Multiannual observations of acetone, methanol, and acetaldehyde in remote tropical atlantic air: implications for atmospheric OVOC budgets and oxidative capacity

Oxygenated volatile organic compounds (OVOCs) in the atmosphere are precursors to peroxy acetyl nitrate (PAN), affect the tropospheric ozone budget, and in the remote marine environment represent a significant sink of the hydroxyl radical (OH). The sparse observational database for these compounds, particularly in the tropics, contributes to a high uncertainty in their emissions and atmospheric significance. Here, we show measurements of acetone, methanol, and acetaldehyde in the tropical remote marine boundary layer made between October 2006 and September 2011 at the Cape Verde Atmospheric Observatory (CVAO) (16.85° N, 24.87° W). Mean mixing ratios of acetone, methanol, and acetaldehyde were 546 ± 295 pptv, 742 ± 419 pptv, and 428 ± 190 pptv, respectively, averaged from approximately hourly values over this five-year period. The CAM-Chem global chemical transport model reproduced annual average acetone concentrations well (21% overestimation) but underestimated levels by a factor of 2 in autumn and overestimated concentrations in winter. Annual average concentrations of acetaldehyde were underestimated by a factor of 10, rising to a factor of 40 in summer, and methanol was underestimated on average by a factor of 2, peaking to over a factor of 4 in spring. The model predicted summer minima in acetaldehyde and acetone, which were not apparent in the observations. CAM-Chem was adapted to include a two-way sea-air flux parametrization based on seawater measurements made in the Atlantic Ocean, and the resultant fluxes suggest that the tropical Atlantic region is a net sink for acetone but a net source for methanol and acetaldehyde. Inclusion of the ocean fluxes resulted in good model simulations of monthly averaged methanol levels although still with a 3-fold underestimation in acetaldehyde. Wintertime acetone levels were better simulated, but the observed autumn levels were more severely underestimated than in the standard model. We suggest that the latter may be caused by underestimated terrestrial biogenic African primary and/or secondary OVOC sources by the model. The model underestimation of acetaldehyde concentrations all year round implies a consistent significant missing source, potentially from secondary chemistry of higher alkanes produced biogenically from plants or from the ocean. We estimate that low model bias in OVOC abundances in the remote tropical marine atmosphere may result in up to 8% underestimation of the global methane lifetime due to missing model OH reactivity. Underestimation of acetaldehyde concentrations is responsible for the bulk (∼70%) of this missing reactivity.

Preimplantation genetic diagnosis of skin fragility-ectodermal dysplasia syndrome

Skin fragility-ectodermal dysplasia syndrome is an autosomal recessive disorder caused by loss-of-function mutations in the desmosomal protein, plakophilin 1. Clinically, there may be considerable morbidity from extensive skin erosions and painful fissures on the palms and soles. In the absence of any specific treatment, prenatal diagnosis is an option for couples at reproductive risk of recurrence. In 2000, we developed and applied a single cell nested polymerase chain reaction protocol to test one couple for compound heterozygous plakophilin 1 gene mutations by preimplantation genetic diagnosis (PGD). Although pregnancy was established, an unrelated trisomy 22 led to a spontaneous abortion. However, eight embryos of known genetic status were cryopreserved at that stage, and we planned to undertake subsequent frozen embryo replacement cycles that might lead to the birth of an unaffected child in this family. Embryo cryopreservation was carried out in June 2000 using standard protocols in a three-step freezing procedure. Four embryos were thawed in March 2003, one of which was viable and was used in a frozen embryo replacement cycle, but pregnancy did not occur. The remaining four embryos were thawed in February 2004, two of which were viable (both carriers of the paternal mutation) and these were used in a second frozen embryo replacement cycle, and a singleton pregnancy was established. The child's plakophilin 1 genotype was assessed by direct nucleotide sequencing across the site of both potential mutations. Following two frozen embryo replacement cycles, and almost 4 years after the initial embryo biopsy and mutation analysis, a pregnancy was achieved that progressed to term with the birth of a healthy baby girl. Nucleotide sequencing of cord blood DNA, taken immediately after delivery, showed that the child was a heterozygous carrier of the paternal mutation but not of the maternal mutation. This case demonstrates the value of embryo cryopreservation, which can increase the number of embryo replacement procedures and hence the cumulative pregnancy rate per retrieval cycle. Moreover, this is the first report of successful full-term pregnancy and birth of a healthy baby following exclusion of a severe genodermatosis by PGD. The successful outcome of PGD in this case illustrates what is technically possible for couples at risk of recurrence of a severe inherited skin disease.

