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J M Fitch

Publications and source records attributed to J M Fitch.

At least 37 records · Page 2Linked to original sources
PubMed1990

Collagen fibrillogenesis in vitro: interaction of types I and V collagen regulates fibril diameter.

The small-diameter fibrils of the chick corneal stroma are heterotypic, composed of both collagen types I and V. This tissue has a high concentration of type V collagen relative to other type I-containing tissues with larger-diameter fibrils, suggesting that heterotypic interactions may have a regulatory role in the control of fibril diameter. The interactions of collagen types I and V were studied using an in vitro self-assembly system. Collagens were purified from lathyritic chick embryos in the presence of protease inhibitors. The type V collagen preparations contained higher molecular weight forms of the alpha 1(V) and alpha 2(V) chains constituting 60-70% of the total. Rotary-shadow electron micrographs showed a persistence of a small, pepsin-sensitive terminal region in an amount consistent with that seen by electrophoresis. In vitro, this purified type V collagen formed thin fibrils with no apparent periodicity, while type I collagen fibrils had a broad distribution of large diameters. However, when type I collagen was mixed with increasing amounts of type V collagen a progressive and significant decrease in both the mean fibril diameter and the variance was observed for D periodic fibrils. The amino-terminal domain of the type V collagen molecule was required for this regulatory effect and in its absence little diameter reducing activity was observed. Electron microscopy using collagen type-specific monoclonal antibodies demonstrated that the fibrils formed were heterotypic, containing both collagen types I and V. These data indicate that the interaction of type V with type I collagen is one mechanism modulating fibril diameter and is at least partially responsible for the regulation of collagen fibril formation.

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PubMed1990

Extracellular matrices of the developing chick retina and cornea. Localization of mRNAs for collagen types II and IX by in situ hybridization.

In the embryonic avian eye, the vitreous and the primary corneal stroma are composed in part of collagen types II and IX. Previous biochemical and immunohistochemical studies have suggested that the production of these molecules changes dramatically during development. In the current investigation, we employed in situ hybridization to determine the temporospatial distribution of the messenger ribonucleic acids (mRNAs) for these collagens in the eyes of selected stages of chick embryos. Our observations suggest that through much of development, the ciliary region is the major source for the production of the collagens found within the vitreous. For the cornea, they confirm that both collagen mRNAs are indeed present, and suggest that each is independently regulated.

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PubMed1989

The dendritic morphology of pyramidal neurons in the rat hippocampal CA3 area. I. Cell types.

Pyramidal neurons from the hippocampal CA3 area of hooded rats were qualitatively and quantitatively described from Golgi-stained tissue. The most numerous of the pyramidal neurons, those with a single apical shaft, fell into two major categories. One category, termed short-shaft pyramidal neurons, is characterized by short apical shafts, a large number of thorny excrescences, and densely branched apical and basilar trees. The second category, long-shaft pyramidal neurons, is characterized by a long apical shaft, a small number of thorny excrescences and relatively less dendritic branching in both the apical and basilar trees. The somata of short-shaft pyramidal neurons tend to be located higher in stratum pyramidale than the somata of long-shaft neurons. Quantitative measurements, which included both analysis of dendritic branching and the distribution of dendritic material sampled at 10% intervals from the cell body, confirmed the qualitative observation that short-shaft neurons had more total dendritic length than long-shaft neurons. The difference in the total dendritic length observed between long- and short-shaft pyramidal neurons could be an indication that each type receives a different number of synapses per neuron. The less commonly observed variants of pyramidal neurons were briefly described but not quantified. This study demonstrates that CA3 pyramidal neurons are not a homogeneous group but that their heterogeneous characteristics fall into two major categories.

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PubMed1989

The dendritic morphology of pyramidal neurons in the rat hippocampal CA3 area. II. Effects of gender and the environment.

