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C Schwarz

Publications and source records attributed to C Schwarz.

At least 109 records · Page 6Linked to original sources
PubMed1991

Functional specificity of a long-range horizontal connection in cat visual cortex: a cross-correlation study.

Anatomical investigations of the visual cortex revealed a regular set of interlaminar connections and long-range horizontal connections. An important component of the intrinsic cortical circuit is the projection from layer 5 to layer 6 over long horizontal distances. Previous work has shown that when layer 5 is locally inactivated, layer 6 cells lose their response in a segment of their receptive fields corresponding to the blocked area in layer 5. It has therefore been proposed that the long receptive fields characteristic of layer 6 cells might be generated by concatenating layer 5 cells with similar orientation preferences. In the present study, we used cross-correlation analysis to examine both source and target cells of the interlaminar connection from layer 5 to layer 6. We found correlated firing between cells separated by up to 4.2 mm, the longest horizontal distance studied. The occurrence of correlated firing depended on the functional properties and on the topographic position of the cells in layer 5 and layer 6. Interactions were only observed if the cells had matching orientation tuning and similar eye preference and if the layer 5 cells lay within the summation area of the layer 6 cells. Both simple and complex cells in layer 6 fired in synchrony with layer 5 cells. In layer 5, mainly standard complex cells, but very few special complex cells, participated in correlated firing with layer 6 cells. These results suggest that cells in layer 6 receive their input from cooriented, coaxially aligned standard complex cells in layer 5. This topographic arrangement and the length summation properties of standard complex cells in layer 5 are well suited to generate long receptive fields in layer 6. Thus, our experiments provide evidence for the functional specialization of a particular component of cortical circuitry.

Animals↗
PubMed1990

Morphological types of projection neurons in layer 5 of cat visual cortex.

Pyramidal cells in layer 5 of the visual cortex have multiple cortical and subcortical projection sites. Previous studies found that many cells possess bifurcating axons and innervate more than one cortical or subcortical target, but cells projecting to both cortical and subcortical targets were not observed. The present study examines the morphology of cells in cat visual cortex projecting to the superior colliculus, the main subcortical target of layer 5, and cells in layer 5 projecting to cortical areas 18 and 19. The neurons that give rise to these different projections were retrogradely labelled and intracellularly stained in living brain slices. Our results show that cells within each projection group have several morphological features in common. All corticotectal cells have a long apical dendrite forming a large terminal tuft in layer 1. Their cell bodies are medium sized to large, and their basal dendrites form a dense and symmetrical dendritic field. Corticocortical cells in layer 5 have a very different morphology: their apical dendrites are short and they never reach higher than layers 2/3. Their cells bodies are small to medium sized and they have fewer basal dendrites than corticotectal cells. Thus there are two morphologically distinct projection systems in layer 5, one projecting to cortical and the other one to subcortical targets, suggesting that these two systems transmit different information from the visual cortex. Among the corticotectal cells with the largest cell bodies we found some cells whose basal and apical dendrites were almost devoid of spines. Spiny and spinefree corticotectal cells also have different intrinsic axon collaterals and therefore play different roles in the cortical circuitry. While many spiny corticotectal cells have axon collaterals that project to layer 6, spinefree corticotectal cells have fewer axon collaterals and these do not arborize in layer 6. We suggest that the two morphological types of corticotectal cells might be related to functional differences known to exist among these cells. We discuss how the presence or absence of spines affects the integration of the synaptic input and how this might be related to the cells' functional properties.

Animals↗
PubMed1990

Radionuclide bone imaging in the early detection of fractures of the proximal femur (hip): multifactorial analysis.

The results of 179 radionuclide bone imaging examinations, 105 gathered retrospectively from the cases of 97 patients referred for assessment of possible occult fracture of the proximal femur (hip) and 74 performed prospectively on 63 patients referred with a diagnosis of obvious or suspected hip fracture, were analyzed in relation to patient age, the interval between injury and imaging, and the type of fracture sustained. Ninety-two examinations were performed less than 72 hours after injury; 31 of these were done at 0-24 hours. For the diagnosis of hip fracture in an individual patient, the overall sensitivity was 0.933; specificity, 0.950; positive predictive value, 0.918; and negative predictive value, 0.960. For the clinically important subgroup of 145 patients with normal or equivocal radiographs, the sensitivity was 0.978. A characteristic pattern for greater trochanter fractures was found. Other diagnoses were scintigraphically established in 41% of patients evaluated. The data suggest that patients of all ages, regardless of the time after injury, can be imaged as soon as they present.