AI-based algorithms for protein surface comparisons

Many current methods for protein analysis depend on the detection of similarity in either the primary sequence, or the overall tertiary structure (the Calpha atoms of the protein backbone). These common sequences or structures may imply similar functional characteristics or active properties. Active sites and ligand binding sites usually occur on or near the surface of the protein; so similarly shaped surface regions could imply similar functions. We investigate various methods for describing the shape properties of protein surfaces and for comparing them. Our current work uses algorithms from computer vision to describe the protein surfaces, and methods from graph theory to compare the surface regions. Early results indicate that we can successfully match a family of related ligand binding sites, and find their similarly shaped surface regions. This method of surface analysis could be extended to help identify unknown surface regions for possible ligand binding or active sites.

Development of memory for pattern and path: further evidence for the fractionation of visuo-spatial memory

Evidence from a number of sources now suggests that the visuo-spatial sketchpad (VSSP) of working memory may be composed of two subsystems: one for maintaining visual information and the other for spatial information. In this paper we present three experiments that examine this fractionation using a developmental approach. In Experiment 1, 5-, 8-, and 10-year old children were presented with a visuo-spatial working memory task (the matrices task) with two presentation formats (static and dynamic). A developmental dissociation in performance was found for the static and dynamic conditions of both tasks, suggesting that the activation of separable subsystems of the VSSP is dependent upon a static/dynamic distinction in information content rather than a visual/spatial one. A highly similar pattern of performance was found for a mazes task with static and dynamic formats. However, one strategic activity, the use of simple verbal recoding, may also have been responsible for the observed pattern of performance in the matrices task. In Experiments 2 and 3 this was investigated using concurrent articulatory suppression. No evidence to support this notion was found, and it is therefore proposed that static and dynamic visuo-spatial information is maintained in working memory by separable subcomponents of the VSSP.

Dissociable lexical and phonological influences on serial recognition and serial recall

The impact of the lexicality of memory items on memory performance was compared in two paradigms, serial recall and serial recognition. Experiments 1 to 3 tested 7- and 8-year-old children. Memory accuracy was only mildly impaired in lists containing nonwords compared with words in a serial recognition task involving judgments of whether the items in two sequences were in the same order (Experiment 1), although a substantial advantage for word over nonword items from the same stimulus pool was found in serial recall (Experiment 2). A stronger influence of lexicality on serial recall than serial recognition was further demonstrated in Experiments 3A and 3B, and in 4A and 4B using adult participants. These experiments also established comparable degrees of sensitivity to the phonological similarity of the memory sequences in the two paradigms. The phonological similarity effect in serial recall was found to arise from increased phoneme order errors, whereas the lexicality effect was due principally to the greater frequency of phoneme identity errors for nonwords. It is proposed that the lexicality effect originates in the redintegration of item information just prior to recall, and that this process is largely bypassed in serial recognition.

Preimplantation genetic diagnosis of compound heterozygous mutations leading to ablation of plakophilin-1 (PKP1) and resulting in skin fragility ectodermal dysplasia syndrome: a case report

A new form of genodermatosis resulting from mutations in the gene plakophilin 1 (PKP1) has recently been identified. The clinical features of a functional knockout of PKP1 are a combination of skin fragility and a form of hypohydrotic ectodermal dysplasia. We have developed a single cell polymerase chain reaction (PCR) assay suitable for preimplantation genetic diagnosis (PGD) and here we report on the clinical application of this assay.

Working memory deficits in children with low achievements in the national curriculum at 7 years of age

BACKGROUND

Close links between children's capacities to store and manipulate information over brief periods have been found with achievements on standardised measures of vocabulary, language comprehension, reading, and mathematics.

AIM

The study aimed to investigate whether working memory abilities are also associated with attainment levels in the national curriculum assessments at 7 years of age.

SAMPLE

Eighty-three children aged 6 and 7 years attending local education authority schools participated in the study.

METHODS

Working memory skills were assessed by a test battery designed to tap individual components of Baddeley and Hitch's (1974) working memory model. Children were assigned to normal and low achievement groups on the basis of their performance on national curriculum tasks and tests in the areas of English and mathematics.

