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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,135 records · Page 63Linked to original sources
PubMed1984

Sensitive direct radio-immunoassay for human renin.

A sensitive direct human renin radio-immunoassay has been developed for clinical use. The antigen source was human renal renin purified from Haas' preparation by pepstatin-C6-sepharose affinity chromatography, this was used to prepare a specific human renin antibody. The radio-immunoassay was performed by the double antibody technique using the delayed tracer addition method. Standard curves were obtained over the range 0.2-8.0 ng/ml. Dilution curves of human renal renin and human plasma were superimposable on the standard curve. Both active and inactive renin were detected by this method, and measurements correlated well with total renin activity after trypsin activation. Intra- and inter-assay coefficients of variance were 4.6% and 5.1%, respectively. Renin concentration was higher in patients with renovascular hypertension (1.97 +/- 0.38 ng/ml, mean +/- s.d., n = 10, P less than 0.01), but lower in primary aldosteronism (0.66 +/- 0.16 ng/ml, n = 13, P less than 0.01) compared with essential hypertension (1.38 +/- 0.34 ng/ml, n = 12). This method provides a new tool for the investigation of the renin-angiotensin system in man.

Humans↗
PubMed1984

Primary and tertiary structure of human renin.

A complete amino acid sequence of human renin was deduced from its complementary DNA (cDNA) sequence. Close similarities were observed in the primary structure of human renin and other aspartyl proteinases. A three-dimensional model of human renin has been constructed assuming that the overall folding of the aspartyl proteinases is very similar. The model is consistent with many biochemical and catalytic properties of human renin previously reported, thereby confirming its usefulness and the strong correspondence between the model and the actual structure of renin. The model should provide the structural basis for the development of a potentially-useful antihypertensive drug.

Amino Acid Sequence↗
PubMed1983

Manganese (II) electron spin resonance and cadmium-113 nuclear magnetic resonance evidence for the nature of the calcium binding site in alpha-lactalbumins.

Bovine and goat alpha-lactalbumins were substituted with 113Cd(II) or Mn(II) at the strong calcium site [Murakami, K., Andree, P.J., & Berliner, L.J. (1982) Biochemistry 21, 5488-5494] and studied by 113 Cd NMR and electron spin resonance. The 113Cd chemical shifts were in the -80 to -85 ppm range vs. Cd(ClO4)2, which was almost identical with that found for several nearly octahedral (oxygen-coordinated) calcium binding proteins such as calmodulin, parvalbumin, and troponin C. The electron spin resonance spectra of bound Mn(II)-alpha-lactalbumin complexes at 9 or 35 GHz were also confirmatory of a highly symmetric (cubic) environment around the Mn(II) with only slight distortions. The near identity of this site in alpha-lactalbumin to those of calcium binding proteins containing an "EF hand domain" was remarkable despite the absence of such a domain sequence in the alpha-lactalbumin structure.

Animals↗
PubMed1983

[Effects of synthetic ovine corticotropin-releasing factor (CRF) on ACTH release in vitro].

The effect of the synthetic ovine corticotropin-releasing factor (CRF) on adrenocorticotropin (ACTH) release was examined by the perifusion method using rat anterior pituitary tissue and rat monolayer cultured pituitary cells. Quartered anterior pituitaries were placed in a chamber and perifused at a rate of 400 microliters/min with Dulbecco's modified Eagle Medium (DMEM, pH 7.4) bubbled with a mixture of 95% O2 and 5% CO2. The perifused medium was fractionated, and the ACTH concentration was measured by radioimmunoassay. In the monolayer cultured pituitary cells, the amount of ACTH released in the culture medium during three hours incubation was assayed by radioimmunoassay. ACTH was released from the perifused anterior pituitary in a dose-related manner by the pulse administration of CRF or arginine vasopressin (AVP) at the concentration of 1 ng/ml, 10 ng/ml and 100 ng/ml. A significant difference was not found between CRF- and AVP-induced ACTH release. In the monolayer cultured pituitary cells, synthetic ovine CRF induced ACTH release in a dose-related manner between 30 pg/ml and 30 ng/ml, but AVP induced a slight ACTH release. ACTH release was pulsatile during the continuous administration of 2.5 ng/ml of CRF for 150 min, although if gradually increased during the continuous administration of 10 ng/ml or 20 ng/ml of CRF. The continuous administration of AVP also caused pulsatile ACTH release at 10 ng/ml, but the ACTH release gradually decreased during the continuous administration of AVP. The interaction between CRF and AVP on ACTH release was examined by two methods. When CRF and AVP were given simultaneously, a mainly additive effect on ACTH release was observed. However, a low concentration of CRF seemed to potentiate AVP-induced ACTH release. These results show that both CRF and AVP have a significant CRF activity on the perifusion system, that AVP induced a slight ACTH release in monolayer cultured pituitary cells, and that CRF acts additively or potently with AVP to control the ACTH release from the anterior pituitary gland.

