Comparative architectural properties of limb muscles in Crocodylidae and Alligatoridae and their relevance to divergent use of asymmetrical gaits in extant Crocodylia

Crocodiles and their kin (Crocodylidae) use asymmetrical (bounding and galloping) gaits when moving rapidly. Despite being morphologically and ecologically similar, it seems alligators and their kin (Alligatoridae) do not. To investigate a possible anatomical basis for this apparent major difference in locomotor capabilities, we measured relative masses and internal architecture (fascicle lengths and physiological cross-sectional areas) of muscles of the pectoral and pelvic limbs of 40 individuals from six representative species of Crocodylidae and Alligatoridae. We found that, relative to body mass, Crocodylidae have significantly longer muscle fascicles (increased working range), particularly in the pectoral limb, and generally smaller muscle physiological cross-sectional areas (decreased force-exerting capability) than Alligatoridae. We therefore hypothesise that the ability of some crocodylians to use asymmetrical gaits may be limited more by the ability to make large, rapid limb motions (especially in the pectoral limb) than the ability to exert large limb forces. Furthermore, analysis of scaling patterns in muscle properties shows that limb anatomy in the two clades becomes more divergent during ontogeny. Limb muscle masses, fascicle lengths and physiological cross-sectional areas scale with significantly larger coefficients in Crocodylidae than Alligatoridae. This combination of factors suggests that inter-clade disparity in maximal limb power is highest in adult animals. Therefore, despite their apparent morphological similarities, both mean values and scaling patterns suggest that considerable diversity exists in the locomotor apparatus of extant Crocodylia.     

Homology in the region containing a tRNATrp gene and a (complete or partial) tRNAPro gene in wheat mitochondrial and chloroplast genomes

Summary We have used bean mitochondrial (mt) and chloroplast (cp) tRNA^Trp as probes to locate the corresponding genes on the mt and cp genomes of wheat and we have determined the nucleotide sequences of the wheat mt and cp tRNATrp genes and of the flanking regions. Sequence comparisons show that the wheat mt and cp tRNA^Trp genes are 97% homologous.On the wheat cp DNA, a tRNA _Pro ^UGG gene was found 139 by upstream of the cp tRNA^Trp gene. On the wheat mt DNA, a sequence of 23 nucleotides completely homologous with the 3' end of this cp tRNA^Pro gene was found 136 by upstream of the rut tRNA^Trp gene, but there is only 38% homology between cp and mt wheat genomes in the intergenic regions. The overall organization of this region in the chloroplast genome (a tRNA^Trp gene separated by about 140 by from a tRNA^Pro gene) is also found in the mitochondrial genome, suggesting that this mitochondrial fragment might have originated from a chloroplast DNA insertion. A comparison of the genes and of the intergenic regions located between the tRNA^Trp gene and the tRNA^Pro (or partial tRNA^Pro) gene shows that there is an almost complete conservation of these sequences in the mitochondrial DNA of wheat and maize, whereas wheat mt and cp intergenic regions show more sequence divergence.Wheat mt tRNA^Trp gene is encoded by the main mt genome (accounted for by the master chromosome) but, in the case of maize mitochondria, this gene was found to be encoded by the 2.3 kb linear plasmid, indicating that this plasmid is not dispensable in maize mitochondria.     

Embryogenesis of the Uropygial Glands in the Laysan Albatross (Phoebastria immutabilis (Rothschild, 1893): Procellariiformes)

An avian uropygial gland is located on the mid‐dorsum of the tail, and is the only external gland found in birds. Most studies have focused on the function, gross anatomy and chemical nature of this gland, with little research on its ontogeny. The purpose of this study was to examine the development of this gland in a series of Laysan Albatross (Phoebastria immutabilis) embryos. Specimens were examined anatomically and histologically. It was found that grooves preceded glandular development by many stages. The embryogenesis of the uropygial gland was divided into 6 phases: preinception, groove inception, mesodermal separation, migrating mesodermal cells, oval shaped “depressions”, constriction and finally glandular inception. No other gland is known to develop similarly, though there may be parallels with femoral gland development. In comparison to other bird species, the length of the development period in the Albatross, as well as other compounding factors, make it difficult to determine the significance of these observations. The development of a mesodermal band, soon to be a connective tissue capsule, is more complex than originally described in ducks. Thus, the unique nature of this gland is established, but the significance of the observations required further studies into uropygial gland development. Anat Rec, 300:1420–1428, 2017. © 2017 Wiley Periodicals, Inc.     

