Single-cell analysis of the nervous system at small and large scales with instant partitions.

Single-cell RNA sequencing is a new frontier across all biology, particularly in neuroscience. While powerful for answering numerous neuroscience questions, limitations in sample input size, and initial capital outlay can exclude some researchers from its application. Here, we tested a recently introduced method for scRNAseq across diverse scales and neuroscience experiments. We benchmarked against a major current scRNAseq technology and found that PIPseq performed similarly, in line with earlier benchmarking data. Across dozens of samples, PIPseq recovered many brain cell types at small and large scales (1,000-100,000 cells/sample) and was able to detect differentially expressed genes in an inflammation paradigm. Similarly, PIPseq could detect expected and new differentially expressed genes in a brain single cell suspension from a knockout mouse model; it could also detect rare, virally-la-belled cells following lentiviral targeting and gene knockdown. Finally, we used PIPseq to investigate gene expression in a nontraditional model species, the little skate (Leucoraja erinacea). In total, PIPSeq was able to detect single-cell gene expression changes across models and species, with an added benefit of large scale capture and sequencing of each sample.

Temperature and pressure dependence of the luminescence of Eu(2+)-doped fluoride crystals Ba(x)Sr(1-x)F(2) (x = 0, 0.3, 0.5 and 1): experiment and model.

This paper summarizes experimental evidence of anomalous luminescence in Eu(2+)-doped fluoride crystals Ba(x)Sr(1-x)F(2) (x = 0, 0.3, 0.5 and 1). Luminescence, luminescence excitation spectra and luminescence kinetics obtained at ambient and high hydrostatic pressure at various temperatures are discussed. Hydrostatic pressure was shown to cause a redshift of normal [Formula: see text] emission and anomalous luminescence. The experimental data shows the existence of temperature- and pressure-induced spectral transformations where the anomalous luminescence is replaced by normal emission of Eu(2+) centers. We present a model that predicts a strong electron-lattice coupling of the trapped excitons as well as the pressure effect of the spectral transformation from anomalous to normal emission.

Enhancement of fibrinolysis in vitro by ultrasound.

The effect of ultrasound on the rate of fibrinolysis has been investigated using an in vitro system. Plasma or blood clots containing a trace label of 125I fibrin were suspended in plasma containing plasminogen activator and intermittently exposed to continuous wave 1-MHz ultrasound at intensities up to 8 W/cm2. Plasma clot lysis at 1 h with 1 microgram/ml recombinant tissue plasminogen activator (rt-PA) was 12.8 +/- 1.2% without ultrasound and was significantly (P = 0.0001) increased by exposure to ultrasound with greater lysis at 1 W/cm2 (18.0 +/- 1.4%), 2 W/cm2 (19.3 +/- 0.7%), 4 W/cm2 (22.8 +/- 1.8%), and 8 W/cm2 (58.7 +/- 7.1%). Significant increases in lysis were also seen with urokinase at ultrasound intensities of 2 W/cm2 and above. Exposure of clots to ultrasound in the absence of plasminogen activator did not increase lysis. Ultrasound exposure resulted in a marked reduction in the rt-PA concentration required to achieve an equivalent degree of lysis to that seen without ultrasound. For example, 15% lysis occurred in 1 h at 1 microgram/ml rt-PA without ultrasound or with 0.2 microgram/ml with ultrasound, a five-fold reduction in concentration. Ultrasound at 1 W/cm2 and above also potentiated lysis of retracted whole blood clots mediated by rt-PA or urokinase. The maximum temperature increase of plasma clots exposed to 4 W/cm2 ultrasound was only 1.7 degrees C, which could not explain the enhancement of fibrinolysis. Ultrasound exposure did not cause mechanical fragmentation of the clot into sedimentable fragments, nor did it alter the sizes of plasmic derivatives as demonstrated by SDS polyacrylamide gel electrophoresis. We conclude that ultrasound at 1 MHz potentiates enzymatic fibrinolysis by a nonthermal mechanism at energies that can potentially be applied and tolerated in vivo to accelerate therapeutic fibrinolysis.

Myocardial contrast two-dimensional echocardiography: dose-myocardial effect relations of intracoronary microbubbles.

