Development of human pancreas

The developmental sequence of human pancreatic secretory proteins has not previously been studied in detail. We applied immunohistochemistry to study 20 fetal and neonatal pancreas' (8th to 39th gestational weeks) using antisera against the following pancreatic secretory proteins: pancreatic secretory trypsin inhibitor (PSTI), serine proteinases (trypsin, chymotrypsin, and elastase I), and amylase. PSTI was first detected in developing buds of the pancreas during the 8th gestational week, and proteinases were observed in acinar cells during the 14th week of gestation. Immunoreactivity for both PSTI and proteinases was found in most acinar cells soon after their appearance. Immunoreactivity for amylase could not be detected in fetal or neonatal pancreas tissue. PSTI was also found in developing islets during the 14th gestational week, but the number of immunoreactive cells had decreased by term. Cells positive for serine proteinases were occasionally in contact with islets in second-trimester fetuses. In discussing these results, we give particular attention to the nonparallel appearance of secretory products in the fetal pancreas, and the significance of cells immunoreactive for secretory proteins in endocrine islets.     

Freeze-fracture studies of the sinoatrial and atrioventricular nodes of the caprine heart,with special reference to the nexus

Summary The caprine sinoatrial node (SAN) and atrioventricular node (AVN) were studied by freeze-fracture techniques, and their nexus or gap junction structure were compared with that of ordinary atrial and ventricular muscle cells. The general features of the nexus in both the SAN and AVN were essentially identical. Approximately two-thirds of the nexuses observed in the nodal cells consisted of typical macular arrangements of nexal particles, and the remaining third, of atypical configurations of either circular arrangements or linear arrays of particles in continuity with the macular nexuses. Such atypical nexuses were never observed in the ordinary adult myocardial cells. Quantitative analysis revealed that all of the nexuses in the nodal cells measured, were less than 0.1 m², whereas the majority of the nexuses in ordinary myocardial cells (64% in the atrium and 76% in the ventricle) were larger than 0.1 m². No significant differences in diameter and center-to-center distance of nexal particle were found between the nodal cells and ordinary myocardial cells.     

Purification and characterization of the tween-hydrolyzing esterase of Mycobacterium smegmatis.

An esterase hydrolyzing Tween 80 (polyoxyethylene sorbitan monooleate) was purified from sonicated cell lysates of Mycobacterium smegmatis ATCC 14468 by DEAE-cellulose, Sephadex G-150, phenyl Sepharose, and diethyl-(2-hydroxypropyl) aminoethyl column chromatography and by subsequent preparative polyacrylamide gel electrophoresis. The molecular weight was estimated to be 36,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 41,000 by gel filtration on a Sephadex G-150 column. The esterase contained a single polypeptide. The esterase was stable to heat treatment at 100 degrees C and to a wide range of pH. The temperature and pH optima for the hydrolysis of Tween 80 were 50 degrees C and 8.3, respectively. The esterase had a narrow substrate specificity; it exhibited a high activity only on compounds having both polyoxyethylene and fatty acyl moieties, such as Tweens. Monoacylglyceride was hydrolyzed more slowly by this esterase and this enzyme exhibited a nonspecific esterase activity on p-nitrophenyl acyl esters, especially those having short chain acyl moieties. The Km and Vmax were 19.2 mM and 1,670 mumol/min per mg of protein for Tween 20, 6.6 mM and 278 mumol/min per mg of protein for Tween 80, and 0.25 mM and 196 mumol/min per mg of protein for p-nitrophenyl acetate, respectively. Observations of the effects of various chemical modifications on the activity of the esterase indicated that tyrosine, histidine, arginine, and methionine (with tryptophan) residues may be active amino acids which play important roles in the expression of Tween 80-hydrolyzing activity of the enzyme.     

A possible role of protein kinase C in signal-induced lysosomal enzyme release

In platelets, activation of protein kinase C and mobilization of Ca2+ were selectively induced by the addition of 1-oleoyl-2-acetyl-glycerol and a low concentration of A23187, respectively (Kaibuchi, K., Takai, Y., Sawamura, M., Hoshijima, M., Fujikura, T. and Nishizuka, Y. (1983) J. Biol. Chem. 258, 6701-6704). Using this procedure evidence was obtained suggesting that the protein phosphorylation and Ca2+ mobilization were both essential and synergistically effective to cause release of lysosomal acid hydrolases such as N-acetylglucosaminidase. A similar observation was made for the lysosomal enzyme release from rat neutrophils.     

