Biomedical subjects

A Hofmann

Publications and source records attributed to A Hofmann.

At least 19 recordsLinked to original sources

PubMed2002

PCSB--a program collection for structural biology and biophysical chemistry.

We present the first package of Java classes specifically aimed at the handling of structural and biophysical problems. To enable object-oriented programming a basis of fundamental Java classes is required which deals with basic operations of vectors, matrices, amino acid sequences, crystal symmetries and PDB files. Five classes, which carry out these basic operations, were constructed and bundled together with several utility functions in the PCSB package. Furthermore, to demonstrate their applicability and to obtain programs handling common tasks in structural laboratories, we present the first six applications of PCSB. All applications are portable to different platforms and require only the Java Runtime Environment to be installed on the system. available as PDF file.

Algorithms↗

PubMed2001

[Post-traumatic kyphosis of the truncal vertebrae].

Assessing the initial post-traumatic situation is of imminent importance in choosing the most suitable approach for primary treatment of thoracic and lumbar spine fractures. Misjudging the static situation of the injured spine is a common reason for selecting an inadequate therapeutic procedure. The consequence is a defective spinal position with the corresponding symptoms, which usually requires a complicated surgical procedure. Our experience is based on 34 patients with a post-traumatic defective position of the thoracic and lumbar spine: 12 patients underwent primary surgical and 22 primary conservative treatment. The aim of our study was to demonstrate the initial situation and primary management as well as subsequent problems and the respective surgical procedure applied in our department for correcting and stabilizing the areas involved and to present intermediate results.

Adolescent↗

PubMed2001

Daytime variations in central nervous system activation measured by a pupillographic sleepiness test.

Pupil size is regulated exclusively by the autonomic nervous system, and in darkness is proportional to the level of central sympathetic tone. Spontaneous pupillary movements, while at rest in darkness and quiet, were recorded for a period of 11 min, using infrared video pupillography. Thirteen young adults took part in a 30-h experiment lasting from 08.00 h to 14.00 h on the following day. Pupillographic testing and completion of a self-rated scale for the estimate of sleepiness were repeated every two hours. Pupillary unrest index (PUI), as a measure of pupil size instability associated with daytime sleepiness, showed the lowest values at 09.00 h, when pupil size was found to be maximal, and 23.00 h. During the course of the day, amplitude spectrum < or = 0.8 Hz and PUI showed increasing values during the afternoon hours, followed by a decrease during the evening. Daytime variations in the pupillary unrest index in healthy normal subjects were found to be positively correlated with the level of alertness. These findings are similar to the daytime variations found by the MSLT (multiple sleep latency test) in young adults.

Adult↗

PubMed2000

S100A1 and S100B interactions with annexins.

Members of the annexin protein family interact with members of the S100 protein family thereby forming heterotetramers in which an S100 homodimer crossbridges two copies of the pertinent annexin. Previous work has shown that S100A1 and S100B bind annexin VI in a Ca(2+)-dependent manner and that annexin VI, but not annexin V, blocks the inhibitory effect of S100A1 and S100B on intermediate filament assembly. We show here that both halves of annexin VI (i.e., the N-terminal half or annexin VI-a and the C-terminal half or annexin VI-b) bind individual S100s on unique sites and that annexin VI-b, but not annexin VI-a, blocks the ability of S100A1 and S100B to inhibit intermediate filament assembly. We also show that the C-terminal extension of S100A1 (and, by analogy, S100B), that was previously demonstrated to be critical for S100A1 and S100B binding to several target proteins including intermediate filament subunits, is not part of the S100 surface implicated in the recognition of annexin VI, annexin VI-a, or annexin VI-b. Evaluation of functional properties with a liposome stability and a calcium influx assay reveals the ability of both S100 proteins to permeabilize the membrane bilayer in a similar fashion like annexins. When tested in combinations with different annexin proteins both S100 proteins mostly lead to a decrease in the calcium influx activity although not all annexin/S100 combinations behave in the same manner. Latter observation supports the hypothesis that the S100-annexin interactions differ mechanistically depending on the particular protein partners.

