Opposite allosteric mechanisms in TetR and CAP

Regulation of the DNA binding affinity of an oligomeric protein can be considered to consist of an intrinsic component, in which the affinity of an individual DNA‐binding domain is modulated in response to effector binding, and an extrinsic component, in which the relative position of the protein's two DNA‐binding domains are altered so that they can or cannot contact both half‐site operators simultaneously. We demonstrated directly that the TetR repressor utilizes an extrinsic mechanism and CAP, the catabolite activator protein, utilizes an intrinsic mechanism.     

Biological properties of two models of calcitonin gene related peptide with idealized amphiphilic alpha-helices of different lengths

Previous studies on calcitonin gene related peptide (CGRP) have demonstrated that it has the characteristics of an amphiphilic peptide, and from an examination of the sequence, we have proposed that it contains an amphiphilic alpha-helix. We have synthesized two analogues of CGRP which have different lengths of idealized amphiphilic alpha-helical secondary structure. The first model, CGRM-1, has been substituted with residues generating an idealized amphiphilic alpha-helix in the region between residues 8 and 25, equivalent to approximately five turns of an alpha-helix. This peptide is not an agonist in any of our bioassays, but it does bind with low affinity to rCGRP receptors in crude liver membranes. Our second model, CGRM-2, has an idealized amphiphilic alpha-helix between residues 8 and 18, which is equivalent to approximately three turns of an alpha-helix. In an in vitro rat vas deferens assay, this peptide is an agonist with a potency one-fourth that of the native hormone. However, the potency of CGRM-2 in an adenylate cyclase assay is much lower, only 1/140th the potency of CGRP. Both model peptides display amphiphilic characteristics commensurate with their design. We conclude that there is an amphiphilic alpha-helix in rCGRP between residues 8 and 18 and that this helix terminates in the vicinity of residue 18.     

The competitive ability of stem cells from mice with Hertwig's anemia

Mice homozygous for the gene, an, have a macrocytic, normochromic anemia. In this report, attempts have been made to cure Hertwig's anemia (an/an) by injecting genetically normal (+/+) stem cells. The anemia of unirradiated an/an mice was alleviated but not completely cured by injection of as many as 3 X 10(7) +/+ bone marrow cells. Lethal irradiation of the an/an recipients was necessary before injections of 10(7) +/+ marrow cells were effective in normalizing the blood parameters. The inability to achieve normal blood values without first destroying the host's own stem cells suggested that the indigenous an/an cells compete effectively with injected +/+ cells. This hypothesis was tested by injecting varying numbers of stem cells from C57BL/6J-+/+ mice, together with stem cells from either WBB6F1-an/an or, as controls, from their WBB6F1-+/+ littermates, into lethally irradiated hosts. The C57BL/6J and WBB6F1 mice have electrophoretically distinguishable hemoglobins. The an/an cells are able to compete in the repopulation of the host hematopoietic tissue as shown by the presence of WBB6F1 hemoglobin in the recipients. The cells from mice with Hertwig's anemia, however, do not compete as effectively as do the same number of cells from the +/+ littermates. These results indicate that the pluripotent hematopoietic stem cells of an/an mice are reduced in number, seeding capacity, or proliferative potential.     

Evolutionary stability: States and strategies

Different aspects and modifications of the definition of an evolutionarily stable (ES) strategy that have been considered in the literature can be incorporated in a unifying concept which regards the population context. This concept of evolutionary stability will generally characterize population states in both pure- and mixed-strategist models. In particular, it includes ES strategies, represented as a phenotype unique in an ES population. For an important class of mixed-strategist models, no strict ESS can exist. This will be the case whenever the success of an individual strategy is considered to follow as an average from the successes of its behavioural components. Instead, ESS results may be obtained from what will be called a “degenerate” form of the model, which is simply an ESS model on the level of elementary actions. Then, however, the correct interpretation of an ESS is not an individual phenotype but rather a population mixture of elementary actions. If an ES state exists in a mixed-strategist model it may be determined by an equilibrium condition; if there is an ES strategy, a different approach—mainly maximum considerations—is needed for finding it. An equilibrium condition does not hold for the components of an ES strategy straightforwardly; but it can be derived in terms of an auxiliary ESS model that considers first-order effects of the components. Several examples illustrate the significance of these results. Particularly, two models on “Games between Relatives” are reconsidered in order to display both their formal interrelation and the different meaning of their results in the context of mixed-strategist models.     

Extension of the range of DNA sequences available for triple helix formation: stabilization of mismatched triplexes by acridine-containing oligonucleotides.

