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Biomedical subjects

S Mikata

Publications and source records attributed to S Mikata.

At least 19 recordsLinked to original sources
PubMed2001

Left-hand-assisted laparoscopic resection of hepatocellular carcinoma in an accessory liver.

We report a left-hand-assisted laparoscopic resection of hepatocellular carcinoma that developed in an accessory liver in a 47-year-old man. Preoperative assessment of the location of the tumor and the feeder vessels by combined selective angiography and computed tomography studies predicted the feasibility of laparoscopic procedures for complete removal of the tumor. In an attempt to avoid direct contact of the tumor capsule with rigid instruments during the operation, left-hand-assisted procedures were attempted. The encapsulated mass, 6 x 5 x 3 cm in size, was located on the posterior side of the left diaphragm, and a thin stalk between the tumor and the margin of the left lateral segment of the liver proper was recognized. Hand-assisted procedures ensured the complete mobilization of the lesion with an adequate margin, without any unexpected capsular tear. Left-hand-assisted laparoscopic procedures would be feasible for the easy and safe resection of localized hepatocellular carcinoma developing in an accessory liver.

Carcinoma, Hepatocellular↗
PubMed2001

Hand-assisted laparoscopic splenectomy for idiopathic thrombocytopenic purpura during pregnancy.

A successful case of a hand-assisted laparoscopic splenectomy with low-pressure pneumoperitoneum for autoimmune thrombocytopenic purpura in a patient at 23 weeks' gestation is reported. Preoperative splenic arterial embolization was performed on the same day as the operation using painless contour embolic material and super-absorbent polymer microspheres. The abdominal wall retraction method first was applied to avoid the effects of pneumoperitoneum on systemic hemodynamic alterations. However, a sufficient surgical view could not be obtained, as the intra-abdominal organs were elevated because of the enlarged uterus. A surgical view with 4 to 6-mm Hg pneumoperitoneum was available for the hand-assisted splenectomy. The postoperative course was uneventful, and the patient vaginally delivered a healthy infant. A hand-assisted laparoscopic splenectomy with low-pressure pneumoperitoneum after splenic arterial embolization would be feasible for patients with autoimmune thrombocytopenic purpura during a relatively advanced pregnancy.

Adult↗
PubMed2000

Ileal perforation due to a Richter hernia at the drain insertion site following an operation for idiopathic rectal perforation: report of a case.

A case of a Richter hernia at the insertion site of the drainage tube following open abdominal surgery is reported. A 54-year-old man underwent an emergency operation for an idiopathic rectal perforation. A partial resection of the rectum and drainage using four 10-mm (outer diameter) drainage tubes with round cross sections was performed. Despite an uneventful early postoperative course, an emergency reoperation was required for peritonitis due to a bowel perforation 14 days after removing the drain inserted into the rectosacral space. A laparotomy revealed an incarcerated Richter hernia with ileal perforation through the 10-mm drainage site. The postoperative course after a partial resection of the ileum and drainage with Penrose drains was uneventful. This is the first report of a Richter hernia through the insertion site of a drainage tube in abdominal surgery. The possible occurrence of a Richter hernia in cases with postoperative drainage using large-size round drainage tubes should thus be considered in such patients.

Drainage↗
PubMed2000

Molecular remodelling of human CD46 for xenotransplantation: designing a potent complement regulator without measles virus receptor activity.

In pig-to-human discordant xenotransplantation, human complement (C) is a major barrier to long survival of xenografts. The current idea on how to cope with this barrier is that human complement regulatory proteins are forcibly expressed on xenografts to serve as safeguards against host C-induced hyperacute rejection of xenografts. Co-expression of decay-accelerating factor (DAF) (CD55) and membrane cofactor protein (MCP) (CD46) would be the first choice for this trial, because most of the human cells are protected from C-mediated damage by two different modes with these two kinds of C-regulators. Many problems have arisen, however, for MCP expression on grafts. (i) MCP acts as a measles virus receptor, which may function to render donor pigs measles virus (MV) sensitive. (ii) MCP signals immune suppression which causes devastation of the recipient's immune responses. (iii) MCP exerts relatively low self-protective activity against C compared with other cofactors; development of more efficient forms is desirable. (iv) Grafts with a high expression level of MCP are difficult to produce. In this study, we made a number of cDNA constructs of MCP, expressed them on swine endothelial cell lines, and tested cell-protective potency and MV susceptibility. The short consensus repeat 1 (SCR1)-deleted MCP with glycosyl phosphatidylinositol (GPI)-anchored form (Delta1MCP-PI) of MCP was found to be most suitable for the purpose of overcoming these problems. However, it was also found that MV induces two modes of cytopathic effect (CPE) on swine endothelial cells, either MCP-dependent or -independent. Here, we discuss these two points which will be raised through study of MCP-transgenic animals.

Animals↗
PubMed1999

Function of human factor H and I on xenosurface.

