Epidermal growth factor (EGF)-induced morphological changes in the basement membrane of chick embryonic skin

Summary The effect of epidermal growth factor (EGF) on the basement membrane structure of chick embryonic skin cultured in a chemically defined medium (BGJb) containing 20 mM hydrocortisone, and EGF at 10, 50, or 100 ng/ml supplemented with 5% delipidized fetal calf serum, was examined by electron microscopy. During development of the epidermis in vitro, EGF (100 ng/ml) caused striking changes to occur in the basement membrane structure and in the keratinization process. The basement membrane frequently became discontinuous with many gaps apparent in section, and occasionally became folded following detachment from the basal surface of the epidermis and protruded into the underlying dermis. In the basal and intermediate cells of EGF-treated epidermis, tonofilament bundles were decreased in number, while desmosomes and hemidesmosomes revealed no significant changes in morphology.     

The augmentation of tumor-specific immunity using haptenic muramyl dipeptide (MDP) derivatives

Summary A previous paper has demonstrated that enhanced tumor-specific immunity could be induced by priming mice with Bacillus Calmette Guerin (BCG) and subsequently immunizing them with syngeneic tumor cells modified with BCG-cross-reactive muramyl dipeptide (MDP) hapten [15]. The present study establishes a tumorspecific immunotherapy protocol for a murine chronic leukemia based on the above T-T cell collaboration between antitumor effector T cells and anti-MDP hapten helper T cells induced by BCG priming. BALB/c mice which had been primed to BCG were injected intravenously (i.v.) with viable, syngeneic BCL1 leukemia cells. One week later, these mice were immunized intraperitoneally (i.p.) with unmodified or MDP hapten-modified, 10,000 R X-irradiated BCL1 cells, followed by 4 booster immunizations at 5-day intervals. The administration of unmodified BCL1 tumor cells into BCG-primed mice failed to prevent them from tumor death due to the persistent growth of preinjected BCL1 cells. In contrast, the immunization of BCG-primed, BCL1 leukemia-cell-bearing mice with MDP-modified BCL1 cells resulted in a high growth inhibition of leukemia cells and protection of these mice from death by leukemia. It was also revealed that potent tumorspecific, T-cell-mediated immunity was generated in mice which survived in this immunotherapy model. Thus, these results indicate that administration of MDP hapten-modified, syngeneic leukemia cells into leukemia-bearing mice which have been primed with BCG results in potent tumor-specific, T-cell-mediated immunity attributable to preventing the growth of disseminated leukemic cells.This work was supported by a Grant-in-Aid for the Special Project Cancer-Bioscience from the Ministry of Education, Science, and Culture, Japan Abbreviations used: TATA, tumor-associated transplantation antigens; MDP, muramyl dipeptide; MTP, muramyl tripeptide; BCG, Bacillus Calmette Guerin     

Electron microscopy of hepatitis B virus core antigen expressing yeast cells by freeze-substitution fixation

We have used the freeze-substitution fixation technique for electron microscopy of yeast cells that express the hepatitis B virus core antigen (HBcAg) following transformation with the cloned gene. Abundant spherical particles were found within the transformed cells. These particles had a uniform size and shape, measured about 21 nm in diameter, had electron-lucent centers, and consisted of many subunits. They were localized in both the cytoplasm and the nucleus. None of these particles was found in the cells of the parent strain. Comparison of the HBcAg particles isolated from the yeast cells and the particles within the yeast cells demonstrated that the 21-nm particles were in fact ultrastructurally superimposable on HBcAg. Thus, the HBcAg particles within the yeast cells were similar to the HBcAg particles in human liver tissues infected with hepatitis B virus, not only in their size and appearance, but also in their intracellular localization. These results suggest that the yeast cell has the same machinery for synthesis and intracellular translocation of the HBcAg polypeptides as the human cell.     

