Assessment of symphysis morphology as a predictor of the direction of mandibular growth

The purpose of this study was to determine whether symphysis morphology could be used as a predictor of the direction of mandibular growth and to assess growth changes of the symphysis. Cross-sectional data included lateral cephalometric radiographs of 115 adults (58 women, 57 men) with the longitudinal sample a subset of 62 subjects (30 females, 32 males) at four age groups. The direction of mandibular growth was evaluated with seven cephalometric measurements that included Y-axis, SN to mandibular plane, palatal plane to mandibular plane, gonial angle, sum of saddle, articulare and gonial angles, percentage lower facial height, and posterior/anterior face height. The mandibular symphyseal dimensions studied were height, depth, ratio (height/depth), and angle. Symphysis morphology was found to be associated with the direction of mandibular growth, especially in male subjects with symphysis ratio having the strongest relationship. A mandible with an anterior growth direction was associated with a small height, large depth, small ratio, and large angle of the symphysis. Conversely, a posterior growth direction was associated with a large height, small depth, large ratio, and small angle of the symphysis. Symphysis dimensions continued to change until adulthood with male subjects having a greater and later occurring change compared with female subjects.     

Peripartum pubic symphysis separation: a case series and review of the literature

Peripartum pubic symphysis separation is a recognized complication of pregnancy with incidence estimates ranging from 1:300 to 1:30,000. Characteristic symptoms of symphyseal separation include suprapubic pain and tenderness with radiation to the back of legs, difficulty ambulating, and occasionally, bladder dysfunction. Clinical history, presenting symptoms, and response to therapy are sufficient to make the diagnosis, although radiographic documentation of symphyseal separation by x-ray or ultrasound are frequently used to confirm the diagnosis. The underlying etiology of symptomatic symphyseal separation has not been fully elucidated. Associations with multiparity, macrosomia, pathological joint loosening, and increased force placed on the pelvic ring have been suggested as possible etiologies. Conservative therapy, including bedrest, pelvic binders, ambulation devices, and mild analgesics usually result in a complete recovery with 4 to 6 weeks. The occurrence of a symphyseal separation should not significantly alter the management of subsequent pregnancies, and conservative therapy is recommended for any recurrence of symptoms. A retrospective review of our experience with 5121 deliveries from 1994 to 1995 found 9 cases of peripartum symphyseal separation, resulting in an incidence of 1 of 569 deliveries. Details regarding this case series and a review of the literature are presented.     

The effect of post milking teat dip and suckling on teat skin condition, bacterial colonisation, and udder health

The aim of this study was to investigate whether in the maxilla and in the mandible the structure of the anterior medial sagittal alveolar and basal bone is related to the overbite. A total of 460 untreated adult subjects were divided into four groups with either deep bite, normal overbite, end-to-end bite, or open bite and were compared. The overbite, lower face height, and anterior alveolar and basal midsagittal cross-sectional areas from the maxilla and the mandible were assessed on lateral cephalometric radiographs. An index was calculated, dividing the sagittal by the vertical dimension of the midsagittal cross-sectional area. A deeper bite coincided with smaller lower face height, larger alveolar and basal areas, and a more widened shape of the symphysis. If the lower face height was introduced as a covariable, the open bite group showed significantly smaller maxillary and mandibular alveolar and basal cross-sectional areas compared with the end-to-end group, the normal overbite group, or the deep bite group. Vertical variation of the overbite probably coincides with a relative hyperdevelopment or hypodevelopment of the symphysis.     