Adult↗
PubMed1989

Excision of integrated simian virus 40 DNA involving homologous recombination between viral DNA sequences.

We have investigated the structure of simian virus 40 (SV40) DNA integrated into the genome of transformed mouse mKS-A cells. We have identified at least six independent integration units containing intact or truncated SV40 DNA sequences. One integration unit was isolated from a genomic mKS-A cell library and investigated by restriction enzyme analysis and partial nucleotide sequencing. This integration unit contains one apparently intact SV40 genome flanked on both sides by truncated versions of the SV40 genome. One of the flanking elements contains a large deletion in the SV40 "late" region and an abbreviated SV40 "early" region. This element was efficiently excised and mobilized after fusion of mKS-A to COS cells. The excision products invariably included the entire SV40 early region even though they were derived from an integrated element lacking this part of the SV40 genome. An analysis of this discrepancy led to the conclusion that the early region sequences were acquired by homologous recombination and, furthermore, that homologous excisional recombination was clearly preferred over non-homologous recombination.

Animals↗
PubMed1989

[Infrarenal aortic aneurysm: results of surgical treatment].

Between 1976 and 1987 93 patients with an infrarenal aortic aneurysm underwent surgical correction. In 62 patients the procedure was performed electively, whilst 13 displayed an unstable aneurysm and in 18 cases a ruptured aneurysm was present at operation. During the past 5 years the mortality was lowered to 2% in elective cases, whereas in cases of ongoing rupture only moderate improvement took place. The most frequent cause of a lethal outcome was pump failure of the heart (6 times), followed by renal insufficiency and haemorrhagic shock and bleeding complications. Among the non-lethal complications, relaparotomy on the basis of postoperative bleeding ranks first, followed by pulmonary insufficiency, peripheral emboli and partial ischemia of the spine. Resection of infrarenal aneurysms should be performed in the stable state of disease, since insufficiency of multiple vital organ systems increases the mortality by up to 20 fold.

Aged↗
PubMed1989

Analysis of a large-T-antigen variant expressed in simian virus 40-transformed mouse cell line mKS-A.

Earlier reports had suggested that the large T antigen expressed in simian virus 40 (SV40)-transformed mKS-A cells may be replication defective. Our experiments support these earlier observations showing that the mKS-A T antigen has a reduced DNA-unwinding activity in vitro. To investigate the molecular basis for this defect, we have isolated from an mKS-A genomic library an EMBL-3 bacteriophage clone carrying in its insert a full-length SV40 DNA element that most likely encodes the expressed T-antigen variant. DNA sequencing revealed only one nonconservative amino acid exchange, Asp to Asn at residue 636. Surprisingly, when a plasmid clone carrying the mKS-A T-antigen-coding sequence was transfected into monkey cells, we found that it replicated quite efficiently, probably suggesting that a high nuclear concentration of the variant T-antigen form compensates for the partial biochemical defect. However, a high nuclear concentration of T antigen was also found in mKS-A T-antigen-transformed mouse cells, yet a fusion of these cells to permissive monkey cells failed to induce in situ replication and excision of integrated SV40 DNA. We discuss possible reasons for the different behavior of T antigen in monkey cells and in mouse cells and suggest that one possibility for the replication-negative phenotype in transformed cells may be related to the fact that T antigen forms a tight complex with the cellular p53 protein in mouse cells but not in monkey cells.

Animals↗
PubMed1988

Surgical therapy of radiation-induced lesions of the colon and rectum.

Thirty-six operations for late sequelae of radiotherapy were carried out in 31 patients from 1971 to 1986. The most frequent indications for surgery were stricture (58 percent) and fistula (29 percent). In the first 8 year period from 1971 through 1978, 13 of 14 operations were diversions (colostomy or by-pass). From 1979 through 1986, a more aggressive approach prevailed. Only 32 percent of the operations were diversions. This more aggressive strategy was accompanied by a decrease of the postoperative mortality rate from 21 percent through 1978 to 0 in the later period. The overall complication rate was 23 percent. Complications were relatively more frequent after two-layer sutured or stapled anastomoses and after resection or fistula closure without temporary colostomy. We conclude that in radiation-induced colonic and rectal lesions, diversion should be performed in patients with unproved cure of disease or tumor persistence. Resection and fistula closure can be carried out safely, and a temporary colostomy is strongly recommended.

Adult↗
PubMed1988

Plasma atrial natriuretic factor in cirrhotic patients with ascites. Effect of peritoneovenous shunt implantation.

