Dieter Hafner

Monitoring of cadmium, copper, lead and zinc status in young children using toenails: comparison with scalp hair

Cadmium, copper, lead and zinc concentrations were determined (atomic absorption spectrometry) in the proximal end of scalp hair (n = 474) and in toenail clippings (n = 461) of children, aged 3-7 years, living in an industrialized and in a rural area of the Federal Republic of Germany. With the exception of Zn in hair, levels of the elements were log-normally distributed. Data are presented as geometric means. Toenail Cd and Pb levels were much higher than those in hair (Cd, 457 vs 90 ng g-1; Pb, 8.5 vs 2.7 micrograms g-1), while Cu and Zn values were similar in both biological media (toenail vs hair: Cu, 7.5 vs 10.6 micrograms g-1; Zn, 129 vs 108 micrograms g-1). In toenails, all elements were positively correlated with each other. In hair, there was a close relationship only between Cd and Pb; Cd and Pb were inversely related to Zn. With the exception of Zn (no correlation), there was a minor relationship between metal levels in hair and those in toenails. Using stepwise regression analysis, seasonal variation was found to be the main factor influencing hair metal levels, while nail metal levels were mainly influenced by place of residence (with the exception of Cu concentrations, for which there were no significant predictors). Multiple correlation coefficient was higher for hair than for nails. It is concluded that, for biological monitoring, toenail clippings are less suitable than hair samples.

Toxin-Gene Profile Heterogeneity among Endemic Invasive European Group A Streptococcal Isolates

We determined the toxin-gene profiles of 239 endemic, invasive group A streptococcal (GAS) isolates that circulated, within a 5-year period, in European university hospitals. Profiling was performed by use of multiplex polymerase chain reaction that screened for 9 streptococcal pyrogenic exotoxins (speA, speB, speC, speF, speG, speH, speJ, ssa, and smeZ). Analysis revealed that invasive GAS isolates do not share a common toxin-gene profile. Although all emm types were characterized by several different toxin-gene profiles, a predominance of 1 or 2 toxin-gene profiles could be observed, reflecting that a few invasive clones have spread successfully throughout the world. Remarkably, statistical pair-wise analysis of individual toxin genes revealed that strains that did not share the predominant profile still showed a nonrandom distribution of key toxin genes characteristic of the specific emm type. This could indicate that M proteins function, directly or indirectly, as barriers for horizontal gene exchange.

Evidence for a Multifactorial Process Involved in the Impaired Flow Response to Nitric Oxide in Hypertensive Patients With Endothelial Dysfunction

The assessment of endothelial function in hypertensive patients receiving acetylcholine has revealed conflicting results. Whether an impaired flow response to acetylcholine is explained solely by a diminished endothelial synthesis of nitric oxide (NO) remains unclear as yet. In the present study, we tested the hypothesis that mechanisms other than reduced NO synthesis contribute to the hypertension-associated impairment of endothelium-dependent vasodilation. Therefore, the dilatory response to endogenous and exogenous NO was measured in resistance arteries and cutaneous microvessels in the forearm circulation of 12 normotensive individuals and 17 hypertensive patients. In addition, the overall dilatory capacity was assessed by peak flow during reactive hyperemia after 3 minutes of ischemia. Forearm blood flow was quantified by venous occlusion plethysmography at rest, during application of the NO donor sodium nitroprusside, and during stimulation of endogenous NO synthesis by acetylcholine and bradykinin. Blood flow velocity in the cutaneous microvasculature was measured with laser-Doppler flowmetry in parallel. Resting forearm flow was comparable in both groups (3.1 +/- 0.2 and 3.4 +/- 0.2 mL.min-1.100mL-1 tissue), whereas blood pressure and thus peripheral vascular resistance was significantly elevated in hypertensive compared with normotensive subjects. Hyperemic peak flow was significantly blunted in hypertensive patients. Sodium nitroprusside, acetylcholine, and bradykinin increased flow in a dose-dependent manner to a comparable extent in the control group (13.3 +/- 0.8, 13.6 +/- 1.3, and 14.6 +/- 0.7 mL.min-1.100mL-1 tissue, respectively). In contrast, in hypertensive patients maximum increase in resting flow was significantly reduced (sodium nitroprusside, -36%; acetylcholine, -44%; and bradykinin, -56%). The flow response after stimulation of endogenous NO synthesis by bradykinin was significantly more blunted compared with that of exogenous NO after application of sodium nitroprusside. In the cutaneous microvasculature, bradykinin-induced increases in blood flow velocity were selectively impaired in hypertensive patients, whereas flow response to acetylcholine was preserved. Thus, we conclude that in arterial hypertension endothelium-dependent, NO-mediated dilation of resistance arteries and cutaneous microvessels of the forearm vasculature is heterogeneously impaired, depending on the type of endothelial receptor stimulated. Furthermore, the present data suggest that in hypertensive patients the impairment of NO-dependent dilation of resistance arteries is caused by at least three different mechanisms: (1) a reduced endothelial synthesis of NO due to either a disturbed signal-transduction pathway and/or a reduced activity of NO synthase, (2) an accelerated NO degradation within the vessel wall, and (3) alterations in the vessel architecture resulting in an overall reduced dilatory capacity of resistance arteries.

