Confusing dinosaurs with mammals: tetrapod phylogenetics and anatomical terminology in the world of homology

At present, three different systems of anatomical nomenclature are available to researchers describing new tetrapod taxa: a nonstandardized traditional system erected in part by Sir Richard Owen and subsequently elaborated by Alfred Romer; a standardized system created for avians, the Nomina Anatomica Avium (NAA); and a standardized system for extant (crown-group) mammals, the Nomina Anatomica Veterinaria (NAV). Conserved homologous structures widely distributed within the Tetrapoda are often granted different names in each system. The recent shift toward a phylogenetic system based on homology requires a concomitant shift toward a single nomenclatural system also based on both evolutionary and functional morphological homology. Standardized terms employed in the NAA and NAV should be perpetuated as far as possible basally in their respective phylogenies. Thus, NAA terms apply to nonavian archosaurs (or even all diapsids) and NAV terms apply to noncrown-group mammals and more basal synapsids. Taxa equally distant from both avians and crown-group mammals may maintain the traditional nonstandardized terminology until a universal anatomical nomenclature for all tetrapods is constructed.     

Tooth agenesis in down syndrome

We studied the frequency and pattern of tooth agenesis in a Danish population with Down syndrome, trisomy 21 (46 females and 54 males). The control group consisted of a normal Danish population (2424 females and 2431 males) [Rølling, 1980: Scand J Dent Res 88:365–369; Ravn and Nielsen, 1973: Tandlaægebladet 77:12–22]. We found that individuals with Down syndrome have an occurrence of agenesis that is some 10 times greater that in the general population with a higher frequency in males than in females. Agenesis occurred more frequently in the mandible than in the maxilla and most often on the left side. The highly significant differences were primarily found in the occurrence of agenesis of the mandibular central incisors, followed by the maxillary lateral incisors and second premolars and the mandibular second premolars. The main components in the pattern of agenesis observed in Down syndrome are supposed to be related to the peripheral nervous systern and abnormal cartilagenous tissue. The present study on Down syndrome suggests that the dentition, with its many different anomalies, from agenesis to malformation, can be used as an indicator in evaluating different aspects in the patheogenetic of aneuploidy conditions. © 1995 Wiley-Liss, Inc.     

Tooth emergence in Australian Aboriginals

Patterns of dental development in 125 Australian Aboriginal boys and girls, in a growth study at Yuendumu in the Northern Territory of Australia, were compared with Australians of European origin using mean tooth emergence curves constructed from the emergence times of right and left side permanent teeth. There were two active phases of tooth emergence separated by a quiescent period of 1.4 years in boys and 1.0 years in girls. Phase one included emergence of the first 12 teeth, that is the first permanent molars and all incisors; phase two included emergence of the canines, premolars and second molars. In Aboriginal girls most teeth emerged earlier than in boys. Compared with the European-descended, the Aboriginal children displayed earlier emergence of most teeth during phase two and a shorter quiescent period between the two phases, an emergence pattern similar to that reported in other non-European populations. In Aboriginals the process tooth emergence and subsequent alignment is aided by adequate space and compensatory bone growth growth in the alveolar regions. These factors, as well as the genetic differences between groups, contribute to the earlier emergence of teeth during phase two in the Aboriginal children.     

Innate immune memory in mammals

Innate and adaptive immunity have evolved as sophisticated mechanisms of host defence against invading pathogens. Classically the properties attributed to innate immunity are its rapid pleiotropic response, and to adaptive immunity its specificity and ability to retain a long-term memory of past infections. It is now clear that innate immunity also contributes to raising a memory response upon pathogenic assault. In this review we will discuss the interaction between bacterial, viral, fungal and parasitic molecular patterns and innate immune cells in which a memory response is imposed, or has the potential to be imposed.     

DNA damage checkpoints in mammals

DNA damage is a common event and probably leads to mutation or deletion within chromosomal DNA, which may cause cancer or premature aging. DNA damage induces several cellular responses including DNA repair, checkpoint activity and the triggering of apoptotic pathways. DNA damage checkpoints are associated with biochemical pathways that end delay or arrest of cell-cycle progression. These checkpoints engage damage sensor proteins, such as the Rad9-Rad1-Hus1 (9-1-1) complex, and the Rad17-RFC complex, in the detection of DNA damage and transduction of signals to ATM, ATR, Chk1 and Chk2 kinases. Chk1 and Chk2 kinases regulate Cdc25, Wee1 and p53 that ultimately inactivate cyclin-dependent kinases (Cdks) which inhibit cell-cycle progression. In this review, we discuss the molecular mechanisms by which DNA damage is recognized by sensor proteins and signals are transmitted to Cdks. We classify the genes involved in checkpoint signaling into four categories, namely sensors, mediators, transducers and effectors, although their proteins have the broad activity, and thus this classification is for convenience and is not definitive.     

Regeneration of kidneys in mammals

Summary Experiments were performed on rats. A detailed morphological analysis was carried out of changes which take place in residual part of the kidney at various periods following operation of ablation of one kidney and partial resection of the other.The changes involve the whole parenchyma of the kidney and consist in increase of the size of the structural elements of the kidney (tubules and Malpighian bodies) caused mostly by cellular hyperplasia with their partial hypertrophy. Besides, the intercellular spaces are enlarged, particularly the tubular lumen and the cavity of Malpighian bodies.Presented by N. N. Zhukov-Verezhnikov, Active Member Acad. Med. Sci. USSR     

Osteoarthritis in two marine mammals and 22 land mammals: learning from skeletal remains

The occurrence of osteoarthritis (OA) in marine mammals is still questionable. Here we investigated the prevalence of OA in marine (dolphin and dugong) and terrestrial mammals (Asian elephant, Asiatic buffalo, camel, cat, cattle, deer, dog, domestic goat, horse, human, hyena, impala, lion, Malayan tapir, Assam macaque, mule, pig, rabbit, red kangaroo, sheep, tiger and waterbuck). Skeletal remains obtained from five institutes were used as subjects; a total of 45 different parts (locations) of bones were observed for OA lesions. The prevalence of OA was reported as number of OA lesions/total number of bones. Our results revealed that the presence of OA in marine species (dolphin and dugong) was 2.44% and 3.33%, respectively. In dolphins, the highest OA occurrence was on the left and right humeral trochlea, with 13.68% and 12.63%, respectively, while the highest number of OA lesions in dugongs was on the lumbar vertebrae (8.79%). No significant difference (P > 0.05) in the prevalence of OA between sexes in dolphins and dugongs was observed, but we found a significant difference (P < 0.05) in 24 bone locations of human bones, which had the highest OA prevalence (48.93%), followed by dogs (3.94%). In conclusion, OA can occur in marine mammals, similar to terrestrial mammals, even though their natural habitat is the ocean.     

根管预备后牙齿力学性能和根管结构的研究

目的　研究根管预备后牙齿力学性能和根管结构的变化。方法　通过构建牙齿的三维有限元模型和牙根管的中心线模型来分别研究牙齿的力学性能和根管结构。结果　分别建立了根管预备前、后牙齿的三维有限元模型和牙根管的中心线模型;并进行了牙齿力学性能的分析和中心线变化的精确比较。结论　所提出的方法支持快速构建精细的牙齿三维有限元模型和牙根管的中心线模型,能够满足各种牙体生物力学分析的需要。