Age-Dependent Changes in Geometry,Tissue Composition and Mechanical Properties of Fetal to Adult Cryopreserved Human Heart Valves

There is limited information about age-specific structural and functional properties of human heart valves, while this information is key to the development and evaluation of living valve replacements for pediatric and adolescent patients. Here, we present an extended data set of structure-function properties of cryopreserved human pulmonary and aortic heart valves, providing age-specific information for living valve replacements. Tissue composition, morphology, mechanical properties, and maturation of leaflets from 16 pairs of structurally unaffected aortic and pulmonary valves of human donors (fetal-53 years) were analyzed. Interestingly, no major differences were observed between the aortic and pulmonary valves. Valve annulus and leaflet dimensions increase throughout life. The typical three-layered leaflet structure is present before birth, but becomes more distinct with age. After birth, cell numbers decrease rapidly, while remaining cells obtain a quiescent phenotype and reside in the ventricularis and spongiosa. With age and maturation–but more pronounced in aortic valves–the matrix shows an increasing amount of collagen and collagen cross-links and a reduction in glycosaminoglycans. These matrix changes correlate with increasing leaflet stiffness with age. Our data provide a new and comprehensive overview of the changes of structure-function properties of fetal to adult human semilunar heart valves that can be used to evaluate and optimize future therapies, such as tissue engineering of heart valves. Changing hemodynamic conditions with age can explain initial changes in matrix composition and consequent mechanical properties, but cannot explain the ongoing changes in valve dimensions and matrix composition at older age.     

Age-Dependent Changes in Intrinsic Neuronal Excitability in Subiculum after Status Epilepticus

Kainic acid-induced status epilepticus (KA-SE) in mature rats results in the development of spontaneous recurrent seizures and a pattern of cell death resembling hippocampal sclerosis in patients with temporal lobe epilepsy. In contrast, KA-SE in young animals before postnatal day (P) 18 is less likely to cause cell death or epilepsy. To investigate whether changes in neuronal excitability occur in the subiculum after KA-SE, we examined the age-dependent effects of SE on the bursting neurons of subiculum, the major output region of the hippocampus. Patch-clamp recordings were used to monitor bursting in pyramidal neurons in the subiculum of rat hippocampal slices. Neurons were studied either one or 2-3 weeks following injection of KA or saline (control) in immature (P15) or more mature (P30) rats, which differ in their sensitivity to KA as well as the long-term sequelae of the KA-SE. A significantly greater proportion of subicular pyramidal neurons from P15 rats were strong-bursting neurons and showed increased frequency-dependent bursting compared to P30 animals. Frequency-dependent burst firing was enhanced in P30, but not in P15 rats following KA-SE. The enhancement of bursting induced by KA-SE in more mature rats suggests that the frequency-dependent limitation of repetitive burst firing, which normally occurs in the subiculum, is compromised following SE. These changes could facilitate the initiation of spontaneous recurrent seizures or their spread from the hippocampus to other parts of the brain.     

Age-Dependent Changes in Calretinin Immunoreactivity and its Protein Level in the Gerbil Hippocampus

Calretinin (CR)-immunoreactive interneurons are well known as the interneuron specific interneurons in the hippocampus. CR-immunoreactive neurons form cellular network and regulate the activity of other GABAergic inhibitory interneurons in the hippocampus. In the present study, we investigated age-related changes in CR-immunoreactive neurons and protein levels in the gerbil hippocampus during normal aging. In all subregions of the gerbil hippocampus, the number of CR-immunoreactive neurons was significantly decreased in the postnatal month 6 (PM 6) group compared to that in the PM 1 group. Thereafter, CR-immunoreactive neurons were decreased with age. In addition, the number of CR-immunoreactive cells in the subgranular zone were significantly decreased in the PM 6 group. We also observed that CR protein levels were decreased gradually with age. These results indicate that both CR immunoreactivity and its protein level were decreased with age in the gerbil hippocampus during normal aging.     

