Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Genetically fused charged peptides induce rapid crystallization of proteins

We utilized electrostatic interaction to induce rapid crystallization of streptavidin. Simply mixing streptavidins possessing either a positively or negatively charged peptide at their C-terminus generated diffraction-quality crystals in a few hours. We modified the streptavidin crystals with fluorescent molecules using biotin, demonstrating the concept of protein crystals as functional biomaterials.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star-black hole, and binary black hole systems. The ability to localize the sources is given as a sky-area probability, luminosity distance, and comoving volume. The median sky localization area (90% credible region) is expected to be a few hundreds of square degrees for all types of binary systems during O3 with the Advanced LIGO and Virgo (HLV) network. The median sky localization area will improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo, and KAGRA (HLVK) network. During O3, the median localization volume (90% credible region) is expected to be on the order of 10 5 , 10 6 , 10 7 Mpc 3 for binary neutron star, neutron star-black hole, and binary black hole systems, respectively. The localization volume in O4 is expected to be about a factor two smaller than in O3. We predict a detection count of 1 - 1 + 12 ( 10 - 10 + 52 ) for binary neutron star mergers, of 0 - 0 + 19 ( 1 - 1 + 91 ) for neutron star-black hole mergers, and 17 - 11 + 22 ( 79 - 44 + 89 ) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3 (HLVK network during O4). We evaluate sensitivity and localization expectations for unmodeled signal searches, including the search for intermediate mass black hole binary mergers.

Effect of GLP-1 receptor agonist on gastrointestinal tract motility and residue rates as evaluated by capsule endoscopy

AIM

This study evaluated the effects of a glucagon-like peptide-1 receptor agonist on gastrointestinal (GI) tract motility and residue rates by examining GI transit time and lumen using capsule endoscopy.

MATERIAL AND METHODS

GI motility and lumen were assessed by capsule endoscopy before and after liraglutide administration in 14 patients with type 2 diabetes mellitus (T2DM).

RESULTS

Gastric transit time in the group with diabetic neuropathy (DN) was 1:12:36±1:04:30h before liraglutide administration and 0:48:40±0:32:52h after administration (nonsignificant difference, P=0.19). Gastric transit time in the non-DN group was 1:01:30±0:52:59h before administration and 2:33:29±1:37:24h after administration (significant increase, P=0.03). Duodenal and small intestine transit time in the DN group was 4:10:34±0:25:54h before and 6:38:42±3:52:42h after administration (not significant, P=0.09) and, in the non-DN group, 3:51:03±0:53:47h before and 6:45:31±2:41:36h after administration (significant increase, P=0.03). The GI residue rate in the DN group was 32.1±24% before administration and 90.0±9.1% after administration (significant increase, P<0.001), and increased in all patients; in the non-DN group, it was 32.1±35.3% before and 78.3±23.9% after administration (significant increase, P<0.001), and also increased in all patients.

CONCLUSION

Liraglutide causes delayed gastric emptying and inhibits duodenal and small intestine motility. However, these GI movement-inhibiting effects may be decreased or absent in patients with DN-associated dysautonomia.

A combination of ultrasound-guided rectus sheath and transversus abdominis plane blocks is superior to either block alone for pain control after gynecological transumbilical single incision laparoscopic surgery

PURPOSE

To investigate the efficacy of the combination of ultrasound-guided rectus sheath (RS) and transversus abdominis plane (TAP) blocks compared with TAP or RS block alone in gynecological single-incision laparoscopic surgery (SILS).

MATERIALS AND METHODS

Bilateral TAP blocks (Group A, n = 12), TAP and RS blocks (Group B, n = 12), and RS blocks (Group C, n = 12) with 40 ml ropivacaine/patient were performed for ovarian tumor SILS. The analgesic effects were evaluated using a numerical rating scale (NRS) at zero, six, 12, 24, and 48 hours post-surgery.

RESULTS

Umbilical pain on completion of general anesthesia was significantly less frequent in Group B (1/12) than Group A (7/12) (p = 0.03). The postoperative NRS scores were significantly lower in Group B than Group A at zero (p = 0.02) and six (p = 0.03) hours and Group C at zero (p = 0.001), six (p = 0.02), and 12 (p = 0.004) hours.

