Boromycin Abrogates Bleomycin-induced G2 Checkpoint

The DNA-damaging agent bleomycin arrests the cell cycle at the G2 phase of Jurkat cells defective in the G1 checkpoint, and microtubule-acting colchicine arrests it at the M phase. Boromycin itself, an actinomycete metabolite, showed no effect on the cell cycle status of Jurkat cells at least up to 340 nM. However, the compound (3.4-340 nM) was found to abrogate bleomycin-induced G2 arrest even at 3.4 nM, resulting in a drastic decrease in cells at the G2 phase and increase in cells at the subG1 phase. On the other hand, boromycin did not show any effect on the colchicine-induced M phase arrest in Jurkat cells, nor on the cell cycle status of the bleomycin-treated or -untreated HUVEC, normal cells conserving both G1 and G2 checkpoints. Furthermore, boromycin potentiated anti-tumor activity of bleomycin in scid mice inoculated with Jurkat cells. These data suggest that boromycin disrupts the cell cycle at the G2 checkpoint of cancer cells selectively, leading to sensitization of cancer cells to anti-cancer reagents.

Oxidant and SDS-stable alkaline protease from Bacillus clausii I-52: production and some properties

AIMS

An investigation was carried out on an oxidative and SDS-stable alkaline protease secreted by Bacillus clausii of industrial significance.

METHODS AND RESULTS

Maximum enzyme activity was produced when the bacterium was grown in the medium containing (g l-1): soyabean meal, 15; wheat flour, 10; liquid maltose, 25; K2HPO4, 4; Na2HPO4, 1; MgSO4.7H2O, 0.1; Na2CO3, 6. The enzyme has an optimum pH of around 11 and optimum temperature of 60 degrees C. The alkaline protease showed extreme stability towards SDS and oxidizing agents, which retained its activity above 75 and 110% on treatment for 72 h with 5% SDS and 10% H2O2, respectively. Inhibition profile exhibited by phenylmethylsulphonyl fluoride suggested that the protease from B. clausii belongs to the family of serine proteases.

CONCLUSIONS

Bacillus clausii produced high levels of an extracellular protease having high stability towards SDS and H2O2.

SIGNIFICANCE AND IMPACT OF THE STUDY

The alkaline protease from B. clausii I-52 is significant for an industrial perspective because of its ability to function in broad pH and temperature ranges in addition to its tolerance and stability in presence of an anionic surfactant, like SDS and oxidants like peroxides and perborates. The enzymatic properties of the protease also suggest its suitable application as additive in detergent formulations.

Surface pH and bond strength of a self-etching primer/adhesive system to intracoronal dentin after application of hydrogen peroxide bleach with sodium perborate

This study compared the dentin bond strength of a self-etching primer/adhesive system with dentin surface pH with or without bleaching and observed the morphological changes in bleached dentin treated with a self-etching primer. Dentin disks were prepared from the coronal-labial region of 32 human anterior teeth. The pulpal surfaces of the dentin disks were polished with 600-grit SiC paper under running water. The dentin surfaces on all specimens were bleached with a mixture of 30% hydrogen peroxide and sodium perborate in 100% humidity at 37 degrees C for one week. The bleaching agent was then rinsed off with water for 5, 15 or 30 seconds. All specimens were stored in water at 37 degrees C. Half of the five-second rinsing specimens were stored in water for an additional week. Dentin surface pH with or without bleaching was examined using a pH-imaging microscope (SCHEM-100). A self-etching primer/adhesive system (Clearfil SE Bond) was applied to bleached or unbleached dentin according to the manufacturer's instructions. After 24-hour water storage, the bonded specimens were prepared for microtensile testing. Microtensile bond strength (microTBS) to dentin was measured using a universal-testing machine (EZ test, Shimadzu, Japan) at a crosshead speed of 1.0 mm/minute. Data were analyzed by one-way ANOVA and Scheffe's test (alpha=0.05). The pH values of the dentin surfaces of the 5 and 15 second rinsing groups were significantly higher than the control group (p<0.05), while the 30-second rinsing and one-week water storage groups had similar surface pH values to the control group (p<0.05). The microTBS of 5, 15 and 30 second rinsing specimens after bleaching were significantly lower than the control specimens (p<0.05). However, after one-week of water storage, the microTBS returned to the control group. The application of a bleaching agent increased the pH value of the dentin surface and decreased the bond strength of the self-etching primer/adhesive system. One-week water storage after bleaching recovered the surface pH and the microTBS to dentin.

