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Biomedical subjects

R Katz

Publications and source records attributed to R Katz.

At least 19 recordsLinked to original sources
PubMed2007

Bronchiectasis: correlation of high-resolution CT findings with health-related quality of life.

AIM: To evaluate the relationship between the severity of bronchiectatic diseases, as evident on high-resolution computed tomography (HRCT) and the patient's quality of life measured using the St George's Respiratory Questionnaire (SGRQ). METHODS AND MATERIALS: Forty-six patients (25 women, 21 men, mean age: 63 years) with bronchiectatic disease as evident on recent HRCT examinations were recruited. Each patient completed the SGRQ and underwent respiratory function tests. HRCT findings were blindly and independently scored by two radiologists, using the modified Bhalla scoring system. The relationships between HRCT scores, SGRQ scores and pulmonary function tests were evaluated. RESULTS: The patients' total CT score did not correlate with the SGRQ scores. However, patients with more advanced disease on HRCT, significantly differed in their SGRQ scores from patients with milder bronchiectatic disease. A significant correlation was found between the CT scores for the middle and distal lung zones and the activity, impacts and total SGRQ scores. No correlation was found between CT scores and respiratory function test indices. However, a significant correlation was found between the SGRQ scores and most of the respiratory function test indices. CONCLUSION: A correlation between the severity of bronchiectatic disease as expressed in HRCT and the health-related quality of life exists in patients with a more severe bronchiectatic disease but not in patients with mild disease. Such correlation depends on the location of the bronchiectasis in the pulmonary tree.

Adult↗
PubMed2005

Statins and cognitive function in the elderly: the Cardiovascular Health Study.

OBJECTIVE: To examine the association of statin drug use on cognitive and MRI change in older adults. METHODS: Participants in the Cardiovascular Health Study, a longitudinal study of people age 65 or older, were classified into three groups determined by whether they were taking statin drugs on a continuous basis, intermittently, or not at all. The untreated group was further divided into categories based on National Cholesterol Education Program recommendations for lipid-lowering treatment. Participants with prevalent or incident clinical TIA or stroke or with baseline Modified Mini-Mental State Examination (3MS) scores at or below 80 were excluded. Outcomes examined included rate of change on the 3MS over an average observational period of 7 years, along with changes in MRI white matter grade and measures of atrophy. RESULTS: Three thousand three hundred thirty-four participants had adequate data for analysis. At baseline, the untreated group in which lipid-lowering drug treatment was recommended were slightly older, less likely to be on estrogen replacement, and had higher serum cholesterol and lower 3MS scores than the statin-treated group. The rate of decline on the 3MS was 0.48 point/year less in those taking statins compared with the untreated group for which treatment was recommended (p = 0.069) and 0.49 point/year less in statin users compared with the group in which lipid-lowering treatment was not recommended (p = 0.009). This effect remained after controlling for serum cholesterol levels. One thousand seven hundred thirty participants with baseline 3MS scores of > 80 underwent cranial MRI scans on two occasions separated by 5 years. There was no significant difference in white matter grade change or atrophy measures between groups. CONCLUSION: Statin drug use was associated with a slight reduction in cognitive decline in an elderly population. This relationship could not be completely explained by the effect of statins on lowering of serum cholesterol.

Aged↗
PubMed2005

The disynaptic group I inhibition between wrist flexor and extensor muscles revisited in humans.

The present studies are designed to further characterise the interneuronal pathway mediating the disynaptic reciprocal group I inhibition between flexors and extensors at the wrist and the elbow levels in humans. In the first series of experiments, we compared the electrical threshold of the reciprocal group I inhibition at the wrist and the elbow level after a prolonged vibration aimed at raising the electrical threshold of the antagonistic activated Ia afferents. Prolonged vibration to the 'conditioning' tendon, which raised significantly the electrical threshold of the inhibition at the elbow level, did not alter it at the wrist level. These results suggest that the dominant input to the relevant interneurones is Ia in origin at the elbow level but Ib in origin at the wrist level. In the second series of experiments, using the spatial facilitation method, we compared the effects on the post-stimulus time histograms of single voluntarily activated motor units of two volleys delivered both separately and together to group I afferents in the nerves supplying the homonymous and antagonistic muscles. At the wrist, but not at the elbow level, the peak of homonymous monosynaptic group I excitation was reduced on combined stimulation, although the antagonistic IPSP was just at the threshold. Because the suppression did not involve the initial bins of the peak, it is argued that the suppression is not due to presynaptic inhibition of Ia terminals, but probably reflects convergence between the homonymous and antagonistic volleys onto the interneurones mediating the disynaptic inhibition. Taken together with the previously reported effects of recurrent inhibition on reciprocal inhibition, these results suggest that inhibition between flexors and extensors is differently organised at the elbow (reciprocal Ia inhibition) and the wrist (non-reciprocal group I inhibition) levels. It is argued that the particular connectivity at the wrist level might correspond to some functional requirements at this ball joint.

