Biomedical subjects
Publications and source records attributed to R Katz.
Unanticipated late effects in neutron and heavy ion therapy, not attributable to overdose, imply a qualitative difference between low and high LET therapy. We identify that difference as 'ion kill', associated with the spectrum of z/beta in the radiation field, whose measurement we label 'ion-kill dosimetry'.
PURPOSE: The overall goals of this study were: 1) to determine whether (and if so, the extent to which) African-Americans differed in their willingness to participate in biomedical studies as compared to non-Hispanic Whites, and 2) to determine the influence that a range of demographic, psycho-social and medico-historical variables had on the comparative willingness of these groups to participate in biomedical research. This report will present preliminary findings on the first goal.METHODS: The Tuskegee Legacy Project (TLP) Questionnaire, a 60 item instrument developed within the Northeastern Minority Oral Health Research Center (a P50 Center supported by the National Institute of Dental and Craniofacial Research at NIH), was administered via a random-digit dial telephone interview by the University of Alabama at Birmingham Survey Research Unit to 840 adult African-Americans and Whites in three city/county areas: Birmingham/Jefferson Cty, AL; Hartford/Hartford Cty, CT and Tuskegee/Macon Cty, AL.RESULTS: The response rates were 70%, 65% and 49% for Birmingham, Tuskegee and Hartford, respectively. A lower percentage of African-Americans (21%) reported that they were either somewhat or very likely to participate as biomedical research subjects than did Whites (29%) (p < 0.0001). In response to 7 prompts on 'who' was conducting a study, African-Americans indicated they were less likely to participate than Whites on 4 specific prompts and more likely to participate on only 1 prompt (p < 0.006 for each). In response to 9 prompts on 'what' a study asked participants to do, African-Americans indicated they were less likely to participate than Whites on only 2 specific prompts (p < 0.001 for each), more likely to participate on 2 prompts (p < 0.001), and were equally or near equally likely to participate on 5 prompts.CONCLUSIONS: The findings from this study show that African-Americans self-reported a lower willingness to participate in biomedical studies than did non-Hispanic Whites, and that African-American subjects were more influenced by the factor of 'who' was running the study than by the factor of 'what' they might have to do as study subjects. Study supported by grant P 50 DE10592 from the NIDCR at NIH.
Disease caused by group A streptococci (GAS) in tropical regions often takes the form of impetigo, whereas pharyngitis tends to predominate in temperate zones. GAS derived from asymptomatic throat infections and pyoderma lesions of rural Aboriginal Australians were evaluated for phylogenetic distant emm genes, which represent ecological markers for tissue site preference. On the basis of the percentage of total isolates from a given tissue, emm pattern A-C organisms exhibited a stronger predilection for the throat, whereas pattern D organisms preferred the skin. Only 16% of isolates collected by active surveillance displayed pattern A-C, which reflects the low incidence of oropharyngeal infection. Importantly, most (70%) pattern A-C organisms were isolated from skin sores, despite their innate tendency to infect the throat. Combined with findings from nontropical populations, analysis of the data supports the hypothesis that GAS tissue preferences are genetically predetermined and that host risk factors for infection strongly influence the differential reproduction of individual clones.
