Apparatus for Streaming Potential Measurements on Granular Filter Media

This paper is intended to provide the necessary information to construct and properly operate a simple streaming potential apparatus capable of measuring the zeta potential of granular media. Through an understanding of the principles of the technique, such a device can readily be used in the study of a variety of granular materials including unstable and dynamic surfaces, as shown for surface coatings and even biofilm growth. The simplified mathematical theory of the streaming potential is herein explained, as well as operational factors and the general reasons for nonreproducible measurements such as electrode maintenance, electrode polarization, nonzero rest potentials, and sample equilibration. This specific apparatus design is intended for use with granular materials and has intentionally been developed in a simplistic fashion to encourage wider usage of the technique. The overall precision of this instrument was ±10% based on a 95% confidence interval. In addition, the accuracy of the device was found to be very good based on comparisons with literature values.     

Abdominal wound tumor recurrence after open and laparoscopic-assisted splenectomy in a murine model

PURPOSE: The cause of abdominal wall tumor recurrences after laparoscopic surgery for cancer remains unknown. A recent study from our laboratory using a murine splenic tumor model suggests that poor surgical technique (i.e., crushing of the tumor) and not the CO2 pneumoperitoneum is responsible for port wound tumors. However, in that experiment no actual laparoscopic procedure or manipulation was performed. The purpose of the current study was to determine the rate of abdominal wound tumors after laparoscopic-assisted splenectomy performed via a CO2 pneumoperitoneum vs. open splenectomy using the mouse splenic tumor model. METHODS: To establish splenic tumors, female BALB/c mice (N=72) were given subcapsular splenic injections of a 0.1-ml suspension containing 10(5) C-26 colon adenocarcinoma cells via a left flank incision at the initial procedure. Eight days later, animals were randomized into one of two groups: 1) laparoscopic-assisted splenectomy, or 2) open splenectomy. Laparoscopic-assisted splenectomy animals had three laparoscopic ports placed and then underwent laparoscopic mobilization of the spleen under a CO2 pneumoperitoneum followed by extracorporeal splenectomy via a subcostal incision. Group 2 animals underwent open splenectomy via a subcostal incision after three port incisions were made in the same locations as for laparoscopic-assisted splenectomy mice. The incision was closed after 20 minutes in both groups. Ten days later, the mice were killed and inspected for abdominal wall tumor implants. The experiment was performed via two separate trials. RESULTS: When results of the two trials were combined, there was no significant difference in the incidence of animals in each group with at least 1 port tumor (open, 21 percent; laparoscopic-assisted splenectomy, 33 percent; P=0.14). However, the overall incidence of port site tumors (number of ports with tumors/total number of ports for each group) was significantly higher in the laparoscopic-assisted splenectomy group than in the open group (20 vs. 7 percent; P=0.01). The subcostal incisional tumor recurrence rate was also higher in the laparoscopic-assisted splenectomy group (50 vs. 21 percent; P=0.02). as was the perioperative mortality rate (21 vs. 7 percent; P=0.08). Results of the two individual trials were also considered separately. The incidence of port wound tumors decreased significantly from the first to the second laparoscopic-assisted splenectomy trial (36 vs. 9 percent; P=0.003), although the incidence of tumors at the subcostal incision and the mortality rate for the two laparoscopic-assisted splenectomy group trials were not significantly different. The open group tumor incidences did not change from trial to trial. CONCLUSIONS: Overall, significantly more port and incisional tumors were noted in the laparoscopic-assisted group. Although not statistically significant, mortality rate of the laparoscopic-assisted group was higher than the open group. The reasons for these findings are unclear. Laparoscopic mobilization was quite difficult and required excessive splenic manipulation, which may have liberated tumor cells from the primary tumor and facilitated port tumor formation. With increased experience, less manipulation was required to complete mobilization. Of note, the incidence of port tumors in the laparoscopic-assisted splenectomy group decreased significantly from the first to the second trials; therefore, it is possible that surgical technique is a factor in port tumor formation. However, the persistently high tumor incidence at the subcostal incision site argues against the hypothesis that the second trial's laparoscopic mobilizations were less traumatic. The CO2 pneumoperitoneum may also be a factor. Further studies are warranted to clarify these issues.     

