Le collagène du byssus de Mytilus edulis L.

Résumé L'autoradiographie révèle, au niveau du pied, une incorporation massive et sélective de la ³H-Proline dans la glande blanche de Mytilus edulis. Cette étude a permis de suivre le processus qui mène de la synthèse de la sécrétion dans la partie basale des cellules jusqu'a son émission dans le sillon pédieux où elle participe à la formation du filament. La collagénase détruit la presque totalité du marquage, attestant ainsi la nature collagénique du produit sécrété. Les autres glandes pédieuses ainsi que la glande du byssus proprement dite, située à la base du pied, montrent une incorporation très faible, sans commune mesure avec celle de la glande blanche. Ceci démontre de façon définitive que le collagène présent dans le filament prend naissance dans cette glande et justifie la dénomination de glande du collagène. Des contrôles réalisés dans différentes régions (bords du manteau, manteau, branchies) montrent que l'injection du précurseur dans le bord palléal constitue une méthode satisfaisante pour marquer de façon relativement rapide et différentielle le collagène de la glande.

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The collagen of the byssus in Mytilus edulis L.II. Autoradiographic study on the incorporation of ³H-Proline

Summary Autoradiographic studies reveal a strong specific incorporation of ³H-Proline in the white gland in the foot of Mytilus edulis. The author could trace the radioactive secretory product from its synthesis in the basal part of the cells down to its outflow into the pedial groove where it takes part in the formation of the filament. Purified collagenase takes out radioactivity from the sections. This observation confirms the collagenous nature of the secretion.The other foot-glands as well as the main byssus gland located at the base of the foot show but a very weak labelling not comparable with that of the white gland. This clearly evidences that the collagen occuring in the filament originates from the latter. The white gland may be properly called: collagen gland.Control sections through different parts of the body (mantle-edge, mantle, gills) confirm that our injection technique of the precursor into the palleal margin is a suitable method for a rather quick and specific labelling of the glandular collagen.

Cette note fait partie d'un travail pour l'obtention d'une thèse de doctorat.     

Evidence for two K+ currents activated upon hyperpolarization ofParamecium tetraurelia

Summary Hyperpolarization of voltage-clampedParamecium tetraurelia in K⁺ solutions elicits a complex of Ca²⁺ and K⁺ currents. The tail current that accompanies a return to holding potential (–40 mV) contains two K⁺ components. The tail current elicited by a step to –110 mV of 50-msec duration contains fast-decaying (3.5 msec) and slow-decaying (20 msec) components. The reversal potential of both components shifts by 55–57 mV/10-fold change in external [K⁺], suggesting that they represent pure K⁺ currents. The dependence of the relative amplitudes of the two tail currents on duration of hyperpolarization suggests that the slow K⁺ current activates slowly and is sustained, whereas the fast current activates rapidly during hyperpolarization and then rapidly inactivates. Iontophoretic injection of a Ca²⁺ chelator, EGTA, specifically reduces slow tail-current amplitude without affecting the fast tail component. Both K⁺ currents are inhibited by extracellular TEA⁺ in a concentration-dependent, noncooperative manner, whereas the fast K⁺ current alone is inhibited by 0.7mm quinidine.     

Detection of Oxidant Producing-sites in Glutaraldehyde-fixed Human Neutrophils and Eosinophils Stimulated with Phorbol Myristate Acetate

