Cobalt Stabilization through Mesopore Confinement on TiO2 Support for Fischer-Tropsch Reaction.

Cobalt supported on mesostructured TiO2 catalysts has been prepared by a wet-impregnation method. The Co/TiO2 catalytic system showed better catalytic performance after support calcination at 380 °C. Co nanoparticles appeared well distributed along the mesopore channels of TiO2. After reduction pretreatment and reaction, a drastic structural change leads to mesopore structure collapse and the dispersion of the Co nanoparticles on the external surface. Along this complex process, Co species first form discrete nanoparticles inside the pore and then diffuse out as the pore collapses. Through this confinement, a strong metal-support interaction effect is hindered, and highly stable metal active sites lead to better performance for Fischer-Tropsch synthesis reaction toward C5+ products.

Reconstruction and catalytic activity of hybrid Pd(100)/(111) monolayer on γ-Al2O3(100) in CH4, H2O, and O2 dissociation.

The importance of the "heterogeneity" of a Pd monolayer induced by interaction with a semi-ionic support in catalysis was evaluated. The geometry of the Pd monolayer was optimized on the (100) plane of γ-Al2O3 at fixed unit cell parameters defined by the oxide. Simulation of the deposition of a whole Pd monolayer in the flat Pd(100) form cut from the bulk led to the formation of a slightly distorted Pd(111) monolayer. The subsequent chemisorption or dissociation of CH4 or H2O on the Pd(111) layer resulted in a new hybrid Pd(100)/(111) structure containing alternating elements of (100) and (111) planes (the parallel bands of squares and triangles), which are similar for both CH4 and H2O reactions, and two isolated Pd mono-vacancies, respectively. The hybrid Pd(100)/(111) layer without chemisorbed species was found to be more stable than the initial distorted Pd(111) layer. The catalytic capabilities of these monolayer structures were investigated for the dissociation of methane and the water-gas shift reaction (WGSR) due to the lower predicted activation barriers for CH4, H2O, and O2 dissociation on the hybrid Pd(100)/(111) layer compared to that on the pure (bulk) Pd(100) surface. Moreover, the exothermic heats of these reactions were calculated to be moderate instead of endothermic heats on the Pd(100) or Pd(111) surfaces. The heats of H2O and NH3 adsorption on various monolayers were tested, revealing their dependence on Pd atomic charges. The relevance of the model of the heterogeneous Pd monolayer for explaining the maximum reaction rate experimentally observed at different Pd coverages was discussed. The transferability of the geometry and the extent of charge inhomogeneity of the hybrid monolayer without vacancies were also tested on the same γ-Al2O3(100) support for Pt, Rh, and Ag.

Comparison of estimated energy requirements in severely burned patients with measurements by using indirect calorimetry.

Severe burn injuries give rise to an extreme state of physiological stress. No other trauma results in such an accelerated rate of tissue catabolism, loss of lean body mass, and depletion of energy and protein reserves. A heightened attention to energy needs is essential, and the significance of adequate nutritional support in the complex management of patients with major burns is very important. The purpose of this study is to compare the results obtained by three of the most popular methods of estimating energy requirements in severely burned adult patients with the measurements of resting energy (REE) expenditure by indirect calorimetry (IC). A prospective study was carried out of 20 patients (male/female ratio, 17/3; mean age, 37.83 ± 10.86 yr), without accompanying morbidities, with burn injuries covering a mean body surface area of 34.27 ± 11.55% and a mean abbreviated burn severity index of 7.44 ± 1.58. During the first 30 days after trauma, the energy requirements were estimated using the Curreri, Long, and Toronto formulas. Twice weekly measurements of REE by IC were obtained. It was found that the Curreri and Long formulas overestimated the energy requirements in severely burned patients, as found by other investigators. However, no significant difference was found between the daily energy requirements calculated by the Toronto formula and the measured REE values by IC. It is concluded that the Toronto formula can be used as an alternative method for estimating the energy requirements of patients with major burns in cases where IC is not available or not applicable.

