Spontaneous release of endogenous aspartate and glutamate from rat striatal slices is increased following destruction of local neurons by ibotenic acid

We sought to determine in rat striatum whether the release of neurotransmitter amino acids aspartate (Asp), glutamate (Glu) and gamma-aminobutyric acid (GABA) were affected by local neurons. To do so, unilateral microinjections of ibotenic acid, an excitotoxin that destroys local neurons without affecting fibers of passage, were made into the striatum. Release of endogenous amino acids from lesioned and intact striatal slices were measured by HPLC one week later. The effectiveness and specificity of the lesion were confirmed by measuring the enzyme activity associated with extrinsic dopamine neurons (tyrosine hydroxylase; 111±14%), intrinsic GABA neurons (glutamic acid decarboxylase; 19±7%) and intrinsic acetylcholine neurons (choline acetyltransferase; 37±10%). Destruction of local striatal neurons markedly attenuated the release of GABA (41±12% of control) elicited by depolarization with K⁺ (35 mM), but did not significantly reduce the K⁺-evoked release of Asp (80±17%) and Glu (92±8%). However, spontaneous release of Asp and Glu was significantly greater than that observed in unlesioned tissue (159±18% and 209±27%, respectively), while the spontaneous release of GABA was not significantly reduced (75±43%). Although release of the neurotransmitter amino acids Asp, Glu and GABA were affected by the lesion, the release of the non-neurotransmitter amino acid tyrosine was unaffected. These data are consistent with the hypotheses that: 1) the predominant source of releasable stores of endogenous Asp and Glu in the striatum arises from extinsic neurons, and 2) that the spontaneous release of Asp and Glu from axon terminals in the striatum may be regulated, at least in part, by local inhibitory neurons.     

Dendritic cell activating factor produced by mouse macrophage hybridoma

A mouse macrophage (M phi) hybridoma which produces a soluble factor responsible for the cooperation between M phi and spleen dendritic cells (DC) was constructed. The antigen-presenting activity and the stimulator cell activity in the allogeneic or syngeneic mixed leukocyte reaction of DC were significantly augmented when DC were incubated with the culture supernatant of the hybridoma treated with various stimulants including latex beads. The monokine present in the culture supernatant of the hybridoma, called dendritic cell-activating factor (DCAF), augmented the production of lymphocyte-activating factor by DC while Ia expression of DCAF-treated DC was not altered. DCAF had no effect on the antigen-presenting activity of peritoneal resident M phi or B cell blasts while the antigen-presenting activity of spleen M phi was enhanced, but the degree of the enhancement was much less than that of spleen DC. DCAF was found to have the following properties: its pI value is between pH 4 and 5; it is stable at pH 2 to 10; and it loses its activity on incubation at 75 C for 30 min. When the culture supernatant of the hybridoma stimulated with latex beads was subjected to gel filtration, the DCAF activity was detected in the 20 Kd to 25 Kd, 30 Kd to 40 Kd, and 50 Kd to 60 Kd molecular weight regions. The 30 Kd to 40 Kd fraction, which is the major peak fraction, was further purified by ion-exchange chromatography followed by gel-filtration chromatography. When each fraction was subjected to SDS-PAGE, a 30 Kd band corresponding to the DCAF activity was observed and DCAF was purified to about 90% purity.     

Identification by molecular cloning of two forms of the alpha-subunit of the human liver stimulatory (GS) regulatory component of adenylyl cyclase

Two DNA molecules complementary to human liver mRNA coding for the alpha-subunit of the stimulatory regulatory component Gs of adenylyl cyclase were cloned. One of the two forms is a full-length cDNA of 1614 nucleotides plus a poly(A) tail of 59 nucleotides. The deduced sequence of 394 amino acids encoded by its open reading frame is essentially identical to that of the alpha-subunits of Gs identified by molecular cloning from bovine adrenals, bovine brain and rat brain. Two independent clones of the other type of cDNA were isolated. Both were incomplete, beginning within the open reading frame coding for the alpha s polypeptide. One codes for amino acids 5 through 394 and the other for amino acids 48 through 394 of the above described cDNA of 1614 nucleotides, and both have the identical 3'-untranslated sequence. They differ from the first cDNA, however, in that they lack a stretch of 42 nucleotides (numbers 214 through 255) and have nucleotides 213 (G) and 256 (G) replaced with C and A, respectively. This results in a predicted amino acid composition of another alpha-subunit of Gs that is shorter by 14 amino acids and contains two substitutions (Asp for Glu and Ser for Gly) at the interface between the deletion and the unchanged sequence. We call the smaller subunit alpha s1 and the larger alpha s2. This is the first demonstration of a structural heterogeneity in alpha s subunits that is due to a difference in amino acid sequence.     

Occurrence and distribution of halophilic vibrios in subtropical coastal waters of Hong Kong.

The summer occurrence and distribution of halophilic vibrios in the subtropical coastal waters of Hong Kong were investigated. The density of vibrios in six sample sites ranged from 90 to 6,700 per ml, which made up 0.41 to 40% of the total bacterial populations of these sample sites. The sucrose-positive vibrios were found to be much more common (88% of total vibrios) than the sucrose-negative ones. A total of 48 strains belonging to six Vibrio species were fully characterized. Among these, Vibrio alginolyticus was the most frequently isolated, followed by V. parahaemolyticus, V. harveyi, V. vulnificus, V. campbellii, and V. fluvialis. The finding that eight of the nine strains of V. harveyi showed a positive Kanagawa reaction warrants further study.     

