An enumerative algorithm for de novo design of proteins with diverse pocket structures

To create new enzymes and biosensors from scratch, precise control over the structure of small-molecule binding sites is of paramount importance, but systematically designing arbitrary protein pocket shapes and sizes remains an outstanding challenge. Using the NTF2-like structural superfamily as a model system, we developed an enumerative algorithm for creating a virtually unlimited number of de novo proteins supporting diverse pocket structures. The enumerative algorithm was tested and refined through feedback from two rounds of large-scale experimental testing, involving in total the assembly of synthetic genes encoding 7,896 designs and assessment of their stability on yeast cell surface, detailed biophysical characterization of 64 designs, and crystal structures of 5 designs. The refined algorithm generates proteins that remain folded at high temperatures and exhibit more pocket diversity than naturally occurring NTF2-like proteins. We expect this approach to transform the design of small-molecule sensors and enzymes by enabling the creation of binding and active site geometries much more optimal for specific design challenges than is accessible by repurposing the limited number of naturally occurring NTF2-like proteins.

Computational design of closely related proteins that adopt two well-defined but structurally divergent folds

The plasticity of naturally occurring protein structures, which can change shape considerably in response to changes in environmental conditions, is critical to biological function. While computational methods have been used for de novo design of proteins that fold to a single state with a deep free-energy minimum [P.-S. Huang, S. E. Boyken, D. Baker, Nature 537, 320-327 (2016)], and to reengineer natural proteins to alter their dynamics [J. A. Davey, A. M. Damry, N. K. Goto, R. A. Chica, Nat. Chem. Biol. 13, 1280-1285 (2017)] or fold [P. A. Alexander, Y. He, Y. Chen, J. Orban, P. N. Bryan, Proc. Natl. Acad. Sci. U.S.A. 106, 21149-21154 (2009)], the de novo design of closely related sequences which adopt well-defined but structurally divergent structures remains an outstanding challenge. We designed closely related sequences (over 94% identity) that can adopt two very different homotrimeric helical bundle conformations-one short (∼66 Å height) and the other long (∼100 Å height)-reminiscent of the conformational transition of viral fusion proteins. Crystallographic and NMR spectroscopic characterization shows that both the short- and long-state sequences fold as designed. We sought to design bistable sequences for which both states are accessible, and obtained a single designed protein sequence that populates either the short state or the long state depending on the measurement conditions. The design of sequences which are poised to adopt two very different conformations sets the stage for creating large-scale conformational switches between structurally divergent forms.

Discovery and engineering of enhanced SUMO protease enzymes

Small ubiquitin-like modifier (SUMO) is commonly used as a protein fusion domain to facilitate expression and purification of recombinant proteins, and a SUMO-specific protease is then used to remove SUMO from these proteins. Although this protease is highly specific, its limited solubility and stability hamper its utility as an in vitro reagent. Here, we report improved SUMO protease enzymes obtained via two approaches. First, we developed a computational method and used it to re-engineer WT Ulp1 from Saccharomyces cerevisiae to improve protein solubility. Second, we discovered an improved SUMO protease via genomic mining of the thermophilic fungus Chaetomium thermophilum, as proteins from thermophilic organisms are commonly employed as reagent enzymes. Following expression in Escherichia coli, we found that these re-engineered enzymes can be more thermostable and up to 12 times more soluble, all while retaining WT-or-better levels of SUMO protease activity. The computational method we developed to design solubility-enhancing substitutions is based on the RosettaScripts application for the macromolecular modeling suite Rosetta, and it is broadly applicable for the improvement of solution properties of other proteins. Moreover, we determined the X-ray crystal structure of a SUMO protease from C. thermophilum to 1.44 Å resolution. This structure revealed that this enzyme exhibits structural and functional conservation with the S. cerevisiae SUMO protease, despite exhibiting only 28% sequence identity. In summary, by re-engineering the Ulp1 protease and discovering a SUMO protease from C. thermophilum, we have obtained proteases that are more soluble, more thermostable, and more efficient than the current commercially available Ulp1 enzyme.

Accurate de novo design of hyperstable constrained peptides

Naturally occurring, pharmacologically active peptides constrained with covalent crosslinks generally have shapes that have evolved to fit precisely into binding pockets on their targets. Such peptides can have excellent pharmaceutical properties, combining the stability and tissue penetration of small-molecule drugs with the specificity of much larger protein therapeutics. The ability to design constrained peptides with precisely specified tertiary structures would enable the design of shape-complementary inhibitors of arbitrary targets. Here we describe the development of computational methods for accurate de novo design of conformationally restricted peptides, and the use of these methods to design 18-47 residue, disulfide-crosslinked peptides, a subset of which are heterochiral and/or N-C backbone-cyclized. Both genetically encodable and non-canonical peptides are exceptionally stable to thermal and chemical denaturation, and 12 experimentally determined X-ray and NMR structures are nearly identical to the computational design models. The computational design methods and stable scaffolds presented here provide the basis for development of a new generation of peptide-based drugs.

