Sensitivity of CFU-GM from normal human bone marrow and leukaemic clonogenic cells (CFU-L) from blood of patients with myelogenous leukaemia to 3'-deoxy-3'-fluorothymidine in comparison to 3'-azido-3'-deoxythymidine

3'-Deoxy-3'-fluorothymidine (FT), a thymidine analogue highly effective against HIV 1 in vitro was investigated as to its in vitro effect on normal human bone marrow CFU-GM (agar colony assay) and on human peripheral myeloid leukaemic clonogenic cells (CFU-L, colony assay in methylcellulose). For comparison, 3'-azido-3'-deoxythymidine (AZT), structurally related and used in AIDS treatment, was included in the study. Both compounds inhibit the formation of clusters and colonies from bone marrow stem cells with an [IC]50 between 10(-6) and 10(-5)M. In concentrations only 5-10 times lower than the [IC]50, FT begins to stimulate cluster and colony formation. AZT and FT also inhibit the formation of clusters and colonies from CFU-L. Compared to CFU-GM, CFU-L were more sensitive to FT, and a stimulation was not seen. It is concluded that similar side effects on bone marrow could be expected for possible use of FT against AIDS as have been found for AZT and that both compounds are potential candidates for anti-leukaemic drugs.     

Changes in TSH-immunoreactivity in the pars tuberalis and pars distalis of the fetal rat hypophysis following maternal administration of propylthiouracil and thyroxine

Summary The pars tuberalis (pt) of the adenohypophysis is unique in its close spatial relationship to the neurohemal contact area of the median eminence. The morphology of pt-specific secretory cells does not resemble cell types of the pars distalis (pd); the functional role of these cells within the endocrine system is still unknown. One group of young mature female Wistar rats received propylthiouracil (PTU), a second group thyroxine (T4) (10 mg/l each in drinking water) from about 3 weeks prior to the expected pregnancy and throughout the experiment. On gestation day 20, the fetuses were obtained by laparatomy. Serial sections from the rostral portion of the pt and from the pd were immunostained using the peroxidase-antiperoxidase method. TSH concentrations were determined by RIA in serum and pituitaries; T4 was measured in serum. An antiserum against rat (r) TSH revealed a moderate positive reaction of nearly all cells of the pt in the control group. In both experimental groups the pt-specific cells showed weak or no immunoreactivity. Sections of all groups were negative with anti(r)-LH,-GH,-PRL. In contrast to controls, only a few immature TSH-cells could be found in sections of the pd in the T4-group, while concentrations of TSH in blood and hypophysis were very low. TSH-cells in the PTU-group were enlarged and less intensely stained. TSH-concentrations were decreased in the hypophysis, blood levels were elevated. All sections of the pd-specific cell populations showed positive immunoreactions with anti(r)-LH,-GH,-PRL. The present results suggest that pt-specific secretory cells of the fetal rat possess TSH immunoreactivity but do not resemble the thyrotropes of the pd. Marked differences in immunoreactivity displayed by the experimental groups indicate that pt-specific cells respond to changes in the fetal thyroid status and are a component of the thyroid-regulating system in addition to the thyrotropes of the pd. This novel aspect of pt function is discussed in connection with recent results concerning melatonin receptors found in the pt and the inhibitory influence of the pineal gland exerted on the thyroid gland.The study was supported by the Deutsche Forschungsgemeinschaft (Wi 558/4-1)     

No evidence of covalent modification of glutamine synthetase in the thermophilic phototropic bacterium Chloroflexus aurantiacus

Abstract Regulation of glutamine synthetase (GS) in the thermophilic green phototrophic bacterium, Chloroflexus aurantiacus , was studied. The enzyme was partially purified from cells grown photosynthetically in media with limiting (1 mM) or non-limiting (10 mM) NH⁺₄-concentrations. GS preparations from both cell types were indistinguishable in respect to pH-optimum of GS-transferase activity, sensitivity to feedback modifiers (AMP, L-alanine, glycine) and lack of Mg-inhibition of transferase activity. In contrast to results obtained with a GS preparation from the facultatively phototrophic bacterium, Rhodopseudomonas sphaeroides , the catalytic properties of Chloroflexus GS did not change during incubation with snake venom phosphodiesterase suggesting the absence of in vivo regulation of Chloroflexus GS by adenylylation/deadenylylation.     

