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Biomedical subjects

V French

Publications and source records attributed to V French.

At least 19 recordsLinked to original sources
PubMed2004

The role of MIP-1alpha in experimental hypersensitivity pneumonitis.

S. rectivirgula (SR) causes Farmer's Lung Disease, a classic example of hypersensitivity pneumonitis (HP). We utilized a model of experimental hypersensitivity pneumonitis (EHP), antibody to MIP-1alpha and MIP-1alpha -/- mice, to test the hypothesis that MIP-1alpha is essential in the development of EHP. Treatment of C57BI/6 mice with anti-MIP-1alpha antibody did not change the extent of pulmonary histology abnormalities, BALF cell number or characteristics, or BALF concentration of IL12p40, TNF, IL1alpha and IL6, after an i.t. challenge with SR. MIP-1alpha -/- animals responded similarly to wild-type (wt) animals in the extent and nature of pulmonary histologic changes and BALF cell number and type after a single i.t. injection of SR There was a dose-response relationship between the amount of SR and BALF IL12p40, MCP-1 and IL6 in both strains, and MIP-1alpha in wild-type animals. We next transferred SR cultured spleen cells from SR sensitized mice (both wt and MIP-1alpha -/-) to naive recipients. Lung histology and BALF characteristics after SR i.t. challenge of the recipients were used to determine if adoptive transfer had occurred. Cultured cells from MIP-1alpha -/- animals were fully capable of transferring EHP to recipients. There was no difference of BALF TNF, IL6 and IL1alpha between the strains, but there was more MCP-1 and IL12p40 in the MIP-1alpha -/- mice than in the control mice. MIP-1alpha is not necessary for the recruitment of cells into the lung and BALF after i.t. administration of SR, or the development of cells able to adoptively transfer EHP.

Alveolitis, Extrinsic Allergic↗
PubMed2002

Temperature modulates epidermal cell size in Drosophila melanogaster.

Most ectotherms show increased body size at maturity when reared under colder temperatures. In principle, temperature could produce this outcome by influencing growth, proliferation and/or death of epidermal cells. Here we investigated the effects of rearing temperature on the cell size and cell number in the wing blade, the basitarsus of the leg and the cornea of the eye of Drosophila melanogaster from two populations at opposite ends of a South American latitudinal cline. We found that, in both strains of D. melanogaster and in both sexes, a decrease in rearing temperature increases the size of the wings, legs and eyes through an effect on epidermal cell size, with no significant change in cell number. Our results indicate that temperature has a consistent effect on cell size in the Drosophila epidermis and this may also apply to other cell types. In contrast, the evolutionary effects of temperature on the different organs are not consistent. We discuss our findings in the context of growth control in Drosophila.

Journal Article↗
PubMed2001

Insect segmentation: Genes, stripes and segments in "Hoppers".

Recent work has revealed that orthologues of several segmentation genes are expressed in the grasshopper embryo, in patterns resembling those shown in Drosophila. This suggests that, despite great differences between the embryos, a hierarchy of gap/pair-rule/segment polarity gene function may be a shared and ancestral feature of insect segmentation.

Animals↗
PubMed2001

The generation and diversification of butterfly eyespot color patterns.

BACKGROUND: A fundamental challenge of evolutionary and developmental biology is understanding how new characters arise and change. The recently derived eyespots on butterfly wings vary extensively in number and pattern between species and play important roles in predator avoidance. Eyespots form through the activity of inductive organizers (foci) at the center of developing eyespot fields. Foci are the proposed source of a morphogen, the levels of which determine the color of surrounding wing scale cells. However, it is unknown how reception of the focal signal translates into rings of different-colored scales, nor how different color schemes arise in different species. RESULTS: We have identified several transcription factors, including butterfly homologs of the Drosophila Engrailed/Invected and Spalt proteins, that are deployed in concentric territories corresponding to the future rings of pigmented scales that compose the adult eyespot. We have isolated a new Bicyclus anynana wing pattern mutant, Goldeneye, in which the scales of one inner color ring become the color of a different ring. These changes correlate with shifts in transcription factor expression, suggesting that Goldeneye affects an early regulatory step in eyespot color patterning. In different butterfly species, the same transcription factors are expressed in eyespot fields, but in different relative spatial domains that correlate with divergent eyespot color schemes. CONCLUSIONS: Our results suggest that signaling from the focus induces nested rings of regulatory gene expression that subsequently control the final color pattern. Furthermore, the remarkably plastic regulatory interactions downstream of focal signaling have facilitated the evolution of eyespot diversity.

Animals↗
PubMed2001

Butterfly eyespot patterns: evidence for specification by a morphogen diffusion gradient.