An exploration of human services system contacts prior to suicide in South Carolina: an expansion of the South Carolina Violent Death Reporting System

OBJECTIVE

To link South Carolina Violent Death Reporting System (SCVDRS) data with state government human services databases, enabling expanded analysis of suicide in South Carolina and providing a model for other jurisdictions.

DESIGN

The SCVDRS database compiles data from vital statistics, coroner reports, and law enforcement incident and supplemental reports. The Office of Research and Statistics, South Carolina Budget and Control Board (ORS) created a "Data Warehouse", to which a variety of state agencies and healthcare providers submit data on a regular basis. A unique identifier was used to link SCVDRS data to the Data Warehouse so that data may be analyzed on aggregate and case-specific levels. Year 2004 suicide data from SCVDRS were linked to South Carolina Uniform Billing codes from hospital in-patient and emergency room billing records, State Department of Mental Health service records, and criminal justice databases.

RESULTS

SCVDRS year 2004 suicide data are augmented by hospitalization and emergency room visit data and diagnoses; State Department of Mental Health service provision; and criminal involvement. Of the 491 suicides occurring in 2004, 282 linked with hospitalization and emergency room data, 196 linked with criminal history databases, and 91 had previous contact with the State Department of Mental Health.

CONCLUSIONS

Linking SCVDRS data to additional human services databases enables greater examination of factors surrounding suicide. Results show the positive benefits of partnerships created through SCVDRS, illustrate how SCVDRS and human service databases may augment each other, and suggest practitioners should explore implementation of prevention programs in specific settings.

The Discriminative Stimulus Effects of γ-Hydroxybutyrate and Related Compounds in Rats Discriminating Baclofen or Diazepam: The Role of GABAB and GABAA Receptors

The discriminative stimulus effects of gamma-hydroxybutyrate (GHB) can be mimicked by GABA(A) receptor-positive modulators (e.g., diazepam) and GABA(B) receptor agonists (e.g., baclofen). The purposes of this study were to see whether stimulus control could be established with baclofen and to further characterize the role of GABAergic mechanisms in the behavioral actions of GHB by evaluating GHB and related compounds in rats discriminating either diazepam or baclofen. Training criteria were satisfied with baclofen and diazepam after 69 and 44 sessions, respectively. GHB and its precursors gamma-butyrolactone and 1,4-butanediol occasioned >80% responding on the drug-associated lever in rats discriminating baclofen and <11% in rats discriminating diazepam. Diazepam and other GABA(A) receptor-positive modulators occasioned intermediate levels of responding on the baclofen lever, whereas baclofen occasioned less than 4% responding on the diazepam lever. The GABA(B) receptor antagonist CGP 35348 [(3-aminopropyl)(diethoxymethyl) phosphinic acid] partially antagonized the effects of baclofen as well as the baclofen-like effects of GHB, and flumazenil partially antagonized the effects of diazepam. This study established stimulus control with baclofen, and substitution data provided direct evidence for a role of GABAergic, especially GABA(B), mechanisms in the discriminative stimulus effects of GHB. The lack of substitution by GHB or its metabolic precursors for diazepam indicates a comparatively smaller role of GABA(A) mechanisms in these effects of GHB. The inability of CGP 35348 to completely attenuate the effects of baclofen and GHB suggests that multiple receptors could be involved in the discriminative stimulus effects of GHB.

Pediatric eighth cranial nerve schwannoma without evidence of neurofibromatosis

Schwannomas of the eighth cranial nerve are rare in children. We report a 4 10/12 - year-old girl with no evidence of neurofibromatosis who presented with facial droop. Radiographic studies revealed a large cerebellopontine angle tumor. At surgery, the tumor was attached to the eighth cranial nerve and histologically was a schwannoma. This is the youngest reported case of unilateral eighth cranial nerve schwannoma in a patient without the stigmata of neurofibromatosis.

ICP-CBF trauma bolt, laboratory evaluation

Thermal diffusion flowmetry is a continuous quantitative technique of measuring regional cerebral blood flow utilizing a silastic strip probe placed through a craniotomy or craniectomy in the operating room. A new bolt like application of this technology is now available for commercial use and is especially designed for bedside placement in trauma patients. This new trauma bolt is tested in juvenile pigs who are subjected to episodes of hypercapnea to increase cerebral blood flow, and records significant changes in blood flow. Another feature of the trauma bolt is a second port for the placement of an intracranial pressure (ICP) monitor. Placement of the probe and ICP monitor were easier than with the silastic probe and had relatively little complication.

