Mathias Bergmann

Expression of presynaptic proteins is closely correlated with the chronotopic pattern of axons in the retinotectal system of the chick

Newly synthesized presynaptic integral membrane proteins in neurons are transported in precursor vesicles from the site of protein biosynthesis in the cell body by fast axonal flow to the presynaptic terminal. We followed the path that presynaptic proteins travel on the way to their central targets of the highly ordered primary visual pathway of the chick and analyzed the developmental changes in the expression of synaptic vesicle protein 2 (SV2), synaptotagmin, and syntaxin. Immunofluorescences revealed that: (1) the onset of protein expression in the retinal ganglion cells occurs in a central to peripheral developmental pattern from embryonic day 4 (E4) onward; (2) the proteins were found first in the inner and later in the outer plexiform layer of the retina; and (3) they were redistributed from the photoreceptor inner segments and cell bodies to the terminals in the outer plexiform layer. From E4 onward, immunopositive axons for SV2, synaptotagmin, and syntaxin were found in the optic nerve, disappearing after E9 for SV2 and synaptotagmin. The optic tract was stained for SV2 and synaptotagmin between E7 and E12, for syntaxin until the posthatching period. Finally, immunoreactivities for the investigated proteins were present at the surface of the tectum from E8 onward, when first retinal axons arrived there. The present study revealed that SV2 and synaptotagmin, but not syntaxin, are expressed in a transient wave that follows the advancement of optic axons and the proteins towards the optic tectum. J. Comp. Neurol. 418:361–372, 2000.

Developmental Expression of Dynamin in the Chick Retinotectal System

Dynamin I, a GTPase involved in the endocytic cycle of synaptic vesicle membranes, is believed to support axonal outgrowth and/or synaptogenesis. To explore the temporal and spatial patterns of dynamin I distribution in neuronal morphogenesis, we compared the developmental expression of dynamin with the expression of presynaptic membrane proteins such as SV2, synaptotagmin, and syntaxin in the chick primary visual pathway. Western blots of retina and tectum revealed a steady increase of synaptotagmin and syntaxin from embryonic Day 7 (E7) to E11, whereas for the same time frame no detectable increase of dynamin was found. Later stages showed increasing amounts of all tested proteins until the first postnatal week. Immunofluorescence revealed that SV2, synaptotagmin, and syntaxin are present in retinal ganglion cell axons from E4 on. In later stages, the staining pattern in the retina and along the visual pathway paralleled the formation and maturation of axons. In contrast, dynamin is not detectable by immunofluorescence in the developing retina and optic tectum before synapse formation. Our data indicate that, in contrast to the early expression of synaptotagmin, SV2, and syntaxin during axonal growth, dynamin is upregulated after synapse formation, suggesting its function predominantly during and after synaptogenesis but not in axonogenesis.

Reconstruction of the medial patellofemoral ligament using the adductor magnus tendon: an anatomic study.

PURPOSE The aims of this study were to evaluate the anatomic feasibility of medial patellofemoral ligament (MPFL) reconstruction using a part of the adductor magnus tendon and to identify possible risks. METHODS Twenty cadaveric knees were dissected. The distal part of the adductor magnus tendon was evaluated with respect to the anatomic topography and its utility for MPFL reconstruction. To estimate the risk of injuring the neurovascular structures, the distance from the adductor tubercle to the adductor hiatus was evaluated. An MPFL reconstruction was carried out by preserving the distal insertion on the adductor tubercle and redirecting the proximal portion of the tendon to the medial aspect of the patella. RESULTS The anatomic investigation showed the following relationships: The mean distance from the adductor tubercle to the adductor hiatus was 99 ± 14 mm (range, 80 to 120 mm). A graft length of 52 ± 5 mm (range, 45 to 63 mm) with the addition of 10 to 20 mm for fixation was found to be necessary for MPFL reconstruction. The difference between the desired graft length and the distance to the adductor hiatus was found to be at least 30 mm in all cases (mean, 46 mm). Leaving the graft attached to the adductor tubercle resulted in a nearly anatomic femoral attachment of the reconstructed MPFL. Complete detachment of the distal adductor magnus attachment was consistently avoidable. CONCLUSIONS The adductor magnus tendon was found to be a useful graft for MPFL reconstruction. However, anatomic dangers (damage to the neurovascular bundle of the adductor hiatus, the saphenous nerve, or the saphenous branch of the descending genicular artery) during graft harvest must be considered. CLINICAL RELEVANCE Anatomic knowledge is essential during adductor magnus tendon harvest to avoid damage to neurovascular structures. The adductor magnus tendon is an interesting alternative graft option for MPFL reconstruction if anatomic dangers are considered and avoided.

