IMMUNOGLOBULIN SYNTHESIS AND SECRETION, III. INCORPORATION OF GLUCOSAMINE INTO IMMUNOGLOBULIN ON POLYRIBOSOMES

Mouse myeloma cells were pulse-labeled in vitro with (3)H-D-glucosamine and (14)C-L-leucine. Analysis on sucrose gradients revealed incorporation of both isotopes into polyribosomes and release of most of such radioactivity after treatment of labeled cells in vitro with puromycin. A mixing experiment excluded the in vitro binding to unlabeled polyribosomes of (3)H-glucosamine in labeled post-ribosomal material. Polyribosomes labeled with (3)H-glucosamine were precipitated with antiserum specific for mouse immunoglobulin. By chromatography and gel filtration, the precipitable radioactivity was shown to be glucosamine covalently bound to heavy and light chains.     

ON THE EFFECT OF THYROTROPIN AND IMMUNOGLOBULINS RELATED TO GRAVES'' DISEASE ON THYROTROPIN SYNTHESIS AND SECRETION

The effect of exogenous thyroxine (T₄), thyrotropin (TSH), long acting thyroid stimulator (LATS), immunoglobulin G fractions from (a) thyrotoxic sera without LATS and (b) sera from patients with ophthalmic Graves' disease, upon serum TSH concentration and pituitary TSH content has been investigated in the guinea-pig. Pituitary TSH content was significantly lower in animals injected with T₄ (1.80 mU), TSH (2.80 mU) and LATS (3.20 mU) than that in the controls (6.40 mU). Thyroidectomy caused a significant elevation in serum TSH concentration (22.30 mU/dl vs 6.67 in sham operated controls) but no significant alteration in pituitary TSH content (4.40 mU vs 3.80 mU in sham operated controls). TSH injections in thyroidectomised animals induced a significant increase in serum TSH concentration (31.60 mU/dl) and the pituitary TSH content (6.50 mU). Two out of four IgG samples from patients with ophthalmic Graves' disease caused a fall in serum TSH concentration (12.90 and 14.40 mU/dl) with a concomitant rise in pituitary TSH content (9.00 and 9.30 mU) in thyroidectomized animals. It is concluded (1) that exogenous TSH induces an enhanced TSH synthesis and release in thyroidectomised guinea-pigs which suggests the presence of a positive ‘short loop’ feedback for TSH and (2) that IgG fractions from some sera of ophthalmic Graves' disease may have the ability to inhibit TSH release from the pituitary. This inhibitory effect, hitherto not described, may be responsible for the diminished TRH induced TSH release in some patients with euthyroid Graves' disease.     

BIOSYNTHESIS OF INSULIN IN BOVINE FETAL PANCREATIC SLICES: THE INCORPORATION OF TRITIATED LEUCINE INTO A SINGLE-CHAIN PROINSULIN, A DOUBLE-CHAIN INTERMEDIATE, AND INSULIN IN SUBCELLULAR FRACTIONS

This communication reports the biosynthesis of insulin in the bovine fetal pancreatic slices in vitro. Double-chain proinsulin and insulin were found as major components in the mitochondrial-granule fraction of bovine fetal pancreas. Tritiated leucine was incorporated into a single-chain proinsulin, a double-chain proinsulin, and insulin. Subcellular fractionation of the slices incubated with tritiated leucine showed that radioactive single-chain proinsulin was present in the deoxycholate-soluble microsomal fraction, deoxycholate-insoluble microsomal fraction, and mitochondrial-granule fraction. Labeled double-chain proinsulin and insulin were present in the deoxycholate-soluble microsomal and mitochondrial-granule fractions. These results are consistent with the hypothesis that insulin is synthesized as a single-chain polypeptide on the ribosomes, and that intracellular proteolysis in the subcellular membranous organelles and beta-granules converts the single-chain proinsulin to insulin via a double-chain intermediate.     