Effects of the calcium entry blocker bepridil on repolarizing and pacemaker currents in sheep cardiac Purkinje fibres

Summary(1) Effects of bepridil (0.3–100 μmol/l) on transmembrane currents which are active during the repolarization of the cardiac action potential were studied in sheep cardiac Purkinje fibres with the two-microelectrode voltage-clamp technique. Transmembrane currents were activated at a frequency of 0.03 Hz. (2) The initial inwardly rectifying current (iK1) was reduced by 1.8 μmol/l bepridil to 70% of the reference iK1-current in the absence of the drug. (3) An initial outward current, which is activated at positive membrane potentials (iinst) was depressed to 70% of reference by 14 μmol/l bepridil. (4) The time-dependent outward current (iK) was decreased by 1.8 μmol/l bepridil to 70% of its amplitude in the absence of bepridil. The biexponential time course of iK-current activation changed to be monoexponential with 100 μmol/l bepridil. The effect of bepridil on iK-current resulted in a shift of the activation curve of iK-current to more positive membrane potentials (10 μmol/l bepridil) and an additional decrease of driving force and/or conductance of the iK-channels with higher bepridil concentrations (100 μmol/l). (5) The transient outward current (ito) was completely blocked by 30 μmol/l bepridil. Inhibition to 70% of reference occurred with 1 μmol/l bepridil. The voltage-dependent inactivation of ito-current was affected by bepridil: the amplitude of the steady-state inactivation curve was reduced and ito-current was inactivated faster after application of bepridil. Bepridil caused no pronounced shift of the steady-state inactivation curve along the voltage axis. (6) The pacemaker current (if) was slightly increased under the influence of low bepridil concentrations (0.3, 1 μmol/l) while it was reduced to 70% of reference by 100 μmol/l bepridil. (7) The blocking action of bepridil on outward currents in sheep cardiac Purkinje fibres will explain the action potential prolongation, which is observed in different mammalian cardiac tissues under the influence of bepridil.

Alterations in the p53 pathway and their association with radio- and chemosensitivity in head and neck squamous cell carcinoma

Chemotherapy and/or radiotherapy are established measures in treatment protocols of head and neck squamous cell carcinoma (HNSCC). However, we still lack reliable predictive markers for the response to radio- and chemotherapy. The p53 pathway is involved in stress response and thus might influence chemo-/radiosensitivity. Using 29 HNSCC cell lines previously characterized for p53 mutations, we simultaneously analyzed several key players in the p53 pathway by RT-PCR, transcript sequencing and immunohistochemistry, and investigated their association with chemosensitivity and radiosensitivity. Cell lines with p53 mutations were slightly more sensitive to cisplatin than those with wild-type p53. The type of mutation did not influence radio- or chemosensitivity. p14(ARF), an activator of p53, was lost or mutated in all cell lines. Three cell lines showed overexpression of HDM-2, a major negative regulator of p53; however, HDM-2 levels did not correlate with radio- or chemosensitivity. HPV-16 oncoproteins were detected in one highly chemoresistant cell line. Our findings suggest that molecular events resulting in the inactivation of the p53 pathway occur in all HNSCC cell lines. However, single alterations in the p53 pathway are not reliable predictors for the response to radio- or chemotherapy in HNSCC.

Development of Resistance to Ciprofloxacin, Rifampin, and Mupirocin in Methicillin-Susceptible and -Resistant Staphylococcus aureus Isolates

ABSTRACT A relationship between resistance to methicillin and resistance to fluoroquinolones, rifampin, and mupirocin has been described forStaphylococcus aureus. Differences in resistance rates may be explainable by a higher spontaneous mutation rate (MR) or a faster development of resistance (DIFF) in methicillin-resistant S. aureus (MRSA). No differences in MR, DIFF, and mutations ingrlA and gyrA were detected between methicillin-susceptible S. aureus and MRSA. The higher resistance rates in MRSA are not the result of hypermutability of target genes or a faster emergence of different mutations and may be the consequence of clonal spread of multiresistant MRSA.