Recent trials measuring exhaled nitric oxide (eNO) concentrations have suggested that it may be a useful measure of ongoing airway inflammation in patients with asthma. The purpose of this study was to examine the relationship between eNO levels and baseline as well as postbronchodilator spirometry, a measurement commonly used in the clinical setting to determine the severity of asthma and as a guide to therapeutic decisions. Forty-nine patients between the ages of 5-16 years with physician-diagnosed asthma who attended the pediatric pulmonary clinic for a routine asthma visit with spirometric evaluation were recruited for the study. eNO levels prior to spirometry were obtained before and after receiving inhaled beta(2) agonist. eNO samples were collected in impermeable bags (Tedlar) and assayed within 24 hr by chemiluminescence. Regression analysis was used to assess the relationships between pre- and postbronchodilator eNO and spirometric variables. eNO was also compared in patients receiving and not receiving inhaled corticosteroids (ICS), as well as those whose therapy had been increased after evaluation by a pediatric pulmonologist or allergist. We found no significant difference between the levels of eNO before and after inhalation of beta(2) agonist (P = 0.60 paired t-test). Positive correlation was found between eNO vs. percentage change in FEV(1) (r = 0.35, P = 0.01) and percentage change in FEF(25-75% )(r = 0.29, P = 0.04). A negative correlation was found between prebronchodilator FEV(1) and eNO (r = -0.29, P = 0.03). Patients on ICS had lower mean eNO levels (29.9 vs. 47.6 parts per billion (ppb), P = 0.053) than those not receiving ICS. Patients whose ICS therapy was increased had higher mean eNO levels (47.2 vs. 26.9 ppb, P = 0.018) than those not having ICS therapy increased. We suggest that eNO levels could be a clinically useful measurement of asthma severity and could be used as an adjunct to spirometry to determine appropriate treatment plans. Longitudinal clinical trials are needed to determine if eNO can enhance therapeutic decisions for asthmatic children.
Unenhanced helical computerized tomography (UHCT) has recently evolved as an accurate imaging modality for determination of the presence or absence of ureterolithiasis in patients with acute flank pain. Functional renal scintigraphy is considered the gold standard for urinary tract obstruction. The objective of this study was to correlate the secondary signs of urinary obstruction on UHCT with findings of functional renal scintigraphy. UHCT was performed in 30 patients admitted to the emergency room with acute flank pain. All patients had a calcified urinary stone identified on UHCT. The location of each urinary stone was classified as ureteral or in the ureterovesical junction. The presence of secondary CT signs of ureteral obstruction was determined for each patient. After oral or intravenous hydration, a technetium-99m diethylene triamine penta-acetic acid renal scan was performed in all patients within 12 h of the CT scan. Follow-up delayed scintigraphic images were obtained at 2 h and 24 h in patients with evidence of ureteral obstruction. The sensitivity, specificity and predictive values of each possible combination of CT findings were determined by comparison with the scintigraphic results. The distal ureter was the most common location for a calculus on UHCT, followed in frequency by the ureterovesical junction, proximal ureter and mid-ureter. The renograms showed high-grade, unilateral obstruction in 12 patients, indeterminate scans in five patients and normal renograms in 13 patients. The sensitivities and specificities of individual CT findings ranged from 50% to 75% and from 8% to 69%, respectively. Perinephric stranding gave the highest positive predictive value (PPV) for obstruction (69% including indeterminate renograms). None of the individual CT findings showed a statistically significant correlation with scintigraphic findings. A combination of one or two positive CT findings had a PPV of only 25% for obstruction. A combination of three or four positive CT findings gave a PPV of 70% for obstruction. Our preliminary study shows that secondary CT signs of ureterolithiasis correlate poorly with the scintigraphic findings and that they do not permit evaluation of the functional status of obstructed kidneys. Even a combination of the most frequent CT findings has a low predictive value, i.e. does not allow a decision to be made as to the most suitable treatment. Therefore, renal scintigraphy should be performed in conjunction with UHCT in all patients with ureteral calculi.
Our aim is to report the computed tomography (CT) features of the long-term failed renal allograft. Ten patients with failed renal transplants in whom the graft was left in situ underwent CT for various unrelated indications. The majority of the failed grafts showed marked shrinkage and coarse punctate diffuse parenchymal calcifications. Small cysts were seen in four grafts. A long-term failed renal transplant appeared on CT as a small rounded soft tissue mass. The graft was almost always heavily calcified. Lack of awareness of the nature of such a mass may mislead the radiologist in interpreting it as a space-occupying lesion.
