Search PubMed⌕ Search

Biomedical subjects

R J Aitken

Publications and source records attributed to R J Aitken.

At least 19 recordsLinked to original sources
PubMed1992

Assessment of non-palpable mammographic abnormalities: comparison between screening and symptomatic clinics.

A retrospective study found that a breast screening clinic generated fewer localization biopsies for non-palpable mammographic abnormalities than a symptomatic clinic (3.36 versus 9.89 per 1000 mammograms, respectively) and that a greater proportion of such biopsies were malignant. This study determined the reason for this difference. There were 108 of 304 (35.5 per cent) and 17 of 130 (13.1 per cent) carcinomas in women attending the screening and breast clinics respectively (relative risk 2.72 (95 per cent confidence interval 1.70-4.34)). This difference was regardless of age. The characteristics of the mammographic abnormality, the Wolfe pattern, a family history of breast carcinoma, parity and age at first pregnancy were similar in both groups. Women attending the screening clinic were referred for localization biopsy after assessment by clinicians and radiologists at a joint clinic; there was no joint assessment for patients attending the breast clinic. The same staff attended both clinics, although the proportion of time spent at each varied. This study suggests that all women with a non-palpable mammographic abnormality should be reviewed at a joint assessment clinic before localization biopsy is recommended.

Biopsy↗
PubMed1992

Reactive oxygen species and human spermatozoa: analysis of the cellular mechanisms involved in luminol- and lucigenin-dependent chemiluminescence.

We have shown that human spermatozoa generate and release reactive oxygen species that can be detected by chemiluminescence techniques. Analysis of the cellular mechanisms responsible for this activity suggests that the probe, luminol, undergoes an intracellular dioxygenation reaction mediated by hydrogen peroxide and a sperm peroxidase located within the acrosome. Support for this model included the following observations: (1) the luminol-dependent signal could be suppressed with peroxidase inhibitors, phenylhydrazine and sodium azide; (2) this suppression could be reversed by the addition of an azide-insensitive peroxidase, horse radish peroxidase (HRP); (3) inhibition of intracellular superoxide dismutase (SOD) with potassium cyanide (KCN) suppressed the luminol signal; (4) peroxidase activity could be detected in purified populations of human spermatozoa with 3,3',5,5' tetramethylbenzidine (TMB); (5) this peroxidase was active at the pH prevailing within the acrosomal vesicle; and (6) peroxidase activity and luminol-dependent chemiluminescence were minimal in spermatozoa exhibiting a congenital absence of acrosomes. Human spermatozoa could also generate lucigenin-dependent chemiluminescent signals that could neither be suppressed with peroxidase inhibitors nor enhanced by the addition of peroxidase. However, these signals could be enhanced by suppression of intracellular SOD with KCN or inhibited by exogenous SOD, suggesting that lucigenin was responding to superoxide anion released into the extracellular space. The ability of chemiluminescent techniques to detect and discriminate the production of superoxide and hydrogen peroxide by spermatozoa should facilitate the further analysis of reactive oxygen species as mediators of normal and abnormal human sperm function.

Acridines↗
PubMed1992

Development of a technique for monitoring the contamination of human semen samples with leukocytes.

OBJECTIVE: To determine whether receptors for the N-formyl chemotactic peptide, FMLP, exist on the surface of human spermatozoa and regulate reactive oxygen species generation by these cells. DESIGN: Chemiluminescent analysis of reactive oxygen species generation by suspensions of human spermatozoa before and after removal of leukocytes using a magnetic cell separation technique. SETTING: Academic Research Institute. PATIENTS: Unselected male volunteers. RESULTS: Human sperm suspensions responded to FMLP and phorbol ester (PMA) with a burst of reactive oxygen species production. Autoradiographic analyses employing 3H FMLP and chemiluminescence studies involving the selective removal of leucocytes with anti-CD 45-coated magnetic beads demonstrated that the FMLP responses were because of leukocyte contamination. In contrast, reactive oxygen species production in response to PMA appeared to reflect the oxidant-generating capacity of both leukocytes and spermatozoa. CONCLUSION: The only cells present in the human ejaculate possessing detectable receptors for FMLP and capable of generating reactive oxygen species in response to this reagent come from the leukocyte population. Luminol-dependent, FMLP-induced, chemiluminescence provides a rational basis for monitoring the presence of leukocytes in suspensions of human spermatozoa.

