Gerinnungsveränderungen bei orthotoper Lebertransplantation am Hund

Bei 16 Hunden wurden bei orthotopen Auto- und Homotransplantationen der Leber Gerinnungsuntersuchungen durchgeführt. Während die Anästhesie, die Präparation der Lebergefäße und Manipulationen an Leber und Lunge keine Gerinnungsveränderungen hervorriefen, kam es nach Anlegen des äußeren venösen Bypass und Entnahme der Leber zu einem Abfall von Fibrinogen, Thrombozyten, Faktor II, Faktor VIII und Antithrombin III. Diese Veränderungen werden als Ausdruck einer Verbrauchskoagulopathie angesehen. Eine leichte Fibrinolyse war gewöhnlich erst am Ende der anhepatischen Phase nachweisbar und dürfte sekundär sein. Nach Implantation der Leber war nach kurzer Latenzzeit ein Wiederanstieg der oben genannten Faktoren und der Thrombozyten zu beobachten. Die möglichen Ursachen für das Auftreten der Verbrauchsreaktion werden diskutiert.

Pediatric anesthesia and postoperative analgesia

Children are not "small adults," particularly when it comes to anesthesia and pain management. The psychological and physiologic uniqueness of children must not be forgotten. Cooperation and communication between the anesthesiologist, surgeon, and pediatrician are essential for successful anesthesia and pain management. Pediatric anesthesiologists involved in the perioperative management of infants and children are very much a part of the "continuity of care" concept.

Murine DNA (cytosine-5-)-methyltransferase: steady-state and substrate trapping analyses of the kinetic mechanism

DNA (cytosine-5-)-methyltransferase is essential for viable mammalian development and has a central function in the determination and maintenance of epigenetic methylation patterns. Steady-state and substrate trapping studies were performed to better understand how the enzyme functions. The catalytic efficiency was dependent on substrate DNA length. A 14-fold increase in KmDNA was observed as the length decreased from 5000 to 100 base pairs and kcat decreased by a third. Steady-state analyses were used to identify the order of substrate addition onto the enzyme and the order of product release. Double-reciprocal patterns of velocity versus substrate concentration intersected far from the origin and were nearly parallel. The kinetic mechanism does not appear to change when the DNA substrate is either 6250 or 100 base pairs in length. Isotope trapping studies showed that the initial enzyme-AdoMet complex was not catalytically competent; however, the initial enzyme-poly(dI.dC-dI.dC) complex was observed to be competent for catalysis. Product inhibition studies also support a sequential ordered bi-bi kinetic mechanism in which DNA binds to the enzyme first, followed by S-adenosyl-L-methionine, and then the products S-adenosyl-L-homocysteine and methylated DNA are released. The proposed mechanism is similar to the mechanism proposed for M. HhaI, a bacterial DNA (cytosine-5-)-methyltransferase. Evidence for an enzyme-DNA-DNA ternary complex is also presented.

Cytomegalovirus activates interferon immediate-early response gene expression and an interferon regulatory factor 3-containing interferon-stimulated response element-binding complex

Interferon establishes an antiviral state in numerous cell types through the induction of a set of immediate-early response genes. Activation of these genes is mediated by phosphorylation of latent transcription factors of the STAT family. We found that infection of primary foreskin fibroblasts with human cytomegalovirus (HCMV) causes selective transcriptional activation of the alpha/beta-interferon-responsive ISG54 gene. However, no activation or nuclear translocation of STAT proteins was detected. Activation of ISG54 occurs independent of protein synthesis but is prevented by protein tyrosine kinase inhibitors. Further analysis revealed that HCMV infection induced the DNA binding of a novel complex, tentatively called cytomegalovirus-induced interferon-stimulated response element binding factor (CIF). CIF is composed, at least in part, of the recently identified interferon regulatory factor 3 (IRF3), but it does not contain the STAT1 and STAT2 proteins that participate in the formation of interferon-stimulated gene factor 3. IRF3, which has previously been shown to possess no intrinsic transcriptional activation potential, interacts with the transcriptional coactivator CREB binding protein, but not with p300, to form CIF. Activating interferon-stimulated genes without the need for prior synthesis of interferons might provide the host cell with a potential shortcut in the activation of its antiviral defense.

DNA binding discrimination of the murine DNA cytosine-C5 methyltransferase

Mammalian DNA cytosine-C5 methyltransferase modifies the CpG dinucleotide in the context of many different genomic sequences. A rigorous DNA binding assay was developed for the murine enzyme and used to define how sequences flanking the CpG dinucleotide affect the stability of the enzyme:DNA complex. Oligonucleotides containing a single CpG site form reversible 1:1 complexes with the enzyme that are sequence-specific. A guanine/cytosine-rich 30 base-pair sequence, a mimic of the GC-box cis-element, bound threefold more tightly than an adenine/thymine-rich sequence, a mimic of the cyclic AMP responsive element. However, the binding discrimination between hemi- and unmethylated forms of these DNA substrates was small, as we previously observed at the K(m)DNA level (Biochemistry, 35, 7308-7315 (1996)). Single-stranded substrates are bound much more weakly than double-stranded DNA forms. An in vitro screening method was used to select for CpG flanking sequence preferences of the DNA methyltransferase from a large, divergent population of DNA substrates. After five iterative rounds of increasing selective pressure, guanosine/cytosine-rich sequences were abundant and contributed to binding stabilization for at least 12 base-pairs on either side of a central CpG. Our results suggest a read-out of sequence-dependent conformational features, such as helical flexibility, minor groove dimensions and critical phosphate orientation and mobility, rather than interactions with specific bases over the course of two complete helical turns. Thus, both studies reveal a preference for guanosine/cytosine deoxynucleotides flanking the cognate CpG. The enzyme specificity for similar sequences in the genome may contribute to the in vivo functions of this vital enzyme.

