Steroid hormones as mediators of neural plasticity

Steroid and thyroid hormone receptors are expressed in the developing brain and persist throughout adult life. They mediate a variety of effects on the brain, ranging from developmental effects of thyroid hormone and the process of sexual differentiation to the cyclic changes during reproductive cycles in adult female animals. This review summarizes data from the author's laboratory on three topics: (1) actions of extradiol and progesterone on the ventromedial nucleus of the hypothalamus in adult female and male rats, showing both the cyclicity and the consequences of brain sexual differentiation; (2) actions of estradiol on the cholinergic neurons of the basal forebrain of the female and male rat, reflecting the plasticity of the adult cholinergic system as well as sex differences which are developmentally programmed; and (3) diverse actions of estrogens, thyroid hormone and glucocorticoids on the morphology of hippocampal neurons. The review concludes by discussing the interactions between "organizational" (i.e. developmental) effects and the "activational" effects of steroids on the mature nervous system in relation to the environmental control of brain gene expression.     

Interactions among leaf photosynthetic rates,flowering and pod set in soybeans

The seasonal maximum in photosynthetic CO₂ exchange rate (CER) and the cessation of leaf expansion in soybeans (Glycine max (L.) Merr) accompany fruiting under normal agricultural conditions. To investigate whether these phenomena were obligatively tied together, we caused early flowering of long-season varieties by imposing artificial short-day treatments. Comparisons of CER and leaf area between vegetative (long-day treatment) and fruiting (short-day treatment) plants of long-season cultivar confirmed the relationship of these phenomena. The same comparisons made between a long-season and a short-season cultivar, both at the same daylength, also confirmed the relationship.     

The binding of dansylated initiation factor 3 to the 30-S subunit of Escherichia coli: a fluorimetric and biochemical study

Initiation factor 3 (IF-3) has been labelled using dansyl (1-dimethylaminonaphthalene-5-sulphonyl) chloride under conditions designed to preserve the biological activity of the factor. The sites of modification of the IF-3 have been determined by peptide mapping and sequencing: about six lysines (73, 80, 91, 96, 99, 112) react in various proportions. However, if an IF-3 molecule bears more than one dansyl group on average then its activity is lost. The extent of incorporation is proportional to the amount of dansyl chloride used in the reaction. Spectrofluorimetric analysis of the dansyl-IF-3 leads to the following conclusions. (a) The motion of the dansyl label does not change greatly upon binding to the 30-S subunit. (b) The label is not close enough to any tryptophan group of the ribosome in the 30-S-subunit . IF-3 complex to allow energy transfer. (c) The IF-3 chain is folded so as to bring the tyrosine groups close to the dansyl-binding sites. (d) The stoichiometry of the binding of IF-3 to 30-S ribosomal subunits is close to 1:1 and the binding constant is 2 x 10(7) M-1. IF-3 also binds non-covalently the fluorescent indicator 8-anilinonaphthalene 1-sulphonate (ANS) with an apparent binding constant of approximately 8000 M-1. An interaction between ANS and poly(A-U-G), both bound to IF-3, was demonstrated. Combining these results with those for dansyl-IF-3 leads to a model for the interaction between IF-3 and the 30-S subunit involving a combination of 'hydrophobic' and electrostatic attraction between the factor and ribosomal RNA.     

Double aneuploidy: partial trisomy 21 and XO/XXX in a family with 12/21 translocation.

A female patient with mild mental retardation with spatial perceptual difficulties, microcephaly, depressed nasal root, receding chin, webbed neck, low hairline, shield chest, cubitus valgus, scoliosis and dermatoglyphic findings not characteristic of Down's syndrome is reported. In addition to X/XXX, she had a partial trisomy 21 of the short arm-centromere-proximal long arm segment due to maternal t(12;21) translocation. Two phenotypically normal siblings carried the balanced translocation.     

Spectral specific responses in the visual behavior of the greenhouse whitefly,Trialeurodes vaporariorum (Homoptera: Aleyrodidae)

Attraction of the greenhouse whiteflyTrialeurodes vaporariorum Westw. to reflected and to transmitted light of various wavelength compositions was measured by trapping and counting adults on greased, colored surfaces. The wavelength composition of the reflecting or transmitting surfaces was spectrophotometrically determined.The whiteflies showed a strongly positive response to surfaces with maximum reflectance or transmittance in the yellow-green region (520–610 nm), and a moderately positive response to ultra-violet (<400 nm). Light in the blue-violet region seemed to inhibit the response, and red (610 to ca. 700 nm) might also be moderately inhibitory.The response to the most excitatory hues sharply decreases with darker shades or with less saturated tints of the same hues.The implications of these responses in the mechanisms of host selection by the greenhouse whitefly are discussed.

