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C Mendoza

Publications and source records attributed to C Mendoza.

At least 55 records · Page 3Linked to original sources
PubMed1998

Treatment of severe male infertility by micromanipulation-assisted fertilization: news and views.

Recent progress in cell micromanipulation has made it possible to achieve fertilization even with highly deficient male gametes, by injecting them directly to oocyte cytoplasm. This technique, known as intracytoplasmic sperm injection (ICSI), has proved efficient in most types of sperm pathology. However, ICSI fails when injected spermatozoa are not capable of supporting the process of oocyte activation or when they carry genetic abnormalities incompatible with normal embryonic development. Abnormalities of oocyte activation and the transmission of genetic anomalies to the progeny are also two major concerns relating to the clinical use of ICSI. The use of micromanipulation-assisted fertilization in cases of male germ cell maturation arrest, namely fertilization by round spermatid injection (ROSI), has brought preliminary clinical results, and the improvement of ROSI clinical efficacy remains a major challenge for future research.

Acrosome Reaction↗
PubMed1998

Human infection with Trypanosoma cruzi induces parasite antigen-specific cytotoxic T lymphocyte responses.

Experimental models of Chagas' disease, an infection caused by the intracellular protozoan Trypanosoma cruzi, have demonstrated the crucial immunoprotective role played by CD8(+) T lymphocytes. These cells dominate inflammatory foci in parasitized tissues and their elimination from mice leads to uncontrolled parasite replication and subsequent death of the infected host. A trypomastigote surface antigen, TSA-1, and two amastigote surface molecules, ASP-1 and ASP-2, were recently identified as targets of CD8(+) cytotoxic T lymphocytes (CTL) in T. cruzi-infected mice. Until now, however, there was no evidence for the development of parasite-specific CTL in T. cruzi-infected humans. In this study, human CTL specific for TSA-1-, ASP-1-, and ASP-2-derived peptides were detected in the peripheral blood mononuclear cells from 21 of 24 HLA-A2(+) T. cruzi-infected patients. CTL recognition was antigen specific, A2-restricted, and CD8(+) T cell-dependent. Demonstration of human CTL against T. cruzi and against target molecules identified using the murine model provides important information for the optimal design and evaluation of vaccines to prevent or ameliorate Chagas' disease.

Animals↗
PubMed1998

Long-term survival in patients with ovarian metastases from colorectal carcinoma.

BACKGROUND: Ovarian metastases (OM) are a relatively uncommon consequence of primary colorectal carcinoma (CRC). The authors present a retrospective review of the impact of elective and therapeutic oophorectomy on the natural history of CRC. METHODS: Patients with primary CRC from January 1964 through March 1996 were reviewed. Survival from the time of OM diagnosis was estimated by the Kaplan-Meier method; differences between groups were based on the log-rank test. RESULTS: A total of 155 patients were studied. Synchronous OM occurred in 90 patients (58.1%); metachronous OM occurred in 65 patients (41.9%). Estimated 5-year survival for patients with synchronous OM was 9%, versus 20% for metachronous OM (P < .0001). Resection of metastatic disease was associated with an improved 5-year survival for synchronous OM (15% vs. 0%, P=.0001) and metachronous OM (24% vs. 0%, P < .0001) if patients were disease-free postoperatively. Other clinical characteristics, including age, menopausal status, stage, and location of primary tumor, had no significant impact on survival. CONCLUSIONS: Ovarian metastases from colorectal carcinoma are associated with a poor outcome. Although there is no survival advantage associated with resection of occult microscopic disease, long-term survival is possible if patients are rendered surgically disease-free.

Adenocarcinoma↗
PubMed1998

Effect of genetically modified, low-phytic acid maize on absorption of iron from tortillas.

