Most endovascular thrombectomy patients have Target Mismatch despite absence of formal CT perfusion selection criteria.

Endovascular thrombectomy (EVT) is the standard of care for large vessel occlusion stroke. Use of Computed Tomographic Perfusion (CTP) to select EVT candidates is variable. The frequency of treatment and outcome in patients with unfavourable CTP patterns is unknown. A retrospective analysis of CTP utilisation prior to EVT was conducted. All CTP data were analysed centrally and a Target Mismatch was defined as an infarct core ≤70 ml, penumbral volume ≥15ml, and a total hypoperfused volume:core volume ratio >1.8. The primary outcome was good functional outcome at 90 days, defined as a modified Rankin Scale (mRS) score 0-2. follow-up infarct volume, core expansion and penumbral salvage volumes were secondary outcomes. Of 572 anterior circulation EVT patients, CTP source image data required to generate objective maps were available in 170, and a Target Mismatch was present in 151 (89%). The rate of 90-day good functional outcome was similar between Target Mismatch (53%) and Large Core Non-Mismatch groups (46%, p = 0.629). Median follow-up infarct volume in the Large Core Non-Mismatch group (104ml [IQR 25ml-189ml]) was larger than that in the Target Mismatch patients (16ml [8ml-47ml], p<0.001). Despite a lack of formal CTP selection criteria, the majority of patients treated at our centres had a Target Mismatch. Patients without Target Mismatch had larger follow-up infarct volumes, but the functional recovery rate was similar to that in Target Mismatch patients. Infarct volumes should be included as objective assessment criteria in the evaluation of the efficacy of EVT in non-Target Mismatch patients.

Association of Collateral Status and Ischemic Core Growth in Patients With Acute Ischemic Stroke.

OBJECTIVE: To test the hypothesis that patients with acute ischemic stroke with poorer collaterals would have faster ischemic core growth, we included 2 cohorts in the study: cohort 1 of 342 patients for derivation and cohort 2 of 414 patients for validation. METHODS: Patients with acute ischemic stroke with large vessel occlusion were included. Core growth rate was calculated by the following equation: core growth rate = acute core volume on CT perfusion (CTP)/time from stroke onset to CTP. Collateral status was assessed by the ratio of severe hypoperfusion volume within the hypoperfusion region of CTP. The CTP collateral index was categorized in tertiles; for each tertile, core growth rate was summarized as median and interquartile range. Simple linear regressions were then performed to measure the predictive power of CTP collateral index in core growth rate. RESULTS: For patients allocated to good collateral on CTP (tertile 1 of collateral index), moderate collateral (tertile 2), and poor collateral (tertile 3), the median core growth rate was 2.93 mL/h (1.10-7.94), 8.65 mL/h (4.53-18.13), and 25.41 mL/h (12.83-45.07), respectively. Increments in the collateral index by 1% resulted in an increase of core growth by 0.57 mL/h (coefficient 0.57, 95% confidence interval [0.46, 0.68], p < 0.001). The relationship of core growth and CTP collateral index was validated in cohort 2. An increment in collateral index by 1% resulted in an increase of core growth by 0.59 mL/h (coefficient 0.59 [0.48-0.71], p < 0.001) in cohort 2. CONCLUSION: Collateral status is a major determinant of ischemic core growth.

Perfusion Computed Tomography Accurately Quantifies Collateral Flow After Acute Ischemic Stroke.

Background and Purpose- This study aimed to derive and validate an optimal collateral measurement on computed tomographic perfusion imaging for patients with acute ischemic stroke. Methods- In step 1 analysis of 22 patients, the parasagittal region of the ischemic hemisphere was divided into 6 pial arterial zones to derive the optimal collateral threshold by receiver operating characteristic analysis. The collateral threshold was then used to define the collateral index in step 2. In step 2 analysis of 156 patients, the computed tomographic perfusion collateral index was compared with collateral scores on dynamic computed tomographic angiography in predicting good clinical outcome by simple regression. Results- The optimal collateral threshold was delay time >6 s (sensitivity, 88%; specificity, 92%). The computed tomographic perfusion collateral index, defined by the ratio of delay time >6 s/delay time >2 s volume, showed a significant correlation with dynamic computed tomographic angiography collateral scores (correlation coefficient, 0.62; P<0.001), with an optimal cut point of 31.8% in predicting good collateral status (sensitivity of 83% and specificity of 86%). When predicting good clinical outcome, the delay time collateral index showed a similar predictive power to dynamic computed tomographic angiography collaterals (area under the curve, 0.78 [0.67-0.83] and 0.77 [0.69-0.84], respectively; P<0.001). Conclusions- Computed tomographic perfusion can accurately quantify collateral flow after acute ischemic stroke.

