Stimulus-Secretion Coupling in Isolated Adrenal Chromaffin Cells: Calcium Channel Activation and Possible Role of Cytoskeletal Elements

Abstract: The catecholamine secretory function of a preparation of isolated bovine adrenal chromaffin cells has been further characterized under conditions designed to elucidate the mechanism of calcium channel activation and the possible role of cytoskeletal elements in stimulus-secretion coupling. Three related sets of data were obtained: (1) Differences in kinetics, Ca dependence, strength, and additivity of the secretory response to acetylcholine (ACh) versus excess K; (2) the effects on secretion of the Ca channel-blocking agents, Ni, Mg, and verapamil; and (3) the Ca dependence of vinblastine action on ACh- and K-evoked secretion. The results suggest that a major portion of the Ca influx required for catecholamine release enters the cell via voltage-dependent Ca channels with some additional Ca influx via the ACh receptor channel. Comparison of the present secretion data with corresponding known electrophysiological properties of isolated chromaffin cells provides added evidence for a role of chromaffin cell action potentials in regulation of Ca influx and the secretory response. Elevated Ca concentrations enhanced K-evoked secretion to levels comparable to that of ACh but did not induce a vinblastine block of K-evoked release. This provides further evidence against a role of microtubules in the common exocytosis event per se. However, a role of cytoskeletal elements in directing the movement of secretory granules, or an action of vinblastine at cholinergic receptors, remain distinct possibilities.     

Effect of Oxotremorine on Ornithine Decarboxylase Activity of the Adrenal Gland in Rat

Abstract: In this work we have studied the mechanism for the increase of adrenal ODC (ornithine decarboxylase, EC 4.1.1.17) activity provoked by oxotremorine, a muscarinic agonist. 1. Oxotremorine increased medullary ODC activity maximally at 2 h. Cortical enzyme responded much more slowly. 2. Blockade of peripheral muscarinic receptors with methylatropine partially reduced the response to oxotremorine in the medulla, but not cortex. 3. Hy-pophysectomy abolished the cortical, but not the medullary, responses to oxotremorine. Methylatropine reduced the effect of oxotremorine on medullary ODC in hypophysectomized rats. 4. In unilaterally splanchnicotomized rats oxotremorine caused an increase of ODC activity of the denervated adrenal gland relative to control value; activities in both medulla and cortex were significantly lower than those observed in the innervated gland. Evidence was obtained for a compensatory increase of ODC activity of the adrenal cortex (but not medulla) on the intact side of unilaterally operated rats. 5. Surgical intervention, in the form of a sham operation for transection of the spinal cord, leads to an increase of ODC activity in both parts of the adrenal gland. Transection of the cord attenuates these increases. 6. The additional increase of medullary ODC activity owing to the administration of oxotremorine to sham-operated rats is partially reduced in the adrenal medulla by muscarinic blockade, and completely in the cortex. This effect of methylatropine in regard to cortical ODC activity was not apparent in the other experiments with intact or unilaterally splanchnicotomized (unoperated side) rats. The results with unilaterally splanchnicotomized rats and those with transected spinal cord suggest that oxotremorine-induced modifications of adrenal ODC activity are centrally mediated, above the level of origin of the splanchnic nerves in the spinal cord (T_8–10). Experiments with hypophysectomized rats show that the response of the adrenal cortex to oxotremorine is entirely mediated by the hypophysis.     

