Biomedical subjects

H Yagi

Publications and source records attributed to H Yagi.

At least 163 records · Page 9Linked to original sources

PubMed1995

Conformational dynamics monitored by His-179 and His-200 of isolated thermophilic F1-ATPase beta subunit which reside at the entrance of the 'conical tunnel' in holoenzyme.

When monitored by 1H NMR at various pH values, most of the C-2 proton signals from 12 His residues of the isolated beta subunit of thermophilic F1-ATPase (TF1) could be separately observed. Two of them were assigned to His-179 and His-200 which reside at the entrance of a 'conical tunnel' to reach catalytic site in the crystal structure of F1-ATPase. His-200 gave doublet, suggesting that this region is not a rigid alpha-helix in the isolated beta subunit. The binding of Mg.AMP-PNP changed the chemical shifts of His-179 and His-200 significantly. Although His-119 located at the opposite side of the conical tunnel was not affected by the nucleotide-binding, it contributed to the stability of beta subunit and the efficiency of the catalysis of the holoenzyme.

Bacillus↗

PubMed1995

NMR solution structure of a nonanucleotide duplex with a dG mismatch opposite a 10S adduct derived from trans addition of a deoxyadenosine N6-amino group to (+)-(7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene: an unusual syn glycosidic torsion angle at the modified dA.

A nonanucleotide, d(G1G2T3C4[BaP]A5C6G7A8G9), in which (+)-(7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (7-hydroxyl group and epoxide oxygen are trans) is covalently bonded to the exocyclic N6-amino group of deoxyadenosine (dA5) through trans addition at C10 of the epoxide (to give a 10S adduct) has been synthesized. The solution structure of the duplex, d(G1G2T3C4[BaP]A5C6G7A8G9).d(C10T11C12G13G14G15A16C17C18+ ++), containing a dG mismatch opposite the modified dA (designated 10S-[BaP]dA.dG 9-mer duplex) has been investigated using a combination of 1D and 2D (including COSY, PECOSY, TOCSY, NOESY, and indirect detection of 1H-31P HETCOR) NMR spectroscopies. The NMR results together with restrained molecular dynamics/energy minimization calculations show that the modified dA5 adopts a syn glycosidic torsion angle whereas all other nucleotide residues adopt anti glycosidic torsion angles. The sugar ring of dA5 is in the C3'-endo conformation, and the sugar rings of the other residues are in the C2'-endo conformation. The hydrocarbon attached at dA5 orients toward the 3' end of the modified strand (i.e., dC6 direction) and intercalates between and parallel to bases of dG13 and dG14 of the complementary strand directly opposite dC6 and dA5, respectively. The edge of the hydrocarbon bearing H11 and H12 is positioned between the imino protons of dG13 and dG14 in the interior of the duplex, whereas H4 and H5 at the opposite edge are positioned near the sugar H1' and H2" protons of dG13 and facing the exterior of the duplex. The mismatched AG base pair is stabilized by dAsyn-dGanti base pairing in which the imino proton and the O6 of dG14 are hydrogen bonded to N7- and the single N6-amino proton, respectively, of the modified dA5. The modified DNA duplex remains in a right-handed helix, which bends at the site of intercalation about 20 to 30 degrees away from the helical axis and toward the direction of the modified strand.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1995

Induction of TCR-gamma delta+ cells from thymocytes stimulated by a fetal liver-derived hepatocyte clone.

We have previously reported that a fetal liver-derived hepatocyte clone, FHC-4D2, can support hematopoiesis in vitro. Here, we show that fetal thymocytes (FT) or adult thymocytes (AT) proliferate on the monolayer of FHC-4D2 cells in the presence of rIL-2. Fresh thymocytes contained few TCR-gamma delta+ cells (< 4% for FT and < 1% for AT); significant numbers of TCR-gamma delta+ cells were detected (2-11% for FT and 15-33% for AT) after the coculture with FHC-4D2 and rIL-2. Although FT-derived TCR-gamma delta+ cells predominantly used the V gamma 5 chain, the major population in AT-derived TCR-gamma delta+ cells used V gamma 1, V gamma 4, or V gamma 7 chains. Both FT- and AT-derived TCR-gamma delta+ cells killed FcR-bearing target cells when incubated with anti-TCR-gamma delta Ab. Half of FT-derived TCR-gamma delta+ cells were CD4-CD8 alpha+8 beta-; the rest were CD4-CD8 alpha-8 beta-. AT-derived TCR-gamma delta+ cells expressed neither CD4 nor CD8 molecules. Separation of thymocytes from FHC-4D2 cells with a membrane filter reduced the proliferative response by two- to threefold. Taken together, these results demonstrate that a fetal hepatocyte clone supports thymocytes to develop preferentially into TCR-gamma delta+ cells in cooperation with rIL-2 through cell-cell contact, that the repertoire and the phenotype of induced TCR-gamma delta+ cells are determined by the age of the mice, and that hepatocytes might thus play an active role in T lymphopoiesis in the fetal liver.

