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Biomedical subjects

S McCall

Publications and source records attributed to S McCall.

At least 19 recordsLinked to original sources
PubMed2002

High magnetic field studies of the hidden order transition in URu2Si2.

We studied in detail the low temperature/high magnetic field phases of URu2Si2 single crystals with specific heat, magnetocaloric effect, and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5 K, and extrapolated to T=0, show a suppression of the hidden-order phase at H0(0)=35.9+/-0.35 T and the appearance of a new phase for magnetic fields in excess of H1(0)=36.1+/-0.35 T observed only at temperatures lower than 6 K. In turn, complete suppression of this high field state is attained at a critical magnetic field H2(0)=39.7+/-0.35 T. No phase transitions are observed above 40 T. We discuss our results in the context of itinerant versus localized f electrons.

Journal Article↗
PubMed2001

Experimenting on the past: the enigma of von Economo's encephalitis lethargica.

Encephalitis lethargica (EL) was a complex and mysterious disease that appeared around the same time as the great influenza pandemic of 1918. The contemporaneous relationship of the 2 diseases led to speculation that they were causally related. Contemporary and subsequent observers conjectured that the influenza virus, directly responsible for the deaths of more than 20 million people, might also have been the cause of EL. A review of the extensive literature by observers of the EL epidemic suggests that most contemporary clinicians, epidemiologists, and pathologists rejected the theory that the 1918 influenza virus was directly responsible for EL. Disappearance of the acute form of EL during the 1920s has precluded direct study of this entity. However, modern molecular biology techniques have made it possible to examine archival tissue samples from victims of the 1918 pandemic in order to detect and study the genetic structure of the killer virus. Similarly, tissue samples from EL victims can now be examined for evidence of infection by the 1918 influenza virus.

Causality↗
PubMed2001

Influenza RNA not detected in archival brain tissues from acute encephalitis lethargica cases or in postencephalitic Parkinson cases.

Encephalitis lethargica (EL) was a mysterious epidemic. temporally associated with the 1918 Spanish influenza pandemic. Numerous symptoms characterized this disease, including headache, diplopia, fever, fatal coma, delirium, oculogyric crisis, lethargy, catatonia, and psychiatric symptoms. Many patients who initially recovered subsequently developed profound, chronic parkinsonism. The etiologic association of influenza with EL is controversial. Five acute EL autopsies and more than 70 postencephalitic parkinsonian autopsies were available in the Armed Forces Institute of Pathology (AFIP) tissue repository. Two of these 5 acute EL cases had histopathologic changes consistent with that diagnosis. The remaining 3 cases were classified as possible acute EL cases as the autopsy material was insufficient for detailed histopathologic examination. RNA lysates were prepared from 29 CNS autopsy tissue blocks from the 5 acute cases and 9 lysates from blocks containing substantia nigra from 2 postencephalitic cases. RNA recovery was assessed by amplification of beta-2-microglobulin mRNA and 65% of the tissue blocks contained amplifiable RNA. Reverse transcription-polymerase chain reaction (RT-PCR) for influenza matrix and nucleoprotein genes was negative in all cases. Thus, it is unlikely that the 1918 influenza virus was neurotropic and directly responsible for the outbreak of EL.

Adult↗
PubMed2000

Object recognition may distort size perception.

Size estimation may be influenced by characteristics recalled about the object viewed. This study evaluated the influence of object familiarity on estimation of size. We compared size estimates of several familiar objects with size estimates of undefined objects matched for dimensions of pattern and color. Those estimating the size of the familiar objects made significantly larger errors than those estimating the size of the undefined objects. In a second study size estimation errors from memory were larger than when objects were directly viewed. Experience with the objects appears to decrease accuracy of estimates of size but errors may be reduced by directly observing the object.

Color Perception↗
PubMed1998

Effects of in-situ calibration of click stimuli on the auditory brainstem response.

