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Biomedical subjects

H Frank

Publications and source records attributed to H Frank.

At least 19 recordsLinked to original sources
PubMed2005

Quantification of phytochelatins in plants by reversed-phase HPLC-ESI-MS-MS.

An on-line HPLC-ESI-MS-MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS-MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 micromol kg(-1) plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions.

Chromatography, High Pressure Liquid↗
PubMed2005

[Histomorphometric evaluation of bone ingrowth of porous titanium by a computer-assisted analyzing system].

The objective of this study was to evaluate the bone ingrowth of a new vacuum plasma sprayed titanium surface (vps-ti) in comparison to cs-titanium implants in a göttinger minipig model. Fifteen göttinger minipigs each received the two implants, vacuum plasma sprayed titanium with a porosity of 50% and a pore size of 200 microm (vps-ti) and an implant with a similar porosity but a different pore size 500 microm (cs-ti), at the proximal femur metaphysis by press-fit technique. The pigs were euthanized at three different postsurgical periods: 4, 8 and 12 weeks. Each femur was harvested and qualitative (macroscopic and microscopic) and quantitative (histomorphometric) histological analysis was done on histological slides. The results indicated that there was a difference in bone ingrowth between the two implants, whereas the bone ingrowth of vps-ti was superior to cs-ti after 4 and 8 weeks healing time. 12 weeks post implantationem no statistiscal difference was evident. The pore size of 200 microm seemed superior to a pore size of 500 microm. Whether or not these effects lead to a better mechanical stability remains unanswered.

Animals↗
PubMed2004

Pregnancy-induced sympathetic overactivity: a precursor of preeclampsia.

BACKGROUND: Preeclampsia has been shown to constitute a state of sympathetic overactivity. However, it remains unclear if the sympathetic activity precedes preeclampsia or represents only a secondary phenomenon. To further investigate this issue, we performed a prospective study in pregnant women considered to be at increased risk for preeclampsia owing to preeclampsia during a preceding pregnancy. MATERIALS AND METHODS: Twenty-two women with a history of preeclampsia were longitudinally studied on three occasions: twice during pregnancy (M1: 22 +/- 4, M2: 33 +/- 5 weeks) and once postpartum (M3: 26 +/- 6 weeks postpartum). We measured muscle sympathetic nerve activity (MSNA), forearm blood flow, and blood pressure at rest and during reactive hyperaemia after forearm occlusion. RESULTS: At M1 and M2, none of the subjects was hypertensive, however, muscle sympathetic nerve activity levels were significantly augmented, compared with their postpartum values (M1: 21 +/- 9, M2: 29 +/- 14, M3: 9 +/- 5 bursts min(-1); P < 0.05). Forearm vascular resistance did not significantly change from M1 through M3 (M1: 16 +/- 9, M2: 15 +/- 7, M3: 16 +/- 7 U; P = NS). Gestational muscle sympathetic nerve activity values did not differ significantly among the subjects with subsequent preeclampsia compared with those who remained normotensive [with preeclampsia (n = 6): M1: 21 +/- 5, M2: 27 +/- 6, M3: 7 +/- 4 bursts min(-1); without preeclampsia (n = 16): M1: 21 +/- 11, M2: 30 +/- 16, M3: 9 +/- 6 bursts min(-1); P = NS]. CONCLUSION: Invariably, all women at risk for preeclampisa showed a pregnancy-induced increase in MSNA (pregnancy-induced sympathetic overactivity, PISO), which normalized after delivery. Most importantly, PISO is not necessarily associated with peripheral vasoconstriction and hypertension. Furthermore, only a subset of patients developed preeclampsia later on. Therefore, we hypothesize that PISO constitutes a precursor of preeclampsia which is physiologically compensated for by vasodilating mechanisms, leading to preeclampsia only when they fail.

Adult↗
PubMed2004

Isolated anti-HBV core phenotype in anti-HCV-positive patients is associated with hepatitis C virus replication.

Recovery from hepatitis B virus (HBV) infection is associated with the presence of antibodies against HBV surface (HBs) antigen and HBV core (HBc) antigen. However, anti-HBs antibodies are lost in many cases, and only anti-HBc antibodies persist. A higher frequency of the anti-HBc-alone pattern has been demonstrated for anti-hepatitis C virus (HCV)-positive patients. In this report, 1126 anti-HCV-positive/anti-HBc-positive patients were studied, and the role of HCV replication in influencing the presence or absence of anti-HBs antibodies was investigated. The anti-HBc-alone phenotype was significantly more frequent in HCV-viraemic than in HCV-recovered patients. This finding represents new information regarding the immunopathogenesis of chronic HCV infection and supports previous data indicating impaired humoral immune responses in HCV infection.