Differential expression of neuronal calcium sensor-1 in the developing chick retina

Neuronal calcium sensor‐1 (NCS‐1) is a Ca2+ binding protein that has been implicated in the regulation of neurotransmission and synaptogenesis. In this study we investigated the developmental expression and localization of NCS‐1 in the chick retina. Single‐ and double‐labeling experiments with three‐dimensional reconstruction as well as ultrastructural data of the distribution of NCS‐1 suggest that this protein is also involved in axonal process outgrowth. We found an early expression of NCS‐1 in ganglion cells and their axons, in amacrine, and in horizontal cells, whereas photoreceptors were immunonegative at embryonic stages. In the early posthatching days we found strong immunostaining for NCS‐1 in horizontal cells and their processes in the outer plexiform layer. In contrast, synaptic vesicle protein 2 (SV2) was prominent only in photoreceptor synaptic terminals. Ultrastructural analysis confirmed that NCS‐1 was localized postsynaptically in horizontal cell processes, whereas presynaptic terminals were immunonegative. However, at late posthatching days we observed that photoreceptor ribbon synapses (from rods and/or cones) also expressed NCS‐1. Thus the results support the notion that NCS‐1 is involved in neuronal process outgrowth and is localized in pre‐ and postsynaptic compartments including mature photoreceptor synapses. J. Comp. Neurol. 449:231–240, 2002.

Developmental expression of amphiphysin in the retinotectal system of the chick: from mRNA to protein

The role of amphiphysin in clathrin‐mediated endocytosis of synaptic vesicles is well established. However, it is still uncertain if the protein is also involved in developmental mechanisms, e.g. axon outgrowth and synapse formation. To investigate the developmental changes in the expression of amphiphysin we used the retinotectal system of the chick, a highly ordered and easily accessible primary neuronal pathway. Reverse transcription polymerase chain reaction (RT‐PCR) of total RNA from chick retina and tectum revealed first transcripts for amphiphysin, dynamin and synaptotagmin at embryonic day 5 (E5) for both regions. Surprisingly, Western blots of the retina revealed an increase of protein expression for amphiphysin only after E11 in the retina and the tectum. Immunofluorescence for amphiphysin was not detectable before E10 in the developing chick retina, while other presynaptic proteins like synaptotagmin showed already intense signals in the inner and outer plexiform layers. Subsequently, amphiphysin immunoreactivity follows the expression of synaptotagmin and synaptic vesicle protein 2 (SV2) as seen in the retina and the tectum, and exhibits the same staining as the other proteins in the mature chick brain. Ultrastructural data revealed for the first time that amphiphysin is not only limited to conventional synapses but is also abundant in retinal ribbon terminals. Taken together our data reveal that: (i) there is a developmental delay between mRNA transcription and protein expression for key proteins involved in endocytosis; (ii) amphiphysin gets upregulated after synapse formation; and (iii) amphiphysin is present in the synaptic vesicle cycle in retinal ribbon synapses.

An anatomical investigation of the cervicothoracic ganglion.

Anatomical variability within the autonomic nervous system has long been accepted. This study evaluated the anatomical variability of the cervicothoracic ganglion (CTG) according to its form and, in addition, provided precise measurements between the CTG and the anterior tubercle of the transverse process of the sixth cervical vertebra (C6TP), the first costovertebral articulation, and the vertebral artery. Forty‐two adult cadavers were dissected, 22 male and 20 females. Five main forms of CTG were documented; spindle (31.9%), dumbbell (23.2%), truncated (21.7%), perforated (14.5%), and inverted‐L (8.7%). The means for length, width, and thickness of the CTG were 18.5 mm, 8.2 mm, and 4.5 mm, respectively. The dimensions were found to be slightly larger in the males than females and on the left sides as compared to the right. The mean shortest distance between the CTGs and the vertebral artery was found to be 2.8 mm, whilst the mean shortest distances to C6TP was 25.7 mm and to the first costovertebral articulation was 1.7 mm. There is great variability in the morphology of the CTG with five common forms consistently seen. The relation to the vertebral artery may influence the form of the ganglion. Two previously undocumented forms are recorded; the truncated which describes the important juxtaposition of the CTG and the vertebral artery and the perforated which describes the piercing of the ganglion itself by the artery. The findings are considered to be of clinical importance to anesthetists, surgeons, neurosurgeons, and anatomists. Clin. Anat. 25:444–451, 2012.

Expression of SV2 in the Developing Chick Cerebellum : Comparison with Calbindin and AMPA Glutamate Receptors 2/3

The well‐organized cerebellum is an ideal model to investigate the developmental appearance and localization of pre‐ and postsynaptic structures. One of the synaptic proteins abundant in the central nervous system and localized in presynaptic vesicle membranes is the synaptic vesicle protein 2 (SV2). SV2 was shown to be involved in priming and modulating synaptic vesicles and having an effect in epileptic diseases. So far there are no data available describing the developmental localization of this protein in the cerebellum. We followed the expression pattern of SV2 and compared it with the expression of the neuronal calcium‐binding protein Calbindin and the AMPA glutamate receptor subunits 2/3 (GluR 2/3), both shown to be early expressed in the developing chick cerebellum predominantly in Purkinje cells. We detected the expression of SV2 in presynaptic terminals (mainly from climbing and mossy fibers) as soon as they are formed at embryonic day 16 in the inner molecular layer. Purkinje cells express Calbindin and GluR 2/3 in the soma and postsynaptically in the primary dendrites at this stage. With ongoing development, the pattern of SV2 expression follows the development of Purkinje cell dendrites in the molecular layer, suggesting a synaptic refinement of labeled climbing and later parallel fibers. Anat Rec, 291:538–546, 2008.

