Photon energy dependence of the sensitivity of radiochromic film and comparison with silver halide film and LiF TLDs used for brachytherapy dosimetry

There is a new radiochromic film, a highly uniform, thin (100-microns) detector whose sensitive layer (6 microns thick) changes from colorless to blue by dye polymerization without processing, upon exposure to ionizing radiation. Because the dose gradients around brachytherapy sources are steep, the high spatial resolution offered by film dosimetry is an advantage over other detectors such as thermoluminescent dosimeters (TLDs). This compares the photon energy dependence of the sensitivities of GafChromic film, silver halide verification film (Kodak X-Omat V Film), and lithium fluoride TLDs (Harshaw), over the photon energy range 28 keV to 1.7 MeV, which is of interest in brachytherapy. Sensitivity of the radiochromic film is observed to decrease by about 30% as effective photon energy decreases from 1710 keV (4-MV x rays) to 28 keV (60-kV x rays, 2-mm A1 filter). In contrast, the sensitivity of verification film increases by 980% and that of LiF TLDs increases by 41%. The variation of the sensitivity of radiochromic film with photon energy is considerably less than that for silver halide film and similar to that for LiF TLDs, but in the opposite direction. Radiochromic film, like LIF TLDs, does not exhibit the drastic sensitivity changes below 127 keV that silver halide film exhibits. Dose distribution in the immediate vicinity of a high activity (370 GBq) brachytherapy 192Ir source has been mapped using radiochromic film and is presented to illustrate the applicability of this new technology to brachytherapy dosimetry.     

Increased Escherichia coli enterotoxin detection after concentrating culture supernatants: possible new enterotoxin detectable in dogs but not in infant mice.

The heat-stable enterotoxin (ST) of Escherichia coli can be detected by infant mouse or dog intestinal loop tests. These tests differ in that the dog assay uses concentrated culture supernatants and is based on measurements of net intestinal absorption, whereas the mouse test uses unconcentrated supernatants and depends on gross fluid accumulation. To compare the relative sensitivities of these assays, culture supernatants of randomly selected E. coli isolates from 34 Bangalee diarrhea patients were tested for ST in dog loops and infant mice. Supernatants were also tested for heat-labile enterotoxin (LT) in dog loops, Y-1 adrenal cells, and Chinese hamster ovary cells. E. coli supernatants that produced positive responses for both ST and LT in the dog loop assay (ST+/LT+) also produced positive responses when tested for ST in infant mice and for LT in cell lines. Supernatants of strains negative for ST and LT in dog loop (ST-/LT) were also negative in other assays. Of 10 strains positive for just ST in the dog loop test (ST+/LT-), only 5 were ST positive in the standard infant mouse test. Supernatants of the other five strains (dog loop positive, mouse test negative) were then concentrated 100-fold and retested in mice. Three of these five gave consistently positive results after concentration, and two were only intermittently positive. Concentrated supernatants of negative control strains (ST-/LT-) were all negative in mice. The dog assay detects more strains producing ST than the infant mouse test. The infant mouse test, which detects only gross fluid accumulation, failed to detect approximately half of the 10 strains which produced ST alone (ST+/LT-; P = 0.025). Concentrating supernatants for the mouse assay increases sensitivity for detection of ST, but certain E. coli strains produce a variety of ST to which infant mice do not respond.     

Four-day incubation period for blood culture bottles processed with the Difco ESP blood culture system.

Blood culture records from 1994 to 1995 from five U.S. medical centers all using the Difco ESP continuous monitoring blood culture system were reviewed retrospectively. Among a total of 7,362 isolates of bacteria and yeasts, only 0.1% of possibly significant isolates would have been missed had blood cultures been routinely incubated for 4 days instead of the 5 days recommended by the manufacturer. Conversely, numerous contaminants, detected only on day 5, would have been eliminated by a 4-day incubation period.     

Norethisterone treatment to control timing of the IVF cycle

The use of norethisterone to control the timing of the precedingmenstrual cycle and in consequence the timing of the in-vitrofertilization (IVF) cycle has been evaluated in a therapeuticIVF programme in which oocyte recovery was limited to 2 dayseach week. A consecutive series of 181 cycles after norethisteroneand 29 untreated controls were compared. Menstruation occurred2– 3 days after norethisterone as planned in 82% of patientsoverall and in 87% of patients whose menstrual cycle lengthvaried by no more than 2 days about the median. Norethisteronetreatment did not significantly affect the outcome of IVF treatmentcompared with the controls in respect to cycles abandoned (12versus 0%, respectively), peak follicular diameter (mean 18.1mm versus 18.3 mm 48 h before laparoscopy), oocyte recoveryrate (4.6 versus 4.5 per patient), oocyte morphology (63% versus52% mature), or fertilization rate (72 versus 65% of matureoocytes). Clinical pregnancies were too few for comparison (rates27 versus 9% per laparoscopy) but the overall rate (23%) indicatedeffectiveness of the methods. Prior norethisterone treatmentappears to be an effective and useful means of controlling thetiming of the oocyte recovery in IVF treatment.     

