970 research outputs found
Quality of capture fishery and aquaculture production statistics for Asia and the Pacific
A review is made of the FISHSTAT NS1 total production statistics and the FISHSTAT AQ aquaculture production statistics for Asia and the Pacific, reported to the FAO. An examination is also made of the quality of these statistics, identifying problems and providing recommendations for possible remedies
Experiences and case studies in the implementation of data collection methods for artisanal fisheries
Details are given of experience gained during the design and implementation of data collection methods for artisanal fisheries in a number of countries under the FAO Technical Cooperation Programme, and other national and regional projects supported by UNDP and Government Cooperation Agencies. Some general approaches that have been introduced in a number of FAO member countries are illustrated and major constraints and problems that are found to be common in the design and implementation of statistical developmental activities are highlighted. It is concluded that statistically-related management tasks are performed more effectively if designated to a national fishery statistical committee or work group with responsibilities and modus operandi as regards system design, development, implementation maintenance and support. Prior to implementing a large-scale system at national level it would be advantageous to develop a prototype system in a geographically limited but representative area. Based on experiences gained from the prototype system, stepwise expansion of the system in other areas may be necessary, by first considering new methodological requirements and operational/logistical constraints
Guidelines for the collection of fishery data for artisanal fisheries
An overview is provided of basic methodological and operational concepts of the statistical monitoring of artisanal fisheries, making specific reference to shore-based sampling surveys. The common characteristics of data collection methods are described and standard procedures for the derivation of estimates from sample magnitudes are discussed. Commonly used approaches for the storage/processing of collected basic data are outlined
The role of fishery co-operatives in coastal fisheries management
Community based approaches to management of coastal fisheries through fishery co-operatives may offer important opportunities. This is shown in the successes achieved in Japan and other countries. In order to play their role, fishery co-operatives need to be socially and economically successful. This inevitable means that they must have been initiated by the fishing communities themselves, the individual fishermen. They need to see the long term benefits of fishery co-operatives and feel the need to join forces. It is a natural step from development of the fisheries and fishery communities to the management of the fisheries. Governments must decentralize the authority over coastal marine areas and initiate programs to provide fishing communities with authority over adjacent resources. Involving fishery co-operatives in management may not be a quick or easy way to success, but it may well be the most effective way
Diagnostic and therapeutic challenges in the Allan-Herndon-Dudley Syndrome
Thyroid hormone (TH) is important for normal brain development. The TH transporter protein monocarboxylate transporter 8 (MCT8) is crucial to maintain adequate TH levels in the brain during development and throughout life. Mutations in MCT8 result in the Allan-Herndon-Dudley syndrome (AHDS), which is characterized by a severe delay in neurocognitive development, combined with abnormal serum thyroid function tests (TFTs). The combination of an increased (F)T3 and decreased (F)T4 and rT3 serum levels are characteristic for the presence of AHDS in male patients with moderate to severe delay in neurocognitive development. Here, we provide an overview of current insights, challenges and pitfalls in the diagnosis and management of patients with AHDS.</p
Diagnostic and therapeutic challenges in the Allan-Herndon-Dudley Syndrome
Thyroid hormone (TH) is important for normal brain development. The TH transporter protein monocarboxylate transporter 8 (MCT8) is crucial to maintain adequate TH levels in the brain during development and throughout life. Mutations in MCT8 result in the Allan-Herndon-Dudley syndrome (AHDS), which is characterized by a severe delay in neurocognitive development, combined with abnormal serum thyroid function tests (TFTs). The combination of an increased (F)T3 and decreased (F)T4 and rT3 serum levels are characteristic for the presence of AHDS in male patients with moderate to severe delay in neurocognitive development. Here, we provide an overview of current insights, challenges and pitfalls in the diagnosis and management of patients with AHDS.</p
Thyroid hormone deiodination
The enzymatic deiodination of thyroid hormone is an important process
since it concerns- among other things- the regulation of thyromimetic activity
at the site of the target organ. To understand the mechanism of this
regulation it is necessary to have a detailed knowledge of the mode of action
of the enzyme(s) involved in the metabolism of thyroid hormone. My investigations
of the deiodination of iodothyronines at the subcellular level, forming
the basis of this thesis, are described in the appendix papers. It is not
intended to deal in extenso with the technical aspects of my studies in the
preceeding chapters. Rather it will be attempted to give a general review of
the literature including- with some emphasis -my own work.
Though not directly related to the subject of this thesis, the biosynthesis
of thyroid hormone in the thyroid gland is treated in the first
chapter. This is done because of possible similarities between thyroid hormone
iodination and deiodination pathways, which are suggested by the finding that
some drugs inhibit both processes. In the same chapter the relationship
between iodothyronine structure and biological potency is described to illustrate
that indeed deiodination has a dramatic effect on the activity of
thyroid hormone. Besides deiodination, other pathways of metabolism are also
considered.
