Leukocyte-depleted blood: a comparison of available preparations.

Febrile nonhemolytic transfusion reactions due to leukoagglutinins are frequently seen in patients who have been given multiple blood transfusions. To prevent or reduce the severity of these reactions, leukocyte-poor blood (that containing fewer than 0.3 X 10(9) leukocytes per unit) is frequently requested by clinicians. Four methods commonly used in Canada to produce leukocyte-poor blood were examined for their relative effectiveness and appropriate use. The mean total leukocyte count per unit was reduced to 0.22 X 10(9) in buffy-coat-poor red blood cell preparations produced by centrifugation with the blood bag inverted, to 0.19 X 10(9) by perfusion through an Imugard filter, to 0.21 X 10(9) by the use of an IBM 2991 automated cell washer and to 0.13 X 10(9) with the use of frozen blood. The proportion of red cells recovered varied from 62% with the inverted-spin method to 85% with the use of frozen blood. Comparison of these data and the percentage of leukocytes removed, the shelf life of the product, the cost of supplies and the preparation time indicated that the use of sophisticated machinery, such as the IBM cell washer, or of glycerolization plus washing of frozen cells is not warranted for most patients. Instead, patients who have febrile nonhemolytic transfusion reactions should initially be treated with a leukocyte-poor red cell preparation produced by the inverted-spin method; only if such reactions recur should the blood bank be requested to provide filtered, washed or frozen red cells.     

Comparative study on the percentage of recovery, survival and mode of sequestration of fresh and frozen preserved (-196 degrees C) human platelets

Platelet concentrates amounting to 142 X 10(9) +/- 11 X 10(9) cells are prepared by cytopheresis from one liter of blood. Ten of the concentrates are labelled with 51Cr and reinfused autologously. The other ten concentrates are frozen with a controlled rate freezer in a medium containing 10% DMSO and 5% glucose for 7 days at -196 degrees C. The fresh platelets have a 51Cr 24 hrs. recovery of 68 +/- 7% and a survival rate (T 1/2) of 10 +/- 1 days. The frozen preserved platelets have a 51Cr 24 hrs. recovery of 54 +/- 6.1%, a T 1/2 of 8.1 days, and significantly increased liver sequestration. There is a correlation between the reversal reaction in vitro after hypotonic shock and the 51Cr 24 hrs. in vivo recovery of fresh platelets and the 51Cr 1st hr. recovery of frozen platelets.     

Improving the quality of washed and buffy coat-free erythrocyte concentrates]

Washing buffy-coat free erythrocyte concentrates three times in bottles used for blood storage will diminish their leukocyte content to 0.22 +/- 0.11 x 10(9) per TE (= 9% of the initial value in whole blood, and the thrombocyte content to 0.3 +/- 0.5 x 10(9) per day (= 2% of the initial value in whole blood). Even 50% of leukocytes (mainly lymphocytes) and 80% of thrombocytes are eliminated simply by buffy coat separation. 30% of erythrocytes are lost by the washing process. Due to increasing haemolysis (0.22%) a subsequent storage of 24 hours should not be exceeded for washed erythrocyte concentrates. Further quality parameters, such as morphological index, pH, ATP, 2,3-P2G and K+ and Na+, were investigated. As far as selected quality parameters are concerned, washing erythrocyte concentrates three times in bottles for blood storage may be compared with washing them once in blood bags. The present findings confirm the conclusion that the washing of erythrocyte concentrates with a solution of sodium chloride in order to eliminate leukocytes may for the most part exclude non-haemolytic febrile transfusion reactions, but not immunization. More effective procedures of eliminating leukocytes, such as filtration, TTK or even glycerin, treatment of erythrocyte concentrates without cryoconservation, are indispensable.     

Detection of beta-adrenergic receptors on rabbit mononuclear cells isolated free of significant contamination by other cell types

In order to study rabbit mononuclear cell surface receptors, it was necessary to develop a procedure to isolate mononuclear cell preparations that are free of significant contamination by other cell types, especially platelets. Centrifugation of dextran-sedimented, anti-coagulated whole blood through Hypaque (density 1.060) at 600 X g for 5 min at 22 degrees C eliminated greater than 93% of starting platelets. A second 5-min Hypaque centrifugation of Hypaque-Ficoll-isolated mononuclear cells (MNC) (approximately 80% lymphocytes) at 450 X g for 5 min at 22 degrees C reduced platelet contamination to less than one platelet per three MNC, and resulted in the overall removal of greater than 99.5% of starting platelets. These relatively pure MNC which were isolated in less than 2 hr were identified as having beta-adrenergic receptors by radioligand binding techniques using [125I]iodohydroxybenzylpindolol [( 125I]IHYP). Binding of [125I]IHYP to intact rabbit MNC was a saturable, stereospecific, and rapid process with a dissociation constant (KD) of 0.53 +/- 0.18 nM and a binding capacity of 3,461 +/- 235 sites/cell.     

