Influence of circle of Willis modeling on hemodynamic parameters in anterior communicating artery aneurysms and recommendations for model selection

Computational fluid dynamics (CFD) has been utilized to calculate hemodynamic parameters in anterior communicating artery aneurysm (AComA), which is located at a junction between left and right A1 and A2 segments. However, complete or half circle of Willis (CoW) models are used indiscriminately. This study aims to suggest recommendations for determining suitable CoW model. Five patient-specific CoW models with AComA were used, and each model was divided into complete, left-half, and right-half models. After validating the CFD using a flow experiment, the hemodynamic parameters and flow patterns in five AComAs were compared. In four out of five cases, inflow from one A1 side had a dominant influence on the AComA, while both left and right A1 sides affected the AComA in the remaining case. Also, the average difference in time-averaged wall shear stress between the complete and half models for four cases was 4.6%, but it was 62% in the other case. The differences in the vascular resistances of left and right A1 and A2 segments greatly influenced the flow patterns in the AComA. These results may help to enhance clinicians' understanding of blood flow in the brain, leading to improvements in diagnosis and treatment of cerebral aneurysms.

The safety and efficacy of intra-arterial low-dose tirofiban administration during endovascular therapy in patients with large ischemic core volume

This study aimed to evaluate the safety and efficacy of intra-arterial (IA) administration of low- dose tirofiban during endovascular therapy in patients with large ischemic core volumes on initial brain CT. Patients were divided into two groups based on the use of IA tirofiban. We identified 87 patients (16 and 71 patients in the tirofiban and no-tirofiban groups, respectively) with acute ischemic stroke due to intracranial artery occlusion who underwent endovascular therapy with a low Alberta Stroke Program Early CT scores (2-5). Multivariate logistic regression analysis revealed no association between IA tirofiban administration and serious postprocedural hemorrhagic complications (adjusted odds ratio (aOR), 0.720; 95% confidence interval (CI) 0.099-5.219; p = 0.960), any radiologic hemorrhage (aOR 0.076; 95% CI 0.003-2.323; p = 0.139), or 3-month mortality (aOR, 0.087; 95% CI 0.005-1.501; p = 0.093). However, IA tirofiban was associated with a lower 90-day mRS score (aOR, 0.197; 95% CI 0.015-1.306; p = 0.017) and change of NIHSS compared with baseline (aOR, 0.698; 95% CI 0.531-0.917; p = 0.010). IA tirofiban administration during endovascular therapy in patients with large ischemic core volumes may be effective and safe.

Investigation of paraclinoid aneurysm formation by comparing the combined influence of hemodynamic parameters between aneurysmal and non-aneurysmal arteries

Numerous studies have evaluated the effects of hemodynamic parameters on aneurysm formation. However, the reasons why aneurysms do not initiate in intracranial arteries are still unclear. This study aimed to investigate the influence of hemodynamic parameters, wall shear stress (WSS) and strain, on aneurysm formation by comparing between aneurysmal and non-aneurysmal arteries. Fifty-eight patients with paraclinoid aneurysms on one side were enrolled. Based on magnetic resonance angiography, each patient's left and right internal carotid arteries (ICAs) were reconstructed. For a patient having an aneurysm on one side, the ICA with the paraclinoid aneurysm was defined as the aneurysmal artery after eliminating the aneurysm, whereas the opposite ICA without aneurysm was defined as the non-aneurysmal artery. Computational fluid dynamics and fluid-structure interaction analyses were then performed for both aneurysmal and non-aneurysmal arteries. Finally, the relationship between high hemodynamic parameters and aneurysm location was investigated. For aneurysmal arteries, high WSS and strain locations were well-matched with the aneurysm formation site. Also, considerable correlations between high WSS and strain locations were observed. However, there was no significant relationship between high hemodynamic parameters and aneurysm formation for non-aneurysmal arteries. The findings are helpful for understanding aneurysm formation mechanism and encouraging further relevant research.

New morphological parameter for intracranial aneurysms and rupture risk prediction based on artificial neural networks

BACKGROUND

Numerous studies have evaluated the rupture risk of intracranial aneurysms using morphological parameters because of their good predictive capacity. However, the limitation of current morphological parameters is that they do not always allow evaluation of irregularities of intracranial aneurysms. The purpose of this study is to propose a new morphological parameter that can quantitatively describe irregularities of intracranial aneurysms and to evaluate its performance regarding rupture risk prediction.

METHODS

In a retrospective study, conventional morphological parameters (aspect ratio, bottleneck ratio, height-to-width ratio, volume to ostium ratio, and size ratio) and a newly proposed morphological parameter (mass moment of inertia) were calculated for 125 intracranial aneurysms (80 unruptured and 45 ruptured aneurysms). Additionally, hemodynamic parameters (wall shear stress and strain) were calculated using computational fluid dynamics and fluid-structure interaction. Artificial neural networks trained with each parameter were used for rupture risk prediction.

RESULTS

All components of the mass moment of inertia (Ixx, Iyy, and Izz) were significantly higher in ruptured cases than in unruptured cases (p values for Ixx, Iyy, and Izz were 0.032, 0.047, and 0.039, respectively). When the conventional morphological and hemodynamic parameters as well as the mass moment of inertia were considered together, the highest performance for rupture risk prediction was obtained (sensitivity 96.3%; specificity 85.7%; area under the receiver operating characteristic curve 0.921).

CONCLUSIONS

The mass moment of inertia would be a useful parameter for evaluating aneurysm irregularity and hence its risk of rupture. The new approach described here may help clinicians to predict the risk of aneurysm rupture more effectively.

Angiographic tapering sign as a surrogate marker for large vessel occlusion due to intracranial atherosclerotic stenosis and its clinical implication: a retrospective matched case-control study

BACKGROUND

The purpose of this study was to investigate whether the initial DSA appearance of the occlusion during mechanical thrombectomy (MT) can help distinguish the nature of the underlying lesion and predict radiological and clinical outcomes.

METHODS

We retrospectively reviewed cases of patients with acute ischemic stroke who underwent MT for anterior circulation occlusion between March 2017 and February 2020. Underlying intracranial atherosclerotic stenosis (ICAS) was determined based on the presence of fixed stenosis after endovascular treatment. Patients were categorized based on the appearance of the occlusion observed in the initial DSA as tapering sign (+) or (-) groups. We performed 1:2 propensity score matching to establish a proper control group among the tapering sign (-) group. We analyzed and compared baseline characteristics and clinical outcomes between the two groups.