RESULTS

Children with low levels of curriculum attainment showed marked impairments on measures of central executive function and of visuo-spatial memory in particular. A single cut-off score derived from the test battery successfully identified the majority of the children failing to reach nationally expected levels of attainment.

CONCLUSIONS

Complex working memory skills are closely linked with children's academic progress within the early years of school. The assessment of working memory skills may offer a valuable method for screening children likely to be at risk of poor scholastic progress.

Phonotactic influences on short-term memory

The impact of phonotactic probabilities on serial recall was investigated in a series of experiments. In Experiments 1A and 1B, 7 and 8 year olds were tested on their serial recall of monosyllabic words and of nonwords varying in phonotactic frequencies. A recall advantage to words over nonwords remained when stimuli were balanced for phonotactic probability, but nonword recall showed superior accuracy for high over low probability nonwords, as in Experiment 2. The nonword frequency effect appears to reflect the frequency of constituent syllables rather than biphones. Both lexicality and high phonotactic frequency led to increased proportions of full over partial recall of the memory stimuli. These findings indicate that decayed memory traces in phonological short-term memory can be reconstructed using either lexical or phonotactic knowledge.

Phonotactic influences on short-term memory

The impact of phonotactic probabilities on serial recall was investigated in a series of experiments. In Experiments 1A and 1B, 7 and 8 year olds were tested on their serial recall of monosyllabic words and of nonwords varying in phonotactic frequencies. A recall advantage to words over nonwords remained when stimuli were balanced for phonotactic probability, but nonword recall showed superior accuracy for high over low probability nonwords, as in Experiment 2. The nonword frequency effect appears to reflect the frequency of constituent syllables rather than biphones. Both lexicality and high phonotactic frequency led to increased proportions of full over partial recall of the memory stimuli. These findings indicate that decayed memory traces in phonological short-term memory can be reconstructed using either lexical or phonotactic knowledge.

Verbal and visuospatial short-term memory in children: evidence for common and distinct mechanisms

This study was designed to identify whether verbal and visuospatial short-term memory performance in children is served by common or distinct mechanisms. Five- and 8-year-old children were tested on their verbal recall of spoken letter names and digits, and on their recall of tapped sequences of blocks. The performance of the children on the verbal and visuospatial serial recall tasks was largely unrelated, extending evidence for dissociable memory systems found in adults. Detailed characteristics of recall, such as serial position functions, migration patterns, and distribution of error types, were similar in the tasks requiring recall of letters and of blocks, although order errors predominated in the block but not the letter recall task for the older children. These results appear to reflect the application of common processes specialized for the extraction of serial order information from the phonological and visuospatial components of short-term memory.

The distribution of alpha- and gamma-tubulin in fresh and aged human and mouse oocytes exposed to cryoprotectant

The distribution of alpha- and gamma-tubulin in human and mouse oocytes has been investigated immunocytochemically. Comparisons have been made between freshly recovered and aged oocytes (both human and mouse), and also between human oocytes before and after exposure to cryoprotectant. Control fresh human oocytes had compact anastral spindles oriented orthogonal to the oolemma, with the pole adjacent to the oolemma being smaller than that directed towards the centre of the oocyte. Each pole was associated with a ring of particulate gamma-tubulin staining that extended a short distance into the body of the spindle. No alpha- and gamma-tubulin staining was found elsewhere in the ooplasm. Human oocytes which had failed to fertilize after an 18 h incubation with spermatozoa and had spent a further 6-8 h in culture showed an increased incidence of spindle abnormalities and of the proliferation of ooplasmic microtubules, which became more pronounced with age post-ovulation. The gamma-tubulin staining pattern of these aged human oocytes revealed greater staining over the whole of the spindle than in fresh oocytes. Examination of mouse oocytes aged in vitro or in vivo showed similar evidence of microtubule proliferation and disorganization, and the gamma-tubulin staining pattern was a sensitive indicator of ageing. The spindles of most fresh human oocytes exposed to 1.5 M dimethyl sulphoxide (DMSO) at 4 degrees C differed from controls in being slightly reduced in size or in having more pointed spindle poles with smaller diameters, both indications that some dismantling of the microtubules had occurred. The distribution of gamma-tubulin in these oocytes extended over more of the spindle. Restoration of DMSO-exposed oocytes to control medium at 37 degrees C for an extended period restored spindle structure to a state closely resembling that in controls. However, recovery of an exclusively polar gamma-tubulin staining did not occur. In both controls and DMSO-exposed human oocytes, chromosomes were arranged on the metaphase equatorial plate. In contrast, exposure of oocytes to 4 degrees C in the absence of DMSO caused dismantling of the spindle. It is concluded that (i) changes in microtubule organization with ageing of oocytes makes them unsuitable for use therapeutically after re-insemination or intracytoplasmic sperm injection, (ii) conditions of cryoprotectant addition previously found optimal for the stabilization of the spindle in the mouse oocyte also appear to be effective in stabilizing the spindle of the human oocyte, and (iii) the distribution of gamma-tubulin in relation to the spindle of the human oocyte appears to be sensitive to age and conditions.

