Solute-specific effects of osmotic stress on Staphylococcus aureus.

AIM: To determine if cell death from osmotic stress is because of lack of sufficient energy to maintain cell metabolism. Additionally, the solute-specific effect of five humectants on bacterial osmoregulation and cell survival was examined. METHODS AND RESULTS: Staphylococcus aureus was placed into 84% relative humidity (RH) broth (five humectants used individually). ATP, ADP and cell viability measurements were determined over time. The results indicate that ATP is not the limiting factor for cell survival under excessive osmotic stress. Although the same RH was achieved with various humectants, the rates of cell death varied greatly as did the sensitivities of the cell populations to osmotic stress. CONCLUSIONS: The results from this study provide strong evidence that mechanisms of osmotic inactivation depend on the solute. The molecular mobility of the system may be an important means to explain these differences. SIGNIFICANCE AND IMPACT OF THE STUDY: By bringing together an understanding of solute-specific effects, microbial physiology and genetics, the mechanisms of inactivation of micro-organisms by solute-specific osmotic stress may be elucidated, and this knowledge may then be exploited to ensure the production of high quality, safe foods.

Early onset prostate cancer: predictors of clinical grade.

PURPOSE: Prostate cancer is typically a disease of elderly men and, therefore, it has not been well characterized in those affected at a young age. With the advent of serum prostate specific antigen testing, we are able to detect prostate cancer in young men even in the absence of symptoms. We studied a large group of early onset prostate cancer cases to illustrate the clinical presentation of men with early onset prostate cancer and to determine the effect of family history on Gleason grade as a reflection of prognosis. MATERIALS AND METHODS: All study participants were enrolled in the University of Michigan Prostate Cancer Genetics Project. Enrollment criterion of the Prostate Cancer Genetics Project includes a diagnosis of prostate cancer at age 55 years or younger. Descriptive statistics and logistic regression were used to characterize early onset prostate cancer and assess the associated prognostic factors. RESULTS: The study group was comprised of 257 men with prostate cancer diagnosed at age 55 years or younger. Median age at diagnosis was 51 years (range 34 to 55) and almost half of the participants reported a negative family history of prostate cancer. In logistic regression analysis having an affected father, an affected first-degree relative or an affected relative of any relation was each a statistically significant predictor of well differentiated (Gleason 6 or less) compared to moderately and poorly differentiated prostate cancer (Gleason 7-10) after adjusting for confounding variables. Men with an affected relative were nearly twice as likely to have well differentiated prostate cancer compared to men without affected relatives. CONCLUSIONS: Family history appears to predict the development of well differentiated tumors independently. In our study men with no family history of prostate cancer had higher grade tumors, which are associated with a more serious prognosis. Future studies of early onset prostate cancer should be directed toward identifying additional risk factors that may be relevant for men without a family history of the disease.

Modeling the growth boundary of Staphylococcus aureus for risk assessment purposes.

Knowing the precise boundary for growth of Staphylococcus aureus is critical for food safety risk assessment, especially in the formulation of safe, shelf-stable foods with intermediate relative humidity (RH) values. To date, most studies and resulting models have led to the presumption that S. aureus is osmotolerant. However, most studies and resulting models have focused on growth kinetics using NaCl as the humectant. In this study, glycerol was used to investigate the effects of a glass-forming nonionic humectant to avoid specific metabolic aspects of membrane ion transport. The experiments were designed to produce a growth boundary model as a tool for risk assessment. The statistical effects and interactions of RH (84 to 95% adjusted by glycerol), initial pH (4.5 to 7.0 adjusted by HC1), and potassium sorbate (0, 500, or 1,000 ppm) or calcium propionate (0, 500, or 1,000 ppm) on the aerobic growth of a five-strain S. aureus cocktail in brain heart infusion broth were explored. Inoculated broths were distributed into microtiter plates and incubated at 37 degrees C over appropriate saturated salt slurries to maintain RH. Growth was monitored by turbidity during a 24-week period. Toxin production was explored by enterotoxin assay. The 1,280 generated data points were analyzed by SAS LIFEREG procedures, which showed all studied parameters significantly affected the growth responses of S. aureus with interactions between RH and pH. The resulting growth/no growth boundary is presented.

