Biomedical subjects

C Gebhardt

Publications and source records attributed to C Gebhardt.

At least 19 recordsLinked to original sources

PubMed2006

The novel, major locus Rpi-phu1 for late blight resistance maps to potato chromosome IX and is not correlated with long vegetation period.

Despite the long history of breeding potatoes resistant to Phytophthora infestans, this oomycete is still economically the most important pathogen of potato worldwide. The correlation of high levels of resistance to late blight with a long vegetation period is one of the bottlenecks for progress in breeding resistant cultivars of various maturity types. Solanum phureja was identified as a source of effective late blight resistance, which was transferred to the cultivated gene pool by interspecific crosses with dihaploids of Solanum tuberosum. A novel major resistance locus, Rpi-phu1, derived most likely from S. phureja and conferring broad-spectrum resistance to late blight, was mapped to potato chromosome IX, 6.4 cM proximal to the marker GP94. Rpi-phu1 was highly effective in detached leaflet, tuber slice and whole tuber tests during 5 years of quantitative phenotypic assessment. The resistance did not show significant correlation with vegetation period length. Our findings provide a well-characterized new source of resistance for breeding early and resistant-to-P. infestans potatoes.

Breeding↗

PubMed2006

Marker-assisted combination of major genes for pathogen resistance in potato.

Closely linked PCR-based markers facilitate the tracing and combining of resistance factors that have been introgressed previously into cultivated potato from different sources. Crosses were performed to combine the Ry ( adg ) gene for extreme resistance to Potato virus Y (PVY) with the Gro1 gene for resistance to the root cyst nematode Globodera rostochiensis and the Rx1 gene for extreme resistance to Potato virus X (PVX), or with resistance to potato wart (Synchytrium endobioticum). Marker-assisted selection (MAS) using four PCR-based diagnostic assays was applied to 110 F1 hybrids resulting from four 2x by 4x cross-combinations. Thirty tetraploid plants having the appropriate marker combinations were selected and tested for presence of the corresponding resistance traits. All plants tested showed the expected resistant phenotype. Unexpectedly, the plants segregated for additional resistance to pathotypes 1, 2 and 6 of S. endobioticum, which was subsequently shown to be inherited from the PVY resistant parents of the crosses. The selected plants can be used as sources of multiple resistance traits in pedigree breeding and are available from a potato germplasm bank.

Animals↗

PubMed2006

Potato chromosomes IX and XI carry genes for resistance to potato virus M.

Two new loci for resistance to potato virus M (PVM), Gm and Rm, have been mapped in potato. The gene Gm was derived from Solanum gourlayi, whereas, Solanum megistacrolobum is the source of the gene Rm. Gm confers resistance to PVM infection after mechanical inoculation. Rm induces a hypersensitive response in potato plants. Two diploid populations segregating for Gm and Rm, bulked segregant analysis (BSA) using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), and available potato molecular maps were instrumental for mapping the resistance loci. The novel locus Gm was mapped to a central region on potato chromosome IX. The locus Rm was placed on the short arm of chromosome XI, close to the marker loci GP250 and GP283, where a hotspot for monogenic and polygenic resistance to diverse pathogens is located in the potato and tomato genome.

Carlavirus↗

PubMed2004

Two allelic or tightly linked genetic factors at the PLRV.4 locus on potato chromosome XI control resistance to potato leafroll virus accumulation.

