Observational study of food safety practices in retail deli departments.

In order to improve the safety of refrigerated ready-to-eat food products prepared at retail deli departments, a better understanding of current practices in these establishments is needed. Food employees in deli departments at six chain and three independent retail establishments in Maryland and Virginia were observed, using notational analysis, as they prepared deli products for sale. The frequency of contact with objects and deli products before sale, hand washing and glove changing during preparation, and equipment, utensil, and surface cleaning and sanitizing was determined. Compliance with the U.S. Food and Drug Administration's 2005 model Food Code recommendations, which must be adopted by the individual state and local jurisdictions that are responsible for directly regulating retail establishments, was also assessed. Observations indicated there were a large number of actions for which hand washing was recommended at independent and chain stores (273 recommended of 1,098 total actions and 439 recommended of 3,073 total actions, respectively). Moreover, 67% (295 of 439) of the actions for which hand washing was recommended at the chain stores and 86% (235 of 273) of those at the independent stores resulted from employees touching non-food contact surfaces prior to handling ready-to-eat food. Compliance with hand washing recommendations was generally low and varied depending on store type with independent stores exhibiting lower compliance than chain stores (5 instances of compliance for 273 recommended actions and 73 instances of compliance for 439 recommended actions, respectively). Potential risk mitigation measures that may reduce the frequency of hand washing actions needed during ready-to-eat food preparation in retail deli departments are discussed. More research is needed to determine the impact of such measures on food safety.

Renal function in the elderly.

Renal size and volume decrease with age, accompanied by intrarenal vascular changes. The number of glomeruli decreases and the mass of the juxtamedullary nephrons falls. The result is a decrease in the filtration area of the glomerular basement membrane and decreased permeability. The glomerular filtration rate (GFR) is reduced with aging. The GFR is approximated by the endogenous creatinine clearance, which falls in parallel with the inulin clearance (the true measure of GFR) and is always greater because of tubular excretion of creatinine. Analytical methods for serum and urine creatinine overestimate its concentration and suffer, to varying degrees, from interferences, making the normal range method dependent. A further uncertainty arises from the use of a correction to standard surface area. Serum creatinine concentration is an insensitive indicator of renal function in the elderly. Deduction of creatinine clearance from serum creatinine concentration, weight and age using one of many formulae gives only approximate values, usually too high, and is unsuitable for debilitated and seriously ill patients. Tubular function, in general, is decreased in the elderly. The ability of the kidney to concentrate urine maximally after water deprivation decreases with age, as does the ability to excrete a water and salt load, particularly during the night. Nocturnal polyuria is common in the elderly. The aged kidney can maintain acid-base balance under normal conditions, but not when subjected to an acid load.

Hematologic side effects of drugs.

Bone marrow and peripheral blood cells may be adversely affected by drugs. Although the risk from most drugs is very small, many cases are reported because of the millions of doses of drugs taken each year by the population. Neutropenia, thrombocytopenia, hemolytic anemia, aplastic anemia, and macrocytic anemia are the commonest effects, in that order. Aplastic anemia is rare, but very serious when it does occur. Adverse effects may be produced by a direct toxic action of the drug or its metabolites on the bone marrow or, less often, on circulating cells. Antineoplastic drugs and chloramphenicol are examples. Most drugs produce their adverse effects through an immunological mechanism. The drug may act as a hapten or may affect the immune system leading to the production of antidrug antibodies and sometimes autoantibodies. Hemolytic anemia may result. Penicillins may behave in this manner. Some drugs act on erythrocytes with enzyme defects, e.g. glucose-6-phosphate dehydrogenase (G-6-PD) abnormalities, to produce hemolysis. In many cases, the mechanism underlying the adverse effect is unknown. The paper lists the drugs reported to have caused some hematological adverse effect and describes the mechanisms in those cases where they are known.

Hyperglobulinemia may spuriously elevate measured serum inorganic phosphate levels.

