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Biomedical subjects

P Wirtz

Publications and source records attributed to P Wirtz.

At least 19 recordsLinked to original sources
PubMed2001

Phylogeography of Ophioblennius: the role of ocean currents and geography in reef fish evolution.

Many tropical reef fishes are divided into Atlantic and East Pacific taxa, placing similar species in two very different biogeographic regimes. The tropical Atlantic is a closed ocean basin with relatively stable currents, whereas the East Pacific is an open basin with unstable oceanic circulation. To assess how evolutionary processes are influenced by these differences in oceanography and geography, we analyze a 630-bp region of mitochondrial cytochrome b from 171 individuals in the blenniid genus Ophioblennius. Our results demonstrate deep genetic structuring in the Atlantic species, O. atlanticus, corresponding to recognized biogeographic provinces, with divergences of d = 5.2-12.7% among the Caribbean, Brazilian, St. Helena/Ascension Island, Gulf of Guinea, and Azores/Cape Verde regions. The Atlantic phylogeny is consistent with Pliocene dispersal from the western to eastern Atlantic, and the depth of these separations (along with prior morphological comparisons) may indicate previously unrecognized species. The eastern Pacific species, O. steindachneri, is characterized by markedly less structure than O. atlanticus, with shallow mitochondrial DNA lineages (dmax = 2.7%) and haplotype frequency shifts between locations in the Sea of Cortez, Pacific Panama, Clipperton Island, and the Galapagos Islands. No concordance between genetic structure and biogeographic provinces was found for O. steincdachneri. We attribute the phylogeographic pattern in O. atlanticus to dispersal during the reorganization of Atlantic circulation patterns that accompanied the shoaling of the Isthmus of Panama. The low degree of structure in the eastern Pacific is probably due to unstable circulation and linkage to the larger Pacific Ocean basin. The contrast in genetic signatures between Atlantic and eastern Pacific blennies demonstrates how differences in geology and oceanography have influenced evolutionary radiations within each region.

Animals↗
PubMed2000

[Progressive dyspnea, angina pectoris and weight loss in a 76-year old patient].

BACKGROUND: Cardiac metastases are a rare finding. The primary diagnosis of a malignant disease by cardial metastases is a curiosity. CASE REPORT: A 76-year-old patient presented with dyspnea, angina pectoris and body weight loss. Echocardiography showed a circular pericardial effusion and intramyocardial masses with high echodensity in the right atrial and the right ventricular wall. MIR was not diagnostic of the intramyocardial masses. The pericardiocentesis was negative. The procedures revealed an intestinal type gastric adenocarcinoma. CONCLUSION: Echocardiography is an established method for the diagnosis of cardiac metastases.

Adenocarcinoma↗
PubMed1999

Intrabody construction and expression. II. A synthetic catalytic Fv fragment.

In general, proteins with structural disulfides cannot be expressed in the reducing environment of the cellular cytoplasm. To overcome this folding problem, we have previously engineered stabilizing mutations, predicted from a consensus sequence analysis, into isolated immunoglobulin VL domains. Here we show that such domains can be used as a framework in the construction of a functional heterodimeric Fv fragment, which was expressed solubly, with high yield in the cytoplasm of Escherichia coli. This designed catalytic intrabody, obtained from grafting the combining site of the esterolytic antibody 17E8, is active in the oxidized and the reduced state. Its construction required no special features on the part of the immunoglobulin, no single-chain linker and introduced no non-natural sequence motifs. The potential to design intrabodies with the recognition sequences of arbitrary immunoglobulins opens novel opportunities for gene therapy, cell biology, metabolic engineering and antibody biotechnology.

Amino Acid Sequence↗
PubMed1999

Mother species-father species: unidirectional hybridization in animals with female choice.

As mitochondria are inherited in a matrilinear way, an animal hybrid contains the mitochondrial DNA of its 'mother species'. Of 80 studies that analysed the mitochondrial DNA of at least five hybrid individuals, 50 showed that all hybrids contained the mitochondrial DNA of only one of the two parental species, indicating either mating of females of species A with males of species B but not vice versa (unidirectional hybridization) or the disappearance of one of the two parental mtDNA types after reciprocal hybridization. I review and discuss factors promoting unidirectional or reciprocal hybridization and present a sexual selection hypothesis for unidirectional hybridization. The inequality of the sexes in parental investment leads to the sex that invests more being the more discriminating one. In the presence of conspecific males, females reject allospecific males and, consequently, a male in an environment of both allospecific sexes is unlikely to mate, while in the absence of conspecific males, females sometimes accept fertilizations by males of other species. Thus, hybrid matings are usually between the females of a rare species and the males of a common species, but not vice versa. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Intrabody construction and expression III: engineering hyperstable V(H) domains.

