Intact Arm Research Articles

Observations on the population dynamics of amphiura filiformis (ophiuroidea: echinodermata) in the southern north sea and its exploitation by the dab, Limanda limanda

Density and growth of an Amphiura filiformis population living at a station in the Oyster Ground (southern North Sea) were monitored during 2 successive years (1982–1984). During this period, the density of adult animals (disk size > 4 mm) was constant and they numerically dominated the 1 mm sieve fraction of the samples. The size distribution of these adults was nearly constant and year classes were not discernable among these larger individuals. Annual recruitment was observed, but growth and survival rates of juveniles were low. During their first year, the disk size of recruits increased from 0.3 to 1.2 mm, and to 2.2 mm in their second year. Approximately 10% of the recruits of the 1982 year class survived the first 8 months. Of the recruits of the 1983 year class only 3% survived after 9 months. Consequently, the contribution by juveniles to the annual production of body tissue was small during the observation period. Adult somatic growth could not be assessed due to the apparent lack of disk growth. Regenerating arms, however, were very common among the larger individuals. Only 4% of the individuals in a sample had intact arms, whereas 55% of the animals (or 20% of all arms) had one or more ‘recent’ distal regenerations distinguishable by their smaller diameter. These regenerations presumably account for a large part of the annual growth and somatic production. Stomach content analysis of demersal fish in this area suggests that Amphiura arms form an important part of the diet of the dab, Limanda limanda. Annual consumption of Amphiura arms by dab was estimated to be 0.84 g wet weight-m −2, which is equivalent to 420 arms or 6% of the arm population. Considering the large number of adult animals in the population and regeneration capabilities of the species, the grazing by dab will have only little if any effect on the population.

The determination of moments for extension of the wrist generated by muscles of the forearm

In deciding on suitable tendon transfers to replace denervated muscle-tendon units, important considerations are the strength and effectiveness of possible substitutes. A method is presented by which the strength of the wrist extensor muscles and their moment arms can be determined. The method can be applied to other muscles at other joints. It involves the use of a force transducer which measures the combined forces of the three wrist extensors in an isometric contraction. This moment for wrist extension, measured in the living intact arm, is the same as the sum of the moments of the three wrist extensor muscles. The contribution of each muscle to the total moment is calculated from ratios that have been developed from a quantitative study of moment arms and muscle masses in sixteen cadaver limbs. It is suggested that the ratio of one moment arm to another is fairly constant from subject to subject, and that muscle masses also have sufficiently similar ratios to each other to serve as the basis for practical estimations by the surgeon. Thus the surgeon needs only one or two direct measurements of moments externally and only one or two skeletal measurements on any living subject to be able to estimate the effectiveness of a number of muscles on the basis of cadaver studies such as this, and to project the behavior of a muscle after it has been transferred to a position where it will have new moment arms.

Unilateral forelimb deafferentation in the monkey: purposive movement.

Monkeys with unilateral dorsal rhizotomy C2-T3 used their denervated limbs to retrieve unseen food pellets when movements of the intact contralateral limb were rendered ineffective by enclosure of the hand within a container. Even after protracted use in this condition, however, the deafferented limb ceased to be used in the test situation when the intact arm was released. These findings cast doubt on interpretations of lack of use of a unilaterally dorsal rhizotomized limb as being due to cross-spinal inhibition or to learned disuse.

The role of skin and muscle resistance vessels in reflexes mediated by the baroreceptor system.

The role of skin and muscle vascular beds in baroreceptor-mediated alterations of peripheral vascular resistance was evaluated in six normal subjects in whom the skin circulation in one forearm was temporarily suppressed by epinephrine iontophoresis. Baroreceptor activity was enhanced by application of negative pressure to the neck (neck suction) and inhibited by application of lower body negative pressure. Forearm blood flow was measured simultaneously in both arms with strain gauge plethysmographs. Since blood flow in the treated arm consisted entirely of muscle flow, skin flow was calculated from the difference between total forearm flow in the intact arm and muscle flow in the treated arm. Vascular resistances were calculated as the ratio of mean arterial pressure to the blood flow of each vascular bed. During neck suction, mean arterial pressure decreased from an average of 89 to 75 mm of Hg (P < 0.005), heart rate decreased from an average of 60 to 55 beats/min (P < 0.005), and total skin and muscle flows remained essentially unchanged. Cutaneous vascular resistance decreased from an average of 75 to 49 mm of Hg/ml per 100 g per min (P < 0.05), muscle vascular resistance from 68 to 51 (P < 0.005), and total forearm vascular resistance from 36 to 24 (P < 0.025). During lower body negative pressure, heart rate increased from an average of 59 to 69 beats/min (P < 0.005), mean arterial pressure did not change significantly, and significant decreases occurred in forearm blood flow from 5.4 to 2.7 ml/100 g per min, in skin blood flow from 3.1 to 1.4, and in muscle blood flow from 2.3 to 1.3. Cutaneous vascular resistance increased from an average of 47 to 110 mm of Hg/ml per 100 g per min (P < 0.05), muscle vascular resistance from 43 to 72 (P < 0.005), and total forearm vascular resistance from 20 to 38 (P < 0.001). These results demonstrate that both the skin and muscle resistance vessels participate in reflex changes initiated by alterations in baroreceptor activity.

