Induction of human vascular endothelial stress fibres by fluid shear stress

Endothelial cells of the arterial vascular system and the heart contain straight actin filament bundles, of which there are few, if any, in the venous endothelium. Since stress fibre-containing endothelial cells within the vascular system tend to be located at sites exposed to particularly high shear stress of blood flow, we have investigated, in an experimental rheological system (Fig. 1), the response of the endothelial actin filament skeleton to controlled levels of fluid shear stress. Here we report that endothelial stress fibres can be induced by a 3-h exposure of confluent monolayer cultures of human vascular endothelium to a fluid shear stress of 2 dynes cm-2, approximately the stress occurring in human arteries in vivo. Fourfold lower levels of shear stress that normally occur only in veins, had no significant effect on the endothelial actin filament system. The formation of endothelial stress fibres in response to critical levels of fluid shear stress is probably a functionally important mechanism that protects the endothelium from hydrodynamic injury and detachment.

Leukocyte counts and activation in spontaneously hypertensive and normotensive rats

The etiology for the progressive organ injury in hypertension is largely speculative. Recent studies have shown that leukocytes play a key role in several cardiovascular diseases. As an initial step toward investigating the role of leukocytes in hypertension, we measured leukocyte counts and spontaneous activation of granulocytes of freshly drawn unseparated blood samples in spontaneously hypertensive rats and in their normotensive counterpart, Wistar-Kyoto rats. The animals were derived from one breeder in the United States and from two breeders in Europe. Total leukocyte counts in young, mature, and old hypertensive rats were 50-100% above the controls. The number of granulocytes in mature and old spontaneously hypertensive rats in more than 100% elevated compared with control rats. In young hypertensive rats the mean granulocyte count was only slightly elevated. The number of spontaneously activated granulocytes, as detected by the nitroblue tetrazolium reduction, increases with age in both species; in mature spontaneously hypertensive rats, it is more than 300% above the values in the controls. Furthermore, in mature hypertensive rats the number of monocytes, activated monocytes, and the lymphocyte count are also significantly elevated over the values in the normotensive controls. It is proposed that these elevated leukocyte counts may constitute an enhanced risk for organ injury in the spontaneously hypertensive rat.

In-vivo antithrombotic potency of placenta protein 4 (annexin V)

The antithrombotic properties of Placenta Protein 4 (PP4) were investigated in laser or photochemically induced thrombus formation models in rats. In both in-vivo test-systems PP4 displayed a significant antithrombotic effect at dose levels as low as 0.3 and 1.0 mg/kg body weight. Bleeding times, surprisingly, were not prolonged significantly at these dose regimens. Maximal inhibition of thrombus formation in the laser-model was observed 15 min after intravenous administration of PP4, but was not recognizable in a clear-cut reaction in the second model. Determination of PP4 plasma levels in two monkeys revealed a half-life of 11.5 and 14.9 min, respectively. The maximal anticoagulant effect was observed between 15 and 30 min after administration of PP4 as determined functionally by means of thrombelastography.

Influence of ADP, blood flow velocity, and vessel diameter on the laser-induced thrombus formation

The laser-induced thrombus model in rat mesenteric arterioles and venules represents a reliable and reproducible in vivo method. It is suitable for basic investigations concerning factors involved in thrombus formation as well as for testing antithrombotic effects of drugs. The laser-induced thrombus formation depends significantly on the presence of ADP, as ADP-utilizing enzymes inhibit thrombosis in the animal model. The instrumental test set-up consists of a 4 W Argon laser (Spectra Physics, Mountain View, CA, USA), a ray adaptation and adjusting device (BTG, Munich, FRG), a microscope (ICM 405, Zeiss, Oberkochen, FRG), and a video system (Sony, Japan). RBC velocity data were recorded with the help of a modified dual-slit technique (acc. to Wayland and Johnson). Results were expressed as number of laser injuries necessary to produce a defined thrombus (minimum size: 1/4 of the vessel diameter) under constant conditions (effective capacity: 30 mW, exposure time: 1/5 sec). The number of laser lesions necessary to induce a defined thrombus decreased with an increase in arteriole diameter (10 to 20 micron) but increased again in larger arterioles and small arteries (greater than 25 micron). On the arteriolar side there are significant correlation coefficients between vessel diameter and RBC velocity (r = 0.69), vessel diameter and No. of laser injuries (r = 0.70), and RBC velocity and No. of laser injuries (r = 0.71). Due to relative low flow conditions in the venules, the number of laser injuries required to induce a defined thrombus does not significantly depend on the vessel diameter.

