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C Gerlach

Publications and source records attributed to C Gerlach.

At least 19 recordsLinked to original sources
PubMed2002

The role of action knowledge in the comprehension of artefacts--a PET study.

Activation of the left ventral premotor cortex (PMv) has in previous imaging studies been associated with the processing of visually presented artefacts. It has been suggested that this activation reflects processing of action knowledge and that action knowledge contributes to the comprehension of artefacts. The purpose of the present study was to test whether activation of the left PMv is common for all tasks involving the comprehension of artefacts or whether it is task specific. This was done by comparing performance and regional cerebral blood flow (rCBF) associated with two categorization tasks and two naming tasks divided by category (natural objects vs artefacts). The left PMv (BA 6/44) was more activated by the categorization task for artefacts than by the categorization task for natural objects and the naming task for artefacts. However, the left PMv was not associated with the contrast between the naming task for artefacts and the naming task for natural objects nor with the processing of artefacts in general. If the PMv does mediate action knowledge, these results suggest that action knowledge does not contribute directly to the comprehension of artefacts but may support the categorization of artefacts. The significance of these findings is discussed in relation to category-specific recognition impairments for artefacts.

Adult↗
PubMed2002

Brain activity related to integrative processes in visual object recognition: bottom-up integration and the modulatory influence of stored knowledge.

We report evidence from a PET activation study that the inferior occipital gyri (likely to include area V2) and the posterior parts of the fusiform and inferior temporal gyri are involved in the integration of visual elements into perceptual wholes (single objects). Of these areas, the fusiform and inferior temporal gyri were more activated by tasks with recognizable stimuli than by tasks with unrecognizable stimuli. We propose that the posterior parts of the fusiform and inferior temporal gyri, compared with the inferior occipital gyri, are involved in higher level integration, due to the involvement of re-entrant activation from stored structural knowledge. Evidence in favor of this interpretation comes from the additional finding that activation of the anterior part of the left fusiform gyrus and a more anterior part of the right inferior temporal gyrus, areas previously associated with access to stored structural knowledge, was found with recognizable stimuli, but not with unrecognizable stimuli. This latter finding also indicates: (i) that subjects may not refrain from (automatically) identifying objects even if they only have to attend to the objects' global shape, and (ii) that perceptual and memorial processes can be dissociated on both functional and anatomical grounds. No evidence was obtained for the involvement of the parietal lobes in the integration of single objects.

Adult↗
PubMed2001

Structural similarity causes different category-effects depending on task characteristics.

It has been suggested that category-specific impairments for natural objects may reflect that natural objects are more globally visually similar than artefacts and therefore more difficult to recognize following brain damage [Aphasiology 13 (1992) 169]. This account has been challenged by the finding that the 'normal' disadvantage claimed for natural objects may be reversed when items from the categories of natural objects and artefacts are matched for visual complexity, familiarity and name frequency [Neuropsychologia 37 (1999) 1263]. In the experiments reported here it was investigated whether category effects could be found on object decision tasks (deciding whether pictures represented real objects or not), when the stimulus material was matched across categories. In experiment 1, a disadvantage for natural objects was found on difficult object decision tasks whereas no category difference was found on easy object decision tasks. In experiment 2 an advantage for natural objects was found during object decisions performed under degraded viewing conditions (lateralized stimulus presentation). It is argued that these findings can be accounted for by assuming that natural objects are more globally visually similar than artefacts, but that this difference between categories affects performance in different ways depending on task characteristics. Thus, the greater overlap between natural objects may be a disadvantage when the demand on perceptual differentiation is high (as it is in difficult object decision tasks). However, when viewing conditions are degraded and performance tends to depend on global shape information (carried by low spatial frequency components), natural objects may fare better than artefacts because the global shape of natural objects reveals more of their identity than the global shapes of artefacts.

Adult↗
PubMed2001

Light-induced autofluorescence spectroscopy for the endoscopic detection of esophageal cancer.