An analysis of multinucleated blastomere formation in human embryos

Human embryos were disaggregated into component blastomeres 42-72 h after insemination. The blastomeres were scored for the number of nuclei present and blastomeres of known nuclear morphology were returned to individual culture drops for 16-20 h, after which they were scored for cleavage and nuclear morphology. In all, 48% of mononucleated blastomeres cleaved during this period, but only 76% of these produced two mononucleated daughter blastomeres; in the remainder, one or more of the blastomeres was abnormally nucleated. During overnight culture, 30% of multinucleated blastomeres and 30% of anucleate blastomeres cleaved, the majority producing abnormally nucleated daughter blastomeres. The majority of blastomeres which showed no sign of cleavage after overnight culture retained the same nuclear morphology as when originally disaggregated. However, a small number of mononucleated blastomeres contained two nuclei after culture, indicating that karyokinesis may have taken place in the absence of cytokinesis. Overall, approximately 30% of blastomeres with more than one nucleus seemed to arise by this mechanism, the remainder probably arising by errors of chromosome segregation and/or packaging at mitosis. In addition, 25/111 mononucleated daughter cells arose either after abnormal division of mononucleated parent cells or after division of multinucleated cells, suggesting that approximately 23% of newly formed mononucleated cells might be chromosomally abnormal. The results of DNA quantitation indicated that very few (12/131, 9.2%) blastomeres (whether uni- or multinucleated) had a DNA content outside the 2-4C range. The embryos used for these studies had been cultured in one of three commonly used in-vitro fertilization (IVF) media: modified T6, Earle's balanced salts or Universal IVF medium (a commercial medium from Medi-Cult). A retrospective analysis was carried out of the number of embryos containing multinucleated blastomeres at disaggregation and of the total proportion of isolated blastomeres which were multinucleated in three groups of embryos, each of which had been cultured in one of the IVF media. Both these parameters were found to vary between cohorts of embryos cultured in the different media. The mechanism(s) by which culture medium composition might affect multinucleation of human blastomeres is discussed, as is the significance of these data for reliable preimplantation diagnosis of genetic status.

Reliability and accuracy of polymerase chain reaction amplification of two unique target sequences from biopsies of cleavage-stage and blastocyst-stage human embryos

Human embryos have been biopsied at either the cleavage or the blastocyst stage of development. One to two blastomeres were removed from cleavage-stage embryos and 2-6 cells from blastocysts. The biopsy specimens were subjected to gene amplification by the polymerase chain reaction (PCR) and a comparison made of amplification efficiencies of two unique target sequences, one located within the beta-globin gene and containing the sickle-cell locus and the other a polymorphic dinucleotide repeat. When the cleavage-stage biopsy sample consisted of an intact blastomere with a clearly discernible nucleus, an amplification efficiency of 89% was achieved for each target locus. This was similar to that achieved with cleavage-stage biopsy samples consisting of two blastomeres or with blastocyst biopsy samples consisting of 2-3 trophectoderm cells. When biopsy samples consisted of four or more trophectoderm cells, both target loci were amplified in all samples tested. When the biopsy sample was heterozygous at the dinucleotide repeat locus and the biopsy consisted of one or more intact cells with a clearly discernible nucleus, both alleles were amplified in > 80% of biopsy samples. When four or more trophectoderm cells were used for the PCR, both alleles were amplified in all heterozygous samples. Target sequences were never amplified from biopsy samples which lysed prior to transfer into the reaction tube. Analysis of DNA fragments amplified from the dinucleotide repeat locus indicated that in most cases faithful amplification of biopsy DNA template had taken place.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of a polymorphic dinucleotide repeat sequence to detect non-blastomeric contamination of the polymerase chain reaction in biopsy samples for preimplantation diagnosis

