IL-4 selectively inhibits IL-2-triggered Stat5 activation, but not proliferation, in human T cells

IL-2 activates several distinct signaling pathways that are important for T cell activation, proliferation, and differentiation into both Th1 and Th2 phenotypes. IL-4, the major cytokine that promotes differentiation of Th2 cells, has been shown to block signaling of the Th1-promoting cytokine IL-12. As IL-2 synergizes with IL-12 in promoting Th1 differentiation, the effects of IL-4 on IL-2 signal transduction were investigated. IL-4 suppressed activation of DNA binding and tyrosine phosphorylation of the transcription factor Stat5 by IL-2, and suppressed the expression of the IL-2-inducible genes CD25, CIS, the PGE2 receptor, and cytokine responsive (CR) genes CR1 and CR8. Activation of Stat5 by cytokines that share a common gamma receptor subunit, IL-2, IL-7, and IL-15, was suppressed by preculture in IL-4. Activation of the Jak1 and Jak3 kinases that are proximal to Stat5 in the IL-2-Jak-STAT signaling pathway was suppressed, and this correlated with inhibition of IL-2Rbeta subunit expression. In contrast to suppression of Stat5, proliferative responses to IL-2 were augmented in IL-4-cultured cells, and activation of proliferative pathways leading to activation of mitogen activated protein kinases, induction of expression of Myc, Fos, Pim-1, and cyclin D3, and decreased levels of the cyclin-dependent kinase inhibitor p27 were intact. These results identify molecular mechanisms underlying interactions between IL-4 and IL-2 in T cells and demonstrate that one mechanism of regulation of IL-2 activity is selective and differential modulation of signaling pathways.

Elevation of cerebral proteases after systemic administration of aluminum

The levels of three proteases in the cerebral cortex of rats following a three week exposure to aluminum, were measured. The activity of apopain (CPP32), an interleukin 1beta converting enzyme (ICE)-like cysteine protease specifically associated with apoptosis, was increased following dosing with aluminum. The activity of calcium-activated neutral protease, calpain, was also increased. However, the enzyme activity of trypsin-like serine protease, known to be elevated by oxidative events, was unchanged. Since aluminum is suspected as a possible factor in the pathogenesis of Alzheimer's disease and other neurological diseases, it is speculated that changed levels in proteolytic enzymes may relate to the neurotoxicity of aluminum.

Expression, purification, and characterization of recombinant Escherichia coli pyridoxine 5'-phosphate oxidase

A previously cloned pdxH gene from Escherichia coli coding for pyridoxine 5'-phosphate oxidase was transferred to a pET22b vector and expressed in E. coli HMS174(DE3) cells. The soluble overexpressed enzyme was rapidly purified in high yield using two chromatography columns with an overall purification of about 2.8-fold. The purified enzyme contained tightly bound FMN. The enzyme exhibited the same spectral properties and similar kinetic constants to those previously reported by G. Zhao and M. E.Winkler (J. Bacteriol. 177, 883, 1995), but differed from the properties reported by other investigators. A rapid procedure was developed for preparing apoPNP Ox in high yield. Both the holo- and apoenzymes were homodimers. The molar absorbtivity coefficient for the protein was determined for the fully active apoPNP Ox from is amino acid composition. Using this value and the spectral properties of the bound FMN it was shown by three different methods that the dimeric enzyme contains two molecules of bound FMN per dimer and not one FMN as previously reported.

An unassembled subunit of NAD(+)-dependent isocitrate dehydrogenase is insoluble and covalently modified

