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Biomedical subjects

O Linderkamp

Publications and source records attributed to O Linderkamp.

At least 145 records · Page 8Linked to original sources
PubMed1984

Contributions of red cells and plasma to blood viscosity in preterm and full-term infants and adults.

In preterm infants, plasma and red blood cells display several specific properties (eg, RBC size, plasma composition) that could influence blood flow behavior. Hemorheologic properties of blood from 20 preterm infants (24 to 36 weeks of gestation), ten full-term neonates, and ten adults were studied by means of a cone-plate viscometer adapted with a Couette-type chamber allowing viscometry at a wide range of shear rates (1.15 to 230/s). Blood viscosity (at given hematocrit of 60%), plasma viscosity, and RBC aggregation were very low in the smallest preterm infants, increased with gestational age, and reached the highest values in the adults. Whole blood viscosity increased directly with increasing plasma viscosity, plasma fibrinogen, and total plasma protein concentration, with the strongest correlations at the lowest shear rate of 1.15/s. The viscosity of RBCs suspended in a nonaggregating buffer solution was similar in all groups, thereby indicating that RBC deformability is similar in preterm infants, full-term neonates, and adults. Because mixing of neonatal and adult blood components occurs in most small preterm infants as a result of the transfusion of adult blood products, viscosities of cross suspensions (neonatal RBCs in adult plasma and adult RBCs in neonatal plasma) were measured. The exchange of neonatal plasma for adult plasma increased blood viscosity values in the neonates to adult values. On the other hand, the exchange of neonatal RBCs for adult RBCs did not affect blood viscosity. These results indicate that viscosity of blood with given hematocrit is lower in preterm infants than in term neonates and adults as a result of low plasma viscosity and low RBC aggregation, and that neonatal RBCs do not possess specific properties that influence blood viscosity.

Adult↗
PubMed1983

Erythrocyte aggregation during normal pregnancy.

Red blood cell aggregation induced by fibrinogen is a major determinant of the non-Newtonian flow behavior of blood and has been suggested as a possible contributing factor for thrombogenesis. Given the elevated fibrinogen levels and the incidence of thrombotic accidents in pregnancy, a study was designed to assess red blood cell aggregation at selected gestational periods. Three separate in vitro aggregation assays were used: (1) aggregation half time, (2) zeta sedimentation ratio, and (3) microscopic aggregation index. Our results indicate that red blood cell aggregation is increased throughout normal pregnancy (i.e., at 10, 25, and 36 weeks and during labor) in comparison to that in nonpregnant women. Significant correlations between plasma fibrinogen concentration and zeta sedimentation ratio (p less than 0.001) or aggregation half time (p less than 0.02) were demonstrated, but the correlation coefficient for the microscopic aggregation index technique did not reach significance (p greater than 0.20). Type O-positive red blood cells suspended in plasma from pregnant women also exhibited increased aggregation (p less then 0.001), thus suggesting plasma rather than cellular factors for the enhanced aggregation. Possible influences of abnormal fibrinogen structure during pregnancy are considered and the implications of increased red blood cell aggregation vis-à-vis altered blood viscosity are discussed.

ABO Blood-Group System↗
PubMed1983

Geometry of neonatal and adult red blood cells.

Red blood cell (RBC) geometry is a determinant of RBC deformability, survival time, osmotic resistance, and oxygen uptake. Because accurate information on the geometry of neonatal RBC appears lacking, a micropipette technique was employed to measure surface area and volume of individual neonatal and adult RBC. In addition, RBC diameter was determined microscopically. From these measurements, surface area index (actual surface area divided by area of sphere of same volume), swelling index (maximal volume divided by actual volume), minimum cylindrical diameter and mean thickness of RBC were calculated. Compared to adult cells, the volume of neonatal RBC was 21% larger, their surface area was 13% greater and their diameter 11% wider. The surface area-to-volume ratio of the neonatal RBC was 1.42 +/- 0.08 and that of the adult RBC was 1.49 +/- 0.06 (P less than 0.05). The minimum cylindrical diameter of the neonatal RBC was 3.04 +/- 0.25 microns and that of the adult RBC was 2.81 +/- 0.23 microns (P less than 0.05). Mean RBC thickness, surface area index and swelling index were not significantly different.

Adult↗
PubMed1982

The effect of moderate hypoxaemia on cardiac performance in the newborn during anaesthesia and surgery - experimental studies in newborn and two-week-old piglets.

