Comparison between epidermal growth factor, transforming growth factor-alpha and EGF receptor levels in regions of adult rat brain.

Examination of adult rat brain regions by specific radioimmunoassays revealed a widespread distribution of transforming growth factor-alpha (TGF-alpha), but not epidermal growth factor (EGF), the peptide that had previously been reported to be present in rodent brain. Polyadenylated RNA samples from the different regions of rat brain were analyzed by Northern blot to identify mRNA species encoding precursor proteins for EGF (preproEGF), TGF-alpha (preproTGF-alpha), and the EGF/TGF-alpha receptor. The results indicate that TGF-alpha is the most abundant ligand for the EGF/TGF-alpha receptor in most parts of the brain analyzed. Message for preproEGF was only detectable after prolonged autoradiographic exposure; levels of preproEGF mRNA were between two and three orders of magnitude lower in brain than those expressed in control tissue (kidney), and one to two orders of magnitude lower than preproTGF-alpha mRNA levels in all brain regions. These results were confirmed by analysis of mRNA by RT/PCR, and support the hypothesis that expression of preproEGF mRNA in the brain is limited to smaller discrete areas, whereas preproTGF-alpha gene expression is almost ubiquitous.     

Isthmotectal axons make ectopic synapses in monocular regions of the tectum in developing Xenopus laevis frogs.

During the development of binocular maps in the tectum of Xenopus laevis, axons that relay input from the ipsilateral eye via the nucleus isthmi undergo a prolonged period of shifting connections. This shifting accompanies the dramatic change in eye position that takes place as the laterally placed eyes of the tadpole move dorsofrontally. There is a concomitant expansion of the proportion of tectum that receives contralateral retinotectal input corresponding to the binocular portion of the visual field. Electrophysiological recording demonstrates that ipsilateral units are present in those rostral tectal zones, and anatomical methods show that the isthmotectal axons arborize densely in the rostral region but also extend sparser branches into the caudal zone, which is occupied by contralateral inputs with receptive fields in the monocular zone of the visual field. A mechanism that aligns the ipsilateral and contralateral maps is activity-dependent stabilization of isthmotectal axons that exhibit firing patterns correlated with those of nearby retinotectal axons. In order for activity patterns to function in stabilizing correct connections and promoting the withdrawal of incorrect connections, synaptic communication of some sort is hypothesized to be essential. We have investigated whether isthmotectal axons make morphologically identifiable synapses during development and where such synapses are located. We find evidence for morphologically identifiable synapses in all regions of the tectum, along with many growth cones and structures that are probably immature synapses. As in the adult, the synapses contain round, clear vesicles, have asymmetric specializations, and terminate on structures that appear to be dendrites. In both adult and tadpole, the rarity of serial synapses involving isthmotectal terminals suggests that the interactions between retinotectal and isthmotectal inputs are mediated by postsynaptic dendrites.     

Surveillance following orchidectomy for stage I testicular seminoma.

An analysis of the primary tumour histopathology was performed on 103 patients managed by orchidectomy and surveillance for stage I seminoma. Patients have been followed for 14-141 months (median 62 months) after orchidectomy. Seventeen patients relapsed, the probability of remaining relapse free at 5 years being 82% (95% confidence intervals, 74%-88%). No patients died of progressive germ cell tumours. The only significant histological factor predicting relapse was the presence of lymphatic and vascular invasion. Four of 42 patients with neither lymphatic or vascular invasion recurred, nine of 53 patients with either lymphatic or vascular invasion recurred and three of eight cases with both lymphatic and vascular invasion recurred (P = 0.05-trend). Though initial recurrence was usually of moderate volume and confined to para-aortic nodes, eight patients were treated with chemotherapy either because of the extent of their initial relapse (four cases), or because of subsequent relapse (four cases). In view of the difficulties of identifying patients at risk and of detecting early relapse, surveillance for stage I seminoma should remain a research protocol.     

An antibody with specificity for surfactant protein C precursors: identification of pro-SP-C in rat lung.