Age Factors↗

PubMed1995

Regulation of the mouse histone H2A.X gene promoter by the transcription factor E2F and CCAAT binding protein.

We have molecularly cloned the genomic gene encoding the mouse histone variant H2A.X and characterized the promoter. The promoter region of the H2A.X gene was characterized by chloramphenicol acetyltransferase analysis using Balb/c 3T3 cells. Maximal promoter activity was found in the construct containing up to -282 base pairs H2A.X upstream region. Within this region, we found two sequences regulating the promoter activation; one was an E2F site and another was a CCAAT box. These sequences were also required for the DNA/protein binding activities. Thus, these activities corresponded to the promoter activities, implying that the promoter activity H2A.X gene was controlled by both the transcription factor E2F and H1TF2 through the E2F and CCAAT element. The CCAAT box binding activity was constitutive when cell cycle was progressed by release from G1 arrest, but transiently transfected chloramphenicol acetyltransferase activity slightly increased when cells entered S phase. Similarly, the level of the smallest form of E2F (free E2F) became higher when cells reentered the cell cycle, indicating that the free E2F was one capable of inducing the promoter activation. Thus, the free E2F and CCAAT DNA binding activity correlated with regulation of the promoter activity.

3T3 Cells↗

PubMed1995

Nuclear magnetic resonance solution structure of an undecanucleotide duplex with a complementary thymidine base opposite a 10R adduct derived from trans addition of a deoxyadenosine N6-amino group to (-)-(7R,8S,9R,10S)-7,8-dihydroxy- 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

The solution structure of a modified undecamer duplex containing (-)-(7R,8S,9R,10S)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene covalently bonded through trans ring opening at C10 of the epoxide by the N6-amino group of deoxyadenosine (dA) was studied. This diol epoxide 1 diastereomer has the benzylic 7-hydroxyl group and the epoxide oxygen cis. The modified nucleotide residue has R chirality at C10 of the hydrocarbon (10R adduct). The undecamer duplex d(C1G2G3T4C5A*6C7G8A9G10G11).d(C12C13T14C15G16T17G18A19C2 0C21G22) has a complementary T opposite the modified dA (dA*6 is the modified dA). Exchangeable and nonexchangeable proton assignments were made using 2D TOCSY, NOESY, and water/NOESY NMR spectroscopy. The hybrid complete relaxation matrix program MORASS was used to generate NOESY distance constraints for iterative refinement using distance-restrained molecular dynamics calculations. The refined structure showed the hydrocarbon intercalated from the major groove between dA*6-T17 and dC5-dG18 base pairs. The modified dA*6 was in the normal anti configuration and showed Watson-Crick base pairing to T17 opposite. The chemical shifts of the hydrocarbon protons and the unusual shifts of sugar protons were accounted for by the intercalated orientation of the hydrocarbon.

Base Composition↗

PubMed1995

Stereo-selectivity and regio-selectivity in the metabolism of 7,8-dihydrobenzo[a]pyrene by cytochrome P450, epoxide hydrolase and hepatic microsomes from 3-methylcholanthrene-treated rats.

