Slow current changes underlying square shaped potential waves in warmedAplysia neurones

Summary On warming, the regularly firing L₁₁ neurone ofAplysia turns into a bursting-type neurone. The bursts of spikes are produced by slow square waves which can also be obtained at room temperature by adding TTX or Co⁺⁺. Experiments with slow ramp voltage clamp show that warming induces a negative slope (or negative resistance) on the current-voltage characteristic and very slow current variations (=10 to 50 sec) in response to potential changes. The square waves are explained by these two phenomena.     

Effects of three synthetic peptides analogous to neurohypophyseal hormones on the excitability of giant neurones ofAchatina fulica Férussac

Summary Deamino-dicarba-(d-d-)oxytocin andd-d-Arg-vasotocin at 10^–4 kg/l showed an excitatory effect on the periodically oxcillating neurone (PON) ofAchatina fulica Férussac.d-d-Arg-vasopressin had no effect.     

Two serotonin-sensitive potassium channels in the identified heart excitatory neurone of the African giant snail,Achatina fulica Fèrussac

Summary By the patch clamp experiments, two serotonin-sensitive K⁺ channels (SL-channel and SS-channel) were demonstrated in the identified heart excitatory neurone (PON) of the African giant snail,Achatina fulica Fèrussac. The activities of both channels could be recorded in the steady state and those activities disappeared on application of 5-HT.     

Inhibitory tripeptide,Lys-Phe-Tyr,as a fragment of physalaemin

Summary Several peptides were separated from-chymotrypsin-treated physalaemin by high voltage paper electrophoresis, and inhibition of the excitability of a molluscan giant neurone (tonically autoactive neurone) by the tripeptide, Lys-Phe-Tyr, was demonstrated.We thank Dr Sadaaki Iwanaga of Osaka University and Dr Atsuo Inoue of Daiichi Pharmaceutical CO for their helpful advice and the donation of the tripeptide (Lys-Phe-Tyr).     

Endogenous oscillatory activity and TTX-sensitive spikes of the heart muscle in early juveniles of the isopod crustaceanLigia exotica

The heart beat of early juveniles of the littoral isopodLigia exotica occurred at a frequency of 250 to 350/min, associated with rhythmic activity of the heart muscle. Each burst was composed of a slow depolarizing potential with superimposed spike potentials. The spike potential was eliminated by perfusion with TTX-containing or Na⁺-free saline. In TTX-saline, the slow potential was unchanged in frequency and amplitude. By current injection into the heart muscle, the rhythm of the slow potential was phase-shifted and its frequency was changed in a membrane potential-dependent manner. These results show that the heart ofLigia early juveniles acts as an endogenous muscle oscillator generating oscillatory slow potentials and Na⁺-dependent spikes.     

Distribution of (Na++K+)-ATPase in the hindgut ofGlossina morsitans morsitans Westwood

Summary (Na⁺+K⁺)-ATPase activity was higher in preparations from the ileum ofGlossina mortisans than in those from the rectum. This result suggests that the ileum as well as the rectum, may play a role in osmoregulation in the tsetse fly.     

Decreased rates of Ca2+-dependent heat production in slow- and fast-twitch muscles from the dystrophic (mdx) mouse

Using a newly developed microcalorimetric approach to assess the rate of energy expenditure for intracellular [Ca²⁺] homeostasis in isolated muscles at rest, we found this was lower inmdx than in control mouse muscles, by 62% and 29% in soleus and extensor digitorum longus, respectively. Differences in total and Ca²⁺-dependent rates of specific heat production betweenmdx and control were enhanced during sustained, KCl-induced stimulation of energy dissipation. These results suggest that the low sacroplasmic energy status of dystrophic muscles is not due to any excessive energy expenditure for intracellular [Ca²⁺] homeostasis.     

