Lysophospholipid-mediated alterations in the calcium transport systems of skeletal and cardiac muscle sarcoplasmic reticulum

Summary The effects of various lysophospholipids on the calcium transport activity of sarcoplasmic reticulum (SR) from rabbit skeletal and canine cardiac muscles were examined. The lipids decreased calcium transport activity in both membrane types; the effectiveness being in the order lysoPC > lsyoPS, lysoPG > lysoPE. The maximum inhibition induced by lysoPC, lysoPG and lysoPS was greater than 85% of the normal Ca²⁺-transport rate. In cardiac SR lysoPE had a maximal inhibition of about 50%. Half maximal inhibition of calcium transport by lysoPC was achieved at 110 nmoles lysoPC/mg SR. At this concentration of lysoPC, the (Ca²⁺ + Mg²⁺)-ATPase and Ca²⁺-uptake activities were inhibited to the same extent (about 60%) in skeletal sarcoplasmic reticulum, while in cardiac sarcoplasmic reticulum, there was less than 20% inhibition of the Ca²⁺ + Mg²⁺-ATPase activity. Studies with EGTA-induced passive calcium efflux showed that up to 200 nmoles lysoPC/mg SR did not alter calcium permeability significantly in cardiac sarcoplasmic reticulum. In skeletal muscle membranes the lysophospholipid mediated decrease in calcium uptake correlated well with the increase in passive calcium efflux due to lysophosphatidylcholine. The difference in the lysophospholipid-induced effects on the sarcoplasmic reticulum from the two muscle types probably reflects variations in protein and other membrane components related to the respective calcium transport systems.     

Towards the biological control of fungal and bacterial diseases of tomato using antagonistic Streptomyces spp.

This investigation was designed to explore the potential of microbial antagonism in the control of some tomato diseases including bacterial, Fusarium and Verticillium wilts; early blight; bacterial canker. Three Streptomyces spp. were used: S. pulcher, S. canescens and S. citreofluorescens.The in vitro studies showed that an 80% concentration of the culture filtrate of either S. pulcher or S. canescens significantly inhibited spore germination, mycelial growth and spotulation of Fusarium oxysporum f.sp. lycopersici, Verticillium albo-atrum and Alternaria solani. The same concentration of filtrate of either S. pulcher or S. citreofluorescens was detrimental to the bacterial populations of Clavibacter michiganensis subsp. michiganensis and Pseudomonas solanacearum.The in vivo studies involved different treatments: soaking tomato seeds in filtrate of the antagonist prior to sowing, inoculation of the soil with the antagonist 7 days before sowing, and coating of tomato seeds with spores of the antagonist before sowing. The seed-coating treatment was the most effective in controlling all the pathogens at 42 and 63 days after sowing. Soil inoculation with the antagonist 7 days prior to sowing was less effective in controlling the tomato pathogens as compared to seed-coating. The seed-soaking treatment was the least effective in controlling the diseases concerned.The results also revealed that seed-coating with antagonistic Streptomyces spp. significantly improved tomato growth.     

Circular dichroism and photocycle kinetics of partially detergent solubilized and partially retinal regenerated bacteriorhodopsin

The circular dichroism (CD) spectra and the kinetics of the M₄₁₂ formation have been determined and compared for bacteriorhodopsin (bR) partially delipidated by the addition of Triton X-100 and partially reconstituted by the addition of retinal to apoprotein at pH 6.8 and 22°C. As the degree of delipidation increases or the fraction of reconstitution decreases, the following observations are made: (a) the shape of the visible CD band changes from biphasic, as found in bR, to a single monomer type band; (b) the CD spectra and the deprotonation rate constants change in a similar way; (c) the relative amplitudes of the components of the deprotonation kinetics do not change upon reconstitution, but change greatly upon delipidation. These results lead to the conclusion that the CD band shape as well as the deprotonation rate constants are sensitive to one type of perturbation, which is linked to the retinal structure within the protein environment, whereas the relative amplitudes of the components of the deprotonation kinetics are sensitive to another type, which may be linked to acid-base equilibria of the amino acid side groups within the active site.     

Inhibitory effect of hena (Lawsonia inermis leaves) and carrot root on aflatoxin production byAspergillus parasiticus

Experiments were undertaken to evaluate the effect of some natural products (hena, and carrot root) on growth and aflatoxins production byAspergillus parasiticus FRR 2752. Powdered hena (0.5 and 5%) inhibited mycelial growth and delayed 1 sporulation ofA parasiticus during 7 days. The inhibition of growth was increased with increasing the added amount. Aflatoxins production byA parasiticus was reduced with 40–100% in the presence of hena (Lawsonia inermis leaves). Carrot root extract stimulated the fungal growth and aflatoxin production, whereas carrot root fibers slightly enriched fungal growth, inhibited aflatoxins production (B₁, G₁, and G₂), but there was no inhibition of aflatoxin B₂ production byA parasiticus.     

Production of dextransucrase by Leuconostoc mesenteroides immobilized in calcium-alginate beads: I. Batch and fed-batch fermentations

In batch fermentation Leuconostoc mesenteroides immobilized in calcium alginate beads produced a total dextransucrase activity equal to about 93% of that by free, suspended bacterial cells under comparable conditions in a bubble column reactor. Continuous sucrose feeding (5 g/L h) to the immobilized-cell culture in the airlift bioreactor increased production of enzymatic activity by about 107% compared with ordinary batch operation of this reactor. About 14% of the enzymatic activity produced by the immobilized cells appears as soluble activity in the cell-free broth compared with about 40% in case of free cells. In an airlift bioreactor, both the soluble and the intact (sorbed and entrapped) enzymatic activity produced by the immobilized bacterial cells was about 34% greater under automatic pH control, compared to that produced in a bubble column reactor with only manual pH control. During formation of dextran by intact enzyme within cells and beads, declines are observed in apparent enzymatic activity.     

