Sleep wake profile and EEG spectral power in young or old senescence accelerated mice

Changes occurring with age in cortical EEG and sleep-wake states architecture were examined in senescence accelerated prone (SAMP8) or senescence resistant (SAMR1) mice (age: 2 and 12 months) under baseline conditions or after a 4 h sleep deprivation (SD). In baseline conditions, an increase in slow wave sleep (SWS) amount (21-24%) occurs at the expense of the wakefulness (W) in old SAMP8 and SAMR1 mice versus young animals. In these conditions, SWS latency is reduced (67-72%). Moreover, in SAMP8 and SAMR1 mice, aging deteriorates paradoxical sleep (PS) architecture with more pronounced changes in SAMP8 (amount: -63%; episode duration: -44%; latency: +286%; circadian component loss; and EEG theta (theta) peak frequency (TPF): -1 Hz). During the 4 h recovery subsequent to a 4 h sleep deprivation, old SAMP8 mice exhibit an enhanced sensitivity resulting in SWS (+62%) and PS (+120%) rebounds, a characteristic of this inbred strain. Results obtained are discussed in line with the age-related learning and memory impairments existing in SAMP8 animals. In particular, the reduced cognitive performances described in old SAMP8 might be linked to the TPF deterioration during PS.     

Comparison of haemopoiesis in young and old mice

Haemopoietic status and functions have been compared in young (2-3-month-old) and old (2-2.5-year-old) BDF1 mice. The parameters measured include total marrow cellularity, CFU-S, CFU-mix, GM-CFC, BFU-E and CFU-F. In all cases the numbers of these cells in the femoral marrow of the old mice was equal to or greater than those in the femoral marrow of young mice. In addition to these parameters we have compared the ability of marrow from young and old mice to repopulate the marrow of recipient mice whose marrow had been eliminated by radiation; to grow in long-term bone marrow cultures; to produce ectopic grafts of marrow beneath the renal capsule of normal recipients; and to supply inhibitor and stimulator of stem cell proliferation in the marrow and to resynthesise these substances. We could detect no differences in any of these functions with the exception of that of resynthesis of the stem cell regulator substances, which appears to be somewhat slower in the old mice. This, however, does not impose any limitation upon the ability of the marrow to function either under normal conditions or in conditions requiring rapid proliferation. Therefore we can find no evidence whatsoever to suggest that aging of the haemopoietic system plays any part in aging of the individual or influencing the life-span.     

Comparison of specific activities of enzymes from young and old dogs and mice

Aldolases A and B (EC 4.1.2.13) and liver cytoplasmic superoxide dismutase (EC 1.15.1.1) have been purified from young and old dogs and mice. The specific activities of these enzymes were measured and show no diminution with age. In addition, dog aldolase B, dog liver superoxide, and mouse liver aldolase were titrated in crude extracts with specific antisera. No accumulation of cross-reacting material with age was detected. The electrophoretic mobilities of these enzymes and the susceptibilities of dog aldolases A and B to trypsin digestion were also unchanged. These results are additional evidence that the accumulation of inactive enzymes is not an invariable concomitant of aging.     

Difference in response of hepatic glutathione S-transferase activities to protein-free diet between young and old C57/BL male mice.

Responses of hepatic glutathione S-transferase (GST) activities to protein-free diet (PFD) and normal diet (ND) refeeding were compared for young (6-month-old) and old (22-month-old) C57/BL male mice. Enzyme activities toward 1-chloro-2,4-dinitrobenzene (CDNB) were not significantly different between young and old rat livers in the basal condition without diet manipulation. When animals were fed PFD for 1 week, GST activities toward CDNB significantly declined in both age groups in comparison to respective basal values, but there was no significant difference in activities between the two age groups after a 7-day PFD. When they were refed with ND for 2 days (on day 2 of ND), the activities in young mice rose to a level significantly higher than the corresponding basal value. In contrast, in old animal livers, the activity slightly but further tended to decline on day 2 of ND. Activities in old rat livers returned to the basal level on day 5 of ND, while activities in young animal livers that increased to levels higher than basal levels due to the overshoot returned to the basal level on day 7 of ND. Enzyme activities toward 1,2-dichloro-4-nitrobenzene (DCNB) were significantly higher in young rat livers than in old ones at the basal period. However, enzyme activities also overshot the basal level on day 2 of ND after 7-day PFD in young mouse livers, while in old mouse livers the activities were lowest on this day. Activities returned to the basal level on day 7 of ND in both age groups. Thus, the greatest difference in enzyme activities between young and old mouse livers for both substrates was observed on day 2 of ND after 7-day PFD, rather than at either the basal period or immediately after 7-day PFD. The results essentially agree with our previous findings on female C57/BL mice as well as female Fischer-344 rats, suggesting that the age-induced changes in the GST system become clearly manifest after diet manipulation of PFD followed by ND refeeding, rather than in values during a basal period without diet manipulation, regardless of sex or species of animal.     

