Effect of ethanol on corticosterone production by dispersed adrenal cells of the rat

The action of ethanol on adrenal steroidogenesis "in vitro" has been studied. It has been found that ethanol did not change the basal production of corticosterone by dispersed adrenal cells, but significantly reduced its response to ACTH stimulation. It is suggested that the inhibitory action of ethanol on steroidogenesis "in vitro" could have a physiological meaning, because the response to ACTH stimulation of adrenal cells from rats treated "in vivo" with ethanol showed a clear dose-related inhibition.     

Regulation of arginine decarboxylase by spermine in osmotically-stressed oat leaves

Biosynthesis of polyamines in plants is controlled primarily by the enzymes ornithine decarboxylase (EC 4.1.1.17) and arginine decarboxylase (ADC: EC 4.1.1.19), which are responsible for the production of putrescine, and S -adenosyl-L-methionine (SAM) decarboxylase (EC 4.1.1.50) that is necessary for the formation of spermidine and spermine (Spm). Little is known about the metabolic or molecular mechanisms regulating the synthesis of these enzymes. We have studied the regulation of ADC synthesis by Spm in osmotically-stressed oat ( Avena sativa L. ev. Victory) leaves, using a polyclonal antibody to oat ADC and a cDNA clone encoding oat ADC. Treatment with Spm in combination with osmotic stress resulted in increased steady-state levels of ADC mRNA, yet the levels of ADC activity decreased. This absence of correlation is explained by the fact that Spm inhibits processing of the ADC proenzyme, which results in increased levels of this inactive ADC form and a consequent decrease in the ADC-processed form. Spermine treatment leads to delayed loss of chlorophyll in dark-incubated and osmotically-treated oat leaves. Thus, post-translational regulation of ADC synthesis by Spm may be important in explaining its anti-senescence properties.     

Mechanisms of polyamine action during senescence responses induced by osmotic stress

The peeled Avena sativa L. leaf-system has been used as a simpleand rapid model, which allows the study of the mechanisms ofpolyamine action during senescence responses induced by osmoticstress. The use of guazatine, an inhibitor of polyamine oxidaseactivity, has demonstrated the existence of a positive correlationbetween high levels of spermidine and spermine and delay ofsenescence in oat leaves and mesophyll protoplasts. The availabilityof antibodies specific for key polypeptides of thylakoid membranesin combination with ultrastructural studies have led to thediscovery that spermine stabilizes the molecular compositionand preserves the integrity of thylakoid membranes. The analysesof malondialdehyde and lipoxygenase levels has revealed thatpolyamines and guazatine treatments may prevent membrane destabilization,at least in part, by inhibiting lipid peroxidation. Finally,the availability of a cDNA coding for oat arginine decarboxylase(ADC) and the generation of ‘site-directed’ antibodiesspecific for ADC have led to the establishment of the basisfor a model of regulation of ADC gene expression in oat leaves. Key words: Avena sativa, polyamines, guazatine, osmotic stress, senescence     

Lindane Administration to the Rat Induces Modifications in the Regional Cerebral Binding of [3H]Muscimol, [3H]-Flunitrazepam, and t-[35S]Butylbicyclophosphorothionate: An Autoradiographic Study

Abstract: The effect of lindane administration on the specific binding of ligands to different sites on the GABA_A receptor-ionophore complex was studied in the rat brain by receptor mapping autoradiography. [³H]Muscimol (Mus), [³H]flunitrazepam (Flu), and t -[³⁵S]butylbicyclophosphorothionate (TBPS) were used as specific ligands of GABA, benzodiazepine, and picrotoxinin binding sites, respectively. Rats received a single oral dose of 30 mg/kg lindane and they were classified into two groups according to the absence or presence of convulsions. Vehicle-treated groups acted as controls. The effect of the xenobiotic on ligand binding was measured in different brain areas and nuclei 12 min or 5 h after its administration. Lindane induced a generalized decrease in [³⁵S]TBPS binding, which was present shortly after dosing. In addition, [³H]Flu binding was increased in lindane-treated animals, this modification also appearing shortly after administration but diminishing during the studied time. Finally, lindane induced a decrease in [³H]Mus binding, which became more evident over time. These modifications were observed both in the presence and in the absence of convulsions. However, an increase in [³H]-Mus binding was detected shortly after lindane-induced convulsions. The observed decrease in [³⁵S]TBPS binding is in agreement with the postulated action of lindane at the picrotoxinin binding site of the GABA_A receptor chloride channel. The effects observed on the binding of [³H]Flu and [³H]Mus may be secondary to the action of lindane as an allosteric antagonist of the GABA_A receptor.     

