3D Bioprinting of Collagen-based Microfluidics for Engineering Fully-biologic Tissue Systems

Microfluidic and organ-on-a-chip devices have improved the physiologic and translational relevance of in vitro systems in applications ranging from disease modeling to drug discovery and pharmacology. However, current manufacturing approaches have limitations in terms of materials used, non-native mechanical properties, patterning of extracellular matrix (ECM) and cells in 3D, and remodeling by cells into more complex tissues. We present a method to 3D bioprint ECM and cells into microfluidic collagen-based high-resolution internally perfusable scaffolds (CHIPS) that address these limitations, expand design complexity, and simplify fabrication. Additionally, CHIPS enable size-dependent diffusion of molecules out of perfusable channels into the surrounding device to support cell migration and remodeling, formation of capillary-like networks, and integration of secretory cell types to form a glucose-responsive, insulin-secreting pancreatic-like microphysiological system.

Rapid model-guided design of organ-scale synthetic vasculature for biomanufacturing

Our ability to produce human-scale bio-manufactured organs is critically limited by the need for vascularization and perfusion. For tissues of variable size and shape, including arbitrarily complex geometries, designing and printing vasculature capable of adequate perfusion has posed a major hurdle. Here, we introduce a model-driven design pipeline combining accelerated optimization methods for fast synthetic vascular tree generation and computational hemodynamics models. We demonstrate rapid generation, simulation, and 3D printing of synthetic vasculature in complex geometries, from small tissue constructs to organ scale networks. We introduce key algorithmic advances that all together accelerate synthetic vascular generation by more than 230 -fold compared to standard methods and enable their use in arbitrarily complex shapes through localized implicit functions. Furthermore, we provide techniques for joining vascular trees into watertight networks suitable for hemodynamic CFD and 3D fabrication. We demonstrate that organ-scale vascular network models can be generated in silico within minutes and can be used to perfuse engineered and anatomic models including a bioreactor, annulus, bi-ventricular heart, and gyrus. We further show that this flexible pipeline can be applied to two common modes of bioprinting with free-form reversible embedding of suspended hydrogels and writing into soft matter. Our synthetic vascular tree generation pipeline enables rapid, scalable vascular model generation and fluid analysis for bio-manufactured tissues necessary for future scale up and production.

FRESH 3D Bioprinting a Ventricle-like Cardiac Construct Using Human Stem Cell-Derived Cardiomyocytes

Here we describe a method to engineer a contractile ventricle-like chamber composed of human stem cell-derived cardiomyocytes using freeform reversible embedding of suspended hydrogels (FRESH) 3D bioprinting. To do this, we print a support structure using a collagen type I ink and a cellular component using a high-density cell ink supplemented with fibrinogen. The gelation of the collagen and the fibrinogen into fibrin is initiated by pH change and enzymatic crosslinking, respectively. Fabrication of the ventricle-like chamber is completed in three distinct phases: (i) materials preparation, (ii) bioprinting, and (iii) tissue maturation. In this protocol, we describe the method to print the construct from a high-density cell ink composed of human stem cell-derived cardiomyocytes and primary fibroblasts (~300 × 10⁶ cells/mL) using our open-source dual-extruder bioprinter. Additional details are provided on FRESH support preparation, bioink preparation, dual-extruder needle alignment, print parameter selection, and post-processing. This protocol can also be adapted by altering the 3D model design, cell concentration, or cell type to FRESH 3D bioprint other cardiac tissue constructs.

Emergence of FRESH 3D printing as a platform for advanced tissue biofabrication

In tissue engineering, an unresolved challenge is how to build complex 3D scaffolds in order to recreate the structure and function of human tissues and organs. Additive manufacturing techniques, such as 3D bioprinting, have the potential to build biological material with unprecedented spatial control; however, printing soft biological materials in air often results in poor fidelity. Freeform Reversible Embedding of Suspended Hydrogels (FRESH) is an embedded printing approach that solves this problem by extruding bioinks within a yield-stress support bath that holds the bioinks in place until cured. In this Perspective, we discuss the challenges of 3D printing soft and liquid-like bioinks and the emergence for FRESH and related embedded printing techniques as a solution. This includes the development of FRESH and embedded 3D printing within the bioprinting field and the rapid growth in adoption, as well as the advantages of FRESH printing for biofabrication and the new research results this has enabled. Specific focus is on the customizability of the FRESH printing technique where the chemical composition of the yield-stress support bath and aqueous phase crosslinker can all be tailored for printing a wide range of bioinks in complex 3D structures. Finally, we look ahead at the future of FRESH printing, discussing both the challenges and the opportunities that we see as the biofabrication field develops.