Immunotoxicity of alcohol in young and old mice. II. Impaired T cell proliferation and T cell-dependent antibody responses of young and old mice fed ethanol-containing liquid diet

The effect of extended ethanol consumption of young and old BALB/c mice on the proliferative response to Concanavalin A (Con A) and T cell-dependent antibody response of their spleen cells to sheep red blood cell (RBC) stimulation was determined. Splenic cells of young (3 months) and old (25 months) BALB/c mice, fed with one of three different diets (ethanol, maltose-substitute and standard mouse chow), were first cultured with Con A to assess T cell proliferation and production of interleukin 2 (IL2). Then, Con A-activated T blast cells from young and old mice were assessed for their proliferative responding capacity to exogenous human recombinant IL2 and crude rat IL2 supernatant. Finally, splenic cells of young and old mice were assessed for their ability to generate plaque-forming cells in response to sheep RBC. The results revealed that both T cell mitogenesis and IL2-dependent proliferation of T blast cells from young and old ethanol diet-fed mice were remarkably diminished as compared to that of young and old maltose-substituted diet (isocaloric control) fed mice, respectively. The ability of T cells from both young and old ethanol diet-fed mice to produce IL2, however, was not affected. Finally, the ability of young and old ethanol diet-fed mice to mount a primary antibody response to SRBC was also significantly reduced. These results taken together demonstrate for the first time that both T cell proliferative activity and T cell-dependent antibody response of young and old ethanol diet-fed mice are impaired; however, with respect to age, a differential effect of immunosuppression of ethanol was not noted.     

Comparison of oxygen kinetics in young and old subjects

Summary Five older men (aged 60–69 yr) and five young men (aged 21–29 yr) with approximately equal levels of age-corrected max were compared with respect to oxygen kinetics at equal absolute workloads (100 watts) and at equal relative workloads (45% max) on a cycle ergometer. At 45% max, half times for response to instantaneous transition from unloaded pedalling were 30.0 s and 27.4 s for old and young respectively (t=0.260,p<0.80). No significant differences were found in the response and by inference none existed in O₂ extraction. Mean half times for heart rate responses at a workload of 100 W were 24.2 s and 20.6 s for old and young groups respectively (t=0.722,p<0.49). Mechanical efficiency estimated from steady state data at 100 W was 19.8% and 20.5% for old and young groups respectively (t=0.574). The close similarity in responses to submaximal work in old and young subjects of equivalent fitness suggests caution in the interpretation of agewise decrements observed in physiological variables which may be sensitive to physical fitness status.     

Age-related decrease in the number of hemopoietic stem cells and progenitors in senescence accelerated mice

Senescence accelerated mice (SAM-P) were used for the study of the possible aging of hemopoiesis. The number of peripheral leukocytes decreased significantly with age, whereas hematocrit showed only a slight decrease. Although the number of total nucleated cells in the bone marrow increased, the number of hemopoietic stem cells (CFU-S) as well as that of granulocyte-macrophage colony forming cells (GM-CFC) showed a decrease in old mice. A significant decrease in the number of GM-CFC was observed in the spleen of old SAM-P mice, whereas no decrease was found in the number of CFU-S. Such a profound reduction of the recruitment of GM-CFC from CFU-S in the spleen together with a reduction of bone marrow hemopoiesis may be responsible for the decrease in the number of peripheral leukocytes in the old mice. SAM-P mice could provide a good model for the study of the aging of hemopoietic system.     

