Synaptic interactions among neurons that coordinate swimmeret and abdominal movements in the crayfish

1. Many interneurons in the crayfish (Procambarus clarkii) abdominal nervous system influence two behaviors, abdominal positioning and swimmeret movements. Such neurons are referred to as dual output cells. Other neurons which influence either one behavior or the other are single output cells. 2. Extensive synaptic interactions were observed between both dual and single output neurons involved in the control of abdominal positioning and swimmeret movements. Over 60% of all neuron pairs examined displayed interactions. Pairs of agonist neurons displayed excitatory interactions, while pairs of antagonists had inhibitory interactions. This pattern of interaction was observed in about 75% of interactive neuron pairs whether abdominal positioning or swimmeret outputs were considered. 3. Evidence for both serial and parallel connectivity, as well as, reciprocal or looping connections was observed. Looping connections can be found both between the abdominal positioning and swimmeret systems and within each system. 4. Most (28/34) single output neurons were not presynaptic to dual output neurons. No single output neurons were found to excite dual output neurons to spiking, although inhibitory interactions and weak excitations were observed. 5. Abdominal positioning inhibitors displayed properties consistent with a role in mediating some of the coordination between the swimmeret and abdominal positioning systems. 6. None of the dual output neurons examined influenced the swimmeret motoneurons directly.     

Single-strand conformation polymorphism (SSCP) analysis of exon 11 of the CFTR gene reliably detects more than one third of non-ΔF508 mutations in German cystic fibrosis patients

Summary In Central Europe, the F508 deletion accounts for approximately 75% of mutations in the cystic fibrosis transmembrane conductance regulator gene causing cystic fibrosis. The remainder comprise a large number of individually infrequent mutations whose detection requires a disproportionately large effort. However, a sizeable proportion of non-F508 mutations have been found to cluster within exon 11. We have taken advantage of this clustering to detect a total of five previously described point mutations present on 26/72 (36%) non-F508 chromosomes by polymerase chain reaction/direct sequencing of exon 11. These exon 11 mutations were then subjected to single-strand conformation polymorphism (SSCP) analysis, which was shown (i) to discriminate reliably between mutant and wildtype alleles and (ii) to generate reproducible mutation-specific band patterns. This analysis thus represents the first attempt to assess SSCP analysis retrospectively, and serves to illustrate the potential of this screening technique in diagnostic medicine.     

Prenatal diagnosis of 21-hydroxylase deficiency congenital adrenal hyperplasia using the polymerase chain reaction

Summary We present an improved method for the prenatal diagnosis of congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency. The polymerase chain reaction (PCR) was used to analyze DNA from an affected index case, the parents, and a cultured chorionic villus sample, for point mutations in the steroid 21-hydroxylase (CYP21) gene. We can predict that the fetus is an unaffected carrier.     

Exclusion mapping of the X-linked dominant chondrodysplasia punctata/ichthyosis/cataract/short stature (Happle) syndrome: possible involvement of an unstable pre-mutation

Summary Homology with the mouse bare patches mutant suggests that the gene for the X-linked dominant chondrodysplasia punctata / ichthyosis / cataract / short stature syndrome (Happle syndrome) is located in the human Xq28 region. To test this hypothesis, we performed a linkage study in three families comprising a total of 12 informative meioses. Multiple recombinations appear to exclude the Xq28 region as the site of the gene. Surprisingly, multiple crossovers were also found with 26 other markers spread along the rest of the X chromosome. Two-point linkage analysis and analysis of recombination chromosomes seem to exclude the gene from the entire X chromosome. Three different mechanisms are discussed that could explain the apparent exclusion of an X-linked gene from the X chromosome by linkage analysis: (a) different mutations on the X chromosome disturbing X inactivation, (b) metabolic interference, i.e. allele incompatibility of an X-linked gene, and (c) an unstable pre-mutation that can become silent in males. We favour the last explanation, as it would account for the unexpected sex ratio (MF) of 1.21 among surviving siblings, and for the striking clinical variability of the phenotype, including stepwise increases in disease expression in successive generations.     

Ammonia regulation of phosphate-activated glutaminase displays regional variation and impairment in the brain of aged rats

The regulation of PAG by ammonia in whole brain (Sprague-Dawley) and regional (Fischer-344) synaptosomal preparations from adult and aged animals was assessed. Whole brain synaptosomal preparations from both age groups displayed a significant decrease in PAG activity with increasing ammonium chloride concentrations, however, the aged rats exhibited a significant attenuation in ammonia-induced PAG inhibition. PAG activity measured in synaptosomes prepared from the striatum (STR), temporal cortex (TCX) and hippocampus (HIPP) was also inhibited by ammonium chloride. The STR showed the greatest degree of ammonia-induced PAG inhibition (55%) followed by the HIPP (30–35%) and the TCX (25–30%). This reduction in PAG activity was significantly attenuated in STR from aged rats at ammonium chloride concentrations greater than 50 M and in the TCX, PAG activity was significantly attenuated in the aged rats at ammonia concentrations of 0.5 and 1.0 mM. Ammonia regulation of PAG activity in the HIPP appeared to be unaffected by age. Ammonium chloride concentrations up to 5 mM had no effect on GLU release from cortical slices, although GLN efflux was significantly enhanced. These findings suggest that isozymes of PAG may exist in different brain regions based on their differential sensitivity to ammonia. The attenuation of ammonia-induced PAG inhibition seen in aged rats may have deleterious effects in the aged brain.Abbreviations PAG phosphate-activated glutaminase: L-glutamine amidohydrolase; EC 3.5.1.2 - STR striatum - TCX temporal cortex - HIPP hippocampus     

