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Biomedical subjects

D Hahn

Publications and source records attributed to D Hahn.

At least 163 records · Page 9Linked to original sources
PubMed1996

Altered expression of nuclear genes encoding chloroplast polypeptides in non-photosynthetic mutants of Chlamydomonas reinhardtii: evidence for post-transcriptional regulation.

In photoautotrophic organisms it is well documented that the expression of nuclear genes encoding plastid proteins can be regulated at various levels. We present here the analysis of a non-photosynthetic strain (CC1051) of the green unicellular alga Chlamydomonas reinhardtii; this strain carries a mutation in the newly identified Cen gene involved in the co-regulated expression of several different nuclear genes encoding plastid proteins. We performed a differential screening strategy to isolate cDNAs corresponding to genes that are differentially expressed in mutant and wild-type strains. Extensive hybridization experiments revealed that the 15 cDNA clones isolated represent five different mRNAs that fail to accumulate in the non-photosynthetic mutant. Comparative analysis of DNA sequencing data showed that they all code for plastid proteins. In particular, we identified genes for the chlorophyll a/b binding protein of the light-harvesting complex II (LHCII), for subunits II and III of photosystem I (PsaD, PsaF), for pentose-5-phosphate 3-epimerase (PPE), an enzyme of the Calvin cycle, and for an unidentified 7 kDa protein with a suggested lumenal location. With the exception of the gene for LHCII, all proteins are encoded by single-copy genes. Evidence from run-on transcription experiments is presented showing that expression of the above mentioned plastid proteins is affected at the post-transcriptional level in the mutant strain CC1051 with a defect in the Cen gene. Our results suggest that the product of the Cen gene is involved in stabilization and/or processing of transcripts from nuclear genes encoding chloroplast proteins.

Amino Acid Sequence↗
PubMed1996

Two cytoplasmic domains of mammalian adenylyl cyclase form a Gs alpha- and forskolin-activated enzyme in vitro.

Mammalian adenylyl cyclases have two homologous cytoplasmic domains (C1 and C2). The first cytoplasmic domain of type I enzyme (IC1) and the second cytoplasmic domain of type II enzyme (IIC2-delta 3, a construct in which 36 N-terminal amino acids of the C2 region are deleted) were expressed and purified to homogeneity. Alone, each had no adenylyl cyclase activity; however, mixing of the two domains in vitro resulted in Gs alpha- and forskolin-activated enzyme activity. The turnover number for Gs alpha- and forskolin-stimulated enzyme activity of the complex between IC1 and IIC2-delta 3 was 8.2 s-1. The concentration of IIC2-delta 3 to achieve half-maximal activation of IC1 was 0.8 and 1.3 microM when stimulated by forskolin and Gs alpha, respectively. The concentration of IIC2-delta 3 needed to complex with IC1 was reduced 10-fold (0.08 microM) when the enzyme was activated by both forskolin and Gs alpha, suggesting that Gs alpha and forskolin increased the affinity of the two cytoplasmic domains for each other.

Adenylyl Cyclases↗
PubMed1996

Vascular patterns in reactive and malignant lymphadenopathy.

A total of 130 superficial lymph nodes were evaluated using color Doppler flow imaging (CDFI) in order to differentiate benign from malignant lymphadenopathy. The patterns of intranodal flow signals detected at standardized conditions by CDFI were classified using eight self-defined criteria and were correlated with the histopathological or clinical diagnosis. Nonparametric discriminant analysis showed that four vascular were suspicious of malignancy: (a) avascular areas, (b) displacement of intranodal vessels, (c) accessory peripheral vessels and (d) aberrant course of central vessels. Of the neoplastic lymph nodes (n = 73), 96% showed at least one pathological vascular pattern. Malignancy could be excluded in 95% of 57 reactive lymph nodes using these four criteria. Most reactive lymph nodes in contrast demonstrated a vascular hilus and/or vessels running at the long axis of the lymph node with branches to the cortex. There was a diagnostic accuracy of 41-82% in the additionally evaluated sonomorphological (size, shape, echogenicity) and Doppler (increased Pourcelot's or pulsatility indices) criteria. The definitive interpretation of the promising results of this retrospective study requires confirmation of examiner independency as well as a prospective evaluation.