Age-Dependent Changes in Brain GABA Turnover Rates in Two Inbred Strains of Mice

gamma-Aminobutyric acid (GABA) steady-state levels and turnover rates have been determined in 15 brain areas of 21-day- and 3-month-old DBA/2J (DBA) and C57B1/6J (C57) mice. These two inbred strains differ by their susceptibility to audiogenic seizures; moreover, the involvement of GABAergic neurotransmission has been suggested in the control of this behavior. Turnover rates are generally higher at 21 days than at 3 months of age. There are few significant differences in the GABA steady-state levels between 21-day-old seizure-prone DBA mice when compared with seizure-resistant C57 mice. In the DBA mice, the steady-state level is higher in the olfactory bulbs and lower in the posterior colliculus and the olfactory tubercles than in the C57 mice. Although there are some significant differences in GABA turnover rates and steady-state levels, intra or inter strains, it is difficult to correlate directly these differences with seizure susceptibility.     

Age-Dependent Changes in Ecosystem Carbon Fluxes in Managed Forests in Northern Wisconsin,USA

The age-dependent variability of ecosystem carbon (C) fluxes was assessed by measuring the net ecosystem exchange of C (NEE) in five managed forest stands in northern Wisconsin, USA. The study sites ranged in age from 3-year-old clearcut to mature stands (65 years). All stands, except the clearcut, accumulated C over the study period from May to October 2002. Seasonal NEE estimates were −655 ± 17.5 g C m^–2 in the mature hardwood (MHW), −648 ± 16.8 in the mature red pine (MRP), −195 ± 15.6 in the pine barrens (PB), +128 ± 17.1 in the young hardwood clearcut (YHW), and −313 ± 14.6 in the young red pine (YRP). The age-dependent differences were similar in the hardwood and conifer forests. Even though PB was not part of either the hardwood or conifer chronosequence, and had a different disturbance agent, it still fits the same general age relationship. Higher ecosystem respiration (ER) in the young than in the mature stands was the combined result of earlier soil warming in spring, and higher temperature and greater biological activity in summer, as indicated by temperature-normalized respiration rates. The fire-generated PB had lower ER than the harvest-generated YHW and YRP, where high ER was sustained partly on account of logging residue. During the main growing season, the equivalent of 31 (MHW), 48 (MRP), 68 (PB), 114 (YHW) and 71% (YRP) of daily gross ecosystem production (GEP) was released in ER during the same day. The lower ER:GEP ratio in the mature stands was driven by greater age-dependent changes in ER than GEP. The magnitude of the increase in ER:GEP ratio in spring and fall was interpreted as the extent of the decoupling of ER and GEP. Decoupling (sustained high ER despite decreasing GEP) was observed in YHW, PB and MHW, whereas in coniferous stands (MRP and YRP) the stable ER:GEP ratio suggested preferential use of new photosynthates in ER. The results indicate that a great part of the variation in landscape-level C fluxes can be accounted for by mean stand age and associated parameters, which highlights the need to consider this source of heterogeneity in regional C balance estimates.     

The Study of Barium Concentration in Deciduous Teeth,Impacted Teeth,and Facial Bones of Polish Residents

The study determines the concentration of Ba in mineralized tissues of deciduous teeth, permanent impacted teeth, and facial bones. The study covers the population of children and adults (aged 6–78) living in an industrial area of Poland. Teeth were analyzed in whole, with no division into dentine and enamel. Facial bones and teeth were subjected to the following preparation: washing, drying, grinding in a porcelain mortar, sample weighing (about 0.2 g), and microwave mineralization with spectrally pure nitric acid. The aim of the study was to determinate the concentration of Ba in deciduous teeth, impacted permanent teeth, and facial bones. The concentration of barium in samples was determined over the ICP OES method. The Ba concentration in the tested bone tissues amounted to 2.2-15.5 μg/g (6.6 μg/g?±?3.9). The highest concentration of Ba was present in deciduous teeth (10.5 μg/g), followed by facial bones (5.2 μg/g), and impacted teeth (4.3 μg/g) (ANOVA Kruskal-Wallis rank test, p?=?0.0002). In bone tissue and impacted teeth, Ba concentration increased with age. In deciduous teeth, the level of Ba decreased with children’s age.     