Substrate specificity of IphP, a cyanobacterial dual-specificity protein phosphatase with MAP kinase phosphatase activity.

The substrate specificity of the cyanobacterial dual-specificity protein phosphatase, IphP, was explored using a variety of potential substrates. The enzyme displayed phosphomonoesterase activity toward a broad range of peptide, protein, and low molecular weight organophosphate compounds. It displayed little or no hydrolase activity toward phosphodiesters, phosphoramides, carboxyl esters, or sulfoesters. However, it did display measurable pyrophosphatase activity, especially toward ADP and ATP. Among the low molecular weight phosphomonoesters, the presence of an aromatic ring either as part of the leaving group alcohol or immediately adjacent thereto, as in 5'-AMP, was a strong positive determinant for hydrolysis. Among peptide and protein substrates, a rough, but imperfect, correlation between charge character and hydrolysis was noted in which proteins and phosphorylation sites of an acidic nature seemed favored. Heparin affected IphP activity in a substrate-dependent manner. Toward small organophosphates, heparin had no significant effect, but it was inhibitory toward most protein and peptide substrates. However, toward phosphoseryl casein and MAP kinase, it enhanced activity as much as 10-fold. This enhancement was attributed to the ability of heparin to bind to these substrate proteins, as well as IphP, and recruit them to the same microenvironment.

Returning to work after heart transplantation.

The purpose of this study was to determine what factors influence a patient's return to work after heart transplantation. Two hundred fifty patients who had undergone heart transplantation were surveyed at seven regional centers in the United States (five of which were Medicare-certified). Of these patients, 45% were employed, 36% were unemployed, 13% were medically disabled, and 6% had retired. A stepwise discriminant analysis resulted in the selection of six variables that helped differentiate those patients who did and those who did not return to work after the transplantation. The factors associated with a patient's return to work included (1) self report of being physically able to work, (2) no loss of health insurance, (3) longer length of time after transplantation, (4) education level of more than 12 years, (5) no loss of disability income, and (6) shorter length of disability before heart transplantation. This information could accurately profile 91% of the patients who were employed, 69% of the patients who were unemployed, and 80% for the entire group. The implication of this study is that social rehabilitation is not synonymous with the medical results of heart transplantation. More attention to social rehabilitation is required if heart transplant recipients are to enjoy a better quality of life and become fully productive members of the community.

The effect of the Valsalva maneuver on the diameter of the common hepatic duct in extrahepatic biliary obstruction.

The internal diameter of the common hepatic duct as measured by ultrasonography is an imperfect predictor of extrahepatic biliary obstruction. This study examined the effect of the Valsalva maneuver on the diameter of the duct in 25 consecutive patients (12 with obstruction; 13 without obstruction) who underwent endoscopic retrograde cholangiopancreatography (ERCP). A normal response was defined as a decrease in the diameter of greater than 1 mm at the level of the portal vein. The response to the Valsalva maneuver improved the predictive outcome (sensitivity, 100%; specificity, 92.3%) suggesting that this maneuver should be part of the routine assessment of the common hepatic duct.

Social rehabilitation and return to work after cardiac transplantation--a multicenter survey.

As the medical results of heart transplantation steadily improve, the social rehabilitation of patients, in particular, their ability to return to some form of employment, is becoming increasingly important. Two-hundred fifty patients were therefore surveyed at 7 heart transplant centers (5 of which were Medicare certified) from different geographic regions in the U.S.A. Over all, 45% were employed, 36% were unemployed, 13% were medically disabled, and 6% were retired. Of those employed, 87% had returned to their previous employment, and only 13% had secured new employment. Of the unemployed, 16% had made job applications, and no fewer than 63% had no current plan to seek employment. Factors found to negatively influence a return to work included the following: (1) length of medical disability prior to transplantation; (2) a patient's self-perception of being physically unable to work; and (3) the potential loss of health insurance and/or disability income. At 2 centers, where there was a definite policy of not supporting a patient's claim for medical disability in the absence of an absolute indication, there were significantly increased numbers who (1) secured new employment and (2) planned to seek employment. More serious attention must be paid to aspects of employment if heart transplant recipients are to become fully productive members of the community.

