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Biomedical subjects

G T Jones

Publications and source records attributed to G T Jones.

At least 19 recordsLinked to original sources
PubMed2004

Micro-venous valves in the superficial veins of the human lower limb.

It is commonly believed that venous valves are not present in veins smaller than 2 mm in diameter. Venous valves, however, have been identified recently in small veins in several regions of the body. This study was undertaken to determine the size distribution of venous valves in the human lower limb micro-venous circulation. Vascular casts were made from six adult lower limbs and the sampled areas were viewed by scanning electron microscopy. In total, 2,376 valves were identified from 410 cm(3) of subcutaneous tissue. The vast majority (94%) of the valves were in veins less than 300 microm in luminal diameter, with 65% of the valves present in venous channels less than 100 microm in luminal diameter. The smallest valves identified were present in venous channels 18 microm in diameter. All valves were bicuspid and often associated with a tributary. Endothelial cells on the vein wall not associated with a valve were fusiform and arranged parallel to the long axis of the vessel, however, the endothelial cells on the luminal and valve sinus surfaces of the cusp were more polyhedral in shape and showed no obvious pattern of alignment. This study provides direct evidence to show that small superficial veins of the human lower limb do contain abundant venous valves and, for the first time, shows that the majority of these valves are present within venous channels less than 100 microm in luminal diameter.

Aged↗
PubMed2004

Parental pain is not associated with pain in the child: a population based study.

BACKGROUND: Child pain is associated with adverse psychosocial factors. Some studies have shown an association between children's and parental pain. Children may "learn" pain behaviour from their parents. OBJECTIVES: To examine whether an association exists between parent and child pain, and, if so, whether this relationship persists after adjusting for psychosocial difficulties in the child. METHODS: 1326 schoolchildren took part in a questionnaire based, cross sectional survey. Parents of study participants were sent a postal questionnaire. Occurrence of body pain was ascertained using blank body manikins and, in children, psychosocial factors were assessed using the Strengths and Difficulties Questionnaire. Three child-parent pain relationships were examined: any child pain with any parental pain or with parental widespread pain; and child low back pain with parental low back pain. RESULTS: The risk of child pain associated with parental reporting of pain was minor, and non-significant. Even when both parents reported widespread pain, the relative risk of pain in the child, after adjusting for age and psychosocial difficulties, was 1.2 (95% CI 0.5 to 3.2). CONCLUSIONS: Parental pain is not a risk for child pain. Pain behaviour is not learned. Rather, child pain is probably attributable to individual factors and the social environment.

Adolescent↗
PubMed2003

Low back pain in schoolchildren: the role of mechanical and psychosocial factors.

BACKGROUND: Low back pain (LBP) in schoolchildren with no apparent clinical cause is known to be a common problem, but considerably less is understood regarding the aetiology of such pain. AIM: To assess the role of both mechanical and psychosocial factors (including emotional and behavioural problems and other somatic pain complaints) in childhood LBP. METHODS: A cross sectional study was carried out in a population of 1446 schoolchildren aged 11-14 years. Information on these potential risk factors for LBP was sought using a self complete questionnaire and a five day bag weight diary. RESULTS: Mechanical factors such as physical activity and school bag weight were not associated with LBP. However, strong associations with LBP were observed for emotional problems, conduct problems, troublesome headaches, abdominal pain, sore throats, and daytime tiredness. CONCLUSION: Results suggest that psychosocial factors rather than mechanical factors are more important in LBP occurring in young populations and could possibly be a reflection of distress in schoolchildren.

Abdominal Pain↗
PubMed2001

Identification of two susceptibility loci for vascular fragility in the Brown Norway rat.

