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Biomedical subjects

R Hoffmann

Publications and source records attributed to R Hoffmann.

At least 145 records · Page 8Linked to original sources
PubMed1999

The MAP kinase ERK2 inhibits the cyclic AMP-specific phosphodiesterase HSPDE4D3 by phosphorylating it at Ser579.

The extracellular receptor stimulated kinase ERK2 (p42(MAPK))-phosphorylated human cAMP-specific phosphodiesterase PDE4D3 at Ser579 and profoundly reduced ( approximately 75%) its activity. These effects could be reversed by the action of protein phosphatase PP1. The inhibitory state of PDE4D3, engendered by ERK2 phosphorylation, was mimicked by the Ser579-->Asp mutant form of PDE4D3. In COS1 cells transfected to express PDE4D3, challenge with epidermal growth factor (EGF) caused the phosphorylation and inhibition of PDE4D3. This effect was blocked by the MEK inhibitor PD98059 and was not apparent using the Ser579-->Ala mutant form of PDE4D3. Challenge of HEK293 and F442A cells with EGF led to the PD98059-ablatable inhibition of endogenous PDE4D3 and PDE4D5 activities. EGF challenge of COS1 cells transfected to express PDE4D3 increased cAMP levels through a process ablated by PD98059. The activity of the Ser579-->Asp mutant form of PDE4D3 was increased by PKA phosphorylation. The transient form of the EGF-induced inhibition of PDE4D3 is thus suggested to be due to feedback regulation by PKA causing the ablation of the ERK2-induced inhibition of PDE4D3. We identify a novel means of cross-talk between the cAMP and ERK signalling pathways whereby cell stimuli that lead to ERK2 activation may modulate cAMP signalling.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Range of activity and metabolic stability of synthetic antibacterial glycopeptides from insects.

Antibacterial glycopeptides isolated from insects are exciting bio-oligomers because they represent a family of compounds in which the structural and functional effects of incorporating short O-linked sugars to protein fragments can be studied. Additionally, their high activity in vitro warrants detailed further drug development efforts. Due to the limited availability of the isolated material, we used synthetic glycopeptides and some analogs to investigate the range of activity of drosocin and pyrrhocoricin. While addition of the Gal-GalNAc disaccharide to the natural mid-chain position generally increased the antibacterial activity of drosocin, pyrrhocoricin lacking sugar appeared to be more potent, with an IC50 against Escherichia coli D22 of 150 nM. Although glycosylated drosocin was active against E. coli in the low microM range in vitro, this peptide was completely inactive when injected into mice. The lack of in vivo activity of drosocin could be explained by the unusually high degradation rate of the peptides in mammalian sera. The early degradation products were inactive in vitro. In contrast, the peptides were considerably more stable in insect hemolymph, where their natural activity is manifested.

Amino Acid Sequence↗
PubMed1999

Conformational studies by NMR of the antimicrobial peptide, drosocin, and its non-glycosylated derivative: effects of glycosylation on solution conformation.

Drosocin is a cationic 19 amino acid peptide secreted by Drosophila in response to septic injury. The sequence (GKPRPYSPRPTSHPRPIRV) contains six Pro and four Arg residues which are incorporated into three repeated triplet sequences Pro-Arg-Pro. The peptide is glycosylated at Thr11 and has potent antimicrobial activity. This activity is markedly reduced on deglycosylation, but a structural basis for this has not been previously established. In the current study, the solution conformations of drosocin and its non-glycosylated derivative were determined by NMR spectroscopy and structure calculations. The NMR and structure studies showed that the peptides have significant populations of essentially random coil conformations in aqueous solution. Addition of 50% trifluoroethanol causes the development of small populations of folded conformations, mainly in the form of turns. In particular, turn elements occur near residues 4-7, 10-13, 17, and 18. No substantial difference was detected in the predominantly random coil conformation of the glycosylated and non-glycosylated forms, but there are subtle differences in the small populations of folded conformers. In particular, the turn at residues 10-13 tends toward a more extended structure on glycosylation, while there is some tightening of the downstream turn at residues 17 and 18. There are a significant number of nuclear Overhauser enhancement contacts between the sugar moiety and the peptide near the glycosylation site, consistent with a close association between them. Despite this close association, the pKa of H13, which is proximate to the glycosylation site, was found to be unaffected by glycosylation.

