Posterior polar cataracts: a predisposition to intraoperative posterior capsular rupture

We performed phacoemulsification or planned extracapsular cataract extraction on posterior polar cataracts in 31 eyes of 22 patients and experienced eight cases of posterior capsular rupture (26%). Capsular rupture occurred during removal of the posterior polar opacity or during cleaning of the posterior capsule after the opacity had been removed. We believe that excessive adherence of the opacity to the posterior capsule and unusual thinness of the capsule predisposed these eyes to posterior capsular rupture.

GABAergic ganglion cells in the rabbit retina

The ganglion cells are the output neurons of the retina. There is, however, relatively little known about the neurotransmitters used by these cells. In the present study, ganglion cells identified with a ganglion cell-specific monoclonal antibody (AB5) are shown in separate double-label experiments to be gamma-aminobutyric acid (GABA)-like immunoreactive and to possess a high-affinity uptake mechanism for [3H]GABA accumulation. The localization of these markers of GABA activity to AB5-labelled ganglion cells provides the first definitive evidence for the presence of a classical transmitter in retinal ganglion cells and suggests that GABA may perform a role as a neurotransmitter in these cells.

Voxel sensitivity function description of flow-induced signal loss in MR imaging: implications for black-blood MR angiography with turbo spin-echo sequences

The conditions in which the image intensity of vessels transporting laminar flow is attenuated in black-blood MR angiography (BB-MRA) with turbo spin-echo (TSE) and conventional spin-echo (CSE) pulse sequences are investigated experimentally with a flow phantom, studied theoretically by means of a Bloch equation-voxel sensitivity function (VSF) formalism, and computer modeled. The experiments studied the effects of: a) flow velocity, b) imaging axes orientation relative to the flow direction, and c) phase encoding order of the TSE train. The formulated Bloch equation-VSF theory describes flow effects in two-dimensional (2D)- and 3D-Fourier transform magnetic resonance imaging. In this theoretical framework, the main attenuation mechanism instrumental to BB-MRA, i.e., transverse magnetization dephasing caused by flow in the presence of the imaging gradients, is described in terms of flow-induced distortions of the individual voxel sensitivity functions. The computer simulations predict that the intraluminal homogeneity and extent of flow-induced image intensity attenuation increase as a function of decreasing vessel diameter, in support of the superior image quality achieved with TSE-based BB-MRA in the brain.

Decreased paraoxonase-1 activity is a risk factor for ischemic stroke in Koreans

Paraoxonase-1 (PON1) is an enzyme associated with HDL in blood and it is considered as an anti-oxidant factor due to its capability to prevent lipid oxidation. In vivo mouse studies also have shown that PON1 is one of the genetic risk factors contributing to atherosclerosis. In this study, we evaluated the serum PON1 activities of sex-age matched Korean healthy control and ischemic stroke patients, and investigated the association of PON1 activity with other metabolic parameters. Statistical analyses revealed that PON1 activity and HDL_cholesterol (HDL_C) in stroke patients were significantly decreased when compared with those of healthy control. Additionally, PON1 activity was negatively correlated with age, whereas it was positively correlated with HDL_C in a stroke group. Overall, the results of this study indicated that decreased serum PON1 activity should be considered as a risk factor for ischemic stroke in Koreans.

Spectral analysis of radial pulse in patients with acute, uncomplicated myocardial infarction

The aim of this study was to examine the frequency spectrum of arterial pulses in 17 patients with acute, uncomplicated myocardial infarction. Recordings of right radial pulses were taken from these patients immediately after their arrival at the emergency room. This information was considered as baseline data and was monitored at the same time each day for up to 7 days. These serial recordings of radial pulses were then analyzed together with recordings from 3 control groups of patients not suffering from myocardial infarction. These included subjects who underwent coronary arteriography (n = 24), coronary angioplasty (n = 18), and mitral valvuloplasty (n = 13). The method of analysis involved a discrete Fourier transformation of radial pulses recorded from an external pulsation transducer to obtain "power spectra" for pulse waves. There was no significant change in the power spectrum for each of the 3 control groups although significant clinical and hemodynamic improvement was observed in the coronary angioplasty and mitral valvuloplasty patients. In sharp contrast, the intensity of the frequency moduli C2 and C3 in the target group fell on arrival at the emergency room and then gradually increased while the average pulse energy (frequency modulus C0) decreased simultaneously with stable recovery from the acute myocardial infarction. In order to investigate the changes in C2 and C3 in the target group, the effective renal plasma flow (ERPF) was first determined for 10 of the 17 patients using intravenous I-131 labelled iodo-ortho-hippurate. A second reading was taken a week later. Eight of the 10 patients were found to have a relatively "higher" ERPF at the onset of acute myocardial infarction with an average reading of 450.1 +/- 168.9 ml/min, compared with the data obtained a week later (374.1 +/- 130.4 ml/min, p < 0.02). An inverse correlation existed between the percentage of "initial drop" in frequency moduli C2 and C3 in the power spectra of the radial pulses and the percentage of "initially higher" ERPF (r = -0.66 and -0.70, respectively, p < 0.05). It is concluded that there was a specific change in the power spectrum of the radial pulses which were recorded and analyzed noninvasively in patients with acute, uncomplicated myocardial infarction. Changes in the ERPF may exert an influence on the frequency moduli C2 and C3 of the power spectra of the radial pulses after heart attack, suggesting that the aorta and the closely organs may cause coupled oscillation. Theoretically this structure is equivalent to a resonance circuit.

