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Biomedical subjects

K Muramoto

Publications and source records attributed to K Muramoto.

At least 127 records · Page 7Linked to original sources
PubMed1984

A rapid sensitive assay for the quantitation of elastin.

A rapid, sensitive and direct assay was developed for the quantitation of elastin using reverse phase high performance liquid chromatography. The method is based on the separation of the alkaline hydrolysis-resistant dipeptide valyl-proline, a dipeptide found in high concentrations in elastin. The methodology is applicable to unlabelled elastin samples in the range of 10-100 micrograms utilizing fluorescamine detection and to hot alkali insoluble as well as soluble forms of elastin. Increased sensitivity was achieved by the use of in vitro radiolabelling of elastin with [3H]proline. This was useful for following synthesis of elastin in cultured cells. Since this technique is not dependent on detection of the elastin-specific crosslink groups, desmosine and isodesmosine, precursor forms of elastin can be measured as well as other forms of elastin deficient in cross-linking. The same chromatographic procedure however, is able to detect these desmosine and isodesmosine crosslinks. Therefore, in cell cultures under the proper radiolabelling conditions, biosynthesis and cross-linking of elastin can be followed simultaneously in a single chromatographic procedure.

Animals↗
PubMed1983

Amygdaloid neuronal responses to complex visual stimuli in an operant feeding situation in the monkey.

In chronically prepared monkeys, 337 neurons were recorded from the anterolateral amygdala during an operant task that required visual discrimination. Twelve percent (39/337) of the neurons responded to one or more of food or non-food visual stimuli. A subset of these responsive neurons was selectively sensitive to the sight of non-food objects with aversive associations. Simultaneous presentation of a food stimulus with the aversive object inhibited the response of these neurons. These response characteristics could not be explained by simple sensory processing of the visual stimuli. It is suggested that the amygdala plays an important role in the elaboration of motivational behavior by using the complex or associative properties of visual stimuli.

Amygdala↗
PubMed1982

Glucoresponsive neurons in rat ventromedial hypothalamic tissue slices in vitro.

Extracellular action potentials were recorded from rat ventromedial hypothalamic nucleus (VMH) tissue slices in vitro. The identified glucoresponsive and non-glucoresponsive neurons were then visually located and observed by intracellular horseradish peroxidase staining. Glucoresponsive neurons, which were predominantly multipolar, were found near the center of the VMH, while non-glucoresponsive neurons, half of which were bipolar and half multipolar, were found randomly throughout the VMH.

Animals↗
PubMed1982

[Studies of blood flow through the spinal cord of rabbit using the H2 clearance method ].

Using the H2 clearance method, spinal cord blood flow of the rabbit could be steadily measured. This allowed examination of blood flow problems using data analysis to provide informed decisions as to whether or not the blood flow through the gray and white matter was distinguishable. Spinal cord blood flow was also compared through the cervical, thoracic, and lumbar cord regions. The results were as follows: 1. The H2 clearance curves consisted of about 70% monoexponential curve (Mono), and 30% biexponenial curve (Bi), with a tendency toward higher values in the latter. 2. In Bi, a significant positive correlation was noted between the total flow values and the initial slope method values. The initial slope method was therefore used for subsequent data analysis. 3. By using a histogram to evaluate the data on each medullary segment, it was possible to separate a subgroup with a peak around 20 ml/100 g/min and another one with a peak around 40 ml/100 g/min. Based on the microangiographic findings, a more abundant vascular distribution was demonstrated in the gray matter than in the white matter. The first subgroup was noted corresponding to the blood flow through the white matter, and the latter through the gray matter. When the blood flow through the white and gray matter was calculated according to the subgroup data base, the flow ratio through the white and gray matter was 1:2. 4. Comparing the blood flow through each spinal cord segment revealed no significant difference at a p level of 0.01.

Animals↗
PubMed1981

Persistent activation of steroidogenesis in adrenocortical cells by photoaffinity labeling of corticotropin receptors.

