Utility of high resolution capillary electrophoresis for monitoring peptide homo- and hetero-dimer formation.

The monomer and disulfide-linked homo-dimer of two different peptides, one with an amino-terminal cysteine, the other with a cysteine at the carboxy-terminal, are shown to be baseline resolved by capillary electrophoresis in less than 15 min. Time-course for homo-dimer formation with both peptides, either under mild (air) or stronger (hydrogen peroxide oxidizing conditions, was easily monitored. Confirmation that the second peak appearing under oxidizing conditions was indeed the homo-dimer was obtained with mass spectrometry. The possibility that stronger oxidizing conditions led to the production of the sulfonic acid derivative of the monomeric peptide, was ruled out through generation of the derivative by performic acid oxidation. As expected, the negative charge of the sulfonic acid moiety gives the peptide a slower electrophoretic mobility than both the monomer and the dimer. Moreover, as would be expected with a sulfonic acid derivative, oxidation to the dimeric form was not possible. This was consistent with the observation that the homo-dimer peak could be reduced to monomeric form in the presence of dithiothreitol. Co-oxidization of the amino- and carboxy-terminal peptides led to the expected production of both homo-dimers and the hetero-dimer, all of which were resolved.

Monoclonal antibodies specific for peptide epitopes of the epidermal growth factor receptor's extracellular domain.

The ErbB tyrosine kinase receptor family plays an important role in normal cellular growth and differentiation. In addition, ErbB receptor family members are commonly amplified and overexpressed in various human neoplasms and tumor-derived cell lines, where it is believed that increased signalling as a result of receptor overexpression may play an important role in oncogenesis. Consequently, ErbB receptor family members are being investigated rigorously as potential biomarkers of cancer and as therapeutic targets in malignant tissues. Numerous studies now demonstrate the existence of "soluble" ErbB (sErbB) analogs in normal and cancerous tissues. These sErbB proteins embody the extracellular domain (ECD) of the receptor only; they are generated by either proteolytic cleavage or from truncated, alternatively spliced mRNA transcripts. Recently, we have identified an alternate transcript of the human c-erbB1 (Epidermal Growth Factor Receptor) proto-oncogene from placenta that encodes a sErbB1 protein of 60-kDa. This protein, p60 sErbB1, is glycosylated and secreted when expressed in transfected tissue culture cells in vitro. Although "soluble" receptor analogs may play important physiological roles in intercellular communication, tissue morphogenesis, tissue regeneration and repair, and embryogenesis by inhibiting or stimulating specific mitogenic and pattern forming signals, their mechanism of action has not been thoroughly elucidated. To further characterize sErbB1 expression in human tissues and cell lines and to better understand their role in carcinogenesis and normal development, we have generated monoclonal antibodies (MAbs) toward specific peptide epitopes of ErbB1 extracellular subdomains III and IV. These antibody reagents are described here and should be useful experimental, preparative, analytical, diagnostic, and therapeutic reagents for the study of sErbB1 molecules in normal development and cancer.

Bilharzia control in Swaziland: the dilemma of development.

PIP: Bilharzia, or schistosomiasis, ranks 2nd to malaria as the major health hazard of the tropics. It is generally associated with hot, humid climates and rural poverty. There is as yet no means of vaccination or inoculation against bilharzia. In fact, some of the development activity in these areas, e.g., dam construction and irrigation projects, has actually helped the spread of the disease. Because it can thrive in a variety of ecological conditions, the control meansures must be site-specific. The UN has funded a pilot project in Swaziland, involving personnel from 3 of its international agencies, to aid in bilharzia control. A complementary program has been funded by USAID (Agency for International Development) for a 5-year period. Both try to avoid the pitfalls of earlier chemical, biological, and mechanical schemes. And both avoid high capital investment. The UN project is attempting to provide clean water to rural inhabitants. This project, in addition to its health and social aspects, also improves the life of women in the area by decreasing the water-carrying work. It has facilitated interbureaucratic cooperation. The US project focusses on safe water provision and sanitation education for the local communities.^ieng

SADCC: challenging the "South African connection.".

