Disseminated tuberculosis in the acquired immunodeficiency syndrome era

To assess the influence of human immunodeficiency virus type 1 (HIV)-induced immunodeficiency on the clinical, radiographic, and pathologic features of disseminated tuberculosis (TB), we studied 79 patients presenting in 1984 through 1987 with miliary or focal disseminated disease due to Mycobacterium tuberculosis, as well as 4 additional non-HIV patients diagnosed after 1987. Clinically defined acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) was present in 51 (Group 1). A total of 20 had TB unrelated to HIV disease (Group 2). The remaining 12 were excluded because the role of HIV could not be determined. Clinical features were similar between groups aside from younger age; lower hemoglobin, total leukocyte, lymphocyte, and platelet counts; and more frequent tuberculin anergy (90 versus 40%) in AIDS/ARC patients (p less than or equal to 0.03). Chest radiographs showed a miliary pattern in about half of each group. Pleural effusion occurred only in AIDS/ARC patients (24%, p = 0.02), but intrathoracic lymphadenopathy was present in about a third of each group. Tissue biopsies (n = 70) usually revealed necrotizing granulomatous inflammation in each group, with a tendency to greater necrosis and more numerous acid-fast bacilli in Group 1. Granulomas were usually poorly formed in AIDS/ARC patients (59 versus 18%, p = 0.01). Autopsy of 9 AIDS/ARC patients with overwhelming miliary TB revealed a "nonreactive" histologic pattern with poorly organized or absent granulomas, extensive necrosis, and numerous bacilli. HIV-related disseminated TB causes a major constitutional illness with a high short-term mortality (25%).(ABSTRACT TRUNCATED AT 250 WORDS)

Photooxidation of oligodeoxynucleotides by UO2(2+)

Photooxidation and consequent cleavage of oligodeoxynucleotides by the uranyl ion is greatly enhanced in the presence of a terminal 5'- or 3'-phosphate group. This enhanced cleavage is confined to nearby phosphodiester bonds in the case of a 5'-phosphate, but is less localized in the case of a 3'-phosphate. Several attempts to use a complementary oligodeoxynucleotide to direct a uranyl "warhead" against an oligodeoxynucleotide target were unsuccessful. Our results are most easily explained if we suppose that uranyl ions form coordination complexes with terminal phosphates and that, on photoexcitation, coordinated uranyl ions extract a hydrogen atom from the CH bond of a nearby deoxyribose residue.

Vistech VCTS 6500 charts--within- and between-session reliability

The aim of the study was to measure the reliability of the Vistech VCTS 6500 charts, in test score units, in order to allow clinicians to derive estimates of what constitutes a clinically meaningful change in performance over time. The reliability of a more familiar test, Bailey-Lovie high contrast visual acuity, was also measured to provide a comparison. Patients with normal vision and with early or subtle eye disease were recruited so that the results would be representative of the population likely to present for primary vision screening. Patients were tested on all three VCTS charts on two separate occasions at least 3 weeks apart to give estimates of within- and between-session reliability. Reliability was found to be low in all circumstances; between-session reliability could be improved by using the mean score for the three charts, but the 95% range of difference scores still encompassed at least one-half of the total performance range of the test. It was concluded that Vistech charts are unlikely to be of use for clinical measurements or for research studies.

Which 3-ribofuranosyl-substituted purine 5'-phosphates undergo template-directed oligomerization?

We have studied the oligomerization reactions of the 2-methylimidazolide derivatives of 3-isoisoguanosine 5'-phosphate (2) and 3-isoxanthosine 5'-phosphate (5) in the presence of a variety of homopolynucleotide templates. In no case did we observe a substantial template-facilitated production of long oligomers. Polyuridylic acid directed the synthesis of low molecular-weight products from both monomers. Polycytidylic acid, polyadenylic acid, polyinosinic acid, and polyguanylic acid were ineffective as templates in the systems that we investigated.