Cerebral blood flow and temporal lobe epileptogenicity

Long-term surface cerebral blood flow (CBF) monitoring was performed to test the hypothesis that temporal lobe epileptogenicity is a function of epileptic cortical perfusion. Forty-three bitemporal 2-hour periictal CBF studies were performed in 13 patients. Homotopic regions of temporal cortex maintained interictal epileptic cortical hypoperfusion and nonepileptic normal cortical CBF. At 10 minutes preictus, a statistically significant, sustained increase in CBF was detected on the epileptic temporal lobe. Two minutes preictus, there was approximation of CBF in the epileptic and nonepileptic temporal lobes. Thereafter, electrocorticographic (ECoG) and clinical seizure onset occurred. The linear relationship between CBF in the two hemispheres (epileptic and nonepileptic) was the inverse of normal (y = -0.347x + 62.767, r = 0.470, df = 95, p < 0.05). The data indicated a direct linear correlation between epileptic cortical CBF and seizure interval (frequency-1), a clinical measure of epileptogenicity (r = 0.610, df = 49, p < 0.05). Epileptogenicity was also found to be a logarithmic function of the difference between nonepileptic and epileptic cortical perfusion (r = 0.564, df = 58, t = 5.20, p < 0.05). The results showed that progressive hypoperfusion of the epileptic focus correlated with a decreased seizure interval (increased epileptogenicity). Increased perfusion of the epileptic focus correlated with an increased seizure interval (decreased epileptogenicity). The fact that CBF alterations precede ECoG seizure activity suggests that vasomotor changes may produce electrical and clinical seizure onset.

Thermal diffusion flowmetry

Continuous monitoring of cerebral blood flow (CBF) has been an area under research to observe immediate changes in blood flow under a wide variety of circumstances. Recently, however, continuous monitoring of blood flow in the trauma cases has provided prognostic and therapeutic help in the management of these patients. Changes in CBF prior to the electrical discharge in the epileptic focus imply that blood flow changes may help in defining the focus. In the neurologically compromised patient, for whatever reason, CBF is an important parameter to follow and may give clues to therapeutic efficacy.

Cerebral bloodflow in and around spontaneous malignant gliomas

Knowledge of the cerebral bloodflow (CBF) in and around malignant gliomas is of crucial importance in developing strategies for hyperthermia-, radiation-, and chemo-therapy of these difficult to cure lesions. To gather data regarding this important physiological variable, the perfusion distributions of 26 patients who had either a glioblastoma multiforme or an anaplastic astrocytoma were determined using stable xenon computed tomography (XeCT). Perfusion values were determined for each of the following anatomical regions: low density tumour core, the enhancing active ring of the tumour, the low density peripheral region of edema, an ipsilateral region of normal brain adjacent to the tumour, and a region of remote normal tissue on the contralateral side of the brain. A multiple regression analysis of the logs of the CBF values was used to analyse: (1) the differences in blood perfusion between the anatomical regions; and (2) the association of blood perfusion with various patient and tumour characteristics. Statistically significant differences in perfusion values were found between all of the anatomically outlined regions with the exceptions that the active tumour and edematous regions do not differ significantly from the ipsilateral normal brain tissue. The ipsilateral normal brain tissue adjacent to the tumour was found to have a relative perfusion (relative to the contra-lateral normal brain tissue perfusion) of 0.84, the edematous tissue had a relative perfusion of 0.52, the active tumour 0.78, and the core 0.39. Significant blood flow was present in the low density tumour core, contradicting the frequent assumption that there is zero or minimal blood flow in such regions. Multiple regression analysis was used to look for other variables that might be associated with blood flow after adjusting for the differences between anatomical regions. This analysis found a significant negative correlation between tumour blood-flow and tumour volume. It also estimated that blood flow in GMB tumours was approximately 67% of that in lower grade tumours. Variables that were found not to be significantly correlated with blood flow were: patient sex, multiple lobe involvement, hemisphere involved, treatment status (initial vs recurrent disease), Karnofsky performance status, age and, lobe involved.

Influence of a 'brain protector' drug 21-amino steroid on the effects of experimental embolic stroke treated by thrombolysis

This study was designed to evaluate the effects of tissue-type plasminogen activator (tPA) and 21- amino steroid (U74006F) in experimental embolic stroke in rabbits. The size of infarction from embolism was compared to controls with tPA alone, 21-amino steroid alone, and in combination. The middle cerebral artery of the rabbit was embolized by injecting an arterial ('white') thrombus in the right internal carotid artery. The rabbit treatment was 2 mg kg-1 of tissue-type plasminogen activator and/or 3 mg kg-1 of 21 amino steroid started at 2 h post-embolization. The animals were terminated 4 h post-treatment and brains were examined for evidence of ischemia and/or hemorrhage. Administration of tissue-type plasminogen activator and/or 21-amino steroid in the raw data show that there is a tendency for all treatments to reduce the ischemic volume when compared to the control group, also it is evident the standard deviation of these estimates is rather large when compared to the differences between treatments. The results of the analysis of variance shows that the differences expressed are not statistically significant. (No statistical differences were found between the treatment groups and the control group.) The results show that administration of tissue-type plasminogen activator and/or 21 amino steroid at 2 h post-embolization alone or in simultaneous administration does not significantly reduce the volume of infarction. Further studies need to be addressed in regards to the region of viable brain in the peri-infarct area, in reducing the time to treatment.