Animals↗

PubMed2000

Structure and mechanism of activity of the cyclic phosphodiesterase of Appr>p, a product of the tRNA splicing reaction.

The crystal structure of the cyclic phosphodiesterase (CPDase) from Arabidopsis thaliana, an enzyme involved in the tRNA splicing pathway, was determined at 2.5 A resolution. CPDase hydrolyzes ADP-ribose 1",2"-cyclic phosphate (Appr>p), a product of the tRNA splicing reaction, to the monoester ADP-ribose 1"-phosphate (Appr-1"p). The 181 amino acid protein shows a novel, bilobal arrangement of two alphabeta modules. Each lobe consists of two alpha-helices on the outer side of the molecule, framing a three- or four-stranded antiparallel beta-sheet in the core of the protein. The active site is formed at the interface of the two beta-sheets in a water-filled cavity involving residues from two H-X-T/S-X motifs. This previously noticed motif participates in coordination of a sulfate ion. A solvent-exposed surface loop (residues 100-115) is very likely to play a flap-like role, opening and closing the active site. Based on the crystal structure and on recent mutagenesis studies of a homologous CPDase from Saccharomyces cerevisiae, we propose an enzymatic mechanism that employs the nucleophilic attack of a water molecule activated by one of the active site histidines.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed2000

Crystal structure of paprika ferredoxin-NADP+ reductase. Implications for the electron transfer pathway.

cDNA of Capsicum annuum Yolo Wonder (paprika) has been prepared from total cellular RNA, and the complete gene encoding paprika ferredoxin-NADP(+) reductase (pFNR) precursor was sequenced and cloned from this cDNA. Fusion to a T7 promoter allowed expression in Escherichia coli. Both native and recombinant pFNR were purified to homogeneity and crystallized. The crystal structure of pFNR has been solved by Patterson search techniques using the structure of spinach ferredoxin-NADP(+) reductase as search model. The structure was refined at 2.5-A resolution to a crystallographic R-factor of 19.8% (R(free) = 26.5%). The overall structure of pFNR is similar to other members of the ferredoxin-NADP(+) reductase family, the major differences concern a long loop (residues 167-177) that forms part of the FAD binding site and some of the variable loops in surface regions. The different orientation of the FAD binding loop leads to a tighter interaction between pFNR and the adenine moiety of FAD. The physiological redox partners [2Fe-2S]-ferredoxin I and NADP(+) were modeled into the native structure of pFNR. The complexes reveal a protein-protein interaction site that is consistent with existing biochemical data and imply possible orientations for the side chain of tyrosine 362, which has to be displaced by the nicotinamide moiety of NADP(+) upon binding. A reasonable electron transfer pathway could be deduced from the modeled structures of the complexes.

Amino Acid Sequence↗

PubMed2000

The annexin A3-membrane interaction is modulated by an N-terminal tryptophan.

The crystal structure of annexin A3 (human annexin III) solved recently revealed a well-ordered folding of its N-terminus with the side chain of tryptophan 5 interacting with residues at the extremity of the central pore. Since the pore of annexins has been suggested as the ion pathway involved in membrane permeabilization by these proteins, we investigated the effect of the N-terminal tryptophan on the channel activity of annexin A3 by a comparative study of the wild-type and the W5A mutant in structural and functional aspects. Calcium influx and patch-clamp recordings revealed that the mutant exhibited an enhanced membrane permeabilization activity as compared to the wild-type protein. Analysis of the phospholipid binding behavior of wild-type and mutant protein was carried out by cosedimentation with lipids and inhibition of PLA(2) activity. Both methods reveal a much stronger binding of the mutant to phospholipids. The structure is very similar for the wild-type and the mutant protein. The exchange of the tryptophan for an alanine results in a disordered N-terminal segment. Urea-induced denaturation of the wild-type and mutant monitored by intrinsic fluorescence indicates a separate unfolding of the N-terminal region which occurs at lower urea concentrations than unfolding of the protein core. We therefore conclude that the N-terminal domain of annexin A3, and especially tryptophan 5, is involved in the modulation of membrane binding and permeabilization by annexin A3.

