Dynamics of Chronic Liver Injury in Experimental Models of Hepatotoxicity

BACKGROUND

In humans, chronic liver disease (CLD) is a serious clinical condition with many life-threatening complications. Currently, there is no therapy to stop or slow down the progression of liver fibrosis. Experimental mouse models of CLD, induced by repeated intraperitoneal injections of carbon tetrachloride (CCL4) and D-galactosamine (D-GalN), can be used to evaluate therapies that cannot be performed in humans. A major drawback of these animal models is the different dynamics of liver fibrosis progression depending on the animal strain, administered hepatotoxin, its dose, duration of intoxication, and frequency of injections. The aim of this study was to describe and compare the dynamics of progression of pathological changes in the BALB/c mouse and Sprague Dawley rat models of CLD induced by CCl4 and D-GalN. We defined the onset and duration of these changes and suggested the optimal time for therapeutic intervention in the analyzed CLD models.

METHODS

CLD was induced by repeated intraperitoneal injection of CCl4 in mice (12.5 μL/100 g bw every 5 days) and rats (25-100 μL/100 g bw twice a week) and D-GalN in mice (75 mg/100 g bw twice a week) and rats (25 mg/100 g bw twice a week). Blood and liver samples were collected at weeks 2, 4, 6, 8, 10, and 12 of intoxication. Liver injury and its progression were assessed by using complete blood count and liver function blood tests as well as by analyzing histopathological changes, including fibrosis, proliferation activity, apoptosis, stellate cell activation, and gene expression.

RESULTS

In mice and rats treated with CCl4, early fibrosis was observed in most pericentral areas from week 2 to 4 of intoxication. Established fibrosis developed in both rats and mice at week 6 of intoxication. Incomplete cirrhosis, defined as the presence of occasional cirrhotic nodules, was observed in rats at week 12 of intoxication. The dynamics of liver fibrosis in CCl4-treated animals were greater than in the D-GalN groups. In D-GalN-intoxicated rats and mice, the first signs of liver fibrosis were observed at weeks 4 and 10 of intoxication, respectively. The rats developed early fibrosis after 8 weeks of D-GalN intoxication. The progression of collagen deposition was accompanied by histological changes and alteration of certain genes and blood liver parameters.

CONCLUSIONS

The dynamics of liver fibrosis in CCl4 treated rodents is greater than in the D-GalN treated ones. In the CCl4 models, two appropriate times for therapeutic intervention are indicated, which to varying degrees reflect the real clinical situation and may potentially differ in the obtained results: early intervention before week 4 of intoxication (early fibrosis) and late intervention after week 8 of intoxication (when signs of established fibrosis are present). Rodent models of D-GalN-induced fibrosis are not recommended due to the long incubation period and weak toxic effect.

An Update on "Reverse Vaccinology": The Pathway from Genomes and Epitope Predictions to Tailored, Recombinant Vaccines

In this chapter, we review the computational approaches that have led to a new generation of vaccines in recent years. There are many alternative routes to develop vaccines based on the concept of reverse vaccinology. They all follow the same basic principles-mining available genome and proteome information for antigen candidates, and recombinantly expressing them for vaccine production. Some of the same principles have been used successfully for cancer therapy approaches. In this review, we focus on infectious diseases, describing the general workflow from bioinformatic predictions of antigens and epitopes down to examples where such predictions have been used successfully for vaccine development.

Differentiation of Cells Isolated from Afterbirth Tissues into Hepatocyte-Like Cells and Their Potential Clinical Application in Liver Regeneration

