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D Schweizer

Publications and source records attributed to D Schweizer.

At least 19 recordsLinked to original sources
PubMed2002

Integration of common bean ( Phaseolus vulgaris L.) linkage and chromosomal maps.

Fluorescent in situ hybridisation of pooled, closely linked RFLP markers was used to integrate the genetic linkage map and the mitotic chromosome map of the common bean. Pooled RFLP probes showed clear and reproducible signals and allowed the assignment of all linkage groups to the chromosomes of two Phaseolus vulgaris cultivars, Saxa and Calima. Low extension values for signals originating from clustered RFLPs suggest that these clones are physically close to each other and that clusters in the genetic map are not a result of suppression of recombination due to the occurrence of chromosome rearrangements. For linkage group K, clustering of markers could be associated with proximity to centromeres. High variation in the number of 45S rDNA loci was observed among cultivars, suggesting that these terminal sites are highly recombinogenic in common bean.

DNA, Ribosomal↗
PubMed2001

A Caenorhabditis elegans cohesion protein with functions in meiotic chromosome pairing and disjunction.

We have studied four Caenorhabditis elegans homologs of the Rad21/Scc1/Rec8 sister-chromatid cohesion protein family. Based on the RNAi phenotype and protein localization, it is concluded that one of them, W02A2.6p, is the likely worm ortholog of yeast Rec8p. The depletion of C. elegans W02A2.6p (called REC-8) by RNAi, induced univalent formation and splitting of chromosomes into sister chromatids at diakinesis. Chromosome synapsis at pachytene was defective, but primary homology recognition seemed unaffected, as a closer-than-random association of homologous fluorescence in situ hybridization (FISH) signals at leptotene/zygotene was observed. Depletion of REC-8 also induced chromosome fragmentation at diakinesis. We interpret these fragments as products of unrepaired meiotic double-stranded DNA breaks (DSBs), because fragmentation was suppressed in a spo-11 background. Thus, REC-8 seems to be required for successful repair of DSBs. The occurrence of DSBs in REC-8-depleted meiocytes suggests that DSB formation does not depend on homologous synapsis. Anti-REC-8 immunostaining decorated synaptonemal complexes (SCs) at pachytene and chromosomal axes in bivalents and univalents at diakinesis. Between metaphase I and metaphase II, REC-8 is partially lost from the chromosomes. The partial loss of REC-8 from chromosomes between metaphase I and metaphase II suggests that worm REC-8 might function similarly to yeast Rec8p. The loss of yeast Rec8p from chromosome arms at meiosis I and centromeres at meiosis II coordinates the disjunction of homologs and sister chromatids at the two meiotic divisions.

Animals↗
PubMed2001

Characterisation of pericentrometric and sticky intercalary heterochromatin in Ornithogalum longibracteatum (Hyacinthaceae).

The hexaploid liliaceous plant Ornithogalum longibracteatum (2n=6x=54) has a heterochromatin-rich bimodal karyotype with large (L) and small (S) chromosomes. The composition and subgenomic distribution of heterochromatin was studied using molecular and cytological methods. The major component of centromeric heterochromatin in all chromosomes is Satl, an abundant satellite DNA with a basic repeat unit of 155 bp and an average A+T content (54%). The major component of the large blocks of intercalary heterochromatin in L chromosomes is Sat2, an abundant satellite DNA with a basic repeat unit of 115 bp and a high A+T content (76%). Additionally, traces of Sat2 can be detected at the centromeric regions of S chromosomes, while minor amounts of Satl are discernible in intercalary heterochromatin of L chromosomes. The chromosomal localisation pattern of Sat2 is consistent with the fluorescent staining pattern obtained with the A+T-specific DNA ligand 4'-6-diamidino-2-phenylindole (DAPI). A+T-rich intercalary heterochromatin is sticky and tends to associate ectopically during mitosis. Sister chromatid exchange clustering was found at the junctions between euchromatin and heterochromatin and at the centromeres. The pattern of mitosis-specific phosphorylation of histone H3 was not uniform along the length of the chromosomes. In all L and S chromosomes, from early prophase to ana-/telophase, there is hyperphosphorylation of histone H3 in the pericentromeric chromatin and a slightly elevated phosphorylated histone H3 level at the intercalary heterochromatin of L chromosomes. Consequently, the overall phosphorylated histone H3 metaphase labelling resembles the distribution of Satl in the karyotype of O. longibracteatum.

