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At least 19 recordsLinked to original sources
PubMed2002

Arm blood flow and metabolism during arm and combined arm and leg exercise in humans.

The cardiovascular response to exercise with several groups of skeletal muscle suggests that work with the arms may decrease leg blood flow. This study evaluated whether intense exercise with the legs would have a similar effect on arm blood flow (Y(arm)) and O(2) consumption (V(O(2))(,arm)). Ten healthy male subjects (age 21 +/- 1 year; mean +/- S.D.) performed arm cranking at 80 % of maximum arm work capacity (A trial) and combined arm cranking with cycling at 60 % of maximum leg work capacity (A + L trial). The combined trial was a maximum effort for 5-6 min. Y(arm) measurement by thermodilution in the axilliary vein and arterial and venous blood samples permitted calculation of V(O(2))(,arm). During the combined trial, Y(arm) was reduced by 0.58 +/- 0.25 l min(-1) (19.1 +/- 3.0 %, P < 0.05) from the value during arm cranking (3.00 +/- 0.46 l min(-1)). The arterio-venous O(2) difference increased from 122 +/- 15 ml l(-1) during the arm trial to 150 +/- 21 ml l(-1) (P < 0.05) during the combined trial. Thus, V(O(2))(,arm) (0.45 +/- 0.06 l min(-1)) was reduced by 9.6 +/- 6.3 % (P < 0.05) and arm vascular conductance from 27 +/- 4 to 23 +/- 3 ml min(-1) (mmHg)(-1) (P < 0.05) as noradrenaline spillover from the arm increased from 7.5 +/- 3.5 to 13.8 +/- 4.2 nmol min(-1) (P < 0.05). The data suggest that during maximal whole body exercise in humans, arm vasoconstriction is established to an extent that affects oxygen delivery to and utilisation by working skeletal muscles.

Adult↗
PubMed2003

Arm blood flow and oxygenation on the transition from arm to combined arm and leg exercise in humans.

The cardiovascular response to exercise with several groups of skeletal muscle implies that work with the legs may reduce arm blood flow. This study followed arm blood flow (Yarm) and oxygenation on the transition from arm cranking (A) to combined arm and leg exercise (A+L). Seven healthy male subjects performed A at approximately 80 % of maximum work rate (Wmax) and A at ~80 % Wmax combined with L at approximately 60 % Wmax. A transition trial to volitional exhaustion was performed where L was added after 2 min of A. The Yarm was determined by constant infusion thermodilution in the axillary vein and changes in biceps muscle oxygenation were measured with near-infrared spectroscopy. During A+L Yarm was lowered by 0.38 +/- 0.06 l min-1 (10.4 +/- 3.3 %, P < 0.05) from 2.96 +/- 1.54 l min-1 during A. Total (HbT) and oxygenated haemoglobin (HbO2) concentrations were also lower. During the transition from A to A+L Yarm decreased by 0.22 +/- 0.03 l min-1 (7.9 +/- 1.8 %, P < 0.05) within 9.6 +/- 0.2 s, while HbT and HbO2 decreased similarly within 30 +/- 2 s. At the same time mean arterial pressure and arm vascular conductance also decreased. The data demonstrate reduction in blood flow to active skeletal muscle during maximal whole body exercise to a degree that arm oxygen uptake and muscle tissue oxygenation are compromised.

Adult↗
PubMedDate not supplied

[Interchangeability among the percentages of body fat estimated by mid-arm adipose area, triceps skinfold thickness and arm-to-arm segmental bioimpedance analysis].

