Distribution of Aerobic Bacteria Which Contain Bacteriochlorophyll a

Sixteen strains of aerobic bacteria which contain bacteriochlorophyll a were isolated from the samples collected in aerobic marine environments: thalli of Enteromorpha linza, Porphyra sp., Sargussum horneri; beach sand; and the surface seawater from Aburatsubo Inlet. When they occurred, their proportions among the aerobic heterotrophic populations ranged from 0.9 to 1.1% in the seaweed samples and from 1.2 to 6.3% in the beach sand samples and were 0.9% in the seawater sample. The results suggested that the aerobic photopigmented bacteria widely inhabit aerobic marine environments.     

Microbiological studies of Tokyo Bay

The generic composition of the heterotrophic bacterial population of Tokyo Bay, which is now highly polluted and eutrophic, was compared with that of the adjacent, less polluted regions of Sagami Bay and Suruga Bay. Members of Vibrionaceae predominated in the bacterial flora of seawater and zooplankton samples from Sagami Bay, Suruga Bay, and the mouth of Tokyo Bay. However,Vibrio spp. formed only a small proportion of the bacterial population of the water and sediment samples from the inner Tokyo Bay; there the Gram-negative, nonmotile, nonpigmented bacteria, which were tentatively identified asAcinetobacter, were predominant. The result of experiments, in which seawater samples from Tokyo Bay were incubated under various experimental conditions, indicated that two significant factors apparently control the growth ofVibrio spp. in seawater; (1) a direct antagonism betweenVibrios and phytoplankton undergoing rapid growth, and (2) a limiting organic nutrient forvibrios.     

Initiation of replication in the Chinese hamster dihydrofolate reductase domain

Two-dimensional (2-D) gel analysis of replication intermediates in the Chinese hamster dihydrofolate reductase domain has suggested that nascent chains can initiate at any of a large number of sites scattered throughout a ～50 kb “initiation locus” (although the level of initiation detected at any given site within this region was relatively low). This result contrasts markedly with data from anin vitro strand switching assay suggesting that >80% of initiations occur within a single 500 bp fragment lying within the initiation locus. In an effort to reconcile these two disparate views of the initiation reaction, we have questioned the validity of our 2-D gel data in several ways. We show here that: 1) the number of replication bubbles detected in the DHFR locus in the early S period is markedly increased when the cells are released from a synchronizing agent that inhibits initiationper se, rather than from aphidicolin, which is a chain elongation inhibitor; 2) initiation in the DHFR domain occurs only during the first 90 min of the S period, as would be expected of an early-firing origin; 3) a pulse of³H-thymidine moves through the structures observed on 2-D gels with the kinetics expected ofbonafide replication intermediates; and 4) preparations of replication intermediates that are subsequently analyzed on 2-D gels appear, by electron microscopy, to represent the typical theta structures and single-forked molecules expected of bidirectional origins of replication; no unusual structures (e.g., microbubbles) were seen.     

Murine p53 inhibits the function but not the formation of SV40 T antigen hexamers and stimulates T antigen RNA helicase activity

We have characterized the effects of p53 on several biochemical activities of simian virus 40 (SV40) large tumor (T) antigen. While p53 induced a strong inhibition of the T antigen DNA helicase activity, surprisingly, its RNA helicase activity was stimulated. This supports the liklihood that the DNA and RNA helicase activities of T antigen reflect discrete functions. p53 did not significantly affect the ATP-dependent conversion of T antigen monomers to hexamers. However, the ability of these hexamers to assemble on a DNA fragment containing the viral origin was impaired by p53. Thus, these results suggest that p53 inhibits the function but not the formation of T antigen multimers. This conclusion was further supported by the observation that the addition of a purified p53:T antigen complex was as inhihitory as free p53 to the DNA helicase activity of free T antigen. Thus our data indicates that the targets of p53 inhibition are the functional units of T antigen, namely the hexamers.     

The 3′→5′ exonuclease associated with HeLa DNA polymerase epsilon

The 3′→5′ exonuclease activity of highly purified large form of human DNA polymerase epsilon was studied. The activity removes mononucleotides from the 3′ end of an oligonucleotide with a non-processive mechanism and leaves 5′-terminal trinucleotide non-hydrolyzed. This is the case both with single-stranded oligonucleotides and with oligonucleotides annealed to complementary regions of M13DNA. However, the reaction rates with single-stranded oligonucleotides are at least ten-fold when compared to those with completely base-paired oligonucleotides. Conceivably, mismatched 3′ end of an oligonucleotide annealed to M13DNA is rapidly removed and the hydrolysis is slown down when double-stranded region is reached. The preferential removal of a non-complementary 3′ end and the non-processive mechanism are consistent with anticipated proofreading function. In addition to the 3′→5′ exonuclease activity, an 5′→3′ exonuclease activity is often present even in relatively highly purified DNA polymerase epsilon preparates suggesting that such an activity may be an essential com-ponent for the action of this enzymein vivo. Contrary to the 3′→5′ exonuclease activity, the 5′→3′ exonuclease is separable from the polymerase activity.     