Effect of pentoxifylline on single red cell deformability

In the present investigation the effect of pentoxifylline on single red cell deformability was determined. The deformability of human red blood cells were measured in a Singlepore Erythrocytes Rigidometer (SER). The new method determines optoelectronically the passage of each individual cell through a singlepore membrane (6 micrometers diameter and 50 micrometers length) under a driving pressure gradient (delta p = 100 Pa, tau = 3 Pa). Venous human blood samples were taken, prepared and divided into three samples. Sample A served as a physiological control, while to sample B and C CaCl2-solution was added. After Ca2+ stress sample C was incubated with 0.36 mmol/l pentoxifylline. The medium passage time (MPT) for sample A was 43.3 +/- 6.5 ms and for sample B 87.5 +/- 14.7 ms. The addition of pentoxifylline to the Ca2+-treated red cell suspension (sample C) reduced the MPT to 51.6 +/- 11.3 ms.

Inhibitory effects of pentoxifylline on LPS-induced leukocyte adhesion and macromolecular extravasation in the microcirculation

Pentoxifylline (PTX) has been shown to combat effectively endotoxin induced symptoms of shock or inflammation by reducing both leukocyte activation and endogenous cytokine formation. With regard to blood perfusion, inflammation is defined as a local reaction to injury of the living microvasculature and its content. Leukocyte margination, rolling, adhesion, and emigration is mediated by adhesion molecules along the endothelium of postcapillary venules and is considered to be an important step in the inflammatory response. Changes in the vascular integrity can be estimated in terms of increased extravasation of macromolecules. Using intravital microscopy with the help of an analogous video image processing system we measured the effect of PTX on lipopolysaccharide (LPS, 15 mg/kg i.v.) induced leukocyte adhesion and extravasation of FITC-rat serum albumin (FITC-RSA) in rat mesenteric venules. The changes in vascular permeability correlates significantly (r = 0.75) with a locally increased number of adherent leukocytes. PTX significantly inhibits both leukocyte adhesion and extravasation of FITC-RSA dose dependently. Our results indicate that PTX effectively preserves vascular integrity in the microcirculation by acting primarily on LPS-induced leukocyte adhesion.

Mediator-induced changes in macromolecular permeability in the rat mesenteric microcirculation

An intravital fluorescence microscopic method for measurement of changes in macromolecular permeability has been established in the mesenterial microcirculation of the rat. After exteriorization of the fat-free distal part of the ileal mesentery, a 1-hr period of stabilization was followed by the injection of FITC-labeled macromolecules. Five minutes later, histamine, leukotriene B4, or leukotriene C4 was topically applied to the tissue by means of a micromanipulator. Areas of 1 mm2 were videotaped with a SIT camera. The fluorescence intensity of these areas was measured by an analogous video image processing system and displayed as gray value histograms. The shift of the frequency of gray levels from lower to upper regions could be attributed to an increase in light intensity in the mesentery, indicating an increase in vessel wall permeability. The sites of action of histamine and leukotriene C4 were very similar. Both mediators affected mainly the larger collecting venules. In contrast, leukotriene B4 exerted its effect at postcapillary venules. Moreover, leukotriene B4-induced extravasation was inhibited by superoxide dismutase, suggesting an involvement of oxygen radicals. The studies with histamine alone and with H1- and H2-antagonists demonstrated that histamine-induced extravasation in the rat mesentery was mediated by H1-histamine receptors. The present study introduces an experimental model for the measurement of changes in macromolecular permeability, which is useful for studying mediator effects and their pharmacological inhibition in the microcirculation of the rat mesentery.

