Advances in treatment of type II diabetes mellitus in the elderly.

Elderly diabetic patients are prone to the acute and subacute consequences of hyperglycemia, which can adversely affect health, well being, and quality of life. Every elderly patient with diabetes should be offered an individualized treatment plan, consisting of education, dietary counseling, and an exercise program. If fasting and postprandial glucose levels do not stay consistently in the desired range, then an oral hypoglycemic agent should be instituted at the lowest possible dose. When the oral hypoglycemic agent fails, it may be possible to achieve good glycemic control with the addition of insulin. Recent developments in insulin administration can optimize glycemic benefits and reduce potential adverse effects.     

Intramembrane translocation and posttranslational palmitoylation of the chloroplast 32-kDa herbicide-binding protein.

The 32-kDa herbicide-binding protein, a component of photosystem II, is synthesized as a membrane-associated 33.5-kDa precursor within the chloroplast. We show that membrane attachment of the precursor and processing to the 32-kDa form occur in the unstacked stromal lamellae. Once processed, the 32-kDa protein translocates, within the thylakoids, to the topologically distinct stacked granal lamellae. Posttranslational palmitoylation of the processed 32-kDa protein is also shown to occur. This modification takes place in a membrane-protected domain and is mainly confined to the protein assembled in the granal lamellae, where functional photosystem II centers are concentrated.     

Assessment of intracardiac shunts with gadolinium-enhanced ultrafast MR imaging.

Dye dilutional techniques are widely accepted for the assessment of intracardiac shunts, but current techniques require arterial access or radioisotope injection. Ultrafast (less than 500 msec) magnetic resonance (MR) imaging is ideally suited for the evaluation of an indicator during passage through the heart. Twenty patients were studied, including 13 with shunts. Four-chamber, T1-weighted images were obtained during bolus injection of gadopentetate dimeglumine. A single image was obtained in 420 msec, with repetitive images acquired after each QRS complex. After the contrast material was injected, there was pronounced signal intensity enhancement in the right atrium, followed by the right ventricular cavity, left atrium, left ventricular cavity, and descending aorta. Patients with substantial intracardiac shunts demonstrated early recirculation. First-pass contrast material-enhanced MR imaging is a promising new technique for the rapid assessment of intracardiac shunts. Combined with anatomic and functional MR imaging techniques, it can help provide a comprehensive noninvasive evaluation of suspected intracardiac shunts or provide follow-up in patients with known shunts.     

Immunocytochemical demonstration of neural cell adhesion molecule (NCAM) along the migration route of luteinizing hormone-releasing hormone (LHRH) neurons in mice.

Contact between the developing forebrain and the ingrowing central processes of the olfactory, vomeronasal and terminal nerves is preceded by a migration of neural cell adhesion molecule (NCAM)-immunoreactive cells from the epithelium of the olfactory pit and the formation of an NCAM-immunoreactive cellular aggregate in the mesenchyme between the olfactory pit and the forebrain. The axons of the olfactory, vomeronasal, and terminal nerves, also NCAM-immunoreactive, grow into the cellular aggregate, which as development proceeds, becomes continuous with the rostral tip of the forebrain. The lateral and more rostral part of the cellular aggregate receives the ingrowing axons of the olfactory nerves and becomes the olfactory nerve layer of the olfactory bulb. The medial, more caudal part receives the central processes of the vomeronasal and terminal nerves. The vomeronasal nerve ends in the accessory olfactory bulb. The central processes of the terminal nerve end in the medial forebrain. Luteinizing hormone-releasing hormone (LHRH)-immunoreactive neurons, like the vomeronasal and terminal nerves, originate from the medial part of the olfactory pit. These LHRH cells migrate into the brain along and within a scaffolding formed by the NCAM-immunoreactive axons of the vomeronasal and terminal nerves, and they are never seen independent of this NCAM scaffold as they cross the nasal lamina propria. The results suggest that: (1) NCAM is likely to be necessary for scaffold formation, and (2) the scaffold may be essential for the subsequent migration of LHRH neurons into the brain. Because they aggregate, migrating LHRH-immunoreactive neurons, on which we did not detect NCAM immunoreactivity, may interact via other cell adhesion molecules (CAM). Inasmuch as the interaction between the LHRH-immunoreactive neurons and the NCAM-immunoreactive scaffold is heterotypic, the possibility of a heterophilic (NCAM to other CAM) interaction is not ruled out. These findings focus our attention on the functional role of NCAM in this migratory system.     