A novel locus for potato resistance to potato leafroll virus (PLRV) was characterized by inheritance studies and molecular mapping. The diploid parental clone DW 91-1187 was resistant to PLRV accumulation in both inoculated plants and their tuber progeny. The resistance to PLRV accumulation present in DW 91-1187 was not transmitted to any F1 offspring when crossed with a PLRV susceptible clone. Instead, one half of the F1 individuals exhibited undetectable amounts of PLRV as determined by ELISA during the primary infection assay, but accumulated PLRV in their tuber progeny plants. The other half was clearly infected both in the inoculated and tuber-born plants. The inheritance of resistance to PLRV accumulation may be explained by a model of two complementary alleles of a single gene ( PLRV.4) or by two complementary genes that are closely linked in repulsion phase. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers linked to the PLRV.4 locus were selected. The two complementary factors were closely linked in coupling phase to the alternative alleles UBC864(600) and UBC864(800) of DNA marker UBC864. These markers may be used for marker-assisted selection of genotypes having both factors for resistance to PLRV accumulation. The PLRV.4 locus was mapped to a central position on linkage group XI of the potato molecular map, where no resistance locus has been mapped previously.

Chromosome Mapping↗

PubMed2003

Structural diversity and organization of three gene families for Kunitz-type enzyme inhibitors from potato tubers (Solanum tuberosum L.).

In the potato, Kunitz-type enzyme inhibitors are abundant and highly polymorphic small proteins found in tubers. DNA sequence analysis of 1596 unselected ESTs (expressed sequence tags) from mature tubers of the cultivars Provita and Saturna resulted in the identification of 55 different DNA sequences with high sequence similarity to Kunitz-type enzyme inhibitors. The frequency of Kunitz-type inhibitor ESTs in Provita was four times higher than in Saturna tubers, and none of the Provita ESTs was identical to any of the Saturna ESTs. A phenogram constructed from the deduced amino acid sequences of the inhibitors revealed three major homology groups-A, B and C. Group A inhibitors were all derived from Provita ESTs. Inhibitor groups A and B were more similar to each other than to group C inhibitors, and for most members within-group similarity was at least 90%. Non-conservative amino acid substitutions and insertion/deletion polymorphisms suggest functional differentiation between members of the gene family. A minimum of 21 genes for Kunitz-type enzyme inhibitors (six for group A, nine for group B and six for group C) was estimated to exist in the potato genome. Genetic mapping and the identification of BAC (bacterial artificial chromosome) clones containing more than one member of the gene family indicated that most inhibitor genes of groups A, B and C are organized in a cluster that maps to a single region on potato chromosome III.

Amino Acid Sequence↗

PubMed2003

Functional comparison of homologous members of three groups of Kunitz-type enzyme inhibitors from potato tubers (Solanum tuberosum L.).

For functional studies, nine cDNAs encoding Kunitz-type enzyme inhibitors from potato tubers were expressed as GST (glutathione S transferase)-tagged fusion proteins in the fission yeast Schizosaccharomyces pombe. The inhibitors represented the three major homology groups A, B and C found in tubers. Members of the same homology group were at least 90% identical in sequence. The purified GST fusion proteins were tested for their ability to inhibit the proteases trypsin, alpha-chymotrypsin, subtilisin, papain and aspergillopepsin I, and for inhibition of the growth of fungi. Fusion proteins belonging to the same and different homology groups were found to exhibit distinct protease inhibition profiles. Removal of the GST tag by cleavage with enterokinase did not change the inhibition profile but increased the inhibitory activity. Group A and B inhibitors affected the proteases to different extents, whereas group C inhibitors showed only weak or no protease inhibition. One fusion protein completely inhibited aspergillopepsin I. One fusion protein each of groups A and B strongly inhibited mycelial growth of the fungus Fusarium moniliforme. The results suggest functional polymorphism among closely related members of the Kunitz-type inhibitor family.

Endopeptidases↗

PubMed2003

[Carcinoma of the pancreas head, papilla Vateri, and cystadenocarcinoma--different biologic entities and different results].

Between 1986-1995 we operated 337 patients with ductal adenocarcinoma of the pancreas, 45 cases of carcinoma of the papilla of Vater and 11 patients with cystadenocarcinoma of the pancreas. The evaluation of prognostic factors showed the influence of lymph node invasion. Furthermore we saw a significant influence of lymph- and haemangiosis carcinomatosa, of tumor-grading and tumor-size. The carcinoma of the papilla showed a better 5-year survival even in nodal-positive patients--this as a result of a different biological behaviour. We think that--instead of missing improvement of cure in ductal adenocarcinoma over the past decade--there is no place for therapeutic nihilism especially in non-ductal cancer, which represents almost 15 % of all pancreatic neoplasms.

