Characterizing the Myoarchitecture of the Supraspinatus and Infraspinatus Muscles With MRI Using Diffusion Tensor Imaging.

BACKGROUND: The societal cost of shoulder disabilities in our aging society keeps rising. Providing biomarkers of early changes in the microstructure of rotator cuff (RC) muscles might improve surgical planning. Elevation angle (E1A) and pennation angle (PA) assessed by ultrasound change with RC tears. Furthermore, ultrasounds lack repeatability. PURPOSE: To propose a repeatable framework to quantify the myocyte angulation in RC muscles. STUDY TYPE: Prospective. SUBJECTS: Six asymptomatic healthy volunteers (1 female aged 30 years; 5 males, mean age 35 years, range 25-49 years), who underwent three repositioned scanning sessions (10 minutes apart) of the right infraspinatus muscle (ISPM) and supraspinatus muscle (SSPM). FIELD STRENGTH/SEQUENCE: 3-T, T1-weighted and diffusion tensor imaging (DTI; 12 gradient encoding directions, b-values of 500 and 800 s/mm2 ). ASSESSMENT: Each voxel was binned in percentage of depth defined by the shortest distance in the antero-posterior direction (manual delineation), i.e. the radial axis. A second order polynomial fit for PA across the muscle depth was used, while E1A described a sigmoid across depth: E 1 A sig = E 1 A range × sigmf 1 : 100 % depth , - EA 1 grad   ,   E 1 A asym + E 1 A shift . STATISTICAL TESTS: Repeatability was assessed with the nonparametric Wilcoxon's rank-sum test for paired comparisons across repeated scans in each volunteer for each anatomical muscle region and across repeated measures of the radial axis. A P-value <0.05 was considered statistically significant. RESULTS: In the ISPM, E1A was constantly negative, became helicoidal, then mainly positive across the antero-posterior depth, respective at the caudal, central and cranial regions. In the SSPM, posterior myocytes ran more parallel to the intramuscular tendon ( PA ≈ 0 ° ), while anterior myocytes inserted with a pennation angle ( PA ≈ - 20 ° ). E1A and PA were repeatable in each volunteer (error < 10%). Intra-repeatability of the radial axis was achieved (error < 5%). DATA CONCLUSION: ElA and PA in the proposed framework of the ISPM and SSPM are repeatable with DTI. Variations of myocyte angulation in the ISPM and SSPM can be quantified across volunteers. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Role of epigenetics and the transcription factor Sp1 in the expression of the D prostanoid receptor 1 in human cartilage.

D prostanoid receptor 1 (DP1), a prostaglandin D2 receptor, plays a central role in the modulation of inflammation and cartilage metabolism. We have previously shown that activation of DP1 signaling downregulated catabolic responses in cultured chondrocytes and was protective in mouse osteoarthritis (OA). However, the mechanisms underlying its transcriptional regulation in cartilage remained poorly understood. In the present study, we aimed to characterize the human DP1 promoter and the role of DNA methylation in DP1 expression in chondrocytes. In addition, we analyzed the expression level and methylation status of the DP1 gene promoter in normal and OA cartilage. Deletion and site-directed mutagenesis analyses identified a minimal promoter region (-250/-120) containing three binding sites for specificity protein 1 (Sp1). Binding of Sp1 to the DP1 promoter was confirmed using electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assays. Treatment with the Sp1 inhibitor mithramycin A reduced DP1 promoter activity and DP1 mRNA expression. Inhibition of DNA methylation by 5-Aza-2'-deoxycytidine upregulated DP1 expression, and in vitro methylation reduced the DP1 promoter activity. Neither the methylation status of the DP1 promoter nor the DP1 expression level were different between normal and OA cartilage. In conclusion, our results suggest that the transcription factor Sp1 and DNA methylation are important determinants of DP1 transcription regulation. They also suggest that the methylation status and expression level of DP1 are not altered in OA cartilage. These findings will improve our understanding of the regulatory mechanisms of DP1 transcription and may facilitate the development of intervention strategies involving DP1.

Epigenetic regulation of 15-lipoxygenase-1 expression in human chondrocytes by promoter methylation.

