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Biomedical subjects

L Geerts

Publications and source records attributed to L Geerts.

At least 37 records · Page 2Linked to original sources
PubMed2000

First trimester diagnosis of monoamniotic twin pregnancies.

This study reports the ultrasound findings and pregnancy outcome for a series of monoamniotic twin pregnancies diagnosed at 11-14 weeks' gestation. Of 315 monochorionic twin pregnancies examined, there were 12 (3.8%) monoamniotic, including four sets of conjoined twins (1.3%). The parents opted for termination of pregnancy in all cases of conjoined twins. In four other cases, there was discordancy for major structural fetal abnormality (kyphoscoliosis, anencephaly, body stalk defect, diaphragmatic hernia), and the cotwin was structurally normal. In the four cases in which both twins were structurally normal, ultrasound examination demonstrated normal nuchal translucency thickness in all cases but cord entanglement was demonstrated from the first trimester. Two cases were managed expectantly; one resulted in livebirth of both twins at 31 weeks' gestation and the second in intrauterine death of both fetuses at 21 weeks. Two pregnancies were treated with Sulindac; one resulted in a single intrauterine death at 30 weeks and delivery of a normal cotwin, the other, in intrauterine death of both fetuses at 31 weeks'. Monoamniotic twin pregnancies are associated with a high risk of fetal abnormalities and perinatal death and the mortality rate is higher than previously reported from series with recruitment later in gestation.

Crown-Rump Length↗
PubMed2000

Fetal heart rate in chromosomally abnormal fetuses.

OBJECTIVES: To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation. METHODS: Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome. RESULTS: In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18. CONCLUSIONS: Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.

Chromosome Aberrations↗
PubMed2000

Early prediction of severe twin-to-twin transfusion syndrome.

This extended series of 303 monochorionic twin pregnancies examined at 10-14 weeks gestation explores the possible association of increased fetal nuchal translucency thickness (NT) in the early prediction of severe twin-to-twin transfusion syndrome (TTS). Of 303 pregnancies, there were 16 in which at least one fetus was structurally or chromosomally abnormal and in the remaining 287 ongoing pregnancies there were 43 (15%) which developed severe TTS. The median fetal NT was 1.0 multiples of the median (MOM) and NT was >95th centile in 47 (8.2%) fetuses and in at least one fetus in 37 (12.9%) pregnancies. The prevalence of increased NT in the pregnancies that developed TTS [17.4% (n = 15) of fetuses and 28% (n = 12) of pregnancies] was significantly higher than in the non-TTS group [6.6% (n = 32) and 10.2% (n = 25) respectively; Z: = -3.4, P: < 0.001 and Z: = 3.2, P: < 0.001 respectively], likelihood ratio of increased fetal NT for prediction of TTS = 3.5 [95% confidence interval (CI) 1.9-6.2]. In 153 of the pregnancies, an ultrasound examination was also performed at 15-17 weeks gestation and intertwin membrane folding was seen in 49 (32%) cases; 21 of these (43%) subsequently developed TTS compared to two (1.9%) of the 104 pregnancies without membrane folding (Z: = 6.6, P: < 0.001), likelihood ratio of membrane folding for prediction of TTS = 4.2 (95% CI 3.0-6.0).

Diseases in Twins↗
PubMed1995

The outcome of babies of mothers with severe rhesus incompatibility treated at Tygerberg Hospital, 1980-1993.

OBJECTIVE: To determine the outcome of babies of mothers with severe rhesus (Rh) incompatibility treated by elective delivery when the amniotic optical density at 450 nm crossed Whitfield's action line (group 1), by plasmapheresis and immunotherapy (group 2) or by means of intra-uterine intravascular transfusions (group 3). STUDY DESIGN: A retrospective study of 55 mothers and their 57 fetuses with severe Rh incompatibility at < 34 weeks' pregnancy duration. MAIN OUTCOME PARAMETERS: Number of mothers in each treatment group, prevalence of intra-uterine death, hydrops, intra-uterine intravascular transfusions, cord haematocrit, cord bilirubin, number of liveborn babies, birth weight, neonatal death, hyaline membrane disease (HMD) and exchange transfusions. STUDY POPULATION AND SETTING: All mothers and babies with severe Rh incompatibility (defined as an amniotic optical density of 450 nm in the upper and upper-mid zone on the Liley chart at < 34 weeks' pregnancy duration, previous fetal hydrops or Rh-related intra-uterine death (IUD), fetal hydrops on ultrasound or a fetal haematocrit < 30% at cordocentesis) treated at Tygerberg Hospital between January 1980 and January 1993. There were 20 fetuses each in groups 1 and 3, and 17 in group 2. RESULTS: A total of 48 babies (84%) were liveborn and of these 74% survived the neonatal period. (ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density.

