Endothelial and vascular smooth muscle cell function on poly(lactic-co-glycolic acid) with nano-structured surface features

Biomaterials that successfully integrate into surrounding tissue should match not only the tissue's mechanical properties, but also its topography. The cellular response to a biomaterial may be enhanced in synthetic polymer formulations by mimicking the surface roughness created by the associated nano-structured extra-cellular matrix components of natural tissue. As a first step towards this endeavor, the goal of the present in vitro study was to use these design parameters to develop a synthetic, nano-structured, polymeric biomaterial that promotes cell adhesion and growth for vascular applications. In a novel manner, poly(lactic-co-glycolic acid) (PLGA) (50/50wt% mix) was synthesized to possess a range (from micron to nanometer) of surface features. Reduction of surface features was accomplished by treating conventional PLGA with various concentrations of NaOH for select periods of time. Results from cell experiments indicated that, compared to conventional PLGA, NaOH treated PLGA enhanced vascular smooth muscle cell adhesion and proliferation. However, PLGA prepared by soaking in NaOH decreased endothelial cell adhesion and proliferation compared to conventional PLGA. After further investigation, this finding was determined to be a result of chemical (and not topographical) changes during polymer synthesis. Surface chemistry effects were removed while retaining nano-structured topography by using polymer/elastomer casting methods. Results demonstrated that endothelial and smooth muscle cell densities increased on nano-structured cast PLGA. For these reasons, the present in vitro study provided the first evidence that nano-structured surface features can significantly improve vascular cell densities; such design criteria can be used in the synthesis of the next-generation of more successful tissue-engineered vascular grafts.     

Nano-structured polymers enhance bladder smooth muscle cell function

It is the hypothesis of the present study that a biocompatible material which mimics the nanometer topography of native bladder tissue will enhance cellular responses and lead to better tissue integration in vivo. Previous in vitro studies have verified the ability to successfully reduce the surface feature dimensions of poly(lactic-co-glycolic acid) (PLGA) and poly(ether urethane) (PU) films into the nanometer regime via chemical etching procedures. Results from these studies also provided the first evidence that bladder smooth muscle cell adhesion was enhanced on chemically treated nano-structured polymeric surfaces compared to their conventional counterparts. Although cell adhesion is necessary for a biomaterial's success, subsequent cell functions (such as long-term cell growth and proliferation) are also critical for tissue ingrowth and long-term implant survival. The present in vitro study, therefore, investigated the function of bladder smooth muscle cells on these novel, nano-structured polymers over the expanded periods of 1, 3 and 5 days. Results indicated that cell number was influenced by both surface roughness and surface chemistry changes; the important contributor, however, was increased nanometer surface roughness. This claim is supported by the fact that cell number was enhanced on nano-structured compared to conventional PLGA and PU once chemistry changes were eliminated using casting techniques.     

Tirapazamine plus carboplatin and paclitaxel in advanced malignant solid tumors: a california cancer consortium phase I and molecular correlative study.

PURPOSE: Tumor hypoxia confers chemotherapy resistance. Tirapazamine is a cytotoxin that selectively targets hypoxic cells and has supra-additive toxicity with platinums and taxanes in preclinical studies. We conducted a Phase I study of tirapazamine, carboplatin, and paclitaxel and assessed potential plasma markers of hypoxia as surrogates for response. EXPERIMENTAL DESIGN: Forty-two patients with advanced solid tumors were treated at four dose levels; parallel dose escalations were carried out in chemotherapy-naive and previously treated subjects. Pre and post-therapy plasma levels of the hypoxia-induced proteins plasminogen activator inhibitor-1 and vascular endothelial growth factor were measured. RESULTS: Three of four chemotherapy-na?ve patients developed dose-limiting toxicities at dose level 4 (grade 3 stomatitis/infection, grade 3 emesis, and grade 4 febrile neutropenia). Four of seven previously treated patients developed dose-limiting toxicities at dose level 3, including one death [grade 3 myalgia, grade 3 infection/grade 4 neutropenia, grade 3 infection/grade 4 neutropenia, and grade 5 infection (death)/grade 4 neutropenia]. Of 38 patients assessable for response, 3 had a complete response, 1 a partial response, 1 an unconfirmed partial response, and 23 had stable disease in at least one evaluation; 10 quickly progressed. One complete responder had normalization of vascular endothelial growth factor and plasminogen activator inhibitor-1 levels. CONCLUSION: Dose levels 3 (carboplatin AUC of 6, 225 mg/m(2) paclitaxel, and 330 mg/m(2) tirapazamine) and 2 (carboplatin AUC 6, 225 mg/m(2) paclitaxel, and 260 mg/m(2) tirapazamine) are the maximum tolerated doses for chemotherapy naive and patients treated previously, respectively. Dose level 3 is the experimental arm of a Phase III Southwest Oncology Group trial (S0003) in advanced non-small cell lung cancer. Potential markers of tumor hypoxia may be useful correlates in studies of hypoxic cytotoxins and are being prospectively investigated in S0003.     

