Fibrillar beta-amyloid evokes oxidative damage in a transgenic mouse model of Alzheimer's disease.

Beta-amyloid is one of the most significant features of Alzheimer's disease, and has been considered to play a pivotal role in neurodegeneration through an unknown mechanism. However, it has been noted that beta-amyloid accumulation is associated with markers of oxidative stress including protein oxidation (Smith et al., 1997), lipid peroxidation (Mark et al., 1997; Sayre et al., 1997), advanced glycation end products (Smith et al., 1994), and oxidation of nucleic acids (Nunomura et al., 1999). Furthermore, studies from cultured cells have shown that beta-amyloid leads to an increase in hydrogen peroxide levels (Behl et al., 1994), and the production of reactive oxygen intermediates (Harris et al., 1995). Taken together, this evidence supports the idea that beta-amyloid plays a key role in oxidative stress-evoked neuropathology. In this study, we examined the induction of oxidative stress in response to amyloid load in a mouse model of Alzheimer's disease. The mice carrying mutant amyloid precursor protein and presenilins-1 (Goate et al., 1991; Hardy, 1997), develops beta-amyloid deposits at 10-12 weeks of age and show several features of the human disease (Holcomb et al., 1998; Matsuoka et al., 2001; McGowan et al., 1999; Takeuchi et al., 2000; Wong et al., 1999). Both 3-nitrotyrosine and 4-hydroxy-2-nonenal (protein and lipid oxidative stress markers, respectively) associate strongly with fibrillar beta-amyloid, but not with diffuse (thioflavine S negative) beta-amyloid, and the levels increase in relation to the age-associated increase in fibrillar amyloid load.From these data we suggest that fibrillar beta-amyloid is associated with oxidative damage which may influence disease progression in the Alzheimer's disease brain.

Lack of nigral pathology in transgenic mice expressing human alpha-synuclein driven by the tyrosine hydroxylase promoter.

alpha-Synuclein has been identified as a major component of Lewy body inclusions, which are one of the pathologic hallmarks of idiopathic Parkinson's disease. Mutations in alpha-synuclein have been found to be responsible for rare familial cases of Parkinsonism. To test whether overexpression of human alpha-synuclein leads to inclusion formation and neuronal loss of dopaminergic cells in the substantia nigra, we made transgenic mice in which the expression of wild-type or mutant (A30P and A53T) human alpha-synuclein protein was driven by the promoter from the tyrosine hydroxylase gene. Even though high levels of human alpha-synuclein accumulated in dopaminergic cell bodies, Lewy-type-positive inclusions did not develop in the nigrostriatal system. In addition, the number of nigral neurons and the levels of striatal dopamine were unchanged relative to non-transgenic littermates, in mice up to one year of age. These findings suggest that overexpression of alpha-synuclein within nigrostriatal dopaminergic neurons is not in itself sufficient to cause aggregation into Lewy body-like inclusions, nor does it trigger overt neurodegenerative changes.

Child factor in measurement dependability.

A primary consideration in longitudinal growth studies is the identification of growth from error components. While previous research has considered matters of measurement accuracy and reproducibility in detail, few reports have investigated the errors of measurement due to aspects of the physiology and cooperation of the child. The present study directly assesses this source of measurement undependability for the first time. Investigation of total measurement error variance in 925 recumbent length replicates taken over stasis intervals in growth identifies that between 60% and 70% of total measurement unreliability is due to a child factor undependability. Individual differences are significant and longitudinal growth analyses should consider two to three times the technical error of measurement statistic as a reasonable estimate of the total unreliability for any single measurement of an infant's recumbent length. These results raise issues regarding analytic methods as applied to serial growth data.

Inflammatory responses to amyloidosis in a transgenic mouse model of Alzheimer's disease.

