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Biomedical subjects

J Katz

Publications and source records attributed to J Katz.

At least 217 records · Page 12Linked to original sources
PubMed1997

Efficiency of EPI cluster sampling for assessing diarrhoea and dysentery prevalence.

This study examines the efficiency of EPI cluster sampling in assessing the prevalence of diarrhoea and dysentery. A computer was used to simulate fieldwork carried out by a survey taker. The bias and variance of prevalence estimates obtained using EPI cluster sampling were compared with those obtained using simple random sampling and cluster (stratified random) sampling. Efficiency ratios, calculated as the mean square error divided by total distance travelled, were used to compare EPI cluster sampling to simple random sampling and standard cluster sampling. EPI cluster sampling may be an appropriate low-cost tool for monitoring trends in the prevalence of diarrhoea and dysentery over time. However, it should be used with caution when estimating the prevalence of diarrhoea at a single point in time because of the bias associated with this cluster sampling method.

Age Factors↗
PubMed1997

Individual differences in self-appraisals and responses to dating violence scenarios.

Previous research suggests that certain types of self-appraisals may predispose individuals to be more or less tolerant of relationship violence. The current study investigates two such appraisals, self-esteem and self-attributions, as correlates of women's responses to hypothetical episodes of relationship violence by their dating partners. Undergraduate women involved in dating relationships (N = 145) reported global self-esteem, attributions for hypothetical partner aggression, and probable responses to the aggression. Results showed that self-esteem and self-attributions emerged as correlates of intentions to forgive violence, whereas only self-attributions emerged as a correlate of intentions to dissolve the relationship. The association between self-attributions and intentions to exit a violent relationship was fully mediated by intentions to forgive the partner. Because self-appraisals may inform prevention programs for women who may experience relationship violence, clinical implications are discussed.

Adolescent↗
PubMed1997

[Multicenter study of Helicobacter pylori infection prevalence in patients with chronic gastroduodenal disease. Various epidemiologic features].

The aim of this study was to establish the prevalence of H. Pylori infection in patients with chronic gastroduodenal pathology, who were treated in the gastroenterology units of four hospitals located in the Federal Capital and its neighbouring areas. 398 patients were studied by means of clinical assessment and epidemiology data. Upper endoscopy was carried out two biopsies were taken of the gastric antrum for a quick ureasa test and histological assessment of the H. pylori state by means of giemsa's stain. The prevalence of infection on the total of the studied population was 75.6%. In patients with gastric ulcer was 70%; in patients with duodenal ulcer it was 77.2% and 78.5% in patients with chronic gastritis. The prevalence of H. Pylori infection on the population according to age groups was: 61.54% in patients between 21 and 40 years; 76.14% in patients between 41 and 60 years, and 68.22% in patients over 60 year. We have tried to obtain a correlation between the prevalence of the infection and some sanitary characteristic (Running water and sewers) on the studied population. It was seen that 225 patients who lived in dwellings with running water and sewers showed a prevalence of infection of 69.34% and in 129 patients who did not have running water or sewer the rate of prevalence of infection was 83.72; a difference which was statistically significant, (with P < 0.01) for the patients who lived in poor sanitary conditions. These data may be important when the design of therapeutic schemes for the eradication of the bacteria is made.

Adult↗
PubMed1996

The Nuremberg Code and the Nuremberg Trial. A reappraisal.

The Nuremberg Code includes 10 principles to guide physician-investigators in experiments involving human subjects. These principles, particularly the first principle on "voluntary consent," primarily were based on legal concepts because medical codes of ethics existent at the time of the Nazi atrocities did not address consent and other safeguards for human subjects. The US judges who presided over the proceedings did not intend the Code to apply only to the case before them, to be a response to the atrocities committed by the Nazi physicians, or to be inapplicable to research as it is customarily carried on in medical institutions. Instead, a careful reading of the judgment suggests that they wrote the Code for the practice of human experimentation whenever it is being conducted.

Codes of Ethics↗
PubMed1996

Classifying visual field data.