Surfactant protein C (SP-C) is a lung-specific, hydrophobic peptide found in organic extracts of pulmonary surfactant. Alveolar SP-C (3.5 kD) is produced from proteolytic cleavage of a larger precursor molecule (pro-SP-C; 21 kD). While SP-C is synthesized by type II cells, the pathways for processing and secretion have remained elusive due, in part, to the lack of monospecific antibodies against SP-C or its precursors. This report describes production and characterization of a new antibody directed against pro-SP-C epitopes. Polyclonal antisera (anti-CPRO-SP-C) was prepared using a synthetic peptide corresponding to a portion of rat SP-C cDNA sequence (Ile26-Ser72). This contained amino acids 3-35 of mature SP-C plus additional C-terminal residues (His59-Ser72). On Western blots, anti-CPRO-SP-C competitively reacted to CPRO-SP-C but not to mature SP-C. Immunoblots of in vitro synthesized pro-SP-C confirmed that the antisera also recognized native protein. Immunocytochemistry with anti-CPRO-SP-C demonstrated staining for pro-SP-C peptides in isolated type II cells as well as in alveolar epithelial cells of rat lung sections. Pro-SP-C preferentially co-localized to cells that stained positive for Maclura pomifera antigen. Anti-CPRO-SP-C staining was not observed in lung interstitium, pulmonary vasculature, or several control tissues (brain, heart, and liver were negative). Western blotting of subcellular fractions demonstrated pro-SP-C peptides in plasma membrane (20 kD) and microsomal (20 and 21 kD) fractions with a 16 kD peptide present in lamellar bodies. No pro-SP-C peptides were detected in purified surfactant. These results demonstrate the use of a synthetic peptide to generate specific antiserum against more hydrophilic domains of pro-SP-C sequences and confirm that SP-C propeptides are unique to the lung.     

Temporary inhibition of platelet function with iloprost (ZK36374) preserves canine platelets during extracorporeal membrane oxygenation

Contact between blood and artificial surfaces results in extensive quantitative and qualitative alterations in platelet function. We evaluated the efficacy of a brief infusion of iloprost (ZK36374), a stable analog of prostacyclin, in preventing these platelet changes during extracorporeal membrane oxygenation. Twelve nonsplenectomized male mongrel dogs (23 to 30 kg) were randomized to treatment (n = 6) and control (n = 6) groups. The treatment animals received an infusion of iloprost at a rate of 150 ng/kg/min with the infusion being terminated 30 minutes after the initiation of extracorporeal membrane oxygenation, despite the fact that all animals were maintained on extracorporeal membrane oxygenation for 3 hours. In the control group, platelet counts dropped to 54% +/- 8.9% (mean +/- standard error of the mean) of initial levels at 30 minutes of extracorporeal membrane oxygenation and gradually rose to 87.2% +/- 6.7% at 3 hours. In contrast, the platelet counts of the iloprost-treated dogs remained stable throughout extracorporeal membrane oxygenation at 98.3% +/- 4.2% of initial counts. Platelet reactivity toward adenosine diphosphate revealed a significant and permanent loss of platelet function in the control group (37.0% +/- 2.1% inhibition). In contrast, the iloprost group demonstrated significant inhibition of platelet reactivity (79.2% +/- 8.3%) during the iloprost infusion but a return to normal function (4.2% +/- 6.7% inhibition) after cessation of drug infusion which persisted throughout extracorporeal membrane oxygenation. Plasma levels of the platelet-specific protein thrombospondin rose progressively from 918 +/- 89 ng/ml to 1465 +/- 239 ng/ml (delta 548 +/- 179 ng/ml) at 30 minutes of extracorporeal membrane oxygenation, which indicates extensive release of platelet granule contents (p less than 0.05). In contrast, plasma thrombospondin levels in the iloprost group demonstrated no additional rise after cessation of the iloprost infusion. In conclusion, iloprost effectively preserves platelet number and function during extracorporeal circulation. The fact that its salutary effects outlast its presence in plasma suggests that prevention of initial platelet-synthetic surface interactions permits the appearance of reduced surface affinity for platelets and, thus, reduced synthetic surface thrombogenicity.     

Flexible Sigmoidoscopy Screening in an Industrial Setting

Little is known about the yield of colorectal cancer screening programs in an industrial setting. We therefore established a flexible sigmoidoscopy screening program at a chemical manufacturing plant and offered testing to all employees over the age of 40. After a Fleet enema preparation had been administered, a digital rectal examination and sigmoidoscopy were performed on each volunteer worker in the medical office of the plant. The plant had an average census of about 650 workers; 202 were screened during a 2-yr period. The mean (+/- SEM) age of participants was 52 +/- 0.4. Sixty-four employees had polyps (31.7%); data on follow-up colonoscopy were available in 69%. Colonoscopy revealed adenomatous polyps in 23 workers (53.5%), hyperplastic polyps in 10 (23%), and no evidence of neoplasia in 10 (23%). Seven workers did not arrange for follow-up colonoscopy and 12 individuals could not be contacted. No cancers were detected. In the 40- to 50-yr age group, polyps were detected in 19.5% of employees (25% adenomatous). Incidental findings were common, and included prostatic nodules, hemorrhoids, diverticulosis, and proctitis, among others. We conclude that screening sigmoidoscopy can be conveniently and economically performed at the workplace, with a high yield and good worker acceptance. The high yield suggests a possible association between polyp formation and work in a chemical plant. The finding of adenomatous polyps in the younger patients suggests that the threshold for flexible sigmoidoscopy at age 50 needs to be reassessed.