The effect of disinfectant solutions on the hardness of acrylic resin denture teeth

This investigation studied the effects of disinfectant solutions on the hardness of acrylic resin denture teeth. The occlusal surfaces of 64 resin denture teeth were ground flat with abrasives up to 400-grit silicon carbide paper. Measurements were made after polishing and after the specimens were stored in water at 37 degrees C for 48 h. The specimens were then divided into four groups and immersed in chemical disinfectants (4% chlorhexidine; 1% sodium hypochlorite and sodium perborate) for 10 min. The disinfection methods were performed twice to simulate clinical conditions and hardness measurements were made. Specimens tested as controls were immersed in water during the same disinfection time. Eight specimens were produced for each group. After desinfection procedures, testing of hardness was also performed after the samples were stored at 37 degrees C for 7, 30, 60, 90 and 120 days. Data were analysed using two-way analysis of variance (anova) and Tukey's test at 95% confidence level. According to the results, no significant differences were found between materials and immersion solutions (P > 0.05). However, a continuous decrease in hardness was noticed after ageing (P < 0.05). It was conclude that the surfaces of both acrylic resin denture teeth softened upon immersion in water regardless the disinfecting solution.

Effects of wet cleaning with disodium octaborate tetrahydrate on dust mites (Acari: Pyroglyphidae) in carpet

In a controlled laboratory study, disodium octaborate tetrahydrate (DOT) applied to carpets with a carpet-cleaning machine at a rate of 509 ml DOT/8.15 liter H2O/100 m2 (two cups DOT/2 gal H2O/100 feet2) reduced survival and population growth of live Dermatophagoides farinae and Dermatophagoides pteronyssinus by > or = 98% compared with water-cleaned and uncleaned carpets at 8 wk postcleaning. Cleaning with DOT was more effective against D. pteronyssinus than D. farinae.

Determination of diterpenoid triepoxides in Tripterygium wilfordii by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatographic (MEKC) method has been established for the identification and determination of diterpenoid triepoxides in the Chinese herb Tripterygium wilfordii Hook F. and its preparations. Studies of the influence of boric acid and borax buffer concentration and pH, and of sodium dodecylsulphate (SDS) concentration have been carried out, and the optimum separation for the triepoxides was achieved using 20 mM boric acid and 10 mM borax with 20 mM SDS as the running buffer. MEKC was found to exhibit good accuracy, precision and repeatability. The sensitivity of the assay was sufficient to monitor the three active components in T. wilfordii and its preparations.

Effect of internal bleaching agents on dentinal permeability of non-vital teeth: quantitative assessment

The aim of this in vitro study was to assess quantitatively dentin permeability of pulpless teeth after intracoronal bleaching therapy with three different agents. Twenty-four maxillary central incisors were randomly assigned to four groups according to the bleaching agent used: I--non-bleached control; II--37% carbamide peroxide; III--sodium perborate/20% hydrogen peroxide paste; IV--27% carbamide peroxide. After standard access and root-canal preparation the access opening, biomechanical preparation and root-canal filling, a cervical glass ionomer plug was prepared and intracoronal bleaching procedures were carried out in a standardized fashion. The access cavities were opened and the teeth were externally sealed and immersed in a 10% copper sulfate aqueous solution for 30 min, in vacuum for the first 5 min. Then, samples were removed, dried with absorbing paper and immersed in a 1% rubianic acid alcohol solution, for the same above-mentioned period in solution and in vacuum. Copper ion penetration was indicated by the rubianic acid staining. Mean values and SD for the experimental groups were: I--7.88% (+/-1.33), II--16.94% (+/-5.72); III--11.45% (+/-3.90) and IV--8.98% (+/-4.19). Data were submitted to one-way anova. The results showed that the 37% carbamide peroxide provided the highest increase in dentin permeability, followed by sodium perborate with 20% hydrogen peroxide. The 27% carbamide peroxide provided the lowest results and showed statistical similarity to the control group. On basis of these findings, it may be concluded that, among the tested intracoronal bleaching agents, 37% carbamide peroxide presented an optimized overall performance in increasing dentinal permeability.