大鼠颈髓中央核向前庭神经外侧核的定位纤维投射

目的　探讨大鼠颈髓中央核向前庭神经外侧核的定位投射。方法　本实验通过向脊髓内单侧注射菜豆—白细胞凝集素 ,在不同节段上对由脊髓向前庭神经核的纤维投射做顺行示踪。结果　在颈髓颈 2和颈 3节段包括颈髓中央核单侧注射示踪剂后 ,应用免疫组织化学法在对侧前庭神经下核以及前庭神经内侧核的大型细胞、小型细胞部和尾部内可见大量标记终末。在对侧前庭神经外侧核由头部至尾部整个范围内 ,标记物数量最多 ;在颈膨大处单侧注射示踪剂后 ,在对侧前庭神经内侧核的大型细胞部见很多标记轴突和终末 ,但在前庭神经外侧核和前庭神经下核内 ,仅见少量标记轴突和终末。在颈膨大以下脊髓节段注射示踪剂后 ,在前庭神经内侧核的大型细胞部、前庭神经下核及前庭神经外侧核的尾部标记纤维和终末仅零星存在。结论　颈部初级传入纤维经过颈中央核中继后 ,可直接投射到对侧前庭神经外侧核 ,同时 ,研究结果亦提示颈髓中央核可能是颈部传入冲动的中继和整合之处     

The organization of spinal motor neurons in a monotreme is consistent with a six‐region schema of the mammalian spinal cord

The motor neurons in the spinal cord of an echidna (Tachyglossus aculeatus) have been mapped in Nissl‐stained sections from spinal cord segments defined by spinal nerve anatomy. A medial motor column of motor neurons is found at all spinal cord levels, and a hypaxial column is found at most levels. The organization of the motor neuron clusters in the lateral motor column of the brachial (C5 to T3) and crural (L2 to S3) limb enlargements is very similar to the pattern previously revealed by retrograde tracing in placental mammals, and the motor neuron clusters have been tentatively identified according to the muscle groups they are likely to supply. The region separating the two limb enlargements (T4 to L1) contains preganglionic motor neurons that appear to represent the spinal sympathetic outflow. Immediately caudal to the crural limb enlargement is a short column of preganglionic motor neurons (S3 to S4), which it is believed represents the pelvic parasympathetic outflow. The rostral and caudal ends of the spinal cord contain neither a lateral motor column nor a preganglionic column. Branchial motor neurons (which are believed to supply the sternomastoid and trapezius muscles) are present at the lateral margin of the ventral horn in rostral cervical segments (C2–C4). These same segments contain the phrenic nucleus, which belongs to the hypaxial column. The presence or absence of the main spinal motor neuron columns in the different regions echidna spinal cord (and also in that of other amniote vertebrates) provides a basis for dividing the spinal cord into six main regions – prebrachial, brachial, postbrachial, crural, postcrural and caudal. The considerable biological and functional significance of this subdivision pattern is supported by recent studies on spinal cord hox gene expression in chicks and mice. On the other hand, the familiar ‘segments’ of the spinal cord are defined only by the anatomy of adjacent vertebrae, and are not demarcated by intrinsic gene expression. The recognition of segments defined by vertebrae (somites) is obviously of great value in defining topography, but the emphasis on such segments obscures the underlying evolutionary reality of a spinal cord comprised of six genetically defined regions. The six‐region system can be usefully applied to the spinal cord of any amniote (and probably most anurans), independent of the number of vertebral segments in each part of the spinal column.     