Base Sequence↗
PubMed2000

Retroperitoneal laparoscopic radical nephrectomy: the Cleveland clinic experience.

PURPOSE: Laparoscopic radical nephrectomy is usually performed by the transperitoneal approach. At our institution the retroperitoneoscopic approach is preferred. We confirm the technical feasibility of retroperitoneoscopic radical nephrectomy, even for large specimens, and compare its results with open surgery in a contemporary cohort. MATERIALS AND METHODS: A total of 47 patients underwent 53 retroperitoneoscopic radical nephrectomies. Data from the most recent 34 laparoscopic cases were retrospectively compared with 34 contemporary cases treated with open radical nephrectomy. RESULTS: For the 53 retroperitoneoscopic radical nephrectomies mean tumor size was 4.6 cm. (range 2 to 12), surgical time was 2.9 hours (range 1.2 to 4.5) and blood loss was 128 cc. Mean specimen weight was 484 gm. (range 52 to 1,328), and concomitant adrenalectomy was performed in 72% of patients. Mean analgesic requirement was 31 mg. morphine sulfate equivalent. Average hospital stay was 1.6 days, with 68% of patients discharged from the hospital within 23 hours of the procedure. Minor complications occurred in 8 patients (17%) and major complications occurred in 2 (4%) who required conversion to open surgery. Various parameters, including patient age, body mass index, American Society of Anesthesiologists status, tumor size (5 versus 6.1 cm.), specimen weight (605 versus 638 gm.) and surgical time (3.1 versus 3.1 hours), were comparable between patients undergoing laparoscopic (34) and open (34) radical nephrectomy. However, laparoscopy resulted in decreased blood loss (p <0.001), hospital stay (p <0.001), analgesic requirements (p <0.001) and convalescence (p = 0.005). Complications occurred in 13% of patients in the laparoscopic group and 24% in the open group. CONCLUSIONS: Retroperitoneoscopy is a reliable, effective and, in our hands, the preferred technique of laparoscopic radical nephrectomy. At our institution retroperitoneoscopy has emerged as an attractive alternative to open radical nephrectomy in patients with T1-T2N0M0 renal tumors.

Adult↗
PubMed2000

Laparoscopic adrenalectomy for large-volume (> or = 5 cm) adrenal masses.

BACKGROUND AND PURPOSE: Laparoscopic adrenalectomy has emerged as the standard of care at many centers for small surgical adrenal masses. However, the role of laparoscopic adrenalectomy in the treatment of large adrenal masses has not been specifically addressed. Our aim was to evaluate the outcome of laparoscopic v open adrenalectomy for large-volume (> or =5 cm) adrenal masses and to compare laparoscopic adrenalectomy for large- and small-volume (<5 cm) masses. PATIENTS AND METHODS: Data from 14 patients with large adrenal masses undergoing laparoscopic adrenalectomy between February 1998 and March 1999 (Group I) were retrospectively compared with 14 contemporary large-volume open adrenalectomies between December 1992 and May 1998 (Group II) and 45 small-volume laparoscopic adrenalectomies between July 1997 and November 1998 (Group III). RESULTS: In Group I and Group II, the mean surgical time (205 min v 216 min) and blood loss (400 mL v 584 mL) were similar. Although the mean adrenal size was also comparable (8 cm v 7.8 cm), the specimen weight of the en bloc adrenal gland and periadrenal fat was greater in Group I (168 g v 106 g). The hospital stay was shorter in Group I (2.4 days v 7.7 days). Minor complications occurred in 21.4% of Group I and 50% of Group II patients. On comparing Group I and Group III (laparoscopic <5 cm), Group I had larger specimen weight (168 g v 51.4 g), longer surgical time (205 min v 158 min), greater blood loss (400 mL v 113 mL), longer hospital stay (2.4 days v 1.5 days), a higher complication rate (21.4% v 8.9%), and a higher incidence of open surgical conversion (14.3% v 2.2%). Over a mean follow-up of 9.9 months, no local or port-site recurrences have been noted in Group I. CONCLUSIONS: Laparoscopic adrenalectomy for large-volume adrenal masses is technically feasible and seems to replicate open surgical oncologic principles of achieving a wide-margin, en bloc excision of the adrenal gland and periadrenal fat. Successful laparoscopic resection is not impacted by the large size of the adrenal mass per se but rather by the presence of local invasion and poorly defined tissue planes that may be encountered in adrenal malignancy. As such, laparoscopic adrenalectomy for large masses should be attempted only by experienced laparoscopic surgeons and then with a low threshold for open conversion.

