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Biomedical subjects

S C Johnson

Publications and source records attributed to S C Johnson.

At least 19 recordsLinked to original sources
PubMed2001

Recurrences of cytomegalovirus retinitis in a human immunodeficiency virus-infected patient, despite potent antiretroviral therapy and apparent immune reconstitution.

We describe a 42-year-old man with human immunodeficiency virus infection who developed multiple recurrences of cytomegalovirus (CMV) retinitis despite receiving highly active antiretroviral therapy and having apparent immune reconstitution as evidenced by CD4(+) T lymphocyte counts of > 200 cells/mm(3). Laboratory investigation during one recurrence of retinitis confirmed that there was active CMV replication in the plasma and vitreous fluid. In addition, lymphoproliferative responses to CMV antigens were absent despite evidence of reactivity to Candida antigen and pokeweed mitogen. The clinical significance of this case and of other recently reported cases is discussed.

AIDS-Related Opportunistic Infections↗
PubMed2001

Brain activation on fMRI and verbal memory ability: functional neuroanatomic correlates of CVLT performance.

We have recently reported (Saykin et al., 1999b) selective activation of left medial temporal lobe structures during processing of novel compared to familiar words using functional magnetic resonance imaging (fMRI). The current study describes the relationship between a widely used clinical test of verbal learning, the California Verbal Learning Test (CVLT), and the previously reported fMRI activations. Thirteen right-handed healthy adult participants were studied with whole brain echo-planar fMRI while listening to novel and recently learned (familiar) words intermixed pseudorandomly in an event-related design. These participants were also tested with the CVLT. Scores for CVLT Trial 1 (immediate encoding of novel words) and recognition discriminability (recognition of familiar vs. novel words) were correlated with fMRI signal change during processing of novel versus familiar words using a covariance model implemented in SPM96. For the novel words analysis, voxels in the right anterior hippocampus correlated significantly with Trial 1 (r = .76 at the maxima). For the recognition analysis, a significant cluster of voxels was found in the right dorsolateral prefrontal cortex (r = .88 at the maxima). Our prior results of separable left medial temporal activation to novel and familiar words, together with results of the covariance analyses reported here, suggest that in addition to the left medial temporal lobe (MTL) regions that are engaged during novel and familiar word processing, the right hippocampus and right frontal lobe are also involved, particularly in those participants with better memory ability. This positive relationship between fMRI activation and CVLT performance suggests a role for these right hemisphere regions in successful memory processing of verbal material, perhaps reflecting more efficient encoding and retrieval strategies that facilitate memory.

Adult↗
PubMed2001

Frontal filament morphogenesis in the salmon louse Lepeophtheirus salmonis.

The objective of the present study was to understand how and when the frontal filament (FF) in the salmon louse Lepeophtheirus salmonis is produced by examining the sequence of morphological changes leading to FF production in the copepodid and early chalimus stages. Atlantic salmon (Salmo salar) were heavily infested with newly molted copepodids. Sea lice were sampled prior to infestation and at 1, 2, 3, 4, 5, 6, 7, 8, and 9 days postinfestation. FF morphogenesis from newly molted copepodid to chalimus II, i.e., through 2 molts, was studied using high-resolution light microscopy of serial transverse and sagittal resin sections. Three groups of cells, identified as A, B, and C, are thought to be involved in the production of the secretions (S1 and S2) that form the filament material. The amount and shape of S1 and S2 and their association with B- and C-group cells, respectively, changed with the molt cycle. The following scenario for FF development is proposed: the first secretion to form after the molt for both copepodid and chalimus stages is S1, and it is formed by B-group cells and becomes the basal plate of the external FE C-group cells produce S2 during mid-intermolt to premolt stage. The S2 becomes the stem of the external FE In premolt larvae, S1 and S2 were contained within a cuticle-lined invagination that had a form similar to that of the extruded filament. The axial duct present in both copepodid and chalimus originates from the A-group cells and probably carries a secretion used to attach the filament to the host. This study provides strong evidence that L. salmonis produces a new filament with each molt, creating the possibility of using a sea lice control method based on interference with filament production more feasible.

Animals↗
PubMed2001

Unilateral acquired nevus flammeus in women.

