A comprehensive examination of protein sequences for evidence of internal gene duplication

Summary We have implemented a routine procedure for screening protein sequences for evidence of intragenic duplications. We tested 163 protein sequences representing 116 superfamilies of unrelated proteins. Twenty superfamilies contain proteins with internal gene duplications. The intragenic duplications detected can be divided into two major types. (1) One or more duplications of all or part of a gene produce a protein with two or several detectable regions of sequence homology. Sequences from 18 superfamilies contained this type of duplication. (2) Repeated reduplication of a small DNA segment can produce a protein that is repetitive over most of its length. Three superfamilies contain such repetitive sequences. We also investigated the limits of detection of ancient duplications using sequences derived by random mutation of a model sequence consisting of ten 10-residue repeats. The original repetitive nature of the sequence was usually detected after 250 point mutations even though the ancestral segment could not be accurately reconstructed.     

Adsorption of non-membrane proteins on the surface of model phospholipid membranes

1. Two new methods are proposed for enhancement of the binding of hydrophilic proteins by liposomes. 2. An alkylating derivative of phosphatidic acid has been obtained by its reaction with N,N,N′-tris(2-chloroethyl)-N′- (p-formylphenyl)propylene-1,3-diamine. The alkylating activity of this derivative is very low due to the electron-acceptor effect of the formyl residue. Phosphatidylcholine liposomes which contain this alkylating derivative in the lipid bilayer may be obtained. The compound residing in the outer monolayer may be reduced by NaBH₄. Upon reduction, the formyl residue is transformed into a hydroxymethyl residue. Therefore, the alkylating group of the compound is activated, and proteins may be attached covalently to the outer monolayer by alkylation with such chemically reactive liposomes. 3. Reaction of alkylating liposomes with myoglobin results in covalent binding of this hydrophilic protein. Complement-mediated leakage of such myoglobin-carrying liposomes may be induced by antibodies against myoglobin. 4. Modification of hydrophilic proteins with dansyl chloride results, even at small extents of modification, in a dramatic increase of the affinity of such proteins to phosphatidylcholine liposomes.     

Cell Cycling of Astrocytes and Their Precursors in Primary Cultures: A Mevalonate Requirement Identified in Late G1, but Before the G1/S Transition, Involves Polypeptides

The relationship between mevalonate and cell cycling was investigated in developing glial cells. Primary cultures of newborn rat brains were serum-depleted (0.1%, vol/vol) for 48 h on days 4-6 in vitro, then returned to 10% calf serum (time 0). After 48 h, 70-80% of the cells were glial fibrillary acidic protein (GFAP)-negative by indirect immunofluorescence; 79 +/- 7% were GFAP-positive after an additional 3 days. Serum shift-up resulted in 12 h of quiescence, and then by 20 h (S phase) in increased proportions of cells synthesizing DNA (from 15 +/- 6% to 75 +/- 4% by bromodeoxyuridine immunofluorescence at 12 h and 20 h, respectively) and rates of DNA synthesis (42 +/- 6 versus 380 +/- 32 cpm/micrograms of protein/h of [3H]thymidine uptake). Additional mevalonate (25 mM) for 30 min at 10 h reversed the inhibition of DNA synthesis apparent with mevinolin (150 microM), an inhibitor of mevalonate synthesis, present from time 0. Cycloheximide added simultaneously with mevalonate prevented this reversal of inhibition. To cause arrest at G1/S, cultures were exposed to hydroxyurea between 10 and 22 h. By 3 h after hydroxyurea removal, bromodeoxyuridine-labeled nuclei increased from 0% to 75 +/- 9%, and DNA synthesis increased 10-fold. Mevinolin failed to inhibit these increases. Thus, primary astroglial precursors stimulated to progress through the cell cycle express a mevalonate requirement in late G1, but before the G1/S transition. The effect of mevalonate was characterized further as being brief (30 min) and as requiring polypeptides.     

