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Biomedical subjects

O Oz

Publications and source records attributed to O Oz.

At least 19 recordsLinked to original sources
PubMed2004

Mucociliary clearance after external dacryocystorhinostomy.

We investigated the nasal mucociliary clearance time in 17 patients who underwent a primary unilateral external dacryocystorhinostomy operation. Mucociliary clearance function in both nasal cavities was assessed with the saccharin test. The results were compared with each other using paired samples t-test. We found significantly worse mucociliary clearance time on the operated side (mean: 6.3 min) than on the non-operated side (mean: 5.5 min) (P = 0.004). External dacryocystorhinostomy negatively affected the mucociliary clearance function in this study.

Adult↗
PubMed2003

Successful surgical repair and good visual outcome of a recurrent macular hole of seven years duration.

PURPOSE: To report anatomical closure and visual improvement in a patient with seven-year history of recurrent macular hole. METHODS: A 68-year-old woman underwent vitrectomy and silicone oil tamponade for a seven-year old recurrent macular hole. RESULTS: Macular hole closed and visual acuity improved form 20/400 to 20/60 at 12 months follow-up. CONCLUSIONS: The eyes with very-long standing macular holes may be considered for surgery. Predictors of successful visual outcome after surgery in very-long standing macular holes should be studied in larger series.

Aged↗
PubMed2001

Nonlinear dynamics applied to blood pressure control.

Hypertension is a very frequent disease, known to trigger a range of severe cardiovascular problems. The elucidation of its pathophysiology requires investigation of the mechanisms responsible for the maintenance of blood pressure in the normal system, and their possible failure in hypertension. Some of these control mechanisms display nonlinear features, indicating that the blood pressure signal might be characterized by nonlinear dynamics. Our aim was thus to investigate the nonlinear properties of the blood pressure signal under normal conditions, and in a cardiovascular system prone to hypertension. Blood pressure was investigated in young spontaneously hypertensive rats (SHR), versus their age-matched normotensive progenitors (WKY). The correlation dimension was computed as quantification of blood pressure control complexity. The parameters required for the calculation procedure of the correlation dimension were carefully determined. The results were tested with surrogate data statistics. assuming linear autocorrelated Gaussian noise as the null hypothesis. Non-integer correlation dimension values were found in both strains, with lower values for SHR than for WKY, in particular following alpha-blockade. In all cases, a statistically significant difference was found between the real and surrogate data. These results show that the nonlinear dynamics parameter D, can be used to detect differences in BP control between prehypertensive SHR and WKY rats as early as 6-7 weeks after birth.

Animals↗
PubMed1999

Correlation dimension estimation: can this nonlinear description contribute to the characterization of blood pressure control in rats?

The application of correlation dimension estimation to the study of cardiovascular control, via the blood pressure (BP) time series was investigated. We chose to calculate the Grassberger-Procaccia (GP) correlation dimension. In order to obtain a reliable estimate of the correlation dimension, we studied impact of various parameters such as the appropriate sampling rate, the time delays, the embedding dimension, the minimal trace length required, and the number of points needed as reference points. We developed a recipe for the reliable treatment of the continuous BP signal in rats, our animal model, and discussed the possible pitfalls which demand special attention. Next, we applied the surrogate data method to a BP time series, looking for the existence of nonlinear components, in order to test whether the nonlinear modeling is necessary for accurately describing the system. We found that, indeed, the correlation dimension does reveal information which cannot be unveiled by the commonly used power spectral technique, thus, making the nonlinear modeling an important approach, providing additional insight into the cardiovascular control system.

Algorithms↗
PubMed1998

Beat-to-beat fluctuations in the BP related signals in rats: can it contribute to the understanding of the development of hypertension?

