Biomedical subjects

Richard Rabold

Publications and source records attributed to Richard Rabold.

8 recordsLinked to original sources

PubMed2007

Variation in senescent-dependent lung changes in inbred mouse strains.

Previous studies from our laboratories showed lung development differences between inbred strains of mice. In the present study, the C57BL/6J (B6) and DBA/2J (D2) strains were examined for senescent-dependent differences with respect to the lung structure and function. Specifically, we hypothesize that senescent changes in lung vary between strains due to identifiable gene expression differences. Quasi-static pressure-volume curves and respiratory impedance measurements were performed on 2- and 20-mo-old B6 and D2 mice. Lung volume at 30 cm H(2)O (V(30)) pressure was significantly (P < 0.01) increased with age in both strains, but the increase was proportionally greater in D2 (68%) than in B6 (40%) mice. In addition, decreased elastic recoil pressure at 50% of V(30) and a reduction in airway resistance as a function of positive end-expiratory pressure were observed in 20-mo-old D2 mice but not in B6 mice. Morphometric analysis of lung parenchyma showed significant decreases in elastic fiber content with age in both strains, but the collagen content was significantly (P < 0.01) increased with age in D2 but not B6 mice at 20 mo. Furthermore, using quantitative RT-PCR methods, gene expression differences between strains suggested that D2 mice significantly (P < 0.05) downregulated the expressions of elastin (Eln) and procollagen I, III, and VI (Col1a1, Col3a1, and Col6a3) in lung tissue at 20 mo of age. These age-dependent changes were accompanied by an increased gene expression in matrix metalloproteinase 9 (Mmp9) in D2 and an increase in tissue inhibitor of matrix metalloproteinase (Timp1 and Timp4) in B6 mice. In conclusion, the results from the present study demonstrate that lung mechanics of both strains show significant age-dependent changes. However, changes in D2 mice are accelerated relative to B6 mice. Moreover, gene expression differences appear to be involved in the strain-specific changes of lung mechanic properties.

Aging↗

PubMed2006

C5 modulates airway hyperreactivity and pulmonary eosinophilia during enhanced respiratory syncytial virus disease by decreasing C3a receptor expression.

Enhanced respiratory syncytial virus disease, a serious pulmonary disorder that affected recipients of an inactivated vaccine against respiratory syncytial virus in the 1960s, has delayed the development of vaccines against the virus. The enhanced disease was characterized by immune complex-mediated airway hyperreactivity and a severe pneumonia associated with pulmonary eosinophilia. In this paper, we show that complement factors contribute to enhanced-disease phenotypes. Mice with a targeted disruption of complement component C5 affected by the enhanced disease displayed enhanced airway reactivity, lung eosinophilia, and mucus production compared to wild-type mice and C5-deficient mice reconstituted with C5. C3aR expression in bronchial epithelial and smooth muscle cells in the lungs of C5-deficient mice was enhanced compared to that in wild-type and reconstituted rodents. Treatment of C5-deficient mice with a C3aR antagonist significantly attenuated airway reactivity, eosinophilia, and mucus production. These results indicate that C5 plays a crucial role in modulating the enhanced-disease phenotype, by affecting expression of C3aR in the lungs. These findings reveal a novel autoregulatory mechanism for the complement cascade that affects the innate and adaptive immune responses.

Animals↗

PubMed2006

Age-dependent changes of airway and lung parenchyma in C57BL/6J mice.

In the current study, we hypothesize that senescent-dependent changes between airway and lung parenchymal tissues of C57BL/6J (B6) mice are not synchronized with respect to altered lung mechanics. Furthermore, aging modifications in elastin fiber and collagen content of the airways and lung parenchyma are remodeling events that differ with time. To test these hypotheses, we performed quasi-static pressure-volume (PV) curves and impedance measurements of the respiratory system in 2-, 20-, and 26-mo-old B6 mice. From the PV curves, the lung volume at 30 cmH(2)O pressure (V(30)) and respiratory system compliance (Crs) were significantly (P < 0.01) increased between 2 and 20 mo of age, representing about 80-84% of the total increase that occurred between 2 and 26 mo of age. Senescent-dependent changes in tissue damping and tissue elastance were analogous to changes in V(30) and Crs; that is, a majority of the parenchymal alterations in the lung mechanics occurred between 2 and 20 mo of age. In contrast, significant decreases in airway resistance (R) occurred between 20 and 26 mo of age; that is, the decrease in R between 2 and 20 mo of age represented only 29% (P > 0.05) of total decrease occurring through 26 mo. Morphometric analysis of the elastic fiber content in lung parenchyma was significantly (P < 0.01) decreased between 2 and 20 mo of age. To the contrary, increased collagen content was significantly delayed until 26 mo of age (P < 0.01, 2 vs. 26 mo). In conclusion, our data demonstrate that senescent-dependent changes in airway and lung tissue mechanics are not synchronized in B6 mice. Moreover, the reduction in elastic fiber content with age is an early lung remodeling event, and the increased collagen content in the lung parenchyma occurs later in senescence.

Aging↗

PubMed2004

Particle effects on heart-rate regulation in senescent mice.

Because epidemiology studies consistently identify the elderly at risk for air pollution-related morbidity and mortality, we developed a model of senescent-dependent susceptibility based on indices of physiological aging. In the current study, we hypothesized that heart-rate regulation during particulate matter (PM) exposure differs with senescence-dependent susceptibility owing to variation in autonomic nervous control. Heart rate (HR) and heart-rate variability (HRV) parameters were measured from 162 samples of 2-min electrocardiograph (ECG) recordings in age-matched healthy (n = 5) and terminally senescent (n = 3) AKR mice during 3-h exposures to filtered-air (FA, day 1) and carbon black (CB, day 4; <200 microg/m(3)). On day 1, HR was significantly (p <.01) depressed during FA in terminally senescent mice. By day 4, HR was further slowed significantly (p <.01) due to the effects of CB exposure for 3 days. The combined effects of terminal senescence and CB exposure acted to depress HR to an average (+/-SEM) 445 +/- 40 bpm, or approximately 80 bpm lower compared to healthy HR responses. The change in rMSSD, an HRV parameter corresponding to relative influences of parasympathetic tone on HR, was significantly (p <.01) greater on day 1 and day 4 in terminally senescent mice compared to healthy mice. In contrast, the LF/HF ratio, an HRV parameter derived from spectral analysis indicating relative changes in cardiac sympathetic tone, was significantly (p <.01) depressed in terminally senescent mice on day 1. By day 4, significant increases in LF/HF were evident in healthy mice during CB exposure, suggesting that HR regulation was associated with an increase in sympathetic tone. Alternatively, terminally senescent mice appeared to modulate a lower HR without change in LF/HF ratio during CB exposure, suggesting an absence of sympathetic tone. In conclusion, older healthy mice increase cardiac sympathetic tone during PM exposure while terminally senescent mice show a greater PM-induced parasympathetic tone in regulating HR. The significance of the current results suggest that PM-induced HR regulatory changes may ultimately depend on the degree of physiological aging.

Aging↗

PubMed2003

Changes in lung permeability and lung mechanics accompany homeostatic instability in senescent mice.

Aging and lung disease are recognized factors that increase mortality risk in subjects exposed to ambient particulate matter (PM). In an effort to understand the mechanisms of enhanced susceptibility, the present study examined an inbred mouse model of senescence to 1) determine changes in lung permeability as animals approach the end-of-life and 2) characterize age-dependent changes in lung mechanics in presenescent and terminally senescent mice. The clearance of technetium-99m (99mTc)-diethylenetriamine pentaacetic acid (DTPA) was used to test the hypothesis that lung permeability increases with age and enhances uptake of soluble components of PM principally during the period several weeks before death in AKR/J mice. Quasistatic pressure-volume curves were conducted on robust and on terminally senescent AKR/J mice several weeks before death to assess the relative importance of lung mechanics. Abrupt body weight loss was used to signal imminent death because it accompanies indexes of physiological aging and terminal senescence. 99mTc-DTPA clearance from the lung 30 min after tracheal instillation was significantly (P < 0.05) enhanced in senescent mice. Age-dependent changes in lung mechanics were indicative of significant (P < 0.05) decrements in lung volume and compliance several weeks before death. Thus, during a period of homeostatic instability leading toward natural death, AKR/J mice showed enhanced permeability of soluble particles despite a decrease in lung volume and concomitant alveolar surface area. These results suggest that pulmonary epithelial-endothelial barrier dysfunction occurs in terminally senescent mice just before death. Furthermore, this senescent-dependent increase in lung permeability may be a contributing factor for increased PM susceptibility in the elderly and patients with lung disease.

Aging↗

PubMed2002

Unstable heart rate and temperature regulation predict mortality in AKR/J mice.

Elderly populations face greater risks of mortality when exposed to changes in environmental stress. The purpose of the following study was to develop an age-dependent susceptibility model that achieved the following three goals: 1) to operationally define homeostasis by assessing the stability and periodicity in physical activity, heart rate (HR), and deep body temperature (T(db)), 2) to specify alterations in activity, HR, and T(db) regulation that signal imminent death, and 3) to test the hypothesis that the decay in homeostasis associated with imminent death incorporates the coincident disintegration of multiple physiological systems. To achieve these goals, the circadian regulation of activity, HR, and T(db) was assessed using radiotelemeters implanted in AKR/J (n = 17) inbred mice at approximately 190 days of age. During a 12:12-h light-dark cycle, weekly measurements were obtained at 30-min intervals for 48-h periods until each animal's natural death. The average (+/-SE) life span of surgically treated animals did not differ from untreated controls (319 +/- 12 vs. 319 +/- 14 days). Cardiac and thermal stability were characterized by a circadian periodicity, which oscillated around stable daily averages of 640 +/- 14 beats/min in HR and 36.6 +/- 0.1 degrees C in T(db). Stable HR and T(db) responses were compared with extreme conditions 3 days before death, during which a disintegration of circadian periodicity was coincident with a fall in the daily average HR and T(db) of approximately 29 and approximately 13% lower (i.e., 456 +/- 22 beats/min and 31.7 +/- 0.6 degrees C), respectively. The results further suggested that multiple predictors of cardiac and thermal instability in AK mice, including significant bradycardia, hypothermia, and a loss of circadian periodicity, forecast life span 5-6 wk before expiration.

Animals↗

PubMed2002

A role for immune complexes in enhanced respiratory syncytial virus disease.

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and viral pneumonia in infants and young children. Administration of a formalin inactivated vaccine against RSV to children in the 1960s resulted in increased morbidity and mortality in vaccine recipients who subsequently contracted RSV. This incident precluded development of subunit RSV vaccines for infants for over 30 years, because the mechanism of illness was never clarified. An RSV vaccine for infants is still not available. Here, we demonstrate that enhanced RSV disease is mediated by immune complexes and abrogated in complement component C3 and B cell-deficient mice but not in controls. Further, we show correlation with the enhanced disease observed in children by providing evidence of complement activation in postmortem lung sections from children with enhanced RSV disease.

Animals↗

PubMed2002

Circadian rhythm variation in activity, body temperature, and heart rate between C3H/HeJ and C57BL/6J inbred strains.

Inbred mice have been routinely used in studies of genetic effects that determine behavioral variation due to circadian rhythm. In addition to activity patterns (Act), we aimed to characterize variations in the circadian rhythm of deep-body temperature (T(db)) and heart rate (HR) in a specific genetic model of differential cardiorespiratory control. Radiotelemeters were implanted in C3H/HeJ (C3; n = 11) and C57BL/6J (B6; n = 11) inbred strains. Reciprocal first-generation offspring, B6C3F1/J (B6F1; n = 8) and C3B6F1 (C3F1; n = 3) mice, were included to initiate an evaluation of heritable phenotypes. Mice were housed individually in a facility maintained at 23-24 degrees C, and the light-dark cycle was set at 12-h intervals. In each animal, repeated measurements were obtained at 30-min intervals, and the circadian patterns of Act, T(db), and HR were assessed by novel statistical methods that detailed the periodic function for each strain. During the dark phase, B6 mice demonstrated two distinct peaks in Act and T(db) relative to a single early peak for C3 mice. In contrast to the parental strains, B6F1 and C3F1 mice demonstrated intermediate second peaks in Act and T(db). With respect to HR, the C3 strain demonstrated a significantly (P < 0.01) greater daily average compared with B6 mice. The circadian rhythm in HR differed significantly from the Act and T(db) patterns in B6 mice (but not in C3 mice); that is, the periodicity in HR for B6 mice preceded the rise and fall in Act and T(db) during both peaks. The B6 phenotype was also observed in F1 mice. In conclusion, these data suggest that the circadian regulation of Act, T(db), and HR vary significantly among C3, B6, and F1 mice. Furthermore, phenotypic differences between C3 and B6 strains can be used to explore the genetic basis for differential circadian regulation of body temperature and HR.

Activity Cycles↗