Congenital nevus flammeus is a benign vascular tumor characterized by pink to pale red patches that thicken as the patient ages, producing a dull red to reddish blue, cobblestone-textured plaque. We present the cases of 3 women with unilateral acquired nevus flammeus on the cheek whose lesions resolved after minimal treatment with a 585-nm pulsed dye laser. The etiology of acquired nevus flammeus is reviewed and tumor response rates to laser surgery are discussed.

Adult↗
PubMed2000

Changes in hydrolytic enzyme activities of naïve Atlantic salmon Salmo salar skin mucus due to infection with the salmon louse Lepeophtheirus salmonis and cortisol implantation.

The changes in the activities of mucus hydrolytic enzymes and plasma cortisol levels were examined following infection of Atlantic salmon Salmo salar with the salmon louse Lepeophtheirus salmonis and these changes were compared with those resulting from elevated plasma cortisol. Salmon were infected at high (Trial 1; 178 +/- 67) and low (Trial 2; 20 +/- 13) numbers of lice per fish and the activities of proteases, alkaline phosphatase, esterase and lysozyme in the mucus, as well as plasma cortisol levels were determined. At both levels of infection, there were significant increases of protease activity over time (1-way K-WANOVA; Trial 1, p = 0.004; Trial 2, p < 0.001). On several sampling days, generally on later days in the infections, the mucus protease activities of infected fish were significantly higher than control fish (Student's t-tests; p < 0.05). In addition, zymography experiments demonstrated bands of proteases at 17 to 22 kDa in the mucus of infected salmon that were absent in the mucus from non-infected fish and absent in the plasma of salmon. The intensity of these protease bands increased in the mucus over the course of both infections. However, plasma cortisol levels were elevated only in the heavily infected fish from the first trial. At high infection levels (Trial 1), alkaline phosphatase activity was higher in the mucus of infected fish at all days (t-test, p < 0.05). However, at the lower infection level (Trial 2), the mucus alkaline phosphatase activity did not differ significantly between infected and non-infected fish. Esterase and lysozyme activities were very low and did not change with time nor between non-infected and infected salmon in either challenge. Mucus enzyme activities of cortisol-implanted salmon did not change over time, nor were there any differences in activities between cortisol-implanted and control salmon. The present study demonstrates biochemical changes resulting from sea lice infection of Atlantic salmon occurring at the site of host-pathogen interaction, the mucus layer. However, the origin of these enzymes, whether host or pathogen, remains to be determined.

Alkaline Phosphatase↗
PubMed2000

The relationship between fMRI activation and cerebral atrophy: comparison of normal aging and alzheimer disease.

Functional MRI has recently been used to examine activation associated with aging and dementia, yet little is known regarding the effect of cerebral atrophy on fMRI signal. The purpose of this study was to examine the relationship between measures of global and regionally specific atrophy and fMRI activation in normal aging and in Alzheimer disease (AD). Two groups of subjects were studied with echoplanar imaging and quantitative structural volumetry: healthy controls spanning a broad age and atrophy range (n = 16) and patients with mild AD (n = 8). Results from a semantic task previously found to activate left inferior frontal (LIFG) and left superior temporal (LSTG) gyri were analyzed. The correlations between clusters of activation in the LIFG and LSTG and measures of local atrophy in the LIFG and LSTG regions were evaluated. For control subjects, there was no significant correlation between activation and regional or total brain atrophy (for LIFG r = -0.03, NS; for LSTG r = 0.20, NS). In contrast, for AD patients, there was a significant positive correlation between atrophy and activation in LIFG (r = 0.70, P = 0.05) but not LSTG (r = 0.00, NS). These results suggest that activation of language regions and atrophy within those regions may be independent among healthy adults spanning a broad age and atrophy range. However, in AD, a relationship exists in the LIFG that may reflect compensatory recruitment of cortical units or disease-specific changes in the hemodynamic response.

Adult↗
PubMed2000

Development of a fluorogenic 5' nuclease PCR assay for detection of the ail gene of pathogenic Yersinia enterocolitica.