The cell membrane-bound forms of mini-factor H with 1-4 short consensus repeats (fH-PI) and factor I (fI-PI) were constructed. Swine endothelial cell (SEC) lines and Chinese hamster ovary (CHO) cell expressing fH-PI or fI-PI were established and confirmed by flow cytometry. The cell lysate of the SEC line expressing fH-PI showed strong cofactor activity for the cleavage of C3b, and fI-PI demonstrated the protease activity for C4b and C3b not only in the fluid phase but also on the cell membrane. In addition, fH-PI blocked human complement-mediated cell lysis by approximately 30-40%. An SEC line with a low expression of fI-PI showed a weak inhibition of cell lysis in human serum, whereas a CHO cell transfectant with a high expression of fI-PI showed over a 60% inhibition of cell lysis. The results suggest that fH-PI and fI-PI have potential for use in clinical xenotransplantation.

Animals↗
PubMed1999

Molecular remodeling of complement regulatory proteins for xenotransplantation.

In pig-to-human discordant xenotransplantation, human complement is a major barrier against long survival of xenografts. Human complement regulatory proteins expressed on xenografts have been adapted as safeguards against host-induced hyperacute rejection of xenografts. For successful xenotransplantation, there have been many attempts to generate molecules with potent human complement regulatory activity but without activities related to harmful functions such as infection, immunosuppression and signal transduction devastating cellular homeostasis. Here, we summarize the strategy by which molecules for xenotransplantation should be designed and propose a GPI-anchored form of monomeric human C4bp as a candidate for efficient protection of swine xenografts from human complement attack.

Acute Disease↗
PubMed1999

Laparoscopically assisted splenectomy following preoperative splenic artery embolization using contour emboli for myelofibrosis with massive splenomegaly.

Laparoscopically assisted splenectomy with an 8- to 10-cm left upper paramedian laparotomy was performed following preoperative splenic artery embolization using painless contour emboli (super absorbent polymer microsphere) with early successful results in two men (46 and 37 years old) with myelofibrosis accompanied by massive splenomegaly. Dissection around the lower part of the spleen and the hilum initially was performed intracorporeally with the usual laparoscopic view under 12 mm Hg pneumoperitoneum. The alternating changes of viewpoints between the direct view through an 8- to 10-cm incision and the usual laparoscopic view with or without application of a retraction method were effective for safe hilar devascularization. Preoperative splenic artery embolization at the distal site was effective for safe dissection around the enlarged spleen. The patients did not complain of pain before operation. Preoperative painless embolization and laparoscopically assisted splenectomy with small laparotomy promotes the feasibility and safety of minimally invasive splenectomy for myelofibrosis with massive splenomegaly.

Adult↗
PubMed1998

Regulation of complement-mediated swine endothelial cell lysis by a surface-bound form of human C4b binding protein.

BACKGROUND: Human C4b-binding protein (C4bp) functions as a cofactor for factor I in the degradation of C4b and C3b and, in addition, accelerates the rate of decay of the C4b2a complex. METHODS: In this study, we constructed a surface-bound form of human C4b-binding protein (C4bp-PI) consisting of a short consensus repeat 1-8 of the alpha-chain of C4bp and a glycosyl phosphatidylinositol (GPI) of the decay-accelerating factor (CD55) and established stable swine endothelial cell (SEC) lines expressing C4bp-PI by transfection of cDNA. Amelioration of complement-mediated lysis by the transfectant molecules was tested as an in vitro hyperacute rejection model of swine to human discordant xenograft, using the lactate dehydrogenase assay. RESULTS: Flow cytometric profiles of the stable SEC lines with C4bp-PI showed a high level of expression of this molecule. The cell lysate of the SEC line with C4bp-PI showed strong cofactor activity in not only C4b but also C3b, whereas the activity of plasma C4bp to bind to C3 was very weak. Approximately 150 x 10(4) molecules of C4bp-PI per SEC blocked human complement-mediated cell lysis by approximately 75%. CONCLUSIONS: The results suggest that the surface-bound form of C4bp will be very useful in clinical xenotransplantation.

Animals↗
PubMed1998

A monomeric human C4b-binding protein (C4bp) more efficiently inactivates C3b than natural C4bp: participation of C-terminal domains in factor I-cofactor activity.

We designed a cDNA construct encoding an artificial membrane molecule consisting of all 8 short consensus repeats (SCRs) of human monomeric C4b-binding protein (C4bp) followed by DAF's GPI anchor, named mC4bp, and expressed the protein on swine endothelial cells (SEC). At the same level of expression, mC4bp protected host cells as effectively as DAF, the most potent complement (C) regulator on the membrane. This result was unexpected from the reported functional properties of natural multimeric C4bp. Here, we investigated the mechanism whereby mC4bp has potent cell-protective activity. Our results were as follows: (1) mC4bp serves more efficiently as a methylamine-treated C3 (C3ma)-inactivating factor I-cofactor than natural C4bp and as efficiently as MCP as a methylamine-treated (C4ma)-inactivating cofactor by fluid-phase cofactor assay: (2) the potency of C3ma inactivation by mC4bp and factor I is quite high compared to those of other cofactors: (3)blocking studies using mAbs against C4bp suggested that both the 48 kDa N-terminal fragment and the C-terminal domain near the portion responsible for bundle formation participate in the high C3ma-inactivating capacity of mC4bp. Thus, acquiring high C3ma-inactivating capacity secondary to monomeric alteration leads to high C regulatory activity of mC4bp. These results infer that mC4bp differs from C4bp in its potent factor I-cofactor activity and is a good candidate as a safeguard against hyperacute rejection of xenografts.