The folding of immunoglobulin domains requires the formation of a conserved structural disulfide. Therefore, as a general rule, they cannot be functionally expressed in the reducing environment of the cellular cytoplasm. We have previously reported that stability engineering can lead to the cytoplasmic expression of functional immunoglobulin V(L) domains. Here we apply rational stability engineering by consensus sequence analysis to V(H) domains. Isolated V(H) domains tend to aggregate more easily than V(L) domains; they do not refold quantitatively and are generally more difficult to handle in vitro. To overcome these problems, we successfully predicted and experimentally verified several stabilizing point mutations in the V(H) domain of a designed, catalytic Fv fragment. The effect of single mutations was additive, and they could be combined in a prototype domain with significantly improved stability against chemical denaturation and a 20-fold increased half time of irreversible thermal denaturation, at physiological temperature. This stabilized, isolated V(H) domain could be expressed solubly in the reducing cellular cytoplasm of Escherichia coli, at a yield of approximately 1.2 mg/L of shake flask culture. It remains fully functional, as evidenced by the successful reconstitution of an esterolytic Fv fragment with the V(L) domain. This success provides further evidence that consensus sequence engineering is a rational, plannable route to the construction of intrabodies.

Amino Acid Sequence↗
PubMed1999

Imaging of thrombi and assessment of left atrial appendage function: a prospective study comparing transthoracic and transoesophageal echocardiography.

OBJECTIVE: To compare the value of current transthoracic echocardiographic systems and transoesophageal echocardiography for assessing left atrial appendage function and imaging thrombi. DESIGN: Single blind prospective study. Patients were first investigated by transthoracic echocardiography and thereafter by a second investigator using transoesophageal echocardiography. The feasibility of imaging the left atrial appendage, recording its velocities, and identifying thrombi within the appendage were determined by both methods. PATIENTS: 117 consecutive patients with a stroke or transient neurological deficit. SETTING: Tertiary cardiac and neurological care centre. RESULTS: Imaging of the complete appendage was feasible in 75% of the patients by transthoracic echocardiography and in 95% by transoesophageal echocardiography. Both methods were concordant for the detection of thrombi in 10 cases. Transoesophageal echocardiography revealed two additional thrombi. In one of these patients, transthoracic echocardiography was not feasible and in the other the thrombus had been missed by transthoracic examination. In patients with adequate transthoracic echogenicity, the specificity and sensitivity of detecting left atrial appendage thrombi were 100% and 91%, respectively. Recording of left atrial appendage velocities by transthoracic echocardiography was feasible in 69% of cases. None of the patients with a velocity > 0.3 m/s had left atrial appendage thrombi. In the one patient in whom transthoracic echocardiographic evaluation missed a left atrial appendage thrombus, the peak emptying velocity of the left atrial appendage was 0.25 m/s. CONCLUSIONS: A new generation echocardiographic system allows for the transthoracic detection of left atrial appendage thrombi and accurate determination of left atrial appendage function in most patients with a neurological deficit.

Adult↗
PubMed1998

Effects of Estradiol (-17beta) on learning, memory and cerebral energy metabolism in male rats after intracerebroventricular administration of streptozotocin.

