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Biomedical subjects

D E Hartley

Publications and source records attributed to D E Hartley.

At least 19 recordsLinked to original sources
PubMed2004

Plasma vasopressin concentrations and Fos protein expression in the supraoptic nucleus following osmotic stimulation or hypovolaemia in the ovariectomized rat: effect of oestradiol replacement.

The set points for vasopressin release in response to increasing plasma osmolality and hypovolaemia alter with reproductive status. Here, we studied stimulated vasopressin release following ovariectomy and oestrogen replacement, neuronal activity being measured in terms of immediate early gene expression. Observations were carried out on three groups of female Sprague-Dawley rats. The first group were ovariectomized. The second group were given a subcutaneous oestrogen implant (20 microg/ml oestradiol-17 beta) at the time of ovariectomy. The final group were left intact and observations performed at oestrus. Two weeks after ovariectomy, vascular cannulae were implanted under anaesthesia and at least 48 h allowed for recovery before hormone release was stimulated by infusion of 1.5 M NaCl for 90 min, or hypovolaemia induced by the removal of 10 mg/kg body weight taken in 1-ml aliquots. Blood pressure was monitored, and blood samples were taken for determination of packed cell volume and plasma vasopressin and osmolality. After a minimum of 48 h, the challenge was repeated, the rats anaesthetized, and perfused with 4% paraformaldehyde. Brain sections were processed for immunocytochemical detection of Fos protein. Vasopressin release in response to both stimuli was reduced in ovariectomized compared to intact rats and the response could be substantially restored by oestradiol replacement. The number of Fos positive cells in the supraoptic nucleus of oestrogen-replaced rats was significantly higher than in the ovariectomized group and not statistically different from the intact group.

Adaptation, Physiological↗
PubMed2003

Oestrogen receptor-beta and neurohypophysial hormones: functional interaction and neuroanatomical localisation.

Oestrogens affect fluid balance, influencing both ingestive behaviour and renal excretion. The renal effects are partly due to altered release of vasopressin and oxytocin. This study was designed to explore the role of oestrogen receptor-beta (ERbeta) in neurohypophysial hormonal function. Following dietary administration, soya isoflavones reach the brain in sufficient concentration to activate ERbeta, but not oestrogen receptor-alpha (ERalpha). ERbeta function was therefore manipulated by feeding rat diets differing in soya isoflavone content. Fluid balance and neurohypophysial hormone release were measured in male rats maintained for 14 days on a soya isoflavone-free diet or one containing 150 microg/g genistein+daidzein. Food and water intake, body weight, urine flow, osmolality and sodium concentrations were determined daily. After 14 days, plasma and urine osmolality and sodium, vasopressin and oxytocin concentrations were determined. There was no significant difference in weight gain between the two groups or in their excretion of sodium and water or plasma sodium and plasma oxytocin. However, plasma vasopressin was significantly lower in the iso-free group. Double-label immunocytochemistry was used to assess colocalisation of ERbeta with the neurohypophysial hormones in male rats. Cell nuclei showing ERbeta immunoreactivity were abundant in the posterior magnocellular paraventricular nucleus (PVNpm) and in the supraoptic nucleus (SON). Vasopressin-immunoreactive neurones were similarly distributed, forming the core of the PVNpm and the ventral portion of the SON; majority were positive for ERbeta. Cells with oxytocin immunoreactivity were located mainly at the periphery of the PVNpm and in the dorsal SON; only approximately a quarter of these cells showed ERbeta immunoreactivity. Thus, the difference in the effects of the soya diet on vasopressin and oxytocin release may be related to the ERbeta-activating properties of this diet and to the preponderance of this receptor in vasopressin as opposed to oxytocin cells.

Animals↗
PubMed2001

Endoluminal aortic grafting with renal and superior mesenteric artery incorporation by graft fenestration.

PURPOSE: To explore the use of juxta- and suprarenal aortic segments for endograft fixation in abdominal aortic aneurysm (AAA) patients and to develop methods of graft implantation that use endograft fenestrations to preserve renal and visceral vessel perfusion. METHODS: From August 1998 to May 2000, 13 AAA patients with unsuitable infrarenal aortic necks were treated with custom-designed endovascular grafts employing the juxta- and suprarenal aortic segments for proximal sealing. Flow to 33 renal and superior mesenteric arteries was maintained via graft fenestrations that were aligned by use of radiopaque graft markers. The fenestration-orifice interface for renal arteries was secured with modified balloon-expandable stents. RESULTS: All fenestrated grafts were deployed as planned, and all target vessels (33/33) were preserved. Two patients did not receive any stents, one being the first in the series and another who had incorporation of a renal accessory artery only. Without the use of transgraft stenting, 5 renal arteries would have been occluded by the endograft or poorly perfused. Procedural success was 100%. No conversion to open operation or graft-related complications occurred. There was no primary endoleak in any patient by angiographic criteria. Two patients required additional surgical procedures related to access vessels. Periprocedural mortality at 30 days was nil. Follow-up ranging from 3 to 24 months on all patients has not demonstrated any proximal or distal endoleaks. One stented renal vessel has occluded; all other arteries remain patent at last examination. CONCLUSIONS: This study has demonstrated the ability to successfully place a multifenestrated endoluminal graft in an aortic aneurysm using juxta- and suprarenal aortic segments to obtain a satisfactory seal. Stenting of the fenestration-renal ostium junction has helped to maintain renal patency.

