Sexual dimorphism and human tooth size differences

Current male/female differences in tooth size are due to the male/female differences in body bulk that exist in any given human population. These differences are residues of the sexual dimorphism that was maintained for adaptive reasons during the Middle Pleistocene. Late in the Pleistocene the development of food processing techniques led to the reduction of both male and female dental dimensions. Dental sexual dimorphism, however, was maintained until the very end of the Pleistocene when the hunting of large game animals by crude techniques was replaced by a focus on great numbers of small game caught by more sophisticated means and by an increasing utilization of plant foods. The subsequent reduction in dimorphism represents the actions of the Probable Mutation Effect operating under conditions of relaxed selection. The conclusion offered is that the smallest degree of sexual dimorphism visible in the modern world is to be found among those populations that are separated by the greatest interval of time from precursors who depended for their survival on a Pleistocene big game hunting mode of subsistence.     

The relationship between brain weight and head circumference from birth to age 18 years

A relation between head circumference and brain weight of humans is generally believed to exist, but the literature contains only two studies which exhibit a quantitative aspect of the relation, showing that brain weight is proportional to the cube of the head circumference from birth through age 3.5 years. By assembling data from autopsy records, we have been able to show that this cubic relationship holds through brain maturation at around age 18 years.     

成都市人乳头瘤病毒16型感染与宫颈病变的相关性分析

本研究旨在探讨人乳头瘤病毒(human papillomavirus,HPV)16感染与宫颈病变的关系,为宫颈癌防治提供科学依据。通过核酸杂交法进行HPV感染分型,纳入1 057例HPV阳性且行组织切片病理学检查的患者,对各级别宫颈病变中HPV16构成比、不同年龄组HPV16阳性患者中宫颈上皮内瘤样病变(cervical intraepithelial neoplasia,CIN)Ⅱ及以上病变的患病率,以及HPV16单一与多重感染患者中CINⅡ及以上病变的患病率进行分析。结果显示,在1 057例HPV阳性患者中,352例感染HPV16,CINⅢ中HPV16构成比最高,各级别病变中HPV16构成比差异有统计学意义。随着病变级别增加,HPV16构成比有增高趋势(P0.05)。不同年龄组HPV16阳性患者中CINⅡ及以上病变的患病率差异有统计学意义(P0.05),且随年龄增加而升高(P0.05)。HPV16单一、双重与三重以上感染患者中,CINⅡ及以上病变的患病率差异有统计学意义(P0.05),且随着感染型别种类增加,患病率降低(P0.05)。本研究显示,HPV16与高级别宫颈病变有较明显的相关性,老年HPV16阳性患者检出宫颈癌的概率更高。因此,应高度重视HPV16持续性感染,做到及时诊断与治疗,以减少宫颈高级别病变和宫颈癌的发生。     

Human tooth development,tooth length and eruption; a study of British archaeological dentitions

Abstract

Human teeth erupt during root growth but few studies report the relationship between fractions of root development and eruption levels. The aim of this study was to assess root stages of deciduous and early erupting permanent teeth (maxillary and mandibular central incisors and first molars) at eruption levels and relate this to root fraction and tooth length. The sample consisted of 620 modern human skeletal remains with developing teeth. Tooth stage (based on Moorrees crown and root stages) and eruption levels of all developing teeth were assessed where possible. Tooth length of isolated teeth was measured. The distribution of root stage at eruption levels was calculated. Results showed that root stage at alveolar eruption was less variable than at partial eruption. Most teeth (72% of 138) at alveolar eruption were at root a quarter (R¼) whereas teeth at partial eruption were at R¼ or root half (R½) (38 and 50% of 128 respectively). These findings suggest that the active phase of eruption is probably a rapid process and occurs during the first half of root growth.     

Cross-country relationships between life expectancy,intertemporal choice and age at first birth

Humans, like other animals, typically discount the value of delayed rewards relative to those available in the present. From an evolutionary perspective, prioritising immediate rewards is a predictable response to high local mortality rates, as is an acceleration of reproductive scheduling. In a sample of 46 countries, we explored the cross-country relationships between average life expectancy, intertemporal choice, and women's age at first birth. We find that, across countries, lower life expectancy is associated with both a smaller percentage of people willing to wait for a larger but delayed reward, as well as a younger age at first birth. These results, which hold when controlling for region and economic pressure (GDP-per capita), dovetail with findings at the individual level to suggest that life expectancy is an important ecological predictor of both intertemporal and reproductive decision-making.     

