Short-term synchronization between motor units in different functional subdivisions of the human flexor digitorum profundus muscle

The ability to independently move the digits is limited by peripheral as well as central factors. A central limitation to independent finger movements might arise from the inability of the human nervous system to activate motor units (MUs) that exert force on one finger without also activating MUs that exert force on adjacent fingers. Short-term synchronization between MU pairs is thought to be the result of the two motoneurons receiving common input from last-order neuronal projections. The human flexor digitorum profundus (FDP) muscle contains four subdivisions, one for each of the fingers. We hypothesized that the distribution of MU synchrony within and between subdivisions of FDP might parallel the ability to selectively activate different functional subdivisions within FDP, and the ability to flex one digit independently of another. We found that the degree of MU synchrony indeed was not uniform among the different functional subdivisions of FDP; MUs acting on ulnar digits (d5, d4) were more synchronized than MUs acting on radial digits (d2, d3). Furthermore, synchrony was observed between MU pairs where each unit acted on a different digit and was highest when both units of a pair acted on the least-independent digits (d4, d5). This indicates that the CNS does not exert completely independent control over the different functional subdivisions of FDP. The strength of synchrony appears related to the inability to produce completely independent forces or movements with the digits. These observations reflect widespread divergence of last-order inputs within the FDP motoneuron pool, and we suggest that the organization of the CNS drive to this muscle contributes to the limited ability of humans to flex one digit in isolation from other digits.     

家兔趾深屈肌肌构筑、肌内神经和运动终板分布

目的:探讨家兔趾深屈肌的肌构筑与肌内神经和运动终板分布的关系。方法:肌构筑法、改良Sihler s染色法、乙酰胆碱酯酶染色法。结果:家兔趾深屈肌为环羽肌。肌质量为(2.30±0.02)g,肌纤维长(1.00±0.01)cm,肌生理横切面积(2.17±0.12)cm2。肌的起端,神经干于腱板上方发出内侧和外侧两条初级支,初级支在肌内发出数目不等的次级支,继而向肌的深面和边缘发出终末支。有的次级支穿越腱板到达对侧。肌表面内、外两缘有线状排列的运动终板带,两带在肌止端相接,呈“V”形。结论:家兔趾深屈肌是环羽肌,倾向力量型设计;肌内神经分支存在越边支配;肌内神经和运动终板的分布与肌纤维排列有关;趾深屈肌有划分亚部的形态学特征。     

Electromyographic evidence of two functional subdivisions in the rhesus monkey's flexor digitorum profundus

The main belly of the macaque's flexor digitorum profundus (FDP) is divided by a dissectible plane into radial and ulnar regions. The present report describes three findings which suggest that the radial and ulnar regions represent separate functional subdivisions of the FDP. First, electromyographic (EMG) recordings during individuated finger movements performed by rhesus monkeys demonstrated different patterns of activation in the radial versus the ulnar region of the FDP. Second, studies of single motor units discriminated from the parent EMG activity also suggested at least two differentially activated motoneuronal pools in the radial versus ulnar region. Third, the finger movements evoked by intramuscular stimulation, delivered through the recording electrodes, indicated that contraction of the radial versus ulnar region produces different patterns of tension on the finger tendons. Together these findings suggest that the radial and ulnar regions of the FDP provide differential tension on the finger tendons to individuate finger movements.     

High-Resolution Computed Tomography Imaging of the Cranial Arterial System and Rete Mirabile of the Cat (Felis catus)

The objective of this study was to investigate the possibility of obtaining high-resolution multiplanar computed tomography (CT) imaging of the cranial arterial circulation of the cat (Felis catus), the rete mirabile, and components of the skull, utilizing preserved cat specimens with an arterial system that was injected with a radiopaque contrast compound in the early 1970s. Review of the literature shows no high-resolution CT studies of the cat's cranial circulation, with only few plain radiographic studies, all with limited cranial vascular visualization. In view of the inability of the radiographic techniques available from 1970s to mid-2000s to provide high-resolution imaging of the arterial circulation within the intact skull and brain of the cat, without dissection and histologic sectioning and disruption of tissues, no further imaging was performed for many years. In 2010, a high-resolution micro CT scanner became available, large enough to scan the entire nondissected head of the arterially injected cats. All the obtained CT images were processed with a software program that provided 3D volume rendering and multiplanar reconstruction with the ability to change the plane angulation and slab thickness. These technical features permitted more precise identification of specific arterial and bony anatomy. The obtained images demonstrated, with a nondestructive method, high-resolution vascular anatomy of the cerebral, orbital, facial arterial system, the rete mirabile, and skull bone components of the cat, with details not previously described in the literature. Anat Rec, 302:1958–1967, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.     