PIP: The Southern African Development Coordination Conference (SADCC) which unites 9 states with a combined population of 60 million, has as its objective the task of promoting economic development and realizing economic independence. In many respects the strain of neocolonialism that Southern Africa faces at this time is even more virulent than that facing West, Central, and East Africa. In the latter regions the surrender of political authority by colonial administrators frequently left the commercial, agricultural, and industrial interests of the European powers in continued control of the economies of the former colonies. The fate of economic development plans was determined by situations and decisions made in places distant from the African continent. In the case of Southern Africa, the withdrawal or expulsion of European colonialists has found whites in neighboring South Africa most eager to step into the economic breech. For most of the Southern African states this variant strain of the neocolonial virus creates a dual problem: the independent states acting separately have been no match for South Africa; and the acquiescence of independent African states in forging economic links with South Africa has impeded the liberation efforts of Africans in Namibia and the Republic of South Africa. Discussion focus turns to the challenges that confront SADCC; transport as the most significant factor accounting for the dependency of SADCC states upon South Africa; the role of minerals in dependency; other aspects of dependency; South Africa's proposed Constellation of States; the origins and objectives of SADCC; and dollars and donors. SADCC planning for economic liberation has been conducted against the background of a counterproposal advanced by South Africa's government, which put the Republic at the center of an expanded network of economic linkages within the entire southern African region. While being formally rejected, the Constellation of States scheme does have direct implications for 3 SADCC states. A marked characteristic of SADCC is the determination of the leaders to avoid having regional cooperation turn into a series of administrative institutions. SADCC needs to be viewed as a process, leading both to coordination of effort and stimulation of economic growth within the region. A manifestation of the SADCC process is the farming out of special projects to the member states. A 2nd manifestation of SADCC as a process has been the escalation in the number of bilateral and multilateral agreements among the SADCC countries since 1979.^ieng

Nine residues influence the binding of alpha-bungarotoxin in alpha-subunit region 185-200 of human muscle acetylcholine receptor.

Identification of residues in the skeletal muscle nicotinic acetylcholine receptor (AChR) that bind snake venom alpha-neurotoxin antagonists of acetylcholine [e.g., alpha-bungarotoxin (alpha-BTx)] provides structural information about the neurotransmitter binding region of the receptor. Using synthetic peptides of the human AChR alpha-subunit region 177-208, we previously localized a pharmacologically specific binding site for alpha-BTx in segment 185-199. To define in more detail the residues that influence the binding of alpha-BTx to this region, we prepared 16 peptide analogues of the alpha-subunit segment 185-200, with the amino acid L-alanine sequentially replacing each native amino acid. Circular dichroism spectroscopy did not reveal changes in the secondary structure of the peptides except for the analogue in which Pro194 was substituted with alanine. This implies that any change in alpha-BTx binding could be attributed to replacement of the native residue's side chain by alanine's methyl group, rather than to a change in the structure of the peptide. The influence of each substitution with alanine was determined by comparing the analogue to the parental sequence alpha 185-200 in solution-phase competition with native human AChR for binding of 125I-labeled alpha-BTx. The binding of alpha-BTx by analogue peptides with alanine substituted for Tyr190, Cys192, or Cys193 was greatly diminished. Binding of alpha-BTx to peptides containing alanine replacements at Val188, Thr189, Pro194, Asp195, or Tyr198 was also reduced significantly (p < 0.003). An unanticipated finding was that substitution of alanine for Ser191 significantly increased alpha-BTx binding (p < 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Omnibus Report: Europe, Middle East, Africa, East Asia and Latin America.

PIP: 5 papers deal respectively with economic development in Europe, the Middle East, Africa, East Asia, and Latin America. In Europe, basic problems include increasing political and military weakness; the high costs of social democracy; problems of the welfare state; the trend toward low or no-growth population rates; declining fertility combined with increasing longevity; increasing demand for social services and health care; industrial decline; continuing decline in economic indices; integration of the Left in European politics; and a pervasive trend toward neoconservatism. The paper on the Middle East focuses on Iran, Saudi Arabia, and the recent Egypt-Israel Treaty, in terms of assessment of the present situation followed by a prognosis for the future. The paper on Africa discusses 4 crises of development: 1) the crisis of national identity; 2) the crisis of poverty; 3) the crisis of colonialism and neocolonialism; and 4) the crisis of popular control over government. The paper on east Asia discusses the "economic miracles" and whether or not they are replicable elsewhere in the Pacific and Asia. Finally, the paper on Latin America focuses on the fact that despite expansion of the urban middle class through economic development and modernization, little economic improvement has resulted. The challenge of the 1980s will be to see whether Latin America can put its economies back on track while managing to channel more of the economic benefits to the "have-nots" and to allow more open, participatory systems.^ieng