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PubMed2006

Stepping stones towards a new prokaryotic taxonomy.

Technological developments provide new insights into prokaryotic evolution and diversity and provoke a continuous need to update taxonomy and revise classification schemes. Our present species concept and definition are being challenged by the growing amount of whole genomic information, which should allow improvements in the natural species definition. The continuous quest for an objective and stable method for sorting strains into coherent homogeneous groups is inherent to prokaryotic systematics and nomenclature. Morphological, biochemical, physiological, phenotypic and chemotaxonomic criteria have been complemented by molecular data and pragmatic, purpose built, species definitions are being replaced by more natural ones based on evolutionary insights. It is imperative to give due consideration to both fundamental and applied aspects of future species concepts and definitions. The present paper discusses the present practice in prokaryotic taxonomy of how this system developed and how it may evolve in the future.

Archaea↗
PubMed1996

Physiological effects of nitrogen starvation in an anaerobic batch culture of Saccharomyces cerevisiae.

The effects of nitrogen starvation on the anaerobic physiology of Saccharomyces cerevisiae were studied in cells cultivated in a bioreactor. The composition of the mineral medium was designed such that the nitrogen source became depleted while there was still ample glucose left in the medium. The culture was characterized by acoustic gas analysis, flow injection analysis and HPLC analysis of extracellular substrates and metabolites. During the cultivation, the macromolecular composition of the cells was analysed with respect to the cellular content of RNA, protein, trehalose and glycogen. During exponential growth under anaerobic conditions, the maximum specific growth rate conditions. Depletion of ammonium in the medium led to an abrupt decrease (mumax) of S. cerevisiae CBS 8066 (0.46 h-1) was identical to the mumax determined under aerobic in the flux through glycolysis. Subsequently, a continuous decrease in the carbon dioxide evolution rate, caused by catabolite inactivation of the hexose-transport system, was observed. The apparent half-life of the transport system under nitrogen starvation was 13 h. During the exponential growth phase, the cellular content of RNA and protein was 15% (w/w) and 60% (w/w), respectively. At the end of the cultivation where the cells had been starved of nitrogen for 18 h, the cellular content of RNA and protein had decreased to 4% (w/w) and 22% (w/w), respectively. The intracellular carbohydrate content increased dramatically as trehalose and glycogen accumulated to final concentrations of 7% (w/w) and 25% (w/w), respectively. Glycerol formation during nitrogen starvation was higher than that accounted for by the formation of organic acids, suggesting a protein turnover of approximately 6% h-1. The growth energetics of S. cerevisiae CBS 8066 also changed as a result of nitrogen starvation, and YxATP was observed to increase from 80 mmol g-1 during the exponential growth phase to more than 130 mmol g-1 towards the end of the cultivation. The presented results illustrate the effect of nitrogen starvation on glycerol formation, protein turnover, catabolite inactivation of the sugar-transport system, the cellular composition, the cell cycle and growth energetics.

Ammonia↗
PubMed1979

Duration of Hydrogen Formation by Anabaena cylindrica B629 in Atmospheres of Argon, Air, and Nitrogen.

The time course of hydrogen formation by Anabaena cylindrica was followed beneath an argon atmosphere alone and also beneath atmospheres of argon, nitrogen, and air in the presence of carbon monoxide (0.2%) and acetylene (5%). Hydrogen production beneath argon alone was comparable in rate and duration (7 to 12 days) to that which occurred beneath air in the presence of carbon monoxide (0.2%) and acetylene (5%). However, much greater longevity (16 to 26 days) and improved rates of hydrogen formation were obtained when algae were incubated beneath argon and particularly nitrogen, each supplemented with carbon monoxide and acetylene. The total hydrogen produced by these cultures was up to three times as much as that released by cultures incubated beneath argon alone. Hydrogen-oxygen ratios for argon cultures either with or without carbon monoxide and acetylene were initially 1:5 but approximated 1:2 when measured over the entire incubation period. In each case oxygen production and nitrogenase activity (acetylene reduction) continued at reduced rates after hydrogen evolution had ceased. The effects of methionine sulfoximine (2 muM), ammonium ions (0.5 mM), or both on oxygen production were generally negligible, while effects on hydrogen production were variable depending on the atmosphere used; in most cases, eventual destabilization of the system occurred. A brief comparison was made of the time courses of anaerobic and aerobic hydrogen formation by the marine cyanobacterium Calothrix membranacea. It was found that shaking of cultures was beneficial for hydrogen production but not strictly necessary. It is concluded that hydrogen production by A. cylindrica in air and particularly nitrogen in the presence of carbon monoxide and acetylene offers the best potential of the atmospheres considered on the basis of four criteria: rates and longevity of hydrogen formation, practicality of the atmosphere used, and tolerance of hydrogen evolution to slight changes in composition of the atmosphere.

