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Biomedical subjects

J B Snyder

Publications and source records attributed to J B Snyder.

6 recordsLinked to original sources
PubMed2005

Experiments with a high-density positronium gas.

We have created a high-density gas of interacting positronium (Ps) atoms by irradiating a thin film of nanoporous silica with intense positron bursts and measured the Ps lifetime using a new single-shot technique. When the positrons were compressed to 3.3 x 10(10) cm-2, the apparent intensity of the orthopositronium lifetime component was found to decrease by 33%. We believe this is due to a combination of spin exchange quenching and PS2 molecule formation associated with colliding pairs of oppositely polarized triplet positronium atoms. Our data imply an effective cross section for this process of 2.9 x 10(-14) cm-2.

Journal Article↗
PubMed1997

Mania in children with pervasive developmental disorder revisited.

OBJECTIVE: Although a small literature of case reports suggests that mania co-occurs with pervasive developmental disorder (PDD), little is known about this overlap. The authors systematically investigated the overlap between mania and PDD in a consecutive sample of referred youths, examining its prevalence and correlates. It was hypothesized that children with PDD plus manic features have both disorders. METHOD: Subjects were consecutively referred children meeting diagnostic criteria on structured interview for PDD without mania (n = 52), the comorbid condition PDD + mania (n = 14), and mania without PDD (n = 114). All subjects were evaluated using a comprehensive diagnostic battery that included assessment of psychopathology (structured diagnostic interview and Child Behavior Checklist), cognition, and functioning. RESULTS: Of the 727 referred children, 52 met criteria for PDD, 114 met criteria for mania, and 14 met criteria for both. The 14 children with both PDD + mania represented 21% of the PDD subjects and 11% of all manic subjects. Clinical characteristics of PDD were similar in PDD subjects with and without mania, and manic features were similar in manic children with and without PDD. CONCLUSIONS: Children with PDD and mania may suffer from two disorders. Comorbid mania among patients with PDD may be more common than previously thought. Identification of the comorbid condition may have important therapeutic and scientific implications.

Bipolar Disorder↗
PubMed1997

Bubble palate and failure to thrive: a case report.

In this report, a mother presents at 29 days postpartum with extremely sore nipples. Her infant is 1 1b 2 oz (511 gms) below birth weight, a continuing weight loss consistent with failure to thrive. Failure to thrive may be caused by a variation in infant palatal structure (VIPS) such as a bubble palate. The mother demonstrated correct latch-on, positioning, and soreness secondary to nipple candidiasis concealing the VIPS as a hidden component to this breastfeeding problem. A thorough assessment of the infant at breast, the infant's oral anatomy and the mother's breasts revealed the VIPS and information necessary for treatment. Alternative positioning and repatterning of oral behavior resolved the breastfeeding problem. A variation in infant palatal structure may be a hidden breastfeeding problem and needs to be considered.

Breast Feeding↗
PubMed1989

Preproenkephalin DNA-binding proteins in the rat: 5' flanking region.

Various extracellular signals (i.e. transmitters, hormones, growth factors, etc.), together with their respective second-messenger pathways, regulate transmitter biosynthesis and neuronal function by altering gene expression. In this study we validated a protocol for isolating rat striatum and adrenal medullary nuclei for the purpose of extracting, identifying, and characterizing, nuclear regulatory factors which may serve a functional role in signal-transduction processes. Through gel retardation studies using a 299 base pair (bp) XmnI-SacI 32P-labeled probe (derived from the 5' untranslated region of the rat preproenkephalin gene), we show that different patterns of retained bands result from nuclear extracts derived from rat adrenal medulla and striatum (as well as from other tissue). These tissue differences may have biological significance since rat adrenal medullae have low basal enkephalin levels while the striatum has high levels of this peptide and its respective mRNA. Additionally, certain retained bands were common to both cytosolic and nuclear compartments, suggesting binding factors may be located in either cell space. An initial biochemical characterization of these factors was also undertaken. Generally, salt levels of 100 mM or more reduced factor binding while 10-50 mM sodium ion levels showed preferentially enhanced bands. Binding activity appeared optimal at pH 6.8. As all retained bands were abrogated by proteinase K treatment, these factors appear to have a significant protein component. Finally, of particular interest is that this 299 bp region contains many sequences showing over 80% sequence identity with several previously characterized transcriptional control elements (i.e. cAMP and phorbol ester inducible enhancers, GCN4, AP1, Sp1, CCAAT binding factor, ATF, and AP2). If binding is confirmed (footprint analysis) and function validated (transfection studies), the evolutionary significance of the apparent presence of gene regulatory sequences and functional element divergence of the DNA region between different species can be evaluated.

Adrenal Medulla↗
PubMed1988

Rat lung antioxidant enzyme activities and their specific proteins during hyperoxia.

The hyperoxia-induced increases in the activity of lung glucose-6-phosphate dehydrogenase (G-6-P) and glutathione reductase (GR) after exposure of rats to greater than 97% O2 for 6 days were accompanied by equivalent increases in the amount of the respective immunoreactive proteins. Hyperoxia also increased lung glutathione (GSH) + oxidized glutathione (GSSG) content and the magnitude of this hyperoxic response of increased GSH + GSSG, G-6-P, and GR (maximal 1.3- to 1.8-fold) declined as a function of age during the first 3 wk of life. Fetal rat lung explants cultured 4 days in 95% O2 showed increased G-6-P and GR activity and increased levels of the specific proteins 1.5-fold those of explants at 2 days of culture. We conclude that the hyperoxic response of increased rat lung G-6-P and GR activity in vivo and in vitro involves not just alteration of enzyme activity but also specific increases in the proteins catalyzing the reactions.

Aging↗