Adolescent↗
PubMed1996

Computer-aided three dimensional assessment of knee-joint cartilage with magnetic resonance imaging.

OBJECTIVE: An MRI-based technique for non-invasive assessment of the quantitative distribution of articular cartilage in the knee-joint was to be developed, and its accuracy and reproducibility tested. DESIGN: Three cadaveric specimens and one patient were studied and MRI measurements compared with anatomical sections or arthroscopy. BACKGROUND: Data on articular cartilage thickness is needed for the design of computer models, determination of cartilage material properties from arthroscopy and staging of osteoarthrosis. METHODS: The knees were imaged using strongly T2-weighted spin-echo and FISP-3D sequences. After digital subtraction and automatic segmentation, three-dimensional reconstruction of the cartilages was performed. Surface areas, volumes and the mean cartilage thickness were calculated, and the regional distribution displayed after trigonometric correction. RESULTS: The difference between MRI volumes and those obtained from the sections ranged from 4 to 21% with a reproducibility of +/-4 to +/-12% after repositioning. The thickness maps obtained with MRI were very similar to those from the sections. In the patient, a full-thickness defect demonstrated with MRI was verified by arthroscopy. CONCLUSIONS: Using the technique presented, the quantitative distribution of knee-joint cartilage may be analysed non-invasively, accurately, and in a very time-effective manner, in cadavers and in living subjects. RELEVANCE: To date there exists no accepted method for the accurate, fast and non-invasive assessment of articular cartilage thickness. Such a technique is, however, very helpful for generating computer models of diarthrodial joints, determination of cartilage material properties during arthroscopy, staging of joint disease, and objective control of chondroprotective treatment.

Journal Article↗
PubMed1996

[Initial experiences with dilatation of dialysis shunts with color-coded duplex ultrasonography monitoring].

PURPOSE: Aim of the study was to evaluate the technical aspects of colour coded duplex sonography guided interventions of peripheral vessels. METHODS: During 15 months 39 stenoses of shunt veins in 24 patients were dilated guided by colour coded duplex sonography. RESULTS: 38 stenoses were dilated without complications. The blood flow volume was increased from 361.9 +/- 83.5 to 718.9 +/- 189.2 ml/min. In one case it was not possible to dilate the stenosis because of a vasospasm. CONCLUSION: PTA guided by colour coded duplex sonography is an alternative to DSA guided interventions of superficial vessels without x-ray exposure or contrast agent application.

Adult↗
PubMed1996

Fluconazole vs. amphotericin B for the treatment of neonatal fungal septicemia: a prospective randomized trial.

OBJECTIVE: Fungal septicemia is a devastating disease in the neonate, especially in the low birth weight preterm infant who is especially vulnerable to disseminated fungal sepsis. The objective of this study was to compare the efficacy, safety and overall convenience of fluconazole vs. amphotericin B for the treatment of disseminated fungal sepsis in neonates. DESIGN: A prospective, randomized, collaborative study conducted at two South African neonatal units. SUBJECTS: Twenty-four infants with proven fungal septicemia were treated from June, 1992, to June, 1993. Twelve received fluconazole, 11 received amphotericin B and 1 was excluded. Assessment of hepatic, renal and hematologic functions were performed before, during and after treatment. The two groups were comparable at the time of enrollment into the study. RESULTS: Infants receiving amphotericin B had significantly higher values of total and direct bilirubin and alkaline phosphatase values at the end of treatment, while the fluconazole group showed a significant increase in the platelet count. The cumulative total numbers of days receiving intravenous therapy for the administration of antifungal drugs were 57 for the fluconazole group and 162 for the amphotericin group; no central lines were needed in the fluconazole group, whereas 3 babies given amphotericin B had central catheters for a cumulative total of 27 days. The case fatality rate was 33% in the fluconazole group and 45% in the amphotericin B group; there was still proof of fungal septicemia at the time of death in 1 patient given amphotericin B and 2 given fluconazole. CONCLUSION: Fluconazole showed fewer side effects than amphotericin B and was more convenient to use.