Dynamic CT but Not Optimized Multiphase CT Angiography Accurately Identifies CT Perfusion Target Mismatch Ischemic Stroke Patients.

Imaging protocols for acute ischemic stroke varies significantly from center to center leading to challenges in research translation. We aimed to assess the inter-rater reliability of collateral grading systems derived from dynamic computed tomography angiography (CTA) and an optimized multiphase CTA and, to analyze the association of the two CTA modalities with CT perfusion (CTP) compartments by comparing the accuracy of dynamic CTA (dCTA) and optimized multiphase CTA (omCTA) in identifying CT perfusion (CTP) target mismatch patients. Acute ischemic stroke patients with a proximal large vessel occlusion who underwent whole brain CTP were included in the study. Collateral status were assessed using ASPECTS collaterals (Alberta Stroke Program Early CT Score on Collaterals) and ASITN/SIR collateral system (the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology) on dCTA and omCTA. Eighty-one patients were assessed, with a median ischemic core volume of 29 mL. The collateral assessment with ASPECTS collaterals using dCTA have a similar inter-rater agreement (K-alpha: 0.71) compared to omCTA (K-alpha: 0.69). However, the agreement between dCTA and CTP in classifying patients with target mismatch was higher compared to omCTA (Kappa, dCTA: 0.81; omCTA: 0.64). We found dCTA was more accurate than omCTA in identifying target mismatch patients with proximal large vessel occlusion.

Influence of occlusion site and baseline ischemic core on outcome in patients with ischemic stroke.

OBJECTIVE: We assessed patient clinical outcomes based on occlusion location, focusing on distal occlusions to understand if occlusion location was an independent predictor of outcome, and tested the relationship between occlusion location and baseline ischemic core, a known predictor of modified Rankin Scale (mRS) score at 90 days. METHODS: We analyzed a prospectively collected cohort of thrombolysis-eligible ischemic stroke patients from the International Stroke Perfusion Imaging Registry who underwent multimodal CT pretreatment. For the primary analysis, logistic regression was used to predict the effect of occlusion location and ischemic core on the likelihood of excellent (mRS 0-1) and favorable (mRS 0-2) 90-day outcomes. RESULTS: This study included 945 patients. The rates of excellent and favorable outcome in patients with distal occlusion (M2, M3 segment of middle cerebral artery, anterior cerebral artery, and posterior cerebral artery) were higher than M1 occlusions (mRS 0%-1%, 55% vs 37%; mRS 0%-2%, 73% vs 50%, p < 0.001). Vessel occlusion location was not a strong predictor of outcomes compared to baseline ischemic core (area under the curve, mRS 0-1, 0.64 vs 0.83; mRS 0-2, 0.70 vs 0.86, p < 0.001). There was no interaction between occlusion location and ischemic core (interaction coefficient 1.00, p = 0.798). CONCLUSIONS: Ischemic stroke patients with a distal occlusion have higher rate of excellent and favorable outcome than patients with an M1 occlusion. The baseline ischemic core was shown to be a more powerful predictor of functional outcome than the occlusion location, but the relationship between ischemic core and outcome does not different by occlusion locations.

A Modified Reach-to-Grasp Task in a Supine Position Shows Coordination Between Elbow and Hand Movements After Stroke.