Photolysis of rat adrenocortical cells in the presence of the photoreactive derivative [(2-nitro-5-azidophenylsulfenyl)Trp9]-adrenocorticotropic hormone (2,5-NAPS-ACTH) at 24 degrees C resulted in persistent activation of corticosterone production. The basal rate of steroidogenesis became maximal when photolysis was performed at 24 degrees C but remained the same as that of control cells when irradiation was performed at 0 degrees C. No increase in basal rate was observed with dark controls or cells photolyzed with [(2,4-dinitrophenylsulfenyl)Trp9]ACTH, a photoresistant analog of the hormone. Prephotolyzed 2,5-NAPS-ACTH failed to induce persistent activation. Both ACTH and 2,4-(dinitrophenylsulfenyl)Trp9-ACTH blocked the photo-induced activation of steroidogenesis elicited by 2,5-NAPS-ACTH. Under photolysis conditions which caused the basal rate of steroidogenesis to become maximal, a 3-fold increase in the basal rate of cAMP formation was observed.

Adrenal Cortex↗
PubMed1981

Preparation of photoreactive derivatives of glutathione and [9-(2-mercaptotryptophan)]corticotropin by selective modification of the sulfhydryl group.

The photoreactive arylsulfenyl chlorides 2-nitro-4-azidophenylsulfenyl chloride (2,4-NAPS-Cl) and 2-nitro-5-azidophenylsulfenyl chloride (2,5-NAPS-Cl) have been used for the selective modification of thiol groups in glutathione and [Trp(SH)9]corticotropin (ACTH). Both reagents reacted rapidly with both types of thiol groups to form unsymmetrical disulfides. The photoreactive derivatives of glutathione and [Trp(SH)9]ACTH were stable to neutral and acidic conditions but were readily cleaved above pH 9 and by beta-mercaptoethanol. Photolysis of the NAPS derivatives of [Trp(SH)9]-ACTH at neutral pH resulted in the formation of covalently liked polymers and dimers which yielded monomer upon treatment with beta-mercaptoethanol. Analysis of the amino acid composition of acid hydrolysates of photolysed monomeric and dimeric products indicated a decrease in proline, valine, tyrosine, and phenylalanine.

Adrenocorticotropic Hormone↗
PubMed1981

Identification of the corticotropin binding domain of bovine serum albumin by photoaffinity labeling.

The interaction of the pituitary hormone corticotropin (ACTH) with bovine serum albumin (BSA) was investigated by photoaffinity labeling with 2-nitro-4-azido-phenylsulfenyl (2,4-NAPS) derivatives of aCTH and [Trp-(SH)9]ACTH. Nearly 30 mol % of tritiated [2,4-NAPS-Trp9]ACTH was covalently bound to BSA at a molar ratio of hormone:BSA of 1.33. The [2,4-NAPS-Trp9] [3H]ACTH-BSA complex was isolated, and the CNBr fragments of the complex were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The radioactivity was predominantly associated with the amino-terminal CNBr fragment corresponding to residues 1-183 in BSA. This result was confirmed by studies of the inhibition of covalent labeling of BSA by photoreactive ACTH. 8-Anilinonaphthalenesulfonic acid which binds to the amino-terminal domain of BSA strongly inhibited the photolabeling of BSA by [2,4-NAPS-Trp9][3H]ACTH. Palmitate and progesterone, known to bind to the carboxy-terminal domains of BSA, did not inhibit the incorporation of [2,4]NAPS-Trp9][3H]ACTH into BSA. The removal of ACTH from the covalent complexes was also investigated. The release of ACTH from the [2,4]NAPSS-Trp9]ACTH--BSA complex by treatment with beta-mercaptoethanol was complete in 6 h, but only 80% of ACTH was released from [2,4]NAPS-Trp9]ACTH--BSA under these conditions.

