[A case of advanced non-small-cell lung cancer responding remarkably to weekly chemotherapy with paclitaxel]

We report a case of advanced non-small-cell lung cancer showing remarkable response to weekly administration of paclitaxel. The patient was a 63-year-old man who had IIIB advanced lung adenocarcinoma. Though he received one course of cisplatin and etoposide, the tumor was not reduced. In addition, because of his nauseous response, he no longer wanted to receive that chemotherapy. The chemotherapy regimen was therefore changed to weekly administration of vinorelbine, but this was not effective. Next, after changing the regimen to the weekly administration of paclitaxel, the tumor was remarkably reduced following 3 courses. This case shows that weekly administration of paclitaxel may be an effective chemotherapy for non-small cell lung cancer not responsive to first-line chemotherapy.

[The usefulness of two-step tuberculin skin testing in nosocomial infection cases]

The usefulness of the two-step tuberculin skin test in the preceding year for the contact investigation was reported, when a pulmonary tuberculosis patient was discovered in our hospital. Four persons showed stronger reaction than the results in two-step tuberculin skin test in the preceding year after nosocomial infection. One of them was diagnosed as pulmonary tuberculosis by chest radiograph, and antituberculosis chemotherapy was started. Other three started chemoprophylaxis. The chemoprophylaxis subjects might increase 4, if basic value of tuberculin reaction had not been available by two-step tuberculin skin test in the previous year. We could identify persons in whom tuberculin reaction became stronger by comparing the test results after exposure with the result of two-step tuberculin skin test in the preceding year. It is considered that two-step tuberculin skin test is very useful to efficiently execute the protective measure.

[Clinical evaluation of patients with pulmonary tuberculosis during the past 10 years in our hospital]

The background of patients who died of active pulmonary tuberculosis during 10 year's period (1989 to 1998). Of 973 tuberculosis patients, 76 patients died, of which 56 died of non-tuberculosis, and 20 died of tuberculosis. A total of 12 patients died within 3 months after being hospitalized. The period from hospitalization to death was significantly shorter in tuberculosis patients with independent gait failure, original treatment, without tuberculosis medical history, and no drug resistance. We considered that in tuberculosis death, severe tuberculosis itself is the cause of early death, and recurrence and drug resistance patients are the most serious problems in later deaths.

Induction of transcription factor AP-2 by cytokines and prostaglandins in cultured mesangial cells

BACKGROUND/AIMS

Activator protein-2 (AP-2) is an important transcription factor for activation of growth- and inflammatory-associated genes. To detect AP-2 in the mesangium, the expression level of AP-2 was examined in cultured mesangial cells in response to various cytokines and prostaglandins. The level was also observed in kidney tissue samples obtained from patients with proteinuria and from a rat nephrosis model.

METHODS

AP-2 was immunohistochemically detected with a specific antibody. The expression level was analyzed by immunoblotting. Human tissue samples were obtained from patients with proteinuria. Kidney samples were also obtained from rats with puromycin aminonucleoside-induced nephrosis.

RESULTS

Pro-inflammatory cytokines, such as IL-6, IL-1 and IL-2, but not TNF-alpha, induced AP-2 expression in a time- and dose-dependent manner in cultured mesangial cells. PGE(2) and PGI(2) also induced AP-2 expression, while PGF(2 alpha) failed to induce this protein. High expression levels of AP-2 were observed in different cell types including mesangial cells of kidney samples from patients with proteinuria. Similar results were obtained from the rat nephrosis model.

CONCLUSION

These findings demonstrate that the primary cytokines induce AP-2 protein in mesangial cells. AP-2 may act as a transcription factor to produce additional cytokines and growth-associated gene products, suggesting an important role for AP-2 for the function of mesangial cells in glomerular disorders.