Adrenal Gland Neoplasms↗
PubMed2000

Isolation and characterization of Suv39h2, a second histone H3 methyltransferase gene that displays testis-specific expression.

Higher-order chromatin has been implicated in epigenetic gene control and in the functional organization of chromosomes. We have recently discovered mouse (Suv39h1) and human (SUV39H1) histone H3 lysine 9-selective methyltransferases (Suv39h HMTases) and shown that they modulate chromatin dynamics in somatic cells. We describe here the isolation, chromosomal assignment, and characterization of a second murine gene, Suv39h2. Like Suv39h1, Suv39h2 encodes an H3 HMTase that shares 59% identity with Suv39h1 but which differs by the presence of a highly basic N terminus. Using fluorescent in situ hybridization and haplotype analysis, the Suv39h2 locus was mapped to the subcentromeric region of mouse chromosome 2, whereas the Suv39h1 locus resides at the tip of the mouse X chromosome. Notably, although both Suv39h loci display overlapping expression profiles during mouse embryogenesis, Suv39h2 transcripts remain specifically expressed in adult testes. Immunolocalization of Suv39h2 protein during spermatogenesis indicates enriched distribution at the heterochromatin from the leptotene to the round spermatid stage. Moreover, Suv39h2 specifically accumulates with chromatin of the sex chromosomes (XY body) which undergo transcriptional silencing during the first meiotic prophase. These data are consistent with redundant enzymatic roles for Suv39h1 and Suv39h2 during mouse development and suggest an additional function of the Suv39h2 HMTase in organizing meiotic heterochromatin that may even impart an epigenetic imprint to the male germ line.

Amino Acid Sequence↗
PubMed2000

Outpatient adrenalectomy.

PURPOSE: To our knowledge we report the initial experience with outpatient, same day laparoscopic adrenalectomy. MATERIALS AND METHODS: Nine select patients were entered into our ambulatory adrenalectomy protocol. Each patient fulfilled certain preoperative and postoperative inclusion criteria, including informed consent, age 70 years or older, body mass index 40 or less, adrenal tumor less than 5 cm., no pheochromocytoma, uncomplicated laparoscopic surgery that was completed by 12 p.m., perioperative hemodynamic stability and pain control by oral analgesics. RESULTS: All 9 patients successfully underwent outpatient laparoscopic adrenalectomy. Average patient age was 53 years and average adrenal tumor size was 2 cm. Mean surgical time was 2.3 hours and mean blood loss was 53 ml. The diagnosis was aldosteroma in 7 cases, enlarging adenoma in 1 and myelolipoma in 1. Average postoperative hospital stay was 416 minutes (range 300 to 570). Postoperative analgesia comprised 6 mg. morphine sulfate and 32 mg. ketorolac. The only complication was a local abscess requiring delayed drainage at 2 weeks. No other patient was rehospitalized for any reason. A followup questionnaire survey revealed excellent patient satisfaction. CONCLUSIONS: To our knowledge we report the initial series of outpatient laparoscopic excision of a solid organ, the adrenal gland. Ambulatory adrenalectomy is feasible and safe, and results in high patient satisfaction. However, ambulatory adrenalectomy should be restricted to highly select patients and performed by minimally invasive surgeons who have considerable experience with laparoscopic adrenal surgery.

Adrenal Gland Neoplasms↗
PubMed1999

Radical nephrectomy and nephroureterectomy in the octogenarian and nonagenarian: comparison of laparoscopic and open approaches.

