Overexpression, purification, and characterization of glutaminase-interacting protein, a PDZ-domain protein from human brain

A human brain cDNA clone coding for a novel PDZ-domain protein of 124 amino acids has been previously isolated in our laboratory. The protein was termed GIP (glutaminase-interacting protein) because it interacts with the C-terminal region of the human brain glutaminase L. Here we report the heterologous expression of GIP as a histidine-tagged fusion protein in Escherichia coli cells. The induction conditions (temperature and isopropyl beta-d-thiogalactopyranoside concentrations) were optimized in such a way that GIP accounted for about 20% of the total E. coli protein. A simple and rapid procedure for purification was developed, which yielded 17 mg of purified GIP per liter of bacterial cell culture. The apparent molecular mass of the protein by SDS-PAGE was 16 kDa, whereas in native form it was determined to be 28 kDa, which suggests dimer formation. The nature and integrity of the recombinant protein were verified by mass spectrometry analysis. The functionality of the GIP protein was tested with an in vitro activity assay: after being pulled down with glutathione S-transferase-glutaminase, GIP was revealed by Western blot using anti-GIP antibodies. Furthermore, the glutaminase activity in crude rat liver extracts was inhibited by the presence of recombinant purified GIP protein.

GaAs(2 5 11): a new stable surface within the stereographic triangle

The atomic structure of GaAs(2 5 11), a hitherto unknown stable surface, has been determined by in situ scanning tunneling microscopy and first-principles electronic structure calculations. This orientation is located within the stereographic triangle, i.e., far away from all low-index surfaces. A low-energy ( 1x1) reconstruction containing arsenic dimers forms on the surface. The analysis of the surface structure shows that, for semiconductor surfaces, the gain in stability due to minimization of the number of dangling bonds is more important than the gain from rendering a semiconducting ground state.

[C reactive protein as marker of infection among patients with severe closed trauma]

BACKGROUND

Injury and infection are characterized by the activation of the acute phase proteins response. C-reactive protein (CRP), an acute phase protein, has been mentioned as an useful indicator of infection and sepsis in critically ill patients.

OBJECTIVE

To study the evolution of serum CRP in patients with severe blunt trauma and to ascertain its ability as a biological marker of infection during the first seven days after injury.

METHODS

We prospectively studied 54 patients with blunt trauma (injury severity score>=16) age>14 years and length of the Intensive Care Unit (ICU) estay>= 7 days, over a 4-month period. Culture-proven infections were collected and serum CRP was determinated every day, during the first week after ICU admission.

RESULTS

Twenty-eight patients (51.8%) developed an infection during the first week, and the median day of diagnosis of infection was day 6. Pneumonia was the most common infection (50%) and Gram-negative bacilli (63.3%) were the most common microorganisms recovered. Serum CRP levels were significantly higher in the infected patients group after day 4, showing a median value higher than 170 mg/l. Based on the receiver operating characteristic (ROC) curve analysis, a cutoff value of 109.5 mg/l for CRP gives a sensitivity of 78.6% and a specifity of 73.1% in predicting the presence of infection.

CONCLUSIONS

The course of serum CRP levels is different in the group of patients with severe blunt trauma and infection, compared with the non-infected group during the first week after injury and it could be an useful supplementary marker for infection after postinjury day 4. A value of 110 mg/l or higher for CRP should suggest an underlying infectious complication.

Ehrlich ascites tumor cells expressing anti-sense glutaminase mRNA lose their capacity to evade the mouse immune system