Direct transesterification of plasma fatty acids for the diagnosis of essential fatty acid deficiency in cystic fibrosis

This study was aimed at redefining criteria for essential fatty acid (EFA) deficiency with the use of the direct transesterification procedure (1986. J. Lipid Res. 27: 114-120) and at determining whether a simple assay of total fatty acids (FA) is as predictive of EFA deficiency as the FA pattern from plasma, red cell, and platelet phospholipids. Fasting blood samples were taken from 163 cystic fibrosis (CF) patients who were encouraged to consume 35-40% of their calories as fat. Their mean (+/- SD) age was 9.6 +/- 4.8 yr. The control group consisted of 44 unaffected siblings aged 13.1 +/- 3.1 yr. The 20:3(n-9)/20:4(n-6) ratio in 77 (47%) CF children was more than 2 SD above the values (mean +/- SD) of 0.021 +/- 0.007 obtained in the 44 controls. Groups of EFA-sufficient (n = 10) and EFA-deficient (n = 7) subjects were selected for further studies. The plasma total FA 20:3(n-9)/20:4(n-6) ratios of 0.029 +/- 0.003 in EFA-sufficient and of 0.216 +/- 0.103 in EFA-deficient was as good a discriminant as FA in phospholipids from plasma, red cell PC, and platelets. Among the 21 individual fatty acids, 20:3(n-9), which was also found in controls, and 16:1(n-7) (palmitoleic) proved to be the most sensitive indices of EFA deficiency. They are equally reliable in plasma, red cells, and platelets, but the inverse linear relationship (r = -0.91) between the n-7 family and 18:2(n-6) proved to be more closely associated with EFA deficiency than the one (r = 0.66) between 20:3(n-9) and 20:4(n-6).(ABSTRACT TRUNCATED AT 250 WORDS)     

A high-performance liquid chromatographic method for the determination of tocopherol in plasma and cellular elements of the blood.

A rapid sensitive, and reproducible procedure is described for the analysis of alpha-tocopherol in blood cells and plasma using high-performance liquid chromatography and fluorometric detection. The cardinal feature for the increased sensitivity of this high-performance liquid chromatographic procedure is that the fluorometric analysis was carried out at a short excitation wavelength (205 nm) which increased the sensitivity of 20-fold over the usual excitation wavelength of 295 nm. Tocopherol levels can be measured in as little as 50 microliters of plasma and 200 microliters of erythrocytes. The tocopherol contentof plasma, red blood cells, platelets, polymorphonuclear leukocytes, and lymphocytes of normal subjects and subjects ingesting additional quantitites of vitamin E are reported. The values for the white cells are approximately 30 times higher than those of the red blood cells (polymorphonuclear leukocytes 4.47 +/- 0.62 micrograms/10(9), lymphocytes 3.89 +/- 0.85 micrograms/10(9), and erythrocytes 1.40 +/- 0.14 micrograms/10(10) cells). The tocopherol contents of the plasma and all the cellular elements of the blood were increased by oral feeding with vitamin E.     

透析式洗涤冰冻红细胞去除白细胞和血小板的方法

目的：用低速离心的方法减少悬浮红细胞中自细胞和血小板的数量,使透析式洗涤机洗涤的冰冻红细胞中白细胞和血小板的残留量小于1％。方法：分别选用低速离心（700和500r／min）和常规离心（3800r／min）全血制备悬浮红细胞,计算白细胞和血小板的清除率;甘油低温冰冻保存,透析式冰冻红细胞洗涤机洗涤冰冻红细胞,对洗涤后的红细胞进行质量检测。结果：500r／min离心后白细胞和血小板的清除率（％）分别为53.82±6.83和85.23±4.21;洗涤后的冰冻红细胞中白细胞和血小板残留量（％）分别为0.843±0.058和0.903±0.035。700r／min离心后白细胞和血小板的清除率（％）分别为23.38±2.36和62.61±3.82;洗涤后的冰冻红细胞中白细胞和血小板残留量（％）分别为0.983±0.024和1.021±0.045。3800r／min离心后白细胞和血小板的清除率（％）分别为9.82±4.12和6.39±3.26;洗涤后的冰冻红细胞中白细胞和血小板残留量（％）分别为3.839±2.896和3.528±2.689。结论：用500r／min离心全血制备的悬浮红细胞,经甘油低温冻存,透析式洗涤机洗涤后,血小板和白细胞的残留量等各项指标均符合国家标准。     

Enhanced thromboxane formation by blood but not whole platelets from spontaneously hypertensive rats.