Beta2-adrenoceptor-mediated prejunctional facilitation and postjunctional inhibition of sympathetic neuroeffector transmission in the guinea pig vas deferens.

This study examines the role of prejunctional and postjunctional beta-adrenoceptors in the modulation of sympathetic cotransmission in the guinea pig vas deferens. The prejunctional involvement of beta-adrenoceptors was evaluated by testing the effects of several agonists and antagonists on the nerve stimulation-evoked overflow of ATP and norepinephrine (NE) from the "in vitro" vas deferens. The nonsubtype-selective beta-adrenoceptor agonist isoproterenol and the beta2-subtype-selective agonist clenbuterol increased, to a similar degree, the overflow of ATP and NE, while the beta1-subtype-selective agonist xamoterol and the beta3-subtype-selective agonist BRL 37 344 had no effect. Pretreatment with ICI 118, 551, a beta2-subtype-selective antagonist, abolished the facilitation of cotransmitter release by isoproterenol and clenbuterol, while the beta1-subtype-selective antagonist atenolol had no effect. Activation of beta-adrenoceptors by either isoproterenol or clenbuterol, but not by xamoterol and BRL 37 344, reduced the amplitude of contractions evoked by exogenously applied ATP. Pretreatment with propranolol or ICI 118, 551, but not atenolol, prevented these inhibitory effects. Isoproterenol in lower concentrations produced dose-dependent reduction of the purinergic but not the adrenergic phase of nerve stimulation-induced contraction of the guinea pig vas deferens. When applied in concentrations greater than 1 microM, isoproterenol, but not clenbuterol, actually produced a concentration-dependent facilitation of contractions evoked by both nerve stimulation and exogenously applied ATP. Antagonists of alpha-adrenoceptors blocked these facilitatory effects. Together, these results demonstrate that beta2-adrenoceptors can influence sympathetic neuroeffector transmission both prejunctionally, where they facilitate equally well the release of sympathetic cotransmitters and postjunctionally, where they inhibit smooth muscle contractions evoked by ATP.

Correlation between the release of the sympathetic neurotransmitter ATP and soluble nucleotidases from the guinea pig vas deferens.

Recently, we have shown that by releasing specific nucleotidases the sympathetic nerves of the guinea pig vas deferens may regulate the metabolism of extracellular adenine nucleotides and consequently, the inactivation of neurotransmitter ATP. Based on the evidence for tetrodotoxin sensitivity and calcium dependence of the nerve stimulation-evoked overflow of enzyme activity, we have suggested that soluble nucleotidases may be stored in synaptic vesicles within the sympathetic nerves and released upon arrival of nerve action potentials by a mechanism similar to that for release of neurotransmitters. To further test this hypothesis we studied the time course of nerve stimulation-evoked overflow of ATP, norepinephrine (NE), releasable ATPase (r-ATPase) activity, and releasable AMPase (r-AMPase) activity under control conditions and in the presence of drugs known to selectively modulate sympathetic neurotransmission. The results show that the time course of overflow of r-ATPase and r-AMPase activities resembles the transient pattern of overflow of ATP but not the tonic pattern of overflow of NE. Vasa deferentia dissected from animals treated with reserpine release ATP, r-ATPase, and r-AMPase, whereas the overflow of NE is completely abolished. Guanethidine, on the other hand, inhibits equally well the overflow of the two neurotransmitters and the releasable nucleotidase activities. Agonists of the alpha(2)-adrenergic receptors abolish the overflow of ATP, r- ATPase, and r-AMPase but not the overflow of NE. This evidence supports the idea that the sympathetic nerves of the guinea pig vas deferens store and release ATP together with specific nucleotidases responsible for the inactivation of this neurotransmitter.

The effect of P2 receptor antagonists and ATPase inhibition on sympathetic purinergic neurotransmission in the guinea-pig isolated vas deferens.

