Characteristics of migrants to Japan with TB and implications for pre-migration TB screening

Background

Japan plans to introduce pre-entry tuberculosis (TB) screening for those traveling from the Philippines, China, Vietnam, Nepal, Indonesia, and Myanmar, who are intending to stay in Japan for more than 90 days, in 2020. According to its screening algorithm, migrants will be screened by chest X-ray and those with abnormal findings will be asked to undergo sputum testing. We analyzed the characteristics of foreign-born TB patients coming from the above six countries, to identify some potential issues.

Methods

Data on foreign-born patients who had been newly notified with active pulmonary TB (PTB) in 2018 and 2017, and who had entered Japan in the same year they were notified, was extracted from the Japan TB Surveillance system. We assumed that these patients approximated to those hypothetical migrants who would be detected by pre-entry TB screening, and analyzed them by basic socio-demographic characteristics, radiological findings, and bacteriological test results.

Results

In 2017 and 2018, a total of 1,915 foreign-born PTB patients were notified from the above six countries. Of them, 19.9% (n = 381) had entered Japan in the same year they were notified. Among the 381, 23.9% (n = 50) had cavitary lesion, 27.3% (n = 57) were smear positive, and 48.9% (n = 73) were culture positive. 34.4% (n = 72) were both smear and culture negative, and the diagnosis would have depended on radiographical presentation. However, among the 72, the majority i.e. 87.5%, presented with non-cavitary pulmonary involvement.

Conclusions

Considering that approximately a third of TB patients who would may detected by the pre-entry screening are likely to be bacteriologically negative, Japan must ensure that the clinics conducting the pre-entry TB screening have access to high-quality radiography with expert interpretations, such as teleradiology and computer-assisted reading.

Key messages

A third of TB patients who would may detected by the pre-entry screening are likely to be bacteriologically negative. It is critical that clinics conducting screening have access to high-quality radiography with expert interpretations, such as teleradiology and computer-assisted reading.

Antimelanoma differentiation-associated protein 5 antibody level is a novel tool for monitoring disease activity in rapidly progressive interstitial lung disease with dermatomyositis

BACKGROUND

Antimelanoma differentiation-associated protein (anti-MDA)5 antibodies are associated with rapidly progressive interstitial lung disease (RP-ILD) in patients with clinically amyopathic dermatomyositis (CADM) or dermatomyositis (DM).

OBJECTIVES

We aimed to evaluate the relevance of monitoring anti-MDA5 antibody levels for the management of RP-ILD in patients with CADM or DM.

METHODS

Twelve patients with CADM (n = 10) or DM (n = 2) accompanied by RP-ILD were included. Baseline characteristics and outcomes were recorded. Serial measurements of anti-MDA5 antibody levels were measured. All patients were treated with corticosteroids, tacrolimus and intravenous cyclophosphamide.

RESULTS

All patients achieved RP-ILD remission after combined immunosuppressive therapy for a mean of 6·8 months, with significant decreases noted in the mean anti-MDA5 antibody levels at remission. Six (50%) patients became anti-MDA5 antibody negative after therapy. After a mean follow-up of 31 months, RP-ILD relapse was observed in four (33%) patients in both the anti-MDA5 antibody sustained positive group and the negative conversion group. However, relapsed patients in the sustained positive group relapsed earlier than those in the negative conversion group. Thus, a decrease in anti-MDA5 antibody levels during remission was associated with longer remission. Relapses were associated with a reincrease of anti-MDA5 antibody levels in four of four (100%) patients. In contrast, none of the patients without reincrease in anti-MDA5 antibody exhibited symptoms of relapse during follow-up. Therefore, reincrease in anti-MDA5 antibody levels was associated with relapse.

CONCLUSIONS

The anti-MDA5 antibody level is a novel parameter for monitoring and a good predictor of RP-ILD relapse in patients with CADM or DM.

