Species-specific signals for the splicing of a short Drosophila intron in vitro

The effects of branchpoint sequence, the pyrimidine stretch, and intron size on the splicing efficiency of the Drosophila white gene second intron were examined in nuclear extracts from Drosophila and human cells. This 74-nucleotide intron is typical of many Drosophila introns in that it lacks a significant pyrimidine stretch and is below the minimum size required for splicing in human nuclear extracts. Alteration of sequences of adjacent to the 3' splice site to create a pyrimidine stretch was necessary for splicing in human, but not Drosophila, extracts. Increasing the size of this intron with insertions between the 5' splice site and the branchpoint greatly reduced the efficiency of splicing of introns longer than 79 nucleotides in Drosophila extracts but had an opposite effect in human extracts, in which introns longer than 78 nucleotides were spliced with much greater efficiency. The white-apricot copia insertion is immediately adjacent to the branchpoint normally used in the splicing of this intron, and a copia long terminal repeat insertion prevents splicing in Drosophila, but not human, extracts. However, a consensus branchpoint does not restore the splicing of introns containing the copia long terminal repeat, and alteration of the wild-type branchpoint sequence alone does not eliminate splicing. These results demonstrate species specificity of splicing signals, particularly pyrimidine stretch and size requirements, and raise the possibility that variant mechanisms not found in mammals may operate in the splicing of small introns in Drosophila and possibly other species.

Regenerative neurite growth modulation associated with astrocyte proteoglycans

Adherent GFAP-positive cells of neocortical origin in vitro produce and release members of three families of sulphated proteoglycans and a sulphated protein that copurifies with heparan sulphate proteoglycan (HSPG). Conditioned medium (CM) and the proteoglycans contained in the CM have neurite growth-promoting activity when immobilized on defined substrates of growth but not when in the nonimmobilized compartment. On a poly-D-lysine substrate, the rank ordering of specific neurite growth activity based on protein concentration was 330 kDa HSPG >> 100 kDa HSPG/chondroitin sulphate (CS) PG mixture or hybrid > 330 kDa CSPG > 50 kDa CSPG/dermatan sulphate (DS) PG mixture or hybrid and the 31 kDa sulphoprotein. Astrocyte CM lost its growth facilitatory activity when prepared and released by astrocytes in the presence of soluble mediators of inflammation. Loss of activity could not be explained by qualitative or quantitative alterations of released proteoglycans but appeared to be associated with the presence of an inhibitor. The sulphoprotein that copurified with HSPG was a potent inhibitor of HSPG-mediated neurite growth.

[Facilitatory effect of Pinellia ternata lectin on quantal release of acetylcholine from nerve terminals]

Pinellia ternata lectin (PTL) extracted from the rhizome of Pinellia ternata Briet by porcine thyroglobulin-Sepharose 4B column exhibits hemagglutination activity and carbohydrate binding specificity for mannan. Here we reported the effects of PTL on the resting membrane potential of muscle fiber and on the release of acetylcholine (ACh) from the motor nerve terminals in the phrenic nerve diaphragm preparations of mice. The results showed that PTL increased the frequency of miniature end-plate potential (MEPP). In 30 min after the treatment of the preparation with lectin 100 micrograms.ml-1, the frequency of MEPP reached 20 times higher than that of the control. Addition of mannan 1 mg.ml-1 restored the raised discharge of MEPP to its control level immediately. Similar to the effect of PTL on MEPP frequency, the amplitude and mean quantal content of end-plate potential also increased after PTL. At 100 micrograms.ml-1, the lectin depolarized the muscle membrane slightly, while at 10 micrograms.ml-1 no effect on the membrane potential was found. These results were interpreted as the intracellular Ca2+ elevation due to a permeability increase of the nerve terminal to ions after PTL.

[Effects of mixture of Astragalus membranaceus, Fructus Ligustri lucidi and Eclipta prostrata on immune function in mice]

A Chinese medicine mixture containing Astragalus membranaceus, Fructus Ligustri Lucidi and Eclipta prostrata(AFE), was fed to mice 9g/kg, 20g/kg, respectively for seven days. Observe the effects of AFE on the immune function in mice. The experiment showed that the two dosages of AFE could obviously raise the conversion percentage of lymphocytes (P < 0.01) and serum IgG level (41%-47%) of the mice. The weights of the thymus and spleensed increased in the two groups compared with those in the normal control. The larger dosage of AFE could also raise activity of Adenosine Deaminase (ADA) obviously (P < 0.01). AFE turned out a resistance to the immunosuppressive effect caused by cyclophosphamide.

