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41.
Cross-linking of B lymphocyte Fc gamma receptors and membrane immunoglobulin inhibits anti-immunoglobulin-induced blastogenesis 总被引:22,自引:0,他引:22
The Fc portion of rabbit anti-mouse immunoglobulin (Ig) antibodies interferes with anti-Ig-induced B lymphocyte activation as measured by DNA synthesis on day 3 of culture or maturation to Ig-secreting cells in the presence of soluble helper factors on day 4 or 5. To investigate this Fc-dependent effect at an earlier stage in B cell activation, rabbit IgG anti-mouse mu-chain- or delta-chain-specific antibodies were compared with their F(ab')2 fragments for the ability to induce mouse B cells to undergo blast transformation, as defined by an increase in cell volume during the first 24 hr of culture. Both F(ab')2 anti-Ig reagents induce blast transformation, although F(ab')2 anti-mu antibodies induce a greater size change than F(ab')2 anti-delta antibodies. Whole anti-mu or anti-delta antibodies do not induce blast transformation; however, in the presence of a monoclonal anti-mouse Fc gamma receptor antibody that blocks IgG binding to Fc gamma receptors (Fc gamma R), whole anti-mu or anti-delta antibodies induce blast transformation as well as their F(ab')2 fragments. Because the anti-Fc gamma R antibody alone has no effect on blast transformation, it appears that the simultaneous binding of membrane IgM (or IgD) and Fc gamma R by whole anti-Ig antibodies prevents this early event in membrane Ig-induced B cell activation. 相似文献
42.
Harris T. R.; Roselli R. J.; Maurer C. R.; Parker R. E.; Pou N. A. 《Journal of applied physiology》1987,62(5):1852-1859
The purpose of these studies was a comparison of [14C]urea (U) and 1,3-[14C]propanediol (Pr) as measures of lung vascular permeability-surface area (PS) under base-line conditions and after lung injury caused by alloxan infusion in isolated perfused dog lungs. Indicator mixtures of 125I-albumin, 51Cr-red blood cells, 3HOH, and U or Pr were injected under base-line conditions, after 1.2 g of alloxan, and after an additional 0.8 g of alloxan. Indicator-dilution curves were analyzed from sampled outflow blood to provide PS, the square root of effective extravascular diffusivity multiplied by exchange surface area (D1/2S), and extravascular lung water (EVLW) from the tracer mean transit times (VW). Results show that alloxan increases PS and D1/2S for U, D1/2S for Pr, and VW and EVLW by desiccation. All indicator-dilution parameters correlate significantly with alloxan dose. Interpretation of Pr transport suggests that materials with lipid and hydrophilic pathways might be used in conjunction with U to minimize the effects of surface area changes and increase the sensitivity of these tracers to permeability alteration. In addition Pr may be a useful alternative to U as a marker of vascular damage. 相似文献
43.
Neurotensin and substance P receptors expressed in Xenopus oocytes by messenger RNA from rat brain 总被引:4,自引:0,他引:4
I Parker K Sumikawa R Miledi 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1986,229(1255):151-159
Xenopus oocytes were induced to acquire sensitivity to neurotensin and substance P, by injecting them with a fraction of poly(A)+ mRNA from rat brain. Non-injected oocytes, and oocytes injected with other brain mRNAs, failed to show responses, suggesting that receptors to these peptides were expressed by specific brain mRNAs. Responses to substance P and neurotensin comprised an oscillatory chloride current, and a smooth current having different ionic basis. These currents resembled those seen during activation of muscarinic and serotonergic receptors, but were not blocked by the corresponding antagonists atropine and methysergide. The responses to substance P, and to a lesser extent to neurotensin, showed a long-lasting desensitization. Similarities between the oscillatory currents evoked by the peptides acetylcholine and serotonin suggest that all these receptors may 'link in' to a common intracellular messenger pathway. 相似文献
44.
45.
George P. Barnes Richard G. Tollefsbol Warren A. Parker John F. Nelson 《Gerodontology》1986,5(2):129-134
Increased longevity and recently intensified emphasis on gerodontology mandate that dental students'exposure to clinical care of the elderly be enhanced. The extent to which individual students can be exposed to geriatric dental care depends on the availability of elderly patients to dental school clinics and the treatment needs of these patients. The purposes of this study were (1) to determine the dental treatment needs of geriatric patients who seek care at a dental school, and (2) to ascertain if differences exist between the needs of older versus relatively young geriatric patients. Data collected on 128 elderly patients during a three month period indicate that 57% of the aged were either edentulous at examination or treatment planned to become edentulous and receive two full dentures. The remaining 43% were treatment planned to remain dentulous and receive therapies other than full upper and lower dentures. More older geriatric patients required full dentures than their younger cohorts. More young elderly required prophylaxes, scalings, root planing therapy, dental restorations, and partial dentures. Additional to their denture requirements, aged patients appear to have sufficient non-prosthetic needs to allow for meaningful gerodontic experience by students. 相似文献
46.
