Understanding and targeting resistance mechanisms in cancer

Resistance to cancer therapies has been a commonly observed phenomenon in clinical practice, which is one of the major causes of treatment failure and poor patient survival. The reduced responsiveness of cancer cells is a multifaceted phenomenon that can arise from genetic, epigenetic, and microenvironmental factors. Various mechanisms have been discovered and extensively studied, including drug inactivation, reduced intracellular drug accumulation by reduced uptake or increased efflux, drug target alteration, activation of compensatory pathways for cell survival, regulation of DNA repair and cell death, tumor plasticity, and the regulation from tumor microenvironments (TMEs). To overcome cancer resistance, a variety of strategies have been proposed, which are designed to enhance the effectiveness of cancer treatment or reduce drug resistance. These include identifying biomarkers that can predict drug response and resistance, identifying new targets, developing new targeted drugs, combination therapies targeting multiple signaling pathways, and modulating the TME. The present article focuses on the different mechanisms of drug resistance in cancer and the corresponding tackling approaches with recent updates. Perspectives on polytherapy targeting multiple resistance mechanisms, novel nanoparticle delivery systems, and advanced drug design tools for overcoming resistance are also reviewed.

[Mid-term outcome of deep layer repair with the long head of the biceps autograft bridging for Kim classification type Ⅰ A delaminiated rotator cuff tear]

Objective: To investigate the mid-term clinical outcome of deep layer repair with the long head of the biceps autograft bridging for Kim classification type ⅠA delaminated rotator cuff tear. Methods: A follow-up study. The clinical data of 42 consecutive patients with Kim classification type ⅠA delaminated rotator cuff tear admitted to the First Affiliated Hospital of Jinan University from January 2018 to June 2019 were retrospectively included. All patients underwent shoulder arthroscopic surgery. During the operation, the autogenous long head of the biceps tendon was transferred to repair the deep layer of delaminated rotator cuff tear. The preoperative and postoperative (last follow-up) visual analogue scale (VAS) for pain, University of California Los Angeles (UCLA) score, Constant-Murley shoulder score, range of motion (ROM) of the shoulder and radiographic results were statistically analyzed. Results: A total of 42 patients were included in this study. There were 18 males and 24 females, with an average age of (64.5±15.2) years and a mean follow-up of (43.9±7.1) months. At the last follow-up, ROM of abduction increased from 80.8°±26.5° to 154.2°±14.3°, and ROM of external rotation increased from 18.2°±13.6° to 31.8°±7.8°; the VAS score of pain decreased from (5.5±1.3) points to (0.7±0.7) points, the UCLA score increased from (21.3±3.7) points to (29.9±2.1) points, and the Constant-Murley score increased from (45.4±10.0) points to (87.2±4.8) points; the differences were all statistically significant (all P<0.001). The X-ray films showed that there were no upward of the humeral head in all the patients. MRI results indicated that rotator cuff re-teared in one case (Sugaya classification type Ⅲ), and healed in other cases (Sugaya classification type Ⅰ-Ⅱ). No complications such as upper limb nerve injury was found in all cases. Conclusion: Deep layer repair with the long head of the biceps autograft bridging can significantly alleviate the pain and improve the function of patients with Kim classification type ⅠA delaminated rotator cuff tear, and the incidence of retear is low.

Overcoming multidrug resistance by knockout of ABCB1 gene using CRISPR/Cas9 system in SW620/Ad300 colorectal cancer cells

Multidrug resistance (MDR) has been extensively reported in colorectal cancer patients, which remains a major cause of chemotherapy failure. One of the critical mechanisms of MDR in colorectal cancer is the reduced intracellular drug level led by the upregulated expression of the ATP-binding cassette (ABC) transporters, particularly, ABCB1/P-gp. In this study, the CRISPR/Cas9 system was utilized to target ABCB1 in MDR colorectal cancer SW620/Ad300 cell line with ABCB1 overexpression. The results showed that stable knockout of ABCB1 gene by the CRISPR/Cas9 system was achieved in the MDR cancer cells. Reversal of MDR against ABCB1 chemotherapeutic drugs increased intracellular accumulation of [3H]-paclitaxel accumulation, and decreased drug efflux activity was observed in MDR SW620/Ad300 cells after ABCB1 gene knockout. Further tests using the 3D multicellular tumor spheroid model suggested that deficiency in ABCB1 restrained tumor spheroid growth and restore sensitivity to paclitaxel in MDR tumor spheroids. Overall, the CRISPR/Cas9 system targeting the ABCB1 gene can be an effective approach to overcome ABCB1-mediated MDR in colorectal cancer SW620/Ad300 cells.

MiR-22-3p regulates the proliferation and invasion of Wilms' tumor cells by targeting AKT3

OBJECTIVE

In this study, the regulatory mechanism of miR-22-3p/AKT3 in the development of Wilms' tumor (WT) was investigated.

PATIENTS AND METHODS

Twenty-seven pairs of surgical tumor specimens and adjacent normal tissues were obtained from Jining No. 1 People's Hospital. The expression level of miR-22-3p in WT tissues and cell lines was measured by quantitative RT-PCR. MTT and transwell assays were performed to analyze cell proliferation and invasion in WT. The relationship between miR-22-3p and AKT3 was verified by a Dual-Luciferase assay. The protein expression of AKT3 was evaluated by Western blotting analysis.

RESULTS

MiR-22-3p was downregulated and AKT3 was upregulated in WT. Functionally, overexpression of miR-22-3p inhibited cell proliferation and invasion in WT. Moreover, miR-22-3p directly targets AKT3. The knockdown of AKT3 suppressed cell proliferation and invasion in WT. In addition, upregulation of AKT3 restored the tumor suppressive effect of miR-22-3p in WT.

