Complete meiosis from human induced pluripotent stem cells

Gamete failure-derived infertility affects millions of people worldwide; for many patients, gamete donation by unrelated donors is the only available treatment. Embryonic stem cells (ESCs) can differentiate in vitro into germ-like cells, but they are genetically unrelated to the patient. Using an in vitro protocol that aims at recapitulating development, we have achieved, for the first time, complete differentiation of human induced pluripotent stem cells (hiPSCs) to postmeiotic cells. Unlike previous reports using human ESCs, postmeiotic cells arose without the over-expression of germline related transcription factors. Moreover, we consistently obtained haploid cells from hiPSCs of different origin (keratinocytes and cord blood), produced with a different number of transcription factors, and of both genetic sexes, suggesting the independence of our approach from the epigenetic memory of the reprogrammed somatic cells. Our work brings us closer to the production of personalized human gametes in vitro.

Myocardial blood flow response to pacing tachycardia and to dipyridamole infusion in patients with dilated cardiomyopathy without overt heart failure. A quantitative assessment by positron emission tomography

BACKGROUND

Myocardial blood flow (MBF) impairment has been documented in advanced dilated cardiomyopathy (DCM) in which hemodynamic factors, secondary to severe ventricular dysfunction, may limit myocardial perfusion. To assess whether MBF impairment in DCM may also be present independent of hemodynamic factors, the present study was designed to quantify myocardial perfusion in patients with mild disease without overt heart failure.

METHODS AND RESULTS

Absolute regional MBF (milliliters per minute per gram) was measured by positron emission tomography and 13N-ammonia in resting conditions, during pacing-induced tachycardia, and after dipyridamole infusion (0.56 mg/kg over 4 minutes) in 22 DCM patients and in 13 healthy subjects. Patients were in New York Heart Association functional class I-II and showed depressed left ventricular (LV) ejection fraction by radionuclide angiography (35 +/- 8%; range, 21% to 48%), normal coronary angiography, and normal or moderately increased LV end-diastolic pressure (9.2 +/- 5.5 mm Hg; range, 2 to 20 mm Hg). There were no differences in arterial blood pressure, heart rate, and rate-pressure product between patients and control subjects in the three study conditions. Compared with control subjects, DCM patients had lower mean MBF at rest (0.80 +/- 0.25 versus 1.08 +/- 0.20 mL.min-1.g-1, P < .01), during atrial pacing tachycardia (1.21 +/- 0.59 versus 2.03 +/- 0.64 mL.min-1.g-1, P < .01), and after dipyridamole infusion (1.91 +/- 0.76 versus 3.78 +/- 0.86 mL.min-1.g-1, P < .01). LV MBF values were related to baseline LV end-diastolic pressure at rest (r = -.57, P < .01) and during pacing (r = -.67, P < .01) but not after dipyridamole infusion (r = .19, P = .40). Five patients had LV end-diastolic pressure > 12 mm Hg; in 4, myocardial perfusion was severely depressed both at baseline and in response to stress.

CONCLUSIONS

In patients with DCM without overt heart failure, myocardial perfusion is impaired both at rest and in response to vasodilating stimuli. The abnormalities in vasodilating capability can be present despite normal hemodynamics; progression of the disease is associated with more depressed myocardial perfusion.

Homogeneously reduced versus regionally impaired myocardial blood flow in hypertensive patients: two different patterns of myocardial perfusion associated with degree of hypertrophy

OBJECTIVES

The aim of this study was to quantitatively measure regional and global myocardial blood flow and coronary reserve in hypertensive patients without coronary artery disease and to assess the correlation with left ventricular mass.

BACKGROUND

The effect of left ventricular hypertrophy on regional vasodilating coronary capability in arterial hypertension is controversial, and no quantitative method has been applied to assess a possible correlation.

METHODS

Positron emission tomography was performed in 50 untreated hypertensive patients and 13 normotensive subjects. Blood flow at baseline and after dipyridamole was globally and regionally measured by using nitrogen-13 ammonia; coronary reserve and resistance were calculated. Left ventricular mass was assessed by two-dimensional echocardiography.

RESULTS

In hypertensive patients, flow at baseline was similar to that of normotensive subjects (p = 0.21), but values were reduced after pharmacologic vasodilation (p < 0.05). This impairment of maximal coronary flow was not correlated with left ventricular mass (p = 0.13). Among hypertensive patients, we identified a group with a homogeneous distribution of perfusion and a group with a heterogeneous flow pattern. Flow was globally reduced in the former group, but it was abnormal only at the site of perfusion defects in the latter. Patients with regional defects showed the highest likelihood of having an increased left ventricular mass.