The active site of cytochrome P450 1A1 has been probed with the substrate 7,8-dihydrobenzo[a]pyrene using a purified, reconstituted system composed of cytochrome P450 1A1, NADPH-cytochrome c reductase and lipid in the presence or absence of epoxide hydrolase. The turnover of the substrate was found to be 38 nmol/nmol of cytochrome P450/min. The metabolic products that were identified are: a phenolic 7,8-dihydrobenzo[a]pyrene (20-29%); 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (17-28%); benzo[a]pyrene (12-19%); 7-hydroxy-7,8-dihydrobenzo[a]pyrene (13-16%); 8-hydroxy-7,8-dihydrobenzo[a]pyrene (7-15%); 3-hydroxybenzo[a]pyrene (7-15%); 4,5-epoxy-4,5,7,8-tetrahydrobenzo[a]pyrene (0-4%); and a triol of 7,8,9,10-tetrahydrobenzo[a]pyrene (0-4%). 9,10-Epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene undergoes rapid hydrolysis to cis- and trans-9,10-dihydroxy-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (2:1) by benzylic attack of water at C-10. Approximately 71% of the trans diols are derived from (+)-(9S,10R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, indicating that cytochrome P450 1A1 has more than a 2:1 preference for selective epoxidation of an enantiotopic face of 7,8-dihydrobenzo[a]pyrene. This stereo-selectivity agrees with the postulated stereo-selectivity predicted by a previously described active site model for cytochrome P450 1A1. Epoxide hydrolase in pure form or in hepatic microsomes catalyzes the hydrolysis of 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, which is inhibited by 1,1,1-trichloropropane 2,3-oxide. The (+)-(9S,10R)-isomer of the epoxide is slightly preferred as a substrate over its enantiomer and is cleaved by benzylic and nonbenzylic attack. Only benzylic attack was found with (-)-(9R,10S)-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed1995

NMR solution structure of a nonanucleotide duplex with a dG mismatch opposite a 10R adduct derived from trans addition of a deoxyadenosine N6-amino group to (-)-(7S,8R,9R,10S)-7,8-dihydroxy-9,10-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene.

A nonanucleotide in which (-)-(7S,8R,9R,10S)-7,8-dihydroxy-9,10-epoxy- 7,8,9,10-tetrahydrobenzo[a]pyrene (7-hydroxy group and epoxide oxygen are trans) is covalently bonded to the exocyclic N6-amino group of deoxyadenosine through trans addition at C10 of the epoxide (10R adduct) has been synthesized. The modified oligonucleotide d(GGTCA*CGAG) was incorporated into the duplex d(GGTCA*CGAG).d(CTCGGGACC), containing a dG mismatch opposite the modified base (dA*). Proton assignments for the solution structure of the duplex containing the 10R adduct were made using 2D TOCSY and NOESY NMR spectra. The complete hybrid relaxation matrix program, MORASS2.0, was used to generate NOESY distance constraints for iterative refinement using distance-restrained molecular dynamics calculations with AMBER4.0. The iteratively refined structure showed the hydrocarbon intercalated from the major groove immediately below the dC4-dG15 base pair and oriented toward the 5'-end of the modified strand. The modified dA is in an anti configuration, with the dG of the GA mismatch turned out into the major groove. Chemical shifts of the hydrocarbon protons and unusual chemical shifts of sugar protons were accounted for by this orientation of the adduct. The information available currently provides the foundation for the rational explanation of observed benzo[a]pyrene (BaP) structures and predictions for other BaP dG and dA adducts.

Base Sequence↗

PubMed1995

Dietary alpha-linolenate/linoleate balance influences learning and memory in the senescence-accelerated mouse (SAM).

The senescence-accelerated mouse (SAMP8) is a model of age-related deterioration of memory and learning ability. A semipurified diet supplemented either with safflower oil (rich in linoleate) or with perilla oil (rich in alpha-linolenate) was fed to SAMP8 mouse dams and their pups. The offspring (males from several mothers) at 28 weeks of age were used for behavioral tests. The proportions of n-3 and n-6 highly unsaturated fatty acids in brain phospholipids reflected the n-3/n-6 balance of the diets. The learning and memory abilities of the two dietary groups were tested with the Sidman active avoidance task and the light and dark discrimination learning test. The group given perilla oil showed much greater improvement in learning in the Sidman active avoidance task than did the group fed safflower oil. In the light and dark discrimination learning test, the total number of responses to positive and negative stimuli was lower in those fed perilla oil, and their responses to positive stimuli were higher than to negative stimuli after the 10th session. Consequently, the correct response ratios of discrimination were higher in the perilla oil group than in the safflower oil group. In the open field test, the total amount of locomotor activity during 5 min was lower in the perilla oil group at 7 months of age than in the group fed safflower oil.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1995

The protective effect of hyperbaric oxygenation on the small intestine in ischemia-reperfusion injury.

