Biomedical subjects

J Herrmann

Publications and source records attributed to J Herrmann.

At least 19 recordsLinked to original sources

PubMed2006

Focusing of scanning light beams below the diffraction limit without near-field spatial control using a saturable absorber and a negative-refraction material.

We show that a scanning light beam can be focused below the diffraction limit without the control of moving near-field elements using the combination of two main components: a light-controlled saturable absorber, which creates seed evanescent components from the beam, and a layer of negative-refraction material, which amplifies the evanescent waves. Focusing to spots with a FWHM in the range of 0.2-0.3 lambda is predicted. For slightly off-resonant input beams, an intensity-dependent phase shift leads to smaller spots.

Journal Article↗

PubMed2006

[Giardia lamblia--cause of urticaria and pruritus or accidental association?].

Three patients with chronic urticaria or pruritus were found to suffer from an asymptomatic intestinal infection caused by the protozoan Giardia lamblia. Treatment with metronidazole per os or tinidazole per os was successful; the pruritic symptoms in one patient improved markedly.Giardia lamblia (Giardia intestinalis) are enteroparasites and produce gastrointestinal symptoms such as acute and chronic diarrhea. Cutaneous manifestations associated with giardiasis occur extremely rarely. Urticaria and itching may be explained as an infection-associated allergy. Hitherto, the following cutaneous signs have been described: urticaria, angioedema, mouth ulcers, pruritus, atopic dermatitis, and anal eczema.We considered that the cutaneous manifestations described here, i. e., urticaria and itching, were secondary to the associated gastrointestinal infection due to Giardia lamblia cysts and trophozoite forms, as they disappeared under specific treatment with metronidazole or tinidazole.

Adult↗

PubMed2005

[Visual field defect after radial optic neurotomy].

Radial optic neurotomy is a novel therapy for the treatment of ischemic central retinal vein occlusion. To date, the visual results are encouraging. Cutting in the optic nerve can cause visual field defects as shown in the presented case. This complication will reduce the value of this new surgical procedure and should be weighed against still unsettled advantages.

Aged↗

PubMed2005

[Diagnostic value of nerve fibre layer photography in glaucoma].

PURPOSE: Primary open-angle glaucoma is characterized by a loss of retinal nerve fibres. The aim of our present study was to evaluate the diagnostic value of retinal nerve fibre layer (RNFL) photography as a routine examination for the early diagnosis of glaucomatous damage. METHODS: Between 1991 and 2000 we monitored 96 patients with ocular hypertension in a prospective study. RNFL photography was performed in 91 subjects. These photos were evaluated by two independent observers. RESULTS: The mean image quality of the photos was mediocre. The correlation coefficient for the intraindividual reproducibility (image quality) was 0.713-0.863 (Kendall's coefficient). For the interindividual reproducibility the correlation coefficient was 0.541-0.581 (Somers' coefficient). Regarding the evaluation "RNFL defect yes/no", the correlations were better but there was a discrepancy between the observers. CONCLUSION: Quality, reproducibility and prognostic value of RNFL photography were disappointing. Although RNFL photography may be convincing and informative in several situations, it is not efficient as a routine technique for the early diagnosis of RNFL damage in glaucoma patients.

Aged↗

PubMed2004

Comparative analysis of adenoviral transgene delivery via tail or portal vein into rat liver.

The potential indications for gene therapy are expanding continuously. Currently, hepatotropic adenoviruses are useful vector systems for targeting liver in experimental animal models. Although this gene delivery technique is widely distributed, there is no common sense about how these viruses should be applied. In general, the local delivery into portal vein and the systemic application via tail vein induces above all substantial transgene expression. We here comparatively analysed both methods and found that the systemic administration of an adeno-virus expressing the green fluorescent protein resulted in a stronger infiltration, a more homogenous distribution, and a higher inter-individual reproducibility of reporter gene expression in rat liver than organ-specific administration via the portal vein.

Adenoviridae↗

PubMed2003

Compression of single-cycle mid-infrared pulses by Raman-active molecular modulators.

