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Biomedical subjects

M Krauss

Publications and source records attributed to M Krauss.

At least 73 records · Page 4Linked to original sources
PubMed1977

Genetic and cytogenetic analysis of the Adh region in Drosophila melanogaster.

Eighteen Adh-negative mutations were selected with 1-pentyn-3-ol after feeding of formaldehyde. Twelve of the 18 were shown by cytological and genetic analysis to be deletions. Cytological examination of the deletions allowed us to localize the Adh gene to a region including bands 35B3-5 on the left arm of chromosome 2. The deletions were also used to order known visible loci located near Adh.--The vital loci near Adh were also investigated. A total of 109 lethal mutations were generated with EMS and 33 of these, localized within a region defined by the overlap of two of the deletions, were found to belong to 13 complementation groups. If one includes three other loci known to belong there (el, Adh and Sco) a total of 16 complemetation groups have been identified in the region close to Adh.

Alcohol Oxidoreductases↗
PubMedDate not supplied

The binding of substituted cis-Pt(II)-diammines to duplex DNA.

The results of a study of the binding to DNA of substituted cis-Pt(II) diammines, (cis-DP) are presented. Computer modeling of a series of cis-Pt(NH2R)2(+2)--where R = H, CH3, cyclopropyl, cyclobutyl, and cyclopentyl--to N7(G) atoms of two adjacent intrastrand guanine bases in a square planar complex in a pentamer duplex of DNA were performed. The stability of the complexes is studied by calculating the relative conformational energy of the cis-DP-DNA complexes with molecular mechanics (MM) and the intrinsic binding energy, which is the relative binding energy for ligand replacement in the presence of the substituents R with quantum mechanics. In the model, the receptor site geometry and the conformation of the DNA is changed little in the accommodation of the series of monosubstituted diammines. These diammines bind to one family of DNA conformations, denoted as IC in a previous study, and this suggests that a common conformational feature in the DNA may exist to explain the smooth trend in activity. The slight increase in van der Waals energy resulting from an increasing number of atoms in the substituents is countered by a larger decrease in the ligand replacement energy as the substituent increases in size. This overall decrease in relative energy is consistent with the slight decrease in activity as the substituent size increases.

Binding Sites↗
PubMedDate not supplied

Theoretical studies of cis-Pt(II)-diammine binding to duplex DNA.

The binding of cis-Pt(II) diammine (cis-DP) to double-stranded DNA was studied with several kinked conformations that can accommodate the formation of a square planar complex. Molecular mechanics (MM) calculations were performed to optimize the molecular fit. These results were combined with quantum mechanical (QM) calculations to ascertain the relative energetics of ligand binding through water vs direct binding of the phosphate to the ammine and platinum, and to guide the selection of DNA conformations to model complex formation. Based on QM and MM calculations, models are proposed that may be characterized by several general features. A structure involving hydrogen bonding between each ammine and distinct adjacent phosphate groups, referred to as closed conformation (CC), has already been reported. This is also found in the crystal structure of small dimers. We report alternative conformations that may be important in platination of duplex DNA. They are characterized by an intermediate conformation (IC), involving hydrogen bonding between one ammine and phosphate group, and an open conformation (OC), without ammine phosphate hydrogen bonding. The IC and OC can be stabilized by water bridges in the space between the ammine and the phosphate groups. Sugar puckers alternate from the type C(2')-endo or C(1')-exo (S), to the type C(3')-endo or C(2')-exo (N), with intermediate types near O(1')-endo (O). In general, the sugar puckers alternate from S to N to S through the platinated region (3'-TpG*pG*p-5'), with the complexed strand exhibiting, (3')-S*-N*-S-(5') alternation, while the complementary strand shows either (3')-S*-N*-S-(5') or (3')-S*-N*-O-(5') alternation. In both the OC and IC, a hydrogen bond is found between the ammine and O4(T) on thymine (T) at the (3') end, adjacent to the complex site. There is a continuous range of backbone conformations through the platinated region which relate the OC to the IC. The models presented suggest that the dynamics of the binding of the cis-Pt(II)-diammines to adjacent N7(G) in double-stranded DNA may encompass several conformational possibilities, and that water bridges may play a roll in supporting open and intermediate conformations. Proton-proton distances are reported to assist in the experimental determination of conformations.

Cisplatin↗
PubMedDate not supplied

Development towards multimedia medical workstations.

In this paper, concepts and examples of medical workstations with multimedia and hypermedia capabilities will be presented. These workstations have special hardware and software requirements. Also described in the article are the developments in Europe (AIM project line) within this area.

Computer Communication Networks↗
PubMedDate not supplied

Binding of polyamine-containing toxins in the vestibule of the nicotinic acetylcholine receptor ion channel.

