Multiple oligomeric structures of a bacterial small heat shock protein

Small heat shock proteins are ubiquitous molecular chaperones that form the first line of defence against the detrimental effects of cellular stress. Under conditions of stress they undergo drastic conformational rearrangements in order to bind to misfolded substrate proteins and prevent cellular protein aggregation. Owing to the dynamic nature of small heat shock protein oligomers, elucidating the structural basis of chaperone action and oligomerization still remains a challenge. In order to understand the organization of sHSP oligomers, we have determined crystal structures of a small heat shock protein from Salmonella typhimurium in a dimeric form and two higher oligomeric forms: an 18-mer and a 24-mer. Though the core dimer structure is conserved in all the forms, structural heterogeneity arises due to variation in the terminal regions.

Characterization of rice small heat shock proteins targeted to different cellular organelles

Small heat shock proteins (sHSPs) are a family of ATP-independent molecular chaperones which prevent cellular protein aggregation by binding to misfolded proteins. sHSPs form large oligomers that undergo drastic rearrangement/dissociation in order to execute their chaperone activity in protecting substrates from stress. Substrate-binding sites on sHSPs have been predominantly mapped on their intrinsically disordered N-terminal arms. This region is highly variable in sequence and length across species, and has been implicated in both oligomer formation and in mediating chaperone activity. Here, we present our results on the functional and structural characterization of five sHSPs in rice, each differing in their subcellular localisation, viz., cytoplasm, nucleus, chloroplast, mitochondria and peroxisome. We performed activity assays and dynamic light scattering studies to highlight differences in the chaperone activity and quaternary assembly of sHSPs targeted to various organelles. By cloning constructs that differ in the length and sequence of the tag in the N-terminal region, we have probed the sensitivity of sHSP oligomer assembly and chaperone activity to the length and amino acid composition of the N-terminus. In particular, we have shown that the incorporation of an N-terminal tag has significant consequences on sHSP quaternary structure.

The prognostic significance of the biomarker p16 in oropharyngeal squamous cell carcinoma

AIMS

There is an increasing incidence of human papillomavirus (HPV)-positive oropharyngeal squamous cell cancers (OPSCC) mostly associated with favourable outcomes. p16 immunohistochemistry is a surrogate marker for HPV positivity in OPSCC. The prognostic strength of p16 over traditional prognostic factors is not fully characterised. In this study, we evaluated the clinical and demographic differences between p16-positive and -negative OPSCC and characterised its prognostic strength versus traditional prognostic factors.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded blocks and clinical information from 217 OPSCC patients, treated with radiotherapy (alone or in combination with other therapies) between 2000 and 2010 were collected retrospectively. Immunohistochemistry for p16 protein was carried out; cancer-specific survival (CSS), recurrence-free survival (RFS) and locoregional control (LRC) were calculated for both univariate and multivariate analyses.

RESULTS

Ninety-two per cent of the OPSCC originated from tonsil and tongue base sites, 61% were p16 positive. Patients with p16-positive OPSCC were younger (P < 0.0001), with lower alcohol (P = 0.0002) and tobacco (P = 0.0001) exposure. The tumours were less differentiated (P = 0.0069), had a lower T stage (P = 0.0027), higher nodal status (P = 0.014) and higher American Joint Committee on Cancer (AJCC) prognostic group (P = 0.0036). AJCC prognostic group was significant for RFS (P = 0.0096) and CSS (P = 0.018) in patients with p16-negative OPSCC, but not those with p16-positive tumours (P = 0.30 and 0.54). Other significant factors for CSS and RFS in univariate analysis were: pretreatment haemoglobin (P < 0.0001 and <0.0001), chemoradiotherapy (P = 0.005 and 0.03) and P16 status (P < 0.0001 and 0.0001). In multivariate analysis, p16 positivity was the strongest independent prognostic variable for both CSS, RFS and LRC (P < 0.0001, hazard ratio 4.15; 95% confidence interval 2.43-7.08), (P < 0.0001, hazard ratio 6.15; 95% confidence interval 3.57-10.61) and (P = 0.001, hazard ratio 3.74; confidence interval 1.76-7.95).

