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1.
2.
In vitro activation of specific helper and suppressor T cells by the type 2 antigen polyvinylpyrrolidone (PVP) 总被引:1,自引:0,他引:1
A M Van Buskirk H Braley-Mullen 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(5):1400-1405
Although type 2 antigens, such as PVP, generally do not activate specific TH, previous studies have established that low doses of PVP (0.0025 microgram) can activate TH in vivo which provide help in primed B cells for PVP-specific IgG responses. Doses of PVP that are optimally immunogenic for IgM antibody production (0.25 to 25 micrograms) preferentially activate PVP-specific TS, which suppress IgG antibody production. In the studies reported here, TH and TS that regulate PVP-specific IgG antibody responses were activated in vitro by culturing normal spleen cells for 4 days with PVP. Induction of the TH and TS is dependent upon the amount of PVP in culture: 10(-4) micrograms PVP activates TH, whereas 10(-2) micrograms PVP preferentially activates TS. TH induced in vitro express Thy-1, L3T4, and I-A determinants and help provided by these TH is similar in magnitude to that provided by TH from mice primed with 0.0025 microgram PVP in vivo. TH can also be activated in vitro if donor mice are treated with Cy before culture of their spleen cells with 10(-2) micrograms PVP. Cy pretreatment prevents TS activation, and TH are then induced in these cultures. The presence of TS does not prevent activation of TH by 10(-2) micrograms PVP, because removal of TS by treatment of T cells with anti-Lyt-2 + complement at the end of culture uncovers TH activity. This TH activity is comparable with that of TH obtained after culture with 10(-4) micrograms PVP. The ability to activate PVP-specific TH and TS in vitro should allow determination of the mechanisms involved in activation of T cells by type 2 antigens and the mechanisms by which TS and TH interact with one another. 相似文献
3.
The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data 总被引:1,自引:0,他引:1
Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the
hominoid primates using DNA-DNA hybridization. From this data set they
estimated a phylogeny that clusters man and chimpanzees using a distance
Wagner procedure. However, no assessment of statistical confidence in this
estimated phylogeny was made, despite the fact that their data set contains
internal inconsistencies concerning the correct branching order. This paper
presents a modification of Pielou's Q- statistic that allows one to make
nonparametric tests of phylogenetic relationship from distance data. The
results of this analysis indicate that the estimated phylogeny of Sibley
and Ahlquist is without statistical significance owing to the internal
inconsistencies of the data set. A survey and additional analyses of other
types of molecular data indicate that the phylogeny that clusters
chimpanzees and gorillas and has the human lineage splitting off earlier is
statistically consistent with all the molecular data (including the DNA-DNA
hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist
can be rejected at the 5% level using the data on restriction- endonuclease
sites in the mitochondrial genome.
相似文献
4.
Jeffery R. Cook Barbara E. Crute Laura M. Patrone Joseph Gabriels Maureen E. Lane Robert G. van Buskirk 《In vitro cellular & developmental biology. Plant》1989,25(10):914-922
Summary We have analyzed the ability of the physical substratum to modulate both the ultrastructural and protein synthetic characteristics
of the Madin-Darby canine kidney (MDCK) renal cell line. When MDCK cells were seeded on Millipore Millicell CM microporous
membrane cell culture inserts they demonstrated a more columnar organization with an increase in cell density sixfold greater
than the same cells seeded on conventional plastic substrata. After 1 wk postseeding on the microporous membrane a partial
basal lamina was noted, with a contiguous basement membrane being apparent after 2 wk. One-dimensional sodium dodecyl sulfate
gel electrophoresis was used to analyze detergent-solubilized proteins from MDCK cells maintained on plastic substrata vs.
microporous membranes. When proteins were pulse-labeled with [35S]methionine, a 55 kDa protein was evident in the cytosolic extract of cells grown on collagen, laminin, and nontreated plastic
substrata; but this labeled protein was not evident in similar extracts from cells grown on collagen and laminin-coated microporous
membranes. To test if the polarized, basement-membrane secreting phenotype of the MDCK cells could be generated on a microporous
membrane without pretreatment with any extracellular matrix (ECM) components, cells were seeded on the Millipore Millicell
HA (cellulosic) microporous membrane. This type of substrata does not need a coating of ECM components for cell attachment.
