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Biomedical subjects

P Ulrich

Publications and source records attributed to P Ulrich.

At least 19 recordsLinked to original sources
PubMed2006

Design and evaluation of immunotoxicity studies.

The evaluation of potential adverse effects of pharmaceuticals on the immune system is part of the standard drug development procedures and needs to be available prior to the start of phase III clinical trials. Although the histopathological assessment of lymphoid organs/tissues is considered fundamental for the identification and characterization of immunotoxic reactions, additional investigations are now recommended by the European guidelines for repeated-dose toxicity testing of medicinal products in order to achieve an accurate assessment of immune system functionality with regard to immunomodulation. In the present paper, we describe and discuss a study design which permits the investigation of the immune function in a 4-week study in rats following immunization by subcutaneous administration of the T-dependent antigen Keyhole Limpet Hemocynin (KLH). This includes assessment of hematology parameters, titration of KLH-specific antibodies in serum, lymphocyte immunophenotyping in blood, thymus, spleen and lymph nodes, macroscopic pathology and histopathological evaluation of the lymphatic organs/tissues and of the injection sites.

Adjuvants, Immunologic↗
PubMed2006

[Frequency and causes of civil and criminal proceedings in radiology. Analysis of a survey].

The eagerness of German patients to go to court on account of actual or suspected malpractice of their physicians has increased over the years, as is the case in other Western countries. Media coverage has given rise to criticism of physicians and their services rendered more than before. This naturally also concerns the discipline of radiology, even though the probability of a radiologist being accused in a lawsuit is clearly minor in comparison to the surgical disciplines. In contrast to other fields, the X-ray pictures are always available for a second opinion. In this study, 4760 radiologists were sent a questionnaire by mail and 1503 answered. The questionnaires were evaluated regarding interrogative and informative data from pending or completed proceedings. Lawsuits were directed towards the assessment of examinations (38%), the actual performance of an examination (30%) and not towards providing patients with information as we had expected. Angiographies, mammographies, and radiographies were the most frequent reasons for instituting proceedings. The majority of litigating patients was between 40 and 50 years old. The proceedings led to civil convictions in 30% and criminal convictions in 5.5%. Of the physicians accused of incorrect conduct, 73% were of the opinion that they had been treated unjustly, 26% supported the reproach as justified, and the rest had formed no opinion. Physicians in private practice and senior consultants (70%) were most frequently sued.

Crime↗
PubMed2005

An European inter-laboratory validation of alternative endpoints of the murine local lymph node assay: first round.

The new OECD guideline 429 (skin sensitization: local lymph node assay) is based upon a protocol, which utilises the incorporation of radioactivity into DNA as a measure for cell proliferation in vivo. The guideline also enables the use of alternative endpoints in order to assess draining lymph node (LN) cell proliferation. Here we describe the first round of an inter-laboratory validation of alternative endpoints in the LLNA conducted in seven laboratories. The validation study was managed and supervised by the Swiss Agency for Therapeutic Products, Swissmedic. Statistical analyses of all data were performed by an independent centre at the University of Bern, Department of Statistics. Ear-draining, LN weight and cell count were used to assess proliferation instead of radioactive labeling of lymph node cells. In addition, the acute inflammatory skin reaction was measured by ear swelling and weight of circular biopsies of the ears to identify skin irritating properties of the test items. Hexylcinnamaldehyde (HCA) and three blinded test items were applied to female, 8--10 weeks old NMRI and BALB/c mice. Results were sent via the independent study coordinator to the statistician. The results of this first round showed that the alternative endpoints of the LLNA are sensitive and robust parameters. The use of ear weights added an important parameter assessing the skin irritation potential, which supports the differentiation of pure irritative from contact allergenic potential. There were absolute no discrepancies between the categorisation of the three test substances A--C determined by each single participating laboratories. The results highlighted also that many parameters do have an impact on the strength of the responses. Therefore, such parameters have to be taken into consideration for the categorisation of compounds due to their relative sensitizing potencies.

Animals↗
PubMed2005

An European inter-laboratory validation of alternative endpoints of the murine local lymph node assay: 2nd round.