Alanine↗

PubMed2000

Monitoring the virus load can predict the emergence of drug-resistant hepatitis B virus strains in renal transplantation patients during lamivudine therapy.

The development of resistant hepatitis B virus (HBV) strains during lamivudine treatment has been described repeatedly. To investigate whether the development of such resistant HBV strains can be predicted in an early phase of therapy, the HBV loads of 11 renal transplantation patients were screened at 3-month intervals by a quantitative HBV polymerase chain reaction (PCR) assay. Lamivudine resistance was detected by sequence analysis. Five patients developed resistance to lamivudine in the 12-15-month follow-up period. In all of them, a virus load of 1x103 HBV DNA copies still was detectable after 3 months of therapy. This was statistically significantly different from those patients who did not develop lamivudine resistance within the observation period, all of whom had no HBV DNA detectable after 3 months of treatment (P=.0022). Thus, virus load testing by use of a sensitive PCR assay allows the early prediction of the emergence of lamivudine-resistant HBV strains.

Adult↗

PubMed2000

Annexin 24 from Capsicum annuum. X-ray structure and biochemical characterization.

This work provides the first three-dimensional structure of a member of the plant annexin family and correlates these findings with biochemical properties of this protein. Annexin 24(Ca32) from Capsicum annuum was purified as a native protein from bell pepper and was also prepared by recombinant techniques. To overcome the problem of precipitation of the recombinant wild-type protein in crystallization trials, two mutants were designed. Whereas an N-terminal truncation mutant turned out to be an unstable protein, the N-terminal His-tagged annexin 24(Ca32) was crystallized, and the three-dimensional structure was determined by x-ray diffraction at 2. 8 A resolution. The structure refined to an R-factor of 0.216 adopts the typical annexin fold; the detailed structure, however, is different from non-plant annexins, especially in domains I and III and in the membrane binding loops on the convex side. Within the unit cell there are two molecules per asymmetric unit, which differ in conformation of the IAB-loop. Both conformers show Trp-35 on the surface. The loop-out conformation is stabilized by tight interactions of this tryptophan with residue side chains of a symmetry-related molecule and enforced by a bound sulfate. Characterization of this plant annexin using biophysical methods revealed calcium-dependent binding to phospholipid vesicles with preference for phosphatidylcholine over phosphatidylserine and magnesium-dependent phosphodiesterase activity in vitro as shown with adenosine triphosphate as the substrate. A comparative unfolding study of recombinant annexin 24(Ca32) wild type and of the His-tag fusion protein indicates higher stability of the latter. The effect of this N-terminal modification is also visible from CD spectra. Both proteins were subjected to a FURA-2-based calcium influx assay, which gave high influx rates for the wild-type but greatly reduced influx rates for the fusion protein. We therefore conclude that the N-terminal domain is indeed a major regulatory element modulating different annexin properties by allosteric mechanisms.

Adenosine Triphosphatases↗

PubMed2000

[Micronuclei as biological markers for the detection of local cancer transformation in the upper aerodigestive tract].

A lot of different endogenous and exogenous factors are accused to promote squamous cell carcinomas in the upper aerodigestive tract. Main risk factors are the chronic tobacco- and alcohol consumption. The fact, that many patients develop syn- or metachronic carcinomas in this area was first described by Slaughter et al. 1953 and explained with the phenomenon of field cancerisation. Concerning to this hypothesis the whole mucosa of the upper aerodigestive-tract is premalignant damaged. In our study the micronucleus-frequency was determined as a biomarker for the genetic injury to prove the fieldcancerisation on the cellular level at 159 people (control-group, abuser, patients with HNSCC). Our results confirm the hypothesis of fieldcancerisation of the mucosa of the upper aerodigestive-tract at strong tobacco- and alcohol consumers and patients with head and neck squamous cell carcinoma. Furthermore there is a highly statistically significant correlation between increasing micronucleus frequency and increasing tobacco abuse. As a final result of our study the micronucleus assay seems to be of good value to show a genotoxic damage in healthy mucosa at people with a high risk to develop HNSCC, but it's not usable to give any answer if and when such carcinomas arise.

