The structure ofHLA-B35 suggests that it is derived fromHLA-Bw58 by two genetic mechanisms

The primary structure ofHLA-B51 andHLA-Bw52 suggested thatHLA-B51 was derived fromHLA-Bw52 by the combination of a genetic exchange withHLA-B8 and a point mutation. To investigate the evolution of theHLA-B5 cross reactive group, theHLA-B35 gene was cloned and the primary structure was determined.HLA-B35 is identical toHLA-Bw58 except in the α₁ domain. The α₁ domain ofHLA-B35 except Bw4/Bw6-associated amino acids is identical to that ofHLA-B51 ^*, which was suspected to be an intermediate gene betweenHLA-B51 andHLA-Bw52. These data suggest thatHLA-B35 has evolved fromHLA-Bw58 in two steps; an in vivo replacement of the α₁ domain withHLA-B51 and genetic exchange with one of theHLA-Bw6 genes. These three genes andHLA-Bw58 are postulated to share a common ancestor.     

Impaired cholesterol esterification in cultured skin fibroblasts from patients with I-cell disease and pseudo-Hurler polydystrophy

Cholesterol esterification was examined in cultured skin fibroblasts from patients with I-cell disease and pseudo-Hurler polydystrophy by incubating cells pretreated without fetal calf serum for 48h, with (14C) cholesterol for 24h. Impaired cholesterol esterification was found in these cells and free cholesterol was accumulated in plasma membrane and Golgi fractions. This impairment was also induced in control cells by adding leupeptin (20 micrograms/ml) or monensin (2 micrograms/ml). These findings suggest the importance of the role of lysosomes for esterification of cholesterol and give a hint as to the basic defect in type C Niemann-Pick disease.     

Effects of pancreastatin on insulin and pancreatic polypeptide secretion in the dog

Porcine pancreastatin (1.19 nmol) was administered into the peripheral vein (i.v.) or the third cerebral ventricle (i.t.v.) of dogs and its effect on the secretion of insulin and pancreatic polypeptide (PP) studied. Neither means of administration had any effect on basal and glucose-induced insulin or PP secretion. However, i.v. pancreastatin did inhibit the i.v. CCK-8-induced insulin but not PP release. Pancreastatin may thus play a role in the regulation of insulin secretion in the canine pancreas.     

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line κ light chain genes and germ-line T-cell receptorβ- and γ-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.     

Ultrastructure of the calcium release channel of sarcoplasmic reticulum

This study is concerned with the characterization of the morphology of the calcium release channel of sarcoplasmic reticulum (SR) from fast-twitch skeletal muscle, which is involved in excitation-contraction coupling. We have previously purified the ryanodine receptor and found it to be equivalent to the feet structures, which are involved, in situ, in the junctional association of transverse tubules with terminal cisternae of SR. The receptor is an oligomer of a single high molecular weight polypeptide and when incorporated into phospholipid bilayers, has channel conductance which is characteristic of calcium release in terminal cisternae of SR. The purified channel can be observed by electron microscopy using different methods of sample preparation, with complementary views being observed by negative staining, double staining, thin section and rotary shadowing electron microscopy. Three views can be observed and interpreted: (a) a square face which, in situ, is junctionally associated with the transverse tubule or junctional face membrane; (b) a rectangle equivalent to the side view; and (c) a diamond shape equivalent to the side view, of which the base portion appears to be equivalent to the transmembrane segment. Negative staining reveals detailed substructure of the channel. A computer averaged view of the receptor displays fourfold symmetry and ultrastructural detail. The dense central mass is divided into four domains with a 2-nm hole in the center, and is enclosed within an outer frame which has a pinwheel appearance. Double staining shows substructure of the square face in the form of parallel linear arrays (six/face). The features of the isolated receptor can be correlated with the structure observed in terminal cisternae vesicles. Sections tangential to the junctional face membrane reveal that the feet structures (23-nm squares) overlap so as to enclose smaller square spaces of approximately 14 nm/side. We suggest that this is equivalent to the transverse tubule face and that the terminal cisternae face is smaller (approximately 17 nm/face) and has larger alternating spaces as a consequence of the tapered sides of the foot structures. Image reconstruction analysis appears to be feasible and should provide the three-dimensional structure of the channel.     

Effects of CCK antagonists on CCK-induced suppression of locomotor activity in mice.

