The taxonomic significance of the trunk limbs of the chydoridae (Cladocera)

Summary The differences in the structure of the trunk limbs allow to outline three sections of Chydoridae (see table I and fig. 1), coinciding with the sections distinguished according to the structure of the head pores.

---

Chydoridae (Cladocera)

Chydoridae (. ), , .

     

Differences in N-acetyllactosamine synthesis between β-1,4-galactosyltransferases I and V

Unlike classical -1,4-galactosyltransferase (-1,4-GalT I), -1,4-GalT V (formerly IV*) has little activity towards 1 mM N-acetylglucosamine [Sato et al. (1998) Proc Natl Acad Sci USA 95: 472-477]. The human -1,4-GalTs I and V were expressed individually in Sf-9 cells by transfection of the full coding sequences, and their N-acetyllactosamine synthetase activities were determined towards different N-acetylglucosamine concentrations. Kinetic studies using the cell homogenates as an enzyme source revealed that -1,4-GalTs I and V possess Km values of 0.6 mM and 33 mM towards N-acetylglucosamine, and of 48 µM and 41 µM towards UDPGal, respectively. No significant inhibition of N-acetyllactosamine synthesis with -lactalbumin was observed for -1,4-GalT V but the significant inhibition with -lactalbumin was observed for -1,4-GalT I.     

Schwermetallaffine Strukturen des peripheren Nerven

Zusammenfassung Konvertiertes Kupfer wurde an axonalen und Schwannschen Zellmembranen, vor allem im nodalen und paranodalen Bereich beobachtet. Kupfer wird offenbar in inner und outer leaflet der unit membrane ein- und an diese angelagert. Denn bei wenig Präzipitat oder geringer Elektronendichte des Niederschlags stellten sich die Membranen als dreischichtiger Komplex dar, der in den Dimensionen der unit membrane entsprach. Bei großen Präzipitatmengen oder bei hoher Elektronendichte des Niederschlags blieb nur die helle Mittelschicht von ca. 30 Å frei. Diese Metallaffinität wird im Zusammenhang mit den cytochemischen AChE-Nachweisverfahren diskutiert, weil bei diesen Methoden Schwermetallionen im Inkubationsmedium verwendet werden, und die Kupferbindungsstellen zum Teil mit den Lokalisationen der AChE identisch sind. Möglicherweise gibt beim cytochemischen AChE-Nachweis schon die Darstellung von unit membranes in unkontrastierten Präparaten Aufschluß auf erfolgte unspezifische Schwermetallbindung. Als weitere Kontrolle wird Inkubation in der verwendeten Schwermetallösung mit nachfolgender Konversion vorgeschlagen.

---

Heavy metal affinity of peripheral nerve structuresI. Possibility of interference with cytochemical localisation of AChE

Summary The ultrastructural localisations of copper in ventral and dorsal roots of the rat were studied by varying fixation and converting medium. Precipitated copper was deposited in axonal membranes (axolemma, membranes of axonal organelles) and Schwann cell membranes (inner and outer plasmalemma, major and minor dense lines in the region of the splitting myelin sheath, terminal loops and Schwann cell interdigitations). Copper obviously was bound within and attached to inner and outer leaflet of these membranes. If there was little or less electron-dense precipitate membranes appeared three-layered, dimensions corresponding to those of the unit membrane. If there was electron-dense or plenty of precipitate only the middle electron-lucent layer of approximately 30 Å was revealed. The predominant deposition on nodal and paranodal membranes may be explained either by facilitated access to this region or by specific metal ion binding sites at those specialised membranes. Metal ion binding is discussed in relation to cytochemical demonstration of AChE activity, because these methods use incubation media containing heavy metal cations and copper binding sites partly correspond with the localisation of AChE activity. The appearance of unit membranes in unstained sections probably could be a hint at unspecific heavy metal ion binding ocouring in demonstration of specific AChE. Therefore control-incubation in the heavy-metal solution with subsequent conversion is suggested.

     

Effect of Intercalators on the Properties of Liquid-Crystalline Dispersions of Nucleic Acid–Chitosan Complex

Molecules of deoxyribonucleic acid and synthetic polydeoxyribonucleotides (NA) in the particles of liquid-crystalline dispersions resulting from interaction with chitosan are accessible to interaction with intercalators. The intercalation is accompanied by alteration in the direction of spatial twist of cholesterics of NA–chitosan complexes. This effect is absent in the case of classical cholesterics produced from NA molecules via phase exclusion, i.e., the cholesteric structure of NA–chitosan complex is very labile as distinct from classical cholesteric NA.     