CONCLUSIONS

In arterial hypertension, left ventricular mass is not correlated with global myocardial blood flow. Nevertheless, patients with ventricular hypertrophy are likely to show a heterogeneous flow pattern with regional defects and almost normal blood flow in nonaffected regions. In hypertensive patients with a homogeneous perfusion pattern during stress, myocardial blood flow frequently shows a diffuse reduction.

Role of 2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the early assessment of response to chemotherapy in metastatic breast cancer patients

We investigated the role of 2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the early evaluation of response to chemotherapy in metastatic breast cancer patients. Breast cancer patients who received an epirubicin/paclitaxel--containing regimen as first-line treatment for metastatic disease were included in this study. A PET study was performed within 1 week before the start of treatment, at day 8 after the first course, and at the end of the planned program of chemotherapy. Tumor response was determined clinically and radiographically every 2 courses of treatment. Thirteen patients with metastatic breast cancer who were referred for treatment protocols with gemcitabine/epirubicin/paclitaxel or epirubicin/paclitaxel chemotherapy regimens were included in this study. All metastatic sites were easily visualized on the baseline FDG-PET images, obtained 50 to 60 minutes after tracer injection. Nine patients who completed the planned courses of chemotherapy and the FDG-PET studies were available for analysis. In the six patients who achieved a response to treatment, median glucose standard uptake value (SUV) (semiquantitative analysis) was 7.65 (range, 3.4-12.3) at baseline, 5.7 (range, 2.8-7.6) at day 8 after the first course, and 1.2 (range, 0.99-1.3) at the end of the 6 planned courses of chemotherapy. Three patients who obtained a stable disease as best response had no significant decrease in tumor glucose SUV compared to baseline levels. Qualitative visual analysis in the six responding patients showed a decrease in delineation of tumor mass from background activity soon after the first course, while the nonresponding patients had no significant modification from basal levels. Semiquantitative FDG-PET scanning of metastatic breast cancer sites showed a rapid and significant decrease in tumor glucose metabolism soon after the first course of treatment in patients who achieved a response to first-line chemotherapy. On the contrary, no significant decrease was observed in nonresponding patients.

Assessment of anatomic and physiological severity of single-vessel coronary artery lesions by dipyridamole echocardiography. Comparison with positron emission tomography and quantitative arteriography

BACKGROUND

The aim of this study was to compare the results of dipyridamole-echocardiography test (DET: two-dimensional echo monitoring during dipyridamole infusion up to 0.84 mg/kg over a period of 10 minutes) with both anatomic and physiological parameters of coronary artery disease severity, assessed by computer-assisted quantitative coronary arteriography, and regional coronary flow reserve, measured by [13N]ammonia (13NH3) and dynamic positron emission tomography (PET), respectively.

METHODS AND RESULTS

We studied 31 patients with a history of chest pain and neither previous myocardial infarction nor resting wall motion abnormalities. Eighteen patients had single-vessel disease (> 50% stenosis of one major coronary vessel), and 13 had normal coronary arteries. The criterion for DET positivity was the appearance of a new transient regional wall motion abnormality. In patients with a positive DET, two parameters were evaluated: the dipyridamole time (ie, the time from the beginning of drug infusion to the development of obvious dyssynergy) and the wall motion score index (WMSI, a semiquantitative integrated estimation of extent and severity of the stress-induced dyssynergy). WMSI was derived by summation of individual segment scores divided by the number of segments interpreted. Quantification of regional myocardial blood flow was obtained by PET measurements of 13NH3 arterial input function and left ventricular myocardial tissue concentration both at control and after dipyridamole (0.56 mg/kg over 4 minutes). Maximal regional blood flow after dipyridamole in the region supplied by the stenotic vessel was significantly lower in the 11 patients with coronary artery disease and positive DET than in the 7 patients with coronary artery disease and negative DET (1.08 +/- 0.33 versus 1.98 +/- 0.37 mL.min-1.g-1, P < .01). In patients with a positive DET, regional coronary flow reserve correlated well with dipyridamole time (r = .87, P < .01) but not with peak WMSI (r = .25, P = NS). Patients with dipyridamole-induced akinesia or dyskinesia (n = 6) had a greater reduction in regional coronary flow reserve than did those showing hypokinesia (n = 5): 1.38 +/- 0.51 versus 2.17 +/- 0.42, P < .05. Percent area reduction was more severe in patients with DET positivity than in those with DET negativity (93.7 +/- 8.7% versus 77 +/- 10.3%, P < .01), and it correlated with regional coronary flow reserve (r = .64, P < .01) and dipyridamole time (r = -.59, P < .01).