Intrasexual competition and body weight dimorphism in anthropoid primates

Body weight dimorphism in anthropoid primates has been thought to be a consequence of sexual selection resulting from male-male competition for access to mates. However, while monogamous anthropoids show low degrees of weight dimorphism, as predicted by the sexual selection hypothesis, polygynous anthropoids show high variation in weight dimorphism that is not associated with measures of mating system or sex ratio. This observation has led many to debate the role of other factors such as dietary constraints, predation pressure, substrate constraints, allometric effects, and phylogeny in the evolution of anthropoid weight dimorphism. Here, we re-evaluate variation in adult body weight dimorphism in anthropoids, testing the sexual selection hypothesis using categorical estimates of the degree of male-male intrasexual competition ("competition levels"). We also test the hypotheses that interspecific variation in body weight dimorphism is associated with female body weight and categorical estimates of diet, substrate use, and phylogeny. Weight dimorphism is strongly associated with competition levels, corroborating the sexual selection hypothesis. Weight dimorphism is positively correlated with increasing female body weight, but evidence suggests that the correlation reflects an interaction between overall size and behavior. Arboreal species are, on average, less dimorphic than terrestrial species, while more frugivorous species tend to be more dimorphic than folivorous or insectivorous species. Several alternative hypotheses can explain these latter results. Weight dimorphism is correlated with taxonomy, but so too are competition levels. We suggest that most taxonomic correlations of weight dimorphism represent "phylogenetic niche conservatism"; however, colobines show consistently low degrees of weight dimorphism for reasons that are not clear.     

Quantitative changes in pharmacodynamic parameters of noradrenaline in different rat aorta preparations: influence of endogenous EDRF

The adaptive nature of taste discrimination has been questioned on the basis that marked differences in taste thresholds for soluble sugars across mammals may not correspond to distinct dietary tendencies and further imply inaccurate prediction of the energetic value of food. Appropriate models of the evolution of taste, however, require not only consideration of adaptations to diet but also recognition of phylogenetic and allometric effects. Here, we analyse these factors in primates exhibiting various diets and covering a wide range of body weights. Taste thresholds for sucrose and fructose are negatively related to body weight overall but are commonly similar in closely related species irrespective of dietary specialisations. By contrast, major interspecific differences in the discrimination of quinine hydrochloride are observed in the absence of any allometric effect. We propose that this asymmetrical differentiation of sweet and bitter taste discrimination reflects divergent evolutionary trends for meeting energy requirements and for avoiding noxious substances.     

Effect of pubic symphysiodesis on acetabular rotation and pelvic development in guinea pigs

OBJECTIVE: To evaluate the effect of premature closure of the pubic symphysis on pelvic development. ANIMALS: 18, 21-day-old male guinea pigs. PROCEDURE: The pubic symphysis was surgically approached in 10 guinea pigs of the symphysiodesis group and in 4 of the sham-operated group; 4 guinea pigs served as unoperated controls. The pubic symphysis was destroyed by use of electrocautery in the 10 guinea pigs of the symphysiodesis group. All guinea pigs were allowed to grow to skeletal maturity and were euthanatized at 33 weeks of age. Body weight was recorded throughout the study and was compared between groups. Histologic examination of the symphyses confirmed premature closure of the pubic symphyseal growth plates in guinea pigs of the symphysiodesis group. Pelvic measurements taken from pretreatment radiographic views and from video images of harvested pelves were compared between groups. RESULTS: There were no significant differences between groups with regard to pretreatment radiographic variables, rate of weight gain, or body weight at any time. Pubic symphysiodesis resulted in significant narrowing of the caudal aspect of the pelvis, narrowing and shortening of the pubic bones, and outward rotation of the acetabula. CONCLUSIONS: The pubic symphyseal growth plates contribute significantly to development of the pelvis. Premature closure of these growth plates (pubic symphysiodesis) results in outward rotation of the acetabula, which might be beneficial in some cases of can be hip dysplasia; however, this rotation is accompanied by concomitant narrowing of the caudal aspect of the pelvis.     

Symphyseal separation and transient femoral neuropathy associated with the McRoberts' maneuver

Many authors have recommended the McRoberts' maneuver as the initial technique in the management of shoulder dystocia. There have been, however, no reported adverse maternal outcomes associated with this technique. We report a case of symphyseal separation and transient femoral neuropathy associated with the McRoberts' maneuver. An overly exaggerated lithotomy position and thigh abduction stretches the articular surfaces of the symphysis pubis and places increased pressure on the femoral nerve by the overlying inguinal ligament.     