Azetidine-based selective glycine transporter-1 (GlyT1) inhibitors with memory enhancing properties

A strategy to conformationally restrain a series of GlyT1 inhibitors identified potent analogs that exhibited slowly interconverting rotational isomers. Further studies to address this concern led to a series of azetidine-based inhibitors. Compound 26 was able to elevate CSF glycine levels in vivo and demonstrated potency comparable to Bitopertin in an in vivo rat receptor occupancy study. Compound 26 was subsequently shown to enhance memory in a Novel Object Recognition (NOR) behavioral study after a single dose of 0.03 mg/kg, and in a contextual fear conditioning (cFC) study after four QD doses of 0.01-0.03 mg/kg.

Three-dimensional printing of complex biological structures by freeform reversible embedding of suspended hydrogels

We demonstrate the additive manufacturing of complex three-dimensional (3D) biological structures using soft protein and polysaccharide hydrogels that are challenging or impossible to create using traditional fabrication approaches. These structures are built by embedding the printed hydrogel within a secondary hydrogel that serves as a temporary, thermoreversible, and biocompatible support. This process, termed freeform reversible embedding of suspended hydrogels, enables 3D printing of hydrated materials with an elastic modulus <500 kPa including alginate, collagen, and fibrin. Computer-aided design models of 3D optical, computed tomography, and magnetic resonance imaging data were 3D printed at a resolution of ~200 μm and at low cost by leveraging open-source hardware and software tools. Proof-of-concept structures based on femurs, branched coronary arteries, trabeculated embryonic hearts, and human brains were mechanically robust and recreated complex 3D internal and external anatomical architectures.

Pediatrician attitudes concerning school-located vaccination clinics for seasonal influenza

OBJECTIVE

Vaccinating all children aged 6 months to 18 years every year has potentially large ramifications for office-based primary care pediatricians. We determined the degree to which pediatricians support routine annual influenza vaccination outside the medical home, especially in school-located mass influenza vaccination clinics.

METHODS

Internet-based survey sent in May and June 2009 to all 623 currently practicing primary care general pediatricians who were members of the Maryland Chapter of the American Academy of Pediatrics.

RESULTS

Of those surveyed, 193 (31%) responded. Approximately 67% reported they vaccinated more than half the children in their practice with at least one dose in the 2008-2009 influenza season, and about half anticipated that, in their office, they would not attain ≥75% coverage of all patients older than 5 months of age. Approximately 27% of respondents predicted they would likely have difficulty obtaining sufficient vaccine to cover commercially insured patients, and 32% were likely to have difficulty getting sufficient vaccine to cover Medicaid, underinsured, and uninsured patients because of ordering or distribution problems. Approximately 78% of respondents cited borderline or poor reimbursement for influenza vaccinations, and 53% had unused vaccine at the end of the 2008-2009 influenza season. Ninety-six percent of respondents supported school-located influenza vaccination programs in their community for their patients.

CONCLUSIONS

These results indicate awareness by primary care pediatricians in Maryland of the potential difficulties involved in implementing universal influenza vaccinations in their practice and their support of school-located vaccination programs managed by the local health department in their community.

Recent developments in the discovery of selective glucocorticoid receptor modulators (SGRMs)

Steroidal glucocorticoids are widely prescribed for the treatment of a variety of inflammatory and autoimmune diseases. Although they are effective, the side-effects associated with chronic glucocorticoid treatment, such as osteoporosis and hyperglycemia, can severely limit their long-term use. Hence, there is a need to develop new effective anti-inflammatory agents for systemic use which are dissociated from their unwanted side effects.

Synthesis and Characterization of Nonsteroidal Glucocorticoid Receptor Modulators for Multiple Myeloma

Structure-activity relationship studies centered around 3'-substituted (Z)-5-(2'-(thienylmethylidene))1,2-dihydro-9-hydroxy-10-methoxy-2,2,4-trimethyl-5H-chromeno[3,4-f]quinolines are described. A series of highly potent and efficacious selective glucocorticoid receptor modulators were identified with in vitro activity comparable to dexamethasone. In vivo evaluation of these compounds utilizing a 28 day mouse tumor xenograft model demonstrated efficacy equal to dexamethasone in the reduction of tumor volume.