Incidence and risk factors for herpes zoster in patients undergoing liver transplantation

BACKGROUND

Herpes zoster (HZ) is the most common manifestation of latent varicella zoster virus reactivation, which occurs naturally as a result of aging or in immunocompromised patients. Solid organ transplant recipients are at increased risk for HZ owing to their chronic immunosuppression. Although several reports investigated risk factors for the development of HZ in heart or renal transplantation, data in liver transplantation (LT) are limited.

METHODS

We evaluated clinical data retrospectively in 377 adult patients undergoing LT between January 2005 and December 2012 in our institution. We analyzed the incidence rate of HZ and the standardized incidence ratio (SIR) by comparing with the general Japanese population. We additionally investigated risk factors for HZ after LT.

RESULTS

HZ developed in 27 (7.16%) of the 377 patients after LT. The incidence rate of HZ after LT was 17.83 per 1000 person-years, which was significantly higher than in the general Japanese population (SIR = 4.61; 95% confidence interval [CI], 4.13-5.14). Multivariate analysis showed that older age (hazard ratio [HR] = 3.95; P < 0.001) and exposure to mycophenolate mofetil (HR = 3.03; P = 0.007) were independent risk factors for HZ after LT.

CONCLUSIONS

This is the first and largest study, to our knowledge, to investigate the incidence rate of HZ and risk factors for development of HZ after LT in the Japanese population. Further investigations to focus on immunosuppressive regimens to reduce the risk for HZ incidence in this high-risk population could establish a new protocol of immunosuppression after LT.

Altered expression of dermokine in skin disorders

BACKGROUND

Although dermokine-β, a glycoprotein expressed in epithelial cells, does not have significant homology to other proteins, its carboxyl-terminal domain shares a high pI value with many cytokines, suggesting similar functions.

OBJECTIVE

To better understand the biology of dermokine, we here determined its localization under pathological conditions and examined factors that regulate its expression.

METHODS

We generated an anti-human dermokine-β/γ monoclonal antibody cross-reacting with the mouse protein. Using this antibody, immunohistological staining and Western blotting of dermokine-β/γ were performed with various tissue samples.

RESULTS

Although human dermokine-β/γ was expressed in almost all granular layers, upper spinous layers of the skin were also stained with anti-dermokine-β/γ antibody in inflammatory skin disorders. Dermokine-β/γ was expressed in keratoacanthoma and a part of well-differentiated squamous cell carcinoma (SCC). However, dermokine-β/γ was not detected in poorly differentiated SCC or tumours derived from non-keratinocytes. In mice, dermokine-β/γ-expressed keratinocytes were increased in models of contact hypersensitivity, ultraviolet-irradiated skin injury and wound healing. Consistent with expanded distribution in inflammatory skin diseases, proinflammatory cytokines such as interleukin-1β, interleukin-12, and tumour necrosis factor-α augmented dermokine-β/γ expression in cultured human keratinocytes. In contrast, growth factors including epidermal growth factor, insulin-like growth factor-I, keratinocyte growth factor and transforming growth factor-α significantly reduced dermokine expression.

CONCLUSION

These results provide novel insights into the physiological and pathological significance of dermokine in the epidermis.

Autoantibody-mediated regulation of B cell responses by functional anti-CD22 autoantibodies in patients with systemic sclerosis