Hepacivirus↗
PubMed2003

Simultaneous hemodialysis during coronary angiography fails to prevent radiocontrast-induced nephropathy in chronic renal failure.

BACKGROUND: Radiocontrast medium- (RM) associated nephrotoxicity continues to be a common cause of acute renal failure and may lead in patients with pre-existing chronic renal insufficiency even to end-stage renal failure requiring chronic dialysis. Since extracorporeal removal of RM after RM administration has been shown to be effective but does not prevent radiocontrast-induced nephropathy, the effect of a simultaneous dialysis during RM administration on renal function is not clear. METHODS: In a prospective, randomized and controlled trial, we studied the effect of a 4-hour online dialysis during RM (iomeprol) application in patients with advanced chronic renal failure (serum creatinine > or = 3 mg/dl) undergoing coronary angiography. All patients received hydration with saline before and after standardized coronary angiography and were randomized to receive a simultaneous high-flux hemodialysis (7 patients, HD group) or to control group (10 patients). 24-hour creatinine clearance (CrCl) was measured in all patients before, 1 week and 8 weeks after coronary angiography. The clinical follow-up comprised 8 weeks after RM application. RM plasma levels were measured in both groups 15, 30, 60 minutes, 2, 4, 12, 24, 48 and 72 hours after application by high-pressure liquid chromatography. RESULTS: At baseline, CrCl (19 +/- 10 vs 17 +/- 7 ml/min), percentage of diabetics (57 vs 70%) and dose of RM (77 +/- 27 vs 86 +/- 21 ml) were similar in both groups. Pharmacokinetics: Total clearance of iomeprol was significantly higher (54 +/- 15 vs 20 +/- 12 ml/min, p < 0.001) and the area under curve (AUC) was significantly lower (23 +/- 10 g x h/l vs 94 +/- 57 g x h/l, p < 0.001) in the HD group compared to control group. RM peak plasma levels 15 min after application were not different in both groups (3.0 +/- 1.1 vs 4.2 +/- 1.7 mmol/l, NS), however, significantly lower 60 min (1.6 +/- 0.4 vs 3.7 +/- 1.5 mmol/l, p < 0.01) and 240 min (0.7 +/- 0.3 vs 2.3 +/- 0.7 p < 0.001) after angiography. CLINICAL RESULTS: CrCl showed no difference 1 week (24 +/- 11 vs 19 +/- 9 ml/min, ns) and 8 weeks (24 +/- 5 vs 20 +/- 9 ml/min, NS) after angiography from baseline or between the groups. In each group, 2 patients developed end-stage renal disease and requested permanent dialysis during the 8-week follow-up. CONCLUSION: Simultaneous dialysis reduces AUC of iomeprol significantly, however, does not influence plasma peak concentration after angiography. Renal function and incidence of end-stage renal failure were not influenced by online-dialysis.

Acute Kidney Injury↗
PubMed2002

Cardiovascular effects of beta-blockers with and without intrinsic sympathomimetic activity. A comparison between celiprolol and metoprolol.

BACKGROUND: Celiprolol, a newer beta-blocking agent, has been reported to have vasodilatory capacity which may be due to partial beta-2-receptor agonistic activity or to alpha-receptor antagonistic or central sympathoinhibitory effects. METHODS: To more critically assess the physiologic effects of celiprolol, we measured sympathetic nerve activity to muscle (MSNA), forearm blood flow (FBF), blood pressure (BP), central venous pressure, and heart rate (HR) in 10 normal volunteers at rest, during unloading of cardiopulmonary baroreceptors with lower body negative pressure (LBNP), and during a cold pressor test (CPT). Responses were compared with those seen with metoprolol and with placebo, i.e. each subject was studied three times. RESULTS: Celiprolol did not alter resting levels of hemodynamics, FBF, and MSNA nor did it alter responses to LBNP or the CPT. In contrast, metoprolol produced significant decreases of FBF and HR, and increases of forearm vascular resistance and BP, but had also no effect on responses to the applied stress tests. CONCLUSIONS: The lack of peripheral vasoconstriction seen after acute administration of celiprolol is most likely due to its partial beta-2-receptor agonistic effect and does not seem to be due to a central or reflex action or to an alpha-blocking effect. Both beta-blockers do not impair fundamental neural mechanisms involved in circulatory homeostasis.

