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Biomedical subjects

G L Loy

Publications and source records attributed to G L Loy.

13 recordsLinked to original sources
PubMed1997

Cerebral and umbilical vascular resistance response to vibroacoustic stimulation in growth-restricted fetuses.

OBJECTIVE: To test the hypothesis that after vibroacoustic stimulation the ratio between cerebral vascular and umbilical vascular resistance in the growth-restricted fetus is different from that in the normal fetus. METHODS: The pulsatility index (PI) of the middle cerebral artery and that of the umbilical artery (UA) were measured by pulsed Doppler velocimetry in 30 normal and 14 growth-restricted fetuses before and after vibroacoustic stimulation. The ratios of cerebral PI to UA PI and the changes in PI after vibroacoustic stimulation were calculated. Comparisons were made using the Wilcoxon rank-sum test or signed-rank test. The statistical power of the study was 80%. RESULTS: Mean (+/- standard deviation) cerebral PI values before vibroacoustic stimulation (1.50 +/- 0.29) in normals and 1.29 +/- 0.26 in the fetal growth restriction [FGR] group) and UA PI values (1.00 +/- 0.18 in normals and 1.15 +/- 0.24 in the FGR group) were significantly different between groups (P < .04) and significantly decreased after vibroacoustic stimulation (P < .05). Although the cerebral to UA PI ratios (1.50 +/- 0.38 in normals and 1.13 +/- 0.33 in the FGR group) were significantly different between groups (P < .008), the values remained the same after vibroacoustic stimulation (P = .39 and .80, respectively). In all fetuses the fetal heart rate accelerated after vibroacoustic stimulation. CONCLUSION: Cerebral vascular resistance was lower and umbilical vascular resistance higher in the growth-restricted fetuses than in normals. The vascular resistance response after vibroacoustic stimulation in the growth-restricted fetus was not significantly different from the response of the normal fetus, suggesting preservation of regulation of resistance.

Acoustic Stimulation↗
PubMed1994

Does chorionic villus sampling compromise fetal umbilical blood flow?

A possible association of limb reduction defects with chorionic villus sampling (CVS) may be related to compromised umbilical blood flow from the trauma of the procedure. We hypothesized that because CVS may disrupt or compromise umbilical blood flow to the fetus, either by vasoconstriction, bradycardia, or emboli, we would detect these changes using Doppler velocimetry. A cohort of 21 consecutive consenting patients undergoing first-trimester elective CVS for prenatal diagnosis were entered into a prospective longitudinal study. Colour flow Doppler velocimetry was performed on fetal umbilical arterial blood flow immediately before and after CVS to measure the pulsatility index, fetal heart rate, per cent flow time, and maximum flow velocity. Measurements were obtained from three consecutive cardiac cycles in three different umbilical segments and averaged. Potentially confounding variables also recorded included gestational age, method of CVS, number of passes, number of aspirations, placental location, tissue sample size, and operator. Umbilical velocimetry values before and after CVS were compared using the paired t-test and showed no statistically significant differences. No differences were found when data were analysed by gestational age, sample size, method, number of aspirations, placental location, or operator. We were unable to detect any significant change in fetal umbilical arterial blood flow velocimetry or heart rate after performing CVS. Umbilical blood flow does not appear to be routinely compromised by CVS.

Bradycardia↗
PubMed1992

Steroid metabolism by ovarian follicles and extrafollicular tissue of the guppy (Poecilia reticulata) during oocyte growth and gestation.

In the viviparous guppy, fertilization and gestation are intrafollicular. Fully developed embryos are ovulated at the end of gestation just prior to parturition. The metabolism in vitro of various radiolabeled steroid precursors by isolated ovarian follicles at various stages of the reproductive cycle and extrafollicular (EF) tissue of the guppy was investigated. While estradiol-17 beta was one of the end products of metabolism in vitellogenic follicles, 17 alpha, 20 beta-P and several 5-reduced metabolites were synthesized by postvitellogenic follicles. The yield of 17 alpha, 20 beta-P, however, was much lower than some 5 beta-reduced metabolites synthesized by postvitellogenic follicles. Gestation stage follicles rapidly converted the precursors into 5-reduced and polar 7-hydroxylated steroids, and their glucuronides. Although postpartum follicles showed very poor potential for steroid metabolism, they synthesized estradiol-17 beta from testosterone. These results demonstrate distinct changes occurring in the steroidogenic potential of the follicles during the reproductive cycle. Unlike in other viviparous vertebrates, no particular steroid seems to be involved in maintaining gestation in the guppy; all the steroid precursors are converted into highly polar metabolites and their conjugates during gestation, thereby facilitating their excretion. The EF ovarian tissue also synthesized 7-hydroxylated steroids and their glucuronides, providing evidence for the first time that the teleost ovarian EF tissue plays a role in steroidogenesis. The possible physiological significance of the synthesis of the novel polar steroids by the follicles and the EF tissue is discussed.

17-alpha-Hydroxyprogesterone↗
PubMed1991

Measurement of leucine and alpha-ketoisocaproic acid fluxes in the fetal/placental unit.

