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Biomedical subjects

E A McLaughlin

Publications and source records attributed to E A McLaughlin.

At least 37 records · Page 2Linked to original sources
PubMed1994

Higher gonadotrophin surge-attenuating factor bioactivity is found in small follicles from superovulated women.

Ovine and rat pituitary bioassays for gonadotrophin surge-attenuating factor (GnSAF) were utilized to determine whether the level of GnSAF bioactivity in pooled human follicular fluid (hFF) from superovulated women varied according to follicle diameter (< or = 11 mm, 12-15 mm and 16-21 mm follicles examined using the ovine bioassay, or < or = 10 mm, 11-13 mm, 14-17 mm, 18-20 mm, 21-24 mm and > or = 25 mm follicles examined using the rat bioassay). When tested using dispersed ovine pituitary cells, GnSAF bioactivity, expressed in terms of the reduction in gonadotrophin-releasing hormone (GnRH)-induced LH secretion, was inversely related to follicle diameter (P < 0.01). In response to 5 microliters hFF/well from follicles of < or = 11, 12-15 and 16-21 mm diameter, GnRH-induced LH secretion was reduced to 40.5 +/- 6.9%, 65.2 +/- 6.6% and 83.7 +/- 7.9% of control respectively. A similar inverse relationship was observed when a second batch of hFF samples from different sized follicles was tested using rat pituitary cell monolayers. Expressing GnSAF bioactivity in terms of the dose required to suppress GnRH-induced LH secretion by rat pituitary cells to 50% of the maximal suppression observed (ED50), the three smallest follicle size pools contained the most GnSAF (ED50 values of 0.13, 2.79 and 5.36 microliters hFF/well from follicles of < or = 10, 11-13 and 14-17 mm respectively). The ED50 values for follicles of 18-20, 21-24 and > or = 25 mm were 8.81, 27.1 and 60.0 microliters hFF/well respectively. Thus hFF from follicles < or = 11 mm was over 450 times more potent than hFF from follicles > or = 25 mm in suppressing GnRH-induced LH release. The ED50 values for inhibin bioactivity (measured as the suppression of basal FSH secretion from rat pituitary monolayers) were much less variable than those for GnSAF bioactivity (between 0.85 and 0.13 microliters hFF/well). Inhibin immunoreactivity, measured by a two-site immunoradiometric assay, followed the same pattern as inhibin bioactivity with lowest concentrations in the smallest follicles (41.96 ng/ml) and highest concentrations in the three largest follicle size groups (56.48-64.48 ng/ml). The specific effects of inhibin on GnRH-induced LH and basal FSH release in these pituitary bioassays were determined by incubating culture dishes with pure recombinant human inhibin at doses of 0.025-25 ng/well. In both the sheep and rat pituitary monolayers, basal FSH was suppressed (ED50 = 0.02 and 0.16 ng/well respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Effects of cryopreservation on the human sperm acrosome and its response to A23187.

The proportion of human spermatozoa from 28 ejaculates to lose their acrosomes during cryopreservation was measured and correlated with the number that became immotile or lost the integrity of their plasma membrane. The ability of washed spermatozoa to acrosome react in response to A23187 before and after cryopreservation was compared. Motility was assessed by time-lapse photography; intact acrosomes were stained with fluorescein conjugated Pisum sativum agglutinin and dead spermatozoa were stained with bisbenzimide (H33258). Twenty-four per cent of spermatozoa lost their acrosomes during freezing and thawing, but the number that did so was not correlated with the number that became immotile or non-viable. Frozen spermatozoa exhibited fewer spontaneous acrosome reactions than did fresh spermatozoa (5 versus 13% after 4 h), but they responded to A23187 in a similar way. Although frozen spermatozoa were significantly more likely to die during the incubation, the data do not suggest that degenerative acrosome loss had a major influence on the results. In the hamster egg test frozen-thawed spermatozoa achieved more penetrations than did fresh spermatozoa when stimulated with 0 or 1 mumol A23187 l-1 but considerably fewer when stimulated with 4 mumol A23187 l-1. The following conclusions were made. First, cryopreservation damage to the acrosome, the plasma membrane and the flagellum can occur independently. Second, acrosome function is maintained after cryopreservation as long as the organelle remains mechanically intact. Third, some spermatozoa that lose their acrosomes during cryopreservation remain viable and can fuse with zona-free hamster eggs.

Acrosome↗
PubMed1992

The yield, motility and performance in the hamster egg test of human spermatozoa prepared from cryopreserved semen by four different methods.