Response of human epileptic temporal lobe cortical blood flow to hyperventilation

Bilateral long-term surface cortical cerebral blood flow (CBF) and electrocorticographic (ECoG) monitoring were performed in eight patients with complex partial seizures. In each patient, the epileptic temporal lobe was localized using ictal ECoG. Mean seizure interval (frequency-1) off anticonvulsant medication, a clinical measure of epileptogenicity, was 1.0 +/- 0.3 h (range: 0.4 to 2.5 h). During 13 interictal hyperventilation periods, 3.6 +/- 0.6 min in duration, the mean decrease in epileptic and nonepileptic temporal cortical CBF was 13.7 +/- 2.3 versus 6.4 +/- 1.9 ml/(100 g min) (t = 2.230, d.f. = 16, P < 0.05), representing 20.9% and 10.8% reduction from baseline CBF during hyperventilation, respectively. Seizure interval decreased (i.e. frequency increased) with increasing magnitude of seizure focus CBF reduction during hyperventilation. Seizure interval was significantly correlated with epileptic temporal lobe CBF decrease during hyperventilation (R = 0.763, d.f. = 5, P < 0.05). The data suggest that, compared to nonepileptic brain, epileptic temporal lobe is particularly prone to hypoperfusion during hyperventilation. Epileptogenicity is a function of this seizure focus susceptibility to ischemia. The finding of abnormal seizure focus autoregulation during hyperventilation has implication for epileptic focus localization with cerebral blood flow analysis.

Continuous regional cerebral cortical blood flow monitoring in head-injured patients

Continuous regional cerebral cortical blood flow (rCoBF) was monitored with thermal diffusion flowmetry in 56 severely head-injured patients. Adequate, reliable data were accumulated from 37 patients (21 acute subdural hematomas, 10 cerebral contusions, 4 epidural hematomas, and 2 intracerebral hematomas). The thermal sensor was placed at the time of either craniotomy or burr hole placement. In 15 patients, monitoring was initiated within 8 hours of injury. One-third of the comatose patients monitored within 8 hours had rCoBF measurements of 18 ml per 100 g per minute or less, consistent with previous reports of significant ischemia in the early postinjury period. Initial rCoBF measurements were similar in the patients with Glasgow Coma Scale scores of 3 to 7 and in those with scores of 8 or greater. In patients with poor outcomes, rCoBF measurements did not change significantly from initial measurements; however, in those patients who had better outcomes, final rCoBF measurements were higher than initial rCoBF measurements. The patients who had better outcomes experienced normalization of rCoBF during the period of monitoring, and patients with poor outcomes had markedly reduced final rCoBF. These changes were statistically significant. When management was based strictly upon the intracranial pressure, examples of inappropriate treatment were found. For example, hyperemia and increased intracranial pressure treated with mannitol caused further rCoBF increase, and elevated intracranial pressure with low cerebral blood flow treated with hyperventilation increased the severity of ischemia. In 3 (5%) of 56 patients, wound infections developed. Continuous rCoBF monitoring in head-injured patients offers new therapeutic and prognostic insights into their management.

Long-term surface cortical cerebral blood flow monitoring in temporal lobe epilepsy

Long-term subdural surface cortical cerebral blood flow (CBF) and electrocorticographic monitoring was performed in 12 patients with complex partial seizures. A total of 40 seizures were analyzed. Baseline CBF values from nonepileptic and epileptic temporal lobe (mean +/- standard error) were 60.0 +/- 1.0 and 50.2 +/- 1.8 ml/100 g per minute, respectively (P < 0.05). In general, clinical seizure onset was preceded by a 20-minute preictal CBF increase from baseline in the epileptic temporal lobe. Peak early postictal CBF values of nonepileptic and epileptic temporal lobes were 57.7 +/- 13.3 and 89.0 +/- 21.7 ml/100 g per minute (P > 0.05) at 5.2 +/- 2.2 and 2.4 +/- 1.0 minutes (P > 0.05) after clinical seizure onset, respectively. Statistically significant differences between nonepileptic and epileptic temporal lobe CBF were detected at 50 minutes (74.0 +/- 14.2 and 37.5 +/- 9.2 ml/100 g per minute, respectively; P < 0.05) and 60 minutes (75.6 +/- 13.6 and 36.1 +/- 8.5 ml/100 g per minute, respectively; P < 0.05) postictal. The data suggest that the optimal times for CBF analysis to differentiate epileptic from nonepileptic temporal lobe are 1) during the interictal period and 2) late (50 to 60 minutes) postictal. The results of this study should improve the understanding of the dynamic cerebral perfusion patterns in the epileptic human brain.

Long-term subdural strip electrocorticographic monitoring of ictal déjà vu

We report a series of 8 patients with ictal déjà vu. Subdural strip electrocorticographic (ECoG) monitoring localized the ictal epileptogenic focus as follows: right (n = 6) and left (n = 2) mesiotemporal lobe. In all 8 patients, the left hemisphere was dominant for language function based on intracarotid amytal testing. In 6 right-handed patients, ictal déjà vu was associated with a right temporal lobe focus. However, in the 2 left-handed patients, the ictal focus was left temporal lobe. Although ictal déjà vu localizes the epileptic focus to temporal lobe, this experimental phenomenon appears to lateralize to the hemisphere nondominant for handedness.

