Carbonic anhydrase III (Car3) is not required for fatty acid synthesis and does not protect against high-fat diet induced obesity in mice

Carbonic anhydrases are a family of enzymes that catalyze the reversible condensation of water and carbon dioxide to carbonic acid, which spontaneously dissociates to bicarbonate. Carbonic anhydrase III (Car3) is nutritionally regulated at both the mRNA and protein level. It is highly enriched in tissues that synthesize and/or store fat: liver, white adipose tissue, brown adipose tissue, and skeletal muscle. Previous characterization of Car3 knockout mice focused on mice fed standard diets, not high-fat diets that significantly alter the tissues that highly express Car3. We observed lower protein levels of Car3 in high-fat diet fed mice treated with niclosamide, a drug published to improve fatty liver symptoms in mice. However, it is unknown if Car3 is simply a biomarker reflecting lipid accumulation or whether it has a functional role in regulating lipid metabolism. We focused our in vitro studies toward metabolic pathways that require bicarbonate. To further determine the role of Car3 in metabolism, we measured de novo fatty acid synthesis with in vitro radiolabeled experiments and examined metabolic biomarkers in Car3 knockout and wild type mice fed high-fat diet. Specifically, we analyzed body weight, body composition, metabolic rate, insulin resistance, serum and tissue triglycerides. Our results indicate that Car3 is not required for de novo lipogenesis, and Car3 knockout mice fed high-fat diet do not have significant differences in responses to various diets to wild type mice.

A gnotobiotic mouse model demonstrates that dietary fiber protects against colorectal tumorigenesis in a microbiota- and butyrate-dependent manner

Whether dietary fiber protects against colorectal cancer is controversial because of conflicting results from human epidemiologic studies. However, these studies and mouse models of colorectal cancer have not controlled the composition of gut microbiota, which ferment fiber into short-chain fatty acids such as butyrate. Butyrate is noteworthy because it has energetic and epigenetic functions in colonocytes and tumor-suppressive properties in colorectal cancer cell lines. We used gnotobiotic mouse models colonized with wild-type or mutant strains of a butyrate-producing bacterium to demonstrate that fiber does have a potent tumor-suppressive effect but in a microbiota- and butyrate-dependent manner. Furthermore, due to the Warburg effect, butyrate was metabolized less in tumors where it accumulated and functioned as a histone deacetylase (HDAC) inhibitor to stimulate histone acetylation and affect apoptosis and cell proliferation. To support the relevance of this mechanism in human cancer, we demonstrate that butyrate and histone-acetylation levels are elevated in colorectal adenocarcinomas compared with normal colonic tissues.

SIGNIFICANCE

These results, which link diet and microbiota to a tumor-suppressive metabolite, provide insight into conflicting epidemiologic findings and suggest that probiotic/prebiotic strategies can modulate an endogenous HDAC inhibitor for anticancer chemoprevention without the adverse effects associated with synthetic HDAC inhibitors used in chemotherapy.

Differential effects of low-level lead exposure on the natural isozymes of erythrocyte 5'-nucleotidase

OBJECTIVE

Erythrocyte pyrimidine 5'-nucleotidase (Pyr-5'-N) is highly sensitive to heavy metal inactivation in vitro and in vivo, and a number of studies have verified its usefulness as a biomarker of acute and chronic lead exposures. Retrospective and prospective studies attempted to determine whether the known linearity of Pyr-5'-N inhibition by lead concentrations above 40 microg/dL whole blood might continue into the lowest range of exposures now considered to be toxic in children (<10-20 microg/dL), thereby extending its value as a biomarker of lead exposure.

DESIGN

Activities of Pyr-5'-N and a lead-insensitive isozyme, deoxyribonucleotidase (d-5'-N), were compared to blood lead and free erythrocyte protoporphyrin (FEP) concentrations.

RESULTS

Pyr-5'-N activities in erythrocytes from 70 children displayed an inverse linear correlation with whole blood lead of 1-35 microg/dL, whereas d-5'-N did not correlate. There was no apparent minimum threshold for Pyr-5'-N inhibition by lead.

