Correlation of 19F-NMR spectra of halothane in rat tumor and non-tumor tissues with membrane alterations

The membrane environments in normal and tumor rat tissue and the effect of hyperthermia thereon are studied with 19F-NMR spectroscopy of the general anesthetic halothane. Normal and tumor cell types are clearly differentiated by the halothane resonance. A hydrophobic environment prominent in tumor tissue is more sensitive to heat treatment than the corresponding environments of normal cells. Studies of extracted lipids suggest that this may be due in part to the considerable difference in lipid temperature response which exists between normal and kidney tumor cells.     

Beta-adrenergic receptor-linked adenylate cyclase in rat posterior pituitary

A specific β-adrenergic-stimulated cyclic AMP generating system has been evidenced in rat posterior pituitary. This is clearly demonstrated by: 1) the adenylate cyclase (AC) affinity for stimulants was in the order ISO > NA > DA, and 2) propranolol, a specific β-adrenergic receptor blocker, was the only antagonist of the system. Clonidine and apomorphine were completely inactive, thus excluding an α-adrenergic and/or dopaminergic component in this AC system. Our data also indicate that dopaminergic receptors present in both pituitary lobes are not coupled to an AC.     

Determination of the molecular mass of bacterial genomic DNA and plasmid copy number by high-pressure liquid chromatography

Relatively rapid methods for the determination of relative genome molecular mass (Mr) and the estimation of plasmid copy number have been developed. These methods are based on the ability of the Bio-Rad high-pressure liquid chromatography hydroxylapatite column to separate and quantify single-stranded DNA, double-stranded DNA, and plasmid DNA. Genome Mr values were calculated from reassociation kinetics of single-stranded DNA as measured with the hydroxylapatite column. Bacteriophage T4 DNA was used to establish a C0t (moles of nucleotides times seconds per liter), or standard reassociation value. From this C0t value, C0t values for Escherichia coli B, Beggiatoa alba B18LD, and Streptomyces coelicolor were determined by comparative calculations. From those calculated C0t values, the Mr values of 1.96 X 10(9) for E. coli, 2.02 X 10(9) for B. alba, and 3.28 X 10(9) for S. coelicolor were estimated. Plasmid concentration was determined from cleared lysates by comparing the integrated area under the phosphate buffer-eluted plasmid peak to values obtained with known amounts of plasmid. The plasmid copy number was estimated by multiplying the ratio between the amounts of plasmid and chromosomal DNA by the ratio between the Mr values of the chromosome and the plasmid. A copy number of 29 was obtained from a culture of E. coli HB101 harboring pBR322 grown to a culture density of 1.6 X 10(9) CFU . ml-1.     

Cytokeratin provides a specific marker for human arachnoid cells grown in vitro

Cells from cranial and spinal arachnoid membranes of humans were grown in culture. Their growth characteristics, morphology and details of their cytoskeletal composition are described. Arachnoid membranes, obtained at autopsy, were finely minced and incubated in tissue culture medium. Monolayers of cells of homogeneous morphology grew from these tissue fragments. The cells were flat and polygonal. They divided slowly to form non-overlapping monolayers of low cell density. Electron microscopic examination of cultured arachnoid cells revealed numerous desmosome-like tight junctions and abundant intermediate filaments (tonofilaments). Both morphological features are characteristic of arachnoid cells in situ, but not of cells in the fibroblast-rich dura mater. Immunofluorescence microscopy with monoclonal antibodies demonstrated cytokeratin in the cytoplasm of primary cultures of arachnoid cells. Thus we demonstrated that these cultured cells retained certain of the specific differentiated properties of arachnoid cells in situ and that they are not fibroblasts (which lack tight junctions and cytokeratins). To our knowledge, there have been no previous reports of in vitro growth of arachnoid cells. This in vitro model should be useful in studying the response of arachnoid cells to a variety of substances thought to be involved in the chronic inflammatory condition of the meninges known as arachnoiditis.     

Heterogeneity of ovine prolactin after labeling with iodine 125: value of labeling with lactoperoxidase]

The authors have shown an heterogeneity of the ovine prolactine molecule after labelling with iodine 125. As well with chloramine T as with lactoperoxydase, it appears three molecular species which react with the immune serum antiprolactine (I.S.). The first species is of high molecular weight and is probably constituted of aggregates. Their combination with the I.S. is non specific and give blanks of high value. The second species is a dimere and the third one is the monomere. The two last species react with the I.S. and can give competition curves when they are choosen as tracer. However, if one uses as tracer a product obtained by labelling with chloramine T, the competition appears for high concentrations of native hormone. As if the I.S. recognizes much more the labelled protein than the native one. But if one uses the same species but labelled with lactoperoxydase, the competition appears for concentrations lower than five nanogrammes. In the same time one can see that the specificity toward different I.S. is modified. The authors think that the labelling with lactoperoxydase better preserves the tertiary structure of the native protein than do the labelling with chloramine T.     

Effects of Δ8- and Δ9-Tetrahydrocannabinol on experimentally induced seizures

Effects of Δ⁸- and Δ⁹-tetrahydrocannabinol (Δ⁸- and Δ⁹-THC) on three experimentally induced seizure models, i.e., audiogenic seizure (AS) test, maximal electroshock seizure (MES) test and pentylenetetrazol (PTZ)-induced seizure test were determined in the audiogenic rat. Both tetrahydrocannabinols possess a dose-related anticonvulsant effect against AS, MES and PTZ-induced maximal seizure. Although anticonvulsant potencies do not significantly differ, Δ⁸THC is three times more neurotoxic than Δ⁹THC. In addition, both THC's are without effect on minimal seizure and lethality induced by PTZ. Furthermore, the low protective indexes (TD50/ED50) determined in this study suggest that Δ⁸ and Δ⁹ THC may have poor therapeutic potentials as antiepileptic drugs.