Search PubMed⌕ Search

Biomedical subjects

C Hessler

Publications and source records attributed to C Hessler.

At least 19 recordsLinked to original sources
PubMed2000

Experimental design optimization of filamentous phage transfection into mammalian cells by cationic lipids.

A previous study showed that filamentous phage could be efficiently transfected into mammalian cells in the presence of the cationic lipid Transfectam. In the present study, we used an experimental plan based on a uniform network (Doehlert) matrix to estimate optimal transfection conditions in two different cell lines, CHO and Cos-7. Using the cationic lipid RPR120535b as a model, we show that optimal conditions can be determined much more readily than with standard response curves. Under optimal conditions as analyzed by FACS, up to 60% of Cos-7 and 50% of CHO cells can be transfected. Furthermore, a comparison of different lipids (Transfectam, RPR120535b, TC1-12 and GAP-DLRIE/DOPE) suggests that lipids with multiple amine groups are more efficient for the transfection of filamentous phage.

Animals↗
PubMed1999

Comparison between targeted and untargeted systemic immunizations with adjuvanted urease to cure Helicobacter pylori infection in mice.

Outbred OF1 mice infected in a first step with a mouse-adapted Helicobacter pylori strain were immunized in a second step by systemic or mucosal routes: systemic immunizations were performed subcutaneously with adjuvanted urease either in the infra or supra-diaphragmatic region of the body, while mucosal immunization was done with urease in the presence of E. coli heat Labile toxin. Mucosal and subcutaneous immunizations induced in infected mice a significant reduction in bacterial density whatever the site of injection but complete eradication was preferentially observed in mice immunized subcutaneously in the back. Systemic immunization with appropriate schedules and formulations could constitute a valuable approach to cure Helicobacter pylori infection.

Adjuvants, Immunologic↗
PubMed1999

Estimation of the noisy component of anatomical backgrounds.

The knowledge of the relationship that links radiation dose and image quality is a prerequisite to any optimization of medical diagnostic radiology. Image quality depends, on the one hand, on the physical parameters such as contrast, resolution, and noise, and on the other hand, on characteristics of the observer that assesses the image. While the role of contrast and resolution is precisely defined and recognized, the influence of image noise is not yet fully understood. Its measurement is often based on imaging uniform test objects, even though real images contain anatomical backgrounds whose statistical nature is much different from test objects used to assess system noise. The goal of this study was to demonstrate the importance of variations in background anatomy by quantifying its effect on a series of detection tasks. Several types of mammographic backgrounds and signals were examined by psychophysical experiments in a two-alternative forced-choice detection task. According to hypotheses concerning the strategy used by the human observers, their signal to noise ratio was determined. This variable was also computed for a mathematical model based on the statistical decision theory. By comparing theoretical model and experimental results, the way that anatomical structure is perceived has been analyzed. Experiments showed that the observer's behavior was highly dependent upon both system noise and the anatomical background. The anatomy partly acts as a signal recognizable as such and partly as a pure noise that disturbs the detection process. This dual nature of the anatomy is quantified. It is shown that its effect varies according to its amplitude and the profile of the object being detected. The importance of the noisy part of the anatomy is, in some situations, much greater than the system noise. Hence, reducing the system noise by increasing the dose will not improve task performance. This observation indicates that the tradeoff between dose and image quality might be optimized by accepting a higher system noise. This could lead to a better resolution, more contrast, or less dose.

Biophysics↗
PubMed1998

Systemic immunization with urease protects mice against Helicobacter pylori infection.

The ability of systemic immunization to induce protection against Helicobacter pylori infection has been evaluated in a mouse model. It was observed that if appropriate formulations and adjuvants were used such immunization elicited in outbred Swiss mice levels of protection similar or better than those induced by the oral route in the presence of cholera toxin or Escherichia coli heat labile toxin. Recombinant urease mixed with adjuvants, which induced strong Th1 and Th2 responses elicited better protection than urease mixed with adjuvants which induced a predominant Th2 type response only. These experiments demonstrate the feasibility of parenteral immunization against H. pylori and suggest that an appropriate balance between Th1 and Th2 type responses is required to achieve complete protection.

Adjuvants, Immunologic↗
PubMed1998

Effects of the nature of adjuvant and site of parenteral immunization on the serum and mucosal immune responses induced by a nasal boost with a vaccine alone.