A pedicled bone graft from the acromion: an anatomical investigation regarding surgical feasibility

OBJECTIVE To investigate the technical feasibility of harvesting a vascularized bone graft from the acromion pedicled on the acromial branch. BACKGROUND Complex fractures of the proximal humerus may result in partial or total avascular necrosis of the head fragment. Treatment of avascular necrosis of the humeral head is dependent upon the stage of disease as well as the dimension and location of necrosis. In general, the outcome is poor and complete restoration of the shoulder function is rarely attained. Contrary to osteonecrosis of carpal bones (where vascularized bone grafts have been routinely carried out for decades), reports of analogous procedures at the humeral head are anecdotal. METHODS Based on selective post-mortem computer-tomographic angiography of 5 and the dissection of 30 embalmed human cadaver shoulders, we describe the anatomy of the acromial branch of the thoracoacromial trunk. The main focus was the constancy of its anatomical course, its dimensions and potential use as a nutrient vessel for a pedicled bone graft from the acromion. RESULTS The course of the acromial branch revealed a constant topographic relationship to anatomical landmarks. Its terminal branches reliably supplied the anterior part of the acromion. The vascularized bone graft could be sufficiently mobilized to allow tension-free transfer to the humeral head as well as to the lateral two-thirds of the clavicle. CONCLUSION We demonstrated the feasibility of vascularized bone graft harvesting from the acromion. This technique could be a joint-preserving procedure for osteonecrosis of the humeral head or may assist in the revision of a clavicular pseudoarthrosis.

Differential appearance of dynamin in constitutive and regulated exo-endocytosis : a single-cell multiplex RT-PCR study.

Neurons in the central nervous system establish, via their axons and dendrites, an extended network that allows synaptic transmission. During developmental maturation and process outgrowth, membrane turnover is necessary for the enlargement and subsequent growth of axons and dendrites from the perikarya to the target cell (constitutive exocytosis/endocytosis). After targeting and synapse formation, small synaptic vesicles are needed for the quantal release of neurotransmitters from the presynaptic terminal with subsequent recycling by regulated exocytosis/endocytosis. An investigation of the onset of the appearance of mRNA and protein in dissociated cultures of neurons from mouse hippocampus or from chick retina has shown an early abundance of proteins involved in exocytosis, such as syntaxin 1, SNAP-25, and synaptotagmin 1, whereas dynamin 1, a protein necessary for clathrin-mediated endocytosis, can be detected only after neurons have established contacts with neighboring cells. The results reveal that constitutive membrane incorporation and regulated synaptic transmitter release is mediated by the same neuronal proteins. Moreover, the data exclude that dynamin 1 takes part in constitutive recycling before synapse formation, but dynamin 2 is present at this stage. Thus, dynamin 2 may be the constitutive counterpart of dynamin 1 in growing neurons. Synapse establishment is linked to an upregulation of dynamin 1 and thereby represents the beginning of the regulated recycling of membranes back into the presynaptic terminal.

Combined maceration procedure permits advanced microsurgical dissection of Thiel-embalmed specimens

INTRODUCTION Due to the realistic colour, texture conservation and preservation of biomechanical properties, Thiel-embalming is becoming the main embalming procedure for clinical courses and research based on human cadaver material. The aim of this study is to establish a new procedure that allows advanced microdissection of small vessels and intraorganic nerves in Thiel-embalmed material. MATERIAL AND METHODS/RESULTS After a classical gross anatomical dissection, human hemipelves underwent repetitive application of 3 consecutive steps: (i) maceration with alloy of nitric acid and MiliQ water 1:10 for 24-48h. (ii) Immersion: the hemipelves were rinsed under tap water for 20-30min. and placed in a water bath for 1h. The nerves become more prominent due to the swelling and increased water content. (iii) microdissection under surgical microscope. To facilitate the organ visualization perfusion with polyurethane (Pu4ii, VasQtec®, Switzerland) in red/blue for arteries/veins respectively has been performed. CONCLUSION By using the proposed procedure, we performed satisfactory microdissection on Thiel-embalmed samples. The combination with polyurethane vascular casting permits visualization of small arterioles and venules in a range of 20-25μm. The method is very suitable for demonstration of somatic and vegetative nerves. Branches of the sacral plexuses and autonomic nerves from the superior and inferior hypogastric plexus have been tracked up to the smallest intraorganic branches in a range of 12.5-15μm. In conclusion, the established combined procedure offers a new possibility for advanced microdissection, which will allow acquisition of clinically relevant information about organ specific micro- vascularization and innervation.