Invasive group A streptococcal infection outbreaks of typeemm118 in a long-term care facility, and of type emm74 in the homeless population, Montréal, Quebec.

BACKGROUND: Two invasive group A streptococcus (iGAS) infection outbreaks occurred in Montreal in 2016 and 2017; one in a long-term care facility (typeemm118) and one in the community, primarily involving homeless people (typeemm74). OBJECTIVE: To describe two recent iGAS outbreaks in Montréal and highlight the challenges in dealing with these outbreaks and the need to tailor the public health response to control them. METHODOLOGY: All cases of iGAS were investigated and the isolates were sent to the laboratory foremmtyping. In both outbreaks, cases of superficial group Astreptococcus(GAS) infection were identified, through 1) systematic case detection accompanied by screening for asymptomatic carriers among residents and employees of the long-term care facility and 2) sentinel surveillance among homeless people. Visits were made to community organizations providing homeless services (including shelters) and social networks were analyzed to establish whether there were any links among cases of GAS infection (both invasive and noninvasive) and locations frequented. In both outbreaks, recommendations were made to service providers regarding enhancement of infection prevention and control measures. RESULTS: In the long-term care facility, five cases of typeemm118 iGAS were identified over a 22-month period, one of which resulted in death. All residents were screened and no carriers were identified. Among the employees, 81 (65%) were screened and fourcarriers were identified. Of those, one was a carrier of typeemm118 GAS. All carriers were treated, and subsequent follow-up sampling on three carriers (including the one withemm118) was negative.In the community, 23 cases of typeemm74 iGAS were detected over a 16-month period, four of which resulted in death. Half of the cases (n=12) were described as homeless, and six others were users of services for the homeless. Sentinel surveillance of superficial infections yielded 64 cultures with GAS, chiefly on the skin, including 51 (80%) of typeemm74. An analysis of the social networks revealed the large number and variety of resources for the homeless used by the cases. Visits to the community organizations providing homeless services revealed the heterogeneity and precariousness of some of these services, the difficulties encountered in applying adequate health and hygiene measures, and the high degree of mobility amongst those who use these services. CONCLUSION: The detection and control of iGAS outbreaks in both long-term care establishments and among community organizations providing homeless services are very complex. An outbreak of iGAS can develop in the background over a long time and be easily overlooked despite cases being admitted to the hospital.Emmtyping and systematic research of previous cases of iGAS are essential tools for the detection and characterization of outbreaks. Close cooperation among public health agencies, clinical teams, community organizations and laboratories is essential for proper monitoring and the reduction of GAS transmission in the community and health care settings.

Investigation of an outbreak of cercarial dermatitis.

We present the investigation of an outbreak of cercarial dermatitis that occurred in a recreational-tourist lake in the Quebec City region (Canada) in the summer of 1999. A case-reporting form was sent to 450 families likely to have activities that would bring them in contact with the lake's water. The snails were characterized and the prevalence of their infestation by schistosomes was investigated. In total, 63 episodes consistent with cercarial dermatitis were reported. Sixty-nine percent of the cases occurred from swimming at the same beach. This location was the one where the only population of snails in the lake was identified. Shoreline residents were informed that they should not feed waterfowl, and a clean-up of the snail population was done at the start of the following summer. There were no cases of cercarial dermatitis at this site the following summer.

Phase II trial of a paclitaxel-carboplatin combination in recurrent squamous cell carcinoma of the head and neck.