Pseudohyperphosphatemia was noted in four patients with hyperglobulinemia when inorganic phosphate levels were measured on the Vickers M-300 discrete automated analyzer (Vickers, Raritan, NJ) used by our clinical laboratory. When the same samples were reanalyzed after protein removal by sulfosalicylic acid precipitation, ultrafiltration, or more extensive dilution, the measured serum inorganic phosphate levels were invariably normal. The addition of human globulin (but not albumin), to pooled normal sera, caused an increase in serum inorganic phosphate levels as measured by the discrete analyzer. The increase correlated with the amount of globulin added (r = 0.72, P less than 0.05), but measured levels did not reach those observed in the hyperphosphatemic, hyperglobulinemic patients. Identification of 13 additional hyperglobulinemia patients revealed that hyperglobulinemia was not invariably associated with hyperphosphatemia. These data suggest that (1) with discrete automated analyzer use, hyperglobulinemia but not hyperalbuminemia may falsely elevate serum inorganic phosphate levels; (2) increased measured serum inorganic phosphate levels appear to be determined by both the concentration and the physicochemical characteristics of the globulin; (3) physicians should avoid prescribing phosphate binders to hyperglobulinemia patients with "hyperphosphatemia" unless they have ascertained that the serum inorganic phosphate level has been measured in a specimen that is free of protein; and (4) the occurrence of "pseudohyperphosphatemia" should suggest the need for an evaluation to rule out the presence of a monoclonal gammopathy.

Drug abuse in the workplace.

A program for drug-testing in the workplace requires careful planning. There should be a written policy, detailing for which drugs should there be testing, personnel to be tested, frequency and mode of testing, and sanctions if the tests are positive. Urine collection is best carried out under direct vision, but this may create problems because of invasion of privacy. A chain of custody for the urine specimen must be established and confidentiality of the employee's name maintained. The choice of drugs depends on the employer's objectives, but the illicit "street" drugs should be included. The drug testing laboratory should be carefully selected. Drug screening should be by an antibody method and all positive screening tests must be confirmed by gas chromatography or, even better, by gas chromatography/mass spectrometry. Concentrations of drugs constituting a positive test should be established. These values are usually set by the manufacturers of the reagent kits. Interpretation of positive results should be made by an expert and not by lay staff. Positive results for some drugs may result from prescription medication or food.

Bacterial toxins.

Many bacterial toxins are proteins, encoded by the bacterial chromosomal genes, plasmids or phages. Lysogenic phages form part of the chromosome. The toxins are usually liberated from the organism by lysis, but some are shed with outer membrane proteins in outer membrane vesicles. An important non-protein toxin is lipopolysaccharide or endotoxin, which is a constituent of the cell wall of gram negative bacteria. Toxins may damage the eukaryotic cell membrane by combining with some structural component, or otherwise alter its function. Many toxins combine with specific receptors on the surface membrane, frequently glycoproteins or gangliosides, and penetrate the cell to reach their intracellular target. A common mechanism of entry is absorptive endocytosis. Many protein toxins have an A-B structure, B being a polypeptide which binds to the receptor and A being an enzyme. Many toxins are activated, either when produced by the bacterium or when bound to the membrane receptor, by proteases (nicking). An enzymatic process common to many toxins is adenosine diphosphate (ADP)-ribosylation of the adenylate cyclase regulatory proteins, leading to an increase in intracellular cyclic adenosine monophosphate (cAMP). This is the mechanism of action of cholera toxin. Diphtheria toxin catalyzes the transfer of ADP-ribose to elongation factor-2, inhibiting protein synthesis. Most toxins act on the target cells to which they bind, but tetanus toxin, and, to a lesser degree, botulinum toxin, ascend axons and affect more distant structures. Although many toxin effects caused by bacteria have been described, only a few toxins have been identified, characterized, and their mode of action determined at the molecular level. The best known of these are discussed.

Comparison ot two methods of measurements of the same substance: an evaluation of some statistical procedures.

Linear regression analysis and calculation of the correlation coefficient are usually used to compare the results of two methods of measurement of the same substance. The limitations of these procedures are illustrated with numerical examples, in which X (the independent variable contains random errors of measurement. Formulas are given for estimating a linear functional relationship in this case. An alternative procedure, not involving linear regression, is described in which means and variances of replicate measurements by each method are compared at various concentrations over the analytical range. The appropriate statistical tests are discussed.

Serum and red cell magnesium levels in patients with premenstrual tension.