The NAD(+)-dependent isocitrate dehydrogenase of Saccharomyces cerevisiae is an octamer composed of four Idh1p subunits and four Idh2p subunits. Isocitrate dehydrogenase functions in the tricarboxylic acid cycle and has also been reported to bind to the 5' nontranslated region of mitochondrially encoded mRNAs. Mutants defective in either or both of these subunits are unable to grow on the nonfermentable carbon source, acetate, but will utilize glycerol or ethanol. Mutant strains lacking Idh2p maintain normal if not elevated levels of mitochondrial Idh1p. In addition to the mature unassembled Idh1p subunit, a complex of bands in the 85- to 170-kDa range (Idh1p-Cpx) is observed using NAD-IDH antiserum. Both Idh1p and Idh1p-Cpx are insoluble within the mitochondrion and are associated with the mitochondrial inner membrane. A histidine-tagged form of Idh1p was expressed in yeast strains. Chemical amounts of the Idh1p-Cpx could be purified from strains lacking Idh2p but not from strains containing normal levels of Idh2p. The data indicate that Idh1p-Cpx is an aggregated and cross-linked form of Idh1p that may be oxidized within the mitochondrion as a consequence of its aborted assembly.

Genetic complexity of the human geranylgeranyltransferase I beta-subunit gene: a multigene family of pseudogenes derived from mis-spliced transcripts

Geranylgeranyltransferase I controls the function of a variety of cellular proteins by attaching a geranylgeranyl group to the carboxy-terminus of proteins. The purified enzyme from rat brain is comprised of two polypeptides, a catalytic alpha-subunit (GGTalpha) and a substrate-binding beta-subunit (GGTbeta). The present paper demonstrates the existence of a GGTbeta multigene family in humans by describing the presence and characterization of at least 13 pseudogenes related to this protein. Sequencing of numerous PCR-derived clones, obtained following amplification of human genomic DNA, revealed multiple, distinct but highly related sequences. All clones had a common deletion of 99-bp that conforms to the GT-AG rule of splicing in eukaryotes, and differed from the human GGTbeta cDNA sequence by multiple nucleotide substitutions. PCR amplification from mRNA, however, yielded only the sequence expected for the expressed GGTbeta protein. This apparent paradox was resolved by cloning and sequencing a complete GGTbeta-specific pseudogene. Multiple features of the cloned gene, in particular the absence of introns, presence of flanking direct repeats, and the lack of sequence similarity with the untranscribed region of the gene, indicate that this clone represents a processed pseudogene possibly resulting from a mis-spliced transcript. Multiple GGTbeta-specific pseudogenes appear to have resulted from more than one retroposition event. These results suggest a potential role for mis-splicing in the evolutionary diversity of pseudogenes.

Effects of IFN-gamma, TNF-alpha and EGF on the expression of HLA class I antigen and the proliferation of human hepatocellular carcinoma HepG2 cells

In this study, the effects of IFN gamma, TNF alpha and EGF on the expression of HLA class I antigen and the proliferation of human hepatocellular carcinoma-HepG2 cells were investigated. In response to IFN gamma or TNF alpha stimulation, the expression of HLA class I mRNA in HepG2 cells was increased by 2-4 fold. Cell surface HLA class I antigen was also increased, but in comparison, the increase was not as high as HLA class I mRNA expression. This is probably due to the limitation of protein translational and post-translational processing. The enhancing effect of EGF on cell surface HLA class I antigen could be noted but was not very significant. IFN gamma and TNF alpha could also inhibit the proliferation of HepG2 cells. Interestingly, the effect of EGF on the proliferation of HepG2 cells depended on its concentration. At low concentrations, EGF increased cell proliferation in terms of thymidine incorporation. However, if the concentration of EGF was relatively high, it could also exert an inhibitory effect on thymidine incorporation into HepG2 cells. The remarkable morphological alteration was observed when HepG2 cells were exposed to EGF at concentrations higher than 5 ng/ml. This morphological alteration might be associated with the inhibitory effect of EGF at high concentrations on the proliferation of HepG2 cells.

Serine phosphorylation of death agonist BAD in response to survival factor results in binding to 14-3-3 not BCL-X(L)

Extracellular survival factors alter a cell's susceptibility to apoptosis, often through posttranslational mechanisms. However, no consistent relationship has been established between such survival signals and the BCL-2 family, where the balance of death agonists versus antagonists determines susceptibility. One distant member, BAD, heterodimerizes with BCL-X(L) or BCL-2, neutralizing their protective effect and promoting cell death. In the presence of survival factor IL-3, cells phosphorylated BAD on two serine residues embedded in 14-3-3 consensus binding sites. Only the nonphosphorylated BAD heterodimerized with BCL-X(L) at membrane sites to promote cell death. Phosphorylated BAD was sequestered in the cytosol bound to 14-3-3. Substitution of serine phosphorylation sites further enhanced BAD's death-promoting activity. The rapid phosphorylation of BAD following IL-3 connects a proximal survival signal with the BCL-2 family, modulating this checkpoint for apoptosis.