RESULTS

A total of 293 patients (tapering sign (+), n=47; tapering sign (-), n=246) were included in the analysis. The procedure time of MT was significantly longer for the tapering sign (+) group, and the successful recanalization rate after MT was significantly lower in the tapering sign (+) group than in the tapering sign (-) group. Logistic regression showed that ICAS-related occlusion was strongly associated with a positive angiographic tapering sign, and the angiographic tapering sign was a negative factor for the first-pass effect during MT. However, a 3-month good functional outcome was not significantly associated with the angiographic tapering sign.

CONCLUSIONS

The tapering sign on the initial DSA could be a surrogate marker for ICAS-related occlusion and procedural difficulty. However, its clinical significance remains unclear.

Endovascular Treatment of Symptomatic Basilar Artery Stenosis

PURPOSE

While symptomatic basilar artery (BA) stenosis is associated with a higher risk of recurrent stroke or death, there is no consensus on the management of these patients who are refractory to antiplatelet therapy. This study retrospectively assesses the outcomes of endovascular treatment (EVT) for symptomatic BA stenosis.

MATERIALS AND METHODS

We conducted a retrospective review of patients with symptomatic BA stenosis who underwent EVT, including angioplasty or stenting, from 2006 to 2018. A total of 15 patients, who experienced transient ischemic attacks or strokes despite dual antiplatelet therapy, were included. EVT was performed under local anesthesia after pretreatment with antiplatelet medications. Angiographic follow-up was performed at 12 and 24 months post-EVT. Clinical outcomes were evaluated using the modified Rankin Scale (mRS).

RESULTS

EVT was successfully completed in all patients. Peri/post-procedural complications occurred in 33% of cases, including in-stent thrombosis, intracranial hemorrhage, and pontine infarction. At long-term follow-up (mean 98.5±80.5 months), 73.3% of patients achieved a favorable functional outcome (mRS≤2) without disability or mortality. Patients with unfavorable outcomes had previous infarcts, with 2 experiencing new pontine infarctions after stenting.

CONCLUSION

This study suggests that EVT, including angioplasty and stenting, may offer promise as a treatment option for symptomatic BA stenosis refractory to medical therapy. However, the procedure carries a notable risk of complications, especially in patients with severe stenosis and previous infarcts. Careful patient selection, based on clinical and radiological criteria, is crucial.

The Current Limitations and Advanced Analysis of Hemodynamic Study of Cerebral Aneurysms

Among the various perspectives on cerebrovascular diseases, hemodynamic analysis-which has recently garnered interest-is of great help in understanding cerebrovascular diseases. Computational fluid dynamics (CFD) analysis has been the primary hemodynamic analysis method, and studies on cerebral aneurysms have been actively conducted. However, owing to the intrinsic limitations of the analysis method, the role of wall shear stress (WSS), the most representative parameter, remains controversial. High WSS affects the formation of cerebral aneurysms; however, no consensus has been reached on the role of WSS in the growth and rupture of cerebral aneurysms. Therefore, this review aimed to briefly introduce the up-to-date results and limitations made through CFD analysis and to inform the need for a new hemodynamic analysis method.

Rupture risk prediction of cerebral aneurysms using a novel convolutional neural network-based deep learning model

BACKGROUND

Cerebral aneurysms should be treated before rupture because ruptured aneurysms result in serious disability. Therefore, accurate prediction of rupture risk is important and has been estimated using various hemodynamic factors.

OBJECTIVE

To suggest a new way to predict rupture risk in cerebral aneurysms using a novel deep learning model based on hemodynamic parameters for better decision-making about treatment.

METHODS

A novel convolutional neural network (CNN) model was used for rupture risk prediction retrospectively of 123 aneurysm cases. To include the effect of hemodynamic parameters into the CNN, the hemodynamic parameters were first calculated using computational fluid dynamics and fluid-structure interaction. Then, they were converted into images for training the CNN using a novel approach. In addition, new data augmentation methods were devised to obtain sufficient training data. A total of 53,136 images generated by data augmentation were used to train and test the CNN.

RESULTS

The CNNs trained with wall shear stress (WSS), strain, and combination images had area under the receiver operating characteristics curve values of 0.716, 0.741, and 0.883, respectively. Based on the cut-off values, the CNN trained with WSS (sensitivity: 0.5, specificity: 0.79) or strain (sensitivity: 0.74, specificity: 0.71) images alone was not highly predictive. However, the CNN trained with combination images of WSS and strain showed a sensitivity and specificity of 0.81 and 0.82, respectively.

CONCLUSION

CNN-based deep learning algorithm using hemodynamic factors, including WSS and strain, could be an effective tool for predicting rupture risk in cerebral aneurysms with good predictive accuracy.

Accelerated tibia fracture healing in traumatic brain injury in accordance with increased hematoma formation

BACKGROUND

Traumatic brain injury (TBI) has been known to accelerate bone healing. Many cells and molecules have been investigated but the exact mechanism is still unknown. The neuroinflammatory state of TBI has been reported recently. We aimed to investigate the effect of TBI on fracture healing in patients with tibia fractures and assess whether the factors associated with hematoma formation changed more significantly in the laboratory tests in the fractures accompanied with TBI.

METHODS

We retrospectively investigated patients who were surgically treated for tibia fractures and who showed secondary bone healing. Patients with and without TBI were divided for comparative analyses. Radiological parameters were time to callus formation and the largest callus ratio during follow-up. Preoperative levels of complete blood count and chemical battery on admission were measured in all patients. Subgroup division regarding age, gender, open fracture, concomitant fracture and severity of TBI were compared.

RESULTS

We included 48 patients with a mean age of 44.9 (range, 17-78), of whom 35 patients (72.9%) were male. There were 12 patients with TBI (Group 1) and 36 patients without TBI (Group 2). Group 1 showed shorter time to callus formation (P <  0.001), thicker callus ratio (P = 0.015), leukocytosis and lymphocytosis (P ≤ 0.028), and lower red blood cell counts (RBCs), hemoglobin, and hematocrit (P <  0.001). Aging and severity of TBI were correlated with time to callus formation and callus ratio (P ≤ 0.003) while gender, open fracture, and concomitant fracture were unremarkable.

CONCLUSION

Tibia fractures with TBI showed accelerated bone healing and superior measurements associated with hematoma formation (lymphocytes, RBCs, hemoglobin, hematocrit). Promoted fracture healing in TBI was correlated with the enhanced proinflammatory state.

LEVEL OF EVIDENCE

III, case control study.

Trends in Mortality from Hemorrhagic Stroke in Korea from 2012 to 2020

Purpose

To analyze trends in mortality rates from hemorrhagic stroke (HS) according to HS subtypes, using nationwide data from January 2012 to December 2020.