Age-Dependent Changes in the Ultrastructure and in the Molecular Composition of Rat Brain Microtubules

An age-dependent increase of a cathepsin D-like protease activity that preferentially degrades high molecular weight microtubule-associated proteins (MAPs) has been previously described. Microtubules (MT) purified from rat brain of different ages in the presence of several protease inhibitors retained undegraded MAPs through cycles of polymerization, and revealed several age-dependent changes in the relative amounts of MAPs and MT-associated kinases. MAP2 immunoreactivity was found significantly lower in MT preparations from aged animals in contrast with a relative increase of tau molecules. In addition, the phosphorylation of MAP2 by its associated cyclic AMP-dependent protein kinase was also altered, consecutively to the partial loss of the enzyme during polymerization cycles and an age-dependent decrease in the ability of the cyclic nucleotide to stimulate MAP2-bound kinase activity. The evidence of an unusually high packing density of sedimented MT from old rat brains further suggested the modification with aging of the physical structure of the arm-like projections of MAPs, in addition to a lower amount in high molecular weight MAPs. These results support the hypothesis of a selective alteration with aging of the mechanical and regulatory properties of brain MT, consecutive to a change in the composition and/or the structure of MAPs.     

Changes of Concentrations of Elements in Deciduous Teeth with Age

The aim of this study was to describe the issue of changes in the concentration of some elements (Mn, Fe, Mg, Cu, K, Cr, Pb, Cd, and Ca) in the mineral composition of deciduous teeth and to answer the question whether there was a tendency to change the metal concentration, depending on children's age. Physiological replacement of deciduous teeth is preceded with the remodeling process occurring in the mineral structure. The elemental composition of deciduous teeth tissue during their natural loss is the result of these transformations. The subject of the study was deciduous teeth taken from the children (n?=?45, aged 5–14 years), residing in southern Poland, obtained as a result of noninvasive physiological replacement. The concentration of metals in samples was determined over the atomic absorption spectroscopy method. The results of the research showed a statistically significant decrease in the concentration of the analyzed elements in deciduous teeth of older children compared to younger children. The total concentration of all metals studied against the Ca content, expressed as the value of the constant cationic equilibrium, did not change in a statistically significant manner, depending on the age of the children (p?>?0.05).     

Cadmium Concentration in Human Autopsy Tissues

The concentration of cadmium in human tissues obtained on the basis of autopsies of non-poisoned Polish people (n = 150), aged from 1 to 80 years, examined between 1990 and 2010, is presented. The following values were found in wet digested samples by flame atomic absorption spectrometry (FAAS) (mean ± SD, median, and range, μg/g of wet weight): brain 0.020 ± 0.031, 0.084, 0–0.120 (n = 41); stomach 0.148 ± 0.195, 0.084, 0–1.25 (n = 89); small intestine 0.227 ± 0.231, 0.130, 0–0.830 (n = 39); liver 1.54 ± 1.55, 1.01, 0.015–9.65 (n = 99); kidney 16.0 ± 13.2, 14.0, 0.62–61.3 (n = 91); lung 0.304 ± 0.414, 0.130, 0–1.90 (n = 25); and heart 0.137 ± 0.107, 0.140, 0.017–0.250 (n = 4). Additionally, results (n = 13 people, aged from 2 to 83 years, 63 samples) obtained by inductively coupled plasma optical emission spectrometry (ICP OES) between 2010 and 2015 are given. The obtained data on Cd concentration in the human body can be used to estimate the amounts occurring in “healthy” people and those occurring in cases of chronic or acute poisonings with Cd compounds, which are examined for forensic purposes or to assess environmental exposure levels.     

Loss of Prion Protein Leads to Age-Dependent Behavioral Abnormalities and Changes in Cytoskeletal Protein Expression

The cellular prion protein (PrPC) is a highly conserved protein whose exact physiological role remains elusive. In the present study, we investigated age-dependent behavioral abnormalities in PrPC-knockout (Prnp0/0) mice and wild-type (WT) controls. Prnp0/0 mice showed age-dependent behavioral deficits in memory performance, associative learning, basal anxiety, and nest building behavior. Using a hypothesis-free quantitative proteomic investigation, we found that loss of PrPC affected the levels of neurofilament proteins in an age-dependent manner. In order to understand the biochemical basis of these observations, we analyzed the phosphorylation status of neurofilament heavy chain (NF-H). We found a reduction in NF-H phosphorylation in both Prnp0/0 mice and in PrPC-deficient cells. The expression of Fyn and phospho-Fyn, a potential regulator for NF phosphorylation, was associated with PrPC ablation. The number of β-tubulin III-positive neurons in the hippocampus was diminished in Prnp0/0 mice relative to WT mice. These data indicate that PrPC plays an important role in cytoskeletal organization, brain function, and age-related neuroprotection. Our work represents the first direct biochemical link between these proteins and the observed behavioral phenotypes.     

