Age-related synaptic changes in the central nucleus of the inferior colliculus of Fischer-344 rats

1999 ◽  
Vol 406 (3) ◽  
pp. 285-298 ◽  
Author(s):  
Robert H. Helfert ◽  
Teresa J. Sommer ◽  
Joshua Meeks ◽  
Phillip Hofstetter ◽  
Larry F. Hughes
Keyword(s):  
Inferior Colliculus ◽  
Central Nucleus ◽  
Fischer 344 Rats ◽  
Fischer 344 ◽  
Age Related ◽  
Synaptic Changes

Age-related synaptic changes in the anteroventral cochlear nucleus of Fischer-344 rats

2003 ◽  
Vol 183 (1-2) ◽  
pp. 18-28 ◽  
Author(s):  
Robert H. Helfert ◽  
Judyann Krenning ◽  
Teresa S Wilson ◽  
Larry F Hughes
Keyword(s):  
Cochlear Nucleus ◽  
Fischer 344 Rats ◽  
Fischer 344 ◽  
Age Related ◽  
Anteroventral Cochlear Nucleus ◽  
Synaptic Changes

scholarly journals Phrenic motor neuron loss in aged rats

2018 ◽  
Vol 119 (5) ◽  
pp. 1852-1862 ◽  
Author(s):  
Matthew J. Fogarty ◽  
Tanya S. Omar ◽  
Wen-Zhi Zhan ◽  
Carlos B. Mantilla ◽  
Gary C. Sieck
Keyword(s):  
Motor Neuron ◽  
Surface Area ◽  
Motor Neurons ◽  
Fiber Type ◽  
Dendritic Morphology ◽  
Diaphragm Muscle ◽  
Specific Force ◽  
Fischer 344 Rats ◽  
Fischer 344 ◽  
Age Related

Sarcopenia is the age-related reduction of muscle mass and specific force. In previous studies, we found that sarcopenia of the diaphragm muscle (DIAm) is evident by 24 mo of age in both rats and mice and is associated with selective atrophy of type IIx and IIb muscle fibers and a decrease in maximum specific force. These fiber type-specific effects of sarcopenia resemble those induced by DIAm denervation, leading us to hypothesize that sarcopenia is due to an age-related loss of phrenic motor neurons (PhMNs). To address this hypothesis, we determined the number of PhMNs in young (6 mo old) and old (24 mo old) Fischer 344 rats. Moreover, we determined age-related changes in the size of PhMNs, since larger PhMNs innervate type IIx and IIb DIAm fibers. The PhMN pool was retrogradely labeled and imaged with confocal microscopy to assess the number of PhMNs and the morphometry of PhMN soma and proximal dendrites. In older animals, there were 22% fewer PhMNs, a 19% decrease in somal surface area, and a 21% decrease in dendritic surface area compared with young Fischer 344 rats. The age-associated loss of PhMNs involved predominantly larger PhMNs. These results are consistent with an age-related denervation of larger, more fatigable DIAm motor units, which are required primarily for high-force airway clearance behaviors. NEW & NOTEWORTHY Diaphragm muscle sarcopenia in rodent models is well described in the literature; however, the relationship between sarcopenia and frank phrenic motor neuron (MN) loss is unexplored in these models. We quantify a 22% loss of phrenic MNs in old (24 mo) compared with young (6 mo) Fischer 344 rats. We also report reductions in phrenic MN somal and proximal dendritic morphology that relate to decreased MN heterogeneity in old compared with young Fischer 344 rats.

Sensitivity to binaural intensity and phase difference cues in kitten inferior colliculus

1990 ◽  
Vol 64 (2) ◽  
pp. 582-597 ◽  
Author(s):  
B. J. Blatchley ◽  
J. F. Brugge
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Phase Difference ◽  
Central Nucleus ◽  
Intensity Difference ◽  
Monotonic Functions ◽  
Age Related ◽  
Highly Correlated ◽  
Intensity Functions ◽  
Almost All

