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At least 127 records · Page 7Linked to original sources
PubMed1997

Sympathetic withdrawal and forearm vasodilation during vasovagal syncope in humans.

Our aim was to determine whether sympathetic withdrawal alone can account for the profound forearm vasodilation that occurs during syncope in humans. We also determined whether either vasodilating beta 2-adrenergic receptor or nitric oxide (NO) contributes to this dilation. Forearm blood flow was measured bilaterally in healthy volunteers (n = 10) by using plethysmography during two bouts of graded lower body negative pressure (LBNP) to syncope. In one forearm, drugs were infused via a brachial artery catheter while the other forearm served as a control. In the control arm, forearm vascular resistance (FVR) increased from 77 +/- 7 units at baseline to 191 +/- 36 units with -40 mmHg of LBNP (P < 0.05). Mean arterial pressure fell from 94 +/- 2 to 47 +/- 4 mmHg just before syncope, and all subjects demonstrated sudden bradycardia at the time of syncope. At the onset of syncope, there was sudden vasodilation and FVR fell to 26 +/- 6 units (P < 0.05 vs. baseline). When the experimental forearm was treated with bretylium, phentolamine, and propranolol, baseline FVR fell to 26 +/- 2 units, the vasoconstriction during LBNP was absent, and FVR fell further to 16 +/- 1 units at syncope (P < 0.05 vs. baseline). During the second trial of LBNP, mean arterial pressure again fell to 47 +/- 4 mmHg and bradycardia was again observed. Treatment of the experimental forearm with the NO synthase inhibitor NG-monomethyl-L-arginine in addition to bretylium, phentolamine, and propranolol significantly increased baseline FVR to 65 +/- 5 units but did not prevent the marked forearm vasodilation during syncope (FVR = 24 +/- 4 vs. 29 +/- 8 units in the control forearm). These data suggest that the profound vasodilation observed in the human forearm during syncope is not mediated solely by sympathetic withdrawal and also suggest that neither beta 2-adrenergic-receptor-mediated vasodilation nor NO is essential to observe this response.

Acetylcholine↗
PubMed1982

Lactate and glucose exchange across the forearm, legs, and splanchnic bed during and after prolonged leg exercise.

The net exchange of glucose and lactate across the leg and the splanchnic bed and the arterialdeep venous (A-DV) differences for these substrates in the forearm were determined in healthy subjects during 3-3.5 h of leg exercise (bicycle ergometer) at 58% maximum O(2) uptake and during a 40-min post-exercise recovery period. Leg glucose uptake rose 16-fold during exercise and throughout the exercise period exceeded splanchnic glucose output. The latter reached a peak increment (3.5 times basal) at 90 min and fell by 60% during the third hour. As a result, blood glucose declined 40%, reaching frank hypoglycemia (blood glucose, <45 mg/dl) in 50% of subjects at 3.5 h. Splanchnic lactate uptake rose progressively during exercise to values four times the basal rate at 3 h in association with a rise in arterial lactate to 1.5 mM. There was, however, no significant net output of lactate from the legs beyond 90 min of exercise. In contrast, the A-DV lactate difference in the forearm became progressively more negative throughout exercise, reaching values three times the basal level at 3.5 h. The rise in arterial lactate during exercise was proportional to the elevation in plasma epinephrine, which rose ninefold. During recovery, splanchnic lactate uptake rose further to values six times the basal rate, whereas lactate output by the legs was no greater than in the basal state. The A-DV lactate difference in the forearm became even more negative than during exercise, reaching values four times basal. During exercise as well as recovery, forearm uptake of blood glucose could account for no more than 25-67% of forearm lactate release. Leg glucose uptake during recovery was threefold to fivefold higher than in the basal state in the face of plasma insulin concentrations that were 60% below basal and in association with a respiratory exchange ratio of 0.7. We conclude that (a) during prolonged leg exercise at 58% maximum O(2) uptake an imbalance between splanchnic glucose production and leg glucose utilization results in a fall in blood glucose that may reach hypoglycemic levels in healthy subjects; (b) there is a marked increase in the uptake of lactate by the splanchnic bed that cannot be attributed to increased output of lactate from the exercising legs; (c) lactate is released by forearm muscle and, together with other relatively inactive muscle, may be an important source of the increased lactate turnover during and after prolonged leg exercise; (d) the increasingly negative A-DV lactate difference in the forearm cannot be accounted for by uptake of blood glucose, suggesting the breakdown of glycogen in forearm muscle during and after leg exercise; (e) increased glucose uptake by the legs in association with hypoinsulinemia during recovery suggests an increase in insulin sensitivity that permits glycogen repletion in previously exercising muscle in the absence of food ingestion; and (f) the evidence for increased lactate output in the forearm and augmented glucose uptake in the legs during recovery raises the possibility that after leg exercise glycogen stores are decreasing in muscle that was relatively inactive (e.g., that of the forearm) while increasing in the previously exercising leg muscles.

