The uptake of liposome-entraped 125I-labelled poly(vinylpyrrolidone) by rat jejunum in vitro

The uptake of free and liposome-entrapped ¹²⁵I-labelled poly(vinylpyrrolidone) was measured in an intestinal sac preparation from adult rats. An an equal concentration of ¹²⁵I-labelled poly(vinylpyrrolidone), the rate of uptake of the liposome-entrapped material was four times that of the free macromolecule.     

Salmonella pathogenicity islands encoding type III secretion systems.

Salmonella enterica harbours two Salmonella pathogenicity islands (SPIs) each encoding a type III secretion system for virulence proteins. SPI1 is required for invasion, while systemic infections and intracellular accumulation of Salmonella are dependent on SPI2 function. This review will describe and compare the genetic organisation, evolution, regulation and molecular functions of SPI1 and SPI2.     

Protein Synthesis in Sonically Damaged Escherichia coli

By gentle sonic treatment, Escherichia coli cells were modified to permit penetration of actinomycin D, adenosine triphosphate, trypsin, ribonuclease, and polyuridylic acid. The behavior of these "soniplasts" as protein-synthesizing particles was investigated.     

Quantitative Beziehungen zwischen Temperaturreiz und Aktionspotentialen der Lorenzinischen Ampullen

Zusammenfassung Es wurden die Aktionspotentiale der afferenten Nervenfasern aus den Lorenzinischen Ampullen des Katzenhaies (Scylliam) untersucht, während an den Ampullen definierte und thermoelektrisch registrierte Temperaturreize gesetzt wurden. Versuche in situ und an isolierten Präparationen ergaben keinen Unterschied. Die Entladung der Ampullen erwies sich als unempfindlich gegen mechanische Reize, dagegen äußerst empfindlich gegen thermische Einwirkung. Temperaturregistrierungen in den Ampullen zeigten, daß bei thermischen Reizen an der unverletzten Haut starke Temperaturänderungen il den Ampullen ablaufen.Bei konstanter Temperatur zeigt die Einzelfaser eine Dauerentladung, deren Frequenz zwischen 15 und 23° ein Maximum bis zu 65 Impulsen · sec^–1 hat und nach den wärmeren und kälteren Temperaturen stetig bis zum Nullwert abfällt; die äußersten Grenzen sind 2 und 34°. Das Frequenzmaximum des Gesamtnerven liegt bei etwa 20°. Die höchste statische Unterschiedsempfindlichkeit der Einzelfaser erreicht im Bereich des positiven Temperaturkoeffizienten +7 Imp · s^–1 · grad^–1, im Bereich des negativen — 20 Imp · s^–1 · grad^–1. Kältesprünge führen im gesamten Aktionsbereich der Einzelfaser zu einer vorübergehenden Frequenzerhöhung bis 180 sec^–1 mit anschließender Adaptation auf einen niedrigeren Dauerwert; die überschießende Frequenzerhöhung hängt dabei neben der Temperatur vor allem auch von deren Änderungsgesehwindigkeit d/dt ab. Die dynamische Unterschiedsempfindlichkeit erreicht dabei bis—90 Imp·s^–1 · grad^–1, wobei der Receptor auch außerhalb des statischen Aktionsbereiches noch dynamisch erregbar ist. — Bei Wärmesprüngen verhält sich die Entladung genau spiegelbildlich zur Abkühlung; nach vorübergehender partieller oder völliger Hemmung der Entladung stellt sie sich wieder auf einen Dauerwert ein.Isolierte Einzelampullen zeigen dieselben Erregungsgesetze, nur gehen hier die Spikes bei Abkühlung in regelmäßige Wellen über, die schwebungsartig moduliert sind und vermutlich durch Synchronisation von Fasern innerhalb der Ampulle zustande kommen.Das Verhalten der Lorenzinischen Ampullen entspricht qualitativ in allen Punkten dem der Kältereceptoren der Warmblüter; quantitativ sind die Ampullen noch etwas empfindlicher.Die Versuche wurden mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt. Den Kollegen an der Zoologischen Station Neapel, insbesondere Herrn Prof. Dr. Reinhard Dohrn, möchte ich an dieser Stelle meinen aufrichtigen Dank für ihre freundliche Hilfe zum Ausdruck bringen.     

