Intraoperative Nerve Stimulation as an Approach for the Surgical Treatment of Genitofemoral Neuralgia

BACKGROUND Genitofemoral neuralgia is a pain syndrome that involves injury to the genitofemoral nerve and is frequently iatrogenic. We report intraoperative nerve localization using ultrasound, nerve stimulation, and the cremasteric reflex in the surgical treatment of genitofemoral neuralgia. CASE REPORT A 49-year-old man with a history of extracorporeal membrane oxygenation with cannulation sites in bilateral inguinal regions presented with right groin numbness and pain following decannulation. His symptoms corresponded to the distribution of the genitofemoral nerve. He had a Tinel's sign over the midpoint of his inguinal incision. A nerve block resulted in temporary resolution of his symptoms. Due to the presence of a pacemaker, peripheral nerve neuromodulation was contraindicated. He underwent external neurolysis and neurectomy of the right genitofemoral nerve. Following direct stimulation and ultrasound for localization, the nerve was further localized intraoperatively using nerve stimulation with monitoring for the presence of the cremasteric reflex. At his 1-month postoperative visit, his right medial thigh pain had resolved and his right testicular pain 50% improved; his residual pain continued to improve at last evaluation 3 months after surgery. CONCLUSIONS We report the successful use of nerve stimulation and the cremasteric reflex to aid in identification of the genitofemoral nerve intraoperatively for the treatment of genitofemoral neuralgia.

Prognostic Significance of Baseline Frailty Status in Traumatic Spinal Cord Injury

BACKGROUND

Literature evaluating frailty in traumatic spinal cord injury (tSCI) is limited.

OBJECTIVE

To evaluate the prognostic significance of baseline frailty status in tSCI.

METHODS

Patients with tSCI were identified in the National Inpatient Sample from 2015 to 2018 and stratified according to frailty status, which was quantified using the 11-point modified frailty index (mFI).

RESULTS

Among 8825 operatively managed patients with tSCI identified (mean age 57.9 years, 27.6% female), 3125 (35.4%) were robust (mFI = 0), 2530 (28.7%) were prefrail (mFI = 1), 1670 (18.9%) were frail (mFI = 2), and 1500 (17.0%) were severely frail (mFI ≥ 3). One thousand four-hundred forty-five patients (16.4%) were routinely discharged (to home), and 320 (3.6%) died during hospitalization, while 2050 (23.3%) developed a severe complication, and 2175 (24.6%) experienced an extended length of stay. After multivariable analysis adjusting for age, illness severity, trauma burden, and other baseline covariates, frailty (by mFI-11) was independently associated with lower likelihood of routine discharge [adjusted odds ratio (aOR) 0.82, 95% CI 0.77-0.87; P < .001] and development of a severe complication (aOR 1.17, 95% CI 1.12-1.23; P < .001), but not with in-hospital mortality or extended length of stay. Subgroup analysis by age demonstrated robust associations of frailty with routine discharge in advanced age groups (aOR 0.71 in patients 60-80 years and aOR 0.69 in those older than 80 years), which was not present in younger age groups.

CONCLUSION

Frailty is an independent predictor of clinical outcomes after tSCI, especially among patients of advanced age. Our large-scale analysis contributes novel insights into limited existing literature on this topic.

Neutrophil-Lymphocyte ratio is associated with poor clinical outcome after mechanical thrombectomy in stroke in patients with COVID-19

Background

The neutrophil–lymphocyte ratio (NLR) is emerging as an important biomarker of acute physiologic stress in a myriad of medical conditions, and is a confirmed poor prognostic indicator in COVID-19.

Objective

We sought to describe the role of NLR in predicting poor outcome in COVID-19 patients undergoing mechanical thrombectomy for acute ischemic stroke.

Methods

We analyzed NLR in COVID-19 patients with large vessel occlusion (LVO) strokes enrolled into an international 12-center retrospective study of laboratory-confirmed COVID-19, consecutively admitted between March 1, 2020 and May 1, 2020. Increased NLR was defined as ≥7.2. Logistic regression models were generated.

Results

Incidence of LVO stroke was 38/6698 (.57%). Mean age of patients was 62 years (range 27–87), and mortality rate was 30%. Age, sex, and ethnicity were not predictive of mortality. Elevated NLR and poor vessel recanalization (Thrombolysis in Cerebral Infarction (TICI) score of 1 or 2a) synergistically predicted poor outcome (likelihood ratio 11.65, p  =  .003). Patients with NLR > 7.2 were 6.8 times more likely to die (OR 6.8, CI95% 1.2–38.6, p  =  .03) and almost 8 times more likely to require prolonged invasive mechanical ventilation (OR 7.8, CI95% 1.2–52.4, p  =  .03). In a multivariate analysis, NLR > 7.2 predicted poor outcome even when controlling for the effect of low TICI score on poor outcome (NLR p  =  .043, TICI p  =  .070).

Conclusions

We show elevated NLR in LVO patients with COVID-19 portends significantly worse outcomes and increased mortality regardless of recanalization status. Severe neuro-inflammatory stress response related to COVID-19 may negate the potential benefits of successful thrombectomy.

Endovascular Thrombectomy for Pediatric Acute Ischemic Stroke

BACKGROUND

Evidence regarding the utilization and outcomes of endovascular thrombectomy (EVT) for pediatric ischemic stroke is limited, and justification for its use is largely based on extrapolation from clinical benefits observed in adults.

METHODS

Weighted discharge data from the National Inpatient Sample were queried to identify pediatric patients with ischemic stroke (<18 years old) during the period of 2010 to 2019. Complex samples statistical methods were used to characterize the profiles and clinical outcomes of EVT-treated patients. Propensity adjustment was performed to address confounding by indication for EVT based on disparities in baseline characteristics between EVT-treated patients and those medically managed.

RESULTS

Among 7365 pediatric patients with ischemic stroke identified, 190 (2.6%) were treated with EVT. Utilization significantly increased in the post-EVT clinical trial era (2016-2019; 1.7% versus 4.0%; P<0.001), while the use of decompressive hemicraniectomy decreased (2.8% versus 0.7%; P<0.001). On unadjusted analysis, 105 (55.3%) EVT-treated patients achieved favorable functional outcomes at discharge (home or to acute rehabilitation), while no periprocedural iatrogenic complications or instances of contrast-induced kidney injury were reported. Following propensity adjustment, EVT-treated patients demonstrated higher absolute but nonsignificant rates of favorable functional outcomes in comparison with medically managed patients (55.3% versus 52.8%; P=0.830; adjusted hazard ratio, 1.01 [95% CI, 0.51-2.03]; P=0.972 for unfavorable outcome). Among patients with baseline National Institutes of Health Stroke Scale score >11 (75th percentile of scores in cohort), EVT-treated patients trended toward higher rates of favorable functional outcomes compared with those treated medically only (71.4% versus 55.6%; P=0.146). In a subcohort assessment of EVT-treated patients, those administered preceding thrombolytic therapy (n=79, 41.6%) trended toward higher rates of favorable functional outcomes (63.3% versus 49.5%; P=0.060).

CONCLUSIONS

This cross-sectional evaluation of the clinical course and short-term outcomes of pediatric patients with ischemic stroke treated with EVT demonstrates that EVT is likely a safe modality which confers high rates of favorable functional outcomes.

