Modulation of GABA Receptor Binding by Ca+2

In frozen-thawed repeatedly washed rat cortical synaptic membranes, Ca2+ (1-5 mM) decreased the binding of [3H]muscimol whereas it increased the binding of [3H]gamma-aminobutyric acid (GABA). However, the binding of [3H]GABA was decreased by the same extent as the binding of [3H]muscimol when the membranes were incubated with baclofen (a selective ligand for the GABAB binding site) and Ca2+. Scatchard analysis of [3H]muscimol binding revealed that Ca2+ reduced the density of GABA binding sites without affecting the dissociation constant. Ca2+ was more potent than Ba2+, Mg2+ was ineffective, and the Ca2+ antagonist La3+ stimulated [3H]muscimol binding. The inhibition of [3H]muscimol binding by Ca2+ was not influenced by calmodulin (50 micrograms/ml), trifluoperazine (10(-5) M), verapamil (10(-6) M), quinacrine (10(-4) M), cordycepin (0.1 mM), leupeptin (20 microM), or soybean trypsin inhibitor (0.1 mg/ml). Moreover, the effect of Ca2+ was additive to that of GABA-modulin. These results indicate that Ca2+ decreases the number of GABAA binding sites while unveiling GABAB binding sites.     

Modulation of endogenous prostaglandins by thymosin-α1 in lymphocytes

The effects of thymosin-α₁ on the stimulation of specific release of prostaglandin E₂ (PGE₂) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α₁ in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE₂ between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α₁ at certain concentrations was able to stimulate PGE₂ release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE₂ after incubation with α₁ in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α₁ was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α₁ after administration of this synthetic molecule show a clear dissociation. A maximum peak of α₁ activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α₁ of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α₁ requires prostaglandin biosynthesis.     

Lymphocyte transformation to connective tissue antigens in adult and juvenile rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, systemic lupus erythematosus, and a nonarthritic control population

Transformation of peripheral blood lymphocytes after exposure to connective tissue antigens was measured in patients with adult (n = 35) and juvenile rheumatoid arthritis (n = 34), osteoarthritis (n = 21), ankylosing spondylitis (n = 15), and systemic lupus erythematosus (n = 26) and in control subjects (n = 36). The connective tissue antigens included homologous cartilage-type proteoglycan, cyanogen bromide-derived peptides of type I, II, and III collagens, and type I and II helical collagens. Lymphocyte transformation was not detected in the osteoarthritic and control groups, with one exception. Sensitization to at least one connective tissue antigen was detected in approximately one-third of the rheumatoid arthritic and lupus patients and in one-quarter of the juvenile rheumatoid patients. In ankylosing spondylitis, positive responses occurred to proteoglycan in 20% of patients tested but never to collagens or peptides. Sensitivity to proteoglycan was detected only in ankylosing spondylitis except for one patient with juvenile rheumatoid arthritis. In patients with systemic lupus erythematosus and both forms of rheumatoid arthritis, lymphocyte transformation was usually more frequently detected to peptides than to the helical collagens. In adult rheumatoid arthritis, type II peptides elicited an elevated number of responses (14%) as did type I (9%) and III (8%) peptides to lesser degrees. Responses to type I (4%) and II (4%) helical collagens were infrequent. Rheumatoid arthritic patients usually exhibited sensitivity to only one antigen and lymphocyte transformation was often detected when the arthritis was improving. In juvenile rheumatoid arthritis, lymphocyte transformation was detected to peptides of type I (16%), II (9%), and III (29%) collagens and to helical type I (12%) and II (8%) collagens. In systemic lupus erythematosus, sensitization was detected to peptides of type I (13%), II (20%), and III (14%) collagens and to helical type I collagen (18%) but not type II collagen. Simultaneous sensitivity to several antigens often occurred in both systemic lupus erythematosus and juvenile rheumatoid arthritis. Examination of individual patients in all three rheumatic disease groups revealed that immune sensitivity developed to collagen peptides rather than to the helical molecules, particularly in the case of type II collagen. Thus, some patients with inflammatory arthritis exhibit immune responses to connective tissue components which are, as a group, characteristic for each type of arthritis. These responses, which were not obviously associated with disease activity, may develop as a result of inflammation or trauma which destroys connective tissue and exposes molecules, in either a native or degraded state, to cells of the immune system. Expression of sensitivity to these tissue antigens may contribute to the chronicity of the inflammatory arthritides.     