CONCLUSIONS

In patients with single-vessel disease, DET shows an excellent specificity but a limited sensitivity; in these patients, DET positivity is associated with a physiologically important coronary stenosis. Severity of the anatomic stenosis and impairment in regional flow reserve are greater when the dipyridamole-induced dyssynergy appears earlier during the test. Therefore, a stratification of the anatomo-physiological severity of coronary artery disease can be obtained with DET, based mainly on the temporal allocation of the transient dyssynergy.

Global alteration in perfusion response to increasing oxygen consumption in patients with single-vessel coronary artery disease

BACKGROUND

Recent evidence suggests that, in coronary artery disease (CAD), myocardial blood flow (MBF) regulation is abnormal in regions supplied by apparently normal coronary arteries. However, the relation between this alteration and MBF response to increasing metabolic demand has not been fully elucidated.

METHODS AND RESULTS

MBF was assessed at baseline, during atrial pacing tachycardia, and after dipyridamole (0.56 mg/kg IV over 4 minutes) in 9 normal subjects and in 24 patients with ischemia on effort, no myocardial infarction, and isolated left anterior descending (n = 19) or left circumflex (n = 5) coronary artery stenosis (> or = 50% diameter narrowing). Perfusion of both poststenotic (S) and normally supplied (N) areas was measured off therapy by positron emission tomography and [13N]ammonia. Normal subjects and CAD patients showed similar rate-pressure products at baseline, during pacing, and after dipyridamole. In CAD patients, MBF was lower in S than in N territories at rest (0.68 +/- 0.14 versus 0.74 +/- 0.18 mL.min-1.g-1, respectively, P < .05), during pacing (0.92 +/- 0.29 versus 1.16 +/- 0.40 mL.min-1.g-1, respectively, P < .01), and after dipyridamole (1.18 +/- 0.34 versus 1.77 +/- 0.71 mL.min-1.g-1, respectively, P < .01). However, normal subjects showed significantly higher values of MBF both at rest (0.92 +/- 0.13 mL.min-1.g-1, P < .05 versus both S and N areas), during pacing tachycardia (1.95 +/- 0.64 mL.min-1.g-1, P < .01 versus both S and N areas), and after dipyridamole (3.59 +/- 0.71 mL.min-1.g-1, P < .01 versus both S and N areas). The percent change in flow was strictly correlated with the corresponding change in rate-pressure product in normal subjects (r = .85, P < .01) but not in either S (r = .04, P = NS) or N regions (r = .08, P = NS) of CAD patients.

CONCLUSIONS

Besides epicardial stenosis, further factors may affect flow response to increasing metabolic demand and coronary reserve in patients with CAD.

Comparative effects of enalapril and verapamil on myocardial blood flow in systemic hypertension

BACKGROUND

The comparative effects of calcium channel blockers and ACE inhibitors on myocardial blood flow (MBF) in hypertensive patients after long-term treatment are still unknown.

METHODS AND RESULTS

Twenty hypertensive subjects with normal coronary arteries were randomly assigned to verapamil 240 to 480 mg/d or enalapril 10 to 40 mg/d. MBF was quantified at rest, during pacing tachycardia, and after dipyridamole by positron emission tomography and 13N-ammonia before and 6 months after treatment after 1 week of pharmacological washout. In both groups, blood pressure and heart rate during flow measurements were not different before and after therapy. Before treatment, mean MBF at rest, during pacing tachycardia, and after dipyridamole infusion was similar in the two groups; however, pacing and dipyridamole flows were significantly lower than those obtained in a control group of normotensive subjects. After treatment, in the enalapril-treated patients, MBF did not change in the three study conditions. In the verapamil-treated patients, MBF did not change at rest and significantly increased during pacing and after dipyridamole. The inhomogeneity of regional MBF distribution, evaluated from the coefficient of variation, decreased at rest after both treatments and, in the enalapril group, also during pacing. No relation was found between changes in MBF and changes in left ventricular mass.

CONCLUSIONS

In arterial hypertension, MBF during pacing tachycardia and after dipyridamole is impaired. Successful therapy with verapamil increases MBF response to these stimuli, independent of changes in perfusion pressure and left ventricular mass. These results suggest that verapamil directly improves coronary microcirculatory function in hypertension. Enalapril does not significantly change MBF but reduces the inhomogeneity of regional flow distribution.