Development of cerebral vasospasm following traumatic intracranial hemorrhage: incidence, risk factors, and clinical outcomes

OBJECTIVE

Limited evidence exists characterizing the incidence, risk factors, and clinical associations of cerebral vasospasm following traumatic intracranial hemorrhage (tICH) on a large scale. Therefore, the authors sought to use data from a national inpatient registry to investigate these aspects of posttraumatic vasospasm (PTV) to further elucidate potential causes of neurological morbidity and mortality subsequent to the initial insult.

METHODS

Weighted discharge data from the National (Nationwide) Inpatient Sample from 2015 to 2018 were queried to identify patients with tICH who underwent diagnostic angiography in the same admission and, subsequently, those who developed angiographically confirmed cerebral vasospasm. Multivariable logistic regression analysis was performed to identify significant associations between clinical covariates and the development of vasospasm, and a tICH vasospasm predictive model (tICH-VPM) was generated based on the effect sizes of these parameters.

RESULTS

Among 5880 identified patients with tICH, 375 developed PTV corresponding to an incidence of 6.4%. Multivariable adjusted modeling determined that the following clinical covariates were independently associated with the development of PTV, among others: age (adjusted odds ratio [aOR] 0.98, 95% CI 0.97–0.99; p < 0.001), admission Glasgow Coma Scale score < 9 (aOR 1.80, 95% CI 1.12–2.90; p = 0.015), intraventricular hemorrhage (aOR 6.27, 95% CI 3.49–11.26; p < 0.001), tobacco smoking (aOR 1.36, 95% CI 1.02–1.80; p = 0.035), cocaine use (aOR 3.62, 95% CI 1.97–6.63; p < 0.001), fever (aOR 2.09, 95% CI 1.34–3.27; p = 0.001), and hypokalemia (aOR 1.62, 95% CI 1.26–2.08; p < 0.001). The tICH-VPM achieved moderately high discrimination, with an area under the curve of 0.75 (sensitivity = 0.61 and specificity = 0.81). Development of vasospasm was independently associated with a lower likelihood of routine discharge (aOR 0.60, 95% CI 0.45–0.78; p < 0.001) and an extended hospital length of stay (aOR 3.53, 95% CI 2.78–4.48; p < 0.001), but not with mortality.

CONCLUSIONS

This population-based analysis of vasospasm in tICH has identified common clinical risk factors for its development, and has established an independent association between the development of vasospasm and poorer neurological outcomes.

Association of Elevated Body Mass Index with Functional Outcome and Mortality following Acute Ischemic Stroke: The Obesity Paradox Revisited

BACKGROUND

Previous literature has identified a survival advantage in acute ischemic stroke (AIS) patients with elevated body mass indices (BMIs), a phenomenon termed the "obesity paradox."

OBJECTIVE

The aim of this study was to evaluate the independent association between obesity and clinical outcomes following AIS.

METHODS

Weighted discharge data from the National Inpatient Sample were queried to identify AIS patients from 2015 to 2018. Multivariable logistic regression and Cox proportional hazards modeling were performed to evaluate associations between obesity (BMI ≥ 30) and clinical endpoints following adjustment for acute stroke severity and comorbidity burden.

RESULTS

Among 1,687,805 AIS patients, 216,775 (12.8%) were obese. Compared to nonobese individuals, these patients were younger (64 vs. 72 mean years), had lower baseline NIHSS scores (6.9 vs. 7.9 mean score), and a higher comorbidity burden. Multivariable analysis demonstrated independent associations between obesity and lower likelihood of mortality (adjusted odds ratio [aOR] 0.76, 95% confidence interval [CI]: 0.71, 0.82, p < 0.001; hazard ratio 0.84, 95% CI: 0.73, 0.97, p = 0.015), intracranial hemorrhage (aOR 0.87, 95% CI: 0.82, 0.93, p < 0.001), and routine discharge to home (aOR 0.97, 95% CI: 0.95, 0.99; p = 0.015). Mortality rates between obese and nonobese patients were significantly lower across stroke severity thresholds, but this difference was attenuated among high severity (NIHSS > 20) strokes (21.6% vs. 23.2%, p = 0.358). Further stratification of the cohort into BMI categories demonstrated a "U-shaped" association with mortality (underweight aOR 1.58, 95% CI: 1.39, 1.79; p < 0.001, overweight aOR 0.64, 95% CI: 0.42, 0.99; p = 0.046, obese aOR 0.77, 95% CI: 0.71, 0.83; p < 0.001, severely obese aOR 1.18, 95% CI: 0.74, 1.87; p = 0.485). Sub-cohort assessment of thrombectomy-treated patients demonstrated an independent association of obesity (BMI 30-40) with lower mortality (aOR 0.79, 95% CI: 0.65, 0.96; p = 0.015), but not with routine discharge.

CONCLUSION

This cross-sectional analysis demonstrates a lower likelihood of discharge to home as well as in-hospital mortality in obese patients following AIS, suggestive of a protective effect of obesity against mortality but not against all poststroke neurological deficits in the short term which would necessitate placement in acute rehabilitation and long-term care facilities.

Nationwide trends in middle meningeal artery embolization for treatment of chronic subdural hematoma: A population-based analysis of utilization and short-term outcomes

Middle meningeal artery (MMA) embolization represents a promising novel treatment modality for chronic subdural hematoma (cSDH), yet utilization and efficacy data are limited. This study evaluates the utilization and short-term outcomes of MMA embolization for cSDH treatment in a large national inpatient registry. cSDH patients treated with MMA embolization and/or surgical evacuation (craniotomy/burr hole drainage) were identified using the National Inpatient Sample (NIS) during 2012-2018 period. Temporal trends, complications, and discharge disposition were evaluated, and propensity score matching was implemented for adjusted comparisons and to mitigate confounding by indication. Among 60,045 cSDH patients identified, 390 (0.6%) underwent MMA embolization. Embolized patients presented more with high acute illness severity subclasses in comparison with surgically evacuated patients (53% vs. 34%, p = 0.004) yet did not experience any procedure-related hemorrhagic or ischemic complications. Although discharge disposition did not differ from those surgically managed, embolized patients had longer mean hospital stays (13 vs. 8 days, p = 0.023) and accrued greater hospital charges (p < 0.001). Following propensity adjustment, length of stay and charges remained greater in the embolization cohort, yet rates of routine discharge increased appreciably (40% vs. 30%, p = 0.141) relative to surgically treated cSDH patients. The utilization of embolization increased exponentially after 2015, reaching an apex in 2018 (3.7% of treated cSDH). This population-based national assessment demonstrates exponential increases in utilization of MMA embolization for cSDH treatment in recent years. Embolized patients had uncomplicated clinical courses and similar discharge dispositions as surgical evacuation patients. Large-scale prospective trials are warranted to further assess the efficacy of this modality.

Pipeline embolization of ruptured, previously coiled cerebral aneurysms: Case series and considerations for management

PURPOSE:

Aneurysmal recurrence represents a significant drawback of endovascular coiling, particularly in aneurysms that have previously ruptured. Given the high recurrence rate of coiled aneurysms and particularly the risk of posttreatment rupture in previously ruptured aneurysms that have been treated by coiling, the question of how best to treat ruptured aneurysms that recur postcoiling remains.

MATERIALS AND METHODS:

We conducted a retrospective analysis of twenty patients who underwent pipeline embolization of previously ruptured, coiled cerebral aneurysms.

