Is the Testis a Chemo-Privileged Site? Is There a Blood-Testis Barrier?

The incidence of testicular cancer, primarily seminoma, has been increasing in many countries, including the United States. The testis is often the site of residual cancer after adequate treatment with systemic chemotherapy. The blood-testis barrier is commonly cited as the explanation for residual tumor within the gonad after chemotherapy and as the indication for delayed orchiectomy. Conversely, complete eradication of viable tumor from the primary site is common and argues against the testis as a "tumor sanctuary." Residual tumor is also demonstrated within metastatic foci, and the disparity between the histopathologic response of the primary tumor and metastatic sites may be best explained by tumor heterogeneity and multiple tumor clones. Regardless of the scientific and academic arguments, delayed radical orchiectomy remains an important part of treatment for patients undergoing primary chemotherapy.     

What Is a Story?

This paper attempts to discover the criteria by which a listener accepts or rejects an item of oral narrative as being a story. The hypotheses are: (1) such criteria relate to structure rather than content, although the listener does not consciously distinguish structure from content; (2) the structure must have a certain minimal and maximal degree of complexity and be of a certain kind; (3) the criteria will hold cross-culturally. Information gathered from ethnographies and folklore literature is inadequate to confirm the hypotheses, but it does not contradict them. An experiment to test hypotheses (1) and (2) produced a certain degree of negative confirmation: listeners rejected as a story any narrative item which did not conform to the structural criteria regarded as minimal by myself; however, they also rejected items which I regarded as well structured but which were bizarre or nonsensical in content. The confusion of structure and content tended to confirm hypothesis (1).     

Is Moyeria a euglenoid?

Moyeria , with a known age span of Middle Ordovician through Silurian, and normally placed in the acritarchs, may have euglenoid affinities. If this conclusion is correct it represents the oldest freshwater protozoan, because Moyeria is abundant in fluvial beds in Pennsylvania and New York, as well as in nearshore marine beds at many localities elsewhere. Paramecium is the only other typically freshwater protozoan with a pre-Cenozoic fossil record (a single, unillustrated Cretaceous report): euglenoids have rare Cenozoic records. As a freshwater taxon, or one capable of living in freshwaters, Moyeria , regardless of taxonomic assignment, provides further evidence about the early complexity of the freshwater ecosystem. □ Euglenoids, freshwater, Ordovician, Silurian, protozoans, acritarchs.     

Is arginine a protein-denaturant?

Arginine is a useful solvent additive for many applications, including refolding and solubilization of proteins from insoluble pellets, and suppression of protein aggregation and non-specific adsorption during formulation and purification. However, there is a concern that arginine may be a protein-denaturant, which may limit the expansion of its applications. Such concern arises from the facts that arginine decreases melting temperature and perturbs the spectroscopic properties of certain proteins and contains a guanidinium group, which is a critical chemical structure for denaturing activity of guanidine hydrochloride. Here, we show that although arginine does lower the melting temperatures of certain proteins, the extent is insufficient to cause denaturation of proteins at or below room temperature. The proteins described here show enzymatic activity and folded structure in the presence of arginine, although the local structure around aromatic amino acids is perturbed by arginine. Arginine differs from guandinine hydrochloride in the mode of interactions with proteins, which may be a primary reason why arginine is not a protein-denaturant.     

Is Chordin a morphogen?

Models employing gradients of diffusible morphogens are often invoked to explain regional specification in the early embryo. In these models, a concentration gradient of a secreted factor generates distinct cell fates, based on the differential response of cells to local concentrations of this morphogen. In recent years, there has been a great deal of focus on the factors involved in the dorsoventral patterning of the vertebrate mesoderm and ectoderm. Dorsoventral specification during amphibian gastrulation is regulated by the antagonistic actions of the Bone Morphogenetic Proteins (BMPs) and a number of dorsally expressed inhibitors, including the secreted factor, Chordin. In a recent paper, Blitz and colleagues explore the possibility that Chordin acts as a long-range factor in the amphibian gastrula embryo, to establish a functional gradient of BMP activity.     

Is tubulin a glycoprotein?