Many investigators are now using stable isotopes in place of radioactive isotopes because of ethical considerations in human research. Our laboratory has had a long history in the development of an ovine model for the study of the physiological and biochemical changes during pregnancy. We wanted to extend some of the hypotheses and experimental protocols developed while using this model system to the human. As a first step in this process, we carried out infusions using a mixture of both 14C and 13C isotopes of the essential amino acid L-leucine. Results from this study showed that turn-over rates calculated using the two isotopes were equal within experimental error (8.99 +/- 0.45 and 8.97 +/- 0.52 mumol/kg.min, respectively). A key step in the development of the techniques for this study involved the use of tert.-butyldimethylsilyl derivatives for the amino acids. Because of the strong M-57 peak seen in the mass spectra of these compounds, we were able to use a relatively inexpensive Hewlett-Packard mass-selective detector for these determinations. Enrichments in triplicate measurements of the same sample had a precision of +/- 0.03%. Similar precision data were obtained in enrichment measurements of the keto acids derived from the amino acids. The combination of the speed of the analysis and the excellent precision have provided us with the opportunity to study uptake and loss across an organ system (i.e. placenta, liver, etc). This tool is now being used to study the detailed flow of amino acids across the placenta during both normal and abnormal pregnancies.

Animals↗
PubMed1990

Versatile stable isotope technique for the measurement of amino acids and keto acids: comparison with radioactive isotope and its use in measuring in vivo disposal rates.

Tracer methods using both carbon-13 and -14 have been utilized for determination of ovine fetal amino acid disposal and the results compared in seven animals. We infused [1-13C]leucine simultaneously with [1-14C]leucine into the fetal circulation of pregnant sheep chronically catheterized during late gestation. Radioactive and stable isotope enrichments of leucine (Leu) and stable isotope enrichments of ketoisocaproic acid (KIC) in the umbilical artery and vein and the maternal artery and uterine vein were measured. Stable isotope enrichments and concentrations of both Leu and KIC were determined from a single 0.2-ml sample by the use of internal standards and electron ionization GC/MS analysis after a simple isolation and derivatization procedure. The KIC/Leu enrichment ratio was measured for the first time in fetal arterial plasma and was 0.66 +/- 0.05 (SE). Fetal leucine disposal rate was 9.0 +/- 0.5 (SE) micron/min/kg. Disposal rates determined by stable isotopes were not different from those determined by radioactive isotopes. The GC/MS stable isotope method provided higher precision in both leucine concentration and enrichment measurements and has been shown to be a general method for the determination of concentration and isotopic enrichment of other amino acids and their corresponding keto acids. Furthermore, this method is ideally suited to clinical studies where large numbers of samples of rather small volume can easily be studied with a short turnaround time.

Amino Acids↗
PubMed1990

Fetoplacental deamination and decarboxylation of leucine.

Fetal and placental metabolism of leucine (Leu) and ketoisocaproic acid (KIC) were studied in seven fetal lambs at 132 +/- 1.3-days gestation. Fetal infusions of [1-13C]Leu, [1-14C]Leu, and antipyrine were carried out for 4 h. Uterine and umbilical blood flows were measured using the antipyrine steady-state diffusion technique. Leu and KIC concentrations, [14C]Leu-specific activities, 14CO2, [13C]Leu, and [13C]KIC enrichment (mole percent enrichment) were measured in the maternal artery, uterine vein, and umbilical artery and vein to calculate net fluxes of tracee and tracer molecules between fetus and placenta and between the uteroplacenta and the maternal circulation. There were net Leu and KIC fluxes into the fetus from the placenta with the KIC flux equal to approximately 19% of the combined Leu plus KIC flux. In addition, there was a net KIC flux into the uterine circulation. The fraction of infused tracer Leu escaping the placenta into the mother was small (approximately 6%). By contrast, there was a rapid exchange of tracer Leu carbon between placenta and fetus resulting in a significant flux of labeled KIC from placenta to fetus. Approximately 20% of the infused tracer carbon was converted to CO2 within the fetus. This rate of conversion was greater than 80% of the total fetoplacental conversion rate and significantly higher than the flux of KIC tracer carbon from placenta to fetus. Fetal KIC decarboxylation rate, calculated from the fetal KIC enrichment data, was 2.83 +/- 0.40 mumol.min-1.kg fetus-1 and approximately 60% of the combined net Leu and KIC flux into the fetus from the placenta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Weather and occurrence of eclampsia.

The authors performed a population-based case-control study of the association between weather and occurrence of eclampsia in Washington State. Women who were recorded as having eclampsia on Washington birth certificates from 1980 to 1983 were compared to a random sample of all women who gave birth during those years. For each woman studied, National Oceanic and Atmospheric Administration weather data were used to determine the temperature, relative humidity, precipitation, and wind speed on the date of birth at the station nearest the hospital of birth. Categorical analysis revealed that eclampsia was not associated with low temperature, high relative humidity, precipitation, or high wind speed. These results were unchanged after adjustment for race, parity, maternal age, and late initiation of prenatal care. These results do not support an association between eclampsia and weather on the date of delivery in this population.