The decreased expression of peroxisome proliferator-activated receptors delta (PPARdelta) is reversed by digoxin in the heart of diabetic rats

The present study is designed to investigate the role of peroxisome proliferator-activated receptors delta (PPARdelta) in the action of digoxin in diabetic rats showing cardiac hypertrophy. We used Wistar rats to induce diabetes by injection of streptozotocin (STZ-rat) and examined the effect of digoxin on PPARdelta expression in these hyperglycemic rats (STZ-rat) at 10 weeks later. We measured the changes of body weight, water intake, and food intake in three groups of age-matched rats; the vehicle treated normal control (Wistar rats), the vehicle treated STZ-rats, and the digoxin-treated STZ-rats. Cardiac output, heart rate, and blood pressure in addition to plasma insulin or glucose level were also determined. The mRNA and protein levels of PPARdelta were measured using Northern and Western blotting, respectively. Cardiac output, heart rate, and blood pressure were markedly reduced while food intake, water intake, and blood glucose were raised in STZ-rats showing lower body weight and plasma insulin as compared with the vehicle-treated controls. After a 20-day of digoxin treatment, cardiac output was raised in STZ-rats but the diabetic parameters were not modified. The PPARdelta expressions, both mRNA and protein, were markedly elevated in the hearts of STZ-rats by digoxin treatment. The related signals with PPARdelta, such as carnitine palmitoyltransferase 1B (CPT1B), acetyl-coenzyme A, carboxylase alpha (ACC1), fatty acid synthase (FAS), and troponin I, were also raised. The increase of cardiac output by digoxin was reversed by the combined treatment with PPARdelta antagonist GSK0660. Thus, we suggest a new finding that PPARdelta is involved in digoxin induced cardiac inrotropic action.

Do physical exercise and reading reduce the risk of Parkinson's disease? a cross-sectional study on factors associated with Parkinson's disease in elderly Chinese veterans

BACKGROUND

The purpose of this study was to investigate risk factors for and factors protecting against Parkinson's disease (PD) in elderly Chinese veterans.

METHODS

Using a database containing detailed information on the health status of the nervous system in elderly Chinese veterans, univariate and multivariate analyses of factors that may be associated with PD were performed. Univariate analysis of qualitative data was done using the Pearson Chi-square and Fisher's exact tests, and the Mann-Whitney U nonparametric test was used for univariate analysis of quantitative data. Multivariate logistic regression analysis was used to identify independent risk factors for and factors protecting against PD in elderly Chinese veterans.

RESULTS

A total of 9,676 elderly Chinese veterans were enrolled, including 228 cases with PD and 183 cases with Parkinson's syndrome, with 9,265 non-PD subjects serving as controls. Age (odds ratio [OR] 1.343, 95% confidence interval [CI] 1.028-1.755) and medical history of essential tremor (OR 1.228, 95% CI 1.081-1.396) were identified as independent risk factors for PD, with age being the most important risk factor. Physical exercise (OR 0.478, 95% CI 0.355-0.643) and reading (OR 0.513, 95% CI 0.357-0.735) were identified as independent factors protecting against PD, and physical exercise showed better protection against PD relative to reading. Smoking, alcohol use, anemia, cerebral trauma, education level, and electromagnetic field exposure showed no association with PD.

CONCLUSION

Physical exercise and reading may be independent factors that protect against PD among elderly Chinese veterans, while advancing age and medical history of essential tremor may be independent risk factors for PD. This study was cross-sectional, so further research is needed to confirm its results.

Black-blood MR angiography with GRASE: measurement of flow-induced signal attenuation

We investigated the feasibility of performing black-blood MR angiography (MRA) with the gradient and spin-echo (GRASE) pulse sequence. Phantom experiments and human testing were conducted, and the results were compared with those of turbo spin-echo (TSE). We demonstrated that both techniques are able to produce signal suppression of flowing fluid to background level. With fewer radiofrequency (RF)-refocusing pulses, GRASE pulse sequences could serve as an alternative black-blood technique of reduced RF power exposure and shorter scan time. These relative advantages of GRASE may become useful when high-resolution images are taken.

