Biomedical subjects

K G Engström

Publications and source records attributed to K G Engström.

At least 37 records · Page 2Linked to original sources

PubMed1995

Cell quality of salvaged blood after total knee arthroplasty. Drain blood compared to venous blood in 32 patients.

We used the ConstaVac drainage retransfusion system in 32 patients operated on with cemented tricompartmental knee arthroplasty. The mean total postoperative bleeding was 1.1 L of which 0.7 L was retransfused within 8 hours postoperatively. Samples were taken from the venous blood and drain blood at 2 hours and 6-8 hours postoperatively. The drain blood had low counts for leukocytes and thrombocytes as compared to venous blood, and fibrinogen was almost absent. Incubation at room temperature slightly lowered glucose and pH which made the erythrocytes swell. There was a slight hemolysis in the drain blood at 2 hours. At 6-8 hours the shed blood was closer to normal, especially with regard to hemolysis, but there was a further decrease in glucose. Within this time, there was no change in acidity and no further swelling of the erythrocytes. No clinical adverse reactions were observed and we consider the observed cellular and chemical changes to be of little importance. The quality of filtered drain blood within the analyzed time limit is considered acceptable for clinical use.

Aged↗

PubMed1995

Growth hormone deficiency impairs blood clotting and reduces factor VII coagulant activity in rat.

To investigate pituitary effects on the vitamin K-dependent coagulation factors, female rats were hypophysectomized (hypox) and treated with growth hormone (GH), cortisone, thyroxine, vitamin K, or saline. After 11 days of treatment, the prothrombin time, platelet count, and factors II, VII, IX, and X were determined. The prothrombin time was 52.9 +/- 1.2% for control rats and 39.1 +/- 0.8% for hypox rats (mean +/- SEM; p < 0.001). All factors decreased after hypophysectomy, reaching significance for factor VII (from 264 +/- 23% to 131 +/- 9%; p < 0.001) and factor IX (from 28.4 +/- 2.2% to 17.1 +/- 2.5%; p < 0.01) while the platelet count was unaffected. When hypox rats were treated with GH, the prothrombin time increased to 50.9 +/- 1.0% (p < 0.001) and factor VII to 299 +/- 10% (p < 0.001). Factor II, IX, and X were slightly increased after GH substitution but not after cortisone, thyroxine, or vitamin K treatment. To summarize, GH is of importance for normal hemostasis in the female rat.

Animals↗

PubMed1994

Optical and mathematical corrections of micropipette measurements of red blood cell geometry during anisotonic perifusion.

Accurate knowledge of red blood cell (RBC) membrane surface area and cellular volume is critical to understanding the geometric factors that affect RBC deformability. A useful method to determine RBC geometry is via micropipette aspiration in which the cell partially enters the tip of a glass pipette with a diameter of about 2 microns. Measurement of the cell while in the pipette allows calculation of cell geometry, but such measurements are subject to several artifacts. Herein, we analyze the effects of three artifacts on calculated RBC geometry during experimental osmotic manipulation. 1) The pipette internal diameter, as measured optically, requires correction for refractive index and focusing errors; 2) the pipette barrel is tapered rather than cylindrical; 3) the observed RBC outline is affected by a diffraction phenomenon. These optical and mathematical errors were all found to influence the calculated RBC geometry; both absolute values and relative changes during osmotic manipulation were affected. For RBC in isotonic medium, use of the above corrections significantly (p < 0.001) reduced the calculated area by 3.7%, the volume by 7.0%, and the minimum cylindrical diameter by 3.9%. The calculated membrane area dilation for cells exposed to hypotonic media was also significantly reduced; at 200 mOsm, the dilation was 2.8% +/- 0.2% without correction vs. 1.5% +/- 0.2% when all corrections were employed (p < 0.01). We therefore suggest that micropipette aspiration of RBC requires use of these correction techniques to obtain accurate values for RBC geometry and that such correction methods are of particular importance when RBC of different sizes are compared.

Adult↗

PubMed1992

Acute and long-term biphasic volume alterations in rat type-II somatotrophs during GH secretory stimulation.

