Sensory Stimulation-dependent Npas4 Expression in the Olfactory Bulb during Early Postnatal Development

The development of the olfactory system is influenced by sensory inputs, and it maintains neuronal generation and plasticity throughout the lifespan. The olfactory bulb contains a higher proportion of interneurons than other brain regions, particularly during the early postnatal period of neurogenesis. Although the relationship between sensory stimulation and olfactory bulb development during the postnatal period has been well studied, the molecular mechanisms have yet to be identified. In this study, we used western blotting and immunohistochemistry to analyze the expression of the transcription factor Npas4, a neuron-specific immediate-early gene that acts as a developmental regulator in many brain regions.We found that Npas4 is highly expressed in olfactory bulb interneurons during the early postnatal stages and gradually decreases toward the late postnatal stages. Npas4 expression was observed in all olfactory bulb layers, including the rostral migratory stream, where newborn neurons are generated and migrate to the olfactory bulb. Under sensory deprivation, the olfactory bulb size and the number of olfactory bulb interneurons were reduced. Furthermore, Npas4 expression and the expression of putative Npas4 downstream molecules were decreased. Collectively, these findings indicate that Npas4 expression induced by sensory input plays a role in the formation of neural circuits with excitatory mitral/tufted cells by regulating the survival of olfactory bulb interneurons during the early stages of postnatal development.

Justicidin A Reduces β-Amyloid via Inhibiting Endocytosis of β-Amyloid Precursor Protein

β-amyloid precursor protein (APP) can be cleaved by α-, and γ-secretase at plasma membrane producing soluble ectodomain fragment (sAPPα). Alternatively, following endocytosis, APP is cleaved by β-, and γ-secretase at early endosomes generating β-amyloid (Aβ), the main culprit in Alzheimer's disease (AD). Thus, APP endocytosis is critical for Aβ production. Recently, we reported that Monsonia angustifolia, the indigenous vegetables consumed in Tanzania, improved cognitive function and decreased Aβ production. In this study, we examined the underlying mechanism of justicidin A, the active compound of M. angustifolia, on Aβ production. We found that justicidin A reduced endocytosis of APP, increasing sAPPα level, while decreasing Aβ level in HeLa cells overexpressing human APP with the Swedish mutation. The effect of justicidin A on Aβ production was blocked by endocytosis inhibitors, indicating that the decreased APP endocytosis by justicidin A is the underlying mechanism. Thus, justicidin A, the active compound of M. angustifolia, may be a novel agent for AD treatment.

Valuable mobile applications for medical practice

While the invention of computers has caused the rapid development of technology and civilization, the marriage of computers with mobile technology has continued to greatly change our daily lives in every aspect. We use smartphones to tell the time instead of watches, and we utilize mobile applications (apps) to communicate by emailing, messaging and social networking, to take, edit and share photos and videos, to navigate, to conduct commercial transactions, and to perform many other everyday routines. Similarly, in the medical field, there are apps that provide medical and drug information, medical practice guidelines, continuing medical education, and many other services. In this article, several selected mobile apps are briefly reviewed from a personal point of view on their utility in daily medical practice.

Recurrence of Left Atrial Myxoma

We present a case of recurrent left atrial myxoma which occurred 7 years and 10 months after initial operation despite resection of originaltumor and adjacent atrial septum. This is the first case report of recurrence in Korea. Among the possible causes of recurrence, regrowth from pretumorous focus seems to be the most suggesting one in this case. Histopathologic findings of recurrent myxoma showed increased cellularity with active proliferation and nuclear hyperchromasia. These findings, together with the rapidity of regrowth, suggest that recurrent myxoma may have 'wilder' behavior. Prolonged postoperative observation is important, even if ample resection was done at the initial operation including atrial septum.

Clinical Observation of Cardiac Myxoma

Cardiac myxoma is rare and has protean clinical manifestations mimicking various disease. Unless clinician has a high index of suspicion, the diagnosis can be easil missed. However diagnosis is all the more important since surgery can be dramatically successful, where as untreated myxoma invariably leads to death. Cardiac myxoma accounts for 50% of primary cardiac tumor and mainly originates in left atrium.(75%). The features of myxoma can be described under the three headings : Constitutional, obstructive, and embolic. From 1977 to 1985, the authors have experienced 30 cases of cardiac myxoma, one of which recurred. Of 29 patients, 8 were male and 21 were female. Their ages ranged from 11 to 55 years with average of 39.8 years. Constitutional manifestation was found in 25 of the 27 patients, obstructive manifestation in 27, and embolic phenomenon in 5. The diagnosis of myxoma was made on the basis of 2-D echocardiography. The sensitivity was 100%. Except 1 case who refused operation, all received surgical treatment. Immediate postoperative complication occurred in 6 patients(23%). Among them serious complication could be found only in 2 cases(7.7%). During long term follow up there was one recurrence and one patient with right ventricular myxoma has tricuspid regurgitation. In other cases, we could not found any problems.