ISSN:0360-4012    

DOI:10.1002/jnr.490140102

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe development in primary dissociated rat brain cultures of 2′,3′ ‐cyclic nucleotide 3′ ‐phosphohydrolase (CNP) activity, the accumulation of CNP protein, and the number of cells accumulating this protein have been quantitatively determined as a function of time in culture. Parallel determinations have been made for the first two parameters for developing rat brain. The developmental profile of CNP enzymatic activity of CNP protein in culture paralleled that observed in rat brain, in which the period of most active development occurred 7–25 days after birth. Mean CNP activities of 5.6 and 8.1 μmol/min/mg total protein were recorded for the cultures and rat brain, respectively, at their maximal levels. The corresponding mean values for the CNP protein accumulation were calculated to be 138 and 150 pmol/mg total protein, respectively. Thus maximal specific activities of the CNP protein were estimated to be about 800 and 1,100 μmol/min/mg CNP protein for culture and rat brain enzyme, respectively. Approximately three million cells expressing CNP appeared in the cultures per dissociated fetal rat brain seeded. Each CNP + oligodendrocyte in culture had an average CNP activity of 3.2 pmol/min, and an average CNP protein content of 0.09 gmol (5.4 × 107molecules), values which remained nearly constant during the course of development. Two pricipal conclusions are drawn from these data. First, the dissociated fetal brain culture system reproduces rather accurately the temporal developmental pattern of CNP expression occurring in the rat brain, but some important quantitativ differences occur which suggest the need for additional environmental stimuli missing in these cultures. Second, the quantitative increases in CNP specific activity and amount of CNP protein occurring during oligodendrocyte differentiation in these cultures are primarily the result of increases in the number of CNP + cells present which upon differentiation express very quickly, via an off‐on regulation, steady‐state le

ISSN:0360-4012    

DOI:10.1002/jnr.490140103

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

年代:1985

数据来源: WILEY

摘要:

AbstractHighly purified cultures of rat astrocytes and oligodendrocytes were examined for their ability to bind and internalize lysosomal enzymes. Astrocytes displayed a saturable uptake to β‐glucosidase and β‐galactosidase. The uptake was specifically inhibited by mannose‐6‐phosphate but not by several other sugars or sugar phosphates, indicating that the process was mediated by mannose‐6‐phosphate receptors. When cells were allowed to take up125I‐β‐glucosidase for 1 hr at 37°C and subcellular organelles were isolated, the enzyme was shown to comigrate with a lysosomal organelle marker enzyme, suggesting that the enzyme was targeted to lysosomal. Astrocyte receptors were probed directly by binding of125I labeled β‐glucosidase to astrocyte membranes at 4 °C. Binding was saturable and competitively inhibited by mannose‐6‐phosphate. In contrase to the astrocytes, cultured oligodendrocytes showed no specific binding or uptake of the lysosomal enzymes. Immunocytochemical staining of mixed glial cultures supported the biochemical data; only the astrocytes stained positive with anti‐mannose‐

ISSN:0360-4012    

DOI:10.1002/jnr.490140104

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe effects of inhibition of glycosylation on nerve growth factor (NGF) binding and neurite outgrowth response of PC12 cells have been examined. Exposure to tunicamycin (1–10 μg/ml) for 24–36 hr eliminates the rapidly dissociating component of NGF binding and decreases the decreases the proportion of PC12 cells capable of elaborating neurits in a dose‐dependent manner. These decreased cellular responses are probably due to an underglycosylation of the NGF receptor, since the effects of tunicamycin are correlated with a decrease in3H‐fucose incorporation rather than a general decline in cellular metabolism as measured by viability and protein syntheses. These results suggest that carbohydrate side chains are important for the function and/or orientation of the NGF receptor in PC12 cells and that the rapidly dissociating component of NGF binding may be associated with a minimum concentration of functional receptors per cell required for the full biologic

ISSN:0360-4012    

DOI:10.1002/jnr.490140105

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe effects of altered thyroid states on regeneration in the nervous system are equivocal. This work was undertaken to examine the influence of propylthiouracil‐induced (PTU‐induced) pre‐ and postnatal hypothyroidism on collateral sprouting of noradrenergic (NA) axons in the habenula (Hb), following lesions in the stria medullaris (SM) of the adult rat. Ten pregnant dams were divided into control and PTU‐treated groups. Control rats had free access to food and water and the hypothyroid group received, in addition, 0.05% (w/v) of PTU in their drinking water, beginning on day 12 of gestation and continuing post partum through lactation until the offspring were weaned at age 22 days. The pregnant dams received, in addition, daily injections of thyroxine (25 μg/kg, ip) and only male pups were used in the study. At weaning he pups were removed from the dams and placed in cages with free access to food and water. The hypothyroid offspring received 0.05% (w/v) PTU in the drinking water until sacrificed at 10 weeks of age. At 6 weeks, some rats in each group received bilateral lesions in the SM and the remainder were sham‐operated. All rats were sacrificed 4 weeks after operation. Thus, four groups wre formed: (1) control/sham, (2) control/lesion, (3) PTU/sham, (4) PTU/lesion. Sprouting of NA fibers in discrete regions of the Hb was identified by norepinephrine (NE) levels and by fluorescence histochemistry. Blood levels of thyroid stimulating hormone (TSH) were determined. The results show that pre‐ and postnatal induced chronic hypothyroidism abolished NA sprouing in the partially deafferented Hb. Furthermore, lesions of the SM resulted in a marked decrease in seru