Using the polymerase chain reaction (PCR), amplification of two different target DNA sequences has been achieved with high frequency using single human blastomeres as template for the duplex reaction. One sequence is located within the beta-globin gene and contains the sickle cell locus, the other is a polymorphic dinucleotide repeat, which, as well as acting as a positive control for amplification, was used to check the origin of the amplified DNA. A comparison of the sequences amplified from the blastomere with sequences amplified from parental samples confirmed that amplification of blastomeric sequences, but not extraneous contaminating DNA, had taken place in most cases. The efficacy of this system for detecting extraneous DNA was checked by deliberately contaminating single blastomeres with foreign cells. The presence of contamination was detected by the amplification of sequences not present in blastomeric DNA and which therefore must have been amplified from extraneous contaminating DNA.

Biopsy of the human blastocyst and polymerase chain reaction (PCR) amplification of the beta-globin gene and a dinucleotide repeat motif from 2-6 trophectoderm cells

Cultured human blastocysts have been biopsied on day 5-6 post insemination and 2-6 extra-embryonic cells from the trophectoderm were removed and their DNA subjected to specific amplification by the polymerase chain reaction (PCR). Simultaneous amplification of part of the beta-globin gene and a dinucleotide repeat sequence has been achieved in a high percentage of cases when using the DNA from both trophectoderm cell biopsies and biopsied blastocysts as template for the PCR. A similar success rate was achieved when serial biopsies were taken from the same blastocyst, thus allowing one cell sample to be held in reserve for use should equivocal results be obtained. Over the entire experimental period (5 months), no contamination was experienced with biopsy or PCR procedures. Following biopsy of the trophectoderm cells all blastocysts had reformed a blastocoele cavity within 3-4 h of the biopsy procedure. Those blastocysts remaining in culture after this time showed a high incidence (78-83%) of hatching and outgrowth.

Cell-cycle control of a large-conductance K+ channel in mouse early embryos

There have been few investigations into the role of ion channels in mammalian early embryonic development, despite studies showing that changes in ion channel activity accompany the early embryonic development of non-mammalian species and the proliferation of mammalian cells. Here we report that a large-conductance, voltage-activated K+ channel is active in unfertilized mouse oocytes but is rarely observed in later embryos. The channel activity is linked to the cell cycle, being active throughout M and G1 phases, and switching off during the G1-to-S transition. These changes in channel activity are accompanied by corresponding shifts in membrane potential. Inactivation of the channel during S/G2 can be prevented by exposing the oocytes to dibutyryl cyclic AMP or forskolin, an activator of adenylyl cyclase. Inhibition of protein synthesis with puromycin did not prevent inactivation of the channel at the end of G1 or its subsequent reactivation at the end of G2, indicating that the channel activity is not regulated by mitosis-promoting factor or cyclins.

Reliability of detection by polymerase chain reaction of the sickle cell-containing region of the beta-globin gene in single human blastomeres

Human preimplantation embryos at various stages of development have been analysed using the polymerase chain reaction to amplify a 680 base pair fragment of the beta-globin gene. Successful amplification was achieved more frequently with DNA from intact embryos containing between one and 11 cells, single cumulus cells, oocytes which had failed to fertilize and polar bodies than from single blastomeres disaggregated from intact embryos and treated in an identical manner. The distribution of nuclei demonstrated using the nuclear chromophore diamino-phenyl-indole showed considerable inter-blastomere variation; however, no clear correlation between staining pattern and successful amplification was observed. The reason for the unreliable amplification of DNA from single blastomeres is unclear but this finding has important implications for preimplantation diagnosis of genetic disease.

Zona pellucida modifications in the mouse in the absence of oocyte activation

Mouse oocytes arrested in metaphase II exhibit zona hardening and a reduced fertilization rate after exposure to the cryoprotectant dimethylsulfoxide (Johnson J, In Vitro Fertil Embryo Transfer 6:168-175, 1989) but do not undergo parthenogenetic activation (Johnson and Pickering, Development 100:313-324, 1987). This paper shows that dimethylsulfoxide causes proteolytic modification of the zona pellucida glycoprotein ZP2 and inhibition of sperm binding. These effects of dimethylsulfoxide are caused by premature exocytosis of the cortical granules, a process that is initiated usually on fertilization. A model for the mechanism of action of dimethylsulfoxide is proposed based on the combined effects of cytoskeletal modification and osmotic shock. The presence of serum before and during the exposure to dimethylsulfoxide was found to reduce significantly these deleterious effects on the mouse zona pellucida without inhibiting the cortical granule release. These results highlight the suitability of dimethylsulfoxide as a tool to study the mechanisms leading to cortical granule release. Use of dimethylsulfoxide allows the separation of oocyte parthenogenetic activation from cortical granule release, and addition of serum allows separation of cortical granule release from the action of the cortical granule contents. Their use allows a dissection of the mechanisms underlying each of these three related events.