Cell Fractionation↗
PubMed1992

Cloning and characterization of the human sperm receptor ligand ZP3: evidence for a second polymorphic allele with a different frequency in the Caucasian and Japanese populations.

The human ZP3 gene, encoding the glycoprotein responsible for sperm-egg recognition, has been cloned using mouse ZP3 DNA as a probe. Genomic and cDNA cloning revealed eight exons, spread over 18 kb, encoding a protein of 424 amino acids with a 67% homology to mouse and hamster ZP3. Southern blotting, gene cloning, and sequence analysis were used to show that ZP3 is not a single-copy gene and that the human genome contains a second polymorphic locus which, due to an extra G residue in exon 8, has the potential to encode a truncated protein of 372 amino acids. Direct sequence analysis of polymerase chain reaction-amplified exon 8 DNA of 56 individuals of various human populations revealed three different sequence patterns: one containing only ZP3-424-coding sequences and two containing ZP3-424- and ZP3-372-coding DNA. The distribution of these three sequence patterns is significantly different between the Caucasian and Japanese populations, as indicated by ZP3-372 allele frequencies of 69 and 21%, respectively. Isolation of ZP3-424 and ZP3-372 cDNAs suggests that both loci represent functional transcription units. Therefore, it is hypothesized that throughout the human population during oogenesis ZP3 is translated from mRNAs derived from two to four transcription units. Provided that ZP3-372 mRNA is translated in vivo, corresponding differences in ZP3-372 protein levels might have an impact on human zona pellucida composition.

Alleles↗
PubMed1992

Analysis of the contraceptive potential of antibodies against native and deglycosylated porcine ZP3 in vivo and in vitro.

We have undertaken a comparative analysis of the contraceptive activity of antibodies directed against the porcine sperm receptor zona pellucida antigen (ZP3) and its Mr = 32,000 polypeptide core (DGZP-32). The strategies employed for this analysis included the induction of active immunity in a primate, the common marmoset, and an in vitro fertilization protocol involving the use of viable human ova. In both experimental situations, antibodies against ZP3 were shown to exhibit contraceptive activity, leading respectively to the induction of long-term infertility in the primate model and to the complete inhibition of human fertilization in vitro. The in vivo studies also revealed that the induction of high titer antibodies against ZP3 was inevitably associated with the appearance of an ovarian pathology characterized by the progressive depletion of the primordial follicle pool within one to two years. This side effect could not be alleviated by the use of DGZP-32 as antigen since the induction of immunity against this polypeptide was also associated with the eventual appearance of an ovarian pathology identical to that observed with ZP3. Furthermore, the DGZP-32 peptide was less effective than ZP3 in inducing the formation of antibodies capable of inhibiting the fertilization of human ova in vitro. We conclude that significant problems remain with the use of deglycosylated zona peptides for the development of contraceptive vaccines and that their potential will not be realized until the epitopes responsible for the induction of infertility and the primordial follicle depletion have been identified and segregated.

Animals↗
PubMed1992

Enhanced detection of reactive oxygen species produced by human spermatozoa with 7-dimethyl amino-naphthalin-1, 2-dicarbonic acid hydrazide.

A new chemiluminescence technique has been assessed for the detection of reactive oxygen species generated by purified populations of human sperm. This revised protocol involves the use of horse-radish peroxidase (HRP) in combination with a luminol analogue, 7-dimethyl amino-naphthalin-1,2-dicarbonic acid hydrazide (DNDH), that exhibits two-three times the quantal efficiency of luminol itself. The chemiluminescent signal generated with these reagents was significantly (P less than 0.001) greater than that obtained with the conventional luminol-based methodology for both the steady-state situation and following stimulation of the sperm with PMA and A23187. Dose-response analyses indicated that the DNDH/HRP chemiluminescence system could give linear standard curves with hydrogen peroxide concentrations into the nmol l-1 range. In contrast, the exponential rise in chemiluminescence recorded with luminol was not observed until hydrogen peroxide concentrations exceeded 10 mumol l-1. It is concluded that the enhanced sensitivity of the DNDH/HRP system to low levels of hydrogen peroxide should facilitate the application of chemiluminescent techniques to the diagnosis of oxidative stress in cases of male infertility.