Birth Certificates↗
PubMed1985

Effect of L-thyroxine on ovarian development and gestation in the viviparous guppy, Poecilia reticulata.

Treatment of female guppies from 1 day postpartum with L-thyroxine-sodium salt (Eltroxin, Glaxo) by immersion (0.5 ppm in 25% seawater renewed daily) significantly shortened the brood interval without affecting the brood size or the weight of the brood. This suggests an acceleration of early development of the fish by thyroxine. The thyroxine treatment also accelerated the development of the next batch of oocytes, particularly exogenous vitellogenesis (yolk-globule stages). The evidence suggests a role of the thyroid in vitellogenesis and gestation in the guppy.

Aging↗
PubMed1984

Serum complement levels and perinatal outcome in pregnancies complicated by systemic lupus erythematosus.

Previous reports suggest an association between maternal serum complement component (C3 and C4) levels and perinatal outcome. Eighteen women with systemic lupus erythematosus (21 pregnancies) were prospectively studied. C3 and C4 levels were measured monthly unless more frequent data were needed for acute medical management. Perinatal outcome was then correlated with both maternal clinical and serologic status before and during pregnancy. Twelve pregnancies were carried to term, 11 of which began in clinical remission. Eight of these 12 had normal C3 and C4 levels at the onset of pregnancy, and 11 were normal at delivery. Four pregnancies were delivered prematurely (with one neonatal death from septic meningitis); all began pregnancy in clinical remission but three had low C3 and C4 levels before delivery. Three pregnancies beginning in clinical remission ended in spontaneous first- or early second-trimester abortions; all had low C3 and C4 levels before aborting. Normal complement component levels were observed in the remaining two pregnancies that were terminated electively; they had no evidence of fetal or placental abnormality. The correlation of maternal serum complement levels and pregnancy outcome in this series suggests that these parameters may help in the assessment of fetal as well as maternal prognosis in lupus-complicated gestations.

Abortion, Spontaneous↗
PubMed1983

Renal histology and pregnancy performance in systemic lupus erythematosus.

Previous reports indicate that maternal and fetal outcome in pregnancies complicated by systemic lupus erythematosus (SLE) may be strongly influenced by the presence of renal disease. As the relationship between renal histology and clinical function in SLE is not consistent, prospective data on the outcomes of such pregnancies would aid patient counselling. Fifteen women with SLE had 18 pregnancies subsequent to renal biopsies, performed from 3 months to 8 years prior to conception. Their renal function was evaluated before, during and after pregnancy. Fourteen of 15 patients had evidence of renal involvement, based on by light and electron microscopic sections: 7 had mesangial involvement (WHO Class II); 5 had active focal or diffuse glomerulonephritis (Classes III and IV); two had membranous involvement (Class V); 1, no evident disease. Perinatal outcome was similar whether lesions were milder (8 continuing pregnancies, 4 term deliveries) or more severe (6 continuing pregnancies, 3 term deliveries). Clinical renal function was normal in all but 3 cases at the beginning of pregnancy; 2 additional patients experienced moderate deteriorations in renal function during pregnancy but recovered normal function in the puerperium. Fetal outcome was abnormal (3 premature deliveries, 1 neonatal death, 1 spontaneous abortion) in all cases where renal function was decreased, while 10 of 13 pregnancies in patients with normal renal function ended in term deliveries. The data suggest that currently preconceptual renal histology provides a less accurate basis for perinatal counselling than does the assessment of clinical renal function.

Female↗
PubMed1980

Increasing dermal perfusion after burning by decreasing thromboxane production.

Decreasing progressive dermal ischemia after burning could theoretically limit the amount of skin necrosis to the zone of coagulation. Methylprednisolone, aspirin, indomethacin, imidazole, dipyridamole, and methimazole have been shown to prevent dermal ischemia, suggesting that prostaglandins and/or thromboxanes may play a role in its pathogenesis. Specific antiprostaglandin antibodies (anti-PgE2, PgF2 alpha, PgI2, and TxA2) were reacted with tissue biopsies of burned guinea pig skin at various time intervals postburn. An immunoperoxidase technique with goat anti-rabbit immunoglobulin and horseradish peroxidase demonstrated the presence of the specific arachidonic acid metabolites. The burned tissue showed high levels of PgE2 and TxA2. The effects of three thromboxane inhibitors, imidazole, methimazole, and dipyridamole, on dermal ischemia were studied. Xenon133 washout studies were performed in burned and unburned areas. Tissue half-life of Xenon was prolonged in burned, untreated areas but this rapidly decreased in antithromboxane-treated burns. Repeated antiprostaglandin and antithromboxane antibody-immunoperoxidase studies on tissue from the thromboxane inhibitor-treated animals showed that PgE2, PgF2 alpha, and PgI2 were at the same levels as in untreated animals, but thromboxane (TxA2) was essentially absent, suggesting that thromboxane may be responsible for the progressive dermal ischemia after burning and that decreasing its production can increase dermal perfusion.

Animals↗