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Electron microscopy of serial sections revealed the occurrence of long non-myelinated segments in myelinated, presumably sensory axons running in the left atrial endocardium of normal adult dogs. Four such non-myelinated segments were analysed in three myelinated axons. They varied from 20 to 150 microns in length, and differed from nodes of Ranvier in being invested by Schwann cells in the manner of unmyelinated nerve fibers. Short non-myelinated portions (20-25 microns long) were associated with a single Schwann cell, whereas the longest such segment (150 microns) had five. The non-myelinated axonal segments were non-varicose and similar in diameter (1.2-3.0 microns) to adjacent myelinated segments, which had myelin sheaths 6-25 lamellae thick. The cytoplasm of the non-myelinated axonal segments contained numerous neurofilaments and microtubules, some mitochondria and smooth endoplasmic reticulum. The short non-myelinated segments were enclosed by perineurium, whereas the long non-myelinated segment was devoid of perineurium at its mid-portion; instead fibroblast-like cells made a loose boundary around the axon at this level. The significance of these non-myelinated segments was discussed with special emphasis on the question of whether they result from focal degeneration of the myelin sheath (demyelination) or are generally present in the preterminal regions of some axons.

Peculiar myelin figures were abundantly found in some basal-granulated cells including S, D1 and I cells in human Brunner's glands. Intense acid phosphatase activity was found in the periphery of the myelin figures, indicating that they were secondary lysosomes or residual bodies. The acid phosphatase activity was also found in some secretory granules. There were some secretory granules which were partly membranous in content, suggesting the initial stage of their degradation into myelin figures. There were also features indicating the fusion of secretory granules with the myelin figures. All these findings suggest that the myelin figures are the products of lysosomal degradation of secretory granules. The rate of occurrence of basal-granulated cells containing myelin figures in Brunner's glands tended to be higher in subjects with duodenal ulcer than in cases of gastric cancer or ulcer.

The katEkatG mutant of E. coli, UM1, had no assayable catalase activities in the extract and showed increased (about 20 fold) sensitivity to killing by H2O2 when compared with its parental strain CSH7. The mutant strain was able to reactivate H2O2-damaged lambda phage. On the other hand, recA and polA mutants were also highly sensitive to H2O2, but they had normal level of catalase activities. RecA derivatives of UM1 were much more sensitive to H2O2 than UM1 and recA strains. The induction of umu operon occurred in UM1 at lower (1/10-1/20) doses of H2O2 than in CSH7. From the results it is concluded that the lethal effect of H2O2 is due to DNA damage induced by it and that catalase and DNA repair systems have a distinct role in protection against H2O2 in E. coli.

Cardiac myocytes have been shown to occur in the tunica media and adventitia at the region near the hepatic end of the portal vein of the mouse and rat, and have been studied by electron microscopy in the mouse portal vein. They measured 3-10 microns in breadth at their nuclear level, possessed centrally located nuclei, and were connected with each other by the intercalated disk. In these myocytes in the mouse portal vein, sarcoplasmic reticulum was represented by a rather simple and loose network of the anastomosing tubules. The membrane-bound granules, which closely resemble the atrial specific granules, were found in many of the mouse portal vein myocytes. Transverse tubules, 40-200 nm in diameter, were sometimes detectable at the Z line level. The nexus occupied about 3-5% of the whole junctional area between cardiac myocytes in the tunica media, whereas in the tunica adventitia the corresponding value was about 17%. Blood capillaries with fenestrated endothelium supplied the cardiac myocytes in the adventitia of mouse portal vein. The closest relationship between the adrenergic axon and portal vein cardiac myocytes was observed to be ca. 0.3 micron apart. The significance of these findings is discussed in relation to pulsations of the portal vein.

To distinguish axons from Schwann cell processes in the denervated (Büngner's bands) and reinnervated peripheral nerves, the nearest-neighbor distance of intermediate filaments (NND) was measured in axons and Schwann cells from denervated and subsequent regenerating peripheral nerves. It was revealed that the NND was much larger in regenerating axons (41.9 +/- 14.1 nm) than in Schwann cell processes (23.1 +/- 7.1 nm in regeneration and 19.7 +/- 5.8 nm in denervation). In addition, the NND was also measured in the normal adult and developing peripheral nerves, and it became clear that in all cases the NND in axons (29.0-41.9 nm) was larger than in Schwann cells (19.7-23.1 nm). Thus, it can be generally considered that the NND is larger in axons than in Schwann cells. This fact can be used for the distinction between axons and Schwann cell processes, when the latter have a profile similar to that of the former as in Büngner's bands and in the regenerating nerves.

