Recurrent axon collaterals of lumbar motor neurons in turtles

A combined morphophysiological study was made of connections between motoneurons on the superfused isolated lumbar spinal cord of Testudo horsfieldi. Postsynaptic potentials of motoneurons, followed by antidromic stimulations of ventral root filaments (VR-PSPs), were recorded intracellularly. Depolarizing VP-PSPs had short latencies (1.0-1.5 mc) and amplitudes in the range of 0.3-3.0 mV. At the constant stimulus intensity, the fluctuations of amplitudes were recorded. In some motoneurons, hyperpolarizing VP-PSRs with the latencies 2.5-3.0 mc were observed. A possible structural basis of VR-PSPs was studied by the horseradish peroxidase (HRP) method. After HRP application on thin ventral root filaments the retrograde staining of motoneurons revealed recurrent axon collaterals of labeled motoneurons. Three-dimensional computer reconstructions showed one to three collaterals given off by motoneuron axons. There were up to 19 points of branching in a single collateral. In some cases the full length of collateral trees reached 4.0 mm. The collateral branches had up to 72 "en passant" and terminal axon swellings. The swellings (presumed contacting boutons) were distributed in the ventral and intermedial gray matter and in the ventromedial while matter and revealed on motoneurons and inerneurons. These data suggest the participation of the motor axon collaterals in the motoneuron--motoneuron communication in the turtle spinal cord whereas only dendro-dendritic contacts had been discussed earlier.     

Termination of the afferent fiber in the spinal cord of the turtle Testudo horsfieldi and three-dimensional reconstruction of the sensory-motoneuron connection

Horseradish peroxidase (HRP) tracing methods and subsequent computer reconstruction were used to study the structural organization of sensory-motoneuron connections in turtles. HRP was applied through suction electrodes to thin dorsal and ventral root filaments of superfused isolated lumbar spinal cord of the turtle Testudo horsfieldi. Single motoneurons were labeled ionophoretically with intracellular glass microelectrodes. Labeled elements were examined under a light microscope. The Eutectic neuron tracing system and its associated program were used for three-dimensional reconstructions and morphometry. The distribution of afferent fibers of the dorsal root and their terminations were presented in a new scheme in which new zones, in addition to those that were already well known, were shown, including the following: in the Lissauer zone, motor nuclei, and ventrolateral funiculus, as well as in the contralateral medial gray matter (laminae IV–V). Unlike in frogs, the motoneuron dendritic field in turtles was restricted to an ellipsoid space with a short axis in the rostrocaudal direction (300–500 µm). The afferent fibers of the dorsal root connected to motoneurons produced very short branches in a restricted rostrocaudal direction (50–70 μm). One fiber collateral of the dorsal root had about 80 synapse-like enlargements (approximately tenfold fewer than in frogs). Putative sensory-motoneuron contacts were found on the I–VII-order dendritic segments of the dorsal and ventro-medial dendritic trees. It was shown that, in turtles, only one first-order collateral of the dorsal root fiber participated in the sensory-motoneuron connection with a small number (about 4) of putative contacts, which is also one order less than in frogs. It is likely that the simplification of the synapse structure in turtles is compensated by a higher efficiency of the signal transmission comparable to that in mammals.     

Characterization of PR-10 genes from eight Betula species and detection of Bet v 1 isoforms in birch pollen

Background  

Bet v 1 is an important cause of hay fever in northern Europe. Bet v 1 isoforms from the European white birch (Betula pendula) have been investigated extensively, but the allergenic potency of other birch species is unknown. The presence of Bet v 1 and closely related PR-10 genes in the genome was established by amplification and sequencing of alleles from eight birch species that represent the four subgenera within the genus Betula. Q-TOF LC-MS^E was applied to identify which PR-10/Bet v 1 genes are actually expressed in pollen and to determine the relative abundances of individual isoforms in the pollen proteome.     

Recent advances in ABE fermentation: hyper-butanol producing Clostridium beijerinckii BA101

This is an overview of the mutant strain Clostridium beijerinckii BA101 which produces solvents (acetone–butanol–ethanol, ABE) at elevated levels. This organism expresses high levels of amylases when grown on starch. C. beijerinckii BA101 hydrolyzes starch effectively and produces solvent in the concentration range of 27–29 g l⁻¹. C. beijerinckii BA101 has been characterized for both substrate and butanol inhibition. Supplementing the fermentation medium (MP2) with sodium acetate enhances solvent production to 33 g l⁻¹. The results of studies utilizing commercial fermentation medium and pilot plant-scale reactors are consistent with the results using small-scale reactors. Pervaporation, a technique to recover solvents, has been applied to fed-batch reactors containing C. beijerinckii BA101, and solvent production as high as 165 g l⁻¹ has been achieved. Immobilization of C. beijerinckii BA101 by adsorption and use in a continuous reactor resulted in reactor productivity of 15.8 g l⁻¹ h⁻¹. Recent economic studies employing C. beijerinckii BA101 suggested that butanol can be produced at US$0.20–0.25 lb⁻¹ by employing batch fermentation and distillative recovery. Application of new technologies such as pervaporation, fed-batch culture, and immobilized cell reactors is expected to further reduce these prices. Journal of Industrial Microbiology & Biotechnology (2001) 27, 287–291. Received 12 September 2000/ Accepted in revised form 27 January 2001     

The effect of diethyl- -fluoroglutarate on phosphates and glutamate in slices of rabbit cerebral cortex

Abstract— The diethyl ester of α-fluoroglutarate (DEFG), an inhibitor of glutamate dehydrogenase, was prepared, and its effect on glutamate and phosphates in slices of rabbit cerebral cortex was examined. The primary effect of the drug on cortical slices incubating in a Krebs-Ringer glucose medium was to decrease the tissue levels of glutamate in association with decreased levels and turnover of high-energy phosphates. Assimilation of exogenous glutamate by the slices was partially blocked in the presence of the drug and severely depressed oxidative phosphorylation resulted when glutamate and DEFG were both present in the incubation mixture. The results suggested a significant relationship between the activity of cerebral glutamate dehydrogenase and oxidative phosphorylation. During incubation in a Krebs-Ringer glucose medium the endogenous pool of free amino acids in the cortical slice partitioned with the medium. Little or no glutamate, aspartate or GABA was present in the medium after incubation, but glycine, alanine, threonine, serine and glutamine did partition to varying degrees, with over one-half of the glutamine present in the incubation medium. With the exception of ‘leakage’ of aspartate, the partitioning patterns were relatively unaffected by the presence of added glutamate or DEFG.     

An overview of the serpin superfamily

Serpins are a broadly distributed family of protease inhibitors that use a conformational change to inhibit target enzymes. They are central in controlling many important proteolytic cascades, including the mammalian coagulation pathways. Serpins are conformationally labile and many of the disease-linked mutations of serpins result in misfolding or in pathogenic, inactive polymers.