A trait of vascular fragility, characterized by the formation of abrupt defects within the elastic laminae of the abdominal aorta, has been identified in Brown Norway (BN) rats. These lesions are greatly exacerbated in F(1) rats from a BN x New Zealand genetically hypertensive (GH) intercross, implying that the genetic background provided by the GH rat influences lesion severity. The F(2) progeny of the BN x GH intercross were used to identify susceptibility loci for the lesions as well as exacerbating loci. Two major quantitative trait loci (QTLs) for number of internal elastic lamina lesions were identified on rat chromosomes 5 and 10, with the maximum "log of the odds ratio" (LOD) scores at D5Rat119 (LOD 5.0) and at D10Mit2 (LOD 4.5), respectively, together contributing 33.5% to the genetic variance. Further analysis revealed that the chromosome 10 locus exhibits a dominant mode of inheritance, with BN alleles being associated with increased lesion number (P < 0.0002) compared with GH homozygotes. This locus was in epistasis to a modifier locus on rat chromosome 2 at D2Mit14 (LOD score 2.12). A second major locus was identified on chromosome 5, exhibiting a semidominant mode of inheritance, again with the BN allele being significantly associated with increased lesion number (P < 0.0001). Furthermore, a locus influencing lesion severity was identified on chromosome 3 wherein GH alleles associated with increased severity. This is the first study to identify susceptibility loci for vascular elastic tissue fragility.

Animals↗
PubMed2001

Familial abdominal aortic aneurysms in the Otago region of New Zealand.

PURPOSE: To investigate the familial incidence and phenotypic characteristics of patients with abdominal aortic aneurysms (AAA) in the Otago region of New Zealand. METHODOLOGY: A retrospective audit based pilot study and a prospective study of patients having abdominal aortic aneurysm repair from September 1988 to September 1999 was performed. RESULTS: 248 probands were enrolled, of which 19.4% had one or more first degree relative affected. The age at diagnosis of the familial (70.2) and non-familial (70.5) patients was similar. The proportion of females was increased in the familial subgroup. Hypercholesterolaemia was the only phenotypic feature to differentiate familial from non-familial patients and was associated with an earlier age of presentation. In the familial families, brothers were the most common relative affected and 77% of the families had two patients with AAA. CONCLUSION: 19.4% of patients operated on in the Otago area for AAA had a familial component to their aneurysm.

Age Distribution↗
PubMed2000

Association of the 4G/5G polymorphism in the promoter region of plasminogen activator inhibitor-1 with abdominal aortic aneurysms.

PURPOSE: A familial component has previously been identified in 11% to 20% of patients with abdominal aortic aneurysms (AAAs). The genetic basis of familial AAA remains elusive, however. Matrix metalloproteinases have been implicated in aneurysm development; and plasmin, a serine protease, activates metalloproteinases. Plasminogen activator inhibitor-1 (PAI-1) regulates plasmin activation through the tissue plasminogen activators. A polymorphism within the promoter area of PAI-1 has been described that modifies PAI-1 expression and consequently plasminogen activation. The 4G homozygous variant is associated with increased PAI-1 expression and consequently reduced plasmin activity and therefore may be selected against in-familial AAA. The purpose of this study was to investigate the incidence of the 4G/5G insertion/deletion polymorphism in the promoter area of the PAI-1 gene in a population with AAA. METHODS: Patients seen at a tertiary referral center for repair of abdominal aortic aneurysms were recruited. DNA was extracted from blood. Primers were designed to amplify a 99 (5G)-base pair (bp) and a 98 (4G)-bp fragment bracketing the polymorphism. The 5' primer was mutated to allow a restriction endonuclease to cleave the 5G polymorphism into a 77-bp and a 22-bp fragment. Samples were run on agarose gels and stained with ethidium bromide. RESULTS: One hundred ninety patients with AAAs, including 39 patients with strong family histories and 163 controls were examined. The frequency of the 4G:5G alleles in the AAA population and in the control population was 0.6:0.4. However, 26% of patients with familial AAA were homozygous 5G compared with 13% of the control population. The 4G-allele frequency was 0.47 in the familial AAAs, compared with 0.62 in the nonfamilial patients (P =.02) and 0.61 in the control population (P =.03). CONCLUSION: The selection against the 4G4G genotype in the familial AAA population may indicate a role for PAI in the development of AAA in this population.

Aged↗
PubMed2000

Indicator-based systems of performance management in the National Health Service: a comparison of the perceptions of local- and national-level managers.

