Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Outcomes of exertional rhabdomyolysis following high-intensity resistance training

BACKGROUND

High-intensity resistance training (HIRT) programmes are increasingly popular amongst personal trainers and those attending gymnasiums. We report the experience of exertional rhabdomyolysis (ER) at two tertiary hospitals in Melbourne, Australia.

AIMS

To compare the clinical outcomes of ER with other causes of rhabdomyolysis.

METHODS

Retrospective cross-sectional study of patients presenting with a serum creatine kinase (CK) of greater than 25 000 units/L from 1 September 2013 to 31 August 2014 at two tertiary referral hospitals in Melbourne, Australia. Records were examined to identify care measures implemented during hospital stay, clinical outcomes during admission and on subsequent follow up.

RESULTS

Thirty four cases of rhabdomyolysis with a CK of greater than 25 000 units/L (normal range: 20-180 units/L) were identified during the 12-month study period. Twelve of the 34 cases (35%) had ER with 10 of 12 related to HIRT. No acute kidney injury, intensive care admission or death were seen among those with ER. All cases were managed conservatively, with 11 admitted and 9 receiving intravenous fluids only. In contrast, patients with rhabdomyolysis from other causes experienced significantly higher rates of intensive care admission (64%, P = 0.0002), acute kidney injury (82%, P = 0.0001) and death (27%, P = 0.069).

CONCLUSION

ER resulting from HIRT appears to have a benign course compared with rhabdomyolysis of other aetiologies in patients with a serum CK greater than 25 000 units/L. Conservative management of ER appears to be adequate, although this requires confirmation in future prospective studies.

Selectively transparent and conducting photonic crystal rear-contacts for thin-film silicon-based building integrated photovoltaics

Wave-optics analysis is performed to show that selectively transparent and conducting photonic crystals (STCPCs) can be utilized as rear contacts to enhance the performance of building-integrated photovoltaics (BIPV). For instance, the current generated in an a-Si:H cell with an STCPC functioning as its rear contact is comparable to that of a similar cell with an optimized ZnO/Ag rear contact. However, the solar lumens (~3.5 klm/m2) and power (~430W/m2) transmitted through the cell with the STCPC rear contact can potentially provide indoor heating and lighting, respectively. Moreover, experimental results show that STCPC rear contacts could be used to control the color temperature of light transmitted through BIPV panels.

Photonic crystal intermediate reflectors for micromorph solar cells: a comparative study

Wave-optics analysis is performed to investigate the benefits of utilizing Bragg-reflectors and inverted ZnO opals as intermediate reflectors in micromorph cells. The Bragg-reflector and the inverted ZnO opal intermediate reflector increase the current generated in a 100 nm thick upper a-Si:H cell within a micromorph cell by as much as 20% and 13%, respectively. The current generated in the bottom muc-Si:H cell within the micromorph is also greater when the Bragg-reflector is used as the intermediate reflector. The Bragg-reflector outperforms the ZnO inverted opal because it has a larger stop-gap, is optically thin, and due to greater absorption losses that occur in the opaline intermediate reflectors.

Modulation of 11beta-hydroxysteroid dehydrogenase expression by bombesin: a possible mechanism for glucocorticoid resistance in androgen independent prostate cancer

Treatment with glucocorticoids is one of a limited number of options for androgen independent prostate cancer. Neuroendocrine differentiation has been shown to contribute to androgen-independent prostate cancer progression. To study the potential link between neuroendocrine differentiation and the glucocorticoid action, we investigated the effects of the product of neuroendocrine differentiation--bombesin on glucocorticoid metabolizing enzymes--11beta-hydroxysteroid dehydrogenases in PC-3 cells. Our Western analysis, RT-PCR, and activity assays demonstrate that while 18-hour exposure to bombesin reduces 11beta-hydroxy-steroid dehydrogenases-1 profiles (activities 25% less, protein level 29% lower, mRNA levels 45% lower), contrarily it increases 11beta-hydroxysteroid dehydrogenases-2 profiles (activities 34%, protein levels 100%, mRNA levels 120%). Blockade bombesin action with bombesin receptor antagonists and the enzyme degrading bombesin prevented these changes, suggesting the observed modulations were bombesin receptor-specific. In addition, bombesin increased the amounts of interleukin-8 and mRNA of vascular endothelial growth factor receptor 2, which were lowered in the presence of cortisol, suggesting that neuropeptide blockade may extend the benefits of glucocorticoids in treating androgen-independent prostate cancer.