We develop a prediction model for classifying an eye according to glaucoma status based on its visual field. We develop measures of both diffuse and localized defects in the visual field as potential predictors of glaucoma. To identify predictors of abnormal fields, we must describe the variability in the fields of normal eyes, hence we first model the mean, variance and correlation structures of normal fields with use of generalized estimating equations. The best measures of diffuse loss include a field's mean level, contrasts of the upper and lower halves, and contrasts of the nasal and temporal halves. Local loss is measured by the depth, area, volume and location of the field's largest defect. We develop logistic regression models to classify eyes as having glaucoma or not. We present ROC curves of the results that are highly competitive with current clinical methods of classification.

Adult↗
PubMed1996

Checkpoints in the progression of autoimmune disease: lessons from diabetes models.

In the last few years, data from experiments employing transgenic models of autoimmune disease have strengthened a particular concept of autoimmunity: disease results not so much from cracks in tolerance induction systems, leading to the generation of anti-self repertoire, as from the breakdown of secondary systems that keep these cells in check. T cells with anti-self specificities are readily found in disease-free individuals but ignore target tissues. This is also the case in some transgenic models, in spite of overwhelming numbers of autoreactive cells. In other instances, local infiltration and inflammation result, but they are well tolerated for long periods of time and do not terminally destroy target tissue. We review the possible molecular and cellular mechanisms that underlie these situations, with a particular emphasis on the destruction of pancreatic beta cells in transgenic models of insulin-dependent disease.

Animals↗
PubMed1996

Evaluation of triple-quantum-filtered 23Na NMR in monitoring of Intracellular Na content in the perfused rat heart: comparison of intra- and extracellular transverse relaxation and spectral amplitudes.

Multiple-quantum filtered (MQF) NMR offers the possibility of monitoring intracellular (IC) Na content in the absence of shift reagents (SR), provided that (i) the contribution from IC Na to the MQF spectrum is substantial and responds to a change in IC Na content, and (ii) the amplitude of the extracellular (EC) MQF component remains constant during a change in IC Na content. The validity and basis for these conditions were examined in isolated perfused rat hearts using SR-aided and SR-free triple-quantum filtered (TQF) 23NaNMR. Despite a myocardial Na content that was only approximately 1/70 that of EC Na. IC Na contributed to over 25% of the total TQF spectrum acquired in the absence of SR. Transverse relaxation times (T2) were approximately twice as long for EC compared to IC Na, despite SR-induced relaxation of T2 for the former pool. However, the efficiency of generation of the TQF signal was similar for IC and EC Na, indicating that a much greater percentage of IC relative to EC Na exhibits TQ coherence. During constant perfusion with ouabain (0.2 mM for 25 min) or with a hypoxic and aglycemic solution (50 min), the amplitude of the IC TQF spectrum increased by approximately 330% and -280%, respectively. In contrast, the amplitude of the EC TQF spectra remained essentially constant for both interventions. The amplitude for IC Na increased approximately 250% relative to baseline during no-flow ischemia (60 min), whereas the amplitude of the EC TQF spectra decreased by approximately 33% before stabilizing. In SR-free experiments, the TQF spectral amplitude increased approximately 2-fold during the constant perfusion interventions, but did not change significantly during no-flow ischemia. These data suggest that the change in the TQF spectral amplitude during constant perfusion interventions is from IC Na, and that TQF techniques in the absence of SR may be useful in monitoring IC Na during these interventions. The fall in the amplitude of the EC TQF spectral amplitude during no-flow ischemia complicates the use of TQF techniques without SR during this intervention.

Animals↗
PubMed1996

New double-quantum filtering schemes.