Fluorescent Dyes↗
PubMed1992

Residual sperm function in oligozoospermia induced by testosterone enanthate administered as a potential steroid male contraceptive.

To investigate the fertility of men who remain oligozoospermic despite sex steroid suppression, the in-vitro fertilizing capacity of residual spermatozoa was assessed in 30 men receiving intramuscular testosterone enanthate (TE). Spermatozoa were prepared by either Percoll or repetitive centrifugation/washing. Although the mean (+/- SEM) pretreatment zona-free hamster oocyte penetration (HOP) rates were similar (59.4 +/- 10.1 and 63.8 +/- 10.8%), following the induction of oligozoospermia the Percoll-prepared spermatozoa exhibited a penetration rate (26.9 +/- 10.2%) which was markedly greater than that obtained for sperm prepared by repetitive washing (0 +/- 0%). In addition, the partners of two men exhibiting a HOP test with Percoll-prepared spermatozoa, conceived despite a sperm concentration of 3 x 10(6) ml-1 and a negative HOP test with spermatozoa prepared by repetitive washing. These results suggest that Percoll preparation optimizes the assessment of in-vitro sperm function and that the fertility of men with TE-induced severe oligozoospermia is suppressed but not abolished.

Adult↗
PubMed1992

Differential contribution of leucocytes and spermatozoa to the generation of reactive oxygen species in the ejaculates of oligozoospermic patients and fertile donors.

Cells isolated from the ejaculates of a high proportion of patients exhibiting oligozoospermia are characterized by generation rates of reactive oxygen species that considerably exceed those obtained for the normal fertile population. The purpose of this study was to resolve the cellular source of this enhanced activity. Semen samples from a cohort of oligozoospermic patients and a group of fertile controls were fractionated on discontinuous Percoll gradients to generate three cell populations (0, 50 and 100%) of differing density. For each fraction, both the steady-state and the phorbol-ester-induced chemiluminescent signals were significantly (P less than 0.001) greater for the oligozoospermic samples than for the fertile controls. In the fertile donors, leucocytes comprised the major source of reactive oxygen species, particularly in the low-density Percoll fractions; in oligozoospermic patients, however, spermatozoa were identified as a second major source of reactive oxygen species. Particularly striking was an intense phorbol-ester-induced chemiluminescent signal generated by oligozoospermic spermatozoa, purified by passage through isotonic Percoll and free of leucocyte contamination, which was 167 times greater than the median signal generated by the corresponding fraction from the fertile controls (P less than 0.001). These results emphasize the importance of spermatozoa as a major source of reactive oxygen species in oligozoospermia and have implications for the diagnosis and treatment of this condition, as well as for the design of appropriate diagnostic strategies.

Cell Separation↗
PubMed1991

Prospective analysis of sperm-oocyte fusion and reactive oxygen species generation as criteria for the diagnosis of infertility.

We have undertaken a prospective analysis of the diagnostic significance of three different criteria of human sperm function including the conventional semen profile, measurements of hamster-oocyte fusion, and determinations of reactive oxygen species generation in 139 couples. The latter, who were characterized by a lack of detectable abnormalities in the female partner, were followed up for a maximum of 4 years to determine the incidence of spontaneous pregnancy in the absence of therapeutic intervention. Assessments of monthly fecundity with life table analysis techniques revealed a highly significant, positive relationship between fertility and hamster-oocyte fusion rates that were measured in the presence of the ionophore, A23187. Conversely, reactive oxygen species generation was shown to be negatively associated with both the outcome of the sperm-oocyte fusion assay and fertility in vivo. The clinical significance of these diagnostic techniques was emphasized by the fact that within the same data set, the conventional semen profile was of no significant diagnostic value.

