Stability of a model of human granulopoiesis using continuous maturation

A class of mathematical models involving a convection-reaction partial differential equation (PDE) is introduced with reference to recovering human granulopoiesis after high dose chemotherapy with stem cell support. The stability properties of the model are addressed by means of numerical investigations and analysis. A simplified model with proliferation rate and mobilization rate independent of maturity shows that the model is stable as the maturation rate grows without bounds, but may go through stable and non-stable regimens as the maturation rate varies. It is also shown that the system is stable when parameters are chosen to approximate a real physiological situation. System characteristics do not change profoundly by introduction of a maturity-dependent proliferation and mobilization rate, as is necessary to make the model operate more in accordance with hematological observations. However, by changing the system mitotic responsiveness with respect to changes in cytokine level, the system is still stable but may show persistent oscillations much resembling clinical observations of cyclic neutropenia. Furthermore, in these cases, changes in the model feedback signal caused by, for instance, an impaired effective cytokine elimination by cell receptors may enforce these oscillations markedly.     

Simultaneous mutations in CA and Vif of Maedi-Visna virus cause attenuated replication in macrophages and reduced infectivity in vivo

Maedi-visna virus (MVV) is a lentivirus of sheep sharing several key features with the primate lentiviruses. The virus causes slowly progressive diseases, mainly in the lungs and the central nervous system of sheep. Here, we investigate the molecular basis for the differential growth phenotypes of two MVV isolates. One of the isolates, KV1772, replicates well in a number of cell lines and is highly pathogenic in sheep. The second isolate, KS1, no longer grows on macrophages or causes disease. The two virus isolates differ by 129 nucleotide substitutions and two deletions of 3 and 15 nucleotides in the env gene. To determine the molecular nature of the lesions responsible for the restrictive growth phenotype, chimeric viruses were constructed and used to map the phenotype. An L120R mutation in the CA domain, together with a P205S mutation in Vif (but neither alone), could fully convert KV1772 to the restrictive growth phenotype. These results suggest a functional interaction between CA and Vif in MVV replication, a property that may relate to the innate antiretroviral defense mechanisms in sheep.     

Die Beutelmeise(Remiz pendulinus) am Oberrhein

Zusammenfassung Eine kritische Untersuchung aller Nachrichten über das Auftreten der Beutelmeise im Oberrheingebiet ergab, daß dieser Vogel hier nur in gewissen Zeitabständen auftritt (um 1820, 1880–1900, 1934/35, seit 1950). Diese Vorstöße wurden homologisiert mit Übervermehrung östlicher Populationen, die dann auf ihrem Zug das Oberrheingebiet berühren. Dabei kommt es gelegentlich zum Übersommern einzelner Tiere, wobei öfter — wohl unverpaarte — Männchen Nester zu bauen beginnen. Doch dürften auch vereinzelt erfolgreiche Bruten stattgefunden haben, wiewohl ein exakter Nachweis aus dem eigentlichen Oberrheingebiet noch aussteht.     

The infundibular organ of the lancelet (Branchiostoma lanceolatum,Acrania): an immunocytochemical study

Reissner's fibers are secretions produced by different ependymal areas of the chordate brain, viz., in adult vertebrates, by the dorsal subcommissural organ, and in all stages of cephalochordates (Branchiostoma lancelets), by the ventral infundibular organ. Fibers produced by these different organs are seemingly identical and the two fiber sources also share some immunocytochemical and lectin-binding properties. The secretions in these two glands are, however, not identical; the infundibular organ cells are strongly reactive with antibodies against vertebrate Reissner's fibers, but they do not react with antibodies raised against the source of the vertebrate fibers, viz., the subcommissural organ. The results support the possibility that, in adult vertebrates, the Reissner's fibers are composed of material not only from the subcommissural organ, but also from another, not yet identified, source that is identical or equivalent to the infundibular organ of the lancelet. There are indications that the infundibular organ is immunocytochemically closely akin to some secretory cells in the vertebrate embryonic brain and also to those that produce the juvenile vertebrate Reissner's fibers, viz., secretory cells in the flexural organ.     