47.
A recently introduced approach far estimating the photosynthetic quantum efficiency (φ) of a freshwater or marine phytoplankton community has been applied for the first time to high latitude polar ecosystems, namely four lakes of southern Victoria Land, Antarctica. Values for φ at various depths ranged from 0.0022–0.1560 when calculated using a recommended mean extinction coefficient for phytoplankton (i.e. k?c= 0.016). By contrast, φ ranged from 0.0037–0.0760 when calculated using an empirically estimated value for k?c of 0.0328. If the recommended k?c= 0.016 more closely approaches an accurate estimate, then the φ valves indicate that the phytoplankton convert light to organic carbon more efficiently than elsewhere. However, if the empirically derived k?c= 0.0328 more closely approaches an accurate estimate, then the φ values indicate the phytoplankton trap light more efficiently than elsewhere. Although we have not resolved whether light conversion (φ) or light trapping are more efficient, the results show that the phytoplankton of these Antarctic lakes are well adapted to performing photosynthesis under extremely low light conditions. 相似文献
48.
This study further defines the craniofacial malformations induced by triamcinolone acetonide in the rhesus monkey. Ten timed-mated pregnant rhesus monkeys (Macaca mulatta) received intramuscular injections of 10 mg/kg TAC on days 23, 25, 27, 29, and 31 of gestation. Results of previous experiments with rhesus and bonnet monkeys and baboons indicated that specific craniofacial and brain malformations could be induced with TAC during this period of pregnancy (Hendrickx et al., '80). Stage-matched TAC-treated and control embryos (stages 17-18 and 22) and age-matched TAC-treated and control fetuses (50, 60, and 70 days gestation) were removed by hysterotomy. Stage 17-18 TAC embryos appeared grossly normal but histologic evaluation revealed a shortened anlage of the posterior cranial base. Stage 22 TAC embryos and all TAC fetuses exhibited craniofacial dysmorphia and encephalocele. The developing sphenoid was the earliest affected and most severely malformed bone. Its defects included reduced anterioposterior and transverse dimensions, reduced orbitosphenoid and alisphenoid, abnormal pituitary fossa, and reduced dorsum and tuberculum sellae. In addition, shortening of the posterior cranial base and decreased cranial base angle was a consistent finding in the treated embryos and fetuses. Decreased ossification and remodeling in the facial bones and abnormal position due to the malformed sphenoid occurred. 相似文献
49.
The optimum conditions for sodium periodate induced lymphocyte transformation occur at low concentrations of NaIO4, low temperature, pH between 6 and 7.5, and with short periods of exposure to the NaIO4. Exposures for prolonged times at elevated temperatures or to NaIO4 at pH above 7.5 result in diminished responses. The finding of maximum lymphocyte response under these conditions is compatible with the proposal that the triggering event in NaIO4 transformation of lymphocytes is the oxidation and cleavage of the two terminal carbon atoms of sialic acid. Exposure of lymphocytes to NaIO4 under conditions of higher temperature, higher pH or longer exposure times does not significantly reduce their ability to respond to phytohemagglutinin (PHA) or pokeweed mitogen (PWM). This finding suggests that these mitogens have different target sites from that of NaIO4 or that they are acting on different populations of lymphocytes. 相似文献
50.
A Structure determination of the naturally occuring marine algal polysaccharide poly-β-D -mannuronic acid is described. The structure consists of 1e → 4e linked D -mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X-ray fiber diffraction photograph obtained from bundles of fibers prepared from Fucus vesiculosus has been indexed to an orthorhombic unit cell in which a =7.6 Å, b (fiber axis) = 10.4 Å, c = 8.6 Å, the unit cell containing two disaccharide chain segments with space group P212121. A sheet-like structure involving one intra-chain, one intra-sheet, and one inter-sheet hydrogen bond per monosaccharide is proposed. Features of the chain-packing arrangement are compared with mannan. 相似文献