From:
Sukie Crandall
Date: 2005-11-09 18:19:14 UTC
Subject: [ferrethealth] Some of the causes of delayed eye opening
To: ferrethealth@smartgroups.com
FYI:
BEGIN QUOTE
The critical period for ocular dominance plasticity in the Ferret's
visual cortex.
- Issa NP, Trachtenberg JT, Chapman B, Zahs KR, Stryker MP
J Neurosci 1999 Aug 15;19(16):6965-78.
Microelectrode recordings and optical imaging of intrinsic signals
were used to define the critical period for susceptibility to
monocular deprivation (MD) in the primary visual cortex of the
ferret. Ferrets were monocularly deprived for 2, 7 or >14 d,
beginning between postnatal day 19 (P19) and P110. The responses of
visual cortical neurons to stimulation of the two eyes were used to
gauge the onset, peak, and decline of the critical period. MDs ending
before P32 produced little or no loss of response to the deprived
eye. MDs of 7 d or more beginning around P42 produced the greatest
effects. A rapid decline in cortical susceptibility to MD was
observed after the seventh week of life, such that MDs beginning
between P50 and P65 were approximately half as effective as those
beginning on P42; MDs beginning after P100 did not reduce the
response to the deprived eye below that to the nondeprived eye. At
all ages, 2 d deprivations were 55-85% as effective as 7 d of MD.
Maps of intrinsic optical responses from the deprived eye were weaker
and less well tuned for orientation than those from the nondeprived
eye, with the weakest maps seen in the hemisphere ipsilateral to the
deprived eye. Analysis of the effects of 7 d and longer deprivations
revealed a second period of plasticity in cortical responses in which
MD induced an effect like that of strabismus. After P70, MD caused a
marked loss of binocular responses with little or no overall loss of
response to the deprived eye. The critical period measured here is
compared to other features of development in ferret and cat.
END QUOTE
Many developmental changes happen in young kits. Here is just
another example since we are on eyes:
BEGIN QUOTE
Age-related fiber order in the optic tract of the ferret.
- Walsh C, Guillery RW
J Neurosci 1985 Nov;5(11):3061-9.
In the ferret's optic tract, the position of retinofugal fibers has
been related to their relative age by preferentially labeling the
oldest fibers. It has been found that fiber order perpendicular to
the pial surface represents the sequence of axon arrivals in the
optic tract, the fibers furthest from the pia being the oldest.
Immature ferrets, less than 34 days post-conception (E34), were given
intravitreal injections of lectin-bound horseradish peroxidase or of
3H-amino acids. After survival times of 24 hr or less, the
contralateral optic tract was uniformly labeled, whereas with longer
survival times unlabeled zones were seen next to the pial border.
These unlabeled zones were largest after injections into the youngest
animals but were never seen when injections were made after E34, no
matter what the survival time. The unlabeled zones were seen in the
tracts of animals having unlabeled regions in the periphery of the
retina. The unlabeled retinal ganglion cells are interpreted as
ganglion cells formed after the injection was made, and unlabeled
axons next to the pia in the tract are interpreted as the axons of
these youngest cells. Some irregularities in the layered arrangement
of the tract are described, and the fiber order in the tract is
contrasted with that in the optic nerve behind the eye. It is shown
that tract order is partially independent of order in the
intraorbital part of the optic nerve. Between the retina and the
optic tract, a sorting of fibers occurs not only in terms of the
pattern of decussation, but also in terms of fiber age.
END QUOTE
Chris, how polluted was the air for those specific kits of your
friend? I have found a study (FERRETS) that mentions delayed eye
opening on high ozone levels, but do not have time to sift through a
pdf:
http://pas.ce.wsu.edu/CE341/vol3draft.pdf
>Review of the
>California Ambient Air Quality Standard
>For Ozone
>Appendix A:
>Review of the Animal Toxicological Studies on the Health
>Effects of Ozone
>Appendix B:
>Recommendation for an Ambient Air Quality Standard for
>Ozone
>Public Review Draft
>June 21, 2004
>California Environmental Protection Agency
If the person was using an electrostatic air "cleaner" a large number
of those produce ozone which is a serious pollutant in breathing
air. (And THAT is just one of the reasons why anyone who needed and
air filter for health reasons gets told by pulmonologists and
allergists to use a Hepa Filter Air Cleaner instead.)
In relation specifically to ferrets cobalt, dichlorbenzenes, and a
few more things show up in a rough check.
-- Sukie (not a vet)
Ferret Health List co-moderator
http://www.smartgroups.com/groups/ferrethealth
FHL Archives fan
http://ferrethealth.org/archive/
replacing
http://fhl.sonic-weasel.org
International Ferret Congress advisor
http://www.ferretcongress.org
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