Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine,with special reference to the interstitial cells of Cajal

Summary Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine were studied by electron microscopy, and three-dimensional cell models were reconstructed from serial ultrathin sections with a computer graphic system. Three types of cells were recognized. The first type was similar in shape to smooth muscle cells, but did not contain an organized contractile apparatus. Many large gap junctions comprising about 4% of the cell surface were present; they connected cells of the first type to each other, to the second type of cell and to smooth muscle cells of the outer circular layer. The second type of cell had a welldemarcated cell body with long slender processes and was characterized by a large amount of glycogen comprising about 9% of the cell volume. The third type of cell was similar to fibroblasts, and contained well-developed Golgi apparatus and rough endoplasmic retiulum. Some of these fibroblast-like cells (a possible subtype) formed small gap junctions. All three types of cells showed close relationships with nerve varicosities. This cellular network consisting of gap-junction-rich cells, glycogen-rich cells and smooth muscle cells may be involved in the pacemaking activity of intestinal movement.     

Comparative analysis of glycoprotein and glycolipid composition of virulent and avirulent strain membranes ofMycoplasma hyopneumoniae

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

小麦体细胞再生株（R1）的染色体变异分析

本文研究了普通小麦(Triticum aestivum)、“宁麦三号”等5个基因型的体细胞再生株(R_1)减数分裂各期的染色体异常行为。结果表明:再生株 R_1代有丝分裂时表现为染色体数量上的变异,最常见的有2n-2类型,其次是2n-1类型,也有少数为2n 1和2n-4等变异类型;再生株 R_1花粉母细胞减数分裂过程中出现单价体、多价体、染色体桥、落后染色体、断片和微核等异常现象,并与各基因型细胞遗传程度上差异有关。     

p140trk mRNA marks NGF-responsive forebrain neurons: evidence that trk gene expression is induced by NGF.

Nerve growth factor (NGF) appears to act as a neurotrophic factor for basal forebrain and caudate-putamen cholinergic neurons. The mechanism by which NGF transduces its signal in these neurons is yet to be defined. Recent data indicate that the product of the trk gene, p140trk, is a critical component of the NGF receptor. Herein, we show that p140trk mRNA is highly restricted in its distribution in the adult rat forebrain, that it is present in cholinergic neurons, and that most if not all cholinergic neurons contain p140trk mRNA. Furthermore, induction of trk expression by NGF suggests that neurotrophin-mediated up-regulation of their receptor tyrosine kinases is an important feature of their actions and that neurotrophins may regulate the activity of responsive neurons through increasing the level of their receptors.     

Antimutagenic and antitumorigenic activities of nordihydroguaiaretic acid.

Nordihydroguaiaretic acid (NDGA), which occurs in the resinous exudates of many plants is used as an antioxidant in fats and oils. In this study we show that NDGA inhibited the mutagenicity of methyl methanesulfonate, benzo[a]pyrene (BP), 2-aminofluorene, and aflatoxin B1 in Salmonella typhimurium strain TA100 or TA98 in the absence and presence of rat hepatic microsomal activation system. The addition of NDGA during and after nitrosation of methylurea (MU) resulted in a dose-dependent inhibition of mutagenicity induced by nitrosation products of MU. In a two-stage skin tumorigenesis protocol using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiating agent followed by twice weekly applications of 12-O-tetradecanoylphorbol-13-acetate (TPA) as tumor promoter, pretreatment of animals with NDGA prior to DMBA application, afforded significant protection against skin tumorigenicity in female SENCAR mice. In additional studies, skin application of NDGA also inhibited the binding of topically applied [3H]BP and [3H]DMBA to epidermal DNA. When assessed in the anti-tumor promotion protocol, pretreatment of animals with NDGA before each application of TPA in DMBA-initiated mouse skin, resulted in 72% decrease in the total number of tumors when compared to non-NDGA pretreated animals. The possible mechanism(s) of the antimutagenic and anti-tumorigenic activities may be due to the multiple effects of NDGA as inhibitor of the carcinogen metabolism and DNA-adduct formation, scavenger of carcinogen free radicals, and as inhibitor of TPA-induced ornithine decarboxylase activity.     

Monoclonal Antibodies against Apple 1-Aminocyclopropane-l-Carboxylate Synthase

1-Aminocyclopropane-l-carboxylate (ACC) synthase from applefruits was purified over 5,000-fold by conventional column chromatography.By immunizing mice with this partially purified enzyme preparation,8 hybridoma lines producing monoclonal antibodies against appleACC synthase were isolated. While all 8 clones immunoprecipitatednative ACC synthase, only two clones recognized the putative(48 kDa) ACC synthase on Western blots. When a partially purifiedACC synthase preparation was incubated with S-adenosyl-L-[carboxyl-¹⁴C]methionine(AdoMet), only one radioactive protein of 48 kDa was detectedon sodium dodecyl sulfate-poly-acrylamide gel electrophoresis.This radioactive protein was specifically immunoprecipitatedby the monoclonal antibodies, indicating that apple ACC synthaseis specifically radiolabeled by its substrate AdoMet, as istomato ACC synthase. Thus, the monoclonal antibodies recognizedboth native and AdoMet-inactivated forms of ACC synthase. Whilethese antibodies failed to im-munoprecipitate ACC synthase isolatedfrom ripe tomato fruits, ripe avocado fruits or auxin-treatedmungbean hypocotyls, they were effective in immunoprecipitatingthe enzyme isolated from ripe pear fruits. (Received August 11, 1990; Accepted October 17, 1990)     

The effect of 25-hydroxycholesterol on accumulation of intracellular calcium.

