3D bioprinting of collagen to rebuild components of the human heart.

Collagen is the primary component of the extracellular matrix in the human body. It has proved challenging to fabricate collagen scaffolds capable of replicating the structure and function of tissues and organs. We present a method to 3D-bioprint collagen using freeform reversible embedding of suspended hydrogels (FRESH) to engineer components of the human heart at various scales, from capillaries to the full organ. Control of pH-driven gelation provides 20-micrometer filament resolution, a porous microstructure that enables rapid cellular infiltration and microvascularization, and mechanical strength for fabrication and perfusion of multiscale vasculature and tri-leaflet valves. We found that FRESH 3D-bioprinted hearts accurately reproduce patient-specific anatomical structure as determined by micro-computed tomography. Cardiac ventricles printed with human cardiomyocytes showed synchronized contractions, directional action potential propagation, and wall thickening up to 14% during peak systole.

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+.

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.

Perineurioma: a benign peripheral nerve tumor.

A unique benign peripheral nerve tumor, called a perineurioma, is described in this report. Light and electron microscopy and immunohistochemistry indicate that this tumor was derived from the perineurial cell. We discuss the ultrastructure, histogenesis, and management of this neoplasm.

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.

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.

Intraneural ganglion: a case report with electron microscopic observations.

We report a case of common peroneal mononeuropathy caused by an intraneural ganglion in a 9-year-old boy. The mass and the contiguous nerve fascicles were excised under the operating microscope. Histologically, the cyst wall was composed of layers of elongated cells merging with fascicles that exhibited changes suggestive of a pressure-ischemia effect. Electron microscopy showed that the cells forming cyst wall were myofibroblasts, similar to the cells found in ganglia arising from joints elsewhere in the body. A review of the English literature on intraneural ganglia discloses 44 additional cases, of which 86% involved the common peroneal nerve. The most common clinical feature was motor dysfunction (followed by pain, sensory loss, and the presence of a palpable mass), and a significant male predominance is noted. The pathogenesis of this nerve lesion is discussed in light of our findings.

Peripheral nerve allograft: an assessment of regeneration across pretreated nerve allografts.

Regeneration across lyophilized and irradiated peripheral nerve allografts was assessed using electrical and histological parameters. Regeneration did occur across these pretreated nerve allografts and was intermediate between that regeneration which occurred across a fresh, untreated nerve allograft and that which occurred across the control autograft.

Peripheral nerve allograft: an immunological assessment of pretreatment methods.

An in vivo immunological assay was used to determine quantitatively the nerve allograft response in a rat model. The nerve allograft was then pretreated with a number of pretreatment methods that have been used clinically and experimentally. Using the same immunological assay to determine quantitatively the nerve allograft response, we found that lyophilization and high doses of irradiation could modify the nerve allograft in such a way as to make it less immunogenetic to the host animal. The other methods of pretreatment did not alter the antigenicity of the allograft.

Progression of partial experimental injury to peripheral nerve. Part 2: Light and electron microscopic studies.

Biopsies from partially lacerated nerves were taken at the sites of proximal stimulus, laceration, and distal recording, and from stimuli and recording sites of control nerves. Electron microscopic examination of the partially lacerated major fasciculus revealed three zones of injury. The laceration zone showed neurotemetic changes, the adjacent or intermediate zone, partial degeneration, and the zone most peripheral to the laceration, changes in ground substance. Progression of the original injury is apparently due to ongoing changes in the intermediate and peripheral zones while much of the relative early recovery is due to reversal of changes in these zones. Regeneration through the laceration of neurotemetic zone is limited but does account for a small amount of late recovery of function.

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.

Experimental interfascicular nerve grafting.

Twenty-nine adult rhesus monkeys underwent complete laceration of both tibial nerves at mid-thigh level and repair by different methods to study the relative efficacy of autogenous interfascicular nerve grafts. Sixteen animals in Group I had an interfascicular graft repair using short sural nerve autografts on one limb and fascicular repair without grafts on the other limb. Thirteen animals in Group II, after having a 1-cm segment of tibial nerve resected, had an interfascicular graft repair without tension in one limb and an epineurial repair under moderate tension in the other limb. Evoked nerve and muscle action potentials and muscle strenght in response to repetitive and tetanic stimulation were recorded as baseline values prelaceration and then on re-exploration at 4, 6, 9, or 12 months. All nerves were examined by light and electron microscopy. Electrophysiological data, particularly muscle strength response, showed non-graft repairs to be superior at 4 and 6 months of regeneration. However, by 9 and 12 months the graft repairs had caught up and were equal to the non-graft repairs. Histologically, it was observed that many axons missed the graft segments and were present in extrafascicular connective tissues. Nonetheless, enough axons regenerated to the distal nerve to explain the success of these relatively short grafts. From the results of these experiments, it is concluded that use of autogenous interfascicular grafts offers no advantage over end-to-end non-graft repair. When and end-to-end repair cannot be achieved, use of short interfascicular nerve grafts is feasible and will work.

Histological studies of experimental interfascicular graft repairs.