It is controversial whether echocardiographic contrast agents prepared by sonication cause transient myocardial depression beyond that known to occur with contrast agents alone. In nine open chest dogs, contrast injections were made into the left anterior descending coronary artery during two-dimensional echocardiography. One hundred forty-four recordings were analyzed subsequently, by an observer who was unaware of other data, for percent depression of systolic wall thickening, duration of regional wall motion abnormalities, peak contrast enhancement and contrast washout. Two microbubble sizes were obtained by sonicating Renografin-76 (meglumine sodium diatrizoate): mean diameter 12 +/- 3 (SEE) and 20 +/- 6 micron. Four doses (range 0.5 to 3 ml) of each of four agents (12 and 20 micron bubbles in Renografin, nonsonicated Renografin and saline solution) were injected in random order. Significant relations were found between percent depression of systolic wall thickening, duration of regional wall motion abnormalities and contrast washout time versus microbubble size (p less than 0.001) and microbubble dose (p less than 0.01). Little increased contrast effect was found at larger doses or with larger microbubbles compared with the smaller doses and size studied. Injections of nonsonicated Renografin caused less depression of systolic wall thickening (p less than 0.05), faster resolution of wall motion abnormalities (p less than 0.05), less contrast (p less than 0.001) and more rapid contrast washout (p less than 0.001) than did 12 micron bubbles in Renografin. A significant correlation was found between the duration of regional wall motion abnormalities and contrast washout time (r = 0.93, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Generating precision microbubbles for use as an echocardiographic contrast agent.

To investigate whether precision microbubbles can be simply generated and used for quantitative contrast echocardiographic studies, precision microbubbles were fabricated in gelatin using a simple generator. The generator consisted of a fluid pump, a generating site containing a narrow bore tube and a bubble stream output port. Up to 5,000 microbubbles/s were generated with a controllable radius of 80 to 150 mu. No detectable interbubble size variation was observed under high power microscopy. To examine whether these bubbles could be used for quantitative contrast echocardiographic studies, they were then infused into a tube with a known flow of degassed water during ultrasonic imaging. The resulting ultrasonic contrast effect in the tube lumen at steady state was recorded and subsequently measured by videodensitometry. The precision microbubbles were visually and microscopically stable during the experimental run. Correlations between microbubble infusion rate and luminal videodensitometry on individual runs were r = 0.89, 0.83, 0.73 and 0.71. It is concluded that precision microbubbles can be generated in sufficient quantities on site to serve as an echocardiographic contrast agent for quantitative studies in vitro and at a very modest cost. These precision microbubbles are sufficiently stable to be collected and stored for short periods of time.

The safety of contrast echocardiography: report of the Committee on Contrast Echocardiography for the American Society of Echocardiography.

The results of a survey of 363 physicians performing echocardiography were evaluated to assess the relative safety of contrast echocardiography. Fifteen physicians reported a variety of transient side effects, including neurologic and respiratory symptoms. Although contrast echocardiography appeared to carry some risk for side effects, that risk was low (0.062%) and no residual side effects or complications were observed. In view of the significant benefits reported for contrast echocardiography, it appears to remain a valuable technique that is safer than currently available alternative diagnostic modalities. However, during contrast echocardiography, precautions should be taken to prevent the injection of visible amounts of air, especially in patients with a right to left shunt or arterial catheters.

Intravenous contrast echocardiography with use of sonicated albumin in humans: systolic disappearance of left ventricular contrast after transpulmonary transmission.

The transmission of echocardiographic contrast medium and the cyclic changes in left ventricular videodensity during transpulmonary contrast echocardiography were investigated in nine adult volunteers with the use of intravenous injections of sonicated albumin (microbubble size 5.2 +/- 2.6 microns). Right and left ventricular and myocardial contrast were quantitated by videodensitometric analysis. The injections caused no symptoms, and no hemodynamic or electrocardiographic changes were observed. All injections resulted in right ventricular contrast. Mean peak right ventricular videodensity was 75 +/- 48 at end-diastole and 61 +/- 36 gray scale U/pixel at end-systole (p less than 0.05). Seventy-eight percent of injections resulted in left ventricular contrast with a mean peak videodensity of 21 +/- 33 gray scale U/pixel. Early systole was associated with a rapid decrease in left ventricular contrast intensity with near total disappearance of contrast by end-systole (from 23 +/- 33 and 17 +/- 23 U/pixel at end-diastole to 6 +/- 10 and 3 +/- 2 at end-systole at the left ventricular base and apex, respectively; p less than 0.05). None of the injections resulted in myocardial contrast enhancement by visual or quantitative analysis. Thus, left ventricular contrast echocardiography can be achieved after intravenous injections of sonicated albumin. Transpulmonary left ventricular contrast echocardiography is associated with near total disappearance of contrast during systole. This may be secondary to the destruction of microbubbles by the high left ventricular systolic pressure. These findings may help explain the limited success of this technique thus far for myocardial perfusion imaging.

