Etiology of the developing eye in myelencephalic blebs (my) mice

The etiology of the eye defects in myelencephalic blebs (my) mutant mice has been poorly understood for almost seventy years. Embryos from 9 to 14 1/2 days of gestation were subjected to Alcian blue 8GX staining for acidic glycosaminoglycan deposition in basement membrane structures of the developing eye in my stock and control specimens. In addition 12 day embryos were subjected to avidinbiotin-peroxidase labelling for laminin. At 9-9 1/2 days of gestation more Alcian blue positive extracellular matrix was found in the region between the optic vesicle and the overlying putative lens ectoderm in the my stock embryos. By 12 days, there was an irregular and lesser amount of deposition of glycosaminoglycans in the len's capsule and in the "inner limiting membrane" of the presumptive neural retina; however, the deposition of laminin appeared to be greater in the inner limiting membrane of the my eye. By 14 days, the damage to the eye in the my embryos can be quite extensive, and the deposition of glycosaminoglycans was very meager in this situation. It appears that irregular deposition of glycosaminoglycans in the extracellular matrix and possible increase in the amount of laminin in basement structures in my embryos indicate disruption of the normal histochemistry involved in the development of the eye. Altered histochemistry may in turn indicate changes in permeability between cells of the developing tissues which result in the blebbing.

Effects of dexamethasone on TRH and TRH precursor peptide (Lys-Arg-Gln-His-Pro-Gly-Arg-Arg) levels in various rat organs

The effect of an acute dexamethasone administration on thyrotropin-releasing hormone (TRH) and TRH precursor peptide (Lys-Arg-Gln-His-Pro-Gly-Arg-Arg) (p-8) levels in various rat organs has been studied. Rats were injected i.p. with 25 micrograms of dexamethasone/100 g body weight (group A), 500 micrograms of dexamethasone/100 g body weight (group B) or saline (group C). The rats were serially decapitated after the injection. TRH and p-8 levels in the hypothalamus, cerebrum, cerebellum and brain stem, stomach and eye and plasma TRH and thyrotropin (TSH) levels were measured by individual radioimmunoassays. P-8 levels in the hypothalamus decreased significantly in both group A and B at 1-4 hours after the injection, and then returned to pretreated levels at 24 hours after the injection. TRH levels in the hypothalamus increased significantly in both group A and group B at 1-4 hours after dexamethasone injection. No changes in p-8 and TRH levels were observed in other organs. In group A, plasma TRH levels tended to decrease at 1-2 hours, then to increase at 3 hours. In group B, plasma TRH levels decreased 1-4 hours after the dexamethasone injection, then increased at 24 hours. The plasma TSH levels decreased significantly at 1-4 hours in group A and group B, returned to pretreatment levels at 24 hours in group A, and increased significantly in group B at 24 hours after dexamethasone injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochrome oxidase in rat ocular tissues with special reference to copper

The localization of cytochrome oxidase, one of the copper metalloenzymes, was determined histochemically and compared with that of copper. Copper and cytochrome oxidase coexisted in the corneal epithelium and endothelium, iris, ciliary body, lens epithelium, and retinal photoreceptor inner segment. In spite of the presence of copper, no cytochrome oxidase was demonstrated histochemically in the retinal pigment epithelium, choroid, sclera, or optic nerve. The coexistence of copper and cytochrome oxidase suggests that copper plays a role in this copper metalloenzyme, while the non-coincidence of localizations of copper and cytochrome oxidase may be attributed to histochemical problems or to some unknown function of copper.

