A re-evaluation of the cytology of cat Pacinian corpuscles

Summary The ultrastructure of cat mesenteric Pacinian corpuscles in cross and longitudinal sections has been examined. The terminal ends of lamellar cells of the inner core have been identified in longitudinal sections through the proximal portion of the inner core. These terminal bulbous expansions contain characteristic concentric membranes of rough endoplasmic reticulum and in some cases masses of oval membranous inclusions. The central axon as seen in cross section is oval in profile, having X-(short) and Y-(long) axes, and each axonal face is characterized by specializations of the axolemma. At the X-axis, the inner lamellae of the inner core tightly abut a smooth axolemma, with no intervening connective tissue matrix, in a manner reminiscent of a neuroepithelium. The axolemma of the Y-axis has numerous axonal spines (microspikes) that project into the cleft in the inner core. The extent of the axolemma having axonal spines can only be appreciated in longitudinal sections. The clefts contain a specialized connective tissue with elastic and collagen fibrils. The connective tissue compartment of fibers and matrix separating individual inner core lamellae is unique, in that it contains extremely thin collagen fibrils measuring approximately 15 nm in diameter. The diameter of collagen fibrils increases as the cleft is approached. Here the fibrils resemble typical endoneural collagen.     

Role and location of NAD malic enzyme in thermogenic tissues of Araceae

This work was done to discover how those nonphotosynthetic tissues of the Araceae that become thermogenic release, as CO2, carbon recently fixed by phosphoenolpyruvate carboxylase. Extracts of clubs of the spadix of Arum maculatum showed no activity for phosphoenolpyruvate carboxykinase and low activities of NADP malic enzyme. NAD malic enzyme activity in the above extracts and in those of thermogenic tissues of other Araceae was appreciable. Analysis of homogenates of clubs of Typhonium giraldii by differential centrifugation and sucrose gradients showed that NAD malic enzyme was confined to mitochondria. Centrifugation of mitochondria after freezing and thawing left all the NAD malic enzyme in the supernatant. NAD malic enzyme in isolated, intact mitochondria was completely latent, and was completely protected from exogenous trypsin. The responses of this latency and protection to different concentrations of Triton X-100 suggested that none of the NAD malic enzyme was accessible from either the outside or the intermembrane space of the mitochondria. Treatment of excised clubs of A. maculatum with 2-N-butylmalonate largely prevented the development of the rapid respiration responsible for thermogenesis, and severely inhibited dark fixation of 14CO2. The conclusion is that in mature clubs of the Araceae phosphoenolpyruvate is converted to malate in the cytosol by phosphoenolpyruvate carboxylase and NAD malate dehydrogenase, and that this malate then enters the mitochondrial matrix where it is converted to pyruvate by NAD malic enzyme.     

Effect of Storm Events on Benthic Nitrifying Activity

Storm events resulted in a marked reduction in the benthic nitrifying activity of a stream receiving geothermal inputs of ammonium. Subsequently, nitrifying activity demonstrated a logarithmic increase until a stable activity was reached 10 to 12 days after the storm event. The rate of increase of poststorm nitrifying activity was used to calculate the nitrifier growth rate in situ (0.0075 to 0.0116 h⁻¹) which was lower than the growth rates observed for laboratory cultures of nitrifying bacteria isolated from the sediments (0.0233 to 0.0990 h⁻¹).     

The cytology of apocrine sweat glands

Summary The apocrine sweat glands of cat and monkey have been studied by light and electron microscopy. The apocrine secretory cells of the cat are columnar cells with prominent apical cytoplasmic caps extending into the gland lumen beyond the zone of terminal bars (zonulae occludentes). Many secretory vacuoles are present in the cytoplasm, and they contain acid mucopolysaccharide demonstrable by light microscopy. These secretory vacuoles arise from prosecretory vacuoles in the region of the Golgi apparatus and are liberated from the apical cell surface as in other merocrine cells. The apocrine duct is short and the cells have scant mitochondria. The apocrine secretory cells of the monkey have secretory vacuoles similar to those of the cat but are fewer in number. The monkey apocrine cells also contain unidentified bodies similar to those seen in Langerhans cells of the epidermis. These cells liberate secretory vacuoles in a merocrine manner. Apocrine or decapitation secretion is regarded as an artifact.This investigation was supported in part by United States Public Health Service research grants GM-03784 and GM-10102 from the Institute of General Medical Sciences.     

Pyruvate metabolism in mitochondria from cucumber cotyledons during early seedling development

Mitochondria were isolated from cucumber cotyledons during earlyseedling growth, and their capacity for pyruvate metabolisminvestigated. The rate of pyruvate oxidation was low. Evidenceis presented that suggests that this is due to low activitiesof the pyruvate transporter. Key words: Cotyledon, cucumber, germination, pyruvate oxidation     

5,7-Diphenyl-3-ureidohexahydroazepin-2-ones as Cholecystokinin-B receptor ligands

A series of 5,7-diphenyl-3-ureidohexahydroazepin-2-one cholecystokinin-B (CCK-B) receptor antagonists was synthesized using Beckmann ring expansion of a suitable 2,4-diphenylcyclohexanone as a key step. SAR studies revealed the importance of the 5-aryl group for high and selective CCK-B receptor affinity, as illustrated in compound (−)-10i (CCK-B IC₅₀ = 6.8 nM).     

Relationships among microarthropods,fungi, and their environment

Temporal and spatial relationships in a maple-forest soil among mycophagous microarthropods, total hyphal length, vesicular-arbuscular mycorrhizal (VAM) fungus spores, microfungus diversity, root biomass and some abiotic variables (temperature, water content, pH, organic matter content) were investigated. Samples were obtained from spring 1991 to winter 1992 at four soil depths. Canonical correspondence analysis was used to analyze the data. Four species of sporulating VAM fungi were identified, along with 23 species of mites and springtails, 9 of which were common. Hyphal length, VAM fungus spores, and soil animals peaked in spring and autumn. Canonical correspondence analysis suggests that animal abundance and success in the soil is dependent on a number of environmental variables. The most important variables that influence microarthropod community structure are: (i) temperature, (ii) water content, (iii) pH, (iv) total length of fungal hyphae, and (v) diversity of darkly-pigmented fungi. However, the relative importance of these variables changes with increasing soil depth. We have also shown a relationship between arthropod populations and their food supply under field conditions, a phenomenon that has been demonstrated previously under controlled laboratory conditions.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.