Alcohol Drinking↗

PubMed2000

[Effect of various bone disinfection and sterilization methods on osteoblast function. A comparative in vitro study].

All sterilization and disinfection procedures for bone grafts are different in regard to influence of bone graft features, which may influence the function of different cell types. We used an in-vitro approach to assess the influence of bone matrix, which was sterilized or disinfected, on osteoblastic activities in-vitro by simulating a cell-transplant-interface. Primary bovine osteoblast cell cultures were established from periosteum. Bone graft specimens made of bovine cortical bone (O 15 mm, 300 microns thickness) were treated in 5 different ways: autoclaved, ethylene-oxide-sterilized, demineralized and low-temperature-plasma-sterilized (DEM-LTP), chemically sterilized (modified Tutoplast method), and 80 degrees C-temperature disinfected. The following cell function parameters were assayed: plating efficiency proliferation by measuring the DNA-content, and MTT-activity, soluble protein and extracellular matrix synthesis, alkaline phosphatase, and osteocalcin expression. All disinfected bone grafts were biocompatible with primary periosteal osteoblasts. Measured cell activities upon bone specimens showed better results than cells of the plastic surface control. The DEM-LTP-bone showed better results in comparison to other groups, and stimulated the proliferation and differentiation.

Animals↗

PubMed2000

Atypical effect of minoxidil sulphate on guinea pig airways.

The effects of minoxidil sulphate, an "atypical" K(ATP) channel opener, and bimakalim, a benzopyran-type classical K(ATP) channel opener, on guinea pig airways in vitro and in vivo and on isolated portal veins from rats and guinea pigs were compared. Minoxidil sulphate inhibited the spontaneous activity of isolated guinea pig and rat portal vein preparations with pD2 values of 7.83+/-0.08 and 7.14+/-0.03, respectively (Emax=100% in both preparations). Bimakalim caused a more potent inhibition with pD2 values of 8.80+/-0.05 and 8.20+/-0.04, respectively (Emax=100% in both preparations). Minoxidil sulphate reduced the spontaneous tone of isolated guinea pig tracheal rings with a pIC50 value of 3.92+/-0.02 and the same efficacy as isoprenaline. Bimakalim was more potent (pIC50=7.25+/-0.02) but less efficacious (Emax=75% of the Emax of isoprenaline). The airway relaxant effect of bimakalim, but not minoxidil sulphate, was antagonised by glibenclamide (pA2=7.50) at concentrations above 0.1 microM. Bombesin-induced bronchoconstriction in anaesthetised, ventilated, normoreactive guinea pigs (measured as increase in total lung resistance) was dose-dependently reversed by intratracheally (i.t.) administered bimakalim (ED50=4 microg/kg; Emax=92% of maximally possible inhibition), but not by minoxidil sulphate, at doses up to 1 mg/kg i.t. In the same animals, following i.t. administration of higher doses, both minoxidil sulphate and bimakalim reduced blood pressure. Airways hyperreactivity to histamine induced by acute treatment of guinea pigs with immune complex was dose-dependently reversed by bimakalim (ED50=0.5 microg/kg i.t., Emax=100%). This effect was antagonised by glibenclamide (30 mg/kg i.v.). Minoxidil sulphate had a biphasic effect on airways hyperreactivity: at 1 microg/kg i.t., airways hyperreactivity was augmented, whereas at doses above 3.2 microg/kg i.t. it caused reversal of airways hyperreactivity. Both of the effects of minoxidil sulphate were insensitive to glibenclamide (30 mg/kg i.v.). It is concluded that the pharmacological profile of minoxidil sulphate in guinea pig airways is completely different from that of classical K(ATP) channel openers such as bimakalim. Minoxidil sulphate is either only weakly active or even inactive at K(ATP) channels in guinea pig airways or interacts with these channels in a different manner. The current results are consistent with there being differences between the K(ATP) channels in airways and blood vessels.