Transmembrane signaling by the alpha subunit of the type I interferon receptor is essential for activation of the JAK kinases and the transcriptional factor ISGF3

The Type I interferon (IFN) receptor has a multisubunit structure. The component of the receptor that has been most thoroughly studied is the alpha subunit. Expression of the alpha subunit in mouse L-929 cells confers antiviral response to human IFN alpha 8, but not to human IFN alpha 2 or IFN beta. This antiviral effect is observed without a significant increase in IFN binding. It has not been determined why mouse cells expressing the human alpha subunit show different response to the antiviral activity of distinct human Type I IFNs. In this report, we demonstrate that the response to human Type I IFNs in mouse cells expressing the alpha subunit is dependent on cross-binding to the mouse receptor. This is supported by the finding that human IFN alpha 8, but not human IFN alpha 2, cross-binds to the mouse receptor even in the absence of expression of the human alpha subunit. We also demonstrate that only mouse cells expressing the human alpha subunit are able to tyrosine-phosphorylate p135tyk2 and JAK-1 and to form the ISGF3 complex in response to human IFN alpha 8. These results demonstrate that the alpha subunit is essential for IFN alpha signaling through the JAK kinases and ISGF3.

The incidence of spontaneous subarachnoid hemorrhage with change in barometric pressure

The authors' observation of an apparent increased incidence of patients presenting with spontaneous subarachnoid hemorrhage (SAH) during stormy weather prompted them to retrospectively review admissions data during an 18-month period to look for an association between SAH and changes in barometric pressure (BMP). Of the 39,049 cases examined, 76 had confirmed SAH. Continuous graphs of BMP were used to categorize days as being "flat" days (change in BMP < or = 0.15; dpHg) or "change" days (change in BMP > 0.15; dpHg). Days on which patients presented with SAH were significantly correlated with change days (P < .004). There was significantly more SAH during the winter months (October to March), than during the remaining summer months (P < .02). The correlation of SAH with change in BMP did not hold if these summer months were examined alone. The risk ratio of having an SAH on an inclement day during the winter months was 1.99 (95% confidence interval, 1.11 to 3.60). The reason for this association is not clear at this time.

A 15-kDa interferon-induced protein is derived by COOH-terminal processing of a 17-kDa precursor

An interferon-induced 15-kDa protein is synthesized from a precursor of higher molecular weight; the precursor contains 165 amino acids (17 kDa), whereas the stable product (15 kDa) contains 156 amino acids. The stable 15-kDa form is derived from the precursor 17-kDa form by the removal of eight amino acids from the COOH terminus and the methionine from the NH2 terminus. The existence of the precursor 17-kDa protein can be demonstrated after brief periods of in vivo labeling with [35S]methionine and by translation of mRNA in vitro.

Interferon-induced nuclear factors that bind a shared promoter element correlate with positive and negative transcriptional control

Human alpha- and beta-interferons (IFNs) stimulate rapid but transient increases in transcription from a set of previously quiescent genes. Protein synthesis is not required for initial stimulation, but duration of the response is limited to a few hours by a process requiring synthesis of new proteins. An IFN-stimulated response element (ISRE) was identified 5' to an inducible gene by deletion analysis and point mutagenesis, and sequence comparisons with other promoters defined the consensus element YAGTTTC(A/T)YTTTYCC. Two classes of IFN-inducible nuclear factors were found that bind to the ISRE. The most rapidly induced factor appeared without new protein synthesis, whereas a second factor required active protein synthesis for its appearance and maintenance. The kinetics of appearance and loss of these binding activities correlate with the activation and repression of IFN-stimulated genes. These different IFN-activated or induced factors may bind sequentially to the same essential promoter element to first increase and then repress transcription.

Transcriptional stimulation by CaPO4-DNA precipitates

Genes in human chromosomes that normally require induction by alpha-interferon are activated after calcium phosphate (CaPO4) transfection, but not after DEAE-dextran transfection. The c-fos gene and genes stimulated by gamma-interferon also are affected by CaPO4-DNA precipitates, but the calcium ionophore A23187 stimulates only c-fos among this group. These results suggest caution not only in choosing gene transfer methods, but also in interpreting experiments aimed at understanding the role of second messengers in gene activation.

