Overexpression of the neuritotrophic cytokine S100beta precedes the appearance of neuritic beta-amyloid plaques in APPV717F mice

Homozygous APPV717F transgenic mice overexpress a human beta-amyloid precursor protein (betaAPP) minigene encoding a familial Alzheimer's disease mutation. These mice develop Alzheimer-type neuritic beta-amyloid plaques surrounded by astrocytes. S100beta is an astrocyte-derived cytokine that promotes neurite growth and promotes excessive expression of betaAPP. S100beta overexpression in Alzheimer's disease correlates with the proliferation of betaAPP-immunoreactive neurites in beta-amyloid plaques. We found age-related increases in tissue levels of both betaAPP and S100beta mRNA in transgenic mice. Neuronal betaAPP overexpression was found in cell somas in young mice, whereas older mice showed betaAPP overexpression in dystrophic neurites in plaques. These age-related changes were accompanied by progressive increases in S100beta expression, as determined by S100beta load (percent immunoreactive area). These increases were evident as early as 1 and 2 months of age, months before the appearance of beta-amyloid deposits in these mice. Such precocious astrocyte activation and S100beta overexpression are similar to our earlier findings in Down's syndrome. Accelerated age-related overexpression of S100beta may interact with age-associated overexpression of mutant betaAPP in transgenic mice to promote development of Alzheimer-like neuropathological changes.     

Extensive Lesions in Rat Insular Cortex Significantly Disrupt Taste Sensitivity to NaCl and KCl and Slow Salt Discrimination Learning

While studies of the gustatory cortex (GC) mostly focus on its role in taste aversion learning and memory, the necessity of GC for other fundamental taste-guided behaviors remains largely untested. Here, rats with either excitotoxic lesions targeting GC (n = 26) or sham lesions (n = 14) were assessed for postsurgical retention of a presurgically LiCl-induced conditioned taste aversion (CTA) to 0.1M sucrose using a brief-access taste generalization test in a gustometer. The same animals were then trained in a two-response operant taste detection task and psychophysically tested for their salt (NaCl or KCl) sensitivity. Next, the rats were trained and tested in a NaCl vs. KCl taste discrimination task with concentrations varied. Rats meeting our histological inclusion criterion had large lesions (resulting in a group averaging 80% damage to GC and involving surrounding regions) and showed impaired postsurgical expression of the presurgical CTA (LiCl-injected, n = 9), demonstrated rightward shifts in the NaCl (0.54 log₁₀ shift) and KCl (0.35 log₁₀ shift) psychometric functions, and displayed retarded salt discrimination acquisition (n = 18), but eventually learned and performed the discrimination comparable to sham-operated animals. Interestingly, the degree of deficit between tasks correlated only modestly, if at all, suggesting that idiosyncratic differences in insular cortex lesion topography were the root of the individual differences in the behavioral effects demonstrated here. This latter finding hints at some degree of interanimal variation in the functional topography of insular cortex. Overall, GC appears to be necessary to maintain normal taste sensitivity to NaCl and KCl and for salt discrimination learning. However, higher salt concentrations can be detected and discriminated by rats with extensive damage to GC suggesting that the other resources of the gustatory system are sufficient to maintain partial competence in these tasks, supporting the view that such basic sensory-discriminative taste functions involve distributed processes among central gustatory structures.     

1H, 13C NMR, and electronic absorption spectroscopic studies of the interaction of cyanide with aurothiomalate

The reaction between cyanide and aurothiomalate (Autm) has been studied by 1H and 13C NMR spectroscopy and by uv spectroscopy. At cyanide:Autm ratios greater than or equal to 2, aurocyanide, [Au(CN)2]-, is the sole product but was also produced at lower ratios. Two intermediates were also identified. These were a mixed ligand complex, [tmAuCN]-, which accounted for over 80% of the gold at a ratio of cyanide to Autm of 1, and a bisthiomalato complex, [Autm2]-, which accounted for 6.8% of the total gold at this ratio of cyanide to Autm. The formation of these complexes may be significant in the antiarthritic activity of Autm since cyanide is produced by potential target cells such as polymorphonuclear leukocytes.     