The aim of the present study was to detect oxidant-producing sites, and to elucidate their dynamic reorganization in human polymorphonuclear leukocytes (PMNs) fixed with glutaraldehyde which preserves cell structure. In biochemical analyses, the detectable O2– generation in unfixed PMNs upon stimulation with phorbol 12-myristate 13-acetate (PMA) in the presence of cytochalasin B was characterized by a lag period of approximately 10sec followed by O2– production. The maximal rate reached was 3.18±0.07nmol/min/1×106 cells (mean±S.D.; n=4) after 30sec of stimulation. PMNs exposed to PMA and cytochalasin B followed by fixation with glutaraldehyde generated O2– without a lag period at a rate of 0.35±0.05nmol/min/1×106 cells (mean±S.D.) by the addition of NADPH as substrate to the cell suspension. In the cytochemical assays, we employed both cells exposed to PMA and cytochalasin B, and then fixed with glutaraldehyde followed by incubation in the cytochemical reaction medium (pre-fixed cells) and cells incubated in the medium containing PMA and cytochalasin B followed by fixation with glutaraldehyde (post-fixed cells). Oxidant reaction in the pre-fixed cells was detected by the addition of NADPH and FAD to the reaction medium. No oxidant-reaction product was seen in pre-fixed cells stimulated for 10sec whereas the oxidant reaction was visualized in intracellular compartments of pre-fixed PMNs stimulated for 20sec. The fact that the pre-fixed PMNs stimulated for 30sec showed increased numbers of oxidant-producing structures compared to those seen in the pre-fixed cells stimulated for 20sec, demonstrates that the amount of the reaction product and the number of oxidant-producing intracellular compartments increases between 20 and 30sec after start of stimulation with PMA. These cytochemical results using the pre-fixed cells coincided with the findings obtained from the biochemical assays in the pre-fixed cells exposed to PMA and cytochalasin B. The oxidant reaction was observed in elongated tubular structures that were arranged in a radial fashion, and were associated with the plasma membrane in the pre-fixed PMNs, whereas post-fixed PMNs exhibited slender spherical or rod-shaped structures of various lengths. The present results indicate that the pre-fixed PMNs can be employed for elucidating the dynamic reorganization of oxidant-producing sites in human PMNs.     

Effects of catecholamines on isolated systemic and branchial vascular beds of the cod,Gadus morhua

Summary The effects of catecholamines on the vascular resistance of the gills, the gas gland and the tail of the Atlantic cod, were studied in isolated preparations perfused at a constant pressure. Adrenaline caused a biphasic response of the gill vasculature with an initial constriction followed by a dilation. The noradrenaline response was usually dilatory, but constrictory responses at all or some concentrations were occasionally seen in some specimens. The branchial dilation was caused by adrenaline concentrations even lower than those found in normal cod plasma (30 nM). The gas gland and the tail vasculature were constricted by both adrenaline and noradrenaline. A flow reduction in the isolated preparations of about 10% at concentrations of adrenaline equalling that in normal cod plasma (30 nM) was increased to about 30% (tail) or 45% (gas gland) at concentrations of adrenaline similar to that found in cod plasma during stress (300 nM).The constrictory responses to adrenaline and noradrenaline were antagonized in all preparations by the alpha adrenoceptor antagonist, phentolamine (10^–6 M) and the dilatory response of the branchial vasculature to these agonists was reduced or abolished by propranolol (10^–6 M).It is concluded that adrenaline, in the concentrations found in cod plasma at rest and after stress, has pronounced effects on the organs studied, especially the gill vasculature, and may thus contribute to the overall control of the circulatory system. The branchial vasculature will also be affected by changes in noradrenaline concentration which occur in animals at rest and under stress.     

An analysis of flash-induced electrical transients of a BLM containing chloroplast lamella extracts

Summary The electrical transients produced by chloroplast bilayer lipid membranes (Chl-BLM) from flash excitation are seen to result from three photocurrents and a discharge current. Each of the three photo-initiated charge transports in Chl-BLM (designated as Components A, B and C) exhibits an action spectrum similar to chlorophyll absorption spectra. The fast components (A and B), which are induced by electron acceptors such as Fe⁺³, have rise-times of 3 sec and 20 msec, and occur in TLM (thin lipid membranes, i.e., colored membranes up to 1 thick) as well as in BLM. Component C is induced by a transmembrane pH difference or applied voltage, has a rise-time of 1 sec, and occurs only in BLM. Component C is associated with exciton dissociation and proton transport. The mobility of the Component A current carriers in TLM is estimated to be about 1×10^–2 cm²/volt sec, and are, hence,electronic. The photovoltage waveforms are described by equations developed, which consider Component A as being caused by a direct charge separation proportional to the illumination intensity (within 0.5 sec), and Components B and C being caused by two types of exciton processes which cause charge transport after the illumination period.     