Mycobacterial infections in AIDS

Tuberculosis (TB) remains uniquely important among acquired immune deficiency syndrome (AIDS)-associated opportunistic infections: it presents the greatest public health hazard worldwide, is the most readily curable, and is largely preventable with existing means. Given the expanding pool of human immunodeficiency virus (HIV) seropositive persons, particularly in developing nations where Mycobacterium tuberculosis remains a leading health problem, one can expect a continued rise in TB cases during the 1990s. Global efforts to eliminate TB are now inextricably entwined with the effectiveness of measures to curtail the HIV epidemic. Mycobacterium avium complex infection, currently an intractable late complication of aids, may increase in clinical importance as success in managing other opportunistic infections and HIV disease itself improves. Understanding of the pathogenesis and management of mycobacterial diseases should increase rapidly given the renewed research spurred on by the advent of HIV.

Altered water metabolism in tuberculosis: role of vasopressin

PURPOSE

Patients with hyponatremia due to tuberculosis have shown variable responses to water loading in previous small studies, ranging from persistent antidiuresis to a normal diuresis. Although tuberculosis is considered a cause of the syndrome of inappropriate antidiuretic hormone secretion (SIADH), circulating vasopressin has been documented in only a few cases. We studied a larger group of patients to determine whether it can be suppressed by a short-term reduction in osmolality.

PATIENTS AND METHODS

Twenty-eight hyponatremic patients (mean age +/- SD: 40 +/- 10 years) with pulmonary or miliary tuberculosis underwent a clinical evaluation, measurement of blood and urine chemistry values, and (in 22) a water load of 20 mL/kg. Volume status was evaluated by urine sodium concentration, blood and urine urea nitrogen, and plasma renin activity. Endocrine, renal, and other recognized causes of SIADH were excluded.

RESULTS

All 22 patients exhibited a decline in urine osmolality and an increase in free water clearance after water loading. Water excretion was fully normal in seven of 22, with the remainder showing variable impairment of diluting ability and/or volume excreted. Plasma vasopressin, measured in 11 of 22 patients as well as in six others not subjected to water loading, was detectable despite hypo-osmolality in 16 of 17. Vasopressin levels declined after water loading, from 1.85 +/- 1.32 to 0.77 +/- 0.25 pg/mL (p less than 0.05). The majority of patients had the euthyroid sick syndrome but normal adrenal responses to cosyntropin. Although several patients had mild volume depletion when studied, this factor did not appear to explain the defect in water excretion. Hyponatremia resolved predictably within days to weeks of antituberculous therapy.

CONCLUSIONS

Circulating vasopressin remains detectable in hyponatremic patients with tuberculosis and is responsive to changes in osmolality. A downsetting of osmoregulation induced by active tuberculosis ("reset osmostat") could explain this abnormality, but we cannot exclude an unidentified non-osmotic stimulus that can be counteracted by water loading.

Cyclization of nucleotide analogues as an obstacle to polymerization

Cyclization of activated nucleotide analogues by intramolecular phosphodiester-bond formation is likely to compete very effectively with template-directed condensation except in the cases of ribo- and arabinonucleotides. This could have excluded derivatives of most sugars from growing polyribonucleotide chains and thus reduced chain-termination in prebiotic polynucleotide synthesis.

Short-term entrainment of ventilation to the walking cycle in humans

We describe a breath-by-breath method to test for entrainment of breathing and walking cycles. Thirty-eight normal subjects walked comfortably on a treadmill while breathing through a pneumotachograph. We analyzed the time intervals between heel strikes and the onset of inspiration (or expiration) for evidence of phase locking between steps and breaths, using Monte Carlo simulation to model the probability that n consecutive inspirations (or expirations) would begin at a constant time interval +/- 0.10 s from heel strikes by chance. We developed empirical criteria for rhythm synchronization during series of four or more breaths, while maintaining an estimated specificity of 95%. The majority of subjects showed some evidence of entrainment (29 +/- 23% of breaths on average), which occurred intermittently, usually lasting less than 10 breaths at a time. The precision of phase locking during spontaneous entrainment was similar to that in 10 subjects who attempted to maintain deliberate entrainment. The results suggest that the walking cadence provides a persuasive, but not dominant, input to the central breathing pattern generator. The present method can detect entrainment even when it occurs sporadically or with varying coupling pattern.

