Oxygen concentration-dependent induction of a 140-kDa protein in magnetic bacterium Magnetospirillum magnetotacticum MS-1

Abstract The magnetic bacterium Magnetospirillum magnetotacticum prefers a microaerobic habitat and should be able to sense oxygen. Therefore, the bacterium was cultured under atmospheres containing 0–5% O₂ and analyzed for oxygen-dependent changes in the levels of its protein components by sodium dodecyl sulfate-polyccrylamide gel electrophoresis (SDS-PAGE). The analysis revealed a marked anaerobic induction of a 140-kDa protein, which was suppressed when M. magnetotacticum was switched from microaerobic (<1% O₂) to aerobic (>1% O₂) growth conditions. Although its function remains to be determined, the 140-kDa protein may serve as a useful tool to gain insight into the physiology of the organism.     

Isolation and characterization of a human hepatic epithelial-like cell line (AKN-1) from a normal liver

Summary The isolation and characterization of human liver cell lines are rather difficult due to limited material and poor growth in cell culture. In this report, we present the isolation, culture and characterization of a new epithelial-like liver cell line (AKN-1) with a heterogeneous cell population and many characteristics of the biliary epithelium. The AKN-1 cell line stained positively with antibodies to epithelial cytokeratin polypetides CK 8, 18, and 19. In addition, the cell line expressed the anti-human epithelial-related antigen (MOC-31), the human epithelial antigen (HEA), and the gamma-glutamyl transpeptidase, the hematopoietic growth factor, stem cell factor, and also its receptor, c-kit. The cell line failed to express albumin and factor 8 by immunohistochemistry. It did show, however, a twofold increase in 7-ethoxyresorufin-O-deethylase activity. Cytogenetic characterization revealed rare breakpoints in chromosome 2, which to our knowledge, have not yet been reported in liver cells.     

Degradation of thyroxine by microsomal particles from rat liver II. Purification of Fe3+-dependent particles and some of their properties

Particles, which catalyze the deiodination of thyroid hormones in the presence of Fe²⁺, have been purified about 25-fold with respect to the rat liver microsomes. This purification involves deoxycholate treatment, trypsin treatment and density gradient centrifugutions.The purified particles range from 1.019 to 1.063 in density and consist of 21% protein, 60% phospholipid and 19% neutral fat. No hemoprotein moiety is associated with the purified particles. The purified particles degrade not only l-thyroxine but also other iodinated thyronines and their derivatives, such as d-thyroxine, l-3′,3,5- triiodothyronine and tetraiodothyropropionic acid. They are inactive towards monoiodotyrosine and diiodotyrosine.Thyroxine is not metabolized in the drug hydroxylation system which involves cytochrome P-450.     

Molecular pathogenesis of malignant melanoma: a different perspective from the studies of melanocytic nevus and acral melanoma

The Clark model for melanoma progression emphasizes a series of histopathological changes beginning from benign melanocytic nevus to melanoma via dysplastic nevus. Several models of the genetic basis of melanoma development and progression are based on this Clark’s multi-step model, and predict that the acquisition of a BRAF mutation can be a founder event in melanocytic neoplasia. However, our recent investigations have challenged this view, showing the polyclonality of BRAF mutations in melanocytic nevi. Furthermore, it is suggested that many melanomas, including acral and mucosal melanomas, arise de novo, not from melanocytic nevus. While mutations of the BRAF gene are frequent in melanomas on non-chronic sun damaged skin which are prevalent in Caucasians, acral and mucosal melanomas harbor mutations of the KIT gene as well as the amplifications of cyclin D1 or cyclin-dependent kinase 4 gene. Amplifications of the cyclin D1 gene are detected in normal-looking ‘field melanocytes’, which represent a latent progression phase of acral melanoma that precedes the stage of atypical melanocyte proliferation in the epidermis. Based on these observations, we propose an alternative genetic progression model for melanoma.     

I-Region genetic restrictions imposed upon the recognition of KLH by murine T-cell clones

Data presented in this paper show that the recognition of keyhole limpet hemocyanin by murine T-cell clones is restricted by products of the I region. These data have been obtained by genetic mapping studies as well as by the use of monoclonal la-specific antibodies which inhibit the ability of antigen-presenting cells to effectively present antigen to such T-cell clones. Use of heterozygous antigen-presenting cells derived from crosses between B6.C-H-2 ^bm12 and B10.A(4R) mice have allowed us to show that both trans-complementing I-A products are used for restriction of recognition of KLH. These data were confirmed using monoclonal Ia antibodies to inhibition recognition of KLH by the same T-cell clones. Thus, we have shown that there exist hybrid molecules formed by free combinatorial association of products encoded within the I-A subregion which restrict the recognition of soluble antigen. Additionally, we have shown that the molecule formed by complementation between the alpha chain encoded within the I-E region and a beta chain encoded within the A region (A_e) can function effectively in presenting KLH to certain murine T-cell clones. These results support the hypothesis that the recognition of individual antigenic epitopes within large multideterminant antigens is under the control of Ir genes.     