The original local lymph node assay (LLNA) is based on the use of radioactive labelling to measure cell proliferation. Other endpoints for the assessment of proliferation are also authorized by the OECD Guideline 429 provided there is appropriate scientific support, including full citations and description of the methodology (OECD, 2002. OECD Guideline for the Testing of Chemicals; Skin Sensitization: Local Lymph Node Assay, Guideline 429. Paris, adopted 24th April 2002.). Here, we describe the outcome of the second round of an inter-laboratory validation of alternative endpoints in the LLNA conducted in nine laboratories in Europe. The validation study was managed and supervised by the Swiss Agency for Therapeutic Products (Swissmedic) in Bern. Ear-draining lymph node (LN) weight and cell counts were used to assess LN cell proliferation instead of [3H]TdR incorporation. In addition, the acute inflammatory skin reaction was measured by ear weight determination of circular biopsies of the ears to identify skin irritation properties of the test items. The statistical analysis was performed in the department of statistics at the university of Bern. Similar to the EC(3) values defined for the radioactive method, threshold values were calculated for the endpoints measured in this modification of the LLNA. It was concluded that all parameters measured have to be taken into consideration for the categorisation of compounds due to their sensitising potencies. Therefore, an assessment scheme has been developed which turned out to be of great importance to consistently assess sensitisation versus irritancy based on the data of the different parameters. In contrast to the radioactive method, irritants have been picked up by all the laboratories applying this assessment scheme.

Animals↗
PubMed2004

Determination of the effect of calcineurin inhibitors on the rat's immune system after KLH immunisation.

The calcineurin inhibitors cyclosporin A (CsA), tacrolimus (FK506) and pimecrolimus (ASM981) are on the market for the oral treatment of psoriasis and atopic dermatitis and topical treatment of atopic dermatitis, respectively. The effect of these treatments on the immune response was investigated in this study after immunisation of rats with keyhole limpet hemocyanin (KLH). Male rats (10 per group) were orally administered pimecrolimus at 10 or 30 mg/kg/day), tacrolimus at 3 mg/kg/day or CsA at 20 mg/kg/day for 4 weeks. Control animals similarly received the vehicle only. The last five animals per group were immunised and challenged with KLH on days 16 and 24, respectively. Eight days after the last injection, the immune function was investigated by detecting KLH-specific antibodies in the serum and by examination of cell infiltration at the site of the KLH-challenge. In addition, a correlation between functional and structural changes was established by quantification of lymphocyte sub-populations in the blood or residing in lymphatic tissue. In KLH-immunised rats, CsA caused complete suppression of the KLH-specific IgM and IgG production, whereas only IgG production was affected by pimecrolimus at 30 mg/kg/day and more so by tacrolimus at 3 mg/kg/day. Immunophenotyping of lymphocyte sub-populations in spleen and lymph node indicated a decrease in T lymphocytes with pimecrolimus at 30 mg/kg/day, tacrolimus and CsA, whereas these changes were marginal for pimecrolimus at 10 mg/kg/day. Immunophenotyping of peripheral white blood cells (WBC) revealed a decrease in the absolute number of T lymphocytes with all three test items. In comparison with non-immunised animals, a slight increase in absolute numbers of T lymphocytes was observed in KLH-immunised animals treated with pimecrolimus at 10 or 30 mg/kg/day. In conclusion, the ability of the immune system to respond to KLH was not affected by pimecrolimus at 10 mg/kg/day whereas a decrease in immune function was noted in the other groups as follows: pimecrolimus (30 mg/kg/day) < tacrolimus (3 mg/kg/day) < CsA (20 mg/kg/day).

Adjuvants, Immunologic↗
PubMed2004

Validation of immune function testing during a 4-week oral toxicity study with FK506.