We studied the effects on the auditory brainstem response (ABR) of applying a computerized calibration procedure for click stimuli that corrects for individual transducer characteristics and ear canal acoustics. The "calibrated" signal at the eardrum possesses a nearly flat spectrum from 500 to 10,000 Hz. ABRs were recorded from normal-hearing subjects using both calibrated and uncalibrated clicks. The preponderance of energy for the latter stimulus was between 1000 and 4000 Hz. When compared to the responses evoked by the uncalibrated signal, ABRs to calibrated clicks displayed shorter component latencies, increased component amplitudes, and a more sensitive wave V relative to behavioral threshold.

Acoustic Stimulation↗
PubMed1995

Immunologic assessment during treatment of rheumatoid arthritis with anti-CD5 immunoconjugate.

OBJECTIVE: To determine if sustained immunologic effects occurred after treatment of patients with rheumatoid arthritis (RA) with an immunoconjugate of murine anti-CD5 monoclonal antibody with ricin A chain (anti-CD5). METHODS: We measured lymphocyte populations, mitogen induced peripheral blood mononuclear cell (PBMC) stimulation, cytokine levels, immunoglobulin levels, in vivo immune function, and clinical outcomes in 9 patients with RA treated with anti-CD5. RESULTS: The treatment of patients with RA with anti-CD5 was associated with marked acute depletion of peripheral blood lymphocytes (p < 0.01) during and immediately after treatment. A sustained decrease in the number of CD3, CD4, CD5, and CD8 bearing lymphocytes persisted for 2 months after treatment (p < 0.05). After 3 months a mild decrease in the number of these lymphocyte populations persisted, but when compared to baseline values, the differences were not found to be statistically significant. Phytohemagglutinin induced PBMC proliferation was decreased at the 3-month followup (p < 0.05). Evaluations of mitogen induced cytokine and immunoglobulin production, immunoglobulin level, autoantibody, and in vivo antibody response to tetanus toxoid did not show any consistent change from baseline. CONCLUSION: Anti-CD5 treatment of RA appears to be associated with a decrease in the population of cells bearing CD5, but does not appear to induce any persistent immunologic abnormalities.

Adolescent↗
PubMed1995

Painful ophthalmoplegia caused by hemangiopericytoma of the cavernous sinus.

Progressive, painful ophthalmoplegia developed in a 34-year-old man. MRI scan revealed an enhancing mass in the left cavernous sinus. Histologic examination of resected tumor revealed reticulin staining and cytologic features of hemangiopericytoma. Characteristics of intracranial hemangiopericytoma are reviewed.

Adult↗
PubMed1994

Collagen-induced arthritis and TCRs in SWR and B10.Q mice expressing an Ek alpha transgene.

B10.Ek alpha transgenic mice were mated with H2-E B10.Q and SWR mice. F1 and F1 x parental strain backcross progeny were tested for arthritis and autoimmune reactivity to mouse type II collagen (MII) after immunization with bovine, chick, deer, or human type II collagen. The results were correlated with the H-2 haplotype (b/q vs q/q) and the TCR V beta profile of peripheral blood T cells in each mouse. Hybrid progeny expressed TCR profiles different from either parent because of the TCR V beta genomic deletions of SWR mice (V beta a), the wild-type TCR allele of C57Bl/10 (B10) mice (V beta b), and the intrathymic negative selection processes resulting from cell surface expression of Ek alpha-A q beta or Eb beta-Ek alpha, together with the integrated retroviral genes Mtv-9 originating in B10 mice and Mtv-7 (Mls-1a) from SWR mice. (B10.Ek alpha x SWR)F1 mice developed higher IgG anti-MII Ab titers, but much milder arthritis than (B10.E x B10.Q)F1 mice. Expression of Ek alpha did not change the level of IgG anti-MII Ab nor the degree of susceptibility to collagen-induced arthritis (CIA) in the H-2q/q and H-2b/q progeny of (B10.Ek alpha x B10.Q)F1 x B10.Q matings, indicating that the Mtv-9-reactive, TCR V beta 5+, and V beta 11+ T cells are not critical to CIA. Among bovine type II collagen-immunized (B10.Ek alpha x SWR)F1 x SWR backcross mice: 1) arthritis severity is associated with the presence of V beta b (p < or = 0.01) and expression of Ek alpha (p < or = 0.05), but not with the MHC haplotype (b/q vs q/q); 2) regression analysis showed a significant association (R = 0.99) between IgG anti-MII Ab titers and the level of Mtv-7-reactive V beta 6+ T cells that was detectable in the IgG1, but not the IgG2a subclass. The data prompt the speculation that Mtv-7-reactive V beta 6+ (or V beta 7+) T cells in (B10.EK alpha x SWR)F1 x SWR mice express Th2-type properties, and thus contribute to the combination of mild arthritis but high anti-MII Ab titers that characterize mice of SWR heritage.

