[Intraoperative rapid frozen section-when meaningful, when necessary?] / Intraoperativer Schnellschnitt ­ wann sinnvoll, wann notwendig?

Intraoperative frozen sections can significantly improve the results of numerous visceral surgical operations. For this a close cooperation between surgery and pathology is a basic prerequisite. The main indications are the diagnostics of unclear intraoperative findings and the assessment of resection margins. Just as in any other procedure, there are also limiting factors to be considered in frozen section examinations.

[Tumor grading of the hepatobiliary system]. / Grading der Tumoren des hepatobiliären Systems.

Tumors of the liver, intrahepatic and extrahepatic bile ducts as well as the gallbladder are very heterogeneous and show different biological behavior. The 4­stage (i.e. well, moderately, poorly and undifferentiated) grading system for hepatocellular carcinoma proposed by the WHO takes tumor size and architecture as well as the extent of cell and nuclear pleomorphism into account. In addition, the WHO defines some special forms of hepatocellular carcinoma. For carcinomas of intrahepatic bile ducts the WHO provides a 3­stage (well, moderately and poorly differentiated) grading system, which is based on architectural and cytological changes. At this localization there are also additional special histological forms that have to be dealt with outside the grading system described. The WHO proposes a 3­stage (well, moderately and poorly differentiated) grading system for carcinomas of the extrahepatic bile ducts and the gallbladder, which considers the proportion of glands contained within the adenocarcinoma. Similar to cancers of the liver and intrahepatic bile ducts there are also numerous special histological forms, which are explained in this article.

[Reference ranges of antioxidant parameters in whole blood (erythrocytes) in a Thüringen region]. / Referenzbereiche antioxidativ wirkender Parameter im Vollblut (Erythrozyten) einer Thüringer Region.

BACKGROUND: The oxidant stress is characterized by measurement of the activities of glutathione peroxidase, superoxiddismutase and also by concentrations of glutathione and selenium in erythrocytes. A standardization of the methods of determination is very important. MATERIAL AND METHODS: In erythrocytes of blood donors (n = 101) the parameters glutathione peroxidase, glutathione, superoxiddismutase and selenium were determined. RESULTS: The following results of the antioxidant parameters in erythrocytes of blood donors were found: Selenium 67.1 +/- 20.1 nmol/mmol Hb, glutathione peroxidase 842 +/- 290 U/mmol Hb, glutathione 108 +/- 48 mumol/mmol Hb, superoxiddismutase 15.8 +/- 6.4 U/mumol Hb. CONCLUSION: Selenium, glutathione peroxidase, glutathione and superoxiddismutase in erythrocytes of blood donors are normally distributed. There are no significant differences between men and women. The use of "own reference values" is necessary because no standardization of the methods of determination exists.

Macroevolution by transposition: drastic modification of DNA recognition by a type I restriction enzyme following Tn5 transposition.

We have characterized a novel mutant of EcoDXXI, a type IC DNA restriction and modification (R-M) system, in which the specificity has been altered due to a Tn5 insertion into the middle of hsdS, the gene which encodes the polypeptide that confers DNA sequence specificity to both the restriction and the modification reactions. Like other type I enzymes, the wild type EcoDXXI recognizes a sequence composed of two asymmetrical half sites separated by a spacer region: TCA(N7)RTTC. Purification of the EcoDXXI mutant methylase and subsequent in vitro DNA methylation assays identified the mutant recognition sequence as an interrupted palindrome, TCA(N8)TGA, in which the 5' half site of the wild type site is repeated in inverse orientation. The additional base pair in the non-specific spacer of the mutant recognition sequence maintains the proper spacing between the two methylatable adenine groups. Sequencing of both the wild type and mutant EcoDXXI hsdS genes showed that the Tn5 insertion occurred at nucleotide 673 of the 1221 bp gene. This effectively deletes the entire carboxyl-terminal DNA binding domain which recognizes the 3' half of the EcoDXXI binding site. The truncated hsdS gene still encodes both the amino-terminal DNA binding domain and the conserved repeated sequence that defines the length of the recognition site spacer region. We propose that the EcoDXXI mutant methylase utilizes two truncated hsdS subunits to recognize its binding site. The implications of this finding in terms of subunit interactions and the malleability of the type I R-M systems will be discussed.