THE EFFECT OF INDOMETHACIN AND ASPIRIN ON ALKALINE PHOSPHATASE SECRETION AND [3H]THYMIDINE INCORPORATION BY HUMAN OSTEOBLASTS

Since it has been suggested that long-term treatment with indomethacinand other non-steroidal anti-inflammatory drugs (NSAIDs) mayresult in destructive changes in the hip joint, we have examinedthe effect of indomethacin and aspirin on the secretory andmitotic activity of human osteoblasts in culture. Both indomethacinand aspirin inhibited the secretion of alkaline phosphataseand the uptake of [³H]thymidine by osteoblasts in a dose-dependentfashion at therapeutic concentrations. Both drugs also inhibitedinsulin- and 1,25-dihydroxycholecalciferol-stimulated alkalinephosphatase production and [³H]thymidine uptake by human osteoblasts.It is concluded that indomethacin and aspirin, and possiblyother NSAIDs, may have an inhibitory effect on osteoblast function. KEY WORDS: Indomethacin, Aspirin, Alkaline phosphatase, Osteoblasts     

LEUCINE tRNA AND CESSATION OF Escherichia coli PROTEIN SYNTHESIS UPON PHAGE T2 INFECTION

The involvement of tRNA in cellular differentiation has been tested by analyzing aminoacyl-tRNA of Escherichia coli after phage T2 infection. One or two minutes after infection, half of one of the five leucine tRNA components (Leu-tRNA(1), CUG responding) undergoes a drastic structural change which leads to inactivity of both leucine acceptor activity and codon response. Whether or not the modification causes cessation of host protein synthesis without inhibiting phage-specific protein synthesis has been examined by analyzing polysome-bound leucine tRNA of E. coli before and after the phage infection. The results presented in this paper indicate that the amount of Leu-tRNA(1) used after infection was greatly reduced as compared to that used in noninfected cells. Studies of the in vitro protein-synthesizing system show that T2 mRNA rarely contains the CUG codon. A mechanism by which host mRNA translation is inhibited by the phage infection is proposed from this available information.     

伯氏疟原虫感染红细胞中的游离氨基酸和多胺生成的研究

伯氏疟原虫氯喹敏感株(CS)和抗氯喹株(CR)感染红细胞中的游离氨基酸量和鸟氨酸脱羧酶活力均相接近,用氯喹10mg/kg im两个株的感染小鼠,20h后对游离氨基酸无抑制作用.氯喹剂量为5mg/kg时,抑制CS和CR感染红细胞的鸟氨酸脱羧酶活力为79.6和55.7％。 CS和CR感染红细胞中的精脒量为139±27和528±140nmol/10~9感染红细胞。环亮氨酸剂量为80mg/kg时,能抑制CS和CR感染红细胞的精脒生成,其抑制率分别为44和57％,加喂甲硫氨酸(100mg/kg)后,精脒量分别上升至294和657nmol/10~9感染红细胞。但是与两者仍有一定差距,故认为在S-腺苷甲硫氨酸合成酶及其后的代谢环节仍有差异.     

SUPPRESSION AND STIMULATION OF IMMUNOGLOBULIN SYNTHESIS BY AGENTS PRESENT IN RHEUMATOID SYNOVIAL EFFUSIONS

Synovial effusions from 14 patients with rheumatoid arthritiscontain factors capable of enhancing and suppressing the productionof immunoglobulin when added to normal peripheral lymphocytecultures in vitro. Utilizing a radioactive immune coprecipitationtechnique it could be demonstrated that enhancement was observedupon addition of relatively small amounts of synovial fluid,while addition of higher amounts resulted in suppression ofimmunoglobulin synthesis. Nine of ten non-rheumatoid joint effusionsshowed neither enhancing nor suppressing activities. The possiblerelationship of these events to lymphokine production in thejoint is discussed.     

EFFECTS OF CYPROHEPTADINE ON INSULIN-INDUCED HYPOGLYCAEMIA SECRETION OF PRL, GH AND CORTISOL

The effect of cyproheptadine hydrochloride on release of prolactin (PRL), growth hormone (GH) and cortisol following insulin-induced hypoglycaemia was investigated in a group of eight adult female and male subjects. The results of this study demonstrated that cyproheptadine does not influence the release of these three hormones under the conditions employed in this study. The conflicting observation concerning the action of cyproheptadine on pituitary function as reported in the literature, may be a reflection of the diversity of pharmacological actions of this drug. Thus, any purported influence this drug might have on pituitary hormonal release should be interpreted with caution.