Sterigmatocystin — incidence, fate and production byA versicolor in ras cheese

Sterigmatocystin (STG) is a toxic metabolite produced by severalAspergillus species. Because of its toxic and carcinogenic properties the occurrence of STG in food is considered to represent a potential hazard to man. The present study was designed to investigate following points:

Elektronenmikroskopische und experimentelle Untersuchungen über die Kragendrüse von Polyxenus lagurus (L.) (Diplopoda,Penicillata)

Zusammenfassung 1. Die unpaare Glandula perioesophagealis von Polyxenus lagurus ist eine endokrine Drüse. Sie liegt zwischen Pharynxdach und Gehirn. Im Bereich des Hinterkopfs umgibt sie den Vorderdarm manschettenförmig.2. Die Drüse ist am Nervus glandulae perioesophagealis, der sich in ihr aufzweigt, befestigt. Viele Axone dieses Nervs führen Neurosekret.3. Die Drüsenzellen sind typische Podocyten. Zwischen ihren Pedicellen erstrecken sich viele weitlumige Interzellularräume. In den Pedicellen findet man zahlreiche Vesikulationen. Benachbarte Pedicellen sind durch Diaphragmata verbunden. DarÜber hinaus sind die Drüsenzellen durch viele Lysosomen und unregelmäßig gewundene, elektronendichte tubuläre Strukturen gekennzeichnet. Das endoplasmatische Retikulum ist spärlich entwickelt.4. Tiere, bei denen experimentell die Häutung ausgelöst wurde, zeichnen sich durch aktivierte Drüsenzellen aus. Die Anzahl der Mitochondrien, Golgi-Komplexe, Lysosomen und freien Ribosomen steigt jetzt an. Das endoplasmatische Retikulum tritt stark in Erscheinung. Es ist tubulär, häufig angeschwollen und mit flockigem Material gefüllt. Seine Membranen sind überwiegend mit Ribosomen besetzt, stellenweise aber auch agranulär. Jetzt treten auch zusammengesetzte Körper auf.

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Electron microscopic and experimental studies on the collar gland of Polyxenus lagurus (L.) (diplopoda, penicillata)

Summary 1. The unpaired glandula perioesophagealis of Polyxenus lagurus is an endocrine gland. It is located in the head between the roof of the pharynx and the brain. In the region of the back of the head it surrounds the foregut like a cuff.2. The gland is attached to an unpaired nervus glandulae perioesophagealis which branches in it. Many axons of this nerve contain neurosecretory granules.3. The gland cells are typical podocytes. Between their pedicles there are many wide intercellular spaces. A large number of cytoplasmic vesicles are found in the pedicles. Neighbouring pedicles are connected by diaphragmata. Moreover, the cells are characterized by many lysosome-like structures and tubular irregularly-bent electron-dense structures. The endoplasmic reticulum is sparsely developed.4. In animals in experimentally-induced molting, the gland cells are activated: the numbers of mitochondria, Golgi complexes, lysosome-like structures and free ribosomes are increased. The endoplasmic reticulum is conspicuous; it is tubular, often swollen, and filled with floccular material. It is predominantly granular but smooth in places. Complex cytoplasmic bodies are detectable.

     

Molecular Analysis of Drought Tolerance in Guava Based on In Vitro PEG Evaluation

Forty landraces of guava were subjected to drought tolerance evaluation based on in vitro polyethylene glycol (PEG) treatment. Nodal stem segments with lateral buds were used as explant. Five concentrations (i.e. 0, 4, 6, 8 and 10 %) of PEG were tested, among which the optimum concentration for screening was determined as 8 %. Analysis of variance showed highly significant variation among the tested landraces, concentrations of PEG and the interaction between them in the percentage of response (%R), number of shoot per explant (NSE) and drought susceptibility index. The average percentage of reduction due to PEG treatment was 48.30 and 52.57 % for the %R and NSE, respectively. Heritability and genetic advance were increased due to drought stress for %R, while they were decreased for NSE, indicating that %R was more related to drought stress than NSE. The molecular analysis of the highest and lowest responsive landraces was performed using sequence related amplified polymorphism (SRAP) and inter-simple sequence repeats (ISSR). Both markers were effective in discriminating the tested landraces and completely separated them into two clusters related to %R under PEG. ISSR showed a higher percentage of polymorphism, polymorphic information content and diversity index compared with SRAP. However, SRAP was more effective than ISSR in showing a higher primer resolving power and a number of unique specific bands for drought tolerance and susceptibility. Drought in vitro evaluation method established here is effective, inexpensive and manageable in genotype screening for drought tolerance in guava and could be used in other woody plant species.     

Novel inhibitors of the methicillin-resistant Staphylococcus aureus (MRSA)-pyruvate kinase

Novel bisindolyl-cycloalkane indoles resulted from the reaction of aliphatic dialdehydes and indole. As bisindolyl-natural alkaloid compounds have recently been reported as inhibitors of the methicillin-resistant Staphylococcus aureus (MRSA)-pyruvate kinase (PK), we tested our novel compounds as MRSA PK inhibitors and now report first inhibiting activities. We discuss structure–activity relationships of structurally varied compounds. Activity influencing substituents have been characterized and relations to antibacterial activities of the most active compounds have been proved.