Charge effects on phospholipid monolayers in relation to cell motility

A new sensitive method for the assay of retinyl ester hydrolase in vitro was developed and applied to liver homogenates of 18 young pigs with depleted-to-adequate liver vitamin A reserves. Radioactive substrate was not required, because the formation of retinol could be adequately quantitated by reversed-phase high-performance liquid chromatography. Optimal hydrolase activity was observed with 500 microM retinyl palmitate, 100 mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, and 2 mg/ml Triton X-100 at pH 8.0. The relative rates of hydrolysis of six different retinyl esters by liver homogenate were: retinyl linolenate (100%), myristate (99%), palmitate (47%), oleate (38%), linoleate (31%), and stearate (29%). The enzyme was found primarily in the membrane-containing fractions of liver (59 +/- 3%, S.E.) and kidney (76 +/- 3%), with considerably lower overall activity in kidney (57-375 nmol/h per g of tissue) than in liver (394-1040 nmol/h per g). Retinyl ester hydrolase activity in these pigs was independent of serum retinol values, which ranged from 3 to 24 micrograms/dl, and of liver vitamin A concentrations from 0 to 32 micrograms/g. Pig liver retinyl ester hydrolase differs from the rat liver enzyme in its substrate specificity, bile acid stimulation, and interanimal variability.     

Magnesium and Manganese Content of Halophilic Bacteria

Magnesium and manganese contents were measured by atomic absorption spectrophotometry in bacteria of several halophilic levels, in Vibrio costicola, a moderately halophilic eubacterium growing in 1 M NaCl, Halobacterium volcanii, a halophilic archaebacterium growing in 2.5 M NaCl, Halobacterium cutirubrum, an extremely halophilic archaebacterium growing in 4 M NaCl, and Escherichia coli, a nonhalophilic eubacterium growing in 0.17 M NaCl. Magnesium and manganese contents varied with the growth phase, being maximal at the early log phase. Magnesium and manganese molalities in cell water were shown to increase with the halophilic character of the logarithmically growing bacteria, from 30 mmol of Mg per kg of cell water and 0.37 mmol of Mn per kg of cell water for E. coli to 102 mmol of Mg per kg of cell water and 1.6 mmol of Mn per kg of cell water for H. cutirubrum. The intracellular concentrations of manganese were determined independently by a radioactive tracer technique in V. costicola and H. volcanii. The values obtained by ⁵⁴Mn loading represented about 70% of the values obtained by atomic absorption. The increase of magnesium and manganese contents associated with the halophilic character of the bacteria suggests that manganese and magnesium play a role in haloadaptation.     

Stereoscopic back-scattered electron imaging of silver-stained proteins in nucleoli

By using simultaneously the AgNOR silver staining method, back-scattered electron imaging mode and stereo-tilt in scanning electron microscopy (SEM), it is possible to observe the nucleus through the cell surface, the nucleolus, and the tri-dimensional distribution of the AgNOR-associated acidic proteins. In C3H10T1:2 cells and their 7-12-dimethylbenz--anthracene-treated transformants, the staining demonstrates several intranucleolar silver-staining granules (SSG), surrounded by a weakly staining region. The SSG may represent the fibrillar center (FC) and the weakly staining region, the fibrillar dense component (FD). This component can link several SSG together to form a rope-like structure. In cells with no visible nucleolus and inactive nucleolar organizer regions (NORs) the silver-staining granules are less numerous, close together and the presumed fibrillar dense components are not visible. The SSG are located more peripheraly, and the weakly staining region and the rope-like structure are less prominent in control cell nucleoli than in transformed cells with a comparatively high rate of RNA synthesis.     

The cya gene region of Erwinia chrysanthemi B374: organisation and gene products

Summary A DNA fragment containing the cya gene region of Erwinia chrysanthemi, B374 was cloned in vivo and transferred into cells of E. coli using a plasmid pULB113 derived from RP4 followed by subcloning in vitro into the vector pBR322. The cya gene encodes a 95 kDal protein that complemented E. coli cya mutants. Apparently, cya genes truncated at the 3 end could still produce proteins complementing cya-defective strains, thus showing that adenylate cyclase truncated at its carboxy-terminal end could synthesise cAMP. A protein of unknown function (40 kDal) is encoded by a gene that is transcribed divergently from the control region of the adenylate cyclase gene.     

