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Biomedical subjects

L Kaufman

Publications and source records attributed to L Kaufman.

At least 163 records · Page 9Linked to original sources
PubMed1992

Fatal pulmonary sporotrichosis caused by Sporothrix schenckii var. luriei in India.

The first case of fatal pulmonary sporotrichosis caused by Sporothrix schenckii var. luriei in a patient from the northwestern region of India is described. In the absence of cultures, the diagnosis was suspected by notation, in lung tissue, of large, thick-walled, hyaline fungal cells that divided internally by septation or a budding process. The thick-walled, internally septated cells often became muriform. The presence of an "eyeglass" configuration of incompletely separated cells characteristic of S. schenckii var. luriei in large numbers aided the diagnosis. The identity of the etiologic agent was confirmed by application of a fluorescent-antibody reagent specific for S. schenckii.

Adult↗
PubMed1992

In vivo relaxation times and hydrogen density at 0.063-4.85 T in rats with implanted mammary adenocarcinomas.

Magnetic resonance (MR) imaging at 0.063 T, 0.17 T, 0.35 T, 2.94 T, and 4.85 T was performed in rats with implanted mammary adenocarcinomas (and in control rats) to study hydrogen density and the effects of magnetic field strength on T1 and T2 relaxation times in vivo. T1 increased by an order of magnitude and T2 decreased by a factor of two between the lowest and highest field strengths. Only about half of the increased water content of tumor, compared with that of muscle, was reflected in increased hydrogen density. The sensitivity of relaxation time change was increased at the lower field strengths. These results are of significance in understanding the effects of field strength on lesion detectability, contrast, and signal-to-noise ratio.

Adenocarcinoma↗
PubMed1992

MR relaxometry imaging. Work in progress.

Acquisition of relaxation rate dispersion curves from magnetic resonance images was demonstrated on a clinical, whole-body imaging system. Study of the behavior of relaxation rates over a range of field strengths probes the structural environment of imaged hydrogen protons and reveals information about the composition of tissue. The authors determined relaxation rates in extremities and heads of healthy volunteers. The sensitivity of the measurement is sufficient to obtain a distinctive relaxation rate dispersion behavior for different tissues.

Adult↗
PubMed1992

Amikacin once daily plus metronidazole versus amikacin twice daily plus metronidazole in colorectal surgery.

Amikacin administered once a day plus metronidazole is compared with amikacin given twice a day plus metronidazole in colorectal surgery (prophylactic or therapeutic antibiotic treatment). A total of 325 patients were studied in this randomized multicenter trial. The results of this trial suggest that a single daily dose of amikacin is equally as effective in combating infectious postoperative complications as twice a day administration. The side effects were similar, with the exception of renal effects, which were somewhat more pronounced in once a day amikacin administration. Nevertheless, all the renal function alterations were transient and we observed no definitive renal insufficiency.

Adult↗
PubMed1991

Advantages and limitations of magnetic source imaging.

The term "magnetic source image" (MSI) describes the distribution of neuronal activity in the brain that can be deduced from measurements of the field pattern it produces across the scalp. The signals which provide the basis for an MSI are obtained from the magnetoencephalogram (MEG) which is conventionally recorded with superconducting detectors. Advances in MSI techniques during the past decade have revealed numerous aspects of the functional organization of human sensory systems that were previously unknown. In addition, studies of spontaneous signals, such as those in the alpha bandwidth, have identified specific cortical areas that support rhythmic activity. Extensions of this approach to cognitive research are able to determine the active cortical areas where spontaneous activity is suppressed when a person is engaged in a task such as mental imagery and auditory memory recall. Because only the component of the intracellular current tangential to the overlying skull contributes to the extracranial field, a confined source--modeled as a current dipole--has a characteristic field pattern that simplifies the pattern recognition problem of identifying the underlying sources. This advantage is illustrated by the identification of simultaneously active sources in auditory primary and association cortex. Their separate localization makes it possible to characterize their functional differences. Because the source strength in an MSI may be inferred without knowledge of the electrical conductivities of intervening tissue, it is also possible to estimate the extent of cortical involvement. From the tangential source strength in an MSI, it is possible in most cases to determine the total source strength by taking account of the orientation of the cortical surface. This provides an objective, quantitative measure of the strength of neuronal activity. At present, the major limitation in more extensive use of MSI is the cost of instrumentation. While it requires no contact with the head, and measurements can commence within a few minutes of the arrival of the subject or patient, the present cost of a large array of sensors is two to three million dollars.

Brain↗
PubMed1991

Quality control in antimicrobial disk susceptibility testing: a Belgian multicenter study.

A Belgian multicenter trial was conducted to evaluate problems encountered with quality control results of antimicrobial disk susceptibility testing and to compare the performance of BBL disks and Rosco tablets. Over a period of four weeks 18 laboratories daily tested three reference strains against eight antibiotics. A standardised method was used by all participants. For all results together 10.4% and 7.3% of the measurements with BBL disks and Rosco tablets, respectively, were outside the recommended range. Major problems were observed for some specific strain-antibiotic combinations. Standard deviations were similar for both systems; their precision was comparable. The results suggest that cooperation between manufacturers and some reference laboratories could be improved in order to establish optimal quality control limits.

