Axons within the brain branch principally by the formation of collaterals rather than by bifurcation of the terminal growth cone (O'Leary and Terashima, 1988). This same behavior is recapitulated in cultures of embryonic hippocampal neurons (Dotti et al., 1988), rendering them ideal for studies on the cell biological mechanisms underlying collateral branch formation. In the present study, we focused on changes in the microtubule (MT) array that occur as these axons branch. In particular, we explored the mechanism by which MT number is locally increased to accommodate the need for more MTs during collateral branch formation. Serial reconstruction analyses indicate that MT number increases by severalfold and that MT length decreases correspondingly within the parent axon in the discrete region giving rise to the branch. These observations strongly suggest that MTs within the parent axon undergo a local fragmentation in this region, and hence raise the possibility that a portion of these new MTs might be destined for transport into the branch. To address this latter issue, we used quantitative immunofluorescence to compare the proportion of newly assembled to total MT polymer in different regions of the axon. As previously reported (Brown et al., 1992), the region of the axon contiguous with the terminal growth cone is particularly rich in newly assembled polymer. In contrast, there was no distinguishable difference in the proportion of newly assembled polymer in the newly formed collateral branches compared to the shaft region of the parent axon. These results indicate that the MTs within the newly formed collateral branches are on average assembled at the same time as those within the parent axon, and thus strongly suggest that the MTs in the collateral branch were assembled in the parent axon and then translocated into the branch. We conclude on the basis of these observations that collateral branch formation requires a local fragmentation of MTs within the parent axon, followed by the partitioning of a portion of the MT fragments into the branch. These short MTs presumably then resume their movement and elongation down the collateral branch as well as down the parent axon for the steady and orderly increase of both MT arrays.

We have used an indirect method to compare the dynamic properties of microtubules (MTs) in the main shaft and distal regions of the axon. Individual MTs are staggered along the length of the axon and consist of a labile domain situated at the plus end of a stable domain (Baas and Black, 1990). As a result of this organization and the plus-end-distal orientation of axonal MTs, the most distal region of the axon consists entirely of labile domains, while the main shaft consists of a mixture of labile and stable domains. In this study, we wished to determine whether the labile domains extending into the distal axon differ in their dynamic properties from the labile domains terminating in the main shaft. To address this issue, we used immunoelectron microscopy to compare the tyrosination state of the labile domains terminating in these 2 axon regions. Because detyrosination is a polymerspecific modification of alpha-tubulin that accumulates with time, the levels of tyrosinated alpha-tubulin will be a reflection of the age, and hence dynamic properties, of the polymer. To maximize our chances of visualizing potential differences, we varied the concentration of the primary antibody in these experiments. Our studies indicate that the stable domains are generally deficient in tyrosinated alpha-tubulin, while the labile domains contain clearly detectable levels. Within the labile domain, the subsection closer to the plus end of the MT contains relatively higher levels of tyrosinated alpha-tubulin than does the subsection farther from the plus end, suggesting that the levels of tyrosinated alpha-tubulin in the labile domain may gradually increase as one moves away from the stable domain toward the plus end of the MT. Although these observations apply to the labile domains in both regions of the axon, the labile domains extending into the distal region contain comparatively higher levels of tyrosinated alpha-tubulin than do the labile domains terminating in the main shaft. These results are consistent with the view that highly dynamic MT polymer is present throughout the axon, but that the polymer nearest the advancing growth cone is particularly dynamic.

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Background: Corona virus infection is a respiratory infection, compromising the normal breathing in critical patients by damaging the lungs. Researches are ongoing to find an efficient treatment strategy for this disease by either inactivating the virus or boosting the immune system of patient or by managing the cytokine storm. Aim: To evaluate the clinical outcomes of Substance P receptor Neurokinin 1 antagonist in Covid 19 patients against the usual treatments as controls. Patients and Methods: It is a randomized clinical trial, open label, having two arms, one receiving normal management and care while other receiving Neurokinin 1 Receptor antagonist, Aprepitant, in addition. Dexamethasone, a corticosteroid is also administered orally to both the groups. PCR positive, hospitalized patients with more than 18 years of age, both genders, moderate to critical phase were included. 18 patients were randomly allocated in both arms, having 10 in group A and 8 in group B. Lab investigations were performed in both the groups before and after the intervention. We report preliminary results for the comparison of Aprepitant 80 mg given once daily for 3 to 5 days vs routine management. The primary outcome was total in hospital days and duration of disease. Results: Mean age of patients in group A was 47.63 +12.07years while 60.90+ 9.75 years in group B. There were 3 males in group A and 8 in group B. There were 2 critical patients in group A and 5 in group B. Biochemical and hematological parameters in both groups didnot show much difference except the C reactive protein reduction in the intervention group, indicative of a reduced inflammation. Oxygen saturation also improved but more patients should be enrolled to get a statistically significant data. One patient was discharged from each group within 5 days and one patient expired in each. Conclusions: It is a pilot study but the findings give a strong clue for the therapeutic potential of Aprepitant. Patients who received a combination therapy of Aprepitant and Dexamethasone were recovered earlier and showed improved clinical outcomes, laboratory findings and reduced C reactive protein which is an inflammatory marker. We suggest here a study on larger sample size to get a deeper insight of its potential and efficacy. It may be more effective in severe to critical patients having respiratory difficulties.

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