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M Mitani

Publications and source records attributed to M Mitani.

At least 73 records · Page 4Linked to original sources
PubMed1990

Intraoperative localization of a cervicomedullary glioma from the killed end potential: illustrative case.

We recorded the intraoperative somatosensory evoked potentials directly from the upper cervical cord and medulla in a patient with an intrinsic tumor at the region of the cervicomedullary junction. The killed end potential, a large positive potential, was obtained at the caudal end of the tumor. This type of potential occurs when an impulse approaches but never passes beyond the recording electrode. Myelotomy guided by the killed end potential enabled appropriate spinal and medullary dissection and led to early encounter with the cervicomedullary tumor.

Adult↗
PubMed1989

Characterization of the critical state in protein folding. Effects of guanidine hydrochloride and specific Ca2+ binding on the folding kinetics of alpha-lactalbumin.

The reversible unfolding and refolding kinetics of alpha-lactalbumin induced by concentration jump of guanidine hydrochloride were measured at pH 7.0 and 25 degrees C using tryptophan absorption at 292 nm, with varying concentrations of the denaturant and free Ca2+. The refolding reaction of alpha-lactalbumin from the fully unfolded (D) state occurs through the two stages: (1) instantaneous formation of a compact intermediate (the A state) that has a native-like secondary structure; (2) tight packing of the preformed secondary structure segments to lead finally to the native structure, this stage being the rate-determining step of the reaction and associated with acquisition of the specific structure necessary for strong Ca2+ binding. Under strongly native conditions, the observed kinetics of refolding is also complicated by the presence of a slow-folding species (10%) in the unfolded state. Considering these facts, the microscopic rate constants in folding and unfolding directions have been evaluated from the observed kinetics and from the equilibrium constants of the transitions among the native (N), A and D states. Close linear relationships have been found in the plots of the activation free energies, obtained from the microscopic rate constants, against the denaturant concentration. They are similar to the linear relationship between the free energy of unfolding and the denaturant concentration. It was demonstrated that the slope of the plots should be approximately proportional to a change in accessible surface area of the protein during the respective activation process, and that only a third of the difference in accessible surface area between A and N is buried in the critical activated state of folding. However, the selective effect of Ca2+ binding on the folding rate constant has been observed also, demonstrating that the specific Ca2+-binding substructure in the N state is already organized in the activated state. Thus, only a part of the protein molecule involving the Ca2+-binding region is organized in the activated state, with the other part of the molecule being left less organized, suggesting that the second stage of folding may be a sequential growing process of organized assemblage of the performed secondary structure segments.

Animals↗
PubMed1989

Anti-tumor cytostatic mechanism and delayed-type hypersensitivity against a syngeneic murine tumor. Comparison between neonatally thymectomized mice and congenitally athymic nude mice.

We studied the anti-tumor mechanism against a syngeneic tumor using a BALB/c-MA tumor system by cytolysis and cytostasis assays in vitro comparing mice neonatally thymectomized at 1 day or 7 days after birth (NTx-1, NTx-7), sham-operated (sham) mice, and congenitally athymic nude BALB/c mice. NTx-1 mice showed more rapid tumor growth and a slightly lower degree of strong cytostatic activity in peritoneal exudate cells (PEC) than NTx-7 or sham mice. Nude mice showed more rapid MA growth than NTx-1 mice and no cytostatic activity in PEC. After immunization with mitomycin C-treated MA (MMC-MA), NTx-1 mice acquired an immunoprophylactic capacity against MA and showed cytostatic activity and delayed footpad reaction (DFR) to MA, however, nude mice showed no acquisition of such an immunity, or cytostatic activity, or DFR to MA. These differences between NTx-1 and nude mice could be well-explained by less capacity of nude mice to produce a macrophage-activating factor, which activates macrophages to exert cytostasis and DFR. However, NTx-1 mice could not reject MA by immunization with MMC-MA in CFA (MMC-MA/CFA), although such immunized sham mice could eliminate MA completely. Both PEC and spleen cells from Sham mice immunized with MMC-MA/CFA showed cytostatic activity, whereas NTx-1 mice showed cytostatic activity of the same level in PEC and less in spleen cells compared to Sham mice. Cytolytic activity was never detected throughout this study in a BALB/c-MA system. These data suggest that cytostasis plays an important role in antitumor immunity against a syngeneic MA tumor and that two types of cytostasis is included from the standpoint of thymus-dependency of ontogenic development, relatively low and high.

