Direct 24-Hour Presumptive Enumeration of Escherichia coli 0157:H7 in Foods Using Hydrophobic Grid Membrane Filter Followed by Serological Confirmation: Collaborative Study

Fifteen laboratories took part in a collaborative study to validate a method for enumerating Escherichia coli 0157:H7. The method is based on use of a hydrophobic grid membrane filter and consists of 24 h presumptive enumeration on SD-39 Agar and serological confirmation to yield a confirmed E. coli 0157:H7 count. Six food products were analyzed: pasteurized apple cider, pasteurized 2% milk, cottage cheese, cooked ground pork, raw ground beef, and frozen whole egg. The test method produced significantly higher confirmed count results than did the reference method for milk, pork, and beef. Test method results were numerically higher than but statistically equivalent to reference method results for cheese, cider, and egg. The test method produced lower repeatability and reproducibility values than did the reference method for most food/inoculation level combinations and values very similar to those of the reference method for the remaining combinations. Overall, 94% of presumptive positive isolates from the test method were confirmed serologically as E. coli 0157:H7, and 98% of these were also biochemically typical of E. coli 0157:H7 (completed test). Corresponding rates for the reference method were 69 and 98%, respectively. On the basis of the results of this collaborative study and the precollaborative study that preceded it, it is recommended that this method be adopted official first action for enumeration of E. coli 0157:H7 in meats, poultry, dairy foods, infant formula, liquid eggs, mayonnaise, and apple cider

Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

Aerobic exercise and lumbar spine bone mineral density in postmenopausal women: a meta-analysis

PURPOSE

To use the meta-analytic approach to examine the effects of aerobic exercise on lumbar spine bone mineral density in postmenopausal women.

DATA SOURCES

Studies were retrieved from computer searches (MEDLINE, Current Contents) as well as cross-referencing from the bibliographies of retrieved studies and review articles.

STUDY SELECTION

A total of 17 effect sizes consisting of 330 subjects (192 exercise, 138 nonexercise) were included from the 10 studies that met the criteria for inclusion: (1) aerobic activity as the only exercise intervention, (2) postmenopausal women as subjects, (3) comparative nonexercise group included, (4) changes in lumbar spine bone mineral density reported, (5) studies published in English-language journals between January 1975 and December 1994.

DATA EXTRACTION

The primary outcome measure of interest was the treatment effect delta3, defined as the percent change in lumbar spine bone mineral density, calculated by subtracting the percent change in the exercise group from the percent change in the nonexercise group.

RESULTS

Using a fixed effects model, bootstrap analysis (10,000 replications) showed that significant changes in lumbar spine bone mineral density occurred (mean +/- SD = 2.83 +/- 0.77%, 95% confidence interval (CI) = 1.33 to 4.35%). This overall average increase was caused primarily by the loss of lumbar spine bone mineral density in the nonexercise group relative to the exercise group (mean +/- SD, exercise = .32 +/- 2.46%, 95% CI = -0.94 to 1.58; nonexercise = -2.51 +/- 2.69%, 95% CI = -4.60 to -0.96).

CONCLUSION

The results of this meta-analysis suggest that aerobic exercise helps to maintain lumbar spine bone mineral density in postmenopausal women.

Dynamic resistance exercise and resting blood pressure in adults: a meta-analysis

With the use of the meta-analytic approach, the purpose of this study was to examine the effects of dynamic resistance exercise, i.e., weight training, on resting systolic and diastolic blood pressure in adults. A total of nine studies consisting of 259 subjects (144 exercise, 115 control) and 18 groups (9 exercise, 9 control) were included in this analysis. With the use of the bootstrap technique (10,000 samples), significant treatment effect (delta 3) reductions were found across all designs and categories for both systolic and diastolic blood pressure [systolic, mean +/- SD = -4.55 +/- 1.75 mmHg, 95% confidence interval (CI) = -1.56 to -8.56; diastolic, mean +/- SD = -3.79 + 1.12 mmHg, 95% confidence interval CI = -1.89 to -6.33]. Delta 3 changes corresponded with relative decreases of approximately 3 and 4% in resting systolic and diastolic blood pressure, respectively. In conclusion, meta-analytic review of included studies suggests that dynamic resistance exercise reduces resting systolic and diastolic blood pressure in adults. However, it is premature to form strong conclusions regarding the effects of dynamic resistance exercise on resting blood pressure. A need exists for additional, well-designed studies on this topic before a recommendation can be made regarding the efficacy of dynamic resistance exercise as a nonpharmacological therapy for reducing resting blood pressure in adults, especially in hypertensive adults.