OBJECTIVE: Twenty-seven patients with recurrent squamous cell carcinoma of the head and neck were entered in a multicenter study to determine the efficacy of the paclitaxel-carboplatin association. METHODS: Standard eligibility criteria applied, i.e. measurable disease, and chemotherapy given as induction treatment or concomitant chemoradiotherapy was allowed if completed more than 6 months prior to the study. Every 21 days, paclitaxel 175 mg/m(2) and carboplatin AUC 6 were administered. The patient group included 3 females and 24 males with a median age of 61 years (range 39-75 years). RESULTS: All patients were assessable for toxicity and 24 for responses. Main grade 3-4 toxicities were: neutropenia (62.9%), febrile neutropenia (18.5%), anemia (11.1%), thrombocytopenia (14.8%), mucositis (7.4%) and vomiting (7.4%). Among the intent-to-treat population, 29.6% of patients had an objective response, with a median response duration of 4.2 months (range 1-5.7 months). Stable and progressive disease were observed in 11.1 and 48.1% of patients, respectively. The median overall survival was 7.2 months (range 0.5-10.9 months). CONCLUSION: From these data, paclitaxel-carboplatin seems to have an activity in recurrent squamous cell carcinoma of the head and neck, but the high level of toxicity highlights the need to search for a safer chemotherapy combination.

Role of dihydropyridine-sensitive calcium channels in meiosis and fertilization in the bivalve molluscs Ruditapes philippinarum and Crassostrea gigas.

Prophase-arrested oocytes of Ruditapes philippinarum can not be fertilized or stimulated by a depolarizing agent such as an excess of KCl, in contrast to the situation found in Crassostrea gigas. We have performed a comparative study between the two situations found in these species. In vitro, both of these oocytes can be triggered to reinitiate meiosis following a treatment by serotonin which promotes an intracellular calcium surge. Ruditapes and Crassostrea oocytes further arrest in metaphase I, at which stage they can be either activated by sperm or by excess KCl. These treatments trigger an intracellular calcium increase. This suggests that functional voltage-operated Ca2+ channels are expressed in Ruditapes during the course of maturation between prophase and metaphase I. Results obtained using pharmacological tools and direct binding of specific dihydropyridines, strongly suggest that these channels are dihydropyridine-sensitive calcium channels. In Ruditapes they become functional after 5-HT stimulation, their number increasing before GVBD. In Crassostrea the dihydropyridine-sensitive Ca2+ channels are already present at prophase stage and their density is constant from prophase to metaphase I. Moreover, we have shown for Ruditapes and Crassostrea that: 1) the addition of 10 microM of S(-)BayK8644, an agonist of dihydropyridine-sensitive calcium channels to metaphase-arrested oocytes releases them from metaphase block; and 2) incubating these oocytes with nicardipine, a potent blocker of dihydropyridine-sensitive Ca2+ channels, inhibits both their activation by excess KCl or fertilization. Taken together these data suggest that the absence of dihydropyridine-sensitive Ca2+ channels in the membrane of prophase-arrested oocytes of Ruditapes may account for their inability to be fertilized at this stage, while the presence of dihydropyridine-sensitive Ca2+ channels in prophase-arrested oocytes of Crassostrea may explain their fertilizability at this stage.

Meiosis reinitiation of mussel oocytes involves L-type voltage-gated calcium channel.

In the present work we assessed the involvement of L-type voltage opening Ca2+ channels in KCl-induced meiosis reinitiation of metaphase-arrested blue mussel (Mytilus galloprovincialis) oocytes by performing binding assays with a tritiated dihydropyridine analog (+)PN 200110. Our data reveal the existence of a single class of dihydropyridine receptors in plasma membrane-enriched rough microsome preparations of mussel oocytes. The apparent affinity (Kd) of characterized receptors equals 1.32 +/- 0.21 microM while their maximal binding capacity (Bmax) is 620 +/- 150 pmol/mg protein. The comparison of the rank order of potency of analogs tested to: 1) inhibit [(+)-[3H]PN 200110 specific binding and 2) block KCl-induced meiosis reinitiation pointed to the pharmacological profile similar to but not identical with those previously described for mammalian dihydropyridine receptors. The efficiencies of all antagonists tested are linearly related (r = 0.995) in binding-(inhibition of [(+)-[3H]PN 200110 specific binding) and biological (inhibition of meiosis reinitiation) assays thus arguing for functional involvement of L-type Ca2+ channels in oocyte activation. Reversibility of antagonist actions on meiosis reinitiation and dependence of receptor binding characteristics on a membrane polarization state further suggested such a role.