Effect of gamma-glutamyl transpeptidase inhibitors on the transport of glutamate into neuronal and glial primary cultures

Inhibitors of gamma-glutamyl transpeptidase (mixture of serine and borate--13 mM, kainic acid--5 mM and 6-diazo-5-oxo-L-norleucine--2 mM) significantly suppressed glutamate uptake into cultured neurones and glial cells. The simultaneous application of any of these inhibitors with ouabain resulted in a further decline in glutamate uptake. It can be speculated that gamma-glutamyl transpeptidase significantly contributes to glutamate transport into nerve cells in the early period of brain development until the Na(+)-K(+)-gradient is fully constituted.

Effect of extracellular calcium, pH and borate on growth oscillations in Lilium formosanum pollen tubes

Calcium ions (Ca(2+)), protons (H(+)), and borate (B(OH)(4)(-)) are essential ions in the control of tip growth of pollen tubes. All three ions may interact with pectins, a major component of the expanding pollen tube cell wall. Ca(2+ )is thought to bind acidic residues, and cross-link adjacent pectin chains, thereby strengthening the cell wall. Protons are loosening agents; in pollen tube walls they may act through the enzyme pectin methylesterase (PME), and either reduce demethylation or stimulate hydrolysis of pectin. Finally, borate cross-links monomers of rhamnogalacturonan II (RG-II), and thus stiffens the cell wall. It is demonstrated here that changing the extracellular concentrations of Ca(2+), H(+) and borate affect not only the average growth rate of lily pollen tubes, but also influence the period of growth rate oscillations. The most dramatic effects are observed with increasing concentrations of Ca(2+) and borate, both of which markedly reduce the rate of growth of oscillating pollen tubes. Protons are less active, except at pH 7.0 where growth is inhibited. It is noteworthy, especially with borate, that the faster growing tubes exhibit the shorter periods of oscillation. The results are consistent with the idea that binding of Ca(2+) and borate to the cell wall may act at a similar level to alter the mechanical properties of the apical cell wall, with optimal concentrations being high enough to impart sufficient rigidity to the wall so as to prevent bursting in the face of cell turgor, but low enough to allow the wall to stretch quickly during periods of accelerating growth.

Low frequency of infertility among workers in a borate processing facility

In order to rule out the possibility of omitting some individuals in the study at field visits described in previous articles, either because of the reluctance of the subject or because of his appointment elsewhere, fertility and infertility states of borate workers of the Borax and Acid Plants in Bandirma, Balikesir are given. Balikesir is one of the four provinces with large borate deposits of Turkey, and Bandirma is 1 of its 19 districts. This county is relatively far away from borate deposits, and drinking water piped out through the springs has a boron amount between 0.10 and 0.82 ppm B. That the participants are occupationally exposed to the mineral in essence is therefore conceivable. At the first phase of the investigation, 191 workers were interviewed, as detailed previously. Among these, there were six infertiles of the primary type with a rate 3.1%. Boron-unrelated infertile couples among sibs were found to be 2.6-3.6%, and 3.2% for three generation marriages-none being higher than those revealed in different sets of controls. In the second stage of work, computerized files of all workers of the facility and all employees of the general management sharing the same location were checked without an interview. Twenty-four subjects (3.4%) out of 712 workers were childless versus 2.7% among 108 employees, and 2.2% among 91 workers of a distantly located sulfuric acid plant of the same complex. The differences were not significant, and these recent findings support the conclusion already reached almost unambiguously that boron exposure at the present levels does not interfere with human reproduction.

Effects of different buffers on the thermostability and autolysis of a cold-adapted protease MCP-01

A cold-adapted protease MCP-01 was obtained from deep-sea psychrotrophic bacterium Pseudoaltermonas sp. SM9913. The effects of four different buffers, all at 50 mmol/l concentration, on its thermostability and autolysis were studied. The autolysis process of MCP-01 was studied by capillary electrophoresis. The thermostability of MCP-01 increased successively in the following order: carbonate < Tris < phosphate < borate. The optimum temperature for casein hydrolysis also increased in the same order. This suggested that the conformation of MCP-01 was flexible and its autolytic susceptibility was affected by some factors in the buffers such as charge and ionic species. The results also showed that different buffers, in addition to affecting the autolysis speed, gave different patterns of autolysis products. In carbonate buffer, Tris buffer, phosphate buffer and borate buffer, the autolysis patterns of MCP-01 were different. These results suggested that protease MCP-01 probably have different conformations in different buffers, thus exposing different autolysis sites on the enzyme surface. In addition, the loss of activity correlated with the speed of autolysis in the four different buffers, showing that autolysis may be a reason for the low thermostability of the enzyme.