Treatment of adult rats with intracerebroventricularly (i.c.v.) injected streptozotocin (STZ) may provide a relevant animal model of chronic neuronal dysfunction that is characterized by a decrease in both the neuronal metabolism of glucose and the formation of energy. The present study was designed to evaluate whether or not rats treated with triplicate i.c.v. STZ injection would show long-term effects in learning and memory behavior as measured by means of a holeboard test, closed field activity, and passive avoidance behavior over a period of 6 weeks. For this purpose, animals with good performance were discriminated from those with poor performance by the holeboard test before i.c.v. administration of STZ. After a 1-week training period with the holeboard all animals improved their abilities in learning and memory, and the improvement was maintained over the investigation period of 6 weeks in the control group. After i.c.v. STZ working memory (WM), reference memory (RM), as well passive avoidance (PA) behavior decreased, deteriorating progressively during the investigation period. The latter were accompanied by a permanent deficit in cerebral energy metabolism. The ongoing deterioration in behavior and the sustained deficit in cerebral energy metabolism occurring after a triplicate i.c.v. STZ administration lead us to assume that this animal model may be appropriate for the investigation of mechanisms characteristic for sporadic Alzheimer disease. In this context, the effect of Estradiol-17beta (E2) on behavior and energy metabolism was studied. We found that E2 slowed down the i.c.v. STZ-induced deterioration in memory functions, partially compensated the learning deficit, and improved the disturbances in cerebral energy metabolism to the extent that it was almost completely normal again. These findings underscore the beneficial effect of E2 in dementia disorders.

Animals↗
PubMed1997

[Septic myocardial aneurysm in mitral valve endocarditis. Clinical and pathological-anatomical findings].

HISTORY AND CLINICAL FINDINGS: A 68-year-old woman was hospitalized because of fever and tiredness for 3 months. Her general condition was clearly impaired. She had a mild fever of 38.5 degrees C and on auscultation a 3/6 systolic murmur, maximal parasternally in the 3rd intercostal space, transmitted to the apex. There were distant râles over both lungs, the neck veins were distended and there was ankle oedema. INVESTIGATIONS: C-reactive protein was raised to 17.3 mg/dl (normal up to 0.9 mg/dl), WBC count 19,300/microliter. beta-haemolysing streptococcus (S. agalactiae) was grown in the blood culture. The ECG showed sinus tachycardia (rate of 98/min) and transthoracic echocardiography demonstrated a small pericardial, enlarged ventricles, marked mitral regurgitation and a large vegetation on the posterior mitral leaflet, as well as a 3 x 4 cm mass in the posterior wall of the ventricle, originating from the posterior mitral valve ring and communicating with the vegetation on the mitral valve. The posterior mitral leaflet was perforated. TREATMENT AND COURSE: As endocarditis of the mitral valve with a complicated course was suspected-abscess of the posterior mitral valve ring and septic myocardial aneurysm with associated pericarditis and haemodynamically insignificant effusion-she was transferred to the intensive care unit where she died suddenly of circulatory arrest only 30 min after transfer. Autopsy confirmed the echocardiographic findings. CONCLUSION: Paravalvular abscess in the course of mitral valve endocarditis is rare, but should be looked for at transthoracic echocardiography so that any necessary surgical intervention can be undertaken early.

Aged↗
PubMed1995

The development of compensatory hypertrophy in the plantaris muscle of the rat.

The aim of this investigation was to study the time course of compensatory hypertrophy (CH) over a seven week period after its surgical induction in the lower limb of the rat. CH of the left plantaris muscle of the rat was induced by denervation of the ipsilateral gastrocnemius and soleus muscles. Muscle fibres were classified as type I, Ic, IIa and IIb. Hypertrophy of the muscle was first observed about ten days after induction of CH. All fibre types appeared to contribute to this hypertrophy. During the period between four and twenty eight days there was a marked increase in the percentage of type I fibres, mainly at the expense of type IIa, as compared with control muscles. During this CH period so called 'intermediate' Ic fibres were found, indicating fibre type transition taking place. The isometric twitch time to peak tension (TPT) of the plantaris muscle was studied in situ. The TPT of CH muscles remained the same during the experimental period of seven weeks. This might be explained by the effect of the increase in type I (slow) fibres being masked by the far larger number of fast fibres, which still accounted for approximately 79% of the total number of fibres after CH.

Aging↗
PubMed1995

[Spiral computerized tomography, multiplane transesophageal echocardiography and magnetic resonance imaging in the diagnosis of thoracic aortic dissection].