Template-directed oligomerization of 3-isoadenosine 5'-phosphate

Template-directed oligomerization of an activated derivative of 3-isoadenosine 5'-phosphate (piA) on polyuridylic acid [poly(U)] was studied. The reaction of ImpiA is more efficient than the corresponding reaction of ImpA, and produces 3'-5'-linked oligomers while the reaction of ImpA gives only 2'-5'-linked oligomers. The base pairing between piA and poly(U) in this system is probably of the Hoogsteen type (involving the 6-amino group and N7 of 3-isoadenosine) rather than of the Watson-Crick type.

Test-retest reliability of the Arden Grating Test: inter-tester variability

The aim of this study was to investigate the test-retest reliability of the Arden Grating Test (AGT), and to assess the extent to which any variance in AGT score on retest can be attributed to intra-subject and inter-tester differences. Twelve patients with various pathologies and whose contrast sensitivity covered a wide range were each tested twice by six testers. It was shown that variance attributable to testing by different clinicians accounted for approximately 25% of the total variance, and that the 95% confidence limits about any observed score were +/- 15 AGT units, which is about one quarter of the total dynamic range of the test. The large range of scores encompassed by the 95% confidence limits represents considerable unreliability, the consequence of which is a high misclassification rate, i.e. many false positives and false negatives, especially in the context of primary vision screening for which it was designed.

Human lens nuclear colour matching and brunescence grading in vivo

The nuclear colour of in vivo human lenses has been investigated by means of a colour matching technique, using 'Munsell' colour samples. Observations covered an extended age range, and included all degrees of nuclear pigmentation. A positive correlation was noted between increasing nuclear pigmentation and age. The colour matching data generated was used as a basis for establishing a system of nuclear brunescence grading. The system of grading consists of a Grade 0 for absence of brunescence, and Grade 1 to Grade 5 for increasing brunescence. The 'Munsell' notation for samples representing these grades are: Grade 0 (5GY 6/1), Grade 1 (5Y 7/4), Grade 2 (2.5Y 7/8), Grade 3 (7.5YR 6/8), Grade 4 (5YR 4/6), and Grade 5 (2.5YR 2.5/2). Assessments of both inter- and intra-observer variability in the use of the derived scale have shown the new colour grading system to be reliable. The measure is simple to use during biomicroscopic slit-lamp examination of the lens, and has the potential for routine clinical application as well as for use in clinical trials where detailed documentation of lens morphology is required. The new colour scale may be used either as an isolated measure, or as part of a battery of lens measures in the Oxford Clinical Cataract Classification and Grading system.

Huematic--an automated scorer for the Farnsworth-Munsell 100 hue test

A cheap, portable automated scorer for the Farnsworth-Munsell (FM) 100 hue test has been developed. It consists of a light pen, a series of omni-directional bar-codes attached to the reverse of the FM 100 hue caps and a small micro-computer. The print-out includes patient details, a linear histogram of the partial errors by cap position, indication of the peak error positions for congenital colour vision deficiencies and appropriate statistical analysis of the total error score. All the results are available within four minutes of completing the testing procedure.

Inter-observer and intra-observer variability of the Oxford clinical cataract classification and grading system

Intra-observer (within observers) and inter-observer (between observers) variability of the Oxford Clinical Cataract Classification and Grading System were studied. Twenty cataracts were examined and scored independently by four observers. On a separate occasion two of the observers repeated the assessments of the same cataracts in the absence of information from the initial observations. The chance corrected and weighted kappa statistics for observer agreement, both for inter-observer and intra-observer variability demonstrated satisfactory repeatability of the cataract grading system. The overall intra-observer mean weighted kappa was kappa w = +0.68 (range SE kappa = 0.012-0.052) and the overall inter-observer mean weighted kappa was kappa w = +0.55 (range SE kappa = 0.011-0.043).

Cataract: the relation between myopia and cataract morphology

The association between high myopia and cataract is already well established and an association between simple myopia and cataract has been suggested, but it has not been clear to what extent the myopia precedes the cataract or is the result of it. The present study compares the refraction of a group of 100 British patients at the time of first presentation with cataract in whom the refraction was also known four years previously, with a group of matched controls in whom the refraction was also known four years previous to presentation. The study shows that simple myopia does not appear to predispose to cataract. It is the development of the cataract itself, in particular nuclear sclerosis, which causes the refractive change towards myopia. The myopic change precedes the development of cataract, and patients over the age of 55 showing a myopic change in refraction have a very high probability of developing nuclear sclerotic cataract. The healthy aging eye and eyes with cortical cataract or subcapsular cataract, but without nuclear sclerosis, continue to show a gradual hypermetropic change with time.