Identification of the peptide bond cleaved during activation of human Clr

CNBr cleavage of unreduced proenzyme Clr yielded fragment CP2b, isolated by gel filtration and highpressure gel permeation chromatography. This fragment (˜ M_τ 55000) comprised at least 4 disulphidelinked peptides, which were separated by gel filtration after reduction and alkylation. Peptide CP2bRA4, overlapping the A- and B-chain regions in proenzyme Clr was digested by V8 staphylococcal protease, and the digest separated by reversed-phase HPLC. N-terminal sequence analysis of peptide CP2bRA4SP9 established that Clr activation involves the cleavage of a single Arg-Ile bond, located in the sequence: Gln-Arg-Gln-Arg-Ile-Ile-Gly-Gly     

Comparison of Three 18F-Labeled Butyrophenone Neuroleptic Drugs in the Baboon Using Positron Emission Tomography

The butyrophenone neuroleptics spiroperidol, benperidol, and haloperidol were radiolabeled with fluorine-18 and studied in baboon brain using positron emission transaxial tomography (PETT). Pretreatment of the baboon with a high pharmacological dose of (+)-butaclamol reduced the specifically bound component of radioactivity distribution in the striatum to approximately the radioactivity distribution found in the cerebellum. Comparative studies of brain distribution kinetics over a 4-h period indicated that either [18F]spiroperidol or [18F]benperidol may be suitable for specific labeling of neuroleptic receptors. In an 8-h study with [18F]spiroperidol, striatal radioactivity did not decline, suggesting that spiroperidol either has a very slow dissociation rate or that it binds irreversibly to these receptors in vivo. [18F]Haloperidol may not be suitable for in vivo PETT studies, because of a relatively high component of nonspecific distribution and a faster dissociation from the receptor. Analysis of 18F in plasma after injection of [18F]spiroperidol indicated rapid metabolism to polar and acidic metabolites, with only 40% of the total radioactivity being present as unchanged drug after 30 min. Analysis of the metabolic stability of the radioactively labeled compound in rat striatum indicated that greater than 95% of [18F]spiroperidol remains unchanged after 4 h.     

Some aspects of the natural history and food selection ofAvahi laniger

Two groups ofAvahi laniger were studied in the Forêt de Analamozoatra near Perinet in the eastern rainforest of Madagascar from August to October 1984. Overlap between the home ranges of neighbouring groups ofA. laniger was minimal. Group size ranged from one to four individuals with a median group size of two. In four out of ten groups a baby was born between August and September.A. laniger were most active after dusk and before dawn. They had an extended resting period around midnight. Their diet consisted mostly of leaves from at least 17 different plant species. They also ate flowers. Fruit eating was recorded twice. Leaves eaten had high contents of protein and sugar but did not contain alkaloids. The concentration of condensed tannins did not differ between food items and non-food items. There was no indication of competition with other prosimians that might explain their nocturnality.     

Use of purified antipeptide sera of selected specificity for the detection of the simian virus 40 large T antigen by western blotting

Western blotting was used as a powerful alternative to immunoprecipitation for the detection of the simian virus 40 (SV40) large tumor (T) antigen. After resolution by electrophoresis on a SDS-polyacrylamide gel of a [¹⁵S]methionine labeled crude extract from SV40 infected monkey kidney cells, the separated proteins were transferred electrophoretically on nitrocellulose paper. T antigen was detected on nitrocellulose strips by using for the first time, specific, purified antipeptide monoclonal antibodies directed against the N- and C-terminal portions of the molecule, and¹²⁵I-labeled Protein A.     

Morphogenic substances released by plant tissue cultures

The release of endogenous substances is a general phenomenon of plant tissue cultures, with some substances having significant developmental effects on the releasing tissues. Their systematic study was initiated with Nandina tissue cultures, and a yellow compound that accumulated in the culture medium was identified as the alkaloid, berberine. The rate of its release was related to the supplies of auxin, cytokinin, and nutrient salts. Addition of berberine \ HCl to nutrient media did not inhibit Nandina tissues, but suppressed shoot formation in Nicotiana stem segments. Growth of Nandina and Nicotiana callus, as well as rooting of Nicotiana stem segments, was promoted by alkaloid addenda.