CONCLUSIONS

MiR-22-3p inhibits the proliferation and invasion of WT cells by downregulating AKT3, indicating that miR-22-3p may be developed as a new biomarker for the diagnosis of WT.

H9N2 influenza virus isolated from minks has enhanced virulence in mice

H9N2 is one of the major subtypes of influenza virus circulating in poultry in China, which has a wide host range from bird to mammals. Two H9N2 viruses were isolated from one mink farm in 2014. Phylogenetic analysis showed that internal genes of the H9N2 viruses have close relationship with those of H7N9 viruses. Interestingly, two H9N2 were separated in phylogenetic trees, indicating that they are introduced to this mink farm in two independent events. And further mice studies showed that one H9N2 caused obvious weight loss and 20% mortality in infected mice, while another virus did not cause any clinical sign in mice infected at the same dose. Genetic analysis indicated that the virulent H9N2 contain a natural mutation at 701N in PB2 protein, which was reported to contribute to mammalian adaptation. However, such substitution is absent in the H9N2 avirulent to mice. Circulation of H9N2 in mink may drive the virus to adapt mammals; continual surveillance of influenza virus in mink was warranted.

Metabolomics for in situ environmental monitoring of surface waters impacted by contaminants from both point and nonpoint sources

We investigated the efficacy of metabolomics for field-monitoring of fish exposed to wastewater treatment plant (WWTP) effluents and nonpoint sources of chemical contamination. Lab-reared male fathead minnows (Pimephales promelas, FHM) were held in mobile monitoring units and exposed on-location to surface waters upstream and downstream of the effluent point source, as well as to the actual effluent at three different WWTP sites in Minnesota. After four days of exposure, livers were collected, extracted, and analyzed by (1)H NMR spectroscopy and GC-MS to characterize responses of the hepatic metabolome. Multivariate statistical analysis revealed distinct metabolite profile changes in response to effluent exposure from each of the three WWTPs. Differences among locations (i.e., upstream, downstream, and effluent) within each of the three sites were also identified. These observed differences comport with land-use and WWTP characteristics at the study sites. For example, at one of the sites, the metabolomic analyses suggested a positive interactive response from exposure to WWTP effluent and nearby nonpoint (likely agricultural related) contamination. These findings demonstrate the utility of metabolomics as a field-based technique for monitoring the exposure of fish to impacted surface waters.

Field-based approach for assessing the impact of treated pulp and paper mill effluent on endogenous metabolites of fathead minnows (Pimephales promelas)

A field-based metabolomic study was conducted during a shutdown of a pulp and paper mill (PPM) to assess the impacts of treated PPM effluent on endogenous polar metabolites in fathead minnow (FHM; Pimephales promelas) livers. Caged male and female FHMs were deployed at a Great Lakes area of concern during multiple periods (pre-, during, and post-shutdown) near the outflow for a wastewater treatment plant. Influent to this plant is typically 40% PPM effluent by volume. Additional FHMs were exposed to reference lake water under laboratory conditions. A bioassay using T47D-KBluc cells showed that estrogenic activity of receiving water near the outflow declined by 46% during the shutdown. We then used (1)H NMR spectroscopy and principal component analysis to profile abundances of hepatic endogenous metabolites for FHMs. Profiles for males deployed pre-shutdown in receiving water were significantly different from those for laboratory-control males. Profiles were not significantly different for males deployed during the shutdown, but they were significant again for those deployed post-shutdown. Impacts of treated effluent from this PPM were sex-specific, as differences among profiles of females were largely nonsignificant. Thus, we demonstrate the potential utility of field-based metabolomics for performing biologically based exposure monitoring and evaluating remediation efforts occurring throughout the Great Lakes and other ecosystems.

Notch1 overexpression promotes cell growth and tumor angiogenesis in myeloma

Patients with multiple myeloma (MM) have increased bone marrow angiogenesis, but the angiogenic properties of myeloma cells and the mechanism of MM-induced angiogenesis have not been completely clarified. Notch1 signal has been identified as a critical factor in the regulation of vessel formation. However, the role of Notch1 in the angiogenesis of MM is unclear. We constitutively overexpressed active Notch1 in RPMI8226 cells to explore the effect of Notch1 signaling on cell growth and tumor angiogenesis in vivo and in vitro. We found that Notch1 overexpression promoted myeloma cells growth and increased drug resistance. Moreover, vascular endothelial growth factor (VEGF) expression was increased. Finally, our in vitro results were supported by the in vivo finding in human myeloma xenograft Nonobese diabetic/severe combined immunodeficient (NOD/SCID) models. Notch1 overexpression in MM cells resulted in up-regulation of VEGF expression, promotion of tumor growth, and increased microvessel density (MVD). Our study suggests that Notch1-induced angiogenesis is partly due to activation of VEGF pathway.

Metabolite profiling and a transcriptional activation assay provide direct evidence of androgen receptor antagonism by bisphenol A in fish

Widespread environmental contamination by bisphenol A (BPA) has created the need to fully define its potential toxic mechanisms of action (MOA) to properly assess human health and ecological risks from exposure. Although long recognized as an estrogen receptor (ER) agonist, some data suggest that BPA may also behave as an androgen receptor (AR) antagonist. However, direct evidence of this activity is deficient. To address this knowledge gap, we employed a metabolomic approach using in vivo exposures of fathead minnows (FHM; Pimephales promelas ) to BPA either alone or in a binary mixture with 17β-trenbolone (TB), a strong AR agonist. Changes in liver metabolite profiles in female FHM in response to these exposures were determined using high resolution (1)H NMR spectroscopy and multivariate and univariate statistics. Using this approach, we observed clear evidence of the ability of BPA to mitigate the impact of TB, consistent with an antiandrogenic MOA. In addition, a transcriptional activation assay with the FHM AR was used to confirm the AR antagonistic activity of BPA in vitro. The results of these in vivo and in vitro analyses provide strong and direct evidence for ascribing an antiandrogenic MOA to BPA in vertebrates.

