Single dose streptozotocin-induced diabetes: considerations for study design in islet transplantation models.

Streptozotocin (STZ)-induced diabetes mellitus (DM) offers a very cost-effective and expeditious technique that can be used in most strains of rodents, opening the field of DM research to an array of genotypic and phenotypic options that would otherwise be inaccessible. Despite widespread use of STZ in small animal models, the data available concerning drug preparation, dosing and administration, time to onset and severity of DM, and any resulting moribundity and mortality are often limited and inconsistent. Because of this, investigators inexperienced with STZ-induced diabetes may find it difficult to precisely design new studies with this potentially toxic chemical and account for the severity of DM it is capable of inducing. Until a better option becomes available, attempts need to be made to address shortcomings with current STZ-induced DM models. In this paper we review the literature and provide data from our pancreatic islet transplantation experiments using single high-dose STZ-induced DM in NCr athymic nude mice with hopes of providing clarification for study design, suggesting refinements to the process, and developing a more humane process of chemical diabetes induction.

Utilization of a test gradient enhances islet recovery from deceased donor pancreases.

BACKGROUND: Islet transplantation is a viable treatment alternative for a select group of patients with type 1 diabetes. However, variables unique to the donor pancreas, such as age, fibrosis and edema, can influence the number and purity of the isolated islets. Thus isolation of a sufficient number of islets for transplantation from the pancreas remains challenging because of the lack of methods enabling reproducible isolation. METHODS: Islets were isolated from 38 consecutive deceased donors using the semi-automated Ricordi method of islet isolation, and purified on a COBE 2991 cell processor using Ficoll-based continuous density gradients. Three different gradient protocols were used. These included a pre-defined gradient using different densities of Ficoll (1.100 g/mL and 1.077 g/mL) mixed with HBSS (group 1), a pre-defined gradient using single-density Ficoll (1.100 g/mL) mixed with University of Wisconsin solution (UW) (group 2) and a variable gradient using single-density Ficoll (1.100 g/mL) with UW and densities selected based on the results of test gradients (group 3). RESULTS: Group 3 yielded a better recovery of islets (74%) than groups 1 (43%) or 2 (37%) (P=0.0144). Viability was significantly higher in groups 2 and 3 (P=0.0115). Purity was not significantly different among the groups. DISCUSSION: This method, using a simple test gradient, is a significant process improvement that can improve islet recovery without loss of viability or purity and increase the number of islet products suitable for transplantation.

Rapid assay for bactericidal antibodies.

Microtiter plates were successfully substituted for tubes in the bactericidal test for opsonic antibodies. This method is efficient and should prove useful for screening large numbers of sera.

Preliminary evaluation of the ligase chain reaction for specific detection of Neisseria gonorrhoeae.

Rapid identification of Neisseria gonorrhoeae in clinical specimens is essential for effective control. Traditional culture requires a minimum of 24 h, and for some specimens harboring gonococci, the gonococci fail to grow or are misidentified. The recently described ligase chain reaction (LCR) is a highly specific and sensitive DNA amplification technique which was evaluated as an alternative to routine culture. Three LCR probe sets were used. Two of the probe sets were directed against the multi-copy Opa genes (Omp-II), while the third set was targeted against the multicopy Pilin genes. Each LCR probe set was evaluated with 260 microorganisms including 136 global isolates of N. gonorrhoeae, 41 isolates of N. meningitidis, and 10 isolates of N. lactamica; 26 nonpathogenic Neisseria strains; and 47 isolates of non-Neisseria species that may reside in clinical specimens. Amplification products were detected by using the IMx LCR format (Abbott Laboratories, Abbott Park, Ill.). Strains of N. gonorrhoeae were assayed at 270 cells per LCR (approximately 6.7 x 10(4) CFU/ml) with the Opa and Pilin probes, producing signals at least 21 and 15 times above background, respectively. In contrast, only background values were observed when testing the probe sets with 124 nongonococcal strains at 1.3 x 10(6) cells per LCR (approximately 3.2 x 10(8) CFU/ml). One hundred urogenital specimens were assayed by LCR, and compared with culture, the three probes were 100% sensitive (8 of 8) and 97.8% specific (90 of 92), resulting in an agreement of 98% (98 of 100). On the basis of the results of these preliminary studies, LCR has the potential to be an accurate and rapid DNA probe assay for the detection of N. gonorrhoeae in clinical specimens.

