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N Klemm

Publications and source records attributed to N Klemm.

14 recordsLinked to original sources
PubMed1991

Irreversible inactivation of diacylglycerol kinase-II requires a mediator.

Cytosolic diacylglycerol kinase was irreversibly inactivated by 5'-AMP since the enzyme remained less active after the removal of 5'-AMP by P-10 gel chromatography. The inactivation was time-dependent, suggesting the involvement of a covalent bond modification. A reconstitution experiment detected a rat brain cytosolic mediator for the effect of 5'-AMP. A protein kinase rich fraction prepared from rat liver was also capable of restoring the sensitivity of diacylglycerol kinase-II to 5'-AMP. We propose that 5'-AMP-activated protein kinase is the mediator which inactivates diacylglycerol kinase-II, possibly by phosphorylation.

Adenosine Monophosphate↗
PubMed1990

Indirect inactivation of rat brain cytosolic diacylglycerol kinase by nucleoside-5'-monophosphate.

Cytosolic diacylglycerol kinase was inhibited drastically by nucleoside monophosphate. The inhibition was relatively specific for adenosine-5'-monophosphate (5'-AMP), although uridine-5'-monophosphate was also effective. The effect of 5'-AMP on diacylglycerol kinase appeared to be indirect since the degree of inhibition lessened with the dilution of the cytosol and the more purified enzyme failed to respond to 5'-AMP. A 5'-AMP-dependent mediator is proposed to be involved in the inactivation of diacylglycerol kinase.

Adenosine Monophosphate↗
PubMed1989

Quantitative benedict test using bicinchoninic acid.

Cupric ion (Cu2+), in complex form, functions as a selective oxidizing agent for a variety of compounds in the qualitative Benedict test. Cupric ion is reduced to cuprous ion (Cu+) in the reaction. We found that the cuprous ion formed in this type of redox reaction could be detected and quantified using 2,2'-bicinchoninic acid. This reagent produced an intense purple complex with cuprous ion. The color development in this modified Benedict test was dependent on pH, temperature, and time. The reaction is insensitive to ethanol and sodium dodecyl sulfate. This improved method of the Benedict test has enhanced sensitivity and makes the quantitation of compounds possible. This method should be useful for studies of Benedict-positive compounds which are available only in small amounts.

Biochemistry↗
PubMed1988

An endogenous regulator of diacylglycerol kinase.

During the initial steps of the subcellular fractionation of rat brain homogenate, we recovered more than 100% of diacylglycerol kinase activity. The unusually high yields prompted us to examine the possibility that we had removed an endogenous inhibitor from diacylglycerol kinase during those steps. Our study revealed the existence of a potent inhibitor of diacylglycerol kinase in the crude synaptosomal-mitochondrial fraction (P2 pellet). The inhibitory substance was water soluble upon organic solvent extraction. The inhibitory activity of the substance was retained after extensive dialysis, suggesting the macromolecular nature of this compound. This substance may represent an important physiological regulator of diacylglycerol kinase.

Animals↗
PubMed1988

Inhibition of rat diacylglycerol kinase activity by synthetic L-lysine containing polypeptides.

We investigated whether or not synthetic polymers of amino acids affected the activity of rat diacylglycerol kinase. Among all the polypeptides of amino acids tested, only the polymers containing significant amounts of basic amino acid residues inhibited diacylglycerol kinase activity. Poly-L-lysine was a better inhibitor than poly-L-arginine. Both the density of positive charge and the nature of spacing amino acids of the inhibitory peptides were determining factors in interacting with the enzyme. Various polyamines were ineffective. Our observation indicated that the activity of diacylglycerol kinase might be controlled by a site which binds to a polycation.

Animals↗
PubMed1986

Neurons reactive to antibodies against serotonin in the stomatogastric nervous system and in the alimentary canal of locust and crickets (Orthoptera, Insecta).