Glutaminase (EC 3.5.1.2) is a key enzyme in rapidly proliferating cells. Using anti-sense technology, an Ehrlich ascites tumor cell line (0.28AS-2) with reduced glutaminase activity has been obtained. We investigated the in vivo growth characteristics of the 0.28AS-2 cells. When injected i.p. into normal Swiss albino mice, the 0.28AS-2 cells were unable to grow. On the contrary, when injected into nude mice, they developed into solid tumors. Mice inoculated with 0.28AS-2 cells kept immunologic memory and rejected a second inoculation with parental Ehrlich ascites tumor cells. Expression of both polymorphic epithelial mucin-1 (MUC-1) and the enzyme N-acetyl-alpha-D-galactosaminidase, proteins implicated in host immune system escape, were markedly diminished in 0.28AS-2 cells. Study of the immune system response in mice inoculated with 0.28AS-2 cells revealed an increase in splenic CD18 cells and the presence of a large number of activated F4/80+ macrophages in the ascites cavity. These features, not observed in mice inoculated with parental Ehrlich ascites tumor cells, indicate that a distinctive, strong immune response occurred in animals inoculated with 0.28AS-2 cells. Our results suggest that inhibition of glutaminase expression using anti-sense technology induces phenotypic changes in Ehrlich ascites tumor cells that allow the development of an effective anti-tumor immune response, which makes the cells unable to develop in vivo tumors.

The C-terminus of human glutaminase L mediates association with PDZ domain-containing proteins

The enzyme glutaminase in brain is responsible for the synthesis of neurotransmitter glutamate. We used the two-hybrid genetic selection system in yeast to look for interactors of glutaminase in human brain. We have identified two proteins containing PDZ domains, alpha1-syntrophin and a glutaminase-interacting protein, named GIP, that showed association with human glutaminase L, as deduced from specificity test of the two-hybrid system. The complete GIP cDNA clone has 1315 nucleotides with a 372-base open reading frame encoding a 124-amino acids protein. Glutaminase associates with both PDZ proteins through its C-terminal end; mutagenesis of single amino acids revealed the sequence -ESXV as essential for the interaction. These data suggest the possibility that PDZ domain-containing proteins are involved in the regulation of glutaminase in brain.

Atomic Structure of the Stoichiometric GaAs(114) Surface

The stoichiometric GaAs(114) surface has been prepared using molecular beam epitaxy followed by annealing in ultrahigh vacuum. Based on in situ scanning tunneling microscopy measurements and first-principles electronic-structure calculations, we determine the surface reconstruction which we call alpha2(2x1). Contrary to what is expected for a high-index surface, it is surprisingly elementary. The (2x1) unit cell contains two As dimers and two rebonded Ga atoms. The surface energy is calculated as 53 meV/Å(2), which falls well within the range of low-index GaAs surface energies.

Identification of two human glutaminase loci and tissue-specific expression of the two related genes

Glutaminolysis is initiated by either of two isoforms, K- and L-types, of the enzyme phosphate-activated glutaminase. The chromosomal localization, genomic organization, and the tissue-specific expression of the genes have been investigated in the human by using isoform-specific cDNA probes. Results obtained from radiation hybrid mapping experiments assigned the K-glutaminase gene to human Chromosome (Chr) 2, and a second locus for L-glutaminase in Chr 12 was identified. Southern blot analysis with the L-cDNA probe showed hybridization to a single restriction fragment, while four to seven fragments were found to hybridize to the K-cDNA probe. The distribution of human glutaminase expression was also investigated: the L-cDNA probe detected a single band of 2.4 kb in liver, brain, and pancreas, whereas a single transcript of approximately 4.4 kb was detected in kidney, brain, heart, placenta, lung, and pancreas by using the K-cDNA probe. This work provides evidence that the human liver and kidney glutaminase isozymes are encoded by separate genes located on different chromosomes; furthermore, the expression pattern in human tissues revealed for both isoenzymes differs notably from the paradigm based upon the isoenzyme distribution in rats.

Ehrlich ascites tumour unbalances splenic cell populations and reduces responsiveness of T cells to Staphylococcus aureus enterotoxin B stimulation

Tumours must avoid host immune response to survive and proliferate; to achieve this purpose, tumours interact with cells of the immune system by means of tumour secreted factors. The alterations of splenic cell populations in mice bearing the Ehrlich ascites tumour have been studied. A rapid and acute response was observed, characterized by a decrease in both CD4 and CD8 T cells, and a transient increase in the number of B cells, which peaked 2 days after tumour inoculation. An increase in macrophage population and in the homing antigen CD18 was also detected. In vitro incubations of splenic cells with the Staphylococcus aureus enterotoxin B (SEB) showed that tumour induces a state of reduced responsiveness to stimulation of T cells, mainly affecting CD8 T cells, and a diminished IFN-gamma expression.