Solid-state C NMR spectroscopy of a C carbonyl-labeled polypeptide

High resolution structural elucidation of macromolecular structure by solid-state nuclear magnetic resonance requires the preparation of uniformly aligned samples that are isotopically labeled. In addition, to use the chemical shift interaction as a high resolution constraint requires an in situ tensor characterization for each site of interest. For (13)C in the peptide backbone, this characterization is complicated by the presence of dipolar coupled (14)N from the peptide bond. Here the (13)C(1)-Gly(2) site in gramicidin A is studied both as a dry powder and in a fully hydrated lipid bilayer environment. Linewidths reported for the oriented samples are a factor of five narrower than those reported elsewhere, and previous misinterpretations of the linewidths are corrected. The observed frequency from oriented samples is shown to be consistent with the recently determined structure for this site in the gramicidin backbone. It is also shown that, whereas a dipolar coupling between (13)C and (14)N is apparent in dry preparations of the polypeptide, in a hydrated bilayer the dipolar coupling is absent, presumably due to a ;self-decoupling' mechanism.

Investigating compensation and recovery of fathead minnow (Pimephales promelas) exposed to 17alpha-ethynylestradiol with metabolite profiling

1H NMR spectroscopy was used to profile metabolite changes in the livers of fathead minnows (Pimephales promelas) exposed to the synthetic estrogen 17alpha-ethynylestradiol (EE2) via a continuous flow water exposure. Fish were exposed to either 10 or 100 ng EE2/L for 8 days, followed by an 8 day depuration phase. Livers were collected after days 1, 4, and 8 of the exposure, and at the end of the depuration phase. Analysis of polar extracts of the liver revealed a greater impact of EE2 on males than females, with metabolite profiles of the former assuming similarities with those of the females (i.e., feminization) early in the exposure. Biochemical effects observed in the males included changes in metabolites relating to energetics (e.g., glycogen, glucose, and lactate) and liver toxicity (creatine and bile acids). In addition, amino acids associated with vitellogenin (VTG) synthesis increased in livers of EE2-exposed males, a finding consistent with increased plasma concentrations of the lipoprotein in the fish. Using partial least-squares discriminant analysis (PLS-DA), the response trajectories of the males at both exposure concentrations were compared. This revealed an apparent ability of the fish to compensate for the presence of EE2 later in the exposure, and to partially recover from its effects after the chemical was removed.

NMR analysis of male fathead minnow urinary metabolites: a potential approach for studying impacts of chemical exposures

The potential for profiling metabolites in urine from male fathead minnows (Pimephales promelas) to assess chemical exposures was explored using nuclear magnetic resonance (NMR) spectroscopy. Both one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy was used for the assignment of metabolites in urine from unexposed fish. Because fathead minnow urine is dilute, we lyophilized these samples prior to analysis. Furthermore, 1D 1H NMR spectra of unlyophilized urine from unexposed male fathead minnow and Sprague-Dawley rat were acquired to qualitatively compare rat and fish metabolite profiles and to provide an estimate of the total urinary metabolite pool concentration difference. As a small proof-of-concept study, lyophilized urine samples from male fathead minnows exposed to three different concentrations of the antiandrogen vinclozolin were analyzed by 1D 1H NMR to assess exposure-induced changes. Through a combination of principal components analysis (PCA) and measurements of 1H NMR peak intensities, several metabolites were identified as changing with statistical significance in response to exposure. Among those changes occurring in response to exposure to the highest concentration (450 microg/L) of vinclozolin were large increases in taurine, lactate, acetate, and formate. These increases coincided with a marked decrease in hippurate, a combination potentially indicative of hepatotoxicity. The results of these investigations clearly demonstrate the potential utility of an NMR-based approach for assessing chemical exposures in male fathead minnow, using urine collected from individual fish.

Anatomically discrete functional effects of adenoviral clostridial light chain gene-based synaptic inhibition in the midbrain

The gene for the Light Chain fragment of Tetanus Toxin (LC) induces synaptic inhibition by preventing the release of synaptic vesicles. The present experiment applied this approach within the rat midbrain in order to demonstrate that LC gene expression can achieve functionally and anatomically discrete effects within a sensitive brain structure. The deep layers of the superior colliculus/deep mesencephalic nucleus (dSC/DpMe) that are located in the rostral midbrain has been implicated in fear-induced increase of the acoustic startle reflex (fear potentiated startle) but exists in close proximity to neural structures important for a variety of critical functions. The dSC/DpMe of adult rats was injected bilaterally with adenoviral vectors for LC, green fluorescent protein, or vehicle. Synaptobrevin was depleted in brain regions of adenoviral LC expression. LC gene expression in the dSC/DpMe inhibited the increase in startle amplitude seen with the control viral infection, and blocked context-dependent potentiation of startle induced by fear conditioning. Although LC gene expression reduced the absolute amount of cue-specific fear potentiated startle, it did not decrease percent potentiated startle to a cue, nor did it reduce fear-induced contextual freezing, nonspecific locomotor activity, or general health, indicating that its effects were functionally and anatomically specific. Thus, vector-driven LC expression inhibits the function of deep brain nuclei without altering the function of surrounding structures supporting its application to therapeutic neuromodulation.

