A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans

The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities.     

Nonlethal G0-ts mutant tsJT60 becomes lethal at the nonpermissive temperature after transformation: a hint for new cancer chemotherapeutics

tsJT60 is a nonlethal temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1) classified as a G0 mutant; i.e., the ts defect is not expressed within the cell growth cycle but is expressed only between the G0 and S phase. tsJT60 clones transformed with oncogenes such as adenovirus E1A, polyoma large T, polyoma middle T, v-Ki-ras, and LTR activated c-myc, or with a chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, grew well at 34 degrees C. However, most of these clones grew slowly at 40 degrees C, producing many floating dead cells, and some clones were killed at 40 degrees C. When they were cultured under conditions inadequate for growth of untransformed cells, such as high cell density or serum restriction, they were killed at 40 degrees C. These and previous results from SV40- and adenovirus-transformed tsJT60 clones favour the idea that transformed tsJT60 cells occasionally enter the G0 phase and are metabolically imbalanced at 40 degrees C during self-stimulation from the G0 to S phase. We propose that a drug which exclusively block, G0-G1 transition would be cytocidal to transformed cells but cytostatic to normal cells.     

Analysis of common antigen of flagella in Bacillus cereus and Bacillus thuringiensis

Abstract Flagellar antigen of Bacillus cereus H.1 was purified and tested for serodiagnostic antigen by ELISA. The antibody against the flagellar antigen of B. cereus H.1 reacted not only with the homologous specific antigen but also reacted with the flagellar antigens of 23 strains of B. cereus . This common flagellar antigen of B. cereus was found to be due to 61-kDa protein by SDS-PAGE and immunoblot assay. Monoclonal antibody H15A5 against common antigenic epitope of B. cereus also reacted with flagellar antigens of 21 strains of Bacillus thuringiensis by ELISA. This monoclonal antibody reacted with the 61-kDa protein of the flagella of B. cereus H.1 and H.2 and B. thuringiensis Kurstaki HD1, Alesti and Aizawai juroi by immunoblot analysis. These results indicated that the common antigenic epitope of the 61-kDa protein existed in the flagella both of B. cereus and B. thuringiensis .     

Photoreduction of autooxidized albumin-heme hybrid in saline solution: revival of its O(2)-binding ability.

Recombinant human serum albumin (rHSA) incorporating 2-[8-[N-(2-methylimidazolyl)]octanoyloxymethyl]-5,10,15,20-tetrakis(alpha,alpha,alpha,alpha-o-pivalamido)phenylporphinatoiron(II)s (Fe(II)Ps) [rHSA-Fe(II)P] is a synthetic hemoprotein which can bind and release O(2) reversibly under physiological conditions (saline solution [NaCl]: 150 mM, pH 7.3) as do hemoglobin and myoglobin. However, the central ferrous ions of Fe(II)Ps are slowly oxidized to O(2)-inactive ferric forms. Based on the UV-vis. absorption spectroscopy, the majority of the autooxidized Fe(III)Ps in albumin are determined to be six-coordinate high-spin complexes with a proximal imidazole and a chloride anion, which show ligand-to-metal charge transfer (LMCT) absorption at 330 nm. Interestingly, photoirradiation of this LMCT band under an argon atmosphere led to reduction of the central ferric iron of Fe(III)P, allowing the revival of the O(2)-binding ability. The ratio of the photoreduction reached a maximum of 83%, which is probably due to the partial dissociation of the axial imidazole. The same photoirradiation under a CO atmosphere provides the corresponding carbonyl rHSA-Fe(II)P. Laser flash photolysis experiments revealed that the reduction was completed within 100 ns. The quantum yields (Phi) of these photoreductions were approximately 0.01.     

Temporal behavioral variation and division of labor among workers in the primitively eusocial wasp,Polistes jadwigae Dalla Torre

The behavior of workers on 2 nests of the Japanese paper wasp,Polistes jadwigae, was recorded on video tape. Young workers performed pulp collection more frequently than middle-aged and old workers, while foraging of flesh (prey) was done mainly by middle-aged workers. Of the 26 behavioral categories, 7 showed negative, 2 concave, and 1 convex relationship to the workers age. Using behavioral profiles, workers could be classified into 3 age groups: 1) young workers (younger than 10 days old, active intranidal workers), 2) middle-aged workers (11–25 days old, extranidal workers) and 3) old workers (older than 26 days old, ‘idlers’). Idlers engaged in foraging and larval feeding significantly less frequency than the young and middle-aged workers, but they performed alerting toward many alien objects. Task specialization among workers irrespective of age polyethism was also suggested.     