RESULTS:

Pipeline embolization device (PED) treatment resulted in complete aneurysmal occlusion in 10 patients (62.5%) at first angiographic follow-up, and 11 patients (68.75%) at last follow-up. No PED-related complications were encountered and there were no peri-procedural or postprocedural hemorrhages, or symptomatic ischemic events following flow diversion.

CONCLUSIONS:

PED as a second-line treatment is a safe and effective modality for achieving aneurysmal occlusion in recurrent, previously ruptured, primarily coiled aneurysms. Additionally, a staged coil-to-PED approach may be considered for the management of acutely ruptured aneurysms to achieve aneurysmal obliteration in an effort to mitigate recurrence, and reduce the amount of postprocedural studies.

Middle Meningeal Artery Embolization Using Combined Particle Embolization and n-BCA with the Dextrose 5% in Water Push Technique for Chronic Subdural Hematomas: A Prospective Safety and Feasibility Study

BACKGROUND AND PURPOSE

Embolization of the middle meningeal artery for treatment of refractory or recurrent chronic subdural hematomas has gained momentum during the past few years. Little has been reported on the use of the n-BCA liquid embolic system for middle meningeal artery embolization. We present the technical feasibility of using diluted n-BCA for middle meningeal artery embolization.

MATERIALS AND METHODS

We sought to examine the safety and technical feasibility of the diluted n-BCA liquid embolic system for middle meningeal artery embolization. Patients with chronic refractory or recurrent subdural hematomas were prospectively enrolled from September 2019 to June 2020. The primary outcome was the safety and technical feasibility of the use of diluted n-BCA for embolization of the middle meningeal artery. The secondary end point was the efficacy in reducing hematoma volume.

RESULTS

A total of 16 patients were prospectively enrolled. Concomitant burr-hole craniotomies were performed in 12 of the 16 patients. Two patients required an operation following middle meningeal artery embolization for persistent symptoms. The primary end point was met in 100% of cases in which there were no intra- or postprocedural complications. Distal penetration of the middle meningeal artery branches was achieved in all the enrolled cases. A 7-day post-middle meningeal artery embolization follow-up head CT demonstrated improvement (>50% reduction in subdural hematoma volume) in 9/15 (60%) patients, with 6/15 (40%) showing an unchanged or stable subdural hematoma. At day 21, available CT scans demonstrated substantial further improvement (>75% reduction in subdural hematoma volume).

CONCLUSIONS

Embolization of the middle meningeal artery using diluted n-BCA and ethiodized oil (1:6) is safe and feasible from a technical standpoint. The use of a dextrose 5% bolus improves distal penetration of the glue.

Decompressive craniectomy with scalp expansion graft using a temporary synthetic skin substitute in the pediatric population: case series and review of the literature

INTRODUCTION

The use of decompressive craniectomy in children is controversial and often reserved for patients with refractory intracranial hypertension. Following decompression, skin closure in select cases can be challenging due to brain herniation and swelling through the craniectomy defect. In these cases, partial cortical debridement is sometimes performed.

METHODS

We describe two cases in which a synthetic skin substitute was used to facilitate a tension-free closure, rather than performing a partial lobectomy.

RESULTS

At 6-month follow-up, both patients are at preoperative cognitive baseline, with some residual hemiparesis.

DISCUSSION

We believe that use of a synthetic skin substitute for skin closure after decompression is a suitable option for closure of traumatic scalp wounds and may contribute to improved functional outcome in patients with severe intraoperative brain swelling.

An unusual case of hemophagocytic lymphohistiocytosis diagnosed by spinal nerve root biopsy

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease process characterized by aberrant immune system activation and an exaggerated inflammatory response. Establishing the diagnosis may be challenging and is achieved by satisfying a number of clinical criteria, in addition to demonstrating tissue hemophagocytosis. This syndrome is rapidly fatal if prompt diagnosis and treatment are not achieved. The authors present the case of a 17-year-old male patient with CNS HLH involving both the brain and spinal cord, highlighting the variable CNS manifestations in pediatric patients with HLH and the challenges that accompany establishing diagnosis.

Molecular Sequence of Events and Signaling Pathways in Cerebral Metastases

Brain metastases are the leading cause of morbidity and mortality among cancer patients, and are reported to occur in about 40% of cancer patients with metastatic disease in the United States of America. Primary tumor cells appear to detach from the parent tumor site, migrate, survive and pass through the blood brain barrier in order to establish cerebral metastases. This complex process involves distinct molecular and genetic mechanisms that mediate metastasis from these primary organs to the brain. Furthermore, an interaction between the invading cells and cerebral milieu is shown to promote this process as well. Here, we review the mechanisms by which primary cancer cells metastasize to the brain via a mechanism called epithelial-to-mesenchymal transition, as well as the involvement of certain microRNA and genetic aberrations implicated in cerebral metastases from the lung, breast, skin, kidney and colon. While the mechanisms governing the development of brain metastases remain a major hindrance in treatment, understanding and identification of the aforementioned molecular pathways may allow for improved management and discovery of novel therapeutic targets.

Successful Treatment of Complex Regional Pain Syndrome with Pseudoaneurysm Excision and Median Nerve Neurolysis

BACKGROUND

Complex regional pain syndrome (CRPS), formerly referred to as reflex sympathetic dystrophy, is a pain syndrome characterized by severe pain, altered autonomic and motor function, and trophic changes. CRPS is usually associated with soft tissue injury or trauma. It has also been described as a rare complication of arterial access for angiography secondary to pseudoaneurysm formation.

CASE DESCRIPTION

A 73-year-old woman underwent catheterization of the left brachial artery for angiography of the celiac artery. The following day, the patient noticed numbness and severe pain in the median nerve distribution of the left upper extremity. Over the next 6 months, the patient developed CRPS in the left hand with pain and signs of autonomic dysfunction. Further work-up revealed the formation of a left brachial artery pseudoaneurysm with impingement on the median nerve. She underwent excision of the pseudoaneurysm with decompression and neurolysis of the left median nerve. Approximately 6 weeks after surgery, the patient had noticed significant improvement in autonomic symptoms.

CONCLUSIONS

This case involves a unique presentation of CRPS caused by brachial artery angiography and pseudoaneurysm formation. In addition, the case demonstrates the efficacy of pseudoaneurysm excision and median nerve neurolysis in the treatment of CRPS as a rare complication of arterial angiography.

Molecular Pathways Mediating Metastases to the Brain via Epithelial-to-Mesenchymal Transition: Genes, Proteins, and Functional Analysis

BACKGROUND

Brain metastases are the leading cause of morbidity and mortality among patients with disseminated cancer. The development of metastatic disease involves an orderly sequence of steps enabling tumor cells to migrate from the primary tumor and colonize at secondary locations. In order to achieve this complex metastatic potential, a cancer cell is believed to undergo a cellular reprogramming process involving the development of a degree of stemness, via a proposed process termed epithelial-to-mesenchymal transition (EMT). Upon reaching its secondary site, these reprogrammed cancer stem cells submit to a reversal process designated mesenchymal-to-epithelial transition (MET), enabling establishment of metastases. Here, we examined the expression of markers of EMT, MET, and stem cells in metastatic brain tumor samples.