Rapid methods for the immunodiagnosis of infectious diseases: recent developments.

Current techniques for rapid diagnosis of microbial infections by direct detection of the microbial agent are compared. The techniques include enzyme immunoassay (EIA) tests, immunofluorescence, latex agglutination assays, and nucleic acid hybridization procedures. It is concluded that, for the near future, the preferred methods for rapid diagnosis will be by (1) EIA tests utilizing monoclonal antibodies and improved enzyme detection systems, and (2) improved latex agglutination procedures for certain antigens. Nucleic acid hybridization techniques, as currently performed, will need to be substantially improved to become the methods of choice.

Sigmoid stricture at colonoscopy--an indication for surgery.

Strictures of the sigmoid colon continue to pose a diagnostic dilemma. They commonly appear to be due to diverticular disease but carcinoma must always be excluded. In some cases diverticula may be present but in others there is no obvious cause for the stricture. In a series of 1039 consecutive colonoscopies performed between 1984 and 1986, 19 cases of sigmoid stricture that could not be negotiated with the colonoscope were encountered. In each case the cause of the stricture could not be demonstrated. Fifteen patients (79%) underwent laparotomy primarily on clinical grounds or with barium enema findings suggestive of carcinoma. A final diagnosis of diverticular disease was made in nine cases and adenocarcinoma is six cases. Barium enema was a poor predictor of malignancy in a stricture. Four patients were treated conservatively and two of these patients continued to have significant symptoms due to diverticular disease. This experience suggests that sigmoid strictures that prevent the passage of a colonoscope should be resected when the cause of the stricture is not apparent.

Use of gonozyme on urine sediment for diagnosis of gonorrhea in males.

We compared enzyme immunoassay (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of gonococcal antigen in urine sediments with urethral swab culture for diagnosis of gonorrhea in men attending a venereal disease clinic. The prevalence of infection was 14% by culture (27/196). The sensitivity of enzyme immunoassay was 93% (25/27) compared with the culture method, and the specificity was 99% (167/169). The ability to detect gonococcal antigen in urine sediment may provide the basis for a noninvasive method of screening for gonococcal infection.

Strain differentiation of Neisseria gonorrhoeae by reverse passive hemagglutination.

A reverse passive hemagglutination test that utilizes human erythrocytes coated with antibody to gonococci was developed to distinguish differences among 11 strains of Neisseria gonorrhoeae. Different rabbits were immunized with each strain of gonococcus. Antibody was purified by passing antiserum over an immunoadsorbent column containing homologous cell walls trapped in a cross-linked polyacrylamide gel. Antibody, after absorption with N. meningitidis, was used for coating 11 individual suspensions of erythrocytes, each with antibody to one gonococcal strain. The panel of coated erythrocytes was added to microtiter trays containing dilutions of homologous bacterial lysate and lysates from 10 heterologous strains. Agglutination titers were highest with homologous lysates, although cross-reactions occurred among some heterologous lysates. Lysates of nongonococcal Neisseria species and of other genera did not agglutinate coated erythrocytes. The reverse passive hemagglutination test can be a useful procedure to distinguish differences among strains of N. gonorrhoeae.

Clinical sevoflurane metabolism and disposition. II. The role of cytochrome P450 2E1 in fluoride and hexafluoroisopropanol formation.

