Factors affecting the formation of polysaccharide depolymerase and glycoside hydrolyase enzymes by Butyrivibrio fibrisolvens NCDO 2249

Specific activities of hemicellulose-degrading polysaccharide depolymerase and glycoside hydrolase enzymes were measured in batch and continuous cultures of Butyrivibrio fibrisolvens NCDO 2249 grown on cellobiose or a hemicellulosic carbohydrate. Enzyme activities were influenced by the growth substrate and by the rate and stage of growth of the micro-organism. In cellobiose batch cultures specific activities were maximal as the growth rate declined and in the initial stages of the stationary phase. The growth substrate did not affect the range of glycoside hydrolases formed, although specific activities were substrate-dependent, with activity increases (up to 200-fold) occurring in enzymes essential for effective substrate utilization. Appreciable xylanase activity was present only in xylan-grown cultures. The substrate effects were also evident in chemostat cultures. The activity response of the nine enzymes monitored to growth rate changes differed in that while the activity of some enzymes, including xylanase, declined at high dilution rates the activities of others were not growth rate-dependent and were maintained over the range of dilution rates examined. Exocellular activities were detected only in spent media from cultures grown with a polymeric (hemicellulosic) carbohydrate.     

Degeneration and regeneration in the superior cervical sympathetic ganglion afterLatrodectus venom

Brain Cell Biology - The effects of the venom of the spider Latrodectus mactans hasselti on the superior cervical ganglion were studied in the guinea pig. Under anaesthesia the ganglion was bathed...     

Optimal dispatching of multipriority jobs to two heterogeneous workstations

The general problem scenario of this paper is the following: Jobs of various priorities, stationed in a common storage area, are waiting to be dispatched to two non-identical workstations. Any of the waiting jobs can be accessed from the storage at any given time. Each job can be processed on either of the workstations, but once a job has been assigned it may not be preempted. By job priority it is meant that a higher priority job has disptach preference over a lower priority job. The processing time of a job on a given workstation is assumed to be random, the distribution being dependent on the job type and the configuration of the workstation. Specifically, the first problem studied considers only two classes of jobs: (1) “hot” jobs, whose processing is to be expedited and thus have the higher dispatch priority, and (2) “routine” jobs which may be assigned to an available workstation only if the workstation has been rejected by all “hot” jobs. The processing times are assumed to be exponentially distributed with means depending on the job class and workstation. We assume that, on the average, one workstation is faster than the other with regard to processing any job. The dispatching objective for each job class is to minimize its expected flowtime. It is shown that threshold dispatching policies are optimal for this problem. That is, the faster processor should be utilized whenever possible, and for each class there exists an explicit threshold such that when the number of jobs of that class in the buffer exceeds this threshold then a job of that class is dispatched to the slower processor, otherwise these jobs wait for the faster processor to become available. For the higher priority jobs, this threshold is shown to be a function only of the various processing rates of the two workstations. For the lower priority jobs, the threshold also depends on the number of higher priority jobs in the buffer. The results is extended to a system with n priority classes. Again, it is shown that when the processing times are exponentially distributed with different rates and the dispatching objective for each class is to minimize its expected flowtime, the optimal dispatching policies are of threshold type. Explicit thresholds are easily derived.     

Both A1 and A2a Purine Receptors Regulate Striatal Acetylcholine Release

The receptors responsible for the adenosine-mediated control of acetylcholine release from immunoaffinity-purified rat striatal cholinergic nerve terminals have been characterized. The relative affinities of three analogues for the inhibitory receptor were (R)-phenylisopropyladenosine greater than cyclohexyladenosine greater than N-ethylcarboxamidoadenosine (NECA), with binding being dependent of the presence of Mg2+ and inhibited by 5'-guanylylimidodiphosphate [Gpp(NH)p] and adenosine receptor antagonists. Adenosine A1 receptor agonists inhibited forskolin-stimulated cholinergic adenylate cyclase activity, with an IC50 of 0.5 nM for (R)-phenylisopropyladenosine and 500 nM for (S)-phenylisopropyladenosine. A1 agonists inhibited acetylcholine release at concentrations approximately 10% of those required to inhibit the cholinergic adenylate cyclase. High concentrations (1 microM) of adenosine A1 agonists were less effective in inhibiting both adenylate cyclase and acetylcholine release, due to the presence of a lower affinity stimulatory A2 receptor. Blockade of the A1 receptor with 8-cyclopentyl-1,3-dipropylxanthine revealed a half-maximal stimulation by NECA of the adenylate cyclase at 10 nM, and of acetylcholine release at approximately 100 nM. NECA-stimulated adenylate cyclase activity copurified with choline acetyltransferase in the preparation of the cholinergic nerve terminals, suggesting that the striatal A2 receptor is localized to cholinergic neurones. The possible role of feedback inhibitory and stimulatory receptors on cholinergic nerve terminals is discussed.     