Coppery titi monkey (Plecturocebus cupreus) pairs display coordinated behaviors in response to a simulated intruder

Mate guarding and coordinated behaviors between partners are important for the maintenance of monogamous pair bonds. To study the effects of a perceived unfamiliar social intruder on females' behavior, we used coppery titi monkeys (Plecturocebus cupreus). We examined the effects of male aggressive temperament on females' behavior and the effects of each behavior performed by the male on the same female behavior. Using a mirror, we simulated a social intruder in the home territory and scored behaviors using an established ethogram. Based on our analysis of self-directed behaviors, females do not recognize themselves in the mirror. We then used general linear mixed models to predict percent change in females' behaviors as a function of (a) males' temperament, (b) males' behavior, and (c) an interaction between males' temperament and behavior. Male temperament did not significantly predict female behavior for any of our best fitting models. For percent change in female lip-smacking, male lip-smacking significantly predicted female lip-smacking (β = 0.74, SE = 0.22, t = 3.39; p = .004). There was a positive correlation between male and female agonistic behaviors such as back-arching/tail-lashing (β = 0.51, SE = 0.23, t = 2.22; p = .04) and for anxiety-related behaviors such as leaving the partner (β = 0.50, SE = 0.19, t = 2.68; p = .015), locomotion duration (β = 0.19, SE = 0.06, t = 2.98; p = .02), and locomotion frequency (β = 0.71, SE = 0.14, t = 5.17; p < .001). These findings on coordination of pair-mate behaviors may explain how titi monkeys display pair bond strength and ensure their reproductive success.     

Alloparenting experience affects future parental behavior and reproductive success in prairie voles (Microtus ochrogaster)

Various hypotheses have been proposed to explain the function of alloparental behavior in cooperatively breeding species. We examined whether alloparental experience as juveniles enhanced later parental care and reproductive success in the prairie vole (Microtus ochrogaster), a cooperatively breeding rodent. Juveniles cared for one litter of siblings (1EX), two litters of siblings (2EX) or no siblings (0EX). As adults, these individuals were mated to other 0EX, 1EX or 2EX voles, yielding seven different pair combinations, and we recorded measures of parental behaviors, reproductive success, and pup development. As juveniles, individuals caring for siblings for the first time were more alloparental; and as adults, 0EX females paired with 0EX males spent more time in the nest with their pups. Taken together, these results suggest that inexperienced animals spend more time in infant care. As parents, 1EX males spent more time licking their pups than 2EX and 0EX males. Pups with either a 1EX or 2EX parent gained weight faster than pups with 0EX parents during certain developmental periods. While inexperienced animals may spend more time in pup care, long-term benefits of alloparenting may become apparent in the display of certain, particularly important parental behaviors such as licking pups, and in faster weight gain of offspring.     

Phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) potentiates cardiac contractility via activation of the ryanodine receptor

Phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) is the most recently identified phosphoinositide, and its functions have yet to be fully elucidated. Recently, members of our muscle group have shown that PI(3,5)P2 plays an important role in skeletal muscle function by altering Ca(2+) homeostasis. Therefore, we hypothesized that PI(3,5)P2 may also modulate cardiac muscle contractility by altering intracellular Ca(2+) ([Ca(2+)](i)) in cardiac myocytes. We first confirmed that PI(3,5)P2 was present and increased by insulin treatment of cardiomyocytes via immunohistochemistry. To examine the acute effects of PI(3,5)P2 treatment, electrically paced left ventricular muscle strips were incubated with PI(3,5)P2. Treatment with PI(3,5)P2 increased the magnitude of isometric force, the rate of force development, and the area associated with the contractile waveforms. These enhanced contractile responses were also observed in MIP/Mtmr14(-/-) mouse hearts, which we found to have elevated levels of PI(3,5)P2. In cardiac myocytes loaded with fura-2, PI(3,5)P2 produced a robust elevation in [Ca(2+)](i). The PI(3,5)P2-induced elevation of [Ca(2+)](i) was not present in conditions free of extracellular Ca(2+) and was completely blocked by ryanodine. We investigated whether the phosphoinositide acted directly with the Ca(2+) release channels of the sarcoplasmic reticulum (ryanodine receptors; RyR2). PI(3,5)P2 increased [(3)H]ryanodine binding and increased the open probability (P(o)) of single RyR2 channels reconstituted in lipid bilayers. This strongly suggests that the phosphoinositide binds directly to the RyR2 channel. Thus, we provide inaugural evidence that PI(3,5)P2 is a powerful activator of sarcoplasmic reticulum Ca(2+) release and thereby modulates cardiac contractility.     