Quantitative determination of the melanin contents in ocular tissues from human blue and brown eyes

This paper deals with our findings on the quantities of melanin in the tissues from blue and brown eyes. The amount of melanin in the iris, ciliary body and retinal pigment epithelium-choroid was separately determined. The results are expressed as the amount of melanin in mg tissue as well as the amount of melanin in the whole tissue. The results showed that there was no statistically significant difference between the melanin content of the iris in blue and brown eyes. However the ciliary body and retinal pigment epithelium-choroid from brown eyes had more melanin than the corresponding tissues from blue eyes. Blue and brown eyes with higher colour intensity had more melanin than the corresponding eyes with lesser intensity of colour. It is suggested that the differences between brown and blue eyes in their melanin content may have relevance to the pharmacokinetics of drugs that bind to melanin. This would mean that the larger amounts of melanin would decrease the initial levels of the drugs and would increase the drug levels after prolonged periods.

Patterns of cytokeratins and vimentin in guinea pig and mouse eye tissue: evidence for regional variations in intermediate filament expression in limbal epithelium

The anatomical distribution of different individual cytokeratin polypeptides and of vimentin was investigated by means of immunofluorescence with 41 monoclonal antibodies in guinea pig and mouse eyes. Simple epithelial type cytokeratins 7, 8, 18, and 19 selectively decorated conjunctival goblet cell clusters in mouse specimens and a continuous superficial cell layer of the corresponding part of guinea pig conjunctiva. A changed pattern of squamous epithelial type cytokeratins was found in the limbal region of the guinea pig eye as compared to the corneal epithelium. Cytokertains 3 and 17, which stained the entire corneal epithelium, were not detected, whereas cytokeratin 4, 5 and 13 were expressed. A focal vimentin and cytokeratin coexpression in the limbus of guinea pig is interpreted as indicating corneal stem cells. Similar patterns of expressions were found in the mouse ocular surface. In both species, a cytokeratin 4 staining of basal conjunctival epithelial cells could be detected. The neuroectodermally derived epithelia of the eye such as the retinal pigment epithelium and the ciliary body epithelia expressed solely the cytokeratin pair 8/18.

Glycosaminoglycans of trabecular meshwork and adjacent tissues of the rabbit eye

Glycosaminoglycans (GAGs) extracted from the trabecular meshwork (TM) of rabbit eyes were analyzed by cellulose acetate electrophoresis and sequential enzymatic degradation, and compared with GAGs extracted from the adjacent tissues including the cornea, sclera, iris and ciliary body. The TM contained hyaluronic acid (HA), chondroitin 4- and/or 6-sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS), heparan sulfate (HS) and an unidentified band of Alcian-blue-stained material which was resistant to degradation by the enzymes and chemicals used. The GAGs of the rabbit TM included: 13.9% HA, 31.6% CS, 47.1% DS, 4.6% KS and 1.2% HS, and were distinct from those of the cornea and the sclera.

Localization of myomodulin-like immunoreactivity in the central nervous system and peripheral tissues of Aplysia californica

The distribution of myomodulin-like peptides in the nervous system of Aplysia californica was examined by using immunocytochemical techniques. Neurons and cell clusters containing immunoreactive material were located in each of the major central ganglia. Myomodulin-like immunoreactivity was also present in fibers in each of the connectives between the ganglia and in peripheral nerves. Varicosities containing immunoreactive material were located on specific regions of peripheral tissues associated with the feeding, digestive, cardiovascular, and reproductive systems. Double-labeling experiments were used to demonstrate myomodulin-like immunoreactivity in two identified neurons, the motor neuron B16 in the buccal ganglion and the widely acting interneuron L10 in the abdominal ganglion. Structures in the eye and cerebral ganglion that may correspond to the optic circadian pacemaker system were also stained. The central and peripheral distribution of myomodulin-like immunoreactivity indicates that this family of neuropeptides is present in specific efferent, afferent, and interneuronal elements that participate in a diversity of neural circuits in Aplysia.