Sediment drifts and deep-sea channel systems, Antarctic Peninsula Pacific Margin

Twelve sedimentary mounds are identified on the upper continental rise of the Pacific Margin of the Antarctic Peninsula. All these mounds are produced by a varying degree of interaction of along-slope bottom water flow with down-slope turbidity currents. These mounds provide a complete range of intermediates between two end members: the sediment drift and the channel levee. Surface sediments on drift 7 suggest that the mechanisms for the supply and transport of sediment include entrainment of material from turbidity currents within ambient bottom currents, and pelagic settling from the sea surface, including biogenic and glacially derived material. The long-lasting activity of these mechanisms is documented by the data provided by four DSDP and ODP drill sites. Bathymetric and seismic data, both at a large, comprehensive scale and at a small, detailed scale, show the geometry of the sedimentary mounds and their relationships with the adjacent turbidity current channel systems. These data allow the determination of some diagnostic criteria to identify the sediment drifts.

Quantitative and qualitative analysis of the effectiveness of a mechanical method for the isolation of preantral follicles from ovine ovaries

The preantral follicles are the major source of oocytes and its utilization has been investigated as an important tool to store large numbers of female gametes for further utilization in reproductive programs. The aim of the present study was to perform quantitative and qualitative analyses of the efficacy of a mechanical method for isolating of preantral follicles from the ovaries of fetuses and from nonpregnant and pregnant ewes, using as reference the population of preantral follicles in situ. In the isolation method the ovaries were cut into fragments in the tissue chopper. Then, the suspension was filtered through nylon mesh filters. The number of isolated follicles per ovary was 1655, 4735 and 4770, respectively, for the fetus, nonpregnant ewe and pregnant ewe. The number of in situ preantral follicles per ovary was 32961, 16627 and 17794, respectively, for the fetus, nonpregnant ewe and pregnant ewe. The follicle recovery rate (number of isolated preantral follicles/number of in situ preantral follicles x 100) was higher in adult ewes (26 and 28%, respectively, for nonpregnant and pregnant ewes) than in fetuses (5%). Histological analysis showed that very few preantral follicles (less than 0.26% in situ and 0.46% after the isolation procedure) were degenerated. In conclusion, this study showed that a mechanical method could be used effectively to isolate a large number of intact ovine preantral follicles. In the future, with improvements in culture systems, the isolation of a great number of oocytes enclosed in preantral follicles will make a valuable contribution to the rare breeds and endangered species, agricultural efficiency and basic research in folliculogenesis.

Microvascular dysfunction in collateral-dependent myocardium

OBJECTIVES

The aim of this study was to evaluate myocardial blood flow regulation in collateral-dependent myocardium of patients with coronary artery disease.

BACKGROUND

Despite great clinical relevance, perfusion correlates of collateral circulation in humans have rarely been estimated by quantitative methods at rest and during stress.

METHODS

Nineteen patients with angina and isolated occlusion of the left anterior descending (n = 14) or left circumflex (n = 5) coronary artery were evaluated. Using positron emission tomography and nitrogen-13 ammonia, we obtained flow measurements at baseline, during atrial pacing-induced tachycardia and after intravenous administration of dipyridamole (0.56 mg/kg body weight over 4 min). Flow values in collateral-dependent and remote areas were compared with values in 13 normal subjects.

RESULTS

Flow at rest was similar in collateralized and remote myocardium (0.61 +/- 0.11 vs. 0.63 +/- 0.17 ml/min per g, mean +/- 1 SD), and both values were lower than normal (1.00 +/- 0.20 ml/min per g, p < 0.01). During pacing, blood flow increased to 0.83 +/- 0.25 and 1.11 +/- 0.39 ml/min per g in collateral-dependent and remote areas, respectively (p < 0.05 vs. baseline); both values were lower than normal (1.86 +/- 0.61 ml/min per g, p < 0.01). Dipyridamole induced a further increase in perfusion in remote areas (1.36 +/- 0.57 ml/min per g, p < 0.01 vs. pacing) but not in collateral-dependent regions (0.93 +/- 0.37 ml/min per g, p = NS vs. pacing); again, both values were lower (p < 0.01) than normal (3.46 +/- 0.78 ml/min per g). Dipyridamole flow in collateral-dependent myocardium was slightly lower in patients with poorly developed than in those with well developed collateral channels (0.75 +/- 0.29 vs. 1.06 +/- 0.38 ml/min per g, respectively, p = 0.06); however, the former showed higher flow inhomogeneity (collateral/control flow ratio 0.58 +/- 0.10 vs. 0.81 +/- 0.22, respectively, p < 0.02). A linear direct correlation was observed between flow reserve of collateral-dependent and remote regions (r = 0.83, p < 0.01).