Objective: A modified reach-to-grasp task has been developed for the purpose of investigating arm-hand coordination in a supine position in the functional magnetic resonance imaging environment. The objective of this study was to investigate the kinematics of the reach-to-grasp task, in stroke and healthy participants. Design: Observational cohort study. Setting: Movement laboratory. Participants: Ten stroke participants and 10 age-matched healthy participants performed 10 repetitions of the modified reach-to-grasp task in two conditions-a natural condition and a standardized condition in a splint. Intervention: Not applicable. Main Outcome Measures: Kinematic variables of start time of transport, start time of aperture, movement duration, time of peak velocity (PV), percentage time of PV, peak deceleration (PD), percentage time of PD, peak aperture (PA), time of PA, and percentage time of PA were recorded. The correlation between key events in the grasp and transport trajectories were investigated. Performance between conditions and groups were compared. Results: Both groups demonstrated a significant correlation between the start time of aperture and the start time of transport and between the time of PA and PV in both conditions. A significant correlation was found between the time of PA and the PD in both conditions for the healthy group, but in neither condition for the stroke group. Movements by participants with stroke had a significantly longer movement duration, a smaller PV, and an earlier absolute time of PV and PD, and an earlier percentage time of PV and PD. They also had a smaller aperture than healthy participants. Wearing the splint resulted in a significantly higher PV, later absolute and percentage time of PV, PD, and PA, and a smaller PA compared to moving without the splint. The timing of transport variables time to peak velocity and time to peak deceleration, were strongest determinants of movement duration. Conclusion: The modified reach-to-grasp movement performed without the constraint of the splint, demonstrates similar motor control and coordination between the grasp and transport components of reach-to-grasp as in seated reach-to-grasp. This provides a new task that may be used to explore reach-to-grasp in the fMRI environment.

Intravenous Thrombolysis May Not Improve Clinical Outcome of Acute Ischemic Stroke Patients Without a Baseline Vessel Occlusion.

Background and Purpose: The benefit of thrombolysis in ischemic stroke patients without a visible vessel occlusion still requires investigation. This study tested the hypothesis that non-lacunar stroke patients with no visible vessel occlusion on baseline imaging would have a favorable outcome regardless of treatment with alteplase. Methods: We utilized a prospectively collected registry of ischemic stroke patients [the International Stroke Perfusion Imaging Registry (INSPIRE)] who had baseline computed tomographic perfusion and computed tomographic angiography. The rates of patients achieving modified Rankin Scale (mRS) 0-1 were compared between alteplase treated and untreated patients using logistic regression to generate odds ratios. Results: Of 1569 patients in the INSPIRE registry, 1,277 were eligible for inclusion. Of these, 306 (24%) had no identifiable occlusion and were eligible for alteplase, with 141 (46%) of these patients receiving thrombolysis. The treated and untreated groups had significantly different median baseline National Institutes of Health Stroke Scale (NIHSS) [alteplase 8, interquartile range (IQR) 5-10, untreated 6, IQR 4-8, P < 0.001] and median volume of baseline perfusion lesion [alteplase 5.6 mL, IQR 1.3-17.7 mL, untreated 2.6 mL, IQR 0-6.7 mL, P < 0.001]. After propensity analysis, alteplase treated patients without a vessel occlusion were less likely to have an excellent outcome (mRS 0-1; 56%) than untreated (78.8%, OR, 0.42, 95% confidence interval, 0.24-0.75, P = 0.003). Conclusions: In this non-randomized comparison, alteplase treatment in patients without an identifiable vessel occlusion did not result in higher rates of favorable outcome compared to untreated. However, treated patients displayed less favorable baseline prognostic factors than the untreated group. Further studies may be required to confirm this data.

[Tissue culture and polyploidy induction of Morinda officinalis].

OBJECTIVE: To establish an effective protocol for plant generation and induce polyploidy of Morinda offcinalis. METHOD: Callus was induced from immature embryo of M. officinalis and polyploidy was inducted by using colchicine treatment method. Chromosome was detected by flow cytometry. RESULT AND CONCLUSION: The highest induction rate of polyploidy was 18.40%, which was obtained with 500 mg x L(-1) colchicine treatment for 5 days. Roots of polyploid were bigger than diploid. Advantages of using immature embryo as explants are easy for sterilization, higher rate of callus induction and low degree dedifferentiation. The induced polyploidy of M. officinalis may have a value for spread of cultivation.

[Advances in the study of fertilization mechanism of angiosperms].

The fertilization of angiosperms is a complicated and ingenious process. When pollen tube arrives at ovary and enters embryo sac by degenerated synergid, two sperm cells are released into the cell. Two sperm cells are connected together at first in the pollen tube, and then separated in the degenerated synergid. One of the two sperm cells moves to the egg cell and fuses with it to form a zygote, and another one to central cell and fuses to form the endosperm, which completes the double fertilization. The process of male and female gamete recognition is a key link but we know nothing about it. This review introduced the study of cell cycle of male and female gametes before fertilization; discussed the question of synergid degeneration; analysed status of research into the movement of both sperm cells in degenerated synergid; and evaluated the preferential fertilization of sperm cells and the egg cell activation of angiosperms. The results of recent research into these questions may help us to understand the fertilization mechanism in angiosperms.

