Flickering fusion pores comparable with initial exocytotic pores occur in protein-free phospholipid bilayers

For the act of membrane fusion, there are two competing, mutually exclusive molecular models that differ in the structure of the initial pore, the pathway for ionic continuity between formerly separated volumes. Because biological “fusion pores” can be as small as ionic channels or gap junctions, one model posits a proteinaceous initial fusion pore. Because biological fusion pore conductance varies widely, another model proposes a lipidic initial pore. We have found pore opening and flickering during the fusion of protein-free phospholipid vesicles with planar phospholipid bilayers. Fusion pore formation appears to follow the coalescence of contacting monolayers to create a zone of hemifusion where continuity between the two adherent membranes is lipidic, but not aqueous. Hypotonic stress, causing tension in the vesicle membrane, promotes complete fusion. Pores closed soon after opening (flickering), and the distribution of fusion pore conductance appears similar to the distribution of initial fusion pores in biological fusion. Because small flickering pores can form in the absence of protein, the existence of small pores in biological fusion cannot be an argument in support of models based on proteinaceous pores. Rather, these results support the model of a lipidic fusion pore developing within a hemifused contact site.     

The future of outcomes measurement: item banking,tailored short-forms,and computerized adaptive assessment

The use of item banks and computerized adaptive testing (CAT) begins with clear definitions of important outcomes, and references those definitions to specific questions gathered into large and well-studied pools, or “banks” of items. Items can be selected from the bank to form customized short scales, or can be administered in a sequence and length determined by a computer programmed for precision and clinical relevance. Although far from perfect, such item banks can form a common definition and understanding of human symptoms and functional problems such as fatigue, pain, depression, mobility, social function, sensory function, and many other health concepts that we can only measure by asking people directly. The support of the National Institutes of Health (NIH), as witnessed by its cooperative agreement with measurement experts through the NIH Roadmap Initiative known as PROMIS (www.nihpromis.org), is a big step in that direction. Our approach to item banking and CAT is practical; as focused on application as it is on science or theory. From a practical perspective, we frequently must decide whether to re-write and retest an item, add more items to fill gaps (often at the ceiling of the measure), re-test a bank after some modifications, or split up a bank into units that are more unidimensional, yet less clinically relevant or complete. These decisions are not easy, and yet they are rarely unforgiving. We encourage people to build practical tools that are capable of producing multiple short form measures and CAT administrations from common banks, and to further our understanding of these banks with various clinical populations and ages, so that with time the scores that emerge from these many activities begin to have not only a common metric and range, but a shared meaning and understanding across users. In this paper, we provide an overview of item banking and CAT, discuss our approach to item banking and its byproducts, describe testing options, discuss an example of CAT for fatigue, and discuss models for long term sustainability of an entity such as PROMIS. Some barriers to success include limitations in the methods themselves, controversies and disagreements across approaches, and end-user reluctance to move away from the familiar.     

Multiple internal resorptions in deciduous teeth: a case report

We report a case of rare multiple internal resorptions. Etiology of multiple internal resorptions is unknown. Interestingly, the patient had an atopic dermatitis, which is possibly related to multiple and rapid internal resorptions.     

Extensive Aberrant Mongolian Spot

A 9-month-old male infant had generalized diffuse blue-gray pigmentation over most of his body, sparing the scalp, face, neck, palms, soles, periumbilical area, genital area, and nipples. Within the lesion, there were several conspicuous macules of considerably darker hue. Histologic examination revealed numerous dermal melanocytes. By 16 months of age, the child's blue-gray pigmentation had decreased substantially.     

Pharmacology of glutamate neurotoxicity in cortical cell culture: attenuation by NMDA antagonists

The antagonist pharmacology of glutamate neurotoxicity was quantitatively examined in murine cortical cell cultures. Addition of 1-3 mM DL-2-amino-5-phosphonovalerate (APV), or its active isomer D-APV, acutely to the exposure solution selectively blocked the neuroexcitation and neuronal cell selectively blocked the neuroexcitation and neuronal cell loss produced by N-methyl-D-aspartate (NMDA), with relatively little effect on that produced by either kainate or quisqualate. As expected, this selective NMDA receptor blockade only partially reduced the neuroexcitation or acute neuronal swelling produced by the broad-spectrum agonist glutamate; surprisingly, however, this blockade was sufficient to reduce glutamate-induced neuronal cell loss markedly. Lower concentrations of APV or D-APV had much less protective effect, suggesting that the blockade of a large number of NMDA receptors was required to acutely antagonize glutamate neurotoxicity. This requirement may be caused by the amplification of small amounts of acute glutamate-induced injury by subsequent release of endogenous NMDA agonists from injured neurons, as the "late" addition of 10-1000 microM APV or D-APV (after termination of glutamate exposure) also reduced resultant neuronal damage. If APV or D-APV were present both during and after glutamate exposure, a summation dose-protection relationship was obtained, showing substantial protective efficacy at low micromolar antagonist concentrations. Screening of several other excitatory amino acid antagonists confirmed that the ability to antagonize glutamate neurotoxicity might correlate with ability to block NMDA-induced neuroexcitation: The reported NMDA antagonists ketamine and DL-2-amino-7-phosphono-heptanoate, as well as the broad-spectrum antagonist kynurenate, were all found to attenuate glutamate neurotoxicity substantially; whereas gamma-D-glutamylaminomethyl sulfonate and L-glutamate diethyl ester, compounds reported to block predominantly quisqualate or kainate receptors, did not affect glutamate neurotoxicity. The present study suggests that glutamate neurotoxicity may be predominantly mediated by the activation of the NMDA subclass of glutamate receptors--occurring both directly, during exposure to exogenous compound, and indirectly, due to the subsequent release of endogenous NMDA agonists. Given other studies linking NMDA receptors to channels with unusually high calcium permeability, this suggestion is consistent with previous data showing that glutamate neurotoxicity depends heavily on extracellular calcium.     

GABAergic neocortical neurons are resistant to NMDA receptor-mediated injury

N-methyl-D-aspartate (NMDA) receptors are thought to mediate much of the central neuronal loss produced by certain neurologic insults, including hypoxia-ischemia, hypoglycemia, and trauma. Therefore, the specific vulnerability of GABAergic inhibitory neurons to NMDA receptor-mediated toxicity might be an important determinant of the potential for epileptogenesis following these insults. We have examined the fate of GABAergic cortical neurons in mouse cell cultured neuronal population) were identified either by immunoreactivity with antisera to GABA or by autoradiography following high-affinity uptake of 3H-GABA. Cultures exposed for 5 min to 20 to 750 microM NMDA showed NMDA concentration-dependent, widespread neuronal loss. However, GABAergic neurons were relatively spared, and thus represented an enhanced fraction of neuronal survivors. These observations suggest that GABAergic cortical neurons may possess some intrinsic resistance to NMDA receptor-mediated neurotoxicity, a property which might convey an anticonvulsant "inhibitory safety factor" to neocortex against certain forms of injury.