Effect of spinal cord and peripheral nerve injury on human cutaneous sensory corpuscles. An immunohistochemical study

This study was aimed at analyzing the changes in cutaneous sensory corpuscles from the territory of lesioned nerves and clinically denervated skin of patients with spinal cord injury using immunohistochemical methods. The morphological and biochemical characteristics of the Schwann-related cells of the mature sensory corpuscles (lamellar cells of Meissner corpuscles and inner-core of Pacinian corpuscles) depend upon the axon. To clarify whether this dependence requires structural and/or functional integrity of sensory axons we analyzed immunohistochemically some axonal, Schwann cell and perineurial cell antigens in cutaneous sensory corpuscles from i) the underlesional levels of patients with spinal cord injury affecting dorsal and lateral funiculi; ii) peripheral nerve entrapment, iii) sectioned and grafted nerves. Skin biopsy samples from the hand or feet were processed for peroxidase-antiperoxidase immunohistochemistry using monoclonal antibodies directed against neurofilament proteins (to label the axons), S-100 protein (to label Schwann-related cells), epithelial membrane antigen (to label the perineurial derivatives), vimentin (to label both Schwann cell and perineurial derivatives). Meissner and Pacinian corpuscles of subjects suffering from spinal cord lesions showed an immunohistochemical profile close to normality, although in many of them S-100 protein was unevenly distributed or absent. Sensory corpuscles of the cutaneous territory of entrapped nerves were in most cases similar to those of normally innervated skin. The most striking finding in these subjects was the hyperinnervation of blood vessels and sweat glands. Finally, nerve section and subsequent unsuccessful graft repair resulted in absence of immunostaining for all the assessed antigens in sensory corpuscles. The present results suggest that structural, but not functional, integrity of the axon is essential in maintaining some immunohistochemical characteristics of the human cutaneous sensory corpuscles. Morphological findings are correlated and discussed in relation to the clinical evaluation of the sensitivity.

Inhibition of glutaminase expression by antisense mRNA decreases growth and tumourigenicity of tumour cells

Phosphate-activated glutaminase has a critical role in tumours and rapidly dividing cells and its activity is correlated with malignancy. Ehrlich ascites tumour cells transfected with the pcDNA3 vector containing an antisense segment (0.28 kb) of rat kidney glutaminase showed impairment in the growth rate and plating efficiency, as well as a shortage in the glutaminase protein and activity. The C-terminal segment used is well conserved in all glutaminase sequences known. The transfected cells, named 0.28AS-2, displayed remarkable changes in their morphology compared with the parental cell line. The 0.28AS-2 cells also lost their tumourigenic capacity in vivo. Control mice developed an ascitic tumour, with a lifespan of 16+/-1 days, when inoculated with 10(7) cells/mouse; on the contrary, animals inoculated with transfected cells up to 2.5 times the cell numbers of control mice did not develop tumours and behaved as healthy animals. The ability to revert the transformed phenotype of antisense-transfected cells confirms the relevance of glutaminase in the transformation process and could provide new ways for the study of gene therapy.

Changes in mRNAs for enzymes of glutamine metabolism in the tumor-bearing mouse

Changes in the relative mRNA levels of phosphate-activated glutaminase (PAG) and glutamine synthetase (GS) in the liver and kidney of mice bearing a highly malignant strain of Ehrlich ascites tumor cells were determined at different days after tumor transplantation. Kidney glutaminase mRNA steadily increased, reaching maximum values at day 10 of tumor growth, while those of glutamine synthetase did not change, resulting in a sustained decrease of the GS/PAG ratio in the kidneys of tumor-bearing animals compared with controls. However, the GS/PAG ratio in the liver significantly increased, mainly due to a strong decrease in PAG, whereas GS mRNA levels remained almost unaffected. These results, combined with those previously reported on enzymatic activities and glutamine concentrations in the host-tumor system, suggest a long-term regulation of the host glutaminase enzymes in order to increase the circulating glutamine levels needed for tumor growth.