Tomato Telotrisomics: Origin, Identification, and Use in Linkage Mapping

Telotrisomics-sporophytes possessing a telocentric chromosome in addition to the normal complement-were obtained and studied for six different chromosome arms of the tomato. They originated in the progeny of the following kinds of chromosomal deviants: terminal deficiency, tertiary monosomic, and compensating trisomic. Cytological studies at meiotic pachytene established that the centromere of three telocentrics was flanked by a heterochromatic chromomere opposite the intact arm and three appeared to have terminal centromeres. Of the latter group the centromere of two appeared to be of normal size, while one was about half normal size, its chromosome being the only one of the six telocentrics to be mitotically unstable. The longer the telocentric arm, the greater the tendency to form trivalents; when trivalents are not formed, the telocentric is invariably univalent, the preferential pairing between the two normal homologues leading exclusively to 12:12+telocentric anaphasic separations. Consistent with this cytological behavior, only one in several hundred trisomic progeny was of primary type, the rest telosomic.-The effects of the extra telocentric chromosome on gross phenotype of the plant are much greater for the long arms, and telocentrics for long arms closely resemble the corresponding primary trisomics. As a result of gametophytic elimination, the telocentric is never substituted for the corresponding normal chromosome, but can be transmitted as an extra element for all studied telocentrics on the female side and for the short arms also on the male side. The rate of female transmission generally exceeds that of the corresponding primary trisomic.-Inheritance studies of three telotriosmics permitted assignment of marker genes to their proper chromosome arms. Since efficiency of the trisomic ratio method is enhanced if the telotrisomic is phenotypically distinguishable from the diploid, trisomics for the long arms are better suited for genetic mapping purposes than those for short arms. In this fashion r and wf were proven to lie on 3S, rv and sf on 3L, var on 7S, and cpt on 8L, with correspondingly closer approximations of centromere positions. The incompletely dominant gene La was assigned to 7L by virtue of dosage effects in heterozygous triplo-7L. Considering their higher rates of transmission and less depressing effects on vigor and fertility, extra telocentrics render telotrisomics more useful for determining arm locations than either secondary or tertiary trisomics.

CUTANEOUS SENSITIVITY OF UNILATERAL ARM AMPUTEES.

Abstract : Measures of tactual acuity and heat and pain sensitivity were obtained from 20 subjects with unilateral arm amputations. The measures were taken 3 in. above the stump and on a homologous area of the intact arm. Corresponding areas were tested in 20 matched controls. The tactual acuity of the stump was significantly greater than that of the intact limb or of either limb of the controls. For heat and pain sensitivity there was no significant difference between the stump and the intact arm. However, both arms of the amputees were significantly less sensitive to heat and pain than either arm of the controls. The results are related to current theories of cutaneous sensitivity.

Perception of Weight and the Phenomenal Regression to the “Real” Weight (Thing Constancy Phenomenon). Experiments on Arm‐Amputated Subjects

The purpose of this paper was to investigate whether the weight of the subject's own arm influences the perception of an external weight to be lifted, when the receptive mechanism is proprioceptive (as is almost the case e. g. when lifting heavy weights). The receptive mechanism of weight perception was briefly discussed. The experiments were performed on 54 war invalids amputated on the upper limb. The experimental arrangement was as follows: The subject had to compare two weights, the one of which (a standard of 3,000 g) was lifted by the arm (the intact arm, or the stump) in an abduced position, the subject standing erect and the armweight acting against gravity, the other one (variable weight) lifted with the subject in a tilting posture, the arm hanging vertically down and the tissues thus passively supporting the arm weight. The weight to be added to the variable weight in order to make the two weights phenomenally equal, showed great individual differences. In experiments with the intact arm, in 19 cases, the additional weight was at the most 300–400 g greater than a weight that corresponds to the difference threshold determined the standard weight and the variable weight both lifted in the erect posture and the arm-weight acting against gravity. The difference is not statistically significant. In 11 cases it was 500–600 g greater, i. e. on the limit of significance, and finally in 24 cases 700–2,800 g greater, which difference is surely significant. In experiments with forearm stumps the corresponding figures were 16: 4: 8, and in experiments with arm stumps 19: 1: 2. It is obvious, that when experimenting with the whole arm, the arm-weight influences the perception of an external weight in most subjects, in experiments on forearm stumps the influence is much less and in experiments on arm stumps hardly observable, quite in accordance with the fact, that the weight of the forearm stump is of course a little less, that of the arm stump considerably less than the weight of the intact arm. Those cases in which (in experiments with the intact arm) the perception of a lifted weight was not affected by the arm weight (19 cases) proved, that the proprioceptive weight perception shows phenomenal regression to a conceptual thing character analogous to the well-known constancy phenomena in the visual field. In a few cases, however, there was reason to believe, that the receptive mechanism was tactual (pressure exerted upon the skin). In these cases the weight perception is of course independent of the arm weight. Financial aid for this research has been granted by the KORDELIN foundation. I hereby wish to express my gratitude to the Head of the Red Cross Invalid Hospital, Dr. REHNBERG for his permission to carry out the investigation on patients at the Hospital. It is a pleasure to record my indeptedness to the nurses and social case workers for their kind assistance in selecting and sending the patients over to the Physiology Institute. I am also grateful to Miss LIISA LAINE, for her valuable help and thoroughness in carrying out a part of the experiments.