Materials and Methods

We used data from the National Health Claims Database provided by the National Health Insurance Service for 2012–2020 using the International Classification of Disease. The age-adjusted mortality rates of HS, which included subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH), were calculated, and additional analyses were conducted according to age and sex.

Results

The age-adjusted mortality rates for HS, SAH, and ICH decreased substantially in both sexes between 2012 and 2020. During the study period, mortality rates for HS decreased from 8.87 deaths per 100,000 inhabitants to 6.27 deaths per 100,000 inhabitants. Regarding SAH, mortality rates decreased from 3.72 deaths per 100,000 inhabitants to 2.57 deaths per 100,000 inhabitants. Concerning ICH, mortality rates decreased from 6.91 deaths per 100,000 inhabitants to 4.75 deaths per 100,000 inhabitants. The average annual percentage change for HS, SAH, and ICH was –0.04, –0.04, and –0.05, respectively. Mortality rates from HS, SAH, and ICH in both sexes decreased from 2012 to 2020 in all age groups.

Conclusion

In Korea, the age-adjusted mortality rate of HS, SAH, and ICH demonstrated a declining trend in both sexes and across all age groups. These results may aid in the design and improvement of preventive strategies.

Delays in Intracerebral Hemorrhage Management Is Associated with Hematoma Expansion and Worse Outcomes: Changes in COVID-19 Era

PURPOSE

The coronavirus disease 2019 (COVID-19) pandemic disrupted the emergency medical care system worldwide. We analyzed the changes in the management of intracerebral hemorrhage (ICH) and compared the pre-COVID-19 and COVID-19 eras.

MATERIALS AND METHODS

From March to October of the COVID-19 era (2020), 83 consecutive patients with ICH were admitted to four comprehensive stroke centers. We retrospectively reviewed the data of patients and compared the treatment workflow metrics, treatment modalities, and clinical outcomes with the patients admitted during the same period of pre-COVID-19 era (2017-2019).

RESULTS

Three hundred thirty-eight patients (83 in COVID-19 era and 255 in pre-COVID-19 era) were included in this study. Symptom onset/detection-to-door time [COVID-19; 56.0 min (34.0-106.0), pre-COVID-19; 40.0 min (27.0-98.0), p=0.016] and median door to-intensive treatment time differed between the two groups [COVID-19; 349.0 min (177.0-560.0), pre-COVID-19; 184.0 min (134.0-271.0), p<0.001]. Hematoma expansion was detected more significantly in the COVID-19 era (39.8% vs. 22.1%, p=0.002). At 3-month follow-up, clinical outcomes of patients were worse in the COVID-19 era (Good modified Rankin Scale; 33.7% in COVID19, 46.7% in pre-COVID-19, p=0.039).

CONCLUSION

During the COVID-19 era, delays in management of ICH was associated with hematoma expansion and worse outcomes.

Source Image Based New 3D Rotational Angiography for Differential Diagnosis between the Infundibulum and an Internal Carotid Artery Aneurysm : Pilot Study

Objective

Distinguishing between an infundibulum and a true aneurysm is clinically important. This study aimed to evaluate whether using source image based new three-dimensional rotational angiography (S-n3DRA) can increase the rate of aneurysm detection and improve distinction between a true aneurysm and an infundibulum.

Methods

Twenty-two consecutive patients with 23 lesions, were evaluated by time-of-flight (TOF) magnetic resonance angiography (MRA), S-n3DRA, and digital subtraction angiography (DSA). The data were retrospectively and independently reviewed by two neurointerventionists, and the diagnoses based on TOF MRA, S-n3DRA, and DSA were compared. The diagnostic efficacy (interobserver agreement and diagnostic performance) of S-n3DRA was compared with that of TOF MRA.

Results

S-n3DRA showed higher interobserver agreement (κ=0.923) than TOF MRA (κ=0.465) and significantly higher accuracy than MRA in distinguishing an aneurysm from an infundibulum (p=0.0039).

Conclusion

Compared to MRA, S-n3DRA could provide better screening accuracy and information for distinguishing an aneurysm from an infundibulum. Therefore, S-n3DRA has the potential to reduce the need for DSA.

The quantitative comparison between high wall shear stress and high strain in the formation of paraclinoid aneurysms

In the hemodynamic study, computational fluid dynamics (CFD) analysis has shown that high wall shear stress (WSS) is an important parameter in cerebral aneurysm formation. However, CFD analysis is not more realistic than fluid–structure interaction (FSI) analysis given its lack of considering the involvement of vascular structures. To investigate the relationship between the hemodynamic parameters and the aneurysm formation, the locations of high WSS and high strain were extracted from the CFD and FSI analyses, respectively. Then the distances between the aneurysm formation site and the locations of high WSS or high strain were calculated. A total of 37 intracranial paraclinoid aneurysms were enrolled for quantitative comparison. Additionally, the dura mater was modeled to facilitate realistic results in FSI analysis. The average distance from the location of the aneurysm formation site to the high strain (1.74 mm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 1.04 mm) was smaller than the average distance to the high WSS (3.33 mm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 1.18 mm). The presence of dura mater also influenced the findings in the aneurysm formation site. High strain extracted by FSI analysis is an important hemodynamic factor related to the formation of cerebral aneurysms. Strain parameter could help to predict the formation of aneurysms and elucidate the appropriate treatment.

Extremely Low Serum Alanine Transaminase Level Is Associated with All-Cause Mortality in the Elderly after Intracranial Hemorrhage

OBJECTIVE

Extremely low alanine transaminase (ALT) levels are associated with all-cause mortality in frail elderly individuals; the clinical significance of ALT as a reliable biomarker is now being considered. Predicting mortality with routine tests at the time of diagnosis is important for managing patients after intracranial hemorrhage. We aimed to investigate whether an extremely low ALT level is associated with mortality in the elderly after intracranial hemorrhage.

METHODS

A retrospective review was performed on 455 patients with intracranial hemorrhage admitted to a university-affiliated tertiary care hospital from February 2014 to May 2019. Multivariate Cox regression analysis was performed for all ages and for each age group to determine whether an extremely low ALT level is an independent predictor of mortality only in the elderly.

RESULTS

Overall, 294 patients were enrolled, and the mean age of the subjects was 59.1 years, with 99 (33.8%) aged ≥65 years. The variables associated with all-cause mortality in all subjects were age, C-reactive protein (CRP) levels, hemoglobin (Hb) levels (<11 g/dL), and initial Glasgow coma scale (GCS) scores. In young patients, CRP, low Hb levels, and initial GCS scores were significantly associated with all-cause mortality. However, in the elderly (≥65 years), the variables significantly associated with allcause mortality were extremely low levels of ALT (<10 U/L) (adjusted hazard ratio, 3.313; 95% confidence interval, 1.232-8.909; p=0.018) and initial GCS scores.