Studies have demonstrated that B cells play important roles in systemic sclerosis (SSc), especially through the CD19/CD22 autoimmune loop. CD22 is a B cell-specific inhibitory receptor that dampens B cell antigen receptor (BCR) signalling via tyrosine phosphorylation-dependent mechanism. In this study, we examined the presence and functional property of circulating autoantibodies reacting with CD22 in systemic sclerosis. Serum samples from 10 tight skin (TSK/+) mice and 50 SSc patients were assessed for anti-CD22 autoantibodies by enzyme-linked immunosorbent assays using recombinant mouse or human CD22. The association between anti-CD22 antibodies and clinical features was also investigated in SSc patients. Furthermore, the influence of SSc serum including anti-CD22 autoantibodies for CD22 tyrosine phosphorylation was examined by Western blotting using phosphotyrosine-specific antibodies reacting with four major tyrosine motifs of CD22 cytoplasmic domain. Anti-CD22 autoantibodies were positive in 80% of TSK/+ mice and in 22% of SSc patients. Patients positive for anti-CD22 antibodies showed significantly higher modified Rodnan skin thickness score compared with patients negative for anti-CD22 antibodies. Furthermore, anti-CD22 antibodies from patients' sera were capable of reducing phosphorylation of all four CD22 tyrosine motifs, while sera negative for anti-CD22 antibodies did not affect CD22 phosphorylation. Thus, a subset of SSc patients possessed autoantibodies reacting with a major inhibitory B cell response regulator, CD22. Because these antibodies can interfere CD22-mediated suppression onto B cell activation in vitro, SSc B cells produce functional autoantibodies that can enhance their own activation. This unique regulation may contribute to the autoimmune aspect of SSc.

The clinical relevance of serum antinuclear antibodies in Japanese patients with systemic sclerosis

Background

Systemic sclerosis (SSc) is a connective tissue disorder with excessive fibrosis of the skin and various internal organs. Although SSc is a heterogeneous disease, it has been reported that the particular antinuclear antibodies (ANA) are often indicative of clinical features, disease course and overall severity.

Objective

To clarify the association of clinical and prognostic features with serum ANA in Japanese patients with SSc.

Methods

We studied 203 Japanese patients diagnosed with SSc, who visited our hospital during the period 1983–2005. Six SSc-related ANA were identified using indirect immunofluorescence, double immunodiffusion and immunoprecipitation assays.

Results

Patients with SSc were classified into six ANA-based subgroups and a group without ANA. As expected, antitopoisomerase I antibody (Ab, n = 64), anti-RNA polymerases (RNAP) Ab (n = 12) and anti-U3 RNP Ab (n = 5) were associated with diffuse cutaneous SSc, whereas anticentromere Ab (ACA, n = 75), anti-Th/To Ab (n = 7) and anti-U1 RNP Ab (n = 10) were frequently detected in patients with limited cutaneous SSc. Clinical features of the ANA-negative group (n = 10) were heterogeneous. Consistent with previous findings in Caucasian and/or black African patients, antitopoisomerase I Ab was associated with the involvement of vascular and pulmonary fibrosis, leading to decreased survival rate. However, no patients with anti-RNAP Ab developed renal crisis and the frequency of isolated pulmonary hypertension in patients with ACA, anti-Th/To Ab or anti-U3 RNP Ab was similar to that in other ANA-based subgroups.

Conclusion

These results indicate that the clinical relevance of SSc-related ANA in Japanese patients differs in some aspects from that in Caucasian and/or black African patients.

A clue for telangiectasis in systemic sclerosis: elevated serum soluble endoglin levels in patients with the limited cutaneous form of the disease

BACKGROUND

The transforming growth factor-beta (TGF-beta) system plays a critical role both in systemic sclerosis (SSc) and hereditary hemorrhagic telangiectasia (HHT). Endoglin, known as a gene responsible for HHT, is a TGF-beta receptor preferentially expressed on endothelial cells. The role of endoglin in SSc is potentially intriguing since limited cutaneous SSc (lcSSc) and HHT share several symptoms, including telangiectasia.

OBJECTIVE

To determine serum levels of soluble endoglin (sEndoglin) and clinical associations in patients with SSc.

METHODS

Serum sEndoglin levels were examined by ELISA in 70 patients with SSc, 20 patients with systemic lupus erythematosus and 20 healthy individuals.

RESULTS

Serum sEndoglin levels were significantly elevated in patients with lcSSc compared with diffuse cutaneous SSc and systemic lupus erythematosus patients as well as normal controls. Patients with elevated sEndoglin levels had telangiectasia more frequently than those with normal sEndoglin levels. Furthermore, pulmonary artery pressure was positively correlated with sEndoglin levels in patients with lcSSc.

