Catecholaminergic contributions to the neuronal machinery of the olfactory bulb: aftoradiographic, immunohistochemical and evoked feild potential studies

aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons.     

Ntau-methylhistidine excretion is a valid index of myofibrillar protein breakdown in the guineapig (Cavia porcellus).

The recovery of radioactivity in the urine of guineapigs following a bolus intravenous dose of chromatographically pure 14C-Ntau-methylhistidine was measured in order to test whether the excretion of Ntau-methylhistidine (Ntau-MH) is a valid index of myofibrillar protein breakdown in these animals. Four male and four female guineapigs were dosed and after 7 days, 91.65+/-2.82% and 3.58+/-0.91% of injected radioactivity was recovered in the excreta and tissues, respectively. The average total recovery of 95.2+/-3.0% was not significantly different from 100%. Male guineapigs excreted the radioactivity more slowly than females (70% of the dose excreted within 74 h vs 39 h, respectively) but cumulative excretion at 7 days was the same for each sex. Chromatographic analysis of the urine showed almost all of the radioactivity to be associated with a single peak corresponding to Ntau-MH, indicating a lack of significant metabolism. These data show that although the clearance of 14C-Ntau-MH is slower than in rats or humans the urinary excretion of Ntau-MH is a valid index for myofibrillar protein degradation in the guineapig.     

Analysis of ligand-binding to the kringle 4 fragment from human plasminogen

The interaction of the isolated human plasminogen kringle 4 with the four -amino acid ligands -aminocaproic acid (ACA), N-acetyl-l-lysine (AcLys), trans-aminomethyl(cyclohexane)carboxylic acid (AMCHA) and p-benzylaminesulfonic acid (BASA) has been further characterized by ¹H-NMR spectroscopy at 300 and 600 MHz. Pronounced high-field shifts, reaching 3 ppm, are observed for AMCHA resonances upon binding to kringle 4, which underscores the relevance of ligand lipophilic interactions with aromatic side chains at the binding site. Ligand titration curves for the nine His and Trp singlets found in the kringle 4 aromatic spectrum reveal a striking uniformity in the kringle response to the various ligands. The average binding curves exhibit a clear Langmuir absorption isotherm saturation profile and the data were analyzed under the assumption of one (high affinity) binding site per kringle. Equilibrium association constants (K _a ) and first order dissociation rate constants (k _off) were derived from linearized expressions of the Langmuir isotherm and of the spectral line-shapes, respectively. The results for the four ligands, at 295 K, pH^* 7.2, indicate that: (a) AMCHA exhibits the strongest binding (K _a =159 mM ^-1) and ACA the weakest (K _a =21 mM ^–1) with AcLys and BASA falling in between; (b) ACA dissociates readily (k _off = 5.3 × 10³ s^–1) and AMCHA associates the fastest (k _off = 2.0 × 10⁸ M ^–1 s^–1) while the kinetics for BASA exchange is relatively slow (k _off = 0.8 × 10³ s^–1, k _on = 0.6 × 10⁸ M ^–1s^–1); (c) the ligand-binding kinetics is close to diffussion-controlled.Abbreviations ACA -aminocaproic acid - AcLys N-acetyl-l-lysine - AMCHA t-aminomethyl(cyclohexane)carboxylic acid - BASA p-benzylaminesulfonic acid - K4 kringle 4 - NOE nuclear Overhauser effect - ppm parts-per-million - pH^* glass electrode pH reading uncorrected for deuterium isotope effects - K _a ligand-kringle 4 equilibrium association constant - k _off ligand-kringle 4 dissociation rate constant - k _on ligand-kringle 4 association rate constant     

Increased Concentrations of 3-Hydroxykynurenine in Vitamin B6 Deficient Neonatal Rat Brain