Amino Acid Sequence↗
PubMed1999

Sequencing of peptides phosphorylated on serines and threonines by post-source decay in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

In the era of complete genome sequences, biochemical and medical research will focus more on the dynamic proteome of a cell. Regulation of proteins by post-translational modifications, which are not determined by the gene sequence, are already intensively studied. One example is phosphorylation of serines and threonines, probably the single most common cellular regulatory mechanism. In this paper we describe the sequencing of mono- and bisphosphorylated peptides, including identification of the phosphorylation sites, by post-source decay (PSD) in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition to dephosphorylation of the parent ions, we studied the influence of the phosphate group on the fragmentation of peptides. Generally, peptides phosphorylated on serine and threonine residues displayed no difference in their fragmentation patterns. The intensities of the resulting fragment ion signals depend only on the peptide sequence and not on either the phosphorylated amino acid or its position in the peptide chain. Phosphorylation increased the bond cleavage C-terminal to the phosphorylation site more than 10-fold, resulting in abundant signals, which typically dominated the PSD spectra. The produced C-terminally phosphorylated b-type fragment ions showed characteristic dephosphorylated fragment ions b(n) -H(3)PO(4) (-98 Da) and b(n) -HPO(3) (-80 Da) of higher abundances than the phosphorylated fragment ion. As a second layer to identify the phosphorylation site, all internally phosphorylated fragment ions were accompanied by minor, but always detectable, signals of the dephosphorylated fragment ions. Interpretation of PSD spectra of phosphopeptides was not more complicated than for unphosphorylated peptides, despite the increased number of obtained fragment ion signals.

Amino Acid Sequence↗
PubMed1999

High level of aspartic acid-bond isomerization during the synthesis of an N-linked tau glycopeptide.

An increased degree of utilization of the potential N-glycosylation site in the fourth repeat unit of the human tau protein may be involved in the inability of tau to bind to the corresponding tubulin sequence(s) and in the subsequent development of the paired helical filaments of Alzheimer's disease. To model these processes, we synthesized the octadecapeptide spanning this region without sugar, and with the addition of an N-acetyl-glucosamine moiety. The carbohydrate-protected, glycosylated asparagine was incorporated as a building block during conventional Fmoc-solid phase peptide synthesis. While the crude non-glycosylated analog was obtained as a single peptide, two peptides with the identical, expected masses, in approximately equal amounts, were detected after the cleavage of the peracetylated glycopeptide. Surprisingly, the two glycopeptides switched positions on the reversed-phase high performance liquid chromatogram after removal of the sugar-protecting acetyl groups. Nuclear magnetic resonance spectroscopy and peptide sequencing identified the more hydrophobic deprotected peak as the target peptide, and the more hydrophilic deprotected peak as a peptide analog in which the aspartic acid-bond just preceding the glycosylated asparagine residue was isomerized resulting in the formation of a beta-peptide. The anomalous chromatographic behavior of the acetylated beta-isomer could be explained on the basis of the generation of an extended hydrophobic surface which is not present in any of the other three glycopeptide variants. Repetition of the syntheses, with altered conditions and reagents, revealed reproducibly high levels of aspartic acid-bond isomerization of the glycopeptide as well as lack of isomerization for the non-glycosylated parent analog. If similar increased aspartic acid-bond isomerization occurs in vivo, a protein modification well known to take place for both the amyloid deposits and the neurofibrillary tangles in Alzheimer's disease, this process may explain the aggregation of glycosylated tau into the paired helical filaments in the affected brains.

Amino Acid Sequence↗
PubMed1999

[Fixed rotatory subluxation of the atlanto-axial joint in polytrauma patients].

Traumatic atlanto-axial instabilities are rare entities in cervical spine injuries. There may be only subtle abnormal findings by plain radiographs, frequently resulting in a missed or delayed diagnosis. We report a polytraumatized patient with severe maxillofacial injuries, where preliminary radiological studies failed to verify rotatory instability of the atlanto-axial joint. A definite diagnosis was only established by further imaging studies, including CT scan reformations.

Adolescent↗
PubMed1999

[Pathogenetic significance of 5-alpha reductase isoenzymes for androgenetic alopecia].

Androgenetic alopecia is the most common form of hair loss in men and women. Although clinically different, the pathogenetic pathways leading to this type of hair loss are similar in both sexes. Recent experimental data enable us to explain some pathogenetic steps suggesting a pivotal role of type 2 5 alpha-reductase in the pathogenesis of androgenetic hair loss. In this review our current knowledge about the pathophysiology and treatment options of androgenetic alopecia is summarized.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

[Classic nail versus DHS. A prospective randomised study of fixation of trochanteric femur fractures].