Activation of an 85 kDa ribosomal S6 kinase during serotonin-induced oocyte maturation.

Oocytes from the Japanese clam Ruditapes philippinarum are naturally blocked at the prophase-I stage of meiosis. Following physiological activation by the neurohormone serotonin (5HT), oocytes undergo germinal vesicle breakdown (GVBD) and reach a second cell cycle arrest in metaphase-I. To identify the kinases activated during meiosis reinitiation, we used a phosphorylation assay following sodium dodecyl sulphate-polyacrylamide gel electrophoresis and in situ renaturation. A soluble 85-kDa serine/threonine kinase (PK85) was highly and consistently activated (up to 17-fold) within 5 minutes following addition of the hormone. This activation occurred 5 to 10 minutes before GVBD and only when 5HT concentration was sufficient to induce meiosis reinitiation. The calcium ionophore A23187 and NH4Cl, two compounds known to induce GVBD by increasing intracellular calcium concentration, also activate PK85. In crude oocyte extracts, the presence of beta-glycerophosphate, NaF, okadaic acid, calyculin A or microcystin, prevented inactivation of PK85, suggesting that it is activated by phosphorylation. Partial purification of PK85 followed by Western blotting showed that this kinase is related to the ribosomal S6 kinase pp90rsk. PK85 phosphorylates the peptides LRRASLG (kemptide) and PLARTLSVAGLPGGK (syntide-2), and to a lesser extent the synthetic polyamino acids poly(R3:S1) while myelin basic protein (MBP), histone III-S, casein, the peptides pEKRPSQRSKYL ((pGlu4)-MBP 4-14), GTFRASIRRLAARRR (NIMA kinase substrate), the protein kinase C (PKC) substrate LRTLRR and the synthetic polyaminoacids poly(R1:P1:T1) were poor substrates. 5HT-induced GVBD and PK85 activation are both inhibited by the phorbol ester 12-myristate 13-acetate (PMA) and this inhibition can be reversed by 5 microM of the bisindolyl-maleimide GF109203X, a potent PKC inhibitor. PMA inhibitory action appears to take place between 5HT binding to its receptor and the intracellular calcium surge since it has no effect on GVBD induced by calcium ionophore A23187 and thapsigargin. Taken together, these results suggest that serotonin-induced activation of PK85 occurs after the intracellular calcium surge in a PKC-independent pathway.

Meiosis reinitiation in Ruditapes philippinarum (Mollusca): involvement of L-calcium channels in the release of metaphase I block.

Prophase-arrested oocytes of Ruditapes philippinarum cannot be fertilised or stimulated by excess KCl, in contrast to the situation found in other bivalve species such as Barnea and Spisula. However, these oocytes can be triggered to reinitiate meiosis following treatment by serotonin or several pharmacological agents (calcium ionophores, thapsigargin, weak bases) which promote an intracellular calcium surge. Ruditapes oocytes further arrest in metaphase I, at which stage they can be activated either by sperm or by excess KCl. This suggests that functional voltage-operated calcium channels are expressed in this species during the course of maturation. Using pharmacological tools and direct binding of specific dihydropyridines, we demonstrate that these channels are L-type calcium channels which become functional after serotonin stimulation, their number increasing before germinal vesicle breakdown. Moreover we establish that: (1) the addition of 20 microM S(-)BayK8644, an agonist of L-type calcium channels, to metaphase-arrested oocytes releases them from metaphase block; (2) incubating these oocytes with PN200-110, a potent blocker of L-type calcium channels, inhibits their activation by both excess KCl and fertilisation. Taken together these data suggest that the absence of L-type calcium channels in the membrane of prophase-arrested oocytes of Ruditapes may account for their inability to be fertilised.