Assessment of the immune system's capability to respond to antigens with the generation of specific antibodies, whilst under the influence of a test article, is required in toxicity tests according to the European guideline for repeated dose toxicity testing of medicinal products. The purpose of this study in rats was to validate methodology for the determination of Keyhole Limpet Haemocyanin (KLH)-specific antibodies under the influence of an immunologically active compound. The immunosuppressant FK506, commercially available as Prograf, was administered orally (gavage) to five rats per sex per group at dosages of 0.5mg/kg per day or 3mg/kg per day, for a period of 4 weeks. On days 14 and 22, KLH was administered subcutaneously, with an adjuvant (AluGel), to the two treated groups and a control (i.e. without FK506 treatment) approximately 1h following administration of FK506. Terminal investigations included haematology parameters, titration of KLH-specific antibodies in serum (ELISA), macroscopic pathology, spleen and thymus weights, immunophenotyping of splenocytes (FACS analysis) and histopathology of the lymphatic tissues. At 3mg/kg per day a minimal reduction of subcutaneous KLH-induced granuloma formation and a moderate to marked reduction of germinal centre development (axillary lymph node and spleen) were observed. Reduced CD4+ (T-cell) counts were found in the spleen of males, consistent with a suppressed production of KLH-specific antibodies (IgG in both sexes, IgM in males only) and a higher incidence of atrophy in the periarteriolar lymphoid sheaths of males. Slight-to-moderate lymphopenia was present in both sexes at 3mg/kg per day. These findings are consistent with the known pharmacological activity of FK506. In conclusion, determination of antibody titres following immunisation of rats with KLH, with concurrent exposure to a drug, appears to be a valid method in the context of the immunotoxicity evaluation required by European regulation.

Animals↗
PubMed2002

[Successful direct transfer of a deep frozen-thawed equine embryo].

Embryos were flushed on day 7 after ovulation from two mares, and frozen using a conventional slow freezing procedure in phosphate buffered (PBS) saline supplemented with 10% FCS, 1.5 mol/L ethylene glycol and 0.25 mol/L sucrose. One of the two embryos was thawed after 10 months of storage in liquid nitrogen and transferred directly (without dilution of the cryoprotectant and quality examination) to a synchronized recipient. This transfer resulted in the birth of a live female foal. To our knowledge, this is the first live foal born after direct transfer of a frozen-thawed equine embryo.

Animals↗
PubMed2001

A cross-link breaker has sustained effects on arterial and ventricular properties in older rhesus monkeys.

Nonenzymatic glycosylation and cross-linking of proteins by glucose contributes to an age-associated increase in vascular and myocardial stiffness. Some recently sythesized thiazolium compounds selectively break these protein cross-links, reducing collagen stiffness. We investigated the effects of 3-phenacyl-4,5-dimethylthiazolium chloride (ALT-711) on arterial and left ventricular (LV) properties and their coupling in old, healthy, nondiabetic Macaca mulatta primates (age 21 +/- 3.6 years). Serial measurements of arterial stiffness indices [i.e., aortic pulse wave velocity (PWV) and augmentation (AGI) of carotid arterial pressure waveform] as well as echocardiographic determinations of LV structure and function were made before and for 39 weeks after 11 intramuscular injections of ALT-711 at 1.0 mg/kg body weight every other day. Heart rate, brachial blood pressure, and body weight were unchanged by the drug. PWV and AGI decreased to a nadir at 6 weeks [PWV to 74.2 +/- 4.4% of baseline (B), P = 0.007; AGI to 41 +/- 7.3% of B, P = 0.046], and thereafter gradually returned to baseline. Concomitant increases in LV end diastolic diameter to 116.7 +/- 2.7% of B, P = 0.02; stroke volume index (SV(index)) to 173.1 +/- 40.1% of B, P = 0.01; and systolic fractional shortening to 180 +/- 29.7% of B, P = 0.01 occurred after drug treatment. The LV end systolic pressure/SV(index), an estimate of total LV vascular load, decreased to 60 +/- 12.1% of B (P = 0.02). The LV end systolic diameter/SV(index), an estimate of arterio-ventricular coupling, was improved (decreased to 54.3 +/- 11% of B, P < 0.002). Thus, in healthy older primates without diabetes, ALT-711 improved both arterial and ventricular function and optimized ventriculo-vascular coupling. This previously unidentified cross-link breaker may be an effective pharmacological therapy to improve impaired cardiovascular function that occurs in the context of heart failure associated with aging, diabetes, or hypertension, conditions in which arterial and ventricular stiffness are increased.

