Comparative gene mapping in the domestic cat (Felis catus).

The genetic map of the domestic cat has been developed as a model for studying both feline analogues of human genetic disease and comparative genome organization of mammals. We present here the results of syntenic mapping of 35 genes based upon concordant occurrence of feline gene homologues with feline chromosomes and previously mapped loci in a panel of 41 rodent x cat somatic cell hybrids. These somatic cell hybrids retain rodent chromosomes and segregate feline chromosomes, but in different combinations in each hybrid cell line. Thirty-three of the 35 new locus assignments extend and reaffirm conserved chromosome segment homologies between the human and cat genomes previously recognized by comparative mapping and zoo-FISH. These results demonstrate the extensive syntenic conservation between the human and feline genomes and extend the feline gene map to include 105 assigned loci.

The gene encoding the Act-2 cytokine. Genomic structure, HTLV-I/Tax responsiveness of 5' upstream sequences, and chromosomal localization.

Act-2 is a cytokine that belongs to a superfamily of structurally related proteins. Act-2 expression is rapidly induced in T cells, B cells, and monocytes upon mitogenic stimulation. The Act-2 genomic locus is on chromosome 17q. The exons and exon/intron splice junctions have been sequenced, as have the sequences upstream of exon 1. A classical TATA box is located immediately upstream of the transcription initiation site. The upstream sequences possess promoter activity and can be functionally activated after treatment of Jurkat T cells with phythohemagglutinin plus phorbol myristrate acetate. In addition, Act-2 promoter chloramphenicol acetyltransferase constructs are expressed in human T cell lymphotropic virus type I (HTLV-I)-infected MT-2 cells and in Jurkat cells which can be induced to express the transactivator gene (tax) product of HTLV-I.

The enucleated arterially perfused cat eye. I. Effects on protein permeability.

Protein permeability of the ciliary epithelium of enucleated arterially perfused cat eyes was studied. Tracer concentrations of 125I-albumin, in an arterial perfusate solution consisting of a balanced salt solution (BSS) without added colloid, was found in the anterior chamber fluid (AH) in a percentage similar to the AH/plasma ratio found for protein in the living cat eye. Stimulation of AH formation by acetylcholine plus eserine increased protein permeability markedly and by a similar amount in eyes perfused either with BSS or with 100% serum. These data indicate that arterial perfusion of the enucleated eye with BSS alone induces no gross abnormality of the blood-aqueous barrier.

Cyclosporin a. Inhibition of experimental autoimmune uveitis in Lewis rats.

Cyclosporin A (CS-A), a selective inhibitor of T lymphocytes, is reported here to prevent S antigen (S-Ag) induced uveitis in Lewis rats. The S-Ag, found in all mammalian retinas, is uveitogenic under experimental conditions and patients with certain uveitic entities demonstrate cell mediated responses to this antigen. Daily treatment with CS-A (10 mg/kg) begun on the same day as S-Ag immunization totally inhibited the development of the uveitis in this experimental autoimmune model. Moreover a greater CS-A dose (40 mg/kg) efficiently prevented the disease process when therapy was started 7 d after S-Ag immunization. Anti-S-Ag antibody titers were observed to be similar in rats either protected or not protected with CS-A. Our data support strongly the need for T cell participation in this disease model. Since ocular inflammatory disease is an important cause of visual impairment, the data further suggest that CS-A may be useful in the treatment of patients with intractable uveitis.

Altered suppressor-cell activities in uveitis.

Suppressor-cell function was evaluated by two in-vitro assay systems in forty patients with intraocular inflammatory disease (uveitis) and in sixteen healthy age-matched controls. A concanavalin-A (Con A)-induced suppressor-cell assay showed that patients with posterior uveitic conditions had greater suppressor activity than did the anterior uveitic group or the control group (p < 0.005); but an assay for non-induced suppressor-cell activity showed that the posterior uveitic group had less suppressor activity (p < 0.001). These findings suggest (a) that at least two cell types may be involved in immunoregulation, and (b) that not all diseases of presumed autoimmune origin are the result of reduced suppressor activity, which has been shown in some "autoimmune" conditions.

Clonidine.

Clonidine hydrochloride has been demonstrated to produce vasoconstriction in the anterior segment of the cat eye. The mode of this action has been found to be due to direct stimulation of alpha-adrenergic receptors. In the intact, enucleated, arterially perfused eye, clonidine was found to decrease the rate of aqueous humor production. We suggest that clonidine, like hydroxyamphetamine hydrobromide, phenylephrine hydrochloride, and dopamine hydrochloride, decreases aqueous humor formation by constriction of afferent ciliary process blood vessels.

Ciliary ganglion stimulation. II. Neurogenic, intraocular pathway for excitatory effects on aqueous humor production and outflow.

Data obtained suggest that preganglionic stimulation of the ciliary ganglion produces an increase of aqueous humor formation and of facility of outflow "C" through the following neurogenic pathway: (1) the preganglionic fibers synapse in the ciliary ganglion as evidenced by depression of the response with nicotine applied topically to the ganglion. (2) The impulse proceeds to the equivalent of an intraocular interneuron which can be blocked by low concentrations of atropine and has been previously identified as being an E-2 receptor site. (3) From the interneuron, activity is ultimately exerted without further synapse on alpha-adrenergic receptors through the release of norepinephrine from the neuronal terminals. The adrenergic mechanism of action is supported by the inhibition of the responses by phenoxybenzamine, bretylium, and guanethidine. Constriction of efferent ciliary process blood vessels by neuron-released norepinephrine seems to be the end effect responsible for the increased production of aqueous humor. The site of the end response to increase "C" is unclear.

Ciliary ganglion stimulation. I. Effects on aqueous humor inflow and outflow.

Stimulation of the ciliary ganglion in an enucleated, arterially perfused cat eye preparation produced a sustained increase in aqueous humor formation and an increase in the rate of aqueous humor outflow. The increased aqueous humor formation induced by ciliary ganglion stimulation has been found to be pressure-dependent and therefore suggests that ultrafiltration may be the underlying mechanism of action. No change in capillary permeability of the ciliary body could be demonstrated.