In vivo interactions of acrylonitrile with macromolecules in rats

The irreversible binding of [2,3-14C]acrylonitrile (VCN) to proteins, RNA and DNA of various tissues of male Sprague-Dawley rats after a single oral dose of 46.5 mg/kg (0.5 LD50) has been studied. Proteins were isolated by chloroform-isoamyl alcohol-phenol extraction. RNA and DNA were separated by hydroxyapatite chromatography. Binding of VCN to proteins was extensive and was time dependent. Radioactivity in nucleic acids was registered in the liver and the target organs, stomach and brain. DNA alkylation, which increased by time, was significantly higher in the target organs, brain and stomach (119 and 81 pmol/mg, respectively, at 24 h) than that in the liver. The covalent binding indices for the liver, stomach and brain at 24 h after dosing were, 5.9, 51.9 and 65.3, respectively. These results suggest that VCN is able to act as a multipotent carcinogen by alkylation of DNA in the extrahepatic target tissues, stomach and brain.     

Presence of mast cell precursors in the yolk sac of mice

Concentration of mast-cell precursors in hematopoietic tissues of mouse embryos was evaluated by a limiting dilution method. Cells from yolk sacs, livers, and bodies of (WB x C57BL/6)F1 (hereafter called WBB6F1)- +/+ embryos were injected directly into the skin of adult WBB6F1-W/Wv mice which were genetically depleted of tissue mast cells. Concentration of mast-cell precursors was calculated from the proportion of injection sites at which mast cells did not appear. Since the concentration of mast-cell precursors in the yolk sac was about 30 times as great as that of embryonic body at Day 9.5 of the pregnancy, the mast-cell precursors seemed to be generated within the yolk sac. The concentration in the yolk sac reached the maximum level at Day 11, and then dropped markedly at Day 13. In contrast, mast-cell precursors increased from Day 11 to Day 15 in the fetal liver. As a result, the concentration of 11-day yolk sacs was comparable to that of 15-day fetal liver. Although intravenous injection of 15-day fetal liver cells (2 x 10(6)) rescued the general mast-cell depletion of WBB6F1-W/Wv mice, the intravenous injection of the same number of 11-day yolk sac cells did not rescue it. In contrast with fetal livers, yolk sacs scarcely contained hematopoietic stem cells which were measured by spleen colony formation. Therefore, the mast-cell precursors of the yolk sac may not originate from such stem cells.     

The effect of vitamin A on limb regeneration in Rana temporaria

Previous experiments in which vitamin A has been administered to developing or regenerating limbs have shown that different limb axes are affected. In regenerating axolotl limbs, serial reduplications in the proximodistal axis are produced. In the developing chick limb bud, mirror-imaged reduplications in the anteroposterior axis are produced. Results reported here on Rana temporaria limb buds reveal that vitamin A causes both effects to occur. That is, limbs are both serially reduplicated in the proximodistal axis and mirror imaged in the anteroposterior axis. Time and concentration effects are explored and the significance of these results for our current understanding of axial organisation in limbs is discussed.     

Behavior of lactating rats in a dual-chambered maternity cage

Videotape sampling of behavior in a dual-chambered apparatus indicates that the continuous monitoring of the amount of time a mother spends in the cage with its litter can be taken as a valid reflection of maternal behavior. Nursing is the principal behavior of lactating females while in the compartment with their litters; lying still, consummatory behavior, and activity occur with greater frequency in the cage away from the litter. Both the time that mothers spend with their litters and nursing behavior displayed a 24-hr rhythm with crest values occurring during the period of light.     

Immunologic and clinical improvement of progressive coccidioidomycosis following administration of transfer factor

Three patients with progressive coccidioidomycosis were given preparations of transfer factor (TF). Adverse reactions to TF were minimal. Following TF administration two of these patients had prolonged clinical remissions in their coccidioidal disease. Cellular immune responses were sequentially evaluated by coccidioidininduced delayed-type skin tests, lymphocyte blast transformation and macrophage inhibition factor production (MIF). These three patients each exhibited different cellular immune patterns before and after TF administration. Two patients converted their coccidioidin skin tests, and one converted lymphocyte transformation response to coccidioidin. Also, TF apparently favorably affected the MIF response in all three patients.