1. Responses of single neurons to monaural or binaural CF tones delivered through a closed and calibrated sound delivery system were studied in the central nucleus of the inferior colliculus (ICC) in ketamine and barbiturate-anesthetized kittens 4-105 days old. 2. Neurons from young kittens had elevated thresholds, some greater than 100 dB in the youngest kittens tested. Average thresholds in the ICC matched those previously measured in the auditory nerve (AN), cochlear nuclei (CN), and auditory cortex (CTX), suggesting that the drop in threshold as a function of age is primarily determined by development at the periphery. 3. Minimal first-spike latencies were relatively long in the youngest kittens, approaching adult values by the end of the third postnatal week. Latencies were distributed between values previously determined for the CN and auditory cortex and can be attributed to the centripetal development of the auditory system. 4. The range of frequencies that were effective in exciting ICC neurons was restricted in young kittens. Neurons having characteristic frequencies (CFs) greater than 7 kHz were not recorded before postnatal day 10. CF distribution matched that obtained in previous experiments from AN, CN, and CTX, reflecting the development of the cochlea. 5. Both monotonic and nonomonotonic spike count-versus-intensity functions were found in the youngest kittens. There was a tendency for monotonic functions from the youngest kittens to be steeper than those from older kittens. No age-related changes in the shapes of non-monotonic functions were found. 6. Sensitivity to interaural intensity difference (IID), tested by holding the intensity to the excitatory ear at a suprathreshold level and increasing the intensity of the stimulus to the inhibitory ear, was exhibited as early as 8 days after birth. The majority of the cells exhibiting sensitivity to IID (89.5%) were classified as EI cells, and almost all IID sensitive cells had CFs between 3 and 25 kHz. Within our sample the shapes of IID functions, as well as the operating range of the IID functions, closely resembled those obtained from the adult cat. Thresholds of excitation and of inhibition were highly correlated, suggesting that the ipsilateral and contralateral inputs to the ICC develop as a matched set. 7. Sensitivity to interaural phase difference (IPD), tested either by shifting the onset phase of a CF tone to one ear relative to the other or by presenting tones of slightly different frequency to the two ears, was present as early as 12 days after birth.(ABSTRACT TRUNCATED AT 400 WORDS)

Upregulation of G protein-linked receptor kinases with advancing age in rat aorta

2001 ◽  
Vol 280 (3) ◽  
pp. R897-R903 ◽  
Author(s):  
William E. Schutzer ◽  
John F. Reed ◽  
Michael Bliziotes ◽  
Scott L. Mader
Keyword(s):  
G Protein ◽  
Rat Aorta ◽  
Aortic Tissue ◽  
Fischer 344 Rats ◽  
Membrane Expression ◽  
Fischer 344 ◽  
Age Related ◽  
Protein Receptor ◽  
Receptor Kinases ◽  
Increased Activity

The age-related decline in β-adrenergic receptor (β-AR)-mediated vasorelaxation is associated with desensitization of β-ARs without significant downregulation. The primary mode of this homologous β-AR desensitization, in general, is via G protein receptor kinases (GRK). Therefore, we hypothesize that age-related changes in GRKs are causative to this etiology in rat aorta. Herein, we investigate the activity and cellular distribution (cytoplasmic vs. membrane) of several GRK isoforms and β-arrestin proteins. GRK activity was assessed in extracts from aortic tissue of 6-wk, 6-mo, 12-mo, and 24-mo-old male Fischer-344 rats using a rhodopsin phosphorylation assay. We also performed immunoblots on lysates from aorta with specific antibodies to GRK-2, -3, -5, and β-arrestin-1. Results show an age-related increase in GRK activity. Furthermore, expression of GRK-2 (cytoplasmic and membrane), GRK-3 (cytoplasmic and membrane), and β-arrestin (soluble) increased with advancing age, whereas GRK-5 (membrane) expression remained unchanged. These results suggest that age is associated with increased activity and expression of specific GRKs. This increase likely results in enhanced phosphorylation and desensitization of β-ARs. These biochemical changes are consistent with observed aging physiology.

Age-related increases in diaphragmatic maximal shortening velocity

1996 ◽  
Vol 80 (2) ◽  
pp. 445-451 ◽  
Author(s):  
S. K. Powers ◽  
D. Criswell ◽  
R. A. Herb ◽  
H. Demirel ◽  
S. Dodd
Keyword(s):  
Force Production ◽  
Specific Force ◽  
Fischer 344 Rats ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Fischer 344 ◽  
Age Related ◽  
Highly Correlated ◽  
Related Increase

Recent evidence demonstrates that aging results in an increase in fast (type IIB) myosin heavy chain (MHC) in the rat diaphragm. It is unknown whether this age-related change in fast MHC influences the diaphragmatic maximal shortening velocity (Vmax). Therefore, we tested the hypothesis that aging is associated with an increase in the diaphragmatic Vmax and that the increase in the Vmax is highly correlated with the percentage of type IIb MHC. In vitro contractile properties were measured with costal diaphragm strips obtained from young (4 mo old; n = 8) and (old 24 mo old; n = 8) male Fischer-344 rats. Diaphragmatic maximal tetanic specific force production was 14.5% lower in the old compared with the young animals (23.0 +/- 0.4 vs. 19.7 +/- 0.8 N/cm2; P < 0.05). In contrast, the diaphragmatic Vmax was significantly higher in the old compared with the young animals (5.5 +/- 0.1 vs. 4.4 +/- 0.3 lengths/s; P < 0.05). Although the percent type IIb MHC was significantly higher (approximately +14%; P < 0.05) in the old compared with the young animals, the correlation between Vmax and percent type IIb MHC was relatively low (r = 0.50; P = 0.05). These data support the hypothesis that an age-related increase in diaphragmatic Vmax occurs; however, factors in addition to type IIb MHC are involved in regulating diaphragmatic Vmax. Interestingly, although aging resulted in a decrease in diaphragmatic maximal specific force production, power output at all muscle loads was maintained in the old animals due to the increase in diaphragmatic shortening velocity.