Adenoviral clostridial light chain gene-based synaptic inhibition through neuronal synaptobrevin elimination

Clostridial neurotoxins have assumed increasing importance in clinical application. The toxin's light chain component (LC) inhibits synaptic transmission by digesting vesicle-docking proteins without directly altering neuronal health. To study the properties of LC gene expression in the nervous system, an adenoviral vector containing the LC of tetanus toxin (AdLC) was constructed. LC expressed in differentiated neuronal PC12 cells was shown to induce time- and concentration-dependent digestion of mouse brain synaptobrevin in vitro as compared to control transgene products. LC gene expression in the rat lumbar spinal cord disrupted hindlimb sensorimotor function in comparison to control vectors as measured by the Basso-Beattie-Bresnahan (BBB) scale (P<0.001) and rotarod assay (P<0.003). Evoked electromyography (EMG) showed increased stimulus threshold and decreased response current amplitude in LC gene-transferred rats. At the peak of functional impairment, neither neuronal TUNEL staining nor reduced motor neuron density could be detected. Spontaneous functional recovery was observed to parallel the cessation of LC gene expression. These results suggest that light chain gene delivery within the nervous system may provide a nondestructive means for focused neural inhibition to treat a variety of disorders related to excessive synaptic activity, and prove useful for the study of neural circuitry.

[A contour map segmentation for laser scanning confocal microscopic biomedical images]

We propose a contour map segmentation method for laser scanning confocal microscopic (LSCM) biomedical images. In this method, an image is first segmented into sub-regions by contour map. Then the sub-regions are merged from top to bottom or from bottom to top, according to a segmentation criterion of intensity homogeneity. The merging procedures continue until no region needs to be merged. The advantage of this method is that the objects with wide intensity ranges and different intensity homogeneity can be segmented properly. In this paper, the region segmentation by contour map is first addressed. Next a region merging according to a segmentation criterion of intensity homogeneity is presented, and then the design of a linear intensity homogeneity segmentation criterion is introduced. Two examples of image segmentation by this method are given at the end of this paper.

A new complex variant t(4;15;17) in acute promyelocytic leukemia: fluorescence in situ hybridization confirmation and literature review

We report a 37-year-old male with acute promyelocytic leukemia (APL) harboring a complex translocation (4;15;17). Karyotypic analysis with R-banding of bone marrow cells revealed 46,XY,t(4;15;17)(q21;q22;q21). Fluorescence in situ hybridization analysis using painting probes for chromosomes 4, 15 and 17 and reverse transcriptase polymerase chain reaction analysis revealed three derivative chromosomes: der(4)t(4;15)(q21;q22), der(15)t(4;15;17)(q21;q22;q21), and del(17)(q21q22). This is the third report of such a translocation and the first confirmed by molecular methods. Considering reported similar cases, it is possible that 4q21 is a nonrandom breakpoint in APL with complex translocations and the gene involved in 4q21 should be investigated.

Determination of perchlorate in tobacco plants and tobacco products

Previous field and laboratory studies with vascular plants have shown that perchlorate is transported from perchlorate fortified soils and is accumulated in the plant tissues and organs. This paper contains results of preliminary investigations on the occurrence of perchlorate in tobacco plants grown in soils amended with a fertilizer whose nitrogen content is derived from naturally occurring sodium nitrate (Chile saltpeter). Ion chromatography (IC) and capillary electrophoresis (CE) were used for quantitative analysis, while nuclear magnetic resonance (NMR) spectroscopy was used for qualitative analysis of perchlorate. Results show that perchlorate is accumulated by tobacco plants into the leaves from soils amended with fertilizers that contain perchlorate. Also, perchlorate can persist over an extended period of time and under a variety of industrial processes as shown by its presence in off-the-shelf tobacco products including cigarettes, cigars, and pouch and plug chewing tobaccos in concentrations ranging from nd to 60.4 +/- 0.8 mg/kg on a wet weight basis.

[Edge-detection and its application in medical image processing]

Edge-detection is all the time a major problem in the computer early vision, and it plays an important role in image processing. This paper reviews classical and new methods of edge-detection and discusses its application in medical image processing.

Diterpenoid alkaloids from the aerial parts of Aconitum anthora L

Isolation and identification of six diterpenoid alkaloids, from Aconitum anthora L. are described. All proton detected 2D NMR techniques have been used for unambiguous 1H and 13C chemical shift assignments of guan-fu-base-Y (6). This is the first investigation of the diterpenoid alkaloids of this plant species.

Ornithine decarboxylase activity and its gene expression are increased in benign hyperplastic prostate

BACKGROUND

Ornithine decarboxylase (ODC) is the first key enzyme in the polyamine biosynthesis pathway. Polyamine is believed to participate in cellular proliferation and differentiation. To study the relationship between ODC and the pathogenesis of benign prostatic hyperplasia (BPH), the polyamine levels, ODC activities, and expression of ODC mRNA in benign hyperplastic and normal human prostates were assayed.

METHODS

Polyamine contents and ODC activities in tissue extracts were determined by reverse-phase high-performance liquid chromatography and spectrophotometric procedures, respectively. The ODC mRNA levels were assayed by Northern blot analysis.

RESULTS

The contents of putrescine, spermidine, and spermine in BPH tissues were 2.2, 3.4, and 6.0 times higher than those in normal tissues, respectively; the ODC activity of BPH tissue was about 3.2 times higher than in normal tissue; the expression level of ODC mRNA in the BPH tissues was greater than that of normal tissues.

CONCLUSIONS

The findings imply that 1) the increased ODC activity and polyamine content in prostatic tissue may correlate with the pathogenesis of BPH, and 2) the high level of ODC activity is induced by the overexpression of ODC mRNA.