The size and shape of growth hormone (GH)-producing rat (type II)-somatotrophs was studied during secretory stimulation by either human GH-releasing hormone (hGHRH(1-29)) or 50 nM extracellular potassium. A new type of perfusion chamber for light microscopy allowed the interpretation of early changes in cell morphology. The exposure to 10 nM hGHRH caused a significant transient decrease in cell volume to 94.4 +/- 2.1% within 2 s. The cell volume recovered to 99.2 +/- 1.3% at 30 s. A second, more gradual volume decrease then followed (60 s), which stabilized at about 92.5 (8 min) and was still present after 20 min of continuous hGHRH exposure. Potassium, 50 mM, gave an immediate and persistent cell volume increase of about 5%. The fluctuation in rat somatotroph volume after hGHRH exposure correlates to a previously observed biphasic GH-secretory pattern involving an initial burst secretion and a second slow phase secretion. The transient early volume decrease may reflect ion fluxes across the membrane and/or the response of the cytoskeleton to calcium mobilization during the GH-secretory onset. The second, persistent, volume decrease closely correlates to the calculated volume of lost GH vesicles.

Animals↗

PubMed1992

Optical evaluation of red blood cell geometry using micropipette aspiration.

Although red blood cell (RBC) geometry has been extensively studied by micropipette aspiration, the small size of RBC and pipettes vs. the optical resolution of light microscopy suggests the need to consider potential errors. The present study addressed such difficulties and investigated four specific problems: (1) use of exact equations to calculate RBC membrane area and volume; (2) calibration of the pipette internal diameter (PID); (3) correction for a noncylindrical pipette barrel; (4) diffraction distortion of the RBC image. The observed PID represents a cylinder lens enlargement that can be theoretically derived from the glass/buffer refractive index ratio (1.49/1.33 = 1.12). This enlargement was experimentally confirmed by: (1) studying pipettes bent to allow measurement through the barrel (horizontal) and at the orifice (vertical), with a resulting diameter ratio of 1.12 +/- 0.01; (2) and by replacing the surrounding buffer with immersion oil and hence abolishing the lens phenomenon (ratio = 1.12 +/- 0.02). In addition, use of aspirated oil droplets demonstrated a 3.2 +/- 0.2% error when the PID is focused at a sharp, maximum diameter. The average pipette cone angle was 1.49 +/- 0.09 degrees and varied considerably with pipette pulling procedures; calculated tongue geometry inside the pipette was affected by the noncylindrical pipette barrel. The RBC diffraction error, demonstrated by touching two aspirated cells held by opposing pipettes, was 0.091 +/- 0.002 microns. The PID, cone angle, and diffraction artifacts significantly (p < 0.001) affected calculated RBC geometry (average errors up to 5.4% for area and 9.6% for volume). Two new methods to calculate, rather than directly measure, the PID from images of a single RBC, during either osmotic or pressure manipulation, were evaluated; the osmotic method closely predicted the PID, whereas the pressure method markedly underestimated the PID. Our results thus confirm the need to consider the above-mentioned phenomena when determining RBC geometric parameters via micropipette aspiration.

Algorithms↗

PubMed1991

Volume regulation in mouse pancreatic beta-cells is mediated by a furosemide-sensitive mechanism.

A possible role for loop diuretic-sensitive Cl-/cation cotransport in volume regulation in the pancreatic beta-cells was investigated by measuring 86Rb+ efflux from beta-cell-rich pancreatic islets as well as the size of isolated beta-cells under different osmotic conditions. Lowering the osmolarity to 262 mosM (83% of control) resulted in a rapid cell swelling which was followed by regulatory volume decrease (RVD). RVD was completely inhibited by furosemide (1 mM), an inhibitor of Cl-/cation co-transport. The hypotonic medium (262 mosM) induced a rapid and strong increase in 86Rb+ efflux from beta-cell-rich mouse pancreatic islets and the furosemide-sensitive portion of the efflux was significantly increased. A slightly less hypotonic medium (285 mosM, 90% of control) induced only cell swelling and no RVD. With this medium only a marginal increase in 86Rb+ efflux was observed. Increasing the osmolarity by adding 50 mM NaCl (final osmolarity: 417 mosM, 132% of control) induced a rapid cell shrinkage but no regulatory volume increase (RVI). When the osmolarity was increased from a slightly hypotonic medium (262 mosM) to an isotonic medium (317 mosM) an initial cell shrinkage was followed by RVI. This RVI was inhibited by 1 mM furosemide. The data suggest that RVD as well as RVI in the beta-cells are mediated by loop diuretic-sensitive cotransport of chloride and cations and that these cells show a threshold for hypotonic stimulation of RVD.

Animals↗

PubMed1991

Early morphological detection of estramustine cytotoxicity measured as alteration in cell size and shape by a new technique of microperifusion.

