PER expressions

For some parameter values the model for the mammalian clock fails to allow entrainment by 24-h LD cycles, regardless of the amplitude of the light-induced change in Per expression. The question arises whether there exists a syndrome corresponding to this mode of dynamic behavior predicted by the model. Indeed there exists such a syndrome, known as the non-24-h sleep-wake syndrome, in which the phase of the sleep-wake pattern continuously varies with respect to the LD cycle that is, the patient free-runs in LD conditions [117]. Disorders of the sleep-wake cycle associated with alterations in the dynamics of the circadian clock belong to the broad class of dynamical diseases [122, 123], although the term syndrome seems more appropriate for some of these conditions. 

Van Gelder We are currently making the JLdjBmal mice to answer that question. Rae Silver has some results relating to this. She has looked for clock gene expression in the melanopsin-positive ganglion cells. Remarkably, she does not find Per expression in those cells. 

Menaker That s true, but we haven t done that. The other thing we must remember is that in our hands the peak of Per expression in the liver varies a good deal from one experiment to another. This has to do with how the rats are responding to the immediate situation that they are in. We need to start measuring feeding behaviour, because they feed at different times under somewhat different circumstances. This changes with age, too. The right way to do your experiment is to get the V er expression and the RNA from the same animals. 

Frisch B, Hardin PE, Hamblen-Coyle MJ, Rosbash MR, HaU JC 1994 A promoterless period gene mediates behavioral rhythmicity and cyclical per expression in a restricted subset of the... 

Hardin We can rescue locomotor activity rhythms with a static per RNA level. What is important here are the protein levels. The other answer we need to find for this story is looking in antennae with anti-PER antibodies to see whether the protein is cychng. The other experiment is to use a luciferase reporter to see whether there are rhythms in PER expression. 

If the model for the oscillator is correct. Per and Cry expression will define solar/ circadian time, driving the activity—rest cycle rather than just being a passive reflection of the activity cycle. Therefore, their expression patterns should exhibit the same phase in the SCN of nocturnal and diurnal species. This is confirmed by examination of Per expression in the SCN of the diurnally active ground squirrel, Spermophilus (Mrosovsky et al 2001). The rhythm of Per1 and Per2 expression in... 

The behaviour of clock-gene products in the SCN provides strong support to the current model of the circadian clockwork as an autonomous intracellular mechanism based upon interlocked feedback and feed-forward loops. Intercellular signalling, more specifically convergent mechanisms for up- and down-regulation of Per expression, is critical to circadian entrainment, which can now be explained in mechanistic terms rather than described by formalisms. 

Hastings Our simple interpretation is that they don t have a clock to shift. As we move the LD schedule they just go completely with it on first cycle. There isn t evidence for any transient re-setting which would indicate that there is inertia in the behaviour that is reflective of a clock mechanism (Reddy et al 2002). I didn t show the LD cycle data, but if you look at Per expression on an LD cycle it is extremely low. The retinal mechanism in these mice is also impaired and Per induction can t be driven with light. 

Sehgal According to some people, the per and timgal4 drivers are markers for all the neurons, or maybe even all the cells in the adult. I agree that they are not found everywhere, but the expression is widespread. One explanation is that the drivers are promiscuous. The other is that there are low levels of expression in these places that we don t detect any other way. I would think that this is kind of supported by some of the doubletime data, where, in a douhktime mutant we get per expression in ectopic locations. This would argue that per is synthesized in a lot of locations where you normally don t detect it because it is destabilized by doubletime. 

The specificity and accuracy of the LR reaction seem higher than those of the BP reaction. In addition, there is almost no possibility that some errors (such as mutation and deletion) occur unlike PCR followed by the BP reaction. Therefore, most of the E. coli colony has correct plasmids. However, we recommend to check at least two colonies per expression plasmid to ensure acquisition of proper plasmids. 

Another important study (Zeng et al., 1994) demonstrated that the overexpression of PER in the Drosophila eyes represses per transcription and suppresses circadian rhythmicity in these cells, without affecting circadian PER oscillations in other per-expressing cells in the brain, or the circadian rhythm in locomotor activity. This work also shows that the action of PER on transcription is intracellular, and suggests that each per-expressing cell contains an autonomous oscillator of which the per feedback loop is a component (Zeng et al., 1994). 