Reduction of peripheral flow reserve impairs endothelial function in conduit arteries of patients with essential hypertension

Background A diminished flow reserve in resistance vessels is a hallmark of hypertensive microvascular disease. Hypertension is associated with structural alterations in the microcirculation and a reduced endothelium-dependent dilation in conduit arteries. Both have been demonstrated to predict future cardiovascular events. Objective We hypothesized that a reduced peripheral flow reserve impairs endothelial function in upstream conduit arteries in patients with arterial hypertension. Design In 43 hypertensive patients (HT) and 38 normotensive controls (NT) endothelial function of the brachial artery was assessed by measurement of flow-mediated dilatation (FMD), using high-resolution ultrasound. Peripheral flow reserve (FR) was determined via measurements of forearm blood flow at rest and during increments of reactive hyperaemia, using venous occlusion plethysmography. Results FMD was markedly impaired in HT (3.6 ± 0.3%) as compared with NT (10.2 ± 0.3%), whereas maximum brachial artery diameter following endothelium-independent dilatation was similar in both groups. In hypertensive patients FR was significantly reduced (HT, 3.2 versus NT, 6.0) during reactive hyperaemia after 5 min of ischaemia. FR was associated with FMD (r = 0.68, P < 0.01). Multiple stepwise regression analysis identified FR as a strong independent variable determining the extent of FMD (r2 = 0.46, P < 0.01). In HT the dose–response curve of FMD upon stepwise increases of FR was shifted significantly to the right. Normalization of FR improved FMD in HT by more than 60%. Conclusions In essential hypertension a reduced FR contributes to the endothelial dysfunction of upstream conduit arteries. These findings may have therapeutic and prognostic implications in patients with arterial hypertension.

Increased prevalence of class I integrons in Escherichia coli, Klebsiella species, and Enterobacter species isolates over a 7-year period in a German university hospital

ABSTRACT The prevalence of integrons in five enterobacterial species was analyzed in 900 blood culture isolates from 1993, 1996, and 1999. Remarkably, the prevalence increased from 4.7% in 1993 to 9.7% in 1996 and finally to 17.4% in 1999 (P < 0.01). Within 7 years the combined percentage of P1 strong promoters and P1 weak plus P2 active promoters with high transcription efficacies has increased from 23.1 to 33.3 and finally 60% (P< 0.05).

Antitumor activity of protein kinase C inhibitors and cisplatin in human head and neck squamous cell carcinoma lines

Protein kinase C (PKC) plays a pivotal role in signal transduction involved in the control of cell proliferation, differentiation and apoptosis. Interference with such signaling pathways may result in altered tumor cell response to antineoplastic drugs. We investigated the effects of two selective PKC inhibitors as single agents and in combination with cisplatin in cell lines derived from squamous cell carcinomas of the head and neck (SCCHN). Safingol (Saf) is directed against the regulatory domain, whereas chelerythrine (Che) interacts with the catalytic domain of PKC. In six SCCHN cell lines (UM-SCC 11B, 14A, 14C and 22B, 8029NA, and a 5-fold cisplatin-resistant subline 8029DDP). PKC activities ranged between 1 and 158 IU/1×107 cells, and they were inversely proportional to the amount of cellular epidermal growth factor receptor. Using the colorimetric MTT assay, PKC inhibitors Saf and Che showed comparable dose-dependent growth inhibition. The 50% inhibitory concentrations (IC50) were between 3.8–8.6 μ M for Saf and 8.5–13.6 μ M for Che with no relationship to PKC activity or cisplatin sensitivity of the respective cell lines. Combinations of cisplatin (IC50 = 0.4–5.8 μ g/ml) and either PKC inhibitor (5 μ M Saf, 10 μ M Che) led to a significant decrease of cisplatin IC50 values in most cell lines. However, comparison with theoretical additive dose–response curves showed additive rather than synergistic effects for both PKC inhibitors.

Occurrence of multidrug resistance to oral antibiotics among Escherichia coli urine isolates from outpatient departments in Germany: Extended-spectrum β-lactamases and the role of fosfomycin

The in vitro activities of fosfomycin and seven other antibiotics commonly used for oral treatment of urinary tract infections (UTIs) were evaluated for 499 Escherichia coli isolated from urine samples during a nationwide laboratory-based surveillance study in 2010. Overall, the highest resistance rates were found for amoxicillin (42.9%), followed by amoxicillin/clavulanic acid (32.7%), trimethoprim/sulfamethoxazole (SXT) (30.9%), ciprofloxacin (19.8%), cefuroxime (10.0%), cefpodoxime (8.6%) and cefixime (8.2%). One-half of the isolates (n=252; 50.5%) were fully susceptible to the eight drugs, whilst only 6 strains (1.2%) were resistant to fosfomycin. Combined resistance to amoxicillin, cefuroxime, ciprofloxacin and SXT was detected in 29 isolates (5.8%). Moreover, 40 isolates (8.0%) produced an extended-spectrum β-lactamase (ESBL), including CTX-M-type ESBLs detected in 39/40 isolates (97.5%) and a TEM-52 ESBL in 1 strain (2.5%). The predominant CTX-M-type ESBL was CTX-M-15 (27/39; 69.2%). Of the 27 CTX-M-15 producers, 19 (70.4%) belonged to the clonal lineage E. coli O25b-ST131. All but one ESBL-producing strains were fosfomycin-susceptible. In view of the emergence of multidrug resistance to standard oral antibiotics, these data support that oral fosfomycin (trometamol salt) may represent a valuable option in the treatment of uncomplicated UTIs.