IS POSTPRANDIAL THERMOPHILY AN EXPERIMENTAL ARTIFACT?

2008 ◽  
Vol 211 (17) ◽  
pp. vii-viii
Author(s):  
J. B. Andersen
Keyword(s):  
Experimental Artifact

The heart works against gravity

1993 ◽  
Vol 265 (4) ◽  
pp. R715-R720 ◽  
Author(s):  
R. S. Seymour ◽  
A. R. Hargens ◽  
T. J. Pedley
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Potential Energy ◽  
Flow Rate ◽  
Viscous Resistance ◽  
Arterial Blood ◽  
Experimental Artifact ◽  
Continuous Stream ◽  
Laboratory Models ◽  
Poiseuille Equation

The circulatory systems of vertebrate animals are closed, and blood leaves and returns to the heart at the same level. It is often concluded, therefore, that the heart works only against the viscous resistance of the system, not against gravity, even in vascular loops above the heart in which the siphon principle operates. However, we argue that the siphon principle does not assist blood flow in superior vascular loops if any of the descending vasculature is collapsible. If central arterial blood pressure is insufficient to support a blood column between the heart and the head, blood flow ceases because of vascular collapse. Furthermore, the siphon principle does not assist the heart even when a continuous stream of blood is flowing in a superior loop. The potential energy gained by blood as it is pumped to the head is lost to friction in partially collapsed descending vessels and thus is not regained. Application of the Poiseuille equation to flow in collapsible vessels is limited; resistance depends on flow rate in partially collapsed vessels with no transmural pressure difference, but flow rate is independent of resistance. Thus the pressure developed by the heart to establish a given flow rate is independent of the resistance occurring in the partially collapsed vessels. The pressure depends only on the height of the blood column and the resistance in the noncollapsed parts of the system. Simple laboratory models, involving water flow in collapsible tubing, dispel the idea that the siphon principle facilitates blood flow and suggest that previously published results may have been affected by experimental artifact.

Intracellular receptors for androgens: Experimental artifact?

Urology ◽  
1983 ◽  
Vol 21 (3) ◽  
pp. 332-333
Author(s):  
Marvin S. Melzer
Keyword(s):  
Experimental Artifact

scholarly journals Ketohexokinase: Expression and Localization of the Principal Fructose-metabolizing Enzyme

2009 ◽  
Vol 57 (8) ◽  
pp. 763-774 ◽  
Author(s):  
Christine P. Diggle ◽  
Michael Shires ◽  
Derek Leitch ◽  
David Brooke ◽  
Ian M. Carr ◽  
...  
Keyword(s):  
Western Blotting ◽  
Cellular Localization ◽  
Splice Variants ◽  
Immunohistochemical Localization ◽  
Nuclear Staining ◽  
Experimental Artifact ◽  
Alternatively Spliced ◽  
Metabolizing Enzyme ◽  
Knockout Animals

Ketohexokinase (KHK, also known as fructokinase) initiates the pathway through which most dietary fructose is metabolized. Very little is known about the cellular localization of this enzyme. Alternatively spliced KHK-C and KHK-A mRNAs are known, but the existence of the KHK-A protein isoform has not been demonstrated in vivo. Using antibodies to KHK for immunohistochemistry and Western blotting of rodent tissues, including those from mouse knockouts, coupled with RT-PCR assays, we determined the distribution of the splice variants. The highly expressed KHK-C isoform localized to hepatocytes in the liver and to the straight segment of the proximal renal tubule. In both tissues, cytoplasmic and nuclear staining was observed. The KHK-A mRNA isoform was observed exclusively in a range of other tissues, and by Western blotting, the presence of endogenous immunoreactive KHK-A protein was shown for the first time, proving that the KHK-A mRNA is translated into KHK-A protein in vivo, and supporting the suggestion that this evolutionarily conserved isoform is physiologically functional. However, the low levels of KHK-A expression prevented its immunohistochemical localization within these tissues. Our results highlight that the use of in vivo biological controls (tissues from knockout animals) is required to distinguish genuine KHK immunoreactivity from experimental artifact.

scholarly journals Detection of plasma proteins in CNS neurons: conspicuous influence of tissue-processing parameters and the utilization of serum for blocking nonspecific reactions.