Response of isolated rat iris dilator to adrenergic and cholinergic agents and electrical stimulation

Responses of isolated rat iris dilator to some agents and to electrical stimulation were examined. Norepinephrine and epinephrine produced contraction, which was antagonized by 0.03 μM phentolamine. Acetylcholine produced relaxation at low concentrations (1 nM ? 1 μM) as great as 80 % of the resting tone while contraction at high concentrations (≥1 μM). Both responses were suppressed by 0.02 μM atropine and enhanced by 0.03 μM physostigmine. Electrical stimulation at low voltage or low frequency (up to 10 Hz) elicited relaxation while stimulation at high voltage or high frequency (30 Hz) produced contraction. Stimulation with intermediate strength elicited biphasic response. The contraction and relaxation induced by electrical stimulation were abolished by 3 μM phentolamine or by 0.05 μM atropine, respectively. Both phases were abolished by tetrodotoxin (0.3 μM). It is suggested that in the rat the cholinergic relaxation of the dilator may assist the cholinergic contraction of the sphincter (1). The pronounced cholinergic relaxation of nonvascular tissue is to be noted.     

Little or no induction of hyperglycemia by 2-deoxy-D-glucose in hereditary blind microphthalmic rats

Studies were made on whether hereditary microphthalmic rats (1), which are congenitally blind, showed a hyperglycemic response to intracerebroventricular injection of 2-deoxy-D-glucose (2DG) in their subjective light period. In contrast to previous findings in normal rats in which 2DG injection caused light-cycle dependent hyperglycemia (2) and bilateral lesion of the suprachiasmatic nucleus (SCN) completely abolished this hyperglycemia (3), 2DG injection caused no and only slight hyperglycemia in male and female rats with hereditary microphthalmia, respectively. Gross and histological examinations indicated that these rats had no optic nerve or retinohypothalamic tract and that their SCN had an abnormal structure. Locomotive activity recordings showed that all the blind rats had a free-running circadian activity rhythm. These findings suggest that the projection sites of the retinohypothalamic tract to the SCN are involved in the mechanism of the hyperglycemic response to 2DG, but that neural cells, which may be responsible for the generation of circadian rhythms, are not. We have reported that when adult rats were blinded by orbital enucleation, their hyperglycemic response to 2DG was suppressed temporarily 3-5 weeks after the operation, but that their plasma insulin level was basically higher and increased further after 2DG injection during this period (4). In congenitally blind rats, however, the basal plasma insulin level was not higher and the level did not change after 2DG treatment. This difference is discussed from the view point of the role of the premature SCN in regulation of the plasma insulin concentration.     

Adaptations for feeding on rock surfaces and sandy sediment by the fiddler crabs (Brachyura: Ocypodidae) Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758)

Two species of fiddler crab, Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758), which belong to the subgenus Gelasimus, dwell on rocky shores and muddy–sandy tidal flats, respectively, in Phuket Is., Thailand. We investigated their feeding ecology in relation to the morphology of their feeding organs: minor food-handling chelipeds and maxillipeds. U. tetragononfed chiefly on rocks covered by filamentous green algae. U. vocansfed on the emerged sand and in shallow water along the shoreline and in pools. While feeding, both crabs made sand pellets beneath their mouthparts and discarded them, indicating that they divided the matter scooped up with their minor chelipeds into edible and inedible fractions by using the maxillipeds in the water passing through their buccal cavity. The morphology of maxillipeds hardly differed between the two species, which means that both species are flotation-feeders. The morphology of their minor chelipeds, however, differed: the tips of the dactyl and pollex were flat in U. tetragononand pointed in U. vocans.When the minor cheliped was closed, U. tetragononhad a hemispherical space in the distal one-fourth of the gape, which was closed by the framing keratin layers and a few setae of the dactyl and pollex. On the other hand, U. vocanshad an ellipsoidal space in the distal half of the gape. We consider these morphological characters to be adaptations to the different feeding substrates for retaining more food-laden sediment. We discuss the role of the setae on the minor chelipeds on the basis of the morphological differences between populations of U. tetragononin Phuket Is. and East Africa where the crab inhabits muddy–sandy tidal flats.