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Biomedical subjects

L Kaufman

Publications and source records attributed to L Kaufman.

At least 19 recordsLinked to original sources
PubMed1992

Behavioral lifetime of human auditory sensory memory predicted by physiological measures.

Noninvasive magnetoencephalography makes it possible to identify the cortical area in the human brain whose activity reflects the decay of passive sensory storage of information about auditory stimuli (echoic memory). The lifetime for decay of the neuronal activation trace in primary auditory cortex was found to predict the psychophysically determined duration of memory for the loudness of a tone. Although memory for the loudness of a specific tone is lost, the remembered loudness decays toward the global mean of all of the loudnesses to which a subject is exposed in a series of trials.

Acoustic Stimulation↗
PubMed1992

Human auditory primary and association cortex have differing lifetimes for activation traces.

The magnetic field pattern over the temporal area of the scalp 100 ms following the onset of a tone burst stimulus provides evidence for neuronal activity in auditory primary and association cortices that overlap in time. Habituation studies indicate that onset and offset features of a tone produce activation traces in primary cortex that are at least partially common, but only the onset produces an appreciable trace in association cortex. The characteristic time constant for the decay of the latter's activation trace is several seconds longer than for the former.

Activation Analysis↗
PubMed1992

Analysis of hybrid imaging techniques.

Hybrid imaging techniques have been proposed as a means of decreasing imaging time without the cost and technical constraints of echo planar imaging. With this technique phase encoding measurements acquired at different echo times in more than one multiecho experiment are used to form a single image. This study analyzes the trade-offs which occur in the selection of this technique over more conventional imaging in terms of signal/noise, contrast, resolution, imaging time, and efficiency. Hybrid imaging is shown to be advantageous when raw speed is essential such as in abdominal or pediatric imaging. When coverage rather than time becomes the important factor, hybrid imaging does not offer a significant advantage over conventional methods. T2 decay will also serve as a roll-off filter which will reduce the spatial resolution, but not the noise, for short TE hybrid imaging.

Brain Neoplasms↗
PubMed1992

Immunohistologic diagnosis of systemic mycoses: an update.

Fluorescent antibody, immunoperoxidase and gold-silver staining methods for the rapid and accurate diagnosis of systemic mycotic infections are currently performed in a few specialized laboratories. These methods have proved applicable to formalin-fixed, paraffin-embedded tissues, and are reliable for identifying therein antigens of infectious dimorphic, monomorphic filamentous, and yeast-like fungal pathogens, i.e., Aspergillus spp., Blastomyces dermatitidis, Candida spp., Coccidioides immitis, Cryptococcus neoformans, Fusarium spp., Histoplasma capsulatum, Paracoccidioides brasiliensis, Pseudallescheria boydii, and Sporothrix schenckii. Most of the available reagents are derived from multiple adsorbed polyclonal antisera. However, problems occur in the production of uniform and standardized species- or genus- specific antibodies. Monoclonal antibodies, although promising, have to date not eliminated these problems. Immunohistologic methods will become more routinely used in clinical laboratories as these problems are resolved and more sensitive and specific reagents become commercially available.

Antibodies, Fungal↗
PubMed1992

Changes in cortical activity when subjects scan memory for tones.

The magnetoencephalogram (MEG) was used to detect regional changes in spontaneous cortical activity accompanying short-term memory search. This method was chosen because magnetic fields are detectable only within a few centimeters of the projections of their sources onto the scalp. The specific hypothesis that auditory cortex is involved in scanning memory for tones was tested by sensing the field of the magnetic counterpart to N100 (N100m) which is known to originate in auditory cortex. N100m was measured at many different positions and the spontaneous cortical rhythms in the alpha bandwidth (8-12 Hz) were measured at the same places. These rhythms were found to be suppressed while subjects scanned memory for musical tones in a Sternberg paradigm. For 3 subjects, both the MEG suppression time (ST) and reaction time (RT) increased linearly with memory set size. The correlation between ST measured over the left hemisphere and set size was significant for two subjects but not significant for the third, and the slopes of the regression lines relating ST to set size were too shallow to be related to the time required to scan memory. However, the correlation between ST of the right hemisphere and set size was highly significant for all subjects, and the slopes of the regression lines were comparable to those relating RT to set size. The electroencephalogram (EEG) recorded with midline electrodes failed to reveal a significant relationship between suppression time and set size for 2 of the subjects, thus ruling out global alpha blockage and generalized arousal as the basis for the task-related suppression duration. The electric N100, measured at Cz, decreased significantly in amplitude with set size for 2 subjects, but it increased significantly in amplitude for the third subject. In contrast, RT increased with set size for all subjects. N100m measured over the right hemisphere was similar to the behavior of N100, while N100m measured over the left hemisphere showed little change in amplitude with set size, thus establishing an asymmetry in N100 between the hemispheres. Since N100 amplitude is normally larger when attention is paid to auditory stimuli, differential attention alone cannot account for the relation between ST and set size. Furthermore, the processing negativity, which may be superimposed on N100 in selective attention tasks, was not discernible for any set size. It was also found that ST prior to the button press was not correlated with RT. Hence, the covariation of set size with ST is not attributable to preparation for a motor response.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1992

Fiberoptic examination of the nasal cavity and nasopharynx in children.

