Potential misinterpretations using models of accelerated aging.
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Aging↗
Biomedical subjects
D E Harrison
Publications and source records attributed to D E Harrison.
Obesity minimizes the immunopotentiation of food restriction in ob/ob mice.
The objective of this study was to investigate food restriction-related changes in several indices of immune competence in young (11 wk old) and adult (33 wk old) female lean (+/?) and obese (ob/ob) C57BL/6J mice. Body weight accumulation, tail length accretion and organ weights were more severely curtailed by food restriction in obese mice than in lean mice. Tail collagen denaturation time increased with age, although the magnitude was greater in obese mice, and this change was minimized by food restriction. Splenocyte mitogen responses were generally not altered with age in lean or obese mice, whereas food restriction augmented these responses in lean mice while having no effect or reducing them in obese mice. The concanavalin A and phytohemagglutinin responses of splenocytes from young and adult obese mice were greater than those for lean mice, whereas the bacterial lipopolysaccharide response was elevated only in adult obese vs. lean mice. Flow cytometric analysis of splenocytes revealed an increase in Thy-1+ cells with food restriction vs. freely fed obese and lean mice, with a proportional decrease in Ig+ cells. Percentages of CD4+ and CD8+ cells increased with food restriction in both lean and obese mice. These results suggest that genetic obesity largely eliminates the immunopotentiating effects of food restriction, although the rate of "aging" may be reduced by food restriction.
Aging↗
Competitive repopulation in unirradiated normal recipients.
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Animals↗
Age-related gliosis in the white matter of mice.
A histopathologic study of the brains from 96 mice, ranging in age from 3 to 57 months in age, documents an age-associated increase in hypertrophic astrocytes in white matter. This report of gliosis is distinct from previously reported proliferation of glial cells in the grey matter. Four genotypes, CBA/HT6J, C57BL/6J, B6CBAT6F1J, and B6C3F1 were positive for this age-related lesion. Most very old mice utilized in this study were calorically restricted, a dietary manipulation long known to result in increased longevity in rodents. Caloric restriction appears to delay the age associated increase of this lesion. Immunoperoxidase staining for the astrocyte-specific glial fibrillary acidic protein (GFAP) confirmed the progressive increase in the density of stainable astrocytes with increase in age. GFAP staining of white matter increased in both diet groups with age. These findings present an interesting model for the study of aberrant cellular activity and perhaps neurodegeneration, modulated by caloric restriction.
Aging↗
Assessing permanent damage to primitive hematopoietic stem cells after chemotherapy using the competitive repopulation assay.
The competitive repopulation assay was used to document the effects of six chemotherapeutic agents on primitive hematopoietic stem cells. The assay measures the relative abilities of donor cells to produce circulating erythrocytes and lymphocytes in lethally irradiated congeneic mice over a period of 6 months. Long-lasting marrow reconstitutive deficits in cells of donor origin occurred after exposure to 5-fluorouracil (5FU), bis-chloronitrosourea (BCNU), cyclophosphamide (CTX), vincristine (VCR), and actinomycin D (ACT) but not after exposure to cytosine arabinoside (ARA). Repopulating abilities were reduced after as little as a single dose of CTX or BCNU. A second dose of BCNU caused even more severe effects. A single dose of 5FU had no effect on repopulating abilities despite a temporary 10-fold reduction in marrow cell number, but multiple doses reduced the marrow stem-cell replicative ability to less than half of the normal control levels. These effects were not reliably predicted or detected by colony-forming assays or by reductions in marrow cell number. Thus, long-lasting proliferative defects in the primitive hematopoietic stem-cell (PHSC) population can result from the use of chemotherapeutic agents. Such findings may have clinical implications, especially in individuals receiving repeated or prolonged administration of these agents or in instances of marrow transplantation.
Animals↗
Genetics of age-related hearing loss in mice: I. Inbred and F1 hybrid strains.
