Biomedical subjects

K A Griffiths

Publications and source records attributed to K A Griffiths.

At least 19 recordsLinked to original sources

PubMed2001

Androgenic anabolic steroids and arterial structure and function in male bodybuilders.

OBJECTIVES: The study examined arterial and cardiac structure and function in bodybuilders using androgenic anabolic steroids (AAS), compared to non-steroid-using bodybuilder controls. BACKGROUND: Adverse cardiovascular events have been reported in bodybuilders taking anabolic steroids. The cardiovascular effects of AAS, however, have not been investigated in detail. METHODS: We recruited 20 male bodybuilders (aged 35 +/- 3 years), 10 actively using AAS and 10 who denied ever using steroids. Serum lipid and hormone levels, carotid intima-media thickness (IMT), arterial reactivity, and left ventricular (LV) dimensions were measured. Vessel diameter was measured by ultrasound at rest, during reactive hyperemia (an endothelium-dependent response, leading to flow-mediated dilation, FMD), and after sublingual nitroglycerin (GTN, an endothelium-independent dilator). Arterial reactivity was also measured in 10 age-matched non-bodybuilding sedentary controls. RESULTS: Use of AAS was associated with significant decreases in high density lipoprotein cholesterol, sex hormone binding globulin, testosterone and gonadotrophin levels, and significant increases in LV mass and self-reported physical strength (p < 0.05). Carotid IMT (0.60 +/- 0.04 mm vs. 0.63 +/- 0.07 mm), arterial FMD (4.7 +/- 1.4% vs. 4.1 +/- 0.7%) and GTN responses (11.0 +/- 1.9% vs. 14.4 +/- 1.7%) were similar in both bodybuilding groups (p > 0.2). The GTN responses were significantly lower and carotid IMT significantly higher in both bodybuilding groups, however, compared with the non-bodybuilding sedentary controls (p = 0.01). CONCLUSIONS: Although high-level bodybuilding is associated with impaired vascular reactivity and increased arterial thickening, the use of AAS per se is not associated with significant abnormalities of arterial structure or function.

Adult↗

PubMed2001

Oestradiol improves arterial endothelial function in healthy men receiving testosterone.

OBJECTIVE: To assess prospectively the effects of low dose oestradiol on arterial endothelial and smooth muscle function in healthy men. Oestrogen use is associated with reduced cardiovascular disease in oestrogen-deficient women, however, the vascular effects of low-dose oestradiol in healthy men have not been investigated previously. PATIENTS AND DESIGN: Twenty-three men (aged 32 +/- 8 years) were randomized to receive depot implants of testosterone (T) alone (group 1, n = 10), or T with either 10 mg (group 2, n = 7) or 20 mg (group 3, n = 6) of oestradiol (E). MEASUREMENTS: Hormone levels, lipids and vascular reactivity were measured before, 1 month and 6 months after hormone implantation. Using high-resolution ultrasound, brachial artery diameter was measured at rest, during reactive hyperaemia (leading to flow-mediated dilatation, FMD, which is endothelium-dependent) and after sublingual nitroglycerin (GTN, an endothelium-independent dilator). RESULTS: Oestradiol produced a dose-dependent increase in plasma oestradiol (at 1 month 96 +/- 7, 149 +/- 6, 192 +/- 23 pmol/l in the 3 groups, respectively, P < 0.001 by ANOVA for trend). Minor side-effects (gynaecomastia, nipple tenderness) indicated that 20 mg oestradiol was the maximum tolerated dose. There was also a dose-dependent increase in FMD with oestradiol dose: at 1 month, - 0.2, + 0.2 and + 1.8% for groups 1-3, respectively (P = 0.31 by ANOVA for trend); and at 6 months, - 0.8, + 0.4 and + 2.2% (P = 0.02). The rise in oestradiol levels following treatment correlated with the improvement in FMD (P = 0.01). GTN responses were similar in the 3 groups throughout the study. CONCLUSION: In healthy young men, oestradiol supplementation is associated with enhanced arterial endothelial function, a key marker of vascular health.

Adult↗

PubMed2001

Doppler sonographic measurements of arterial blood flow and their repeatability in the equine foot during weight bearing and non-weight bearing.