CONCLUSIONS

Despite rest hypoperfusion, collateral-dependent myocardium maintains a vasodilator reserve that is almost fully utilized during increases in oxygen consumption. A global microvascular disorder might hamper adaptation to chronic coronary occlusion.

Alteration in regulation of myocardial blood flow in one-vessel coronary artery disease determined by positron emission tomography

The behavior of myocardial blood flow (MBF) regulation in territories supplied by angiographically normal vessels of patients with coronary artery disease (CAD) has been poorly investigated. Resting MBF and coronary reserve were evaluated in 32 patients with stable angina, no previous myocardial infarction, and isolated left anterior descending or left circumflex coronary artery stenosis (> or = 50% diameter narrowing). MBF was measured, in the absence of any medical therapy, by means of dynamic positron emission tomography and 13N-ammonia. MBF measurements at baseline and after intravenous dipyridamole (0.56 mg/kg administered over 4 minutes), were obtained both in the stenosis-related regions and in contralateral territories. As a control group, 14 normal subjects were evaluated according to the same protocol. At rest, the 32 patients with CAD had similar MBF values in the stenotic and remote regions (0.76 +/- 0.21 and 0.77 +/- 0.19 ml/min/g, respectively, p = NS); both these values were significantly (p < 0.01) reduced with respect to mean MBF in normal subjects (1.03 +/- 0.25 ml/min/g). The dipyridamole study was completed in 30 patients; these patients had lower values of maximal MBF in the stenotic than in the remote regions (1.52 +/- 0.65 vs 1.76 +/- 0.68 ml/min/g, p < 0.05); however, both these values were significantly reduced (p < 0.01) with respect to mean dipyridamole MBF in normal subjects (3.66 +/- 0.92 ml/min/g). Thus, in patients with CAD, resting and maximal MBF can be reduced not only in myocardial territories supplied by stenotic arteries, but also in territories supplied by angiographically normal arteries.

CSF phosporylated TAU protein levels correlate with cerebral glucose metabolism assessed with PET in Alzheimer's disease

One major goal of drug development would be the establishment of biomarkers as objective indicators of normal biological and pathogenetic processes, or pharmacological response to a therapeutic intervention. A potential approach is to investigate proteins in CSF linked to key neuropathological features of Alzheimer's disease (AD). Recently CSF phosphorylated-Tau (p-Tau) levels have been reported to reflect neurofibrillary changes within the brain of patients with AD, however the use of serial CSF investigations in order to monitor the disease progression is not applicable. PET with FDG reveals characteristic patterns in AD patients, however so far no correlation between in vivo metabolic information and pathological features has been reported. In the present study, we tested whether CSF Tau levels correlate with metabolic rate for glucose consumption in a cohort of 28 AD patients. We found a statistically significative correlation between both CSF total and p-TAU protein and relative metabolic indexes obtained from 18FDG-PET scans in parietal, temporal and occipital lobes bilaterally. These results indicate the existence of a correlation between impairment of cerebral metabolism, estimated throughout FDG-PET, and CSF Tau protein levels.

Residual coronary reserve identifies segmental viability in patients with wall motion abnormalities

OBJECTIVES

The aim of this study was to determine whether the presence of residual coronary reserve can in itself identify viable segments.

BACKGROUND

Experimental data suggest that despite hypoperfusion at rest, viable myocardium may exhibit persistence of coronary reserve. Preliminary observations in patients show that in basally dyssynergic areas, a residual vasodilator capability is present despite hypoperfusion at rest and that a flow-mediated increase in regional wall motion identifies residual viability.

METHODS

Fourteen patients with evidence of previous myocardial infarction, infarct-related single-vessel coronary artery disease and impaired regional ventricular function at rest underwent positron emission viability imaging by fluorine-18 deoxyglucose. In addition, blood flow at rest and vasodilator capability were regionally evaluated in all patients by means of nitrogen-13 ammonia.