Arginine Decarboxylase Is Localized in Chloroplasts

Plants, unlike animals, can use either ornithine decarboxylase or arginine decarboxylase (ADC) to produce the polyamine precursor putrescine. Lack of knowledge of the exact cellular and subcellular location of these enzymes has been one of the main obstacles to our understanding of the biological role of polyamines in plants. We have generated polyclonal antibodies to oat (Avena sativa L.) ADC to study the spatial distribution and subcellular localization of ADC protein in different oat tissues. By immunoblotting and immunocytochemistry, we show that ADC is organ specific. By cell fractionation and immunoblotting, we show that ADC is localized in chloroplasts associated with the thylakoid membrane. The results also show that increased levels of ADC protein are correlated with high levels of ADC activity and putrescine in osmotically stressed oat leaves. A model of compartmentalization for the arginine pathway and putrescine biosynthesis in active photosynthetic tissues has been proposed. In the context of endosymbiote-driven metabolic evolution in plants, the location of ADC in the chloroplast compartment may have major evolutionary significance, since it explains (a) why plants can use two alternative pathways for putrescine biosynthesis and (b) why animals do not possess ADC.     

ATP sulfurylase from trophosome tissue of Riftia pachyptila (hydrothermal vent tube worm)

ATP sulfurylase (ATP: sulfate adenylyltransferase, EC 2.7.7.4) was extensively purified from trophosome tissue of Riftia pachyptila, a tube worm that thrives in deep ocean hydrothermal vent communities. The enzyme is probably derived from the sulfide-oxidizing bacteria that densely colonize the tissue. Glycerol (20% v/v) protected the enzyme against inactivation during purification and storage. The native enzyme appears to be a dimer (MW 90 kDa +/- 10%) composed of identical size subunits (MW 48 kDa +/- 5%). At pH 8.0, 30 degrees C, the specific activities (units x mg protein-1) of the most highly purified sample are as follows: ATP synthesis, 370; APS synthesis, 23; molybdolysis, 65; APSe synthesis or selenolysis, 1.9. The Km values for APS and PPi at 5 mM Mg2+ are 6.3 and 14 microM, respectively. In the APS synthesis direction, the Km values for MgATP and SO4(2-) are 1.7 and 27 mM, respectively. The Km values for MgATP and MoO4(2-) in the molybdolysis reaction are 80 and 150 microM, respectively. The Kia for MgATP is 0.65 mM. APS is a potent inhibitor of molybdolysis, competitive with both MgATP and MoO4(2-) (Kiq = 2.2 microM). However, PPi (+ Mg2+) is virtually inactive as a molybdolysis inhibitor. Oxyanion dead end inhibitors competitive with SO4(2-) include (in order of decreasing potency) ClO4- greater than FSO3- (Ki = 22 microM) greater than ClO3- greater than NO3- greater than S2O3(2-) (Ki's = 5 and 43 mM). FSO3- is uncompetitive with MgATP, but S2O3(2-) is noncompetitive. Each subunit contains two free SH groups, at least one of which is functionally essential. ATP, MgATP, SO4(2-), MoO4(2-), and APS each protect against inactivation by excess 5,5'-dithiobis-(2-nitrobenzoate). FSO3- is ineffective as a protector unless MgATP is present. PPi (+Mg2+) does not protect against inactivation. Riftia trophosome contains little or no "ADP sulfurylase." The high trophosome level of ATP sulfurylase (67-176 ATP synthesis units x g fresh wt tissue-1 from four different specimens, corresponding to 4-10 microM enzyme sites), the high kcat of the enzyme for ATP synthesis (296 s-1), and the high Km's for MgATP and SO4(2-) are consistent with a role in ATP formation during sulfide oxidation, i.e., the physiological reaction is APS + MgPPi in equilibrium SO4(2-) + MgATP.     

