Regulation of endothelial cell function by GRGDSP peptide grafted on interpenetrating polymers

Vascular endothelium plays an important role in preventing thrombogenesis. Bioactive molecules such as fibronectin-derived peptide Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) can be used to modify the surface of cardiovascular implants such as vascular grafts to promote endothelialization. Here we conjugated GRGDSP peptide to the nonfouling surface of an interpenetrating polymer network (IPN), and investigated the effects of the immobilized GRGDSP molecules on EC functions under static and flow conditions at well-defined GRGDSP surface densities (approximately 0 to 3 pmol/cm2). EC adhesion and spreading increased with GRGDSP surface density, reached a plateau at 1.5 pmol/cm2, and increased further beyond 2.8 pmol/cm2. Cell adhesion and spreading on GRGDSP induced two waves of extracellular signal-regulated kinase (ERK) activation, and 0.2 pmol/cm2 density of GRGDSP was sufficient to activate ERK. EC proliferation rate was not sensitive to GRGDSP surface density, suggesting that cell spreading at low-density of GRGDSP is sufficient to maintain EC proliferation. EC migration on lower-density GRGDSP-IPN surfaces was faster under static condition. With the increase of GRGDSP density, the speed and persistence of EC migration dropped quickly (0.2-0.8 pmol/cm2) and reached a plateau, followed by a slower and gradual decrease (1.5-3.0 pmol/cm2). These data suggest that the changes of EC functions were more sensitive to the increase of GRGDSP density at lower range. Under flow condition with shear stress at 12 dyn/cm2, EC migration was inhibited on GRGDSP-IPN surfaces, which may be attributed to the assembly of large focal adhesions induced by shear stress, suggesting a catch-bond characteristic for RGD-integrin binding. This study provides a rational base for surface engineering of cardiovascular implants.     

Extended long-term culture reveals a highly quiescent and primitive human hematopoietic progenitor population

Long-term culture-initiating cells (LTC-IC) are hematopoietic progenitors able to generate colony-forming unit-cells (CFU) after 5 to 8 weeks (35 to 60 days) of culture on bone marrow (BM) stroma and represent the most primitive progenitors currently detectable in vitro. We have recently reported that long-term cultures initiated with CD34+CD38- cells from BM or cord blood are able to continue generating CFU for at least 100 days, ie, beyond the standard LTC-IC period. In this report, single-cell cultures from cord blood and retroviral marking of cord blood and BM were used to study whether the subpopulation of CD34+CD38- cells able to generate CFU beyond 60 days ("extended long-term culture-initiating cells" or ELTC-IC) are functionally distinct from LTC-IC in terms of timing of initial clonal proliferation and generative capacity. All cord blood LTC-IC formed clones of greater than 50 cells by day 30. In contrast, cord blood ELTC- IC proliferated later in culture, 50% forming clones after day 30. Although efficient retroviral marking of LTC-IC was seen (25% to 45%), marking of ELTC-IC was inefficient (< 1%), consistent with a more quiescent progenitor population. There was a positive correlation between time of clonal proliferation and generative capacity. ELTC-IC generated threefold to fourfold more progeny than did LTC-IC (P < .002). These studies show that there is a functional hierarchy of progenitors in long-term culture which correlates with their level of quiescence. By extending the LTC-IC assay, a more primitive progenitor may be studied that may be functionally closer to the human long-term repopulation stem cell in vivo.     