1996 ◽  
Vol 44 (6) ◽  
pp. 591-603 ◽  
Author(s):  
T Moos ◽  
P E Høyer
Keyword(s):  
Plasma Proteins ◽  
Processing Parameters ◽  
Circumventricular Organs ◽  
Neuronal Somata ◽  
Tissue Processing ◽  
Axonal Projections ◽  
Experimental Artifact ◽  
Nonspecific Staining ◽  
Cryostat Sections ◽  
The Brain

Despite the presence of a blood-brain barrier (BBB), plasma proteins have been detected intraneuronally in regions with axonal projections confined to the CNS. This finding raises the question of whether plasma proteins are taken up from the brain interstitium or whether the results are due to experimental artifact. We examined the effect of various protocols for tissue processing on the intraneuronal distribution of plasma proteins using immunohistochemistry. The detection level of plasma proteins decreased after prolonged fixation, irrespective of the fixative and embedding method employed. In cryostat sections, attempts to block nonspecific staining by serum protein caused considerable nonspecific staining in itself. When nonspecific staining was blocked with a serum-free buffer, specifically labeled neuronal perikarya were found in cryostat sections of brains fixed by perfusion with paraformaldehyde without postfixation. Albumin and IgG occurred predominantly in neurons having projections beyond the BBB but also sparsely in neurons having projections confined to the CNS. Transferrin was evenly distributed within neuronal somata, irrespective of the orientation of projections. The immunoreaction product of the three plasma proteins exhibited a specific intraneuronal localization in the differently projecting neurons. In circumventricular organs, plasma proteins were observed extracellularly and in projecting fibers. In conclusion, plasma proteins are present in neurons with projections confined to the CNS and are probably taken up from the brain interstitium.

scholarly journals Why do people show minimal knowledge updating with task experience: Inferential deficit or experimental artifact?

2009 ◽  
Vol 62 (1) ◽  
pp. 155-173 ◽  
Author(s):  
Christopher Hertzog ◽  
Jodi Price ◽  
Ailis Burpee ◽  
William J. Frentzel ◽  
Simeon Feldstein ◽  
...  
Keyword(s):  
Experimental Artifact ◽  
Knowledge Updating ◽  
Task Experience

Anoxic Mineralization: Environmental Reality or Experimental Artifact?

2008 ◽  
Vol 28 (1) ◽  
pp. 47-49 ◽  
Author(s):  
P.M. Bradley ◽  
F.H. Chapelle ◽  
F.E. Löffler
Keyword(s):  
Experimental Artifact

On the investigation of homeopathic potencies using low resolution NMR T2 relaxation times: an experimental and critical survey of the work of Roland Conte et al

2001 ◽  
Vol 90 (01) ◽  
pp. 5-13 ◽  
Author(s):  
LR Milgrom ◽  
KR King ◽  
J Lee ◽  
AS Pinkus
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Nitric Acid ◽  
Magnetic Resonance ◽  
Spin Relaxation ◽  
Relaxation Times ◽  
Critical Survey ◽  
Low Resolution ◽  
T2 Relaxation ◽  
Experimental Artifact ◽  
Experimental Protocols

AbstractWe have attempted to reproduce differences in low resolution nuclear magnetic resonance (NMR) T2 spin–spin relaxation times between homeopathically potentised and unpotentised Nitric acid (nit-ac) solutions previously reported by Conte, et al. Using similar instrumentation and experimental protocols, we have shown that it is likely that Conte's original results are attributable to experimental artifact originating in the glassware used for the manufacture of the NMR tubes.

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