Effect of orchard and postharvest application of daminozide on ethylene synthesis by apple fruit

The effects of daminozide (butanedioic acid-2,2-dimethylhydrazide) on ethylene synthesis by apple fruits were investigated. The objective was to determine the effects of postharvest applications as compared to the standard application of diaminozide in the orchard. Immersion in a solution containing 4.25 g L^–1 active ingredient for 5 min delayed the rise in ethylene production in individual Cox apples at 15°C by about 2 days, whereas orchard application of 0.85 g L^–1 caused delays of about 3 days. Both modes of application depressed the maximal rate of ethylene production attained by ripe apples by about 30%. Daminozide did not affect the stimulation of respiration by ethylene treatment of Gloster apples, but it delayed the increase in ethylene synthesis. Daminozide applied immediately after harvest delayed the rise in ethylene synthesis in Golden Delicious held at 15°C, but it was less effective when applied 48 h after harvest or when apples were held at 5°C. Exposure to 1–2 l L^–1 ethylene for 48 h was less effective in promoting the rise in ethylene in daminozidetreated Cox and Gloster apples than in untreated fruit. High (100–1000 l L^–1) concentrations of ethylene more or less overcame the daminozide effect. Apples absorbed about 40% of surface-applied [¹⁴C]daminozide in 48 h, but more than 90% of the radioactivity in the fruit was recovered from the peel and outer 1 cm of the cortex. Daminozide was partly converted to carbon dioxide and other metabolites.     

Ultrastructure and behaviour of the spindle pole body of the aphid-pathogenic fungusErynia neoaphidis

Summary A detailed account of the ultrastructure and behaviour of the spindle pole body (SPB) of the entomophthoraceous fungusErynia neoaphidis is presented for the first time.The SPB consists of extranuclear (ENC) and intranuclear (INC) components. The ENC is a saucepan-shaped structure which lies in a pocket of the nuclear envelope. It is composed of a forked, fibrillar handle and a shallow, cylindrical pan. The pan has a wall of two layers, both of which are thickened with a regular periodicity so that they appear to be beaded. It is postulated that the pan is formed from rough endoplasmic reticulum and that it synthesizes the amorphous, electron-dense material coating the ENC.The INC is a saucer-shaped, electron-dense plaque in which the ends of the spindle microtubules terminate. During metaphase, a clear zone separates the INC from the nuclear envelope and persists until telophase. The roles of the amorphous, electron-dense material and the clear zone as well as the method of SPB replication are discussed.     

Hydrodynamic characteristics of two-phase inverse fluidized bed

Hydrodynamic characteristics of a new mode of liquid-solid fluidization, termed as inverse fluidization in which low density floating particles are fluidized with downward flow of liquid, are experimentally investigated. The experiments are carried out with low density particles (<534 kg/m³) which allow high liquid throughputs in the system. During the operation, three regimes, namely, packed, semi-fluidization and fully fluidization are encountered. Empirical correlations are proposed to predict the pressure drop in each regime. A computational procedure is developed to simulate the variation of pressure drop with liquid velocity.List of Symbols Ar modified Archimedes number, d _p ³ (– _s)g/² - d _p particle diameter, mm - f friction factor (eq. 2) - g acceleration due to gravity, m/s² - H total bed height, m - H _c height of the column, m - H_f height of fluidized bed, m - H₀ height of initial bed, m - H_p height of the packed bed, m - (p) pressure drop across the bed, N/m² - (p) _f pressure drop across fluidized bed section, N/m² - (p) _p pressure drop across the packed bed section, N/m² - (p) _sf total pressure drop in semifluidization regime, N/m² - Re Reynolds number, d _pU ₁/ - Re_m modified Reynolds number, d _pU ₁/(1– _p) - U ₁ superficial liquid velocity, m/s - U_mf minimum fluidization velocity, m/s - U_osf onset fluidization velocity, m/s Greek Letters _f voidage of fluidized bed - _p voidage of packed bed - liquid viscosity, kg/ms - liquid density, kg/m³ - _s particle density, kg/m³     

Identification and characterization of the functional alpha origin of DNA replication of the R6K plasmid and its relatedness to the R6K beta and gamma origins

