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Biomedical subjects

M Linton

Publications and source records attributed to M Linton.

11 recordsLinked to original sources
PubMed2001

Correlated motion and oscillation of neighboring cells in vitro.

It has long been realized that fibroblastic and epithelial cells establish recognizable patterns in tissue culture. This behavior implies that neighboring cells interact with one another to produce organized populations. Interaction between cells that are separated by many intervening cells is also possible and is demonstrated here using a special configuration of a biosensor referred to as electric cell-substrate impedance sensing (ECIS). Normally the electrical impedance of a single electrode covered with a confluent cell layer is measured, and the morphological changes of the cells are reflected in the impedance. In this case the cells are cultured on two closely spaced electrodes whose impedances are measured independently as a function of time, and communication between the cell populations is revealed as a correlation between these two time series. We also report for the first time another striking manifestation of dynamic cell interaction, where confluent layers of Madin-Darby canine kidney cells (MDCK) on a single electrode are observed to oscillate in synchrony with a period of approximately 2.5 h.

Animals↗
PubMed2001

The effect of growth stage and growth temperature on high hydrostatic pressure inactivation of some psychrotrophic bacteria in milk.

The effect of high hydrostatic pressure on the survival of the psychrotrophic organisms Listeria monocytogenes, Bacillus cereus, and Pseudomonas fluorescens was investigated in ultrahigh-temperature milk. Variation in pressure resistance between two strains of each organism were studied. The effect of growth stage (exponential and stationary phase), growth temperature (8 and 30 degrees C) on pressure resistance, and sublethal pressure injury were investigated. Exponential-phase cells were significantly less resistant to pressure than stationary-phase cells for all of the three species studied (P < 0.05). Growth temperature was found to have a significant effect at the two growth stages studied. Exponential cells grown at 8 degrees C were more resistant than those grown at 30 degrees C, but for stationary-phase cells the reverse was true. B. cereus stationary-phase cells grown at 30 degrees C were the most pressure resistant studied. L. monocytogenes showed the most sublethal damage compared to B. cereus and P. fluorescens. B. cereus spores were more resistant to pressure than vegetative cells. Pressure treatment at 400 MPa for 25 min at 30 degrees C gave a 0.45-log inactivation. Pressure treatment at 8 degrees C induced significantly less spore germination than at 30 degrees C. This study indicates the importance of the history of a bacterial culture prior to pressure treatment and that bacterial spores require more severe pressure treatments, probably in combination with other preservation techniques, to ensure inactivation.

Animals↗
PubMed2000

High pressure processing of foods for microbiological safety and quality (a short review).

Consumers are demanding foods that are "natural", of good nutritional and sensory quality, free from chemical preservatives, microbiologically safe and with extended shelf-life. High pressure processing can, potentially, meet these criteria. Recent advances in equipment design now allow foods to be processed up to 900 MegaPascals (130,000 psi). However, further work is required to more fully understand the factors that can affect the response of microorganisms, including pathogens, to pressure so that treatments can be optimised and microbiological safety can be assured. This paper describes how the pressure resistance of microorganisms can vary depending on factors such as species, strain, stage of growth and food composition. Strategies for overcoming the problem of pressure resistance will be discussed, for example the use of pressure cycling and the combination of pressure with mild heat. The current commercial uses of high pressure to preserve foods will be reported and potential applications will also be discussed.

Bacteria↗
PubMed1999

Inactivation of Escherichia coli O157:H7 in orange juice using a combination of high pressure and mild heat.

The effect of high pressure on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice was investigated over the pH range 3.4 to 5.0. The pH of commercial, sterile orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, or 5.0. The juice was then inoculated with 10(8) CFU ml(-1) of E. coli O157:H7. The inoculated orange juice was subjected to pressure treatments of 400, 500, or 550 MPa at 20 degrees C or 30 degrees C to determine the conditions that would give a 6-log10 inactivation of E. coli O157:H7. A pressure treatment of 550 MPa for 5 min at 20 degrees C produced this level of kill at pH 3.4, 3.6, 3.9, and 4.5 but not at pH 5.0. Combining pressure treatment with mild heat (30 degrees C) did result in a 6-log10 inactivation at pH 5.0. Thus, the processing conditions (temperature and time) must be considered when pressure-treating orange juice to ensure microbiological safety.