Mechanical overload and skeletal muscle fiber hyperplasia: a meta-analysis

With use of the meta-analytic approach, the purpose of this study was to examine the effects of mechanical overload on skeletal muscle fiber number in animals. A total of 17 studies yielding 37 data points and 360 subjects met the initial criteria: 1) "basic" research studies published in journals, 2) animals (no humans) as subjects, 3) control group included, 4) some type of mechanical overload (stretch, exercise, or compensatory hypertrophy) used to induce changes in muscle fiber number, and 5) sufficient data to accurately calculate percent changes in muscle fiber number. Across all designs and categories, statistically significant increases were found for muscle fiber number [15.00 +/- 19.60% (SD), 95% confidence interval = 8.65-21.53], muscle fiber area (31.60 +/- 44.30%, 95% confidence interval = 16.83-46.37), and muscle mass (90.50 +/- 86.50%, 95% confidence interval = 61.59-119.34). When partitioned according to the fiber-counting technique, larger increases in muscle fiber number were found by using the histological vs. nitric acid digestion method (histological = 20.70%, nitric acid digestion = 11.10%; P = 0.14). Increases in fiber number partitioned according to species were greatest among those groups that used an avian vs. mammalian model (avian = 20.95%, mammalian = 7.97%; P = 0.07). Stretch overload yielded larger increases in muscle fiber number than did exercise and compensatory hypertrophy (stretch = 20.95%, exercise = 11.59%, compensatory hypertrophy = 5.44%; P = 0.06). No significant differences between changes in fiber number were found when data were partitioned according to type of control (intra-animal = 15.20%, between animal = 13.90%; P = 0.82) or fiber arrangement of muscle (parallel = 15.80%, pennate = 11.60%; P = 0.61). The results of this study suggest that in several animal species certain forms of mechanical overload increase muscle fiber number.

Two-Day Hydrophobic Grid Membrane Filter Method for Yeast and Mold Enumeration in Foods Using YM-11 Agar: Collaborative Study

Twenty laboratories participated in a collaborative study to validate a 2-day hydrophobic grid membrane filter method using YM-11 agar for enumeration of yeast and mold in foods. Six naturally contaminated food products were included in the study: garlic powder, raw ground beef, walnuts, flour/meal, orange juice, and yogurt. The test method produced significantly higher results than the 5-day pour plate reference method for orange juice and significantly lower, though numerically similar, results for walnuts and yogurt. Differences between the test and reference methods were not significant for garlic powder, raw ground beef, or flour/meal. Repeatability and reproducibility were similar for both the test and reference methods in all cases. The hydrophobic grid membrane filter method for enumeration of yeast and mold in foods has been adopted by AOAC INTERNATIONAL.

Aerobic exercise and normotensive adults: a meta-analysis

Using the meta-analytic approach, the purpose of this study was to examine the effects of aerobic exercise on resting systolic (SYS) and diastolic (DIA) blood pressure in normotensive adults: The results of 35 human clinical training studies published in English-language journals between 1963 and 1992 and representing 1,076 subjects (800 exercise, 276 control) met criteria for inclusion. Across all categories and designs, statistically significant post-exercise reductions were found for both SYS and DIA blood pressure (mean +/- SD, SYS: -4.4 +/- 6.6 mm Hg, 95% CI, -6.2 to -2.6 mm Hg; DIA: -3.2 +/- 3.2 mm Hg, 95% CI, -4.0 to -2.2 mm Hg). When partitioned according to type of study: 1) (randomized controlled trials (RCT), 2) controlled trials (CT), and 3) no controls (NC), the following changes were noted: RCT, SYS: -4.5 +/- 7.2 mm Hg, 95% CI, -7.1 to -1.2 mm Hg; DIA: -3.8 +/- 2.9 mm Hg, 95% CI, -5.0 to -2.6 mm Hg; CT, SYS: -2.8 +/- 6.9 mm Hg, 95% CI, -10.0 to 4.4 mm Hg; DIA: -5.0 +/- 3.7 mm Hg, 95% CI, -8.9 to -1.1 mm Hg; NC, SYS: -4.7 +/- 6.1 mm Hg, 95% CI, -7.5 to 1.9 mm Hg; DIA: -1.7 +/- 3.0 mm Hg, 95% CI, -3.2 to -0.36 mm Hg. We concluded that aerobic exercise results in small reductions in resting SYS and DIA blood pressure among normotensive adults.