Journal Article↗
PubMed2025

Genomic insights into a diarrheal outbreak in Bangladesh reveal novel ETEC lineages and expansion of CS23 colonization factor.

Enterotoxigenic Escherichia coli (ETEC), a leading cause of diarrhea, is defined by heat-stable (ST) and/or heat-labile (LT) toxins and associated colonization factors (CFs). However, there is still a knowledge gap in understanding ETEC's evolution, particularly in endemic regions like Bangladesh. This study investigates the genomic attributes contributing to the rise of ETEC-associated diarrhea in Bangladesh during 2022-2023. Whole genome sequencing of 325 ETEC isolates (2022-2023), compared with historical strains (1980-2021), revealed significant evolutionary changes. Our findings showed a significant shift in ETEC toxin from LT to ST over the period 2013-2023. The most frequent virulence profile during this period was CFA/I + CS21 compared with previous years (1980-2021). The emergence of CS23-positive ETEC was reported for the first time in Bangladesh, which was considered a less common CF in previous studies. Notably, we report the four novel lineages "L26-L29" in this study through phylogenetic analysis, partly encompassing emergent CS23-positive ETEC strains. Additionally, the high prevalence of multi-drug-resistant ETEC strains and the presence of ESBL-CTX-M-resistant gene during 2022-2023 are a matter of great concern, underscoring the need for preventive measures. The switch of distinct toxin and CF combinations, the rapid emergence of CS23, ESBL-CTX-M resistance, and novel lineages may be the reason behind the increased number of ETEC diarrheal cases between 2022 and 2023. These findings highlight the rapid ETEC evolution that underscores the necessity of continued genomic surveillance to track ongoing changes.IMPORTANCEThis study expands on previous evidence, demonstrating a remarkable genomic diversity in ETEC strains from 2022 to 2023, particularly in virulence factors and AMR genes. The combined findings from these studies will be important for mitigating future diarrheal outbreaks by informing preventive measures, including future vaccine targets, and implementing antibiotic stewardship programs against ETEC infection. Importantly, this research underscores the necessity of continued genomic surveillance to track ongoing changes in ETEC. Such monitoring is essential for understanding the pathogen's evolving population structure, transmission dynamics, and resistance mechanisms.

Bangladesh↗
PubMedDate not supplied

Stresses exerted in the hindlimb muscles of common chimpanzees (Pan troglodytes) during bipedal locomotion.

Recent studies have indicated that chimpanzee bipedality is mechanically inefficient and dynamically unlike that of humans, thus undermining the chimpanzee analogy for mechanical aspects of the early evolution of hominid bipedalism. This paper continues this theme by measuring the forces and stresses engendered by the muscles during bipedal locomotion, for an untrained chimpanzee and for data from chimpanzees which have been encouraged to walk bipedally, presented in the literature. Peak stresses in the triceps surae were lower for the untrained chimpanzee than for the trained subjects because during the late stance phase, when peak ankle moments occur, the centre of pressure of the ground reaction force on the foot of the untrained chimpanzee stayed close to the ankle joint. In contrast, for the trained subjects it moved closer to the toes, as in human bipedalism. Quadriceps and hip extensor stresses are approximately 30% larger for the untrained chimpanzee than for the trained subjects, because the trained chimpanzees walked with a more erect posture. These results may reflect the way in which muscles can develop in response to training, since research on humans has shown that muscle physiological cross-sectional area increases as a result of exercise, resulting in smaller stresses for a given muscle force. During a slow walk, untrained chimpanzees were found to exert far greater muscle stresses than humans do when running at moderate speed, particularly in the muscles that extend the hip, because of the bent-hip, bent-knee posture.