Protective effect of Shigyaku-to,a traditional Chinese herbal medicine,on the infection of herpes simplex virus type 1 (HSV-1) in mice

The antiviral activity of Shigyaku-to (TJS-109), a traditional Chinese herbal medicine, was investigated in mice infected with herpes simplex virus type 1 (HSV-1). TJS-109 is a combination of the medicinal plant extracts fromZingiberis siccatum rhizoma,Aconiti tuber andGlycyrrhizae radix in a specific proportion. Mice infected with a 10 LD₅₀ dose of HSV-1 were treated with TJS-109 orally at doses of 1.25 to 20 mg/kg 2 days before, and 1 and 4 days after the infection. The treated groups had 80% (1.25 mg/kg), 40% (5 mg/kg) and 23% (20 mg/kg) mortality rates 25 days after the infection as compared with a 100% mortality rate in control mice treated with saline. When HSV-1 infected mice (recipients) received CD8⁺T cell fractions derived from spleens of mice treated with TJS-109 (donors), 70% of recipients survived, as compared with 0% survivors in the groups of mice treated with saline, B cell fractions, CD4⁺ T cell fractions or macrophage-enriched fractions prepared from the same donors. TJS-109 did not show any virucidal activities against HSV-1 or any virostatic activities on the growth of HSV-1 in Vero cells. These results suggest that TJS-109 protected mice exposed to lethal amounts of HSV-1 through the activation of CD8⁺ T cells.     

Effects of physalaemin,a vase-active peptide from amphibian skin,on the excitability of an identifiable molluscan giant neurone ofAchatina fulica Férussac

Summary We examined effects of several vasoactive peptides (substance P, physalaemin, neurotensin, bradykinin, angiotensin etc.) on the excitability of molluscan giant neurones identified in the subesophageal ganglia ofAchatina fulica Férussac. Of these peptides, only physalaemin showed a remarkable excitatory effect on a giant tonically autoactive neurone.     

Action of juvenile hormone on the follicle cells ofRhodnius prolixus: Evidence for a novel regulatory mechanism involving protein kinase C

Summary Juvenile hormone (JH) is known to act on the membranes of the follicle cells ofRhodnius, activating a specific Na⁺, K⁺-ATPase. This leads to a decrease in volume of the cells and the appearance of spaces between them (patency). The addition of an inhibitor of protein kinase C, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), to the medium in vitro inhibits the action of JH on the follicle cells. PDBU (phorbol-12,13-dibutyrate) mimics the action of JH in vitro and the response of the follicle cells to, PDBU is blocked by ouabain. It is concluded that the activation of protein kinase C is a required step in the chain of events leading to activation of the JH-dependent ATPase and set in train by the binding of JH to the membrane.     

Displacement activity of some natural cularine alkaloids at striatal3H-SCH 23 390 and3H-raclopride binding sites

Five natural cularines isolated from the aerial parts ofSarcocapnos crassifolia (Fumariaceae) and a cularioid isolated from the bark ofGuatteria ouregou (Annonaceae) were tested for their ability to displace³H-SCH 23 390 and³H-raclopride from their striatal binding sites. Celtisine, breoganine and cularidine were able to inhibit the binding at D-1 and D-2 dopaminergic sites at nanomolar concentrations. Other alkaloids were active at micromolar concentrations. These data suggest that the presence of an oxepine system in the isoquinoline skeleton could lead to compounds which would be very active and possibly selective at dopaminergic receptor sites.     

Araplysillins-I and-II: Biologically active dibromotyrosine derivatives from the spongePsammaplysilla arabica

Summary Araplysillins-I and-II, two novel dibromotyrosine derivatives, were isolated fromPsammaplysilla arabica and their structure was elucidated by spectroscopic methods. They proved to be inhibitors of Na⁺/K⁺ ATPase and to have antimicrobial activity.     

Selective blockade of components of potassium activation inMyxicola axons

Summary The K⁺ conductance inMyxicola giant axons activates in two phases which are pharmacologically separable. The fast phase of K⁺ activation is specifically inhibited by 4-aminopyridine and by the substitution of D₂O for H₂O. We suggestMyxicola giant axons, like the amphibian node of Ranvier, may possess more than one variety of K⁺ channel.     