MATERIALS AND METHODS

Immunohistochemical analyses were performed to establish the markers of EMT and MET. Co-expression of these markers was determined by immunofluorescence analysis. Gene-expression analysis was conducted using tissues from brain metastases of primary adenocarcinoma of the lung compared to non-metastatic tissue. Cell proliferation was carried out using 3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide S-phase entry analysis, by determining the 5-ethynyl-2'-deoxyuridine incorporation. Scratch wound and chemotactic migration assays were performed in an astrocytic setting.

RESULTS

Metastatic brain tumor samples displayed expression of epithelial markers (zinc finger protein SNAI1 and Twist-related protein-1), as well as the mesenchymal marker vimentin. The stem cell marker CD44 was also highly expressed. Moreover, co-expression of the epithelial marker E-cadherin with the mesenchymal marker vimentin was evident, suggesting a state of transition. Expression analysis of transcription factor genes in metastatic brain tumor samples demonstrated an alteration in genes associated with neurogenesis, differentiation, and reprogramming. Furthermore, tumor cells grown in astrocytic medium displayed increased cell proliferation and enhanced S-phase cell-cycle entry. Additionally, chemotactic signaling from the astrocytic environment promoted tumor cell migration. Primary tumor cells and astrocytes were also shown to grow amicably together, forming cell-to-cell interactions.

CONCLUSION

These findings suggest that cellular reprogramming via EMT/MET plays a critical step in the formation of brain metastases, where the cerebral milieu provides a microenvironment suitable for the development of metastatic disease.

Extension of resolution and oligomerization-state studies of 2,4'-dihydroxyacetophenone dioxygenase from Alcaligenes sp. 4HAP

The enzyme 2,4'-dihydroxyacetophenone dioxygenase (DAD) catalyses the conversion of 2,4'-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid. This enzyme is a very unusual dioxygenase in that it cleaves a C-C bond in a substituent of the aromatic ring rather than within the ring itself. Whilst it has been shown that DAD is a tetramer in solution, the recently solved crystal structure of the Alcaligenes sp. 4HAP enzyme was in fact dimeric rather than tetrameric. Since the use of limited chymotrypsinolysis, which apparently results in removal of the first 20 or so N-terminal residues of DAD, was necessary for crystallization of the protein, it was investigated whether this was responsible for the change in its oligomerization state. Gel-filtration and analytical ultracentrifugation studies were conducted, which confirmed that chymotrypsinolysed DAD has an apparent molecular weight of around 40 kDa, corresponding to a dimer. In contrast, the native enzyme has a molecular weight in the 70-80 kDa region, as expected for the tetramer. The structural basis for tetramerization has been investigated by the use of several docking servers, and the results are remarkably consistent with the tetrameric structure of a homologous cupin protein from Ralstonia eutropha (PDB entry 3ebr).

X-ray, spectroscopic and normal-mode dynamics of calexcitin: structure-function studies of a neuronal calcium-signalling protein

The protein calexcitin was originally identified in molluscan photoreceptor neurons as a 20 kDa molecule which was up-regulated and phosphorylated following a Pavlovian conditioning protocol. Subsequent studies showed that calexcitin regulates the voltage-dependent potassium channel and the calcium-dependent potassium channel as well as causing the release of calcium ions from the endoplasmic reticulum (ER) by binding to the ryanodine receptor. A crystal structure of calexcitin from the squid Loligo pealei showed that the fold is similar to that of another signalling protein, calmodulin, the N- and C-terminal domains of which are known to separate upon calcium binding, allowing interactions with the target protein. Phosphorylation of calexcitin causes it to translocate to the cell membrane, where its effects on membrane excitability are exerted and, accordingly, L. pealei calexcitin contains two protein kinase C phosphorylation sites (Thr61 and Thr188). Thr-to-Asp mutations which mimic phosphorylation of the protein were introduced and crystal structures of the corresponding single and double mutants were determined, which suggest that the C-terminal phosphorylation site (Thr188) exerts the greatest effects on the protein structure. Extensive NMR studies were also conducted, which demonstrate that the wild-type protein predominantly adopts a more open conformation in solution than the crystallographic studies have indicated and, accordingly, normal-mode dynamic simulations suggest that it has considerably greater capacity for flexible motion than the X-ray studies had suggested. Like calmodulin, calexcitin consists of four EF-hand motifs, although only the first three EF-hands of calexcitin are involved in binding calcium ions; the C-terminal EF-hand lacks the appropriate amino acids. Hence, calexcitin possesses two functional EF-hands in close proximity in its N-terminal domain and one functional calcium site in its C-terminal domain. There is evidence that the protein has two markedly different affinities for calcium ions, the weaker of which is most likely to be associated with binding of calcium ions to the protein during neuronal excitation. In the current study, site-directed mutagenesis has been used to abolish each of the three calcium-binding sites of calexcitin, and these experiments suggest that it is the single calcium-binding site in the C-terminal domain of the protein which is likely to have a sensory role in the neuron.

Structural evidence for the partially oxidized dipyrromethene and dipyrromethanone forms of the cofactor of porphobilinogen deaminase: structures of the Bacillus megaterium enzyme at near-atomic resolution

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses an early step of the tetrapyrrole-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor, which is covalently linked by a thioether bridge to an invariant cysteine residue (Cys241 in the Bacillus megaterium enzyme). The cofactor is extended during the reaction by the sequential addition of the four substrate molecules, which are released as a linear tetrapyrrole product. Expression in Escherichia coli of a His-tagged form of B. megaterium PBGD has permitted the X-ray analysis of the enzyme from this species at high resolution, showing that the cofactor becomes progressively oxidized to the dipyrromethene and dipyrromethanone forms. In previously solved PBGD structures, the oxidized cofactor is in the dipyromethenone form, in which both pyrrole rings are approximately coplanar. In contrast, the oxidized cofactor in the B. megaterium enzyme appears to be in the dipyrromethanone form, in which the C atom at the bridging α-position of the outer pyrrole ring is very clearly in a tetrahedral configuration. It is suggested that the pink colour of the freshly purified protein is owing to the presence of the dipyrromethene form of the cofactor which, in the structure reported here, adopts the same conformation as the fully reduced dipyrromethane form.

The structure of endothiapepsin complexed with a Phe-Tyr reduced-bond inhibitor at 1.35 Å resolution

Endothiapepsin is a typical member of the aspartic proteinase family. The catalytic mechanism of this family is attributed to two conserved catalytic aspartate residues, which coordinate the hydrolysis of a peptide bond. An oligopeptide inhibitor (IC50 = 0.62 µM) based on a reduced-bond transition-state inhibitor of mucorpepsin was co-crystallized with endothiapepsin and the crystal structure of the enzyme-inhibitor complex was determined at 1.35 Å resolution. A total of 12 hydrogen bonds between the inhibitor and the active-site residues were identified. The resulting structure demonstrates a number of novel subsite interactions in the active-site cleft.

Crystallization and preliminary X-ray characterization of the tetrapyrrole-biosynthetic enzyme porphobilinogen deaminase from Bacillus megaterium

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses a key early step in the biosynthesis of tetrapyrroles in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. PBGD from B. megaterium was expressed and the enzyme was crystallized in a form which diffracts synchrotron radiation to high resolution.

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses an early step of the tetrapyrrole-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor which is covalently linked by a thioether bridge to an invariant cysteine residue. Expression in Escherichia coli of a His-tagged form of Bacillus megaterium PBGD permitted the crystallization and preliminary X-ray analysis of the enzyme from this species at high resolution.

