Biomedical subjects

R Pelletier

Publications and source records attributed to R Pelletier.

At least 19 recordsLinked to original sources

PubMed2000

Evidence for a genetic predisposition towards acute rejection after kidney and simultaneous kidney-pancreas transplantation.

BACKGROUND: In vitro production of tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin 10 (IL-10), and transforming growth factor-beta (TGF-beta) correlate with their respective genetic polymorphisms. We analyzed the relationship between these genetic polymorphisms and posttransplant outcome. METHODS: Using DNA polymerase chain reaction (PCR) technology, polymorphisms for TNF-alpha, IFN-gamma, IL-10, and TGF-beta were determined for 82 kidney (K) and 19 simultaneous kidney-pancreas (SKP) recipients. These results were analyzed with regard to the incidence of acute rejection (AR), and the timing and severity of the first AR episode. RESULTS: A high TNF-alpha production phenotype correlated with recurrent acute rejection (AR) episodes (P<0.026). Compared with the low TNF-alpha production phenotype, more patients with the high production phenotype had a post-AR serum creatinine >2.0 mg/dl, but this was not statistically significant (64 vs. 35%, P=0.12). There was no relationship between TNF-alpha genotype and the time to first AR episode or incidence of graft loss. IFN-gamma production phenotype showed no correlation with any of these clinical outcome parameters. There was an increase in AR incidence as the IL-10 production phenotype increased (low, intermediate, high), but only in low TNF-alpha producer phenotypes (P=0.023). CONCLUSIONS: Patients with a polymorphic cytokine genotype putatively encoding for high in vivo TNF-alpha production, and to a lesser extent IL-10 cytokine genotypes putatively encoding for higher levels of in vivo IL-10 production, had a worse clinical outcome regarding AR episodes. These data support the hypothesis that the strength of alloimmune responsiveness after transplantation in part is genetically determined.

Acute Disease↗

PubMed2000

Genome organization in the human sperm nucleus studied by FISH and confocal microscopy.

The sperm nucleus has a unique chromatin structure where the DNA is highly condensed and associated with specific proteins, the protamines. It is a nondividing cell which is also transcriptionally inactive. After fusion with an oocyte, the sperm nucleus undergoes decondensation and, in the same time, starts replication and transcription. It has been suggested that somatic chromosomes during interphase are organized in territories which display a cell type and cell cycle specific distribution. The purpose of this work was to investigate whether chromosomes would also have a specific distribution in the sperm nucleus, which could be related to its inactive state, and have implications on the early stages of fertilization. In the present study, centromeric and telomeric sequences were detected by fluorescent techniques performed on human decondensed spermatozoa. Chromosome painting probes were used to detect the chromosome X and chromosome 13 on interphase sperm nuclei. The fluorescent signals were captured in 3D with a confocal microscope. For each of these chromatin structures, the volume, position, and distribution of the signals were analyzed in samples of 30 nuclei with the help of image analysis software. The centromeres appeared grouped in several foci that were randomly distributed within the sperm nucleus. The telomeres gave an approximately haploid number of small signals, evenly distributed throughout the nucleus. The chromosomes X and 13 occupied 4.7% and 3. 7% of the total nuclear volume, respectively. Interestingly, the X chromosome territory showed a preferential position in the anterior half of the volume of the nucleus, whereas chromosome 13 had a random position. This work shows a particular distribution of chromosome territories in the human sperm nucleus that could be related to mechanisms implicated in its specific functions. The analysis of more chromosomes and chromosomal structures, including the Y chromosome, would help to understand the structure of the human sperm chromatin, and its fundamental and clinical implications.

Cell Nucleus↗

PubMed2000

Follicular development and atresia in the B6.Y(TIR) sex-reversed mouse ovary.

The B6.Y(TIR) mouse fails to develop normal testes despite transcription of Sry, the primary testis-determining gene on the Y chromosome. Consequently, B6.Y(TIR) fetuses with bilateral ovaries develop into apparently normal but infertile females. This infertility can be mainly attributed to oocyte incompatibility for postfertilization development. In addition, abnormality in preovulatory follicles and rapid loss of oocytes have been observed in XY ovaries. This study examined the effect of gonadotropins on follicular development and atresia in B6.Y(TIR) prepubertal females. The results show that untreated XY females had fewer late preantral follicles and their frequency of atresia was lower. No other difference was found when they were compared with XX females. After treatment with gonadotropins for 24 h, frequency of atresia decreased in both XX and XY ovaries. After 48 h, most preovulatory follicles in XY ovaries were nonatretic, but the oocytes often were denuded. Immunocytochemical staining for connexin 43 detected punctate foci along the oocyte plasma membrane. The density of these foci changed during follicular development, which was similar in XX and XY ovaries. In conclusion, follicular development and atresia under the control of gonadotropins is not influenced by defective oocytes until the preovulatory phase.