The auditory-evoked brainstem response (ABR) was used to assess hearing loss in five inbred strains of mice and all ten combinations of F1 hybrids. The inbred strains are CBA/H-T6J (CH), DBA/2J (D2), C57BL/6J (B6), BALB/cByJ (BY) and WB/ReJ (WB). The F1 hybrids are CHD2, CHB6, CHBY, CHWB, D2B6, D2BY, D2WB, B6BY, B6WB, and BYWB. At middle age (12, 16 months), mice were tested with click stimuli. At a relatively old age (23 months, near inbreds' median life span), they were tested with both click and tone-pip stimuli. The CH mice and their four F1 hybrid strains exhibit lower thresholds than the other strains, with the F1 strains being most sensitive (i.e., hybrid vigor). The D2 inbred and the three D2 F1 hybrids (excluding CHD2) exhibit the earliest and most severe hearing losses. The B6, BY and WB inbred strains exhibit severe hearing losses between 16 and 23 months of age; however, the B6BY, B6WB and BYWB F1 hybrids have significantly lower thresholds than their parental strains (genetic complementation). These data support a genetic model for recessive alleles at three different loci which contribute to age-related hearing loss. The CH mice have none of the recessive alleles, and the D2 mice are homozygous recessive for all three; the B6, BY and WB inbred strains are homozygous recessive respectively for one of the three loci.
Acoustic Stimulation↗
Husbandry factors and the prevalence of age-related amyloidosis in mice.
A retrospective study of the prevalence of amyloidosis in mice from several facilities was done. Amyloid deposition is an age-related lesion. The influence of common laboratory factors on the occurrence of this lesion was analyzed. This study documented genotypic difference in susceptibility to amyloidosis and showed that caging and pathogen status both impact on the number of cases of amyloidosis seen in a population. The lowest percentage of affected mice was seen when the animals were individually caged in a specific pathogen-free facility where conditions of stress were minimized.
Age Factors↗
Primitive hemopoietic stem cells: direct assay of most productive populations by competitive repopulation with simple binomial, correlation and covariance calculations.
Quantitative analyses of primitive hemopoietic stem cell (PHSC) populations are important both for basic biology and for clinical applications. Unfortunately, many conventional assays fail to measure long-term repopulating ability and maximal differentiating ability, the most important characteristics of the PHSC. The competitive repopulation assay described here focuses on this characteristic, assaying the precursors from which most differentiated cells are descended over large fractions of the life span in laboratory mice. Thus long-term repopulating ability and the ability to differentiate into both myeloid and lymphoid lineages are measured directly from 2.5 to 12.5 months after transplantation. This technique also has found high correlations between granulocytes, macrophages, and T and B lymphocytes as early as 3 weeks after transplantation. All or most differentiated cells of these widely disparate types appear to be descended from a common precursor cell, while myeloid-specific or lymphoid-specific precursors produce few or no descendants. However, large increases in variances between 3 and 6 weeks and 12 weeks after transplantation suggest that most of the initially active multilineage precursors are exhausted. Thus the ability to differentiate into widely disparate lineages does not establish long-term repopulating ability.
Animals↗
The same exhaustible multilineage precursor produces both myeloid and lymphoid cells as early as 3-4 weeks after marrow transplantation.