Presynaptic inhibition of Ia terminals and postactivation depression at the Ia fibre-motor neuron (MN) synapses were compared in the upper and lower limbs of both sides in subjects from different populations: 49 spastic patients with hemiplegia [mainly with a lesion in the middle cerebral artery (MCA) area], two tetraplegics and 35 healthy subjects. Presynaptic inhibition was assessed using D1 inhibition of the soleus and the flexor carpi radialis (FCR) H reflexes elicited by electrical stimuli applied to the nerve supplying antagonistic muscles, and postactivation depression was explored by varying the time interval between two consecutive H reflexes. In normal subjects no right-left asymmetry was found in the amount of presynaptic Ia inhibition, homosynaptic depression or the H(max)/M(max) ratio. In the hemiplegic side of patients with MCA area lesions, the H(max)/M(max) ratio was significantly increased in the soleus but not in the FCR. Presynaptic inhibition of Ia terminals, which was significantly reduced at the cervical level on the hemiplegic side (and also, but to a lesser extent, on the unaffected side), was unchanged at the lumbar level. Homosynaptic depression was similarly reduced at the cervical and lumbar levels on the hemiplegic side but not modified on the unaffected side. It is argued that the decrease in presynaptic inhibition of Ia terminals is more a correlate of spasticity than a mechanism underlying it. The decrease in postactivation depression, which very probably contributes to the exaggeration of the stretch reflex characterizing spasticity, might be a consequence of the changes in the pattern of activation of Ia afferents and MNs following the motor impairment.
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Our armamentarium for the treatment of erectile dysfunction has recently been expanded by addition of Viagra and the MUSE. However, their long-term results are still unknown. The insertion of a penile prosthesis is invasive, expensive, and irreversible, but under optimal condition provides an acceptable, definitive solution for erectile dysfunction. We evaluated our long-term results with penile prosthesis insertion (PPI). From 1987-1998, 57 patients underwent PPI in our department. Mean age was 55 years and the common causes of erectile dysfunction were atherosclerotic disease (23), radical pelvic surgery (15), and diabetes mellitus (14). Semirigid prostheses were inserted in 12 and inflatable prostheses in 45, including 42 single-component and 3 multi-component prostheses. Recently we interviewed these patients by telephone, using a standard questionnaire. Those not satisfied with the surgical results (83% of the living patients) were examined in our clinic. Mean follow-up was 53 months. In 37 (84%) the prosthesis was mechanically functional (rates after 1, 5 and 10 years were 87.8%, 80%, and 75%, respectively). In only 2 (2.5%) had serious complications led to prosthesis removal. All mechanical failures had occurred in those with inflatable prostheses after a mean of 48.5 months (range 4-113). At the time of the survey 68% were sexually active and 64% were satisfied with the surgical result. We conclude that PPI is safe treatment for erectile dysfunction. Although the rate of mechanically functioning prostheses decreases with time, modern multi-component prostheses may lead to better mechanical results.
AIM: The aim of this study was to present the computed tomography (CT) appearance of trichobezoars, phytobezoars and other unusual ingested material. MATERIALS AND METHODS: Seven patients diagnosed on CT with bezoars in the stomach or small intestine were reviewed with special attention on the characteristics of the intraluminal mass and the presence of proximal dilatation. RESULTS: There were six women and one man aged 14-81 years. CT was performed because of abdominal pain and a palpable abdominal mass. In none of the cases was the diagnosis suspected clinically. Four patients had a trichobezoar occupying the entire lumen of the stomach. It appeared as a concentric inhomogeneous mass with entrapped air, surrounded by contrast material. In the other three patients the bezoar was confined to the small intestine and was composed respectively of vegetable fibres, ingested toilet paper and an olive stone. The first two had a mottled appearance whereas the last one was small, spherical and well defined. Variable proximal dilatation of the small bowel was present in all three. CONCLUSION: With the increased use of CT in the evaluation of patients with non-specific abdominal pain, it is important to recognize the CT appearance of bezoars, as this diagnosis is often not suspected clinically.