1. Intracellular microelectrodes were used to record the transmembrane potential and excitatory junction potentials (e.j.p.s) produced by sympathetic nerve stimulation (1 Hz) in smooth muscle cells of the guinea-pig isolated vas deferens. 2. The symmetrical 3'-urea of 8-(benzamido)naphthalene-1,3,5-trisulphonic acid (NF023) produced a concentration-dependent inhibition of e.j.p. magnitude (IC(50)=4. 8x10(-6) M), but had no effect on the resting membrane potential of the smooth muscle cells. 3. Pyridoxal-5-phosphate (P-5-P) also depressed e.j.p. magnitude in a concentration-dependent manner, but was less potent than NF023 (IC(50)=2.2x10(-5) M). At 10(-4) M and above P-5-P significantly depolarized the smooth muscle cells. 4. The nucleoside triphosphatase inhibitor 6-N,N-diethyl-D-beta, gamma-dibromomethyleneATP (ARL 67156) (5x10(-5) M) significantly increased e.j.p. amplitude. ARL 67156 (10(-4) M) further increased e. j.p. amplitude such that they often reached threshold for initiation of action potentials, causing muscle contraction and expulsion of the recording electrode. 5. After reduction of e.j.p.s by NF023 or P-5-P (both 10(-5) M), subsequent co-addition of ARL 67156 (10(-4) M) significantly increased their magnitude. 6. The overflow of endogenous ATP evoked by field stimulation of sympathetic nerves (8 Hz, 1 min) was measured by HPLC and flurometric detection. ARL 67156 (10(-4) M) enhanced ATP overflow by almost 700% compared to control. 7. We conclude that for electrophysiological studies NF023 is preferable to other P2X receptor antagonists such as pyridoxalphosphate -6-azophenyl-2',4'-disulphonic acid (PPADS), suramin or P-5-P. Furthermore, breakdown of endogenous ATP by nucleoside triphosphatases is an important modulator of purinergic neurotransmission in the guinea-pig vas deferens.

Modulation of purinergic neurotransmission.

During the past 25 years ATP has become accepted as an important neurotransmitter at a wide variety of neuroeffector junctions, usually acting as a cotransmitter with NA, ACh, nitric oxide or a neuropeptide such as NPY or VIP. The details of the storage and release of ATP with its cotransmitters has yet to be resolved. However, recent studies indicate that there is more than one population of storage vesicles in the nerves, since the release of the various cotransmitters varies over time and can be differentially modulated by drugs. The subclassification of P2 receptors has advanced dramatically in the past few years due to the use of molecular biology methods allowing the cloning and expression of 14 different subclasses of P2 receptors, seven P2X and seven P2Y. Determination of the functional significance of the various receptor subtypes would be helped by the development of selective agonists and antagonists. The neurotransmitter action of ATP at visceral and vascular smooth muscle P2X receptors has been elucidated in considerable detail. ATP induces a transient inward current via ligand-gated channels, which produces EJPs, action potentials and a phasic contraction of the effector tissue. ATP's neurotransmitter actions appear to be curtailed by the action of ATPases. It has been assumed that this ATPase activity is due to membrane bound ecto-ATPases on the surface of the effector tissue, however, the recently identified soluble ATPase released during nerve stimulation could also be involved in inactivation of ATP. The relative importance of ecto-ATPase and the releasable ATPase is yet to be determined.

Differential cotransmission in sympathetic nerves: role of frequency of stimulation and prejunctional autoreceptors.

