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Biomedical subjects

S J Pickering

Publications and source records attributed to S J Pickering.

At least 37 records · Page 2Linked to original sources
PubMed1991

The incidence of abnormal morphology and nucleocytoplasmic ratios in 2-, 3- and 5-day human pre-embryos.

Human cleaving pre-embryos at 2 and 3 days and cavitated pre-embryos at 5 days post-insemination have been examined for cell number and the incidence of mononucleated cells. At least 60% of polynucleate or anucleate cells have been detected at all these stages and regardless of morphological grading at day 2. It is concluded that even by the time at which pre-embryo replacement would occur therapeutically, the majority of pre-embryos are unlikely to have full developmental potential. The possible origins of the abnormalities of nucleocytoplasmic ratios are discussed.

Blastocyst↗
PubMed1990

Dimethylsulphoxide affects the organisation of microfilaments in the mouse oocyte.

The effect of dimethylsulphoxide (DMSO) on microfilament organisation has been studied in the mouse oocyte after staining with (NBD)-phallacidin. The cortical actin meshwork was disrupted by exposure of oocytes to 1.5 M DMSO at 37 degrees C, and this disruption was associated with changes in the cell surface, especially microvilli length and distribution, as observed by scanning electron microscopy. The irregular distribution of actin filaments observed also appears to lead to an irregular expansion of the cell after DMSO removal. However, when exposure to DMSO was combined with cooling, the effects on the microfilament system were much reduced. The reversibility of DMSO action is considered and the potential implications of microfilament disruption on the viability and functions of the oocyte discussed.

Actin Cytoskeleton↗
PubMed1990

Acid Tyrode's solution can stimulate parthenogenetic activation of human and mouse oocytes.

Fresh and aged (24 hours after ovulation) human oocytes and recently ovulated mouse oocytes may be activated by exposure to acidified Tyrode's solution. No activation of either type of human oocyte was observed after exposure to hyaluronidase or pronase, but significant numbers of fresh mouse oocytes were activated after exposure to pronase but not to chymotrypsin. The implications of these results for the manipulation of human and mouse eggs in vitro are discussed.

Animals↗
PubMed1990

Transient cooling to room temperature can cause irreversible disruption of the meiotic spindle in the human oocyte.

The effect on the microtubule system of human oocytes of cooling to room temperature for either 10 or 30 minutes has been investigated. Changes in spindle organization were found in all oocytes cooled for 30 minutes compared with control oocytes kept at 37 degrees C throughout. These changes included reduction in spindle size, disorganization of microtubules within the spindle itself, and sometimes a complete lack of microtubules. In some oocytes, chromosome dispersal from the metaphase plate was associated with these changes. Cooling the oocyte to room temperature for only 10 minutes produced a similar pattern of disruption to spindle structure in many cases. The spindles in oocytes that were cooled for either 10 or 30 minutes and then allowed to recover at 37 degrees C for either 1 or 4 hours were found to resemble those in noncooled control oocytes in less than one half of the cases examined, although in only a few cases did the chromosomes remain dispersed. The significance of these findings for the handling of oocytes during gamete intrafallopian transfer and in vitro fertilization procedures is discussed in relation to the levels of aneuploidy detected in early human embryos.

Chromosomes↗
PubMed1990

The hardening effect of dimethylsulphoxide on the mouse zona pellucida requires the presence of an oocyte and is associated with a reduction in the number of cortical granules present.

When mouse ovulated oocytes were exposed to 1.5 M-dimethylsulphoxide (DMSO) the resultant hardening of the zona pellucida was not a direct effect but required the presence of an oocyte. The hardening of the zona pellucida when zonae used were aged in vitro was also dependent upon the presence of the oocyte. Protocols of DMSO exposure that induce zona-hardening also caused depletion of the numbers of cortical granules underlying the oocyte surface, whereas protocols without effect on the zona did not reduce significantly the cortical granule count. It is proposed that the effects of DMSO may be mediated by a release of cortical granule contents.

Animals↗
PubMed1989

Measurement of HPRT activity in the human unfertilized oocyte and pre-embryo.

The hypoxanthine phosphoribosyl transferase (HPRT) and adenine phosphoribosyl transferase (APRT) activities in individual non-fertilized human eggs and in human pre-embryos (4-cell to blastocyst stage) have been analysed. A wide spread of activities was observed, the mean values of which decline with time post-ovulation for both eggs and advancing pre-embryonic stages. The variation in activities was less in groups of eggs or pre-embryos recovered from a single ovulatory cycle. The activity of HPRT, but not of APRT, was readily detectable in single 4-cell and 8-cell blastomeres. When pre-embryos at various preimplantation stages were exposed to alpha-amanitin, to block transcription of mRNA from the pre-embryonic genome, no clear effect on HPRT activity was observed. It is concluded that the HPRT and APRT activities measured in the pre-embryos studied here are likely to be maternally inherited, and that use of a direct assay for HPRT activity for the pre-implantation diagnosis of Lesch-Nyhan disease would be premature.