Animals↗
PubMed1989

Role of cytostasis in antitumor immunity against syngeneic X5563 plasmocytoma: comparative study of cytostasis and cytolysis using variant tumors and neonatally thymectomized mice.

The mechanism of antitumor immunity against syngeneic X5563 plasmocytoma was investigated with cytostasis and cytolysis assays by changing the host-tumor interrelationship using neonatally thymectomized (NTx) mice and spontaneous variant tumors. Immunization with mitomycin C-treated X5563 cells (MCC-X5563) in complete Freund's adjuvant (CFA) induced an effective anti-X5563 immunoprophylaxis in vivo. Such immunized mice and X5563 tumor-bearing mice showed cytostatic, but not cytolytic, activity in their peritoneal exudate cells (PEC) in vitro. Both cytostatic and cytolytic activities were induced in PEC of regressor (R1 and R2) variant tumor-bearing mice. But NTx mice, which could exert cytostatic activity and no cytolytic activity, could reject about one-half of R1 variant tumors. Immunizations using a progressor P1 variant tumor, obtained from R1 tumor after nearly complete rejection, did not give a prophylactic effect in vivo, nor did they induce in vitro cytolytic activity although a low degree of cytostatic activity was detected. These results suggest that cytostasis is the common and basic effector mechanism of antitumor resistance against syngeneic original or variant X5563 tumors, and that the collaboration of cytolysis and cytostasis exerts strong resistance against regressor variants.

Animals↗
PubMed1989

Surgical indications in children with cerebral palsy.

We have presented our approach to the surgical consideration for the upper extremities of a child with cerebral palsy. This is basically a coordinated approach involving many team members, and is the only way to achieve predictable postoperative results.

Cerebral Palsy↗
PubMed1988

Human IFN-gamma production is inhibited by a synthetic peptide homologous to retroviral envelope protein.

A synthetic 17 amino acid peptide (CKS-17) homologous to a highly conserved region of human and animal retroviral transmembrane proteins was investigated for its influence on the in vitro production of IFN-gamma from human peripheral mononuclear cells. The results showed that CKS-17 coupled to a carrier protein, BSA, inhibited production of IFN-gamma in a dose-dependent manner. Controls, consisting of BSA, which had undergone the coupling procedure or neurotensin coupled to BSA in an identical manner as CKS-17, showed no such inhibition. Reduction in IFN-gamma production could not be attributed to decreased viability of cells, delay of IFN-gamma production or to involvement of suppressor cells. Moreover, inhibition of IFN-gamma production was not related to the inhibition of DNA synthesis. The inhibition appeared to be a direct effect of CKS-17 on IFN-gamma-producing cells. Kinetic studies revealed that this suppression occurred when CKS-17 was introduced to the culture concurrent with or within 48 h after introduction of IFN inducers. Preincubation experiments showed that the presence of CKS-17 in the culture medium was not necessary to exert its inhibitory effect. These results suggest that a portion of retroviral envelope proteins possess important immunomodulatory actions.

Amino Acid Sequence↗
PubMed1988

In vitro production of feline IgG: quantification by an enzyme-linked immunosorbent assay (ELISA).

We report here on the development of a sensitive and convenient enzyme-linked immunosorbent assay (ELISA) for feline IgG by using commercially available reagents and optimizing their concentrations. The reagents employed include goat anti-cat IgG antibody and alkaline phosphatase-conjugated goat anti-cat IgG antibody. The assay described is sensitive, reproducible, and highly specific for feline IgG. The assay was applied for the measurement of feline IgG synthesized and secreted in vitro by peripheral blood mononuclear cells cultured with or without a polyclonal B-cell activator. The amounts of secreted IgG in the supernatants measured by an ELISA correlated well with the numbers of IgG-secreting cells which were induced upon stimulation with pokeweed mitogen and determined by a reverse hemolytic plaque assay.

Animals↗
PubMed1987

Suppressive effect on polyclonal B-cell activation of a synthetic peptide homologous to a transmembrane component of oncogenic retroviruses.

Purified feline leukemia virus, UV light-inactivated feline leukemia virus, and a synthetic peptide (CKS-17) homologous to a well-conserved region of the transmembrane components of several human and animal retroviruses were each studied for their effects on IgG production by feline peripheral blood lymphocytes. Using a reverse hemolytic plaque assay, both the viable virus and the UV-inactivated feline leukemia virus, but not the CKS-17, activated B lymphocytes to secrete IgG. When staphylococcal protein A, a polyclonal B-cell activator, was used to stimulate IgG synthesis by feline lymphocytes, the viable virus, the UV-inactivated virus, and the CKS-17 peptide each strongly suppressed IgG secretion without compromising viability of the lymphocytes. These findings suggest that the immunosuppressive influences of feline leukemia virus on immunoglobulin synthesis may reside in a conserved portion of the envelope glycoprotein that includes the region homologous to CKS-17.