Adult↗
PubMed1996

Mechanisms of postprandial protein accretion in human skeletal muscle. Insight from leucine and phenylalanine forearm kinetics.

The relative role of protein synthesis and degradation in determining postprandial net protein deposition in human muscle is not known. To this aim, we studied forearm leucine and phenylalanine turnover by combining the arteriovenous catheterization with tracer infusions, before and following a 4 h administration of a mixed meal in normal volunteers. Forearm amino acid kinetics were assessed in both whole blood and plasma. Fasting forearm protein degradation exceeded synthesis (P < 0.01) using either tracer, indicating net muscle protein loss. The net negative forearm protein balance was quantitatively similar in whole blood and in plasma. After the meal, forearm proteolysis was suppressed (P < 0.05- < 0.03), while forearm protein synthesis was stimulated (P < 0.05- < 0.01). However, stimulation of protein synthesis was greater (P < 0.05- < 0.01) in whole blood (leucine data: +50.4 +/- 7.8 nmol/min x 100 ml of forearm; phenylalanine data: +30.4 +/- 11.6) than in plasma (leucine data: +17.8 +/- 5.6 nmol/min x 100 ml of forearm; phenylalanine data: +5.7 +/- 2.1). Consequently, the increment of net amino acid balance was approximately two to fourfold greater (P < 0.04- < 0.03) in whole blood than in plasma. In conclusion, meal ingestion stimulates forearm protein deposition through both enhanced protein synthesis and inhibited proteolysis. Plasma data underestimate net postprandial forearm protein synthesis, suggesting a key role of red blood cells and/or of blood mass in mediating mealenhanced protein accretion.

Adult↗
PubMed2003

Vitamin C improves attenuated angiotensin II-induced endothelium-dependent vasodilation in human forearm vessels.

Endothelial dysfunction might be related to an increase in superoxide anion production in patients with hypertension, hypercholesterolemia, diabetes mellitus, and heart failure. Studies in animal models indicate that angiotensin II increases superoxide anion production by vascular tissues. We examined whether angiotensin II attenuates endothelium-dependent vasodilation via an increase in superoxide anion production in human forearm vessels in vivo. Forearm blood flow was measured in 23 healthy young men. We examined forearm vasodilator responses to an intra-arterial infusion of acetylcholine (4, 8, and 16 microg/min) and sodium nitroprusside (0.8, 1.6, and 3.2 microg/min) before and during an intra-arterial infusion of anglotensin II (n=8), angiotensin II plus vitamin C (n=8), and vitamin C alone (n=4). Angiotensin II attenuated the forearm vasodilatory response to acetylcholine (p<0.05), and this attenuated response was abolished by vitamin C. Angiotensin II did not alter the forearm vasodilatory response to sodium nitroprusside, and vitamin C infusion did not affect the forearm vasodilatory response to either acetylcholine or sodium nitroprusside. The forearm vasodilator response to acetylcholine did not change during infusion of norepinephrine (n=3), which reduced forearm blood flow to a degree similar to that by angiotensin II infusion. These results suggest that angiotensin II attenuates endothelium-dependent forearm vasodilation, and vitamin C improves this impairment. Thus, angiotensin II likely attenuates endothelium-dependent vasodilation via an increase of superoxide anion production in the human forearm in vivo.

Adult↗
PubMed1999

Effects of branched-chain-enriched amino acids and insulin on forearm leucine kinetics.