SEA0400, a novel and selective inhibitor of the Na+-Ca2+ exchanger, attenuates reperfusion injury in the in vitro and in vivo cerebral ischemic models

The effect of the newly synthesized compound 2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400) on the Na+-Ca2+ exchanger (NCX) was investigated and compared against that of 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea (KB-R7943). In addition, the effects of SEA0400 on reperfusion injury in vitro and in vivo were examined. SEA0400 was extremely more potent than KB-R7943 in inhibiting Na+-dependent Ca2+ uptake in cultured neurons, astrocytes, and microglia: IC50s of SEA0400 and KB-R7943 were 5 to 33 nM and 2 to 4 microM, respectively. SEA0400 at the concentration range that inhibited NCX exhibited negligible affinities for the Ca2+ channels, Na+ channels, K+ channels, norepinephrine transporter, and 14 receptors, and did not affect the activities of the Na+/H+ exchanger, Na+,K+-ATPase, Ca2+-ATPase, and five enzymes. SEA0400, unlike KB-R7943, did not inhibit the store-operated Ca2+ entry in cultured astrocytes. SEA0400 attenuated dose- dependently paradoxical Ca2+ challenge-induced production of reactive oxygen species, DNA ladder formation, and nuclear condensation in cultured astrocytes, whereas it did not affect thapsigargin-induced cell injury. Furthermore, administration of SEA0400 reduced infarct volumes after a transient middle cerebral artery occlusion in rat cerebral cortex and striatum. These results indicate that SEA0400 is the most potent and selective inhibitor of NCX, and suggest that the compound may exert protective effects on postischemic brain damage.

Suppression of thymic development by the dominant-negative form of Gads

Gads, a hematopoietic-lineage-specific Grb2 family member, is involved in the signaling mediated by the TCR through its interactions with SLP-76 and LAT. Here, we generated transgenic mice expressing Grf40-dSH2, an SH2-deleted dominant-negative form of Gads, which is driven by the lck proximal promoter. The total number of thymocytes was profoundly reduced in the transgenic mice, whereas in the double-negative (CD4(-)CD8(-)) thymocyte subset, in particular the CD25(+)CD44(-) pre-T cell population, it was significantly increased. However, CD5 expression, which is mediated by pre-TCR stimulation, was significantly suppressed on the CD4(-)CD8(-) thymocytes of the transgenic mice. Furthermore, the SLP-76-dependent signaling was markedly suppressed as well. These data suggest that Gads plays an important role in the pre-TCR as well as TCR signaling in thymocytes.

Detection of mycoplasma in mastitic milk by PCR analysis and culture method

Mycoplasma alkalescens, M. bovigenitalium, M. bovirhinis and M. bovis were directly detected from milk specimens by a polymerase chain reaction (PCR) when milk specimens were centrifuged and treated with mycoplasmal lysis buffer. The sensitivity of this PCR method was 110 to 1,400 colony forming units (CFU). This method was useful for the detection of mycoplasmas in milk specimens from cows at an early stage of mycoplasmal mastitis since a small amount of mycoplasma could be detect in milk without culture. The results were available within 12 hr, which is faster than conventional culture techniques. M. bovirhinis was detected in more than 70% of mastitic milk specimens when mycoplasmas were detected in milk specimens from 30 cows with mastitis by this PCR method.

[Fukuronori (Gloiopeltis furcata) extract: 90-day dietary toxicity study in F344 rats]

Fukuronori extract (FE), which is mainly composed of polysaccharides, and is an extract of the seaweed Gloiopeltis furcata, is permitted for use as a food thickening agent by the Ministry of Health and Welfare, Japan. In order to study the subchronic toxicity of FE, F344 rats of both genders were administered FE at concentrations of 0% (basal diet, control group), 0.5%, 1.5% and 5.0% in basal powder diet for 90 days, and observation of general condition, recording of body weight and food consumption, examination of hematology and blood chemistry, measurement of organ weight, and pathological examination were performed. Food consumption tended to increase in both sexes given FE at 1.5% and 5.0% throughout most of the experimental period. This was, however, considered not to be a toxic effect because the differences in body weight were small. Total cholesterol and triglycerides in serum decreased significantly (p < 0.05) and not significantly, respectively, in males of the 5.0% group. These changes were considered to be related to the intake of FE, but the differences were slight and within physiological ranges. Hematological and pathological examination revealed neither any particular adverse effect nor any significant difference from the control. Hence, dietary intake of 5.0% of FE, 3,362 mg/kg/day for males and 3,594 mg/kg/day for females as mean daily intake, for 90 days was considered to be a no observable adverse effect level in rats.