On the activity of γ-aminobutyric acid and glutamate transporters in chick embryonic neurons and rat synaptosomes

The uptake of radioactive -aminobutyric acid (GABA) andd-aspartate and the effect of SKF 89976-A, a non-substrate inhibitor of the GABA transporter, on this uptake have been investigated. Neuronal cultures from eight-day-old chick embryos grown for three or six days in vitro, were used as a model. For comparison, we also used the P₂-fraction from rat. Neuronal cultures grown for three and six days expressed high-affinity uptake systems for [³H]GABA and ford-[³H]aspartate with an increasing V_max during this period. The lipophilic non-substrate GABA uptake inhibitor, SKF 89976-A, inhibited transporter mediated uptake of GABA both in cell cultures from chicken, and in P₂-fractions from rat. The results also showed that SKF 89976-A was a poor inhibitor of the uptake ofd-aspartate. We found no non-saturable uptake ofd-aspartate.     

Cloning, sequencing and expression of the gene encoding the extracellular neutral protease, vibriolysin, of Vibrio proteolyticus.

The gene (nprV), encoding the extracellular neutral protease, vibriolysin (NprV), of the Gram- marine microorganism, Vibrio proteolyticus, was isolated from a V. proteolyticus DNA library constructed in Escherichia coli. The recombinant E. coli produced a protease that co-migrated with purified neutral protease from V. proteolyticus on non-denaturing polyacrylamide gels, and that demonstrated enzymatic specificity towards the neutral protease substrate N-[3-(2-furyl)acryloyl]-L-alanylphenylalanine amide. The nucleotide (nt) sequence of the cloned nprV gene revealed an open reading frame encoding 609 amino acids (aa) including a putative signal peptide sequence followed by a long 'pro' sequence consisting of 172 aa. The N-terminal aa sequence of NprV purified from cultures of V. proteolyticus, identified the beginning of the mature protein within the aa sequence deduced from the nt sequence. Comparative analysis of mature NprV to the sequences of the neutral proteases from Bacillus thermoproteolyticus (thermolysin) and Bacillus stearothermophilus identified extensive regions of conserved aa homology, particularly with respect to active-site residues, zinc-binding residues, and calcium-binding sites. NprV was overproduced in Bacillus subtilis by placing the DNA encoding the 'pro' and mature enzyme downstream from a Bacillus promoter and signal sequence.     

Phylogenetic evidence for the herbaceous origin of angiosperms

The ancestral angiosperm is commonly interpreted as an arborescent to shrubby magnolialean with large, multiparted, complex flowers. We examined this hypothesis using a phylogenetic analysis of new and reevaluated characters polarizabled with outgroup comparison. Our cladistic analysis of basal angiosperms placed the nonmagnolialeanChloranthaceae andPiperaceae at the bottom of the tree. We further inferred the probable ancestral states of characters not polarizable with outgroup comparison by examining their distribution among taxa at the base of our cladogram. The sum of ancestral character states suggests that the protoangiosperm was a diminutive, rhizomatous to scrambling perennial herb, with small, simple flowers.     

Gustatory sensitivities of the hamster's soft palate

The response properties of taste receptors distributed on thesoft palate of the hamster were studied by recording integratedresponses from the greater superficial petrosal (GSP) nerveStimuli were concentration series of sucrose, NaCl, HCl andquinine hydrochloride (QHCl), and several other 0.1 M saltsand 0.5 M sugars. For comparison, integrated responses wererecorded from the chorda tympani (CT) nerve in many of the sameanimals from which recordings were made from the GSP. Responsesin each preparation were scaled relative to the phasic responseto 0.1 M NaCl and were then expressed for each nerve as a proportionof the total response magnitude (TRM)—the sum of all theresponses to the four concentration series. In this way, therelative response of each nerve to all of the stimuli couldbe evaluated. There were significant differences between theGSP and CT nerves in the responses to NaCl, QHCl and sucrose.Both the phasic and tonic responses to sucrose were larger inthe GSP than in the CT, whereas the tonic responses to NaCland QHCl were smaller. The slopes of the concentration-responsefunctions for NaCl, HCl and sucrose were significantly differentbetween the two nerves. The responses to 0.1 M sodium and lithiumsalts were significantly greater in the CT than in the GSP;whereas the 0.5 M sugars elicited responses in the GSP thatwere 2–3 times greater than in the CT nerve. A comparisonof the relative responsiveness to 0.3M sucrose, 0 3 M NaCl,0.01 M QHCl, 0.01 M HCl and distilled water among the GSP, CT,glossopharyngeal (IXth) nerve and superior laryngeal nerve (SLN)indicated that the vast majority of information about sucroseand NaCl is transmitted to the brainstem by the VIIth nerve. ¹Present address: Department of Oral Physiology, Kagoshima UniversityDental School, Kagoshima 890, Japan