Toxic, viral and surgical injuries can pose medical indications for liver transplantation. The number of patients waiting for a liver transplant still increases, but the number of organ donors is insufficient. Hepatocyte transplantation was suggested as a promising alternative to liver transplantation, however, this method has some significant limitations. Currently, afterbirth tissues seem to be an interesting source of cells for the regenerative medicine, because of their unique biological and immunological properties. It has been proven in experimental animal models, that the native stem cells, and to a greater extent, hepatocyte-like cells derived from them and transplanted, can accelerate regenerative processes and restore organ functioning. The effective protocol for obtaining functional mature hepatocytes in vitro is still not defined, but some studies resulted in obtaining functionally active hepatocyte-like cells. In this review, we focused on human stem cells isolated from placenta and umbilical cord, as potent precursors of hepatocyte-like cells for regenerative medicine. We summarized the results of preclinical and clinical studies dealing with the introduction of epithelial and mesenchymal stem cells of the afterbirth origin to the liver failure therapy. It was concluded that the use of native afterbirth epithelial and mesenchymal cells in the treatment of liver failure could support liver function and regeneration. This effect would be enhanced by the use of hepatocyte-like cells obtained from placental and/or umbilical stem cells.

Assessment of animal experimental models of toxic liver injury in the context of their potential application as preclinical models for cell therapy

Preclinical animal models allow to study development and progression of several diseases, including liver disorders. These studies, for ethical reasons and medical limits, are impossible to carry out in human patients. At the same time, such experimental models constitute an important source of knowledge on pathomechanisms for drug- and virus-induced hepatotoxicity, both acute and chronic. Carbon tetrachloride, D-Galactosamine, and retrorsine are xenobiotics that can be used in immunocompetent animal models of hepatotoxicity, where chemical-intoxicated livers present histological features representative of human viruses-related infection. A prolonged derangement into liver architecture and functions commonly lead to cirrhosis, eventually resulting in hepatocellular carcinoma. In human, orthotopic liver transplantation commonly resolve most the problems related to cirrhosis. However, the shortage of donors does not allow all the patients in the waiting list to receive an organ on time. A promising alternative treatment for acute and chronic liver disease has been advised in liver cell transplantation, but the limited availability of hepatocytes for clinical approaches, in addition to the immunosuppressant regiment required to sustain cellular long-term engraftment have been encouraging the use of alternative cell sources. A recent effective source of stem cells have been recently identified in the human amnion membrane. Human amnion epithelial cells (hAEC) have been preclinically tested and proven sufficient to rescue immunocompetent rodents lethally intoxicated with drugs. The adoption of therapeutic procedures based on hAEC transplant in immunocompetent recipients affected by liver diseases, as well as patients with immune-related disorders, may constitute a successful new alternative therapy in regenerative medicine.

A New Strain Collection for Improved Expression of Outer Membrane Proteins

Almost all integral membrane proteins found in the outer membranes of Gram-negative bacteria belong to the transmembrane β-barrel family. These proteins are not only important for nutrient uptake and homeostasis, but are also involved in such processes as adhesion, protein secretion, biofilm formation, and virulence. As surface exposed molecules, outer membrane β-barrel proteins are also potential drug and vaccine targets. High production levels of heterologously expressed proteins are desirable for biochemical and especially structural studies, but over-expression and subsequent purification of membrane proteins, including outer membrane proteins, can be challenging. Here, we present a set of deletion mutants derived from E. coli BL21 Gold (DE3) designed for the over-expression of recombinant outer membrane proteins. These strains harbor deletions of four genes encoding abundant β-barrel proteins in the outer membrane (OmpA, OmpC, OmpF, and LamB), both single and in all combinations of double, triple, and quadruple knock-outs. The sequences encoding these outer membrane proteins were deleted completely, leaving only a minimal scar sequence, thus preventing the possibility of genetic reversion. Expression tests in the quadruple mutant strain with four test proteins, including a small outer membrane β-barrel protein and variants thereof as well as two virulence-related autotransporters, showed significantly improved expression and better quality of the produced proteins over the parent strain. Differences in growth behavior and aggregation in the presence of high salt were observed, but these phenomena did not negatively influence the expression in the quadruple mutant strain when handled as we recommend. The strains produced in this study can be used for outer membrane protein production and purification, but are also uniquely useful for labeling experiments for biophysical measurements in the native membrane environment.

