A Systematic Review of Randomized Clinical Trials on the Efficacy and Safety of Pitavastatin

BACKGROUND

A subpopulation of statin users such as subjects with chronic kidney disease (CKD), Human Immune virus (HIV), acute coronary syndrome (ACS), revascularization, metabolic syndrome, and/or diabetes may particularly benefit from pitavastatin pharmacotherapy.

AIM

The current systematic review aimed systematically to evaluate the effect of pitavastatin on primary cardiac events in subjects receiving pitavastatin in comparison to the other four statin members.

METHODS

We conducted a systematic review on phases III and IV of randomized controlled trials (RCT-s, 11 trials) for subjects with primary cardiac events who received pitavastatin. Subjects diagnosed with any type of dyslipidemia (population 4804) and received pitavastatin (interventions) versus comparator (comparison) with the primary efficacy endpoint of minimization of LDL-C and non- HDL-C, had an increase in HDL-C and/or reduction in major adverse cardiac events (MACE, cardiovascular death, myocardial infarction (fatal/nonfatal), and stroke (fatal/nonfatal) and/or their composite (outcomes). The secondary safety endpoint was the development of any adverse effects.

RESULTS

In the included trials (11), participants (4804) were randomized for pitavastatin or its comparators such as atorvastatin, pravastatin, rosuvastatin, simvastatin and followed up for 12 to 52 weeks. In terms of the primary outcome (reduction in LDL-C), pitavastatin 4 mg was superior to pravastatin 40 mg in three trials, while the 2 mg pitavastatin was comparable to atorvastatin 10 mg in four trials and simvastatin 20 and 40 mg in two 2 trials. However, rosuvastatin 2.5 mg was superior to pitavastatin 2 mg in two trials. Pitavastatin increased HDL-C and reduced non-HDL-C in eleven trials. Regarding the safety profile, pitavastatin has proved to be tolerated and safe.

CONCLUSION

The FDA-approved indications for pitavastatin included primary dyslipidemia and mixed dyslipidemia as a supplementary therapy to dietary changes to lower total cholesterol, LDL-C, apolipoprotein B (Apo B), triglycerides (TG), and enhance HDL-C. Pitavastatin might be suitable for subjects with diabetes, ACS (reduced revascularization), metabolic syndrome, CKD, HIV, and subjects with low levels of HDL-C. We highly recommend rational individualization for the selection of statin.

Randomized Clinical Trials on the Efficacy and Safety of Tocilizumab in Subjects with Rheumatoid Arthritis: A Systematic Review

BACKGROUND

The current therapy of Rheumatoid Arthritis (RA) is confronted with many challenges such as inadequate response, infection, and treatment failure.

AIM AND OBJECTIVE

The main objective was to assess the efficacy and safety of tocilizumab (TCZ) in subjects with RA using the available evidence from published randomized controlled trials.

METHODS

The current systematic review was performed on nine randomized controlled trials from 2002 to 2016 for TCZ in subjects with rheumatoid arthritis. The primary outcomes were the clinical improvement in American College Rheumatology 20% (ACR20) or Disease Activity Score remission (DAS28), in addition to other outcomes such as ACR50 and ACR70 in the intention-to-treat population.

RESULTS

We have conducted a systematic review on nine randomized controlled trials, with 4129 [100%] enrolled, of which 3248 [78.7%] were on the intention-to-treat. 2147 (66.1%) were treated with TCZ and 1101 (33.9%) have had received placebo or methotrexate or other conventional Disease- Modifying Anti-rheumatic Drugs (cDMARD) or biologic Disease-Modifying Anti-rheumatic Drugs (bDMARDs). In subjects taking TCZ with or without concomitant methotrexate, compared to placebo, subjects treated with TCZ 4 or 8 mg/kg were substantially and statistically significantly more likely than placebo or methotrexate to achieve the ACR20 and/or DAS28. There were no statistically significant differences in serious adverse events such as serious infection; however, subjects on TCZ were more likely to have increased lipid profiles.