Circulatory adaptation to hypoxaemia was studied under anaesthetic and surgical conditions in 10 newborn (age 8-42 h, weight 850-1800 g) and 8 two-week-old piglets (12-16 days, 1400-3600 g). Arterial PO2 was lowered from 60-100 mmHg to 30-40 mmHg by reducing FiO2 (concentration of oxygen during inspiration) at otherwise constant conditions; control studies were performed under the same standard conditions maintaining normoxaemia during the whole experiment in 8 newborn and 8 two-week-old piglets of comparable weight. In both hypoxic groups a prompt compensatory, statistically significant increase of cardiac performance defined by aortic blood pressure, cardiac output, peak aortic flow, stroke volume and cardiac power appeared within a few minutes of hypoxaemia, reaching a maximum half an hour later. Thereafter cardiac performance decreased steadily leading to cardiac failure. Newborns survived 197 +/- 96 min and two-week-old animals 172 +/- 128 min. Peripheral vascular resistance decreased significantly at the time of compensatory increase of cardiac performance, but increased subsequently to a maximum shortly before cardiac failure. Compensatory increase of cardiac performance was more distinct in newborn than in two-week-old piglets. Heart rate increased steadily during exposure to hypoxaemia in both groups reaching a maximum 110 min later and falling back to pre-experimental levels at the end of study. The newborn normoxic controls tolerated the experimental model significantly longer (461 +/- 167 min; P less than 0.001) than the newborn hypoxic piglets. Their response pattern, however, was basically similar. Increase of cardiac performance reached its maximum not before 130 min after the end of the pre-experimental period with subsequent fatal decrease of cardiac performance leading to cardiac failure. Two-week-old normoxic control animals responded qualitatively identically compared with the two-week-old hypoxic animals. Despite normoxaemia their average survival time did not differ significantly (209 +/- 86 min). In all four groups severe metabolic acidosis appeared in most instances during the study, irrespective of hypoxaemia or normoxaemia. Failure of stress tolerance depended on the decrease of pH per hour. This relation was more distinct in normoxic animals. In both hypoxic groups survival time correlated well with the increase of heart rate during hypoxaemia (R = 0.71 in newborn, P less than 0.05; R = 0.86 in two-week-old piglets, P less than 0.01, respectively). This correlation could not be found in the normoxic piglets.

Adaptation, Physiological↗
PubMed1982

Deformability of density separated red blood cells in normal newborn infants and adults.

The deformability of neonatal and adult red blood cells (RBC) was studied using both unseparated and density (i.e., age) fractionated RBC. Blood samples were obtained from 10 normal newborn infants (placental blood) and 10 adults. Deformability was measured by direct microscopic observation of RBC subjected to shear stresses of 2.5-500 dynes/cm2 using a counter-rotating Rheoscope. There was no significant difference in deformability between unseparated neonatal and adult RBC at any shear stress. The 3% least dense ("youngest") RBC showed significantly decreased hemoglobin concentrations (MCHC), increased volumes (MCV) and elevated deformability at any shear stress when compared to the 3% most dense ("oldest") cells, with the values for the unseparated RBC lying between these two extremes. The least dense neonatal RBC had a significantly lower MCHC and higher deformability than the least dense adult cells; however, the most dense neonatal RBC had lost more volume than the adult cells (33 versus 17%), had a higher MCHC, and were less deformable than the most dense adult cells. This indicates that the accelerated decrease in deformability of aging neonatal RBC is related to the more pronounced increase in MCHC, which is the principal determinant of the internal viscosity of the RBC.

Adult↗
PubMed1982

Geometric, osmotic, and membrane mechanical properties of density-separated human red cells.