Efficacy of sodium borate in the prevention of fatty liver in dairy cows

The effects of sodium borate (100 mg/kg body weight, p.o., 15 days) from a month before expected calving until a month after calving were evaluated in dairy cows susceptible to fatty liver. Cows received either sodium borate (n = 13) or no treatment (n = 10). All cows had mild fatty livers and increased plasma triglycerides and very low density lipoprotein (VLDL) concentrations at the beginning of the experiment. The control group of cows developed significant fatty liver after calving, and 2 of them had severe fatty liver associated with clinical and biochemical abnormalities. There were no clinicopathological signs related to sodium borate administration. Serum triglycerides and VLDL concentrations before calving decreased significantly at calving and after calving in controls, and they were within the normal range only after calving. There were significant alterations during the experiment in some hematological and chemical variables between groups, within period, but they were within the normal range. Unlike treated cows, serum triglycerides and VLDL concentrations correlated with liver fat content after calving in untreated cows. Our results document that sodium borate decreases the degree of fatty liver in dairy cows during early lactation.

Action of palytoxin on apical H+/K+-ATPase in rat colon

Palytoxin stimulated a cation-dependent short-circuit current (Isc) in rat distal and proximal colon in a concentration-dependent fashion when applied to the mucosal surface of the tissue. The distal colon exhibited a higher sensitivity to the toxin. The palytoxin-induced Isc was blocked by vanadate but was resistant to ouabain or scilliroside, suggesting the conversion of a vanadate-sensitive H+/K+-ATPase into an electrogenic cation transporter. Cation substitution experiments with basolaterally depolarized tissues suggested an apparent permeability of the palytoxin-induced conductance of Na+>K+>Li+. Immunohistochemical control experiments confirmed the absence of the Na+/K+-ATPase in the apical membrane. Consequently, the pore-forming action of palytoxin is not restricted to Na+/K+-ATPase but is also observed with the colonic H+/K+-ATPase.

Affinity labeling of the guanine nucleotide binding site of transducin by pyridoxal 5'-phosphate

Transducin (T), a guanine nucleotide binding regulatory protein composed of alpha-, beta-, and gamma-subunits, serves as an intermediary between rhodopsin and cGMP phosphodiesterase during signaling in the visual process. Pyridoxal 5'-phosphate (PLP), a reagent that has been used to modify enzymes that bind phosphorylated substrates, was probed here as an affinity label for T. PLP inhibited the guanine nucleotide binding activity of T in a concentration dependent manner, and was covalently incorporated into the protein in the presence of [3H]NaBH4. Approximately 1 mol of 3H was bound per mol of T. GTP and GTP analogs appreciably hindered the incorporation of 3H to T, suggesting that PLP specifically modified the protein active site. Interestingly, PLP modified both the alpha- and beta-subunits of T. Moreover, PLP in the presence of GDP behaved as a GTP analog, since this mixture was capable of dissociating T from T:photoactivated rhodopsin complexes.

