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Biomedical subjects

A Weber

Publications and source records attributed to A Weber.

At least 235 records · Page 13Linked to original sources

[Towards gene therapy in familial hypercholesterolemia].

Familial hypercholesterolemia (FH) is an inherited disease caused by a defect in the gene encoding the Low Density Lipoprotein receptor (LDL-R). The ex vivo hepatic gene therapy which restore the expression of the normal protein in hepatocytes should correct the disease. Improved transduction efficiency and long lasting expression of the transduced gene remain the main goals of gene therapy research. We developed an efficient and reliable method for in vivo transduction of human, mouse and primate primary hepatocytes. A retroviral vector bearing the LDL-R cDNA driven by the liver-type pyruvate kinase promoter allows high and tissue specific expression of the gene in primary hepatocytes. A second vector with a housekeeping promoter corrects the LDL-R deficiency in fibroblasts from a FH patient. Ex vivo preclinical studies in non-human primates will provide new insight in transduced cells biology after reimplantation.

Animals↗

Internucleosomal DNA fragmentation in cultured cells under conditions reported to induce apoptosis may be caused by mycoplasma endonucleases.

DNA fragmentation is a common biochemical hallmark of apoptosis. It is catalyzed by endogenous Ca2+, Mg(2+)-dependent endonuclease(s). Although the exact identity of the apoptotic endonuclease is still a matter of debate, a number of candidate nucleases have been proposed like NUC18, DNase II and DNase I. Relatively large amounts of nucleases are also expressed by mycoplasmas, cell wall-less bacteria of the class Mollicutes, which are found as contaminants in up to 45% of the continuous cell lines in current use. In order to clarify the effect of these pathogens on the investigation of apoptosis in cell culture systems, we looked for biochemical markers (DNA fragmentation, nuclease expression) and morphological changes characteristic of apoptosis (cell shrinkage, chromatin condensation, apoptotic bodies) in Mycoplasma hyorhinis-free and -infected cultures of the human pancreatic adenocarcinoma cell line PaTu 8902 and of mouse NIH 3T3 fibroblasts. For that purpose we employed cells cultured under standard conditions and cells exposed to the protein synthesis inhibitor cycloheximide, which is known to induce apoptosis in various cell systems. After exposure to cycloheximide only the mycoplasma-positive cells exhibited internucleosomal DNA degradation. In contrast, nuclease activities in the molecular range of 47 to 54 kDa were detected in cell homogenates and culture supernatants of infected cultures of both control and cycloheximide-treated cells, whereas mycoplasma-free cultures were nuclease-negative. The expression of the nucleases and the cycloheximide-induced DNA fragmentation were suppressed by the prokaryote-specific protein synthesis inhibitor chloramphenicol. Moreover, partially purified nucleases from supernatants of infected cells were able to cleave the DNA of isolated substrate nuclei at internucleosomal sites. These data indicate that DNA ladder formation in cell culture systems can also be caused by mycoplasmal nucleases which apparently penetrate the host cells after cycloheximide treatment or more generally after cellular stress. Therefore, internucleosomal DNA fragmentation in established cell lines has to be regarded with care, unless mycoplasmal infection can be excluded, or the existence of endogenous endonucleases can be proven. The presence of endonucleolytic activities of about 47 to 54 kDa molecular mass has now to be regarded as highly indicative of contaminations with M. hyorhinis. In contrast, the expression of an apoptotic morphology was not restricted to infected cells; in both mycoplasma-free and -contaminated cultures, cells with condensed chromatin were observed after staining with the DNA binding dye Hoechst 33342. Electron microscopic studies revealed that most of the cells containing compacted DNA were phagocytosed by unaffected fellow cells. Presumably because of the relatively long exposure (72 h) to cycloheximide we also observed secondary necrosis as indicated by the parallel occurrence of morphological characteristics of apoptosis (chromatin condensation) and necrosis (loss of membrane integrity and organelle swelling).

3T3 Cells↗

Oral pH-modified release budesonide versus 6-methylprednisolone in active Crohn's disease. German/Austrian Budesonide Study Group.

