Regenerative fidelity in the paired claw closer muscles of lobsters

1989 ◽  
Vol 67 (6) ◽  
pp. 1573-1577 ◽  
Author(s):  
Karla S. Kent ◽  
Joanne Pearce ◽  
Christine Gee ◽  
C. K. Govind
Keyword(s):  
Homarus Americanus ◽  
External Morphology ◽  
Limb Loss ◽  
Fiber Composition ◽  
Slow Band ◽  
A Minor

The paired claws in the lobster Homarus americanus are bilaterally asymmetric, consisting of a major (crusher) and a minor (cutter) claw. The fiber composition of the claw closer muscles is correspondingly asymmetric: the cutter muscle has predominantly fast fibers with a small ventral slow band, whereas the crusher muscle has 100% slow fibers. Loss of the paired claws results in regeneration of new ones, which resemble their predecessors in external morphology and in the fiber composition of the closer muscle. Such regenerative fidelity prevails even when the paired claws and closer muscles are symmetric and of the cutter type, and even when they have undergone two successive cycles of limb loss and regeneration. Therefore the type of closer muscle and the configuration of the paired claws is not altered by loss and regeneration.

Regional Differentiation of Neuromuscular Synapses in a Lobster Receptor Muscle

1979 ◽  
Vol 79 (1) ◽  
pp. 99-114
Author(s):  
DENNIS E. MEISS ◽  
C. K. GOVIND
Keyword(s):  
Large Amplitude ◽  
Small Amplitude ◽  
Homarus Americanus ◽  
Membrane Properties ◽  
Muscle Membrane ◽  
Regional Differentiation ◽  
Muscle Fibres ◽  
Flexor Muscle ◽  
Neuromuscular Synapses ◽  
A Minor

Properties of the synapses and muscle fibres of the distal accessory flexor muscle (DAFM) were examined in the first and second walking legs of the lobster, Homarus americanus. Stimulation of the single excitor axon produces large amplitude, poorly facilitating excitatory postsynaptic potentials (EPSPs) in the distally located fibres and small amplitude, highly facilitating EPSPs in the proximally located fibres. The input resistances (Rin) of the muscle fibres were correlated with EPSP properties such that small amplitude, highly facilitating EPSPs occurred in fibres with low Rin and large amplitude, poorly facilitating EPSPs occurred in fibres with higher Rin. All muscle fibres were similar for other membrane electrical properties. Regression analyses however show a minor contribution of Rin to the size of intracellularly recorded synaptic potentials and to their facilitation properties. Thus, differences in muscle membrane properties cannot explain the observed diversity in EPSPs. Instead EPSP diversity is based on differences in transmitter output at single synaptic foci: highly facilitating synapses with low quantal release occur only on proximally located muscle fibres and poorly facilitating synapses with high release occur only on distally located ones. Thus, the EPSP diversity from the single excitor axon to the lobster DAFM is largely presynaptic in origin.

Spontaneous generation of bilateral symmetry in the paired claws and closer muscles of adult snapping shrimps

Development ◽  
1987 ◽  
Vol 100 (1) ◽  
pp. 57-63
Author(s):  
J. Pearce ◽  
C.K. Govind
Keyword(s):  
Bilateral Symmetry ◽  
External Morphology ◽  
Spontaneous Generation ◽  
Unusual Condition ◽  
Fibre Composition ◽  
Snapping Shrimps ◽  
A Minor

Adult snapping shrimps Alpheus heterochelis (Say) have paired asymmetric claws consisting of a major or snapper claw and a minor or pincer claw. An unusual condition of bilateral symmetry consisting of paired snapper claws arose spontaneously in several snapping shrimps by transformation of the pincer to a snapper in the presence of an existing contralateral snapper claw. Transformation in the external morphology and fibre composition of the closer muscle was completed within two intermoult periods in the majority of cases where true symmetry was achieved and once established became permanent. Thus snapping shrimps, which are by nature solitary, when continually exposed to each other in the laboratory may transform their pincer to a snapper without any trauma to the existing snapper claw.

Rating Post-Operative Backs (Part I)

1997 ◽  
Vol 2 (4) ◽  
pp. 1-3
Author(s):  
James B. Talmage
Keyword(s):  
Spinal Stenosis ◽  
Foot Drop ◽  
Neurogenic Claudication ◽  
Root Damage ◽  
Fourth Edition ◽  
Minor Strain ◽  
Injury Model ◽  
Strain Type ◽  
A Minor ◽  
Anterior Tibialis

Abstract The AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition, uses the Injury Model to rate impairment in people who have experienced back injuries. Injured individuals who have not required surgery can be rated using differentiators. Challenges arise when assessing patients whose injuries have been treated surgically before the patient is rated for impairment. This article discusses five of the most common situations: 1) What is the impairment rating for an individual who has had an injury resulting in sciatica and who has been treated surgically, either with chemonucleolysis or with discectomy? 2) What is the impairment rating for an individual who has a back strain and is operated on without reasonable indications? 3) What is the impairment rating of an individual with sciatica and a foot drop (major anterior tibialis weakness) from L5 root damage? 4) What is the rating for an individual who is injured, has true radiculopathy, undergoes a discectomy, and is rated as Category III but later has another injury and, ultimately, a second disc operation? 5) What is the impairment rating for an older individual who was asymptomatic until a minor strain-type injury but subsequently has neurogenic claudication with severe surgical spinal stenosis on MRI/myelography? [Continued in the September/October 1997 The Guides Newsletter]

Pelvic Impairments

2018 ◽  
Vol 23 (4) ◽  
pp. 9-10
Author(s):  
James Talmage ◽  
Jay Blaisdell
Keyword(s):  
Pelvic Ring ◽  
Reproductive Organs ◽  
High Impact ◽  
Pelvic Fractures ◽  
Motor Dysfunction ◽  
Impact Event ◽  
Concomitant Injuries ◽  
Rating Process ◽  
Pass Through ◽  
A Minor

Abstract Pelvic fractures are relatively uncommon, and in workers’ compensation most pelvic fractures are the result of an acute, high-impact event such as a fall from a roof or an automobile collision. A person with osteoporosis may sustain a pelvic fracture from a lower-impact injury such as a minor fall. Further, major parts of the bladder, bowel, reproductive organs, nerves, and blood vessels pass through the pelvic ring, and traumatic pelvic fractures that result from a high-impact event often coincide with damaged organs, significant bleeding, and sensory and motor dysfunction. Following are the steps in the rating process: 1) assign the diagnosis and impairment class for the pelvis; 2) assign the functional history, physical examination, and clinical studies grade modifiers; and 3) apply the net adjustment formula. Because pelvic fractures are so uncommon, raters may be less familiar with the rating process for these types of injuries. The diagnosis-based methodology for rating pelvic fractures is consistent with the process used to rate other musculoskeletal impairments. Evaluators must base the rating on reliable data when the patient is at maximum medical impairment and must assess possible impairment from concomitant injuries.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

Psychoanalysis—A Minor Classic

1956 ◽  
Vol 1 (12) ◽  
pp. 366-367
Author(s):  
EPHRAIM ROSEN
Keyword(s):  
A Minor
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