In Situ Models, Physico-Chemical Aspects

1994 ◽  
Vol 8 (2) ◽  
pp. 125-133 ◽  
Author(s):  
J.M. Ten Cate
Keyword(s):  
Single Point ◽  
Limiting Factor ◽  
Model Parameters ◽  
Laboratory Findings ◽  
Physiological Processes ◽  
Physico Chemical ◽  
Crystallite Surface ◽  
Mineral Loss

In situ (intra-oral) caries models are used for two purposes. First, they provide information about oral physiological processes. Such information helps to detail our knowledge of the oral ecosystem and to verify conclusions from in vitro experiments. Second, in situ models are utilized to test preventive agents in the phase between laboratory testing and clinical trials. Most investigations involving enamel inserts have been aimed at testing new dentifrices. The experimental designs of such studies usually do not allow one to draw conclusions on physico-chemical processes, e.g., because of single point measurements. Studies of model parameters (lesion type, lesion severity, and de/remineralization in time) constitute only a minority of the research reports. The most striking observation obtained with in situ models has been the significant differences in de/remineralization observed among individuals and, more importantly, within one individual during different time periods and between different sites in the same mouth (for review, see ten Cate et al., 1992). Regardless of this, some general findings can be inferred: During in situ demineralization, up to 62 vol%μm/day may be removed from enamel. For dentin specimens, this value may be as high as 89 vol%μm/day. For remineralization, during fluoride dentifrice treatment, a median deposition rate of 0.7%/day (for lesions with integrated mineral loss values between 2000 and 4000 vol%μm) is found. The rate of deposition seems to be correlated with the extent of the pre-formedlesion. This suggests that the number of sites (crystallite surface) available for calcium phosphate precipitation is an important parameter. However, the rate at which mineral ions are supplied (by saliva) could also be a limiting factor, as is shown in a theoretical analysis of mass-balance of enamel constituents. The few studies that have monitored caries development in time reveal that mineral loss (and also lesion progression in depth) from enamel in situ is linear in time. This is in contrast to results from laboratory findings.

scholarly journals In situ and in vitro estimation of mineral release from common feedstuffs fed to cattle

2017 ◽  
Vol 155 (7) ◽  
pp. 1160-1173 ◽  
Author(s):  
D. ZANETTI ◽  
A. C. B. MENEZES ◽  
F. A. S. SILVA ◽  
L. F. COSTA E SILVA ◽  
P. P. ROTTA ◽  
...  
Keyword(s):  
Release Rate ◽  
Soluble Fraction ◽  
Limiting Factor ◽  
Asymptotic Model ◽  
Mineral Absorption ◽  
Large Variability ◽  
Group 4 ◽  
Ruminal Degradation

SUMMARYThe objective of the current study was to quantify the dry matter (DM) digestibility, and total ash (TA) and mineral release from 12 concentrate and 12 forage feedstuffs commonly fed to cattle using in situ and in vitro methods. Concentrate and forage feedstuffs were incubated in the rumen of ruminally cannulated beef bulls at eight different time points. Two different trials were conducted for concentrates and forages, with maximum incubation time of 72 and 120 h, respectively. The residue from samples incubated for 24 h were treated with pepsin and hydrochloric acid to simulate abomasum digestion in vitro. The initial and residual samples after in situ and in vitro incubations were measured. An asymptotic model was adopted for estimating solubility of minerals, disappearance rate of DM, and TA. Correlations between feedstuff contents and mineral release were evaluated. Residual samples from rumen fermentation after 24 h were incubated in simulated abomasal conditions and mineral release was measured. Cluster analysis was performed to group feedstuffs in relation to TA release. Large variability was observed between concentrate and forage feedstuffs for all constituents analysed. Large variability was observed for the effective ruminal degradation of TA and individual mineral release. When feedstuffs were clustered according to the immediately soluble fraction (‘a’), the insoluble by potentially releasable fraction (‘b’) and the release rate of ‘b’ (‘kd’,/h) estimates of TA ruminal release, four groups were identified. From group ‘1’ to group ‘4’, an increase in the soluble fraction and a reduction in both moderate releasable fraction and release rate was observed. Neutral detergent fibre content had a negative correlation with mineral release in the rumen, while mineral content had a positive correlation. These results demonstrate that mineral solubilization in the digestive tract is not the limiting factor for mineral absorption from the feedstuffs tested.

