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H Franke

Publications and source records attributed to H Franke.

At least 19 recordsLinked to original sources
PubMed1999

An improved low-permeability in vitro-model of the blood-brain barrier: transport studies on retinoids, sucrose, haloperidol, caffeine and mannitol.

Primary cultures of porcine brain capillary endothelial cells grown on collagen coated polycarbonate membranes were used to build up an in vitro-model for the blood-brain barrier. Improved cultivation techniques allowed cell-storage and experiments under serum-free conditions. We employed this model to perform permeability studies in vitro with the radioactively labelled marker substances sucrose, retinoic acid, retinol, haloperidol, caffeine, and mannitol. Permeability values obtained with this blood-brain barrier model (1. 0x10-6 cm/s for sucrose, 6.2x10-6 cm/s for retinoic acid, 4.8x10-6 cm/s for retinol, 49.5x10-6 cm/s for haloperidol, 62.4x10-6 cm/s for caffeine, and 1.8x10-6 cm/s for mannitol) show a good correlation to data which are already known from in vivo-experiments. As judged by the sucrose permeability our blood-brain barrier model is less permeable than numerous other models published so far. Therefore it represents a powerful tool for in vitro-prediction of blood-brain barrier permeability of drugs and offers the possibility to scan a large quantity of drugs for their potential to enter the brain.

Animals↗
PubMed1998

Hydrocortisone reinforces the blood-brain properties in a serum free cell culture system.

The increasing number of newly developed drugs demands for functional in vitro models of the blood-brain barrier to determine their brain uptake. Cultured cerebral capillary endothelial cells are considered to be such a model, however in serum containing media they exhibit low electrical resistances and high permeabilities compared to the in vivo situation. Here we report the establishment of a serum-free cell culture model. Withdrawal of serum already caused a twofold increase of transendothelial resistance (TER), which in presence of serum is about 100-150 Omega x cm2. We tested several supplements and found that hydrocortisone is a potent stimulator for the formation of barrier properties. TERs up to 1000 Omega x cm2 were measured in the presence of physiological relevant hydrocortisone concentrations. In correspondence to the TER increase hydrocortisone decreased cell monolayer permeability for sucrose down to 5x10(-7) cm/s, which is close to the in vivo value of 1.2x10(-7) cm/s and by a factor of five lower compared to cultures without hydrocortisone and in presence of serum.

Animals↗
PubMed1998

Hydrocortisone reinforces the blood-brain barrier properties in a serum free cell culture system.

The increasing number of newly developed drugs demands for functional in vitro models of the blood-brain barrier to determine their brain uptake. Cultured cerebral capillary endothelial cells are considered to be such a model, however in serum containing media they exhibit low electrical resistances and high permeabilities compared to the in vivo situation. Here we report the establishment of a serum-free cell culture model. Withdrawal of serum already caused a twofold increase of transendothelial resistance (TER), which in presence of serum is about 100-150 omega.cm2. We tested several supplements and found that hydrocortisone is a potent stimulator for the formation of barrier properties. TERs up to 1000 omega.cm2 were measured in the presence of physiological relevant hydrocortisone concentrations. In correspondence to the TER increase hydrocortisone decreased cell monolayer permeability for sucrose down to 5 x 10(-7) cm/s, which is close to the in vivo value of 1.2 x 10(-7) cm/s and by a factor of five lower compared to cultures without hydrocortisone and in presence of serum.

Animals↗
PubMed1998

Differential age-dependent expression of alpha2 adrenoceptor- and P2 purinoceptor-functions in rat locus coeruleus neurons.

Whole-cell patch clamp recordings were made in a pontine slice preparation of the rat brain containing the nucleus locus coeruleus (LC). In a first series of experiments, it was demonstrated that tyrosine hydroxylase-positive LC neurons of young (10-14 days of age) rats are multipolar with numerous dendrites. When pipettes filled with the marker molecule biocytin were used for recording, all cells exhibiting outward current responses to noradrenaline (100 microM) showed the morphology typical for LC neurons. At a holding potential of -80 mV, noradrenaline (100 microM) produced a comparably small outward current both in LC neurons of young (8-14 days) and older (18-23 days) rats. In contrast, 2-methylthio ATP (2-MeSATP; 100 microM) caused a relatively small inward current in the young animals, while inward current responses were much larger in most older animals (8 out of a total of 11). It is suggested that after birth there are probably no functional P2 purinoceptors present at LC neurons. Thereafter, P2 purinoceptor-function increases with age, reaching maturity only in animals older than 18 days.