Sex differences in the dendritic structure of hippocampal CA3 pyramidal neurons were studied in Golgi-stained tissue from hooded rats that had been raised in either a relatively complex or an isolated environment from weaning for one month. Pyramidal neurons were sampled from both the short-shaft and long-shaft neuron categories as described by Fitch et al. The pattern of sex differences varies in different parts of the apical dendritic tree. In the apical tree proximal to the soma, females had more dendritic material than males. This pattern was attributable to the sex differences in the short-shaft neurons of rats from the more complex environment. The direction of sex differences was reversed in the distal apical dendritic tree where males had more dendritic material than females. As in the proximal dendritic tree, this pattern of sex differences stemmed from the short-shaft neurons of rats from the more complex environment. There were no sex differences in the basilar dendritic tree. Thus sex differences in the pyramidal neurons of hippocampal area CA3 vary with the portion of the dendritic tree examined, the type of pyramidal neuron, and the rearing environment of the animal.

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PubMed1989

Independent deposition of collagen types II and IX at epithelial-mesenchymal interfaces.

Previous studies have demonstrated the presence of type II collagen (in mature chickens predominantly a 'cartilage-specific' collagen) in a variety of embryonic extracellular matrices that separate epithelia from mesenchyme. In an immunohistochemical study using collagen type-specific monoclonal antibodies, we asked whether type IX collagen, another 'cartilage-specific' collagen, is coexpressed along with type II at such interfaces. We confirmed that, in the matrix underlying a variety of cranial ectodermal derivatives and along the ventrolateral surfaces of neuroepithelia, type II collagen is codistributed with collagen types I and IV. Type IX collagen, however, was undetectable at those sites. We observed immunoreactivity for type IX collagen only within the notochordal sheath, where it first appeared at a later stage than did collagen types I and II. We also observed type II collagen (without type IX) beneath the dorsolateral ectoderm at stage 16; this correlates with the period during which limb ectoderm has been reported to induce the mesoderm to become chondrogenic. Finally, in older hind limbs we observed subepithelial type II collagen that was not associated with subsequent chondrogenesis, but appeared to parallel the formation of feathers and scales in the developing limb. These observations suggest that the deposition of collagen types II and IX into interfacial matrices is regulated independently, and that induction of mesenchymal chondrogenesis by such matrices does not involve type IX collagen. Subepithelial type IX collagen deposition, on the other hand, correlates with the assembly of a thick multilaminar fibrillar matrix, as present in the notochordal sheath and, as shown previously, in the corneal primary stroma.

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PubMed1988

Acquisition of type IX collagen by the developing avian primary corneal stroma and vitreous.

Previous investigations from our laboratory and others have demonstrated that type II collagen, once thought to be a cartilage-specific molecule, is also a component of both the primary corneal stroma and the vitreous of embryonic chickens. In the present immunohistochemical study we have examined the expression in these embryonic matrices of another "cartilage-specific" collagen, type IX, along with type II. In the cornea, type IX collagen is in the primary stroma, but is not detectable in the mature, secondary stroma. Even within the primary stroma this collagen has a brief, transitory existence. It first appears in the peripheral stroma at the time the endothelial cells begin to migrate along its posterior surface, and spreads throughout the stroma during the following 24-36 hr. The epitopes on type IX collagen then suddenly become undetectable just before this matrix swells and becomes populated by the periocular mesenchymal cells (future keratocytes). In comparison, collagen type II (along with type I) is present in the stroma before and long after these events. Deposition of immunodetectable type IX collagen in the developing corneal stroma thus seems to be independent of type II. In the vitreous, we observed type IX collagen along with type II as soon as authentic vitreous could be identified and at all subsequent stages of development. In this tissue, therefore, the expression of collagen types IX and II appears to be coordinate.

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PubMed1988

Collagen type I and type V are present in the same fibril in the avian corneal stroma.