Mutations in the amyloid precursor protein (APP) and presenilin-1 and -2 genes (PS-1, -2) cause Alzheimer's disease (AD). Mice carrying both mutant genes (PS/APP) develop AD-like deposits composed of beta-amyloid (Abeta) at an early age. In this study, we have examined how Abeta deposition is associated with immune responses. Both fibrillar and nonfibrillar Abeta (diffuse) deposits were visible in the frontal cortex by 3 months, and the amyloid load increased dramatically with age. The number of fibrillar Abeta deposits increased up to the oldest age studied (2.5 years old), whereas there were less marked changes in the number of diffuse deposits in mice over 1 year old. Activated microglia and astrocytes increased synchronously with amyloid burden and were, in general, closely associated with deposits. Cyclooxygenase-2, an inflammatory response molecule involved in the prostaglandin pathway, was up-regulated in astrocytes associated with some fibrillar deposits. Complement component 1q, an immune response component, strongly colocalized with fibrillar Abeta, but was also up-regulated in some plaque-associated microglia. These results show: i) an increasing proportion of amyloid is composed of fibrillar Abeta in the aging PS/APP mouse brain; ii) microglia and astrocytes are activated by both fibrillar and diffuse Abeta; and iii) cyclooxygenase-2 and complement component 1q levels increase in response to the formation of fibrillar Abeta in PS/APP mice.

Nutrient composition of human milk.

A complex interplay of maternal homeostatic mechanisms influences nutrient transfer to nursing infants, and with a few exceptions, excess maternal intake or a moderate deficiency in the maternal diet does not appreciably alter nutrient transfer to infants unless it has persisted for some time. Milk vitamins D and K contents, even in apparently well-nourished women, may not always provide adequate amounts for infants. Investigations provide evidence that human milk possesses many unique characteristics and that maternal and environmental influences are stronger than previously recognized and appreciated. A complete body of knowledge does not exist to serve as a basis for dietary recommendations to ensure optimal nutrition for mothers and infants. The success of lactation usually is measured in terms of infant performance, and cost and consequence to the mother are seldom considered. Human milk feeding is recommended for the entire first year of life, but few studies focus on the nursing dyad for more than 3 months' duration. Continued study is needed so that nutritional adequacy may be maintained and appropriate dietary guidance can be provided. When human milk feeding is not practiced, modern and reliable data on human milk constituents and their significance to infants also are essential for the preparation of formulas, especially those not based on bovine milk. The adequacy of human milk substitutes cannot be predicted from compositional analysis because of possible differences in compartmentalization and molecular form of nutrients, and such preparations must be evaluated using specific indices of nutrient use, together with traditional anthropometric measures in infants.

Brain expression of presenilins in sporadic and early-onset, familial Alzheimer's disease.

BACKGROUND: Mutations in the presenilin proteins cause early-onset, familial Alzheimer's disease (FAD). MATERIALS AND METHODS: We characterized the cellular localization and endoproteolysis of presenilin 2 (PS2) and presenilin 1 (PS1) in brains from 25 individuals with presenilin-mutations causing FAD, as well as neurologically normal individuals and individuals with sporadic Alzheimer's disease (AD). RESULTS: Amino-terminal antibodies to both presenilins predominantly decorated large neurons. Regional differences between the broad distributions of the two presenilins were greatest in the cerebellum, where most Purkinje cells showed high levels of only PS2 immunoreactivity. PS2 endoproteolysis in brain yielded multiple amino-terminal fragments similar in size to the PS1 amino-terminal fragments detected in brain. In addition, two different PS2 amino-terminal antibodies also detected a prominent 42 kDa band that may represent a novel PS2 form in human brain. Similar to PS1 findings, neither amino-terminal nor antiloop PS2 antibodies revealed substantial full-length PS2 in brain. Immunocytochemical examination of brains from individuals with the N141I PS2 mutation or eight different PS1 mutations, spanning the molecule from the second transmembrane domain to the large cytoplasmic loop domain, revealed immunodecoration of no senile plaques and only neurofibrillary tangles in the M139I PS1 mutation stained with PS1 antibodies. CONCLUSIONS: Overall presenilin expression and the relative abundance of full-length and amino-terminal fragments in presenilin FAD cases were similar to control cases and sporadic AD cases. Thus, accumulation of full-length protein or other gross mismetabolism of neither PS2 nor PS1 is a consequence of the FAD mutations examined.

Nutritional guidance is needed during dietary transition in early childhood.