Animals↗

PubMed2000

Emergence of resistance of Candida albicans to clotrimazole in human immunodeficiency virus-infected children: in vitro and clinical correlations.

Oropharyngeal candidiasis (OPC) is a common opportunistic infection in human immunodeficiency virus (HIV)-infected patients and other immunocompromised hosts. Clotrimazole troches are widely used in the treatment of mucosal candidiasis. However, little is known about the potential contribution of clotrimazole resistance to the development of refractory mucosal candidiasis. We therefore investigated the potential emergence of resistance to clotrimazole in a prospectively monitored HIV-infected pediatric population receiving this azole. Adapting the National Committee for Clinical Laboratory Standards M27-A reference method for broth antifungal susceptibility testing of yeasts to clotrimazole, we compared MICs in macrodilution and microdilution assays. We further analyzed the correlation between these in vitro findings and the clinical response to antifungal therapy. One isolate from each of 87 HIV-infected children was studied by the macrodilution and microdilution methods. Two inoculum sizes were tested by the macrodilution method (10(3) and 10(4) CFU/ml) in order to assess the effect of inoculum size on clotrimazole MICs. The same isolates also were tested using a noncolorimetric microdilution method. Clotrimazole concentrations ranged from 0.03 to 16 microg/ml. Readings were performed after incubation for 24 and 48 h at 35 degrees C. For 62 (71.2%) of 87 clinical isolates, the MICs were low (< or =0.06 microg/ml). The MIC for 90% of the strains tested was 0.5 microg/ml, and the highest MIC was 8 microg/ml. There was no significant difference between MICs at the two inoculum sizes. There was 89% agreement (+/-1 tube) between the microdilution method at 24 h and the macrodilution method at 48 h. If the MIC of clotrimazole for an isolate of C. albicans was > or =0.5 microg/ml, there was a significant risk (P < 0.001) of cross-resistance to other azoles: fluconazole, > or = 8 microg/ml (relative risk [RR] = 8.9); itraconazole, > or =1 microg/ml (RR = 10). Resistance to clotrimazole was highly associated with clinically overt failure of antifungal azole therapy. Six (40%) of 15 patients for whom the clotrimazole MIC was > or =0.5 microg/ml required amphotericin B for refractory mucosal candidiasis versus 4 (5.5%) of 72 for whom the MIC was <0.5 microg/ml (P = 0.001; 95% confidence interval = 2.3 to 22; RR = 7.2). These findings suggest that an interpretive breakpoint of 0.5 microg/ml may be useful in defining clotrimazole resistance in C. albicans. The clinical laboratory's ability to determine MICs of clotrimazole may help to distinguish microbiologic resistance from the other causes of refractory OPC, possibly reducing the usage of systemic antifungal agents. We conclude that resistance to clotrimazole develops in isolates of C. albicans from HIV-infected children, that cross-resistance to other azoles may develop concomitantly, and that this resistance correlates with refractory mucosal candidiasis.

AIDS-Related Opportunistic Infections↗

PubMed2000

Seeking medical advice if HIV symptoms are suspected. Qualitative study of beliefs among HIV-negative gay men.

OBJECTIVE: To identify beliefs associated with seeking medical advice promptly when symptoms of HIV infection are suspected among HIV-negative gay men. DESIGN: Qualitative study of beliefs among focus group participants. SETTING: Quebec city, Que, metropolitan area. PARTICIPANTS: Referred sample of 20 HIV-negative gay men 18 to 45 years old who attended bars, university, or gay associations in Quebec city. METHOD: Three focus groups of five to seven subjects were formed and each 2-hour session was tape-recorded. MAIN OUTCOME FINDINGS: Participants thought that seeking medical advice promptly when symptoms of HIV are suspected would help them be informed about their health status and would eliminate unnecessary anxiety and fear, but would force them to face reality and make major changes. Barriers were the quality of the relationship with their physicians and concern about discussing their sexual lives. Normative beliefs were sought from members of community groups, circles of close friends, health providers, and the media. CONCLUSIONS: Several beliefs could influence the motivation of seronegative gay men to seek medical advice promptly when symptoms of HIV infection are suspected. These beliefs should be integrated into programs promoting early consultation with physicians and into clinical counseling, as integration could facilitate early treatment and care. Physicians should give special attention to establishing relationships of trust with these patients.

