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Biomedical subjects

A D Cameron

Publications and source records attributed to A D Cameron.

At least 55 records · Page 3Linked to original sources
PubMed1994

Midtrimester chorionic villus sampling: an alternative approach?

OBJECTIVE: Our purpose was to audit midtrimester chorionic villus sampling after a positive maternal serum screening test for autosomal trisomy. STUDY DESIGN: From January 1990 until July 1993 chorionic villus sampling was offered to all screened positive women. RESULTS: Five hundred fifty-one mothers had chorionic villus sampling. The mean age was 31.7 years. The mean gestational age was 18.2 weeks. The mean time for direct karyotyping was 4.4 days and for culture results 20.2 days. Results were obtained in 99.6% of samples: direct plus culture results in 94%, direct results alone in 2.3%, and culture results alone in 3.3%. Fourteen pregnancies had abnormal karyotypes. There were five cases of placental mosaicism and one false-positive result. The loss rate was 0.4%. CONCLUSION: Midtrimester chorionic villus sampling, which is easier to perform than cordocentesis, provides a rapid and reliable karyotype. The complication rate is comparable to that of other invasive procedures.

Adult↗
PubMed1994

Growth and branching habit of rooted cuttings collected from epicormic shoots of Betula pendula Roth.

Patterns of shoot growth and branching were studied over two growing seasons in rooted cuttings collected from both epicormic shoots and seedlings of Betula pendula Roth. Epicormic shoots were induced to sprout on stumps and small logs of 5-, 10- and 30-year-old trees. The use of epicormic shoots enhanced the rooting capacity of stem cuttings collected from these shoots but did not appear to reverse the process of maturation. In this study, maturation was based on characteristics typical of mature trees but not necessarily those of the mother plant, because it was not possible to root cuttings, for comparison, from 5-, 10- and 30-year-old ortets, other than from epicormic shoots. There was evidence of the persistence of mature characteristics through an increase in shoot plagiotropism with increasing ortet age. Rooted cuttings from both seedlings and epicormic shoots, however, assumed an increasingly orthotropic habit with a smaller shoot angle at the end of the first growing season than at the beginning and this continued into the second growing season. Other indications of maturation, such as delayed bud flushing and the incidence of flowering with increasing ortet age, were also evident in rooted cuttings from epicormic shoots. There was a clear difference in branching habit depending on cutting source. Rooted cuttings derived from epicormic shoots produced nearly twice as many lateral branches compared with rooted cuttings collected from seedlings, but this was not an effect of maturation. There was some evidence that rooted cuttings derived from seedlings grew taller than rooted cuttings from epicormic shoots.

Journal Article↗
PubMed1993

Distal pocket polarity in ligand binding to myoglobin: deoxy and carbonmonoxy forms of a threonine68(E11) mutant investigated by X-ray crystallography and infrared spectroscopy.

The crystal structures of the deoxy and carbonmonoxy forms of a distal pocket myoglobin mutant in which valine68(E11) is replaced by threonine have been solved to 2.1- and 2.2-A resolution, respectively. This substitution has been shown previously to cause large decreases in the rate of oxygen binding and to lower the equilibrium association constants for O2 and CO. The synchrotron Laue method was used for the rapid acquisition of X-ray diffraction data to overcome problems caused by the very rapid rate of autooxidation of the mutant protein. The refined deoxy structure shows that the noncoordinated water molecule in the distal pocket is in a position to form strong hydrogen bonds with both the N epsilon-H of the distal histidine64 and O gamma of threonine68 with no other unexpected alterations in the protein structure. In the carbonmonoxy form, the bound ligand is well-defined and inclined away from the two hydrogen-bonding groups, refining to a position in which the Fe-C-O angle is 162 degrees. This value is very close to that previously observed in recombinant wild-type and position-64 (E7) mutants of sperm whale myoglobin (160-170 degrees). The similarity of the CO conformations contrasts with the 150-fold range in equilibrium binding constants (KCO) among the distal pocket myoglobin mutants and indicates that CO affinities cannot be predicted from the coordination geometry of the bound ligand. Furthermore, a comparison of the infrared stretching frequencies of CO in wild-type, valine64 and threonine68 single mutant, and valine64-threonine68 double mutant pig carbonmonoxymyoglobins shows a lack of correlation between KCO and vCO. These effects can be understood in terms of the stability of noncovalently bound water in deoxymyoglobin and electrostatic interactions between bound ligands and the distal pocket residues.

Animals↗
PubMed1992

The effect of acute and chronic antihypertensive therapy on maternal and fetoplacental Doppler velocimetry.