Amino Acid Sequence↗
PubMed1986

Evidence for identity between the equilibrium unfolding intermediate and a transient folding intermediate: a comparative study of the folding reactions of alpha-lactalbumin and lysozyme.

The refolding kinetics of alpha-lactalbumin at different concentrations of guanidine hydrochloride have been investigated by means of kinetic circular dichroism and stopped-flow absorption measurements. The refolding reaction consists of at least two stages, the instantaneous accumulation of the transient intermediate that has peptide secondary structure and the subsequent slow process associated with formation of tertiary structure. The transient intermediate is compared with the well-characterized equilibrium intermediate observed during the denaturant-induced unfolding. Stabilities of the secondary structures against the denaturant, affinities for Ca2+, and tryptophan absorption properties of the transient and equilibrium intermediates were investigated. In all of these respects, the transient intermediate is identical with the equilibrium one, demonstrating the validity of the use of the equilibrium intermediate as a model of the folding intermediate. Essentially the same transient intermediate was also detected in the folding of lysozyme, the protein known to be homologous to alpha-lactalbumin but whose equilibrium unfolding is represented as a two-state reaction. The stability and cooperativity of the secondary structure of the intermediate of lysozyme are compared with those of alpha-lactalbumin. The results show that the protein folding occurring via the intermediate is not limited to the proteins that show equilibrium intermediates. Although the unfolding equilibria of most proteins are well approximated as a two-state reaction, the two-state hypothesis may not be applicable to the folding reaction under the native condition. Two models of protein folding, intermediate-controlled folding model and multiple-pathway folding model, which are different in view of the role of the intermediate in determining the pathway of folding, are also discussed.

Guanidine↗
PubMed1986

Innocuous character of [ethylenebis(oxyethylenenitrilo)]tetraacetic acid and EDTA as metal-ion buffers in studying Ca2+ binding by alpha-lactalbumin.

The binding of EGTA and EDTA to alpha-lactalbumin, first demonstrated by Kronman and Bratcher (Kronman, M. J., and Bratcher, S. C. (1983) J. Biol. Chem. 258, 5707-5709) and afterwards regarded as a significant source of error in estimating the binding constant of Ca2+ to the protein, has been investigated by comparison of the thermal unfolding curves of the protein in the absence and presence of the chelators and also by measuring the NMR spectra of the protein, the chelators, and the protein-chelator mixtures. The unfolding curve in the presence of a large excess of each chelator has been found to be identical to that in the absence of chelator, indicating that there is essentially no interaction between the chelators and alpha-lactalbumin. The NMR results have also supported this conclusion, and the innocuous character of these chelators as metal-ion buffers in studying the Ca2+-binding properties of alpha-lactalbumin is demonstrated. In order to re-examine the binding constant for Ca2+ of alpha-lactalbumin without the aid of chelating metal-ion buffers, the thermal unfolding curve of the protein in the presence of 0.1 mM excess Ca2+ but without chelators has been compared with the unfolding curve in the absence of Ca2+ at a constant concentration of Na+ (0.010 or 0.10 M) at pH 7.0. The binding constant of alpha-lactalbumin can be calculated from the increment of melting temperature caused by the presence of Ca2+ and from the enthalpy and heat capacity changes in the unfolding. Because Ca2+ binding to the unfolded protein can be neglected under the conditions employed, the binding constant evaluated corresponds to the binding constant to protein that has native structure. The constant obtained is 3-5 X 10(9) M-1 after corrections for binding of Na+ to the protein and for ionic strength, and this shows excellent agreement with the corresponding value previously estimated (2.9 +/- 1.0 X 10(9) M-1), although the latter value was obtained in the presence of EDTA. The apparent Ca2+-binding constant that has been discussed in most previous studies, without taking account of the folding-unfolding equilibrium associated with the binding process, also depends on the concentration of monovalent cations such as Na+, and the present results lead to values of 1.5 X 10(8) and 8.7 X 10(6) M-1 at 0.01 and 0.1 M Na+, respectively.

Buffers↗
PubMed1986

Purification and characterization of prolactin receptors from rat ovary.

