Diversity in the immune system: “Preconceived ideas” or ideas preconceived?

Two concepts of the evolution and regulation of expression of the combining site repertoire of the immune system, are compared. One view is based on the Associative Recognition Theory as formulated by the author and the other is based on the Idiotype Network Idea as conceived by Jerne. The two concepts are analyzed from the point of view of their logic, internal consistency and factual support.     

Mesenchymal control of branching pattern in the fetal mouse lung

The effect of mesenchyme on specialization of respiratory epithelium in the fetal mouse was tested in organ cultures. Heterologous combinations were made between respiratory and non-respiratory lung epithelia and the corresponding mesenchymes. Isolated terminal respiratory buds of fetal mouse lungs were recombined with mesenchyme from chick lung parabronchi, mouse trachea or from the avascular, non-respiratory air sacs of chick lungs. Isolated non-branching chick air sacs were combined with mouse terminal bud mesenchyme or mesenchyme from the respiratory branches of chick lungs. Air sac epithelia branched in a pattern characteristic of the chick lung when combined with chick respiratory mesenchyme and in a pattern characteristic of mouse lung when combined with mouse terminal bud mesenchyme. Mouse terminal bud epithelia did not branch with either mouse tracheal mesenchyme or chick air sac mesenchyme but branched in a chick pattern with chick parabronchial mesenchyme. Electron microscopic examination of the cultures showed that all chick air sac epithelial cultures failed to produce surfactant (lamellar bodies) even when they branched. Control cultures of mouse terminal buds contained large numbers of lamellar bodies; mesenchyme which suppressed branching reduced the number of lamellar bodies to only a few in a small proportion of the cells. Culture medium supplemented with growth factors and hormones increased the number of lamellar bodies in heterologous mouse combinations but did not bring the number to control levels. Supplemented medium had no effect on lamellar body production by chick air sac epithelium. The results indicate that branching pattern is determined by the mesenchyme surrounding the epithelial primordium. However, the capacity to synthesize surfactant is determined by the source of the epithelium; mesenchyme may control the degree of expression but not the absolute presence or absence of the differentiated condition.     

Novel extracellular enzymes (ligninases) of Phanerochaete chrysosporium

Abstract 3 New spectrophotometric enzyme assays were developed for the study of microbial lignin-degrading enzymes. The conversion of 2-methoxy-3-phenylbenzoic acid to 2-hydroxy-3-phenylbenzoic acid led to the discovery of an extracellular, aromatic methyl ether demethylase produced by the white-rot fungus Phanerochaete chrysosporium . The conversion of methyl 2-hydroxy-3-phenylbenzoate to 2-hydroxy-3-phenylbenzoic acid allowed the identification of an extracellular, aromatic methyl ester esterase produced by this fungus. The Phanerochaete sp. also excreted an enzyme complex that oxidized 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, probably to aliphatic products. All 3 novel enzyme activities were produced together with, and probably comprise a part of, the Phanerochaete ligninolytic enzyme complex. Unlike previously known ligninases, these enzymes did not oxidize 3,4-dimethoxybenzyl alcohol. All 3 were H₂O₂-dependent and were activated by Mn²⁺ ions.     

棉纤维细胞伸长生长与过氧化物酶和IAA氧化酶的关系

棉纤维细胞于开花当天从棉胚珠表皮上发生,随即开始伸长生长,星S型生长曲线。棉纤维细胞的可溶性蛋白、过氧化物酶活性和IAA氧化酶活性同伸长生长的关系不大;而离子型结合的细胞壁蛋白质含量、过氧化物酶活性和IAA氧化酶活性同棉纤维细胞的伸长生长关系较大,表现在棉纤维细胞快速伸长期活性较低,而在伸长生长停止时出现活性高峰,同棉纤维细胞的伸长生长有负相关现象。     

Alpha 1- and beta 2-adrenergic receptors co-expressed on cloned MDCK cells are distinct glycoproteins

We have explored the molecular differences between alpha 1- and beta 2-adrenergic receptors that are co-expressed by a clonally-derived cell line, Madin-Darby canine kidney clone D (MDCK-D). MDCK-D membranes were pre-labeled with selective alpha 1- and beta-adrenergic radioligands and were then solubilized with the non-ionic detergent digitonin. Solubilized alpha 1- and beta 2-adrenergic receptors were retained by immobilized wheat germ agglutinin and were eluted following addition of N-acetyl-D-glucosamine or sialic acid. Both receptors were also retained by immobilized Limax flavus lectin, a sialic acid-binding lectin. Lectins that were specific for N-acetyl-D-glucosamine residues did not bind to these receptors. These results indicate that both alpha 1 and beta 2 receptors are sialylated glycoproteins. The solubilized alpha 1- and beta 2-adrenergic receptors migrated with different elution profiles from an Ultragel AcA 34 column. The apparent molecular sizes of the digitonin-receptor complexes were 68A for the alpha 1 receptor and 55A for the beta 2 receptor. These results show that alpha 1- and beta 2-adrenergic receptors can be present on the same cell as distinct sialic acid-containing glycoproteins.     