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Zusammenfassung Die Attraktion der Weißen Fliege zu remittiertem und transmittiertem Licht verschiedener Wellenlängen-Kombinationen (spektrometrisch bestimmt) wurde gemessen durch Fang und Auszählen von angeflogenen Adulten an geleimten, farbigen Oberflächen. Die Weißen Fliegen zeigten eine starke positive Reaktion zu Oberflächen mit maximaler Remission oder Transmission im Gelg-Grün-Bereich (520–610 nm) und eine mäßige positive Reaktion zu UV (<400 nm). Licht im Blau-Violett-Bereich scheint die Reaktion zu hemmen und Rot (610 bis etwa 700 nm) scheint ebenfalls hemmend zu sein.Die Reaktion zu den Farbtönen mit höchster Wirksamkeit nimmt stark ab bei geringerer Intensität (Schwarzverhüllung) oder geringerer Sättigung (Weissverhüllung) der Farbtöne.Die Bedeutung dieser Reaktionen für den Mechanismus der Wirtswahl der Weißen Fliege wird diskutiert.

     

Purification of rheumatoid synovial collagenase and its action on soluble and insoluble collagen.

1. The neutral collagenase released into the culture medium by explants of ehrumatoid synovial tissue has been purified by ultrafiltration and column chromatography, utilising Sephadex G-200, Sephadex QAE A-50 and Sephadex G-100 superfine. 2. The final collagenase preparation had a specific activity against thermally reconstituted collagen fibrils of 312 mug collagen degraded min-1 mg enzyme protein-1, representing more than a 1000-fold increase over that of the active culture medium. 3. Electrophoresis in polyacrylamide disc-gels with and without sodium dodecyl sulphate showed the enzyme to migrate as a single protein band. Elution experiments from polyacrylamide gels and chromatography columns have provided no evidence for the existence of more than one collagenase. 4. The molecular weight of the enzyme, as determined by dodecylsulphate-polyacrylamide gel electrophoresis, was 33000. 5. Data obtained from sutdies with the ion-exchange resin and from gel electrophoresis in acid and alkaline buffer systems suggested a basically charged enzyme. 6. It did not hydrolyse the synthetic collagen peptide Pz-Pro-Leu-Gly-Pro-D-Arg and non-specific protease activity was absent. 7. The collagenase attacked undenatured collagen in solution at 25 degrees C resulting in a 58% loss of viscosity and producing the two characteristic products TCA(3/4) and TCB(1/4). 8. At 37 degrees C and pH 8.0 both reconstituted collagen fibrils and gelatin were degraded to peptides of less than 10000 molecular weight. 9. As judged by the release of soluble hydroxyproline peptides and electron microscopic appearances the enzyme degraded human insoluble collagens derived from tendon and soft juxta-articular tissues although rates of attack were less than with reconstituted fibrils. 10. The data suggests that pure rheumatoid synovial collagenase at 37 degrees C and neutral pH can degrade gelatin, reconstituted fibrils and insoluble collagens without the intervention of non-specific proteases. 11. The different susceptibilities of various collagenous substrates to collagenase attack are discussed.     

Inhibition of human collagenase activity by a small molecular weight serum protein.

Fractionation of human serum proteins by gel filtration in Sephadex G-200 revealed two regions of collagenase inhibition which corresponded to α₂-macroglobulin and a smaller serum component which eluted after α₁-antitrypsin. The smaller collagenase inhibitor, having a molecular weight of 40,000 was separated from α₁-antitrypsin by chromatography in Sephadex DEAE A.50. It was found to inhibit human collagenases derived from skin, rheumatoid synovium, gastric mucosa and granulocytes, but not the neutral proteases trypsin and papain. Purified preparations of α₁-antitrypsin inhibiting trypsin and papain had no effect on the collagenase activities. The small collagenase inhibitor may have importance as a regulatory factor in the control of collagenase activity in vivo.