The distribution, supramolecular form, and arrangement of collagen types I and V in the chicken embryo corneal stroma were studied using electron microscopy, collagen type-specific monoclonal antibodies, and a preembedding immunogold method. Double-label immunoelectron microscopy with colloidal gold-tagged monoclonal antibodies was used to simultaneously localize collagen type I and type V within the chick corneal stroma. The results definitively demonstrate, for the first time, that both collagens are codistributed within the same fibril. Type I collagen was localized to striated fibrils throughout the corneal stroma homogeneously. Type V collagen could be localized only after pretreatment of the tissue to partially disrupt collagen fibril structure. After such pretreatments the type V collagen was found in regions where fibrils were partially dissociated and not in regions where fibril structure was intact. When pretreated tissues were double labeled with antibodies against types I and V collagen coupled to different size gold particles, the two collagens colocalized in areas where fibril structure was partially disrupted. Antibodies against type IV collagen were used as a control and were nonreactive with fibrils. These results indicate that collagen types I and V are assembled together within single fibrils in the corneal stroma such that the interaction of these collagen types within heterotypic fibrils masks the epitopes on the type V collagen molecule. One consequence of the formation of such heterotypic fibrils may be the regulation of corneal fibril diameter, a condition essential for corneal transparency.

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PubMed1988

Multiple-reaction cycling: a method for enhancement of the immunochemical signal of monoclonal antibodies.

Most current studies using immunochemical and immunohistochemical procedures to detect antigen-antibody complexes employ some type of indirect method. Such procedures afford signal amplification because several marker-conjugate molecules can bind to each primary antibody molecule. We have observed that for monoclonal antibodies an even greater amplification can be afforded simply by performing two (or more) reaction cycles (i.e., primary antibody, secondary antibody-primary antibody, secondary antibody-etc). In the present report, we demonstrate the utility of this method for immunohistochemical (immunofluorescence) and immunochemical (ELISA: enzyme-linked immunosorbent assay) procedures employing well-characterized monoclonal antibodies directed against avian type IV (basement membrane) collagen.

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PubMed1988

Corneal collagen fibrils: dissection with specific collagenases and monoclonal antibodies.

To investigate the relationship of collagen types I and V within corneal fibrils, and the collagenolytic mechanisms potentially involved in corneal development and remodeling, we have incubated cryostat sections of avian corneas with collagenases that specifically degrade collagen types I or V to digest selectively the collagen in situ. These preparations were then analyzed by immunofluorescence histochemistry and immunoelectron microscopy using anti-collagen type-specific monoclonal antibodies. Digestion of corneal sections with the type I-specific collagenase ("I'ase") exposed antigenically masked type V collagen, indicating that epitopes on type V collagen in heterotypic fibrils are inaccessible to the antibody due to their interaction with type I collagen. Sections digested with the type V collagen-degrading enzyme ("V'ase") showed no removal of type V collagen. However, after the fibrillar structure was disrupted by acetic acid treatment before enzyme digestion, the type V collagen was then degraded. Likewise, prior digestion of type I collagen by I'ase also rendered type V collagen susceptible to digestion by V'ase. These results suggest that the cleavage sites on type V collagen also are buried within heterotypic fibrils and therefore inaccessible to the enzyme. They also document, for the first time, V'ase activity against type V collagen in situ. Electron microscopic observations of sections partially digested with the I'ase revealed many short striated fibrillar segments from which smaller filaments protrude. Both the striated regions and some of the filaments were labeled by an antibody against type I collagen; anti-type V antibody reacted preferentially with the thin filaments. Thus avian corneal fibrils contain type I collagen, in which filaments of type V collagen are embedded. Complete removal of the fibrillar stromal matrix in the course of normal or pathological remodeling requires at least two different collagenases acting in concert.

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PubMed1986

Fibroblasts promote the formation of a continuous basal lamina during myogenesis in vitro.