CONCLUSION

TCZ mono-therapy or in combination with methotrexate is valuable in diminishing rheumatoid arthritis disease activity and improving disability. Treatment with TCZ was associated with a significant surge in cholesterol levels but no serious adverse effects. Randomized clinical trials with safety as the primary outcome are warranted to report these safety issues.

Scoping review of six retrospective studies: Risk factors associated with the case fatality rate of people infected with coronavirus disease 2019

Background:

It would be rational to describe the pattern of the clinical characteristics of the survivors and the nonsurvivors during the critical intensive-infection era of coronavirus disease 2019 (COVID-19). The explicit objective of the current scoping review was to delineate the predictive risk factors associated with case fatality rate (CFR).

Methods:

Six retrospective studies of subjects infected with COVID-19 published between December 1, 2020, and March 30, 2020, describing nonsurvivors in Wuhan/Hubei, China, were identified.

Results:

There were 1769 subjects with a mean age of 52 years, and 65.9% were male. The highest comorbidity reported was cardiovascular diseases at 22.2% (393/1769). The overall number of cases admitted to the intensive care unit was 228 (12.9%). The reported overall CFR was 7.7% (136/1769), with the highest at 28.2% (54/191), and the lowest at 1.4% (15/1099). The mean duration of onset until death for nonsurvivors was 15.3 days.

Conclusion:

We have found that older age, male gender, the longer duration from onset till death (days), development of acute respiratory distress syndrome/shock, preexisting diabetes, and preexisting cardiovascular diseases were the major risk factors associated with high CFR.

Systematic Review of Glucagon-Like Peptide One Receptor Agonist Liraglutide of Subjects with Heart Failure with Reduced Left Ventricular Ejection Fraction

BACKGROUND

The major cardiovascular outcome trials on glucagon-like peptide one-receptor agonists have examined its effect on hospitalization of subjects with heart failure; however, very limited trials have been conducted on subjects with reduced left ventricular ejection fraction (r- LVEF) as a primary outcome.

OBJECTIVE

We have conducted a systematic review of two major (FIGHT and LIVE) placebo-controlled trials of liraglutide and its clinical effect on the ejection fraction of subjects with heart failure.

METHODS

Medline data was retrieved for trials involving liraglutide from 2012 to 2020. The inclusion criteria for trials were: subjects with or without type 2 diabetes mellitus (T2DM), subjects with heart failure with rLVEF, major trials (phase II or III) on liraglutide, trials included liraglutide with defined efficacy primary outcome of patients with heart failure with rLVEF. The search was limited to the English language, whereby two trials [FIGHT and LIVE] had been included and two trials were excluded due to different primary outcomes. Participants (541) had been randomized for either liraglutide or placebo for 24 weeks.

RESULTS

In the FIGHT trial the primary intention-to-treat, sensitivity, and diabetes subgroup analyses have shown no significant between-group difference in the global rank scores (mean rank of 146 in the liraglutide group versus 156 in the placebo group; Wilcoxon rank-sum P=.31), number of deaths, re-hospitalizations for heart failure, or the composite of death or change in NT-pro BNP level (P= .94). In the LIVE trial, the change in the left ventricular ejection fraction (LVEF) from baseline to week 24 was not significantly different between treatment groups. The overall discontinuation rate of liraglutide was high in the FIGHT trial (29%, 86) as compared to that in the LIVE trial (11.6%, 28).

CONCLUSION

FIGHT and LIVE trials have demonstrated that liraglutide use in subjects with heart failure and rLVEF was implicated with an increased adverse risk of heart failure-related outcomes.

The early mortality rate of people infected with coronavirus (COVID-2019) in Wuhan, China: Review of three retrospective studies

Background:

The infection with coronavirus and non-survivor cases have been escalated since the first inception between January and March 2020. Therefore, reviewing the collated clinical characteristics of non-survivors might assist in current preventive efforts, triaging, and management of survivors. The aim of this review was to summarize the clinical characteristics of non-survivor cases due to the infection caused by a novel coronavirus and to identify the relevant data that might put the new cases at increased mortality.