Adrenergic beta-Antagonists↗
PubMed2001

Long-term results after microvascular decompression in essential hypertension.

BACKGROUND AND PURPOSE: In 1998, 8 patients with severe, intractable arterial hypertension and MR tomography-demonstrated neurovascular contact of a looping artery at the root entry zone of cranial nerves IX and X, causing neurovascular compression, underwent neurosurgical decompression. The short-term results showed a normalization of blood pressure with a markedly reduced antihypertensive drug regimen in 7 patients. To determine the longer-term outcome concerning blood pressure and secondary organ damage after neurovascular decompression, we studied these 8 operated patients prospectively for a mean follow-up of 3.5 years after surgical intervention. METHODS: Eight hypertensive patients who had undergone microsurgical decompression were monitored every 6 months after surgery to assess blood pressure (by 24-hour ambulatory pressure readings) and the need for antihypertensive medication. To evaluate secondary organ damage, echocardiographic assessment of left ventricular hypertrophy, fundoscopic assessment of hypertensive lesions, and analysis of renal function and proteinuria were done. RESULTS: Three of the 8 operated patients remained normotensive in the long-term period with decreased antihypertensive medication. Two patients required gradual increases of antihypertensive medication after the first postoperative year, after which arterial blood pressure levels were 10% to 15% lower than preoperative levels. Three patients suffered serious cardiovascular and renal complications, with the incidence of lethal intracerebral hemorrhage in 1 patient and end-stage renal disease in 2 patients, of whom 1 experienced sudden cardiac death. CONCLUSIONS: The long-term results verify that microsurgical decompression is a successful alternative therapy in a certain subgroup of patients with arterial hypertension due to neurovascular compression. However, the relevance of the looping artery in the other cases, who did not improve, is not clear. Prospective studies to elucidate the pathophysiological role of neurovascular abnormalities and arterial hypertension are needed.

Adult↗
PubMed2001

Developmental inhibitory gate controls the relay of activity to the superficial layers of the visual cortex.

A developmental reduction in the radial transmission of synaptic activity has been proposed to underlie the end of the critical period for experience-dependent modification in layers II/III of the visual cortex. Using paired-pulse stimulation, we investigated in visual cortical slices how the propagation of synaptic activity to the superficial layers changes during development and how this process is affected by sensory experience. The results can be summarized as follows. (1) Layers II/III responses to repetitive stimulation of the white matter become increasingly depressed between the third and sixth week of postnatal development, a time course that parallels the end of the critical period. (2) Paired-pulse depression is reduced after dark rearing and also by blocking inhibitory synaptic transmission. (3) Paired-pulse depression and its regulation by age and sensory experience is more pronounced when stimulation is applied to the white matter than when applied to layer IV. Together, these results are consistent with the idea that the maturation of intracortical inhibition reduces the capability of the cortex to relay incoming high-frequency patterns of activity to the supragranular layers.

Aging↗
PubMed2001

Haloacetates in fog and rain.

Atmospheric haloacetates can arise from photochemical degradation of halogenated hydrocarbons and from direct anthropogenic emissions. Furthermore, there is also evidence of natural sources although these are quantitatively uncertain. As haloacetates are highly soluble in water, hydrometeors are most significant for their deposition. Fogwater (96 samples) and rainwater samples (over 100 samples) were collected from July 1998 to March 1999 at an ecological research site in northeastern Bavaria, Germany. They were analyzed for monofluoroacetate (MFA), difluoroacetate (DFA), trifluoroacetate (TFA), monochloroacetate (MCA), dichloroacetate (DCA), trichloroacetate (TCA), monobromoacetate (MBA), and dibromoacetate (DBA). The major inorganic ions were also determined. High concentrations of up to 11 microg/L MCA, 5 microg/L DCA, 2 microg/L TCA, and 2 microg/L TFA were found in fogwater associated with westerly winds. Backward trajectories were calculated to determine the origin of the air masses. MBA and DBA have highest concentrations in fogwater advected with air originating from the Atlantic, suggesting the marine origin of these two compounds. All analyzed substances show higher average concentrations in fog than in rain. Estimates of the deposition of haloacetates suggest that the contribution of fog may be more important than rain for the total burden of a forest ecosystem.