The Effect of a Physical Activity Program on the Total Number of Primary Care Visits in Inactive Patients: A 15-Month Randomized Controlled Trial

Background

Effective promotion of exercise could result in substantial savings in healthcare cost expenses in terms of direct medical costs, such as the number of medical appointments. However, this is hampered by our limited knowledge of how to achieve sustained increases in physical activity.

Objectives

To assess the effectiveness of a Primary Health Care (PHC) based physical activity program in reducing the total number of visits to the healthcare center among inactive patients, over a 15-month period.

Research Design

Randomized controlled trial.

Subjects

Three hundred and sixty-two (n = 362) inactive patients suffering from at least one chronic condition were included. One hundred and eighty-three patients (n = 183; mean (SD); 68.3 (8.8) years; 118 women) were randomly allocated to the physical activity program (IG). One hundred and seventy-nine patients (n = 179; 67.2 (9.1) years; 106 women) were allocated to the control group (CG). The IG went through a three-month standardized physical activity program led by physical activity specialists and linked to community resources.

Measures

The total number of medical appointments to the PHC, during twelve months before and after the program, was registered. Self-reported health status (SF-12 version 2) was assessed at baseline (month 0), at the end of the intervention (month 3), and at 12 months follow-up after the end of the intervention (month 15).

Results

The IG had a significantly reduced number of visits during the 12 months after the intervention: 14.8 (8.5). The CG remained about the same: 18.2 (11.1) (P = .002).

Conclusions

Our findings indicate that a 3-month physical activity program linked to community resources is a short-duration, effective and sustainable intervention in inactive patients to decrease rates of PHC visits.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00714831","term_id":"NCT00714831"}}NCT00714831     

Structures of the Substrate-free and Product-bound Forms of HmuO,a Heme Oxygenase from Corynebacterium diphtheriae: X-RAY CRYSTALLOGRAPHY AND MOLECULAR DYNAMICS INVESTIGATION*?

Heme oxygenase catalyzes the degradation of heme to biliverdin, iron, and carbon monoxide. Here, we present crystal structures of the substrate-free, Fe³⁺-biliverdin-bound, and biliverdin-bound forms of HmuO, a heme oxygenase from Corynebacterium diphtheriae, refined to 1.80, 1.90, and 1.85 Å resolution, respectively. In the substrate-free structure, the proximal and distal helices, which tightly bracket the substrate heme in the substrate-bound heme complex, move apart, and the proximal helix is partially unwound. These features are supported by the molecular dynamic simulations. The structure implies that the heme binding fixes the enzyme active site structure, including the water hydrogen bond network critical for heme degradation. The biliverdin groups assume the helical conformation and are located in the heme pocket in the crystal structures of the Fe³⁺-biliverdin-bound and the biliverdin-bound HmuO, prepared by in situ heme oxygenase reaction from the heme complex crystals. The proximal His serves as the Fe³⁺-biliverdin axial ligand in the former complex and forms a hydrogen bond through a bridging water molecule with the biliverdin pyrrole nitrogen atoms in the latter complex. In both structures, salt bridges between one of the biliverdin propionate groups and the Arg and Lys residues further stabilize biliverdin at the HmuO heme pocket. Additionally, the crystal structure of a mixture of two intermediates between the Fe³⁺-biliverdin and biliverdin complexes has been determined at 1.70 Å resolution, implying a possible route for iron exit.     

Scorpion toxins for the reversal of BoNT-induced paralysis

The botulinum neurotoxins, characterized by their neuromuscular paralytic effects, are the most toxic proteins known to man. Due to their extreme potency, ease of production, and duration of activity, the BoNT proteins have been classified by the Centers for Disease Control as high threat agents for bioterrorism. In an attempt to discover effective BoNT therapeutics, we have pursued a strategy in which we leverage the blockade of K⁺ channels that ultimately results in the reversal of neuromuscular paralysis. Towards this end, we utilized peptides derived from scorpion venom that are highly potent K⁺ channel blockers. Herein, we report the synthesis of charybdotoxin, a 37 amino acid peptide, and detail its activity, along with iberiotoxin and margatoxin, in a mouse phrenic nerve hemidiaphragm assay in the absence and the presence of BoNT/A.