5(Z)-Benzylidene-1,2-dihydro-9-hydroxy-10-methoxy-2,2,4-trimethyl-5H-1-aza-6-oxa-chrysenes as non-steroidal glucocorticoid receptor modulators

A series of 5-benzylidene-1,2-dihydro-2,2,4-trimethyl-5H-1-aza-6-oxa-chrysenes was synthesized and profiled for their ability to act as selective glucocorticoid receptor modulators (SGRMs). The synthesis and structure-activity relationships for this series of compounds are presented.

Chromium(0)-Promoted Multicomponent Cycloaddition of Tethered Diynes with Cyclic Trienes: Application to the Total Synthesis of 9-epi-Pentalenic Acid

An efficient protecting group controlled regioselective chromium(0)-mediated three-component higher order cycloaddition of tethered diynes with cyclic trienes that generates five rings and six stereogenic centers in one step is described. Following a sequence of reactions featuring a chemoselective Baeyer-Villiger rearrangement and a regioselective cyclopropane hydrogenolysis, the total synthesis of 9-epi-pentalenic acid was achieved.

Profile: Dr. Alan Hudson. Interview by Cynthia Martin

Besides enviable success as a healthcare leader, primarily as President and CEO for 10 years at the University Health Network in Toronto, Dr. Alan R. Hudson is a neurosurgeon whose many awards and professional activities have helped to establish him as a world-class research.

Reassessment of lymphocytic atypia in the diagnosis of mycosis fungoides

The manifestations of mycosis fungoides in its early stage may mimic clinically and histologically those of many benign inflammatory dermatoses. Therefore, the diagnosis of mycosis fungoides remains a major challenge for dermatologists and dermatopathologists. For many years, it has been proposed that atypical lymphocytes within the epidermis constitute one of the diagnostic features in mycosis fungoides. Presence of dermal atypical lymphocytes remains controversial as a diagnostic criterion. We reassessed the feasibility of applying lymphocytic atypia within epidermis and dermis as diagnostic criteria discriminating between mycosis fungoides and spongiotic dermatitis. Thirty cases of mycosis fungoides and 30 cases of spongiotic dermatitis were retrieved from archival hematoxylin and eosin-stained histologic sections. Punch biopsy sections were examined by light microscopy; epidermal and dermal lymphocytes were photographed at 1000x (oil immersion). A total of 92 ektachrome slides (35 mM) were developed, coded, and ordered randomly. For each slide, cells were interpreted as typical or atypical lymphocytes by seven pathologists. Atypical epidermal lymphocytes were judged to be present in 9 +/- 2 out of 16 (56%) cases of mycosis fungoides photographed as compared with 8 +/- 3 out of 16 (50%) in spongiotic dermatitis. Dermal lymphocytic atypia was thought to be present in 14 +/- 6 out of 30 (47%) patients with mycosis fungoides. Thirteen +/- 6 out of 30 (43%) patients with non-mycosis fungoides also displayed dermal lymphocytic atypia. No statistical significance was observed in these comparisons (t test, P >.05). Furthermore, atypia of lymphocytes was deemed to be present in 41, 38, 59, 70, 23, 47, and 40 out of 92 slides examined by the investigators, suggesting that observer variation is a very significant factor in our present study. We conclude that it is not possible to distinguish mycosis fungoides from spongiotic dermatitis merely based on lymphocytic atypia within epidermis or dermis.

Increased p53 staining in normal skin of posttransplant, immunocompromised patients and implications for carcinogenesis

The p53 tumor suppressor gene is a transcriptional activator involved in control of cell cycle. Nonmelanoma skin cancers and premalignant lesions in transplant patients have been associated with an increased rate of p53 mutation. It is possible that normal skin in transplant patients also has a more labile p53 tumor suppressor gene, predisposing them to the development of nonmelanocytic cutaneous malignancies. To test this hypothesis, we looked at p53 expression in normal skin from posttransplant, immunocompromised patients and compared this to p53 expression in normal skin from immunocompetent patients. Twenty-three skin biopsies of normal, non-sun-exposed skin from 23 immunosuppressed transplant patients and 6 skin biopsies of normal, non-sun-exposed skin from 3 immunocompetent patients were stained for p53 immunoreactivity. The skin biopsies from the immunocompromised patients showed increased staining for p53 when compared to the skin biopsies from the immunocompetent patients (mean = 7.52/mm for the immunocompromised patients and mean = 1.05/mm for the normal control group). Background levels of p53 mutation may be increased in normal skin of posttransplant immunocompromised patients. This background increase in p53 expression could reflect mutation of the gene, which may play a role in the subsequent development of cutaneous malignancies in this subgroup of patients.