A review of sunscreen safety and efficacy

Sexual dimorphism in primate species expresses the effects of phylogeny, life history, behavior, and ontogeny. The causes and implications of sexual dimorphism have been studied in several different primates using a variety of morphological databases such as body weight, canine length, and coat color and ornamentation. In addition to these different patterns of dimorphism, the degree to which a species is dimorphic results from a variety of possible causes. In this study we test the general hypothesis that a species highly dimorphic for one size-based index of dimorphism will be equally dimorphic (relative to other species) for other size-based indices. Specifically, the degree and pattern of sexual dimorphism in Cebus and several other New World monkey species is measured using craniometric data as a substitute for the troublesome range of variation in body weight estimates. In general, the rank ordering of species for dimorphism ratios differs considerably across neural vs. non-neural functional domains of the cranium. The relative degree of sexual dimorphism in different functional regions of the cranium is affected by the independent action of natural selection on those regions. Regions of the cranium upon which natural selection is presumed to have acted within a species show greater degrees of dimorphism than do the same regions in closely related taxa. Within Cebus, C. apella is consistently more dimorphic than other Cebus species for facial measurements, but not for neural or body weight measurements. The pattern in C. apella indicates no single best measurement of the degree of dimorphism in a species; rather, the relative degree of dimorphism applies only to the region being measured and may be enhanced by other selective pressures on morphology.     

Neuropathology in cats experimentally infected with feline immunodeficiency virus: a morphological, immunocytochemical and morphometric study

Head flexion and extension movements near the natural head position (NHP) were analysed for the location of the mean instantaneous centre of rotation (ICR). Forty-six healthy young adults (30 women and 16 men) with sound dentitions, free from cranio-cervical disorders, performed habitual movements that were automatically detected and measured by an infrared three-dimensional motion analyser. ICR and curvature radius were calculated for each movement and subject. In both extension and flexion, ICR position changed during the motion. The movement was symmetrical in all subjects. No gender or flexion/extension differences were found for both ICR position and relevant curvature radius. On average, ICR relative to NHP soft-tissue nasion was located at about 150% of the soft-tissue nasion-right tragus distance, with an angle of about 220 degrees relative to the true horizontal. Results suggest that head flexion or extension is always performed with a combination of rotation (atlanto-occipital joint) and translation (cervical spine) even in the first degrees of motion. Moreover, NHP at rest seems to be some degree more flexed and anterior than head position during movements. These relative positions and their muscular determinants could also influence mandibular posture at rest and during functional movements.     

Heterochrony and allometry: the analysis of evolutionary change in ontogeny

The connection between development and evolution has become the focus of an increasing amount of research in recent years, and heterochrony has long been a key concept in this relation. Heterochrony is defined as evolutionary change in rates and timing of developmental processes; the dimension of time is therefore an essential part in studies of heterochrony. Over the past two decades, evolutionary biologists have used several methodological frameworks to analyse heterochrony, which differ substantially in the way they characterize evolutionary changes in ontogenies and in the resulting classification, although they mostly use the same terms. This review examines how these methods compare ancestral and descendant ontogenies, emphasizing their differences and the potential for contradictory results from analyses using different frameworks. One of the two principal methods uses a clock as a graphical display for comparisons of size, shape and age at a particular ontogenic stage, whereas the other characterizes a developmental process by its time of onset, rate, and time of cessation. The literature on human heterochrony provides particularly clear examples of how these differences produce apparent contradictions when applied to the same problem. Developmental biologists recently have extended the concept of heterochrony to the earliest stages of development and have applied it at the cellular and molecular scale. This extension brought considerations of developmental mechanisms and genetics into the study of heterochrony, which previously was based primarily on phenomenological characterizations of morphological change in ontogeny. Allometry is the pattern of covariation among several morphological traits or between measures of size and shape; unlike heterochrony, allometry does not deal with time explicitly. Two main approaches to the study of allometry are distinguished, which differ in the way they characterize organismal form. One approach defines shape as proportions among measurements, based on considerations of geometric similarity, whereas the other focuses on the covariation among measurements in ontogeny and evolution. Both are related conceptually and through the use of similar algebra. In addition, there are close connections between heterochrony and changes in allometric growth trajectories, although there is no one-to-one correspondence. These relationships and outline links between different analytical frameworks are discussed.     

