Biomedical subjects

C Wirtz

Publications and source records attributed to C Wirtz.

14 recordsLinked to original sources

PubMed2005

Robot-assisted craniotomy.

In the Special Research Centre 414 of the German Research Funding (DFG, Bonn) a system for robot-assisted cranial surgery was developed. It is designed for the accurate and safe execution of craniotomies and repositioning of bone pieces. The system is intended for use in the surgical therapy of craniosynostosis. Preoperatively, CT imaging is performed. In a computerized planning system the position and shape of the intended craniotomy is intuitively planned on a virtual model of the patient's skull. Intraoperatively, after conventional removal of the covering soft tissue, the robot performs the craniotomy autonomously. Extensive testing in phantom studies and animal tests confirmed the reliability and accuracy of the system. A thorough risk analysis of the system was performed. In this paper, the first clinical use of the system on a patient is described and the clinical importance is discussed.

Bone Cysts↗

PubMed2003

[Continuous biochemical tissue monitoring during acute hypoxia].

Oxygen deficiency during critical illness is known to cause profound changes in cellular metabolism with subsequent organ dysfunction. Clinical treatment in these patients is focussed on rapid reoxygenation to avoid a prolonged impaired synthesis of cellular high-energy phosphates (ATP). The effect of this therapeutical intervention on the level of the cell, however, has not yet been objectivized. The aim of the present experimental study was to biochemically monitor different tissues during hypoxia and reoxygenation using in vivo microdialysis. Eighteen adult male CD-rats (412-469 g; Ivanovas, Kisslegg, Germany) were normoventilated under general anaesthesia (FiO2 = 0.21). Ten were then subjected to a period of hypoxia (FiO2 = 0.1, 40 min) and reoxygenated with FiO2 = 0.21, while eight control animals were continuously ventilated with FiO2 = 0.21. In addition to invasive haemodynamic monitoring, biochemical tissue monitoring was performed using CMA 20 microdialysis probes, which were inserted into the muscle (m), subcutaneous space (s), liver (l) and peritoneal cave (p) with semicontinuous analyses of lactate and pyruvate at intervals of 15 minutes. Hypoxia induced a significant decrease in mean arterial pressure compared to the control group (p < 0.05). At the same time significant increases in blood lactate (12.3 + 4.1 mmol/l (hypoxia) vs. 1.5 +/- 0.3 mmol/l (control); p < 0.05) and in negative base excess (17.3 + 7 mmol/l (hypoxia) vs. 2.6 + 1.8 mmol/l (control), p < 0.05) occurred. Compared to unchanged levels in the control animals, the interstitital lacate/pyruvate ratio in the investigation group rose to significantly higher values (455 + 199% of baseline (m), 468 + 148% (p), 770 + 218% (l) and 855 + 432% (s) (p < 0.05). An immediate return to the baseline values after the start of reoxygenation was noted in the L/P ratio during the observation period. Using microdialysis, it was possible to objectify the effect of oxygen deficiency and restoration on tissue metabolism. Regarding clinical and preclinical practice, microdialysis monitoring should be performed to include biochemical cellular effects as an additional target for therapeutical interventions.

Acute Disease↗

PubMed2000

Ring-closing alkyne metathesis. Application to the total synthesis of sophorolipid lactone.

The first total synthesis of a major component of the microbial biosurfactant sophorolipid has been achieved. This approach to the 26-membered macrolide 1 containing a Z-configured alkene group in its lipidic tether spanning the sophorose backbone is based on a ring-closing metathesis reaction of diyne 21 catalyzed by Mo[N(t-Bu)(Ar)](3) (5; Ar = 3,5-dimethylphenyl) activated in situ by CH(2)Cl(2), followed by Lindlar reduction of the resulting cycloalkyne 22. The two beta-glycosidic linkages of compound 21 were installed by means of the glucal epoxide method and a modified Koenigs-Knorr reaction promoted by AgOTf/lutidine, respectively.

Journal Article↗

PubMed2000

Nasal lavage mediator profile and cellular composition of nasal brushing material during latex challenge tests.