We show theoretically how high-order stimulated Raman scattering in the impulsive pump-probe regime can be used for generation of single mid-infrared (MIR) single-cycle pulses. The propagation of MIR probe pulses in a hollow waveguide filled with a Raman-excited gaseous medium, with a probe delay in the maximum of the molecular oscillations, results in spectral broadening covering almost 2 octaves. The spectral phases of this broadening can be compensated for by use of an output glass window with anomalous dispersion in the MIR. The spectral and temporal characteristics of the output pulses and the mechanism of pulse compression are studied by use of numerical and analytical solutions, and compression of a 70-fs input pulse at 4 microm to a single-cycle 6.5-fs output pulse is shown.

Journal Article↗

PubMed2003

Further aspects of the general antimicrobial properties of pinniped skin secretions.

In 2 pinniped species with varying hair densities (the northern fur seal Callorhinus ursinus, and the common seal Phoca vitulina), the enzyme lysozyme and the peptide group beta-defensins are demonstrated for the first time as products of the apocrine glands and the sebaceous glands in the common integument of mammals. These antimicrobial substances are also found in the epithelial lining of the hair follicles, between the corneal lamellae of the epidermis, and in dermal histiocytes. Thus, it becomes obvious that another general defense mechanism against microbes, in addition to free sugars (Meyer et al. [2000] Aspects of general properties of skin secretions in the common seal Phoca vitulina. Dis Aquat Org 41:77-79), is active on the skin surface of haired marine mammals to which glandular lysozyme and defensins are regularly transported, so that this biotope is protected against the proliferation of potential pathogens, e.g. bacteria and fungi.

Animals↗

PubMed2003

Transport and transformation of de-icing urea from airport runways in a constructed wetland system.

Urea, NH2-CO-NH2, is used as a de-icing agent at Kalmar Airport, southeast Sweden. During 1998-2001, urea contributed on average 30% of the yearly nitrogen (N) transport of 41,000 kg via Törnebybäcken stream to the coastal zone of the Baltic Sea. In order to reduce stream transport of N from airport, agricultural and other diffuse sources, a wetland was constructed in 1996. Annual wetland retention of total-N varied in the range of 2,500-8,100 kg (6-36% of influent) during 1998-2001, according to mass balances calculated from monthly sampling. During airport de-icing, January-March 2001,660 kg urea-N out of 2,600 kg applied urea-N reached the wetland according to daily sampling. This indicated that 75% of the urea was transformed before entering the wetland. Urea was found to be only a minor part (8%) of total-N in the wetland influent. Calculations of cumulative urea-N loads at the wetland inlet and outlet respectively, showed a significant urea transformation during February 2001 with approximately 40% of the incoming urea-N being transformed in the wetland system. These results show that significant amounts of urea can be transformed in a wetland system at air temperatures around 0 degree C.

Aircraft↗

PubMed2002

Experimental evidence for supercontinuum generation by fission of higher-order solitons in photonic fibers.

We report on an experimental study of supercontinuum generation in photonic crystal fibers with low-intensity femtosecond pulses, which provides evidence for a novel spectral broadening mechanism. The observed results agree with our theoretical calculations carried out without making the slowly varying envelope approximation. Peculiarities of the measured spectra and their theoretical explanation demonstrate that the reason for the white-light generation in photonic crystal fibers is fission of higher-order solitons into redshifted fundamental solitons and blueshifted nonsolitonic radiation.

Journal Article↗

PubMed2002

Prognostic implication of cardiac troponin T increase following stent implantation.

OBJECTIVE: To identify the incidence and clinical significance of myocardial injury following elective stent implantation. DESIGN: Prospective clinical study with 278 consecutive patients undergoing stenting of de novo coronary or saphenous vein graft lesions. Incidence of periprocedural myocardial injury was assessed by analysis of 12 lead ECG, creatine kinase (CK; upper limit of normal (ULN) 70 IU/l for women, 80 IU/l for men), and cardiac troponin T (cTnT; point of care test; threshold 0.1 ng/ml) before and 6, 12, and 24 hours after the intervention. Major adverse cardiac events (MACE: acute myocardial infarction, bypass surgery, and cardiac death) were recorded during clinical follow up (mean (SD) 7.8 (5.3) months). RESULTS: Following elective stenting, the rate of a positive cTnT status was 17.3%, the rate of CK increase of 1-3x ULN 14.7%, the rate of CK increase of > 3x ULN 1.4%, and the rate of Q wave myocardial infarction 0.4%. Cardiac mortality during follow up was higher in patients with postprocedurally increased CK (7.1% v 1.3%, p = 0.01, log rank) and cTnT (9.1% v 0.9%, p < 0.001, log rank). In addition, postprocedurally increased cTnT was associated with a higher overall incidence of MACE (13.1% v 4.0%, p < 0.01, log rank) and was identified as an independent factor for MACE during follow up (hazard ratio 3.27, 95% confidence interval 1.14 to 9.41, p = 0.028). CONCLUSIONS: Following elective stent implantation, a positive cTnT status identified patients at risk of a worse long term outcome. Treatment strategies have to be developed that lead to prognostic improvement by reducing periprocedural myocardial injury.