Aged↗

PubMed2002

The adenoma-carcinoma sequence applies to epithelial tumours of the papilla of Vater.

Adenomas of the papilla of Vater are relatively rare tumours. They are of particular interest, not only because of their particular topography, but also because the adenoma-carcinoma sequence - accepted in the colorectum - has also been postulated to apply to the papilla of Vater. In fact, ampullary adenoma is often considered to be a precancerous lesion. To investigate this hypothesis, we reviewed the surgical specimens obtained during Whipple's procedures carried out to treat histologically confirmed carcinoma of the ampulla. A total of 37 surgical specimens obtained since January 1991 were reexamined for the presence of coexisting adenomatous structures. Such adenomatous residues were confirmed in 24/37 (65 %) cases. In 13/37 (35 %) cases, no residual adenoma was found. A comparison of the two groups revealed that detection of coexisting adenomatous structures decreased with increasing tumour progression. In similar manner, this also applied to the degree of malignancy: with increasing grade of malignancy the rate of detectable adenomatous structures decreased significantly. It may be assumed that these observations are due to the 'overgrowth' of preexisting adenomas by carcinomatous tissue. Further evidence is provided by the histological observation of transitional stages from adenoma with mild, moderate and severe cellular atypia to invasive carcinoma. These findings support the hypothesis of an adenoma-carcinoma sequence.

Adenoma↗

PubMed2002

Results of surgical therapy of adenocarcinomas of the esophagogastric junction according to a standardized surgical resection technique.

AIM: The aim of this retrospective analysis was to exclusively present the surgical results of patients with type-I-III adenocarcinomas of the esophagogastric junction thereby providing a basis for comparison with other approaches. METHODS: 56 patients with Barrett's carcinomas and 74 patients with cardial and subcardial tumors were operated on and evaluated. The surgical procedure for type-II/III carcinomas was identical: total gastrectomy, omentectomy and splenectomy with lymph node dissection after a combined left thoraco-abdominal incision. Both tumor entities were summarized into 1 group and compared with the results of surgery for Barrett's carcinomas: subtotal esophagectomy and proximal stomach resection with lymph node dissection after right thoracotomy and an additional abdominal incision. RESULTS: In 93% of all patients an R0 resection was possible. In patients with Barrett's carcinomas pulmonal complications (41%) were the predominant postoperative problems. The 30-day lethality (5.3%) was higher in the group of patients with type-I carcinomas compared to those with type-II/III carcinomas (1.4%). Tumor infiltration and nodal involvement determined the prognosis after R0 resection. The presence of Barrett's mucosa in type-I adenocarcinomas and the histological assessment according to Lauren's classification into type-II/III carcinomas also influenced the long-term prognosis. CONCLUSION: After R0 resection it is not the tumor location but tumor infiltration, lymph node status and a differentiated histological assessment that determine the prognosis of patients with adenocarcinomas of the esophagogastric junction.

Adenocarcinoma↗

PubMed2001

The antiepileptic drug losigamone decreases the persistent Na+ current in rat hippocampal neurons.

The tetronic acid derivative losigamone is a new anticonvulsant drug with a mechanism of action that was previously unknown. The drug decreases the frequency of spontaneous action potentials and suppresses repetitive firing of neurons. Here we tested the hypothesis that losigamone suppresses the persistent Na+ current (I(NaP)) in hippocampal neurons of rat brain slices and in cultured hippocampal neurons. Whole-cell voltage clamp recordings from neurons of juvenile rats (P15-P25) were performed with pipettes filled with Cs-gluconate or CsF. After pharmacological block of K+ and Ca2+ currents I(NaP) was revealed by applying slow depolarizing voltage ramps from -70 to 0 mV. Losigamone (100-200 microM) was dissolved in DMSO (0.1%) and was applied by bath application or local pressure application. Losigamone induced a decrease in amplitude of I(NaP) at depolarized membrane potentials which was reversible in cultured neurons. When tetrodotoxin (TTX) was added to the bath, I(NaP) was blocked and only a residual non-specific outward cation current (I(cat)) remained. Losigamone had no obvious effect on responses to voltage ramps under these conditions. Thus, losigamone did not affect I(cat) or induce any additional currents. The data suggest that losigamone decreases neuronal excitability via a decrease in I(NaP).