OBJECTIVE: Corticosteroids are effective in acute Crohn's disease (CD). The present study assessed the effectiveness and safety of oral pH-modified release budesonide (BUD) in patients with active CD in comparison with 6-methylprednisolone (MPred). DESIGN: This was a prospective multicentre, randomized, double-blind, double-dummy study. METHODS: A total of 67 patients with active CD (CDAI > 150) were included. Patients were treated with 3 x 3 mg BUD (n = 34) or MPred (n = 33) according to a weekly tapering schedule (48-32-24-20-16-12-8 mg). The primary aim was remission of CD (CDAI < 150 and decrease by at least 60 points from baseline) after eight weeks. RESULTS: Baseline demographics, disease activity and localization of CD in the small bowel and the colon were similar in both treatment groups. On an intention-to-treat basis 19/34 patients in the BUD group (55.9%) and 24/33 patients in the MPred group (72.7%) were in remission after eight weeks (P = 0.237). Therapy failed in 15/34 patients (44.1%) of the BUD group and in 9/33 patients (27.3%) of the MPred group. The mean CDAI decreased from 262 +/- 50 to 118 +/- 69 in the BUD-group and from 262 +/- 81 to 95 +/- 61 in the Mored group (P = 0.183, final CDAI BUD vs. MPred). Steroid-related side effects appeared in 28.6% of the patients in the BUD group and in 69.7% of the patients in the Mored group (P = 0.0015). CONCLUSIONS: Oral pH-modified release budesonide (3 x 3 mg/day) is almost as effective as a conventional corticosteroid in patients with active CD but causes significantly less corticosteroid-related side effects.

Administration, Oral↗

[Educational and occupational expectations of tomorrow's generation of physicians].

As a result of increased competition on the market for young doctors and the continuing debate on the kind and extent of reforms planned for university courses, it is becoming increasingly difficult for students of human medicine to plan their occupational future. Against this background, the aim of this study was to evaluate the expectations regarding training and occupation of students embarking on their course and to carry out extensive analysis of the results taking socio-demographic variables into consideration. The study was designed as a survey using standardised, anonymous questionnaires, which took place at the beginning of two terms (summer term 95 and winter term 95/96) and was carried out with students attending the lectures on "Occupational opportunities". Sociodemographic factors, the student's educational history, expectations of university training, estimation of occupational opportunities and the medical discipline the student hoped to work in, were all taken into consideration. 212 (female: 110/male: 102) (78%) of the 271 students registered for the course took part in the survey. All the students were in their first term. The median age was 20 (range 18-32). 55% of those taking part in the survey came from academic families, 15% with doctors in the family. On the average, 12 months had elapsed since leaving school and starting university. 21% had taken up another course of study before turning to medicine, 20% had already completed some other occupational training, in particular in non-medical health services. For the great majority (97%) the quality of the course is very important and great emphasis is laid on how knowledge is conveyed in lectures. Correspondingly, 86% regarded personal contact with the lecturers as important. Two-thirds of those taking part in the survey had heard of the concept "problem-oriented learning", 91% could imagine having part of their training abroad. Every second student regarded his own occupational changes skeptically, and 50% of first-term students could imagine their occupational futures outside the classical occupational fields in clinics and general practice. Qualified teaching with personal contact with the lecturers is regarded as particularly important despite the general complaint of mass teaching and anonymity. Bearing this in mind, future reforms should, in particular, aim at strengthening personnel and financial resources. With recognisable occupational flexibility already apparent at the beginning of medical studies, more information should be provided on training for alternative medical occupations.

Adolescent↗

[Internal hazardous substance burden of persons from various regions of origin--studies of lead, mercury, arsenic and cadmium exposure].