Aging↗
PubMed2001

Pharmaceutical intervention of advanced glycation endproducts.

Recent studies have revealed that reducing sugars, such as glucose, react with proteins through non-enzymatic glycosylation to form irreversible, covalently cross-linked proteins known as advanced glycation endproducts (AGEs). Furthermore, it has been demonstrated that this naturally occurring process, accelerated in diabetics due to hyperglycaemia, impairs biological functions leading to cardiovascular disorders, as well as diabetic and age-related complications. Pharmaceutical intervention to prevent or reverse these complications have focused on inhibiting the formation of AGEs by compounds such as dimethyl-3-phenacylthiazolium chloride or breaking the glucose derived cross-links by selective cleavage. Intervention targeted at AGE cross-links in vivo offers a way to interfere with age-related changes of tissues.

Animals↗
PubMed2001

Intralaboratory validation of alternative endpoints in the murine local lymph node assay for the identification of contact allergic potential: primary ear skin irritation and ear-draining lymph node hyperplasia induced by topical chemicals.

We validated a two-tiered murine local lymph node assay (LLNA) with a panel of standard contact (photo)allergens and (photo)irritants with the aim of improving the discrimination between contact (photo) allergenic potential and true skin (photo)irritation potential. We determined ear weights to correlate chemical-induced skin irritation with the ear-draining lymph node (LN) activation potential. During tier I LLNAs, a wide range of concentrations were applied on three consecutive days to the dorsum of both ears. Mice were exposed to UVA light immediately after topical application to determine the photoreactive potential of some test chemicals. Mice were killed 24 h after the last application to determine ear and LN weights and LN cell counts. It was possible to classify the tested chemicals into three groups according to their threshold concentrations for LN activation and skin irritation: (1) chemicals with a low LN activation potential and no or very low skin irritation potential; (2) chemicals with a marked LN activation potential higher than a distinct skin irritation potential; and (3) chemicals with LN activation potential equal to or lower than their skin irritation potential. Group 1 consisted only of contact allergens, indicating that LN activation in the absence of skin irritation points to a contact allergenic activity. Since groups 2 and 3 comprised irritants and contact allergens, a tier II LLNA protocol was used to finally differentiate between true irritants and contact allergens. Briefly, mice were pretreated with mildly to moderately irritating concentrations of the chemical to the shaved back and after 12 days were challenged on the ears as described above in order to elicit a contact allergenic response in the ear skin and the ear-draining LN. With this approach, tier II LLNAs have to be conducted only in cases for which skin irritation potential is in the range of LN activation potential and no structure-activity relationship data indicating a contact allergenic hazard are available.

Administration, Topical↗
PubMed2001

Cytokine expression profiles during murine contact allergy: T helper 2 cytokines are expressed irrespective of the type of contact allergen.

We have investigated the cytokine response pattern following sensitisation (induction) of BALB/c mice with different chemicals (dinitrochlorobenzene, dinitrofluorobenzene, oxazolone, glutaraldehyde, formaldehyde, trimellitic anhydride, croton oil) and elicitation (challenge) of contact allergy in sensitised animals. The results of our investigations showed that different chemicals induced both T helper (Th) 1 cytokines [interleukin (IL) 2, interferon beta (IFNgamma) [corrected] and Th2 cytokines (IL-4, IL-10) at different stages during murine contact allergy. We also confirmed our previous findings that IL-4 and IL-10 release were up-regulated during the challenge phase regardless the contact allergen used, whereas the release of IFNgamma [corrected] did not show a clear preference for being up- or down-regulated. In our hands, the increased expression of Th2 cytokines after challenge exposure to contact allergens appeared as a stable marker of secondary contact allergenic responses. Quantitative differences in the expression of IL-4 were observed between different contact allergens. The present results clearly indicate that skin sensitisers were able to elicit cytokine response patterns, which could not be related to a clear-cut Th1 or Th2 type of cytokine response. Furthermore, dermal application of contact allergens produced different kinetics of cytokine secretion upon induction and challenge. In our hands, the co-expression of Th1 and Th2 type cytokines appeared as a universal consequence of dermal application of contact allergens to responsive mice. Our results indicate that co-expression of Th1 and Th2 cytokines during contact allergy is an important feature of murine contact allergy in responsive mice and that chemicals differ in their potency to induce the expression of these cytokines. Furthermore, the results do not support the view that different chemicals induce Th1 or Th2 cytokines in a mutually exclusive manner depending on their preference for inducing either contact or respiratory allergy. The results are expected to renew the discussion about the usefulness of the Th1/Th2 paradigm in certain areas of immunotoxicology.

