Contact-mediated acceleration of migration of melanoma B16 cells depends on extracellular calcium ions

The escape of malignant cells from primary tumour and their active migration to the surrounding tissues are among the most important steps in the metastatic process. During migration, tumour cells interact with neighbouring neoplastic and normal cells and such interactions may affect their motile activity. We investigated the effect of extracellular calcium ions on migration of mouse melanoma B16 cells stimulated by homotypic cell-to-cell contacts. It was found that the decreasing of extracellular Ca2+ influx into B16 cells by lowering Ca2+ concentration in culture medium, or by the application of 0.5 mM La3+ (non-selective inorganic Ca2+ channels blocker), reduced the contact-mediated acceleration of migration of melanoma cells but only slightly affected the basal motile activity of non-stimulated single, separated cells moving without contacts with neighbouring ones in sparse culture. Since it was suggested that contact-mediated acceleration of migration of melanoma B16 cells may be controlled by mechanosensitive and/or voltage-gated ion channels, the presented data support the concept that these channels may affect cell migration by regulation of extracellular Ca2+ influx into stimulated cell.

[Laparoscopic cholecystectomy in elderly patients]

The report presents results of the treatment of cholecystolithiasis in old patients (65 years). We compared two groups of the patients: first group treated using laparoscopic method, second group (control) where we performed classic cholecystectomy. Both of these groups were comparable according to age and sex.

NMR spectra of fluorinated carbohydrates

Recent advances in structural and conformational analysis of fluorinated carbohydrates by NMR spectroscopy are reviewed. Characteristic 1H, 13C, and 19F NMR chemical shifts and coupling constants for selected examples are given and the spectral data of a series of fluorinated carbohydrates were collected in continuation of the review of Csuk and Glänzer [Adv. Carbohydr. Chem. Biochem., 46 (1988) 73-177].

[Gastric neurilemmoma complicated by gastroduodenal intussusception and with bleeding from the digestive tract]

A case of Gastric Neurilemmoma with bleeding and gastroduodenal intussusception was described.

Asymmetric hydrogenation of dehydrodipeptide esters bearing different protective groups

N-[(Z)-N-Benzoyl- or N-Boc-(2-fluorophenyl)dehydroalanyl]-(R)- or (S)-phenylalanine esters were synthesized and hydrogenated to give the corresponding dipeptide derivatives with optical yields in the range of 53-87% de using the cationic rhodium complexes of PROPRAPHOS and BPPM. The efficiency of chiral diphosphine ligands as well the effect of the chiral center in the substrate on the catalytic asymmetric induction was studied.

Unusual amino acids. VIII. Asymmetric hydrogenation of some heteroaryl-N-Cbz and N-Boc aminocinnamic acid derivatives

(Z)-alpha-[(Benzyloxy)- or (tert.-butyloxy)carbonylamino]-beta (thienyl)- or (furyl)-acrylic acids and their esters were prepared by known methods and hydrogenated to the corresponding optically active alanine derivatives with optical yields in the range of 58-93% ee using the cationic rhodium complex of "PROPRAPHOS".

Changes in morphology of human skin fibroblasts induced by local anaesthetics: role of actomyosin contraction

Local anaesthetics block action potentials in the membranes of excitable cells but their effects on non-excitable cells are less well known. Some local anaesthetics are applied directly onto the skin, and for this reason the effect of procaine (p-aminobenzoic acid diethylamino-etyl ester hydrochloride) and tetracaine (4-[butylamino]benzoic acid 2-[dimethylamino]ethyl ester) upon the morphology and cytoskeleton organisation of human skin fibroblasts was investigated. The time lapse video recording of fibroblasts cultured in serum-enriched medium revealed that the cells rapidly change shape after the addition of the anaesthetic. These effects were fully reversible. The microscopic observations were confirmed by quantitative analysis of projected cell area and cell shape parameters. Local anaesthetics significantly changed the actin cytoskeleton organisation, inducing total disappearance of stress fibres. Serum-starvation or myosin light chain kinase inhibitors, KT 5926 inhibitor (8R*,9S*,11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-14-n-propoxy-2,3 ,9, 10-tetrahydro-8,11-epoxy,1H,8H,11H-2,7b,11a-triazadibenzo[a,g]c ycloocta[cde] trinden-1-one or wortmannin, which induce the 'relaxed' morphology of the cells, prevent both the anaesthetic-induced changes in cell shape and the disassembly of stress fibres. Together, the observations suggest that local anaesthetics affect the actomyosin system, inducing contraction.