Fertilization biology of the abalone Haliotis laevigata: laboratory and field studies

1999 ◽  
Vol 56 (9) ◽  
pp. 1668-1678 ◽  
Author(s):  
Russ Babcock ◽  
John Keesing
Keyword(s):  
Field Experiments ◽  
Nearest Neighbor ◽  
Field Studies ◽  
Fertilization Success ◽  
Limiting Factor ◽  
Fertilization Rates ◽  
Abalone Species ◽  
Nearest Neighbor Distances

A combination of laboratory and field experiments with the commercial abalone species Haliotis laevigata showed that fertilization may be a limiting factor in some exploited populations when distances separating spawning individuals are too large. The effects of gamete age, gamete concentration, and gamete contact time in the laboratory were used to model fertilization success in situ and compared with experimental fertilization rates in the field. Highest fertilization rates in vitro (80%) were found for sperm concentrations in the range of 1 × 104 to 1 × 106·mL-1. Fertilization rates of 48 ± 1.7% (95% CI) were measured at separation distances of 2 m and dropped to 2.8 ± 0.7% (95% CI) at 16 m downstream, agreeing closely with rates predicted by the model. Recruitment failures reported for South Australian populations of H. laevigata have occurred when densities fell below ca.0.3 animals·m-2, or mean nearest-neighbor distances between 1 and 2 m. This density corresponds well to critical nearest-neighbor distances for fertilization success. Stocks at higher densities are predicted to have higher fertilization rates (ca.90%) such that fertilization success is not a factor limiting recruitment.

Triple-point magnetic flux rope analysis for the 2020 April 19 CME observed in situ by Solar Orbiter, Bepi Colombo, and WIND

2021 ◽  
Author(s):  
Andreas J. Weiss ◽  
Christian Möstl ◽  
Emma Davies ◽  
Matthew J. Owens ◽  
Tanja Amerstorfer ◽  
...  
Keyword(s):  
Triple Point ◽  
Single Point ◽  
Flux Rope ◽  
Radial Distance ◽  
Field Measurements ◽  
Model Parameters ◽  
Magnetic Flux Rope ◽  
Point Analysis ◽  
Point Combination

<p>We present initial results for a triple-point analysis for the in situ magnetic field measurements of a CME observed at three independent locations. On the 19th of April 2020, Solar Orbiter observed a CME in situ at a radial distance of around 0.8 au. This CME was subsequently also detected by the Wind and Bepi Colombo satellites closer to Earth. This triple in situ measurement of a CME provides us the unique opportunity to test the consistency of the measurements with our own 3D Coronal Rope Ejection (3DCORE) model. A triple measurement allows for up to seven different data combinations to be analyzed (three single-point, three dual-point, and one single triple-point combination) which gives us information on how our analysis pipeline responds to multi-point measurements and how the results change with measurements at differing radial and longitudinal distances. The goal of this study is to test whether all three in situ measurements can still be described by a slightly bent flux rope geometry and how adding additional measurements can improve the accuracy of inferred model parameters.</p>

scholarly journals Effect of starch on the cariogenic potential of sucrose

2005 ◽  
Vol 94 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Cecilia C. C. Ribeiro ◽  
Cínthia P. M. Tabchoury ◽  
Altair A. Del Bel Cury ◽  
Livia M. A. Tenuta ◽  
Pedro L. Rosalen ◽  
...  
Keyword(s):  
Animal Studies ◽  
Amylase Activity ◽  
Negative Control ◽  
Cross Sectional ◽  
Dental Biofilm ◽  
Enamel Demineralization ◽  
Two Phases ◽  
Mineral Loss