The intramedullary hip screw system Classic-Nail and the Dynamic Hip Screw (DHS) were evaluated in a prospective-randomized clinical trial for operative treatment of trochanteric femur fractures. Hundred and ten geriatric patients (mean age 82 years) were runningly included in the study (56 Classic Nail, 54 DHS). No significant differences between the two study groups were observed with regard to treatment and follow-up data. With the Classic-Nail one complete femur shaft fracture and one incomplete fracture occurred at the tip of the nail intraoperatively and could successfully be fixed with cerclage wires. In the DHS group two patients underwent reoperation for significant loss of reduction early postoperatively. At an average follow-up of 3.7 months all fractures were healed with no difference in functional outcome between the two groups.--Classic Nail and DHS both lead to equally good results in the operative treatment of trochanteric femur fractures.

Aged↗
PubMed1999

[Value of MRI in traumatic disco-ligament instability of the lower cervical spine].

The diagnostic accuracy of magnetic resonance imaging (MRI) for traumatic discoligamentous instabilities of the lower cervical spine was evaluated. MRI findings were correlated with the intraoperative findings. Fifteen patients were included in the study (11 males, 4 females, 33 years old on average). Indication for surgery was established with dynamic a.p. instability under fluoroscopy. In the operation, all patients showed complete traumatic rupture of the intervertebral disc. In contrast, MRI sequences revealed only eight mild and four severe disc lesions. Intraoperatively ruptures of the anterior and posterior longitudinal ligaments were verified in 7 patients each. MRI studies depicted only five ruptures of the anterior and three ruptures of the posterior longitudinal ligaments. In three cases MRI demonstrated no pathological findings (3 of 15 false-negative results). MRI and intraoperative findings showed no statistical correlation. MRI is of only limited value in diagnosing traumatic discoligamentous instabilities of the lower cervical spine.

Adolescent↗
PubMed1999

[Strabismus and diplopia as complications after cataract surgery with IOL implantation].

UNLABELLED: In our Department of Orthoptics we have seen an increasing number of patients suffering from diplopia after cataract surgery with IOL implantation. Between 1993 and 1997 the total number of patients with this problem was 24 (2.7 % of all patients, mean age 71 years, age range 38-88). We addressed the question of whether there is a common pattern of motility dysfunction. METHODS: After evaluation of the clinical history and the basic ophthalmological findings the following parameters were examined: binocular function (Bagolini test), squint angles (Maddox cross), ocular motility. RESULTS: The 24 patients could be divided up into three groups. Group 1 consisted of 9 patients (mean age 82 years, range 64-88) who complained about diplopia because of strabismus incomitans with vertical deviation and restricted motility on the first day after surgery. In 8 of the 9 patients strabismus surgery was done. Group II consisted of 10 patients (mean age 66 years, range 38-77) who noticed diplopia and strabismus within 7 days after surgery. We found various kinds of heterotropia. Seven of these patients were operated on and two had a prism correction. Group III consisted of 5 patients (mean age 67 years, range 61-78). Their already known strabismus paralyticus or concomitans deteriorated, leading to diplopia in some cases. All patients in this group were operated on. DISCUSSION: For group I we believe that retro-, para- or peribulbar anesthesia caused the motility dysfunction. In groups II and III it is unlikely that local anesthesia had a causative role. The prolonged disruption of binocular vision and the abrupt change in the sensory situation after the cataract operation with lens implantation may be the leading causes for strabismus or deterioration of a preexisting strabism, respectively. CONCLUSIONS: These patients need a subtil meticulous diagnostic work-up and follow-up because of the possibility of early surgical therapy, which has a good prognosis. Evaluation of binocular vision and eye movements prior to cataract surgery appears to be helpful for later strabismic surgery.

Adult↗
PubMed1999

Recurrence of hepatitis C virus after loss of virus-specific CD4(+) T-cell response in acute hepatitis C.