A potassium conductance activated by hyperpolarization in paramecium

Summary Voltage clamp studies show that the wild-type membrane ofParamecium tetraurelia contains a conductance component which is sensitive to hyperpolarization. This component manifests itself as anomalous, or inward going, rectification of membrane voltage in response to applied constant current pulses and as a hyperpolarizing spike when no K is added to the external solution (Y. Satow, C. Kung, 1977.J. Comp. Physiol. 11999). Like the conductances which underlie anomalous rectification in other cells, the hyperpolarization-sensitive conductance inParamecium is specific for K, and the magnitude of the voltage-dependent conductance change depends not only on voltage but also on external potassium concentration. The internal potassium ion concentration ofParamecium is calculated to be between 17 and 18mm.     

Effects of GABA antagonists,SR 95531 and bicuculline,on GABAA receptor-regulated chloride flux in rat cortical synaptoneurosomes

Synaptoneurosomes isolated from cerebral cortices of male Sprague-Dawley rats were used for studying GABA_A receptor-regulated chloride influx. The in vitro effects of GABA antagonists, SR 95531 (a pyridazinyl GABA derivative) and bicuculline, on pentobarbital-stimulated, muscimol-stimulated or flunitrazepam-enhanced, muscimol-stimulated chloride uptake were studied. The chloride uptake was determined at 30°C, for 5 sec. Pentobarbital and muscimol produced a maximal stimulation of chloride uptake in cortical synaptoneurosomes at 500 M and 50M, respectively. SR 95531 as well as bicuculline had no effect on the basal uptake of chloride. Whereas, SR 95531 (0.3–30 M) and bicuculline (0.1–100 M), when added 5 min before muscimol (50 M), produced a significant concentration-dependent inhibition of muscimol (50 M)-stimulated chloride uptake (IC₅₀ s of 0.89±0.11 M and 13.45±2.10M, respectively). In studies of the inhibitory effects of SR 95531 and bicuculline on pentobarbital (500 M)-stimulated chloride uptake, the IC₅₀ s were 0.81±0.12 M and 3.86±1.14 M, respectively. SR 95531 exhibited a more potent inhibitory effect than bicuculline on flunitrazepam-enhanced, muscimol-stimulated chloride uptake. The results revealed that SR 95531 has a more potent antagonistic effect than bicuculline on GABA_A-regulated chloride flux.     

After hyperpolarization conductance time-course and repetitive firing in a motoneurone model with early inactivation of the slow potassium conductance system

Early inactivation of the slow potassium conductance system (GK), responsible for the spike afterhyperpolarization (AHP) in spinal alpha motoneurones, has been introduced in a motoneurone model whose G _K kinetics give rise to an exponentially decaying AHP conductance. After this modification, the model displays a plateau shaped time-course of the AHP conductance and a faster shortening of the first interval during repetitive firing induced by current steps of increasing intensities. Both features increase the resemblance between the model and the motoneurone behaviour. Comparison with real motoneurones also suggests that G _K inactivation may be more developed in slow than in fast motoneurones.     

Frequency response characteristics of a multi-loop representation of the segmental muscle stretch reflex

This paper continues the investigation of a three-loop representation of the segmental muscle stretch reflex system introduced in a preceding communication. Frequency response characteristics were computed for open-loop conditions, control and disturbance signal inputs under a variety of conditions: (i) in parallel and in series peripheral arrangements of muscle compartments, (ii) various patterns of central connectivity, (iii) various recruitment levels of motor units, (iv) various overall reflex gains, (v) absence or presence of muscle spindle accleration sensitivity. These computations disclosed a number of mechanisms by which the nervous system might improve system stability and behaviour. These mechanisms are discussed with regard to physiological data.     

