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J M Rees

Publications and source records attributed to J M Rees.

At least 19 recordsLinked to original sources
PubMed2001

Value of the hamster oocyte test and computerised measurements of sperm motility in predicting if four or more viable embryos will be obtained in an IVF cycle.

The experimental group consisted of men from 81 couples waiting for in vitro fertilization (IVF), about half of whom had sperm dysfunction defined by a negative post-coital test. A diagnostic semen sample was subjected to a hamster oocyte penetration test (HOPT) after stimulation of the acrosome reaction with A23187 +/- pentoxifylline and to computerized sperm motility measurements (CASA) as well as conventional semen analysis according to the WHO protocol. Logistic regression was used to identify parameters that predicted the probability of achieving four or more viable embryos at IVF among the 65 couples from whom four or more oocytes were collected. The number of oocytes available and whether the woman had previously been pregnant (ever pregnant) were important factors but once these had been taken into account a number of sperm parameters had additional predictive power. The most useful of these were the percentage sperm static (CASA) or the percent sperm progressively motile (conventional semen analysis) in the Percoll preparation. A model incorporating the number of oocytes collected, ever pregnant and percentage sperm static achieved 85% correct prediction of outcome in the experimental dataset but only 62% correct prediction in an independent set of 280 IVF cycles. The percentage of hamster oocytes penetrated was a significant predictor but had no advantage over simple motility measurements. The results illustrate the difficulty of basing a prognosis for achieving satisfactory fertilization in IVF on the properties of spermatozoa.

Adult↗
PubMed1996

Birth weight associated with lowest neonatal mortality: infants of adolescent and adult mothers.

OBJECTIVE: We tested the hypothesis that survival is highest for infants born in the same weight range whether mothers are adolescent or adult, comparing the weights at which infants of these mothers achieve lowest neonatal mortality. METHODS: The relationship between birth weight and neonatal mortality was studied in births to 16.4 million women using the National Center for Health Statistics 1983-1987 national linked birth/infant death data sets. Neonatal mortality rates were calculated for 500 g birth weight categories. Births for maternal ages < or = 15 years, 16 years, and 17 to 18 years were compared with births to adults 19 to 34 years of age, whites and blacks considered separately. The birth weight categories associated with minimum neonatal mortality and the weight range corresponding with greatest survival were determined for each age and racial group. RESULTS: Minimum neonatal mortality rates occurred at the same birth weights (3500 to 4499 g white and 3000 to 3999 g black) whether mothers of the infants were adolescents or adults. The most favorable range of birth weight, in which survival was greatest, commenced at 3000 g for all mothers, terminating at 3999 g for most black adolescents and black adults, 4499 g for most white adolescents, and 4999 g for white adults. Of infants born to mothers < or = 16 years old, 33% were lighter and 1.5% were heavier than the favorable birth weight range. CONCLUSION: The birth weight categories with minimum neonatal mortality and the birth weight range in which neonatal survival was greatest were comparable for infants of adolescents and adults. Lower birth weights, occurring more frequently in births to teenage mothers, were associated with higher neonatal mortality. Assisting adolescent mothers to bear infants with birth weights in the range corresponding with low neonatal mortality is an appropriate goal of clinical management.

Adolescent↗
PubMed1994

Pentoxifylline acts synergistically with A23187 to increase the penetration of zona-free hamster oocytes by cryopreserved human spermatozoa.

The number of cryopreserved human spermatozoa which penetrated zona-free hamster oocytes after stimulation with 2 mumol A23187 per litre was increased by the further addition of 0.6 or 3.6 mmol pentoxifylline per litre. With spermatozoa prepared by washing by repeated centrifugation, the median numbers of sperm heads/egg were 1.9, 7.9 and 10.8 in the presence of 0, 0.6 or 3.6 mmol pentoxifylline per litre, respectively. A similar effect was observed with spermatozoa prepared on a Percoll gradient. As A23187 inhibited sperm motility, and this was exacerbated by pentoxifylline, the increased penetration rate of hamster oocytes cannot be explained by improved sperm motility. The number of spermatozoa stimulated to acrosome react by 2 mumol A23187 per litre was increased 3-fold by 3.6 mmol pentoxifylline per litre and 4-fold by 5 mmol caffeine per litre. These data suggest that cAMP may act synergistically with Ca2+ to stimulate the acrosome reaction. Pentoxifylline may improve the fertility of poor-quality human spermatozoa by enhancing their ability to respond to the Ca2+ signal produced by binding to the zona pellucida.

Acrosome↗
PubMed1992

Weight gain in adolescents during pregnancy: rate related to birth-weight outcome.