Allergens↗
PubMed2001

Release of mast cell tryptase from human colorectal mucosa in inflammatory bowel disease.

BACKGROUND: Histologic detection of mast cells cannot adequately reflect their function and state of activation, since degranulated mast cells may escape from histologic assessment. To better define the role of mast cells in inflammatory bowel disease, the spontaneous secretion of mast cell tryptase, a highly mast cell specific protease, was measured from colorectal samples. METHODS: After detection of the initial basal tryptase release, gut mucosal samples were incubated in a modified Hanks/RPM1 medium using a mucosa oxygenation system. Spontaneous tryptase secretion from 153 viable samples of 22 controls, 30 patients with Crohn disease (CD) and 19 with ulcerative colitis (UC) was followed over 4 h. Tryptase was measured by radioimmunoassay. RESULTS: The rates of the initial basal tryptase release revealed that mast cell activation occurs during active inflammation in CD and UC. While the time course of tryptase release was similar in all three groups, spontaneous tryptase secretion (over 4 h) was found to be significantly enhanced and prolonged only in UC (P < 0.01 compared to controls), but not in CD. CONCLUSIONS: This study provides clear evidence from viable endoscopic colorectal samples that mast cell mediators were secreted during active inflammation in CD and UC. However, the extent of mast cell involvement and activation differs considerably between CD and UC. Significantly increased rates of tryptase secretion were found both in non-inflamed and inflamed tissue of UC, indicating that mast cell involvement is a typical feature of UC.

Adult↗
PubMed2001

Protein glycation, diabetes, and aging.

Biological amines react with reducing sugars to form a complex family of rearranged and dehydrated covalent adducts that are often yellow-brown and/or fluorescent and include many cross-linked structures. Food chemists have long studied this process as a source of flavor, color, and texture changes in cooked, processed, and stored foods. During the 1970s and 1980s, it was realized that this process, called the Maillard reaction or advanced glycation, also occurs slowly in vivo. Advanced glycation endproducts (AGEs) that form are implicated, causing the complications of diabetes and aging, primarily via adventitious and crosslinking of proteins. Long-lived proteins such as structural collagen and lens crystallins particularly are implicated as pathogenic targets of AGE processes. AGE formation in vascular wall collagen appears to be an especially deleterious event, causing crosslinking of collagen molecules to each other and to circulating proteins. This leads to plaque formation, basement membrane thickening, and loss of vascular elasticity. The chemistry of these later-stage, glycation-derived crosslinks is still incompletely understood but, based on the hypothesis that AGE formation involves reactive carbonyl groups, the authors introduced the carbonyl reagent aminoguanidine hydrochloride as an inhibitor of AGE formation in vivo in the mid 1980s. Subsequent studies by many researchers have shown the effectiveness of aminoguanidine in slowing or preventing a wide range of complications of diabetes and aging in animals and, recently, in humans. Since, the authors have developed a new class of agents, exemplified by 4,5-dimethyl-3-phenacylthiazolium chloride (DPTC), which can chemically break already-formed AGE protein-protein crosslinks. These agents are based on a new theory of AGE crosslinking that postulates that alpha-dicarbonyl structures are present in AGE protein-protein crosslinks. In studies in aged animals, DPTC has been shown to be capable of reverting indices of vascular compliance to levels seen in younger animals. Human clinical trials are underway.

Aging↗
PubMed2000

An advanced glycation endproduct cross-link breaker can reverse age-related increases in myocardial stiffness.