Discrete trait and dental morphometric affinities of the Tabun 2 mandible

Evolutionary scenarios of Near Eastern Middle Paleolithic hominids depend to an extent upon whether the terminal Middle Pleistocene Tabun 2 mandible has its primary affinities with the late archaic (Neandertal sensu lato) or early modern (Qafzeh-Skhul) human lineage in the region. Since the specimen has been assigned to each group or seen as bridging them, we have re-examined its morphological affinities relative to these two samples, as well as to European samples of later Pleistocene hominids. This has been done with respect to posterior corporeal and ramal discrete traits, symphyseal morphology, and proportional morphometric patterns along the dental arcade. Taking within and between sample ranges of variation into account, the lateral corporeal and ramal discrete characters are either ambiguous or suggest Neandertal affinities. Anterior symphyseal morphology is largely unknown, but a mentum osseum is indicated by a moderate incisura mandibulare anterior, and the tuber symphyseos did not extend superiorly toward the alveoli, a non-modern arrangement. The lingual symphysis presents the largest planum alveolare known for a Near Eastern Middle Paleolithic hominid. Morphometric analysis of proportions along the dental arcade separate Tabun 2 from Near Eastern and European early modern humans and place it among the late archaic humans. It is dentally closest to the Near Eastern late archaic human lineage and the Krapina sample. These analyses therefore indicate that it is best seen as part of the Near Eastern late archaic human lineage with only the mentum osseum and incisure shape indicating any approach to the Qafzeh-Skhul humans within the Near Eastern Middle Paleolithic.     

Position of the mental foramen in adult black Zimbabwean mandibles: a clinical anatomical study

OBJECTIVE: To provide some anatomical information on the shape, size, and position of the mental foramen among Black Zimbabweans that could be used as reference material by dental and other health practitioners during clinical practice in Zimbabwe. DESIGN: Cross sectional anatomical study. SETTING: Department of Anatomy, Faculty of Medicine, University of Zimbabwe, Mount Pleasant, Harare, Zimbabwe. SUBJECTS: 32 mandibles derived from adult Black Zimbabweans. MAIN OUTCOME MEASURES: The shape of the mental foramen, its relation to the lower teeth and its position in relation to the mandibular symphysis, the posterior border of the ramus of the mandible, the lower border of the mandible, and the alveolar margin. RESULTS: The shape of the mental foramen was round in 14 out of 32 mandibles (43.8%) and was oval in the remaining 18 (56.3%). The percentage of occurrence of the mental foramen was highest below the lower second premolar tooth on the right side (position 4) and posterior to it on the left side (position 5). In the vertical plane, the mental foramen lay slightly below the midpoint of the distance between the lower border of the mandible and the alveolar margin (44.1% and 45.5% for the right and left sides respectively). In the horizontal plane, it lay approximately one quarter (27.3% for the right and 27.4% for the left sides) of the distance from the mandibular symphysis to the posterior border of the ramus of the mandible. CONCLUSION: The percentage distribution of the mental foremen in relation to the lower teeth in the adult Black Zimbabwean mandible was at variance with that of other population groups. However, the quantitative position of the mental foremen was bilaterally symmetrical in the adult Black Zimbabwean mandible. The latter observation is of clinical significance to dental and other health practitioners in Zimbabwe with regards to the achievement of effective mental nerve block anaesthesia and the prevention of damage to the mental nerve during surgical procedures on the lower jaw.     