[¹⁴C]Glucosamine is incorporated $\text{in vivo}$ in mouse brain into the major protein species present in purified tubulin preparations when analyzed both by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by isoelectric focusing. The radioactivity incorporated into tubulin can be recovered as a mixture of glucosamine and galactosamine.     

Is homocysteine a pro-oxidant?

High plasma homocysteine concentrations have been found to be associated with atherosclerosis and thrombosis of arteries and deep veins. The oxidative damage mediated by hydrogen peroxide production during the metal-catalyzed oxidation of homocysteine is to date considered to be one of the major pathophysiological mechanisms for this association.

In this work, a very sensitive and accurate method was employed to measure the effective production of H₂O₂ during homocysteine oxidation. Furthermore, the interaction of homocysteine with powerful oxidizing species (hypochlorite, peroxynitrite, ferrylmyoglobin) was evaluated in order to ascertain the putative pro-oxidant role of homocysteine.

Our findings indicate that homocysteine does not produce H₂O₂ in a significant amount (1/4000 mole/mole ratio of H₂O₂ to homocysteine). Moreover, homocysteine strongly inhibits the oxidation of luminol and dihydrorhodamine by hypochlorite or peroxynitrite and rapidly reduces back ferrylmyoglobin, the oxidizing species, to metmyoglobin.

All these results should, in our opinion, lead to a rethinking of the commonly held view that homocysteine oxidation is one of the main causative mechanisms of cardiovascular damage.     

Is Pneumocystis a Plant?

Pneumocystis, an AIDS-associated opportunistic pathogen of the lung has some unusual features. This article focuses on work done by my group to understand the organism's distinct sterols. Although Pneumocystis is closely related to fungi, it lacks the major fungal sterol, ergosterol. Several delta(7) 24-alkysterols synthesized by P. carinii are the same as those reported in some basidiomycete rust fungi. The 24-alkylsterols are synthesized by the action of S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT). Fungal SAM:SMT enzymes normally transfer only one methyl group to the C-24 position of the sterol side chain and the cells accumulate C28 24-alkylsterols. In contrast, the P. carinii SAM:SMT and those of some plants catalyze one or two methyl transfer reactions producing both C28 and C29 24-alkylsterols. However, unlike most fungi, plants, and the kinetoplastid flagellates Leishmania and Trypanosoma cruzi, P. carinii does not appear to form double bonds at C-5 of the sterol nucleus and C-22 of the sterol side chain. Furthermore, the P. carinii SAM:SMT substrate preference for C30 lanosterol differs from that of homologous enzymes in any other organisms studied. C31 24-Methylenelanosterol and C32 pneumocysterol, products of SAM:SMT activity on lanosterol, can accumulate in high amounts in some, but not all, human-derived Pneumocystis jiroveci populations.     

Is it a revolution?

Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence properties is also discussed.

Is there a role for eIF5A in translation?

Summary. The putative translation factor eIF5A is essential for cell viability and is highly conserved from archaebacteria to mammals. This factor is the only cellular protein that undergoes an essential posttranslational modification dependent on the polyamine spermidine, called hypusination. This review focuses on the functional characterization of eIF5A. Although this protein was originally identified as a translation initiation factor, subsequent studies did not support a role for eIF5A in general translation initiation. eIF5A has also been implicated in nuclear export of HIV-1 Rev and mRNA decay, but these findings are controversial in the literature and may reflect secondary effects of eIF-5A function. Next, the involvement of eIF5A and hypusination in the control of the cell cycle and proliferation in various organisms is reviewed. Finally, recent evidence in favor of reconsidering the role of eIF5A as a translation factor is discussed. Future studies may reveal the specific mechanism by which eIF5A affects protein synthesis.     

Is a cultural ethology possible?

The possibility, desirability, and potential outcomes of applying ethological methods to the study of culture-specific human behaviors are investigated. Ethology and culture are explored. A new term, instruction, and its use in cultural ethology are proposed. Genetics and survival value are related to cultural ethology. A cultural ethology is given a possible theoretical foundation, and current attempts at a cultural ethology are appraised. A research program in cultural ethology and related fields is proposed.This article is a completely rewritten version of a paper of the same title delivered at the annual meeting of the Southern Anthropological Society at Gainesville, Florida, in February 1968 and published inResearch Previews 15(1): 37–47, April 1968.