CONCLUSIONS

Linearity of Pyr-5'-N inhibition by lead extends throughout the range of clinical concern in pediatric cases. Pyr-5'-N/d-5'-N activity ratios may provide an even more sensitive, internally controlled biomarker of low-level lead overburden, since both isozymes vary comparably in activity as a function of reticulocytosis and mean red cell age.

The red blood cell utilization review experience

The Joint Commission on Accreditation of Healthcare Organizations catalyzed peer-review of blood transfusion and gave it new form in 1984. This process became mostly comprehensive, retrospective, bi-level, and chart-based with an initial screening phase followed by physician- review. Studies were identified and evaluated to test the efficacy of this process, which has recently come under question. In two-thirds of the studies, transfusions were judged appropriate in over 90% of cases. In most hospitals reporting, there were no inappropriate transfusions. It is concluded that the process often results in too few inappropriate cases to readily identify opportunities for improvement.

Reasons for proficiency testing failures in clinical chemistry and blood gas analysis: a College of American Pathologists Q-Probes study in 665 laboratories

OBJECTIVE

To determine the reasons for proficiency testing (PT) failures from 41 chemistry and blood gas analytes using data collected to benchmark performance.

DESIGN

Self-administered survey requesting number of challenges by analyte encompassing nine PT events. When the challenge resulted in a self-defined failure, further information was requested concerning the magnitude of the failure (as a standard deviation index) and categorization of the type of failure into six major groups (Methodologic, Technical, Clerical, Survey, Unexplained, or Other) and then into subgroups.

PARTICIPANTS

Laboratories enrolled in the 1992 College of American Pathologists Q-Probes program.

MAIN OUTCOME MEASURES

Rate of PT failures and reasons for failure.

RESULTS

Proficiency testing data from 670,489 challenges performed in 665 laboratories revealed 9268 (1.4%) unacceptable results. Failure types were distributed as follows: Methodologic, 33.5%; Technical, 17.4%; Clerical, 11.1%; Survey, 7.8%; Unexplained, 25.7%; and Other, 7.4%.

CONCLUSIONS

Individual analyte PT failure is a common event in the participating laboratories, but failures in successive or alternate events are rare. Analysis of the reasons for failed events indicates that most identified reasons occurred in either the Methodologic or Technical categories (50.9%). Analysis of the failure types suggested investigation pathways based on the magnitude of the failure that could reduce the 25.7% rate of unexplained failures.

The use of Q-Probes in modifying transfusion practice

Interinstitutional comparison is a powerful tool to examine quality issues in transfusion medicine. The large and varied database comprised by participants in the College of American Pathologists' (Northfield, Ill) Q-Probes program facilitates peer comparison and allows for extensive categorization of practices. Measurements of autologous blood transfusion practices in 1990, and again in 1992, in two autologous blood transfusion Q-Probes studies revealed reductions in unwarranted collections of autologous blood for surgical procedures with low requirements for blood replacement and in unwarranted transfusions of available autologous units. These changes followed recommendations for improvement by the Q-Probes' authors. The effects of forces from outside hospitals on transfusion practice were revealed in the 1992 study in the higher autologous blood discard rates in those US states that require an explanation of transfusion options to patients prior to elective surgery.

Hemolytic anemia associated with lead poisoning from shotgun pellets and the response to Succimer treatment

Symptomatic lead poisoning with severe hemolytic anemia was observed in a patient with retained shot gun pellets. Surgical resection of the retained pellets and the use of a newer chelating agent, Succimer (2,3-dimercaptosuccinic acid) successfully lowered blood lead level. Hemolytic anemia was associated with deficient erythrocyte pyrimidine 5'-nucleotidase, and lowering of the lead level corrected the deficiency, suggesting that the enzyme deficiency is responsible for the hemolysis associated with lead poisoning. This case illustrates that retained lead pellets from shotgun wounds can cause severe lead poisoning.