Adenine Phosphoribosyltransferase↗
PubMed1989

Alternative routes for the establishment of surface polarity during compaction of the mouse embryo.

During the process of compaction, mouse 8-cell blastomeres flatten upon each other and polarize along an axis perpendicular to cell contacts. If the process of flattening is prevented, polarization can still occur, but does so in a lower proportion of cells than for control populations, and without the normal contact-directed orientation. We compared contact-directed and noncontact-directed processes to see if they involve common mechanisms. In nonflattened cells, surface polarization was favored in cells with nuclei located close to the cell surface, and the positions of surface poles and of nuclei tended to coincide. We present evidence that microtubules are involved in the development of microvillous poles associated with nuclei. In contrast it is known that polarization of microvilli occurs in the absence of microtubules if blastomeres are allowed to flatten. We conclude that surface polarization of mouse blastomeres can be accomplished by at least two alternative routes. One requires flattening but is independent of microtubules, and another can occur without flattening but involves a microtubule-mediated interaction between the nucleus and the cell cortex. It seems that both these pathways operate in the undisturbed embryo.

Animals↗
PubMed1989

Urokinase: a treatment for relapsing peritonitis due to coagulase-negative staphylococci.

Four consecutive patients with relapsing peritonitis due to coagulase-negative staphylococci have been successfully treated by the addition of urokinase to their treatment regime, having failed to respond to appropriate antibiotic therapy alone. The organisms isolated from each episode of peritonitis in an individual patient were shown to be identical by antibiotic sensitivity, phage typing, slime production and immunoblot analysis. The action of urokinase is unknown but it may act by fibrinolysis, allowing antibiotics access to a source of infection previously protected by fibrin. The technique described is a simple, safe and effective treatment of relapsing peritonitis due to coagulase-negative staphylococci, and its use can markedly reduce the morbidity associated with this infection.

Bacterial Typing Techniques↗
PubMed1989

Are human spermatozoa separated on a Percoll density gradient safe for therapeutic use?

Motile morphologically normal human spermatozoa can be separated from semen by buoyant density centrifugation on Percoll (Pharmacia Fine Chemicals AB, Uppsala, Sweden) gradients. In this study, the authors have examined (1) the efficiency of washing procedures to remove contaminating Percoll particles from the separated spermatozoa, and (2) the potential of Percoll particles, which contain silica, to cause an inflammatory response when used for intrauterine insemination, or when introduced into the fallopian tube during gamete intrafallopian transfer (GIFT) procedures, as assessed by an intraperitoneal injection into mice. Although Percoll was phagocytosed at the injection site, and therefore cannot be presumed to be totally inert, no generalized inflammatory response was detected. A double spin and wash technique was found to remove most residual Percoll from the spermatozoa, as assessed by scanning electron microscopy. These results suggest that procedures involving the use of Percoll for the separation of human spermatozoa for in vitro fertilization, GIFT, or intrauterine insemination should include stringent washing protocols that will remove most, if not all, contaminating Percoll from the sample.

Cell Separation↗
PubMed1988

Intraperitoneal teicoplanin in the treatment of peritonitis associated with continuous ambulatory peritoneal dialysis.

The efficacy of teicoplanin in the treatment of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) was evaluated in a randomised comparison with vancomycin. The dosage regimen used was 50 mg of vancomycin or teicoplanin per 2 1 bag of dialysate for 48 h followed by 25 mg per bag for a further five days. Twelve episodes of peritonitis were studied. There was no significant difference in the bacteriological or clinical cure rates of either antibiotic.

Anti-Bacterial Agents↗
PubMed1988

The influence of cooling on the properties of the zona pellucida of the mouse oocyte.

Mouse oocytes were exposed to a variety of cooling regimes prior to insemination in vitro. Exposure to 4 degrees C, but not to 25 degrees C, was associated with a reduced fertilization rate, but development to the blastocyst stage of those oocytes that fertilized was not consistently different from that of non-cooled controls. The reduced fertilization rate seems to result from an effect of cooling on the zona pellucida, since it was not observed if the zona was removed prior to insemination, and since cooling rendered the zona pellucida resistant to the action of chymotrypsin. Using chymotrypsin resistance as an assay, the nature of the cooling-induced effect on the zona was investigated. It is suggested that rapid cooling to 4 degrees C may promote release of cortical granules and a premature zona reaction.

Animals↗
PubMed1988

Cytoskeletal organization in fresh, aged and spontaneously activated human oocytes.