Radiometric homogenization of the color cryosection images from the VHP lungs for 3D segmentation of blood vessels

This work deals with the problem of radiometric inhomogeneities found on the physical color images of the anatomical cryosections from the Visible Human Project (VHP) male body. Our goal is to extract very thin structures, like the blood vessel tree from the lungs. Current segmentation methods applied to VHP color images are disturbed by discontinuous, inter-slice radiometric variations; we thus devised an adaptive correction that is propagated along a series of parallel slices, taking advantage of the structural coherence between consecutive slices. No blurring is introduced, and fine details and texture are respected. Results of 3D segmentation of fine blood vessels on the corrected volume are presented.

Plant regeneration from callus and suspension cultures of Valeriana edulis ssp. procera via simultaneous organogenesis and somatic embryogenesis

Plants of the genus Valeriana produce irioid esters of biotechnological interest, known as valepotriates. The regeneration of Valeriana edulis ssp. procera via indirect organogenesis and somatic embryogenesis from leaf-derived callus and suspension cultures, is presented. For induction of callus, leaves were cultured on semisolid MS medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin. Embryogenic and organogenic callus development was observed after 16 weeks. Calli were transferred to semisolid and liquid Murashige and Skoog (MS) medium supplemented with kinetin and 1-naphthaleneacetic acid (NAA). Appearance of shoot and somatic embryo occurred 4 weeks later. Shoots were rooted and somatic embryos were germinated and were transferred to the greenhouse. A better organogenic and embryogenic response was observed from suspension cultures. Histological observations of morphogenic callus revealed that both somatic embryos and shoots arose from the same type of callus.

Molecular cloning, sequencing and expression studies of the human breast cancer cell glutaminase

Phosphate-activated glutaminase (GA) is overexpressed in certain types of tumour but its exact role in tumour cell growth and proliferation is unknown. Here we describe the isolation of a full-length cDNA clone of human breast cancer ZR75 cells, by a combination of lambdagt10 cDNA library screening and the rapid amplification of cDNA ends ('RACE') technique. The cDNA of human GA is 2408 nt with a 1806-base open reading frame encoding a 602-residue protein with a predicted molecular mass of 66309 Da. The deduced amino acid sequence contains a putative mitochondrial import presequence of 14 residues at the N-terminal end. Heterologous expression and purification in Escherichia coli yielded a product of the expected molecular size that was recognized by using antibodies against the recombinant human GA. Sequence analyses showed that human GA was highly similar to the rat liver enzyme. Northern gel analysis revealed that the gene is present in human liver, brain and pancreas, in which a major transcript of 2.4 kb was demonstrated, but not in kidney, heart, skeletal muscle, lung or placenta. These results strongly suggest that the first human GA cloned, the GA from ZR-75 breast cancer cells, and presumably those from human liver and brain, are liver-type isoenzymes, in sharp contrast with the present view that considers the kidney type as the isoform expressed in all tissues with GA activity, with the exception of postnatal liver.

Upregulation of glyceraldehyde-3-phosphate dehydrogenase mRNA in the spleen of tumor-bearing mice

The influence of tumor implantation on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels and stability was determined in the spleen of tumor-bearing mice. While GAPDH mRNA levels were not altered in skeletal muscle, kidney and liver from tumor-bearing mice, tumor implantation led to a 5.6-fold increase in the levels of splenic GAPDH mRNA. An enhanced message stability was observed in splenocytes from tumor-bearing animals, suggesting the involvement of post-transcriptional mechanisms in the selective GAPDH mRNA accumulation after tumor implantation. The GAPDH activity/glycolytic flux ratio was 18.5 in the spleen of healthy mice. Therefore, the three-fold increase in the glycolytic flux observed after tumor implantation could hardly justify the necessity for the upregulation of GAPDH.