The effects of iron supplementation in preweaning piglets

The trial was carried out at a commercial pig farm in Bukit Pelanduk, Negeri Sembilan, Malaysia. The objective of the study was to assess the efficacy of supplemental iron in drinking water and iron in paste form in comparison with the iron dextran injection. A total of 12 litters were used divided into three treatments : iron dextran injection (ID), Fedexx" - iron in paste form (IP) and Opti-iron" - iron in drinking water (IW). Hemoglobin level and growth performance parameters were monitored weekly over a period of 28 days. ID piglets had significantly higher (p < 0.05) body weight and weekly weight gain compared with IW piglets at 21 and 28 days of age whereas no significant different (p > 0.05) results were found between IP and IW piglets. Hemoglobin level from days 0 to 28 showed statistical difference (p > 0.05) between piglets in IP and IW groups. Mild anemia was found in IP piglets but not for ID and IW piglets compared with normal value (> 9 g/dL). Hemoglobin (Hb) levels were positively correlated (p < 0.05, r = .47) with body weight at 28 days of age. In conclusion, pigs supplemented with iron in paste form and drinking water had poorer growth performance than iron dextran injection piglets. Piglets given iron in paste form had mild anemia. It is advisable to give multiple doses of oral iron to piglets in order to prevent iron deficiency anemia. During the first 4 weeks of life, the body weights of the piglets increased by up to 5-fold. The dietary requirement for iron during this period is 7 mg per day but only 1 mg per day can be supplied by the sow's milk (Cunha, 1977; Miller and Ullrey, 1997; Roberts, 1998). The need to provide the piglets with an adequate amount of iron before weaning is therefore imperative because sow's milk alone will not meet the iron requirements of rapid growth and expanding blood volume (Hannan, 1971). Several different methods can be used to offer iron to preweaning piglets. The most common administration method for iron in piglets is through an intramuscular injection of iron dextran complex at 3 days of age. A single dose of 200 mg/ml iron-dextran is effective against iron deficiency anemia. However, the method is very stressful to the piglets. They will suffer more pain if a greater dosage of iron is given intramuscularly. Furthermore, poor iron injection techniques may cause considerable trauma to the muscles, staining of hams or create abscesses and lead to downgrading of the carcasses (Roberts, 1998). Since there are several drawbacks to the iron injection, alternative methods need to be considered in intensive farming i.e. supply iron orally (Miller and Ullrey, 1997). The oral administration of iron has two advantages: cost and the fact that absorption is regulated by the intestinal mucosae. However, oral administration requires multiple doses. This is because a single dose may not be sufficient to protect the piglets from iron deficiency anemia for the first 4 weeks post-partum. The iron bioavailability in oral iron depends greatly on iron status of animals (Amine et al., 1972; Susan and Wright, 1985). In addition, dietary factors such as amino acids and protein sources (Martinez et al., 1981), pectin content, phytate (Morris and Ellis, 1982) and the other minerals (Elvehjem and Hart, 1932; Hedges and Kornegay, 1973; Suttle and Mills, 1966) may also influence the bioavailability of iron. Oral iron can be given as paste or drinking water. Early administration of oral iron within the first few days of life will meet the iron needs of the suckling pig. However, it is critical to administer early before gut closure to large molecules (Harmon et al., 1974; Thoren-Tolling, 1975). This study was conducted to determine the efficacy of iron supplementation in drinking water or paste form in comparison with the injection of iron compounds in suckling pigs.