Acetates↗
PubMed2001

Capillary electrophoresis with on-chip four-electrode capacitively coupled conductivity detection for application in bioanalysis.

Microchip capillary electrophoresis (CE) with integrated four-electrode capacitively coupled conductivity detection is presented. Conductivity detection is a universal detection technique that is relatively independent on the detection pathlength and, especially important for chip-based analysis, is compatible with miniaturization and on-chip integration. The glass microchip structure consists of a 6 cm etched channel (20 microm x 70 microm cross section) with silicon nitride covered walls. In the channel, a 30 nm thick silicon carbide layer covers the electrodes to enable capacitive coupling with the liquid inside the channel as well as to prevent interference of the applied separation field. The detector response was found to be linear over the concentration range from 20 microM up to 2 mM. Detection limits were at the low microM level. Separation of two short peptides with a pI of respectively 5.38 and 4.87 at the 1 mM level demonstrates the applicability for biochemical analysis. At a relatively low separation field strength (50 V/cm) plate numbers in the order of 3500 were achieved. Results obtained with the microdevice compared well with those obtained in a bench scale CE instrument using UV detection under similar conditions.

Calibration↗
PubMed2001

Afterload reduction in severe aortic regurgitation.

This study was designed to assess the effects of afterload reduction in asymptomatic patients with severe aortic regurgitation (AR) and maintained LV function by cine-MRI. We studied 13 patients at baseline and after 0.2 mg/kg Hydralazine (I.V.). Patients were stratified according to the volumetric LV response to acute afterload reduction: Group I comprised patients with improved LV response; Group II comprised patients with unchanged or deteriorated LV response. Baseline LV function and severity of AR were not significantly different between groups. However, regurgitant fraction decreased (50 +/- 12 vs. 36 +/- 9%; P < 0.03) and cardiac output increased (4.9 +/- 1.4 vs. 7.1 +/- 1.6l/minute; P < 0,001) in Group I and remained unchanged in Group II (54 +/- 10 vs. 55 +/- 10%, P = n.s. and 5.5 +/- 1.4 vs. 6.6 +/- 0.9l/minute; P = n.s.) during maximal vasodilation. Beat-to-beat analysis revealed a decrease of left ventricular endsystolic volume index in group I (48 +/- 13 vs. 37 +/- 9 ml/beat; P < 0.05) and no change in group II (61 +/- 20 vs. 62 +/- 20 ml/beat; P = n.s.). In the natural history of chronic AR, the absence of improved LV performance during acute vasodilation using beat-to-beat analysis by MRI may identify patients with more advanced cardiac adaptation to chronic volume overload.

Adult↗
PubMed2001

The effects of ACE inhibitor therapy on left ventricular myocardial mass and diastolic filling in previously untreated hypertensive patients: a cine MRI study.

Cardiac remodeling in case of hypertension induces hypertrophy of myocytes and elevated collagen content and, subsequently, impaired diastolic filling of the left ventricle. The purpose of this prospective study was to evaluate changes of left ventricular (LV) myocardial mass, as well as diastolic filling properties, in hypertensive patients treated with the ACE inhibitor fosinopril. Sixteen hypertensive patients with echocardiographically documented LV hypertrophy and diastolic dysfunction received fosinopril (10-20 mg daily). Measurements of LV myocardial mass and properties of diastolic filling (peak filling fraction (PFF); peak filling rate (PFR)) were performed prior to medication, as well as after 3 and 6 months of therapy using cine magnetic resonance imaging (MRI). Ten healthy subjects served as a control group. LV myocardial mass (g/m2) decreased continuously within 3-6 months of follow-up by 32% (148 +/- 40 vs. 120 +/- 26 vs. 101 +/- 22 g/m2; P < 0.0001/0.005). The extent of regression correlated to the severity of LV hypertrophy at baseline (r = 0.77; P < 0.004). Early diastolic filling increased significantly within 6 months of therapy (PFF (%): 36 +/- 6 vs. 61 +/- 7, P < 0.0001; PFR (mL/second): 211 +/- 48 vs. 282 +/- 48, P < 0.001). Cine MRI can be used to assess the time course of pharmacological effects on cardiac remodeling in the course of hypertension. ACE inhibitor therapy results in a significant reduction of LV mass within 3 months and is accompanied by a normalization of diastolic filling that is completed after 6 months.

Adult↗
PubMed2001

Characterization of atherosclerotic plaque by magnetic resonance imaging.