BACKGROUND: Assessing nutritional status based on the upper limbs is useful at the clinical level. The aim of this study is to evaluate the agreement degree of the body fat percentages (%BF) estimated by the mid-arm adipose area (%BFARM), the Siri triceps skin-fold equation (%BFTRICEPS) and the arm-to-arm segmental bioimpedance analysis (%BFBIA), as well as the Siri four-skinfold equation (%BFSIRI), assessing their interchangeability. METHODS: A cross-sectional study. Body fat assessments were made on a total of 145 subjects (83 males, 62 females) anthropometrically and by bioelectrical impedance analysis (Omron BF 300). The agreement between methods were analyzed using the interclass correlation coefficient (ICC) and the Bland-Altman method. RESULTS: The ICC between %BFARM and %BFTRICEPS was 0.8322 (CI .95% 0.7672-0.8791); between %BFARM-%BFBIA 0.7337 (0.6305-0.8080) and between %BFTRICEPS-%BFBIA 0.9290 (0.9015; 0.9488). For the Bland-Altman method, the agreement interval between %BFARM-%BFTRICEPS (-11.2; 16.96) and between %BFARM-%BFBIA (-13.04; 21.76) exceeded the cutoff point (+/- 10%), but not between %BFTRICEPS-%BFBIA (-6.64; 9.6), %BFSIRI-%BFTRICEPS (-5.27; 4.52) and %BFSIRI-%BFBIA (-6.31; 8.52). The BMI has no bearing on the results. CONCLUSIONS: The method utilized influences the nutritional assessment made based on the upper limbs. The mid-arm adipose area method overestimated the %BF with relationship to the Siri triceps skinfold or four-skinfold equation and to the bioelectrical impedance analysis, and although this result suggests that mid-arm adipose area may not be a good indicator of global adiposity, this must be confirmed against a gold standard.

Adipose Tissue↗
PubMed1990

The relative accuracy of simultaneous same arm, simultaneous opposite arm and sequential same arm measurements in the validation of automated blood pressure measuring devices.

With the increasing demand for accurate BP measuring devices there comes also the need for validation. Most validation procedures assess the accuracy of a test device against a known standard, most commonly a mercury sphygmomanometer. The best method for assessing device accuracy is to measure BP simultaneously in the same arm with the test device and a mercury sphygmomanometer. This is not always possible because the deflation mechanism of the test device interferes with the ability of an observer to auscultate the Korotkov sounds accurately. In this study a mathematical method of sequential comparison between the test device and a mercury standard in the same arm is described which is almost as accurate as simultaneous measurement in the same arm.

Adult↗
PubMed1996

Self-moved target eye tracking in control and deafferented subjects: roles of arm motor command and proprioception in arm-eye coordination.

1. When a visual target is moved by the subject's hand (self-moved target tracking), smooth pursuit (SP) characteristics differ from eye-alone tracking: SP latency is shorter and maximal eye velocity is higher in self-moved target tracking than in eye-alone tracking. The aim of this study was to determine which signals (motor command and/or proprioception) generated during arm motion are responsible for the decreased time interval between arm and eye motion onsets in self-moved target tracking. 2. Six control subjects tracked a visual target whose motion was generated by active or passive movements of the observer's arm in order to determine the role played by arm proprioception in the arm-eye coordination. In a second experiment, the participation of two subjects suffering complete loss of proprioception allowed us to assess the contribution of arm motor command signals. 3. In control subjects, passive movement of the arm led to eye latencies significantly longer (130 ms) than when the arm was actively self-moved (-5 ms:negative values meaning that the eyes actually started to move before the target) but slightly shorter than in eye-alone tracking (150 ms). These observations indicate that active movement of the arm is necessary to trigger short-latency SP of self-moved targets. 4. Despite the lack of proprioceptive information about arm motion, the two deafferented subjects produced early SP (-8 ms on average) when they actively moved their arms. In this respect they did not differ from control subjects. Active control of the arm is thus sufficient to trigger short-latency SP. However, in contrast with control subjects, in deafferented subjects SP gain declined with increasing target motion frequency more rapidly in self-moved target tracking than in eye-alone tracking. 5. The deafferented subjects also tracked a self-moved target while the relationship between arm and target motions was altered either by introducing a delay between arm motion and target motion or by reversing target motion relative to arm motion. As with control subjects, delayed target motion did not affect SP latency. Furthermore, the deafferented subjects adapted to the reversed arm-target relationship faster than control subjects. 6. The results suggest that arm motor command is necessary for the eye-to-arm motion onset synchronization, because eye tracking of the passively moved arm was performed by control subjects with a latency comparable with that of eye-alone tracking of an external target. On the other hand, as evidenced by the data from the deafferented subjects, afferent information does not appear to be necessary for reducing the time between arm motion and SP onsets. However, afferent information appears to contribute to the parametric adjustment between arm motor command and visual information about arm motion.