An evolutionarily conserved glycine-tyrosine motif forms a folding core in outer membrane proteins

An intimate interaction between a pair of amino acids, a tyrosine and glycine on neighboring β-strands, has been previously reported to be important for the structural stability of autotransporters. Here, we show that the conservation of this interacting pair extends to nearly all major families of outer membrane β-barrel proteins, which are thought to have originated through duplication events involving an ancestral ββ hairpin. We analyzed the function of this motif using the prototypical outer membrane protein OmpX. Stopped-flow fluorescence shows that two folding processes occur in the millisecond time regime, the rates of which are reduced in the tyrosine mutant. Folding assays further demonstrate a reduction in the yield of folded protein for the mutant compared to the wild-type, as well as a reduction in thermal stability. Taken together, our data support the idea of an evolutionarily conserved ‘folding core’ that affects the folding, membrane insertion, and thermal stability of outer membrane protein β-barrels.

Reverse Vaccinology: The Pathway from Genomes and Epitope Predictions to Tailored Recombinant Vaccines

In this chapter, we review the computational approaches that have led to a new generation of vaccines in recent years. There are many alternative routes to develop vaccines based on the technology of reverse vaccinology. We focus here on bacterial infectious diseases, describing the general workflow from bioinformatic predictions of antigens and epitopes down to examples where such predictions have been used successfully for vaccine development.

Extremely fast increase in the organic loading rate during the co-digestion of rapeseed oil and sewage sludge in a CSTR--characterization of granules formed due to CaO addition to maintain process stability

In a co-digestion system running with rapeseed oil and sewage sludge, an extremely fast increase in the organic loading rate was studied to develop a procedure to allow for flexible and demand-driven energy production. The over-acidification of the digestate was successfully prevented by calcium oxide dosage, which resulted in granule formation. Mineralogical analyses revealed that the granules were composed of insoluble salts of long chain fatty acids and calcium and had a porous structure. Long chain fatty acids and calcium formed the outer cover of granules and offered interfaces on the inside thereby enhancing the growth of biofilms. With granule size and age, the pore size increased and indicated degradation of granular interfaces. A stable biogas production up to the organic loading rate of 10.4 kg volatile solids m(-3) d(-1) was achieved although the hydrogen concentration was not favorable for propionic acid degradation. However, at higher organic loading rates, unbalanced granule formation and degradation were observed. Obviously, the adaption time for biofilm growth was too short to maintain the balance, thereby resulting in a low methane yield.

A prospective, randomized, unicenter study comparing laparoscopic and open treatments of acute appendicitis

BACKGROUND

Appendectomy in the course of acute appendicitis is one of the most frequently performed surgical procedure in general surgery. The aim of this study was to compare the results of laparoscopic and conventional treatments for acute appendicitis in a prospective, randomized, unicenter study.

METHODS

The study involved 200 patients treated for acute appendicitis in the Department of General and Vascular Surgery at Ceynowa Hospital in Wejherowo, Poland.

RESULTS

The mean operative time for open surgery was 36.99 min. For laparoscopic method the operation was longer, requiring 47.75 min. Suction drainage was applied in 23 patients treated conventionally and 50 patients treated laparoscopically ( p < 0.05). The requirement for analgesia, measured by the number of metamizole ampules, was significantly higher in the conventional group. Pain on postoperative days 2 and 7 measured using a visual analog scale, was significantly more severe for the patients treated conventionally. The hospital stay in both groups did not differ significantly: 5.03 days for the conventional group and 4.71 days for the laparoscopic group. The time until return to work and social activities in the laparoscopic group (15.85 days) and was significantly shorter than in the conventional group (19.65 days). Seven complications occurred in the conventional group (6.7%) and nine (9.4%) in the laparoscopic group. The difference was not statistically significant. No deaths occurred.

CONCLUSIONS

On the basis of the conducted study, it may be assumed that laparoscopic appendectomy is a safe procedure, and that postoperative morbidity is comparable with that for a conventional operation. There was less postoperative pain and shorter recovery time after laparoscopic surgery than after the open procedure.

Asymmetric hydrogenation of dehydrodipeptides bearing different protecting groups

N-[(Z)-N-Benzoyl- or N-boc-(2-fluorophenyl)dehydroalanyl]-(R)- or (S)-phenyl-alanines 1,2,5 and 6 were hydrogenated in the presence of chiral and achiral rhodium complexes. The optical induction is compared to the results obtained using the corresponding esters as substrates.

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.