CONCLUSION

The combination of RS and TAP blocks reduced early postoperative pain compared with RS or TAP block alone for gynecological SILS.

Novel method of screening the oxidation and reduction abilities of photocatalytic materials

A methodology for understanding the photocatalytic abilities of materials is presented. The conversion of simple organic molecules was monitored in situ in photocatalytic microreactors.

Analysis of cytochrome P450 gene polymorphism in a lupus nephritis patient in whom tacrolimus blood concentration was markedly elevated after administration of azole antifungal agents

WHAT IS KNOWN AND OBJECTIVE

Both itraconazole (ITCZ) and voriconazole (VCZ) are potent inhibitors of cytochrome P450 (CYP) 3A, and their effects have been reported to be equal. However, ITCZ is metabolized by CYP3A, whereas VCZ is mainly metabolized by CYP2C9 and CYP2C19 and only partially by CYP3A. We experienced the case of a patient who showed a 5-fold increase in trough levels of tacrolimus (FK) level after switching from ITCZ to VCZ. Our objective is to discuss the mechanism of the increase drug-drug interaction in terms of serum concentration of the azole drugs and patient pharmacogenomics.

CASE SUMMARY

A 53-year-old woman was treated with FK (1 mg/day) for lupus nephritis. Because fungal infection was suspected, she received ITCZ (100 mg/day). When ITCZ was replaced with VCZ (400 mg/day), the blood concentration of FK increased markedly from 6·1 to 34·2 ng/mL. During coadministration with FK, the levels of ITCZ and VCZ were 135·5 ng/mL and 5·5 μg/mL, respectively, with the VCZ level around 3-fold higher than the previously reported level (1·4-1·8 μg/mL). Her CYP genotypes were CYP2C19*1/*2, CYP3A4*1/*1 and CYP3A5*3/*3.

WHAT IS NEW AND CONCLUSION

The patient was a CYP2C19 intermediate metabolizer (IM) and deficient in CYP3A5. The increase in plasma VCZ level appears to have been at least in part, associated with the CYP2C19 IM phenotype. One possible explanation for the marked increase in blood FK concentration was increased inhibition of CYP3A because of the impaired metabolism and subsequent increased plasma concentration of VCZ. This case shows that the severity of drug interactions may be influenced by metabolic gene polymorphism.

Domain-based assays of individual antibody concentrations in an oligoclonal combination targeting a single protein

Quantitation of individual monoclonal antibodies (mAbs) within a combined antibody drug product is required for preclinical and clinical drug development, including pharmacokinetic (PK), toxicology, stability, and biochemical characterization studies of such drugs. We have developed an antitoxin, XOMA 3AB, consisting of three recombinant mAbs that potently neutralize the known subtypes of type A botulinum neurotoxin (BoNT/A). The three mAbs bind nonoverlapping BoNT/A epitopes with high affinity. XOMA 3AB is being developed as a treatment for botulism resulting from BoNT/A. To develop antibody-specific assays, we cloned, expressed, and purified BoNT/A domains from Escherichia coli. Each mAb bound only to its specific domain with affinity comparable to the binding to holotoxin. mAb-specific domains were used to develop an enzyme-linked immunosorbent assay (ELISA) for characterization of the integrity and binding activity of the three mAbs in the drug product. An electrochemiluminescence bridging assay that is robust to interference from components in serum was also developed, and we demonstrate that it can be used for PK assays. This type of antigen engineering to generate mAb-specific domains is a general method allowing quantitation and characterization of individual mAbs in a mAb cocktail that binds the same protein and is superior to anti-idiotype approaches.

[Stanford type A acute aortic dissection with congenital complete absence of the left pericardium; report of a case]

A 52-year-old woman who presented with acute onset of chest pain was diagnosed with Stanford type A acute aortic dissection by computed tomography at another hospital. She was referred to our department for emergency surgery. The left pericardium visualized via a median sternotomy was clearly defective, and the left phrenic nerve was located ventral to the defect. The ascending aorta and total arch were replaced with an aortic valve and a prosthetic graft, respectively. Postoperative chest radiography excluded left phrenic nerve palsy. The postoperative course was uneventful and the patient was discharged on postoperative day 17.

