Anatomical macroelements in the study of craniofacial rat growth.

In order to avoid the arbitrary division of biological structures, rational polynomial interpolants are utilized to study growth. The major advantage of this method is the elimination of artificial internal element boundaries through anatomical structures. Since the boundary element methodology is employed in the finite element setting, other benefits, without additional computer coding, include the ability to use elements with any number of sides and reference frame invariance. Longitudinal landmark coordinates from midsagittal X-ray tracings of 22 albino female rat skulls of various ages were averaged. The skull was partitioned into three macroelements: a neural skull and two functionally distinct portions of the facial skull--olfactory and respiratory. The digital computer programming was carried out in the computer mathematics environment of Mathematica. Maximum elongation ratios were calculated for approximately 400 interior points. The elongation ratios in the neural skull compared well with previously documented growth behavior of internal brain structures. The calculated ratios from the facial skull were used to analyze the behavior of macroelement interpolation close to common anatomical boundaries.     

Biology of the rice rat (Oryzomys palustris natator) in a laborabory environment. X. Postweaning growth of the skull.

A survey of skull development of the rice rat (Oryzomys palustris natator) covering a period of 21 days to 16 months involving equal numbers of males and females (108) was undertaken using various skull parameters. Sexual dimorphism in relation to body weight and length emerged before that of the skull which was only clearly marked by 2 months. A number of the skull parameters by virtue of their individual growth potential did not show sexual differences in size for a long time, whereas others were clearly marked. Once the differences between the sexes had been established they were maintained. One parameter - lenght of cranium - represents those parameters which show changes and it was found that the male rat continued to show a steady linear increase in length up to 16 months, whereas the female cranial length shows a deceleration with termination around 12 months. The skull differences are mirrored in the weight and length findings and it suggested that the earlier sexual maturity of the females is compensated by an earlier cessation of growth compared to the males which mature later and have a correspondingly later cessation.     

Postnatal growth of skull linear measurements of Cape Hare Lepus capensis in northern China: an analysis in an adaptive context

304 skulls of Cape hare (Lepus capensis) were collected from two climatically distinct localities in northern China. With eye lens weight as a continuous age variable, postnatal growth patterns of 25 cranial linear measurements in relation to sex, growth season and region were analysed to understand the morphological basis of life history adaptation. In almost all the skull measurements, no significant differences were found between either sex or growth seasons. Principal component analysis revealed that facial elements accounted for the greatest proportion of skull morphological variation. Von Bertalanffy function was applied to describe growth trajectories of the skull elements. Based on this model, the growth rates of skull elements and the age at which they reached a certain proportion (95%) of asymptotes were compared. The results showed that skull growth exhibited an allometric pattern, with neural components attaining their final size more rapidly (at about 2–3 months old in tympanic bulla and 4–6 months old in others) than did the facial, which continued to grow well into postnatal life (at 6–10 months old). The earlier establishment of neurocranial morphology was associated with a fully developed central nervous system, which may play a key role in improving the survival of animals during the early phase of life. There was a regional difference in developmental rate of the hare skull. For all the skull parameters, northern hares had a more rapid rate of cranial growth compared to the southern, i.e. skull elements of juveniles from northern population were relatively larger at comparable ages and achieved adult size 0.5–4.0 months earlier than those from the south. In adult hares, however, no significant regional differences in any of the skull parameters were present. Adaptive explanations for the regional difference in ontogenetic pattern of skull morphology include age‐specific thermoregulation constraint, season‐related food availability and age‐dependent predation pressure. Based on the findings of this study, it is suggested that the postnatal growing period represents a crucial time of life, and that improvement of survivorship when young by growth adaptation forms an important aspect of the hare's life history strategies. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 78 , 343–353.     

Determination of the thermogenesis curves and studies of the thermodynamics and thermokinetics of seed germination

The thermogenesis curves of the germination of different rice and tree seeds were determined and studied by using a newly constructed microcalorimeter. The thermogenesis curves of the germination of the seeds demonstrate the existence of physiological triphasic patterns, which include imbibition, activation and growth stages in the germination process. The thermodynamics and thermokinetics of the main growth phase of the growth stage in the germination process have been studied. The growth heat effect (deltaH), the growth rate constant (k), the growth inhibitory factor (s) and deceleration rate constant (beta) have been determined and calculated, In addition, the experimental thermokinetic equations of the growth stage in the seed germination process have been established.     