The present study describes a new microscopic perifusion technique for detecting momentary alterations in cell volume and shape. The method has been applied for evaluating early signs of cytotoxicity following chemotherapeutic treatments. The effects of estramustine phosphate (EMP) have been evaluated. EMP is a complex between oestradiol-17 beta and the alkylating agent nor-nitrogen mustard and has recently demonstrated a marked cytotoxicity against malignant glioma cells. The results showed a concentration-dependent increase in cell size and a concomitant decrease in shape factor following EMP-treatment of glioma cells. These changes correlated with cytotoxicity evaluated as cell proliferation and cell membrane alterations shown by 86Rb fluxes and ultrastructural visible membrane damage. The colon cancer line HT-29 displayed no reactions at all following EMP treatment. It is suggested that acute alterations in cell morphology and shape display a strong correlation to the cytotoxicity of EMP encountered by traditional cell culture systems. The findings are discussed with respect to cell membrane disturbances caused by EMP and its potential role as an early test of cytotoxicity.

Cell Line↗

PubMed1990

Insulin-driven erythropoiesis may underlie impairment of erythrocyte deformability in hyperinsulinaemic, hyperglycaemic ob/ob-mice.

The circulating erythrocytes in hyperglycaemic and hyperinsulinaemic obese (ob/ob) mice are enlarged with a decreased erythrocyte filtrability and an abnormally low resistance to osmotic stress. These changes probably reflect aberrations of erythropoiesis, as evidenced by endhanced staining for iron in the bone marrow, reticulocytosis, and increased erythrocyte volume fraction. Mature erythrocytes, reticulocytes, and late-phase basophilic erythroblasts were found to have larger diameters than their counterparts in control mice while myelopoiesis appeared to be unaffected. The average erythrocyte also displayed an increased cell volume and a decreased haemoglobin concentration. It is suggested that the stimulation of the erythroid cell line in ob/ob-mice might be a consequence of the hereditary hyperinsulinaemia.

Animals↗

PubMed1990

Morphology and filterability of red blood cells in neonatal and adult rats.

Red blood cell (RBC) deformability in rats of various ages was assessed by filtration (3 micron Nucleopore membranes). Neonatal rat RBC (1 d old) had lower filterability, both in terms of RBC incremental volume (9.97 +/- 1.85 versus 0.33 +/- 0.28 nL at 180 d of age, mean +/- SD, p less than 0.001) and the number of filter clogging particles (25.7 +/- 3.1 versus 18.9 +/- 3.4 RBC x 10(3)/s, p less than 0.001). The lower filterability correlated with a larger RBC volume (169 +/- 12.6 versus 69 +/- 3.2 microns 3, p less than 0.001) and with a wider minimum cylindrical diameter (3.87 +/- 0.15 versus 2.84 +/- 0.05 microns, p less than 0.001). Almost all of the neonatal RBC had a minimum cylindrical diameter exceeding the 3 microns nominal pore size of the filters. The calculated resistance to initial folding was also significantly greater, as indicated by a static bending analysis of initial deformation. However, when the larger size of neonatal RBC was taken into consideration, and thus their greater projected area on which forces are applied, they appear to be at least as deformable as the adult type RBC. This finding may explain the contradiction between RBC filtration experiments and other approaches based on RBC deformations in shear flow, which have been unable to detect a hampered flexibility of neonatal RBC. In view of the more pronounced differences between neonatal and adult RBC in rats than in human subjects, the rat is an interesting model for studying this physiologic phenomenon in newborns.

Aging↗

PubMed1990

Effect of hypophysectomy and growth hormone substitution on red blood cell morphology and filterability in rats.

Growth factors, including insulin, are known to stimulate erythroid cell formation in vitro. This somatotrophic effect of insulin might be involved in blood abnormalities in diabetes mellitus. We therefore investigated whether growth hormone (GH) affects the morphology or filterability of circulating red blood cells (RBCs) in hypophysectomized rats. After hypophysectomy, rats became anemic with a decrease in hematocrit, hemoglobin concentration, RBC count, and reticulocytes. The RBC membrane area was enlarged, giving an increased area-to-volume ratio compared with the control RBCs. The calculated minimum cylindrical diameter (MCD) and resistance to initial folding of the RBC decreased after hypophysectomy, and was confirmed by an enhanced filtration of RBCs through 3 microns Nucleopore membranes. The number of filter clogging particles was also lower in hypophysectomized rats than in control rats. Substitution for 21 days with bovine GH (via subcutaneously implanted osmotic minipumps) normalized RBC morphology and filterability. After withdrawal of GH, all parameters returned toward the presubstitutional levels. Neither cortisone nor thyroxine had any measurable effect on RBC morphology or deformability, indicating that GH deficiency contributes to the abnormal RBC morphology and rheology seen after hypophysectomy.

Animals↗

PubMed1989

Volume regulation in mouse pancreatic islet cells as studied by a new technique of microperifusion.