The expression of steroidogenic acute regulatory protein (StAR) in bovine adrenocortical cells

StAR protein may facilitate rapid transfer of cholesterol from the outer to the inner mitochondrial membrane, the site at which cholesterol is converted to pregnenolone by the cholesterol side chain cleavage complex. We have studied the effect of ACTH treatment on StAR mRNA and protein levels in bovine adrenocortical cells in primary culture. Cells were initially cultured for 3 days after isolation, and then treated with ACTH (10(-8) M) for various times up to 24 hours. Northern analysis of total BAC mRNA, using a [alpha32P]-labelled cDNA probe encoding a 5' region of bovine StAR mRNA, revealed two principal hybridising species of 1.6 and 3.0 kb. Western immunoblot analysis revealed a principal band at 30 kDa. Levels of both StAR mRNA and protein showed an increase at 1 hour, reached a maximum at around 6 hours and declined to basal levels at 24 hours. Cortisol secretion (measured by RIA) showed a similar change over the same period. From these results it appears that StAR mRNA and protein levels in BAC are acutely regulated in concert with ACTH-stimulated cortisol secretion.     

The effect of a carbonated beverage on the wear of human enamel and dental ceramics

Ochratoxins, of which ochratoxin A (OA) is the most prevalent, are secondary fungal metabolites of some toxigenic species of Aspergillus and Penicillium. OA has been shown to be nephrotoxic, hepatotoxic, teratogenic, carcinogenic and immunosuppressive. The natural occurrence of OA in food and feed stuffs is widespread, especially in temperate areas such as Canada, Denmark, Germany, Sweden and the United Kingdom, and detectable amounts were even found in randomly collected human milk samples in Germany, Sweden and Italy. Of greatest concern in humans is its implicated role in an irreversible and fatal kidney disease referred to as Balkan Endemic Nephropathy. The mean dietary intake for humans in the European Union was found to be in the range of 1 to 2 ng/kg bw/day. Compared with the Provisional Tolerable Daily Intake (PTDI) proposed by the WHO of 16 ng OA/kg bw/day for humans, the average OA intake in Europe seems to be rather low. The main contributor to the OA intake in humans are cereals and cereal products, other possible contributors are coffee, beer, pork, products containing pig blood/plasma, pulses and spices. Only very few countries have regulations for OA in food and feed products. Based on the current literature, the mechanisms involved in the toxicity of OA indicate three major effects: (1) inhibition of mitochondrial respiration correlated with a depletion of ATP; (2) inhibition of tRNA-synthetase accompanied by a reduced protein synthesis; and (3) enhanced lipid peroxidation. Generation of free radicals and lipid peroxidation as an important mode of action of OA in vitro and in vivo is discussed in detail, as well as counteracting effects of dietary antioxidants.     

KENYAN BARLEYS FROM 1982/83 CROP AND WATER SENSITIVITY

The Kenyan Barleys from 1982/83 harvest were considered to be highly water sensitive. The results obtained suggest that the barleys were highly water sensitive because of the surface activity of mixed populations of micro-organisms in presence of excess water. As a result of the metabolic activities of the micro-organisms on the surface of the grains the entry of oxygen into the grains was impeded     

In Vitro Topographical Characterization as a Predictor of in Vivo Controlled Release Quinidine Gluconate Bioavailability

