Budding yeast Mph1 promotes sister chromatid interactions by a mechanism involving strand invasion.

Stalling of replication forks at lesions is a serious threat to genomic integrity and cell viability. Cells have developed a variety of pathways that allow continuation of synthesis, including translesion synthesis, postreplication repair and homologous recombination. We have devised a sensitive genetic system for detection of sister chromatid interactions in Saccharomyces cerevisiae. A 266bp sequence duplication in the KanMX4 module was generated and reversions were scored via G418 resistant colonies. Both 4-NQO induced and spontaneous reversions are strictly dependent on RAD52. Damage-induced reversions are also largely dependent on RAD51. Thus, most damage-induced events require a strand invasion step. Induced reversions were not affected in rev3 mutants and partially reduced in rad30 mutants indicating an involvement of Pol η. In cells lacking Mph1, a member of the FANCM family of DNA helicases, that has been implicated in a pathway for fork reactivation involving homologous recombination, damage-induced events are significantly reduced. Together with the spontaneous mutator phenotype of mph1 mutants this data strongly suggest that Mph1 has an additional function in recombination besides its previously described ability to disrupt D-loops. We propose that Mph1 promotes D-loop formation.

Archaeal DNA uracil repair via direct strand incision: A minimal system reconstituted from purified components.

Hydrolytic deamination of DNA cytosine residues results in U/G mispairs, pre-mutagenic lesions threatening long-term genetic stability. Hence, DNA uracil repair is ubiquitous throughout all extant life forms and base excision repair, triggered by a uracil DNA glycosylase (UDG), is the mechanistic paradigm adopted, as it seems, by all bacteria and eukaryotes and a large fraction of archaea. However, members of the UDG superfamily of enzymes are absent from the extremely thermophilic archaeon Methanothermobacter thermautotrophicus DeltaH. This organism, as a hitherto unique case, initiates repair by direct strand incision next to the DNA-U residue, a reaction catalyzed by the DNA uridine endonuclease Mth212, an ExoIII homologue. To elucidate the detailed mechanism, in particular to identify the molecular partners contributing to this repair process, we reconstituted DNA uracil repair in vitro from only four purified enzymes of M. thermautotrophicus DeltaH. After incision at the 5'-side of a 2'-d-uridine residue by Mth212 DNA polymerase B (mthPolB) is able to take over the 3'-OH terminus and carry out repair synthesis generating a 5'-flap structure that is resolved by mthFEN, a 5'-flap endonuclease. Finally, DNA ligase seals the resulting nick. This defines mechanism and minimal enzymatic requirements of DNA-U repair in this organism.

Yeast MPH1 gene functions in an error-free DNA damage bypass pathway that requires genes from Homologous recombination, but not from postreplicative repair.

The MPH1 gene from Saccharomyces cerevisiae, encoding a member of the DEAH family of proteins, had been identified by virtue of the spontaneous mutator phenotype of respective deletion mutants. Genetic analysis suggested that MPH1 functions in a previously uncharacterized DNA repair pathway that protects the cells from damage-induced mutations. We have now analyzed genetic interactions of mph1 with a variety of mutants from different repair systems with respect to spontaneous mutation rates and sensitivities to different DNA-damaging agents. The dependence of the mph1 mutator phenotype on REV3 and REV1 and the synergy with mutations in base and nucleotide excision repair suggest an involvement of MPH1 in error-free bypass of lesions. However, although we observed an unexpected partial suppression of the mph1 mutator phenotype by rad5, genetic interactions with other mutations in postreplicative repair imply that MPH1 does not belong to this pathway. Instead, mutations from the homologous recombination pathway were found to be epistatic to mph1 with respect to both spontaneous mutation rates and damage sensitivities. Determination of spontaneous mitotic recombination rates demonstrated that mph1 mutants are not deficient in homologous recombination. On the contrary, in an sgs1 background we found a pronounced hyperrecombination phenotype. Thus, we propose that MPH1 is involved in a branch of homologous recombination that is specifically dedicated to error-free bypass.

[Initial experiences in diagnosis of graft rejection following clinical heart transplantation. Detection of graft-directed activated T-cells]. / Erste Erfahrungen zur Abstossungsdiagnostik nach klinischer Herztransplantation. Der Nachweis transplantatgerichteter aktivierter T-Zellen.