Adult↗
PubMed1994

The relation between upper arm dimensions and maximal oxygen uptake during arm exercise.

The relationship between upper arm dimensions and maximal oxygen uptake (VO2peak) during arm exercise was investigated. Nineteen almost untrained male subjects (22 +/- 2 yrs, 183 +/- 5.5 cm, 74 +/- 7.5 kg; mean +/- SD) volunteered to take part in the study. The following anthropometrical upper arm data were obtained for each subject: upper arm circumference, biceps and triceps skinfold thickness, upper arm length. From these data the cross-sectional area of the muscles, of the muscles plus bone of the upper arm, and the upper arm muscle volume were calculated. Upper arm volume was determined by water immersion. The subjects performed arm cranking with an increasing load of 10 watt each minute (Wpeak 125 +/- 17.4 watt, VO2peak: 2.54 +/- 0.33 l/min; mean +/- SD). Multiple regression analyses showed that VO2peak could be best explained by the cross-sectional area of the muscles plus bone of the upper arm (r = 0.65, p < 0.005). Other factors did not add significantly. The variables as body mass, fatfree body mass, upper arm volume and total arm volume correlated less well with VO2peak (r < 0.5). In conclusion it is suggested to use the easily obtainable cross-sectional area of the muscles plus bone of the upper arm to standardize VO2peak of arm cranking.

Adult↗
PubMed1991

Assembly and characterization of five-arm and six-arm DNA branched junctions.

DNA branched junctions have been constructed that contain either five arms or six arms surrounding a branch point. These junctions are not as stable as junctions containing three or four arms; unlike the smaller junctions, they cannot be shown to migrate as a single band on native gels when each of their arms contains eight nucleotide pairs. However, they can be stabilized if their arms contain 16 nucleotide pairs. Ferguson analysis of these junctions in combination with three-arm and four-arm junctions indicates a linear increase in friction constant as the number of arms increases, with the four-arm junction migrating anomalously. The five-arm junction does not appear to have any unusual stacking structure, and all strands show similar responses to hydroxyl radical autofootprinting analysis. By contrast, one strand of the six-arm junction shows virtually no protection from hydroxyl radicals, suggesting that it is the helical strand of a preferred stacking domain. Both junctions are susceptible to digestion by T4 endonuclease VII, which resolves Holliday junctions. However, the putative helical strand of the six-arm junction shows markedly reduced cleavage, supporting the notion that its structure is largely found in a helical conformation. Branched DNA molecules can be assembled into structures whose helix axes form multiply connected objects and networks. The ability to construct five-arm and six-arm junctions vastly increases the number of structures and networks that can be built from branched DNA components. Icosahedral deltahedra and 11 networks with 432 symmetry, constructed from Platonic and Archimedean solids, are among the structures whose construction is feasible, now that these junctions can be made.

Base Sequence↗
PubMed1995

Isolated effects of peripheral arm and central body cooling on arm performance.