BACKGROUND: Genetically modified, low-phytic acid strains of maize were developed to enhance mineral absorption, but have not been tested previously in humans. OBJECTIVES: We evaluated the mineral and phytic acid contents of a low-phytic acid "flint" maize (LPM, the lpa-1-1 mutant) and its parent, wild-type strain (WTM) and measured iron absorption from tortillas prepared with each type of maize and from a reference dose of ferrous ascorbate. DESIGN: Proximate composition and mineral and phytic acid contents were measured by standard techniques. Iron absorption from tortillas was evaluated by using the extrinsic tag method and was measured as the incorporation of radiolabeled iron into the red blood cells of 14 nonanemic men 2 wk after intake. RESULTS: The phytic acid content of LPM was 3.48 mg/g, approximately 35% of the phytic acid content of WTM; concentrations of macronutrients and most minerals were not significantly different between strains. Iron absorption results were adjusted to 40% absorption of ferrous ascorbate. Iron absorption was 49% greater from LPM (8.2% of intake) than from WTM (5.5% of intake) tortillas (P < 0.001, repeated-measures analysis of variance). CONCLUSION: Consumption of genetically modified, low-phytic acid strains of maize may improve iron absorption in human populations that consume maize-based diets.

Adult↗
PubMed1998

Differentiation of spermatogenic cells during in-vitro culture of testicular biopsy samples from patients with obstructive azoospermia: effect of recombinant follicle stimulating hormone.

In-vitro differentiation of spermatogenic cells is a potential approach to the treatment of male sterility due to spermatogenic arrest. This is a pilot study evaluating meiotic, morphogenetic and cytoplasmic maturation of spermatogenic cells from 18 patients with obstructive azoospermia, during in-vitro culture of partly disintegrated testicular biopsy samples in the presence or absence of recombinant follicle stimulating hormone (rFSH). Meiotic progression was detectable only in the presence of rFSH in culture medium. FSH-dependent condensation, peripheral migration and protrusion of spermatid nuclei, together with FSH-independent flagellar growth, were the main events indicating post-meiotic sperm cell differentiation. rFSH also promoted the progression of spermatid cytoplasmic maturation, reflected by acceleration of acrosomal development. These differentiation events appeared to be mediated by humoral activity of Sertoli cells, without the need for a direct Sertoli-sperm cell contact. These findings provide a background for similar studies in patients with non-obstructive azoospermia. If reproducible in the latter group, transmeiotic in-vitro differentiation of primary spermatocytes may be useful in cases of complete maturation arrest, whereas the development of culture-specific forms may help select viable spermatids in cases of complete spermiogenesis failure.

Acrosome↗
PubMed1998

Spermatids as gametes: indications and limitations.

The feasibility of achieving viable embryos, developing to term after transfer into the uterus, by fertilizing oocytes with spermatids has been demonstrated both in animal studies and in preliminary human clinical trials. Here we review the current clinical indications of spermatid conception and discuss the predictable success rates associated with each of these indications. Potential health hazards relating to the use of spermatids for conception are updated taking into account the risk of abnormal or incomplete epigenetic modifications of newly discovered human imprinted genes. We also add new experimental data showing the occurrence of spermatids in patients lacking spermatozoa and demonstrating that round spermatids recovered from patients with complete spermiogenesis failure (no elongated spermatids or spermatozoa ever detected in the patient's history) are often deficient in the factor(s) responsible for oocyte activation. The possible consequences of this deficiency for the occurrence of abnormal fertilization patterns and for the impairment of further preimplantation and post-implantation development are discussed. It is concluded that the development of diagnostic tests to assess the intrinsic quality of spermatids, with regard to their ability to act as gametes, is urgently needed as part of pre-treatment diagnosis before infertile couples are included in a spermatid conception programme. Centres wishing to use spermatids in human assisted reproduction should also be prepared to offer adequate diagnostic methods to control genomic imprinting abnormalities in the progeny.

Female↗
PubMed1998

Germ cell apoptosis in men with complete and incomplete spermiogenesis failure.