Biomarkers↗

PubMed2001

Supercontinuum generation of higher-order solitons by fission in photonic crystal fibers.

The nonlinear pulse propagation in photonic crystal fibers without slowly varying envelope approximation is studied using an improved variant of first-order wave equation. Supercontinuum generation is shown to be caused by a novel mechanism of spectral broadening through fission of higher-order solitons into redshifted fundamental solitons and blueshifted nonsolitonic radiation. Good agreement with experimental observations is found, and subcycle pulse compression is studied.

Journal Article↗

PubMed2001

Lipid microparticles as a parenteral controlled release device for peptides.

To investigate the potential of physiological lipids as an alternative to synthetic polymeric materials such as poly(lactide-co-glycolide), peptide-containing glyceryl tripalmitate microparticles were prepared. A modified solvent evaporation method and a melt dispersion technique without the use of organic solvent were employed. Thymocartin (TP-4), an immunomodulating tetrapeptide and insulin were chosen as model peptides and incorporated as a solid or dissolved in 100 microl aqueous solution. The resulting microparticles were characterized with respect to particle size and morphology, biocompatibility, drug content (encapsulation efficiency) and in vitro release behavior. Electron spectroscopy for chemical analysis was used to investigate the adsorption of the model peptides to the lipid matrix material. The modified solvent evaporation as well as the melt dispersion method were suitable for the preparation of microparticles in the size range of 20-150 microm with an acceptable yield. The biocompatibility of the glyceryl tripalmitate microparticles after implantation into NMRI-mice was comparable to poly(lactide-co-glycolide) microparticles. The encapsulation efficiency for both model peptides was high (>80%) even at high theoretical loadings when the peptide was incorporated as a solution with the melt dispersion technique. The in vitro release behavior was substantially influenced by the physicochemical properties of the model peptides used in this study.

Drug Delivery Systems↗

PubMed2001

Plaque distribution and vascular remodeling of ruptured and nonruptured coronary plaques in the same vessel: an intravascular ultrasound study in vivo.

OBJECTIVES: This study was designed to identify potential differences between the intravascular ultrasound (IVUS) characteristics of spontaneously ruptured and nonruptured coronary plaques. BACKGROUND: The identification of vulnerable plaques in vivo may allow targeted prevention of acute coronary events and more effective evaluation of novel therapeutic approaches. METHODS: Intravascular ultrasound was used to identify 29 ruptured plaques in arteries containing another nonruptured plaque in an adjacent segment. Intravascular ultrasound characteristics of these plaques were compared with plaques of computer-matched controls without evidence of plaque rupture. Plaque distribution was assessed by measuring the eccentricity of lumen location (inside the total vessel). Lumen cross-sectional area narrowing was calculated as [1 - (target/reference lumen area)] x 100%. A remodeling index was calculated as lesion/reference arterial area (>1.05 = compensatory enlargement, <0.95 = shrinkage). RESULTS: Among the three groups of plaques, there was no significant difference in quantitative angiographic parameters, IVUS reference dimensions and IVUS lumen cross-sectional area narrowing. There was a difference in plaque distribution; lumen location by IVUS was significantly more eccentric in ruptured than in nonruptured (p = 0.002) and control plaques (p < 0.0001). The arc of disease-free vessel wall was larger in ruptured than in control plaques (p < 0.0001). The remodeling pattern of ruptured and nonruptured plaques differed significantly from that of the control plaques (p = 0.0001 and 0.003); compensatory enlargement was found in 66%, 48%, and 17%, whereas shrinkage was found in 7%, 10% and 48%, respectively. CONCLUSIONS: Intravascular ultrasound assessment of plaque distribution and vascular remodeling may help to classify plaques with the highest probability of spontaneous rupture.