OBJECTIVE: To assess dietary nutritional quality during dietary transition to a modified adult-style diet in the second year of life. DESIGN: A total of 55 children from 12 to 18 months old and their parents were studied. Dietary intake and indices of growth were measured monthly. Dietary data were collected monthly and tabulated using the Minnesota Nutrient Data System. Data were evaluated using repeated-measures analysis of variance, time trend, and correlational analyses. RESULTS: Mean energy intake increased from 12 to 18 months of age (926+/-24 kcal to 1062+/-33 kcal) with contributions from energy-yielding macronutrients remaining relatively constant. Throughout the study, fat intakes were below 30% of energy for 22% to 33% of the sample. Micronutrient intake patterns were diverse with intake for some nutrients (vitamins A, C, B(6), B(12), and D and calcium) remaining above recommended levels despite changes over the course of the study. Folate intakes increased from 79% of the recommended value at 12 months old to approximately 100% at 18 months old. Zinc and vitamin E intakes were well below recommended levels throughout the study, and iron decreased markedly from 96% of the recommended level at 12 months old to 76% at 18 months old. APPLICATIONS/CONCLUSIONS: These data show that intakes of some key nutrients are low during the period of dietary transition in early childhood, and intakes for some nutrients actually decrease despite increases in energy intake. Furthermore, because a considerable portion of children studied were consuming low-fat diets, it is clear that many parents are not following the only pediatric nutrition recommendations that currently exist. These findings argue strongly for the development of dietary guidance that not only addresses fat restriction, but also assists parents in selecting diets that support optimum growth and development in young children.nutrient intake, infants, dietary density.

Breast-feeding through the first year predicts maternal control in feeding and subsequent toddler energy intakes.

OBJECTIVE: Current recommendations for infant feeding encourage breast-feeding through the first year. This research was conducted to evaluate associations among breast-feeding, maternal control of child feeding, and the dietary intake of toddlers during the second year of life. In particular, we sought to determine whether breast-feeding through the first year and subsequent toddler intake was mediated via maternal control of child feeding. DESIGN/SUBJECTS: Fifty-five white infants and their mothers were monitored longitudinally from age 12 or 13 months to age 18 months. MAIN OUTCOME MEASURES: Breast-feeding through the first year and maternal control in infant feeding were evaluated as predictors of energy intake at age 18 months. STATISTICAL ANALYSES PERFORMED: Regression analysis was used to evaluate predictors of toddler energy intake at age 18 months. A mediation model tested if the relationship between breast-feeding and infant intake was mediated by maternal control in feeding. RESULTS: Breast-feeding through the first year was associated with higher toddler energy intakes at age 18 months through its influence on maternal control in feeding. Mothers who breast-fed their infants for at least 12 months used lower levels of control in feeding. Lower levels of maternal control in feeding were associated with higher toddler energy intakes. The highest energy intakes among children aged 18 months were observed among taller and leaner toddlers. APPLICATIONS/CONCLUSIONS: Our findings suggest that breast-feeding through the first year may have an effect on children's energy intake by shaping mothers' child-feeding practices. These findings may be used by clinicians to assist parents in making informed decisions about choice of infant-feeding method and to provide anticipatory guidance regarding infant-feeding style when initiating dietary diversity.

Characterization of pathology in transgenic mice over-expressing human genomic and cDNA tau transgenes.

To examine the normal cellular function of tau and its role in pathogenesis, we have created transgenic mice that overexpress a tau transgene derived from a human PAC that contains the coding sequence, intronic regions, and regulatory regions of the human gene. All six isoforms of human tau are represented in the transgenic mouse brain at the mRNA and protein level and the human tau is distributed in neurites and at synapses, but is absent from cell bodies. A comparison between the genomic tau mice and mice that overexpress a tau cDNA transgene shows that overall, the distribution of tau is similar in the two lines, but human tau is located in the somatodendritic compartment of many neurons in the cDNA mice. Tau-immunoreactive axonal swellings were found in the spinal cords of the cDNA mice, which correlated with a hind-limb abnormality, whereas neuropathology was essentially normal in the genomic mice up to 8 months of age.

A loss of function mutation of presenilin-2 interferes with amyloid beta-peptide production and notch signaling.