Adrenocorticotropic Hormone↗
PubMed1983

A distinct zinc binding site in the alpha-lactalbumins regulates calcium binding. Is there a physiological role for this control?

A distinct zinc binding site has been found in several alpha-lactalbumin species: bovine, human, guinea pig, and rabbit. Binding of Zn(II) or Al(III) to the calcium forms of these proteins causes exclusion of calcium and return of the protein to its "apo conformation" as determined by fluorescence emission spectral parameters. Zn(II) and Al(III) dissociation constants are in the low micromolar range. In addition, determinations of Zn(II) binding were made by electron spin resonance by observing free unliganded Mn(II), which was displaced upon Zn(II) binding. Co(II) and Cu(II) were also shown to bind to the zinc site while also expelling Ca(II). The most appropriate model that describes cation binding to alpha-lactalbumins is of two physically distinct but mutually exclusive sites for calcium and zinc, respectively, where the protein cannot bind cations at both sites simultaneously. Kinetic parameters for lactose biosynthesis show absolutely no difference between the apo or Zn(II) and Ca(II) forms of alpha-lactalbumin. At physiological concentrations of zinc (approximately 50 microM) and calcium (approximately 1 mM), a ca. 40% rate enhancement due to calcium was observed, which was totally accounted for by calcium activation of galactosyl transferase. While either conformer of alpha-lactalbumin [Ca(II) or Zn(II)] is kinetically equivalent, the Ca(II) form probably dominates under physiological conditions.

Aluminum↗
PubMed1983

Role of AMP deaminase reaction in the response of phosphofructokinase to the adenylate energy charge.

The role of NH+4 ion and AMP deaminase reaction in the activation of phosphofructokinase with respect to its response to the adenylate energy charge was investigated using permeabilized yeast cells. (a) Phosphofructokinase and AMP deaminase were activated by the decrease in the adenylate energy charge. The addition of NH+4 further stimulated the phosphofructokinase activity in the presence of intracellular level of K+, and the optimal energy charge value giving the maximal response of the enzyme was shifted from 0.3 to the value above 0.5. (b) The increase in NH+4 ion produced through the activation of AMP deaminase by spermine which shows no direct action on the phosphofructokinase activity can activate phosphofructokinase with shift of the optimal energy charge value of the enzyme to 0.5 in the presence of K+, whereas the optimal energy charge value for AMP deaminase reaction was not affected by the addition of spermine. Phosphofructokinase can be activated most effectively by the physiological decrease in the energy charge under the condition of increased NH+4 in the presence of K+. The possibility that the interaction of phosphofructokinase with AMP deaminase under hypoxic condition might be a contributing factor to the Pasteur effect is discussed.

AMP Deaminase↗
PubMed1983

A novel purification method of human renin.

Human renal renin was isolated from a partially purified preparation, Haas' preparation step 5 material, with a remarkably high yield of 28% by a newly developed method. This method consisted of only four steps including affinity chromatography on pepstatin-aminohexyl-agarose, chromatofocusing, gel filtration and DEAE-chromatography after the initial extraction and concentration. This method enabled us to obtain pure human renin without another affinity column used by other investigators. Pure human renin had a molecular weight of 40,000 daltons as estimated by gel filtration and sodiumdodecylsulfate-polyacrylamide gel electrophoresis. The pI of purified renin was 5.6.