BACKGROUND: Recent studies have shown that airborne latex allergens cause allergic rhinitis and bronchial asthma. OBJECTIVE: The aim of this study was to investigate the association between the development of rhinitis reactions during workplace-related inhalative challenge tests and nasal allergic inflammation. METHODS: Thirty-two health care workers (HCWs) with suspected respiratory hypersensitivity to latex allergens underwent an inhalative workplace-related challenge test with powdered latex gloves. Nasal lavage fluid (NALF) and nasal brushing (NAB) material were collected before and after exposure (30 min, 2, 6 and 24 h) to determine mediator and cellular composition. In addition, lung function parameters and nasal flow were recorded. Furthermore, six healthy controls underwent nasal brushing and nasal lavage without latex allergen challenge at the same time intervals. RESULTS: Twenty-six HCWs showed acute rhinitis by contact to airborne latex allergen exposure and 10 of them had an additional asthma response. Only in responders, significantly increased eosinophil levels were found 6 h (P < 0.00001) and 24 h (P < 0.0005) post-challenge when compared with the prechallenge values. The ECP levels measured 2, 6 and 24 h post-challenge in the responder group were significantly elevated when compared with the prechallenge values as well as with the non-responders (6 h: P < 0.05, 24 h: P < 0.00001 afterwards). Only in some concentrated NALF samples of responders collected 30 min post-challenge (seven out of 15) tryptase concentration above the detection limit were found. The NO derivative concentrations in NALF were significantly increased 6 h post-challenge compared with the prechallenge values (P < 0.05) and were significantly higher in responders than in non-responders and in controls (P < 0.002). IL-5 levels increased post-challenge in the responder group with a pronounced effect 6 h after challenge (P < 0.001). Overall, a variety of parameters was significantly correlated (e.g. ECP with NO derivatives, r = 0.792 P < 0.002). CONCLUSIONS: Our data demonstrate for the first time that nasal and bronchial hyperreactivity to airborne latex allergens are associated with an increase of eosinophils and mediators (e.g. ECP, NO derivatives, IL-5, tryptase) in nasal mucosa. The combined use of NAB (for cells) and NALF (for mediators) appears to be a useful model to monitor nasal inflammation during workplace-related challenge tests.

Administration, Inhalation↗

PubMed2000

Allelic loss involving the tumor suppressor genes APC and MCC and expression of the APC protein in the development of dysplasia and carcinoma in Barrett esophagus.

Samples of Barrett metaplastic specialized epithelium (SE), low-grade dysplasia (LGD), high-grade dysplasia (HGD), and invasive adenocarcinoma (CA) derived from 36 esophagectomy specimens were studied for loss of heterozygosity (LOH) in APC and MCC and for expression of APC protein. Of 18 cases that were heterozygous (informative) for APC, LOH was found in none of 14 SE samples, 2 of 8 LGD samples, 3 of 11 HGD samples, and 5 of 17 CA samples. Immunohistochemically, markedly reduced expression of APC protein (< 50% positive cells) was found in 3 of 19 HGD samples and 4 of 35 CA samples but not in SE or LGD samples. Of 17 cases informative for the MCC gene, LOH was detectable in 1 of 14 SE samples, none of 7 LGD samples, none of 9 HGD samples, and 4 of 16 CA samples. Allelic loss of APC and/or loss of APC protein expression occurs earlier in the metaplasia-dysplasia-carcinoma sequence in Barrett esophagus than LOH in the MCC gene. The determination of alterations at APC or MCC would be of limited importance for the surveillance of patients with Barrett esophagus.

Adenocarcinoma↗

PubMed1998

[Prognostic factors in stomach carcinoma].

The classical prognostic factors of the pTNM system are still most valid. Nevertheless, vascular invasion as well as the molecular marker E-cadherin proved to be independent new prognostic factors responsible for a significant shift in patient survival. Thus, in pTNM-stage II patients, a highly significant drop in survival is observed when patients showing no E-cadherin expression and at the same time vascular invasion are compared with E-cadherin-positive patients who do not show vascular invasion (Fig. 11). These conspicious shifts in survival underline the necessity to continue our search for new molecular and non-molecular markers which in future may help us to predict the outcome of gastric cancer patients more precisely and more individually.

Antigens, CD↗

PubMed1998

[Protein expression of hMSH2 and hMLH1 in HNPCC: evaluation of a prescreening method].

We show that immunohistochemistry for hMSH2 and hMLH1 is an easy and reproducible routine procedure. The interpretation of the staining results is unequivocal and investigator-independent. It is now necessary to validate the specificity and sensitivity of the method in a multicenter study with tumors of known mutations. As a consequence perhaps MIN testing may be replaced by immunohistochemistry as a first-line pretesting for HNPCC, reducing cost and time required.

Adaptor Proteins, Signal Transducing↗

PubMed1997

[Exposure testing with powdered gloves in 60 health care workers with latex allergy].