The objective assessment of cataract

The objective assessment of cataract is central to any epidemiological or therapeutic study of cataract. The objective methods consist of: 1: A resolution target projection ophthalmoscope (Acuity scope) for the estimation of potential visual acuity. 2: The Oxford Clinical Cataract Classification and Grading System, which records and quantifies the features of the lens that are visible at the slit-lamp microscope. This system is essential since photographic methods cannot define the morphology of cataract. 3: Two photographic methods; slit-lamp photography and retro-illumination photography are needed to give a comprehensive statement about the amount of cataract. The negatives are measured by computerised image analysis systems.

The Oxford Clinical Cataract Classification and Grading System

A composite slit-lamp based system for the clinical classification and grading of cataract is described. Cataract features are classified morphologically, and individual features are graded by comparison with standard diagrams mounted adjacent to the slit-lamp. Attention has been paid to relevant aspects of measurement theory, with equal interval steps between the grades. The image degrading effect of the cataract is assessed using a 'resolution target projection ophthalmoscope'. The method may be used in conjunction with photographic and image analysing techniques.

Acid maltase deficiency in an adult. Evidence for improvement in respiratory function with high-protein dietary therapy

Acid maltase deficiency (AMD) in the adult is associated with progressive ventilatory muscle weakness and death from respiratory failure, but effective therapy is not available at present. Because recent evidence suggests that muscle catabolism may contribute to muscle weakness in AMD, we treated a 55-yr-old man with AMD and severe ventilatory muscle weakness with a high-protein (1.6 g/kg), weight-reducing diet for 27 months. High-protein dietary therapy was associated with striking improvement in respiratory function, including measures of ventilatory muscle strength and endurance. We suggest that high-protein dietary therapy may be useful in adults with AMD and respiratory insufficiency.

Steady-state response of conscious man to small expiratory resistive loads

To determine the predominant steady-state ventilatory responses to mild expiratory flow-resistive loads, we subjected 14 normal subjects to expiratory resistances of 0-10 cm H2O/L/sec (R0-R3). Breathing patterns and abdominal muscle activity (EMG) were recorded during quiet breathing, and when ventilation was augmented by dead space breathing (7 subjects) or treadmill walking (7 subjects). Expiratory loading increased expiratory time (TE), tidal volume and mean inspiratory flow rate, while decreasing inspiratory duty cycle and respiratory frequency. Minute ventilation (VI) remained constant. These load responses were most prominent during quiet breathing, and were attenuated or abolished as VI increased. Abdominal EMG was negligible during quiet breathing, increased when VI increased, but showed no consistent response to R1-R3. Thus, the principal defense against mild expiratory loads is prolongation of expiration, accompanied by enhanced inspiratory drive. Abdominal muscle expiratory activity is elicited by increasing ventilation, but occurs only sporadically with expiratory loading of the magnitude studied.

Laser treatment of primary ring-shaped epithelial iris cyst

This is the first report of a ring-shaped, primary cyst of the iris pigment epithelium. The patient, a 28-year-old woman, presented with angle closure glaucoma. Ocular pressure was controlled medically, and the iris cyst was treated by argon laser photocoagulation. The derivation of the cyst, differential diagnosis, and mechanism of angle closure glaucoma are discussed.

A computer-based data acquisition system for breathing and exercise entrainment studies

An interactive, real-time, computer-based data acquisition system was designed to obtain data for breathing and exercise entrainment studies. By timing the steps of subjects walking on a treadmill relative to different points in the respiratory cycle (e.g. the beginning and end of inspiration), the relation between gait and ventilation can be followed on a breath-by-breath basis. Accurate establishment of the beginning and end of respiratory events from a pneumotachygraph signal was assured by using tidal volume thresholds for (1) noise, (2) minimum valid volume and (3) minimum duration.