Pertussis Toxin Attenuates 5-Hydroxytryptamine1A Receptor-Mediated Inhibition of Forskolin-Stimulated Adenylate Cyclase Activity in Rat Hippocampal Membranes

The inhibition of forskolin-stimulated adenylate cyclase activity by 5-hydroxytryptamine (5-HT) receptor agonists was measured in rat hippocampal membranes isolated from animals treated with vehicle or islet-activating protein (IAP; pertussis toxin). In vehicle-treated animals, 5-HT, 8-hydroxy-2-(di-n-propylamino)tetralin, buspirone, and gepirone were potent in inhibiting forskolin-stimulated adenylate cyclase activity with EC50 values of 60, 76, 376, and 530 nM, respectively. IAP treatment reduced by 30-55% the 5-HT1A agonist inhibition of adenylate cyclase activity via 5-HT1A receptors. The data indicate that the inhibitory guanine nucleotide-binding protein or Go (a similar GTP-binding protein of unknown function purified from brain) mediates the 5-HT1A agonist inhibition of hippocampal adenylate cyclase.     

Multiple roles of the mitogen-activated protein kinase kinase/mitogen-activated protein kinase cascade in Xenopus laevis

Mitogen-activated protein kinase (MAPK) was originally identified as a serine/threonine protein kinase that is rapidly activated in response to various growth factors and tumor promoters in mammalian cultured cells. The kinase cascade including MAPK and its direct activator, MAPK kinase (MAPKK), is now believed to transmit various extracellular signals into their intracellular targets in eukaryotic cells. It has been reported that activation of MAPKK and MAPK occurs during the meiotic maturation of oocytes in several species, including Xenopus laevis . Studies with neutralizing antibodies against MAPKK, MAPK phosphatases and constitutively active MAPKK or MAPK have revealed a crucial role of the MAPKK/MAPK cascade in a number of developmental processes in Xenopus oocytes and embryos.     

Two genes controlling acute phase responses by the antitumor polysaccharide,lentinan

Lentinan, a -1,6;1,3-glucan, is tumor-specific for transplantable mouse solid-type tumors and it also stimulates the production of acute phase proteins (APPs). The APP response to lentinan is of the delayed type (DT-APR) and differs from that to lipopolysaccharide, which is acute. We found that the responses were genetically controlled in mice and that low responsiveness is dominant (Maeda et al. 1991). Using 123 segregants of crosses between SWR/J (a high responder) andMus spretus (a low responder), we analyzed the linkage between DT-APR responsiveness and the DNA polymerase chain reaction-simple sequence lenght polymorphism (PCR-SSLP) phenotype using 80 chromosome-specific microsatellite markers. We identified two loci (ltn1.1 andltn1.2) responsible for DT-APR.ltn1.1 is closely linked toD3Mit11 on chromosome 3 andltn1.2 toD11Nds9 on chromosome 11 (P<0.001). The linkage analysis also suggested thatltn1.2 is the major determinant for DT-APR. Correlation between lentinan-specific IL-6 mRNA expression (the late expression) controlled recessively and DT-APR induction suggests that theltn1 loci control some process(es) of IL-6 expression in the regulation step before NF-IL6.     

Cloning and sequence analysis of theMaackia amurensis haemagglutinin cDNA

Maackia amurensis haemagglutinin (MAH) is a leguminous lectin which preferentially binds to a cluster of sialylatedO-linked carbohydrate chains (Konami Y, Yamamoto K, Osawa T, Irimura T (1994)FEBS Lett 342:334–38). In the present study a 950 bp cDNA clone encoding MAH was isolated from a cDNA library constructed from germinatedMaackia amurensis seeds. From the nucleotide sequence, MAH was predicted to consist of 285 amino acid residues containing a signal peptide of 29 amino acids. The results also confirmed our previous findings from the amino acid sequence analysis, which indicated that two highly conserved amino acid residues in all other well-known leguminous lectins were replaced in MAH. These residues were lysine-105 and aspartic acid-135. The corresponding amino acid residues in other leguminous lectins were glycine and asparagine, respectively. These differences were due to the presence of nucleotides AAA and GAT in place of AAT/C and GGA/T.Abbreviations MAH Maackia amurensis haemagglutinin.