Action of rat liver Galβ1-4GlcNAc α(2-6)-sialyltransferase on Manβ1-4GlcNAcβ-OMe,GalNAcβ1-4GlcNAcβ-OMe,Glcβ1-4GlcNAcβ-OMe and GlcNAcβ1-4GlcNAcβ-OMe as synthetic substrates

Incubation of synthetic Man\1-4GlcNAc-OMe, GalNAc1-4GlcNAc-OMe, Glc1-4GlcNAc-OMe, and GlcNAc1-4GlcNac-OMe with CMP-Neu5Ac and rat liver Gal1-4GlcNAc (2-6)-sialyltransferase resulted in the formation of Neu5Ac2-6Man1-4GlcNAc-OMe, Neu5Ac2-6GalNAc1-4GlcNAc-OMe, Neu5Ac2-6Glc1-4GlcNAc-OMe and Neu5Ac2-6GlcNAc1-4GlcNAc-OMe, respectively. Under conditions which led to quantitative conversion of Gal1-4GlcNAc-OEt into Neu5Ac2-6Gal1-4GlcNAc-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz¹H-NMR spectroscopy.Abbreviations 2D 2-dimensional - CMP cytidine 5-monophosphate - CMP-Neu5Ac cytidine 5-monophospho--N-acetylneuraminic acid - COSY correlation spectroscopy - DQF double quantum filtered - HOHAHA homonuclear Hartmann-Hahn - MLEV composite pulse devised by M. Levitt - Neu5Ac N-acetylneuraminic acid - Neu5Ac2en 2-deoxy-2,3-didehydro-N-acetylneuraminic acid     

Fine structure of the spermatozoon of the sea cucumber,Leptosynapta clarki (Echinodermata: Holothuroidea)

Summary The spermatozoon of the holothurian Leptosynapta clarki has a small circular head measuring about 3.0 at the greatest diameter, a midpiece containing a single mitochondrion and a tail flagellum measuring between 35 and 45 in length. The acrosomal region contains a granule measuring 0.7 in diameter which consists of electron dense material arranged in concentric lamellae. Five concentric very electron dense lamellae alternate with areas of much less electron dense material in the central region of the granule. This granule rests in an anterior nuclear depression.The nucleus is circular in shape and contains one or two unbound vacuoles which frequently contain a fine granular material. Posteriorly the nucleus is bounded by a large mitochondrion and an occasional Golgi complex. The proximal centriole which contains a lateral arm of dense material lies in a deep fossa projecting into the nucleus. The distal centriole lies posteriorly in the mitochondrial mass and gives rise to nine satellite projections and their Y-shaped connective extensions.The tail contains the 9 + 2 tubule arrangement and tapers at its distal end.This investigation was supported by a National Research Council grant to F. S. Chia.     

The Effect of Phenylalanine on DOPA Synthesis in PC12 Cells

DOPA synthesis from phenylalanine was studied in PC12 cells incubated with m-hydroxybenzylhydrazine, to inhibit aromatic L-amino acid decarboxylase. DOPA synthesis rose with increasing concentrations of either phenylalanine or tyrosine; maximal rates (~55 pmol/min/mg protein for tyrosine; ~40 pmol/min/mg protein for phenylalanine) occurred at a medium concentration of ~10 M for either amino acid. The K_m for either amino acid was about 1 M (medium concentration). At tyrosine concentrations above 30 M, DOPA synthesis declined; inhibition was observed at higher concentrations for phenylalanine (300 M). These effects were most notable in the presence of 56 mM potassium. Measurements of intracellular phenylalanine and tyrosine suggested the K_m for either amino acid is 20–30 M; maximal synthesis occurred at 120–140 M. In the presence of both phenylalanine and tyrosine, DOPA synthesis was inhibited by phenylalanine only at a high medium concentration (1000 M), regardless of medium tyrosine concentration. The inhibition of DOPA synthesis by high medium tyrosine concentrations was antagonized by high medium phenylalanine concentrations (100, 1000 M). Together, the findings indicate that for PC12 cells, phenylalanine can be a significant substrate for tyrosine hydroxylase, is a relatively weak inhibitor of the enzyme, and at high concentrations can antagonize substrate inhibition by tyrosine.     