Insights into the mechanism of pyrrole polymerization catalysed by porphobilinogen deaminase: high-resolution X-ray studies of the Arabidopsis thaliana enzyme

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses a key early step of the haem- and chlorophyll-biosynthesis pathways in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The active site possesses an unusual dipyrromethane cofactor which is extended during the reaction by the sequential addition of the four substrate molecules. The cofactor is linked covalently to the enzyme through a thioether bridge to the invariant Cys254. Until recently, structural data have only been available for the Escherichia coli and human forms of the enzyme. The expression of a codon-optimized gene for PBGD from Arabidopsis thaliana (thale cress) has permitted for the first time the X-ray analysis of the enzyme from a higher plant species at 1.45 Å resolution. The A. thaliana structure differs appreciably from the E. coli and human forms of the enzyme in that the active site is shielded by an extensive well defined loop region (residues 60-70) formed by highly conserved residues. This loop is completely disordered and uncharacterized in the E. coli and human PBGD structures. The new structure establishes that the dipyrromethane cofactor of the enzyme has become oxidized to the dipyrromethenone form, with both pyrrole groups approximately coplanar. Modelling of an intermediate of the elongation process into the active site suggests that the interactions observed between the two pyrrole rings of the cofactor and the active-site residues are highly specific and are most likely to represent the catalytically relevant binding mode. During the elongation cycle, it is thought that domain movements cause the bound cofactor and polypyrrole intermediates to move past the catalytic machinery in a stepwise manner, thus permitting the binding of additional substrate moieties and completion of the tetrapyrrole product. Such a model would allow the condensation reactions to be driven by the extensive interactions that are observed between the enzyme and the dipyrromethane cofactor, coupled with acid-base catalysis provided by the invariant aspartate residue Asp95.

Crystallization and preliminary X-ray characterization of the tetrapyrrole-biosynthetic enzyme porphobilinogen deaminase from Arabidopsis thaliana

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses a key early step of the haem-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor which is covalently linked by a thioether bridge to an invariant cysteine residue. Since PBGD catalyses a reaction which is common to the biosynthesis of both haem and chlorophyll, structural studies of a plant PBGD enzyme offer great potential for the discovery of novel herbicides. Until recently, structural data have only been available for the Escherichia coli and human forms of the enzyme. Expression in E. coli of a codon-optimized gene for Arabidopsis thaliana PBGD has permitted for the first time the crystallization and preliminary X-ray analysis of the enzyme from a plant species at high resolution.

An analysis of subdomain orientation, conformational change and disorder in relation to crystal packing of aspartic proteinases

The analysis reported here describes detailed structural studies of endothiapepsin (the aspartic proteinase from Endothia parasitica), with and without bound inhibitors, and human pepsin 3b. Comparison of multiple crystal structures of members of the aspartic proteinase family has revealed small but significant differences in domain orientation in different crystal forms. In this paper, it is shown that these differences in domain orientation do not necessarily correlate with the presence or absence of bound inhibitors, but appear to stem at least partly from crystal contacts mediated by sulfate ions. However, since the same inherent flexibility of the structure is observed for other enzymes in this family such as human pepsin, the native structure of which is also reported here, the observed domain movements may well have implications for the mechanism of catalysis.

Crystallization and preliminary X-ray diffraction analysis of the protease from Southampton norovirus complexed with a Michael acceptor inhibitor

Noroviruses are the predominant cause of human epidemic nonbacterial gastroenteritis. Viral replication requires a cysteine protease that cleaves a 200 kDa viral polyprotein into its constituent functional parts. Here, the crystallization of the recombinant protease from the Southampton norovirus is described. Whilst the native crystals were found to diffract only to medium resolution (2.9 Å), cocrystals of an inhibitor complex diffracted X-rays to 1.7 Å resolution. The polypeptide inhibitor (Ac-EFQLQ-propenyl ethyl ester) possesses an amino-acid sequence designed to match the substrate specificity of the enzyme, but was synthesized with a reactive Michael acceptor group at the C-terminal end.

Synthesis of Fibrils in Vitro by a Solubilized Cellulose Synthase from Acetobacter xylinum

A digitonin-solubilized cellulose synthase was prepared from Acetobacter xylinum. When this enzyme was incubated under conditions known to lead to active synthesis of 1,4-beta-D-glucan polymer (cellulose), electron microscopy revealed that clusters of fibrils were assembled within minutes. Individual fibrils are 17 +/- 2 angstroms in diameter. Evidence that the fibrils were freshly synthesized and cellulosic in nature was their incorporation of the tritium from UDP-[(3)H]glucose (UDP, uridine 5'-diphosphate), their binding of gold-labeled cellobiohydrolase, and an electron diffraction pattern with 004, 200, and 012 reflections (characteristic of cellulose synthesized in vivo) but missing 110 and 110 reflections. The small size of the fibrils is atypical of native A. xylinum cellulose microfibrils. The fibrils synthesized in vitro resemble, in morphology and size, the fibrillar cellulose produced when A. xylinum is cultured in the presence of agents that interfere with the normal process of crystallization of the microfibrils. The solubilized enzyme unit may therefore be producing a basic fibrillar structure that, in vivo, interacts laterally with other fibrils to produce native cellulose microfibrils.

Chlamydomonas agglutinin is a hydroxyproline-rich glycoprotein

The mt(+) sexual agglutinin from Chlamydomonas reinhardi is shown to contain approximately 12% hydroxyproline, and two inhibitors of hydroxyproline formation, alpha,alpha'-dipyridyl and 3,4-dehydroproline, are shown to block the production of agglutinin activity in an in vivo bioassay system. These results indicate that the agglutinin glycoprotein may be related to a class of hydroxyproline-rich glycoproteins found in the extracellular matrix of higher plants, several of which have been shown to have lectin activity.

Milk, Fat, Protein, Somatic Cell Score, and Days Open Among Holstein, Brown Swiss, and Their Crosses

The objectives of this study were to compare Holstein (HO), Brown Swiss (BS), and their crosses for milk, fat, and protein yields, somatic cell score (SCS), days open (DO), and age at first calving (AFC), and to estimate the effects of heterosis and recombination. First through fifth lactation records were obtained from 19 herds milking crosses among BS and HO. The edited data set included 6,534 lactation records from 3,473 cows of the following breed combinations: 2,125 pure HO, 926 pure BS, 256 BS sire x HO dam (SH), 105 backcrosses to BS (SX), 18 HO sire x BS dam, and 43 backcrosses to HO. Least squares means for daily milk, fat, and protein yields, mature-equivalent milk, fat, and protein yields, SCS, DO, and AFC were calculated for breed combinations with a model that included fixed effects of age within parity (except for AFC), days in milk for daily yield and SCS, herd-year-season of calving, and breed combination. Cow and error were random effects. Breed combination was replaced with regressions on coefficients for heterosis and recombination in a second analysis. Last, data were analyzed with a 5-trait animal model that included a single pedigree file for both breeds and coefficients for heterosis and recombination. The least squares means for fat production were 1.21, 1.15, 1.27, and 1.16 kg for HO, BS, SH, and SX, respectively, which corresponds to a heterosis estimate of 7.30% and a recombination estimate of -3.76%. Heterosis and recombination estimates for protein production were 5.63% and -3.31%, respectively. Heterosis estimates increased for fat yield (10.38%) and protein yield (7.07%) when maternal grandsire identification from a known artificial insemination sire was required. Regression coefficients indicated an 11.44-d reduction in DO due to heterosis. Heterosis estimates for SCS were inconsistent. Regression on heterosis for SCS was significant and favorable (-0.22) when the breed of sire was BS, but nonsignificant and unfavorable when sire breed was HO (0.43). Heterosis estimates were favorable for all traits, whereas recombination effects tended to be unfavorable for yield traits. Reduced performance of future generations did not appear to be the result of inseminating crossbred cows with inferior sires. Results indicated that first-generation crosses among BS and HO compared favorably with HO. Yield in subsequent generations was somewhat below expectations, perhaps due to recombination loss in HO.