Although amino acid mixtures enriched in branched-chain amino acids (BCAA) and deficient in aromatic amino acids (AAA) are often used together with insulin and glucose in clinical nutrition, their physiological effects on muscle protein anabolism are not known. To this aim, we studied forearm leucine kinetics in post-absorptive volunteers, before and after the systemic infusion of BCAA-enriched, AAA-deficient amino acids along with insulin and the euglycaemic clamp. The results were compared with the effects of insulin infusion alone. A compartmental leucine forearm model was employed at steady state. Hyperaminoacidaemia with hyperinsulinaemia (to approximately 80-100 micro-units/ml) increased the leucine plasma concentration (+70%; P<0.001), inflow into the forearm cell (+150%; P<0.01), disposal into protein synthesis (+100%; P<0.01), net intracellular retention (P<0.01), net forearm balance (by approximately 6-fold; P<0.01) and net deamination to alpha-ketoisocaproate (4-methyl-2-oxopentanoate) (+9%; P<0.05). Leucine release from forearm proteolysis and outflow from the forearm cell were unchanged. In contrast, hyperinsulinaemia alone decreased plasma leucine concentrations (-35%; P<0.001) and leucine inflow (-20%; P<0.05) and outflow (-30%; P<0.01) into and out of forearm cell(s), it increased net intracellular leucine retention (P<0.03), and it did not change leucine release from forearm proteolysis (-20%; P=0.138), net leucine deamination to alpha-ketoisocaproate, leucine disposal into protein synthesis or net forearm protein balance. By considering all data together, leucine disposal into protein synthesis was directly correlated with leucine inflow into the cell (r=0.71; P<0.0001). These data indicate that the infusion of BCAA-enriched, AAA-deficient amino acids along with insulin is capable of stimulating forearm (i.e. muscle) protein anabolism in normal volunteers by enhancing intracellular leucine transport and protein synthesis. These effects are probably due to hyperaminoacidaemia and/or its interaction with hyperinsulinaemia, since they were not observed under conditions of hyperinsulinaemia alone.

Adult↗
PubMed1981

Different behavior of the resistance vessels of the human calf and forearm during contralateral isometric exercise, mental stress, and abnormal respiratory movements.

Experiments were conducted in normal human volunteers to compare the response of the forearm and calf vessels to contralateral isometric exercise, mental stress, resisted breathing, coughing, and the Valsalva maneuver. Blood flows were measured by means of strain-gauge plethysmography, arterial blood pressure by auscultation, and heart rate by electrocardiography. Isometric exercise of one forearm (at one-third maximal voluntary contraction) for 90 seconds caused an increase in blood pressure and heart rate; the vascular resistance decreased in the resting forearm, and increased in the calf. The decrease in forearm resistance was greater with the subjects supine and attenuated with the subjects standing or reclining head-down. With arterial occlusion of the exercising forearm just prior to cessation of the handgrip, the blood pressure and the calf resistance remained elevated, while the heart rate returned to control. The forearm resistance increased during the occlusion period and remained elevated throughout it. Mental stress caused an increase in heart rate and blood pressure and a dilation of the forearm but not of the calf vessels; these changes were smaller in standing than in supine subjects. Resisted breathing and coughing caused an increase in heart rate and in forearm blood flow, but not in calf blood flow. The Valsalva maneuver was followed by decreases in blood flow to the upper and lower limbs. The different responses in forearm and calf vessels can be explained by a central component which triggers a vasodilator pathway (possibly cholinergic) which is distributed to forearm but not to calf vessels.

Adult↗
PubMed1997

[Some blood flow parameters of forearm arteries in patients with "sleeve" arteriovenous shunts].