In six normal adult horses, pulsed-wave Doppler sonographic inspections were made of the left and right lateral palmar proper digital artery (LPPDA) of each thoracic limb. Using a two-period, crossover design with repeated measures, each LPPDA was inspected on four occasions throughout the day over a 7 hour period and, on each occasion, with the limb weight bearing and non-weight bearing. In comparison with the observations made during weight bearing, there were significant increases (P<0.001) in blood-flow velocities when the limb was non-weight bearing. There was no relationship between blood velocities and the time of day, the order in which the inspections were made, resting heart rate, age of the horse, or hoof angle. In both weight bearing and nonweight bearing, the Doppler waveform demonstrated a systolic peak followed by at least two diastolic peaks and an end diastolic plateau. Horses that moved least during sonographic inspections had the lowest co-efficients variation.

Animals↗

PubMed2001

Postprandial arterial vasodilation in the equine distal thoracic limb.

The effects of feeding on blood flow to the equine foot are poorly understood. In a temperature-controlled room, duplex Doppler ultrasonographic observations were made pre- and postprandially of the lateral proper palmar digital artery of 5 horses, randomly assigned to twice and 4 times daily feeding in an unbalanced 2 period crossover design. Arterial diameter and blood velocity were measured over 4 h and additional observations made of heart rate, blood pressure, total plasma protein, packed cell volume, plasma glucose and insulin. There was no effect of the feeding regimen on any variable. Postprandially, there were significant increases in arterial diameter, blood velocity, total plasma protein, plasma glucose and insulin; the other variables were unchanged. It appeared that the normal postprandial response was an increase in blood flow to the foot. The value of ultrasonography for noninvasive investigation of the peripheral vasculature of the conscious horse was established; and in the future it may have a role in the diagnosis of vascular diseases of the foot.

Animal Feed↗

PubMed2000

Coenzyme Q improves LDL resistance to ex vivo oxidation but does not enhance endothelial function in hypercholesterolemic young adults.

Oxidative modification of low-density lipoprotein (LDL) may cause arterial endothelial dysfunction in hyperlipidemic subjects. Antioxidants can protect LDL from oxidation and therefore improve endothelial function. Dietary supplementation with coenzyme Q (CoQ(10)) raises its level within LDL, which may subsequently become more resistant to oxidation. Therefore, the aim of this study was to assess whether oral supplementation of CoQ(10) (50 mg three times daily) is effective in reducing ex vivo LDL oxidizability and in improving vascular endothelial function. Twelve nonsmoking healthy adults with hypercholesterolemia (age 34+/-10 years, nine women and three men, total cholesterol 7.4+/-1.1 mmol/l) and endothelial dysfunction (below population mean) at baseline were randomized to receive CoQ(10) or matching placebo in a double-blind crossover study (active/placebo phase 4 weeks, washout 4 weeks). Flow-mediated (FMD, endothelium-dependent) and nitrate-mediated (NMD, smooth muscle-dependent) arterial dilatation were measured by high-resolution ultrasound. CoQ(10) treatment increased plasma CoQ(10) levels from 1.1 +/-0.5 to 5.0+/-2.8 micromol/l (p =.009) but had no significant effect on FMD (4.3+/-2.4 to 5.1+/-3.6 %, p =.99), NMD (21.6+/-6.1 to 20.7+/-7.8 %, p = .38) or serum LDL-cholesterol levels (p = .51). Four subjects were selected randomly for detailed analysis of LDL oxidizability using aqueous peroxyl radicals as the oxidant. In this subgroup, CoQ(10) supplementation significantly increased the time for CoQ(10)H(2) depletion upon oxidant exposure of LDL by 41+/-19 min (p = .04) and decreased the extent of lipid hydroperoxide accumulation after 2 hours by 50+/-37 micromol/l (p =.04). We conclude that dietary supplementation with CoQ(10) decreases ex-vivo LDL oxidizability but has no significant effect on arterial endothelial function in patients with moderate hypercholesterolemia.

Adolescent↗

PubMed2000

Oral vitamin C and endothelial function in smokers: short-term improvement, but no sustained beneficial effect.