二尖瓣疾病左心室充盈压的多普勒评估

由于在瓣膜区域、左心室松弛性和僵直性等方面易于发生混淆．传统多普勒测量对二尖瓣疾病病人左心房压的预测上受到限制。然而，在犬和临床研究中，组织多普勒成像所测定的充盈早期二尖瓣血流速率起始段和房室环的充盈早期速率之间的时间窗（time interval between the onset of early diastolic mitral inflow velocity and annular early diastolic velocity，TE-Ea）与左心室舒张时间常数（time constant of left ventricular relaxation，t）良好相关，并且不受上述瓣膜区域、左心室舒张和僵直等变量的影响。因此在病人人群中开展这项研究，检验其用途。     

Detection of platelet-directed immunoglobin G in sera using the peroxidase-anti-peroxidase (PAP) slide technique

An immunohistochemical procedure for the detection of immunoglobulin G adherent to platelets is described. The peroxidase anti-peroxidase method is used to detect antibody activity directed against platelets from normal donors in the sera from 305 individuals. These subjects were divided into three groups: group 1, patients referred for tissue typing; group 2, healthy normal females; group 3, healthy normal males. In group 1, 28% of the sera were found to be positive; in most of these a history of prior transfusions was obtained. In group 2, 7.4% were found to be positive, most having previous pregnancies. Only 1% were found to be positive in group 3, and no reason for presensitization was found. Results from the indirect immunofluorescence technique served as a control and as a means to compare the sensitivity. Under the conditions chosen, the peroxidase anti-peroxidase test was two to eight times more sensitive than the immunofluorescence technique. Specificity of the peroxidase anti-peroxidase technique was demonstrated using a monospecific anti-PLA1 antiserum. It is concluded that the peroxidase anti-peroxidase slide technique may be a useful tool in the study of platelet-related immunophenomena.     

Human platelets exert cytotoxic effects on tumor cells

Monocytes are thought to play a role in host resistance to tumor cell growth in animals and humans. In addition, platelets are known to be involved in tumor metastases. To investigate the interaction of these two cell types and their effect on tumor cells, human monocytes and platelets were examined using an in vitro monocyte-tumor cell cytotoxicity assay. Monocytes alone resulted in 32% +/- 1.5 (mean +/- SEM) tumor cell kill. When platelets were added to monocytes in a 1:1 ratio, an increase in cytotoxicity to 61% +/- 3.2 was observed. The cytotoxicity noted when platelets were added to a fixed number of monocytes and tumor cells was dependent on the number of platelets added. A decrease in cytotoxicity from 32% +/- 1.5 to 12% +/- 2.3 was observed when contaminating platelets were removed from monocyte preparations. Platelets added to tumor cells in the absence of any monocytes were also toxic, resulting in a maximum kill of 95% at a 4:1 platelet/tumor cell ratio. Secreted products of freshly isolated platelets may be responsible for much of the observed cytotoxicity, since supernatants from the platelets were toxic for tumor cells. Platelets pretreated with a cyclooxygenase inhibitor (ASA) or a lipoxygenase inhibitor had decreased cytotoxicity compared with untreated platelets. Our results indicate that products of platelet arachidonate metabolism are toxic for tumor cell lines. They also suggest that the role of the platelet must be considered when studying monocyte-tumor cell cytotoxicity.     

Elevated NAD(P) glycohydrolase activity: a possible enzymatic marker for malignancy in Burkitt's lymphoma cells

A comparative analysis of enzymatic activities has been performed on 47 human continuous lymphoid lines: 22 tumors derived from Burkitt's lymphoma lines, 6 other lymphomatous long-term cultures, and 19 nonmalignant ties determined on the cell extracts. 4 showed no significant differences between the various lines. They included adenosine diphosphoribose incorporation, glucose-6-phosphate dehydrogenase, cyclic-AMP phosphodiesterase, and glutathione reductase. However, striking differences of activity were found for the enzyme, NAD(P) glycohydrolase (EC 3.2.2.6). Activity levels were, as a mean, four times higher in Burkitt's lymphoma-derived cell lines than in nonmalignant control lines, and the difference was highly significant (p less than 0.02). All Burkitt cell lines containing translocations of chromosome 8 with either chromosomes 2, 14 or 22 showed an increased activity. The specificity and significance of this possible enzymatic marker of Burkitt's lymphoma cells is discussed.