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D J Lamb

Publications and source records attributed to D J Lamb.

At least 73 records · Page 4Linked to original sources
PubMed1997

The possible role of copper ions in atherogenesis: the Blue Janus.

It has been proposed that the oxidative modification of low density lipoprotein (LDL) is a key event in human atherogenesis. Copper ions can catalyse the oxidative modification of LDL in vitro and there is some evidence that they may also participate in the oxidation of LDL within the arterial wall. However, copper ions also form an intrinsic constituent of superoxide dismutase and caeruloplasmin, enzymes that may be involved in preventing oxidative injury. Atherosclerotic lesions frequently contain considerable quantities of extracellular matrix molecules. These may contribute to the expansion of the arterial neointima, causing luminal narrowing. They may also play a beneficial role by stabilising the plaque. Copper is an essential component of lysyl oxidase, an enzyme involved in the biosynthesis of collagen, which is a major constituent of the extracellular matrix. The impact of alterations in body copper status on atherogenesis is therefore difficult to predict. Experimental and epidemiological data are conflicting and therefore do not provide a clear resolution of this issue. We have reviewed the biochemical and cellular effects of copper ions that may play a role in atherogenesis.

Arteriosclerosis↗
PubMed1997

Apoptotic frequency is increased in spermatogenic maturation arrest and hypospermatogenic states.

PURPOSE: Increased testicular apoptosis has been observed in maturation arrest and hyposper-matogenesis states in rodent models, but this process has not yet been characterized in humans. We hypothesized that increased cell death present with accelerated apoptosis is significant in pathophysiology of many male infertility states associated with abnormal spermatogenesis. We examined frequency of apoptotic bodies in human testis biopsy specimens from infertile men using morphometric analysis of hematoxylin and eosin stained paraffin sections. MATERIALS AND METHODS: Testis biopsy specimens were obtained for routine clinical purposes from azoospermic and severely oligozoospermic men and were stained with hematoxylin and eosin. Apoptotic bodies were identified using established morphometric criteria. Apoptotic indexes, defined as apoptotic bodies per total number of cells and per Sertoli cells, were calculated after counting all intratubular spermatogenic cells and Sertoli cells in 20 tubules. RESULTS: A total of 51 biopsies was performed in 50 men. Significantly increased apoptotic body per total cell and apoptotic body per Sertoli cell ratios were observed in maturation arrest and hypospermatogenesis states in comparison to Sertoli cell only and normal spermatogenesis (p < 0.05, Mann-Whitney test). CONCLUSIONS: Increased apoptosis in maturation arrest and hypospermatogenesis states compared to normal but obstructed spermatogenesis and Sertoli cell only were observed, indicating a prominent role for this form of programmed cell death in human male infertility.

Apoptosis↗
PubMed1997

Progression of metastatic human prostate cancer to androgen independence in immunodeficient SCID mice.

Prostate cancer mortality results from metastasis to bone and hormone-independent tumor growth. Models to study these progressive changes are lacking. Here we describe the propagation of advanced human prostate cancer by direct transfer of surgical samples from patients into immune-deficient male SCID mice. Explants from six of eight patients formed prostate tumors and two showed unique cytogenetic, biologic and molecular features that were retained through six or more passages. One grew in an androgen-independent fashion, whereas the second formed tumors that regressed following castration then regrew. Micrometastatic disease was detected in the hematopoietic tissues of half of the recipient mice. Thus selected specimens of advanced human prostate cancer can be propagated in SCID mice in a manner that recapitulates the clinical transition from androgen-sensitive to androgen-independent growth, accompanied by micrometastasis.

Androgens↗
PubMed1997

Absence of DAZ gene mutations in cases of non-obstructed azoospermia.

Sequenced-tagged site (STS) analysis of the Y chromosome long arm (Yq) of azoospermic males has identified a minimum common deleted region of several hundred kilobases in approximately 13% of cases. A candidate azoospermia gene, DAZ (deleted in azoospermia), has been isolated from this region. DAZ has also been shown to be absent in severely oligozoospermic males albeit at a much lower frequency. These data, although highly suggestive, do not constitute formal proof that DAZ actually plays a role in azoospermia, as no small intragenic deletions, rearrangements or point mutations in the gene have been found. In this study we report the screening of DNA from 168 azoospermic/oligospermic males for the presence of the DAZ gene. Deletions involving DAZ were detected in five out of 43 (11.6%) azoospermic males whereas none were found in the remaining 125 oligospermic patients. We present the genomic structure of the 5' end of the DAZ gene together with its sequence analysis in 30 non-obstructed azoospermic males. No mutations in DAZ were found in any of the patients sequenced. These data provide no formal proof that DAZ is AZF. Thus the possibility is still valid that another gene(s) mapping to the deletion interval may be responsible for, or contribute to, the observed phenotypes. Alternatively, if DAZ is AZF, they suggest that the most frequent cause of gene inactivation is via large deletions possibly mobilized by Y chromosome repetitive sequences.

