Activity toward thrombin-antithrombin of heparin immobilized on two hydrogels.

Commercially obtained (Diosynth) heparin was covalently bonded to poly (vinyl alcohol) (PVA) hydrogels and to polyethylene oxide (PEO) hydrogels activated by tresyl chloride. We found that as tresyl chloride activation of PVA increased, the specific activity of the bound heparin toward thrombin and antithrombin decreased by nearly a factor of 10 and that commercial heparin bound to PEO had nearly ten-fold greater activity than when bound to PVA at comparable concentrations. These findings suggest that the long 'leash' provided by PEO hydrogels may give the heparin more access to the thrombin-antithrombin pair than the tight bond to PVA, and that crowding of heparin units on a surface limits access of the thrombin-antithrombin pair.

Small granule-containing cells in the heart of the toad (Bufo melanostictus).

This study reveals the presence of small granule-containing cells in the heart of the toad, Bufo melanostictus. The cells were small in size (5-25 microns in diameter) and located in the interatrial septum. The small cells occurred singly or in small clusters within the cardiac ganglia or near the myocardial cells. They were characterized by numerous large dense core vesicles (80-300 nm) in their cytoplasm. With 5-hydroxydopamine treatment, the granularity of the large dense core vesicles was greatly intensified. The large dense core vesicles were variable in size and shape and extended into the long and short processes of the cells. Some of these processes were in close contact with myocardial cells. Other cytoplasmic organelles included rough endoplasmic reticulum, free ribosomes, randomly distributed mitochondria and glycogen particles. Individual cells or cell clusters were usually ensheathed by a thin layer of cytoplasm from sheath cells. The small granule-containing cells in the present study correspond to the catecholamine-containing (SIF) cells described by earlier workers. These cells presumably regulate muscular and ganglionic activities by virtue of their close association.

The localization of vagal neurons in the terrapin (Trionyx sinensis) as revealed by the retrograde horseradish peroxidase method.

After the application of horseradish peroxidase in Nonidet P40 solution to the right cervical vagus in the terrapin, the neurons giving origin to efferent fibers and the transganglionic sensory fibres are labeled. The neurons forming the vagus nerve at the mid-cervical level are located in the dorsal motor nucleus of the vagus nerve (DMX), in the nucleus ambiguus (NA), in an area located ventral to the DMX, and less definitely in the nucleus of the spinal accessory nerve. The DMX and NA neurons are bilaterally distributed with a predominant ipsilateral component. Labeled DMX neurons appear to have a slightly more extensive distribution than those in mammals and their dendrites extend to the nucleus of the tractus solitarius, hypoglossal nucleus (HN), lateral wall and floor of the 4th ventricle and a region dorsomedial to the HN. Some recurrent collaterals of the DMX neurons loop round the medial longitudinal fasciculus to end in a region immediately ventrolateral to the DMX. Transganglionic sensory fibers course with the tractus solitarius and spinal tract of the trigeminal nerve to end in the respective nucleus associated with the tract.