CONCLUSION

Abnormal expression/function of endoglin may be linked to lcSSc-specific manifestations.

Identification of a novel autoantibody reactive with 155 and 140 kDa nuclear proteins in patients with dermatomyositis: an association with malignancy

OBJECTIVE

Myositis-specific autoantibodies (MSAs) are a useful tool in diagnosis, defining clinical subsets and predicting prognosis of dermatomyositis (DM) and polymyositis (PM). In this study, we identified a novel MSA reactive with 155 and 140 kDa nuclear proteins [anti-155/140 antibody (Ab)] and determined the clinical feature of DM patients positive for this autoantibody (autoAb).

METHODS

Sera from 52 Japanese patients with DM, 9 with PM, 48 with systemic lupus erythematosus (SLE), 126 with systemic sclerosis and 18 with idiopathic interstitial pneumonia were examined by immunoprecipitation assays. Positive sera were further characterized by immunodepletion and immunofluorescence staining.

RESULTS

Seven of the 52 (13%) Japanese patients with DM immunoprecipitated 155 and 140 kDa proteins from 35S-labelled K562 leukaemia cell extract. No patients with SLE, systemic sclerosis or idiopathic interstitial pneumonia as well as healthy controls were positive for this autoAb. Patients with anti-155/140 Ab developed heliotrope rash, Gottron's papules or sign and flagellate erythema significantly more frequently than those negative. Notably, internal malignancy was found at significantly higher frequency in those positive than those negative (71 vs 11%; P < 0.005). In contrast, none of these patients positive for this autoAb had interstitial lung disease.

CONCLUSIONS

This novel MSA is associated with cancer-associated DM and may serve as a diagnostic serological marker for this specific subset.

Blue-dye technique complements four-node sampling for early breast cancer

AIMS

To examine four-node axillary sampling assisted by a blue dye (4NAS/dye) technique as a sentinel node biopsy (SNB) for breast cancer.

METHODS

Lymphatic mapping was performed by injection of patent blue for 33 consecutive cases with breast cancer. Axillary sampling was performed until four nodes were obtained. This was followed by back-up axillary lymph node dissection to examine the feasibility of 4NAS/dye. The same study with 30 cases was conducted at an independent hospital to confirm the feasibility of this method. This method was then applied to 101 consecutive clinically node-negative patients to avoid axillary-node dissection, with intraoperative diagnosis made by frozen section examination.

RESULTS

The median numbers of blue-stained nodes and nodes excised by 4NAS/dye were 1.7 and 3.4, respectively. The identification rate of sentinel lymph nodes (SNs) was 81.8% using the dye alone and 97.0% when the combination was used. Pathological examination revealed that the nodal status was correctly predicted by the dye alone in 62.5% of cases with metastasis, whereas in 100% by 4NAS/dye. The dye alone was not sufficient to identify SNs, especially in cases with prior excisional biopsy. The identification rate of SNs and the accuracy rate in another feasibility study were 100% and 92.5% in 30 consecutive cases, respectively. 4NAS/dye successfully detected SNs in 100 of 101 cases of the subsequent observational study with an acceptable post-operative axillary morbidity and thus succeeded as an SNB.

CONCLUSIONS

The 4NAS/dye method is reliable for the detection of SNs. This method could be applied to observational studies without radio-isotope.

Determination of first cleavage plane: the relationships between the orientation of the mitotic apparatus for first cleavage and the position of meiotic division-related structures in starfish eggs

In order to understand when the orientation of the first cleavage plane is fixed along the animal-vegetal axis in starfish eggs, the behavior of the sperm aster was examined by indirect immunofluorescence staining. After duplication, the sperm aster organizes the mitotic apparatus for first cleavage perpendicular to the cleavage plane. The sperm aster located in the egg periphery just after fertilization and moved to the site close to the animal pole rather than the egg center by meiosis II. At early metaphase II, duplication of the sperm aster was detected but the axis of the resultant sperm diaster randomly pointed. Subsequently, its axis had already turned perpendicular to the animal-vegetal axis before pronucleus fusion. These results indicate that the orientation processes of the sperm diaster consist of positioning before its duplication and successive determining its azimuth. Furthermore, the azimuth and position of the mitotic apparatus for first cleavage did not change by shifting or eliminating the meiotic division-related structures such as the germinal vesicle, meiotic spindle, and female pronucleus by micromanipulation. These results show that none of them determines the first cleavage plane. Therefore, we discuss the pointing mechanism of the first cleavage plane without the influence of these meiotic division-related structures.