The effect of boromycin on the Ca2+ homeostasis

A boron-containing antibiotic, boromycin (BM), was found to influence the Ca2+ homeostasis in both excitable and non-excitable cells. In non-excitable cells (human erythrocytes and leucocytes) it inhibited the resting passive 45Ca2+ transport in 10(-6)-10(-5) mol/L concentrations. In human erythrocytes, the passive 15Ca2+ transport induced by the presence of 1 mmol/L NaVO3 was inhibited by boromycin (90% inhibition) as well. The inhibitory effect of BM on the NaVO3-induced passive 45Ca2+ transport was diminished in the presence of inhibitory concentrations of nifedipine (10 micromol/L -60% inhibition) or of those of K+o (75 mmol/L -20% inhibition). On the other hand, in rat brain synaptosomes, and rat cardiomyocytes, BM stimulated the passive 45Ca2+ transport in 'resting' cells at similar concentrations. In rat cardiomyocytes the stimulation was transient. The stimulatory effect on the passive 45Ca2+ transport in rat brain synaptosomes was accompanied with the increase of cytoplasmic Ca2+ concentration measured by means of the entrapped fluorescent Ca2+ chelator fura-2. The stimulatory effect of BM was diminished when synaptosomes were pre-treated with veratridine (10 micromol/L) which itself stimulated the passive 45Ca2+ transport. At saturating concentrations of veratridine, no stimulatory effect of BM was observed. These results could be explained by the indirect interaction of BM with both Ca2+ and Na+ transport systems via transmembrane ionic gradients of monovalent cations and could be useful in determining whether the cells belong to excitable, or non-excitable cells.

Requirement of borate cross-linking of cell wall rhamnogalacturonan II for Arabidopsis growth

Turgor-driven plant cell growth depends on wall structure. Two allelic l-fucose-deficient Arabidopsis thaliana mutants (mur1-1 and 1-2) are dwarfed and their rosette leaves do not grow normally. mur1 leaf cell walls contain normal amounts of the cell wall pectic polysaccharide rhamnogalacturonan II (RG-II), but only half exists as a borate cross-linked dimer. The altered structure of mur1 RG-II reduces the rate of formation and stability of this cross-link. Exogenous aqueous borate rescues the defect. The reduced cross-linking of RG-II in dwarf mur1 plants indicates that plant growth depends on wall pectic polysaccharide organization.

Requirement of borate cross-linking of cell wall rhamnogalacturonan II for Arabidopsis growth

Turgor-driven plant cell growth depends on wall structure. Two allelic l-fucose-deficient Arabidopsis thaliana mutants (mur1-1 and 1-2) are dwarfed and their rosette leaves do not grow normally. mur1 leaf cell walls contain normal amounts of the cell wall pectic polysaccharide rhamnogalacturonan II (RG-II), but only half exists as a borate cross-linked dimer. The altered structure of mur1 RG-II reduces the rate of formation and stability of this cross-link. Exogenous aqueous borate rescues the defect. The reduced cross-linking of RG-II in dwarf mur1 plants indicates that plant growth depends on wall pectic polysaccharide organization.

An alternative pathway for metabolism of leukotriene D(4): effects on contractions to cysteinyl-leukotrienes in the guinea-pig trachea

Contractions of guinea-pig tracheal preparations to cysteinyl-leukotrienes (LTC(4), LTD(4) and LTE(4)) were characterized in organ baths, and cysteinyl-leukotriene metabolism was studied using radiolabelled agonists and RP-HPLC separation. In the presence of S-hexyl GSH (100 microM) the metabolism of [(3)H]-LTC(4) into [(3)H]-LTD(4) was inhibited and the LTC(4)-induced contractions were resistant to CysLT(1) receptor antagonism but inhibited by the dual CysLT(1)/CysLT(2) receptor antagonist BAY u9773 (0.3 - 3 microM) with a pA(2)-value of 6.8+/-0.2. In the presence of L-cysteine (5 mM), the metabolism of [(3)H]-LTD(4) into [(3)H]-LTE(4) was inhibited and the LTD(4)-induced contractions were inhibited by the CysLT(1) receptor antagonist ICI 198,615 (1 - 10 nM) with a pA(2)-value of 9.3+/-0.2. However, at higher concentrations of ICI 198,615 (30 - 300 nM) a residual contraction to LTD(4) was unmasked, and this response was inhibited by BAY u9773 (1 - 3 microM). In the presence of the combination of S-hexyl GSH with L-cysteine, the LTD(4)-induced contractions displayed the characteristics of the LTC(4) contractile responses, i.e. resistant to CysLT(1) receptor antagonism, increased maximal contractions and slower time-course. This qualitative change of the LTD(4)-induced contraction was also observed in the presence of S-decyl GSH (100 microM), GSH (10 mM) and GSSG (10 mM). S-hexyl GSH, S-decyl GSH, GSH and GSSG all stimulated a formation of [(3)H]-LTC(4) from [(3)H]-LTD(4). In conclusion, GSH and GSH-related compounds changed the pharmacology of the LTD(4)-induced contractions by stimulating the conversion of LTD(4) into LTC(4). Moreover, the results indicate that, in addition to the metabolism of LTC(4) into LTD(4) and LTE(4), also the formation of LTC(4) from LTD(4) may regulate cysteinyl-leukotriene function.