Contrasting localizations of MALS/LIN-7 PDZ proteins in brain and molecular compensation in knockout mice

Proteins containing PDZ (postsynaptic density-95, discs large, zonula occludens) domains play a general role in recruiting receptors and enzymes to specific synaptic sites. In Caenorhabditis elegans, a complex of three PDZ proteins, LIN-2/7/10, mediates basolateral targeting of a receptor tyrosine kinase. Homologs of these LIN proteins have also been identified in higher organisms, and here we analyze the MALS/Veli (mammalian LIN-7/vertebrate homolog of LIN-7) proteins in brain. Immunohistochemical staining and in situ hybridization show that MALS occur differentially in discrete populations of neurons throughout the brain. Most neurons express only one MALS protein, although some cells contain two or even all three MALS isoforms. At the subcellular level, MALS proteins are found in both dendritic and axonal locations, suggesting that they may regulate processes at both pre- and postsynaptic sites. Targeted disruption of MALS-1 and MALS-2 does not yield a detectable phenotype, and hippocampal synaptic function and plasticity are intact in the MALS-1/2 double knockouts. Interestingly, MALS-3 protein is dramatically induced in the MALS-1/2 double knockouts, implying that dynamic changes in protein expression may play an important regulatory role for this family of synaptic PDZ proteins.

Effect of a nitric oxide synthase inhibitor on lens-induced myopia

PURPOSE

It has still not been determined whether the retinal mechanism causing form-deprivation myopia (FDM) is different from that causing lens-induced myopia (LIM). We previously reported that FDM was blocked by an intravitreal injection of the nitric oxide (NO) synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME). In this study, we investigated the effect of L-NAME on LIM in chicks.

METHOD

The left eyes of 6-day-old chicks were injected with 30 microl of nontoxic concentrations of L-NAME (< or = 360 mM) or saline. The right eyes were injected with 30 microl of saline. A -16 dpt lens was placed in front of the left eye for 6 days. Another group of 6 chicks were injected with 180 mM L-NAME (left eye) and with saline (right eye) before placing -16 dpt lenses in front of both eyes. After removing the lens, the refraction and the axial length were measured. The effect of L-NAME (180 mM) on the retina of a separate group of chicks was examined by electroretinography 60 min after an intravitreal injection in non-LIM-treated eyes.

RESULTS

The eyes of chicks that were injected with 180 or 360 mM L-NAME were less myopic and had significantly shorter axial lengths than control eyes. A significant decrease of the On response and an increase of the Off response were observed.

CONCLUSION

The injection of L-NAME into developing chick eyes that were then covered with a -16 dpt lens resulted in a modifications of retinal function and an inhibition of the development of myopia. These results, combined with the earlier findings, suggest that NO modulates a common retinal pathway that leads to both LIM and FDM.

Mechanism of action of benzene toxicity: cell cycle suppression in hemopoietic progenitor cells (CFU-GM)

The aim of this study was to clarify previously reported controversial data and hypotheses concerning the effect of benzene on the cell cycle of hemopoietic stem cells. In this study, the bromodeoxyuridine UV (BUUV) suicide assay was performed in normal C57BL/6 and p53 knockout (KO) C57BL/6 mice during and after exposure to 300 ppm of benzene for 2 weeks. Our kinetic studies revealed that the cell cycle of hemopoietic myeloid progenitor cells (colony-forming unit granulocyte-macrophage [CFU-GM]), rather than being stimulated, was suppressed by exposure to benzene. The fraction of CFU-GM in S phase was significantly depressed, from 37.1% in controls to 16.3% in normal mice. BrdUrd incorporation in both groups revealed significantly different slopes for untreated and benzene-exposed normal C57BL/6 mice. p53 appeared to induce suppression of both the number and the cycling fraction of hemopoietic progenitor cells, as demonstrated by the lack of benzene-induced suppression of these parameters in p53 KO mice. The likelihood that suppression of bone marrow cellularity and cell cycling is mediated by p53 was supported by the upregulation of p21, a cyclin-dependent kinase inhibitor. Our present study revealed the mechanism of action of benzene hematotoxicity. Benzene suppresses the cell cycle by p53-mediated overexpression of p21, a cyclin-dependent kinase inhibitor, resulting not simply in suppression of hemopoiesis but rather in a dynamic change of hemopoiesis during and after benzene exposure. Thus, the controversies raised by previously reported data are resolved by our present findings of hemopoietic stem cell kinetics.