Effects of a zinc-deficient diet on tissue zinc concentrations in rabbits

Young male New Zealand White rabbits given a diet containing 2 ppm of Zn (Zn-deficient diet) ceased to grow after 5 wk. Control rabbits given diets containing 80 or 85 of ppm Zn and experimental animals given 7 ppm of Zn (low-Zn diet) grew normally. The rabbits given the Zn-deficient diet also exhibited alopecia, skin lesions, and frequent pasteurella infections. These conditions were not observed in rabbits fed the other diets. The testes and thymus were smaller in the rabbits fed the Zn-deficient diet than in rabbits fed the control diet. Serum Zn concentrations in rabbits given the low- or Zn-deficient diets reached new lower levels after 2 wk, and these concentrations were maintained for up to 12 wk. The serum Zn concentration was, however, lower in the rabbits fed the Zn-deficient diet (approximately .35 micrograms/ml compared with .8 micrograms/ml for rabbits fed the low-Zn diet and 1.4 micrograms/ml for rabbits fed the control diet). Tissue Zn concentrations generally declined in rabbits fed the low- and Zn-deficient diets, but this response depended on the particular tissue and diet. Zinc levels in bone decreased by approximately 45% and in fur by 20 to 30% on either low-Zn or Zn-deficient treatments. With a Zn-deficient diet, Zn in liver and testes decreased by 20%, Zn in skin by 35%, and Zn in brain by 10%. The Zn concentration in the skeletal muscle and thymus was, however, maintained. In the eye, Zn concentration in the aqueous humor declined by approximately 20% in rabbits fed the Zn-deficient diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary structure and relative potency of an analog of beta-PDH (pigment-dispersing hormone) from the crayfish Procambarus clarkii

A pigment-dispersing hormone (PDH) from eyestalks of the crayfish Procambarus clarkii was purified by gel filtration, cation-exchange chromatography, partition chromatography, and reversed-phase HPLC. Based on automated sequencing and by the identical chromatographic behavior of the native PDH and the synthetic amidated form of the deduced sequence, the primary structure of Procambarus PDH has been established as: Asn-Ser-Glu-Leu-Ile-Asn-Ser-Ile-Leu-Gly-Leu-Pro-Lys-Val-Met-Asn-Glu-Ala- NH2. This peptide differs from beta-PDH of the fiddler crab Uca pugilator at a single position, Glu17 in place of Asp17. Because of this substitution, Procambarus PDH was 4 to 7-fold less potent than beta-PDH in causing pigment dispersion in the erythrophores, leucophores, and melanophores of Uca. In contrast, Procambarus PDH was 4-fold more potent than beta-PDH in eliciting pigment dispersion in the erythrophores of Procambarus. These peptides displayed less marked differences in potency in triggering leucophore pigment dispersion and light-adaptational distal eye pigment movement in Procambarus. These findings indicate that the structural requirements for PDH-receptor interactions vary with the species and with the target cell type within a given species.

Zebrafish pax[zf-a]: a paired box-containing gene expressed in the neural tube

Murine and human sequences homologous to the paired box of the Drosophila segmentation gene paired have been reported previously. Here we describe a zebrafish (Brachydanio rerio) paired box-containing clone, pax[zf-a], which is clearly distinct from reported vertebrate Pax genes. The putative protein encoded by pax[zf-a] contains a paired box and a paired-type homeobox separated by a glycine-rich, acidic linker and a carboxy-terminal end which is remarkably rich in serine, threonine and proline residues. By in situ hybridization to embryonic tissue sections and whole mount embryos, pax[zf-a] transcripts were found within restricted regions of the central nervous system and the eye. In contrast to the murine Pax genes recently characterized, pax[zf-a] is not expressed in the segmented mesoderm. At the 17 h stage, pax[zf-a] expression is detected in a defined area of the diencephalon which circumscribes the presumptive thalamus. This suggests an involvement of pax[zf-a] in pattern formation in the rostral brain. The pax[zf-a] gene is also expressed throughout the hindbrain and spinal cord. This hybridization signal is restricted to a longitudinal column which includes the basal plate. Later in development, at 36 h post-fertilization, pax[zf-a] transcripts are no longer restricted to a specific region of the diencephalon, but are distributed over the entire developing brain.