Inflammatory response, growth, and thyroid hormone concentrations are affected by long-term boron supplementation in gilts

An experiment was conducted to determine the long-term effects of dietary boron (B) on growth performance, immune function, and plasma and serum characteristics in gilts. Fifty weanling gilts were allotted to 10 pens based on weaning weight and litter origin. Pens were randomly assigned to receive one of two dietary treatments. Treatments consisted of a basal diet low in B (control) and the basal diet supplemented with 5 mg B/kg diet as sodium borate. Gilts remained on their respective experimental diets and with their penmates throughout the nursery, growing, and finishing phases. The B concentration of the basal diet was 0.98, 2.1, and 2.2 mg/kg diet during the nursery, growing, and finishing phases, respectively. At the end of each production phase, animals were weighed and feed consumption was determined to assess growth performance variables. In addition, blood samples were obtained from three randomly selected gilts per pen at the completion of each phase. Boron had no affect (P > 0.58) on growth performance during the nursery phase, but gilts receiving supplemental B had increased (P < 0.05) ADG at the end of the finishing phase and over the entire growing-finishing period. Serum concentrations of triiodothyronine (T3) tended (P < 0.07) to be reduced by dietary B at the end of the nursery phase, but serum thyroxine (T4) was not affected (P = 0.46) by B. At the completion of the growing phase, supplemental B decreased (P < 0.05) the concentrations of T3 and T4 in the serum. In addition, serum concentrations of total cholesterol and the activity of alkaline phosphatase were increased (P < 0.05) by dietary B at the end of the growing phase. Serum concentrations of urea N tended (P < 0.09) to be increased by B at the end of the growing phase. Beginning at d 95 of the experimental period, measures of immune function were assessed in randomly selected gilts. Boron decreased (P < 0.05) the inflammatory response to an intradermal injection of phytohemagglutinin. Boron did not affect (P > 0.30) the blastogenic response of isolated lymphocytes to mitogen stimulation or the humoral immune response against a sheep red blood cell suspension. Results indicate that B may affect serum thyroid hormone concentrations, the inflammatory response, and growth in pigs.

Brief exposure to low-pH stress causes irreversible damage to the growing root in Arabidopsis thaliana: pectin-Ca interaction may play an important role in proton rhizotoxicity

The viability of Arabidopsis thaliana (strain Landsberg) roots exposed to a low pH (4.5 or 4.7) solution that contained 100 microM CaCl(2) was examined by staining with fluorescein diacetate-propidium iodide. The elongation zone of growing roots lost viability within 1-2 h following exposure to low pH, but non-growing roots showed no damage under the same treatment. Low-pH damage in growing roots was irreversible after 1 h incubation at pH 4.5 as judged by regrowth in growing medium at pH 5.6. Growing lateral roots also lost viability in the same treatment, whereas non-growing lateral roots remained viable during and after the treatment. The low-pH damage was ameliorated by the simultaneous application of calcium, indicating the involvement of a calcium-requiring process in overcoming proton toxicity. At pH 5.0, growing roots required 25 microM of calcium to maintain elongation, and at pH 4.8 and pH 4.5 more than 250 microM and 750 microM, respectively. The low-pH damage was ameliorated by divalent cations in the order of Ba2+, approximately Sr2+>/=Ca2+>Mg2+. The monovalent cation K+ showed no ameliorative effect, but borate showed a strong ameliorative effect with Ca2+. These results indicate that the primary target of proton toxicity may be linked to a disturbance of the stability in the pectic polysaccharide network, where calcium plays a key role in plant roots.