Animals↗

PubMed2001

Enhanced spontaneous transmitter release is the earliest consequence of neocortical hypoxia that can explain the disruption of normal circuit function.

After the onset of an acute episode of arrested circulation to the brain and consequent cerebral hypoxia, EEG changes and modifications of consciousness ensue within seconds. This in part reflects the rapid effect of hypoxia on the neocortex, where oxygen deprivation leads to impaired neuronal excitability and abnormal synaptic transmission. To identify the cellular mechanisms responsible for the earliest changes in neocortical function and to determine their time course, we have used patch-in-slice recording techniques to investigate the effects of acute hypoxia on the synaptic and intrinsic properties of layer 5 neurons. Coronal slices of mouse somatosensory cortex were maintained at 37 degrees C and challenged with episodes of hypoxia (3-4 min of exposure to 95% N(2), 5% CO(2)). In recordings with cell-attached patch electrodes, activation of ATP-sensitive potassium channels first became detectable 211 +/- 11 sec (range, 185-240 sec; n = 6 patches) after the onset of hypoxia. Similar recording techniques revealed no alterations in the properties of Na(+) currents in the first 4 min after the onset of hypoxia. The earliest hypoxia-induced disturbance was a marked increase in the frequency of spontaneous EPSCs and IPSCs, which began within 15-30 sec of the removal of oxygen. This rapid synaptic effect was not sensitive to TTX and was present in Ca(2+)-free perfusate, indicating that the hypoxia had a direct influence on the vesicular release mechanisms. The incoherent, massive increase in miniature PSCs would be expected to deplete the readily releasable pool of vesicles in cortical terminals, and to thereby markedly distort the neuronal interactions that underlie normal circuit function.

Adenosine Triphosphate↗

PubMed2001

The expression of substance P and its neurokinin-1 receptor mRNA in the bovine corpus luteum of early developmental stage.

Related to all leukocytes, 90% of eosinophils are recruited into the bovine corpus luteum of early developmental stage. We here describe a simultaneous appearance of substance P (SP)-positive fibre-like structures and the neurokinin-1 (NK-1) receptor mRNA for SP. Substance P was depicted by using indirect immunohistology and immunofluorescence localization. The dot blot analysis confirmed the presence of SP at the protein level. Using nested reverse transcribed-polymerase chain reaction (RT-PCR) analysis, a 358 bp long partial bovine receptor mRNA for SP (NK-1) was sequenced in the spinal cord. The mRNA for SP and for the NK-1 receptor were then detected in the corpus luteum of early developmental stage with RT-PCR and nested RT-PCR. We conclude: The production of SP and the expression of NK-1 receptor mRNA may be involved in the selective recruitment of eosinophils into the bovine corpus luteum of early developmental stage.

Animals↗

PubMed2001

Prognostic importance of isolated peritumoral lymphangiosis carcinomatosa in lymph-node-negative colorectal carcinoma.