Chromate reduction inStreptomyces

Summary Streptomyces species 3M grew in peptone yeast extract medium with 1000 g/ml K₂Cr₂O₇. Incubation of the chromate with different cell fractions in the presence of NADH and NADPH resulted in a decrease of Cr⁶⁺ in the reaction mixture. The level of Cr⁶⁺ was reduced by 82.7% by a particulate cell fraction obtained by centrifugation at 105,000×g for 1 h, in the presence of NADH. The reducing enzyme was associated with this cell fraction. The enzyme was constitutive and reduced Cr⁶⁺ to Cr³⁺.     

Symbioramide,a novel Ca2+-ATPase activator from the cultured dinoflagellateSymbiodinium sp.

Summary A novel sphingosine derivative, symbioramide, has been isolated from the laboratory-cultured dinoflagellateSymbiodinium sp. as a sarcoplasmic reticulum (SR) Ca²⁺-ATPase activator, and its structure elucidated to be1 on the basis of spectral and chemical means.Acknowledgments. We thank Ms M. Hamashima and Ms A. Muroyama for their technical assistance.     

Interactions between two identified cells in the visceral ganglion of the snail,Helix pomatia

Summary An interneurone, making excitatory synaptic connections with a second neurone has been identified in the brain ofHelix pomatia. The results suggest that the connection is monosynaptic.We thank the M.R.C. for a Training Grant to S.E.J.     

Plakorin,a potent Ca2+-ATPase activator from the Okinawan marine spongePlakortis sp.

Summary A new cyclic peroxide, plakorin, which is a potent sarcoplasmic reticulum (SR) Ca^a+-ATPase activator has been isolated from the Okinawan marine spongePlakortis sp., its structure was elucidated on the basis of spectral data.Acknowledgments. We thank Ms M. Hamashima and Ms A. Muroyama for their technical assistance.     

Cell-to-cell transmission in the activation of in situ nematocytes in acontia ofCalliactis parasitica

Summary It is reported that Ca²⁺-induced discharge of in situ nematocytes of acontia ofCalliactis parasitica can occur by cell-to-cell transmission along the acontial filament at a speed that averages 9.8·10^–3 cm^–1. The discharge is preceded by protrusion of nematocytes that proceeds along the acontium at a slightly higher speed.     

Hydrolysis of isoprenyl diphosphates with the acid phosphatase fromCinnamomum camphora

Direct observations of the enzymatic hydrolysis of C₁₀ acyclic allylic isoprenyl diphosphates by an acid phosphatase from the leaves ofCinnamomum camphora (camphor tree) were made using¹H and³¹P NMR spectrometers. The measurements indicated that the allylic primary diphosphates, geranyl diphosphate and neryl diphosphate, were hydrolyzed to their corresponding alcohols in a sequential manner via their corresponding monophosphates, whereas the allylic tertiary diphosphate, linalyl diphosphate, was hydrolyzed only to its corresponding monophosphate.     

Effect of xanthurenic acid on P-450-dependent biotransformation by molting glands in vitro

Incubation of molting glands from the crayfishProcambarus clarkii (Y-organ) and the silkwormBombyx mori (prothoracic gland) with 23,24-[²H₄]-2-deoxyecdysone resulted in the production of deutero-ecdysone; this biotransformation was inhibited in the presence of xanthurenic acid. When the experiments were performed under an¹⁸O₂ atmosphere, the¹⁸O atom was introduced into ecdysone, as confirmed by mass spectrometry. We therefore suggest that xanthurenic acid inhibits P-450-dependent hydroxylation of 2-deoxyecdysone. However, deutero-2-deoxyecdysone was not converted to 3-dehydroecdysone when using Y-organs in vitro, although it is a major product. We therefore conclude that the biosynthetic pathway of ecdysteroids inP. clarkii branches at an early step.