Recently published papers: A series of negative results

Studies with negative results rarely hit the headlines. But the results are often just as important as the positive ones. A number of 'negative headline' studies are looked at in this review: intensive insulin therapy regime, thrombolysis in cardiac arrest, the effects of nutritional guidelines and rapid response outreach teams.     

Structural polymorphism of glycophorins demonstrated by immunoblotting techniques

We have explored the polymorphism of the glycophorin system in the human erythrocyte membrane using the immunoblotting techniques and examining 52 individuals selected without prior bias as to their serologic state and ten documented serologic variants of M, N, S, s blood group system. Polyclonal antisera to alpha glycophorin and to alpha glycophorin CNBr carboxyl terminal fragment C (residues 82-131) and M and N specific monoclonal antibodies (MoAbs) were used. The first two reagents detect specific regions of the alpha glycophorin molecule and all electrophoretically resolved species of glycophorins immunologically related to alpha and delta glycophorins (delta glycophorin, [alpha-delta] hybrids and other glycophorins with an alteration in the carboxyl terminal segment); the M and N MoAbs identified the glycophorin species containing or lacking the M or N determinant in the amino terminal octapeptide structures. We find that immunoblotting confirmed in all cases the serologically determined phenotype; we also find that polymorphic forms of the glycophorin system are relatively infrequent; immunoblotting, independent from serologic testing, was capable of detecting five mutants, two most likely S-s-U-phenotypes; a new glycophorin species was detected in normal red cells with both antiglycophorin and antipeptide C sera, which is not evident with MoAbs; immunoblots of known glycophorin variants (En(a-), U-, Mg, Mi I, II, III, V, and Sta) confirmed but also extended our knowledge of the abnormal glycophorins involved; and the He+ and Wrb(-) cells showed normal patterns.     

Peroxisome proliferator-activated receptor-gamma protects against hepatic ischemia/reperfusion injury in mice

The function of peroxisome proliferator-activated receptor-gamma (PPARgamma) in hepatic inflammation and injury is unclear. In this study, we sought to determine the role of PPARgamma in hepatic ischemia/reperfusion injury in mice. Male mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 8 hours of reperfusion. PPARgamma was found to be constitutively activated in hepatocytes but not in nonparenchymal cells. Upon induction of ischemia, hepatic PPARgamma activation rapidly decreased and remained suppressed throughout the 8-hour reperfusion period. This reduced activation was not a result of decreased protein availability as hepatic nuclear PPARgamma, retinoid X receptor-alpha (RXRalpha), and PPARgamma/RXRalpha heterodimer expression was maintained. Accompanying the decrease in PPARgamma activation was a decrease in the expression of the natural ligand 15-deoxy-Delta(12,14)-prostaglandin J(2). This was associated with reduced interaction of PPARgamma and the coactivator, p300. To determine whether PPARgamma activation is hepatoprotective during hepatic ischemia/reperfusion injury, mice were treated with the PPARgamma agonists, rosiglitazone and connecting peptide. These treatments increased PPARgamma activation and reduced liver injury compared to untreated mice. Furthermore, PPARgamma-deficient mice had more liver injury after ischemia/reperfusion than their wild-type counterparts. Conclusion: These data suggest that PPARgamma is an important endogenous regulator of, and potential therapeutic target for, ischemic liver injury.     

Thrombospondin mediates the cytoadherence of Plasmodium falciparum- infected red cells to vascular endothelium in shear flow conditions

Cerebral malaria is thought to involve specific attachment of Plasmodium falciparum-infected knobby red cells to venular endothelium. The nature of surface ligands on host endothelial cells that may mediate cytoadherence is poorly understood. We have investigated the effects of soluble thrombospondin, rabbit antiserum raised against thrombospondin, and human immune serum on cytoadherence of parasitized erythrocytes in ex vivo mesocecum vasculature. Preincubation of infected red cells with soluble thrombospondin or human immune serum inhibits binding of infected red cells to rat venular endothelium. Infusion of the microcirculatory preparation with rabbit antithrombospondin antibodies before perfusion of parasitized erythrocytes also resulted in decreased cytoadherence. In addition, incubation of infected cells with human immune sera obtained from malaria patients significantly inhibited the observed cytoadherence. Our results indicate that thrombospondin mediates binding of infected red cells to venular endothelium and may thus be involved in the pathogenesis of cerebral malaria.     

Nurses best practices for the management of thrombotic thrombocytopenic purpura

A group of Canadian apheresis nurses developed best practice for in the management of thrombotic thrombocytopenic purpura (TTP). The recommendations address issues related to infusion protocols, preventing and managing adverse events, comprehensive patient assessments, treatment procedures, as well as pre- and post- treatment care. The Canadian group encourages institutes to include nurses on committees that examine recommendations for TTP management.     