Autoantibodies to a collagen-specific molecular chaperone, heat-shock protein 47, in systemic sclerosis

Heat-shock proteins are highly conserved and immunogenic proteins, which may be involved in the initiation and perpetuation of autoimmune diseases. Heat-shock protein 47 (HSP47) is expressed by collagen-secreting cells such as fibroblasts and serves as a collagen-specific molecular chaperone that plays a crucial role in collagen metabolism. Abnormal collagen accumulation and autoimmunity are characteristics of systemic sclerosis (SSc). We determined the presence and prevalence of autoantibodies to HSP47 in patients with SSc and also in tight-skin (TSK/+) mice, an animal model for SSc. Anti-HSP47 autoantibodies were present in SSc patients with a frequency of 26%, while patients with systemic lupus erythematosus, those with dermatomyositis, those with keloid and healthy subjects did not have anti-HSP47 antibodies. IgG1 and IgG2 were the major Ig isotypes of the autoantibodies. Patients positive for anti-HSP47 had a significantly shorter duration of disease than those who were negative. Anti-HSP47 autoantibodies were also positive in 79% of TSK/+ mice. Thus, autoantibodies to HSP47 were present in the sera from SSc patients as well as those from TSK mice, and may be associated with the pathogenesis of SSc.

Up regulated expression of fractalkine/CX3CL1 and CX3CR1 in patients with systemic sclerosis

BACKGROUND

Fractalkine expressed on endothelial cells mediates activation and adhesion of leucocytes expressing its receptor, CX(3)CR1. Soluble fractalkine exhibits chemotactic activity for leucocytes expressing CX(3)CR1.

OBJECTIVE

To determine the role of fractalkine and its receptor in systemic sclerosis (SSc) by assessing their expression levels in patients with this disease.

METHODS

The expression of fractalkine and CX(3)CR1 in the skin and lung tissues was immunohistochemically examined. Circulating soluble fractalkine levels were examined by enzyme linked immunosorbent assay (ELISA). Blood samples from patients with SSc were stained for CX(3)CR1 with flow cytometric analysis.

RESULTS

CX(3)CR1 levels on peripheral monocytes/macrophages and T cells were found to be raised in patients with diffuse cutaneous SSc. The numbers of cells expressing CX(3)CR1, including monocytes/macrophages, were increased in the lesional skin and lung tissues from patients with diffuse cutaneous SSc. Fractalkine was strongly expressed on endothelial cells in the affected skin and lung tissues. Soluble fractalkine levels were significantly raised in sera and were associated with raised erythrocyte sedimentation rates, digital ischaemia, and severity of pulmonary fibrosis.

CONCLUSIONS

Up regulated expression of fractalkine and CX(3)CR1 cooperatively augments the recruitment of mononuclear cells expressing CX(3)CR1 into the affected tissue of SSc, leading to inflammation and vascular injury.