Effects of the reproductive status on morphological oocyte quality and developmental competence of oocytes after in vitro fertilization and somatic cell nuclear transfer in cat

This study was conducted to examine the effects of the reproductive cycle of donor cat on the quality of oocytes at recovery and developmental competence of oocytes after in vitro fertilization (IVF) and somatic cell nuclear transfer (NT). Based on the presence or absence of follicles and corpora lutea, the ovarian pairs collected were classified into inactive, follicular or luteal stages. After collection of oocytes, the oocytes were classified into four grades according to the morphological condition of oocyte cytoplasm and cumulus cells. A total of 16 558 oocytes were obtained from 198 ovarian pairs. The total mean numbers of oocytes and the mean numbers of oocytes with high quality (grade I) were significantly higher in ovarian pairs at the inactive stage (111.1 and 19.0 oocytes, respectively) than in ovarian pairs at the follicular stage (67.1 and 11.4 oocytes, respectively). A significant difference in the proportions of oocytes with grade I out of the total examined oocytes was observed between the follicular and luteal stages of ovaries (14.9% vs 20.2%, p < 0.05). The proportions of IVF embryos cleaved and developed to blastocysts significantly decreased with decreased quality of oocytes at recovery, irrespective of the reproductive status of ovaries. Moreover, there were no significant differences in the proportions of cleavage and development to the blastocyst stage of IVF and NT embryos among three oestrous stages of ovaries. These results indicate that the reproductive cycle stage of donor cat ovaries has no apparent effects on the in vitro development of oocytes after IVF and NT, but the quality of oocytes at recovery influences the development of IVF embryos.

The FLT3 inhibitor PKC412 exerts differential cell cycle effects on leukemic cells depending on the presence of FLT3 mutations

PKC412 is a staurosporine derivative that inhibits several protein kinases including FLT3, and is highly anticipated as a novel therapeutic agent for acute myeloblastic leukemia (AML) carrying FLT3 mutations. In this study, we show that PKC412 exerts differential cell cycle effects on AML cells depending on the presence of FLT3 mutations. PKC412 elicits massive apoptosis without markedly affecting cell cycle patterns in AML cell lines with FLT3 mutations (MV4-11 and MOLM13), whereas it induces G2 arrest but not apoptosis in AML cell lines without FLT3 mutations (THP-1 and U937). In MV4-11 and MOLM13 cells, PKC412 inactivates Myt-1 and activates CDC25c, leading to the activation of CDC2. Activated CDC2 phosphorylates Bad at serine-128 and facilitates its translocation to the mitochondria, where Bad triggers apoptosis. In contrast, PKC412 inactivates CDC2 by inducing serine-216 phosphorylation and subsequent cytoplasmic sequestration of CDC25c in THP-1 and U937 cells. As a result, cells are arrested in the G2 phase of the cell cycle, but do not undergo apoptosis because Bad is not activated. The FLT3 mutation-dependent differential cell cycle effect of PKC412 is considered an important factor when PKC412 is combined with cell cycle-specific anticancer drugs in the treatment of cancer and leukemia.

A combination chemotherapy of weekly paclitaxel and doxifluridine (5’-DFUR: an intermediate metabolite of capecitabine) in patients with unresectable or recurrent gastric cancer in an outpatient setting. Final results of a multicenter phase II trial