OBJECTIVE AND DESIGN: 15-Lipoxygenase-1 (15-LOX-1) catalyzes the biosynthesis of many anti-inflammatory and immunomodulatory lipid mediators and was reported to have protective properties in several inflammatory conditions, including osteoarthritis (OA). This study was designed to evaluate the expression of 15-LOX-1 in cartilage from normal donors and patients with OA, and to determine whether it is regulated by DNA methylation. METHODS: Cartilage samples were obtained at autopsy from normal knee joints and from OA-affected joints at the time of total knee joint replacement surgery. The expression of 15-LOX-1 was evaluated using real-time polymerase chain reaction (PCR). The role of DNA methylation in 15-LOX-1 expression was assessed using the DNA methyltransferase inhibitor 5-Aza-2'-desoxycytidine (5-Aza-dC). The effect of CpG methylation on 15-LOX-1 promoter activity was evaluated using a CpG-free luciferase vector. The DNA methylation status of the 15-LOX-1 promoter was determined by pyrosequencing. RESULTS: Expression of 15-LOX-1 was upregulated in OA compared to normal cartilage. Treatment with 5-Aza-dC increased 15-LOX-1 mRNA levels in chondrocytes, and in vitro methylation decreased 15-LOX-1 promoter activity. There was no difference in the methylation status of the 15-LOX-1 gene promoter between normal and OA cartilage. CONCLUSION: The expression level of 15-LOX-1 was elevated in OA cartilage, which may be part of a repair process. The upregulation of 15-LOX-1 in OA cartilage was not associated with the methylation status of its promoter, suggesting that other mechanisms are involved in its upregulation.

The Montreal Plastic Surgery Residency Bootcamp: Structure and Utility.

Transitioning from medical school to surgical residency is a difficult endeavor. To facilitate this period, the University of Montreal's plastic surgery program developed and implemented an intensive 1-month bootcamp rotation. It is the only one of its kind and length amongst plastic surgery residency programs in North America. It includes didactic teachings in anatomy, cadaveric dissections, and surgical approaches for an array of procedures. Clinical and technical skills are reviewed with senior residents and attending surgeons. Research opportunities and case scenarios are also covered. An anonymous online 30-question survey was sent to all residents who participated in the bootcamp rotation between 2013 and 2020. Questions evaluated residents' knowledge of anatomy, basic surgical skills, common approaches, flap knowledge, and on-call case management, before and after the bootcamp. Seventeen plastic surgery residents responded to this questionnaire (81%). The majority confirmed that the bootcamp helped them prepare for residency, research, and on-calls, and also helped them expand their knowledge of anatomy and surgical skills. The residents responded positively to the bootcamp's structure and implementation. This study proposes that surgical programs could benefit from a bootcamp rotation at the beginning of their curriculum. The purpose is to facilitate the transition between medical school and postgraduate training, and to ensure a basic level of competence for all junior residents. Further prospective studies could demonstrate the bootcamp's impact in board certification rates and acceptance into fellowship training programs.

Intersession Repeatability of Diffusion-Tensor Imaging in the Supraspinatus and the Infraspinatus Muscles of Volunteers.

BACKGROUND: Quantifying the rotator cuff (RC) muscles' viscoelasticity could provide outcome relevant information in patients with RC tears. MR-elastography requires robust diffusion-tensor imaging (DTI) to account for tissue anisotropy in muscles stiffness computation. PURPOSE: To assess the repeatability of DTI parameters in the supraspinatus and infraspinatus muscles and to explore DTI tractography conformity with the muscles' anatomy. STUDY TYPE: Prospective. SUBJECTS: Six healthy volunteers underwent three consecutive shoulder MRI sessions about 10 minutes apart. FIELD STRENGTH/SEQUENCE: 3T/T1-vibe Dixon and Spin echo EPI DTI (12 gradient encoding directions, b-values 500 and 800 sec/mm2 ). ASSESSMENT: Supraspinatus and infraspinatus muscles were segmented on the T1-vibe Dixon sequence. DTI image quality was assessed using a quantitative threshold based on the signal-to-noise ratio (SNR). The eigenvalues ( λ 1 , λ 2 , λ 3 ), fractional anisotropy (FA) and mean diffusivity were calculated. DTI tractography was visually assessed. STATISTICAL TESTS: DTI parameters within-subject intersession repeatability was assessed with Bland-Altman analysis and the coefficient of variation (CV). Repeatability was considered good for CV < 10%. RESULTS: The SNR between diffusion-weighted and non-diffusion-weighted images was greater than 3, which aligns with standards for estimating DTI parameters. The FA showed the lowest mean bias (-0.007; 95% confidence interval [CI] -0.031 to 0.018) whereas the λ1 had the highest mean bias (0.146 × 10-3  mm2 /sec; CI -0.034 to 0.326 × 10-3  mm2 /sec). CVs of the DTI parameters varied between 3.5% (FA) and 8.4% (λ3 ) for the supraspinatus and between 3.2% (λ1 ) and 6.8% (λ3 ) for the infraspinatus. Tractography provided muscle fiber representations in three-dimensional space concordant with RC anatomy. DATA CONCLUSION: DTI of the supraspinatus and infraspinatus muscles achieved an adequate SNR, allowing the measurement of the DTI metrics with good repeatability, and thus can be used for optimizing stiffness estimation in these anisotropic tissues. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Comparison of four transdiaphragmatic approaches to remove cavoatrial tumor thrombi: a pilot study.