Germ cell apoptosis was evaluated in 11 men suffering from nonobstructive azoospermia and enrolled in a spermatid conception programme. In six of these patients, round spermatids (Sa stage) were the most advanced spermatogenic cells recovered from testicular biopsy samples. This condition is referred to as complete spermiogenesis failure. In the remaining five men, a few late elongated spermatids (Sd stage) were unexpectedly found in the testicular biopsy samples on the day of treatment. This condition is referred to as incomplete spermiogenesis failure. Germ cell apoptosis in both groups of patients was examined by analysing cell smears prepared from mechanically disintegrated testicular tissues using terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL), which detects apoptosis-specific DNA fragmentation, and annexin-V binding, detecting apoptosis-related translocation of plasma membrane phosphatidylserine to the membrane's outer surface. Both methods were combined, in double-fluorescence labelling preparations, with immunocytochemical detection of proacrosin, a specific germline marker. Patients with complete spermiogenesis failure had significantly higher frequencies of primary spermatocytes and round spermatids carrying the apoptosis-specific DNA damage in comparison with patients with incomplete spermiogenesis failure. Surprisingly, apoptosis-related phosphatidylserine externalization occurs rarely until the advanced stages of spermiogenesis. Since externalized phosphatidylserine is expected to be involved in the recognition of apoptotic cells by phagocytes, apoptotic spermatocytes and round spermatids may not be removed easily by phagocytosis. The high frequency of DNA damage in round spermatids from patients with complete spermiogenesis failure explains the low success rates of spermatid conception in these cases. The evaluation of apoptosis can help predict success rates of spermatid conception.

Annexin A5↗
PubMed1998

Human spermatogenesis in vitro: respective effects of follicle-stimulating hormone and testosterone on meiosis, spermiogenesis, and Sertoli cell apoptosis.

In spite of the availability of abundant data about in vitro spermatogenesis in laboratory animals, studies on human in vitro spermatogenesis are scarce. This study employed a relatively simple culture system, involving all cell types of seminiferous tubules, to analyze the effects of FSH and testosterone (T) on different characteristics of human germ and Sertoli cells in culture. By using fluorescence in-situ hybridization, we show that in vitro reduction of germ cell ploidy can be stimulated by FSH but not by T. FSH, but not T, also induced unexpectedly rapid (24-48 h) morphological changes resembling spermiogenesis, although individual changes (spermatid nucleus condensation and protrusion, cell body elongation, and flagellar growth) proceeded in an uncoordinated way and mostly resulted in the development of abnormal forms of elongated spermatids. Though ineffective alone, T potentiated the effects of FSH on meiosis and spermiogenesis. These effects of T were probably caused by the prevention of Sertoli cell apoptosis, an effect that could not be mimicked by FSH. These data show that, in the presence of high concentrations of FSH and T, human spermatogenesis can proceed in vitro with an unusual speed, but the resulting gametes are morphologically abnormal. The potential practical relevance of these findings to assisted reproduction remains to be assessed.

Adult↗
PubMed1998

Atypical microangiopathy in a patient treated with ticlopidine.

Microangiopathies are rare complications during treatments with ticlopidine. We describe an atypical microangiopathy, affecting almost exclusively myocardium, and thrombocytopenia, shortly after onset of ticlopidine. The patient died a few days after. Autopsy showed no bleedings or large thrombi in most organs, but were compatible with microangiopathy in myocardial small vessels.

Humans↗
PubMed1997

Theoretical description of the polymerase chain reaction.

Taking into account expressions for the efficiency of the polymerase chain reaction (PCR) recently deduced from enzymological considerations, and making use of a continuous model based on the law of mass action, closed form solutions are derived that enable a complete description of the standard and quantitative competitive PCR methods. The resulting behaviour is in reasonable agreement with that from a previous, empirical, discrete approach; but the latter is nonetheless shown to overestimate the amplification yield by as much as 30% due to the weak assumption of a constant efficiency during the cycle duration. The present formalism will facilitate the implementation of accurate fitting procedures of experimental data to manage quantification.

Animals↗
PubMed1997

Enzymological considerations for a theoretical description of the quantitative competitive polymerase chain reaction (QC-PCR).

The enzymological principles of the polymerase chain reaction (PCR) and of the quantitative competitive PCR (QC-PCR) are developed, proposing a theoretical framework that will facilitate quantification in experimental methodologies. It is demonstrated that the specificity of the QC-PCR, i.e. the ratio of the target initial velocity to that of the competitor template, remains constant not only during a particular amplification but also for increasing initial competitor concentrations. Linear fitting procedures are thus recommended that will enable a quantitative estimate of the initial target concentration. Finally, expressions for the efficiency of the PCR and QC-PCR are derived that are in agreement with previous experimental inferences.