Thomas Willis,a pioneer in translational research in anatomy (on the 350th anniversary of Cerebri anatome)

The year 2014 marked the 350th anniversary of the publication in London of Cerebri anatome, a ground‐breaking work of neuroscience heavily influenced by the political and cultural context of Baroque Europe and mid‐17th century England. This article aims to review the work of the English physician and anatomist Thomas Willis, specifically with regard to the contents of his Cerebri anatome. Willis's academic and professional career was influenced by the turbulent period of the English Civil War during which he studied medicine. Willis went from chemistry to dissection arguably because of his need to justify the body‐brain‐soul relationship. As a result, he became a fellow of a select club of eminent experimentalists, and afterward was a Fellow of the Royal Society. Later on, he went to London, leaving the academic life to dedicate himself fully to the profession of medicine. As a physician, Willis did not base his practice on aphorisms but on a ‘bench to bedside’ approach to medicine, while studying neuroanatomy – covering embryology, comparative anatomy and pathological anatomy – as a basis for the comprehension of neurological pathology. He developed innovative anatomical methods for the preservation and dissection of the brain, injection of coloured substances and illustration of his findings. In Cerebri anatome, Willis recognized the cerebral cortex as the substrate of cognition. He also claimed that the painful stimuli came from the meninges, but not from the brain itself. He explained for the first time the pathological and functional meaning of the brain's circular arterial anastomosis, which is named after him. He also specified some features of the cranial origin of the sympathetic nerves and coined the term ‘neurologie’. Cerebri anatome marked the transition between the mediaeval and modern notions of brain function, and thus it is considered a cornerstone of clinical and comparative anatomy of the nervous system. The new contributions and methods employed by Willis justify his place as a father of neurology and a pioneer of translational research.     

Age estimation in the Mediterranean bottlenose dolphin Tursiops truncatus (Montagu 1821) by bone density of the thoracic limb

The determination of age is an important step in defining the life history traits of individuals and populations. Age determination of odontocetes is mainly based on counting annual growth layer groups in the teeth. However, this useful method is always invasive, requiring the cutting of at least one tooth, and sometimes the results are difficult to interpret. Based on the concept that bone matrix is constantly deposited throughout life, we analysed the bone mineral density of the arm and forearm of a series of bottlenose dolphins (Tursiops truncatus, Montagu 1821) stranded along the Italian coast of the Adriatic Sea or maintained in confined waters. The bone mineral density values we obtained were evaluated as possible age predictors of the Mediterranean population of this species, considering age as determined by counting growth layer groups in sections of the teeth and the total body length of the animal as references. Comparisons between left and right flipper showed no difference. Our results show that bone mineral density values of the thoracic limb are indeed reliable age predictors in Tursiops truncatus. Further investigations in additional odontocete species are necessary to provide strong evidence of the reliability of bone mineral density as an indicator of growth and chronological wear and tear in toothed-whales.     

Haemostatic mechanisms of the armadillo Chaetophractus villosus (Xenarthra, Dasypodidae)

Haemostatic mechanisms in humans are formed by two activation pathways, named tissular factor pathway and contact system pathway, and a common pathway, that promotes the formation of the fibrin clot. These mechanisms have also been identified in other mammals. In this work we evaluate their presence in the armadillo Chaetophractus villosus, a mammal of the neotropical Xenarthra Order. Twenty animals (ten males and ten females), previously adapted to captivity, were used. Fibrinogen (Fbg) was measured at the beginning and at the end of the experimental period; prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) were measured at the same time during the experience. Neither Fbg nor the other parameters evaluated showed sex-related differences, but Fbg diminished during the experimental period. TT related to PT and APTT showed longer times and larger dispersion of the individual values. Compared to the human beings, PT and TT were longer and APTT was shorter. Considering those results, we conclude that C. villosus has the same basic coagulation system as human beings. However, in this species the contact system pathway seems to play a greater role in the activation of the coagulation system than it does in man, and the common pathway appears to limit the velocity of the system.     