CONCLUSION

Extremely low ALT level (<10 U/L) at the time of diagnosis is a significant risk factor for all-cause mortality in the elderly after intracranial hemorrhage.

Prediction of rupture risk in cerebral aneurysms by comparing clinical cases with fluid-structure interaction analyses

Cerebral aneurysms should be treated on the basis of accurate rupture risk prediction. Nowadays, the rupture risk in aneurysms has been estimated using hemodynamic parameters. In this paper, we suggest a new way to predict the rupture risks in cerebral aneurysms by using fluid–structure interaction (FSI) analysis for better decision-making regarding treatment. A patient-specific model was constructed using digital subtraction angiography of 51 cerebral aneurysms. For each model, a thin-walled area (TWA) was first predicted using computational fluid dynamics (CFD), and then the highest equivalent strain in the TWA was calculated with FSI by varying wall thicknesses and mechanical properties. A critical curve was made from 16 FSI results for each patient-specific model to estimate the rupture risk. On average, the equivalent strains of the ruptured aneurysms were higher than those of the unruptured aneurysms. Furthermore, the patterns of critical curves between unruptured and ruptured aneurysms were clearly distinguishable. From the rupture risk evaluation based on the cut-off value, 24 of the 27 unruptured aneurysms and 15 of the 24 ruptured aneurysms were matched with actual-clinical setting cases. The critical curve proposed in the present study could be an effective tool for the prediction of the rupture risk of aneurysm.

Evaluation of the angiographic outcomes after clipping of intracranial aneurysms: determination of predisposing factors for occurrence of aneurysm remnants

Objectives: Aneurysm remnants after microsurgical clipping have a risk of regrowth and rupture and have not been validated in the era of three-dimensional angiography. Therefore, this study aimed to evaluate the angiographic outcome using three-dimensional rotational images and determine the predictors for remnants after microsurgical clipping.Methods: Between January 2014 and May 2017, 139 aneurysms in 106 patients who were treated with microsurgical clipping, were eligible for this study. For the determination of aneurysm remnants after microsurgical clipping, the angiographic outcomes were evaluated using follow-up digital subtraction angiography within 7 days for unruptured aneurysms or within 2 weeks for ruptured aneurysms. According to the Sindou classification, the aneurysm remnants were dichotomized, and subgroup analysis was performed to identify the predictors of aneurysm remnants after clipping with various imaging parameters and clinical information.Results: The overall rate of aneurysm remnants was 29.5% (41/139), in which retreatments were needed in 6.5% (9/139). The neck size and maximum diameter of aneurysms were independent predisposing factors for the aneurysm remnants that need retreatment (OR: 2.30; p < 0.001; OR: 1.38; p < 0.001, respectively).Conclusions: This study demonstrated a low incidence of aneurysm remnants after microsurgical clipping which need to retreatment. However, selective postoperative angiography could provide us clear information of surgical result and evidence for long-term follow-up for some aneurysms with larger neck size (>5.7 mm) and maximum diameter (>7.1 mm).

Endovascular Treatment for Intracranial Aneurysms: A Nationwide Survey in Korea

Purpose

In Korea, endovascular treatment (EVT) for intracranial aneurysms (IAs) has increased steadily. We conducted a nationwide survey to evaluate the current status of EVT for IAs and to identify treatment preference in the real world.

Materials and Methods

A Google online survey was distributed to representative clinicians at hospitals treating IAs, where members of Korean Society of Interventional Neuroradiology (KSIN). The data was collected from October 2017 to December 2017. The responding hospitals were divided into 2 groups (tertiary and non-tertiary hospitals). And variable factors involved in decision making for treatment were evaluated.

Results

In total, 73 hospitals (tertiary: 37, non-tertiary: 36) responded to the survey. Most hospitals that responded had over 100 cases of diagnostic angiography (93%) and over 50 cases of EVT for IAs (74%) performed in 2016. The proportion of EVT for ruptured aneurysms in non-tertiary hospitals was significantly higher than tertiary hospitals (49% vs. 9%). The proportion of EVT for unruptured aneurysms at non-tertiary hospitals was significantly higher than tertiary hospitals (66% vs. 44%). Most physicians tended to make decision for treatment on location, shape, and size of unruptured IAs and patients’ age, more than the results from previous clinical trials for unruptured IAs. Although EVT was preferred for older patients (age >70) with unruptured IAs (99%), surgical clipping was still considered as the first treatment of choice for younger patients (age 30 to 50 years) at considerable rates (56%). Over two-thirds of respondents preferred surgical clipping for middle cerebral artery aneurysms, while EVT was preferred initially at other locations.

Conclusion

This nationwide survey showed that EVT is considered as the first treatment modality for IAs and there is a discrepancy between current guidelines and real-world practice for decision making of treatment options.

Rete middle cerebral artery anomalies: a unifying name, case series, and literature review

OBJECTIVE

Rete middle cerebral artery (MCA) is extremely rare and has not been frequently discussed. Rete MCA is a weblike anomaly of the MCA that does not coalesce and forms a prominent, large single branch from the plexiform vessels in the fetal stage. The purpose of this study was to further elucidate the clinical and radiological characteristics of patients with rete MCA.

METHODS

A total of 2262 cerebral digital subtraction angiography procedures were performed on 1937 patients at the authors' institution from February 2013 to May 2017. Data analysis included age, sex, clinical symptoms, underlying diseases, coexisting cerebral arterial anomalies, and operative methods and findings.

RESULTS

Rete MCAs were found in 13 patients, and the incidence of this anomaly was 0.67% (13 of 1937) in this study. Of the 13 patients, 3 had hemorrhagic strokes, 6 had ischemic strokes, and 4 had no symptoms. Eight patients underwent conservative treatment, and 5 patients underwent surgical treatment. Rete MCA is considered a congenital disease of the cerebral vasculature with the possibility of an acquired abnormality, such as an aneurysm, caused by hemodynamic stress. Although an epidemiological survey of rete MCA was not conducted, it is assumed that rete MCA has a high prevalence in Asia. Ischemic and hemorrhagic stroke events are fairly common in rete MCA.

CONCLUSIONS

Clinicians should understand the radiological and clinical features of patients with rete MCA to avoid misdiagnosis and unnecessary treatment. This anomaly should be differentiated from other vascular diseases and patients presenting incidentally should be carefully monitored because of their vulnerability to both hemorrhagic and ischemic strokes.

