Cold stress in captive great apes recorded in incremental lines of dental cementum

Incremental lines in dental cementum of museum specimens of 11 free-ranging great apes were compared to the respective structures in 5 captive specimens of known age-at-death, and with many known life-history parameters. While the dental cementum of the free-ranging apes was regularly structured into alternating dark and light bands, 4 out of 5 captive animals showed marked irregularities in terms of hypomineralized bands which could all be dated to the year 1963. Cementum preservation was insufficient in the fifth specimen and did not permit such a differentiation. All 4 captive apes had been kept in a zoo located in the northern hemisphere, where 1963 was characterized by an extremely cold winter. Since cold stress is a calcium-consuming process, the lack of available calcium in newly forming cementum could be responsible for the observed hypomineralization. The appositional growth characteristics of dental cementum serve as a record for such life-history events.     

Incremental lines of dental cementum in biological age estimation

The aim of this study is to evaluate the use of counting incremental lines of dental root cementum for biological age determination, and to compare it with alternative methods. Two samples were taken: 51 teeth from 49 individuals of known age obtained at the Stomatological Clinic, Vilnius University, as well as the canine teeth from the remains of 48 individuals from the mass graves of Tuskulenai in Vilnius (inhumed 1944-47). In the latter sample, the chronological age of 43 individuals was known through personal identification. Undecalcified teeth were sectioned with the Leica SP 1600 microtome diamond saw, and incremental line count as a blind test was made on sections of 35 to 100 microns thickness. Incremental line count was possible in 82-86 percent of cases. The results of three independent counts showed that intra-observer bias has no significant impact. Biological age was estimated by adding incremental line number to the average age of tooth eruption. It was found that mean absolute error was 6.46 years for the 1st sample, 6.27 years for the 2nd sample, and in some cases exceeded 10 years. For the 2nd sample, the results were compared to those of other methods such as endocranial suture ossification, pubic symphysis morphology and the "combined" method of Nemeskéri. All four methods yield a similar correlation in regard to an individual's chronological age. The highest correlation was found for the combined method, and the lowest one for public symphysis morphology. All correlations had a similar standard error. Thus our assessment is less enthusiastic than in some past studies; it is suggested that the incremental lines rather have a similar use as other methods.     

On the validity of individual age-at-death diagnosis by incremental line counts in human dental cementum. Technical considerations

Histological analysis of 91 roots from 80 freshly extracted teeth from patients with known calendar age and life-history parameters revealed that the validity of a chronological age-at-death diagnosis based on the count of incremental lines in human dental cementum is essentially dependent from two parameters: method of analysis, and pathological state of the investigated tooth. In this paper, we want to contribute to the establishment of a methodological standard procedure by comparison of our own results with otherwise published research designs. We conclude that as long as the necessary prerequisites are met, the quantitative analysis of cementum annulli will lead to a rather precise chronological age-at-death diagnosis. In addition, a qualitative analysis permits the ontogenetic dating of certain individual life-history parameters (e.g. previous pregnancies).     

Age determination and age structure in the edible dormouse Glis glis based on incremental bone lines

1. Absolute age was estimated from incremental bone layers of the mandible in 109 edible dormice Glis glis collected between May and September 1997 in mixed beech and fir forests of central Slovenia. 2. Mandible cross-sections of juveniles obtained in September showed a great number of vascular canals and no resting lines. In the remaining animals (n = 81), the number of resting lines varied between one and seven, with two or three lines being the most common condition (62% of specimens). Among these adult animals, which hibernated at least once, females attained higher mean (3.3 years) and maximum age (7 years) than males (mean = 2.2, maximum = 6 years). 3. The frequency distribution of age classes suggested unequal reproductive success between years but there was no indication of any lack of litters in years of low mast production.     

Transgene copy number comparison in recombinant mammalian cell lines: critical reflection of quantitative real-time PCR evaluation

Nucleic acid quantification is a relevant issue for the characterization of mammalian recombinant cell lines and also for the registration of producer clones. Quantitative real-time PCR is a powerful tool to investigate nucleic acid levels but numerous different quantification strategies exist, which sometimes lead to misinterpretation of obtained qPCR data. In contrast to absolute quantification using amplicon- or plasmid standard curves, relative quantification strategies relate the gene of interest to an endogenous reference gene. The relative quantification methods also consider the amplification efficiency for the calculation of the gene copy number and thus more accurate results compared to absolute quantification methods are generated. In this study two recombinant Chinese hamster ovary cell lines were analysed for their transgene copy number using different relative quantification strategies. The individual calculation methods resulted in differences of relative gene copy numbers because efficiency calculations have strong impact on gene copy numbers. However, in context of comparing transgene copy numbers of two individual clones the influence of the calculation method is marginal. Therefore especially for the comparison of two cell lines with the identical transgene any of the relative qPCR methods was proven as powerful tool.     

