GAP-43 is expressed by nonmyelin-forming Schwann cells of the peripheral nervous system.

Recently it has been demonstrated that the growth-associated protein GAP-43 is not confined to neurons but is also expressed by certain central nervous system glial cells in tissue culture and in vivo. This study has extended these observations to the major class of glial cells in the peripheral nervous system, Schwann cells. Using immunohistochemical techniques, we show that GAP-43 immunoreactivity is present in Schwann cell precursors and in mature non-myelin-forming Schwann cells both in vitro and in vivo. This immunoreactivity is shown by Western blotting to be a membrane-associated protein that comigrates with purified central nervous system GAP-43. Furthermore, metabolic labeling experiments demonstrate definitively that Schwann cells in culture can synthesize GAP-43. Mature myelin-forming Schwann cells do not express GAP-43 but when Schwann cells are removed from axonal contact in vivo by nerve transection GAP-43 expression is upregulated in nearly all Schwann cells of the distal stump by 4 wk after denervation. In contrast, in cultured Schwann cells GAP-43 is not rapidly upregulated in cells that have been making myelin in vivo. Thus the regulation of GAP-43 appears to be complex and different from that of other proteins associated with nonmyelin-forming Schwann cells such as N-CAM, glial fibrillary acidic protein, A5E3, and nerve growth factor receptor, which are rapidly upregulated in myelin-forming cells after loss of axonal contact. These observations suggest that GAP-43 may play a more general role in the nervous system than previously supposed.     

Use of Ultrafiltration To Isolate Viruses from Seawater Which Are Pathogens of Marine Phytoplankton

Viruses may be major structuring elements of phytoplankton communities and hence important regulators of nutrient and energy fluxes in aquatic environments. In order to ascertain whether viruses are potentially important in dictating phytoplankton community structure, it is essential to determine the extent to which representative phytoplankton taxa are susceptible to viral infection. We used a spiral ultrafiltration cartridge (30,000-molecular-weight cutoff) to concentrate viruses from seawater at efficiencies approaching 100%. Natural virus communities were concentrated from stations in the Gulf of Mexico, a barrier island pass, and a hypersaline lagoon (Laguna Madre) and added to cultures of potential phytoplankton hosts. By following changes in in vivo fluorescence over time, it was possible to isolate several viruses that were pathogens to a variety of marine phytoplankton, including a prasinophyte (Micromonas pusilla), a pennate diatom (likely a Navicula sp.), a centric diatom (of unknown taxa), and a chroococcoid cyanobacterium (a Synechococcus sp.). As well, we observed changes in fluorescence in cultures of a cryptophyte (a Rhodomonas sp.) and a chlorophyte (Nannochloropsis oculata) which were consistent with the presence of viral pathogens. Although pathogens were isolated from all stations, all the pathogens were not isolated from every station. Filterability studies on the viruses infecting M. pusilla and the Navicula sp. showed that the viruses were consistently infective after filtration through polycarbonate and glass-fiber filters but were affected by most other filter types. Establishment of phytoplankton-pathogen systems will be important in elucidating the effect that viruses have on primary producers in aquatic systems.     

A cosmid clone for the 5HT1A receptor (HTR1A) reveals a TaqI RFLP that shows tight linkage to dna loci D5S6, D5S39, and D5S76.

A human neuroreceptor clone (G21), which was isolated by cross-hybridization with the human clone for the beta 2-adrenergic receptor, has recently been shown to encode the gene for the 5HT1A receptor (HTR1A) subtype. In situ hybridization to human metaphase chromosomes mapped the G21 sequence to chromosome 5 at bands 5q11.2-q13. The clone G21 recognizes a SacI RFLP with low heterozygosity (0.13). To increase the informativeness of the HTR1A locus we have isolated two new cosmid clones containing the receptor gene. No polymorphic microsatellites were present in the cosmids. However, one cosmid revealed a new TaqI RFLP that showed tight linkage to new highly polymorphic microsatellites for the loci D5S76, D5S39, and D5S6 in seven British and Icelandic reference pedigrees (maximum LOD of 13.2 with D5S76).     

The circular dichroism of tumor necrosis factor-α: Measurement into the vacuum UV and analysis for secondary structure

The circular dichroism (CD) spectrum of tumor necrosis factor-α has been measured into the vacuum UV to 168 nm. Analysis of the CD for secondary structure is in good agreement with X-ray diffraction results, but the analysis is somewhat unstable. Adding the CD of this protein together with its X-ray determined secondary structure to the basis set should improve subsequent analyses of CD spectra for other all-β proteins.     

