Showing papers by "William Wallace published in 2002"

Testicular changes during infantile ‘quiescence’ in the marmoset and their gonadotrophin dependence: a model for investigating susceptibility of the prepubertal human testis to cancer therapy?

Abstract: BACKGROUND: Inexplicably, boys treated with some therapies for cancer at age 2–10 years, a time of supposed ‘testicular quiescence’, are at risk of low sperm counts/infertility in adulthood Our aims were to use the marmoset as a surrogate for man to establish testicular cell function/activity during ‘quiescence’ between the neonatal period and puberty, and to test if any cell activity could be suppressed by prior treatment with a GnRH antagonist METHODS AND RESULTS: Based on immunoexpression studies, functional development of Sertoli cells (SGP-2, androgen receptor) and Leydig cells (3β-hydroxysteroid dehydrogenase) was detectable at an age (35 weeks) when the testis is considered to be quiescent, and in advance of the pubertal rise in blood testosterone levels (50–60 weeks) Other changes at 35 weeks were the appearance of focal seminiferous tubule lumens and proliferating germ cells [indicated by immunoexpression of proliferating cell nuclear antigen (PCNA)] Treatment from 25 to 35 weeks with GnRH antagonist largely (>85%) prevented these changes However, the PCNA-labelling index of spermatogonia in GnRH antagonist-treated animals did not differ from controls (413 versus 436%) though total spermatogonia volume per testis was reduced by 41% Some protein markers (inhibin-α, estrogen receptor-β) showed little change with age or treatment Beyond 35 weeks, GnRH antagonist-treated animals showed a delay in the pubertal rise in plasma testosterone levels CONCLUSIONS: These findings reinforce the view that the ‘childhood’ testis is not quiescent This may explain the damaging effects of some cancer therapies on subsequent fertility of boys and raises the issue of protective intervention The present studies suggest that GnRH antagonist-based intervention might be only partially successful Identification of the factors regulating spermatogonial development in the infant marmoset may aid in the design of such strategies

Investigation of suppression of the hypothalamic–pituitary–gonadal axis to restore spermatogenesis in azoospermic men treated for childhood cancer

Abstract: BACKGROUND Does suppression of the hypothalamic-pituitary-gonadal (HPG) axis restore spermatogenesis in men rendered azoospermic following treatment of childhood cancer? METHODS Seven men with azoospermia secondary to treatment for childhood cancer, median age (range), 22.2 (18-25.3) years, aged 10.4 (4.4-13.3) years at original diagnosis, participated. Each subject underwent semen analysis and testicular biopsy, followed by treatment with medroxyprogesterone acetate (MPA), 300 mg i.m. repeated after 12 weeks, with 800 mg testosterone pellets s.c. on day 1 to suppress the HPG axis. Hormone and semen analysis was performed every 6 weeks for 48 weeks. A second testicular biopsy was performed at week 48. RESULTS Before HPG axis suppression, mean +/- SEM plasma LH was 9.0 +/- 1.8 U/l, testosterone 17.9 +/- 1.5 nmol/l and FSH 22.4 +/- 4.4 U/l. Median (range) venous plasma and seminal plasma inhibin B levels were 10.0 (7.8-35) and 11.2 (7.8-770) ng/l respectively. During HPG suppression, FSH and LH levels were undetectable for > or =12 weeks followed by a gradual return to pretreatment concentrations by 48 weeks. All men remained azoospermic at study completion and complete absence of germ cells on biopsies was demonstrated by immunocytochemistry for all specimens pre- and post-HPG axis suppression. CONCLUSIONS HPG axis suppression with MPA-testosterone for > or =12 weeks did not restore spermatogenesis in azoospermic men treated with gonadotoxic radiotherapy and chemotherapy for childhood cancer.

Detection of Pathogenic Organisms in Food, Water and Body (Postprint)

Abstract: : The construction of specific bioluminescent bacteriophage for detection of pathogenic organism can be developed to overcome interferences in complex matrices such as food, water and body fluids Detection and identification of bacteria often require several days and frequently weeks by standard methods of isolation, growth and biochemical test Immunoassay detection often requires the expression of the bacterial toxin, which can lead to non-detection of cells that may express the toxin under conditions different from testing protocols Immunoassays require production of a specific antibody to the agent for detection and interference by contaminants frequently affects results PCR based detection may be inhibited by substances in complex matrices Modified methods of the PCR technique, such as magnetic capture-hybridization PCR (MCH-PCR), appear to improve the technique by removing the DNA products away from the inhibitors However, the techniques required for PCR-based detection are slow and the procedures require skilled personnel working with labile reagents Our approach is based on transferring bioluminescence (lux) genes into a selected bacteriophage Bacteriophages are bacterial viruses that are widespread in nature and often are genus and species specific This specificity eliminates or reduces false positives in a bacteriophage assay The phage recognizes a specific receptor molecule on the surface of a susceptible bacterium, attaches and then injects the viral nucleic acid into the cell The injected viral genome is expressed and then replicated, generating numerous exact copies of the viral genetic material including the lux genes, often resulting in an increase in bioluminescence by several hundred fold

Detection of pathogenic organisms in food, water, and body fluids

Abstract: The construction of specific bioluminescent bacteriophage for detection of pathogenic organism can be developed to overcome interferences in complex matrices such as food, water and body fluids. Detection and identification of bacteria often require several days and frequently weeks by standard methods of isolation, growth and biochemical test. Immunoassay detection often requires the expression of the bacterial toxin, which can lead to non-detection of cells that may express the toxin under conditions different from testing protocols. Immunoassays require production of a specific antibody to the agent for detection and interference by contaminants frequently affects results. PCR based detection may be inhibited by substances in complex matrices. Modified methods of the PCR technique, such as magnetic capture-hybridization PCR (MCH-PCR), appear to improve the technique by removing the DNA products away from the inhibitors. However, the techniques required for PCR-based detection are slow and the procedures require skilled personnel working with labile reagents. Our approach is based on transferring bioluminescence (lux) genes into a selected bacteriophage. Bacteriophages are bacterial viruses that are widespread in nature and often are genus and species specific. This specificity eliminates or reduces false positives in a bacteriophage assay. The phage recognizes a specific receptor molecule on the surface of a susceptible bacterium, attaches and then injects the viral nucleic acid into the cell. The injected viral genome is expressed and then replicated, generating numerous exact copies of the viral genetic material including the lux genes, often resulting in an increase in bioluminescence by several hundred fold.