AIM OF THE STUDY: The aim of this study was to investigate the concentration of metals of environmental-medical relevance in biological materials in persons seeking asylum with regard to their country of origin. COLLECTIVE AND METHOD: During medical examination after entry into Germany of persons seeking asylum, samples were taken for determination of the following biological monitoring parameters: lead in blood, and arsenic, cadmium and mercury in urine. A total of 103 males were investigated (13 from former Yugoslavia, 29 from the former USSR, 33 Africans and 28 Asians) ranging from 16 to 53 years of age (median 27 years). 34 male Germans without occupational exposure to these substances and a similar age structure (age 25-36 years; median 26 years) served as a control group. RESULTS: The countries of origin had a significant influence on all the biological monitoring parameters investigated. The mean blood lead concentration in the Asians of 75.4 micrograms/L was the highest level found, while the lowest concentration of 38.0 micrograms/L was measured in the German controls. Also the level of arsenic excreted in the urine was on average much higher in the persons seeking asylum than in the German controls. In the Africans a mean level of 9.7 micrograms/g creatinine was reached. The Germans had the lowest arsenic concentrations in urine of 5.3 micrograms/g creatinine. There were, however, considerable interindividual fluctuations, which are probably due to oral uptake of arsenic compounds as a result of eating seafoods. The highest mean concentration of mercury excreted in urine was found in the German controls. Values of 0.9 microgram/g creatinine were determined. The men seeking asylum from former Yugoslavia had significantly higher values than other groups for cadmium excreted in urine. The median of 0.6 microgram/g creatinine was nearly three times as high as found in the Germans. CONCLUSIONS: For all parameters investigated, with the exception of mercury, higher internal exposure was found in the persons seeking asylum than in the German controls. This may be due to individual life style, dietary habits or environmental conditions in the country of origin. For clinical environmental medicine, the 95th percentile, as the upper limit of the reference range, can only be regarded as an orientation aid for classifying the exposure to hazardous substances of an individual compared to other persons from the same environment.

Adolescent↗

Ion channels in the chloroplast envelope membrane.

Isolated chloroplast envelope membranes were fused with azolectin liposomes. Ion transport across the membrane of these liposomes was investigated by the patch-clamp technique and in planar bilayers. Our results show that the chloroplast envelope contains voltage-dependent anion- and cation-selective channels as well as anion- and cation-selective pores with high conductances. At least one of the high-conductance pores could be located in the chloroplast outer envelope membrane. The low-conductance chloride channel and the potassium channel showed complex gating behavior with subconductant states. Potassium channel gating was affected by monovalent and divalent cations as well as by millimolar concentrations of ATP. Low concentrations of Cs+ induced a flickering block. Voltage dependence of the open probability reveals that macroscopic currents of potassium channels are rectified with preferential potassium uptake into the chloroplast. Flux measurements and determinations of the stroma pH of intact chloroplasts confirm the presence of a potassium channel that is regulated by divalent cations (Mg2+) and by ATP. The fully open potassium channel revealed a conductance of lambda approximately equal to 100 pS in asymmetric KCl (250/20 mM KCl), and the fully open chloride channel revealed a conductance of lambda approximately equal to 60 ps in 100 mM Tris/HCl. One high-conductance channel, mainly active at holding potentials > 60 mV, was slightly selective for glutamate anions (PK+/PGlu- approximately equal to 2) and revealed fast voltage-dependent gating. This high-conductance channel had a conductance of lambda approximately equal to 540 pS (in 250/20 mM potassium glutamate) and was closed most of the time. A second type of high-conductance channel, mainly open and active at holding potentials below 30 mV, was slightly selective for cations (PGlu-/PK+ approximately equal to 2) with a conductance of lambda approximately equal to 1.14 nS (in 250/20 mM potassium glutamate).

Adenosine Triphosphate↗

Requirement of pointed-end capping by tropomodulin to maintain actin filament length in embryonic chick cardiac myocytes.

Control of actin filament length and dynamics is important for cell motility and architecture and is regulated in part by capping proteins that block elongation and depolymerization at both the fast-growing (barbed) and slow-growing (pointed) ends. Tropomodulin is a capping protein for the pointed end of the actin filament; it is associated with the free, pointed ends of the thin filaments in striated muscle, where it is thought to bind to both tropomyosin and actin. In embryonic chick cardiac myocytes, tropomodulin assembles after the thin, as well as the thick, filaments have become organized into periodic I and A bands, suggesting that tropomodulin might be involved in maintaining actin filament length. Here we show that microinjection of an antibody that inhibits tropomodulin's pointed-end-capping activity in vitro results in a marked elongation of actin filaments from their pointed ends and a > 80% reduction in the percentage of beating cells. This demonstrates that pointed-end capping by tropomodulin is required to maintain actin filament length in vivo and that this is essential for contractile function in embryonic chick cardiac myocytes.

Actins↗

An actin monomer binding activity localizes to the carboxyl-terminal half of the Saccharomyces cerevisiae cyclase-associated protein.