BACKGROUND & AIMS: The prospective comparison of patients with acute hepatitis C virus (HCV) who spontaneously clear the virus with those who cannot achieve viral elimination and progress to chronic hepatitis offers the unique opportunity to analyze natural mechanisms of viral elimination. METHODS: We studied the HCV-specific CD4(+) T-cell response in 38 patients with acute HCV and correlated the clinical course with the antiviral immune response. The individual HCV-specific T-cell response was assessed in a proliferation assay ((3)H-thymidine uptake) and an enzyme-linked immunospot assay. RESULTS: Patients were classified according to their clinical course and pattern of CD4(+) T-cell responses in 3 categories: first, patients mounting a strong and sustained antiviral CD4(+)/Th1(+) T-cell response who cleared the virus (HCV RNA-negative; n = 20); second, patients who were unable to mount an HCV-specific CD4(+) T-cell response and developed chronic disease (n = 12); and third, patients who initially displayed a strong CD4(+) T-cell response and eliminated the virus (HCV PCR-negative) but subsequently lost this specific T-cell response (n = 6). The loss of the HCV-specific CD4(+) T-cell response was promptly followed by HCV recurrence. CONCLUSIONS: The results indicate that a virus-specific CD4(+)/Th1(+) T-cell response that eliminates the virus during the acute phase of disease has to be maintained permanently to achieve long-term control of the virus. The induction and/or maintenance of virus-specific CD4(+) T cells could represent a promising therapeutic approach in HCV infection.

Acute Disease↗
PubMed1999

Mechanisms of acute lumen gain and recurrent restenosis after rotational atherectomy of diffuse in-stent restenosis: a quantitative angiographic and intravascular ultrasound study.

OBJECTIVES: This quantitative angiographic and intravascular ultrasound study determined the mechanisms of acute lumen enlargement and recurrent restenosis after rotational atherectomy (RA) with adjunct percutaneous transluminal coronary angioplasty in the treatment of diffuse in-stent restenosis (ISR). BACKGROUND: In-stent restenosis remains a significant clinical problem for which optimal treatment is under debate. Rotational atherectomy has become an alternative therapeutic approach for the treatment of diffuse ISR based on the concept of "tissue-debulking." METHODS: Rotational atherectomy with adjunct angioplasty of ISR was used in 45 patients with diffuse lesions. Quantitative coronary angiographic (QCA) analysis and sequential intravascular ultrasound (IVUS) measurements were performed in all patients. Forty patients (89%) underwent angiographic six-month follow-up. RESULTS: Rotational atherectomy lead to a decrease in maximal area of stenosis from 80+/-32% before intervention to 54+/-21% after RA (p < 0.0001) as a result of a significant decrease in intimal hyperplasia cross-sectional area (CSA). The minimal lumen diameter after RA remained 15+/-4% smaller than the burr diameter used, indicating acute neointimal recoil. Additional angioplasty led to a further decrease in area of stenosis to 38+/-12% due to a significant increase in stent CSA. At six-month angiographic follow-up, recurrent restenosis rate was 45%. Lesion and stent length, preinterventional diameter stenosis and amount of acute neointimal recoil were associated with a higher rate of recurrent restenosis. CONCLUSIONS: Rotational atherectomy of ISR leads to acute lumen gain by effective plaque removal. Adjunct angioplasty results in additional lumen gain by further stent expansion and tissue extrusion. Stent and lesion length, severity of ISR and acute neointimal recoil are predictors of recurrent restenosis.

Aged↗
PubMed1999

Interleukin 10 (IL-10): an immunosuppressive factor and independent predictor in patients with metastatic renal cell carcinoma.

Interleukin 10 (IL-10) is an immunosuppressive factor and has been detected in tumour cell cultures of renal cell carcinoma and of malignant melanoma. IL-10 has been described as a cytokine of the Th2 response; it is able to suppress antigen-presenting cells (APCs) and may lead to down-regulation of HLA class I and II molecules on dendritic cells and to anergy of T-lymphocytes. We evaluated pretreatment serum levels of soluble IL-10 and various clinical parameters to determine their prognostic value in 80 advanced renal cell carcinoma patients seen at our institution between May 1990 and April 1996. For statistical evaluation we used both univariate and multivariate Cox proportional hazards models. An elevated pretreatment serum level of IL-10 was a statistically independent predictor of unfavourable outcome (P < 0.0028), in addition to the well-known clinical and biochemical risk factors. These data support risk stratification for future therapeutic trials and identify a predictor which needs to be validated in prospective studies and may potentially influence decision making in palliative management of patients with metastatic renal cell carcinoma. These data also suggest a potential role of IL-10 in the development of advanced renal cell carcinoma and in the future design of therapeutic strategies.

Adult↗
PubMed1999

Prognostic impact of in vivo soluble cell adhesion molecules in metastatic renal cell carcinoma.