Recent reports have suggested that sympathetic nerves may store separately and release independently the cotransmitters ATP and norepinephrine (NE). It is conceivable therefore that the quantity of each neurotransmitter that is released from the nerves is not fixed but rather may vary, possibly with the frequency of stimulation. To test this hypothesis we studied the concomitant release at various frequencies and cooperative postjunctional actions of ATP and NE during the first 10 s of electrical field stimulation of the guinea pig vas deferens. We found that at lower frequencies (8 Hz), prejunctional inhibition of the release of NE, which occurs via alpha2-adrenoceptors, modulates the ultimate composition of the cocktail of cotransmitters by limiting the amount of NE that is coreleased with ATP. As the frequency of stimulation increases (above 8 Hz), the autoinhibition of the release of NE is overridden and the amount of NE relative to ATP increases. The smooth muscle of the guinea pig vas deferens reacts to changes in composition of the sympathetic neurochemical messages by increasing the amplitude of its contractions due to the enhancement by NE of the contractile responses triggered by ATP. This evidence suggests that the prejunctional alpha2-adrenoceptor may function as a sensor that "reads" the frequency of action potentials produced during a burst of neuronal activity and converts that information into discrete neurochemical messages with varying proportions of cotransmitters. The mechanism for decoding the informational content of these messages is based on the cooperative postjunctional interactions of the participating cotransmitters.

Neuronal release of soluble nucleotidases and their role in neurotransmitter inactivation.

Efficient control of synaptic transmission requires a rapid mechanism for terminating the actions of neurotransmitters. For amino acids and monoamines, this is achieved by their uptake into the cell by specific high-affinity transporters; acetylcholine is first broken down in the extracellular space and then choline is taken up by the cell. Because ATP is hydrolysed to adenosine by membrane-bound enzymes (ectonucleotidases) that are present in most tissues, it has been assumed that these enzymes terminate the neurotransmitter actions of ATP in the brain and in the periphery. We show here, however, that stimulation of sympathetic nerves innervating the guinea-pig vas deferens releases not only neuronal ATP, but also soluble nucleotidases that break down this ATP to adenosine, indicating that inactivation of ATP is increased by nerve activity. This release of specific nucleotidases together with ATP represents a new mechanism for terminating the actions of a neurotransmitter.

Differences between the regulation of noradrenaline and ATP release.

1. We have studied the effects of adrenergic receptor agonists and antagonists and various calcium channel antagonists on the overflow of adenine nucleotides (ATP, ADP, AMP), adenosine (ADO) and noradrenaline (NA) from superfused guinea-pig vasa deferentia evoked by electrical field stimulation (EFS). 2. Samples of superfusate were taken at 10 s intervals for analysis of purines (HPLC with fluorescence detection) and of NA (HPLC with electrochemical detection). During 1 min of EFS the overflow of ATP peaked at about 20 s and then abruptly decreased even though stimulation continued. The overflow of NA reached a peak at about 40 s and remained at a constant level for the duration of the stimulation. 3. Pretreatment with the alpha 2-receptor antagonists idazoxan and yohimbine produced a substantial increase in the overflow of NA and a lesser increase in the overflow of ATP, indicating that endogenously released NA has a greater influence on its own release than on that of ATP. Interestingly, certain alpha 2-agonists. e.g. xylazine and clonidine, produce a greater reduction in ATP release than NA. Together the results suggest that the release of ATP and NA may be regulated by different subsets of prejunctional alpha 2-receptors. 4. The N-type calcium channel antagonist omega-conotoxin reduced the EFS-evoked release of NA to a greater extent than ATP while the P-type calcium channel antagonist omega-agatoxin did the reverse. These results indicate that NA release may be more dependent on calcium influx through N-type channels whereas ATP release is coupled to calcium entry through P-type channels. 5. These differences in the pharmacological regulation of ATP and NA release lend credence to the idea that these two co-transmitters originate from different release sites in adrenergic nerves.

Evidence for the differential release of the cotransmitters ATP and noradrenaline from sympathetic nerves of the guinea-pig vas deferens.