[Acute ischemia of the leg as a result of femoral artery injury in the course of continuous arteriovenous hemofiltration]

The acute ischaemia of an inferior limb in the course of continuous arteriovenous hemofiltration (CAVH) after cannulization, in the patient with multiorgan insufficiency caused by acute pancreatitis was performed. In spite of the complete artery closing, hemofiltration course was proper.

Regulation of the glutamate dehydrogenase activity in rat islets of Langerhans and its consequence on insulin release

Kinetic properties of glutamate dehydrogenase (GDH) and the effects on its activity of several putative modulators were examined in mitochondrial extracts of rat pancreatic islets. In the presence of 40 mmol/L NH4Cl and 0.1 mmol/L NADH, stepwise elevation of the 2-oxoglutarate concentration from 0.005 to 0.05 mmol/L increased glutamate formation, whereas further increases led to a progressive decrease of the reaction velocity. Adenosine diphosphate (ADP) at 0.1 mmol/L partially and at 1 mmol/L completely reversed the inhibitory effect of 2-oxoglutarate. The sensitivity to activation by either ADP or leucine was dependent on 2-oxoglutarate concentrations. At higher concentrations of the latter, greater amounts of the activators were needed to attain maximal effect. In the absence of allosteric activators, sulfate or phosphate at 20 mmol/L partially released the inhibitory effect of 2-oxoglutarate levels and increased the maximal velocity (Vmax) for the reaction. In the presence of 0.1 mmol/L ADP, both anions prevented the inhibition by higher concentrations of 2-oxoglutarate, whereas with 1 mmol/L ADP their only effect was a slight increase in the Vmax. Mg2+ and naturally occurring polyamines decreased glutamate formation in a dose-dependent manner; with 0.1 mmol/L ADP, inhibition was seen at all 2-oxoglutarate concentrations studied, whereas with 1 mmol/L ADP, it was noticeable at substrate concentrations higher than 0.5 mmol/L. This inhibitory effect on GDH activity was partially attenuated by sulfate. Addition of either 2 mmol/L spermidine or extra magnesium (final 2.5 or 5 mmol/L) to the perifusion buffer markedly attenuated the insulin release elicited by alpha-ketoisocaproate. It is suggested that naturally occurring polyamines, magnesium, and phosphate act as physiological modulators of GDH activity in pancreatic beta cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzamide-induced changes in the actin cytoskeleton in human skin fibroblasts

The incubation of human skin fibroblasts in the presence of 10 mM benzamide in Joklik's modification of Eagle's Minimal Essential Medium caused an extensive reorganization of actin filaments. The disappearance of stress fibers and changes in cell morphology were observed, whereas no changes in the microtubule architecture were noticed. The observed effects appeared fully reversible within 3 hours after the removal of benzamide. The results are discussed in relation to the two known activities of benzamide as an anaesthetic and an inhibitor of ADP-ribosylation.

Inhibition of glutamate dehydrogenase in brain mitochondria and synaptosomes by Mg2+ and polyamines: a possible cause for its low in vivo activity

Magnesium and the polyamines putrescine, spermidine, and spermine inhibited the activity of glutamate dehydrogenase in permeabilized rat brain mitochondria in a concentration-dependent manner. The inhibitory effect was observed on both the reductive amination of 2-oxoglutarate and oxidative deamination of glutamate, as well as in the presence and absence of ADP and leucine, the allosteric activators of the enzyme. Kinetic studies at various concentrations of substrates showed that inhibition by magnesium and spermine was very pronounced at 2-oxoglutarate concentrations less than 0.5 mM and NADH levels less than 0.08 mM. The presence of the former compounds also accentuated the inhibitory effect of high concentrations of 2-oxoglutarate (> 2.0 mM) and NADH (> 0.32 mM). Addition of magnesium and spermine to suspensions of synaptosomes decreased the amount of ammonia produced from glutamate. It is suggested that polyamines and magnesium, normal constituents of mammalian brain, are responsible, at least in part, for the low glutamate dehydrogenase activity in vivo.