OBJECTIVES: To retrospectively compare the outcome of laparoscopic and open radical nephrectomy or nephroureterectomy in patients 80 years old or older, inasmuch as the tolerance profile of major laparoscopic renal surgery in comparison to open surgery in the elderly patient has not been previously reported. METHODS: Since September 1997, 11 patients 80 years old or older underwent retroperitoneal laparoscopic radical nephrectomy or nephroureterectomy for cancer. These patients were compared with 6 consecutive patients 80 years old or older who underwent comparable open surgery at our institution since January 1994. No tumor had computed tomographic evidence of lymphatic, vascular, or perirenal extension. RESULTS: Baseline parameters were comparable between the laparoscopic and open groups. The laparoscopic group had a similar median surgical time (210 minutes versus 175 minutes; P = 0.1) and blood loss (150 mL versus 125 mL; P = 0.8) compared with the open group. However, specimen weight was larger in the laparoscopic group (568 g versus 292 g; P = 0.04). Moreover, the laparoscopic group had a quicker resumption of oral intake (less than 1 day versus 4 days; P <0.001), decreased narcotic requirements (14 mg versus 326 mg; P = 0.004), shorter hospital stay (2 days versus 6 days; P <0.001), and faster convalescence (14 days versus 42 days; P <0.001) compared with the open group. CONCLUSIONS: Retroperitoneal laparoscopic radical nephrectomy and nephroureterectomy are well tolerated by the elderly patient. Although our sample size was small, it appears that laparoscopy is an excellent alternative to open surgery for excision of selected renal malignancies in the octogenarian and nonagenarian population.

Aged↗
PubMed1999

The Tpv2 family of retrotransposons of Phaseolus vulgaris: structure, integration characteristics, and use for genotype classification.

The Tpv2 family of transposable elements of common bean, Phaseolus vulgaris, belongs to the Ty1/copia group of long terminal repeat (LTR) containing retrotransposons. By reverse transcriptase (RT)-PCR and by analysis of genomic clones, we characterized four of the approximately 40 copies present in the Phaseolus genome, and the genomic environment of their integration sites. Tpv2 integrated preferentially into actively transcribed regions. While none of the isolated elements had all the functional domains necessary for transposition, analysis of bean cultivars suggested that some members of the Tpv2 family transposed in recent breeding history. Probes derived from Tpv2, as well as flanking genomic sequences, may be useful for classifying Phaseolus cultivars.

Amino Acid Sequence↗
PubMed1999

Elimination and rearrangement of parental rDNA in the allotetraploid Nicotiana tabacum.

Origin and rearrangement of ribosomal DNA repeats in natural allotetraploid Nicotiana tabacum are described. Comparative sequence analysis of the intergenic spacer (IGS) regions of Nicotiana tomentosiformis (the paternal diploid progenitor) and Nicotiana sylvestris (the maternal diploid progenitor) showed species-specific molecular features. These markers allowed us to trace the molecular evolution of parental rDNA in the allopolyploid genome of N. tabacum; at least the majority of tobacco rDNA repeats originated from N. tomentosiformis, which endured reconstruction of subrepeated regions in the IGS. We infer that after hybridization of the parental diploid species, rDNA with a longer IGS, donated by N. tomentosiformis, dominated over the rDNA with a shorter IGS from N. sylvestris; the latter was then eliminated from the allopolyploid genome. Thus, repeated sequences in allopolyploid genomes are targets for molecular rearrangement, demonstrating the dynamic nature of allopolyploid genomes.

Base Sequence↗
PubMed1999

Quantitative karyotyping and dual-color FISH mapping of 5S and 18S-25S rDNA probes in the cultivated Phaseolus species (Leguminosae)

Double-color fluorescence in situ hybridization (FISH) followed by DAPI counterstaining allowed the chromosomal assignment of 5S and 18S-25S rRNA genes in the four cultivated Phaseolus Species; P. vulgaris, P. coccineus, P. acutifolius, and P. lunatus (all: 2n = 2x = 22). The rRNA gene loci display variation between species as reflected in differences of signal size and (or) number. From one to three pairs of 5S sites and one to seven pairs of 18S-25S sites were found in the diploid complements of the four taxa studied. Intraspecific variation was studied in P. vulgaris, and it is shown that the number of 18S-25S rDNA sites differs between cultivars. Cytogenetic mapping was complemented by karyotype analyses. Each of the four cultivated Phaseolus species exhibits a characteristic heterochromatin endowment, with P. acutifolius var. latifolius having the highest amount of C-band material. Quantitative karyotyping in combination with cytogenetic mapping allowed the identification of homeologous chromosomes in the different species.