Protein Tyrosine Kinase Activity and Its Endogenous Substrates in Rat Brain: A Subcellular and Regional Survey

The rat CNS contains high levels of tyrosine-specific protein kinases that specifically phosphorylate the tyrosine-containing synthetic peptide poly(Glu80,Tyr20). The phosphorylation of this peptide is rapid and occurs with normal Michaelis-Menten kinetics. Using this peptide to assay for enzyme activity, we have measured the protein tyrosine kinase activity in homogenates from various regions of rat CNS. A marked regional distribution pattern was observed, with high activity present in cerebellum, hippocampus, olfactory bulb, and pyriform cortex, and low activity in the pons/medulla and spinal cord. The distribution of protein tyrosine kinase activity was examined in various subcellular fractions of rat forebrain. The majority of the activity was associated with the particulate fractions, with enrichment in the crude microsomal (P3) and crude synaptic vesicle (LP2) fractions. Moreover, the subcellular distribution of pp60csrc, a well-characterized protein tyrosine kinase, was examined by immunoblot analysis using an affinity-purified antibody specific for pp60csrc. The subcellular distribution of pp60csrc paralleled the overall protein tyrosine kinase activity. In addition, using an antibody specific for phosphotyrosine, endogenous substrates for protein tyrosine kinases were demonstrated on immunoblots of homogenates from the various regions and the subcellular fractions. The immunoblots revealed numerous phosphotyrosine-containing proteins that were present in many of the CNS regions examined and were associated with specific subcellular fractions. The differences in tyrosine-specific protein kinase activity, and in phosphotyrosine-containing proteins, observed in various regional areas and subcellular fractions may reflect specific functional roles for protein tyrosine kinase activity in mammalian brain.     

Immunohistochemical localization of Na+-dependent glucose transporter in rat jejunum

Summary Glucose is actively absorbed via a Na⁺-dependent active glucose transporter (Na-GT) in the small intestine. We raised a polyclonal antibody against the peptide corresponding to amino acids 564–575 of rabbit intestinal Na-GT, and localized it immunohistochemically in the rat jejunum. By means of immunofluorescence staining, Na-GT was located at the brush border of the absorptive epithelial cells of the intestinal villi. Electron-microscopic examination showed that Na-GT was localized at the plasma membrane of the apical microvilli of these cells. Little Na-GT was found at the basolateral plasma membrane. Along the crypt-villus axis, all of the absorptive epithelial cells in the villus were positive for Na-GT. In addition to the brush border staining, the supranuclear positive staining, which was shown to be the Golgi apparatus by use of electron microscopy, was seen in cells located between the base to the middle of the villus. Cells in crypts exhibited little or no staining for Na-GT. Goblet cells scattered in the intestinal epithelium were negative for Na-GT staining. These observations show that Na-GT is specific to the apical plasma membrane of the absorptive epithelial cells, and that the onset of Na-GT synthesis may occur near the crypt-villus junction.     

Analysis of intergenic spacer regions in the nuclear rDNA of Pharbitis nil.

The nucleotide sequence of a 4.2-kb EcoRI fragment from the intergenic region between the genes for 25S and 18S ribosomal RNA of Pharbitis nil Choisy was determined. The region contained a unique repetitive family of DNA sequences, called the RsaI family, composed of 32-bp units. The 32-bp unit was tandemly repeated in the intergenic region, and four subfamilies of repeating units were clustered as discrete blocks. The RsaI family of repeats was shown to be specific to the genus Pharbitis by Southern blot hybridization.     