Outbred OF1 mice were immunized subcutaneously with flu vaccine, either in the neck or in the lumbar region (back), in combination with adjuvants inducing either a Th1- or a Th2-type response, referred to as adjuvants A1 and A2, respectively. After two parenteral immunizations, the mice were boosted intranasally with nonadjuvanted vaccine. The serum response was analyzed after each immunization by measuring specific immunoglobulin A (IgA), IgG1, and IgG2a antibody levels, while the local response (same isotypes) was measured in the salivary glands after the mucosal boost by ELISPOTs. We observed that systemic priming at any of the two sites with a Th2 rather than a Th1 adjuvant dramatically enhanced the mucosal IgG1 and IgA responses following a mucosal boost with unadjuvanted vaccine. In addition, as judged by the IgG2a/IgG1 ratios and serum IgA levels, immunization of mice in the back induced a rise in Th2 response compared to neck immunization with adjuvant A1. In contrast, such back immunization with adjuvant A2 reversed the Th1-Th2 balance in favor of the Th1 response compared to neck immunization. Similar differences were observed in mucosal antibody levels according to the site of priming with one given adjuvant; priming in the back with adjuvant A1 increased the mucosal IgA and IgG1 responses compared to neck priming, while the local IgG2a levels were decreased. The reverse was true for adjuvant A2. Back versus neck priming with this latter adjuvant decreased the mucosal IgG1 response, while local IgG2a levels were increased. The different lymphatic drainages of the two sites of parenteral immunization may explain these differences, due to the targeting of particular lymphoid inductive sites. Some of these sites may represent crossroads between systemic and mucosal immunity.

Adjuvants, Immunologic↗
PubMed1996

Breast hamartoma with invasive ductal carcinoma. Report of two cases and review of the literature.

Two cases of well-defined masses also containing clinical and radiographical abnormalities suggestive of malignancy, subsequently found to be invasive ductal carcinomas in breast hamartomas are described. The patients were 53 and 78 years old. Both presented with a generally soft palpable breast lump, containing a firm area which in one case invaded and ulcerated the skin. Mammography demonstrated two typical hamartomas: one containing a spiculated opacity, the other irregular opacities with suspicious calcifications, suggesting the presence of carcinomas in these benign lesions. The cut surface of these well-circumscribed masses measured 5 cm and 7 cm. The microscopic appearance was characteristic of breast hamartoma (sharp circumscribed "pseudocapsule" surrounding breast fibrocystic changes with variable amounts of adipose tissue) with the firm area in each case corresponding to invasive ductal carcinoma. In one case the invasive ductal carcinoma was confined to the hamartoma, whereas in the other malignant tumor, cells extended beyond the surrounding breast tissue and infiltrated the skin. These findings raise the question of secondary involvement of a hamartoma by invasive carcinoma. Breast hamartomas are probably underrecognized lesions. In our view, these findings do not justify a more aggressive approach towards the management of breast hamartomas.

Adult↗
PubMed1996

Survey on image quality and dose levels used in Europe for mammography.

Quality assurance programmes are becoming a common practice in the field of mammography. At the present time several recommendations exist and different test objects are used to optimize this radiological procedure. The goal of this study was to check if geographically distant centres using different quality control procedures were comparable when using a common objective way of assessing image quality. The results show that consensus still needs to be found among radiologists to reach a satisfactory level of harmony between patient doses and image quality in Europe.

Europe↗
PubMed1995

Traumatic chest lesions in patients with severe head trauma: a comparative study with computed tomography and conventional chest roentgenograms.

In patients with severe craniocerebral trauma, who need a continuous positive-pressure breathing, the detection of pulmonary and mediastinal traumatic lesions, especially pneumothorax, may alter the management. The aim of this study is to evaluate the efficiency and accuracy of conventional supine chest roentgenograms to detect the associated traumatic chest lesions in severe craniocerebral trauma and to compare their value as a diagnostic method for the identification of unsuspected lesions with a limited chest computed tomographic (CT) examination. Forty-seven consecutive patients with severe craniocerebral trauma underwent head CT and a prospective limited CT examination of the thorax in the same session. Nine patients (19.1%) presented a pneumothorax, bilateral in one case. Six pneumothoraces (60%) were identified both on conventional chest roentgenograms and CT, whereas in four cases (40%), the lesion was only detectable on CT. The CT study also showed 31 areas of pulmonary parenchymal contusions in 19 subjects (40%), whereas the conventional chest roentgenograms demonstrated 17 areas of contusions in 11 (23%) subjects. One thoracic aorta and one right diaphragm rupture were detected on CT study. On the conventional chest roentgenograms the mediastinal vascular injury was overlooked, whereas the right diaphragmatic rupture was highly suspected. The limited chest CT examination supplied additional information in 30% of patients. In 12.7% of patients, this information was clinically significant enough to alter the management. In patients with severe craniocerebral trauma evaluation of associated chest trauma by a supplementary limited chest CT, examination provides more and precise information about the size and severity of mediastinal and pulmonary lesions with a superior detectability of pneumothorax.