The binding of antigen-loaded carrier to mononuclear cells of heart transplant recipients has been investigated by means of an antigen-specific rosette technique. The increase of rosette forming cells and the inhibition of this reaction with monoclonal antibodies against activated T-cells is a sign of a beginning rejection. 3-6 days later infiltrating immunological competent cells are seen in biopsy.

[Immunologic characterization of the rejection of the allogenic transplanted kidney in pigs with and without immunosuppression]. / Immunologische Charakterisierung der Rejektion allogen transplantierter Nieren beim Schwein mit und ohne Immunsuppression.

After allogenic renal transplantation in pigs kinetics of the immunological reactivity have been investigated in order to diagnose rejection crisis. In a first series of 26 transplants without any immunosuppression we secured the diagnosis of rejection in 95% of cases of acute or chronic rejection by a combination of antigen-specific rosette test, inhibition of this parameter by autologous serum, complement dependent cytotoxicity and antibody dependent cell-mediated cytotoxicity. The antigen-specific rosette test reacts very early, 2-3 days before a bad clinical feeling in the course of acute rejection or 5-14 days by chronic rejection. Under the therapy with prednisolone and azathioprine we could not reach any prolongation of survival by arbitrary donor-recipient-selection. Under immunosuppression antibodies have never been observed by acute rejection in CDC and ADCC. In every case of acute rejection an increasing rosette formation of specific antigen binding cells appeared 2-3 days before an increasing of serum creatinine. In the case of other complications like infection or thrombosis this test is not reacting. However, by thrombosis of arteria or vena renalis there can be an increased specific rosette formation either independent of this process by beginning of immune reaction or by causal connection of both processes (necrotizing thrombotic rejection). So we have given the evidence, that the antigen-specific rosette test on a high level meets all requirements of a specific diagnosis of rejection under immunosuppression in pig.

[Clinical value of various parameters in antenatal diagnosis of fetal hypotrophia (intrauterine retardation) (author's transl)]. / Zur klinischen Wertigkeit verschiedener Parameter bei der antenatalen Diagnostik der fetalen Hypotrophie.

Retrospective evaluation of percental frequency of pathological data gained by prepartual monitoring in pregnancies at risk of 180 small for gestational age infants and 130 eutrophic ones at term (postnatal classification). Parameters of interest were continuous maternal gain of weight, monthly progress of the size of the uterus, continuous ultrasomic cephalometria, maternal urinary estriol and serum heat stable alkaline phosphatase as well as amnioscopia and cardiotokographia with and without oxytocin challenge test. -- It seems that there is a significant better prediction of fetal retardation with the help of common clinical methods as well as with ultrasonic and that they are superior to the examined biochemical, cardiotocographical and amnioscopical parameters. With regard to possible additional disturbances of the fetoplacental unit--especially of respiratory placental function--in suspected intrauterine retardation the complete monitoring program should be taken.

[Mode of delivery, postnatal condition and neonatal outcome in preterm infants]. / Art der Geburtsbeendigung, Zustandsdiagnostik und kindlicher Ausgang bei Frühgeburt.

There were under examination 578 preterm infants of two groups--28. up to 31. and 32. up to 36. week of gestation--after birth of vertex as well as breech prevention. Postnatal condition and neonatal outcome were put into relation to the mode of delivery. We compared Apgar-Score (one and five minute value), morbidity on respiratory distress syndrom as well as rate of survival and neonatal mortality in spontaneous delivery with and without episiotomia, with specula delivery, Shute-forceps and vacuum extraction of vertex presentation as well as with breech presentation after vaginal delivery and primary Caesarean section. In respect of the management of the second stage of labour it is our opinion that prophylactic additional measures in preterm delivery of vertex presentation after 32 weeks of gestation are not necessary and that this question should be examined in a larger study of much more cases. But we were able to demonstrate that up to 32. week of gestation well-timed episiotomia of optimal size is necessary. Our good experiences in breech presentation between 31. and 35. week of gestation treated by obligate Caesarean section have to prove true in future.

The spectral emissivity of the anode of a carbon arc.

Data in the literature on the spectral emissivity of carbon and graphite show a great divergence, ranging from 0.75 to 0.99 in the visible region. A new determination has been undertaken at a number of wavelengths using an integrating sphere and modulated light. Emissivities ranging from 0.99 in the visible to 0.96 at 0.28 micro and 1.7 micro have been found for several different graphite anodes; the values for lampblack anodes are about 0.005 lower. There is a good agreement with the highest values thus far published. Most of the literature data on the spectral radiance of the anode are consistent with the emissivities found by the present author.