Biomedical subjects
M Gross
Publications and source records attributed to M Gross.
The catalytic activities of monomeric enzymes show complex pressure dependence.
High hydrostatic pressures in the biologically relevant range (< or = 1,200 bar) are known to cause dissociation of oligomeric enzymes in vitro, whereas protein denaturation requires pressures far beyond this range. Pressure-induced inactivation phenomena attributable to neither of these effects are shown to occur in monomeric enzymes. Three different types of pressure dependence can be distinguished: (1) a linear dependence of catalytic rate constants on pressure, as predicted by the activated complex theory, observed for lysozyme and thermolysin; (2) a biphasic profile consisting of two linear contributions, found for trypsin; (3) maximum curves, as observed for both directions of the octopine dehydrogenase reaction. The third case may be ascribed to a pressure-induced decrease in the partial specific volume of the protein, resulting in reduced flexibility of the active site. This mechanism may also apply to the pressure-induced inactivation of assembly systems stabilized against dissociation in the cell.
Ergometer exercise in myoadenylate deaminase deficient patients.
Three patients with primary myoadenylate deaminase deficiency were subjected to exercise on a bicycle ergometer at 125 W for 30 minutes. Blood samples prior to, during, and at the end of exercise were analyzed for lactate, ammonia, and hypoxanthine. In addition, urinary hypoxanthine excretion was measured. In these patients the serum lactate level increased to concentrations between 7.9 and 9.0 mmol/l at the end of exercise whereas the mean lactate level in nine control subjects at the end of exercise was 3.3 mmol/l (range 1.1-8.1 mmol/l). There was no difference to control subjects in the exercise-induced increase in plasma levels of ammonia and hypoxanthine or in the increase in urinary hypoxanthine excretion. The findings support the hypothesis of a reduced substrate supply to the citric acid cycle in myoadenylate deaminase deficiency. The normal formation of ammonia and hypoxanthine excludes a marked loss of adenine nucleotides in working muscles in these patients.
Diagnosis and treatment of the N0 neck in carcinomas of the upper aerodigestive tract: current status of diagnostic procedures.
Diagnostic procedures currently utilized for determining nodal status in patients with head and neck primary carcinomas are reviewed. Diagnostic procedures include clinical palpation, computed tomography, magnetic resonance imaging and ultrasound. Each technique is discussed on the basis of clinical experience at the Technical University of Munich.
Myoadenylate deaminase deficiency with severe rhabdomyolysis.
A 13-year-old Turkish girl was admitted because of recurrent episodes of muscle pain and weakness since the age of 5 years. As an outpatient she developed severe acute rhabdomyolysis (myoglobinuria and increased serum creatine kinase level of 19,000 units/l). The acute rhabdomyolysis and the preceding episodes of muscle pain and weakness had been induced by exercise. There was no increase in plasma ammonia level during ischaemic forearm exercise test and bicycle ergometry. Myoadenylate deaminase deficiency was proven both histochemically and biochemically. The girl was found to be homozygous for the C 34-T mutation of the AMPD1 gene causing primary myoadenylate deaminase deficiency in skeletal muscle. Both parents and her brother were heterozygous for that mutation. Myoadenylate deaminase deficiency has to be considered as a cause of severe rhabdomyolysis.
Effects of acute stimulant medication on cerebral metabolism in adults with hyperactivity.
Recent work in our laboratory has demonstrated both global and regional reductions in cerebral glucose metabolism in adult subjects with attention-deficit hyperactivity disorder (ADHD). The purpose of the present study was to examine the effects of an acute dose of stimulant medication on cerebral metabolism in adults with ADHD using positron emission tomography with fluorodeoxyglucose-18 as the tracer. Each subject underwent scanning twice, once off-drug and again after receiving a single oral dose of either dextroamphetamine (0.25 mg/kg) or methylphenidate (0.35 mg/kg). Subjects completed behavioral self-report measures before and after the scan and performed an auditory continuous performance task during the tracer uptake period. Neither drug changed global metabolism. Both drugs increased systolic blood pressure, and dextroamphetamine improved performance on the auditory attention task. Each stimulant produced a differential pattern of increases and decreases in regional metabolism throughout the regions of interest that were sampled. Rather than increasing glucose utilization in specific brain regions with lowered metabolic rates in adults with ADHD, stimulants may act by altering glucose use throughout the brain.
[Spiral CT in aortic aneurysms. 2D and 3D reconstructions and CT angiography].
Spiral CT was performed in 8 normals and 40 patients with alterations of the large thoracic and abdominal vessels. It proved to be the ideal basis for 2D and 3D reconstructions. In 2D reconstruction the topographic aspects of aortic aneurysms were displayed better compared to the axial scans. In 3D reconstruction the segmentation of small vessels, and vessels running parallel to the scan plane showed problems. Stenoses were displayed unsatisfactory. In patients with aortic aneurysms 3D reconstruction showed well the location and dimension of the aneurysm as well as its position to branching arteries and the intraarterial thrombus. In case of dissecting aneurysms the true and the false lumen could clearly be distinguished. Colour-coded 3D reconstruction proved to be valuable to illustrate topographic information that could be detected only with difficulty on examining the original axial scan.