Some principles in the dental crown construction in permanent maxillary centrals of Slovenians

To increase the understanding of the incisors crown form, the lingual fossa depth, crown width and crown thickness between lingual marginal ridges of the permanent maxillary centrals were measured on 257 stone casts of Slovene children. The right-left, male-female differences, as well as the correlations between the variables themselves were analysed. Male centrals exhibited wider and thicker crown compared to female centrals, while the lingual fossa depth showed no sex differences. A positive correlation in terms of positive allometry between lingual fossa depth and crown width was established. A negative lingual fossa depth-crown thickness correlation was found with female left centrals. High right-left symmetry was established, except for the directional asymmetry of all three measured variables on female centrals. The results indicate that the positive correlation in terms of positive allometry between the thickness of the lingual marginal ridges and the crown width is one of the basic principles of the crown formation for the permanent maxillary centrals. Usually we have to work with absolute thickening of the lingual marginal ridges because relative thickening on the account of the crown thickness is less usual. The latter possibility is less favourable for the firmness of the dental crown.     

The sea horse comes of age: Theoretical comment on Rehbein, Killiany, and Mahut (2005) and Killiany, Rehbein, and Mahut (2005).

Impairments in various aspects of learning and memory have been ascribed to the effects of damage to the hippocampal formation in adult nonhuman primates. Whether these effects reflect disturbance of a unitary process or multiple processes within the hippocampus and whether other systems may participate in these functions is unclear. After making hippocampal ablations in infant rhesus monkeys (Macaca mulatta), L. Rehbein, R. Killiany, and H. Mahut (2005) (see record 2005-06959-001) and R. Killiany, L. Rehbein, and H. Mahut (2005) (see record 2005-06959-002) reported a dissociation of effect between tasks of recognition memory and contextual retrieval (impaired) and associative learning (spared). The findings point to an ontogenetic dissociation of function within the hippocampal formation and, at the same time, support the view of the coexistence of at least two neural systems that underlie memory and learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Playing with the face: Playful facial “chattering” and signal modulation in a monkey species (Theropithecus gelada).

Darwin (1872), in The expression of emotions in man and animals, underlined that human facial expressions represent a shared heritage of our species with nonhuman primates. Play is a fertile field to examine the role of facial expressions that we share with our common ancestors because the primate play face is homologous to human laughter. Here, we focus on the use of two playful expression variants (PF: play face, mouth opened with only the lower teeth exposed; FPF: full play face, lower/upper teeth and gums exposed via the actively retraction of the upper lip) in Theropithecus gelada. During ontogeny PF was replaced by FPF; in older subjects PF was virtually absent. The ontogenetic transition appears to reflect the phylogenetic sequence of the two playful displays with FPF considered a derived form of PF. This age-trend bias of facial displays is probably due to their different roles in communication. The correspondence between facial signals emitted and elicited is a valuable criterion to evaluate playmates' attentional state. Adults were more sensitive than immatures in responding to the play faces of others. Probably, previous playful experience, social competence, and neural circuit maturation are at the basis of adult sensitiveness. Similar to humans, where unconscious laughing is deserved for close friends and/or relatives, FPF was extremely frequent during gelada mother-offspring play. Probably, under some intimate circumstances, facial displays should be primarily linked to the spontaneous expression of emotional states of the sender more than to the strategic transfer of actual information to the receiver. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Comparative study of craniofacial morphology in Japanese and Australian aboriginal populations