Chromatography, Affinity↗
PubMed1983

A specific radioimmunoassay for corticotropin releasing factor (CRF) using synthetic ovine CRF.

This newly developed specific radioimmunoassay for corticotropin releasing factor (CRF) had a sensitivity range of 25 pg/tube to 4 ng/tube. Intra and interassay coefficient of variation were 4.6% and 9.8%, respectively. Rat median eminence extracts showed a parallel dose response curve with synthetic ovine CRF and a significant cross reaction was not evident with other tested neuropeptides. The highest mean levels of CRF were found in the median eminence (6.61 ng/mg protein). Considerable amounts of CRF were found in the arcuate nucleus, paraventricular nucleus, dorsomedial nucleus, suprachiasmatic nucleus and ventromedial nucleus. The immunoreactive CRF of the rat medial basal hypothalamus coeluted with bioassayable CRF and with iodinated CRF on Sephadex G-75 chromatography. The results indicate that rat hypothalamus contains a CRF similar to ovine CRF.

Animals↗
PubMed1983

Sulfhydryl groups of chicken liver purine nucleoside phosphorylase.

Purine nucleoside phosphorylase purified from chicken liver was inactivated by the sulfhydryl reagent, 4,4'-dithiodipyridine. The inactivation was strongly prevented by the substrates, inosine, phosphate and arsenate. Inactivated enzyme could be reactivated by dithiothreitol. The stoichiometry of modification of sulfhydryl groups was 1.2 residues per mol of the enzyme subunit. The enzyme had five sulfhydryl groups per subunit. One of the five sulfhydryl groups was very reactive with 4,4'-dithiodipyridine, three groups were reactive with excess, 4,4'-dithiodipyridine and another one was masked.

Animals↗
PubMed1983

Biomicroscopic study of the vitreous in macular breaks.

The vitreous in 74 eyes with macular breaks was studied using the El Bayadi-Kajiura preset lens mounted on a slit lamp. Fifteen of the eyes had macular breaks secondary to various causes, and 59 eyes had idiopathic senile macular breaks. Vitreous traction, indicated by the presence of opercula or visible vitreous strands, was present in 29 (49%) of the idiopathic cases. In 17 of 31 eyes without posterior vitreous detachment (PVD), an operculum was seen. In these eyes, intravitreous traction was suspected to be the cause of macular breaks. Opercula were seen attached to the posterior hyaloid membrane in six of the nine eyes with partial PVD. An operculum corresponding to the macular break was observed on the posterior hyaloid membrane in only five of 19 eyes with complete PVD. Of the 15 eyes with macular breaks secondary to various causes, complete PVD was seen in 10 eyes, one of which had an operculum. One eye had no PVD, and four eyes had partial PVD. Opercula were detected in two of the latter eyes. In one eye of the senile group and one eye of the secondary group, partial PVD caused traction at the edges of the macular break, resulting in retinal detachment.

Adult↗
PubMed1983

Vitreous floaters.

The vitreous changes in 148 eyes with sudden onset of floaters were evaluated biomicroscopically and documented photographically using an El Bayadi-Kajiura aspherical preset lens mounted on a photo slit lamp. Posterior vitreous detachment (PVD) was found in 83% of the eyes. In those eyes, the primary causes of floaters were prepapillary glial tissue on the posterior hyaloid membrane and minimal vitreous hemorrhage. In eyes with no PVD, intravitreous fiber-like opacities corresponding to the patient's symptoms were present in the posterior vitreous cavity near the retina. These opacities were found on the plicated membranes of Cloquet's canal, or were associated with liquefaction of the gel. The symptoms of patients 50 years of age or older were related to the acute onset of PVD in 95% of the cases. The complaint of multiple small floaters was frequently associated with vitreous hemorrhage and retinal breaks.

Adult↗