Microvascular pericyte contractility in vitro: comparison with other cells of the vascular wall

Collagen lattices containing bovine retinal pericytes (RPs), vascular smooth muscle cells (VSMCs), pulmonary microvessel endothelial cells (PMECs), or aortic endothelial cells (AECs) were prepared and contraction was quantitated by measuring the resulting change in lattice area. VSMCs were the most efficient at lattice contraction followed by RPs and then PMECs. AECs did not contract the lattices. To document further that these observations represent contraction, cells were grown on inert silicone rubber sheets. Substratum wrinkling was indicative of tension development and quantitated as percent of cells contracted. RPs were more contractile than PMECs, and AECs were incapable of developing tension. VSMCs were less contractile than RPs, unlike the comparative contractility observed with the lattice system. Alteration of actin-containing filaments by cytochalasin B significantly reduced RP contraction of silicone rubber and inhibited their contraction of collagen lattices in a dose-dependent manner. Rhodamine-phalloidin staining of contracting RPs revealed microfilament bundle orientations that suggested their association in the force applied for contraction. RP, VSMC and PMEC contraction of collagen lattices was directly proportional to the concentration of fetal calf serum. Also, RP contraction was greater in calf serum than calf plasma-derived serum, an indication that RPs respond to substances that appear continuously and episodically in blood. These in vitro findings support the theory that pericytes in vivo are contractile but that endothelial cells may also contribute to microvascular tonus.     

Approaches used to examine the mechanism and regulation of hexose transport in rat myoblasts

This review discusses some of the approaches and general criteria that we have used to examine the properties of the hexose transport system in undifferentiated L6 rat myoblasts. These approaches include studying the kinetics of hexose transport in whole cells and plasma membrane vesicles, the effects of various inhibitors on hexose transport, the isolation and characterization of hexose transport mutants, and the use of cytochalasin B (CB) to identify the transport component(s). Transport kinetics indicated that two transport systems are present in these cells. 2-Deoxy-D-glucose is transported primarily by the high affinity system, whereas 3-O-methyl-D-glucose is transported by the low affinity system. Furthermore, these two transport systems are inactivated to different extents by CB. CB has a higher binding affinity for the low affinity hexose transport system. The inhibitory effect of various hexose analogues also revealed the presence of two hexose transport systems. The effects of various ionophores and energy uncouplers on hexose transport suggest that the high affinity system is an active transport process, whereas the low affinity system is of the facilitated diffusion type. The high affinity system is also sensitive to sulfhydryl reagents, whereas the low affinity system is not. Further evidence for the presence of two transport systems comes from the characterization of hexose transport mutants. Two of the mutants isolated are shown to be defective in the high affinity transport system, but not in the low affinity transport system. These mutants are also defective in the CB low affinity binding site. Based on our results a tentative working model for hexose transport in L6 rat myoblasts is presented.     

Comparative effects of trichothecene mycotoxins on bovine platelet function: Acetyl T-2 toxin,a more potent inhibitor than T-2 toxin

The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10^?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds.     

Transport kinetics of maltotriose in strains ofSaccharomyces

Summary Maltotriose transport was studied in two brewer's yeast strains, an ale strain 3001 and a lager strain 3021, using laboratory-synthesized¹⁴C-maltotriose. The maltotriose transport systems preferred a lower pH (pH 4.3) to a higher pH (pH 6.6). Two maltotriose transport affinity systems have been indentified. The high affinity system hasK _m values of 1.3 mM for strain 3021 and 1.4 mM for strain 3001. The low affinity competitively inhibited by maltose and glucose withK _i values of 58 mM and 177 mM. respectively, for strain 3021, and 55 mM and 147 mM, respectively, for strain 3001. Cells grown in maltotriose and maltose had higher maltotriose and maltose transport rates, and cells grown in glucose had lower maltortriose and maltose transport rates. Early-logarithmic phase cells transported glucose faster than either maltose or maltotriose. Cells harvested later in the growth phase had increased maltotriose and maltose transport activity. Neither strain exhibited significant differences with respect to maltose and maltotriose transport activity.     

Calcium flux and ornithine decarboxylase activity in cultured endothelial cells

This brief communication reports the observation that calcium influx appears to be a requirement in the serum-induction of ornithine decarboxylase (ODC) activity in cultured aortic endothelial cells. Addition of 35% fetal calf serum causes an increase in endothelial ODC activity within three hours to levels that are 16 times those of baseline. Preincubation of EC with lanthanum chloride (LaCl) or the addition of ethylene glycol (β-aminoethyl ether)-N-N′ tetraacetic acid (EGTA) to the medium inhibits the serum-induction of ODC. The displacement of the lanthanum ions with EGTA reverses the inhibition which demonstrates the viability of the LaCl₃-pretreated cells, and lends support to the view that calcium may be involved in the induction of ODC.     

Rapid fibroblast growth factor-induced increases in protein phosphorylation and ornithine decarboxylase activity: regulation by heparin and comparison to nerve growth factor-induced increases.