Immunohistochemistry in diagnostic dermatopathology

This article briefly reviews many immunohistochemical stains that have been in use for years, emphasizing their diagnostic use and potential pitfalls. Several newer immunostains are described in a more comprehensive fashion, including brief summaries from recently published studies.

Isolated suprascapular nerve palsy: a review of nine cases

BACKGROUND

In nine patients, suprascapular nerve palsy followed serious accidents associated with fractures of the cervical vertebrae, clavicle or scapula and after weight lifting, wrestling and a fall on the elbow or shoulder.

METHOD

All patients were examined as to muscle wasting, weakness and shoulder fixation. EMG examination was done in all cases and six patients underwent surgical exploration.

RESULTS

The palsy was incomplete on clinical and EMG examination in all patients. On exploration, scarring, entrapment, tethering or kinking at the suprascapular notch was four and two had post-traumatic neuromas.

CONCLUSIONS

In contrast to published studies, none of our patients presented with shoulder pain, a spontaneous onset nor with involvement limited to the infraspinatus muscle. The differential diagnosis should include C5 root lesion, brachial plexus neuritis, frozen shoulder and tear of the rotator cuff.

A persistent median artery causing carpal tunnel syndrome in a patient with chronic renal failure: case report

A 63-year-old woman presented with carpal tunnel syndrome 6 years after being diagnosed as having chronic renal failure and 1 year after the start of hemodialysis treatment. Symptoms were in the hand contralateral to the side of the arteriovenous fistula used for hemodialysis. During surgery, a large, patent, noncalcified median artery was found pulsating in the carpal tunnel; this pulsation was causing the compression of the median nerve. The flexor retinaculum was decompressed, and the median artery was transposed. This is the first reported case of a persistent median artery in a hemodialysis patient who has symptoms contralateral to the vascular access. The pathophysiology and epidemiology of carpal tunnel syndrome in chronic renal failure patients is reviewed. In addition, the role of the median artery in the vascularization of the hand and the management of a persistent median artery causing carpal tunnel syndrome are reviewed.

Aggressive fibrous tissue lesions in the upper extremity: treatment and results

The oncologic and functional results of treatment of aggressive fibromatosis were reviewed in 16 patients. Five had undergone previous resections. Complete surgical excision, the recommended primary treatment modality for aggressive fibromatosis tissue lesions, could only be performed in five patients. Radiation was administered in 13 patients and mainly used when the resection margins were positive. One patient required reoperation for recurrence. Complete detailed follow-up data were available in 15 patients. Functional analysis revealed 11 good-excellent, 2 fair, and 2 poor results using the Enneking classification. Local control was achieved with a combination of surgery and radiation, maintaining good-excellent function in most patients. The local nature of this tumor can be controlled with surgery and radiation while preserving function in the upper extremity.

Shoulder arthrodesis with plate fixation: Functional outcome analysis

Fifty-seven patients underwent shoulder arthrodesis with a single plate. The technique utilized included both glenohumeral and acromiohumeral arthrodesis. A 10-hole plate was used for internal fixation. The position utilized was 30° abduction, 30° internal rotation, and 30° flexion. Forty-six patients underwent the procedure for brachial plexus injury, six patients for multidirectional shoulder instability, two patients for osteoarthritis, two patients for failed total shoulder arthroplasties, and one for infection. The patients were independently reviewed by a research clinician and their function assessed according to their ability to perform activities of daily living, subjective satisfaction with the procedure, and the degree of pain they felt in their shoulder. Fifty-four shoulders fused within 10° of the desired position. Three patients required secondary bone grafting. The complication rate was 14%. Patient satisfaction was highest in those patients undergoing the procedure for brachial plexus injury, osteoarthritis, and failed total shoulder arthroplasty (p = 0.0046). Four patients with multidirectional shoulder instability continued to complain of instability in spite of solid arthrodesis (p < 0.01). The difference in the cumulative activities of daily living score between the brachial plexus injury and poor hand function group and the multidirectional shoulder instability group and patients with other diagnoses was significant (p = 0.0001). Preoperative diagnosis, hand function, and work status were significant determinants of patient satisfaction and the cumulative activities of daily living score (p = 0.0001).