GABA production in rat islets of Langerhans

Homogenates of pancreatic islets catalyzed breakdown of L-glutamate to GABA with a rate of 0.24 +/- 0.04 nmol.min-1 x mg-1 protein at 37 degrees C. The formation of GABA was stimulated by addition of pyridoxal phosphate in the range 0.05-1 microM (0.97 +/- 0.02 nmol.min-1 x mg protein-1 at a saturating cofactor concentration), which indicates that the process was catalyzed by glutamic acid decarboxylase. The half-maximal effect was obtained with 0.1 microM PLP. Kinetic analyses of the results showed that the Vmax and Km for the reaction were 1.12 nmol.min-1 x mg protein-1 and 0.66 mM, respectively. The pH optimum was 7.0. Subcellular fractionation revealed that 51% of GAD activity was present in the cytosol, 17% in microsomes, 9% in secretory granules, 5% in mitochondria, and 11% in cell debris. Comparison of the kinetic properties of the cytosolic and microsomal forms of the enzyme showed that their Km for glutamate was the same, but that the cytosolic GAD had a lower Km for PLP. GABA synthesis in the nominal absence of PLP was enhanced by malate (twofold increase at 5 mM) and citrate (threefold increase at 5 mM), but was unaffected by ATP and chloride. However, if the islet homogenate was prepared and incubated in the presence of PLP, neither malate nor citrate influenced enzyme activity. Aspartate and AOA were powerful inhibitors of glutamate breakdown. Freshly isolated islets contained approximately 4 mM GABA, whereas the concentration was < 0.1 mM in whole pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamate production in islets of Langerhans: properties of phosphate-activated glutaminase

Homogenates of rat pancreas, pancreatic islets, and HIT-T15 cells (a clonal line derived from B cells) catalyzed the breakdown of glutamine to glutamate. This activity was markedly stimulated by the addition of orthophosphate and was much greater in homogenates from islets and the B-cell-derived clonal cell line than in those from whole pancreas. Islet glutaminase was half-maximally stimulated with 40 mmol/L phosphate. Kinetic analyses of the rates of glutamine hydrolysis showed that the Vmax for the reaction increased with the increase in phosphate concentration, whereas the Km for glutamine (2.6 +/- 0.2 mmol/L) was unaltered. The pH optimum for enzyme activity was 8.0 to 8.5 at all phosphate concentrations studied. Glutamine breakdown was enhanced by adenosine triphosphate ([ATP] approximately 100% at 10 mmol/L) and citrate (approximately 30% at 10 mmol/L), but it was unaffected by malate, 2-oxoglutarate, lactate, and ammonia. Glutamate significantly inhibited glutamine hydrolysis. Freshly isolated islets had a low content of both glutamate and glutamine. After culturing for 1 hour in an amino acid-containing medium, the concentrations of glutamine and glutamate increased. Subsequent perifusion without amino acids caused a loss of glutamine and a concomitant increase in glutamate level. Perifusion with 1 mmol/L glutamine led to an increase in both internal glutamine and glutamate. The addition to the perifusion medium of either 10 mmol/L glutamine, 10 mmol/L orthophosphate, or both substantially enhanced insulin release evoked by 10 mmol/L leucine.(ABSTRACT TRUNCATED AT 250 WORDS)

Differentialin vivo andin vitro effect of gentamicin on glutamate synthesis and glutamate deamination in rabbit kidney-cortex tubules and mitochondria