CONCLUSION

This study shows that p16 is the single most important prognostic variable in OPSCC, surpassing traditional prognostic factors for both CSS and RFS. Furthermore, disease stage has no prognostic significance in p16-positive patients, highlighting the need for routine p16 assessment in OPSCC.

Dependence on emergency care among young adults in the United States

BACKGROUND

Young adults have a high prevalence of many preventable diseases and frequently lack a usual source of ambulatory care, yet little is known about their use of the emergency department.

OBJECTIVE

To characterize care provided to young adults in the emergency department.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analysis of visits from young adults age 20 to 29 presenting to emergency departments (N = 17,048) and outpatient departments (N = 14,443) in the National Hospital Ambulatory Medical Care Survey and National Ambulatory Medical Care Survey.

MAIN MEASURES

Visits to the emergency department compared to ambulatory offices.

RESULTS

Emergency department care accounts for 21.6% of all health care visits from young adults, more than children/adolescents (12.6%; P < 0.001) or patients 30 years and over (8.3%; P < 0.001). Visits from young adults were considerably more likely to occur in the emergency department for both injury-related and non-injury-related reasons compared to children/adolescents (P < 0.001) or older adults (P < 0.001). Visits from black young adults were more likely than whites to occur in the emergency department (36.2% vs.19.2%; P < 0.001) rather than outpatient offices. The proportion of care delivered to black young adults in the emergency department increased between 1996 and 2006 (25.9% to 38.5%; P = 0.001 for trend). In 2006, nearly half (48.5%) of all health care provided to young black men was delivered through emergency departments. The urgency of young adult emergency visits was less than other age groups and few (4.7%) resulted in hospital admission.

CONCLUSIONS

A considerable amount of care provided to young adults is delivered through emergency departments. Trends suggest that young adults are increasingly relying on emergency departments for health care, while being seen for less urgent indications.

Microencapsulation of a hydrophilic drug into a hydrophobic matrix using a salting-out procedure. I: Development and optimization of the process using factorial design

The congealable disperse phase method for preparing sustained release microspheres involves an emulsification process using water as the external phase and molten hydrophobic wax as the disperse phase into which the drug is loaded. Attempts to entrap highly water-soluble drugs using this process have often resulted in low loading efficiency as the drugs partition into the external water phase during emulsification and are lost. A novel method employing salts and wetting agents was developed to improve the loading efficiency of the highly water-soluble drug, guaifenesin, using this method. The drug/wax ratio (D/W) and the presence of salts and wetting agents greatly influenced microsphere properties. To optimize the process for drug loading efficiency and release rate, three different D/Ws, salts and wetting agents were chosen and a full 3(3) factorial design experiment was performed. Any significant differences among the levels of the variables and their individual and joint effects on entrapment efficiency and T50 (time for 50% drug release) were determined. Entrapment efficiencies in the range 35.1-86.3% were obtained for the various factor-level combinations of the variables. Particle size was in the range 140-385 microm and T50 was 0.59-2.72 h for the microspheres obtained. The D/W and type of salt used significantly affected drug entrapment and T50, while the nature of wetting agent was not significant at p < 0.05. The microspheres prepared using 1:4 D/W showed the highest entrapment efficiency and slowest drug release.

An unusual case of laryngeal spindle cell carcinoma metastasising to the orbit and heart

We report the first case in the world literature of laryngeal spindle cell carcinoma metastasising to the orbit. A 65-year-old woman was previously treated for T3 N0 Mx laryngeal spindle cell carcinoma, with laryngectomy and post-operative radiotherapy. Five months following this treatment, she developed proptosis, diplopia and reduced right visual acuity, secondary to an enlarging mass within the right orbit. This was biopsied, and subsequent histology confirmed a diagnosis of metastatic spindle cell carcinoma. Subsequent post-mortem examination demonstrated additional pulmonary, hepatic and cardiac metastatic disease, in the absence of any other primary tumour or locoregional disease. The radiological investigation of patients with laryngeal spindle cell carcinoma is discussed and contrasted with that of laryngeal squamous cell carcinoma.