In this prospective study, a flexible fiberoptic nasolaryngoscope with color video camera was used to examine the nasal cavity and nasopharynx in 180 pediatric patients. The relative size of the adenoid tissue was judged by endoscopy, which lead to a classification into 3 types according to the distance from the vomer to the adenoid tissue. The condition of the nasopharyngeal orifice of the Eustachian tube was also described and differentiated into 3 types relating to the condition of adenoid tissue. Assessment was performed by correlating these measurements with the tympanogram, lateral X-ray and clinical complaints. The authors conclude that: (1) fiberoptic examination allows direct visualization of the size and condition of the adenoid tissue, as well as of the condition of the nasopharyngeal orifice of the Eustachian tube. (2) The size of the adenoid tissue correlates very well with the nasal obstruction complaints as well as with the type of tympanogram. (3) The condition of the nasopharyngeal orifice of the Eustachian tube significantly corresponds with the type of tympanogram. (4) For the indication of adenoidectomy, fiberscopy gives more accurate information than standard X-ray. (5) With a correct choice of premedication and local anesthesia, it is a minor invasive technique which is very well tolerated by children. It is possible in all cases, provided it is performed by a skilled endoscopist and preceded by careful explanation to the child. (6) Finally, thanks to the possibility of direct visualization of the fiberscopic image via a monitor, it allows a better explanation of the indication for adenoidectomy to the child's parents.

Acoustic Impedance Tests↗
PubMed1992

SPECT imaging of serotonin2 receptors in depression.

Changes of serotonin2 (5HT2) receptors have been described in depression, and long-term antidepressant treatment has been shown to decrease the number of 5HT2 receptors. In this study, single photon emission computed tomography (SPECT), with 2-123I-ketanserin as a ligand, was used to investigate 5HT2 receptors in vivo in the brain of depressed patients and normal volunteers. A higher uptake of the tracer was observed in the parietal cortex of the patients, and there was a right greater than left asymmetry in the infero-frontal region of the depressed subjects and not in that of the control subjects. These findings could indicate changes in 5HT2 receptors in major depression.

Adolescent↗
PubMed1992

Meningitis due to Prototheca wickerhamii in a patient with AIDS.

The first documented case of algal meningitis due to Prototheca wickerhamii is reported in a patient with AIDS. The initial CSF culture yielded only Cryptococcus neoformans. P. wickerhamii was isolated on four subsequent lumbar punctures. The patient died, and at autopsy the alga was isolated from leptomeninges over the brain and about the spinal cord. Histologic sections from numerous locations of the brain revealed masses of cryptococci and prototheca.

AIDS-Related Opportunistic Infections↗
PubMed1992

Aspergillosis of the prostate associated with an indwelling bladder catheter: case report and review.

Fungal prostatitis is an uncommon disease whose presentation is usually similar to that of benign prostatic hypertrophy and is usually diagnosed unexpectedly after surgery for relief of prostatic obstruction. To our knowledge, we report the first case of prostatic aspergillosis that developed as a complication of indwelling bladder catheterization. This unusual manifestation of invasive aspergillosis occurred in a patient at risk for invasive fungal disease because of chronic corticosteroid use and recent administration of broad-spectrum antibiotics. The previously reported cases of prostatic aspergillosis are reviewed.

Aspergillosis↗
PubMed1992

Laboratory methods for the diagnosis and confirmation of systemic mycoses.

The concomitant use of culture and nonculture techniques for the diagnosis and confirmation of systemic mycotic infections is recommended and assessed. A diagnosis based upon a single specimen and method, especially when the results are negative, is not always conclusive. In many situations, a single specimen and test method cannot be relied upon for the diagnosis of a fungal infection. The testing of multiple or serial specimens with a battery of procedures increases the chances for establishing a rapid and definitive diagnosis. Positive cultures generally provide unequivocal evidence of infection. In the absence of such data, results obtained by the use of nonculture techniques such as direct examination, conventional and immunohistologic staining, exoantigen identification, DNA hybridization, immunodiffusion, complement fixation, enzyme immunoassay, and radioimmunoassay can allow detection and identification of the etiologic fungus or provide immunologic evidence of a specific fungal infection.

Animals↗
PubMed1992

Magnetic source images determined by a lead-field analysis: the unique minimum-norm least-squares estimation.