Action Potentials↗
PubMed2005

Post-activation depression in various group I spinal pathways in humans.

This investigation was designed to study the effects of post-activation depression in different spinal pathways fed by group I afferents available to investigation in human subjects. It was precipitated by a recent investigation in the cat showing that-contrary to the general assumption-post-activation depression is not a widespread phenomenon in the spinal cord. In 24 healthy subjects comparison was made between the effects of low and high-test stimulus rates on the monosynaptic Ia excitation, known to be subject to post-activation depression, and on oligosynaptic pathways fed by group I afferents. Both the amplitude of monosynaptic H reflexes and the amount of heteronymous monosynaptic Ia facilitation were significantly smaller at high than at low-test stimulus rates (1-2 s compared with 6-8 s between two consecutive stimuli). So was the amount of reciprocal Ia inhibition of tibialis anterior motoneurones. In contrast, the amount of other non-monosynaptic group I effects directed to the same motor nuclei (peroneal-induced excitation of quadriceps motoneurones, disynaptic non-reciprocal group I inhibition of flexor carpi radialis motoneurones, and D1 inhibition of flexor carpi radialis and soleus H reflexes) were enhanced at high stimulus rates. Results in humans confirm that post-activation depression depends on the type of group I afferents, and/or on the target neurones. The functional significance of the discrepancy between post-activation depression in pure Ia pathways and in other group I pathways is discussed with regard to the fusimotor-driven servo-assistance from Ia afferent discharges.

Adult↗
PubMed2004

The role of sildenafil in the treatment of erectile dysfunction in patients with pelvic fracture urethral disruption.

PURPOSE: Erectile dysfunction (ED) is a common sequel of pelvic fracture urethral disruption (PFUD). After repair of the urethral injury ED may be the most devastating long-term effect for the patient. Some patients with ED may regain normal erectile function. We prospectively studied the response to sildenafil and the erectile function of patients with ED due to PFUD. MATERIALS AND METHODS: The erectile function of patients referred to us with PFUD for urethroplasty were prospectively evaluated before surgery. Patients underwent nocturnal penile tumescence testing and, if results were abnormal, penile duplex ultrasonography with intracavernous injection and arteriography were performed to diagnose the etiology of ED. Patients were questioned about erectile function every 3 months after surgery and if they complained of ED they were offered 100 mg sildenafil. Patients were followed for at least 18 months after surgery. RESULTS: A total of 29 consecutive patients were evaluated and 22 (76%) of them had ED before surgery. Sufficient followup was available for 15 of the patients. Overall 47% of these patients responded favorably to sildenafil. Of the patients 60% with neurogenic ED and 20% of those with arterial ED responded to this treatment. In 33% of the patients ED resolved within the followup period. All patients with spontaneous resolution of ED previously responded to sildenafil (71% of sildenafil responders). CONCLUSIONS: In patients with ED due to PFUD, those with neurogenic ED are more likely to respond to sildenafil than those with arterial damage. Favorable response to sildenafil may predict spontaneous resumption of normal erectile function over time.

Adolescent↗
PubMed2003

Evidence for recurrent inhibition of reciprocal inhibition from soleus to tibialis anterior in man.

Reciprocal inhibition between ankle flexors and extensors has been the subject of numerous studies in Man. They have demonstrated that this reciprocal inhibition is in all likelihood caused by a disynaptic pathway at least partly fed by Ia afferents. It is thus generally agreed that this reciprocally organized inhibition between ankle flexors and extensors in Man is similar to the reciprocal Ia inhibition described in the cat. This conclusion has, however, been challenged, when Jankowska and McCrea described in the cat a non-reciprocal group I inhibition involving interneurones co-excited by Ia and Ib afferents and mediating inhibition to both antagonistic and non-antagonistic motoneurones. The only way to distinguish between reciprocal Ia inhibition and non-reciprocal group I inhibition is to test if the inhibition is blocked by recurrent inhibition, since only Ia interneurones are inhibited by recurrent inhibition. In the present study, reciprocal inhibition from soleus to tibialis anterior was thus investigated following activation of soleus-coupled Renshaw cells in normal human subjects. It was found that reciprocal inhibition induced in tibialis anterior motoneurones by the activation of soleus group I afferents is deeply depressed by activation of soleus-coupled Renshaw cells. This finding provides the missing data to identify disynaptic inhibition between antagonistic ankle muscles as a reciprocal Ia inhibition.

