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Biomedical subjects

P Hahn

Publications and source records attributed to P Hahn.

At least 19 recordsLinked to original sources
PubMed2001

The LMP1 gene isolated from Russian nasopharyngeal carcinoma has no 30-bp deletion.

The Epstein-Barr virus (EBV) is tightly linked to the induction of undifferentiated nasopharyngeal carcinoma (NPC), a tumour endemic in certain areas of southeast Asia. The LMP1 gene encoded by EBV is a classical oncogene due to its ability to transform rodent fibroblasts. LMP1 is absolutely essential for transformation of B cells by the virus and is one of the few EBV genes found to be expressed in NPC. It was originally shown that the LMP1 gene from NPC harbours a deletion of 30 bp in the 3' part of the gene. However, this deletion is also present in the virus spread in healthy people of the areas endemic for NPC and also in other EBV-positive tumours as well as in healthy carriers. We isolated and sequenced the LMP1 gene obtained from tissue of 7 Russian patients with NPC and 1 German patient with an NPC-like tumour of the parotid gland (PG) and compared them with the LMP1 gene isolated from peripheral blood lymphocytes (PBLs) of 6 Russian and 4 German healthy EBV-positive carriers. Neither the Russian NPC cases nor the German NPC-like tumour harboured an LMP1 gene with the 30-bp deletion, while 1 Russian and 2 German carriers contained the LMP1 gene with the 30-bp deletion. In addition, the LMP1 gene isolated from PBLs of the German patient was virtually identical to the gene isolated from the primary tumour. Functional analysis showed no correlation between the presence or absence of the 30-bp deletion and the level of induction of the transcription factors NFkappaB and jun/AP-1 caused by LMP1. These data indicate that the 30-bp deletion is not a factor predisposing for NPC. Comparison of the DNA sequences revealed that the LMP1 genes present in the NPCs most likely represent the "strain" persisting in the general population.

Adolescent↗
PubMed2001

Nonlinear dynamic properties of low calcium-induced epileptiform activity.

The analysis of the dynamic properties of epileptiform activity in vitro has led to a better understanding of the time course of neural synchronization and seizure states. Nonlinear analysis is thus potentially useful for the prediction of seizure onset. We have used nonlinear analysis methods to investigate the development of activity in the low calcium model of epilepsy in brain slices. This model is particularly interesting since neurons synchronize in the absence of synaptic transmission. The dynamic properties calculated from extracellular recordings of activity were used to analyze the transition to synchronous firing and their relation to neuronal excitability. The global embedding dimension, local dimension and the Lyapunov exponent were calculated from time segments corresponding to the onset, transition and fully developed stages of activity. The analysis was repeated for recordings made in the presence of various levels of DC electric fields to modulate neuronal excitability. The global and local dimensions did not change once activity was first initiated, even in the presence of the electric field. The maximum Lyapunov exponents increased during the onset of activity but decreased when the applied hyperpolarizing electric field was large enough to partially suppress the activity. These findings establish a relationship between neuronal excitability and the maximum Lyapunov exponent, and suggest that the Lyapunov exponent may be used to distinguish between various states of the neural network and might be important in seizure prediction and control.

Action Potentials↗
PubMed2001

Phenotypic characteristics of human monocytes undergoing transendothelial migration.

In our study we characterised the immunophenotype of monocytes that migrated through an endothelial cell (EC) monolayer in vitro. We found that monocyte migration led to an enhanced expression of CD11a, CD33, CD45RO, CD54 [intercellular cell-adhesion molecule (ICAM)-1] and human leucocyte antigen-DR. The most striking increase was observed for ICAM-1 when ECs were activated with tumour necrosis factor-alpha and interleukin-1alpha. The results of our study indicate the following: (1) there is a characteristic immunophenotype on the surface of monocytes after transendothelial migration; (2) this phenotype seems to be induced by interactions between monocytes and ECs; and (3) this change is enhanced by the pretreatment of ECs with cytokines. Taken together, the results suggest that local cytokine production activating ECs is sufficient to enhance monocyte migration and that this, in turn, can induce changes consistent with an activated phenotype known to be interactive between antigen-presenting cells and T cells. These results have implications for our pathogenetic insights into rheumatoid arthritis.

Cell Movement↗
PubMed2001

Chemomechanical caries removal: a comprehensive review of the literature.