BACKGROUND: Any innovative optical system that facilitates the early endoscopic detection of neoplastic change in the GI mucosa has the potential to greatly improve survival and quality of life for patients prone to have GI malignancies develop. The present article describes light-induced autofluorescence spectroscopy with violet-blue excitation light for in vivo diagnosis of cancerous tissue of the esophagus during routine endoscopy. METHODS: One hundred twenty-nine endogenous fluorescence spectra were obtained from normal mucosa and malignant lesions in 9 patients with squamous cell cancer and 4 with adenocarcinoma of the esophagus. Following spectrographic measurements, biopsy specimens were obtained for definitive classification of the spectra. A special light source capable of delivering either white or violet-blue light for excitation of tissue autofluorescence by means of an endoscope was used. Endogenous fluorescence spectra emitted by tissues were detected with a fiberoptic probe and analyzed with a spectrograph. RESULTS: Squamous cell cancer and adenocarcinoma of the esophagus exhibit specific changes in the emitted fluorescence spectra as compared with normal mucosa. Based on the results obtained in earlier studies, malignant and benign spectra were differentiated with the aid of a mathematical algorithm. By using this algorithm, a sensitivity of 97% and specificity of 95% were obtained for the diagnosis of esophageal carcinoma. CONCLUSIONS: Light-induced fluorescence spectroscopy is useful for the endoscopic detection of squamous cell cancer and adenocarcinoma of the esophagus. This spectroscopic study provides a basis for the design of a simplified autofluorescence imaging system for detection of esophageal neoplasms.

Adenocarcinoma↗
PubMed2001

Endoscopic fluorescence spectroscopy in the upper GI tract for the detection of GI cancer: initial experience.

OBJECTIVE: The aim of this study was to investigate autofluorescence spectroscopy using violet-blue excitation light for the in vivo diagnosis of GI cancer during routine endoscopy. METHODS: Fluorescence spectra were obtained from normal mucosa and cancerous lesions of the esophagus and stomach. The spectroscopic system used comprised a special light source capable of delivering either white or violet-blue light to induce autofluorescence of tissue via the endoscope. Endogenous fluorescence spectra emitted by the tissue were recorded with a fiberoptic probe and analyzed with a spectrographic detector system consisting of a polychromator with a photodiode array and an optical multichannel analyzer. The data of each spectrum were sampled within the range of 450-700 nm and stored in a personal computer. RESULTS: Esophageal squamous cell cancer, adenocarcinoma of the esophagus, and adenocarcinoma of the stomach show specific differences in the emitted fluorescence spectra compared with normal mucosa. CONCLUSIONS: Light-induced fluorescence spectroscopy might be a useful tool for the endoscopic in vivo detection of dysplasia and early carcinoma in the upper GI tract. Further trials are needed to test the validity of this new optical detection system.

Adenocarcinoma↗
PubMed2001

Gene expression of stromelysin and aggrecan in osteoarthritic cartilage.

OBJECTIVE: To analyze cartilage gene expression of patients with osteoarthritis (OA) in correlation with radiographic and histological findings. MATERIALS AND METHODS: Twenty-one patients with OA of the knee admitted for total knee replacement were analyzed clinically and radiographically by the Kellgren and Lawrence system. During surgery, cartilage samples from the medial and lateral condyles and tibial plateaus were harvested separately. Specimens were analyzed histologically (Mankin score) and total RNA was extracted directly from cartilage tissue. Steady state levels of stromelysin (MMP-3), aggrecan (AGG) and the house-keeping gene beta-actin were measured using quantitative PCR. RESULTS: Histology of medial and lateral knee compartments corresponded to radiographic changes (Spearman correlation coefficient: r = 0.7 (p < 0.01)). There was a positive correlation between MMP-3 and AGG gene expression (r = 0.4; p < 0.01). We found considerable variation of expression levels of MMP-3 and AGG and no correlation of gene expression with histological or radiographic scoring. CONCLUSION: The positive correlation between AGG and MMP-3 suggests a common regulation of anabolic and catabolic metabolism. There was no simple dependency between gene expression and histological and radiological findings in cartilage.

Aged↗
PubMed2000

Categorization and category effects in normal object recognition: a PET study.

To investigate the neural correlates of the structural and semantic stages of visual object recognition and to see whether any effects of category could be found at these stages, we compared the rCBF associated with two categorization tasks (subjects decided whether pictures represented artefacts or natural objects), and two object decision tasks (subjects decided whether pictures represented real objects or nonobjects). The categorization tasks differed from each other in that the items presented in the critical scan window were drawn primarily from the category of artefacts in the one task and from the category of natural objects in the other. The same was true for the object decision tasks. The experiment thus comprised a two-by-two factorial design. The factors were Task Type with two levels (object decision vs. categorization) and Category also with two levels (natural objects vs. artefacts). The object decision tasks were associated with activation of areas involved in structural processing (fusiform gyri, right inferior frontal gyrus). In contrast, the categorization tasks were associated with activation of the left inferior temporal gyrus, a structure believed to be involved in semantic processing. In addition, activation of the left premotor cortex was found during the categorization of artefacts compared with both the categorization of natural objects and object decision to artefacts. These findings suggest that the structural and semantic stages are dissociable and that the categorization of artefacts, as opposed to the categorization of natural objects, is based, in part, on action knowledge mediated by the left premotor cortex. However, because artefacts and natural objects often caused activation in the same regions within tasks, processing of these categories is not totally segregated. Rather, the categories differ in their weight on different forms of knowledge in particular tasks.