Adenovirus E1B 19-kDa death suppressor protein interacts with Bax but not with Bad

Adenovirus E1B 19-kDa protein (19K) is a member of the Bcl-2 family of suppressors of apoptosis. The suppressors function through heterodimerization with the death promoters, Bax and related proteins, thus establishing a set point within the cell that determines whether or not apoptosis is executed in response to a death signal. Sequence similarities between 19K and Bcl-2 are largely restricted to short Bcl-2 homology (BH) domains that mediate interaction with Bax. The BH1 sequence in 19K is degenerate but nevertheless contains a conserved glycine residue found in all family members that when mutated to alanine in Bcl-2 results in loss of Bcl-2 function and ability to dimerize with Bax (Yin, X.-M., Oltvai, Z. N., and Korsmeyer, S. J. (1994) Nature 369, 321-323). Here, we show that the analogous mutation in BH1 of 19K also abrogates the anti-apoptotic properties of 19K and its ability to interact with Bax, thus establishing the critical importance of this residue within BH1 and the likely similarity of Bcl-2 and 19K function. In distinct contrast to Bcl-2, however, 19K interaction was not detected with Bad, a Bcl-2/Bcl-XL dimerizing protein that can potentially regulate a Bax middle dotBcl-2/Bcl-XL survival set point and reinstate susceptibility to a death signal. Furthermore, the anti-apoptotic function of 19K was not overcome by enforced expression of Bad in transfected cells. This feature of 19K may provide adenovirus with a selective advantage in evading premature induction of apoptosis by the host cell.

Pw1, a novel zinc finger gene implicated in the myogenic and neuronal lineages

The cellular and molecular processes leading to the establishment of the skeletal muscle lineage in the vertebrate are not well understood. The MyoD-related family of myogenic regulatory factors (MRFs) are expressed during somitogenesis although cells with myogenic capacity are present prior to gastrulation. We propose that regulatory genes exist that guide the skeletal muscle lineage during early development. In an effort to identify these regulatory genes, we performed a differential screening to isolate transcripts that are present in myogenic cells and in the embryo prior to MRF expression but absent in nonmyogenic fibroblasts. We report here the identification of Pw1. The Pw1 transcript is approximately 8.5 kb long and encodes a large protein containing 12 widespread C2H2 zinc fingers and 3 motifs containing periodic prolines and acidic residues. Consistent with the possibility that Pw1 is a transcription factor, we observe nuclear localization of the protein. Pw1 is strongly expressed upon gastrulation and subsequently becomes restricted to skeletal muscle and subregions of the central nervous system. Pw1 is initially expressed in all mesodermal cells early in development; however, its maintained expression in adult differentiated muscle suggests a specific role in the skeletal muscle lineage. Pw1 expression is cell cycle specific with levels highest during late M-phase. The gene is intronless which may facilitate transcription during cell division. At present, the precise function of Pw1 is not understood; however, we note that Pw1 maps to the proximal region of chromosome 7 near the axial segmentation mutant pudgy which shows severe perturbation of axial skeletal and muscle structures.