Animals↗
PubMed1994

Exacerbation of collagen-induced arthritis in rats by rat cytomegalovirus is antigen-specific.

Collagen-Induced Arthritis (CIA) is an experimentally induced and genetically controlled animal model of chronic joint inflammation. In rats, there are informative strain differences in susceptibility to CIA. DA rats (RT1avl) develop severe CIA after immunization with bovine (BII), chick (CII), or homologous rat (RII) type II collagens. In contrast, the MHC-congenic DA. 1N(BN) and WF.1N(BN) rats (RT1n) are relatively resistant to CIA and develop moderate CIA in response to immunization with CII but not BII or RII. We previously found that simultaneous infection with rat cytomegalovirus (RCMV) greatly exacerbates the severity of arthritis that develops in BII-immunized DA rats. To examine the mechanism of RCMV amplification of CIA, the effect of simultaneous infection with RCMV on arthritis and autoimmunity to type II collagen was determined in WF.1N and DA.1N rats after immunization with BII, CII and RII. RCMV increased the incidence of CIA and the level of autoimmunity to type II collagen (skin-testing and IgG antibody titer) selectively in DA.1N and WF.1N rats immunized with CII, but not in littermates immunized with BII, although the transient reversal of CD4+/CD8+ mononuclear cell ratios in peripheral blood that is associated with RCMV infection occurred equally in both BII- and CII- immunized DA.1N rats. Likewise, RCMV infection moderately increased the levels of anti-RII autoimmunity and arthritis in DA rats sub-optimally immunized with RII but had no consistent effect on either anti-RII immunity or arthritis in RII-immunized DA.1N and WF.1n rats. The data show that RCMV augments arthritis only in rats that are genetically susceptible to CIA and that are appropriately immunized with a species of type II collagen that is arthritogenic for the MHC-haplotype being tested. Two possible mechanisms are suggested by these data: RCMV-associated increases in anti-RII autoimmunity in rats with CIA may result from amino acid sequence homologies between RCMV and type II collagen; alternatively, virus-induced pro-inflammatory cytokines may activate RII-reactive lymphocytes thereby potentiating autoimmunity and arthritis.

Animals↗
PubMed1993

Effects of gold sodium thiomalate, cyclosporin A, cyclophosphamide, and placebo on collagen-induced arthritis in rats.

The prophylactic and therapeutic effects of gold sodium thiomalate, cyclosporin A, cyclophosphamide, and placebo on collagen-induced arthritis (CIA) were evaluated in DA rats. Prophylactic treatment with cyclosporin A and cyclophosphamide suppressed the arthritis incidence, clinical inflammation, destructive bone changes, and development of anti-collagen antibody in DA rats subsequently injected with porcine type-II collagen. Therapeutic treatment with cyclosporin A and cyclophosphamide had a definite suppression on established CIA when started 21 days after the initial collagen injection, but the suppression was less marked than that of prophylactic treatment. Gold had no impact on CIA in DA rats when administered either prophylactically or therapeutically.

Animals↗
PubMed1993

Immunomodulation in vivo by the Mycoplasma arthritidis superantigen, MAM.

Mycoplasma arthritidis produces a potent superantigen (MAM) that activates specific murine and human T lymphocytes to proliferate and secrete lymphokines. We show here that MAM also influences both T- and B-cell functions in vivo. Lymphocytes from mice injected with MAM exhibit a suppression of proliferative responses to MAM in vitro but only a partial suppression of responses to other mitogens. This T-cell anergy not only decreased contact sensitivity to dinitrofluorobenzene but also prolonged survival of skin transplants. In contrast, B-cell reactivity is increased following in vivo injection of MAM, as evidenced by enhanced antibody responses to sheep red blood cells and ovalbumin. Also, there is a marked decrease in the ability of splenocytes from MAM-injected mice to produce interleukin-2 (IL-2) but a marked increase in their ability to produce IL-4 and IL-6. The combined results suggest that MAM induces a lymphokine profile that favors activation of B-cell functions, with a resulting potential for triggering of autoimmune disease.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Encephalocraniocutaneous lipomatosis and the Proteus syndrome: distinct entities with overlapping manifestations.