Antihypertensive effects of aerobic exercise. A brief meta-analytic review of randomized controlled trials

The purpose of this study was to examine the antihypertensive effects of lower extremity aerobic exercise on resting systolic and diastolic blood pressure among hypertensive adults. Nine studies representing a total of 245 subjects (147 exercise, 98 control) met the criteria for inclusion. Using the meta-analytic technique, exercise-induce effect size reductions significantly different from zero were found for both resting systolic and diastolic blood pressure (mean +/- SD, systolic: 0.63 +/- 0.66, 95% confidence interval, 0.12 to 1.14; diastolic: 0.35 +/- 0.19, 95% confidence interval, 0.19 to 0.49). Effect sizes corresponded with decreases of approximately 7 +/- 5 and 6 +/- 2 mm Hg for resting systolic and diastolic blood pressure, respectively. None of the changes were significant for the control groups. The results of this study suggest that lower extremity aerobic exercise has an antihypertensive effect on resting systolic and diastolic blood pressure in adults. However, a need exists for more meticulously controlled investigations on this topic.

Interactions between Ca2+ and cAMP messenger system in regulation of airway smooth muscle contraction

Cholinergic stimuli acting via muscarinic receptors stimulate airway smooth muscle to contract and beta-adrenergic stimuli induce it to relax. Cholinergic agonists stimulate intracellular Ca2+ release and Ca2+ influx, and beta-adrenergic agonists stimulate adenosine 3',5'-cyclic monophosphate (cAMP) production. Since it was found that cAMP alters cholinergic agonist-induced changes in cellular Ca2+ metabolism, it was postulated that cAMP brought about a relaxation of this smooth muscle primarily by altering Ca2+ metabolism. More recently, it has become clear that when cholinergic agonists, as well as histamine and serotonin, act, the hydrolysis of polyphosphoinositols is stimulated, diacylglycerol production is increased, and coordinated changes in Ca2+ metabolism and protein kinase function occur. These agonists also act to inhibit adenylate cyclase activity. Conversely, it has been found that in the absence of agonist activation, cAMP increases Ca2+ influx without stimulating contraction and that in the presence of muscarinic agonists, it acts to inhibit polyphosphoinositide hydrolysis. In addition, cAMP has been shown to alter the state of phosphorylation of a number of cellular proteins, an effect that is independent of any effect on cellular Ca2+ metabolism. Based on these newer data, an expanded model of Ca2(+)-cAMP interactions in the regulation of airway smooth muscle tone is presented. A key feature of this model is the operation of dual, reciprocal inhibitory signals by which the Ca2+ and cAMP messenger systems modulate each other's expression.

Protein phosphorylation changes in bovine carotid artery smooth muscle during contraction and relaxation

The protein phosphorylation changes associated with the contraction and relaxation of bovine carotid artery smooth muscle were studied using two-dimensional gel electrophoresis of labeled phosphoproteins. Muscle was stimulated with histamine, angiotensin II, 12-deoxyphorbol 13-isobutyrate (DPB) or high extracellular K+. Histamine induced a rapid and sustained contraction which was associated with an early (2 min) phosphorylation of 20 kDa myosin light chain (MLC) and two cytosolic proteins, Nos. 1 and 2, and with the late (60 min) phosphorylation of MLC, two isoelectric variants of desmin and ten other cytosolic proteins. Additionally, there was a decrease in the extent of phosphorylation of two cytosolic proteins, Nos. 9 and 10. Angiotensin II induced a rapid but transient contraction which was associated with the same early (2 min) phosphorylation changes, but with none of the late (60 min) changes. Elevation of the extracellular K+ concentration to 110 mM led to a sustained contraction which was associated with the phosphorylation of MLC and proteins Nos. 1 and 2 at both 2 and 60 min, but none of the other late phase phosphoproteins were seen. Addition of DPB, an activator of protein kinase C, induced a slowly developing but sustained contractile response which was associated with none of the early (5 min) phosphorylation changes. However, nearly all of late (60 min) protein phosphorylation changes were the same as those seen after histamine action. Addition of forskolin to either control or histamine-treated muscle led to an increase in the phosphorylation of three cytosolic proteins (Nos. 3, 8 and 13), and in the histamine-contracted muscle the dephosphorylation of MLC and proteins Nos. 4, 9, 10, 15 and 16. Similarly, forskolin induced a relaxation of DPB-treated muscle and the dephosphorylation of proteins Nos. 4, 9, 10, 15 and 16. These results suggest that there are two pathways by which histamine activates contraction: a Ca2+-calmodulin pathway which initiates the response, and a protein kinase C pathway which, along with the Ca2+-calmodulin pathway, sustains contraction.