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by 153Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMDDPA into BMDDXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.

Absorptiometry, Photon↗
PubMed1993

Prevention of multiple pregnancies in an in vitro fertilization program.

OBJECTIVE: To limit the high number of multiple pregnancies in an IVF program. SETTING: In Vitro Fertilization Laboratory, Fertility Department, Public Hospital. INTERVENTIONS: The number of embryos transferred was limited to two instead of three. RESULTS: Limiting the number of embryos transferred to only two did not influence the take home baby rate but eliminated triplet and quadruplet gestations. Moreover, the number of patients with good quality supernumerary embryos available for cryopreservation increased. CONCLUSIONS: To reduce the high frequency of multiple gestations in an IVF program, the number of embryos replaced should be limited to a maximum of two.

Cryopreservation↗
PubMed1993

A monozygotic twin pregnancy after application of zona rubbing on a frozen-thawed blastocyst.

Assisted hatching techniques enhance the success rate of implantation of in-vitro fertilized human embryos. We report here the successful transfer of a frozen-thawed human blastocyst on which we applied a non-invasive zona rubbing technique (reduction of the thickness of the zona pellucida by gentle rubbing with a microneedle). The implantation in the uterus led to the delivery of healthy monozygotic twins.

Blastocyst↗
PubMed1991

Sperm morphology and IVF pregnancy rate: comparison between Percoll gradient centrifugation and swim-up procedures.

Many groups currently use two methods for the separation of motile spermatozoa, swim-up (S-up) and centrifugation on discontinuous Percoll gradient (PGC), and comparison of results indicates that PGC is superior. In this study we have attempted to identify the factors explaining this difference. This laboratory has long-standing expertise in seminology, thus the parameters of sperm morphology were the obvious first choice for detailed study. First, the respective effects of S-up and PGC on sperm morphology were analysed in different types of ejaculates: 62 semen samples with normal parameters and 41 with poor parameters. Both separation techniques resulted in improved morphology in the final preparation but only the increase of morphologically normal spermatozoa in the final Percoll suspension was significant. Second, application of these techniques in our in-vitro fertilization (IVF) programme revealed that, together with the improvement of sperm morphology, a higher pregnancy rate was obtained after PGC. The ongoing pregnancy rates per oocyte retrieval were 21.1% for the S-up technique and 33.3% for the PGC technique. These data show that spermatozoa selected by PGC present an improved morphology which we believe to be linked to improvement of the quality of the in-vitro fertilized embryos and ultimately the percentage of successful IVF results.

Adult↗
PubMed1989

[Vasectomy and its reversibility].

The authors report their experience of 2000 vasectomies. They discuss the indications, the technical aspects, the complications, the immunological consequences and the pathological results on the vas deferens, the epididymis and the testis. They report thereafter their experience of vaso-vasostomies (320 cases). They discuss their results on a mechanical (repermeabilization) and functional (% of pregnancies) point of view.

Adult↗
PubMed1988

Studies on the mechanism of the glucose-induced cAMP signal in glycolysis and glucose repression mutants of the yeast Saccharomyces cerevisiae.

When glucose is added to cells of the yeast Saccharomyces cerevisiae grown on non-fermentable carbon sources, a cAMP signal is induced which triggers a protein phosphorylation cascade. Addition of glucose or fructose to cells of a phosphoglucose isomerase mutant also induced the cAMP signal indicating that metabolization of the sugar beyond the sugar phosphate step is not necessary. Glucose 6-phosphate might stimulate the triggering reaction since induction with fructose shows a significant delay. Experiments with double and triple mutants in hexokinase 1, hexokinase 2 or glucokinase indicated that the presence of one of the three kinases was both necessary and enough for induction of the cAMP signal by glucose and the presence of one of the two hexokinases necessary and enough for induction by fructose. The product of the kinase reaction itself however does not appear to be the trigger of the reaction: when the increase in the level of glucose 6-phosphate and fructose 6-phosphate was measured as a function of time after addition of different glucose concentrations, no correlation was observed with the increase in the cAMP level. From the dependence of the cAMP increase on the external concentration of glucose, a rough estimate was obtained of the Km of the triggering reaction: about 25 mM. This value clearly fits with the Km of the low-affinity glucose carrier (about 20 mM) and differs by at least an order of magnitude from the Km values of the high-affinity glucose carrier and the three kinases. The present results situate the primary triggering reaction at the level of transport-associated phosphorylation. The main (= low-affinity) glucose carrier appears to be the receptor while association of the corresponding kinase is needed for induction of the signal. Since it is known that the presence of the kinases influences the characteristics of sugar transport, no definite conclusion can be given on whether the necessity of the kinases reflects the need for a certain type of transport or the need for phosphorylation of the sugar. The increase in the level of fructose 1,6-bisphosphate, on the other hand, correlated very well with the cAMP increase. However, it clearly lagged behind the cAMP increase, confirming the previously suggested importance of the cAMP signal for the stimulation of glycolytic flux at the level of phosphofructokinase 1.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Transport↗
PubMed1988