Vasoactive intestinal polypeptide (VIP)- and neuropeptide Y (NPY)-containing nerve fibres in the penile cavernous tissue of green monkeys (Cercopithecus aethiops)

Summary The cavernous body of green monkeys contains many unmyelinated and few myelinated axons. The unmyelinated axons form terminals in the adventitia of the arteries, between trabecular muscle cells, in the interstitium, and close to endothelium cells of the sinuses. All terminals displayed predominantly small clear vesicles and very few large granular vesicles; small granular vesicles were not seen. However, in rabbit penises, terminals with many large granular vesicles are prominent. Immunohistochemistry (PAP technique) showed a dense network of VIP- and NPY-reactive fibres around the arteries and around trabecular muscles. The density of nerve fibres was particularly high around the subendothelial cushions of the helicine arteries. Double staining for NPY and VIP revealed that both peptides were colocalized. Immunocytochemistry (preembedding PAP technique) showed VIP- and NPY-reactivity in terminals with small clear vesicles; the reaction product was bound to the cytoplasmic face of different membrane types. Although the intracellular localization of the reaction product is probably due to artefactual displacement during preparation, the uniformity of the terminals questions the view that large and small granular vesicles in all species characterize peptidergic and noradrenergic terminals, respectively. The essential findings can be summarized as (1) a high degree of uniformity of nerve terminals, (2) colocalization of VIP and NPY, (3) heavy innervation of the subendothelial cushions of the helicine arteries, and (4) possible innervation of endothelial cells.     

Stimulation of non-specific resistance to tumors in the mouse using a poly(maleic-acid-styrene)-conjugated neocarzinostatin

Summary The development of non-specific resistance to tumors following stimulation with poly(maleic-acid-styrene)-conjugated neocarzinostatin (SMANCS), a polymer-conjugated derivative of neocarzinostatin, was investigated in mice. The growth of syngeneic solid tumors (Meth-A fibrosarcoma and RL 1 leukemia) inoculated into BALB/c mice was suppressed after one treatment with SMANCS at doses ranging from 0.14 mg/kg to 3.4 mg/kg i.v. 24 h before tumor implantation. Since previously observations concerning SMANCS have shown that it disappeared within 1.5 h after i.v. administration in mice and that it was inactivated quickly in plasma, SMANCS evidently inhibited tumor growth by mediating non-specific resistance. In addition, the non-specific resistance to tumors stimulated by SMANCS could be passively transferred to untreated mice by serum which was shown to contain interferon (IFN) from 12 h to 20 h after SMANCS administration. However, the resistance was not produced by serum prepared from mice at 8 h or 32 h after administration presumably because of the observation that the interferon activity was only demonstrated from 12 h to 28 h after SMANCS stimulation. When the serum specimens were treated with anti-IFN- antiserum, the antitumor activity of the sera was abrogated. However, no significant change was detected in the antitumor activity of the specimens following treatment with anti-IFN-/ antiserum. Treatment of mice with SMANCS and anti-IFN- antiserum together resulted in the elimination of the non-specific resistance to tumors. The IFN induced in the sera of mice by SMANCS was shown to be 57% IFN- and 41% IFN-/. Half of the interferon produced in SMANCS-stimulated mice could be eliminated by treatment with anti-IFN-, and treatment of SMANCS-stimulated mice with both anti-IFN- and anti-IFN-/ antisera resulted in a total absence of detectable interferon. These findings suggest that while the administration of SMANCS induces both IFN- and IFN-/ production, in this case, it is only the former which mediates the non-specific resistance to tumors.     