Materials and Methods:

We have identified three published articles on novel coronavirus reported during December 01, 2020, to March 15, 2020, which have described the mortality rate in Wuhan, Hubei, China.

Results:

The mean duration of studies (i.e., the three retrospective studies with 278 cases) was 24.7 days, and the duration of onset to dyspnea was variable between 8 and 5 days. The main reported complications were acute respiratory distress, pneumonia, acute kidney injury, and acute cardiac disease. The overall major comorbidity reported was cardiovascular diseases at 23.7% (66 of 278). The reported overall mortality rate was 8.3% (23 of 278), with the highest mortality rate of 15.0% (6 of 41) reported in Jin Yintan Hospital at Wuhan city.

Conclusions:

The clinical characteristics of the non-survivors from the novel coronavirus included adult males, aged older than 50 years, having comorbidities of cardiovascular disease, respiratory distress syndrome, acute kidney injury, and diabetes with higher admission to the intensive care unit. The mortality rate was high in two of the reported studies (15.0% and 11.0%), which was decreased in the later-dated study to 3.4%.

UTP reduces infarct size and improves mice heart function after myocardial infarct via P2Y2 receptor

Pyrimidine nucleotides are signaling molecules, which activate G protein-coupled membrane receptors of the P2Y family. P2Y(2) and P2Y(4) receptors are part of the P2Y family, which is composed of 8 subtypes that have been cloned and functionally defined. We have previously found that uridine-5'-triphosphate (UTP) reduces infarct size and improves cardiac function following myocardial infarct (MI). The aim of the present study was to determine the role of P2Y(2) receptor in cardiac protection following MI using knockout (KO) mice, in vivo and wild type (WT) for controls. In both experimental groups used (WT and P2Y(2)(-/-) receptor KO mice) there were 3 subgroups: sham, MI, and MI+UTP. 24h post MI we performed echocardiography and measured infarct size using triphenyl tetrazolium chloride (TTC) staining on all mice. Fractional shortening (FS) was higher in WT UTP-treated mice than the MI group (44.7±4.08% vs. 33.5±2.7% respectively, p<0.001). However, the FS of P2Y(2)(-/-) receptor KO mice were not affected by UTP treatment (34.7±5.3% vs. 35.9±2.9%). Similar results were obtained with TTC and hematoxylin and eosin stainings. Moreover, troponin T measurements demonstrated reduced myocardial damage in WT mice pretreated with UTP vs. untreated mice (8.8±4.6 vs. 12±3.1 p<0.05). In contrast, P2Y(2)(-/-) receptor KO mice pretreated with UTP did not demonstrate reduced myocardial damage. These results indicate that the P2Y(2) receptor mediates UTP cardioprotection, in vivo.

A novel stone retrieval basket for more efficient lithotripsy procedures

This paper presents the development of an improved stone retrieval device that uses a newly designed cage of Nitinol wires encompassing a mesh basket made of a material that is laser resistant. Current methods to extract large stones involve imaging, using a laser to fragment the stones and then using existing cage-like baskets to trap the fragments individually and extracting them one at a time. These procedures are tedious, and may result in leaving some fragments behind that can reform causing the need for another procedure. The device presented in this paper will have a mesh-like sack which will consist of a laser resistant material of polytetrafluoroethylene (PTFE) enclosed within a newly designed Nitinol cage. Two alternate designs are provided for the cage in this paper. The handle of the device is revised to allow for a 3 Fr (1 mm) opening such that a laser's fiber optic cable can enter the device. Using this device a laser can be used to fragment the stone, and all the fragments are retained in the basket in both the design options. The basket can then be retracted allowing for the retrieval of all the fragments in one shot. The stone retrieval basket presented in this paper will significantly improve the efficiency and effectiveness of lithotripsy procedures for removal of large kidney and biliary tract stones.

