Experimental studies of rapid bioerosion of coral reefs in the Galápagos Islands

Experimental carbonate blocks of coral skeleton,Porites lobata (PL), and cathedral limestone (LS) were deployed for 14.8 months at shallow (5–6 m) and deep (11–13m) depths on a severely bioeroded coral reef, Champion Island, Galápagos Islands, Ecuador. Sea urchins (Eucidaris thouarsii) were significantly more abundant at shallow versus deep sites.Porites lobata blocks lost an average of 25.4 kg m^–2yr^–1 (23.71 m^–2yr^–1 or 60.5% decrease yr^–1). Losses did not vary significantly at depths tested. Internal bioeroders excavated an average of 2.6 kg m^–2 yr^–1 (2.41 m^–2 yr^–1 or 0.6% decrease yr^–1), while external bioeroders removed an average of 22.8 kg m^–2 yr^–1). (21.31 m^–2 yr^–1). or 59.9% decrease yr^–1). few encrusting organisms were observed on the PL blocks. Cathedral limestone blocks lost an average of 4.1 kg m^–2 yr^–1). (1.81 m^–2 yr^–1). or 4.6% decrease yr-'), also with no relation to depth. Internal bioeroders excavated an average of 0.6 kg m^–2 yr^–1). (0.31 m^–2 yr^–1). or 0.7% decrease yr^–1). and external bioeroders removed an average of 3.5 kg m^–2 yr^–1). (1.51 m^–2 yr^–1). or 3.9% decrease yr^–1). from the LS blocks. Most (57.6%) encrustation occurred on the bottom of LS blocks, and there was more accretion on block bottoms in deep (61.4 mg cm^–2 yr^–1). versus shallow (35.0 mg cm^–2 yr^–1) sites. External bioerosion reduced the average height of the reef framework by 0.2 cm yr^–1). for hard substrata (represented by LS) and 2.3 cm yr^–1). for soft substrata (represented by PL). The results of this study suggest that coral reef frameworks in the Galápagos Islands are in serious jeopardy. If rates of coral recruitment do not increase, and if rates of bioerosion do not decline, coral reefs in the Galápagos Islands could be eliminated entirely.     

Impregnated bednets and the dose-severity relationship in malaria

The finding that insecticide-impregnated bednets decrease symptomatic malaria and death more than infection has been interpreted as providing evidence that dose influences seventy o f disease in malaria. The complications o f this argument in areas where much o f the population has a background parasitaemia have already been considered. In this article, Judith Glynn, Jo Lines and David Bradley explore whether or not the results of impregnated bednet trials can help to determine the existence of a dose-severity relationship for malaria.     

Phosphorus-31 nuclear magnetic resonance studies of bioenergetics in wild-type and adenosinetriphosphatase(1-) Escherichia coli cells

By use of 31P NMR, the transmembrane pH gradient (delta pH) and the intracellular levels of phosphorylated metabolites were measured in aerobic suspensions of wild-type Escherichia coli cells in the presence and absence of the adenosinetriphosphatase (ATPase) inhibitor dicyclohexylcarbodiimide (DCCD); the same parameters were also determined in E. coli mutants deficient in ATPase activity under both anaerobic and aerobic conditions. A method is described by which dense suspensions of E. coli cells (approximately 3 X 10(11) cells/mL) were oxygenated so that steady-state O2 levels in the suspensions were far greater than the Km for O2 consumption. Under these conditions, in wild-type MRE600 cells, the intracellular concentrations of PI, NTP, and NDP were measured to be 3.0 +/- 1.5, 8 +/- 1, and 1.2 +/- 1 mM, respectively, while the intracellular pH was approximately 7.5 over the external pH range studied (6 to approximately 7.0). Upon treatment with DCCD, the intracellular NTP level was drastically reduced and intracellular Pi concentration increased in respiring wild-type cells; in the same cells, however, DCCD did not affect the intracellular pH and the delta pH. During respiration in the presence of lactate, ATPase- cells established a delta pH but failed to synthesize any detectable levels of NTP. Conversely, ATPase- cells accumulated high levels of NTP but did not generate a delta pH during glycolysis under anaerobic conditions. These results are in complete agreement with the generally accepted chemiosmotic hypothesis. 31P NMR data on intact ATPase- NR70 cells were in agreement with the previously proposed [Rosen, B. P., Brey, R., & Hasan, S. (1978) J. Bacteriol. 134, 1030] existence of a proton leak in this strain which is sealed by DCCD or by spontaneous mutation into strain NR71. However, the NMR data also indicated that other major differences exist between NR71 and NR70 cells.     

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.      

