Ring-14 and trisomy 14q in the same child

The case of a male child with three cell lines is described: one cell line with ring chromosome 14, another trisomic for 14q, due to a derived metacentric 14q;14q, and a third one with a normal male karyotype. The clinical findings are compatible with those of the r(14) syndrome.     

Mammalian Pex14p: membrane topology and characterisation of the Pex14p-Pex14p interaction

Peroxisomal biogenesis is a complex process requiring the action of numerous peroxins. One central component of this machinery is Pex14p, an intrinsic peroxisomal membrane protein probably involved in the docking of Pex5p, the receptor for PTS1-containing proteins (peroxisomal targeting signal 1-containing proteins). In this work the membrane topology of mammalian Pex14p was studied. Using a combination of protease protection assays and CNBr cleavage, we show that the first 130 amino acid residues of Pex14p are highly protected from exogenously added proteases by the peroxisomal membrane itself. Data indicating that this domain is responsible for the strong interaction of Pex14p with the organelle membrane are presented. All the other Pex14p amino acid residues are exposed to the cytosol. The properties of recombinant human Pex14p were also characterised. Heterologous expressed Pex14p was found to be a homopolymer of variable stoichiometry. Finally, in vitro binding assays indicate that homopolymerisation of Pex14p involves a domain comprising amino acid residues 147-278 of this peroxin.     

Metabolism of phytol-U-14C and phytanic acid-U-14C in the rat

The metabolism of uniformly-labeled (14)C-phytol, (14)C-phytenic acid, and (14)C-phytanic acid was studied in the rat. Conversion of both phytol and phytenic acid to phytanic acid was demonstrated. Tracer doses of phytol-U-(14)C given orally were well absorbed (30-66%), and approximately 30% of the absorbed dose was converted to (14)CO(2) in 18 hr. After intravenous injection, 20% appeared in (14)CO(2) in 4 hr. Phytanic acid-U-(14)C given intravenously was oxidized at a comparable rate (22-37% in 4 hr) and was as rapidly oxidized as palmitic acid-1-(14)C (21% in 4 hr). Metabolism of these substrates was also studied in rats previously maintained on a diet containing 5% phytol by weight, which causes accumulation of phytanic acid, phytenic acid, and, to a lesser extent, phytol in blood and tissues. Despite the large body pools of preformed, unlabeled substrate in these animals, the fraction of an administered dose of phytol-U-(14)C or phytanic acid-U-(14)C converted to (14)CO(2) was not significantly diminished. These studies indicate that the rat has an appreciable capacity to degrade the highly branched carbon skeleton of phytol and its derivatives. Twenty-four hours after administration of phytol-U-(14)C, the lipid radioactivity remaining in the body was widely distributed among the tissues, highest concentrations being found in liver and adipose tissue. Four hours after intravenous administration of phytanic acid-U-(14)C, all of the major lipid classes in the liver contained radioactivity, most in triglycerides and phospholipids and least in cholesterol esters and lower glycerides. There was no demonstrable incorporation of mevalonate-2-(14)C or acetate-1-(14)C into liver phytanic acid when they were given intravenously to a rat previously fed phytol. Endogenous biosynthesis, if it occurs at all, must be extremely limited.     

The interchange of 14C-kinetin and 14C-gibberellic acid between the bark and xylem of willow

Summary Considerable two-way interchange of label derived from ¹⁴C-GA₃ and ¹⁴C-kinetin has been shown to occur between the xylem and extra-cambial tissue of Salix viminalis L. Radial translocation of both growth substances from the transpiration stream to the sieve-tube sap has been demonstrated by the use of an aphid technique. This is the first record of the bark-xylem interchange of these two growth hormones.A high percentage of ¹⁴C-label is present in compounds other than GA₃ and kinetin 8 hours after application.Mechanisms of lateral transfer are discussed together with their possible physiological significance.This work was carried out during the tenure of an N.E.R.C. studentship by M.R.B.     

Metabolic conversion of exogenous14C-aspartate and14C-gIutamate in the dark byFucus serratus L

The rates of uptake of exogenous L[U-¹⁴C] aspartate and glutamate into tissues of vegetative growing tips ofFucus serratus and their metabolism were studied in the dark. In these non-photosynthetic conditions, aspartate was fixed and metabolically converted more rapidly than glutamate. Radioactivity from¹⁴C-aspartate was principally transferred into glutamate. On the other hand, metabolism of absorbed¹⁴C-glutamate was very slow and its rate did not increase during incubation time, but produced more diversified soluble radioactive compounds. Thus inF. serratus, glutamate principally seems to be in the dark more a temporary¹⁴CO₂ storage product coming from β-carboxylation than a rapidly turned over intermediate.     

