Circular permutation of polypeptide chains: implications for protein folding and stability.
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Amino Acid Sequence↗
Biomedical subjects
M Hahn
Publications and source records attributed to M Hahn.
Intervertebral variation in trabecular microarchitecture throughout the normal spine in relation to age.
The vertebral bodies of the complete spine (C-3-L-5) were removed in 26 autopsy cases without evidence for primary or secondary bone disease (13 males aged 19-79 years and 13 females aged 17-90 years). A sagittal segment through the center of all vertebral bodies was embedded undecalcified in hydroxyethylmethacrylate and processed to so-called surface stained block grindings. Histomorphometric analysis of the complete segment was performed using a computer-assisted image analysis system (IBAS 2000). The structural parameters investigated were bone volume (BV/TV) and trabecular interconnection quantificated by trabecular bone pattern factor (TBPf). A close correlation of BV/TV and TBPf was found in all vertebral bodies irrespective of vertebral region (r = 0.8, p < 0.001). This indicates that the age-related decrease of trabecular bone mass is primarily the consequence of the transformation from plates to rods and the loss of whole trabecular structures. This basic principle is valid throughout the complete spine. However, the systematic analysis of vertebral trabecular bone from C-3 to L-5 revealed a significant intervertebral variation of trabecular microarchitecture. The density of trabecular structure of cervical vertebrae is much higher than that of thoracic and lumbar vertebrae (p < 0.001). The extent of age-related loss of trabecular bone mass and structure showed a decrease within the spine from the caudal to the cranial region (p < 0.05). The loss of bone volume in individuals between the ages of 30 and 80 years in the lumbar spine was 53%, whereas in the thoracic spine the decrease was 41%, and in the cervical spine only 24%.(ABSTRACT TRUNCATED AT 250 WORDS)
Absorptiometry, Photon↗
Circular permutations of protein sequence: not so rare?
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Algorithms↗
Local cold exposure test as therapy control in patients with Raynaud's phenomenon: comparison between laser Doppler fluxmetry and simultaneous red blood cell velocity measurements in nailfold capillaries.
Synchronous measurement of laser Doppler flux (LDF) and capillary red blood cell velocity (CBV) was performed in adjacent areas of the same nailfold during a local cold stress test in 12 healthy controls (eight women and four men) and in 22 patients (17 women and seven men) with secondary Raynaud's phenomenon before and after treatment. Two questions were addressed: Are there any differences in the signal pattern between LDF and RBV? Is it possible to detect early on in therapy, before clinical benefit becomes obvious, whether a treatment is successful or not? Despite the fact that the resulting signal patterns recorded by these two techniques are widely compatible, certain differences could be observed. In healthy controls, decrease of values during cooling time and increase after cooling were more distinct in RBV than in LDF. Compared with control values, CBV and LDF in patients with Raynaud's phenomenon were lower. After cooling CBV took an average of 3 min to reach initial value again as compared with 40 s in healthy controls. During 4 min observation time, pretest values of LDF were not achieved again in patients, whereas it took 50 s in healthy controls. If, after a few days of vasospasmolytic therapy, test results improved or normalized, clinical symptoms subsided gradually during the next weeks. Clinical improvement was not observed in those patients in whom cutaneous blood flow remained decreased despite therapy. CBV indicated this more clearly than LDF. Duration of flow stop at the end of cooling showed a marked improvement in patients treated successfully. Discrepancies between CBV and LDF are interpreted as being due to LDF detecting other vessels in addition to the superficial, nutritional capillaries. LDF seemed to be a poor tool for evaluating the effect of treatment. Determination of CBV and flow stop duration during local cold exposure may help in early selection of the best treatment for a patient with Raynaud's phenomenon by predicting later possible clinical benefit.
Adult↗
A case of contact dermatitis from lichens in southern Germany.
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Aged↗
Structural heterogeneity within the axis: the main cause in the etiology of dens fractures. A histomorphometric analysis of 37 normal and osteoporotic autopsy cases.