[Advances in cell biological researches on male sterility of higher plants].

Male sterility of higher plants is multiform in pollen abortion and has varied and complicated mechanisms. It is an active field to probe the mechanisms. Recently, some new results in this field have been obtained by using the methods of cell biology, including the structure and function of tapetal cell, the changes in Ca(2+) distribution, ATPase activity distribution, cytoskeleton array and programmed cell death in anther cells. All of the results gave us some new understanding for the process of pollen abortion. These results will make a link between the researches of individual and molecular level in male sterility of higher plants, and help us understand the mechanisms of male sterility of higher plants. This paper summarizes the knowledge about aborting process of male sterile anther obtained by the methods of cell biology.

[The distribution of ATPase in developmental anther of rice].

The distribution of ATPase was studied using lead precipitation technique during anther development in rice. The ATPase reactive precipitates (ppts) were located mostly in the nucleus of microspore mother cells (MMC) and only a few in the cytoplasm (Plate I-1). Anther wall had differentiated into four layers of cells and a few precipitates were located in the cells except the nucleus of tapetal cells where there were many ATPase reactive precipitates (Plate I-2). After meiosis of MMC, tapetal cells formed many endoplasmic reticula in its cytoplasm but still contained a few ppts. In the cells of epidermis, endothelium and middle layer, the ppts increased evidently in plasma membrane and near cytoplasm than before (Plate I-5). There were a large number of ppts located in the pollen wall during pollen development (Plate I-6), suggesting that ATPase is necessary for the construction of pollen wall. The exine of pollen wall of rice was constructed during microspore development and consisted of sporopollenin which came from tapetal cells. The ppts in exine also came from tapetal cell (Plate II-7). The intine of pollen wall was constructed during the stage of 2-cellular pollen and consisted of cellulose material coming from vegetative cell of pollen. The ATPase and ppts in intine came from vegetative cell of pollen (Plate III-7). Vegetative cell contained more ppts than generative cell during the development of 2-cellular pollen (Plate II-4, 5). The amount of ppts between two sperm cells in a pollen grain was also different (Plate IV-3,4). The physiological functions of ATPase located in different cells and different parts in the cells during anther development of rice were analyzed.

[Calcium distribution in fertile and sterile anthers of a genic male sterile Chinese cabbage].

Potassium antimonite was used to locate calcium in the fertile and sterile anthers of a genic male sterile Chinese cabbage (Brassica campestris L. ssp. chinensis Makino) to probe the relation between Ca(2+) and fertility and sterility of anthers of the cabbage. During fertile anther development, calcium granules increase in number in anther wall cells after meiosis, and then appeared also in locule, suggesting a calcium influx into locule from anther wall cells (Plate I-4). Then the number of calcium granules in microspore cytoplasm also increased at early stage (Plate II-1), accumulated mainly on the membrane of small vacuoles which were fusing to form big ones to make a polarity in the cell and to prepare asymmetric division of microspore (Plate II-3,4). After microspore division and the big vacuole decomposition, many calcium granules accumulated again on the membrane of the vacuoles (Plate III-1,2), displaying calcium regulates vacuole formation and decomposition during pollen development. In sterile anthers, abnormal distribution of calcium granules first appeared in callus wall of microspore mother cell (Plate IV-1). However, only a few calcium granules appeared in early microspores, which then could not form small vacuoles and finally a big vacuole (Plate IV-2,3). The aborting microspores degenerate by cytoplasm shrinking (Plate IV-5,6). The difference pattern of distribution of calcium granules between the fertile and sterile anthers indicates that anomalies in the distribution of calcium accumulation are correlated with the failure of pollen development and pollen abortion.

[The dynamic of calcium distribution during megasporegenesis of lettuce (Lactuca sativa L.)].

