Ploidy in cyanobacteria

A recently developed real-time PCR method for the determination of genome copy numbers was optimized for the application to cyanobacteria. Three species were chosen to represent a fresh water species, a salt water species, and two strains of a widely used laboratory species. Synechococcus PCC 7942 and Synechococcus WH7803 were found to contain 3-4 genome copies per cell and are thus oligoploid, confirming earlier publications. In contrast, Synechocystis PCC 6803 is highly polyploid. The motile wild-type strain contains 218 genome copies in exponential phase and 58 genome copies in linear and in stationary growth phase. The GT wild-type strain contains 142 genome copies in exponential phase and 42 genome copies in linear and stationary growth phase. These are the highest numbers found for any cyanobacterial species. Notably these values are much higher than the value of 12 genome copies published for the 'Kazusa' strain more than 20 years ago. The results reveal that for Synechocystis PCC 6803 strain differences exist and that the ploidy level is highly growth phase-regulated. A compilation of the ploidy levels of all investigated cyanobacterial species gives an overview of the genome copy number distribution and shows that monoploid, oligoploid, and polyploid cyanobacteria exist.     

Ploidy and the evolution of parasitism

Levels of parasitism are continuously distributed in nature. Models of host-parasite coevolution, however, typically assume that species can be easily characterized as either parasitic or non-parasitic. Consequently, it is poorly understood which factors influence the evolution of parasitism itself. We investigate how ploidy level and the genetic mechanisms underlying infection influence evolution along the continuum of parasitism levels. In order for parasitism to evolve, selective benefits to the successful invasion of hosts must outweigh the losses when encountering resistant hosts. However, we find that exactly where this threshold occurs depends not only on the strength of selection, but also on the genetic model of interaction, the ploidy level in each species, and the nature of the costs to virulence and resistance. With computer simulations, we are able to incorporate more realistic dynamics at the loci underlying species interactions and to extend our analyses in a number of directions, including finite population sizes, multiple alleles and different generation times.     

Ploidy and morphology in osteosarcoma

In a cytometric DNA study of high-grade osteosarcoma, the relationship between DNA content and morphology was analyzed. The investigation, based on microspectrophotometry of tissue sections and flow cytometry (FCM), included both primary lesions and recurrences. FCM analysis, applied to a consecutive series of 47 primary osteosarcomas, disclosed that 2 were diploid and 45 were nondiploid, 8 of which were tetraploid. Multiple aneuploid peaks were detected in 13 tumors. Among the nondiploid tumors, there was no clear relationship between the peak DNA value(s) and the histologic subtype (osteoblastic, chondroblastic, fibroblastic) or grade (III-IV). The proliferative activity, as reflected by the percentage of S-phase cells, could be determined in 38 of the 47 tumors analyzed by FCM. The percentage was higher for aneuploid than for tetraploid lesions; however, the distribution of S-phase cells was not related to the histologic subtype or the grade of the tumors. To assess the reliability of a single sample for FCM, the DNA content of biopsy and surgical specimens was compared in 20 tumors; there was complete agreement in all cases with respect to the classification of the lesion as diploid, tetraploid or aneuploid. Analysis by FCM or microspectrophotometry of 12 local recurrences and 16 metastases and the corresponding 19 primary tumors showed that an aneuploid characteristic of the primary lesion was retained during progression of the disease. In 12 tumors analyzed by microspectrophotometry in tissue sections, comparison of chondroblastic and osteoblastic/fibroblastic areas within the same lesion consistently disclosed hyperploidy in both areas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ploidy patterns in cervical dysplasia