Although there is evidence that the deformability of the entire red blood cell (RBC) decreases during aging, reports on changes in relevant specific properties associated with the aging process are limited and not in total agreement. The purpose of this study was to evaluate some of the factors that might contribute to this decreased deformability. Geometric, osmotic, and membrane mechanical properties of unfractionated, top ("young") and bottom ("old") RBC from 5 healthy adult donors were measured using micropipette techniques. Surface area, volume, and diameter of RBC were measured at osmolalities of 297, 254, 202, and 153 mosm/kg. Two membrane mechanical properties, surface shear modulus of elasticity (mu) and time constant (tc) of viscoelastic recovery, were studied only in isotonic media. At each of the osmolalities, volume and surface area of the bottom cells were about 25% lower than those of the top cells. Bottom cells showed smaller increases in volume with decreasing osmolality than top cells; the surface area remained constant with changing osmolality for all three groups. The surface area-to-volume ratio and the minimum cylindrical diameter of the bottom cells were essentially identical to the top cells. However, both the surface area index (actual are of RBC divided by area of a sphere of same volume) and the swelling index (maximal volume divided by actual volume) of the bottom cells were significantly lower than top RBC. The shear modules of elasticity (mu) was about 0.006 dyne/cm in all 3 RBC populations, indicating that the forces necessary to deform a portion of the membrane did not change with RBC aging. The viscoelastic time constant (tc) was 0.148 +/- 0.020 (SD) sec for the bottom RBC and 0.099 +/- 0.017 sec for the top cells. This difference indicates that shape recovery following membrane deformation is delayed in old RBC. The membrane surface viscosity (eta), calculated as the product of tc times mu was 0.95 +/- 0.22 x 10(-3) dyne-sec/cm for the bottom cells and 0.54 +/- 0.15 x 10(-3) for the top RBC. These data indicate that the relative deficit in membrane surface area and the increased membrane viscosity of old RBC may be important determinants for their decreased deformability and their eventual removal from the circulation.

Biomechanical Phenomena↗
PubMed1981

Blood volume in newborn piglets: effects of time of natural cord rupture, intra-uterine growth retardation, asphyxia, and prostaglandin-induced prematurity.

Blood volume (BV), red cell mass (RCM; Cr-51) and plasma volume (125I-labeled albumin) were measured in 205 piglets from 28 litters shortly after birth. Spontaneous cord rupture in healthy piglets occurred during delivery (n = 25) or within 190 sec of birth (n = 82). Spontaneous and induced delay of cord rupture resulted in a time-dependent increase in BV and RCM. BV (x +/- S.D.) at birth was 72.5 +/- 10.5 ml/kg (RCM, 23.6 +/- 4.6 ml/kg) in the 25 piglets with prenatal cord rupture and 110.5 +/- 12.9 ml/kg (RCM, 38.4 +/- 7.0 ml/kg) in 17 piglets with late spontaneous cord rupture. The mean blood volume of all the 107 healthy piglets with spontaneous cord rupture was 90.2 +/- 12.7 ml/kg (RCM, 30.1 +/- 4.8 ml/kg). RCM was significantly (P less than 0.05) increased in nine piglets with intra-uterine growth retardation (RCM, 35.8 +/- 11.2 ml/kg) and in 13 with metabolic acidosis but without signs of asphyxia (RCM, 35.8 +/- 6.7 ml/kg). In five piglets with cord wrapping, prenatal cord rupture, and acute asphyxia, BV (57.8 +/- 7.3 ml/kg) was significantly decreased. In five other piglets with prenatal cord rupture and acute asphyxia, BV (67.9 +/- 10.0 ml/kg) corresponded to that of the normal piglets with prenatal cord rupture. However, delay of cord rupture to 60 sec after birth did not increase BV (66.0 +/- 11.8 ml/kg) in four piglets with acute asphyxia. Forty-one premature piglets delivered 6 days before normal term had their cords ruptured prenatally or within 5 sec of birth. Their hematocrit at birth (0.337 +/- 0.028 liters/liter) was significantly decreased compared to the normal full-term piglets with corresponding time of cord rupture (0.384 +/- 0.033 liters/liter). RCM in 18 piglets with prostaglandin-induced prematurity (18.9 +/- 3.4 ml/kg) was significantly lower than in 23 piglets whose births had been induced by ovarectomy of their mother (RCM, 22.1 +/- 3.2 ml/kg).

Animals↗
PubMed1980

Blood volume and hematocrit in various organs in newborn piglets.

Plasma volume and red cell mass of various organs in piglets aged 24 hr (n = 7) and 7 (n = 6), and 14 (n = 6) days were measured using 99mTc-labeled albumin and 51Cr-labeled red blood cells. Organ activities were counted in a whole-body counter. Blood volume and hematocrit were calculated. The blood volumes in microliters/g varied markedly between various organs. The lowest blood volumes at 24 hr of age were found in skin (21.9 +/- 5.0 microliter/g), brain (33.3 +/- 8.4), and skeletal muscle (35.5 +/- 7.4). The highest values at this age were noted in liver (670.0 +/- 89.1), lung (533.8 +/- 80.7), spleen (332.0 +/- 82.8), and kidney (300.6 +/- 55.5). Blood volumes of about 150 microliters/g were observed in heart muscle and thyroid gland and those of about 100 microliters/g in thymus and gastrointestinal tract. The total blood volume was 100.2 +/- 3.9 microliters/g at 24 hr and remained unchanged during the first 2 wk of life. A significant decrease in relative blood volume with growth was noted in liver and lung (P less than 0.01), and in skeleton (P less than 0.05). The blood volume, contained in the great vessels outside the organs, increased from 29.5 +/- 5.5% of total blood volume at 24 hr to 31.2 +/- 5.7% at 7 days and to 38.2 +/- 7.5% at 14 days of life. The total body-venous hematocrit ratio was about 0.84. Accordingly, tissue hematocrits of most organs were below the venous hematocrit. Only in spleen was the tissue/venous hematocrit ratio (TH/VH) higher than 1.0. TH/VH of brain, gastrointestinal tract, thyroid gland, and thymus approached unity. The lowest TH/VH was found in kidney (0.54 +/- 0.08 at day 1). In skin, the TH/VH decreased from 0.98 +/- 0.10 to 0.82 +/- 0.07 during the first 2 wk of life.