Cryptococcal pneumonia: a fulminant presentation

A 32-year-old presented with fulminant, bilateral airspace pneumonia due to Cryptococcus neoformans while under cytotoxic therapy for advanced Hodgkin's disease. We alert physicians to this rapidly progressive form of cryptococcosis which has been poorly described previously and which may closely mimic bacterial pneumonia.

Clinical inferences and decisions--III. Utility assessment and the Bayesian decision model

It is accepted that errors of misclassifications, however small, can occur in clinical decisions but it cannot be assumed that the importance associated with false positive errors is the same as that for false negatives. The relative importance of these two types of error is frequently implied by a decision maker in the different weighting factors or utilities he assigns to the alternative consequences of his decisions. Formal procedures are available by which it is possible to make explicit in numerical form the value or worth of the outcome of a decision process. The two principal methods are described for generating utilities as associated with clinical decisions. The concept and application of utility is then expanded from a unidimensional to a multidimensional problem where, for example, one variable may be state of health and another monetary assets. When combined with the principles of subjective probability and test criterion selection outlined in Parts I and II of this series, the consequent use of utilities completes the framework upon which the general Bayesian model of clinical decision making is based. The five main stages in this general decision making model are described and applications of the model are illustrated with clinical examples from the field of ophthalmology. These include examples for unidimensional and multidimensional problems which are worked through in detail to illustrate both the principles and methodology involved in a rationalized normative model of clinical decision making behaviour.

Effects of thoracic volume and shape on electromechanical coupling in abdominal muscles

To assess the effects of lung volume and chest wall configuration on electromechanical coupling of the abdominal muscles, we examined the relationship between abdominal muscle pressure ( Pmus ) and electrical activity ( EMGab ) in eight normal subjects during expiratory efforts at lung volumes ranging from functional residual capacity (FRC) to FRC + 2.0 liters. At and above FRC, increases of lung volume did not significantly alter either the Pmus - EMGab relationship or abdominal surface linear dimensions, although expiratory efforts displaced the abdomen inward from its relaxed position. We attribute the constancy of delta Pmus /delta EMG above FRC to the negligible effects of increasing lung volume on abdominal configuration and muscle length. Expiratory efforts performed at lung volumes below FRC resulted in a wider range of abdominal indrawing . Under these conditions the EMGab required to augment Pmus by 30-40 cmH2O increased as the abdomen was displaced inward. This decrease of delta Pmus /delta EMGab appears to reflect muscle shortening, flattening of the abdominal wall, and possibly deformation of the rib cage.

Clinical inferences and decisions--I. Diagnosis and Bayes' theorem

Clinical decisions are based upon inferences derived from test evidence where data is collected as a means of hypothesis testing. In medicine, the initial expectation of a clinical state is rarely expressed in the classical scientific language of a null hypothesis where alternative outcomes are assumed to be equally probable, because clinical experience reinforces the maxim that common events occur commonly. The collection of test evidence in clinical practice, therefore, is directed towards overturning prior likelihoods for a clinically pathological state which are far from mere chance expectations. The extent to which any test evidence can modify such prior expectations not only depends on its relevance to the clinical state in question (i.e. the hypothesis) but also is largely influenced by the inherent error rates in the test itself. Clinical decision models should reflect these facts. Using examples from the field of ophthalmology, this paper presents a normative model using Bayes' theorem of conditional probabilities which provides a rational framework upon which to base or appraise clinical decisions. Parts II and III of the series will expand this clinical application of decision theory to show how it may be used in the absence of hard test evidence and also where a different emphasis or utility may be placed on false positive or false negative errors.

Doctors, contraception, and sterilisation

Images

Some factors influencing vision through meshes

The problems associated with vision through mesh window screening materials are discussed and a laboratory experiment using a 1/8th replicate 2th factorial design is described which shows the relative effects on vision of main effects and first-order interactions. Two criteria of visibility were used: a Landolt ring, measuring changes in visual acuity, and paired ratio scaling giving direct magnitude estimates of “ease of seeing” through the material. The laboratory results were validated in a short field experiment in which the effects on visibility of three isolated variables was determined by paired comparisons. Some suggestions for future experiments are also discussed.