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K Sachs

Publications and source records attributed to K Sachs.

17 recordsLinked to original sources
PubMed2002

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c.

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.

Journal Article↗
PubMed2000

Diffusible ligand all-trans-retinal activates opsin via a palmitoylation-dependent mechanism.

In rhodopsin's function as a photoreceptor, 11-cis-retinal is covalently bound to Lys(296) via a protonated Schiff base. 11-cis/all-trans photoisomerization and relaxation through intermediates lead to the metarhodopsin II photoproduct, which couples to transducin (G(t)). Here we have analyzed a different signaling state that arises from noncovalent binding of all-trans-retinal (atr) to the aporeceptor opsin and enhances the very low opsin activity by several orders of magnitude. Like with metarhodopsin II, coupling of G(t) to opsin-atr is sensitive to competition by synthetic peptides from the COOH termini of both G(t)alpha and G(t)gamma. However, atr does not compete with 11-cis-retinal incorporation into the Lys(296) binding site and formation of the light-sensitive pigment. Blue light illumination fails to photorevert opsin-atr to the ground state. Thus noncovalently bound atr has no access to the light-dependent binding site and reaction pathway. Moreover, in contrast to light-dependent signaling, removal of the palmitoyl anchors at Cys(322) and Cys(323) in the rhodopsin COOH terminus impairs the atr-stimulated activity. Repalmitoylation by autoacylation with palmitoyl-coenzyme A restores most of the original activity. We hypothesize that the palmitoyl moieties are part of a second binding pocket for the chromophore, mediating hydrophobic interactions that can activate a large part of the catalytic receptor/G-protein interface.

Acylation↗
PubMed2000

Assays for activation of opsin by all-trans-retinal.

The data collected with the techniques discussed in this chapter suggest significant differences between the active conformation(s) of the opsin/atr complex, which are reversibly formed in the dark, and the active conformation (R*) of the meta-II photoproduct. First, there is good evidence for noncovalent opsin/atr complexes with considerable activity (although covalent binding of atr is found in mutant opsins. Even more intriguing, all-trans-retinal in an amount that saturates the activity of the opsin/atr complex toward Gt does not measurably inhibit the access of 11-cis-retinal to the light-sensitive binding site during regeneration (Fig. 2C). On the other hand, forced protonation at or near Glu-134 appears to be an integral mechanism for both the meta-II and the opsin-like activities (Fig. 4). Thus, it is not inconceivable that these two activities of the receptor arise from two fundamentally different conformations, one meta-II-like and one opsin-like. They would be similar with respect to the Gt (or RK) protein-protein interaction but different in their mode of retinal-protein interaction.

Animals↗
PubMed1998

Palmitoylation of rhodopsin with S-protein acyltransferase: enzyme catalyzed reaction versus autocatalytic acylation.

Protein palmitoylation in vitro was studied using bovine rhodopsin as the substrate and a partially purified acylating enzymatic activity (PAT) from placental membranes. PAT incorporates fatty acid into rhodopsin with higher efficiency (10 times higher initial rate), as compared to autoacylation. The activity is sensitive to heat and trypsin, indicating a protein-mediated enzymatic process and requires the native conformation of rhodopsin. The presence of deacylated, free cysteine residues in dark-adapted rhodopsin increases palmitoylation via PAT. The sites for non-enzymatic and enzymatic palmitoylation could not be distinguished by peptide mapping. The reversible palmitoylation described here will provide a tool for the study of the role of palmitoylation in photoreceptor function.

Acetyltransferases↗
PubMed1995

[Influence of bacterial infection and formalin vapors on the course of ovalbumin induced experimental bronchospastic reaction in guinea pigs].

The pathomechanism of the bronchospastic reaction is not fully explained. Ovalbumin induced bronchospastic reaction in guinea pigs is widely accepted as a classical experimental model and was appleid in this study. The bronchoconstriction, bronchial hypersensitivity and humoral immune response were measured after bronchial infection and chemical injury by formalin vapours. The intensity of the bronchospasm was measured by Lundberg index, the haemolytic activity of complement and the level of circulating immune complexes were measured at the beginning and at the end of the experiment. The increase of the bronchospastic reaction and bronchial hypersensitivity was observed bacterial infection and after formalin vapours too. Bronchial infection and chemical irritation of bronchial tree lead to the increase of the circulating immune complexes level and to the decrease of the haemolytic activity of the complement.

Animals↗
PubMed1995

[Histology of the respiratory system after exposure to bacterial infection and formalin vapors used to induce experimental bronchospasm].

The purpose of the research was to observe the influence of the bacterial infection and inhalation vapours on the histologic picture of bronchi and lungs in the course on the experimental asthma induced in guinea pigs. The animals were divided into 6 groups. The animals were immunized by ovalbumin. Group I was control and was subjected to inhalations of physiologic salt solutions. Group II was immunized by the soluble of ovalbumin intraperitoneally and was inhaled with the solution of ovalbumin. Group III was subjected only to inhalation of the ovalbumin. Group IV was inhaled with the solution of formalin alternately. Group V experienced only formalin inhalations. Group VI was infected with Pseudomonas aeruginosa strain and inhaled with the solution of ovalbumin. On the histologic examination of the lung tissue the authors found the atrophy of the lymphatic system, the hypertrophy of the mucous membrane and muscular coat of the bronchi, the accumulation of large amount of mucus in their lumen and the exfoliation of the bronchial epithelium.

Animals↗
PubMed1994

[Behavior of some parameters of the autonomic nervous system in patients with bronchial asthma].

It is well known that beta receptors play a crucial role in maintaining tonus of smooth muscles of the airways. In this study the authors have indirectly assessed the beta receptor performance by measuring serum cAMP levels before and after intravenous administration of Salbutamol. Parallelly the activity of the parasympathetic system was analysed. The observed increases of serum cAMP dependent on different duration of the disease. The age of the patients did not affect the observations. These results may imply that disturbances of beta-2 receptors function are acquired in patients with bronchial asthma.

Adult↗
PubMed1994

[Influence of bacterial infection during ovalbumin induced experimental asthma in guinea pigs].

The pathomechanism of bronchial asthma is not fully explained. The immunologic reactions in the bronchial epithelium may be better understood by an experimental approach in laboratory animals. Ovalbumin induced asthma in guinea pigs is widely accepted as an experimental model of bronchial asthma and was applied in this study. The bronchoconstriction, bronchial hypersensitivity and humoral immune response were measured after bronchial infection (intranasal Pseudomonas aeruginosa application). The increase of the bronchospastic reaction and bronchial hypersensitivity was observed after intranasal Pseudomonas aeruginosa application. Bacterial infection lead to the increase of the circulating immune complexes level and to the decrease of the haemolytic activity of the complement in serum.

Animals↗
PubMedDate not supplied

The athletic polydrug abuse phenomenon. A case report.

A case of a power weight lifter who is ingesting large doses of anabolic steroids plus other drugs to counteract their short-term side effects is presented. This type of polydrug abuse phenomenon which is unique to the competitive athlete is widespread despite the lack of convincing evidence that anabolic steroids increase muscular strength. The vast extent of this drug abuse problem is poorly appreciated by the general medical community. The potential complications of the long-term usage of these drugs such as liver failure, hepatocellular carcinoma, and peliosis hepatitis make these drugs extremely dangerous.

Adult↗