Male-male behavior and sexual dimorphism of the ear of a zaprochiline tettigoniid (Orthoptera: Tettigoniidae)

The external anatomy of the auditory system of an undescribed zaprochiline tettigoniid (Genus nov. 22 Sp. 1, Australian National Insect Collection, Canberra) shows sexual dimorphism: the male appears to have no auditory spiracle equivalent to that seen in the female. Nocturnally active males aggregate around female required nectar sources in a random manner with regard to each other. There is limited evidence, either from song interaction or from their behavior in the field, that males respond to each other by acoustic cues. Laboratory trials, testing male phonotaxis, showed that movement was random with respect to a target group of caged calling males. In the field, the only signs of agonistic behavior consisted of an increased calling rate when males were close together. Taken together, these data suggest that the male may not preceive sound in the same way as the female.     

Effect of background fluorophores on the NADH fluorescence probe signal

Summary Analysis of the errors caused by a drift in background fluorescence is performed for a fluorescence probe operated in a backscatter configuration. In some cases, significant errors can result if changes in background fluorophores during the course of fermentation are not accounted for. It is shown that the probe's sensitivity to background fluorophores must be considered to calibrate a fluorescence probe properly.     

Nitric oxide mediates iron release from ferritin

Nitric oxide (NO) synthesis by cytotoxic activated macrophages has been postulated to result in a progressive loss of iron from tumor target cells as well as inhibition of mitochondrial respiration and DNA synthesis. In the present study, the addition of an NO-generating agent, sodium nitroprusside, to the iron storage protein ferritin resulted in the release of iron from ferritin and the released iron-catalyzed lipid peroxidation. Hemoglobin, which binds NO, and superoxide anion, which reacts with NO, inhibited nitroprusside-dependent iron release from ferritin, thereby providing evidence that NO can mobilize iron from ferritin. These results suggest that NO generation in vivo could lead to the mobilization of iron from ferritin disrupting intracellular iron homeostasis and increasing the level of reactive oxygen species.     

Ion transport in ‘tight’ epithelial monolayers of MDCK cells

Summary Cultured monolayers of MDCK cells grown upon filter supports display many features ofin vivo epithelia. Previously reported values of transmonolayer resistance of 100 cm^–2 (Misfeldt, Hamamoto & Pitelka, 1976; Cereijido, Robbins, Dolan, Rotunno & Sabatini, 1978) indicate a leaky epithelium. This paper describes the properties of a strain of MDCK cells which displays entirely different electrophysiological properties. The results show that (i) the mean transmonolayer resistance is 4.16 k cm^–2, (ii) transmonolayer ion transport is of small magnitude since the mean spontaneous open circuit PD is only 2.17 mV basal surface positive and isotopic Na and Cl flux measurements fail to demonstrate a significant net flux, (iii) the action of ouabain, amiloride and ion substitutions are consistent with transmonolayer net Na movement being largely responsible for the spontaneous PD, and (iv) asymmetry in the localization of the Na-K ATPase is evident on the basis of³H-ouabain binding to cell monolayer.     

Placental transfer of glucose

The rates of glucose transfer from maternal blood to pregnant uterus and from placenta to fetus were measured in eight sheep at spontaneously occurring glucose concentrations (control state) and while the fetus, the mother, or both were receiving a constant infusion of glucose. In addition two fetuses received insulin infusions. In the control state the net glucose flux from placenta to fetus was only 27 +/- 2.6% (SEM) of the net flux from the uterine circulation to the pregnant uterus. An empirical equation describing the relationship between placental glucose transfer and arterial plasma glucose concentrations was derived from the data and compared with equations constructed on the basis of methematical models of placental function. This analysis indicates that: (1) placental glucose transfer is mediated by carriers with Km approximately equal to 70 mg/dl; (2) the rate of glucose transfer from mother to fetus is limited primarily by the transport characteristics and glucose consumption rate of the placenta; (3) under normal conditions of placental perfusion, glucose transfer is approximately 15% less than it would be if placental blood flows were infinitely large.     

Ultrastructural aspects of early immune damage to Taenia crassiceps metacestodes

Siebert, A. E. Jr., Good A. H. and Simmons J. E. 1978. Ultrastructural aspects of early immune damage to Taenia crassiceps metacestodes. International Journal for Parasitology8: 45–53. Changes in the ultrastructure of the tegument and subtegumental cells of intraperitoneally implanted Taenia crassiceps metacestodes were studied by transmission electron microscopy over a 4-week period. Death of metacestodes without involvement of host inflammatory cells is indicated initially by vacuolization of the larval tegument followed by loss of the tegument and subsequent death of the larvae. Changes in the tegument involve loss of the glycocalyx, reduction in the numbers of mitochondria and microtriches present, and loss of secretory capacity. Subtegumental cells show an accumulation of secretory vacuoles and marked disruption of nuclear morphology. Tegument damage is attributed to a complement-mediated lysis of the outer tegument membrane and death of the larvae probably results from loss of tegument function.