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Biomedical subjects

A Messinger

Publications and source records attributed to A Messinger.

6 recordsLinked to original sources
PubMed2001

Neuronal representations of stimulus associations develop in the temporal lobe during learning.

Visual stimuli that are frequently seen together become associated in long-term memory, such that the sight of one stimulus readily brings to mind the thought or image of the other. It has been hypothesized that acquisition of such long-term associative memories proceeds via the strengthening of connections between neurons representing the associated stimuli, such that a neuron initially responding only to one stimulus of an associated pair eventually comes to respond to both. Consistent with this hypothesis, studies have demonstrated that individual neurons in the primate inferior temporal cortex tend to exhibit similar responses to pairs of visual stimuli that have become behaviorally associated. In the present study, we investigated the role of these areas in the formation of conditional visual associations by monitoring the responses of individual neurons during the learning of new stimulus pairs. We found that many neurons in both area TE and perirhinal cortex came to elicit more similar neuronal responses to paired stimuli as learning proceeded. Moreover, these neuronal response changes were learning-dependent and proceeded with an average time course that paralleled learning. This experience-dependent plasticity of sensory representations in the cerebral cortex may underlie the learning of associations between objects.

Animals↗
PubMed1998

Charge displacements in interfacial layers containing reaction centers.

Reaction centers from the photosynthetic bacterium Rhodobacter sphaeroides were oriented in phospholipid interfacial layers adsorbed to a Teflon film separating two electrolyte-filled compartments of a Teflon cell. Light-induced voltage changes were measured as a function of time across electrodes immersed in the cell compartments. The experimental system is characterized both experimentally and theoretically to relate the measured signals to the light-induced displacement currents in the reaction centers. Mathematical relations between the measured signals and the distances and geometries of the charge-transfer reactions are derived. At pH 8.0 the reaction centers were found to be oriented with approximately 60% of the population oriented with the donor facing the aqueous phase. The density of the reaction centers in the layer was approximately 10(11) cm-2, which is close to that found in the native system. Reconstitution of the secondary quinone, QB, in 90% of the RCs was achieved with an approximately 100-fold excess of ubiquinone in the vesicle preparation.

Electrochemistry↗
PubMed1993

Far-infrared study of the vibrational modes of 5'-GMP gels and crystals of Na+ and K+.

Five Far-Infrared (50-600 cm-1) spectra are presented: the sodium and potassium salts of 5' Guanosine Monophosphate (GMP), each salt in both the gel and crystal conformations, and poly(rG). Measurements were performed at a sample temperature of 10 K under vacuum with a liquid He-cooled bolometer. The spectra were fit with Lorentzians and assignments are suggested. There are noteworthy differences in oscillator strengths and frequencies of the bands between all spectra. We report the tentative observation of a 100 cm-1 mode which is in the neighborhood of a mode observed by Raman spectroscopy in solution (1) and dried gels (2).

Crystallization↗
PubMed1989

Orbital roof fractures in the pediatric population.

Twenty-three patients aged 3.3 +/- 1.6 years (mean +/- SD) presented between January of 1984 and September of 1987 with fronto-orbital trauma resulting in fractures of one (N = 20) or both (N = 3) orbital roofs. All patients had computed tomography (CT) with axial and coronal sections that revealed three fracture patterns of the orbital roof (nondisplaced, superiorly displaced, and inferiorly displaced fractures). Orbital dystopia was exhibited in 35 percent (N = 8) of the patients. Exophthalmos was noted in 61 percent (N = 14) of the patients. Only 30 percent of the patients (N = 7) sustained associated maxillofacial fractures. Eight percent of fractures exhibited orbital encephaloceles. All patients lacked frontal sinus pneumatization. The majority of children with orbital roof fractures do not exhibit concomitant facial fractures. CT utilizing both axial and coronal sections is valuable in defining the extent and pattern of the fracture as well as in identifying associated neurologic injuries. Large, displaced orbital roof fractures, which occurred in 3 of 13 patients with displaced fractures in our series, should undergo early reduction to avoid late development of encephalocele.

Child, Preschool↗
PubMed1985

A method for lining the superiorly based pharyngeal flap.

The development of a mucosal flap as a lining for a superiorly based pharyngeal flap has undergone many modifications. The technique described herein uses tissue from the nasal surface of the soft palate with its base at the uvula. Its ease of construction is based on the adaptive use of modern vascular instruments. Since 1979 a total of 32 pharyngeal flaps have been lined in this manner. The results, as determined by a trained speech pathologist and the use of the oral panendoscope, have been quite good. This method offers a number of advantages, including the ability to line the pharyngeal flap with a shortened soft palate or one that is difficult to mobilize due to scarring, no through-and-through incision into the soft palate, and no exposed raw surfaces that can contribute to recurrence of velopharyngeal incompetence.

Adult↗