BACKGROUND: Whole body cooling impairs manual arm performance. The independent contributions of local (peripheral) and/or whole body (central) cooling are not known. Therefore, a protocol was developed in which the arm and the rest of the body could be independently cooled. METHODS: Biceps temperature (Tmus), at a depth of 20 mm, and esophageal temperature (Tes) were measured. Six subjects were immersed to the clavicles in a tank (body tank) of water under 3 conditions: 1) cold body-cold arm (CB-CA); 2) warm body-cold arm (WB-CA); and 3) cold body-warm arm (CB-WA). In the latter two conditions, subjects placed their dominant arm in a separate (arm) tank. Water temperature (Tw) in each tank was independently controlled. In conditions requiring cold body and/or cold arm, Tw in the appropriate tanks was 8 degrees C. In conditions requiring warm body and/or warm arm, Tw in the appropriate tanks was adjusted between 29 and 38 degrees C to maintain body/arm temperature at baseline values. A battery of 6 tests, requiring fine or gross motor movements, were performed immediately before immersion and after 15, 45, and 70 minutes of immersion. RESULTS: In CB-CA, Tes decreased from an average of 37.2 to 35.6 degrees C and Tmus decreased from 34.6 to 22.0 degrees C. In WB-CA, Tmus decreased to 18.1 degrees C (Tes = 37.1 degrees C), and in CB-WA, Tes decreased to 35.8 degrees C (Tmus = 34.5 degrees C). By the end of immersion, there were significant decrements (43-85%) in the performance of all tests in CB-CA and WB-CA (p < 0.0002); scores for each test were similar in these two conditions. There was no significant change in scores throughout the CB-WA condition. In both conditions with arm cooling (i.e., WB-CA and CB-CA), Tmus accounted for 85-98% of the variance in all tests. When the core was cooled in the CB-WA condition, Tes was significantly correlated to scores in only two tests (accounted for 90 and 93% of the variance) although the actual effect was small. In the CB-CA condition, partial correlations indicated that Tes accounted for 4-10% of the variance in scores of 4 tests. CONCLUSIONS: We conclude that cooling of the body and/or the arm elicits large decrements in finger, hand and arm performance. The decrements are due almost entirely to the local effects of arm tissue cooling.

Adult↗
PubMed1999

Computer simulation of flagellar movement: VII. Conventional but functionally different cross-bridge models for inner and outer arm dyneins can explain the effects of outer arm dynein removal.

Outer arm dynein removal from flagella by genetic or chemical methods causes decreased frequency and power, but little change in bending pattern. These results suggest that outer arm dynein operates within bends to increase the speed of bend propagation, but does not produce forces that alter the bending pattern established by inner arm dyneins. A flagellar model incorporating different cross-bridge models for inner and outer arm dyneins has been examined. The inner arm dynein model has a hyperbolic force-velocity curve, with a maximum average force at 0 sliding velocity of about 14 pN for each 96 nm group of inner arm dyneins. The outer arm dynein model has a very different force-velocity curve, with a maximum force at about 10-15% of V(max). The outer arm dynein model is adjusted so that the unloaded sliding velocity for a realistic mixture of inner and outer arm dyneins is twice the unloaded sliding velocity for the inner arm dynein model alone. With these cross-bridge models, a flagellar model can be obtained that reduces its sliding velocity and frequency by approximately 50% when outer arm dyneins are removed, with little change in bending pattern. The addition of outer arm dyneins, therefore, gives an approximately 4-fold increase in power output against viscous resistances, and outer arm dyneins may generate 90% or more of the power output. Cell Motil.

Animals↗
PubMed1997

Arm-movement-related neurons in the primate superior colliculus and underlying reticular formation: comparison of neuronal activity with EMGs of muscles of the shoulder, arm and trunk during reaching.

Neuronal activity was recorded from the superior colliculus (SC) and the underlying reticular formation in two monkeys during an arm reaching task. Of 744 neurons recorded, 389 (52%) clearly modulated their activity with arm movements. The temporal activity patterns of arm-movement-related neurons often had a time course similar to rectified electromyograms (EMGs) of particular muscles recorded from the shoulder, arm or trunk. These reach cells, as well as the muscles investigated, commonly exhibited mono- or biphasic (less frequently tri- or polyphasic) excitatory bursts of activity, which were related to the (pre-)movement period, the contact phase and/or the return movement. The vast majority of reach cells exhibited a consistent activity pattern from trial to trial as did most of the muscles of the shoulder, arm and trunk. Similarities between the activity patterns of the neurons and the muscles were sometimes very strong and were especially notable with the muscles of the shoulder girdle (e.g. trapezius descendens, supraspinatus, infraspinatus or the anterior and medial deltoids). This high degree of co-activation suggests a functional linkage, though not direct, between the collicular reach cells and these muscles. Neuronal activity onset was compared with that of 25 muscles of the arms, shoulders and trunk. The majority of cells (78.5%) started before movement onset with a mean lead time of 149+/-90 ms, and 36.5% were active even before the earliest EMG onset. The neurons exhibited the same high degree of correlation (r=0.97, Spearman rank) between activity onset and the beginning of the arm movement as did the muscles (r=0.98) involved in the task. The mean neuronal reach activity (background subtracted) ranged between 7 and 193 impulses/s (mean 40.5+/-24.2). The mean modulation index calculated [(reach activity background activity)/reach activity+background activity)] was 0.75+/-0.23 for neurons (n=358) and 0.87+/-0.14 for muscles (n=25). As the monkeys fixated the reach target constantly during an arm movement, neuronal activity which was modulated in this period was not related to eye movements. The three neck muscles investigated in the reach task exhibited no reach-related activity modulation comparable to that of either the reach cells or the muscles of the shoulder, arm and trunk. However, tonic neck muscle EMG was monotonically related to horizontal eye position. The clear skeletomotor discharge characteristics of arm-movement-related SC neurons revealed in this study agree with those already known from other sensorimotor regions (for example the primary motor, the premotor and parietal cortex, the basal ganglia or the cerebellum) and are consistent with the possible role of this population of reach cells in the control of arm movements.

