Intracellular recordings from nonspiking interneurons in a semiintact,tethered walking insect

Nonspiking interneurons were investigated in a tethered, walking insect, Carausius morosus, that was able to freely perform walking movements. Experiments were carried out with animals walking on a lightweight, double-wheel treadmill. Although the animal was opened dorsally, the walking system was left intact. Intracellular recordings were obtained from the dorsal posterior neuropil of the mesothoracic ganglion. Nonspiking inter-neurons, in which modulations of the membrane potential were correlated with the walking rhythm, were described physiologically and stained with Lucifer Yellow. Interneurons are demonstrated in which membrane potential oscillations mirror the leg position or show correlation with the motoneuronal activity of the protractor and retractor coxae muscles during walking. Other interneurons showed distinct hyperpolarizations at certain important trigger points in the step cycle, for example, at the extreme posterior position. Through electrical stimulation of single, nonspiking interneurons during walking, the motoneuronal activity in two antagonistic muscles—protractor and retractor coxae—could be reversed and even the movement of the ipsilateral leg could be influenced. The nonspiking interneurons described appear to be important premotor elements involved in walking. They receive, integrate, and process information from different leg proprioceptors and drive groups of leg motoneurons during walking.     

The evolution of male-female dimorphism: Older than sex?

This contribution considers the evolution of a dimorphism with respect to cell fusion characteristics in a population of primitive cells. These cells reproduce exclusively asexually. The evolution towards asymmetric fusion behaviour of cells is driven by selection promoting horizontal transfer of an endosymbiontic replicator. It is concluded that evolution of asymmetric cell fusion in this scenario is more likely than evolution of sexual differentiation in a sexually reproducing population. Pre-existing dimorphism with respect to cell fusion may thus have been the basis for the establishment of sexual differentiation at the level of gamete fusion, and this in turn is fundamental to the evolution of two different sexes, male and female.     

Purification of Two Dipeptidyl Aminopeptidases II from Rat Brain and Their Action on Proline-Containing Neuropeptides

From the soluble and membrane fractions of rat brain homogenate, two enzymes that liberate dipeptides of the type Xaa-Pro from chromogenic substrates were purified to homogeneity. The two isolated dipeptidyl peptidases had similar molecular and catalytic properties: For the native proteins, molecular weights of 110,000 were estimated; for the denatured proteins, the estimate was 52,500. Whereas the soluble peptidase yielded one band of pI 4.2 after analytical isoelectric focusing, two additional enzymatic active bands were detected between pI 4.2 and 4.3 for the membrane-associated form. As judged from identical patterns after neuraminidase treatment, both peptidases contained no sialic acid. A pH optimum of 5.5 was estimated for the hydrolysis of Gly-Pro- and Arg-Pro-nitroanilide. Substrates with alanine instead of proline in the penultimate position were hydrolyzed at comparable rates. Acidic amino acids in the ultimate N-terminal position of the substrates reduced the activities of the peptidases 100-fold as compared with corresponding substrates with unblocked neutral or, especially, basic termini. The action of the dipeptidyl peptidase on several peptides with N-terminal Xaa-Pro sequences was investigated. Tripeptides were rapidly hydrolyzed, but the activities considerably decreased with increasing chain length of the peptides. Although the tetrapeptide substance P 1-4 was still a good substrate, the activities detected for the sequential liberation of Xaa-Pro dipeptides from substance P itself or casomorphin were considerably lower. Longer peptides were not cleaved. The peptidases hydrolyzed Pro-Pro bonds, e.g., in bradykinin 1-3 or 1-5 fragments, but bradykinin itself was resistant. The enzymes were inhibited by serine protease inhibitors, like diisopropyl fluorophosphate or phenylmethylsulfonyl fluoride, and by high salt concentrations but not by the aminopeptidase inhibitors bacitracin and bestatin. Based on the molecular and catalytic properties, both enzymes can be classified as species of dipeptidyl peptidase II (EC 3.4.14.2) rather than IV (EC 3.4.14.5). However, some catalytic properties differentiate the brain enzyme from forms of dipeptidyl peptidase II of other sources.     