Expression of rabbit IL-4 by recombinant myxoma viruses enhances virulence and overcomes genetic resistance to myxomatosis

Rabbit IL-4 was expressed in the virulent standard laboratory strain (SLS) and the attenuated Uriarra (Ur) strain of myxoma virus with the aim of creating a Th2 cytokine environment and inhibiting the development of an antiviral cell-mediated response to myxomatosis in infected rabbits. This allowed testing of a model for genetic resistance to myxomatosis in wild rabbits that have undergone 50 years of natural selection for resistance to myxomatosis. Expression of IL-4 significantly enhanced virulence of both virulent and attenuated virus strains in susceptible (laboratory) and resistant (wild) rabbits. SLS-IL-4 completely overcame genetic resistance in wild rabbits. The pathogenesis of SLS-IL-4 was compared in susceptible and resistant rabbits. The results support a model for resistance to myxomatosis of an enhanced innate immune response controlling virus replication and allowing an effective antiviral cell-mediated immune response to develop in resistant rabbits. Expression of IL-4 did not overcome immunity to myxomatosis induced by immunization.     

Decreased pancreatic exocrine response to cholecystokinin in Zucker obese rats

Cholecystokinin (CCK), one of the peptides secreted by the gastrointestinal tract during a meal, stimulates release of enzymes into pancreatic juice and is a trophic hormone for the pancreas. Administration of CCK also decreases food intake, and obese rats have been shown to have a higher threshold than lean rats for this apparent effect on satiety. In this study experiments were designed to compare the sensitivity of obese and lean rats to the effects of CCK octapeptide (CCK-8) on pancreatic structure and exocrine function. In both growing and adult Zucker rats DNA content of the pancreas from obese rats was decreased compared with that from lean rats [2.42 +/- 0.21 vs. 3.07 +/- 0.18 mg (P less than 0.01) and 2.46 +/- 0.25 vs. 3.01 +/- 0.19 mg (P less than 0.05), respectively], and in adult obese rats this was accompanied by decreased pancreas size on both absolute weight and percent of body weight bases. In adult obese Bar Harbor mice, although DNA content of the pancreas was also decreased [1.70 +/- 0.10 vs. 2.41 +/- 0.11 mg (P less than 0.01)], pancreas weight was not different (0.30 +/- 0.01 vs. 0.32 +/- 0.01 g). In young rats growth of the pancreas was stimulated by 2 micrograms/kg CCK-8 administered subcutaneously or 100 mg/kg of a trypsin inhibitor administered orally twice daily for 2 wk. Although both treatments increased weight and DNA and protein content of the pancreas, the increases in DNA and protein content were smaller in obese than lean rats, indicating a decreased responsiveness to both trophic agents. Administration of CCK-8 stimulated smaller increases in pancreatic juice volume and amylase release in obese compared with lean rats, indicating decreased pancreatic exocrine function in response to CCK. In adults the CCK-8 dose-response curve for amylase release from dispersed pancreatic acini of obese rats was similar to that of lean rats, indicating normal sensitivity in vitro. Thus, in obese rats and mice DNA content of the pancreas is decreased when compared with that of lean rats and mice, and this is accompanied by decreased in vivo responses to CCK in obese rats.     

p53 alterations in oesophageal cancer: association with clinicopathological features, risk factors, and survival.

AIM: To characterise the spectrum of p53 alterations (gene mutations and protein accumulation) in a consecutive series of surgically resected oesophageal cancers, and to evaluate associations with clinicopathological findings (age, sex, tumour histology, grade, and stage), potential risk factors (alcohol, tobacco, hot beverage consumption, history of gastrooesophageal reflux disease and antacid use), and survival. METHODS: The case series comprised 61 sequentially accrued patients with primary oesophageal carcinomas. Genomic DNA was extracted from banked (frozen) tumours and matched normal mucosal tissue; p53 mutations (exons 4-10) were studied by means of polymerase chain reaction (PCR)/single strand conformation polymorphism (SSCP) analysis and DNA sequencing. Immunohistochemistry (DO7, CM1) was used to assess cell nuclear p53 protein accumulation. Risk factor data, overall and disease free survival were measured prospectively, and analysis was carried out at the univariate level using Kaplan-Meier survival curves with log rank tests, and in multivariate analysis using Cox's proportional hazards models (parsimonious and fully adjusted). RESULTS: p53 mutations were found in 59% (36 of 61) and p53 protein accumulation was detected in 39% (24 of 61) of oesophageal cancers. Eighty eight per cent (23 of 26) of poorly differentiated tumours had p53 alterations compared with 57% (20 of 35) of moderate/well differentiated tumours (odds ratio (OR) = 5.575; p = 0.013). p53 mutations increased significantly with increasing consumption of hot beverages (measured by the average temperature of beverage, number consumed daily, and an index made by multiplying the two variables together) using both univariate (OR = 18.6; p = 0.0025) and multivariate (OR = 24.5; p = 0.0025) analysis. p53 alterations were associated with reduced disease free and overall survival (p = 0.051, log rank), with a univariate (unadjusted) hazard ratio (HR) of 2.241 (95% confidence limits (CL) = 0.973, 5.159; p = 0.058) for overall survival. By multivariate analysis adjusted for other relevant variables, the HR for tumours with p53 alterations was estimated at 2.913 (95% CL = 1.069, 7.936; p = 0.036) for overall survival. CONCLUSIONS: This study reports novel p53 mutations (exon 10), and an association between increasing consumption of hot beverages as a risk factor for p53 mediated oesophageal cancer. p53 is a potentially useful prognostic marker in this disease.     