Histology-based morphology of the neurocentral synchondrosis in Alligator mississippiensis (Archosauria, Crocodylia)

Morphology of the neurocentral synchondroses--thin cartilaginous layers between centra and neural arches--are documented in the extant crocodilian, Alligator mississippiensis (Archosauria, Crocodylia). Examination of dry skeletons demonstrates that neurocentral suture closure occurs in very late postnatal ontogeny (after reaching sexual maturity and/or body size ca. 40% from the upper range). Before sexual maturity (body length (BL) ≥ ca. 1.80 m), completely fused centra and neural arches are restricted to the caudal vertebral series. In contrast, the presacral vertebrae often remain unfused throughout postnatal ontogeny, retaining open sutures in very mature individuals (BL ≥ 2.80 m). These unfused centra and neural arches are structurally supported by the relatively large surface area of the neurocentral junctions, which results from primarily horizontal (mediolateral) increases with strong positive allometry. Cleared and stained specimens show that the cartilaginous neurocentral synchondrosis starts to form after approximately 40 embryonic days. Histological examination of the neurocentral junction in dorsal and anterior caudal vertebrae of six individuals (BL = 0.28-3.12 m) shows : (1) neurocentral fusion is the result of endochondral ossification of the neurocentral synchondrosis, (2) the neurocentral synchondrosis exhibits bipolar organization of three types of cartilaginous cells, and (3) complex neurocentral sutures (i.e., curved, zigzagged, and/or interdigitated boundaries) come from clumping of bone cells of the neural arches and centra into the neurocentral synchondrosis. The last two morphological features can be advantageous for delaying neurocentral fusion, which seems to be unique in crocodilians and possibly their close relatives, including nonavian dinosaurs and other Mesozoic archosaurs.     

Molecular structures of centromeric heterochromatin and karyotypic evolution in the Siamese crocodile (Crocodylus siamensis) (Crocodylidae, Crocodylia)

Crocodilians have several unique karyotypic features, such as small diploid chromosome numbers (30–42) and the absence of dot-shaped microchromosomes. Of the extant crocodilian species, the Siamese crocodile (Crocodylus siamensis) has no more than 2n = 30, comprising mostly bi-armed chromosomes with large centromeric heterochromatin blocks. To investigate the molecular structures of C-heterochromatin and genomic compartmentalization in the karyotype, characterized by the disappearance of tiny microchromosomes and reduced chromosome number, we performed molecular cloning of centromeric repetitive sequences and chromosome mapping of the 18S-28S rDNA and telomeric (TTAGGG) _n sequences. The centromeric heterochromatin was composed mainly of two repetitive sequence families whose characteristics were quite different. Two types of GC-rich CSI-HindIII family sequences, the 305 bp CSI-HindIII-S (G+C content, 61.3%) and 424 bp CSI-HindIII-M (63.1%), were localized to the intensely PI-stained centric regions of all chromosomes, except for chromosome 2 with PI-negative heterochromatin. The 94 bp CSI-DraI (G+C content, 48.9%) was tandem-arrayed satellite DNA and localized to chromosome 2 and four pairs of small-sized chromosomes. The chromosomal size-dependent genomic compartmentalization that is supposedly unique to the Archosauromorpha was probably lost in the crocodilian lineage with the disappearance of microchromosomes followed by the homogenization of centromeric repetitive sequences between chromosomes, except for chromosome 2.     

腰椎侧隐窝和椎弓上切迹的应用解剖学

本文观测了100例成人腰椎侧隐窝的出现率、形态位置、横径、矢径和椎弓上切迹的宽度.通过统计学处理,表明椎弓上切迹的宽度与侧隐窝矢径两者有相关关系,根据椎弓上切迹的宽度可推断出侧隐窝的矢径.对临床诊断有一定的意义.     