Summary The functional R6K origin is composed of two DNA elements, one of 580 bp carrying the origin sequences and the other of 277 bp containing the seven 22 bp direct repeats previosly identified as also required for and origin activity. These two genetic elements are separated by approximately 3,000 bp of R6K sequences which are dispensable for origin activity. The function of the origin depends on the presence in cis of the 580 bp and the 277 bp fragments and requires that they be oriented as in the intact R6K. Activation of the origin depends on the R6K replication initiation protein .Within the 580 bp of the origin, there is a sequence of 98 bp which appears as an inverted repeat of 96 bp in the replicon. Deletion of the 96 bp or 98 bp results in inactivation of the and the origins respectively. These long repeats are palindromic and it is suggested that these may serve as the recognition signals for initiation of DNA replication in the and the origins of R6K. DNA homology analysis performed on , and origin sequences, also reveals 10–23 bp sequences in the and the origins that are related to the family of 22 bp direct repeats in the origin which were shown previously to be binding sites for the protein.     

Characterization of glycoconjugates of guinea pig seminal vesicle by lectin histochemistry

In the present study, the expression of glycoconjugates in the guinea pig seminal vesicle was localized and partially characterized by lectin histochemistry using a battery of 30 different lectins specific for different carbohydrate residues. The results indicate that the glandular epithelium of the guinea pig seminal vesicle exhibits complex glycoconjugates rich in Man, -GlcNAc, -Gal, /-GalNAc, Fuc and complex NeuAc(2,6)Gal/GalNAc residues, as shown by its positive reactions to most lectins used. The Golgi region of the luminal secretory epithelial cells expresses a complex glycoconjugate pattern, as shown by its strong reactions to Man-(PSA, GNA), -GlcNAc-(S-WGA, PWA, DSA, UDA), -Gal- (RCA-I and -II), /-GalNAc-(SBA, Jac, VVA, BPA) and complex NeuAc-(SNA) specific lectins, indicating that the secretory epithelial cells are active in glycosylation and secretion process. It was also shown in the present study that the basal and luminal epithelial cells are different in their glycoconjugates. The basal epithelial cells are rich in NeuAc(2,3)Gal residues as they are stained specifically by MAA. The fibroblasts in the epithelial-smooth muscle interface and the smooth muscle cells close to the glandular epithelium are shown to express more glycoconjugates as they are stained intensely by GS-I-B4, GS-II and SBA. However, their role in the epithelial-stromal interaction in the seminal vesicle remains to be elucidated. In summary, the present study reports for the first time on the lectin binding patterns of the guinea pig seminal vesicle, and the results show that the seminal vesicle epithelium elaborates and secretes glycoconjugates in a complex pattern. Some of the lectins might be useful as histochemical markers for the secretory activity and specific structural components in the guinea pig seminal vesicle. © 1998 Chapman & Hall     

State and time delay estimation of continuous microorganisms cultivation

A continuous fermentation model taking into account the culture memory is used for a state estimation design. The influence of the culture memory on the process dynamics is accounted for by a time delay parameter. The proposed procedure of on-line state estimation in the case when the delay has a constant value is based on the extended Kalman observer. The case when the delay parameter is evaluated on-line is also considered. An adaptive state and parameter algorithm on the base of the extended Kalman filter is proposed. The theoretical results are applied to continuous culture for growth of a strain of Saccharomyces cerevisiae.List of Symbols X, S mg/l Biomass concentration and substrate concentration respectively - S ⁰ mg/l Feed substrate concentration - Z mg/l Past substrate concentration - µ h^–1 Specific growth rate taking into account culture memory - h^–1 Specific consumption rate - h Time delay parameter denoting culture memory - D h^–1 Dilution rate - State variables vector - W _ij Gain coefficient for on-line state and parameter estimation - F Substrate feed rate vector - () Gain coefficient matrix - R Square symmetric Riccati matrix - K Matrix of coefficients - K(t) Delay kernel taking account of culture memory - Denote an estimation value The partial support by Bulgarian National Science Research Foundation under Grant SRTS 428/94 Modeling and Control of Fermentation Processes Taking the Memory Effect into Account is gratefully acknowledged.     

