Myhill's work in recursion theory

AbstractIn this paper we discuss the following contributions to recursion theory made by John Myhill: (1) two sets are recursively isomorphic iff they are one-one equivalent; (2) two sets are recursively isomorphic iff they are recursively equivalent and their complements are also recursively equivalent; (3) every two creative sets are recursively isomorphic; (4) the recursive analogue of the Cantor–Bernstein theorem; (5) the notion of a combinatorial function and its use in the theory of recursive equivalence types

A novel technology to target adenovirus vectors : application in cells involved in atherosclerosis

In this thesis a novel technology is described to target adenovirus vectors. Adenovirus vectors are powerful tools to modulate gene expression. The use of these vectors however, is hampered by the fact that many for gene therapy interesting cell types do not, or only at low levels express the CAR receptor, necessary for infection. We developed a linker protein consisting of the virus-binding moiety of CAR genetically fused to the chicken protein avidin. Biotinylated ligands for cell specific receptors are bound to the linker protein via the avidin-biotin interaction. This now targeting protein is used to redirect adenovirus vectors to previously refractory cell types. Using this technology endothelial cell lines as well as primary endothelial cells can by infected at low MOI__s using an biotinylated cyclic RGD peptide. Primary bone marrow derived macrophages and macrophage cell lines are easily infected using a biotinylated dA6dG10 oligo nucleotide ligand. In vivo experiments showed a marked reduction of adenovirus mediated transgene expression by the liver, the organ responsible for virus uptake when unmodified adenovirus vectors are administered, after addition of several different ligands to the virus via the linker protein.LEI Universiteit LeidenNetherlands Heart foundationErfelijke aandoeningen, vroegdiagnostiek en behandelin

Multiple sclerosis in a South African-born White man and woman

No Abstract

Fibrinogen E fragment selectively disrupts the vasculature and inhibits the growth of tumours in a syngeneic murine model

We recently demonstrated that a fragment of human fibrinogen, fibrinogen E fragment, inhibits the migration and differentiation of human endothelial cells in vitro. Here we show that it exerts similar effects on murine endothelial cells in vitro, and selectively disrupts tumour endothelium in vivo, causing widespread intravascular thrombosis and retarding the growth of CT26 tumours in a syngeneic murine model

Characterisation of fish leucocytes : an immunocytochemical and functional study in carp (Cyprinus carpio L.)

A panel of monoclonal antibodies (MAbs) against carp serum immunoglobulin (Ig), WCIs or carp thymocytes (T), WCTs were used for the characterisation of carp leucocytes. Unfortunately, all WCTs and some WCIs react with common carbohydrate determinants present on all leucocytes and Ig. Most WCIs react specific with protein determinants at the heavy chain of Ig. Consequently, B lymphocyte (sub) populations, plasma cells and Ig-binding cells could be studied. Ig molecules are found in clusters at the cell membrane of B cells and plasma cells, and in contrast to mammalian plasma cells, most carp plasma cells still have Ig at their surface membrane. Mainly the dull surface Ig-positive (sIg +) cells were stimulated by the mammalian B cell mitogen LPS and not by PHA (T cell mitogen) in vitro , whereas the sIg-negative (sIg -) cells were stimulated by PHA and not by LPS. The percentages of B cells and plasma cells showed an increase during ontogeny and reached a plateau at about 3 months and 8 months of age respectively. It is suggested that full development of the carp (humoral) immune system needs at least 8 months (at 21-22 °C). Three different subpopulations of B cells and plasma cells and at least two Ig isotypes can be distinguished based upon their reactivity with WCI 4 arid WCI 12. The distribution of the three B cell subpopulations appeared to be organ and age dependent which indicates functional differences between the Ig isotypes. Fc-like receptors were mainly demonstrated on gut macrophages while pronephros macrophages and neutrophilic granulocytes did not show Ig binding. Consequently, other forms of antigen opsonisation (e.g. complement) may play a role in phagocytosis by these non Ig-binding cells. Several procedures were tested for obtaining MAbs specific for Ig -lymphoid cells. It is concluded that the presence of immunodominant carbohydrate determinants is the major problem for obtaining specific MAbs. Tolerisation of mice against these determinants or the use of isolated membrane lysates from (sIg -) PBL appeared promising but till now only specific thrombocyte markers have been obtained. The use of more purified antigen is recommended in further attempts. The data presented in this thesis can be used for fundamental studies on cell interactions in the immune response, but also for more applied investigations on fish health control

Epenthesis and vowel intrusion in Central Dhofari Mehri

The paper discusses epenthesis and vowel intrusion in the Central Dhofari variety of Mehri, one of six endangered Modern South Arabian languages indigenous to southern Arabia. Mehri is spoken by members of the Mahrah tribe in southern Oman, eastern Yemen, parts of southern and eastern Saudi Arabia and in communities in parts of the Gulf and East Africa. The estimated number of Mehri speakers is between 100,000–180,000. Following Hall (2006), this study distinguishes between two types of inserted vowels: epenthetic vowels, which repair illicit syllable structures, and intrusive vowels, which transition between consonants. The paper examines how the properties of epenthetic and intrusive vowels as proposed by Hall relate to Mehri

Pre-aspirated sonorants in Shehret, a Modern South Arabian language

This paper examines pre-aspirated sonorants in the Central and Eastern varieties of Shehret, an endangered Modern South Arabian language (MSAL) spoken by c. 50,000 speakers in Dhofar, southern Oman. We assume pre-aspirated sonorants fall in the class of breathy sonorants, acknowledged to be typologically rare [1], [2], and phonotactically tightly restricted [3]. Shehret pre-aspirated sonorants are restricted to the offset of stressed word-final syllables in a closed set of words [4]; they contrast both with non-pre-aspirated sonorants and with strings of /h/ followed by a sonorant (/hS/ realised as [həS] with epenthesis), giving a /hS/ versus /hS/ phonological sequence contrast; pre-aspiration also characterises voiceless obstruents in the language. Western Shehret apparently lacks pre-aspirated sonorants [6]. While related Soqotri exhibits a post-aspirated palatal glide [7], pre-aspirated sonorants appear not to be attested elsewhere within the Semitic language family