Compared to the past, caries removal has become more efficient, however inherent fundamental drawbacks of the drilling approach have remained: unpleasantness to patients, need for local anesthesia, and potential adverse effects to the pulp due to heat and pressure. Chemomechanical caries removal, introduced almost three decades ago, was claimed to be a non-invasive alternative for the removal of carious dentine. In essence, the technique involved applying a solution onto the decayed dentinal tissue, allowing it to soften it, and, finally, scraping it off with blunt hand instruments. The partially degraded collagen in carious dentine was chlorinated by chemomechanical caries removal solutions. This chlorination affected the secondary and/or quaternary structure of collagen, by disrupting hydrogen bonding. Carious material removal was thus facilitated. The purpose of this paper is to perform a comprehensive review of the literature regarding chemomechanical caries removal, including the most recently available product, the initial reports on which warrant renewed interest in the approach.

Aminobutyrates↗
PubMed2001

Influence of resin cement viscosity on microleakage of ceramic inlays.

OBJECTIVES: The aim of the present investigation was to evaluate the effect of the different viscosities of two resin luting cements on microleakage of ceramic inlays at dentinal margins. The effect of the width of the space between inlay and tooth, on the quality of the marginal seal was also investigated. METHODS: Mesial and distal class V cavities were prepared in 48 extracted third molars. The incisal margins of the cavities were in enamel and the cervical margins in dentin. Subsequently, Empress inlays with different cervical margin gap dimensions were fabricated. The mean cervical gap dimensions in the respective groups were as follows: group 1 (27 microm); group 2 (232 microm); group 3 (406 microm). Half the inlays in each group (16) were cemented with a low viscous resin luting cement, and half (16) with a highly viscous resin luting cement. The teeth were subjected to occlusal loading with synchronized thermal cycling in a masticatory simulator. Then, the specimens were immersed in basic fuchsin solution, and dye penetration along the cavity walls was measured. In addition, marginal adaptation was analyzed in the SEM at baseline and after loading, using a replica technique. RESULTS: With regard to dye penetration at dentinal margins, the highly viscous cement performed statistically significantly better at dentin/composite margins than the low viscous cement (p=0.0158). These findings are supported by SEM analysis. SIGNIFICANCE: It is assumed that polymerization stress within the luting cement could not be completely compensated for by larger luting spaces. Highly viscous luting cements are recommended for cementing class V inlays in larger luting spaces.

Aluminum Silicates↗
PubMed2001

Tensile bond strengths of four different dentin adhesives on irradiated and non-irradiated human dentin in vitro.

This study evaluated the influence of irradiation on dentin bond strength. Sixty irradiated and 60 non-irradiated human third molars were used. The irradiation dose of 60 Gy was fractionally applied over 6 weeks (2 Gy day(-1), 5 days week(-1). All teeth were prepared in a special manner allowing the simulation of intra-pulpal pressure and dentin perfusion. Dentin specimens with a thickness of 2.0 mm were obtained under standardized conditions. The specimens were randomly assigned to four experimental groups. Tensile bond strength of four different dentin bonding agents (Scotchbond 1, Solobond Plus, Prime&Bond 2.1 and Syntac) was evaluated using an Instron Universal testing machine. Pairwise comparison did not show any significant differences between the irradiated and non-irradiated groups. The influence of the different dentin adhesives was significant (P=0.0001; ANOVA). Compared with Solobond Plus and Prime&Bond 2.1, the use of Scotchbond 1 resulted in a significantly higher tensile bond strength in non-irradiated specimen (P< 0.05; closed test procedure based on Kruskal-Wallis test). Within the limitations of an in vitro study, it can be concluded that adhesive restoration procedures can be successfully used in patients irradiated for cancer of the head and neck.

Adhesives↗
PubMed2001

[Stener lesion yes or no? Diagnosis by ultrasound].

25 patients with clinical signs for ulnar collateral ligament injury to the metacarpophalangeal joint of the thumb were examined by ultrasonography before operation to verify Stener's lesion. The results were compared with intraoperative findings. In 18 patients (74%), ultrasound and surgical exploration yielded equivalent results. Seven patients showed signs of Stener's lesion in ultrasound that could not be verified during surgery. No Stener's lesion was missed.

Adult↗
PubMed2001

Characterization of a vitamin D receptor knockout mouse as a model of colorectal hyperproliferation and DNA damage.

