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Biomedical subjects

I L Pike

Publications and source records attributed to I L Pike.

At least 19 recordsLinked to original sources
PubMed2000

Pregnancy outcome for nomadic Turkana pastoralists of Kenya.

The outcome of an individual pregnancy is a key component of overall reproductive success and is strongly influenced by environmental, behavioral, and biological variation within populations. This prospective study examined the outcomes of 68 pregnancies among nomadic Turkana of Kenya from July 1993 to July 1994. A total of 12 women experienced pregnancy losses, and 3 women experienced live births with a subsequent perinatal death. The following characteristics are associated with increased risk for experiencing a fetal or perinatal death: severe morbidity episodes, shorter nonpregnant intervals, lower third-trimester weight, higher third-trimester summed skinfolds but limited third-trimester reduction in summed skinfolds, and higher activity levels late in gestation. Turkana newborns measured within 48 hr of birth (n = 19) weighed an average of 2,860 +/- 640 g and had a mean ponderal index of 2.72 +/- 0.46. Variation in birth weight was predicted by preterm delivery, delivery during the wet season, and maternal morbidity levels. Birth length averaged 50.8 +/- 6.8 cm and was positively influenced by full term delivery, better maternal health, and birth during the dry season. These results suggest complicated pathways linking the physical environment, subsistence requirements, heterogeneity in maternal fitness, behavior, and pregnancy outcome. The results augment the larger picture of reproductive success for Turkana nomads who live in a highly variable savanna environment.

Birth Weight↗
PubMed1998

An alternative method for assessing early mortality in contemporary populations.

Biological anthropologists are interested in a population's early mortality rates for a variety of reasons. Early mortality (infant or juvenile) is of obvious importance to those interested in demography, but early mortality statistics are useful for life history analysis, paleodemography, and human adaptability studies, among others. In general, the form of mortality statistics is derived from demography, where chronological age is the gold standard for statistical calculation and comparison. However, there are numerous problems associated with the collection, analysis, and interpretation of early mortality statistics based on age, particularly for anthropological research, which is often conducted in small or non-calendrical-age numerate populations. The infant mortality rate (IMR), for example, is notoriously difficult to determine in populations where accurate accounting of age is not routine, and yet it is widely used in demography, public health, medicine, and social science research. Here we offer an alternative to age-based early mortality statistics that makes use of human biologists' interest in, and skill at, assessing human growth and development. Our proposal is to use developmental stages of juveniles instead of relying exclusively on age as the basis for mortality statistics. Death or survival according to a developmental stage (such as crawling or weaning) may provide more accurate data that are also more closely related to the cause of death. Developmental stages have the added advantage of putting infants and children back at the center of the discussion of early mortality by focusing on their activities in relation to their environment. A case study from the Turkana population of Kenya illustrates the use of developmental stages in describing early mortality.

Cause of Death↗
PubMed1995

Clinical intracytoplasmic sperm injection (ICSI) results from Royal North Shore Hospital.

The technique of intracytoplasmic sperm injection (ICSI) was first introduced to the Royal North Shore Hospital in April 1993 as part of a controlled study of 100 patient cycles in which sibling oocytes were inseminated by either subzonal insemination (SUZI) or ICSI. This trial showed direct sperm injection to be superior in terms of fertilization. In that study, 58 embryo transfers of 101 ICSI-derived embryos resulted in 10 pregnancies. No miscarriages have occurred and a total of 10 fetal hearts (9.8% per embryo transferred) were detected on ultrasound. There have been 10 deliveries of 10 babies. Since the beginning of 1994, intracytoplasmic injection has been used exclusively for patients requiring micromanipulation to achieve fertilization. There have been 200 patient cycles with 1650 oocytes collected (8.8 oocytes per cycle). Of these oocytes, 1548 were mature (94%) and were subjected to ICSI, and normal fertilization occurred in 874 (56%) of the injected oocytes. The number of oocytes which cleaved and were suitable for fresh transfer or cryopreservation was 818 (94%). There have been 153 fresh embryo transfers of 326 embryos. Twenty-six pregnancies (17% per embryo transfer) have resulted, 22 of which proceeded to ultrasound examination in which 23 fetal hearts were detected (7% per embryo transferred). Three miscarriages have occurred, leaving 19 ongoing pregnancies. There have been 127 cryopreservation procedures involving 492 embryos. To date, there have been 47 embryo thaw cycles, and 93 of the 115 (81%) thawed embryos survived and were transferred. These 47 embryo transfers resulted in 10 pregnancies (21% per embryo transfer), one of which one has miscarried.(ABSTRACT TRUNCATED AT 250 WORDS)

Australia↗
PubMed1994

Injection of multiple sperm into the perivitelline space as a treatment of male infertility.

