Science Progress (2002), 85 (2)
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Science Progress (2002), 85 (2), 113–130
The birds from Las Hoyas
JOSÉ LUIS SANZ AND FRANCISCO ORTEGA
Information on the first steps of the avian evolutionary history has dramatically
increased during the last few years. The fossil record provides a general
view of the morphological changes of the avian flight apparatus from nonvolant
ancestors (non-avian theropod dinosaurs) to the first derived fliers
of the Early Cretaceous. The Las Hoyas bird record includes three genera:
Iberomesornis, Concornis and Eoalulavis. This fossil material has yielded
information about the early avian evolutionary history. These Early
Cretaceous birds (some 120 Myr old) had a wingbeat cycle and breathing
devices similar to those of extant birds. The function of the rectricial fan
was also similar. In the evolutionary transition from cursorial ancestors to
derived fliers it is possible to verify a trend to increase lift. Primitive wing
aspect ratio morphotypes were elliptical ones, other derived morphotypes
appeared, for example, in the Neornithes (extant birds). Some primitive
fliers, like the Las Hoyas genus Eoalulavis, had an alula (feathers attached
to the first digit of the hand) similar to that of present day birds, indicating
braking and manoeuvring skills similar to those of their extant relatives.
Primitive avian life habits are poorly understood. Some evidence from the
Las Hoyas bird record indicates that Early Cretaceous birds were present
in the trophic chains.
Keywords: avian evolutionary history
Science Progress (2002), 85 (2), 131–150
Clinical aspects of photodynamic
therapy
HUGH BARR, CATHERINE KENDALL, JANELLE REYESGODDARD
AND NICOLAS STONE
Photodynamic therapy is a method for local destruction of tissue or organisms
by generating toxic oxygen and other reactive species using light
absorbed by an administered or an endogenously generated photosensitiser.
It is a highly promising treatment for patients with cancer. More recently it
has found increasing use as a method of therapy for non-cancerous illnesses.
It depends on the exploitation of natural and vital reactions widespread
in nature that have driven and preserved life on this planet.
Following administration of a photosensitiser or its precursor there is an
accumulation or retention in areas of cancer and disease relative to
adjacent normal tissue. The photosensitiser is inactive until irradiated by
light, following which cellular destruction occurs. The clear attraction of
this method is the possibility of some targeting of the disease by drug and
by the area irradiated. This explanation although oversimplified has been
the reason for the scientific and clinical interest in photodynamic therapy.
An understanding of evolutionary photobiology is enormously helpful to
understand disease response and clinical outcomes.
Keywords: photydynamic therapy, cancer
Science Progress (2002), 84 (2), 151–173
Development of the sensory
organs
PHILIPPA H. FRANCIS-WEST, RAJ. K. LADHER AND
GARY C. SCHOENWOLF
The sensory organs – the eye, ear, and nose- are formed, in part, from
ectodermal thickenings: placodes. Their development is distinct from that
of other regions of the developing body and they are essential for the development
of other structures. For example, the olfactory placode which gives
rise to the nose is essential for the functional development of the reproductive
organs and hence fertility. Recently much progress has been made in
the understanding of placode development, at both a molecular and
embryological level. This is important as abnormal development of
placodes occurs in a number of human syndromes. Furthermore, knowledge
of placode development will give insight into therapeutic strategies to
prevent degenerative change such as deafness. This review highlights the
current knowledge of placode development and the future challenges in
unravelling the cascades of signalling interactions that control development
of these unique structures.
Keywords: sensory organs
Science Progress (2002), 85 (2), 175–197
A new method for measuring
intramolecular charge transfer
CHARLES A. SCHMUTTENMAER
The direct measurement of intramolecular electron transfer through detection
of the electromagnetic (EM) waveform that is emitted during this process is
reviewed. The waveform is detected in the time-domain via free-space electrooptic
sampling and then related to the dynamics of the charge transfer
event. Electromagnetic generation from two systems, Betaine-30 in chloroform
and DMANS in toluene, are studied to illustrate this technique. A
finite-difference time-domain calculation with a time-dependent polarization
is used to model the EM generation and propagation through the solution.
This method is very general since the movement of charge itself generates
the EM waveform, and is sensitive to charge transfer occurring on a 0.1–10 ps
timescale. The potential for studying the primary steps of charge transfer in
photosynthetic bacteria is also discussed.
Keywords: measuring intramolecular change transfer