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Denny Sakkas

Publications and source records attributed to Denny Sakkas.

24 records · Page 2Linked to original sources
PubMed2002

The apoptotic profile of human cumulus cells changes with patient age and after exposure to sperm but not in relation to oocyte maturity.

OBJECTIVE: To determine the expression of apoptosis-associated molecules on cumulus cells removed from individual oocytes of different maturity, inseminated oocytes and to investigate the possibility of an age-dependent expression. DESIGN: Analysis of apoptosis in cumulus cells isolated from oocytes of different stages of maturity. SETTING: Assisted reproductive technology program of the Birmingham Women's Hospital, Birmingham, UK. PATIENT(S): Patients undergoing intracytoplasmic sperm injection or IVF cycles. MAIN OUTCOME MEASURE(S): Percentage of positive cumulus cells when assessed for nuclear DNA damage using the terminal deoxyuridine nucleotide end-labeling assay or stained with antibodies [Fas, Fas ligand, the antiapoptotic protein Bcl-xl, and the RNA-binding protein (TIAR)]. RESULT(S): Cumulus cells collected from mature oocytes showed no significant difference in the percentage of apoptotic markers compared to those recovered from immature oocytes, whereas those from patients >/=38 years differed significantly. When cumulus cells were exposed to sperm the levels of apoptotic markers altered significantly from those not exposed to sperm. CONCLUSION(S): The results show that the cumulus cells of human oocytes are equipped with a mechanism to undergo apoptosis and that patient age and the exposure of cumulus cells to sperm can alter their profiles of apoptotic markers.

Adult↗
PubMed2002

Nature of DNA damage in ejaculated human spermatozoa and the possible involvement of apoptosis.

Numerous studies have shown the presence of DNA strand breaks in human ejaculated spermatozoa. The nature of this nuclear anomaly and its relationship to patient etiology is however poorly understood. The aim of this study was to investigate the relationship between nuclear DNA damage, assessed using the TUNEL assay and a number of key apoptotic markers, including Fas, Bcl-x, and p53, in ejaculated human spermatozoa from men with normal and abnormal semen parameters. We also determined the nature of the DNA damage by examining the percentage of ejaculated spermatozoa exhibiting DNA damage using the comet assay and by challenging sperm chromatin to attack by micrococcal nuclease S7 and DNase I. We show that TUNEL positivity and apoptotic markers do not always exist in unison; however, semen samples that had a low sperm concentration and poor morphology were more likely to show high levels of TUNEL positivity and Fas and p53 expression. In addition, the DNA damage in ejaculated human sperm is represented by both single- and double-stranded DNA breaks, and access to the DNA is restricted by the compacted nature of ejaculated spermatozoa. This DNA protection is poorer in men with abnormal semen parameters. We propose that the presence of DNA damage is not directly linked to an apoptotic process occurring in spermatozoa and arises due to problems in the nuclear remodeling process. Subsequently, the presence of apoptotic proteins in ejaculated spermatozoa may be linked to defects in cytoplasmic remodeling during the later stages of spermatogenesis.

Apoptosis↗
PubMed2001

Identification and localization of T-type voltage-operated calcium channel subunits in human male germ cells. Expression of multiple isoforms.

Low voltage activated, voltage-operated Ca(2+) channels are expressed in rodent male germ cells and are believed to be pivotal in induction of the acrosome reaction in mouse spermatozoa. However, in humans, very little is known about expression of voltage-operated Ca(2+) channels in male germ cells or their function. We have used reverse transcription-polymerase chain reaction, in situ hybridization, and patch clamp recording to investigate the expression of low voltage activated voltage-operated Ca(2+) channels in human male germ cells. We report that full-length transcripts for both alpha(1G) and alpha(1H) low voltage activated channel subunits are expressed in human testis. Multiple isoforms of alpha(1G) are present in the testis and at least two isoforms of alpha(1H), including a splice variant not previously described in the human. Transcripts for all the isoforms of both alpha(1G) and alpha(1H) were detected by reverse transcription-polymerase chain reaction on mRNA isolated from human spermatogenic cells. In situ hybridization for alpha(1G) and alpha(1H) localized transcripts both in germ cells and in other cell types in the testis. Within the seminiferous tubules, alpha(1H) was detected primarily in germ cells. Using the whole cell patch clamp technique, we detected T-type voltage-operated Ca(2+) channel currents in isolated human male germ cells, although the current amplitude and frequency of occurrence were low in comparison to the occurrence of T-currents in murine male germ cells. We conclude that low voltage activated voltage-operated Ca(2+) channels are expressed in cells of the human male germ line.

Animals↗
PubMed2000

Possible consequences of performing intracytoplasmic sperm injection (ICSI) with sperm possessing nuclear DNA damage.

A number of studies have confirmed that sperm with damaged nuclear DNA are present in human ejaculate. It appears that these sperm are more likely to occur in men with low concentrations of sperm, or poor sperm motility or morphology. In assisted reproductive techniques, in particular intracytoplasmic sperm injection (ICSI), there is a higher statistical chance that sperm possessing damaged DNA will be selected and used to fertilize oocytes. In light of this observation, the question of whether human sperm with damaged DNA can impair fertilization and embryo development is examined.

Journal Article↗
PubMedDate not supplied

Abnormal spermatozoa in the ejaculate: abortive apoptosis and faulty nuclear remodelling during spermatogenesis.

The mechanisms responsible for producing abnormal spermatozoa in the ejaculate are relatively unknown. Numerous studies have now shown the presence of nuclear DNA strand breaks in human ejaculated spermatozoa and the abnormal persistence of apoptotic marker proteins. The reason why human spermatozoa, in particular from men with abnormal semen parameters, possess these abnormalities is still not clear. Two processes that have been linked to the presence of nuclear DNA strand breaks in spermatozoa are anomalies in apoptosis during spermatogenesis or problems in the replacement of histones with protamines during spermiogenesis. Understanding the mechanisms responsible for producing abnormal spermatozoa in the human will improve knowledge about certain causes of male infertility.

Apoptosis↗