Electric Stimulation↗
PubMed2003

Complete solo laparoscopic radical prostatectomy: initial experience.

OBJECTIVES: To demonstrate the feasibility of "complete solo" (CS) laparoscopic radical prostatectomy (LRP) performed solely with robotic manipulation of the laparoscope and without any human assistant at all. A comparison was made between CS LRP and the standard technique to identify the advantages and drawbacks. METHODS: Sixteen consecutive patients undergoing CS LRP were compared with the last 16 patients undergoing standard LRP. The standard procedure was performed with five trocars and one human assistant. Therefore, the surgeon had three instruments immediately available and could switch quickly from one to another, while the assistant held the laparoscope and a retractor. The CS method used a voice-controlled robotic arm to manipulate the laparoscope and a mechanical arm for the assisting instrument. RESULTS: The mean operative time in the CS and standard groups was 324 and 347 minutes, respectively (P >0.5). An additional human assistant was required, for 1 hour, in 3 patients of each group. No significant difference was noted between the two groups in terms of catheterization time, hospital stay, positive margin rate, complications, short-term cancer control, or functional results. The CS method has been demonstrated to be highly cost-effective compared with the standard technique. CONCLUSIONS: The CS LRP is feasible and compares favorably with the standard technique. It offers unique advantages in terms of direct control of the operative view, standardization of the assistance, and higher stability of the laparoscope, thus greatly enhancing the surgeon's comfort. The diminished need for human operative assistance provides significant economic and organizational benefits.

Aged↗
PubMed2003

Low fluence.

The question of the appropriate extrapolation to low dose has long been a subject of controversy. A linear no-threshold model is favored by regulatory bodies as the basis of RBE assignments and estimates of radiation hazards to the general population. This model is largely supported by extensive application of the linear-quadratic survival formula "fitted" statistically to a wide variety of experimental data obtained at doses typically exceeding 1 Gy, and then extrapolated to mGy for practical applications, and even to the prediction of hazards from single electrons. Such extrapolations are questionable at best, and may even prove hazardous for risk evaluations. Fluence and geometry rather than dose based data are proposed as a basis for a limiting "threshold" for a "low dose" extrapolation. The proposed threshold is one where the fluence of particles is one per square micron, where on average only 2/3 of the 1 micrometers2 pixels covering an irradiated area are traversed by one or more particles. The corresponding dose threshold is determined by the LET of the bombarding radiation. For relativistic electrons this dose is about 0.032 Gy.

Cell Physiological Phenomena↗
PubMed2003

Transurethral incision of ureteroneocystostomy strictures in kidney transplant recipients.

OBJECTIVES: To report the treatment of patients who presented with vesico-ureteric stricture after kidney transplantation, using a minimally invasive endourological approach. PATIENTS AND METHODS: Patients (10 men and four women, mean age 34 years, range 22-55) were assessed at presentation by serum creatinine level, ultrasonography and intravenous pyelography when the serum creatinine level was < 200 micromol/L. When there was hydronephrosis of the allograft a percutaneous antegrade pyelogram was taken, followed by inserting a nephrostomy. After decompression a stent nephrostomy was passed into the bladder and the strictures at the vesico-ureteric junction incised along the stent during cystoscopy. RESULTS: All 14 patients were treated endourologically by an endoscopic incision through the bladder; 13 fared well and one died from sepsis and transplantation problems. The mean follow-up was 8 months. CONCLUSIONS: Simple incision of the stricture via cystoscopy was safe and effective, and succeeded in most patients. The endourological management of ureteric lesions is feasible and is currently our first-line management of ureteric complications after kidney transplantation.

Adult↗
PubMed2002

Unenhanced spiral CT for the assessment of renal colic. How does limiting the referral base affect the discovery of additional findings not related to urinary tract calculi?