The cytoskeleton of the human oocyte (microtubules and actin filaments) has been examined using fluorescence microscopy. In unfertilized oocytes in metaphase of the second meiotic division, microtubules were found exclusively within the spindle which was located at the periphery of the cell and oriented radially, with its long axis perpendicular to the surface membrane. The spindle was anastral and slightly pointed at each pole, the chromosomes being arranged on a metaphase plate at the equator. When treated with taxol, the oocyte spindle became astral and microtubules appeared in the cortex of the oocyte in the form of small strands or bundles. Polymerized actin was found to be present in a dense filamentous layer throughout the cortex of the unfertilized oocyte. Aged unfertilized oocytes displayed an increased incidence of disrupted or abnormal cytoskeletal organization. In parthenogenetically activated oocytes in anaphase and telophase, microtubules were again found predominantly in the spindle but in addition, cortical strands or bundles of microtubules were often present. Oocytes in late telophase sometimes showed the presence of a concentrated ring of actin in the cleavage furrow between the oocyte and the second polar body. Activated oocytes in early interphase contained a dense cortical mesh of microtubules and a midbody remnant between the oocyte and the polar body. The cytoskeletal organizations of mouse and human oocytes are compared.

Age Factors↗
PubMed1988

Anti-glomerular basement membrane antibody-mediated nephritis complicating transplantation in a patient with Alport's syndrome.

Loss of an allograft caused by anti-GBM antibody-mediated nephritis is a rare complication of renal transplantation in Alport's syndrome. We describe a patient in whom this occurred. He belongs to the subgroup of patients with hereditary nephritis and deafness with an abnormal Goodpasture antigen, and he developed a high level of circulating anti-GBM antibodies within 20 days of transplantation of a kidney with a presumably normal Goodpasture antigen. The antibody titer fell, only to rise again when he developed evidence of acute infection with CMV. Coincident with this second rise in antibody titer he developed an anti-GBM antibody-mediated crescentic nephritis with resultant loss of graft function and transplant nephrectomy. This case provides support for the hypothesis that the abnormality in the basement membrane in some patients with Alport's syndrome involves the Goodpasture antigen, and raises the possibility that viral infection may have triggered autoantibody production.

Adult↗
PubMed1988

Cytocortical organization during natural and prolonged mitosis of mouse 8-cell blastomeres.

Late 8-cell blastomeres were harvested within the first 45 min after entering mitosis. Some mitotic cells were analysed within the ensuing 2 h for the organization of their surface in relation to their progress through mitosis. Whereas in most late interphase cells microvilli were restricted to a discrete polar region, in mitotic cells at all stages from early metaphase to immediately postcytokinesis microvilli were found to be present over more of the cell surface. Other mitotic cells were placed in nocodazole to arrest them in M-phase for up to 10 h. They were found to show an even more extensive distribution of microvilli over the whole surface, the longer periods of incubation yielding more extended coverage such that many cells no longer appeared to have any residual surface polarity. Removal from nocodazole at all time points from 1 to 10 h resulted in most cells completing mitosis to yield pairs of cells which, in most cases, resembled pairs derived from nonarrested blastomeres and in which a defined polar area of microvilli was restored. However, the percentage of differentiative divisions decreased after 6 h arrest. If, instead of removing cells from nocodazole, they were placed in both nocodazole and cytochalasin D (CCD) for periods of up to 3 h, most microvilli retracted to reveal a tight polar zone of CCD-resistant microvilli. This result suggests that a heterogeneity of cytocortical organization may still exist within the arrested mitotic cell. We propose a model to explain the origin of this heterogeneity of organization and its relationship to the generation of cell diversity.

Animals↗
PubMed1988

The influence of cell contact on the division of mouse 8-cell blastomeres.

The pattern of division of polarized 8-cell blastomeres with respect to the axis of cell polarity has been compared (i) for cells dividing alone with cells dividing in pairs, and (ii) for early and late dividing cells within a pair. Cell interactions do not seem to influence significantly the overall pattern of division within the population. The only significant difference found was that the second dividing cell in a pair tended to divide in the same way as its earlier dividing companion slightly more frequently than expected. These results suggest that cell interactions immediately prior to and during division do not influence strongly the orientation and position of the division plane. In contrast, interactions between the cells within an intact early 8-cell embryo, which is subsequently disaggregated to singletons or pairs, do influence the type of progeny generated at division to the 16-cell stage, and seem to do so via an effect on the size of the microvillous region generated at the cell apex.

Animals↗
PubMed1987

Redistribution of microtubules and pericentriolar material during the development of polarity in mouse blastomeres.

The distribution of microtubules and microtubule organizing centers (MTOCs) during the development of cell polarity in eight-cell mouse blastomeres was studied by immunofluorescence and immunoelectron microscopy using monoclonal anti-tubulin antibodies and an anti-pericentriolar material (PCM) serum. In early eight-cell blastomeres microtubules were found mainly around the nucleus and in the cell cortex, whereas PCM foci were observed dispersed in the cytoplasm. During the eight-cell stage, microtubules disappeared from the area adjacent to the zone of intercellular contact and accumulated in the apical part of the cell while their number decreased in the basal domain. The PCM also relocalized to the apical domain of the cell, but this occurred after the redistribution of the microtubules by a mechanism that involved the microtubule network. The possible roles of both MTOCs and microtubules in establishing cell polarity are discussed.

Animals↗