Hyperbaric oxygenation has been used as the method of treatment in several ischemic diseases, but its effectiveness still remains controversial. The authors investigated the effect of hyperbaric oxygenation on ischemia-reperfusion injury of the small intestine using a rat model. Wistar King A Makino (WKAM) rats were subjected to 120 minutes of superior mesenteric artery occlusion before reperfusion, with 90 minutes of hyperbaric oxygenation (two absolute atmospheric pressure in an experimental hyperbaric chamber) during ischemia in group A and immediately after reperfusion in group B, and no hyperbaric oxygen was provided to group C. Jejunal samples 1.5 cm in length were taken at the end of ischemia in all groups, at 30 minutes after reperfusion in groups A and C, and at 120 minutes after reperfusion in groups B and C, for the measurement of adenine nucleotides (high-performance liquid chromatography method) and for histological examination (hematoxylineosin [HE] staining). The survival rate was significantly higher in group A than in group C. The amount of adenosine triphosphate in the samples was not significantly different among the three groups, whereas the energy charge at the end of ischemia was significantly higher in group A than in group C. Histologically, the damage to the mucosa and the longitudinal muscle layer decreased in group A compared with that observed in groups B and C. These results suggest that hyperbaric oxygenation during ischemia is able to ameliorate ischemia-reperfusion injury in the rat small intestine.

Animals↗

PubMed1995

A novel point mutation (R243Q) in exon 7 of the c-erbA beta thyroid hormone receptor gene in a family with resistance to thyroid hormone.

Resistance to thyroid hormone (RTH) is characterized by variable tissue hyporesponsiveness to thyroid hormones. Recently, a large number of different point mutations have been identified in the c-erbA beta thyroid hormone receptor (TR beta) in subjects with RTH. We describe a Japanese family with RTH with a novel point mutation in exon 7 of the TR beta gene. A single nucleotide substitution, guanine for adenine, was identified at the second position of codon 243 located in the hinge domain between the ligand binding and DNA binding domains in one of the two alleles of the proband and his mother, resulting in the substitution of the normal arginine (CGG) with a glutamine (CAG). Except for one family, point mutations so far described in RTH are clustered at exons 8-10 of the TR beta gene. This report presents a novel mutation in the characteristic portion in exon 7 of the TR beta.

Amino Acid Sequence↗

PubMed1995

Cutaneous colonization with staphylococci influences the disease activity of Sézary syndrome: a potential role for bacterial superantigens.

It has previously been shown that circulating Sézary cells respond in vitro to superantigenic staphylococcal exotoxins in a manner that is restricted by their V beta usage. This study was conducted to examine whether cutaneous colonization with Staphylococcus aureus influences the activity of the skin lesions of Sézary syndrome, and whether S. aureus isolated from patients with Sézary syndrome stimulates circulating Sézary cells in vitro. Two patients with Sézary syndrome, whose skin was colonized with S. aureus, were treated with antibacterial agents, and the relation between the severity of the skin disease and the degree of S. aureus colonization was assessed. In addition, the patients' peripheral blood mononuclear cells were cultured in the presence of mitomycin C-treated S. aureus or superantigenic staphylococcal toxins. The antibacterial treatment improved the skin disease, and eliminated S. aureus in both patients. In one patient, 98% of the peripheral blood mononuclear cells bore V alpha 2V beta 17 of the T-cell receptor, indicative of the presence of an extremely high percentage of circulating Sézary cells. The peripheral blood lymphocytes from this patient responded well in vitro to superantigenic staphylococcal enterotoxin (SE), but not to SEA or toxic shock syndrome toxin-1, or to mitomycin-treated S. aureus isolated from the same patient. Cutaneous colonization by S. aureus influences the disease activity of CTCL, possibly by activation of Sézary cells by bacterial superantigenic exoproteins.

Aged↗

PubMed1995

A sex reversal infant with XX karyotype and complete male external genitalia.

The unusual case of a Japanese newborn XX male is presented. Examination of chromosomes in amniotic fluid cells had shown a normal female karyotype (46,XX), but ultrasonography revealed a penis and a scrotum. The neonate had normal male external genitalia, and serum levels of luteinizing hormone, follicle stimulating hormone, and testosterone were all within the normal range. High resonance chromosome analysis revealed an excess portion on the short arm of one of the X chromosomes. We examined his genomic DNA by polymerase chain reaction (PCR) and detected two Y specific regions in his genomic DNA, the sex-determining region Y (SRY) and pseudoautosomal boundary Y. Nucleotide sequencing of the PCR products of SRY indicated no mutation. These findings suggested that the translocation or insertion of an SRY region on the X chromosome led to the development of testicles and a male phenotype.

