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Biomedical subjects

M Hein

Publications and source records attributed to M Hein.

At least 19 recordsLinked to original sources
PubMed2005

Effects of xenon anaesthesia on the circulatory response to hypoventilation.

BACKGROUND: Circulatory response to hypoventilation is aimed at eliminating carbon dioxide and maintaining oxygen delivery (DO(2)) by increasing cardiac output (CO). The hypothesis that this increase is more pronounced with xenon than with isoflurane anaesthesia was tested in pigs. METHODS: Twenty pigs received anaesthesia with xenon 0.55 MAC/remifentanil 0.5 microg kg(-1) min(-1) (group X, n=10) or isoflurane 0.55 MAC/remifentanil 0.5 microg kg(-1)min(-1) (group I, n=10). CO, heart rate (HR), mean arterial pressure (MAP) and left ventricular fractional area change (FAC) were measured at baseline, after 5 and 15 min of hypoventilation and after 5, 15 and 30 min of restored ventilation. RESULTS: CO increased by 10-20% with both anaesthetics, with an equivalent rise in HR, maintaining DO(2) in spite of a 20% reduction in arterial oxygen content. Decreased left ventricular (LV) afterload during hypoventilation increased FAC, and this was more marked with xenon (0.60-0.66, P<0.05 compared with baseline and isoflurane). This difference is attributed to negative inotropic effects of isoflurane. Increased pulmonary vascular resistance during hypoventilation was found with both anaesthetics. CONCLUSION: The cardiovascular effects observed in this model of moderate hypoventilation were sufficient to maintain DO(2). Although the haemodynamic response appeared more pronounced with xenon, differences were not clinically relevant. An increase in FAC with xenon is attributed to its lack of negative inotropic effects.

Analysis of Variance↗
PubMed2005

Haemodynamic effects of haemorrhage during xenon anaesthesia in pigs.

BACKGROUND: It was hypothesized that xenon would stabilize mean arterial pressure (MAP) in haemorrhagic shock, recovery, and volume resuscitation, because a higher MAP has been observed with xenon, when compared with isoflurane anaesthesia. The responses to haemorrhage and subsequent volume replacement were therefore compared between xenon and isoflurane anaesthesia, in pigs. METHODS: Pigs were randomized to anaesthesia with xenon 0.55 MAC (group Xe, n=9) or isoflurane 0.55 MAC (group Iso, n=9), each with remifentanil 0.5 microg kg(-1) min(-1). MAP, heart rate, cardiac output (CO), and left ventricular fractional area change (FAC) were collected at control (1), after haemorrhage (20 ml kg(-1)) (2), after 10 min of recovery (3), after volume replacement (4), and 30 min later (5). Data were analysed by two-way repeated measures anova. RESULTS: Blood loss decreased MAP (Xe: 103 [21] to 53 [24] mm Hg; Iso: 92 [18] to 55 [14] mm Hg) and CO (Xe: 4.1 [0.8] to 2.6 [0.5] litre min(-1); Iso: 5.1 [1.1] to 3.8 [1.2] litre min(-1)), in spite of significant tachycardia. MAP and CO recovered to about 75% of control, and subsequent volume replacement completely reversed symptoms in both groups, but increased FAC only with xenon. CONCLUSION: Haemodynamic response to acute haemorrhage appeared faster with xenon/remifentanil than with isoflurane/remifentanil anaesthesia. In particular MAP decrease and short-term recovery were more marked with xenon (P<0.02). In the xenon group, volume replacement increased FAC compared with control and isoflurane (P<0.02).

Anesthetics, Inhalation↗
PubMed2005

Entanglement in spin chains and lattices with long-range Ising-type interactions.

We consider N initially disentangled spins, embedded in a ring or d-dimensional lattice of arbitrary geometry, which interact via some long-range Ising-type interaction. We investigate relations between entanglement properties of the resulting states and the distance dependence of the interaction in the limit N-->infinity. We provide a sufficient condition when bipartite entanglement between blocks of L neighboring spins and the remaining system saturates and determine S(L) analytically for special configurations. We find an unbounded increase of S(L) as well as diverging correlation and entanglement length under certain circumstances. For arbitrarily large N, we can efficiently calculate all quantities associated with reduced density operators of up to ten particles.

Journal Article↗
PubMed2005

A double-blinded, placebo-controlled trial of garlic as a mosquito repellant: a preliminary study.

