Solution structure of the N‐terminal domain of DC‐UbP/UBTD2 and its interaction with ubiquitin

DC‐UbP/UBTD2 is a ubiquitin (Ub) domain‐containing protein first identified from dendritic cells, and is implicated in ubiquitination pathway. The solution structure and backbone dynamics of the C‐terminal Ub‐like (UbL) domain were elucidated in our previous work. To further understand the biological function of DC‐UbP, we then solved the solution structure of the N‐terminal domain of DC‐UbP (DC‐UbP_N) and studied its Ub binding properties by NMR techniques. The results show that DC‐UbP_N holds a novel structural fold and acts as a Ub‐binding domain (UBD) but with low affinity. This implies that the DC‐UbP protein, composing of a combination of both UbL and UBD domains, might play an important role in regulating protein ubiquitination and delivery of ubiquitinated substrates in eukaryotic cells.     

Snapshot prediction of carbon productivity,carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region''s phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a ‘snapshot'' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.     

Adaptation of human left ventricular volumes to the onset of supine exercise

The purpose of this study was to measure the changes and rates of adaptation of left ventricular volumes at the onset of exercise. Eight asymptomatic subjects, in whom intramyocardial markers had been implanted 3-6 years previously during aortocoronary bypass surgery, exercised in the supine position at a constant workload of 73.6 W for 5 min. Six also exercised first at 16.4 W, and then against a workload which progressively increased by 8.2 W every 15 s. Cardiac volumes were measured by computer assisted analysis of the motion of the implanted markers. In the constant workload test, cardiac output increased rapidly from 5.7 +/- 1 min-1 to 10.3 +/- 1.9 1 min-1 by 2 min and then increased more slowly to 10.8 +/- 2.0 1 min-1 by 5 min. The cardiac output increase was mainly due to an increase in heart rate from 68 +/- 12 beats min-1 to 120 +/- 16 beats min-1 with minimal changes in stroke volume. The time constant for the early increase in cardiac output was 45s and for heart rate, 35s. With progressively increasing workloads, there was an almost linear increase of heart rate and cardiac output, but these increased at a slower rate than during the early phase of the constant load exercise test. In conclusion: rapid changes in cardiac output during supine exercise were produced by changes in heart rate; changes in stroke volume provided minor adjustments to cardiac output; the end-diastolic volume was almost constant.     

Reducing HIV Risk among Transgender Women in Thailand: A Quasi-Experimental Evaluation of the Sisters Program

Transgender women are particularly at risk of HIV infection, but little evidence exists on effective HIV prevention strategies with this population. We evaluated whether Sisters, a peer-led program for transgender women, could reduce HIV risks in Pattaya, Thailand. The study used time-location sampling to recruit 308 transgender women in Pattaya into a behavioral survey in 2011. Coarsened exact matching was used to create statistically equivalent groups of program participants and non-participants, based on factors influencing likelihood of program participation. Using multivariable logistic regression, we estimated effects of any program participation and participation by delivery channel on: condom use at last sex; consistent condom and condom/water-based lubricant use in the past 3 months with commercial, casual, and regular partners; and receipt of HIV testing in the past 6 months. Program coverage reached 75% of the population. In a matched sub-sample (n = 238), participation in outreach was associated with consistent condom/water-based lubricant use with commercial partners (AOR 3.22, 95% CI 1.64–6.31). Attendance at the Sisters drop-in center was associated with receiving an HIV test (AOR 2.58, 95% CI 1.47–4.52). Dedicated transgender-friendly programs are effective at reducing HIV risks and require expansion to better serve this key population and improve HIV prevention strategies.     

Effect of the uvs-2 allele of Neurospora crassa on the mutagenic potency of two N-hydroxylaminopurines and 2-aminopurine in the ad-3 forward-mutation test