BACKGROUND: Sevoflurane is metabolized to free fluoride and hexafluoroisopropanol (HFIP). Cytochrome P450 2E1 is the major isoform responsible for sevoflurane metabolism by human liver microsomes in vitro. This investigation tested the hypothesis that P450 2E1 is predominantly responsible for sevoflurane metabolism in vivo. Disulfiram, which is converted in vivo to a selective inhibitor of P450 2E1, was used as a metabolic probe for P450 2E1. METHODS: Twenty-one patients within 30% of ideal body weight, who provided institutional review board-approved informed consent and were randomized to receive disulfiram (500 mg oral, n = 11) or nothing (control, n = 10) the night before surgery, were evaluated. All patients received sevoflurane (2.7% end-tidal, 1.3 MAC) in oxygen for 3 h after propofol induction. Thereafter, sevoflurane was discontinued, and anesthesia was maintained with propofol, fentanyl, and nitrous oxide. Blood sevoflurane concentrations during anesthesia and for 8 h thereafter were measured by gas chromatography. Plasma and urine fluoride and total (unconjugated plus glucuronidated) HFIP concentrations were measured by an ion-selective electrode and by gas chromatography, respectively, during anesthesia and for 96 h postoperatively. RESULTS: Patient groups were similar with respect to age, weight, sex, case duration, and intraoperative blood loss. The total sevoflurane dose, measured by cumulative end-tidal sevoflurane concentrations (3.7 +/- 0.1 MAC-h; mean +/- SE), total pulmonary uptake, and blood sevoflurane concentrations, was similar in both groups. In control patients, plasma fluoride and HFIP concentrations were increased compared to baseline values intraoperatively and postoperatively for the first 48 and 60 h, respectively. Disulfiram treatment significantly diminished this increase. Plasma fluoride concentrations increased from 2.1 +/- 0.3 microM (baseline) to 36.2 +/- 3.9 microM (peak) in control patients, but only from 1.7 +/- 0.2 to 17.0 +/- 1.6 microM in disulfiram-treated patients (P < 0.05 compared with control patients). Peak plasma HFIP concentrations were 39.8 +/- 2.6 and 14.4 +/- 1.1 microM in control and disulfiram-treated patients (P < 0.05), respectively. Areas under the plasma fluoride- and HFIP-time curves also were diminished significantly to 22% and 20% of control patients, respectively, by disulfiram treatment. Urinary excretion of fluoride and HFIP was similarly significantly diminished in disulfiram-treated patients. Cumulative 96-h fluoride and HFIP excretion in disulfiram-treated patient was 1,080 +/- 210 and 960 +/- 240 mumol, respectively, compared to 3,950 +/- 560 and 4,300 +/- 540 mumol in control patients (P < 0.05). CONCLUSIONS: Disulfiram, an effective P450 2E1 inhibitor, substantially decreased fluoride ion and HFIP production during and after sevoflurane anesthesia. These results suggest that P450 2E1 is a predominant P450 isoform responsible for human sevoflurane metabolism in vivo.

Antigen detection for the diagnosis of gonorrhea.

We compared the diagnostic value of an enzyme immunoassay method for detection of gonococcal antigen in genital secretions with culture results and direct Gram stain for Neisseria gonorrhoeae in 1,171 men and 723 women attending a sexually transmitted disease clinic. When compared with culture results in men, the immunoassay provided a sensitivity of 94% and a specificity of 98% and was essentially equivalent to the urethral Gram stain. The predictive value of a positive immunoassay was 97% in men with a urethral discharge in whom the prevalence of gonorrhea was 36%, and 30% in men without urethral discharge, who had a 2% prevalence of gonorrhea (P less than 0.001). The sensitivity of the immunoassay was 95% in men with and 67% in men without urethral discharge (P less than 0.01). In women, the immunoassay resulted in a sensitivity of 78% and a specificity of 98% compared with cervical culture and had a significantly better sensitivity than the cervical Gram stain (78 versus 48%, P less than 0.001). Analysis of patients with discrepant culture and immunoassay results suggested that most culture-negative, immunoassay-positive patients probably did not have gonorrhea. After treatment, all but 1 of 59 originally culture- and immunoassay-positive patients became negative in both tests by 3 days. Results of the immunoassay were not affected by transport or by refrigeration for up to 30 days.