Differential response of muscle phosphocreatine to creatine supplementation in young and old subjects

This study compared the effects of short-term creatine supplementation on muscle phosphocreatine, blood and urine creatine levels, and urine creatinine levels in elderly and young subjects. Eight young (24 +/- 1.4 years) and seven old (70 +/- 2.9 years) men ingested creatine (20 g day-1) for 5 days. Baseline muscle phosphocreatine measurements were taken pre- and post-supplementation using nuclear magnetic resonance spectroscopy (NMR). On the first day of supplementation subjects had blood samples taken immediately before and hourly for 5 h following ingestion of 5 g of creatine, and a pharmacokinetic analysis of plasma creatine levels was conducted. Twenty-four hour urine collections were conducted for 2 days prior to the supplementation period and for 5 days during supplementation. Old subjects had significantly higher baseline plasma creatine levels than young subjects (68.5 +/- 12.5 vs. 34.9 +/- 4.7 micromol L-1; P < 0.02). There were no significant differences between groups in plasma creatine pharmacokinetic parameters (i.e. area under the curve, elimination rate constant, absorption rate constant, time to maximum concentration, and maximum concentration) following the 5 g oral creatine bolus. Urine creatine, assessed pre and on 5 days of supplementation, increased (P < 0.001), with no difference between groups. Urine creatinine did not change as a result of creatine supplementation. Young subjects showed a significantly greater increase in muscle phosphocreatine compared with old subjects, and post-supplementation muscle phosphocreatine levels were greater in young subjects (young 27.6 +/- 0.5; old 25.7 +/- 0.8 mmol kg-1 ww) (P=0.02). There were no differences in blood or urine creatine between groups in response to supplementation, but old subjects had a relatively small increase (young 35% vs. old 7%) in muscle phosphocreatine after supplementation.     

Immunological senescence. II. Normal in vitro colony formation by B cells from old mice.

The in vitro frequency and proliferative capacity of B cells and B-cell precursors in old mice was assessed. The mitogenic response to the B-cell mitogens lipopolysaccharide (LPS) and dextran sulphate decline later and at a slower rate than the T-cell response to phytohaemagglutinin and concanavalin A. The response to precursor B-cell mitogen dextran sulphate was not depressed in the bone marrow of aging mice. In addition, the dose response and kinetics of LPS and mercaptoethanol stimulated B-cell colony formation in agar was identical in spleen cells from young and old mice. These results indicate that the intrinsic proliferative capacity of B cells from old mice is normal.     

Learning capabilities and CA1-prefrontal synaptic plasticity in a mice model of accelerated senescence

SAMP8 mice represent a suitable model of accelerated senescence as compared with SAMR1 animals presenting normal aging. Five-month-old SAMP8 mice presented reflex eyelid responses like those of SAMR1 controls, but were incapable of acquiring classically-conditioned eye blink responses in a trace (230 milliseconds [ms] of interstimulus interval) paradigm. Although SAMP8 mice presented a normal paired-pulse facilitation of the hippocampal CA1-medial prefrontal synapse, an input/output curve study revealed smaller field excitatory postsynaptic potentials (fEPSPs) in response to strong stimulations of the CA1-prefrontal pathway. Moreover, SAMP8 mice did not show any activity-dependent potentiation of the CA1-prefrontal synapse across the successive conditioning sessions shown by SAMR1 animals. In addition, SAMP8 mice presented a functional deficit during an object recognition test, continuing to explore the familiar object when controls moved to the novel one. Alert behaving SAMP8 mice presented a significant deficit in long-term potentiation (LTP) at the CA1-medial prefrontal synapse. According to the present results, SAMP8 mice present noticeable functional deficits in hippocampal and prefrontal cortical circuits directly related with the acquisition and storage of new motor and cognitive abilities.     

Suppression of natural killer cell activity in young and old mice

Spleen cells from female mice of the recombinant inbred strain BPS lack natural killer (NK) cytolytic activity, and can suppress the cytolytic activity of normal NK effector cells. The suppressor cells are not typical B cells, T cells, macrophages, or NK cells; they lack the characteristics and surface markers of each of these cell types. In BPS mice, suppressor cell activity is a dominant and significant characteristic of spleen cells at every age tested (2 weeks to 18 months). In other strains of mice which are normally classified as high-responders in NK assays, such as the C57BL strain, these suppressor cells are less prominent but can be detected when separated (on the basis of their higher density) from other spleen cell populations. As mice of the high-responder strains age, however, the suppressor cells become a significant part of the spleen cell population.     