The hypothesis that the ingestion of garlic provides protection against bloodsucking pests such as mosquitoes was investigated using a randomized, double-blinded, placebo-controlled crossover study. Subjects were asked to consume either garlic (one visit) or a placebo (the other visit). They were then exposed to laboratory-reared Aedes aegypti (Linnaeus) (Diptera: Culicidae). The numbers of mosquitoes that did not feed on the subjects, the number of mosquito bites, the weights of the mosquitoes after feeding and the amounts of blood ingested were determined. The data did not provide evidence of significant systemic mosquito repellence. A limitation of the study is that more prolonged ingestion of garlic may be needed to accomplish repellence.

Aedes↗
PubMed2002

Pesticide use and practices in an Iowa farm family pesticide exposure study.

Residents of Iowa were enrolled in a study investigating differences in pesticide contamination and exposure factors between 25 farm homes and 25 non-farm homes. The target pesticides investigated were atrazine, metolachlor, acetochlor, alachlor, 2,4-D, glyphosate, and chlorpyrifos; all were applied to either corn or soybean crops. A questionnaire was administered to all participants to determine residential pesticide use in and around the home. In addition, a questionnaire was administered to the farmers to determine the agricultural pesticides they used on the farm and their application practices. Non-agricultural pesticides were used more in and around farm homes than non-farm homes. Atrazine was the agricultural pesticide used most by farmers. Most farmers applied pesticides themselves but only 10 (59%) used tractors with enclosed cabs, and they typically wore little personal protective equipment (PPE). On almost every farm, more than one agricultural pesticide was applied. Corn was grown by 23 (92%) farmers and soybeans by 12 (48%) farmers. Of these, 10 (40%) grew both soybeans and corn, with only 2 (8%) growing only soybeans and 13 (52%) growing only corn. The majority of farmers changed from their work clothes and shoes in the home, and when they changed outside or in the garage, they usually brought their clothes and shoes inside. Applying pesticides using tractors with open cabs, not wearing PPE, and changing from work clothes in the home may increase pesticide exposure and contamination. Almost half of the 66 farm children less than 16 years of age were engaged in some form of farm chores, with 6 (9%) potentially directly exposed to pesticides, while only 2 (4%) of the 52 non-farm children less than 16 years of age had farm chores, and none were directly exposed to pesticides. Farm homes may be contaminated with pesticides in several ways, resulting in potentially more contamination than non-farm homes, and farm children may be directly exposed to pesticides through farm chores involving pesticides. In addition to providing a description of pesticide use, the data presented here will be useful in evaluating potential contributing factors to household pesticide contamination and family exposure.

Adolescent↗
PubMed2001

Antibacterial properties of human amnion and chorion in vitro.

OBJECTIVE: The purpose of the present study was to explore the direct effects of amnion and chorion on bacterial growth in vitro including the antibacterial spectrum. Chorioamniotic membranes were obtained under sterile conditions from 13 healthy women undergoing elective cesarean section at term. Likewise, chorioamniotic membranes were obtained from 10 healthy women with spontaneous vaginal delivery at term. Five strains of Hemolytic streptococci group B (GBS) were tested and one clinical isolate of the following species or bacterial groups: Hemolytic streptococcus group A, Staphylococcus aureus, Staphylococcus saprophyticus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter calcoaceticus and Lactobacillus species. Bacteriological media included (1) blood-agar medium; (2) a transparent agar medium for submerged cultures; and (3) a nutrient broth medium. RESULTS: An inhibitory effect of fetal membranes against a range of bacteria was found. Consistent results were obtained in experiments with cultures on agar and cultures suspended in agar (membranes from eight women in both studies). In experiments with liquid cultures (seven women) only chorion showed a marginal inhibitory effect. All strains were inhibited, but the most pronounced inhibition was obtained for streptococcus group A, S. aureus and S. saprophyticus by both chorion and amnion. CONCLUSION: This study demonstrated an inhibitory effect of the fetal membranes on a diverse panel of bacteria

Agar↗
PubMed2001

An in vitro study of antibacterial properties of the cervical mucus plug in pregnancy.

