Intestinal absorption of 14C from 14C-phenanthrene, 14C-benzo[a]pyrene and 14C-tetrachlorodibenzo-para-dioxin: approaches with the Caco-2 cell line and with portal absorption measurements in growing pigs

The aim of this work was to study the transfer through the intestinal barrier of two polycyclic aromatic hydrocarbons (PAHs) (benzo[a]pyrene and phenanthrene) and a dioxin (2,3,7,8-tetrachlorodibenzo-para-dioxin) which differed in their physicochemical properties. Both in vitro and in vivo assays were performed. For the in vitro study, Caco-2 cells, cultivated on permeable filters, permitted to measure the transepithelial permeability of the studied 14C-labelled molecules. For the in vivo study, portal absorption kinetics were evaluated in pigs fed contamined milk. The results showed that all the molecules were absorbed and demonstrated a differential intestinal absorption for the studied molecules. Phenanthrene appeared to be the fastest and most uptaken compound, followed by benzo[a]pyrene and finally 2,3,7,8-tetrachlorodibenzo-para-dioxin. Their absorption levels were respectively 9.5, 5.2 and 1.4% after a 6 h-exposure in vitro and 86.1, 30.5 and 8.3% in vivo for the 24 h following ingestion. These findings suggest that the physicochemical properties of the xenobiotics and intestinal epithelium play key roles in the selective permeability and in the bioavailability of the tested micropollutants.     

Maternal uniparental disomy for human chromosome 14, due to loss of a chromosome 14 from somatic cells with t(13;14) trisomy 14.

Uniparental disomy (UPD) for particular chromosomes is increasingly recognized as a cause of abnormal phenotypes in humans. We recently studied a 9-year-old female with a de novo Robertsonian translocation t(13;14), short stature, mild developmental delay, scoliosis, hyperextensible joints, hydrocephalus that resolved spontaneously during the first year of life, and hypercholesterolemia. To determine the parental origin of chromosomes 13 and 14 in the proband, we have studied the genotypes of DNA polymorphic markers due to (GT)n repeats in the patient and her parents' blood DNA. The genotypes of markers D14S43, D14S45, D14S49, and D14S54 indicated maternal UPD for chromosome 14. There was isodisomy for proximal markers and heterodisomy for distal markers, suggesting a recombination event on maternal chromosomes 14. In addition, DNA analysis first revealed--and subsequent cytogenetic analysis confirmed--that there was mosaic trisomy 14 in 5% of blood lymphocytes. There was normal (biparental) inheritance for chromosome 13, and there was no evidence of false paternity in genotypes of 11 highly polymorphic markers on human chromosome 21. Two cases of maternal UPD for chromosome 14 have previously been reported, one with a familial rob t(13;14) and the other with a t(14;14). There are several similarities among these patients, and a "maternal UPD chromosome 14 syndrome" is emerging; however, the contribution of the mosaic trisomy 14 to the phenotype cannot be evaluated. The study of de novo Robertsonian translocations of the type reported here should reveal both the extent of UPD in these events and the contribution of particular chromosomes involved in certain phenotypes.     

Storage Pools and Turnover Systems in Growing and Non-growing Cells: Experiments with 14C-Sucrose, 14C-Glutamine, and 14C-Asparagine

¹⁴C-labelled sucrose, glutamine, and asparagine have been suppliedto aseptically cultured carrot explants that either grew rapidlyby cell division or, by contrast, only slowly by cell expansion.The radioactive substrates were supplied in a brief ‘pulse’followed by a much longer period during which the tissues weresupplied with ¹²C-substrates. The passage of ¹⁴C through thevarious soluble compounds of the tissue and into the proteinwas followed. Alternatively, the ¹⁴C-labelled compound was suppliedthroughout the entire period of an experiment while the tissuealso received ¹²C-sucrose. The pulse-labelling experiments demonstrateturnover and the fate of the breakdown products, as well asthe emphasis placed on this kind of metabolism by cells at differentlevels of activity in their growth. The long-term labellingexperiments show the different ways in which carbon from varioussources may be used and how these pathways are affected by growth.The amount of ¹⁴C present in the various free (ethanol soluble)and combined (ethanol insoluble, acid-hydrolysable compounds—proteins)was determined, as well as the specific activity of the carbonin each compound. The fate of ¹⁴C supplied as sucrose had muchin common with ¹⁴C supplied as glutamine, with respect to theease with which it entered both the protein being synthesizedand the carbon dioxide evolved, but it was very different from¹⁴C supplied as asparagine. To interpret these data, compartmentsor pools of metabolites are postulated in the organized cell;exogenous ¹⁴C-sucrose and ¹⁴C-glutamine readily furnish carbonfor pools of amino-acids en route to protein, which are protectedfrom both the stored compounds and those which arise after proteinbreakdown. However, exogenous ¹⁴C-asparagine enters, is accumulated,and persists in the pool of stored compounds which also receivethe nitrogen-rich substances that arise from protein breakdown.The kinetic data and the specific activities of the carbon inits various forms require that protein breakdown and re-synthesisoccur concomitantly, that the stimulus to grow, exerted by coconutmilk, accentuates protein synthesis and also the pace of itsturnover, that some respired carbon dioxide arises from protein,and that this moiety of the respiration is increased by thecoconut-milk stimulus as it accentuates the pace of cyclicalturnover. In similar experiments with free cells from differentplants, the same general conclusions apply, but the rates ofturnover of protein are greater in free cells than in tissueexplants. Some specific differences, however, exist. Cells ofArachis, the only legume investigated, permit ¹⁴C-asparagineto contribute, like ¹⁴C-glutamine, to both protein synthesisand respired ¹⁴CO₂; it is not merely segregated in a storagepool. Thus, by virtue of their organization, plant cells maintainthe same substances simultaneously in distinct phases or compartments,where they play distinctive roles, without mingling. Geneticsendows each cell with the information that makes its biochemicalreactions feasible; the organization of the cells determineshow far the feasible becomes practised in cells in any givensituation.     