Animals↗
PubMed1986

Linear growth measurement: a comparison of single arm-lengths and arm-span.

An investigation was done to determine whether the arm-lengths of 44 children with myelomeningocele differed from those of 96 control children; whether the level of the meningocele lesion has any effect on arm-length; and to compare the relationship between arm-length and both stature and age. Mean total arm-lengths did not differ significantly between the two groups of children. However, the mean arm-spans of children with high myelomeningocele lesions differed significantly from those of control children. Within the myelomeningocele group, the height of the lesion had no significant effect on any of the arm-length variables. Very high positive correlations were found between upper-arm and total arm-lengths and stature, and between arm-span and stature in the control children. These results suggest that arm-length may be used as an alternative measure of linear growth in children, and that a single arm-length will be the most accurate indicator of growth of children with myelomeningocele.

Arm↗
PubMed1991

Arm blood flow at rest and during arm exercise.

To test the applicability of a dye-dilution method to quantitate total arm blood flow at rest and during arm exercise, indocyanine green was infused at a constant rate into the brachial artery. Eight subjects performed continuous 30-min arm exercises with an increase in intensity every 10 min (30, 60, and 90 W). The loads corresponded to 29 +/- 1, 48 +/- 2, and 78 +/- 4% (means +/- SE) of the maximal O2 uptake (VO2max 2.13 +/- 0.08 l/min) during arm exercise. VO2max during arm exercise was 61 +/- 1.7% of that during leg exercise. The dye concentration was analyzed in blood samples from three arm veins, two ipsi- and one contralateral, at shoulder level. Corresponding dye concentrations in both ipsilateral veins and a stable concentration difference between ipsi- and contralateral veins were achieved. Total arm blood flow was calculated to be 0.21 +/- 0.04 l/min at rest and 2.43 +/- 0.14 l/min at 90 W. Arm O2 uptake rose from 9 +/- 2 to 323 +/- 21 ml/min. Arm blood flow and O2 uptake each correlated linearly with both work load (r = 0.98) and pulmonary O2 uptake (r greater than or equal to 0.98). Mechanical efficiency for the arm and body was 34-44 and 16-19%, respectively. We conclude that arm blood flow can be determined by continuous infusion of indocyanine green.

Adult↗
PubMed1996

Should we embrace new drugs with open arms? Experience from a community-based, open-arm, randomized clinical trial of combination antiretroviral therapy in advanced HIV disease.