In this paper we describe a test for Nijhout's (1978, 1980a) hypothesis that the eyespot patterns on butterfly wings are the result of a threshold reaction of the epidermal cells to a concentration gradient of a diffusing degradable morphogen produced by focal cells at the centre of the future eyespot. The wings of the nymphalid butterfly, Bicyclus anynana, have a series of eyespots. each composed of a white pupil, a black disc and a gold outer ring. In earlier extirpation and transplantation experiments (Nijhout 1980a; French and Brakefield, 1995) it has been established that these eyespots are indeed organised around groups of signalling cells active during the first hours of pupal development. If these cells were to supply the positional information for eyespot formation in accordance with Nijhout's diffusion-degradation gradient model, then, when two foci are close together. the signals should sum, and this effect should be apparent in the detailed shape of the resulting pigment pattern. We give an equation for the form of the contours that would be obtained in this manner. We use this to test the morphogen gradient hypothesis on measurements of the outlines of fused eyespots obtained either by grafting focal cells close together, or by using a mutation (Spotty) that produces adjacent fused eyespots. The contours of the fused patterns were found to satisfy our equation, thus corroborating Nijhout's hypothesis to the extent possible with this particular type of experiment.

Animals↗
PubMed1999

Correlated responses to selection on body size in Drosophila melanogaster.

Correlated responses to artificial selection on body size in Drosophila melanogaster were investigated, to determine how the changes in size were produced during development. Selection for increased thorax length was associated with an increase in larval development time, an extended growth period, no change in growth rate, and an increased critical larval weight for pupariation. Selection for reduced thorax length was associated with reduced growth rate, no change in duration of larval development and a reduced critical larval weight for pupariation. In both lines selected for thorax length and lines selected for wing area, total body size changed in the same direction as the artificially selected trait. In large selection lines of both types, the increase in size was achieved almost entirely by an increase in cell number, while in the small lines the decrease in size was achieved predominantly by reduced cell size, and also by a reduction in cell number. The implications of the results for evolutionary-genetic change in body size in nature are discussed.

Animals↗
PubMed1998

Body size and cell size in Drosophila: the developmental response to temperature.

In Drosophila, like most ectotherms, development at low temperature reduces growth rate but increases final adult size. Cultures were shifted from 25 degrees C to low (16.5 degrees C) or to high (29 degrees C) temperature at regular intervals through larval and pupal stages, and the flies of both sexes showed an increase or decrease, respectively, in the size of thorax, wing and abdominal tergite. Size changes in the wing blade resulted from changes in the size of the epidermal cells (with only a small increase in cell number in males reared at low temperature). The temperature-shifts became less effective as they were made at successively later developmental stages, demonstrating a cumulative effect of temperature on adult size. The thorax and wing develop from the same imaginal disc, with most cell division occurring in larval stages, but they differ in timing of temperature sensitivity, which extends only to pupariation or into the late pupal stage, respectively. Growth of the adult abdomen occurs largely after pupariation but its size is temperature-sensitive through both larval and pupal stages. We discuss growth control in Drosophila and the likely effects of temperature on food assimilation, growth efficiency and allocation of nutrients to the production of different tissues.

Journal Article↗
PubMed1997

Pattern formation in colour on butterfly wings.

Butterflies have uniquely vivid and varied wing-colour patterns. Recent studies show that their formation involves novel expression of homologues of Drosophila appendage-patterning genes, notably Distal-less. Pattern diversity can arise at several developmental stages, either through mutation or in response to environmental conditions. Many loci are known (e.g. in Heliconius) that have major effects on the colour pattern and these invite molecular analysis.

Animals↗
PubMed1997

Joint regulation of cell size and cell number in the wing blade of Drosophila melanogaster.

We used Drosophila melanogaster to test for compensatory control of cell area and cell number in the regulation of total wing area. In two random bred wild-type base stocks collected from different geographic locations we found a negative association between the area and the number of cells in the wing blade. Three replicate lines were selected for increased or decreased wing area, with cell area maintained at the same level as in the three controls. After eight generations of selection, despite a large and highly significant difference in wing area between the large, control and small selection lines, cell area did not differ significantly between them. Rather, the difference in wing area between selection regimes was attributable to differences in cell number. Over the course of selection, the initially significant negative correlation between cell area and cell number in the wing increased, providing evidence for compensatory regulation of cell area and cell number. As a result of the increasingly negative association between the two traits, the variance in wing area declined as selection proceeded. It will be important to discover the mechanisms underlying the compensatory regulation of cell area and cell number.

Animals↗
PubMed1997

The genetics and development of an eyespot pattern in the butterfly Bicyclus anynana: response to selection for eyespot shape.

The normally circular eyespots on the wing of the butterfly Bicyclus anynana were selected to become elliptical in two divergent lines, with antero-posterior elongation of the eyespots in one line and proximodistal elongation in the other. Selection was continued for nine generations, and symmetrical realized heritabilities of approximately 15% were achieved initially. The elliptical eyespot shapes characteristic of each line were still produced when the signaling center of the eyespot (the focus) was surgically rotated by 90 or 180 degrees or when an eyespot was induced ectopically by localized damage. We conclude that selection changed general properties of the epidermis that responds to signals emanating from the eyespot focus but did not affect the mechanism of focal signaling.

Animals↗
PubMed1996

Development, plasticity and evolution of butterfly eyespot patterns.