Hemopoietic precursors with the ability to differentiate into wide varieties of cell types are considered primitive, as are precursors with long-term repopulating ability. Here we study the populations of marrow precursors from which both myeloid and lymphoid lineages are descended shortly after transplantation. Surprisingly, few or none of these precursors show long-term repopulating ability. Equal portions of a mixture of marrow cells from C57BL/6J (B6) and congenic B6-Hbbd Gpi-1a mice are transplanted into a group of recipients. Three weeks later, highly significant correlations between percentages of B6 type T cells, B cells, granulocytes, and platelets in each recipient indicate that many lymphoid and myeloid cells are descended from common precursors. After 4-6 weeks, most correlations between lymphoid and myeloid cells improve, indicating that most or all differentiated cells are descended from common precursors. The more differentiated myeloid-specific precursors found in spleen colony-forming cell assays apparently fail to contribute significantly to the differentiated myeloid cell populations tested. By using the binomial model, in which variability of the data among the recipients is inversely related to the number of precursors in the mixture, donor precursor concentrations are estimated as approximately 21 per 10(5) marrow cells after 3 weeks, falling 3-fold to 6.6 per 10(5) after 4-6 weeks. This trend continues, with higher correlations, greater variabilities, and donor precursor concentrations of 1.9 per 10(5) marrow cells after 12-14 weeks and 1.4 per 10(5) after 24 weeks. Strong increases in variances between 3 and 12 weeks after transplantation suggest that most or all of the initially active multilineage precursors are exhausted during this time period. The fact that the ability of a hemopoietic stem cell to differentiate into widely disparate lineages is not associated with long-term repopulating ability requires a change in stem cell definitions, since primitive hemopoietic stem cells have traditionally been defined by both these abilities.
Animals↗
Evaluating functional abilities of primitive hematopoietic stem cell populations.
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Age Factors↗
Cellular determinants of age-related decrements in the T-cell mitogen response of B6CBAF1 mice.
Age-related changes in the cellular composition of the immune system that are associated with an impaired proliferative response to T-cell mitogens were identified for B6CBAF1 mice. The frequencies of precursors of Con A-induced IL-2-secreting cells (pHTL) and of Con A-induced cytotoxic cells (pCTL), determined by limiting dilution analysis, were lower for splenocytes from old mice, as were the proliferative responses to Con A and PHA, determined in conventional high cell density cultures for the same mice. The pHTL frequency correlated with the proliferative response to Con A (r2 = .94) and to PHA (r2 = .83) among old mice, but not among young; there were no correlations of pCTL frequency with proliferative responses. The reduced pHTL frequency in old mice resulted from: (a) an age-related doubling of the number of splenic B cells that diluted T cells, and (b) a 67% decline in the absolute number of Con A-reactive pHTL cells in the spleen that appeared despite the maintenance of normal numbers of total splenic CD4+ and CD8+ cells. Thus, both a decline in absolute pHTL numbers and an increase in the number of non-T cells in the spleen result in a diminished pHTL frequency that is closely linked to the impaired mitogen response observed for old B6CBAF1 mice.
Aging↗
Polygenic influences on the length of oestrous cycles in inbred mice involve MHC alleles.
Genetic influences on female reproductive cycles were analysed in histocompatibility-congenic strains of mice. Oestrous cycles of young, virgin mice of inbred-congenic strains, hybrid crosses (F1), and parental-hybrid backcrosses (F2) were monitored for 3 months. Oestrous cycles were categorized by length (inter-oestrous interval): 4, 5, 6, or 7-14 days. Mice with the following H-2 haplotypes had a greater proportion of 5-day oestrous cycles: H-2b, H-2r, H-2h2, H-2h4, and H-2i5. In contrast, the H-2k and H-2d haplotypes had mostly 4-day oestrous cycles. Influences of H-2 haplotype were seen on two genetic backgrounds, C57BL/10Sn and C3H. Non-H-2 alleles were also implied by different patterns of cycles between strains with the same H-2b haplotype: C57BL/10Sn with predominantly 5-day cycles vs. C57BL/6J with a mix of 4- and 5-day cycles. The genetic basis for strain differences was investigation in F1 hybrids and their backcrosses. F1 hybrids of an H-2b (C57BL/10Sn; 5-day cycles) and an H-2k (B10.BR; 4-day cycles) strain had mostly 5-day cycles, indicating dominance of an H-2b allele(s). However, F1 hybrids from the reciprocal B6 x B10 cross (both H-2b) also display a preponderance of 5-day cycles, indicating dominance of a non-H-2 autosomal allele from the C57BL/10Sn strain. Among F2 mice, a '4-day' phenotype segregated with homozygosity for the k haplotype (P < 0.05, chi 2). These findings demonstrate the influence of genetic differences at the major histocompatibility complex on oestrous cycles.