Selenium-dependent regulation of type I 5'-deiodinase expression.
Selenite concentration regulates activity and expression of the p27 substrate-binding subunit of type I 5'deiodinase (5'-D) and of a protein labeled with bromoacetylthyroxin (BrAcT4), or p30, with yet unknown function in a porcine-kidney epithelial cell line (LLC-PK1) cultured in serum-free medium. p27 is metabolically labeled by 75-selenite and affinity labeled by BrAc[125I]T4. Compared with glutathione peroxidase, expression of the p27 5'D subunit (5'-DI) is observed at 10-fold-lower concentrations of selenium in the growth medium, suggesting an intracellular hierarchy of selenite utilization. Selenium deficiency retards cell growth and prevents 5'-DI expression and may thus impair thyroid hormone action in vivo.
Induction of cytotoxic T lymphocytes against the Plasmodium falciparum circumsporozoite protein by immunization with soluble recombinant protein without adjuvant.
Immunization of mice with irradiated malaria sporozoites induces protection that is dependent on CD8+ T cells, and adoptive transfer of CD8+ cytotoxic T lymphocyte (CTL) clones against rodent malaria circumsporozoite (CS) protein and sporozoite surface protein 2 completely protects against sporozoite challenge. Thus, there are now efforts to develop vaccines that induce CTL against the CS protein and sporozoite surface protein 2. Until recently, it was thought that induction of CTL required production of target proteins within cells, breakdown of the proteins to peptides in the cytoplasm, and transport of the peptides to the cell surface in combination with class I major histocompatibility complex molecules. It has now been shown that immunization with peptides in Freund's complete adjuvant and with soluble protein in liposomes can induce CTL. To determine whether we could induce CTL against the Plasmodium falciparum CS protein by immunization with soluble protein, B10.BR mice were immunized intravenously, intraperitoneally, or intramuscularly with a recombinant P. falciparum CS protein called RLF mixed with the adjuvant DETOX (monophosphoryl lipid A, cell wall skeleton of Mycobacteria phlei, and squalane). Two weeks after the last dose, spleen cells from mice immunized intravenously, but not intraperitoneally or intramuscularly, had peptide-specific, major histocompatibility complex-restricted, CD8+ T-cell-dependent cytolytic activity against peptide 368-390 from the 7G8 P. falciparum CS protein. To determine whether the adjuvant was required for induction of the cytolytic activity, mice were immunized with RLF without adjuvant, and similar cytolytic activity was demonstrated. The finding that we could induce CTL by administration of soluble protein without adjuvant markedly broadens the possibilities for vaccinologists working to develop methods of inducing CTL in humans.
Vitamin E, LDL, and endothelium. Brief oral vitamin supplementation prevents oxidized LDL-mediated vascular injury in vitro.
In previously reported in vitro studies, we found that heme, a physiologically widespread hydrophobic iron compound, can rapidly generate oxidized low-density lipoprotein (LDL), which then becomes cytotoxic to cultured vascular endothelial cells; both LDL oxidation and endothelial cytotoxicity were inhibited by incubation with exogenous alpha-tocopherol (vitamin E) or ascorbic acid (vitamin C). Seeking relevance to in vivo conditions, we performed a study in which 10 human volunteers were given daily antioxidant supplements of 800 IU of DL-alpha-tocopherol acetate alone or in combination with 1000 mg of ascorbic acid for 2 weeks. LDL resistance to heme oxidation ex vivo, as measured by the lag time for conjugated-diene formation, increased by as much as threefold from a mean +/- SD of 58 +/- 11 to 104 +/- 18 minutes (P < .001); LDL alpha-tocopherol increased from 11 +/- 2 to 26 +/- 6 molecules per LDL particle (P < .001); and most impressively, cytotoxicity to porcine aortic endothelial cells incubated with LDL conditioned with heme plus H2O2 or with copper was completely prevented (cytotoxicity before supplementation was 42 +/- 12%, decreasing after supplementation to 3 +/- 2%, P < .001). These measurements reverted to their presupplement levels within 2 weeks after participants stopped taking antioxidant supplements and were reproduced in 4 subjects taking 800 IU of DL-alpha-tocopherol acetate supplements alone but not in the same subjects taking 1000 mg ascorbic acid supplements alone. In conclusion, oral vitamin E supplementation increases LDL alpha-tocopherol content, increases LDL resistance to oxidation, and decreases the cytotoxicity of oxidized LDL to cultured vascular endothelial cells.
High-speed, light-intensified digital imaging of vocal fold vibrations in high optical resolution via indirect microlaryngoscopy.