Fractures of the odontoid process are potentially serious injuries; Type II and III fractures, as described by Anderson and D'Alonzo, are seen in the emergency room especially in young adolescents and individuals over 60 years of age. The etiology of these fractures is still controversial. Malunion and nonunion in both types of fractures are presumed to be due to insufficient external or internal fixation, but this theory has not been fully explained. To examine these issues, the authors expanded their prior studies of the anatomy of the axis. For histomorphometric analysis of cancellous and cortical bone, the axis was removed in 37 autopsies (26 normal and 11 osteoporotic cases) and sectioned in the sagittal plane to a thickness of 1 mm using a surface-stained block-grinding technique. The base of the dens is the region of least resistance for fractures because of its reduced trabecular bone volume, a poorer trabecular interconnection, and a cortical thickness one-third that of the axis. In all cases, trabeculae were disconnected from the trabecular lattice, and in 30%, microcallus formations were demonstrated in the base of the dens. A special filigree type of trabeculae in the base of the dens is often seen in patients with osteoporosis; microarchitectural differences of cancellous bone between the base of the dens and the other regions of the axis are also markedly increased. The authors infer from the data that the bone structure of the axis is responsible for the location, distribution, and frequency of fractures of the odontoid process in normal healthy bone and this frequency is greatly increased in individuals with osteoporosis. The deficiency of bone mass within the base also suggests a new explanation for the occurrence of nonunions, even after treatment of fractures of the base of the dens.
Adolescent↗
Semiautomated quantitative detection of loss of heterozygosity in the tumor suppressor gene p53.
The most frequently altered gene in diverse tumor types is the tumor suppressor gene p53. Typically, normal function is inactivated by point mutation of one allele and deletion of the other. Therefore, loss of heterozygosity (LOH) of intragenic polymorphic markers is a strong indication for p53 involvement in a cancerous lesion. This study shows that a highly polymorphic short tandem repeat (STR) within intron 1 of p53 is an excellent marker for quantitative evaluation of LOH in tumor samples, whose multicolor, fluorescently tagged PCR products are analyzed and quantitated on an automated DNA sequencer. The range of error was analyzed in detail. Discrete allelic profiles were obtained following amplification of DNA from microdissected cell samples of patients with urogenital tumors. By calculating qLOH, the relative allele ratio of a tumor compared with healthy tissue, a quantitative expression for the LOH is obtained. PCR-based tumor DNA typing using fluorescent STR primers and automated analysis provides an enhanced level of accuracy and sensitivity required for routine analysis in clinical practice, where large numbers of tumor samples have to be processed.
Alleles↗
Gunshot wounds to the forearm.
The rising incidence of civilian gunshot wounds has been well documented. Approximately 4% to 20% of these wounds consist of injuries to the forearm. An organized approach to the treatment of these injuries should be used to obtain an optimal result. Factors to be considered in treatment include the type of weapon and bullet involved, the neurovascular status of the patient, the possibility of compartment syndrome, the presence and type of fracture, and soft-tissue injury.
Algorithms↗
Native-like in vivo folding of a circularly permuted jellyroll protein shown by crystal structure analysis.
A jellyroll beta-sandwich protein, the Bacillus beta-glucanase H(A16-M), is used to probe the role of N-terminal peptide regions in protein folding in vivo. A gene encoding H(A16-M) is rearranged to place residues 1-58 of the protein behind a signal peptide and residues 59-214. The rearranged gene is expressed in Escherichia coli. The resultant circularly permuted protein, cpA16M-59, is secreted into the periplasm, correctly processed, and folded into a stable and active enzyme. Crystal structure analysis at 2.0-A resolution, R = 15.3%, shows cpA16M-59 to have a three-dimensional structure nearly identical with that of the parent beta-glucanase. An analogous experiment based on the wild-type Bacillus macerans beta-glucanase, giving rise to the circularly permuted variant cpMAC-57, yields the same results. Folding of these proteins, therefore, is not a vectorial process depending on the conformation adopted by their native N-terminal oligopeptides after ribosomal synthesis and translocation through the cytoplasmic membrane.
Amino Acid Sequence↗
The effect of rapid local cooling on human finger nailfold capillary blood pressure and blood cell velocity.
1. The effect of a rapid local reduction in finger temperature on finger nailfold capillary blood pressure and blood cell velocity was investigated in healthy subjects. 2. Cooling was achieved by placing the finger into an adjustable copper cylindrical finger holder, which incorporated a Peltier element within its base; thus the entire finger from just distal to the nailfold to the interphalangeal joint was cooled. The Peltier element was cooled to 8 degrees C for 5 min. 3. Finger tip temperature was reduced to 76 +/- 12% of its resting value during cooling (28.8 +/- 4.8 degrees C (mean +/- S.D.) baseline versus 22.1 +/- 6.4 degrees C in the fifth minute of cooling, P = 0.012); this was accompanied by a reduction in capillary blood cell velocity similar to that described previously in cooling experiments using cold air (baseline median, 671 microns s-1 (range, 29-4421 microns s-1) versus median during cooling, 221 microns s-1 (range, 6.7-2579 microns s-1), P = 0.012). 4. The magnitude and timing of the capillary pressure response to cooling and recovery varied between individuals. In the group as a whole, there was no significant fall in capillary pressure during cooling (basal before cooling, 16.7 +/- 3.7 mmHg versus minimum during cooling, 15.1 +/- 3.5 mmHg, P = 0.12), whereas capillary pulse pressure amplitude was reduced (basal before cooling, 5.3 +/- 3.1 mmHg versus minimum during cooling, 3.7 +/- 2.6 mmHg, P = 0.028). 5. During the recovery phase, post cooling, both capillary pressure and capillary pulse pressure amplitude were markedly elevated compared to baseline or the cooling phase.(ABSTRACT TRUNCATED AT 250 WORDS)
Acclimatization↗
The immortalized astroglial cell line RC7 is a new model system for the study of nerve growth factor (NGF) regulation: stimulation by interleukin-1 beta and transforming growth factor-beta 1 is additive and affected differently by dibutyryl cyclic AMP.