BACKGROUND AND OBJECTIVE: Type 1 sensitization to natural rubber latex occurs in up to 22% of health care workers. Most sensitizations are due to the use of powdered latex gloves. Work place-associated exposure tests were performed to ascertain how frequently persons who developed breathing difficulties, rhinitis/conjunctivitis or obstructive respiratory tract illness when using powdered latex gloves are allergic to latex. PATIENTS AND METHODS: 60 persons (48 women and 12 men; mean age 29 +/- 7 years) with type 1 sensitization to natural rubber latex were studied. The past history was obtained through a questionnaire specially designed for those with latex allergy. Diagnostic measures included prick tests with different latex allergens, measuring the concentrations of total and latex-specific IgE and exposure trials, related to the work place, with powdered vinyl and latex gloves. RESULTS: The prick tests with various latex allergens produced significant skin reactions in 59 subjects, 58 had latex-specific IgE antibodies (0.47 kU/l- > 100 kU/l). Exposure tests with powdered latex gloves produced rhinitis in 55 and conjunctivitis in 38 persons, urticaria in 3 and cough in 19. Whole-body plethysmography demonstrated a significant rise in respiratory tract resistance in 13, a reduction in 1-second expiratory volume of at least 20% in 15. Abnormal values in both tests were noted in 8 subjects. CONCLUSION: The breathing difficulty reported by all subjects was in most cases due not to bronchial obstruction but to obstructed nasal breathing. In cases with breathing difficulty on exposure to latex gloves a latex allergy should be considered as the cause. Powdered latex gloves present a danger to health care personnel and should no longer be used.

Adult↗

PubMed1995

Design and implementation of the stavudine parallel-track program.

In a randomized, double-blind, large, simple trial, the safety and efficacy of two weight-adjusted dose levels of stavudine were evaluated in patients with advanced human immunodeficiency virus (HIV) infection. All patients were refractory to or intolerant of both zidovudine and didanosine. Patients weighing > or = 60 kg received 20 or 40 mg of stavudine twice daily. The dose was reduced to 15 or 30 mg for patients weighing 40-59 kg and to 10 or 20 mg for those weighing < 40 kg. The primary efficacy end points were survival and time to clinical progression of HIV disease. The primary safety end point was time to dose-limiting neuropathy. A total of 8127 patients were enrolled as of 31 July 1993. Although many patients who might have benefitted from stavudine were reached by the parallel-track program, a review of demographic data revealed disproportionate representation by white men from large metropolitan areas on both coasts.

Adult↗

PubMed1993

Interaction of thiazide and loop diuretics with the basolateral para-aminohippurate transport system in isolated S2 segments of rabbit kidney proximal tubules.

The effect of thiazide and loop diuretics on the tubular uptake of [3H]para-aminohippurate ([3H]PAH), a marker of the organic anion transport system, was tested in vitro on single S2 segments of the proximal tubule of rabbit kidneys. Because the tubules were not perfused, and hence were collapsed, the tubular [3H] PAH uptake reflects [3H]PAH transport across the contraluminal membrane. The diuretics were added to the bath solution in at least six different concentrations. The concentration of [3H]PAH in the bath solution amounted to 1.3 mumol/l, and was 12 times lower than the PAH concentration (16 mumol/l) at half-maximum PAH uptake. The results show that all of the nine diuretics tested inhibited [3H]PAH uptake. The IC50 values of the individual drugs ranged from 3 to 400 mumol/l. In general, thiazide diuretics had a lower affinity to the PAH transporter than loop diuretics. This probably results from differences in the pKa values which range from 3.6 to 4.1 for the loop diuretics and from 9.2 to 10 for the thiazide diuretics. Furthermore, there was a highly significant dependence of affinity on the hydrophobic properties of the diuretics. At concentrations 10- to 100-fold lower than the IC50 values all diuretics stimulated [3H]PAH uptake which may indicate a positive cooperative interaction of these drugs with the PAH transporter. Within the group of loop diuretics the order of the affinity to the PAH transporter and to the Na, 2 Cl, K cotransporter in the thick ascending limb of Henle's loop was identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Clinical safety profile of sotalol in patients with arrhythmias.

