Assessing vulnerability to embolism and hydraulic safety margins in reed-like Restionaceae

The African Restionaceae (Poales), the dominant graminoid layer in the megadiverse Cape Floristic Region of South Africa, are distributed across a wide range of moisture availability, yet currently there is very little known about the underlying hydraulics of this group. We tested two methods for measuring culm vulnerability to embolism, the optical and pneumatic methods, in three species of Cannomois ranging in habitat from semi-riparian (Cannomois virgata) to dryland (Cannomois parviflora and C. congesta). Estimates of culm xylem vulnerability were coupled with measures of turgor loss point (ΨTLP) and minimum field water potential (ΨMD) to assess hydraulic safety margins. The optical and pneumatic methods produced similar estimates of P50, but differed for P12 and P88. All three species were quite vulnerable to embolism, with P50 of -1.9 MPa (C. virgata), -2.3 MPa (C. congesta), and -2.4 MPa (C. parviflora). Estimates of P50, ΨTLP and ΨMD aligned with habitat moisture stress, with highest values found in the semi-riparian C. virgata. Consistent differences in P50, ΨMD and ΨTLP between species resulted in consistent hydraulic safety margins across species of 0.96 ± 0.1 MPa between ΨMD and P50, with onset of embolism occurring 0.43 ± 0.04 MPa after ΨTLP for all three species. Our study demonstrates that restio occupancy of dry environments involves more than the evolution of highly resistant xylem, suggesting that other aspects of water relations are key to understanding trait-environment relationships in this group.

Effect of Erythropoietin Therapy on Diet and Dialysis Clearances in Hemodialysis Patients

Treatment of renal anemia with recombinant human erythropoietin in chronic hemodialysis patients has been reported to lead to increased appetite, and in several studies, to an increase in predialysis serum urea, potassium and creatinine values. We recorded dietary intake, and dialysis clearances for creatinine, urea and uric acid in a group of 12 anemic hemodialysis patients treated with recombinant erythropoietin (epoetin beta). A gradual increase was noted in dietary intake of calories, carbohydrate and sodium during the study period, attaining statistical significance after 10–12 months of therapy. A trend toward increased dietary intake of protein, lipid and potassium was observed, but the differences did not achieve statistical significance. Although a trend toward decreased dialysis clearance at higher hematocrits was found for creatinine clearances did not change significantly for any of the solutes examined, and linear regression analysis did not demonstrate a strong relationship between dialyzer clearance and hematocrit values within the range observed in this study.

The acceptability of the female condom: perspectives of family planning providers in New York City, South Africa, and Nigeria

This article seeks to fill the gap in female condom acceptability research by examining family planning (FP) providers' attitudes and experiences regarding the female condom in three countries (South Africa, the US, and Nigeria) to highlight providers' potential integral role in the introduction of the female condom. The case studies used data drawn from three independent projects, each of which was designed to study or to change FP providers' attitudes and practices in relation to the female condom. The case study for New York City used data from semistructured interviews with providers in one FP consortium in which no special female condom training had been undertaken. The data from South Africa were drawn from transcripts and observations of a female condom training program and from interviews conducted in preparation for the training. The Nigerian study used observations of client visits before and after providers were trained concerning the female condom. In New York City, providers were skeptical about the contraceptive efficacy of the female condom, with only 8 of 22 providers (36%) reporting they would recommend it as a primary contraceptive. In South Africa, providers who had practiced insertion of the female condom as part of their training expressed concern about its physical appearance and effects on sexual pleasure. However, they also saw the female condom as a tool to empower clients to increase their capacity for self-protection. Structured observations of providers' counseling interactions with clients following training indicated that Nigerian providers discussed the female condom with clients in 80% of the visits observed. Despite the lack of a uniform methodology, the three case studies illuminate various dimensions of FP providers' perceptions of the acceptability of the female condom. FP providers must be viewed as a critical factor in female condom acceptability, uptake, and continued use. Designing training programs and other interventions that address sources of provider resistance and enhance providers' skills in teaching female condom negotiation strategies may help to increase clients' use of the female condom.