The molecular mechanism of neural induction: neural differentiation of Triturus ectoderm exposed to Hepes buffer

Summary Ectoderm was isolated from early gastrula stages of Triturus alpestris and cultured in salt solution buffered with either bicarbonate or Hepes as the principal buffer substance. When bicarbonate was the principal buffer substance or when bicarbonate was omitted, the isolated ectoderm formed atypical epidermis. When Hepes was added as a buffer substance, neural tissue was formed in a high percentage of cases. The differentiation of neural tissue depends on the pH of the Hepes buffer. Hepes in the protonated form, which prevails at lower pH, seems to evoke neural differentiation at a much higher rate. Hepes could either enhance the NA⁺/H⁺ antiport system or it could directly bind to plasma membrane constituents. In both cases conformational changes in the plasma membrane could generate signals which finally lead to neural differentiation.     

2'', 3''-Cyclic Nucleotide 3''-Phosphohydrolase and Lipids of Myelin from Multiple Sclerosis and Normal Brains

Abstract: A study of purified myelin samples from normal-appearing white matter of 10 multiple sclerosis (MS) brains was undertaken and the results were compared with 10 age-matched control brains. Statistical evaluations were carried out with Student's r-test for differences. In pathological samples the yield of myelin came to only two-thirds of the corresponding controls. Enzyme assays of the 2', 3'-cyclic 3'-phosphohydrolase revealed an obviously significant reduction of specific activity to one-half in MS myelins. In myelin the contents of protein, lipid classes as cholesterol, glycolipids and phospholipids did not differ significantly. No cholesterol esters or any lysophospholipid were detectable either in MS or in controls. Within the individual phospholipids the main components were in the same order, while a significant decrease of the acidic representatives and of sphingomyelin occurred. Analysis of the fatty acid pattern of phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylethanolamine (PE), including the aldehydes from the last, revealed quite similar values with no significant differences, except C22: 4 fatty acid in the PE fraction and C20: 1 fatty acid in PS, which were reduced in MS myelin samples.     

Molecular organization of the outer membrane of Salmonella typhimurium different release of lipopolysaccharide from wild type and lipopolysaccharide mutant cells by EDTA treatment

Cells of Salmonella typhimurium wild type and of several well defined lipopolysaccharide mutants were treated with EDTA. The percentage release of lipopolysaccharide and phospholipid was determined. The results obtained show that the release of lipopolysaccharide by EDTA declines along with the gradually diminishing chain length of the lipopolysaccharide, althought the total amount of lipopolysaccharide was found to increase at the same time in the respective mutants. Implications of these findings for the organization of the outer membrane are discussed.     

Die Induktionsfähigkeit des Hypophysenvorderlappens vom Rind in Gastrulen von Triton alpestris

Ohne ZusammenfassungHerrn Prof. Dr.Walter Schoeller zum 75. Geburtstag gewidmet.Ausgeführt mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Die Selbstdifferenzierungsfähigkeit und Induktionsfähigkeit medianer und Lateraler Teile der Rumpfmedullarplatte bei Urodelen

Ohne Zusammenfassung     

Die lichtabhängige Vakuolisation der Chloroplasten in Nikotinlösungen

Ohne ZusammenfassungDie vorliegende Arbeit wurde als Teil einer Dissertation am Botanischen Institut der Universität Münster (Westfalen) ausgeführt.Meinem hochverehrten Lehrer, Herrn Prof. Dr. S. Strugger, bin ich für die Überlassung des Arbeitsplatzes und für die ständige Förderung meiner Arbeit zu größtem Dank verpflichtet.