Organ size

II. PLgel ORGANIC SIZE EXCLUSION CHROMATOGRAPHY (SEC) COLUMNS... 

Dawley E.M. (1998). Species, sex and seasonal differences in vomeronasal organ size. Micros Res Tech 41, 506-518. 

Hyperplasia An increase in the number of cells within a tissue leading to an increase in tissue or organ size. 

A. Organ Size, Blood Flow, and Partition Coefficient... 

Weinkove D, Neufeld TP, Twardzik T, Waterfield MD, Leevers SJ 1999 Regulation of imaginal disc cell size, cell number and organ size by Drosophila class IA phosphoinositide 3-kinase and its adaptor. Curr Biol 9 1019-1029... 

Bohni R, Riesgo-Escovar J, Oldham S et al 1999 Autonomous control of cell and organ size by CHICO, a Drosophila homolog of vertebrate IRS1-4. Cell 97 865-875... 

To summarize, modulating signalling by this pathway alters three parameters growth rate, cell size and organ size. What is unclear is the nature of the relationship... 

Nasmyth In this particular case I was getting the impression that timers would be one way of determining final organ size. In this particular case you clearly get regulation through death. 

Nurse I wondered whether it might be worth revisiting the issue of what determines organ size, because this is obviously relevant to a number of issues that have risen. Martin Raff, do you have any thoughts about overall organ size and how that is regulated ... 

Nurse If instead of a whole dozen fates you have, let s say, just five, you end up with an imaginal disc that is smaller over all, compared with the one with all dozen. This suggests that determining the overall proper organ size requires a proper mixture of cells with all the cell fates, rather than a limited set. Would this be consistent ... 

Raff The reason this is such an important example is because it is the only clear example in which an extracellular inhibitor is known to play a crucial part in determining organ size. 

Raff One of the questions we haven t really addressed is what is actually being controlled in the control of organ or organism size Is it total cell mass, or total cell number, or both ... 

Rehner In bithorax mutants the haltere disc grows just like a wing disc it is an obvious example where a Hox gene determines organ size. The mechanism is not understood. 

In addition to the pore size-particle size retention relationship problems mentioned above, other factors can influence a filter medium s retention characteristics. Absorptive retention can be influenced by the organism size, organism population, pore size of the medium, pH of the filtrate, ionic strength, surface tension, and organic content. Operational parameters can also influence retention, such as flow rate, salt concentration, viscosity, temperature, filtration duration, filtration pressure, membrane thickness, organism type, and filter medium area [52,53]. 

It is possible to predict what happens to Vd when fu or fur changes as a result of physiological or disease processes in the body that change plasma and/or tissue protein concentrations. For example, Vd can increase with increased unbound toxicant in plasma or with a decrease in unbound toxicant tissue concentrations. The preceding equation explains why because of both plasma and tissue binding, some Vd values rarely correspond to a real volume such as plasma volume, extracellular space, or total body water. Finally interspecies differences in Vd values can be due to differences in body composition of body fat and protein, organ size, and blood flow as alluded to earlier in this section. The reader should also be aware that in addition to Vd, there are volumes of distribution that can be obtained from pharmacokinetic analysis of a given data set. These include the volume of distribution at steady state (Vd]SS), volume of the central compartment (Vc), and the volume of distribution that is operative over the elimination phase (Vd ea). The reader is advised to consult other relevant texts for a more detailed description of these parameters and when it is appropriate to use these parameters. 

So far we have not included the relaxation processes (T and 72), and for many pulse sequences we can leave out this aspect to make the math simpler. We know that relaxation is going on, but in many cases this is merely a technicality and is not essential in understanding the pulse sequence. In general, pulses are on the timescale of microseconds (p,s), delays for evolution are on the order of milliseconds (ms), and delays for buildup of NOE can be hundreds of ms. For organic-sized molecules, we can safely ignore relaxation for delays in the [is or ms range. Of course, for some experiments such as NOE, the relaxation process is central to the experiment so we cannot ignore it. 

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