Biopsies of sutured and grafted primate peripheral nerves were examined by light and electron microscopy after the final set of electrical measurements had been recorded. Inspection of all proximal stumps showed the expected regenerative activity which was not affected by the nature of the nerve repair. Transverse sections through the epineurial, interfascicular, and graft suture lines showed a similar pattern in all animals and at this site nerves sutured by epineurial technique could only be distinguished from those sutured by fascicular technique by loci of the non-absorbable suture. Fascicular repairs, whether done fascicle-to-fascicle or with interposition of grafts, had a more lengthy neuroma than did the epineurial repairs. Maintenance of fascicular architecture through the course of the grafts was variable. Fascicular structure was frequently absent in the central graft segments and in segments close to the second suture site. The method of repair used more proximally could not be distinguished by evaluation of distal stump segments. Measurements of myelinated fiber size made of distal stump axons revealed no statistical difference between the methods of repair.

Experimental study of fascicular nerve repair with and without epineurial closure.

Microscopic fascicular repair without closure of epineurium was compared with microscopic epineurial repair in 12 rhesus monkeys. Measurements of evoked nerve action potentials, and responses to repetitive and tetanic stimulation made at one interval 3, 6, 9, or 12 months postoperatively, were compared to baseline preoperative studies. Histological evaluation included light and electron microscopic preparations and studies of distal stump myelinated fiber maturity. Electrical measures of regeneration indicated that recovery was more advanced in the limb with epineurial repair in eight animals, whereas in four there was no difference between fascicular and epineurial repair. Fascicular repair appeared not to fare as well as epineurial repair because, although neuromas developed with both, the length of the neuroma was greater with fascicular than with epineurial repair. The relatively lengthy neuroma in the nerve with fascicular repair was due to axonal disorganization and connective tissue proliferation along the length of the dissection necessary for the repair. Nonetheless, studies of myelinated fiber distribution in the distal stump showed no significant differences. Similar studies were conducted in 11 primates, where epineurial repair was matched with fascicular repair in which the epineurium was closed. Here, regeneration as measured by both electrical and histological studies was comparable. Histological study showed less disorganization at the repair site in the nerve with fascicular suture and epineurial closures than in that with epineurial suture. However, studies of distal stump myelinated fiber maturity demonstrated no significant differences. Thus, there seems to be no advantage in either resecting or closing epineurium in fascicular nerve repair.

Biomechanical study of full-contact karate contrasted with boxing.

It is known that boxers suffer a characteristic cumulative brain injury from repeated blows to the head that correlates well with the number of bouts fought. Much less is known about full-contact karate (kickboxing), which is relatively new. In full-contact karate, punches and kicks are actually landed, rather than being focused to culminate just short of an opponent, as practiced in traditional karate. Although a combatant can win on points, the surest means of victory is a knockout. Consequently, fighters strive to land blows to the head. To investigate the relative force of kicks and punches, a dummy head was mounted 175 cm above the floor (to simulate a 50th-percentile man standing erect) and 125 cm above the floor (to simulate the man in a crouched position) on a universal joint permitting motion about three axes. The mechanism was contrived to provide constant rotational stiffness, and springs provided constant restorative moments about the three axes. The texture of soft tissue was simulated by a mask of visco-elastic foamed materials. Fourteen karate experts punched and kicked the dummy. Accelerometer measurements in the 90- to 120-G range indicated that safety-chops (hand protectors) and safety-kicks (foot padding) did not reduce acceleration of the dummy. Ten-ounce boxing gloves mitigated peak acceleration to some extent. Kicks and punches produced accelerations in the same range. Violent acceleration of the head by any means produces injury. The authors conclude that, if full-contact karate is widely practiced, cases of kickboxer's encephalopathy will soon be reported.

Progression of partial experimental injury to peripheral nerve. Part 1: Periodic measurements of muscle contraction strength.

Isometric measurements of muscle contraction in response to single as well as tetanic volleys of supramaximal stimuli were recorded from the limbs of 32 monkeys with noninjured or partially lacerated tibial nerves. Nerve action potentials (NAP) and muscle action potentials (MAP) were also determined at intervals varying from 1 hour to 52 weeks after injury. Limbs with mobilized noninjured nerve sustained small but definite decreases in muscle contraction strength particularly if the interval between operations was brief. Partially lacerated nerves had immediate averaged decreases in single twitch and supramaximal contraction strengths of 32.8% and 30.4% despite maintenance of NAP velocity. One week following injury, muscle contraction had decreased by another 21.6% and 19.7% respectively while NAP velocity was decreased by 18.5%. Measurements were also reduced at 2, 4, and 8 weeks and to a lesser degree at 12 weeks; at 24 and 36 weeks, muscle contraction was less than pre-injury data but not when compared to recordings 15 minutes after injury. Values recorded at 52 weeks reflected partial reinnervation of Achilles musculature. Studies over a 24-hour period following partial laceration demonstrated significant further decreases in muscle power by 8 hours. The authors conclude that nerve activity following partial laceration fluctuates as function diminishes during the early hours to weeks following injury.

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.

Peripheral nerve injury by chymopapain injection.

Chymopapain injected into the intervertebral disc space (chemonucleolysis) has been used clinically in patients with disc disease with success. Neurosurgical complications secondary to the procedure have, however, been reported. In this study, the authors have investigated the possible neurotoxic effect of chymopapain on the peripheral nerve in rat and primate models. While the extrafascicular injection caused no nerve fiber damage, the intrafascicular injection caused dose-related nerve fiber damage in both species.

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.

Complex formation between selenium and methylmercury.

Methylmercury, after incubation at 3k7 degrees C and pH 7.0 with selenite in the presence of rat erythrocytes, can be extracted into benzene as an unstable 2 : 1 complex with selenium. The same complex, possibly bis-methylmercury selenide, is formed when methylmercury is treated with hydrogen selenide at pH 7.0 in the absence of erythrocytes.