scholarly journals Induction of G1 checkpoint in the gastric mucosa of aged rats

1999 ◽  
Vol 277 (5) ◽  
pp. G929-G934 ◽  
Author(s):  
Zhi-Qiang Xiao ◽  
Yingjie Yu ◽  
Ahmed Khan ◽  
Richard Jaszewski ◽  
Murray N. Ehrinpreis ◽  
...  
Keyword(s):  
Gastric Mucosa ◽  
Proliferative Activity ◽  
Protein A ◽  
S Phase ◽  
Aged Rats ◽  
Fischer 344 Rats ◽  
Protein Levels ◽  
Fischer 344 ◽  
Age Related ◽  
P53 Status

Although in Fischer 344 rats aging is found to be associated with increased gastric mucosal proliferative activity, little is known about specific changes in the regulatory mechanisms of this process. To determine whether changes in cell cycling events could partly contribute to the age-related rise in gastric mucosal proliferative activity, the present investigation examines changes in cyclin-dependent kinase (Cdk2) activity and the regulation of this process in the gastric mucosa of Fischer 344 rats aged 4 (young), 13 (middle aged), and 24 (old) mo. We observed that aging is associated with a progressive rise in activity and protein levels of Cdk2 in the gastric mucosa. This is also found to be accompanied by a concomitant increase in cyclin E but not cyclin D1 levels. On the other hand, the levels of p21Waf1/Cip1 (total as well as the fraction associated with Cdk2), a nuclear protein that is known to inhibit different cyclin-Cdk complexes, are found to decline in the gastric mucosa with advancing age. In contrast, with aging, there was a steady rise in p53 levels in the gastric mucosa. We have also observed that the levels of phosphorylated retinoblastoma protein, a form that participates in regulating progression through the S phase, are markedly elevated in the gastric mucosa of aged rats. In conclusion, our data suggest that, in the gastric mucosa, aging enhances transition of G1 to S phase as well as progression through the S phase of the cell cycle. However, the age-related decline in p21Waf1/Cip1 in the gastric mucosa appears to be independent of p53 status.

Age-related immunosenescence in Fischer 344 rats: influence of exercise training

1992 ◽  
Vol 73 (5) ◽  
pp. 1932-1938 ◽  
Author(s):  
I. Nasrullah ◽  
R. S. Mazzeo
Keyword(s):  
Endurance Training ◽  
Interleukin 2 ◽  
Cytolytic Activity ◽  
Treadmill Running ◽  
Target Cells ◽  
Fischer 344 Rats ◽  
Middle Aged ◽  
Fischer 344 ◽  
Age Related ◽  
Old Rats

The present investigation examined the extent to which 15 wk of endurance training could influence immune function in young, middle-aged, and older animals. Forty-eight male Fischer 344 rats were divided into trained and untrained groups. Training consisted of treadmill running at 75% maximal running capacity for 1 h/day, 5 days/wk, for 15 wk. Animals were killed at 8, 17, and 27 mo, at which time splenocytes were isolated. The capacity for lymphocyte proliferation in response to mitogen (concanavalin A, ConA), interleukin-2 (IL-2) production, and cytolytic activity against YAC-1 target cells was determined. ConA-induced proliferation declined significantly with age. Training suppressed the proliferative response in the young (-41%) and middle-aged animals (-27%) compared with the age-matched controls; however, training improved this response (+58%) in the older group. IL-2 production followed a pattern similar to that for mitogen-induced proliferation, such that production declined with age and was reduced with training in young and middle-aged animals but was significantly more improved in the older animals than in age-matched controls. The ability to lyse target cells, measured as percent cytotoxicity, declined steadily with advancing age at all effector-to-target cell ratios tested: 52, 14, and -16% for 8-, 17-, and 27-mo-old rats, respectively. It was concluded that the capacity for ConA-induced splenocyte proliferation, IL-2 production, and cytolytic activity declines significantly with advancing age. Furthermore, 15 wk of endurance training suppressed proliferation and IL-2 production in young animals but improved these responses in older animals. Training had no effect on cytolytic activity.

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