OBJECTIVE: To evaluate whether cervical mucus plugs are antibacterial in vitro. STUDY DESIGN: Cervical mucus plugs from 56 healthy women in labor were studied by 2 different antimicrobial assays: (1) analysis of the inhibition by the cervical mucus plug of several gram-positive and gram-negative bacteria by overlaying the cervical mucus plug onto an agar plate with imbedded bacteria, and (2) determination of the antibacterial property of the cervical mucus plug material by radial diffusion assay with group B Streptococcus and Escherichia coli. RESULTS: In the agar overlay assay, there was complete inhibition of clinical isolates of Staphylococcus saprophyticus, E coli, and Pseudomonas aeruginosa and patient-variable partial-to-complete inhibition of Enterococcus faecium, Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus agalactiae. In the radial diffusion assay, cervical mucus plugs had activity toward group B Streptococcus equivalent to 0.075 microg/mL of gentamicin and toward E coli equivalent to 0.5 microg/mL of gentamicin. CONCLUSION: A low-molecular substance with antibacterial activity in the cervical mucus plug may protect the fetus against ascending infections.

Anti-Bacterial Agents↗
PubMed2000

Liquid crystals based on fluorinated carbohydrates.

Fluorine introduced in the hydrophilic or the hydrophobic region of amphiphiles influences the thermomesomorphy of amphiphilic and monophilic fluorosugars in a very specific manner. This paper is the first review about chiral mesogens based on fluorinated carbohydrates. It covers the literature published so far. Analytical objectives are given to: (i) Effects of fluorine atoms on the H-bonding network of the hydrophilic region of sugar amphiphiles; (ii) Effects of perfluoroalkyl chains compared to alkyl chains; (iii) Polymorphism, e.g., also formation of smectic S(C)* phases.

Carbohydrates↗
PubMed2000

NMR spectra of fluorinated carbohydrates.

Recent advances in structural and conformational analysis of fluorinated carbohydrates by NMR spectroscopy are reviewed. Characteristic 1H, 13C, and 19F NMR chemical shifts and coupling constants for selected examples are given and the spectral data of a series of fluorinated carbohydrates were collected in continuation of the review of Csuk and Glänzer [Adv. Carbohydr. Chem. Biochem., 46 (1988) 73-177].

Carbohydrates↗
PubMed2000

Noninvasive glucose measurement by monitoring of scattering coefficient during oral glucose tolerance tests. Non-Invasive Task Force.

BACKGROUND: Continuous glucose monitoring by means of optical glucose sensors would allow patients with diabetes to check their metabolic control to their convenience. In an earlier study, we showed that noninvasive glucose monitoring is feasible for rapid changes in blood glucose by means of measuring the scattering coefficient of human skin. In this study, we investigated whether also slower changes in blood glucose, this time induced by an oral glucose load, can also be monitored by this approach. METHODS: Five healthy subjects and 13 patients with type 2 diabetes have been given a 75-g oral glucose load. Portable noninvasive systems were used to measure the skin tissue scattering coefficient. For this purpose, two optical sensor heads were attached directly to the skin of each volunteer. Light was applied to the skin and the reflected light intensity was registered. RESULTS: In 8 of 10 measurements, correlation of changes in scattering coefficient with changes in glycemia was acceptable. In 19 of 26 measurements (73%) of patients with type 2 diabetes the observed changes in the scattering coefficient also correlated in acceptable manner. The accordance between the simultaneous measurements of the two sensor heads was acceptable in 13 of 18 volunteers and patients studied. There were virtually no differences in the quality of the measurements between healthy volunteers and patients with diabetes. CONCLUSIONS: This study shows that also slow changes in blood glucose induced by an oral glucose load can be monitored by registration of scattering coefficient changes. It remains to be elucidated why this has not been possible in all experiments.

Adult↗
PubMed1999

Inhaled nitric oxide as a prophylactic treatment against reperfusion injury of the lung.

BACKGROUND: Inhaled Nitric Oxide (NO) has been found to be effective in clinical treatment of reperfusion injury after lung transplantation. This study was designed to determine a possible prophylactic role to reduce severe reperfusion injury. METHODS: In 12 minipigs the left lung was selectively perfused with cold Euro-Collins solution. After 90 minutes of warm ischemia the lungs were reperfused and the contralateral pulmonary artery and main bronchus clamped. Hemodynamic and respiratory parameters were monitored for 7 hours. 6 animals were used as controls. 6 pigs formed the NO group and were ventilated continuously with 40 ppm nitric oxide (NO) starting 30 minutes prior to reperfusion. RESULTS: In the control group right heart failure developed within 1.9 +/- 0.8 hours of reperfusion. Lung compliance was significantly reduced. A significant increase of pulmonary vascular resistance (PVR) was found. All animals of the NO group survived the reperfusion period of 7 hours. PVR was decreased compared to controls (p = 0.03). AaDO2 was lower, but not significantly different. The dynamic compliance of the lung was significantly higher (p = 0.007) in the NO group. CONCLUSIONS: The prophylactic institution of inhaled NO reduces reperfusion injury of the lung. Short-term use of inhaled NO should be adopted as a prophylactic agent after transplantation of lungs preserved in Euro-Collins solution.