[Give cosmic sense to next generations through cosmic/space biology]

Life sciences are currently most important fields for every person. Each subject of life sciences is deeply correlated to cosmic events, and young generations can be more interested in life sciences if they know this correlation. In this respect, cosmic/space biology can play essential roles in fostering the science-oriented generations. Some approaches to realize the above concepts are presented.

Sylvian fissure and medial temporal lobe structures in patients with schizophrenia: a magnetic resonance imaging study

Volumes of the medial temporal lobe structures (i.e. the amygdala, hippocampus, and parahippocampal gyrus), Sylvian fissure, and inferior horn of the lateral ventricle relative to the cerebral hemisphere were measured in 24 patients with schizophrenia and 23 normal controls using magnetic resonance imaging. The patients had significantly larger Sylvian fissures and inferior horns bilaterally than the controls. In the patients the right Sylvian fissure size showed a significant positive correlation with the duration of illness. Moreover, earlier onset of illness was significantly correlated with decreased volume of the left medial temporal lobe structures. These results replicate previous finding of inferior horn enlargement and suggest the significance of the Sylvian fissure and the medial temporal lobe structures in pathophysiology of schizophrenia.

Association of nonpolio enteroviral infection in the central nervous system of children with febrile seizures

OBJECTIVE

To clarify the relationship between enteroviral infection and febrile seizures.

STUDY DESIGN

Cerebrospinal fluid (CSF), serum, throat swab, and rectal swab samples were collected for virologic examination from 67 children with febrile seizures from April 1997 to March 1999. Those samples were examined for the presence of enterovirus using cell culture and 2 polymerase chain reaction (PCR) methods.

RESULTS

No enterovirus was isolated from cell culture of CSF, throat swab, or rectal swab samples. All samples were screened for the presence of enteroviral sequences using a sensitive PCR method (PCR-Fukushima). We obtained positive results from 14 of 67 CSF samples, 10 of 62 serum samples, 12 of 64 throat swab samples, and 13 of 64 rectal swab samples. Of 21 patients in whom febrile seizures had developed during the summer months (June through August), 13 (61.9%) had positive PCR results in the CSF. Forty-seven of the 49 samples with a positive result using PCR-Fukushima were reexamined independently for the presence of the enteroviral genome using another PCR method (PCR-Mitsubishi). PCR-Mitsubishi had slightly lower sensitivity than PCR-Fukushima but identified genotypes of enterovirus by subsequent sequence analysis of the PCR products. The presence of the enteroviral genome was confirmed in 39 of the samples (83.0%). In 8 of the 9 enteroviruses detected in the CSF and/or serum samples using PCR-Mitsubishi, the genotypes were identified as coxsackieviruses group A, which are usually difficult to isolate using cell culture methods.

CONCLUSIONS

These findings proved that the causative agents of febrile illness associated with seizures in summer were primarily enteroviruses, especially coxsackieviruses group A, and that febrile seizures might be caused by enteroviral infection in the central nervous system.

Preoperative diagnosis of intraductal papillary-mucinous tumors of the pancreas with attention to telomerase activity

BACKGROUND

It has been reported that, in patients with intraductal papillary-mucinous tumor (IPMT) of the pancreas, it is difficult to distinguish adenoma from carcinoma preoperatively. Recently, it has also been reported that telomerase activity was detected in many patients with carcinoma. In this report, the authors used the method of telomerase repeat amplification protocol (TRAP) assay on pancreatic juice retrieved by endoscopic retrograde pancreatic juice aspiration (ERP aspiration).

METHODS

Pancreatic juice was collected from 28 patients (13 with intraductal carcinoma and 15 with adenoma) using ERP aspiration at either Hiroshima University Hospital or its affiliated hospitals. Two samples of pancreatic juice were collected from each patient. Each sample was examined by cytology for Papanicolaou staining and TRAP assay.

RESULTS

Four of 13 IPMT patients (31%) with intraductal carcinoma were diagnosed accurately by cytology. Seven of nine patients who were classified with benign tumors by cytologic assessment had tumors that expressed telomerase activity. Overall, 11 of 13 IPMT patients (85%) with intraductal carcinoma were diagnosed correctly by cytology associated with telomerase activity. All of the IPMT patients with adenoma were classified with benign tumors by cytologic assessment, and telomerase activity was not expressed.