[Localization of bovine cornea-specific protein in mouse and human eyes]

Rats were immunized by purified bovine cornea-specific protein (CSP) and anti-CSP polyclonal antibody was produced. Localization of CSP in mice and human eyes was examined by immunohistochemical methods with light microscopy using this antibody. In mice CSP was found in the corneal epithelium, keratocytes, corneal endothelium, conjunctival epithelium and lens epithelium. In human eyes CSP was found in the corneal epithelium, keratocytes and conjunctival epithelium, but it was not found in the lens. These results confirmed a difference in localization of CSP between mice and human eyes. It was suggested that the production of CSP might be associated with phylogenesis and that CSP might also be associated with the development of the cornea.

A G beta protein in the Drosophila compound eye is different from that in the brain

A G protein beta subunit gene (Gbe) is expressed only in the eyes of adult D. melanogaster. This gene was identified by probing a Drosophila head cDNA expression library with monoclonal antibodies to a previously characterized Drosophila G protein beta subunit (Gbb). Immunoblot and Northern analyses demonstrate that Gbe protein and mRNA is not present in Drosophila mutants that lack eyes. Immunocytochemical and in situ hybridization analyses further demonstrate that Gbe is expressed in the eyes but not in the brain, whereas Gbb is abundantly expressed in the brain. The Gbe product is approximately 45% identical to previously identified G beta subunits and defines a new G beta class. Its localization suggests a possible role in phototransduction.

Rapid high voltage isoelectric focusing of proteins in rod gels

A rapid procedure of isoelectric focusing (IEF) of proteins in polyacrylamide rod gels (i.d., 1.1 mm; length, 7.5 cm) is described. The time required for IEF can be reduced to 0.5 h by using high voltages up to 3000 V in the presence or absence of urea in the gels. When used as the first dimension of a two-dimensional technique for IEF sodium dodecyl sulphate electrophoresis, high voltage IEF gives smaller protein spots on the second dimension gel, associated with an increase in resolution. The method has been tested by a two-dimensional separation of an eye sample of the goodeid fish Xenotoca eiseni.

Regulation of acetylcholine receptors on chick ciliary ganglion neurons by components from the synaptic target tissue

Chick ciliary ganglion neurons have nicotinic acetylcholine receptors (AChRs) that mediate synaptic transmission through the ganglion. A soluble component of about 50 kDa from embryonic eye tissue, the synaptic target of the ganglion, increases the development of ACh sensitivity by the neurons 10-fold over a 1-week period in culture. The increased sensitivity does not arise from a change in agonist affinity or esterase activity. Both the basal ACh response obtained in the absence of the 50-kDa component and the elevated responses obtained with it can be inhibited by neuronal bungarotoxin (nBgt) but not by alpha-bungarotoxin (alpha Bgt). Increases of less than twofold are observed for the binding of anti-AChR monoclonal antibody 35 (mAb 35), nBgt, and alpha Bgt to the neurons under these conditions. Extract fractions containing the 50-kDa component also enable the neurons to enhance their ACh responses through a cAMP-dependent mechanism. Either the 50-kDa fraction induces the appearance of a new type of AChR regulated by cAMP, or it alters the function of existing AChRs. The 50-kDa fraction produces no change in neuronal growth but can increase GABA responses sixfold, indicating that its effects are not confined to AChRs. It is not clear whether a single molecular species is responsible for the diverse regulatory effects or whether several types of active components are present in the fraction. The component which enhances ACh sensitivity is trypsin-sensitive and heat-labile, as expected for a protein. The component may be widely distributed since the 50-kDa fraction from a number of tissues can increase the ACh response. The fraction from eye tissue, however, has a specific activity 5-10 times greater than that of the liver fraction. A wide distribution would suggest multiple targets and roles for the component during development.