Adenosine Triphosphate↗
PubMed1998

Expression of tenascin, fibronectin, and laminin in rat liver fibrogenesis--a comparative immunohistochemical study with two models of liver injury.

The aim of this study was to follow semiquantitatively by immunohistochemical means the alterations of the expression of the hepatic glycoproteins tenascin, fibronectin, and laminin in two different models of chronic liver injury, i.e. thioacetamide-induced liver cirrhosis and fibrosis after bile duct ligation. The tenascin distribution pattern observed during cholostasis-induced liver fibrosis showed some similarities, but also some differences in comparison with the results obtained after TAA intoxication. Most importantly, the data show that tenascin staining was detectable in almost all areas of the chronically injured livers up to 3 and 6 months in bile duct-ligated and chemically-injured livers, respectively. Thus, tenascin does not seem to play only a transient role in the fibrogenetic process as previously suggested. Laminin was strongly stained in proliferating ductules, whereas only a weak continuous distribution was observed along the sinusoidal wall. Furthermore, our findings confirm the role of fibronectin as a pacemaker of fibrosis. Regional differences in the kinetics of the expression of the glycoproteins may reflect local differences in their production by parenchymal or non parenchymal cells or regional patterns of proteolytic activity.

Animals↗
PubMed1997

Histological and biochemical changes induced by total bile duct ligation in the rat.

The aim of the present investigation was to assess in a correlated biochemical and morphological study the dynamics of fibrogenesis after bile duct ligation and to compare the time course of alterations with those occurring in thioacetamide induced liver fibrosis. The data show that, after bile duct obstruction, the deposition of connective tissue elements and formation of ductular proliferates rapidly set in. The index of fibroplasia correlated well with the changes of the OH-proline concentration of the liver. Comparing the biliary fibrosis with the thioacetamide induced liver fibrosis, the progress of the former occurred more rapidly, even though in both cases only a few necroses were observed. Therefore, we suggest that in biliary fibrosis other mechanisms are responsible for the rapid onset of production of extracellular material and proliferative processes than in thioacetamide-induced liver fibrosis.

Alanine Transaminase↗
PubMed1996

Model analysis of the contrasting effects of GM-CSF and G-CSF treatment on peripheral blood neutrophils observed in three patients with childhood-onset cyclic neutropenia.

Human cyclic neutropenia (CN) is a rare haematological disorder characterized by regular fluctuation in the serial count of blood neutrophils. The oscillations occur at subnormal levels with a stable 3-week period. To reduce the risk of serious infections during the severe neutropenic nadir phases (< 0.25 x 10(9) neutrophils/l) patients are usually treated with recombinant growth factors. Compared with G-CSF, which has been shown to enhance the amplitudes substantially, the response to GM-CSF is poor: neutrophil numbers are not amplified, the cycles remain unchanged or are dampened. However, two cases with a modest neutrophil increase have been reported in the literature. In a recently published clinical study the different effects of GM-CSF and G-CSF application have been investigated in the same patients. Based on a mathematical model of CN we previously proposed, the detailed neutrophil data measured in this study are analysed by simulation. The contrasting clinical results can be quantitatively explained by the model concept of regulatory control together with possible individual feedback defects, i.e. abnormally reduced mitotic responsiveness of granulopoietic progenitor cells to GM-CSF and G-CSF.

Cell Division↗
PubMed1995

Electrical resistance measurements on cerebral capillary endothelial cells--a new technique to study small surface areas.

We present a new method which allows resistance measurements in selected cell monolayer areas with a size of less than one mm2. Up to now cell-covered macroscopic filters with areas up to 5 cm2 have been used giving reliable results only in the absence of inhomogeneities or contaminating cells. The new measuring device is posed on the microscope optic to allow an optical characterization of the measuring area and enables us to scan the cell-covered filter. This method has been applied to determine a reversible modulation of the tightness of intercellular contacts between epithelial or endothelial cells in culture. Tight junction resistance is modulated by Ca2+ and basic amino acids in cultured porcine cerebral microvascular endothelial cells that represent the blood-brain barrier.

Animals↗
PubMed1995

Influence of chronic alcohol treatment on the GFAP-immunoreactivity in astrocytes of the hippocampus in rats.