Rapid Degeneration of Cultured Human Brain Pericytes by Amyloid β Protein

Abstract: Amyloid β protein (Aβ) deposition in the cerebral arterial and capillary walls is one of the major characteristics of brains from patients with Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Vascular Aβ deposition is accompanied by degeneration of smooth muscle cells and pericytes. In this study we found that Aβ_1–40 carrying the "Dutch" mutation (HCHWA-D Aβ_1–40) as well as wild-type Aβ_1–42 induced degeneration of cultured human brain pericytes and human leptomeningeal smooth muscle cells, whereas wild-type Aβ_1–40 and HCHWA-D Aβ_1–42 were inactive. Cultured brain pericytes appeared to be much more vulnerable to Aβ-induced degeneration than leptomeningeal smooth muscle cells, because in brain pericyte cultures cell viability already decreased after 2 days of exposure to HCHWA-D Aβ_1–40, whereas in leptomeningeal smooth muscle cell cultures cell death was prominent only after 4–5 days. Moreover, leptomeningeal smooth muscle cell cultures were better able to recover than brain pericyte cultures after short-term treatment with HCHWA-D Aβ_1–40. Degeneration of either cell type was preceded by an increased production of cellular amyloid precursor protein. Both cell death and amyloid precursor protein production could be inhibited by the amyloid-binding dye Congo red, suggesting that fibril assembly of Aβ is crucial for initiating its destructive effects. These data imply an important role for Aβ in inducing perivascular cell pathology as observed in the cerebral vasculature of patients with Alzheimer's disease or HCHWA-D.     

Incorporation of 5-bromo-2′deoxyuridine (BUdR) in Dictyostelium discoideum DNA

The modality of incorporation of 5-bromo-2′deoxyuridine (BUdR) in the DNA of Dictyostelium discoideum was studied after one generation of growth of the amoebae in the presence of different concentrations of the drug. The analog was incorporated following the semiconservative pattern of DNA replication. BUdR incorporation in monosubstituted DNA has been measured both by CsCl isopycnic centrifugation or by base analysis chromatography; substitution of thymidine by its analog reaches a maximal value of 30% (60% in the substituted strand). Up to 20% substitution it is proportional to the drug concentration in the growth medium. In these conditions, thymidine substitution is higher in repetitive sequences of the DNA than in unique sequences; the percent of increase of thymidine substitution in repetitive fractions versus total DNA is inversely proportional to thymidine substitution in total DNA.     

Effects of prolonged omnilateral gravistimulation on the ultrastructure of statocytes and on the graviresponse of roots

Statocytes of vertically growing roots of Lepidium sativum L. exhibit a strict polarity: The nucleus is positioned near the proximal periclinal cell wall, amyloplasts are sedimented on a complex of rough endoplasmic reticulum (ER) consisting of parallel cisternae near the distal periclinal cell wall.When 24 h old, vertically grown roots are rotated for an additional 20 h on a horizontal clinostat, this polarity is destroyed. Furthermore, the prolonged omnilateral stimulation leads to a damage of the statocytes, which in some cases ends in the self-destruction of the sensitive cells. The different components of the ultrastructural respones of the statocytes are: Displacement of the nucleus; changes in amount and distribution of the ER; loss of amyloplast starch; confluence of lipid droplets to large aggregates: a considerable increase of the lytic compartment. In addition, even anticlinal cell walls may be lysed up to small stumps. As all these effects are clearly restricted to the statocytes, only these cells are able to respond to the continuously changing direction of the gravity vector, thus perceiving gravity as such.After being exposed horizontally, the graviresponse of rotated roots is delayed as compared to the controls. About 20% of the rotated roots do not respond (curve) at all, but grow perpendicular in relation to the gravity vector. Perception of gravity is inevitably correlated with the polarity and the integrity of the statocytes.Abbreviation ER endoplasmic reticulum A preliminary report was presented at the Fall Meeting of the German Society for Cell Biology in Salzburg, Austria, September 1979 (Hensel and Sievers 1979)This paper represents part of a dissertation (D 5) of W. H.     

Intraspecific host discrimination and larval competition inMicroplitis croceipes,Microplitis demolitor,Cotesia kazak (HYM.: Braconidae) andHyposoter didymator HYM: Ichneumonidae), parasitoids ofHeliothis virescens (LEP.: Noctuidae)

Intraspecific host discrimination and larval competition were studied forMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga), andHyposoter didymator (Thunberg), solitary endoparasitoids of the tobacco budworm,Heliothis virescens (F.). In ovipositional choice tests between unparasitized and parasitized hosts, the mean number of ovipositions for unparasitized hosts was significantly higher than the mean number of ovipositions for hosts parasitized once by a conspecific female forC. kazak andH. didymator, demonstrating that females of these two species discriminate against hosts recently (within a few seconds) parasitized by a conspecific female. No significant difference in oviposition occurred between these two kinds of hosts forM. croceipes andM. demolitor. Mean percent parasitization by a second conspecific female was determined at 24, 48, and 72 h delays in time between the first and second female attack, and with no delay. Except for the 0 h time delay forC. kazak andH. didymator, percent parasitization by a second conspecific female generally decreased as the delay in time between the first and second female attack increased. When the second parasitization immediately followed the first, one parasitoid larva always eliminated the other by physical combat. With a 24 or 48 h delay between the first and second parasitization, the younger larva was the victor over the older larva forM. croceipes, M. demolitor andC. kazak in at least 50% of the cases. Elimination of older larvae by younger larva was by physical attack. However, forH. didymator, the older instar was the victor, and elimination of younger larvae by older larvae was probably through physiological processes. Further, older larvae ofH. didymator apparently killed the eggs of the second female by physiological processes.