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11.
Taurine, a sulfated beta-amino acid, is conditionally essential during development. A maternal supply of taurine is necessary for normal fetal growth and neurologic development, suggesting the importance of efficient placental transfer. Uptake by the brush-border membrane (BBM) in several other tissues has been shown to be via a selective Na(+)-dependent carrier mechanism which also has a specific anion requirement. Using BBM vesicles purified from the human placenta, we have confirmed the presence of Na(+)-dependent, carrier-mediated taurine transport with an apparent Km of 4.00 +/- 0.22 microM and a Vmax of 11.72-0.36 pmol mg-1 protein 20 s-1. Anion dependence was examined under voltage-clamped conditions, in order to minimize the contribution of membrane potential to transport. Uptake was significantly reduced when anions such as thiocyanate, gluconate, or nitrate were substituted for Cl-. In addition, a Cl(-)-gradient alone (under Na(+)-equilibrated conditions) could energize uphill transport as evidenced by accelerated uptake (3.13 +/- 0.8 pmol mg-1 protein 20 s-1) and an overshoot compared to Na+, Cl- equilibrated conditions (0.60 +/- 0.06 pmol mg-1 protein 20 s-1). A Cl(-)-gradient (Na(+)-equilibrated) also stimulated uptake of [3H]taurine against its concentration gradient. Analysis of uptake in the presence of varying concentrations of external Cl- suggested that 1 Cl- ion is involved in Na+/taurine cotransport. We conclude that Na(+)-dependent taurine uptake in the placental BBM has a selective anion requirement for optimum transport. This process is electrogenic and involves a stoichiometry of 2:1:1 for Na+/Cl-/taurine symport. 相似文献
12.
M. Moyer F. Bullrich J. B. Sheffield 《In vitro cellular & developmental biology. Plant》1990,26(11):1073-1078
Summary When embryonic retina is dissociated into a single cell suspension and maintained in stationary culture, a population of flat
cells is found on the culture dish. We have carried out a morphologic and immunologic study of the emergence of this population
in vitro. Ten- and fourteen-day-old chick embryo retinas were dissociated with trypsin, seeded on glass cover slips for various
times, and prepared for scanning electron microscopy (SEM) and immunofluorescence (IF) for Vimentin, an intermediate filament
protein. SEM indicates that the characteristic flat cell morphology is initiated in some cells in as little as 30 min after
the start of the culture. Not all of the cells that attach flatten. As incubation proceeds, small clusters of cells that had
formed in suspension attach to the substrate, and flat cells emerge from them. The flattened cells are positive for Vimentin
by IF within 10 min of attachment. The percent of fluorescent cells found on the substrate is constant during the time in
culture. This suggests that flat cells do not attach first, followed by neural cells, but that the neural cells and flat cells
attach to the dish at the same rate. When aggregates that had formed in suspension attach to the substrate, they are anchored
by flat cells that migrate out of the aggregate. Since Vimentin appears in the cultured cells within 10 min, it is unlikely
that it has been newly synthesized. Thus, the same cells that contained Vimentin in the retina now express it as flat cells.
this supports the hypothesis that flat cells derive from the same cells in the retina that give rise to Müller cells. We have
also observed the emergence of a population of cells with short (0.5μm) microvilli that appear within 8 h of culture. They
seem to be a distinct subpopulation of the cells on the upper portion of attached clusters.
This research was supported in part by grant EY-04892 and RR-0715 from the National Institutes of Health, Bethesda, MD, and
a grant from the W.W. Smith Foundations 相似文献
13.
Teresa L. Johnson Mary Pat Moyer 《In vitro cellular & developmental biology. Plant》1990,26(11):1095-1100
Summary Normal human colon mucosa cells and cells obtained from histologically normal tissues near that cancer were fused with human
colon cancer cells. Resultant hybrid populations of normal and malignant cell fusions behaved as nonmalignant cells in culture,
were unable to grow in soft agar, did not express tumor-associated antigens, and were nontumorigenic in nude mice. Autofusion
of the cancer cell population led to a phenotype intermediate between normal and malignant cells. That is, the cultures had
a much lower plating efficiency in soft agar, and the tumors had a longer latency and slower growth rate in nude mice. This
is the first cell culture system to demonstrate that normal epithelial cells can suppress malignancy of their autologous cancer
cells, and is a prelude to more extensive studies of genetic events involved in malignant conversion of human colonic epithelium.
