the origin of each artery except one, the dorsal abdominal. Outflow from the dorsal abdominal is controlled downstream by valves located at the origin of the segmental lateral arteries. The responses to a particular hormone were sometimes different between the hearts of American and Japanese lobsters. Accepted: 11 May 1998     

Demonstration and ontogenesis in the rat of a serum protein analogous to human thyroxine binding globulin

It has been reported evidence based on equilibrium binding, electrophoretic, immunoelectrophoretic studies, that the rat possesses a major high affinity thyroid hormone binding protein, with an electrophoretic mobility and binding properties similar to those of the human thyroxine binding globulin (TBG). It is shown that in the sera of postnatal developing animals, between 3 and 21 days, the thyroxine (T4) and the triiodothyronine (T3) binding activities increase up to 10 times over adult or foetal levels, due to a high transient post-natal surge of the rat TBG. In the adult serum, the TBG persists in decreased amounts: it then yields the predominant role as T4 carrier to the thyroid binding prealbumin (TBPA), but retains the major role as binder of T3, i.e. of the biologically active thyroid hormone.     

Binding activities of thyroxine binding globulin versus thyroxine binding prealbumin in rat sera: differential modulation by thyroid hormone ligands, oleic acid and pharmacological drugs

We use gel equilibration and electrophoretic techniques to compare the binding properties of thyroxine binding globulin and thyroxine binding prealbumin in rat sera. The evidence indicates that TBG bears the serum lowest capacity highest affinity sites for thyroxine (T4) and triiodothyronine (T3) (Ka1 greater than or equal to 10(9) M-1) as well as weaker saturable T3 sites (Ka2 approximately 10(8) M-1). TBPA bears for T4 only Ka2 approximately 10(8) M-1 sites and for T3 only Ka approximately 10(6) M-1 sites. Consistent with these parameters are the specific responses of TBG and TBPA binding activities to varying serum concentrations of T4, T3, oleic acid, the drugs diphenylhydantoin or salicylate. The primary attack of these compounds is aimed at TBG. Small T4, oleate or DPH doses chase the TBG-bound T4 to TBPA, high doses of T4 or oleate but not of DPH inhibiting the T4 binding to both proteins. In the T3-serum interactions, all tested compounds displace the TBG-bound hormone without chasing it to TBPA. The high reactivity of TBG sites designates the protein as crucially involved in modulating the free vs bound serum levels of T4 and T3 against physiological or pathological variations of binding competitors.     

Mechanosensory interneurons (MSIs) in the crayfish 6th abdominal ganglion are inhibited by activation of other MSIs

1. Identified mechanosensory interneurons (MSIs) in the 6th abdominal ganglion of the crayfish Procambarus clarkii have been shown to inhibit other projecting MSIs. 2. Interneurons sensitive to water-current stimulation of the tailfan, and which inhibited the tactile response of other MSIs when activated by depolarizing currents, were identified by iontophoresis of fluorescent dye. 3. Ten inhibitory interneurons have been identified, including both non-adapting, directional cells and phasic "touch" cells. 4. Inhibition triggered by activation of the identified cells was not widespread among fibers in the connectives. 5. Inhibition recorded intracellularly was mediated by compound inhibitory postsynaptic potentials of long duration (300-400 msec) and latencies of 13-15 msec, and therefore was apparently polysynaptic. 6. Depolarization and/or activity in MSIs, which modulates the stimulus response characteristics of related cells is a possible mechanism for contrast enhancement among directional or frequency-selective interneurons.     

Compensatory payments and vasectomy acceptance in urban Sri Lanka

The effects of different levels of compensatory payment for vasectomy on sterilization acceptance were examined in 496 vasectomized men in urban Sri Lanka. The results indicate that compensatory payments significantly enhanced the participation of economically poor men in vasectomy programs, especially those who had already achieved a large family size. The proportion of poor acceptors (those with a monthly income of Rs 1000 or less) increased with higher levels of payment; the acceptor's level of education was negatively correlated with the compensation amount, and the mean age of the youngest child was higher among those who received higher payments. 60% of vasectomy acceptors reported using contraception immediately before the vasectomy, suggesting a high level of motivation not to have another child. Respondents cited high effectiveness, no extra expense, and no side effects for their wives as the main reasons for selecting vasectomy over other means of contraception, regardless of the amount of payment received. Only 5% said cash payment was an important reason for choosing vasectomy, and this response did not vary significantly by level of payment. There was no influence of payment level on postoperative complications or satisfaction. While compensatory payments significantly enhanced the participation of poor men in vasectomy programs, they were not effective in attracting poorer men with few children or those whose last child was relatively young. Overall, this study's findings suggest that the decision to provide compensatory payments and how much to provide should be based on economic and political factors, not on the grounds that higher compensatory payments have led to the recruitment of ineligible men or that the promotion of vasectomy has been at the expense of a loss in the quality of services provided.