The peripheral nerve allograft in the primate immunosuppressed with Cyclosporin A: I. Histologic and electrophysiologic assessment

Nerve regeneration across peripheral nerve allografts and control autografts in primates immunosuppressed with Cyclosporin A was quantitatively evaluated by electrophysiologic and histologic methods. Twelve cynomolgus monkeys received 3-cm autografts and allografts in contralateral ulnar nerves. They were immunosuppressed with Cyclosporin A at 25 mg/kg per day or placebo vehicle. Morphometric analysis of nerve graft and distal nerve segments was assessed at 1 year after engraftment. Quantitative electrophysiologic studies were performed percutaneously at 6 and 12 months, and compound action potentials were measured directly across the nerve grafts at 1 year. Excellent regeneration was seen across autografts and allografts in Cyclosporin A-treated and placebo-treated recipients.

Clinical application of peripheral nerve transplantation

Surgical reconstruction of extensive peripheral nerve injuries frequently exhausts the patient's own source of expendable autogenous nerve grafts. Nerve allografts would offer a limitless supply of graft material. A 23-cm, 10-cable sciatic nerve allograft was performed in an 8-year-old boy in September of 1988. The patient was managed with Cyclosporin A for 2 years. Forty-four months after the transplant surgery and 19 months after the cessation of Cyclosporin A therapy, the patient has evidence of nerve regeneration across the allograft with recovery of functional sensibility in his foot. In the selected patient with an otherwise irreparable nerve injury, consideration can be given to the use of a nerve allograft.

Arteriovenous malformation of the pyriformis muscle manifesting as a sciatic nerve tumor

We present a patient with an intramuscular pelvic arteriovenous malformation that was initially diagnosed as a tumor of the sciatic nerve sheath. Endovascular embolization, attempted as a preoperative maneuver, was complicated by diffuse pulmonary emboli and death. To our knowledge, this is the first such reported case. Its presentation here broadens the differential diagnosis of sciatic nerve sheath tumors, emphasizes the diagnostic and management issues of masses presenting as peripheral nerve tumors, and provides clinicopathological evidence regarding the cause of neurological symptoms.

Petrous meningiomas: a review of seventeen cases

Seventeen patients with petrous meningiomas managed at St. Michael's Hospital, during the years 1973-1987, were retrospectively reviewed. There were 15 females and 2 males; their ages ranged from 42 to 68 years (mean age: 53 years). The clinical presentation most commonly included headache and eighth cranial nerve dysfunction; the average duration of symptoms was 6 years (3 month-27 years). Computed tomography was performed in 15 cases. The mean tumour size was 2.5 centimeters (0.5-4 cm). The most common site of tumour origin was at or medial to the porus acousticus. Meningioma was suspected preoperatively in 10 of the 15 patients who had preoperative CT scans. Complete excision was obtained in 12 cases. There were no operative deaths after initial resections. Postoperative morbidity included worsening of pre-existing hearing loss in six patients, transient facial nerve palsies in six, permanent facial nerve palsies in four and new facial or corneal hypesthesia in three. Two patients developed cerebrospinal fluid fistulae. Tumour recurrence occurred into two patients in whom a complete resection was anticipated. Also, in two patients with incompletely resected tumours second operations were required. Fourteen patients are alive, 13 of whom care for themselves independently. The average follow-up was 5 years (6 months-9 years). It seems appropriate to recommend initial radical surgical excision of these benign tumours, where possible, in order to prevent tumour recurrence.

A versatile mercury vapour generating system suitable for long-term inhalation experiments

A mercury vapour generating system is described that is based on the reduction of HgCl2 by SnCl2 in the input airstream of the inhalation chamber. The solutions of the two chemicals are pumped by peristaltic pumps from reservoirs through a miniature mixing chamber into the upper part of a sloping glass tube (reduction chamber) through which air is sucked into the inhalation assembly. The liquid flows down the slope and through a port into a Quickfit flask. Reservoirs can be filled and the collecting flask emptied without interruption of exposure. The desired vapour concentration is achieved by varying the rate of mercury injection and the rate of airflow. Concentration in the inhalation chamber can be measured by passing air through a mercury vapour monitor or by radioactivity when 203HgCl2 is used and a known volume of air is passed through a hopcalite absorber. Operation instructions and an experimental example with mice are given.