Base Sequence↗
PubMed1997

Molecular biology and function of the androgen receptor in genital development.

PURPOSE: The rapidly growing field of molecular biology has caused exponential growth in our knowledge of the processes of embryogenesis. Since the cloning of the androgen receptor gene in 1988, investigators have been able to clarify many of the molecular events of male sexual differentiation that are mediated through the androgen receptor. We reviewed the current state of knowledge of the androgen receptor and its role in male genital development. MATERIALS AND METHODS: An intensive literature search was conducted to review reports on the androgen receptor and sexual differentiation since 1988. This review also includes ongoing research from our laboratory on the role of the androgen receptor in human genital development, as well as collaboration with other investigators. RESULTS: We reviewed the basic molecular biology of androgenic action mediated through the androgen receptor. This information has been integrated into the current understanding of human male sexual differentiation to clarify how androgens virilize the undifferentiated embryo. Defects in function of the androgen receptor may be manifested as a spectrum of phenotypes of the androgen insensitivity syndrome, and these phenotypes of male pseudohermaphroditism have been reviewed on a clinical and molecular basis. New molecular techniques have augmented the evaluation and diagnosis of the androgen insensitivity syndrome, and some groups have successfully diagnosed the condition prenatally. CONCLUSIONS: Basic scientific research of androgen receptor function and its role in male sexual development has provided a clearer understanding of the mechanisms responsible for the spectrum of defects secondary to the androgen insensitivity syndrome. This knowledge will enable clinicians to offer more accurate diagnosis and insightful counseling to affected patients and their families.

Disorders of Sex Development↗
PubMed1997

Intracytoplasmic sperm injection for treatment of the infertile male.

Intracytoplasmic sperm injection (ICSI) with in vitro fertilization represents one of the most significant advances in fertility technology. In this relatively new procedure, a single viable sperm is microinjected into an oocyte that has been extracted transvaginally. After fertilization occurs, the embryo is transferred into the uterus. This procedure now affords men who were previously thought to be irreversibly infertile the chance to initiate their own biologic pregnancy. However, because of the procedure's significant costs and its potential risk to the mother, careful selection of couples following a thorough male factor evaluation is mandatory.

Congenital Abnormalities↗
PubMed1997

A comparison of two methods for recording the retruded jaw relation in edentulous subjects.

The purpose of this study on 19 edentulous patients was to compare the retruded jaw relations recorded on wax rims at the registration stage with those recorded on finished dentures at insertion. An intra-oral centre-point trace served as the reference point for both sets of measurements. Results showed the two techniques to give mean retruded positions 0.25 mm apart in the occlusal-sagittal plane, but the distributions of the two sets of results differed; those recorded on finished dentures had greater precision, with smaller range and standard deviation. The work confirms the usefulness of a post insertion check record carried out on complete dentures to minimise any occlusal errors introduced at the registration stage.

Aged↗
PubMed1996

Molecular determinants of sexual differentiation.

The processes of sexual differentiation have been greatly clarified by molecular biologic discoveries over the past five years. Gonadal differentiation into a testis or ovaries is controlled by a multitude of genes beginning with SRY which is believed to represent the testis determining factor. Other genes involved include SF-1, WT-1, DAX-1, and SOX9. The fully developed testis produces Mullerian inhibiting substance and testosterone to create the male phenotype; the female phenotype develops in their absence. This hormonally-driven process also requires additional factors and appropriate receptors. Errors in this pathway may be manifested clinically as intersex disorders, and the study of these disorders has helped to further elucidate the molecular mechanisms of sexual differentiation.

Animals↗
PubMed1996

Androgen receptor gene mutations are rarely associated with isolated penile hypospadias.

PURPOSE: Hypospadias has no known single etiology but it has been linked to androgen insensitivity caused by mutations of the androgen receptor gene. The purpose of this study was to search for such mutations in cases of various degrees of isolated hypospadias to determine whether such an association exists and, if so, with any particular anatomical subgroup. MATERIALS AND METHODS: Isolated deoxyribonucleic acid from the penile tissue of 40 patients undergoing reconstructive surgery was screened for mutations of the coding regions of the androgen receptor gene using single strand conformational polymorphism analysis. In cases with abnormal single strand conformational polymorphism findings sequence analysis of the deoxyribonucleic acid was performed to define the mutation. RESULTS: A missense mutation of exon 2 of the androgen receptor gene was noted in 1 patient with isolated distal penile shaft hypospadias. Sequence analysis revealed that the mutation changed amino acid residue 546 from proline to serine. No abnormalities were detected in the other 39 patients. CONCLUSIONS: Isolated distal shaft hypospadias is associated with mutations of the androgen receptor gene but these mutations appear to be a rare cause of hypospadias.