Detecting Human CD34 + and CD34 - Hematopoietic Stem and Progenitor Cells Using a Sysmex Automated Hematology Analyzer

In clinical medicine, particularly in the newly developing stem cell therapies required to support the practice of regenerative medicine, the measurement of both CD34+ and CD34- hematopoietic stem cells (HSC)/hematopoietic progenitor cells (HPC) is important in obtaining more accurate information about the total HSC/HPC content in various stem/progenitor cell sources. We report the results of an investigation into methods of detecting CD34+ and CD34- HSC/HPC using the immature information (IMI) channel incorporated into the Sysmex XE-2100 and SE-9000 automated hematology analyzers. In this study, CD34+ and CD34- HSC/HPC were separated by immunologic methods and quantified by flow cytometry (FACScan) and IMI channel analysis. In addition, CD34-/CD133+ HSC were prepared by a sequential antibody-based positive selection strategy. These cells appeared in the same area as CD34+ cells in the IMI channel of the automated hematology analyzer. These findings confirmed that an automated hematology analyzer can be used to measure both CD34+ and CD34- HSC. These results may explain the difference in HSC/HPC counts sometimes observed between the automated hematology analyzer and flow cytometric methods for CD34+ measurement. The results of this study demonstrated the potential of automated cell counting methods for measuring HSC content in cellular products for both research and clinical applications.

Gene expression profile analysis of regenerating liver after portal vein ligation in rats by a cDNA microarray system

AIMS

We assessed changes in gene expression of hypertrophied liver after portal vein ligation (PL) in a test group of rats compared to a control group, which had the same size liver but no PL.

METHODS

The portal veins of the left and median lobes in the test group were ligated in an initial operation. Four days after the PL, the liver volume of the posterior caudate lobe (5%) increased two-fold and comprised 10% of the liver. A 90% hepatectomy was then performed, leaving only the hypertrophied posterior caudate lobe, and leaving the normal anterior and posterior caudate lobes (10%) in the control (sham) group. A comparison of the expression profiles between two groups was performed using cDNA microarrays and the hepatic ATP level was measured.

RESULTS

The survival rate for the PL group was significantly higher than for the sham group at 4 days after the hepatectomy (56.3% and 26.7%, P < 0.05). Gene expression of cyclin D1, proliferating cell nuclear antigen, cyclin A and B was upregulated, and the cyclin-dependent kinase inhibitor was downregulated. Increases were observed in: (i) pyruvate dehydrogenase, the tricarboxylic acid cycle cycle regulator, (ii) acyl-CoA dehydrogenase, the oxidation regulator, and (iii) cytochrome oxidases, the oxidative phosphorylation regulator. Hepatic ATP concentration after hepatectomy was better maintained in the PL group than in the sham group (0.48 +/- 0.01 micromol/ml vs. 0.33 +/- 0.01 micromol/ml, P < 0.05).

CONCLUSION

The regenerating liver increased tolerance for extended hepatectomy compared to normal liver. It is believed that this is because the induced rapid regeneration of the remaining liver after hepatectomy increases ATP metabolism.

Longitudinal analysis of serum KL-6 levels in patients with systemic sclerosis: association with the activity of pulmonary fibrosis

OBJECTIVE

To determine whether changes in serum KL-6 levels reflect the activity of pulmonary fibrosis (PF) in patients with systemic sclerosis (SSc).

METHODS

KL-6 levels were determined by ELISA in 39 SSc patients. In a retrospective longitudinal study, 250 serum samples were analyzed during a follow-up period of 0.3-6.1 years.

RESULTS

KL-6 levels at the first visit were higher in patients with SSc, especially with PF, compared with healthy controls. In the longitudinal study, KL-6 levels in 4 patients with anti-topo I Abs increased rapidly, parallel to the progression of PF. Four patients with inactive PF exhibited elevated, but stable levels of KL-6 during the follow-up. The 31 patients with almost normal KL-6 levels during the follow-up exhibited no deterioration or new onset of PF.

CONCLUSION

Rapidly increased serum KL-6 levels during disease course were associated with new onset or deterioration of PF.