Increased serum levels of immunoreactive thromboxane B2 (iTXB2) were observed in spontaneously hypertensive rats of the Okamoto-Aoki strain (SHR) compared with normotensive Wistar-Kyoto rats (WKY). Serum iTXB2 levels in whole blood allowed to clot at 37 degrees C for 1 hour were significantly greater in SHR than WKY at 8, 16-20, and 38 weeks of age, whereas formation of iTXB2 by thrombin-stimulated whole platelets from 6 16-week-old SHR and 6 age-matched WKY was 399 +/- 44 and 377 +/- 38 ng/10(9) platelets/30 min, respectively. No significant difference in radioconversion of exogenous arachidonic acid to TXB2 was observed in whole platelets from SHR (18.2 +/- 2.5%, n = 4) and WKY (20.1 +/- 3.0%, n = 4) at 16 weeks of age. These results support the proposal that enhanced ability of blood from SHR to generate iTXB2 is independent of the stage of hypertension development. This enhancement probably depended on factors or blood elements other than platelets since no difference in formation was observed on stimulation of whole platelets.     

Oxygen binding and acid base status of the blood from the freshwater turtle, Phrynops hilarii

Oxygenation studies with the whole blood of Phrynops hilarii show a P50 of 38 torr at extracellular pH (pHe) of 7.4 which corresponds to an intracellular pH (pHi) of 7.05 at 25 degrees C. The blood CO2 Bohr effect was -0.56 when related to pHi. pHi is related to pHe by the following equation: pHi = 0.75.pHe + 1.54 (r = 0.99); pHi = 0.72. pHe + 1.72 (r = 0.96) at 10 and 25 degrees C respectively. Blood pHe, for 25 degrees C, was 7.519 +/- 0.254 (n = 6). Blood gas partial pressures were: pCO2 = 25.8 +/- 3.8 torr (n = 6); pO2 = 61.7 +/- 21.2 torr (n = 6). The major red cell phosphates, in mmole/l erythrocytes, n = 6, were: ATP (3.66 +/- 0.86); GTP (0.53 +/- 0.28); 2.3-DPG (0.32 +/- 0.12) and inorganic phosphates (2.00 +/- 0.35). The plasma inorganic ion composition, n = 6, was, in mEq/l: K+ (3.04 +/- 0.40); Na+ (148.4 +/- 12.6); Ca2+ (4.75 +/- 1.32); Cl- (106.6 +/- 5.0). Additional blood parameters of interest (n = 6) were: lactate (2.07 +/- 1.72 mM in plasma); erythrocytes/mm3 (416 X 10(3) +/- 4.6 X 10(3)); leucocytes/mm3 (44636 +/- 2618); haematocrit (%) (14.5 +/- 3.6); haemoglobin, g/dl (3.2 +/- 0.5); plasma protein g/dl (4.4 +/- 0.4); osmolarity (293 +/- 10 mOsm/l). The non-bicarbonate buffer value was -22.6 mmol/kg H2O/pH. For a constant CO2 content, delta pHe/delta t = 0.0141 +/- 0.002 (n = 18) and delta pHi/delta t = 0.0157 +/- 0.003 (n = 18).     

Large-scale isolation of polymorphonuclear leucocytes from bovine blood

A method for the isolation of an enriched population (greater than 96%) of bovine polymorphonuclear leucocytes (PMNs) from 70 liters of blood was developed using a two-step procedure involving separation of the blood, in a packed red blood cell fraction containing the PMNs and a plasma fraction, by continuous flow blood separation. Hypotonic lysis of erythrocytes was then followed by centrifugation at 200 g sedimenting the PMNs. The yield was 93 +/- 30 g, the recovery was 62 +/- 20%, viability was greater than 95%. Since bovine blood can be obtained in unlimited amounts, the procedure described here can be applied to obtain large amounts of bovine PMNs for incubation studies and large-scale purification of intracellular enzymes suitable for biochemical characterization.     