Eroding the barriers between public and private health care

A Concordat with the Private and Voluntary Health-care Provider Sector (Department of Health (DoH), 2000a) proposed a strategy to remove barriers between public and private health-care providers. The document set out a broad framework to enable the NHS to use a wider range of services more imaginatively to meet local health needs. It was recommended that decision-making be devolved to the local level to enable more tailored services to be available to the community. Primary care groups (PCGs) were therefore encouraged to commission services from the private sector. This was especially relevant to relieve pressure on hospital beds during the winter months (DoH, 2000b).

MEIG1 localizes to the nucleus and binds to meiotic chromosomes of spermatocytes as they initiate meiosis

Meiosis, the fundamental evolutionarily conserved differentiative process by which haploid gametes are produced, is a complex and tightly regulated nuclear process. The murine Meig1 gene was previously shown to have a germ cell-specific transcript which is abundantly expressed during meiosis, in both males and females, suggesting that it is involved in meiotic processes. Protein analysis revealed that MEIG1 appears in multiple phosphorylated forms, including two dimeric forms of M(r) 31,000 and 32,000, which exhibit a developmentally regulated switch in their relative abundance. The tyrosine-phosphorylated M(r) 31,000 form becomes the dominant form once the cells enter meiosis. In this study we show that the M(r) 31,000 dimeric form appears in the nuclear fraction of testicular protein extract, whereas the M(r) 32,000 dimeric form and the monomeric forms of MEIG1 remain cytoplasmic. The appearance in the nuclear fraction is developmentally regulated, coinciding with progression of the first spermatogenic wave through meiotic prophase I. Utilizing immunocytochemistry we show that nuclear localization is apparent in primary spermatocytes through their maturation into elongated spermatozoa, but not in either somatic cells or germ cells from early postnatal pups. We also show that MEIG1 associates specifically with meiotic chromosomes in vivo. These results indicate that in germ cells, the M(r) 31,000 dimeric form enters the nucleus during the first meiotic prophase and binds to the meiotic chromatin. Possible nuclear functions, as well as possible modes of nuclear localization, are discussed.

Tlk, a novel evolutionarily conserved murine serine threonine kinase, encodes multiple testis transcripts

Hypothesizing that genes important in meiotic processes in mammals might have evolutionarily conserved counterparts in lower organisms, we used the yeast IME2 meiotic gene (serine threonine kinase) as a probe for screening a mouse testis cDNA library. This screening resulted in identification of a novel putative serine threonine kinase. Although it did not exhibit significant homology to IME2, it did show significant sequence homology to the Tousled kinase in Arabidopsis. Tousled is associated with various differentiative processes including differentiation of the reproductive organs. The new murine gene was designated accordingly Tlk (Tousled like kinase). Tousled like kinase sequences have been reported to occur in C. elegans and in the human. Positive hybridization signals obtained in zooblot analysis suggest evolutionary conservation of Tlk throughout the phylogenetic ladder. Four distinct Tlk transcripts were detected in mouse testis, at least one of which is testis-specific. Northern and in situ hybridization analyses revealed that in normal testis, Tlk is expressed predominantly in pachytene spermatocytes and in round spermatids. Transcripts differ from one another in their 3' untranslated region, resulting from use of different polyadenylation sites, and in the length of their 5' region. Within the coding region, three of the putative peptides share the kinase and C-terminal domains but differ in their N-terminal domain, suggesting that the latter may be involved in the regulation of Tlk's function. We conclude that although Tlk might have an essential role in all tissues, these kinases are likely to take part in the complex array of phosphorylations involved in regulating spermatogenesis.

