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Biomedical subjects

V Smith

Publications and source records attributed to V Smith.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

Brain mechanisms in fatal cardiac arrhythmia.

Intravenous injection of histamine to rabbits was used as a prototype in an investigation of the mechanism of sudden death due to anaphylaxis and other causes. The "dive" reflex, bradycardia due to activation of the ophthalmic branch of the fifth cranial nerve, was induced in thirty-seven of the animals while they inhaled a very small amount of cigarette smoke. Associated with the resulting bradycardia were lowered blood pH and increased serum content of lactic acid and potassium and increased peripheral arterial constriction with elevation of diastolic blood pressure. Intravenous injection of 1 ml of histamine in the presence of the dive reflex induced potentially fatal ventricular arrhythmia, but no cardiac disturbance when administered while the dive reflex was inactive, thereby strongly suggesting that sudden death in anaphylaxis may involve an overzealous response to a normally protective neural reflex.

Adrenergic Fibers↗
PubMedDate not supplied

Medullary ray nodule of the kidney.

In this short report we describe three preterm infants who died within the first 8 months of life (corrected age). All presented similar histological features within the kidney, showing medullary ray nodules composed of tubules lined by low columnar epithelium with clear cytoplasm. The immunohistochemical profile of these lesions was identical and suggested origin from distal convoluted tubule or collecting duct. The aim of this report is to draw attention to this entity and to suggest a possible origin of these lesions.

Bronchopulmonary Dysplasia↗
PubMedDate not supplied

Leishmania infecting man and wild animals in Saudi Arabia. 5. Diversity of parasites causing visceral leishmaniasis in man and dogs in the south-west.

Kala-azar (VL), mainly affecting infants and young children, is being increasingly reported in the south-west of Saudi Arabia, 305 cases being diagnosed in 1988. Most cases arise in scattered locations in the foothills west of the Asir mountains at altitudes between about 500 and 1000 m, although case clusters are apparent in some villages. Some cases also occur between the foothills and the Red Sea coast. The incidence in the south-west was calculated to be of the order of 6 to 8/10,000 population per year, but a random serological survey using the enzyme-linked immunosorbent assay and direct agglutination techniques indicated a seropositivity rate of about 3.7% in 706 apparently healthy children. Most patients are Saudi or Yemeni and cases are being increasingly identified also in the Yemen Arab Republic. In the foothills of both countries the causative organism is Leishmania donovani s.l. zymodeme LON-42, which also occurs on the eastern littoral of Ethiopia. By isoenzyme electrophoresis, it is readily separated from L. infantum, which has been identified in feral dogs, the 2 organisms being sympatric. The infection was found in 6.7% of 89 dogs, but their seropositivity rate was 19.3%. Although L. infantum has not yet been recognized in man in Saudi Arabia, it has been identified in a child in the coastal plain of the Yemen Arab Republic. Further research needed to provide a rational basis for control is discussed.

Adolescent↗
PubMedDate not supplied

Leishmania infecting man and wild animals in Saudi Arabia. 6. Cutaneous leishmaniasis of man in the south-west.

Cutaneous leishmaniasis (CL) is common on the high plateaux and foothills of the Asir range in the south-west of Saudi Arabia and Yemen. In 1987 1198 and 1104 cases were reported among the Saudi populations of Asir and Al-Baha provinces, representing an estimated annual incidence of 12 and 38 per 10,000 respectively. The incidence rises from October to December, then declines to a minimum between May and August. The prevalence of Phlebotomus sergenti, a proven local vector in the highlands, is roughly in inverse proportion. Cases occur at all ages, over 60% have only a single lesion, and the head and neck are most commonly affected. Apart from a few patients who develop leishmaniasis recidivans, most respond well to sodium stibogluconate, or self-heal. Of 44 isolates typed by isoenzyme electrophoresis, 42 were Leishmania tropica belonging to 5 distinctive zymodemes. LON-72 (34 isolates), LON-73 (1), LON-71 (2) and LON-10 (2) were found at altitudes around 2000 m, 3 of them in a single village. Three isolates of LON-63 were found at altitudes between 600 and 1000 m in widely separated foci. L. tropica LON-10 and LON-71 have been isolated also from P. sergenti from highland foci. LON-72 failed to produce lesions in BALB/c mice and gave rise to only transitory lesions in the footpads of hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMedDate not supplied

Penicillin resistant Neisseria gonorrhoeae in low prevalence areas: implications for cost-effective management.