Simultaneous Measurements of Steady State Chlorophyll a Fluorescence and CO(2) Assimilation in Leaves: The Relationship between Fluorescence and Photosynthesis in C(3) and C(4) Plants

Rates of CO₂ assimilation and steady state chlorophyll a fluorescence were measured simultaneously at different intercellular partial pressures of CO₂ in attached cotton (Gossypium hirsutum L. cv Deltapine 16) leaves at 25°C. Electron transport activity for CO₂ assimilation plus photorespiration was calculated for these experiments. Under light saturating (1750 microeinsteins per square meter per second) and light limiting (700 microeinsteins per square meter per second) conditions there was a good correlation between fluorescence and the calculated electron transport activity at 19 and 200 millibars O₂, and between fluorescence and rates of CO₂ assimilation at 19 millibars but not 200 millibars O₂. The values of fluorescence measured at about 220 microbars intercellular CO₂ were not greatly affected by increasing O₂ from 19 to 800 millibars. Fluorescence increased with light intensity at any one intercellular CO₂ partial pressure. But the values obtained for fluorescence, expressed as a ratio of the maximum fluorescence obtained in DCMU-treated tissue, over the same range of CO₂ partial pressure at 500 microeinsteins per square meter per second were similar to those obtained at 1000 and 2000 microeinsteins per square meter per second. There were two phases in the observed correlation between fluorescence and calculated electron transport activity: an initial inverse relationship at low CO₂ partial pressures which reversed to a positive correlation at higher values of CO₂ partial pressures. Similar results were observed in the C₃ species Helianthus annuus L., Phaseolus vulgaris L., and Brassica chinensis. In all C₄ species (Zea mays L., Sorghum bicolor L., Panicum maximum Jacq., Amaranthus edulis Speg., and Echinochloa frumentacea [Roxb.] Link) examined changes in fluorescence were directly correlated with changes in CO₂ assimilation rates. The nature and the extent to which Q (primary quencher) and high-energy state (q_E) quenching function in determining the steady state fluorescence obtained during photosynthesis in leaves is discussed.     

Chromosomal localization of the human alpha 1-antitrypsin gene (PI) to 14q31-32.

In situ hybridization of a recombinant cDNA probe containing the human alpha 1-antitrypsin gene to metaphase chromosomes demonstrated significant hybridization to chromosomal segment 14q31-32. A high percentage of cells analyzed (31%) displayed labeling on chromosome 14. Of all labeled sites on chromosome 14, 60% were found on segment 14q31-32. These results refine the previous assignment of the human alpha 1-antitrypsin gene to segment 14q24.1-32.1.     

Influences of medium consistency and shoot density on in vitro shoot proliferation of Populus alba × P. grandidentata

The in vitro shoot proliferation of Populus alba × P. grandidentata was affected by the medium consistency and shoot density, but not by three sizes of vessels. After 4 weeks of culture, the fresh weight and number of shoots per explant on liquid medium were significantly greater than those on agar-solidified medium. In particular, 3.2 shoots, 7 mm or longer per explant, were produced on liquid medium compared with 1.6 shoots per explant or agar-solidified medium. The fresh weight per explant after 4 weeks of culture on liquid medium and agar-solidified medium were 0.68 and 0.25 g, respectively. Increasing the number of shoots per vessel slowed the growth of the explants as measured by fresh weight and the number of shoots produced. There was little difference in the number of shoots produced between vessels with 1 or 2 shoots per vessel, but there were many fewer shoots produced when 3 shoots were placed in each vessel.Journal Paper No. J-11977 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 2210.     

Sequence homology between human alpha 1-antichymotrypsin, alpha 1-antitrypsin, and antithrombin III

alpha 1-Antichymotrypsin mRNA was isolated by specific polysome immunoprecipitation from turpentine-treated baboon liver. The highly enriched mRNA was used for synthesis and cloning of the corresponding cDNA. Baboon alpha 1-antichymotrypsin cDNA clones were identified by hybrid-selected translation, and the insert DNA fragment from one of the putative clones was used as a probe to screen a human liver cDNA library comprised of 40 000 independent transformants. One of the human cDNA clones was unambiguously identified to contain alpha 1-antichymotrypsin DNA sequences by comparison of its 5'-terminal nucleotide sequence with the N-terminal amino acid sequence of the protein. This cDNA clone, designated phACT235, contains 1524 base pairs of human DNA, which was sequenced in its entirety. The inserted DNA codes for a 25 amino acid signal peptide sequence and the entire mature alpha 1-antichymotrypsin of 408 amino acid residues. Comparison of the amino acid sequence of alpha 1-antichymotrypsin with that of the human alpha 1-antitrypsin has revealed a homology level similar to that between chymotrypsin and trypsin.     

Thyroid hormones in cyclostomes and fish and their role in regulation of intermediary metabolism

1. Experimental data obtained in cyclostomes and fish concerning the plasma levels of thyroxine and tri-iodothyronine as well as their influence on intermediary metabolism of lipids, carbohydrates, and proteins are reviewed. 2. The information dealing with the physiological role of thyroid hormones in regulation of metabolic processes seems to be scarce in cyclostomes and controversial in fishes. 3. Nevertheless, the data covered in the review support the generalization that thyroid hormones, probably along with some other hormones, exert a regulatory action on the metabolic processes already on the lower stage of the evolution of poikilothermic vertebrates.     

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