Liposomes prepared with 25-hydroxycholesterol and egg phosphatidylcholine (PC) were incubated with bovine arterial smooth muscle cells for 8 h at 37 degrees C. Cells incubated in the absence of liposomes or with liposomes containing cholesterol and PC were used as controls. The results indicated that calcium accumulated in the smooth muscle cells incubated in the presence of 25-hydroxycholesterol containing liposomes in an amount proportional to the time of incubation. The calcium accumulation, as indicated by kinetic analysis, resulted from an increased compartment size. (Ca(2+)+Mg2+)-ATPase exhibited decreased activity after pretreatment with 25-hydroxycholesterol containing liposomes and the increased intracellular calcium content was directly proportional to the decreased (Ca(2+) + Mg2+)-ATPase activity. When lipids in the cell membrane were examined, a failure to change the cholesterol/phospholipids ratio in the membrane was noted. The 25-hydroxycholesterol content in the membrane determined by HPLC did not increase. An increase in sphingomyelin and a decrease in phosphatidylethanolamine and acidic phospholipids in the membrane was noted. We suggest that the accumulation of intracellular calcium comes from both an increase of calcium influx and a decrease of (Ca(2+) + Mg2+)-ATPase activity, which may be the consequence of changes in membrane phospholipid composition.     

Sequence diversity within the argF, fbp and recA genes of natural isolates of Neisseria meningitidis: interspecies recombination within the argF gene

Studies of natural populations of Neisseria meningitidis using multilocus enzyme electrophoresis have shown extensive genetic variation within this species, which, it has been proposed, implies a level of sequence diversity within meningococci that is greater than that normally considered as the criterion for species limits in bacteria. To obtain a direct measure of the sequence diversity among meningococci, we obtained the nucleotide sequences of most of the argF, recA and fbp genes of eight meningococci of widely differing electrophoretic type (from the reference collection of Caugant). Sequence variation between the meningococcal strains ranged from 0-0.6% for fbp, 0-1.3% for argF, and 0-3.3% for recA. These levels of diversity are no greater than those found within Escherichia coli 'housekeeping' genes and suggest that multilocus enzyme electrophoresis may overestimate the extent of nucleotide sequence diversity within meningococci. The average sequence divergence between the Neisseria meningitidis strains and N. gonorrhoeae strain FA19 was 1.0% for fbp and 1.6% for recA. The argF gene, although very uniform among the eight meningococcal isolates, had a striking mosaic structure when compared with the gonococcal argF gene: two regions of the gene differed by greater than 13% in nucleotide sequence between meningococci and gonococci, whereas the rest of the gene differed by less than 1.7%. One of the diverged regions was shown to have been introduced from the argF gene of a commensal Neisseria species that is closely related to Neisseria cinerea. The source of the other region was unclear.     

Kinetic properties of aromatase mutants Pro308Phe, Asp309Asn, and Asp309Ala and their interactions with aromatase inhibitors.

Mutant forms of aromatase cytochrome P-450 bearing modifications of amino acid residues Pro308 and Asp309 and expressed in transfected Chinese hamster ovary cells were subjected to kinetic analysis and inhibition studies. The Km for androstenedione for expressed wild type (11.0 +/- 0.3 nM SEM, n = 3) increased 4-, 25- and 31-fold for mutants Pro308Phe, Asp309Asn and Asp309Ala, respectively. There were significant differences in sensitivity among wild type and mutants to highly selective inhibitors of estrogen biosynthesis. 4-Hydroxyandrostenedione (4-OHA) a strong inhibitor of wild type aromatase activity (IC50 = 21 nM and Ki = 10 nM), was even more effective against mutant Pro308Phe (IC50 = 13 nM and Ki = 2.8 nM), but inhibition of mutants Asp309Asn and Asp309Ala was considerably less (IC50 = 345 and 330 nM and Ki = 55 and 79 nM, respectively). Expressed wild type aromatase and Pro308Phe aromatase were strongly inhibited by CGS 16949A (IC50 = 4.0 and 4.6 nM, respectively) whereas mutants Asp309Asn and Asp309Ala were markedly less sensitive (IC50 = 140 and 150 nM, respectively). CGS 18320B produced similar inhibition. Kinetic analyses produced Ki = 0.4 nM for CGS 16949A inhibition of wild type versus 1.1, 37 and 58 nM, respectively, against Pro308Phe, Asp309Asn and Asp309Ala. The results demonstrate significant changes in function resulting from single amino acid modifications of the aromatase enzyme. Our data indicate that mutation in Asp309 creates a major distortion in the substrate binding site, rendering the enzyme much less efficient for androstenedione aromatization. The substitution of Pro308 with Phe produces weaker affinity for androstenedione in the substrate pocket, but this alteration favors 4-OHA binding. Similarly, mutant Pro308Phe exhibits a slightly greater sensitivity to inhibition by CGS 18320B than does the wild type. These results indicate that residues Pro308 and Asp309 play critical roles in determining substrate specificity and catalytic capability in aromatase.