This study was supported by The University of Texas Health Science Center at San Antonio Center for Human Cell Biotechnology
and a graduate student stipend (T. J.) from the Department of Cellular and Structural Biology. 相似文献
14.
Jack T. Moyer 《Ichthyological Research》1990,36(4):459-467
Chaetodontoplus mesoleucus occurs at Bantayan Island in a habitat of small patches of mixed scleractinian and alcyonacean corals of low diversity and
simple structure. Male-female pairs were predominant, and the sex-ratio showed only a slight skew towards females. However,
the presence of single male, two-female social groups demonstrates that the species is polygamous. Small size of social groups
is attributed to a preference for a habitat lacking structural complexity. The species did not occur on complex coral reefs.
Social and spawning behavior are nearly identical to that of most pomacanthids for which data are available, and although
sex-change was not demonstrated, size-related dominance hierarchies and close phylogenetic relationships to sex-changing pomacanthids
suggest protogynous hermaphroditism in this species. Behaviorally,C. mesoleucus appears quite similar to a large group of species proposed herein to represent a generalized pomacanthid behavioral type.
Divergences from this generalized type by members ofGenicanthus, eastern PacificHolacanthus, and western AtlanticPomacanthus are discussed. Evidence is given to suggest the phylogenetic derivation of the subgenusCentropyge (genusCentropyge) from an ancestor of the subgenusXiphipops type. Color dimorphism and “rendezvous sites” are briefly discussed. 相似文献
15.
16.
Emile CL. Marnette Harm Houweling Herman Van Dam Jan Willem Erisman 《Biogeochemistry》1993,23(2):119-144
The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982
to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying
lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur
budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO4
2− concentrations after a decrease of atmospheric input. However, SO4
2− concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused
the unexpectedly high SO4
2− concentrations. The possible supply of SO4
2− from the sediment through regulation by (K-)Al-SO4 containing minerals or desorption of SO4
2− from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite,
basaluminite and jurbanite indicated that SO4
2− concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO4
2− from peaty sediments may account for the estimated SO4
2− supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments
and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation
of reduced S, the amount of SO4
2− may be provided which complements the decreasing depositional SO4
2− input. In future research these two mechanisms need to be investigated. 相似文献
17.
The ps/hr gene (B5R open reading frame homolog) of rabbitpox virus controls pock color, is a component of extracellular enveloped virus, and is secreted into the medium. 总被引:1,自引:1,他引:0
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Wild-type rabbitpox virus (RPV) produces red hemorrhagic pocks on the chorioallantoic membranes (CAMs) of embryonated chicken eggs. Like the crmA (SPI-2) gene of cowpox virus, disruption of the RPV ps/hr gene results in a mutant which produces white pocks on the CAMs. An examination of the properties of the RPV(ps/hr) mutant in cell culture also reveals a significantly reduced host range, defined as the inability to form plaques, compared with wild-type virus. One of several cell types on which RPV(ps/hr) mutants fail to produce plaques is chicken embryo fibroblasts, cells which have been traditionally used to propagate spontaneously arising white pock mutants isolated from CAMs. The inability of the RPV(ps/hr) mutant to form plaques in chicken embryo fibroblasts correlates with a failure of a low multiplicity of infection to spread to neighboring cells and to form extracellular enveloped virus (EEV), although the formation and yields of infectious intracellular naked virus appear relatively normal. The gene product of the ps/hr gene, initially synthesized as a 45-kDa glycoprotein, is found as a component of EEV, but not intracellular naked virus, and as a smaller, secreted soluble protein of 35 kDa. Production of the secreted 35-kDa protein was found to be independent of any viral morphogenesis, suggesting two distinct pathways for release of the ps/hr gene product from the cell, i.e., as a component of the EEV particle and as a separately secreted glycoprotein. 相似文献
18.