The purpose of the study was to determine prognostic significance of pretreatment serum levels of different molecules involved in cell to cell interactions along with other clinical parameters in patients with metastatic renal cell carcinoma. sICAM-1, sVCAM-1 and sELAM-1 serum levels were determined by ELISA assays in sera from 99 patients with histologically confirmed progressive metastatic renal cell carcinoma prior to initiation of systemic therapy. Kaplan-Meier survival analysis, log-rank statistics and two-proportional Cox regression analyses were employed to identify risk factors and to demonstrate statistical independence. In univariate analyses, the following pretreatment risk factors could be identified: serum sICAM-1 level > 360 ng ml(-1), erythrocyte sedimentation rate > 70 mm h(-1), serum C-reactive protein level > 8 mg l(-1), serum lactic dehydrogenase level > 240 U/l and neutrophil count > 6000 microl(-1). Multivariate analyses demonstrated statistical independence for serum sICAM-1 level, erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) level as pretreatment predictors of overall patient survival. The prognostic significance of sICAM-1 might indicate a role of this molecule for tumour progression, potentially in association with the abrogation of anti-tumour immune responses. The possibility of defining a pretreatment risk model based on sICAM-1 level, ESR and CRP also warrants further investigation, with regard to a possible linkage between acute phase proteins and sICAM-1 levels.

Carcinoma, Renal Cell↗
PubMed1999

The potential role of cytokines and T cells in alopecia areata.

T cells play an important role in alopecia areata (AA) because AA can be reinduced by the injection of hair follicle-specific CD8+ T cells into AA scalp biopsies, which were grafted onto scid mice, and the depletion of CD8+ T cells restores hair growth in the Dundee experimental bald rat. Moreover, AA can be transferred by grafting of alopecic skin from C3H/HeJ mice with AA-like hair loss onto unaffected littermates, but the onset of AA is inhibited by i.p. injection of anti-CD44v10 antibodies. Interestingly, grafted anti-CD44v10-treated mice have decreased numbers of CD8+ T cells within the skin. Beside T cells several clinical and experimental data point towards cytokines that might be crucial inducers of hair loss in AA. An aberrant expression of cytokines of the Thl type and IL-1beta has been detected in scalp areas involved by AA, and polymorphisms of cytokine genes such as IL-1-receptor antagonist, IL-1alpha, and TNF-alpha have been shown to determine disease susceptibility and severity. Moreover, IL-1 has been shown to be a potent inhibitor of human hair growth in vitro. Such IL-1-incubated hair follicles show ultrastructural changes similar to those observable in vivo. On the other hand mice transgenic for IL-1alpha develop patchy hair loss and during the depilation-induced hair cycle in C57/BL6 mice, members of the IL-1 family are overexpressed with the onset of spontaneous catagen. Taking all of the presently available data together, we may hypothesize that CD8+ T cells are of crucial importance in AA by their interaction with MHC-I restricted autoantigens, and cytolysis of their target cells. Hair loss, however, may occur because proinflammatory cytokines may interfere with the hair cycle leading to premature arrest of hair cycling.

Alopecia Areata↗
PubMed1999

Chemical synthesis, antibacterial activity and conformation of diptericin, an 82-mer peptide originally isolated from insects.

The small amounts of antibacterial peptides that can be isolated from insects do not allow detailed studies of their range of activity, side-chain sugar requirements, or their conformation, factors that frequently play roles in the mode of action. In this paper, we report the solid-phase step-by-step synthesis of diptericin, an 82-mer peptide, originally isolated from Phormia terranovae. The unglycosylated peptide was purified to homogeneity by conventional reversed-phase high performance liquid chromatography, and its activity spectrum was compared to that of synthetic unglycosylated drosocin, which shares strong sequence homology with diptericin's N-terminal domain. Diptericin appeared to have antibacterial activity for only a limited number of Gram-negative bacteria. Diptericin's submicromolar potency against Escherichia coli strains indicated that, in a manner similar to drosocin, the presence of the carbohydrate side chain is not necessary to kill bacteria. Neither the N-terminal, drosocin-analog fragment, nor the C-terminal, glycine-rich attacin-analog region was active against any of the bacterial strains studied, regardless of whether the Gal-GalNAc disaccharide units were attached. This suggested that the active site of diptericin fell outside the drosocin or attacin homology domains. In addition, the conformation of diptericin did not seem to play a role in the antibacterial activity, as was demonstrated by the complete lack of ordered structure by two-dimensional nuclear magnetic resonance spectroscopy and circular dichroism. Diptericin completely killed bacteria within 1 h, considerably faster than drosocin and the attacins; unlike some other, fast-acting antibacterial peptides, diptericin did not lyse normal mammalian cells. Taken together, these data suggest diptericin does not belong to any known class of antibacterial peptides.

Algorithms↗