Adolescent↗
PubMed1993

Facial thermography during nasal provocation tests with histamine and allergen.

Changes of skin temperature (T degree) of the nose area during nasal provocation tests with histamine and allergen were followed by means of an infrared thermography camera. By a colimator system in which temperatures measured on a given surface can be integrated and averaged, thermography allows the continuous and quantitative recording of the temperature during the whole procedure in a completely noninvasive way. In 10 normal subjects, increasing doses of histamine induced a dose-dependent rise of the nose external temperature. No significant change was observed with the vehicle solution. In six subjects allergic to grass pollen, the nebulization of increasing concentrations of a pollen extract induced a dose-dependent rise in T degree. The T degree rise observed after histamine or allergen corresponded to a marked nasal obstruction. The nebulization of the highest dose of the pollen extract did not induce any T degree rise in six nonallergic subjects. The continuous recording of the skin temperature by a noninvasive method might yield additional information on the vascular changes rapidly occurring during nasal challenges.

Adult↗
PubMed1992

[Eosinophilic gastroenteritis: two case reports].

Eosinophilic gastroenteritis is a rare lesion that may present a diagnostic problem to the surgeon. It may be confused with a malignant tumor because it often presents with intestinal obstruction. We treated two cases at the Hôpital de zone de Morges. In one case the lesion was in the gastric antrum and in the other the ascending colon. Only 27 cases of colonic eosinophilic gastritis are described in the medical literature.

Aged↗
PubMed1991

Image quality index (IQI) for screen-film mammography.

A suitable quantity for evaluating the image quality in mammography is the smallest visible size of an object. This quantity, called the image quality index (IQI), can be derived from the basic image parameters: contrast, MTF, Wiener spectrum. Several evaluation methods of the IQI, all based on statistical decision theory, have been considered. An experimental visibility test using simulated microcalcifications has been performed in order to compare the results obtained with different IQI models. A previous approach, based on simplifying assumptions, yields a good correlation with the visibility test but fails to predict the actual size of the visible objects. Improved models have been derived for an ideal observer and for a 'quasi-ideal' one with perfect or with realistic visual characteristics. The experimental visual results are well modelled by the IQI method, provided that a suitable threshold signal-to-noise ratio is used for each of these models.

Animals↗
PubMed1991

Influence of anode and filter material on image quality and glandular dose for screen-film mammography.

The influence of anode and filter materials on the performance (image quality and dose) of a mammography system is investigated. The image quality is evaluated with the image quality index method. A computer simulation has been developed to calculate the physical parameters of the image quality index (contrast, resolution and noise) as well as the mean glandular dose. The calculations take into account the successive steps of the process: x-ray production, filtration, interaction with the test object, anti-scatter grid, interaction with the image detector (screen-film system). An excellent correlation is obtained between the results predicted by the model and those of experimental measurements, suggesting that the model may be used for the prediction of the performance of mammographic equipment. The experimental conclusions are confirmed: the use of a tungsten anode with a rhodium filter allows a dose reduction without a significant degradation of image quality. The computer program can also be used to simulate the influence of factors which are difficult to combine in practice, e.g., various anode and filter materials, monoenergetic x-rays, etc.

Electrodes↗
PubMed1991

Atypical hyperplasia of the breast: mammographic appearance and histologic correlation.

The mammograms and histologic slides of 58 cases of atypical hyperplasia (AH) of the breast were retrospectively reviewed to determine the geographic correlation (direct, near, or remote) between mammographic abnormalities (if present) and the histologic findings. A direct mammographic-histologic correlation was found in 24 of the 58 cases (41%), near correlation in 15 (26%), and remote correlation in 19 (33%). Clustered microcalcifications were the most common mammographic abnormality that was directly correlated with AH at histologic examination. Atypical ductal hyperplasia was much more frequently associated with a direct mammographic-histologic correlation than was atypical lobular hyperplasia (48% vs 9%). The authors conclude that, although no pathognomonic appearance of AH was discovered, mammographic abnormalities similar to those of small cancers could be directly correlated with histologic findings in 41% of cases. Since AH has been shown to be associated with a five- to tenfold increased risk of subsequent invasive carcinoma, frequent clinical and at least yearly mammographic follow-up is suggested once AH is discovered.

Adult↗