Complement C3b Inactivator Proteins↗
PubMed1998

Prevention of hyperacute rejection by phosphatidylinositol-anchored mini-complement receptor type 1.

Complement receptor type 1 (CR1, CD35) contains both factor I cofactor activity and convertase decay accelerating activity, but is, in general, thought to be an extrinsic regulator of complement activation. In this study, we prepared a phosphatidylinositol (PI)-anchored mini-CR1, which is composed of the short consensus repeat (SCR) 8-11 of CR1 and the PI anchor of DAF, and expressed it stably on a swine endothelial cell (SEC) line. We then examined the intrinsic regulatory activity of the mini-CR1, with respect to complement-mediated cell lysis as an in vitro hyperacute rejection model of a swine to human discordant xenograft. Flowcytometric profiles of the stable SEC lines with mini-CR1 showed a moderate level of expression for this molecule. Mini-CR1 blocked human complement-mediated cell lysis by approximately 50-70% on SEC. From the data of this study and our previous studies, mini-CR1 was more effective than membrane cofactor protein (MCP, CD46), and as effective as decay accelerating factor (DAF, CD55) in this system. The results suggest that PI-anchored mini-CR1 represents a useful molecule for clinical xenotransplantation.

Animals↗
PubMed1997

The regulation of membrane cofactor protein (CD46) expression by the 3' untranslated region in transgenic mice.

Regulation of the membrane cofactor protein (MCP: CD46) was examined. While the expression of MCP in mice carrying MCP(BC2) cDNA with 125 bp of 3' untranslated region (3'UT) was minimal, that in mice carrying MCP cDNA without total 3' UT was evident in many organs. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis clearly showed the presence of mRNA even in transgenic mice with 3' UT, suggesting that the expression was regulated at the post-transcriptional stage. The in vitro expression data of MCP molecules on the stable Chinese hamster ovary (CHO) cell clone corresponded to that in transgenic mice. The first 125 bp downregulated the expression of MCP molecules in combination with not only beta-actin, but also SR alpha, promoter. Also, this region inhibited expression of decay accelerating factor (DAF: CD55) molecules when it was inserted into cDNA of DAF. Furthermore, the first 32 bp of the 3' UT revealed the same downregulation effect as 125 bp on MCP molecules. These findings indicated that the first 125 bp (and the first 32 bp in particular) of 3' UT regulate the expression of MCP molecules in transgenic mice.

Animals↗
PubMed1997

Essential initial immunostimulation in graft coronary arteriosclerosis induction detected by retransplantation technique in rats: the participation of T cell subsets.

Graft coronary arteriosclerosis occurs as chronic rejection after heart transplantation. In the previous studies, we have examined the minimum period of allogeneic stimulation to induce this change, using heterotopic rat heart transplantation and a retransplantation model. Retransplantation of allografts back into the donor strain did not prevent graft arteriosclerosis if the grafts had resided in the primary recipient for up to five days. In this study, the participation of the T cell subset causing graft coronary arteriosclerotic change was assessed using the same model. The transplanted rats in fully allogeneic or non-MHC antigen mismatch combinations were treated with a short-course administration of FK506. The graft was removed and retransplanted into the donor strain rats to escape from further immunological stimulation. CD4+ T cells and/or CD8+ T cells of first recipient rats in both combinations were eliminated by monoclonal antibodies. The grade of arteriosclerosis in the retransplanted hearts was evaluated on a basis of a scale from 0-4 according to the histological appearance of the vessel injury on day 40 after initial engraftment. While neither anti-CD4 nor anti-CD8 monoclonal antibody alone had little effect, the administration of both mAbs reduced this arteriosclerotic change and development. In conclusion, the T cell subsets, CD4+ T cell and CD8+ T cell play a certain role in the induction of the graft coronary arteriosclerotic change.

Animals↗
PubMed1996

C5b-8 step lysis of swine endothelial cells by human complement and functional feature of transfected CD59.

The authors established several swine endothelial cell (SEC) lines expressing human CD59 by transfection of cDNA, and assessed the function of the transfectant molecules in comparison with those of membrane cofactor protein (MCP) and decay-accelerating factor (DAF) in an in vitro hyperacute rejection model of swine to human discordant xenograft. At the usual expression rate, DAF and MCP protected SEC from human complement mediated cell lysis, but CD59 did not block human complement attack on SEC. However, CD59 protects SEC from cell lysis when sufficiently expressed as in human umbilical vein (HUVEC). The authors examined why CD59 needed so many molecules to protect human complement-mediated SEC lysis and found that SEC underwent lysis by human C5b-8. The degree of C5b-8 step lysis of SEC was approximately 70% of the total activation (C5b-9). Additionally, CD59 protected human complement activities less efficiently at the C5b-8 step than at the C9-step. Therefore, to overcome human complement mediated SEC lysis, C8 activity must be inhibited by dense expression of CD59.

Animals↗