Biomedical subjects

O Linderkamp

Publications and source records attributed to O Linderkamp.

At least 55 records · Page 3Linked to original sources

PubMed1999

[Trans-scleral diode laser coagulation for therapy of acute retinopathia praematurorum].

BACKGROUND: Lens opacities were noted in single cases after transpupillar laser photocoagulation in retinopathy of prematurity (ROP) using the laser indirect ophthalmoscope. The diode laser with its wavelength in the near infrared (810 nm) makes lens sparing transscleral retinal coagulation possible. PATIENTS AND METHODS: In a controlled clinical study 60 eyes of 30 very low birth weight infants (gestational age 23-31 weeks, mean 26.6 +/- 1.8 weeks; birth weight 510-1200 g, 856 +/- 170 g) with threshold ROP were treated with diode laser photocoagulation. One eye of each infant was coagulated transsclerally while the fellow eye had transpapillary coagulation using the laser indirect ophthalmoscope. Follow-up ranged from 2 to 38 months (19 +/- 11 months). RESULTS: In 29 (97%) out of 30 eyes treated transsclerally and in 30 (100%) out of 30 eyes treated transpapillary the outcome was a flat, attached retina. Three eyes had a second laser treatment and 2 eyes had additional retinal detachment surgery. One eye (3%) with zone I disease failed after transscleral laser treatment and additional retinal detachment surgery with partially detached retina (stage 4 B) No adverse side effects as a result of laser treatment were noted except for a small amount of retinal/preretinal bleeding in the ridge and a vitreous bleeding. There were no adverse side effects (e.g., bleeding, cataract formation) in the anterior segments of the eyes. CONCLUSION: Transscleral diode laser coagulation for treatment of threshold ROP proved to be as effective as transpapillary diode laser photocoagulation. Only minor side effects were noticed. Transscleral diode laser photocoagulation is an advantageous treatment method in eyes with preexisting risk of cataract formation in transpapillary laser treatment.

Child, Preschool↗

PubMed1999

Deformability and geometry of neonatal erythrocytes with irregular shapes.

More stomatocytes, spherocytes, and erythrocytes with spicules and protrusions are found in blood from newborn infants than in blood from adults. The objective of this study was to measure volume, surface area, membrane rigidity, and viscosity of red blood cells (RBC) with irregular shapes in preterm and full-term neonates. RBC from 13 full-term and 12 preterm (25-36 wk of gestation) infants were studied by means of a micropipette system. In full-term neonates and in preterm infants, 19 and 26% of RBC, respectively, showed shapes different from those of discocytes. Keratocytes, spherocytes, akanthocytes (in full-term infants), and elliptocytes (in preterm infants) had smaller volumes than did discocytes (p < 0.05). Spherocytes showed decreased and elliptocytes had increased excess surface area and swelling capacity compared with discocytes, indicating both volume and membrane loss for spherocytes and only volume loss for elliptocytes. Immature RBC and knizocytes had similar large volumes and surface areas, suggesting that knizocytes in neonates are relatively young RBC. Increased membrane rigidity was found only in stomatocytes. Membrane viscosity was decreased in immature RBC and knizocytes and increased in stomatocytes, keratocytes, akanthocytes, and elliptocytes when compared with discocytes. There were inverse relationships between RBC volume and membrane rigidity (r=-0.42) and between RBC volume and membrane viscosity (r=-0.72). This suggests that volume loss of neonatal RBC is associated with impaired membrane deformability. Moreover, we conclude that the geometry and membrane deformability of some of the irregularly shaped neonatal RBC resemble properties of RBC in hemolytic anemias (e.g. spherocytosis).

Biomechanical Phenomena↗

PubMed1998

Fas or ceramide induce apoptosis by Ras-regulated phosphoinositide-3-kinase activation.