A new technique was designed to analyse whether pancreatic islet cells are able to regulate their volume in anisotonic media. The projected cell area of individual cells was continuously observed, and the corresponding volume calculated during microperifusion with media of different osmolarities. In isotonic medium (317 mosmol) the cell volume was stable during perifusion and decreased by 17 or 25% when the osmolarity was increased (sucrose) to 417 or 517 mosmol. Reducing the medium osmolarity to 285 mosmol resulted in a volume reduction of about 7%. No evidence for cell volume regulation was observed in these media. However, reducing the medium osmolarity to 262 mosmol induced an immediate and rapid cell swelling of approximately 14%, after which the initial cell volume was regained within 9 min. The data suggest that the pancreatic islet cells are equipped with mechanisms for regulatory volume decrease that appear to be activated when the cell volume is increased above a certain limit.

Animals↗

PubMed1989

A new red blood cell filtration device with improved time resolution and its application to the impaired RBC deformability in the diabetic ob/ob mouse.

A new filtration device and blood handling technique for the assessment of RBC deformability in small blood samples is described and used to study RBC deformability in adult obese-hyperglycemic ob/ob-mice and normoglycemic controls. The new filtration device was designed to improve the time resolution during RBC incubation. Test and control RBC suspensions were directly filtered from two identical incubation chambers under a constant pressure of 1200 Pa. Nuclepore filters (3 microns) were mounted on top of several standard test tubes into which the filtrate was subsequently collected and weighed. Because the RBCs were resuspended to a very low (0.01%) hematocrit, the average number of RBCs passing each pore was less than 10. Therefore, any detectable difference must reflect the physical properties of RBCs, e.g. shape or viscoelasticity, whereas the role of white blood cells is negligible. When ob/ob-mouse RBCs were studied with the new technique they showed impaired filtrability as compared with control RBCs, both when incubated without glucose and with glucose present at the same concentration as that recorded in the RBC donating mouse.

Animals↗

PubMed1989

Red blood cell filterability during incubation and its dependence on RBC shape, glucose and serum albumin: a study in the diabetic ob/ob-mouse.

Red blood cell (RBC) filterability in the obese-hyperglycaemic ob/ob-mouse is markedly impaired compared with the lean controls. A new RBC filtration device with improved time resolution was used to study this phenomenon in relation to RBC shape-transformations and the effects of glucose and albumin. In ob/ob-mice, but not in controls, filterability increased with time; however, the difference between the mice remained significant after 2 h. Stomatocytosis (cup shaped RBCs) was in the order of 80-90% in both types of mice and 56% in human blood. The proportion of stomatocytes decreased linearly with time, most rapidly in the ob/ob-mice. Only 1% echinocytes (crenated RBCs) was seen after 2 h of incubation. In the absence of serum albumin stomatocytosis was initially 40% and declined further during incubation. Echinocytes showed the opposite reaction, increasing from about 10% to 55%. Glucose, 20 mM, caused an immediate increase in filterability but had no corresponding effect on the RBC shape transformations.

Animals↗

PubMed1988

Increased size and biconcavity in red blood cells of obese-hyperglycaemic mice.

Blood from non-inbred obese-hyperglycaemic ob/ob-mice or normoglycaemic controls was fixed in glutaraldehyde and embedded in plastic on glass slides. In vertically oriented red blood cells (RBCs) the diameter, central thickness, and toroidal thickness were measured at the diametrical cross section. For each RBC, the area, volume, and cross-sectional profile were calculated and used to analyze the mechanical properties of the corpuscle. In both types of mice, the diameter correlated positively with the central thickness and negatively with the toroidal thickness, suggesting a variation not only in size but also in biconcavity; the smaller the diameter, the more biconcave the disc. However, ob/ob-mouse RBCs were both larger and more biconcave than those in control mice. These differences in size and shape are suggested to explain why ob/ob-mouse RBCs exhibit a decreased deformability in filtration experiments.

Animals↗

PubMed1987

Altered shape and size of red blood cells in obese hyperglycaemic mice.

Red blood cells (RBCs) from hyperglycaemic ob/ob-mice, normoglycaemic controls, and a healthy man were sucked into a narrow capillary, photographed and measured. Mouse RBCs had a smaller diameter than human ones. Although of normal diameter, the ob/ob-mouse RBCs exhibited increased area and volume, and more frequently than control RBCs had a minimum cylindrical diameter greater that 3 micron. Cross-sectional profiles with minimum bending resistance were computed for RBCs of mean area and volume. The diameters of these theoretical profiles agreed closely with those empirically observed, in both mice and man. The profile of ob/ob-mouse RBCs predicted a greater resistance to corpuscle bending than the control profile. It is concluded that changes in shape and size explain the decreased filtrability of diabetic ob/ob-mouse RBCs. The results also suggest that the actually occuring smooth biconcavity is in general the RBC shape with maximum flexibility.