Contributions of the parietal and frontal lobes to sustained attention and habituation

The parietal cortex may be important in sustaining attention toward visual stimuli in peripheral space whereas the frontal cortex may mediate selective attention through habituation to peripheral stimuli. To test this hypothesis, patients with focal lesions of either the parietal or frontal cortex or both and normal controls were studied using a paradigm known as Troxler fading. Accordingly, if one fixates on a centrally located stimulus and attends to a stationary stimulus in peripheral vision, the peripheral stimulus quickly fades from awareness (i.e. Troxler fading: Troxler [Verschwinden, unseres, Opthal, Vol. 2, pp. 51-53. Fromann, Jena, 1804]). Movement of the peripheral stimulus on the retina normally prevents Troxler fading. Results indicated that patients with parietal lesions not only reported accelerated Troxler fading but also reported fading of moving peripheral stimuli contralateral to their brain lesion. In contrast, patients with frontal lesions rarely reported Troxler fading. In one patient with a left parietal and a right frontal lobe lesion fading was hemi-spatially dissociated, being accelerated in right hemispace but absent in left hemispace. These observations suggest that the parietal and frontal cortices play complementary roles in attentional processing.

Surface cortical cerebral blood flow monitoring and single photon emission computed tomography: prognostic factors for selecting temporal lobectomy candidates

A series of 23 patients with medically intractable temporal lobe epilepsy was studied with surface cortical cerebral blood flow monitoring, single photon emission computed tomography (SPECT) and subdural strip electrocorticographic (ECoG) monitoring for localization of the seizure focus. All patients underwent anterior temporal lobectomy and seizure outcome was determined after a mean of 9 months (range: 3-17 months). Invasive and non-invasive cerebral blood flow (CBF) parameters with prognostic value for seizure-free outcome were: (a) inter-ictal seizure focus with CBF < 65 ml/100 gm-min; (b) inter-ictal seizure focus CBF < or = normal temporal lobe CBF; and (c) concordance of inter-ictal and/or early post-ictal SPECT and ictal ECoG for seizure focus localization. These results should improve prognostic value of invasive and non-invasive cerebral blood flow data for selection of temporal lobectomy candidates.

Spinal epidural hematoma in a hemophilic infant

PURPOSE

Although intracranial hemorrhage remains a leading cause of death in hemophilia, spinal epidural hematoma is seen rarely. Decompressive laminectomy has a high associated morbidity, and recent reports have suggested that patients can be treated conservatively without surgical intervention.

PATIENTS AND METHODS

We present a case of spontaneous spinal epidural hematoma diagnosed by MRI scan in a 6-month-old hemophilic infant. Immediate treatment with factor VIII replacement was instituted.

RESULTS

There was rapid and complete clinical and radiographic resolution.

CONCLUSION

This case shows that selected hemophilic patients with spinal epidural hematoma can be spared surgical decompression by prompt medical attention.

Cerebral blood flow (CBF) monitoring in intensive care by thermal diffusion

Continuous monitoring of cortical blood flow (CoBF) in the intensive care unit is possible with thermal diffusion techniques. The normal brain flow limits have been established when electrical activity ceases and when infarction is likely to occur. With continuous monitoring of CoBF one can see immediate changes in flow and approaching these levels may be anticipated. The thermal diffusion system we have employed is based on the thermal conductivity of cortical tissue. As blood flow increases through the tissue, the conduction of energy away from the flow probe allows the sensor to detect changes in flow. This form of monitoring has been carried out in patients with subarachnoid hemorrhage, resection of cerebral mass lesions, severe craniotrauma, and intractable epilepsy. In subarachnoid hemorrhage, vasospasm can be identified and the efficacy of treatment determined with continuous monitoring of CoBF. During resection of mass lesions, increases in blood flow can be readily detected to document the recovery of brain tissue. Continuous monitoring of CoBF in epilepsy patients is now possible with the implantation of subdural electrodes. The increase in blood flow can be documented and it is apparent that a period of elevation of blood flow is quite short. Therefore, this may be helpful in determining when other forms of CBF determination, such as Single Photon Emission Computed Tomographic (SPECT) scanning should be performed. In patients with cranial trauma, different patterns of CoBF changes are apparent. Some patients may develop increased CoBF prior to elevation of intracranial pressure (ICP); other patients demonstrate a drop in CoBF as a response to increased ICP.(ABSTRACT TRUNCATED AT 250 WORDS)

Metallic postoperative artifacts on cervical MR

Spectroscopy of cervical diskectomy specimens obtained from sheep demonstrated that metallic susceptibility artifacts are produced by microscopic amounts of nickel, copper, and zinc. Sufficient quantities of metals to produce artifacts are deposited only by contact of metal drill bits and suction tips. If these instruments do not come in contact during surgery, susceptibility artifacts are not observed.