We demonstrate a rapid and transient activation of phosphoinositide-3-kinase (PI-3-K) by Fas receptor triggering or cellular treatment with synthetic C6-ceramide. The stimulation of PI-3-K is critical for Fas or C6-ceramide-induced programmed cell death because transfection with a transdominant inhibitory PI-3-K construct or pre-treatment with the PI-3-K inhibitor wortmannin almost completely prevented Fas or C6-ceramide-mediated apoptosis. Treatment with the caspase inhibitor Ac-YVAD-cmk or cellular transfection with transdominant inhibitory N17Ras prevented PI-3-K stimulation by Fas, suggesting that Fas activates PI-3-K via caspases and Ras. N17Ras expression also prevented C6-ceramide-initiated PI-3-K stimulation. The notion of a PI-3-K regulation by Ras upon Fas receptor ligation or ceramide treatment is supported by co-immunoprecipitation experiments revealing an activation-dependent association of PI-3-K and Ras.

Androstadienes↗

PubMed1998

Cellular stimulation via CD95 involves activation of phospho-inositide-3-kinase.

Several distinct intracellular pathways have been recently shown to be activated during CD95/Fas/APO-1-mediated apoptosis. Here, we demonstrate that CD95 ligation induces a rapid and transient tyrosine phosphorylation and activation of phosphoinositide-3-kinase (PI-3-K) in Jurkat T lymphocytes or CD95-sensitive glioma cells. Experiments using p56lck-deficient or p56lck-reconstituted Jurkat clones and the tyrosine kinase inhibitor herbimycin A revealed that tyrosine phosphorylation and activation of PI-3-K by CD95 depends on expression of Src-like tyrosine kinases, in particular p56lck. PI-3-K stimulation seems to be critical for CD95 receptor signalling since, first, inhibition of PI-3-K prevents CD95-mediated apoptosis and, second, CD95 receptor ligation fails to induce tyrosine phosphorylation or activation of PI-3-K in CD95-resistant glioma cells. Thus, PI-3-K activation may be an early signalling event during CD95-induced apoptosis, and failure to stimulate PI-3-K may predict tumor cell resistance to CD95-triggered apoptosis.

Apoptosis↗

PubMed1998

Cardiorespiratory stability of premature boys and girls during kangaroo care.

The objective of the investigation was to study the stability of the cardiorespiratory system of 20 premature boys and girls during maternal kangaroo care (KC) and in the incubator. Stability of heart rate, respiration and oxygen saturation was compared in a pretest-test-posttest design by means of a stability score. The three stability items and the total stability did not change significantly during the three conditions. In some individuals the stability either increased or decreased markedly during Kangaroo Care. The boys showed significantly less cardiorespiratory stability both during kangaroo care and in the incubator compared to the girls.

Female↗

PubMed1998

Meconium aspiration syndrome complicated by massive intravascular thrombosis.

Fetal aspiration of meconium in amniotic fluid during fetal distress by newborn infants can induce the meconium aspiration syndrome (MAS), a form of neonatal respiratory distress. Should this event occur, admission to a Neonatal Intensive Care Unit and vigorous airway management and monitoring are required. We present a term gestation resulting in MAS complicated by a massive intravascular thrombosis. Despite airway management considered appropriate, the infant developed respiratory distress a few hours after birth and died 5 days later. Postmortem examination showed a diffuse alveolar damage of the lungs with alveoli filled with meconium and amniotic epithelial cells as well as disseminated thrombi in the pulmonary vascular tree, portal system, suprahepatic veins, and peripheral arterial vascular tree.

Diagnosis, Differential↗

PubMed1998

Isolation of Klebsiella planticola from newborns in a neonatal ward.

This is the first report on the isolation of Klebsiella planticola from neonates. Over a period of 1 year, oropharyngeal and rectal swab specimens from 131 newborns on a neonatal ward were monitored for Klebsiella spp. Thirteen strains of K. planticola could be isolated, and these represented 9% of all Klebsiella spp. found. Capsule type K27 predominated, followed by capsule type K68. Our findings suggest a significant rate of colonization by K. planticola among neonates.