Beyond water activity: recent advances based on an alternative approach to the assessment of food quality and safety.

Water, the most abundant constituent of natural foods, is a ubiquitous plasticizer of most natural and fabricated food ingredients and products. Many of the new concepts and developments in modern food science and technology revolve around the role of water, and its manipulation, in food manufacturing, processing, and preservation. This article reviews the effects of water, as a near-universal solvent and plasticizer, on the behavior of polymeric (as well as oligomeric and monomeric) food materials and systems, with emphasis on the impact of water content (in terms of increasing system mobility and eventual water "availability") on food quality, safety, stability, and technological performance. This review describes a new perspective on moisture management, an old and established discipline now evolving to a theoretical basis of fundamental structure-property principles from the field of synthetic polymer science, including the innovative concepts of "water dynamics" and "glass dynamics". These integrated concepts focus on the non-equilibrium nature of all "real world" food products and processes, and stress the importance to successful moisture management of the maintenance of food systems in kinetically metastable, dynamically constrained glassy states rather than equilibrium thermodynamic phases. The understanding derived from this "food polymer science" approach to water relationships in foods has led to new insights and advances beyond the limited applicability of traditional concepts involving water activity. This article is neither a conventional nor comprehensive review of water activity, but rather a critical overview that presents and discusses current, usable information on moisture management theory, research, and practice applicable to food systems covering the broadest ranges of moisture content and processing/storage temperature conditions.

A food polymer science approach to structure-property relationships in aqueous food systems: non-equilibrium behavior of carbohydrate-water systems.

Descriptions of the functional significance of carbohydrates based on the familiar equilibrium thermodynamics of very dilute solutions fail for pragmatical time scales and conditions, which are far from equilibrium. This is not too surprising, since limiting partial-molar properties reflect the independent behavior of solute in the limit of infinite dilution where free volume is maximum at a given temperature, while Tg'-Wg' properties reflect the cooperative behavior of solute-plasticizer blends at the limiting minimum value of free volume to observe relaxation within experimental time scales. Carbohydrate-water systems, with well-characterized structure and MW above and below the entanglement limit, provide a unique framework for the investigation of non-equilibrium behavior. Thermal analysis by DSC reveals the central role of water as a plasticizer for carbohydrates and of the glass transition as a physicochemical parameter that governs their properties, processing, and stability. A classical polymer science approach is used to study structure-property relationships of carbohydrates as water-compatible food polymers, which are treated as homologous systems of polymers, oligomers, and monomers with their plasticizers and solvents. Mechanical relaxation behavior is described by a "transformation map" of the critical variables of moisture content, temperature, and time. The glass curve is a reference contour, which represents the limiting isogram for free volume, local viscosity, relaxation rates, and rotational and translational mobility. Map domains are discussed as aspects of "water dynamics," to dispel the myth of "bound water," and "glass dynamics," to relate to macroscopic structure and collapse phenomena. A particular glass with invariant composition and Tg (prepared by freeze-concentration) is identified as a pivotal and practical reference state. The Tg observed during DSC analysis is often an effective Tg, resulting from instantaneous relative relaxation rates and non-uniform distribution of total sample moisture. Non-equilibrium melting, annealing, and gelation/recrystallization of kinetically metastable, partially crystalline carbohydrate systems exhibit non-Arrhenius kinetics which depend on the magnitude of delta T above the appropriate Tg, as defined by WLF relaxation transformations. Thermally reversible aqueous gels (crystallized from an under-cooled, rubbery melt) are described by a "fringed micelle" structural model for a three-dimensional polymer network, composed of microcrystalline junction zones crosslinking plasticized amorphous regions of flexible-coiled, entangled chain segments.

Human tumor cell line resistance to chemotherapeutic agents does not predict resistance to natural killer or lymphokine-activated killer cell-mediated cytolysis.

