Bariloche protein symposium argentine society for biochemistry and molecular biology

154
BIOCELL, 27 (Suppl. I), 2003
LI-P26.
SOY PROTEIN-WAX BASED EDIBLE BILAYER FILMS
Denavi Gabriela, Mauri Adriana, Añón, María C.
Centro de Investigación y Desarrollo en Criotecnología de
Alimentos, La Plata (1900), Argentina. E-mail:
[e-mail]
Among the various edible films and coatings used to maintain or
improve food quality, stability and safety, composite hydrocolloid-
lipid films are particularly desirable since they have acceptable
structural integrity and good barrier properties to water vapour.
The first film characteristic is imparted by the hydrocolloids while
the second one by the lipids.
The objective of this research was to produce and characterise
bilayer films based on soybean proteins and waxes.
Protein films were obtained by casting from a commercial soybean
protein isolate dispersion (5% w/v) at pH 10.5, using glycerol as
plasticizer (2.5% w/v). Wax layer was applied on the protein film
from the molten state. Three types of waxes were used: carnauba,
bees and sunflower. Films mechanical, barrier and physical
properties were studied and compared with protein control films.
All composite films had lower water vapour permeability (WVP)
than protein films but the best results were obtained with beeswax.
Its WVP value (8.5 10
-13
g m
-1
s
-1
Pa
-1
) is nearer the ones for synthetic
films. Wax presence also reduced film moisture content and water
solubility, but not as much as was expected, probably due to the
thin thickness of the lipid layer (10-20 
µm). Mechanical properties
of bilayer films with different waxes were similar; they presented
a higher tensile strength than protein films without affecting
elongation at break. Colour parameters (L, a and b) were similar
for all films, suggesting that no wax crystallization took place.
Microstructure study and thermal analysis would  prove it.
LI-P27.
MDCK CELLS PROLIFERATION DEPENDS ON
SPHINGOSINE KINASE ACTIVITY
Leocata Nieto Francisco, Corominas Ana, Speziale Emir and
Sterin-Speziale Norma.
Cát. de Biología Celular. Facultad de Farmacia y Bioquímica.
UBA. IQUIFIB-CONICET. E-mail:  [e-mail]
Sphingosine-1-phosphate (S1P) is involved in regulation of cell
proliferation. In contrast, ceramide (Cer) and sphingosine (Sph)
have a growth -inhibitory and pro-apoptotic effects. In this study
we demonstrate, by using an inhibitor of sphingosine kinase, DL-
threo-dihydrosphingosine (tDHS), that proliferation of MDCK cells
depends on SK activity, since a decrease of total cell number and
viability was observed. At 25 
µM of tDHS: 25% of the cells present
in the control with 72% of  viability (vs. 97% of the control) was
obtained. To distinguish if cell dead was due to an accumulation
of Cer and/or Sph, we studied the incorporation of 3H-palmitic
acid in MDCK cells treated with tDHS (25 
µM), Fumonisine (50
µM) and tDHS+Fumonisine. In cells treated with tDHS, we
observed an increase of radioactive Cer (10% of radioactivity
associated to products vs. 6,8% of the control) while a decrease
with Fumonisine (4,8% vs. 6,8%) and no change with
tDHS+Fumonisine (7,0% vs.6,8%) was obtained. No changes in
radioactive Sph was observed with any treatment (control: 18,7%;
tDHS: 15,9%; Fumonisine: 17,2%; tDHS+Fumonisine: 16,1%).
The presence of Fumonisine plus tDHS lead to an increase in
total cell number, respect to the cells treated with tDHS only.
Theses data suggest that the inhibition of SK leads to an
accumulation of Cer that induce the activation of cell death
program.
LI-P28.
PROSTAGLANDIN  D
2
 INDUCES CCT
α TRANSLOCATION
FROM THE ENDOPLASMIC RETICULUM TO THE
NUCLEUS
Favale N, Sterin-Speziale N, Fernández-Tome M.
Cátedra de Biología Celular. Facultad de Farmacia y Bioquímica.
UBA. IQUIFIB-CONICET. E-mail: [e-mail]
Phosphatidylcholine (PC) is a main lipid of biomembranes with
structural and functional importance. In previous works, we have
demonstrated that papillary PC synthesis is regulated by the action
of endogenous-synthesised prostaglandin D
2
 (PGD
2
) which
modulates nuclear cytidylyltransferase (CCT), which has been
reported as the rate-limiting enzyme of PC synthesis. We also found
that PC synthesis is modulated by MAPK activation. Two CCT
isoforms have been described: CCT
β, associated to endoplasmic
reticulum and reported as the responsible for the extra-nuclear
PC synthesis, and CCT
α which is confined to nuclear compartment
but whose function has not been fully understood. In the present
work we studied the effect of PGD
2
 and MAPK activation on the
compartmentalization of CCT
α in renal papillary cells by using
westernblot analysis. At microsomal compartment, we found two
positive immunoreactive bands: 40 and 80 KDa, but no protein
was detected in isolated nuclei. When papillary tissue was pre-
treated with PGD
2
, the presence of CCT
α in microsomal
membranes diminished with the parallel increase of the 80 KDa
band in isolated nuclei, indicating CCT
α translocation to this
compartment. Such effect seems to be mediated by MAPK
activation since it is prevented by U0126. These results suggest
that the increased PC synthesis by PGD
2
 stimulation could be due
to CCT activation by translocation from endoplasmic reticulum to
nuclear compartment.
LI-P29.
FLUNITRAZEPAM OVERCOMPENSATES THE EFFECTS
OF LIDOCAINE ON THE THERMOTROPIC
EQUILIBRIUM OF DIPALMITOYL PHOSPHATIDYL-
CHOLINE
Sanchez JM
1
, Bianconi L
2
, García DA
1
, de Paula E
3
, Perillo MA
1
1
Biofísica-Química. Depto.Química. FCEFyN, UNC, Argentina,
2
Dept.Bioquimica, UFRJ, Brasil, 
3
Lab. Biomembranas, Inst.
Biología, UNICAMP, Brasil. E-mail: [e-mail]
Previously, by analysing erythrocyte morphology, we demonstrated
that in the presence of either flunitrazepam (FNT) or lidocaine
(LC) the plasma membrane curvature changed but in opposite
directions. Moreover, each drug could compensate the effect of
the other one in a dose-dependent manner [Chem.Biol.Int.
129(2000)263]. In order to get deeply in the molecular mechanism
of this phenomena, in the present work we investigated by HDSC
the effect of FNT, LC and FNT+LC on the stability of multilamellar
vesicles of dpPC. Only in samples submitted to a second
temperature scanning, LC decreased both the enthalpy (
∆H
p
) as
well as the temperature (T
mp
) of the pre-transition (L
â’
→
→
 
P
â’ 
) and
increased the width of the heat absorption peak, reflecting a
decrement in the cooperative of the phase transition. The presence
of 59
µM FNT, reverted the effect of LC on T
mp
 and tended to
increase 
∆H
p
 above the values obtained with the control (dpPC
without any drug). FNT alone increased the 
∆H of both the pre-
and the main transition. The former was reverted by LC. The effects
of LC on decreasing T
mp
 and T
mc
 were also observed in the presence
of FNT. The relative concentration of each drug in the bilayer,
their effects on hydrogen bonds network and water structure at
the lipid-water interface.
Supported by Foncyt, ACC, SeCyT-UNC, CAPES/SPU.

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