The effect of gentamicin on both glutamate synthesis and glutamate deamination was studied in kidney-cortex mitochondria and tubules isolated from both control and gentamicin-treated animals. In kidney-cortex mitochondria which were permeabilized in order to make a free access of substrates and antibiotic to the glutamate dehydrogenase, gentamicin appeared to be a very potent inhibitor of glutamate synthesis, resulting in about 60% decrease of the enzyme activity at 5 mM concentration. Other aminoglycoside antibiotics decreased the enzymatic activity, in the following order: gentamicin > neomycin = tobramycin = kanamycin > biodacyna > amikacin > streptomycin. This, in principle, corresponds to their known nephrotoxic potential observed in vivo. The inhibitory action of antibiotics was abolished by neither ADP nor leucine, allosteric activators of glutamate dehydrogenase. Surprisingly, gentamicin did not decrease the rate of ammonia formation from glutamate when added to both renal tubules and mitochondria isolated from control rabbits. This indicates that the antibiotic exerts its inhibitory effect on glutamate dehydrogenase activity in the direction of glutamate synthesis only. In contrast, the rate of both glutamate deamination and glutamate synthesis was about 40% lower in renal tubules and mitochondria isolated from kidney-cortex of animals which were given antibiotics for 10 days. In view of these results it seems that (i) the depression of ammoniagenesis in gentamicin-treated animals may be due to a decrease of glutamate dehydrogenase content and (ii) under conditions in vitro the aminoglycoside inhibits the enzyme activity in the direction of glutamate synthesis while it does not affect the glutamate deamination.

Recovery of impaired gluconeogenesis in kidney-cortex tubules of gentamicin-treated rabbits

Rabbits were given gentamicin over a period of 10 days. At 1, 3, 5 and 10 days renal proximal tubules were isolated and glucose synthesis from several substrates was measured. A relationship between the inhibition of renal gluconeogenesis, accompanied by a decline of both pyruvate carboxylase and phosphoenopyruvate carboxykinase (PEPCK) activities, and an increased gentamicin level in kidney-cortex was noticed after 5 days of therapy. Both the rates of glucose formation from various substrates as well as pyruvate carboxylase and the cytosolic PEPCK activity recovered fully within 3 weeks after cessation of antibiotic treatment while an increase of activity of the mitochondrial PEPCK occurred during chronic administration of the drug for 10 days. It is concluded, that gentamicin-induced inhibition of gluconeogenesis is one of the events occurring during complex action of this drug on renal cortex.

Classification of brain tumours by CT-image Walsh spectra

Besides clinical and anamnestic data, image information from CT-image data in the tumour border was used for classification of brain tumours. If the image regions are properly selected a classification rate of 85% is obtained with a hierarchic classifier, although our study is based on only 139 patients.

Calcium-dependent effect of gentamicin on glucose formation in isolated rabbit kidney-cortex tubules

In contrast to the inhibition by gentamicin of glucose production from propionate, pyruvate and lactate in renal tubules incubated at 2.5 mM Ca2+, this antibiotic does not affect gluconeogenesis from propionate and lactate, and significantly stimulates this process from other substrates at 0.5 mM Ca2+. This may be due to the gentamicin-induced increase of the cytosolic manganese content (from 1.7 to 2.7 nmol/mg protein), resulting in a stimulation of cytosolic phosphoenolpyruvate carboxykinase activity. At 2.5 mM Ca2+ the cytosolic Mn content (2.7 nmol/mg protein) seems to be high enough to accomplish activation of the enzyme.

Effect of various aminoglycoside antibiotics on glucose formation in isolated rabbit kidney-cortex tubules

The effect of six aminoglycoside antibiotics on the rate of gluconeogenesis was studied in isolated rabbit kidney-cortex tubules incubated with various substrates. All antibiotics studied did not affect glucose formation from both malate and 2-oxoglutarate. The rank order of the drug-induced inhibition of glucose formation from lactate, pyruvate and propionate was the following: neomycin = gentamicin greater than tobramycin greater than kanamycin = amikacin greater than streptomycin. This in principle corresponds to their ability to diminish pyruvate carboxylation in isolated kidney-cortex mitochondria, as well as to their known nephrotoxic potential observed in vivo. Aminoglycoside antibiotics decreased the respiration of tubule suspension incubated with various substrates. However, the rank order of the inhibition by antibiotics of oxygen uptake was different from that observed for gluconeogenesis, suggesting that the rate of energy generation does not limit glucose formation under conditions studied.