Application of antimony microelectrodes to intracellular pH monitoring

Some novel studies of the properties of the antimony microelectrode used for intracellular pH measurements are described. First, it is shown that currents in the picoampere range, such as those encountered as leakage in some electrometers, induce important changes in pH sensitivity. The response time of the electrode has also been measured and indicates that the electrode exhibits a rapid time course which would be very useful for dynamic cytoplasmic pH investigations. An example of internal pH recording during cellular acidification in Xenopus laevis oocyte is also presented.     

Enzyme-amplified enzyme-linked immunosorbent assay for gibberellin A4 based on the NAD-dependent redox cycle

An antiserum against gibberellin A₄ (GA₄) raised in rabbits and its partially purified antibodies were used to develop radioimmunoassay (RIA) and indirect enzyme-linked immunosorbent assays (ELISAs) for GA₄. Of three immunoassays tested, an ELISA based on the NAD-dependent redox cycle (enzyme-amplified ELISA) had highest sensitivity. Levels of methylated GA₄ detected by this most sensitive method ranged from 0.1 fmol/assay (3.5 fg/assay) to 0.1 pmol/assay (3.5 pg/assay) suggesting applicability of this method to the detection of gibberellins in purified plant extracts.     

Extrachromosomal human immunodeficiency virus type-1 DNA can initiate a spreading infection of HL-60 cells

In this report, we describe a human immunodeficiency virus type-1 (HIV-1)-infected promyelocytic cell line, OM, derived from HL-60 cells. Although the OM cell line was biologically cloned twice, the pattern of HIV-1 expression during culture appeared analogous to a classical acute spreading infection and was inhibited by both azidothymidine and recombinant soluble CD4 treatment. The number of OM cells actually expressing HIV-1 at the beginning of culture was 0%, reached a peak of nearly 100% at 6 weeks, and then fell to less than 10% HIV-1+ cells by 10 weeks. Clonal analysis of the surviving cells verified that stable HIV-1+ OM cells resulted from the spreading infection. Southern analysis confirmed the transmission of HIV-1 through these OM cultures and the occurrence of stable clones which resulted. The initial percentage of OM cells actually harboring the HIV-1 genome was less than 0.1%, indicating nonfaithful transmission of an unintegrated HIV-1 genome during clonal expansion. These results demonstrate that extrachromosomal HIV-1 DNA can contribute to the spread of HIV-1 infection and give rise to cells which have stably integrated HIV-1 provirus.     

A fluorogenic method for the demonstration of human serum 5′-nucleotide phosphodiesterase isozymes after polyacrylamide gel electrophoresis

A rapid fluorogenic method for the demonstration of 5′-nucleotide phosphodiesterase in human serum has been developed. This method uses the substrate 4-methylumbelliferyl 5′-thymidylate impregnated in agarose gels or filter paper strips. Zymograms are developed in less than 30 min at 25°C, and the sensitivity of this method has been compared with that of the indigogenic method.     

An approach to the identification of adenosine''s inhibitory site on adenylate cyclase

The separate and combined effects of molybdate and dithiothreitol on the stability of human uterine 9 S estrogen receptor were studied. Maximal, short-term, protection of the 9 S estrogen receptor was achieved by the joint inclusion of both stabilizing agents in cytosol buffers. This molybdate—dithiothreitol-mediated stability was dependent on reducing agent concentration inferring sulphydryl involvement in 9 S receptor protection by molybdate. The study also showed that molybdate—dithiothreitol could not prevent the gradual decay of the 9 S estrogen receptor to the 4 S form in cytosols stored at 4°C over prolonged periods.     

Structural Characteristics of the Short-Tail Fibers of T4 Bacteriophage

The characteristics of pure preparations of short-tail fibers of bacteriophage T4 have been studied in the optical and electron microscope. Three main structures were observed: 1) spheres of 8.1 nm diameter; 2) fibers 43 nm long and 3.8 nm thick; and 3) fibers 54 nm long and 3.2 nm thick. Both types of fibers exhibited a regular beaded appearance. The 43-nm fibers were the most abundant structure. During the process of purification of the short-tail fibers, the formation of aggregates was observed each time the material containing the short-tail fibers was dialyzed against saline solutions. These aggregates became increasingly fibrous (as observed in the optical microscope) as the material used was increasingly enriched in short-tail fibers. Finally, most of the aggregates were of the fibrous type when they were formed from a purified preparation of short-tail fibers. In the electron microscope, it was found that the filamentous aggregates were organized in well-defined bundles. The amino acid composition of the highly purified short-tail fibers was also determined. Among the known fibrous proteins, the ones that most resemble the amino acid composition of the short-tail fibers are actin and fibrinogen. These observations are discussed in relation to the T4 short-tail fiber structure and their localization on the hexagonal baseplate of the T4 tail structure.     

Increased Noradrenergic Metabolism in the Cerebellum of the Mouse Mutant Dystonia Musculorum

Abstract: The neurological mouse mutant dystonia musculorum exhibits bizarre appendicular and truncal dystonia without known cerebellar histopathology. We evaluated striatal dopamine and cerebellar norepinephrine metabolism in this mutant and compared the results with those obtained in wild-type BALB/c and B6C3 controls. Tyrosine hydroxylase activity and dopamine metabolite levels (homovanillic acid and 3,4-dihydroxyphenylacetic acid) in the striatum of the mutant were similar to controls. Tyrosine hydroxylase activity and the steady-state level of 3-methoxy-4-hydroxyphenethyleneglycol, a metabolite of norepinephrine, in the cerebellum were 38% and 42-66%, respectively, greater in the mutant. However, the level of norepinephrine was similar (∼350 ng/g). Further, a Purkinje cell-specific marker, cGMP-dependent protein kinase, was unchanged in the mutant and no Purkinje cell pathology was observed with light microscopy. The lack of Purkinje cell derangement and similar levels of cerebellar norepinephrine and cGMP-dependent protein kinase activity suggest that increased norepinephrine metabolism in the cerebellum of this mutant is not a morphological response to gross target cell loss during morphogenesis. The observed changes may be a reaction to abnormal impulse traffic or altered input/output pathways to the mutant cerebellum during its development.     

Comparative phytotoxicity of nitrapyrin and ATC to several leguminous species

Summary The relative toxicity of nitrapyrin 2-chloro-6-(trichloromethyl) pyridine and ATC (4-amino-1, 2, 4-triazole) on the growth of chick peas (Cicer arietinum L.) cow peas (Vigna sinensis L.), green beans (Phaseolus vulgaris L.), green peas (Pisum sativum L.) and mung beans (Phaseolus aureus Roxb.) and their effectiveness as nitrification inhibitor were studied under greenhouse conditions. ATC produced no toxicity symptoms in green peas, whereas resulted in leaf chlorosis in cow peas, chick peas and green beans. However, nitrapyrin toxicity appeared as leaf chlorosis in cow peas, and interveinal chlorosis in chick peas. Moreover, nitrapyrin-treated green beans and peas developed leaf curling and cupping. Although ATC had no significant effect on growth, a suppression in plant growth was associated with nitrapyrin application. Furthermore, green beans was the most resistant and chick peas the most sensitive to nitrapyrin. Nitrapyrin was more effective nitrification inhibitor than ACT, especially at the lower rates.