Anti-Bacterial Agents↗

PubMed1998

Longitudinal evaluation of salivary cortisol levels in full-term and preterm neonates.

The aim of the present study was to test the practicability of sequential cortisol determinations in saliva of low birth weight neonates and to evaluate the impact of systemic and inhaled glucocorticoid therapy on saliva concentrations of cortisol in preterm neonates with bronchopulmonary dysplasia (BPD). Salivary cortisol levels were measured by RIA in saliva samples from 10 full-term and 10 preterm healthy neonates and from 20 preterm neonates with BPD during systemic [dexamethasone (DEX); n = 10] or topical steroid therapy [budesonide (BUD); n = 10]. Saliva samples of each individual were collected on 3 consecutive days at 06.00, 12. 00, 18.00 and 24.00 h. Cortisol levels in saliva ranged from 0.8 to 60.6 nmol/l (median 6.5 nmol/l) in full-term neonates, from 0.6 to 52.1 nmol/l (median 5.5 nmol/l) in preterm neonates, from 0.4 to 14. 0 nmol/l (median 1.0 nmol/l) in preterm neonates treated with DEX and from 0.4 to 15.2 nmol/l (median 2.5 nmol/l) in preterm neonates treated with BUD. Autocorrelation analysis revealed a distinct endogenous cortisol rhythm in 2 of the 10 healthy full-term neonates and in 3 of the 10 healthy preterm neonates with a wavelength of 12-30 h. Salivary cortisol levels in preterm neonates treated with DEX or BUD were significantly lower than those measured in healthy preterm neonates. These results demonstrate that the measurement of salivary cortisol levels is a reliable and practicable way of assessing adrenal function in full-term and preterm neonates. This study also shows for the first time that some neonates display an endogenous cortisol rhythm which is not coupled to the exogenous day/night cycle. Furthermore, systemic and nebulized glucocorticoids suppress adrenal function in low-birth-weight neonates. After treatment these children should be closely monitored for potential adrenal insufficiency.

Administration, Topical↗

PubMed1998

Do healthy premature infants fed breast milk need vitamin E supplementation: alpha- and gamma-tocopherol levels in blood components and buccal mucosal cells.

Prematurely born, low birth weight infants are generally considered to be marginally vitamin E-deficient. Vitamin E deficiency has so far been defined as a low plasma alpha-tocopherol level (below 500 microg/dL) accompanied by a low tocopherol to lipid ratio or increased hydrogen peroxide hemolysis of erythrocytes. In the present study, we determined alpha- and gamma-tocopherol in plasma, red blood cells, platelets, buccal mucosal cells, monocytes, and polymorphonuclear leukocytes of premature infants to assess vitamin E status. Fourteen healthy, premature infants with birth weight (mean +/- SD) 1439 +/- 364 g and gestational age 30 +/- 1.7 wk were enrolled in the study. Alpha- and gamma-tocopherol were determined in cord blood and on d 0 to 1, 7, 14, 28, and 42 after birth in plasma and various cell types. Moreover, two randomly selected human milk samples were studied in each mother. Although subclinical or biochemical vitamin E deficiency was seen in healthy, premature infants in the first 6 wk of life in plasma and buccal mucosal cells, the other cells showed no such deficiency during the study. We conclude that these infants do not need routine vitamin E supplementation.

Birth Weight↗

PubMed1998

Passive deformability of mature, immature, and active neutrophils in healthy and septicemic neonates.