The goal of this study was to investigate the alterations in blood pressure control in young spontaneously hypertensive rats (SHR), as reflected in the power distribution of blood pressure fluctuations. We studied six SHR preceding the onset of overt hypertension, compared to six age matched control rats, the normotensive Wistar-Kyoto rats (WKY), and analyzed the power density distribution of several blood pressure related signals, namely: arterial blood pressure (ABP), systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP) and heart rate (HR). ABP fluctuations exhibited a basic difference in the power distribution pattern between the strains: at low frequencies (< 0.15 Hz) more power was observed in WKY than in SHR, while in the (0.35-1.00 Hz) range, more power was observed in SHR. These significant differences in patterns which existed at baseline, were abolished by prazosin (2.5 mg/kg). Observing the power distribution in the BP related signals, the patterns were different from that found in the ABP itself. At baseline, in SBP and DBP, the most dominant power was located at low frequencies < 0.04 Hz, like in ABP. However, unlike ABP, the remainder of the power was located in the high frequency region (HF: 1.5-3.0 Hz), mainly in SHR. Prazosin had a marked effect on PP power spectra; it shifted the power to the HF region in both strains. In PP, power spectra differences observed between the strains at baseline in HF were eliminated by prazosin. This seems to indicate that, in SHR compared to WKY, respiratory fluctuations which are low at baseline in PP, are a mechanical reflection of the higher sympathetic tone in SHR before alpha1 sympathetic blockade. This study supports previous findings in which differences in cardiovascular control occur in SHR already at the prehypertensive stage. The above results suggest that alpha1 sympathetic control is altered in the SHR strain, and therefore, when this limb is blocked, some of the differences between the strains disappear. Furthermore, the analysis of the BP related signals enable us to identify alterations existing in the control mechanisms in SHR, which involve adjunct control mechanisms enhanced under alpha1 sympathetic blockade. Finally, an important result is, that for all BP related signals under study, excluding HR, the response to alpha1-blockade reduces the power density in the 0.07-0.15 Hz region indicating that this region is directly associated with the activity of alpha control.

Adrenergic alpha-Antagonists↗
PubMed1998

Nonmalignant renal disease in pediatric patients with Beckwith-Wiedemann syndrome.

OBJECTIVE: The objective of this retrospective review was to determine the incidence and spectrum of nonmalignant renal disease in patients with Beckwith-Wiedemann syndrome. MATERIALS AND METHODS: Patient records were obtained from the Beckwith-Wiedemann Registry of the National Cancer Institute. Imaging findings and medical records of 152 neonates, infants, children, and adults with Beckwith-Wiedemann syndrome (age range, 1 day to 30 years old; median age, 1 year 3 months old) were retrospectively reviewed by three radiologists. Available pathologic material also was reviewed. RESULTS: Thirty-eight (25%) of 152 patients with Beckwith-Wiedemann syndrome had 45 nonmalignant renal abnormalities, including medullary renal cysts (n = 19, 13%), caliceal diverticula (n = 2, 1%), hydronephrosis (n = 18, 12%), and nephrolithiasis (n = 6, 4%). Thirty-three (87%) of the 38 patients with nonmalignant renal disease were asymptomatic. Clinical manifestations of the remaining five patients included urinary tract infections (n = 4) and flank pain due to obstructive stone disease (n = 1). Nonmalignant renal disease was mistaken for Wilms' tumor in two patients, resulting in unnecessary nephrectomies. Seven children (18%) had Wilms' tumor and nonmalignant renal disease. CONCLUSION: Nonmalignant renal abnormalities occur in approximately 25% of patients with Beckwith-Wiedemann syndrome but are generally asymptomatic. Nonmalignant renal abnormalities should be considered in the differential diagnosis of a mass revealed during screening sonography of a patient with Beckwith-Wiedemann syndrome to avoid unnecessary surgery.

Adolescent↗
PubMed1997

Autonomic response to change of posture among normal and mild-hypertensive adults: investigation by time-dependent spectral analysis.

In this study, we applied the time-dependent spectral analysis approach (SDA) to investigate the autonomic changes occurring during a transition from supine to standing position (CP), in normal and unmedicated mild hypertensive subjects. The SDA method enables an accurate follow-up of the instantaneous changes in autonomic activity, even during the unsteady phase of the transition, where sudden changes in heart rate (HR) and arterial blood pressure (ABP) are observed. We were able to quantify the vagal withdrawal (reflected in the high frequency component of the time-dependent spectrum of HR fluctuations) in the immediate response to CP and the more slowly following sympathetic increase (reflected in the low frequency component of ABP). This general pattern was observed in both groups. In addition, our results identified an altered sympathetic response to CP in mild-hypertensives, as compared to normal adults. Their basal sympathetic activity is enhanced (higher mean HR and increased low frequency fluctuations in ABP) and their response to CP is reduced, as reflected only in the LF content of ABP fluctuations, relative to normals. No difference was observed in HR fluctuations, showing that there is no parasympathetically mediated alteration of the baroreflex control of HR in mild-hypertension.

Adult↗
PubMed1997

The diastolic decay constant in spontaneously hypertensive rats versus WKY rats as an indicator for vasomotor control.

