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J C McLachlan

Publications and source records attributed to J C McLachlan.

13 recordsLinked to original sources
PubMed1990

Identification of a novel growth factor with transforming activity secreted by individual chick embryos.

Previously we have developed a microassay for anchorage independent growth (AIG) of fibroblasts in soft agar, which can detect very small quantities of transforming growth factors (TGFs). Using this assay, we have shown that small pieces of dissected chick embryo tissue will stimulate AIG of both NR6 and NRK 49f cells, and that this property can be used to map production of growth factors with transforming activity in individual early embryos. We now show that this activity can be transferred to conditioned medium (CM) prepared using chick embryo tissue. Using two cell lines with differential responsiveness to TGFs, and by coincubating normal and heat-treated CM with trypsin, Con-A and neutralising antibodies, we show that CM contains at least two different growth factors with transforming activity. One of these is heat-stable, and stimulates colony formation in NRK 49f cells in the presence of EGF, but not in its absence. This activity corresponds to a TGF beta-like molecule. The other component is a heat-labile glycoprotein, which has TGF alpha-like properties, but does not appear to behave like known TGFs with these properties. It therefore appears to be a novel growth factor. Both activities are present from the intermediate primitive streak stage of development.

Animals↗
PubMed1990

Looping of chick embryo hearts in vitro.

Heart rudiments were removed from chick embryos at times earlier than any previously reported, and cultured in vitro, in order to test the widely reported view that looping is an intrinsic process. This view is based on experiments that are inadequately reported in certain key details. An organ culture technique was employed which combined ease of observation with good nutrient and mechanical support for the explants. A total of 23 hearts from stages before the onset of looping were examined. Hearts from as early as the six-somite stage looped normally in these experimental conditions. The view that heart looping is an intrinsic phenomenon is therefore confirmed.

Animals↗
PubMed1988

Direct demonstration of production of transforming growth factor activity by embryonic chick tissue.

The presence of transforming growth factor activity in early chick embryos was directly demonstrated by the ability of limb and tail buds to induce anchorage independent division in NRK 49 f cells. Colony number increased with limb bud number and developmental stage. Medium conditioned by tail buds contained some stimulating effect, and strongly promoted the action of other transforming growth factors.

Animals↗
PubMed1988

A microwell assay for anchorage independent cell growth.

We describe modifications of the conventional assay for anchorage independent growth of fibroblasts that enable the assay to be carried out in microwell plates, as opposed to the conventional Petri dishes. The microwell assay is a good discriminator of final EGF concentrations in the range 10-100 picograms/ml, and can be used to detect absolute amounts of EGF below 2 pg. Addition of TGF beta to EGF enhances colony formation in the microassay in the usual manner. We describe the use of this microassay to identify and map local production of transforming growth factor activity by the component pieces of individual chick embryos. Transforming activity was identified in all the stages tested (Hamburger and Hamilton stages 13-23). Highest levels were found near the mid-line of the embryo. No clear differences in the cranio-caudal axis have so far been identified. This technique will enable the spatial and temporal distribution of transforming activity throughout vertebrate embryos to be completely mapped. It seems likely that this mapping process will help elucidate the normal role of transforming growth factors in embryos.

Animals↗
PubMed1988

Limb reduplicating effects of chorio-allantoic membrane and its components.

The abilities of the chorion, the allantois, the chorio-allantoic membrane (CAM) and the yolk sac of the chick embryo to induce limb reduplications when grafted to the anterior margin of the embryonic chick limb were investigated. One chorion graft out of 27 (3.7%), two yolk sac grafts out of 30 (6.7%), five chorio-allantoic membrane grafts out of 35 (14.3%) and 26 allantois grafts out of 82 (31.7%) resulted in the formation of an extra Digit 2 or other digit of more posterior character. Allantois therefore possesses much greater ability to induce reduplications than the other membranes tested, and in view of its ease of isolation, offers a possible route for the further characterisation of this activity. The implications of these findings for theories of limb development are considered.

Allantois↗
PubMed1986

Self-assembly of structures resembling functional organs by pure populations of cells.

It is proposed that self-assembly of structures resembling organs can occur by virtue of the properties of the component cells alone. This property is derived from regional specializations of the individual component cells, and can arise in pure populations. This kind of self-assembly is distinct from the phenomenon of 'sorting out' of heterogeneous cell populations, to which this description is usually applied. It is associated with the expression of the differentiated state of the cell. Examples are drawn from the formation of blood vessels, muscles, cartilage elements, kidney, and neurectodermal derivatives.

Animals↗
PubMed1985

Stimulation of division in mouse 3T3 cells by coculture with embryonic chick limb tissue.

Two regions of the chick limb bud--the apical ectodermal ridge and the zone of polarizing activity--have been shown to influence cell division and pattern formation during normal development and following surgical manipulation. In this study, using a simple coculture system, together with autoradiography, we have shown that these morphogenetically active regions of the limb bud can stimulate quiescent 3T3 cells to initiate DNA synthesis to a significantly greater degree than comparable but morphogenetically inactive regions of the limb bud.

Animals↗
PubMed1980

The effect of 6-aminonicotinamide on limb development.

The morphological effect of the nicotinamide analogue 6-aminonicotinamide on the development of the embryonic chick limb was studied, with special reference to muscle, cartilage, feather germ formation, and ossification. No evidence was found to support theories of control of differentiation by nicotinamide-like substances, although the effect of nicotinamide analogues has often been quoted as evidence for such theories. However, the effect of 6-AN in shortening the limb provides an opportunity to study the interaction of various tissues in normal growth and development, and the results are used to shed further light on the processes involved in muscle splitting, and feather germ formation.

6-Aminonicotinamide↗
PubMed1979

Muscle-forming potential of the non-somitic cells of the early avian limb bud.

It has recently been shown that the musculature of the chick wing arises by migration of cells from the somites, and that on morphological grounds this process begins at about stage 14. We have carried out grafts of wing anlagen separate from the somites from quail donors to the extra-embryonic coelom of chicks, and find that anlagen from as early as stage 10 (11 pairs of somites) can give rise to muscle. We discuss the possible reasons for this finding, and conclude that in the absence of the cells normally giving rise to the musculature, mesodermal cells themselves can give rise to muscle.

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