Short Communication: Effect of Vacuum and Ratio on the Performance of a Monoblock Silicone Milking Liner

The vacuum and teat-cup chamber ratio are important operating parameters that affect milking performance by milking machines. In addition, the design and composition of materials are major elements affecting the performance characteristics of (teat-cup) milking machine liners. The objective of this experiment was to determine the effects of vacuum and teat-cup chamber ratio on the performance of a unique mono-block silicone milking machine liner that is round in the open position and triangular in the collapsed position. System vacuum settings (set at receiver) were 40.6, 43.9, and 47.3 kPa, whereas teat-cup chamber ratios were 60:40, 65:35, and 70:30. Milk yield was greatest at a vacuum of 43.9 kPa. Manual adjustments and kickoffs were very low (<2%) at all vacuum levels and for all ratios. The interaction of vacuum level and ratio was significant for milking duration, peak flow rate, and average flow rate, but not for milk yield. Average and peak milk flow rates increased at each increasing vacuum level and each wider ratio, whereas milking duration decreased.

Variability in Holstein heifer heart-girth measurements and comparison of prediction equations for live weight

Measurement of heart-girth (chest circumference) is commonly used to estimate dairy heifer body weight from previously derived equations or tables. In this experiment, variability of heart-girth measurements as they are taken in the field was analyzed to determine the standard deviation within a group of 26 Holstein heifers of various ages weighing 42-590 kg. Standard deviations were 2.19 cm among 26 observers and 2.74 cm within any one observer. Repeatability between two heart-girth measurements by an individual observer on the same animal using a blind heart-girth tape was >0.99. Correlation coefficients between two measurements by different observers using blind measuring tapes on the same animal also were >0.99, with 99% of total differences due to observer and heifer, indicating very little random variation. A second part of this study was the validation of the most recently derived equation to calculate body weight from heart-girth. The equation was validated with data sets from universities across the United States and field data collected specifically for this study. Experimental and field data comprised of heart-girth and body weight measurements upheld the previously derived equation and support its continued use. These results allow more precise interpretation of heart-girth data collected from field studies with Holstein dairy heifers and provide more complete validation of existing body weight-prediction equations.

High resolution structure of BipD: an invasion protein associated with the type III secretion system of Burkholderia pseudomallei

Burkoldheria pseudomallei is a Gram-negative bacterium that possesses a protein secretion system similar to those found in Salmonella and Shigella. Recent work has indicated that the protein encoded by the BipD gene of B. pseudomallei is an important secreted virulence factor. BipD is similar in sequence to IpaD from Shigella and SipD from Salmonella and is therefore likely to be a translocator protein in the type-III secretion system of B. pseudomallei. The crystal structure of BipD has been solved at a resolution of 2.1 A revealing the detailed tertiary fold of the molecule. The overall structure is appreciably extended and consists of a bundle of antiparallel alpha-helical segments with two small beta-sheet regions. The longest helices of the molecule form a four-helix bundle and most of the remaining secondary structure elements (three helices and two three-stranded beta-sheets) are formed by the region linking the last two helices of the four-helix bundle. The structure suggests that the biologically active form of the molecule may be a dimer formed by contacts involving the C-terminal alpha-helix, which is the most strongly conserved part of the protein. Comparison of the structure of BipD with immunological and other data for IpaD indicates that the C-terminal alpha-helix is also involved in contacts with other proteins that form the translocon.

Structure of the Neuronal Protein Calexcitin Suggests a Mode of Interaction in Signalling Pathways of Learning and Memory

The three-dimensional structure of the neuronal calcium-sensor protein calexcitin from Loligo pealei has been determined by X-ray analysis at a resolution of 1.8A. Calexcitin is up-regulated following Pavlovian conditioning and has been shown to regulate potassium channels and the ryanodine receptor. Thus, calexcitin is implicated in neuronal excitation and plasticity. The overall structure is predominantly helical and compact with a pronounced hydrophobic core between the N and C-terminal domains of the molecule. The structure consists of four EF-hand motifs although only the first three EF hands are involved in binding calcium ions; the C-terminal EF-hand lacks the amino acids required for calcium binding. The overall structure is quite similar to that of the sarcoplasmic calcium-binding protein from Amphioxus although the sequence identity is very low at 31%. The structure shows that the two amino acids of calexcitin phosphorylated by protein kinase C are close to the domain interface in three dimensions and thus phosphorylation is likely to regulate the opening of the domains that is probably required for binding to target proteins. There is evidence that calexcitin is a GTPase and the residues, which have been implicated by mutagenesis in its GTPase activity, are in a short but highly conserved region of 3(10) helix close to the C terminus. This helix resides in a large loop that is partly sandwiched between the N and C-terminal domains suggesting that GTP binding may also require or may cause domain opening. The structure possesses a pronounced electropositive crevice in the vicinity of the 3(10) helix, that might provide an initial docking site for the triphosphate group of GTP. These findings elucidate a number of the reported functions of calexcitin with implications for neuronal signalling.

Short Communication: Genetic Correlation Between Test-Day Electrical Conductivity of Milk and Mastitis

Electrical conductivity (EC) of milk is an indicator of mastitis. If EC shows genetic variation and is genetically correlated to mastitis, it could be used in a breeding program that includes selection for improved mastitis resistance. In this study, daily records of EC and mastitis from about 1,500 Holstein cows were analyzed. A bivariate animal model was used for estimation of (co)variance components, including fixed effects of age of calving, herd-test-day, and days in milk, in addition to random additive genetic effects and permanent environmental effects. For EC, the estimated heritability was moderate (0.22 to 0.39), whereas for mastitis, the heritability was low (0.013). The genetic correlation between EC and mastitis was estimated to be 0.75, and genetic improvement of mastitis resistance should be feasible through selection for reduced EC.

Electrical treatment of reduced consciousness: experience with coma and Alzheimer's disease

The right median nerve can be stimulated electrically to help arouse the central nervous system for persons with reduced levels of consciousness. The mechanisms of central action include increased cerebral blood flow and raised levels of dopamine. There is 11 years of experience in the USA of using nerve stimulation for acute coma after traumatic brain injury. There is a much longer period of experience by neurosurgeons in Japan with implanted electrodes on the cervical spinal cord for persons in the persistent vegetative state (PVS). But the use of right median nerve electrical stimulation (RMNS) for patients in the subacute and chronic phases of coma is relatively new. Surface electrical stimulation to treat anoxic brain injury as well as traumatic brain injury is evolving. Novel applications of electrical stimulation in Amsterdam have produced cognitive behavioural effects in persons with early and mid-stage Alzheimer's disease employing transcutaneous electrical nerve stimulation (TENS). Improvements in short-term memory and speech fluency have also been noted. Regardless of the aetiology of the coma or reduced level of awareness, electrical stimulation may serve as a catalyst to enhance central nervous system functions. It remains for the standard treatments and modalities to retrain the injured brain emerging from reduced levels of consciousness.