In this report we describe the development and evaluation of a fluorogenic PCR assay for the detection of pathogenic Yersinia enterocolitica. The assay targets the chromosomally encoded attachment and invasion gene, ail. Three primer-probe sets (TM1, TM2, and TM3) amplifying different, yet overlapping, regions of ail were examined for their specificity and sensitivity. All three primer-probe sets were able to detect between 0.25 and 0.5 pg of purified Y. enterocolitica DNA. TM1 identified all 26 Y. enterocolitica strains examined. TM3 was able to detect all strains except one, whereas TM2 was unable to detect 10 of the Y. enterocolitica strains tested. None of the primer-probe sets cross-reacted with any of the 21 non-Y. enterocolitica strains examined. When the TM1 set was utilized, the fluorogenic PCR assay was able to detect </=4 Y. enterocolitica CFU/ml in pure culture and 10 Y. enterocolitica CFU/ml independent of the presence of 10(8) CFU of contaminating bacteria per ml. This set was also capable of detecting </=1 CFU of Y. enterocolitica per g of ground pork or feces after a 24-h enrichment in a Yersinia selective broth.

Animals↗
PubMed2000

Evaluation of covert video surveillance in the diagnosis of munchausen syndrome by proxy: lessons from 41 cases.

OBJECTIVE: In 1993, Children's Healthcare of Atlanta at Scottish Rite (formery Scottish Rite Children's Medical Center, Atlanta, GA) added facilities to perform inpatient covert video surveillance (CVS) of suspected cases of Munchausen syndrome by proxy (MSBP). Forty-one patients were monitored from 1993 to 1997. This study was performed to review our experience with these cases. How useful was video surveillance in making the diagnosis? What were the characteristics of families with children who were victims of MSBP? METHODOLOGY: Medical, social work, security, and administrative records of all children who underwent covert video monitoring at Children's Healthcare of Atlanta at Scottish Rite from 1993 through 1997 were reviewed retrospectively by a team of physicians, risk managers, and social workers. RESULTS: A diagnosis of MSBP was made in 23 of 41 patients monitored. CVS was required to make the diagnosis in 13 (56.1%) of these 23, and supportive of the diagnosis in 5 (21.7%) cases. In 4 patients, this surveillance was instrumental in establishing innocence of the parents. MSBP was more common in Caucasian patients than in other ethnic groups seen at our hospital. Fifty-five percent of mothers gave a history of health care work or study, and another 25% had previously worked in day care. Although many of caretakers fit the profile of MSBP, such as excessive familiarity with medical staff, eagerness for invasive medical testing, and history of health care work, these characteristics were not sensitive indicators of MSBP in our study. Even when present, they were not sufficiently compelling to make the diagnosis. CONCLUSIONS: CVS is required to make a definitive and timely diagnosis in most cases of MSBP. Without this medical diagnostic tool, many cases will go undetected, placing children at risk. All tertiary care children's hospitals should develop facilities to perform CVS in suspected cases.

Adult↗
PubMed2000

Characterization of proteases in the skin mucus of Atlantic salmon (Salmo salar) infected with the salmon louse (Lepeophtheirus salmonis) and in whole-body louse homogenate.

As part of an investigation of the biochemical interactions between the salmon louse Lepeophtheirus salmonis and Atlantic salmon Salmo salar, we characterized protease activity in the skin mucus of noninfected Atlantic salmon and Atlantic salmon infected with L. salmonis and in an L. salmonis whole-body homogenate. Zymography revealed that mucus from infected salmon contained a series of low-molecular-mass (17-22 kDa) serine proteases that were not present in the mucus of noninfected salmon. Based on molecular mass, inhibition studies, and affinity chromatography, the series of proteases was identified as being trypsin-like. Similar proteases were observed in the L. salmonis homogenate and in mucus from noninfected Atlantic salmon following a 1-hr incubation with live L. salmonis. An antibody raised against Atlantic salmon trypsin failed to recognize any proteases in the mucus of noninfected salmon or infected salmon or in the L. salmonis homogenate. Collectively, these findings suggest that the trypsin-like proteases present in the mucus of infected Atlantic salmon were produced by L. salmonis, possibly to aid in feeding and evasion of host immune responses.

Animals↗
PubMed2000

Advances in HIV/AIDS therapy.