Sincein vitroand animal studies suggest that the combination of starch with sucrose may be more cariogenic than sucrose alone, the study assessedin situthe effects of this association appliedin vitroon the acidogenicity, biochemical and microbiological composition of dental biofilm, as well as on enamel demineralization. During two phases of 14 d each, fifteen volunteers wore palatal appliances containing blocks of human deciduous enamel, which were extra-orally submitted to four groups of treatments: water (negative control, T1); 2 % starch (T2); 10 % sucrose (T3); and 2 % starch+10 % sucrose (T4). The solutions were dripped onto the blocks eight times per day. The biofilm formed on the blocks was analysed with regard to amylase activity, acidogenicity, and biochemical and microbiological composition. Demineralization was determined on enamel by cross-sectional microhardness. The greatest mineral loss was observed for the association starch+sucrose (P<0·05). Also, this association resulted in the highest lactobacillus count in the biofilm formed (P<0·05). In conclusion, the findings suggest that a small amount of added starch increases the cariogenic potential of sucrose.

scholarly journals Tetracycline-regulated expression enables purification and functional analysis of recombinant connexin channels from mammalian cells

2004 ◽  
Vol 383 (1) ◽  
pp. 111-119 ◽  
Author(s):  
Irina V. KOREEN ◽  
Wafaa A. ELSAYED ◽  
Yu J. LIU ◽  
Andrew L. HARRIS
Keyword(s):  
Mammalian Cells ◽  
Cultured Cells ◽  
Expression System ◽  
Physiological Processes ◽  
Messenger Molecules ◽  
One Step ◽  
Cellular Control

Intercellular coupling mediated by gap junction channels composed of connexin protein underlies numerous physiological processes, such as cellular differentiation, tissue synchronization and metabolic homoeostasis. The distinct molecular permeability of junctional channels composed of different connexin isoforms allows cellular control of coupling via regulation of isoform expression. However, the permeability properties of most connexin isoforms have not been well characterized due to the difficulty of manipulating and measuring the diffusible concentrations of cytoplasmic messenger molecules and metabolites, and to a lack of control over channel isoform composition, in vivo. Here we present a method to express and purify active connexin hemichannels of a single isoform or a consistent ratio of two isoforms from cultured cells using the Tet-On inducible expression system and one-step anti-haemagglutinin immunoaffinity purification. The procedure yields 10–20 μg of pure connexin protein from 2.5×108 HeLa cells. The purified channels are shown to be useful for in vitro permeability analysis using well established techniques. This method has substantial advantages over existing methods for heterologous connexin expression, such as the ease of co-expression of two isoforms at a constant ratio, consistently high expression levels over many passages, and the ability to study channel properties in situ as well as in purified form. Furthermore, the generic cloning site of the new pBI-GT vector and the commercial availability of anti-haemagglutinin (clone HA-7)–agarose make this affinity tagging and purification procedure easily applicable to other proteins.

scholarly journals Health Concerns of Various Nanoparticles: A Review of Their in Vitro and in Vivo Toxicity

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 634 ◽  
Author(s):  
Marziyeh Ajdary ◽  
Mohammad Moosavi ◽  
Marveh Rahmati ◽  
Mojtaba Falahati ◽  
Mohammad Mahboubi ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Protein Corona ◽  
In Vitro Models ◽  
The Body ◽  
Limiting Factor ◽  
Key Factors ◽  
Cytotoxic Effects ◽  
Physico Chemical

Nanoparticles (NPs) are currently used in diagnosis and treatment of many human diseases, including autoimmune diseases and cancer. However, cytotoxic effects of NPs on normal cells and living organs is a severe limiting factor that hinders their use in clinic. In addition, diversity of NPs and their physico-chemical properties, including particle size, shape, surface area, dispersity and protein corona effects are considered as key factors that have a crucial impact on their safe or toxicological behaviors. Current studies on toxic effects of NPs are aimed to identify the targets and mechanisms of their side effects, with a focus on elucidating the patterns of NP transport, accumulation, degradation, and elimination, in both in vitro and in vitro models. NPs can enter the body through inhalation, skin and digestive routes. Consequently, there is a need for reliable information about effects of NPs on various organs in order to reveal their efficacy and impact on health. This review covers the existing knowledge base on the subject that hopefully prepares us better to address these challenges.