The influence of long term application of 5% (v/v) ethanol over a period of 36 weeks and 10% (v/v) ethanol over a period of 4,12 and 36 weeks to Wistar rats was investigated. The qualitative alterations of astrocytes and quantitative changes of glial fibrillary acidic protein-immunoreactivity (GFAP-IR) in selected regions of the dorsal hippocampus were examined, using anti-GFAP and the avidin-biotin immunoperoxidase technique. After prolonged (36 weeks) consumption of 5% (v/v) ethanol insignificant alterations were observed. The administration of 10% (v/v) ethanol over 4 and 12 weeks led to an increase of the total GFAP-IR in the examined brain regions. Hypertrophy of the cell bodies and cytoplasmic processes were seen. After 36 weeks decreased total GFAP-IR was measured in all examined brain regions. Cell bodies and fibrillary processes stained less heavily, the number and length of the fibrillary processes decreased and the number of astrocytes in certain hippocampal regions (e.g. in stratum moleculare of the dentate gyrus) appeared reduced. The results show that exposition to ethanol led to the appearance of different astrocytic phenotypes, depending on the concentration and duration of ethanol application, on the age of animals and on hippocampal regions. It is suggested that GFAP can be used as a specific marker for ethanol-induced alterations of astrocytes.

Animals↗
PubMed1995

The effect of continuous G-CSF application in human cyclic neutropenia: a model analysis.

Human cyclic neutropenia (CN) is a rare haematological disorder characterized by oscillations of blood neutrophils at subnormal levels with a stable period of approximately 21 d. During the phase of severe neutropenia (neutrophils < 250 cells/microliters), which last 4-10 d, the patients are endangered by serious infections. Several authors report that continuous G-CSF application can elevate the blood neutrophils to such a level that the risk of infections is significantly reduced. Although the characteristic cycles are not eliminated by G-CSF, the period of the oscillations is shortened to 12-14 d. Based on a previously proposed computer-simulation model of human CN, the effects of continuous G-CSF application on CN are studied. It is shown how the known different cell-kinetic effects of G-CSF on granulopoiesis explain the clinical data in CN. The reduced length of the cycles emerges as a result of the transit time reduction of the post-mitotic granulopoietic cells by G-CSF. The measured increase of the neutrophil maxima is reproduced by the additional mitoses of the immature granulopoietic bone marrow cells induced by G-CSF. The slight elevation of the neutrophil nadirs can be attributed to a weak effect of G-CSF on the assumed underlying defect in CN (an abnormally small variance of the granulopoietic bone-marrow transit time).

Cell Cycle↗
PubMed1995

[Laparoscopic sigmoid resection].

Laparoscopic colorectal surgery not only presupposes knowledge in conventional surgery of the large bowel but also requires extensive experience in laparoscopic techniques. Furthermore every individual of the operating team should have suitable experience to guarantee effective co-operation. The presented study reports on 41 laparoscopic resections of sigmoid colon and upper rectum. The operations were carried out on 31 patients with benign and 10 patients with malignant diseases. In 1 case we had to change to an open procedure. Postoperative complications were seen in 10 patients, one of whom died (secondary haemorrhage 2; anastomotic leakage 1, Douglas haematoma 1, inflammation of the drainage tract 6). Preoperative management, intraoperative procedures and postoperative results are described and discussed.

Adult↗
PubMed1994

Zonal differences in lipoprotein formation in the thioacetamide-induced micronodular-cirrhotic rat liver.

The aim of the studies was to answer the question to what extent thioacetamide-induced structural alterations of hepatic architecture leading to fibrosis and micronodular pseudolobuli affect the formation of very low density lipoproteins and the zonation of lipoprotein metabolism observed in normal and acutely injured livers. Therefore, the number of the VLDL particles/Golgi complex and the relative specific volume of Golgi complexes as well as the number and relative specific volume of VLDL-filled vesicles was determined in lobular and nodular zones of normal and the micronodular-cirrhotic livers, respectively. The perinodular and centrinodular regions were morphometrically analysed in nodules with diameters between 0.3 and 0.5 mm. -Generally, in thioacetamide-induced micronodular liver cirrhosis a zonality was observed with respect to the amount of VLDL particles as well as the number and volume of organelles involved in the formation and secretion of hepatic lipoproteins. However, the number of VLDL particles/Golgi complex was significantly reduced to 52% in the centrinodular and to 71% in the perinodular region of cirrhotic livers when compared with the corresponding periportal and perivenous area, respectively. Furthermore, the relative specific volume of the Golgi complexes markedly increased in the perinodular region, thus abolishing the zonal difference observed in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Isolation and characterization of hepatocytes from chronic cholestatic damage to rat livers after bile duct ligation].