Foraging behavior of specialist and generalist caterpillars on plantain (Plantago lanceolata) altered by predatory stinkbugs

Summary To examine the effects of predators and plant genotype on the behavior, patterns of herbivory, growth and survivorship of caterpillars, we used an experimental garden in which we contrasted two hostplant genotypes of plantain (Plantago lanceolata), two kinds of herbivores (specialist Junonia coenia vs. generalist Pyrrharctia isabella) and two levels of caterpillar predation (with and without Podisus maculiventris stinkbugs). Each of the replicate plots per treatment contained two plants of the same genotype. The stinkbugs reduced the survivorship of the specialist caterpillars but not that of the generalists, which reflects the differences in predatoravoidance behaviors of these species. Nonetheless, the stinkbugs influenced the behavior of both caterpillar species. When stinkbugs were present, both specialist and generalist caterpillars were less likely to be found on the plant upon which they were initially placed (=initial plant), and they were more likely to be off both plants within the plot than larvae in the absence of predators. Consequently in the presence of the stinkbug predators, the proportion of the initial plants consumed was less than in the absence of the predators. Plant genotype influenced plant size and the proportion of individual plants eaten, but it did not affect larval location on the plots. Neither presence of predators nor plant genotype had an effect on relative growth rate of the caterpillars.     

The flow of jelly within a honeybee colony

Summary The flow of jelly from 100 nurse bees to the members of two normal-sized colonies was measured during one night. To follow the flow, nurses were injected with ¹⁴C-phenylalanine. They incorporated this label into the protein of their hypopharyngeal (brood food) glands and their own body protein. When they were allowed trophallactic contacts during the investigation period a loss of label and a shift away from the abdomen was observed, indicating protein synthesis in the hypopharyngeal glands from previously stored protein. Very young larvae were fed less frequently than older ones. Younger workers received larger amounts of jelly than older ones, but considerable amounts were given to foragers. Drones behaved similarly. Between one-third and one-half of the distributed jelly was given to imagines; 10% and 16% of all workers received radioactive jelly from 100 nurses in the two colonies during one night. Thus, jelly is a very important food for adult honey bees. There was a remarkable exchange of label within the class of nurses themselves that is interpreted as communication within the social system.Abbreviation dpm decays per minute     

A novel technique for the measurement of disruption in high-pressure homogenization: Studies on E. coli containing recombinant inclusion bodies

The high-pressure homogenization of Escherichia coli, strain JM101, containing inclusion bodies of recombinant porcine somatotropin was investigated. A novel technique employing an analytical disc centrifuge was used to monitor the disruption. This a direct technique which measures cell disintegration rather than soluble protein release. The technique is particularly suited to measurements where the disruption approaches 100%. The disk centrifuge provides a size distribution of the homogenate, and furnishes evidence for the preferential disruption of larger cells. For E. coli containing inclusion bodies, and increase in the cell feed concentration from 145 g/L (wet weight) to 330 g/L resulted is poorer homogenization. Poorer disruption was also obtained by lowering the feed temperature from 20 degrees C to 5 degrees C. Only slight variations in performance were obtained by increasing the feed pH from 7.5 to 9.0 or by storing the feed at 4 degrees C for 24 h prior to disruption. Comparison with uninduced E. coli strain JM101, showed that the disruption obtained is higher for bacteria containing a recombinant inclusion body.     

Dynamics of distribution in animal communities: Theory and analysis

Theoretical and analytical problems of the dynamics of distribution and abundance in animal communities were examined. In many communities, species with low abundance and of limited spatial occurrence (i.e., rare species) typically form a conspicuous peak when a frequency distribution of the number of species is constructed with respect to the proportion of sites occupied within an area of distribution. Models of distribution dynamics, including a new model proposed here, were compared with a range of animal community data using a new procedure to assess single- and bi-modal patterns in frequency distributions of spatial occurrence. Data reveal that single-modality with an excess of rare species occurs more frequently than bimodality. Even when bimodality is detected, the mode representing wide-spread species is in the majority of cases smaller than that for rare species. Thus, a new model in which the rate of local extinctions is assumed to be negatively related to patch occupancy (or population abundance) is in better agreement with observed data than earlier models. Some problems of analysis, in particular model assumptions and testing, are discussed.