Anti-Bacterial Agents↗
PubMed1991

On cortical folds and neuromagnetic fields.

A folded cortical source of neuromagnetic fields, similar in configuration to the visual cortex, was simulated. Cortical activity was modelled by different distributions of independent current dipoles. The map of the summed fields of the dipoles of this cruciform model changed, depending upon the statistical distribution of the electrical activity of the dipoles and its geometry. Arrays of dipoles of random orientations and strengths produced field patterns that could be interpreted as due to moving neural currents, although the geometry of the neural tissue remained unchanged and the average activity remained approximately constant. The field topography at any instant was apparently unrelated to the depth or orientation of the underlying structure, thus raising questions about how to interpret topographic MEG and EEG displays. Furthermore, asynchronous activity (defined as independent directions and magnitudes of activity of the dipoles) did not result in less field power than when the dipoles were synchronized, i.e., when the direction of current flow was correlated across all of the dipoles within the cruciform structure. Therefore, in this model 'alpha blockage' cannot be mimicked by desynchronization. More generally, for the cruciform or any other symmetrically folded and active cortical sheet, 'blockage' cannot be attributed to desynchronization. The same is true for the EEG except that smooth unfolded sheets of radially oriented dipoles would result in enhancement of voltage due to synchronization. Such radial dipoles do not contribute to the MEG. Blockage was simulated by reducing the amount of activity within different portions of the synchronized cruciform model. This resulted in a dramatic increase in the net field because attenuation broke the symmetry of the synchronized cruciform structure. With asynchronous dipoles populating the structure, the attenuation of the same portion of the structure had no easily discerned effect on the net field. However, maps of average field power were consistently related to the position of the region of attenuated activity. The locations of regions of attenuated activity were determined by taking the difference between the mean square field pattern obtained when all portions of the cruciform structure were active and the pattern obtained when a portion of the structure was relatively inactive. When activity of the same portions were incremented rather than attenuated, the resulting plot of average power was essentially the same as that of the attenuated portion derived by taking these differences between power distributions. The major conclusions are that the concepts of synchronization and desynchronization have no explanatory power unless the physical conditions under which they occur are specified precisely.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain↗
PubMed1991

MR imaging of excessively obese patients: the use of an open permanent magnet.

Excessive obesity can pose a limitation to both clinical and radiographic evaluation. Although CT and MR have revolutionized head and body imaging, patients with weights above 300 lb present a restriction of these imaging modalities. Magnetic resonance imaging (MRI) is well suited for imaging excessively obese patients, because the RF used does not have difficulty in penetrating large amounts of adipose tissue as ionizing radiation or sound waves does. The limitations of conventional MR imaging in these obese patients are the gantry size and the table weight limit. The recent development of a new low field MR imager with a larger gantry size and greater weight capacity, has the potential for imaging obese patients that cannot be evaluated by standard CT or MR. In this paper, we report our experience in imaging nine excessively obese patients with weights between 350 and 490 lb using a permanent magnet operating at 0.064 T.

Adolescent↗
PubMed1991

Nasal and retrobulbar mass in a cat caused by Pythium insidiosum.

Nasal and retrobulbar infection caused by the Oomycete Pythium insidiosum is described in a cat. The diagnosis was established on three criteria. The staining of broad, sparsely septate hyphal elements in biopsy tissue using a fluorescein-labelled antiglobulin specific for P. insidiosum, detection of antibodies to P. insidiosum by an immunodiffusion test, and isolation of the aetiological agent in pure culture from the biopsy tissue. Treatment with ketoconazole for 6 weeks resulted in clinical improvement, but proptosis of the left eye slowly appeared after the discontinuation of treatment. This case represents a new host for P. insidiosum, namely, a domestic, shorthaired cat, from North Carolina, U.S.A.

Animals↗
PubMed1991

Asymptomatic blastomycosis of the central nervous system with progression in patients given ketoconazole therapy: a report of two cases.

Ketoconazole (KTZ) has largely replaced amphotericin B as first-line therapy for blastomycosis. However, KTZ penetrates poorly into the central nervous system (CNS), and therapeutic failure may be caused by initially unrecognized CNS infection. Two patients (22% [2/9] of all culture-proven cases of blastomycosis at Grady Memorial Hospital, Atlanta, over 15 years) developed CNS blastomycosis while receiving KTZ. Neither initially had CNS symptoms; both had cutaneous and pulmonary disease that responded to KTZ. If KTZ or other fungistatic imidazoles are to continue as primary therapy for blastomycosis, studies are needed to improve the ability to identify patients likely to experience treatment failure or develop CNS disease. Possibly all patients with disseminated blastomycosis, even those without CNS symptoms, should have lumbar puncture and computed tomography of the head before therapy. Critical evaluation of their immune function also may be required before making a therapeutic decision to use KTZ or amphotericin B.

Aged↗
PubMed1991

Magnetic resonance imaging characteristics of multiple sclerosis plaques imaged with two-dimensional and three-dimensional Fourier transform techniques at low and mid field strengths.