[Cation channels formed in lipid bilayer by Pinellia ternata lectin]

Pinellia ternata lectin (PTL), a protein exhibiting hemagglutination activity and carbohydrate binding specificity to mannan was purified from rhizome of Pinellia ternata. In this work the actions of PTL on artificial lipid bilayer were investigated by means of the two-compartment system of Mueller and Rudin. The lipid bilayer with resistance more than 10G omega was formed by a solution of lecithin and cholesterol (20 mg/ml and 5 mg/ml respectively) in N-decane. The electrical properties of the lipid bilayer were investigated in voltage clamp mode. Several minutes after the addition of PTL (2 micrograms/ml) in one compartment the channel-like noise as well as a decrease of the resistance of the bilayer were observed. These actions were inhibited by mannan significantly. The resistance increase of the bilayer with PTL-channels could be observed from 2G omega to control level (greater than or equal to 10 G omega) immediately after addition of 40 micrograms/ml mannan. The discrete conduction steps were recorded at low concentration of PTL and at low holding potential. The predominant unit conductance was 35pS in symmetric KCl solution of 100 mmol/L. The selectivity of PTL-channel was estimated from Goldman-Hodgkin-Katz equation by measurement of the reversal potential in an asymmetrical salt solution. The results showed that PTL-channels were cation selective.

Altered processing of integrin receptors during keratinocyte activation

We used monoclonal antibodies against specific integrin subunits to examine the role of integrin receptors in keratinocyte activation. We found that before activation, beta 1 subunits in keratinocytes showed a diffuse distribution, whereas after activation, keratinocytes organized beta 1 receptors into marginal adhesion plaques. In immunoprecipitation experiments with antibodies against beta 1 integrin subunits, we found mostly immature subunits synthesized in keratinocytes freshly harvested from skin. Moreover, integrin receptor complexes immunoprecipitated from these cells by monoclonal antibodies against alpha 2, alpha 3, or alpha 5 subunits contained only immature beta 1 subunits. With keratinocytes cultured 4-7 days, anti-beta 1 antibodies immunoprecipitated mostly mature beta 1 subunits, and integrin complexes immunoprecipitated from cultured cells by anti-alpha subunit antibodies contained mostly mature beta 1 subunits. Antibodies directed against beta 1 subunits also inhibited keratinocyte migration. Based on these results, we suggest that up-regulation of migration by activated keratinocytes depends on changes in processing of pre-beta 1 subunits to mature beta 1 subunits. We also studied the distribution of integrin subunits in skin and on keratinocytes migrating out of skin explants. Whereas beta 1, alpha 2, and alpha 3 subunits were detected in keratinocytes in skin and migrating out of explants, alpha 5 subunits were observed only in migrating cells.

Analyses of Phaseolus vulgaris L. and P. coccineus Lam. hybrids by RFLP: preferential transmission of P. vulgaris alleles

Restriction fragment length polymorphism (RFLP) was determined among P. vulgaris genotypes and Phaseolus species using 19 probes. The incidence of polymorphism was high (70-86%) between species, but relatively low (22-26%) between genotypes of P. vulgaris. Suitable probes were identified for the analysis of P. vulgaris and P. coccineus hybrids. The segregation pattern in F2 populations was Mendelian for two probes (LHB and VEE20) and non-Mendelian for GS-g, CHS, and CHI. Statistical analyses indicated gametic selection with preferential transmission of the P. vulgaris alleles, which may account for the selective recovery of P. vulgaris progeny types observed earlier. The available hybrids of P. vulgaris and P. coccineus and the high degree of interspecific RFLP will facilitate the construction of a linkage map for Phaseolus.

[Histopathological studies on glottic cancer by serial sections]

In 31 glottic cancer specimens from partial laryngectomy, the histopathological findings were compared with vocal cord motility and 5-year survival rate. Among the 31 cases, 7 had ventricular involvements, in which 3 were transglottic tumors; 2 had had their framework destroyed. Eight cases had anterior commissure involvement. Only one had the tendon affected. Of 20 cases with mobile cords, the lesions were entirely superficial to the conus elasticus. Only a few specimens showed minimal invasions of the arytenoid region. Of 8 cases with limited vocal cord motility, invasion of the thyroarytenoid muscle was quite apparent, 4 specimens had the arytenoid areas surrounded by nests of tumor cells, and one case had local recurrence 12 months after operation. There were 3 cases with vocal cord fixation, 2 with subglottic extensions showed cricoid cartilage involvement and had had recurrences 10 and 12 months after operation. Another one with transglottic lesion was controlled by middle portion subtotal laryngectomy. Nine cases had subglottic involvement. One with transglottic lesion had recurrence, the other with arytenoid invasion had local recurrence. In two more recurrent cases, tumors cells spreaded submucosally toward the infraglottic area.

Activation of human keratinocyte migration on type I collagen and fibronectin

The purpose of our studies was to learn more about the regulation of keratinocyte migration. Human keratinocytes freshly harvested from skin were relatively immotile cells, whereas keratinocytes harvested from cell culture migrated on type I collagen or fibronectin as measured in a phagokinesis assay. Development of migratory competence by keratinocytes varied depending on the culture substratum. Cells cultured on plastic were activated more quickly and to a greater extent than cells cultured on dermis. The effect of the culture substratum on migratory competence was reversible. That is, cells cultured on plastic showed reduced activity after subculture on dermis. Cells cultured on dermis showed increased activity after subculture on plastic. Freshly isolated as well as cultured keratinocytes contained beta 1 integrin subunits, but only cultured cells were able to organize the subunits into focal adhesions. These adhesion sites also contained vinculin. In epidermal explants, beta 1 integrin subunits were mostly in basal cells, often more prominent between lateral cell borders than at the epidermal-dermal interface. In keratinocytes that migrated out of skin explants, there appeared to be an increase in the intensity of beta 1 integrin subunit immunostaining, possibly because of the change in shape of migrating cells. Also, beta 1 integrin subunits were found around and beneath migrating keratinocytes. These results show that changes in the distribution of beta 1 integrin subunits accompany development of migratory competence.