Platelets and leukocytes in the lungs after acute hypobaric hypoxia

To determine if decompression from sea level causes aggregation and embolization of platelets or leukocytes to the lungs, we have measured the accumulation of 51Cr-labeled platelets or 111In-labeled leukocytes in the lungs of rabbits decompressed to 440 or 350 Torr for 18 or 40 h. To be certain that any increased accumulation of labeled platelets (or leukocytes) in the lungs was not just caused by an increased pulmonary blood volume we also labeled the rabbits red blood cells with 59Fe. There was no detectable accumulation of labeled platelets in the lungs on decompression. In control animals there were 22 times as many labeled leukocytes in the lungs as could be accounted for by the volume of blood in the lungs. In experimental animals at 326 Torr for 18 h this figure was reduced to 13.6. Hypobaric hypoxia caused an increase in circulating granulocytes from a mean of 3.3 +/- 1.6 X 10(9)/l to 5.3 +/- 2.1 X 10(9)/l. (P less than 0.005). Our results suggest that decompressions to 6,100 m for 18 h does not cause platelet sequestration in the lungs but does cause a significant reduction in leukocytes in the lungs and a peripheral granulocytosis.     

Seasonal variation in various blood indices of the kangaroo rat, Dipodomys panamintinus

1. Various blood indices in the Panamint kangaroo rat revealed seasonal fluctuations. The red blood cell count during winter and summer averaged 7.2 +/- 1.0 X 10(6) and 9.2 +/- 0.2 X 10(6)/mm3 respectively. 2. The mean cell hemoglobin during winter and summer averaged 25 +/- 10.8 pg and 18.6 +/- 3.7 pg respectively. 3. These fluctuations may reveal a rapid rate of red blood cell destruction during winter in combination with a change in diet, concomitant to this, is an increase in mean cell hemoglobin of the surviving red blood cells.     

Human prothrombinase complex assembly and function on isolated peripheral blood cell populations

A membrane-bound Ca2+-dependent complex of the cofactor Factor Va and the enzyme Factor Xa comprises the prothrombinase coagulation complex which catalyzes the proteolytic conversion of prothrombin to thrombin. Analyses of the kinetics of prothrombin activation permit calculation of the stoichiometry and binding parameters governing the functional interactions of Factor Va and Factor Xa with isolated thrombin-activated human platelets and isolated leukocyte subpopulations. Our kinetic approach indicates that Factor Xa binds to approximately 2700 +/- 1000 (n = 8) functional sites on the surface of thrombin-activated platelets with an apparent dissociation constant (Kd) equal to 1.18 +/- 0.53 X 10(-10) M and kcat equal to 19 +/- 7 mol of thrombin/s/mol of Factor Xa bound. The store of Factor V in normal platelets prevents an analogous determination of the functional Factor Va platelet binding sites. Factor Va and Factor Xa titrations performed using platelets from a Factor V antigen-deficient individual indicate that Factor Va and Factor Xa form a 1:1 stoichiometric complex on the surface of thrombin-activated platelets. Both binding isotherms are governed by the same apparent Kd (approximately equal to 10(-10) M) and expressed the same kcat/site (14-17 s-1. Factor Xa-platelet binding parameters are not altered by the use of different platelet agonists, the choice of anticoagulant, or platelet washing procedure. Kinetics of prothrombin activation indicate also that monocytes, lymphocytes, and neutrophils possess, respectively, 16,000, 45,000, and 8,000 Factor Va-Factor Xa receptor sites/cell, which are all governed by apparent KdS approximately equal to 10(-10) M. Enzymatic complexes bound to monocytes or neutrophils exhibit kcat values similar to the platelet-bound complex. Complexes bound to lymphocytes are only 25% as active.     