4-aminopyridine acts as a weak base and a Ca2+ mobilizing agent in triggering oocyte meiosis reinitiation and activation in the Japanese clam Ruditapes philippinarum.

Ovarian oocytes of the prosobranch mollusc Patella vulgata and the pelecypod Ruditapes philippinarum are arrested during prophase of the first maturation division. Release from this blockade, which is revealed by germinal vesicle breakdown, drives these oocytes to a second arrest in metaphase I, at which time the oocytes become fertilizable. The respective roles of Ca2+ and H+ ion movements during this early step in meiosis reinitiation has not been fully established yet. In this work we reveal the presence of acidic vesicles and report that bafilomycin A1 and N,N'-dicyclohexylcarbodiimide, two inhibitors of the vacuolar-type H(+)-ATPase, applied to Ruditapes oocytes, produce a significant inhibition of their response to the natural neurohormone serotonin. Since sodium deprivation did not affect this response, this suggests that a v-type ATPase pump, possibly located in the membrane of these acidic vesicles, may play a subtle role in the cascade of events that releases oocytes from their prophase block. We then describe how 4-aminopyridine, a drug reputed to be a K+ channel antagonist, triggers both meiosis reinitiation and activation of Patella and Ruditapes oocytes. This agent acts as a weak base, its effect depending on external pH. Moreover, using the fluorescent probes BCECF and Fluo-3/AM, we observe that this drug both alkalinizes the endoplasm and promotes an intracellular Ca2+ surge. This dual effect may explain why Ruditapes oocytes no longer stop in metaphase under these conditions and behave like other bivalve species which are directly fertilizable at the germinal vesicle stage.

Inhibition of protein synthesis affects histone H1 kinase, but not chromosome condensation activity, during the first meiotic division of pig oocytes.

The influence of protein synthesis on the regulation of the first meiotic division was studied in pig oocytes. We show that histone H1 kinase activity gradually increases during in vitro culture of pig oocytes, reaching maximum in metaphase I stage after 24 hr of culture. However, in the presence of the protein synthesis inhibitor cycloheximide, histone H1 kinase is not activated during the whole culture period, and after 24 hr it is approximately at the same level as in prophase-stage oocytes. The gradual increase in phosphorylation of six proteins of molecular weights 39, 48, 53, 66, 96, and 120 kDa, observed during the first 24 hr of culture, was not detected when cycloheximide was added to the culture medium. Similarly, the decrease in phosphorylation of a 90-kDa protein was not seen in cycloheximide-treated oocytes. On the other hand, the levels of both MPF components, p34cdc2 and cyclin B, which were found to be nearly constant during the first meiotic division, were not influenced by cycloheximide treatment as revealed by Western blotting. The process of germinal vesicle breakdown (GVBD) was totally blocked by cycloheximide. The condensation of chromatin, however, was not influenced, suggesting that GVBD and chromosome condensation could be regulated independently. The different degrees of MPF activation involved in these processes, as well as the nature of the protein(s) which must be synthesized for triggering GVBD, are discussed.

Thimerosal triggers meiosis reinitiation in oocytes of the Japanese clam Ruditapes philippinarum by eliciting an intracellular Ca2+ surge.

Ovarian oocytes of the bivalve mollusc Ruditapes philippinarum are arrested during first meiotic prophase. Release from this blockade is triggered by the neurohormone serotonin (5HT or 5-hydroxytryptamine), which promotes germinal vesicle breakdown and drives these oocytes to a second arrest in metaphase I. 5HT action involves binding to a specific G protein-coupled receptor which results in a transient rise in IP3 and in the intracellular free Ca2+ concentration. Here we analyze the cytological effects and mode of action of the sulphydryl reagent thimerosal which could also trigger meiosis reinitiation in Ruditapes. No metaphase I spindle formed under these conditions since thimerosal was found to be able to preclude or reverse tubulin polymerization when applied to prophase- or to metaphase-arrested oocytes, respectively. Our results strongly suggest that the common final target for 5HT and thimerosal actions consists in a transient rise in internal free Ca2+ level that we could follow using Fluo3/AM as a probe. The effect of thimerosal in promoting oocyte maturation and increasing intracellular free Ca2+ concentration was improved by excess KCI. In addition, thimerosal, but not KCI, was found to facilitate 5HT-induced maturation at subthreshold hormone concentrations which, by themselves, did not produce an intracellular Ca2+ surge. These data suggest that thimerosal may inhibit Ca2+ pumps of the endoplasmic reticulum and unmask the plasma membrane voltage-sensitive Ca2+ channels which also appear after 5HT-induced GVBD.