Correspondence of Apoproteins of Light-Harvesting Chlorophyll a/b Complexes Associated with Photosystem I to cab Genes: Evidence for a Novel Type IV Apoprotein

Apoproteins of spinach and pea light-harvesting chlorophylla/b complexes associated with photosystem I (LHCI) were identifiedby their chlorophyll fluorescence spectra and protein sequences.Spinach LHCI holocomplex consisted of four apoproteins of 25kDa, 23 kDa, 21 kDa and 20.5 kDa. LHCI subcomplex isolated bysucrose density gradient centrifugation fluoresced at 680 nmwith a shoulder around 700–710 nm at 77 K. It containedthe 23 kDa protein of which the N-terminal sequence correspondedto Type II gene of LHCI. Another LHCI subcomplex isolated bygel electrophoresis emitted at 679 nm and contained the 25 kDaprotein, of which the N-terminus was blocked. Its internal sequenceswere determined after protease treatment and found to be homologousto Type III gene of LHCI. An oligomeric subcomplex of LHCI isolatedby gel electrophoresis emitted at 726 nm and consisted of the21 kDa and 20.5 kDa apoproteins. N-terminal sequence of the20.5 kDa component corresponded to the Type I gene of LHCI.The 21 kDa component did not have any clear homologue, but itsN-terminal sequence was weakly but significantly homologousto all LHC components particularly to Type I LHCI among others.It was, thus, concluded that the 21 kDa protein is the fourthtype of LHCI apoprotein. Similar sequence homology was foundfor pea LHCI apoproteins. (Received September 10, 1990; Accepted November 22, 1990)     

Identification and genetic analysis of semidwarfism-related proteins in rice (Oryza sativa L.)

Summary By transferring a semidwarf gene (sd-1) from Taichung Native 1 into a tall Japanese cultivar, Norin 29, through seven backcrosses, a semidwarf near-isogenic line SC-TN1 was obtained. The proteins of the embryo in Norin 29 and SC-TN1 were separated by two-dimensional electrophoresis. Most of the proteins showed the same electrophoretic pattern. However, it was found that there was a difference in the appearance of two basic glycoproteins designated as SRP-1 and SRP-2. These proteins exhibited the same molecular mass, but different isoelectric points. Hybridization results indicated that a single locus controls SRP-1 and SRP-2 with codominant alleles. The gene symbol Srp was given to this locus, with alleles Srp-1 and Srp-2 responsible for SRP-1 and SRP-2, respectively. Srp-2 was found in all of the semidwarf cultivars and lines having sd-1, except a tall cultivar Tsaiyuan-chung. This finding suggests that Srp-2 may be closely linked with sd-1. The amounts of these proteins markedly increased after water absorption of the seed, suggesting that these proteins may be related to the early development of the plant.     

13C-n.m.r. analysis of some sulphate derivatives of chitosan.

Positions of substitution with sulphate in three water-soluble sulphated derivatives of chitosan were analysed by 13C n.m.r. The structures of N-acetylchitosan 3,6-O-disulphate, sodium chitosan N-, 6-O-disulphate, and sodium chitosan 6-O-monosulphate were confirmed.     

The influence of experimentally produced oligohydramnios on lung growth and pulmonary surfactant content in fetal rabbits.

To study the effect of oligohydramnios on lung growth and biochemical lung development in fetal rabbits, amniotic fluid was drained through a tube inserted into the maternal peritoneal cavity on the 23 day of gestation. Littermate fetuses without an amniotic shunt were used as controls. The fetuses were delivered abdominally on the 28 day of gestation. In a total of 8 pregnant does, 17 fetuses underwent amniotic shunting and 22 fetuses were used as controls. The amniotic shunt produced a significant reduction in the amniotic fluid volume. There were no differences in the wet weights of the fetal body, liver or brain between the two groups. However, the amniotic shunt significantly decreased the wet weight of the fetal lung, fetal lung wet weight/body weight ratio, and protein concentration per lung as compared to the control fetuses. In the fetal liver and brain tissues, no changes were found in the concentrations of total phospholipids, phosphatidylcholine (PC) or disaturated phosphatidylcholine (DSPC, the main component of lung surfactant) per g of wet tissue and per mg of protein. However, the lungs of the fetuses with amniotic shunts contained significantly more PC and DSPC, and the L/S ratio was higher than in the control fetuses. These results suggest that the oligohydramnios produced by an amniotic shunt causes pulmonary hypoplasia, but raises the pulmonary surfactant content of fetal rabbit lung.