Saccular or dissecting aneurysms involving the basilar trunk: Endovascular treatment and clinical outcome

Objectives: Basilar artery trunk aneurysms (BTAs) are a rare pathology and difficult to treat. We present our experience regarding angiographic results and clinical outcomes for 16 BTAs treated by reconstructive endovascular treatment (EVT) using stent or balloon. Methods: Between January 2003 and December 2014, 15 patients (mean age, 58.6 years; 11 males) with 16 BTAs were enrolled. Clinical manifestation, outcomes and procedural complications were evaluated retrospectively, and follow-up angiography was performed 12 and 24 months after procedure. Results: Subarachnoid hemorrhage (SAH) developed in seven aneurysms and nine were found incidentally. In one case, SAH followed by acute infarction on pons. The location of the aneurysms was the pure basilar artery (BA) trunk in 13 and the junction of the BA and the superior cerebellar artery in 3. Reconstructive EVT was technically successful in 15 aneurysms (93.8%) and failed in one due to the difficulty of vascular access. Stent/balloon-assisted coiling was performed in 13 aneurysms and sole stent therapy in two aneurysms. One patient had periprocedural complication of acute in-stent thrombosis. All treated patients had no symptoms with the usual activities except three patients, who died from myocardial infarction, aneurysmal rebleeding, and cerebellar infarction. Angiographic follow-up was performed in nine aneurysms; three aneurysms were recanalized (33.3%) and six aneurysms had no interval change (66.7%). There was no significant event during the follow-up period (mean, 23.5 months). Conclusion: In the treatment of BTAs, reconstructive EVT may provide a feasible and safe option to microsurgery.

Radiographic and microsurgical characteristics of proximal (A1) segment aneurysms of the anterior cerebral artery

BACKGROUND

Proximal A1 segment aneurysms of the anterior cerebral artery (ACA) radiologically resemble internal carotid artery bifurcation (ICBIF) aneurysms because of their anatomical proximity. However, proximal A1 aneurysms exhibit distinguishing features, relative to ICBIF aneurysms. We report our experience of managing proximal A1 aneurysms, then compare them to ICBIF aneurysms.

METHODS

Among 2191 aneurysms treated between 2000 and 2016 in a single institution, we retrospectively reviewed 100 cases categorized as ICBIF or A1 aneurysms. We included aneurysms originating from the ICBIF and ACA, proximal to the anterior communicating artery (A1 segment) and divided them into two groups: proximal A1 (n = 32) and ICBIF (n = 50). If any portion of the aneurysm involved the ICBIF, it was classified as ICBIF. Aneurysms wholly located in the A1 segment were classified as proximal A1. Patient factors and angiographic factors were evaluated and compared.

RESULTS

The proximal A1 group exhibited differences in aneurysm size (p = 0.013), posterior aneurysm direction (p = 0.001), and A1 perforators as incorporating vessels (p = 0.001). The proximal A1 group tended to rupture more frequently when the aneurysm was smaller (p = 0.046). One case of morbidity occurred in the proximal A1 group.

CONCLUSION

Compared to ICBIF aneurysms, proximal A1 aneurysms were smaller and directed posteriorly, with incorporating perforators. Because of these characteristics, it may be difficult to perform clipping with 360° view in microsurgical field. Therefore, when planning to treat proximal A1 aneurysms, different treatment strategies may be necessary, relative to those used for ICBIF aneurysms.

Extremely high strength and work hardening ability in a metastable high entropy alloy

Design of multi-phase high entropy alloys uses metastability of phases to tune the strain accommodation by favoring transformation and/or twinning during deformation. Inspired by this, here we present Si containing dual phase Fe42Mn28Co10Cr15Si5 high entropy alloy (DP-5Si-HEA) exhibiting very high strength (1.15 GPa) and work hardening (WH) ability. The addition of Si in DP-5Si-HEA decreased the stability of f.c.c. (γ) matrix thereby promoting pronounced transformation induced plastic deformation in both as-cast and grain refined DP-5Si-HEAs. Higher yet sustained WH ability in fine grained DP-5Si-HEA is associated with the uniform strain partitioning among the metastable γ phase and resultant h.c.p. (ε) phase thereby resulting in total elongation of 12%. Hence, design of dual phase HEAs for improved strength and work hardenability can be attained by tuning the metastability of γ matrix through proper choice of alloy chemistry from the abundant compositional space of HEAs.

Prepuncture Ultrasound Examination Facilitates Safe and Accurate Common Femoral Artery Access for Transfemoral Cerebral Angiography

Objective

We aimed to introduce our method involving prepuncture ultrasound scan for cannulation of the common femoral artery (CFA) during transfemoral cerebral angiography (TFCA), and to assess the clinical and radiological outcomes.

Material and Methods

Our study included 90 patients who underwent prepuncture ultrasound examination of the inguinal area for TFCA between April 2015 and June 2015. Prior to skin preparation and draping of the inguinal area, we identified the CFA and its bifurcation using ultrasound. Based on the ultrasound findings, we marked cruciate lines in the inguinal area. Thereafter, we inserted a puncture needle at the interface between the horizontal and vertical lines at a 30-45° angle, simultaneously palpating the pulsation of the femoral artery. After TFCA was completed, femoral artery angiography was performed in the anteroposterior and oblique directions. Clinical and radiological parameters, including CFA cannulation, the ultrasound scan time, the first pass success rate, the time required for the passage of the wire, and complications, were evaluated.

Results

The mean ultrasound scan time of the CFA and its bifurcation was 72.6 seconds, and the mean time between administration of local anesthesia and wire passage was 67.44 seconds. The first pass success rate was 77.8% (70/90 patients), and the CFA puncture rate was 98.8% (89/90 patients). Although minor complications were noted in 7 patients, no patient reported serious complications (a large hematoma [≥ 5 cm], pseudoaneurysms, dissection, and/or a retroperitoneal hematoma.).

Conclusion

Prepuncture ultrasound examination might be a simple, safe, and accurate technique for cannulation of the CFA during TFCA.

Enhanced strength and ductility in a friction stir processing engineered dual phase high entropy alloy

The potential of high-entropy alloys (HEAs) to exhibit an extraordinary combination of properties by shifting the compositional regime from the corners towards the centers of phase diagrams has led to worldwide attention by material scientists. Here we present a strong and ductile non-equiatomic HEA obtained after friction stir processing (FSP). A transformation-induced plasticity (TRIP) assisted HEA with composition Fe50Mn30Co10Cr10 (at.%) was severely deformed by FSP and evaluated for its microstructure-mechanical property relationship. The FSP-engineered microstructure of the TRIP HEA exhibited a substantially smaller grain size, and optimized fractions of face-centered cubic (f.c.c., γ) and hexagonal close-packed (h.c.p., ε) phases, as compared to the as-homogenized reference material. This results in synergistic strengthening via TRIP, grain boundary strengthening, and effective strain partitioning between the γ and ε phases during deformation, thus leading to enhanced strength and ductility of the TRIP-assisted dual-phase HEA engineered via FSP.