Advances in HIV/AIDS therapy have been rapid and profound. An improved understanding of HIV pathogenesis has demonstrated the need for aggressive antiretroviral therapy in most persons with HIV infection. Combinations of at least three drugs are necessary to fully suppress viral replication. Suppression of viral replication prevents the development of drug resistance and allows immune reconstitution to occur. Current therapies do have limitations including side effects, cross-resistance, adherence challenges, and drug interactions. However, most patients have derived great benefit from these therapies. The consequences of immune reconstitution have included resolution of existing opportunistic infections and a markedly reduced risk of new infections. In certain settings, immune reconstitution may allow the discontinuation of opportunistic infection prophylaxis or treatments. The net result has been a substantial improvement in the quality and quantity of life for HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed1999

Brain activation during working memory 1 month after mild traumatic brain injury: a functional MRI study.

OBJECTIVE: To assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury (MTBI). BACKGROUND: Many individuals complain of memory difficulty shortly after MTBI. Memory performance in these individuals can be normal despite these complaints. METHODS: Brain activation patterns in response to a working memory task (auditory n-back) were assessed with functional MRI in 12 MTBI patients within 1 month of their injury and in 11 healthy control subjects. RESULTS: Brain activation patterns differed between MTBI patients and control subjects in response to increasing working memory processing loads. Maximum intensity projections of statistical parametric maps in control subjects showed bifrontal and biparietal activation in response to a low processing load, with little additional increase in activation associated with the high load task. MTBI patients showed some activation during the low processing load task but significantly increased activation during the high load condition, particularly in the right parietal and right dorsolateral frontal regions. Task performance did not differ significantly between groups. CONCLUSION: MTBI patients differed from control subjects in activation pattern of working memory circuitry in response to different processing loads, despite similar task performance. This suggests that injury-related changes in ability to activate or to modulate working memory processing resources may underlie some of the memory complaints after MTBI.

Adult↗
PubMed1999

Transvaginal ultrasound-guided aspiration of pelvic abscesses.

OBJECTIVE: To assess the utility of a less invasive approach to the care of women with a pelvic abscess, we retrospectively reviewed the outcome of women with pelvic abscesses managed by transvaginal ultrasound-guided aspiration. METHODS: A retrospective analysis of 27 pelvic abscesses in 22 consecutive women undergoing transvaginal drainage, including 13 tuboovarian abscesses (TOAs) and 14 postoperative abscesses (POAs). All patients received broad-spectrum intravenous antibiotics from the time infection was diagnosed to resolution of signs and symptoms. Chart review and examination of ultrasound files were utilized to extract demographic clinical, laboratory, and outcome data. RESULTS: The mean age for the study group was 30 years old. Mean duration from diagnosis to drainage was 5.6 days (TOA) and 2.0 days (POA), P < 0.01. The mean diameter of the abscesses was 86 mm. The volume of purulent material drained ranged from 70-750 mL. Perceived adequacy of drainage was correlated with lack of abscess septation. Cultures for aerobic and anaerobic pathogens were positive in 51% of cases (79% POA versus 23% TOA, P < 0.05) with 1.9 organisms/ positive culture. Transvaginal drainage was successful in 25 of 27 abscesses. No complications were reported. CONCLUSION: In skilled hands, transvaginal guided aspiration of pelvic abscess is a highly successful technique with minimal risk to the patient. Follow-up studies are needed to assess the long-term sequelae, such as frequency of infertility, ectopic pregnancy, and chronic pelvic pain.

Abscess↗
PubMed1999

Identification of a pathogen-binding lectin in salmon serum.

A mannose-binding lectin was isolated from the blood serum of Atlantic salmon (Salmo salar). Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing and non-reducing conditions revealed a multimeric structure composed of 17000 Mr subunits. Hexosamine analysis and glycosidase digestion showed that the lectin is not glycosylated and amino acid analysis revealed no unusual compositional features. Using ruthenium red staining, the lectin was shown to bind Ca2+ ions. N-terminal sequencing by Edman degradation gave: H2N-TGAKGAEEGVVPAETRNQXPTGWFQFGS. A database search revealed no similarity to protein sequences deposited to date. Binding experiments using biotinylated lectin revealed that it specifically recognizes and binds to mannose on the surfaces of two salmon pathogens, Vibrio anguillarum and Aeromonas salmonicida, implying an immunological role for this lectin in Atlantic salmon.