Digital imaging of vocal fold vibrations is mainly limited by lighting problems. We present a new technique for high optical resolution of vocal fold vibrations (via indirect microlaryngoscopy) using a light intensifier camera. Superficial epithelial structures and secretions can be followed during vibrations by means of high magnification. Recordings of up to 2.4 seconds and 6,000 frames per second, combined with simultaneous recording of acoustic and electroglottographic signals, are possible. This technique allows instant slow-motion monitor control and subsequent documentation on a normal video recording system. We also present preliminary findings of typical vocal fold motion patterns.
A histological processing technique that preserves the integrity of calcified tissues (bone, enamel), yolky amphibian embryos, and growth factor antigens in skeletal tissue.
We have devised a processing technique to embed calcified tissues, such as bone and tooth enamel, in paraffin, to preserve the delicate antigenic sites of molecules such as growth factors. The same technique, omitting the decalcification step, allows delicate tissues, such as axolotl embryos (Ambystoma mexicanum) containing large yolk masses, to be easily handled during tissue processing and to be serially sectioned. Specimens were all fixed in periodate-lysine-paraformaldehyde (PLP) fixative at 5 degrees C. Bone and teeth were decalcified in an EDTA-G solution at -4 degrees C. Maintaining a temperature of 5 degrees C, the decalcified samples were then washed (with PBS, pH 7.2, under vacuum) to remove glycerol. Both the decalcified tissues and the yolky embryos were dehydrated through an ascending series of isopropanol and embedded in low melting-point paraffin under vacuum. Acidic fibroblast growth factor (aFGF) was located in cells of the expanded cambial layer in the early fracture calluses of male CD-1 mice, demonstrating retention of antigenic sites. The results reported here have not previously been obtained with existing processing and embedding techniques.
Innovations in surgery. A proposal for phased clinical trials.
There is an urgent need for the staged, controlled, introduction of new technology and new procedures to surgery. A classification system in four stages is proposed, which would allow for prospective assessment of new devices or methods before they are released for use by the surgical community. The proposal recognises the unique nature of a surgical operation and its learning curve. The issues of randomisation and of informed consent are discussed, and are shown not to be barriers to clinical trials, but necessary adjuncts to orderly testing. The importance of continued surveillance of innovations is emphasised.
Expression of four growth factors during fracture repair.
Fracture repair offers an opportunity to study the physiology of bone formation at the fracture site. Isolation of growth factors from bone matrix has implicated growth factors as participants in bone physiology. We therefore examined the expression patterns of aFGF, IGF-I, PDGF, and TGF-beta during fracture repair. An animal model has been developed to study repair of tibial fractures. The model provides both reproducible and quantifiable results, allowing the fracture repair process to be divided into four stages (Bourque et al., Lab. Anim. Sci 42: 369-374, 1992). Fractured tibiae were examined immunohistochemically with polyclonal antibodies to four growth factors. PDGF was visualized in macrophages in close proximity to the periosteum during stage 1. aFGF was visualized in cells of the expanded cambial layer and was associated with a rapid increase in the population of fibroblast-like mesenchymal cells during stage 2. IGF-I was visualized in young chondroblasts at the edge of the cartilage mass replacing the fibrous callus during stage 3. TGF-beta was visualized in calcified matrix producing chondrocytes at the edge of ossification fronts penetrating the cartilage callus during stage 4. The immunohistochemical results suggest that these growth factors act as local simulators of the repair process.
Mitochondrial DNA affinity of several Jewish communities.
The mitochondrial DNA (mtDNA) of 332 individuals from Israel, including 270 Jews (originating from 7 communities) and 62 Arabs, was analyzed. Each mtDNA haplotype was determined by the fragment patterns of restriction enzymes HpaI, BamHI, HaeII, MspI (HpaII), and AvaII. The variability of the total sample and of each community was high. Of 40 different haplotypes, 20 were found more than once. Most haplotypes are typical of Caucasians, but African types were found among Ethiopian Jews and to a lesser extent among Arabs. The communities differed in their haplotypes: Chi-square tests among six communities showed significant differences for most pairwise comparisons and nonsignificant differences involving mainly the Moroccan Jews. In a genetic distance analysis only the Ethiopian Jews appeared to be distinguished from the other communities. According to a GST analysis, approximately 30% of the variation among the mtDNA restriction maps is attributable to differences between communities.
[3-dimensional imaging of aortic aneurysms using spiral computed tomography].
Explore the source record for details and available documents.
[Individual adjustment of tracheal valves in voice prosthesis patients with morphologically aberrant stoma relations].
We present a new method of individual tracheal valve fitting for laryngectomized patients with voice prosthesis. In cases with morphologically poor tracheostoma the adhesion of the tracheal cannula or valve ring might be impaired by reduced contact surface to the skin. In some cases obligatory circumferential occlusion leads to stretching and higher tension of the adhering ring. Our technique of individual fitting with a silicon adapter permits airtight, tension-free adherence of tracheal valves, or, if desired, facilitation of stoma-closing with a finger, when the tracheostoma is deformed or too big.
[3D reconstruction of CT data sets. A methodologic comparison].
Explore the source record for details and available documents.