Intergenic complementation truncation mutants of cyclin-dependent kinase

The Saccharomyces cerevisiae genes PHO80 and PHO85 encode, respectively, a cyclin and cyclin-dependent kinase, which negatively regulate PHO5 gene transcription by phosphorylating the transcription activator Pho4p. Cyclin-dependent kinases (CDKs) are highly conserved proteins, both within and between species. It was previously demonstrated, using reporter genes activated in yeast by Pho4p, that hybrid proteins in which over two-thirds of Pho85p were replaced with the homologous region from human Cdk2 retained the function of native Pho85p with respect to promoter repression. In the present study, various truncated forms of the hybrid human-yeast CDKs were tested for function. Surprisingly, truncations in which significant portions of the C-terminal region of the 291-residue hybrid CDK were deleted retained activity. Genes encoding human Cdk2 proteins which terminated after amino acids 151, 140, 130, 120 and 90 each complement a chromosomal pho85 gene disruption in which the HIS3 gene is inserted at codon 49. Truncated Cdk2 proteins containing less than 60 amino acids failed to complement the pho85::HIS3 gene disruption. Although the functional C-terminal truncations disrupt the ATP-binding and active sites of Cdk2, reporter gene repression mediated by these truncated proteins is apparently due to phosphorylation of Pho4p, since a gene in which the essential lysine codon at position 33 was converted to an arginine codon does not complement the chromosomal gene disruption. The human Cdk2 truncations were demonstrated to function through intergenic complementation. The intact Cdk2-Pho85 hybrid CDK complemented the pho85 mutation in yeast strains in which the entire PHO85 coding region was deleted from chromosome XVI. The C-terminal Cdk2 truncations, however, were non-functional in these strains and thus dependent for activity on the pho85 coding region which remained in the mutant pho85::HIS3 chromosomal locus. These genetic results are consistent with a model involving protein fragment complementation in which the active site of the CDK is bisected.

STEAP: a prostate-specific cell-surface antigen highly expressed in human prostate tumors

In search of novel genes expressed in metastatic prostate cancer, we subtracted cDNA isolated from benign prostatic hypertrophic tissue from cDNA isolated from a prostate cancer xenograft model that mimics advanced disease. One novel gene that is highly expressed in advanced prostate cancer encodes a 339-amino acid protein with six potential membrane-spanning regions flanked by hydrophilic amino- and carboxyl-terminal domains. This structure suggests a potential function as a channel or transporter protein. This gene, named STEAP for six-transmembrane epithelial antigen of the prostate, is expressed predominantly in human prostate tissue and is up-regulated in multiple cancer cell lines, including prostate, bladder, colon, ovarian, and Ewing sarcoma. Immunohistochemical analysis of clinical specimens demonstrates significant STEAP expression at the cell-cell junctions of the secretory epithelium of prostate and prostate cancer cells. Little to no staining was detected at the plasma membranes of normal, nonprostate human tissues, except for bladder tissue, which expressed low levels of STEAP at the cell membrane. Protein analysis located STEAP at the cell surface of prostate-cancer cell lines. Our results support STEAP as a cell-surface tumor-antigen target for prostate cancer therapy and diagnostic imaging.

Multiple organ failure: by the time you predict it, it's already there

OBJECTIVE

Validate an at-risk population to study multiple organ failure and to determine the importance of organ dysfunction 24 hours after injury in determining the ultimate severity of multiple organ failure.

METHODS

We evaluated 105 patients admitted to five academic trauma centers during a 1-year period who survived for more than 24 hours with Injury Severity Scores > or = 25 and who received 6 or more units of blood. Organ dysfunction was scored daily with a modified multiple organ failure scoring system made up of individual adult respiratory distress syndrome score, renal dysfunction, hepatic dysfunction, and cardiac dysfunction scores. Multiple organ failure (MOF) severity was quantitated using the maximum daily multiple organ failure score and the cumulative sum of daily multiple organ failure scores for the first 7 days (MOF 7) and 10 days (MOF 10). Independent variables included markers of tissue injury, shock, host factors, physiologic response, therapeutic factors, and organ dysfunction within the first 24 hours after admission. Data were subjected to a conditional stepwise multiple regression analysis, first excluding and then including 24-hour MOF as an independent variable.

RESULTS

Of the 105 high-risk patients, 69 (66%) developed a maximum daily multiple organ failure score > or = 1; 50 (72%) did so on day 1 one and 60 (87%) did so by day 2. In multiple regression models, the multiple correlation coefficient increased from 0.537 to 0.720 when maximum MOF was the dependent variable, from 0.449 to 0.719 when maximum daily MOF was the dependent variable, from 0.519 to 0.812 when MOF 7 was the dependent variable, and from 0.514 to 0.759 when MOF 10 was the dependent variable.

CONCLUSION

We have confirmed that the population of patients with Injury Severity Scores > or = 25 who received 6 or more units of blood represent a high-risk group for the development of multiple organ failure. Our data also indicate that multiple organ failure after trauma is established within 24 hours of injury in the majority of patients who develop it. It appears that multiple organ failure is already present at the time when most published models are trying to predict whether or not it will occur.

