Detection of Clostridium difficile toxin: comparison of enzyme immunoassay results with results obtained by cytotoxicity assay

Several kinds of laboratory techniques are available to detect Clostridium difficile toxin in fecal samples. Because questions have been raised about the reliability of immunoassays compared to the accepted standard, cytotoxicity assay, we studied three enzyme immunoassays (EIAs) and one rapid EIA, which demonstrated relatively good sensitivities and specificities compared to cytotoxicity assay.     

Teachers' perceptions of and responses to adolescents with chronic pain syndromes

OBJECTIVE: To examine factors that influence teachers' perceptions of and responses to chronic pain in students. METHODS: Two-hundred and sixty classroom teachers responded to a vignette describing a student with limb pain. The 2 x 2 x 2 factorial design included conditions that varied by (a) the presence or absence of documented organic evidence for the pain, (b) cooperative vs. confrontational parent-teacher interactions, and (c) the presence or absence of communication from the medical team. Teachers rated pain severity and impairment, relief from classroom responsibilities, extent of accommodations the student would require in school, and sympathy for the student and family. RESULTS: Documented medical evidence supporting the pain was the most influential factor affecting teachers' responses to pain. Parental attitude also influenced responses. Communication from the medical team influenced teachers' decisions about relief from responsibilities but did not affect other reactions. CONCLUSIONS: Teachers' responses to students with pain are influenced by situational factors. Efforts to increase school functioning in youth with chronic pain should incorporate attempts to help teachers respond to pain adaptively.     

Idiopathic hemochromatosis

Hemochromatosis is a rare disorder in which about four times the normal amount of iron is absorbed in the intestine, resulting in the accumulation of iron in the skin, liver, pancreas and heart. Radiographic features may include a small liver on plain abdominal films, increased hepatic density on computed tomographic imaging, and loss of liver signal on magnetic resonance imaging as a result of the strong paramagnetic effect of iron. Management includes phlebotomy and supportive treatment of damaged organs.     

Molecular basis for the thiol sensitivity of insulin-degrading enzyme

Insulin-degrading enzyme (IDE) is a ubiquitous zinc-metalloprotease that hydrolyzes several pathophysiologically relevant peptides, including insulin and the amyloid beta-protein (Abeta). IDE is inhibited irreversibly by compounds that covalently modify cysteine residues, a mechanism that could be operative in the etiology of type 2 diabetes mellitus (DM2) or Alzheimer's disease (AD). However, despite prior investigation, the molecular basis underlying the sensitivity of IDE to thiol-alkylating agents has not been elucidated. To address this topic, we conducted a comprehensive mutational analysis of the 13 cysteine residues within IDE. Our analysis implicates C178, C812, and C819 as the principal residues conferring thiol sensitivity. The involvement of C812 and C819, residues quite distant from the catalytic zinc atom, provides functional evidence that the active site of IDE comprises two separate domains that are operational only in close apposition. Structural analysis and other evidence predict that alkylation of C812 and C819 disrupts substrate binding, whereas alkylation of C178 interferes with the apposition of active-site domains and subtly repositions zinc-binding residues. Unexpectedly, alkylation of C590 was found to activate hydrolysis of Abeta significantly, while having no effect on insulin, demonstrating that chemical modulation of IDE can be both bidirectional and highly substrate selective. Our findings resolve a long-standing riddle about the basic enzymology of IDE with important implications for the etiology of DM2 and AD. Moreover, this work uncovers key details about the mechanistic basis of the unusual substrate selectivity of IDE that may aid the development of pharmacological agents or IDE mutants with therapeutic value.     

From the Cover: Pre-Columbian transregional captive rearing of Amazonian parrots in the Atacama Desert

The feathers of tropical birds were one of the most significant symbols of economic, social, and sacred status in the pre-Columbian Americas. In the Andes, finely produced clothing and textiles containing multicolored feathers of tropical parrots materialized power, prestige, and distinction and were particularly prized by political and religious elites. Here we report 27 complete or partial remains of macaws and amazon parrots from five archaeological sites in the Atacama Desert of northern Chile to improve our understanding of their taxonomic identity, chronology, cultural context, and mechanisms of acquisition. We conducted a multiproxy archaeometric study that included zooarchaeological analysis, isotopic dietary reconstruction, accelerated mass spectrometry radiocarbon dating, and paleogenomic analysis. The results reveal that during the Late Intermediate Period (1100 to 1450 CE), Atacama oasis communities acquired scarlet macaws (Ara macao) and at least five additional translocated parrot species through vast exchange networks that extended more than 500 km toward the eastern Amazonian tropics. Carbon and nitrogen stable isotopes indicate that Atacama aviculturalists sustained these birds on diets rich in marine bird guano-fertilized maize-based foods. The captive rearing of these colorful, exotic, and charismatic birds served to unambiguously signal relational wealth in a context of emergent intercommunity competition.