Animals↗
PubMed1991

Scale model studies of the transport of airborne pollutants on coalfaces.

Studies have been carried out to investigate airflows in coalmine models, with special regard to the transport of airborne pollutants, and to examine how they relate to what happens at full-scale in an actual underground mine. If such models can be shown to provide data representative of actual mine ventilation engineering, then they can provide cost-effective alternatives to full-scale investigations. The work set out in the first instance to identify the properties of: (a) the bulk airflow and associated transport of airborne pollutants along a longwall coalface; and (b) the transport of material out of regions that were partially enclosed or poorly ventilated (e.g. in the cutting zone, in headings). For the former, an appropriate quantity is the dispersivity of the coalface airflow, for the latter the mean retention time. Both quantities may be rendered non-dimensional with respect to dimensions characteristic of the system and to velocities of the airflow. Their behaviour in relation to a third dimensionless quantity, the flow Reynolds' number is also important. Experiments were performed, using smoke or dust tracers, to investigate how these properties are interrelated and how they scale between small-scale and full-scale systems. They were carried out in a 1/10-scale laboratory model, in a full-scale surface model, and underground in an actual coalmine. The basis of most of the experiments was the 'tracer decay' method, in which the transport properties of the aerodynamic system under investigation were determined from observations of the changes in tracer concentration with time immediately following the removal of the tracer source. During these experiments, the feasibility of using small-scale models to investigate ventilation problems was clearly indicated and preliminary scaling relationships which may be used as an initial basis for predicting the transport and local build-up of pollutants in mines were developed. It is expected that applications of the ideas and methodology described will be relevant to other industries.

Air Movements↗
PubMed1991

Non-palpable mammographic abnormalities.

The radiological characteristics of non-palpable mammographic abnormalities are reviewed and their diagnostic limitations discussed. Alternative methods of detection and diagnosis are reviewed. The development of needle localization for non-palpable mammographic abnormalities is traced from the initial crude excisions through to stereotactic needle localization. Non-palpable carcinomas have a greater proportion of favourable histopathologies. However, the preferred management of these early lesions has yet to be determined.

Biopsy, Needle↗
PubMed1990

Outcome of surgery for non-palpable mammographic abnormalities.

Four hundred and ninety-three women underwent 515 localization biopsies for non-palpable mammographic abnormalities. The mammographic abnormality was located with a hooked wire in 509 cases. Specimen radiology was performed on all excised tissue. The mammographic abnormality was visualized in the first piece of tissue excised in 402 (78.1 per cent) cases and complete excision was achieved in 476 (92.4 per cent). A palpable nodule was removed in 38 (7.4 per cent) cases and in 17 (44.7 per cent) was shown to contain a carcinoma. The mammographic abnormality was missed in 14 (2.7 per cent) cases or only partly excised in 13 (2.5 per cent). Overall 144 (28.0 per cent) localization biopsies were malignant. The mammographic abnormality was not visualized on the specimen radiograph more frequently in women aged under 55 years, in women with dense breast (Wolfe grade DM or DY) or in those whose mammographic abnormality contained only microcalcification. The 27 women in whom the mammographic abnormality was not visible on the specimen radiograph underwent repeat mammography 2 months later. Only two women required a further localization biopsy and the mammographic abnormality was recovered in the first piece of tissue excised. Women with a carcinoma underwent mastectomy or wide local excision, and residual carcinoma at the localization biopsy site was found in 64 (44.4 per cent) cases. Oestrogen receptor analysis by ligand binding assay was possible in only 71 (49.3 per cent) carcinomas. If the specimen radiograph does not show the mammographic abnormality within pieces of tissue excised and there is no palpable nodule it may be best to conclude the biopsy. In this series these missed lesions were usually benign. Only rarely is a second localization biopsy required and this is performed without difficulty.

Adult↗
PubMed1990

Analysis of sperm function in globozoospermia: implications for the mechanism of sperm-zona interaction.

