Dobutamine in elderly septic shock patients refractory to dopamine

The hemodynamic effects of dobutamine (2.5–20 g/kg per min) were studied in six elderly patients with septic shock which was refractory to dopamine (15 g/kg per min). Dobutamine infusion resulted in significant increases in cardiac index (CI), stroke index (SI) and left ventricular stroke work index (LVSWI) and similar declines in heart rate (HR), mean pulmonary artery pressure (MPAP), pulmonary capillary wedge pressure (PCWP), systemic vascular resistance (SVR) and total pulmonary resistance (TPR). Dose response curves demonstrated a linear rise in CI with increasing doses of dobutamine and parallel decreases in HR and PCWP. MAP was unchanged. These data indicate that dobutamine may be a useful adjunct to dopamine therapy in the management of elderly patients with septic shock.     

Isolation and Quantitation of the Platelet Membrane Glycoprotein Deficient in Thrombasthenia Using a Monoclonal Hybridoma Antibody

We used the hybridoma technique to characterize further the platelet glycoprotein abnormality in Glanzmann's thrombasthenia. Spleen cells from Balb/c mice immunized with human platelets were fused to mouse myeloma cell line Sp2/0-Ag14. Hybridoma lines producing a variety of antiplatelet antibodies were isolated by hypoxanthine-aminopterin-thymidine selection and cloned, and purified monoclonal IgG from six lines was prepared. One of these lines, 8aB5-9, produced an antibody, Tab, that binds to a protein on normal but not thrombasthenic platelets. We isolated this protein from Triton X-100 solubilized normal platelet membranes by affinity chromatography on Tab-Sepharose. As determined by SDS polyacrylamide gel electrophoresis, the isolated protein is a complex of glycoproteins IIb and IIIa, because the two subunits comigrate with glycoproteins IIb and IIIa of whole platelets and show identical changes in mobility after disulfide bond reduction. We prepared (125)I-Tab to determine the number of glycoprotein IIb-IIIa complexes on normal and thrombasthenic platelets by a direct binding assay. Platelets from 17 normal donors bound 39,000+/-4,600 (SD) Tab molecules/platelet. Platelets from four patients with thrombasthenia lacked Tab binding sites (<5%). Five obligate and four presumed heterozygotes for thrombasthenia bound 24,500+/-5,800 Tab molecules/platelet. The platelet alloantigen, Pl(Al), is not that recognized by Tab, because platelets from three Pl(Al)-negative subjects bound Tab normally. Studies with the Tab antibody have (a) enabled quantitation of the number of glycoprotein IIb-IIIa complexes on normal platelet membranes, (b) demonstrated that thrombasthenic homozygotes lack and heterozygotes have a partial deficiency of this complex, and (c) made possible the isolation of this membrane protein which may be required for normal platelet aggregation and clot retraction.     

Cutaneous blisters and carbon monoxide poisoning

We present the cases of three patients with skin blisters following carbon monoxide (CO) poisoning. Their blisters appeared to be related to the severity of the poisoning (HbCO levels of more than 40%). Two of the three patients died despite aggressive initial 100% surface oxygen followed by hyperbaric oxygen therapy. The pathophysiology of this type of blister remains unresolved. It could result from pressure necrosis alone or from a combination of pressure necrosis and direct CO inhibition of tissue oxidative enzymes. Although skin involvement as a result of CO poisoning is less frequently reported today than in the past (perhaps because of misidentified burns or because of more aggressive resuscitation and treatment protocols), the physician should recognize that such blisters may signal severe CO poisoning.     

Textural features of hypoxia PET predict survival in head and neck cancer during chemoradiotherapy

European Journal of Nuclear Medicine and Molecular Imaging - The aim of this study was to investigate whether textural features of tumour hypoxia, assessed with serial [18F]fluoromisonidazole...     

ADAMTS13 and TTP

Thrombotic thrombocytopenic purpura (TTP) has been a mysterious and deadly disease that often could be treated effectively by plasma exchange, but without real understanding of the underlying pathophysiology. Recent advances now suggest that deficiency of a specific von Willebrand factor (VWF) cleaving protease promotes tissue injury in TTP. VWF multimers participate in the formation of platelet thrombi. Proteolytic cleavage of VWF multimers normally limits platelet thrombus growth, and failure to cleave VWF appears to encourage microvascular thrombosis. The VWF cleaving protease proves to be a new member of the ADAMTS family of metalloproteases, designated ADAMTS13. Autoantibodies that inhibit ADAMTS13 cause sporadic TTP, and mutations in the ADAMTS13 gene cause an autosomal recessive form of chronic relapsing TTP. Further studies of ADAMTS13 seem likely to change our approach to the diagnosis and treatment of TTP and other thrombotic microangiopathies.     

