Germ cell development in Meishan and White Composite gilts

This study compared dynamics of the germ cell population in two swine breeds that differ in prolifacy, White Composite (WC) and Meishan (MS), during fetal and neonatal life and in mature sows. Germ cell populations developed in a similar pattern in these two diverse breeds during fetal life. Maximal germ cell number was observed at 90 days postcoitum (dpc) in both WC and MS gilts, and substantial oogonial apoptosis was evident thereafter with approximately 30% of maximal numbers present at 25 days postpartum (dpp). Neither gilt nor sow germ cell number was correlated with maternal ovulation rate. Postnatal MS gilts had larger pools of primordial follicles and consistently greater proportions and numbers of primary and secondary follicles compared to postnatal WC gilts, indicative of enhanced follicular recruitment and primordial follicle activation. Occasional antral follicles were present in MS ovaries by 25 dpp and numerous surface follicles were observed at 56 dpp in MS but not WC ovaries, indicative of more rapid ovarian maturation and early onset of puberty. Total germ cell number is unlikely to influence or to predict subsequent ovulation rate. These observations highlight important developmental events during late fetal and early postnatal life that prepare the ovarian environment for early onset of puberty and subsequent ovulation in MS gilts.     

Stimulus representation in SOP: II. An application to inhibition of delay

The componential extension of SOP accounts for conditioned response (CR) timing in Pavlovian conditioning by assuming that learning accrues with relative independence to stimulus elements that are differentially occasioned during the duration of the conditioned stimulus (CS). SOP, using a competitive learning rule and the assumption that temporal learning emerges via resolution of what is equivalent to an "AX+BX-" discrimination, predicts a progressive increase in the latency of the CR over training, or what Pavlov refer to as "inhibition of delay." Other componential models, which use noncompetitive learning rules, do not predict inhibition of delay. Either type of model makes the prediction indicated, independently of the length of the CS-unconditioned stimulus (US) interval. We report two experiments that demonstrated inhibition of delay when rabbits were trained with relatively long, but not with short, CS-US intervals. To account for this divergence, we assumed that the SOP stimulus trace involves two kinds of elements, some with a temporally distributed pattern of activity over the duration of the CS duration, and some with a randomly distributed pattern. This stimulus representation, not only allows for inhibition of delay with long but not short CS-US intervals, but in combination with SOP's performance rule deduces CR's with "Weber variability."     

Combinatorial discovery of tumor targeting peptides using phage display

Peptides possess appropriate pharmacokinetic properties to serve as cancer imaging or therapeutic targeting agents. Currently, only a small number of rationally-derived, labeled peptide analogues that target only a limited subset of antigens are available. Thus, finding new cancer targeting peptides is a central goal in the field of molecular targeting. Novel tumor-avid peptides can be efficiently identified via affinity selections using complex random peptide libraries containing millions of peptides that are displayed on bacteriophage. In vitro and in situ affinity selections may be used to identify peptides with high affinity for the target antigen in vitro. Unfortunately, it has been found that peptides selected in vitro or in situ may not effectively target tumors in vivo due to poor peptide stability and other problems. To improve in vivo targeting, methodological combinatorial chemistry innovations allow selections to be conducted in the environment of the whole animal. Thus, new targeting peptides with optimal in vivo properties can be selected in vivo in tumor-bearing animals. In vivo selections have been proven successful in identifying peptides that target the vasculature of specific organs. In addition, in vivo selections have identified peptides that bind specifically to the surface of or are internalized into tumor cells. In the future, direct selection of peptides for cancer imaging may be expedited using genetically engineered bacteriophage libraries that encode peptides with intrinsic radiometal-chelation or fluorescent sequences.     

Extraction buffer effects on detection of transient gene expression in white spruce

β-Glucuronidase (GUS) and luciferase (LUC) reporter genes were introduced into white spruce (Picea glauca [Moench] Voss) cultured cells via particle bombardment. Transient expression of these genes was evaluated by extracting the enzymes using 3 buffers. Different buffers resulted in significantly different sensitivities of GUS and LUC detection. In the case of cobombardment, the buffer that gave high levels of expression of one reporter gene did not necessarily result in a better detection of the second reporter gene. This study indicates that appropriate buffers should be used for maximum detection of reporter genes.     

