Further studies on polyploid amphibians

The manner in which centromere regions of mitotic chromosomes are distributed with respect to the age of their DNA was studied. Cells of the Indian deer, Muntiacus muntjak, were grown in the presence of bromodeoxyuridine (BrdU) for two generations and stained with the fluorescent dye Hoechst 33258. Chromatids containing granddaughter DNA appear dim when compared with those containing grandparental DNA. The frequencies of the various anaphase patterns of bright and dim centromere regions were binomially distributed, indicating random distribution of chromatids with respect to the age of their DNA templates.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.     

Biosynthesis of saturated and unsaturated fatty acids by a T-strain mycoplasma (Ureaplasma).

A human T mycoplasma (Ureaplasma urealyticum) incorporated radioactivity into its lipids from [1-14C]acetate in the growth medium. Methanolysis of the lipids showed the label to be confined almost entirely to the methyl esters of the fatty acids. About 80% of the label was associated with the methyl esters of the saturated fatty acids, and the rest was found in the unsaturated methyl ester fraction. Gas-liquid chromatography of the saturated methyl esters showed the label to be present in the peaks of palmitate, myristate, and stearate, whereas in the unsaturated methyl ester fraction most of the radioactivity emerged in the peak of palmitoleate. The addition of either oleic or palmitic acid to the growth medium markedly decreased the organisms' incorporation of radioactivity from acetate. It is concluded that the T mycoplasma strain is capable of de novo synthesis of both saturated and unsaturated fatty acids, in this respect differing from all of the Mycoplasma and Acholeplasma strains investigated to date.     

The Rab11-family interacting proteins reveal selective interaction of mammalian recycling endosomes with the Toxoplasma parasitophorous vacuole in a Rab11- and Arf6-dependent manner

After mammalian cell invasion, the parasite Toxoplasma multiplies in a self-made membrane-bound compartment, the parasitophorous vacuole (PV). We previously showed that Toxoplasma interacts with many host cell organelles, especially from recycling pathways, and sequestrates Rab11A and Rab11B vesicles into the PV. Here, we examine the specificity of host Rab11 vesicle interaction with the PV by focusing on the recruitment of subpopulations of Rab11 vesicles characterized by different effectors, for example, Rab11-family interacting roteins (FIPs) or Arf6. Our quantitative microscopic analysis illustrates the presence of intra-PV vesicles with FIPs from class I (FIP1C, FIP2, FIP5) and class II (FIP3, FIP4) but to various degrees. The intra-PV delivery of vesicles with class I, but not class II, FIPs is dependent on Rab11 binding. Cell depletion of Rab11A results in a significant decrease in intra-PV FIP5, but not FIP3 vesicles. Class II FIPs also bind to Arf6, and we observe vesicles associated with FIP3-Rab11A or FIP3-Arf6 complexes concomitantly within the PV. Abolishing FIP3 binding to both Rab11 and Arf6 reduces the number of intra-PV FIP3 vesicles. These data point to a selective process of mammalian Rab11 vesicle recognition and scavenging mediated by Toxoplasma, suggesting that specific parasite PV proteins may be involved in these processes.     

1.5-Mb YAC Contig in Xq28 Formatted with Sequence-Tagged Sites and Including a Region Unstable in the Clones

A contig of 20 yeast artificial clones (YACs) has been assembled across 1.5 Mb of Xq28 and formatted with nine previously reported probes and nine STSs developed from the sequence of probes and end fragments of YACs. YAC end fragments were obtained by subcloning, Alu-vector PCR, or primer-ligation PCR methods. Eighteen of the YACs were recovered from a library specific for Xq24-q28; two that fill a gap were obtained from a second library made from total human DNA. One region, containing probes pX78c and 2A1.1, was unstable in YACs, but it was possible to generate a self-consistent map of DNA over the entire contig. Overlaps were confirmed by Southern blot analyses of YAC DNAs, and pulsed-field gel electrophoresis confirmed the extent of the contig and identified at least four CpG islands in the region.     

Abnormalities of T cells isolated from mediastinal lymph nodes and peripheral blood of patients with lung carcinoma: deficit in PHA-induced expression of HLA class II antigens and in autologous mixed lymphocyte reactions

Summary A reduced percentage of T cells isolated from mediastinal lymph nodes and peripheral blood of patients with lung carcinoma acquired HLA Class II antigens following in vitro stimulation with PHA. Furthermore T cells were functionally abnormal in autologous and allogeneic mixed lymphocyte reactions (MLR). The immunoregulatory properties of HLA Class II antigens and autologous MLRs suggest that these abnormalities may affect the interaction of the host's immune system with tumor cells.     

Olive flowering trends in a large Mediterranean area (Italy and Spain)

The aim of this study was to investigate the main climatic and biological trends related to olive flowering in central-southern Italy compared to those in Andalusia, Spain. Results since 1982 were compared for the two long-series monitoring areas of Cordoba and Perugia, and since 1992–1999 for the short-series areas. The relationship between climatic trends and the biological response of the olive, a widespread culture in the Mediterranean basin, were investigated. An aerobiological method involving capturing pollen released into the atmosphere was utilised as a bioindicator of flowering phenology. The study results confirm the strong relationship between flowering periods and spring temperature trends for the olive. Temperature during March, April and May was the parameter most related to flowering date in the study areas, particularly in Italy. In some cases we found a significant correlation between flowering and past autumn temperatures, probably due to their effect on floral bud dormancy induction, but this phenomenon appeared to be of minor importance in the studied areas. The phenological trend results show the continuous advance of flowering dates to the late 1990s, followed by a relatively stationary time series related to a short-term temperature fluctuation in the Mediterranean area. This latter period probably represents a mesoscale event forced by a macroscale event—the North Atlantic Oscillation. The results reveal that the trend towards increased temperatures, and the consequent flowering advance of some species, indicated some years ago is nowadays not as clear as was expected and should be confirmed over the next few years in the Mediterranean areas under investigation.     

Uridine enhances the cytotoxic effect of D-glucosamine in rat C6 glioma cells

This paper studies the influence of uridine on the effects exerted by D-glucosamine in rat C6 glioma cells. 2 mM uridine increased markedly both the cytotoxic effect of the aminosugar and the inhibition of thymidine incorporation into acid-insoluble fraction. Furthermore the complete resumption of the capacity to incorporate either 3H-thymidine or 3H-mannose which was observed after the removal of the aminosugar, was impeded when the cells were treated contemporaneously with D-glucosamine and uridine. An exposure for 4 hr to 20 mM glucosamine alone enhanced about 15-fold the cellular pool of UDP-N-acetylhexosamines; the addition of 2 mM uridine intensified the expansion of this pool, which became about 35-fold the control value. The findings suggest a connection between the accumulation of UDP-N-acetylhexosamines in the cells and the appearance of D-glucosamine cytotoxicity.