OBJECTIVES: To test the hypothesis that antioxidant therapy would improve endothelial function in smokers. BACKGROUND: Several studies have documented a beneficial effect of short-term oral or parenteral vitamin C on endothelial physiology in subjects with early arterial dysfunction. Possible long-term effects of vitamin C on endothelial function, however, are not known. METHODS: We studied the effects of short- and long-term oral vitamin C therapy on endothelial function in 20 healthy young adult smokers (age 36 +/- 6 years, 8 male subjects, 21 +/- 10 pack-years). Each subject was studied at baseline, 2 h after a single dose of 2 g vitamin C and 8 weeks after taking 1 g vitamin C daily, and after placebo, in a randomized double-blind crossover study. Blood samples were analyzed for plasma ascorbate levels and endothelial function was measured as flow-mediated dilation of the brachial artery, using high resolution ultrasound. Nitroglycerin-mediated dilation (endothelium-independent) was also measured at each visit. RESULTS: At baseline, plasma ascorbate level was low in the smokers (42 +/- 21 micromol/liter; normal range, 50 to 150 micromol/liter), increased with vitamin C therapy after 2 h to 120 +/- 54 micromol/liter (p < 0.001) and remained elevated after eight weeks of supplementation at 92 +/- 32 micromol/liter (p < 0.001, compared with placebo). Flow-mediated dilation, however, increased at 2 h (from 2.8 +/- 2.0% to 6.3 +/- 2.8%, p < 0.001), but there was no sustained beneficial effect after eight weeks (3.9 +/- 3.2%, p = 0.26). Nitroglycerin-mediated dilation was unchanged throughout. CONCLUSION: Oral vitamin C therapy improves endothelial dysfunction in the short term in healthy young smokers, but it has no beneficial long-term effect, despite sustained elevation of plasma ascorbate levels.

Administration, Oral↗

PubMed1999

Arterial endothelial dysfunction related to passive smoking is potentially reversible in healthy young adults.

BACKGROUND: Passive smoking is associated with early arterial damage, but the potential for reversibility of this damage is unknown. OBJECTIVE: To assess the reversibility of arterial endothelial dysfunction, a key marker of early atherosclerosis. DESIGN: Cross-sectional study. SETTING: Academic medical center. PARTICIPANTS: 60 healthy persons 15 to 39 years of age: 20 with no exposure to active or passive smoking, 20 nonsmoking passive smokers (exposure to environmental tobacco smoke for > or = 1 hour per day for > or = 2 years), and 20 former passive smokers. MEASUREMENTS: Arterial endothelial function measured by noninvasive ultrasonography. RESULTS: Endothelium-dependent dilatation was significantly better in former passive smokers (5.1% +/- 4.1% [range, -1.2% to 15.6%]) than in current passive smokers (2.3% +/- 2.1% [range, -0.2% to 6.7%]) (P = 0.01), although both groups were significantly impaired compared with nonsmoking controls (8.9% +/- 3.2% [range, 2.1% to 16.7%]) (P < or = 0.01 for both comparisons). CONCLUSIONS: In healthy young adults, arterial endothelial dysfunction related to passive smoking seems to be partially reversible.

Adolescent↗

PubMed1999

Sonographic observations of the peripheral vasculature of the equine thoracic limb.

Investigations of the equine peripheral vascular system have been constrained by the lack of a non-invasive method of examining the arteries and veins of the limbs of the conscious horse. Precise correlations were established between the gross anatomical features of the peripheral vessels and their B-mode sonographic appearance in each thoracic limb of 35 horses. A sonographic imaging protocol was established. Additional Doppler sonographic recordings defined the arterial waveforms and demonstrated that blood flow to the foot could be evaluated in the lateral proper digital artery, distal to the level of the coronary band. Valves (with 2-4 cusps) were identified in the lumina of the medial and lateral palmar common digital veins and those of the medial and lateral palmar proper digital veins. Spontaneous echo contrast, a smoke-like haze of echoic blood, was seen in the lateral and medial palmar common digital veins, the distal deep palmar venous arch and communicating branches, and the palmar proper digital veins, and occasionally seen in the distal deep palmar arterial arch and distal proper palmar digital arteries. The value of duplex sonography (B-mode and Doppler) for anatomical and physiological studies of the peripheral vasculature of the horse was clearly established. Such data could be applied to the investigation of diseases affecting the peripheral circulation.