A randomized blinded clinical trial of two antivenoms, prepared by caprylic acid or ammonium sulphate fractionation of IgG, in Bothrops and Porthidium snake bites in Colombia: correlation between safety and biochemical characteristics of antivenoms

A randomized blinded clinical trial was performed in 53 patients bitten by Bothrops sp. and Porthidium sp. in Antioquia and Chocó, Colombia, in order to compare the efficacy and safety of two antivenoms made of whole IgG obtained by either ammonium sulphate (monovalent anti-B. atrox) or caprylic acid (polyvalent) fractionation. Additionally, antivenoms were compared by electrophoretic and chromatographic analyses and anticomplementary activity in vitro. With a protocol of 2, 4 and 6 antivenom vials for the treatment of mild, moderate and severe envenomings, respectively, both antivenoms were equally efficient to neutralize the most relevant signs of envenoming and to clear serum venom levels in patients from the first hour and later on. Three patients with severe envenoming and initially treated with less than six vials on admission had persistent or recurrent venom antigenemia within 12-48 h. Monovalent antivenom fractionated by ammonium sulphate precipitation had higher amounts of protein aggregates and nonimmunoglobulin proteins than polyvalent antivenom fractionated by caprylic acid precipitation. Both antivenoms presented anticomplementary activity in vitro, being higher in the monovalent product. In agreement, monovalent antivenom induced a significantly higher incidence of early antivenom reactions (52%) than polyvalent antivenom (25%).

Subcutaneous fat necrosis of the newborn

Subcutaneous fat necrosis of the newborn (SFN) is an uncommon disease that affects newborns who have suffered from tissue hypoxia during or following delivery. This disease appears during the first weeks of life. It consists of indurate, erythematous or purple-erythematous nodules and plaques in the skin. Histology of a biopsy specimen shows granulomatous necrosis in the subcutis with radial crystals in lipocytes and giant cells. Spontaneous resolution in a few weeks is usual, but the mobilization of calcium from the necrosed subcutis together with the action of some hormones may cause hypercalcemia and certain serious complications. A newborn female child developed SFN after dystocic delivery causing cerebral frontal lobe hemorrhage. The skin nodules resolved spontaneously in a few weeks and no complications were observed 1 year later.

Involvement of essential cysteine and histidine residues in the activity of isolated glutaminase from tumour cells

The pH dependence of the phosphate-activated glutaminase isolated from Ehrlich tumour cells suggests a functional role for two prototropic groups with apparent pKa of 9.3 and 7.7 at the active site of the protein; these pKa values are compatible with cysteine and histidine residues, respectively. This possibility was investigated by chemical modification studies of the purified enzyme. N-Ethylmaleimide fully inactivated the purified glutaminase; the reaction order was very close to 1.0, suggesting that N-ethylmaleimide modifies glutaminase at a single essential site. Spectrophotometric studies of the isolated protein treated with diethyl pyrocarbonate indicate that two histidine residues are modified. Since glutaminase is loosely associated to the inner mitochondrial membrane, modification experiments were also carried out using mitochondrial membrane fractions. N-Ethylmaleimide and diethyl pyrocarbonate gave similar results in mitochondria membrane-bound enzyme to those obtained with purified enzyme. Glutamate, which behaves as a competitive inhibitor of the enzyme, partially protected the inactivation caused by N-ethylmaleimide in membrane-bound experiments. The results suggest the existence of a critical histidine residue(s) in the tumour glutaminase, and strongly support the notion that a cysteine residue, which is located at (or near) the active site, is involved in the catalytic mechanism as well.