UNLABELLED: The aim of the study was estimation of some blood flow parameters in arteries of both forearms in patients with "sleeve" arterio-venous fistula (AVF) created for hemodialysis. From 1988 to 1996 145 radio-cephalic AVF's with "sleeve" anastomoses were created in our Department. Duplex-Scan examinations were performed in 30 patients aged from 22 to 68 years. There are 15 women and 15 men with primary AVF lasting over 12 months. The B&K Medical System 3535 with 7.5 MHz transducer was used for all measurements. Diameter of radial artery (TP) in forearms with AVF fistula was on average 4.7 mm, and in ulnar artery (TL) 2.6 mm. In forearms without AVF diameters were, respectively 2.4 mm and 2.3 mm. Volume flow in forearms with AVF was in TP 1056, and in TL 169 ml/min. In forearms without AVF these flows were 59 and 63 ml/mm, respectively. Resistance index in forearms with AVF was 0.29 in TR and 0.47 in TL, however in forearms without AVF 0.76 in both arteries. Pulsatility index on the side of AVF was 0.8 in TR and 1.8 in TL, however on the side without AVF 4.1 in both arteries. These differences were statistically significant. CONCLUSIONS: 1. In arteries of forearm with AVF diameter and volume blood flow increases, however resistance and pulsatility indices decreases. 2. Volume flow in ulnar artery in forearms with AVF is similar to flow in both arteries in forearm without AVF.

Adult↗
PubMed1999

[Forearm bone mineral density in healthy children].

OBJECTIVE: In order to establish the normal patterns of forearm bone mineral density (BMD), BMD in the cortical and trabecular parts of the distal forearm were studied in a normal pediatric population. PATIENTS AND METHODS: BMD was measured by dual-energy X-ray absorptiometry (HOLOGIC QDR-1000) in the distal third forearm of 246 normal children and adolescents (111 boys and 135 girls) ranging from 2.8 to 20.8 years of age. BMD was correlated by multiple regression analysis with age, weight, body mass index (BMI), sex and pubertal Tanner stage. RESULTS: Forearm BMD increased progressively with age, weight, height, BMI and maturity, with the maximal increase in all forearm bone sites occurring at the onset of puberty in girls and boys. A statistically significant correlation was found between forearm BMD and all of these variables (r = 0.65 to 0.92). Mean BMD was higher in boys than in girls in cortical, trabecular and cortical-trabecular sites of the distal forearm. Maximal differences in BMD between boys and girls occurred at 17-18 years of age, especially the trabecular-dominated (ultradistal) part of the distal forearm (0.446 vs 0.384 g/cm2). CONCLUSIONS: Forearm BMD studies permit information of both cortical and trabecular bone mineralization to be obtained at the same time. This study reports normative data for forearm BMD in a healthy pediatric population. The values obtained may be used as a reference of normality when evaluating bone density in situations where skeletal mineralization may be compromised.

Adolescent↗
PubMed2001

Prediction of bone mineral density of lumbar spine, hip, femoral neck and Ward's triangle by forearm bone mineral density.

Bone mineral density (BMD) of dual energy X-ray absorptiometry (DEXA) at both radius and ulna were measured to evaluate the correlation of those and BMD at lumbar (L) spine, hip, femoral neck and Ward's triangle. The 64 simple linear regression analysis was calculated to postulate the predicted equation by using the BMD at supradistal, distal 1/10, distal 1/6 and distal 1/3 of both forearms as independent variables, while the dependent variables were BMD at L1-L4 spine, total hip, femoral neck and Ward's triangle. 115 patients aged between 41-79 years (mean age 55.97+/-8.34 years) from the menopausal clinic, Pramongkutklao Hospital, were scanned at both forearms by Panasonic (DXA-70) DEXA and at non forearm regions by Hologic (QDR 4500) DEXA on the same day. The results showed that the BMD of each of the 4 parts of both radius and ulna had positive correlation to those of L-spine, total hip, femoral neck and Ward's triangle with r = 0.4012 to 0.7032 (P<0.001 for all). The greater distal of the forearm, the better correlation of BMD to the non forearm BMD. The 64 simple linear regression equations were constructed with regression coefficient ranging from 0.6048 to 1.9011 (P<0.001 for all). When considering the non forearm BMD, the mean BMD at Ward's triangle significantly declined more rapidly than that of L-spine, total hip and femoral neck (P<0.05 for all). It indicated that there was an early change of BMD at Ward's triangle. However, this change followed the forearm BMD. Distal forearm BMD was the earliest sign of bone loss. We can predict non forearm BMD by supradistal and distal 1/10 of forearm BMD.

Absorptiometry, Photon↗
PubMed1991

Cyclic intramuscular temperature fluctuations in the human forearm during cold-water immersion.