Key safety parameters of sotalol were examined in 1,288 patients entered into recent controlled trials of ventricular (85% of patients) or supraventricular arrhythmias (15%). Most patients were middle-aged male Caucasians with significant heart disease. The most serious adverse event was proarrhythmia, occurring in 56 patients (4.3%). Of these, 27 had hemodynamic compromise due to malignant ventricular arrhythmias. Most had a history of sustained ventricular tachycardia, myocardial infarction, congestive heart failure (CHF) or cardiomyopathy, or a combination of these. The other 29 had nonsevere events; 38% continued taking sotalol. Proarrhythmia was manifested by torsades de pointes in 24 of the 56 patients. No universal causal relation was found with commonly associated factors such as bradycardia, hypokalemia and long QT interval. The mean QT and QTc at baseline within 1 week of a severe proarrhythmic event were greater than those of patients not having proarrhythmia. Nineteen patients (1%) discontinued therapy with sotalol because of drug-related CHF. Predisposing conditions included low initial baseline ejection fraction, history of CHF, cardiomyopathy or cardiomegaly, or both, male gender and age greater than 65 years. Heart failure usually occurred within 7 to 30 days of initiating therapy. The most common reason for premature discontinuation of the drug in patients treated for sustained ventricular tachycardia was ineffectiveness (39%), whereas adverse effects were the most common reasons among patients treated for complex ventricular ectopy (21%). Dyspnea and bradycardia were the most common cardiovascular effects, and fatigue, dizziness and asthenia the most common noncardiac, adverse effects. Although frequently reported, these adverse effects resulted in discontinuation of only 1 to 4% of the patients at risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗

PubMed1988

[Breast carcinoma in men: radiotherapy and treatment results].

The treatment of 34 men with stage T1 N0 M0 to T3/4 N1 M0 mammary carcinomas was followed by a five-year survival rate of 70%. Three patients suffering from initial remote metastases died after 2 to 3.5 years. The probability of a five-year survival decreases with increasing tumor growth and axillary involvement. The prognostic effect of receptor state and grading could not be investigated in our patients. Our own data as well as recent data from literature suggest that, with respect to TNM stages in mammary carcinoma, there is no prognostic difference between men and women. It is not very clear at present if postoperative irradiation exerts a favorable influence on the survival rate. However, it reduces the local recurrence risk for men and women. 45 Gy in five weeks should be considered as a minimum dose. The indications for postoperative irradiation are discussed.

Adenocarcinoma↗

PubMed1988

[The role of postoperative radiotherapy in the treatment of hypernephroid carcinoma].

The following results can be derived from the clinical and radiobiological literature as well as from the authors's own experiences with 91 patients analyzed retrospectively and evaluated with respect to their risk factors. 1. A postoperative irradiation is very probably sensible in patients with tumor perforation through the renal capsule (T3/T4) and with venous or lymph node manifestations. 2. The operation method is essential, above all the transabdominal technique and the quality of lymph dissection. 3. Prospective studies are necessary in order to clear up the role of radiotherapy in patients with lymph node manifestations and the other two risk factors mentioned in item 1. 4. Further studies on the tumor biology of the hypernephroid carcinoma are necessary in order to gain prognostic criteria allowing a pretherapeutic sensitivity recognition. 5. The effect of a supplementary radiotherapy can be only that of local recurrence prevention in case of a locally advanced tumor and the absence of demonstrable remote metastases. This seems justified, because the local recurrence rate in our own patients was only 3.3%.

Carcinoma, Renal Cell↗

PubMedDate not supplied

[MRI-controlled outcome after core decompression of the femur head in aseptic osteonecrosis and transient bone marrow edema].

PURPOSE: We evaluated the signal changes of avascular necrosis and transient bone marrow oedema before and after core decompression of the femoral head to deduce prognostic factors for this operative procedure. METHOD: 38 to 40 cases with core decompression (35 patients, medium age 44 years) were analysed with a mean follow-up time of 26 months. Preoperatively patients were staged by the ARCO classification. MR-images were judged in accordance to the criteria of Mitchell and Steinberg. The clinical outcome was analysed according to the hip index of Merle D'Aubigne. RESULTS: All hips with transient bone marrow oedema showed normal signal patterns at an average of 3 months after core decompression. In stage I and II, all patients with a preoperative necrosis area less than 30% of the femoral head showed a reduction of the necrotic zone and good clinical results. An unchanged or progressive appearance was observed in necrotic lesions with more than 30% head involvement. Because of failure a renewed operation had to be done in all patients with stage III and IV. CONCLUSION: In the case of transient bone marrow oedema, a restitutio ad integrum can be achieved with core decompression. In stage I and II of avascular necrosis, the successful outcome depends on the lesion size of the femoral head. Necrotic lesions less than 30% seem to have the best prognosis. In stage III and IV, core decompression cannot be recommended.

Adult↗