Historically, the UK Government has policed the use of National Health Service (NHS) resources through the centralization of control. With the majority of resource-draining decisions being taken by clinicians, however, professional financial accountability is becoming more important within the NHS management structure. Variations in clinical performance can be monitored through the use of performance indicators, although these are not without their problems. The use of league tables of such indicators in the national press is now infamous and there is much anecdotal evidence about the intraorganizational conflict arising from the use of such tables. A questionnaire survey and interview study of clinical directors, clinical service directors and business managers in several Scottish NHS Trusts was undertaken to ascertain the perceptions of local-level managers on the issue of performance indicators. Interviews were also carried out with a number of personnel in the Scottish Office Department of Economics and Information, the Division of Health Gain and the Finance Directorate. This paper explores the differences between the perceptions of the managers at these two levels of the NHS with regards to issues of performance measurement, intraorganizational conflict and corporate vision.

Administrative Personnel↗
PubMed1999

Venous morphology predicts class of chronic venous insufficiency.

OBJECTIVES: this study aimed to determine specific morphological differences in long saphenous veins from patients with various grades of chronic venous insufficiency. DESIGN: comparable veins from a control group were compared with patients with either primary varicose veins or those with associated skin changes including venous ulcers. MATERIALS: below-knee segments of saphenous vein were examined from a total of 64 patients. METHODS: veins were examined for elastic-tissue disruption and endothelial-cell changes and comparisons made between clinical groups. RESULTS: elastic-tissue disruption, as measured by fragmentation of the elastic lamina and the percentage of the intimal-medial boundary containing elastin, increased with increasing severity of venous disease. Moreover, endothelial cells became more densely packed, as measured by endothelial cell and endothelial-cell nuclei density, with increasing severity of disease. Other measures such as the density of multinucleated "giant" endothelial cells and the number of nuclei per "giant" cell did not correlate with venous disease, however. CONCLUSIONS: this study demonstrates that several morphological characteristics of superficial saphenous veins correlate with severity of venous disease. In particular, the alterations to the structure of elastic tissue within these veins appears indicative of the progressive nature of chronic venous insufficiency.

Aged↗
PubMed1998

Venous endothelial changes in therapeutic arteriovenous fistulae.

Specimens of veins of therapeutic arteriovenous fistulae from five patients were examined by an en face immunohistochemical technique to investigate endothelial morphology and the presence of the vasoactive peptide endothelin-1 (ET-1). These were compared with control segments of long saphenous veins from six patients. Venous endothelium from the arteriovenous shunts was mostly intact even overlying phlebosclerotic plaques. Occasional small areas of denudation, with associated platelets, were present in the depressions of 'jet' lesion however. The endothelial cells were generally elongated and interspersed with foci of polyhedral cells. The control saphenous veins contained elongated endothelial cells without detectable denudation. Image analysis of histological sections of veins from the shunts indicated significantly less intact elastic tissue than control veins but greater mononucleated endothelial cell density in en face preparations. ET-1 staining was considerably stronger in endothelium from the fistulae than in the control saphenous veins and was most intense over the raised crescentic ridges of jet lesions, stenoses and phlebosclerotic plaques. Endothelial mitoses and cells with hyperchromatic nuclei stained more strongly for ET-1 than surrounding cells. These results indicate that the endothelial cells lining veins associated with arteriovenous fistulae are dynamically altered by the increased haemodynamic stresses associated with these shunts. Furthermore ET-1 may act as a localising factor associated with intimal thickening at sites of 'jet' lesions, stenosis and phlebosclerosis.

Adult↗
PubMed1996

Endothelin-1 is increased overlying atherosclerotic plaques in human arteries.

The distribution of Endothelin-1 (ET-1), a potent vasoactive peptide, within endothelium of human atherosclerotic arteries was examined using a novel en face immunohistochemical technique. The vast majority of endothelial cells were immunoreactive for ET-1. Staining intensity was increased in areas overlying atherosclerotic plaques, calcified media, fatty streaks and about flow dividers, compared with adjacent regions. Multinucleated 'giant' endothelial cells were more common in regions containing strong ET-1 staining than elsewhere. Clusters of leucocytes (probably monocytes) were frequently observed adhering to the endothelial monolayer but not neighbouring regions of denudation. Occasionally underlying macrophage/foam cells and smooth muscle cells were exposed to the surface and included in the en face (Häutchen) preparation. Smooth muscle cells did not stain for ET-1 while macrophages and the larger foam cells were positive for ET-1. These results support the hypothesis that expression of ET-1, at sites containing atheromatous disease, may be involved in the development of atherosclerosis.