In a recent study, Zeng et al. (1994) showed that the overexpression of PER in photoreceptor cells in Drosophila eyes suppresses circadian rhythms in these cells, but not in other per-expressing cells located in the brain. The experiment was performed by means of a construct containing the promoter region of the Drosophila opsin gene followed by a fragment of per. 

To determine the volume of the PER, we employ a similar procedure to that given for calculating VcstR In this instance, the PER equation is used. The PER expression for component A specifically is... 

In a problem, identify given and wanted quantities that are related by a Per expression. Set up and solve the problem by dimensional analysis. 

Let s examine this basic days-in-3-weeks problem in detail. The 7 days in each week relationship between these two units can be stated as 7 days per week. We call this a Per expression. This Per expression can also be written as a fraction or a ratio 7 days/week, or an equality, 7 days = 1 week. Similarly, there are 24 hours Per day (24 hours/day or 24 hours = 1 day) and 60 minutes Per hour (60 minutes/hour or 60 minutes = 1 hour). Any Per expression can be written as a fraction or an equality. We will identify Per expressions in examples by the symbol Per. 

The mathematical requirement for a Per expression between units for the two quantities is that they are directly proportional to each other. What you pay for raw hamburger at the grocery store in units of money, for example, is directly proportional to the amount you buy in units of weight. Two pounds cost twice as much as one pound. If hamburger is priced at 2.25 dollars Per pound (2.25 dollars/pound), three pounds—three times as many pounds—cost 6.75 dollars—three times as many dollars. 

A Per expression can be used as a conversion factor. In a problem setup, a conversion factor is written as a fraction. Each Per expression yields two conversion factors, one the reciprocal of the other. For example, 7 days Per week produces... 

In this form, the proportionality constant becomes a Per expression. 

Now write the Per expression between days and weeks. Think, days =... 

We will write Per expressions over the arrows of unit paths in examples throughout this book. We call the combination of these two lines a Per/Path. So, if you are asked to write a Per/Path, you are being asked to write these two lines. 

Some problems have more than one step in their unit paths. To solve a problem by dimensional analysis, you must know the Per expression for each step. 

Most people do not know the number of hours in a week, so they cannot use a one-step unit path from hours to weeks, hours —> weeks. But there is an intermediate time unit that breaks the unit path into two steps, each of which has a familiar conversion factor. Can you write the two-step unit path, plus the Per expression for each step Try it as you analyze the problem by listing the Given, the Wanted, and the Per/Path ... 

Which among the following might he Given quantities and, therefore, starting points for a dimensional analysis setup, and which are Per expressions that are used as conversion factors (a) 10 days (b) 2000 pounds = 1 ton (c) 2.54 centimeters per inch. 

Conversions from one metric unit to another are applications of dimensional analysis. Goal 8 says you should be able to make these conversions among the unit, kilounit, centiunit, and milliunit. In this context, unit (u) may be gram (g), meter (m), or liter (L). These relationships are summarized here as Per expressions and their resulting conversion factors ... 

The two conversion factors in the preceding example can be combined 1000 mm/m and 100 cm/m show that both 1000 mm and 100 cm equal 1 m. Therefore, 1000 mm = 100 cm. This equality can be written as a Per expression, 1000 mm/100 cm, which reduces to 10 mm/cm. This relationship is well known to those accustomed to working with metric units. Thus, Example 3.11 can be solved by either of the following one-step setups ... 

The Per expression is written rather than —------because the purpose of this... 

This is another problem you can work by applying dimensional analysis. We assume that you already know the Per expression. Set up and solve completely. Round off the answer to the correct number of significant figures. 

The discussion in this part of the text further explains the relationship between direct proportionalities and Per expressions. You will find yourself doing this type of thinking continually throughout this course, in many other science courses, and, as discussed in the body of the text, in common everyday situations. Be sure to Leant It Now. ... 

We can describe direct proportionalities between measured quantities with Per expressions. 

The problem can be solved by dimensional analysis if the Given and Wanted can be linked by one or more Per expressions and you know the conversion factor for each expression. 

Dimensional analysis Directly proportional Given quantity (Given) Inversely proportional Per expression (Per) Proportional reasoning Proportionality constant The symbol =... 

Dimensional analysis. Per expression, conversion factor, unit Path, G/vew quantity, I/IAwied quantity... 

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