Maternal investment increases with altitude in a frog on the Tibetan Plateau.

Reproducing females can allocate energy between the production of eggs or offspring of different size or number, both of which can strongly influence fitness. The physical capacity to store developing offspring imposes constraints on maximum clutch volume, but individual females and populations can trade off whether more or fewer eggs or offspring are produced, and their relative sizes. Harsh environments are likely to select for larger egg or offspring size, and many vertebrate populations compensate for this reproductive investment through an increase in female body size. We report a different trade-off in a frog endemic to the Tibetan Plateau, Rana kukunoris. Females living at higher altitudes (n = 11 populations, 2000-3500 m) produce larger eggs, but without a concomitant increase in female body size or clutch size. The reduced diel and seasonal activity at high altitudes may impose constraints on the maximum body size of adult frogs, by limiting the opportunity for energy accumulation. Simultaneously, producing larger eggs likely helps to increase the rate of embryonic development, causing tadpoles to hatch earlier. The gelatinous matrix surrounding eggs, more of which is produced by large females, may help buffer developing embryos from temperature fluctuations or offer protection from ultraviolet radiation. High-altitude frogs on the Tibetan Plateau employ a reproductive strategy that favours large egg size independent of body size, which is unusual in amphibians. The harsh and unpredictable environmental conditions at high altitudes can thus impose strong and opposing selection pressures on adult and embryonic life stages, both of which can simultaneously influence fitness.

Does maternal care evolve through egg recognition or directed territoriality?

The mechanism that facilitates the evolution of maternal care is ambiguous in egg-laying terrestrial vertebrates: does the ability of mothers to recognize their own eggs lead them under some circumstances to begin providing care or can maternal care evolve from simply being in close proximity to the eggs (e.g. through territorial behaviour)? This question is difficult to answer because in most species, parental care is either absent altogether or present; in only a few species we have the opportunity to observe intraspecific variation in the expression of parental care. We studied a population of long-tailed skinks (Eutropis longicaudata) in which females have recently evolved maternal care from a noncaring state. Females on Orchid Island, Taiwan, remain with their eggs during incubation and when doing so, actively deter egg predation by egg-eating snakes (Oligodon formosanus); in all other populations, females lack post-ovipositional maternal care. Nest-guarding females on Orchid Island (i) showed antipredator behaviours only in the original nest site in which they laid eggs, even after we removed all of the eggs or substituted them with those of a conspecific; (ii) protect any eggs present inside the original nest site (even when the eggs belong to a conspecific); and (iii) develop this behaviour while gravid (i.e. prior to laying eggs). This supports the hypothesis that long-tailed skinks cannot recognize their own eggs, suggesting that maternal care is a directed form of territoriality only expressed towards egg-eating snakes and only during reproduction. Nest guarding is among the most primitive forms of parental care, and the recent evolution of this behaviour in a single population provides insight into one of the mechanisms by which parental care can originate in terrestrial vertebrates.

Reversible inhibition of tomato fruit senescence by antisense RNA.

Ethylene controls fruit ripening. Expression of antisense RNA to the rate-limiting enzyme in the biosynthetic pathway of ethylene, 1-aminocyclopropane-1-carboxylate synthase, inhibits fruit ripening in tomato plants. Administration of exogenous ethylene or propylene reverses the inhibitory effect. This result demonstrates that ethylene is the trigger and not the by-product of ripening and raises the prospect that the life-span of plant tissues can be extended, thereby preventing spoilage.

Phosphonate analogues of pyruvate. Probes of substrate binding to pyruvate oxidase and other thiamin pyrophosphate-dependent decarboxylases.

A number of enzymes catalyze the removal of carbon dioxide from pyruvate through covalent participation of the coenzyme thiamin pyrophosphate. The conversions of the decarboxylated adduct, hydroxyethyl thiamin pyrophosphate, to subsequent products distinguishes the function of these enzymes. Acetaldehyde is produced by pyruvate decarboxylase, acetic acid by pyruvate oxidase and acetyl coenzyme A by pyruvate dehydrogenase. Differences and details of steps prior to decomposition of hydroxyethyl thiamin pyrophosphate can be evaluated through the use of two substrate analogues, methyl acetylphosphonate and acetylphosphonate. Methyl acetylphosphonate and acetylphosphonate are competitive inhibitors toward pyruvate with Escherichia coli pyruvate oxidase and E. coli pyruvate dehydrogenase but the value of the Ki for the oxidase is more than three orders of magnitude higher than for the dehydrogenase. Yeast pyruvate decarboxylase is not inhibited at all under the same conditions. The binding of methyl acetylphosphonate results in ligand-induced changes in the near ultraviolet circular dichorism spectrum of the oxidase. This spectral perturbation is only seen in the presence of the cofactor, thiamin pyrophosphate, strongly suggesting that the inhibitor is binding at the same site as the substrate, pyruvate, on the enzyme. Kinetic data suggest that lipid activators of pyruvate oxidase increase the affinity of the enzyme for pyruvate and its analogues.

An elevated PSA, which normalizes, does not exclude the presence of prostate cancer.

The purpose of this study was to determine the incidence of prostate cancer in patients who have an elevated referral prostate-specific antigen (PSA), which subsequently falls to within their normal age-specific reference range prior to prostate biopsy. The study demonstrated that of the 160 patients recruited, 21 (13%) had a repeat PSA level which had fallen back to within their normal range. Five of these 21 patients (24%) were diagnosed with prostate cancer following biopsy, two of whom had a benign prostate examination. The study, therefore, demonstrates that normalisation of the PSA level prior to biopsy does not exclude the presence of prostate cancer even when the prostate feels benign.

The time course of the strial changes produced by intravenous furosemide.

The ultrastructural abnormalities produced in the stria vascularis by intravenous furosemide (80 mg/kg) were investigated in 14 guinea pigs. The changes consisted of marginal cell swelling, shrinkage of the intermediate cells and enlargement of the intercellular spaces, as described in other intoxications. The cytological derangements (including characteristic dilatation of the Golgi membranes) differed in detail from those arising after a comparable dose of ethacrynic acid. The morphological alterations were already present at 2 min, were maximal at 10 min, recovered only slowly at first and had not disappeared entirely at 180 min. For comparison, the fall in the endocochlear potential had a latent period of 20 s and was greatest at 2.3 min; its recovery was rapid initially but also incomplete at 180 min. Thus, no gross discrepancy in the time courses occurred, even if the correlation was imperfect. That reported previously must be due, therefore, to the much longer delays found following intraperitoneal administration.

Using qualitative methods to evaluate health service delivery in three rural Colorado communities.

Qualitative and quantitative methods can be used simultaneously for hypothesis generation and testing. A pilot study was conducted in 1991 in three rural Colorado communities to clarify health service delivery problems related to cancer. The analysis focused on the perceptions of three types of respondents in each community related to whether cancer was a major problem, whether health services were adequate in their community, and what perceived solutions could be implemented. Respondents included community influentials, health care providers, and cancer patients or family members. Semistructured phone interviews were used to collect perceptions of these community members. Transcripts from the three communities were combined, coded, and tallied. Several distinct themes emerged from the analysis. These included: cancer was a major problem; public and provider education was needed; community systems and support to identify and solve health problems were lacking; medical networking needed to be expanded; transportation was a problem for remote communities; inability to pay for services was a problem for rural communities. Most respondents identified the problems as relevant to other chronic and acute diseases as well as cancer. This method identified the critical problems for the majority of the people without losing sight of the outlier responses.