ISSN:0360-4012    

DOI:10.1002/jnr.490140106

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe effect of spinal dorsal funicular lesions (T 12) upon the frequency of boutons on, and diameters of the somata of pyramidal cells in layer VB of hindlimb cortex was studied. Adult rats sustained bilateral damage to either the dorsal column (DC, n = 10) alone or DC combined with the corticospinal tract (CS) (DC+CS, n = 34) and were utilized 1, 2, 3, 7, 14, 30, 45, 60, 90, or 120 days postoperatively (DPO). Neurons randomly sampled from 44 lesioned and 13 unoperated cases were analyzed for the number of silver‐impregnated boutons (Rasmussen method) on the circumference of the soma as well as diameters of the soma, nucleus, and nucleolus. Analyses of variance comparing across lesioned and normal groups were significant for bouton counts on the soma (P<0.01), and diameters (long axis) of somata (P<0.01) and their nuclei (P<0.05). Both lesioned groups exhibited significant decreases from normal for these latter three parameters. With respect to survival time for the DC+CS‐lesioned animals we noted the following: (1) Bouton counts on the soma significantly decreased below normal between 1 and 60 DPO; this decrease was most dramatic during the first three days postlesion. (2) Somal diameter (long axis) significantly decreased below normal between 2 and 120 DPO (except at 14 and 90 DPO). (3) Nuclear diameter (long axis) significantly decreased below normal only at 90 DPO. (4) Bouton counts on somata of neurons in layers VB and IV [Ganchrow and Bernstein, 1981] of hindlimb cortex correlated negatively and significantly across 120 postlesion days. The rapid shrinkage and reduced afferentation of layer VB somata during the first week following DC+CS lesions suggest initial, retrograde reactions to CS axotomy. Since bouton counts on layer VB somata were significantly less (P<0.05) in DC‐ than DC+CS‐lesioned rats, it is hypothesized that CS axotomy regulated a set‐point for increased afferentation which was maintained on the shrunken somata between 7 an

ISSN:0360-4012    

DOI:10.1002/jnr.490140107

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe potassium‐induced stimulation of oxygen consumption in brain slices has a threshold value of 15–20 mM potassium, and it reaches its maximum at 35–50 mM. Although this phenomenon now has been known for almost 50 years, its physiological role remains undetermined. One reason for this may be that the high concentration of potassium that are required for this response also have many other consequences, e.g., a depolarization of the cells, and that the different effects to some extent may mask each other. For this reason this investigation studied the effects of cesium, which evokes a maximal stimulation of oxygen consumption already at 15 mM. Like potassium, concentrations of cesium that stimulate oxygen consumption also lead to an enhanced swelling. Unlike potassium, the sodium content is affected very little by these concentrations of cesium, whereas cesium and chloride contents are increased. On this basis it is concluded that the cesium‐induced stimulation of oxygen uptake is a metabolic manifestation of an active uptake of cesium and chloride, which secondarily leads to an uptake of water, i.e., the cesium‐induced swelling. Analogously, it is suggested that the potassium‐induced stimulation of oxygen uptake represents an active accumulation of potassium a

ISSN:0360-4012    

DOI:10.1002/jnr.490140108

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

年代:1985

数据来源: WILEY

摘要:

AbstractVelocity sedimentation analysis of acetylcholinesterase (AChE) molecular forms was performed separately in endplate‐rich and endplate‐free regions of the diaphargm muscle of the rat, guinea pig, rabbit, dog, and pig, and in mm. erectores trunci and m. vastus lateralis in man. Several high‐ionic‐strength media were first tested to achieve better solubilization of AChE from rat muscles than by the usual 1 M NaCl‐ Triton X‐100 medium. Ninety‐five percent of the rat diaphragm was solubilized in a single extraction step by medium containing 1 M lithium chloride instead of NaCl. Homologous molecular forms of AChE were found in all species. The asymmetric forms were invariably present in the endplate regions of muscles but their activity in endplate‐free regions was much lower than in endplate regions in all investigated mammals except in man. Essentially the same pattern of AChE molecular forms was present in both regions in human muscles. High extrajunctional activity of the asymmetric forms makes human muscles similar to immature rodent muscles in vivo and in culture. The pattern of AChE molecular forms in the endplate region of the diaphragm in senile 24‐month‐old rats was not significantly different from that in 3‐month‐old animals. The persistence of the asymmetric AChE forms in the diaphragm of senile rats suggests that neuromuscular interactions do not become deficient