Risk of hepatitis C infection in neonates transfused with blood from donors infected with hepatitis C

This look-back study was undertaken to identify newborn infants who had been infected with the hepatitis C virus (HCV) as a result of transfusions received before the introduction of routine screening in 1991 and to determine the transmission rates and persistence of transfusion-transmitted HCV infection acquired in the neonatal period. A total of 24 infants, transfused between 1980 and 1991, were identified as having received potentially infected blood from 11 blood donors. Ten of the donors had been administered batches of anti-D in 1977 known to have transmitted HCV genotype 1b infection. HCV RNA was detected in five of these donors when tested in 1994-95; the past donations of five of the donors, who had received anti-D immunoglobulin and had serological evidence of previous HCV infection but who were PCR negative when tested in 1994-95, were considered of lower risk. The source and time of acquisition of HCV infection for the one remaining donor in the study was not determined. Twenty-one (88%) of the 24 children were living at time of lookback. The median age at transfusion was 12 days. The median age at time of testing was 6.3 years. One child, who tested negative, was excluded from further analysis of HCV transmission, due to incomplete transfusion records. Overall, 12 of 20 (60%) children tested were positive for anti-HCV and seven (35%) were HCV RNA positive. Twelve (71%) of the 17 recipients of viraemic blood were ELISA positive and seven (41%) were PCR positive. Resolved HCV infection, as determined by ELISA pos, RIBA pos or indeterminate and PCR negativity, occurred in five of 12 (42%). In many instances there was more than one recipient per HCV infected donation. All of the reported children are clinically asymptomatic. However, the duration of HCV infection is relatively short and there is evidence of a degree of hepatitis in five of the seven children who are HCV RNA positive as judged by mildly elevated transaminase levels. The three who have undergone liver biopsy show mild hepatitis. The lower rates of persistence of HCV infection in this study may be due to the young age at exposure or to the source of infection which for all but one of the children was linked to one HCV genotype from female donors. Sharing of units of blood among multiple infants should be discouraged.

Gelatin/chondroitin 6-sulfate microspheres for the delivery of therapeutic proteins to the joint

OBJECTIVE

To develop a biodegradable, inflammation-responsive microsphere system for the intraarticular delivery of therapeutic proteins.

METHODS

Microspheres were synthesized by complex coacervation. Radiolabeled protein release and microsphere degradation were assessed by exposing the microspheres to human synovial fluids (SF) and recombinant gelatinase. Microsphere degradation was confirmed by scanning electron microscopy (SEM). Microsphere biocompatibility was evaluated in vitro by incubating the microspheres with human synoviocytes, and in vivo by injection into mouse joints.

RESULTS

Optimal microsphere formulation was developed. Significant (up to 100%) release of encapsulated protein occurred in SF samples with measurable metalloprotease activity, while release was minimal in SF with negligible activity. Dissolution of microspheres exposed to gelatinase was confirmed by SEM. Microspheres were found to be noncytotoxic in vitro, and noninflammatory in vivo.

CONCLUSION

Microsphere encapsulation is an inflammation-responsive and biocompatible system of protein delivery that holds promise for use in the delivery of therapeutic proteins to the joint.

Functional genetic tests of DNA mismatch repair protein activity in Saccharomyces cerevisiae

Hereditary non-polyposis colorectal cancer (HNPCC) is associated with mutations in four different genes encoding proteins involved in DNA mismatch repair (DMR). As many as 30% of the observed sequence variations in human DMR genes predict minor alterations in the encoded protein, such as amino acid (aa) replacements or small in-frame deletions/insertions. For such sequence variants, a functional genetic test will be required to discriminate mutations from polymorphisms. We have constructed a series of isogenic yeast strains in which individual genes involved in DMR are disrupted, and have standardized an assay which measures GT tract stability (Strand et al., 1993) to characterize these gene products. Disruptions of the yeast MSH2, MLH1, and PMS1 genes result in, respectively, a 290-, 450- and 390-fold increased tract instability over the wild type (wt) strain under optimized assay conditions. Expression of the wt MSH2 and PMS1 gene from plasmids results in complementation of the corresponding chromosomal gene disruption. Two different aa replacements which correspond to previously observed sequence variants of the human MSH2 gene, and implicated in HNPCC, were created in the conserved aa of the yeast MSH2 gene by site directed mutagenesis. Conversion of the Pro640 in the yeast protein to Leu resulted in a complete loss of protein function. In contrast, a yeast MSH2p protein in which the His658 is changed to Tyr retains full function in this in vivo assay. These results indicate that the Pro-->Leu and His-->Tyr variants observed in humans constitute, respectively, a mutation and a polymorphism. The system described here may be used for further structure/function analysis of yeast DMR proteins. Such studies may provide insight into the effects that specific sequence variations observed in human DMR proteins have on their function.