Ultrasound enhancement of thrombolysis and reperfusion in vitro.

OBJECTIVES: The aims of this study were 1) to develop an in vitro flow system in which reperfusion mediated by ultrasound-accelerated thrombolysis could be studied, and 2) to test whether ultrasound-accelerated thrombolysis could hasten reperfusion in this system. BACKGROUND: Ultrasound has been shown to increase tissue plasminogen activator (t-PA)-induced thrombolysis in vitro as assessed by radioactive fibrinogen release from labeled clots and in an animal in vivo model. METHODS: To test whether reperfusion is accelerated, we created obstructive whole blood clots in an in vitro flow system. Four control clots were exposed to ultrasound only without any thrombolytic agent (group 1). Sixteen clots were exposed to continuous infusion of recombinant tissue-type plasminogen activator rt-PA and randomized to either continuous wave ultrasound exposure at a frequency of 0.5 MHz and an intensity of 8 W/cm2 (group 2) or to no ultrasound (group 3). Flow distal to the clot and the rate of release of radiolabeled fibrin products were used as an index of reperfusion and thrombolysis, respectively. Samples were obtained for measurements of lytic variables such as plasminogen, fibrinogen and rt-PA concentrations. RESULTS: Flow was significantly higher in the rt-PA-treated clots within 10 min of exposure to ultrasound than in those without such exposure (9.4 +/- 9.9% of maximal flow in group 2 vs. 0.5 +/- 1.5% in group 3, p < 0.05). The maximal difference in flow between groups 2 and 3 was achieved at 25 min (61.0 +/- 30.4% vs. 14.2 +/- 14.7%, p = 0.03). Thrombolysis was significantly higher after 15 min of ultrasound exposure (12.8 +/- 9.1% in the ultrasound-treated group 2 vs. 4.0 +/- 3.9% in group 3, p < 0.05). The maximal difference between groups 2 and 3 occurred at 25 min (26.7 +/- 13.1% vs. 7.24 +/- 5.7%, p < 0.004). Neither flow nor clot lysis occurred in group 1. Plasminogen and fibrinogen concentrations and rt-PA antigen concentrations were consistent with those observed during fibrinolytic therapy in vivo. CONCLUSIONS: Continuous wave ultrasound at 0.5 MHz and an intensity of 8 W/cm2 accelerates rt-PA-induced thrombolysis and reperfusion in vitro.

Microbubbles have intracardiac velocities similar to those of red blood cells.

The slope of an individual contrast trajectory on M-mode echocardiography represents the projection of the intracardiac velocity vector of a microbubble in the direction of the sound beam. Doppler echocardiography measures this projection of red blood cell velocity. To ascertain whether microbubbles have similar intracardiac velocities to those of red blood cells, 11 subjects were studied during intravenous injections of 5% dextrose solution. The flow across the tricuspid and pulmonary valves was examined. Microbubble velocity was measured by M-mode contrast slope analysis and simultaneously by Doppler technique. Results from both methods were correlated with red blood cell velocity measured by Doppler recording at the same time in the cardiac cycle, shortly before appearance of contrast medium (3 to 8 beats before the corresponding contrast velocity measurements). In all subjects, 10 sets of three velocities each (M-mode slope and Doppler data before and during contrast injection) were obtained for each valve. Visual inspection of the Doppler tracings showed similar velocity profiles before and during contrast appearance; the signal intensity was greater with contrast. Quantitatively, microbubble velocity assessed by M-mode trajectory slopes correlated well with the Doppler-derived velocity of red blood cells (r = 0.98, p less than 0.001, slope of the regression line = 0.99, standard error of the estimate = 7 cm/s). Doppler velocities measured with and without contrast medium showed a similar correlation (r = 0.99, p less than 0.001, slope of regression = 1.01, standard error of the estimate = 6 cm/s). In individual subjects, the correlation coefficient between microbubble and red blood cell velocities ranged form 0.978 to 0.998.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility of quantitative myocardial contrast echocardiography.