Decreased elasticity of the cardiovascular system is one of the hallmarks of the normal aging process of mammals. A potential explanation for this decreased elasticity is that glucose can react nonenzymatically with long-lived proteins, such as collagen and lens crystallin, and link them together, producing advanced glycation endproducts (AGEs). Previous studies have shown that aminoguanidine, an AGE inhibitor, can prevent glucose cross-linking of proteins and the loss of elasticity associated with aging and diabetes. Recently, an AGE cross-link breaker (ALT-711) has been described, which we have evaluated in aged dogs. After 1 month of administration of ALT-711, a significant reduction ( approximately 40%) in age-related left ventricular stiffness was observed [(57.1 +/- 6.8 mmHg x m(2)/ml pretreatment and 33.1 +/- 4.6 mmHg x m(2)/ml posttreatment (1 mmHg = 133 Pa)]. This decrease was accompanied by improvement in cardiac function.

Aging↗
PubMed2000

Expression of mRNAs encoding for two different olfactory receptors in a subset of olfactory receptor neurons.

Evidence has accumulated to support a model for odorant detection in which individual olfactory receptor neurons (ORNs) express one of a large family of G protein-coupled receptor proteins that are activated by a small number of closely related volatile chemicals. However, the issue of whether an individual ORN expresses one or multiple types of receptor proteins has yet to be definitively addressed. Physiological data indicate that some individual ORNs can be activated by odorants differing substantially in structure and/or perceived quality, suggesting multiple receptors or one nonspecific receptor per cell. In contrast, molecular biological studies favor a scheme with a single, fairly selective receptor per cell. The present studies directly assessed whether individual rat ORNs can express multiple receptors using single-cell PCR techniques with degenerate primers designed to amplify a wide variety of receptor sequences. We found that whereas only a single OR sequence was obtained from most ORNs examined, one ORN produced two distinct receptor sequences that represented different receptor gene families. Double-label in situ hybridization studies indicated that a subset of ORNs co-express two distinct receptor mRNAs. A laminar segregation analysis of the cell nuclei of ORNs labeled with the two OR mRNA probes showed that for one probe, the histogram of the distribution of the cell nuclei along the depth of the epithelium was bimodal, with one peak overlapping the (unimodal) histogram for the other probe. These results are consistent with co-expression of two OR mRNAs in a population of single ORNs.

Amino Acid Sequence↗
PubMed2000

Significance of resting and stimulated cerebral blood flow for predicting the risk of hemodynamic cerebral ischemia in a model of chronic hemodynamic insufficiency.

OBJECTIVE: It has been postulated that patients with a compromised cerebrovascular reserve capacity (RC), defined as cerebral blood flow (CBF) response to acetazolamide (ACZ) (by percent), are at higher risk for ischemic stroke. The value of CBF and RC for predicting the risk of hemodynamically induced impairment of cerebral function is examined. METHODS: Both common carotid arteries were occluded in 22 Wistar-Kyoto rats. Thirty-one days later, mean arterial blood pressure was reduced to 40 mm Hg for 30 minutes. Laser Doppler scanning of CBF at resting conditions and after intraperitoneal administration of ACZ (0.1 mg/g body weight) was performed 30 minutes and 28 days after occlusion as well as before and during hypotension. Memory and motor functions were examined before and after CBF measurements. RESULTS: After occlusion, CBF dropped significantly and ACZ did not increase CBF. Four weeks later, resting CBF had significantly improved but remained impaired, as did RC, showing a distinct interindividual variability. Hypotension reduced CBF by 57 +/- 4% (P < 0.001) and significantly impaired memory and motor functions. CBF during hypotension correlated with resting CBF before hypotension (r = 0.495, P = 0.027) and with CBF before (r = 0.392, P = 0.048) and after (r = 0.476, P = 0.034) ACZ, as determined 4 weeks after occlusion. There was no correlation with RC (r = 0.091, P = 0.702). Neurological tests performed 1 day after hypotension correlated with CBF during hypotension (memory function, P = 0.03; motor function, P = 0.02) but not with RC. CONCLUSION: In this model of chronic hemodynamic insufficiency, the risk of impairment to global cerebral function was predicted by resting CBF and CBF after ACZ but not by RC determined with ACZ.

Acetazolamide↗