A link between copper and dental caries in human teeth identified by X-ray fluorescence elemental mapping

Quantitative X-ray fluorescence imaging of sections of human teeth revealed an increased concentration of copper and zinc in carious regions of dentine compared with unaffected portions of the tooth. Higher-resolution images provided strong evidence that the copper was transported and localized mainly in the dentinal tubules. While similar levels of zinc were found in these areas and concentrated in the tubules, zinc was also more evident in the hydroxyapatite, and the increase in zinc levels compared with the levels in background (normal) areas was less than that for copper. These results suggest a role for copper and zinc in the formation and progression of dental caries and present a potential point of intervention for treatment. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Dedicated to the memory of the late Harold Eastgate.     

Relationship between age and deposit of peritubular dentine

Peritubular dentine is a mineralised deposit formed centripetally in the dentine tubules with advancing age, so that the tubular diameter is smaller in teeth from older persons. The aim of the present study was to investigate the relationship between age in humans and the amount of peritubular dentine and the extent of the consequent obliteration of the tubules, and to find out whether this relationship was strong enough to be used as a parameter for age estimation. Fifty mandibular central and lateral human incisors were ground on the lingual aspect of the root and examined in a scanning electron microscope (SEM). The number of open tubules was counted and the diameter of the tubules measured both before and after etching with 35% orthophosphoric acid. The difference in the number of tubules in unetched and etched specimens was taken to be the number of occluded tubules, and the difference in radii before and after etching to be the thickness of peritubular dentine. The results did not demonstrate a significant relationship between age and the reduction in the number of tubules. One explanation might be that a certain age has to be reached before obliterated dentine tubules can be observed. The correlation between age and the thickness of peritubular dentine was not significant in teeth extracted because of periodontal disease, so these teeth were excluded from the regression analysis with age as the dependent variable. Only the thickness of peritubular dentine was included in the regression (r=0.69); this factor was a better indicator of age than the tubular diameter, but not so closely related to age that it can be recommended for general use in forensic and archaeological age estimations.     

The trade-off between tooth strength and tooth penetration: predicting optimal shape of canine teeth

We investigate the shape of canine teeth under the assumption that the tooth's morphology is optimized by the evolutionary trade-off to minimize breakage and maximize ease of the penetration of prey. A series of experiments using artificial teeth to puncture the hides of a deer Odocoileus virginianus and pig Sus scrofa domesticus were conducted to establish the relationships between the tooth shape and the force needed to puncture the hide. The shapes of these teeth were also used in a beam theory analysis to calculate the strength of the teeth. Because the relative costs of puncturing and breakage were not known, a complete prediction of tooth shape was not possible. Instead, we used two independent measures of tooth shape: aspect ratio (total tooth length/tooth width at base) and rate of taper along the shank of the tooth. We quantified rate of taper in several species of felids, and by assuming this was the optimal design, we determined the relative costs of breakage and puncturing that would produce such a taper. Then, we used the relative costs to predict the aspect ratio of the optimum tooth. The average predicted value is about 2.5, very close to the average value in extant species of cats.     

The relationship between diet and tooth complexity in living dentigerous saurians