The aim of this study was the evaluation of spiral computed tomography (Spiral-CT), multiplane transesophageal echocardiography (multiplane TEE) and magnetic resonance imaging (MRI) in the diagnosis of thoracic aortic dissection. 41 patients were examined: 30 with clinically suspected acute aortic dissection (14 Stanford A, 7 Stanford B), 11 with aortic repair (7/11 with persisting distal dissection). In 14 patients there was involvement of the supraaortic vessels. Sensitivity of Spiral-CT, multiplane TEE and MRI in the detection of aortic dissection was 100%, specificity was 100, 92, and 91%. In the assessment of involvement of aortic arch vessels sensitivity was 100, 67, and 60%, specificity was 100, 95, and 90%. The new imaging modalities Spiral-CT and multiplane TEE are equal to MRI in the detection of aortic dissection. In the assessment of the supraaortic branches Spiral-CT is superior to multiplane TEE and MRI and might become the method of choice.

Adult↗
PubMed1995

Adolescent diabetes management and mismanagement.

OBJECTIVE: To document the existence and prevalence of adolescent-generated diabetes management techniques. RESEARCH DESIGN AND METHODS: One hundred forty-four adolescents completed the confidential questionnaire developed for this study. Glycohemoglobin was also obtained for each individual. RESULTS: Within the 10 days before their clinic visit, many adolescents admitted to engaging in various mismanagement behaviors, with 25% admitting to missing shots. Parents tend to underestimate adolescent mismanagement. Missing shots was significantly related to poor control (P < 0.01). Older adolescents engaged in more mismanagement than their younger cohorts (P < 0.001). The questionnaire factored into two subscales: blatant mismanagement and faking. CONCLUSIONS: This study shows the importance of recognizing the prevalence of mismanagement among adolescents.

Adolescent↗
PubMed1995

[Hearing screening within the scope of pediatric U5 preventive examination: can diagnosis be improved by use of a parent questionnaire?].

OBJECTIVE: Assessment of a) the efficacy of hearing loss screening in baby check-ups at the age of 6 to 8 months b) the efficiency and efficacy using parent questionnaires about hearing loss risk factors and parents' concern about the child's hearing as part of baby check-up. METHODS: The analyses are based on 7282 baby check-ups carried out in 47 pediatricians' offices in the Düsseldorf area from July 1991 to March 1993: 3385 of these check-ups were performed in the traditional manner (period A; July 1, 1991, to January 1, 1992; 3897 check-ups involved parent questionnaires (period B June 1, 1992, to March 31, 1993). All children who failed the tests and a random sample of those who had passed the test when tested in the traditional manner, were offered extensive hearing assessment. RESULTS: In period A, 4.3% of the children failed the test as compared to 21.7% with the first version of the questionnaire and 14.3% with a revised questionnaire in period B. Compliance to the offer of extensive hearing assessment was unsatisfactory (53% in period A and 63% in period B). The first extensive hearing examination failed to distinguish healthy children from children with probable sensorineural hearing loss in about 30% of the patients, mainly because of glue ear. One child with sensorineural hearing loss was identified by the screening in period A as compared to six children in period B. CONCLUSIONS: 1) The systematic use of parent questionnaires in baby check-ups at ages 6 to 8 months is likely to increase the efficacy of the screening. 2) The efficiency of the questionnaires currently in use, however, needs to be improved and can be improved with the data from the study. 3) The compliance with extensive hearing testing in children who have failed the screening test must be improved. 4) Due to the high prevalence of conductive hearing loss in this age group, treatment of potential glue ear problems is mandatory before referral for extensive testing for sensorineural hearing loss.

Deafness↗
PubMed1994

[Cerebral circulation in patients with dilated cardiomyopathy and aortic valve diseases].

The present study was performed in order to investigate the effect of dilated cardiomyopathy and severe aortic valve disease on cerebral blood flow. Cerebral perfusion was determined in 39 healthy volunteers representing two control groups of different age (77.7 +/- 8.7; 79.7 +/- 8.1 ml/100 g/min), in 7 patients with dilated cardiomyopathy (64.0 +/- 4.7 ml/100 g/min), in 11 patients with severe aortic stenosis (71.1 +/- 14.8 ml/100 g/min), and in 6 patients with severe aortic regurgitation (54.6 +/- 5.8 ml/100 g/min). Regional cerebral blood flow was measured with the 133Xenon inhalation method. Cerebral blood flow in severe aortic regurgitation patients (p = 0.006) was markedly and significantly reduced versus controls, whereas in dilated cardiomyopathy patients (p = 0.197) and in patients with severe aortic stenosis (p = 0.111) cerebral blood flow was not significantly reduced. A chronic adaptation of cerebral blood flow to the profound reduction of cardiac output is assumed in dilated cardiomyopathy patients. The collapsing pulse and the maximal reduction of mean arterial blood pressure in severe aortic regurgitation patients cause the reduction of autoregulatory capacity of cerebral blood flow with subsequent decrease of brain perfusion. Measurement of cerebral blood flow appears to be suitable for evaluation of perfusion deficits due to cardiac abnormalities. It provides an additional parameter for estimating the indication of valve replacement in patients with aortic valve disease.