This research uses the diastolic decay constant (tau) to investigate the short term mechanism responsible for vasomotor control, mainly the alpha-sympathetic control system. Previous studies have shown that vasomotor control is altered in spontaneously hypertensive rats (SHR) preceding the phase of overt hypertension. The diastolic decay, according to the two element Windkessel model, displays an exponential shape with a decay constant, tau, depending on both the vascular resistance and the compliance. In our experiments, we used tau to characterize vasomotor activity and its control in the normotensive rats as well as in the spontaneously hypertensive rats (SHR) prone to hypertension. The beat to beat value of tau was evaluated from a continuous arterial blood pressure (ABP) signal, measured in the tail artery of the conscious, unrestrained rat. Four months old prehypertensive SHR were compared to their age matched normotensive controls (WKY). To study vasomotor regulation, we computed gains and delay times by investigating the compensatory response in tau to changes in mean ABP (MBP). These parameters are expected in the short term to be neurally controlled by the sympathetic system, mainly alpha-sympathetic. Our set of experiments consisted of changing MBP by performing successive injections in bolus of increasing doses of the vasoconstrictor angiotensin II. This procedure was repeated under double cardiac autonomic blockade of the vagal and beta 1 = sympathetic limbs. Our results show that, under baseline conditions, the absolute gain and delay times of tau are reduced in SHR compared to WKY. Double cardiac blockade decreases the absolute gain in both strains, while abolishing the baseline strain differences. These results reinforce our assumption that, in SHR, the alpha-sympathetic system is in a basic state of excitation even prior to the onset of overt hypertension and therefore reacting with reduced sensitivity (lower gain) to changes in MBP.

Adrenergic beta-Antagonists↗
PubMed1996

Nonlinear analysis of BP signal. Can it detect malfunctions in BP control?

In the present study, our aim was to evaluate the applicability of the nonlinear technique to the investigation of cardiovascular control. We applied an approach known as the "surrogate data method" to test for nonlinear components in the blood pressure (BP) signal. Our results strongly indicate that there are nonlinear components in the BP time series taken from a Wistar-Kyoto rat (WKY), suggesting that the use of nonlinear methods may provide new information about the BP control system. We developed a procedure appropriate for the stable and reliable calculation of the Grassberger-Procaccia correlation dimension (D) of the arterial BP signal. The saturation value D was 5.48 +/- 0.30 for the WKY group and 5.92 +/- 0.26 for the spontaneously hypertensive rat (SHR) group, with P < 0.001. We also found that in the WKY group D displays a significant response to complete alpha 1 blockade and bleeding, whereas no response is observed in the SHR group. These results imply that differences in the control mechanisms may be detected by the nonlinear dynamics approach both under baseline conditions and when interfering with cardiovascular control.

Adrenergic alpha-Antagonists↗
PubMed1995

Insight into blood-pressure control in SHR via the response to acute hemorrhage: a spectral analysis approach.

In this study we investigated, by means of the spectral analysis approach, the possible alterations in the activity of the pressor-control mechanisms in relation to the development of essential hypertension. Since the maintenance of controlled arterial blood pressure (ABP) levels is achieved by a continuously fluctuating control system, instantaneous ABP varies continuously in direct correlation with the activation of various control branches. The power spectrum of ABP fluctuations thus provides a quantitative measure of the activity of the various controlling mechanisms. Two strains of rats, Spontaneously Hypertensive Rats (SHR) and Wistar-Kyoto normotensive rats (WKY), were subjected to acute hemorrhage, a procedure known to trigger a strong response, of both the neural (autonomic nervous system) and the hormonal (renin-angiotensin and vasopressin) systems. ABP was continuously recorded from the caudal artery in conscious, 1-month-old SHR and WKY. Three groups of rats were studied. Group 1, acute 2-ml hemorrhage; Groups 2, injection of prazosin (2.5 mg/kg) or Group 3, captopril (4 mg/kg), each followed by bleeding as in the group 1. Spectral analysis of ABP fluctuations was performed on time traces of 20 min duration. The low-frequency part of the power spectrum was analyzed. Three frequency bands were investigated: 0.004-0.04 Hz, 0.04-0.07 Hz and 0.07-0.1 Hz. In SHR, although the baseline mean ABP levels were similar to those of WKY, ABP fluctuations were significantly dampened in SHR in each of the three frequency ranges. Hemorrhage induced, in both strains, a similar fall in mean ABP accompanied by an increase in the slow ABP fluctuations. However, in SHR, the response was significantly greater that that of WKY. The steepest response was observed in the slowest, 0.004-0.04 Hz frequency band, 8.7 +/- 1.7 vs. 1.5 +/- 0.4 times the baseline levels. However, this intense increase in power after hemorrhage brought the two strains to similar levels. The difference in the response to bleeding was eliminated, in the three frequency ranges, by alpha 1 blockade. Captopril reduced the response to bleeding in SHR, to the level observed in WKY in all three frequency bands. Spectral analysis of the spontaneous oscillations in ABP unmasks abnormalities which conventional blood pressure measurements cannot detect in 1-month-old, still normotensive SHR. It thus, provides a tool to study the dynamics of the abnormalities which precede the development of hypertension. Bleeding amplifies the malfunction observed in SHR under baseline conditions, since the mean ABP levels were similar in both strains before and after bleeding, SHR seem to retain the ability to respond to a fall in blood volume by requiring a greater recruitment of the control mechanisms than WKY.