The Saccharomyces cerevisiae adenylyl cyclase complex contains at least two subunits, a 200-kDa catalytic subunit and a 70-kDa cyclase-associated protein, CAP (also called Srv2p). Genetic studies suggested two roles for CAP, one as a positive regulator of cAMP levels in yeast and a second role as a cytoskeletal regulator. We present evidence showing that CAP sequesters monomeric actin (Kd in the range of 0.5-5 microM), decreasing actin incorporation into actin filaments. Anti-CAP monoclonal antibodies co-immunoprecipitate a protein with a molecular size of about 46 kDa. When CAP was purified from yeast using an anti-CAP monoclonal antibody column, the 46-kDa protein co-purified with a stoichiometry of about 1:1 with CAP. Western blots identified the 46-kDa protein as yeast actin. CAP also bound to muscle actin in vitro in immunoprecipitation assays and falling ball viscometry assays. Experiments with pyrene-labeled actin demonstrated that CAP sequesters actin monomers. The actin monomer binding activity is localized to the carboxyl-terminal half of CAP. Together, these data suggest that yeast CAP regulates the yeast cytoskeleton by sequestering actin monomers.

Actins↗

The 2-oxoglutarate/malate translocator of chloroplast envelope membranes: molecular cloning of a transporter containing a 12-helix motif and expression of the functional protein in yeast cells.

The 2-oxoglutarate/malate translocator of spinach chloroplasts transports carbon skeletons into chloroplasts for net glutamate synthesis. A sequence of a endoprotease Lys-C peptide derived from the purified protein allowed the design of an oligonucleotide which was then used for a hybridization screening of a cDNA library. A 1945 bp insert of 1 of the isolated clones codes for the entire 569 amino acid residues of the precursor protein corresponding to a molecular mass of 60,288 Da. There was no significant homology to the mitochondrial 2-oxoglutarate/malate carrier from bovine heart or to any other known protein. The translocator protein is composed of a hydrophilic N-terminal region (the transit peptide) with a length of about 90-100 amino acid residues which shows, in contrast to presequences of other known envelope membrane proteins, typical features of higher plant chloroplast transit sequences. The mature protein contains 12 putative transmembrane segments in alpha-helical conformation. It is suggested that this translocator, in contrast to other known transporters of organellar origin which are all homodimers with a 6 + 6 helix folding pattern, may function as a monomer. The in vitro synthesized precursor protein is directed to chloroplasts where it is inserted into the chloroplast envelope membrane in a protease-resistant manner. The cDNA coding for the precursor protein was cloned into the yeast expression vector pEVP11, and this construct was used to transform cells from the fission yeast Schizosaccharomyces pombe. The 2-oxoglutarate/malate translocator could be functionally expressed in the transformed yeast cells, and the recombinant protein showed substrate specificities identical to those of the authentic chloroplast protein.

Amino Acid Sequence↗

[Epitheloid osteosarcoma. Differential diagnostic problems].

The case of a 23-year-old female patient suffering from a rare variety of osteosarcoma of the distal femur with epithelial differentiation and only traces of osteoid is reported. The tumour cells reacted strongly to antibodies against vimentin. Metastases were found in the fifth rib and the right kidney. There was no response to chemotherapy. One year after implantation of a tumour prosthesis of the knee a thigh amputation was necessary because of a local failure. The patient died 2.5 years after the tumour had initially been diagnosed. Other reports of this rare type of epitheloid osteosarcoma illustrate the difficulties involved in reaching a correct diagnosis. This tumour can be mistaken for a skeletal metastasis of an epithelial tumour.

Adult↗

Ceftazidime pharmacokinetics in preterm infants: effects of renal function and gestational age.