The second chapter concerns the in vivo investigation of thyroid hormone
deiodination under physiological and pathological conditions. This includes
the effects of internal and external factors which affect deiodination, such
as dietary intake, drugs, stress and illness. Since much work has been done
to find an explanation for the effect of calorie restriction on deiodination
at the molecular level, the role of the diet is emphasized. This appears
particularly important since nutritional status must be considered to contribute
to the change in thyroid hormone metabolism found in other situations,
for example in systemic illness.
The in vitro observations of the enzymatic deiodination of thyroid
hormone are described in chapter 3. A distinction has been made between
(early) reports on the analysis of iodide production using chromatography,
and (more recent) studies dealing with the detection of specific metabolites,
often by means of radioimmunoassay. My investigations which belong to the
latter category are presented in the appendix paper
Substitution of cysteine for selenocysteine in the catalytic center of type III iodothyronine deiodinase reduces catalytic efficiency and alters substrate preference
Human type III iodothyronine deiodinase (D3) catalyzes the conversion of
T(4) to rT(3) and of T(3) to 3, 3'-diiodothyronine (T2) by inner-ring
deiodination. Like types I and II iodothyronine deiodinases, D3 protein
contains selenocysteine (SeC) in the highly conserved core catalytic
center at amino acid position 144. To evaluate the contribution of SeC144
to the catalytic properties of D3 enzyme, we generated mutants in which
cysteine (D3Cys) or alanine (D3Ala) replaces SeC144 (D3wt). COS cells were
transfected with expression vectors encoding D3wt, D3Cys, or D3Ala
protein. Kinetic analysis was performed on homogenates with dithiothreitol
as reducing cofactor. The Michaelis constant of T(3) was 5-fold higher for
D3Cys than for D3wt protein. In contrast, the Michaelis constant of T(4)
increased 100-fold. The D3Ala protein was enzymatically inactive.
Semiquantitative immunoblotting of homogenates with a D3 antiserum
revealed that about 50-fold higher amounts of D3Cys and D3Ala protein are
expressed relative to D3wt protein. The relative substrate turnover number
of D3Cys is 2-fold reduced for T(3) and 6-fold reduced for T(4)
deiodination, compared with D3wt enzyme. Studies in intact COS cells
expressing D3wt or D3Cys showed that the D3Cys enzyme is also active under
in situ conditions. In conclusion, the SeC residue in the catalytic center
of D3 is essential for efficient inner-ring deiodination of T(3) and in
particular T(4) at physiological substrate concentrations
Substitution of cysteine for a conserved alanine residue in the catalytic center of type II iodothyronine deiodinase alters interaction with reducing cofactor
Human type II iodothyronine deiodinase (D2) catalyzes the activation of
T(4) to T(3). The D2 enzyme, like the type I (D1) and type III (D3)
deiodinases, contains a selenocysteine (SeC) residue (residue 133 in D2)
in the highly conserved catalytic center. Remarkably, all of the D2
proteins cloned so far have an alanine two residue-amino terminal to the
SeC, whereas all D1 and D3 proteins contain a cysteine at this position. A
cysteine residue in the catalytic center could assist in enzymatic action
by providing a nucleophilic sulfide or by participating in redox reactions
with a cofactor or enzyme residues. We have investigated whether D2
mutants with a cysteine (A131C) or serine (A131S) two-residue amino
terminal to the SeC are enzymatically active and have characterized these
mutants with regard to substrate affinity, reducing cofactor interaction
and inhibitor profile. COS cells were transfected with expression vectors
encoding wild-type (wt) D2, D2 A131C, or D2 A131S proteins. Kinetic
analysis was performed on homogenates with dithiothreitol (DTT) as
reducing cofactor. The D2 A131C and A131S mutants displayed similar
Michaelis-Menten constant values for T(4) (5 nM) and reverse T(3) (9 nM)
as the wt D2 enzyme. The limiting Michaelis-Menten constant for DTT of the
D2 A131C enzyme was 3-fold lower than that of the wt D2 enzyme. The wt and
mutant D2 enzymes are essentially insensitive to propylthiouracil
[concentration inhibiting 50% of activity (IC(50)) > 2 mM] in the presence
of 20 mM DTT, but when tested in the presence of 0.2 mM DTT the IC(50)
value for propylthiouracil is reduced to about 0.1 mM. During incubations
of intact COS cells expressing wt D2, D2 A131C, or D2 A131S, addition of
increasing amounts of unlabeled T(4) resulted in the saturation of
[(125)I]T(4) deiodination, as reflected in a decrease of [(125)I]T(3)
release into the medium. Saturation first appeared at medium T(4)
concentrations between 1 and 10 nM. In conclusion: substitution of
cysteine for a conserved alanine residue in the catalytic center of the D2
protein does not inactivate the enzyme in vitro and in situ, but rather
improves the interaction with the reducing cofactor DTT in vitro
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