T2-weighted MR imaging of the liver: optimization of hybrid-RARE sequences

The objectives of this study were to optimize T2-weighted hybrid-RARE pulse sequences for clinical MR imaging of the liver, and to compare them to the conventional spin-echo (CSE) sequence. Specifically, the ranges of the echo train length (ETL) and the effective echo time (TEeff) were investigated to optimize image quality and liver-spleen contrast, in healthy volunteers. A total of thirteen volunteers were scanned at 1.5 Tesla with an extensive array of hybrid-RARE scans. The images were analyzed quantitatively with respect to CNR (contrast-to-noise ratio of spleen vs. liver), SNR (signal to noise ratio of the spleen), SIR (signal intensity ratio of liver and spleen) and CDR (contrast difference ratio between the spleen and liver). The images were also analyzed qualitatively with respect to image sharpness, vascular artifacts, ghosting, chemical shift, and truncations. Results of quantitative analysis indicated that CDR and SIR of hybrid-RARE at higher ETL (> 13) were consistently better than both the reference CSE and the lower ETL sequences (p < 0.05) at all TEeff. SNR was slightly inferior for all hybrid-RARE sequences than for the CSE sequence. Image quality for hybrid-RARE sequences with ETL > 13 proved to be consistently better than that for the CSE (TE = 90 ms) with respect to imaging sharpness, vascular artifacts and ghosting artifacts (p < 0.05). In conclusion, the optimized hybrid-RARE sequences with ETL greater than or equal to 13 are capable of producing sharp and relatively artifact free images with the advantage of a much greater acquisition time efficiency.

A noninvasive pre-atrial activity recording by signal averaging using esophageal electrode

A noninvasive method employing the technique of signal averaging has been developed for recording sinoatrial (S-A) activity (pre-P wave). Recordings were obtained in man at the time of right heart catheterization. A bipolar esophageal electrode was utilized to record the prominent P waves that were used for triggering in the averaging process. After summing 150 beats, which had coefficients of correlation 0.97 or larger, deflections of small amplitude (less than 40 microV) were obtained preceding the atrial activity. Direct catheter recordings were also taken for comparison. With the new noninvasive method, the sinoatrial conduction time (SACT) estimated for patients with sick sinus syndrome (SSS) was 106 +/- 24 ms (101 +/- 20 ms for the same group measured directly). The SACT for healthy subjects used as the control group was 55 +/- 18 ms. There was good correlation between the pre-atrial activity recorded noninvasively by the esophageal electrode method and invasively from the direct catheter method. The linear correlation coefficient between these two techniques was 0.89 (P less than 0.001) in 17 patients.

Quantitative analysis of high-frequency components of signal-averaged QRS complex in Chinese patients with acute myocardial infarction. A prospective study for prediction of ventricular tachycardia

A prospective study was undertaken of the high-frequency components of the terminal portion of the QRS complex in 38 Chinese patients with acute myocardial infarction (AMI) (mean age 62 +/- 5.6 years) within the first week after the acute event (5.5 +/- 1.2 days). Another 44 normals served as controls (mean age 57 +/- 9.6 years). The electrocardiogram was averaged at a filter band pass of 80-300 Hz. The low voltage span (LVS) of the signals less than 40 microV in the terminal portion of QRS, the root-mean-square (RMS) voltage (V) of terminal 40 msec of the QRS complex, and the total duration of signal-averaged QRS vector complex were measured in both the normal subjects and patients. The LVS was abnormally prolonged in 16 of 38 patients (42%), and in only 16% of normals (p less than 0.05). The RMS-V was abnormal (less than 25 microV) in 29 of 38 patients (76%), and in only 20% of normals (p less than 0.0005), and the signal-averaged QRS vector complex was abnormal (greater than 120 msec) in 26 of 38 patients (68%), and only 9% of normals (p less than 0.005). There was no significant correlation between any of the signal-averaged parameters, the site of AMI and total creatine kinase (CK) or CK-MB values. The signal-averaged parameters also showed no relationship to either the cardiothoracic (C/T) ratio or the left ventricular ejection fraction, determined by the Tc-99 m pertechnetate first pass blood pool technique. Holter ECG monitoring was performed twice in all AMI patients, at 7 to 18 days after the acute event (12 days average) and 3 weeks after the first recording. There were only four episodes of non-sustained ventricular tachycardia (VT), all during the second monitoring period. Three episodes (10%) occurred in patients with positive late potentials (LPs), defined by an RMS-V less than 25 microV in the terminal portion of QRS vector; one episode (11%) occurred in patients with negative LPs (9 patients). Although the incidence of LPs is significantly higher in patients with an AMI than in normal controls, the LPs detected by body surface signal-averaged ECG did not predict the occurrence of in- and out-of-hospital VTs. Thus, after AMI, Chinese patients may not be as prone to develop VTs as are Caucasians. Furthermore, the appearance of LPs is independent of cardiac size and left ventricular ejection fraction.

Assessment of heart wall motion: modified spatial modulation of magnetization for MR imaging

This paper reports a new noninvasive method for detecting a regional myocardial infarction. The method consists of superimposing a magnetization grid onto different image planes of the human heart. In this study the spatial modulation of magnetization (SPAMM) in magnetic resonance imaging was modified to accommodate the use of a conventional clinical magnet. The percentages of circumferential shortening (PCS) and the percentages of wall thickening (PWT) during a cardiac cycle were estimated by measuring the amount of deformation of each grid from the end of the diastole to the end of the systole. A small data base was established on 10 subjects (6 normal volunteers and 4 patients). Patients with regional myocardial infarction, when monitored by the modified SPAMM investigation, showed smaller values of PCS and PWT in the areas where myocardial infarction was diagnosed by catheterization. The amount in decrement was directly proportional to the severity of the regional lesions.