Two alternatively spliced Meig1 messenger RNA species are differentially expressed in the somatic and in the germ-cell compartments of the testis

Previous studies regarding the transcriptional pattern of the murine Meig1 gene (formally designated meg1) suggested that its transcription is restricted to germ cells at the first meiotic prophase, in both primary spermatocytes and primary oocytes. However, protein analysis revealed that certain forms of the MEIG1 protein exist in testes of early postnatal pups at stages that have no germ cells in the testis, excluding very few primitive type A spermatogonia cells. This suggested that MEIG1 expression is not confined to germ cells. In this study, we show that testicular somatic cells do, indeed, express MEIG1. This is especially evident in Leydig cells, where this protein is highly abundant. We also demonstrate that alternatively spliced mRNAs of Meig1 are differentially transcribed in the germ cell and the somatic compartments of the testis. There is a very low level of somatic transcript, whether labile or transcriptionally regulated, in contrast to the abundant MEIG1 protein in the somatic cells. This implies that the somatic transcript is very efficiently translated and reconfirms that protein levels do not necessarily reflect transcript abundancy. Structural features of the Meig1 transcript that would be expected to inhibit translation are discussed in light of the efficient translation of this RNA species.

The human Pim-2 proto-oncogene and its testicular expression

In this study we describe the cloning of a human gene, encoding a protein that shares 90% identity and 93% similarity at the primary structure level, with the mouse Pim-2 gene. The gene was designated hPim-2. Structural features suggest that like the mouse Pim-2, hPim-2 is also a serine threonine kinase. At the RNA level, two hPim-2 transcripts were identified. The first, 2.2 kb, is highly expressed in hematopoietic tissues and in leukemic and lymphoma cell lines (K-562, HL-60 and RAJI). It also shows considerable high levels in testis, small intestine, colon and human colorectal adenocarcinoma cells (SW480). A second transcript, 5.0 kb in size, could be detected only in spleen, thymus, small intestine and colon and in the K-562 and RAJI cell lines. In situ hybridization analysis of biopsies taken from testes of men with complete or partial spermatogenesis revealed that the gene is expressed in primary spermatocytes. In the absence of germ cells, signal could be detected over specific cells in the well developed interstitial region. These results suggest a role for hPim-2 in proliferating cells as well as during meiosis. A possible connection between hPim-2 and apoptosis is discussed.

Developmental schedule of the postnatal rat testis determined by flow cytometry

Analysis of the biochemical events and the genes expressed at various postnatal developmental stages in the testis of mammals is of great importance for understanding spermatogenesis in general and meiosis in particular. A prerequisite for such an analysis is the characterization of a detailed developmental schedule of the postnatal testis. In this study we used four-parameter flow cytometry analysis to determine a detailed testicular developmental schedule in rats as compared to mice. A dot plot of forward-scatter/side-scatter of testicular cell suspensions from mature animals revealed 7 distinct subpopulations within the testis. These, when analyzed by fluorescence parameters, were divided into 4 levels of fluorescence: cells containing 4d DNA, 2d DNA, and 2 levels of haploid cells. Observing the acquisition pattern of these subpopulations during postnatal development, we were able to suggest the following developmental schedule for the rat. At postnatal Days 6-7, the testis contains somatic cells and spermatogonia cells only. By Days 13-14, leptotene spermatocytes appear; by Days 17-18, zygotene spermatocytes are present; by Days 19-20 and Days 22-23, early and late pachytene spermatocytes, respectively, are seen. Haploid round spermatids first appear at Days 24-25 and elongating spermatids by Days 30-31; by Day 36, elongated spermatozoa can be found.