The minimum norm least-squares approach based on lead field theory provides a unique inverse solution for a magnetic source image that is the best estimate in the least-squares sense. This has been applied to determine the source current distribution when the primary current is confined to a surface or set of surfaces. In model simulations of cortical activity of the human brain, the magnetic field pattern across the scalp is interpreted with prior knowledge of anatomy to yield a unique magnetic source image across a portion of cerebral cortex, without resort to an explicit source model.

Artifacts↗
PubMed1992

Oral Histoplasma capsulatum infection in association with HIV infection: a case report.

The fungus Histoplasma capsulatum causes histoplasmosis, the most common endemic respiratory mycosis in the United States. Disseminated histoplasmosis in adults is often associated with immunosuppression, such as occurs in HIV infection. We report a case of oral histoplasmosis in an HIV-seropositive patient who presented with an ulceration on the left tip of the tongue, extending to the floor of the mouth, but was otherwise free of any active systemic disease. Histoplasma capsulatum was shown, by both histopathology and staining with a fluorescent antibody reagent specific for the organism, to be present in the lesion and was deduced to be the causative organism.

HIV Infections↗
PubMed1992

Disseminated histoplasmosis in a badger (Meles meles) in Denmark.

We report the first case of disseminated histoplasmosis in an animal in Scandinavia. Yeast cells compatible with those of Histoplasma capsulatum var. capsulatum were found in the skin, liver, spleen, a kidney, and a lymph node of a wild badger (Meles meles). The diagnosis was confirmed by electron microscopy and immunofluorescence staining of the yeast cells in tissue sections.

Animals↗
PubMed1992

Western immunoblot analysis and serologic characterization of Blastomyces dermatitidis yeast form extracellular antigens.

A major 98-kDa extracellular protein antigen of Blastomyces dermatitidis was shown in Western blot (immunoblot) analysis to be highly reactive with serum antibodies from patients with blastomycosis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of yeast form B. dermatitidis culture filtrates and cell extracts demonstrated over 50 proteins, only 24 of which were immunoreactive. Of these, a 98-kDa protein was found to be the most specific and was isolated. This protein was found in both broth culture filtrates and extracts of yeast forms. Western blot tests with this antigen detected serum antibodies in 91% of 32 patients with clinically proven blastomycosis, in contrast to an enzyme-linked immunosorbent assay (ELISA) with DEAE-purified antigen, which detected 88% of the cases. The Western blot test also exhibited lower reactivity with a panel of sera from patients with heterologous fungal infections that were cross-reactive in the ELISA with DEAE-purified B. dermatitidis antigen. The 98-kDa protein electroeluted from polyacrylamide gels was identical to the diagnostic A antigen used in the blastomycosis immunodiffusion test. Comparison of the 98-kDa antigen with a previously described 120-kDa yeast form cell wall protein antigen of B. dermatitidis showed that these two antigens are almost identical.

Antibodies, Fungal↗
PubMed1992

Comparative evaluation of a chemiluminescent DNA probe and an exoantigen test for rapid identification of Histoplasma capsulatum.

A chemiluminescent DNA probe (Accuprobe) assay developed by Gen Probe, Inc., for the rapid identification of Histoplasma capsulatum was evaluated and compared with the exoantigen test by using 162 coded cultures including Histoplasma capsulatum var. capsulatum, Histoplasma capsulatum var. duboisii, Histoplasma capsulatum var. farciminosum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasiliensis, and morphologically related saprobic fungi. Each test uses a chemiluminescent, acridinium ester-labeled, single-stranded DNA probe that is complementary to the rRNA of the target organism. Lysates of the test cultures were prepared by sonication with glass beads and heat treated. After the rRNA was released from the target organism, the labeled DNA probe combined with the target H. capsulatum rRNA to form a stable DNA-RNA hybrid. A hybridization protection assay was used, and the chemiluminescence of hybrids was measured initially with a Leader 1 luminometer as relative light units and later during the investigation with a probe assay luminometer as probe light units. Of the 162 coded mycelial cultures tested by the Accuprobe assay, 105 were identified as H. capsulatum. The test could be performed with an inoculum of a few square millimeters (1 to 2 mm2) of growth. In the primary evaluation, the Accuprobe identified 103 of the 105 cultures as H. capsulatum within 2 h. The remaining two cultures, contaminated with bacteria, had to be purified before the Accuprobe assay identified them correctly as H. capsulatum. Since each coded culture was concurrently tested for H. capsulatum, B. dermatitidis, and C. immitis exoantigens, the identification of all three dimorphic pathogens was provided simultaneously. Of the 162 coded cultures tested, 105 were identified by the exoantigen test as H. capsulatum, 12 were identified as B. dermatitidis, 13 were identified as C. immitis, and 32 were negative for H. capsulatum, B. dermatitidis, and C. immitis. The bacterial contamination in two isolates did not interfere with the exoantigen testing. The exoantigen test required 7- to 10-day-old colonies and required 48 to 72 h of incubation before definitive identification was obtained.

Antigens, Fungal↗
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↗