Journal Article↗
PubMed1999

Random amplified polymorphic DNA analysis, genome size, and genomic in situ hybridization of triploid viviparous onions

Triploid viviparous onions (Allium cepa L. var. viviparum Metzg. (ALEF.), auct.), (2n = 3x = 24), are known in some countries only as a rare relic crop, while in other parts of the world they are still traditionally or even commercially cultivated. Results indicating an identical random amplified polymorphic DNA (RAPD) banding pattern and the same DNA content (2C = 43.4 pg) establish the high genetic similarity and the unique origin of the Croatian clone Ljutika and the Indian clone Pran. In order to determine the parental Allium species of these natural triploid hybrids, genomic fluorescent in situ hybridization (GISH) was applied. Biotinylated genomic DNAs from six diploid Allium species (A. cepa L., A. fistulosum L., A. roylei Stearn, A. vavilovii M. Pop. et Vved., A. galanthum Kar. et Kir., A. oschaninii O. Fedtsch.) were used as probes in this study. While probes obtained from genomic DNA of A. cepa, A. vavilovii, and A. roylei hybridized to somatic chromosomes of Ljutika probes from A. fistulosum, A. galanthum, and A. oschaninii did not. The DNA probes of A. cepa and A. roylei each completely or predominantly labelled one genome (eight chromosomes). A few chromosomes, the markers of the triploid karyotype, were not completely labelled by any probe applied. Our GISH results indicate that triploid viviparous onions might possess a complex triparental genome organization.

Journal Article↗
PubMed1999

Chromatin-association of the Polycomb group protein BMI1 is cell cycle-regulated and correlates with its phosphorylation status.

The human proto-oncogene Bmi1 is a member of the mammalian Polycomb Group (Pc-G) genes. The subnuclear distribution of the BMI1 protein was studied in several primary human and tumor-derived cell lines using immunohistochemical and biochemical methods. In primary and tumor cells, nuclear BMI1 shows a fine-grain distribution over chromatin, usually dense in interphase nuclei and significantly weaker along mitotic chromosomes. In addition, BMI1 preferentially associates with several distinct heterochromatic domains in tumor cell lines. In both primary and tumor cell lines a marked cell cycle-regulation of Pc-G-chromatin interaction is observed: nuclear BMI1-staining dissipates in late S phase and is re-established early in G(1)-phase. Chromatin-association of BMI1 inversely correlates with its phosphorylation status in a cell cycle-dependent fashion: at G(1)/S, hypophosphorylated BMI1 is specifically retained in the chromatin-associated nuclear protein fraction, whereas during G(2)/M, phosphorylated BMI1 is not chromatin-bound. Our findings indicate a strict cell cycle-controlled regulation of Pc-G complex-chromatin association and provide molecular tools for improving our understanding of Pc-G complex regulation and function in mammalian cells.

Cell Cycle↗
PubMed1999

Financial analysis of needlescopic versus open adrenalectomy.

PURPOSE: Needlescopic adrenalectomy, partially incorporating 2 mm. instrumentation, is currently our preferred technique for transperitoneal endoscopic adrenalectomy. Although this minimally invasive technique results in decreased morbidity and shorter hospital stay, to our knowledge financial implications vis-à-vis open adrenalectomy have not been elucidated. We retrospectively compared the costs of needlescopic adrenalectomy to traditional open adrenalectomy. MATERIALS AND METHODS: From September 1997 through March 1998, 15 patients underwent needlescopic adrenalectomy. Financial records of these patients were compared to those of 15 contemporary patients undergoing open adrenalectomy between January 1995 and May 1997. Adrenal pathology and tumor size were comparable between the 2 groups. Yearly costs were adjusted for inflation to 1998 dollars using a 4% annual rate. Needlescopic financial data are expressed as a ratio of open adrenalectomy costs, which are expressed as a unit of 1. RESULTS: Overall, needlescopic adrenalectomy resulted in a 17.9% decrease in total hospital costs compared to open adrenalectomy. While the needlescopic approach was associated with an 18.1% increase in intraoperative costs, postoperative costs were 63.4% lower. CONCLUSIONS: These data demonstrate that in addition to providing a shorter hospital stay, decreased morbidity and quicker recovery, needlescopic adrenalectomy also is 17.9% less expensive than open adrenalectomy.