Detection of Helicobacter pylori by polymerase chain reaction assay using gastric biopsy specimens taken for CLOtest

The concordance rate between a rapid urease test (CLOtest) and polymerase chain reaction (PCR) assay for the detection of Helicobacter pylori in gastric biopsy samples was investigated. To avoid the bias produced by patchy distribution of the organism in the stomach, the samples used for these two tests were not obtained from two different sites of the antrum. Instead, the PCR assay was performed with the the same biopsy sample that was taken for the CLOtest. Among 82 biopsy samples included for this study, 56 were positive and 26 were negative by CLOtest. Of the 56 CLOtest-positive samples, 52 (93%) were also positive by PCR assay, and of the 26 CLOtest-negative samples, 20 (78%) were negative by PCR assay. The total concordance rate of these two tests was 87.6%. Of the 4 cases with CLOtest-positive and PCR-negative results, 3 had been treated with long-term H2 blockers. Of the 6 patients with CLOtest-negative and PCR-positive results, 4 suffered from recurrent or poorly healing duodenal ulcers. Interestingly, a significantly lower density of the PCR products was observed during electrophoresis analysis for all the 6 cases, presumably due to a small number of H. pylori in these samples. These results indicated that PCR might be used as a complementary assay for CLOtest. False negative results by CLOtest might occur when only a small amount of H. pylori was present in the samples, which could be detected by subsequent PCR assays using the same biopsy specimens. The clinical significance of such CLOtest-negative and PCR-positive cases requires further study.

In vivo role of the Sp1 site neighboring sterol-responsive element-1 in controlling low-density lipoprotein receptor gene expression

The in vivo role of the crucial Sp1 site neighboring sterol-responsive element-1 (SRE-1) in controlling LDL receptor gene expression in the presence or absence of sterols was examined. For this purpose the Xenopus laevis system was utilized as there are two different genes for LDL receptors in frogs which differ in their promoter region in the Sp1-binding sequence of repeat 3 present immediately adjacent to SRE-1. DNase I footprinting of promoters of both receptors showed differences in the affinity of this Sp1 site to purified transcription factor Sp1. Transcript levels of both LDL receptors were measured in livers of frogs on normal and cholesterol-enriched diets. Basal levels and extent of repression of LDL receptor gene on sterol administration were found to be dependent on the nature of the Sp1 site of repeat 3 under in vivo conditions. We conclude that this Sp1 site acts as a constitutive positive transcriptional element that forms a part of the active transcription complex irrespective of cellular sterol levels.

"Childhood" viruses as a cause of pneumonia in adults

Respiratory viruses are a common cause of morbidity in childhood. Except in the child with immunodeficiency, the common respiratory viruses rarely pose a serious threat to life. Because infection with most of these viruses in childhood is nearly universal and usually bestows partial immunity, the "childhood respiratory viruses" are not generally thought of as being a cause of disease in adults. However, adults who work around children, who are frequently exposed to other adults and children with respiratory tract infections (as in a hospital clinic setting), or who are military recruits appear to be at risk of infection or reinfection with one of these agents. In addition, adults with immune deficiency are at a significant risk for serious infection. The risk of serious disease can be reduced by maximizing immunity with (re)immunization and optimal treatment of any underlying disorders. Tobacco smoke and respiratory irritants should be avoided and adults at risk for severe disease should avoid contact with infected children and adults as much as possible. Specific chemotherapy for viral pneumonia, when available, may reduce morbidity in selected individuals.

Shape response of human erythrocytes to altered cell pH

Alteration of red blood cell (RBC) pH produces stomatocytosis (at low pH) and echinocytosis (at high pH). Cell shrinkage potentiates high pH echinocytosis, but shrinkage alone does not cause echinocytosis. Mechanisms for these shape changes have not been described. In this study, measured dependence of RBC shape on cell pH was nonlinear, with a broad pH range in which normal discoid shape was maintained. Transbilayer distribution of phosphatidylcholine and phosphatidylserine, measured by back-extraction of radiolabeled lipid, was the same in control and altered pH cells. Possible roles of pH-titratable inner monolayer phospholipids were examined by assessing pH-dependent shape in cells in which their levels had been perturbed. In metabolically depleted cells and calcium-treated cells, which have altered levels of phosphatidic acid, phosphatidylinositol-4-phosphate, and/or phosphatidylinositol-4,5-bisphosphate, low cell pH was stomatocytogenic and high cell pH was echinocytogenic, as in control cells. Thus, neither change in membrane lipid asymmetry nor normal levels of the pH-titratable inner monolayer lipids is necessary for cell pH-mediated shape change.