Aged↗
PubMed1996

The effect of L-dopa on the healing of a rat mandibular defect.

PURPOSE: This study was designed to evaluate the effect of L-dopa on healing of a surgically created bony defect in the adult male rat. MATERIALS AND METHODS: Thirty-six animals underwent surgery to create a 4-mm circular defect in the left mandibular angle. They were then randomly divided into two equal groups, one receiving 0.2 g/kg/day of L-dopa for 10 days by orogastric gavage, the other group acting as a control. Six experimental and six control animals were killed at 2 weeks, and five experimental and six control animals were killed at 4 and 6 weeks postoperation. Healing was classified as complete, partial, or incomplete based on gross and radiographic observations. RESULTS: Gross observation of the experimental mandibles showed five completely healed defects (31.25%), five partially healed defects (31.25%), and six defects with no healing (37.5%). Control mandibles showed three defects with partial healing (16.67%) and 15 with no healing (83.33%). Radiographs were taken of randomly chosen mandibles in each control and experimental group. Of the six experimental mandibles, one showed no healing, three showed partial healing, and two showed complete healing of the defect. The six control mandibles showed three defects with no bone formation and three with partial healing. CONCLUSIONS: The data from this study indicate that L-dopa had a promoting effect on the bony healing of defects in the rat mandible.

Administration, Oral↗
PubMed1995

Ultrastructure of the afferent arteries of experimental femoral arteriovenous fistulae in rabbits.

Using transmission electron microscopy, the aorta and ilio-femoral arteries of 12 normocholesterolemic rabbits with femoral arteriovenous fistulae were investigated (49 to 895 days post-operatively) to determine whether the fibrofatty lesions in arteries proximal to chronic fistulae were ultrastructurally consistent with human atherosclerosis. The contralateral ilio-femoral arteries from the same animals and the vessels of 4 additional rabbits (2 with femoral arteriotomies) served as control material for comparison. There were microfractures adjacent to complete tears of the internal elastic lamina which had abrupt margins. These tears were observed mostly in the ilio-femoral arteries proximal to the fistula. They were most numerous, extensive and associated with considerable intimal proliferation near the fistula. Further proximally the tears were associated with progression to severe atrophy of the wall, the media in places being reduced in width to no more than 2 or 3 smooth muscle cells without any evidence of cellular degeneration. Intimal proliferation near the fistula and the naturally occurring intimal thickenings at branching sites proximal to the fistula, not only extended peripherally and progressed with time post-operatively, but exhibited ultrastructural changes consistent with atherosclerosis. These changes comprised dystrophic basement membrane, granulovesicular degeneration (matrix vesicles) and necrosis of smooth muscle cells, disruption of the elastic laminae, the appearance of extracellular and to a lesser extent intracellular lipid, adherence of monocytes, accumulation of foam cells, intimal fibrin deposition and sub-endothelial hemorrhage. Such results indicate that augmented hemodynamic stresses associated with femoral arteriovenous fistulae are consistent with those of human atherosclerotic lesions.

Animals↗
PubMed1995

The ultrastructure of arteries proximal to chronic experimental carotid-jugular fistulae in rabbits.

The afferent arteries from 11 normocholesterolemic rabbits with carotid-jugular arteriovenous fistulae ranging in duration from 107 to 718 days were examined by transmission electron microscopy to determine long term effects of an arteriovenous shunt on the afferent artery. Extensive tears and fragmentation of the internal elastic lamina of the elastic common carotid arteries were observed in all animals. Fragmentation and loss of elastic tissue as well as loss of muscle in the media accompanied progressive mural atrophy and tortuosity. Close to the fistula and in regions of tortuosity, fibromusculoelastic intimal proliferation was superimposed on the atrophic medial changes. The accumulation of matrix vesicles (cell debris), bizarre shaped smooth muscle cells, irregularly thickened multilaminated and reticulated basement membrane material beneath the endothelium and about smooth muscle cells, and abnormal shaped collagen fibrils were observed in the intima. Lipid was frequently found in the extracellular matrix and within smooth muscle cells while monocytes and lipid-laden macrophages were a feature of the more advanced intimal changes. These experiments confirm that in the absence of hypercholesterolemia the hydraulic stresses associated with an arteriovenous shunt cause severe mural atrophy and proliferative changes in the intima similar in nature to those of atherosclerosis.