The developmental and genetic bases for the formation, plasticity and diversity of eyespot patterns in butterflies are examined. Eyespot pattern mutants, regulatory gene expression, and transplants of the eyespot developmental organizer demonstrate that eyespot position, number, size and colour are determined progressively in a developmental pathway largely uncoupled from those regulating other wing-pattern elements and body structures. Species comparisons and selection experiments suggest that the evolution of eyespot patterns can occur rapidly through modulation of different stages of this pathway, and requires only single, or very few, changes in regulatory genes.

Adaptation, Biological↗
PubMed1996

Segmentation (and eve) in very odd insect embryos.

The formation of segments in the Drosophila early embryo is understood in greater detail than any other complex developmental process. Now, by studying other types of insect embryo, we can hope to deduce something of the ancestral mechanism of segmentation and the ways in which it has been modified in evolution. The parasitic wasp, Copidosoma floridanum, is spectacularly atypical of insects in that the small egg cell divides extensively, with no initial syncytial phase, and forms eventually some 2000 embryos. This process raises intriguing questions about the control of embryonic polarity and segmentation.

Animals↗
PubMed1995

Thermal evolution of growth efficiency in Drosophila melanogaster.

Drosophila melanogaster shows geographic clines in body size, with genetically larger flies being found further from the equator and at higher altitudes. In the laboratory, evolution at lower temperatures results in genetically larger flies, and development at low temperature increases adult body size. This study demonstrates that when newly hatched larvae from laboratory temperature selection lines were raised on fixed amounts of food (yeast) at the same temperature, larvae from the lines with the cold evolutionary history required less food to produce a given size of adult. Larvae from both high- and low-temperature selection lines required more food, however, to make a given size of adult when grown in the cold than when grown in the hot. The opposite associations between growth efficiency and adult body size seen with evolution or development at low temperature are puzzling, and suggest that different mechanisms may underlie the size changes. Since environmental and evolutionary effects of temperature on body size seem to be widespread among ectotherms, some basic aspects of thermal physiology must be involved.

Analysis of Variance↗
PubMed1995

Eyespot development on butterfly wings: the epidermal response to damage.

Eyespot colour patterns decorate the wings of many butterfly species. The eyespot is specified in the early pupal epidermis by signals from a central "focus," and it has been suggested that the focus is the source of a diffusible morphogen gradient. We show that ectopic eyespots can be induced in nonfocal positions throughout the distal, but not the proximal, wing epidermis of Bicyclus anynana by mild epidermal damage inflicted at 12-18 hr (into a 6- to 7-day pupal period). Damage may lower, locally and transiently, the threshold for response to morphogen. Here, we have tested two predictions of the gradient model. As predicted, mild damage close to the focus (parafocal) locally extends the eyespot, making it markedly asymmetrical, even after early operations (1 or 6 hr), when remote epidermis is non-responsive. Early parafocal operations also have an unexpected result, however, reducing the extent of the eyespot in other directions, perhaps through a long-range "wound effect" on the signaling activity of the focal cells. The model also correctly predicts that increasing the severity of a nonfocal operation will prolong the transient damage and hence give ectopic eyespots after early (1- or 6-hr) operations. We do not, however, find the expected size increase in ectopics induced by the later (12 or 18 hr) severe damage. Similarly, we demonstrate the predicted effect of early (1 or 6 hr) mild damage in increasing the response to a subsequent (18 hr) operation at the same position. The gradient model is therefore supported by most aspects of eyespot induction in response to epidermal damage.

Animals↗
PubMed1995

Eyespot development on butterfly wings: the focal signal.

The eyespot colour pattern on butterfly wings is specified in the early pupal epidermis by signals from a central "focus." In Bicyclus anynana we show that a small square of focal epidermis, grafted to a range of distal wing sites, induces eyespot formation in surrounding host tissue. Signaling is limited to the focus, and even an adjacent (parafocal) graft does not maintain its normal fate (of contributing to the eyespot) and does not influence its surroundings. Along the wing, there is an abrupt change in the epidermis, as a focus grafted to a proximal site provokes no host response. The results of several grafting experiments demonstrate that their different response properties are autonomous to small areas of the distal and proximal epidermis and that the nonresponding proximal tissue can nonetheless transmit the focal sign. The Bicyclus dorsal forewing has a small anterior and a large posterior eyespot, and we show that this results mainly from a difference in focal signals, not in the epidermal response. A grafted posterior focus induces a large eyespot, whereas an anterior focus induces a small eyespot. Furthermore, the anterior and posterior eyespots differ in proportions, and this difference also depends on the identity of the focus, not on the responding epidermis. Eyespots are specified over many cell diameters from the focus by a mechanism which could consist of one long-range signal, such as a morphogen gradient or of a cascade of short-range interactions initiated by the focus. Focal control of the difference in size and proportion between the anterior and posterior eyespot is more readily compatible with a gradient mechanism. Neither model, however, readily explains why the pattern induced by a grafted focus is smaller, but its peripheral gold annulus is broader than in the corresponding control eyespot. Also, there is no direct evidence for long-range gradients, in the butterfly wing or any other insect epithelium.

Animals↗
PubMed1994

Insect wings. Patterns upon patterns.

Butterfly wing patterns may be generated by an extra coordinate system superimposed on a basic wing-patterning system similar to that of the fruit-fly Drosophila melanogaster.

Animals↗