Triterpenes from Periandra dulcis roots

Three oleanane triterpenes were isolated from the roots of Periandra dulcis,and identified as 3β-hydroxy-25-al-olean-18-en-30-oic acid (periandric acid I), 3β-hydroxy-25-al-olean-12-en-30-oic acid (periandric acid II) and 3-oxo-25-hydroxy-olean-12-en-30-oic acid. The former two compounds (periandric acids I and II) were identical with the aglycones obtained by hydrolysis of periandrin I and II, respectively and the latter one was a new triterpene.     

饲料硒和维生素E对大鼠机体抗氧化能力的影响

 用克山病病区粮配成基础低硒饲料,补充硒和/或维生素E组成四种不同水平的饲料,饲喂雄性断乳大鼠,观察其对机体抗氧化能力的影响。评价指标是用抗坏血酸诱发的红细胞溶血率、被O~-_2(超氧阴离子)氧化的血红蛋白量和组织中的TBA值。动物饲养13周后,自尾静脉取血,测定溶血率和血红蛋白被氧化的百分率,和全血SeGSHPx(含硒谷胱甘肽过氧化物酶)活力。15周后将动物断头杀死,立即取出心脏和肝脏测定SeGSHPx活力和TBA值。结果表明在克山病病区粮的饲料中补充硒或维生素E,或者二者同时补充均明显提高组织中的SeGSHPx活力和降低组织中的TBA值。不论在硒缺乏时或硒充足时,饲料中补充维生素E显著降低抗坏血酸诱发的红细胞溶血率,对O~-_2氧化血红蛋白无保护作用。在维生素E缺乏时,仅补充硒对溶血无作用。不论饲料中维生素E缺乏或者充足,补充硒对O~-_1氧化血红蛋白均有显著保护作用。     

Selenium modifies carcinogen metabolism by inhibiting enzyme induction

Since selenium has been found to exert a protective action against carcinogenesis in various systems, the mechanism where-by sodium selenite inhibits DNA binding of the carcinogen, 7,12-dimethylbenz[a]anthracene, was investigated. It was found that selenite preferentially reduced DNA binding occurring through ananti-dihydrodiol epoxide metabolite of this carcinogen by inhibiting the induction of an enzyme system that generates this specific reactive metabolite.     

Analysis of fluorescence transients of DCMU-treated leaves of Triticum species to provide estimates of the densities of photosystem II reaction centres

The fluorescence of the chlorophyll associated with photosystem II was studied in seedling and flag leaves of Triticum species. Seedling leaves of the diploid species T. urartu had higher values of t (the normalised area over the fluorescence induction curve of DCMU treated leaves) than those of the other species studied which included hexaploid T. aestivum. However this difference was not evident when leaves were grown in a low light intensity (40 µmol quanta of photosynthetically active radiation m^–2 s^–1). The smaller total number of chlorophyll molecules per photosystem II reaction centre (chl/RCII) in T. urartu (177) as compared with the other species (mean 234) was deduced from the observed differences in t. As a consequence of its lower chl/RCII, despite slightly lower chlorophyll content (mg m^–2), T. urartu had a greater density of reaction centres than the other species (2880 cf 2230 nmol m^–2 of leaf). Consistent with the lower chl/RCII of T. urartu, it had a higher chlorophyll a/b ratio than the other genotypes. Seedling leaves of T. urartu had higher light saturated rates of photosynthesis than those of the other species, when grown at high light, a difference associated with reaction centre density.In flag leaves, when the complications due to variable development and senescence patterns were eliminated, t of the diploid species including T. urartu was lower than that of T. aestivum. The lower apparent chl/RCII of T. urartu arose partly because the molar extinction coefficient of the chlorophyll in the leaves of T. urartu was greater than in T. aestivum. However, the density of PS II reaction centres was slightly lower for the diploid species studied because their chlorophyll contents were lower than the hexaploids.The validity of the method for estimating chl/RCII from fluorescence transients is discussed. The possibility is considered that the difference in apparent chl/RCII of flag and seedling leaves of R. urartu as compared to the other five genotypes is a consequence of its different adaptive response to the spectral quality of the light.     

Chlorophyll-protein and polypeptide composition of Mn-deficient sugar beet thylakoids

The chlorophyll-protein and polypeptide composition of manganese deficient and control sugar beet thylakoids was examined using three different detergent-electrophoresis systems. On a per chlorophyll basis, manganese deficiency reduced the amounts of CPa complex (separated by sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis), and CP 47 and CP 43 complexes (separated by octylglucoside/SDS-polyacrylamide gel electrophoresis) without decreasing the amounts of light harvesting complexes. Lithium dodecylsulfate/Triton X-100 polyacrylamide gel electrophoresis showed that manganese deficiency decreased several thylakoid polypeptides, including a chlorophyll b containing 30 kilodalton chlorophyll-protein complex, but did not decrease the amounts of 28 and 29 kilodalton light-harvesting chlorophyll b-containing polypeptides.