The buccal capsule of the free-living nematode Caenorhabditis elegans has been analysed by serial section electron microscopy. Whereas the regions classically identified in the rhabditid buccal capsule can be distinguished, the cuticle lining does not constitute separate cuticular plates, but rather, structural–functional differentiations within a cuticle continuous with that of the esophagus. Only the lip region (cheilostom) is lined by body wall cuticle. The prostom cuticle is underlain by two rings of syncytial arcade cytoplasm connected to nine cell bodies. The mesostom cuticle is underlain by the nonmuscular epithelial cells of the esophagus, whereas the cuticle of the metastom and telostom is underlain by esophageal muscle cells m1 and m2. During moulting, buccal cuticle is produced later than body cuticle and its formation is characterized by accumulation of dense granules in both arcade and esophageal cytoplasm. It is concluded that the buccal capsule should be considered as "astomatous" in the terminology of K. A. Wright.

The effects of road building and selective tractor harvesting on storm runoff were assessed for a small (424 ha) coastal watershed in northern California. Road building alone did not significantly affect the storm runoff. After road building and logging, lag time was decreased approximately 1.5 hours, and the very small storm volumes (less than 1209 m 3) and storm peaks (less than 566 L/s) were increased by about 132 and 111%, respectively. Storm volumes and peaks of large storms (occurring less frequently than eight times a year) were not significantly increased by either roads or logging, even though more than 15% of the watershed was compacted in roads, skid trails, and landings. Although a decrease in lag time showed that the average storm hydrograph was shifted forward in time, only the small storm hydrographs were changed in shape. We speculate that the rate of delivery of water to the stream channel during large channel-forming flows was governed by infiltration and subsurface flow rates on the 85% of the watershed that was unaffected by roads, landings, or skid trails. From these findings we conclude that, in a rain-dominated hydrologic environment, logging and forest road construction (as carried out in this study) are not likely to change the flow regime of a stream adversely.Res., I7(4), 907-917, 1981.

The electron trapping characteristic of a solid dielectric material (polymethylmethacrylate) is exploited to study electrical discharge propagation in laboratory‐scale space charge clouds. Similarities with the static and dynamic behaviors of thundercloud electricity are identified, and a combination of theoretical and empirical scaling relationships enables a rough translation of parameters from laboratory scale to thundercloud scale. Applications of the laboratory technique to specific thunderstorm situations reinforce the value of discharge structure studies in exposing the very important space charge configuration that gives rise to lightning.

Trichinella spiralis has been examined by electron microscopy after fixation in situ in the intestine of mice. The worms lie within the cytoplasm of cells of the intestinal mucosa and may occupy both absorptive and goblet cells. They cause little damage to host cells. A few worms have been seen protruding from tissue by SEM techniques. These unusual observations suggest that the nematodes may be capable of exit and reentry into the epithelium.

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The 'tunnel' within which the nematode Trichuris muris is contained was examined by light, scanning, and transmission electron microscopy. The amount of worm covered by the tunnel varied with age. Young larval worms were completely embedded in the host's intestinal mucosa whereas older larvae and adults had part, if not all, of the posterior region protruding into the lumen. All worms were found to have heads embedded in the tissue and in no cases were whole worms found free in the lumen.The 'tunnel' was shown to be a syncytial protoplasmic mass with recognizable cellular elements such as nuclei, lipid droplets, mitrochondria, and mucous droplets anteriorly whereas more distal to the head these elements became increasingly scarce and degenerated. The syncytium is bordered apically, laterally, and basally by cell membrane. The basal lamina can be identified beneath the basal membrane of the syncytium indicating that syncytium formation occurs in the epithelial sheet only and does not extend into the lamina propria. Evidence suggests that the nematode initially induces a syncytium about its head, feeds on the syncytial cytoplasm, and then moves on to initiate extension of the syncytium. The result of this movement is a 'tunnel' snaking across the caecum and colon.

Two sites of protein-DNA interaction have been identified in vivo and in vitro in the proximal promoter regions of an H4 and an H3 human histone gene. In proliferating cells, these genes are transcribed throughout the cell cycle, and both the more distal site I and the proximal site II are occupied by promoter-binding factors. In this report we demonstrate that during the shutdown of proliferation and onset of differentiation of the human promyelocytic leukemia cell line HL-60 into cells that exhibit phenotypic properties of monocytes, histone gene expression is down-regulated at the level of transcription. In vivo occupancy of site I by promoter factors persists in the differentiated HL-60 cells, but protein-DNA interactions at site H are selectively lost. Furthermore, in vitro binding activity of the site II promoter factor HiNF-D is lost in differentiated cells, and nuclear extracts from differentiated cells do not support in vitro transcription of these histone genes. Our results suggest that the interaction of HiNF-D with proximal promoter site II sequences plays a primary role in rendering cell growth-regulated histone genes transcribable in proliferating cells. It appears that while cell-cycle control of histone gene expression is mediated by both transcription and mRNA stability, with the shutdown of proliferation and onset of differentiation, histone gene expression is regulated at the transcriptional level.