RESULTS

Of a total of 252 segments, 133 were dyssynergic at rest. Of these 133 segments, 60 (group 1) showed normal metabolic activity and only mild reduction in myocardial blood flow. The other 73 segments showed a marked reduction in flow; of these, 25 (group 2, viable) had persistent metabolic activity, whereas 48 (group 3, necrotic) did not. Despite similar levels of hypoperfusion at rest, group 2 segments showed a preserved coronary reserve that was virtually absent in necrotic segments (2.6 +/- 1.3 vs. 1.3 +/- 0.5, p < 0.01). This value was similar to that observed in viable group 1 segments (2.5 +/- 1.6, p = NS).

CONCLUSIONS

In addition to characterizing myocardium at risk, imaging of coronary flow at baseline and after dipyridamole by positron emission tomography provides helpful information on myocardial viability that may integrate the "static" viability information obtained with the baseline flow/metabolic approach.

A homology model of the pore region of HCN channels

HCN channels are activated by membrane hyperpolarization and regulated by cyclic nucleotides, such as cyclic adenosine-mono-phosphate (cAMP). Here we present structural models of the pore region of these channels obtained by using homology modeling and validated against spatial constraints derived from electrophysiological experiments. For the construction of the models we make two major assumptions, justified by electrophysiological observations: i), in the closed state, the topology of the inner pore of HCN channels is similar to that of K(+) channels. In particular, the orientation of the S5 and S6 helices of HCN channels is very similar to that of the corresponding helices of the K(+) KcsA and K(+) KirBac1.1 channels. Thus, we use as templates the x-ray structure of these K(+) channels. ii), In the open state, the S6 helix is bent further than it is in the closed state, as suggested (but not proven) by experimental data. For this reason, the template of the open conformation is the x-ray structure of the MthK channel. The structural models of the closed state turn out to be consistent with all the available electrophysiological data. The model of the open state turned out to be consistent with all the available electrophysiological data in the filter region, including additional experimental data performed in this work. However, it required the introduction of an appropriate, experimentally derived constraint for the S6 helix. Our modeling provides a structural framework for understanding several functional properties of HCN channels: i), the cysteine ring at the inner mouth of the pore may act as a sensor of the intracellular oxidizing/reducing conditions; ii), the bending amplitude of the S6 helix upon gating appears to be significantly smaller than that found in MthK channels; iii), the reduced ionic selectivity of HCN channels, relative to that of K(+) channels, may be caused, at least in part, by the larger flexibility of the inner pore of HCN channels.

Regional myocardial blood flow in stable angina pectoris associated with isolated significant narrowing of either the left anterior descending or left circumflex coronary artery

Myocardial perfusion measurements were obtained with positron emission tomography under basal conditions and after intravenous dipyridamole infusion (0.56 mg/kg over 4 minutes) to determine if myocardial perfusion is maximized in areas of resting wall motion abnormalities in patients with stable angina. Thirty-three patients with no history of myocardial infarction, and with coronary stenosis > 50% involving the left anterior descending (n = 24) and left circumflex (n = 9) coronary arteries were evaluated. Quantitative perfusion images were recorded twice in each subject using nitrogen-13 ammonia at baseline and after intravenous administration of dipyridamole. Computer-assisted analysis of left ventriculograms showed abnormal wall motion in the stenosis-related regions in 16 patients (group 1), and normal regional function in 17 (group 2). The flow values in the anterior and posterolateral wall were considered to reflect left anterior and left circumflex coronary artery flow, respectively. Quantitative angiography showed that coronary stenosis severity was higher in group 1 than in group 2 (cross-sectional area reduction 94 +/- 7% vs 87 +/- 11%; p < 0.05). Resting blood flow in the stenosis-related areas was significantly lower than in contralateral regions in group 1 (0.66 +/- 0.19 vs 0.77 +/- 0.26 ml/min/g; p < 0.05), but not in group 2 (0.73 +/- 0.18 vs 0.78 +/- 0.21 ml/min/g; p = NS). Dipyridamole significantly (p < 0.01) increased myocardial blood flow in both stenotic and remote regions in both groups 1 (0.95 +/- 0.41 vs 1.57 +/- 0.70 ml/min/g) and 2 (1.54 +/- 0.53 vs 2.01 +/- 0.84 ml/min/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Flow-function relation in patients with chronic coronary artery disease and reduced regional function. A positron emission tomographic and two-dimensional echocardiographic study with coronary vasodilator stress

OBJECTIVES

We sought to elucidate the flow-function relation in chronic postischemic dysfunction during vasodilator stress.

BACKGROUND

In patients with ischemia and regional dysfunction, stress echocardiography can elicit three responses in the dysfunctioning segments: no change, improvement or worsening. The physiology underlying these responses is unclear.