Aortic Aneurysm, Abdominal↗
PubMed2001

Fenestration in endovascular grafts for aortic aneurysm repair: new horizons for preserving blood flow in branch vessels.

PURPOSE: To describe techniques for deploying fenestrated stent-grafts that use partial graft deployment and guided tracking of the fenestration to the arterial orifice. TECHNIQUE: Fenestrations have been added to custom-made tube grafts and commercially manufactured Zenith stent-graft systems to preserve perfusion of aortic side branches. Partial device deployment, orientation markers on the endograft, and intraoperative angiography enable maneuvering of the fenestration over the orifice of the target vessel with the aid of guiding catheters. Placement of a Palmaz stent overlapping the fenestration and vessel orifice secures the junction. Two variations of fenestration have preserved blood flow in renal arteries during endovascular repair of abdominal aortic aneurysms (AAAs); similar techniques have maintained flow to the celiac axis in a thoracic aortic aneurysm. CONCLUSIONS: Accurate placement of a fenestration over the orifice of a target vessel is feasible, but long-term maintenance of position is dependent on secure graft fixation. This capability brings us a step closer to overcoming the problem of inadequate necks in infra-renal AAAs, especially when the neck is foreshortened by asymmetry of the renal origins. It may also pave the way for the eventual replacement of the entire aorta with an endoluminal graft.

Aged↗
PubMed2001

Analytical modeling and numerical simulation of forces in an endoluminal graft.

PURPOSE: To utilize mathematical analysis and computational fluid dynamics (CFD) to investigate the forces acting within the pressurized aorta and upon a stent-graft and how these forces may affect the ongoing performance of the stent-graft. METHODS: Analytical force balance analysis and CFD simulations using the Fluent code were used to mimic blood flow through a bifurcated stent-graft in a person at rest. Steady-state blood flow was assumed in which the inlet pressure approximated the mean blood pressure (100 mm Hg) and the blood flow velocity was an approximation of the peak systolic flow rate (0.6 m/s). Two sizes of endoluminal grafts were analyzed: the larger graft had an inlet diameter of 3 cm and outlet diameters of 1 cm; the smaller graft diameters measured 2.4 cm proximally and 1.2 cm distally. The endografts were studied in 2 configurations: with the limbs straight and with one bent. RESULTS: For the larger graft model, the normal peak blood flow induced a downward force of 7 to 9 N on the bifurcated grafts. Bending one of the limbs of the graft produced a sideways force of 1.3 N. For the smaller endograft, the downward force was in the range of 3.1 to 5.1 N and the sideways force on a curved limb was approximately 1.5 N. The magnitude of the forces given by the analytical formulae and the CFD results agreed to within 2 significant figures. CONCLUSIONS: These results suggest that the downward force on a bifurcated stent-graft, which may exceed the force required to dislodge it when relying on radial attachment alone, is determined mostly by the proximal graft diameter. Curvature of the graft limbs creates an additional sideways force that works to displace the distal limbs of the graft from the iliac arteries.

Angioplasty↗
PubMed2001

Evaluation of patient selection guidelines for endoluminal AAA repair with the Zenith Stent-Graft: the Australasian experience.

PURPOSE: To review the patient selection guidelines for endovascular repair of abdominal aortic aneurysms (AAA) using the Zenith Endovascular Graft and establish an order of importance for each criterion. METHODS: The Zenith Endovascular Graft Research Database was interrogated for information on 238 patients (209 men; mean age 74.9 +/- 0.9 years, range 50-94) treated with a Zenith bifurcated graft from 1994 to 1998. The common complications of endoluminal AAA repair (endoleak, migration, graft occlusion, graft kinking, conversion, and deployment failure) were analyzed to determine any associations with selection criteria. RESULTS: By 1998, 69% of endograft patients did not meet the recommended guidelines; however, primary and secondary aneurysm exclusion rates were 87% and 94%, respectively. Over a median follow-up of 13.4 months (interquartile range 2.8-24.0), 38 (16%) patients developed 28 (74%) early and 10 (26%) late type-I endoleaks. The endoleak rate in necks < or = 10 mm long was 57% (8/14). Endoleak was associated with a neck contour change >3 mm (p = 0.003) and neck length <20 mm (p = 0.045). The risk of proximal endoleak was 4 times greater if at least one of the proximal neck guidelines was breached; combined guideline deviations of "contour change and large diameter" (p = 0.0004), "contour change and short length" (p = 0.006), "large diameter and short length" (p = 0.01), and "contour change and angle" (p = 0.03) also increased the risk of endoleak. Endograft migration was seen in 10 (4.2%) cases; only neck diameter >28 mm (p = 0.0024) was associated with this complication. CONCLUSIONS: Proximal neck contour, length, and diameter are the most important criteria in terms of endoleak development. Breaching the proximal neck length criterion resulted in a 4-fold increase in endoleak, and combined deviations from the guidelines multiplied the effect. Necks < or = 10 mm long are unsuitable for the standard Zenith graft.