Effect of pentoxifylline on sickle cell thalassaemia: haemorheological and clinical results

The effect of pentoxifylline on the deformability of red cells in sickle cell thalassaemia was investigated. The fluidity of the blood in sickle cell thalassaemia is disturbed and is accompanied by violent pains and irreversible tissue damage caused by capillary occlusions. After treating a 15-years-old female patient with pentoxifylline (2 g orally each day), the fluidity of the blood improved distinctly, and this correlated with a condition free of clinical symptoms. Erythrocyte filtration by Nuclepore filter increased significantly over the 6-month examination period (initial value: V rel = 0.068 +/- 0.008; after 6 months medication: 0.246 +/- 0.030). In addition, in the single-pore erythrocyte rigidometer (SER) a significantly improved passage time of individual erythrocytes could be demonstrated (initial value: 62.43 +/- 15.72 ms; after 4 weeks medication: 28.13 +/- 7.0 ms). The hitherto high number of rheological occlusions in the SER (48 +/- 30.9 from 200 individual passages) almost completely disappeared after treatment (1.7 +/- 1.2).

Surprising effects of the sequential administration of pentoxifylline and low dose acetylsalicylic acid on thrombus formation

The effect of the combined oral administration of pentoxifylline (pof) and low dose acetylsalicylic acid (ASA) was evaluated with the help of the laser-induced thrombosis in rat mesenteric arterioles. Laser-induced thrombosis is inhibited in a dose-dependent way by both drugs. The administration of ASA, either simultaneously with or 1 hour prior to pof, does not show any effects in the laser model. On the contrary, the administration of pof followed 1 h later by ASA not only exhibited a significant effect but also produced a supraadditive inhibition of the laser-induced thrombus formation. Specific investigations concerning the time interval between the administration of both drugs determined that a significant effect can be achieved only after an interval of 30 to 90 minutes (principle of HWA 5112). The striking results could also be shown in diseased animals after sequential chronic administration of pof 1 h prior to ASA. HWA 5112 exhibits significant effects on laser-induced thrombus formation in the following chronic animal models: 1. adjuvant arthritic rats, 10----1 mg/kg for 21 days; 2. spontaneously hypertensive stroke-prone rats, 10----1 mg/kg three times within 24 h; 3. cholesterol-induced atherosclerosis in rabbits, 10----1 mg/kg for 14 days. The reported data clearly demonstrate that the sequential drug administration of first pentoxifylline followed 30 to 90 min later by ASA exhibits a supraadditive antithrombotic effect.

In vivo analysis of antithrombotic effectiveness of recombinant hirudin on microvascular thrombus formation and recanalization

PURPOSE

This study was undertaken to evaluate in vivo the effect of recombinant hirudin (r-hirudin [HBW 023]), a potent thrombin inhibitor, on the process of microvascular thrombus formation and recanalization.

METHODS

Thrombosis was induced photochemically in distinct arterioles (n = 25) and venules (n = 30) of the ear of 16 hairless hr/hr mice (8 to 10 weeks old, 25 to 30 g of body weight). r-Hirudin (1 mg/kg of body weight) was administered intravenously directly before thrombus induction; saline-treated animals served as controls. Thrombus formation (i.e., first platelet deposition at the endothelial lining [FPD]; inner luminal diameter reduction to 50% [D/2]; complete vessel occlusion [CVO]), vessel recanalization, microcirculatory parameters, and leukocyte-endothelial cell interaction were analyzed by means of intravital fluorescence microscopy.