Multiple Bcl-2 family members demonstrate selective dimerizations with Bax

A family of Bcl-2-related proteins regulates cell death and shares highly conserved BH1 and BH2 domains. BH1 and BH2 domains of Bcl-2 were required for it to heterodimerize with Bax and to repress apoptosis. A yeast two-hybrid assay accurately reproduced this interaction and defined a selectivity and hierarchy of further dimerizations. Bax also heterodimerizes with Bcl-xL, Mcl-1, and A1. A Gly-159-->Ala substitution in BH1 of Bcl-xL disrupted its heterodimerization with Bax and abrogated its inhibition of apoptosis in mammalian cells. This suggests that the susceptibility to apoptosis is determined by multiple competing dimerizations in which Bax may be a common partner.

Molecular analysis of 13 cases of MLL/11q23 secondary acute leukemia and identification of topoisomerase II consensus-binding sequences near the chromosomal breakpoint of a secondary leukemia with the t(4;11)

Rearrangements of the MLL (Mixed Lineage Leukemia) gene in the human 11q23 cytogenetic locus have been detected in secondary (therapy-related) acute leukemias in patients who have received topoisomerase II inhibitors for prior, independent neoplasms. The topoisomerase II inhibitors implicated in MLL/11q23 secondary leukemias all inhibit the religation step of reaction catalyzed by topoisomerase II. This results in the stabilization of a 'cleavable complex' with double-strand DNA breaks at the point of topoisomerase II binding. This raises the possibility that the cleavable complex participates in the translocation process in MLL/11q23 secondary leukemias. Here we report that the MLL/11q23 breakpoints in 13/13 patients with secondary leukemia map to the same breakpoint cluster region (bcr) noted in de novo MLL/11q23 acute leukemias and the presence of in vivo topoisomerase II inhibitor-induced cleavage sites in MLL/11q23 bcr. We have also cloned and sequenced the breakpoint from a MLL/11q23 secondary acute leukemia. This analysis revealed sequences similar to the consensus sequence for vertebrate topoisomerase II binding and cleavage close to the 11q23 and 4q21 breakpoints. These results support a role for topoisomerase II in mechanism generating translocations in MLL/11q23 secondary acute leukemia.

[An analysis of ocular manifestations in cases with tumors of accessory nasal sinuses]

The ocular manifestations of 60 cases with tumors of accessory nasal sinuses were reported. They were proptosis, impairment of ocular movement, diplopia, decrease or loss of visual acuity, ptosis, etc. Of them, 42 patients came to the ophthalmology department first. All the patients were diagnosed by computerized tomography (CT scan) and pathological findings. Operative treatment was applied in 48 cases. 32 cases had improvement in ocular symptoms. Particular attention was paid to the analysis of the causes of the patients, ocular symptoms and signs. They are due to the close anatomical relationship between accessory nasal sinuses and the orbit and optic nerve canal. CT scan is helpful to the early diagnosis of the disease.

The use of combination internal fixation and hybrid external fixation in severe proximal tibia fractures

Forty-eight patients with 50 severe fractures of the proximal tibia were followed prospectively for 2-4 years (mean 2.7 years) to evaluate the use of limited internal fixation combined with external fixation in the treatment of these injuries. There were 27 men and 21 women ranging in age from 20 to 74 years. Fractures were classified according to the A0 system (Mast J, Ganz R, Jacob R: Planning and reduction technique in fracture surgery. Berlin, Springer-Verlag, 1989), which included 5 A3, 6 C1, 16 C2, and 23 C3 fractures. All patients in this series healed; 48 fractures healed in an average of 12 weeks without subsequent surgery. There were two (4%) nonunions requiring bone graft. The average hospital special surgery knee score was 90 (68-100). Grading criteria for anatomical outcome revealed there were 17 (34%) excellent results, 24 (48%) good results, 6 (12%) fair results, and 3 (6%) poor results. In conclusion, this treatment method is associated with a high percentage of good and excellent results. Combined internal and external fixation combines the advantages of anatomic, stable fixation with less soft-tissue dissection and eliminates the need for large implants.