Influence of tissue plasminogen activator and heparin on cerebral ischemia in a rabbit model

BACKGROUND AND PURPOSE

The aims of this study were to verify that tissue-type plasminogen activator given either 1 or 2 hours after experimental embolic stroke in rabbits diminishes the volume of resulting ischemic brain and to ascertain the effect of the simultaneous administration of heparin.

METHODS

We embolized the middle cerebral artery of rabbits by injecting performed autologous arterial ("white") thrombus into one internal carotid artery. Treatment with 2 mg/kg tissue-type plasminogen activator, alone or in combination with heparin, was commenced either 1 or 2 hours after embolization. The animals were killed 5 hours after treatment commenced, and their brains were examined for evidence of ischemia and hemorrhage.

RESULTS

Administration of tissue-type plasminogen activator significantly diminished the size of the resulting brain ischemia. Administration of heparin, with or instead of tissue-type plasminogen activator, did not result in a significant decrease in the volume of cerebral ischemia, but it also did not lead to hemorrhagic transformation of the stroke.

CONCLUSIONS

In the rabbit model, administration of tissue-type plasminogen activator within 2 hours diminished the volume of brain rendered acutely ischemic by embolic stroke. Since the simultaneous administration of heparin during this same period did not result in any instances of hemorrhagic transformation, tissue-type plasminogen activator may have some place for use in such circumstances to mitigate a tendency to further embolic or thrombotic events.

Instrumentation for microsurgical osseous dissection. Technical note

The use of the operating microscope has revolutionized the surgical approach to many neurosurgical diseases. The microscope has provided magnification, binocular vision, and excellent lighting in the depths of neurosurgical wounds, allowing the performance of exceedingly delicate procedures that were previously impossible. Occasionally, an operative approach demands microscopic bone dissection. Instrumentation has been developed for working with soft tissue, but special instruments for osseous dissection have not been available. A set of newly developed punches and curettes with a bayonetted offset is described. These keep the surgeon's hand out of the operating field and allow unimpeded visualization through the operating microscope. These prototype instruments have been used successfully in over 100 microscopic neurosurgical procedures.

Treatment of malignant brain tumors with focused ultrasound hyperthermia and radiation: results of a phase I trial

Hyperthermia delivered by scanned focused ultrasound was combined with external beam radiation to treat 15 patients with primary malignant tumors of the brain. A preliminary craniectomy was performed to avoid attenuation of the ultrasound beam by the skull, and multiple thermal sensors were employed to ascertain intratumoral temperatures. The target temperature was 42.5 degrees C at the tumor boundary. This was attained at more than one point during every complete treatment, while a mean temperature in excess of 42 degrees C was achieved within the scanned tumor volume during at least 1 treatment in 11 patients. Technical problems and toxicities are described.

Continuous regional cerebral blood flow monitoring in acute craniocerebral trauma

Regional cortical cerebral blood flow (rCBF) and intracranial pressure (ICP) were monitored continuously with a combined thermal diffusion probe/ICP monitor in 12 patients (8 men and 4 women; mean age, 31 years; range, 7-65 years) with acute head injuries. The mean Glasgow Coma Scale score at admission was 6 (range, 4-12). The rCBF/ICP probes were placed during surgical procedures (n = 11) or in an intensive care unit (n = 1) for subdural hematomas (n = 7), cerebral contusions (n = 4), and an epidural hematoma (n = 1). No probe-related complications occurred. Reduced CBF often occurred and was often inversely proportional to elevations in ICP. Posttraumatic cerebral arterial vasospasm in one patient was detected by rCBF monitoring and confirmed by angiography. In 6 patients who progressed to brain death, rCBF patterns disappeared, which correlated with their clinical and electroencephalographic examinations. Several patients with severe, diffuse brain injuries and high ICP had hyperemic rCBF patterns. In 2 of these patients, increases in rCBF preceded rises in ICP, which implied loss of autoregulation as a mechanism in the development of malignant cerebral edema. This method of CBF monitoring has not yet been established for clinical decision making. The early detection of ischemic or hyperemic responses by continuous CBF monitoring could hasten intervention aimed at restoring adequate tissue perfusion. The technique could also serve as an index of the efficacy of therapeutic interventions and is suitable to gain more insight into the pathophysiology of head injury, especially the relationship of CBF to ICP.

Continuous postoperative monitoring of cortical blood flow and intracranial pressure

A new technique to continuously monitor cortical blood flow and intracranial pressure in postoperative patients is described. A thermal diffusion flow probe with a pressure port is left in contact with the cortex at craniotomy. Postoperative intracranial pressure--cortical blood flow can be monitored and acute changes or trends are readily detected. The thermal flow probe has been previously compared with radioactive xenon (133Xe) clearance and hydrogen clearance methods of measuring cortical blood flow in animals. The technique gives a real-time quantitative indication of flow. Changes in cortical blood flow can be observed within a few seconds and the effects of treatment can be readily observed. Changes in flow due to vasospasm have been demonstrated in subarachnoid hemorrhage. It is anticipated that information learned from this method will aid in the management of patients with head trauma, tumors, and subarachnoid hemorrhage.