Potassium antimonite was used to deposit calcium in the young ovule of lettuce (Lactuca sativa L.) at megasporogenesis stage to study the relationship between calcium and megaspore degeneration. At the megaspore mother cell stage, few calcium granules were formed in the cell (Plate I-1, 2). After meiosis of megaspore mother cell and forming an arrayed tetrad in a line (Plate I-3), three megaspores degenerated one by one from the micropyle end. In the process of degeneration, the numbers of calcium granules decreased in the three megaspores. After the first megaspore degenerated, the number of calcium granules decreased in the second megaspore, which began to degenerate (Plate II-7, 8). The third megaspore also had its number of calcium granules diminishing before it degenerated (Plate III-13, 14). The fourth megaspore always accumulated many calcium granules in the cytoplasm during its development (Plate IV-17, 18) and finally becomes functional one that will develop into an embryo sac (Plate IV-20). Megaspore degeneration is a process of programmed cell death which may be closely related with change in calcium content: when a megaspore of tetrad decreases calcium content the cell begins to degenerate, and when calcium increases in the cell, it will continue to develop into a functional megaspore. This is the first report about calcium distribution in megaspores of a tetrad during megasporogenesis in higher plants and will open a door to study the physiological function of calcium in megasporogenesis.

[Isolation of egg cells and zygotes from Torenia fournieri].

Torenia fournieri is a special plant with embryo sac partly protruding through the micropyle of ovule, and its egg cell, two synergids and part of the central cell can be clearly observed using light microscope (Plate I-1, 2). The feature of embryo sac of T. fournieri makes it easy to isolate egg cell and zygote, especially for physiologically mature and vigorous egg cell to study its fertilization mechanism. Egg cells of T. fournieri were isolated from embryo sacs 2 d after anthesis using enzymatic digestion or mechanical dissection after mild osmotic shock (Plate I-3, 4). About 5% egg cells (2-3 from 50 ovules) could be mechanically dissected within 2 h. When 0.1% cellulase and 0.1% pectinase were added into the solution, about 18% egg cells (8-10 from 50 ovules) could be isolated within 2 h (Plate I-5). Although egg cells could be isolated by mechanical dissection, they can be used in in vitro fertilization to probe fertilization mechanism without deleterious effect of enzymatic action on the surface of egg cell. But it is easier to isolate egg cells by using enzymatic digestion, and more egg cells can be obtained for the research of molecular biology. Using enzymatic digestion method, the zygote of Torenia fournieri was also isolated from the pollinated ovules (Plate I-7-10). Basing on our successful isolation of mature sperm cells, the isolation of egg cells of T. fournieri will make in vitro fertilization possible for the first time in a dicot plant.

[The distribution of calcium in the stigma and style of tobacco during pollen germination and tube growth].

After pollen grains of tobacco landed on stigma they begin to hydrate and form many small vesicles containing some calcium grains in cytoplasm. The calcium stored in pollen wall is released into tectum of stigma to make a calcium-rich environment. When a pollen tube penetrates the tectum and grows between stigma cells, numerous calcium precipitates appear in the tip tube wall. The length of style of tobacco is 4 cm, and the pollen tube need take 44 h to reach the ovary. The style was artificially divided into 4 stages and each 1 cm respectively. There were only a few of calcium precipitates in the transmitting tissue of style from anthesis to 11 h after pollination. A calcium gradient in the transmitting tissue of style was formed at 22 h after pollination: only a few calcium precipitates found in the transmitting tissue of the style under stigma and at stage 1, 2 and 3, and many of them were located in the transmitting tissue of style near ovary (stage 4). When the flowers were emasculated and unpollinated at 1 d after anthesis, no calcium gradient in the transmitting tissue of style could be identified because some precipitates were also accumulated in the transmitting tissue at stage 1. When a flower without pollination was kept for 3 d, some calcium precipitates were formed in the cells of stigma, and the cells of the whole transmitting tissue contained the same quantity of calcium precipitates. To check the ability of pollen to germinate and grow in a low calcium environment, pollen grains were cultured in a medium containing 0-0.1% CaCl(2).2H(2)O. The result of in vitro assay confirmed that tobacco pollen can germinate and the pollen tube can grow in an environment with a very low concentration of calcium, which may be similar to the environment in the stigma. A few calcium precipitates were accumulated in stigma and upper transmitting tissue of tobacco to make a calcium gradient in the style. If the calcium in the style at 1 cm increases it will be increased more at 4 cm, and more in ovules, and more in synergid cells to keep the calcium gradient. When the emasculated flowers were not pollinated for 3 days the calcium in upper transmitting tissue evidently increases. The calcium in style is abundant in all plants, but the distribution of calcium in style is different between different plant species. For this difference, it may differ from types of style, and in the plants with short style the calcium gradient in the style is too small to be detected. But for tobacco with style 4 cm long, the gradient can be identified using antimonate method.