Child↗
PubMed1995

Transition metal ions within human atherosclerotic lesions can catalyse the oxidation of low density lipoprotein by macrophages.

The oxidation of low density lipoprotein (LDL) in the arterial wall may contribute to atherogenesis. The oxidation of LDL by cells usually requires catalytically active transition metal ions. We show here some that gruel samples from human advanced atherosclerotic lesions are capable of catalysing the oxidation of LDL by macrophages as measured by thiobarbituric acid-reactive substances, enhanced electrophoretic mobility and increased macrophage uptake. This catalysis could be inhibited by pretreatment of the gruel with Chelex-100, which binds transition metal ions. The presence of catalytically active transition metal ions in atherosclerotic lesions may help to explain why LDL oxidation occurs at these sites.

Animals↗
PubMed1995

Genes involved in testicular development and function.

The development of the testis requires the highly regulated expression of a series of genes. Many of the genes involved are transcription factors, such as steroid hormone receptors and growth factors. Investigators have used gene cloning, mutation analysis, transgenic mice, and gene-deletion studies to define the role of specific genes in testicular development and function. In the past 5 years, investigators have defined a gene on the Y chromosome, SRY, thought to be required for testis determination. This protein is a member of a larger family of related transcription factors. Expression of this gene triggers a cascade of events that leads to the development of the Sertoli cell, Leydig cells, and the testis. The development of the male phenotype is dependent on the presence and action of androgens, which exert their effect after combining with a receptor in the nucleus of the target cell that stimulates gene transcription. Defects in the androgen receptor gene lead to a full spectrum of morphological defects in the male. Interestingly, mutations in other members of the steroid receptor superfamily, such as the estrogen receptor gene, also affect male fertility. A number of "orphan" receptors (i.e., receptors whose ligans have not been identified) are also required for normal testicular development and function, as are several genes normally thought to be tumor-suppressor genes (e.g., Wilms' tumor-suppressor gene). In contrast, alpha-inhibin has been thought to be an endocrine hormone, yet it functions as a tumor-suppressor gene in the testis. Testicular development and normal spermatogenesis require the proper function and coordination of a large number of transcription factors, steroid hormone and orphan receptors, and growth factors. There are likely to be a large number of other, as yet unidentified genes that are necessary for male gonadal development.

Animals↗
PubMed1995

Steroid-regulated growth of DDT1MF-2 cells is profoundly influenced by culture conditions.

DDT1MF-2 cells provide an ideal model for studying tumor-growth-stimulation by steroids. These cells progress to a rapidly proliferating, androgen-independent state after prolonged culture without androgen. After brief culture in different lots of fetal bovine serum (FBS), some lots induced a permanent state of hormone-independence in cells that had been androgen-responsive. To test the hypothesis that factors influenced androgen-responsive growth even after removal of serum, hormone-responsive DDT1MF-2 cells (7000 cells/well) were plated in medium Dulbecco's Modified Eagle Medium/F-12 Nutrition Mixture (1:1)/1% ITS with (a) 0.1% FBS, (b) 0.1% NuSerum (c) 0.1% Hyclone, or (d) MCDB-110/0.1% ITS with 5 ng/ml bFGF. On Days 2-8, medium was replaced with D-MEM/F12/ITS with 10 nM testosterone (T), 10 nM triamcinolone acetonide (TA), or ethanol (control) and the cells counted. While testosterone induced a 1.4-fold increase in cell growth after exposure to FBS or NuSerum, maximal testosterone effect (3-6-fold increase) was observed after Hyclone. Hydroxyflutamide antagonized the fivefold increase in growth observed with testosterone, with a slight decrease of growth with cAMP for cells plated in Hyclone. Androgen-independent cells were unaffected by testosterone, hydroxyflutamide, or 8Br-cAMP [medium (a)]. Maximal inhibition by triamcinolone acetonide (0.25 of control) was observed with medium (d). The effect of testosterone and triamcinolone acetonide on secretion of mitogenic activity into conditioned medium was also evaluated. Although conditioned media from control and testosterone-treated cells were mitogenic in a dose-dependent manner, the media from cells treated with triamcinolone acetonide and testosterone+TA conditioned medium was not mitogenic--but, of note, it was not growth inhibitory.

Cell Division↗
PubMed1995

A quality control system for the optimized sperm penetration assay.