Postoperative monitoring of cerebral blood flow in patients harboring intracranial aneurysms

Fifteen patients harbouring intracranial aneurysms were monitored postoperatively. A thermal diffusion flow probe was placed on the cortex, in an area of interest, and continuous recording of cerebral blood flow (CBF) was carried out for 1-4 days. Vasospasm can also be detected by clinical deterioration, increased velocity by transcranial Doppler, and by angiographical evidence of decrease in vessel calibre. A comparison was made between these methods of determining vasospasm and changes in CBF. Three patients had unruptured aneurysms and no evidence of vasospasm. These patients had a range of CBF from 44 to 100 cc 100 g-1 min-1 with a daily mean of 78 cc 100 g-1 min-1. One patient was operated on, in a delayed fashion, after a period of vasospasm on post-subarachnoid haemorrhage (SAH) Day 18 and was found to have a CBF of 40 cc 100 g-1 min-1 when the pCO2 was 21 Torr and the mean blood pressure (BP) was 99 Torr. The development of vasospasm was correlated with a CBF of less than 40 cc 100 g-1 min-1. Some patients with vasospasm also develop a significant drop in CBF during the period of monitoring. Using these criteria, CBF monitoring predicted the development of vasospasm in seven patients, was compatible with the clinical course in three patients and was misleading in two patients. In the seven patients in which CBF predicted vasospasm, changes were seen in CBF prior to changes observed by clinical examination, transcranial Doppler, and/or angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of dural arteriovenous malformations of the anterior cranial fossa

Eight patients with dural arteriovenous malformations (AVM's) of the anterior cranial fossa are presented, and the pertinent literature is reviewed. Unlike cases of dural AVM's in other locations, sudden massive intracerebral hemorrhage was the most frequent reason for presentation. Other symptoms included tinnitus, retro-orbital headache, and a generalized seizure. The malformations were supplied consistently by the anterior ethmoidal artery, usually in combination with other less prominent feeding vessels. The lesion's venous drainage was through the superior sagittal sinus via a cortical vein; in addition, in two cases a subfrontal vein drained the AVM. A venous aneurysm was encountered near the site of anastomosis with the dural feeder in most cases, and was found in all patients who presented with hemorrhage. The AVM was obliterated surgically in six patients, with favorable results achieved in five. One patient died postoperatively from a pulmonary complication. Because of their anatomy and proclivity for hemorrhage, these vascular malformations represent a unique group of dural AVM's. Surgical management of anterior fossa dural AVM's carries low morbidity, and is indicated when the lesions have caused hemorrhage or when there is an associated venous aneurysm.

Reconstruction of the MCA bifurcation after excision of a giant aneurysm. Technical note

A patient with a giant aneurysm of the left middle cerebral artery (MCA) presented with a history of subarachnoid hemorrhage and ischemic symptoms. When the aneurysm was explored, its base was found to be very firm and atherosclerotic. Temporary clips were applied to the MCA, the aneurysm was excised, and the MCA bifurcation was reconstructed using microsurgical techniques. Good flow in the reconstructed MCA trunk was demonstrated by intracranial Doppler ultrasonography. A description of the operative procedure is presented.

Aneurysms of the basilar artery treated with circulatory arrest, hypothermia, and barbiturate cerebral protection

Complete circulatory arrest, deep hypothermia, and barbiturate cerebral protection are efficacious adjuncts in the surgical treatment of selected giant intracranial aneurysms. These techniques were utilized in seven patients, one with a large and six with giant basilar artery aneurysms; four had excellent results, one had a good result, one had a fair outcome, and one died. The rationale for the use of complete cardiac arrest with extracorporeal circulation, hypothermia, and barbiturate cerebral protection is outlined. The surgical and anesthetic considerations are reviewed. The perioperative morbidity and long-term results support the use of these techniques in selected patients with complex intracranial vascular lesions.

Surgical management of large AVM's by staged embolization and operative excision

A series of 20 patients with giant arteriovenous malformations (AVM's) managed with staged embolization and surgical resection is presented. Complete excision was accomplished in 18 of these patients. There were no deaths and only three complications, of which one was disabling. Further evidence for the presence of low perfusion surrounding the AVM, emphasizing the risk of normal perfusion pressure breakthrough, is provided by cortical perfusion pressure, cortical cerebral blood flow (CBF), and stable xenon computerized tomography CBF measurements. The staged approach to giant AVM management is a proposed method to render AVM's that were previously considered inoperable or marginally operable into totally excisable lesions, while maintaining an acceptable level of morbidity and mortality.

