Deformation of cholesteric elastomers by uniaxial stress along the helix axis.

The deformation of cholesteric elastomers by mechanical stress applied parallel to the helix axis is studied by calculation of the free-energy density. The Frank-elasticity contribution is taken into account. A chiral solvent, present at cross-linking time, is in general considered to be replaced after cross-linking by a solvent with different chirality. Two special cases considered are zero and unchanged solvent chirality, the first known as that of imprinted cholesteric elastomers, the latter equivalent to intrinsic cholesteric elastomers with chemically attached chiral groups. Depending on material parameters and imposed strain, the director can show a tilt towards the helix axis up to the maximum tilt, corresponding to a nematic state. In case of intrinsic elastomers with low conformation anisotropy, direct transitions from untilted to nematic states can be induced by straining. The helix structure of the director field is coarsened with an average wave number different to that of the information inscribed in the network at cross-linking time, if this lowers the average free-energy density. Switching between different states can be achieved with electric fields of reasonable values applied parallel to the helix axis. Spectra of the reflection of polarized light are calculated.

The role of Frank elasticity in cholesteric elastomers.

The effect of Frank elasticity on deformations of cholesteric elastomers by mechanical stress applied perpendicular to the helix axis is studied by numerical minimization of the free energy. Above a critical strain, a solution with an only oscillating director is found to be stable in comparison to a distorted helix. At the critical strain, the contractions perpendicular to stress change discontinuously. The critical strain is found to increase with increasing Frank elasticity contribution to the free energy density, and to diverge when the conformation anisotropy of the polymer backbone vanishes. The results are compared with recent experiments which indicated that, in case of weak conformation anisotropies, the Frank elasticity contribution to the free energy cannot be neglected.

Photonic defect modes in cholesteric liquid crystal films.

We discuss the properties of photonic defect modes in cholesteric liquid crystals. Twist defects, isotropic defect layers, and combinations of both are considered. After deriving the reflection and transmission properties of the defects, we study the effect of a finite sample thickness on the defect mode's amplitude and on the required polarization of incident light to excite the defect mode.

Incidence of myocardial infarctions in HIV-infected patients between 1983 and 1998: the Frankfurt HIV-cohort study.

OBJECTIVE: To investigate whether the use of highly active antiretroviral therapy (HAART) is associated with an increased incidence of myocardial infarctions (MI) in HIV infected patients. DESIGN: Retrospective analysis of a cohort of 4993 HIV infected patients treated at our hospital between January, 1 1983 and December, 31 1998. The incidence of myocardial infarctions during 4 observation periods with different antiretroviral treatment strategies are compared. Possible risk factors for MI are evaluated by univariate analysis and using a multiple regression model. RESULTS: 29 patients with MI were diagnosed between 1983 and 1998. The incidence of MI per 1000 patient-years increased from 0.86 (1983-86), 1.14 (1987-90), 0.59 (1991-94) to 3.41 (1995-98) respectively (p = 0.002). Age >40, previous HAART therapy, homo-, or bisexual mode of HIV transmission and previous AIDS diagnosis were significantly associated with MI in univariate analysis. Age >40 and previous HAART therapy remained significantly associated with MI in a multiple regression model. CONCLUSION: The incidence of MI in HIV infected patients increased in our cohort after the introduction of HAART.

[Atherosclerosis--a chronic infectious disease caused by Chlamydia pneumoniae]. / Arteriosklerose--eine chronische Infektionskrankheit durch Chlamydia pneumoniae.

Recent investigations allow a controversial but convincing interpretation of the pathogenesis of atherosclerosis (arteriosclerosis). Atherosclerosis can be apparently the result of ultrachronic persistent infection by Chlamydia pneumoniae and not the result of heterogenous risk factors. The main arguments for the chlamydial genesis are: Correlation of coronary heart disease and other atherosclerotic diseases and antibodies against Chlamydia pneumoniae. Chlamydia pneumoniae could be detected with different techniques (PCR, ICC, immunohistology, electromicroscopy, culture) in a high percentage in atheromas from different sites. Three successful international studies with macrolides in coronary heart disease. Target cells of atherosclerosis (endothelia, macrophages, muscle cells) can be infected by Chlamydia pneumoniae in vitro. Provocation of an arteriitis in animal experiments. The reduction of incidence of atherosclerotic diseases since the 1960s, probably due to advanced antibiotic therapy. Elevated acute-phase proteins and other inflammatory signs (CRP, WBC count, fibrinogen) briefly before occurrence of myocardial infarction. There are good arguments for intervention studies in coronary heart disease and other manifestations of atherosclerosis. The relevant antibiotics are licensed for chlamydial infections, cheap and safe. Meticulous records and long-term observation of patients need to be developed, sometimes contrary to interests of the pharmaceutical industry.