CT examination of the manipulation system in the giant panda (Ailuropoda melanoleuca)

The manipulation mechanism of the giant panda ( Ailuropida melanoleuca ) was examined by means of CT (computed tomography) and 3-dimensional (3-D) Volume Rendering techniques. In the 3-D images of the giant panda hand, not only the bones but also the muscular system was visualised. Sections of the articulated skeleton were obtained. It was demonstrated that the hand of the panda is equipped with separately moulded manipulation units as follows: (1) the radial sesamoid (RS), the radial carpal, and the first metacarpal (R–R–M) complex; and (2) the accessory carpal (AC) and the ulnar (A–U) complex. When the giant panda grasps anything, the R–R–M complex strongly flexes at the wrist joint, the RS becomes parallel with the AC, and the phalanges bend and hold the object. It is shown that the well-developed opponens pollicis and abductor pollicis brevis muscles envelop and fix the objects between the R–R–M complex and the phalanges during grasping.     

Development and innervation of soleplates in the freely grafted extensor digitorum longus (EDL) muscle in the rat

The ultrastructural events in the establishment of the neuromuscular junction of the freely grafted extensor digitorum longus (EDL) muscle of the rat were studied 1–120 days after grafting. The original axons and muscle fibers, including soleplates, degenerated during the first few days, but Schwann cells and basal laminae persisted. Myofibers regenerated within the original basal laminae. Indentations of the sarcolemma, termed “presumptive synaptic clefts” (PSC), wer found on myotubes from 7-day grafts. Schwann cells and residual acetylcholinesterase were invariably associated with the PSC, suggesting that the PSC developed at the site of the original soleplate. Nerves entered the grafts 10 days postoperatively and contacted the PSC of the regenerating muscle fibers on the 18–20th day. The secondary synaptic clefts of these “reconstructed” soleplates extended far beyond the subaxonal region. A second type of soleplate appeared on the 18–20th day. These soleplates were similar to those found in embryonic muscle and were considered to have been induced to form “de novo” by the presence of the nerves. When grafts were placed in permanently denervated limbs the “reconstructed” soleplates appeared, but the “de novo” type did not. These results shows that information directing the morphogenesis and innervation of the soleplate persists after the original muscle fibers and axons of a graft degenerate and regenerate.     

Macroscopic and histotopographic study of the deep transverse perineal muscle (musculus transversus perinei profundus) in elderly Japanese

Although the deep transverse perineal (DTP) muscle is welt known as the core of the urogenital diaphragm, most recent studies have denied its existence. In students' dissection classes, we cut the surfaces of 93 macroscopically identified urogenital diaphragms (59 male cadavers) and found the distinct sheet-like DTP in 24.7% (23 of 93 sides). Another 17 cadavers (mean age 81.4 years) were used for histology. In histology of 12 males, we consistently identified the DTP as a small muscle bundle immediately lateral to the bulbourethral gland. Thus, the macroscopicically unclear morphology of the DTP (19.4%, 18 of 93 sides) seemed to be overestimated. The histologically proven DTP was continuous with a "tail" or inferolateral protrusion of the external urethral sphincter or urethral rhabdospincter. However, the histology revealed that a sheet-like DTP was not usual (16.7%, two of 12 cadavers). Likewise, in histology of five females, the tail always continued to a muscle mass immediately lateral to the greater vestibular gland and far dorsal to the external urethral sphincter. Thus, the female topohistology seemed to be consistent with the male unclear DTP. Because of the limited incidence of a sheet-like DTP and the unclear fascial structure containing numerous vessels around the rather small DTP, in most elderly cadavers the urogenital diaphragm was likely to be a macroscopic entity rather than a histologic one. However, we believed that the histologically proven DTP was present in elderly men and women even if it had changed as a result of degeneration with aging.     

The femur, fibula, ulna (FFU) complex in siblings

Two siblings affected with the Femur, Fibula, Ulna (FFU) complex are reported. The FFU complex is relatively common, but was not previously reported in relatives.     

Brachial Plexus in the Pampas Fox (Lycalopex gymnocercus): a Descriptive and Comparative Analysis

Twenty thoracic limbs of ten Lycalopex gymnocercus were dissected to describe origin and distribution of the nerves forming brachial plexuses. The brachial plexus resulted from the connections between the ventral branches of the last three cervical nerves (C6, C7, and C8) and first thoracic nerve (T1). These branches connected the suprascapular, subscapular, axillary, musculocutaneous, radial, median and ulnar nerves to the intrinsic musculature and connected the brachiocephalic, thoracodorsal, lateral thoracic, long thoracic, cranial pectoral and caudal pectoral nerves to the extrinsic musculature. The C7 ventral branches contribute most to the formation of the nerves (62.7%), followed by C8 (58.8%), T1 (40.0%) and C6 (24.6%). Of the 260 nerves dissected, 69.2% resulted from a combination of two or three branches, while only 30.8% originated from a single branch. The origin and innervation area of the pampas fox brachial plexus, in comparison with other domestic and wild species, were most similar to the domestic dog and wild canids from the neotropics. The results of this study can serve as a base for comparative morphofunctional analysis involving this species and development of nerve block techniques. Anat Rec, 300:537–548, 2017. © 2016 Wiley Periodicals, Inc.     