Effects of intrauterine devices on the surface ultrastructure of human endometrium before and after removal

The effects of copper-releasing IUDs on the endometrial ultrastructure were evaluated in 101 women. Endometrial samples were obtained in the secretory phase of the menstrual cycle, both during and after IUD use, and were evaluated using both scanning and electron microscopy. The degree and extent of changes to the surface ultrastructure of the endometrium were found to be related to the copper surface area of the IUD. Regardless of the duration of IUD use, by one month after IUD removal the endometrial ultrastructure had returned to its normal state. The results of this study show that the effects of copper-releasing IUDs on the endometrial ultrastructure are essentially limited to the time the IUD isin utero.

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Resumen En 101 mujeres fueron evaluados los efectos de los DIU liberadores de cobre en la ultraestructura endometrial. Se obtuvieron muestras endometriales en la fase secretoria del ciclo menstrual, antes y durante el uso del DIU, que fueron evaluadas usando el microscopio de barrido y la microscopía electrónica. Se encontró que el grado y la extensión de los cambios ultraestructurales en la superficie del endometrio estaban relacionados con el área de la superficie de cobre del DIU. Independiente de la duración de uso del DIU, leugo de un mes de haber sido quitado, la ultraestructura endometrial había regresado a su estado normal. Los resultados de este estudio muestran que los efectos de los DIU liberadores de cobre en la ultraestructura endometrial, están esencialmente limitados al tiempo que el DIU permanece en el útero.

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Resumé Les effets sur l'ultrastructure de l'endomètre des DIU libérant du cuivre ont été évalués chez 101 femmes. Des échantillons de l'endomètre ont été prélevés pendant la phase sécrétoire du cycle menstruel, avant et après l'utilisation du dispositif, pour être analysés par scintigraphie et au microscope électronique. On a constaté que le degré et l'étendue des changements à la surface de l'ultrastructure endométriale dépendaient de l'aire de cuivre que présentait le DIU. Quelle qu'ait été la durée d'utilisation du dispositif, un mois après son retrait l'ultrastructure de l'endomètre était revenue à son était normal. Les résultats de cette étude montrent que les effets des DIU au cuivre sur l'ultrastructure endométriale sont essentiellement limités au temps de séjour du dispositif dans l'utérus.

     

Integration of distributed cortical systems by reentry: a computer simulation of interactive functionally segregated visual areas

A computer model based on visual cortex has been constructed to analyze how the operations of multiple, functionally segregated cortical areas can be coordinated and integrated to yield a unified perceptual response. We propose that cortical integration arises through the process of reentry--the ongoing, parallel, recursive signaling between separate maps along ordered anatomical connections. To test the efficacy of this reentrant cortical integration (RCI) model, we have carried out detailed computer simulations of 3 interconnected cortical areas in the striate and extrastriate cortex of the macaque. The simulated networks contained a total of over 222,000 units and 8.5 million connections. The 3 modeled areas, called VOR, VOC, and VMO, incorporate major anatomical and physiological properties of cortical areas V1, V3, and V5 but are vastly simplified compared with monkey visual cortex. Simulated area VOR contains both orientation and directionally selective units; simulated area VMO discriminates the direction of motion of arbitrarily oriented objects; and simulated area VOC responds to both luminance and occlusion boundaries in the stimulus. Area VOC is able to respond to illusory contours (Kanizsa, 1979) by means of the same neural architecture used for the discrimination of occlusion boundaries. This architecture also generates responses to structure-from-motion by virtue of reentrant connections from VMO to VOC. The responses of the simulated networks to these illusions are consistent with the perceptual responses of humans and other species presented with these stimuli. The networks also respond in a consistent manner to a novel illusion that combines illusory contours and structure-from-motion. The response synthesized to this combined illusion provides a strong argument supporting the need for a recursive reentrant process in the cortex. Functional integration of the simulated areas in the RCI model were found to depend upon the combined action of 3 reentrant processes: (1) conflicting responses among segregated areas are competitively eliminated, (2) outputs of each area are used by other areas in their own operations, and (3) outputs of an area are "reentered" back to itself (through lower areas) and can thus be used iteratively to synthesize responses to complex or illusory stimuli. Transection of the reentrant connections selectively abolished these integrative processes and led to failure of figural synthesis. The proposed model of reentry suggests a basis for understanding how multiple visual areas as well as other cortical areas may be integrated within a distributed system.