Obstruction of narrow vessels by rigid neutrophils may contribute to ischemic organ injury. In septicemia, a substantial portion of the neutrophils may become activated and the number of circulating immature neutrophils may rise sharply. Volume and deformability of mature (PMN) and immature neutrophils in healthy preterm and full-term infants and in septicemic neonates were studied by means of a micropipette system. Membrane cytoplasm tongues were aspirated into 2.5-microm (diameter) pipettes over a period of 60 s. Volume and tongue growth of mature resting PMN were similar in healthy preterm and full-term neonates and adults. Compared with mature PMN (about 360 fl), the volumes of band cells (415 fl), metamyelocytes (470 fl), and less mature cells (myeloblasts, promyelocytes, and myelocytes; 490 fl) were significantly increased (p < 0.005). Final tongue lengths of band cells, metamyelocytes, and less mature cells were decreased by about 50, 60, and 70%, respectively, when compared with passive mature cells. In septic neonates, the percentage of immature neutrophils was increased, but the deformability and volume of the cell subpopulations were not affected by septicemia. Active PMN were characterized by pseudopod formation. More active PMN were found in group B streptococcal (14% of total PMN), gram-negative (12%), and Staphylococcus epidermidis septicemia (8%) than in healthy neonates and adults (4%). The main bodies of active PMN were less deformable than passive PMN, and the pseudopods showed very little membrane deformation. The increased number of rigid active and immature neutrophils may contribute to impaired microcirculation and the high risk for organ injury in septic patients.

Adult↗

PubMed1998

Wolf-Hirschhorn syndrome: case report and review of the chromosomal aberrations associated with diaphragmatic defects.

A female fetus showing severe growth retardation was delivered at 31 weeks of gestation because of fetal distress. At birth, the infant showed bradycardia and no spontaneous breathing. Although high frequency oscillatory ventilation was started, severe asphyxia persisted and the infant died of respiratory insufficiency. At the autopsy, the propositus showed microcephaly, prominent glabella, broad bridge of the nose, ocular hypertelorism, poorly differentiated and low-set ears, bilateral palatoschisis, and micrognathia. Midline closure defects of the cervical spine bodies, lower jaw, and skull base were seen at postmortem radiography. An extreme hypoplasia of both lungs, a large defect of the left diaphragm with upward displacement of viscera, and multiple cortical cysts in both kidneys were seen at postmortem examination. Karyotyping revealed a chromosomal imbalance with 46, XX, del(4) (pter-->13), characterizing the Wolf-Hirschhorn syndrome. Because diaphragmatic defects can occur in association with specific recognizable patterns of human malformation careful pathologic and genetic workup of all affected infants in crucial for accurate genetic counseling.

Abnormalities, Multiple↗

PubMed1998

[A method for reducing the risk of infection in newborn and premature infants with stomas].

Prematures and neonates with stomas have a high risk of developing sepsis by bacterial translocation, particularly when combined with parenteral nutrition. We studied a group of 35 newborns where split ileo- or jejunostomas were implanted in their first week of life. To prevent the development of a non-used distal bowel and a short bowel syndrome, the proximal bower content was transferred into the aboral stoma via the new continuous extracorporal stool transport (CEST) technique a few days after surgery. By using CEST the sepsis rate was reduced from 9 (without CEST) to only 0.8 cases of sepsis in 1000 days.

Bacterial Translocation↗

PubMed1997

Stimulation of TK1 lymphoma cells via alpha 4 beta 7 integrin results in activation of src-tyrosine- and MAP-kinases.

The lymphocyte integrin alpha 4 beta 7 is a cell surface adhesion receptor involved in initiating lymphocyte homing to gut-associated/mucosal lymphoid tissues by binding the mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Other known ligands are vascular cell adhesion molecule-1, fibronectin, and the alpha 4 integrin chain itself. Here, we demonstrate that stimulation of the alpha 4 beta 7 integrin through its alpha 4 subunit (mAb R1-2), beta 7 subunit (mAb M293), or the combinatory epitope (mAb DATK32) enhances tyrosine phosphorylation of several cellular proteins in the murine TK1 lymphoma cell line. The two src-kinases p56lck and p59fyn were identified as possible mediators and substrates of the detected tyrosine phosphorylation. Furthermore, we observed activation of the MAP-kinases ERK1/2.

Animals↗

PubMed1997

Fas- or ceramide-induced apoptosis is mediated by a Rac1-regulated activation of Jun N-terminal kinase/p38 kinases and GADD153.