The aim of these investigations was the isolation and characterisation of hepatocytes from chronic injured rat livers after bile duct ligation. In three months old female Uje:WIST rats the distal common bile duct was double ligated. 14 days after the ligation 80% of the rats survived. The content of hepatic OH-prolin was increased in relation to shamoperated control animals. The histological examination showed a marked fibrous and oedematous spreading of the portal tract as well as an extensive bile duct proliferation after 14 days. A correlation between OH-prolin content of the liver and index of fibrosis was found. 14 days after ligation the hepatocytes were isolated according to Seglen (7). The yield of hepatocytes isolated from the liver of cholestatic rats and from control animals was on average 4 x 10(8) cells with a viability of 80%. Ultrastructural the most hepatocytes showed intact organells without injury. We can conclude, that it is possible to isolate hepatocytes from chronic cholestatic rat livers with a good yield and viability as well as with an intact ultrastructure. These cells are suitable for additional metabolic investigations.

Animals↗
PubMed1993

Quantification of the cell kinetic effects of G-CSF using a model of human granulopoiesis.

Using a mathematical model of normal human granulopoiesis, the most important influences of granulocyte colony-stimulating factor (G-CSF) on the regulation of white cell production can be quantified. G-CSF increases the blood neutrophils via three effects: reduction of the transit time of the postmitotic granulopoietic bone marrow cells; additional mitoses of the early granulopoietic bone marrow cells; and possibly demargination. The application of G-CSF in vivo results in a summation of the single effects. For a G-CSF application of 5 days at a daily dose of 10 micrograms/kg, the reduction of postmitotic bone marrow transit time from 6 days to 1.5 days together with demargination with a rate of 10% per hour explains the initial increase of the blood neutrophils until day 1. Both effects fail to explain the sustained increase thereafter. Enhanced amplification of the early granulopoietic bone marrow cells is also necessary to reproduce the sustained increase. Depending on the individual clinical data, approximately 5 additional mitoses occur, evenly distributed to the myeloblasts, promyelocytes and myelocytes. If the above three effects of G-CSF are assumed, the model predicts bone marrow data in accordance with clinical observations.

Bone Marrow Cells↗
PubMed1992

The visceral yolk sac--an important site of synthesis and secretion of apolipoprotein B containing lipoproteins in the feto-placental unit of the rat.

Rat fetuses exhibit a high serum LDL concentration at term. Delivery caused a marked decrease of the LDL apolipoprotein (apo) B concentration independent of whether this occurred on days 21, 22 or 23 of gestation. The interruption of the yolk sac circulation by a ligature in situ for 6 h led to the same alterations of the LDL-apo B concentration as Caesarean section. Immunoelectronmicroscopic studies provided evidence that the epithelial cells of the visceral yolk sac exhibited electron dense LDL-sized and apo B containing particles which were localized over the compartments of the Golgi complexes, endoplasmatic reticulum, secretory vesicles and intercellular spaces, but not over the cell nuclei, mitochondria or lysosomes. ApoB containing LDL-sized particles could be obtained by ultracentrifugation from the disrupted material of the microsomal fraction of yolk sac homogenates. Isolated segments of the yolk sac membranes were capable to secrete apoB containing lipoproteins floating in the d less than 1.020 g/ml as well as in the d = 1.020-1.064 g/ml fraction with a 10-fold higher amount of apoB in the higher density class. Incorporation experiments with [35S] methionine gave evidence that these lipoproteins were at least partially provided with newly synthesized apoB predominantly found in the LDL fraction. The size of the negatively stained particles in the d = 1.020-1.064 g/ml fraction secreted from yolk sac segments corresponded to that of LDL from fetal rat serum. In contrast their acylglycerol content was significantly higher, whereas the percentage contribution of total cholesterol and protein was markedly reduced in comparison with serum LDL of the fetus. In summary, biochemical and ultrastructural studies provide clear cut evidence that the rat yolk sac is able to synthesize and to deliver apo B containing lipoproteins in the density ranges of VLDL, IDL and particular of LDL thus contributing to the supply of serum lipoproteins in the rat fetus. By recalculation of recent tracer kinetic data (Plonné et al. (1990) J. Lipid Res. 31, 747) using a mathematical step function model it was possible to assess the contribution of the rat yolk sac to the LDL influx into the fetal serum.

Animals↗