PubMed Health⌕ Search

Biomedical subjects

D Maxwell

Publications and source records attributed to D Maxwell.

At least 37 records · Page 2Linked to original sources
PubMed1995

Abscisic acid induced protection against photoinhibition of PSII correlates with enhanced activity of the xanthophyll cycle.

The exogenous application of abscisic acid (ABA) to barely seedlings resulted in partial protection of the PSII photochemistry against photoinhibition at low temperature, the effect being most pronounced at 10(-5) M ABA. This was accompanied by higher photochemical quenching (qP) in ABA-treated leaves. A considerable increase (122%) in the amount of total carotenoids and xanthophylls (antheraxanthin, violaxanthin and zeaxanthin) was also found in the seedlings subjected to ABA. The activity of the xanthophyll cycle measured by the epoxidation state of xanthophylls under high-light treatment was higher in ABA-treated plants compared with the control. This corresponds to a higher value (0.411) of non-photochemical quenching (qNP) observed in ABA-treated than in control (0.306) leaves.

Abscisic Acid↗
PubMed1993

Drilling the posterior wall of the petrous pyramid: a microneurosurgical anatomical study.

Posterior approaches to the petroclival area requiring extensive drilling of the posterior pyramidal wall have been described in the last 10 years. If hearing is to be preserved, damage to the inner-ear structures must be avoided; however, the fine points of this pyramidal drilling technique have never been reported in detail. A microneurosurgical anatomical study was undertaken in 15 cadavers to determine the relationships between bone landmarks and labyrinthine structures that could be used to give some practical drilling guidelines. Drilling of the posterior pyramidal wall is facilitated on identification of the intersection of the petrous ridge with the most anterior portion of the bone ledge covering the sigmoid sinus (petrosigmoid intersection), the bony operculum of the endolymphatic sac, and the petrous ridge. Drilling may proceed rather safely at a minimum depth of 2.5 mm in an area 0.9 cm anterior and 1 cm inferior to the petrosigmoid intersection and petrous ridge, respectively. From there, identification of the vestibular aqueduct, genu, and horizontal portion is necessary to safely open the posterior wall of the internal auditory canal. The vestibular aqueduct represents the lateral and superior limits of drilling. The bone between these areas may then be safely drilled to a depth of at least 2.5 mm. A microneurosurgical dissection of the posterior pyramidal wall conducted in cadaveric material according to these guidelines did not violate any inner-ear structures.

Ear, Middle↗
PubMed1992

The role of transvaginal sonography in the early detection of congenital heart disease.

The antenatal diagnosis of congenital heart disease by fetal echocardiography is rarely achieved before 18-20 weeks' gestation. Transvaginal sonography allows examination of fetal anatomy at earlier gestations than the transabdominal approach. In a screening study of 270 low-risk women between 8 and 14 weeks' gestation using a 5 MHz vaginal transducer, it was possible to obtain adequate four-chamber views in over 70% from 12 weeks. In a second study of 32 women at high risk of congenital heart disease scanned between 14 and 15 weeks' gestation, satisfactory views were obtained transvaginally in 21 women. Seven of the remainder had normal cardiac anatomy confirmed by transabdominal scanning. In three of the four where normal cardiac anatomy could not be demonstrated by either transvaginal or transabdominal scanning, severe congenital heart disease was diagnosed and later confirmed. It is unlikely that transvaginal sonography will replace abdominal scanning for the screening of low-risk pregnancies, but it is a valuable addition to the early examination of those women identified as being at high risk of congenital heart disease.

Journal Article↗
PubMed1992

Preoperative radiological evaluation of the liver by computerized tomographic portography in patients with hepatic tumors.

The main objective of preoperative imaging studies is to define as accurately as possible the number, size, location, and relationship of tumor masses in the liver to pertinent portal and hepatic venous vasculature. Computerized tomographic portography images hepatic veins and segmental portal vein branches and identifies the anatomical location of tumor nodules with excellent sensitivity and a low false-positive rate. The intraoperative correlation of computerized tomographic portography on 30 patients in the last 20 months at this institution shows a sensitivity of 88 per cent with a low rate of false-positivity. The ability to detect metastatic lesions in the liver by computerized tomographic portography diminishes when the lesions are noted to be less than 1 cm. The authors conclude that the preoperative interpretation of the computerized tomographic portogram provides valuable information not previously available to the surgeon operating on the liver.

