Higher organization and histone modification of the plant nucleus and chromosome

Plants have a wide range of genome sizes. The length of each DNA molecule is usually much longer than the diameter of the cell and the length of each metaphase chromosome is effectively shortened to progress through mitosis. Thus some questions arise, such as: How is genomic DNA folded and shortened into chromosomes? What kind of proteins and/or their modifications contribute to chromosome structure? Are there any upper limits for the ratio of DNA volume to nuclear volume? This review attempts to answer these questions based on recent advances in chromosome research. Genomic DNA is first folded into nucleosomal fibers and then superfolded into metaphase chromosomes to sufficiently shorten its length to less than the upper limit for normal progression of cell division. Nucleosomes play structural roles, not only for DNA folding, but also for determination of euchromatin, heterochromatin, and centromeres, together with post-translational modifications and replacement of core histones with histone variants, and for the regulation of their structure and transcriptional status. More than 200 proteins of human metaphase chromosomes have been identified, including 5 types of nucleosome histones. They are categorized into 4 groups, and a 4-layer model of the human metaphase chromosome has been developed. There are upper limits for DNA volume. In all plants examined to date the DNA volume does not exceed 3% of the nuclear volume. Histone modification also has an impact on the spatial distribution of chromosomes within a nucleus, which seems to be related to the plant genome size. These points are discussed as well, as they are essential to maintain proper nuclear functions.

Transmission of alien chromosomes from selfed progenies of a complete set of Allium monosomic additions: the development of a reliable method for the maintenance of a monosomic addition set

Selfed progeny of a complete set of Allium fistulosum - Allium cepa monosomic addition lines (2n = 2x + 1 = 17, FF+1A-FF+8A) were produced to examine the transmission rates of respective alien chromosomes. All eight types of the selfed monosomic additions set germinable seeds. The numbers of chromosomes (2n) in the seedlings were 16, 17, or 18. The eight extra chromosomes varied in transmission rate (%) from 9 (FF+2A) to 49 (FF+8A). The complete set of monosomic additions was reproduced successfully by self-pollination. A reliable way to maintain a set of Allium monosomic additions was developed using a combination of two crossing methods, selfing and female transmission. FF+8A produced two seedlings with 18 chromosomes. Cytogenetical analyses, including GISH, showed that the seedlings were disomic addition plants carrying two entire homologous chromosomes from A. cepa in an integral diploid background of A. fistulosum. Flow cytometry analysis showed that a double dose of the alien 8A chromosome caused fluorescence intensity values spurring in DNA content, and isozyme analysis showed increased glutamate dehydrogenase activity at the gene locus Gdh-1.

Short communication: the cell cycle dependent phosphorylation of histone H3 is correlated with the condensation of plant mitotic chromosomes

Mitotically dividing cells of Secale cereale, Hordeum vulgare and Vicia faba were studied by indirect immunofluorescence using an antibody recognizing phosphorylated histone H3. The study revealed the following features: (i) the H3 phosphorylation starts at prophase and ends at telophase in the pericentromeric chromatin, is associated with the condensation of mitotic chromosomes and is independent of the distribution of late replicating heterochromatin. (ii) Compared with other chromosome regions, the pericentromeric chromatin is histone H3 hyperphos- phorylated. (iii) The study of a semi-dicentric chromo- some revealed that only at intact centromeres is the chromatin hyperphosphorylated at H3.

Clinical stage IE primary lymphoma of the nasal cavity: radiation therapy and chemotherapy

PURPOSE

To determine the appropriate radiation therapy and chemotherapy for primary lymphoma of the nasal cavity to improve the local control and survival rates.

MATERIALS AND METHODS

Of the 25 adult patients with stage IE nasal lymphoma, nine underwent local radiation therapy alone and 16 underwent radiation therapy and chemotherapy (intravenous infusion). Radiation doses to the involved area were 22-54 Gy (median dose, 49 Gy).

RESULTS

The 5- and 10-year cause-specific survival rates were 91% and 73%, respectively. The 5- and 10-year disease-free survival rates were 83% and 59%, respectively. Eight patients developed recurrent disease: six at the local site, one in the cervical nodes, and one in the small intestine. Five of the six patients with local recurrence received less than 50 Gy. Four of the six patients developed recurrent disease in the treated area; the other two patients developed marginal recurrences. Prognostic factors such as age, sex, maximum tumor size, and lactate dehydrogenase level were of limited value.

CONCLUSION

The most common recurrence site was the local site. To improve the local control rate, the involved area should be treated with high-dose radiation therapy. The clinical results did not demonstrate the usefulness of combination chemotherapy for stage IE nasal lymphoma.

[Performance study of teleradiology network systems with CRT monitors: ROC analysis of an observation study of simulated lung nodules]

PURPOSE

To evaluate the diagnostic performance of commercially available CRT monitors used in a teleradiology system by determining the rate of detection of simulated lung nodules.

