The Formation of Otoliths in the Frog Rana esculenta. Scanning Electron Microscopic and X-Ray Diffraction Studies

Two crystal forms of calcium carbonate were observed: calcite (utricle) and aragonite (saccule, lagena, endolymphatic sac). The first step in otolith formation is the appearance of organic structures in the macula. The subsequent step is characterized by fast growing primitive crystals with a prismatic habitus that successively transform into adult or mature crystals. With the metamorphosis, the aragonite crystals of the endolymphatic organ show clear signs of erosion that can be related to a process of CaCO₃ mobilization from such deposits.     

FAST (Flexible Analysis by Software Tool) and CHAMP (CHemico-physical AMinoacidic Parameter data bank): a new tool to investigate protein structure

A flexible package designed to study protein structure is described.The package is devoted to the analysis of protein sequencesby drawing structural profiles of specific structure-relatedamino acid parameters. An Aminoacidic Parameters Data Bank (CHAMP)containing 32 different series of physico-chemical parametersof amino acids is available. Sequences can be loaded from anyASCII format data bank or from keyboard. The program possessesa routine which enables easy updating of the protein data bankand CHAMP Data Bank. FAST reads statistical correlations betweentwo plots in order to identify structural similarities. Plotscan be printed, saved or used for correlation, comparison orgraph overlap by using common spreadsheets (e.g. Lotus 123).Plots can be smoothed by a running mean or a running median.The program also has a special feature—a global flexibilityanalysis of proteins. The package runs on IBM or compatiblesand requires DOS 3.0 or later. Received on June 20, 1989; accepted on August 2, 1989     

Picolinic acid, a catabolite of tryptophan, as the second signal in the activation of IFN-gamma-primed macrophages.

We have studied the effects of picolinic acid, a product of tryptophan degradation, on the activation of mouse peritoneal macrophages (M phi). Picolinic acid acts synergistically with IFN-gamma in activating M phi from C57BL/6 mice. Moreover, M phi from C3H/HeJ mice and C3H/HeN that do not become cytotoxic in response to IFN-gamma alone could be fully activated by exposure to picolinate plus IFN-gamma. These results indicate that picolinic acid is a potent costimulator of M phi activation that functions as a second signal. Inasmuch as we have previously demonstrated that the activation of cytotoxic M phi correlates with specific changes in ribosomal RNA (rRNA), we investigated whether picolinic acid could modify M phi RNA metabolism. Picolinic acid inhibited the synthesis of total M phi RNA, the accumulation of newly synthesized 28S rRNA, and augmented the steady state levels of rRNA precursors (pre-rRNA). These changes in RNA metabolism were similar to those previously described in murine M phi activated in vitro or in vivo to express tumoricidal activity. These results demonstrate that picolinic acid is a potent, biologic M phi second signal, suggest that the changes in rRNA are causally connected with the expression of tumoricidal activity, and suggest the existance of an autocrine effect mediated by picolinic acid.     

Effect of Glutathione and N-Acetylcysteine on in Vitro and in VIVO Cardiac Toxicity of Doxorubicin

The effects of two sulfhydryl compounds, glutathione (GSH) and N-acetylcysteine (NAC), on the cardiotoxicity of doxorubicin (DXR) were tested on in vitro and in vivo models. DXR was administered to rats as 4 weekly i.v. doses of 3mg/kg. GSH (1.5 mmoles/kg), given i.v. 10 min before and 1 hr after DXR, was found to prevent the development of the delayed cardiotoxic effects of DXR, as assessed by electrocardiographic and mechanical parameters, as well as by histological examination of left ventricular preparations. In contrast, equimolar oral doses of NAC (1 hr before and 2hrs after DXR) were found to be ineffective. Both GSH and NAC prevented the negative inotropic effect produced by DXR on isolated rat atria. A good correlation exists between the cardioprotective effects of the two agents and their ability to enhance the non-protein sulfhydryl group content of the myocardium. Differences observed in vivo between GSH and NAC might be accounted for by pharmacokinetic factors.     

Regional Reductions of Transketolase in Thiamine-Deficient Rat Brain

Abstract: Thiamine deficiency impairs oxidative metabolism and causes metabolic encephalopathy. An early reduction in transketolase (TK) activity may be an important pathogenic event. To assess the role of TK, we have delineated the regional/cellular distribution of TK protein and mRNA in adult rat brain in pyrithiamine-induced thiamine deficiency. TK activity declined in both vulnerable and spared regions. Immunoblots showed a parallel reduction of TK protein. With a few exceptions, immunocytochemistry indicated an overall decline of TK immunoreactivity and the decrease was not specific to vulnerable areas. In contrast to the pronounced, general decline of TK protein, in situ hybridization revealed a regional decrease of 0–25% of TK mRNA in thiamine deficiency. Northern blots indicated a similar level of TK mRNA in whole brain in thiamine deficiency. These results show that the decline of TK activity results from a proportional decrease of TK protein, and the deficiency may be due to an instability of TK protein or an inhibition of TK mRNA translation. The lack of correlation of the distribution, and the absence of specific alteration, of TK in affected regions suggest that the reduced TK may not be linked directly to selective vulnerability in thiamine deficiency.     

Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content

The aim of this study was to investigate whether, when muscle glycogen is reduced, a pre-exercise infusion of branched-chain amino acids (BCAA) modifies exercise performance or the metabolic and respiratory responses to incremental exercise. Six moderately trained volunteers took part in the following protocol on two occasions. On day 1, at 9 a.m. in the postabsorptive state, they performed a graded incremental exercise (increases of 35 W every 4 min) to exhaustion (Ex-1). A meal of 1,000 kcal (4,200 kJ; 60% protein, 40% fat) was consumed at 12 p.m. No food was then allowed until the end of the experiment (20–21 h later). A 90-min period of exercise at alternating high and moderate intensities, designed to deplete muscle glycogen, was performed between 6 p.m. and 7.30 p.m. The morning after (day 2), the subjects randomly received either a mixed solution of BCAA (260 mg × kg^–1 × h^–1 for 70 min), or saline. They then repeated the graded incremental exercise to exhaustion (Ex-2). Metabolic and respiratory measurements suggested a muscle glycogen-depleted state had been achieved. No significant differences were observed in total work performed, maximal oxygen uptake or plasma ammonia, alanine, and blood pyruvate concentrations in the two treatments. After BCAA infusion, higher blood lactate concentrations were observed at maximal power output in comparison with those during saline [BCAA 4.97 (SEM 0.41) mmol × l^–1, Saline 3.88 (SEM 0.47) mmol × l^–1,P < 0.05]. In summary, in conditions of reduced muscle glycogen content, after a short period of fasting, BCAA infusion had no significant effect on the total work that could be performed during a graded incremental exercise.     

Water stress,temperature, and light effects on the capacity for isoprene emission and photosynthesis of kudzu leaves

Kudzu (Pueraria lobata (Willd) Ohwi.) is a vine which forms large, monospecific stands in disturbed areas of the southeastern United States. Kudzu also emits isoprene, a hydrocarbon which can significantly affect atmospheric chemistry including reactions leading to tropospheric ozone. We have studied physiological aspects of isoprene emission from kudzu so the ecological consequences of isoprene emission can be better understood. We examined: (a) the development of isoprene emission as leaves developed, (b) the interaction between photon flux density and temperature effects on isoprene emission, (c) isoprene emission during and after water stress, and (d) the induction of isoprene emission from leaves grown at low temperature by water stress or elevated temperature. Isoprene emission under standard conditions of 1000 mol photons·m^-2·s^-1 and 30°C developed only after the leaf had reached full expansion, and was not complete until up to two weeks past the point of full expansion of the leaf. The effect of temperature on isoprene emission was much greater than found for other species, with a 10°C increase in temperature causing a eight-fold increase in the rate of isoprene emission. Isoprene emission from kudzu was stimulated by increases in photon flux density up to 3000 mol photons·m^-2·s^-1. In contrast, photosynthesis of kudzu was saturated at less than 1000 mol·m^-2·s^-1 photon flux density and was reduced at high temperature, so that up to 20% of the carbon fixed in photosynthesis was reemitted as isoprene gas at 1000 mol photons·m^-2·s^-1 and 35°C. Withholding water caused photosynthesis to decline nearly to zero after several days but had a much smaller effect on isoprene emission. Following the relief of water stress, photosynthesis recovered to the prestress level but isoprene emission increased to about five times the prestress rate. At 1000 mol photons·m^-2·s^-1 and 35°C as much as 67% of the carbon fixed in photosynthesis was reemitted as isoprene eight days after water stress. Leaves grown at less than 20°C did not make isoprene until an inductive treatment was given. Inductive treatments included growth at 24°C, leaf temperature of 30°C for 5 h, or witholding water from plants. With the new information on temperature and water stress effects on isoprene emission, we speculate that isoprene emission may help plants cope with stressful conditions.     

Release of cholecystokinin in the central nervous system

The octapeptide cholecystokinin (CCK) is one of the most abundant neuropeptides of the central nervous system. A number of features (for instance heterogeneity of the regional distribution, subcellular localization at the nerve terminal level, calcium-dependent release upon nervous tissue depolarization) support the candidacy of CCK as a neurotransmitter. The reported co-existence of CCK and dopamine in some meso-limbic neurons has led to speculation that the neuropeptide may interact with the catecholamine in neuropsychopathologies linked to dopamine dysfunctions, like schizophrenia. Data from the experimental animals have so far generated conflicting results. It should be noted that the interactions between CCK and dopamine, and, in particular, the effects of CCK and dopamine on each other release, both in vitro and in vivo, have been poorly investigated and would require special attention. Evidence is accumulating that CCK may participate in the expression of anxiety. Indeed antagonists at the central CCK receptors exhibit anxiolytic activity in the laboratory animal. An interesting linkage appears to exist in the brain between 5-hydroxytryptamine (5-HT) and CCK. Activation of 5-HT₃ receptors was found to increase CCK release from rat cortical or nucleus accumbens synaptosomes. Interestingly, antagonists at 5-HT₃ receptors appear to possess anxiolytic activity. Recent studies carried out in conscious unrestrained rats show that the calcium-dependent, tetrodotoxin-sensitive release of CCK-like immunoreactivity evoked in the rat frontal cortex by veratrine infusion can be inhibited by submicromolar concentrations of 5-HT₃ receptor antagonists. It seems legitimate to conclude that 5-HT and CCK interact in the living brain, the former increasing the release of the latter through activation of receptors of the 5-HT₃ type. On the basis of this interaction both 5-HT₃ and CCK receptor antagonists may become novel anxiolytics.