Acute Disease↗
PubMed1995

Thoracic splenosis: MR demonstration.

A previously diagnosed case of thoracic splenosis is presented along with recently acquired magnetic resonance (MR) images. The salient features of this interesting acquired condition are reviewed along with discussion of the MR findings and diagnostic implications of this rare complication of trauma.

Adult↗
PubMed1995

Effect of haemorrhage on the power of low frequency blood pressure fluctuations in young spontaneously hypertensive rats.

1. Before the onset of hypertension low frequency (0.04-0.1 Hz) MAP fluctuations are reduced in SHR when compared to WKY. We studied the effect of haemorrhage under alpha1 blockade or angiotensin converting enzyme inhibition (CEI) on the power spectra (PS) of each strain. 2. MAP was recorded from the caudal artery in conscious, 1 month old SHR and WKY. Three groups of rats were studied. Group 1, acute 2 mL haemorrhage; groups 2 and 3, injection of prazosin (0.25-2.5 mg/kg) or captopril (0.5-4 mg/kg), followed by haemorrhage, as in group 1. The PS was divided into 3 frequency bands, 0.004-0.04, 0.04-0.07 and 0.07-0.1 Hz. 3. In SHR, although the baseline MAP levels were similar to those of WKY, the PS was significantly damped in each of the 3 frequency bands. 4. Haemorrhage induced a similar MAP fall in both strains accompanied by an increase in the slow MAP fluctuations. However, in SHR the PS response was significantly greater than in WKY. The biggest response was in the slowest (0.004-0.04 Hz) frequency band, 8.7 +/- 1.7 vs 1.5 +/- 0.4 times baseline levels, respectively. 5. The difference between the two strains in the PS response to haemorrhage was eliminated by alpha1 blockade. The exaggerated response observed in haemorrhaged, unblocked SHR was reduced in the 3 frequency bands. 6. Captopril reduced the PS response to haemorrhage in SHR to the level observed in WKY in all 3 frequency bands. 7. The enhanced amplification of the MAP fluctuations in haemorrhaged SHR may indicate that SHR requires greater recruitment of control mechanisms than WKY to maintain MAP at a similar level to WKY.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1992

Silver binding nucleolar organizer regions in adrenocortical neoplasia.

The possible contribution of the silver colloid technique for staining nucleolar organizer regions in the distinction between benign and malignant adrenocortical neoplasms was investigated. Nine cases of adenoma, eight cases of carcinoma, nine cases of hyperplasia and four normal adrenal cortex specimens were examined. The mean silver binding nucleolar organizer region (Ag-NOR) value in adenoma was 4.29, and in carcinoma 7.16 (P less than 0.001). Adenomas with diameters greater than 3 cm had significantly higher Ag-NOR counts than smaller adenomas. For normal cortex, the mean Ag-NOR value was 2.05 and in hyperplasia, 3.62. The results indicate that the Ag-NOR technique can help in differential diagnosis between benign and malignant adrenocortical lesions and thus may have a prognostic value.

Adenoma↗
PubMed1988

Effect of localized surface cooling of the heart muscle on the high-frequency content of ECG waveforms in dogs.