Perimesencephalic Nonaneurysmal Subarachnoid Hemorrhage After Clipping of an Unruptured Aneurysm

BACKGROUND

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is a benign form of subarachnoid hemorrhage with an excellent clinical outcome. The cause of PNSAH remains unknown. We report a case of PNSAH in a patient with a history of clipping of an unruptured aneurysm. PNSAH after clipping of an unruptured aneurysm is extremely rare.

CASE DESCRIPTION

A 56-year-old man with a history of clipping surgery for an unruptured aneurysm 10 months previously presented with severe headache. No precipitating causes were shown; however, the patient had been engaged in an exertional activity before the event. After conservative treatment, he was discharged home without any complication from the hemorrhage.

CONCLUSIONS

On the basis of this case report, clinicians should consider the possibility of PNSAH in a patient who had an unruptured aneurysm previously treated with clipping. Nevertheless, diagnostic workup can be more important than keeping in mind that a subarachnoid hemorrhage might be a PNSAH.

MAGNETOCALORIC RESPONSE OF NON-STOICHIOMETRIC Ni2MnGa ALLOYS AND THE INFLUENCE OF CRYSTALLOGRAPHIC TEXTURE

Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni2+xMn1-xGa family, with x between 0.08 and 0.24, were evaluated for the purpose of finding composition(s) with an enhanced magnetocaloric effect (MCE) close to room temperature. Differential scanning calorimetry (DSC) was successfully used to screen alloy composition for simultaneous magnetic and structural phase transformations; this coupling needed for a giant MCE. The alloy with x = 0.16 showed an excellent match of transformation temperatures and exhibited the highest magnetic entropy change, ΔSM, in the as-annealed state. Furthermore, the MCE increased by up to 84 % with a 2 Tesla (T) field change when the samples were thermally cycled through the martensite to austenite transformation temperature while held under a constant mechanical load. The highest ΔSM measured for our x = 0.16 alloy for a 2 T magnetic field change was -18 J/kg-K. Texture measurements suggest that preferential orientation of martensite variants contributed to the enhanced MCE in the stress-assisted thermally cycled state.

Cerebral hemorrhage after endovascular treatment of bilateral traumatic carotid cavernous fistulae with covered stents

Bilateral traumatic carotid-cavernous fistulae (TCCFs) is rarely encountered neurovascular disease. For treatment of TCCF, detachable balloons have been widely used. Nowadays, transarterial and/or transvenous coil embolization with placement of covered stents is adopted as another treatment method. We experienced a patient with a bilateral TCCFs who was successfully treated with covered stents. However, cerebral hemorrhage occurred in the bed of previous infarction one day after treatment. Hyperperfusion syndrome was considered as a possible cause of the hemorrhage, so that barbiturate coma therapy was started and progression of hemorrhage was stopped. We emphasize that cerebral hyperperfusion hemorrhage can occur even after successful endovascular treatment of TCCF.

Mortality after acute renal failure: models for prognostic stratification and risk adjustment

To adjust adequately for comorbidity and severity of illness in quality improvement efforts and prospective clinical trials, predictors of death after acute renal failure (ARF) must be accurately identified. Most epidemiological studies of ARF in the critically ill have been based at single centers, or have examined exposures at single time points using discrete outcomes (e.g., in-hospital mortality). We analyzed data from the Program to Improve Care in Acute Renal Disease (PICARD), a multi-center observational study of ARF. We determined correlates of mortality in 618 patients with ARF in intensive care units using three distinct analytic approaches. The predictive power of models using information obtained on the day of ARF diagnosis was extremely low. At the time of consultation, advanced age, oliguria, hepatic failure, respiratory failure, sepsis, and thrombocytopenia were associated with mortality. Upon initiation of dialysis for ARF, advanced age, hepatic failure, respiratory failure, sepsis, and thrombocytopenia were associated with mortality; higher blood urea nitrogen and lower serum creatinine were also associated with mortality in logistic regression models. Models incorporating time-varying covariates enhanced predictive power by reducing misclassification and incorporating day-to-day changes in extra-renal organ system failure and the provision of dialysis during the course of ARF. Using data from the PICARD multi-center cohort study of ARF in critically ill patients, we developed several predictive models for prognostic stratification and risk-adjustment. By incorporating exposures over time, the discriminatory power of predictive models in ARF can be significantly improved.

Portal vein opacification during ERCP in patients with pancreatitis

We report two cases of portal vein visualization during ERCP in patients with pancreatitis, one from inadvertent cannulation of the superior mesenteric vein, and in the other, through a preexisting fistula. Prompt recognition of this potentially significant event will obviate confusion and unnecessary prolongation of the procedure.

Depiction of diaphragmatic muscle slips on supine plain radiographs: a sign of pneumoperitoneum

PURPOSE

To describe the diaphragm muscle slip sign, a previously unreported finding of pneumoperitoneum on plain radiographs.

MATERIALS AND METHODS

Diaphragmatic muscle slips were observed on supine plain abdominal (n = 6) or recumbent frontal chest (n = 3) radiographs in nine patients. Computed tomographic (CT) confirmation was available in six patients; free air was depicted on upright chest radiographs in the other three patients.

RESULTS

Muscle slips of the costal portion of the diaphragm were depicted in the right upper quadrant as they indented the adjacent air-filled peritoneal cavity. On supine radiographs, these discrete muscle bundles appeared as two or three large, arcuate interfaces or as bands of increased opacity of similar dimensions, with their long axes directed vertically. These smoothly marginated bundles were parallel to the dome and converged superomedially. On the CT scans, the costal muscle slips were clearly defined as bands or small peripheral triangles impinging on the parietal peritoneum.

CONCLUSION

Depiction of the undersurface of the long costal muscle slips of the diaphragm on supine plain radiographs is a sign of pneumoperitoneum.

Visualization of the extrahepatic segment of the ligamentum teres: a sign of free air on plain radiographs

PURPOSE

To assess visualization of the extrahepatic segment of the ligamentum teres on plain radiographs, the ligamentum teres sign, which is an indicator of pneumoperitoneum.

MATERIALS AND METHODS

The ligamentum teres was recognized in 12 patients with pneumoperitoneum. Findings from supine radiographs were correlated with those from oblique radiographs and computed tomograms.