Cryoprotection of human oocytes: inappropriate exposure to DMSO reduces fertilization rates

Human oocytes were exposed to the cryoprotectant dimethyl-sulphoxide (DMSO) at either 4 or 37 degrees C. Subsequent fertilization of these oocytes showed that exposure to DMSO at 37 degrees C was associated with a greatly reduced fertilization rate when compared to untreated control oocytes, whereas no such reduction was seen in oocytes exposed to DMSO at 4 degrees C. The significance of these results for the potential cryopreservation of human oocytes is discussed.

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.

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.

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.

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.

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.

A technique for quantifying the amount of macromolecule injected into cells of the early mouse embryo

A simple technique for the quantification of the volume injected into an individual mouse egg or blastomere is described. The method does not seem to have deleterious effects on development, allows the progeny of the injected cell to be identified and permits the measurement of the injected volume to be made up to 48 h after the time of injection.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The effect of dimethylsulphoxide on the microtubular system of the mouse oocyte

The effect of dimethylsulphoxide (DMSO) on the organization of the microtubular system of the mouse oocyte has been examined. Exposure to DMSO causes the immediate appearance of multiple, cold-resistant microtubular asters associated with the foci of pericentriolar material (PCM) normally present in the oocyte. More prolonged exposure to DMSO leads to progressive disassembly of the spindle, and as a result dispersal of the chromosomes and polar PCM foci occurs, and tubulin polymerization becomes confined to PCM-organized asters. Those astral microtubules located between the PCM foci and the cortex of the oocyte appear to be particularly stable, resulting in the development of lengthening radial bundles of microtubules between the PCM and the surface and the progressive movement of the PCM foci towards the centre of the cell. In contrast, after activation of the oocyte the microtubules generated in the presence of DMSO remain located in a cortical mesh. The effects of DMSO do not appear to be fully reversible in most oocytes. We discuss the implications of these results both for the cytoplasmic organization of the oocyte and zygote, and for the attempts at cryopreservation of human oocytes for therapeutic use in infertility programmes.

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.

The influence of cooling on the organization of the meiotic spindle of the mouse oocyte

The effect of cooling on the organization of the microtubule system of the mouse oocyte has been investigated. Cooling to 25, 18 or 4 degrees C for varying periods of time resulted in a progressive disassembly of the spindle and the dispersal of the chromosomes. The extent of the changes observed was greater at lower temperatures and with longer periods of exposure. Transfer of oocytes from either 37 or 4 to 24 degrees C resulted in the rapid and transient appearance of polar asters and of multiple cytoplasmic asters associated with the pericentriolar material present at the spindle poles and in the cytocortex of the oocyte. This transient aster formation appeared to be driven by the elevated levels of free tubulin released during spindle disassembly. An apparent reversal of many of the changes induced by low temperature was observed in many but not all oocytes on their restoration to 37 degrees C for 1 h. These results have implications for our understanding of microtubule organization in the oocyte, and for the handling of oocytes during IVF and GIFT therapeutic procedures and during the cryopreservation of oocytes.

The generation of cell surface polarity in mouse 8-cell blastomeres: the role of cortical microfilaments analysed using cytochalasin D

The mechanism by which a surface pole of microvilli is generated in mouse 8-cell blastomeres has been investigated. 4-cell and 8-cell embryos (or cell couplets) were incubated for precise times during their respective cell cycles in medium containing cytochalasin D (CCD) to disrupt the microfilament system. The blastomeres were analysed immediately for the distribution and state of organization of their microvilli, using three morphological techniques. The results indicate that the surface pole, characterized by microvilli containing CCD-resistant core filaments, is not generated by the gradual segregation of stable microvilli to the apical surface. An alternative model is proposed, based upon (a) the stabilization of the apical cytocortex prior to the elongation of apical microvilli and (b) the destabilization of cytocortical elements in contact areas and the shortening and loss of basolateral microvilli.