Coronary Artery Disease↗

PubMed2001

Abnormal coronary flow velocity reserve after coronary intervention is associated with cardiac marker elevation.

BACKGROUND: Residual reduction of relative coronary flow velocity reserve (rCVR) after successful coronary intervention has been related to microvascular impairment. However, the incidence of cardiac enzyme elevation as a surrogate marker of an underlying embolic myocardial injury in these cases has not been studied. METHODS AND RESULTS: A series of 55 consecutive patients with successful coronary stenting, periprocedural intracoronary Doppler analysis, and determination of creatine kinase (CK; upper limit of normal [ULN] for women 70 IU/L, for men 80 IU/L) and cardiac troponin T (cTnT; bedside test, threshold 0.1 ng/mL) before and 6, 12, and 24 hours after intervention were studied. Postprocedural rCVR was the only intracoronary Doppler parameter that independently correlated with cTnT (r=-0.498, P<0.001) and CK outcome (r=-0.406, P=0.002). Receiver operating characteristic analysis identified a postprocedural rCVR of 0.78 as the best discriminating value, with a sensitivity of 83.3% and 69.2% and a specificity of 79.1% and 76.2% for detection of cTnT and CK elevation, respectively. Stratified according to this cutoff value, the incidence of cTnT elevation was 52.6% in patients with (n=19) and 5.6% in patients without (n=36) a postprocedural rCVR <0.78 (P<0.001), associated with a CK elevation >1 times the ULN in 36.8% and 5.6% (P=0.005) of patients, respectively. CONCLUSIONS: Cardiac marker elevation can frequently be found after coronary procedures that are associated with a persistent reduction of rCVR, indicating procedural embolization of atherothrombotic debris with microvascular impairment and myocardial injury as a potential underlying mechanism.

Aged↗

PubMed2001

Development and characterization of lipid microparticles as a drug carrier for somatostatin.

Somatostatin, a therapeutic peptide with a high therapeutical potential but a very short biological half-live was encapsulated within microparticles by a modified solvent evaporation method and a melt dispersion method without the use of organic solvent. As the use of synthetic polymer matrix materials often goes along with detrimental effects on incorporated peptides, we investigated the potential of physiological lipids such as glyceryl tripalmitate (Dynasan 116) as an alternative matrix material. The two preparation methods were evaluated with respect to surface topography, particle size distribution, encapsulation efficiency, in-vitro release behavior and modification of the resulting microparticles. Microparticles with a suitable particle size distribution for i.m. or s.c. injection could be prepared with both methods. The encapsulation efficiency of the peptide into glyceryl tripalmitate microparticles was substantially influenced by the preparation method and the physical state of the peptide to be incorporated. The melt dispersion technique and the incorporation of the drug as an aqueous solution gave the best results with actual drug loadings up to 9% and an encapsulation efficiency of approximately 90%. Microparticles prepared by the melt dispersion technique crystallized in the unstable alpha-modification. The peptide was released almost continuously over 10 days with no burst effect, 20-30% of the incorporated somatostatin was not released in the monitored time period.

Calorimetry, Differential Scanning↗

PubMed2001

[Biochemical markers of ischemic and non-ischemic myocardial damage].

BACKGROUND: Biochemical markers have been an integrative part of non-invasive diagnostic strategies in cardiology for nearly 50 years, experiencing a renascence by the recently acknowledged prognostic potential of cardiac troponins in acute coronary syndromes. DIAGNOSIS: According to the guidelines of the National Academy of Clinical Biochemistry and the International Federation of Clinical Chemistry cardiac troponin T and cardiac troponin I should be considered as the new "gold markers" of ischemic myocardial injury. One characteristic feature of these new markers is the improved diagnostic potential, reflected by the choice of two cut-off values to distinguish minor myocardial injury from acute myocardial infarction. In addition, cardiac troponins allow risk stratification in the clinical setting of acute coronary syndromes: approximately threefold higher mortality rate for patients with rest angina or ST segment elevation and cardiac troponin elevation on admission. Other indications for cardiac marker analysis are monitoring of therapeutic success in case of invasive and non-invasive reperfusion strategies and non-invasive diagnosis of non-ischemic myocardial injury (myocarditis, cardiac contusion and chemotherapy). CONCLUSION: Biochemical cardiac markers are a useful tool in the diagnosis of both ischemic and non-ischemic myocardial injury. Among these, cardiac troponins seem to become the gold markers for the new millennium.