Chromosome studies in 14 patients with disseminated sclerosis

Summary Short term lymphocyte cultures were performed in 14 patients with disseminated sclerosis. The karyotype of all patients was normal, but the frequency of structural chromosome aberrations was increased as compared to 10 healthy controls of same age. There were chromatid type aberrations including gaps and breaks of one or both chromatids and chromosome type aberrations such as acentric fragments dicentis, rings and other abnormal chromosomes. These results confirm the findings of Khondkarian et al. (1967).

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Zusammenfassung Bei 14 Patienten mit multipler Sklerose wurden kurzfristige Lymphocytenkulturen durchgeführt. Alle Patienten hatten ein normales Karyogramm, Strukturanomalien waren jedoch häufiger als bei den 10 gesunden Kontrollpersonen gleichen Alters. Sie bestanden aus Gaps und Brüchen eines oder beider Chromatiden, azentrischen Fragmenten, dizentrischen Chromosomen, Ringen und anderen anormalen Chromosomen. Diese Ergebnisse bestätigen die Befunde von Khondkarian et al. (1967).

     

The production of ryegrass labelled with carbon-14

Summary The construction and operation of a growth chamber for producing plant material labelled with carbon-14 to a specified degree of uniformity is described.The specific activity of the plant material is measured by a method based on scintillation counting.     

Arrangement of subunits in microtubules with 14 profilaments

The structure of 14-protofilament microtubules reassembled from dogfish shark brain tubulin was analyzed by high resolution electron microscopy and optical diffraction. The simultaneous imaging of the protofilaments from near and far sides of these tubules produces a moire pattern with a period of approximately 96 nm. Optical diffraction patterns show that the 5-nm spots that arise from the protofilaments for the two sides of the tubule are not coincident but lie off the equator by a distance of 1/192 nm-1. These data provide evidence that in reassembled microtubules containing 14 protofilaments, the protofilaments are tilted 1.5 degrees with respect to the long axis of the tubule, giving a left-handed superhelix with a pitch of 2.7 micron. The hypothesis is that the tilt of the protofilaments occurs to accommodate the 14th protofilament. It is determined that when the 14th protofilament is incorporated, the 3-start helix is maintained, but the pitch angle changes from 10.5 degrees to 11.2 degrees, the angle between protofilaments measured from the center of the microtubule changes by 2 degrees, and the dimer lattice is discontinuous. These observations show that the tubulin molecule is sufficiently flexible to accomodate slight distortions at the lateral bonding sites and that the lateral bonding regions of the alpha and beta monomers are sufficiently similar to allow either alpha-alpha and beta-beta subunit pairing or alpha-beta subunit pairing.     

A ring 14 chromosome with deleted short arm

Summary A male infant with cri du chat syndrome was found to have a deletion of the short arm of No. 5 chromosome and which was due to maternal reciprocal translocation t(5;6)(p13;q27). His elder sister and his grandfather were also identified as the translocation carriers.     

阿霉素处理的肿瘤抗原致敏树突状细胞的抗肿瘤免疫研究

研究表明化疗药物作用于肿瘤细胞后可有效激发免疫应答,这与肿瘤细胞的性质和化疗药物有关。该研究主要探讨阿霉素（adriamycin,ADM）处理小鼠宫颈癌u14细胞获得的肿瘤抗原致敏树突状细胞（dendriticceils,DCs）的免疫应答及对肿瘤的杀伤效应。分别应用ADM和反复冻融法处理小鼠宫颈癌U14细胞,取其离心上清液,致敏小鼠骨髓来源的DC,观察DC诱导的淋巴细胞增殖反应和细胞毒性T淋巴细胞（cytotoxicTlymphocyte,CTL）对宫颈癌细胞的细胞毒效应。结果显示：ADM处理的U14细胞抗原致敏后的DC组所激发和扩增的T细胞数及对宫颈癌细胞的杀伤效果显著高于对照组（P〈0．05）。因而提示ADM处理的肿瘤抗原能有效地致敏DC并产生抗肿瘤免疫效应。