Growth layers in dental cementum ofSaguinus monkeys in South America

Dark stained layers were observed in the cementum of the teeth ofSaguinus monkeys living in South America. Since the number of layers correlated with the degree of attrition in the incisor, the dark layers probably showed the growth lines. The teeth of the monkeys captured at the beginning of the wet season showed the incremental dark line around most of the exterior of the cementum.     

Incremental cementum lines in the teeth of tropical African mammals

The correlation of series of two darkly-staining lines in the tooth cementum of tropical African mammals from areas of bimodal equatorial rainfall is briefly reviewed, and contrasted with the findings in southern Africa where bi-annual lines are claimed for areas of unimodal rainfall. A sample of African buffalo teeth from a unimodal rainfall area in southern Tanzania was examined and the conclusion reached that, in general, one dark line per year was formed. A miscellaneous selection of mainly known age animals was also examined with varied results. Anomalies in the apparent formation of cementum lines are discussed.     

Determination of age in the Japanese monkey from growth layers in the dental cementum

The teeth of 14 Japanese monkeys (Macaca fuscata) were examined to establish an exact method of determining age by histological observation of dental cementum. The cementum showed annual growth layers, which were especially remarkable in the incisor root and in the molar cementum deposited at the junction of the roots. The layer of cementum formed in winter appears as a dark layer in stained sections and as a translucent layer in unstained ground sections. In the incisor the first dark and light layers are formed at the age of three years, whereas in the molar they do not appear at a definite age. The layers are thick and clear in the upper medial incisor. As a result, the age of a Japanese monkey can be determined by adding two to the number of dark layers and an outer light layer. It is interesting that the formation of the cementum of the first molar begins a few years after its eruption. The relation between this fact and the pressure of occlusion is discussed.     

Incremental lines in root cementum of human teeth —A reliable age marker?

In root cementum of teeth, alternating dark and light lines become visible in cross-sections under the light microscope. These lines bear an apparent resemblance to the annual rings of trees. Numerous studies have been done to correlate the number of cementum lines with the dental age by examining a great number of teeth of known age. Our study used a different approach. If lines in root cementum develop in an annual rhythm and are thus comparable to annual rings of trees, the same or at least a very similar number of these structures should be found in all areas of the root cementum of the same tooth. We counted cementum lines in the buccal, lingual, distal and mesial region of different sections, all from the middle third of the same root. This was repeated in eight teeth. To our surprise, we had immense difficulty in counting reproducible line numbers in the same cementum area at repeated counts. Nevertheless, the same tooth was found to differ markedly in the number of lines in different sections as well as in different regions of the same sections. These differences cannot be ascribed to variations caused by difficulties with reproducible line counting. Therefore, we are more than skeptical about the reliability of counting lines in root cementum as a method for determining the age of human teeth.     

Age determination from dental microstructure in juveniles

The crypts outside St Bride's Church, London, contain a documented collection of skeletal remains dating from the mid-18th century. Some of these remains became mixed during post-war restoration work on the church. The worst example of such mixing involves ten infants that were boxed all together with their corresponding coffin plates. All the infants were aged between 1 and 4 years at death. Recognized skeletal aging criteria proved unsuccessful in identifying the bodies. A more precise method of age estimation was utilized in order to separate these individuals. Age was determined using the incremental markers found in dental microstructure which are thought to be formed in circadian and circaseptan rhythms. The resulting age estimates were compared with the real ages obtained from the coffin plates and death certificates. Confident identification was achieved in eight out of ten cases. This study illustrates the potential value of a little-known aging method in circumstances where commonly used methods have proved unsuccessful. © 1995 Wiley-Liss, Inc.     

Outcome prediction based on microarray analysis: a critical perspective on methods

Background  

Information extraction from microarrays has not yet been widely used in diagnostic or prognostic decision-support systems, due to the diversity of results produced by the available techniques, their instability on different data sets and the inability to relate statistical significance with biological relevance. Thus, there is an urgent need to address the statistical framework of microarray analysis and identify its drawbacks and limitations, which will enable us to thoroughly compare methodologies under the same experimental set-up and associate results with confidence intervals meaningful to clinicians. In this study we consider gene-selection algorithms with the aim to reveal inefficiencies in performance evaluation and address aspects that can reduce uncertainty in algorithmic validation.     

Accuracy in the chromatographic determination of extreme enantiomeric ratios: A critical reflection

The chromatographic quantitation of very low amounts of an enantiomer in the presence of its antipode can be an extraordinary challenge. If resolution of the peaks is not complete even at extreme mass ratios an integrator will yield inaccurate results due to geometric effects. A given resolution can be adequate for peaks of similar size but result in severe overlap if one of the signals is markedly smaller. If tailing occurs, which is more the rule than the exception, the problem is especially severe for last eluted small peaks. Additional obstacles are detector nonlinearity and other sources of unsatisfactory calibration curves, overloading phenomena, and the possible lack of standards of highest optical purity. These problems have been studied by computer simulations and the liquid chromatographic separation of (R,S)-phenylethyl naphthoic acid amide on a chiral stationary phase. © 1995 Wiley-Liss, Inc.     