The value of unenhanced spiral CT (UESCT) for investigating acute flank pain suggestive of urinary tract calculi is increasingly appreciated in the last few years. Recent studies have identified the advantages of UESCT in recognizing alternative findings within or outside the urinary tract. We sought to determine how narrowing the referral base for the UESCT would affect the discovery of potentially significant alternative findings in patients with acute flank pain suggestive of renal colic. Between January 1999 and December 1999, 425 patients, 271 (63.8%) men and 154 (36.2%) women who were 1-90 years old (mean 45.7 years old) with acute flank pain were studied with UESCT. CT studies were solely ordered by urologists, and only patients with intractable renal colic or patients that returned more than once to the emergency room with the complaint of acute flank pain were studied. A calculus within the ureter was diagnostic of an obstructive stone. Any other abnormality within the abdomen and pelvis was reported. A ureteral calculus was detected on 251 (59%) CT scans. Nineteen (4.5%) CT scans were consistent with recent excretion of a stone. In 112 (26.3%) CT scans, the cause for the patient's acute flank pain could not be explained. Forty-three (10.1%) alternative significant diagnoses that explain the patient's complaints were found. Nineteen (44%) were findings related to the urinary tract, and 24 (56%) were not related to the urinary tract. Ninety-seven (22.3%) additional findings not significant to the patient's current complaint were also reported. Even when narrowing the indications for the UESCT, about 10% of significant alternative findings to urinary stones were encountered. The variety of diagnoses found unexpectedly on the UESCT that alter a patient's management demonstrates the pivotal role of UESCT in triaging these patients rapidly towards optimal therapy. The UESCT can be used as a useful screening tool, sometimes revealing the exact pathology and sometimes directing the radiologist to the modality by which to continue.

Adolescent↗
PubMed2002

Chemical bonds broken in latent tracks of light ions in plastic track detectors.

When a swift ion is slowed down through a plastic detector it creates a latent track. In nuclear track detectors, this latent track can be specifically etched by an appropriate chemical solution. This enlargement process is due to a higher etch velocity (VT) along the ion's path than in the non-damaged part of the detector. The etched track velocity is definitely linked to the damage created by the incoming ion in the detector material. A relationship between the physical parameters of the energy deposition and the variation in this etched track velocity with the ion energy cannot easily be explained. We present here our study on the chemical damage created by several ions in a cellulose nitrate type detector and our first attempt to simulate them by the use of the hit theory.

Boron↗
PubMed2001

Modulation of presynaptic inhibition of la afferents during voluntary wrist flexion and extension in man.

Changes in presynaptic inhibition of Ia terminals directed to flexor carpi radialis (FCR) motoneurones (MNs) were investigated in normal human subjects at rest and during voluntary wrist flexion and extension. To that end, two independent methods were used: (1) the radial-induced D1 inhibition of the FCR H reflex, which assesses the excitability of PAD (primary afferent depolarisation) interneurones controlling presynaptic inhibition of Ia terminals mediating the afferent volley of the FCR H reflex; and (2) the heteronymous monosynaptic Ia facilitation induced in the FCR H reflex by intrinsic muscle Ia afferent stimulation, which assesses the ongoing presynaptic inhibition of Ia terminals. With respect to results at rest, it was found that at the onset of (and during tonic) voluntary wrist flexion, D1 inhibition was reduced and heteronymous monosynaptic Ia facilitation was increased. This suggests that, as in the lower limb, presynaptic inhibition is decreased on Ia terminals projecting to MNs involved in the voluntary contraction. In contrast with results observed in the lower limb, presynaptic inhibition of Ia terminals to FCR MNs was also found to be reduced at the onset of a voluntary contraction involving the antagonistic wrist extensors, suggesting that presynaptic inhibition of Ia terminals projecting to wrist flexors and extensors might be mediated through the same subsets of PAD interneurones. This is in keeping with other features showing that the organisation of reflex pathways between wrist flexors and extensors differs from that observed at other (elbow, ankle) joints.

Electric Stimulation↗
PubMed2001

[Reevaluation of physiological mechanisms generating the stretch reflex: new hypotheses on the physiopathology of spasticity].