Immunoreactive neurons in the stomatogastric nervous system and in the alimentary tract of the locust Schistocerca gregaria and the crickets Gryllus bimaculatus and Acheta domesticus have been examined using antibodies against serotonin (5-hydroxytryptamine; 5-HT). For comparative anatomical analysis cobalt chloride infusion was applied. The innervation of the visceral muscles was studied electron microscopically. In all three species the majority of the 5-HT-immunoreactive cell bodies of the stomatogastric nervous system occur in the frontal ganglion in which 30-40% of the total number of cell bodies react with anti-5-HT. In the occipital ganglion only two to four cell bodies (1-2%) are 5-HT-immunoreactive. Single immunoreactive cell bodies were observed in the ventricular ganglia in only a few preparations. The 5-HT-immunoreactive neurons in the frontal ganglion are pseudounipolar or multipolar. The main process of the 5-HT-immunoreactive neurons of the frontal ganglion descend along the entire stomatogastric nervous system. Some arborizations of these processes ascend into the brain and others supply the neuropil of all stomatogastric ganglia. Side branches leave the stomatogastric nervous system and form a plexus along the surface of the entire intestinal tract from where 5-HT-immunoreactive fibers supply: all muscle layers of the muscularis; the external dilator muscles of the foregut and probably some somatic muscles, neurohaemal organs and Malpighian tubules (excretory system). Serotonin-immunoreactive fibers further proceed into salivary gland and the retrocerebral complex (corpora cardiaca and corpora allata). The retrocerebral glandular complex and the hindgut receive additional immunoreactive neurons from the central nervous system. Electron microscopic analysis of nerves innervating the muscle layers of the alimentary tract revealed one type of 5-HT-immunoreactive and one or two types of non-5-HT-immunoreactive fibers. All fiber types contact the sarcolemma of muscle fibers without any obvious synaptic membrane specializations. The 5-HT-immunoreactive fibers are in some regions in close contact with the haemolymph. These regions can be regarded as sites of neurohormonal release. The distribution of serotonin-immunoreactive neurons suggests that 5-HT acts as a neurotransmitter and/or modulator on intestinal muscles and some somatic muscles and glandular cells, and as a neurohormone released from neurohaemal sites into the body fluid.

Animals↗
PubMed1985

Dopamine-beta-hydroxylase-like immunoreactive neurons in two insect species, Calliphora erythrocephala and Periplaneta americana.

The localization of dopamine-beta-hydroxylase in the cephalic central nervous system of the blowfly (Calliphora erythrocephala) and the cockroach (Periplaneta americana) was investigated. Immunoreactive neurons were demonstrated in both species. The results were compared with the known distribution of catecholamines in the brain of both species. In certain cell groups and neuropilar regions of both species D beta H-immunoreactivity coincides with the presence of catecholamines. Additionally D beta H immunoreactivity was found in several cell bodies and neuropilar regions in which no catecholamines could be detected. A correlation between the presence of octopamine and anti-D beta H labelling was not found. Thus it seems that the D beta H-immunoreactivity neither indicates the presence of octopamine nor is it limited to noradrenaline-containing neurons. Parallel findings in vertebrates are discussed.

Animals↗
PubMed1979

Neuroleptic and dopamine receptors: autoradiographic localization of [3H]spiperone in rat brain.

Rats were administered [3H]spiperone (SP: spiroperidol) by tail vein injection and 2 h later the brain was processed for light microscopic autoradiography. High densities of autoradiographic grains were found in all areas known to have a dopaminergic innervation, including the olfactory tubercles, nucleus accumbens, nucleus caudate-putamen, lateral septum, zona incerta, nucleus subthalamicus, arcuate nucleus, nucleus of the central amygdala, areas in the ventral tegmentum and the claustrum. There were also increased autoradiographic grain densities in other areas such as the midbrain and the frontal cortex indicating that binding occurred to other neurotransmitter receptors besides dopamine receptors. These studies delineate with a high resolution at an anatomical level the major binding sites for neuroleptic drugs in the forebrain. They suggest which areas of the brain are the most involved in neuroleptic drug action and they add further evidence that important regions are those receiving a dense dopaminergic innervation.

Animals↗
PubMed1977

Origin, destination and mapping of tritocerebral neurons of locust.

The connectivities of the tritocerebrum of locust (Locusta migratoria L., Schistocerca gregaria (Forsk.)) were studied histologically and by means of cobalt chloride infusion. Its neuropil consists partly of fibers which traverse the tritocerebrum and areas consisting of neuropilar agglomerizations ("glomeruli"). The following direct connections between the tritocerebrum and other regions were observed: connections to 1) dorsal and lateral brain regions (mushroom body, optic lobe), 2) the ventral nerve cord, 3) the stomatogastric nervous system (here the protocerebrum and the subesophageal ganglion are also involved in these connections), 4) the retro-cerebral glands (corpora cardiaca, corpora allata), and 5) muscles of the foregut.

Animals↗