Dental incremental lines in some small species of the European vespertilionid bats

The dentine and cementum of the mammals exhibit incremental lines (IL) that may be seen as dark and light rings in properly prepared sections of teeth. Counting of IL provides a potential method to evaluate the absolute age of many wild species. The aim of the present study was to evaluate IL in small bat species and to test whether the number of IL is associated with the absolute age of bat when its minimal age was known based on ringing data. Teeth of 26 specimens of the following species were examined:Myotis daubentonii (n = 12),Barbastella barbastellus (n = 4),M. brandtii (n = 2),M. nattereri (n = 2),Pipistrellus nathusii (n = 2),Plecotus auritus (n = 2),M. dasycneme (n = 1),Vespertilio murinus (n = 1). Transverse morphological sections of canines, incisors and postcanine teeth were analysed by a light microscopy. In 4 cases, the minimal age of animals examined in this study was known. The IL were revealed in the dentine of 14 bats examined. The cementum of all animals was devoid of IL. The mean distance between the first and second juxtaposed IL ofM. daubentonii was 3.2 ± 0.2 mm, but it was significantly fewer among the subsequent adjacent lines. Due to a thinness of the IL, an accurate counting was considerably difficult in the canines containing more than 10 IL, as well as in the incisors and postcanine teeth with more than 3-6 IL. The IL of roots showed the most contrast, but they were almost obscured from view at the cingulum and crown. In bats of known-age, the numbers of IL were significantly lower than minimal age of those animals examined, and IL were either revealed only in certain teeth or absent entirely in all teeth. The present findings suggest that the number of the IL varies in different teeth and is strongly dependent on section level. Consequently, age determination in small bats using dental IL is doubtful and requires a reevaluation.     

Age determination in human adults by dental histology

Dentine root transparency (RDT) has been measured on 70 histological sections of teeth from 46 individuals of known sex and age. In order to obtain the estimates of individual chronological age, Bang & Ramm (1970) equations have been applied to the value obtained by the measurements. Using the percentage ratio hx100/H (after Lemendin & Cambray 1981)--were h is the extension of the root transparency zone (in mm) and H is the total root length (in mm), some regression functions have been elaborated. The error of the age estimates obtained following Bang & Ramm was quite high in percentage, being comprised between +/- 5 years only in 21.13% of the cases.     

P-glycoprotein as multidrug transporter: a critical review of current multidrug resistant cell lines

MDR has been studied extensively in mammalian cell lines. According to usual practice, the MDR phenotype is characterized by the following features: cross resistance to multiple chemotherapeutic agents (lipophilic cations), defective intracellular drug accumulation and retention, overexpression of P-gp (often accompanied by gene amplification), and reversal of the phenotype by addition of calcium channel blockers. An hypothesis for the function of P-gp has been proposed in which P-gp acts as a carrier protein that actively extrudes MDR compounds out of the cells. However, basic questions, such as what defines the specificity of the pump and how is energy for active efflux transduced, remain to be answered. Furthermore, assuming that P-gp acts as a drug transporter, one will expect a relationship between P-gp expression and accumulation defects in MDR cell lines. A review of papers reporting 97 cell lines selected for resistance to the classical MDR compounds has revealed that a connection exists in most of the reported cell lines. However, several exceptions can be pointed out. Furthermore, only a limited number of well characterized series of sublines with different degrees of resistance to a single agent have been reported. In many of these, a correlation between P-gp expresson and transport properties can not be established. Co-amplification of genes adjacent to the mdr1 gene, mutations [122], splicing of mdr1 RNA [123], modulation of P-gp by phosphorylation [124] or glycosylation [127], or experimental conditions [26,78] could account for some of the complexity of the phenotype and the absence of correlation in some of the cell lines. However, both cell lines with overexpression of P-gp without increased efflux [i.e., 67,75] and cell lines without P-gp expression and accumulation defects/increased efflux [i.e., 25,107] have been reported. Thus, current results from MDR cell lines contradict - but do not exclude - that P-gp acts as multidrug transporter. Other models for the mechanism of resistance have been proposed: (1) An energy-dependent permeability barrier working with greater efficacy in resistant cells. This hypothesis is supported by studies of influx which, although few, all except one demonstrate decreased influx in resistant cells; (2) Resistant cells have a greater endosomal volume, and a greater exocytotic activity accounts for the efflux. Furthermore, large amounts of P-gp in the plasma membrane altering the ultrastructure and generalized changes, such as increases or decreases in membrane fluidity, alterations in lipid composition, changes in transmembrane pH gradient and membrane potential have been described in MDR cell lines and could account for some of the findings.