METHODS

Seventeen patients with ischemia and left ventricular dysfunction underwent evaluation of regional function by two-dimensional echocardiography and myocardial blood flow by positron emission tomography and 13N-ammonia. Flow (ml/min per g) and function (regional wall motion score [RWMS] from 1 = normal to 4 = dyskinetic) were evaluated both at rest and after dipyridamole (0.56 mg/kg body weight over 4 min).

RESULTS

In 45 normal segments, rest to dipyridamole flow increased from 0.83 +/- 0.22 (mean +/- 1 SD) to 1.87 +/- 0.90 (p < 0.01) with a hyperkinetic contraction pattern. Among dysfunctioning segments, responders (n = 11) showed an upsloping flow-function curve during stress (i.e., increased function [RWMS rest 2.5 +/- 0.5 vs. dipyridamole 1.2 +/- 0.4] and increased flow [rest 0.69 +/- 0.30 vs. dipyridamole 1.89 +/- 1.43, p < 0.01]); nonresponders (n = 20) had a flat flow-function curve during dipyridamole (i.e., fixed function [RWMS rest and dipyridamole 2.6 +/- 0.5] and no flow increase [rest 0.64 +/- 0.24 vs. dipyridamole 0.87 +/- 0.51, p = NS): Ischemic segments (n = 9) exhibited a downsloping flow-function curve during dipyridamole (i.e., worsened function [RWMS rest 2 +/- 0.5, dipyridamole 3.1 +/- 0.6] and no significant flow change [rest 0.67 +/- 0.29 vs. dipyridamole 0.79 +/- 0.23, p = NS]).

CONCLUSIONS

Myocardial segments with rest dysfunction and a contractile reserve elicitable by a vasodilator stress more often exhibit residual flow reserve, whereas segments with a fixed or worsening mechanical response during stress show a flat flow response.

Synchronization of the EEG and sedation induced by neuroleptics depend upon blockade of both D1 and D2 dopamine receptors

Blockade of dopamine (DA) receptors by neuroleptics tends to produce sedation, as shown by increased sleeping time, reduction of the arousal response to sensory stimuli and slowing of the electrical (EEG) activity of the brain. The EEG and behavioural effects of the selective compounds, SCH 23390 and raclopride, which block either D1 or D2 receptor subtypes, respectively were evaluated. Groups of rabbits were prepared for the measurement of EEG activity (neocortex and hippocampus). The EEG was analyzed visually and by spectral power analysis. Gross behaviour was also observed. The D1 antagonist, SCH 23390, by itself (0.03-0.3 mg/kg i.v.) produced small changes in the EEG and no evidence of sedation. Periods of slow waves occurred sporadically. Computerized EEG analysis showed moderate increases of total power density. The D2 receptor blocker, raclopride, alone (1-3 mg/kg i.v.) produced changes of the activity of the EEG, mostly, short periods of slow waves and slight increases of total power. No sedation was noted. Although both selective antagonists were studied at larger doses than those minimally effective, they produced slight EEG and behavioural changes which were not comparable with the marked actions produced by classical neuroleptics, such as haloperidol. However, when raclopride (1 mg/kg) was given after treatment with SCH 23390 (0.03 mg/kg) there was a marked synchronized activity in the EEG, associated with a state of sedation and diminished responsiveness to sensory stimuli. The data indicate that EEG synchronization and sedation, classically associated with treatment with neuroleptics, do not depend upon the selective blockade of either D1 or D2 receptors but, instead, require concurrent blockade of both subtypes of receptor.

Isolated ovine primordial follicles cryopreserved in different concentrations of ethylene glycol

Cryopreservation of primordial follicles represents an opportunity to preserve female gametes, and consequently to protect the reproductive capacity of humans and animals, as well as to safeguard genetic material from endangered animal species or rare breeds. The aim of this work was to assess the toxicity of different concentrations of ethylene glycol (EG) to primordial follicles, and verify the viability of these follicles after the freezing-thawing procedure. Primordial follicles were isolated from ovine ovaries and exposed to different EG concentrations to evaluate the cryoprotectant (CPA) toxicity before and after cryopreservation. After isolation of primordial follicle (control), the number (mean+/-S.E.M.) of viable primordial follicles/ml was 3764+/-795.21. The number of viable follicles in the toxicity test using EG at 0, 0.5, 1.0, 1.5, 2.0, and 2.5 M was 1096+/-447.9, 960+/-446.67, 948+/-366.14, 832+/-313.59, 856+/-280.67, and 700+/-255.02, respectively. The number of viable follicles at concentrations of 2.5 M was less than for controls. After cryopreservation, the numbers decreased to 0+/-0, 148+/-85.46, 764+/-246.69, 824+/-291.9, 844+/-296.27, and 588+/-200.65, respectively for 0, 0.5, 1.0, 1.5, 2.0, and 2.5 M EG. The number of viable follicles at 0, 0.5, and 2.5 M was less than for controls. In conclusion, after the freezing and thawing procedure, concentrations of 1.0, 1.5, and 2.0 M EG can be successfully used for the cryopreservation of isolated follicles in sheep.