Dietary marine lipids suppress murine autoimmune disease

Dietary marine lipids reduce both mortality and the severity of glomerulonephritis in inbred murine strains which develop spontaneous autoimmune disease. The protective effects of marine lipids appear to be accounted for by the major n-3 fatty acids in these preparations, 20:5 and 22:6. The n-3 fatty acids in dietary fish oil are extensively incorporated into several lipid classes in the spleen of autoimmune mice, including phosphatidylinositol, phosphatidylethanolamine, plasmalogens and saturated ether-linked phospholipids as well as diacylphosphoglycerides. The effects of dietary marine lipids on autoimmune disease in experimental models are highly specific. Careful controlled trials will be required to establish the role of dietary marine lipids in the therapy of human autoimmune disease.

Basement membrane and human epidermal differentiation in vitro

To test the role of basement membrane in differentiation of human epidermis reconstituted on human dermis, we prepared dermis with and without basement membrane and cultured epidermal cells on these two dermal substrata. The absence of basement membrane components was confirmed by immunofluorescence staining for laminin and type IV collagen and by electron microscopy. A high degree of differentiation of reconstituted epidermis did not require basement membrane as shown by the development of basal, spinous, and granular cell layers, and synthesis of 58 and 65-67 kDa keratins when epidermis was attached directly to dermis. On the other hand, we found that the basement membrane regulated the adhesive interaction between the epidermis and dermis. On dermis with basement membrane, attached epidermal cells formed hemidesmosomes and mechanically stable bonding. In the absence of basement membrane, the epidermal cells did not form hemidesmosomes, and bonding between the epidermis and dermis was unstable. Moreover, dermis from which the basement membrane was removed was reorganized by the epidermal cell layer.

Helicase, DNA-binding, and immunological properties of replication-defective simian virus 40 mutant T antigens

Simian virus 40 T antigen (TAg) exhibits nonspecific and origin-specific DNA binding (ori binding) and ATPase and helicase activities, all of which are related to its roles in viral DNA replication. We have characterized some of the properties of four replication-defective but transformation-competent mutant TAgs, C6-2, T22, C11, and C8A. C6-2 and T22 TAgs were each previously determined to lack ori-binding properties, while C11 TAg was reported to lack ATPase activity. The C8A TAg did not exhibit defects in either ori-binding or ATPase functions. We have analyzed additional aspects of these mutant TAgs pertaining to their helicase, DNA-binding, and immunological properties. With the exception of the C11 TAg, all the other TAgs exhibited helicase activity. The lack of helicase activity by C11 TAg was consistent with its previously shown inability to hydrolyze ATP or to replicate viral DNA. These results therefore show that ori-binding and helicase activities are separate functions of TAg. Wild-type and mutant TAgs bound with similar efficiency to either native or denatured calf thymus DNA-cellulose, indicating no marked differences in their nonspecific DNA-binding properties. We also tested the binding of wild-type and mutant TAgs to a monoclonal antibody, PAb 100, that was previously shown to recognize an extremely small class of TAg that may represent a unique conformational form of the protein. Interestingly, while less than 10% of the wild-type, C6-2, C11, and T22 mutant TAgs were recognized by PAb 100, more than 60% of the C8A mutant TAg was bound by this antibody. Therefore, although no defect in biochemical function was observed with the C8A TAg, its deficiency in viral DNA replication may be related to an unusual conformation, as detected by its dramatically increased recognition by PAb 100. These results show that the helicase activity of TAg is not required for its transformation function.

Lymphocyte phenotypes at tumor margins in patients with head and neck cancer

Lymphocyte phenotypes were identified by monoclonal antibodies and avidin-biotin peroxidase reagents and enumerated in tumor tissue removed from 26 patients with head and neck cancer. T lymphocytes (T11) were the predominate phenotype at the tumor margin, with twice as many helper/inducer (T4) as suppressor/cytotoxic (T8) lymphocytes. Patients with Stage II and III carcinoma of the glottis, tongue, and hypopharynx had significantly increased numbers of all T lymphocyte phenotypes when compared to patients with Stage IV disease, thus achieving statistical significance for the T11 and T8 phenotypes. All patients were followed for 2.5 years; those patients who remained free of malignant disease had an increased number of all T lymphocyte phenotypes compared to patients with recurrent malignancy, but this did not achieve statistical significance. Thus, increased numbers of T11 positive lymphocytes of both the T4 and T8 subsets in the tissue at the margins of head and neck tumors were associated with a more favorable prognosis. These results support the concept of an immunologic reaction at the tumor margin, which may be limiting the growth and spread of tumor.