A commentary on the growth of the human brain and skull

This paper tests the suggestion put forth by Tanner ('55) and Eichorn and Bayley ('62) to the effect that the brain participates in the parapubertal spurt of growth which characterizes many of the dimensions of the human body. To this end, longitudinal data consisting of oriented head roentgenograms of 11 boys were examined. Two measurements were taken directly from each lateral head film: (1) skull length, measured from glabella to opisthocranion, and (2) endocranial length, the maximum length of the endocranial contour in the mid-sagittal plane. While many of the individual cumulative curves depicting growth in skull length exhibit a parapubertal acceleration, all of the curves for endocranial length comprise segments of a parabolic arc representing a single decelerating phase of growth. Mean incremental curves, mathematically fitted, further emphasize the differences in velocity and pattern of size attainment for the two dimensions tested. The data here presented, then, fail to implicate the brain in the general spurt of growth evident for the external dimensions of the head at adolescence. It is suggested that two discrete systems are evident in the growth of the skull: a rapidly growing neural system essentially completed by adolescence, and a facial system of slower growth and longer duration. The conventional measurement of skull length cuts across both systems, appraising neural growth and the cerebral skeletal envelope prior to adolescence, and then superimposing the facial component, the forward projection of the frontal sinus, during adolescence and post-adolescence.     

检测大肠杆菌群体生长动力学过程4种方法的比较

用浊度测定、菌落形成数计数（CFU）、流式细胞计数（FCT）,以及MTT还原测脱氢酶活力4种检测方法,测定了E．coliCVCC249群体的生长量,并通过Logistic模型、Sigmoid模型,以及正态分布方程拟合由上述生物量所表征的群体生长动力学过程曲线．结果表明,对浊度和流式检测数据,Logistic和Sigmoid方程可给出较好的拟合度,而对CFU法和脱氢酶活力检测法,仅有正态分布方程能呈现更好的拟合．通过应用有限时域向前差分的方法,消除不能增殖的休止细胞对浊度生长过程曲线的影响,以模拟菌群增殖的过程曲线．在此基础上,求得菌群生长的即时速度（advancingvelocity,Vad。）和即时速度的瞬变率,以此为据将E．coliCVCC249生长过程划分为线性增长期、指数增长期、指数减速期、线性减速期,以及衰亡期5个阶段．此外,对新的划分生长阶段的方法与经典方法的不同,以及R。（拟合决定系数）能否作为确定模型是否拟合的唯一判据,进行了讨论．     

Studies on orthocephalization. 2. Flexions of the rat head in the period between 14 and 60 days after gestation

The present paper considers the significance of a variety of cranial flexions in the process of orthocephalization of the rat skull between 14 and 60 days postnatally. The study is based on a sample of 27 male rats, who have been x-rayed at 14, 30 and 60 days with subsequent analyses of the photographs obtained. In this period the angle between the cranial base and the facial part of the skull becomes more obtuse, i.e. the skull becomes more orthocranial. The cranial base becomes at the same time more airobasal (lordotic). Angular changes between the individual bones in the cranial vault straightens the vault markedly. By this it becomes orthodorsal. As the angle between the basisphenoid and the parietal bones stays more or less constant between 14 and 60 days, the impression is created that both the anterior and posterior parts of the neural skull rotate upwards relative to this bone complex. Thus, orthocephalization in the period between 14 and 60 days both consists of flexions between the facial and neural parts of the skull (prebasal flexions), and may be more importantly of interosseous ventral and dorsal flexions.     

An imprinted gene network that controls mammalian somatic growth is down-regulated during postnatal growth deceleration in multiple organs