RESULTS

Hirudin significantly delayed the process of thrombus formation compared with saline-treated controls in both arterioles (FPD: 381 +/- 80 vs 137 +/- 25 seconds, P < 0.05; D/2: 627 +/- 49 vs 501 +/- 71 seconds; CVO: 925 +/- 78 vs 854 +/- 60 seconds) and venules (FPD: 173 +/- 11 vs 59 +/- 4 seconds; D/2: 342 +/- 54 vs 228 +/- 27 seconds; CVO: 541 +/- 85 vs 344 +/- 43 seconds; P < 0.05). In addition, r-hirudin-treated animals showed an increased rate of vessel recanalization at 24 hours after thrombus induction (arterioles: 54% [7 of 13] vs 0% [0 of 12], P < 0.05; venules: 77% [10 of 13] vs 53% [9 of 17]), whereas microcirculatory parameters and leukocyte-endothelial cell interaction were not affected.

CONCLUSION

Our data indicate that r-hirudin not only counteracts the process of thrombus formation but also promotes vessel recanalization, thus supporting its use in clinical microvascular surgery.

Pharmacological characterization of a new 4-amidinophenyl-alanine thrombin-inhibitor (CRC 220)

The new thrombin inhibitor CRC 220 was characterized in vivo for its antithrombotic effects. CRC 220 led to a dose-dependent prolongation of clotting parameters as determined in rats, rabbits, dogs, sheeps, pigs and monkeys. We evaluated the efficacy of CRC 220 to prevent thrombus formation in arteries and in the microcirculation in different animal models. In a rabbit model of tissue factor-induced coagulation activation, infusion of 0.5 mg/kg x h CRC 220 (3 hours) led to a significant prevention of fibrinogen decrease. In a rat model of lethal LPS-induced DIC CRC 220 significantly prevented the mortality rate after a 4h-infusion of 0.75 mg/kg x h. Thrombin-induced platelet aggregation in rat lungs could be prevented by the i.v. bolus injection of CRC 220. A dose of 0.3 mg/kg leads to a reduction of more than 80% of platelet deposition in the lung, significant inhibition was still observed 90 minutes after CRC 220 administration; at this time the inhibitor had already been cleared from plasma. Arterial thrombosis was induced in rabbits by squeezing and stenosis of the A. carotis. The i.v. bolus administration of CRC 220 dose-dependently prevented thrombus formation, an ED50 of 0.03 mg/kg was calculated. This dose was associated with only a minor prolongation of aPTT.

Effects of platelet activating factor on rat platelets in vivo

Platelet activating factor (PAF) is not able to aggregate rat platelets in vitro. Due to the agonist effects of PAF on multiple cells, a possible role of PAF in the activation of rat platelets in vivo where different cells may influence each other was investigated. The pulmonary microembolization of 51Cr-labelled activated platelets was used as in vivo model. This model allowed us to monitor platelet behaviour by means of non-invasive methods. In contrast to results obtained in vitro, PAF activated rat platelets in vivo. The pulmonary microembolization of the platelets was dose-dependent and rapidly reversible. About 0.5 microgram/kg PAF caused a half-maximal rise of platelet-bound radioactivity in the thorax. Activation of the platelets by PAF was followed by extreme desensitization, so that a second injection of PAF did not provoke a significant response of the platelets. Platelet function was, however, not completely impaired because they still accumulated in the thorax after the application of ADP (50 micrograms/kg). That pulmonary entrapment had taken place was shown by a 3-fold increase in lung specific radioactivity. This was accompanied by a short-lasting thrombocytopenia. The PAF antagonist, WEB 2170 (30 micrograms/kg), significantly inhibited the microembolization of the platelets induced by PAF. Under in vitro conditions leukocytes purified from rat blood and activated by PAF were able to induce platelet aggregation. These results demonstrate that a PAF-specific activation of rat platelets is achievable in vivo which is probably mediated by other cells.

