3-D Ultrastructure of O. tauri: Electron Cryotomography of an Entire Eukaryotic Cell

The hallmark of eukaryotic cells is their segregation of key biological functions into discrete, membrane-bound organelles. Creating accurate models of their ultrastructural complexity has been difficult in part because of the limited resolution of light microscopy and the artifact-prone nature of conventional electron microscopy. Here we explored the potential of the emerging technology electron cryotomography to produce three-dimensional images of an entire eukaryotic cell in a near-native state. Ostreococcus tauri was chosen as the specimen because as a unicellular picoplankton with just one copy of each organelle, it is the smallest known eukaryote and was therefore likely to yield the highest resolution images. Whole cells were imaged at various stages of the cell cycle, yielding 3-D reconstructions of complete chloroplasts, mitochondria, endoplasmic reticula, Golgi bodies, peroxisomes, microtubules, and putative ribosome distributions in-situ. Surprisingly, the nucleus was seen to open long before mitosis, and while one microtubule (or two in some predivisional cells) was consistently present, no mitotic spindle was ever observed, prompting speculation that a single microtubule might be sufficient to segregate multiple chromosomes

Cerebrospinal fluid leakage as complication of treatment with cabergoline for macroprolactinomas.

Item does not contain fulltextTreatment of patients with prolactinomas consists primarily of dopamine agonists (DA). Cerebrospinal fluid (CSF) leakage has sporadically been reported in patients with macroprolactinomas treated with short-acting DA such as bromocriptine. Little is known on the incidence of this complication in patients treated with the long-acting D2 specific DA cabergoline. We report three patients with CSF leakage shortly after initiation of cabergoline treatment for macroprolactinoma. All three patients responded rapidly to cabergoline (CAB) by shrinkage of the tumor and release of the optic chiasm compression. The CSF leakage occurred within 10 days after initiation of treatment. CAB treatment was not discontinued. In one patient the CSF leakage ceased spontaneously, with no additional therapy. The second patient had a surgical repair of the CSF fistula, permitting cabergoline to be continued without a recurrence of the CSF leakage. The third patient refused surgical repair of the sellar defect. In this patient the cabergoline dosage was temporarily decreased with no effect on the CSF leakage. Four years later, the CSF leakage is unchanged in this patient, whilst no other complications occurred during the follow-up. No infectious complications occurred in these three patients. In conclusion, patients with large, invasive macroprolactinomas are at risk of CSF leakage during medical treatment with CAB. It is advisable to warn these patients for occurrence of this complication and to monitor them closely especially during the first months of treatment

Hearing loss and brain plasticity: the hyperactivity phenomenon

Many aging adults experience some form of hearing problems that may arise from auditory peripheral damage. However, it has been increasingly acknowledged that hearing loss is not only a dysfunction of the auditory periphery but also results from changes within the entire auditory system, from periphery to cortex. Damage to the auditory periphery is associated with an increase in neural activity at various stages throughout the auditory pathway. Here, we review neurophysiological evidence of hyperactivity, auditory perceptual difficulties that may result from hyperactivity, and outline open conceptual and methodological questions related to the study of hyperactivity. We suggest that hyperactivity alters all aspects of hearing—including spectral, temporal, spatial hearing—and, in turn, impairs speech comprehension when background sound is present. By focusing on the perceptual consequences of hyperactivity and the potential challenges of investigating hyperactivity in humans, we hope to bring animal and human electrophysiologists closer together to better understand hearing problems in older adulthood