15050

Background: Paclitaxel (PTX) and 5’-DFUR have single-agent activity in gastric cancer and have distinct mechanisms of action and no overlap of key toxicities. Synergistic interaction between PTX and 5’-DFUR is mediated by taxane-induced up-regulation of thymidine phosphorylase, which converts 5’-DFUR to 5-FU. We conducted a combination phase II study of PTX and 5’-DFUR in patients with unresectable or recurrent gastric cancer to evaluate the efficacy and safety in an outpatient. Methods: Eligibility criteria included patients with histologically proven unresectable or recurrent gastric cancer who had measurable lesions fitting RECIST, up to one prior chemotherapy, a performance status of 0–2 and adequate organ function. According to our results of phase I study (Proc ASCO 2004, Abstr. 4228), the treatment included PTX 70 mg/m2 i.v. on days 1, 8, and 15 every 4 weeks and 5’-DFUR 600 mg/body p.o. everyday until there was disease progression or the appearance of unacceptable toxicity. Primary endpoint was: RR; and secondary endpoints were OS, PFS, TTF and onset rate of adverse events. Results: Between June 2004 and July 2006, 42 patients were enrolled in this study: including 34 men; 8 women; median age of 70 years (range, 44–85 years); and PS levels were, zero with 27, one with 13 and two with 2 patients. In 42 eligible patients, clinical usefulness was evaluated resulting in response rate of 40.5% (CR, 1; PR, 16; SD, 17; PD, 6; and NE, 2 patients). The first-line therapy involved 28 patients in whom the response rate was 50.0%. The second-line therapy involved 13 patients (all TS-1 failure) in whom the response rate was 23.1%. OS was 371 days, PFS was 170 days and TTF was 147 days. All patients were treated in outpatient. Severe adverse events were found in 2 patients to discontinue the present treatment, though other adverse events were relatively mild without death due to the present therapy. Commonly observed grade 3/4 adverse events were neutropenia (26.2%), appetite loss (4.8%), neuropathy (4.8%), and fatigue (4.8%). Conclusions: The outpatient combination of a weekly PTX and 5’-DFUR chemotherapy is active and well tolerated.

No significant financial relationships to disclose.

UGT1As polymorphisms predict toxicity in colorectal cancer patients treated with different recommended doses of irinotecan oriented by UGT1A1*28 polymorphism based on previous phase I study

14511

Background: We have presented at 2006 ASCO annual meeting about a genetic UGT1A1 polymorphism oriented phase (P) I study of Irinotecan and 5’-DFUR for metastatic colorectal cancer (MCRC) to determine the maximum tolerated dose (MTD) and the recommend doses (RD) for each UGT1A1 *1/*1 and *1/*28 genotypes. The RD of biweekly Irinotecan administration was 150 mg/m2 for patients (pts) with wild *1/*1 genotype and 70 mg/m2 of Irinotecan for mutated *1/*28. Now we are carrying out a *28 oriented P II study based on this RD. Here we report the profiles of toxicities in the P II study of irinotecan and 5’-DFUR to analyze other kinds of UGT1As polymorphisms in relation to irinotecan toxicities. Patients & Methods: Eligibility criteria were as follows; histologically proven CRC with unresectable metastatic lesions, PS 0–1, age<76, adequate organ functions, and written informed consent. Twenty one pts with wild type genotype and 9 pts with mutated genotype were enrolled. Irinotecan was infused 150 mg/m2 for pts with *1/*1 genotype and 70 mg/m2 for *1/*28. Hematological and non-hematological toxicities were graded, and UGT1As polymorphisms (UGT1A1*6 and *7, UGT1A7*1*2*3*4, UGT1A9*22) were analyzed. Results: Grade (G)3 & 4 toxicities were observed in 6 of 22 (27%) wild type pts and in 3 of 9 (33%) mutated pts, and in 9 of 31 (29%) all pts. There was no significant difference on the profiles of toxicities between the pts with wild genotype and mutated genotype, irrespective of the difference of the quantity of irinotecan. So, the RD was thought to be adequate. In pts with UGT1A1*6 allele, G3 & 4 toxicities were observed 6/11 (55%), on the other hand 3/20 (15%) in pts without *6 allele (p=0.038). G3 & 4 toxicities were also more frequent in pts with UGT1A7*3 alleles than pts without *3 allele (p<0.10). Conclusions: The profiles of toxicities of pts with *1/*1 or *1/*28 genotypes were similar irrespective of the difference of the quantity of irinotecan. The result indicated that the RD of latest PI for each group was adequate, and this P II study is suitable to analyze other kinds of polymorphisms that have correlation to irinotecan toxicities. UGT1A1*6 and UGT1A7*3 allele will be a novel predictor for toxicity of irinotecan.