Decreased growth hormone receptor expression in long bones from toothless (osteopetrotic) rats and restoration by treatment with colony-stimulating factor-1

Growth hormone (GH) is known to regulate growth and development of skeletal tissues. This study examined the distribution of growth hormone receptor (GHR) expression in tibias from normal and osteopetrotic tl/tl rats. For normal 2 week-old rats, GHR expression was detected immunocytochemically in cells of the articular and epiphyseal cartilage, primary and secondary ossification centres, zone of resting cartilage and bone marrow. Within the marrow, GHR immunopositive cells were concentrated in the central cone and largely excluded from the zone of immature progenitors at the periphery. For the marrow haemopoietic compartment, GHR expression was almost restricted to the nucleus in large mononuclear cells, adipocytes and megakaryocytes. A population of small lymphocytelike cells in the marrow periphery expressed GHR on the plasma membrane. GHR was not detected in mature erythroid cells, macrophages, granulocytes, or osteoclasts. The expression of GHR was significantly reduced in bone marrow cells of the tl/tl rat (p < 0.001) compared with normal animals. Injection of recombinant CSF-1 into tl/tl rats every 48 hours for 2 weeks from birth restored GHR-positive cells to the central core of the marrow space. The most striking change was the appearance of substantial numbers of mononuclear cells expressing abundant GHR on the cell surface. We infer that these cells are a novel subset of CSF-1 responsive cells involved in bone resorption. The differences in relative expression of GHR by bone marrow cells in untreated and CSF-1-treated tl/tl rats suggests a CSF-1-dependent recruitment of cells bearing surface GHRs.

Poly(alpha-hydroxy acids): carriers for bone morphogenetic proteins

A broad spectrum of cells and cell products is associated with bone homeostasis and the renewal of bone following injury. The coupled interactions among cells provide the power behind sculpting of bone, sustaining form, and ensuring functionality. Local and systemic regulatory molecules (e.g. growth factors, hormones) direct cellular interactions through autocrine, paracrine, and hormonal pathways. Recently, genes for a class of osteogenic regulatory molecules have been cloned, and gene product expression has enabled investigators to assess safety and efficacy in animal studies. The molecules are known as bone morphogenetic proteins (BMPs). Therapeutic applications of BMPs depend on a carrier system. A carrier could spatially and temporally localize BMP for regional needs and be custom-tailored for acute craniofacial applications or for recalcitrant extremity non-unions. The poly(alpha-hydroxy acids) (PHAs) may be suitable for these applications. Therefore, the purposes of this paper are (i) to mention, briefly, basic concepts of the bone wound continuum and the possible therapeutic roles of BMPs; (ii) to outline several properties of selected PHAs relevant to bone regeneration dynamics; and (iii) to review selected preclinical studies with PHAs.

Structure and activity of granulocyte colony-stimulating factor derived from CHO cells containing cDNA coding for alternatively spliced sequences

Two different cDNAs have been isolated, coding for two forms of granulocyte colony-stimulating factor (G-CSF): one for a polypeptide of 174 amino acids and the other for a polypeptide of 177 amino acids. In this paper, we have expressed these two forms in Chinese hamster ovary cells and characterized the purified proteins for activity and conformation. In vitro mitogenic assay showed a 50-fold lower activity for the 177 form than for the 174 form. In vitro receptor binding assay showed that binding of the 177 form to the purified extracellular domain of G-CSF receptor was also diminished, while the 174 form complexed with the receptor. Circular dichroic spectra showed that both forms are similar in the secondary structure, but are slightly different in the tertiary structure. Infrared spectra also showed a slight difference between the two forms. Both techniques also demonstrated differences in stability; i.e., the 174 form is more stable than the 177 form during storage or against heat denaturation.

Controlled release, biodegradable cytokine depots: a new approach in cancer vaccine design

Experimental studies using murine tumor models have demonstrated that potent systemic immunity can be generated using tumor vaccines engineered by gene transfer to secrete certain cytokines. The underlying physiological principle behind these strategies involves the sustained release of high doses of cytokine at the site of the tumor. In some cases, this paracrine approach appears to enhance tumor antigen presentation and avoids systemic cytokine toxicity. The widespread clinical use of autologous cytokine gene transduced tumor vaccines may be limited by the technical difficulty and labor intensity of individualized gene transfer. We have therefore explored an alternate approach to generating sustained release of cytokines local to the tumor cells. High doses of granulocyte-macrophage colony-stimulating factor encapsulated in cell-sized gelatin-chondroitin sulfate microspheres were mixed with irradiated tumor cells prior to s.c. injection. This vaccination scheme resulted in systemic anti-tumor immune responses comparable to granulocyte-macrophage colony-stimulating factor gene transduced tumor vaccines.