New double-quantum filtering (DQF) schemes are theoretically developed by reformulating the equations describing the double-quantum (DQ) signal. The equations describing the second- and third-rank DQ signals are simplified by restricting the RF phases as required for DQF. The equations are then factorized into two terms representing the separate contribution to the DQ signal from the RF pulses involved in the preparation and evolution times. This allows analysis of the DQ signal of a particular DQF scheme separately for each of these times in a concise manner. By use of the reformulated equations, the conventional DQF scheme is shown to be only one of four possible DQF schemes. The three new DQF schemes offer some desirable properties over the conventional DQF scheme. In the conventional DQF scheme, the third-rank DQ signal declines rapidly to null as the flip angles of the creation and readout RF pulses deviate from 90 degrees to 54.7 degrees or 125.3 degrees. In addition, the second- and third-rank DQ signals in the conventional DQF scheme are opposite in their polarities, resulting in attenuation of the total DQ signal due to destructive interference between them. In one of three new DQF schemes, the DQ signal does not vanish at 54.7 degrees and 125.3 degrees, but varies smoothly with the same functional dependence on the RF flip angles as the second-rank DQ and triple-quantum signals. Furthermore, in two of the three new DQF schemes, the second- and third-rank DQ signals have the same polarity so that the total DQ signal may be enhanced through constructive interference between them. These features of new DQF schemes have been confirmed experimentally.

Gels↗
PubMed1996

Chemical-Shift-Selective Acquisition of Multiple-Quantum-Filtered 23Na Signal

Equations describing the multiple-quantum (MQ) signal produced by an MQ pulse sequence are systematically derived in both absence and presence of refocusing RF pulses. When the RF pulses in an MQ pulse sequence satisfy certain conditions, these equations may be arranged in a factorized form. The off-resonance effects on the MQ signal due to chemical shift can then be analyzed separately during the preparation and evolution times. Using the reformulated equations, the dependence of the amplitude of an MQ signal on the phase shift induced by the resonance offset during the preparation and evolution times is demonstrated. By use of the new equations, it is shown that the off-resonance effects, occurring during both the preparation and evolution times, may be described in terms of the same physical process, i.e., interference between echo and antiecho. In applying the off-resonance effects for the elimination of the MQ signal in the presence of chemical shift, it is possible to suppress the MQ signal over a wider off-resonance bandwidth by use of the nonrefocused preparation and evolution times than by use of a single time. Furthermore, by taking an alternative approach in deriving the equations, the interference between echo and antiecho due to the resonance offset is shown to be insensitive to the flip angle of the creation RF pulse (usually the second pi/2 RF pulse). The theoretical findings were experimentally verified by use of a phantom containing sodium in agarose.

Journal Article↗
PubMed1996

Bronchoscopic findings in post-obstructive pulmonary oedema.

PURPOSE: To present the first photographed bronchoscopic findings associated with negative pressure pulmonary oedema (NPPE). CLINICAL FEATURES: A previously healthy patient underwent anterior C3-C4 disc removal and arthrodesis. Following tracheal extubation he developed acute respiratory distress manifested as stridor, tachypnoea, restlessness, and desaturation. Once the trachea was reintubated, he displayed the classic findings of pulmonary oedema. Bronchoscopy was performed to confirm tracheal tube position and to rule out tracheal injury secondary to surgical manipulation. Diffuse punctate haemorrhages were noted throughout the visualised tracheobronchial tree. CONCLUSION: We believe that these haemorrhages represent disruption of the bronchial vasculature and may contribute to the clinical presentation of NPPE.

Acute Disease↗
PubMed1996

Rate of progression in open-angle glaucoma estimated from cross-sectional prevalence of visual field damage.

PURPOSE: To estimate the rate of visual field loss in persons with open-angle glaucoma. METHODS: The visual field data obtained by Goldmann perimetry from 151 persons with open-angle glaucoma from the Baltimore Eye Survey were graded on a nine-level severity scale. Approximately one half of these persons had previously diagnosed glaucoma and were being treated. Using regression analysis, their scores were compared to other features, including age, vertical cup/disk ratio, treatment status, gender, race, and intraocular pressure. These data were used to estimate the average rate of progressive field loss and blindness in glaucoma. RESULTS: Among 112 black subjects, the severity of visual field damage was significantly associated with age (P < .02), history of glaucoma treatment (P < .04), and intraocular pressure (P < .0001). Using the relationship between age and damage, we estimated that the rate of deterioration of black glaucoma subjects was two grading levels per decade, which is consistent with previous reports. For 39 white subjects, the inclusion of age improved the model relationship between damage score and other variables. The best estimate of individual damage rate for whites was similar to that in blacks. However, the statistical association of age and damage in whites was less strong than in blacks, possibly because of fewer white subjects in the sample. CONCLUSIONS: While glaucoma is a frequent cause of visual disability, rate of progressive visual field loss is not sufficient to lead to bilateral blindness in the majority of those affected. Aggressiveness of glaucoma therapy should be related to the rate of visual field loss stressing confirmation of field progression.