CNTF and LIF act on neuronal cells via shared signaling pathways that involve the IL-6 signal transducing receptor component gp130.

Ciliary neurotrophic factor (CNTF) has a variety of actions within the nervous system. While some of the actions of leukemia inhibitory factor (LIF) on neurons resemble those of CNTF, LIF also has broad actions outside of the nervous system that in many cases mimic those of interleukin-6 (IL-6). Comparison of the tyrosine phosphorylations and gene activations induced by CNTF and LIF in neuron cell lines reveals that they are indistinguishable and also very similar to signaling events that characterize LIF and IL-6 responses in hematopoietic cells. We provide a basis for the overlapping actions of these three factors by demonstrating that the shared CNTF and LIF signaling pathways involve the IL-6 signal transducing receptor component gp130. Thus, the receptor system for CNTF is surprisingly unlike those used by the nerve growth factor family of neurotrophic factors, but is instead related to those used by a subclass of hematopoietic cytokines.     

Protection against acute paraquat toxicity by ambroxol

An expression vector for G-CSF, pASLB3-3, was constructed and introduced into Namalwa KJM-1 cells (Hosoi et al., 1988), and cells resistant to 100 nM of methotrexate (MTX) were obtained. Among them, the highest producer, clone SC57, was selected and the productivity of this clone was further characterized. The maximal production of G-CSF was at the most 1.8 g/ml/day using a 25 cm² tissue culture flask, even though the cell number was above 7×10⁵ cells/ml. The limiting factors at high density were analyzed as the deficiency of nutrients, such as glucose, cysteine and serine, and pH control. The depression of specific G-CSF productivity per cell under the batch culture conditions was overcome by using a perfusion culture system, Biofermenter^TM (Sato, 1983) with modifications of nutrients supplementation by a dialysis membrane and/or dissolved oxygen (DO) supplementation by microsilicone fibers. ITPSGF medium was modified to elevate concentrations of amino acids and glucose by 2.0- and 2.5-times, respectively. Under the control of pH at 7.4 and DO at 3 ppm, the specific G-CSF productivity was not depressed even at high cell density (above 1×10⁷ cells/ml), and the amount of G-CSF reached 41 g/ml. These results indicated the possibility of finding the optimum culture conditions for the production of recombinant proteins by Namalwa KJM-1 cells.Abbreviations ABTS 2,2-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid - BSA Bovine Serum Albumin - BSA-PBS Phosphate-buffered Saline without Ca²⁺ and Mg²⁺ containing Bovine Serum Albumin - dhfr Dihydrofolate Reductase - DO Dissolved Oxygen - G-CSF Granulocyte Colony-stimulating Factor - HEPES 4-(2-Hydroxyethyl)-1-piperazineethansulfonic Acid - IFN Interferon - MTX Methotrexate - PBS(-) Phosphate-buffered saline without Ca²⁺ and Mg²⁺ - Tween-PBS Phosphate-buffered saline without Ca²⁺ and Mg²⁺ containing 0.05% of Tween 20     

Expression of anchorin CII mRNA by cultured chondrocytes

The establishment of a cell culture system promoting chondrocyte differentiation has been utilized to better characterize phenotypic stages of chondrogenesis at the cellular level. Although the expression of the type II collagen gene has been studied during “in vitro” chondrocyte differentiation, little is known about the expression of the gene coding for its receptor: anchorin CII. The modulation of the anchorin mRNA steady state level in chick embryo chondrocytes at different developmental stages is described here.The anchorin mRNA level was low in dedifferentiated chondrocytes, progressively increased after the cell transfer into suspension (a condition promoting differentiation), reached its maximal value after 4 weeks and decreased after 5 weeks.Therefore anchorin CII mRNA reaches its maximum level in hypertrophic stage II chondrocytes.     

Epidermal growth factor stimulate cell proliferation and inhibits prolactin secretion of the human decidual cells in culture

Epidermal growth factor (EGF) has been found to be mitogenic in a variety of tissues. We investigated the biological effect of EGF on early pregnant human decidua and the non-pregnant decidualized human endometrium in the primary cell culture. EGF had a stimulatory action on cell proliferation in the early pregnant decidual cells and an inhibitory effect on prolactin (PRL) secretion from the decidual cells. The addition of progesterone into culture medium suppressed cell proliferation of decidual cells, whereas it enhanced PRL secretion from decidua. The analysis of the specific receptor for EGF in the early pregnant decidua and non-pregnant decidualized endometrium revealed that both tissues had a single component EGF receptor with a dissociation constant of nM order. These results suggest that EGF may play a role in the growth and function of endometrial stromal cells.