The generation of cell surface polarity in mouse 8-cell blastomeres: the role of cortical microfilaments analysed using cytochalasin D

The mechanism by which a surface pole of microvilli is generated in mouse 8-cell blastomeres has been investigated. 4-cell and 8-cell embryos (or cell couplets) were incubated for precise times during their respective cell cycles in medium containing cytochalasin D (CCD) to disrupt the microfilament system. The blastomeres were analysed immediately for the distribution and state of organization of their microvilli, using three morphological techniques. The results indicate that the surface pole, characterized by microvilli containing CCD-resistant core filaments, is not generated by the gradual segregation of stable microvilli to the apical surface. An alternative model is proposed, based upon the stabilization of the apical cytocortex prior to the elongation of apical microvilli and the destabilization of cytocortical elements in contact areas and the shortening and loss of basolateral microvilli.

The cytoskeleton, endocytosis and cell polarity in the mouse preimplantation embryo

The process of cell polarization in mouse 8-cell embryos includes the formation of a polar cluster of cytoplasmic endocytotic organelles (endosomes) subjacent to an apical surface pole of microvilli. A similar polar morphology, supplemented by basally localized secondary lysosomes, is evident following division to the 16-cell stage in outside blastomeres, precursors of the trophectodermal lineage. The roles of microfilaments and microtubules in generating and stabilizing endocytotic and surface features of polarity (visualized by horseradish peroxidase incubation and indirect immunofluorescence labeling, respectively) have been evaluated by exposure of 8- and 16-cell embryos and 8-cell couplets to drugs (cytochalasin D, colcemid, nocodazole) that disrupt the cytoskeleton. The generation of endocytotic polarity is dependent upon intact microtubules and microfilaments, but the newly established endocytotic pole in blastomeres from compacted 8-cell embryos appears to be stabilized exclusively by microtubules. Polarized endocytotic organelles at the 16-cell stage are more resistant to drug treatment than at the 8-cell stage (probably due to microfilament interactions) indicating a maturation phase in the polar cell lineage. Microtubules are also responsible for the orientation of endocytotic clusters along the cell's axis of polarity. In contrast, the generation and stability of polarity at the cell surface appears relatively independent of cytoskeletal integrity. The results are discussed in relation to the mechanisms that may control the development and stabilization of polarization during cleavage.

Changes in the distribution of membranous organelles during mouse early development

The unfertilized oocyte, fertilized egg and early embryo (2-cell to 16-cell) of the mouse have been examined immunocytochemically for the distribution of antigens associated with the endoplasmic reticulum, the lysosomal and acidic vesicle fraction (100 kD antigen), Golgi apparatus (135 kD antigen) and coated vesicles (clathrin). The distribution of these antigens has also been examined in isolated 8-cell and 16-cell-stage blastomeres of various ages and phenotypes. Endoplasmic reticulum is detected only weakly in the oocyte and egg, but is seen abundantly at later stages both in association with the nuclear membrane and evenly distributed throughout the cytoplasm, except in regions of cell:cell apposition from which it is excluded. Intracellular clathrin is associated with the spindle in mitotic and meiotic cells. During interphase, clathrin is distributed throughout the cell until the mid-8-cell stage when it is concentrated into the apical region of the cell under the region of membrane at which a surface pole of microvilli will form subsequently. Thus, the cytoplasmic polarization of clathrin precedes overt polarization at the surface. At mitosis, the clathrin relocates to the spindle and is distributed to both daughter cells. It resumes an apical location beneath the surface pole of microvilli in polar daughter 1/16 cells, but remains dispersed in apolar daughter 1/16 cells. Both the lysosomal and Golgi antigens are distributed throughout the cytoplasm until the early 16-cell stage. In pairs of 16-cell blastomeres both antigens aggregate in a single cluster and do so whether the surface phenotype of the blastomeres is polar or apolar. The position of this cluster is not consistently related to the point of contact with the other cell in the pair but there is a suggestion that in cells with a polar surface phenotype the polar foci of Golgi/lysosomal antigens are located between the nucleus and the surface pole at earlier time points, but shift to a position between the basolateral membrane and the nucleus at the later time point. In intact 16-cell embryos also, the aggregated Golgi/lysosomal antigens of polar cells appear to localize to the basal region. The distributions of these various organelles in embryonic cells reported here show a number of differences from those reported previously for mature, differentiated cells.