The Immunological Identification of Brain Proteins on Cellulose Nitrate in Human Demyelinating Disease

Abstract: An immunological technique has been employed to identify proteins, separated in polyacrylamide gels, which show changes in brain samples from cases of multiple sclerosis and subacute sclerosing panencephalitis. Sodium dodecylsulphate-treated proteins in particulate and soluble fractions were separated in polyacrylamide slab gels, transferred electrophoretically onto cellulose nitrate sheets, incubated with specific antisera and visualized by an immunoperoxidase method. Protein bands showing changes were identified using antisera raised against the myelin basic and Wolfgram proteins, the neurofilament triplet proteins, tubulin and glial fibrillary acidic protein. In addition to the loss of myelin proteins, decreases in the neurofilament proteins and in tubulin were seen in both multiple sclerosis and subacute sclerosing panencephalitis samples. The distribution of glial fibrillary acidic protein polypeptides in the particulate and soluble fractions of plaque samples appeared to vary according to the degree of fibrosis. Changes in the levels of the myelin-associated glycoprotein, the lower molecular weight component of the Wolfgram protein, albumin and immunoglobulin G, none of which were visualized by protein staining, were also seen. This immunological technique has allowed a closer examination of changes occurring in brain protein spectra in multiple sclerosis and subacute sclerosing panencephalitis.     

Defense by symbiotic crustacea of host corals elicited by chemical cues from predator

Summary Observations and experiments carried out on a coral reef off the Pacific coast of Panamá demonstrated that shrimp (Alpheus lottini) and crab (Trapezia spp.) symbionts that protect their host coral (Pocillopora elegans) can detect an approaching sea star predator (Acanthaster planci) by chemical cues. Simulated feeding attacks by Acanthaster in sealed transparent bags elicited only 0.5 defensive responses (snipping at spines and tube feet, jerking the sea star, and snapping) per 3 min; defensive behavior increased significantly to 4 and 5 responses, respectively, for Acanthaster in perforated bags and for Acanthaster in direct contact with coral. Neutralized (boiled) Acanthaster elicited only 3 defensive interactions per 3 min compared with 12 interactions for live Acanthaster. Simulated feeding attacks by Oreaster, a non-corallivorous sea star, elicited only 0.5 defensive responses per 3 min, whereas Oreaster introduced with Acanthaster water increased the level of defensive responses to 7. These results suggest that chemical, and to a lesser extent visual (physical presence and movements of sea star), cues stimulate the defensive behavior of the symbiotic crustaceans. The ability to detect a predator at a distance is probably advantageous because in responding only to an actual threat it minimizes the time the defending symbionts spend in an exposed position on the terminal branches of the host coral and because it alerts the crustaceans to sea stars feeding at night.     

Elementary steps of the (Na+ + K+)-ATPase mechanism, studied with formycin nucleotides.

1. Formycin triphosphate (FTP), a fluorescent analogue of ATP, is a substrate for (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3), with properties similar to those of ATP. 2. FTP and formycin diphosphate (FDP) bind to the enzyme with high affinity and, on binding, the nucleotide fluorescence is enhanced 3-4-fold. It is therefore possible, with a stopped-flow fluorimeter, to measure the rates of binding and release of FTP and FDP under conditions in which turnover does not occur. 3. When the enzyme-FTP complex is exposed to conditions permitting turnover (Mg2+, Na+ +/- K+), changes in fluorescence occur which can be explained by supposing that they reflect the interconversion of states with or without bound nucleotides. A rapid fall in fluorescence, that we attribute to the rapid release of FDP from newly phosphorylated enzyme, is followed by a steady state in which low fluorescence suggests that little nucleotide is bound. Eventually, exhaustion of FTP allows rebinding of FDP to the enzyme, which is signalled by a rise in fluorescence. 4. The estimated rate of FDP release from newly formed phosphoenzyme is unaffected by the presence of K+ (0-2 mM) or the concentration of FTP (1-20 micron). 5. Experiments with [gamma-32P]FTP show that about 1 mol of 32P is incorporated per mol of enzyme. The rate of phosphorylation of the enzyme by [gamma-32P]FTP has been measured with a rapid-mixing-and-quenching apparatus. 6. Kinetic data from the fluorescence and phosphorylation experiments show that the behaviour of the enzyme, at least at the low nucleotide concentrations employed, is consistent with the Albers-Post model, and is difficult to reconcile with models in which K+ acts at or before the step in which FDP is released during turnover.     

Use of the Concept of the "Corporation": A Choice Between Colloquialism or Distortion

The choice facing anthropologists wishing to use the concept of corporateness has been to use either a model unique to the law of property in Western societies or a looser definition which does not justify replacement of traditional terms. This paper suggests that alternative models may be more appropriate where it is necessary to depict arrangements involving group tenure .