Mechanical properties of rat cerebral arteries as studied by a sensitive device for recording of mechanical activity in isolated small blood vessels*

A sensitive device for recording of mechanical activity in isolated small blood vessels with calibres down to 100 μm is described. This equipment was used to examine the mechanical properties of rat cerebral arteries. The ultrastructure of the preparations was investigated by light-, transmission, and scanning electron-microscopy. In general the walls of the middle cerebral and basilar arteries consisted of 3 layers of smooth muscle cells, which occupied approximately 80% of the total wall thickness. The present technique preserved the integrity of the vessel wall and caused no observable damage to the smooth muscle or endothelial cells. Neither the basilar nor the middle crebral arteries developed spontaneous phasic contractions under standard conditions. Potassium excess (124 mM) induced a biphasic contractile response characterized by a fast and partly transient increase in tension (phase A), followed by a slowly developing sustained contraction (phase B). The responses to K⁺ were strong, highly reproducible and not influenced by pH changes in the range 6.9-7.8, making K⁺-stimulation suitable for testing of vascular contractility. Length-tension measurements were performed on relaxed and K⁺-activated basilar arteries. The mechanical behaviour of the vessels conformed to a sliding-filament model of muscular contraction. Using the “Maxwell model” of a muscle, the length at which the contractile element produced maximum active tension was established. The passive wall tension at this length (? 1 mN/mm) averaged only about 20% of the total wall tension the arteries were capable of producing when activated by K⁺. Under isometric conditions the K⁺-contracted basilar artery developed a maximum active wall stress of approximately 240 mN/mm². In the light of the mechanical data obtained from the length-tension measurements, the optimum resting wall tension for registration of vascular responses is discussed. It appears that the present in vitro system can be of great value in investigations of the smooth muscle function in small blood vessels.     

Comparison of two dengue NS1 rapid tests for sensitivity,specificity and relationship to viraemia and antibody responses

Background  

Dengue is a major public health problem in tropical and subtropical countries. Rapid and easy diagnosis of dengue can assist patient triage and care-management. The detection of DENV NS1 on rapid lateral flow tests offers a fast route to a presumptive dengue diagnosis but careful evaluations are urgently needed as more and more people use them.     

Changes in acid-base, electrolyte and hemoglobin concentrations during infusion of hydroxyethyl starch 130/0.42/6 : 1 in normal saline or in balanced electrolyte solution in children

Introduction: A balanced volume replacement strategy is a well established concept for correcting hypovolemia using plasma adapted isotonic crystalloid solutions with a physiological electrolyte pattern and acetate as bicarbonate precursor. Recently, third‐generation hydroxyethyl starch (HES) has also become available in a balanced electrolyte solution instead of normal saline. Therefore, in this prospective non‐interventional clinical study, the perioperative administration of HES 130/0.42/6 : 1 in normal saline (ns‐HES) and in balanced electrolyte solution (bal‐HES) was evaluated in children with a focus on acid‐base, electrolyte and hemoglobin changes. Methods: Following local ethics committee approval, pediatric patients aged up to 12 years with an ASA risk score of I–III undergoing perioperative administration of HES (ns‐HES from May 2006 to December 2007, bal‐HES from January 2008 to January 2009) were included. Patient demographics, the performed procedure, adverse drug reactions, hemodynamic data and the results of blood gas analysis were documented with a focus on changes in acid‐base, electrolyte and hemoglobin concentrations. Results: Of 396 enrolled patients (ASA I–III; age 2.3 ± 3, range day of birth – 12 years; body weight 10.8 ± 9, range 0.9–52 kg), 249 received ns‐HES and 147 bal‐HES (mean volume infused 9.9 ± 4 and 9.4 ± 6.9 ml·kg^?1, respectively). After HES infusion, hemoglobin decreased in both groups, whereas bicarbonate and base excess (BE) decreased only with ns‐HES and remained stable with bal‐HES (BE before infusion: ns‐HES ?1.8 ± 2.8, bal‐HES ?1.7 ± 2.7 mmol·l^?1; after infusion: ns‐HES ?2.6 ± 2.4; bal‐HES ?1.6 ± 2.6 mmol·l^?1, P < 0.05). Chloride (Cl) concentrations increased in both groups and were significantly higher with ns‐HES (Cl before infusion: ns‐HES 105.6 ± 3.7, bal‐HES 105.1 ± 2.8 mmol·l^?1; after infusion: ns‐HES 107.7 ± 3.2, bal‐HES 106.3 ± 2.9 mmol·l^?1, P < 0.01). No serious adverse drug reactions were observed. Conclusion: Infusion related iatrogenic acid‐base and electrolyte alterations can be minimized by using hydroxyethyl starch in a balanced electrolyte solution instead of normal saline.     