Animals↗
PubMed2004

Speech and language deterioration in benign rolandic epilepsy.

A 5-year-old boy presented with typical clinical and electrophysiologic features of benign rolandic epilepsy. His neurodevelopment, language, and behavior prior to the onset of epilepsy were appropriately normal. He demonstrated marked deterioration of language and cognitive function during the course to a mild and then a moderate disability range. Serial sleep electroencephalographic recordings initially showed continuous and bilateral rolandic discharges with evolution to localized left rolandic spikes. Language and cognitive improvements were subsequently seen. Educational support and evolution of the electroencephalogram to a localized focus could have been contributory. It is anticipated, however, that he will have significant long-term problems in complex language.

Anomia↗
PubMed1992

Nursing knowledge and human science: ontological and epistemological considerations.

This article examines the meaning of human science in relation to extant nursing knowledge. The origins of the human science tradition are traced to the philosopher Wilhelm Dilthey, who challenged the dominance of the positivist perspective for generating knowledge of the human lifeworld. Specific ontological and epistemological criteria for human science are proposed. Four nursing frameworks, Paterson and Zderad's humanistic nursing, Newman's model of health as expanding consciousness, Watson's human science and human care, and Parse's theory of human becoming, are found to have consistencies and inconsistencies with the human science tradition. It is proposed that the human science perspective is present in and will continue to be reflected in the evolution of nursing science.

Humans↗
PubMed1994

Childhood acute lymphoblastic leukaemia and aplastic anaemia.

Aplastic anaemia (AA) can be associated with disorders that are known to exhibit clonal haematopoiesis, like paroxysmal nocturnal haemoglobinuria (PNH), myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML). It appears that the long term survivors of severe AA treated with immunosuppressive agents such as ATG have a continuing, late mortality caused by the evolution of clonal disorders which are not usually seen when bone marrow transplant is used. In children, typical AA may precede the onset of acute lymphoblastic leukemia (ALL). The aplastic phase is often transient and remission may be spontaneous or rapidly induced by steroid, and followed a few months later by acute leukaemia. This modality of presentation may be observed in up to 2-3% of all cases of paediatric ALL. A 13-year old girl who presented with two spontaneously reversible episodes of marrow aplasia has been reported recently. She developed ALL 8 months later. Southern analysis showed identical clonal immunoglobulin heavy chain gene rearrangement bands in her leukaemic cells as well as the marrow cells obtained at the two aplastic episodes. Hypoxanthine phosphoribosyltransferase polymorphism studies showed that all the ALL blast cells, bone marrow and peripheral cells during the two aplastic episodes all exhibited clonal haematopoiesis with the same X-chromosome inactivated. This case provides strong evidence that AA and ALL can represent evolution of the same abnormal clone.

Adolescent↗
PubMed1994

Blood-brain barrier permeability in staphylococcal cerebritis and early brain abscess.

The pattern of radiographic enhancement in cases of brain abscess has been extensively studied, but the magnitude of blood-brain barrier (BBB) damage that accompanies enhancement has not. The question of whether BBB permeability increases continuously as a cerebritis evolves into an abscess was studied. The tracers 3H-labeled aminoisobutyric acid and 14C-labeled butanol were used in a rat Staphylococcus aureus cerebritis model to measure simultaneously BBB permeability and blood flow. The rats were examined at 1, 2, 3, 5, or 7 days after inoculation, and tissue samples were collected from the cerebritis site and uninoculated regions. Permeability of the BBB in the cerebritis region increased to five times the normal values by 72 hours after inoculation, then reached a plateau. The plasma volume in the cerebritis region increased to six times greater than the normal value at 72 hours, then remained unchanged. Uninoculated brain in both ipsilateral and contralateral hemispheres showed no significant changes. Cerebral blood flow was not substantially altered at the inoculated or uninoculated sites. In this model, incidence of BBB damage rises rapidly, reaches a plateau, and does not continue to increase despite the ongoing evolution of a cerebritis into an abscess. The BBB damage is accompanied by an increase in the regional plasma volume, a novel finding that has not been previously reported in central nervous system inflammation. These results suggest that the vascular events contributing to brain edema formation become established early in the cerebritis phase and imply that control of the host's inflammatory response is important in the management of cerebritis-associated brain edema.