Structure and physical chemistry of membranes

Summary With the concept of the unit membrane as a central theme, a number of current problems for the theory of membrane structures are discussed from the point of view of the physical chemist. In view of the wide variety of chemical compositions of membranes, some current opinions of the forces maintaining the integrity of membranes are of limited generality. The thermodynamic status of the membrane is discussed, and it is suggested that the new small-systems thermodynamics can be usefully employed as a conceptual basis for discussing fluctuations and phase-changes in membranes. Arguments are given to suggest that the lipid interior of membranes is more ordered and crystalline than is currently supposed. The role of water in membrane structures remains an enigma.     

UDP-GlcNAc: Galβ3GalNAc-Mucin: (GlcNAc → GalNAc) β6-N-Acetylglucosaminyltransferase and UDP-GlcNAc: Galβ3(GlcNAcβ6) GalNAc-Mucin (GlcNAc → Gal)β3-N-Acetylglucosaminyltransferase from Swine Trachea Epithelium

Summary Two specific -N-acetylglucosaminyltransferases involved in the branching and elongation of mucin oligosaccharide chains, namely, a 1,6 N-acetylglucosaminylsaminyltransferase that transfers N-acetylglucosamine from UDP-N-acetylglucosamine to Gal3GalNAc-Mucin to yield Gal3(GlcNAc6)GalNAc-Mucin and a 3-N-acetylglucosaminyl transferase that transfers N-acetylglucosamine from UDP-N-acetylglucosamine to Gal3(GlcNAC6)GalNAc-mucin to yield GlcNAc3Gal3 (GlcNAc6)GalNAc-Mucin were purified from the microsomal fraction of swine trachea epithelium. The 1,6-N-acetylglucosaminyltransferase was purified about 21,800-fold by procedures which included affinity chromatography on DEAE columns containing bound asialo Cowper's gland mucin glycoprotein with Gal1,3GalNAc side chains. The apparent molecular weight estimated by gel filtration was found to be about 60 Kd. The purified enzyme showed a high specificity for Gal1,3GalNAc chains and the most active substrates were mucin glycoproteins containing these chains. The apparent Km of the 6-glucosaminyltrans-ferase for Cowper's gland mucin glycoprotein containing Gal1,3GalNAc chains was 0.53 µM; for UDP-N-acetylglucosamine, 12 µM; and for Gal 1,3GalNAc NO₂ø, 4 mM. The activity of the 6-glucosaminyltransferase was dependent on the extent of glycosylation of the Gal3GalNAc chains in Cowper's gland mucin glycoprotein.The best substrate for the partially purified 3-Glucosaminyltransferase was Cowper's gland mucin glycoprotein containing Gal1,3(GlcNAc6)GalNAc side chains. This enzyme showed little or no activity with intact sialylated Cowper's gland mucin glycoprotein or derivatives of this glycoprotein containing GalNAc or Gal1,3GalNAc side chains.The radioactive oligosaccharides formed by these enzymes in large scale reaction mixtures were released from the mucin glycoproteins by treatment with alkaline borohydride, isolated by gel filtration on Bio-Gel P-6 and characterized by methylation analysis and sequential digestion with exoglycosidases. The oligosaccharide products formed by the 6- and 3-glucosaminyltransferases were shown to be Gal3(GlcNAC6) GalNAc and GlcNAc3 Gal3(GlcNAC6)GalNAc respectively.Taken collectively, these results demonstrate that swine trachea epithelium contains two specific N-acetylglucosaminyltransferases which catalyze the initial branching and elongation reactions involved in the synthesis of O-linked oligosaccharide chains in respiratory mucin glycoproteins. The first enzyme a 6-glucosaminyltransferase converts Gal3GalNAc chains in mucin glycoproteins to Gal3(GlcNAc6)GalNAc chains. This product is the substrate for a second 3-glucosaminyltransferase which converts the Gal3(GlcNAc6)GalNAc chains to GlcNAc3Gal(GlcNAc6)GalNAc chains in the glycoprotein. The 3-glucosaminyltransferase did not utilize Gal3GalNAc chains as a substrate and this results in an ordered sequence of addition of N-acetylglucosamine residues to growing oligosaccharide chains in tracheal mucin glycoproteins.Abbreviations NeuNAc N-acetylneuraminic acid - GalNAcol N-acetylgalactosaminitol - CGMG Cowper's gland mucin glycoprotein - GalNAc-CGMG Cowper's gland mucin glycoprotein containing GalNAc side chains O-glycosidically linked to serine or threonine - Gal3GalNAc-CGMC Cowper's gland mucin glycoprotein containing Gal3GalNAc side chains - MES 2-(N-morpholino) Ethane Sulfonic acid - PBS Phosphate Buffered Saline     