Living saurian reptiles exhibit a wide range of diets, from carnivores to strict herbivores. Previous research suggests that the tooth shape in some lizard clades correlates with diet, but this has not been tested using quantitative methods. I investigated the relationship between phenotypic tooth complexity and diet in living reptiles by examining the entire dentary tooth row in over 80 specimens comprising all major dentigerous saurian clades. I quantified dental complexity using orientation patch count rotated (OPCR), which discriminates diet in living and extinct mammals, where OPCR‐values increase with the proportion of dietary plant matter. OPCR was calculated from high‐resolution CT‐scans, and I standardized OPCR‐values by the total number of teeth to account for differences in tooth count across taxa. In contrast with extant mammals, there appears to be greater overlap in tooth complexity values across dietary groups because multicusped teeth characterize herbivores, omnivores, and insectivores, and because herbivorous skinks have relatively simple teeth. In particular, insectivorous lizards have dental complexities that are very similar to omnivores. Regardless, OPCR‐values for animals that consume significant amounts of plant material are higher than those of carnivores, with herbivores having the highest average dental complexity. These results suggest reptilian tooth complexity is related to diet, similar to extinct and extant mammals, although phylogenetic history also plays a measurable role in dental complexity. This has implications for extinct amniotes that display a dramatic range of tooth morphologies, many with no modern analogs, which inhibits detailed dietary reconstructions. These data demonstrate that OPCR, when combined with additional morphological data, has the potential to be used to reconstruct the diet of extinct amniotes. J. Morphol. 278:500–522, 2017. © 2017 Wiley Periodicals, Inc.     

Brief communication: discrimination between European-American and African-American children based on deciduous dental metrics and morphology

This study employs metric and morphological features of the deciduous dentition for discriminating between European-American and African-American children and providing allocation rules (regression equations). Five logistic regression equations are presented, with the percentage of correct allocation to group of between 90.1-92.6%. All five equations employ three metric traits (the mesiodistal diameters of the mandibular deciduous canines and anterior and posterior deciduous premolars) and one morphological feature (cusp number of the maxillary deciduous anterior premolar). In addition to these four variables, only two or three additional morphological features are added in carious combinations in the final equations. Correct allocation to group is 4-12% greater when combining metric and morphological features compared to using the features separately.     

Apoptosis in developmental and repair-related human tooth remodeling: a view from the inside

Apoptosis is a key phenomenon in the regulation of the life span of odontoblasts, which are responsible for dentin matrix production of the teeth. The mechanism controlling odontoblasts loss in developing, normal, and injured human teeth is largely unknown. A possible correlation between apoptosis and dental pulp volume reduction was examined. Histomorphometric analysis was performed on intact 10 to 14 year-old premolars to follow dentin deposition and evaluate the total number of odontoblasts. Apoptosis in growing healthy teeth as well as in mature irritated human teeth was determined using a modified TUNEL technique and an anti-caspase-3 antibody. In intact growing teeth, the sequential rearrangement of odontoblasts into a multi-layer structure during tooth crown formation was correlated with an apoptotic wave that leads to the massive elimination of odontoblasts. These data suggest that apoptosis, coincident with dentin deposition changes, plays a role in tooth maturation and homeostasis. Massive apoptotic events were observed after dentin irritation. In carious and injured teeth, apoptosis was detected in cells surrounding the lesion sites, as well as in mono-nucleated cells nearby the injury. These results indicate that apoptosis is a part of the mechanism that regulate human dental pulp chamber remodeling during tooth development and pathology.     

哺乳动物牙釉质碳氧稳定同位素揭示早期人类演化与环境关系

早期人类演化、扩散、技术发展与自然环境的关系一直是学术界关注的前沿与热点.本文梳理了环境变化与早期人类演化关系研究中牙釉质碳氧稳定同位素分析的研究历史、原理以及取样方法,与此同时,介绍了不同学者利用哺乳动物牙釉质碳氧稳定同位素分析在早期人类演化与环境关系探索的相关研究进展,并对东非早期人类奥杜威技术向阿舍利技术转变过程...     