Increased concentrations of the endogenous tryptophan metabolite 3-hydroxykynurenine (3-HK) were measured in the brains of vitamin B6 deficient neonatal rats. Mean concentrations of 3-HK in B6 deficient cerebellum, corpus striatum, frontal cortex, and pons/medulla ranged from 9.7 to 18.6 and 102 to 142 nmol/g of wet tissue at 14 and 18 days of age, respectively. 3-HK was not significantly increased in control neonatal or adult rat brain, vitamin B6 deficient rat brain at 7 days of age, or in brains from adult rats deprived of vitamin B6 for 58 days. The administration of daily intraperitoneal injections of vitamin B6 from the 14th to the 18th day of age decreased the concentration of 3-HK to control levels. 3-HK has been shown by other investigators to produce seizures when injected into the cerebral ventricles of adult rodents. Thus, our studies show the accumulation in brain of a putative endogenous convulsant as the result of a nutritional deficiency.     

Extracellular and cell-bound lipase activity in relation to growth of Geotrichum candidum

Summary The imperfect fungus Geotrichum candidum produced extracellular lipase in a basic peptone-salt medium. By adding olive oil or Tween 80 to the basic medium the lipase yields could be enhanced and the maximal yields were found with Tween 80, which resulted in a sixfold increase in extracellular lipase activity as compared with basic medium. During the early phase of growth in medium with olive oil the proportion of cell-bound activity was higher than that of extracellular activity, and a delay in the secretion of extracellular lipase was found. The proportion of cell-bound activity from growth in basic medium and in basic medium with Tween 80 was lower than that of extracellular activity during the entire growth phase. Analyses by polyacrylamide gel electrophoresis showed that the lipase activity from growth in all three media could be ascribed to equivalent protein bands at 57 000 and 61 000 daltons. Immunodiffusion showed that the cell-bound preparation contained lipase that was immunologically identical with purified extracellular lipase from G. candidum.     

Identification of thiol groups and a disulfide crosslink site in bovine myelin proteolipid protein

The existence of disulfide crosslinks limits the number of possible folded structures a protein can assume. Thus localization of disulfide and thiol groups is a key to understanding the conformation and orientation of myelin proteolipid protein (PLP) in the myelin membrane. [¹⁴C]Carboxamidomethylated PLP was fragmented with chymotrypsin, and the resulting mixture was partially separated by reversed-phase HPLC. Purified ¹⁴C-labeled peptides and a disulfide containing peptide were characterized by amino acid analysis. These experiments showed that Cys-32 and Cys-34 are free thiols, and are presumably on the interior of the cell or within the membrane bilayer, and that Cys-200 and Cys-219 are joined by a disulfide bond, and are probably located on the extracellular face of the membrane. Sequence analysis experiments indicate that Cys-5, Cys-6 and Cys-9 are linked by disulfides, probably to other parts of the protein on the extracellular face of the membrane.     

Higher rate of evolution of X chromosome alpha-repeat DNA in human than in the great apes.

The rate of introduction of neutral mutations is lower in man than in other primates, including the chimpanzee. This species is generally regarded as our closest relative among the great apes. We present here an analysis of sequences of X chromosomal alphoid repetitive DNA from man and the great apes, which supports the closer relationship between man and chimpanzee and indicates a considerably increased rate of recombination in the human repeat DNA. These results indicate that the 'molecular clock' is running more quickly in man.     

Seasonal variations in hematocrit, red cell hemoglobin and nucleoside triphosphate concentrations, in the European eel Anguilla anguilla

Eels acclimatized in nature show a significant annual variation in erythrocytic guanosine triphosphate (GTP) concentration, temperature range 0.5-17 degrees C. A similar but smaller annual variation is also present in eels acclimated in the laboratory at constant temperature, 17 degrees C. Hematocrit and blood oxygen capacity showed no seasonal variation. Natural minimal and maximal red cell GTP concentrations were found at the end of the dormancy period (March) and in the late summer, respectively. Furthermore, a chronological connection of the erythrocytic GTP values versus ambient temperature, in the natural environment, demonstrates a hysteresis. This allows for a prediction of a slowly progressing enhancement of the temperature effect on Hb-O2 binding throughout autumn, whereas a relatively fast and pronounced enhancement predictably takes place in spring (April-May) coincident with the "awakening" of the eels.