This paper reports the outcome of 274 treatment cycles using multiple injection of sperm into the perivitelline space as a treatment of male factor infertility. A total of 170 couples underwent this form of treatment; 59.1% of cycles had at least one oocyte normally fertilized with an overall normal fertilization rate of 17.2%. The development rate of normally fertilized embryos was high (98.5%) and resulted in a pregnancy rate (positive human chorionic gonadotrophin 18 days after embryo transfer) of 21.4% per embryo transfer procedure (a maximum of 3 embryos were transferred per procedure). The relationship between the number of sperm injected and the fertilization rate and other factors affecting the outcome are discussed.

Female↗
PubMed1992

Actions of platelet activating factor (PAF) on gametes and embryos: clinical aspects.

Platelet activating factor (PAF) is a phospholipid widespread in body tissues. Previous reviews have discussed its production by preimplantation embryos and the evidence implicating it as an autocrine mediator in aspects of gamete and embryo physiology. Human spermatozoa contain variable amounts of PAF, the amount contained depending on the source and method of preparation of the sperm. Incubation of human sperm with PAF tends to increase their forward velocity, especially in samples with slow motility. PAF treatment causes an increase in the proportion of acrosome-reacted sperm and in their ability to penetrate both zona-free hamster ova and cervical mucus. PAF has been found in human follicular fluid at ovulation. A role for PAF in ovulation has been suggested, because PAF antagonists reduce the rate of ovulation in rats. In some studies, modest improvements to mouse in vitro fertilization (IVF) rates have been achieved with PAF supplementation of media under specific conditions. Furthermore, in the rabbit and mouse, PAF antagonists have been reported to inhibit fertilization in vivo and in vitro respectively. However, addition of PAF to human IVF medium, but only at the time of insemination and fertilization, had no effect on either fertilization or pregnancy rates. Sensitive bio- and immuno-assays have shown that PAF is secreted by human embryos into their fluid milieu. PAF secretion by these zygotes during culture, although markedly variable, has been correlated with the achievement of pregnancy and pregnancy outcome. Although the secretion of PAF by the mouse embryo decreases during culture in vitro, exogenous PAF enhances embryo viability during culture. Similarly, culture of human zygotes in PAF-supplemented medium prior to embryo transfer significantly increases the chance of achieving pregnancy. Both the implantation and live-birth rates are increased in human IVF by addition of PAF to the medium.

Embryo, Mammalian↗
PubMed1989

Supplementation of in-vitro fertilisation culture medium with platelet activating factor.

The supplementation of culture medium with platelet activating factor (PAF) on the subsequent implantation and pregnancy potential of pre-embryos produced by in-vitro fertilisation was studied. Pre-embryo culture medium was supplemented with 0 (control), 0.186, 0.93, or 1.49 mumol/1 PAF. Pre-embryos were transferred to PAF-containing medium 15-17 h after insemination (ie, just before syngamy) for 24 h and then transferred to the uterus. For 185 women receiving control pre-embryos, the pregnancy rate (positive beta human chorionic gonadotropin per oocyte retrieval) was 10.2%, while 166 women who received PAF treated pre-embryos (all concentrations combined) achieved a pregnancy rate of 17.5%. This difference was significant. The pregnancy rates per pre-embryo transferred were 6.1% and 9.4% for the control and PAF groups, respectively. The percentage of positive pregnancy tests that resulted in a viable pregnancy (presence of fetal heart at 8 weeks) was 78.9% in the controls and 75.9% in the PAF group. There was no difference in the average number of embryos transferred in either group. The increase in the pregnancy rate after a short exposure of pre-embryos to PAF in vitro suggests that PAF mediates pre-embryo development.

Chorionic Gonadotropin↗
PubMed1987

Use of a bioassay for embryo-derived platelet-activating factor as a means of assessing quality and pregnancy potential of human embryos.

The production of an embryo-derived platelet-activating factor (PAF) was recently shown to have a correlation with embryo quality and viability. The detection of this factor was used as a means of examining the effect of various aspects of the in vitro fertilization and embryo transfer procedure on human preimplantation embryo quality. Embryos that resulted in pregnancy produced significantly higher levels of embryo-derived PAF in vitro than embryos that failed to result in pregnancy. Of a further 85 embryos, 43% had a level of embryo-derived PAF that fell in the same range as the embryos that resulted in pregnancy. The production of embryo-derived PAF was related to the type of treatment used to induce follicular development (with clomiphene citrate and human menopausal gonadotropin commencing on day 5 giving best results); the size and estradiol production of the follicles producing the embryo; the age of the embryo culture medium; and the morphology and cell number of the embryos.

Biological Assay↗
PubMed1986

Failure of implantation in human in vitro fertilization and embryo transfer patients: the effects of altered progesterone/estrogen ratios in humans and mice.

Daily blood samples were taken for progesterone (P) and estradiol (E2) measurements from women who showed a platelet response consistent with the presence of viable embryos after in vitro fertilization and embryo transfer procedures. A comparison of steroid levels between those women who became pregnant and those who did not revealed the following: at and after the time of transfer, women who failed to become pregnant had significantly higher E2 levels and a lower ratio of P/E2 than women who became pregnant. The P/E2 ratio was a better predictor of implantation failure than was the absolute level of either hormone. Experiments were done in mice to test the hypothesis that P could protect implantation of the embryo against the inhibitory effects of high E2. In mice, implantation was inhibited by relatively high levels of E2. This effect was overcome by concomitant administration of P. There was a significant dose-response-related interaction of P with the E2.

