PubMed Health⌕ Search

Biomedical subjects

A S Fox

Publications and source records attributed to A S Fox.

At least 19 recordsLinked to original sources
PubMed2005

Comparison of fMRI motion correction software tools.

Motion correction of fMRI data is a widely used step prior to data analysis. In this study, a comparison of the motion correction tools provided by several leading fMRI analysis software packages was performed, including AFNI, AIR, BrainVoyager, FSL, and SPM2. Comparisons were performed using data from typical human studies as well as phantom data. The identical reconstruction, preprocessing, and analysis steps were used on every data set, except that motion correction was performed using various configurations from each software package. Each package was studied using default parameters, as well as parameters optimized for speed and accuracy. Forty subjects performed a Go/No-go task (an event-related design that investigates inhibitory motor response) and an N-back task (a block-design paradigm investigating working memory). The human data were analyzed by extracting a set of general linear model (GLM)-derived activation results and comparing the effect of motion correction on thresholded activation cluster size and maximum t value. In addition, a series of simulated phantom data sets were created with known activation locations, magnitudes, and realistic motion. Results from the phantom data indicate that AFNI and SPM2 yield the most accurate motion estimation parameters, while AFNI's interpolation algorithm introduces the least smoothing. AFNI is also the fastest of the packages tested. However, these advantages did not produce noticeably better activation results in motion-corrected data from typical human fMRI experiments. Although differences in performance between packages were apparent in the human data, no single software package produced dramatically better results than the others. The "accurate" parameters showed virtually no improvement in cluster t values compared to the standard parameters. While the "fast" parameters did not result in a substantial increase in speed, they did not degrade the cluster results very much either. The phantom and human data indicate that motion correction can be a valuable step in the data processing chain, yielding improvements of up to 20% in the magnitude and up to 100% in the cluster size of detected activations, but the choice of software package does not substantially affect this improvement.

Algorithms↗
PubMed2004

Functional but not structural subgenual prefrontal cortex abnormalities in melancholia.

Major depression is a heterogeneous condition, and the search for neural correlates specific to clinically defined subtypes has been inconclusive. Theoretical considerations implicate frontostriatal, particularly subgenual prefrontal cortex (PFC), dysfunction in the pathophysiology of melancholia--a subtype of depression characterized by anhedonia--but no empirical evidence has been found yet for such a link. To test the hypothesis that melancholic, but not nonmelancholic depression, is associated with the subgenual PFC impairment, concurrent measurement of brain electrical (electroencephalogram, EEG) and metabolic (positron emission tomography, PET) activity were obtained in 38 unmedicated subjects with DSM-IV major depressive disorder (20 melancholic, 18 nonmelancholic subjects), and 18 comparison subjects. EEG data were analyzed with a tomographic source localization method that computed the cortical three-dimensional distribution of current density for standard frequency bands, allowing voxelwise correlations between the EEG and PET data. Voxel-based morphometry analyses of structural magnetic resonance imaging (MRI) data were performed to assess potential structural abnormalities in melancholia. Melancholia was associated with reduced activity in the subgenual PFC (Brodmann area 25), manifested by increased inhibitory delta activity (1.5-6.0 Hz) and decreased glucose metabolism, which themselves were inversely correlated. Following antidepressant treatment, depressed subjects with the largest reductions in depression severity showed the lowest post-treatment subgenual PFC delta activity. Analyses of structural MRI revealed no group differences in the subgenual PFC, but in melancholic subjects, a negative correlation between gray matter density and age emerged. Based on preclinical evidence, we suggest that subgenual PFC dysfunction in melancholia may be associated with blunted hedonic response and exaggerated stress responsiveness.

Adult↗
PubMed2000

Effects of intracerebroventricular leptin administration on feeding and sexual behaviors in lean and obese female Zucker rats.

Obese Zucker rats (fa/fa) are characterized by inadequate leptin signaling caused by a mutation in the leptin receptor gene. Obese Zucker females are infertile and hyporesponsive to the inductive effects of ovarian hormones on sexual behaviors. Leptin treatment reverses aspects of reproductive dysfunction due to perturbations in energy balance in other animal models. Our first experiment tested the hypothesis that intracerebroventricular (icv) leptin administration would enhance the display of sexual behaviors in obese Zucker females. A second experiment compared lean and obese Zucker females' responses to leptin, during fed and fasted conditions. Ovariectomized (OVX) Zucker rats were implanted with lateral ventricular cannulae. In Experiment 1, fasted, obese females received estradiol benzoate, progesterone, and icv injections of 3, 18, or 36 microg murine leptin or vehicle. Leptin administration reduced food intake, but did not enhance sexual behaviors. In Experiment 2, steroid-replaced, OVX lean and obese females (from a different source than those in Experiment 1) received icv injections of vehicle or 3 or 36 microg leptin under fed and fasted conditions. Leptin treatment reduced food intake and weight gain in the fed, but not the fasted, condition in both genotypes. Sexual receptivity and locomotion were not affected, but icv leptin injections reduced proceptive behaviors in ad libitum-fed rats. These data confirm previous reports that centrally administered leptin decreases food intake and weight gain in obese Zucker rats; results from Experiment 2 suggest that lean and obese females are similarly responsive to these actions of leptin. Contrary to our hypothesis, leptin treatment did not stimulate sexual behaviors; rather, the hormone appears to inhibit the display of sexual proceptivity in ad libitum-fed lean and obese Zucker female rats.