The vitamin D receptor knockout (VDR-KO) mouse presents with a skeletal phenotype typical for complete lack of genomic 1,25-dihydroxycholecalciferol effects. Our previous data from human colorectal tissue suggest that the steroid hormone and its receptor may have protective function against tumour progression. In order to investigate the relevance of the vitamin D system for pre-malignant site-directed changes in the colon, we characterized the amount and site-specific distribution of the VDR along the large intestine in wild-type (WT), heterozygote (HT) and KO mice. We also evaluated expression of proliferating cell nuclear antigen (PCNA), of cyclin D1 and the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress. In colon ascendens, proliferative cells were dispersed all along the crypt and expression levels of all three markers were high in WT mice. A decrease of VDR expression did not affect expression significantly. In colon descendens, however, fewer proliferative cells were solely located in the lower third of the crypt, and an inverse relationship between VDR reduction, PCNA positivity and cyclin D1 expression was found in HT and KO mice. In parallel to enhanced proliferation a highly significant increase of 8-OHdG positivity occurred. Therefore, the sigmoid colon of VDR-KO mice, fed on an appropriate lactose/calcium-enriched diet to alleviate impaired calcium homeostasis-related phenotypic changes, is an excellent model for investigating induction and prevention of pre-malignant changes in one of the hotspots for human colorectal cancer incidence.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Comparative analysis of the expression of the Epstein-Barr virus (EBV) anti-apoptotic gene BHRF1 in nasopharyngeal carcinoma and EBV-related lymphoid diseases.

Epstein-Barr virus (EBV) has been identified in a wide range of neoplastic and non-neoplastic disorders. The EBV open reading frame BHRF1 encodes a protein with partial sequence and functional homology to the anti-apoptotic onco-protein Bcl-2 and may therefore have a role in the proliferation of EBV positive cells. We have developed a rat monoclonal antibody against pBHRF1, which can detect BHRF1 in paraffin sections. While a number of mutant versions of BHRF1 were recognised, the monoclonal did not detect the BHRF1 homologue encoded by Herpesvirus papio or two mutants with deletions in the BH2 region. This novel rat monoclonal antibody (6A9) was used to examine tissue sections from 39 cases of non-keratinising undifferentiated nasopharyngeal carcinoma (NPC), 6 cases of metastatic NPC, 7 cases of EBV-positive NPC with squamous differentiation from Chinese patients, 15 cases of EBV-positive post-transplant lymphoproliferative disorder (PTLD), 6 EBV-containing lymphoblastoid cell lines, and 2 cases of oral hairy leukoplakia (OHL). In 11 cases of undifferentiated NPC, RT-PCR data were available for comparison with the immunohistochemistry. Both cases of OHL and two cases of LCL were positive for BHRF1 but none of the PTLD showed positive staining. All cases of undifferentiated NPC were positive for Bcl-2 but only one BHRF1 positive cell was identified in 1 of 39 cases of primary undifferentiated NPC. The 6A9 antibody produced less background staining and no nuclear positivity compared with the commercially available mouse monoclonal 5B11. It is concluded that BHRF1 can not be detected by immunohistochemistry in NPC and therefore it appears not to play a significant anti-apoptotic role in the progression of this EBV-associated tumour. The 6A9 monoclonal appears to be superior to 5B11 for the detection of pBHRF1 in tissue sections.

Amino Acid Sequence↗
PubMed2000

Surface markers and transendothelial migration of dendritic cells from elderly subjects.

Age-related changes of immune functions have been extensively investigated in both humans and animal models; nevertheless, the literature on potential alterations of dendritic cells, potent antigen presenting cells responsible for initiating immune responses, with aging is very scarce. We studied the immuno-phenotype of peripheral blood dendritic cells of elderly and young subjects by three-color flow cytometry. In addition, the capacity of transendothelial migration, an important step in inflammatory reactions, of peripheral blood dendritic cells of elderly subjects was investigated in an in vitro model. The expression of HLA-DR in the peripheral blood dendritic cells of the elderly subjects was significantly decreased when compared to the young control subjects. The expression of various other surface markers was similar in the young and elderly subjects. The ability of transendothelial migration of dendritic cells was found to be unimpaired in the elderly subjects. Both in the young and elderly subjects a significantly higher expression of CD29, CD86, HLA-DR, and HLA-DQ in the dendritic cells that had migrated through the endothelium in comparison to nonadherent, nonmigrating cells was found. In the migrating dendritic cells of the elderly subjects a significantly increased expression of CD11c was observed, whereas the expression of CD54 was significantly enhanced in the migrating dendritic cells of the young subjects only. In conclusion, our results demonstrate intact functions and a normal immunophenotype of dendritic cells derived from elderly subjects. Dendritic cells thus seem to be functional and therefore are not responsible for the well-known decline of T cell functions with aging.

Aged↗
PubMed2000

Effect of different luting procedures on the seating of ceramic inlays.