Adenosine Triphosphate↗

PubMed2000

Prevalence of GB virus C/hepatitis G virus RNA and anti-E2 glycoprotein antibodies in homosexual men with HIV coinfection.

BACKGROUND: The objective of this cross-sectional, nonrandomized, prospective study was to generate data on the prevalence of GB virus C (GBV-C)/hepatitis G virus (HGV) in a cohort of HIV-infected homosexuals from Munich. PATIENTS: A total of 71 HIV-infected homosexual men were analyzed for prevalence of GBV-C RNA and antibodies to the E2 envelope glycoprotein (E2Ab). 475 healthy volunteer blood donors in southern Bavaria served as a control group. RESULTS: The prevalence of GBV-C RNA was 27% (control group: 2.3%) and the prevalence of E2Ab was 35% (control group: 6%). The total prevalence for present and past infection was 62%. The differences between the HIV-infected patients and the control group were significant (p < 0.0001). GBV-C RNA and E2Ab were not detected simultaneously in any serum sample. The E2Ab positive patients were older than the GBV-C RNA positives (mean 46 years versus 39 years, p = 0.0350). The GBV-C RNA and E2Ab negative patients were older than the GBV-C RNA positives (mean 47 years versus 39 years, p = 0.0236). The E2Ab positive patients had suffered sexually transmitted diseases more frequently than the patients negative for markers of GBV-C infection (p = 0.0308). E2Ab positive patients also had higher mean levels of alanine aminotransferase compared to patients without evidence of GBV-C infection (p = 0.0164). 59.4% of all individuals were anti-HBc IgG positive. CONCLUSION: The data can be interpreted as indirect evidence for sexual transmission of GBV-C.

Adult↗

PubMed2000

Cultivated H-RS cells are resistant to CD95L-mediated apoptosis despite expression of wild-type CD95.

OBJECTIVE: In most cases of classic Hodgkin's disease (HD), Hodgkin and Reed-Sternberg (H-RS) cells clonally derive from germinal-center B cells. Within their rearranged immunoglobulin genes, somatic mutations rendering potentially functional immunoglobulin gene rearrangements nonfunctional were detected, indicating that H-RS cells do not express a B-cell receptor. Under physiologic conditions, these cells would undergo apoptosis within the germinal center. However, H-RS cells clonally expand, disseminate, and lead to clonal relapse of HD, indicating their resistance to induced programmed cell death. The underlying mechanism remains to be elucidated. MATERIALS AND METHODS: [corrected] Analysis of receptor-ligand interactions in primary H-RS cells is difficult to perform due to their scarcity in vivo and their low proliferation rate in vitro. Therefore, two [corrected] B-cellular H-RS cell lines (L1236 and L428) were used to test for the expression of CD95 by flow cytometry and for the induction of apoptosis after incubation with CD95L obtained from retrovirally transduced murine myoblasts. Sequence analysis of CD95 cDNA obtained from these H-RS cell lines was performed. RESULTS: Expression of CD95 on the cell surface was detected in both cell lines. However, after incubation with CD95L, the cells did not undergo apoptosis. To test whether mutations within the CD95 cDNA sequence caused resistance to apoptosis in H-RS cells, sequence analysis of CD95 cDNA obtained from L1236 and L428 was performed. In both cell lines, CD95 was not affected by somatic mutations. CONCLUSIONS: Our results indicate that the two H-RS cell lines L1236 and L428 are resistant to CD95-mediated apoptosis induced via CD95L, although wild-type CD95 is expressed. For further characterization of the mechanisms leading to prevention of apoptotic cell death in H-RS cells, it is necessary to determine impairments within the signaling cascade following CD95 activation.

Apoptosis↗

PubMed2000

Studies on the influence of a Se-restricted diet on the effects of long-term increased copper intake in guinea pigs.