Wristband identification error reporting in 712 hospitals. A College of American Pathologists' Q-Probes study of quality issues in transfusion practice

The correct wristband identification of patients is essential to prevent acute, hemolytic transfusion reactions from incompatible transfusion. We compared wristband identification errors for 712 hospitals. Phlebotomists checked patient wristbands on 2,463,727 occasions, finding 67,289 errors; in 33,308 instances, patient wristbands were missing entirely. The median total error rate was 2.2%; 10% of participants had error rates of 10.9% or greater. Absent wristbands represented 49.5% of errors; multiple wristbands with different information, 8.3%; wristbands with incomplete data, 7.5%; erroneous data, 8.6%; illegible data, 5.7%; and patients wearing wristbands with another patient's identifying information, 0.5%. The monitoring for errors by phlebotomy staff was the most important policy associated with lower error rates. Initial placement of wristbands by nursing staff was the only policy associated with increased error rates. We conclude that wristband identification error rates depend on differences in hospital policy and procedure and should be responsive to quality improvement efforts.

Preoperative autologous blood donation in 612 hospitals. A College of American Pathologists' Q-Probes study of quality issues in transfusion practice

We compared predeposit autologous blood utilization practices in 612 hospitals (where 107,559 autologous and 2,504,522 homologous units were transfused in all of 1989). Participating blood bankers prospectively followed up donors who presented for initial donation during an 11-week period in early 1990. They recorded the number of autologous donors whose blood was drawn (n = 22,276); units that were donated (n = 40,163), transfused (n = 23,988), crossed over (n = 937), and discarded (n = 15,443); and donors transfused with autologous blood only (n = 11,923) or donors who received homologous blood (n = 2002). Most donors (89.7%) avoided homologous blood, including donors (39.5%) who did not require transfusion. Units that were donated for low-risk surgery represented 23.1% of all units that were collected, and the rate of donation for these procedures was directly proportional to the percentage of donors who did not require transfusion and to the discard rate. We concluded that a major focus of quality improvement in autologous transfusion practice should be the reduction of donations for surgical procedures for which blood replacement is rarely needed.

The battle of Gettysburg

When a small, struggling, rural healthcare facility mustered the courage to purchase a state-of-the-art hospital information system, the results were dramatic. Today, receivables have risen significantly, and overall operating efficiency has measurably improved.

Immunoblotting and dot immunobinding. Emerging techniques in protein immunochemistry

Immunoblotting (also known as Western blot) and dot immunobinding (also known as dot blot) immunoassays, used extensively in immunochemical research, have great potential significance for diagnostic testing in the clinical laboratory. Immunoblotting has distinct versatility in immunochemical test applications. Immunoblotting combines the power of gel electrophoresis for resolving the electrophoretic variants of immunologically cross-reacting proteins with the ease and sensitivity of immunodetection on a solid-phase immunoassay. The potential for diagnostic applications includes: assay of antigens from pathologic serum samples, body fluids, and tissue; assay of patient serum samples for antibody against known antigen; and separation and assay of patient immunoglobulin. The usefulness of these applications is enhanced by the possibility of simultaneous use of nonantibody ligand, reversible protein staining, or, in the case of enzyme proteins, the use of substrate to detect activity. Dot immunobinding, in a similar fashion, permits assays of multiple specimens simultaneously on single strips of blotting media using sample sizes as small as 0.1 microL. Also, both immunoblotting and dot immunobinding techniques permit sequential probing of antigens with different antisera, with subsequent elution and recovery of specific antibody probes.

Toward meaningful blood usage review: comprehensive monitoring of physician practice

During a one-year period, all blood transfusions at an acute care Veterans Administration hospital were concurrently reviewed. Inappropriate transfusion episodes represented less than 2% of the total according to clinical criteria established for purposes of screening cases. The percentage of episodes reviewed that did not meet the screening criteria decreased progressively (3.6% to 0.3%) during the study period. Episodes in which red blood cells (RBC) or fresh frozen plasma (FFP) alone and RBC and FFP together were transfused comprised almost all of the cases that were unjustified by peer review. The findings indicated that, although comprehensive review may document the overall appropriateness of clinical transfusion practice, more detailed profiling of clinical circumstances of each episode is necessary to provide convincing arguments for major revisions in hemotherapy practice.