Magnesium deficiency has been implicated as a possible causative factor in premenstrual tension (PMT). We have assessed serum and red cell magnesium concentration in nine normal premenopausal women and 26 PMT patients, using atomic absorption spectrometry. The following means +/- SEM were obtained from serum and red cell magnesium, respectively, in mg/100 ml: normal subjects: 1.7 +/- 0.04 and 4.5 +/- 0.25 PMT patients: 1.8 +/- 0.05 and 3.1 +/- 0.24. Mean red cell magnesium level was significantly (p less than 0.01) lower in PMT patients. Red cell magnesium determinations should be included in the evaluation of PMT.

Effect of vitamin B-6 on plasma and red blood cell magnesium levels in premenopausal women.

The effect of 100 mg of vitamin B6 twice a day on plasma and red blood cell (RBC) magnesium was evaluated in nine premenopausal subjects during the period of one month. According to reported normal ranges for plasma and RBC magnesium (1.7 to 2.3 and 4.7 to 7.0, mg per dl, respectively), three subjects had low plasma magnesium, and all subjects had low RBC magnesium during the control period. Following vitamin B6 administration, the mean plasma and RBC magnesium levels were significantly elevated, with a doubling of RBC levels after four weeks of therapy. These results support the postulate that vitamin B6 plays a fundamental role in the active transport of minerals across cell membranes.

Lead toxicity and heme biosynthesis.

Lead intoxication results in a disturbance of heme biosynthesis, its degree depending on the severity and duration of exposure to lead. A mild secondary, sideroblastic anemia is common; basophilic stippling may occur, especially in severe lead poisoning. Increased excretion in the urine of delta-aminolevulinic acid and coproporphyrin III may occur; porphobilinogen excretion is not usually increased. Delta-aminolevulinate dehydratase, coproporphyrin oxidase, and ferrochelatase activities are reduced; delta-aminolevulinate synthetase activity is increased. Erythrocyte protoporphyrin (FEP and ZPP) is increased. Recent knowledge of the heme biosynthetic enzymes is reviewed and the significance of FEP and ZPP discussed. A brief history is given of the relationship of lead toxicity to the porphyrins.

Measurement of salicylsalicylic acid and salicylic acid in plasma by high pressure liquid chromatography.

Salicylsalicylic acid (SS) and salicylic acid (SA) both appear in plasma after the oral ingestion of the former. They can be estimated in the presence of each other after extraction into dichloromethane using high pressure liquid chromatography. SS is unstable in plasma, being converted to SA in vitro. Conversion can be prevented by using ethylene diaminetetraacetic (EDTA) as an anticoagulant and carrying out the extraction in the cold. An aliquot of the extract is dried and dissolved in methanol. Weak solutions of SS in methanol are unstable at room temperature. Methanolysis can be prevented by the addition of dilute hydrochloric acid. By adding phenylbutazone to the plasma as an internal standard, variations in extraction and sample application are nullified. Quality control is achieved by concurrent extraction of two different plasma standards containing SS and SA in known amounts. About 40 ng of SS and SA can be detected; reproducibility at 200 ng and above is better than 6.5 percent.

The measurement of total serum proteins by the Biuret method.

The biuret reaction for proteins provides a simple and precise method for measuring serum proteins; Beer's law is obeyed to at least 10 g per dl. Several stable biuret reagents are available. Hemoglobin is the only important cause of interference which cannot be minimized by use of a sample blank. The mechanism of the biuret reaction is described and attention is drawn to the heterogeneity of the serum proteins and to the use of a certified albumin standard.

Measurement of enzymes in environmental intoxications.

The paper details the enzymes which have been shown to be affected by certain zenobiotics, principally industrial pollutants, toxic metals, toxic gases and food additives. The role of mixed function oxidases is discussed and methods of assessing their activity indicated.

Quality control of gamma counters. I. Experimental evaluation of sources of error.

Errors of counting rate as large as 2 percent may occur through variations in instrumental parameters during the measurement of I-125 activity using a gamma counter. Much larger errors result from failure to maintain constant sample geometry; in particular, the slope of calibration curves depends on sample volume.

McArdle's disease: a review.

The clinical features of McArdle's disease (inherited deficiency of skeletal muscle phosphorylase) and the histological and biochemical changes are described. Their possible causes are discussed in the light of recent knowledge of the biochemistry of muscular contraction. Diagnostic tests are detailed. Attention is drawn to the possibility that the disease may be due to primary defect of motoneurons.