The effect of an open arm in the enrollment to a randomized clinical trial comparing zidovudine (ZDV) plus didanosine (ddI) versus ZDV plus zalcitabine (ddC) was assessed. HIV-infected individuals were eligible to participate in this protocol if they were ddI and ddC naive, had CD4 counts of 50-350/mm3, and were residents of the province of British Columbia. Participating individuals could choose between open-label ZDV/ddI, ZDV/ddC, or randomization to open-label ZDV/ddI or ZDV/ ddC. Study drugs were made available free of charge for all participants through a centralized drug distribution system. There is no other source of these drugs in the province. Primary care physicians were required to renew the patient's prescription every 2 months. Enrollment was initiated in November 1992 and was closed in March 1994 when the randomized arm of the protocol met the predetermined target sample size of 120 evaluable participants. A total of 582 patients received combination therapy in the province through this protocol: 138 (28%) enrolled in the randomized arm and 444 (76%) in the open arm. In the latter group, 320 (72%) were initially prescribed ZDV/ddI and 124 (28%) were prescribed ZDV/ddC. The enrollment rate was strikingly higher in the open arm, with 168 patients enrolled in the first 2 months compared with 138 patients enrolled in the randomized arm over 17 months. Of the 78 study physicians, 69 enrolled patients in the open arm and 23 enrolled patients in the randomized arm of the study. Experienced physicians were more likely to refer patients for randomization (p = 0.025). No statistically significant differences were observed between patients enrolled in either study arm. Our results illustrate the challenge posed to recruitment into clinical trials by the coexistence of an open arm. This is despite the noncoercive, open-label and community-based nature of our randomized protocol and the high priority given to it by a variety of local and national organizations. It is clear that an increased commitment by all interested parties will be required if randomized clinical trials are to be carried out with coexistent open arms.

Adult↗
PubMed1997

Effects of arm support on shoulder and arm muscle activity during sedentary work.

The aim of this study was to evaluate different arm supports by comparing the activity of shoulder and arm muscles during various work tasks, with and without the lower arm supported. Twelve female subjects, aged between 23 and 37 years, were asked to perform three types of tasks: typing, simulated assembly work (in two different positions), and pipetting. The supports used were: fixed arm support (FIX), horizontal movable arm support (HOR), and spring-loaded arm support (SLA). During the experiments, the electromyograms (EMG) of four muscles were simultaneously recorded: m. deltoideus anterior and lateralis, m. trapezius pars descendens and m. extensor carpi radialis brevis. Normalization was made against maximum isometric contraction. The mean values of the normalized EMG levels showed a reduced EMG level of the shoulder muscles when using arm supports in all the tasks, and for all muscles but the wrist extensor, compared to the EMG levels without arm supports. The horizontal movable support was more effective in reducing the EMG levels of the shoulder muscles than other arm supports, in tasks at table height. Thus, it is possible to reduce muscle activity of the shoulder region by using arm supports. Further research is needed to make biomechanical calculations to compare the EMG level of these muscles using suspension and the effects of inclination of work task.

Adult↗
PubMed1993

Pulmonary rehabilitation that includes arm exercise reduces metabolic and ventilatory requirements for simple arm elevation.

Simple arm elevation results in increased metabolic and ventilatory requirements in patients with chronic airflow obstruction (CAO). These demands contribute to the dyspnea that is frequently reported when these patients perform activities of daily living involving the arms. We hypothesized that a comprehensive pulmonary rehabilitation (PR) program that includes upper extremity training would lower the ventilatory requirement for arm elevation. Metabolic and ventilatory responses to 2 min of simple arm elevation were studied in 14 patients with CAO before and after PR. Respiratory muscle strength was determined in 11 patients by measurement of maximal transdiaphragmatic pressure (Pdimax). Oxygen uptake (VO2), carbon dioxide production (VCO2), heart rate (HR), minute ventilation (VE), tidal volume (VT), and respiratory rate were measured at rest with the arms down and during 2 min of arm elevation. Before PR, arm elevation led to significant increases in VO2, VCO2, HR, and VE. After PR, pulmonary function, Pdimax, and resting metabolic and ventilatory parameters with the arms down were unchanged; however, during arm elevation, VO2, VCO2, and VE were significantly less than they were before PR. We conclude that a comprehensive PR program that includes upper extremity exercises leads to a reduction in the ventilatory requirement for simple arm elevation. This type of program may allow patients with CAO to perform sustained upper extremity activities with less dyspnea.

Aged↗
PubMed2002

Do psychological variables modify motor recovery among patients with mild arm paresis after stroke or traumatic brain injury who receive the Arm Ability Training?