The purpose of the present study was to investigate the intramuscular temperature fluctuations in the human forearm immersed in water at 15 degrees C. Tissue temperature (Tt) was continuously monitored by a calibrated multicouple probe during 3 h immersion of the forearm. The probe was implanted approximately 90 mm distal from the olecranon process along the ulnar ridge. Tt was measured every 5 mm, from the longitudinal axis of the forearm (determined from computed tomography scanning) to the skin surface. Along with Tt, rectal temperature, skin temperature and heat loss of the forearm were measured during the immersions. Five of the six subjects tested showed evidence of cyclic temperature fluctuations in the forearm limited to the muscle tissue. The first increase of the muscle temperature was observed 75 (SE 6) min after the onset of the immersion, and the duration of the cycle averaged 36 (SE 3) min. The maximum increase of the muscle temperature, which ranged between 0.4 degrees C and 1.0 degrees C, was measured at the axis of the forearm, and was inversely correlated to the circumference of the subject's forearm (P less than 0.05). No corresponding increases of the skin temperature and heat loss of the forearm were observed for the complete duration of the immersion. These data support the hypothesis of a significant contribution of the muscle vessels during cold-induced vasodilatation in the forearm.

Adolescent↗
PubMed2000

Cardiovascular responses to cold-water immersions of the forearm and face, and their relationship to apnoea.

Apnoea as well as cold stimulation of the face or the extremities elicits marked cardiovascular reflexes in humans. The purpose of this study was to investigate whether forearm immersion in cold water has any effect on the cardiovascular responses to face immersion and apnoea. We recorded cardiovascular responses to coldwater immersions of the forearm and face in 19 (part I) and 23 subjects (part II). The experimental protocol was divided in two parts, each part containing four tests: I1, forearm immersion during eupnoea; I2, face immersion during eupnoea; I3, forearm and face immersion during eupnoea; I4, face immersion during apnoea; II1, apnoea without immersion; II2, forearm immersion during apnoea; II3, face immersion during apnoea; and II4, forearm and face immersion during apnoea. The water temperature was 9-11 degrees C. Cold-water immersion of either the forearm or face was enough to elicit the most pronounced thermoregulatory vasoconstriction during both eupnoea and apnoea. During eupnoea, heart rate responses to forearm immersion (3% increase) and face immersion (9% decrease) were additive during concurrent stimulation (3% decrease). During apnoea, the heart rate responses were not affected by the forearm immersion. The oxygen-conserving diving response seems to dominate over thermoregulatory responses in the threat of asphyxia. During breathing, however, the diving response serves no purpose and does not set thermoregulatory adjustments aside.

Adult↗
PubMed1992

Maintenance of forearm vasodilator action of atrial natriuretic factor in congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

Infusions of atrial natriuretic factor (ANF) are frequently associated with attenuated natriuretic and diuretic responses in patients with congestive heart failure. However, ANF infusions result in systemic vasodilation, suggesting that end organ responsiveness to ANF may not be uniformly decreased. To determine if the vasodilator effects of ANF were altered in heart failure, strain-gauge plethysmography was utilized to measure forearm blood flow responses to the intraarterial infusion of ANF using a dose range that was low enough to avoid systemic effects. In 9 control subjects, ANF infusions of 0.5, 1.0, 2.0 and 4.0 micrograms/min/100 ml forearm volume significantly increased forearm blood flow from 3.21 +/- 1.71 to 5.69 +/- 3.14, 6.20 +/- 2.57, 6.64 +/- 2.53 and 6.97 +/- 2.49 ml/min/100 ml forearm volume, respectively (all p less than 0.01). In 7 patients with heart failure, ANF infusion significantly increased forearm blood flow from 2.19 +/- 0.98 to 3.18 +/- 1.70, 3.76 +/- 2.0 and 4.42 +/- 2.80 ml/min/100 ml forearm volume for the 0.5, 1.0 and 2.0 micrograms doses, respectively (all p less than 0.05). By analysis of variance, the forearm blood flow responses pooled over all doses were not significantly different between the 2 groups. At the 2.0 micrograms dose, the peak increase in forearm blood flow in normal subjects represented a 107% increase over baseline compared with a 102% increase in patients with heart failure. In summary, these data demonstrate that intraarterial administration of ANF in patients with heart failure resulted in dose-related increases in forearm blood flow. The responses were not significantly different from normal subjects expressed both as an absolute response and as a percent increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

The relative proportions of fat, muscle and bone in the normal human forearm as determined by computed tomography.