Animals↗
PubMed1999

Cervical Papanicolaou smear abnormalities in inner city Bronx adolescents: prevalence, progression, and immune modifiers.

BACKGROUND: The aim of this study was to quantify the prevalence of cervical smear abnormalities in sexually active adolescents and identify the effect of immune-modifying conditions. METHODS: Two hundred seventy-one females ages 13-22 years attending a clinic for sexually transmitted disease (STD) evaluation had cervical Papanicoloau (Pap) smears and completed sexual history questionnaires. Results of all follow-up Pap smears were obtained. Medical charts were available for 54 patients with cytologic follow-up and were reviewed for the presence of immune-modifying conditions. Follow-up smear results for patients with and without immune-modifying conditions were compared. Abnormality rates for all cervical smears seen in 1995 at Montefiore Medical Center were also obtained. RESULTS: The smear abnormality rate for adolescents was 20. 7% (abnormal squamous cells of undetermined significance [ASCUS], 12. 2%; low grade squamous intraepithelial lesion [LGSIL], 7.7%; high grade squamous intraepithelial lesion [HGSIL], 0.7%) compared with all adult females, for whom the rate was 13.2% (ASCUS, 9.9%; LGSIL, 2.5%; HGSIL, 0.6%; carcinoma 0.2%) (P < 0.0002). Of 20 initial ASCUS patients, 6 (30%) showed LGSIL or HGSIL on follow-up. Chart review allowed the clinical immune status of 54 patients to be determined. Of 14 patients with an immune-modifying condition (9 HIV positive patients, 3 receiving oral steroids, 1 liver transplant patient receiving steroids, and 1 with intestinal lymphangiectasia), 11 (78. 6%) developed or maintained an abnormality on cytologic follow-up. Of 40 patients with no identifiable immune-modifying condition, 11 (27.5%) developed or maintained an abnormality on cytologic follow-up (P < 0.00082). CONCLUSIONS: Sexually active adolescents are at higher risk of developing a significant cervical smear abnormality, especially LGSIL. Patients with an atypical Pap smear or immune-modifying condition require more attentive gynecologic monitoring. Cancer (Cancer Cytopathol)

Adolescent↗
PubMed1998

Are there risk factors for hepatitis B infection in inner-city adolescents that justify prevaccination screening?

PURPOSE: This study was undertaken to determine if homelessness could serve as a marker for previous hepatitis B infection (HBI), and thus justify prevaccination screening. METHODS: One hundred sexually active 13-21-year-olds (mean = 17 years), 74% female, attending an inner-city hospital-based adolescent clinic (HOSP), and 48 sexually active 13-21-year-olds (mean = 19 years), 40% female, attending a clinic based at an urban drop-in center (UDC) for street youth were consecutively enrolled, screened for HBI serum markers and administered a structured interview about sexual practices, sexual abuse, prior sexually transmitted diseases (STDs), and injection drug use. RESULTS: For the HOSP group, 7% were homeless and 4% were HBI positive. In the UDC group, 96% were homeless and 23% were HBI positive. Homelessness was significantly associated with HBI (p < 0.001), and this was corroborated by logistic regression analysis (p < 0.01). Other factors significantly associated with HBI in adolescents included a history of anal sex (p < or = 0.002), anal-receptive sex (p < or = 0.01), genital Chlamydia (p < or = 0.03), prostitution (p < or = 0.03), and sexual abuse (p < or = 0.002). For both populations, gender, sexual orientation, intravenous drug use, and genital sex were not related to HBI. CONCLUSION: These data indicate that homelessness and associated high-risk sexual practices may be indications for prevaccination screening for HBI in adolescents.

Adolescent↗
PubMed1996

Parity diagnosis and ovulation in Culiseta inornata (Diptera:Culicidae).

The hypothesis that ovulation in mosquitoes results in the formation of a single basal dilatation per ovariole, regardless of previous history of the ovariole, was supported for known 1- and 2-parous Culiseta inornata (Williston). The examination of histological sections of whole ovaries of Cs. inornata, before and after ovulation in the 1st gonotrophic cycle, indicated that the pedicel is destroyed during ovulation. Dissections revealed that 88% of 1- dilated ovarioles in 1-pars lacked a pedicel, and 90% of 2-pars had a mean of only 12.5 2-dilated ovarioles (10% had none). Criteria are proposed for the separation of nulliparous, 1-parous and 2-parous (anautogenous) Cs. inornata. Fifty percent of nullipars and 42% of 1-pars had a mean of 2.6 and 2.0 rogue ovarioles, respectively. The criteria account for rogue ovarioles in nullipars, but misdiagnose 2-pars as 1-pars when the former have few (or lack) diagnostic ovarioles. This diagnostic error can be reduced using structural differences in rogue versus diagnostic ovarioles.

