Effect of oxygen fluctuations on recombinant Escherichia coli fermentation

Escherichia coli DH5alpha, carrying the pUC19 plasmid for the lacZ fragment of beta-galactosidase and ampicillin resistance, was grown in a batch fermentor under conditions of fluctuating oxygen supply. A Monte Carlo method was used to control the on/off supply of air to simulate circulation of cells in a large fermentor. Rapid changes in oxygen supply reduced the rates of oxygen uptake the carbon dioxide release and prolonged the active second growth phase in batch culture, compared to growth with continuous aeration. Amplification of the plasmid was observed during the stationary phase when air supplied continuously, but not during the Monte Carlo experiments.     

Scaled-up proliferation and regeneration of Nerine in liquid cultures Part I. The induction and maintenance of proliferating meristematic clusters by paclobutrazol in bioreactors

The natural propagation rate of bulb forming Amaryllidaceae including Nerine is low. Conventional micropropagation techniques are labor intensive and therefore expensive. Liquid cultures facilitate: scaling up, automation and cost reduction of micropropagation. Inflorescence-derived explants of Nerine were cultured on 2,4-dichlorophenoxyacetic acid (2,4-d) and 6-benzyladenine (BA) supplemented Murashige & Skoog (MS) medium. Callus-like tissue interspersed with nodular tissue, as well as direct organogenesis developed at the junction between flower pedicel and peduncle. Subculture of nodular tissue to 1-naphthalene acetic acid (NAA), BA and paclobutrazol (PAC) supplemented liquid medium in Erlenmeyer flasks or bubble bioreactors resulted in proliferation of rounded, compact, easily crumbled meristematic clusters. Growth and proliferation in bioreactors were higher than in shaken flasks and were affected differently by the inoculum to medium ratio in the two types of culture vessel. Nerine cultures showed low sensitivity to high aeration rates in bubble bioreactors despite the accumulation of debris. It was therefore possible to increase aeration rates without reducing the proliferation rate or damaging the quality of the meristematic aggregates. The conditions in semi-continuous culture in flasks and bioreactors were more favorable and increased the growth value by 100% and 140%, respectively. The total protein content increased by 180% in flasks and 90% in bioreactors. Although the presence of PAC throughout the culture period decreased growth and proliferation, it was a promotive bioregulator for meristernatic cluster formation. Proembryogenic clusters developed upon the removal of PAC. The use of meristematic clusters for micropropagation in scaled-up liquid cultures is discussed.     

Extravascular circulation in the pituitary of Mugil cephalus (Teleostei)

Summary Extravascular circulation in the pituitary of Mugil cephalus was investigated by injecting live fish with horseradish peroxidase and studying the distribution of the enzyme in the gland. The principal components of the extravascular circulatory system are the pericapillary spaces, and, arising from them, the interlobular and circumhypophyseal spaces. Extensions of these spaces penetrate the glandular parenchyma of the pars distalis, where they merge with pericellular spaces. In the neurohypophysis, pericapillary spaces are connected to the periaxonal spaces.Capillaries penetrating from the proximal neurohypophysis into the pars distalis are accompanied by neurosecretory axons. These axons form a mass of tissue which is limited near the capillaries by the pericapillary spaces and near the adenohypophysis by the interlobular spaces. Toward the interior of the adenohypophysis the amount of nervous tissue accompanying the capillaries progressively diminishes, thus reducing the distance between pericapillary and interlobular spaces. Within the pars distalis, the neurosecretory axons accompanying the capillaries are sparse, and the secretory and stellate cells are mostly located directly adjacent to the pericapillary spaces. In the neuro-intermediate lobe, interlobular spaces outline the neuro-adenohypophyseal boundary.The relationship between extravascular spaces and hormone-secreting cells varies in the different regions of the adenohypophysis depending upon the type of neurosecretory innervation in the respective region. In the regions of prolactin and gonadotropin cells, where neurosecretory axons are in direct contact with the secretory cells, the hormone-secreting and stellate cells are adjacent to the pericapillary spaces. In the regions of ACTH and STH cells, secretory and stellate cells are found adjacent to the interlobular spaces, which are interposed between the cells and the neurosecretory axons.Abbreviations AH adenohypophysis - CH circumhypophyseal - DNH distal neurohypophysis - HRP horseradish peroxidase - NH neurohypophysis - NS neurosecretory - PD pars distalis - PI pars intermedia - PPD proximal pars distalis - RNH rostral neurohypophysis - RPD rostral pars distalis This research was supported by a grant from the National Council for Research and Development, Israel, and the GKSS Geesthacht-Tesperhude, Federal Republic of Germany     