Ocular distribution of 70-kDa heat-shock protein in rats with normal and dystrophic retinas

Stress proteins are thought to play an important role in cellular development and in survival mechanisms. We compared the immunolocalization of the 70-kDa stress protein (SP70) in the ocular tissue of the normal Sprague-Dawley (SD) rat with that in the Royal College of Surgeons (RCS) rat with retinal dystrophy. SP70 was present in the maturing ocular tissues of both rat strains. However, once retinal degeneration began in the RCS rat, the retinal pigment epithelium and photoreceptor cells showed increased immunostaining for SP70 over that observed in age-matched SD rats. In late stages of retinal degeneration, immunostaining for SP70 was considerably reduced in the RCS retina, whereas normal distribution of immunostaining for SP70 in the SD retina was preserved, albeit decreased, through postnatal day 180. The optic nerve, ciliary body, and corneal epithelium were also influenced by the dystrophic disease condition, although the pattern of changes in SP70 immunostaining differed for each tissue. These results suggest that the genetic defect in the RCS rat produces a state of metabolic stress in all ocular tissues as the degeneration progresses, but that the subsequent rise in ocular SP70 is insufficient to prevent progression of the disease.

Analysis of flavins in ocular tissues of the rabbit

Riboflavin is the precursor of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), coenzymes required for the activity of flavoenzymes involved in the transfer of electrons in oxidation-reduction reactions. Flavins are light sensitive and rapidly degrade when exposed to light in the near ultraviolet and visible wavelengths. Some of the byproducts of flavin photodegradation are toxic. A quantitative survey of flavins in rabbit ocular tissues is reported. Adult male Dutch-Belt Rabbits were fed purified diets containing 3, 30, or 300 mg riboflavin/kg for 1 month. A method of aqueous extraction and high-performance liquid chromatography with fluorescence detection was used to measure riboflavin, FMN, and FAD in cornea, lens cortex, lens nucleus, retina, and blood. The retina contained the highest flavin concentration. In all tissues, the primary flavin was FAD followed by FMN and riboflavin. The highest concentration of riboflavin occurred in the cornea followed by the retina, lens cortex, and lens nucleus. A trend toward increasing concentrations of riboflavin occurred in the retina and blood in response to excess dietary riboflavin, but the concentration changes were not statistically significant. The highest concentration of FAD and FMN occurred in the retina followed by the cornea and the lens cortex and nucleus. The relative contribution of riboflavin, FMN, and FAD to the total flavin pool was markedly different in the various tissues of the eye. The proportion of tissue flavins present as riboflavin decreased from anterior to posterior. It was highest in the cornea followed by lens and retina. The pattern of distribution for FMN was: cornea greater than retina greater than lens cortex and nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

[Study of eye proteoglycans by means of infrared spectroscopy]

The infrared spectra of standard hyaluronic acid, proteochondroitin sulfate, aggregates of proteoglycans and spectra of the vitreous body, cornea and sclera were obtained in the region of 4000-400 cm-1. The comparative analysis of the spectra of these tissues and spectra made it possible to identify greater absorption bands of these biopolymers.

Immunohistochemical localization of metallothionein in the eye of rats

In order to elucidate possible physiological roles of metallothionein (MT), we have studied immunohistological localization of MT in the eye of the rat, using an avidin-biotin peroxidase complex method. As a result, strong MT immunostaining was observed in the epithelium of the lens and cornea. In the retina, considerably strong MT immunostaining was observed in the pigment cell layer while the nerve fiber layer and inner plexiform layer showed weak MT staining. Glial cells in the optic nerve were found to have marked MT staining. The present result is consistent with the hypothesis that MT may be involved not only in activation of zinc enzymes and cell proliferation through supply of zinc ions, but also in a protective mechanism in the blood-retina barrier.