Prolactin receptors were purified to homogeneity by two affinity chromatography steps using concanavalin A-Sepharose and human growth hormone (hGH)-Sepharose. The purified receptors showed specificity and high affinity for lactogenic hormones and a binding capacity of 20 nmol/mg of protein. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis analysis revealed that purified receptors were composed of two major protein bands of Mr = 41,000 and 88,000, which were identified as radioactive bands by binding of 125I-hGH to blotted renatured receptors and by autoradiogram of free and 125I-radiolabeled purified receptors. Autoradiographic analysis of SDS-polyacrylamide gel electrophoresis of cross-linked 125I-hGH-receptor or hGH-125I-iodinated receptor complexes showed two radioactive bands of Mr = 63,000 and 106,000. Analysis of the free receptors by high performance liquid chromatography using Superose 12 revealed two peaks of binding activity for 125I-hGH eluting in the positions of Mr approximately 150,000 and 250,000. After cross-linking with 125I-hGH, SDS-polyacrylamide gel electrophoresis analysis revealed that both peak fractions contained two binding species with Mr = 63,000 and 106,000. Chromatography of 125I-hGH-receptor complexes showed two radioactive fractions with approximate Mr approximately 180,000 and 300,000. The treatment of 125I-iodinated receptors with SDS and reductant resulted in the dissociation of the higher Mr form into the lower Mr form upon gel filtration. Chromatofocusing of free receptors showed three isoforms with pI 4.0, 5.0, and 5.3. These results indicate that detergent-solubilized prolactin receptors appear to be aggregated forms of holoreceptor containing two binding species of Mr = 41,000 +/- 2,000 and 88,000 +/- 3,000.

Animals↗
PubMed1986

Antigen-specific augmentation of delayed-type hypersensitivity by immune serum factor in mice: augmentation of anti-tumor cytostatic activity.

A humoral factor capable of augmenting delayed-type hypersensitivity antigen specificity (DAF) is present in the serum of mice sensitized with heterologous erythrocytes to induce a delayed footpad reaction (DFR). In the present study, a similar factor was identified when xenogeneic tumor cells were used as antigens. This factor also could augment the in vitro anti-tumor cytostatic activity against homologous tumor cells, which correlated with in vivo DFR to the same tumor cells. The cytostatic activity augmented by the transfer of this factor had the following characteristics: The activity appeared in the whole peritoneal exudate cells (PEC) from serum recipients at 4 days after the antigenic challenge. Such an activity was revealed in the collaboration of plastic dish-nonadherent and -adherent PEC as the primary and final effectors, respectively. The appearance of primary effector cells for such an activity was also accelerated in spleen and lymph node cells. However, a sufficient number of macrophages were always required as the final effectors in their functional expression. These primary effectors were sensitized T lymphocytes which produced lymphokine(s) such as macrophage-activating factor(s) and which contributed to this augmented cytostatic activity through the activation of macrophages. Thus, this immune serum factor seems to exert functional expression by accelerating the generation of lymphokine-producing delayed-type T lymphocytes, which is also responsible for cytostatic anti-tumor immunity.

Animals↗
PubMed1986

Long-term follow-up on tendon transfers to the extensors of the wrist and fingers in patients with cerebral palsy.

Thirty-eight patients with cerebral palsy had tendon transfers to improve extension of the wrist and fingers. The 10 patients who had poor hand placement, sensibility, or motor control failed to improve in functional grasp or release. The remaining 28 patients, with better preoperative criteria, had improved function. On long-term follow-up, 5 of the 12 patients with transfers to the wrist extensor had extension contractures with difficulty in release, and in seventeen patients transfers to the finger extensors resulted in improved finger extension and release, with no sacrifice in the ability to grasp.

Adolescent↗
PubMed1986

Allograft rejection and immune responses against allogeneic antigens in neonatally thymectomized mice.

Skin allograft survival and immune responses against allogeneic antigens homologous to skin grafts were observed in BALB/c Cr Slc (BALB) mice (H-2d) thymectomized at 1 day after birth and grafted with skin from major histocompatibility complex (MHC)-incompatible, fully allogeneic C3H/HeN (C3H) (H-2k) or MHC-compatible allogeneic DBA/2 Cr Slc (DBA) mice (H-2d), at 14 weeks of age. In neonatally thymectomized (NTx) BALB mice, survival of C3H skin grafts was not prolonged at all, but survival of DBA skin grafts was prolonged significantly, although the survival periods of DBA skin grafts were very different among individual recipients. In NTx recipients grafted with C3H skin, delayed foot-pad reaction (DFR) was not reduced, but cytotoxic lymphocyte (CTL) activity and cytotoxic antibody (CTAb) production were appreciably depressed. CTL and CTAb were reduced profoundly and consistently in all NTx mice grafted with DBA skin, while DFR was reduced to various degrees in each. The degrees of depression of DFR in these NTx mice correlated well with the prolongation of DBA skin survival, although the sample number was small. The rejection of skin allografts appears to be attributable largely to a T cell subset, the function of which can be expressed as DFR. Thymus dependency in the ontogenic development is low as compared with other T cell subsets.