Computed tomography has been used to establish the proportions of fat, muscle and bone present in the normal human forearm. Subjects were healthy young volunteers, eight males and eight females. A series of six cross-sectional scans at right angles to the long axis of the forearm was obtained, the scans being made at equidistant intervals between the olecranon process and the ulnar styloid. The volumes occupied by fat, muscle and bone were calculated for the complete forearm. Total forearm volume calculated by this method agreed closely with that measured by water displacement. For the male subjects, forearm composition was 72.1 +/- 4.4% muscle (mean +/- SD), 15.0 +/- 5.3% fat and 12.9 +/- 1.2% bone. Female forearms had less muscle (P less than 0.001) and more fat (P less than 0.001) than those of the male subjects: 58.5 +/- 4.0% muscle, 29.3 +/- 5.0% fat and 12.3 +/- 1.4% bone. Forearm muscle volume was significantly correlated (r = 0.75; P less than 0.05) with lean body mass in the male subjects; the range of values for lean body mass in the female subjects was too small to permit calculation of the equivalent relationship. Forearm fat content, as a percentage of total volume, was proportional to whole body fat content as estimated from skinfold thickness (males, r = 0.84; P less than 0.01; females, r = 0.77; P less than 0.05). These relationships enable estimates of the volumes of forearm tissue components to be derived from anthropometric measurements.

Adipose Tissue↗
PubMed1991

Role of the wrist cuff in forearm plethysmography.

1. To determine whether a wrist cuff is necessary to measure the forearm blood flow correctly, we studied the effects of wrist cuff inflation to supra-venous and supra-systolic pressure values over a large range of forearm blood flow values: in the basal state, during post-occlusive hyperaemia of the hand, and during heating of the hand with warm air. Eleven healthy men participated, and the study was carried out at two different ambient temperatures of 20 and 25 degrees C. 2. In the basal state, the measured forearm blood flow was lowest with the wrist cuff at supra-systolic pressure. With the wrist cuff at supra-venous pressure the forearm blood flow was also lower than with an uninflated cuff, but only significantly so when the basal forearm blood flow was higher (at a room temperature of 25 degrees C). 3. During post-occlusive hyperaemia, inflating the wrist cuff to supra-systolic pressure produced the lowest forearm blood flow value at both room temperatures. In addition, with the wrist cuff at supra-venous pressure, forearm blood flow values were lower than with the uninflated cuff, but the supra-venous cuff pressure was clearly less efficient in excluding the hand blood flow than the supra-systolic cuff pressure. 4. During heating of the hand, both supra-systolic and supra-venous cuff pressures were effective in excluding the hand blood flow at both room temperatures. The forearm blood flow measured with the wrist cuff at supra-systolic pressure was lower than that measured with the wrist cuff at supra-venous pressure, but the difference was only significant at a room temperature of 20 degrees C. 5. In conclusion, we have demonstrated that a wrist cuff at supra-systolic pressure is most appropriate for the exclusion of the hand circulation in order to measure the forearm blood flow correctly.

Forearm↗
PubMed2001

Analysis of circadian and ultradian rhythms of skin surface properties of face and forearm of healthy women.

Biologic rhythms of cells and organisms are well documented and have been extensively studied at the physiologic and molecular levels. For the skin, many circadian changes have been investigated but few systematic studies comparing skin at different body sites have been reported. In this study we investigated facial and forearm skin circadian rhythms in eight healthy Caucasian women. Noninvasive methods were used to assess skin capacitance, sebum excretion, skin temperature, transepidermal water loss, and skin surface pH on fixed sites of the face and the volar forearm during a 48 h span under standardized environmental conditions. Using the cosinor or ANOVA methods, circadian rhythms could be detected for sebum excretion (face), transepidermal water loss (face and forearm), skin temperature (forearm), pH (face), and capacitance (forearm). No circadian rhythmicity was found for the other biophysical parameters. In addition to the 24 h rhythm component, rhythms with periods of 8 h were found for sebum excretion, of 8 and 12 h for transepidermal water loss (face and forearm), and of 12 h for skin temperature (forearm). Our study confirms that rhythms of skin surface parameters are readily measurable and that these rhythms differ between different sites. Furthermore, we demonstrate for the first time that, for transepidermal water loss (face and forearm), sebum excretion, and skin temperature (forearm), in addition to circadian rhythms, ultradian and/or component rhythms can be detected.