The subunit structure of a major glutathione S-transferase form, MT, in rat testis. Evidence for a heterodimer consisting of subunits with different isoelectric points

A major glutathione S-transferase form (pI 5.7) in rat testis (MT) purified by S-hexyl-glutathione affinity chromatography, followed by chromatofocusing, showed two polypeptide of pI 6.7 (Yn1) and 6.0 (Yn2), having apparently the same molecular mass of 26 kDa on two-dimensional gel electrophoresis. Rechromatofocusing of the MT preparation after 4 M guanidine hydrochloride treatment revealed two additional protein peaks (pI 6.2 and 5.4). These were identified as the two homodimers consisting of the subunits of MT, Yn1Yn1 and Yn2Yn2, respectively. Furthermore, MT could be reconstituted from Yn1Yn1 and Yn2Yn2. These results indicate that MT is a heterodimer, Yn1Yn2, consisting of subunits with very similar molecular masses but different isoelectric points. The Yn1Yn1 form had glutathione S-transferase activities towards 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene. However, the Yn2Yn2 form had no activity towards any of the substrates examined. N-terminal amino acid sequences of subunits Yn1 and Yn2 revealed differences at two positions in the first 20 residues; the amino acid compositions of these subunits were also similar but not identical, indicating that these two subunits are different in the primary structure. Subunits Yn1 and Yn2 are immunologically related to each other and also to subunits 3 (Yb1) and 4 (Yb2) but they are not identical. These four subunits also showed a high degree of similarity in N-terminal amino acid sequences. Subunits Yn1 and Yn2 seem to belong to the rat GST 3-4 family or class mu. Subunits Yn1 and 4 can make a heterodimer, which is detectable not only in rat testis, but also in the heart, kidney and lung. The Yn1Yn1 form was not detected in the testis, but is present in rat brain [Tsuchida et al. (1987) Eur. J. Biochem. 170, 159-164]. The Yn2Yn2 form seemed to differ from GST 5-5 and may be a new form of rat glutathione S-transferase.     

Physical mapping of the virion and the prophage DNAs of a temperate Lactobacillus phage phi FSW

We analysed the physical structure of the DNA of phi FSW, which is a temperate phage of Lactobacillus casei S-1. A circular restriction map of the virion DNA has been constructed with three restriction endonucleases, BamHI, SalI and XhoI. Other data indicated that the phage genome was circularly permuted. In lysogens, the DNA of the prophage was found to be linearized at a specific site and integrated into a specific locus of the host genome, with the same orientation in each case, as evidenced by Southern filter hybridization. We compared the physical structure of phi FSW with its three virulent mutants. One of them had a restriction map indistinguishable from that of phi FSW and two of them contained host-derived DNA sequence(s) in a specific region of the phi FSW genome (V-region). The prophage integration site was mapped on a different segment of the phage genome to the V-region. Derivation of virulent mutants from phi FSW is discussed in relation to the physical structure of the phage genome.     

Retinoic acid-induced differentiation of human neuroblastoma: a cell variant system showing two distinct responses

Retinoic acid (RA) has been shown to induce the differentiation of human neuroblastoma cells in vitro. In this study, we describe two variants of the SK-N-SH human neuroblastoma cell line that have dramatically different responses to RA. RA induces neuronal-like differentiation characterized by extensive neurite outgrowth, thick neurite bundles, and large cellular aggregates of SK-N-SH-N (SH-N) cells. In contrast, RA treatment of SK-N-SH-F (SH-F) cultures transforms the small neuroblast cells into large flattened, fibroblastic or epithelial-like cells. Karyotype analysis verified that the SH-N and SH-F cultures were derived from a common precursor cell. Confirmation of their markedly different responses to RA was obtained by metabolic labelling of glycoproteins and SDS-PAGE analysis. While both sublines showed very similar Coomassie-labelled protein bands and glycoprotein profiles in control cultures, dramatic differences between the lines were revealed following RA treatment. In contrast to their similar protein profiles, untreated SH-N and SH-F cells had quite different patterns of ganglioside biosynthesis in that GM3 was detected in SH-F cells but not in SH-N, while GM1 was only detected in SH-N. Cellular RA binding protein (CRABP) was detected in both SH-F and SH-N cells and their RA-transformed derivatives. These results demonstrate heterogeneity in the response to RA of neuroblastoma cells derived from a common origin that cannot be accounted for by differences in CRABP content. The SH-N and SH-F neuroblastoma sublines should provide a useful system for further studies of the molecular processes through which RA exerts its differentiation-inducing activity on this type of tumor.     

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 ± 0.22 1·min⁻¹ and 171.6 ± 19.2 beats·min⁻¹, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE.