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G S Roth

Publications and source records attributed to G S Roth.

At least 37 records · Page 2Linked to original sources
PubMed2001

Dietary caloric restriction prevents the age-related decline in plasma melatonin levels of rhesus monkeys.

Rhesus monkeys exhibit an age-associated decrease in peak plasma melatonin levels analogous to that reported for humans. This decrease is essentially abolished in monkeys subjected to a 30% reduction in caloric intake over a 12-yr period. The caloric restriction (CR) effect does not seem to be a reversal, but rather a long-term prevention, of the age-related decline in hormone concentrations. The age effect does not seem to be due to a phase shift in the peak of melatonin secretions, as has been observed in some populations of aged humans. It is also extremely unlikely that the CR effect simply reflects a phase shift, since old monkeys on the diet have nocturnal melatonin levels equal to or greater than adult fully fed controls. Thus, if peak times (approximately 0200 h) were actually shifted, maximal levels in old CR monkeys would be even higher. These findings, coupled with previous observations in humans, suggest that peak plasma melatonin levels may represent a possible candidate "biomarker of aging" in primates. Moreover, this index of age-associated physiological decrement seems to be inhibited by dietary CR.

Aging↗
PubMed2000

Development of an adenoviral vector for intracerebral delivery of the dopamine D(2) receptor.

The age-related loss of striatal dopamine D(2) receptors (D(2)R) has been observed in numerous species, including rodents, monkeys, and man, and is partly responsible for impaired motor function in aged mammals. We have developed an adenoviral vector designed for intracerebral transfer of cDNA for D(2)R. Results of in vitro studies demonstrated that the vector produced abundant message for D(2)R and that the vector was membrane bound and capable of binding appropriate ligand. Results of in vivo studies provided clear evidence of D(2)R production when injected into the striatum of rats. The D(2)R produced were capable of binding appropriate ligand. In addition, evidence of functional receptors was produced by demonstrating apomorphine-induced rotational behavior in rats receiving a unilateral injection of the vector. Despite these successes, we have been unable to demonstrate improvement in the motor behavior of aged rats receiving bilateral injections of the vector. A major problem with this vector as with similar adenoviral vectors is the loss of expression beginning 3-5 days after injection to undetectable levels at 21 days. Because of the lack of motor functional effects in aged rats and the loss of expression of the vector, other strategies for development of the vector are being pursued. Regarding functional effects, we have examined the feasibility of manipulating hippocampal acetylcholine (ACh) release through D(2)R manipulation to improve memory performance. Using microdialysis, we have demonstrated in vivo in rats that treatment with a D(2)R agonist increases hippocampal ACh release while treatment with a D(2)R antagonist attentuates this effect as well as impairs performance in a complex maze task. In addition, a D(2)R null mutant mouse is being used to examine possible therapeutic effects of the vector. These mice show specific motor deficits. Recent studies using positron emission tomography have also demonstrated the feasibility of in vivo imaging of the vector. Thus, use of adenoviral vectors specific for neurotransmitter receptors can provide a highly useful research tool for examining age-related alterations in behavioral function and a possible strategy for therapeutic intervention.

Acetylcholine↗
PubMed2000

In vivo imaging of adenovirus-mediated over-expression of dopamine D2 receptors in rat striatum by positron emission tomography.

PET was used to provide in vivo imaging of the over-expression of dopamine D2 receptor (D2R) induced by adenovirus vector-mediated gene transfer in rat striatum. The uptake of three kinds of D2R-specific ligands, [11C]raclopride, [11C]nemonapride and [11C]N-methylspiperone, measured by PET was higher in the striatum injected with the vectors for D2R than the contralateral striatum injected with a control vector 2-3 days after injection. However, the uptake of [11C]SCH 23390, a dopamine D1 receptor specific ligand, or [11C]beta-CIT-FP, a dopamine transporter specific tracer, was not different between bilateral striata. Co-injection of excess unlabeled raclopride inhibited the uptake of [11C]raclopride. At day 16 the increased uptake of [11C]raclopride declined to basal level, consistent with past in vitro assessment of this vector. In vivo imaging of D2R will permit longitudinal assessment of the efficiency of this and similar vectors in rat brain that can be related to functional changes being observed.

Adenoviridae↗
PubMed2000

Short-term calorie restriction improves disease-related markers in older male rhesus monkeys (Macaca mulatta).

Calorie restriction (CR) is widely known for its effects on life span, physiological aging and age-related disease in laboratory rats and mice. Emerging data from CR studies in rhesus monkeys suggest that this nutritional intervention paradigm may also have beneficial effects in long-lived mammals. Studies from our laboratory and others have suggested that young- or adult-onset CR might have beneficial effects on cardiovascular disease and diabetes. For example, long-term CR reduced body fat and serum triglycerides, and increased a subfraction of HDL cholesterol associated with decreased cardiovascular disease risk. These studies suggested that long-term CR begun in young or adult animals might have important effects on markers relevant to age-related disease. Few studies have examined the effects of CR initiated in older animals (rodents or monkeys), and the temporal nature of some potentially beneficial effects of CR is unknown. The present study examined several markers related to diabetes and cardiovascular disease in thirteen older adult (> 18 year) non-obese (body fat < 22%), male rhesus monkeys during a short-term CR paradigm. Specifically, we collected these data at baseline (ad libitum feeding), 10, 20, and 30% CR, and at 6 and 12 months on 30% CR. Fasting and peak insulin were significantly reduced as were the acute and second-phase insulin responses. CR also marginally reduced triglycerides (50% reduction), but had no effect on total serum cholesterol or blood pressure. Interestingly, the observed glucoregulatory changes emerged prior to any evidence of a change in body composition suggesting that certain effects of CR may not be wholly dependent on changes in body composition in older monkeys.

Aging↗
PubMed2000

Effects of reduced energy intake on the biology of aging: the primate model.

Dietary energy restriction is the only proven method for extending lifespan and slowing aging in mammals, while maintaining health and vitality. Although the first experiments in this area were conducted over 60 y ago in rodents, possible applicability to primates has only been examined in controlled studies since 1987. Our project at the National Institute on Aging began with 3-0 male rhesus and 30 male squirrel monkeys of various ages over their respective life spans. Subsequently, it has been expanded to include female rhesus monkeys, and several other laboratories have initiated related studies. Experimental animals are generally fed 30% less than controls, and diets are supplemented with micronutrients to achieve undernutrition without malnutrition. These calorically restricted (CR) monkeys are lighter, with less fat and lean mass than controls. Bone mass is also slightly reduced, but in approximate proportion to the smaller body size. CR animals mature more slowly and achieve shorter stature than controls as well. Metabolically, CR monkeys have slightly lower body temperature and initial energy expenditure following onset of restriction, and better glucose tolerance and insulin sensitivity. The latter suggest a reduced predisposition towards diabetes as the animals age. Other potential anti-disease effects include biomarkers suggestive of lessened risk of cardiovascular disease and possibly cancer. Candidate biomarkers of aging, including the age-related decrease in plasma dehydroepiandrosterone sulfate (DHEAS), suggest that the CR animals may be aging more slowly than controls in some respects, although sufficient survival data will require more time to accumulate. In summary, nearly all CR effects detected in rodents, which have thus far been examined in primates, exhibit similar phenomenology. Potential applicability of these beneficial effects to humans is discussed.

Aging↗
PubMed2000

The roles of dopamine oxidative stress and dopamine receptor signaling in aging and age-related neurodegeneration.

Aging is accompanied by a decline of functions controlled by the central dopaminergic system, such as reduced locomotor activity, motivation, impairment of memory formation, and learning deficits. The molecular mechanisms underlying age-related impairment of dopaminergic functions are unknown. Current literature and our own recent work, which are reviewed and summarized in the present paper, suggest that dopamine oxidative stress and its subsequent signaling may contribute to the aging of dopaminergic system.

Aging↗
PubMed2000

Age-related decline in Ras/ERK mitogen-activated protein kinase cascade is linked to a reduced association between Shc and EGF receptor.

Numerous studies have demonstrated that the proliferative capacity of cells declines with age. Using rat primary hepatocytes as a model system, we recently demonstrated that this age-related decline in the proliferative response to mitogenic stimulation is associated with decreased activities of both extracellular signal-regulated kinase (ERK) and p70 S6 kinase (p70(S6k)). To unravel the molecular basis for age-related defects in the ERK pathway, we have now characterized the upstream signaling events that occur after epidermal growth factor (EGF) stimulation in young and aged hepatocytes. As previously noted for ERK, the activities of both MEK (the kinase immediately upstream of ERK) and Ras following EGF stimulation were significantly lower in aged hepatocytes. An examination of the EGF receptor (EGFR) revealed a similar amount of EGFR in the two age groups. Likewise, EGFR and Shc, an adaptor protein that plays a crucial role in linking EGFR to Ras activation, underwent tyrosine phosphorylation to a similar degree in both young and aged hepatocytes. However, in aged cells Shc was unable to form stable complexes with EGFR after EGF stimulation. Our results suggest that a decrease in the association between Shc and EGFR in aged cells underlies the age-related declines in the ERK signaling cascade and in proliferative capacity.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Locomotor activity in female rhesus monkeys: assessment of age and calorie restriction effects.

As a component of a long-term, longitudinal study of aging in this primate model, the objective of the current experiment was to assess age and diet effects on locomotor activity in a cross-sectional analysis. By attaching a motion detection device to the home cage, locomotor activity was monitored over a week in a group (N = 47) of female rhesus monkeys (Macaca mulatta) 6-26 yrs of age. About half these monkeys composed a control group fed a nutritionally fortified diet near ad libitum levels, whereas an experimental group had been fed the same diet at levels 30% less than comparable control levels for approximately 5 yrs prior to testing. Among control monkeys, a marked age-related decline in activity was noted when total activity was considered and also when diurnal and nocturnal periods of activity were analyzed separately. When comparing activity levels between control and experimental groups, only one significant diet effect was noted, which was in the youngest group of monkeys (6-8 yrs of age) during the diurnal period. Monkeys in the experimental group exhibited reduced activity compared to controls. Body weight was not consistently correlated to activity levels. In some older groups, heavier monkeys tended to show greater activity, but in younger groups the opposite pattern was observed.

Age Factors↗
PubMed1999

Dopamine stimulates redox-tyrosine kinase signaling and p38 MAPK in activation of astrocytic C6-D2L cells.

An increase in dopamine (DA) availability in rat brain has been suggested to participate in certain neurodegenerative processes. However, the regulatory effects of DA on glial cells have not been extensively studied. Using a rat C6 glioma cell line stably expressing recombinant D2L receptors, we have found that micromolar levels of DA stimulate mitogenesis and glial fibrillary acidic protein (GFAP) expression, both serving as parameters of reactive gliosis. This mitogenesis occurs about 29 h after exposure to DA and requires D2-receptor-mediated intracellular redox-tyrosine kinase activation. Either DA or quinpirole, a D2 receptor agonist, stimulates protein tyrosine phosphorylation. Application of either DPI, a potent inhibitor of NADPH-dependent oxidase, or NAC, an anti-oxidant, effectively prevented DA-induced tyrosine phosphorylation and DNA synthesis. Preincubation of (+)-butaclamol, a D2 receptor antagonist, inhibits both DA-stimulated tyrosine phosphorylation and mitogenesis. DA at micromolar levels also stimulates GFAP expression. This DA-regulated GFAP expression can be completely inhibited by SB203580, a selective p38 MAPK inhibitor, but not influenced by (+)-butaclamol and genistein, a protein tyrosine kinase inhibitor. Thus, our data suggest that regulation of DNA synthesis and GFAP expression induced by DA is mediated by independent signaling pathways. The mitogenesis requires a D2-receptor-mediated protein tyrosine kinase cascade, while GFAP expression needs a D2-receptor-independent p38 MAPK activation. This observation may help to understand the processes of reactive gliosis in some dopaminergic-related neurodegenerative diseases.

Animals↗
PubMed1999

Death of PC12 cells and hippocampal neurons induced by adenoviral-mediated FAD human amyloid precursor protein gene expression.

We used adenoviral-mediated gene transfer of human amyloid precursor proteins (h-APPs) to evaluate the role of various h-APPs in causing neuronal cell death. We were able to infect PC12 cells with very high efficiency because approximately 90% of the cells were cytochemically positive for beta-galactosidase activity when an adenoviral vector containing LacZ cDNA was used to infect cells. Cells infected with adenovirus containing h-APP cDNA showed high-level transcription and expression of h-APP as measured by reverse transcriptase-polymerase chain reaction and Western immunoblot analyses, respectively. Intracellular and extracellular levels of h-APP were elevated approximately 17-and 24-fold in cultures infected with recombinant adenovirus containing wild-type mutant and 13- and 17-fold with V642F mutant. No elevation in h-APP was seen in cultures infected with antisense h-APP or null adenovirus. H-APP levels were maximal 3 days after infection. Overexpression of V642F mutant h-APP in PC12 cells and hippocampal neurons resulted in about a twofold increase in death compared with overexpression of wild-type h-APP. These results demonstrate the usefulness of recombinant adenoviral mediated gene transfer in cell culture studies and suggest that overexpression of a familial Alzheimer's disease mutant APP may be toxic to neuronal cells.

Adenoviridae↗
PubMed1999

Cellular proliferation potential during aging and caloric restriction in rhesus monkeys (Macaca mulatta).

Caloric restriction (CR) is the most successful method of extending both median and maximal lifespans in rodents and other short-lived species. It is not yet clear whether this method of life extension will be successful in longer-lived species, possibly including humans; however, trials in rhesus monkeys are underway. We have examined the cellular proliferative potential of cells from CR and AL (ad libitum fed) monkey skin cells using two different bioassays: colony size analysis (CSA) of dermal fibroblasts isolated and cloned directly from the skin and beta-galactosidase staining at pH 6.0 (BG-6.0) of epidermal cells in frozen sections of skin. Decreases in both proliferative markers occurred with age, but no differences were observed between CR and AL animals. Skin biopsies were obtained from AL and CR rhesus monkeys from two different aging colonies, one at the National Institute on Aging (NIA) and one at the University of Maryland-Baltimore (UMB). These biopsies were used as a source of tissue sections and cells for two biomarkers of aging assays. The CR monkeys had been maintained for 9-12 years on approximately 70% of the caloric intake of control AL animals. In the CSA studies, the fraction of small clones increased significantly and the fraction of large clones decreased significantly with increasing age in AL monkeys. The frequency of epidermal BG-6.0 staining cells increased with age in older (>22 years) AL monkeys, but most predominately in those of the UMB colony, which were somewhat heavier than the NIH AL controls. Old monkeys on CR tended to have fewer BG-6.0-positive cells relative to old AL-derived epidermis, but this effect was not significant. These results indicate that cellular proliferative potential declined with age in Macaca mulatta, but was not significantly altered by CR under these conditions. Although these experiments are consistent with an absence of effect of CR on monkey skin cell proliferative potential, we have found in previous experiments with mice that a longer duration of CR (as a fraction of total lifespan) was needed to demonstrate CR-related improvement in clone size in mice. Further studies on the now mid-aged monkeys will be needed as their age exceeds 20 years to conclusively rule out an effect of CR on proliferative potential of skin cells from these primates.

Aging↗
PubMed1999

Mechanisms of age-related changes in gonadotropin-releasing hormone receptor messenger ribonucleic acid content in the anterior pituitary of male rats.

To determine the mechanism(s) of age-related changes in gonadotropin release from pituitary gonadotrophs in male rats, we measured the number of GnRH (gonadotropin-releasing hormone) receptor containing cells and expression of GnRH receptor mRNA per cell in the anterior pituitary. An in situ hybridization procedure was performed using young (six months) and old (24-25 months) Wistar rats. An image analysis system was employed for the autoradiographic analysis. The number of pituitary cells increased during aging (approximately 45%, p < 0.01). On the other hand, the number of GnRH receptor mRNA-containing cells decreased (approximately 25%, p < 0.05). The percentage of these cells in old rats decreased to less than a half of that in young animals (p < 0.01). GnRH receptor mRNA per cell in old rats was only 7% lower than in young (p < 0.01). These results suggest that loss of pituitary gonadotroph GnRH receptors and response is primarily due to the loss of gonadotrophs, and that the death mechanism(s) are responsible for decreased stimulation of Gn release during aging.

Aging↗
PubMed1999

Calorie restriction in nonhuman primates: effects on diabetes and cardiovascular disease risk.

The effects of calorie restriction (CR) on life span, disease, and aging in physiological systems have been documented extensively in rodent models. However, whether CR has similar effects in longer-lived species more closely related to humans remains unknown. Studies of CR and aging using nonhuman primates (rhesus monkeys) have been ongoing for several years at the National Institute on Aging and the University of Wisconsin-Madison. The majority of data published from these studies are consistent with the extensive findings reported in rodents. For example, monkeys on CR weigh less and have less body fat. Monkeys on CR also exhibit lower body temperature, fasting blood glucose and insulin, and serum lipids. In addition, insulin sensitivity is increased in monkeys on CR. Recent efforts in the NIA study have focused on the effect of this intervention on risk factors for various age-related diseases, in particular for diabetes and cardiovascular disease. We have shown that monkeys on CR have lower blood pressure, reduced body fat, and a reduced trunk:leg fat ratio. Also, monkeys on CR have reduced triglycerides and cholesterol and have increased levels of HDL2B. Low levels of this HDL subfraction have been associated with increased cardiovascular disease in humans. In short-term studies, older (> 18 years) monkeys on CR exhibit reductions in insulin and triglycerides before changes in body composition and fat distribution became evident. These and other findings have suggested that CR might have beneficial effects on certain disease risk factors independent of reductions in body weight or prevention of obesity.

Aging↗
PubMed1999

Loss of D2 receptor binding with age in rhesus monkeys: importance of correction for differences in striatal size.

The relation between striatal dopamine D2 receptor binding and aging was investigated in rhesus monkeys with PET. Monkeys (n = 18, 39 to 360 months of age) were scanned with 11C-raclopride; binding potential in the striatum was estimated graphically. Because our magnetic resonance imaging analysis revealed a concomitant relation between size of striatum and age, the dynamic positron emission tomography (PET) data were corrected for possible partial volume (PV) artifacts before parameter estimation. The age-related decline in binding potential was 1% per year and was smaller than the apparent effect if the age-related change in size was ignored. This is the first in vivo demonstration of a decline in dopamine receptor binding in nonhuman primates. The rate of decline in binding potential is consistent with in vitro findings in monkeys but smaller than what has been measured previously in humans using PET. Previous PET studies in humans, however, have not corrected for PV error, although a decline in striatal size with age has been demonstrated. The results of this study suggest that PV correction must be applied to PET data to accurately detect small changes in receptor binding that may occur in parallel with structural changes in the brain.

Aging↗
PubMed1999

Calorie restriction in primates: will it work and how will we know?

Dietary caloric restriction is the most robust and reproducible means of slowing aging and extending lifespan and healthspan in short-lived mammals and lower organisms. Numerous aspects of this paradigm have been investigated in laboratories around the world since its inception more than 60 years ago. However, two questions about calorie restriction remain unanswered to this day: (1) By what mechanism does it work? and (2) Will it work in humans? This review will focus on the latter with particular emphasis on evaluation criteria, current studies in primate models, available data, and plans for actual human caloric restriction interventions.

Aging↗
PubMed1999

Intrastriatal dopamine injection induces apoptosis through oxidation-involved activation of transcription factors AP-1 and NF-kappaB in rats.

ABSTRACT More and more evidence suggests that increases in dopamine (DA) in striata may participate in neurodegenerative processes during acute ischemia, hypoxia, and excitotoxicity. With a rat model of intrastriatal DA injection, we studied the molecular events involved in DA toxicity. Intrastriatal injections of DA in amounts from 1 to 2 micromol result in apoptotic cell death, as indicated by terminal deoxynucleotidyl transferase labeling of DNA strand breaks and Klenow polymerase-catalyzed [(32)P]deoxycytidine triphosphate-labeled DNA laddering. Injections of DA produce a strong and prolonged activated protein 1 (AP-1) activity that contains c-fos, c-jun, and phosphorylated c-jun protein. DA injections also stimulate the activity of nuclear factor-kappaB (NF-kappaB), an oxidative stress-responsive transcription factor. Injection of curcumin at a dose that selectively inhibits AP-1 activation without affecting NF-kappaB activity attenuates DNA laddering induced by DA. Preinjection with SN50, a specific permeable recombinant NF-kappaB translocation inhibitor peptide, reduces DA-induced NF-kappaB activation and apoptosis. Moreover, preinjection of the antioxidant GSH significantly inhibits both DA-induced activation of transcription factors AP-1 and NF-kappaB and subsequent apoptosis. Thus, our data suggest that DA-oxidative stress-induced apoptosis in vivo is mediated by activation of transcription factors AP-1 and NF-kappaB.

Animals↗