Triple helix formation usually requires an oligopyrimidine*oligopurine sequence in the target DNA. A triple helix is destabilized when the oligopyrimidine*oligopurine target contains one (or two) purine*pyrimidine base pair inversion(s). Such an imperfect target sequence can be recognized by a third strand oligonucleotide containing an internally incorporated acridine intercalator facing the inverted purine*pyrimidine base pair(s). The loss of triplex stability due to the mismatch is partially overcome. The stability of triplexes formed at perfect and imperfect target sequences was investigated by UV thermal denaturation experiments. The stabilization provided by an internally incorporated acridine third strand oligonucleotide depends on the sequences flanking the inverted base pair. For triplexes containing a single mismatch the highest stabilization is observed for an acridine or a propanediol tethered to an acridine on its 3'-side facing an inverted A*T base pair and for a cytosine with an acridine incorporated to its 3'-side or a guanine with an acridine at its 5'-side facing an inverted G*C base pair. Fluorescence studies provided evidence that the acridine was intercalated into the triplex. The target sequences containing a double base pair inversion which form very unstable triplexes can still be recognized by oligonucleotides provided they contain an appropriately incorporated acridine facing the double mismatch sites. Selectivity for an A*T base pair inversion was observed with an oligonucleotide containing an acridine incorporated at the mismatched site when this site is flanked by two T*A*T base triplets. These results show that the range of DNA base sequences available for triplex formation can be extended by using oligonucleotide intercalator conjugates.     

Gametic and pleiotropic defects in mouse fetuses with Hertwig''s macrocytic anemia

Pleiotropic effects on germ cell number, hematologic status, and body size are described in 12- to 15-day WBB6F1 normal (+/-) and defective (an/an) mouse fetuses, with special emphasis on gametogenesis. Differences between genotypes were apparent by Day 12. At 12 days, normal testes contained many germ cells and frequent normal mitoses, and the number of germ cells increased rapidly from Day 12 to Day 15. By contrast, 12-day an/an testes contained fewer germ cells, frequently degenerating, and many abnormal mitoses. Their number of germ cells decreased rapidly, so that almost none persisted to Day 15. Normal ovaries contained many germ cells, with much normal mitosis on Day 12 and 13, followed by meioses, but the smaller an/an ovaries contained few germ cells, with little mitosis, some meiosis, and very much degeneration. The erythrocyte counts of both normal and anemic fetuses increased approximately fourfold between 12 and 15 days, but at comparable ages, total counts were always lower in an/an fetuses than in normal littermates. At all ages, Hertwig's anemic (an/an) fetuses were somewhat smaller than their normal littermates. Although both W/Wv and Sl/Sld mice also show macrocytic anemia and germ cell failure, the great difference in etiology of their germ cell defects indicates that an/an gene action must be qualitatively different from that in either W/Wv or Sl/Sld mice.     

Hydra as a model organism for the study of morphogenesis

Pattern formation in hydra is controlled by two sets of morphogens: an activator and an inhibitor o f head and bud formation, and an activator and an inhibitor o f foot formation.     

Effects of ornithine or arginine administration on serum amino acid levels

In healthy humans after overnight fasting, an oral administration of ornithine induced a new steady state: an accumulation of serum alanine and proline, a decrease in serum valine concentration, transient reductions in serum urea and urinary urea contents, and then an increased urea excretion. On the other hand, an oral administration of arginine resulted in an anabolic state: decreases in serum leucine and isoleucine concentrations, reductions in serum glucose and free fatty acid contents and a rapid increase in serum insulin level. It was assumed that the effect of ornithine administration may be exerted through an activation of hepatic System A transport and that of arginine is an insulin-mediated action.     

Limiting Factors Impacting on Voluntary First Person Informed Consent in the Philippines

How well can institutional guidelines help ensure the dignity, rights, safety and well being of research participants in an underdeveloped country? In this paper I describe the limits of informed consent as an instrument for the protection of participants in the context of the Philippines. I bring to this paper my experiences as an advocate of rights, a member of an ethics review board, a researcher on the ethics of research and as an observer of the dynamics of clinical practice in an academic public teaching hospital of the University of the Philippines where I am professor.     

Biological epimorphism,adequate design,and the problem of regeneration

It is pointed out that the property of an organism of regenerating certain lost parts is a subproperty of the general property of reproduction. The principle of adequate design imposes an upper limit upon the total number of subproperties which an organism can possess. Therefore with increasing complexity of an organism in some direction, which by definition is the same as an increase of the total number of subproperties, the number of subproperties needed for regeneration must decrease.     

The effect of error fields on the dynamics of a tearing mode in a tokamak

The features of the tearing mode dynamics in a tokamak that manifest themselves in an irregular mode rotation are demonstrated by using an algorithm for data processing that is based on the concept of the instantaneous frequency of an analytic signal. A model is developed in which the tearing mode is treated as an object to be controlled by means of an external quasistatic magnetic field with an appropriate spatial structure. It is shown that the model dynamics of the mode agrees well with the dynamics of tearing modes observed in experiments in which they are influenced by the magnetic field of the halo current.     

