The "fire stick farming" hypothesis: Australian Aboriginal foraging strategies, biodiversity, and anthropogenic fire mosaics.

Aboriginal burning in Australia has long been assumed to be a "resource management" strategy, but no quantitative tests of this hypothesis have ever been conducted. We combine ethnographic observations of contemporary Aboriginal hunting and burning with satellite image analysis of anthropogenic and natural landscape structure to demonstrate the processes through which Aboriginal burning shapes arid-zone vegetational diversity. Anthropogenic landscapes contain a greater diversity of successional stages than landscapes under a lightning fire regime, and differences are of scale, not of kind. Landscape scale is directly linked to foraging for small, burrowed prey (monitor lizards), which is a specialty of Aboriginal women. The maintenance of small-scale habitat mosaics increases small-animal hunting productivity. These results have implications for understanding the unique biodiversity of the Australian continent, through time and space. In particular, anthropogenic influences on the habitat structure of paleolandscapes are likely to be spatially localized and linked to less mobile, "broad-spectrum" foraging economies.

Palliative treatment of esophageal carcinoma using esophageal dilation and prosthesis.

Esophageal cancer is incurable in most patients. Tumor anatomy must be carefully defined using radiographic and endoscopic techniques. These techniques can also provide useful information to plan palliative treatment. The goals of palliation must be explicitly discussed and defined with the patient and family. Palliative manipulation is best done by a physician with experience in the procedures, after consideration of all available options to ensure effective palliation with minimal risk of complications. Esophageal dilation is an integral part of most palliative treatment programs, either as sole or adjunctive therapy. Dilation can maintain luminal patency in most patients and can be performed easily, effectively, and safely in an outpatient setting. An esophageal prosthesis can further alleviate symptoms in patients in whom more conventional palliative techniques are unsuccessful. Because prosthesis placement is associated with a relatively high rate of complications, it should be reserved for patients with advanced refractory disease or tracheo-esophageal fistula, for whom no other palliative alternatives exist.

Changing patterns of proteoglycan synthesis during chondrogenic differentiation.

The pattern of proteoglycan synthesis was examined in the cartilages of the anterior and the posterior limbs, the vertebra and the sterna of the developing chick embryo, during chondrogenic differentiation. At stage 18, the limb primordia synthesize small monomeric proteoglycans. In all nine cartilages examined, there was a shift during differentiation from small to larger intermediate forms followed by a transition toward the aggregate forms. As development proceeds, the proportion of aggregates increases and the small proteoglycans almost disappear. Chondrogenic differentiation is thus marked by a increase in the size of the proteoglycan molecules, and an increase in the proportion of the large proteoglycan aggregates.

Electrophysiological effects of antidepressants on mammalian hearts and crayfish giant axon.

Cardiotoxicity is known to occur in patients with or without preexisting cardiac diseases during treatments with the tricyclic antidepressants, amitriptyline and imipramine. The antiarrhythmic action of tricyclics was also demonstrated in clinical studies and in animal experiments. Bupropion, a novel antidepressant, is being studied in man and to date has been found to be effective and devoid of cardiovascular toxicity. This study was intended to show the direct effect of tricyclic antidepressants on excitable membrane and to compare their potential toxicity with bupropion in isolated tissues. In crayfish giant axon, all antidepressants exhibited local anesthetic-like action by reducing the action potential amplitude and maximal rate of upstroke (dv/dt). The tricyclics slowed spontaneous sinus discharges in rat atrium and prolonged the duration of evoked action potential in guinea pig atrium with a concomitant decrease in dv/dt. A quinidine-like action of the tricyclic agents is displayed in the termination of spontaneous depolarization and the suppression of dv/dt of evoked action potential in canine Purkinje fibers. The membrane depressant action of antidepressants resulted in the reduction of dv/dt and increased membrane refractoriness in both atrial and ventricular tissues; excitation is blocked even when resting membrane potential remained fully polarized. The present results confirmed the direct quinidine-like action on cardic tissues, which is probably related to the antiarrhythmic and/or cardiotoxic manifestation in man and animals. On on excitable tissues studied, tricyclic antidepressants are the most potent in blocking membrane excitation, while bupropion is the least toxic on the molar basis.

Identification and characterization of a novel gene that is upregulated in leukaemia cells by nitric oxide.

Nitric oxide (NO) inhibits growth and induces differentiation in acute myeloid leukaemia (AML) cells. To identify genes associated with these processes, we studied the effect of NO on AML gene expression using the technique of Representational Difference Analysis. Exposure of HL-60 cells to the NO donor DETA-NO for 24 h induced the expression of a novel gene that was named rno (regulated by nitric oxide). Treatment of HL-60 cells with dimethyl sulphoxide induced expression of rno, but treatment with Vitamin D3 or all-trans retinoic acid did not. Upregulation of rno by NO was cGMP independent. Northern blot analysis indicated that constitutive expression of the novel gene was limited to leucocytes. Three isoforms of rno were identified. An rno cDNA clone was obtained by screening a human leucocyte library. The nucleotide sequence of the open reading frame shared significant homology with that of the human ribonuclease/angiogenin inhibitor (RI). The predicted amino acid sequence indicated that, like RI, rno is leucine and cysteine rich and is comprised of a series of repetitive elements (leucine-rich repeats) that may mediate macromolecular interactions. Enhancement of expression of rno may be a component of the process by which differentiation and growth inhibition of leukaemia cells is induced by NO.