人乳头瘤病毒（HPV）感染与阴道微生态的相关性研究

目的 探讨人乳头瘤病毒（HPV）与阴道微生态的相关性。为阴道微生态失衡患者及时纠正阴道菌群的紊乱,避免或减少其感染HPV及宫颈癌的防治提供科学依据。方法 选取2015年5月－2016年6月在我院妇科门诊就诊的1412例患者进行HPV、阴道微生态检测。分析阴道菌群及微生态结果与HPV感染的相关性。结果 1412例患者中HPV阳性有542例,占38.39%,HPV阴性有870例,占61.61%。分别以革兰阳性大杆菌、革兰阴性短杆菌、革兰阳性杆菌、革兰阳性球菌/链球菌为优势菌及无优势菌的患者,HPV感染率分别为34.45%、49.16%、33.33%、39.28%、38.70%,OR值分别为0.654（0.526-0.815）、1.818（1.426-2.318）、1.426（0.515-1.209）、1.039（0.483-2.236）、1.014（0.601-1.711）。细菌性阴道病（BV）、滴虫性阴道炎（TV）、需氧性阴道炎（AV）、外阴阴道假丝酵母菌病（VVC）的HPV感染阳性率分别为27.49%、1.29%、7.38%、12.54%,P值分别为0.000、0.754、0.570、0.318。结论 HPV感染与革兰阴性短杆菌及BV显著相关,革兰阳性大杆菌与HPV的感染呈负相关,菌群紊乱及BV可能增加HPV感染的风险。     

人乳头瘤病毒感染与肿瘤的相关性研究进展

人乳头瘤病毒(Human papillomavirus,HPVs)是一种嗜人体皮肤和黏膜的DNA病毒,约80%有性行为的女性可能感染HPV。宫颈癌是最常见的恶性肿瘤之一,是女性肿瘤中仅次于乳腺癌的第二个常见的恶性肿瘤,高危型HPV感染是其主要致病因素,则宫颈癌是目前唯一病因明确的妇科恶性肿瘤。HPV感染亦与其他恶性肿瘤的发生、发展密切相关,可引起除宫颈癌外的其他泌尿生殖道肿瘤,以及消化道系统、呼吸道系统、眼科、皮肤等其他系统或器官肿瘤。对HPV感染所致肿瘤的相关研究进展进行了综述,为肿瘤病因和发生机理的研究提供了新的思路。     

肠道微生物代谢产物—S-雌马酚与 人类健康关系研究进展

大豆异黄酮是一种年销量很大、市场普及率较高的保健品。具有抗氧化、抗肿瘤等功能,对延缓女性衰老和改善更年期综合征有很好效果。但研究表明,大豆异黄酮的保健功能主要归功于其肠道代谢产物S-雌马酚。S-雌马酚是豆类食品在肠道内经特定微生物代谢后产生的一种高度稳定小分子,其与雌激素的结构和功能高度相似,能与β-雌激素(ER-β)受体结合。具有防治更年期综合征、心血管疾病和多种雌素依赖性癌症的功能。到目前为止,雌马酚的功能及其与人类健康之间的关系还有待进一步研究。本文结合国内外最新研究进展,着重介绍雌马酚的生理功能及其与各类疾病的研究进展,展望雌马酚在各类疾病防治中可能发挥的重要作用。     

Season of birth and reproductive performance: an analysis of family reconstitutions of 800 women born in The Netherlands at the end of the 19th century

Background: Several studies have reported associations between season of birth and reproductive characteristics such as menarcheal age, fecundability, and twinning, but the results are inconsistent with respect to the location of high- and low-risk seasons. To assess whether this disagreement could be due to the use of populations from different geographic areas and time frames instead of different etiologic pathways, we investigated the season-of-birth dependency of a variety of reproductive outcomes within one time- and arealimited population. Methods: In a historic follow-up study, the reconstituted families of 800 women born between 1873 and 1887 in or near Rotterdam, The Netherlands, were used to determine eight types of reproductive outcome: childlessness, interval to first pregnancy, pregnancy interval, stillbirth, neonatal death, postneonatal death, multiple birth, and gender of offspring. The relation of these outcomes with season of birth was modeled using cosinor functions with periods of 1 year or a half year. Data were analyzed by use of logistic regression or general estimation equations (GEE), dependent on whether outcomes could occur more than once per woman. Results: Peaks in the model-based risks of reproductive failure were found within two small temporal ranges, January 1 to February 11 and July 1 to August 11 for all outcomes except gender. The picture did not change after controlling for known and possible risk factors, including age, offspring's birth cohort, and some social variables. Conclusions: This study reconfirms the idea that seasonal factors around conception or birth influence later reproductive characteristics. Observing the consistency of the location of high-risk seasons across a variety of outcomes, the explanation of season-of-birth dependency of different reproductive outcomes need not involve multiple etiological pathways. (Chronobiology International, 18(3), 525-539, 2001)