Human atrial natriuretic factor (ANF) levels were measured before and after peritoneovenous shunt implantation in 10 cirrhotic patients with ascites, in whom sodium retention is a major clinical problem. The mean preoperative plasma level of ANF was 82 ng/L (normal range, 5-80 ng/L). Peritoneovenous shunting resulted in a significant rise in plasma ANF to 308 ng/L (p less than 0.0025) immediately after operation. This was followed by a constant fall until the seventh postoperative day, when mean plasma ANF was still significantly elevated (149 ng/L) compared with the preoperative value (p less than 0.01). Three months after shunt implantation mean plasma ANF had returned to the preoperative level (75 ng/L). Mean sodium excretion increased from 2.6 mEq/h preoperatively to 10.2 mEq/h at the second postoperative day (p less than 0.025). No direct relationship was noted between changes in plasma ANF level and changes in urinary sodium excretion after shunt implantation. These data demonstrate an intact ANF release response to intravascular volume expansion in cirrhotic patients with ascites, but exclude ANF as the diminished natriuretic factor as proposed by the overflow theory of ascites formation. Sodium excretion and fluid retention seem to be the result of vascular underfill and fluid maldistribution, and hormonal changes are likely to be secondary to them.

Aged↗
PubMed1988

[Experimental bile duct replacement using deep seromuscular stomach wall grafts].

Numerous materials and experimental designs were tested hitherto concerning their usefulness as a substitute of the ductus choledochus. However, an ideal substitute to discover failed. We had tested a serous muscular stomach wall patch, flapped at the gastroepiploic vasa, in 6 pigs. Choledochus epithelium did not grow in every case. A scarred shrinking with following stenosis of the transplant resulted in all cases with a longer observation period. We concluded from that a serous muscularly flapped stomach wall transplant does not suit as a bile duct substitute.

Animals↗
PubMed1987

Event-related cross-correlations between spike trains illustrated on interactions between motor units and muscle spindle afferents.

A method is presented for computing correlation coefficients of two (or more) output spike trains in temporal relation to one (or more) input even trains. These event-related correlation functions are computed by convolving the output spike trains, represented as point processes, with rectangular pulses of selectable width, and by then calculating linear correlation coefficients for the pairs of amplitude values obtained from the two convolved processes in temporal relation to the input events. The merits of this technique are illustrated on stimulus trains delivered to motor units (MUs) and output spike trains recorded from muscle spindle afferents of the same cat hindlimb muscle. The correlation functions obtained show the temporal course of the correlated firings of the two afferents (mostly Ia afferents from primary muscle spindle endings) as a function of time from MU activation; they are compared with the conventional cross-correlation histograms (CCHs) between afferents and with peri-stimulus time histograms (PSTHs) between stimulus and afferent firing patterns. Stimulus-related cross-correlation functions as displayed here can be calculated for any three spike trains. Possible extensions of the method to larger numbers of input and output channels are also discussed.

Action Potentials↗
PubMed1987

[Diagnosis of peritoneovenous shunt occlusion].

Reaccumulation of ascitic fluid after peritoneovenous shunt implantation demands accurate diagnostic procedure. Between 1973 and 1985 81 peritoneovenous shunts have been implanted at the IInd Surgical Department of the University of Vienna. In the same time 34 reoperations in 17 patients have been performed for reasons of shunt-dysfunction. Besides thorax x-ray, diagnosis was established in 11 cases by means of Doppler ultrasound investigation, in 26 cases by technetium scan and in 15 cases by shunt angiography. Shuntography proved to be the method of choice, with no false results. Doppler ultrasound results were unclear in a high percentage, thus this method is not used any more.

Ascites↗
PubMed1987

Length of stay.

Explore the source record for details and available documents.

Humans↗
PubMed1987

[Transplantation of gastrointestinal tumors to immunodeficient nude mice as an in vivo model of tumor biology].

Serial transplantation of ten different types of tumours, both primary tumours and their metastases, to 170 nude mice was conducted for biological analysis of human gastro-intestinal carcinomas, with particular reference being made to the aspect of tumour growth. The types transplanted included seven colorectal carcinomas, one oesophageal carcinoma, one gastric lymphoma, and two gastric carcinomas.--Tumour growth was quantitatively monitored by means of a standardised measuring method and was statistically evaluated. The qualitative aspects of tumour growth were micromorphologically investigated. Tumour transplants were allowed to reach a defined size and were then retransplanted within the nude mouse system, with up to six tumour passages being conducted. The investigations were evaluated, with particular reference being made to comparison between primary tumours, on the one hand, and their metastases, on the other.--The average primary tumour take rate amounted to 83 per cent and was generally higher for metastatic tumours. Statistically significant findings were obtained to the effect of growth of metastases which was faster than that of their own primary tumours (p 0.05), where as no qualitative differentiation between primary tumour and metastases was possible on the basis of the micromorphological aspect. Growth of metastases.