Administration, Inhalation↗
PubMed1998

Gene transfer into rat heart-derived endothelial cells.

OBJECTIVE: Progressive graft arteriosclerosis is responsible for the majority of late deaths in cardiac transplant recipients. Despite many investigations, the pathogenesis of this disease remains undetermined and its control inadequate. A somatic gene transfer during the cold ischemic time and thus before transplantation might be a new therapeutic tool. This approach allows a long incubation time of the DNA and a safe transfer with liposomes and transferrin with less adverse effects for the organ recipient. METHODS: The target cells (microvascular endothelial cells (MVECs)) for this gene transfer were isolated from rat hearts by perfusion with collagenase via an aortic cannulae. The cells were purified by changing the medium 30 min after subcultivation in order to remove fibroblasts and smooth muscle cells. The endothelial cells (ECs) were identified by typical morphology and the uptake of Dil-Ac-LDL. The gene transfer was carried out with a beta-galactosidase reporter plasmid (pCMVbeta), cationic liposomes (Lipofectin), and transferrin. Different transfection solutions were prepared with or without serum, and with different plasmid-liposome ratios and transferrin concentrations. The transfer rate was monitored with a semiquantitative orthonitrophenyl-beta/-D-galactoside (ONPG) assay and histologically by X-Gal staining. The cytotoxicity of this procedure was determined with a colorimetric ELISA with Alamar blue. The cardioplegic property of the transfection solution was tested in a Langendorff perfusion system monitoring the coronary blood flow over time after a cold ischemic time of 4 h. RESULTS: The maximal gene expression could be detected after transfection with 4 microl Lipofectin, 2 microg pCMVbeta, and 16 microg transferrin/200 microl transfection solution. Under these conditions 60% of the cells showed a blue staining with X-Gal. Only 20% of the cells died during transfection. The lowest cytotoxicity during cold ischemic time for ECs was assessed with normal cell culture medium and the Buckberg solution. The best coronary flow rates after 4 h cold ischemia of the heart were measured for cardioplegia with St. Thomas and Buckberg solutions. In summary, the best transfection solution with a good cardioplegic property was the Buckberg solution. CONCLUSIONS: Finally, the results of this study show that an effective DNA delivery with a low toxicity into ECs is possible with a combination of liposomes and transferrin. This method might be useful for a safe and effective gene transfer into solid organs during the cold ischemic time and thus a therapeutic tool for chronic rejection.

Animals↗
PubMed1997

The impact of intraoperative brachytherapy on surgery of Ewing's sarcoma.

Surgery of Ewing's sarcoma sometimes results in an inadequate surgical margin. The influence of intraoperative brachytherapy on local control of the tumor, operation time, blood loss, and surgical complications was evaluated, comparing the results of 20 patients who received brachytherapy to a series of 42 patients receiving surgery without brachytherapy. The dose of intraoperative brachytherapy ranged between 9 Gy and 21 Gy. The average operation time was longer in 20 cases with brachytherapy (7.9 h) than in 42 cases without brachytherapy (4.3 h) (P < 0.0001). The average blood loss in the groups with (3531 ml) and without brachytherapy (3515 ml) was comparable (P = 0.3840). The surgical complication rate in patients receiving brachytherapy was also similar to that of untreated patients (30% versus 31%, P = 0.7690). Local relapse developed in 1 of 20 patients who received brachytherapy and 1 of 42 patients without brachytherapy. On the basis of this analysis, it can be concluded that this procedure is safe and does not increase of the acute complication rate. The latest results of local controls are awaited.

Adolescent↗
PubMed1997

Peripheral noradrenergic turnover in streptozotocin-induced diabetic rats.