Adult↗
PubMed1993

Demineralized bone powder. Clinical applications for bone defects of the hand.

The results of 20 consecutive cases of bone defects of the hand treated by curettage and implantation of demineralized bone powder compare well with a similarly matched retrospective group managed with autogenous grafts and curettage alone. Results revealed "excellent" (16 patients) or "good" bone healing (4 patients) in the bone powder group on independent radiographic evaluation. Bone bridging was noted at an average of 9.9 weeks. All defects healed without recurrence, resorption or refracture, with follow-up of 4 to 36 months. In the conventionally managed retrospective group there was a 25% failure rate necessitating re-operation. Demineralized bone powder provides a rapid, safe and effective method of management of bone defects of the hand.

Adult↗
PubMed1993

[Effect of frequent ventricular extrasystole on brain circulation in patients with coronary heart disease].

Animal experiments using the microsphere method indicate a 8% reduction of mean cerebral blood flow during parasystolic rhythm induced by ventricular pacing in comparison to a control group with sinus rhythm. The parasystolic rhythm causes changes of systemic arterial blood pressure, which are comparable to the hemodynamic effects of frequent premature ventricular contractions. Because a reduction of cerebral blood flow induced by frequent premature ventricular beats can be assumed by the results of the laboratory investigations, cerebral blood flow was determined in a clinical study in 19 coronary artery disease patients and in 11 healthy, age-adjusted volunteers using the 133Xenon-inhalation method, in order to investigate the effect of ventricular ectopics on cerebral perfusion. Simultaneously Holter monitoring was performed during cerebral blood flow measurements. Cerebral blood flow was estimated by the initial slope index, which is calculated from the early decay of the clearance curve, and by the mean cerebral blood flow index, which is calculated by the stochastic method. Grey matter blood flow is estimated by the two-compartment analysis. Cerebral blood flow in coronary artery disease patients is reduced versus controls. The initial slope indices were 45.2 +/- 5.1 s-1 and 57.4 +/- 7.2(-1), respectively (p < 0.01). In patients with frequent ventricular ectopic activity (739/h) an additional reduction of cerebral blood flow was observed. The initial slope index was 42.6 +/- 6.3 s-1 (p < 0.01). The reduction of cerebral blood flow in coronary artery disease patients is partially due to the coincidence of coronary and cerebral artery disease. Frequent ventricular premature contractions might cause an additional reduction.

Adult↗
PubMed1993

[Effect of a filter system on measurement data and bacterial contamination in lung function studies].

80 measurements of the airway resistance of 20 patients did not yield any significant differences with or without using a bacterial filter (Pall PF 30) (p = 0.1213). Likewise, lung function tests conducted in 61 further patients did not reveal any relevant changes caused by introducing the filter, in respect of the lung function parameters VKin, FEV1, PEF, FEF25, FEF50, FEF75 and TLCO. In these studies the flow receptors were examined for contamination by bacteria. The introduction of the bacterial filter reduced the total count of identified germs from 108, 615 to 307, i.e. by 99.7 per cent, the greatest contamination being found in those parts that were close to the patient (57.6% with filter, 97.1% without filter). Germs of the resident flora of the mouth and pharynx were identified, and occasionally also potential infectious agents such as staphylococcus aureus and streptococcus pneumoniae. The use of a filter system results in a marked decrease in the exposition to germs in lung function tests, without exercising any adverse effect on the measurement data (cross-contamination risk: 0.00078%). This is also achieved--albeit to a lesser extent--by changing those parts of the flow receptor that are close to the patient (cross-contamination risk: 0.0841%). Hence, the use of a filter system appears particularly meaningful in patients with considerable immunodeficiency (advanced stages of HIV infection).

Airway Resistance↗