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Biomedical subjects

R Sato

Publications and source records attributed to R Sato.

At least 415 records · Page 23Linked to original sources
PubMed1979

Circular dichroism spectra of purified cytochromes P-450 from rabbit liver microsomes.

Circular dichroism (CD) spectra were measured for cytochromes P-450 (P-450) purified from phenobarbital- and 3-methylcholanthrene-induced rabbit liver microsomes. No striking difference in alpha-helix content was seen between phenobarbital-induced P-450 (PB P-450) (50%), phenobarbital-induced P-448 (PB P-448) (40%) and 3-methylcholanthrene-induced P-448 (MC P-448) (45--50%) in terms of ultraviolet CD spectra. Strong negative CD spectra associated with 3-methylcholanthrene transitions for MC P-448 in the near-ultraviolet region (250--310 nm) and weaker negative CD spectra associated with Soret transitions for PBP-448 ([theta] = 50 000) and MCP-448 ([theta] = 160 000), indicated that structures of these preparations are strikingly different from each other. Reduction of P-450 and P-448 led to a remarkable decrease of the Soret CD trough, suggesting that reduction was accompanied by a striking conformational change in the vicinity of the heme. Since CO complexes of reduced P-450 and P-448 showed a CD trough and an S-shaped CD, respectively, associated with the absorption peak at 450 nm, the heme vicinities are remarkably different from each other. The CD spectra in the visible region are also discussed. It was noticed that P-420, the denatured form of P-450, exhibited no CD spectra in the Soret and visible regions.

Animals↗
PubMed1979

Mutant and immunochemical studies on the involvement of cytochrome b5 in fatty acid desaturation by yeast microsomes.

The involvement of cytochrome b5 in palmitoyl-CoA desaturation by yeast microsomes was studied by using yeast mutants requiring unsaturated fatty acids and an antibody to yeast cytochrome b5. The mutants used were an unsaturated fatty acid auxotroph (strain E5) and a pleiotropic mutant (strain Ole 3) which requires either Tween 80 and ergosterol or delta-aminolevulinic acid for growth. Microsomes from the wild-type strain possessed both the desaturase activity and cytochrome b5, whereas those from mutant E5 contained the cytochrome but lacked the desaturase activity. Microsomes from mutant Ole 3 grown with Tween 80 plus ergosterol were devoid of both the desaturase activity and cytochrome b5, but those from delta-aminolevulinic acid-grown mutant Ole 3 contained cytochrome b5 and catalyzed the desaturation. The cytochrome b5 content in microsomes from mutant Ole 3 could be varied by changing the delta-aminolevulinic acid concentration in the growth medium, and the desaturase activity of the microsomes increased as their cytochrome b5 content was increased. The antibody to yeast cytochrome b5, but not the control gamma-globulin fraction, inhibited the NADH-cytochrome c reductase and NADH-dependent desaturase activities of the wild-type microsomes. It is concluded that cytochrome b5 is actually involved in the desaturase system of yeast microsomes. The lack of desaturase activity in mutant Ole 3 grown with Tween 80 plus ergosterol seems to be due to the absence of cytochrome b5 in microsomes, whereas the genetic lesion in mutant E5 appears to be located at ther terminal desaturase.

Cytochromes↗
PubMed1979

Interaction between NADPH-cytochrome P-450 reductase and cytochrome P-450 in the membrane of phosphatidylcholine vesicles.

Cytochrome P-450 and NADPH-cytochrome P-450 REDUctase, both purified from liver microsomes of phenobarbital-pretreated rabbits, have been incorporated into the membrane of phosphoaditylcholine vesicles by the cholate dialysis method. The reduction of cytochrome P-450 by NADPH in this system is biphasic, consisting of two first-order reactions. The rate constant of the fast phase, in which 80--90% of the total cytochrome is reduced, increases as the molar ratio of the reductase to the cytochrome is increased at a fixed ratio of the cytochrome to phosphatidylcholine, suggesting that the rate-limiting step of the fast phase is the interaction between the reductase and the cytochrome. The rate constant of the fast phase also increases when the amount of phosphatidylcholine, relative to those of the two proteins, is decreased. This latter observation suggests that the interaction between the two proteins is effected by their random collision caused by their lateral mobilities on the plane of the membrane of phosphatidylcholine vesicles. The rate constant of the slow phase as well as the fraction of cytochrome P-450 reducible in the slow phase, on the other hand, remains essentially constant even upon alteration in the ratio of the reductase to the cytochrome or in that of the two proteins to phosphatidylcholine. No satisfactory explanation is as yet available for the cause of the slow-phase reduction of cytochrome P-450. The overall activity of benzphetamine N-demethylation catalyzed by the reconstituted vesicles responds to changes in the composition of the sysTEM IN A SIMILAR WAY TO THE FAST-PHASE REDUCTION OF CYTOCHROME P-450, though the latter is not the rate-limiting step of the overall reaction.

Animals↗
PubMed1979

Inhibition of the binding of cytochrome b5 to phosphatidylcholine vesicles by cholesterol.

The binding of cytochrome b5 to single-walled liposomes of egg phosphatidylcholine was inhibited by the presence of cholesterol in the lipid bilayer under conditions where a limited amount of liposomes was incubated with the cytochrome. Since similar conditions seem to apply for the binding of cytochrome b5 to erythrocyte ghosts, this observation supports the conclusion of Enomoto and Sato (Enomoto, K. and Sato, R. (1977) Biochim. Biophys. Acta 466, 136--147) that the localization of cholesterol on the outer surface of the ghost membrane prevents the binding of cytochrome b5 to this surface. The finding reported by Roseman et al. (Roseann, M.A., Holloway, P.W. and Calabro, M.A. (1978) Biochmi. Biophys. Acta 507, 552--556) that cholesterol did not prevent the cytochrome binding to phosphatidylcholine liposomes in the presence of a large excess of liposomes could be confirmed in the present study, but this does not contradict the abovementioned conclusion.