Laser-assisted nerve repair in primates

Studies on the peripheral nerves in rats and other species have helped in the development of laser-assisted nerve anastomosis (LANA), but offer little in evaluating the efficacy of this technique in primates. The authors present a study of LANA in the peripheral nerves of rhesus monkeys. Twelve adult rhesus monkeys underwent bilateral resection of a portion of the peroneal nerve followed by placement of autogenous sural nerve interposition fascicular grafts. The grafts were completed with conventional microsurgical suture technique on one side and with LANA on the other. At 5, 8, 10, and 12 months, the grafted nerves were evaluated for continuity, nerve conduction, and histology (both light and electron microscopy). No significant difference in continuity, conduction velocity, nerve degeneration, nerve regeneration, axon fiber number, or axon fiber density was found in any animal between grafts performed by conventional microsuture and LANA grafts. There was no difference in distal or proximal myelinated fiber density between the LANA grafts and the conventional microsuture grafts. It was concluded that LANA is as effective as microsurgical suture nerve anastomosis in a primate model of nerve repair and grafting.

Intra-aortic balloon counterpulsation: a treatment for ischaemic stroke?

Intra-aortic balloon counterpulsation (IABC) augments cardiac output (CO) and pulse pressure (PP) allowing patients with low output heart failure to be supported for a period of time. Augmentation of CO and PP may also be beneficial to the patient with acute cerebral ischaemia. In this paper we investigated the possibility of using IABC to increase local cerebral blood flow (CBF) in ischaemic brain. In 12 anaesthetized mongrel dogs, a canine stroke model was produced by occluding the left internal carotid and middle cerebral arteries with aneurysm clips. Six dogs were then treated with IABC for 2 h, and 6 other dogs acted as controls (no IABC). Haemodynamic data were measured continuously and CBF (microsphere technique) and CO measurements were performed pre- and post-occlusion, and then twice during the treatment period. In the IABC-treated animals, PP increased from 32 +/- 5.9 to 39 +/- 7.8 mmHg (p less than 0.01) but CO and local CBF in the ischaemic brain did not change significantly during IABC. However, in 4 dogs with significant increases in CO due to IABC [1.7 +/- 0.3 to 2.8 +/- 0.7 l/min (p less than 0.05)], local CBF in ischaemic brain also increased significantly from 22 +/- 12 to 26 +/- 11 cc/100 g/min (p less than 0.05). In the control animals, CO and local CBF did not change significantly during the observation period. These data suggest that augmentation of CO and PP by IABC results in an increase in local CBF in ischaemic brain. IABC may be an effective treatment for ischaemic stroke in those patients with compromised cardiac performance whose cardiac output and pulse pressure can be augmented by IABC.

The effects of dose of elemental mercury and first-pass circulation time on exhalation and organ distribution of inorganic mercury in rats

The lung plays a major role in the removal of dissolved elemental mercury (Hg0) from the bloodstream. During the first passage through the lung after an intravenous dose of Hg0 dissolved in aqueous buffer, from 10 to 17% was exhaled depending on the dose (0.11 or 1.1 micrograms Hg/rat) and the injection site (jugular versus tail vein). Furthermore, evidence is presented that subsequent exhalation over the next 50 s, before the rats were killed and the mercury determined in the lung at that time, was largely Hg0-extracted during the first pass. The total mercury extracted during the 60 s period was in the range of 40-49% of the dose. The oxidation of Hg0 to Hg2+ in red cells is important in limiting the availability of Hg0 to certain tissues. Thus, after a short residence time in blood (0.6 s after jugular vein injection), 12.9-17% is exhaled in the first pass as compared to 10.4-12.2% with a longer residence time (1.8 s after tail vein injection). Furthermore, there was a general tendency, even at 60 s after dosing, for certain tissues - lung, brain, and heart - to have higher values after dosing from the jugular vein. It was estimated that the half-time for oxidation was 3.3 s. Our results confirm previous observations that the form of inorganic mercury greatly influences the short-term deposition in certain tissues. Thus as compared to Hg2+, administration of Hg0 increases lung levels 5-10-fold; brain, 4-fold; and heart, 3-fold. Blood levels are lower after Hg0, particularly after the higher dose. Such findings are consistent with a model wherein Hg0 is in part oxidized by red blood cells, the remainder rapidly diffusing in tissues where it is also oxidized to Hg2+.