CONCLUSIONS

In this study, the authors found that telomerase activity was expressed with a comparatively high probability in intraductal carcinoma. These results suggest that telomerase activity in pancreatic juices may be used as an adjunct to cytologic diagnosis and may aid further in distinguishing between benign IPMT and malignant IPMT of the pancreas preoperatively.

Stargazin regulates synaptic targeting of AMPA receptors by two distinct mechanisms

Stargazer, an ataxic and epileptic mutant mouse, lacks functional AMPA (alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate) receptors on cerebellar granule cells. Stargazin, the mutated protein, interacts with both AMPA receptor subunits and synaptic PDZ proteins, such as PSD-95. The interaction of stargazin with AMPA receptor subunits is essential for delivering functional receptors to the surface membrane of granule cells, whereas its binding with PSD-95 and related PDZ proteins through a carboxy-terminal PDZ-binding domain is required for targeting the AMPA receptor to synapses. Expression of a mutant stargazin lacking the PDZ-binding domain in hippocampal pyramidal cells disrupts synaptic AMPA receptors, indicating that stargazin-like mechanisms for targeting AMPA receptors may be widespread in the central nervous system.

[Superbugs viewed from cosmobiology]

Superbugs (microorganisms living in unfamiliar and very harsh environments) are located in the center of scientific interests in the sense that 1) most of their habitats belong to marginal regions of the biosphere, 2) clues for the elucidation of the origin of life can be deduced from them, and 3) they are deeply correlated to the extraterrestrial life. Not only for the basic scientific interests, but also for the applied fields, the spot light is shed to them. We, human beings, have been deeply dependent on other organisms through the global material flow they make. Microorganisms together with plants are the leading characters in this process. Also implicit, our future is surely correlated to microorganisms including superbugs. In this special issue, superbugs; thermophilic, psychrophilic barophilic etc. are summarized, and future development on the study on the superbugs are introduced.

The human homolog of Saccharomyces cerevisiae Mcm10 interacts with replication factors and dissociates from nuclease-resistant nuclear structures in G(2) phase

Mcm10 (Dna43), first identified in Saccharomyces cerevisiae, is an essential protein which functions in the initiation of DNA synthesis. Mcm10 is a nuclear protein that is localized to replication origins and mediates the interaction of the Mcm2-7 complex with replication origins. We identified and cloned a human cDNA whose product was structurally homologous to the yeast Mcm10 protein. Human Mcm10 (HsMcm10) is a 98-kDa protein of 874 amino acids which shows 23 and 21% overall similarity to Schizosaccharomyces pombe Cdc23 and S. cerevisiae Mcm10, respectively. The messenger RNA level of HsMcm10 increased at the G(1)/S-boundary when quiescent human NB1-RGB cells were induced to proliferate as is the case of many replication factors. HsMcm10 associated with nuclease-resistant nuclear structures throughout S phase and dissociated from it in G(2) phase. HsMcm10 associated with human Orc2 protein when overexpressed in COS-1 cells. HsMcm10 also interacted with Orc2, Mcm2 and Mcm6 proteins in the yeast two-hybrid system. These results suggest that HsMcm10 may function in DNA replication through the interaction with Orc and Mcm2-7 complexes.

Interactions between Mcm10p and other replication factors are required for proper initiation and elongation of chromosomal DNA replication in Saccharomyces cerevisiae

BACKGROUND

MCM10 is essential for the initiation of chromosomal DNA replication in Saccharomyces cerevisiae. Previous work showed that Mcm10p interacts with the Mcm2-7 protein complex that may be functioning as the replication-licensing factor. In addition, Mcm10p is required during origin activation and disassembly of the prereplicative complex, which allows smooth passage of replication forks.

RESULTS

We show that an mcm10 mutation causes a slow progression of DNA synthesis and a loss of chromosome integrity during the S phase and prevents entry into mitosis, despite apparent completion of chromosomal DNA replication at nonpermissive temperatures. Furthermore, Mcm10p interacts genetically with the origin recognition complex (ORC) and various replication elongation factors, including a subunit of DNA polymerases epsilon and delta. Mcm10p is an abundant protein (approximately 4 x 10(4) copies per haploid cell) that is almost exclusively localized in the chromatin and/or nuclear matrix fractions during all phases of the cell cycle. When it is visualized by the chromosome-spreading method followed by immunostaining, Mcm10p forms punctate foci on chromatin throughout the cell cycle and these foci mostly overlap with those of Orc1p, a component of ORC.