Fetal neuroblastoma: prenatal diagnosis and natural history

Obstetrical sonography has helped diagnose and define the features of some congenital malformations and tumors. We present five fetal neuroblastomas detected by routine prenatal sonography. All were adrenal tumors diagnosed between 26 and 39 weeks gestation. All 5 tumors were completely resected postnatally and the patients have remained disease free from 2 months to 10 years after resection without adjuvant therapy. A literature review collated 16 other cases of fetal neuroblastoma detected by sonography between 29 and 38 weeks gestation. These cases included 1 cervical, 1 thoracic, and 14 adrenal tumors. Thirteen neonates had Evans stage I or II tumors, and three had more advanced disease. Eleven mothers did not have hypertension or preeclampsia during the pregnancy, and the neonates all had stage I or II disease. Four mothers had hypertension or preeclampsia. Three of these neonates had stage IV or IVS disease with liver metastases, and all three had fetal hydrops. Review of the congenital neuroblastoma literature documented 71 cases diagnosed soon after birth, and several of these cases had unusual features that could have been detected by prenatal ultrasound. Four of the tumors were so large that dystocia resulted and fetal dismemberment was required for delivery. Eight of the tumors metastasized to the placenta, and 1 metastasized to the umbilical cord with subsequent fetal death. We conclude that fetal neuroblastoma can be diagnosed by prenatal sonography. Accurate staging is difficult by sonography, but in mothers with no preeclampsia symptoms the chance of widely disseminated disease is small.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of magnetic resonance imaging to track controlled drug release and transport in the brain

A method has been developed to track controlled drug release and transport in the brain. This method entails the use of a polymeric implant to release, over time, a paramagnetically labelled compound into the brain. Magnetic resonance imaging is used to determine the evolving concentration distribution. This method is well suited to other types of intracranial drug delivery systems as well as to track transport in other organs of the body.

In vitro release of hydrophobic drugs from polyanhydride disks

We have evaluated the feasibility of using polyanhydride disks containing hydrophobic antiproliferative agents for controlled drug release after glaucoma filtration surgery. Taxol and VP-16 were the most potent inhibitors of fibroblast proliferation tested, with ID50s of 3 ng/mL and 200 ng/mL, respectively. In vitro release of taxol occurred at concentrations exceeding its ID50 for at least 100 days; VP-16 was released for 31 days. The media into which the drugs were released were able to inhibit fibroblast proliferation in vitro, indicating that the bioactivity of the drugs withstood incorporation into, and release from, the polyanhydride. Polyanhydride disks containing taxol and VP-16 merit testing in animal models of glaucoma filtration surgery.

High-level transcription from the adenovirus major late promoter requires downstream binding sites for late-phase-specific factors

The adenovirus major late promoter (MLP) is active during both the early and late phases of infection. During the early phase the activity of the MLP is similar to those of the other early viral promoters, but during the late phase the rate of transcription from the MLP becomes much greater by comparison. We report here that sequence-specific binding proteins are induced during the late phase which interact with three regions in the first intron of the MLP transcription unit from positions +37 to +68, +80 to +105, and +105 to +125 relative to the transcription initiation site. To measure the significance of these binding sites for transcription during the late phase, we constructed MLP-beta-globin fusions and substituted them for early region 3 in adenovirus recombinants. Deletion of the binding sites caused significant reductions in the rate of transcription, specifically during the late phase of infection. Deletion of all three sites reduced the rate of transcription 25- to 50-fold and the accumulation of cytoplasmic MLP-beta-globin RNA 200-fold. These results indicate that the high rate of transcription from the MLP during the late phase of infection results from the interaction of virus-induced transcription factors with three binding sites in the first intron of the major late transcription unit.