Administration, Oral↗
PubMed1996

Evaluation of purified UspA from Moraxella catarrhalis as a vaccine in a murine model after active immunization.

Moraxella catarrhalis causes otitis media, laryngitis, and respiratory infections in humans. A high-molecular-weight outer membrane protein from this bacterium named ubiquitous surface protein A (UspA) is present on all isolates. A monoclonal antibody (MAb) to UspA that recognizes a conserved epitope of this protein has been shown to promote pulmonary clearance of bacteria in passively immunized mice. In the present study, M. catarrhalis heterologous isolates were screened by dot blot with a panel of four additional MAbs specific for surface-exposed epitopes of UspA from M. catarrhalis isolate 035E. Three of the MAbs were specific for 035E, and the fourth reacted with 17 (74%) of the 23 isolates tested. Thus, UspA contains highly conserved, semiconserved, and variable surface-exposed epitopes. The UspA was purified from the 035E isolate by ion-exchange and size-exclusion chromatography, formulated with the adjuvant QS-21, and used to immunize BALB/c mice. Upon pulmonary challenge with either 035E or the heterologous isolate TTA24, significantly fewer bacteria were recovered from the lungs of immunized mice 6 h postchallenge than from control mice. The immune sera from mice or guinea pigs contained high titers of antibodies to the homologous isolate and heterologous isolates in a whole-bacterial-cell enzyme-linked immunosorbent assay. Sera against UspA, whether prepared in mice or guinea pigs, had complement-dependent bactericidal activity toward homologous and 11 heterologous M. catarrhalis isolates. These results indicate that the conserved epitopes of the UspA are highly immunogenic and elicit broadly reactive and biologically functional antibodies. UspA may offer protection against M. catarrhalis infections and is being further evaluated as a vaccine candidate.

Animals↗
PubMed1996

The relationship between the palatal form and the maxillary sinus in orang-utan.

The relationship between the palatal form and the maxillary sinus was studied in 40 skulls of male and female Bornean orangutans (Pongo satyrus borneensis) ontogenetically. Univariate analyses of the measurements of the palate and the maxillary sinus showed that the sexual dimorphism appeared earlier in palatal length than in the maxillary sinus volume. Bivariate statistical analyses, including correlation and linear regression analyses, revealed close relationships between the characteristics of the palate and the maxillary sinus for both the growth period and the adult status. Partial correlation coefficients showed, however, that these relations were highly influenced by the skull size. Except significant correlations between the maxillary sinus width and the palatal volume in the adult status, all partial correlation coefficients were clearly below the Pearson's correlation coefficients. In contrast to the situation in humans, this study suggests that under physiological conditions the influence of the palatal form on the maxillary sinus size in the orang-utan is very small. Alterations of the craniofacial morphology during the evolution of the hominids, such as facial reduction and decrease of the maxillary sinus size, are considered important factors which led to changes of the relations between the palatal form and the maxillary sinus.

Animals↗
PubMed1996

Clavicular nonunion. 31/32 healed after plate fixation and bone grafting.

We report the long-term results in 32 patients with established nonunion of the clavicle; 15 treated with AO Dynamic Compression Plate and autologous cancellous bone graft and 17 treated with an AO reconstruction plate and autologous cancellous bone graft. The patients were followed up for a mean of 8 (4-21) years from injury and 7 (4-12) from non-union operation, both by clinical review and radiographs. 31/32 nonunions united successfully. One fracture which initially failed to unite was replated and subsequently united. 6 compression plates and 7 reconstruction plates were removed for discomfort or cosmesis. None broke. Both plates give equally good results, but we feel that the reconstruction plate is easier to contour to the complex form of the clavicle.

Activities of Daily Living↗
PubMed1995

[Quantification of lymph node perfusion using color duplex ultrasonography].