This in vitro study evaluated the effect of different luting procedures on the proper seating of ceramic inlays and on the marginal seal through microleakage testing. Sixty mesial-, occlusal-, distal- (MOD) cavities were prepared in third molars, and distributed among four groups. In the control group 1, the cavity surface was treated with dentin and enamel bonding agents; ceramic inlays were placed into the cavity and light cured. In group 2, the dentin and enamel bonding agents were cured prior to the placing of the inlays, and following the insertion. In group 3, the inlays were luted without enamel bonding. In group 4, the inlays were cemented using a one-bottle bonding and two times light curing. The groups with only one time light curing at the end of the luting process exhibited the smallest luting space following cementation. The smallest dye penetration values were obtained for the two groups with separate light curing of the dentin bonding agent. Reducing the film thickness of polymerized dentin bonding agents, i.e. by changing the composition of the bonding agents, could facilitate proper seating of ceramic inlays together with a better marginal seal.

Acid Etching, Dental↗
PubMed2000

An in vitro assessment of the strength of porcelain veneers dependent on tooth preparation.

The treatment of teeth using veneer restorations combines aesthetic and functional improvements with a low destructive technique. Different kinds of tooth preparation techniques are described in the literature for this kind of restoration. This in vitro study aimed to examine the influence of the incisal preparation on the loadability of teeth restored with porcelain laminate veneers. Thirty-six selected mandibular incisors were randomly assigned to three groups with 12 teeth per group. In the first group, only the facial surface was prepared. In the second group, the preparation included a rounded incisal edge and a distinct chamfer lingually. The third group served as an unprepared control. Empress(R) veneers were then fabricated and cemented with a low viscous luting composite material. After 120 days storage in Ringer's solution, the specimens were loaded incisally to the point of failure. Statistical analysis of the results showed significant differences between the series (P=0.0103). Group 2 (with preparation of the incisal edge) exhibited the lowest fracture resistance (466+/-99 N) (N, mean forces). When prepared only facially, the teeth restored with Empress veneers reached the strength of unprepared teeth. Compared with the biting force described for incisors in the literature, the in vitro loadability reached in this investigation seems to jusitify the clinical use of both preparation designs tested.

Aluminum Silicates↗
PubMed2000

[Bursitis of the ulnar recess].

We investigated 20 patients suffering from wrist pain accompanied by local swelling of the recessus ulnaris. Pain could be produced by direct pressure to the recessus ulnaris or by rotation of the forearm during prehension grip. One group (n = 14) had no previous operation or trauma. A second group (n = 6) had undergone previous surgery or suffered from trauma. All patients were treated by injection of cortisone and lidocaine into the recessus ulnaris. In the first group, ten (71%) remained pain-free during a period of 19 (9 to 40) months. In the second group, no improvement could be achieved. Based on anatomy and evolution of the recessus ulnaris, we try to establish a theory of the pathology.

Adult↗
PubMed2000

[Strategy for defect coverage in extensive degloving and crush injuries of 4 fingers].

Severe crush injuries with avulsion require specific treatment strategies. Usually we find complete loss of soft tissue, nerves and vessels, where only tendons and parts of the phalanges are preserved. Primary reconstructive procedures are usually not possible due to the complexity of the injury with severely destroyed structures. Bone shortening should be avoided in order to maintain finger length and motion. Therefore, emergency soft-tissue coverage represents the first step. Later, sensibility and mechanical stability of the skin should be restored. In our clinic, seven patients with this injury pattern were treated. Three cases involved four finger crush-avulsion injuries. In all cases, we performed a primary soft-tissue coverage with a pedicled flap. In a second session, the skin areas of the first web space of both feet were transplanted as neurovascular flaps. With this strategy, a useful hand function could be restored. The functional results are described and advantages and disadvantages of various techniques discussed.

Adult↗
PubMed2000

[Bone growth after finger replantation in childhood].

Following replantation in childhood, growth disorders of the affected epiphysis can influence function and aesthetic appearance of the hand. In a retrospective study long-term results of replantation in the upper limb in childhood were analysed with respect to factors influencing further growth. 22 patients with 29 replanted fingers were reviewed clinically and radiologically after an average interval of ten years. An average bone growth of 93% compared to the contralateral non-injured side was found. With the epiphysis affected, bone growth was reduced to 86% of the contralateral side. Analysis of single phalanges showed a growth rate of 71 to 100% in phalanges distal to the amputation and also in phalanges initially severed. Potential factors influencing bone growth were assessed separately. Best results were achieved in straight injuries without epiphyseal affection. An influence of anoxia time or number of anastomosed vessels could not be found. Even though replantation in childhood affects growing bone, almost normal bone growth can be expected afterwards.

Adolescent↗