Cholesterol↗
PubMed1979

Information transmission in multi-input-output stochastic neuron models.

The Shannon's information theory in multi-way channels (Shannon, 1961) is applied to multi-input-output relations of the stochastic automaton models for interaction of excitatory and inhibitory impulse sequences proposed in the previous papers (Tsukada et al., 1977). In these models, the output spike train depends upon several statistical characteristics (mean frequency, standard deviation, form, order-dependence or order-independence, etc.) of the excitatory and inhibitory input spike trains. By the use of the multiple-access channel in information theory, some stochastic properties of temporal pattern discrimination in neurons are analyzed and discussed with biological systems.

Action Potentials↗
PubMed1979

Primary structure of the membrane-binding segment of rabbit cytochrome b5.

The primary structure of the membrane-binding segment of rabbit cytochrome b5 has been determined. This segment, prepared by trypsin digestion of the intact protein, consists of 43 amino acid residues and corresponds to the COOH-terminal end (residues 91-133) of the parent molecule. Deduction of the primary structure was based on automated sequence analysis of the whole segment as well as manual and dansyl-Edman degradations of peptide fragments produced by CNBr cleavage and partial acid hydrolysis. The sequence obtained is: Leu-Ser-Lys-Pro-Met-Glu-Thr-Leu-Ile-Thr-Thr-Val-Asn-Ser-Asn-Ser-Ser-Trp-Trp-Thr-Asn-Trp-Val-Ile-Pro-Ala-Ile-Ser-Ala-Leu-Ile-Val-Ala-Leu-Met-Tyr-Arg-Leu-Tyr-Met-Ala-Asp-Asp. This sequence is 63 to 81% homologous with respect to those determined for the membrane-binding segments of equine, porcine and bovine cytochrome b5. The interaction of this segment with phospholipid bilayer membranes is discussed, and a prediction of its secondary structure is also presented.

Amino Acid Sequence↗
PubMed1979

Early tangential excision and immediate mesh autografting of deep dermal hand burns.

Thermal injuries to the hand constitute not only one of the most common burns, but one of the most difficult for the burn surgeon to treat. Early wound closure is mandatory if maximum functional return is to be attained and scarring minimized. Over the last three and one-half years, 60 patients with deep dermal dorsal hand and finger burns were treated by tangential excision and immediate mesh autografting. All patients were admitted to the hospital within 24 hours of injury and excision was performed between the third to the tenth post burn day. Operative technique consisted of sequential eschar excision using the Humby knife or Goulian-Weck dermatome until viable dermis was visible. Mesh autograft, ratio 1 to 1(1/2) without expansion, was applied. There was 100% graft take in all but four hands. Hand function with full range of motion returned by the tenth postoperative day. Complications were minor. Patient follow-up ranged from six months to three and one-half years. No patient has required subsequent surgery for scar revision or contracture release. Range of motion in all patients has been excellent and all patients have continued to maintain normal hand function. The cosmetic appearance has been good except for the early "mesh" appearance of the graft which has become less apparent with time. In summary, early tangential excision and immediate mesh autografting of deep dermal dorsal hand burns has fulfilled the following burn principles-preservation of tissue, prevention of wound infection, maintenance of function and early wound closure.

Adolescent↗
PubMed1979

Periarteritis nodosa in spontaneously hypertensive rats -- incidence and distribution.

SHR rats (Nihon Rat Inc.) were used to study spontaneous arterial lesions morphologically resembling human periarteritis nodosa (PN). Male SHR rats (159) developed PN in 76.1%, whereas females (39) in 10.3% during a period of 2 to 15 months of age. The frequency of PN in male SHR rats tended to increase with ageing and reached 100% at 9 months of age. PN lesions were widely distributed with only the lungs, brain and aorta being spared. PN in females was restricted to the tongue, parametrium and mesenterium. Male SHR rats with hypertension of more than 180 mm Hg showed PN in 81.7%, whereas in females with the same hypertension PN was found in only 17.4%. Although there was apparent sex difference in the incidence and background of hypertension, male SHR rats might be a useful animal model of human PN.

Age Factors↗
PubMed1979

A routine method for assaying the anti-toxoplasma IgM antibodies. Latex agglutination test on human sera preabsorbed with protein A-bearing staphylococcal cells.

The authors investigated the procedure which demonstrates, by means of the latex agglutination test (LA) the residual IgM antibody activities in sera preabsorbed with protein A-bearing Staphylococcus aureus and evaluated the usefulness of this technique with the following results. (1) LA (Toxotest-LA, Eikenkagaku Co.) gave clear-cut and reproducible agglutination patterns. Its specificity was comparable to that of HA and its sensitivity was somewhat lower than that of HA. (2) The absorption of 0.2 ml of 1:10 dilution of many test sera with the sediment of 0.5 ml of a 10% bacterial suspension for ten minutes or more provides the suitable condition for the absorption procedure. (3) HA-positive 183 sera revealed no residual antibody activities after absorption. These are supposed to derive from persons with a long-standing infection. Sera from 4 laboratory infection cases, from 2 toxoplasmic lymphadenopathy cases and from a pregnant woman, showed more or less residual activities. In 5 out of 7 sera tested, the residual activities were 2-ME sensitive, indicating the presence of specific IgM antibodies. (4) The specific and the total IgM were reduced slightly by the absorption procedure.

Absorption↗