Complement component C1r mediated cleavage of the heavy chain of the major histocompatibility class I antigens.

Apart from cleaving C1s, we demonstrate for the first time that: 1) at concentrations found in serum, the activated forms of the complement components C1r in addition to C1s can cleave the heavy chain of MHC class I antigens, 2) the cleavage by C1r and C1s is seemingly dependent upon a native configuration of the MHC class I antigen, since heat denaturation of the HLA antigens reduce the cleavage. The proteolytic fragments following C1 cleavage were characterized by precipitation with Con A-Sepharose, anti-MHC class I and anti-beta 2-microglobulin antibodies. The proteolysis of the alpha-chain of MHC class I was shown to take place between the alpha 2- and alpha 3- domains as estimated by the Con A-Sepharose precipitation pattern on SDS-PAGE. The alpha 1/alpha 2 fragment was still shown to interact with beta 2-microglobulin as shown by immunoprecipitation.     

In situ hybridization study of chromogranin A and B mRNA in carcinoid tumors

Summary The distribution of the mRNAs for chromogranin A and B was analyzed by in situ hybridization with ³⁵S-labeled oligonucleotide probes in formalin-fixed paraffin-embedded carcinoid tumor tissues. All the 15 mid-gut carcinoid tumors examined contained both mRNAs for chromogranin A and B at high level in tumor cells. Sixteen of 18 bronchial carcinoid tumors but only 2 of 5 rectal carcinoid tumors expressed one or both species of chromogranin mRNAs. The same tendency was seen with the argyrophil reaction according to Grimelius where most of the mid-gut tumor cells were uniformly stained, while considerable variation in reactivity was seen in some of the bronchial and rectal carcinoid tumor cells. The sequential sections were stained with a monoclonal antibody against chromogranin A and a polyclonal antiserum which reacts with both chromogranins. The expression of the mRNA for chromogranin A on the carcinoid tumors was almost concordant with that of chromogranin B as well as with the chromogranin A protein, whereas almost all tumors stained positively with the polyclonal antibodies. Analyses of mRNA expression of chromogranin A before and after interferon therapy on 4 patients with mid-gut carcinoids indicated an inhibition at pre-translational level. In conclusion, the mRNAs for chromogranin A and B are good markers for the carcinoid tumors, especially of mid-gut origin. Fore-gut, mid-gut and rectal carcinoid tumors are different in their endocrine properties regarding the expression of the chromogranins.     

Novel Form of ClpB/HSP100 Protein in the Cyanobacterium Synechococcus

Synechococcus sp. strain PCC 7942 has a second clpB gene that encodes a 97-kDa protein with novel features. ClpBII is the first ClpB not induced by heat shock or other stresses; it is instead an essential, constitutive protein. ClpBII is unable to complement ClpBI function for acquired thermotolerance. No truncated ClpBII version is normally produced, unlike other bacterial forms, while ectopic synthesis of a putative truncated ClpBII dramatically decreased cell viability.     

A possible new locus of alkaline phosphatase expressed in human testis

Summary Human testes contain trace amounts of heat-stable placental-like alkaline phosphatase. Using a recently described allotype-specific monoclonal antibody (F₁₁) toward placental alkaline phosphatase (PLAP), we show that the frequencies of reactivity of the testis enzymes differ greatly from those of the placental phenotypes. By means of the enzyme inhibitors L-Phe, L-Phe-gly-gly, L-Leu, and L-Leu-gly-gly, the testis enzyme can be clearly distinguished in all cases from the placental enzyme. These results argue that the testis enzyme is not a product of the placental gene and suggest the possible existence of a new locus of alkaline phosphatase.     

Methanol production from lignin-related substances by Phanerochaete chrysosporium

Methanol production resulting from the demethoxylation of lignin-related substances by Phanerochaete chrysosporium K-3 was studied in the presence or absence of glutamic acid in order to determine if methanol formation involved the ligninolytic system of the fungus. The general pattern was that methanol formation, calculated as percentage of theoretical yield, decreased in the order guaiacyl > syringyl > veratryl (3,4-dimethoxy) compounds. Methoxyhydroquinone and vanillic acid were most easily demethoxylated, while methanol production decreased with increasing molecular weight for the same type of structure (i.e. guaiacyl). Glutamic acid inhibited the demethoxylation of many of the compounds tested. The demethoxylation of the 4-methoxy group of veratric acid was particularly inhibited by glutamic acid suggesting a participation of the ligninolytic system, while the 3-methoxy group was influenced to a lesser extent.
The demethoxylating enzyme acting on lignin-related phenols is probably a peroxidase, while the identity of the enzyme demethoxylating dimethoxy compounds is not known with certainty, although a peroxidase type of enzyme reaction is anticipated also here.     

Effects of ethidium bromide on DNA loop organisation in human lymphocytes measured by anomalous viscosity time dependence and single cell gel electrophoresis.

The effects of ethidium bromide (EtBr) on human lymphocytes were studied by the method of anomalous viscosity time dependence (AVTD) and by the comet assay. EtBr at low concentrations increased the maximum viscosity and time of radial migration as measured with AVTD at neutral conditions of lysis. A pronounced relaxation of DNA loops was observed with the neutral comet assay. The maximal comet length corresponded to 2 Mb DNA loops. At high concentrations of EtBr, 2 mg/ml, significant reduction in AVTD below control level was seen that suggested hypercondensation of chromatin. The hypercondensation was directly observed with the neutral comet assay. EtBr did not induce DNA strand breaks as measured by the alkaline comet assay. The hypercondensed nuclei could be decondensed by irradiation with gamma-rays or exposure to light. The data provide evidence that EtBr at high concentrations resulted in hypercondensation of chromatin below control level. The comet assay confirmed that the increase in AVTD peaks deals with relaxation of loops and AVTD decrease is caused by chromatin condensation. The prediction of the AVTD theory for a correlation between time of radial migration and condensation of chromatin was verified. Further, the data show that the comet assay at neutral conditions of lysis is rather sensitive to DNA loop relaxation in the absence of DNA damage. Finally, donor specificity was found for the hypercondensation.     

Arginase,an s-phase enzyme in a human cell line

Suspension cultures of ‘Chang liver’ cells were synchronized by preincubation in a glutamine-deficient medium or by thymidine blockade. Specific arginase activity varied in the synchronized cultures, being high when the number of S-phase cells was maximal. A relationship between high arginase activity and a high percentage of (S+G₂) cells was also found when unsynchronized cells were separated by velocity sedimentation. The increase in arginase activity near the G₁/S border was totally inhibited in the presence of cycloheximide. The rate of decrease in activity after addition of the drug indicated that the variations in the rate of synthesis of the enzyme, while the rate of degradation was more or less constant, corresponding to 4–6% per h. The role of arginase in cells lacking a urea cycle and the regulation of arginase activity in ‘Chang liver’ cells is discussed.