Ultrasound-enhanced polymer degradation and release of incorporated substances

The effect of ultrasound on the degradation of polymers and the release rate of incorporated molecules within those polymers was examined. Up to 5-fold reversible increases in degradation rate and up to 20-fold reversible increases in release rate of incorporated molecules were observed with biodegradable polyanhydrides, polyglycolides, and polylactides. Up to 10-fold reversible increases in release rate of incorporated molecules within nonerodible ethylene/vinyl acetate copolymer were also observed. The release rate increased in proportion to the intensity of ultrasound. Temperature and mixing were relatively unimportant in effecting enhanced polymer degradation, whereas cavitation appeared to play a significant role. Increased release rates were also observed when ultrasound was applied to biodegradable polymers implanted in rats. Histological examination revealed no differences between normal rat skin and rat skin that had been exposed to ultrasonic radiation for 1 hr. With further study, ultrasound may prove useful as a way of externally regulating release rates from polymers in a variety of situations where on-demand release is required.

Polyanhydride microsphere formulation by solvent extraction

A novel process based on solvent extraction was developed to produce drug-loaded polyanhydride microspheres for controlled-release applications. The technique consists of adding a chloroform solution of polyanhydride and drug into a stirred silicone oil phase containing suspended droplets of surfactant. No chemical reaction, heating, nor contact with water was required in this process. The microspheres produced were capable of releasing various dyes for prolonged periods of time.

Adenovirus early region 1A protein increases the number of template molecules transcribed in cell-free extracts

Protein encoded by adenovirus early region 1A (E1A) stimulates transcription from adenovirus promoters in vivo. Here we show that this effect can be observed in vitro. In a run-off transcription assay from the adenovirus serotype 2 (Ad2) major late promoter, extracts prepared 20 hr postinfection were 5-15 times more active than mock-infected-cell extracts prepared in parallel. Similar results were observed for in vitro transcription from the protein IX and E3 adenovirus promoters, whereas a 2-fold increase was observed for the human beta-globin promoter. The increased activities of infected-cell extracts did not depend on the expression of viral late proteins or the small E1A-encoded proteins but did require expression of the large E1A protein. These results are consistent with the large E1A protein stimulating transcription in vitro as it does in vivo. By limiting in vitro transcription to one initiation per template, we found that the higher activity of an infected-cell extract was due to an increase in the number of templates transcribed. These results suggest that the large E1A protein either increases the number of active transcription factors in infected cells or facilitates the interaction of cellular transcription factors with promoter DNA.

Primer-dependent eukaryotic RNA polymerase capable of accurate transcription from the adenovirus major late promoter in a reconstituted system

A sensitive assay for detection of eukaryotic RNA polymerase II has been developed. This assay depends on the ability of polymerase II to elongate a small RNA primer, oligo(U), hybridized to a single-stranded homopolymeric DNA template, poly(dA). The poly(dA).oligo(U)-dependent RNA polymerase II from calf thymus has been purified approximately 10,000-fold using this assay. The purified enzyme contains four polypeptides of apparent Mr 180,000, 140,000, 24,000, and 16,000 and is fully active in accurate initiation of transcription from the adenovirus major late promoter in the presence of transcription factors from HeLa cells. The poly(dA).oligo(U)-dependent RNA polymerase activity can be detected in crude cell extracts from a variety of tissue culture cells and appears to be largely due to polymerase II, since 90-95% of this activity is inhibited by alpha-amanitin at a concentration of 1 microgram/ml.

The expression of the SV40 early region in the transformed human cell line SV80

The one complete copy of the SV40 early region present in human cells of the transformed line SV80 carries a duplication of the 5' portion of the early region, including its transcriptional control region and splicing signals (W. Gish and M. Botchan, personal communication). Novel SV40-specific RNA species of sufficiently large size, 3.8 and 4.2 kb, to be expressed from the duplicated early transcriptional control region were detected in SV80 cytoplasmic and nuclear RNA preparations by blot hybridization. The results of transcription in a cell-free system of a plasmid, pSV80-04, representing this SV80 cell SV40 DNA integrate (W. Gish and M. Botchan, personal communication) and of nuclease protection experiments with end-labelled pSV80-04 DNA fragments support the conclusion that the duplicated early sequences are transcribed in SV80 cells. It has also been established that the duplicated early splicing signals are functional in SV80 cells. These results are discussed in relation to the large amounts of SV40 early mRNA and T-antigen synthesized in cells of the SV80 line.