Animals↗

PubMed1986

Decreased deformability of erythrocytes in hyperglycaemic non-inbred ob/ob mice.

The deformability of erythrocytes from non-inbred ob/ob mice and lean controls was analyzed by filtration through Nuclepore polycarbonate under constant pressure. At the age of 1-2 months there was no difference in erythrocyte filtrability between the two types of mice, whereas from 3 months the ob/ob mouse erythrocytes exhibited a markedly decreased deformability. The filtrability of erythrocytes was sensitive to osmotic pressure (NaCl or glucose). However, the difference between normal and ob/ob mouse erythrocytes was not due to acute osmotic effects of the hyperglycaemia in the ob/ob mice. When filtration was performed in the same glucose concentration as that recorded in the blood of the erythrocyte-donor animal, the difference in filtrability between adult normal and ob/ob mice remained large and significant (p less than 0.01). Moreover, the most pronounced hyperglycaemia occurred in young ob/ob mice with normal erythrocyte filtrability. It is suggested that non-inbred ob/ob mice are a useful model for studying the damaging influence of diabetes on erythrocyte deformability.

Animals↗

PubMedDate not supplied

Analysis of flow acceleration during erythrocyte filtration: dependence of hematocrit and cell rigidity.

At flow onset the blood filtration rate accelerates to a steady state, this may affect the interpretation of red blood cell (RBC) filterability. We studied the acceleration of flow while the pressure is built up across the filter to analyse effects of various hematocrits and RBC rigidity by glutaraldehyde (GA) hardening. This was analysed by a new filtration system with high time resolution and unlimited filtration volume. The system uses a digital balance that samples the accumulated weight (e.g., filtration rate through 5 microns Nucleopore membranes) with on-line computer communication. The filtration is computer controlled via a pneumatic valve. White blood cells (WBC) were removed prior to filtration by a WBC-eliminating filter to avoid clogging artifacts. When flow is initiated a steady state is reached at 0.3-0.4 s. This timing was also tested and confirmed by a video monitoring technique of filtration flow into a horizontal pipette. The digital balance has a mathematical function to reduce the effects of vibration noise; when this function was activated the apparent acceleration was retarded to 1.2 s. With any of these techniques the steady state timing did not vary with the hematocrit, however, the volume of filtered suspension during acceleration varied with both the hematocrit and the GA hardening (p < 0.001). Extrapolation to yield the initial filtration rate from the relative flow curve (RBC suspension divided by buffer flow) varied depending on if the acceleration phase was included or not. In the most unfavourable situation, with GA-hardened RBC, this difference was 340% (p < 0.01). The slope to calculate clogging rate was affected in a similar way. Moreover, with the most GA-hardened RBC a delay in flow onset was observed with this technique. The acceleration phenomenon may cause artifacts in systems employing volume-derived filtration kinetics because of fixed volumes of filtrated medium.

Erythrocyte Aggregation↗

PubMedDate not supplied

Use of polyester leukocyte elimination filters in blood filterability research.

We tested a new routine to eliminate leukocytes for blood rheology measurements using commercial leukocyte absorbing filters (here PALL RC400). These filters were punched out and fitted in smaller chambers through which blood was filtered under controlled suction pressure (< 30 mm Hg). This technique resulted in a very effective leukocyte elimination to 0.0022% but also a platelet reduction to 0.2%. The process causes a small but significant hemolysis with free hemoglobin, of the order of 0.06% of the filtered erythrocytes. A small fraction of the erythrocytes were retained in the filter, versus plasma, to reduce the hematocrit on the order of 1.4%. The leukocyte filtration did not cause any detectable functional trauma to the erythrocytes, measured as micro-pore filterability of normal and glutaraldehyde (GA) hardened erythrocytes. However, when 10% of the erythrocytes were hardened with GA, which caused an increase in pore clogging slope (p < 0.05), the additional passage through the leukocyte elimination filter removed this measured change in clogging. This observation suggests that the leukocyte elimination filter may selectively remove, not only leukocytes and platelets, but also hardened erythrocytes. Reticulocyte counting did not reveal any selective removal of young erythrocytes. In general, we find the presented method reproducible, efficient and easy for eliminating leukocytes for blood rheology research although the risk of removing undeformable erythrocytes must be considered.

Adult↗