Adult↗
PubMed1991

Effect of H1-receptor blockade on late cutaneous reactions to antigen: a double-blind, controlled study.

This study is of the effect of the blockade of histamine H1 receptors by a long-acting antihistamine on the immediate and late clinical response to antigen (Ag) and on the recruitment of eosinophils in the late-phase cutaneous reaction. Ten adult volunteers with late-phase reactions to the intradermal injection of either Dermatophagoides pteronyssinus or Phleum pratense (timothy) pollen performed a double-blind, crossover study. Each volunteer took astemizole, 10 mg, or identical placebo, daily for 2 weeks. Ag in the concentration that induced a late reaction in the screening visit was injected intradermally at the end of each drug period. The early reaction was measured serially for 30 minutes and the late reaction at 4 and 6 hours. Biopsies of the Ag and control sites were also performed at 6 hours. After a 6-week washout period, subjects then took the opposite medication for 2 weeks and returned for skin testing and biopsy. Skin testing demonstrated that astemizole inhibited the immediate response to both histamine and allergen but had no effect on the late response at 4 hours and at 6 hours. Biopsy specimens revealed no significant effect on eosinophil recruitment at 6 hours. We conclude that histamine H1-receptor blockade has no effect on the late cutaneous reaction to Ag.

Antigens↗
PubMed1991

Flecainide in the treatment of fetal tachycardias.

Fourteen mothers were treated with flecainide for fetal atrial tachycardias associated with intrauterine cardiac failure. Twelve of the 14 fetuses responded by conversion to sinus rhythm. One of the 12 fetuses subsequently died in utero. The remaining fetuses suffered no morbidity and were alive and well 3 months to 2 years after delivery. The two fetuses in whom atrial tachycardia did not convert with flecainide were successfully treated with digoxin. These results compare favourably with previous forms of antiarrhythmic treatment. After recent reports of the side effects of flecainide treatment, however, it has been advised that this drug should be confined to high risk patients and those with life threatening arrhythmias. The use of flecainide for fetal arrhythmias should be limited to patients with severe fetal hydrops and supraventricular tachycardias. It should not be the first drug of choice in atrial flutter.

Cardiac Output, Low↗
PubMed1991

Balloon dilatation of the aortic valve in the fetus: a report of two cases.

Because they had irreversible damage to the left ventricular myocardium none of 12 patients with critical aortic stenosis diagnosed prenatally survived after postnatal treatment. This experience prompted three attempts at intrauterine balloon dilatation of the aortic valve in two fetuses with this condition. On each attempt the balloon catheter was successfully delivered to the left ventricle. In the first fetus the aortic valve was not crossed and the fetus died the next day. In the second fetus the balloon was correctly positioned across the aortic valve and inflated in the valve ring. After delivery, a further balloon angioplasty was performed; this relieved the stenosis but the patient died five weeks later from persisting left ventricular dysfunction related to endocardial fibroelastosis. Balloon angioplasty is feasible in fetal life but the prognosis depends on the ability of the relief of stenosis to limit, prevent, or allow regression of left ventricular damage before delivery.

Adult↗
PubMed1989

Visualization of fetal intra-abdominal organs in second-trimester severe oligohydramnios by intraperitoneal infusion.

Fetal intraperitoneal infusion of saline was performed in two patients with severe oligohydramnios at 24 and 25 weeks' gestation in order to enhance visualization of intra-abdominal organs. Renal agenesis was easily diagnosed. The technique can be considered as an alternative to artificial instillation of amniotic fluid in the differential diagnosis of conditions associated with severe oligohydramnios.

Abdomen↗
PubMed1988

Chorionic villus sampling in a high-risk population--4 years' experience.

Between August 1982 and July 1986 a total of 163 pregnancies in 136 patients with a high genetic risk have had prenatal diagnosis by chorionic villus sampling. Villi were not obtained in five pregnancies (two of which subsequently miscarried), and 11 fetal losses followed successful sampling (four in pregnancies in which the fetus was shown to be affected). The rate of fetal loss fell with increasing experience of the team. Three sets of twins were all sampled successfully.

Abortion, Spontaneous↗