Pentoxifylline: its influence on the interaction of blood cells with the vessel wall

PTX counteracts the increased microvessel permeability which is a feature of the inflammatory aspect of atherogenesis. Furthermore, PTX inhibits oxLDL-induced leukocyte adhesion and, via its positive influence over fibrinolysis and anti-aggregatory factors (e.g. prostacyclin), inhibits thrombus formation. PTX thereby preserves the integrity of the walls of the microcirculatory blood vessels, while reducing the likelihood of thrombosis and its potentially life-threatening sequelae.

Effects of tiaprofenic acid on urinary pyridinium crosslinks in adjuvant arthritic rats: comparison with doxycycline

OBJECTIVE AND DESIGN

To study the effects of tiaprofenic acid and doxycycline on urinary pyridinium crosslinks and paw swelling in adjuvant arthritic rats, and to gain additional information on the drugs' inhibitory potential vs. in vitro targets, such as enzyme activity of matrix metalloproteinases and cytokine generation.

MATERIAL

124 male Wistar Lewis rats; for the in vitro studies human matrix metalloproteinases and human mononuclear cells were used.

TREATMENT

Arthritis was induced by injection of complete Freund adjuvant. Drugs (2, 15, 50 mg tiaprofenic acid/kg; 5, 15, 30 mg doxycycline/kg) were administered daily p.o. until day 21. In the in vitro studies 10-1000 mumoles/l of these drugs were used.

METHODS

Urinary levels of pyridinoline and deoxypyridinoline, determined by HPLC/fluorescence, and paw volumes were the measurements in the rat study. In the in vitro studies enzyme activities were assessed using fluorogenic peptide substrates; cytokines were determined by ELISA.

RESULTS

On day 21 of disease crosslink excretion was about twofold higher compared to the healthy controls. After administering daily 15 or 30 mg/kg tiaprofenic acid p.o. this increase was almost completely prevented whereas the paw volumes were suppressed by about 50%. Up to 50 mg/kg doxycycline did not display significant suppressive effects on crosslinks and paw volumes. In vitro 50-100 mumol/l of both drugs inhibited the activities of selected metallo-proteinases, but only doxycycline suppressed the generation of IL-1 beta/TNF alpha in human mononuclear cells, whereas tiaprofenic acid was virtually inactive in that model.

CONCLUSIONS

In arthritic rats tiaprofenic acid has not only the capability to suppress paw inflammation, but also to prevent with high potency the excretion of pyridinium crosslinks. Doxycycline without inherent antiinflammatory activity does not exhibit such preserving effects on collagen degradation in this model. Thus the mode of action of cartilage protecting drugs within the complex pathogenesis of arthritis will need further elucidation.

Antibodies to PECAM-1 and glucocorticoids reduce leukocyte adhesion in adjuvant arthritis of the rat knee synovium in vivo

OBJECTIVE AND DESIGN

To demonstrate the effect of monoclonal antibodies to the adhesion-molecule PECAM-1 (CD31) and of prednisolone on leukocyte adhesion in rat adjuvant arthritis.

MATERIAL

Adjuvant arthritis was induced in male CD-rats (five groups of n = 6) 18 days prior to measurements.

TREATMENT

Mouse-monoclonal antibody to rat CD-31 at 200 microg/kg or prednisolone at 24 mg/kg were administered i.v. 15 minutes prior to measurements.

METHODS

Venules within the intact rat-knee synovium were focused by confocal laser scanning microscopy. Numbers of rolling and adherent leukocytes were assessed in vivo.

RESULTS

Induction of arthritis significantly increased rolling and adherent leukocytes compared to healthy controls. Both monoclonal antibodies to PECAM-1 and prednisolone significantly reduced adherent, but not rolling leukocytes in arthritic animals.

CONCLUSIONS

The method used is well suited for in vivo quantification of leukocyte adhesion under the influence of antiadhesive therapies. PECAM-1 might be an interesting target for novel therapies in rheumatoid arthritis.