The globozoospermic condition has provided a unique opportunity to determine how the abnormal mitochondrial organization and acrosomal loss associated with this syndrome, influence sperm function. Despite the abnormal midpiece architecture, the movement characteristics of the spermatozoa, in terms of the curvilinear, path, and progressive velocities, amplitude of head displacement, and hyperactivation were all within the normal range. Similarly, the behavior of the spermatozoa on Percoll gradients was normal, although the capacity of the isolated fractions to generate reactive oxygen species was negligible. Of particular significance was the fact that the globozoospermic spermatozoa were incapable of sperm-oocyte fusion or binding the human zona pellucida, even after an intracellular calcium signal had been generated with the ionophore A23187. The sudden induction of sperm-zona interaction could, however, be achieved by the use of a ferrous ion promoter system to induce limited lipoperoxidation. This result demonstrates that the enhancing effect of peroxidation on sperm-zona adhesion involves a direct action on the properties of the sperm-plasma membrane, rather than an indirect consequence of acrosomal damage and acrosin leakage. Such findings emphasize the value of specific teratozoospermic conditions, such as globozoospermia, in dissecting the mechanisms that regulate human sperm function.

Adult↗
PubMed1990

Evaluation of human sperm function.

Our understanding of the causes of male infertility and our ability to develop an appropriate range of diagnostic tests are both dependent upon a knowledge of the cellular mechanisms responsible for the regulation of human sperm function. This review examines the intra- and extracellular factors regulating four separate components of human sperm function: sperm transport, sperm-egg recognition, the acrosome reaction and sperm-oocyte fusion. Within each of these areas the fundamental nature of the process, the control mechanisms involved, the availability of appropriate diagnostic tests and the relationship with human infertility have been considered.

Acrosome↗
PubMed1990

The effect of iron and iron chelators on the in-vitro block to development of the mouse preimplantation embryo: BAT6 a new medium for improved culture of mouse embryos in vitro.

The effect of iron and iron chelators on the development of the mouse embryo in vitro from the 1-cell stage to the blastocyst has been investigated. An adverse effect of iron was found. The high affinity iron chelator, desferal, also blocked development, whilst transferrin (whether as apoprotein or saturated with iron), DETAPAC and EDTA promoted development. The addition of transferrin permitted development to the blastocyst stage of embryos from stains normally exhibiting the 2-cell block. Under such circumstances both the rate of embryonic development and the proportion of embryos reaching the blastocyst stage approached levels found in vivo. Based on these results, a new medium, BAT6, is described for the optimal in-vitro culture of mouse embryos.

Animals↗
PubMed1990

Analysis of the relationship between reactive oxygen species production and leucocyte infiltration in fractions of human semen separated on Percoll gradients.

We have shown previously that the reactive oxygen species generated by washed human ejaculates originate from cells which can be isolated in the low density region of discontinuous Percoll gradients. In this study we have used a simplified two-step (40/80%) Percoll gradient to separate human ejaculates (n = 109) into two populations of spermatozoa, exhibiting either a high or a low capacity for reactive oxygen species generation. We have then examined the relationships between this activity and other properties of the isolated fractions, with particular emphasis on the presence of leucocytes, which we have quantified using a monoclonal antibody directed against the common leucocyte antigen. The low-density cells recovered from the 40%/80% interface of the Percoll gradients, differed from the high-density fraction in exhibiting significantly reduced sperm motility, poorer sperm morphology, and a considerably enhanced capacity for reactive oxygen species production (P less than 0.001). In six cases the elevated levels of reactive oxygen species generation were associated with leucocyte concentrations in excess of 1 x 10(6) per 10(7) sperm, suggesting that leucocytes enter the seminal compartment in an activated, oxygen-radical generating, state. However, in the majority of cases exhibiting high levels of reactive oxygen species production, leucocyte numbers were low or absent and the semen profiles were unremarkable, except that seminal sperm concentrations tended to be low. These results suggest that the oxidative stress responsible for defective sperm function involves reactive oxygen species originating from two sources; the sperm and infiltrating leucocytes.

Cell Separation↗