Random priming PCR strategy to amplify and clone trace amounts of DNA

Here we report a new methodology to study trace amounts of DNA of unknown sequence using a two-step PCR strategy to amplify and clone target DNA. The first PCR is carried out with a partial random primer comprised of a specific 21-nucleotide 5' sequence, a random heptamer, and a 3' TGGC clamp. The second PCR is carried out with a single 19-nucleotide primer that matches the specific 5' sequence of the partial random primer. Using human and Mycoplasma genitalium DNA as examples, we demonstrated the efficiency of this approach by effectively cloning target DNA fragments from 1 pg DNA sample. The cloning sensitivity could reach 100 fg target DNA templates. Compared to the strategy of first adding adapter sequences to facilitate the PCR amplification of unknown sequences, this approach has the advantage of allowing for the amplification of DNA samples in both natural and denatured forms, which provides greater flexibility in sample preparation. This is an efficient strategy to retrieve sequences from trace DNA samples from various sources.     

Rescue of the neural tube defect of loop-tail mice by a BAC clone containing the Ltap gene

The mouse mutant loop-tail (Lp) is an accepted model for the study of neural tube defects (NTDs) in humans. Whereas Lp/+ heterozygotes show a mild tail defect (looped), homozygous Lp/Lp embryos show a very severe form of NTD, with a completely open neural tube from the hindbrain region to the caudal portion of the spinal cord (craniorachischisis). We have recently identified a positional candidate for Lp on chromosome 1, designated as Ltap. Here, we have used an in vivo complementation approach in transgenic mice to attempt to correct the looped-tail phenotype with a bacterial artificial chromosome clone (BAC280A23) that harbors a full-length copy of the Ltap gene. Genotype:phenotype correlations in Lp/+ heterozygotes carrying BAC280A23 show that this clone can rescue the looped-tail phenotype in two independent founder lines (P < 0.05 and P < 0.0001). Importantly, BAC280A23 is also observed to rescue the lethal NTD of Lp/Lp homozygotes, because several viable transgenic Lp/Lp mice could be identified and appeared normal (P < 0.05). Results from these gain-of-function transgenic animals strongly suggest that the positional candidate Ltap present in this BAC is indeed the gene that is defective in loop-tail.     

Curly bare (cub), a new mouse mutation on chromosome 11 causing skin and hair abnormalities,and a modifier gene (mcub) on chromosome 5

In the outcrossing of a new recessive mouse mutation causing hair loss, a new wavy-coated phenotype appeared. The two distinct phenotypes were shown to be alternative manifestations of the same gene mutation and attributable to a single modifier locus. The new mutation, curly bare (cub), was mapped to distal Chr 11 and the modifier (mcub) was mapped to Chr 5. When homozygous for the recessive mcub allele, cub/cub mice appear hairless. A single copy of the dominant Mcub allele confers a full, curly coat in cub/cub mice. Reciprocal transfer of full-thickness skin grafts between mutant and control animals showed that the skin phenotype was tissue autonomous. The hairless cub/cub mcub/mcub mice show normal contact sensitivity responses to oxazolone. The similarity of the wavy coat phenotype to those of Tgfa and Egfr mutations and the map positions of cub and mcub suggest candidate genes that interact in the EGF receptor signal transduction pathway.     

Violent coalitionary attacks and intraspecific killing in wild white-faced capuchin monkeys (<Emphasis Type="Italic">Cebus capucinus</Emphasis>)

During 12 years of observation, we have observed three confirmed and two inferred lethal coalitionary attacks on adult male white-faced capuchins (Cebus capucinus) by members of two habituated social groups at Lomas Barbudal Biological Reserve, Costa Rica. In one case, an alpha male was badly wounded and evicted from his group, and when later found by his former groupmates he was attacked by several of them and died less than 24 h later. In two other cases, lone extra-group males were mobbed by adult and immature males of a bisexual group. One victim's abdomen was torn open and he died less than 24 h later. A second victim was quite badly bitten but may have escaped. The fourth and fifth cases resulted from intergroup encounters. One victim lost the use of both arms but may have survived, whereas the other died of unknown causes within an hour of the attack. The observed death rate from coalitionary aggression at our site is approximately the same as that reported for eastern chimpanzees. Because at least three of the five observed incidents involved large coalitions attacking lone victims, they support the general hypothesis that imbalances of power contribute to intraspecific killing in primates. However, the occurrence of lethal coalitional attacks in a species lacking fission–fusion social organization poses a challenge to the more specific version of the imbalance-of-power hypothesis proposed by Manson and Wrangham in 1991 to explain chimpanzee and human intergroup aggression.