Native associations of early hematopoietic stem cells and stromal cells isolated in bone marrow cell aggregates

In suspensions of murine bone marrow, many stromal cells are tightly entwined with hematopoietic cells. These cellular aggregations appear to exist normally within the marrow. Previous studies showed that lymphocytes and stem cells adhered to stromal cells via vascular cell adhesion molecule 1 (VCAM1). Injection of anti-VCAM1 antibody into mice disrupts the aggregates, showing the importance of VCAM1 in the adhesion between stromal cells and hematopoietic cells in vivo. Early hematopoietic stem cells were shown to be enriched in aggregates by using a limiting-dilution culture assay. Myeloid progenitors responsive to WEHI-3CM in combination with stem cell factor (c-kit ligand) and B220- B-cell progenitors responsive to insulin-like growth factor-1 in combination with interleukin-7 are not enriched. We propose a scheme of stromal cell-hematopoietic cell interactions based on the cell types selectively retained within the aggregates. The existence of these aggregates as native elements of bone marrow organization presents a novel means to study in vivo stem cell-stromal cell interaction.     

Thrombin-stimulated immunoprecipitation of phosphatidylinositol 3-kinase from human platelets.

Growth factors and transforming proteins that activate tyrosine phosphorylation have been shown to cause an increased labeling of 3-phosphate-containing phosphatidylinositols. Turnover correlates with the formation of a complex between phosphatidylinositol 3-kinase, the activated protein-tyrosine kinase, and other proteins thought to participate in transmembrane signaling. When human platelets are treated with thrombin, labeling of 3-phosphate-containing phosphatidylinositols is stimulated with a time course and concentration dependence consistent with a role for these lipids in platelet activation. We now report that when human platelets are stimulated with thrombin, a complex forms between phosphatidylinositol 3-kinase, a protein-serine/threonine kinase, and an uncharacterized platelet membrane protein. The complex is immunoprecipitated from detergent lysates of thrombinstimulated platelets by a rabbit antiserum prepared against a peptide from the cytoplasmic domain of the mouse platelet-derived growth factor (PDGF) receptor. The antigen is not the PDGF receptor, since complex formation is not stimulated by PDGF and thrombin-induced complexes are not precipitated by another rabbit antiserum against the same peptide or by monoclonal anti-human PDGF receptor antibodies. Formation of the complex is rapid (within 30 sec) and occurs at thrombin concentrations that stimulate platelet aggregation and secretion (50% of maximal complex formation at 0.03 unit of thrombin per ml). We propose that the complex initiates formation of 3-phosphate-containing phosphatidylinositols that may function in platelet activation.     

Identification of myotubularin as the lipid phosphatase catalytic subunit associated with the 3-phosphatase adapter protein, 3-PAP

Myotubularin is a dual-specific phosphatase that dephosphorylates phosphatidylinositol 3-phosphate and phosphatidylinositol (3,5)-bisphosphate. Mutations in myotubularin result in the human disease X-linked myotubular myopathy, characterized by persistence of muscle fibers that retain an immature phenotype. We have previously reported the identification of the 3-phosphatase adapter protein (3-PAP), a catalytically inactive member of the myotubularin gene family, which coprecipitates lipid phosphatidylinositol 3-phosphate-3-phosphatase activity from lysates of human platelets. We have now identified myotubularin as the catalytically active 3-phosphatase subunit interacting with 3-PAP. A 65-kDa polypeptide, coprecipitating with endogenous 3-PAP, was purified from SDS/PAGE, subjected to trypsin digestion, and analyzed by collision-induced dissociation tandem MS. Three peptides derived from human myotubularin were identified. Association between 3-PAP and myotubularin was confirmed by reciprocal coimmunoprecipitation of both endogenous and recombinant proteins expressed in K562 cells. Recombinant myotubularin localized to the plasma membrane, causing extensive filopodia formation. However, coexpression of 3-PAP with myotubularin led to attenuation of the plasma membrane phenotype, associated with myotubularin relocalization to the cytosol. Collectively these studies indicate 3-PAP functions as an "adapter" for myotubularin, regulating myotubularin intracellular location and thereby altering the phenotype resulting from myotubularin overexpression.     

Effect of menstrual cycle phase on dopamine D2 receptor availability in female cynomolgus monkeys

Sex differences have been reported in a variety of affective and neurodegenerative disorders that involve dysfunctional dopamine (DA) neurotransmission. In addition, there is evidence for differences in sensitivity to the abuse-related effects of psychostimulants across the menstrual cycle which may result from effects of ovarian hormones on DA function. The goal of the present study was to extend previous work examining menstrual cycle-related changes in DA D2 receptor availability in humans to drug-naive female cynomolgus monkeys (n=7) using the selective D2-like receptor ligand [(18)F]fluoroclebopride (FCP) and a high-resolution microPET P4 scanner. Menstrual cycle phase was characterized by daily vaginal swabs and measurements of serum progesterone levels. PET studies were conducted once during the luteal phase and once during the follicular phase. Regions of interest in the caudate nucleus, putamen, and cerebellum were defined on coregistered MRIs. Distribution volumes were calculated for FCP in each structure and the distribution volume ratio (DVR) for both brain regions relative to the cerebellum was used as a measure of D2 receptor availability. FCP DVRs were significantly higher in the luteal phase compared to the follicular phase in both the caudate nucleus (11.7% difference, p=0.02) and putamen (11.6% difference, p=0.03). These findings extend earlier work in humans and suggest that changes in DA receptor availability may be involved in the variation in symptoms of various neuropsychiatric disorders across the menstrual cycle, including differences in sensitivity to the abuse-related effects of stimulants.