In the present study, we show that Fas receptor ligation or cellular treatment with synthetic C6-ceramide results in activation or phosphorylation, respectively, of the small G-protein Rac1, Jun N-terminal kinase (JNK)/p38 kinases (p38-K), and the transcription factor GADD153. A signaling cascade from the Fas receptor via ceramide, Ras, Rac1, and JNK/p38-K to GADD153 is demonstrated employing transfection of transdominant inhibitory N17Ras, N17Rac1, c-Jun, or treatment with a specific p38-K inhibitor. The critical function of this signaling cascade is indicated by prevention of Fas- or C6-ceramide-induced apoptosis after inhibition of Ras, Rac1, or JNK/p38-K.

Antigens, Surface↗

PubMed1997

L-selectin regulates actin polymerisation via activation of the small G-protein Rac2.

L-selectin mediated adhesion to endothelial cells is a crucial step in the immune response to pathogens (1, 2) and in lymphocyte homing (3, 4). Selectin molecules mediate leukocyte rolling on endothelial cells, the initial step of adhesion (5, 6). We have previously shown that stimulation of Jurkat T-lymphocytes via L-selectin results in activation of the p21Ras pathway and synthesis of reactive oxygen intermediates (7). Here, we show that cellular stimulation via L-selectin induces a change of cytoskeleton organisation demonstrated by a tenfold increase of actin filament polymerisation. This actin polymerisation is mediated by a Ras and Rac2 regulated pathway, since inhibition of Ras by transient transfection of transdominant inhibitory N17Ras or suppression of Rac2 protein expression by antisense oligonucleotides prevents L-selectin triggered actin polymerisation. Our results point to a signaling cascade from L-selectin via Ras and Rac2 to actin filaments, which might be important for leukocyte adhesion.

Actin Cytoskeleton↗

PubMed1997

Transscleral vs transpupillary diode laser photocoagulation for the treatment of threshold retinopathy of prematurity.

OBJECTIVE: To evaluate the efficacy and safety of transscleral diode laser photocoagulation for the treatment of threshold retinopathy of prematurity (ROP). PATIENTS: Fifty eyes of 25 preterm infants (birth weight, 510-1200 g [864+/-178 g ¿mean+/-SD¿]; gestational age, 24-29 weeks [26.7+/-1.7 weeks]) with threshold ROP were treated with diode laser photocoagulation (wavelength, 810 nm). One eye of each infant was treated transsclerally while the fellow eye had transpupillary coagulation using the laser indirect ophthalmoscope. Follow-up ranged from 2 to 22 months (10.0+/-5.3 months). MAIN OUTCOME MEASURE: The regression of acute ROP and the incidence of adverse treatment effects. RESULTS: In 25 (100%) of the eyes treated transpupillarly and in 24 (96%) of the eyes treated transsclerally, ROP regressed after a single or a second laser treatment and the outcome was a flat, attached retina. One eye (4%) with disease in zone I failed to improve after transscleral laser treatment and ROP progressed to stage 4B with a partially attached retina, although additional retinal detachment surgery with an encircling band was performed. No adverse side effects as a result of diode laser treatment were noted except for a small amount of retinal-preretinal bleeding in the ridge in 9 (36%) of the transsclerally and in 5 (20%) of the transpupillarly coagulated eyes. There were no adverse side effects (eg, cataract formation) in the anterior segments of the eyes. CONCLUSIONS: The results suggest that transscleral diode laser coagulation is as effective in the treatment of threshold ROP as transpupillary diode laser photocoagulation. Only minor side effects were noted. Transscleral diode laser photocoagulation seems to be an advantageous treatment method if transpupillary treatment bears an increased risk of cataract formation.

Acute Disease↗

PubMed1997

Assessment of energy expenditure in metabolic disorders.