Presenilin-1 (PS1) facilitates gamma-secretase cleavage of the beta-amyloid precursor protein and the intramembraneous cleavage of Notch1. Although Alzheimer's disease-associated mutations in the homologous presenilin (PS2) gene elevate amyloid beta-peptide (Abeta42) production like PS1 mutations, here we demonstrate that a gene ablation of PS2 (unlike that of PS1) in mice does not result in a severe phenotype resembling that of Notch-ablated animals. To investigate the amyloidogenic function of PS2 more directly, we mutagenized a conserved aspartate at position 366 to alanine, because the corresponding residue of PS1 is known to be required for its amyloidogenic function. Cells expressing the PS2 D366A mutation exhibit significant deficits in proteolytic processing of beta-amyloid precursor protein indicating a defect in gamma-secretase activity. The reduced gamma-secretase activity results in the almost complete inhibition of Abeta and p3 production in cells stably expressing PS2 D366A, whereas cells overexpressing the wild-type PS2 cDNA produce robust levels of Abeta and p3. Using highly sensitive in vivo assays, we demonstrate that the PS2 D366A mutation not only blocks gamma-secretase activity but also inactivates PS2 activity in Notch signaling by inhibiting the proteolytic release of the cytoplasmic Notch1 domain. These data suggest that PS2 is functionally involved in Abeta production and Notch signaling by facilitating similar proteolytic cleavages.

Maternal folate status during extended lactation and the effect of supplemental folic acid.

BACKGROUND: Folate requirements during lactation are not well established. OBJECTIVE: We assessed the effects of dietary and supplemental folate intakes during extended lactation. DESIGN: Lactating women (n = 42) were enrolled in a double-blind, randomized, longitudinal supplementation trial and received either 0 or 1 mg folic acid/d. At 3 and 6 mo postpartum, maternal folate status was assessed by measuring erythrocyte, plasma, milk, and dietary folate concentrations; plasma homocysteine; and hematologic indexes. Infant anthropometric measures of growth, milk intake, and folate intake were also assessed. RESULTS: In supplemented women, values at 6 mo for erythrocyte and milk folate concentrations and for plasma homocysteine were not significantly different from those at 3 mo. In supplemented women compared with unsupplemented women at 6 mo, values for erythrocyte folate (840 compared with 667 nmol/L; P < 0.05), hemoglobin (140 compared with 134 g/L; P < 0.02), and hematocrit (0.41 compared with 0.39; P < 0.02) were higher and values for reticulocytes were lower. In unsupplemented women, milk folate declined from 224 to 187 nmol/L (99 to 82 ng/mL), whereas plasma homocysteine increased from 6.7 to 7.4 micromol/L. Dietary folate intake was not significantly different between groups (380+/-19 microg/d) and at 6 mo was correlated with plasma homocysteine in unsupplemented women (r = -0.53, P < 0.01) and with plasma folate in supplemented women (r = 0.49, P < 0.02). CONCLUSIONS: A dietary folate intake of approximately 380 microg/d may not be sufficient to prevent mobilization of maternal folate stores during lactation.

Human milk: nutritional aspects of a dynamic food.

The composition and volume of human milk progressively changes with the onset and duration of lactation and can be influenced by maternal nutritional factors. Current evidence indicates that infant demand is the major determinant of the quantity of milk transferred to the nursing infant. Human milk is remarkable for its variability, and ranges of intakes of milk constituents are comparable with normal patterns of infant growth and development. Lipids are by far the most variable constituents in human milk with both long-term maternal nutrition states and daily intake capable of exerting an influence. Maternal vitamin intake bears a strong relationship to milk content, and appropriate intakes of vitamins D and K may not always be furnished to nursing infants. Major and trace minerals in human milk are not greatly affected by maternal diet, with selenium and iodine being notable exceptions. Compartmentalization and molecular forms of the trace elements in human milk are associated with high infant bioavailability. The success of lactation should be measured using maternal and infant indices of nutritional adequacy.

Self-selected diets of lactating women often fail to meet dietary recommendations.