Brief exposure to low-pH stress causes irreversible damage to the growing root in Arabidopsis thaliana: pectin-Ca interaction may play an important role in proton rhizotoxicity

The viability of Arabidopsis thaliana (strain Landsberg) roots exposed to a low pH (4.5 or 4.7) solution that contained 100 microM CaCl(2) was examined by staining with fluorescein diacetate-propidium iodide. The elongation zone of growing roots lost viability within 1-2 h following exposure to low pH, but non-growing roots showed no damage under the same treatment. Low-pH damage in growing roots was irreversible after 1 h incubation at pH 4.5 as judged by regrowth in growing medium at pH 5.6. Growing lateral roots also lost viability in the same treatment, whereas non-growing lateral roots remained viable during and after the treatment. The low-pH damage was ameliorated by the simultaneous application of calcium, indicating the involvement of a calcium-requiring process in overcoming proton toxicity. At pH 5.0, growing roots required 25 microM of calcium to maintain elongation, and at pH 4.8 and pH 4.5 more than 250 microM and 750 microM, respectively. The low-pH damage was ameliorated by divalent cations in the order of Ba2+, approximately Sr2+>/=Ca2+>Mg2+. The monovalent cation K+ showed no ameliorative effect, but borate showed a strong ameliorative effect with Ca2+. These results indicate that the primary target of proton toxicity may be linked to a disturbance of the stability in the pectic polysaccharide network, where calcium plays a key role in plant roots.

Fixation of transsynaptically transported WGA-HRP and fluorescent dyes used in combination

The transsynaptic transport of WGA-HRP is a powerful tool for the identification of last order interneurones in the spinal cord, but differentiation of primarily labelled motoneurones from transsynaptically labelled interneurones can be difficult. We therefore combined the transsynaptic labelling of interneurones with WGA-HRP and the labelling of motoneurones with fluorescent dyes (fluorogold, red beads, fast blue, DAPI) by injecting a mixture of the tracers into the nervi mediani of rats. The influence of different fixatives on the simultaneous preservation of WGA-HRP and fluorescence is evaluated. It is shown that, of several perfusion protocols, only perfusion with paraformaldehyde in addition to 1.4% lysine and 0.23% periodate allowed simultaneous visualisation of transsynaptic WGA-HRP and fluorescent dyes.

Stabilization and preservation of Lactobacillus acidophilus in saccharide matrices

Lyophilization and vacuum- or spray-drying are some of the most useful techniques for preserving foods, agricultural products, and pharmaceuticals. Biological materials, however, can be irreversibly damaged during these treatments. Therefore, it is essential to design protective agents to preserve protein activity and cell viability. In this paper we examine the use of alpha, alpha-trehalose-borate systems as protectants for Lactobacillus acidophilus during freeze- and vacuum-drying. Trehalose was found to be an effective protectant for freeze-dried and vacuum-dried samples, and it is equivalent to a protective formulation which is in current industrial use. It is known from our previous work on enzymes that the presence of borate can dramatically enhance the protective ability of trehalose. In this work, the addition of trehalose-borate to bacterial concentrate greatly improves the recovery of viable cells after storage. This improvement was seen in freeze-dried samples stored at 37 degrees C as well as for vacuum-dried samples held at room temperature. A tailored buffering strategy was tested to counteract the high pH resulting from the addition of borate to the mixture. Use of citric or lactic acids in combination with ammonium hydroxide gave a protectant solution with high pH (resulting in effective crosslinking between trehalose and borate) but a dry product with reduced pH upon rehydration (conducive to cell survival). These results raise exciting possibilities for protection of more labile prokaryotic species as well as simple eukaryotes.

DNA and buffers: the hidden danger of complex formation

The free solution electrophoretic mobility of DNA differs significantly in different buffers, suggesting that DNA-buffer interactions are present in certain buffer systems. Here, capillary and gel electrophoresis data are combined to show that the Tris ions in Tris-acetate-EDTA (TAE) buffers are associated with the DNA helix to approximately the same extent as sodium ions. The borate ions in Tris-borate-EDTA (TBE) buffers interact with DNA to form highly charged DNA-borate complexes, which are stable both in free solution and in polyacrylamide gels. DNA-borate complexes are not observed in agarose gels, because of the competition of the agarose gel fibers for the borate residues. The resulting agarose-borate complexes increase the negative charge of the agarose gel fibers, leading to an increased electroendosmotic flow of the solvent in agarose-TBE gels. The combined results indicate that the buffers in which DNA is studied cannot automatically be assumed to be innocuous.