Surgical exploration of enlarged lymph nodes at the root of the neck

Surgical exploration of presumed enlarged lymph nodes at the root of the neck may sometimes result in the exposure of neurogenic lesions. Careful exposure of the lesion should precede mobilization and excision to prevent unavoidable iatrogenic injury. Experiences with 45 neoplasms in this region are described.

The peripheral nerve allograft: an assessment of regeneration across nerve allografts in rats immunosuppressed with cyclosporin A

Lewis rats (RT1(1] were the recipients of 3-cm nerve grafts from syngeneic Lewis donors or allogeneic ACI (RT1a) donors. Microneurosurgical repair of the nerve graft to the transected sciatic nerve of the recipient animal was performed with 10-0 epineurial sutures. Recipients were randomly allocated to cyclosporin A (CsA) immunosuppressed or untreated groups. Cyclosporin A was administered in the minimal effective dosage to prevent nerve allograft rejection across this major histocompatibility disparity (5 mg/kg per day). Nerve regeneration across the nerve grafts was assessed by sciatic function index (SFI) and toe spread index (TSI) determinations serially and by electrophysiologic, histologic, and morphologic assessments 14 weeks after engraftment. Sciatic nerve regeneration across allogeneic nerve grafts in cyclosporin A immunosuppressed recipients was significantly superior compared to the untreated controls (p less than 0.008) and not significantly different from that across the syngeneic control animals.

Preliminary experiences with brachial plexus exploration in children: birth injury and vehicular trauma

The application of microsurgical techniques to the peripheral nervous system has made possible the reconstruction of the brachial plexus after vehicular and penetrating injuries. We now report our preliminary experiences utilizing these same techniques in the microsurgical management of brachial plexus birth injury. In contrast to other authors and in distinction from our own experiences with vehicular trauma in children, we did not find lesions requiring reconstruction by grafting or neurotization in any of seven plexus explorations for birth injury. The history of the surgical management of brachial plexus birth injury is reviewed, and the rationale for exploration is developed in the context of the natural history of the condition. Differences between our experiences and the existing literature are analyzed, with particular regard for timing of operation and technique of intraoperative assessment of nerve injury. All children with birth injuries of the brachial plexus require careful, repeated neurological evaluation during the first few months of life. Although the great majority make a rapid and satisfactory spontaneous recovery, the minority who do not recover are destined to suffer significant, life-long disability. Microsurgical brachial plexus exploration may benefit this select group of patients.

Shoulder arthrodesis using a pelvic-reconstruction plate. A report of eleven cases

Eleven adults who had a flail shoulder due to brachial plexus palsy had arthrodesis of the shoulder using a single ten-hole pelvic-reconstruction plate. Both the glenohumeral and the acromiohumeral joints were fused with the shoulder in the position of 30 degrees of abduction, 30 degrees of flexion, and 30 degrees of internal rotation. No bone graft was used. The patients were immobilized in a spica cast for six weeks postoperatively. At an average follow-up of twenty-five months after the operation, the position of the arthrodesis had been maintained and solid fusion had occurred in each shoulder. No patient required removal of the plate. The pelvic-reconstruction plate is malleable and is more easily contoured in the operating room than a dynamic-compression plate. We recommend the use of a malleable pelvic-reconstruction plate when performing arthrodesis of the shoulder.

Thoracic outlet syndrome with congenital pseudarthrosis of the clavicle: treatment by brachial plexus decompression, plate fixation and bone grafting

Although a number of cases of congenital pseudarthrosis of the clavicle have been described in the literature, they provide little direction for the treatment of this condition when it is associated with thoracic outlet syndrome. The authors describe their experience with such a case in a 20-year-old woman. Symptoms of pain in the ulnar distribution of the right forearm and discoloration of the hand with abduction of the extremity had developed over 3 years. The radial pulse was obliterated by abduction of the arm. Exploration of the brachial plexus revealed a constricting band arising from the distal fragment of the clavicle running to the first rib which, together with the mass of the pseudarthrosis, comprised the thoracic outlet. The patient was successfully treated by division of the fibrous band, reduction of the clavicle, internal fixation with a plate and iliac crest bone grafting. At follow-up the patient had a full range of motion in the shoulder and was asymptomatic.

