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PubMed2025

Borrelia burgdorferi loses essential genetic elements and cell proliferative potential during stationary phase in culture but not in the tick vector.

The Lyme disease agent Borrelia burgdorferi is a polyploid bacterium with a segmented genome in which both the chromosome and over 20 distinct plasmids are present in multiple copies per cell. This pathogen can survive for at least 9 months in its tick vector in an apparent dormant state between blood meals, without losing cell proliferative capability when re-exposed to nutrients. Cultivated B. burgdorferi cells grown to stationary phase or resuspended in nutrient-limited media are often used to study the effects of nutrient deprivation. However, a thorough assessment of the spirochete's ability to recover from nutrient depletion has been lacking. Our study shows that starved B. burgdorferi cultures rapidly lose cell proliferative ability. Loss of genetic elements essential for cell proliferation contributes to the observed proliferative defect in stationary phase. The gradual decline in copies of genetic elements is not perfectly synchronized between chromosomes and plasmids, generating cells that harbor one or more copies of the essential chromosome but lack all copies of one or more non-essential plasmids. This phenomenon likely contributes to the well-documented issue of plasmid loss during in vitro cultivation of B. burgdorferi. In contrast, B. burgdorferi cells from ticks starved for 14 months showed no evidence of reduced cell proliferative ability or plasmid loss. Beyond their practical implications for studying B. burgdorferi, these findings suggest that the midgut of the tick vector offers a unique environment that supports the maintenance of B. burgdorferi's segmented genome and cell proliferative potential during periods of tick fasting.IMPORTANCEBorrelia burgdorferi causes Lyme disease, a prevalent tick-borne illness. B. burgdorferi must survive long periods (months to a year) of apparent dormancy in the midgut of the tick vector between blood meals. Resilience to starvation is a common trait among bacteria. However, this study reveals that, in laboratory cultures, B. burgdorferi poorly endures starvation and rapidly loses viability. This decline is linked to a gradual loss of genetic elements required for cell proliferation. These results suggest that the persistence of B. burgdorferi in nature is likely shaped more by unique environmental conditions in the midgut of the tick vector than by an innate ability of this bacterium to endure nutrient deprivation.

Borrelia burgdorferi↗
PubMed1989

Selenium intake with diet in Italy: a pilot study.

Selenium is an element essential to man. The main environmental pathway of Se-exposure for the general population is through food. As is true for all essential elements, not only deficient but also excessive exposure results in adverse health effects. Between these extremes there is a range of safe and adequate Se intakes. In 1980 the Italian National Research Council recommended 50-200 micrograms/day as an interval adequate to meet nutritional requirements, being at the same time below the threshold of toxic effects. Therefore the evaluation of dietary Se intake has become very important. The purpose of this work is the estimation of dietary intakes of Se using data on the amount and composition of an average Italian diet. Complete meals from a factory canteen were analyzed and calculations of weekly intake of Se carried out. Analyses were performed by means of Inductively-coupled Plasma Atomic Emission Spectrometry. The results obtained, related to the average and indicative food consumption of Italian people, showed that the daily intake is well within the recommended range.

Diet↗
PubMed1990

[An insufficiency of essential trace elements and its manifestations in pathology].

There exist 11 essential elements (iron, copper, iodine, zinc, chromium, cobalt, molybdenum, manganese, nickel, selenium and fluorine) vitally important for human health. The deficiency of these trace elements results in many pathological processes, including such world-wide human diseases, as iron-deficient anemias and other forms of hyposiderosis, endemic hypothyroid goiter, endemic fluorine deficiency states, particularly manifested by dental caries in children and osteoporosis of the advanced age. Selenium deficiency causes endemic cardiopathy in China, is a risk factor for the development and severe course of congestive cardiopathies, as well as myocardial infarction in a number of European countries. Correction of selenium deficiency with sodium selenite reduced to the minimum the mortality rate from endemic cardiopathy in China (Keshan disease) and had a favourable effect on other forms of cardiovascular pathology. Essential trace element deficiency results in many forms of embryonal and fetal pathology and decreases the antitumour resistance in man. New essential trace elements are still being identified and their number reached 19 at present. Development of pathological anatomy of essential trace element deficiency is an important task of modern medicine.

Animals↗
PubMed1989

Patient classification system evaluation. Part 1: Essential system elements.

How can nurse executives assure optimum patient classification system performance? This two-part series advances a framework for patient classification system (PCS) evaluation. Using an expanded definition of a PCS, part one presents a discussion of the six system elements considered essential to a fully operational PCS. Part Two offers a description of PCS selection criteria as well as keys to successful system implementation. Application of this evaluation framework allows for rapid problem identification and remediation, assists with PCS selection, and enhances overall system performance.

Evaluation Studies as Topic↗
PubMedDate not supplied

PIXE determination of essential trace elements in some traditional Chinese medicines.

The essential trace elements in 30 traditional Chinese medicines, (24 tonics and 6 nontonics) were determined by proton-induced X-ray emission. The authors' previous suggestion that traditional Chinese medicines may be classified by the order of magnitude of their essential trace elements, thus indicating their pharmacological effects, is not justified. The pharmacological effect of a trace element or its essentiality may be dependent on some ligand that can be chelated with it. A nonlinear mapping algorithm, however, shows that the 30 traditional Chinese medicines are nearly separated into two groups, indicating their tonic or nontonic pharmacological effects.

Drugs, Chinese Herbal↗
PubMed1987

Biological and health implications of toxic heavy metal and essential trace element interactions.

Human civilization and a concomitant increase in industrial activity has gradually redistributed many toxic metals from the earth's crust to the environment and increased the possibility of human exposure. Among the various toxic elements, heavy metals cadmium, lead, and mercury are specially prevalent in nature due to their high industrial use. These metals serve no biological function and their presence in tissues reflects contact of the organism with its environment. They are cumulative poison, and are toxic even at low dose. Studies of metabolism and toxicity of these elements have revealed important interactions between them and some essential dietary elements like calcium, zinc, iron, selenium, copper, chromium, and manganese. In general, a deficiency of these essential elements increases toxicity of heavy metals, whereas an excess appears to be protective. While most of the observations are on laboratory animals, limited human data are in agreement with the results of animal experiments. These suggest that the dietary presence of the essential elements may contribute to the protection of man and animal from the effects of heavy metal exposure, while their deficiency may increase toxicity. Appropriate dietary manipulation thus may be valuable in the prevention and treatment of heavy metal toxicity.

Animals↗