Cancer cells selected for resistance to natural product chemotherapeutic agents typically display cross-resistance to a variety of structurally and mechanistically diverse agents, a phenomenon known as multidrug resistance. Preliminary studies involving cells selected for multidrug resistance in vitro have suggested that the development of resistance to these agents might simultaneously confer resistance to some forms of immunotherapy. Using human tumor cell line models, we have investigated the relationship between either intrinsic or selected multidrug resistance and sensitivity to natural killer (NK) or lymphokine-activated killer (LAK) cell-mediated cytolysis. We compared the NK and LAK cell susceptibility of three human tumor cell lines displaying distinct mechanisms of selected drug resistance with that of the parental drug-sensitive lines. We also evaluated the NK and LAK susceptibility of five established renal cell carcinoma lines, all of which were found to be intrinsically resistant to doxorubicin and vinblastine. The drug-resistant cell lines were variably sensitive to NK-mediated lysis. In contrast, all drug-resistant cell lines tested were LAK cell sensitive. The NK and LAK cell-mediated cytolytic sensitivities of the drug-resistant cell lines correlated well with those of the drug-sensitive parental lines, suggesting that susceptibility to lysis was related intrinsically to each tumor type, and not to the resistance phenotype. We attempted to correlated the NK sensitivity of these cells with the cell surface expression of Class I or II histocompatibility antigens, or the presence or absence of the membrane inhibitor of complement-mediated reactive lysis. None of these phenotypic markers were found to predict NK resistance. We therefore conclude that these cells, which are either spontaneously resistant to commonly utilized antitumor agents or are multidrug resistant as a result of drug exposure in vitro, remain sensitive to LAK cell-mediated cytolysis. Our studies suggest that interleukin 2-induced LAK cells may be useful in the therapy of some chemotherapy-resistant cancers.

Strategies of disattention and auditory hallucinations in schizophrenics.

Disattentional strategies used by schizophrenics to attenuate auditory stimulation from the environment were proposed as extraordinary conditions of attention which facilitate the misperception of lexical thought as a voice and create an auditory hallucination. Two strategies were studied. The switching strategy involved concentration upon an external visual display to prevent a clearly audible list of words from registering. The holding strategy required mentally repeating a word in the list so as to ignore the words that followed. Process (N = 32) and reactive (N = 32) schizophrenics, 46 of whom had a history of auditory hallucinations, served as subjects. Effectiveness of the two disattentional strategies was tested by subsequent inability of the schizophrenic to recognize words from the taped list. Process schizophrenics with auditory hallucinations were able to use switching effectively but not holding. In contrast, reactive schizophrenics suffering auditory hallucinations successfully used holding but not switching. Both effects were confirmed relative to hallucinating controls given standard memory instructions. Strategy effects were not apparent in nonhallucinating schizophrenics. These results suggest that different disattentional strategies may have been practiced by hallucinating schizophrenics in keeping with their premorbid status and style of attention deployment. A proposal functionally relating disattention to the genesis of auditory hallucinations was suggested.

Dietary fat and exercise conditioning effect on metabolic parameters in the horse.

Four isocaloric diets containing 4, 8, 12 and 16% dietary fat (as soybean oil) were fed to four horses at four intervals according to a Latin square design. After 3 weeks of conditioning at each interval, diet effects were evaluated by trotting all horses at 3.2 m/sec for 6 hours. Pre- and posttrotting responses were measured in muscle and liver glycogen, serum long-chain fatty acids, serum electrolytes, serum enzymes, serum cholesterol, plasma glucose, packed cell volume and hemoglobin. Dietary fat was highly correlated with exercise-induced plasma glucose changes and with cholesterol concentrations. Regardless of the diet, linoleate concentration was about eight times higher than that of the other fatty acids, and it increased slightly as dietary fat levels increased. Stearate concentration also increased with increasing dietary fat but palmitic and oleic acid decreased. Increases in fat intake also resulted in slight increases in liver glycogen at the resting level. Conditioning resulted in a significant decrease in exercise-induced fluctuations of serum enzymes and electrolytes but significantly increased elevations of plasma long-chain fatty acid concentrations. Resting muscle glycogen increased by 37% during the study as a result of conditioning, but there was no effect on liver glycogen at rest or after exercise. Feeding of the four levels of dietary fat in the form of soybean oil had no adverse effects and proved a safe and efficient method of providing concentrated energy to working horses.