Maturation and polarization of the endocytotic system in outside blastomeres during mouse preimplantation development

The maturation and distribution of the endocytotic apparatus in outside cells of cleavage-stage mouse embryos have been studied to determine the nature and sequence of changes associated with the differentiation of the polarized trophectoderm epithelium of the blastocyst. Various quantitative and qualitative techniques used at the light and electron microscopic levels have revealed an incremental pattern of endocytotic maturation and polarization. Oocytes, eggs and blastomeres within embryos up to the early 8-cell stage contain clusters of prelysosomal endocytotic vesicles (endosomes) distributed randomly in the cortical cytoplasm. During the 8-cell stage and continuing into the early 16-cell stage, endosomes become progressively localized in the apical cytoplasm beneath the microvillous pole. Endosome polarization is initiated prior to overt polarization of the surface membrane. Concomitant with endosome polarization, pinocytotic activity at the cell surface, revealed by horseradish peroxidase labelling, becomes segregated preferentially to the apical rather than the basolateral membrane. The final maturation phase occurs at the late 16-cell stage when secondary lysosomes, characterized by trimetaphosphatase reactivity, form and polarize in the basal cytoplasm.

Developmental variability within and between mouse expanding blastocysts and their ICMs

We have attempted to reduce the developmental heterogeneity amongst populations of mouse blastocysts by synchronizing embryos to the first visible signs of blastocoel formation. Using embryos timed in this way, we have examined the extent of variation of inside and outside cell number and of inside cell size, nuclear DNA content and developmental potential, between and within embryos of a similar age postcavitation. The overall impression gained is one of wide heterogeneity in inside:outside cell number ratios and in cell cycling and its relation to cavitation among embryos of similar age postcavitation. However, the simplest explanation of our results suggests that cavitation generally begins at a time when most outside cells are in their sixth developmental cell cycle and that outside cells, as a population, are a little ahead of inside cells in their cell cycling. Additionally we present evidence that, within at least some individual inner cell masses (ICM), there is intraembryo variation in the time at which inside cell developmental potential becomes restricted.

Microtubules influence compaction in preimplantation mouse embryos

The role of microtubules during compaction of the 8-cell-stage mouse embryo was investigated using the drugs Taxol (which leads to a non-controlled polymerization of tubulin) and Nocodazole (which causes depolymerization of microtubules). Taxol inhibits compaction in most non-compacted embryos and reverses it in already compacted embryos. These effects were observed on both cell flattening (as judged by phase-contrast microscopy) and on cell surface polarization (as judged by scanning electron microscopy and the surface binding of fluorescent concanavalin A). In contrast Nocodazole does not inhibit cell flattening, but rather accelerates its completion. Nocodazole influences the detailed organization of the surface pole and appears to reduce the incidence of surface polarization but does not reverse polarity once established to a significant extent. We conclude that microtubules exercise a constraining role during compaction, influencing cell shape, cell organization and the time at which compaction takes place.

Changes in actin distribution during fertilization of the mouse egg

Unfertilized mouse oocytes and eggs 1–8 h after fertilization in vitro were examined at the light microscope level for structural changes, distribution of actin (as assessed by both antiactin antibodies and NBD-phallicidin), surface binding of concanavalin A (Con A) and chromosomal distribution and condensation. The influence of cytochalasin D on these events was also assessed. Changes in actin distribution were associated with rotation of the second anaphase spindle, formation of the second polar body, the events following incorporation of the sperm nucleus, and formation and migration of the pronuclei. Cytochalasin D prevented spindle rotation, polar body formation, pronuclear migration and the restoration of Con A binding over the site of sperm entry and the site of polar body formation, but did not affect sperm fusion and entry, the loss of Con A binding at the site of sperm entry and pronuclear formation.

Changes in actin distribution during fertilization of the mouse egg

Unfertilized mouse oocytes and eggs 1-8 h after fertilization in vitro were examined at the light microscope level for structural changes, distribution of actin (as assessed by both antiactin antibodies and NBD-phallicidin), surface binding of concanavalin A (Con A) and chromosomal distribution and condensation. The influence of cytochalasin D on these events was also assessed. Changes in actin distribution were associated with rotation of the second anaphase spindle, formation of the second polar body, the events following incorporation of the sperm nucleus, and formation and migration of the pronuclei. Cytochalasin D prevented spindle rotation, polar body formation, pronuclear migration and the restoration of Con A binding over the site of sperm entry and the site of polar body formation, but did not affect sperm fusion and entry, the loss of Con A binding at the site of sperm entry and pronuclear formation.