Requirement of one functional RAS gene and inability of an oncogenic ras variant to mediate the glucose-induced cyclic AMP signal in the yeast Saccharomyces cerevisiae.

Addition of glucose to Saccharomyces cerevisiae cells grown on a nonfermentable carbon source triggers a cyclic AMP (cAMP) signal, which induces a protein phosphorylation cascade. In a yeast strain lacking functional RAS1 and RAS2 genes and containing a bcy mutation to suppress the lethality of RAS deficiency, the cAMP signal was absent. Addition of dinitrophenol, which stimulates in vivo cAMP synthesis by lowering intracellular pH, also did not enhance the cAMP level. A bcy control strain, with functional RAS genes present, showed cAMP responses similar to those of a wild-type strain. In disruption mutants containing either a functional RAS1 gene or a functional RAS2 gene, the cAMP signal was not significantly different from the one in wild-type cells, indicating that RAS function cannot be a limiting factor for cAMP synthesis during induction of the signal. Compared with wild-type cells, the cAMP signal decreased in intensity with increasing temperature in a ras2 disruption mutant. When the mutant RAS2Val-19, which carries the equivalent of the human H-rasVal-12 oncogene, was grown under conditions in which RAS1 expression is repressed, the cAMP signal was absent. The oncogene product is known to be deficient in GTPase activity. However, the amino acid change at position 19 (or 12 in the corresponding human oncogene product) might also have other effects, such as abolishing receptor interaction. Such an additional effect probably provides a better explanation for the lack of signal transmission than the impaired GTPase activity. When the RAS2Val-19 mutant was grown under conditions in which RAS1 is expressed, the cAMP signal was present but significantly delayed compared with the signal in wild-type cells. This indicates that oncogenic RAS proteins inhibit normal functioning of wild-type RAS proteins in vivo and also that in spite of the presence of the RAS2(Val-19) oncogene, adenyl cyclase is not maximally stimulated in vivo. Expression of only the RAS(Val-19) gene product also prevented most of the stimulation of cAMP synthesis by dinitrophenol, indicating that lowered intracellular pH does not act directly on adenyl cyclase but on a step earlier in the activation pathway of the enzyme. The results obtained with the control bcy strain, the RAS2(Val-19) strain under conditions in which RAS1 is expressed, and with dinitrophenol show that the inability of the oncogene product to mediate the cAMP signal is not due to feedback inhibition by the high protein kinase activity in strains containing the RAS2(Val-19) oncogene. Hence, the present results show that the RAS protein in S. cerevisiae are involved in the transmission of the glucose-induced cAMP signal and that the oncogenic RAS protein is unable to act as a signal transducer. The RAS protein in S. cerevisiae apparently act similarly to the Gs proteins of mammalian adenyl cyclase, but instead of being involved in hormone signal transmission, they function in a nutrient-induced signal transmission pathway.

Cyclic AMP↗
PubMed1983

Subacute sclerosing panencephalitis: fundus changes and histopathologic correlations.

This paper describes the fundus changes in 2 patients with subacute sclerosing panencephalitis (SSPE). In both cases the ocular involvement preceded the neurological symptoms by several months. In one patient a localized serous detachment in the macular region was associated with retinal infiltrates and in the second patient an atypical unilateral macular chorioretinitis was first diagnosed. The diagnosis of SSPE was suspected when neurological signs appeared and it was confirmed by the typical EEG changes and especially by the high titers of measles antibodies in serum and CSF. The affected left eye of the second patient could be studied histopathologically and presented mainly pigment epithelial changes at the level of the scar, edema of the external plexiform layer, retinal folds and a detachment and rupture of the internal limiting membrane.

Adolescent↗