Peripheral Nerve Phospholipid Composition: Development in Normal Nerve and Age-Dependent Changes in Wallerian Degenerated Nerve

Abstract: The phospholipid composition of normal peripheral nerve as a function of developmental age as well as that of Wallerian-degenerated nerve as a function of age at nerve transection and duration of Wallerian degeneration have been quantitated in rabbit sciatic nerve. During development, increases in the proportions of ethanolamine plasmalogen, sphingomyelin, and combined phosphatidyl serine plus phosphatidyl inositol and decreases in the proportions of phosphatidyl choline and phosphatidyl ethanolamine correlated well with the concurrent myelin accretion. During Wallerian degeneration, age-dependent changes in phospholipid composition were observed. The large and statistically significant increase in the proportion of phosphatidyl choline and decrease in the proportion of ethanolamine plasmalogen were manifest promptly in nerves transected at 2 weeks of age but in a delayed manner in nerves transected at 8, 12, and 20 weeks of age. The rate of loss of individual phospholipids was greater in nerves transected at younger ages. The findings from normal developing peripheral nerve may well serve as baseline data for subsequent studies of phospholipid composition in pathological peripheral nerve. The Findings from Wallerian-degenerated peripheral nerve provide additional evidence for age-dependent chemical changes occurring in Wallerian-degenerated peripheral nerve that may be of significance in explaining the superior functional recovery from peripheral nerve injury observed in younger compared with older subjects.     

Seasonal Variation in Human Salivary Cortisol Concentration

Measurement of cortisol concentration can contribute important information about an individual's ability to adjust to various environmental demands of both physical and psychosocial origin. However, one uncertainty that affects the possibilities of correctly interpreting and designing field studies is the lack of observations of the impact of seasonal changes on cortisol excretion. For this reason, the month‐to‐month changes in diurnal cortisol concentration, the awakening cortisol response (ACR), maximum morning concentration, and fall during the day were studied in a group of 24 healthy men and women 32 to 61 yrs of age engaged in active work. On one workday for 12 consecutive months, participants collected saliva at four time points for determination of cortisol: at awakening, +30 min, +8 h, and at 21:00 h. Data were analyzed by a repeated measures design with month (12 levels) and time‐of‐day (4 levels) as categorical predictors. Cortisol concentrations were analyzed on a log scale. The diurnal pattern of cortisol was similar across months (interaction between month and time of day: p>0.4). The main effects of month and time‐of‐day were statistically significant (p <0.001). Highest concentrations were observed in February, March, and April, and lowest concentrations were observed in July and August. There were no statistically significant effects in any of the other measures, or between men and women. In conclusion, a seasonal variation in salivary cortisol concentrations was detected in an occupationally active population. Thus, seasonal variation needs to be taken into account when designing and evaluating field studies and interventions and when making comparisons across studies.     

Changes in the Concentration of Microelements in the Teeth of Rats in the Final Stage of Type 1 Diabetes,with an Absolute Lack of Insulin

The mineral content of tooth hard tissue may influence the rate of decay change. Considering this fact, we aimed at examining if type 1 diabetes might be a contributing factor to the appearance of tooth decay. The experiment was conducted on female Wistar rats. To induce diabetes, rats were intravenously injected with 1 mL streptozocine 0.01 M citrate buffer. The control group of rats was injected with 1 mL 0.01 M citrate buffer only. After 10 days, teeth and blood serum samples were obtained. Fluoride concentration was determined by potentiometer method, and calcium and magnesium, by AAS. Serum concentrations of glucose and estradiol in the diabetic rats were significantly higher compared to the control group. In the experimental group, a statistically significant decrease of fluorine concentration in both teeth and serum were observed. Calcium and magnesium concentrations in blood serum and dental magnesium concentration were significantly higher in rats with type 1 diabetes compared with the control. A downward trend in the content of dental calcium in streptozotocin-induced diabetic rats was observed. The results obtained indicate that caries initiation and progression could be promoted by metabolic changes associated with diabetes affecting the mineral composition of tooth hard tissue.     

