Endothelial cell hypoxia associated proteins are cell and stress specific.

Vascular endothelial cells (EC) are one of the initial cells exposed to decreases in blood oxygen tension. Bovine EC respond not only by altering secretion of vasoactive, mitogenic, and thrombogenic substances, but also by developing adaptive mechanisms in order to survive acute and chronic hypoxic exposures. EC exposed to hypoxia in vitro upregulate a unique set of stress proteins of Mr 34, 36, 39, 47, and 56 kD. Previous studies have shown that these proteins are cell associated, upregulated in a time and oxygen-concentration dependent manner, and are distinct from heat shock (HSPs) and glucose-regulated proteins (GRPs). To further characterize these hypoxia-associated proteins (HAPs), we investigated their upregulation in human EC from various vascular beds and compared this to possible HAP upregulation in other cell types. Human aortic, pulmonary artery, and microvascular EC upregulated the same set of proteins in response to hypoxia. In comparison, neither lung fibroblasts, pulmonary artery smooth muscle cells, pulmonary alveolar type II cells, nor renal tubular epithelial cells upregulated proteins of these Mr. Instead, most of these cell types induced synthesis of proteins of Mrs corresponding to either HSPs, GRPs, or both. Further studies demonstrated that exposure of EC to related stresses such as cyanide, 2-deoxyglucose, hydrogen peroxide, dithiothreitol, and glucose deprivation did not cause upregulation of HAPs. Evaluation of cellular damage during hypoxia using phase-contrast microscopy, trypan blue exclusion, chromium release, and adherent cell counts showed that EC survived longer with less damage than any of the above cell types. The induction of HAPs, and the lack of induction of HSPs or GRPs, by EC in response to hypoxia may be related to their unique ability to tolerate hypoxia for prolonged periods.

Effect of hypoxia on endothelial cell surface glycoprotein expression: modulation of glycoprotein IIIa and other specific surface glycoproteins.

Exposure to hypoxia alters many aspects of endothelial cell metabolism and function; however, changes in surface glycoconjugates under these conditions have not been extensively evaluated. In the current studies, we examined surface glycoproteins of cultured bovine aortic (BAEC) and pulmonary arterial (BPAEC) endothelial cells under standard culture conditions (21% oxygen) and following exposure to hypoxia (0% oxygen) for varying time periods (30 min to 18 h) using a system of biotinylation, lectin binding (concanavalin A, Con A; Griffonia simplicifolia, GSA; Arachis hypogaea, PNA; Ricinus communis, RCA; or Triticum vulgaris, WGA), subsequent strep-avidin binding, and staining. Using these methods, we identified differences in lectin binding between the two cell types cultured in 21% oxygen with all lectins except PNA. With exposure to 0% oxygen, there was no change in lectin binding to most surface glycoproteins. Several surface glycoproteins, including glycoprotein IIIa on both cell types, demonstrated a time-dependent decrease in lectin binding; in addition, there was an increase in lectin binding to a few specific surface glycoproteins on each cell type within 30-60 min of exposure to 0% oxygen. These changes in specific surface glycoproteins were confirmed in both cell types by 125I labeling. Increased lectin binding was observed for Con A binding BAEC glycoproteins at molecular weight (MW) 116, 130, and 205 kDa, GSA binding BAEC glycoproteins at MW 120 and 205 kDa, and RCA binding BPAEC glycoproteins at MW 140 and 205 kDa. Increased binding of WGA or PNA was not observed during exposure to hypoxia. The specificity of lectin binding was further confirmed by competitive inhibition with the appropriate sugar. These studies demonstrate that there are baseline differences between BAEC and BPAEC cell surface glycoproteins and that exposure to hypoxia is associated with little change in lectin binding to most surface glycoproteins. There is, however, increased surface expression of a few glycoproteins that differ depending of the origin of the endothelial cell. Although the mechanism of this increase in lectin binding is not yet clear, subsequent studies suggested that it is due to increased availability of select carbohydrate moieties. The time course of these alterations suggests a possible role in the endothelial cell response to decreases in ambient oxygen tension.

Comparison of hetastarch to albumin for perioperative bleeding in patients undergoing abdominal aortic aneurysm surgery. A prospective, randomized study.

The effects of hetastarch and human albumin solutions on perioperative bleeding and coagulation parameters during abdominal aortic aneurysm repair were compared. In two randomized groups of 20 patients, albumin 5% (group 1) or hetastarch 6% (group 2) 1 g/kg was given during surgery. The remaining perioperative fluids consisted of lactated ringers and packed red blood cells. Perioperative coagulation measurements included partial thromboplastin time, prothrombin time, activated clotting time, platelet count, and bleeding time. Estimated blood loss and the total amount of crystalloid and blood infused were also measured. The surgeon, blind to the colloid used, subjectively rated bleeding on a scale of 1 to 10. There was no significant difference between groups for any measured parameter at any time. Measurements of coagulation function were within normal limits for both groups. Hetastarch does not cause clotting disorders in patients undergoing abdominal aortic aneurysm repair, at least if the quantities used in this study are not exceeded.

Assessment of biopsy techniques and histopathologic interpretations of primary cutaneous malignant melanoma.

The biopsy techniques utilized for diagnosis in 1,161 patients with primary cutaneous malignant melanoma treated at the New York University Medical Center were reviewed. Eight hundred sixty-four (74%) biopsies were of the excisional type and 269 (23%) were incisional. Twenty-eight biopsies (3%) could not be assessed. Two hundred fifty-two consecutive patients referred for treatment of malignant melanoma to the authors for the last three years were studied to determine whether standard techniques of biopsy and uniform criteria for histopathologic diagnosis and staging were being utilized. One hundred forty-nine of these patients (59%) had total excisional biopsies of their lesions and 103 (41%) had incisional biopsies. Of the latter group, 66 (64%) were for lesions less than 2 cm in diameter and were situated in areas other than the face. The biopsy specimens obtained from 123 patients were reviewed by at least one other pathologist as well as our own (A.B.A.). For these 123 patients a difference of histologic diagnosis between pathologists occurred in 11 (9%). In 58 (47%) there was a discrepancy in assignment of Clark levels or a failure to assess Clark levels. Tumor thicknesses as measured by Breslow were read in only 22 (18%) of these 123 patients. The inadequacies of many of the biopsy specimens and discrepancies in histopathologic interpretation indicate that acceptable biopsy techniques and reproducible diagnostic criteria have not yet been generally adapted for primary cutaneous malignant melanomas.