Nerve growth factor (NGF) synthesis was studied with an astroglial cell line derived from rat cerebellar astrocytes by transfection with a simian virus 40 T containing retroviral vector. As in primary astrocytes, NGF synthesis/secretion could be stimulated dose-dependently with interleukin-1 beta (IL-1 beta) and transforming growth factor-beta 1 (TGF-beta 1). We therefore have used this cell line as a model system to analyze putative intracellular signalling pathways underlying the effects of these factors. Protein kinase C inhibitors (calphostin and Ro 31-8830) as well as a lipoxygenase inhibitor (nordihydroguaiaretic acid) did not affect stimulation of NGF synthesis/secretion by IL-1 beta or TGF-beta 1. However, dibutyryl cyclic AMP partly inhibited the stimulation by TGF-beta 1 but did not affect that evoked by IL-1 beta. This finding, together with the fact that IL-1 beta and TGF-beta 1 stimulate NGF production/secretion in an additive manner, indicates that different intracellular signalling pathways are involved in the mediation of IL-1 beta and TGF-beta 1 induced NGF production/secretion.
Animals↗
[Imaging of alloplastic ligament implant. An in vivo and in vitro study exemplified by Kevlar].
Neither native X-ray nor CT or NMR allow to evaluate intraarticular implantation results of Kevlar -49 directly. In animal trials, the course of an artificial ligament may only be presumed from connective tissue ingrowth. Although soft tissue structure appears much better in NMR than in CT, direct proof of ligament continuity is still impossible. As soon as the connective tissue becomes continuous, it appears clearly and allows indirect evaluation of the prosthesis, as integrity can be judged by its shape like in natural cruciate ligament. Anatomic preparations show that connective tissue fills up the small space between the two cords of a Kevlar -49 two bundle prosthesis eight weeks after implantation, so that imaging systems show only one intraarticular bundle.
Animals↗
[Micro-callus formation of spongiosa. An up to now underestimated repair mechanism of the skeletal system].
Microcallus formations are demonstrable in nearly all cancellous bones by means of suitable preparation techniques. Histologically, these structures are immature fibrous bone formed in local overloaded parts of the trabeculae. Using a preparation technique that allows combined two- and three-dimensional analysis, 26 normal human spines and 11 osteoporotic spines were investigated for microcallus. Microcallus formations occur frequently in people over 45 years of age. They are mainly localized in the lower thoracic and lumbar spine and occur significantly more frequent in females than in males. The number of microcallus formations depends more on the microarchitecture of the cancellous bone than on individual trabecular parameters. In about 33% of cases microfractures are demonstrable in the centre of the microcallus formation. In non-invasive studies the bone mass could be misinterpreted due to microcallus. Although it indicates instability of the bone structure, microcallus formation is not a purely negative mechanism. It stabilizes and regenerates the bone tissue. Furthermore, complete new trabeculae can be formed due to bridges of microcallus between residual trabeculae. Osteoporosis is not the result of an inability to form microcallus.
Adolescent↗
Crystallographic studies of DNA helix structure.
X-ray crystallography can reveal the three-dimensional structure of short fragments of DNA or RNA with unique precision. It provides information concerning both the global helical structure and the geometry of local features such as base-pair stacking patterns and backbone conformation. An analysis of the structures of a family of DNA decamers with related sequences, crystallizing in a number of different lattices, defines the ranges in which conformational parameters can vary in B-DNA helices and shows the correlations between them. Thus, these studies show the static structures and give insight into the mechanics of DNA helices by showing how a change of one local conformational parameter will influence others. Crystal structures are also used to assess the competing influences of nucleotide sequence and environment on the three-dimensional DNA structure. To extrapolate from DNA crystal structures to physical characteristics and function of these molecules in solution or embedded into a defined sequence context remains a major challenge.
Base Sequence↗
Polyostotic heterogeneity of the spine in osteoporosis. Quantitative analysis and three-dimensional morphology.