Physical Attractiveness of an Animal Species as a Decision Factor for its Preservation

ABSTRACT

This experimental study examines how framing an animal species as endangered affects its perceived attractiveness and how an animal's perceived attractiveness affects support for its conservation. Undergraduate students were shown a flyer from a fictitious environmental organization pleading for the protection of either a bat or an ape. The flyer contained either no picture, a picture of an attractive member of its species, or a picture of an unattractive member of its species. For both species, an animal's attractiveness substantially increased support for its protection. There was also more support for saving the species that was larger in size and more resembled humans. In a second experiment, participants rated an unattractive animal as more attractive if it was framed as endangered. There was no such effect for an animal originally perceived as attractive. The implications of the results for environmental policy and conservation support are discussed.     

Telomeres, telomerase and senescence

Eukaryotic chromosomes end with tandem repeats of simple sequences. These GC rich repeats allow telomere replication and stabilize chromosome ends. Telomere replication involves an equilibrium of sequence loss and addition at the ends of chromosomes. Repeats are added de novo by telomerase, an unusual DNA polymerase. Telomerase is an RNP in which an essential RNA component provides the template for the added telomere repeats. Telomere length maintenance plays an essential role in cell viability.     

Design and inhibitory properties of synthetic Bowman-Birk loops.

A cyclic tridecapeptide based on the sequence of an anti-tryptic loop of a Bowman-Birk inhibitor was synthesized, and demonstrated to be active as an inhibitor of trypsin. Molecular modeling of this sequence suggested an improved sequence which demonstrated an order of magnitude improvement in the inhibitory constant.     

Rights, indirect harms and the non-identity problem

The non‐identity problem is the problem of grounding moral wrongdoing in cases in which an action affects who will exist in the future. Consider a woman who intentionally conceives while on medication that is harmful for a fetus. If the resulting child is disabled as a result of the medication, what makes the woman's action morally wrong? I argue that an explanation in terms of harmful rights violations fails, and I focus on Peter Markie's recent rights‐based defense. Markie's analysis rests on the notion of an indirect harm, and I show that the calculation of an indirect harm relies on an improper baseline for the determination of whether or not an action adversely affects a patient's interests. I also defend an impersonal duty‐based analysis of the wrongdoing in non‐identity cases against an objection by Markie. I close by arguing that the rights‐based analysis is insensitive to context and that context is morally relevant in the determination of the moral valence of actions in cases of non‐identity. This failure provides a pro tanto reason to favor an impersonal duty‐based analysis of the wrongdoing in non‐identity cases.     

Maternal aggression and intermale social aggression: a behavioral comparison

The aggressive behavior of alpha male rats and lactating females were each examined toward an intact adult male rat, a castrated adult male rat, an anesthetized adult male rat, a nonlactating adult female rat, an adult albino guinea pig (male or female), or an albino mouse (male or female). When in their living colony, females displayed high levels of aggressiveness toward all stimulus objects except a mouse. The aggression toward the intruding males occurred whether the female's pups were present or not. Alpha males were aggressive toward the same stimuli except an intruding female rat and a mouse. When tested in an unfamiliar colony, the males but not the females (with or without pups present) were aggressive toward an adult male rat. Half of the females but none of the males displayed defensive burying toward an anesthetized intruder. It is suggested that the attack on an adult female, the absence of attack outside of the resident colony, and the tendency to display defensive burying are features of the aggressiveness of lactating females that are fundamentally different from the aggressiveness of alpha males. The form of the aggression (lateral attack vs. lunge attack) was only quantitatively different in males and females.     

1H, 13C and 15N backbone and side chain resonance assignments of a 28 kDa active mutant of maize ribosome-inactivating protein (MOD)

We report the full resonance assignments of MOD, which is an active mutant of maize ribosome-inactivating protein (mRIP). mRIP is a unique RIP which is synthesized as an inactive precursor and processed by removal of an internal inactivation region to yield an active form.     

Sex-Specific Audience Effect in the Context of Mate Choice in Zebra Finches

Animals observing conspecifics during mate choice can gain additional information about potential mates. However, the presence of an observer, if detected by the observed individuals, can influence the nature of the behavior of the observed individuals, called audience effect. In zebra finches (Taeniopygia guttata castanotis), domesticated males show an audience effect during mate choice. However, whether male and female descendants of the wild form show an audience effect during mate choice is unknown. Therefore, we conducted an experiment where male and female focal birds could choose between two distinctive phenotypes of the opposite sex, an artificially adorned stimulus bird with a red feather on the forehead and an unadorned stimulus bird, two times consecutively, once without an audience and once with an audience bird (same sex as test bird). Males showed an audience effect when an audience male was present and spent more time with adorned and less time with unadorned females compared to when there was no audience present. The change in time spent with the respective stimulus females was positively correlated with the time that the audience male spent in front of its cage close to the focal male. Females showed no change in mate choice when an audience female was present, but their motivation to associate with both stimulus males decreased. In a control for mate-choice consistency there was no audience in either test. Here, both focal females and focal males chose consistently without a change in choosing motivation. Our results showed that there is an audience effect on mate choice in zebra finches and that the response to a same-sex audience was sex-specific.