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81.
JD Loike J el Khoury L Cao CP Richards H Rascoff JT Mandeville FR Maxfield SC Silverstein 《Canadian Metallurgical Quarterly》1995,181(5):1763-1772
We have examined the capacity of four different chemoattractants/cytokines to promote directed migration of polymorphonuclear leukocytes (PMN) through three-dimensional gels composed of extracellular matrix proteins. About 20% of PMN migrated through fibrin gels and plasma clots in response to a gradient of interleukin 8 (IL-8) or leukotriene B4 (LTB4). In contrast, < 0.3% of PMN migrated through fibrin gels in response to a gradient of tumor necrosis factor alpha (TNF) or formyl-methionyl-leucyl-phenylalanine (FMLP). All four chemoattractants stimulated PMN to migrate through gels composed of collagen IV or of basement membrane proteins (Matrigel), or through filters to which fibronectin or fibrinogen had been adsorbed. PMN stimulated with TNF or FMLP adhered and formed zones of close apposition to fibrin, as measured by the exclusion of a 10-kD rhodamine-polyethylene glycol probe from the contact zones between PMN and the underlying fibrin gel. By this measure, IL-8- or LTB4-treated PMN adhered loosely to fibrin, since 10 kD rhodamine-polyethylene glycol permeated into the contact zones between these cells and the underlying fibrin gel. PMN stimulated with FMLP and IL-8, or FMLP and LTB4, exhibited very little migration through fibrin gels, and three times as many of these cells excluded 10 kD rhodamine-polyethylene glycol from their zones of contact with fibrin as PMN stimulated with IL-8 or LTB4 alone. These results show that PMN chemotaxis is regulated by both the nature of the chemoattractant and the composition of the extracellular matrix; they suggest that certain combinations of chemoattractants and matrix proteins may limit leukocyte movements and promote their localization in specific tissues in vivo. 相似文献
82.
A modification of the method of Sen and Widdas (J. Physiol. London 160:392-403, 1962) was used to measure the rate of exit of several nonelectrolytes from erythrocytes of various species. In spite of additional errors introduced by the larger half-saturation values of the carriers (phi) and concentrations, it was possible to distinguish between systems with small values of phi, systems with relatively large values of phi, and systems involving only simple diffusion. Approximate values of phi in millimoles and of maximum transfer rate (K) in isotonic units per minute were obtained using times and initial slopes measured on experimental curves. The following values in the foregoing units were obtained: human glucose, phi = 1.8, 1.0, K = 0.8, 1.1; human glycerol, phi = 178, 94, K = 4.3, 3.3; sheep thiourea, phi = 56, 56, K = 0.9, 0.6; and rabbit glycerol, phi = 328, 64, K = 2.2, 1.0. Simple diffusion was demonstrated for the following systems: ox-ethylene glycol; ox-glycerol; sheep-ethylene glycol; and sheep glycerol. 相似文献
83.
The ionic components of the action potential (AP) in rabbit right papillary muscle (RRPM) were determined by simple methods such as changes in external concentrations of sodium and calcium ions and addition of MnCl2 ot the perfusion fluid. Two components (fast and slow) were clearly visible in the upstroke of AP in normal Tyrode solution. MnCl2 (5 mmol/l) eliminated the slow component which forms the overshoot (OS) leaving the fast one unaffected, indicating that the former was related to a slow inward current. Mn also drastically reduced AP duration without changing the slope of phase 3 of repolarization. Reduction of Na concentration to 90 mmol/l did not affect the peak voltage of the OS but shortened AP. This low-Na solution reduced both (Vmax)f and the amplitude of the fast component. Ca-free solution reduced OS and increased AP duration. In high-Ca Tyrode (7.2 mmol/l) OS was increased and AP shortened. The effects of MN were reversed in this solution. The results suggest that the upstroke of the RRPM action potential is determined by two different ionic currents: a fast Na current responsible for the fast component and a slow inward current carried mainly by Ca, this latter being responsible for the slow component in the upstroke and for the plateau phase. The existence of propagated, Ca-dependent slow responses was demonstrated. Emphasis is placed on the fact that the major determination of the repolarization process in this type of AP is probably the inactivation of the slow inward Ca current. 相似文献
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AIMS: To further understand the morphological and functional recovery of corneal epithelium following excimer laser photorefractive keratectomy (PRK). METHODS: The right eyes (group 1) of 15 male, New Zealand white rabbits weighing 2-3 kg underwent PRK. The left eye of each rabbit (group 2) underwent simple mechanical de-epithelialisation and were examined as treated controls. Both eyes of another eight rabbits (group 3) served as untreated controls. All eyes underwent a corneal epithelial permeability study by fluorophotometry at 2, 4, and 8 weeks after surgery. Five animals in groups 1 and 2 were sacrificed at 9, 10, and 12 weeks after surgery. The animals in group 3 were sacrificed at the end of the 12 week experimental period. Both eyes of each sacrificed animal were enucleated immediately and processed for both haematoxylin and eosin stain and electron microscopic study. The electron micrograph was magnified to 14,000x and the extent of hemidesmosome formation was quantified and analysed. RESULTS: The corneal epithelial barrier to sodium fluorescein was subnormal and returned to a normal barrier state 4 weeks after PRK in group 1 whereas it was normal in group 2 throughout the examination period. The extent of hemidesmosome formation was abundant yet subnormal in both groups 1 and 2 up to 12 weeks, when compared with that in group 3. CONCLUSION: The corneal epithelium regained its functional barrier 4 weeks after PRK in rabbits while the extent of hemidesmosome formation was still subnormal 12 weeks after mechanical de-epithelialisation, with or without PRK. 相似文献
87.