Secondary structure extensions in Pyrococcus furiosus ferredoxin destabilize the disulfide bond relative to that in other hyperthermostable ferredoxins. Global consequences for the disulfide orientational heterogeneity

The single cubane cluster ferredoxin (Fd) from the hyperthermophilic archaeon Pyrococcus furiosus (Pf) possesses several unique properties when compared even to Fds from other hyperthermophilic archaea or bacteria. These include an equilibrium molecular heterogeneity, a six- to seven-residue increase in size, an Asp rather than the Cys as one cluster ligand, and a readily reducible disulfide bond. NMR assignments and determination of both secondary structure and tertiary contacts remote from the paramagnetic oxidized cluster of Pf 3Fe Fd with an intact disulfide bond reported previously (Teng Q., Zhou, Z. H., Smith, E. T., Busse, S. C., Howard, J. B. Adams, M. W. W., and La Mar, G. (1994) Biochemistry 33, 6316-6328) are extended here to the 4Fe oxidized cluster WT (1H and 15N) and D14C (1H only) Fds with an intact disulfide bond and to the 4Fe oxidized WT Fd (1H and 15N) with a cleaved disulfide bond. All forms are shown to possess a long (13-member) alpha-helix, two beta-sheets (one double-, one triple-stranded), and three turns outside the cluster vicinity, each with tertiary contacts among themselves as found in other Fds. While the same secondary structural elements, with similar tertiary contacts, are found in other hyperthermostable Fds, Pf Fd has two elements, the long helix and the triple-stranded beta-sheet, that exhibit extensions and form multiple tertiary contacts. All Pf Fd forms with an intact disulfide bond exhibit a dynamic equilibrium heterogeneity which is shown to modulate a hydrogen-bonding network in the hydrophobic core that radiates from the Cys21-Cys48 disulfide bond and encompasses residues Lys36, Val24, Cys21, and Cys17 and the majority of the long helix. The heterogeneity is attributed to population of the alternate S and R chiralities of the disulfide bond, each destabilized by steric interactions with the extended alpha-helix. Comparison of the chemical shifts and their temperature gradients reveals that the molecular structure of the protein with the less stable R disulfide resembles that of the Fd with a cleaved disulfide bond. Both cluster architecture (3Fe vs 4Fe) and ligand mutation (Cys for Asp14) leave the disulfide orientational heterogeneity largely unperturbed. It is concluded that the six- to seven-residue extension that results in a longer helix and larger beta-sheet in Pf Fd, relative to other hyperthermostable Fds, more likely serves to destabilize the disulfide bond, and hence make it more readily reducible, than to significantly increase protein thermostability.

Ribose biosynthesis and evidence for an alternative first step in the common aromatic amino acid pathway in Methanococcus maripaludis

An acetate-requiring mutant of Methanococcus maripaludis allowed efficient labeling of riboses following growth in minimal medium supplemented with [2-(13)C]acetate. Nuclear magnetic resonance and mass spectroscopic analysis of purified cytidine and uridine demonstrated that the C-1' of the ribose was about 67% enriched for 13C. This value was inconsistent with the formation of erythrose 4-phosphate (E4P) exclusively by the carboxylation of a triose. Instead, these results suggest that either (i) E4P is formed by both the nonoxidative pentose phosphate and triose carboxylation pathways or (ii) E4P is formed exclusively by the nonoxidative pentose phosphate pathway and is not a precursor of aromatic amino acids.

Characterization of UDP amino sugars as major phosphocompounds in the hyperthermophilic archaeon Pyrococcus furiosus

The archaeon Pyrococcus furiosus is a strictly anaerobic heterotroph that grows optimally at 100 degrees C by the fermentation of carbohydrates. It is known to contain high concentrations of novel intracellular solutes such as beta-mannosylglycerate and di-myo-inositol 1,1'-phosphate (DIP) (L. O. Martins and H. Santos, Appl. Environ. Microbiol. 61:3299-3303, 1995). Here, 31P nuclear magnetic resonance (NMR) spectroscopy was used to show that this organism also accumulates another type of phospho compound, as revealed by a major multiplet signal in the pyrophosphate region. The compounds were purified from cell extracts of P. furiosus by anion-exchange and gel filtration chromatographic procedures and were structurally analyzed by 1H, 13C, and 31P NMR spectroscopy. They were identified as two uridylated amino sugars, UDP N-acetylglucosamine and UDP N-acetylgalactosamine. Unambiguous characterizations and complete assignments of 1H and 13C resonances from such sugars have not been previously reported. In vitro 31P NMR spectroscopic analyses showed that, in contrast to DIP, which is maintained at a constant intracellular concentration (approximately 32 mM) throughout the growth phase of P. furiosus, the UDP amino sugars accumulated (to approximately 14 mM) only during the late log phase. The possible biochemical roles of these compounds in P. furiosus are discussed.

2D 1H and 3D 1H-15N NMR of zinc-rubredoxins: contributions of the beta-sheet to thermostability

Based on 2D 1H-1H and 2D and 3D 1H-15N NMR spectroscopies, complete 1H NMR assignments are reported for zinc-containing Clostridium pasteurianum rubredoxin (Cp ZnRd). Complete 1H NMR assignments are also reported for a mutated Cp ZnRd, in which residues near the N-terminus, namely, Met 1, Lys 2, and Pro 15, have been changed to their counterparts, (-), Ala and Glu, respectively, in rubredoxin from the hyperthermophilic archaeon, Pyrococcus furiosus (Pf Rd). The secondary structure of both wild-type and mutated Cp ZnRds, as determined by NMR methods, is essentially the same. However, the NMR data indicate an extension of the three-stranded beta-sheet in the mutated Cp ZnRd to include the N-terminal Ala residue and Glu 15, as occurs in Pf Rd. The mutated Cp Rd also shows more intense NOE cross peaks, indicating stronger interactions between the strands of the beta-sheet and, in fact, throughout the mutated Rd. However, these stronger interactions do not lead to any significant increase in thermostability, and both the mutated and wild-type Cp Rds are much less thermostable than Pf Rd. These correlations strongly suggest that, contrary to a previous proposal [Blake PR et al., 1992, Protein Sci 1:1508-1521], the thermostabilization mechanism of Pf Rd is not dominated by a unique set of hydrogen bonds or electrostatic interactions involving the N-terminal strand of the beta-sheet. The NMR results also suggest that an overall tighter protein structure does not necessarily lead to increased thermostability.