The oocyte metaphase arrest.

Usually, oocyte meiosis reinitiation appears as a two step process during which release from the prophase block is followed by a second arrest in metaphase I or II. In this review, we will examine the mechanisms required to maintain the metaphase arrest and stabilize MPF activity at this stage. Then, we will analyse the processes required to exit from the metaphase block. These may drive the cells forward to the metaphase-anaphase transition, as a result of fertilization, activation or protein synthesis inhibition. Instead, inhibiting protein phosphorylation drives the oocyte back to interphase. All these treatments result in derepression of DNA synthesis.

The release from metaphase arrest in blue mussel oocytes.

In Mytilus edulis, shed oocytes are arrested at metaphase I of meiosis until fertilization. We previously suggested (Dubé and Dufresne, J. Exp. Zool. 256:323-332, 1990) that such a metaphase arrest depends upon a continuous synthesis of short-lived proteins, the destruction of which is sufficient to induce meiosis resumption. We further investigated the mechanism of metaphase release in blue mussel oocytes as triggered either by fertilization or by inhibition of protein synthesis (emetine) or phosphorylation (6-dimethylaminopurine, 6-DMAP). Treatment of unfertilized oocytes (UF) with emetine induces completion of the first meiotic cycle including extrusion of the polar body, followed by chromosome decondensation and by the formation of large membrane-bound nuclei, as visualized by Hoechst staining and transmission electron microscopy (TEM). Inhibition of protein phosphorylation with 6-DMAP induces directly chromosome decondensation and the formation of multiple nuclei surrounded by nuclear membrane. These interphasic nuclei exhibit continuous 3H-thymidine incorporation. p13 precipitation of p34 and associated proteins reveals "putative" cyclins in UF, no longer detected after metaphase/anaphase transition due to fertilization or emetine treatment. In the presence of 6-DMAP, new migrating forms are observed. The phosphorylated p34cdc2 homolog becomes dephosphorylated after fertilization or emetine treatment, whereas 6-DMAP induces its phosphorylation on tyrosine. Histone H1 kinase activity is reduced after these treatments, compared to the UF sample. Our results suggest that the metaphase/anaphase transition triggered by fertilization in blue mussel oocytes is induced by the rapid destruction of a set of continuously synthesized proteins accompanied by decreased histone H1 kinase activity. These events can be mimicked by inhibiting protein synthesis. Inhibition of protein phosphorylation would drive the cell to interphase without commitment to meiosis I.

Reception and transduction of the serotonin signal responsible for meiosis reinitiation in oocytes of the Japanese clam Ruditapes philippinarum.