Adrenocorticotropic Hormone↗
PubMed1980

Photoreactive derivatives of corticotropin. 2. Preparation and characterization of 2-nitro-4(5)-azidophenylsulfenyl derivatives of corticotropin.

Two new photoreactive arylsulfenyl chlorides, 2-nitro-4-azidophenylsulfenyl chloride (2,4-NAPS-Cl) and 2-nitro-5-azidophenylsulfenyl chloride (2,5-NAPS-Cl), have been synthesized and used for the selective modification of corticotropin (ACTH). Both reagents reacted rapidly with N-acetyltryptophanamide and ACTH under acidic conditions. The NAPS derivatives of ACTH were purified by partition chromatography and characterized by absorption spectra, amino acid analysis, and peptide mapping. The spectral changes caused by photolysis as well as the kinetics of photolysis are described. Tritiated 2,5-NAPS-ACTH was attached covalently to a pituitary protein fraction FI by photolysis. The photolabeling of FI was blocked in the presence of excess ACTH.

Adrenocorticotropic Hormone↗
PubMed1980

Photoaffinity labeling of corticotropin receptors.

A photoaffinity label for corticotropin (ACTH) receptors was prepared by selective chemical modification of the single tryptophan residue in the hormone by reaction with 2-nitro-5-azidophenylsulfenyl chloride. The photoreactive derivative, [(2-nitro-5-azidophenylsulfenyl)-Trp9]ACTH (2,5-NAPS-ACTH), stimulated corticosterone synthesis to 60% of the maximal rate induced by ACTH in isolated rat adrenocortical cells. 2.5-NAPS-ACTH caused only a marginal stimulation of cyclic AMP production compared to the unmodified hormone. Stimulation of corticosterone production and cyclic AMP accumulation induced by ACTH were both inhibited in a competitive manner by 2,5-NAPS-ACTH. Photolysis of adrenocortical cells in the presence of 2,5-NAPS-ACTH resulted in a 40% inactivation of ACTH receptors mediating steroidogenesis, as shown by the decrease in response to subsequent stimulation with ACTH. No loss of function was observed when photolysis was conducted in the presence of the photoresistant analog [(2,4-dinitrophenylsulfenyl)-Trp9]ACTH. Covalent attachment of the hormone to the receptors was also demonstrated by photolyzing adrenocortical cells in the presence of tritiated 2,5-NAPS-ACTH of high specific radioactivity (90 Ci/mmol) and analyzing the cell proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A protein with an approximate molecular weight of 100,000 was specifically labeled by this procedure. The unique labeling of an adrenocortical cell protein and the concomitant loss of ACTH responsiveness suggest that physiologically relevant receptors are photolabeled by this method.

Adrenal Cortex↗
PubMed1979

Retrograde transport of horseradish peroxidase in sciatic nerve of rats and dystrophy mice.

The relationship between nerve or muscle activity and retrograde HRP transport was studied in rat Sciatic nerve and in dystrophy mice. sciatic nerve stimulation facilitated transport to 250% of control level, while colchicine decrease transport depending on dosage. Tendonectomy as well as colchicine treatment ultimately decreased HRP transport, but before the decrease, there was a transient facilitatory phase in both colchicine treated and tendonectomized rats. In dystrophy mice, almost twice as much nerve trunk injected HRP was transported as in control mice. This suggests that retrograde transport level increases in some stage of dystrophy.

Animals↗
PubMed1978

Isolation and primary structure of adrenocorticotropin from several species of whale.

The isolation of adrenocorticotropin (ACTH) from fin (Balaenoptera physalus), sei (Blaenoptera borelis) and sperm (Physeter catodon) whale pituitaries is described. Their primary structures have been elucidated by the fluorescein isothiocyanate method and revealed to be identical to the structure of the human hormone. Fin whale exhibited an identical steroidogenic activity to that of the porcine hormone.

Adrenal Cortex↗