Self-assembling peptide/thermoresponsive polymer composite hydrogels: effect of peptide-polymer interactions on hydrogel properties

We have investigated the effect of doping the self-assembling octapeptide FEFEFKFK (F, phenylalanine; E, glutamic acid; K, lysine) hydrogels with various amounts of thermoresponsive conjugate of FEFEFKFK and poly(N-isopropylacrylamide) (PNIPAAm) in order to create novel hydrogels. The samples were characterized using a range of techniques including microdifferential scanning calorimetry (μDSC), oscillatory rheology, transmission electron microscopy (TEM), atomic force microscopy (AFM), and small angle neutron scattering (SANS). The peptide from the conjugate was shown to be incorporated into the peptide fiber, resulting in the polymer being anchored to the peptide fiber. The conjugation of the polymer to the peptide and its anchoring to the peptide fibers did not affect its lower critical solution temperature (LCST). On the other hand, it did result in a decrease in the LCST enthalpy and a significant increase in the G' of the hydrogels, suggesting the presence of hydrogen bond interactions between the peptide and the polymer. As a result, the polymer was found to adopt a fibrillar arrangement tightly covering the peptide fiber. The polymer was still found to go through a conformational change at the LCST, suggesting that it collapses onto the peptide fiber. On the other hand, the fibrillar network was found to be mainly unaffected by the polymer LCST. These changes at the LCST were also found to be fully reversible. The nature of the interaction between the polymer and the peptide was shown to have a significant effect on the conformation adopted by the polymer around the fibers and the mechanical properties of the hydrogels.

A 3-year prospective study of the effects of adjuvant treatments on cognition in women with early stage breast cancer

The neuropsychological performance of 85 women with early stage breast cancer scheduled for chemotherapy, 43 women scheduled for endocrine therapy and/or radiotherapy and 49 healthy control subjects was assessed at baseline (T1), postchemotherapy (or 6 months) (T2) and at 18 months (T3). Repeated measures analysis found no significant interactions or main effect of group after controlling for age and intelligence. Using a calculation to examine performance at an individual level, reliable decline on multiple tasks was seen in 20% of chemotherapy patients, 26% of nonchemotherapy patients and 18% of controls at T2 (18%, 14 and 11%, respectively, at T3). Patients who had experienced a treatment-induced menopause were more likely to show reliable decline on multiple measures at T2 (OR=2.6, 95% confidence interval (CI) 0.823–8.266 P=0.086). Psychological distress, quality of life measures and self-reported cognitive failures did not impact on objective tests of cognitive function, but were significantly associated with each other. The results show that a few women experienced objective measurable change in their concentration and memory following standard adjuvant therapy, but the majority were either unaffected or even improve over time.

The transport of group 2 capsular polysaccharides across the periplasmic space in Escherichia coli. Roles for the KpsE and KpsD proteins

The cell surface expression of group 2 capsular polysaccharides involves the translocation of the polysaccharide from its site of synthesis on the inner face of the cytoplasmic membrane onto the cell surface. The transport process is independent of the repeat structure of the polysaccharide, and translocation across the periplasm requires the cytoplasmic membrane-anchored protein KpsE and the periplasmic protein KpsD. In this paper we establish the topology of the KpsE protein and demonstrate that the C terminus interacts with the periplasmic face of the cytoplasmic membrane. By chemical cross-linking we show that KpsE is likely to exist as a dimer and that dimerization is independent of the other Kps proteins or the synthesis of capsular polysaccharide. No interaction between KpsD and KpsE could be demonstrated by chemical cross-linking, although in the presence of both KpsE and Lpp, KpsD could be cross-linked to a 7-kDa protein of unknown identity. In addition, we demonstrate that KpsD is present not only within the periplasm but is also in both the cytoplasmic and outer membrane fractions and that the correct membrane association of KpsD was dependent on KpsE, Lpp, and the secreted polysaccharide molecule. Both KpsD and KpsE showed increased proteinase K sensitivity in the different mutant backgrounds, reflecting conformational changes in the KpsD and KpsE proteins as a result of the disruption of the transport process. Collectively the data suggest that the trans-periplasmic export involves KpsD acting as the link between the cytoplasmic membrane transporter and the outer membrane with KpsE acting to facilitate this transport process.