RESULTS

The extrahepatic segment of the ligamentum teres, which extended between the umbilicus and the ligamentum teres notch at the inferior border of the liver, was visualized on supine radiographs. The ligamentum teres appeared in the right upper quadrant as an obliquely oriented, straight, or slightly arcuate interface with a sharply demarcated inferolateral margin or as a similarly positioned, well-defined band of soft tissue of varying length. The falciform ligament was also seen in six of the 12 patients as a long, thin line that ran vertically to the right of the midline and joined the ligamentum teres caudally near or at the umbilicus. Even though there were other signs of pneumoperitoneum in all cases, the ligamentum teres sign was the most prominent in three cases.

CONCLUSION

Visualization of the extrahepatic segment of the ligamentum teres on supine radiographs requires the anterior accumulation of extraluminal, intraperifoneal gas and is another sign of moderate to massive amounts of free air.

Transpyloric spread of gastric tumors: comparison of adenocarcinoma and lymphoma

OBJECTIVE

Our objective was to determine the relative frequency of transpyloric tumor spread in gastric antral carcinoma and lymphoma.

MATERIALS AND METHODS

We reviewed the medical records of 127 cases of pathologically proven gastric malignant tumors, including 102 carcinomas and 25 lymphomas, over a 10-year period. The antrum had carcinoma in 64 cases and lymphoma in 15. We reviewed upper gastrointestinal barium studies and correlated the findings of transpyloric tumor extension with the results of surgery, pathology, and endoscopy.

RESULTS

Tumor extension into the duodenal bulb occurred in 16 (25%) of 64 patients with carcinoma and in six (40%) of 15 patients with lymphoma of the gastric antrum. Transpyloric spread of antral carcinoma as revealed by barium study was much more common in our series than has been stated in the literature.

CONCLUSION

Duodenal invasion of an antral carcinoma is not rare. Because of the higher incidence of carcinoma, transpyloric spread of gastric tumor as revealed by barium studied should not by itself suggest the diagnosis of lymphoma.

Wedge-shaped intrahepatic cholangiocarcinoma: MRI-pathologic correlation

On magnetic resonance imaging (MRI) studies, wedge-shaped areas of signal abnormality noted in association with liver lesions have been attributed to secondary phenomena and are said to be substantially larger than the actual tumor. We describe the MRI and pathological appearance of a wedge-shaped cholangiocarcinoma. In cases where therapy might be affected, biopsy of wedge-shaped MRI abnormalities associated with hepatic malignancy should be considered for accurate tumor staging.

Evidence suggesting a role for phospholipase C isozyme, PLC-delta 1 in corticomedullary osmotic gradients in rat kidneys

We determined the distributional patterns of phospholipase C isozymes within the rat kidneys. PLC-beta1 was localized in the inner medulla at the highest degree followed by the inner stripe of the outer medulla, the cortex and the outer stripe of the outer medulla. PLC-gamma1 was distributed homogeneously along the corticomedullary axis. PLC-delta1 showed gradual increase from the cortex to the inner medulla. Tissue osmotic gradients were measured using 4 slices, resulting in gradual increase from the cortex to the inner medulla. The pattern of PLC-delta1 appeared very similar to the osmotic gradient in the kidney. The results suggest that the distinct patterns of the PLC isozymes may be associated with different signal transduction pathways along the corticomedullary axis and PLC-delta1 may play a role in the osmoregulation of the medullary region.

CT in patients with blunt abdominal trauma: clinical significance of intraperitoneal fluid detected on a scan with otherwise normal findings

OBJECTIVE

The purpose of this study was to determine the clinical significance of intraperitoneal fluid seen on CT scans with otherwise normal findings in patients with blunt abdominal trauma.

MATERIALS AND METHODS

We retrospectively analyzed the CT scans of 60 patients with blunt abdominal trauma who had scans showing normal findings except for the presence of intraperitoneal fluid. The location of the fluid was determined (pouch of Douglas, pelvis, paracolic gutters, mesentery, Morison's pouch, perihepatic or perisplenic spaces). The amount of fluid in each location was categorized as minimal, moderate, or marked. The total volume of fluid in each patient was estimated as small (+1), intermediate (+2), or large (+3) on the basis of the sum of the amount of fluid in the individual peritoneal locations. The amount and location of fluid were compared between patients who required exploratory laparotomy and those who were managed conservatively.

RESULTS

In most patients, the total fluid volume was small (44 patients, 73%) as opposed to intermediate (11 patients, 18%) or marked (five patients, 8%). Thirty-seven patients had fluid in one location, 12 patients had fluid in two locations, and 11 patients had fluid in three or more locations. Intraperitoneal fluid tended to accumulate in the pouch of Douglas (67%) and Morison's pouch (33%). Patients requiring laparotomy had a higher total fluid volume score compared with the patients managed conservatively (2.2 versus 1.3, p < .002) and had larger amounts of fluid in the upper abdomen. Laparotomy was required in only one patient (2%) who had a small amount of fluid compared with three patients (27%) with intermediate and two patients (40%) with marked amounts. Mesenteric and/or bowel injuries were noted in all six patients at laparotomy. One patient had a small superficial liver laceration that was not diagnosed with CT. No other injuries to the solid viscera were missed on the scans. Two of the four patients with mesenteric fluid seen on the CT scan had mesenteric lacerations found during surgery, and the remaining two did well with conservative management.

CONCLUSION

Patients with blunt abdominal trauma who have small amounts of intraperitoneal fluid as the sole abnormality shown by CT may generally be treated conservatively. However, patients with even a small quantity of mesenteric fluid may benefit from peritoneal lavage to help exclude bowel or mesenteric injury. Intermediate and large amounts of fluid are less common as the sole CT abnormality but have a higher likelihood of being associated with bowel or mesenteric injury.

Varices in portal hypertension: evaluation with CT

The portosystemic collateral channels that can develop in portal hypertension are numerous, widespread, and varied in appearance. The reported prevalences of varices at each anatomic site vary according to the diagnostic modality used. Dynamic computed tomography (CT) performed with a bolus of contrast material demonstrates collateral vessels with exquisite detail. On CT scans, varices appear as well-defined found, tubular, or serpentine structures that are smooth, have homogeneous attenuation, and enhance with contrast material to the same degree as adjacent vessels. In 60 consecutive patients with varices and evidence of cirrhosis, the most common portosystemic collateral channels were coronary venous collateral vessels in the lesser omentum, seen in 80% of cases. Esophageal, paraumbilical, abdominal wall, perisplenic, retrogastric, paraesophageal, omental, retroperitoneal-paravertebral, and mesenteric varices were also found, along with spontaneous splenorenal and gastrorenal shunts. Knowledge of the CT appearance and the prevalence of varices at each anatomic site will improve diagnostic accuracy.