An evaluation of monitoring possibilities of argatroban using rotational thromboelastometry and activated partial thromboplastin time

Background: Rotational thrombelastometry/thrombelastography with ROTEM^® and TEG^® is becoming available bedside in an increasing number of intensive care units, where many patients with heparin-induced thrombocytopenia (HIT) are treated. The study has been performed in an effort to find out whether ROTEM^® could be an alternative to activated partial thromboplastin time (aPTT) when argatroban is used for anticoagulation.
Methods: Argatroban was added in vitro to a series of citrated whole-blood samples from 10 healthy volunteers to obtain whole-blood concentrations of 0, 0.125, 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 mg/l. ROTEM^® and whole-blood aPTT analyses were performed at each argatroban concentration. Correlation analyses were performed using the Spearman correlation analysis.
Results: There was a significant and strong correlation between argatroban concentrations and clotting time (CT in ROTEM^® analysis with INTEM) ( P <0.0001 and r =0.98). Also, the ROTEM^® time to maximum clot formation velocity (MAXV-t) appeared to have a very strong and highly significant correlation to argatroban concentrations ( P <0.0001 and r =0.95). When we studied the correlation between aPTT and CT, we found a highly significant and strong correlation between these two analyses ( P <0.0001 and r =0.97), especially so in the clinically relevant therapeutic range up to 100 s aPTT prolongation for HIT patients.
Conclusion: A significant and strong correlation was found between argatroban concentrations and several ROTEM^® parameters. Rotational thrombelastometry/thrombelastography has a potential role in increasing the safety of argatroban anticoagulation in critically ill patients.     

Immunophenotypes of Reed-Sternberg cells: a study of 19 cases of Hodgkin's disease in plastic-embedded sections

The immunophenotype of Reed-Sternberg (RS) cells in Hodgkin's disease (HD) has not been clearly defined, partly owing to difficulties in studying RS cells in cell suspensions or identifying them with certainty in frozen sections. We studied the immunophenotype of RS cells with a recently developed plastic section immunohistochemical technique on acetone-fixed tissues that affords superior morphological detail while preserving a wide variety of lymphoid differentiation antigens. Nineteen cases of HD [16 nodular sclerosing (NS), 2 mixed cellularity (MC), and 1 lymphocyte depleted (LD)] were embedded in plastic and stained for pan-B, pan-T, and various T-subset markers, as well as leukocyte common antigen (CD45), interleukin-2 (IL-2) receptor (CD25), and RS cell markers CD15 and CD30. RS cells were positive for CD45, CD15, CD30, and CD25, except for 3 cases (2 NS, 1 MC) that were CD15 negative and 2 cases (NS) that were CD45 negative. In 10 cases (NS), RS cells were positive for at least two pan-T-cell markers and CD4; pan-B cell markers were uniformly negative. RS cells in 6 cases (3 NS, 2 MC, 1 LD) were positive for at least one T-cell marker (CD2) and one B-cell marker (CD22). Two cases of NSHD showed no T- or B-cell marking. These data provide further evidence that RS cells in some cases of NSHD have T-cell phenotypes and that RS cells are not homogeneous in their immunoreactivity.     

Pattern of expression of HLA-DR and HLA-DQ antigens and mRNA in myeloid differentiation

We examined the expression of HLA-DR and HLA-DQ antigens and mRNA from myeloid and lymphoid cells obtained from normal volunteers and established cell lines. Cytofluorometric analysis and immunoprecipitation were performed using murine monoclonal antibodies specific for HLA-DR (L-243) and HLA-DQ (Leu 10). The expression of mRNA for HLA-DR and HLA-DQ chains was determined by Northern blot and RNA dot-blot analysis. Lymphoid cell lines expressed both HLA-DR and HLA-DQ antigens, with consistently higher levels of expression of DR. Myeloid cell lines of early myeloblast or bipotent (myeloid-erythroid) phenotype (KG-1, KG-1a, HEL) expressed HLA-DR at high levels, whereas cell lines manifesting a greater degree of myeloid maturation (ML-3, HL- 60, U937) expressed DR at low or undetectable levels. The HLA-DQ antigen was expressed at low levels on the surface of KG-1 and KG-1a cells but was not detectable on other myeloid cell lines. The expression of mRNA for HLA-DR and HLA-DQ chains paralleled the pattern of expression of the respective antigens. The HL-60 and U-937 cells stimulated to differentiate in vitro to macrophages with 1,25 dihydroxyvitamin D3 [1,25(OH)2D3] were induced to express detectable levels of HLA-DR antigens. Exposure to gamma-interferon (gamma-IFN) increased the expression of HLA-DR antigens by all myeloid cell lines. Induction of differentiation in vitro with either 1,25(OH)2D3 or dimethyl sulfoxide potentiated this effect of gamma-IFN. Expression of the HLA-DQ antigens was increased on KG-1 myeloblasts after exposure to gamma-IFN. HLA-DQ expression could not be detected on other myeloid cell lines after exposure to gamma-IFN, nor was HLA-DQ expression stimulated by gamma-IFN after HL-60 and U-937 cells were induced to differentiate to macrophagelike cells in vitro. These results provide additional evidence that expression of the HLA-DR and HLA-DQ genes may be independently regulated in human myeloid cells.     

Can the Ottawa and Pittsburgh rules reduce requests for radiography in patients referred to acute knee clinics?

Our aim was to study the role of the Ottawa and Pittsburgh rules to reduce the unnecessary use of radiographs following knee injury. We prospectively reviewed 106 patients who were referred to our clinic over a 3-month period. The Ottawa and Pittsburgh rules were applied to individual patients to evaluate the need for radiography. One hundred and one patients (95%) had radiography of their knee. Five patients (5%) had a fracture of their knee and in all cases, the Ottawa and Pittsburgh knee rules were fulfilled. Using the Ottawa rules, 27 radiographs (25%) could have been avoided without missing a fracture. Using the Pittsburgh rules, 32 radiographs (30%) could have been avoided. The Ottawa and Pittsburgh rules have a high sensitivity for the detection of knee fractures. Their use can aid efficient clinical evaluation without adverse clinical outcome and may reduce healthcare costs.