Aged↗
PubMed2000

Age-related improvements in auditory backward and simultaneous masking in 6- to 10-year-old children.

This study investigated the development of auditory frequency and temporal resolution using simultaneous and backward masking of a tone by a noise. The participants were 6- to 10-year-old children and adults. On the measure of frequency resolution (the difference in the detection threshold for a tone presented either in a bandpass noise or in a spectrally notched noise), 6-year-old children performed as well as adults. However, for the backward masking task, 6-year-olds had, on average, 34 dB higher thresholds than adults. A negative exponential decay function fitted to the backward masking data for subjects of all ages indicated that adult-like temporal resolution may not be reached until about 11 years of age. These results show that, measured by masking, frequency resolution has reached adult-like performance by 6 years of age, whereas temporal resolution develops beyond 10 years of age. Six-year-old children were also assessed with tests of cognitive ability. Improvements in both frequency and temporal resolution were found with increasing IQ score.

Adult↗
PubMed1986

Valved latex balloons and water-soluble contrast opacified polymer. Simple detachable balloon system.

Latex balloons of different shapes, sizes and volume, incorporating a simple valve mechanism, were produced cheaply. These balloons are ethylene oxide sterilized and are available on 'the shelf' for use at any time. A contrast soluble polymer consisting of 2 hydroxy-ethyl-methacrylate, a cross linker, Iopamidol and water-soluble free radical curing system has been developed. The polymer sets in 10 minutes and there is no 'dead volume' problem. The balloons and polymer were evaluated in dog arteries, including histologic studies and have been subsequently used in 7 patients without any complications.

Animals↗
PubMed1984

Embolization of small vessels with a double-lumen microballoon catheter. Part I: Design and construction.

Existing coaxial balloon catheters cannot be passed through the smaller catheters used for superselective angiography; nor can they be used by themselves for selective catheterization, as the balloons are easily damaged. The authors describe the principles and construction of double-lumen catheters ranging from 0.45 to 0.85 mm in outer diameter, which may be passed through 4.1-6.0 F catheters to engage smaller vessels. Double-lumen catheters with an outer diameter of 0.45-0.56 mm permit injection of ethanol or a mixture of isobutyl-2-cyanoacrylate, iophendylate, and tantalum powder. The 0.85-mm size is best suited for low-viscosity silicone rubber opacified with tantalum.

Catheterization↗
PubMed1984

Embolization of small vessels with a double-lumen microballoon catheter. Part II: Laboratory, animal, and histological studies. Work in progress.

A double-lumen microballoon catheter system measuring 0.5-0.85 mm in outer diameter (1.3-2.8 F) was fabricated for passage through standard 4.1 and 5 F catheters. By arresting circulation with the balloon, embolization with low-viscosity silicone rubber, ethanol, or isobutyl-2-cyanoacrylate can proceed in a methodical, unhurried manner, permitting precise control of tissue penetration and preventing paradoxical embolization of other vessels. Problems such as gluing the catheter in situ with cyanoacrylate did not occur. The catheter may also be inserted during surgery to control embolization at a remote site, which did result in the catheter being glued in situ in one case.

Animals↗
PubMed1982

Angiographic findings in normal and diseased gallbladders including ischaemic cholecystitis and infarction of the gallbladder.

Angiographic studies were performed on 60 normal and diseased gallbladders obtained from cholecystectomy specimens and necropsy examinations. The normal macro and microangiographic pattern was confirmed, as was the reduction in the number of blood vessels in chronic cholecystitis and cholelithiasis. Histological correlation however showed that the degree of arteriographic change paralleled the degree of histological disease. The microvascular pattern was directly related to the degree of mucosal villous atrophy, a change which may be important in the pathogenesis of some types of gallbladder disease. The most severe angiographic changes occurred in the case of ischaemic cholecystitis, and contrasted with the normal blood vessel pattern in a case of thin walled infarction of the gallbladder.

Angiography↗
PubMedDate not supplied

Gincosan (a combination of Ginkgo biloba and Panax ginseng): the effects on mood and cognition of 6 and 12 weeks' treatment in post-menopausal women.

As memory and concentration impairments are a frequent complaint in post-menopausal women, this well-defined population was selected to investigate the effect on mood and cognition of chronic treatment with Gincosan. In a double-blind placebo controlled study, post-menopausal women aged 51-66 were randomly assigned to 12 weeks' treatment with Gincosan (320mg/day), containing 120mg Ginkgo biloba, and 200mg Panax ginseng (n = 30), or matched placebo (n = 27). They were given measurements of mood, somatic anxiety, sleepiness, and menopausal symptoms and a battery of cognitive tests before treatment and after 6 and 12 weeks of treatment. There were no significant effects of Gincosan treatment on ratings of mood, bodily symptoms of somatic anxiety, menopausal symptoms, or sleepiness or on any of the cognitive measures of attention, memory or frontal lobe function. Thus, after chronic administration, Gincosan appeared to have no beneficial effects in post-menopausal women.

Affect↗