Introduction: Surgical treatment of kidney cancer with a tumor thrombus spreading through the inferior vena cava (IVC) up to the right atrium remains a challenge.The aim of this article was to 1. assess the safety and feasibility of four transdiaphragmatic surgical approaches to the right atrium from the abdominal cavity; 2. to evaluate the feasibility of palpation and displacement of thrombi below the diaphragm. Material and methods: Four cadaveric specimens preserved with the Thiel method to assess each surgical access: 1) extrapericardial T-shaped diaphragmotomy, 2) extrapericardial T-shaped + circular diaphragmotomy, 3) transpericardial T-shaped diaphragmotomy with longitudinal pericardiotomy, 4) transpericardial T-shaped + circular diaphragmotomy with longitudinal and circular pericardiotomy.Different diameters and density of tumor thrombus simulators, placed at various levels from the cava-diaphragm junction, were used to evaluate the palpation and displacement of the thrombus. Two surgeons performed each assessment independently. Results: Approaches 2, 3 and 4 were significantly better than approach 1, regarding the feasibility of palpation, according to both surgeons (surgeon 1 Chi-square 21.56, p = 0.001; surgeon 2 Chi-square 27.83, p <0.0001). Approach 1 also showed a significant higher number of impossible displacements recorded by both surgeons (surgeon 1 Chi-square 19.02, p = 0.004; surgeon 2 Chi-square 20.01, p = 0.003). Only surgeon 1 recorded a significant lower number of easy palpations at 4 cm from the cava-diaphragm junction (Chi-square 14.10, p = 0.007). There were no high-risk complications in any approach. Conclusions: The transdiaphragmatic access to the right atrium from the abdominal cavity is feasible using three of the four surgical approaches. They are an adequate alternative to sternotomy.

The vascular exploration of the proximal femoral artery perforator region, an ideal donor site to choose cutaneous flaps of thin, supple, and glabrous skin: A cadaveric study.

BACKGROUND: The thigh region is a well-known area for harvesting cutaneous flaps for microsurgery replacement, given the characteristics of the skin: thin, flexible, and glabrous. We investigated the vascular pattern of 32 cadaveric anteroproximal thighs for the possibility of an extended harvesting area, which we call the proximal femoral artery perforator region. MATERIALS AND METHODS: We injected colored, radio opaque latex in the external iliac artery and investigated the perforator branches from the superficial circumflex iliac, femoral common, superficial, and deep femoral (profunda femoris) arteries to the skin of the proximal femoral artery perforator region. This region was divided into 3 equal subregions (superior, medial, and lateral), and their perforators were counted and measured. RESULTS: There was no significant difference in the number of arterial pedicles across the three subregions: 30 superior, 35 inferolateral, and 27 inferomedial. The perforators had a cutaneous path in 81% of the cases, while 6% were musculocutaneous and 5% septocutaneous, without a significant difference in their proportion in the three subregions. The mean length and diameter of the pedicles were 5.39 ±â€¯2.1 cm and 1.07 ±â€¯0.4 mm, respectively, without significant differences in the three subregions. CONCLUSIONS: The proximal femoral artery perforator region is a suitable area to generate flaps of various sizes and shapes, as needed by the surgeon. All perforators were constant and possessed a sufficient diameter and length for a successful anastomosis during the surgical procedure. The donor site retains all technical advantages to successfully replace areas of glabrous skin.

The median sacral artery in rectal blood supply: A cadaveric study.