Lectin-induced cytotoxic activity in spleen cells from young and old mice. Age-related changes in types of effector cells, lymphokine production and response.

Concanavalin A (Con A)-induced cytotoxic activity, interferon (IFN) and interleukin-2 (IL-2) levels in cultures of spleen cells from young (2-3 months) and old (22-24 months) C57BL/6 female mice were studied. Con A-activated spleen cells from old mice attained significantly higher cytotoxic activity compared with activated spleen cells from young mice. Activated spleen cells from old and young mice showed differences in their ability to lyse different types of target cells. Both could lyse P-815 cells, neither could lyse K562 cells, and only activated cells from old mice could lyse EL-4 cells. Cytotoxic spleen cells from the old mice were more sensitive to anti-asialo-GM-1 and anti-Lyt-2.2 plus complement (C) treatment. While levels of IL-2 produced by spleen cells from young mice were higher, the addition of exogenous IL-2 had no effect on cytotoxic activity of the spleen cells from old mice. Exogenous IL-2, however, could lower cytotoxic activity of Con A-activated spleen cells from young mice. Activated spleen cells from old mice generated higher levels of IFN-gamma while the addition of an anti-IFN-gamma antibody boosted the level of cytotoxicity by Con A-activated spleen cells from young mice. These results suggest that IFN-gamma may act as a feedback inhibitory signal regulating the levels of cytotoxicity induced in spleen cells from young mice in response to Con A. The cytotoxic activity generated in Con A-activated spleen cells from old mice reflects a defect in this feed-back regulation.     

Estrogen effects on object memory and cholinergic receptors in young and old female mice.

We investigated whether object recognition memory is modulated by estrogen in young (5 month) and aged (24 month) female C57Bl/6J mice, and if cholinergic muscarinic receptors might contribute to this response. Mice that were ovariectomized, or ovariectomized plus estradiol-treated three weeks before behavioral testing or quantitative autoradiography were compared to intact mice. Memory for a previously encountered object deteriorated significantly between 3 and 6h after initial exposure, regardless of animal age. In both young and aged mice, estradiol-treated mice showed significantly greater recall than did ovariectomized mice. In both age groups, the apparent number of [(3)H]pirenzepine/M(1)-like and [(3)H]AFDX384/M(2)-like muscarinic receptor binding sites was reduced in the basal forebrain as well as its projection areas following ovariectomy, but this decrease was not alleviated by estrogen. Aging poorly affected object memory, but reduced muscarinic binding in some cortical subregions and in the caudate nucleus. These findings suggest that estrogen effects on memory in C57Bl/6J mice are not due to changes in the number of muscarinic receptors.     

Physiology of IgD. IX. Effect of IgD on immunoglobulin production in young and old mice

Weekly i.p. injections of IgD from birth in (SJL X BALB/c)F1 mice were found to accelerate the development of IgG- and IgA-secreting cells and to increase the numbers of Ig-secreting cells of all isotypes in 17-28-day-old mice, but not in 7-10-day-old mice. Similarly, repeated weekly injections of IgD in normal adult BALB/c mice increased the numbers of reverse plaque-forming cells/spleen for all isotypes studied, including IgM, IgG1, IgG2, and IgA, but not for IgD itself. No such effect was observed in IgD-treated aged (20 months old) BALB/c mice. The absence of an effect of IgD on Ig secretion appeared to correlate with a lack of induction of receptors for IgD on T cells of the host, both in 7-10-day-old and in aged mice. In 7-10-day-old mice this lack of induction appeared due to their very low numbers of L3T4+ T cells. A comparison was made between the effect of a single injection of IgD or lipopolysaccharide (LPS) on numbers of Ig-secreting cells in the spleen determined 1-7 days after injection. Both agents caused increases, but the increase in IgM-producing cells was much greater after LPS (day 4), while IgD caused a relatively greater increase in IgG2 and IgA (days 4-7). Increases in IgG1 and IgG3-producing cells induced by LPS and IgD were of similar magnitude (days 6-7). IgD production, however, was not increased. The number of cells producing antibody of anti-trinitrophenyl (TNP) specificity was enhanced by LPS (day 4), but not by a single injection of IgD, although more than one injection of IgD caused a significant increase in anti-TNP-producing cells above background. LPS, but not IgD, caused B cell proliferation in vitro in the presence or absence of gamma-irradiated T delta cells. However, in vivo, IgD injections caused a significant increase in the percentage of lymphoid follicles with germinal centers in lymph nodes from 17-21-day-old and normal adult mice, but not in 7-10-day-old or aged mice. Such an effect was also absent in 24-28-day-old mice, where germinal center development, even in untreated mice, was very high.     