Focal enhancement of the liver on CT: a sign of SVC obstruction

We describe a case in which a focus of intense contrast enhancement within the anterior aspect of the medial segment of the left lobe of the liver was detected on abdominal CT. This led to the diagnosis of clinically unsuspected superior vena cava obstruction.

Idiopathic localized dilatation of the ileum in adults: findings on barium studies

OBJECTIVE

Idiopathic localized dilatation of the ileum is a rare entity characterized by a sharply demarcated segmental dilatation of the small bowel that is in line with the lumen. It is probably congenital in origin. Although more commonly diagnosed in children, it presents in adults as occult gastrointestinal (GI) bleeding or less often with abdominal pain. On pathologic examination, the mucosa may be ulcerated, but otherwise the wall is relatively normal. We analyzed the radiographic findings in nine previously unreported cases of this condition in adults.

MATERIALS AND METHODS

Collaborative efforts resulted in the collection of nine cases from multiple institutions. In five cases, an enteroclysis had been performed; in three, a conventional small bowel series had been performed; and in one, the lesion was seen on a barium enema with reflux into the ileum. The mean age of patients was 52 years. In seven cases, pathologic correlation was available. In the other two patients, long-term clinical follow-up and repeat studies confirmed the diagnosis. Resected specimens showed a thin but otherwise normal wall with normal ganglion cells and nerve plexuses. Ulceration was noted in six of the seven resected cases. Two cases contained heterotopic gastric mucosa. GI bleeding and/or anemia was the most common (77%) presenting symptom. Abdominal pain and/or obstruction was present in slightly less than half the patients (44%).

RESULTS

Lesions were 6-21 cm long and 4-13 cm wide, and all were located in the ileum. The dilated segments were bilobate in three cases, multilobate in three, spherical in two, and tubular in the other. The dilated area was always in line with the long axis of the bowel, not projecting to the side. No surrounding masses were seen. Except in three patients in whom ulcers were noted, the mucosa was normal.

CONCLUSION

Idiopathic localized dilatation of the ileum should be suspected whenever a sharply demarcated area of lobulated small bowel dilatation is seen in a middle-aged patient with occult GI bleeding. The axial orientation distinguishes this condition from small bowel diverticula (including Meckel's). The lack of surrounding mass, mucosal irregularity, hypermotility, or fistulae help differentiate it from other causes of small bowel dilatation.

Inflammatory fibroid polyp of the esophagus in an HIV-infected individual: case study

We report an unusual case of a large esophageal inflammatory fibroid polyp in a man infected with the human immunodeficiency virus complaining of dysphagia. Barium studies and computed tomography demonstrated a long, submucosal-appearing, distal esophageal mass which extended into a hiatal hernia. Inflammatory fibroid polyps should be considered in the differential diagnosis of submucosal and polypoid esophageal masses, although distinctive radiographic features are not found.

Chyloperitoneum: CT diagnosis

We describe a patient with ovarian cancer in whom computed tomography revealed a fat-fluid level within ascites, indicating chyloperitoneum. The significance of this finding is discussed, and a mechanism underlying the unusual radiological appearance is suggested.

Extraluminal air. Diagnosis and significance

This article reviews the more common causes of extraluminal gas collections and their manifestations both on plain films and other imaging studies when appropriate.

Liver infarction following unrecognized right hepatic artery ligation at laparoscopic cholecystectomy

Parenchymal liver complications thus far reported following laparoscopic cholecystectomy include abscess, biloma, contusion/laceration, and hematoma. We report a case of liver infarction following unrecognized ligation of the right hepatic artery (HA) during laparoscopic cholecystectomy.

Phosphorylation of ribosomal protein S6 and its regulation during differentiation of human leukemic cells

We attempted to study the role of protein tyrosine kinase (PTK) and protein kinase C (PKC) in the cascade of phosphorylation of ribosomal protein S6 during differentiation of leukemic cells (HL-60, THP-1, and RWLeu-4). Neither activation nor inhibition of colony stimulating factor-1 (CSF-1) receptor's PTK activity with CSF-1 or genistein respectively affected the phosphorylation of S6. However, vanadate which is a protein tyrosine phosphatase (PTP) inhibitor showed enhancement of S6 phosphorylation. Dimethylsulfoxide which does not affect either PTK or PKC demonstrated no change in S6 phosphorylation. PKC activation by acute 12-0-tetradecanoyl phorbol-13-acetate (TPA) treatment induced monocytic differentiation and S6 phosphorylation. Surprisingly, the more prominent phosphorylation of S6 protein was observed in PKC-depleted cells by prolonged TPA treatment. Our results suggest that PTK/PTP play a lesser role in S6 phosphorylation of HL-60 cells than PKC does. In addition, two different mechanisms seem to be involved in TPA-induced S6 phosphorylation during HL-60 differentiation: PKC activation by acute TPA treatment and PKC depletion which may lead to the synthesis of some endogenous protein responsible for the differentiation by chronic TPA treatment.

Purification of an SOS repressor from Bacillus subtilis

We have identified in Bacillus subtilis a DNA-binding protein that is functionally analogous to the Escherichia coli LexA protein. We show that the 23-kDa B. subtilis protein binds specifically to the consensus sequence 5'-GAACN4GTTC-3' located within the putative promoter regions of four distinct B. subtilis DNA damage-inducible genes: dinA, dinB, dinC, and recA. In RecA+ strains, the protein's specific DNA binding activity was abolished following treatment with mitomycin C; the decrease in DNA binding activity after DNA damage had a half-life of about 5 min and was followed by an increase in SOS gene expression. There was no detectable decrease in DNA binding activity in B. subtilis strains deficient in RecA (recA1, recA4) or otherwise deficient in SOS induction (recM13) following mitomycin C treatment. The addition of purified B. subtilis RecA protein, activated by single-stranded DNA and dATP, abolished the specific DNA binding activity in crude extracts of RecA+ strains and strains deficient in SOS induction. We purified the B. subtilis DNA-binding protein more than 4,000-fold, using an affinity resin in which a 199-bp DNA fragment containing the dinC promoter region was coupled to cellulose. We show that B. subtilis RecA inactivates the DNA binding activity of the purified B. subtilis protein in a reaction that requires single-stranded DNA and nucleoside triphosphate. By analogy with E. coli, our results indicate that the DNA-binding protein is the repressor of the B. subtilis SOS DNA repair system.