Transcription of interferon-stimulated genes is induced by adenovirus particles but is suppressed by E1A gene products

Interferon treatment of cell cultures results in the rapid transcriptional induction of a specific set of genes. In this paper we explore the effect of cellular infection by several adenoviruses, both wild type and mutant, on the expression of these genes. Infection with adenovirus induces the transcription of the interferon-stimulated genes in the absence of any protein synthesis. In fact, the inhibition of protein synthesis during a wild-type infection produces enhanced stimulation of transcription of these genes. Experiments with viral mutants indicate the ability to specifically suppress this transcription maps to the E1A gene. In addition, the E1A gene products are capable of suppressing the specific transcriptional induction of interferon-stimulated promoters during cotransfection experiments and therefore presumably during viral infection. The dual effect of adenovirus on the expression of interferon-stimulated genes may represent an example of action and evolutionary reaction between virus and host.

Interferon-induced transcription of a gene encoding a 15-kDa protein depends on an upstream enhancer element

A human gene encoding an interferon-induced 15-kDa protein has been isolated from a genomic library. The gene appears to be single-copy and is composed of two exons, the first of which contains the ATG translation initiation codon. In vitro nuclear run-on assays showed that the transcription rate of the gene is stimulated after interferon treatment. To analyze transcriptional regulatory sequences, we constructed recombinant plasmids for use in transient transfection assays of HeLa cells. Constructs containing 115 nucleotides 5' to the transcription initiation site were found to be fully inducible by interferon. Assays of deletion mutants identified a critical element for interferon induction located between -115 and -96, just upstream of the "CCAAT box." Moreover, a DNA fragment including this region can confer interferon inducibility on a heterologous promoter (thymidine kinase) when cloned in either orientation upstream of the gene or downstream of the gene. These are properties characteristic of an enhancer element that is active only after treatment with interferon. This regulatory sequence may be shared by a group of interferon-induced genes, since a very similar sequence is present within the functional region near the RNA start site of another interferon-induced gene.

Characterization of human p53 antigens employing primate specific monoclonal antibodies

p53 is a cellular protein whose levels are some 1500-2000 times higher in adenovirus and SV40-transformed human cell lines than in homologous nontransformed cells. Monoclonal antibodies have been produced that detect p53 of primate origin but not of rodent origin. These monoclonal antibodies have been employed to study the properties of p53 antigens from human cell lines. Human p53 proteins of at least five different apparent molecular-weight classes in SDS-polyacrylamide gels have been detected. In some cell lines, at least two distinct molecular-weight species are expressed and these two forms have similar or identical partial peptide maps. Both molecular-weight forms can be resolved into seven or eight species upon isoelectric focusing in a two-dimensional gel system. There is also some indication of differences in the partial peptide maps of human p53 antigens derived from different human transformed cell lines. A radioimmunometric assay was employed to study the steady-state levels of oligomeric p53 in normal and transformed cell lines. Antibody affinity chromatography has been employed to purify p53 protein which was then used to quantitate the steady-state levels of p53 in different human cell lines. Normal cells had little or no detectable p53 antigen. Transformed cells or tumor-derived cell lines varied between no detectable p53 protein and 450 micrograms of p53 protein/g of cellular protein (in SV80 cells). There was a great diversity in the levels of p53 antigen in human cells. SV40- and adenovirus-transformed cells had by far the highest levels of p53 antigen. These are the viruses whose tumor antigens have been shown to be associated in an oligomeric complex with p53 in transformed cells. Eleven out of fifteen human tumor derived or transformed cell lines contained greater than five-fold higher levels of p53 antigen than normal human cells.

Globin synthesis in hybrid cells constructed by transplantation of dormant avian erythrocyte nuclei into enucleated fibroblasts

The polypeptides synthesized by mature embryonic erythrocytes prepared from the peripheral blood of 14- to 15-day-old chicken embryos were analyzed by two-dimensional gel electrophoresis. Fewer than 200 species of polypeptides were detected; the major polypeptides made at this time were identified as the alpha A-, alpha D-, and beta-globin chains. The dormant erythrocyte nuclei were next reactivated to transcriptional competence by transplantation into enucleated mouse or chicken embryo fibroblasts, with frequencies of cytoplast renucleation of about 50 and 90%, respectively. Since large numbers of hybrid cells could be constructed, a biochemical analysis was possible. Electrophoretic analysis of the [35S]methionine-labeled polypeptides made in the hybrid cell types showed that polypeptides having the mobilities of only two (alpha A and alpha D) of the three major adult globin chains were made as major constituents of the hybrid cells. However, analysis of 14C-amino acid-labeled polypeptides revealed that a beta-like polypeptide that lacked methionine was also synthesized in large amounts. This polypeptide was tentatively identified as the early embryonic globin species rho. Globin synthesis was detected as early as 3 h after nuclear transplantation and as late as 18 h, the last time measured in these experiments. It appeared that globin polypeptides made at very early times were translated at least partially from chicken messenger ribonucleic acid introduced into the hybrid cells during fusion, whereas those made at later times were translated primarily from newly synthesized globin messenger ribonucleic acid. The potential usefulness of this hybrid cell system in analyzing mechanisms regulating globin gene expression is discussed.