Major Topics in Quantitative Microradiography of Enamel and Dentin: R Parameter, Mineral Distribution Visualization, and Hyper-Remineralization

1997 ◽  
Vol 11 (4) ◽  
pp. 403-414 ◽  
Author(s):  
J. Arends ◽  
J.L. Ruben ◽  
D. Inaba
Keyword(s):  
Mineral Content ◽  
Dissolution Kinetics ◽  
Lesion Length ◽  
Computer Assisted ◽  
Average Amount ◽  
Mineral Distribution ◽  
Loss Parameter ◽  
Mineral Loss

Three aspects of quantitative transverse microradiography are described and discussed: (1) the average mineral loss parameter of enamel or dentin lesions (R) in vol%; (2) mineral distribution visualization of lesions by means of a computer-assisted videodensitometric (CAV) method; and (3) the microradiography of hyper-remineralized lesions. "R", defined as the average amount of mineral lost (or gained) in a lesion per unit lesion length, is a useful parameter in dental caries. The results show that, in vitro, R is about constant over the demineralization period for enamel and dentin. This was found even for quite different dissolution kinetics. R is strongly reduced by the presence of small amounts of fluoride in the demineralizing system. R of dentin lesions is smaller than for enamel lesions. We conclude that the mineral loss value (ΔZ) and the lesion depth (ld) are in general dependent parameters during in vitro or in situ studies on enamel or dentin. During lesion formation, mineral loss from the lesion and acid penetration in the tissue are obviously linked. This is possible only if the mineral content in the lesion does not change very much after passage of the lesion front. The CAV method presented is illustrated for enamel lesions formed in vitro and in situ.

scholarly journals Establishing F1A-CreERT2 Mice to Trace Fgf1 Expression in Adult Mouse Cardiomyocytes

Cells ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 121
Author(s):  
Yi-Chao Hsu ◽  
Yu-Fen Chung ◽  
Mei-Shu Chen ◽  
Chi-Kuang Wang ◽  
Si-Tse Jiang ◽  
...  
Keyword(s):  
Troponin T ◽  
Lineage Tracing ◽  
Mouse Line ◽  
Protein Coding ◽  
Physiological Processes ◽  
Mrna Variants ◽  
Alternatively Spliced

Fibroblast growth factor 1 (FGF1) regulates many biological and physiological processes. In mice, Fgf1 gene contains at least three upstream promoters and are alternatively spliced to the first protein coding exon, giving rise to different Fgf1 mRNA variants (1A, 1B and 1G). Among them, the Fgf1A transcript is predominantly expressed in the heart. FGF1 can induce cardiomyocyte regeneration and cardiogenesis in vitro and in vivo. Here, we generated a novel mouse line using the Fgf1A promoter (F1A) driving the expression of the inducible Cre recombinase (CreERT2). We firstly demonstrated that the highest mRNA expression of CreERT2 were detected in the heart specifically of F1A-CreERT2 mice, similar to that of Fgf1A mRNA. The F1A-CreERT2 mice were crossed with ROSA26 mice, and the F1 mice were analyzed. The LacZ-positive signals were detected exclusively in the heart after tamoxifen administration. The CreERT2-mediated recombination in the tissues is monitored through LacZ-positive signals, indicating the in situ localization of F1A-positive cells. Consistently, these F1A-positive cells with RFP-positive signals or LacZ-positive blue signals were co-localized with cardiomyocytes expressing cardiac troponin T, suggesting cardiomyocyte-specific activation of Fgf1A promoter. Our data suggested that the F1A-CreERT2 mouse line could be used for time-dependent and lineage tracing of Fgf1A-expressing cells in vivo.

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

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