Adolescent↗

PubMed1999

Functional genomic mapping of an early-activated centromeric mammalian origin of DNA replication.

Ors12, a mammalian autonomously replicating sequence (812 bp), was previously isolated by extrusion of African green monkey (CV-1 cells) nascent DNA from active replication bubbles. It contains a region of alpha-satellite extending 168-bp from the 5'-end, and a nonrepetitive portion extending from nucleotide position 169 to nucleotide 812 that is present in less than nine copies per haploid genome. Ors12 is capable of transient autonomous DNA replication in vivo and in vitro, associates with the nuclear matrix in a cell cycle-dependent manner, and hybridizes at the centromeric region of six CV-1 cell chromosomes as well as a marker chromosome. To demonstrate that DNA replication initiates at ors12 at a native chromosomal locus, a 14.2 kb African green monkey genomic clone was isolated and sequence information was obtained that allowed us to generate eight sets of PCR primers spanning a region of 8 kb containing ors12. One set of primers occurred inside ors12. These primers were used to amplify nascent DNA strands from asynchronously growing CV-1 and African green monkey kidney (AGMK) cells, using noncompetitive and competitive PCR-based mapping methodologies. Both assays showed that DNA replication in vivo initiates preferentially in a 2.3 kb region containing ors12, as well as at a second site located 1.7 kb upstream of ors12. This study provides the first demonstration of genomic function for a centromeric mammalian origin of DNA replication, originally isolated by nascent strand extrusion.

Animals↗

PubMed1999

Identification of initiation sites for DNA replication in the human dnmt1 (DNA-methyltransferase) locus.

Vertebrates have developed multiple mechanisms to coordinate the replication of epigenetic and genetic information. Dnmt1 encodes the maintenance enzyme DNA-methyltransferase, which is responsible for propagating the DNA methylation pattern and the epigenetic information that it encodes during replication. Direct sequence analysis and bisulfite mapping of the 5' region of DNA-methyltransferase 1 (dnmt1) have indicated the presence of many sequence elements associated with previously characterized origins of DNA replication. This study tests the hypothesis that the dnmt1 region containing these elements is an origin of replication in human cells. First, we demonstrate that a vector containing this dnmt1 sequence is able to support autonomous replication when transfected into HeLa cells. Second, using a gel retardation assay, we show that it contains a site for binding of origin-rich sequences binding activity, a recently purified replication protein. Finally, using competitive polymerase chain reaction, we show that replication initiates in this region in vivo. Based on these lines of evidence, we propose that initiation sites for DNA replication are located between the first intron and exon 7 of the human dnmt1 locus.

Chromosome Mapping↗

PubMed1999

Carboxy-substituted cinnamides: a novel series of potent, orally active LTB4 receptor antagonists.

A series of carboxy-substituted cinnamides were investigated as antagonists of the human cell surface leukotriene B4 (LTB4) receptor. Binding was determined through measurement of [3H]LTB4 displacement from human neutrophils. Receptor antagonism was confirmed through a functional assay, which measures inhibition of Ca2+ release in human neutrophils. Potent antagonists were discovered through optimization of a random screening hit, a p-(alpha-methylbenzyloxy)cinnamide, having low-micromolar activity. Substantial improvement of in vitro potency was realized by the attachment of a carboxylic acid moiety to the cinnamide phenyl ring through a flexible tether, leading to identification of compounds with low-nanomolar potency. Modification of the benzyloxy substituent, either through ortho-substitution on the benzyloxy phenyl group or through replacement of the ether oxygen with a methylene or sulfur atom, produced achiral antagonists of equal or greater potency. The most potent compounds in vitro were assayed for oral activity using the arachidonic acid-induced mouse ear edema model of inflammation. Several compounds in this series were found to significantly inhibit edema formation and myeloperoxidase activity in this model up to 17 h after oral administration. Representatives of this series have been shown to be potent and long-acting orally active inhibitors of the LTB4 receptor.