Inhibition of aberrant crypt growth by non-steroidal anti-inflammatory agents and differentiation agents in the rat colon

Aberrant crypts are aggregates of single to multiple colonic crypts evidencing hallmarks of dysplasia and may be the earliest detectable pathological lesions for colon cancer. The aberrant crypt assay has been developed in 2 protocols. In one, putative chemoprevention agents are tested for inhibitory effects when administered concomitantly with a carcinogen. In the other, the objective of this study, aberrant crypts were induced in F344 rats by parenteral injection of the colon carcinogen azoxymethane (AOM) and allowed to develop for 4 weeks, when an average of 90-100 aberrant crypt foci per colon were found in the methylene blue-stained colon. Then, during the second 4 weeks of the experiment, aberrant crypts were allowed to further develop to a frequency of > 150 foci per colon, a time when multi-crypt foci were observed. During this time we tested the inhibitory effects of 4 analgesic drugs and 2 differentiation agents for effects of aberrant crypt growth and development. We found the non-steroidal anti-inflammatory drugs piroxicam, aspirin and ibuprofen, but not acetaminophen, to be effective in suppressing aberrant crypt formation or the progression to foci of multiple aberrant crypts. Treatment with chemosuppressing agents 13-cis-retinoic acid (13-cRA) and 4-hydroxyphenretinamide (4-HPR), known differentiating agents, however, did suppress expansion of aberrant crypt foci, with 13-cRA being the much more potent agent.

Bad, a heterodimeric partner for Bcl-XL and Bcl-2, displaces Bax and promotes cell death

To extend the mammalian cell death pathway, we screened for further Bcl-2 interacting proteins. Both yeast two-hybrid screening and lambda expression cloning identified a novel interacting protein, Bad, whose homology to Bcl-2 is limited to the BH1 and BH2 domains. Bad selectively dimerized with Bcl-xL as well as Bcl-2, but not with Bax, Bcl-xs, Mcl-1, A1, or itself. Bad binds more strongly to Bcl-xL than Bcl-2 in mammalian cells, and it reversed the death repressor activity of Bcl-xL, but not that of Bcl-2. When Bad dimerized with Bcl-xL, Bax was displaced and apoptosis was restored. When approximately half of Bax was heterodimerized, death was inhibited. The susceptibility of a cell to a death signal is determined by these competing dimerizations in which levels of Bad influence the effectiveness of Bcl-2 versus Bcl-xL in repressing death.

Expression of MHC class I antigen in Morris rat hepatoma and normal liver

Expression of major histocompatibility complex (MHC) class I antigen in Morris rat hepatoma 7777 and normal rat liver tissues was studied by immunohistochemical techniques, Western blot and radiobinding assay. It was found that hepatoma tissue displayed a pattern of enhanced MHC class I antigen expression compared with normal liver. This phenomenon may represent an uncommon pattern of MHC class I antigen expression of liver tumor. The influence of enhanced MHC class I antigen expression on the development and spread of tumors as well as the possible mechanisms of this enhancement are discussed.

Collapse of intertrochanteric hip fractures fixed with sliding screws

A retrospective analysis of postoperative fracture collapse was performed using data from 142 patients with intertrochanteric hip fractures fixed anatomically with sliding screws. Of the 142 patients, 80 had unstable, three- or four-part hip fractures. Significant collapse (as defined by strict radiographic criteria relating the height of the femoral head to the greater trochanter and by Doppelt's criteria) was seen in 26 of the unstable fractures. The degree of collapse was classified as type I (minimal), type II (moderate), and type III (severe). Average follow-up was 31 months. An in-depth clinical and radiographic analysis was performed evaluating pain, limp, abductor weakness, and leg-length discrepancy. The numerical degree of both vertical and horizontal fracture collapse was also analyzed. Of the patients with moderate or severe collapse, 93% had a poor functional result, whereas all the patients with minimal collapse remained asymptomatic. Although postoperative fracture impaction of hips fixed with sliding screws may promote early healing, a high rate of union, and a low rate of hardware failure, excessive collapse is a problem that needs to be addressed.