OBJECTIVE: To develop a quality control system for the optimized sperm penetration assay (SPA) and to use this system to monitor interassay variability and stability over time. DESIGN: Four semen donors were tested consecutively for a period of weeks (7 to 139 weeks) with the SPA. Their average semen analyses and SPA scores were evaluated to monitor natural biologic variation. Intra-assay variation was obtained by dividing 11 semen samples into three aliquots and testing each separately in the SPA. A single ejaculate from seven individuals was aliquoted and frozen to be used as a control. They were tested on different assay days in 1986 and subsequently in 1991 to evaluate the assay stability over time. MAIN OUTCOME MEASURES: Results were expressed as a sperm capacitation index (mean number of sperm penetrations per ovum). RESULTS: Consecutive weekly semen analyses and SPAs on donors exhibited coefficients of variation ranging from 20% to > 40%. In contrast, these variations were much greater than intra-assay variability. Analysis of frozen semen specimens tested in several SPAs also displayed a low coefficient of variation. When aliquots of these frozen samples were tested in the SPA 5 years later, there were no differences in the observed values, showing the remarkable stability of this assay over time. The lower limit of the normal fertile range did not change over a period of 2 years. CONCLUSIONS: Results show that using fresh semen samples as a positive control in the SPA is inadequate. This deficiency has been overcome with the use of frozen semen controls. With frozen semen for quality control, the optimized SPA developed in this laboratory is a highly reproducible assay that meets the strict criteria required for clinical laboratory certification.

Animals↗
PubMed1994

Iron released from transferrin at acidic pH can catalyse the oxidation of low density lipoprotein.

Low density lipoprotein (LDL) oxidation within the arterial wall may contribute to the disease of atherosclerosis. We have investigated the conditions under which transferrin (the major iron-carrying protein in plasma) may release iron ions to catalyse the oxidation of LDL. Transferrin that had been incubated at pH 5.5 released approximately 10% of its bound iron in 24 h, as measured by ultrafiltration and atomic absorption spectroscopy. Furthermore, transferrin co-incubated with LDL and L-cysteine at pH 5.5 resulted in the oxidation of the LDL as measured by thiobarbituric acid-reactive substances and electrophoretic mobility. This effect was observed at transferrin concentrations as low as 40% of its average plasma concentration. The release of iron from transferrin in atherosclerotic lesions due to a localised acidic pH may help to explain why LDL oxidation occurs in these lesions.

Humans↗
PubMed1994

Acidic pH enables caeruloplasmin to catalyse the modification of low-density lipoprotein.

LDL oxidation within the arterial wall may contribute to the disease of atherosclerosis. There is some evidence that elevated plasma levels of copper are associated with an increased risk of coronary artery disease. We have investigated the conditions under which caeruloplasmin (the plasma copper carrier protein) can catalyse the macrophage-mediated modification of LDL. Low concentrations of CuSO4 (< 1 microM) could catalyse the macrophage-mediated modification of LDL. Native caeruloplasmin was unable to catalyse the modification of LDL at pH 7.4, but could do so after preincubation at acidic pH. After preincubation at acidic pH, concentrations of caeruloplasmin as low as 30 micrograms/ml (about one-tenth of the human plasma level) could catalyse significant LDL oxidation when added to macrophages. The activation of copper in caeruloplasmin in atherosclerotic lesions due to a localised acidic pH may help to explain why LDL oxidation occurs in these areas of the body.

Animals↗
PubMed1994

Animal models that mimic human male reproductive defects.

All stages of male reproductive development and function are highly regulated, not only by the gonadotropins FSH, LH, and testosterone, but also by local control signals regulating cell function, mitosis, meiosis, and differentiation. The present approach to the treatment of many types of male infertility focuses on the use of suboptimal or defective sperm with protocols designed to overcome specific abnormalities. Elucidation of the molecular events required for normal male reproduction using animal model systems will eventually permit the design of new diagnostic procedures and therapeutic modalities. These advances may lead to enhancement or restoration of fertility in previously sterile men.

Animals↗
PubMed1994

Evaluation of sperm function. What is available in the modern andrology laboratory?

Tests of sperm function markedly improve the clinician's ability to diagnose male factor infertility accurately. An understanding of the patient's sperm defect may improve the clinical management of male infertility. A wide spectrum of therapeutic options is available to the urologist treating the infertile male. IVF is now routinely employed for many types of male factor infertility with promising results. Micromanipulation has permitted men who, in the not so distant past, were considered infertile to experience fatherhood. In light of these promising therapeutic advances, accurate assessment of sperm function becomes crucial. Treatment options may be selected on the basis of specific functional defects of sperm. Sperm with an inability to bypass cervical mucus may be adequately treated with IUI. Oligospermic men with sperm capable of ova penetration can be treated with IVF, whereas men whose sperm are incapable of zona binding/penetration may be treated with micromanipulation. Sperm function assays provide a rationale for the selection of specific therapies to treat or bypass identified defects, and by providing comprehensive and accurate diagnosis, they make possible individually tailored therapies. Such individualized treatment choices may improve success rates for many male factor patients.

Cervix Mucus↗