To determine whether myocardial contrast echocardiography is quantitatively reproducible, repeated intracoronary injections of sonicated albumin (5%) were performed in eight open chest dogs. Paired injections were performed at baseline, during ischemia produced by ligation of a coronary artery, and during hyperemia induced by intravenous infusion of 0.75 mg/kg body weight of dipyridamole. Contrast washout curves were generated for the left anterior descending coronary artery territory (ischemic area) and left circumflex coronary artery territory (nonischemic area) by beat per beat analysis of frozen end-diastolic frames of left ventricular short-axis views. Peak contrast intensity, contrast washout half-time and area under the curve were derived from these curves. A total of 75 contrast washout curves were analyzed for the study of interinjection, intraobserver and interobserver reproducibility. The correlation coefficients between measurements obtained from paired injections of the echocardiographic contrast agent (interinjection reproducibility) ranged from 0.78 for peak contrast intensity to 0.87 for area under the curve. Percent error varied between 14.7% and 24.7%. The intraobserver variability in measurements was less than the interinjection variability, with a cumulative mean percent error of 17.8% and correlation coefficients of 0.72 (peak contrast intensity), 0.95 (area under the curve) and 0.96 (washout half-time). Interobserver correlation for all indexes was high (r = 0.92 to 0.96). It is concluded that peak contrast intensity, contrast washout half-time and the area under the curve derived from myocardial contrast washout curves can be measured reproducibly from videotapes. In addition, the variability between two injections attempted under identical conditions is greater than reader variability from videotapes.

Spontaneous contrast in the inferior vena cava in a patient with constrictive pericarditis.

A 66 year old black man was examined because of fatigue and progressive right heart failure. A striking finding on his echocardiogram was intense and slow-moving contrast in the inferior vena cava. Cardiac catheterization revealed constrictive pericarditis, and pericardiectomy was performed. Postoperatively, spontaneous contrast was no longer present. This case helps explain the origin of spontaneous inferior vena cava contrast.

Myocardial perfusion imaging in humans by contrast echocardiography using polygelin colloid solution.

This study evaluated the myocardial contrast effect and safety of polygelin colloid solution selectively injected into the coronary arteries in 25 patients during two-dimensional echocardiography. Six patients (group I) had selective intracoronary injections of nonagitated and 19 (group II) of hand-agitated polygelin colloid solution. Myocardial contrast was seen on two-dimensional echocardiographic cross sections in three patients of group I and in all patients of group II; in 16 patients it was also seen on M-mode echocardiograms. The contrast effect lasted for 15 to 60 seconds. The intensity of myocardial opacification was not significantly influenced by the amount of polygelin colloid solution injected, heart rate or cardiac size. The total number of contrast-enhanced segments after right and left coronary artery injections delineated the entire cross-sectional area in any given view. None of the patients developed symptoms during or immediately after the injections. One patient had transient second degree atrioventricular block after a right coronary wedge injection, one patient showed a QRS axis shift and two others had transient T wave changes. There were no aortic blood pressure changes and no significant serum enzyme (creatine kinase [CK], CK-MB fraction, glutamic oxaloacetic transaminase) elevation or alterations of left ventricular function assessed echocardiographically. It is concluded that hand-agitated polygelin colloid solution is a useful and safe intracoronary contrast agent for delineating myocardial perfusion areas on two-dimensional echocardiography in humans.

Embolic potential of left ventricular thrombus after myocardial infarction: a two-dimensional echocardiographic study of 119 patients.