Factors Enhancing the Host-Cell Penetration of Toxoplasma gondii

The penetration into HeLa cells of Toxoplasma gondii was studied with a cell culture technique. The influence on the rate of penetration and the number of penetrating Toxoplasma parasites was tested by use of preparations of disintegrated parasites mixed with test parasites. These preparations were found to contain factors enhancing the penetrating rate of the parasites. This effect was demonstrable by use of untreated parasites as well as parasites lacking active motility owing to a previous exposure to Formalin. The preparations of disintegrated parasites contained, in addition, components inhibitory to the penetration-enhancing factors. These inhibitory components were able to reduce the penetrating capacity of normal Toxoplasma parasites, suggesting that the studied enhancing factors may play a role in the natural process of penetration. The efficacy of various techniques for disintegration of Toxoplasma parasites was investigated for release of penetration-enhancing factors from Toxoplasma parasites. The methods used resemble those used for liberation of lysosomal enzymes. Reduced osmotic pressure was obviously not adequate for release of enhancing factors, whereas the freezing and thawing procedure, sonic treatment, and irradiation produced high yields. It was difficult to evaluate the effect of incubation at acid pH on release of enhancing activity, because the penetration-promoting factors seemed unstable on both the acid and the alkaline sides of pH 7.6.     

Sample displacement chromatography of Atlantic Salmon (Salmo salar) thrombin

A modified method of sample displacement chromatography (SDC) was used to purify active salmon thrombin on a heparin-coupled matrix to near homogeneity in milligram amounts from 117 ml plasma. This was achieved by combining a low-pressure multi-column affinity chromatography system with non-homogenous sample application in the order of increasing affinity to Heparin Sepharose. The results suggest that this modified method could be useful in protein purification. Some characteristics of salmon thrombin are presented.     

Notes on inland water molluscs from Egypt (Mollusca: Gastropoda,Bivalvia)

Abstract

A report on two new collections of fresh- and brackish water molluscs in Egypt is filling gaps in the generally known distribution pattern. The recent status of the mollusc fauna of Birket Qarun (Fayum), changed by introduction of marine species into the brackish water lake, is documented.     

Nitric oxide (NO)--production and regulation of insulin secretion in islets of freely fed and fasted mice

Production of nitric oxide through the action of nitric oxide synthase (NOS) has been detected in the islets of Langerhans. The inducible isoform of NOS (iNOS) is induced by cytokines and might contribute to the development of type-1 diabetes, while the constitutive isoform (cNOS) is thought to be implicated in the physiological regulation of insulin secretion. In the present study we have detected and quantified islet cNOS- and iNOS-derived NO production concomitant with measuring its influence on insulin secretion in the presence of different secretagogues: glucose, L-arginine, L-leucine and α-ketoisocaproic acid (KIC) both during fasting and freely fed conditions. In intact islets from freely fed mice both cNOS- and iNOS-activity was greatly increased by glucose (20 mmol/l). Fasting induced islet iNOS activity at both physiological (7 mmol/l) and high (20 mmol/l) glucose concentrations. NOS blockade increased insulin secretion both during freely fed conditions and after fasting. L-arginine stimulated islet cNOS activity and did not affect islet iNOS activity. l-leucine or KIC, known to enter the TCA cycle without affecting glycolysis, did not affect either islet cNOS- or iNOS activity. Accordingly, insulin secretion stimulated by L-leucine or KIC was unaffected by addition of L-NAME both during feeding and fasting. We conclude that both high glucose concentrations and fasting increase islet total NO production (mostly iNOS derived) which inhibit insulin secretion. The insulin secretagogues L-leucine and KIC, which do not affect glycolysis, do not interfere with the islet NO-NOS system.