Regulatory issues in aging pharmacology

Many current drugs increase the average lifespan by preventing fatal diseases or by slowing down the progressive degenerative diseases that increase mortality. The existing strategies and guidelines for the development and regulatory approval of new drugs are designed for such compounds. Rapid advances in understanding molecular mechanisms of aging make it possible to envisage future drugs that extend the lifespan by regulating aging mechanism outside of disease pathways. Strategies for development and regulatory approval of such drugs remain to be defined. Since the drug candidates will be given to healthy, elderly subjects, safety requirements will be extremely high. Clinical studies of many years' duration will be necessary to prove changes in longevity. These time intervals may exceed those of patent protection and thus minimize commercial incentives. Despite these challenges, two broadly defined pathways are feasible. First, it may be possible to obtain public funding for studies with voluntary participation of humans consuming existing drugs or natural compounds in the 'expected to be safe' category. Second, the development of novel drugs may proceed on the basis of well-defined biomarkers of aging that can serve as surrogate end points in clinical studies. The emerging approaches will prompt the regulatory agencies into taking the first steps towards regulatory guidance.     

Hormonal and experiential predictors of infant survivorship and maternal behavior in a monogamous primate (Callicebus cupreus)

To better understand the roles that hormones and experience play in infant survival and maternal behavior in a biparental primate species, we analyzed urinary estrone (E(1)C) and pregnanediol glucuronide (PdG) from 24 socially housed titi monkey (Callicebus cupreus) females over 54 pregnancies (N = 1,430 samples). Pregnancies were categorized according to whether the infant survived (N = 35) or not (N = 19), and by maternal parity (primiparous: N = 9; multiparous: N = 45). Mothers of infants that survived had a significantly greater drop in PdG from the third trimester to the first week postpartum than mothers of infants that did not survive. Multiparous mothers had a greater increase in PdG from the first to the third trimester as well as greater increases in the E(1)C:PdG ratio from the first to the third trimester and from the third trimester to the first week postpartum. There were positive relationships between third trimester PdG and maternal carrying and nursing during the first week postpartum, and between maternal age and carrying during the infant's first month of life. There was a negative correlation between maternal age and PdG during the third trimester. These results suggest that elevated progesterone during late pregnancy followed by progesterone withdrawal immediately following parturition is associated with greater probability of infant survivorship and maternal behavior in this species, and that older females engage in more postpartum maternal care.     

The low density lipoprotein receptor regulates the level of central nervous system human and murine apolipoprotein E but does not modify amyloid plaque pathology in PDAPP mice

Apolipoprotein E (apoE), a chaperone for the amyloid beta (Abeta) peptide, regulates the deposition and structure of Abeta that deposits in the brain in Alzheimer disease (AD). The primary apoE receptor that regulates levels of apoE in the brain is unknown. We report that the low density lipoprotein receptor (LDLR) regulates the cellular uptake and central nervous system levels of astrocyte-derived apoE. Cells lacking LDLR were unable to appreciably endocytose astrocyte-secreted apoE-containing lipoprotein particles. Moreover, cells overexpressing LDLR showed a dramatic increase in apoE endocytosis and degradation. We also found that LDLR knock-out (Ldlr-/-) mice had a significant, approximately 50% increase in the level of apoE in the cerebrospinal fluid and extracellular pools of the brain. However, when the PDAPP mouse model of AD was bred onto an Ldlr-/- background, we did not observe a significant change in brain Abeta levels either before or after the onset of Abeta deposition. Interestingly, human APOE3 or APOE4 (but not APOE2) knock-in mice bred on an Ldlr-/- background had a 210% and 380% increase, respectively, in the level of apoE in cerebrospinal fluid. These results demonstrate that central nervous system levels of both human and murine apoE are directly regulated by LDLR. Although the increase in murine apoE caused by LDLR deficiency was not sufficient to affect Abeta levels or deposition by 10 months of age in PDAPP mice, it remains a possibility that the increase in human apoE3 and apoE4 levels caused by LDLR deficiency will affect this process and could hold promise for therapeutic targets in AD.