It was the aim of this study to record quantitatively and qualitatively the distribution of the three-dimensional microarchitecture throughout the human spine in osteoporosis. Bone biopsies of the iliac crest and the complete spine of 26 autopsy cases without skeletal disease and 11 female patients with proven osteoporosis were removed. Grindings of all vertebrae by a technique which we developed allowed two- and three-dimensional measurements simultaneously. The analysis included an evaluation of trabecular bone volume, trabecular interconnection, and trabecular thickness, as well as a qualitative investigation of the structure of cancellous bone. The bone loss in osteoporosis is a loss of structure. The relative loss of the trabecular microarchitecture is greater in the iliac crest than in the lumbar spine. It is a gradual change from normal bone to osteoporosis. Transformation from plates to rods and the loss of whole trabeculae are caused by perforations. The polyostotic heterogeneity in osteoporosis is remarkable. Adjacent vertebrae may show differences of up to 100% in bone structure and bone volume. This explains the difficulties in early diagnosis of osteoporosis. Due to the polyostotic heterogeneity it is impossible to define a threshold mineral content for osteoporotic fractures.
Aged↗
3D computed X-ray tomography of human cancellous bone at 8 microns spatial and 10(-4) energy resolution.
Human cancellous bone was imaged and its absorptive density accurately measured in three dimensions (3D), nondestructively and at high spatial resolution by means of computerized microtomography (microCT). Essential for achieving the resolution and accuracy was the use of monoenergetic synchrotron radiation (SR) which avoided beam hardening effects, secured excellent contrast conditions including the option of energy-modulated contrast, and yet provided high intensity. To verify the resolution, we selected objects of approximately 8 micron size that could be observed on tomograms and correlated them in a unique manner to their counter images seen in histological sections prepared from the same specimen volume. Thus we have shown that the resolution expected from the voxel size of 8 microns used in the microCT process is in effect also attained in our results. In achieving the present results no X-ray-optical magnification was used. From microCT studies of composites (Bonse et al., X-ray tomographic microscopy (XTM) applied to carbon-fibre composites. In: Materlik G, ed. HASYLAB Jahresbericht 1990. Hamburg: DESY, 1990; 567-568) we know that by including X-ray magnification a resolution below 2 microns is obtained. Therefore, with foreseeable development of our microCT method, the 3D and nondestructive investigation of structures in mineralized bone on the 2 micron level is feasible. For example, it should be possible to study tomographically the 3D distribution and amount of osteoclastic resorption in the surrounding bone structure.
Aged↗
Detection of Mycobacterium leprae by three-primer PCR.
Recently, polymerase chain reaction has been introduced for the species-specific assessment of Mycobacterium leprae (1). To avoid Southern blotting techniques using radioactively labelled oligonucleotide probes, the aim of this study was to establish a three primer-based single-step PCR technique. Using primers designed for this purpose we amplified a part of the gene encoding for the 16S ribosomal RNA of slowly growing mycobacteria. Due to the species-specific antisense primer a second, smaller fragment specific for M. leprae was amplified. Our results show that the employment of a second antisense primer in the PCR may be a substitution for Southern blot hybridization.
Base Sequence↗
Mycobacterium leprae DNA content, cellular and cytokine patterns in skin lesions of leprosy patients undergoing multidrug therapy (MDT).
Skin biopsies from untreated and MDT-treated patients were examined for infiltrating cells and cells producing the cytokines TNF-alpha, IFN-gamma, and IL-1 beta using immunohistochemistry. Biopsy specimens from untreated tuberculoid leprosy patients were characterized by the presence of cells producing TNF-alpha, IFN-gamma, and IL-1 beta and of subepidermal Langerhans cells. These cells were rarely found or completely absent in biopsies of untreated lepromatous leprosy patients, but tended to increase under MDT. In a short-term therapy trial for three months with brodimoprim, dapsone, and rifampicin, 12 patients were monitored by follow-up biopsies. Semiquantitative PCR for mycobacterial DNA revealed two groups of patients: one group in which mycobacterial DNA in follow-up biopsies remained constant and a second group in which a decrease of mycobacterial DNA during therapy was noted. Immunophenotyping in these follow-up biopsies revealed that in the latter group IFN-gamma-positive cells and Langerhans cells were present and gamma delta T cell receptor-positive cells tended to decrease during therapy. In contrast, in patients whose mycobacterial DNA did not change during therapy, these phenotypical manifestations were not observed. We therefore, conclude that assessment of mycobacterial DNA in combination with phenotyping of infiltrating cells and determination of cytokine patterns may be useful tools in establishing criteria for the effectiveness and duration of MDT in patients with leprosy.
Anti-Bacterial Agents↗