Electron microscopic studies were made of the regeneration of minced smooth muscle of the vas deferens of the guinea-pig 3 days to 15 weeks after operation. At 3--5 days the mince contained degenerating smooth muscle cells and dedifferentiating cells showing characteristics of embryonic smooth muscle cells: numerous free ribosomes, well developed rough endoplasmic reticulum and Golgi apparatus with few peripherally placed myofilaments associated with dense bodies. During the first two weeks of regeneration, scattered cells surrounded by debris and collagen were separated by a large extra-cellular space. After three weeks, extracellular space was reduced to near normal values. Regenerating cells had a shorter length than normal cells, but during later stages of regeneration they showed an increase in diameter. Muscle effector bundles began to form after 2 to 3 weeks. Initially there were large gaps between the muscle cells, but at later stages of bundle formation, the extracellular space between the muscle cells was much reduced. From 3 weeks, arterioles appeared between the smooth muscle bundles in the regenerating areas. Regeneration of individual smooth muscle cells was complete by 15 weeks after the operation.

Basal laminae (BL) were separated from Schwann cells of rat sciatic nerves by means of weak sonication, and the anionic sites of the BL were demonstrated by using cationized ferritin (CF) or ruthenium red (RR). CF particles were deposited in clusters at intervals of 100-150 nm on the interstitial side of the BL facing the connective tissue, while the cellular side facing the Schwann cell plasmalemma showed only an occasional deposition of CF particles. RR-positive sites were found only on the interstitial side with a pattern of distribution comparable to that of CF-binding sites. These results indicate that the patterns of anionic site distribution are different between the inner and outer surfaces of the Schwann cell BL.

Electron microscopy of the rat cardiac ganglion shows occurrence of small granule-containing cells that form reciprocal synaptic junctions with cholinergic terminals. At the synaptic junctions which are from axon to granule-containing cell, the intraaxonal vesicles are clustered against the junctional axolemma, but dense-cored vesicles in the postsynaptic cell do not cluster towards the membrane densities in these synapses. By contrast, the synaptic zone polarized in the opposite direction shows an absence of axonal vesicles in close proximity to the postsynaptic axolemma, but there is a marked aggregation of dense-cored vesicles towards the presynaptic specializations of granule-containing cells. The synaptic zones are multifocal rather than bifocal, and the minimal distance separating each synaptic zone is about 0.3 mu. These findings may indicate that cholinergic excitation of some or all granule-containing cells causes a reciprocal inhibition of one or more cholinergic terminals.

An electron-microscopic study has been made of adrenergic and cholinergic nerve fibres and synapses in the pelvic ganglion of the guinea-pig at intervals of up to 60 days following section of the hypogastric and pelvic nerves. Transection of the hypogastric nerves led to degeneration of 80-90% of the cholinergic nerve profiles and synapses in the ganglion. The small number of adrenergic nerves and synapses did not change, but 30-60 days after section, this number increased 8-10 times. Transection of the pelvic nerves led to degeneration of about 15% of the cholinergic nerve terminals, but no change in adrenergic terminals. After transection of both hypogastric and pelvic nerves, only about 1% of cholinergic nerves survived, but after 30-60 days, the number of adrenergic nerves increased 8-10 times. It is concluded that following cholinergic nerve degeneration in the ganglion, adrenergic nerves, probably originating as collateral sprouts from postganglionic neurones and granule-containing cells, can replace them to some extent.

A semi-quantitative electron-microscopic study of neuronal cell bodies, nerve profiles and synapses in the anterior pelvic ganglia of the guinea-pig has been carried out following in vivo labelling of adrenergic nerve endings with 5-hydroxydopamine. Ganglion cells of three main types have been distinguished: 1) the majority (about 70%) not containing granular vesicles, probably cholinergic elements; 2) those containing large granular vesicles of uniform size (80-110 nm), with granules of medium density and prominent halos; and 3) those containing vesicles of variable size (60-150 nm), with very dense eccentrically placed granular cores. Some non-neuronal 'granule-containing' cells were present, mainly near small blood vessels. Some 95% of the total axon profiles within the ganglia were cholinergic, the remaining 5% were adrenergic. However, 99% of synapses (i.e. axons within 50 nm of nerve cell membrane with pre- and post-synaptic specialisations) were cholinergic, and 1% were adrenergic. Only three examples of nerve cell bodies exhibiting both cholinergic and adrenergic synapses were observed. Unlike the para- and prevertebral ganglia, the pelvic ganglia contained large numbers of axo-somatic synapses. As many as 20% of the nucleated neuronal cell profiles displayed two distinct nuclei.