A switch in the phosphorylation state of the dimeric form of the Meg1 protein correlates with progression through meiosis in the mouse

meg1 is a murine gene that encodes for a 0.75-kb transcript that in mature male mice is expressed exclusively in the testis. This transcript starts to accumulate in early stages of the first meiotic prophase and reaches a peak in pachytene spermatocytes. In females, meg1 transcripts are detectable only in ovaries of embryos with oocytes that have reached the prophase stage of the first meiotic division. No meg1 transcripts can be detected in adult ovaries. meg1 is, therefore, assumed to be involved with meiotic processes. In this study, specific polyclonal antibodies were raised against the Meg1 protein and were used to demonstrate that this protein is indeed specific to the testis. Western blot analysis of immunoprecipitated Meg1 protein revealed multiple bands (in the range of M(r) 12,000-18,000), some of which where recognized by anti-phosphotyrosine antibodies, suggesting that in vivo, Meg1 appears in multiple phosphorylated forms. Western analysis of purified M(r) 15,000 recombinant Meg1 protein, under nonreducing conditions, revealed an apparent M(r) 31,000 band, suggesting that Meg1 can form a homodimer via S-S bonds. Analysis of Meg1 from postnatal testes at different developmental stages revealed that in addition to the multiple monomeric forms of Meg1, two dimeric forms of about M(r) 31,000 and M(r) 32,000 were consistently detected. A developmentally regulated switch in the relative predominance of these two dimeric forms was apparent. The M(r) 31,000 form, which is tyrosine phosphorylated, becomes the predominant form once the cells enter meiosis. These results suggest that dimerization and phosphorylation/dephosphorylation reactions might regulate the function of Meg1 during meiosis.

Proenkephalin gene expression in testicular interstitial cells is down-regulated coincident with the appearance of pachytene spermatocytes

Two distinct forms of proenkephalin messenger RNA (mRNA) are present in the murine testis, a family of 1.7 kilobases (kb), germ cell-specific transcripts and a 1.45-kb form that is also found in somatic tissues. In situ hybridization and molecular analysis of purified spermatogenic cell types were used to characterize the cellular localization of these different transcripts during development of the mouse testis. Both forms of proenkephalin mRNA were observed in isolated germ cells by RNA gel-blot analysis, but in distinct developmental patterns; the 1.7-kb transcripts were present in cells undergoing meiosis and spermiogenesis, whereas the 1.45-kb mRNA was detected primarily in type B spermatogonia. In contrast, in situ hybridization analysis did not detect significant amounts of the 1.45-kb transcript in any spermatogenic cell type. Using transcript-specific probes, distinct patterns of developmental expression were evident for the two mRNAs. The 1.45-kb transcript was the only form detected in the prepubertal testis, where it was localized mainly in interstitial cells. In contrast, the 1.7-kb transcripts were the major mRNAs observed in the adult testis and were localized to spermatogenic cells. A transition from the prepubertal to the adult pattern occurred on or about postnatal day 21, when proenkephalin-expressing pachytene spermatocytes begin to populate the seminiferous tubules. In situ hybridization analysis further demonstrated that proenkephalin gene expression in mutant (at/at) mice, which lack germ cells, was identical to that observed in the early prepubertal testis. These results suggest that the 1.45-kb proenkephalin mRNA is developmentally down-regulated in mouse interstitial cells and that this process requires ongoing spermatogenesis.

Developmentally regulated expression during gametogenesis of the murine gene meg1 suggests a role in meiosis

Previous studies have shown that in adult male mice, expression of the meg1 gene is restricted to meiotic and early postmeiotic testicular germ cells. We have now analyzed the expression of meg1 during postnatal testicular development and the comparable meiotic stages in the female. The 0.75 kb transcript for meg1 begins to accumulate in testes at d8-9 of postnatal (pn) development, coincident with the entry of germ cells into meiosis, and is expressed most abundantly at pn d14 and subsequent stages, when the spermatocytes have entered pachytene. In situ hybridization analysis shows that meg1 is expressed at very low levels in leptotene cells and increases as the cells progress through zygotene and pachytene stages. In the embryonic ovary, meg1 is not detected until after day 15 of gestation when the cells have entered the pachytene stage of meiosis I. In situ hybridization analysis suggests that meg1 transcripts are expressed at higher levels in degenerating rather than in healthy pachytene stage oocytes; meg1 is not expressed in any cells of the adult ovary, regardless of the stage of follicular development. These results suggest that meg1 is indeed a meiosis-associated gene in both male and female germ cells through the pachytene stage of meiosis I and appears to exhibit sex-specific differences in its expression thereafter.