In mammals, somatic growth is rapid in early postnatal life but decelerates with age and eventually halts, thus determining the adult body size of the species. This growth deceleration, which reflects declining proliferation, occurs simultaneously in multiple organs yet appears not to be coordinated by a systemic mechanism. We, therefore, hypothesized that growth deceleration results from a growth-limiting genetic program that is common to multiple tissues. Here, we identified a set of 11 imprinted genes that show down-regulation of mRNA expression with age in multiple organs. For these genes, Igf2, H19, Plagl1, Mest, Peg3, Dlk1, Gtl2, Grb10, Ndn, Cdkn1c, and SLC38a4, the declines show a temporal pattern similar to the decline in growth rate. All 11 genes have been implicated in the control of cell proliferation or somatic growth. Thus, our findings suggest that the declining expression of these genes contributes to coordinate growth deceleration in multiple tissues. We next hypothesized that the coordinate decline in expression of these imprinted genes is caused by altered methylation and consequent silencing of the expressed allele. Contrary to this hypothesis, the methylation status of the promoter regions of Mest, Peg3, and Plagl1 did not change with age. Our findings suggest that a set of growth-regulating imprinted genes is expressed at high levels in multiple tissues in early postnatal life, contributing to rapid somatic growth, but that these genes are subsequently downregulated in multiple tissues simultaneously, contributing to coordinate growth deceleration and cessation, thus imposing a fundamental limit on adult body size.     

Ontogenic growth changes of the skull base in four genera of nonhuman primates.

Cross-sectional studies of the degree of the cranial base flexion were carried out in infant, juvenile and adult skulls in four genera of nonhuman primates (P. paniscus, H. lar, P. urinus, and M. mullatta). The cephalometric observations of the cranial base included linear and angular measurements of each specimen. The data obtained in this study showed that the anterior portion of the cranial base exhibits a significant shortening trend as the mammalian evolutionary scale ascends. Moreover, the growth pattern of the anterior portion of the skull base follows that of the facial bony structures. The ontogenic growth changes of the posterior portion of the skull base follows the growth pattern of the endocranial cavity. The significant trend of elongation in this area directly contributes to the posterior migration of the foramen magnum. The magnitude of these growth changes decreases as the evolutionary scale ascends. The angular measurements of the cranial flexion showed a less obtuse cranial base angle in young specimens and the ones higher on the mammalian scale. The skull kyphosis was less pronounced in these specimens and the anatomical features of the cranial base were more humanlike, including the balance of the head expressed by the position of the foramen magnum.     

Kinetics of Candida lipolytica yeast growth and biosynthesis of alpha-keto acids with thiamine deficiency in media with different carbon sources

The growth kinetics of Candida lipolytica on glucose, acetate and hexadecane was studied in batch cultures at thiamine deficiency. The growth at the deceleration phase is of a linear character. The transition from the exponential phase to the linear one is accompanied with the accumulation of alpha-keto acids in the cultural broth, which is also observed in the stationary phase. The rate of acid production in the linear phase increases as the specific growth rate decreases, and reaches the maximum value in media with different carbon sources at mu = 0.01--0.06 h-1. Apparently, the deceleration of growth is due to a decrease in the activity of a thiamine-dependent enzyme (pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase or transketolase) which is a limiting point of biosynthetic processes. Here, a linear growth is determined by the constant activity of this enzyme per unit volume of the cultural broth which, in turn, depends on the constant concentration of the coenzyme, thiamine diphosphate, in the same volume.     

Roentgen cephalometric studies on skull development in rats. II. Normal and hypophysectomized males; sex differences

Growth of the skull in normal male rats of the Long-Evans strain has been studied by serial roentgen cephalometry (under anesthesia) from 27 to 280 days of age, and has been compared with the retardation following hypophysectomy and with growth data obtained on females in an earlier similar study. The dimensions measured represented major skull regions and segments, and in some instances allowed calculation of indices (e.g., neurocranial width/length ratio) which would show changing proportions. In general, the skull showed the more rapid and prolonged growth characteristic of male rats' skeletal development when compared with that of females. Viscerocranial (“facial”) length and width were notable in this respect. On the other hand, growth in neurocranial width and height ceased at a time and size much like that in females. Examination of the possibility that the adult female skull might correspond closely to that of an immature male disclosed that though this might be true for the neurocranium, facial dimensions showed distinctive sex differences. After hypophysectomy at 27 days of age males (as also females) showed marked reduction of growth but not complete cessation. Dimensional increases were between one-fifth and one-fourth of the normal gains. The ratios computed showed that the proportions of infancy were retained after early hypophysectomy.     