A metric study of 71 Japanese and 106 Australian aboriginal precontemporary crania was undertaken using direct measurements and cephalograms. Compared with Australian aboriginals, the Japanese are characterized by smaller cranial length, cranial base length, nasal floor length, palatal length, mandibular dimensions (except symphysis height), facial depth, posterior face height, and facial profile angle and larger cranial breadth and height, maxillary breadth, palatal breadth, anterior face height, and occlusal and mandibular plane angles. These differences confirm the previously described brachycephalic tendency in aboriginals and the dolichocephalic form in the Japanese. The differences are also consistent with the expected functional differences between the Australian aboriginal hunter-gatherer group masticating more resistant food with larger, more anteriorly located, more powerful masseter muscles and the Japanese group masticating less resistant food with correspondingly less robust masticatory musculature. The results highlight the differences in craniofacial morphology between groups with different genetic backgrounds subjected to significantly different environmental influences.     

Special relationships instead of female dominance for redfronted lemurs, Eulemur fulvus rufus

Most lemurs yet studied in detail exhibit some mode of adult female social dominance over males. The known exception, a brown lemur subspecies known as rufous or redfronted lemurs (Eulemur fulvus rufus), forms multimale-multifemale social groups within which unambiguous dominance relations are not observed among adults. Resting groups of redfronted lemurs consistently include huddling adult male-female pairs whose males selectively scentmark and rub their heads in the scentmarks of their female huddling partners. Quantitative observations confirmed that some of these male-female pairs maintain special relationships satisfying all criteria originally developed in research on cercopithecine monkeys. Observations before, during, and after mating season, intergroup encounters, male transfers, and changes in male-female affiliations illuminated developmental and functional aspects of male-female partnerships. Each adult female in two semi-free-ranging study groups shared high rates of association, grooming, and agonistic support and low rates of agonistic interaction with one unrelated or distantly related adult male partner. Such affinity characterized small proportions of adult male-female relationships. Several males directed not only support but also aggression toward adult females with whom they sought to affiliate. All bonded males sought to copulate with their partners, and some appeared to ignore estrus in nonpartners. All females accepted copulation attempts from partners and some seemed to prefer their partners as mates. Partial synchronization of brief estrus periods together with concealed ovulation appeared to minimize chances for polygynous mating. Results support the view that the male-female pair is the fundamental social unit of E. fulvus and suggest that female partnership with individual males obviates dominance behavior, including female dominance, in this lemurid primate.     

Development, microevolution, and social behavior.

The central questions of social development—from the roots of mother–infant attachment to the plasticity of aggressive behavior—pivot on the relations between genetic and ontogenetic sources of variance. It is proposed that (a) developmental, experiential, and microevolutionary processes typically collaborate, rather than compete, in achieving social adaptation; (b) social behavior patterns are mostly closed to modification in the course of development and across generations, but avenues of vulnerability exist in ontogeny and microevolution for dynamic, rapid, and reversible changes in key features; (c) a general avenue for change is delay or acceleration in the developmental onset of one or more features of the behavior pattern, which in turn modifies the functions and properties of the adaptive configuration; and (d) the features of social behavior that are open to rapid change in ontogeny should be open as well to rapid changes in microevolution, although different underlying processes may be involved. Empirical findings from the investigation of aggressive interactions are used to illustrate this proposal on the dual genesis and coincident adaptation of social behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Male and female sexual behavior potential of male rats prenatally exposed to the influence of alcohol, stress, or both factors.

Adult sexual behaviors were characterized in male rats prenatally exposed to ethanol, stress, or ethanol combined with stress; 60% to 75% of each group exhibited female-typical lordosis. A substantial proportion of males subjected to alcohol (44%) or to alcohol with stress (54%) failed to ejaculate. The adult genitalia and testicular size appeared normal in all groups. Either alcohol or stress can suppress fetal plasma testosterone. Thus, exposing pregnant dams to alcohol, particularly in association with stress, may alter the hormonal milieu of their male fetuses sufficiently to block full masculinization and defeminization of sexually dimorphic copulatory behavior potentials, but not anatomy. It appears that certain pharmacological and stressful factors can interact during fetal ontogeny to influence the process of sexual behavior differentiation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)