[Study on the level of soluble interleukin-2 receptor, expression of membrane interleukin-2 receptor and T lymphocyte subpopulations in pulmonary tuberculosis]

OBJECTIVE

To evaluate the significance of soluble interleukin-2 receptor (sIL-2R), membrane interleukin-2 receptor (mIL-2R) and T lymphocyte subpopulations in development of pulmonary tuberculosis.

METHODS

The level of sIL-2R, expression of mIL-2R and the profile of T lymphocyte subpopulations in patients with pulmonary tuberculosis were tested by sandwiched ELISA and alkaline phosphatase-antialkaline phosphate (APAAP) methods.

RESULTS

The levels of sIL-2R, CD8 were higher, and expression of mIL-2R, CD4, CD4/CD8 ratio were lower in pulmonary tuberculosis than those in normal controls (P < 0.001). And the changes of all indicators in patients with cavitation were more obvious than those in patients without (P < 0.001), the changes in progressive stage were more obvious than those in stable and improving stages (P < 0.001).

CONCLUSION

The results indicated that the patients, condition and prognosis of pulmonary tuberculosis were related to the changes of sIL-2R level, mIL-2R expression and T lymphocyte subpopulations.

1H NMR investigation of the electronic and molecular structure of the four-iron cluster ferredoxin from the hyperthermophile Pyrococcus furiosus. Identification of Asp 14 as a cluster ligand in each of the four redox states

The molecular and electronic structure of the four-iron cluster of the ferredoxin (Fd) from the hyperthermophilic archaeon, Pyrococcus furiosus, Pf (which has only three Cys in the cluster binding consensus sequence), has been investigated by 1H NMR in order to determine the identity of the noncysteinyl cluster ligand in each of the four redox states [Gorst, C. M., Zhou, Z. H., Ma, K., Teng, Q., Howard, J. B., Adams, M. W., & La Mar, G. N. (1995) Biochemistry 34, 8788-8795], and to characterize the electron spin ground state for the reduced cluster which at 10 K exhibits an unusual predominant S = 3/2 ground state [Conover, R. C., Kowal, A. T., Fu, W., Park, J. -B., Aono, S., Adams, M. W. W., & Johnson, M. K. (1990) J. Biol. Chem. 265, 8533-8541]. It is demonstrated that a combination of 1D and 2D NMR tailored to relaxed resonances allows the location of four hyperfine shifted and paramagnetically relaxed spin systems which dictates that all four cluster ligands are amino acid side chains, rather than a solvent water/hydroxide at the unique non-Cys ligation site. Three of the ligands could be sequence-specifically assigned to the three Cys residues (positions 11, 17, and 56) in the consensus sequence for cluster binding, hence identifying the fourth ligand as Asp 14. It is concluded that the identification of Asp ligation to a 4Fe cluster is readily achieved in the reduced, but not in the oxidized cluster of Fd. Analysis of the relaxation properties and pattern of the hyperfine shifts in Pf Fd reveals very strong similarities to other Fds with S = 1/2 ground states, leading to the conclusion that the S = 3/2 ground state is not detected in solution at ambient temperatures, and this in independent of the redox state of the two remaining Cys residues in the protein (positions 21 and 48). However, the electron self-exchange rate for 4Fe Pf Fd is significantly slower than for other 4Fe Fd with complete Cys ligation. Changes in the pattern of hyperfine shifts between oxidized and reduced clusters for the four ligands in Pf Fd reveal that the most significant variation occurs for the Asp 14 orientation, suggesting that the altered Asp orientation may "gate" the electron transfer.

Experimental study of fat embolism syndrome

To find the diagnostic methods for subclinical stage fat embolism syndrome (FES), we established an experimental animal model, using fat intravenous injection. The fat was obtained from the long bone marrow cavity of homologous dogs. Fourteen healthy mongrel dogs received 0.7 ml/kg fluid marrow fat injection and all of them developed FES within 48 hours. The blood samples collected from the pulmonary vessels by floating catheter and peripheral vein at different time intervals were subjected to blood gas analysis and were frozen sectioned rapidly. The sections were stained with oil red 'O'. Positive result was seen 2 hours after fat injection in both pulmonary and peripheral blood. Computer image analysis showed that the number and diameter of fat droplets in pulmonary vascular blood were obviously higher and larger than those in peripheral vein blood. These findings were correlated well with blood gas changes and clinical features. The demonstration of fat droplets from pulmonary or peripheral blood by oil red 'O' staining combined with blood gas changes (PaO2 < 7.99 kPa, P(A-a)O2 > 6.09 kPa) may be rapid and specific for early diagnosis of FES. In the treatment of FES, dexamethason can stabilize the cellular membranes and inhibit the neutrophil response to fatty acid and the release of phospholipase A2, arachidonic acid and platelet aggregation.