Sulfated cholecystokinin octapeptide (CCK-8) was administered either intraperitoneally or into the cerebral ventricle of fully conscious mice, and locomotor activity was quantified. CCK-8 administered by either route suppressed locomotor activity. Subcutaneously administered selective CCK-A receptor antagonist, L-364,718 (1 mg/kg), reversed the inhibitory effect of centrally as well as peripherally administered CCK-8, but the selective CCK-B receptor antagonist, L-365,260 (1 mg/kg), did not. These results demonstrate that centrally as well as peripherally administered CCK-8 suppresses locomotor activity in mice through an interaction with CCK-A, but not CCK-B, receptors.     

Application of the tryptophanase promoter to high expression of the tryptophan synthase gene inEscherichia coli

Summary The application of an inducible regulation system using the trytophanase operon promoter (TPase promoter; P_tna) was examined for its high expression of the tryptophan synthase (TS) gene in Escherichia coli. The main problem in the application of P_tna for industrial purposes is catabolite repression by glucose, since glucose is the most abundant carbon source. However, this problem could be avoided by changing glucose to an organic acid, such as succinate, fumarate, malate and acetate, in the course of cultivation after glucose initially added was completely consumed. Under these conditions, l-tryptophan was also used to induce tryptophan synthase. Thus, the specific activity of TS in E. coli strain no. 168 harbouring pBR322F-P_tnaTS was increased 500-fold compared to that of the cultured host strain. About 1 mol l-tryptophan/l reaction mixture was formed from indole and l-serine at 37° C for 3.5 h. Offprint requests to: H. Yukawa     

Three-dimensional ultrastructure of anionic sites of the glomerular basement membrane by a quick-freezing and deep-etching method using a cationic tracer

The ultrastructure of anionic sites in the lamina rara externa (LRE) of rat glomerular basement membrane (GBM) was studied in three dimensions by a quick-freezing and deep-etching method using polyethyleneimine (PEI) as a cationic tracer. Results were compared with those obtained with conventional ultrathin sections examined by transmission electron microscopy. Examination with the quick-freezing and deep-etching method was done without (group 1) or with (group 2) contrasting/fixation with a phosphotungstic acid and glutaraldehyde mixture and post-fixation with osmium tetroxide, which were necessary for visualization of PEI particles by conventional ultrathin sections. Using the quick-freezing and deep-etching method without following contrasting/fixation and post-fixation (group 1), many PEI particles were observed to decorate around fibrils, which radiated perpendicularly from the lamina densa to connect with the podocyte cell membrane. The arrangement of PEI particles was not as regular as that previously reported using conventional ultrathin sections. In contrast, the tissue that was studied with quick-freezing and deep-etching followed by contrasting/fixation and post-fixation (group 2) showed a shrunken appearance. The arrangement of PEI particles was regular (about 20 particles/1000 nm of LRE) as that previously observed using conventional ultrathin sections. However, the number of PEI particles on the LRE was markedly decreased and interruption of decorated fibrils was prominent, as compared with group 1. Ultrastructural examination using conventional ultrathin sections with contrasting/fixation and post-fixation (group 3) demonstrated PEI particles on the LRE in reasonable amounts (18-21 particles/1000 nm of LRE) with fairly regular interspacing (45-65 nm) as reported previously.(ABSTRACT TRUNCATED AT 250 WORDS)     

The physiological role of oxygen-sensitive pyruvate dehydrogenase in mitochondrial fatty acid synthesis in Euglena gracilis

In Euglena gracilis a malonyl-CoA-independent fatty acid-synthetic system, in which fatty acids are synthesized directly from acetyl-CoA as both primer and C2 donor, occurs in mitochondria, and the system contributes to the wax ester fermentation. The activity of fatty acid synthesis in the mitochondrial system was enhanced about six times when an artificial acetyl-CoA-regenerating system was present, indicating that the fatty acid-synthetic activity is controlled by the ratio of acetyl-CoA against CoA. When fatty acids were synthesized using pyruvate instead of acetyl-CoA as substrate, a high activity, about 30 times higher than that from acetyl-CoA, was found under anaerobic conditions (below 10(-5) M oxygen), while in aerobiosis fatty acids were not synthesized at all. CoA, NADH, and NADP+ were required as cofactors for fatty acid synthesis from pyruvate. It was indicated that high activity of fatty acid synthesis from pyruvate due to the high ratio of acetyl-CoA against CoA was maintained by the action of the oxygen-sensitive pyruvate dehydrogenase found in Euglena mitochondria. When [2-14C]pyruvate was fed into intact mitochondria under anaerobic conditions, radioactive fatty acids were formed in the presence of malate, which provided reducing power for the matrix.