Animals↗
PubMed1995

Comparison of rapid diagnostic methodologies for Chlamydia and gonorrhea in an urban adolescent population: a pilot study.

PURPOSE: To compare a combination DNA probe test which detects both N. gonorrhoeae (GC) and C. trachomatis (CT) to the current culture methodologies among a population of female adolescents at an urban teaching center. In addition, the probe test for CT was compared to a direct immunofluorescence test. METHODS: All sexually active female adolescents between the ages of 13-21 years who sought care at an urban teaching center from June 1991 through November 1991 and who required testing for sexually transmitted diseases (STDs) were recruited for this study. RESULTS: The probe test was demonstrated to be 66.6% sensitive and 94.9% specific when compared to tissue culture for CT and 50% sensitive and 98.2% specific when compared to culture for GC. We found an overall prevalence of 23.5% for CT and 3.5% for GC. CONCLUSIONS: The two rapid diagnostic tests for CT evaluated in this study demonstrated similar sensitivities. However the probe test offers advantages in that it is easier to perform, skill at reading fluorescence is not required, and one specimen yields results for both CT and GC.

Adolescent↗
PubMed1994

How do dilatations form in mosquito ovarioles?

Ovariolar dilatations have been used to estimate parity status in mosquitoes for over 40 years. The theoretical basis for this parity-diagnostic method, which was established for mosquitoes by Polovodova 1, has been challenged by a number of Russian researchers. The findings of this new school of researchers have elicited little response from those currently using the method outside Russia, except for a recent paper by Hoc and Charlwood2. This has stimulated Andrew Fox and Reinhart Brust to review the formation of ovariolar dilatations here, and compare what they term the Old and the New Schools. Although the basic application of Polovodova's method is unaffected by the premise of either School, a clear understanding of ovarian dynamics is needed to understand the method and its limits.

Journal Article↗
PubMed1994

Rogue ovarioles and criteria for parity diagnosis in Culex tarsalis (Diptera: Culicidae) from Manitoba.

Rogue ovarioles were identified in laboratory-reared nulliparous and 1-parous Culex tarsalis Coquillett and in wild nulliparous C. tarsalis. Parity-diagnostic criteria were extrapolated from analysis of known nullipars and 1-pars. Diagnostic criteria were based, in part, on the number of ovarioles with no dilatation and a pedicel of greater than or equal to six adjacent cells. The high proportion of ovarioles lacking pedicels in known 1-pars and the small number of diagnostic ovarioles found in 2-pars support the findings of other researchers that ovulation destroys the pedicel and any previously formed dilatations.

Animals↗
PubMed1989

Chlamydia trachomatis and parainfluenza 2 virus: a shared antigenic determinant?

A tracheal aspirate from which parainfluenza 2 (PI-2) virus but not chlamydiae was isolated demonstrated positive immunofluorescence of elementary body- and reticulate body-like particles on direct examination with anti-chlamydia monoclonal antibodies (Syva Co.). In subsequent studies, we found this reagent to show specific staining of this strain of PI-2 as well as of 3 of 18 additional PI-2 strains that were evaluated.

Antigens, Viral↗
PubMed1983

Tuberculin skin testing in Vietnamese refugees with a history of BCG vaccination.

Among 50 Indo-Chinese children 18 years of age or younger who were screened at the Albany County (New York) Health Department, during 1979, 14 had a history of BCG vaccination. These patients were not intradermally tested with 5 TU of PPD because it was assumed that the reactions would not be interpretable. To test this hypothesis, nine patients were available for testing. Six patients had a negative reaction, two had a reaction greater than 10 mm of induration, and one had an equivocal reaction. Nine of the 36 patients without a history of BCG vaccination also had positive reactions to the same dose of PPD. All patients with positive reactions had normal chest x-ray films and received isoniazid prophylaxis, regardless of BCG history in accordance with Centers for Disease Control recommendations. A history of BCG vaccination should not preclude skin testing with PPD (given in tuberculin units), and a patient with a positive reaction should receive appropriate treatment.

Adolescent↗
PubMed1977

The management vf essential hypertension with once daily administration of timolol maleate and bendrofluazide.

A placebo controlled-blind study performed on new patients presenting with mild to moderate essential hypertension. A once daily combined dose of timolol maleate and bendrofluazide in a 4:1 ratio was administered ot each patient after a four week placebo period. The starting dose was timolol 10 mg and bendrofluazide 2-5 mg and this dose was increased in steps of timolol 10 mg and bendrofluazide 2-5 mg until blood pressure was controlled. Eleven out of twelve patients achieved normotension, the falls in diastolic and systolic blood pressure being highly significant on active treatment compared with placebo. The once daily regimen of timolol and bendrofluazide resulted in good control of blood pressure with no more side-effects than occurred on the placebo. A combination of these two drugs in one tablet would appear to be both practical and advantageous and should increase patient compliance in taking medication.

Adolescent↗