Inheritance of mitochondrial aldehyde dehydrogenase: genotyping in Chinese,Japanese and South Korean families reveals dominance of the mutant allele

Summary Genotyping of mitochondrial aldehyde dehydrogenase (ALDH I) was performed in enzymatically amplified DNA of 20 Chinese, Japanese and South Korean families (85 individuals) and in 113 unrelated persons by employing allele-specific oligonucleotide probes and dot blot hybridization. Genotyping individuals with phenotypic deficiency of ALDH I activity always showed the presence of at least one mutant allele. The data are compatible with a model assuming dominant inheritance of the mutant allele, which we have previously suggested on the basis of a population study.     

Fossile Reptil-Eischalen (Chelonia,Crocodilia, Dinosauria) aus dem unteren Barremium von Galve (Provinz Teruel,SE-Spanien)

The Lower Cretaceous vertebrate bearing sediments of Galve (province of Teruel, SE Spain) have yielded some hundred fossil eggshell fragments, all slightly diagenetically altered. Concerning their microstructure, an assignment of the material to different taxa of reptiles was possible. The eggshell assemblage of Galve consists of a-c) three types of chelonian eggshells, one of them probably representing the subfamily Batagurinae, which would extend this taxon back into the Lower Cretaceous, d) the oldest known crocodilian eggshells, with lacunae systems on the outer surface, comparable to Recent taxa, and e-f) two different types of dinosaurian eggshells. In correspondence to the suggested fluviatile paleoenvironment of Galve, the fossil eggshells described herein are fragmented and represent mostly turtles and crocodiles.     

Continuous microbial production ofl-leucine with cell retention

Summary Continuous production ofl-leucine was carried out withCorynebacterium glutamicum, strain ATCC 13032 starting from-ketoisocaproic acid as the precursor, glucose as the carbon source and ammonium sulphate as the nitrogen source, with biotin in a mineral medium. By means of cross-flow microfiltration or centrifugal separation for cell retention in continuous fermentation an increase in cell density was achieved and the product solution was obtained cell-free. The cells were concentrated to over 70 g cell dry mass/1. In experiments of up to 42 days, conversion rates of 85%–99% andl-leucine yields of 85%–93% were achieved. With a substrate residence time of 3.6 h, 114 mmol/1l-leucine was produced with a space-time yield of 97 g/1 per day. A scale-up of the fermentation volume from 4 to 1001 provided comparable results.     

Effects on microbial activity by extraction of indigenous cells from soil slurries

Abstract: Possible effects on the physiological activity and culturability of soil microorganisms by different soil dispersion procedures, and effects on activity caused by extracting bacteria from soil, were investigated. There was no apparent difference in cfu's with dispersion of a silty loam soil and a loamy sand soil with pyrophosphate as compared to dispersion in NaCl. Substrate-induced respiration was reduced in the silty loam soil, and methanol oxidation was reduced in the loamy sand soil with dispersion in pyrophosphate, and the soil pH was irreversibly increased by the treatment. Extracted bacterial fractions had lower numbers of culturable cells as percentage of the total number of bacteria in each fraction, lower respiration rates and no methanol oxidation activity as compared to the soil slurry both before and after extraction. The physiological activity was apparently not affected by the number of cells extracted. This indicates that the increased extraction rate of indigenous soil bacteria obtained by effective disruption of aggregates and detachment of cells from surfaces, only results in increased extraction of cells that have been physiologically changed as a result of the extraction process.     

A novel family of linear plasmids with homology to plasmid pAL2-1 of Podospora anserina

Three recently isolated wild-type strains of the ascomycete Podospora anserina were analyzed for the presence of linear mitochondrial plasmids. In one of these strains, designated Wa6, at least 12 distinct plasmid-like elements were identified. From molecular analyses a minimum number of 78 individual linear molecules with proteins bound to their 5′ ends was estimated. In addition, the different members of this family of typical linear plasmids were shown to possess a common central region and terminal sequences which differ from one plasmid to another due to the presence of different numbers of a 2.4 kb sequence module. Finally, the pWa6 plasmids share a high degree of sequence similarity with pAL2-1, a linear plasmid previously identified in mitochondria of a long-lived mutant of P.anserina. A mechanism is proposed which explains the generation of these distinct, closely related extrachromosomal genetic traits.