Animals↗
PubMed1980

[Collodion baby and harlequin fetus. Comparison of 2 cases].

Two cases of severe congenital ichthyosis are presented: "collodion baby" and "harlequin fetus". The collodion baby is no clinical entity, but a symptom occurring in several forms of ichthyosis. In our patient the collodion skin was a symptom of ichthyosis congaenita (lamellar ichthyosis). Treatment with orally administered steroids was life-saving. The harlequin fetus represents a distinct entity characterized by a lethal genotype. There is a molecular defect of keratinization.

Female↗
PubMed1980

[Cardiovascular adaptation of the newborn to stress situations: effects of hypoxia on newborn and 14-day-old piglets (author's transl)].

-Newborn and 14-day-old piglets (in a developmental stage equivalent to that of a 3-month-old infant) compensate sustained hypoxemia by increasing cardiac performance. -This compensation can be maintained for only roughly 30 min. -Newborn piglets free from hypoxemia are able to tolerate the stress of anesthesia, artificial respiration, and operation significantly longer than those with additional hypoxemia. -14 day-old piglets without hypoxemia are not able to tolerate the stress of anesthesia, artificial respiration, and operation longer than those with additional hypoxemia. -The reactions of the cardiovascular system to anesthesia, artificial respiration, and operation in present or absent additional hypoxemia are qualitatively identical and are also identical in time in the newborn hypoxic, the 14-day-old hypoxic, and normoxic animals, whereas they appear significantly later in newborn control piglets.

Animals↗
PubMed1980

Tc-99m-labeled red blood cells for the measurement of red cell mass in newborn infants: concise communication.

In vitro and in vivo investigations were performed to examine the binding of Tc-99m to neonatal red blood cells (RBC). Labeling efficiency was about 90%, and unbound Tc-99m less than 3% after one washing, in premature and full-term newborns and in children. Thus presence of high percentages of fetal hemoglobin (Hb F) did not influence the labeling of RBCs with Tc-99m. RBCs of 11 newborns were hemolysed and the distribution of Tc-99m on RBC components was analyzed. Although Hb F percentage averaged (60.0 +/- 8.1)% (s.d.), only (11.9 +/- 3.7)% of Tc-99m was bound by Hb F, whereas (45.0 +/- 6.1)% was associated with Hb A. RBC membranes bound (13.7 +/- 4.3)% and (29.3 +/- 4.0)% were found unbound in hemolysates. These results indicate that Tc-99m preferentially binds to beta chains. In vivo equilibration of Tc-99m RBCs and of albumin labeled with Evans blue was investigated in five newborn infants. Tc-99m RBCs were stable in each case during the first hour after injection. Elution of Tc-99m from RBCs was (3.4 +/- 1.5)% per hour. Body-to-venous hematocrit ratio averaged 0.86 +/- 0.03.

Child↗
PubMed1979

[Radiologic findings in newborns with group B streptococcal septicemia: clinical importance of heart size and lung manifestations (author's transl)].

Chest radiographs of thirteen neonates with group B streptococcal septicemia were evaluated for signs of early diagnosis. Six of the neonates had chest radiographs as seen in idiopathic respiratory distress syndrome (RDS). Seven patients had radiologic findings consistent with neonatal pneumonia. The children with RDS were in general smaller and born prematurelly, but three neonates with x-rays resembling RDS had normal birth weights and thus were mature. Cardiomegaly was observed in a high percentage with a prevalence in children with RDS. Heart size increased in two of the three children who died, but became normal in patients recovering from infection. Three patients had pleural effusions.

Birth Weight↗