Adult↗
PubMed2000

Light-induced autofluorescence spectroscopy for tissue diagnosis of GI lesions.

BACKGROUND: The present article describes light-induced autofluorescence spectroscopy using violet-blue excitation light for endoscopic in vivo measurements in the upper GI tract. The spectra of normal mucosa, cancer, and dysplastic lesions of the esophagus and stomach are presented and compared. METHODS: Over 120 spectra were obtained in 11 patients of normal mucosa and malignant lesions in the esophagus and stomach during routine endoscopy. A special light source capable of delivering either white or violet-blue light was used for the excitation of tissue auto-fluorescence via the endoscope. Endogenous fluorescence spectra emitted by the tissue were collected with a fiberoptic probe and analyzed with a spectrograph. After spectrographic measurements biopsies were taken for definitive classification of histopathologic status. RESULTS: As compared with normal mucosa, (pre) cancerous lesions were associated with special changes in the emitted fluorescence spectra. The spectrographic records were influenced by the intensity of the illumination and on the position of the probe (distance and angle). CONCLUSION: Fluorescence spectroscopy with a slightly modified conventional light source might be useful for the endoscopic detection of dysplasia and early-stage carcinoma in the upper GI tract. Prospective trials need to determine the sensitivity and specificity of this new method.

Adenoma↗
PubMed1999

The proliferation-associated nuclear protein Ki-67 in the bovine system: partial characterisation and its application for determination of the proliferation of Theileria-infected bovine cells.

Theileria annulata-infected bovine cells as well as mitogen-stimulated bovine peripheral blood mononuclear cells (PBMC) express a proliferation-associated nuclear protein equivalent to the human Ki-67 protein. In analogy to the human system, the expression of the bovine Ki-67 protein is restricted to proliferating cells only, since (a) Ki-67 expression paralleled [3H]-thymidine incorporation in concanavalin A (Con A)-stimulated bovine PBMC, (b) Ki-67 was not detectable in quiescent bovine cells, and (c) Ki-67 expression in Theileria-infected cells is related to the presence of the parasites within the cytoplasm of the host cells; upon treatment with the theilericidal drug buparvaquone the parasites are destroyed and the cells cease to proliferate and to express the Ki-67 protein. Western-blot analysis of lysates of proliferating bovine cells revealed that the prototype monoclonal antibody Ki-67 and the new equivalent antibody MIB-1 detected one prominent protein band with an apparent molecular weight of 430 kDa. Two cDNA clones (pUC18.B1.Ki-67 and pUC18.B2.Ki-67) were isolated from a lambdagt11 cDNA library of T. annulata-infected bovine cells by immunoscreening with the monoclonal antibody MIB-1. Comparison of these cDNA sequences with those of the human Ki-67 protein revealed 60-70% identity. Within the "Ki-67 motif", identity proved to be 80% at the amino acid level. The remarkable identity between bovine and human Ki-67 proteins suggests that MIB-1 can be used as a marker for cell proliferation in animal research. In this context we could identify proliferating cells in lymph nodes of Theileria-infected animals and, furthermore, we could distinguish between infected and uninfected proliferating cells using MIB-1 and an antiserum against a recombinant parasite protein designated SA288.

Amino Acid Sequence↗
PubMed1999

Perceptual differentiation and category effects in normal object recognition: a PET study.

The purpose of the present PET study was (i) to investigate the neural correlates of object recognition, i.e. the matching of visual forms to memory, and (ii) to test the hypothesis that this process is more difficult for natural objects than for artefacts. This was done by using object decision tasks where subjects decided whether pictures represented real objects or non-objects. The object decision tasks differed in their difficulty (the degree of perceptual differentiation needed to perform them) and in the category of the real objects used (natural objects versus artefacts). A clear effect of task difficulty was found in both the behavioural and in the PET data. In the PET data, the increase in task difficulty was associated with increased regional cerebral blood flow in the posterior part of the right inferior temporal gyrus and in the anterior part of the right fusiform gyrus. This may be the neural correlate of matching visual forms to memory, and the amount of activation in these regions may correspond to the degree of perceptual differentiation required for recognition to occur. With respect to behaviour, it took significantly longer to make object decisions on natural objects than on artefacts in the difficult object decision tasks. Natural objects also recruited larger parts of the right inferior temporal and anterior fusiform gyri compared with artefacts as task difficulty increased. Differences in the amount of activation in these regions may reflect the greater perceptual differentiation required for recognizing natural objects. These findings are discussed in relation to category-specific impairments after neural damage.