The Choroid Plexuses and the Barriers Between the Blood and the Cerebrospinal Fluid

1. The fluid homeostasis of the brain depends both on the endothelial blood–brain barrier and on the epithelial blood–cerebrospinal fluid (CSF) barrier located at the choroid plexuses and the outer arachnoid membrane.2. The brain has two fluid environments: the brain interstitial fluid, which surrounds the neurons and glia, and the CSF, which fills the ventricles and external surfaces of the central nervous system.3. CSF acts as a fluid cushion for the brain and as a drainage route for the waste products of cerebral metabolism.4. Recent findings suggest that CSF may also act as a third circulation conveying substances secreted into the CSF rapidly to many brain regions.     

The art of arteriogenesis

The identification of collateral artery growth (arteriogenesis) as the only mechanism to compensate for the loss of an occluded artery forced us to define the mechanisms responsible for this type of vessel growth. To achieve this, a variety of coronary as well as peripheral models of arteriogenesis have been developed. Based on these studies it is obvious that arteriogenesis obeys different mechanisms than angiogenesis, the sprouting of capillaries. Upon occlusion of an artery, the blood flow is redirected into preexisting arteriolar anastomoses that experience increased mechanical forces such as shear stress and circum ferential wall stress. The endothelium of the arteriolar connections is then activated, resulting in an increased release of monocyte-attracting proteins as well as an upregulation of adhesion molecules. Upon adherence and extravasation, monocytes promote arteriogenesis by supplying growth factors and cytokines that bind to receptors that are expressed on vascular cells within a limited time frame. Animal studies evidenced that factors, such as monocyte chemoattractant protein-1, granulocyte-monocyte colony-stimulating factor, or transforming growth factor-β₁, that either attract or prolong the lifetime of monocytes efficiently enhance collateral artery growth, an effect that was seen only to a minor degree after application of a single growth factor. Bone marrow-derived stems cells and endothelial progenitor cells do not incorporate in growing arteries but, rather, function as supporting cells. Complete elucidation of the mechanisms of arteriogenesis may lead to efficacious therapies counteracting the devastating consequences of vascular occlusive diseases.     

Movement of different-shaped particles in a pan-coating device using novel video-imaging techniques

The purpose of this study was to investigate the effects of particle shape on the movement of particles in a pan-coating device using novel video-imaging techniques. An area scan CCD camera was installed inside a 24-in pan coater at the same location as that of a spray nozzle, and the movement of particle was tracked using machine vision. A white tracer particle was introduced inside a bed of black-coated particles. The effects of pan loading, pan speed, and particle shape on the movement of particles was studied. The response variables were circulation time, surface time, projected area of particle per pass, dynamic angle of repose, cascading velocity, and dispersion coefficient. Experiments were conducted at 3 different pan speeds, 6, 9, and 12 rpm, and 2 fill levels (ratio of bed depth to pan diameter), one eighth and one quarter, and data were collected over a 30-minute time period. The differences in circulation times of spheres and tablets, with similar volume equivalent diameter as that of the sphere, were found to be insignificant at the 95% confidence interval. The circulation time ranged from 2.8 to 10.8 seconds depending on the operating condition and increased with increasing pan load and decreasing pan speed. The distributions of circulation time, surface time, and projected surface area were found to be nonnormal. The dynamic angle of repose for tablets was higher than for spheres. Also, the bed surface for spheres was much flatter in comparison with tablets where the bed shape attained a “wave-like” form. The average velocity of tablets in the cascading layer was found to be significantly higher than spheres. A linear model (R ²>0.98) best described the variation of velocity as a function of pan speed for all of the operating conditions. Published: October 6, 2005     