We tested the influence of in vivo volume resuscitation on intrinsic contractile properties of left ventricular (LV) preparations of endotoxemic guinea pigs. Escherichia coli endotoxin (LPS)-injected animals were divided into nonresuscitated and resuscitated groups. Volume resuscitation improved cardiac output and stroke volume, increased arterial pH and body temperature, and decreased mortality. In isovolumetric LV preparations isolated 4 h after LPS injection, LV systolic pressures (in mmHg) preparations isolated 4 h after LPS injection, LV systolic pressures (in mmHg) of LPS with (42 +/- 3) and without (42 +/- 2) fluid resuscitation were consistently less than control values (70 +/- 3). LV end-diastolic pressure-volume (compliance) decreased in LPS-nonresuscitated hearts, while LV compliance of LPS-resuscitated hearts was similar to control. Thus, intravascular volume expansion selectively improved LV diastolic compliance of LPS hearts without affecting LV systolic function. These findings suggest that LV systolic and diastolic dysfunctions associated with endotoxemia and Gram-negative sepsis may involve separate pathogenic mechanisms. 相似文献
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89.
LM Hansen FR Batzer JN Gutmann SL Corson MP Kelly B Gocial 《Canadian Metallurgical Quarterly》1996,11(3):486-489
A prospective measurement of follicle stimulating hormone (FSH) and oestradiol between cycle days 2 and 5 was conducted to investigate the intra- and inter-cycle variability in a healthy population of women with regular menstrual intervals. Daily serum samples were obtained from 44 women for a total of 66 cycles on cycle days 2, 3, 4 and 5. FSH concentrations were consistent on all cycle days measured. Oestradiol concentrations on cycle day 2 were not different from cycle day 3, but concentrations on cycle day 4 and cycle day 5 were statistically different from both cycle day 2 and cycle day 3 by analysis of variance (P < or = 0.05). Evaluation of functional ovarian reserved by cycle day 3 FSH measurement has become the standard in most assisted reproductive technology programmes. The recent change in FSH standardization coupled with the inflexibility of cycle day 3 testing has led to a re-evaluation of testing protocols. Cycle day 3 appears to have emerged as a dictum because most ovulation induction protocols are initiated on cycle day 3, 4 or 5. Flexibility of sampling day can be introduced as suggested by these results. The additional information ascertained from oestradiol testing as applied to evaluation of ovarian reserve warrants further investigation. 相似文献
90.
FR Lima AG Trentin D Rosenthal C Chagas V Moura Neto 《Canadian Metallurgical Quarterly》1997,154(1):167-175
Degradation and utilization of protein by Prevotella ruminicola B1(4), a proteolytic bacterium that is prominent in the rumen, was examined. In preliminary experiments, proteinaceous N sources produced faster growth rates than did NH4Cl, based on changes in optical density over time. However, ammonium chloride produced a greater maximum cell density than did proteinaceous N sources. Of the proteinaceous N sources, an enzymatic hydrolysate of soybean protein with a relative peptide size of 3 AA residues produced a greater growth rate and maximum cell density compared with the other proteinaceous N sources. Further experiments revealed that P. ruminicola B1(4) grew faster and to a greater final dry weight with soybean protein than with casein. Degradation of both proteins was low as was indicated by the slow disappearance of soluble protein, low concentrations of free AA and peptides, and the decrease in ammonia concentrations over time. Patterns of degradation did differ between the two proteins, however. Accumulation of peptides and free AA from soybean protein peaked 2 h earlier than those from casein, and concentrations of free AA and peptides from soybean protein were lower on average than those from casein. Prevotella ruminicola B1(4) preferentially utilized Asp, Ile, Leu, Lys, and Arg from soybean protein compared with casein. The relative size of peptides that accumulated from both proteins, as determined by the ratio of ninhydrin reaction after HCl hydrolysis to ninhydrin reaction before HCl hydrolysis, suggested that part of the proteolytic activity of P. ruminicola B1(4) is a dipeptidase. Our findings suggest that P. ruminicola may have a greater impact on peptide degradation than on protein degradation in the rumen. 相似文献