1. Experiments were carried out to quantify the stimulation-evoked overflow of catecholamines and purines (ATP, ADP, AMP and adenosine) from an in vitro sympathetic nerve-smooth muscle preparation of the guinea-pig vas deferens and from isolated bovine adrenal chromaffin cells. The superfused preparations were stimulated for 60 s with electrical field stimulation (EFS; vas deferens), dimethylphenylpiperazinium (chromaffin cells) or KCl (both preparations). 2. Samples of superfusate were taken at 10 s intervals during the 60 s stimulation period for analysis of purines by HPLC-fluorescence detection and catecholamines by HPLC-electrochemical detection. 3. The evoked overflow of catecholamines and purines from chromaffin cells occurred with the same time course and in a constant ratio of approximately 4:1 (catecholamine to purine). These findings are compatible with the release of catecholamines and purines from a homogeneous population of exocytotic vesicles in the chromaffin cells. 4. The evoked overflow of purines and noradrenaline (NA) from the vas deferens preparation differed from the pattern of overflow from chromaffin cells and there was also some temporal disparity in the overflow of the two cotransmitters. The evoked overflow of ATP exceeded that of NA. In addition, the overflow of NA was tonic while the overflow of ATP and the other purines was phasic. 5. The EFS-evoked overflow of NA and the purines from the guniea-pig vas deferens preparation was examined after treatment with the neuronal amine-uptake inhibitors desipramine and cocaine, the alpha 1-adrenoceptor agonist methoxamine, the alpha 1-adrenoceptor antagonist prazosin, the alpha 2-adrenoceptor antagonists idazoxan and yohimbine, the noradrenaline-depleting drug reserpine and the adrenergic neuron-blocking agent guanethidine. The results of these studies, together with an analysis of the metabolic degradation of extracellular ATP, indicated that the temporal disparity in the overflow of NA and ATP is unlikely to be due to differences in the clearance of the cotransmitters or to the release of purines from non-neuronal sites. These results indicate that evoked overflow of the cotransmitters accurately reflects release from nerves. This pattern of release from nerves suggests that the two cotransmitters are released from two separate populations of exocytotic vesicles. 6. Superfusion of the vas deferens with exogenous epsilon-ATP, a fluorescent derivative of ATP, revealed that there was essentially no metabolism of the nucleotide over 60 s unless the tissue was subjected to EFS. Upon EFS, there was a rapid and nearly complete degradation of ATP with a corresponding increase in ADP, AMP and adenosine. This indicates the presence of a nerve stimulation-dependent metabolism of ATP.

Urinary excretion of glycosaminoglycans in patients with postmenopausal osteoporosis.

The organic bone matrix contains glycosaminoglycans (GAG) of which the precise function and importance in bone mineralisation are still unclear. We examined 85 persons--35 healthy women (25 premenopausal [preMP] mean aged 40.7 years; 10 menopausal [MP] mean aged 59.3 years) and 50 patients with postmenopausal osteoporosis [PMOP] at a mean age 60.4 years. The dynamic of urinary excretion of GAG was measured in 24-hour collected urine by precipitation with cetylpyridinum chloride and spectrophotometry at 560 nm, corrected for the level of excretion of creatinine. There was a significant increase in GAG excretion in patients with PMOP compared with healthy persons (8.25 mg/g and 9.53 mg/g vs 24.11 mg/g; p < 0.0001). A significant positive correlation was established between GAG and calcium urinary excretion and a negative one between GAG and serum estradiol levels. During the treatment with calcitonin the excretion of GAG was decreased which can be used for monitoring the changes of bone metabolism.

[Calcium-phosphorus metabolism and calcitrophic hormones in patients with active acromegaly with and without osteoporosis]. / Kaltsievo-fosforen obmen i kaltsitrofichni khormoni pri bolni s aktivna akromegaliia sus i bez osteoporoza,

Calcium-phosphor metabolism was studied in patients with active acromegaly with or without osteoporosis, mean age 45.2 +/- 11.4 years and mean duration of the basic disease 5.52 +/- 3.6 years. No significant deviations and no direct relation with the high serum growth hormone and prolactin levels were found. The normal basic secretion of the calcitrophic hormones--parathyroid hormone and calcitonin and their normal response to the hypercalcemia after intravenous calcium load of the patients with and without osteoporosis reject their direct participation in the pathogenesis of osteopenia. The changed skeletal sensitivity to calcitrophic hormones closely connected with the patients' age and the duration of the basic disease in combination with many other factors probably plays a major role in the pathogenesis of osteopenia.