Dependence of the parasitoid Gonia cinerascens on the hormones of its lepidopterous hosts

Development of first instar larvae of Gonia cinerascens, which rest in the muscles of host caterpillars, is triggered by the release of the host's ecdysteroids when the juvenile hormone is absent. Ecdysteroids act on the parasitoid directly and at the same time induce physiological and biochemical changes in the host, which are indispensable for the parasitoid's development. These changes do not occur when metamorphosis of the host is suppressed with the juvenile hormone. Normally the parasitoids initiate development at the larval-pupal transformation of the host, but under experimental conditions, they do so whenever a high ecdysteroid titre is coupled with the proper internal environment in the host, that is in decapitated caterpillars, isolated host abdomens, and when implanted into host pupae. Activated parasitoids moult into the second instar and migrate to the exuvial space of the host; this migratory behaviour is also triggered by ecdysteroids and may be induced experimentally in the first instar parasitoids. Unknown clues direct the migrating parasitoids under the wings and appendages of the host pharate pupal stage. The second instar parasitoids, which anchor to the integument of the host pupae, apparently develop independently of the host's hormones: they can produce third instar larvae, pupae, and adult flies when cultured in vitro.     

Schistosoma mansoni: effects of antimony on immature and adult worms.

Immature Schistosoma mansoni in mice are less susceptible to antimony therapy than adult worms. KSb tartrate inhibited phosphofructokinase (PFK) (EC 2.7.1.11) to a greater extent in extracts of 3-week-old worms than adults, and inhibited production of lactate in both immature and adult worms in vitro. In vivo, KSb tartrate was accumulated similarly by 3-week-old worms and by adults: measurements of hexosephosphate following drug treatment suggested similar inhibition of PFK in the two worm stages. If antimony acts by inhibition of PFK it is not clear why the young worms are more resistant to chemotherapy than adults.     

Studies on hemolysis of human erythrocytes by linoleic acid

The results presented in this paper show that lysis of human erythrocytes by linoleic acid is not caused by peroxidation of the fatty acid. Peroxidase, superoxide dismutase and scavengers of O ₂ ⁻ and OH had no effect on the lysis while catalase showed only marginal inhibition suggesting that O ₂ ⁻ , OH, O ₂ ⁻ and H₂O₂ do not play any direct role in hemolysis by linoleic acid. Generators of H₂O₂ inhibited the lysis completely and methemoglobin cells were more resistant to hemolysis by linoleic acid. The fatty acid did neither bind to nor fomed complex with red cell ghosts. Membrane oxidation of sulphydryl groups was also not involved in the lysis. Β-Carotene, retinol and bile salts enhanced the lysis, while, cholesterol but not cholesterol acetate, inhibited it. Taurocholate-pretreated cells were more susceptible to linoleic acid lysis. These observations suggested-that lysis by linoleic acid may be due to its detergent property.     

Ecdysterone antagonism,mimicry, and synergism of juvenile hormone action on the Monarch butterfly reproductive tract

Previous research on Monarch butterflies has shown that juvenile hormone (JH) stimulates the development of the ovary and certain reproductive glands of both sexes. Ecdysterone injections into intact Monarchs demonstrate that low doses of this hormone inhibit ovarian development, and higher doses stimulate the male and female reproductive glands. In addition, experiments using neckligatured adults show that ecdysterone stimulates the reproductive glands of both sexes, in the apparent absence of JH, with the most pronounced effect being observed on the female colleterial gland. Other studies with neck-ligatured animals demonstrate that ecdysterone also synergizes with JH on the female gland and all three male glands. The feasibility of using Monarch reproductive glands for studies on the mode of action and interaction of JH and ecdysterone, and the possibility of a rôle of ecdysterone in the normal regulation of Monarch oögenesis, are discussed.     

Photophosphorylation and related properties of reaggregated vesicles from spinach Photosystem I particles

