Cytochrome P-450 and chromosome damage by cyclophosphamide in LEC strain rats predisposed to hereditary hepatitis and liver cancer

LEC strain rats predisposed to hereditary hepatitis and liver cancer were examined for hepatic drug-metabolizing ability and the inducibility of chromosome damage by cyclophosphamide (CP) in somatic cells. Whereas the hepatic cytochrome P-450 contents and the activities of cytochrome P-450-catalyzed monooxygenases were lower in females than in males of both LEC and control LEA strains, male LEC rats exhibited significantly reduced cytochrome P-450 contents and monooxygenase activities compared with male LEA rats. When exposed to CP, a promutagen/procarcinogen requiring P-450-dependent metabolic activation, the frequencies of chromosome aberrations and sister-chromatid exchanges (SCEs) in bone marrow cells tended to be lower in females than in males of each strain and lower in LEC than in LEA rats of the same sex. In particular, the CP-induced SCEs were substantially lower in LEC rats. However, no such sex and strain differences were found in the SCE frequencies in regenerating hepatocytes of partially hepatectomized rats exposed to CP.     

Switch circular DNA formed in cytokine-treated mouse splenocytes: evidence for intramolecular DNA deletion in immunoglobulin class switching

We have characterized circular DNA in mouse splenocytes treated with the mitogen lipopolysaccharide (LPS) and various cytokines, including transforming growth factor beta (TGF-beta) and interleukin 4 (IL-4). Using probes of immunoglobulin heavy chain constant genes (CH), excision products of class switch recombination were identified. The majority of the clones contained the 3' portion of the switch mu (S mu) region and the 5' portion of other switch regions. Some clones contained 3'-S gamma sequences instead of 3'-S mu. This indicates that isotype switching may occur not only from C mu, but also from one of the C gamma genes to other CH genes further down-stream. In the presence of LPS, the cytokine TGF-beta enhanced the detection of 5'-S alpha-positive clones, while the lymphokine IL-4 enhanced 5'-S gamma 1 positives. The data support the notion that TGF-beta and IL-4 can direct isotype-specific class switching.     

Carbachol-Induced Cosecretion of Immunoreactive Atrial Natriuretic Peptides with Catecholamines from Cultured Bovine Adrenal Medullary Cells

The distribution and secretion of atrial natriuretic peptides (ANPs) were investigated in bovine adrenal medulla. (1) Cultured bovine adrenal medullary cells (2 x 10(6)/dish) contained 100.4 +/- 6.0 fmol of immunoreactive ANP (IR-ANP) and 207.3 +/- 6.6 nmol of catecholamines as epinephrine plus norepinephrine. (2) Stimulation of nicotinic but not muscarinic acetylcholine receptors caused a cosecretion of IR-ANP and catecholamines corresponding to the ratio of IR-ANP to catecholamines in cultured bovine adrenal medullary cells. (3) Carbachol-stimulated secretion of IR-ANP was dependent on the presence of extracellular Ca2+. (4) Chromaffin granules isolated from bovine adrenal medulla contained large amounts of IR-ANP and catecholamines, in the same ratio as did cultured adrenal medullary cells. (5) Reverse-phase HPLC analysis showed that both stored and secreted IR-ANP consisted of two components, which eluted at the position of ANP(99-126) or ANP(1-126). These results indicate that ANPs are stored as ANP(99-126) and ANP(1-126) in chromaffin granules, and are cosecreted in parallel with catecholamines in a Ca2+-dependent manner by the stimulation of nicotinic acetylcholine receptors.     

Occurrence of differentiated keratin peptide(K1) in cultured human squamous cell carcinomas.

To date, the largest keratin peptide(K1, 68 KD) has been absent in cultured human squamous cell carcinomas. Using a low salt aqueous solution, not containing high salt and Triton X-100, as a washing buffer for keratin extraction, followed by two dimensional polyacrylamide gel electrophoresis, immunological techniques and Northern blot analysis, we demonstrated K1 peptide in two kinds of cultured human squamous cell carcinomas. Until now keratin extraction has been done using high salt/Triton X-100 solution during which K1 peptide may be removed together developed an affinity with the buffer. Many investigators may have therefore overlooked K1.     

Photolabeled sites with a tetrodotoxin derivative in the domain III and IV of the electroplax sodium channel.

Forty three percent of the labeled sites, at least, in the electroplax sodium channel with a photoactivable tetrodotoxin derivative were identified by probing protease-digested labeled fragments with several sequence-directed antibodies. They are located in the loop between segments S5 and S6 of domain IV, as well as the region containing transmembrane segment S6 and adjacent extracellular and cytoplasmic sequences in domain III. No photolabeled fragments were detected in the corresponding region of domain I. These results suggest that C-11 of tetrodotoxin where the photoreactive moiety is attached orients to the region between S5 and S6 in domain III and IV. Probable orientation of the tetrodotoxin molecule in sodium channels is considered by taking together with the recent report of the site-directed mutagenesis.