Comparison of arterial wall properties in young and old racing greyhounds

Arteries were obtained from several sites in young (YGH) and old racing greyhounds (OGH). Segments were used for the determination of arterial wall mechanics under conditions of active (norepinephrine) and passive (Ca2+ free and 2 mM EGTA) smooth muscle. Contiguous segments were used for the chemical analysis of connective tissue, water and electrolyte content. The passive stiffness of arteries from OGH was consistently greater than that of the YGH. Collagen content and the collagen-elastin ratio were larger at all sites in the OGH. However, the connective tissue changes were not considered to be of sufficient magnitude to explain the changes in passive mechanics. Maximum values of active stress development were generally lower in arteries from the OGH as was their relative cell content. Active stress development normalized to smooth muscle cell cross-section was not uniformly changed in arteries from OGH. In spite of the lower active stress development in some arteries, the ability of smooth muscle to constrict lumen diameter was not different between OGH and YGH at transmural pressures in the physiological range. While a number of changes occur in arteries of purebred greyhounds with aging, they appear to occur in such a fashion that normal function is not grossly altered.     

Normal immune function in young and old DNA polymerase-beta deficient mice

The effect of the DNA polymerase-beta (beta-pol) deficiency on mitogenic response and cytokine production was studied in spleen lymphocytes from 4-5- and 20-22-month-old beta-pol(-/+) mice and their age-matched wild-type littermates. The proliferative response of lymphocytes to Concanavalin A (Con A) and lipopolysaccharide (LPS) was measured by [3H]thymidine incorporation, and the induction of cytokine production (interleukin (IL)-2, IL-4, and interferon necrosis factor (IFN)-gamma) was assessed by enzyme-linked immunosorbent assay. There was no significant difference in Con A- or LPS-induced proliferation or cytokine production in young beta-pol(-/+) mice compared with young wild-type littermates or in old beta-pol(-/+) mice compared with old wild-type littermates. However, mitogen-induced proliferation and cytokine production changed significantly with age. The proliferative response to Con A and to LPS, and the IL-2 production was significantly lower, and IL-4 and IFN-gamma levels were significantly higher in lymphocytes from old beta-pol(-/+) mice and old wild-type mice than in lymphocytes from young beta-pol(-/+) mice and young wild-type littermates. In addition, flow cytometric analysis showed no significant differences between young beta-pol(-/+) mice and young wild-type littermates or between old beta-pol(-/+) mice and old wild-type littermates in the proportion of B- and T-cell populations, and T-cell subsets. However, the number of lymphocytes expressing CD4+ phenotype slightly decreased and the proportion of lymphocytes expressing CD44/Pgp-1 (memory) phenotype increased with age. Thus, we found no evidence for alteration in immune function in DNA polymerase-beta deficient mice, although they exhibit a decline in immunologic function with age.     

Ability of monophosphoryl lipid A to augment the antibody response of young mice.

Treatment with nontoxic monophosphoryl lipid A increased the magnitude of the immunoglobulin M (IgM) antibody response to type III pneumococcal polysaccharide in young (2- to 4-week-old) mice. This was accompanied by the appearance of significant numbers of IgG1- and IgG3- secreting antibody-forming cells in 4-week-old mice. These findings indicate that monophosphoryl lipid A can be used as an adjuvant to improve the immunogenicity of poorly immunogenic antigens in young, immunologically immature animals.