Metabolism of 14C-Chlorobenzilate and 14C-Chloropropylate by Rhodotorula gracilis

Rhodotorula gracilis metabolizes Chlorobenzilate (ethyl 4,4'-dichlorobenzilate) and Chloropropylate (isopropyl 4,4'-dichlorobenzilate) to several metabolites in a basal medium supplemented by sucrose and by several intermediates of the citric acid cycle. Three identified metabolites resulting from the degradation of either acaricide, were 4,4'-dichlorobenzilic acid, 4,4'-dichlorobenzophenone, and carbon dioxide. Chlorobenzilate, i.e., ethyl ester of 4,4'-dichlorobenzilic acid, was more easily hydrolyzed than Chloropropylate, i.e., isopropyl ester of this acid, so that larger amounts of carbon dioxide and 4,4'-dichlorobenzophenone were obtained from Chlorobenzilate degradation. Regardless of acaricides used, longer incubation caused a higher accumulation of 4,4'-dichlorobenzophenone. The probable steps of the degradation pathway are: Chlorobenzilate (or Chloropropylate) --> 4,4'-dichlorobenzilic acid --> 4,4'-dichlorobenzophenone plus carbon dioxide. It appears that the decarboxylation of 4,4'-dichlorobenzilic acid to 4,4'-dichlorobenzophenone was hindered by alpha-ketoglutarate and enhanced by succinate.     

Plant uptake of 14C-EDTA, 14C-Citrate, and 14C-Histidine from chelator-buffered and conventional hydroponic solutions

Chelator-buffered hydroponic solutions provide low and buffered free-metal concentrations and allow the easy calculation of nutrient species expected in these solutions. Some researchers suspect that the solutions allow plant uptake of chelates and that this uptake explains the failure of the free-ion activity model using these solutions. To determine the amount and method of chelate uptake, swiss chard was grown in solution culture in growth chambers for about three wks and then transferred to solutions containing ¹⁴C-EDTA, ¹⁴C-citrate, or ¹⁴C-L-histidine for a 21-hour assay. Much higher root and shoot ¹⁴C were found from treatments containing metabolites histidine (2706097 shoot Bq ¹⁴C) or citrate (2241953 shoot Bq ¹⁴C) than EDTA (280110 shoot Bq ¹⁴C). Passive transpirational flow could explain all of the EDTA uptake, but active uptake would be required to explain most of the citrate and histidine uptake even assuming some adsorption of ligand bound to roots. Swiss chard grown in solutions with the same total EDTA concentrations, but different amounts of Fe bound to EDTA, had 3-fold differences in root and shoot ¹⁴C concentrations. In a second experiment, swiss chard roots removed more EDTA from solutions containing mostly M-EDTA⁰ than M-EDTA^1- or M-EDTA^2- (288140, 245051, and 192559 Bq ¹⁴C, respectively) suggesting plant selectivity for EDTA and a non-apoplastic route of uptake or an effect resulting from root cell-wall adsorption. Results indicated buffering of metals by ligands allowed some ligand uptake with much more uptake occurring with metabolites citrate and histidine than EDTA. A passive or indiscriminate form of uptake does not appear to explain all EDTA uptake with a selectivity by swiss chard for M-EDTA complexes of lower charge.     

Effect of papaverine on the absorption and metabolism of 14C- adenosine and 14C-adenine in thymocytes

Some peculiarities of adenosine and adenine nucleotide metabolism in rat thymocytes were investigated. It was shown that the uptake of labelled adenosine or adenine by thymocytes is markedly inhibited by papaverine due to the decrease of the adenylate kinase activity, on the one hand, and to the acceleration of ATP catabolism and inosine and hypoxanthine release into the environment, on the other. ATP catabolism occurs in a special compartment which in [14C] adenosine and [14C] adenine prelabelled thymocytes has a higher specific radioactivity as compared with the whole cell. In [14C] adenine-prelabelled thymocytes and extracellular medium, papaverine does not influence the content but increases the specific radioactivity of adenosine.     

CD14 and apoptosis

In addition to its role as a mediator of innate pro-inflammatory responses following bacterial lipopolysaccharide (LPS) binding, the 55kDa glycosyl-phosphatidylinositol-linked macrophage plasma membrane glycoprotein CD14 is now also known to play a role in phagocytic clearance of apoptotic cells. Although apoptotic cell-associated ligand(s) for CD14 await definition, initial findings suggest that ligand binding occurs close to, or at the same site as, LPS binding. Significantly, in contrast to LPS clearance and in keeping with the non-phlogistic nature of apoptosis, CD14-dependent engulfment of apoptotic cells fails to elicit pro-inflammatory cytokine release from macrophages. Therefore CD14 may be regarded as an innate immune receptor both for microbial products—after binding which activates inflammatory responses—and for self components, which either fail to induce, or alternatively actively suppress, inflammatory responses. Here we review current knowledge of the structure and functions of CD14, its ligands, its possible modes of signal transduction and its place in the panoply of macrophage molecules implicated in apoptotic-cell clearance.     

GALNT14与肿瘤

在过去的一个多世纪,许多肿瘤标志物被发现,其中包括多肽N-乙酰半乳糖胺基转移酶(polypeptide N-acetylgalactosaminyltransferase,ppGALNAc-T,简称GALNT)家族中的多个成员。GALNT家族是催化黏蛋白O-糖基化修饰的起始酶,其能够影响黏蛋白的O-糖基化,从而影响肿瘤细胞的发生、预后、增殖与迁移等。GALNT14是该家族中最新发现的成员之一,近年的研究发现,GALNT14在多种肿瘤中表达异常,并与肿瘤细胞的发生、侵袭、转移和凋亡等有关。本文主要对GALNT14蛋白的结构特点及其在肿瘤中的作用进行综述,为进一步研究GALNT14与肿瘤发病机制的关系以及作为潜在的药物靶点提供参考。