Horizons in plant pathology I. The “host” and the “parasite”: Need for a broadened outlook

Summary A critical appraisal of the celebrated couplet of plant pathology host and parasite is presented in the preceding pages. Author's own evaluation opens new vistas, displays several new ideas and an altogether new interpretation of this central theme of plant pathology incorporating biochemical concepts.     

Voltage-dependent calcium current in dissociated smooth muscle cells of the buccal mass of Aplysia

Summary Isolated smooth muscle cells of the buccal mass of Aplysia contracted in response to depolarization elicited by a patch electrode in whole-cell configuration. With cesium-containing pipet solution and tetraethylammonium and 4-aminopyridine in the external solution depolarization elicited inward current. The voltage-dependent inward current was blocked completely by lanthanum (10 mmol·1^-1), inhibited 80–90% by nifedipine (1 mol·l^-1), and was dependent upon extracellular calcium. These results showed that the voltage-dependent inward current was due to activation of voltage-dependent calcium channels (VDCaCH). Minimal depolarization to begin activating VDCaCH was-60 to-30 mV. Inward current peaked within 8 ms and then decreased rapidly to a lower level of relatively non-inactivating current. The initial peak current could be mostly inactivated by a depolarization to-20 mV for 500 ms. Nifedipine reduced both the peak current and the relatively non-inactivating current. Nifedipine inhibited high potassium-elicited contractions of both intact and dissociated muscle. These results suggested that VDCaCH mediates calcium influx which triggers contraction in molluscan smooth muscle fibers.Abbreviations ACh acetylcholine - ATP adenosine triphosphate - EGTA ethyleneglycol-bis(-aminoethyl ether) N,N,N,N-tetraacetic acid - GTP guanosine triphosphate - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid - MCG metacerebral giant cell - RNI relatively non-inactivating - SCP small cardioactive peptide - TEA-4AP-IO external solution containing Instant Ocean, tetraethylammonium chloride, and 4-aminopyridine (described in Methods) - TEA tetraethylammonium chloride - VDCaCH voltagedependent calcium channel - 4-AP 4-aminopyridine - 5-HT 5-hydroxytryptamine or serotonin     

Ultrastructure of Sporothrix schenckii treated with iodine-potassium iodide solution

The ultrastructural changes produced by iodine-potassium iodide solution on yeast cells of Sporothrix schenckii were investigated by transmission electron microscopy in order to clarify the mechanism of oral potassium iodide therapy for sporotrichosis. Yeast cells were dipped with solutions containing various concentrations of iodine. The rate of germination decreased markedly between the range of iodine concentrations from 0.63 g/ml to 5.0 g/ml. No significant ultrastructural changes were seen at the concentration of the iodine of 1.25 g/ml (80% germination) or less. In the concentration of 2.5 g/ml (50% germination), normal cells and degenerated cells coexisted. When the cells were treated with 5.0 g of iodine per ml (0% germination) or more, their interior structures were completely destroyed. It is assumed that iodine treatment of the organism causes rapid destruction in the whole cell.     