Orcadian Changes in Stimulus Threshold and in the Effect of a Local Anaesthetic Drug in Human Teeth: Studies with an Electronic Pulptester

An electronic puiptester with constant testing current was used to study the stimulus threshold in human teeth of 28 healthy volunteers and the duration of local anaesthesia by articaine plus epinephrine in 55 patients with caries who underwent a filling therapy. In 21 out of the 28 volunteers, significant daily variations in stimulus threshold were detected by cosinor analysis. Acrophases, however, were scattered over the 24-hr scale. In patients, the local anaesthetic effect was studied at four different times of day (0800,1100,1400 and 1700 hr). The electronic device allowed one to accurately determine the time to peak effect (T_max), duration of effect (E_max, time to return to baseline threshold (T_ret) and the area under the time-effect curve (AUC) as a measure of the total local anaesthetic effect. Significant diurnal variations in AUC and E_max were found in 36 patients with the 0.8 ml dose, with peak and trough values at 1400 and 1700 hr, respectively. No differences in effect were found with the low dose of 0.4 ml applied to 19 patients either at 1400 or 1700 hr giving evidence for a circadian phase-dependency in the dose-response relationship of a local anaesthetic drug. The results clearly demonstrate that this electronic device is suitable for exact evaluation of circadian changes in local anaesthetic effects. Under drug-free control conditions, however, the low stimulus frequence of 5 Hz of this device obviously does not allow to discriminate between stimuli modified by pain perception and/or alertness.     

被子植物助细胞中钙含量的变化

助细胞是被子植物受精过程中花粉管进入胚囊并释放精子及其内容物的场所,而助细胞中不同时期的钙含量与受精作用的顺利完成密切相关。在大多数植物中,助细胞是成熟胚囊中钙含量最高的细胞。传粉后在花粉管中所产生的信号诱导下,助细胞中钙含量还可能继续增加。花粉管进入退化助细胞后,在超高钙环境中破裂并释放精子,精子沿退化助细胞转移到受精靶区实现双受精。随后助细胞中的钙含量迅速降低。因此钙在吸引花粉管、雄配子释放甚至雄配子转移等过程中都发挥了重要作用。     

The Anthropology of Modern Human Teeth: Dental Morphology and Its Variation in Recent Human Populations

The Anthropology of Modern Human Teeth: Dental Morphology and Its Variation in Recent Human Populations. G. Richard Scott and Christy G. Turner 11. New York: Cambridge University Press, 1997.382 pp.     

The Identification of Proteoglycans and Glycosaminoglycans in Archaeological Human Bones and Teeth

Bone tissue is mineralized dense connective tissue consisting mainly of a mineral component (hydroxyapatite) and an organic matrix comprised of collagens, non-collagenous proteins and proteoglycans (PGs). Extracellular matrix proteins and PGs bind tightly to hydroxyapatite which would protect these molecules from the destructive effects of temperature and chemical agents after death. DNA and proteins have been successfully extracted from archaeological skeletons from which valuable information has been obtained; however, to date neither PGs nor glycosaminoglycan (GAG) chains have been studied in archaeological skeletons. PGs and GAGs play a major role in bone morphogenesis, homeostasis and degenerative bone disease. The ability to isolate and characterize PG and GAG content from archaeological skeletons would unveil valuable paleontological information. We therefore optimized methods for the extraction of both PGs and GAGs from archaeological human skeletons. PGs and GAGs were successfully extracted from both archaeological human bones and teeth, and characterized by their electrophoretic mobility in agarose gel, degradation by specific enzymes and HPLC. The GAG populations isolated were chondroitin sulfate (CS) and hyaluronic acid (HA). In addition, a CSPG was detected. The localization of CS, HA, three small leucine rich PGs (biglycan, decorin and fibromodulin) and glypican was analyzed in archaeological human bone slices. Staining patterns were different for juvenile and adult bones, whilst adolescent bones had a similar staining pattern to adult bones. The finding that significant quantities of PGs and GAGs persist in archaeological bones and teeth opens novel venues for the field of Paleontology.