Hypothermia is known to affect the electrophysiology of the myocardium in various ways. A marked increase in action potential duration, combined with a decrease in rate of depolarization and conduction velocity, has been observed. We studied the effect of localized hypothermia of the ventricular myocardium on the high-frequency (HF) components of the ECG waveform. Signals were obtained from 6 anesthetized dogs using simultaneous recording of three orthogonal body surface leads before, during, and following surface cooling of different areas of the epicardium. Computer analysis included digital averaging and filtering in a frequency range of 150-250 Hz. For each intervention in each animal, the variance of the average nonfiltered QRS complex was used for a quantitative estimate of the total power, whereas the variance of the derived filtered wave (HF QRS complex) expressed the power content in the HF range. The total power increased during localized cooling of the anterior as well as the inferior epicardial surface, while a clear reduction of power was observed in the HF range. This reduction was shown to be lead dependent and nonuniformly distributed during the course of the QRS. In all cases, hypothermia of either anterior or inferior ventricular epicardium produced a zone of reduced amplitude in the HF QRS complex of at least one lead. Thus, typical changes in the morphology of the HF QRS complex are reliable markers for cooling-induced localized electrophysiological (EP) variations. Therefore, the HF analysis of the body surface ECG may provide noninvasive insight into the EP properties of the myocardium.

Animals↗
PubMed1987

Spectral analysis of heart rate fluctuations. A non-invasive, sensitive method for the early diagnosis of autonomic neuropathy in diabetes mellitus.

Early detection and a quantitative evaluation of the degree of diabetic autonomic neuropathy were performed in 23 diabetic patients and 22 controls by computerized spectral analysis of beat-to-beat R-R interval variations on a continuous electrocardiogram. Simultaneous recording of cardiac and respiratory activity, R-wave detection by a fast peak detection algorithm and spectrum computation by Fast Fourier transform enabled the study of the power spectrum of heart rate fluctuations. The power of fluctuations at different frequencies is the result of sympathetic and vagal input into the sinoatrial node: this input is derived from vasomotor, baroreceptor and respiratory control loops. A marked reduction in the power of heart rate (HR) fluctuations, at all frequencies, was found in the diabetic patients as compared to controls. This indicates a depression of both parasympathetic and sympathetic activity. The difference was especially pronounced in subjects below age 65. The lowest activity was found in diabetics with concomitant peripheral neuropathy. The method described here is simple, objective, quantitative and very sensitive. It may facilitate the screening of diabetic patients for autonomic neuropathy and enable a convenient quantitative follow-up.

Adult↗
PubMed1987

Hemodynamic regulation in SHR: investigation by spectral analysis.

This work is based on the premise that hypertension in the spontaneously hypertensive rat (SHR) is a consequence of an imbalance in autonomic cardiovascular control. Spontaneous, instantaneous fluctuations in heart rate (HR) and arterial blood pressure (ABP) were studied by spectral analysis in age-matched groups of SHR and normotensive Wistar-Kyoto (WKY) rats. Continuous recordings of ABP and HR made in conscious, unrestrained, young 1-, 2-, 3-, and 6-mo-old rats show that power spectra of HR fluctuations were similar in both strains, whereas ABP fluctuations were significantly different in the low, presumably vasomotor frequency range being reduced in SHR as compared with age-matched WKY rats. In 1-mo-old rats, the difference between strains became smaller with urethan anesthesia and disappeared with spinalization, suggesting that it might have originated in some disparity between the strains at the level of the central nervous system. Low doses of phentolamine elicited a fall in low-frequency ABP fluctuations of WKY but a rise in SHR, whereas larger doses produced a fall in the power of both. In SHR, reduction in the power spectrum of ABP fluctuations in the presence of unaltered HR fluctuations may indicate an impaired control of sympathetic drive to resistance vessels compared with WKY. Note that in young SHR, hypertension also cannot be detected by conventional measurement. Fluctuations in ABP in WKY may reflect an optimal level of sympathetic activity; reduction in fluctuations may be associated with an increase or decrease in sympathetic activity at the vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Spectral analysis of fluctuations in heart rate: an objective evaluation of autonomic nervous control in chronic renal failure.

A quantitative, noninvasive method of assessing autonomic control, based on the spectral analysis of beat-to-beat fluctuations in heart rate (HR), was applied to patients with chronic renal failure (RF). Since the power spectrum of HR fluctuations measures the dynamic nervous control of HR, it can be used to quantitate a normal control system as opposed to a disturbed or depressed system. Indeed, in RF patients, a strong reduction in the HR power spectrum was observed in all frequency ranges, both sympathetically and parasympathetically mediated. A similar depression in autonomic control was demonstrated in patients on hemodialysis or peritoneal dialysis. RF patients not yet undergoing dialysis show a lesser degree of depression. Spectral analysis of HR fluctuations in RF patients makes it possible to quantitate autonomic dysfunction and to reliably measure its development as a function of time, and requires only a 10-min standard electrocardiogram recording.

Adult↗