Methods have been developed to investigate recurrent inhibition (RI) in humans. A conditioning reflex discharge is used to evoke in motoneurones (MNs) supplying homonymous and synergistic muscles, an inhibition the characteristics of which are consistent with RI: it appears and increases with the conditioning motor discharge, has a short latency and a long duration, and is enhanced by an agonist of acetylcholine. As in the cat, homonymous RI exists in all explored motor nuclei of the limbs except those of the digits and the pattern of distribution of heteronymous RI closely matches that of monosynaptic Ia excitation. However, striking inter-species differences exist concerning the distribution of heteronymous RI since it is much more widely extended in the human lower limb than in the cat hindlimb, whereas it is more restricted in the upper limb than in the cat forelimb. Changes in transmission in the recurrent pathway have been investigated during various voluntary or postural contractions involving different (homonymous, synergistic, antagonistic) muscles and it has been found that the activation of Renshaw cells (RCs) by the voluntary motor discharge via recurrent collaterals was powerfully controlled by descending tracts: for example, during homonymous contraction, RI evoked by a given conditioning reflex discharge is much smaller during strong than during weak contraction, which suggests that the descending control of RCs might contribute to the regulation of muscle force. The finding that RC inhibition is more marked during phasic than during tonic contraction of similar force of the homonymous muscle is discussed in relation with the projections of RCs to Ia interneurones mediating reciprocal inhibition. Only in patients with progressive paraparesis is there evidence for decreased RI at rest which may contribute to the exaggeration of the passively-induced stretch reflex underlying spasticity. However, despite the seemingly normal RI at rest in most patients, the control of RCs during voluntary movements is disturbed in these patients, which probably contributes to their motor disability.
Studies of the structure of particle tracks have led to models of track effects based on radial dose and radiobiological target theory that have been very successful in describing and predicting track effects in physical, chemical, and biological systems. For describing mammalian cellular inactivation two inactivation modes are required, called gamma-kill and ion-kill, the first due to synergistic effects of delta rays from adjacent ion paths thus resembling the effects from gamma rays, and the second to the effects of single ion transits through a cell nucleus. The ion-kill effect is more severe, where the fraction of cells experiencing ion kill is responsible for a decrease in the oxygen enhancement ratio, and an increase in relative biological effectiveness, but these are accompanied by loss of repair, hence to a reduction in the efficiency of fractionation in high LET therapy, as shown by our calculations for radiobiological effects in the "spread out Bragg Peak".
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Acute hyperparathyroidism is a rare and dangerous condition. It is supposed to result from transformation of a mild chronic form into an acute and stormy illness. The causes and the mechanism of such a transformation are usually unknown. A case of acute hyperparathyroidism is presented in which hemorrhage into a parathyroid adenoma was recognized and diagnosed as the immediate cause of the transformation from the mild long-standing form of the disease into the severe acute form.
We present a unique case of a 37-yr-old patient who underwent a left partial glossectomy, modified neck dissection, and radiation therapy in December 1990. In June 1991 the patient developed a 0.6 cm erythematous nodule in the left upper portion of her neck adjacent to the surgical scar. A fine-needle aspiration (FNA) of the nodule was performed. Cytologic examination revealed the presence of numerous organisms morphologically consistent with Entamoeba gingivalis. Although E. gingivalis can be found in specimens from the oral cavity, especially following radiation, it is rare to find these organisms within lesions of the head and neck region. In this case, it is believed that the patient had an increased number of organisms within her oral cavity secondary to radiation therapy. Radiation therapy also may have contributed to the formation of a fistula tract between the oral cavity and the surgical incision site which resulted in the formation of a small inflammatory nodule in the upper portion of the neck. The organisms could then travel from the oral cavity to the nodule in the neck thus explaining their presence in the FNA material.
Despite the importance of grandparenthood in the personal and family context, as well as its increasing economic, political and legal implications, research addressing its meaning and significance has been sparse and characterized by theoretical and methodological limitations. The main theoretical limitation is the lack of a clear definition at the conceptual level. Methodological limitations include not only the use of small and non-inclusive samples, most of which pertain to only one or two generations, but also the lack of a well-developed multidimensional measurement approach. The aim of the present paper is to describe the status of research on the meaning of grandparenthood, and discuss its conceptual and methodological developments, especially regarding measurement issues. An example of an ongoing research program is provided as a guideline for future research.
The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 microm sites.