The cytology of phytophthora infestans

Summary Phytophthora infestans has three kinds of somatic nuclei: an oval shaped nucleus (approx. 3.1×2.7 ) which stains diffusely except for a crescent shaped Feulgen positive cap which stains intensely; a granular nucleus whose contents are organized into a fairly constant number of stained bodies, and, a deeply staining condensed nucleus. The capped nucleus is thought to be metabolic or resting and the granular nucleus is thought to be dividing as it is most commonly found in hyphal tips. Attenuated forms of all three kinds of nuclei are found.Nuclear division is mitotic and intranuclear. Eight—ten chromosomes are seen at metaphase.Sporangia have a mean of 6.3 nuclei which is constant for age and strain of culture. Sporangia become multinucleate as a result of nuclear migration and not by division in the developing sporangium. Zoospores are usually uninucleate.The nuclear cap is persistent throughout nuclear division when it also divides. It is associated with flagella production and nuclear migration and has some of the properties of a blepharoplast.     

A comparative assessment of TLC overlay technique and microwell adsorption assay in the examination of influenza A and Sendai virus specificities towards oligosaccharides and sialic acid linkages of gangliosides

Influenza A and Sendai viruses bind toneolacto-series gangliosides isolated from human granulocytes. Differences in receptor specificity of influenza viruses A/PR/8/34 (H1N1), A/X-31 (H3N2), and parainfluenza Sendai virus (HNF1, Z-strain) were determined by two direct solid phase binding assays: the overlay technique, which combines high-resolution in the separation of gangliosides on thin-layer chromatograms with direct binding; and the microwell adsorption assay as a convenient binding assay which is performed in microtitre wells to estimate the avidity of binding to an isolated ganglioside. Both methods were applied for comparative binding studies. Viruses were found to exhibit specificity for oligosaccharides and sialic acids as well as for chain length of the neutral carbohydrate backbone, whereas differing fatty acids (C_24:1 and C_16:0) in the ceramide portion had no impact on virus adsorption. Terminal sialyloligosaccharides Neu5Ac2-3Gal1-4Glc-R of G_M3, and Neu5Ac2-3Gal1-4GlcNAc-R as well as Neu5Ac2-6Gal1-4GlcNAc-R ofneolacto-series gangliosides with nLcOse₄Cer and nLcOse₆Cer backbone, exhibited significant specific receptor activity towards the different viruses. To compare the data revealed from both test systems, values of virus binding were ascertained by a non-parametric statistical approach based on rank correlation. The rank correlation coefficientr _s was calculated according to Spearman from each virus binding towards G_M3, IV³Neu5Ac-nLcOse₄Cer, IV⁶Neu5Ac-nLcOse₄Cer and VI³Neu5Ac-nLcOse₆SCer. The rank correlation coefficients 0.74, 0.95 and 0.92, which were determined for A/PR/8/34 (H1N1), A/X-31 (H3N2) and Sendai virus (HNF1, Z-strain), respectively, indicated that both assays generate highly correlated experimental data. Based on these results, analyses of virus binding on thin-layer chromatograms as well as in microwells were found equivalent tools for ganglioside receptor studies. Abbreviations: BSA, bovine serum albumin; GSL(s), glycosphingolipids; HPTLC, high performance thin-layer chromatography; PBS, phosphate buffered saline; Neu5Ac,N-acetylneuraminic acid [35];r _s = rank correlation coefficient according to Spearman. The designation of the glycosphingolipids follows the IUPAC-IUB recommendations [36]. LacCer or lactosylceramide, Gal1-4Glc1-1Cer; lacto-N-neotetraosylceramide or nLcOse₄Cer, Gal1-4GlcNAc1-3Gal1-4Glc1-1Cer; lacto-N-norhexaosylceramide or nLcOse₆Cer, Gal1-4GlcNAc1-3Gal1-4GlcNAc1-3Gal1-4Glc1-1Cer; G_M3 (according to Svennerholm [37]) or II³Neu5AcLacCer.     

Isoform-Specific Membrane Translocation of Protein Kinase C After Ischemic Preconditioning

Mild cerebral anoxic/ischemic/stress insults promote tolerance and thereby protect the brain from subsequent lethal anoxic/ischemic insults. We examined whether specific activation of PKC , , , or isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKC, , , and . PKC showed a significant translocation to the membrane fraction from 30 min to 4 h and PKC at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKC showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKC was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKC and PKC may be associated with IPC-induced tolerance in the rat hippocampus.     

