88 research outputs found
Studies in neuraminidases
In this thesis, the
work undertaken
in
an attempt to
gain
insight
into the catalytic
function
of neuraminidase
is described.
The history,
properties and
importance
of neuraminidases are
reviewed
in Chapter One. Chapter Two
contains an account of the
production of neuraminidase from
Streptomycesgriseus
by induction,
of
its
preparation and purification
to
homogeneity,
of
its
character-
isation as a glycoprotein of
32,000
molecular weight and of its
structural and catalytic properties.
In Chapter Three,
chemical
modification methods were employed to seek information regarding
the nature of the amino acid residues essential
in the activity of
S.
griseus,
Cl.
perfringens and
influenza
virus neuraminidases.
In
all the three
enzymes the results obtained suggested that
arginine, tryptophan and carboxylic groups were crucial
for the
enzyme activity.
Based on these
findings,
a mechanism
for
neura-
minidase action was proposed.
The
extensively purified neuraminidase
from S.
griseus was used,
in
conjunction with an isoelectric focussing technique, to investigate
the sialylation
differences in human Interferons. The
results to
these experiments, reported
in Appendix I, suggest that fibroblast
(and
not
leucocyte
or lymphoblastoid) interferon contains neuramini-
dase
-releasable s ialic acid residues
.
The
experiments reported
in
Appendix Il, in
which rabbits were
immunised
with colominic acid or
fetuin,
were conducted to raise antibodies specific to sialic acid
in
an attempt todesign a radloimmunoassay for free
sialic acid
Trypanosomiasis vector control in Africa and Latin America
Vectors of trypanosomiasis – tsetse (Glossinidae) in Africa, kissing-bugs (Triatominae) in Latin America – are very different insects but share demographic characteristics that render them highly vulnerable to available control methods. For both, the main operational problems relate to re-invasion of treated areas, and the solution seems to be in very large-scale interventions covering biologically-relevant areas rather than adhering to administrative boundaries. In this review we present the underlying rationale, operational background and progress of the various trypanosomiasis vector control initiatives active in both continents
Effect of aging in functional redox state of single isolated skeletal muscle fibres
[EN] Skeletal muscle constantly produces reactive oxygen
species (ROS). During contractile activity ROS are generated in skeletal muscle fibres. There is
considerable support for an involvement of ROS in the
process of aging. Several studies indicate that adaptive
responses of skeletal muscle that are activated and
regulated by ROS are disrupted during aging.
The aim of this study was to monitor, in real time,
intracellular ROS production in single skeletal muscle
fibres from old and young mice and study the effect of
contractile activity in these cells. Following evaluate and
correlate the potential changes in intracellular ROS
production with glutathione redox state and antioxidant
enzymatic activities in muscle.
Single skeletal muscle fibres were isolated from the
Flexor Digitorus Brevis muscle from young (2-4 monthold) and old (26-28 month-old) C57BL/6 mice. Fibres
were loaded with DCFH-DA, a fluorophore probe that
allows the quantification of intracellular ROS generation
by fluorescence microscopy imaging. Contractile activity
was induced in fibres by electrical stimulation.
Glutathione redox state and activity of antioxidant
enzymes were analysed in gastrocnemious muscle.
Intracellular basal level of ROS was higher in fibres from
old mice. Contractile activity induced increase of ROS
generation in fibres from young mice. However, this
response was attenuated in fibres from old mice.
Glutathione redox state was significant different, in
favour of oxidized glutathione, in muscles from old mice.
Glutathione peroxidase and catalase activities were
significantly augmented in muscles from old mice.