Base Sequence↗

PubMed1995

Purification, and properties of a base non-specific acid ribonuclease from bullfrog (Rana catesbeiana).

An acid ribonuclease (RNase RCL2) was purified to homogeneity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) from a homogenate of bullfrog liver (Rana catesbeiana). The apparent molecular weight estimated from SDS-PAGE was ca. 25kDa. The pH optimum of the RNase was 5.0. The RNase released mononucleotides from RNA in the order of 3'-UMP, 3'-GMP and 3'-AMP. The N-terminal amino acid sequence of RNase RCL2 was determined up to the 20th residue, and it was found to have a 5 residue sequence homology with that of oyster acid RNase [H. Watanabe et al. J. Biochem. (Tokyo), 114, 800 (1993)]. Thus, RNase RCL2 seems to be a member of the RNase T2 family RNases. This is the first evidence of the RNase T2 family RNase in amphibians.

Amino Acid Sequence↗

PubMed1995

Most thymocytes die in the absence of DNA fragmentation.

Most thymocytes are known to be depleted from the thymus during T cell development, with the process of thymocyte death considered to be apoptosis. In this study we examined the mechanism of thymocyte death in the thymus of 6-week-old mice by using terminal deoxynucleotidyl transferase to detect DNA fragmentation or double strand breaks (TUNEL method). The TUNEL positive thymocytes were scattered throughout the cortex. Double staining of the section with the TUNEL method and acid phosphatase (ACP) activity showed that all the TUNEL positive cells were phagocytosed by ACP positive macrophages. An ultra-structural study revealed the presence of a substantial number of extremely small, unphagocytosed thymocytes throughout the cortex. These small unphagocytosed thymocytes were apparently dead cells, as based on several morphological features: 1) The majority were much smaller than red blood cells; 2) the nuclei were also considerably small; and 3) the extent of chromatin condensation was enormous. Importantly, these unphagocytosed dead thymocytes were TUNEL negative. These results indicate that: 1) DNA fragmentation, which is detected by the TUNEL method, is not involved in the cell death process of small unphagocytosed dead thymocytes shown in the present study; and that 2) typical apoptosis, which is characterized by DNA fragmentation, is not the dominant type of cell death in the normal murine thymus. Processes of cell death other than typical apoptosis taking place in most thymocytes require further investigation.

Animals↗

PubMed1995

Neurologic changes in visceral leishmaniasis.

Neurologic changes in visceral leishmaniasis (VL) are rarely reported. From January 1992 to April 1993, 111 patients with VL were seen at Soba University Hospital in Khartoum, Sudan. Fifty-two (46%) patients had neurologic symptoms or signs; the most common symptom was a sensation of burning feet. Four patients had foot drop. Five patients had deafness and one patient had multiple cranial nerves palsies. None of our patients had vitamin deficiency or any of the other known causes of neuropathy. Nerve conduction studies in 15 patients showed evidence of axonal degeneration and demyelination, which were confirmed by histopathology and electron microscopy of nerve biopsies. There was no direct parasitic infection of the nerve and there was no neuritis. In most patients, the sensory symptoms disappeared within two weeks in most of our patients after specific anti-leishmanial treatment. Motor recovery was much slower. Audiographic studies in five patients with deafness showed it to be sensory-neural. Hearing returned to normal after treatment with sodium stibogluconate. Further studies are needed to define the etiology of the nerve pathology in patients with VL.

Adolescent↗

PubMed1994

Effect of DNA base sequence on the configuration of deoxyadenosine adducts formed by the Fjord region diol epoxide, (+)-(1R,2S,3R,4S)-3,4-dihydroxy-1,2-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene.