Adult↗
PubMed1998

Brain activation during word identification and word recognition.

Previous memory research has suggested that the effects of prior study observed in priming tasks are functionally, and neurobiologically, distinct phenomena from the kind of memory expressed in conventional (explicit) memory tests. Evidence for this position comes from observed dissociations between memory scores obtained with the two kinds of tasks. However, there is continuing controversy about the meaning of these dissociations. In recent studies, Ostergaard (1998a, Memory Cognit, 26:40-60; 1998b, J. Int. Neuropsychol. Soc., in press) showed that simply degrading visual word stimuli can dramatically alter the degree to which word priming shows a dissociation from word recognition; i.e., effects of a number of factors on priming paralleled their effects on recognition memory tests when the words were degraded at test. In the present study, cerebral blood flow changes were measured while subjects performed the word identification (reading) and recognition memory tasks used previously by Ostergaard. The results are the direct comparisons of the two tasks and the effects of stimulus degradation on blood flow patterns during the tasks. Clear differences between word identification and word recognition were observed: the latter task evoked considerably more prefrontal activity and stronger cerebellar activation. Stimulus degradation was associated with focal increases in bilateral fusiform regions within the occipital lobe. No task, degradation, or item repetition effects were demonstrated in mesial temporal regions, no repetition effects were observed in any region, and there was no evidence for different effects of stimulus degradation in the priming and recognition memory conditions. Power limitations may have contributed to the null effects.

Adult↗
PubMed1998

Comparative study on effects of pentoxifylline, prednisolone and colchicine in experimental alveolitis.

Neutrophil alveolitis is a hallmark of cryptogenic fibrosing alveolitis (CFA), known for its poor prognosis. Corticosteroids, as the remedy of choice, are ineffective in a majority of patients. More and more evidence indicates that pentoxifylline (POF) could be an effective therapeutic alternative. Furthermore, colchicine has been proposed for therapy of CFA for many years now. We conducted an experimental study comparing the efficacy of these drugs in preventing neutrophil alveolitis in vivo. Alveolitis was induced in male rats by intratracheal instillation of bleomycin. Treatment consisted of daily injections of POF i.p., colchicine i.p., or prednisolone i.m. After 8 days the animals were sacrificed and body weights, cell differentials in BAL, amount of proliferating interstitial cells as determined by KI-67 staining of lung tissue, and collagen concentrations in lungs were determined. Bleomycin instillation was followed by a significant weight loss in the animals, a neutrophil alveolitis in BAL and an increased amount of proliferating cells in lung interstitium. POF significantly inhibited any of the parameters named, whereas prednisolone and colchicine had little effect. Data cannot be applied directly in human disease. There are however many similarities between CFA and bleomycin-induced lung injury and alveolitis. We conclude that POF is an effective inhibitor of neutrophil alveolitis, whereas neither colchicine nor prednisolone exerted significant influence in our model. We suggest POF effects should be further investigated regarding anti-inflammatory and anti-fibrotic properties.

Animals↗
PubMed1997

Ki-67 expression during rat liver regeneration after partial hepatectomy.

Antibodies to the cell-cycle-associated Ki-67 protein have been widely used for more than a decade as markers of proliferative cells. The prototype antibody Ki-67 reacted only with snap-frozen human tissue, but a novel antibody, MIB-1, was able to detect the Ki-67 antigen in paraffin wax-embedded human tissue. The ability of MIB-5, a novel antibody reactive with the rat equivalent Ki-67 protein, to immunohistochemically detect cycling parenchymal and littoral cells in the regenerating rat liver is reported. Rats underwent a standard two-thirds partial hepatectomy (PH), and groups of three animals were killed at intervals for up to 192 hours after PH. DNA synthesis was monitored by flash labeling with bromodeoxyuridine, and the response was as expected with a significant upsurge in hepatocyte labeling at 16 to 17 hours after PH. On the other hand, MIB-5 labeled a relatively constant percentage of hepatocytes (4%-8%) during the first 16 hours after PH, before a large proportion became labeled, also at 17 hours. The temporal pattern of MIB-5 labeling was similar to that of bromodeoxyuridine labeling, although, as expected, MIB-5 indices were higher. Semiquantification of Ki-67 messenger RNA (mRNA) levels by reverse-transcription polymerase chain reaction showed modest (fourfold to fivefold) increases in abundance during the first 12 hours after PH, but then levels increased dramatically to be at least 15-fold those of intact liver at 36 hours after PH. Much higher than normal levels of Ki-67 mRNA persisted throughout the period of study and even at 96 hours after PH they were still ninefold greater than normal. This study has shown the usefulness of the MIB-5 antibody to monitor proliferation in the rat liver, and furthermore, the pattern of expression of both the mRNA and the protein suggest that the Ki-67 protein, with hitherto unknown function, is more abundant in DNA synthesis and mitosis than in the early or even very late first G1 phase.