CONCLUSIONS

These results suggest that Mcm10p, like the Mcm2-7 proteins, is a critical component of the prereplication chromatin and acts together with ORC during the initiation of chromosomal DNA replication; in addition, Mcm10p plays an important role during the elongation of DNA replication.

Characterization of the yeast Cdc7p/Dbf4p complex purified from insect cells. Its protein kinase activity is regulated by Rad53p

The yeast Saccharomyces cerevisiae Cdc7p/Dbf4p protein kinase complex was purified to near homogeneity from insect cells. The complex efficiently phosphorylated yeast Mcm2p and less efficiently the remaining Mcm proteins or other replication proteins. Significantly, when pretreated with alkaline phosphatase, Mcm2p became completely inactive as a substrate, suggesting that it must be phosphorylated by other protein kinase(s) to be a substrate for the Cdc7p/Dbf4p complex. Mutant Cdc7p/Dbf4p complexes containing either Cdc7-1p or Dbf4-1 approximately 5p were also partially purified from insect cells and characterized in vitro. Furthermore, the autonomously replicating sequence binding activity of various dbf4 mutants was also analyzed. These studies suggest that the autonomously replicating sequence-binding and Cdc7p protein kinase activation domains of Dbf4p collaborate to form an active Cdc7p/Dbf4p complex and function during S phase in S. cerevisiae. It is shown that Rad53p phosphorylates the Cdc7p/Dbf4p complex in vitro and that this phosphorylation greatly inhibits the kinase activity of Cdc7p/Dbf4p. This result suggests that Rad53p controls the initiation of chromosomal DNA replication by regulating the protein kinase activity associated with the Cdc7p/Dbf4p complex.

Assessment of the otolith-autonomic response using spectral analysis of the R-R interval and blood pressure

The effects of otolith stimulation on systolic blood pressure (SBP) and R-R interval fluctuations were investigated in 12 healthy subjects and 5 patients with loss of labyrinthine function. The vestibular otolith organs were stimulated by centrifugal forces, the constant rotation of a chair fixed outside of the rotation axis on the horizontal plane. The chair was fixed along the direction of centrifugal force (eccentric rotation [ECR]) or along the tangent line (eccentric lateral rotation [ECLR]). The ECR stimulates both the utricular and saccular maculae, whereas the ECLR stimulates only the utricular maculae. Spectral analysis showed that in the healthy subjects, low-frequency SBP increased significantly during ECR but not during ECLR. There was no significant increase in low-frequency SBP in patients with labyrinthine loss. In the R-R interval analysis, however, the low- and high-frequency components did not change significantly in the healthy subjects during ECR. Our findings indicate that stimulation of the otolith maculae, especially the saccular organs, predominantly produces augmentation of the alpha-sympathetic activities rather than cardiac sympathovagal outflow to the heart.

Characterization of fission yeast cohesin: essential anaphase proteolysis of Rad21 phosphorylated in the S phase

Cohesin complex acts in the formation and maintenance of sister chromatid cohesion during and after S phase. Budding yeast Scc1p/Mcd1p, an essential subunit, is cleaved and dissociates from chromosomes in anaphase, leading to sister chromatid separation. Most cohesin in higher eukaryotes, in contrast, is dissociated from chromosomes well before anaphase. The universal role of cohesin during anaphase thus remains to be determined. We report here initial characterization of four putative cohesin subunits, Psm1, Psm3, Rad21, and Psc3, in fission yeast. They are essential for sister chromatid cohesion. Immunoprecipitation demonstrates stable complex formation of Rad21 with Psm1 and Psm3 but not with Psc3. Chromatin immunoprecipitation shows that cohesin subunits are enriched in broad centromere regions and that the level of centromere-associated Rad21 did not change from metaphase to anaphase, very different from budding yeast. In contrast, Rad21 containing similar cleavage sites to those of Scc1p/Mcd1p is cleaved specifically in anaphase. This cleavage is essential, although the amount of cleaved product is very small (<5%). Mis4, another sister chromatid cohesion protein, plays an essential role for loading Rad21 on chromatin. A simple model is presented to explain the specific behavior of fission yeast cohesin and why only a tiny fraction of Rad21 is sufficient to be cleaved for normal anaphase.