Heterogeneity in the immunolocalization of cytokeratin specific monoclonal antibodies in the rat eye: evaluation of unusual epithelial tissue entities

The immunocytochemical localization of cytokeratin and vimentin in rat eye tissues was investigated using a panel of 39 monoclonal antibodies specific for single or multiple of cytokeratin polypeptides and one polyclonal anti CK20 antiserum. The retinal and the ciliary body pigment epithelial only expressed cytokeratins 8 and 18, whereas the fetal retinal pigment epithelium and focally the adult epithelium, in the transition zone of retina and ciliary body, exhibited a reactivity for cytokeratin 19. In contrast, the non-pigmented ciliary epithelium was positive for vimentin only. In the rat conjunctiva distributed goblet cell clusters were selectively stained with cytokeratin 7, 8, 18 and 19 specific monoclonal antibodies. Among them a group of cytokeratin 8 and 18 specific monoclonal antibodies which stained the goblet cells as well as cytokeratin 8 and 18 positive internal controls did not react with either the cytokeratin 8 and 18 positive neuroectodermal cells of the rat eye nor the rat choroid plexus epithelium. This indicates differences in the phenotype e.g. conformational epitope changes, of neuroectodermal derived and other cytokeratins. The corneal and conjunctival epithelium showed a more complex distribution of squamous epithelium type cytokeratins. The limbal region as a transient zone connecting both epithelia exhibited a changing cytokeratin pattern. In general, the study emphasized the necessity to work with an enlarged antibody panel to avoid misleading results in the immunolocalization of cytokeratins.

Histamine: a putative afferent neurotransmitter in Limulus eyes

Histamine has been proposed as a photoreceptor neurotransmitter in two major groups of arthropods, the insects and the crustacea. In this study biochemical and immunocytochemical approaches were used to examine the synthesis, endogenous content, and cellular distribution of histamine in the visual system of the horseshoe crab Limulus polyphemus, an ancient chelicerate arthropod. Studies with this animal have been critical to our understanding of the basic processes of vision. High-voltage paper electrophoresis was used to assay for histamine synthesis in Limulus tissues incubated with radiolabeled histidine; histamine synthesis was detected in the lateral, median, and ventral eyes and optic nerves and in the visual centers in the brain. Endogenous histamine, assayed as its orthophthalaldehyde derivative by high-performance liquid chromatography and electrochemical detection, was also detected in these tissues. Immunocytochemical analyses, with an antiserum directed against a protein conjugate of histamine, revealed histamine-like immunoreactivity in the somata of photoreceptors in each of the eyes and in the regions of the brain where the photoreceptors terminate. Histamine-like immunoreactivity was also intense in the cell bodies and axon collaterals of eccentric cells in the lateral eye and in eccentric cell projections in the brain. These results show that histamine is a major biogenic amine in the Limulus visual system, and they suggest that this amine is involved in transmitting visual information from the eyes to the brain and in lateral inhibition, a fundamental mechanism for processing visual information in the lateral eye.

Forage-related nitrate toxicoses possibly confounded by nonprotein nitrogen and monensin in the diet used at a commercial dairy heifer replacement operation

Two clinically different episodes of nitrate toxicosis in heifers at the same dairy were evaluated to determine whether dietary supplements could have contributed to the confounding signs of illness. The first episode followed a 24-hour period of feeding mismanagement and resultant overconsumption of both a protein/nonprotein nitrogen supplement and a monensin supplement. This episode was characterized by ataxia, bloating, and death, without the classic clinical signs of dyspnea, salivation, cyanosis, and dark-colored blood, or the cardinal histologic changes of cyanosis, tissue staining, petechiations, or congestion. Approximately 5 weeks later, another episode developed, without the feeding mismanagement or the presence of supplements, and was characterized by classic signs of nitrate toxicosis along with response to methylene blue treatment. In both episodes, the feed source was the same, with high concentrations of nitrate. Heifers of both episodes had high ocular nitrate values, confirming the toxicoses. The difference was the availability of supplements. Calculation of exposure makes it unlikely that either the nonprotein moiety or the monensin moiety could have reached toxic values. However, the cell-level effects of monensin may have caused the animals to not display classic signs of nitrate toxicosis, confusing the diagnosis and treatment. This report demonstrates how field toxicosis can differ from reports of toxicoses caused by single etiologic agents. Practitioners must be aware of the potential for interactions between (and confounding by) commercially used feed components.

