Lipids in the laminated layer of liver, lung and daughter hydatid cysts of equine Echinococcus granulosus (Cestoda)

Lipids extracted from the laminated layers of horse liver and lung hydatids, including a daughter liver cyst, were analysed using TLC. No differences in lipid composition was detected in 11 liver cysts, whether from the same or different livers, and di- and triacylglycerols, cholesterol, wax and steryl esters, oleic acid, sphingomyelin, phosphatidyl choline, phosphatidyl inositol and ceramide hexosides were detected. The daughter cyst differed from its "parent" cyst in lacking diacylglycerols and wax and steryl esters. The lung cyst differed from the liver cysts in that cholesterol, wax and steryl esters and diacylglycerols were not detected.     

A proton nuclear magnetic resonance assignment and secondary structure determination of recombinant human thioredoxin

Two-dimensional 1H NMR spectroscopy has been applied to a structural analysis of the reduced form of a recombinant human thioredoxin, a ubiquitous dithiol oxidoreductase recently isolated from an immunocompetent lymphoblastoid cell line. The sequential assignment of the spectrum, including all proline residues, has been accomplished by using experiments to demonstrate through-bond and through-space connectivities. The secondary structure has been determined by a qualitative interpretation of nuclear Overhauser effects, NH exchange data, and 3JHN alpha coupling constants. The secondary structure was found to be similar to that of the X-ray structure of Escherichia coli thioredoxin, consisting of a mixed five-stranded beta-sheet surrounded by four alpha-helices. The assignment and structural characterization of human thioredoxin was facilitated by the increased resolution and sensitivity afforded by a magnetic field strength of 600 MHz and required the use of two temperatures and two pH conditions to resolve ambiguities caused by a duplication of resonances. This duplication, extending from Phe-41 to Val-59, and including Lys-3-Ile-5, Val-24, Val-25, Asn-39, and Ile-101-Glu-103, appears to be due to heterogeneity arising from the presence or absence of the N-terminal methionine.     

Theoretical calculation of tautomer equilibria in solution: 4-(5-)methylimidazole

A combination of quantum mechanical calculations and molecular dynamics simulations has been used to calculate the tautomer ratio of 4-(5-)methyl imidazole in solution, and the results are in good agreement with experiment.     

GABA A -receptors: Structural requirements and sites of gene expression in mammalian brain

GABA_A-receptors, the major synaptic targets for the neutotransmitter GABA, are gated chloride channels. By their allosteric drug-induced modulation they serve as molecular control elements through which the levels of anxiety, vigilance, muscle tension and epileptiform activity can be regulated. Despite their functional prominence, the structural requirements of fully functional GABA_A-receptors are still elusive. Expression of cDNAs coding for the ₁- and ₁-subunits of rat brain yielded GABA-gated chloride channels which were modulated by barbiturates but displayed only agonistic responses to ligands of the benzodiazepine receptor. GABA_A-receptors with fully functional benzodiazepine receptor sites were formed when the ₁- and ₁-subunits were coexpressed with the ₂-subunit of rat brain. These receptors, however, failed to show cooperativity of GABA in gating the channel. In order to determine the subunit repertoire available for receptor assembly in different neuronal populations in vivo, the sites of subunit gene expression were (₁, ₂, ₃, ₅, ₆, ₁, ₂, ₃, ₂) mapped by in situ hybridization histochemistry in brain sections. The mRNAs of the ₁-, ₁- and ₂-subunits were co-localized e.g. in mitral cells of olfactory bulb, pyramidal cells of hippocampus as well as granule cells of dentate gyrus and cerebellum. The lack of colocalization in various other brain areas points to an extensive receptor heterogeneity. The presence of multiple GABA_A-receptors in brain may contribute to synaptic plasticity, differential responsiveness of neurons to GABA and to variations in drug profiles.Special issue dedicated to Dr. Erminio Costa     

Tissue architectural features for the grading of prostatic carcinoma

In research for the development of a computer-aided workstation for the objective grading of prostatic carcinoma, tissue architectural (histometric) features were analyzed in ten cases each of well-differentiated, moderately differentiated and poorly differentiated carcinoma (as subjectively graded by the consensus of a panel of experts). Sections were cut at 4 microns, stained by the Feulgen reaction and digitized by two different video-based photometric systems. Some images were interactively segmented, considering the histometric clues to be studied; others were automatically segmented by an expert system-guided technique. The latter procedure produced good results, with over 90% of the nuclei judged to be correctly segmented in 64% of the fields studied and over 80% in another 24% of the fields. While the number of nuclei per field provided some separation of well-differentiated from other lesions, the number of nuclei per gland distinguished between well-differentiated and moderately differentiated lesions. Simplicial decomposition of the images also provided a measure of the degree of differentiation, as did the "texture" of the nuclear placement, based on two run-length statistics. Combination of the run-length features distinguished the three categories of lesions with statistical significance. The results of this study provided insights into the problems (such as the effect of field boundaries) faced in the design of an computer-aided grading system. They also showed the value of expert system-guided scene segmentation and of such histometric features as the field cellularity and the number of nuclei per gland for the discrimination between lesions of different grades of differentiation.     

Human metallothionein genes: structure of the functional locus at 16q13

The functional human metallothionein (MT) genes are located on chromosome 16q13. We have physically mapped the functional human MT locus by isolation and restriction digest mapping of cloned DNA. The mapped region contains all sequences on chromosome 16 that hybridize to metallothionein gene probes and comprises 14 tightly linked MT genes, 6 of which have not been previously described. This analysis defines the genetic limits of metallothionein functional diversity in the human genome.     

Regulation of aromatase mRNA and estradiol biosynthesis in rat ovarian granulosa and luteal cells by prolactin

Regulation by PRL of aromatase (P450arom) mRNA and protein and estradiol (E) biosynthesis was examined in granulosa cells during early stages of luteinization in vitro and in vivo. PRL caused a dose-dependent (10-1000 ng/ml) decrease in P450arom mRNA and E biosynthesis (greater than 99%) in luteinized rat granulosa cells in vitro, even when the cells were cultured in the presence of insulin and hydrocortisone (hormones known to synergize with PRL to induce proteins in mammary tissue) or in the presence of forskolin (a nonhormonal stimulator of cAMP). PRL also prevented the marked increases in aromatase mRNA and E biosynthesis stimulated by FSH and forskolin in nonluteinized preovulatory granulosa cells in culture. These effects of PRL on granulosa cells in culture were specific for aromatase and were not observed for other proteins, such as cholesterol side-chain cleavage cytochrome P450 (P450scc) and alpha 2-macroglobulin. PRL also decreased P450arom mRNA and protein during the early stages of luteinization in vivo. PRL administered to rats beginning day 1 postovulation to mimic hormone release during pseudopregnancy reduced the progressive increase in P450arom mRNA occurring in corpora lutea on days 3-4 in ovulated rats not treated with PRL. CB 154, a dopamine agonist that inhibits pituitary release of PRL, caused P450arom mRNA and protein to decrease 50% if given to pregnant rats on days 8-10 of gestation, but increased P450arom mRNA and protein if given to pregnant rats on days 10-12 of gestation. These diverse effects of PRL in pregnancy suggest that placental factors may modify the response of luteal cells to PRL during gestation.(ABSTRACT TRUNCATED AT 250 WORDS)