Animals↗
PubMed1997

Orthostatic sympathetic derangement in subjects with fibromyalgia.

OBJECTIVE: To assess the sympathetic-parasympathetic balance in individuals with fibromyalgia (FM), and its response to orthostatic stress, by power spectral analysis of heart rate variability. METHODS: We studied 19 women with FM and 19 age matched controls. A high resolution electrocardiogram was obtained in supine and standing postures after achieving a stable heart rate. Spectral analysis of R-R intervals was done by the fast Fourier transform algorithm. RESULTS: Analyses of the different frequency components revealed significant difference between the 2 groups in the low frequency (0.050-0.150 Hz) band, which reflects modulation of the sympathetic nervous system. Controls displayed an increased power spectral density upon standing (+0.081 +/- 0.217 Hz); individuals with FM had a discordant response (-0.057 +/- 0.097 Hz) (p = 0.018). CONCLUSION: In FM, there is a deranged sympathetic response to orthostatic stress. This abnormality may have implications regarding the pathogenesis of FM.

Adult↗
PubMed1996

Orally effective CVS-1123 prevents coronary artery thrombosis in the conscious dog.

BACKGROUND: We examined the oral efficacy of a direct thrombin inhibitor, CVS-1123 [(CH3CH2CH2)(2)-CH-CO-Asp (OCH3)-Pro-Arg-CHO; MW, 575]. The object was to determine whether thrombin inhibition could reduce the incidence of occlusive coronary artery thrombosis in response to arterial wall injury. METHODS AND RESULTS: Arterial wall injury was induced in conscious dogs by a 150-muA anodal current applied to the intimal surface of the circumflex coronary artery 30 minutes after oral CVS-1123 (20 mg/kg every 8 hours for three doses; n = 11) or placebo containing diluent (n = 10). Dogs were monitored for 8 hours and at 24 hours. The coronary artery remained patent for 24 hours in 8 of 11 CVS-1123-treated dogs. All dogs (n = 10) in the placebo group developed a sustained, occlusive arterial thrombus. Two hours after the initial oral dose, the plasma CVS-1123 concentration was 13 +/- 1 microgram/mL, reaching a maximum of 15 +/- 1 micrograms/mL after the second dose and 4.4 +/- 0.5 micrograms/mL at 24 hours. Ex vivo platelet aggregation to gamma-thrombin was inhibited and activated partial thromboplastin time was increased after treatment with CVS-1123 (P < .05). CONCLUSIONS: The direct thrombin inhibitor CVS-1123 is effective after oral administration in reducing the incidence of primary thrombus formation in an experimental model of arterial wall injury. Thrombin-specific inhibitors, such as CVS-1123, may be alternative antithrombotic agents in clinical settings in which heparin-associated thrombosis is a complicating factor or when long-term anticoagulation is required.

Administration, Oral↗
PubMed1996

The occurrence and identification of round spermatids in the ejaculate of men with nonobstructive azoospermia.

OBJECTIVE: To evaluate the occurrence of round spermatids in the ejaculate of men suffering from nonobstructive azoospermia as a prerequisite for the therapeutic use of round spermatid injection into oocytes. DESIGN: Prospective study. SETTING: University-based diagnostic and research laboratory. PATIENT(S): Azoospermic men previously thought to be definitively infertile whose cases were revisited in view of the novel method of fertilization by round spermatid injection into oocytes. INTERVENTION(S): Smear preparations of cells from patients' ejaculates were stained by three different methods: Papanicolaou, fluorescein-labeled Pisum sativum agglutinin binding, and antiacrosin antiserum immunolabeling. MAIN OUTCOME MEASURE(S): Search for round spermatids in smear preparations of cells from azoospermic ejaculates. RESULT(S): Of 124 azoospermic men examined, 36 (69%) had round spermatids in the ejaculate. the quantity of round spermatids was not related to serum FSH concentration. CONCLUSION(S): Variable quantities of round spermatids can be detected in the ejaculate of most patients with nonobstructive azoospermia. High serum FSH levels do not predict the absence of spermatids.

Acrosin↗