The ploidy patterns determined for groups of patients with cervical dysplasia (cervical intraepithelial neoplasia [CIN]) were subjected to statistical analysis. The patterns were based on the measurement of at least 100 Feulgen-stained nuclei from 30 patients with normal cervices, 10 cases of CIN I, 18 cases of CIN II and 33 cases of CIN III. The scale of the patterns was a log transformation of the ratio of the total extinction (optical density) of the nuclei to that of the 2N reference; this widens the intervals for higher ploidies, alleviating sampling requirements for intervals in which occurrences are rare and helping to maintain a reasonable sample size-to-dimensionality ratio. Pairwise discriminant analyses showed clear distinctions between the ploidy pattern for normal cases and those for CIN I, CIN II and CIN III. The distinctions between the different grades of CIN, based on these modest sample sizes, were less clearcut, largely due to pronounced patient-to-patient variability. Analysis of variance confirmed that the patient groups constitute statistically distinct entities. An aneuploid pattern did not seem to develop until CIN III lesions were involved. The diagnostic and prognostic significance of these preliminary findings require further study using larger data sets and correlations to patient survival.     

Ploidy of endothelium in high-grade astrocytomas

To determine the ploidy and proliferative activity of the endothelium in high-grade astrocytomas, the nuclear DNA content of 11 high-grade astrocytomas, including two gliosarcomas, was measured by cytophotometry. This technique allowed comparison of the endothelial population with the astrocytic population. In all cases, the endothelium was diploid, with an average of 24.6% of cells in the S + G2M phases of the cell cycle. In contrast, the astrocytic population displayed marked DNA abnormalities. The two gliosarcomas had a marked difference in proliferative activity of the endothelium with 4% and 40% of cells, respectively, in the S + G2M phases. These data indicate that the vast majority of endothelial cells compromising the vascular hypercellularity observed in high-grade astrocytomas are in the normal cell cycle whereas in many cases the malignant astrocytes are not. The nuclear DNA content of gliosarcomas appears to be similar to other high-grade astrocytomas.     

Ploidy reduction in Saccharomyces cerevisiae

Large-scale transitions in genome size from tetraploid to diploid were observed during a previous 1800-generation evolution experiment in Saccharomyces cerevisiae. Whether the transitions occurred via a one-step process (tetraploid to diploid) or through multiple steps (through ploidy intermediates) remained unclear. To provide insight into the mechanism involved, we investigated whether triploid-sized cells sampled from the previous experiment could also undergo ploidy loss. A batch culture experiment was conducted for approximately 200 generations, starting from four triploid-sized colonies and one contemporaneous tetraploid-sized colony. Ploidy reduction towards diploidy was observed in both triploid and tetraploid lines. Comparative genomic hybridization indicated the presence of aneuploidy in both the founder and the evolved colonies. The specific aneuploidies involved suggest that chromosome loss was not haphazard but that nearly full sets of chromosomes were lost at once, with some additional chromosome mis-segregation events. These results suggest the existence of a mitotic mechanism allowing the elimination of an entire set of chromosomes in S. cerevisiae, thereby reducing the ploidy level.     

Ploidy and gene conversion in Archaea

The genome copy numbers of seven crenarchaeal species of four genera have been reported. All of them are monoploid and thus this seems to be a characteristic feature of Crenarchaeota. In stark contrast, none of six species representing six euryarchaeal genera is monoploid. Therefore Euryarchaea are typically oligoploid or polyploidy and their genome copy numbers are tightly regulated in response to growth phase and/or growth rate. A theoretical consideration called 'Muller's ratchet' predicts that asexually reproducing polyploid species should not be able to exist. An escape from Muller's ratchet would be a mechanism leading to the equalization of genome copies, such as gene conversion. Using two species of methanogenic and halophilic archaea, it was shown that heterozygous cells containing different genomes simultaneously can be selected, exemplifying gene redundancy as one possible evolutionary advantage of polyploidy. In both cases, the genomes were rapidly equalized in the absence of selection, showing that gene conversion operates at least in halophilic and methanogenic Euryarchaea.     

