Transcription of a single mannose receptor gene by macrophage and retinal pigment epithelium.

To determine if the macrophage mannose receptor transcript is present in mouse, rat, pig, and human retinal pigment epithelium (RPE), primary cultures and/or freshly dissected retinal pigment epithelium from four different species were used to isolate total RNA. RT-PCR was used to amplify segments of the macrophage mannose receptor from each sample. Amplified products were sequenced and compared with known sequences of the macrophage mannose receptor. Macrophage mannose receptor transcripts were identified in all RPE samples. Comparison between sequences identified in RPE with macrophage sequences from the same species revealed 100% identity. Sequence homology between the different species was 74% or greater. These data are consistent with the transcription of a single mannose receptor gene by these two phagocytic cell types.

Mannose receptor is expressed in normal and dystrophic retinal pigment epithelium.

In normal retinas, the phagocytosis of shed photoreceptor outer segments is mediated in part through a mannose receptor protein located in the apical retinal pigment epithelium membrane. As dystrophic rats of the Royal College of Surgeons have a defect in which the retinal pigment epithelium (RPE) is unable to phagocytize the shed outer segments, it is hypothesized that mannose receptor expression will be lost with the progression of photoreceptor degeneration. Immunohistochemical and molecular techniques have been used to study the developmental expression of the mannose receptor in normal and dystrophic retinal pigment epithelium. By immunofluorescence, the mannose receptor is localized to the retinal pigment epithelium, apical membrane region, beginning around 5 days postnatally in both normal and dystrophic retinas. In immunoblots, bands at 175 kDa are labelled by an anti-mannose receptor antibody in apical membrane samples from both normal and dystrophic RPE at all developmental times sampled. RT-PCR analysis reveals that mannose receptor message is present in normal and dystrophic RPE samples at all developmental time points examined. The present study demonstrates that the expression of the mannose receptor begins prior to outer segment differentiation and the initiation of phagocytosis in both normal and dystrophic RPE. Expression of the mannose receptor continues to be unchanged during the progression of photoreceptor degeneration in the dystrophic retina.

Transforming growth factor alpha and its receptor in neural retina.

Transforming growth factor alpha (TGF-alpha) stimulates mitosis of many ectodermal cells but has not previously been studied for its role in neural tissues such as retina. We examined bovine retina for the presence of TGF-alpha mRNA, TGF-alpha protein and for the presence and location of the TGF-alpha/EGF receptor. Biochemical studies demonstrated a high level (770 fmol/mg protein) of specific, high affinity (Kd = 2 nM) TGF-alpha/EGF receptors in membrane homogenates of neural retina, but undetectable binding to homogenates of retinal pigment epithelium. Light microscopic autoradiograms of sections of neural retinal tissue incubated with 125I-EGF indicated that specific TGF-alpha/EGF receptors were present on one or more cell types of the retina with the exception of the outer segments of the photoreceptor cells. In addition, retinal cells appear to synthesize TGF-alpha since both mRNA for TGF-alpha and TGF-alpha protein (4.2 ng/mg protein) were detected in retinal extracts using cDNA hybridization and TGF-alpha RIA techniques. The role(s) of TGF-alpha and its receptor in retina is unknown, but it is possible that they interact via an autocrine/paracrine mechanism to influence retinal regeneration, proliferative retinopathies or neural transmission.

The effect of the route of delivery of urogastrone on intestinal regeneration.

Urogastrone (UG) administered subcutaneously increases the rate of intestinal regeneration (neomucosal growth) on patched intestinal defects. Our purpose was to determine the optimal route of delivery of UG for intestinal regeneration. In 22 New Zealand white rabbits (2.1 to 3.4 kg) 2 X 5 cm ileal defects were patched with adjacent cecal serosal surface. Group I (n = 6) served as controls. Group II (n = 5), group III (n = 6), and group IV (n = 5) received UG, 1.5 micrograms/kg/hr, intravenously, subcutaneously, and intraluminally via miniosmotic pumps. Neomucosal growth was assessed 7 days after patching. Serum UG levels were detectable in only the intravenous group. Coverage of the patched defect and neomucosal area was significantly greater and contraction of the defect less in the groups receiving UG (p less than 0.05). Neomucosal area was highest in the intravenous group (286 +/- 16 mm2), intermediate in groups III and IV (236 +/- 19 and 215 +/- 20 mm2), and lowest in the control group (152 +/- 17 mm2; p less than 0.05). Sucrase and maltase activities were significantly higher in the intravenous group. Crypt cell production rate and ornithine decarboxylase activity were greater in the UG-treated animals. UG stimulated intestinal regeneration by all routes of delivery. The intravenous route had the greatest effect and was associated with the highest serum levels of UG. These findings have implications for the mechanism of the trophic effect of UG on the intestinal epithelium.

Immunocytochemical distribution of a breast carcinoma associated glycoprotein identified by monoclonal antibodies.

A glycoprotein, BCA-225 (Mr 225,000-250,000), has been identified in cells and spent medium of clone 11 T47D breast carcinoma cells by three murine monoclonal antibodies, CU18, CU26, and CU46. The antigen was localized in paraffin sections of 167/178 (94%) Bouin's-fixed human breast carcinoma tissues and few other carcinomas (1/8 lung [squamous], 4/4 uterine cervix) in an intracellular pattern, whereas an apical or glycocalyx distribution was seen in several normal tissues, benign lesions, and malignant tumors. Although the immunocytochemical staining patterns observed with these antibodies have many similarities to those described with other previously reported monoclonal antibodies, notable differences include the lack of reactivity of CU18, CU26, and CU46 with lactating mammary gland and with gastrointestinal malignancies. BCA-225 binds to wheat germ lectin, not to concanavalin A, but monoclonal antibody binding does not appear to involve the carbohydrate component of the molecule. The frequency of the immunocytochemical detection of BCA-225 in breast carcinomas and its restricted distribution in other human tissues suggest considerable clinical potential for this antigen and its corresponding monoclonal antibodies.