Maternal and feto-placental Doppler flow velocity waveforms were studied during acute and chronic antihypertensive therapy in patients with pregnancy-induced hypertension. Eight primigravidae were acutely treated with oral nicardipine. Diastolic blood pressure fell at 30, 45 and 60 min after nicardipine. The uteroplacental systolic/diastolic ratio rose significantly at 30 min, but this change was no longer apparent at 60 min. Umbilical artery and maternal brachial artery systolic/diastolic ratios were unchanged. Fifteen patients with mild pre-eclampsia were chronically treated with oral pindolol. Diastolic blood pressure fell significantly within 24 h. The uteroplacental systolic/diastolic ratio rose 3 days after pindolol. Brachial artery or umbilical artery systolic/diastolic ratios were unchanged. A control group of 15 patients with untreated mild pre-eclampsia showed a significant rise in uteroplacental and umbilical artery systolic/diastolic ratios within 7 days of starting recordings. In patients with pregnancy-induced hypertension, acute and chronic blood pressure reduction was associated with no change in umbilical artery or maternal brachial artery Doppler systolic/diastolic ratios and a transient rise in the uteroplacental systolic/diastolic ratio.

Blood Pressure↗
PubMed1992

The ultrasonic assessment of discordant growth in twin pregnancies.

Discordant fetal growth, as defined by an intertwin weight difference (calculated as a percentage of the weight of the larger twin) of 20% or more, is associated with an increased perinatal mortality and morbidity. In this study, the accuracy of ultrasound estimation of fetal weight by abdominal circumference and biparietal diameter measurements in 107 twin pregnancies was assessed. Discordant growth greater than 20% as measured by ultrasound was found to have a sensitivity of 5-25%, a specificity of 87-95%, a positive predictive value of 12-43% and a negative predictive value of 80-85% at gestations ranging from 28 weeks to term. ROC calculations showed that changes in the discordance level used did not improve the value of the test. These results indicate that ultrasound measurement of fetal weight alone cannot be used accurately to assess discordant growth in twin pregnancies.

Journal Article↗
PubMed1991

The role of postnatal x-ray pelvimetry after caesarean section in the management of subsequent delivery.

The purpose of this study was to investigate the influence of postnatal x-ray pelvimetry after caesarean section on the management of the subsequent pregnancy. The case records of 331 women delivered by casearean section in their first pregnancy were reviewed. By standard radiological criteria, the pelvis was considered to be inadequate in 248 (75%) of them and adequate in 83 (25%). Of the women with a radiologically inadequate pelvis, 172 underwent an elective caesarean section. Seventy-six were allowed vaginal delivery: 51 of these women delivered vaginally and 25 required an emergency caesarean section. Of the women with a radiologically adequate pelvis, 61 achieved a vaginal delivery and 22 were delivered by caesarean section. All of the three cases of uterine rupture occurred in women with a radiologically adequate pelvis. This study suggests that x-ray pelvimetry is not a good predictor of the outcome of a trial of vaginal delivery. We conclude that the practice of routine postnatal pelvimetry should be abandoned.

Birth Weight↗
PubMed1990

Prenatal diagnosis of an intra-abdominal sacrococcygeal teratoma.

The prenatal diagnosis of a presacral (type IV) sacrococcygeal teratoma (SCT) is described. The initial ultrasound appearance was suggestive of a lower urinary tract obstruction, but further ultrasonic examination and radiological imaging using contrast medium led to the diagnosis of SCT. This is the first prenatal diagnosis of a totally intra-abdominal SCT.

Adult↗
PubMed1990

Second-trimester placental biopsy for rapid fetal karyotyping.

Since January 1988 the technique of first-trimester chorionic villus sampling (placental biopsy) has been extended to include cases in the second trimester. To date, 40 procedures have been performed. The main indication for the late chorionic villus sampling was a low serum alpha-fetoprotein value in association with an increased risk for Down syndrome (n = 28), abnormal ultrasonographic finding (n = 7), and failed amniotic cell culture (n = 3). Successful karyotype results were achieved in all but two cases. Most results were obtained within 48 hours with direct cytogenetic techniques. No cases of mosaicism were found. The highest yield of abnormal karyotypes was obtained from the cases with abnormal ultrasonographic findings (one trisomy 21, two 45,X). One case of trisomy 21 was identified in the 28 cases of low serum alpha-fetoprotein. No spontaneous losses have occurred. The technique is easy to learn, does not differ from first-trimester procedures, and may have a lower complication rate than cordocentesis. The reporting of cases to the CVS Newsletter should help evaluate late chorionic villus sampling as another method for rapid fetal karyotyping.

Adult↗
PubMed1990

Autotetraploid plants from callus cultures of Betula pendula Roth.

Autotetraploid plants with 2n = 56 chromosomes were found in a population of plants derived from callus cultures of stem internodes of silver birch (Betula pendula Roth) with 2n = 28 chromosomes. These plants were readily identified by their twisted, pubescent foliage and slow rate of growth, and by cytological examination. The frequency of autotetraploidy varied with the auxin used in the culture medium. When indole-3-butyric acid was used, autotetraploids accounted for 3.8% of the total study population, whereas when naphthaleneacetic acid was used, the frequency of autotetraploidy increased to 11.0%. The remainder of the plants in the study population were morphologically normal with 2n = 28 chromosomes. The autotetraploids have potential value as breeding material for the production of triploid birches (2n = 42), which are known to be fast growing, through crosses with diploid silver birch.