BACKGROUND: The prognostic value of microinvasion of lymph vessels and lymph nodes has become increasingly important; there is a wide range in prognosis of patients with nodal-negative tumor stages after curative resection for colorectal cancer. AIM: Detection of the prognostic importance of isolated lymph-vessel invasion as a possible precursor of lymph-node metastasis in patients with nodal-negative tumor stages. PATIENTS/METHODS: Retrospective analysis of 894 patients with R0-resected colorectal cancer, uni- and multivariate analysis of tumorbiologic prognostic factors, immunohistochemical proof of tumor cells in negative lymph nodes (pN0) using the epithelial marker HEA-125 (human epithelial antigen). RESULTS: The incidence of lymph-vessel invasion (L) was 37.7% in total. A pN0,L1 status was found in 144 patients (16.1% of all analyzed patients). Comparing patients with pN0,L1 status to those with pN+,L0 status showed that both groups have similar rates of overall survival and tumor relapse. Lymph-node status, lymph-vessel invasion, depth of tumor infiltration (pT) stage, and age were detected as independent prognostic factors by multivariate analysis. After reanalysis of 54 cases primarily classified as 18.5% pN0,L1, microinvasion in lymph nodes was detected by immunohistochemistry. We found a higher rate of tumor relapse (approximately 20%) for those patients. In regard to the overall survival rate, however, there was no difference when compared to patients without immunohistochemical proof of microinvasion. CONCLUSION: Isolated lymph-vessel invasion in nodal-negative tumor stages and a lymph-node-positive tumor status have equivalent prognostic importance in colorectal cancer.

Aged↗

PubMed2001

Keratinocyte-specific onset of serine protease BSSP expression in experimental carcinogenesis.

Malignant transformation of mouse skin by chemical carcinogens and tumor promoters, such as the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, is a multistage process leading to the formation of squamous cell carcinomas. In an effort to identify target genes whose expression is associated with skin tumorigenesis we combined elements of suppression subtractive hybridization with differential screening to isolate genes that are differentially upregulated in mouse skin after short-term treatment with 12-O-tetradecanoylphorbol-13-acetate and that exhibit a high constitutive expression in squamous cell carcinomas. Here, we report the detailed analysis of one of these cDNAs encoding the serine protease BSSP in mouse skin. Phorbol ester application increases BSSP expression in keratinocytes of the epidermis and the hair follicle several-fold starting 4 h post- treatment. Transcriptional activation of BSSP by 12-O-tetradecanoylphorbol-13-acetate was found to be independent of c-Fos expression and resistant to downregulation by glucocorticoids. By monitoring BSSP expression throughout experimental skin carcinogenesis we found strong constitutive expression in hyperplastic epidermis as well as in proliferatively active keratinocytes of benign and malignant skin tumors. These results establish a novel link between expression of an as yet ill-defined serine protease and skin carcinogenesis.

Animals↗

PubMed2001

[Pancreaticojejunal anastomosis. Indication, technique and results].

Pancreaticojejunal anastomosis. Indication, technique and results. Pancreaticojejunal anastomoses are performed for the treatment of chronic pancreatitis and after resection of pancreatic carcinomas. In chronic pancreatitis by drainage procedures (Partington-Rochelle and Puestow-Gillesby) one can expect good long term results, if the diameter of the pancreatic duct is at least 1 cm and the length of the anastomosis 6 cm. The duodenumpreserving head resection (Beger or Frey) is a combination of resection and drainage and is significant in the therapy of inflammatory head processes. In the surgical treatment of pancreatic carcinomas pancreaticojejunostomies are applied after head resection (Whipple-, pyloruspreserving modification). The end-to-side mucosa-mucosa anastomosis offers the best results concerning postoperativ complications and mortality rates.

Chronic Disease↗

PubMed2001

A major quantitative trait locus for resistance to Potato leafroll virus is located in a resistance hotspot on potato chromosome XI and is tightly linked to N-gene-like markers.

Potato leafroll virus (PLRV) causes one of the most widespread and important virus diseases in potato. Resistance to PLRV is controlled by genetic factors that limit plant infection by viruliferous aphids or virus multiplication and accumulation. Quantitative trait locus (QTL) analysis of resistance to virus accumulation revealed one major and two minor QTL. The major QTL, PLRV.1, mapped to potato chromosome XI in a resistance hotspot containing several genes for qualitative and quantitative resistance to viruses and other potato pathogens. This QTL explained between 50 and 60% of the phenotypic variance. The two minor QTL mapped to chromosomes V and VI. Genes with sequence similarity to the tobacco N gene for resistance to Tobacco mosaic virus were tightly linked to PLRV.1. The cDNA sequence of an N-like gene was used to develop the sequence characterized amplified region (SCAR) marker N127(1164) that can assist in the selection of potatoes with resistance to PLRV.