颈椎管侧弯实验形态学变化及其临床意义

目的：观察脊柱颈段侧屈时椎管内解剖结构及容积变化的规律。 方法：在新鲜尸体的颈椎上，采用液体石蜡椎管灌注法和直接观察。 结果：侧弯运动时，上颈椎向侧弯方向倾斜，并将髓核向对侧挤移，致使埘侧下位神经根受到明显的牵拉。 结论：侧弯(旋转)伴有一定程度的旋转(侧弯)，行颈部推拿术治疗时应避免过度侧弯。     

Morphogenesis of the second pharyngeal arch cartilage (Reichert's cartilage) in human embryos

This study was performed on 50 human embryos and fetuses between 7 and 17 weeks of development. Reichert's cartilage is formed in the second pharyngeal arch in two segments. The longer cranial or styloid segment is continuous with the otic capsule; its inferior end is angulated and is situated very close to the oropharynx. The smaller caudal segment is in contact with the body and greater horn of the hyoid cartilaginous structure. No cartilage forms between these segments. The persistent angulation of the inferior end of the cranial or styloid segment of Reichert's cartilage and its important neurovascular relationships may help explain the symptomatology of Eagle's syndrome.     

脊柱腰段外侧区的解剖及其临床意义

目的：为腰椎间盘穿刺除髓核的进针部位提供解剖学资料。方法：解剂观察成人尸15具(男11、女4)脊柱腰段外侧医血管抻经的配布及无血管神经区的位置与范围。结果：脊柱腰段外侧无血管神经区的范围L1～L5为正方形，长(上下距离)最小均值为25.03±3．46mm，最大均值为27．52±5．56mm；宽(前后距离)最小均值为23．75±6．67mm，最大均值为32．8l±4．37mm；L5～S1区为三角形，长平均为16．42±3．80mm，宽平均为13.63±3.37mm。结论：经L1～L5外侧区的椎问盘外侧面进针行相应髓桉除术是安全的。L5～S1外侧无血管神经区范围较小，进针较困难。     

Ontogeny of the Orbital Glands and Their Environs in the Pantropical Spotted Dolphin (Stenella attenuata: Delphinidae)

The nasolacrimal duct (NLD) connects the orbital (often associated with the Deep Anterior Orbital gland: DAOG, a.k.a. Harderian gland) and nasal regions in many tetrapods. Adult cetaceans are usually said to lack an NLD, and there is little agreement in the literature concerning the identity of their orbital glands, which may reflect conflicting definitions rather than taxonomic variation. In this study, we examined an embryological series of the pantropical spotted dolphin (Stenella attenuata), and report numerous divergences from other tetrapods. Underdeveloped eyelids and a few ventral orbital glands are present by late Stage (S) 17. By S 19, circumorbital conjunctival glands are present. In S 20, these conjunctival glands have proliferated, eyelids (and scattered palpebral glands) have formed, and a duct similar to the NLD has appeared. Subsequently, both the palpebral glands and the NLD are progressively reduced by S 22, even as the conjunctival glands exhibit regional growth. In most tetrapods examined, the ontogeny of the NLD follows a series of three stages: Inception of NLD, Connection of orbit and nasal cavity by the NLD and Ossification (i.e., formation of the bony canal surrounding the NLD, emerging into the orbit via the lacrimal foramen in the lacrimal bone). In contrast, the dolphin NLD originates at the same time as the lacrimal bone, and a lacrimal foramen fails to develop. The cetacean fossil record shows that a lacrimal foramen was present in the earliest ancestral amphibious, freshwater forms, but was soon lost as the lineage invaded the oceans. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:77–87, 2018. © 2017 Wiley Periodicals, Inc.     

The immunoglobulin lambda-like gene cluster (14.1, 16.1 and F lambda 1) contains gene(s) selectively expressed in pre-B cells and is the human counterpart of the mouse lambda 5 gene

A human immunoglobulin (Ig)-related gene, covering approximately 8 kb, was isolated from a cosmid genomic library, by hybridization with a C lambda probe and with a lambda-like probe. This gene was identified as 14.1 It belongs to the human lambda-like cluster which is composed of three genes (14.1, 16.1 and F lambda 1) that do not rearrange. Sequence data indicate that 14.1 is organized similarly to the mouse lambda 5 gene. It contains three exons with lengths of 69, 38, and 106 codons as compared with 65, 38, and 106 for exons 1, 2, and 3 of mouse lambda 5, respectively. The corresponding homology values were 61, 66 and 75.5%. Using a 14.1 specific probe containing exon 1, we showed that this gene was selectively expressed in human pre-B cell lines. It is likely to encode a 213-amino acid lambda-like light chain that would associate with mu chains and play an important role in the early steps of B cell differentiation.     