Though ampicillin is no longer recommended as first-line therapy for infections caused by Neisseria gonorrhoeae, the cost and efficacy of this policy in low prevalence areas has not been investigated. The problem was highlighted by an outbreak of penicillin-resistant N. gonorrhoeae in an area where the proportion of resistance had previously been only 0.14%. A decision analysis was performed to determine the cost-effectiveness of beta-lactamase screening and alternative therapies for patients attending sexually transmitted diseases clinics. Empiric therapy with an inexpensive agent active against resistant strains, such as ciprofloxacin, was the most cost-effective approach and remained more cost-effective than alternative strategies whenever the proportion of resistant isolates exceeded 3%. Ceftriaxone was less cost-effective. In low prevalence areas, and in areas where the return rate of recalled patients is high, ampicillin therapy was cost-effective, but beta-lactamase screening should be performed routinely.

Ampicillin↗
PubMedDate not supplied

Dose minimization in computed tomography overscanning.

The relationship of noise and dose in overscanning in computed tomography is reviewed to show that maximal variance reduction is obtained when the overscanning weights are proportional to the x-ray flux. It is also shown that maximal motion artifact suppression requires that the weights vary smoothly from zero at the beginning and ending of the scan to one in the central portion of the scan. Optimal noise and dose considerations suggest that the x-ray flux should be varied during the course of a scan in order to be proportional to the desired weighting. Computer simulations of a head phantom with a moving pin are used to show that such x-ray flux variations do achieve maximal artifact suppression with no additional dose to the patient over a standard (non-overscanned) scan.

Models, Theoretical↗
PubMedDate not supplied

Structured noise in computed tomography: effects of periodic error sources.

The artifact in computed tomography (CT) images due to cyclic projection errors, such as errors due to periodic fluctuations in x-ray intensity, is derived and verified by computer simulation. Depending upon the relative phase of the error between projections, the artifact is shown to be described by a Bessel function (or functions) of the radial argument which is sinusoidally modulated as a function of angle. Because of the nature of Bessel functions, the artifact is essentially zero up to some minimum radius. When the effects of sampling are neglected, a single fundamental artifact is shown to occur. In fourth-generation scanners, the fundamental artifact (neglecting sampling) will occur at a detector fan angle of about about 39 degrees (depending on the ratio of the axis-to-detector, source-to-axis distances). The radius of appearance of this fundamental artifact is independent of the frequency of the periodic error signal and will only be visible in fourth-generation CT scanners with detector fan angles greater than about 39 degrees. The effects of sampling are derived and illustrated by simulation for first-, third-, and fourth-generation CT-scanner geometries. It is shown that the effect of sampling is to cause an infinite number of such artifacts to be superimposed in the final image. The radius of appearance of all but the fundamental artifact are shown to be dependent on the frequency of the periodic signal. It is shown that by judicious choice of the sampling parameters relative to the frequency of the periodic error, the artifact can be effectively eliminated.

Technology, Radiologic↗
PubMedDate not supplied

Temperature distribution measurements in two-dimensional NMR imaging.

This paper represents a preliminary study of the effects of regional temperature distribution in two-dimensional nuclear magnetic resonance (NMR) T1 imaging. It is found, as expected, that variations in local temperature appear as variations in the corresponding T1 image. The potential use of NMR T1 imaging in temperature measurements is evaluated in the case of water and blood samples. Using containers where the temperature could be either known or directly controlled with reasonable accuracy, images are obtained with samples having at least two regions at different temperatures. As expected, T1 is found to vary linearly with 1/T over the range of 0 degrees C to about 40 degrees C for blood. The potential use of T1 imaging in hyperthermia applications is also discussed.

Blood↗
PubMedDate not supplied

Dose parameters of 125I and 192Ir seed sources.

As mandated by an NCI brachytherapy contract, we measured dosimetric parameters for 192Ir seeds and two models of 125I seeds. Measurements were with LiF powder in a water-equivalent phantom. Data were corrected for background, sample mass, and finite detector volume. Selected parameters were also investigated through Monte Carlo calculations. Results are presented in terms of a dose parametrization that is described in detail, and are compared to published data. Our results agreed well with published data for relative quantities such as radial and angular dose dependence. Our measured value for the 192Ir dose factor was 4.55 cGy(H2O) cm2 mCi-1 h-1, also in good agreement with commonly used values. However, the measured dose factors for 125I seed models 6702 and 6711 were 1.18 and 1.06 cGy(H2O) cm2 mCi-1 h-1, values well below those in general use.

Brachytherapy↗
PubMedDate not supplied

The relationship between the stages of change for exercise and health insurance costs.

OBJECTIVE: To determine the relationship between the stages of exercise participation and health insurance costs. METHODS: A hurdle model was used to examine health survey and health insurance costs data by stage of exercise participation. RESULTS: Employees classified in the maintenance stage (regular exercisers) of exercise adoption had lower costs and a lower probability of being classified in the high-cost group than did employees classified in the other stages of change for exercise participation. CONCLUSION: This study offers evidence that the health insurance of individuals classified in the maintenance stage of exercise costs less than does that of individuals classified in other stages of exercise adoption.

Adult↗