The small Photosystem I particles prepared from spinach chloroplasts by the action of Triton X-100 (TSF 1 particles) reaggregate into membrane structures when they are incubated with soybean phospholipids and cholate and then subjected to a slow dialysis. The membranes so formed are vesicular in nature and show the capability of catalyzing phenazine methosulfate-mediated cyclic photophosphorylalation at rates which are usually about 20% of those observed with chloroplasts, but higher rates have been obtained. When coupling factor is removed from the chloroplasts by treatment with EDTA, a requirement for coupling factor can be shown for the subsequent ATP formation. The uncouplers carbonylcyanide 3-chlorophenyl-hydrazone, valinomycin, Triton X-100 and NH⁺₄ are effective with the reformed vesicles, which do not show the typical light-induced pH gradient observed with chloroplasts. Incubation of the TSF 1 particles with phospholipids alone allows for the formation of membrane vesicles, but such vesicles are only slightly active in ATP formation. In most properties investigated, the reformed membrane vesicles resemble the original chloroplast membrane so far as phenazine methosulfate-mediated cyclic photophosphorylation is concerned, which indicates a high degree of selectivity in the reaggregation process. The major difference between chloroplasts and the reformed vesicles is the failure of the latter to show a light-induced pH gradient.     

Honey: Single food stuff comprises many drugs

Honey is a natural food item produced by honey bees. Ancient civilizations considered honey as a God gifted prestigious product. Therefore, a huge literature is available regarding honey importance in almost all religions. Physically, honey is a viscous and jelly material having no specific color. Chemically, honey is a complex blend of many organic and inorganic compounds such as sugars, proteins, organic acids, pigments, minerals, and many other elements. Honey use as a therapeutic agent is as old as human civilization itself. Prior to the appearance of present day drugs, honey was conventionally used for treating many diseases. At this instant, the modern research has proven the medicinal importance of honey. It has broad spectrum anti-biotic, anti-viral and anti-fungal activities. Honey prevents and kills microbes through different mechanism such as elevated pH and enzyme activities. Till now, no synthetic compound that works as anti-bacterial, anti-viral and anti-fungal drugs has been reported in honey yet it works against bacteria, viruses and fungi while no anti-protozoal activity has been reported. Potent anti-oxidant, anti-inflammatory and anti-cancerous activities of honey have been reported. Honey is not only significant as anti-inflammatory drug that relieve inflammation but also protect liver by degenerative effects of synthetic anti-inflammatory drugs. This article reviews physico-chemical properties, traditional use of honey as medicine and mechanism of action of honey in the light of modern scientific medicinal knowledge.     

Mechanism of action of Clostridium perfringens enterotoxin. Effects on membrane permeability and amino acid transport in primary cultures of adult rat hepatocytes

Purified enterotoxin from the bacterium Clostridium perfringens rapidly decreased the hormonally induced uptake of α-aminoisobutyric acid in primary cultures of adult rat hepatocytes. At 5 min after toxin addition the decrease in α-aminoisobutyric acid uptake appeared not due to increased passive permeation (estimated with l-glucose) or to increased α-aminoisobutyric acid efflux. When short uptake assay times were employed a depression of α-aminoisobutyric acid influx was observed in toxin-treated hepatocytes. The depression of α-aminoisobutyric acid influx was correlated with a rapid increase in intracellular Na⁺ (estimated using ²²Na⁺) apparently effected by membrane damage. In contrast, the uptake of cycloleucine in the presence of unlabeled α-aminoisobutyric acid (assay for Na⁺-independent amino acid uptake) by hepatocytes treated with toxin for 5 min was decreased to only a small extent or not at all depending upon experimental design. At later times, C. perfringens enterotoxin increased the exodus of l-glucose, $\text{3-O-}\text{methylglucose}$ and α-aminoisobutyric acid from pre-loaded cells indicating that the toxin effects progressive membrane damage. When enterotoxin was removed by repeated washing after 5–20 min the decay of α-aminoisobutyric acid uptake ceased and appeared to undergo recovery towards the hormonally induced control level. The degree of recovery of α-aminoisobutyric acid uptake was inverse to the length of time of exposure to toxin. Adding at 10 min specific rabbit antiserum against C. perfringens enterotoxin without medium change also reversed the effect of toxin on increased intracellular ²²Na⁺, and on the exodus (from preloaded cells) of α-aminoisobutyric acid, L-glucose, and $\text{3-O-}\text{methylglucose}$.