Clomipramine actions on firing rate in septal nuclei of the rat are not related to anaesthesia (urethane).

An increased firing rate in lateral septal nuclei (LSN) appears in urethane-anesthetized rats after several acute drug and non-drug human antidepressant treatments. A still more pronounced increase in firing rate is produced in LSN after clomipramine (CMI) long-term treatment. In spite of urethane is a widely used anesthetic for single unit extracellular recordings, it modifies evoked potentials wave-form. Therefore, present study discards urethane interaction with CMI in LSN single unit extracellular recordings. CMI was acutely injected (1.25 mg/kg: IP) either to urethane-anesthetized, or non-anesthetized encephale-isolé rats. The CMI treated groups showed higher rates of firing in LSN regardless of the use of general anesthesia during recordings. Another group of urethane-anesthetized rats received intracerebroventricular (ICV) microinjections of CMI (100 micrograms/10 microliters/1 min). An amount of 42.8% of LSN-recorded neurons responded with a long-lasting increased firing rate. Results discard urethane and CMI interactions. Additionally, systemic actions of CMI on firing rate of LSN are reproduced by ICV/route microinjections.     

Are dead Triatoma infestans a competent vector of Trypanosoma cruzi?

After Triatoma infestans death, Trypanosoma cruzi survived several days, maintaining the ability to infect a vertebrate host. Dead bugs from an endemic area collected during an official spraying campaign showed mobile rectal trypanosomes up to 14 days after vector death. Two days after vector death 2,760 trypomastigotes were found alive in its rectal material. However, the number of mobile trypomastigotes decreased significantly from the 5th day after death. Laboratory proofs with third and fifth nymphal stage showed similar results. Living trypanosomes were found in their rectal material at 10 days in third stage and even at 30 days in fifth nymphal stage. The mean number of trypomastigotes had no changes up to 10 days in third nymphal stage and increased significantly from 1 to 10 days in the fifth stage. Conjunctival instillation as well as intraperitoneal inoculation to mice, of metacyclic forms from dead T. infestans produced infection in the vertebrate host. Present results show that human contact with dead vector is highly probable in summer and living and infective T. cruzi are available for transmission in the vector.     

Induction in the developing compound eye of Drosophila: multiple mechanisms restrict R7 induction to a single retinal precursor cell.

The development of the Drosophila R7 photoreceptor cell is determined by a specific inductive interaction between the R8 photoreceptor cell and a single neighboring precursor cell. This process is mediated by bride of sevenless (boss), a cell-surface bound ligand, and the sevenless (sev) tyrosine kinase receptor. The boss ligand is expressed specifically on the surface of the R8 cell, whereas the sev receptor is expressed on 5 cells contacting the developing R8 cell and other cells not in contact with R8. By altering the spatial and temporal expression of boss, we demonstrate that sev-expressing cells that do not contact R8 can assume an R7 cell fate. By contrast, the sev-expressing precursor cells to the R1-R6 photoreceptor cells that do contact R8 are nonresponsive to the inductive cue. Using the rough and Nspl mutations, we demonstrate that an early commitment to an R1-R6 cell fate blocks the pathway of sev activation in these cells.     

Use of inosine-containing oligonucleotide primers for enzymatic amplification of different alleles of the gene coding for heat-stable toxin type I of enterotoxigenic Escherichia coli.

A method which employs the polymerase chain reaction (PCR) to identify Escherichia coli strains containing the estA gene was developed. This gene codes for heat-stable enterotoxin type I. The use of an inosine-containing pair of amplification primers allowed the amplification of a specific 175-bp DNA fragment from several different estA alleles. The amplified fragments were identified and distinguished by allele-specific oligonucleotide hybridization and characterized by restriction endonuclease analysis. An extension of the classical two-primer PCR proved to be a very simple and rapid method to identify and characterize the estA alleles. Besides the inosine-containing pair of primers, which recognized all described alleles, additional oligonucleotides were used as primers. The sequence of each of these primers was allele specific, and each was amplification compatible with one of the inosine-containing primers. Thus, in one PCR the 175-bp fragment typical for all estA alleles and an allele-specific fragment of different size were produced. These fragments could be separated by agarose gel electrophoresis and were recognized by ethidium bromide staining. Twenty-seven E. coli strains were tested with this amplification system. The presence or lack of the genetic information for production of heat-stable enterotoxin type I was perfectly consistent with the ability of these strains to produce this enterotoxin, as determined by enzyme-linked immunosorbent assay.     

Enzymatic characterization of Vibrionaceae strains isolated from environment and cold-blooded animals.

Enzymatic profiles were determined by the API ZYM system for 15 strains of non 01 Vibrio cholerae, 4 strains of V. metschnikovii, 9 strains of V. anguillarum, 6 strains of Plesiomonas shigelloides and 115 strains motile Aeromonas sp. All of the tested strains produced alkaline phosphatase, leucine aminopeptidase and did not possess alpha-fucosidase and alpha-mannosidase. Some differences in enzymatic activities among the tested Vibrionaceae strains were noted. The strains of non 01 V. cholerae, V. metschnikovii, V. anguillarum and P. shigelloides did not produce trypsin, whereas all of the tested Vibrio sp. strains appeared to be positive for this enzyme. Only the strains of P. shigelloides produced BI-Phospho-hydrolase. The lack of acid phosphatase activity was observed among the strains of V. anguillarum.     

