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.     

Biochemical switching device realizing McCulloch-Pitts type equation

We analyzed cyclic enzyme systems, one of the best candidates for biochemical switching devices, especially focusing on their control mode against external perturbations. Since these systems have the reliability of ON-OFF types of operation (McCulloch-Pitts' neuronic equation), we shall present here the mechanical difference between these systems and electronic switching circuit, especially on the mnemonic mechanism of biochemical switching devices.     

A comparative 1H NMR study of mouse alpha(1-53) and beta(2-53) epidermal growth factors

The three-dimensional structure of the mouse epidermal growth factor (EGF) in solution was studied by comparison of the 1H NMR spectra of alpha EGF (1-53) and beta EGF (2-53, des-asparaginyl 1 form). Using pH dependence of chemical shifts and a two-dimensional difference spectrum, the effect of the N-terminal deletion was investigated based on the complete assignment of the proton resonances. The affected residues were all found to be located exactly in the triple-stranded, beta-sheet core in the N-terminal domain of the EGF molecule.     

Arterial receptors for adrenal steroids and transport of electrolytes in vascular smooth muscle

The role of arterial receptors to mineralocorticoids (MC) and glucocorticoids (GC) in the induction by MC and GC of changes in transmembrane transport of sodium (Na+) and water was investigated. Implantation of Silastic rubber strips impregnated with 11-desoxycorticosterone acetate (DOCA) in rabbits was followed by a marked increase in vascular smooth muscle cell membrane permeability to Na+ and hypertension. Both of these effects were preventable with progesterone, an anti-MC at the steroid-receptor level, implanted in relative excess simultaneously with DOCA, in approximately 50% of the implanted animals. The other 50% were hydroxylating in vivo progesterone to 11-desoxycorticosterone (DOC) efficiently enough not to yield the necessary ratio of progesterone to DOC for the sufficient MC receptor blockage. In vascular smooth muscle cell culture, grown in the presence of steroids, GC but not MC increased intracellular water space. This increase was preventable by a potent synthetic anti-GC,RU 38486, a steroid with high affinity for GC receptors, added to culture medium along with GC. These results provide evidence that both the in vivo effect of MC on Na+ permeability and the induction of hypertension, and the in vitro effect of GC on water transport in cultured vascular smooth muscle cells are elicited through the receptor-mediated molecular mechanism(s) for action of these steroids in the arterial wall.     

Analgesia and plasma beta-endorphin-like immunoactivity in compound 48/80-induced hypovolemia of the rats

The effects of subcutaneous (s.c.) administration of compound 48/80 (a well known histamine liberator) on latency to thermoalgesic stimulus, hematocrit (Hct) and plasma levels of beta-endorphin-like immunoreactivity (beta-END-LI) were investigated in male rats. The s.c. administration of compound 48/80 in doses ranging from 0.5 to 5.0 mg/kg into the rats produced significant analgesia in the hot plate test and increased Hct in a dose-dependent manner. Concomitant variation was observed between the analgesia and the increase of Hct. This analgesic effect, but not the increase of Hct, was diminished by pretreatment with the opiate receptor antagonist, naloxone (5 mg/kg, s.c.). A significant increase of plasma beta-END-LI was observed by s.c. injection of compound 48/80. Together with a previous finding that compound 48/80 induced-hypovolemia increases the renin release from kidney and then causes water intake in the rats, it is suggested that s.c. administration of compound 48/80 induced analgesia mediated through stimulation of an opioid system, may be closely related to stimulation of the renin-angiotensin system.     

