The effect of perinatal oestrogen treatment on the troph-hormone secreting cells of the anterior pituitary of the rat

Late effect of the perinatal administration of oestradiol dipropionate on pituitary gonadotrophs and the morphology of the LH-RH neuronal system was tested both in male and female rats. Oestrogen caused a severe reduction in the number and size of immunodetectable gonadotrophs in both sexes. By the 90th day of life, however, immunomorphology and distribution of the gonadotroph cells had became normal, and also the LH-RH system of the animals was similar to that of the intact controls. The lack of vaginal cycles indicated, however, that oestrogen might have permanently impaired higher brain centers regulating cyclic gonadotroph hormone release.     

The importance of FeEDTA for reversibility of phosphate-induced chlorosis in maize (Zea mays L.)

Chlorosis induced with a supraoptimum dose of phosphorus in nutrient solution (69 mg P l^-1) was reverted by spraying of leaves of chlorotio maize plants (Zea mays L.) with FeEDTA. Biomass formation, chlorophyll and iron content were decreased in the above-ground parts of plants grown under chlorosis-inducing conditions. Spraying always decreased content of inorganic phosphorus (P_i/Fe ratio was significantly changed), increased chlorophyll content in old plants and stimulated dry mass formation at supraoptimum phosphorus doses. FeEDTA application improved phosphate utilization (portion of phosphate in organic bonds was increased). This may be the basis of chlorosis-reverting effect of FeEDTA.     

Stoicheiometry of dicyclohexylcarbodiimide-ATPase interaction in mitochondria

1. The oligomeric dicyclohexylcarbodiimide (DCCD)-binding protein of mitochondrial ATPase was studied using (a) the relationship between [¹⁴C]DCCD binding and inhibition of ATPase activities and (b) the analysis of the kinetics of inhibition. 2. The [¹⁴C]DCCD binding to bovine heart mitochondria is linearly proportional to the inhibition of ATP hydrolysis up to a 50% decrease of the original activity resulting in 0.6 mol DCCD bound covalently to the specific inhibitory site (Hous?t?k, J., Svoboda, P., Kopecký, J., Kuz?ela, S?. and Drahota, Z. (1981) Biochim. Biophys. Acta 634, 331–339) per mol of the fully inhibited enzyme. 3. Kinetics of the inhibition of both the ATPase activity (heart and liver mitochondria) and ADP-stimulated respiration (liver) reveal that 1 mol DCCD per mol ATPase eliminates both the synthetic and the hydrolytic activities. It is inferred that the activity-binding correlation underestimates the number of DCCD-reactive sites. 4. The second-order rate constant of the DCCD-ATPase interaction (k) is inversely related to the concentration of membranes, indicating that DCCD reaches the inhibitory site by concentrating in the hydrophobic (phospholipid) environment. 5. At a given concentration of liver mitochondria, comparable k values are obtained both for the inhibition of ATP hydrolysis (k=5.35·10²M^?1·min^?1) and ADP-stimulated respiration (k=5.67·10²M^?1·min^?1). 6. It is concluded that both the synthetic and the hydrolytic functions of ATPase are inhibited via a common single DCCD-reactive site. This site is represented by one of the several polypeptide chains forming the oligomer of the DCCD-binding protein. The inhibitor-ATPase interaction does not exhibit cooperativity, indicating that the preferential reactivity towards DCCD is an inherent property of the inhibitory site.     

Neurons containing luteinizing hormone-releasing hormone in the indusium griseum of the rat

The authors detected LH--RH-containing neurons in the dorsal part of the hippocampus and in the indusium griseum of the rat. LH--RH-containing nerve fibres interconnect the organum subfornicale (OSF) and the dorsal hippocampus. Axons leaving the OSF can be traced backwards, then around the splenium of the corpus callosum, from where they run forwards in the stria longitudinalis medialis (SLM). LH--RH fibres of the SLM give axon collaterals to the cingulate cortex, then intermingle with the LH--RH system of the septum pellucidum. Following coronal transection of the SLM, it could be determined that LH--RH fibres form bidirectional connection between the septum and different regions of the hippocampus.     

Dictyostelium myosin II heavy-chain kinase A is activated by heparin, DNA and acidic phospholipids and inhibited by polylysine, polyarginine and histones.