Prospective randomized study to compare imipenem 1.5 grams per day vs. 3.0 grams per day in infections of granulocytopenic patients.

The objective of this presented prospective randomized study was to compare the efficacy of empirical antimicrobial monotherapy with imipenem 3 x 0.5 g per day to 3 x 1.0 g per day for treatment of infections in neutropenic patients. A total of 192/220 febrile episodes were evaluable for clinical efficacy. The overall response rate was 53/93 (57%) vs. 57/99 (58%). Of the different infection types, fever of unknown origin (FUO) showed the best response, with defervescence in 29/41 (71%) and 36/42 (86%) cases, respectively (not significant). Unfavourable results were found in pneumonias [5/20 (25%) vs. 4/23 (17%)]. The median time until persistent defervescence was equal in both groups (2 days), likewise the median duration of imipenem therapy in responders (7 days). The most frequent micro-organisms were Gram-negative, documented in 22% of the febrile episodes in the lower dosage group vs. 17% of all episodes in the patients with imipenem 3.0 g per day (Gram-positives 17% vs. 14%, fungal 5% vs. 8%). In the lower dosage group, fever with abdominal symptoms occurred less frequently (8% vs. 15%), and significantly more patients tolerated imipenem without any side-effects (95.8% vs. 79.4%), especially regarding severe nausea/vomiting (2.1% vs. 11.8%). Of the initial non-responders, 35/40 (88%) vs. 41/42 (98%) were cured after therapy modification. There was no significant difference in the use of further antibiotics such as aminoglycosides, glycopeptides, ceftazidime or amphotericin B, except a marginally higher use of metronidazole in patients with imipenem 3.0 g per day (3% vs. 10%). Overall, we found no significant differences in efficacy between the two study groups, but more frequent side-effects with imipenem 3.0 g per day.

[Antibiotic therapy in leukopenia]. / Antibiotikatherapie bei Leukopenie.

Intensified chemotherapy-induced long-term neutropenia is the main cause for morbidity and mortality of patients with hematologic malignancies. The successful management of neutropenia is based on hygienic procedures antimicrobial prophylaxis and therapy, and diagnostics. Until today, Co-Trimoxazole or fluoroquinolenes and oral amphotericine B are the prophylactic standard. The initial therapy of febrile neutropenia has to be started empirically before identification of causative pathogens or infectious foci. The febrile episodes should be treated with broad spectrum antibiotics (combinations or monotherapy) due to the spectrum of microorganisms or resistance situation at hospital. In case of non-response after 3-4 days the initial therapy should be modified, in addition to further antibacterial therapy the start with an antifungal drug has to be recommended. In patients with pulmonary infiltrates the early treatment with amphotericine B has been shown to be more advantageous than delayed antifungal therapy. Furthermore, the antibiotic therapy is based on proven microorganisms, susceptibility testing and infectious foci. The value of interventional treatment with G-CSF or GM-CSF is controversely discussed. An uncompromising handling of febrile neutropenia is necessary to reduce the mortality due to infections in patients with hematologic malignancies.

Piperacillin/tazobactam versus cefepime as initial empirical antimicrobial therapy in febrile neutropenic patients: a prospective randomized pilot study.