Milk Urea Nitrogen Concentration: Heritability and Genetic Correlations with Reproductive Performance and Disease

The objectives of this study were to estimate the heritability of milk urea nitrogen (MUN) concentration and describe the genetic relationship between MUN and reproductive performance and between MUN and diseases in Holsteins. Dairy Records Management Systems (Raleigh, NC) provided lactation data. The Danish Agricultural Advisory Center provided breeding value estimates for diseases. Infrared (IR) and wet chemistry (WC) data were analyzed separately. Heritabilities and genetic correlations for 2 different measures of MUN and reproductive performance were estimated with an animal model using ASREML. Heritabilities for MUN were estimated using all lactations combined (lactations 1 through 5) and separately for first lactation and second lactation. Genetic correlations with reproduction and health were estimated separately for parities 1 and 2. Herd-test-day or herd-year-season along with age at calving and days in milk were included as fixed effects in all models. Heritability estimates for all lactations combined were 0.15 for WC MUN and 0.22 for IR MUN. Genetic correlations between WC MUN and 2 measures of reproductive performance, days to first service, and first service conception were not different from zero. In contrast, the genetic correlation between WC MUN and days open of 0.21 in first lactation and 0.41 in second lactation indicated that higher WC MUN values were associated with increased days open. Correlations among estimated breeding values for MUN and estimated breeding values for Danish diseases identified no significant relationships. Although the results of this study indicate that heritable variation for MUN exists, the inability to identify significant genetic relationships with several measures of disease or reproductive performance appears to limit the value of MUN in selection for disease resistance and improved reproduction.

Structure ofChlorobium vibrioforme5-aminolaevulinic acid dehydratase complexed with a diacid inhibitor

The structure of Chlorobium vibrioforme 5-aminolaevulinic acid dehydratase (ALAD) complexed with the irreversible inhibitor 4,7-dioxosebacic acid has been solved. The inhibitor binds by forming Schiff-base linkages with lysines 200 and 253 at the active site. The structure reported here provides a definition of the interactions made by both of the substrate molecules (A-side and P-side substrates) with the C. vibrioforme ALAD and is compared and contrasted with structures of the same inhibitor bound to Escherichia coli and yeast ALAD. The structure suggests why 4,7-dioxosebacic acid is a better inhibitor of the zinc-dependent ALADs than of the zinc-independent ALADs.

Structure of yeast 5-aminolaevulinic acid dehydratase complexed with the inhibitor 5-hydroxylaevulinic acid

The X-ray structure of the enzyme 5-aminolaevulinic acid dehydratase (ALAD) from yeast complexed with the competitive inhibitor 5-hydroxylaevulinic acid has been determined at a resolution of 1.9 A. The structure shows that the inhibitor is bound by a Schiff-base link to one of the invariant active-site lysine residues (Lys263). The inhibitor appears to bind in two well defined conformations and the interactions made by it suggest that it is a very close analogue of the substrate 5-aminolaevulinic acid (ALA).

The atomic resolution structure of methanol dehydrogenase fromMethylobacterium extorquens

The crystal structure of methanol dehydrogenase (MDH) from Methylobacterium extorquens has been refined without stereochemical restraints at a resolution of 1.2 A. The high-resolution data have defined the conformation of the tricyclic pyrroloquinoline quinone (PQQ) cofactor ring as entirely planar. The detailed definition of the active-site geometry has shown many features that are similar to the quinohaemo-protein alcohol dehydrogenases from Comamonas testosteroni and Pseudomonas putida, both of which possess MDH-like and cytochrome c-like domains. Conserved features between the two types of PQQ-containing enzyme suggest a common pathway for electron transfer between MDH and its physiological electron acceptor cytochrome cL. A pathway for proton transfer from the active site to the bulk solvent is also suggested.

The structure of the C-C bond hydrolase MhpC provides insights into its catalytic mechanism

2-Hydroxy-6-ketonona-2,4-diene-1,9-dioic acid 5,6-hydrolase (MhpC) is a 62 kDa homodimeric enzyme of the phenylpropionate degradation pathway of Escherichia coli. The 2.1 A resolution X-ray structure of the native enzyme determined from orthorhombic crystals confirms that it is a member of the alpha/beta hydrolase fold family, comprising eight beta-strands interconnected by loops and helices. The 2.8 A resolution structure of the enzyme co-crystallised with the non-hydrolysable substrate analogue 2,6-diketo-nona-1,9-dioic acid (DKNDA) confirms the location of the active site in a buried channel including Ser110, His263 and Asp235, postulated contributors to a serine protease-like catalytic triad in homologous enzymes. It appears that the ligand binds in two separate orientations. In the first, the C6 keto group of the inhibitor forms a hemi-ketal adduct with the Ser110 side-chain, the C9 carboxylate group interacts, via the intermediacy of a water molecule, with Arg188 at one end of the active site, while the C1 carboxylate group of the inhibitor comes close to His114 at the other end. In the second orientation, the C1 carboxylate group binds at the Arg188 end of the active site and the C9 carboxylate group at the His114 end. These arrangements implicated His114 or His263 as plausible contributors to catalysis of the initial enol/keto tautomerisation of the substrate but lack of conservation of His114 amongst related enzymes and mutagenesis results suggest that His263 is the residue involved. Variability in the quality of the electron density for the inhibitor amongst the eight molecules of the crystal asymmetric unit appears to correlate with alternative positions for the side-chain of His114. This might arise from half-site occupation of the dimeric enzyme and reflect the apparent dissociation of approximately 50% of the keto intermediate from the enzyme during the catalytic cycle.

A brief history of the development of mannequin simulators for clinical education and training

Simulation for medical and healthcare applications, although still in a relatively nascent stage of development, already has a history that can inform the process of further research and dissemination. The development of mannequin simulators used for education, training, and research is reviewed, tracing the motivations, evolution to commercial availability, and efforts toward assessment of efficacy of those for teaching cardiopulmonary resuscitation, cardiology skills, anaesthesia clinical skills, and crisis management. A brief overview of procedural simulators and part-task trainers is also presented, contrasting the two domains and suggesting that a thorough history of the 20+ types of simulator technologies would provide a useful overview and perspective. There has been relatively little cross fertilisation of ideas and methods between the two simulator domains. Enhanced interaction between investigators and integration of simulation technologies would be beneficial for the dissemination of the concepts and their applications.

A brief history of the development of mannequin simulators for clinical education and training

Simulation for medical and healthcare applications, although still in a relatively nascent stage of development, already has a history that can inform the process of further research and dissemination. The development of mannequin simulators used for education, training, and research is reviewed, tracing the motivations, evolution to commercial availability, and efforts toward assessment of efficacy of those for teaching cardiopulmonary resuscitation, cardiology skills, anaesthesia clinical skills, and crisis management. A brief overview of procedural simulators and part-task trainers is also presented, contrasting the two domains and suggesting that a thorough history of the 20+ types of simulator technologies would provide a useful overview and perspective. There has been relatively little cross fertilisation of ideas and methods between the two simulator domains. Enhanced interaction between investigators and integration of simulation technologies would be beneficial for the dissemination of the concepts and their applications.