Adenocarcinoma↗
PubMed1987

[Prognostic factors in cardia cancer].

Among 164 patients operated upon for adenocarcinoma of the cardia 102 (61%) were resected, 87 of them with curative intent. The mortality within 30 days was 20%, and the 5-year survival 15%. A total gastrectomy was performed in 36 patients, whereas a proximal partial gastrectomy was carried out in 66 cases. The median survival was 19 months after total gastrectomy, and 11 months after proximal resection (Breslow: 0.22). Only in stages N0 and N1 total gastrectomy resulted in a significantly longer (32 months) median survival than proximal resection (11 months; p = 0.03). The impact of total gastrectomy was more pronounced in the diffuse type according to Lauren, whereas lymphadenectomy was more effective in stages N0 and N1 and in Lauren's intestinal type. It is concluded that total gastrectomy should be carried out in all cases of carcinoma of the cardia.

Adenocarcinoma↗
PubMed1987

[Risk factors for morbidity and mortality in resection of cancer of the cardia].

Operations were performed on 166 patients for adenocarcinoma of the cardia, between 1970 and 1986, with resections being applied to 102 of them (6.1 per cent), including 87 curative approaches with complete removal of tumours and no macroscopic evidence of metastases. Total gastrectomy with oesophagectomy was performed on 36 patients and proximal oesophagogastrectomy on 66, in 43 of these via left thoracic incision. Regional lymph nodes were free of tumour in 29 patients (28 per cent). The other approaches to proximal resection were thoracoabdominal in eight cases, abdominal in 13, and transmediastinal in two. Leakage of oesophageal anastomosis occurred in 19 cases and was followed by septicaemia and death in 13. Overall mortality during hospitalisation amounted to 22.5 per cent, including two patients who died on the 30th postoperative day as a result of dehiscence and septicaemia. Mortality figures were 17 per cent following total gastrectomy and 19 per cent in the wake of proximal gastrectomy by thoracic incision. Mortality amounted to 48 per cent in the 23 cases on which abdominal, thoraco-abdominal, and transmediastinal operations had been performed. Multiple logistic regression was used to determine age, ECG, spread of lymph nodes, and surgical techniques as potential risk factors. Emphasis in the context of surgical techniques was laid on proximal versus total gastrectomy, incision on both sides of the diaphragm, palliative resection, and anastomotic suturing (using one-layer or two-layer techniques or mechanical staples). Tumour spread to lymph nodes and proximal resection were the only independent variables associated with dehiscence. Electrocardiogram (ECG), lymph node involvement, and palliative resection proved to be of relevance to prognostication of lethality. No statistical correlations were found to exist between lethality, on the one hand, and surgical approach, age of patient, incision on either side of the diaphragm or suturing, on the other. The conclusion was drawn that in cases of cardia carcinoma total gastrectomy does not aggravate the risk of lethality, as compared to cardia resection.

Adenocarcinoma↗
PubMed1986

Effect of the prokinetic drug cisapride on gastrointestinal hormone release.

The influence of the prokinetic drug cisapride on the release of gastrointestinal hormones was studied in volunteers. First, acute effects of single doses of cisapride compared with saline were investigated. Cisapride at doses of 8 mg and 20 mg intravenously significantly increased plasma concentrations of pancreatic polypeptide (hPP) by 145% and 146%, respectively. Cholecystokinin (CCK) levels were increased by 176% at 8 mg cisapride, whereas gastrin and insulin levels remained unchanged. Enhancement of PP and CCK secretion was almost completely abolished by pretreatment with 1 mg atropine. Carbachol (250 micrograms subcutaneously) increased PP release by 62% but did not affect the other hormones. Second, the influence of a 1-week treatment (10 mg three times daily, given orally) on plasma hormone levels was studied. After 1 week the postprandial CCK release was diminished by 58%. Basal levels and postprandial responses of gastrin, PP, and insulin were not altered by prolonged cisapride administration. It is concluded that acute application of cisapride stimulates secretion of PP and CCK via atropine-sensitive mechanisms and that chronic treatment with cisapride diminishes CCK release by an unknown mechanism.

Adult↗