A total of 58 multiple sclerosis lesions from 16 patients were used to characterize the performance of a low field system for the detection of edematous (e.g., water-elevating) brain lesions. Contrast, signal-to-noise, and their product (signal difference to noise) were measured for two-dimensional and three-dimensional Fourier transform techniques at low field strength (640 G) and compared to two-dimensional sequences at mid field strength (3,500 G). The results showed numerically that low-field strength magnetic resonance imaging can reliably detect multiple sclerosis lesions, and, by extension, other water-elevating lesions, although with lower confidence levels.

Adult↗
PubMed1991

Forces and torques produced by a 640-gauss permanent magnet of ferromagnetic objects.

Magnetic forces and torques were measured in a 640-G permanent magnet. The forces on external objects were directed in such a way and of such a strength that the likelihood of injury from unsupported ferromagnetic objects was very small. The forces and torques on ferromagnetic objects within the subject were comparable to those produced by gravitational and inertial efforts in daily living.

Equipment Safety↗
PubMed1991

Effect of isepamicin dosing scheme on concentration in cochlear tissue.

To investigate the possible effect of the dosing scheme of aminoglycosides on their concentration in the cochlear tissue, we gave two groups of 12 guinea pigs subcutaneous doses of 45 mg of isepamicin (ca. 30 mg of active product) per kg of body weight daily for eight consecutive days. The first group received the drug by continuous infusion, while the second group received it by single daily injection. On the final day of administration, the animals were sacrificed and the cochlear tissue was removed. The tissues from the cochleas of pairs of guinea pigs were pooled. The isepamicin concentrations in the cochlear duct tissue (organ of Corti plus lateral wall) and the cochlear nerve tissue were determined separately. Hearing levels before and after treatment were assessed by means of frequency-specific auditory brain stem responses (ABR). The creatinine level in serum was determined on the last day of the administration. None of the animals in either group showed signs of renal insufficiency or of hearing impairment. The median isepamicin concentration in the cochlear duct was 2.40 micrograms/mg of protein after continuous administration and 2.50 micrograms/mg of protein after once-daily administration, compared with the concentration in the cochlear nerve, where it was 1.93 micrograms/mg of protein after continuous administration and 2.59 micrograms/mg of protein after once-daily administration. These differences are statistically insignificant. The results give evidence for linear uptake kinetics of isepamicin in the inner ear tissue and may be directly relevant to the clinical dosing of the drug.

Animals↗
PubMed1991

Pharmacodynamic parameters and toxicity of netilmicin (6 milligrams/kilogram/day) given once daily or in three divided doses to cancer patients with urinary tract infection.

The pharmacologic parameters and toxicity of netilmicin (6 mg/kg/day) given once daily (qd) or thrice daily (tid) for the treatment of urinary tract infections were studied in a randomized prospective study of 60 cancer patients. The overall efficacy was 96%. Nephrotoxicity, assessed by the measure of urinary excretion of phospholipids, was lower for the patients receiving the qd regimen than for those receiving the tid regimen. Elevation of serum creatinine (20% over baseline) occurred in one patient receiving the qd regimen and in three receiving the tid regimen. Cochleotoxicity, assessed by pure-tone audiometry (250 to 18,000 Hz) occurred in one patient receiving the qd regimen and none receiving the tid regimen. Concentrations in sera were measured on days 1 and 5. No significant accumulation was observed in either group. Median serum bactericidal titers, expressed as reciprocal values (percentage of the sera with a titer greater than or equal to 8), were measured against 25 test organisms in samples collected 6 h after the administration of netilmicin and were, for the qd group, 16 (82%) against members of the family Enterobacteriaceae and less than 2 (8%) against Pseudomonas aeruginosa, and for the tid group, 4 (57%) against members of the Enterobacteriaceae and less than 2 (0%) against P. aeruginosa. The rate of killing in serum was rapid (2 to 3 log in 2 h against P. aeruginosa; 3 to 5 log in 2 h against members of the Enterobacteriaceae) and correlated with the sampling time and hence the concentration in serum of netilmicin. The duration of the postantibiotic effect in serum depended also on the strain and the sampling time of the serum.

Adult↗
PubMed1991

Impact of section doubling on lesion contrast.

Misregistration between section position and a feature of interest, such as a lesion, can result in loss of contrast on magnetic resonance images. Because the section direction typically has the poorest resolution, reduction of section misregistration can improve lesion contrast. Lesions occur at random sites; hence, to reduce misregistration, it is necessary to repeat imaging with a small amount of offset. This is impractical. Therefore, a reconstruction algorithm that yields offset sections was implemented, in which sections were produced with a zero- and a half-section shift. This algorithm was tested in 14 patients with multiple sclerosis. As expected, because of randomness associated with section placement relative to lesions, the half-shifted sections provided greater contrast as often as the zero-shifted sections. The combined set improved contrast significantly in 39% of lesions; improvement was greatest in lesions with lesser contrast. Signal-to-noise ratios were not affected by this process, which appears to be useful in magnetic resonance image reconstruction.

Adult↗