[Treatment of patients with postmenopausal and steroid-induced osteoporosis using sodium fluoride combined with vitamin D2 and calcium gluconate]. / Lechenie na bolni s postmenopauzalna i steroidindutsirana osteoporoza s natriev fluorid v kombinatsiia s vitamin D2 i kaltsiev gliukonat.

9 patients with postmenopausal and 5 patients with steroid-induced osteoporosis, mean age 57.9 +/- 7.76 years, were treated in the course of one year with sodium fluoride (Fluosen) in a dose of 45 mg/24 h in combination with calcium gluconate (2 g/24 h) and oil solution of vit D2 (2 mg/week). In the course of the treatment a considerable easing of the pains in the most affected parts of the skeleton was found and the height remained at the same level before and after the treatment. This correlates with the statistically significant increase of the serum levels of the total alkaline phosphatase and its bone isoenzyme by keeping a normal kalium phosphorous balance as well as with the x-ray data for retaining the bone changes liked with the osteoporosis.

[Some new points of view of cavity form]. / Niakoi novi vuzgledi za kavitetnata forma.

The discovery of new data about the anatomy and physiology of the dental tissues, the improvement of the diagnostics of dental caries and the development of stomatological materials and technique are preconditions for a change of some concepts for the preparation of the cavities and their form. A new trend in cavity preparation is discussed on the base of literature data, characterized by maximum sparing of the hard dental tissues and a change in some of the geometric characteristics of the cavity form but the basic requirements for the biological and technical expedience remain unaltered.

Preventive effect of captopril on the development of experimental hypertension in rats.

The arterial blood pressure (BP), the ratio between gram myocardial mass per 100 g body mass (R), the plasma renin activity (PRA) and the aldosteron content in the blood plasma (PA) were investigated in a model of renal hypertension, 30 days after the operation, in the following groups of male Wistar rats: operated and treated throughout the entire experimental period with captopril Pharmachim in a dose of 30 mg/kg body mass twice daily orally, and two control groups--operated and treated with saline, and non-operated animals of the same age, treated only with saline. BP, R and PA increase significantly in the control group with experimental hypertension. In the group treated with captopril PRA was more than doubled compared with the two control groups, with a considerable decrease in PA compared with the control group with hypertension. The results obtained for the captopril-treated experimental group (with the exception of PRA) are identical and close to the data for the control non-operated animals, i.e. the treatment of the experimental animals with captopril prevents the development of arterial hypertension and of myocardial hypertrophy with the coarctation hypertension model used.

[Treatment of patients with postmenopausal osteoporosis and steroid-induced osteoporosis with the preparation Rocaltrol (1,25/OH/2 vitamin D3)]. / Lechenie na bolni s postmenopauzna osteoporoza i steroidindutsirana osteoporoza s preparata rokaltrol (1,25/OH/2 vitamin D3).

A clinical trial of the drug "Rocaltrol" was carried out on 16 patients with osteoporosis, II of them with menopause osteoporosis and 5 with steroid-induced osteoporosis. The mean age of the patients was 53.1 +/- 11.1 years. The mean daily dose of the drug was 0.46 +/- 0.08 mg/24h. The treatment lasted 6 months. All patients showed improvement of the general condition and of calcium balance. Reliable increase of the total calcium and phosphorus levels and of the 24-hour calcium urine excretion were established, the maximal values being at the end of the third month. The X-ray examination showed stabilization of the bone changes and lack of new compression fractures. It is supposed that the drug improves the intestinal resorption of calcium and phosphorus and suppresses the bone resorption. This is proved by the reliable decrease of serum alkaline phosphatase level after the 6 month treatment. In all patients clinical improvement was established with diminishing of the bone aches and retaining the body height before and after the treatment.