Analyses were made of the requirements for the formation of a continuous basal lamina during myogenesis of quail muscle in vitro. A culture system was developed in which mass cultures of differentiating muscle cells were embedded in a native gel of rat tail collagen. Fibroblastic cells, which were also present in the cultures, migrated into the gel and within a few days surrounded the newly formed myotubes. In this environment, a continuous basal lamina was formed at the surface of the myotubes as demonstrated by immunofluorescent staining with monoclonal antibodies against type IV collagen, laminin, and heparan sulfate, as well as by electron microscopic immunolocalization. To distinguish between the role of the fibroblasts and the collagen gel in promoting basal lamina formation, clones of quail muscle cells lacking fibroblasts were subsequently embedded in a native rat tail collagen gel. Under these conditions, only very limited fluorescent staining for basement membrane components was observed associated with the myotubes. However, the introduction of chick muscle or skin fibroblasts into the clonal cultures just before gel formation resulted in the formation of an extensive basal lamina on the surface of the myotubes. Conditioned medium from fibroblast cultures by itself was not effective in promoting basal lamina formation. These results clearly show that during myogenesis in vitro fibroblasts must be in close proximity to the myotubes for a continuous basal lamina to form. These results probably relate closely to the interactions that must occur during myogenesis in vivo between the muscle cells and the surrounding connective tissue including the developing tendons.

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PubMed1986

Embryonic avian cornea contains layers of collagen with greater than average stability.

A unique morphological feature of the embryonic avian cornea is the uniformity of its complement of striated collagen fibrils, each of which has a diameter of 25 nm. We have asked whether this apparent morphological uniformity also reflects an inherent uniformity of the structural and physical properties of these fibrils. For this we have examined the in situ thermal stability of the type I collagen within these fibrils. Corneal tissue sections were reacted at progressively higher temperatures with conformation-dependent monoclonal antibodies directed against the triple-helical domain of the type I collagen molecule. These studies show that the cornea contains layers of collagen fibrils with greater than average stability. The two most prominent of these extend uninterrupted across the entire width of the cornea, and then appear to insert into thick bundles of scleral collagen, which in turn appear to insert into the scleral ossicles, a ring of bony plates which circumscribe the sclera of the avian eye. Once formed, the bands may act to stabilize the shape of the cornea or, conversely, to alter it during accommodation.

Animals↗
PubMed1986

Organization of collagen types I and V in the embryonic chicken cornea.

The distribution and organization of type I and type V collagens were studied in the embryonic chicken cornea using anti-collagen, type specific, monoclonal antibodies and immunoelectron microscopy. These studies were performed on lathyritic 17-day corneas treated at 4 degrees C or 37 degrees C. At the lower temperature, collagen fibril structure is disrupted; at the higher temperature, normal fibril structure is maintained. Corneas from non-lathyritic 17-day chick embryos, reacted at the two different temperatures, were studied for comparison. In Bowman's membrane, the thin (20 nm) fibrils were labelled by antibodies against both type I and type V collagen under all conditions studied. In the corneal stroma, the striated collagen fibrils (25 nm) were labelled with the antibodies against type I collagen in all cases, and by antibodies against type V collagen under conditions where fibril structure was disrupted. These results are consistent with the concept of heteropolymeric fibrils consisting of both type I and type V collagen molecules assembled such that the epitopes on the type V molecule are unavailable to antibody unless the fibrillar structure is disrupted. We suggest that the interaction of type V collagen with type I collagen may be responsible for the small diameter fibrils and the rigid control of fibril structure found in the cornea.

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PubMed1985

Sex differences in the dendritic branching of dentate granule cells following differential experience.

Male and female hooded rats were raised from weaning in either a complex or an isolated environment in two separate replications. After one month, the brains were Golgi-Cox stained and dendritic fields of dentate gyrus granule cells were quantified. There was a sex difference in response to the environment. Females raised in the complex environment had more dendrite per neuron than females from the isolated environment in both replications. This difference was evident chiefly in the length of dendritic branches. Males showed few differences in response to the environments in either replication and, to the extent that there were differences, there was a slight tendency for isolated males to have more dendrite per neuron than males from the complex environment. In comparisons between the sexes within an environment, males had more dendritic material per neuron than females in the isolated environment while females had a larger dendritic tree than males in the complex environment. The above pattern of differences was not altered when hemisphere or location of the cell body within the granule cell layer were taken into account, although the shape of the dendritic tree varied with the cell's position in the layer in all groups. Thus, females show greater structural change in the dentate granule cells in response to these environments than do males.