Animals↗

PubMed1998

Vascular reactivity is impaired in genetic females taking high-dose androgens.

OBJECTIVE: To assess the vascular effects of high-dose androgen treatment in genetic females. BACKGROUND: Male gender is an independent risk factor for coronary artery disease, suggesting either a protective effect of estrogens and/or a deleterious effect of androgens. We have recently demonstrated that androgen deprivation is associated with enhanced vascular reactivity in adult men, however, the effects of androgen excess on vascular function in humans has not been reported previously. METHODS: We studied vascular reactivity in two groups of genetic females: 12 female-to-male transsexuals receiving long-term high-dose androgens, and 12 healthy female control subjects, matched for age and smoking history. Using external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (leading to flow-mediated dilatation [FMD], which depends on normal endothelial function) and after sublingual nitroglycerin (NTG), an endothelium-independent dilator. RESULTS: Testosterone levels were higher (15.2+/-8.7 vs. 1.9+/-1.3 mmol/L, p < 0.001) and high-density lipoprotein cholesterol levels were lower (1.2+/-0.2 vs. 1.6+/-0.4 mmol/L, p=0.02) in the transsexuals compared with the control subjects. In each group, nine of 12 subjects were current or ex-smokers, leading to impaired FMD in both groups (5.1+/-3.7% in the transsexuals vs. 6.9+/-4.1% in controls, p=0.28). The NTG response was significantly decreased in the transsexuals (15.9+/-4.9% vs. 22+/-5.8% in controls, p=0.01), independent of the effects of age, cholesterol or vessel size. CONCLUSIONS: Long-term treatment with high-dose androgens is associated with impaired vascular reactivity in genetic females, consistent with a deleterious effect of androgen excess on arterial physiology.

Adult↗

PubMed1995

Correction of distortion in US images caused by subcutaneous tissues: results in tissue phantoms and human subjects.

PURPOSE: To correct distortion in ultrasonic images caused by refraction at fat-muscle interfaces in the subcutaneous tissues. MATERIALS AND METHODS: A forward-propagation technique was developed that used a priori information of the acoustic properties of the layers. The thickness and shape of these tissues were measured, and a correction was applied for the different velocities in the tissues. A synthetic-aperture scanning technique was used to allow correction to be applied with data obtained in a single scan. The technique was tested in three tissue phantoms with overlying aberrating layers (six images) and in eight volunteer subjects (37 images). The superior mesenteric artery and the aorta were used as test sites within the body, because it is relatively easy to obtain double images of these vessels owing to refraction of the scanning beam by the rectus muscles. RESULTS: Distortions such as double-image artifacts and texture disruption were corrected with use of this technique. Six of the six phantom images and 22 of the 37 images in humans were corrected with use of this technique. CONCLUSION: The forward-propagation technique compensates for refraction at subcutaneous fat-muscle interfaces.

Abdominal Muscles↗

PubMed1995

Transducer rotation: a useful scanning maneuver in three-dimensional ultrasonic volume imaging.

In ultrasonic volume imaging, the effect of rotating the transducer about the central axis of the imaging plane is equivalent to rotation of the insonified volume. The authors present schematics to depict the action and sonograms in two cases (a hand immersed in water and a 36-week fetus) to demonstrate this phenomenon. This maneuver can be used to "rotate" the imaged structures, which enhances their three-dimensional representation.

Female↗

PubMed1995

Volume imaging: three-dimensional appreciation of the fetal head and face.

Quasi-three-dimensional volume imaging provides an inexpensive means of evaluating the usefulness of three-dimensional imaging. The technique works most efficiently with water-skin interfaces and therefore we investigated its application in obstetrical ultrasonography. Three-dimensional perspectives of the normal and abnormal fetal head and face were spectacular and at times provided more information than the two-dimensional images. The ability of an inexperienced observer to interpret the three-dimensional image more easily may have a role in training sonographers and counseling parents whose fetuses have structural defects. Volume imaging has certain limitations and can only be used as a complementary technique.

Artifacts↗

PubMed1994

Real-time quasi-three-dimensional viewing in sonography, with conventional, gray-scale volume imaging.