Autonomy and the subjective character of experience

In his famous paper, What Is It Like To Be a Bat?, Thomas Nagel argues against a reductive physicalist account of consciousness by highlighting what he calls "the subjective character of experience." In this paper I will argue that Nagel's insight is important for understanding the value placed on patient autonomy in medical ethics. Appreciation of the subjective character experience brings with it the necessity for an epistemological humility with respect to the lives of others and what can be said to be "right" for them. Appreciation of the subjective character of experience lies at the heart of empathy and our capacity to make decisions that genuinely reflect respect for the patient's autonomy. Through the example of a case involving extreme medical intervention, I identify some impediments to the proper recognition of autonomy. These kind of cases highlight the significance of affective responses with respect to the subjective character of experience, and, by extension, to our capacity to imagine and act in accordance with another's perspective. I argue that affective responses are appropriate and needed considerations in the case where one must attempt to assume another's perspective in order to respect autonomy. I conclude that understanding that experience has an irreducibly subjective character is essential to respecting patient autonomy.

Coordinate expression of OPN and associated receptors during monocyte/macrophage differentiation of HL-60 cells

Promyelocytic leukemia HL-60 cells promoted by PMA to differentiate along the monocyte pathway adhere to tissue culture plates. To explore the regulation of adhesion molecules in cells promoted to differentiate, the expression and secretion of osteopontin (OPN) and expression of associated cell surface receptors, CD44 and integrin subunits alpha(v), beta3, beta1, were examined. Results were as follows: 1) PMA induced OPN mRNA and OPN secretion into media; 2) untreated cells expressed beta1 and CD44 mRNA, and PMA induced alpha(v), and beta3 mRNA and increased beta1 and CD44 mRNA expression; 3) PMA increased levels of alpha(v), beta3, beta1 and CD44 protein on the cell surface; and 4) retinoic acid, which promotes granulocytic differentiation of HL-60 cells, did not affect OPN, alpha(v), beta3, beta1, or CD44 mRNA or protein expression. These data suggest that induction of OPN and associated receptors may play a role during monocytic differentiation of HL-60 cells.

A novel P-selectin glycoprotein ligand-1 monoclonal antibody recognizes an epitope within the tyrosine sulfate motif of human PSGL-1 and blocks recognition of both P- and L-selectin

Interactions between P-selectin and P-selectin glycoprotein ligand-1 (PSGL-1) mediate the earliest "rolling" of leukocytes on the lumenal surface of endothelial cells at sites of inflammation. Previously, PSGL-1 has been shown to be the primary mediator of interactions between neutrophils and P-selectin, but studies on the ability of PSGL-1 to mediate interactions between P-selectin and other subsets of leukocytes have yielded variable and conflicting results. A novel IgG monoclonal antibody (MoAb) to human PSGL-1 was generated, and the specificity of this MoAb was confirmed by both flow cytometric analysis and Western blotting of cells transfected with human PSGL-1. This newly developed MoAb, KPL1, inhibited interactions between P-selectin expressing COS cells and either HL60 cells, neutrophils, or lymphocytes. Furthermore, KPL1 completely inhibited interactions between P-selectin and either purified CD4 T cells or neutrophils in a flow assay under physiological conditions, but had no effect on interactions of T cells or neutrophils with E-selectin. In addition, KPL1 blocked interactions between lymphoid cells transfected with L-selectin and COS cells expressing PSGL-1. The KPL1 epitope was mapped to a site within a consensus tyrosine sulfation motif of PSGL-1, previously shown to be essential for interaction with P-selectin and now shown to be essential for interaction with L-selectin, and to be distinct from the epitope identified by the PL1 function blocking anti-PSGL-1 MoAb. Two-color flow cytometry of normal leukocytes showed that while natural killer (NK) cells (CD16(+)), monocytes, CD4 and CD8 T cells, and alpha/beta and gamma/delta T cells were uniformly positive for PSGL-1, B cells expressed low levels of the KPL1 epitope. This low level of KPL1 staining was also observed immunohistologically in germinal centers, which had no detectable KPL1 staining, whereas T-cell areas (interfollicular region) were positive for KPL1. Interestingly, plasma cells in situ and interleukin-6-dependent myeloma cell lines were KPL1(+). Thus, PSGL-1 is expressed on essentially all blood neutrophils, NK cells, B cells, T cells, and monocytes. Variation in tyrosine sulfation during B-cell differentiation may affect the ability of B cells to interact with P- and L-selectin.