Hemodynamics during liver transplantation: the interactions between cardiac output and portal venous and hepatic arterial flows.

Liver blood flow and systemic hemodynamics were measured intraoperatively in 34 patients after liver transplantation. Ultrasound transit-time flow probes measured hepatic arterial and portal venous flow over 10 to 75 min 1 to 3 hr after reperfusion. Cardiac output was measured by thermodilution. Mean cardiac output was 9.5 +/- 2.8 L/min; the mean total liver blood flow of 2,091 +/- 932 ml/min was 23% +/- 11% of cardiac output. Mean portal flow of 1,808 +/- 929 ml/min was disproportionately high at 85% +/- 10% of total liver blood flow. Correlation analysis showed a significant (p less than 0.01; r = 0.42) correlation between cardiac output and portal venous flow and a trend toward negative correlation (p = 0.087) between cardiac output and hepatic arterial flow. These data show that increased flow in the newly transplanted liver is predominantly portal venous flow and is associated with high cardiac output and reduced hepatic arterial flow. In the last 13 patients studied, portal flow was reduced by 50% and the hepatic artery response was measured. We saw a significant (p less than 0.05) increase in hepatic artery flow from 322 +/- 228 to 419 +/- 271 ml/min, indicating an intact hepatic arterial buffer response. The hepatic artery response also showed that it is a reversible rather than a fixed resistance that contributes to the low hepatic artery flow in these patients.     

Bmp15 mutations and ovarian function

BMP15, also known as growth and differentiation factor 9B (GDF9B), is a member of the transforming growth factor beta superfamily (TGFbeta) which in humans, rodents and sheep is expressed exclusively in the oocyte. BMP15 is closely related to GDF9, another oocyte-specific member of this superfamily which has been shown to be essential for early ovarian folliculogenesis. Inactivation of the BMP15 gene in mice has shown only minor effects on fertility. However, Inverdale and Hanna lines of sheep carry naturally occurring mutations in BMP15 which highlight differences in the action of this gene between mice and other mammals. Sheep which are heterozygous show an increase in ovulation rate whereas homozygotes are infertile. The granulosa cell receptor which mediates the BMP15 response has not yet been identified, but the discovery that a point mutation in the BMP1B receptor in Booroola sheep is responsible for increased ovulation rate highlights the importance of the TGFbeta signalling molecules in early folliculogenesis.     

Immune system dysfunction contributes to the aetiology of spontaneous hypertension

Spontaneously hypertensive rats (SHRs) have a depressed T lymphocyte system, especially a reduced activity of the suppressor T cells, and it has been postulated that an auto-immune defect may be important in the aetiology of hypertension in these rats. In an earlier study we demonstrated that chronic immunosuppressive therapy prevents approximately 50% of the hypertension in the SHR. In the present study, an attempt was made to correct the immune imbalance by implanting thymic tissue from normotensive rats into SHRs. Weekly thymic implants from Wistar donor rats into 16-week-old SHRs produced a maximal reduction (P less than 0.05) in the tail-cuff pressure, after 4 weeks, to a level of 156 +/- 2.3 mmHg (n = 8) in thymus-implanted SHRs versus 189 +/- 2.5 mmHg (n = 6) in sham-implanted SHRs. Also, neonatal thymic implants delayed development of spontaneous hypertension and attenuated the final hypertensive state. Mean arterial pressure averaged 186 +/- 2.8 mmHg in 22-week-old, neonatally sham-implanted SHRs, while it was reduced (P less than 0.05) to 164 +/- 4.2 mmHg in the neonatally thymus-implanted SHRs at this time. The thymic implants had little effect on total T cell, helper T cell or suppressor T cell counts. However, the antihypertensive effect of the thymic implants was associated with a substantial increase in the blastogenic responsiveness of suppressor T cells from the SHRs. These results support the hypothesis that immunological dysfunction plays an important role in the aetiology of spontaneous hypertension.     

Plasma angiotensin-converting enzyme activity in patients with bronchial carcinoma

Plasma angiotensin-converting enzyme (ACE) activities were measured in 58 consecutive patients presenting with bronchial carcinoma. The mean ACE activity before treatment was significantly lower than that of a control population (P less than 0.005). There was a significant and direct relationship between the initial plasma ACE activity and survival time (P less than 0.01) which could not be explained by further analysis for age, clinical staging, or respiratory function, as judged by % FEV. There was a significant increase in plasma ACE activity (P less than 0.03) in nine patients with three or more plasma samples after treatment with chemotherapy or radiotherapy. These results suggest that low plasma ACE activity is associated with poor prognosis in bronchial carcinoma.