Animals↗
PubMed1994

Ultrastructural changes in arteries proximal to short-term experimental carotid-jugular arteriovenous fistulae in rabbits.

The afferent arteries of 10 carotid-jugular arteriovenous fistulae in rabbits were examined by transmission electron microscopy to determine the early ultrastructural changes in the vicinity of haemodynamically induced tears of the internal elastic lamina. No significant changes appeared to precede the development of the tears but radially orientated partial fractures were observed adjacent to some major tears. The elastic tissue tears became more numerous, extended proximally along the artery and with time involved the innermost medial elastic laminae. Endothelial discontinuities were present over only a few early tears and the small size suggested repair was rapid. Endothelial cells overlying the elastic tissue tears increased in density and thickness. They were adherent to the underlying matrix and eventually to the thickened and multilaminated basal lamina. In the floor of the tears between the edges of the torn internal elastic lamina there were some smooth muscle cells of the synthetic type, degenerative and necrotic muscle cells and areas devoid of matrix with scarce proteoglycan material suggestive of oedema. Sixteen days post-operatively the smooth muscle cells in the floor of the tears were all of the contractile variety with thickened basal laminae overlaid by a relatively normal endothelial layer. There was no suggestion that inflammatory cells were responsible for the elastic tissue tears. The abrupt edges and the adjacent microfractures are consistent with the concept of mechanical failure of the elastic tissue.

Animals↗
PubMed1993

Endothelium in the aorta and ilio-femoral arteries proximal to femoral arteriovenous fistulae in rabbits.

The endothelium and underlying internal elastic lamina of the aorta and ilio-femoral arteries from 15 rabbits with femoral arteriovenous fistulae (2 to 92 days postoperatively) and 3 rabbits with control femoral arteriotomies were examined using the en face technique and scanning electron microscopy. The rapidity of development of the tears in the internal elastic lamina of the muscular ilio-femoral arteries was greater than in fistulae involving the elastic common carotid artery. The elastic tissue tears appeared to have a predilection for certain anatomical regions possibly related to regions of specific hemodynamic stress. A few tears were observed in the aorta near the origin of the renal arteries. Initially the elastic tissue tears in the afferent ilio-femoral arteries were longitudinally orientated and the endothelium overlying the elastic tissue tears soon exhibited increased cell density relatively restricted to the floor of the tears. This cellular pattern was similar to that in the carotid-jugular fistulae. With time the endothelium assumed a more conventional morphology.

Animals↗
PubMed1992

Endothelium and elastic tears in the afferent arteries of experimental arteriovenous fistulae in rabbits.

The endothelium and underlying internal elastic lamina of the arteries from 16 carotid-jugular arteriovenous fistulae in rabbits were examined using the en face technique and scanning electron microscopy respectively. Tears appeared in the internal elastic lamina of the arteries 3 days post-operatively. The overlying endothelium exhibited cytoplasmic pallor, loss of argyrophilia of cell borders, and at times attenuated endothelial cells bridging thrombus covered regions of denudation. Early endothelial lesions repaired rapidly and were found only 3-7 days post-operatively despite progressive increase in frequency and extent of tears and the development of interconnecting longitudinal tears with time. Following repair endothelial cells over the tears were small with hyperchromatic nuclei and oriented mostly parallel to the arterial axis. Endothelial cell density overlying these elastic tissue tears increase to three times that in contralateral arteriotomized common carotid arteries. These endothelial changes were sharply delineated by the margins of the elastic tears. Cell density over the tears reached its maximum 9-11 days post-operatively with mitotic figures both in the floor of the tears and over islands of residual elastic lamina. With time the cell density progressively diminished and endothelial cells assumed a more conventional elongated spindle shape.

Animals↗