Early differential expression of two glutaminase mRNAs in mouse spleen after tumor implantation

The influence of progressive tumor growth on phosphate-activated glutaminase (PAG) expression in splenocytes from mice bearing Ehrlich ascites carcinoma cells was investigated. Implantation of Ehrlich ascites tumor cells in the peritoneal cavity of mice led to a 2.3-fold stimulation of spleen PAG activity 48 h later. Four days after tumor implantation the glutaminase activity had returned to nearly basal value and remained at this level throughout the tumor development. Northern blot analysis indicated that two species of glutaminase mRNA were expressed in the spleen, which showed a differential expression pattern during the first 2 days after tumor implantation. The abundance of the transcript of higher electrophoretic mobility (approximately 3 kb) constantly increased over the first 2 days of tumor growth. The mRNA of lower electrophoretic mobility (approximately 6 kb) peaked at 12 h after tumor implantation and returned to control values at 48 h. These results demonstrate that tumor has the capability of altering glutaminase expression in the host spleen.

Roughness feature of metaphase chromosome spreads and nuclei for automated cell proliferation analysis

As a step towards automation of mitotic index estimation for cell proliferation studies, a roughness feature of surface-intensity images is introduced: the mean depth-width ratio of extrema (MDWRE). This feature allows identification of variable-shaped metaphases and interphase nuclei in the presence of many artefacts (one metaphase per hundreds of nuclei and thousands of artefacts). The texture of the cytological objects (seen as rough surfaces) is quantified by scanning, in one dimension, the lines contained in a closed contour. MDWRE proves to be suitable for image magnifications by a factor of as low as ten, making faster scanning of slides possible. The use of this feature gives +14%, +65%, +133% and +133% better performance figures than classical textural features derived from co-occurrence matrices, such as contrast, energy, entropy and angular second moment, respectively, and +51% better than the relative extrema density (RED). The MDWRE per object and the shape of the histogram of the depth-width ratio of grey-level roughs have been shown to be very useful as textural features for the classification of metaphase images.

[The absence of interference between GSM mobile telephones and implantable defibrillators: an in-vivo study. Groupe Systèmes Mobiles]

INTRODUCTION AND OBJECTIVES

The electromagnetic field created by mobile telephones can cause pacemaker dysfunction. Although implantable cardioverter defibrillators are also susceptible to electromagnetic interference, few studies have addressed this issue and compatibility with the GSM mode has not been tested. This study was developed to detect possible "in vivo" interference between GSM mobile telephones and implantable cardioverter defibrillators.

MATERIAL AND METHODS

The study group is composed of 30 patients with 8 different models of defibrillators. Twenty six had endocardial leads and 4 epicardial. Three GSM mobile phones were used: Siemens S3 COM and Motorola 6200 in all cases and Ericsson GA 318 in one. The tests were performed under continuous electrocardiographic monitoring. All therapies were deactivated and sensitivities were set to maximal parameters. The telephones were positioned in close contact to the defibrillator can and precordium, in two different angles. Three situations were evaluated: calling, established contact for 15 seconds and ringing. The protocol was repeated during pacing to assess the possibility of pacemaker mode inhibition.

RESULTS

No cases of electromagnetic interference were observed. One patient presented non-sustained ventricular tachycardia episodes during the tests that were detected by the defibrillator.

CONCLUSIONS

These results suggest that electromagnetic interference by GSM mobile phones are not a probable cause of implantable defibrillators dysfunction.

Early tumor effect on splenic Th lymphocytes in mice

Tumors are characterized by their ability to avoid the host immune system. Ehrlich ascites tumor cells were used to investigate the early alterations of the host immune system after tumor inoculation. The results show that frequencies of splenic Th lymphocytes were drastically reduced during tumor growth, reaching a minimum only two days after tumor inoculation. The frequency of splenic CD4+ lymphocytes expressing IFN-gamma was significantly increased, although the total number was unchanged, suggesting that there was no net induction of Th1-type response. Splenic macrophages were increased, in both frequency and cell number, after four days of tumor growth. The same pattern was observed when mice were inoculated with cell free ascitic fluid. TGF-beta precursors were detected in tumor cells as well as in ascitic fluid. The data suggest that tumor actively interacts with host immune system by means of tumor cell secreted factors.