Chromosome Mapping↗

PubMed2001

Organization of genes controlling disease resistance in the potato genome.

Nineteen single dominant genes (R genes) for resistance to viruses, nematodes, and fungi have been positioned on the molecular map of potato using DNA markers. Fourteen of those genes are located in five "hotspots" for resistance in the potato genome. Quantitative trait loci (QTL) for resistance to late blight caused by the oomycete Phytophthora infestans, to tuber rot caused by the bacterium Erwinia carotovora ssp. atroseptica, and to root cyst nematodes have been identified on all 12 potato chromosomes. Some QTL for resistance to different pathogens are linked to each other and/or to resistance hotspots. Based on the genetic clustering with R genes, we propose that some QTL for resistance have a molecular basis similar to single R genes. Mapping potato genes with sequence similarity to cloned R genes of other plants and other defense-related genes reveals linkage between candidate genes, R genes, and resistance QTL. To explain the molecular basis of polygenic resistance in potato we propose (a) genes having structural similarity with cloned R genes and (b) genes involved in the defense response. The "candidate gene approach" enables the identification of markers highly useful for marker-assisted selection in potato breeding.

Animals↗

PubMed2000

Prognostic factors in the operative treatment of ductal pancreatic carcinoma.

BACKGROUND AND AIMS: The average 5-year survival rate following resection of a ductal adenocarcinoma of the pancreas is 10%, worldwide. Despite increasing resection rates, only about 20% can be operated on with curative intent. A differential histopathological analysis of the resected tumors may help to justify expanding the surgical procedure by extended lymph-node dissection. PATIENTS/METHODS: Between January 1986 and December 1995, a total of 113 patients underwent resection with curative intent for a ductal pancreatic carcinoma with regional lymph-node dissection. All histological findings were reviewed and reclassified in accordance with the 1997 Union Internationale Contra la Cancrum (UICC) classification. Survival data for all of these patients were obtained from family doctors and registration offices. Independent prognostic factors were statistically analyzed. RESULTS: Of the 113 patients, 93 received an R0 resection. The postoperative mortality rate was 2.2% (2 of 93). More than one-half of the tumors had a diameter of between 2.1 cm and 4 cm. Among the 22 tumors measuring up to 2 cm in diameter, 41% already had lymph-node metastasis and 86% invasion of the lymphatic vessels. Carcinomas measuring between 4.1 cm and 6 cm were all associated with lymph-vessel invasion. Perineural invasion was present in 50% of the tumors. A noteworthy finding was the fact that 64% of the 25 tumors with negative lymph nodes had lymph-vessel invasion, and 48% perineural invasion. The cumulative 5-year survival rate of the R0-resected patients was 10. 5%. Patients with lymph-node-negative stages survived significantly longer (26.5%) than patients with lymph-node-positive stages (5%). Furthermore, a significant difference was seen between pN1a and pN1b (16.7% vs 2.2%). Multivariate analysis identified tumor grading, tumor size and lymph vessel invasion as independent prognostic factors. CONCLUSIONS: Apart from the factors tumor size and tumor grading, lymph-vessel invasion appears to be of special significance for the long-term prognosis. Already in the pN0 stage, the latter was present in 64% of the cases and must be considered a precursor of lymphogenic metastasization. Since lymph-vessel invasion was demonstrated in 86% of tumors measuring less than 2 cm, the therapeutic consequence for all ductal pancreatic tumors is an extended lymphatic and soft tissue dissection that goes beyond the regional lymph-node stations.

Aged↗