This study of 459 subjects from prenatal clinics for teenagers at three universities across the United States, addresses questions about gestational weight gain in adolescents raised by the 1990 Institute of Medicine Report. Rate and pattern of gain, independent of pregravid weight, are based on serial measures of mothers with favorable and unfavorable outcomes. Rate of gain (determined by using regression statistics) from weeks 15 to 40 was 0.588, 0.510, and 0.488 kg/wk for mothers of term infants weighing 3000-4000 g, term infants weighing < 3000 g, and preterm infants, respectively. The significantly lower percentage of infants weighing 3000-4000 g vs < 3000 g needing intensive care at birth (6% vs 15%, respectively, P < 0.05) further indicates the superior outcome among mothers with higher rates of gain. Rate of gain of mothers of infants weighing 3000-4000 g (favorable outcome) equaled the highest amount provisionally recommended, suggesting that restricting natural gain of adolescents to recommended rates may result in smaller than optimal infants.

Adolescent↗
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

The cost of burn care and the federal government's response in the 1990s.

This article attempts to predict the federal government's response to the cost of burn care in the 1990s by examining the explosive growth of health care costs in the 1980s and the impact that this had on hospitals with burn centers. The Prospective Payment System (PPS) was enacted in 1983, which limited the government's liability to hospitals by effectively capping the amount of federal dollars in the system. The inequities of the classification of burn patients by the PPS is discussed and a proposal for modification is outlined.

Burn Units↗
PubMed1991

The effect of A23187 concentration and exposure time on the outcome of the hamster egg penetration test.

We investigated the conditions required to enhance the performance of human sperm in the hamster egg penetration test with the free acid form of A23187. The best performance was observed after stimulation with 2 microM A23187 for 1 h when the median penetration rate with sperm from fertile donors was 100% of eggs with 5.8 decondensed sperm heads/egg. Extending the stimulation period with 2 microM A23187 to 2 or 3 h, resulted in a progressive decrease in the penetration rate. In the absence of A23187, the penetration rate was lower (0.7 decondensed sperm heads/egg after 1 h) but increased with stimulation time. A similar picture was observed with sperm from patients taken for an IVF programme. For a pool of cryopreserved semen, the coefficient of variation of the penetration rate after stimulation with 2 microM A23187 for 1 h, expressed as decondensed sperm heads/egg, was 11% within and 20% between assays. There was no correlation between the outcome of the hamster egg penetration test and the percentage motility, velocity or lateral head displacement of the sperm measured after the same stimulation regime. However, in IVF patients the initial velocity and lateral head displacement of the sperm (zero time) were correlated with the best result from the hamster egg penetration test (r = 0.62 and 0.57 respectively). No motility changes characteristic of capacitation were detected. We conclude that stimulation with 2 microM A23187 (free acid) for 1 h prior to the addition of the zona free hamster eggs can produce a high penetration rate with fertile samples and provides a convenient and robust protocol for the assay. However, when carried out in this way the test does not assess the ability of the sperm to capacitate.

Acrosome↗
PubMed1990

Management of obesity in adolescence.

A great deal of the discouragement about treating adolescents who are obese is related to the traditional treatment approaches. Obesity is a complex problem needing comprehensive treatment. Focusing on weight loss as a short-term goal is unreasonable because of individual variation in the physiologic potential to lose weight. Short-term goals and rewards are related to adopting daily habits that will lead to a decrease in energy storage in the long term. Support for changing habits and improving psychosocial adjustment is a necessary component of effective treatment, enabling patients and their families to make changes.

Adolescent↗
PubMed1990

Effect of caffeine and of pentoxifylline on the motility and metabolism of human spermatozoa.

Human spermatozoa were washed and incubated with 6 mM-caffeine or 0.15-1.2 mM-pentoxifylline. Sperm motility was measured by time-lapse photography, the rate of glycolysis by the release of tritiated water from 1 mM-[3-3H]D-glucose and the rate of mitochondrial respiration by the release of 14CO2 from 1 mM-[U-14C]-L-lactate or 1 mM-[2-14C]pyruvate. Caffeine stimulated the majority of spermatozoa to convert from the 'rolling' to the 'yawing' mode of progression with a concomitant increase in lateral head displacement from 4.1 +/- 0.09 microns (343) to 6.7 +/- 0.25 microns (105) (mean +/- s.e.m. (number of spermatozoa)). There was a 45% decline in the percentage of progressively motile spermatozoa and a very small decrease in their velocity. Pentoxifylline had only a slight effect on lateral head displacement or percentage motility but produced a significant increase in velocity. Both compounds increased the rate of glycolysis by greater than 40% but elevated the rate of 14CO2 production to a smaller extent. The concentrations of ATP and ADP changed very little. We conclude that the glycolytic pathway in human spermatozoa can respond efficiently to changes in energy demand.

Adenosine Diphosphate↗