Our goal was to determine whether basal sympathetic tone to the kidney and various peripheral tissues is altered in conscious diabetic rats. Norepinephrine (NE) turnover was determined by measuring the decline in tissue NE concentration ([NE]) at 4 and 8 h after administering alpha-methyl-p-tyrosine to animals from each of three groups, diabetic (STZ injected 4 weeks prior to experimentation), diabetic + insulin (STZ injected; insulin injected; 2 U/day per rat for 4 weeks) and control (n = 18-20 per group). Various peripheral tissues (duodenum, left ventricle of the heart, kidney, skeletal muscle, left adrenal gland and liver) were examined. [NE] was significantly increased in the kidney and liver, but decreased in the duodenum of the diabetic compared to the control rats. In contrast to the changes in [NE], the rate constant, which provides an index of sympathetic tone, increased in the duodenum and liver, and a decreased in the adrenal gland. The turnover of NE, which is a composite of [NE] and rate constant, increased in the kidney and liver, and decreased in the adrenal gland of diabetic rats. Chronic treatment of diabetic rats with insulin normalized NE turnover in the liver, but not in the adrenal gland. Diabetic rats treated with insulin exhibited a reduced turnover of NE in the kidneys. These data demonstrate that there are differential changes in the [NE], rate constant, and turnover of NE in diabetic rats. Overall, these data indicate that there is increased noradrenergic activity to the kidney, possibly related to sodium retention, and a differential change in noradrenergic activation to various peripheral tissues in diabetic rats.

Animals↗
PubMed1995

Generation and assembly of secretory antibodies in plants.

Four transgenic Nicotiana tabacum plants were generated that expressed a murine monoclonal antibody kappa chain, a hybrid immunoglobulin A-G heavy chain, a murine joining chain, and a rabbit secretory component, respectively. Successive sexual crosses between these plants and filial recombinants resulted in plants that expressed all four protein chains simultaneously. These chains were assembled into a functional, high molecular weight secretory immunoglobulin that recognized the native streptococcal antigen I/II cell surface adhesion molecule. In plants, single cells are able to assemble secretory antibodies, whereas two different cell types are required in mammals. Transgenic plants may be suitable for large-scale production of recombinant secretory immunoglobulin A for passive mucosal immunotherapy. Plant cells also possess the requisite mechanisms for assembly and expression of other complex recombinant protein molecules.

Amino Acid Sequence↗
PubMed1993

Possible imbalance of the immuno-hormonal axis in multiple myeloma.

A comparative study of some immunologic aspects and hormonal balance was performed on 49 multiple myeloma (MM) patients and 29 healthy persons. Functional immunoregulatory imbalances were evident in the majority of patients with MM, as demonstrated by a significant reduction in the mitogenic response of peripheral blood lymphocytes (PBL) to phytohemagglutinin, increased mean stimulation indices of PBL to pisum sativatum agglutinin, wheat germ agglutinin (WGA) and dextran sulphate. Our results appear to provide important evidence in support of the existence of hormonal imbalance in MM: increased cortisol levels, augmented concentrations of follicle stimulating hormone, luteinizing hormone and 17 beta-estradiol and an increased estrogen to androgen ratio in male patients; decreased estrogen values and estrogen to androgen ratios were evident in female patients. Triiodothyronine and thyroxine mean concentrations were also found to be markedly diminished in MM patients. Our studies suggest some potentially important interactions between the immune and endocrine systems in multiple myeloma.

Adult↗
PubMed1992

Implications of a non-lamellar lipid phase for the tight junction stability. Part I: Influence of basic amino acids, pH and protamine on the bilayer-hexagonal II phase behaviour of PS-containing PE membranes.

Inverted lipid micelles have been proposed, among other biological functions, to constitute the structural basis of the so-called tight junctions, a special cell cell contact found in epithelia and endothelial, which act as a barrier for the paracellular solute passage. As a model system for the opening and closing of this gate, we investigated the formation of the inverted hexagonal phase (HII phase) in lipid bilayer systems consisting of egg phosphatidylethanolamine (egg PE) and mixed egg PE/bovine brain phosphatidylserine (BBPS) membranes. The formation of the HII phase was modulated by Ca2+ ions, pH, basic amino acids and protamine. The lamellar-HII phase transition temperature TH of pure egg PE membranes at pH 7.0 was lowered with increasing Ca2+ concentration. This effect was attenuated by the presence of 50 mM lysine methyl ester. In the mixed lipid system, this effect was also observed, but even more pronounced. However this effect could be compensated for by raising the Ca2+ concentration from 2 to 10 mM. This was not observed in the pure PE system. In the absence of Ca2+, lysine methyl ester and protamine lowered TH in both monocomponent and mixed lipid systems, whereas lysine caused the opposite effect. The pH-dependence of mixed lipid systems, which were investigated up to a BBPS content of 20 mol%, clearly shows that increasing PS content stabilizes the lamellar phase even at low pH. The results obtained with model membranes are discussed with respect to biological implications of the lamellar-HII phase transition for the modulation of tight junction stability.

Amino Acids↗