Different procedures were investigated for the dilution of human cryopreserved semen and the preparation of an enriched population of motile spermatozoa for assisted reproduction. The dilution of a 0.25 ml straw of cryopreserved human semen by addition of 2.0 ml Ham's F-10 buffer in one step caused a large decrease in the proportion of motile spermatozoa. This was due to osmotic stress because many of the diluted spermatozoa exhibited swollen tails. To a large extent the damage could be avoided by adding the buffer in 0.10-ml aliquots at 30-s intervals. Spermatozoa obtained after such dilution of cryopreserved human semen were subjected to the swim-up procedure, to centrifugation on two-step gradients of Nycodenz or Percoll, or to filtration through glass fibre paper and compared with respect to yield, motility parameters and penetrating ability in the hamster egg test. The swim-up procedure yielded spermatozoa with excellent motility but only 12% of the available motile spermatozoa were recovered. On both Nycodenz and Percoll gradients, greater than 40% of the available motile spermatozoa were recovered and the average velocity of the spermatozoa was not significantly less than for the swim-up technique. When A23187 was used to promote acrosome reactions in the hamster egg test, Percoll-prepared spermatozoa achieved an average of 8.6 decondensed sperm heads/egg compared to 1.9 for Nycodenz and 1.3 for the swim-up procedure. The yield from glass fibre paper filtration was only 12% and the velocity of the spermatozoa and their performance in the hamster egg test was significantly poorer than in all the other methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Controlling the swimming speed of human sperm by varying the incubation temperature and its effect on cervical mucus penetration.

The objective of the present experiments was to study the effect of sperm velocity as a single variable on the ability of sperm to penetrate cervical mucus in a modified Kremer test. Sperm incubated at 13, 22 and 37 degrees C exhibited progressive velocities of 25 +/- 1.7, 40 +/- 2.1 and 56 +/- 2.1 microns sec-1 (mean +/- SEM, n = 6) respectively, but the percentage of progressively motile sperm, their lateral head displacement and the viscoelastic properties of cervical mucus remained comparatively unchanged over this temperature range. The number of sperm which penetrated the mucus and the percentage of successful collisions were correlated strongly with the average velocity of the sperm population (r = 0.82 and r = 0.72 respectively). It is concluded that sperm velocity has an important influence on the penetration of cervical mucus because it governs the frequency of collisions with the mucus interface and is determined by the thrust generated by the flagellum which also determines the ability of the sperm to traverse the mucus interface.

Cervix Uteri↗
PubMed1992

Motility characteristics and membrane integrity of cryopreserved human spermatozoa.

The motility characteristics of washed spermatozoa from 50 normal ejaculates were measured by time-lapse photography, before and after cryopreservation. Plasma membrane integrity was assessed by the hypo-osmotic swelling test and with the supravital fluorescent dye bisbenzimide (H33258). There was a marked decline in the percentage of progressively motile spermatozoa after cryopreservation, the extent varying widely among donors. Results were, however, consistent between different ejaculates from the same individual. The ability of spermatozoa to survive cryopreservation could not be predicted from the properties of the semen beforehand. The mean velocity of the spermatozoa was significantly reduced after freezing, but the lateral head displacement was unaltered. There was a significant reduction in the proportion of spermatozoa with intact plasma membranes after cryopreservation and the results of the hypo-osmotic swelling test and H33258 tests correlated closely. There was no correlation between the declines in the percentage of motile spermatozoa, or intact spermatozoa and the sperm velocity. We conclude that membrane rupture is not the sole cause of loss of motile spermatozoa during freezing and that the decrease in the proportion of motile spermatozoa is caused, at least in part, by a separate process from that responsible for the decrease in the average swimming speed of spermatozoa.

Analysis of Variance↗
PubMed1992

The contribution of the toxicity of a glycerol-egg yolk-citrate cryopreservative to the decline in human sperm motility during cryopreservation.

The contribution of the toxicity of glycerol-egg yolk-citrate (GEYC) cryopreservative medium to the loss of function of human spermatozoa during cryopreservation was determined by investigating the effect of mixing semen with the medium on sperm motility. The percentage of progressively motile spermatozoa, velocity (micron s-1) and lateral head displacement (micron) (mean +/- SEM, n = 28) were 55 +/- 4.1, 47 +/- 2.7, 4.4 +/- 0.2 and 32 +/- 3.8, 40 +/- 2.5, 3.6 +/- 0.25 and 15 +/- 2.5, 28 +/- 1.1, 2.8 +/- 0.15 in suspensions of washed spermatozoa prepared from fresh, GEYC-treated and frozen-thawed semen, respectively. The variables changed only slightly after incubation for 3 h. The toxicity of GEYC did not vary significantly between samples which survived the complete freeze-thaw cycle well or very poorly. The toxicity of GEYC is responsible for about 50% of the loss of progressively motile spermatozoa during the complete cryopreservation process, but has little effect on the quality of motility. Susceptibility to GEYC does not explain observed differences in the ability of semen samples to survive freezing.

Citrates↗
PubMed1992

Postgraduate prosthetic training within the community dental service.

There is a need for clinical prosthetics training for community dentists. This was apparent when a postgraduate course, which dealt with prosthetic care of elderly people, was organised for dentists working in the community dental service. Over 100 community dentists applied for 40 places. At the outset they were asked to complete a questionnaire which addressed their professional career together with their current prosthetic experience. The majority of participants were employed at dental officer level; 18 per cent were at senior dental officer level. Many of the dentists worked in districts where one or more community dentists provided all the prosthetic treatment within the community dental service. The majority of districts receive their prosthetic patients as a result of referrals from a variety of sources. Only eight dentists saw the majority of their patients at domiciliary visits; many did not see any patients in this manner. The course participants considered that their greatest clinical weakness in prosthetic skills was in the production of copy dentures and in denture design. Many of the dentists who attended the course did not provide a prosthetic service but most of them said that they anticipated that the necessity for this would increase in the future.