Animals↗
PubMed1985

Maternal blood platelet physiology and luteal-phase endocrinology as a means of monitoring pre- and postimplantation embryo viability following in vitro fertilization.

The discovery that the fertilized mouse ovum triggers an increased demand for platelets and results in thrombocytopenia during the preimplantation phase of pregnancy provides a monitor for embryo survival and viability. This paper reports a study in which the platelet count was significantly reduced throughout the human preimplantation phase of pregnancy and returned to normal following embryo implantation. The human embryo was shown to produce a platelet activating factor in vitro which caused the reduction in platelet count after embryo transfer. This factor in the embryo culture medium could be measured using a bioassay which provided a means of assessing embryo viability prior to transfer. Some women showed no reduction in platelets after transfer. These embryos failed to produce a platelet activating factor in vitro and pregnancy was not established. Other women displayed a reduction in platelets following transfer but failed to become pregnant. All of these women had elevated luteal-phase plasma E2 levels compared to pregnant patients, which may have interfered with the implantation process. Our observations provide a possible rapid and simple means for monitoring the viability of human embryos cultured in vitro and the survival of embryos in utero.

Blood Platelets↗
PubMed1985

Metabolism of glucose by preimplantation mouse embryos in the presence of glucagon, insulin, epinephrine, cAMP, theophylline and caffeine.

Neither insulin nor epinephrine influenced the incorporation of glucose into the acid-soluble or acid-insoluble glycogen pool of mouse embryos at the morula-early blastocyst stage during 5 h culture in the presence of radiolabelled glucose. During a 5 h chase culture of pulse-labelled embryos at this stage of development, acid-soluble glycogen labelled during the pulse was not utilized by the embryo but acid-insoluble glycogen was reduced. Addition of glucagon, insulin, epinephrine, cAMP, theophylline or caffeine during chase culture had no effect on the turnover of label in the glycogen pools of the embryo. These results indicate that the turnover of embryonic glycogen observed in vivo is not due to the direct effect of the hormones that regulate glycogen metabolism in the mother. Insulin was found to stimulate incorporation of glucose into non-glycogen macromolecules during both pulse and chase culture. Thus, whilst an effect of insulin on glycogen metabolism was absent, the anabolic effects of this hormone appear to have been expressed in the embryo at this stage of development.

Animals↗
PubMed1984

Synthesis and degradation of labelled glycogen pools in preimplantation mouse embryos during short periods of in vitro culture.

The incorporation and turnover of glucose carbon by mouse embryos during short periods of in vitro culture were studied using [U-14C]glucose as marker. Particular attention was given to the synthesis and degradation of the acid-soluble and acid-insoluble glycogen pools. During a 5-h culture period, incorporation into all fractions isolated increased during development from the 1-cell to the early blastocyst stage. During maturation of the blastocyst, incorporation into acid-insoluble glycogen fell whilst that into acid-soluble glycogen continued to rise linearly over this 24 h period. At the late blastocyst stage over 80% of total glucose carbon accumulated was in this latter fraction. The decrease in acid-insoluble glycogen observed above was found to occur as a sudden change between 96 and 104 h post-hCG. The turnover of glucose carbon incorporated into the glycogen pools was studied using pulse-chase culture techniques. The results indicate that the considerable amounts of glycogen accumulated at the later stages of preimplantation development cannot act as a major energy source in vitro except in the absence of energy substrates. Under these conditions of energy starvation, however, the breakdown of acid-insoluble glycogen is inhibited. The findings show that the late preimplantation embryo accumulates large amounts of acid-soluble glycogen in vitro due to increased rate of synthesis and low rate of degradation. It is suggested that the falling levels of glycogen reported in the uterine embryo are most likely a result of environment factors other than the availability of energy substrates.

Animals↗
PubMed1984

Studies of the distribution of glycogen between the inner cell mass and trophoblast cells of mouse embryos.

Autoradiographic and histochemical techniques were used to determine the localization of glycogen synthesized during in-vitro culture of preimplantation mouse embryos. During early cleavage embryos accumulated little glycogen and that which was synthesized was spread evenly in the blastomere cytoplasm. However, morula and early blastocyst stages accumulated relatively large amounts of glycogen, especially in the peripheral or trophoblastic cells in comparison to the inner cells or inner-cell-mass cells. Immunosurgical techniques were used to study the incorporation of radiolabelled glucose into the biochemical pools of inner-cell-mass and trophoblastic cells during culture for 24 h. In general, trophoblastic cells incorporated considerably more isotope than did inner-cell-mass cells, especially into the acid-soluble glycogen fraction. However, inner cell masses isolated on Day 4 of pregnancy incorporated more glucose into acid-soluble glycogen than did inner cells isolated from blastocysts at the end of culture for 24 h in isotope.

Animals↗