The mutagenic potencies of 3 purine analogs were determined in the ad-3 forward-mutation test in growing cultures of heterokaryon 59 (H-59), a nucleotide excision repair-deficient (uvs-2/uvs-2) 2-component heterokaryon of Neurospora crassa. Two N-hydroxylaminopurines, 2-amino-6-N-hydroxylaminopurine (AHA) and 6-N-hydroxylaminopurine (HAP), were potent and strong mutagens, respectively, whereas 2-aminopurine (AP) was a moderate mutagen. Dose-response curves showed that AHA and HAP were about equally mutagenic at low doses but that AHA was more mutagenic than HAP at high doses. Comparison of these results in H-59 with our earlier results in heterokaryon 12 (H-12) of N. crassa, which is identical to H-59 except for being DNA-repair-proficient (uvs-2+/uvs-2+), shows that the defect in nucleotide excision repair due to uvs-2 has little or no effect on the mutagenic potencies of these 3 purine analogs. Therefore, the nucleotide excision-repair pathway in N. crassa that is deficient in H-59 does not appear to have a major role in the repair of pre-mutational lesions induced by these 3 purine analogs. On the other hand, based on the controls of these experiments, the frequency of spontaneous ad-3 mutants was 4 greater in H-59 than in H-12. This result suggests that the nucleotide excision-repair pathway in N. crassa that is inactivated by the uvs-2 mutation has a major role in the repair of lesions that would lead to spontaneous mutation at the ad-3+ region if they were not repaired.     

An in-vivo measurement and analysis of viscoelastic properties of the spinal cord of cats

An in-vivo experimental technique was employed to determine the linear and nonlinear characteristics of viscoelastic properties of the spinal cord of anesthetized cats. The stress relaxation and recovery curves were reproducible in a group of cat experiments. The data of linear viscoelastic properties were used to develop a power law model with Boltzmann's convolution integral. The model was capable of predicting a prolonged stress relaxation and recovery curve. For larger deformation, the results were quantified using a nonlinear analysis of viscoelastic response of the spinal cord under the uniaxial experiment.     

Effect of the homokaryotic state of the uvs-2 allele in Neurospora crassa on formaldehyde-induced killing and ad-3 mutation

Formaldehyde was tested for its killing and mutagenic activities in the ad-3 forward-mutation test in Neurospora crassa. The test was conducted in 3 two-component heterokaryons (dikaryons) of N. crassa in order to determine the effect of the uvs-2 allele, which causes a defect in nucleotide excision repair, on formaldehyde-induced killing and the induction of ad-3 mutants. These dikaryons were homokaryotic for uvs-2+ (H-12), homokaryotic for usv-2 (H-59), and heterokaryotic for uvs-2 (H-71). Formaldehyde induced killing and ad-3 mutants in H-12, but the presence of uvs-2 in the homokaryotic state (H-59) resulted in a 9-fold increase in killing and a 40-fold increase in the induction of ad-3 mutants. This increased sensitivity to formaldehyde-induced killing and mutation conferred by uvs-2 in the homokaryotic state (H-59 vs. H-12) is similar to that noted by others in Escherichia coli. Salmonella typhimurium and Saccharomyces cerevisiae. The dikaryon heterokaryotic for uvs-2 (H-71) has the same sensitivity to formaldehyde-induced ad-3 mutation as H-12, indicating that uvs-2 is recessive to uvs-2+.     

Structure-function analysis with tissue-type plasminogen activator. Effect of deletion of NH2-terminal domains on its biochemical and biological properties

Tissue-type plasminogen activator (t-PA) is a mosaic protein containing several distinct structural domains attached to the serine protease catalytic unit present at its COOH terminus. To investigate structure-function relationships in t-PA, we deleted the NH2-terminal domains, finger and epidermal growth factor, by genetic engineering. The genes for the parent and mutant t-PA were expressed in a bovine papilloma virus-dependent mammalian cell system. The secreted proteins were purified to homogeneity. The mutant protein was processed to the expected size of about 60 kDa compared to approximately 68 kDa for the parent t-PA, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fibrin autography. While the mutant t-PA had amidolytic activity comparable to native t-PA, it did not bind appreciably to fibrin. Consequently, fibrin-dependent enzymic activity, i.e. plasminogen activation in the presence of soluble fibrin and fibrinolysis were lower than with native recombinant t-PA. The effect of deletion of NH2-terminal domains on the plasma half-life (t1/2) was investigated by injecting native and mutant t-PA into mice. While the majority of the t-PA disappeared initially with a t1/2 of about 2 min, mutant t-PA cleared at a much slower rate with t1/2 of about 50 min. These findings suggest that the NH2-terminal domains of t-PA not only determine its specificity for binding to fibrin but also mediate its clearance from plasma in vivo. Furthermore, the catalytic unit in t-PA seems to function autonomously.