BACKGROUND: Atherosclerosis, the most common disease in the industrialized world, is still one of the most poorly explained and little understood problems in medicine. It is important to obtain reliable images of lipid-rich type IV and Va plaques, which, upon rupture, are most likely to cause acute ischemic events. The development of noninvasive methods to detect atherosclerotic plaque lesions and assess their composition promises to play an important role in the management of patients in the future. METHODS: This review highlights the advantages and disadvantages of magnetic resonance imaging (MRI) and intravascular ultrasound, compared with histopathologic findings, in detecting and determining the extent of atheromatous plaques. RESULTS: Compared with intravascular ultrasound, MRI has been found to be superior in delineating lipid plaque components. Intravascular ultrasound, despite its better spatial resolution, is an invasive method and does not provide information on complex features of stenotic vessels. In vitro studies show that MRI of atherosclerotic plaques makes it possible to characterize the lesions in detail in terms of size, shape, and plaque tissue components. CONCLUSIONS: Although MRI is in its early stages, it shows potential as a noninvasive method that can be used to evaluate atherosclerotic plaque and distinguish its components.

Arteries↗
PubMed2001

Induction of autoantibodies to the adrenal cortex and pancreatic islet cells by interferon alpha therapy for chronic hepatitis C.

BACKGROUND/AIMS: Interferon alpha (IFN-alpha) therapy for chronic hepatitis C may trigger induction of autoimmunity against several organs. Immune reactions against distinct adrenocortical protein antigens involved in adrenal autoimmune disease have not been reported to date. Therefore, we investigated the development of highly sensitive and specific adrenal autoantibodies in patients with chronic hepatitis C in response to IFN-alpha treatment. In addition, we studied induction of pancreatic islet and thyroid autoantibodies. PATIENTS/METHODS: Sera of 75 patients (42 males, 33 females; mean age 47 (13) years) were analysed before, during, and after IFN-alpha therapy (9-18x10(6) IE/week; mean duration 8.3 (3.5) months). Autoantibodies (Abs) to adrenal 21-hydroxylase (21OH-Abs), and to islet glutamic acid decarboxylase (GAD65-Abs) and protein tyrosine phosphatase (IA2-Abs) were determined by a radiobinding assay using (35)S labelled protein generated by an in vitro translation system. Thyroid antibodies were measured by a commercially available ELISA. RESULTS: Thirteen of 75 patients were initially positive for some of the autoantibodies. During or after IFN-alpha therapy, 3/62 initially negative patients (4.8%) developed 21OH-Abs. GAD65-Abs or IA2-Abs appeared in 5/62 and 1/62 patients, respectively (9.7% in total). In 12/62 patients (19.4%), thyroid specific antibodies appeared. In none of the 21OH-Ab positive subjects was adrenal dysfunction observed, and no patient with islet autoantibodies developed diabetes mellitus or impaired glucose tolerance. CONCLUSIONS: IFN-alpha induces 21OH-Abs in some cases, while islet and thyroid specific autoantibodies are more frequently found. However, our results indicate for the first time that the adrenal cortex also has to be considered as a potential target of IFN-alpha related autoimmunity.

Adrenal Cortex↗
PubMed2001

Comparative study of composite resin placement: centripetal buildup versus incremental technique.

An in vitro study was performed to evaluate the effect of two different proximal restoration techniques with different matrix systems on the marginal seal and microhardness of Class II composite restorations. Results indicated that the lowest, however, not significantly different, microleakage was achieved in totally bonded deep Class II restorations prepared with margins surrounded by enamel when using transparent matrices and reflective wedges in combination with the centripetal buildup technique. Highest surface hardness of composite resin was related to transparent matrices and reflecting wedges.

Coloring Agents↗
PubMed2001

[Sensitive and rapid analysis of nitrophenols and herbicides by capillary zone electrophoresis (CZE)].

11 Nitrophenols and some acidic herbicides have been separated by modified CZE. Good separation of such compounds can be achieved in less than 10 min by simply modifying the run buffer with organic solvents such as methanol, acetonitrile in a concentration of 40% (V/V). The limits of detection (LODs) for nitrophenols by UV-absorption at 215 nm were 0.5 mg/L-1.1 mg/L. Solid phase extraction was used to preconcentrate nitrophenols and some herbicides to reach an LOD at microgram/L levels. Typical samples have been analyzed.

Electrophoresis, Capillary↗