Comparison of fixed concentration and fixed ratio options for dilution susceptibility testing of gram-negative bacilli to ampicillin and ampicillin/sulbactam

Ampicillin combined with sulbactam was tested at both fixed ratio (2:1 and 1:1) and fixed sulbactam concentrations (4 µg/ml, 8 µg/ml and 16 µg/ml) against 2440 consecutively isolated gram-negative bacilli. Sulbactam significantly enhanced the spectrum of ampicillin activity. Overall, at 8 µg/ml ampicillin inhibited 50 % of theEnterobacteriaceae isolates, whereas 69 % to 84 % of the isolates were inhibited by the various sulbactam combinations. The widest spectrum of activity for ampicillin/sulbactam was achieved by testing at a fixed sulbactam concentration of 16 µg/ml, followed by the 1:1 ratio and the fixed 8 µg/ml (84 %, 76 % and 74 % inhibited, respectively). The amount of sulbactam at the susceptible breakpoint concentrations of ampicillin markedly affected the percentage of susceptible strains. Combinations that include 8 µg/ml of sulbactam are suggested for consideration.     

Rapid detection (4 h) of methicillin-resistant Staphylococcus aureus by a bioluminescence method.

A 4-h bioluminescence method for methicillin susceptibility determination was compared with reference methods. Of the Staphylococcus aureus strains tested, 80 were methicillin resistant, 180 were methicillin susceptible, and 10 were borderline susceptible. There was 100% correlation between bioluminescence and reference methods for methicillin-susceptible and methicillin-resistant strains. All borderline-susceptible strains were identified as methicillin resistant by bioluminescence.     

Detection of two forms of GP330. Their role in Heymann nephritis.

Heymann nephritis is characterized by glomerular immune deposits that contain a glycoprotein called gp330. The deposits are believed to result from shedding of immune complexes formed on podocytes. Complexes are also shed from proximal tubule cells, when antibodies combine with gp330 on the cell surface. We performed the present study to investigate what portion of the gp330 molecule is shed, using a rabbit antiserum against a peptide deduced to be in the cytoplasmic domain of gp330, as well as a rabbit antiserum and two monoclonal antibodies that recognize extracellular epitopes of gp330. The anti-cytoplasmic peptide antiserum precipitated from Fx1A (a crude renal cortical membrane preparation), a protein with a mass of about 440 kd that was reactive with two monoclonal anti-gp330 antibodies. (In our experiments, the protein called gp330 generally has a mass estimated to be about 440 kd.) The anti-cytoplasmic peptide antiserum also reacted with a truncated gp330 protein produced in transfected COS cells. Immunohistochemical studies showed that all the antibodies recognized the same group of epithelial cells. However, as seen in immunoultrastructural studies of proximal tubules, the anti-cytoplasmic peptide antiserum reacted only with components at the base of microvilli, whereas the anti-gp330 ectodomain antibodies identified material not only at the base, but over the surface of microvilli as well. In rats with Heymann nephritis, glomerular deposits and material shed into tubule lumens reacted with antibodies against extracellular epitopes of gp330, but not with the anti-cytoplasmic peptide antiserum. We propose that there are two forms of gp330 on the cell surface of proximal renal tubules. One form is restricted to coated pit regions at the base of microvilli and has a cytoplasmic domain containing a sequence deduced from a partial complementary DNA encoding gp330. The other form is present over microvilli (and possibly at the base of microvilli as well) and lacks the cytoplasmic domain deduced from the complementary DNA. The complexes that are shed in Heymann nephritis contain either a portion of gp330 cleaved from the full-length molecule or a form of gp330 that lacks the cytoplasmic domain.