Receptor mediated targeting of liposomes

The targeting of liposomes to cells and the delivery of the liposomal contents into the cells have been investigated using either α-melanocyte stimulating hormone or Ricin-B-chain as ligands for promoting the binding of liposomes to cells. α-melanocyte stimulating hormone has been conjugated to liposomes and to Ricin-A-chain via the Lys₁₁ residue without significant loss of biological activity. The resulting conjugates were found to bind to Bl6 melanoma cells which express receptors for the hormone. Hormone targeted ricin was shown to be toxic to the cells, indicating receptor mediated internalisation of the conjugate. The hormone targeted liposomes however were unable to mediate the delivery of cytotoxic levels of methotrexate. Ricin-B-chain, a lectin which mediates membrane translocation of the toxic ricin-A-chain, was examined for its applicability for targeting of liposomes to cells. This lectin was shown to promote the binding of liposomes to cells and to mediate the delivery of cytotoxic concentrations of methotrexate. Further evidence of functional ricin-B-chain mediated intracellular delivery of the liposomal contents was shown by liposome mediated transformation of cells, and delivery of nuclease into the cell resultin in digestion of genomic DNA. The study demonstrates that α-melanocyte stimulating hormone is unsuitable as a ligand by which to achieve delivery of large quantities of material into cells, although cell-specific targeting can be achieved. Ricin-B-chain is however ideally suited for this task, though is less cell-specific. This finding may be of use in studies in which investigators wish to achieve intracellular delivery of compounds

A COMPARATIVE MAPPING OF ENZYMES INVOLVED IN HEXOSEMONOPHOSPHATE SHUNT AND CITRIC ACID CYCLE IN THE BRAIN *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66082/1/j.1471-4159.1963.tb05042.x.pd

An enzyme histochemical study of torpedoes and dendritic swellings in the cerebellum

In 8 cases, the following enzymes were studied in the dendritic swellings and torpedoes of Purkinje cells of cerebellum: succinic dehydrogenase, cytochrome oxidase, lactic dehydrogenase, NAD-diaphorase, alkaline phosphatase, acid phosphatase, acetyl cholinesterase and nonspecific cholinesterase. Activity of the oxidative enzymes was always extremely high in the dendritic swellings, but varied greatly among cases in the torpedoes; 4 cases showed very weak activity of oxidative enzymes in torpedoes, while 4 other cases showed an intense reaction. Dendritic swellings and torpedoes exhibited no alkaline phosphatase, acetyl cholinesterase, or nonspecific cholinesterase activity. In Dendritenanschwellungen und Torpedos der Purkinje-Zellen des Kleinhirns von 8 Fällen wurden die folgenden Enzyme untersucht: Bernsteinsäure-Dehydrogenase, Cytochrom-Oxidase, Milchsäure-Dehydrogenase, NAD-Diaphorase, alkalische Phosphatase, saure Phosphatase, Acetylcholinesterase und unspezifische Cholinesterase. Die Aktivität der oxidativen Enzyme war in den Dendritenanschwellungen immer sehr hoch, in den Torpedos aber von Fall zu Fall sehr unterschiedlich: 4 Fälle zeigten nur sehr geringe Aktivität, die 4 anderen jedoch eine sehr intensive Reaktion. Die Dendritenanschwellungen und Torpedos zeigten keine Aktivität der alkalischen Phosphatase, Acetylcholinesterase oder unspezifischen Cholinesterase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47226/1/401_2004_Article_BF00687526.pd

The Reconstruction Problem in Microdosimetry

A generalised formulation of microdosimetry clarifies the linkages between the spatial distribution of energy deposits, their proximity function, and the specific energy. The role of the proximity function suggest that it may replace, for various purposes, the inchoate distribution. The Fourier transform of the proximity function is the product of the Fourier transform of the inchoate distribution with its conjugate. This operation causes the loss of phase information, and the reconstruction problem - the reconstruction of the inchoate distribution from its proximity function - can, therefore, not be resolved by a mere deconvolution. For any finite point pattern one can, however, show that its proximity function permits, in principle, the reconstruction. Numerical examples with 2-dimensional patterns of up to 30 points have consistently led to unique solutions, apart from reflections. While there is a finite algorithm, it is readily seen that the number of steps becomes excessive when the number of points in the pattern increases. The reconstruction problem can, thus, be solved in principle but not necessarily in practice. A more general approach must thus be based on numerical optimisation. The algorithm starts with an assumed initial point pattern and utilises a suitable measure for the difference between its proximity function and that of the original pattern. Minimising this difference can lead to the original or to a similar pattern. With simple algorithms one obtains convergence only for patterns of few points; but improved optimisation methods are likely to provide more general solutions

Thermal aspects of the smelting of iron ore in reconstructed South African Iron Age furnaces

SYNOPSIS A study was made of the smelting process in two experimental furnaces patterned on Iron Age furnaces excavated at Melville Koppies Nature Reserve, Johannesburg. In a number of smelting experiments, the influences of air supply, temperature, time of operation, fuel consumption, and other operational factors were investigated. Metallurgical and metallographic aspects of the furnace operation and smelting products are discussed, and the experiments are compared with similar research work conducted in Europe and Africa. SAMEVATTING Daar is 'n studie gemaak van die smeltproses in twee eksperimentele oonde wat gebou is volgens die patroon van oonde uit die Ystertydperk wat in die Natuurreservaat Melville Koppies, Johannesburg, uitgegrawe is. Die invloed van die lugtoevoer, temperatuur, bewerktyd, brandstofverbruik en ander bedryfsaspekte is in 'n aantal smelteksperimente ondersoek. Die metallurgiese en metallografiese aspekte van die oondbedryf en smeltprodukte word bespreek, en die eksperimente word vergelyk met deeglike navorsingswerk wat in Europa en Afrika gedoen is. Introduction The work described in this paper is a continuation of the archaeo-metallurgical investigations undertaken over the past ten years at the Archaeological Research Unit of the University of the Witwatersrandl-3. One of the previous studies on the correlation of slag characteristics and operational furnace temperatures had led to the conclusion that further work in this field, based on smelting experiments, would be desirable3. The present paper reports on such experiments, and on the results obtained by temperature measurements in furnaces and by the construction of temperature profiles. Since slag is the principal, and often the only, preserved material from ancient smelting sites, various methods were investigated by which information on the thermal characteristics of the smelting process could be obtained from samples of slag: chemical/physical analysis, phase-diagram studies, determination of liquidus temperatures, and metallographic examinations. In addition, the problem of preheating ofthe air injected into such furnaces was investigated