Animals↗
PubMed1997

[Pentoxifylline inhibits experimental bleomycin-induced fibrosing alveolitis].

Therapy of idiopathic pulmonary fibrosis (IPF) is directed at 1) inhibition of alveolitis and tissue damage, and 2) inhibition of matrix deposition. We and others have identified pentoxifylline (POF) as a promising drug in achieving these aims. For further clarification, we established a model of bleomycin-induced fibrosing alveolitis. Fisher 344 rats (n = 7 per group) were given bleomycin intratracheally once (0.7 U/100 g bw) and treated with POF (1.5 or 3 mg/kg bw per day i.p.), prednisolone (15 mg/kg bw i.m. per day), or sodium chloride solution (NaCL). The extent of inflammatory reactions was determined after 8 days by differentiation of cells of broncho-alveolar lavage (BAL) and by quantification of proliferating cells in lung interstitium subsequent to staining of the Ki-67 antigen. POF inhibited neutrophil alveolitis in BAL and reduced the amount of proliferating cells in the lungs significantly while prednisolone and NaCL did not. Both POF and prednisolone exerted a positive influence on postoperative weight loss as well as on lung weight increase subsequent to bleomycin instillation. The postoperative body weight loss and the lung weight increase after bleomycin instillation are most likely due to an inflammatory reaction subsequent to operation and bleomycin deposition. Tumor necrosis factor alpha (TNF-alpha) has been shown to be a key cytokine in bleomycin-induced fibrosing alveolitis as well as in IPF; it also exerts catabolizing effects. Since both POF and prednisolone are known to effectively inhibit proinflammatory cytokines and, among those, TNF-alpha, nonspecific antiinflammatory effects probably explain the benefits. Additionally, however, this study proved POF to be more effective in inhibition of BAL neutrophils and number of proliferating cells in lung interstitium. Further, it has been shown that POF, but not prednisolone, inhibits activation of neutrophil granulocytes and formation of reactive oxygen species. Thus we believe that the mechanism of action of xanthines might contribute to therapy of IPF. For further clarification, a prospective clinical study of POF in IPF therapy has been initiated.

Animals↗
PubMed1991

Immunobiochemical and molecular biologic characterization of the cell proliferation-associated nuclear antigen that is defined by monoclonal antibody Ki-67.

The monoclonal antibody Ki-67 detects a human nuclear antigen that is present in proliferating cells, but absent in quiescent cells. The aim of this study was to characterize the Ki-67 antigen by means of immunobiochemical and molecular biology techniques. Enzymatic digestion experiments showed that this antigen is highly susceptible to protease treatment, and the antigen cannot be extracted by 0.1 normal HCl, indicating that Ki-67 antigen is a nonhistone protein. Immunoblot analysis of cell lysates with Ki-67 showed a double band with apparent molecular weights of 395 kd and 345 kd, regardless of whether the gels were run under reducing or nonreducing conditions. It is noteworthy that these bands were exclusively detectable in lysates prepared from proliferating cells, whereas they were absent in lysates obtained from quiescent cells. These immunobiochemical data are further substantiated by our molecular cloning approaches. By means of immunocloning with Ki-67, the authors isolated and sequenced several cDNA fragments from lambda gt11 libraries. A 1095-bp fragment gave a strong hybridization signal at 7.5 to 9.5 kb in Northern blot analysis with RNA prepared from proliferating cells, whereas it was negative with RNA prepared from quiescent cells. This cDNA fragment could be bacterially expressed, and in subsequent immunoblot analysis Ki-67 reacted exclusively with those fusion proteins that were derived from bacteria containing the insert in the right reading frame.

Antibodies, Monoclonal↗
PubMed1990

[Coincidence of silicosis and lupus erythematosis].

From 1975 to 1989 37 patients with Lupus erythematodes exposed to quartz dust over many years were observed. Thirty of them suffered from silicosis. The coincidence of silicosis and Lupus erythematodes can be an expression of a common pathogenesis.

Antibodies, Antinuclear↗