Guinea pigs were exposed to Se-restriction/deficiency in combination with drinking water containing 200 or 300 mg Cu/l for 6-30 weeks. Under the influence of Se-restriction/deficiency Cu excretion by bile was diminished, the Cu content of the kidneys was increased and disturbances of liver function were seen in animals exposed for prolonged periods. Some parameters of the immune system, such as the phagocytic activity of peritoneal macrophages, mitogenicity of spleen lymphocytes and the amount of lymphatic spleen tissue were also adversely affected. These effects correlated in part with the liver damage and the copper content of the kidneys. Conclusion are drawn with respect to the Idiopathic Copper Toxicosis/Indian Childhood Cirrhosis.

Animals↗

PubMed2000

Exfoliative cytology of normal buccal mucosa to predict the relative risk of cancer in the upper aerodigestive tract using the MN-assay.

The high frequency of second or third primary tumors was first explained by Slaughter et al. with the concept of field cancerisation. Another theory postulates micrometastatic lesions as a reason for this phenomenon. The micronuclei (MN)-assay was evaluated to provide evidence for the concept of field cancerisation and to quantify the premalignant field change of normal mucosa in order to predict the individual cancer risk. MN-assay was carried out in 55 patients with squamous cell carcinoma of the head and neck, in 16 patients with a leucoplakia and in 99 healthy controls. A detailed questionnaire for population monitoring was completed. Buccal cytosmears of healthy mucosa of the study participants were examined for the MN count per 1000 cells. There was a direct correlation between tobacco abuse and increasing MN count as a sign of a cytogenetic damage of buccal mucosa cells. Alcohol did not influence the formation of MN. Both buccal sites were damaged in the same degree as proof of field cancerisation. The relative cancer risk (odds ratio) for smoking healthy controls with a definite MN frequency was estimated. Our study underscores the importance of the MN-assay as a biomarker to predict the relative cancer risk in the upper aerodigestive tract under suspicion of the individual susceptibility and the exposition to known carcinogenic agents such as tobacco and alcohol. The concept of field cancerisation was confirmed.

Biomarkers↗

PubMed2000

Filtered platelet concentrates from pooled buffy coats show comparable storage lesions when stored for 9 d at 20-24 degrees C or when supplemented with thromboSol at 2-6 degrees C.

The present study investigated the quality of platelet concentrates from pooled buffy coat (PCBC) along different production steps and during storage to characterize storage lesions reflected by platelet activation, changing metabolic and cell turnover status (pH, LDH activity). These criteria were compared in conventionally stored PCBCs (20-24 degrees C, n = 8, Group I) to cold stored PCBCs (2-6 degrees C, n = 8, Group II) when supplemented with ThromboSol. Platelet activation was measured on days 1, 3, 7 and 9 by flow cytometry using fluoresceinisothiocyanate-labeled monoclonal antibodies (mAbs) against glycoprotein IIb/IIIa (CD41a, PAC-1 and LIBS-1), P-selectin (CD62P) or CD40 ligand receptor (CD40L) in combination with a phycoerythrin-labeled panspecific platelet marker against GPIb (CD42b). The platelet activation assessed with mAbs PAC-1, CD41a, LIBS-1 and CD40L showed an overall activation of 98 +/- 4% (mean value +/- 1 SD) at day 7 in both groups, except for CD62P, which was significantly lower in Group II. A storage-dependent greater platelet loss occurred in Group II compared to Group I, 42% vs. 19% (p < 0.05 on day 9). We could demonstrate that platelets stored in ThromboSol show about the same in-vitro activation as conventionally stored PCBCs, but their clinical usefulness needs to be investigated.

Adult↗

PubMed2000

[Spine stabilizing muscles in golfers].

Although golf is perceived as a sport with low risk for injury, majority of golf players complain about problems along the spine. One possible reason could be poor physical condition. To see if golf players in general show deficits in spine-stabilizing muscles, twenty-three male golfers without back pain were examined with regard to their maximal isometric strength of trunk muscles. They were compared with persons of same age and constitution that do no sports. The Golf players have highly significant stronger lumbar extensors and show muscular dysbalance in lateral flexors and rotators of the spine. Specific training for well-balanced strengthening of spine-stabilizing muscles seem to be advisable, because muscular dysbalance can contribute to the development of back pain.

Back Pain↗