Real-time three-dimensional views of the fetus can be obtained with minor modification to conventional scanners. The modification consists of placing a divergent lens in the out-of-scan plane of the transducer to generate a beam fan-beam in the insonated volume. All of the echoes from which insonates a volume rather than a slice of tissue. Scanning is performed using oblique angles of incidence to provide total reflection conditions. Echoes are then received only from anterior surfaces, automatically generating the three-dimensional views. Intriguing portrayal of fetal detail can be obtained with this form of imaging which is likely to expand the clinical utility of sonographic examinations.

Journal Article↗

PubMed1993

Thickness of tissues intervening between the transducer and fetus and models for fetal exposure calculations in transvaginal sonography.

In transvaginal scanning the tissues intervening between the fetus and transducer are relatively thin. The average thickness in the first trimester is 25 mm and reduces to 15 mm by the third trimester; the minimum thicknesses are 14 and 8 mm, respectively. Two models are proposed for calculating exposure in transvaginal scanning. The models are considered in terms of the overlying tissues and the target tissues. A fixed path, constant attenuation of 0.3 dB/MHz describes the properties of the overlying tissues throughout pregnancy. In the model used in first-trimester scanning, the target tissues of the embryo/fetus are considered to have properties similar to those of soft tissues, and they attenuate the energy at the same rate as the overlying tissues. In the model used in second- and third-trimester scanning, the bony structures of the fetus are the target tissues. These reflect 30% of the incident energy and attenuate all of the transmitted energy at their surface.

Extraembryonic Membranes↗

PubMed1991

Is the quality of transvaginal images superior to transabdominal ones under matched conditions?

Transvaginal images, under matched conditions, are in general superior in quality to transabdominal sonograms. The difference is, however, not dramatic and instances frequently occur when the same quality and even inferior images are obtained on transvaginal examinations. The dominant factor is the amount of overlying tissues. For the same thickness, subcutaneous tissues have greater degrading characteristics. Subcutaneous tissues also mar the quality of images by giving rise to strong multiple reflection artifacts. The major factors for image degradation are associated with a moderate increase in the width of the ultrasonic beam and a large increase in the side lobes. The dramatic superiority of transvaginal imaging described in previous comparison studies is due principally to the use of higher frequencies, more strongly focused beams and closer positioning of tissues to the transducer.

Journal Article↗

PubMed1989

New class of pulsed Doppler US ambiguity at short ranges.

A form of range ambiguity in Doppler ultrasound has been identified. It occurs when a high pulse repetition frequency (prf) is used with a superficial range gate. "Phantom" range gates are then generated at depths beyond the desired range gate, and these may produce artifactual signals. Extremely high prf values should not normally be used, and duplex machines should be programmed to display phantom range gates wherever they fall within the displayed field of view.

Humans↗

PubMed1988

Ultrasonic characterization of splenic tissue in myelofibrosis: further evidence for reversal of fibrosis with chemotherapy.

Fibrosis in patients with myelofibrosis (MF) is seen not only in the bone marrow but also around the metaplastic foci in the spleen and liver. Following our observation of reversal of bone marrow fibrosis in MF patients treated with chemotherapy, we undertook ultrasonic splenic tissue characterization studies using sound speed measurements to assess the effect of such therapy on the splenic fibrosis. Single studies in 19 patients showed overlapping ranges among the three sub-groups classified according to the grade of bone marrow fibrosis, but the mean values in these sub-groups showed a trend towards decreasing sound speed with increasing marrow fibrosis. Sequential studies in 9 of these patients showed increased splenic sound speed with decreasing marrow fibrosis in 8 patients following treatment, with a reversal of this pattern seen in 1 patient 1-2 years post-treatment. These results suggest simultaneous reversal of fibrosis in the bone marrow and the spleen in MF patients receiving effective chemotherapy.

Bone Marrow↗

PubMed1987

Splenic blood flow measurements by Doppler ultrasound: a preliminary report.

Splenic blood flow and splenic volume were measured by Doppler and cross sectional ultrasound in 72 human subjects consisting of 61 patients with splenomegaly and 11 normal subjects. This non-invasive and relatively simple method yielded satisfactory results in 76% of the subjects studied; failures were due to obesity, debility, distorted vascular anatomy, and excessive gas in the stomach. These preliminary results suggest that the Doppler ultrasound technique is a practical clinical method for measuring splenic blood flow.

Adult↗