Journal Article↗
PubMed1989

Can platelet volume predict progressive hypertensive disease in pregnancy?

Increase in platelet size has been found in conditions with increased platelet destruction and use. This increase in platelet size can be found in patients with moderate or severe hypertension in pregnancy, even in the presence of a normal platelet count. The goal of this study was to investigate whether an increase in platelet size was present before the manifestation of the disease and therefore could be used to predict the progression of the disease before it is clinically apparent. Three hundred normal primigravid pregnancies were studied between 28 and 30 weeks' gestation, and blood was taken to assess platelet count and mean platelet volume. Two hundred sixteen patients had no hypertensive problems during their pregnancy, 84 developed hypertension, 62 had mild hypertension only with diastolic blood pressures between 90 and 99 mm Hg, 13 had moderate hypertension with diastolic blood pressures between 100 and 109, and nine had severe hypertension with diastolic blood pressure above 110. No difference was found between these groups in the parameters measured. Therefore it was felt that platelet volume may not be a useful screening test in a low-risk population. A second study was carried out to investigate the serial changes in these parameters in patients at risk of progressive disease. Thirty-four patients with essential hypertension were followed from 24 weeks with serial blood sampling to study changes in platelet size. An additional 40 patients with mild pregnancy-induced hypertension were also studied. From these patient groups, 20 patients developed severe hypertension. The mean platelet volume increased significantly at least 1 week before the hypertension became clinically apparent. There was no change in platelet count at this time. It is concluded that increasing platelet size can predict which patients are likely to progress to severe disease before it becomes clinically obvious.

Blood Platelets↗
PubMed1988

Doppler waveforms in the fetal aorta and umbilical artery in patients with hypertension in pregnancy.

Pulsed Doppler ultrasound assessment of blood flow was performed in the fetal aorta and umbilical arteries of 41 patients with hypertension in pregnancy. Patients were grouped according to severity of the hypertension and the presence or absence of chronic hypertension. Doppler abnormalities were seen in two patients with chronic hypertension, both of whom delivered small for gestational age infants. Only one patient with mild to moderate preeclampsia had abnormal aortic Doppler assessment and was also delivered of a small for gestational age infant. The highest number of abnormal Doppler waveforms in both fetal aorta and umbilical artery were found in patients with severe preeclampsia. Abnormalities were detected more frequently in the fetal aorta than in the umbilical artery. Doppler assessment was often abnormal before a nonstress test or biophysical profile. The number of abnormal Doppler values correlated with perinatal outcome in patients with severe preeclampsia.

Adult↗
PubMed1985

Immunoreactive prostacyclin and thromboxane metabolites in normal pregnancy and the puerperium.

Prostacyclin and thromboxane have been implicated in the pathophysiology of several disorders of pregnancy, but there is little information on concentrations of these prostaglandins in normal pregnancy. The aim of our study was to determine the range of values throughout normal pregnancy and the puerperium and to compare this with concentrations in normal non-pregnant women. Measurement was by radioimmunoassay of prostacyclin and thromboxane metabolites. We observed a significant difference in prostacyclin metabolites in the first trimester, (mean 19.9, SEM 0.96 pg/ml) compared with the normal non-pregnant group (mean 15.9, SEM 0.68 pg/ml). There were no significant differences between values in the normal non-pregnant group and those in the second and third trimester or postnatally. The increase in prostacyclin in the first trimester may be associated with placentation and physiological vasodilation, and insensitivity to angiotensin II seen in early pregnancy. We noted a significant reduction in thromboxane metabolites in the second (mean 133, SEM 14.9 pg/ml) and third (mean 123, SEM 10.7 pg/ml) trimesters and the puerperium (mean 119, SEM 6.3 pg/ml) compared with the values in the normal non-pregnant group (mean 142, SEM 4.9 pg/ml). This may be due to increased platelet stability or decreased thromboxane synthesis.

Epoprostenol↗
PubMed1984

Topical pramoxine and hydrocortisone foam versus placebo in relief of post partum episiotomy symptoms and wound healing.

A double-blind randomised controlled trial, comparing pramoxine hydrochloride 1 per cent and hydrocortisone acetate 1 per cent in a mucoadhesive foam base, with simple aqueous foam (B.P.), in relieving episiotomy discomfort and episiotomy healing in 40 patients was carried out. Simple aqueous foam was more effective with regard to wound healing and episiotomy discomfort as measured by analgesic consumption. Pramoxine and hydrocortisone foam offers no advantage over simple aqueous foam in the treatment of post partum episiotomy discomfort.

Administration, Topical↗