Participation of the disulfide bridge in the redox cycle of the ferredoxin from the hyperthermophile Pyrococcus furiosus: 1H nuclear magnetic resonance time resolution of the four redox states at ambient temperature

The oxidized and reduced forms of the [4Fe-4S]-containing ferredoxin from the hyperthermophilic archaeon Pyrococcus furiosus, Pf, have been investigated by 1H nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy and thiol titrations. We have identified and isolated at Ambient temperature four distinct redox states for the [4Fe-4S] form of the ferredoxin. These states differ in the redox state of the cluster, which is coordinated by Cys 11, Asp 14, Cys 17, and Cys 56, and of a disulfide bridge between Cys 21 and Cys 48. The protein, as isolated under anaerobic conditions, designated 4Fe FdBred, contains the reduced cluster and two free thiols. The cluster, but not the thiols, is readily oxidized by brief exposure to O2 to yield 4Fe FdBOX. Prolonged O2 treatment (> 24 h at 30 degrees C) is required to generate the protein with a disulfide (4Fe FdAOX) while this fully oxidized form is readily converted by brief reduction with sodium dithionite to the protein with a reduced cluster and a disulfide (4Fe FdAred). Analyses of the magnitude and the number of hyperfine-shifted resonances in each of the four redox states are discussed.

1H NMR investigation of the paramagnetic cluster environment in Pyrococcus furiosus three-iron ferredoxin: sequence-specific assignment of ligated cysteines independent of tertiary structure

One- and two-dimensional 1H NMR data tailored to detect paramagnetically relaxed protons near the S = 1/2, three-iron-sulfur cluster of the ferredoxin from the hyperthermophile Pyrococcus furiosus are analyzed to sequence specifically assign the hyperfine shifted ligated cysteine signals, to determine the nature of the secondary structural elements on which these cysteines reside, and to define the tertiary contacts of the cluster with the remainder of the previously characterized secondary structure remote from the cluster [Teng, Q., Zhou, Z.-H., Busse, S.C., Howard, J.B., Adams, M. W. W., & La Mar, G. N. (1994) Biochemistry 33, 6316-6326]. Inspection of the geometry of the cluster ligating cysteines in the six structurally characterized cubane ferredoxin (Fd) clusters reveals a pattern of distances from the cluster iron(s) that indicate that each Cys will exhibit one backbone proton that will allow the detection of dipolar connectivities to the backbone of adjacent residues. It is expected that the first and last of the Cys in the cluster consensus binding sequence will exhibit weakly relaxed peptide NH and strongly relaxed C alpha H signals, while the two central Cys in that sequence will exhibit strongly relaxed peptide NH but weakly relaxed C alpha H peaks. These dipolar contacts are clearly observed for the three ligated Cys in 3Fe P. furiosus Fd, providing the first sequence specific assignment of ligated cysteines which do not explicitly require knowledge of the tertiary structure of the protein. This approach is proposed to have very general application to cubane ferredoxins. A combination of steady-state NOEs and short mixing time NOESY experiments demonstrate that Cys17 is on a short helix through Leu20 and that Cys56 likely initiates a type I turn, as observed in the crystal structure of the 3Fe Fd for Desulfovibrio gigas [Kissinger, C. R., Sieker, L. C., Adman, E. T., & Jensen, L. H. (1991) J. Mol. Biol. 219, 693-715]. The observed relaxation rates of resolved or partially resolved signals are shown to correlate with their proximity to the various iron in the cluster, as determined for the homologous residues in D. gigas Fd, providing additional qualitative information on tertiary contacts of the cluster.

Solution 1H NMR determination of secondary structure for the three-iron form of ferredoxin from the hyperthermophilic archaeon Pyrococcus furiosus

Two-dimensional 1H NMR data have been used to make sequence-specific assignments and define the secondary structure of the three-iron form of the oxidized ferredoxin, Fd, from the hyperthermophilic archaeon Pyrococcus furiosus, Pf. Signals for at least some protons were located for 65 of the 66 amino acids in the sequence, in spite of the paramagnetic (S = 1/2) ground state, but not all could be assigned. Unassigned and missing signals could be qualitatively correlated with the expected proximity of the protons to the paramagnetic cluster. The secondary structure was deduced from qualitative analysis of the 2D nuclear Overhauser effect, which identified two antiparallel beta-sheets, one triple-stranded including Ala1-Ser5, Val39-Glu41, and Thr62-Ala66, and one double-stranded consisting of Glu26-Asn28 and Lys32-Glu34, as well as an alpha-helix involving Glu43-Glu54. Three tight type I turns are located at residues Asp7-Thr10, Pro22-Phe25, and Asp29-Gly31. Comparison with the crystal structure of Desulfovibrio gigas, Dg, Fd (Kissinger et al., 1991) reveals a very similar folding topology, although several secondary structural elements are extended in Pf relative to Dg Fd. Thus the beta-sheet involving the two termini is expanded to include the two terminal residues and incorporates a third strand from the internal loop that is lengthened by several insertions in Pf relative to Dg Fd. The double-stranded beta-sheet in the interior of Pf Fd is lengthened slightly due to a much tighter type I turn between the two strands. The helix near the C-terminus is three residues longer in Pf than in Dg Fd, as well as being shifted toward the N-terminus. The disulfide link between the two nonligating Cys residues (Cys21 and Cys48) is conserved in Pf Fd, but the link near the C-terminus is in the middle of the long alpha-helix in Pf Fd, instead of at the N-terminus of the helix as in Dg Fd. The extensions of the beta-sheets and alpha-helix increase the number of main-chain hydrogen bonds in Pf Fd by approximately 8 relative to those in Dg Fd and likely contribute to its remarkable thermostability (it is unaffected by anaerobic incubation at 95 degrees C for 24 h).(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of high pressure on the association of melittin to membranes

To determine the underlying basis for the sensitivity of peripheral peptides to lipid packing, we monitored the change in association of melittin to different membranes under hydrostatic pressure by fluorescence polarization and by fluorescence intensity in the presence of aqueous quenchers. Association to lysophosphatidylcholine micelles or to membranes composed of dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine, or dioleoylphosphatidylcholine was found to be stable from 1 to 2000 atm. Similar results were obtained using multilamellar vesicles, small unilamellar vesicles, or large unilamellar vesicles. Thus, the increase in lipid chain packing induced by pressure does not alter the association of bound complexes. This result indicates similar compressibilities of the peptide and the head group binding region. Increasing the ionic strength to increase the charge of the free peptide also resulted in a pressure-insensitive complex showing that the hydration does not change upon binding. This conclusion is substantiated by a lack of van't Hoff delta H to dioleoylphosphatidylcholine large unilamellar vesicles. To gain a more molecular picture of these associations, the rotational properties of the tryptophan side chain of bound melittin as a function of lipid packing was also studied. These data indicate subtle differences in peptide orientation in different lipids.