Identification and characterization of the regulated pattern of expression of a novel mouse gene, meg1, during the meiotic cell cycle

The gene designated meg1 (meiosis expressed gene) is a new mouse gene identified during a search for mammalian genes potentially involved in meiotic processes. Two classes of complementary DNAs were isolated from an adult mouse testis complementary DNA library, which shared the same 3' end including the entire putative coding region but differed in their 5' ends. Only one of these complementary DNA classes appeared to correspond to the very abundant 0.75-kilobase testicular transcript of meg1. Sequence analysis predicts a 10.8-kilodalton protein which is highly charged and lysine rich. It is also relatively rich in potential phosphoacceptor amino acids (approximately 17%), several of which are located in phosphorylation consensus sequences. The pattern of expression of meg1 was studied utilizing a combined Northern blot and in situ hybridization analysis. Of the adult tissues examined, meg1 transcripts were detected exclusively in testis. Analysis of mRNA from testes of two germ cell deficient mutant strains did not reveal significant levels of meg1 transcripts. Analysis of RNA from enriched populations of spermatogenic cells from adult testes and localization by in situ hybridization revealed that meg1 transcripts are most abundant in pachytene spermatocytes. These results suggest a role for meg1 during germ cell differentiation, possibly during meiotic prophase.

Production of F1 and F 2 diploid gynogenetic tilapias and analysis of the "Hertwig curve" obtained using ultraviolet irradiated sperm

In this study, a Hertwig effect with a non-typical biphasic curve was obtained using sperm irradiated with increasing intensities of UV. The first phase of the UV curve appeared to be quite different from that normally demonstrated using γ or x-ray irradiation. This difference is characterised throughout the length of the first phase by (1) low and stable embryo hatching rates of about 3.5%, and (2) exclusive formation of haploid embryos at any irradiation intensity. Additionally, at both phases, the ability of the sperm to induce morula formation was not affected at all, and no aneuploidy nor chromosomal fragments could be seen. Therefore, it was suggested that in this fish the lethal effect of UV irradition on sperm is mainly expressed on early differentiative events during embryogenesis, which lead to a degeneration of the embryos during early stages of their development. The possible mechanism by which haploidy is achieved during the first phase is discussed. Two generations of diploid gynogenetic tilapias were induced by activating Oreochromis aureus eggs with UV-irradiated O. niloticus sperm and by using the heat-shock technique, at optimized conditions, for the prevention of the second polar body extrusion. Species specific dominant genetic markers (serum esterases and tail striation) were used to confirm the exclusive content of the maternal genome in gynogenetic offspring. Very low survival rates (0.36%) were shown in F1 gynogenetic fish as well as a high incidence of malformations among survivors. In the second gynogenetic generation, both significantly higher survival rates (3.6%) and a considerably reduced incidence of malformations were obtained. We suggest that low frequencies of recombination occur in this species and cause a rapid increase in the inbreeding level. This is followed by the expression of lethal and defective genes that are considerably reduced after second generation selection.

The induction of triploidy in Oreochromis aureus by heat shock

Triploid fish were obtained using heat-shock treatment. The optimal conditions for the heat shock (39.5±0.2°C for 3.5-4 min) as well as the exact zygote age (3 min) at which this heat shock was applied were studied. Results showed that this treatment gives rise to 100% of triploid fish with a satisfactory survival rate of 61% beyond the yolk sac resorption. The genital papillae of this triploid fish were underdeveloped in comparison to normal diploid fish. However, no morphological or growth-rate differences between diploid and triploid fish could be observed up to the age of 6 months. Triploidy was assessed by the karyotyping of embryo cells or adult PHA-stimulated lymphocytes, or by erythrocyte measurements. The occurrence of a heat-shock sensitive event at the zygotic age of 6 min is discussed.