Administration, Oral↗

PubMed1999

Inhibition of FEN-1 processing by DNA secondary structure at trinucleotide repeats.

The mechanism by which trinucleotide expansion occurs in human genes is not understood. However, it has been hypothesized that DNA secondary structure may actively participate by preventing FEN-1 cleavage of displaced Okazaki fragments. We show here that secondary structure can, indeed, play a role in expansion by a FEN-1-dependent mechanism. Secondary structure inhibits flap processing at CAG, CGG, or CTG repeats in a length-dependent manner by concealing the 5' end of the flap that is necessary for both binding and cleavage by FEN-1. Thus, secondary structure can defeat the protective function of FEN-1, leading to site-specific expansions. However, when FEN-1 is absent from the cell, alternative pathways to simple inhibition of flap processing contribute to expansion.

DNA↗

PubMed1999

Calcium-dependent actin filament-severing protein scinderin levels and localization in bovine testis, epididymis, and spermatozoa.

We assessed the levels and localization of the actin filament-severing protein scinderin, in fetal and adult bovine testes, and in spermatozoa during and following the epididymal transit. We performed immunoblots on seminiferous tubules and interstitial cells isolated by enzymatic digestion, and on bovine chromaffin cells, spermatozoa, aorta, and vena cava. Immunoperoxidase labeling was done on Bouin's perfusion-fixed testes and epididymis tissue sections, and on spermatozoa. In addition, immunofluorescence labeling was done on spermatozoa. Immunoblots showed one 80-kDa band in chromaffin cells, fetal and adult tubules, interstitial cells, spermatozoa, aorta, and vena cava. Scinderin levels were higher in fetal than in adult seminiferous tubules but showed no difference between fetal and adult interstitial cells. Scinderin levels were higher in epididymal than in ejaculated spermatozoa. Scinderin was detected in a region corresponding with the subacrosomal space in the round spermatids and with the acrosome in the elongated spermatids. In epididymal spermatozoa, scinderin was localized to the anterior acrosome and the equatorial segment, but in ejaculated spermatozoa, the protein appeared in the acrosome and the post-equatorial segment of the head. In Sertoli cells, scinderin was detected near the cell surface and within the cytoplasm, where it accumulated near the base in a stage-specific manner. In the epididymis, scinderin was localized next to the surface of the cells; in the tail, it collected near the base of the principal cells. In Sertoli cells and epididymal cells, scinderin may contribute to the regulation of tight junctional permeability and to the release of the elongated spermatids by controlling the state of perijunctional actin. In germ cells, scinderin may assist in the shaping of the developing acrosome and influence the fertility of the spermatozoa.

Animals↗

PubMed1998

Prophylactic cholecystectomy is not indicated following renal transplantation.

BACKGROUND: The appropriate management of gallstones in patients undergoing renal transplantation is controversial. Screening for gallstones and subsequent prophylactic cholecystectomy has been recommended by some authors for kidney transplant candidates. Our program does not practice routine pretransplant screening for gallstones, and we reviewed our data to determine the outcome of our management approach. METHODS: We reviewed the records of the 1,364 currently followed patients who have undergone kidney transplant at our institution since 1985 in order to evaluate the morbidity and mortality of biliary disease in the post-transplant period. We attempted to contact all patients by telephone or mail survey for the presence of biliary tract disease or operations. RESULTS: Six hundred and sixty-two patients were fully evaluated. Fifty-two (7.85%) required cholecystectomy for stone disease. Seven patients underwent incidental cholecystectomy during other operations, 2 patients developed acalculus cholecystitis, and 14 patients with asymptomatic cholelithiasis are being followed up. Surgical indications included 38 biliary colic, 9 acute cholcystitis, 3 gallstone pancreatitis, and 2 patients who were asymptomatic. Fifty-two patients underwent 30 laparoscopic cholecystectomies, 20 open cholecystectomies, and 2 conversions. Surgery occurred from 7 days to 9.6 years following transplantation. Overall, the median hospital stay (no postoperative stay) was 4 days (range 1 to 57). Patients undergoing laparoscopy had a median stay of 2 days compared with 7 days for those undergoing an open procedure. Complications were seen in 6 patients (11.5%) with no morbidity and no graft loss. The 1-, 2-, and 5-year graft survival was 98%, 96%, and 85%, respectively, in patients undergoing cholecystectomy. CONCLUSIONS: Transplant patients are not at an increased risk for developing biliary tract disease compared with nontransplant patients. Gallstone disease does not have a negative impact on graft survival. Treatment of gallstones has a low risk and does not represent an increased risk of complications in patients following renal transplantation.