Cellular and Vacuolar Fusion of Protoplasts Electrofused Using Platinum Microelectrodes

Protoplasts isolated from cultured cells of Coptis japonicaand Euphorbia millii were electrically fused using platinummicroelectrodes. The process involved two stages, cellular andvacuolar fusion, which are characterized respectively by transientwrinkling of the membrane and the formation of a dark-red precipitate. (Received June 12, 1987; Accepted October 13, 1987)     

Uptake of Gibberellin Methyl Esters by Spores and Induction of Dark Germination in Lygodium japonicum

In the fern Lygodium japonicum, the effect of the exogenousapplication of two gibberellin methyl esters, gibberellin A₄methyl ester (GA₄Me) and gibberellin A₂₀ methyl ester (GA₂₀Me)on spore germination in the dark and uptake of GA₄Me and GA₂₀Meby spores was investigated. Tritiated GA₄Me and GA₂₀Me wereprepared and used as radioactive tracers. The activity of GA₄Mewas more than 100-fold that of GA₂₀Me for the induction of sporegermination. When treated for 24 h, the activity for inducingspore germination remained after removal of the gibberellinmethyl esters from the medium. The amount of GA₄Me taken upby spores was more than three times that of GA₂₀Me throughoutthe 24 h time course of treatment. The uptake of both gibberellinmethyl esters was proportional to the external concentrationfor the range of concentrations between 10^–9 M and 10^–6M. When treated with the tritiated gibberellin methyl estersat 10^–6 M and 10^–7 M for 24 h, most of the gibberellinmethyl esters taken up by the spores were not metabolized. Althoughthe uptake of the two gibberellin methyl esters differed by3- to 5- fold, their abilities to induce spore germination differedby more than 100-fold. Therefore, the difference in the activityof the two gibberellin methyl esters regarding the inductionof spore germination could not be explained solely by the differencein their uptake. (Received January 11, 1988; Accepted May 26, 1988)     

Formation of UDP-Xylose and Xyloglucan in Soybean Golgi Membranes

Soybean (Glycine max) membranes co-equilibrating with Golgi vesicles in linear sucrose gradients contained UDP-glucuronate carboxy-lyase and xyloglucan synthase activities. Digitonin solubilized and increased the activity of the membrane-bound UDP-glucuronate carboxy-lyase. UDP-xylose did not inhibit the transport of UDP-glucuronate into the lumen of Golgi vesicles but repressed the decarboxylation of the translocated UDP-glucuronate. The results suggest that UDP-glucuronate is transported into the vesicles by a specific carrier and decarboxylated to UDP-xylose within the lumen. On incubation of UDP-[¹⁴C]glucuronate with Golgi membranes in the presence of UDP-glucose, [¹⁴C]xylose-labeled xyloglucan was formed. Although the K_m value of UDP-glucuronate for the decarboxylation was 240 micromolar, the affinity of UDP-glucuronate for xyloglucan formation (31 micromolar) was similar to that of UDP-xylose (28 micromolar), suggesting a high turnover of UDP-xylose. The biosynthesis of UDP-xylose from UDP-glucuronate probably occurs in Golgi membranes, where xyloglucan subsequently forms from UDP-xylose and UDP-glucose.     

Nonshivering thermogenesis and brown fat in spontaneously hypertensive rats

Oxygen consumption was measured before and during infusion of the catecholamine isoproterenol in age-matched spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive rats. Mass-independent rates of oxygen consumption of anesthetized 7-week-old rats were similar in the WKY and SHR rats (11.08 +/- 0.74 and 11.33 +/- 0.82 ml O2 min-1 kg-.67, respectively). Catecholamine infusion elicited increased total oxygen consumption in both WKY and SHR animals (15.0 +/- 1.0 and 14.9 +/- 1.2 ml O2 min-1 kg-.67, respectively), and the magnitude of these increases did not significantly differ. To assess whether there were changes in the metabolic state of brown adipose tissue, the major site of catecholamine-induced thermogenesis in rats, enzymes whose activity is proportional to aerobic capacity were assayed in vitro. In both the interscapular and cervical brown fat depots, maximal citrate synthase and maximal HOAD (beta-hydroxyacyl-CoA dehydrogenase) activities were similar in SHR and WKY rats. There were also no significant differences in brown fat protein content, suggesting no differential growth of this tissue in the two rat strains. Our results indicate that the nonshivering thermogenic capacity of the hypertensive SHR rats does not differ from that of the normotensive WKY animals.