OBJECTIVE: To assess longitudinally nutrient intakes of lactating women during the postpartum period. DESIGN: Dietary data from lactating women were collected by means of 2-day food records at 3 and 6 months postpartum. Intake of energy and selected nutrients was tabulated and compared with dietary standards. SUBJECTS: The 52 lactating women enrolled in the study lived in a university community, were apparently healthy, had a body mass index within normal range, were successfully nursing a term infant, and planned to nurse for at least 6 months. STATISTICAL ANALYSES PERFORMED: Paired t tests and Stuart-Maxwell chi(2) analyses. RESULTS: Mean energy intakes were below the Recommended Dietary Allowance. Mean intakes of most nutrients met or exceeded recommended standards except for zinc and vitamins D and E at both 3 and 6 months postpartum. Calcium and folate intakes were also below standards at 6 months. Although mean iron intake exceeded the standard at both measurement times, there was a significant decline from 3 to 6 months. Relative frequencies of mothers meeting various percentages of standards differed significantly from 3 to 6 months for calcium; iron; folate; and vitamins E, D, and B-6. At 6 months, significant increases were noted in the number of women reporting calcium, folate, and vitamin B-6 intakes at less than one half of the recommended amounts. APPLICATIONS/CONCLUSIONS: Guidance for lactating women should stress food sources of nutrients likely to be limited in their diets: calcium; zinc; folate; and vitamins E, D, and B-6.

Maternal folate status and lactation.

Folate plays an essential role in DNA, RNA, and protein biosynthesis. For this reason, the physiological need for this vitamin is increased during periods of rapid anabolic activity such as pregnancy and lactation. Although the importance of folate and the consequences of suboptimal folate status during pregnancy, especially during the periconceptional period, are well appreciated, little is known about the value of folate during lactation. The limited number of studies available on folate intake during lactation suggest that many women do not consume an adequate amount of folate and that recommended target intakes may be too low. Although inadequate maternal folate intake does not affect milk folate concentration unless maternal deficiency is severe, potential consequences of suboptimal folate nutrition to both the mother and her future offspring should also be considered.

Do milk-borne cytokines and hormones influence neonatal immune cell function?

Cytokines, growth factors and various hormones collectively control the proliferation, survival, differentiation and function of immune cells. A wide array of these compounds is present in maternal milk and ingested by neonates during a period of rapid maturation of gut-associated and peripheral lymphoid tissues. The functional consequences of most milk immunomodulatory constituents in neonates are unknown. However, there is evidence that milk prolactin acts as a developmental regulator of the neonatal immune system, supporting the premise that milk constituents with immunomodulatory activity may serve as neonatal immunodevelopment agents.

Regulation of milk lipid secretion and composition.

Triacylglycerols make up 98% of the lipid content of milk, ranging in different species from 0 to 50% of the total milk volume. The fatty aid composition of the triacylglycerols depends on the species, the dietary fatty acid composition, and the carbohydrate-to-lipid ratio of the diet. The rate of lipid synthesis in the lactating mammary gland depends on the stage of mammary development and is decreased by fasting and starvation in ruminants and rodents but not in species that fast during lactation, such as seals and hibernating bears. Regulatory agents include insulin, prolactin, and non-esterified fatty acids. Dietary trans fatty acids may depress milk lipid synthesis under certain conditions. Evidence is presented that fatty acids may play a major regulatory role in acute changes in de novo mammary fatty acid synthesis, acting primarily on the activity of acetyl coenzyme A carboxylase.

Milk-borne prolactin and neonatal development.

Milk is primarily regarded as a food furnishing essential nutrients for infant growth and development, but milk can also serve as a vehicle for mother to neonate transfer of molecules that regulate development. A wide array of biologically active compounds such as hormones, cytokines and enzymes are present in milk, especially early milk. The premise that prolactin (PRL) in milk is an important and possibly essential developmental factor for the newborn is explored. Both PRL and structurally modified isoforms are abundant in early milk and gradually diminish with the progression of lactation. Milk PRL is absorbed and biologically active in the neonate. Assays of PRL variants, experimental paradigms to test them as developmental regulators and the body of evidence supporting the hypothesis that milk PRL regulates differentiation and maturation of neonatal neuroendocrine, reproductive, and immune systems is presented.