The assessment of energy expenditure is valuable for the management of children with various conditions such as obesity and failure to thrive. Total daily energy expenditure (TDEE) includes resting energy expenditure (REE), energy expenditure during physical activity, dietary thermogenesis and growth. TDEE can be assessed by using the double-labelled water technique, but it has complex pitfalls and potential sources of errors and is impractical for everyday use. As REE is a substantial part of TDEE (65%-70%) and computerised indirect calorimeters have become recently available, this non-invasive, relatively cheap and easy to use technique is valuable for the assessment of short-term changes in energy metabolism. This can be used to assess REE of children with inborn errors of metabolism, whilst well and during episodes of metabolic decompensation and therefore to accurately determine energy intake.

Calorimetry, Indirect↗

PubMed1997

Effects of high-frequency oscillatory ventilation on circulation in neonates with pulmonary interstitial emphysema or RDS.

OBJECTIVE: Mechanical ventilation may impair cardiovascular function if the transpulmonary pressure rises. Studies on the effects of high-frequency oscillatory ventilation (HFOV) on cardiovascular functions have yielded conflicting results. This study was done to compare alterations in left ventricular output and blood flow velocities in the anterior cerebral artery, internal carotid artery, and celiac artery using a Doppler ultrasound device before and 2 h after initiating HFOV in neonates with respiratory distress syndrome (RDS) or pulmonary interstitial emphysema (PIE). DESIGN: Prospective clinical study. SETTING: Neonatal intensive care unit in a perinatal center. PATIENTS: 18 critically ill infants (postnatal age 47 +/- 12 h; mean +/- SD) were studied before and during HFOV (piston oscillator). Indications for HFOV were severe respiratory failure due to PIE (n = 10) and severe surfactant deficiency (RDS, n = 8). In the RDS group, gestational age was 27 +/- 6 weeks (range 26-31 weeks) and birth-weight 1620 +/- 380 g (range 850-1970 g). In the PIE group, gestational age was 28 +/- 2 weeks (range 26-36 weeks) and birth-weight 1740 +/- 470 g (range 890-2760 g). MEASUREMENTS AND MAIN RESULTS: During HFOV, mean airway pressure was maintained at the same level as during intermittent mandatory ventilation in both groups (RDS, 12 +/- 2 cmH2O; PIE, 10 +/- 2 cmH2O). Compared to intermittent mandatory ventilation, several of the 12 parameters studied changed significantly (p < 0.004) during HFOV. In the RDS group, the partial pressure of oxygen in arterial blood/fractional inspired oxygen (PaO2/FIO2) ratio increased from 56 +/- 9 to 86 +/- 7 and partial pressure of carbon dioxide in arterial blood (PaCO2) decreased from 49 +/- 4 to 35 +/- 3 mmHg. In the PIE group, PaO2/FIO2 ratio increased from 63 +/- 8 to 72 +/- 7 and PaCO2 decreased from 63 +/- 7 to 40 +/- 5 mmHg. In the PIE group, heart rate decreased (135 +/- 15 before HFOV vs 115 +/- 14 min-1 during HFOV) and mean systolic blood pressure increased (before 43 +/- 4 vs 51 +/- 4 mmHg during HFOV) significantly, whereas these parameters did not change in the RDS group. Left ventricular output increased significantly in the PIE group (210 +/- 34 before vs 245 +/- 36 ml/kg per min during HFOV; p < 0.004), but not in the RDS group (225 +/- 46 before vs 248 +/- 47 ml/kg per min during HFOV; k < 0.05). Shortening fraction and systemic resistance did not change in either group. In the PIE group, mean blood flow velocities in the internal carotid artery (+59%), anterior cerebral artery (+65%) and celiac artery (+45%) increased significantly but did not change in the RDS group. CONCLUSIONS: The results show that HFOV as used in this study, improves oxygenation, CO2 elimination, and circulation in infants with RDS and PIE. However, systemic, cerebral, and intestinal circulation improved more in neonates with PIE than in those with RDS. This may be due to higher pulmonary compliance in infants with PIE when compared to those with RDS.

Blood Flow Velocity↗