Use of site-directed mutagenesis to define the limits of sequence variation tolerated for processing of the M13 procoat protein by the Escherichia coli leader peptidase.

Leader peptidase cleaves the leader sequence from the amino terminus of newly made membrane and secreted proteins after they have translocated across the membrane. Analysis of a large number of leader sequences has shown that there is a characteristic pattern of small apolar residues at -1 and -3 (with respect to the cleavage site) and a helix-breaking residue adjacent to the central apolar core in the region -4 to -6. The conserved sequence pattern of small amino acids at -1 and -3 around the cleavage site most likely represents the substrate specificity of leader peptidase. We have tested this by generating 60 different mutations in the +1 to -6 domain of the M13 procoat protein. These mutants were analyzed for in vivo and in vitro processing, as well as for protein insertion into the cytoplasmic membrane. We find that in vivo leader peptidase was able to process procoat with an alanine, a serine, a glycine, or a proline residue at -1 and with a serine, a glycine, a threonine, a valine, or a leucine residue at -3. All other alterations at these sites were not processed, in accordance with predictions based on the conserved features of leader peptides. Except for proline and threonine at +1, all other residues at this position were processed by leader peptidase. None of the mutations at -2, -4, or -5 of procoat (apart from proline at -4) completely abolished leader peptidase cleavage in vivo although there were large effects on the kinetics of processing.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmembrane cation movements during infection of Lactobacillus lactis by bacteriophage LL-H.

Phage LL-H-induced cation (K+, Na+, Mg2+, Ca2+, Cd2+) movements in Lactobacillus lactis bacteria have been studied. The effects of the m.o.i. and external cation concentration have been quantified. LL-H-induced effluxes showed cation specificity: K+ but practically no Mg2+ was lost during LL-H infection at low and moderate m.o.i. (up to about 100). Simultaneously to K+ efflux, divalent cation influxes were observed. These were dependent on the m.o.i. and on concentrations of external divalent cations and were concomitant with phage DNA transport, as concluded from the timing of the first phage-promoted biochemical changes in host cell metabolism and from electron microscopical observations. Host energy was not mobilized with phage-induced divalent cation influx. Several features of divalent cation influxes support the view that divalent cations have to be cotransported into the cell as counterions of LL-H DNA. Phage DNA associated with divalent cations may be the basic feature of the divalent cation dependence of LL-H infection.

Manipulation of intracellular magnesium content in polymyxin B nonapeptide-sensitized Escherichia coli by ionophore A23187.

Escherichia coli B cells were sensitized to ionophore A23187 by polymyxin B nonapeptide, and the induced magnesium and potassium ion fluxes were studied. Combined ionophore treatment permeabilized the cytoplasmic membrane of E. coli in an ion-specific manner and allowed the manipulation of intracellular Mg2+ content from the outside. A23187-induced Mg2+ efflux or influx was dependent on the free Mg2+ concentration gradient between the outside and inside of the cytoplasmic membrane and on the pH gradient. Most of the intracellular Mg2+ was bound, whereas only 1 to 2 mM was free in solution in the cellular sap.

Involvement of the bacterial groM gene product in bacteriophage T7 reproduction. II. A reduced level of ion concentrations causes the blockage of T7 maturation in K-12-M cells.

Cellular leakage observed in Escherichia coli K-12-M shortly after T7 infection might be the cause of arrested phage morphogenesis. We observed in this strain, but not in the normal host, a drastic reduction of the intracellular concentration of potassium (60%), magnesium (40%), putrescine (90%), and spermidine (40%), whereas ATP was not significantly reduced. Leakage started about 1 min after the addition of phage and was arrested 3 to 5 min postinfection. Larger molecules such as o-nitrophenyl-beta-D-galactopyranoside could not enter the cells, showing that the permeability of the membrane was not generally affected. To prevent their leakage, we increased the outside concentrations of several small molecules and ions. The yield of progeny phage was substantially increased by the addition of 100 mM MgSO4.