Regional concordance and discordance between rest thallium 201 and sestamibi imaging for assessing tissue viability: comparison with postrevascularization functional recovery

BACKGROUND

Whether the combined analysis of rest 201Tl and sestamibi uptake provides additional information regarding myocardial viability in patients with coronary artery disease is still to be investigated.

METHODS AND RESULTS

To this aim we studied 22 patients with previous myocardial infarction and regional ventricular dysfunction by quantitative rest sestamibi and 201Tl scintigraphy. All patients underwent revascularization, and echocardiography was repeated 11 +/- 2 weeks later. Concordant results were obtained in 80 of 105 dyssynergic segments. Fifty-one segments showed normal and 29 abnormal activity. Follow-up echocardiography showed increased wall motion contractility in 76% of segments with maintained 201Tl and sestamibi uptake and in only 17% of segments characterized by subthreshold activities. Twenty-five segments, or 24%, showed sestamibi/201Tl mismatch. Eleven of 12 segments with normal sestamibi/abnormal 201Tl activity did not improve after revascularization, whereas 11 of 13 segments with abnormal sestamibi but normal 201Tl showed postoperative improvement of regional wall motion.

CONCLUSIONS

In patients with previous myocardial infarction, sestamibi and 201Tl showed concordant results in most segments. However, in segments with mismatch a maintained sestamibi uptake was a poor indicator of tissue viability, whereas significant 201Tl uptake reflected tissue viability in most segments.

Cryopreservation of isolated ovine primordial follicles with propylene glycol and glycerol

OBJECTIVE

To verify the viability of isolated primordial follicles to different propylene glycol (PROH) and glycerol (GLY) concentrations before and after cryopreservation.

DESIGN

Isolated primordial follicles were stained with trypan blue to evaluate the effect of different PROH and GLY concentrations before and after cryopreservation.

SETTING

Laboratorio Renzo Giuliani, University of Florence, Italy.

PATIENT(S)

Thirty- to forty-day-old lambs.

INTERVENTION(S)

: Isolation of primordial follicles with subsequent exposure to cryoprotectant and freezing.

MAIN OUTCOME MEASURE(S)

Histologic structure and follicular mortality.

RESULT(S)

After the isolation procedure (control), the mean number of live primordial follicles/mL was 2,688 and 4,452 in the GLY and PROH groups, respectively. When GLY was used, the number of live follicles before cryopreservation was 820, 756, 640, 524, 564, and 460 follicles/mL with concentrations of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 mol/L, respectively. After cryopreservation, this number decreased to 0, 12, 36, 100, 84, and 68 follicles/mL, respectively, with the same concentrations. When PROH was used, the number of live follicles before cryopreservation was 4,216, 3,880, 3,560, 1,812, 704, and 568 follicles/mL with concentrations of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 mol/L, respectively. After cryopreservation, this number decreased to 0, 116, 336, 472, 360, and 244 follicles/mL, respectively, with the same concentrations.

CONCLUSION(S)

Both cryoprotectants were shown to preserve isolated primordial follicles after cryopreservation.

Protein Aggregation and Molecular Crowding: Perspectives From Multiscale Simulations

Cells are extremely crowded environments, thus the use of diluted salted aqueous solutions containing a single protein is too simplistic to mimic the real situation. Macromolecular crowding might affect protein structure, folding, shape, conformational stability, binding of small molecules, enzymatic activity, interactions with cognate biomolecules, and pathological aggregation. The latter phenomenon typically leads to the formation of amyloid fibrils that are linked to several lethal neurodegenerative diseases, but that can also play a functional role in certain organisms. The majority of molecular simulations performed before the last few years were conducted in diluted solutions and were restricted both in the timescales and in the system dimensions by the available computational resources. In recent years, several computational solutions were developed to get close to physiological conditions. In this review we summarize the main computational techniques used to tackle the issue of protein aggregation both in a diluted and in a crowded environment.