Vertebrobasilar insufficiency. Part 2. Microsurgical treatment of intracranial vertebrobasilar disease

Posterior circulation transient ischemic attacks have an associated risk of subsequent infarction of approximately 5% per year. Intracranial vertebrobasilar thrombo-occlusive lesions appear particularly likely to result in repetitive ischemic symptoms and in infarction due to hemodynamic insufficiency. The authors present their experience with 45 patients with symptomatic intracranial vertebrobasilar vascular disease despite maximal medical therapy. The specific operative approaches for intracranial vertebral artery endarterectomy and extracranial to intracranial posterior circulation revascularization procedures are outlined.

Vertebrobasilar insufficiency. Part 1: Microsurgical treatment of extracranial vertebrobasilar disease

Extracranial vertebrobasilar artery thrombo-occlusive disease may cause repetitive transient ischemic episodes and, less frequently, brain-stem or cerebellar infarction. This report describes 40 patients who experienced repetitive vertebrobasilar ischemic symptoms despite maximal medical therapy. The natural history, pathogenesis, and treatment options for each causative lesion are reviewed. The operative approaches to symptomatic disease of the proximal vertebral arteries, arterial compression by cervical osteophytes, traumatic lesions of the vertebral arteries, and thrombo-occlusive pathology of the distal extracranial vertebral arteries are outlined. Specific anesthetic and surgical techniques that have proved successful while achieving zero operative mortality and low perioperative morbidity rates are reported.

Clinical vasospasm after subarachnoid hemorrhage: response to hypervolemic hemodilution and arterial hypertension

Delayed neurologic deterioration from vasospasm remains the greatest cause of morbidity and mortality following subarachnoid hemorrhage. The authors assess the incidence and clinical course of symptomatic vasospasm following subarachnoid hemorrhage using a uniform management protocol over a 24-month period. One hundred eighteen consecutive patients were admitted to the neurovascular surgery service within 2 weeks of subarachnoid hemorrhage not attributed to trauma, tumor, or vascular malformation (113 patients had aneurysms). Early surgery was performed whenever possible, and hypertensive hypervolemic hemodilution therapy was instituted at the first sign of clinical vasospasm. Forty-two patients (35.6%) developed characteristic signs and symptoms of clinical vasospasm with angiographic verification of spasm in 39 cases. All patients with clinical vasospasm received hypervolemic hemodilution therapy aiming for a hematocrit of 33-38%, a central venous pressure of 10-12 mm Hg (or a pulmonary wedge pressure of 15-18 mm Hg), and a systolic arterial pressure of 160-200 mm Hg (120-150 mm Hg for unclipped aneurysms) for the duration of clinical vasospasm. Over the course of treatment, 60% of patients with clinical vasospasm had sustained improvement by at least 1 neurologic grade, 24% maintained a stable neurologic status, and 16% continued to worsen. At the end of hypervolemic hemodilution therapy, 47.6% had become neurologically normal, 33.3% had a minor neurologic deficit, and 19% had a major neurologic deficit or were dead. There were 3 instances of cardiopulmonary deterioration (7%), all of which were in patients without Swan-Ganz catheters, and all resolved with appropriate diuresis. One patient rebled and died while on hypervolemic hemodilution therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of asymptomatic carotid atherosclerosis

The detection, evaluation, and treatment of patients with asymptomatic carotid artery disease are controversial issues. In this review, these issues are addressed and the appropriate application of medical and surgical therapies is discussed. There seem to be two subgroups of asymptomatic patients with angiographically defined lesions (marked stenosis or large, deep, and compound ulcers) who have a significant risk of subsequent cerebral infarction. These patients should be considered for carotid endarterectomy at a surgical center with an established low incidence of perioperative complications.

Occipital artery to extradural vertebral artery bypass procedure. Case report

A 17-year-old boy suffered blunt trauma to the posterior cervical spine and later developed vertebrobasilar transient ischemic attacks refractory to medical management. At angiography, a pseudoaneurysm of the distal left vertebral artery was found. By means of a posterior midline approach, an extradural occipital artery to vertebral artery anastomosis was performed and the affected vertebral artery was clipped distal to the pseudoaneurysm. The indications for this procedure, the operative approach, and the clinical outcome are described.

Multiple intracranial aneurysms: determining the site of rupture

A retrospective hospital chart and radiograph review was performed of all patients with multiple intracranial aneurysms seen over a 52-month period. Sixty-nine patients with a total of 205 aneurysms were studied. Among the patients with aneurysms, the incidence of multiple aneurysms was 33.5%. Multiple aneurysms were much more common in women, with a female to male ratio of 5:1 for all patients and 11:1 for patients with three or more aneurysms. Common locations for multiple aneurysms were the posterior communicating artery (22%), middle cerebral artery (21.5%), anterior communicating artery (12%), and ophthalmic artery (11%). However, locations with the highest probability of rupture were the anterior communicating artery (62%), posterior inferior cerebellar artery (50%), and basilar artery summit (50%). The middle cerebral artery was the least likely site for rupture. In contrast to previous studies, in this series irregularity of contour was more important than size in identifying the site of rupture. Using a simple algorithm outlined in the text, it was possible to identify the site of aneurysm rupture in 97.5% of cases.