Wavelet-based decomposition of high resolution surface plasmon microscopy V(Z) curves at visible and near infrared wavelengths.

Surface plasmon resonance is conventionally conducted in the visible range and, during the past decades, it has proved its efficiency in probing molecular scale interactions. Here we elaborate on the first implementation of a high resolution surface plasmon microscope that operates at near infrared (IR) wavelength for the specific purpose of living matter imaging. We analyze the characteristic angular and spatial frequencies of plasmon resonance in visible and near IR lights and how these combined quantities contribute to the V(Z) response of a scanning surface plasmon microscope (SSPM). Using a space-frequency wavelet decomposition, we show that the V(Z) response of the SSPM for red (632.8 nm) and near IR (1550 nm) lights includes the frequential response of plasmon resonance together with additional parasitic frequencies induced by the objective pupil. Because the objective lens pupil profile is often unknown, this space-frequency decomposition turns out to be very useful to decipher the characteristic frequencies of the experimental V(Z) curves. Comparing the visible and near IR light responses of the SSPM, we show that our objective lens, primarily designed for visible light microscopy, is still operating very efficiently in near IR light. Actually, despite their loss in resolution, the SSPM images obtained with near IR light remain contrasted for a wider range of defocus values from negative to positive Z values. We illustrate our theoretical modeling with a preliminary experimental application to blood cell imaging.

Renal resistive index after captopril test by echo-Doppler in essential hypertension.

In 45 patients with essential hypertension and 15 age-matched normotensive control subjects, the renal resistive index, as an expression of arterial impedance, was determined using Doppler ultrasound. In both kidneys the resistive index was assessed at baseline and after captopril test (50 mg orally). In the moderate and severe hypertensives, compared to mild hypertensives and control subjects, the baseline resistive index was significantly higher (P less than .05). Following captopril, the resistive index increased only in normotensives (P less than .05) and in mild hypertensives (P less than .05). Univariate and multivariate analyses show that the duration and severity of hypertension correlated with an increase of the resistive index both in basal and in dynamic conditions. Thus, the use of the resistive index, as determined by echo-Doppler, could provide useful information for the assessment of renal vascular impedance in essential hypertensive patients. This would help us detect the evolution of hypertensive disease to the higher degrees of severity that are correlated to renal arteriolar damage.

[Color-Doppler ultrasonography and hypertension. Functional assessment of the renal region]. / Eco color Doppler e malattia ipertensiva. Valutazione funzionale del distretto renale.

Color-Doppler US can be used for the morphofunctional assessment of most arterial districts. In hypertension, color-Doppler US can be used to study the renal arteries for both the diagnosis of renovascular hypertension and better physiopathologic assessment of renal arterial blood flow in essential hypertension. To this purpose, we studied renal flow characteristics with the resistive index in both basal conditions and after pharmacologic stimulation with angiotensin-converting enzyme inhibitors. The resistive index was seen to rise in parallel with hypertension severity, as measured by mean arterial pressure; the change was statistically significant (p < 0.05). Values rose step by step from 57.4 (+/- 4.96) in the right renal artery and from 56.6 (+/- 4.18) in the left one in controls, up to 62.2 (+/- 6.6) in the right and 62.3 (+/- 7) in the left renal arteries of severe hypertensives. After pharmacologic stimulation in controls and in mild hypertensives, resistive index values rose significantly (+2.32 +/- 2.1 and +3.5 +/- 5.2, respectively), while in more advanced stages of the disease this index remained unvaried from a statistical point of view (+0.5 +/- 1.7 in moderate and -0.2 +/- 2.1 in severe hypertensives). These data can be explained by reduced capability of renal blood flow autoregulation, as a consequence of a defined vascular damage. In the follow-up of more severe stages of the disease, although pharmacologic treatment had been optimized and mean arterial pressure values reduced (109.08 vs. 118.25 mmHg), even after a prolonged therapeutic wash-out, an abnormal RI response persisted in controls (-1.79 +/- 2.62 vs. -0.94 +/- 1.64), due to persistent arteriolar damage. To date, it is still to be defined if our studies can be applied not only to populations but also to single patients.

Assessment of renal resistance index after captopril test by Doppler in essential and renovascular hypertension.

Ultrasonic duplex scanning has been validated as a noninvasive method to evaluate the kidney arteries and hemodynamic characteristics of renal blood flow in patients with renal artery stenosis. The purpose of our study was to assess the changes in renal vascular impedance in 22 patients with renovascular hypertension, as compared with 45 essential hypertensives and 15 normotensives, by using the Doppler parameter resistance index (RI) before and after a captopril oral test. After the captopril test the delta RI decreased significantly in the stenotic artery (P < 0.05). Univariate analysis showed that PRA values after captopril correlated inversely with the changes of RI only in the stenotic artery (P < 0.05). Thus, our findings suggest that the application of the captopril test to renal echo-Doppler may represent a feasible, noninvasive, and inexpensively useful tool in the screening studies aimed at diagnosing renovascular hypertension.