Seasonal and Ontogenetic Variation in Subcutaneous Adipose Of the Bowhead Whale (Balaena mysticetus)

Cetacean evolution was shaped by an extraordinary land‐to‐sea transition in which the ancestors of whales became fully aquatic. As part of this transition, these mammals evolved unusually thick blubber which acts as a metabolic reservoir as well as an insulator and provides buoyancy and streamlining. This study describes blubber stratification and correlates it to seasonal variation, feeding patterns, and ontogeny in an arctic‐adapted mysticete, the bowhead whale (Balaena mysticetus). Bowheads are unique among mammals for possessing the largest known blubber stores. We found that adipocyte numbers in bowheads, like other mammals, do not vary with season or feeding pattern but that adipocyte size and structural fiber densities do vary with blubber depth. Anat Rec, 298:1416–1423, 2015. © 2015 Wiley Periodicals, Inc.     

Projections of the temporo-parietal cortex on vestibular complex in the macaque monkey (Macaca fascicularis)

Summary Connections of the posterior parietal cortex (area 7) with the vestibular complex have been studied in 4 macaque monkeys by anterograde axonal transport methods. WGA-HRP and tritiated amino-acids have been injected in the posterior part of area 7 including the caudal end of the superior bank of superior temporal sulcus and the lateral sulcus. Labeled terminals were observed in the vestibular nuclei complex and distributed bilaterally with a greater ipsilateral contribution. Two main groups of area 7 efferences were found to project to vestibular complex: a) A first group terminates on vestibular nuclei (the inferior vestibular nucleus and the caudal part of the medial nucleus) mainly connected with cerebello-spinal system, b) A second group terminates on vestibular nuclei (the medial and the superior vestibular nuclei and the y group) mainly involved in vestibulo-ocular mechanisms. The prepositus hypoglossi nucleus has also been found to receive area 7 projections. It is concluded that the possible control played by area 7 on the vestibulo-ocular reflex might be exerted through these direct cortico-vestibular projections.     

Comparative anatomy and ontogeny of appendicular skeleton of Pseudopus apodus (Pallas, 1775) (Anguimorpha,Anguidae) and a pattern of hindlimb loss in Anguinae

We present a detailed anatomy of the pectoral girdles, pelvic girdles, and hindlimbs of adult and juvenile specimens of Pseudopus apodus (Pallas, 1775). We compared the individual bones of the appendicular skeleton of P. apodus with those of Anguis fragilis and species of Ophisaurus living in North America, North Africa, and Southeast Asia. We found no anatomical features in P. apodus in common with the species of Ophisaurus living in only North America, North Africa, and Southeast Asia. Additionally, we present the prehatching ontogeny of the pelvic girdle of P. apodus and A. fragilis and the prehatching ontogeny of the hindlimb of P. apodus. In the ontogeny of the pelvic girdle of P. apodus, it is possible to distinguish the ossification centers of ilium, ischium, and pubis. In contrast, in the ontogeny of A. fragilis, no ossification centers of ilium, ischium, and pubis are present, and no hindlimb element was detected. In Stage 1 of ontogeny in Pseudopus, the femur and tibia are present; in Stage 2, the nodule representing the fibula appears; and in Stage 3, in addition to the femur, tibia, and fibula, four tarsal elements are present. This anatomical condition corresponds to the anatomical composition of the hindlimb of the adult O. koellikeri. In Stage 4, the involution of all tarsal elements and fibula begins, and in the last two prehatching stages, only femur and tibia remain; this condition is present not only in the adults of Pseudopus, but also in those of several other species of Ophisaurus.