No significant financial relationships to disclose.

Ovarian follicular and corpus luteum changes, progesterone concentrations, estrus and ovulation following estradiol benzoate/progesterone based treatment protocol in cross-bred cows

The objectives of the present study were to investigate the effects of the stage of the estrous cycle at the start of an estradiol benzoate (EB) and progesterone (P) based treatment protocol on new follicular wave emergence, subsequent estrus and ovulation. The experiment was conducted using a crossover design with each cow (five cross-bred cows) being assigned to one of three groups at 3-month intervals within a 1-year period. Estrous cycle stage in individual cows was initially synchronized with prostaglandin F(2)alpha. After detection of estrus, each cow was injected intramuscularly (i.m.) with 2 mg EB and 200 mg P (EB/P) on day 5, 12 or 17 of the estrous cycle (estrus=day 0), followed by 1 mg EB i.m. 12 days after the EB/P treatment. Ovarian ultrasonographic examinations showed that the emergence of a new follicular wave occurred after EB/P treatment in all groups and the mean interval from EB/P treatment to wave emergence did not differ among the groups (3.2-3.8 days). All cows in each group exhibited behavioral estrus and ovulated the newly formed dominant follicle. However, cows in the day-17 group exhibited estrus 1-3 days before the second EB injection. The concentrations of progesterone showed faster reduction, during the treatment period, in the day-12 and -17 groups compared to the day-5 group. These results indicate that the EB/P treatment induces an emergence of a new follicular wave, irrespective of the estrous cycle stage at the start of treatment, but the effect of EB/P protocol on estrous/ovulation synchronization is influenced by the stage of the estrous cycle.

A combination phase I study of biweekly docetaxel and 5’-DFUR in patients with unresectable or recurrent gastric cancer

14115

Background: Docetaxel (DOC) and 5’-DFUR (an intermetamolite of capecitabine) have single-agent activity in gastric cancer and have distinct mechanisms of action and no overlap of key toxicities. Synergistic interaction between DOC and 5’-DFUR is mediated by taxane-induced up-regulation of thymidine phosphorylase. The objectives of this study were to determine the maximum tolerated dose (MTD), the dose limiting toxicity (DLT) and the recommended dose (RD) of the combination therapy of biweekly DOC and 5’-DFUR. The DLT was set in low grade to treat the patients in the outpatient clinic. Methods: Eligibility criteria included patients with histologically proven unresectable or recurrent gastric cancer, no requirement of prior chemotherapy, a performance status of 0–2, adequate organ function and written informed consent. DOC was administered by 1-hour intravenous infusion (level 1, 2, 3, 4: 30, 35, 40, 45 mg/m2) biweekly for 4 weeks. 5’-DFUR was administered orally at a fixed dose of 600mg/body everyday. Toxicity and efficacy were evaluated during the 2 cycles for 8 weeks. Three or 6 patients were enrolled at each dose level. Administration of DOC was skipped in the event of grade 2 hematologic toxicity. DLT was defined as grade 3 hematologic toxicity, grade 2 non-hematologic toxicity. The MTD was defined as the dose level at which at least two of three patients or three of six patients presented with DLT. Results: Twelve patients with a median age of 58 years (range, 29 to 75) were enrolled in this study. Five patients have received prior chemotherapy. Eight patients were unresectable and 4 had recurrent tumors. At level 1 (n=3), 2 (n=3), 3 (n=3), no patients developed DLT. Two patients developed DLT at level 4 (n=3). All DLT was neutropenia. Only 1 developed grade 4 neutropenia at level 4. Non-hematological toxicity was uncommon. Level 4 was determined as the MTD. Of 8 evaluable patients, responses included 4 PR, 3 SD and 1 PD for an overall response rate of 50%. Conclusions: The MTD of DOC in this combination is 45 mg/m2 and the RD is 40 mg/m2. This regimen is well-tolerated with high response rate in outpatient setting. A phase II study is necessary to evaluate the response of this regimen.

No significant financial relationships to disclose.