OBJECTIVE: The objectives of this study were (1) to determine the effects of gestational age on ceftazidime pharmacokinetics in the preterm infant, (2) to relate these effects to changes in glomerular filtration rate (GFR), and (3) to establish appropriate dosage recommendations for preterm infants on day 3 of life. METHODS: Multiple-dose pharmacokinetics of ceftazidime (administered twice daily in a 25 or 50 mg/kg body weight intravenous dose) were evaluated in 136 preterm infants on day 3 of life. Blood samples were collected from an arterial catheter 0, 1/2, 1, 2, 4, 8, and 12 hours after the intravenous dose. An HPLC method was used to determine ceftazidime concentrations in serum. The GFR was studied simultaneously by means of the 24-hour continuous inulin infusion technique. RESULTS: The total body clearance, volume of distribution, and elimination serum half-life of ceftazidime (mean +/- SD) were 55.7 +/- 34.4 ml/hr (37.3 +/- 11.9 ml/hr/kg), 496 +/- 228 ml (350 +/- 96 ml/kg), and 6.95 +/- 2.32 hours, respectively. The mean +/- SD peak and trough levels were 114.9 +/- 39.4 and 33.9 +/- 17.8 mg/L. All infants had a serum trough level above 5 mg/L. Clearance and volume of distribution of ceftazidime and GFR increased significantly with increasing gestational age, whereas serum trough levels and serum half-life of ceftazidime decreased significantly with increasing gestational age. Ceftazidime clearance increased significantly with increasing GFR. Prenatal exposure to indomethacin resulted in significantly lower GFR values and ceftazidime clearances. CONCLUSIONS: Dosage recommendations for ceftazidime administration in preterm infants during the first week of life should be based on gestational age and GFR. Additional adjustments in dosage are indicated in preterm infants who are exposed prenatally to indomethacin.

Ceftazidime↗

Are activating mutations of the adrenocorticotropin receptor involved in adrenal cortical neoplasia?

The objective of this study was to investigate the presence of activating mutations of the ACTH receptor gene in benign and malignant adrenocortical tumours. Genomic DNA was extracted from a variety of adrenocortical neoplasms from 16 patients and the entire ACTH receptor gene was then amplified by the polymerase chain reaction and sequenced. No mutations were detected within the coding region of the ACTH receptor gene in the 16 adrenocortical tumours studied. It is likely that mutations of the coding region of the ACTH receptor gene do not play a major role in adrenocortical tumourigenesis.

Adenoma↗

The molecular pathology of pituitary hormone deficiency and resistance.

In this chapter, we have reviewed the fast-moving area of the molecular pathology of pituitary hormone deficiencies and resistance. Examples have been described affecting all levels of pituitary function, i.e. the releasing hormone, its receptor, the pituitary hormone and its receptor, and the development of the pituitary gland. Other examples in these genes, and in those in which no mutation has yet been found, will undoubtedly be discovered in the next few years, throwing light on the structural basis of the gene product's function and allowing a greater understanding of endocrine physiology and pathophysiology. The main reason for this rapid progress in knowledge is the recent technological advances in mutation detection, which bring this activity within the grasp of the majority of reasonably equipped laboratories. Technological advancement, however is not all that it takes to carry out this work. The conditions caused by genetic damage such as we have described are rare, and there is clearly a requirement for great awareness on the part of the clinical endocrinologist. Patients in whom it is suspected that mutations such as these may occur require careful clinical and biochemical work-up. Indeed, in many instances, careful thought has to go into deciding what the phenotype of a particular mutation might be. Thus, the requirement for close collaboration between clinical and molecular endocrinologists has to be the important message for the future in this area of research.

Adrenocorticotropic Hormone↗

Investigation, management and therapeutic outcome in 12 cases of childhood and adolescent Cushing's syndrome.