INTRODUCTION: Insufficient blood supply to the posterior rectal remnant after proctectomy is a possible mechanism for anastomotic leakage. The median sacral artery (MSA) is not generally considered to participate in the rectal blood supply, although some case studies have reported the rectum being supplied by it. The aim of this study is to elucidate the anatomy of the MSA in relation to the posterior rectal wall. METHODS: Nineteen embalmed cadavers (12 males, seven females; mean age: 76 ± 9 years) were injected with a colored radio-opaque mixture in the aortic bifurcation, radiographed and subsequently dissected along the sacrum. The relationship between the MSA and the rectum was observed and the diameter of the MSA was measured 2 cm below the aortic bifurcation. RESULTS: MSAs were identified in 16 (84.2%) of the 19 cadavers. Nine MSAs (47.4%) reached the rectal wall and penetrated it. MSAs that reached the posterior rectum took two different routes in the presacral space. Dissection and radiography showed four penetrating MSAs (21.1%) ending in a branching pattern and five (26.3%) as a tapering vessel. Seven MSAs (36.8%) did not reach the rectal wall. The mean MSA diameter was 1.98 ± 0.12 mm. CONCLUSIONS: Almost half the MSAs reached and penetrated the posterior rectal wall, suggesting possible participation in the rectal blood supply. A large portion of the MSAs that penetrate the rectal wall run outside surgical margins and could continue to provide blood supply to the rectal remnant, potentially preventing anastomotic leakage.

Accuracy of unguided and ultrasound guided Coracohumeral ligament infiltrations - a feasibility cadaveric case series.

BACKGROUND: Coracohumeral ligament (CHL) thickening, contracture, and fibroplasia have been identified in glenohumeral idiopathic adhesive capsulitis (GHIAC). The CHL is the main structure responsible for the range of motion limitations. Favorable outcomes have been reported with CHL surgical release. Intra-articular glenohumeral joint corticosteroid infiltrations are utilized to disrupt the inflammatory process and reduce pain in GHIAC. The aim of this study was to investigate whether the CHL could be accurately targeted with a periligamentous infiltration. METHODS: A convenience sample of 12 unembalmed cadaver shoulders (mean age: 74.5 years, range 66-87 years) without evidence of previous injury or surgery were utilized in this exploratory double factor feasibility cadaveric (unguided and ultrasound (US) guided) case series. Two clinicians trained in musculoskeletal infiltration techniques carried out the infiltrations on each shoulder with colored latex. One clinician infiltrated without guidance, the other with US-guidance. The injecting clinicians were blinded to the others infiltration procedure and the order was randomized. An anatomist blinded to the infiltration order performed a shoulder dissection and recorded the infiltrate location. Percentage calculation for accuracy of infiltration and a chi-square evaluation of the difference between unguided and US-guided infiltrations was applied. RESULTS: An accuracy of 75% was achieved for unguided infiltration and 80% for US-guided infiltration techniques. Chi-squared indicated there was no significant difference (p = 0.82) between the unguided and US-guided techniques. CONCLUSION: US-guided and unguided infiltrations achieved good accuracy targeting the CHL, suggesting infiltrations can specifically and accurately target the CHL. In vivo investigation using such infiltration techniques are warranted.

Accuracy of Two Ultrasound-Guided Coracohumeral Ligament Injection Approaches: A Cadaveric Study.

BACKGROUND: Glenohumeral idiopathic adhesive capsulitis is a common shoulder condition that hinders functionality. Addressing the pathology has been extensively researched. Ultrasound (US)-guided injections have shown their efficacy. However, no study has been conducted to compare anatomical accuracy between different approaches in targeting the coracohumeral ligament (CHL). OBJECTIVE: To investigate whether US-guided injection of the CHL can be performed accurately using either the rotator interval (RI) or the coracoidal (CO) approach. METHODS: An experimental cadaveric case series. SETTING: Anatomy laboratory. SPECIMENS: Both shoulders of 13 Thiel-embalmed cadavers. INTERVENTIONS: Three physiatrists each injected a 0.1 mL bolus of colored dye in both shoulders of each cadaver using either the RI or the CO approach under US guidance. Each cadaver received a total of six injections (three injections per shoulder). The accuracy of the injection was determined following shoulder dissection by an anatomist. MAIN OUTCOME MEASURE: The accuracy of the US-guided injection of the CHL. RESULTS: The RI approach yielded 36 accurate injections, giving it an accuracy of 100%. With the CO approach two injections were deemed inaccurate yielding an accuracy of 94%. There was no significant difference in accuracy between all operators. CONCLUSIONS: US-guided injection of the CHL can be performed accurately with both the RI and CO approaches. The RI approach was likely to be more accurate.

Ultrasound-Guided Cervical Facet Joint Injections: A Viable Substitution for Fluoroscopy-Guided Injections?