Applications of nuclear magnetic cross-relaxation spectroscopy to tissues

Magnetic cross-relaxation in aqueous heterogeneous systems is a long established phenomenon that makes the observable decay constants for the system mixtures of more fundamental relaxation times which characterize the relaxation of the coupled components. By exploiting the magnetic relaxation coupling between the water spins and the immobilized spins in a tissue, the water-proton-signal intensity may be used to map indirectly a frequency response that is directly related to the 1H NMR spectrum of the immobilized components of the tissue. This method is applied to a number of rat tissues to determine whether there are significant differences among tissues that might be exploited in applications of this experiment to diagnostic magnetic imaging. Significant differences are found among nine rat tissues studied, which suggests that the experimental approach may be used to super-impose fundamentally new information, the dynamic character of the usually unobservable immobilized macromolecular components of the tissue, on a magnetic image.

Ultrastructural study on a variety of non-neural cells immunoreactive for nerve growth factor receptor in developing rats

The occurrence of nerve growth factor receptor (NGFR) immunoreactivity was newly demonstrated in mesenchymal cells of lung bud and lateral palatine processes. Nerve fibers and enclosing Schwann cells with or without immunoreaction were present only in the periphery of the immunoreactive mesenchymal cell aggregation, but were not found within them. The NGFR-immunoreactive cells in immature skeletal muscles were revealed by immunoelectron microscopy to be perimysial cells without myofilament bundles, but not myoblastic cells. NGFR immunoreactivity was detected in noninnervated epithelial cells performing the invagination such as epithelial cells of the renal glomerulus and the lens placode. The immunoreactivity was also expressed in the innermost cells of the theca cell layer of the postnatal ovary and they contained no lipid droplets. In postnatal lymphatic tissues, NGFR-immunoreactive cells were identified as the interdigitating cells which were located in the internodular and deep cortex of the lymph nodes, in the marginal zone of the splenic white pulp, and in the medulla of the thymus. These findings suggest a potentially more widespread involvement of nerve growth factor and NGFR in the program of ontogeny than expected.

A new type of lesion associated with severe fur damage in Canadian ranch foxes and an investigation of possible causes

In the silver fox, as in its wild ancestor, the red fox (Vulpes vulpes L.), the annual growing phase (anagen) of guard hair follicles occupies at least four months. Severe damage to the hair coat near the end of this growing period was reported in 1985 on many ranches in New Brunswick and Nova Scotia. A histological analysis of serial sections of skin biopsies showed a marked increase in nuclear aberrations in the hair matrix of anagen guard hair follicles. These nuclear aberrations indicated that cells were undergoing apoptosis, a controlled form of cell death. Tissues from affected and unaffected foxes for histological and toxicological analysis, as well as other data, were obtained during visits to 26 ranches in 1986 and 34 ranches in 1987. Histological sections of the 1987 skin samples showed the mean percentage of nuclear aberrations in 43 unaffected foxes to be 0.08 +/- 0.01 (SEM), while that for 49 affected foxes was 0.51 +/- 0.23. The four foxes with the most severe coat damage also had the highest incidences of guard hair matrix cells with nuclear aberrations, ranging from 20 to 100 times greater than the mean for unaffected foxes. The mitotic index of the hair matrix, which normally remains fairly constant during the hair growth phase, was similar for unaffected and affected foxes (1.83 +/- 0.06 and 1.97 +/- 0.07 respectively). Although our analyses of field data have not established a specific environmental factor associated with increased nuclear aberrations, the possible involvement of toxic agents in follicle damage may warrant further investigation.