Prophase-arrested oocytes of Ruditapes philippinarum are triggered to undergo germinal vesicle breakdown under the influence of the neurohormone serotonin (5HT) and then arrest in metaphase 1. Our data show that these oocytes possess a single class of original 5HT receptors. Their binding parameters have been determined on semipurified membrane preparations incubated with [3H]5HT. No significant differences were observed when comparing 5HT-competent and -incompetent batches as well as prophase- or metaphase-arrested oocytes. Specific experiments including incubation with mastoparan or mas 7, GTP iontophoresis, and IP3 quantification strongly suggest that these receptors must be coupled with G-proteins to be functional. Peak change in IP3 mass occurs at 3 min and is likely to trigger the 5HT-dependent Ca2+ transient that begins at this time. In metaphase-arrested oocytes, binding of 5HT to its receptors no longer produces a Ca2+ surger. This is likely to result from a negative retrocontrol loop which would involve kinase C and exert its effect upstream of the Ca2+ surge. Indeed, the phorbol ester PMA proved able to reduce the Ca2+ response and to block 5HT action when applied during the first 3 min corresponding to the hormone-dependent period. Such an inhibition was reversed in the presence of 5 microM of the C kinase inhibitor GF109203X and could be bypassed by ionophore, ammonia, and thapsigargin, which trigger a receptor-independent Ca2+ surge.

Differences in tyrosine phosphorylation of oocyte key proteins during 5HT-induced meiosis reinitiation in two bivalve species.

The neurohormone serotonin (5HT) triggers meiosis reinitiation in oocytes of the pelecypod molluscs Spisula solidissima and Ruditapes philippinarum. However, while Spisula oocytes complete maturation, Ruditapes oocytes arrest in metaphase I. Anti-phosphotyrosine antibody revealed that serotonin triggered an early tyrosine phosphorylation of p42mapk which was transient in Spisula, but persisted in Ruditapes. Moreover, dephosphorylation of tyrosine residues of p34cdc2 was only observed in Spisula oocytes, simultaneously with germinal vesicle breakdown. The possibility is discussed that such differences may account for maintenance of the metaphase I block.

Chromatin condensation and histone H1 kinase activity during growth and maturation of rabbit oocytes.

Fully grown rabbit oocytes, isolated from preovulatory follicles, exhibit highly condensed bivalents within an intact germinal vesicle while a very low level of histone H1 kinase activity could be detected in their extracts. Chromatin condensation started in growing oocytes isolated from antral follicles presenting a diameter of 0.5 mm. This event was accompanied by a transient rise in histone H1 kinase activity which culminated in large antral follicles measuring 0.75 to 1 mm in diameter. However, the extent of histone H1 kinase activity observed in these growing oocytes remained far less important than that recorded in extracts prepared from in vitro cultured metaphase I and metaphase II oocytes. Moreover, this activity was insufficient to induce germinal vesicle breakdown which will only occur with an increasing efficiency, following in vitro culture of medium, large, and fully grown antral follicles.

Evidence for the involvement of internal calcium stores during serotonin-induced meiosis reinitation in oocytes of the bivalve mollusc Ruditapes philippinarum.

In contrast to the situation found in the bivalves Barnea candida and Spisula solidissima, prophase-arrested oocytes of Ruditapes philippinarum cannot be fertilized when removed from the ovary. They must first undergo germinal vesicle breakdown under the influence of the neurohormone serotonin (5-HT), which drives them to a second block occurring in metaphase of the first maturation division. In the studies described in this paper, we investigate the possibility that calcium is involved as a second messenger in controlling this first step in the reinitiation of meiosis. Our data show that, in addition to 5-HT, ionophore, thapsigargin, and the weak bases ammonia and procaine can also induce prophase-arrested oocytes of Ruditapes to resume meiosis. 5-HT, thapsigargin, and ammonia all trigger a surge of intracellular Ca2+ and are effective even in the absence of external Ca2+. That such Ca2+ transients, which are enhanced in the presence of external Ca2+, actually play a key role in the process of meiosis reinitation is shown by the fact that loading the oocytes with BAPTA/AM or treating them with D-600 blocks maturation. In contrast, excess KCl, which has been shown to trigger meiosis reinitiation of prophase-arrested oocytes of Barnea and Spisula and to activate metaphase I-arrested oocytes of Ruditapes, does not produce any significant intracellular Ca2+ transient nor does it reinitiate meiosis, when added to Ruditapes prophase-arrested oocytes. These data suggest that such voltage-operated Ca2+ channels may only appear during the course of maturation and that both intracellular and extracellular Ca2+ are involved in triggering 5-HT-dependent release from the prophase block in this species.