ISSN:0360-4012    

DOI:10.1002/jnr.490140109

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe aim of these investigations was to advance our knowledge of the influence of extrinsic ocular muscle (EOM) stretching on cell excitability of the retinocortical pathway. The initial goal was the lateral geniculate; however, histologic analysis indicated that most cells that responded to stretching were located near its superior edge, in an area analogous to the perigeniculate. Rabits were anaesthetized and prepared for single‐cell recordings. The extraocular muscles were detached from the eye and attached to a rigid tungsten hook. The hook was soldered to the pivot of a galvanometer that was controlled by a waveform generator. Precise and repeated length changes were obtained with extension and relaxation ramps of constant velocity. Thirty percent of the unit (N = 250) responded to EOM stretching. These stimuli evoked either an excitation or a decrease of the units' spontaneous activity. Several experimental controls provided evidence that the signals that evoked the geniculate responses originated from proprioceptors belonging to the EOM. Most responding cells had their receptive fields located eccentrically (≥50°). Also, cells that reacted to EOM stretching responded to optic nerve stimulation with a significantly shorter latency than cells that were unresponsive. Pairing the EOM stretching with light stimuli produced the following results. In about half of the units the light‐evoked responses augmentded, but in 28% of the cells the light‐evoked discharges decreased. These effects were obtained even though EOM stretching delivered singly failed to elicit a reaction from the cell. Histologic reconstructions indicated that cells were distribution in a discrete region lying rostral and dorsomedial to the lateral geniculate nucleus. This area has been associated with the perigeniculate nucleus in cats

ISSN:0360-4012    

DOI:10.1002/jnr.490140110

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe effects of corticosterone (B) and its reduced metabolite 5 ç‐dihydrocorticosterone (DHB) on CNS activity in the rat were examined. Two indices of brain excitability were evaluated: (1) amplitude of population responses (evoked potentials [EP] to sciatic nerve stimulation and 2) changes in the rate of firing of tonically discharging neuron‐both at pontine brainstem regions of the reticular formation. Experiments were carried out in adrenalectomized rats, and recordings were under urethane anesthesia. Steroids wer dissolved in a 4:1 saline:Cremophor‐El (Sigma) solution and does of 750 μg/0.5 ml were injected (IV). The effects of B on EPs were bidirectional. Increases (8 animals) and decreases (6 animals) of the amplitude responses in different animals were observed. In 4 animals, no changes were detected. In contrast, injection of DHB produced a consistent and significant reduction of brainstem sciatic evoked potentials in 10 of 12 animals tested; 2 animals did not respond to the steroid. At the neuronal level, the effects of the steroids were evaluated by the change they induced in the mean firing frequency (P<0.01) measured during 5‐min intervals as determined by a one‐way analysis of variance and analysis with a test of multiple comparisons. Only cells that fired in stationary mode for 15 min before the steriod injection were stuided. A more consistent pattern of responses to B was observed at the single‐cell level. From 31 neurons that responded to the hormone, of 76 examined, 27 showed an increase in their firing rate and only 4 neurons showed a decrease. The increase in firing rate has an onset latency of 2–5 min (x= 3.5, SE 0.43) with a duration of 16–25 min (x= 17.5, SE 2.7). Of 69 neurons that were tested with DHB, 51 showed a significant decrease in their mean firing frequency. Onset latency of the effect was 2–8 min (x= 40.0, SE 1.21) and the duration of the induced changes was 16–40 min (x= 30.0, SE 3.47). Central interactions of DHB and B when sequentially administered were examined in 28 neurons. Of these, 21 responded to DHB administration with a significant decrease in their firing rates. In 11 of these neurons, injection of B, 5 min after DHB, was followed by a rapid (1–2 min) return of the neurons to baseline firing rates. In the other 10 neurons, injection of corticoterone altered neither the median return time (30 min) nor the slope of recovery to baseline firing levels. The results presented support the notion that nuclear saturated 3.20 oxygenated steroids are endowed with CNS depressant potency and support the contention that ring A‐reduced metabolites of ovarian and adrenal steroids may fulfill an important biologic role in modulating brain excitability. Further, the data support the concept that steroid interaction at nonnuclear site (S) may complement actions at the neclear level as well as the notion that a hormones may act at mult

ISSN:0360-4012    

DOI:10.1002/jnr.490140111

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

年代:1985

数据来源: WILEY