PURPOSE: The Arm Ability Training improves motor function among stroke and traumatic brain injury patients with mild arm paresis. There is, however, a considerable variability in motor recovery among patients receiving the Arm Ability Training. The study investigated whether psychological variables can explain the variability in motor recovery. METHODS: In a sample of 33 patients receiving the Arm Ability Training both motor performance (by use of the standardised arm function test TEMPA) and cognitive functions (attention, perceptual abilities, and learning) as well as depression were assessed before training was commenced. Both univariate correlational analyses and stepwise multiple regression were used to investigate these variables' ability to predict motor improvement (TEMPA difference scores from pre to post test after 3 weeks). RESULTS: The degree of motor dysfunction of the affected arm explained most (70%) of the variance of motor improvement scores of the standardised arm function test (TEMPA). Psychometric scores showed no or at the most weak associations with motor improvement (explaining at the most 10% of the variance). CONCLUSIONS: Psychological variables had not been critical modifiers of motor recovery among stroke and traumatic brain injury patients with mild arm paresis receiving the Arm Ability Training.

Adolescent↗
PubMed1991

Inactive renin release from the human arm vascular wall during upper arm occlusion: relation to beta-adrenoceptors.

To investigate the extrarenal release of renin, plasma active renin (PAR) and plasma trypsin activatable or inactive renin (PIR) in blood taken simultaneously from bilateral median cubital veins were measured in seven normal men before and after occlusion of the right upper arm with a standard cuff inflated halfway between systolic and diastolic blood pressures for 15 min. After 15 min, both PAR (P less than 0.05) with PIR (P less than 0.01) increased significantly in occluded arms compared with 0 min. PIR rose significantly (P less than 0.01) in occluded arms compared with controls at 15 min, but PAR was unchanged. The same studies were repeated after pretreatment with oral doses of either 1 mg prazosin or 10 mg propranolol at 1600 h and 2400 h on the previous day and 1 hour before the experiment. After prazosin, both PAR (P less than 0.05) and PIR (P less than 0.01) in occluded arms increased significantly at 15 min compared with those at 0 min and PIR rose significantly (P less than 0.01) in occluded arms compared with controls at 15 min, as observed in the control studies. On the other hand, after propranolol, the significant increment of PAR in the occluded arms was abolished. Moreover, the significant difference of PIR between the occluded and the control arms at 15 min was also abolished. These results indicate that inactive renin may be present in the vascular wall of the arm and released into circulation by a stimulus such as arm occlusion by mechanisms related to beta-adrenoceptors.

Administration, Oral↗
PubMed1998

Cellular and molecular mechanisms of arm regeneration in crinoid echinoderms: the potential of arm explants.

Crinoid echinoderms can provide a valuable experimental model for studying all aspects of regenerative processes from molecular to macroscopic level. Recently we carried out a detailed study into the overall process of arm regeneration in the crinoid Antedon mediterranea and provided an interpretation of its basic mechanisms. However, the problem of the subsequent fate of the amputated arm segment (explant) once isolated from the animal body and of its possible regenerative potential have never been investigated before. The arm explant in fact represents a simplified and controlled regenerating system which may be very useful in regeneration experiments by providing a valuable test of our hypotheses in terms of mechanisms and processes. In the present study we carried out a comprehensive analysis of double-amputated arm explants (i.e. explants reamputated at their distal end immediately after the first proximal amputation) subjected to the same experimental conditions as the regenerating donor animals. Our results showed that the explants undergo similar regenerative processes but with some significant differences to those mechanisms described for normal regenerating arms. For example, whilst the proximal-distal axis of arm growth is maintained, there are differences in terms of the recruitment of cells which contribute to the regenerating tissue. As with normal regenerating arms, the present work focuses on (1) timing and modality of regeneration in the explant; (2) proliferation, migration and contribution of undifferentiated and/or dedifferentiated/transdifferentiated cells; (3) putative role of neural growth factors. These problems were addressed by employing a combination of conventional microscopy and immunocytochemistry. Comparison between arm explants and regenerating arms of normal donor adults indicates an extraordinary potential and regenerative autonomy of crinoid tissues and the cellular plasticity of the phenomenon.

Animals↗