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PubMed1984

Dual origin of glomerular basement membrane.

The histogenesis of renal basement membranes was studied in grafts of avascular, 11-day-old mouse embryonic kidney rudiments grown on chick chorioallantoic membrane (CAM). Vessels of the chick CAM invade the mouse tissue during an incubation period of 7-10 days and eventually hybrid glomeruli composed of mouse epithelium and chick endothelium form. Formation of basement membranes during this development was followed by immunofluorescence and immunoperoxidase stainings using polyclonal and monoclonal antibodies against mouse and chick collagen type IV and against mouse laminin. These antibodies were species-specific as shown in immunochemical and immunohistologic analyses. The glomerular basement membrane contained both mouse and chick collagen type IV, demonstrating its dual cellular origin. All other basement membranes were either exclusively of chick origin (mesangium, vessels) or of mouse origin (tubuli, Bowman's capsule).

Allantois↗
PubMed1984

Organization of collagen types I and V in the embryonic chicken cornea: monoclonal antibody studies.

To determine whether type V collagen is antigenically masked in situ by its fibrillar organization, two different methods were used to perturb selectively the structure of collagen fibrils in sections of embryonic chicken corneas. The experimentally modified tissues were probed by immunohistochemical procedures with monoclonal antibodies against types V and I. A lathyritic agent was used to block crosslinking of newly synthesized collagen. This results in reversible temperature-sensitive alterations in fibrillar packing, such that freshly formed collagen fibrils retain their aggregated state at 37 degrees C but become dissociated upon cooling. Type V-specific immunofluorescence remained masked at 37 degrees C but was revealed at 0 degree C. The effect of temperature was partially reversible, indicating that type V collagen is normally unavailable for antibody binding because of its fibrillar arrangement. In sections of normal corneas, treatment with corneal collagenase, which degrades type I collagen, but not type V, also unmasked the latter. This implicates type I collagen as the masking agent. We propose that collagen types I and V are incorporated together in heterotypic fibrils.

Animals↗
PubMed1984

Monoclonal antibodies against chicken type IV and V collagens: electron microscopic mapping of the epitopes after rotary shadowing.

The location of the epitopes for monoclonal antibodies against chicken type IV and type V collagens were directly determined in the electron microscope after rotary shadowing of antibody/collagen mixtures. Three monoclonal antibodies against type IV collagen were examined, each one of which was previously demonstrated to be specific for only one of the three pepsin-resistant fragments of the molecule. The three native fragments were designated (F1)2F2, F3, and 7S, and the antibodies that specifically recognize each fragment were called, respectively, IA8 , IIB12 , and ID2 . By electron microscopy, monoclonal antibody IA8 recognized an epitope located in the center of fragment (F1)2F2 and in tetramers of type IV collagen at a distance of 288 nm from the 7S domain, the region of overlap of four type IV molecules. Monoclonal antibody IIB12 , in contrast, recognized an epitope located only 73 nm from the 7S domain. This result therefore provides direct visual evidence that the F3 fragment is located closest to the 7S domain and the order of the fragments must be 7S-F3-(F1)2F2. The epitope for antibody ID2 was located in the overlap region of the 7S domain, and often several antibody molecules were observed to binding to a single 7S domain. The high frequency with which antibody molecules were observed to bind to fragments of type IV collagen suggests that there is a single population of type IV molecules of chain organization [alpha 1(IV)]2 alpha 2(IV), and that four identical molecules must form a tetramer that is joined in an antiparallel manner at the 7S domain. The monoclonal antibodies against type V collagen, called AB12 and DH2 , were both found to recognize epitopes close to one another, the epitopes being located 45-48 nm from one end of the type V collagen molecule. The significance of this result still remains uncertain, but suggests that this site is probably highly immunoreactive. It may also be related to the specific cleavage site of type V collagen by selected metalloproteinases and by alpha-thrombin. This cleavage site is also known to be located close to one end of the type V molecule.

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