Animals↗
PubMed1986

Disposition of carumonam (AMA-1080/Ro 17-2301), a new N-sulfonated monocyclic beta-lactam, in rats and dogs.

Rats and dogs were given a single 20-mg/kg dose of [14C]carumonam intramuscularly or intravenously. In rats, the level in plasma of [14C]carumonam administered intramuscularly peaked (29.1 micrograms/ml) 15 min after dosing and then declined with an apparent elimination half-life of 16.2 min. Intramuscular injection of [14C]carumonam to dogs gave a peak level (36.8 micrograms/ml) in plasma at 20 min and an apparent elimination half-life of 51.7 min. After administration of the intravenous dose, apparent elimination half-lives were 13.1 and 52.7 min in rats and dogs, respectively. In both animals, the radioactivity in plasma was made up largely (greater than 80%) of unchanged carumonam, which was protein bound to only a small extent. In rats given [14C]carumonam intramuscularly, radioactivity was distributed widely in tissues, with relatively high concentrations in the kidney and liver. The radioactivity concentration in the rat fetus was relatively low, as was that in milk. In both rats and dogs carumonam did not undergo extensive metabolism; the most prominent metabolite was AMA-1294, the compound resulting from beta-lactam ring hydrolysis. [14C]carumonam and metabolites were mostly eliminated from the bodies within 72 h in rats and 120 h in dogs. In both animals, a large amount of the dosed radioactivity was excreted in the urine largely as unchanged antibiotic. The remainder was eliminated in the feces via bile. AMA-1294 was eliminated from the bodies of rats and dogs at a considerably slower rate than was unchanged carumonam. In rats, [14C]carumonam was eliminated by both glomerular filtration (67%) and tubular secretion (33%); the renal elimination of [14C]AMA-1294 was only by glomerular filtration.

Animals↗
PubMed1986

Differing contribution of various effector cells in the elimination of syngeneic or allogeneic cells.

The growth of Meth A (MA) tumors was suppressed in tumor-antigen-specific manner in BALB/c mice immunized with mitomycin C-treated MA (MMC-MA) cells in saline or in Freund's complete adjuvant (FCA). The antitumor activity of their peritoneal exudate cells (PEC) was detected by in vivo neutralization test and in vitro cytostasis assay but not by in vitro cytolysis assay. Positive delayed footpad reaction was elicited by footpad injection of MMC-MA cells in such immunized mice, before or after the inoculation of viable MA cells. Expression of cytostatic activity in PEC required the interaction of non-adherent and adherent cells. Normal PEC could exert the cytostatic activity in the presence of a nonadherent population of immune PEC. These findings suggest that cytostatic macrophages are activated after the interaction between sensitized lymphocytes and tumor-specific antigens and that they play an important role in the principal effector mechanism in this syngeneic system. On the other hand, immunization with MMC-MA in FCA or viable MA cells also induced PEC the antitumor activity detected by in vivo neutralization test in allogeneic C57BL/6 hosts. Immunization with viable MA cells induced not only cytolytic but also cytostatic activity, whereas, immunization with MMC-MA in FCA induced cytostatic activity but not cytolytic activity. In contrast to a syngeneic system, cytolytic activity was effectively induced against allogeneic MA cells together with cytostatic activity. We conclude that there are various effector cells contributing to the elimination of syngeneic or allogeneic murine tumor cells.

Animals↗
PubMed1985

Adult T-cell leukemia in two siblings. Acute crisis of smoldering disease in one patient.

Two cases of human T-cell leukemia virus (HTLV)-positive adult T-cell leukemia (ATL) in brother and sister are presented. Six of 15 members of this family were seropositive for antibodies for ATL-associated antigens (ATLA). The sister of the ATL patient developed overt ATL after 5 years and 8 months of smoldering ATL. Immunologic examinations during the smoldering phase were normal except for negative skin tests for purified protein derivative. Factors leading to the induction of ATL among HTLV carriers remain to be studied.

Acute Disease↗