In conclusion, the process of aging modifies the basal
redox status in skeletal muscle fibres in favour of
oxidation and induces adaptation mechanisms of
antioxidant defences. These are not able to neutralize
the increase of basal oxidation, but they might lead to
the attenuation of ROS produced by contractile activity
observed in fibres from old mice
Involvement of Reactive Oxygen Species (ROS) inskeletal muscle function during ageing: Study in amodel of isolated single skeletal muscle fibre
[ES] Suplemento de la revista Free Radical Biology and Medicine: Involvement of Reactive Oxygen Species (ROS) inskeletal muscle function during ageing: Study in amodel of isolated single skeletal muscle fibre
Is the even distribution of insecticide-treated cattle essential for tsetse control? Modelling the impact of baits in heterogeneous environments
Background:
Eliminating Rhodesian sleeping sickness, the zoonotic form of Human African Trypanosomiasis, can be achieved only through interventions against the vectors, species of tsetse (Glossina). The use of insecticide-treated cattle is the most cost-effective method of controlling tsetse but its impact might be compromised by the patchy distribution of livestock. A deterministic simulation model was used to analyse the effects of spatial heterogeneities in habitat and baits (insecticide-treated cattle and targets) on the distribution and abundance of tsetse.
Methodology/Principal Findings:
The simulated area comprised an operational block extending 32 km from an area of good habitat from which tsetse might invade. Within the operational block, habitat comprised good areas mixed with poor ones where survival probabilities and population densities were lower. In good habitat, the natural daily mortalities of adults averaged 6.14% for males and 3.07% for females; the population grew 8.46in a year following a 90% reduction in densities of adults and pupae, but expired when the population density of males was reduced to <0.1/km2; daily movement of adults averaged 249 m for males and 367 m for females. Baits were placed throughout the operational area, or patchily to simulate uneven distributions of cattle and targets. Gaps of 2–3 km between baits were inconsequential provided the average imposed mortality per km2 across the entire operational area was maintained. Leaving gaps 5–7 km wide inside an area where baits killed 10% per day delayed effective control by 4–11 years. Corrective measures that put a few baits within the gaps were more effective than deploying extra baits on the edges.
Conclusions/Significance:
The uneven distribution of cattle within settled areas is unlikely to compromise the impact of insecticide-treated cattle on tsetse. However, where areas of >3 km wide are cattle-free then insecticide-treated targets should be deployed to compensate for the lack of cattle
Improving the cost-effectiveness of visual devices for the control of Riverine tsetse flies, the major vectors of Human African Trypanosomiasis
Control of the Riverine (Palpalis) group of tsetse flies is normally achieved with stationary artificial devices such as traps or insecticide-treated targets. The efficiency of biconical traps (the standard control device), 161 m black targets and small 25625 cm targets with flanking nets was compared using electrocuting sampling methods. The work was done on Glossina tachinoides and G. palpalis gambiensis (Burkina Faso), G. fuscipes quanzensis (Democratic Republic of Congo), G. f. martinii (Tanzania) and G. f. fuscipes (Kenya). The killing effectiveness (measured as the catch per m2 of cloth) for small targets plus flanking nets is 5.5–15X greater than for 1 m2 targets and 8.6–37.5X greater than for biconical traps. This has important implications for the costs of control of the Riverine group of tsetse vectors of sleeping sickness
Towards an optimal design of target for tsetse control: comparisons of novel targets for the control of palpalis group tsetse in West Africa
Background: Tsetse flies of the Palpalis group are the main vectors of sleeping sickness in Africa. Insecticide impregnated targets are one of the most effective tools for control. However, the cost of these devices still represents a constraint to their wider use. The objective was therefore to improve the cost effectiveness of currently used devices.
Methodology/Principal Findings: Experiments were performed on three tsetse species, namely Glossina palpalis gambiensis and G. tachinoides in Burkina Faso and G. p. palpalis in CĂ´te d'Ivoire. The 1Ă—1 m2 black blue black target commonly used in W. Africa was used as the standard, and effects of changes in target size, shape, and the use of netting instead of black cloth were measured. Regarding overall target shape, we observed that horizontal targets (i.e. wider than they were high) killed 1.6-5x more G. p. gambiensis and G. tachinoides than vertical ones (i.e. higher than they were wide) (P<0.001). For the three tsetse species including G. p. palpalis, catches were highly correlated with the size of the target. However, beyond the size of 0.75 m, there was no increase in catches. Replacing the black cloth of the target by netting was the most cost efficient for all three species.