PURPOSE: 20 parameters were defined to differentiate benign from malignant lymphadenopathy using computer assisted analysis of the lymph node perfusion demonstrated by colour Doppler flow imaging. MATERIAL AND METHODS: In 112 lymph nodes a computer assisted analysis of 10 consecutive colour Doppler flow sonograms was performed after digital data transfer to a work station. Planimetric results, the colour coded Doppler shift frequency, changes of the perfusion during the heart cycle and the perfusion in the adjacent tissue were analysed using 20 parameters. RESULTS: Discriminant analysis resulted in 7 parameters which reclassified correctly 82% of the lymph nodes (sensitivity 84%, specificity 80%). 72% of the lymph nodes could be classified in the three groups reactive lymphadenopathy, lymph node metastasis and malignant lymphoma. CONCLUSIONS: Clinically known subjective signs of malignancy (increased size, low echogenicity, alterations of the perfusion) can be analysed quantitatively to differentiate benign from malignant lymphadenopathy.

Diagnosis, Differential↗
PubMed1995

Contributions of 31P-magnetic resonance spectroscopy to the understanding of dilated heart muscle disease.

In the present work, we studied clinical and haemodynamic correlates of impaired cardiac high-energy phosphate metabolism in patients with heart failure due to dilated cardiomyopathy (DCM). Myocardial 31P-magnetic resonance (MR) spectra were obtained at 1.5 T in 14 volunteers and 23 patients with DCM (mean ejection fraction 34%) in order to quantify the creatine phosphate (CP)/ATP ratio. In addition, patients underwent cardiac catheterization and echocardiography. Compared to volunteers (2.02 +/- 0.11), CP/ATP ratios were significantly reduced in DCM patients (1.54 +/- 0.10; P < 0.05), indicating impaired high-energy phosphate metabolism. CP/ATP ratios correlated with the clinical severity of heart failure estimated from the NYHA class (r = 0.47, P < 0.01); also, CP/ATP correlated with left ventricular ejection fraction (r = 0.54, P < 0.01) and left ventricular end-diastolic wall thickness (r = 0.51, P < 0.01). Thus, 31P-MR spectroscopy can detect abnormal cardiac high-energy phosphate metabolism in patients with heart failure due to DCM. These abnormalities correlate with clinical and haemodynamic parameters. Future studies will have to determine whether 31P-MR spectroscopy can contribute to the routine clinical evaluation of patients with heart failure.

Adenosine Triphosphate↗
PubMed1995

Growth pattern of the maxillary sinus in orang-utan based on measurements of CT scans.

The postnatal growth of the maxillary sinus was analyzed in 20 male and 20 female skulls of orang-utan (Pongo satyrus borneensis) in 5 age steps. Coronal CT scans were carried out of all skulls using a computed tomograph Siemens SOMATOM DR. The distances between the CT scans were always 4 mm. The outline of the maxillary sinus was surrounded on the CT scans with a planimeter and then the volumes were calculated. Using a growth model introduced by Fanghänel (1974), growth functions for the volume measurements for male and female animals were calculated separately. The growth curves showed a particular course, which was characterized by a quick rise until the age of 15 years. After the age of 20 years the curves for females orang-utan became gradually flat. At the age of 21 to 23 years the confidence intervals of the growth curves for male and female orang-utan began to drift apart, indicating the appearance of a sexual dimorphism. Using the basicranial length as an indicator of skull size, it becomes evident, that the sexual difference in the maxillary sinus' volume is probably based on the fact, that the maxillary sinus' volume of the male orang-utan increases further on following a common growth pattern.

Animals↗
PubMed1995

[Nonobstructive mesenteric ischemia--a diagnostic problem in internal intensive care].

Four cases of acute gut ischemia in elderly patients due to non-occlusive disease (NOD) are presented. Bowel necrosis occurred after episodes of hypotension in the course of myocardial infarction, arrhythmias and sepsis. Symptoms and clinical findings were blurred by the underlying extraintestinal disease. Angiography showed coexistent atherosclerosis but no occlusion of the major celiac and mesenteric vessels. At laparotomy (three cases) or autopsy (one case) extensive small and large bowel necroses were detected. Early laparotomy (possibly preceded by laparoscopy) is recommended for patients with suspected acute gut ischemia even if angiography fails to reveal occlusion of the large splanchnic arteries.

Aged↗