Transcription of adenovirus cores in vitro

Transcription in whole HeLa cell extracts of the nucleoprotein core complexes released from adenovirus type 2 or type 5 virions has been examined. The average length of transcripts from deproteinized DNA templates increased steadily during a 90-min reaction in vitro, exhibiting an elongation rate of approximately 70 nucleotides per minute. On the other hand, transcripts made from viral core templates were restricted to a length of less than 2000 nucleotides. Accordingly, efficient transcription of cores (50 nucleotides elongated/min) ceased after 10-20 min of incubation in whole-cell extracts. Deproteinized viral DNA and viral nucleoprotein complexes appeared to support the initiation of a similar number of transcripts per template molecule, but the rate of initiation was faster when cores were provided as templates. Deproteinized viral DNA supported the synthesis of VA-RNA and of transcripts that hybridized to the region of the viral genome containing the 5' portion of the major late transcriptional. Viral cores also directed the synthesis of RNA products which hybridized to fragments of the viral genome containing E1A, E1B, and E4 regions. The results of nuclease protection experiments indicated that the presence of core proteins did not preclude accurate initiation of transcription from the E4 region.

Specific transcription of an adenoviral gene that possesses no TATA sequence homology in extracts of HeLa cells

Transcription of the adenovirus type 2 (Ad2) IVa2 gene, which contains no TATA-like sequence in the region immediately upstream of the IVa2 cap sites (Baker, C. C., and Ziff, E. B. (1981) J. Mol. Biol. 149, 189-221), has been examined in extracts of HeLa cells (Manley, J. L., Fire, A., Cano, A., Sharp, P. A., and Gefter, M.L. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 3855-3859). Run-off transcripts of the predicted length of those initiated at the IVa2 cap sites were synthesized from different Ad2 DNA templates, each of which also contained the major late transcriptional control region. Mapping of the 5' ends of the RNA made from one template by a nuclease protection assay established the fidelity of initiation of IVa2 transcription in vitro. The efficiency of IVa2 expression in whole HeLa extracts was influenced quite dramatically by monovalent and divalent metal ion concentrations and the concentration of extract protein present in the reaction mixture. Under certain conditions, IVa2 run-off transcripts were made almost as efficiently as those from the Ad2 major late transcriptional control region. However, conditions promoting optimal IVa2 transcription in vitro did not favor recognition of the major late transcriptional control region, and vice versa: the synthesis of IVa2 and major late run-off transcripts responded differently to all parameters tested.

Purification of a factor that restores translation of vesicular stomatitis virus mRNA in extracts from poliovirus-infected HeLa cells

It was previously shown that the poliovirus-induced inhibition of translation of capped mRNAs can be reversed by a protein found in preparations of the eukaryotic initiation factor eIF-4B [Rose, J. K., Trachsel, H., Leong, K. & Baltimore, D. (1978) Proc. Natl. Acad. Sci. USA 75, 2732--2736]. This "restoring factor" has now been purified from a high-salt wash of rabbit reticulocyte ribosomes by taking advantage of its tight association with factor eIF-3 at low salt concentrations. It did not copurify with the major Mr 80,000 polypeptide of eIF-4B preparations but did copurify with a Mr 24,000 polypeptide previously shown to bind to the cap structures of mRNAs [Sonenberg, N., Rupprecht, K. M., Hecht, S. M. & Shatkin, A. J. (1979) Proc. Natl. Acad. Sci. USA 76, 4345--4349]. Both the electrophoretic mobility and the tryptic peptide pattern of the restoring factor were indistinguishable from those of the cap-binding protein, and the restoring factor could be crosslinked to the 5'-terminal cap on mRNA. Thus, is appears that poliovirus inhibits cellular protein synthesis by inactivation of some crucial property of the cap-binding protein.

Inhibition of translation by poliovirus: inactivation of a specific initiation factor

Translation of vesicular stomatitis virus (VSV) mRNA, like host mRNA translation, is inhibited in cells infected with poliovirus. To study the mechanism of poliovirus-induced inhibition of protein synthesis, we prepared extracts from poliovirus-infected and uninfected HeLa cells. Poliovirus mRNA was translated in lysates from both infected and uninfected cells, while VSV mRNA was translated only in the lysate from uninfected cells. Addition of purified translation initiation factors to the extract from infected cells showed that one factor, eIF-4B, could restore VSV mRNA translation in the infected lysate, but did not increase poliovirus mRNA translation. Further experiments involving translation of VSV mRNA in mixed extracts from poliovirus-infected and uninfected cells showed (i) that there was not an excess of an inhibitor of VSV mRNA translation in the infected lysate, but (ii) that an acitivity that caused a slow inactivation of eIF-4B was present in the infected lysate. Inactivation of eIF-4B appears to be the mechanism by which poliovirus infection causes a selective inhibition of translation.