Left ventricular thrombus complicating myocardial infarction was diagnosed by two-dimensional echocardiography in 119 patients. The infarct site was anterior in 98 patients and inferior in 11. Systemic embolism occurred in 26 patients (stroke in 18, lower limb embolism in 7 and mesenteric embolism in 1). A protruding configuration of the thrombus was more common in the patients with embolism than in those without (23 [88%] of 26 versus 17 [18%] of 93) (p less than 0.01). Free mobility of the thrombus was found in 15 (58%) of 26 and 3 (3%) of 93 cases, respectively (p less than 0.01). In predicting embolism, protruding thrombus configuration had a sensitivity of 88% and a specificity of 82%, and positive and negative predictive accuracy was 57 and 96%, respectively. For free mobility of the thrombus, sensitivity was 58%, specificity 97%, positive predictive accuracy 85% and negative predictive accuracy 89%. In the 46 patients whose echocardiogram was obtained during the hospital admission for the index infarct, repeat echocardiograms were obtained during oral anticoagulant therapy. Twelve of these 46 patients had embolism and 2 of the 12 died. In seven of these patients, full dose oral anticoagulant therapy had been given before embolism occurred and in five it was started after an embolic event. The thrombus decreased in size or disappeared in six patients; in four the thrombus showed no change, and in two of these four emboli recurred despite anticoagulation. It is concluded that two-dimensional echocardiography may help delineate the embolic potential of left ventricular thrombus complicating myocardial infarction and may be of value in weighing the benefits and disadvantages of oral anticoagulant therapy.

Quantitative assessment of the immediate results of coronary angioplasty by myocardial contrast echocardiography.

A low pressure gradient across the residual lesion and a minimal percent residual stenosis are markers of a successful coronary angioplasty. A more physiologic method of assessing the results of coronary angioplasty would involve assessment of myocardial perfusion in the affected coronary bed. Contrast two-dimensional echocardiography provides information about regional myocardial perfusion. To assess the correlation between pre- to postcoronary angioplasty changes in gradient or percent stenosis and the increase in peak contrast intensity, 23 consecutive patients were studied during coronary angioplasty. In 19 of the 23 patients, the coronary angioplasty was successful and in 15 (79%) of the 19, an adequate echocardiographic study was obtained. Mild and transient side effects of echo contrast were observed in 3 of the 15 patients. The gradient across the residual lesions decreased from 52 +/- 12 to 11 +/- 4 mm Hg (mean +/- SD), the diameter of the stenotic lesion decreased from 89 +/- 10 to 25 +/- 16% and corrected peak contrast intensity (peak contrast - baseline contrast in gray level U/pixel) increased from 15 +/- 16 to 50 +/- 26. All these differences were significant at the p less than 0.001 level. Corrected peak contrast intensity correlated exponentially with the decrease in pressure gradient (r = 0.82, p less than 0.001). The correlation curve had a greater increase in peak contrast intensity at gradient decreases greater than 45 mm Hg. Corrected peak contrast intensity did not correlate with decrease in diameter of the stenotic lesion (r = 0.19).

Accuracy of echocardiography versus electrocardiography in detecting left ventricular hypertrophy: comparison with postmortem mass measurements.

The accuracy of electrocardiography, M-mode echocardiography and two-dimensional echocardiography in predicting left ventricular hypertrophy was compared in 50 patients who came to autopsy within 6 months after the studies were performed. Several methods for determining left ventricular hypertrophy were examined for each of the three techniques. M-mode echocardiography was technically adequate to evaluate the presence or absence of left ventricular hypertrophy more often than either electrocardiography or two-dimensional echocardiography. Measurements from M-mode echocardiography also correlated best with autopsy measurements. Both echocardiographic techniques had a higher sensitivity than electrocardiographic criteria in diagnosing left ventricular hypertrophy. Two-dimensional echocardiography was not shown to improve the M-mode assessment of left ventricular hypertrophy. In an attempt to simplify both M-mode left ventricular mass calculations and the diagnosis of left ventricular hypertrophy for the clinician, a left ventricular mass nomogram was constructed, enabling quick insertion of standard M-mode echocardiographic measurements.

Myocardial perfusion imaging by contrast echocardiography with use of intracoronary sonicated albumin in humans.