Phase II trial of edatrexate plus carboplatin in metastatic non-small-cell lung cancer: a Southwest Oncology Group study

Background: Edatrexate and carboplatin are each active single agents in the treatment of non-small-cell lung cancer (NSCLC). Preclinical studies in NSCLC lines have demonstrated schedule-dependent synergy of edatrexate followed by carboplatin. In a phase I trial, we demonstrated the tolerability of this combination, the ability of ice-chip cryotherapy to ameliorate dose-limiting mucositis, and promising activity in NSCLC. This phase II trial (SWOG 9207) was undertaken to investigate the efficacy of this regimen in stage IV NSCLC. Methods: A total of 24 patients with stage IV disease were accrued to this Southwest Oncology Group (SWOG) multicenter study. Treatment consisted of edatrexate 80 mg/m² (50% dose on day 8) intravenously weekly for 5 weeks, then every other week, and carboplatin 350 mg/m² every 28 days. Results: Of the 24 patients, 23 were assessable for toxicity and response; one was ineligible for study entry. Myelosuppression was the most significant toxicity; grade 3–4 neutropenia was seen in 8/23 patients. Two patients died of neutropenic sepsis during the first cycle of therapy, in both instances associated with the presence of pleural effusions. Although mild mucositis was common, it was dose-limiting (grade 3) in only three patients. Objective response was observed in 3/23 patients (13%). The median survival time was 7 months, and 30% of patients remained alive at one year. Conclusions: This study suggests that ice-chip cryotherapy is effective in reducing the severity of mucositis typically associated with this edatrexate schedule of administration. However, unexpectedly severe myelosuppression resulted in death from neutropenic sepsis in two patients with third space fluid collections, leading to a protocol amendment to exclude such patients from study entry. Furthermore, response and median survival with this dose schedule of edatrexate and carboplatin do not appear to be improved compared to other chemotherapeutic regimens tested by SWOG in this patient population. Received: 12 August 1996 / Accepted: 8 May 1997     

Molecular basis of altered red blood cell membrane properties in Southeast Asian ovalocytosis: role of the mutant band 3 protein in band 3 oligomerization and retention by the membrane skeleton

Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.     

Avoiding occlusal derangement in facial fractures: An evidence based approach

Facial fractures with occlusal derangement describe any fracture which directly or indirectly affects the occlusal relationship. Such fractures include dento-alveolar fractures in the maxilla and mandible, midface fractures – Le fort I, II, III and mandible fractures of the symphysis, parasymphysis, body, angle, and condyle. In some of these fractures, the fracture line runs through the dento-alveolar component whereas in others the fracture line is remote from the occlusal plane nevertheless altering the occlusion. The complications that could ensue from the management of maxillofacial fractures are predominantly iatrogenic, and therefore can be avoided if adequate care is exercised by the operating surgeon. This paper does not emphasize on complications arising from any particular technique in the management of maxillofacial fractures but rather discusses complications in general, irrespective of the technique used.KEY WORDS: Complication, fracture, malocclusion, mandible, midface fracture     

A systematic review of the results of surgery and radiotherapy on tumor control for pediatric craniopharyngioma

Objective

Craniopharyngiomas are rare tumors with bimodal incidence in the pediatric and adult age groups. Treatment strategies range from aggressive resection to planned limited resection combined with adjuvant therapies. Currently there is no consensus for standard of care for pediatric craniopharyngioma.

Materials and methods

We performed a systematic review of the published literature on pediatric craniopharyngioma. Patients were grouped based on extent of resection into gross total resection (GTR), subtotal resection (STR), and biopsy procedures. These groups were compared with respect to tumor control. Chi square was used to compare rates of recurrence. Kaplan–Meier was used to generate progression-free survival (PFS) estimates. Cox proportional hazard modeling was used to evaluate risk of progression. Each extent of resection group was also subdivided based on adjuvant therapy and compared.

Results

A total of 109 studies described extent of resection resulting in a cohort of 531 patients. Recurrence data were available for 377 patients. There was no difference in 1- or 5-year PFS between the groups who underwent GTR and STR combined with radiation (XRT; log-rank; p?=?0.76; 1-year PFS 89 vs 84 %; 5-year PFS 77 vs 73 %, respectively). One-year PFS was 84 % for STR+XRT compared to 76 % for STR alone while 5-year PFS was 73 % for STR+XRT compared to 43 % for STR alone (log-rank; p?=?0.003).

Conclusion

Although there are limitations of a systematic review of retrospective data, our results suggest that STR+XRT of pediatric craniopharyngioma is associated with similar rates of tumor control as GTR.     

Contrapositioning in a case of visual neglect

Abstract

We describe a series of drawing/copying impairments in a patient with left neglect consequent upon right hemisphere damage. The patient bisects lines significantly to the right of true centre and omits stimuli located on the contralesional side of cancellation tasks. Some of her copies, however, also contain errors whereby elements from left space are transposed to positions in right-sided space. Providing the patient with verbally encoded spatial information appears to facilitate this process. The phenomenon is interpreted against a background of earlier studies of visual allesthesia and current theories of propositional and analogical representation.