Hyperventilation-induced changes of the blood picture

In a controlled study of 11 male volunteers the following changes (means +/- SD) were observed in venous blood during (D) and 75 min after (A) a period of 20 min of voluntary hyperventilation in comparison with before (B) hyperventilation (P values referring to the difference between D and B) erythrocyte count 5.18 +/- 0.17 X 10(6) (B), 5.70 +/- 0.21 X 10(6) (D) (P less than 0.001), and 5.18 +/- 0.16 X 10(6)/microliter (A); hemoglobin 15.7 +/- 0.6 (B), 17.2 +/- 0.7 (D) (P less than 0.001), and 15.8 +/- 0.6 g/dl (A); centrifuged hematocrit 46.6 +/- 1.0 (B), 50.4 +/- 1.7 (D) (P less than 0.001), and 47.0 +/- 1.8% (A). The platelets increased from 159 +/- 30 X 10(3) (B) to 205 +/- 40 X 10(3) (D) (P less than 0.001) and returned to 157 +/- 26 X 10(3)/microliter (A). The leukocytes (WBC) were 4,210 +/- 630 (B), 6,220 +/- 1,660 (D) (P less than 0.001), and 6,190 +/- 1,870/microliter (A) (P less than 0.002, as compared with B). The rise of WBC during hyperventilation was mainly due to a 83% increase of lymphocytes, whereas a 93% increase of neutrophil leukocytes accounted for the increased WBC 75 min posthyperventilation. The increase of the ratio of band forms to segmented neutrophils from 9 (B) to 19% (A) (P less than 0.01) indicates that band forms were released from the bone marrow. The results show that WBC and platelets can be mobilized by hyperventilation by as yet unidentified mechanisms.     

Detection of human P2X7 nucleotide receptor polymorphisms by a novel monocyte pore assay predictive of alterations in lipopolysaccharide-induced cytokine production

The nucleotide receptor P2X(7) is expressed by most leukocytes and initiates signaling events that amplify numerous LPS responses. We tested the hypothesis that loss-of-function polymorphisms in the human P2X(7) gene predispose to the production of an anti-inflammatory mediator balance. Accordingly, we developed a novel P2X(7) pore assay in whole blood that magnifies the activity from wild-type alleles and preserves the gene dosage effect for the 1513 C polymorphism (AA, 69 +/- 4; AC, 42 +/- 4; and CC, 6 +/- 1-fold stimulation). Thirty of 200 healthy individuals were identified as having low P2X(7) pore activity. Seven low pore subjects were 1513 CC, 3 and 11 participants had the other known variants 946 GA and 1729 TA respectively; the remaining 9 volunteers likely have novel polymorphisms. Because platelets are a large source of extracellular ATP during inflammation, whole blood was treated ex vivo with Salmonella typhimurium LPS in the absence of exogenous nucleotides. LPS-stimulated whole blood from individuals in the low pore activity group generated reduced plasma levels of TNF-alpha (p = 0.036) and higher amounts of IL-10 (p < 0.001) relative to the high pore controls. This reduction in the TNF-alpha to IL-10 ratio persisted to at least 24 h and is further decreased by cotreatment with 2-methylthio-ATP. The ability of P2X(7) polymorphisms to regulate the LPS-induced TNF-alpha to IL-10 ratio suggests that 15% of healthy adults may exhibit anti-inflammatory mediator responses during major infectious perturbations of the immune system, which can be predicted by P2X(7) pore activity.     

Effect of hematocrit on cerebral blood flow with induced polycythemia

Cerebral blood flow (CBF) is lowered during polycythemia. Whether this fall is due to an increase in red blood cell concentration (Hct) or to an increase in arterial O2 content (Cao2) is controversial. We examined the independent effects of Hct and Cao2 on CBF as Hct was raised from 30 to 55% in anesthetized 1- to 7-day-old sheep. CBF was measured by the radiolabeled microsphere technique before and after isovolemic exchange transfusion with either oxyhemoglobin-containing erythrocytes (in 5 control animals) or with methemoglobin-containing erythrocytes (in 9 experimental animals). Following exchange transfusion in the control animals, Hct rose (30 +/- 1 vs. 55 +/- 1%, mean +/- SE), Cao2 increased (15.1 +/- 0.8 vs. 26.7 +/- 0.9 vol%), and CBF fell (66 +/- 9 vs. 35 +/- 5 ml X min-1 X 100 g-1). Because the fall in CBF was proportionate to the rise in Cao2, cerebral O2 transport (CBF X Cao2) was unchanged. Following exchange transfusion in the experimental animals, Hct rose (32 +/- 1 vs. 55 +/- 1%) but Cao2 did not change. Nevertheless, CBF still fell (73 +/- 4 vs. 48 +/- 2 ml X min-1 X 100 g-1) and, as a result, cerebral O2 transport also fell. The latter cannot be attributed to a fall in cerebral O2 uptake, as cerebral O2 uptake was unaffected during each of these conditions. Comparison of the two groups of animals showed that approximately 60% of the fall in CBF may be attributed to the increase in red cell concentration alone. It is probable that this effect is due largely to changes in blood viscosity.     