Animals↗
PubMed1993

Patient care information systems and physicians: the transition from technology icon to health care instrument.

We have discussed several important transitions now occurring in PCIS that promise to improve the utility and availability of these systems for the average physician. Charles Babbage developed the first computers as "thinking machines" so that we may extend our ability to grapple with more and more complex problems. If current trends continue, we will finally witness the evolution of patient care computing from information icons of the few to clinical instruments improving the quality of medical decision making and care for all patients.

Attitude to Computers↗
PubMed2001

[Refractory hypotension sustained during general anesthesia due to chronic treatment with angiotensin-converting enzyme inhibitors].

Perioperative management of angiotensin-converting enzyme inhibitors (ACEI) is controversial because of associated hypertensive episodes during induction and maintenance of anesthesia. A 71-year-old woman with a non-functioning thyroid node was scheduled for thyroid lobectomy. Her medical history included high blood pressure and she was being chronically treated with ACEI, which were taken until the morning of surgery. After induction of anesthesia, arterial hypotension refractory to crystalloid therapy developed and worsened in spite of administration of a gelatin-type colloid (Gelafundina). The patient did not respond to ephedrine or dopamine and required stabilization with adrenalin in continuous perfusion for 12 hours. Later evolution was satisfactory and recovery took place without sequelae. We discuss the anesthetic implications of chronic ACEI treatment and possible hemodynamic repercussions of associated administration with gelatin-type solutions or human albumin.

Aged↗
PubMed1991

Evolutionary dynamics of plants and animals: a comparative approach.

Patterns of longevity and rate of appearance of taxa in the fossil record indicate a different evolutionary dynamic between land plants and marine invertebrates. Among marine invertebrates, rates of taxonomic turnover declined through the Phanerozoic, with increasingly extinction-resistant, long-lived, clades coming to dominate. Among terrestrial vascular plants, rates of turnover increased through the Phanerozoic, with short-lived, extinction-prone clades coming to dominate from the Devonian to the present. Terrestrial vertebrates appear to approximate the marine invertebrate pattern more closely than the plant record. We identify two features which individually or jointly may have influenced this distinction. First, land plants continuously invaded stressful environments during their evolution, while marine invertebrates and terrestrial vertebrates did not. Second, the relative structural simplicity and indeterminate mode of plant growth vs. the relative structural complexity and determinate mode of animal growth may have influenced the timing of major clade origin in the two groups.

Adaptation, Biological↗
PubMed1994

Recent approaches in the analysis of weightlessness effects on arthropod development.

The concept of Biological Development refers to the extremely complex process by which every biological organism reproduces starting from a huge single cell, the fertilized egg. It includes all aspects of cellular and intercellular structure and function. In spite of many recent advances, especially at the molecular and genetical level, we are still far from fully understanding the details and mechanisms at work in developmental systems. It is even unclear what physical mechanisms are used by the different molecular components resulting in the emergence of these higher levels of organization. Newman and Comper, have extensively discussed the "generic" physical forces potentially involved in pattern formation, arguing that among others, gravitational effects could be involved in the production of cytoplasmic, tissue and extracellular matrix components rearrangements playing a role in morphogenesis. Although plagued with the problem of being a very weak force, specially at the tiny dimensions of cells, gravity is one of the "generic" physical forces that have been continuously operating on biological organisms during evolution. Few scientists would argue against the idea that at least in the early times of evolution, gravity could have been involved in shaping the spatial inhomogeneities behind the initial phases of development.

Animals↗
PubMed2001

T-mechanism applied to urinary diversion: the orthotopic T-pouch ileal neobladder and cutaneous double-T-pouch ileal reservoir.

PURPOSE: As the evolution of lower urinary tract reconstruction continues, newer and improved forms of urinary diversion have developed. Critical components of continent urinary reservoirs included an antireflux and continent mechanism that is effective, durable, easily constructed, and associated with little morbidity. MATERIALS AND METHODS: We describe the flap valve known as the T-mechanism as it applies to an afferent antireflux mechanism in an orthotopic ileal reservoir (T-pouch) and as an antireflux and efferent continence mechanism in the continent cutaneous ileal reservoir (double T-pouch). CONCLUSIONS: We believe the T-mechanism is an extremely effective and versatile flap-valve technique that can be easily learned and applied to the construction of continent urinary diversions.

