ISSN:0022-3034    

DOI:10.1002/neu.480070402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractNerve terminal regions in walking leg opener muscles of several crayfish of different ages (0 to 245 days after hatching) were examined by means of electron microscopy. This muscle is innervated by two axons (excitatory and inhibitory) and at maturity contains three classes of synapse: excitatory and inhibitory neuromuscular synapses, and inhibitory axo‐axonal synapses. The muscle itself is initially a syncytium, which gradually becomes subdivided into distinct “muscle fibers” as the animal matures. Innervation was not found in the opener muscle just before or just after hatching, but was present in restricted locations on the inner side of the muscle within a few days of hatching. As the muscle enlarged and became subdivided, innervation appeared in various other locations. Synaptic contacts were located in young stages soon after hatching, and in later stages. Morphological differences characteristic of excitatory and inhibitory nerve terminals could be found even at the earliest stages of innervation. Both excitatory and inhibitory synapses, but particularly the former, showed evidence of progressive enlargement to a final size within the first two months, and no evidence for further enlargement of existing synapses thereafter. Synaptic maturation also involved the appearance of presynaptic “dense bodies” thought to be regions at which transmitter substance is preferentially released. Nerve terminals at different levels of maturation were observed in opener muscles of young crayfish. Clear evidence for differential maturation of the three types of synapse present in this muscle was obtained. The inhibitory neuromuscular synapses attained their final average size and developed their dense bodies sooner than the excitatory neuromuscular synapses. The inhibitory axo‐axonal synapses were the last to appear an

ISSN:0022-3034    

DOI:10.1002/neu.480070403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThe accumulation and distribution of proteolipid proteins in rat brain and selected brain regions (cerebellum, cerebral cortex, basal ganglia, and hippocampus) were studied during early postnatal development. In whole brain an eightfold increase of proteolipid was observed between ten and 33 days after birth. This was reflected in the separate regions examined where the proteolipid protein content increased six‐ to ten‐fold during the same period. The basal ganglia and cerebral cortex contributed the greatest amount to the total proteolipid present. However, at 28–33 days the greatest concentration (mg/g tissue) was observed in the basal ganglia and hippocampus.When the proteolipid protein preparations were examined by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, distinctive, heterogeneous patterns for each brain region were obtained. Proteolipid from basal ganglia (the region richest in white matter) consisted primarily of two major protein bands with apparent molecular weights of approximately 21,500 and 26,000. Both of these bands dramatically increased in quantity during myelination, and the larger protein coelectrophoresed with isolated myelin proteolipid protein. Both bands were also found present in proteolipid preparations from the other brain regions but in varying amounts relative to the total. The data suggest that the increase in proteolipid observed during this developmental period was due in large measure to the accumulation of myelin‐specific proteolipids, but also that a significant proportion of the increase was due to the accumulation of nonmyelin com

ISSN:0022-3034    

DOI:10.1002/neu.480070404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractFast‐2, a membrane mutant ofParamecium aurelia, is due to a single‐gene mutation and has behavioral abnormalities. Intracellular recordings through changes of external solutions were made. The mutant membrane hyperpolarized when it encountered solutions with low K+concentration. This hyperpolarization and other associated activities were best observed in Ca‐ or Na‐solutions devoid of K+. Membrane potential was plotted against the concentration of K+(0.5 to 16 mM) in solutions of fixed Na+or Ca++concentration. The slopes of the curves for the mutant membrane were steeper than those for the wild type at the lower concentrations of K+. Inclusion of 2 mMtetraethylammonium chloride (TEA‐Cl) counteracted the mutational effects. Spontaneous action potentials in Ba‐solution and the electrically evoked action potentials in various solutions are normal in this mutant. We conclude that the resting permeability to K+relative to the permeabilities to Na+and Ca++has been increased by t

ISSN:0022-3034    

DOI:10.1002/neu.480070405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractStop‐flow techniques were used to determine how temperature affected the axonal transport of dopamine‐β‐hydroxylase (DBH) activity in rabbit sciatic nervesin vitro.These nerves were cooled locally to 2°C for 1.5 hr, which caused a sharp peak of DBH activity to accumulate above the cooled region. Accumulated DBH was then allowed to resume migration at various temperatures. From direct measurements of the rate of migration, we found that the axonal transport velocity of DBH was a simple exponential function of temperature between 13°C and 42°C. Over this range of temperatures, the results were well described by the equation:V= 0.546(1.09)T, whereVis velocity in mm/hr, andTis temperature in degrees centigrade. TheQ10between 13°C and 42°C was 2.33, and an Arrhenius plot of the natural logarithm of velocity versus the reciprocal of absolute temperature yielded an apparent activation energy of 14.8 kcal. Transport virtually halted when temperature was raised to 47°C, although only about half of the DBH activity disappeared during incubation at this temperature. Another transition occurred at 13°C; below this temperature, velocity fell precipitously. This was not an artifact peculiar to the stop‐flow system since the rate of accumulation of DBH activity proximal to a cold‐block also decreased abruptly when the temperature above the block was r

ISSN:0022-3034    

DOI:10.1002/neu.480070406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractThis report describes the fast axonal transport of [3H]‐leucine‐labeled proteins in regenerating rat sciatic motor nerves. A normal rate of fast transport (383 ± 33 mm/day) was present in the regenerating sprouts, as well as in the central stumps. The rapidly transported proteins passed the level of axotomy without impediment, and accumulated in the endings of the regenerating sprouts, as shown by electron microscope autoradiography. In addition, transported proteins accumulated in terminal neuromas. The relative amount of protein‐incorporated radioactivity in the crest of fast transport in the regenerating nerves was increased compared to control nerves. These results are interpreted to suggest that the mechanism of fast transport is the same in regenerating sprouts as in normal axons; during regeneration fast transport appears to add newly synthesized materials to the growi

ISSN:0022-3034    

DOI:10.1002/neu.480070407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

摘要:

AbstractPostsynaptic potentials (PSPs) recorded from leech Retzius cells in response to stimulation of interganglionic connective could not be reversed by soma depolarization or abolished by 40 mMMg ion, nor could input resistance changes be detected during them. Alteration of external Cl and K over a tenfold range provided no clear evidence that the PSPs involved a conductance change to either ion. The method of extrapolation yielded an apparent PSP equilibrium potential of about −20 mV. The steep portion of the relationship between Retzius cell action potential amplitude and membrane potential extrapolated to an apparent reversal potential of −13 mV. It is likely that the connective‐to‐Retzius cell PSPs were principally electrical events. Their apparent reversal potentials could have been in the range associated with chemical synapses because they traversed an electrical synapse with a variable coupling resistance, or because the polarizing currents, passing “backwards” across electrical synapses, changed the amplitude of the presynaptic action

ISSN:0022-3034    

DOI:10.1002/neu.480070408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480070401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1976

数据来源: WILEY