Beverages↗
PubMed1999

Survival of Escherichia coli O157:H7 during storage in pressure-treated orange juice.

The effect of a high-pressure treatment on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice during storage at 3 degrees C was investigated over the pH range of 3.4 to 5.0. The pH of shelf-stable orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, and 5.0 and inoculated with 10(8) CFU ml(-1) of E. coli O157:H7. The orange juice was then pressure treated at 400 MPa for 1 min at 10 degrees C or was held at ambient pressure (as a control). Surviving E. coli O157:H7 cells were enumerated at 1-day intervals during a storage period of 25 days at 3 degrees C. Survival of E. coli O157:H7 during storage was dependent on the pH of the orange juice. The application of high pressure prior to storage significantly increased the susceptibility of E. coli O157:H7 to high acidity. For example, after pressure treatment, the time required for a 5-log decrease in cell numbers was reduced from 13 to 3 days at pH 3.4, from 16 to 6 days at pH 3.6, and from >25 to 8 days at pH 3.9. It is evident that the use of high-pressure processing of orange juice in order to increase the juice's shelf-life and to inactivate pathogens has the added advantage that it sensitizes E. coli O157:H7 to the high acid conditions found in orange juice, which results in the survival of significantly fewer E. coli O157:H7 during subsequent refrigerated storage.

Escherichia coli↗
PubMed1998

Designing an effective counteradvertising campaign--Arizona.

In this report, the authors describe an innovative antitobacco advertising campaign in Arizona that was aimed at youth. The campaign utilizes traditional as well as non-traditional methods of research to determine the attitudes, behavior and values of today's adolescents. These creative methodologies led to rigorously tested and well-received media strategies.

Adolescent↗
PubMed1994

Nursing assistance for families of patients.

With deinstitutionalization, families have become the primary caregivers of persons with mental illness. Mental health professionals and family members must work together to prevent damage to our most valuable resource, the family. Nurses, who often provide the most continuous care for seriously mentally ill persons, are in a unique position to reach out to families and provide the help that they need as primary caregivers. Let us not fail our patients or their families.

Caregivers↗
PubMed1988

Caesarean section: a national study.

Although the use of caesarean section (CS) continues to be debated, the demographic characteristics of the affected population have received little attention. This paper shows that in New Zealand during 1983-84, a CS was performed on 9.6% of delivered women between the ages of 15-44. The rate increased with maternal age (p less than 0.01), and was highest for 'single' women (11.3/100) and Pacific Island women aged 35-44 (21/100). There was a significantly (p less than 0.05) high rate in the Auckland and South Otago hospital board districts, but a low rate (p less than 0.05) in the Ashburton, Nelson, Canterbury, Southland, Taumaranui, Waiapu, Wairarapa, Wanganui, and Wellington board districts. The rate was also high (p less than 0.01) in the principal teaching hospitals. Long labour (15.2%), malposition and malpresentation of the fetus (14.7%) were the leading reasons for performing a CS. The paucity of national data on a number of other highly relevant birth and maternal factors hinders the further definition of the epidemiological patterns of CS in New Zealand.

Adolescent↗
PubMed1985

Comparison of the use of reserpine versus alpha-methyldopa for second step treatment of hypertension in the elderly.

A retrospective chart analysis was conducted on all new elderly hypertensive patients referred to a community hypertension clinic who were being treated with either reserpine or alpha-methyldopa plus a diuretic. There were no significant differences between the two groups on entry in age, gender, co-morbid diagnoses, or systolic or diastolic blood pressure. There were no significant differences between the two groups in terms of side effects over three years, but the proportion of persons having compliance problems was significantly lower in the reserpine group. Mean diastolic pressures were significantly lower after one, two, and three years, and systolic pressures were lower after one and two years in the reserpine group. Reserpine is at least as effective as alpha-methyldopa in treating hypertension in the elderly and is associated with fewer problems in compliance.

Aged↗