Sonicated albumin has been proposed as a near ideal echocardiographic contrast agent with little myocardial toxicity or hemodynamic effect. Its use has not yet been reported in humans, partly because of difficulties in preparation. With use of the newly modified sonication method, 10 ml of 5% albumin was sonicated for 75 s with a 5.0 ml slow infusion of air. This resulted in microbubbles with a mean diameter (+/- SD) of 5 +/- microns). Fourteen patients undergoing routine coronary angiography were studied. One patient had normal coronary arteries; the other 13 had significant coronary artery disease. In a subgroup of nine patients, sonicated albumin and sonicated diatrizoate meglumine sodium (microbubble diameter 9 +/- 3 microns) were injected several minutes apart, using the same technique. Videodensity-time curves were obtained from a region of interest in the myocardium. Corrected peak contrast intensity (baseline contrast intensity subtracted from peak contrast intensity, gray scale U/pixel) for sonicated albumin and for sonicated diatrizoate meglumine sodium was 51 +/- 26 and 52 +/- 19, respectively (p = 0.89). Washout half-time (T1/2) for the two agents was 5.5 +/- 4.5 and 16.0 +/- 12.2 s, respectively (p = 0.01). One patient with unstable angina experienced transient chest pain after repeated albumin injections. No electrocardiographic changes, blood pressure changes or wall motion abnormalities were observed. Administered by intracoronary injection, sonicated 5% albumin is a safe and effective echocardiographic contrast agent for myocardial perfusion imaging, yielding excellent myocardial contrast with physiologic washout time.

How good is communication between primary care physicians and subspecialty consultants?

We prospectively studied the communication between 27 referring practitioners and their consultants for 464 consecutive patient referrals from a general internal medicine group practice at a university medical center. The rates of referral among practitioners varied from 0 to 28.1 per 100 patients visits. Though referring physicians provided patient background information in 98% of the cases, they made explicit the purpose of the referral in only 76% of the cases. They contacted consultants directly in only 9% of the cases. In return, consultants communicated their findings to referring practitioners in only 55% of the consultations. Referring physicians who personally contacted consultants or who supplied them with more clinical information were more likely to learn the results of the consultation. While communication between the referring physicians and consultants in this setting is limited, it may be improved if referring physicians supply more clinical information to consultants and contact them directly.

Cardiac catheterization under echocardiographic control in a pregnant woman.

A 22 year old woman had signs of rheumatic mitral and aortic valve disease early in pregnancy. Cardiac catheterization was performed during her third month of pregnancy under two-dimensional echocardiographic control without the use of ionizing radiation. Severe mitral stenosis with mild aortic stenosis was found. Five cubic centimeters of 5 percent dextrose in water were injected by hand to obtain left ventriculograms and supravalvular aortograms of sufficient quality to diagnose valvular regurgitation. The use of "echo-catheterization" may have significant advantages in selected clinical situations.

Systematic analysis of contrast echocardiograms.

Contrast echocardiography was first described in 1968. Since then, many reports have described clinical and experimental uses for the technique. Contrast echocardiography is performed at least occasionally in most echocardiography laboratories, but most physicians use this technique merely to determine the presence of a shunt or, more rarely, for structure identification. Contrast echocardiography can provide much more information. Some different types of information available from contrast echocardiographic records are discussed, including timing of contrast appearance within the cardiac cycle, relative timing of appearance in different cardiac structures, relative intensity of contrast opacification, cyclical changes in contrast opacification, negative contrast effect, slope of contrast trajectories on M-mode contrast echocardiography, and clearance times.

Two-dimensional echocardiographic appearance of left ventricular thrombi with systemic emboli after myocardial infarction.

To test the hypothesis that left ventricular (LV) thrombi that project into the lumen and are mobile are more likely to embolize than those that do not have these characteristics, the 2-dimensional echocardiograms of 16 patients with LV thrombi after myocardial infarction were retrospectively reviewed. Ten had evidence of peripheral embolization and 6 did not. The studies were reviewed in random order by an observer blinded to the clinical data. Each echocardiogram was graded as showing a protruding or nonprotruding thrombus and the presence or absence of increased mobility. The thrombus projected into the lumen on the echocardiograms of 8 of 10 patients who had had emboli and in 0 of 6 who had not. The thrombus had increased mobility in 4 of 10 patients with emboli and 0 of 6 without. Thus, LV thrombi that project into the lumen and have increased mobility are more likely to embolize than those without these characteristics.