Protein synthesis controls cyclin stability in metaphase I-arrested oocytes of Patella vulgata.

The metaphasic block of Patella vulgata oocytes depends on protein synthesis as an emetine treatment triggers metaphase/anaphase transition and leads to the sequential disappearance of cyclin A and B. Both cyclins are stable in metaphase-arrested oocytes which indicates that inhibition of protein synthesis activates cyclin proteolysis. The use of extracts prepared from metaphase-arrested oocytes and from emetine-treated oocytes fully confirms these in vivo findings. Considering previous observations about the regulation of protein synthesis throughout the cell cycle, we propose the involvement of a transient inhibition of translation in the activation of cyclin proteolysis and in exit from the M-phase arrest.

Release from the metaphase I block in invertebrate oocytes: possible involvement of Ca2+/calmodulin-dependent kinase III.

Full grown mature oocytes of the prosobranch gastropod mollusc Patella or the bivalves Mytilus or Ruditapes provide an excellent model for studying the mechanisms which trigger cyclin degradation and exit from the M phase. They are naturally arrested in metaphase of the first maturation division and their fertilization or artificial activation rapidly results in destruction of the cyclins and completion of meiosis. In this paper, we establish the presence of Ca2+/calmodulin-dependent kinase III or eEF-2 kinase in these oocytes and describe how the protein synthesis inhibitor emetine is able to release them from the metaphase block. Using the fluorescent Ca2+ indicator dye, fluo-3, we demonstrate moreover that both fertilization or KCl-dependent activation of Ruditapes and Mytilus oocytes actually trigger a measurable transient increase in cytosolic free Ca2+ concentration. We also show that the activations triggered by these signals as well as by the ionophore A 23187 can be reversibly blocked by the calmodulin antagonists TFP (30 microM) and W7 (100 microM), while these drugs have no effect upon emetine-dependent activations. Finally, we report that the rate of protein synthesis, measured in pulse experiments, decreases at each meiotic and mitotic cleavage following fertilization of metaphase I-arrested oocytes of Mytilus. On the basis of these experiments and as a working hypothesis, we thus propose that the Ca2+ surge which activates the oocyte may inhibit protein synthesis by triggering a transient phosphorylation of eEF-2. This would result in disappearance of the putative short-lived proteins which protect cyclins from degradation during the metaphase block.

Okadaic acid accelerates germinal vesicle breakdown and overcomes cycloheximide- and 6-dimethylaminopurine block in cattle and pig oocytes.

Pig and cattle oocytes, when released from the follicle, spontaneously resume first meiotic division within 20 or 8 hr, respectively. In oocytes of both species, the activity of histone H1 kinase increases during maturation, exhibiting a maximum in metaphase I. Treatment of these oocytes with okadaic acid results in acceleration of germinal vesicle breakdown (GVBD) and of histone H1 kinase activation. This effect is more important in pig oocytes, in which the acceleration rises for 6 hr, as compared to 2 hr in cattle. Moreover, under these conditions, H1 kinase activity measured after 12 hr of culture appears higher than that observed in control metaphase I oocytes. When added to prophase oocytes, both cycloheximide and 6-DMAP (6-dimethylaminopurine) block GVBD and histone H1 kinase activation. Okadaic acid, at a concentration of 2.5 microM, is able to release the inhibitory effect exerted by cycloheximide on histone H1 kinase activity; however, GVBD occurred only in two-thirds of pig and one-quarter of cattle oocytes after 20 hr of culture. In addition, okadaic acid fully reverses the effect of 6-DMAP on H1 kinase activity and on GVBD in both species. The opposite effects of 6-DMAP and okadaic acid on MPF activation are discussed, as well as the nature of the protein, which has to be synthesized during the first meiotic division and may be involved in the MPF activation cascade.