The carcinogen (+)-(1R,2S,3R,4S)-3,4-dihydroxy-1,2-epoxy-1,2,3,4- tetrahydrobenzo[c]phenanthrene (in which the 4-OH group and epoxide oxygen are cis) was reacted with duplexes formed from self-complementary oligodeoxyribonucleotides, producing 1S or 1R configured adducts through trans or cis epoxide ring opening, respectively, by the exocyclic amino group of a central target A. Sequences containing 5'-AT-3' generated much higher S vs R ratios than the average of 3.38 observed with calf thymus DNA samples, while sequences containing 5'-TA-3' generated much lower ratios. Sequences with G in the position immediately 5' to the central AT or TA, and C in the position immediately 3', generated moderately higher ratios than did sequences with adjacent 5'C and 3'G. When thymidine was replaced by deoxyuridine in several sequences, the ratios of S vs R configured dA adducts and dA adducts vs dG adducts were substantially and uniformly reduced, but otherwise varied with the choice of nearest neighbors in patterns similar to those observed with the T containing sequences. Two hypothetical mechanisms are proposed to explain the effect of nearest neighbors on the S vs R dA adduct ratio; in both, diol epoxide intercalation precedes covalent bonding. In one mechanism, intercalation to the 5' side of the target A yields an S adduct while intercalation to the 3' side yields an R adduct, and the extent of adduct formation follows the nearest neighbor series G > C > T.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Stimulation of in vitro hematopoiesis by a murine fetal hepatocyte clone through cell-cell contact.

We have previously shown that a fetal liver-derived epithelial cell clone, FHC-4D2, could support hematopoiesis in vitro through its colony-stimulating factor (CSF) activities in a short-term culture. In this study, since FHC-4D2 cells were found capable of maintaining hematopoietic progenitors in the coculture for a long time, we examined how FHC-4D2 could exert hematopoietic supporting activity in a long-term culture by coculturing adult bone marrow (BM) cells or fetal liver (FL) cells on a monolayer of FHC-4D2 cells. This clone could maintain the colony-forming unit of granulocytes and macrophages (CFU-GM) of BM for > or = 12 weeks under the coculture condition, but the fibroblastic cell clone from the fetal liver, FHC-4A3, could not support the survival of CFU-GM, even for 1 week. In addition to BM CFU-GM, the FHC-4D2 clone also supported the survival of FL CFU-GM, burst-forming unit of erythroid cells (BFUe), and colony-forming unit of mixed progenitors (CFU-Mix) for longer than 4 weeks. When BM cells were separated by a membrane filter from the FHC-4D2 cells in the coculture, the comparable number of CFU-GM was maintained at day 3, but virtually no hematopoietic progenitors were detected at the end of the first week. CFU-GM were present in both nonadherent and adherent cells to the FHC-4D2 cells at day 3 of the coculture, but at day 7, the adherent population contained greater number of CFU-GM. CFU-GM derived from the adherent cells formed larger colonies and contained more bipotential CFU-GM than the nonadherent population. When BM cells from mice given 5-fluorouracil were cocultured with FHC-4D2 cells under the limiting dilution condition, interleukin-3 (IL-3)-responsive CFU-GM were induced from immature hematopoietic progenitor cells that were otherwise unresponsive to IL-3. From these data we conclude that the FHC-4D2 clone could generate and maintain IL-3-responsive hematopoietic progenitors via close contact and that, in the fetal liver, the contact between hepatocytes and hematopoietic cells may be critically important in inducing the differentiation of resting, IL-3-unresponsive immature hematopoietic cells into CFU-GM (progenitors responsive to IL-3) and in triggering the self-renewal of CFU-GM.

Animals↗

PubMed1994

Keratinocyte differentiation is induced by cell-permeant ceramides and its proliferation is promoted by sphingosine.

Ceramide and sphingosine have been suggested to be intracellular modulators of cell growth and differentiation. The effects of these sphingolipids on the growth and differentiation of keratinocytes were examined using cultured human keratinocytes (the squamous cell carcinoma cell line, DJM-1). The synthetic short-chain cell-permeant analogues of ceramides, N-acetylsphingosine, N-hexanoylsphingosine and N-octanoylsphingosine, significantly promoted differentiation as confirmed by upregulation of cornified envelope formation, synthesis of involucrin and increased transglutaminase activity, and inhibited proliferation as shown by a reduction in cell numbers, DNA amount and thymidine incorporation. Generally, these activities were greater the longer the N-acyl carbon chain. On the other hand, sphingosine at an appropriate concentration modestly stimulated the proliferation of cultured cells. Our results suggest the possibility that the growth and differentiation of keratinocytes are at least partially regulated by ceramide and sphingosine.

Carcinoma, Squamous Cell↗