Humans↗
PubMed2001

[A.A. Malinovskiĭ and significance of the system approach in gerontology].

A.A Malinovsky allocated 4 most important principles of the system theory: discreteness/rigidity of system, presence of feedback, occurrence of new properties at association of elements in system, a continuity and the maximal fitness in evolution. He believed that the essential factor determining life longevity of the individual are his species-specific characteristics. A.A. Malinovsky together with coworkers has revealed the attributes most connected to increase of terms of life: a high degree of the cephalization and the big sizes of a body. He also emphasized, that with an exit on a high intellectual level people have occupied especially position at which the biological factors influencing life longevity, began to lose paramount signification, value of long life has increased. The increase of life longevity has resulted in the important consequence--to increase of the number of diseases at late age. The diseases with hereditary predisposition have got the big weight. A.A. Malinovsky considered 4 basic levels of a condition of functions of an organism. The level of the maximal pressure--mobilization of all forces of an organism on type of "emergency alarm", promotes wear process of an organism and disorder of its separate functions. Damage of the weakest link translates an organism from a stable condition in pathological when the depression of one function reduces a level of others which in turn, even more can suppress the first, resulting in to a vicious circle (a positive feedback). A.A. Malinovsky has entered concept about increasing "disregulation" of the functions of an organism during ageing as to the main reason limiting human life. He assumed, that such rigid system (organism) which has strong link (subsystem), and other subsystems function approximately at one level has the greatest stability. It is possible, that presence of weakest links is connected to size of a genetic load. Our paper demonstrates the importance of A.A. Malinovsky system approach for such field of knowledge as gerontology.

Aging↗
PubMed2005

Speciation through competition: a critical review.

We examined causes of speciation in asexual populations in both sympatry and parapatry, providing an alternative explanation for the speciation patterns reported by Dieckmann and Doebeli (1999) and Doebeli and Dieckmann (2003). Both in sympatry and parapatry, they find that speciation occurs relatively easily. We reveal that in the sympatric clonal model, the equilibrium distribution is continuous and the disruptive selection driving evolution of discrete clusters is only transient. Hence, if discrete phenotypes are to remain stable in the sympatric sexual model, there should be some source of nontransient disruptive selection that will drive evolution of assortment. We analyze sexually reproducing populations using the Bulmer's infinitesimal model and show that cost-free assortment alone leads to speciation and disruptive selection only arises when the optimal distribution cannot be matched--in this example, because the phenotypic range is limited. In addition, Doebeli and Dieckmann's analyses assumed a high genetic variance and a high mutation rate. Thus, these theoretical models do not support the conclusion that sympatric speciation is a likely outcome of competition for resources. In their parapatric model (Doebeli and Dieckmann 2003), clustering into distinct phenotypes is driven by edge effects, rather than by frequency-dependent competition.

Biological Evolution↗
PubMed1985

Conservative treatment of Legg-Calvé-Perthes condition.

As we continue to learn more about the evolution of Legg-Calvé-Perthes condition, several advantages to early conservative treatment become apparent. First, since it may take as long as 6 months to determine the extent of femoral head involvement in patients who present early in the disease process, nonoperative methods may be used to improve the range of motion and to contain the femoral head within the acetabulum, thus minimizing further deformity. Second, since the duration of treatment need no longer be as extensive as was previously thought, the argument that nonoperative means are unrealistic for patient needs is not valid. Finally, it has been recognized that with moderate sphericity and moderate retention of the shape of the femoral head, as evaluated in relationship to secondary changes in the acetabulum, the patient can reach at least middle age before having significant secondary arthritic problems. A relatively conservative approach is therefore in order for most children whose disease is discovered in the early phases. Of course, it must be recognized that social problems develop in the older child, especially in girls, that contraindicate nonoperative care. Surgical considerations are indicated for many children in the older age group with more than one half of the femoral head involved, as well as in those with unsuccessful nonoperative efforts at containment.

Braces↗