Analysis of intracellular ice nucleation in Xenopus oocytes by differential scanning calorimetry

Intracellular ice formation (IIF) plays a central role in cell damage during cryopreservation. We are investigating the factors which trigger IIF in Xenopus oocytes, with and without aquaporin water channels. Here, we report differential scanning calorimeter studies of Xenopus control oocytes which do not express aquaporins. Stage I to VI oocytes (which increase progressively in size) were investigated with emphasis on stage I and II because they are translucent and can also be studied under the cryomicroscope. Measurements were made in 1, 1.5, and 2M ethylene glycol (EG) in frog Ringers plus SnoMax. A multistep freezing protocol was used in which the samples were cooled until extracellular ice formation (EIF) occurred, partially remelted, slowly recooled through the EIF temperature, and then rapidly (10 degrees C/min) cooled. EIF in the 1, 1.5, and 2M EG occurred at -6.4, -7.8, and -8.9 degrees C, respectively. Freezing exotherms of individual stage I-VI oocytes were readily visible. A general trend was observed in which the IIF temperature of the early stage oocytes (I-III) was well below T(EIF) while the later stages (IV-VI) froze at temperatures much closer to T(EIF). Thus, in 1.5M EG, T(IIF) was -21.1, -25, and -26.6 degrees C in stages I-III, but was -17 and -8.5 degrees C for stage IV and V-VI. Concurrently, the percentage of oocytes in which IIF was observed fell dramatically from a high of 40 to 72% in early stages (I-III) to a low of only 7% in stage V-VI because, particularly in the later stages, IIF was hidden in the EIF exotherm. We conclude that early stage oocytes are a good model system in which to investigate modulators of IIF, but that late stage oocytes are damaged during EIF and infrequently supercool.     

Fractures in late medieval skeletal populations from Serbia

Bone fractures were analyzed from skeletal remains of 861 adult individuals from six cemeteries dating to the Late Medieval period in Serbia. Results of the study were compared to other cemetery populations (635 individual skeletons) of the same date and region in an attempt to understand fracture patterns. The association of types of fractures and their prevalence with sex, age at death, cemetery site, and information deriving from historical sources are discussed. Results showed that the long bone fracture frequency was 0.7%, and the majority of the fractures were the result of direct force. This rate is similar to some studies of contemporary British skeletal samples. However, it is much lower than for some other Old World sites. Cranial vault fractures had a rate of 6.7%, and of the facial skeleton, 1.3%; the frontal bone was the most affected of bones of the cranial vault. Injuries were more common on the upper extremities (0.8%) compared to the lower (0.6%). However, the fibula was the most fractured bone (2.8%), followed by the ulna (2.4%). This pattern is similar to three of six Late Medieval urban sites in Britain. These findings suggest that this rural community was exposed to a low risk of trauma, probably related mostly to accidents sustained during farming, and rarely to interpersonal violence.     

The association of Shiga-like toxin with detergent-resistant membranes is modulated by glucosylceramide and is an essential requirement in the endoplasmic reticulum for a cytotoxic effect

Receptor-mediated internalization to the endoplasmic reticulum (ER) and subsequent retro-translocation to the cytosol are essential sequential processes required for the productive intoxication of susceptible mammalian cells by Shiga-like toxin-1 (SLTx). Recently, it has been proposed that the observed association of certain ER-directed toxins and viruses with detergent-resistant membranes (DRM) may provide a general mechanism for their retrograde transport to endoplasmic reticulum (ER). Here, we show that DRM recruitment of SLTx bound to its globotriosylceramide (Gb(3)) receptor is mediated by the availability of other glycosphingolipids. Reduction in glucosylceramide (GlcCer) levels led to complete protection against SLTx and a reduced cell surface association of bound toxin with DRM. This reduction still allowed efficient binding and transport of the toxin to the ER. However, toxin sequestration within DRM of the ER was abolished under reduced GlcCer conditions, suggesting that an association of toxin with lipid microdomains or rafts in the ER (where these are defined by detergent insolubility) is essential for a later step leading to or involving retro-translocation of SLTx across the ER membrane. In support of this, we show that a number of ER residents, proteins intimately involved in the process of ER dislocation of misfolded proteins, are present in DRM.     

Optimal pennation angle of the primary ankle plantar and dorsiflexors: variations with sex, contraction intensity, and limb

Ultrasonography was used to measure the pennation angle of the human tibialis anterior (TA), lateral gastrocnemius (LG), medial gastrocnemius (MG), and soleus (Sol). The right and left legs of 8 male and 8 female subjects were tested at rest and during maximum voluntary contraction (MVC). Joint angles were chosen to control muscle tendon lengths so that the muscles were near their optimal length within the length-tension relationship. No differences in pennation angle were detected between the right and left legs. Another consistent finding was that the pennation angle at MVC was significantly greater than at rest for all muscles tested. Optimal pennation angles for the TA, MG, and Sol were significantly greater for the men than for the women. Optimal pennation angles for the TA, LG, MG, and Sol for the male subjects were 14.3 degrees, 23.7 degrees, 34.6 degrees, and 40.1 degrees respectively, whereas values of 12.1 degrees, 16.3 degrees, 27.3 degrees, and 26.3 degrees were recorded for the female subjects. The results of this study suggest the following: (1) similar values for pennation angle can be used for the right and left TA, LG, MG, and Sol; (2) pennation angle is significantly greater at MVC than at rest for all muscles tested; and (3) sex-specific values for optimal pennation angle should be used when modeling the force-generating potential of the primary muscles responsible for ankle plantar and dorsiflexion.     

Identification of 491 proteins in the tear fluid proteome reveals a large number of proteases and protease inhibitors

Background  

The tear film is a thin layer of fluid that covers the ocular surface and is involved in lubrication and protection of the eye. Little is known about the protein composition of tear fluid but its deregulation is associated with disease states, such as diabetic dry eyes. This makes this body fluid an interesting candidate for in-depth proteomic analysis.     

Mining literature for systems biology

Currently, literature is integrated in systems biology studies in three ways. Hand-curated pathways have been sufficient for assembling models in numerous studies. Second, literature is frequently accessed in a derived form, such as the concepts represented by the Medical Subject Headings (MeSH) and Gene Ontologies (GO), or functional relationships captured in protein-protein interaction (PPI) databases; both of these are convenient, consistent reductions of more complex concepts expressed as free text in the literature. Moreover, their contents are easily integrated into computational processes required for dealing with large data sets. Last, mining text directly for specific types of information is on the rise as text analytics methods become more accurate and accessible. These uses of literature, specifically manual curation, derived concepts captured in ontologies and databases, and indirect and direct application of text mining, will be discussed as they pertain to systems biology.