Adult↗
PubMed1996

Respiratory complications of gastroesophageal reflux disease.

There is a relationship between gastroesophageal reflux disease and certain respiratory symptoms and findings. Among these are cough, laryngitis, and wheezing dyspnea. The pathophysiology of these conditions can vary from actual aspiration of gastric content to esophageal mucosal inflammation with the respiratory symptoms induced by a vagally mediated reflex mechanism.

Gastroesophageal Reflux↗
PubMed1996

The cause-specific prevalence of visual impairment in an urban population. The Baltimore Eye Survey.

BACKGROUND: Whereas population-based data on the causes of bilateral blindness have been reported, little information is available on the distribution of causes of central vision loss less severe than the criteria used to define legal blindness. This visual impairment is responsible for a high proportion of eye care service use and results in important reductions in functional status. METHODS: Data from the Baltimore Eye Survey were used to estimate the cause-specific prevalence of visual impairment (best-corrected visual acuity worse than 20/40 but better than 20/200) among black and white residents of east Baltimore who were 40 years of age or older. Eligible subjects underwent a screening examination at a neighborhood location and, for those whose best-corrected visual acuity was less than 20/30, a definitive ophthalmologic examination at the Wilmer Eye Institute. RESULTS: The prevalence of visual impairment was 2.7% in whites and 3.3% in blacks; the age-adjusted relative prevalence (B/W) was 1.75 (P = 0.01). The leading causes of visual impaired eyes were cataract (35.8%), age-related macular degeneration (14.2%), diabetic retinopathy (6.6%), glaucoma (4.7%), and other retinal disorders (7.3%). Cataract, diabetic retinopathy, and glaucoma were more common as a cause of visual impairment among blacks, whereas macular degeneration was more frequent among whites. More than 50% of all subjects had the potential for improvement in vision with appropriate surgical intervention. CONCLUSION: Visual impairment is a prevalent condition among inner city adults 40 years of age or older. The distribution of causes suggests that improvements in the visual health of the population could be achieved with more effective delivery of efficacious ophthalmologic care.

Adult↗
PubMed1996

Detection of incident field loss using the glaucoma hemifield test.

PURPOSE: To examine different definitions of incident visual field loss among patients with elevated intraocular pressure and varying numbers of abnormal glaucoma hemifield test results over an average of 6 years of follow-up. METHODS: A cohort of patients with annual C-30-2 Humphrey visual fields were followed for a minimum of 5 years. Three different definitions of field loss were compared: 1, 2, or 3 consecutive annual abnormal glaucoma hemifield test results. RESULTS: Of 253 subjects, 506 eyes were followed for 5 to 9 years. If incident field loss was defined as one or more normal fields followed by one abnormal glaucoma hemifield test result, the incidence of field loss was 63.6 per 1000 person-years of follow-up. For two or three consecutive abnormal glaucoma hemifield test results, the rates were 27.6 and 19.2 per 1000 person-years of follow-up, respectively. Among patients with field loss in one eye at the start of the study, the incidence of field loss in the fellow eye using 1, 2, or 3 consecutive abnormal fields as the definition of incident field loss was 60.9, 55.5, and 25.5 per 1000 person-years of follow-up, respectively. Three years after incident field loss, 31.9% (1 abnormal test result), 76.5% (2 abnormal test results), and 88.5% (3 abnormal test results) of eyes with incident field loss had an abnormal hemifield test result. For eyes with one, two, and three consecutive abnormal glaucoma hemifield test results at the start of the study, 59.2%, 83.6%, and 89.1%, respectively, had an abnormal field 3 years later. CONCLUSIONS: One abnormal glaucoma hemifield test result is not a consistent criterion for defining incident field loss. The use of two or three consecutive abnormal fields to define incident field loss makes it more likely that subsequent test results will be abnormal.

Adult↗