The meteorological sensitivity of ischaemic heart disease mortality events in Birmingham, UK

Winter ischaemic heart disease (IHD) mortality events (ME) were identified in order to establish their degree of meteorological sensitivity. Sensitivity was evaluated using regression of surface meteorological and large-scale atmospheric circulation variables on daily mortality for each mortality event. Critical meteorological variables affecting IHD mortality appear to be local surface dry-bulb and dew-point temperature and large-scale southerly and westerly wind components, atmospheric pressure and vorticity. The rate of change and departure from normal conditions of these variables appear to be especially important for engendering IHD mortality events. Associated with IHD mortality are two broad types of weather conditions: (1) blustery westerly flows and rapidly changing weather from the west and (2) climatologically strong northeasterly to southeasterly flows of cold air, which bring rapidly changing and anomalous thermal conditions to the study area. The general atmospheric circulation patterns that produce these conditions are identified and the implications of results for weather and health studies are discussed. Received: 24 October 2000 / Revised: 16 April 2001 / Accepted: 18 April 2001     

Cranial circulation of the pen-tailed tree shrewPtilocercus lowii and relationships of Scandentia

The major cranial arteries and veins are described for a 30-mm crown-rump length fetus of the pen-tailed tree shrewPtilocercus lowii, and comparisons are made with cranial vessels reported in the tree shrewTupaia and with the vascular pattern reconstructed for primitive eutherians.Ptilocercus shares a number of derived features of the cranial circulation withTupaia, which, therefore, represent synapomorphies of tree shrews (Tupaiidae, Scandentia). Included are (1) the enclosure of the intratympanic portion of the internal carotid artery in a bony canal that is floored proximally and distally by the entotympanic and by the petrosal in between, (2) the enclosure of the intratympanic portion of the stapedial artery by the petrosal in a canal on the promontorium and within the epitympanic crest beneath the tympanic roof, (3) the absence of an exit for the arteria diploëtica magna, (4) an alisphenoid canal, (5) a maxillary artery that passes medial to the mandibular nerve beneath foramen ovale, and (6) a laryngeopharyngeal artery. Some of these derived features, however, are also found in certain other eutherians (e.g., numbers 2, 3, and 6 in Euprimates) and, therefore, may be used in future studies to assess the higher-level affinities of Scandentia.     

Morphological arrangement of the coronary vasculature in a shark (Squalus sucklei) and a teleost (Oncorhynchus mykiss)

The coronary circulation is of great importance in maintaining cardiovascular function and consequently it has been extensively studied in many mammalian species. However, much less attention has been paid to the coronary circulation in other vertebrates. For example, while elasmobranch fishes are of special interest as they are the most ancient lineage of vertebrates to possess a coronary circulation, only qualitative studies exist on their coronary circulation and most concern the architecture of the large arteries. Our study tested the prediction that the coronary circulation of sharks is better developed than previously thought. However, to test this idea, a methodology was needed to quantify vascularity, vessel morphology and oxygen diffusion distances in a heart with predominantly spongy myocardium. Here, we describe this methodology using dogfish and rainbow trout and suggest that the dogfish spongy myocardium appears to rely predominantly on the coronary circulation for its oxygen supply, an arrangement that contrasts with the spongy myocardial tissue of rainbow trout. In support of this suggestion, the density of the microvasculature of the spongy myocardial tissue of dogfish exceeded that of their compact tissue. Although vascularity in the compact myocardium of dogfish was significantly lower than trout, intervascular distances were similar on account of a significantly larger vessel diameter in dogfish, which corresponds to a larger red blood cell size of the dogfish when compared to trout. J. Morphol. 277:896–905, 2016. © 2016 Wiley Periodicals, Inc.