Triphasic reduction of cytochrome b and the protonmotive Q cycle pathway of electron transfer in the cytochrome bc1 complex of the mitochondrial respiratory chain

Reduction of cytochrome b in isolated succinate-cytochrome c reductase is a triphasic reaction. Initially, there is a relatively rapid, partial reduction of the cytochrome b, the rate of which matches the rate of reduction of cytochrome c1. This is followed by partial or complete reoxidation of the b, which is then followed by slow rereduction. At very low concentrations of succinate, the initial partial reduction of b is followed by reoxidation, but the third (rereduction) phase is absent, owing to insufficient substrate to rereduce the cytochromes. If antimycin is added at various times during the triphasic reaction, it inhibits the reoxidation and also inhibits the rereduction phase. Antimycin does not inhibit the initial phase of b reduction and, if added before or during this phase, it causes reduction of b to proceed to completion as a monophasic reaction. Myxothiazol inhibits the first phase of b reduction and the subsequent reoxidation, but does not inhibit the third, slow phase of b reduction. The resulting monophasic reduction of b which is observed in the presence of myxothiazol is slower than that in the presence of antimycin. The combination of both inhibitors, whether added together or successively during the triphasic reaction, completely inhibits b reduction. The triphasic reduction of cytochrome b is consistent with electron transfer by a protonmotive Q cycle in which there are two pathways for cytochrome b reduction. One pathway allows the initial phase of cytochrome b reduction by a myxothiazol-sensitive reaction in which reduction of b by ubisemiquinone is linked to reduction of iron-sulfur protein and cytochrome c1 by ubiquinol. In the second phase of the triphasic reaction, the b cytochromes are reoxidized by ubiquinone or ubisemiquinone through an antimycin-sensitive reaction. If oxidation of ubiquinol by iron-sulfur protein is blocked, either by myxothiazol or by reduction of iron-sulfur protein and cytochrome c1, the b cytochromes can be reduced by reversal of the antimycin-sensitive pathway, thus accounting for the third phase of b reduction.     

The influence of experimental deformation on craniofacial development in rats

Cranial deformation was produced experimentally in rats 8 to 40 days old for the purpose of studying the rotation of the craniofacial bones and the modification of the growth rates of the functional cranial components. One hundred and twenty four skulls (65 males and 59 females) were employed, classified as: deformed , deformed-hydrocephalic, sham-operated and controls. A midsagittal diagram was drawn for each skull and the angle subtended by each bone with respect to the vestibular plane was measured. Growth indices were worked out for both the neural skull and the facial skull. Deformation altered the rotation of the parietal, interparietal and basisphenoidal bones and restricted the rotation of the fronto-ethmo-facial complex. Alteration of the longitudinal growth rates of the dorsal and basilar components of the neurocranium and the splanchnocranium produced the persistence of the klinorynchal state.     

Tissue origins and interactions in the mammalian skull vault.

During mammalian evolution, expansion of the cerebral hemispheres was accompanied by expansion of the frontal and parietal bones of the skull vault and deployment of the coronal (fronto-parietal) and sagittal (parietal-parietal) sutures as major growth centres. Using a transgenic mouse with a permanent neural crest cell lineage marker, Wnt1-Cre/R26R, we show that both sutures are formed at a neural crest-mesoderm interface: the frontal bones are neural crest-derived and the parietal bones mesodermal, with a tongue of neural crest between the two parietal bones. By detailed analysis of neural crest migration pathways using X-gal staining, and mesodermal tracing by DiI labelling, we show that the neural crest-mesodermal tissue juxtaposition that later forms the coronal suture is established at E9.5 as the caudal boundary of the frontonasal mesenchyme. As the cerebral hemispheres expand, they extend caudally, passing beneath the neural crest-mesodermal interface within the dermis, carrying with them a layer of neural crest cells that forms their meningeal covering. Exposure of embryos to retinoic acid at E10.0 reduces this meningeal neural crest and inhibits parietal ossification, suggesting that intramembranous ossification of this mesodermal bone requires interaction with neural crest-derived meninges, whereas ossification of the neural crest-derived frontal bone is autonomous. These observations provide new perspectives on skull evolution and on human genetic abnormalities of skull growth and ossification.     

The effect of ionizing radiation on the viability of Trichomonas vaginalis.

1. The effects of continuous gamma radiation on the viability of Trichomonas vaginalis (ATCC 30001) were assessed by a colony count technique. 2. A triphasic survival curve showed an initial shoulder (Dq) of 3 Gy followed by three linear curves with D0 values of 34, 300, and 90 Gy. 3. Sterilization of 10(6) cells/ml occurred from 1600 to 1800 Gy of radiation. 4. Population growth, subsequent to radiation exposure of 17-100 Gy, showed an increased lag time followed by a faster rate of growth, compared with unirradiated cells. 5. Trichomonas vaginalis is more sensitive to ionizing radiation than free-living protozoa and appears as radiosensitive as those parasitic protozoa examined in radioattenuation experiments.     