Identification that KfiA, a protein essential for the biosynthesis of the Escherichia coli K5 capsular polysaccharide, is an alpha -UDP-GlcNAc glycosyltransferase. The formation of a membrane-associated K5 biosynthetic complex requires KfiA, KfiB, and KfiC

The Escherichia coli K5 capsular polysaccharide consists of the repeat structure -4)GlcA-beta(1,4)-GlcNAc-alpha(1- and requires the KfiA, KfiB, KfiC, and KfiD proteins for its synthesis. Previously, the KfiC protein was shown to be a beta-UDP-GlcA glycosyltransferase, and KfiD was shown to be a UDP-Glc dehydrogenase. Here, we demonstrate that KfiA is an alpha-UDP-GlcNAc glycosyltransferase and that biosynthesis of the K5 polysaccharide involves the concerted action of the KfiA and KfiC proteins. By site-directed mutagenesis, we determined that the acidic motif of DDD, which is conserved between the C family of glycosyltransferases, is essential for the enzymatic activity of KfiA. In addition, by Western blot analysis, we determined that association of KfiA with the cytoplasmic membrane requires KfiC but not KfiB, whereas the interaction of KfiC with the cytoplasmic membrane was dependent on both KfiA and KfiB. Likewise, KfiB was only detectable in cytoplasmic membrane fractions when both KfiA and KfiC were present. These data suggest that the interaction between the KfiA, KfiB, and KfiC proteins is essential for the stable association of these proteins with the cytoplasmic membrane and the biosynthesis of the K5 polysaccharide.

Regulation of the Escherichia coli K5 capsule gene cluster: evidence for the roles of H-NS, BipA, and integration host factor in regulation of group 2 capsule gene clusters in pathogenic E. coli

The expression of Escherichia coli group 2 capsules (K antigens) is temperature dependent, with capsules only being expressed at temperatures above 20 degrees C. Thermoregulation is at the level of transcription, with no detectable transcription at 20 degrees C. Using the E. coli K5 capsule gene cluster as a model system, we have shown that the nucleoid-associated protein H-NS plays a dual role in regulating transcription of group 2 capsule gene clusters at 37 and 20 degrees C. At 37 degrees C H-NS is required for maximal transcription of group 2 capsule gene clusters, whereas at 20 degrees C H-NS functions to repress transcription. The BipA protein, previously identified as a tyrosine-phosphorylated GTPase and essential for virulence in enteropathogenic E. coli, was shown to play a similar role to H-NS in regulating transcription at 37 and 20 degrees C. The binding of integration host factor (IHF) to the region 1 promoter was necessary to potentiate transcription at 37 degrees C and IHF binding demonstrated by bandshift assays. The IHF binding site was 3' to the site of transcription initiation, suggesting that sequences in the 5' end of the first gene (kpsF) in region 1 may play a role in regulating transcription from this promoter at 37 degrees C. Two additional cis-acting sequences, conserved in both the region 1 and 3 promoters, were identified, suggesting a role for these sequences in the coordinate regulation of transcription from these promoters. These results indicate that a complex regulatory network involving a number of global regulators exists for the control of expression of group 2 capsules in E. coli.

Regulation of cloned cardiac L-type calcium channels by cGMP-dependent protein kinase