An assessment of the effects of internal neurolysis on a chronically compressed rat sciatic nerve

Chronically compressed nerves were treated with three surgical modalities. Simple decompression was compared to internal neurolysis with and without the addition of extrafascicular steroid. Electrophysiologic, histologic, and morphometric assessments were performed. Compressed control nerves demonstrated changes compatible with severe nerve compression (Wallerian degeneration). With simple decompression, improvement in histologic and electrophysiologic parameters occurred. When internal neurolysis was added to the decompression, further improvement in histologic and electrophysiologic parameters was noted. There was no added improvement with the addition of steroids.

A model of chronic nerve compression in the rat

This article describes a model of chronic nerve compression in the rat. The sciatic nerve of adult male Sprague Dawley rats was banded with a 1-cm Silastic tube for varying periods of time. Morphometric analysis, electrodiagnostic studies, and histological evaluation were carried out 3, 5, 8, and 12 months after banding. Histological evaluation at 3 months was normal. At 5 months perineurial thickening was demonstrated. In the periphery of the fascicles, segmental demyelination was noted; central fibers appeared normal. At 8 months there was further epineurial and perineurial thickening. Marked thinning of the myelin was noted in all fibers and evidence of Wallerian degeneration was apparent. Progressive connective tissue and nerve fiber changes were noted at 12 months. Nerve conduction studies after 3 months of compression demonstrated an increase in conduction velocity compared to the normal unbanded control nerves. Progressive slowing of conduction velocity was noted from 5 through 12 months.

Comparison of the protection given by selenite, selenomethionine and biological selenium against the renotoxicity of mercury

The protective effect of selenite, seleno-dl-methionine and biological selenium against the renotoxicity of mercury was tested in rats. As the source of biological selenium, the liver soluble fraction of rats given 60 mumoles/kg selenite 3 days before sacrifice was used. The aim of the experiments was to test whether protective efficiency follows the reported order of ability to form HgSe. Mercury was given subcutaneously in doses of 2.5, 5.0 and 7.5 mumoles/kg HgCl2 and selenium was given in equimolar doses at the same time as Hg2+. Liver soluble fraction, biological selenium or liver soluble fraction supplemented with selenite or seleno-dl-methionine were given orally, while in experiments without liver soluble fraction the two selenium compounds were given subcutaneously. Biological selenium was tested only at the two lower dose levels. Both biological selenium and seleno-dl-methionine decreased the urinary excretion of mercury in the first 48 h, but less so than selenite and only selenite decreased the renal content of mercury at the end of this period. Urinary alkaline phosphatase activity and plasma urea nitrogen at the 2.5 and 5.0 mumoles/kg dose levels decreased in the order of no selenium greater than biological selenium greater than seleno-dl-methionine greater than selenite. As the reported HgSe formation increases in the same order, the experiments support the role of HgSe formation in the protective effect. The degree of necrotic damage in the P2 and P3 regions of the proximal tubular cells increased in the same order as the biochemical indicators at the 5.0 and 7.5 mumoles/kg dose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Injury to the brachial plexus during Putti-Platt and Bristow procedures. A report of eight cases

Eight patients with documented recurrent anterior dislocation of the shoulder sustained iatrogenic brachial plexus injuries during either Putti-Platt or Bristow procedures. Two patients also sustained axillary artery injuries. There were six males and two females. Postoperatively, complete paralysis of the musculocutaneous nerve was noted in six cases and incomplete paralysis in one case. Two patients had complete axillary nerve palsies. There were two cases of partial paralysis of the radial, median, and ulnar nerves, respectively. Seven of the patients underwent brachial plexus exploration an average of 16 weeks following their initial operation (range, 4 to 40). Suture material was removed from around or within two musculocutaneous nerves and one ulnar, one median, and one axillary nerve. Two lacerated musculocutaneous nerves were amenable to delayed primary repair. Two musculocutaneous, one median and one axillary nerve required grafting. Injury to the brachial plexus was associated with inadequate knowledge of regional anatomy, blind clamping of axillary artery lacerations, use of axillary incisions which limited exposure, and failure to identify the musculocutaneous nerve during Bristow procedures. If a brachial plexus injury occurs during a Putti-Platt or a Bristow procedure and the lesion does not rapidly, progressively, and completely recover, the brachial plexus should be explored since there is a high likelihood of structural neurologic injury.

Giant-cell tumor of the middle cranial fossa. Case report

The authors report the case of a 23-year-old man with a giant-cell tumor of the right middle cranial fossa floor. His presentation and management are described, and some aspects of this rare neoplasm of the skull base are reviewed. The role of adjuvant radiotherapy is discussed.