Main Immunogenic Region of Torpedo Electroplax and Human Muscle Acetylcholine Receptor: Localization and Microheterogeneity Revealed by the Use of Synthetic Peptides

Most anti-nicotinic acetylcholine receptor (AChR) antibodies in myasthenia gravis are directed against an immunodominant epitope or epitopes [main immunogenic region (MIR)] on the AChR alpha-subunit. Thirty-two synthetic peptides, corresponding to the complete Torpedo alpha-subunit sequence and to a segment of human muscle alpha-subunit, were used to map the epitopes for 11 monoclonal antibodies (mAbs) directed against the Torpedo and/or the human MIR and for a panel of anti-AChR mAbs directed against epitopes on the alpha-subunit other than the MIR. A main constituent loop of the MIR was localized within residues alpha 67-76. Residues 70 and 75, which are different in the Torpedo and human alpha-subunits, seem to be crucial in determining the binding profile for several mAbs whose binding to the peptides correlated very well with their binding pattern to native Torpedo and human AChRs. This strongly supports the identification of the peptide loop alpha 67-76 as the actual location of the MIR on the intact AChR molecule. Residues 75 and 76 were necessary for binding of some mAbs and irrelevant for others, in agreement with earlier suggestions that the MIR comprises overlapping epitopes. Structural predictions for the sequence segment alpha 67-76 indicate that this segment has a relatively high segmental mobility and a very strong turning potential centered around residues 68-71. The most stable structure predicted for this segment, in both the Torpedo and human alpha-subunits, is a hairpin loop, whose apex is a type I beta-turn and whose arms are beta-strands. This loop is highly hydrophilic, and its apex is negatively charged. All these structural properties have been proposed as characteristic of antibody binding sites. We also localized the epitopes for mAbs against non-MIR regions. Among these, the epitope for a monoclonal antibody (mAb 13) that noncompetitively inhibits channel function was localized within residues alpha 331-351.     

Evidence for Functional Activity of Up-Regulated Nicotine Binding Sites in Rat Striatal Synaptosomes

A number of studies have found that the chronic administration of nicotine causes an increase in the density of nicotinic binding sites in the brain, but it is not known whether these additional binding sites are functionally active receptors. In this study, the effects of 1-week administration of the potent nicotinic agonist, (+)-anatoxin-a (96 nmol/day via osmotic minipumps), was assessed on [3H]nicotine binding and [3H]dopamine uptake and release in rat striatal synaptosomes. Chronic (+)-anatoxin-a treatment resulted in a 32% increase in the Bmax of [3H]nicotine binding in anatoxin-treated animals compared to control. There was a 43% increase in the activity of 3 microM nicotine to release [3H]dopamine from synaptosomes of anatoxin-treated animals, but the release induced by 20 mM K+ depolarization was unaffected. There was no effect of chronic (+)-anatoxin-a treatment on the uptake of [3H]dopamine. A strong positive correlation (r = 0.64) was found between the density of [3H]nicotine binding sites and the nicotine-induced stimulation of [3H]dopamine release in individual animals. These results indicate that (+)-anatoxin-a, like nicotine, produces an up-regulation of nicotine binding sites following chronic administration, and that these additional sites are functional receptors capable of mediating the release of dopamine from striatal synaptosomes.     

Presymptomatic testing for Huntington's disease

Summary Presymptomatic testing for Huntington's disease (HD) is possible through the use of restriction fragment length polymorphisms (RFLPs) at the closely linked D4S10 locus. Recombination between the HD and D4S10 loci will occur in 4%–5% of meioses, and is a well-recognised complication of predictive testing. Recombination between RFLPs within the D4S10 locus is a rare event and can usually be ignored. We report a case where such an intra-locus recombination frustrated attempts to predict the chance of a high-risk individual inheriting the HD gene.     

The expression of a highly expressed Bacillus subtilis gene is not reduced by introduction of multiple codons normally not present in such genes

A recombinant DNA Proteus mirabilis L-form expression system, LVI (pJS127), was used to synthesize human fusion interferon alpha 1 (f-IFN-alpha 1). In the expression plasmid used, the complete coding sequence of IFN-alpha 1 was linked to the streptococcal speA promoter and the 5' end of the speA structural gene including its signal sequence coding region. LVI (pJS127) was capable of complete secretion into the culture medium of biologically active f-IFN-alpha 1 whose identity was confirmed by immunological and chemical evidence. In particular, bacterial L-forms were for the first time shown to be capable of correct signal peptide processing, as determined by N-terminal sequencing of the secreted f-IFN.     

Experimental investigations of benthic reentry by migrating meiobenthic copepods

The resettlement behavior of meiobenthic copepods, which actively migrated from sediments in a seagrass bed, was investigated in a shallow subtidal area in Tampa Bay, Florida, U.S.A. Experimental studies were conducted to determine whether meiobenthic copepods after emerging from sediments at sunset reenter the sedimentary substratum or select other subhabitats, water and seagrass blades. Migrating copepods were collected with emergence traps and transferred to experimental aquaria in the field which contained sediment, seagrass-blade and water treatments. Settlement into each type of treatment was measured in separate 2-h and 9-h experiments. Differences in densities of copepod taxa retrieved from emergence traps and introduced into experimental aquaria were recorded as were differing relative proportions of each copepod species returning to the substratum treatments. Settlement patterns of total copepods and three dominant copepod species, Zausodes arenicolus, Halicyclops sp. and Robertsonia hamata, departed from those expected by chance. The populations of R. hamata and Halicyclops sp. which settled were generally skewed towards males and a close matching of males and copepodites within treatment dishes was evident. Similar to nighttime-emergence patterns, timing and magnitude of postmigration reentry differs among copepod taxa and such reentry may be linked to reproductive events. Complex behavioral processes previously noted for fish and macrofaunal organisms in seagrass beds may also be important in recruitment and reassortment of meiobenthic copepods.     

Heat treatment of ripening apples: Differential effects on physiology and biochemistry

Apples ( Malus domestica Borkh.) were heated for 4 days at 38°C immediately after harvest and then placed at 20°C for 7–10 days. Protein synthesis, ethylene production and fruit softening were reversibly inhibited by the heat treatment. Fruit respiration, membrane permeability and chlorophyll degradation in the fruit peel were enhanced during the treatment. The heat-treated apples ripened normally but more slowly than untreated apple We hypothesize that heat treatment differentially affects processes which normally increase simultaneously during fruit ripening, by inhibiting those processes which require tie novo protein synthesis and enhancing those that do not.