Growth of the skull in the mutant dwarf mouse

By following the development of individual mice from birth to 200 days of age, it was found that the skull of the homozygous mutant (dwdw) was 5% shorter than that of the normal phenotype at birth and some 30% shorter at 200 days of age. During post-natal growth of the skull, the cranium was least altered but the facial skeleton was greatly affected. The differences seen in different parts of the skull are attributed to the peak growth velocities of the various parts occurring at different times.     

Follow-up study of small-for-dates babies.

A group of small-for-dates full-term babies whose intra-uterine growth was followed by serial ultrasonic cephalometry were examined at a mean age of 4 years. Those children whose skull growth had begun to slow in utero before 34 weeks'' menstrual age were more likely to have a height and weight less than the 10th centile. When the onset of growth failure had occurred before 26 weeks there was a lower developmental quotient at follow-up using the Griffiths extended scales. Prolonged slow growth in utero therefore seems to be followed by slow growth and development after birth.     

Negative effect of Hox gene expression on the development of the neural crest-derived facial skeleton

Diencephalic, mesencephalic and metencephalic neural crest cells are skeletogenic and derive from neural folds that do not express Hox genes. In order to examine the influence of Hox gene expression on skull morphogenesis, expression of Hoxa2, Hoxa3 and Hoxb4 in conjunction with that of the green fluorescent protein has been selectively targeted to the Hox-negative neural folds of the avian embryo prior to the onset of crest cell emigration. Hoxa2 expression precludes the development of the entire facial skeleton. Transgenic Hoxa2 embryos such as those from which the Hox-negative domain of the cephalic neural crest has been removed have no upper or lower jaws and no frontonasal structures. Embryos subjected to the forced expression of Hoxa3 and Hoxb4 show severe defects in the facial skeleton but not a complete absence of facial cartilage. Hoxa3 prevents the formation of the skeleton derived from the first branchial arch, but allows the development (albeit reduced) of the nasal septum. Hoxb4, by contrast, hampers the formation of the nasal bud-derived skeleton, while allowing that of a proximal (but not distal) segment of the lower jaw. The combined effect of Hoxa3 and Hoxb4 prevents the formation of facial skeletal structures, comparable with Hoxa2. None of these genes impairs the formation of neural derivatives of the crest. These results suggest that over the course of evolution, the absence of Hox gene expression in the anterior part of the chordate embryo was crucial in the vertebrate phylum for the development of a face, jaws and brain case, and, hence, also for that of the forebrain.     

Variability,morphometrics, and co-variation of the os lacrimale in Cervidae

In Ruminantia, the lacrimal bone forms a considerable part of the facial skeleton, and the morphology of its facial facet is highly variable when compared to other mammals. In this study, we quantify the species-specific variability in size and shape of the lacrimal facial facet in species of Cervidae (deer) and relate it to systematics and various aspects of their ecology and behavior. We sampled 143 skull specimens from 10 genera; 12 Moschus and 3 Tragulus specimens were used as outgroups. We find that size and shape of the lacrimal facial facet allow differentiating most species analyzed here, except for Mazama gouazoubira and Capreolus capreolus. Size and shape of the lacrimal facial facet vary widely across Cervidae regardless of their systematic relationships, ecology or behavior. Thus, we could not detect a unique signature of adaptational criteria in lacrimal morphology. Our data indicate that the lacrimal facial facet scales allometrically with skull size, in particular, the lacrimojugal length scales positively and the lacrimomaxillar length scales negatively. However, correlation analyses did not reveal any differences in the integration of the lacrimal bone with any specific skull module in any of the species compared. Lastly, we could not ascertain any correlation between the size and position of the preorbital depression with the size and shape of the lacrimal facial facet. We conclude that the lacrimal facial facet is highly flexible and may rapidly adjust to its surrounding bones. Its allometric growth appears to be an example of exaptation: changes in size and shape in the context of the increase of the skull length provide lacrimal contacts, in particular, a lacrimojugal one, which may serve to reduce mechanical loads resulting from increasingly larger antlers in large cervids.