Angiogenic and astroglial responses to vascular endothelial growth factor administration in adult rat brain

The effects of exogenous vascular endothelial growth factor (VEGF) on angiogenesis, blood-brain barrier permeability and astroglial proliferation in the adult rat CNS in situ were investigated. Recombinant human VEGF(165) (25 or 50 ng/ml) was delivered for up to 1 week using either intracerebral osmotic minipumps or less traumatic subdural gelatin sponge placement. By 3 days, VEGF delivery caused significantly increased cerebral angiogenesis (25 ng/ml was most effective) in both experimental models when compared to saline controls; VEGF infusion resulted in a 100% increase in an index of vascular proliferation, and gelatin sponge delivery produced a 65% increase. The blood-brain barrier hallmark endothelial glucose transporter-1 was not present in nascent vascular sprouts. Infusion of VEGF produced extensive protein leakage that persisted after saline-induced permeability was mostly resolved, while gelatin sponge administration caused milder barrier dysfunction. Administration of the angiogenic factor had unexpected proliferative effects on astroglia in both models, resulting in an 80-85% increase in mitotically active astroglia when compared to controls. Immunohistochemical results and semi-quantitative reverse transcriptase-polymerase chain reaction indicated that the VEGF receptors flk-1 and flt-1 were up-regulated in response to the infusion trauma; flt-1 was localized to reactive astroglia, while flk-1 was expressed in vascular endothelium but predominantly in neuronal somata and processes adjacent to the delivery site. mRNA for the VEGF(121), VEGF(165) and VEGF(188) isoforms was also increased after delivery of the recombinant protein. These data show that VEGF application has substantial proliferative effects on CNS endothelium and astroglia and causes up-regulation of its own message. Flt-1 and flk-1 receptor mRNAs and proteins are up-regulated in both vascular and non-vascular cell types following infusion trauma. From these results we suggest that administered VEGF has heretofore unanticipated pleiotrophic effects in the adult CNS.

Preparation and characterization of two-phase melt systems of lidocaine

The melting point of lidocaine was significantly lowered when mixed with thymol and/or aqueous ethanol. Mixtures of lidocaine and thymol at ratios within the range of 30:70-70:30 (w:w) became homogeneous oils at 25 degrees C. In a pH 9.2 carbonate buffer containing 25% ethanol, lidocaine (5%, w:w) also liquefied at 25 degrees C. The studies led to the development of novel two-phase melt systems of lidocaine (TMS) which consisted of a highly concentrated oil phase of lidocaine and an alcoholic aqueous phase. A compositional phase diagram showed that in aqueous dispersions of lidocaine, concurrent use of thymol and ethanol depressed the melting point of lidocaine more effectively than when they were used individually. Both thymol and aqueous ethanol were necessary as melting point depressing agents to achieve the highest possible lidocaine concentration of 87% (w:w) in the oil phase of a TMS at 25 degrees C. Containing an internal oil phase and an external aqueous phase at ambient temperature, such a TMS can be readily formulated into topical O/W cream after addition of proper surfactants and thickening agents. In an anesthetic activity test using mouse tail-flick model, a 5% lidocaine cream prepared was highly effective as shown by the prolonged latency time of the mice to a heat stimulus as compared with a placebo (P<0.05).

Regulation of toxin synthesis in Clostridium difficile by an alternative RNA polymerase sigma factor

Clostridium difficile, a causative agent of antibiotic-associated diarrhea and its potentially lethal form, pseudomembranous colitis, produces two large protein toxins that are responsible for the cellular damage associated with the disease. The level of toxin production appears to be critical for determining the severity of the disease, but the mechanism by which toxin synthesis is regulated is unknown. The product of a gene, txeR, that lies just upstream of the tox gene cluster was shown to be needed for tox gene expression in vivo and to activate promoter-specific transcription of the tox genes in vitro in conjunction with RNA polymerases from C. difficile, Bacillus subtilis, or Escherichia coli. TxeR was shown to function as an alternative sigma factor for RNA polymerase. Because homologs of TxeR regulate synthesis of toxins and a bacteriocin in other Clostridium species, TxeR appears to be a prototype for a novel mode of regulation of toxin genes.