Effects of propentofylline (HWA 285) on laser-induced thrombus formation in healthy and diseased rat mesenteric arterioles

The antithrombotic effects of the xanthine derivative propentofylline (HWA 285) were investigated in the laser-induced thrombus model in healthy and diseased rat mesenteric arterioles. Laser-induced platelet thrombi were documented by the help of an intravital microscope and a video system. The statistical comparison of drug-treated and untreated animals, in respect to the number of laser shots necessary to induce a defined thrombus, served as a quantitative measure for a potential antithrombotic drug effect. Propentofylline and acetylsalicylic acid, in single dosages of 10 and 30 mg/kg orally, significantly increased the number of laser shots required to produce a defined thrombus. Moreover, the drug decreased the laser-induced thrombus formation in a chronic experiment in adjuvant arthritic rats. After oral administration of 30 mg/kg for 21 days, propentofylline and pentoxifylline reduced significantly the thrombus formation, whereas acetylsalicylic acid exerted no effect.

Effects of different mediators or cytokines and monoclonal antibodies to adhesion molecules on leukocyte adhesion in rat mesenteric venules

Leukocyte adhesion (LA) to the endothelium of postcapillary venules is considered to be an important step in the inflammatory response. The recruitment of blood leukocytes into sites of inflammation involves a well-coordinated and dynamic sequence of events in which several cellular adhesion molecules (CAMs) and chemotactic cytokines play an active role. The aim of the present study was to elucidate receptor-mediated interaction in mesenteric venules of leukocyte rolling/adhesion and plasma leakage. We applied intravital microscopic techniques, with the help of an analogous video image processing system, to measure changes in the microvascular integrity. Rat monoclonal antibodies (MoAb) to different CAMs were administered before inflammatory stimuli were applied. Topical application of different doses of either lipo-polysaccharide (LPS), fMet-Leu-Phe, zymosan, complement C5a, Tnf-alpha, interleukin-1beta (IL-1beta), IL2 or IL-6 resulted in a dose-dependent increase in LA. The injection of a MoAb (1 mg/kg), 15 min prior to the LPS challenge, resulted in (1) total inhibition of LA, when MoAb to rat L-section, LFA1-beta and VLA-4 were used, (2) a moderate effect with LFA-1beta and Mac-1 MoAb, and (3) only a weak influence on LA by the MoAb to rat ICAM-1 (1 mg/kg). No effects were seen with IgG1 control MoAb. LA in acute models of inflammation can be regarded as a consequence of time-dependent differential effects of CAMs, as observed through the application of different MoAb.

Purification of 7 alpha-hydroxysteroid dehydrogenase from Escherichia coli strain 080

Purification studies of 7 alpha-hydroxysteroid dehydrogenase (7 alpha-HSDH) (EC 1.1.1.159) from Escherichia coli 080 showed that 1.59-fold purification could be achieved by heating (60 degrees C for 10 min) the ultracentrifuged enzyme preparation, and 6.46-fold purification was achieved by subsequent precipitation with ammonium sulfate. Further purification on Sephadex G-100 gel gave 10.1-fold purification. After pooling and concentrating the active fractions obtained from the Sephadex G-100 filtration, an 11.1-fold purification was achieved using DEAE-cellulose chromatography. The purified enzyme produced a single band on polyacrylamide gel electrophoresis and its molecular weight was determined to be 54,000. The enzyme was immunogenic and showed immunoprecipitation with homologus antisera.

Haemorheological studies of the sickle cell phenomenon in European red deer (Cervus elaphus)

It was demonstrated that the appearance of sickle-shaped erythrocytes can be induced by oxygenating the blood of European red deer (Cervus elaphus). The process was reversible. Blood cell counts with the exception of a slight reduction in red cell number and protein fractions did not show any abnormal values. The blood, which was examined at least 18 h after sampling, exhibited considerable deviations of blood gas values. In addition, highly significant haemorheological changes due to the sickle-shaped and oxygenated erythrocytes were detected.