A partial basement membrane was formed below cells where the basal surface of the cell was planar, but not in areas where
the cell formed large cytoplasmic extensions into the filter. This led us to the conclusion that the microporous nature of
the substrata can dictate both ultrastructural and protein synthetic activities of MDCK cells. Furthermore, we suggest that
both the planar nature of the basal surface and the microporosity of the substrate are corequisites for the deposition of
the basement membrane. 相似文献
5.
Dr AR Holmes RD Cannon HF Jenkinson 《Journal of industrial microbiology & biotechnology》1995,15(3):208-213
The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed. 相似文献
6.
Jeffery R. Cook Robert G. van Buskirk 《In vitro cellular & developmental biology. Animal》1996,32(5):300-306
Summary Laminin synthesis and deposition are concomitant with the development of a basal lamina between the human epidermis and the
underlying dermis. One of the challenges in tissue engineering of human epidermal models is to develop substrates and conditions
that encourage the development of a basement membrane. The purpose of this study was to determine if actin filaments and/or
microtubules are involved in the synthesis/secretion of laminin by normal human epidermal keratinocytes (NHEK)in vitro. NHEK synthesize and secrete laminin subunits B1, B2, and M but little, if any, of laminin subunit A. Data indicate that
disruption of microfilaments by the destabilizing agent, cytochalasin D, had no apparent effect on the relative synthesis
rates of most cytosolic proteins as, revealed by one-dimensional sodium dodecyl sulfate (SDS) gel electrophoresis. This drug,
however, increased laminin B2 synthesis several fold over untreated controls. This enhanced synthetic rate was independent
of the type of collagen, matrix on which the NHEK were grown. Similar increases in synthesis of the M and B1 laminin chains
were not observed. To determine if this increase in synthesis lead to increases in laminin B2 secretion, laminin B2 was immunoprecipitated
from both the apical and basal domains of NHEK cells grown on microporous membranes. While more laminin B1, B2, and M were
secreted basally than apically, an observation consistent with laminin’s role in basal lamina formation, cytochalasin D had
no apparent effect on either basal or apical laminin B2 secretion. Experiments with the microtubule destabilizer, nocodazole,
showed no similar effects on laminin synthesis and/or secretion. We conclude that (a) disruption of the actin network in NHEK
selectively increases the synthesis of laminin B2, (b) the secretion of laminin B2 from NHEK cells is not governed by either
the microfilamentous cytoskeleton or the amount of laminin synthesized by NHEK, and (c) disruption of the microtubular network
does not alter laminin synthesis or secretion. 相似文献
7.
8.
Modeling the biomechanics of the mandible: a three-dimensional finite element study. 总被引:37,自引:0,他引:37
R T Hart V V Hennebel N Thongpreda W C Van Buskirk R C Anderson 《Journal of biomechanics》1992,25(3):261-286
Three-dimensional finite element models of a partially edentulated human mandible were generated to calculate the mechanical response to simulated isometric biting and mastication loads. The level of mesh refinement was established via a convergence test and showed that a model with over 30,000 degrees of freedom was required to obtain analysis accuracy. The functional loading cases included muscle loading based on an algorithm that assigns muscle forces in accordance with muscle cross-sectional area, while maintaining static equilibrium. Results were found for isometric application of unilateral and bilateral bite and mastication loading, and two different sets of displacement boundary conditions were imposed at the condyles. The mechanical response is shown in terms of displacements, principal strains, and a new measure called the 'mechanical intensity scalar'. For each load case studied, there was substantial bending in the molar region of the corpus and high tensile strains in the anterior portion of the ramus. 相似文献
9.
Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed. 相似文献
10.