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.     

Stress fibers in the mesenteric mesothelial cells of the large intestine of the bullfrog,Rana catesbeiana

Summary Actin-containing cytoplasmic fibers were visualized in the mesenteric mesothelial cells of the large intestine of bullfrog tadpoles by rhodamine-phalloidin staining of en face preparations of mesothelial cells. These fibers were concurrently stained by immunofluorescence using antibodies to myosin or -actinin. Electron microscopy showed the presence of bundles of microfilaments in the basal cytoplasm of the cells. Such fibers in the mesothelial cells may be comparable to the stress fibers present in cultured cells. The mesothelial cells initially formed axially oriented stress fibers when they changed from a rhombic to a slender spindle-like shape. On the other hand, stress fibers disappeared as cells transformed from elongated to polygonal shapes during the period of metamorphic climax. Expression of stress fibers in these cells appears to be related to the degree of tension loaded on the mesentery, which may be generated by mesenteric winding. These stress fibers in the mesothelial cells may serve to regulate cellular transformation. They may also help to maintain cellular integrity by strengthening the cellular attachment to subepithelial tissue against tensile stress exerted on the mesentery.     

ent-Kaurene Synthesis and Endogenous Levels of Gibberellins in a Shoot Forming Tobacco Crown Gall Tissue

The in vitro ent-Mcaurene synthesizing capacity, as well asthe endogenous GA content of shoot-forming tobacco crown gallsinduced by a nopaline-type Ti plasmid, was studied. For determinationof the ent-kaurene synthesizing capacity, an HPLC procedurepreceded by sample clean-up was used and the GA content wasexamined by GC-SIM. Kaurene synthesis reached a maximum at thebeginning of the logarithmic phase of growth. There was a clearcorrelation between the ent-kaurene synthesizing capacity andthe content of C₂₀-GAs. It seems that gibberellin synthesisis related to growth and development of the tissue. The natureof the GAs identified suggests, that the GA metabolism mightbe an unusual one. (Received October 12, 1987; Accepted April 11, 1988)     

Mutations in a Saccharomyces cerevisme host showing increased holding stability of the heterologous plasmid pSRI

Summary We have isolated Saccharomyces cerevisiae mutants, smp, showing stable maintenance of plasmid pSRI, a Zygosaccharomyces rouxii plasmid. The smp mutants were recessive and were classified into at least three different complementation groups. The three mutants also showed increased stability of YRp plasmids and the mutations are additive for plasmid stability. One mutation, smp1, confers a respiration-deficient (rho ⁰) phenotype and several Rho^– mutants independently isolated by ethidium bromide treatment of the same yeast strain also showed increased stabilities of pSR1 and YRp plasmids. The wild-type S. cerevisiae cells showed a strongly biased distribution of pSR1 molecules as well as YRp plasmids to the mother cells at mitosis, while the smpf mutant did not show this bias. Another mutation, smp3, at a locus linked to ade2 on chromosome XV, confers temperature-sensitive growth. The SMP3 gene encodes a 59.9 kDa hydrophobic protein and disruption of the gene is lethal.     

Immunofluorescence Microscopy of Microtubule Arrangement in Root Cells of Pisum sativum L. var Alaska

The arrangement of wall microtubules (MTs) in Pisum sativumroots was viewed immunofluorescently using cryosectioning. Mostcells in the tip region of pea roots (0–2 mm from tip)had wall MTs arranged transversely to the root axis. In theregion elongating at a higher rate (2–4 mm), wall MTsof epidermal, cortical and stelar cells were all transverselyarranged. In the region of about 5 mm from the tip, in whichcell elongation had already ceased, wall MTs in cortical cellschanged from a transverse to an oblique arrangement in relationto the root axis. Some cells had a crossed arrangement of wallMTs, which was interpreted as representing two sets of unidirectional,oblique wall MTs in opposite cell cortices of a single cell.This change was completed within a region of 1-mm width. Sinceroots elongated at a rate of 0.6 mm h^–1, it means thatthe arrangement of wall MTs changed within 2 h. An oblique arrangementof wall MTs was also observed in stelar cells. As the cellsaged, the oblique arrangement tended to change to a steeperor even a longitudinal one. (Received January 24, 1986; Accepted May 15, 1986)     