OBJECTIVES: To evaluate the feasibility of ultrasound (US)-guided cervical facet injections and to identify the potential obstacles to routine use of this technique. METHODS: After Institutional Review Board approval, 4 cadavers were used in this study. Age, sex, body mass index, and neck circumference were recorded. A total of 40 facet injections were performed from C2-C3 to C6-C7 under US guidance with radiodense colored latex. Visibility of cervical tissues and the needle was graded as complete, partial, or null (no injection was performed in this case). Frontal and lateral radiographs were taken, followed by cadaveric dissection to assess contrast and the latex distribution, which were recorded as intra-articular (success), peri-articular (success), or absent (failure). A 2-tailed Fisher exact test and Pearson χ(2)test were used to evaluate difference between success and failure rates for qualitative variables. RESULTS: Seventy-eight percent (31 of 40) of US-guided facet joint injections were successful. No statistically significant differences were found regarding body mass index, neck circumference, needle caliber, operators, and between left and right sides. All failures involved C2-C3 and C6-C7 levels, and this result was statistically significant (Pearson χ(2) = 20.645; P < .001). CONCLUSIONS: Although US-guided cervical facet joint injections are feasible, substantial obstacles may prevent their routine use. The main obstacle is to effectively identify and target the correct cervical level in a prone position.

Cutaneous vascularization of the femoral triangle in respect to groin incisions.

OBJECTIVE: The purpose of this anatomic study was to describe the cutaneous vascularization of the femoral triangle and its variation to evaluate the potential consequences of the classic incisions used in vascular surgery. The ultimate goal was to suggest surgical approaches that would take into account the vascularization of the inguinal region to potentially reduce the vascular lesions and wound complications at the groin. METHODS: The cutaneous arteries of the femoral triangle were studied in 11 lower limbs from 6 human embalmed cadavers. The technique included embalming of the cadavers, radiopaque latex injection, radiographs, and anatomic dissection. RESULTS: The comparison of the vascular patterns revealed that despite the high variability of the arborization of the cutaneous arteries, their distribution patterns share many characteristics. The main vascularization of the femoral triangle comes from three arteries: the superficial circumflex iliac, the superficial epigastric, and the external pudendal. The first two arteries originate generally through a common trunk that buds laterally from the femoral artery at about 1.5 cm below the inguinal ligament. This study shows that the classic vertical incision at the groin would lead to damage of the cutaneous branches that cross over the femoral artery in its proximal part (the superficial epigastric artery in 82% and the common trunk of the superficial epigastric and circumflex iliac arteries in 18%); these lesions could lead to the postsurgical disruption of the dermal blood flow. CONCLUSIONS: The classic incisions could disrupt the cutaneous blood supply and thus increase the risk of tissue necrosis around the wound, explaining the observed postsurgical complications and infections. We propose to lower the vertical incision to start 2 cm under the inguinal ligament to reduce lesions of the cutaneous arteries and the potential devascularization of the wounds.

The aponeurotic expansion of the supraspinatus tendon: anatomy and prevalence in a series of 150 shoulder MRIs.

OBJECTIVE: To describe the aponeurotic expansion of the supraspinatus tendon with anatomic correlations and determine its prevalence in a series of patients imaged with MRI. MATERIALS AND METHODS: In the first part of this HIPAA-compliant and IRB-approved study, we retrospectively reviewed 150 consecutive MRI studies of the shoulder obtained on a 1.5-T system. The aponeurotic expansion at the level of the bicipital groove was classified as: not visualized (type 0), flat-shaped (type 1), oval-shaped and less than 50% the size of the adjacent long head of the biceps section (type 2A), or oval-shaped and more than 50% the size of the adjacent long head of the biceps section (type 2B). In the second part of this study, we examined both shoulders of 25 cadavers with ultrasound. When aponeurotic expansion was seen at US, a dissection was performed to characterize its origin and termination. RESULTS: An aponeurotic expansion of the supraspinatus located anterior and lateral to the long head of the biceps in its groove was clearly demonstrated in 49% of the shoulders with MRI. According to our classification, its shape was type 1 in 35%, type 2A in 10 % and type 2B in 4%. This structure was also identified in 28 of 50 cadaveric shoulders with ultrasound and confirmed at dissection in 10 cadavers (20 shoulders). This structure originated from the most anterior and superficial aspect of the supraspinatus tendon and inserted distally on the pectoralis major tendon. CONCLUSION: The aponeurotic expansion of the supraspinatus tendon can be identified with MRI or ultrasound in about half of the shoulders. It courses anteriorly and laterally to the long head of the biceps tendon, outside its synovial sheath.