Die Feinstruktur der Zirbeldrüse normaler,trächtiger und experimentell beeinflußter Meerschweinchen

Zusammenfassung In der Meerschweinchenzirbeldrüse lassen sich elektronenmikroskopisch helle und dunkle Pinealzellen sowie einzelne Gliazellen nachweisen. In den bei weitem überwiegenden hellen Pinealzellen zeichnet sich ein Teil der vesicle-crowned rodlets (VCR) durch lokale Auftreibungen aus. Von VCR deutlich abzugrenzen sind die vesicle-crowned balls (VCB). Erstmalig beschrieben wird das Vorkommen von sog. Zylindern, die als Vorstufen von VCB aufgefaßt werden. In den relativ seltenen dunklen Pinealzellen, die sich durch chromatinreiche Kerne und elektronendichtes Zytoplasma auszeichnen, sind Vesikel, VCR, VCB und Zylinder seltener als in hellen Pinealzellen. Die reichlich vorhandenen marklosen Nervenfasern finden sich vor allem in perivasculären Räumen, seltener im Parenchym. Synapsen zwischen Nerven und Pinealzellen wurden nicht beobachtet. In den Zirbeldrüsen trächtiger Meerschweinchen zeichnen sich in der 2. Hälfte der Tragzeit die hellen Pinealzellen durch stärkere Lappung der Kerne, gehäuftes Auftreten von laktiven Zonen, Vermehrung von Mitochondrien, glattem ER, agranulären Vesikeln, VCR, VCB und Zylindern aus. Die dunklen Pinealzellen nehmen während der Tragzeit an Zahl zu. Post partum bilden sich diese Veränderungen innerhalb einer Woche zurück. Längerer Aufenthalt der Tiere in Dunkelheit führt zu einer Aktivierung der hellen Pinealzellen mit auffallender Vermehrung der VCR und zu einer Zunahme der dunklen Zellen. Unter Dauerbelichtung kommt es in den hellen Zellen zu einer Abnahme fast aller Zellorganellen und zu einer starken Vermehrung der VCR, die nach 70 Tagen auch Formveränderungen aufweisen. Nach Reserpinbehandlung beobachtet man eine Verminderung und degenerative Veränderungen der VCR. Es wird diskutiert, daß die VCR als prae- bzw. postsynaptische Strukturen der Erregungsübertragung von Nerven zu Pinealzellen bzw. von Pinealzellen untereinander dienen könnten.

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The fine structure of the pineal gland of normal, pregnant and experimentally affected guinea-pigs

Summary By means of electron microscopy light and dark pinealocytes can be distinguished in the guinea-pig pineal gland. Glial cells are rare. In the light pinealocyte. the most frequent cell type, some vesicle-crowned rodlets (VCR) show circumscribed thickenings. From these structures vesicle-crowned balls (VCB) have to be clearly distinguished. Furthermore cylinders occur, which, it is suggested, are precursors of VCB. Dark pinealocytes characterized by chromatin-rich nuclei and electron-dense cytoplasm are rare and contain fewer vesicles, VCR, VCB and cylinders than light pinealocytes. Numerous non-myelinated nerve fibres are situated within perivascular spaces, a few also in the parenchyma. Synapses between nerve fibres and pinealocytes were not observed. In the pineal gland of pregnant guinea-pigs the following changes can be observed in the second half of gestation. The light cells show many nuclear indentations and an increase of active zones, mitochondria, smooth ER, agranular vesicles, VCR, VCB, and cylinders respectively. The dark cells increase in number. After birth these changes reverse to normal within one week. Constant darkness leads to an activation of the light cells accompanied by an increase of the VCR and to an increase in number of the dark cells. Under constant illumination the light cells show a decrease of their organelles and a strong increase of the VCR. After 70 days the VCR also show a change in shape. Following reserpine treatment the VCR decrease in number and show signs of degeneration. It is discussed that the VCR function as pre- or postsynaptic structures and that they are involved either in transmitting impulses from nerve fibres to pinealocytes or from one pinealocyte to the other.

Untersuchung unter Leitung von Univ.-Doz. Dr. L. Vollrath.