Several wasp venoms contain philanthotoxins (PhTXs) that act as noncompetitive inhibitors (NCIs) on cation-selective ion channels including the nicotinic acetylcholine receptor (nAChR). In the search for a ligand with high affinity and specificity for the nAChR we tested a series of newly developed PhTX analogues. Modulation of the structural elements of PhTXs can significantly influence their binding affinities. This approach resulted in the development of the photolabile compound MR44. In photoaffinity labelling studies 125I-MR44 was used to map the ligand-binding site at the Torpedo californica nAChR. Upon UV irradiation of the receptor-ligand complex, 125I-MR44 was mainly incorporated into the receptor alpha-subunit. Proteolytic mapping and microsequencing identified the site of 125I-MR44 cross-linking within the sequence alphaHis-186 to alphaLeu-199 that in its C-terminal region partially overlaps with the agonist-binding site. Since bound agonists had only minor influence on 125I-MR44 photocrosslinking, the site where the hydrophobic head group of 125I-MR44 binds must be located outside the zone that is sterically influenced by agonists bound at the nAChR. A possible site of interaction of 125I-MR44 would be the N-terminal region of the labelled sequence, in which aromatic amino-acid residues are accumulated. We suggest that the polyamine moiety of 125I-MR44 interacts with the high affinity non-competitive inhibitor site deep in the ion channel, while the aromatic ring of this compound binds in the vestibule of the nAChR to a hydrophobic region on the alpha-subunit that is located close to the agonist binding site.

Animals↗
PubMedDate not supplied

Ab initio structure of the active site of phosphotriesterase.

This research exploits two recent developments to obtain a fundamental understanding of the metalloenzyme active site using the bimetallic enzyme phosphotriesterase as an example of this class. First is the theoretical prediction that the structure and spectroscopy of a native metalloenzyme active site is qualitatively determined by the supermolecule complex of the metal(s) and the first shell of ligands with proper charge states including waters directly bonded to ionic ligands. The second is the development of an effective potential for representing the molecular environment interacting with an all-electron active site in the quantum Hamiltonian. The GAMESS suite of electronic structure codes has implemented this new methodology, effective fragment potentials (EFP), to make theoretical calculations on structure, spectroscopy, and reactivity tractable for systems involving hundreds of atoms. Since there are transition metal cations at the active site of these enzymes, the all-electron part of the complex is calculated with relativistic compact effective potentials (CEP) and their concomitant basis sets. A realistic representation of the active site with its protein environment can be obtained using a combination of the CEP and EFP. This presentation will determine the inherent electronic and structural characteristics of phosphotriesterase using ab initio quantum mechanical methods. A single X-ray structure for the Zn-Zn enzyme is leveraged to obtain the structure of the Cd-Cd enzyme and to examine the consequences of protonating the active site.

Aryldialkylphosphatase↗
PubMedDate not supplied

[Randomised trial of acupuncture compared with conventional massage and "sham" laser acupuncture for treatment of chronic neck pain - range of motion analysis].

AIM: The aim of this study was to compare the effects of acupuncture on active motion of the cervical spine in patients with chronic neck pain with those of "sham" laser acupuncture and massage. MATERIAL AND METHODS: 177 patients with chronic neck pain were included in this prospective, randomized, placebo-controlled study. The patients were allocated by external randomization to five treatments over three weeks with acupuncture, massage and "sham" laser acupuncture. The range of active motion was measured by means of a 3D ultrasound real time motion analyzer. RESULTS: The analysis of cervical motion in three directions showed the largest increase in range of motion 14 days after acupuncture. Compared to massage, a significant improvement in total range of motion was seen in those patients treated by acupuncture immediately (p = 0,03) and one week (p = 0,03) weeks after therapy. There was no significant difference in those patients treated by sham laser acupuncture. CONCLUSION: The results of the study indicate that acupuncture is superior to conventional massage for improving active range of motion in patients with chronic neck pain. Because of its positive effects, its acceptance among patients and the lack of severe side effects, acupuncture can be recommended for the treatment of chronic neck pain, although there was no significant difference in results between "sham" laser acupuncture and acupuncture.

Acupuncture Therapy↗
PubMedDate not supplied

Forest fertilization with wood ash: effect on the distribution and storage of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs).

Before wood ash can be safely used as a fertilizer in forests, possible negative effects such as input of organic contaminants or remobilization of contaminants already stored in the soil must be investigated. The objective of this study was to examine the effects of wood ash application on concentrations, storage, and distribution of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in a Swiss forest soil. In May 1998, we added 8 Mg wood ash ha(-1) to a forest soil. We determined 20 PAHs and 14 PCBs in the organic layer, in the bulk mineral soil, and in soil material taken from preferential flow paths and from the matrix before and after the wood ash application. In the control plots, the concentrations of PAHs in the organic layer indicated moderate pollution (sum of 20 PAHs: 0.8-1.6 mg kg(-1)), but sum of PCB concentrations was high (21-48 microLg kg(-1)). The wood ash had high concentrations of PAHs (sum of 20 PAHs: 16.8 mg kg(-1)), but low concentrations of PCBs (sum of 14 PCBs: 3.4 microg kg(-1)). The wood ash application increased the PAH concentrations in the organic horizons up to sixfold. In contrast, PCB concentrations did not change in the Oa horizon and decreased up to one third in the Oi and Oe horizons. The decrease was probably caused by the mobilization of stored PCBs because of the high pH of the wood ash. This probably results in a higher mobility of dissolved organic matter, acting as PCB carrier. In the mineral soil, the preferential flow paths of the A horizon contained more PAHs and PCBs (+20 +/- 15% and +43 +/- 60%, respectively) than the matrix. This was particularly true for higher molecular weight compounds (molecular weight > 200 g mol(-1)). Below 50 cm depth, concentrations of PAHs and PCBs were smaller in the preferential flow paths, suggesting that in deeper depths, processes acting as sinks dominated over inputs in the preferential flow paths.

Conservation of Natural Resources↗