Aeromonas↗
PubMed1999

Enhancement of anti-Aeromonas salmonicida activity in Atlantic salmon (Salmo salar) macrophages by a mannose-binding lectin.

We investigated the effects of a calcium-dependent mannose-binding lectin isolated from the serum of Atlantic salmon on Aeromonas salmonicida viability and the anti-A. salmonicida activity of Atlantic salmon macrophages. In the absence of other factors, binding of this lectin at concentrations of 0.8, 4.0 and 20.0 ng ml(-1) to virulent A. salmonicida failed to significantly reduce (P> 0.05) cell viability. However, binding of the lectin to A. salmonicida did result in significant (P < or = 0.05) dose-dependent increases in phagocytosis, and bactericidal activity. Significant increases (P < or = 0.05) were also observed in phagocyte respiratory burst activity within the lectin concentration range of 4.0-20.0 ng ml(-1) but the stimulation was not dose dependent at these lectin concentrations. At the lowest lectin concentration tested (0.32 ng ml(-1)), a significant decrease (P < or = 0.05) in respiratory burst was observed. The structure and activity of this lectin are similar to that of mammalian mannose-binding lectins, which are known to play a pivotal role in innate immunity. The presence of this lectin may be an important defense mechanism against Gram-negative bacteria such as A. salmonicida.

Aeromonas↗
PubMed1999

Neuroanatomic substrates of semantic memory impairment in Alzheimer's disease: patterns of functional MRI activation.

Impairment in semantic processing occurs early in Alzheimer's disease (AD) and differential impact on subtypes of semantic relations have been reported, yet there is little data on the neuroanatomic basis of these deficits. Patients with mild AD and healthy controls underwent 3 functional MRI auditory stimulation tasks requiring semantic or phonological decisions (match-mismatch) about word pairs (category-exemplar, category-function, pseudoword). Patients showed a significant performance deficit only on the exemplar task. On voxel-based fMRI activation analyses, controls showed a clear activation focus in the left superior temporal gyrus for the phonological task; patients showed additional foci in the left dorsolateral prefrontal and bilateral cingulate areas. On the semantic tasks, predominant activation foci were seen in the inferior and middle frontal gyrus (left greater than right) in both groups but patients showed additional activation suggesting compensatory recruitment of locally expanded foci and remote regions, for example, right frontal activation during the exemplar task. Covariance analyses indicated that exemplar task performance was strongly related to signal increase in bilateral medial prefrontal cortex. The authors conclude that fMRI can reveal similarities and differences in functional neuroanatomical processing of semantic and phonological information in mild AD compared to healthy elderly, and can help to bridge cognitive and neural investigations of the integrity of semantic networks in AD.

Aged↗
PubMed1999

Polysubstance abuse and traumatic brain injury: quantitative magnetic resonance imaging and neuropsychological outcome in older adolescents and young adults.

Few studies have examined the consequences of alcohol and drug abuse on TBI though they commonly co-occur. Both TBI and substance abuse independently result in neuropathological changes in the brain such as ventricular enlargement and cortical atrophy, thus it is reasonable to hypothesize that the combination of the two would result in more significant cerebral damage. In this study, 3 groups of patients--traumatically brain injured (TBI) with substance abuse (N = 19), TBI without substance abuse (N = 19), and substance abuse with no TBI (N = 16)--were compared with normal controls (N = 20) on several quantitative MRI (QMRI) measures. Since TBI most frequently occurs in older adolescents and young men, we examined only male participants between 16 and 30 years of age. Comparing young substance abusers to controls resulted in no QMRI differences. When controlling for head injury severity, the effects of substance abuse in combination with TBI resulted in greater atrophic changes than seen in any other group. TBI and substance abuse patients' neuropsychological test performances also were examined, and no differences were found among patient groups on any measures. These findings have implications for the deleterious interaction of substance abuse combining with TBI to result in greater neuropathological changes that can be detected by QMRI techniques.

Adolescent↗