The objective of the presented prospective, randomized study was to compare the efficacy of empirical antimicrobial monotherapy with piperacillin/tazobactam (PIP/TAZ) to cefepime (CEFP) for treatment of infections in neutropenic patients. From a total of 102 febrile episodes 100 were evaluable. The most frequent microorganisms were gram-negative, documented in 22% vs. 24% of the febrile episodes (gram-positives 18% vs. 16%, fungi 2% vs. 4%). The response rate was similar with 22/51 (43%) of episodes treated with PIP/TAZ vs. 19/49 (39%) with CEFP. Of the different infection types classified at the end of the febrile episodes, patients with fever of unknown origin (FUO) and primary bacteremias showed the best initial responses with 25/44 (57%) and 11/22 (50%). Lower initial response rates were found in pneumonias with totally 3/13 (23%) and other clinically documented infections with 2/21 (10%), without any difference between both groups. Gram positive infections showed a higher response with PIP/TAZ than with CEFP (4/9 vs. 0/8), gram negative responded less frequently (3/11 vs. 7/13). The median time until persistent defervescence was equal in both groups (2.5 vs. 2 days), likewise the response rates after the different steps of therapy modifications (change to imipenem or ceftazidim, or addition of gentamycin, vancomycin or amphotericin B). Totally, 96% of febrile episodes responded in both therapy arms. Overall, we found no significant differences in efficacy between the two therapeutic regimens. In conclusion, PIP/TAZ as well as CEFP might be a sufficient initial therapy for febrile neutropenia, but further randomized trials with larger patient numbers are necessary.

[Arteriosclerosis as a sequela of chronic Chlamydia pneumoniae infection]. / Arteriosklerose als Folge einer chronischen Infektion durch Chlamydia pneumoniae.

In the last years several new data allow a controversial but convincing interpretation of the pathogenesis of atherosclerosis (arteriosclerosis). Atherosclerosis can be apparently the result of ultrachronic persistent infection by Chlamydia pneumoniae and not the result of different risk factors. The main arguments for the chlamydial genesis are: 1. Correlation of coronary heart disease and other atherosclerotic disease with antibodies against C. pneumoniae. 2. C. pneumoniae could be detected with different techniques (PCR, immunohistology, electromicroscopy, culture) in a high percentage in atheromas from different sites. 3. Three international studies with macrolides in coronary heart disease were successful. 4. The target cells of atherosclerosis (endothelia, macrophages, muscle cells) can be infected by C. pneumoniae in vitro. 5. Positive animal experiments. The Koch-Henle criteria for the proof of the etiology are largely fulfilled--even if there are doubts about the validity of these criteria in chronic local infections. A number of unexplainable aspect of atherosclerosis can be seen in a new light. The higher incidence of coronary heart disease in young males has a parallel in the remarkable androtropism of many bacterial diseases (pneumococcal pneumonia, tuberculosis). The reduction of incidence of atherosclerotic diseases since 1965 can be explained by the much higher intake of doxycyclin and macrolides. The low incidence of coronary heart disease in France--sometimes regarded as an effect of red wine--can be explained as a result of a much higher use of antichlamydial antibiotics. The increase of inflammatory parameters (C-reactive protein, fibrinogen, leucocytes) before acute coronary infarction are not risk factors but signs of an active chronic infection. The interpretation is possible, that atherogenic changes in lipids like increase of LDL and decrease of HDL are not risk factors but consequence of chronic arterial infection by chlamydia. The low incidence of atherosclerosis in the tropics--despite high frequency of chlamydial infection--is difficult to explain. Vascular infection can be related with the age of the patient at the primary infection. With low hygiene, intestinal primary infections in early childhood can be possible. Arterial infection would be thus a result of a primary infection in adolescence ("yet another poliomyelitis story"). There are good arguments for the thesis that C. pneumoniae is the primary cause of atherosclerosis and not a secondary invader. The consequence, nevertheless, is similar: Antibiotics get a key role. The macrolides roxithromycin, azithromycin, clarithromycin and the tetracyclin doxycyclin fulfill the criteria as potential antichlamydial agents. In general a longer treatment (6 to 8 to 12 weeks) seems advisable. It is necessary to start international studies with antibiotics in coronary infarction and other clinical manifestations of atherosclerosis. The relevant antibiotics licensed for chlamydial infections are cheap and safe. Despite of the urgent need for controlled studies, it seems already justified to treat high-risk patients with antibiotics. Meticulous protocols and long-term control of patients are necessary to evaluate the therapeutic effects. Preventive studies in patients without clinical manifestation of atherosclerosis are urgently needed. The risks of resistance or side effects are neglectable, but the organisation of such studies would be very difficult.