Nuclear mechanics during constricted migration

Cell migration through narrow interstitial space in tissues is commonly seen in both physiological and pathological conditions. For example, immune cells have to squeeze through vasculature and extracellular matrix to reach the wound or diseased sites, and similarly cancer cells need to crawl through porous space in tissues to invade surrounding tumor-free regions. Therefore, the bulky stiff nucleus in the cell becomes a barrier during constricted migration making such process pore-size dependent with smaller pores exponentially alleviate the passage capability. However, in some cases, cells can actively deform their nuclei to squeeze through constrictions although some price needs to be paid. In this review, we focus on:(1) nuclear structures and morphological regulations,(2) proposed mechanisms that drive constricted migration,(3) short-term consequences such as nuclear envelope (NE) rupture and DNA damage during such process,(4) biophysical factors that facilitate NE rupture, and (5) long term consequences such as genomic variation caused by repetitive NE rupture. Both experimental results and modeling are provided with the intention to better understand the constricted migration.

Study of Effects of Low Doses UV Radiation on Microporous Polysulfone Membranes in Sterilization Process

Synthetic membranes have gained an important place in chemical technology and are used in a broad range of applications. UV irradiation is an age old process used for disinfection as well as for sterilization purposes. It is used for sterilizing equipment in which polysulfone (PSf) membranes are used. As a result, short time UV irradiation of polymer membranes has acquired importance in recent times. In the present study, microporous polysulfone membranes with0.108 mmthickness have been prepared using phase inversion method. Effect of UV irradiation on the membranes for short time intervals (0 - 60 minutes) has been investigated using UV-Vis and FTIR spectrophotometer, and SEM. The performance of the membranes has studied by filtration techniques. UV-Vis and IR spectra analysis and SEM images obtained suggest that chains scission and crosslink have occurred simultaneously in the irradiated membranes by UV radiation in a dose dependant manner. The pure water flux (PWF) values of irradiated membranes obtained from filtration studies were higher compared to that of the control membrane. These results show that a very short UV irradiation (2 minutes) affected the physicochemical characteristics of microporous polysulfone membrane which it increases with increase in time.

Protective Effect of <i>Lepedium sativum</i>against 2, 4-Dichlorophenoxyacetic Acid Hepatotoxicity: An Electron Microscopic Study

Medicinal plants have been used to treat many diseases with fewer side effects compared to clinical medicines. The need for treatment by medicinal plants has been increasing in response to the accumulation of environmental pollutants. The herbicide 2, 4-Dichlorophenoxyacetic acid has been considered as fast spreadable environmental pollutant, which may cause many disorders in animals and possibly in humans. The aim of this study is to assess the protective and/or curative effect of Lepidium sativum against hepatotoxicity induced by 2, 4-D herbicide in rats. 25 Albino Wistar rats were grouped into 4 groups: a control group, the curative group treated for 4 weeks with LS water extract after a single dose 2, 4-D LD50 administration, protective group which was treated for 4 weeks with LS water extract prior to the 2, 4-D LD50 administration, and LS only group that was given the LS water extract as a positive control. Using transmission electron microscope, the histological features showed that curative group hepatocytes still suffered from focal necrosis and vacuolation of hepatocytes as a result of 2, 4-D toxic effect whereas in the protective group hepatocytes were less accentuated expressed as less frequent necrotic area, and still large mitochondria were present with numerous undissolved lipid droplets and a small amount of rough endoplasmic reticulum. For the LS only group, nearly normal cells with centric nucleus, normal small mitochondria were at a normal nucleus-cytoplasmic ratio, but a few lipid droplets were noticed. This study proved that curative group has an advantage over the protective group that could be presented in the nucleus with narrow nuclear pores and intact nuclear envelope with dense small mitochondria and normal rough endoplasmic reticulum that were recorded as in the control group. Thus, Lepidium sativum administration to the rats prior or post to intoxication was effective in minimizing the 2, 4-D-induced damages likely through a free radical scavenging activity in liver tissue.

Human neuronal tau promoting the melting temperature of DNA

The hyperchromic effect of ultraviolet spectroscopy shows that adding recombinant human neuronal tau to the solution of calf thymus DNA will promote the melting temperature (Tm) from 67℃ to 81 ℃. Similar result has been detected when adding tau to plasmid pBluescript-Ⅱ SK, by raising Tm from 75℃ to 85℃. The kinetics of thermal denaturation of DNA with tau is much slower than that of control. It suggests that tau may stabilize the double helix conformation of DNA.

Self-organization model on receptive field of neuron with asymmetric time window of synaptic modification

The spatial-temporal response properties of some simple neurons in visual pathway arise basically prior to birth. In the absence of visual experience, how do these neurons develop in visual system? Based on Wimbauer network with delay, a four-layer feed-forward network model is proposed, which is characterized by modifying the Hebb learning rule through introducing the asymmetric time window of synaptic modification found recently in neurobiology. The model can not only generate by self-organization more diversified spatial-temporal response characteristics of neu-ronal receptive field than earlier models but also provide some explanations for the possible mechanism underlying the development of receptive fields of contrast polarity sensitive neurons found in visual system of vertebrate. Thus the proposed model may be more widely applicable than Linsker model and Wimbauer model.

Neurotransmitter and receptor in pigeon retinotectal transmission

THE retina in birds projects to the contralateral tectum. Our previous study and some otherphysiological, histochetnical and neurochemical evidence have suggested that the retino-tectal projection in birds might use glutamate as an excitatory transmitter. However, very lit-tle is known about its particular receptor type(s), because there are at least three major phar-macologically defined types of glutamate receptors: NMDA, AMPA/Kainate, andmetabotropic glutamate receptors.

Sensitivity of LS neurons to optic flow stimuli

LS (lateral suprasylvian area) is an important area in the extrastriate visual cortex of the cat.The receptive fields of cells in LS are much larger than those of primary visual cortex. MostLS neurons can give strong responses to moving stimuli and about 80% of the cells are sensi-tive to the direction of motion. LS is mainly involved in the analysis of moving informationand is thought to be analogous in function to the middle temporal area (MT) of macaque mon-