Development and clinical application of nucleated red blood cell counting and staging on the automated haematology analyser XE-2100

We initially developed a new flow cytometric (FCM) reference method for the enumeration and staging of nucleated red blood cells (NRBC) in 1997 [Wang et al., 1998 (XIth International Symposium on Technological Innovations in Laboratory Haematology, Banff, Canada, 1998); Tsuji et al., 1999 (Cytometry, 1999)]. The method used CD45 antibody and propidium iodide staining to separate NRBCs from other cells. Accuracy and precision were enhanced because larger numbers of cells were counted than was possible with the manual method. We also developed a method for automated NRBC counting on a haematology analyser, the XE-2100 (Wang, 1988). NRBC were separated from other cells using a special lysing buffer and a fluorescent dye. The XE-2100 was found to detect peripheral and cord blood NRBC accurately and precisely when compared with cell morphology or FCM control methods. The FCM NRBC staging method was established through the identification of different NRBC populations following the novel staining and lysing method. To evaluate the method further, we sorted samples containing NRBCs using a FACSort and investigated NRBC staging on the Sysmex XE-2100 based on the cell sorting results. Data were analysed using special software (ida). First, we used the data in various parameter combinations. We then established gates to classify the NRBC populations. Finally, we analysed blood specimens from patients with different types of diseases to explore possible clinical applications.

Performance characteristics of the Sysmex XT-2000i hematology analyzer

The XT-2000i is a new hematology analyzer combining aperture impedance and optical technologies. It is capable of generating a 30-parameter hematologic assay on peripheral blood at a throughput of 80 samples per hour. We have evaluated the performance characteristics of the XT-2000i analyzer and compared them with those of the state-of-the-art XE-2100 analyzer and the manual differential count. The XT-2000i compared favorably with the XE-2100 analyzer and exceeded the manufacturer's specifications in all parameters tested. The XT-2000i has a user-friendly graphical user interface, and there was virtually no downtime during the period of evaluation. This analyzer can be recommended as a backup to the XE-2100 analyzer or as a stand-alone analyzer in a laboratory with moderate volume and a broad complexity of samples.

Response of the cortex to the mitotic apparatus during polar body formation in the starfish oocyte of Asterina pectinifera

In order to understand the mechanism of unequal division, polar body formation was investigated using the oocytes of the starfish, Asterina pectinifera. Cortical actin filaments were quantitatively measured after staining the maturing oocytes with fluorescently labeled phalloidin using a computer and image-processing software. Before polar body formation, at first the actin filaments at the animal pole decreased and subsequently the animal pole bulged. On the other hand, actin filaments surrounding the animal pole increased gradually and made a cleavage furrow around the animal pole as the bulge grew. Then the furrow ingressed and finally a polar body formed. When the surface force was calculated according to the cell shape, the surface force decreased at the animal pole but the force at the contractile ring increased. When by micromanipulation the mitotic apparatus was detached and translocated to the cortex other than the animal pole, polar body formation occurred all over the cortex of the oocyte, which indicates that the response of the whole cortex to the mitotic apparatus is equal. These results indicate that the decrease in the actin filaments and surface force near the centrosome of the mitotic apparatus as well as the increase in the actin filaments and surface force at some distance of the centrosome is important for cytokinesis.

Displacement of the mitotic apparatus which induces ectopic polar body formation or parthenogenetic cleavage in starfish oocytes

When the mitotic apparatus (MA) at meiosis I and II in starfish oocytes was detached from the animal pole and translocated to the other cortex, MA induced polar body formation, which indicates reattachment of MA to the cortex. MA attachment was so strong that MA at meiosis II was frequently broken into two parts during detachment and from the remnant part remaining at the cortex an aster derived and a nucleus derived from the detached part. When they were apart until the cleavage stage, the oocyte divided into the aster-containing and nucleus-containing blastomeres and, further, only the former blastomere divided repeatedly. This result indicates that the centrosome in the peripheral aster, which presumes to be discarded into the second polar body, always has the capacity of duplication but the centrosome in the inner aster, which stays in the oocyte interior, has not the capacity and confirms our previous report ( Saiki and Hamaguchi (1998) Dev. Biol. 203, 62-74). Furthermore, it is found by observing meiotic MA formation that this peculiar centrosome delivery at meiosis II is ensured by the fact that the attachment of the aster staying in the oocyte interior to the cortex occurs earlier than centrosome duplication.