Fibroblast growth factors (FGFs), like nerve growth factor (NGF), induce morphological differentiation of PC12 cells. This activity of FGF is regulated by glycosaminoglycans. To further understand the mechanisms of FGF and glycosaminoglycan actions in PC12 cells, we studied the regulation of protein phosphorylation and ornithine decarboxylase (ODC) activity by FGF in the presence and absence of heparin. As with NGF, aFGF and bFGF increased the incorporation of radioactive phosphate into the protein tyrosine hydroxylase (TH). The increase in TH phosphorylation was localized to the tryptic peptide, T3. Both T3 and T1 phosphorylations occur in response to NGF, but there was no evidence that aFGF or bFGF stimulated the phosphorylation of the T1 peptide. This result suggests differential regulation of second messenger systems by NGF and FGF in PC12 cells. Heparin, at a concentration that potentiated aFGF-induced neurite outgrowth 100-fold (100 micrograms/ml), did not alter the ability of aFGF to increase S6 phosphorylation or ODC activity. One milligram per milliliter of heparin, a concentration that inhibited bFGF-induced neurite outgrowth, also inhibited bFGF-induced increases in S6 phosphorylation and ODC activity. These observations suggest (i) that acidic and basic FGF activate a protein kinase, possibly protein kinase C, resulting in the phosphorylation of peptide T3 of TH; (ii) that the FGFs and NGF share some but not all second messenger systems; (iii) that heparin potentiates aFGF actions and inhibits bFGF actions in PC12 cells via distinct mechanisms; (iv) that heparin does not potentiate the neurite outgrowth promoting activity of aFGF by enhancing binding to its PC12 cell surface receptor; and (v) that heparin may coordinately regulate several activities of bFGF (induction of protein phosphorylation, ODC and neurite outgrowth) via a common mechanism, most likely by inhibiting the productive binding of bFGF to its PC12 cell surface receptor.     

Demonstration of vasoproliferative activity from mammalian retina

Vasoproliferative activity has been demonstrated in extracts of retinas from human, bovine, and feline sources. These retinal extracts are capable of stimulating (a) proliferation and thymidine uptake of bovine vascular endothelial cells in culture and (b) neovascularization on the chick chorioallantoic membrane. Extracts of skeletal muscle, cardiac muscle, and liver lack similar stimulatory activity. The activity is nondialyzable, stable at 56 degrees C, and inactivated at 100 degrees C. Retinal extracts stimulate the proliferation of corneal fibroblasts but have no effect on the proliferation of vascular smooth muscle cells. Indirect evidence suggests the liberation of a vasoproliferative factor from retina in several ocular disorders. The data in this report represent the first direct demonstration of vasoproliferative activity from mammalian retina.     

Fiber micro-architecture in the longitudinal-radial and circumferential-radial planes of ascending thoracic aortic aneurysm media

It was recently demonstrated by our group that the delamination strength of ascending thoracic aortic aneurysms (ATAA) was lower than that of control (CTRL, non-aneurysmal) ascending thoracic aorta (ATA), and the reduced strength was more pronounced among bicuspid (BAV) vs. tricuspid aortic valve (TAV) patients, suggesting a different risk of aortic dissection for BAV patients. We hypothesized that aortic valve morphologic phenotype predicts fiber micro-architectural anomalies in ATA. To test the hypothesis, we characterized the micro-architecture in the longitudinal-radial (Z-RAD) and circumferential-radial (Θ-RAD) planes of human ATA tissue that was artificially dissected medially. The outer and inner-media of CTRL-ATA, BAV-ATAA and TAV-ATAA were imaged using multi-photon microscopy in the Z-RAD and Θ-RAD planes to observe collagen and elastin. Micrographs were processed using an image-based tool to quantify several micro-architectural characteristics. In the outer-media of BAV-ATAA, elastin was more undulated and less aligned about the Θ-axis when compared with CTRL-ATA, which is consistent with increased tensile stretch at inflection point of Θ-strips of adventitial-medial half of BAV-ATAA (1.28) when compared with CTRL-ATA (1.13). With increasing age, collagen became more undulated about the Z-axis within the outer-media of TAV-ATAA, and elastin became more oriented in the Z-axis and collagen less radially-oriented within the inner-media of TAV-ATAA. This discrepancy in the micro-architecture with fibers in the inner layers being more stretched and with disrupted radially-oriented components than fibers in the outer layers may be associated with the development, progression and vascular remodeling in aneurysms arising in TAV patients.     

吐鲁番市胃食管反流病发生相关危险因素分析（附280例报道）

目的：探讨280例胃食管反流病（GERD）的分布特点及危险因素。方法：对临床诊断和胃镜确诊的280例GERD患者进行临床和风险因子相关性分析。结果：不论汉族还是维族,男性患者比例均明显高于女性;汉族患者高发年龄段早于维族患者（z=-2．939,P=0．003,）;汉族和维族患者占反流性食管炎和Barrett食管比例分别为42．4％、81_3％及56．5％、18．8％,其中汉族患者Barrett食管比例较高（X2=14．358,P=0．000）;肥胖、习惯性便秘、重体力活动者、饮食习惯不良在维族患者中的比例较高（P〈0．001）。结论：GERD与性别、年龄密切相关,男性多于女性,汉族患者发病年龄高峰旱于维族患者;汉族患者Barrett食管发生比例高于维族患者;肥胖、习惯性便秘、重体力活动、饮食习惯不良可能是GERD尤其是维族人群GERD的危险因素。