Conclusion/Significance: Reducing the size of the current 1*1 m black-blue-black target to horizontal designs of around 50 cm and replacing black cloth by netting will improve cost effectiveness six-fold for both G. p. gambiensis and G. tachinoides. Studying the visual responses of tsetse to different designs of target has allowed us to design more cost-effective devices for the effective control of sleeping sickness and animal trypanosomiasis in Africa
Prospects for the development of odour baits to control the tsetse flies Glossina tachinoides and G. palpalis s.l.
Field studies were done of the responses of Glossina palpalis palpalis in CĂ´te d'Ivoire, and G. p. gambiensis and G. tachinoides in Burkina Faso, to odours from humans, cattle and pigs. Responses were measured either by baiting (1.) biconical traps or (2.) electrocuting black targets with natural host odours. The catch of G. tachinoides from traps was significantly enhanced (~5Ă—) by odour from cattle but not humans. In contrast, catches from electric targets showed inconsistent results. For G. p. gambiensis both human and cattle odour increased (>2Ă—) the trap catch significantly but not the catch from electric targets. For G. p. palpalis, odours from pigs and humans increased (~5Ă—) the numbers of tsetse attracted to the vicinity of the odour source but had little effect on landing or trap-entry. For G. tachinoides a blend of POCA (P = 3-n-propylphenol; O = 1-octen-3-ol; C = 4-methylphenol; A = acetone) alone or synthetic cattle odour (acetone, 1-octen-3-ol, 4-methylphenol and 3-n-propylphenol with carbon dioxide) consistently caught more tsetse than natural cattle odour. For G. p. gambiensis, POCA consistently increased catches from both traps and targets. For G. p. palpalis, doses of carbon dioxide similar to those produced by a host resulted in similar increases in attraction. Baiting traps with super-normal (~500 mg/h) doses of acetone also consistently produced significant but slight (~1.6Ă—) increases in catches of male flies. The results suggest that odour-baited traps and insecticide-treated targets could assist the AU-Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) in its current efforts to monitor and control Palpalis group tsetse in West Africa. For all three species, only ~50% of the flies attracted to the vicinity of the trap were actually caught by it, suggesting that better traps might be developed by an analysis of the visual responses and identification of any semiochemicals involved in short-range interaction
Updating the Northern Tsetse Limit in Burkina Faso (1949–2009): Impact of Global Change
The northern distribution limit of tsetse flies was updated in Burkina Faso and compared to previous limits to revise the existing map of these vectors of African trypanosomiases dating from several decades ago. From 1949 to 2009, a 25- to 150-km shift has appeared toward the south. Tsetse are now discontinuously distributed in Burkina Faso with a western and an eastern tsetse belt. This range shift can be explained by a combination of decreased rainfall and increased human density. Within a context of international control, this study provides a better understanding of the factors influencing the distribution of tsetse flies
Phylogeography and Population Structure of Glossina fuscipes fuscipes in Uganda: Implications for Control of Tsetse
Glossina fuscipes fuscipes is the most common species of tsetse in Uganda, where it transmits human sleeping sickness and nagana, a related disease of cattle. A consortium of African countries dedicated to controlling these diseases is poised to begin area wide control of tsetse, but a critical question remains: What is the most appropriate geographical scale for these activities? To address this question, we used population genetics to determine the extent of linkage between populations of tsetse confined to discrete patches of riverine habitat. Our results suggest that Uganda was colonized by two distinct lineages of G. f. fuscipes, which now co-occur only in a narrow band across central Uganda. Evidence for interbreeding at the zone of contact and movement of genes from the south to the north suggest that this historical genetic structure may dissolve in the future. At smaller scales, we have demonstrated that exchange of genes among neighboring populations via dispersal is at equilibrium with the differentiating force of genetic drift. Our results highlight the need for investment in vector control programs that account for the linkage observed among tsetse populations. Given its genetic isolation and its location at the far edge of G. fuscipes' range, the Lake Victoria region appears to be an appropriate target for area wide control
- …