Adult↗

PubMed1998

Disomy rates for chromosomes 14 and 21 studied by fluorescent in-situ hybridization in spermatozoa from three men over 60 years of age.

In order to further investigate the paternal-age effect on meiotic non-disjunction rates for the chromosomes 14 and 21, we examined spermatozoa from three men aged > 60, using multicolour fluorescent in-situ hybridization (FISH). More than 10,000 sperm cells were analysed for each of the three subjects (A, B and C), by simultaneously hybridizing two YAC probes specific for chromosomes 14 and 21 respectively using two-colour FISH. The results show that the disomy 21 rates observed in the spermatozoa of two out of the three men aged > 60 years were higher (1.02 and 1.17% respectively) than the rates observed in eight control adults aged < 30 years (mean frequency 0.48%) analysed under similar conditions. These results suggest that there may be a small effect of age on male non-disjunction rates for chromosome 21. However, before any firm conclusions could be drawn, a much bigger sample of older men would have to be compared with a paired control population using the same FISH experimental approach.

Adult↗

PubMed1997

Deletion analysis of ors12, a centromeric, early activated, mammalian origin of DNA replication.

We have generated a panel of deletion mutants of ors12 (812-bp), a mammalian origin of DNA replication previously isolated by nascent strand extrusion from early replicating African Green monkey (CV-1) DNA. The deletion mutants were tested for their replication activity in vivo by the bromodeoxyuridine substitution assay, after transfection into HeLa cells, and in vitro by the Dpnl resistance assay, using extracts from HeLa cells. We identified a 215-bp internal fragment as essential for the autonomous replication activity of ors12. When subcloned into the vector pML2 and similarly tested, this subfragment was capable of autonomous replication in vivo and in vitro. Several repeated sequence motifs are present in this 215-bp fragment, such as TGGG(A) and G(A)AG (repeated four times each); TTTC, AGG, and CTTA (repeated 3 times each); the motifs CACACA and CTCTCT, and two imperfect inverted repeats. 22 and 16 bp long, respectively. The overall sequence of the 215-bp fragment is G/C-rich (50.2%), by comparison to the 186-bp (33.5% G/C-rich) minimal sequence required for the autonomous replication activity of ors8, another functional ors that was similarly isolated and characterized.

Base Sequence↗

PubMed1997

Meiotic behaviour of sex chromosomes investigated by three-colour FISH on 35,142 sperm nuclei from two 47,XYY males.

Meiotic segregation of sex chromosomes from two fertile 47,XYY men was analysed by a three-colour fluorescence in situ hybridisation procedure. This method allows the identification of hyperhaploidies (spermatozoa with 24 chromosomes) and diploidies (spermatozoa with 46 chromosomes), and their meiotic origin (meiosis I or II). Alpha-satellite probes specific for chromosomes X, Y and 1 were observed simultaneously in 35,142 sperm nuclei. For both 47,XYY men (24,315 sperm nuclei analysed from one male and 10,827 from the other one) the sex ratio differs from the expected 1:1 ratio (P < 0.001). The rates of disomic Y, diploid YY and diploid XY spermatozoa were increased for both 47,XYY men compared with control sperm (142,050 sperm nuclei analysed from five control men), whereas the rates of hyperhaploidy XY, disomy X and disomy 1 were not significantly different from those of control sperm. These results support the hypothesis that the extra Y chromosome is lost before meiosis with a proliferative advantage of the resulting 46,XY germ cells. Our observations also suggest that a few primary spermatocytes with two Y chromosomes are able to progress through meiosis and to produce Y-bearing sperm cells. A theoretical pairing of the three gonosomes in primary spermatocytes with an extra sex chromosome, compatible with active spermatogenesis, is proposed.