We have studied three children with cutaneous (epidermal nevi), subcutaneous (lipomas, plantar skin thickening), vascular (hemangioma, lymphangioma), skeletal (osteoma, exostosis, localized hypertrophy), and neurological (hydrocephaly, lissencephaly, partial agenesis of the corpus callosum) developmental defects associated with the Proteus syndrome and related hamartoneoplastic conditions. We compared our findings in these three patients with those of 50 others with Proteus syndrome and nine with encephalocraniocutaneous lipomatosis (ECCL) reported in the literature. We found that Proteus syndrome and ECCL have distinct identities even though some clinical manifestations are shared by both and a few patients have manifestations of both conditions.

Bone Neoplasms↗
PubMed1992

Immunogenetics of collagen-induced arthritis in rats. Both MHC and non-MHC gene products determine the epitope specificity of immune response to bovine and chick type II collagens.

Seven inbred, RT1-congenic rat strains were immunized with native bovine (BII), porcine (PII), or chick (CII) type II collagen and observed for onset, incidence, and severity of arthritis. Clinical results were compared with IgG reactive with native rat type II collagen (RII) and the purified, renatured cyanogen-bromide peptides of BII, CII, or RII. Immunodominant responses to CB11, CB9,7, and CB12 of RII were identified. Secondary responses to CB8 and CB10 also occurred. Reproducible patterns of peptide reactivity were defined in each strain and reflected both RT1 and non-RT1 genotypes plus the species of immunizing collagen. BN non-RT1 gene products moderated clinical arthritis but increased the levels of reactivity to CB11 in three strains carrying RT1l,n,av1 haplotypes. WF (RT1u) rats were susceptible to collagen-induced arthritis (CIA) and developed very high levels of autoantibodies with dominant responses to rat CB11 after CII injections and to rat CB11 and CB9,7 after BII injections. DA (RT1av1) rats developed the most severe arthritis but had only moderate (total) levels of anti-RII IgG: a broad response to CB11, CB10, and CB9,7 after CII injections but predominantly to CB12 and CB9,7 after BII injections. Three RT1n strains--DA.1N(BN), WF.1N(MAXX), and BN--were resistant to BII-induced CIA but developed mild arthritis after immunization with CII. After BII: BN IgG reacted with CB9-7, CB11, and CB12; DA.1N and WF.1N IgG reacted with CB9,7 and CB12. After CII: BN IgG reacted broadly with CB11, CB9-7, CB12, and CB8; WF.1N IgG reacted to CB9-7, CB11, CB8, and CB12; DA.1N IgG reacted with CB8, CB11, and CB9-7. Thus, selective induction of CIA in BN, WF.1N, and DA.1N rats by CII correlated with serum IgG reactivity to rat CB11, but overall strain results identified no single cyanogen-bromide peptide as expressing the sole "arthritogenic" epitope in CIA.

Animals↗
PubMed1991

Pediatric ABR screening: pass-fail rates in awake versus asleep neonates.

The auditory brainstem response (ABR) is commonly used as a neonatal hearing screening tool. The degree to which myogenic and/or movement artifact can confound the ABR in neonates, and the effect this has on screening pass-fail rates, although widely recognized, have not been reported. This study addressed these aspects in a clinical setting. Fifty-two high-risk neonates were screened in various states of activity (asleep, awake-calm, awake-active). Pass-fail rates between asleep and awake babies were significantly different (p less than 0.5), with the awake group displaying a much higher failure rate. There was no significant difference between the awake-calm and awake-active groups. Results indicate that activity state should be noted and considered along with the other factors that are generally blamed for false-positive results in neonatal ABR screenings.

Activity Cycles↗