Principal coagulation factors and natural anticoagulants in the armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae)

Blood coagulation is an important process regulated by a large number of proteins, which transform fibrinogen into fibrin. This mechanism was identified in several species other than humans. In this work we study the coagulation factors and principal natural anticoagulants in armadillos (Chaetophractus villosus). Coagulation factors FVII, FXII, FIX, FXI, FX, FVIII, FV, antithrombin (AT), protein C (PC), and protein S (PS) were identified. The activities of all factors were homogeneous for both sexes. Correlation studies showed associations between FVII and FX, FVII and FIX, FVII and FXI, FIX and FXI, and FIX and FX. Sex-related differences were observed for PS but not for AT or PC. There was positive correlation between PS and FV in females. These data constitute the first contribution to the knowledge of the proteins participating in the coagulation in this species and they demonstrate that the hemostatic process is similar in the armadillos and man.     

Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra,Folivora) of Patagonia

This article presents a morphofunctional analysis of the hind limb of Santacrucian (Early Miocene) sloths from southernmost Patagonia (Argentina). These fossil sloths were mid sized to large animals, ranging from 40 to 120 kg, and their postcranial skeleton was markedly different in shape compared with that of extant tree sloths, which vary from 2 to 10 kg. The functional anatomy of the hind limb of Santacrucian sloths was compared with that of living xenarthrans (tree sloths, anteaters, and armadillos), which involved reconstruction of the hind limb musculature and comparative and qualitative morphofunctional analyses, and hypotheses on the biological role of the hind limb in terms of preferences in substrate, posture, and strategies of locomotion were formulated. The hind limb of Santacrucian sloths bears strong resemblances to that of living South American anteaters in stoutness of skeletal elements, form of the characteristics related to muscular and ligamentous attachments, and conservative, pentadactylous strong‐clawed pes. The musculature was very well developed, allowing powerful forces, principally in entire limb adduction, crus flexion and extension, pes extension, and toe prehension. These functional features, together with those of the forelimb, are congruent with climbing behavior, and support the hypothesis that Santacrucian sloths were good but slow climbing mammals. However, their climbing strategies were limited, owing principally to their comparatively large body size, and they relied to a large extent on their powerful musculature and curved manual and pedal unguals for both moving and standing on the arboreal supports. Anat Rec, 298:842–864, 2015. © 2015 Wiley Periodicals, Inc.     

Anatomy, histology, histochemistry and fine structure of the Harderian gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the Harderian gland of the armadillo Chaetophractus villosus were described. The gland is the largest structure in the bony orbit. It is situated in the anteroventral region of the orbit. Obvious structural differences are not observed between males and females. The gland is compound-branched tubulo-alveolar, being characterized by a single layer of columnar cells surrounded by myoepithelial cells. It possesses a single excretory duct opened into the inner canthus. All glandular cells show yellow-green autofluorescence and additionally some glandular lumen may contain dense autofluorescent solid accretions. There are two peculiar and outstanding cytoplasmic features. One is represented by the smooth endoplasmic reticulum (SER), forming a closely woven meshwork. The other one is represented by membranous bodies apparently derived from the SER, RER and cytoskeleton with a Star of David configuration situated in the supranuclear region. Three types of vesicles are detected in the cytoplasm. Histochemical staining methods reveal lipids, proteins, neutral and acidic containing glycoconjugates in secretory vesicles. The mechanism of secretion appears either merocrine or apocrine. The epithelium of the intra- and inter-lobular excretory ducts suggests secretory activity. Tubulo-acinar glands similar to those seen in the lacrimal gland and nictitans glands are found related to the intralobular and main excretory ducts. The capillary network is characterized by fenestrated endothelium. The stroma possesses unmyelinated axons and plasma cells. The normal secretion of the secretory endpieces, particularly lipids, proteins and glycoconjugates, is complemented by mucous and serous secretions released by ductal cells and glands associated to the ducts.