One of the most pervasive and unambiguous material symbols of prestige, wealth, and spiritual status in the pre-Columbian Americas were long, slender, and brightly colored feathers often worn in elaborated headdresses (1–4). Feather use and its representation in iconography is recurrently found as a marker of leadership and association with divinity from incipiently stratified communities to consolidated empires (5, 6). In the Andes, the colorful feathers of tropical parrots were often imported from the eastern Amazonian tropical forests by little-understood mechanisms of exchange and trade (7–9). Although many feathers were transported and maintained in special containers, some tropical birds might have been taken and moved across the Andes alive. The archaeological finding of actual tropical macaws and amazon parrots in specific ritual and funerary contexts provides a unique opportunity to explore the origin of these birds and the management strategies related to their procurement, handling in captivity, and ceremonial interment. Here we reconstructed some of these practices by conducting a multiproxy study involving direct accelerated mass spectrometry (AMS) radiocarbon dating, stable isotope analysis, and paleogenomic sequencing of an assemblage of macaw and amazon parrot remains recovered from archaeological sites located in the Atacama Desert of northern Chile.The Atacama Desert provides remarkable conditions for the preservation of organic materials such as bone, tendons, muscles, skin, and feathers (10–12). The evidence associated with the preservation and use of tropical bird feathers in this region has been a topic of recurrent discussion regarding the nature of the social interaction between societies located on both sides of the Andes (8, 13). The Andes were not the only place where these birds and their feathers were widely circulated. Scarlet macaws (Ara macao) were transported and held captive for feathers to mark status and for ceremonial purposes by Ancestral Pueblo, Mimbres, Paquimé, and other pre-Hispanic societies across the arid southwestern US and northwestern Mexico (14–16). Moreover, recent technical advances in the study of the pre-Columbian avicultural practices open up a series of possibilities for improving our understanding about ancient social, economic, and religious practices in the Americas, as well as of animal husbandry, procurement strategies, feeding ecology, and biogeography of tropical bird species that are presently threatened (17–19).     

Reciprocal entorhinal-hippocampal connections established by human fetal midgestation

Little is known about the timing or sequence of genesis of connections between different areas of the developing human cerebral cortex. It has been shown that connections between areas V1 and V2 of the visual isocortex are established at about 37 weeks of gestation (Burkhalter [1993] Cerebr. Cortex 3:476–487), suggesting that cortico-cortical connections appear late in the 40-week human gestational period. However, there are indications from other studies that connections between subdivisions of the hippocampal formation may be established much earlier, by about 20 weeks of human gestation. To investigate this possibility, the lipophilic bidirectional tracer 1,1′ dioctadecyl-3,3,3′,3-tetramethylindocarbocyanine perchlorate (DiI) was used to study connections between the entorhinal cortex, hippocampus, and temporal lobe neocortex in paraformaldehyde-fixed postmortem fetal tissue. The DiI transport revealed robust reciprocal connections between the entorhinal cortex, hippocampus, and subiculum, which were consistently present at 19 weeks of gestation (the earliest age studied), and which were anatomically similar to those in adult primates. Specifically, projections to the hippocampus and subiculum originated from neurons in the entorhinal cortex (EC) layers 2 and 3, whereas reciprocal projections to the EC originated from pyramidal neurons in the cornu ammonis region CA1 and the subiculum. In contrast, the perforant pathway projection from EC to the dentate gyrus, and all connections with the neocortex, reached only rudimentary stages of development by 22 weeks of gestation (the latest age studied). These findings suggest that hippocampal pathways develop prior to isocortical pathways, and that reciprocal entorhinal-hippocampal projections may be among the first cortico-cortical connections to be established in the human brain. © 1996 Wiley-Liss, Inc.     

An evolutionary perspective on maladaptive traits and cultural conformity

The problem of maladaptive cultural traits is explored through the notion of adaptive psychological mechanisms. It is suggested that the theory of a specific conformity mechanism is plausible, supported by multidisciplinary data, and helpful in explaining the proliferation and persistence of human maladaptive behavior. © 1996 Wiley-Liss, Inc.     

The vcop scale: A measure of overprotection in parents of physically vulnerable children

A scale is developed for measuring the overprotecting vs. optimal developmental stimulation tendencies for parents of physically “vulnerable” children. A series of items were administered to parents whose parenting techniques had been rated as either highly overprotective or as optimal by a group of MDs and other professionals. Correlations were estimated between each of the items and parental tendencies as rated by professionals. Twenty-eight items were selected that provided maximum prediction of overprotection. The resulting R² was extraordinarily high (.94). Coefficient alpha and test-retest coefficients were acceptable. It is hoped that release of the new instrument (VCOPS) at this time will allow others to join in determining the clinical and experimental validity of this scale.