INTRODUCTION: Spasticity has been defined as tendon reflex exaggeration and increased muscle reflex contraction in response to its stretch (Lance, 1980). It has been generally admitted that stretch reflex exaggeration was due to myotatic reflex hyperexcitability (Ia fibre-motoneurone synapses). This interpretation has been recently revisited taking into account neurophysiological data obtained in cat and recent data obtained in spastic patients. PROBLEMATICS: Myotatic reflex has been described in decerebrate cat in 1924 by Liddel and Sherrington. In 1943, Lloyd demonstrated that myotatic reflex was due to monosynaptic Ia fibre motoneurone alpha synapses. Almost all the following studies of stretch reflexes were devoted to monosynaptic reflexes both in animal and humans. In fact, the existence of group II fibres coming also from spindles and some restricted experiments performed in man have led to discuss the role of group II fibres in the static component of the stretch reflexes. RESULTS: Recent studies performed in humans have shown that group II fibres play an important role in the development of stretch reflexes in leg muscles and that in spastic hemiplegic patients group II fibres facilitatory effects was deeply increased. DISCUSSION: Results obtained both in humans and animals suggest that group II fibres play also a role in a stretch reflex and led to consider that the pathophysiological modifications of group II effects could contribute to spasticity. CONCLUSION: Modifications of network fed by group II fibres and modifications of muscular fibres intrinsic properties are likely to play a role in the developments of spasticity in humans.

Animals↗
PubMed2001

Elevated blood viscosity in systemic lupus erythematosus.

OBJECTIVES: It has been proposed that elevated blood viscosity contributes to atherothrombotic and thromboembolic processes. We evaluated whether there is increased blood viscosity in systemic lupus erythematosus (SLE) that might contribute to cardiovascular complications and reduced tissue perfusion. METHODS: Blood viscosity profiles were evaluated in SLE patients to determine whether rheologic disturbances contribute to the cardiovascular risk profile. Blood viscosity profiles were evaluated in 27 patients with SLE and 46 age- and gender-matched controls. Blood viscosity was measured at 37 degrees C and shear rates of 1 s(-1) and 100 s(-1), then corrected to the average hematocrit of the SLE patients. RESULTS: Corrected blood viscosity values were higher in SLE patients than in controls at 100 s(-1) (P =.002). Positive correlations were found between the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index for SLE, which quantifies damage to 12 organ systems and fibrinogen (rho =.39; P =.042) and plasma viscosity (rho =.38; P =.049). CONCLUSIONS: Our data indicate that blood viscosity values at a standard hematocrit are elevated in SLE patients. Further investigations are needed to evaluate whether the increased blood viscosity values in SLE patients contribute to cardiovascular complications and tissue ischemia. CLINICAL RELEVANCE: Because blood viscosity values correlate with the clinical severity of SLE, blood viscosity may contribute to the cardiovascular complications and reduced tissue perfusion in SLE patients. Semin Arthritis Rheum 31:52-57.

Adult↗
PubMed2001

Renal lymphoma. The diagnostic and therapeutic roles of fine-needle aspiration.

This study focused on 19 patients with renal lymphoma (RL) from whom 20 initial (1 patient with fine-needle aspiration [FNA] specimens of masses in both kidneys) and 1 repeated FNA specimen were obtained. Of the 19 patients, 10 had secondary RL, 8 primary RL, and 1 transplant RL. The FNA samples were studied by smears (all cases), tissues (11), phenotyping by immunostaining (13) or flow cytometry (4), and gene rearrangement (3). The final diagnoses included 1 T-cell lymphoma and 18 B-cell lymphomas. Of the 20 original specimens, 14 were reported as positive for lymphoma, 3 suggestive of lymphoma, 1 positive for transitional cell carcinoma, and 2 unsatisfactory. The follow-up specimen showed reactive changes. Tissue correlation, available in 11 cases, confirmed a positive cytodiagnosis (7), provided a final diagnosis in the cytologically inconclusive cases (3), or revised the misdiagnosis of transitional cell carcinoma from smears (1). The phenotyping elucidated the B vs T lineage of the lymphoma in all tested cases, confirmed the positive cytodiagnosis in 10 cases, confirmed the reactive cytodiagnosis in 1 case, and helped achieve a conclusive diagnosis in 2 cases suggestive of lymphoma. Gene rearrangement studies showed light chain restriction in the 2 tested cases. FNA has an essential role in treatment planning for RL. Although FNA usually is diagnostically conclusive, a high index of suspicion and awareness of atypical or misleading cytomorphologic features are important for a correct interpretation, especially for primary RL. Ancillary testing is essential for the diagnosis in problematic cases and lays the foundation for the differential diagnosis.

Adult↗