OBJECTIVE: Cushing's syndrome in childhood and adolescence is rare. We analysed the clinical presentation, investigation, management and therapeutic outcome in 12 paediatric patients with Cushing's syndrome. DESIGN: Retrospective review of case notes. PATIENTS: Twelve patients, 7 males and 5 females, aged 7.6-17.8 years with Cushing's syndrome who were admitted to St Bartholomew's Hospital between 1978 and 1993, were studied. Aetiologies of the Cushing's syndrome patients were: Cushing's disease (9), adrenal adenoma (1), nodular adrenocortical dysplasia (1) and ectopic ACTH syndrome (1). One further male patient, aged 17.8 years who presented with Nelson's syndrome after bilateral adrenalectomy for Cushing's disease in 1978, is described. MEASUREMENTS: Presenting symptoms, endocrine tests for hypercortisolism, imaging studies, simultaneous bilateral inferior petrosal sinus sampling and therapeutic strategies are discussed. RESULTS: The dominant clinical features were obesity, short stature, virilization, headaches, fatigue and emotional lability. Investigations confirmed Cushing's syndrome by demonstrating absent cortisol circadian rhythm and impaired suppression on low dose dexamethasone test and differentiated Cushing's disease from other aetiologies by high dose dexamethasone and hCRH tests. In Cushing's disease, pituitary CT scan identified a microadenoma in 4 out of 9 subjects. In 5 of the 9 patients (3 with a normal pituitary CT, 2 with a suggested microadenoma), a pituitary MRI scan was performed and confirmed the CT findings. Inferior petrosal sinus catheterization for ACTH in 4 patients confirmed excess pituitary ACTH secretion, correctly lateralizing the tumour in all cases. Cushing's disease was treated by transsphenoidal surgery alone in 6 patients and combined with pituitary irradiation in 3 patients. Of these 9 patients, 7 are cured and 2 are in remission. The patient with Nelson's syndrome is cured after total hypophysectomy. CONCLUSIONS: This series describes the clinical features, aetiologies and management of juvenile Cushing's syndrome. Investigation with low and high-dose dexamethasone suppression tests and hCRH test identified the aetiology in each case. Collaboration between paediatric and adult endocrine units together with an experienced neurosurgeon and a radiotherapist contributed to the successful therapeutic outcome of these patients.

Adenoma↗

Absence of mutations in the MEN2A region of the ret proto-oncogene in non-MEN 2A phaeochromocytomas.

OBJECTIVE: To determine the presence of abnormalities of the MEN2A region of the ret proto-oncogene in phaeochromocytomas/paragangliomas (PHAEO) of different aetiologies. DESIGN: Total RNA was extracted from tumours and used as templates for reverse transcriptase polymerase chain reactions. A ret primer pair, which encompasses the region which is mutated in the germ-line of patients with MEN 2A, was used. The resulting 262-bp product was sequenced. PATIENTS: Ten PHAEOs were examined. Four tumours were from von Hippel-Lindau disease patients; five were sporadic, isolated tumours; one from a patient with multiple endocrine neoplasia type 2A (MEN 2A). The medullary thyroid cancer from the single MEN 2A patient was also examined. RESULTS: A heterozygous TGC to CGC mutation of codon 634 (cysteine to arginine) was found in the PHAEO and medullary thyroid cancer from the MEN 2A patient. The 262-bp ret fragment was not found in two tumours (one malignant PHAEO and one secretory paraganglioma), although the intra-cellular ret tyrosine kinase domain was detected in these tumours. The cysteine codons were normal in all other non-MEN 2A PHAEOs. CONCLUSION: Mutations of key cysteine codons of the ret proto-oncogene may be specific to MEN 2A.

Adrenal Gland Neoplasms↗

Macromolecular mechanisms of sputum inhibition of tobramycin activity.

Tobramycin, an aminoglycoside antibiotic, is used in the treatment of Pseudomonas aeruginosa infections in cystic fibrosis patients. Tobramycin bioactivity, however, is antagonized by sputum. Glycoproteins (mucins) and high-molecular-weight DNA make up 2 to 3% (P. L. Masson and J. F. Heremans, p. 412-475, In M. J. Dulfano, ed., Sputum: Fundamentals and Clinical Pathology, 1973) and 3 to 10% (W. S. Chernick and G. J. Barbero, Pediatrics 24:739-745, 1959, and R. Picot, I. Das, and L. Reid, Thorax 33:235-242, 1978) of the dry weight of sputum, respectively. tobramycin binds to both mucins and DNA obtained from sputum (R. Ramphal, M. Lhermitte, M. Filliat, and P. Roussel, J. Antimicrob. Chemother. 22:483-490, 1988). In vitro, recombinant human DNase (rhDNase) hydrolyzes high-molecular-weight DNA of > 50 kb within sputum to fragments of 2 to 4 kb. Studying dialyzable tobramycin, we examined drug binding to whole sputum and to "mock sputum," which consisted of porcine gastric mucin and calf thymus DNA. We also studied the effects of rhDNase treatments of sputum, mock sputum, and calf thymus DNA on tobramycin binding. We found that treatments of sputum, mock sputum, and calf thymus DNA with rhDNase did not significantly increase the tobramycin bioactivity within the dialysates; surprisingly, sputum binding of tobramycin was increased by rhDNase. We conclude that rhDNase does not increase the bioactivity of tobramycin in sputum.

Adult↗