CcpC, a novel regulator of the LysR family required for glucose repression of the citB gene in Bacillus subtilis

Synergistic carbon catabolite repression of the Bacillus subtilis aconitase (citB) gene by glucose and a source of 2-ketoglutarate is dependent on DNA sequences located upstream of the gene. Mutations in a dyad symmetry element centered at position -66 and in a repeat of the downstream arm of the dyad symmetry at position -27 cause derepressed citB expression. In this work, a protein able to bind to a DNA fragment containing these elements was purified and identified. This protein, named CcpC (Catabolite control protein C), shares sequence similarity with members of the LysR family of transcriptional regulators. In addition to binding to the citB promoter, CcpC bound to the promoter of the citZ gene, which encodes the cell's major citrate synthase and is subject to carbon catabolite repression. In a ccpC null mutant, expression of both citB and citZ was derepressed in glucose-glutamine minimal medium, indicating that CcpC is a negative regulator of citB and citZ gene expression. DNase I footprinting experiments showed that CcpC binds to two sites within the citB promoter region, corresponding to the dyad symmetry and -27 elements. In the presence of citrate, a putative inducer, only the dyad symmetry element was fully protected by CcpC. When the dyad symmetry element was mutated, CcpC was no longer able to bind to either the dyad symmetry or -27 elements. Repression of citB and citZ gene expression during anaerobiosis also proved to be mediated by CcpC.

Vascular, glial and neuronal effects of vascular endothelial growth factor in mesencephalic explant cultures

Vascular endothelial growth factor is a highly conserved, heparin-binding protein which mediates a number of critical developmental processes in both vertebrates and invertebrates, including angiogenesis, vasculogenesis and hematopoiesis. We employed an organotypic rat explant model (produced from embryonic day 17 fetuses) to assess the effects of vascular endothelial growth factor on brain microvasculature in general and the ventral midbrain specifically. Immunohistochemistry using antisera to rat endothelial cell antigen and laminin demonstrated a robust, dose-dependent effect of vascular endothelial growth factor, resulting in increased vessel neogenesis, branching and lumen size by three days in vitro. This effect was blocked by addition of an anti-vascular endothelial growth factor antibody. At higher doses of vascular endothelial growth factor, the effect was attenuated, though a statistically significant increase in both astrocyte, and neuronal density was observed using antisera to glial and neuronal markers. Tyrosine hydroxylase-immunoreactive (i.e. dopaminergic) neurons, particularly, exhibited increased survival in response to vascular endothelial growth factor application. Vascular endothelial growth factor had a mitogenic effect on endothelial cells and astrocytes, but not dopaminergic neurons, as demonstrated by the addition of [3H]thymidine to the cultures 2 h after the cultures were established. Similarly, results of a radioreceptor assay indicated that specific vascular endothelial growth factor binding sites were present on blood vessels and astrocytes, and were up-regulated by exposure to vascular endothelial growth factor. We conclude that, in explants of the ventral mesencephalon, exogenously applied vascular endothelial growth factor is mitogenic for endothelial cells and astrocytes, and promotes growth/survival of neurons in general and dopaminergic neurons in particular.

Patterns of brain angiogenesis after vascular endothelial growth factor administration in vitro and in vivo

Vascular endothelial growth factor (VEGF) is a secreted endothelial cell mitogen that has been shown to induce vasculogenesis and angiogenesis in many organ systems and tumors. Considering the importance of VEGF to embryonic vascularization and survival, the effects of administered VEGF on developing or adult cerebrovasculature are unknown: can VEGF alter brain angiogenesis or mature cerebrovascular patterns? To examine these questions we exposed fetal, newborn, and adult rat cortical slice explants to graduated doses of recombinant VEGF. The effects of another known angiogenic factor, basic fibroblast growth factor (bFGF), were evaluated in a comparable manner. In addition, we infused VEGF via minipump into the adult cortex. Significant angiogenic effects were found in all VEGF experiments in a dose-responsive manner that were abolished by the addition of VEGF neutralizing antibody. Fetal and newborn explants had a highly complex network of branched vessels that immunoexpressed the flt-1 VEGF receptor, and flk-1 VEGF receptor expression was determined by reverse transcription-PCR. Adult explants had enlarged, dilated vessels that appeared to be an expansion of the existing network. All bFGF-treated explants had substantially fewer vascular profiles. VEGF infusions produced both a remarkable localized neovascularization and, unexpectedly, the expression of flt-1 on reactive astrocytes but not on endothelial cells. The preponderance of neovascularization in vitro and in vivo, however, lacked the blood-brain barrier (BBB) phenotype marker, GLUT-1, suggesting that in brain the angiogenic role of VEGF may differ from a potential BBB functional role, i.e., transport and permeability. VEGF may serve an important capacity in neovascularization or BBB alterations after brain injury.