Adrenalectomy↗
PubMed1999

Retroperitoneoscopic surgery is not associated with increased carbon dioxide absorption.

PURPOSE: Previous studies have suggested that retroperitoneal laparoscopy is associated with greater carbon dioxide absorption and related postoperative morbidity, such as subcutaneous emphysema and pneumothorax. We prospectively compared the effects of carbon dioxide absorption during transperitoneal and retroperitoneal laparoscopic renal and adrenal surgery at our institution. MATERIALS AND METHODS: Data were collected prospectively on 51 patients who underwent laparoscopic renal (26) or adrenal (25) surgery via the transperitoneal (18) or retroperitoneal (33) approach from September 1997 to February 1998. RESULTS: There was no significant difference in carbon dioxide elimination in patients who underwent transperitoneal laparoscopy compared to retroperitoneoscopy at any interval. Subcutaneous emphysema occurred in 12.5% of the transperitoneal and 45% of the retroperitoneal group (p = 0.09). Patients with subcutaneous emphysema had greater carbon dioxide elimination during the first 2.5 hours of insufflation compared to those without subcutaneous emphysema and, thereafter, carbon dioxide elimination decreased to baseline. CONCLUSIONS: In contrast to previous reports our prospective nonrandomized study suggests that retroperitoneoscopy is not associated with greater carbon dioxide absorption compared to transperitoneal laparoscopy. Patients with subcutaneous emphysema exhibited only transient increases in carbon dioxide absorption above control levels.

Absorption↗
PubMed1998

Molecular-cytogenetic characterization of the Vicia faba genome--heterochromatin differentiation, replication patterns and sequence localization.

A comprehensive survey of the molecular-cytogenetic features of the Vicia faba chromosome complement (2n = 12) is given. It includes previous as well as new original data. Various Giemsa, restriction endonuclease and fluorochrome banding patterns, azacytidine-mediated segment extension, replication patterns, lateral A/T asymmetry and sequence localization data for tandemly arranged simple sequence repeats, dispersed repeats and coding sequences as well as histone acetylation patterns are considered. This allows not only to distinguish and characterize telomeres, subtelomeres, centromeres and the NOR, but also the structure of the 5S rRNA gene loci and two main types of interstitial heterochromatin. Additionally, it offers physical landmarks within euchromatic areas. Thus, the field bean genome, exemplified by the reconstructed karyotype ACB, belongs to the cytogenetically best investigated plant genomes.

Chromosome Banding↗
PubMed1997

Ribosomal transcription units integrated via T-DNA transformation associate with the nucleolus and do not require upstream repeat sequences for activity in Arabidopsis thaliana.

Ribosomal repeat units of Arabidopsis thaliana were introduced into the A. thaliana genome via Agrobacterium-mediated transformation. Ribosomal transgenes integrated into chromosomal regions outside the nucleolus organizers. Cytological data suggest that the transgenes associate with a nucleolus. To allow detection of transgenic rRNA, a short extension was inserted into the V1 variable region of the 25S ribosomal gene. The RNA transcript from the transgene undergoes a series of maturation steps, including correct processing of the 5' end of 25S rRNA. Using primer extension analysis, expression of a complete rDNA repeat unit was compared with the activity of a repeat unit lacking a sequence called 'upstream Sal repeats'. No qualitative or quantitative differences were detected, suggesting that upstream repeat sequences of the rDNA intergenic region do not act as transcriptional enhancers for RNA polymerase L in A. thaliana.

Arabidopsis↗