We have studied the effect of 8-bromo-cyclic GMP (8-Br-cGMP) on cloned cardiac L-type calcium channel currents to determine the site and mechanism of action underlying the functional effect. Rabbit cardiac alpha(1C) subunit, in the presence or absence of beta(1) subunit (rabbit skeletal muscle) or beta(2) subunit (rat cardiac/brain), was expressed in Xenopus oocytes, and two-electrode voltage-clamp recordings were made 2 or 3 days later. Application of 8-Br-cGMP caused decreases in calcium channel currents in cells expressing the alpha(1C) subunit, whether or not a beta subunit was co-expressed. No inhibition of currents by 8-Br-cGMP was observed in the presence of the protein kinase G inhibitor KT5823. Substitutions of serine residues by alanine were made at residues Ser(533) and Ser(1371) on the alpha(1C) subunit. As for wild type, the mutant S1371A exhibited inhibition of calcium channel currents by 8-Br-cGMP, whereas no effect of 8-Br-cGMP was observed for mutant S533A. Inhibition of calcium currents by 8-Br-cGMP was also observed in the additional presence of the alpha(2)delta subunit for wild type channels but not for the mutant S533A. These results indicate that cGMP causes inhibition of L-type calcium channel currents by phosphorylation of the alpha(1C) subunit at position Ser(533) via the action of protein kinase G.

Treatment of invasive thymoma with single-agent ifosfamide

PURPOSE

To evaluate single-agent ifosfamide in the treatment of invasive thymoma.

PATIENTS AND METHODS

Fifteen patients (eight male and seven female) with histologically confirmed invasive thymoma were treated. The median age was 48 years (range, 23 to 76 years). Four patients had stage III disease, seven patients had stage IVa disease, and four patients had stage IVb disease. The most common histologic type was lymphoepithelial. Seven patients had received prior treatment, including one patient who received chemotherapy. Ifosfamide 1.5 g/m(2) was given on days 1 to 5, with mesna as a uroprotector.

RESULTS

Thirteen patients were assessable for response. Five complete responses (38.5%; 95% confidence interval [CI], 17.7% to 64.5%) and one partial response (7.7%; 95% CI, 1.4% to 33.3%) were seen. The median duration of complete response was 66+ months (range, 25 to 87 months), and the estimated survival rate 5 years after ifosfamide treatment was 57% (SE, 32% to 79%). The most frequent toxicities were nausea, vomiting, and leucopenia, but these were well tolerated.

CONCLUSION

Single-agent ifosfamide possesses significant activity against invasive thymoma and is comparable to currently used combination regimens. The inclusion of ifosfamide in combination therapy, particularly in place of cyclophosphamide in regimens such as cisplatin, doxorubicin, and cyclophosphamide, needs to be evaluated.

Studies of the microvascular endothelium in uninvolved skin of patients with systemic sclerosis: direct evidence for a generalized microangiopathy

Various parameters for assessing endothelial cell (EC) metabolism, including immunohistochemistry and adenosine uptake, have been compared in the clinically uninvolved skin of patients with diffuse systemic sclerosis (DSS), CREST, incomplete CREST syndrome (ICREST), primary Raynaud's disease (1 degree RD) and normal controls. Evidence of platelet adhesion to EC, decreased EC storage of factor VII-related antigen, changes in EC morphology and decreased adenosine uptake by EC, were found in the dermal microvasculature of normal skin of patients with DSS, CREST and ICREST, but not in 1 degree RD. These data indicate that a generalized microvascular endothelial dysfunction is present in the skin of patients with the systemic forms of scleroderma.

Chemotherapy of primary (in situ) testicular tumours: response in advanced metastatic disease

Five patients in whom primary testicular tumours were left in situ during chemotherapy for extensive metastatic disease are described. In four patients, the response of the primary and secondary tumour was comparable. In the fifth a small tumour in the testis became palpable during chemotherapy at the same time as metastases, and regressed on treatment. One possible explanation for the latter observation is protection from chemotherapy of a small, possibly partly intratubular primary, by the blood-testis barrier.

Computed tomography of paranasal sinus tumors

Thirty-two patients with histologically proved malignant disease involving the paranasal sinuses were studied by CT. The radiological features of tumor were sinus opacification, a soft-tissue mass, bone erosion and/or displacement, sclerosis, and new-bone formation. Measurements of tissue densities were not helpful in distinguishing tumor from benign disease. Significantly greater tumor extent was demonstrated by CT than by conventional methods in 15 patients; the additional tumor most commonly involved the pterygoid region or orbit. The clinical importance of various directions of tumor spread is emphasized.