The pH dissolution profiles and bioavailability data of six quinidine gluconate controlled release products were obtained, and attempts were made to identify a dissolution condition that is most indicative of in vivo bioavailability. This was achieved by graphically displaying the pH dissolution profiles of the six products in multi-dimensional graphs utilizing a topographical plotting technique. These graphs were found to be quite effective in illustrating: a) the effects of pH and buffer composition on the dissolution rate of the test products, and b) the in vitro condition that best correlates with in vivo data. It was found that for the quinidine gluconate controlled release dosage forms studied, dissolution carried out in pH 5.4 phosphate buffer was most meaningful in showing the differences among dosage forms and for predicting in vivo bioavailability     

Predictive validity of the potentiated startle response as a behavioral model for anxiolytic drugs

The fear-potentiated startle (PSR) paradigm is a putative behavioral model for the determination of anxiolytic properties of drugs. The present study further investigated the predictive validity of the model. Predictive validity is high, when only drugs clinically used as anxiolytics attenuate PSR dose dependently. Results showed that startle potentiation decreased dose dependently after the administration of the anxiolytics CDP (2.5-10 mg/kg, IP) and alprazolam (1-3 mg/kg, IP). After administration of the clinically non-anxiolytic drugs amitriptyline (2.5-10 mg/kg, IP), carbamazepine (5-20 mg/kg, IP), fentanyl (0.0025-0.04 mg/kg, SC), naloxone (2.5-10 mg/kg, IP), nicotine (0.4-1.6 mg/kg, IP), alcohol (500-2000 mg/kg, IP), and d-amphetamine (0.6-2.4 mg/kg, IP), a dose-dependent decrease in startle potentiation was not found. The PSR correctly discriminated most of the drugs tested in clinically anxiolytic and clinically non-anxiolytic drugs. However, haloperidol behaved as a false positive, and results of nicotine and alcohol were at variance with results reported by others.     

Diffuse alveolar damage in the horse

In a preliminary study the principles of standard gynaecological surgery, new operative laparoscopic techniques and mechanical elevation of the abdominal wall are combined. These early results indicate an advantage to both patient and hospitals from this approach. Further studies are required to verify our impressions that minilaparotomy combined with no insufflation laparoendoscopy will open up the concept of operative laparoscopic surgery to most gynaecologists.     

Initial characterization of autoprocessing and active-center mutants of CMV proteinase

Human cytomegalovirus (CMV) encodes a unique serine proteinase that is required in the maturation of the viral capsid. The CMV proteinase can undergo autocatalytic activation and is subject to proteolytic self-inactivation. Mutant enzyme forms were prepared to eliminate the initial autoprocessing site and thus form an active single-chain protein for structure-function studies. Two mutants of CMV proteinase were cloned and expressed in Escherichia coli. The A143V mutant was a conservative substitution at the first internal cleavage site. The S132A mutant modified one of the triad of residues responsible for catalytic activity. Through the use of computer-controlled high-cell-density fermentations the mutant proteins were expressed in E. coli at approximately 170 mg/L as both soluble (approximately 40% of total) and inclusion-body forms (approximately 60% of total). The soluble enzyme was purified by standard methods; inclusion-body protein was isolated by standard methods after refolding and solubilization in guanidine or urea. Sedimentation equilibrium and sedimentation velocity analyses reveal that the enzyme undergoes concentration-dependent aggregation. It exhibits a monomer <==> dimer equilibrium (Kd = 1 microM) at low concentrations and remains dimeric at high concentrations (28 mg/ml). Differential scanning calorimetry data for protein thermal unfolding fit best to a non-two-state model with two components (Tm = 52.3 and 55.3 degrees C) which subsequently aggregate upon unfolding. Analysis of the short-UV circular dichroism spectra of protein forms resulting from expression as soluble molecules (not refolded) reveals that the two mutants have very similar secondary structures which comprise a mixed structural motif of 20% alpha-helix, 26% beta-sheet, and 53% random coil. Though soluble and active (A143V mutant only), CD analysis revealed that protein refolded from inclusion bodies did not exhibit spectra identical to that of protein expressed only in soluble form.