Adult↗
PubMed1990

A comparison of the freezing of human semen in the uncirculated vapour above liquid nitrogen and in a commercial semi-programmable freezer.

The cooling rates inside 0.25-ml semen straws filled with glycerol, egg yolk, citrate buffer were compared between a standard vapour freezing procedure and freezing in a Nicool LM-10 semi-programmable freezer. During vapour freezing, the cooling rate at the bottom of the straw was much faster than at the top and there was considerable variation between replicates. By contrast, position within the straw did not affect the cooling rate in the Nicool LM-10 procedure and replicates were more consistent. More motile spermatozoa survived the Nicool freezing procedure and their lateral head displacement was greater than vapour frozen spermatozoa. However the percentage of intact spermatozoa and their velocity was very similar after the two procedures. We conclude that the freezing procedure using the Nicool LM-10 provides a comparatively economical way to achieve consistent semen freezing for research studies.

Cell Membrane↗
PubMed1988

An evaluation of the role of relaxin in the penetration of cervical mucus by spermatozoa.

Relaxin-like immunoreactivity was measured in seminal plasma from men who were separated into two groups, on the basis of a previous positive or negative result in a postcoital cervical mucus penetration test. There was no difference in the relaxin concentration between the groups. The effect of exogenous porcine relaxin (0, 10 or 100 ng/ml) on human cervical mucus penetration in vitro by washed human spermatozoa was studied using a capillary tube preparation. In the positive postcoital test group the highest relaxin concentration (100 ng/ml) tended to inhibit cervical mucus penetration, although this effect was only significant for one of the parameters measured (number of spermatozoa penetrating to the 10-mm mark). The same trend was apparent for the negative postcoital test group, but no differences were significant. The results are in direct contrast to previous reports that relaxin can stimulate human spermatozoa motility and cervical mucus penetration.

Cervix Mucus↗
PubMed1986

Norethisterone treatment to control timing of the IVF cycle.

The use of norethisterone to control the timing of the preceding menstrual cycle and in consequence the timing of the in-vitro fertilization (IVF) cycle has been evaluated in a therapeutic IVF programme in which oocyte recovery was limited to 2 days each week. A consecutive series of 181 cycles after norethisterone and 29 untreated controls were compared. Menstruation occurred 2-3 days after norethisterone as planned in 82% of patients overall and in 87% of patients whose menstrual cycle length varied by no more than 2 days about the median. Norethisterone treatment did not significantly affect the outcome of IVF treatment compared with the controls in respect to cycles abandoned (12 versus 0%, respectively), peak follicular diameter (mean 18.1 mm versus 18.3 mm 48 h before laparoscopy), oocyte recovery rate (4.6 versus 4.5 per patient), oocyte morphology (63% versus 52% mature), or fertilization rate (72 versus 65% of mature oocytes). Clinical pregnancies were too few for comparison (rates 27 versus 9% per laparoscopy) but the overall rate (23%) indicated effectiveness of the methods. Prior norethisterone treatment appears to be an effective and useful means of controlling the timing of the oocyte recovery in IVF treatment.

Female↗
PubMed1986

Identification of relaxin immunoreactivity in human follicular fluid.

Relaxin immunoreactivity has been found in samples of human follicular fluid collected from artificially stimulated pre-ovulatory follicles. The crude extract caused a reduction in the height of the contractions in a rat uterine strip bioassay. The reactive material eluted from Sephadex G50 in two major peaks. The first contained approximately 60% of the immunoreactivity and had an elution position corresponding to that of porcine relaxin, indicating a mol. wt of approximately 6000 daltons. The second peak was of a lower mol. wt, but its exact size and significance are unknown. A possible role for relaxin in the process of follicular rupture is suggested.

Biological Assay↗
PubMed1985

Endometriosis and ovulatory disorder: reduced fertilisation in vitro compared with tubal and unexplained infertility.

In-vitro fertilisation (IVF) was carried out once for each of 104 couples who had a single cause of infertility. The group with tubal damage was used as the reference for normal fertilising capacity of both oocytes and sperms: the IVF rates were 68% (71/105) per mature oocyte and 88% (37/42) for couples from whom mature oocytes were recovered. Couples with poor sperm/mucus penetration had reduced IVF rates: 32% (12/38) per oocyte and 60% (9/15) per couple. Sperm function, which was judged normal by means of standard seminal analysis and mucus penetration, was confirmed by normal IVF in unexplained infertility: 63% (37/59) per oocyte and 90% (18/20) per couple. Despite favourable sperm function in their partners, women with endometriosis (without tubal damage) had reduced IVF rates: 33% (19/58) per oocyte and 60% (9/15) per couple. These findings indicate that ovulatory disorder is present in endometriosis and suggest that it causes the associated infertility.

Adult↗