MATERIALS AND METHODS

Three types of CRT monitors were tested in the observation study. They had matrix sizes of 1024 x 768(16 inches, color), 1024 x 768(20 inches, color) and 1600 x 1125(24 inches, black and white). Twenty chest radiographs were obtained by Fuji computed radiography(FCR) of an anthropomorphic chest phantom with ten simulated nodules on its surface. These FCR films were digitized by a film digitizer with 125 DPI(1024 x 1024 matrix sizes)and 12 bit gray scales, and the image data were transferred from Shinshu University Hospital to other hospitals where interpretation was carried out by the radiologists. Ten radiologists of three hospitals were asked to interpret independently both the original FCR films and the images shown on the CRT monitors and to indicate the presence or absence of simulated nodules on the images by using a five-category rating scale. Receiver operating characteristics(ROC)curves were generated, and the results of interpretation on the FCR films and CRT monitors were compared.

RESULTS

Performance of the all readers was slightly better with the CRT monitors than on the FCR films, although the differences were not statistically significant. There were no statistically significant differences in performance depending on the type of CRT monitor.

CONCLUSION

Performance of the CRT monitors was comparable to that of FCR radiography in terms of interpreting the simulated lung nodules.

[High-speed/high resolution teleradiology system based on university microwave network]

A high-speed, high-resolution teleradiology system with full duplexing based on the Shinshu University Video and Communication Network System (SUNS) using Giga-Herz microwaves is described. The LAN at Nagano Red-Cross Hospital and The Radiology Department of Shinshu University Hospital are interfaced to a personal computer with a laser film digitizer, interactive display, and network interface. The throughput per digitized high-resolution radiographic image was 65 sec, and the mean transmission rate was 805 kilobit per sec. Teleradiology conferencing is also possible with this system. Radiologists at both hospitals interactively observe the same high-resolution images on the CRT screen using mouse cursor synchronization.

[Micro-wave local area network for radiological image transmission]

Shinshu University consists of five campuses in different locations, a situation that presents some problems in communication. To solve this problem, the Shinshu University Video and Data Network System (SUNS), which includes a high-speed audio-visual transfer function, has been developed and utilized for pre- and postgraduate education, administrative teleconferences, and local telephone (PBX) and Fax services. In 1988, a cooperative group for the study of radiographic image processing was organized, consisting of staff members of Shinshu University Hospital in Matsumoto, the Faculty of Engineering in Nagano (75 km from Matsumoto) and the Faculty of Textile Science and Technology in Ueda (45 km from Matsumoto). The system has been developed with a pair of personal computer (PC)-based interactive image workstations and high-speed digital telecommunication interfaces to the SUNS. A transmission time of 878 kbps has been attained, including the time needed for read/write onto the PC hard disk. Image data thus transferred from the hospital have been utilized for the study of image processing by researchers in the Faculty of Engineering, and the processed images have been sent back to the hospital for evaluation of clinical efficacy of the processing by diagnostic radiologists. This kind of microwave network is a promising alternative for high-speed data transmission for radiological images and their processing.

[Radiation therapy of intracranial germinoma]

The appropriate radiation dose and field for the treatment of intracranial germinoma were investigated in 33 patients. Recurrences were observed in 4 cases treated with local field irradiation only, and all of them were recognized at the margin of the radiation field or under the dose (less than 25 Gy) area. This suggests that whole cranial irradiation (dose of 25 to 30 Gy) should be added even if the tumor is solitary. The effective dose for cerebrospinal dissemination appears to be 25-35 Gy, but prophylactic CNS irradiation seems unnecessary for patients who have not undergone surgical procedures. Changes in mental status were seen in 5 patients (26.3%). Doses of over 59 Gy may be related to this complication.

Unique DNA plasmid pRS64 associated with chromosomal DNAs of the plant pathogenic fungus Rhizoctonia solani

Unique DNA sequences homologous to the linear DNA plasmid pRS64 were investigated in chromosomal DNAs of isolates belonging to anastomosis group 4 (AG-4) of the plant pathogenic fungus Rhizoctonia solani. Chromosome-sized DNAs of isolates RI-64 and 1271 of AG-4 were separated into six bands by orthogonal-field-alternation gel electrophoresis and hybridized to a cloned segment of pRS64. A small chromosome-sized DNA band of approximately 1.1 Mb carried the sequences homologous to pRS64 DNA. Sequences homologous to pRS64 were also maintained within the chromosomal DNA of isolate 127.1 of AG-4 which does not possess the plasmid. The plasmid showed no homology to the mitochondrial DNA of isolate 1271. The possibility that the linear plasmid pRS64 may act as a transposable genetic element is discussed.