Primary structures of the mRNAs encoding the rat precursors for bradykinin and T-kinin. Structural relationship of kininogens with major acute phase protein and alpha 1-cysteine proteinase inhibitor

Three types of cloned cDNA sequences for rat low molecular weight prekininogens were isolated and determined by molecular cloning and sequence analysis. The deduced amino acid sequences indicated that one, termed K-prekininogen, represents the counterpart of the known low molecular weight prekininogen present in other mammals, while the other two, called T-prekininogens, contain a novel T-kinin sequence which was recently identified from rat plasma. Although T- and K-prekininogens are highly homologous with each other, both of the T-prekininogens contain methionine, instead of arginine or lysine, as an amino acid preceding T-kinin and exhibit two consecutive amino acid deletions in the preceding region of T-kinin as compared with K-prekininogen. The former finding accounts for the previous observation of strong resistance of T-kininogens to cleavage with trypsin or kallikreins, while the latter finding has been explained by the structural analysis of genomic clones in which T-kinin-coding exon is contracted at its intron junction. A partial nucleotide sequence reported recently for the rat major acute phase protein (alpha 1-MAP) mRNA was found to be extremely related to the corresponding portion of the rat T-prekininogen mRNA. Furthermore, consistent with the previous report of the structural identity of major acute phase protein and alpha 1-cysteine proteinase inhibitor, kininogen closely resembles not only the former but also the latter in the amino acid compositions. The interrelationship among the triad of these proteins has been discussed.     

Light and electron microscopic studies on capillaries of the goat cardiac muscle with special reference to the topographical relationship between the vessels and Purkinje fibers

The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells.     

Fate of recombinants of the rat mandibular epithelium with cranial ectomesenchymal cells of different sources in vitro

The recombinants of the mandibular molar bud epithelia with cranial ectomesenchymal cell groups from several different sources--mandibular molar area, tongue anlagen, and lateral nasal process--were cultured. Dental laminalike buds were developed in each of the recombinants (incidence of development 38-86%). In the heterotrophic recombinants, heterotypic differentiation of mandibular epithelium was also induced. However, the foreign ectomesenchymal cells were not induced heterotypically by the epithelial genetic factor, but the mesenchymal genetic factor is maintained. It is suggested that mandibular molar bud epithelia have potency to proliferate into mesenchyme under non-organ-specific influences of ectomesenchymal cells and that presumptive mandibular mucosal epithelia have multipotency for differentiation sensitive to inductive influences by the heterotypic cranial ectomesenchymal cells but that the mandibular molar bud epithelia have no heterotypic inductive activity for the differentiation of cranial ectomesenchymal cells.     

The APC/C activator Cdh1 regulates the G2/M transition during differentiation of placental trophoblast stem cells

Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1^GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1^GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation.     

Changes in Volatile C6-Aldehydes Emitted from and Accumulated in Tea Leaves

C₆-Aldehydes emitted from intact tea leaves were analyzed quantitatively.Emission of the aldehydes increased temporarily in mid-May whenenzymatic activities involved in aldehyde formation from lipidsbegan to increase. Levels of C₆-aldehydes in tea leaves alsoincreased temporarily. However, the accumulated C₆-aldehydesdid not always correspond to emitted ones. (Received December 1, 1991; Accepted March 18, 1992)     

Uncoupling of Rat Cerebral Cortical α2-Adrenoceptors from GTP-Binding Proteins by N-Ethylmaleimide

Pretreatment of membranes from rat cerebral cortex with N-ethylmaleimide (NEM) decreased [3H]-clonidine binding in a concentration-dependent manner. The Bmax values of high-affinity sites for [3H]clonidine were reduced by 50 microM NEM treatment. Treatment with 500 microM NEM diminished the sum of Bmax of both high- and low-affinity components. GTP, Na+, and Mn2+ exerted little effect on [3H]clonidine binding in NEM-treated membranes. The addition of purified GTP-binding proteins caused an increase in the binding to the membranes pretreated with 50 microM NEM, but did not increase [3H]-clonidine binding in membranes treated with 500 microM NEM. In contrast, NEM pretreatment inhibited islet activating protein (IAP)-catalyzed ADP ribosylation of membrane-bound (41,000-dalton) and purified (39,000/41,000-dalton) GTP-binding proteins. From these results, it is suggested that two or three categories of essential sulfhydryl groups are involved in the coupling between agonist, alpha 2-adrenoceptor, and GTP-binding protein. One is a highly sensitive site to NEM (a concentration range of 1-50 microM), which is probably a cysteine residue, IAP-catalyzed ADP-ribosylating site on the alpha-subunit of GTP-binding protein. Other sites have low sensitivity to NEM (a concentration range of 0.1-1 mM), and are the binding domain of agonist and/or the coupling domain of GTP-binding protein on the alpha 2-adrenoceptor. In addition, Ki-ras p21 protein may lack the capacity to couple with the alpha 2-adrenoceptor.     

Extensin Secreted into the Culture Medium by Tobacco Cells I. Purification and Some Properties

The medium of 12-day-old culturs of tobacco cells (Nicotianatabacum L., var Xanthi; line XD-6S) contain c.a. 160mg/literof protein, of which 14% of the constituent ami no acids werefound to be hydroxyproline. By sequential column chromatographiesand CsCl density-gradient centrifugation, a basic hydroxyproline-richglycoprotein was purified from the medium and found to havean amino acid composition typical of extensin; with a high levelof hydroxyproline (33mole%), tyrosine (13%), and lysine (14%).The glycoprotein contained 42% (w/w) of sugars, among whicharabinose was the major component (85%). The proportion of thisextensin in the proteins in the culture medium was estimatedto be much higher than that of arabino-galactan protein (about5 times higher) on a protein basis, with extensin comprisingbetween 25% and 41%, and probably about 37% of the proteinsin the medium. (Received September 19, 1988; Accepted December 26, 1988)     

Regulation of mast cell differentiation

Mast cells are a unique class of blood cell. Unlike most blood cells, undifferentiated precursors of mast cells migrate in the bloodstream, invade tissues, proliferate there and then differentiate. Even after differentiation, some mast cells may proliferate extensively. Differentiation of mast cells is regulated by both diffusible growth factors and direct contact with fibroblasts.     

A scanning calorimetric study of the thermal denaturation of the lysozyme of phage T4 and the Arg 96----His mutant form thereof

High-sensitivity scanning calorimetry has been employed to study the reversible thermal unfolding of the lysozyme of T4 bacteriophage and of its mutant form Arg 96----His in the pH range 1.80-2.84. The values for t1/2, the temperature of half-denaturation, in degrees Celsius and for the enthalpy of unfolding in kilocalories per mole are given by (standard deviations in parentheses) wild type t1/2 = 9.63 + 14.41 pH (+/- 0.58) delta Hcal = 5.97 + 2.33t (+/- 4.20) mutant form t1/2 = -19.84 + 21.31 pH (+/- 0.51) delta Hcal = -8.58 + 2.66t (+/- 4.48) At any temperature within the range -20 to 60 degrees C, the free energy of unfolding of the mutant form is more negative than that of the wild type by 3-5 kcal mol-1, indicating an apparent destabilization resulting from the arginine to histidine replacement. The ratio of the van't Hoff enthalpy to the calorimetric enthalpy deviates from unity, the value expected for a simple two-state process, by +/- 0.2 depending on the pH. It thus appears that the nature of the unfolding of T4 lysozyme varies with pH in unknown manner. This complication does not invalidate the values reported here for the temperature of half-completion of unfolding, the calorimetric enthalpy, the heat capacity change, or the free energy of unfolding.