A novel five-transmembrane hematopoietic stem cell antigen: isolation, characterization, and molecular cloning

Phenotypic analysis of hematopoietic stem and progenitor cells (HSCs) has been an invaluable tool in defining the biology of stem cell populations. We have recently described the production of AC133, a monoclonal antibody (MoAb) that binds to a novel cell surface antigen present on a CD34(bright) subset of human HSCs. This antigen is a glycosylated protein with a molecular weight of 120 kD. Here, we report the molecular cloning of a cDNA encoding this antigen and show that it does not share homology with any previously described hematopoietic or other cell surface antigen(s). The AC133 polypeptide has a predicted size of 97 kD and contains five-transmembrane (5-TM) domains with an extracellular N-terminus and a cytoplasmic C-terminus. Whereas the expression of tetraspan (4-TM) and 7-TM molecules is well documented on mature and immature hematopoietic cells and leukocytes, this 5-TM type of structure containing two large (255-amino acid [aa] and 290-aa) extracellular loops is unique and does not share sequence homology with any known multi-TM family members. Expression of this protein appears limited to bone marrow in normal tissue by immunohistochemical staining; however, Northern analysis suggests that the mRNA transcript is present in a variety of tissues such as the kidney, pancreas, placenta, and fetal liver. The AC133 antigen is also expressed on subsets of CD34+ leukemias, suggesting that it may be an important early marker for HSCs, as well as the first described member of a new class of TM receptors.

Effect of erythropoietin therapy on diet and dialysis clearances in hemodialysis patients

Treatment of renal anemia with recombinant human erythropoietin in chronic hemodialysis patients has been reported to lead to increased appetite, and in several studies, to an increase in predialysis serum urea, potassium and creatinine values. We recorded dietary intake, and dialysis clearances for creatinine, urea and uric acid in a group of 12 anemic hemodialysis patients treated with recombinant erythropoietin (epoetin beta). A gradual increase was noted in dietary intake of calories, carbohydrate and sodium during the study period, attaining statistical significance after 10-12 months of therapy. A trend toward increased dietary intake of protein, lipid and potassium was observed, but the differences did not achieve statistical significance. Although a trend toward decreased dialysis clearance at higher hematocrits was found for creatinine clearances did not change significantly for any of the solutes examined, and linear regression analysis did not demonstrate a strong relationship between dialyzer clearance and hematocrit values within the range observed in this study.

Effect of erythropoietin administration on blood and plasma viscosity in hemodialysis patients

The effect of recombinant human erythropoietin (EPO) on whole blood and plasma viscosity was studied in six anemic hemodialysis (HD) patients, and five equally anemic placebo treated HD patients. Viscosity was determined pre- and postdialysis using cone-plate viscometry. Predialysis values for hematocrit and whole blood viscosity increased significantly over a 12 week period in the EPO but not the placebo treated group; plasma viscosity did not change in either group. Whole blood viscosity measured before and after a single HD session during week 12 revealed a significant rise. This change, expressed as a percent of the predialysis values, was similar in the two groups. Thus, the rise in whole blood viscosity seen in EPO treated patients is a result of the increase in erythrocyte concentration and not a result of an effect of EPO on plasma. In addition, EPO does not seem to alter the acute effect of HD on blood viscosity.