Genetic Parameters for Test-Day Electrical Conductivity of Milk for First-Lactation Cows from Random Regression Models

Electrical conductivity (EC) of milk has been introduced as an indicator trait for mastitis during the last few decades. The correlation of EC to mastitis, easy access to EC data, and the low cost of recording are properties that make EC a good indicator trait for mastitis. In this study, EC was measured daily during the lactation and available from 2101 first-lactation Holstein cows in 8 herds in the United States. Data were analyzed with an animal model that included herd-test-day, age at calving and days in milk (DIM) as fixed effects, and random additive genetic and permanent environmental effects. A repeatability model and 5 random regression (RR) models with increasing order of Legendre polynomials were used. The goodness of fit for the different models was evaluated based on several tests. Our results indicate that the best model was a RR model with a fourth-order Legendre polynomial for both additive genetic and permanent environmental effects. Heritability estimates obtained with this model were from 0.26 to 0.36. Due to the relatively high heritability obtained for EC of milk, EC might be a potential indicator trait to use in a breeding program designed to reduce the incidence of mastitis.

Crystallization and X-ray analysis of the Y75N mutant of Mucor pusillus pepsin complexed with inhibitor

Y75N mutant Mucor pusillus pepsin has been overexpressed in yeast, purified and cocrystallized with the iodine-containing human renin inhibitor CP-113972 [(2R,3S]-isopropyl 3-[(L-prolyl-p-iodo-L-phenylalanyl-S-methyl-cysteinyl)amino-4]-cyclohexyl-2-hydroxybutanoate] for X-ray crystallography. Tetragonal complex crystals with space group P4(3)2(1)2 were produced by the hanging-drop vapour-diffusion method and diffracted to 3.0 A. The crystals exhibited unit-cell parameters a = b = 182.5, c = 99.1 A and contained four molecules in the asymmetric unit. A 96% complete data set was collected at 298 K using Cu Kalpha X-rays from a rotating-anode generator. Solution of the crystal structure of Y75N mutant M. pusillus pepsin is under way by molecular replacement using the molecular coordinates of wild-type M. pusillus pepsin as a model.

Crystallization and preliminary X-ray analysis of the controller protein C.AhdI from Aeromonas hydrophilia

Single crystals of purified homodimeric controller protein from Aeromonas hydrophilia (C.AhdI) have been grown under several different conditions using vapour diffusion. X-ray diffraction data have been collected using synchrotron radiation from crystals of both the native and a selenomethionine (SeMet) derivative of the protein. The native crystal form belongs to space group P2(1) and data were collected to a resolution of 2.2 A. Two crystal forms of the SeMet protein have been obtained and were found to belong to space groups P1 and P2(1); data have been recorded to 2.0 and 1.7 A resolution, respectively, for the two crystal forms. Three-wavelength MAD data were collected to 1.7 A for the SeMet derivative crystal, which is isomorphous with the native P2(1) crystal.

Heritability of intramammary infections at first parturition and relationships with sire transmitting abilities for somatic cell score, udder type traits, productive life, and protein yield

The objective of this study was to determine the relationships among daughter intramammary infections at first parturition and sire transmitting abilities for somatic cell score, udder type traits, productive life, and protein yield. Quarter milk samples from 958 daughters (in eight Pennsylvania herds and one Nebraska herd) of 182 Holstein sires were collected within a few days of first calving and cultured to determine intramammary infection status. A total of 446 cows had intramammary infections in 835 quarters at first parturition. Incidence of intramammary infections at first parturition and the proportion of quarters infected per cow were regressed on age at first calving, days in milk at sample collection, herd-season of calving (a classification variable), and sire transmitting abilities taken one at a time. Linear effects, non-linear effects, and odds ratios were estimated for sire transmitting abilities. Separate, preplanned analyses were conducted on data from one herd that gave all heifers an intramammary antibiotic infusion in each quarter 30 d prior to the expected calving date. Separate analyses were also conducted on dependent variables that considered intramammary infections at first parturition from: all organisms, coagulase-negative staphylococci, coliform species, streptococci other than Streptococcus agalactiae, and the most common environmental organisms (coliform species and streptococci other than Streptococcus agalactiae). Daughters of sires that transmit the lowest somatic cell score had the fewest intramammary infections at first parturition. Daughters of sires that transmit longer productive life, shorter teats, and closely spaced front teats had fewer intramammary infections at first parturition. Selection for lower somatic cell score, longer productive life, shorter teats, or closely spaced front teats may reduce the incidence of intramammary infections at first parturition.

The structure of endothiapepsin complexed with the gem-diol inhibitor PD-135,040 at 1.37 A

The crystal structure of endothiapepsin complexed with the gem-diol inhibitor PD-135,040 has been anisotropically refined to a resolution of 1.37 A. The structure of this inhibitor complex is in agreement with previous structures of endothiapepsin gem-diol inhibitor complexes that have been used to develop proposed catalytic mechanisms. However, the increase in resolution over previous structures confirms the presence of a number of short hydrogen bonds within the active site that are likely to play an important role in the catalytic mechanism. The presence of low-barrier hydrogen bonds was indicated in a previous one-dimensional H NMR spectrum.

Electrical treatment of coma via the median nerve

The median nerve is a portal to interact with the injured comatose brain. Peripheral nerve electrical stimulation has a central nervous system effect. Two to three weeks of right median nerve stimulation (RMNS) can hasten awakening from deep coma by increasing the dopamine levels. Three cases of electrically treated GCS-4 teenagers with acute diffuse brain injuries from motor vehicle crashes are presented by video. Pilot studies of RMNS for acute post-traumatic coma states have been done over the last ten years at East Carolina University and the University of Virginia. The neurophysiological effects of RMNS have been well documented at several neurosurgical centers in Japan using neuroimaging and spinal fluid assays. RMNS is a safe, inexpensive, non-invasive therapy for neuro-resuscitation of coma patients. When employed early in the coma, the time in the ICU may be shortened and the quality of the final outcome may be enhanced.

5-Aminolaevulinic acid dehydratase: metals, mutants and mechanism

5-Aminolaevulinic acid dehydratase catalyses the formation of porphobilinogen from two molecules of 5-aminolaevulinic acid. The studies described highlight the importance of a bivalent metal ion and two active-site lysine residues for the functioning of 5-aminolaevulinic acid dehydratase. Dehydratases fall into two main categories: zinc-dependent enzymes and magnesium-dependent enzymes. Mutations that introduced zinc-binding ligands into a magnesium-dependent enzyme conferred an absolute requirement for zinc. Mutagenesis of lysine residues 247 and 195 in the Escherichia coli enzyme lead to dramatic effects on enzyme activity, with lysine 247 being absolutely essential. Mutation of either lysine 247 or 195 to cysteine, and treatment of the mutant enzyme with 2-bromethylamine, resulted in the recovery of substantial enzyme activity. The effects of the site-directed alkylating inhibitor, 5-chlorolaevulinic acid, and 4,7-dioxosebacic acid, a putative intermediate analogue, were investigated by X-ray crystallography. These inhibitors reacted with both active-site lysine residues. The role of these two lysine residues in the enzyme mechanism is discussed.