In vitro organogenesis of elephant apple (Feronia limonia)

Elephant apple (Feronia limonia L.). was micropropagated on MS medium containing 4.4 M benzyladenine and 4.6 M kinetin using cotyledon explants taken from in vitro-grown seedlings. Adventitious buds formed on the cotyledon developed into shoots that were rooted in half-strength MS medium containing 0.57 M indoleacetic acid and 0.49 M indolebutyric acid. Plants were successfully established in soil.Abbreviations BA 6-benzyladenine - IAA 3-indoleacetic acid - IBA 3-indolebutyric acid - MS Murashige & Skoog     

Cytokine production in whole blood cell cultures of patients undergoing therapy with biological response modifiers or 5-fluorouracil

We have measured the levels of interferon (IFN), tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-1, and IL-2 in the whole blood cell culture supernatants of 43 tumor patients undergoing a treatment with biological response modifiers or a conventional therapy with 5-fluorouracil and leucovorin. In the blood cell cultures of the 16 patients who received 5-fluorouracil and leucovorin IFN levels decreased (P0.01) and TNF levels rose (P0.05) during each therapy cycle. However, in the blood samples a declining number of total leukocytes and lymphocytes was measured (P0.05). Progressive disease could be correlated to a tendency towards lower IFN levels in the pretherapeutic cultures of these patients. The second group analyzed consisted of 8 patients receiving a low-dose IL-1 therapy. In this group we found either an unchanged or an augmented IFN production of the blood cells during treatment. In the group of 13 patients receiving low-dose recombinant IL-2 (4.5×10⁶IU m^–2 day^–1) significantly increasing IFN levels were seen in the blood cell cultures during the therapy (P0.05), although total leukocyte counts decreased. In this group, 4 had stable disease for at least 2 months and 9 patients had tumor progression under therapy. In the cultures of the latter a tendency towards lower IFN values was found. Finally, the cytokine production in the blood cell cultures of 6 patients receiving a combination therapy of IFN and high-dose IL-2 was studied. During this therapy a dramatically reduced production not only of IFN but also of all other measured cytokines was found. In this group all patients had tumor progression under therapy. It is concluded that the measurements of cytokine production in a reproducible whole blood culture system may be useful for monitoring immunological therapies and may help us to find out which doses of biological response modifiers have enhancing or suppressive effects on the functions of the immune cells.     

Über das Wachstum der Pankreaszellen von Säugetieren als Monolayer Cultures

Zusammenfassung Fetale menschliche Pankreaszellen bilden sowohl spontan auf zuerst gewachsenem Zellrasen (self-aggregation) als auch in Rollröhrchen (48 rph) (rotation-mediated-aggregation) histotypische Aggregate, die A- und B-Zellen enthalten. In der Nährlösung dieser 6–17 Tage lang gewachsenen Gewebestückchen konnte, Insulin (=IRI=immunoreactive-insulin) nachgewiesen werden.

---

Monolayer cultures of pancreatic tissueII. Formation of histotypic aggregates from cell suspensions of fetal human pancreas

Summary Fetal Pancreas cells of man, whether in self-aggregation or rotation-mediated-aggregation, form spontaneously histotypical aggregates containing A- and B-cells. It is possible by means of an immunological method to determine insulin (=IRI=immuno-reactive-insulin) in the nutrient medium of these 6 to 17 days old tissue aggregates.

     

Natural abundance of 15N in tropical plants with emphasis on tree legumes

Natural abundance of ¹⁵N ( ¹⁵N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The ¹⁵N values of non-N₂-fixing trees in Brazil were +4.5±1.9, which is lower than those of soil nitrogen (+8.0±2.2). In contrast, mimosa and kudzu had very low ¹⁵N values (–1.4+0.5). The ¹⁵N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N₂-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The ¹⁵N values of non-N₂-fixing trees in Thailand were +4.9±2.0. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low ¹⁵N values, close to the value of atmospheric N₂ (0), pointing to a major contribution of N₂ fixation in these plants. Cassia spp. and Tamarindus indica had high ¹⁵N values, which confirms that these species are non-nodulating legumes. The ¹⁵N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N₂-fixing trees, indicating a small contribution of N₂ fixation in these legumes.     