Ploidy Reductions in Murine Fusion-Derived Hepatocytes

We previously showed that fusion between hepatocytes lacking a crucial liver enzyme, fumarylacetoacetate hydrolase (FAH), and wild-type blood cells resulted in hepatocyte reprogramming. FAH expression was restored in hybrid hepatocytes and, upon in vivo expansion, ameliorated the effects of FAH deficiency. Here, we show that fusion-derived polyploid hepatocytes can undergo ploidy reductions to generate daughter cells with one-half chromosomal content. Fusion hybrids are, by definition, at least tetraploid. We demonstrate reduction to diploid chromosome content by multiple methods. First, cytogenetic analysis of fusion-derived hepatocytes reveals a population of diploid cells. Secondly, we demonstrate marker segregation using ß-galactosidase and the Y-chromosome. Approximately 2–5% of fusion-derived FAH-positive nodules were negative for one or more markers, as expected during ploidy reduction. Next, using a reporter system in which ß-galactosidase is expressed exclusively in fusion-derived hepatocytes, we identify a subpopulation of diploid cells expressing ß-galactosidase and FAH. Finally, we track marker segregation specifically in fusion-derived hepatocytes with diploid DNA content. Hemizygous markers were lost by ≥50% of Fah-positive cells. Since fusion-derived hepatocytes are minimally tetraploid, the existence of diploid hepatocytes demonstrates that fusion-derived cells can undergo ploidy reduction. Moreover, the high degree of marker loss in diploid daughter cells suggests that chromosomes/markers are lost in a non-random fashion. Thus, we propose that ploidy reductions lead to the generation of genetically diverse daughter cells with about 50% reduction in nuclear content. The generation of such daughter cells increases liver diversity, which may increase the likelihood of oncogenesis.     

Vaccine prophylaxis in elderly patients

In 1997-1999 observation was made on elderly people living in old people's homes and in families, as well as groups of young males living in hostel-type homes, altogether 4,518 subjects. Standard inactivated whole-virion influenza vaccine was introduced in a dose of 0.5 ml subcutaneously in a single injection or intranasally in two administrations. In control groups placebo was used. The frequency of seroconversions to vaccine strains of influenza viruses was significantly less in elderly people than in young people following both subcutaneous and intranasal immunization (on the average, by 15-20%). In young people the prophylactic effectiveness of the vaccine introduced intranasally was the same as after subcutaneous immunization with the effectiveness index (EI) being equal to 2.1-2.8. In elderly people the effectiveness of the vaccine after subcutaneous immunization was the same as in young people (EI = 1.7-2.7), but insufficient after intranasal immunization (EI < or = 1.6). The preparation "Amber elixir plus" enhanced the effectiveness of immunization against influenza in elderly people.     

人工雌核发育草鱼染色体倍性的鉴定

运用经典的红细胞及细胞核体积大小测量方法以及流式细胞仪,检测了人工诱导雌核发育草鱼染色体倍性与DNA含量.雌核发育草鱼红细胞体积为(333.5±41.94)μm3,细胞核体积为(20.7±2.378)μm3;与所测普通草鱼红细胞体积(343.8±50.1)μm3,细胞核体积(21.2±1.98)μm3,没有显著差异.雌核发育草鱼DNA含量(2C)平均为2.23pg,普通草鱼DNA含量(2C)2.20pg,两者无显著差异.研究结果表明,人工雌核发育草鱼与普通草鱼具有相同的染色体倍性.     

Free-tissue transfer in elderly patients

A retrospective survey was undertaken to evaluate the success of free-tissue transfer (free flap) in the elderly. During a 70-month period, 199 free flaps were performed in 151 patients at the Western Pennsylvania Hospital, 60 of these involving 47 patients over the age of 60. Primary coverage rates differed significantly between the elderly and younger age groups (68.5 versus 85.3 percent, respectively); however, eventual coverage rates (92.6 versus 96.3 percent), minor complication rates (34.0 versus 34.6 percent), mortality rates (2.1 versus 1.0 percent), flap revision rates (32 percent of patients versus 30 percent), and length of postoperative hospitalization (18.7 versus 18.8 days) were not significantly different in the two groups. Among the elderly, significant increases in flap loss rates were noted with the use of end-to-side arterial anastomosis, placement of the anastomosis within a zone of injury, and the use of the gracilis muscle donor site. Our data suggest that the primary cause of free-flap failure is construction of the anastomosis within a zone of injury. Free-tissue transfer is a valuable option in the repair of tissue defects in the elderly and should not be denied as a treatment because of patient age.