Orthopoxvirus fusion inhibitor glycoprotein SPI-3 (open reading frame K2L) contains motifs characteristic of serine proteinase inhibitors that are not required for control of cell fusion. 总被引:1,自引:0,他引:1
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The cowpox virus (CPV) SPI-3 gene (open reading frame K2L in vaccinia virus) is one of three orthopoxvirus genes whose products are members of the serpin (serine proteinase inhibitor) superfamily. The CPV SPI-3 gene, when overexpressed by using the vaccinia virus/T7 expression system, synthesized two proteins of 50 and 48 kDa. Treatment with the N glycosylation inhibitor tunicamycin converted the two SPI-3 proteins to a single 40-kDa protein, close to the size of 42 kDa predicted from the DNA sequence, suggesting that the SPI-3 protein, unlike the other two orthopoxvirus serpins, is a glycoprotein. Immunoblotting with an anti-SPI-3 antibody showed that the SPI-3 protein is synthesized early in infection prior to DNA replication. SPI-3 inhibits cell-cell fusion during infections with both CPV and vaccinia virus. A transfection assay was devised to test engineered mutants of SPI-3 for the ability to inhibit fusion. Two mutants with C-terminal deletions of 156 and 70 amino acids were completely inactive in fusion inhibition. Site-directed mutations were constructed near the C terminus of SPI-3, in or near the predicted reactive-site loop which is conserved in inhibitory serpins. Substitutions within the loop at the P1 to P1' positions and P5 to P5' positions, inclusive, did not result in any loss of activity, nor did changes at the P17 to P10 residues in the stalk of the reactive loop. Therefore, SPI-3 does not appear to control cell fusion by acting as a serine proteinase inhibitor. 相似文献
19.
Toshiyuki Takahashi Mary P. Moyer Martin Cano Qiming J. Wang Thomas E. Adrian Charles P. Mountjoy Warren Sanger Hiroshi Sugiura Hiroyuki Katoh Parviz M. Pour 《Cell and tissue research》1995,282(1):163-174
Spontaneously immortal pancreatic cell lines are not available. By use of a defined culture medium, such a line (TAKA-1) was established from the Syrian golden hamster. Cytological, cytogenetic, molecular biological, enzymatic and receptor patterns as well as antigenicity were studied and were compared with those of the normal hamster pancreatic ductal cells in vivo. TAKA-1 cells grew exponentially in a monolayer on collagen gel in a defined medium but did not proliferate in soft agar. Ultrastructurally, the cells closely resembled the normal hamster pancreatic ductal cells. Similarities and dissimilarities were found between the normal ductal cells and TAKA-1 cells. Similarities included the presence of cytokeratin, carbonic anhydrase and some tumor-associated antigens. However, unlike the normal ductal cells, TAKA-1 cells expressed blood group A angigen and anti-vimentin, showed affinity to selected lectins, and an abnormality of chromosome 3, which is suggested to be associated with immortality. Moreover, unlike the hamster pancreatic ductal cancer cells but like the normal hamster pancreatic ductal cells, TAKA-1 cells did not have a c-Ki-ras mutation. EGF, TGF- and secretin, but not CCK or GRP, bound to the TAKA-1 cells. TAKA-1 cells produced TGF-, and their growth was stimulated by exogenous EGF in serum-free medium. This cell line presents a suitable model for biologic and pathologic study of the hamster pancreatic ductal cells in vitro. 相似文献
20.
Development and testing of a filter system for isolation of Giardia lamblia cysts from water.
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An inexpensive, practical, and reliable method for isolation of Giardia lamblia cysts from potable and environmental water has been developed from commercially available components. This system was successfully used to isolate cysts from well water associated with a family outbreak of giardiasis. 相似文献