Dictyostelium myosin II heavy-chain kinase A (MHCK A) is activated by autophosphorylation. Heparin and DNA, as well as vesicles composed of phosphatidylserine or phosphatidylinositol, were found to increase the initial rate of MHCK A autophosphorylation 5-10-fold in a Ca(2+)-independent manner. The negatively charged molecules also increased the activity of the autophosphorylated MHCK A by about 2-fold. In contrast, positively charged polypeptides such as poly(D-lysine), poly(L-lysine), poly(L-arginine) and histones strongly inhibited (IC50 of 0.5 micrograms/ml) the activity of the active, autophosphorylated MHCK A. Similar levels of inhibition, on a weight basis, were observed for poly(L-lysine) fractions with molecular weights from 3800 to 150,000-300,000. The inhibition was competitive with respect to peptide substrate and mixed with respect to ATP. At much higher concentrations poly(L-lysine) also inhibited the ability of MHCK A to autophosphorylate. It is proposed that negatively charged compounds and autophosphorylation increase the activity of MHCK A by weakening the interaction between the catalytic domain and a positively charged autoinhibitory domain.     

Surface immobilization of anchorage-dependent mammalian cells

Anchorage-dependent HeLa cells were successfully cultured on two fibrous materials (A07 and R100) with porosities of 75-125 and 40 mum, void fractions of 92% and 81%, and fiber diameters of 7.6 and 10.2 mum, respectively, in 100-mL spinner flasks and 2-L stirred tank bioreactors. The matrix was formed into a fixed vertical spiral configuration. All cultures displayed rapid (/=95%) to the matrix, uniform coverage of the immobilizing area with viable cells, and no significant amount of cell debris in the medium. Spinner flask cultures indicated that the denser material R100 showed better results in terms of final cell density. The growth of HeLa cells on material R100 in both culture systems was similar to that observed in tissue culture dishes (specific growth rate approximately 0.03-0.04 h(-1), maximum cell density of 8 x 10(6)-9 x 10(6) cells . mL(-1), and yields of 0.4 x 10(8) cells . mM(-1) on glucose and 2 x 10(8)-3 x 10(8) cells . mM(-1) on glutamine). Scale-up of this culture technique in a 2-L bioreactor under perfusion with pH and dissolved oxygen (DO) control yielded cell densities of up to 1.6 x 10(6) cells . mL(-1). Two other anchorage-dependent mammalian cells (ADC) known to be cultured with difficulty in roller bottles or with micro carriers were easily grown on material R100 in spinner flasks. The performance of this culture technique was compared to other ADC culture systems.     

Twinning and mitotic crossing-over: some possibilities and their implications

Mitotic crossing-over does occur in man and is much more frequent and important than generally assumed. Its postzygotic occurrence before an embryo differentiates into MZ twins is theoretically predicted to have disrupting effects on genomic imprinting and cis-acting sequences, with consequences ranging from early lethality to MZ twin discordance. Some predictions are at odds with classical views on twinning and include a high discordance rate of MZ twins for some genetic diseases. A review of MZ twin discordance and an attempt at explaining some of the data lead one to hypothesize both the existence of a sex differences in the rate of mitotic crossing-over and the impossibility for crossed X chromosomes to undergo inactivation. The close interrelationship of twinning and midline malformations further suggests a major role of mitotic crossing-over in the induction of the twinning process itself. The model can be tested with molecular methods and provides a new approach for the gene mapping of so-called multifactorial diseases and of rarer disorders with apparently irregular inheritance.     

Distribution of deletions and seven point mutations on CYP21B genes in three clinical forms of steroid 21-hydroxylase deficiency

To characterize mutations in the CYP21B gene that are responsible for congenital adrenal hyperplasia (CAH), DNA samples from 91 French patients have been studied by allelic-specific oligonucleotide hybridization and Southern blot analysis. Seven sites mostly found in the CYP21A pseudogene and deletions of the functional CYP21B gene have been screened. Gene conversions involving small DNA segments accounted for 57% of the tested mutations and probably cause 74% of the mutations responsible for the disease. Complete deletion of the CYP21B gene accounted for 18% of the CAH mutations in the whole sample and for 21% in the classical form of the disease. Three mutations were found associated with specific clinical forms of the disease: a G-C substitution in the seventh exon was associated with the late-onset form of the disease, and both an 8-bp depletion in the third exon and complete deletion of CYP21B were associated with the salt-wasting form.     

Interaction with functional membrane proteins--a common mechanism of toxicity for lipophilic environmental chemicals?

1. The effects of several phenols, anilines and aliphatic alcohols on yeast plasma membrane H(+)-ATPase and purine transport system as well as on Na+, K(+)-ATPase and adenosine uptake by Chinese hamster ovary cells (CHO) were investigated. 2. In all cases an inhibition was observed, which could be correlated with the octanol/water partition coefficients of the substances tested, thus making quantitative structure-activity predictions possible. 3. The observed effects correlated well with the influence of the chemicals on cell growth. 4. The results suggest a common mechanism of toxicity by the action of hydrophobic xenobiotics on biomembranes.