Alleles↗
Difficulties with studying accelerated aging.
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Aging↗
Most primitive hematopoietic stem cells are stimulated to cycle rapidly after treatment with 5-fluorouracil.
To test whether primitive hematopoietic stem cells (PHSC) cycle rapidly during recovery from an initial 5-fluorouracil (5-FU) treatment, two doses of 5-FU were administered 1, 3, 5 or 8 days apart. Cells from treated marrow donors were mixed with untreated competitor marrow that would produce genetically distinguishable erythrocytes and lymphocytes, using hemoglobin (Hb) and glucosephosphate isomerase (GPI) transplantation markers. These cell mixtures were injected into lethally irradiated hosts. Functional abilities of donor marrow populations were assessed after 3, 6, and 12 months as percentages of donor type Hb and GPI in the host's circulating erythrocytes and lymphocytes, respectively. Bone marrow from mice treated with two doses of 5-FU 3 to 5 days apart was severely affected, producing circulating erythroid and lymphoid cells an average of only 25% of normal for doses 3 days apart, and 14% of normal for doses 5 days apart. Two doses of 5-FU administered 1 day or 8 days apart had much smaller effects, producing circulating cells 75% or 58% of normal. Thus, most PHSC are stimulated to proliferate rapidly 3 to 5 days after treatment with 5-FU, but far fewer PHSC proliferate as early as 1 day, or as late as 8 days, after the 5-FU treatment.
Animals↗
Lymphoid and erythroid repopulation in B6 W-anemic mice: a new unirradiated recipient.
The W-anemic family of mouse mutants is an important model for studying repopulation in unirradiated recipients. This is the first study of blood lymphoid cell repopulation in adult W-anemic mutants given high doses of marrow cells, and it shows a wide difference in repopulation rates of circulating lymphoid and erythroid cells. This study also offers an improved model for marrow transplantation, using W alleles that are spontaneous mutations on the widely used inbred strain C57BL/6J (B6). Unirradiated B6-W41J/W41J or -W41J/W39J recipients of 2 x 10(6) B6 marrow cells are completely repopulated with donor erythrocytes after 3 months, whereas complete repopulation of lymphocytes requires a year. Surprisingly, the eventual degree of repopulation is independent of the severity of the mutation. The new mutants are not as anemic as the commonly used WBB6F1-W/Wv anemic mutants, they have a much higher ability to form macroscopic spleen colonies (spleen colony-forming units, CFU-S), and B6-W41J/W41J mice are fertile. Nevertheless, lymphoid and erythroid repopulation occur to a similar extent in B6-W41J/W41J or -W41J/W39J and in WBB6F1-W/Wv anemic mutants. Repopulation is more rapid in the latter, but host cells may be damaged by B6 reactions against the WB parent. Avoiding graft-versus-host reactions, hybrid resistance, and similar complications are important advantages in using donors and unirradiated recipients all on the B6 mouse genetic background. Additionally, congenic B6 mice provide a variety of genetic markers, allowing myeloid and lymphoid repopulation to be readily quantitated.
Anemia↗
Effects of transplantation on the primitive immunohematopoietic stem cell.
Transplantation has strong deleterious effects on the primitive immunohematopoietic stem cells (PSC) from which circulating lymphocytes and erythrocytes are descended. We studied these effects over 300-400 d, testing whether PSC numbers, repopulating abilities, or both, were reduced. Equivalent PSC numbers were estimated in recipients of mixtures of genetically different cells, using the binomial model with covariance. Percentages of lymphocyte and erythrocyte types were closely correlated, as were percentages of either type sampled at intervals of several months. This suggests that the same PSC produced lymphoid and myeloid cells, and that most circulating cells were descended from the same PSC over hundreds of days. Equivalent PSC concentrations were approximately 1/10(5) fresh marrow cells, and were about twofold lower using previously transplanted marrow. However, such marrow repopulated only one-seventh to one-eighth as well as fresh marrow. Apparently, transplantation not only reduces PSC concentrations, but also reduces the repopulating ability per PSC. This may result from excessive stimuli to differentiate that overbalance the stimuli for PSC to replenish themselves.