A genetic UGT1A1 polymorphism oriented phase I study of irinotecan (CPT-11) and doxifluridine (5’-DFUR: An intermediate form of capecitabine for metastatic colorectal cancer (MCRC)

3602

Background: 5-Fluorouracil plus CPT-11 is one of the standard 1st-line therapies in patients (pts) with metastatic colorectal cancer (MCRC). Although it has been reported that individuals carrying the (TA) 7 allele in the TATAA promoter of UGT1A1 increased risk of severe toxic event occurrence after CPT-11 administration, there is no report about phase I study based on the polymorphism of UGT1A1. Here we report the results from a genetic UGT1A1 polymorphism oriented phase I study of CPT-11 and 5’-DFUR to determine the maximum tolerated dose (MTD) and the recommend doses (RD) for each UGT1A1 genotypes. Methods: Eligibility criteria were as follows; histologically proven CRC with unresectable metastatic lesions, PS 0–2, age<76, adequate organ functions, and written informed consent. CPT-11 was infused (level 1, 2, 3 and 4: 70, 100, 120, 150 mg/m2, respectively) biweekly and 5’-DFUR was administered orally (800 mg/body, <1.39 m2; 600 mg/body) on 5 consecutive days with 2 days’ rest for more than 12 weeks. DLT were determined as grade 3 hematological and non-hematological toxicities. Genotypes were determined by analyzing the sequence of TATA box of UGT1A1 of genomic DNA from pts. Results: Eighteen pts with wild 6/6 allele and 9 pts with mutated 6/7 allele were registered. In pts with 6/6 allele, MTD was not observed up to level 4 (150 mg/m2). In pts with mutated 6/7 allele, on the other hand, MTD was observed at level 2 (100 mg/m2). We recommend doses of 70 mg/m2 of CPT-11 for pts with mutated 6/7 allele and 150 mg/m2 of CPT-11 for pts with wild 6/6 allele, respectively. Conclusions: The recommended phases II/III starting doses of biweekly CPT-11 administration are 150 mg/m2 for pts with wild 6/6 allele and 70 mg/m2 of CPT-11 for pts with mutated 6/7 allele, and 5’ -DFUR 800 mg/body on every 5 days per week. This combination therapy may be administered safely for all pts according to the TATAA promoter polymorphism of UGT1A1. The gene polymorphism should be taken into consideration to provide more precise information to guess the individual toxicities.

No significant financial relationships to disclose.

Meiotic Competence of Canine Oocytes Embedded in Collagen Gel

The present study was conducted to examine the meiotic competence of canine oocytes embedded in collagen gel, and to investigate the effects of timed exposure of the oocytes embedded in collagen gel to gonadotrophins during maturation culture, on their nuclear maturation. Cumulus-oocyte complexes (COCs) were collected from bitches at the anoestrous and dioestrous stages of the reproductive cycle. In the first experiment, half of the COCs were embedded in collagen gels. The COCs with or without collagen-gel embedding were cultured in a TCM-199 medium supplemented with 0.1 IU/ml human menopausal gonadotropin (hMG) and 10 IU/ml human chorionic gonadotropin (hCG) for 72 h. In the second experiment, the COCs embedded in collagen gels were cultured in TCM-199 medium with gonadotrophins (hMG and hCG) for various periods (0, 24, 48 and 72 h) and then cultured in the medium without gonadotrophins until reaching total culture period (72 h). The percentage of the oocytes reaching metaphase I and metaphase II (MI/MII) was significantly higher (p < 0.05) in COCs with collagen-gel embedding than in COCs without collagen-gel embedding. The percentage of oocytes that were arrested at the germinal vesicle stage was significantly lower (p < 0.05) in oocytes cultured with gonadotrophins than in oocytes cultured without gonadotrophins. However, there were no significant differences in the percentages of oocytes that reached each stage of meiosis among the groups, irrespective of the duration of exposure to gonadotrophins. These observations indicate that embedding of COCs by collagen gel enhances the meiotic competence of canine oocytes, but removal of hormone supplement from maturation medium does not improve the ability of the oocytes to reach MII stage.