Blood antioxidant status and erythrocyte lipid peroxidation following distance running

The relationship between prolonged exercise, oxidative stress, and the protective capacity of the antioxidant defense system has been determined. Venous blood samples were removed from seven trained athletes before and up to 120 h after completion of a half-marathon for measurements of blood antioxidants, antioxidant enzymes, and indices of lipid peroxidation. Plasma creatine kinase (CK) activity, an index of muscle damage, increased (P less than 0.05) to a maximum 24 h after the race but this was not accompanied by changes in conjugated dienes and thiobarbituric acid reactive substances (TBARS), which are indices of lipid peroxidation. An increase (P less than 0.05) in plasma cholesterol concentration (4%) immediately after the race was similar to the change in plasma volume (6%). However, transient increases (P less than 0.05) immediately postrace in the plasma concentrations of uric acid (24%), vitamin A (18%), and vitamin C (34%) were only partly accounted for by the fluid shifts. The immediate postrace increases in alpha- and gamma-tocopherol did not attain statistical significance. Erythrocyte antioxidant enzyme activities were unaffected by the exercise but the alpha- and gamma-tocopherol concentrations progressively increased (P less than 0.001 and P less than 0.05, respectively) up to 48 h postrace. Paradoxically, 24 h after the race erythrocyte susceptibility to in vitro peroxidation was markedly elevated (P less than 0.01). This enhanced susceptibility to peroxidation was maintained even at 120 h postrace and did not correspond to changes in the age of the red cell population. A decrease (P less than 0.001) in total erythrocyte glutathione immediately after the half-marathon was mainly due to a reduction in the reduced form (GSH). The results show that when trained athletes run a comparatively short distance sufficient to result in some degree of muscle damage but which is insufficient to cause elevations in plasma indices of lipid peroxidation, significant alterations in erythrocyte antioxidant status do occur.     

Bone marrow transplantation for leukemia and aplastic anemia: management of ABO incompatibility.

Between February 1971 and October 1980, 34 patients with leukemia or aplastic anemia received bone marrow transplants from HLA-identical siblings whose lymphocytes did not react in a mixed leukocyte culture. The donors of 10 patients were ABO-incompatible, and for five pairs the ABO incompatibility was major. Plasma exchanges followed by a red blood cell exchange transfusion reduced the anti-A titres to 1:4 or less in these patients. The ABO incompatibility had no adverse effect on the results of marrow transplantation. Twenty-two patients, including 16 of the 20 who received their transplant after Jan. 1, 1980, are still living. Seven of the 15 patients with acute leukemia have survived 89 to 466 days, and 4 of the 6 with chronic myelogenous leukemia (CML) have survived 117 to 545 days. Of the 13 patients with aplastic anemia, 11 are alive up to 8 years after transplantation. Marrow transplantation, when possible, is the treatment of choice for young patients with acute leukemia in remission and for patients with aplastic anemia. Marrow transplantation may also prove to be effective in patients with CML.     

Light Requirement for AgNO(3) Inhibition of Ethrel-Induced Leaf Abscission from Cuttings of Vigna radiata

To obtain information regarding the antiethylene properties and binding site of Ag⁺, studies were initiated to define conditions under which Ag⁺ does or does not inhibit ethylene action. AgNO₃, applied as a leaf spray, inhibited 2-chloroethylphosphonic acid (Ethrel)-induced leaf abscission from green cuttings of Vigna radiata in white light but lost considerable activity in the dark. In the absence of Ethrel, AgNO₃ stimulated abscission in the dark. When cuttings were dark-aged for 24 hours prior to treatment with AgNO₃ and aged for an additional 24 hours in the dark after treatment, good inhibition of subsequent Ethrel-induced abscission was restored by returning the cuttings to light. However, when dark aging was preceded by far-red irradiation, considerably less inhibition of Ethrel-induced abscission was restored in the light. AgNO₃ was completely inactive on cuttings aged in the dark and treated with Ethrel in the dark. Light is required for the antiethylene activity of AgNO₃ with regard to leaf abscission of Vigna.     

An improved method for the extraction of corticosterone from cell homogenates and subcellular fractions of the rat adrenal cortex

An improved technique is described for the extraction and analysis of corticosterone (11β,21-dihydroxy-4-pregnene-3,20-dione) from homogenates and subcellular fractions of the rat adrenal cortex. Factors influencing complete extraction of corticosterone were the nature of the organic solvent system and the concentration of the tissue being extracted. The continued activity of steroidogenic enzymes during subcellular fractionation was prevented by 0.1 mM 1-benzylimidazole. For optimum extraction, homogenates were diluted 1:12 (v/v) in 0.25 M sucrose, containing 0.1 M potassium hydroxide. Dilute homogenate was mixed with absolute ethanol (1:10, v/v) and extracted three times with diethyl ether (1:5, v/v). Following extraction, corticosterone in each sample was isolated by thin-layer chromatography (TLC), quantitated by radioimmunoassay (RIA), and corrected by measuring the recovery of added ³H corticosterone. With these procedures, 90–100% of corticosterone found in extracts of adrenal homogenates was recovered in extracts of subcellular fractions of the homogenates.