Angina, Unstable↗

PubMed2001

Is the decision for colorectal resection justified by histopathologic findings: a prospective study of 100 patients with advanced ovarian cancer.

OBJECTIVE: We compare the indication for colorectal resection in patients with advanced ovarian cancer with histopathologic findings. We describe the effect on pelvic control and morbidity associated with surgery. METHODS: Between February 1995 and March 2001, 100 patients with FIGO stage IIIc ovarian cancer underwent pelvic en bloc resection with excision of the rectosigmoid colon as part of primary or secondary cytoreductive surgery. Decision for resection was made by the surgeon when tumor involvement of the cul-de-sac was suspected. Rectosigmoid infiltration was histopathologically defined as infiltration of the serosa or deeper. RESULTS: In 73 of 100 patients (73%) tumor involvement of the rectum was confirmed histopathologically: infiltration of the serosa in 28 (28%) patients, infiltration of the muscularis in 31 (31%) patients, and infiltration of the mucosa in 14 (14%) patients; in 27 (27%) patients no infiltration was found. Histopathologically confirmed pelvic R0 resection was achieved in 85 (85%) patients. In 11 (11%) patients the pelvic resection margins were tumor-involved and in four (4%) patients visible parametric tumor remained in situ. Pelvic recurrence occurred in 4 (4.7%) of 85 optimally debulked patients compared with 9 (60%) of 15 patients with suboptimal pelvic resection status (P < 0.05). End colostomy could be prevented in 94 (94%) of 100 patients. CONCLUSION: Pelvic en bloc surgery with rectosigmoid resection was justified by histopathologic outcome since deperitonealization with preservation of the rectosigmoid would have left tumor in situ in 73% of patients with suspected cul-de-sac involvement.

Adult↗

PubMed2001

Improved detection and analysis of sensed and paced events in dual chamber pacemakers with extended memory function. A prospective multicenter trial in 626 patients.

PATIENTS AND METHODS: This prospective study analyzed the incidence of atrial arrhythmias in a population of 626 patients in 173 medical centers of eleven European countries and Japan with indication for a dual chamber pacemaker system. The accuracy of the new Automatic Interpretation for Diagnosis Assistance (AIDA) program which is included in Chorus pacemakers was evaluated and the AIDA analysis was compared to and proven with Holter monitoring. Data stored in the pacemakers' memories for the first 24 hours (D1) were compared with simultaneously recorded 24-hour surface electrocardiograms, and data stored over the following 28 days (D28) were examined against reported intercurrent symptoms. RESULTS: At D1, atrial arrhythmias were detected by AIDA in 60 of 626 patients (12%), consisting of atrial fibrillation (n = 29), atrial flutter (n = 4), and miscellaneous arrhythmias (n = 17), and closely corroborated by Holter monitoring (sensitivity 93.7%, specificity 94.9%). At D28, 149 of 386 patients (49%) had had episodes of automatic mode switch prompted by atrial arrhythmias. Symptoms were reported by 81 patients (54%), 92 (62%) had no histories of atrial arrhythmias, and 57 patients (38%) were neither symptomatic nor had histories of atrial arrhythmias. An inverse relationship was found between the number of atrial paced events and the occurrence of atrial arrhythmias (p < 0.001). A history of atrial arrhythmias and older age were associated with a higher risk of atrial arrhythmias (p < 0.05). In contrast, gender, hypertension, concomitant heart disease, or type of atrial lead fixation system were not related with the occurrence of atrial arrhythmias. CONCLUSION: AIDA allowed to confirm, or disprove, the occurrence of atrial arrhythmias as a source of symptoms reported during long-term follow-up. It could also be used to examine the efficacy of antiarrhythmic therapy, and be of assistance when weighing the needs for anticoagulation in patients experiencing asymptomatic atrial arrhythmias.

Adult↗