Activity Cycles↗
PubMed1997

Attenuation of forearm vasodilator responses to mental stress by regional beta-blockade, but not by atropine.

Forearm blood flow during mental stress (Stroop's colour word conflict test) was studied in 18 healthy men before and during regional beta-adrenoceptor blockade (propranolol 0.5 mg), muscarinic receptor blockade (atropine 0.2 mg) and combined blockade, and compared with results obtained in untreated controls. Forearm blood flow was measured with venous occlusion plethysmography, and forearm vascular resistance was calculated. Arterial and venous blood sampling was performed for determination of adrenaline and noradrenaline in plasma. Mental stress increased heart rate, systolic and diastolic blood pressures and forearm blood flow, and lowered the forearm vascular resistance, to the same degree as in our previously studied controls. Neither of the intra-arterially administered drugs had any discernible systemic effects. Beta-blockade increased forearm vascular resistance by 32% and decreased forearm blood flow by 21% compared with unblocked levels during mental stress, whereas forearm vasodilation was maintained throughout the stress test in the control group (P < 0.05). Intra-arterial atropine had no certain effects. Arterial adrenaline levels during mental stress were similar in the receptor-blocked and control groups. In conclusion, the sustained forearm vasodilation during mental stress appears to be partly mediated via beta 2-adrenoceptor stimulation (i.e. by adrenaline), but we obtained no support for a cholinergic vasodilating mechanism.

Adrenergic beta-Antagonists↗
PubMed2000

Forearm rotation alters interosseous ligament strain distribution.

Recent interest in reconstruction of the interosseous ligament (IOL) of the forearm has led to questions concerning optimal placement of the reconstructive graft as well as the ideal rotational position of the forearm during graft tensioning. We therefore studied the strain distribution in the IOL to determine which fibers are strained in different positions of forearm rotation. Five cadaveric human forearms were subjected to compressive axial load (simulating power grip) and the strain values across the entire IOL were measured with the forearm in neutral, supination, and pronation. The strain distribution in the IOL changed with forearm rotation. The highest overall strain was found in neutral. In neutral and pronation, higher strain was observed in the proximal region of the IOL. In supination, however, higher average strain was seen in the distal region of the IOL. These results suggest that a reconstructive graft placed in the proximal region of the IOL and tensioned in neutral rotation would provide balanced constraint in different positions of forearm rotation. A graft placed in the distal region and tensioned in forearm neutral, however, may limit forearm rotation.

Adolescent↗
PubMed1995

A comparison of malreduction after plate and intramedullary nail fixation of forearm fractures.

A study was performed to compare the degree of malreduction after intramedullary nail and plate fixation of the forearm and to determine if the degree of malreduction was clinically significant. Eight matched pairs of forearms, including the wrist and elbow joints, were harvested from cadaver upper extremities. The forearms were put through a full range of motion, and physiological loads were applied to simulate those during normal use. Standardized anteroposterior and lateral radiographs of each forearm were obtained with the specimen intact, and after an osteotomy and internal fixation of one bone, both bones, and with gap at the osteotomy sites. In each forearm pair, plating was randomly performed in one specimen and intramedullary nailing was performed in the matching contralateral specimen. Forearm architecture was assessed by quantification of the magnitude and location of maximum radial bow and radial angulation. In this study, plate fixation was superior to nail stabilization in restoration of the normal radial architecture. Plating did not change any of the radiographic indices (magnitude and location of maximum radial bow and radial angulation) at any stage of testing. None of the radiographic indices was changed by nailing of only one of the forearm bones. The magnitude of maximum radial bow and the radial angulation were changed by nailing both forearm bones after osteotomy and both forearm bones with a gap (p < 0.05). Despite this, both techniques were well within the limits of what is radiographically acceptable for reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Nails↗