Molecular dynamics computations and solid state nuclear magnetic resonance of the gramicidin cation channel

This paper reports on a coupled approach to determining the structure of the gramicidin A ion channel, utilizing solid state nuclear magnetic resonance (NMR) of isotopically labeled gramicidin channels aligned parallel to the magnetic field direction, and molecular dynamics (MD). MD computations using an idealized right-handed beta-helix as a starting point produce a refined molecular structure that is in excellent agreement with atomic resolution solid state NMR data. The data provided by NMR and MD are complementary to each other. When applied in a coordinated manner they provide a powerful approach to structure determination in molecular systems not readily amenable to x-ray diffraction.

Effect of salt and membrane fluidity on fluorophore motions of a gramicidin C derivative

We have used fluorescence spectroscopy to investigate the effect of salt and membrane fluidity on the rotational motion of a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) derivative of gramicidin C (dansyl-gC) in dimyristoylphosphatidylcholine bilayers, under conditions where the peptide is a formyl-NH to formyl-NH terminal dimer, and in octyl glucoside micelles, where the peptide is an intertwined helical dimer. Energy-transfer experiments showed no changes in either conformation or dimer aggregation under the conditions explored here (15-40 degrees C, 1-350 bar, 0-0.33 M Mg2+, and 0-1 M Na+). The addition of permeable (Na+) or nonpermeable (Mg2+) ions did not affect the temperature or pressure behavior of dansyl rotation. However, fluorescence lifetime measurements indicated an increase in solvent accessibility in the presence of sodium. In bilayers, the temperature dependence of the fluorescence polarization and lifetime shows strong interactions between the dansyl residue and the peptide, and at no time did the dansyl motions become solvent controlled as has been observed for aqueous solvent peptides [Scarlata, S. F., Rholam, M., & Weber, G. (1984) Biochemistry 23, 6789]. In micelles, the change in rotational motion with temperature followed solvent expansion, showing that in this case the dansyl residue does not associate extensively with the peptide. Our results indicate that because of the extensive coupling between the dansyl residue and the rest of the peptide, membrane fluidity does not play a major role in controlling side-chain motions.

Experimental determination of torsion angles in the polypeptide backbone of the gramicidin A channel by solid state nuclear magnetic resonance

An analytical method for the determination of torsion angles from solid state 15N nuclear magnetic resonance (n.m.r.) spectroscopic data is demonstrated. Advantage is taken of the 15N-1H and 15N-13C dipolar interactions as well as the 15N chemical shift interaction in oriented samples. The membrane-bound channel conformation of gramicidin A has eluded an atomic resolution structure determination by more traditional approaches. Here, the torsion angles for the Ala3 site are determined by obtaining the n.m.r. data for both the Gly2-Ala3 and Ala3-Leu4 peptide linkages. Complete utilization of the orientational constraints derived from these orientation-dependent nuclear spin interactions in restricting the conformational space is most effectively achieved by utilizing spherical trigonometry. Two possible sets of torsion angles for the Ala3 site are obtained (phi, psi = -129 degrees, 153 degrees and -129 degrees, 122 degrees), both of which are consistent with a right-handed beta-helix. Other functional and computational evidence strongly supports the set for which the carbonyl oxygen atom of the Ala3-Leu4 linkage is rotated into the channel lumen.

Solid-state nuclear magnetic resonance derived model for dynamics in the polypeptide backbone of the gramicidin A channel

The dynamics of the backbone of the gramicidin A transmembrane cation channel in dimyristoylphosphatidylcholine bilayers have been investigated using solid state 15N nuclear magnetic resonance (n.m.r.) spectroscopy. With the temperature-dependent fluidity of the bilayer, the rates of motions in the helical gramicidin channel can be modulated. It is shown that in the gel phase, all substantial motions of the channel are slow on the timescale of the n.m.r. experiment (3.5 kHz). The use of oriented samples in which the axis of global channel rotation is aligned parallel to the magnetic field enables separation of global and local dynamics. Spectra obtained from oriented bilayer samples containing single-site 15N-labeled gramicidin at 8 degrees C are analyzed to yield a spatial model for local backbone motion. This model includes the axis of motion, the mean orientation, and the maximum amplitude of displacement for individual peptide planes. Specific sites in the first turn of the amino terminus were investigated, with emphasis on the Ala3 and Leu4 linkages, for which the orientation of the 15N chemical shift tensor with respect to the molecular frame has been determined. The effect of two well-characterized bilayer defect structures, parabolic focal conics and oily streaks, is included in the spectral simulations. It is found that only relatively small amplitude motions are possible at the two sites, with amplitudes of not more than +/- 8 degrees and +/- 15 degrees for the Ala3 and Leu4 sites, respectively. Detailed characterization of the bilayer surface geometry in the oriented samples is presently the major limiting factor in the use of this technique for probing the spatial extent of local motions in integral membrane proteins.