Dependency of red blood cell passage time on pore geometry in the single-pore erythrocyte rigidometer (SER)

Employing the "Singlepore Erythrocyte Rigidometer" (SER) in which small pore diameters were used, significant differences were measured between red blood cells from adjuvant arthritic rats compared to control from non-diseased animals. The results changed to opposite values using higher pore diameters, which may be due to differences in cell "rigidity" and MCV.

Evidence from comparative investigations that impaired platelet activation is not specific for stroke-prone spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Platelet behavior of Sprague Dawley (SD), Wistar (WI), Wistar-Kyoto (WKY), spontaneously hypertensive (SHR), and stroke-prone spontaneously hypertensive rats (SHRSP) was studied in vivo to evaluate the importance of hypertension-related hemostatic disorders.

METHODS

The study was based on the model of stimulus-induced pulmonary microembolization of labeled platelets. After injection of 51Cr-labeled homologous platelets into urethane-anesthetized rats, the organ distribution of the platelets was continuously monitored by gamma detectors. Count rates of two detectors--one placed above the animals' thoraxes (C1), the other above their abdomens (C2)-and the ratio of C1:C2 were calculated. The following platelet activators were applied intravenously: adenosine diphosphate (ADP; 50 micrograms/kg), collagen (100 micrograms/kg), and thrombin (50 IU/kg).

RESULTS

All three substances caused a reversible pulmonary accumulation of the labeled platelets and hence an increase in C1/C2 (delta C1/C2%). ADP induced a shift of 75% in SD, 52% in WI, 32% in WKY, 30% in SHR, and 31% in SHRSP. Thrombin-mediated shift was 79% in SD, 64% in WI, 58% in WKY, 48% in SHR, and 54% in SHRSP. Collagen induced a shift of 85% in SD, 96% in WI, 84% in WKY, 56% in SHR, and 62% in SHRSP.

CONCLUSIONS

Because indistinguishable results were observed in both hypertensive strains, we conclude that impaired platelet aggregation is not specific for SHRSP. Hence, it may not primarily be responsible for the increased occurrence of stroke in these animals.

A microtitration procedure for quantitative determination of staphylocoagulase using fibrinogen-coated red blood cells

A microhemagglutination procedure, using fibrinogen-coated erythrocytes of rabbit or pig for quantitation of staphylocoagulase, is shown to be more sensitive than the standard tube test.

Red cell membrane abnormalities in two cases with a special type of a hereditary megaloblastoid hemolytic anemia

Case reports are presented of two related patients suffering from a hereditary megaloblastoid hemolytic anemia which at the moment cannot be categorized into one of the well-known entities. The main characteristics of the disease consisted of constant jaundice, macrocytic normochromic anemia, marked hemolysis without a substantial decrease in osmotic resistance, increased iron turnover and hepatic hemosiderosis at a relatively young age. One patient had to undergo splenectomy due to hemolytic crises, the other one cholecystectomy due to gallstones. In contrast to their uncharacteristic morphology in smear, red cells displayed highly variable forms ("lumpy", "Y", "U", drumstick forms) when examined in transmission and scanning electron microscopes. These changes corresponded well with reduced filtrability and aggregability of erythrocytes. The apparent relative blood viscosity was unchanged. The protein pattern of ghosts in SDS gel-electrophoresis revealed neither defects nor additional bands. Changes in the lipid composition of the membrane were indirectly deduced from electron spin-resonance studies, which showed an additional signal at g = 2.192. Similarly, the lipid related membrane mobility agent A2C failed to exert the usual stabilizing effect against osmotic stress. The negative surface potential, estimated by free flow electrophoresis, was only altered in the splenectomized patient. It is concluded that the primary abnormal physical properties of the enlarged red cell contribute at least in part to the marked hemolysis. The similar findings in the two related patients and the fact that the disorder was obviously congenital suggest a special subtype of a megaloblastoid hemolytic anemia.