Axon swellings produced in vivo in isolated segments of nerves

Within 3–5 hrs after cutting rat and cat sciatic nerves into segments which had no connection with the cell body, club-shaped axon swellings were observed at both ends of the segments. The swollen portion of these axons showed increased histochemical reactions for DPN-diaphorase, lactic dehydrogenase, malic dehydrogenase, succinic dehydrogenase, and protein; the increase lasted for 24–48 hrs after the nerve was cut. The swollen axons were morphologically and histochemically similar to, but never as markedly changed, as those observed in the proximal stumps of severed nerves. The development of axon swellings was prevented by depolarization of the entire segment with KCl; however, if KCl was applied selectively to the stumps of the segment, it appeared to intensify rather than prevent the swelling. It was also noted that the extent of axon swelling was inversely proportional to the length of the segment. These observations suggested that the development and extent of axon swelling was related to the intensity of local injury currents in the tissue. Innerhalb von 3–5 Std nach Zerschneidung des Nervus ischiadicus von Ratten und Katzen in Segmente, die keine Verbindung mit dem Zellkörper besitzen, sind zylinderförmige Axonschwellungen an beiden Enden der Segmente zu beobachten. Der angeschwollene Teil dieser Axone zeigt verstärkte histochemische Reaktionen auf DPN-Diaphorase, Milchsäure-Dehydrogenase, Apfelsäure-Dehydrogenase, Bernsteinsäure-Dehydrogenase und Protein; dieser Anstieg hält 24–48 Std nach der Durchtrennung des Nervs an. Die Axonschwellungen sind sowohl morphologisch als auch histochemisch ähnlich — jedoch niemals in gleich starker Ausprägung — jenen, die in den proximalen Stümpfen von verletzten Nerven beobachtet werden.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47224/1/401_2004_Article_BF00684398.pd

Search for characteristic structural features of mammalian mitochondrial tRNAs.

A number of mitochondrial (mt) tRNAs have strong structural deviations from the classical tRNA cloverleaf secondary structure and from the conventional L-shaped tertiary structure. As a consequence, there is a general trend to consider all mitochondrial tRNAs as "bizarre" tRNAs. Here, a large sequence comparison of the 22 tRNA genes within 31 fully sequenced mammalian mt genomes has been performed to define the structural characteristics of this specific group of tRNAs. Vertical alignments define the degree of conservation/variability of primary sequences and secondary structures and search for potential tertiary interactions within each of the 22 families. Further horizontal alignments ascertain that, with the exception of serine-specific tRNAs, mammalian mt tRNAs do fold into cloverleaf structures with mostly classical features. However, deviations exist and concern large variations in size of the D- and T-loops. The predominant absence of the conserved nucleotides G18G19 and T54T55C56, respectively in these loops, suggests that classical tertiary interactions between both domains do not take place. Classification of the tRNA sequences according to their genomic origin (G-rich or G-poor DNA strand) highlight specific features such as richness/poorness in mismatches or G-T pairs in stems and extremely low G-content or C-content in the D- and T-loops. The resulting 22 "typical" mammalian mitochondrial sequences built up a phylogenetic basis for experimental structural and functional investigations. Moreover, they are expected to help in the evaluation of the possible impacts of those point mutations detected in human mitochondrial tRNA genes and correlated with pathologies.journal articleresearch support, non-u.s. gov't2000 Octimporte

Serum peptide reactivities may distinguish neuromyelitis optica subgroups and multiple sclerosis

Objective: To assess in an observational study whether serum peptide antibody reactivities may distinguish aquaporin-4 (AQP4) antibody (Ab)–positive and -negative neuromyelitis optica spectrum disorders (NMOSD) and relapsing-remitting multiple sclerosis (RRMS). Methods: We screened 8,700 peptides that included human and viral antigens of potential relevance for inflammatory demyelinating diseases and random peptides with pooled sera from different patient groups and healthy controls to set up a customized microarray with 700 peptides. With this microarray, we tested sera from 66 patients with AQP4-Ab-positive (n = 16) and AQP4-Ab-negative (n = 19) NMOSD, RRMS (n = 11), and healthy controls (n = 20). Results: Differential peptide reactivities distinguished NMOSD subgroups from RRMS in 80% of patients. However, the 2 NMOSD subgroups were not well-discriminated, although those patients are clearly separated by their antibody reactivities against AQP4 in cell-based assays. Elevated reactivities to myelin and Epstein-Barr virus peptides were present in RRMS and to AQP4 and AQP1 peptides in AQP4-Ab-positive NMOSD. Conclusions: While AQP4-Ab-positive and -negative NMOSD subgroups are not well-discriminated by peptide antibody reactivities, our findings suggest that peptide antibody reactivities may have the potential to distinguish between both NMOSD subgroups and MS. Future studies should thus concentrate on evaluating peptide antibody reactivities for the differentiation of AQP4-Ab-negative NMOSD and MS