Development of preimplantation rabbit embryos in vivo and in vitro

Qualitative patterns of protein synthesis in preimplantation rabbit embryos grown in vivo and in vitro were examined by SDS polyacrylamide gel electrophoresis followed by autoradiography. The results demonstrate that (1) most qualitative changes in the pattern of protein synthesis occur during cleavage, (2) the blastocyst period of development is characterized by a remarkably uniform and constant pattern of protein synthesis, and (3) the qualitative pattern of protein synthesis in embryos cultured in vitro from the 1-cell to the blastocyst stage is essentially identical to the pattern of protein synthesis in embryos grown to a comparable stage in vivo.These results indicate that no “special” maternal factors, such as uterine proteins, are required in vitro either for the qualitative changes in the pattern of protein synthesis during cleavage, or for the initial expression of a pattern of protein synthesis characteristic of the entire blastocyst period. From these studies we conclude that, once fertilized, the rabbit egg proceeds through cleavage and blastocyst formation on its own endogenous developmental program.     

Growth of a Molecular Base for Feeding: The Mind Body Dualism

It is often difficult to identify the ‘who, when, and where’ of advances in medicine and surgery because it's a rare advance indeed (such as the use of digitalis by William Withering) that can be clearly related to the astuteness of one person at one time and place.     

A Hidden Markov Model approach to variation among sites in rate of evolution

The method of Hidden Markov Models is used to allow for unequal and unknown evolutionary rates at different sites in molecular sequences. Rates of evolution at different sites are assumed to be drawn from a set of possible rates, with a finite number of possibilities. The overall likelihood of phylogeny is calculated as a sum of terms, each term being the probability of the data given a particular assignment of rates to sites, times the prior probability of that particular combination of rates. The probabilities of different rate combinations are specified by a stationary Markov chain that assigns rate categories to sites. While there will be a very large number of possible ways of assigning rates to sites, a simple recursive algorithm allows the contributions to the likelihood from all possible combinations of rates to be summed, in a time proportional to the number of different rates at a single site. Thus with three rates, the effort involved is no greater than three times that for a single rate. This "Hidden Markov Model" method allows for rates to differ between sites and for correlations between the rates of neighboring sites. By summing over all possibilities it does not require us to know the rates at individual sites. However, it does not allow for correlation of rates at nonadjacent sites, nor does it allow for a continuous distribution of rates over sites. It is shown how to use the Newton-Raphson method to estimate branch lengths of a phylogeny and to infer from a phylogeny what assignment of rates to sites has the largest posterior probability. An example is given using beta-hemoglobin DNA sequences in eight mammal species; the regions of high and low evolutionary rates are inferred and also the average length of patches of similar rates.      

Development of preimplantation rabbit embryos in vivo and in vitro. I. An ultrastructural comparison

Ultrastructural criteria have been used to assay the normality of fertilized rabbit ova allowed to develop in vitro. The developmental sequences in nucleoli, ribosomes and polysomes, the endoplasmic reticulum, mitochondria, intercellular junctional complexes, and crystalline inclusions have been examined during the first 6 days of embryogenesis.By these criteria, no evidence is found that rabbit embryos require special “growth factors” unique to the maternal reproductive tract during the first 4 days of development. The evidence suggests, however, that specific embryo-uterine interaction may become essential, possibly only briefly, during day 5 of pregnancy.     

Govindjee, Fork, D.C.: Charles Stacy French 1907–1985 National Academy of Sciences, Washington 2006. 28 pp.

Book Reviews

Govindjee, Fork, D.C.: Charles Stacy French 1907–1985 National Academy of Sciences, Washington 2006. 28 pp.     

CD28 interaction with filamin-A controls lipid raft accumulation at the T-cell immunological synapse

During physiological T-cell stimulation by antigen presenting cells (APCs), a major T-cell membrane rearrangement is known to occur leading to the organization of 'supramolecular activation clusters' at the immunological synapse. A possible role for the synapse is the generation of membrane compartments where signalling may be organized and propagated. Thus, engagement of the costimulatory molecule CD28 at the immunological synapse promotes the organization of a signalling compartment by inducing cytoskeletal changes and lipid raft accumulation. We identified the actin-binding protein Filamin-A (FLNa) as a novel molecular partner of CD28. We found that, after physiological stimulation, CD28 associated with and recruited FLNa into the immunological synapse, where FLNa organized CD28 signalling. FLNa knockdown by short interfering RNA (siRNA) inhibited CD28-mediated raft accumulation at the immunological synapse and T-cell costimulation. Together, our data indicate that CD28 binding to FLNa is required to induce the T-cell cytoskeletal rearrangements leading to recruitment of lipid microdomains and signalling mediators into the immunological synapse.     

A potential role for the Src-like adapter protein SLAP-2 in signaling by the colony stimulating factor-1 receptor

The development of macrophages from myeloid progenitor cells is primarily controlled by the growth factor colony stimulating factor-1 (CSF-1) and its cognate receptor, a transmembrane tyrosine kinase encoded by the c-Fms proto-oncogene. The CSF-1 receptor exerts its biological effects on cells via a range of signaling proteins including Erk1/2 and Akt. Here we have investigated the potential involvement of the Src-like adapter protein (SLAP-2) in signaling by the CSF-1 receptor in mouse bone marrow-derived macrophages. RT-PCR analysis revealed constitutive expression of the SLAP-2 gene in bone marrow macrophages. Surprisingly, co-immunoprecipitation and GST binding experiments demonstrated that the CSF-1 receptor could bind to SLAP-2 in a ligand-independent manner. Furthermore, the binding of SLAP-2 to the CSF-1 receptor involved multiple domains of SLAP-2. SLAP-2 also bound c-Cbl, with the interaction being mediated, at least in part, by the unique C-terminal domain of SLAP-2. Overexpression of SLAP-2 in bone marrow macrophages partially suppressed the CSF-1-induced tyrosine phosphorylation and/or expression level of a approximately 80 kDa protein without affecting CSF-1-induced global tyrosine phosphorylation, or activation of Akt or Erk1/2. Significantly, CSF-1 stimulation induced serine phosphorylation of SLAP-2. Pharmacologic inhibition of specific protein kinases revealed that CSF-1-induced phosphorylation of SLAP-2 was dependent on JNK activity. Taken together, our results suggest that SLAP-2 could potentially be involved in signaling by the CSF-1 receptor.