Screening systems for detecting inhibitors of cell wall transglycosylation in Enterococcus. Cell wall transglycosylation inhibitors in Enterococcus

We devised two screening systems to detect cell wall transglycosylation inhibitors. One screen utilizes a mutant of Enterococcus faecalis strain A256 that is dependent on vancomycin or moenomycin for growth. In the absence of transglycosylation inhibitors the strain fails to grow, while in the presence of inhibitors, cells are rescued. A second screening organism E. faecalis strain MDD212 utilizes a translational fusion of the lacZ gene to the vanH promoter in a derivative of E. faecalis that contains a vancomycin resistance determinant. Induction of beta-galactosidase occurs when cells are exposed to inhibitors of transglycosylation. Our natural products drug source of fungal fermentations was tested with these screens. Several cultures that produced the same family of compounds, called the thielavins, were detected. Thielavin B inhibited the formation of peptidoglycan in an in vitro assay, suggesting that these screening systems can detect compounds that interfere with cell wall transglycosylation.

Developmental expression of calcium-binding protein-containing neurons in neocortical transplants

The present study examined the development of calcium binding protein-containing neurons in a timed series of fetal neocortical transplants. The immunoexpression of parvalbumin and calbindin, which are subpopulations of GABAergic neurons, have been widely studied in normal development and in disease and injury states. Because of their purported resistance to oxidative injury by their ability to buffer Ca++ influx, these neurons have been particularly studied following ischemia. Because it is likely that oxidative stress is associated with the grafting procedure, we sought to determine if these neurons displayed enhanced survival characteristics. Normally, parvalbumin and calbindin represent about 5-10% of cortical neurons. Within 2-4 wk after grafting the expression of both proteins increased markedly in that a relatively larger number of neurons (27% for parvalbumin) were immunopositive. This increase was transitory, however, and by 4 mo and beyond, confocal microscopic data showed a reduction of over 50% of parvalbumin (+) neurons and processes. Calbindin (+) processes showed a qualitative change in that they were smaller with less terminal branching. Electron microscopy confirmed a substantial reduction in parvalbumin synaptic contacts. Interestingly, in older grafts, remaining parvalbumin neurons were those that were strongly NSE (+) suggesting a link between normal metabolism and Ca++ buffering in grafted neurons. It is possible that in early grafts certain neuronal populations transiently upregulated calcium binding proteins as a defensive mechanism against Ca++ influx associated with oxidative stress. Over time, however, following physiological normalization within grafts, the calcium binding protein (+) neurons are diminished, possibly due to lack of appropriate afferent input to the interneuronal pool.

Molecular analysis of lytic genes of bacteriophage 80 alpha of Staphylococcus aureus

Nucleotide sequencing of a 3779-bp fragment of the Staphylococcus aureus bacteriophage 80 alpha revealed two open reading frames: ORF1, designated as lytA, which encodes a polypeptide of 481 amino acids with an apparent M(r) of 53.81 kDa; and ORF2, designated as holin, which encodes for a hydrophobic polypeptide of 145 amino acids with an apparent M(r) of 15.58 kDa and exhibits two putative transmembrane helices. Both genes showed 100% sequence homology to that of the peptidoglycan hydrolase and holin genes of the S. aureus phage phi 11 reported earlier. In addition, the downstream sequences of the lytA gene were homologous to the phage attachment site (attP) of the phage phi 11. Based on our data we propose that the lytic system of the phage 80 alpha evolved from that of phage phi 11.