Selective ultrasound guided pectoral nerve targeting in breast augmentation: How to spare the brachial plexus cords?

Subpectoral breast augmentation surgery under regional anesthesia requires the selective neural blockade of the medial and lateral pectoral nerves to diminish postoperative pain syndromes. The purpose of this cadaver study is to demonstrate a reliable ultrasound guided approach to selectively target the pectoral nerves and their branches while sparing the brachial plexus cords. After evaluating the position and appearance of the pectoral nerves in 25 cadavers (50 sides), a portable ultrasound machine was used to guide the injection of 10 ml of 0.2% aqueous methylene blue solution in the pectoral region on both sides of three Thiel's embalmed cadavers using a single entry point-triple injection technique. This technique uses a medial to lateral approach with the entry point just medial to the pectoral minor muscle and three subsequent infiltrations: (1) deep lateral part of the pectoralis minor muscle, (2) between the pectoralis minor and major muscles, and (3) between the pectoralis major muscle and its posterior fascia under ultrasound visualization. Dissection demonstrates that the medial and lateral pectoral nerves were well stained while leaving the brachial plexus cords unstained. We show that 10 ml of an injected solution is sufficient to stain all the medial and lateral pectoral nerve branches without a proximal extension to the cords of the brachial plexus.

Calretinin regulates Ca2+-dependent inactivation and facilitation of Ca(v)2.1 Ca2+ channels through a direct interaction with the α12.1 subunit.

Voltage-gated Ca(v)2.1 Ca(2+) channels undergo dual modulation by Ca(2+), Ca(2+)-dependent inactivation (CDI), and Ca(2+)-dependent facilitation (CDF), which can influence synaptic plasticity in the nervous system. Although the molecular determinants controlling CDI and CDF have been the focus of intense research, little is known about the factors regulating these processes in neurons. Here, we show that calretinin (CR), a Ca(2+)-binding protein highly expressed in subpopulations of neurons in the brain, inhibits CDI and enhances CDF by binding directly to α(1)2.1. Screening of a phage display library with CR as bait revealed a highly basic CR-binding domain (CRB) present in multiple copies in the cytoplasmic linker between domains II and III of α(1)2.1. In pulldown assays, CR binding to fusion proteins containing these CRBs was largely Ca(2+)-dependent. α(1)2.1 coimmunoprecipitated with CR antibodies from transfected cells and mouse cerebellum, which confirmed the existence of CR-Ca(v)2.1 complexes in vitro and in vivo. In HEK293T cells, CR significantly decreased Ca(v)2.1 CDI and increased CDF. CR binding to α(1)2.1 was required for these effects, because they were not observed upon substitution of the II-III linker of α(1)2.1 with that from the Ca(v)1.2 α(1) subunit (α(1)1.2), which lacks the CRBs. In addition, coexpression of a protein containing the CRBs blocked the modulatory action of CR, most likely by competing with CR for interactions with α(1)2.1. Our findings highlight an unexpected role for CR in directly modulating effectors such as Ca(v)2.1, which may have major consequences for Ca(2+) signaling and neuronal excitability.

A cadaver study to determine the minimum volume of methylene blue or black naphthol required to completely color the nerves relevant for anesthesia during breast surgery.

Regional anesthesia for breast surgery may require a large amount of local anesthetic solution to provide an adequate blockade of all relevant structures. The purpose of this study was to determine the minimal volume of fluid required to anesthetize all nerves to adequately provide anesthesia for breast surgery. This is an open randomized study. Cadavers were embalmed using Thiel's technique and were injected with different volumes of 0.2% methylene blue or 0.2% black naphthol for a superficial cervical plexus block (2, 5, 10, or 15 mL), an interscalene block (5, 10, 15, or 20 mL), paravertebral blocks from C(8) to T(6), and intercostal nerve blocks at 8 cm from the midline (2 or 3 mL) under ultrasound-guided or assisted techniques. The following minimal volumes of fluid were required for complete coloration of the nerves: 2 mL for the supraclavicular nerves; 20 mL for the nerve roots from C(5) to C(7), inclusive, if intraneural injection was avoided; 3 mL per root for the nerve roots from C(8) to T(6), inclusive, for a paravertebral block; and 2 mL per nerve for intercostal nerve blocks at T(4) and lower. With 20 mL of solution at the interscalene level, the roots of C(3) and C(4) were also colored; therefore, a separate injection for the supraclavicular nerves was unnecessary. We conclude that regional anesthesia for complex breast surgery can be achieved with a volume of local anesthetic as low as 41 mL.

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.

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.