Stereospecificity and electrogenicity of amino acid transport in Riccia fluitans

In the aquatic liverwort Riccia fluitans, membrane depolarization (_m), change in membrane conductance (g_m), and current-voltage (I-V) characteristics in the presence of different amino acids as well as the uptake of ¹⁴C-labeled amino acids were measured. L-isomers of the tested amino acids generate larger electrical effects (_m, g_m) than D-isomers, and the I-V characteristics show that the positive electrical inward-current of 20 mA m^-2 generated by 0.5 mM D-serine is only about 50% of the current generated by adding 0.5 mM L-serine. Whereas - and -amino acids rapidly depolarize the membrane to the same extend, with -aminobutyric acid (-AB) and dipeptides no significant electrical effects have been measured. The uptake kinetics of ¹⁴C-labeled amino acids display three components: (I) A saturable high-affinity component with K_s-values of 48 M D-alanine, 12 M -aminoisobutyric acid (AIB), 9 M L-alanine, 8 M L-proline, and 6 M L-serine, respectively; (2) an apparently linear low-affinity component, and (3) an also linear but unspecific component at concentrations >20 times the given K_s-value. Uptake of ¹⁴C-labeled AIB can be inhibited competitively by all tested neutral amino acids, the L-isomers being more effective than the D-isomers, as well as by ammonium or methylamine. Vice versa, AIB competitively inhibits uptake of L-serine and L-alanine. It is concluded that an uncharged stereospecific carrier for the investigated amino acids exists in the plasmalemma of Riccia fluitans. Accumulation ratios of about 50 suggest secondary active transport driven by a transmembrane electro-chemical gradient (mainly _m) which is generated by the electrogenic proton pump. It is suggested that this carrier binds to the amino group forming either a charged binary complex with positively charged amines (Felle 1980), or an uncharged complex with -AB or dipeptides, whereas electrogenic transport of - and -amino acids is mediated by a ternary carrier complex, probably charged by a proton.Symbols and Abbreviations _m membrane potential (mV) - E_co equilibrium potential (mV) of the transport system - g_m membrane (slope) conductance (Sm^-2) - g_m change in g_m - I-V curve current-voltage curve - AIB -aminoisobutytric acid - -AB -aminobutyric acid     

Myosatellite cells associated with different muscle fibre types in the Atlantic hagfish (Myxine glutinosa,L.)

Summary The incidence of myosatellite cells associated with white and red muscle fibres of the parietal muscle and red fibres of the craniovelar muscle was estimated by quantitative electron microscopy in the Atlantic hagfish (Myxine glutinosa, L.). Myosatellite cell nuclei constitute 3, 11 and 23 % of the total number of nuclei inside the basal lamina of the three types of muscle fibres, respectively. However, the total number of nuclei is highest in white fibres, most of the nuclei belonging to striated muscle cells. Myosatellite cell profiles in transverse sections constitute 23, 41 and 61 % of the number of muscle fibre profiles of the three types, respectively. The intervals between adjacent myosatellite cells are 135 m in white fibres, 55 m in red parietal fibres, and only 25 m in craniovelar fibres. Since craniovelar fibres are also comparatively thin, myosatellite cells constitute a significant fraction of the volume inside the basal lamina in these fibres. The myosatellite cells are 30–50 m long and up to 5 m thick. Some myosatellite cells possess few organelles, whereas others appear to contain many free ribosomes, granular endoplasmic reticulum, prominent Golgi apparatus and lysosome-like bodies.This investigation was supported by the Norwegian Research Council for Science and the Humanities (NAVF grant No. C20.30–37). The authors are indebted to Jorunn Line Vaaland and Berit Branil for technical assistance, and to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supplying the hagfish     

Stimulation of membrane-associated polysaccharide synthetases by a membrane potential in developing cotton fibers

Conditions which induce a transmembrane electrical potential, positive with respect to the inside of membrane vesicles, result in a substantial (4–12-fold) stimulation of the activity of membrane-associated -glucan synthetases in a membrane preparation derived from the developing cotton (Gossypium hirsutum L.) fiber. Induction of electrical potentials which are negative with respect to the inside of the membrane vesicle results in little or no stimulation of -glucan synthesis. Those products whose synthesis is stimulated are mainly -1,3-glucan, but there is also a considerable increase in -1,4-glucan. No -1,4-glucan (starch) was detected in the reaction products. A transmembrane pH gradient was found to have no effect on -glucan synthesis. The results indicate that a transmembrane electrical potential can influence, either directly or indirectly, the activity of membrane-associated polysaccharide synthetases.Abbreviations UDP-glucose uridine-5-diphosphoglucose - PEG polyethylene glycol - BTP bistrispropane (1,3-bis[tris(hydroxymethyl)methylamino]propane) - MES 2(N-morpholino)ethanesulfonic acid - VAL valinomycin