Spatial structure of the basic chain of the neurotoxin I molecule from the venom of cobra Naja naja oxiana and its crystal packing

The structure of the alpha-carbon chain was solved by molecular replacement method at 2.7 A resolution. Neurotoxin I (NTX-I) is one of the main protein components purified from the venom of the central asian cobra Naja naja oxiana. NTX-I is known to bind specifically to acetylcholine receptors thus preventing the transmission of the neuroconductivity signal from synapses to muscles. NTX-I crystals were grown either by vapour diffusion or dialysis methods using specially prepared microdialysis cell. The intensities of reflections from native NTX-I crystals were measured in the range of 38.0-2.1 A-1 by omega-scan method with a Syntex P21 diffractometer operated in automatic regime. To determine the position and mode of packing of NTX-I molecule in unit cell program packages MERLOT and BLANC were applied running on a NORD-500 computer.     

Partitioning of beta-galactosidase fusion proteins in PEG/potassium phosphate aqueous two-phase systems.

Four different beta-galactosidase fusion proteins have been partitioned in poly(ethylene glycol) (PEG) 4000/potassium phosphate aqueous two-phase systems. The partition coefficients (K) of staphylococcal protein A-beta-galactosidase (SpA beta gal) (K = 3.5) and staphylococcal protein A-streptococcal protein G-beta-galactosidase (AG beta gal) (K = 2.8) were compared with the partition coefficients of their constituent molecules, beta-galactosidase, SpA, and protein AG. It was found that by fusing beta-galactosidase to the smaller proteins SpA and protein AG, their partition coefficients were increased four to five times. Experimental data were fitted into, and found to agree with, the Albertsson partition model of interacting molecules. The compatibility with PEG and potassium phosphate of beta-galactosidase, SpA, and two different versions of the SpA beta gal protein, displayed as precipitation curves, showed a relationship to the protein partition coefficients in PEG/potassium phosphate systems. High solubility in one phase component was accompanied by preferential partitioning to the phase rich in the same component in the PEG/potassium phosphate system. Also, a changed linker region in SpA beta gal resulted in a more soluble protein. This, together with the improved K values of the target proteins by fusion, shows that it is possible to use beta-galactosidase as an affinity handle.     

Effect of different physico-chemical conditions on malolactic fermentation of fourLactobacillus plantarum wild strains isolated from wines of northwestern Spain

Summary Four strains ofLactobacillus plantarum, were tested for malolactic fermentation under conditions of variations in temperature, pH and SO2, L-malate and ethanol levels. When the pH value was below 3.5, malolactic fermentation was lower and was more sensitive to temperature changes. Malolactic fermentation decreased when the SO2 and ethanol levels were increased. The effects of L-malate levels were not significant.     

Changes in levels of mRNA coding for catecholamine synthesizing enzymes and neuropeptide Y in the adrenal medulla of the newborn rat.

We have measured levels of mRNA coding for the catecholamine synthesizing enzymes tyrosine hydroxylase (TH), dopamine beta-hydroxylase (D beta H), phenylethanolamine N-methyltransferase (PNMT) and for neuropeptide Y (NPY) in rat adrenal medulla by using in situ hybridization histochemistry. Ages of one day before birth (E21), 12 h, 24 h, 2 days and 4 days after birth and in adults were studied. TH, D beta H and NPY mRNA levels increased markedly postnatally. Twelve hours after birth the levels of mRNA for TH, D beta H and NPY were, respectively, 512 +/- 18%, 370 +/- 24% and 253 +/- 21% of E21 levels. At 24 h of age NPY mRNA level was 437 +/- 73% of fetal value. In contrast, the levels of mRNA coding for PNMT increased more slowly and reached 196 +/- 9% of E21 level on postnatal day four and was further increased in adult rats.     

Interannual variability of phytoplankton productivity and related parameters in Lake Constance: no response to decreased phosphorus loading?

In meso-eutrophic Lake Constance (Germany-Austria-Switzerland),phytoplankton bioraass, pigments and water transparency, aswell as primary productivity, have been followed between 1980and 1989. During this period, municipal phosphorus loading declinedsignificantly. Since 1981, soluble reactive phosphorus (SRP)concentrations during deep lake mixing have decreased from 3.0to currently 1 6 mmol m^–3 at a rate of 7% year^–1.Nitrate concentrations, by contrast, continued to rise. Duringthe period of maximum phosphorus loading, flushing through theoutlet and sedimentation were about equally important sinksof phosphorus from the euphotic zone. Recently, however, sedimentationand subsequent burial of P in the bottom deposits contributedabout three-quarters to the overall P-losses from the systemMain reasons for this shift are unchanged settling fluxes ofphosphorus out of the euphotic zone and decreasing concentrationsof total phosphorus in the water. Only during spring, do concentrations of soluble reactive phosphoruswithin the euphotic zone decrease in proportion to the formationof particulate organic matter. Later during the season, euphoticSRP concentrations continue to be low but are no longer matchedby high plankton biomass because phosphorus is efficiently removedby settling of particles In spite of the observed dramatic decreasein phosphorus loading since 1980, chlorophyll concentrationsand water transparency, as well as annual phytoplankton productivity(300 g C m^–2), have not shown a consistent downward trend.However, the intensity of phosphorus regeneration within theeuphoric zone, which can be used as a measure of the degreeof nutrient limitation, is likely to have increased significantlyThe most probable explanation for the insensitivity of importanttrophic state indicators to reduced nutrient loading is that,in Lake Constance, biomass accumulation to a greater extentis controlled by losses, mainly grazing by zooplankton and sedimentation,than by primary resources. This is concluded from the observationthat phytoplankton biomass always falls far short of the nutrient-dependentcarrying capacity of the system.