Comparative analysis of different flow cytometry-based immunophenotypic methods for the analysis of CD59 and CD55 expression on major peripheral blood cell subsets

BACKGROUND: Flow cytometry-based immunophenotypic techniques for the analysis of CD55 and CD59 expression on the major cell populations present in blood are the preferred method for the diagnostic screening of paroxysmal nocturnal hemoglobinuria (PNH). METHODS: In the present study, we comparatively analyze the effects of stain-lyse-and-then-wash techniques and lyse-wash-and-then-stain procedures on the detection of both CD55 and CD59 expression on the major peripheral blood (PB) leucocyte subsets, as analyzed by flow cytometry. Our major goal was to establish the minimum amounts of anti-CD55 and anti-CD59 reagents required to be added to a minimum volume of blood, which would allow an optimal staining for both antigens on red cells, platelets, and leucocytes present in a single tube. RESULTS: Our results show that upon comparing stain-lyse-and-then-wash techniques with lyse-wash-and-then-stain protocols, the presence of important amounts of red cells at the time peripheral blood leucocytes are stained for CD55 and CD59 is associated with a significantly (P < 0.01) lower and more heterogeneous pattern of antigen expression on almost all major PB leucocyte subsets, supporting the need to use red cell lysing procedures prior to the staining of leucocytes. Identical, optimal patterns of antigen staining for CD55 and CD59 were obtained upon incubating 3 microL of blood with 10 microL of each of these monoclonal antibody (mAb) reagents (protein concentration of 0.05 microg/microL and 0.2 microg/microL respectively) for 30 min (room temperature [RT]) using a non-lyse-non-wash sample preparation procedure. This latter procedure allowed for the simultaneous analysis of CD55 and CD59 expression on red cells, platelets, neutrophils, monocytes, and lymphocytes present in the sample through the combined staining of CD55 and CD59 with CD64-fluorescein isothiocyante (FITC) plus CD61-peridinin chlorophyll protein (PerCP) and CD45-PerCP. CONCLUSIONS: In summary, our results show that the sample preparation protocol has a significant impact on the quality of the staining obtained for the CD55 and CD59 antigens on the major PB leucocyte subsets; additionally, we propose a simple and reliable stain-non-lyse-non-wash method for the simultaneous analysis of CD55 and CD59 expression on PB red cells, platelets, neutrophils, monocytes, and lymphocytes, which could be reached through the use of two triple stainings.     

Exercise responses in pregnant sheep: oxygen consumption, uterine blood flow, and blood volume

In an attempt to explore the acute maternal responses to exercise we measured oxygen consumption, uterine blood flow, and blood volume in 13 chronically catheterized pregnant sheep at rest and while exercising on a treadmill. With maximal exercise O2 consumption increased 5.6 times, from a resting value of 5.8 +/- 0.3 (SE) to 32.1 +/- 2.8 ml X min -1 X kg -1, cardiac output increased 2.7 times, from 149 +/- 8 to 404 +/- 32 ml X min -1 X kg -1, and arteriovenous oxygen content difference increased 2.1 times, from 3.9 +/- 0.2 to 8.0 +/- 0.4 ml X dl -1. Total uterine blood flow decreased from a mean resting value of 292 +/- 6 to 222 +/- 19 ml X min -1 X kg fetus -1 near exhaustion during prolonged (40 min) exercise at 70% maximal oxygen consumption. Maternal blood volume decreased 14% (P less than 0.01) from 67.5 +/- 3.7 to 57.8 +/- 3.6 ml X kg -1 during this exercise period, with a 20% decrease in plasma volume without a change in red cell volume. We conclude that uterine blood flow decreases during maternal exercise. However, hemoconcentration helps to maintain a relatively constant oxygen delivery to the uterus.     

Colony-forming fibroblast precursors of the circulating blood

Colony-forming fibroblast precursors were detected in circulating blood of adult guinea pigs by CFUf in vitro colony assay. SFU amount to 0.9 +/- 0.2 (M +/- m) per 10(5) explanted leucocytes ranging from 0.04 X 10(-5) to 3.0 X 10(-5) for individual donors. The presence of collagen type I and lack of factor VIII antigen and of FC-receptors proved that CFU-derived colonies in the blood cultures were composed of fibroblasts.