Molecular cloning and characterization of the Endo B cytokeratin expressed in preimplantation mouse embryos

A cDNA clone of a keratin-related, intermediate filament protein, designated Endo B, was constructed from size-fractionated parietal endodermal mRNA and characterized. The 1466-nucleotide cDNA insert contains an open reading frame of 1272 nucleotides that would result in 5' and 3' noncoding sequences of 54 and 60 nucleotides, respectively. The predicted amino acid composition, molecular weight (47,400), and peptide pattern correlate well with data obtained on the isolated protein. The predicted amino acid sequence fits easily into the general domain structure suggested for all intermediate filament proteins with a unique amino-terminal head domain, a large conserved central domain of predominantly alpha-helical structure, and a relatively unique carboxyl-terminal or tail domain. Over the entire molecule, Endo B is 43% identical with human 52-kDa epidermal type I keratin. However, over two of the three regions contained in the central domain that are predicted to form coiled-coil structures, the Endo B is 54-68% identical with other type I keratin sequences. This homology, along with the presence of the completely conserved sequence DNARLAADDFR-KYE, which is found in all type I keratins, permits the unambiguous identification of Endo B as a type I keratin. Comparison of the Endo B sequence to other intermediate filament proteins reveals 22 residues which are identical in all intermediate filament proteins regardless of whether filament formation requires only one type of protein subunit (vimentin, desmin, glial fibrillar acidic protein, or a neurofilament protein) or two dissimilar types (type I and type II keratins). Endo B mRNA was detectable in RNA isolated from F9 cells treated with retinoic acid for 48 h. Approximately three to five genes homologous to Endo B were detected in the mouse genome.     

Control of chromatophore movements in dermal chromatic units of blue damselfish--I. The melanophore

Mechanisms controlling pigment movements in the melanophore of the blue damselfish, Chrysiptera cyanea, were studied. Histological observations revealed that the melanophore had three-dimensionally developed processes to envelop overlying small iridophores, and thus participated in the construction of a simple dermal chromatophore unit. Nervous stimulation, catecholamines and melatonin brought about melanosome aggregation in the melanophore. The actions of the nervous stimulation and catecholamines were antagonized by alpha adrenolytic agents. A beta adrenergic agonist, metaproterenol, adenosine and adenine nucleotides, and alpha-MSH acted as pigment-dispersing agents. These results indicate that the melanophore of the present material is controlled quite orthodoxly by adrenergic nerves and endocrines, notwithstanding the fact that it has quite a unique morphology among fish species, and that its motile rate is remarkably high.     

Interaction of alpha-chymotrypsin with dimyristoyl phosphatidylcholine vesicles

The amidolytic activity of chymotrypsin for Suc-Ala2-Pro-Phe-MCA was somewhat enhanced by dimyristoyl PC at low ionic strength, but not at high ionic strength. The activity was strongly inhibited by pure egg yolk PA. The inhibition by 200 ng PA was neutralized by addition of 1 microgram dimyristoyl PC or pure egg yolk PC, which formed vesicles with the PA. The Km and kcat (s-1) values of chymotrypsin for hydrolysis of Suc-Ala2-Pro-Phe-MCA changed from 15 microM to 42 microM, 0.1 mM and 0.5 mM, and from 1.5 to 2.7, 3.7, and 1.0 in the presence of 1 microgram dimyristoyl PC, 0.5 micrograms pure egg yolk PE and 0.2 microgram egg yolk PA, respectively. Gel-filtration chromatography showed that dimyristoyl PC formed a complex with chymotrypsin, but did not interact with the substrate, indicating that the basic globular protein, chymotrypsin, interacted with net-neutral PL.