Adult↗

PubMed1997

Increased aneuploid frequency in spermatozoa from a Hodgkin's disease patient after chemotherapy and radiotherapy.

The frequency of sperm aneuploidy was investigated by fluorescence in situ hybridization (FISH) in a Hodgkin's disease patient shortly after he had received chemotherapy and radiotherapy. Sperm karyotyping of the same patient had previously shown multiple structural abnormalities in most spermatozoa immediately after radiotherapy (day 0), whereas most spermatozoa collected 5 wk later (day 38) exhibited normal metaphase divisions (Rousseaux et al., 1993). Variations in the frequency of aneuploidy could not be detected by sperm karyotyping. Multicolor FISH on interphase spermatozoa revealed an increase in the rate of disomy for chromosomes 1, 6, 11, X, and Y at day 0 as well as at day 38. The high frequency of 24,XY (nondisjunction at meiosis I) and 24,XX (nondisjunction at meiosis II) spermatozoa (8.46% and 1.64% at day 0, respectively) from the Hodgkin's disease patient suggests that both meiosis I and II are affected and that the X chromosome is frequently involved in such malsegregation events. The rate of 46,XY diploidy was also increased in the patient's sperm, up to 0.62% at day 0. While radiotherapy probably affected the postmeiotic cells (spermatids), the patient's cancer and/or chemotherapy are the two major factors that could have affected the dividing spermatogonia and/or spermatocytes, resulting in high aneuploidy rates.

Aneuploidy↗

PubMed1996

Increased incidence of hyperhaploid 24,XY spermatozoa detected by three-colour FISH in a 46,XY/47,XXY male.

Meiotic segregation of gonosomes from a 46,XY/47,XXY male was analysed by a three-colour fluorescence in situ hybridisation (FISH) procedure. This method allows the identification of hyperhaploid spermatozoa (with 24 chromosomes), diploid spermatozoa (with 46 chromosomes) and their meiotic origin (meiosis I or II). Alpha satellite DNA probes specific for chromosomes X, Y and 1 were observed on 27,097 sperm nuclei. The proportions of X- and Y-bearing sperm were estimated to 52.78% and 43.88%, respectively. Disomy (24,XX, 24,YY, 24,X or Y,+1) and diploidy (46,XX, 46,YY, 46,XY) frequencies were close to those obtained from control sperm, whereas the frequency of hyperhaploid 24,XY spermatozoa (2.09%) was significantly increased compared with controls (0.36%). These results support the hypothesis that a few 47,XXY germ cells would be able to complete meiosis and to produce mature spermatozoa.

Adult↗

PubMed1995

Sperm nuclei analysis of a Robertsonian t(14q21q) carrier, by FISH, using three plasmids and two YAC probes.

The meiotic segregation of chromosomes 14 and 21 was analysed in 1116 spermatozoa from an oligoasthenospermic carrier of a Robertsonian translocation t(14q21q), and in 16,392 spermatozoa from a control donor, using two-colour fluorescence in situ hybridisation (FISH). Two YAC probes (cloned in yeast artificial chromosomes) specific for regions on the long arms of these chromosomes were co-hybridised. Of the spermatozoa, 12% were unbalanced, resulting from adjacent segregations. Chromosomes X, Y and 1 were also simultaneously detected in 1335 spermatozoa from the same carrier. Whereas gonosomal disomy rates were not significantly different from those of the control donors, disomy 1 were slightly but significantly increased to 0.7%. The diploidy rate was also slightly increased to approximately 1% in the translocation carrier.

Adult↗

PubMed1995

Human sperm chromosome analysis after microinjection into hamster oocytes.

PURPOSE: Subzonal sperm insemination (SUZI) into hamster oocytes was performed to establish the karyotypes of the fertilizing spermatozoa. METHODS: Spermatozoa from two males with normal semen parameters were microinjected. Of 72 (52 + 20) analyzed sperm chromosome metaphases, only 1 (1.4%) was considered abnormal, showing a structural abnormality. RESULTS: No hyperhaploidy was observed. Rates of sperm chromosomal abnormalities after microinjection were not higher than those reported previously using zona-free egg insemination, suggesting that the SUZI procedure per se does not increase sperm chromosomal abnormalities. CONCLUSIONS: The use of subzonal insemination into hamster oocytes for the study of human sperm chromosomes in males with low sperm counts is discussed.

Animals↗