Analysis of Variance↗
5-Fluorouracil spares hemopoietic stem cells responsible for long-term repopulation.
The long-term immunohemopoietic reconstituting ability of bone marrow, treated with a single administration of 5-fluorouracil (5-FU), was measured to determine whether 5-FU caused any deleterious effect upon primitive stem cells (PSCs). Cells from 5-FU-treated marrow donors were mixed in four different proportions of total marrow contents with untreated competitor marrow containing genetically distinguishable hemoglobin (Hb) and glucosephosphate isomerase (GPI) transplantation markers. These cell mixtures were introduced into lethally irradiated hosts. The functional ability of the donor cell population was assessed by measuring the percentage of donor type Hb and GPI found in the host's circulating erythrocytes and lymphocytes, respectively. Bone marrow from mice treated with 5-FU 1, 5, and 8 days prior to transplantation produced circulating lymphoid and erythroid cells as well as equal fractions of untreated fresh marrow when surveyed approximately 90 days after transplantation. Normal reconstitutive ability was thus maintained despite a tenfold reduction in marrow cell numbers when donor mice had been treated with 5-FU 5 days prior to transplantation. Donor marrow treated with 5-FU 15 days prior to transplantation had slightly decreased repopulating ability in one of two experiments. A second round of repopulation was stimulated subsequent to the initial 90-day screening by giving hosts a sublethal (500 rad) dose of irradiation. After 3-4 months, Hb and GPI parameters were the same as preirradiation values. Thus, the radioresistance of 5-FU treated PSCs remains comparable to that of fresh marrow, and their relative repopulating ability was not comprised by the additional stress of sublethal irradiation. After both rounds of repopulation the myeloid and lymphoid pathways were repopulated equally well by PSCs surviving 5-FU treatment. Repopulation of both pathways to the same extent suggests a common precursor as the proliferative agent. These results indicate that the PSCs were unaffected after a single treatment with 5-FU, although they were concentrated tenfold.
Animals↗
Numbers and functions of transplantable primitive immunohematopoietic stem cells. Effects of age.
This report introduces a new method in immunology, a use of the binomial formula with covariance to estimate numbers and proliferative patterns of the most primitive lymphoid precursors. We studied the primitive stem cells (PSC) from which most circulating lymphocytes and erythrocytes were descended during 300 to 400 days in recipients of genetically distinguishable marrow mixtures in competitive repopulation. Equivalent PSC concentrations (Eq. PSC Conc. or Conc.) were estimated, with the notion of common PSCs contributing equally in lymphoid and myeloid compartments. Similar estimation was done for common PSCs from which lymphocytes (and erythrocytes) drawn at successive sampling times about 100 days apart were descended. The percentages of lymphocyte and erythrocyte types, P1 and Pe, measured in each recipient were closely correlated, especially after 6 months and later. Close correlations were also found in cells sampled at successive one hundred day intervals, especially after the first. Apparently a few PSCs or their direct descendents produced most of the blood lymphocytes and E, and this production continued for many months. Concentrations of these PSCs (Equivalent PSC concentrations) were about one per 10(5) marrow cells from young donors. This is much lower than previous estimates, probably because our methods focus only on the most interesting precursors, those from which most of the circulating cells were descended. Equivalent PSC concentrations were about two-fold higher in old donors; old marrow produced correspondingly higher P1 and Pe values, but these declined with time. There were also small increases with time in the P1 and Pe values with young donors. To explain the temporal trends, we suggest that excess concentrations of precursors less primitive than PSC are present in old marrow, and their contribution to the differentiated cell population gradually declines. Possibly such precursors, as well as true PSC, proliferate in old donors to compensate for deficiencies that develop with age.
Aging↗