<Superscript>15</Superscript>N natural abundance of fossil peat reflects the influence of animal-derived nitrogen on vegetation

'¹⁵N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '¹⁵N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '¹⁵N signatures of peat layers. At two sites ¹⁵N-enriched peat '¹⁵N signatures of up to +17‰ were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '¹⁵N. Less ¹⁵N enriched '¹⁵N signatures (e.g. -1.9‰ to +3.9‰) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that ¹⁵N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology.     

What are mycoplasmas: the relationship of tempo and mode in bacterial evolution

In phenotype the mycoplasmas are very different from ordinary bacteria. However, genotypically (i.e., phylogenetically) they are not. On the basis of ribosomal RNA homologies the mycoplasmas belong with the clostridia, and indeed have specific clostridial relatives. Mycoplasmas are, however, unlike almost all other bacteria in the evolutionary characteristics of their ribosomal RNAs. These RNAs contain relatively few of the highly conserved oligonucleotide sequences characteristic of normal eubacterial ribosomal RNAs. This is interpreted to be a reflection of an elevated mutation rate in mycoplasma lines of descent. A general consequence of this would be that the variation associated with a mycoplasma population is augmented both in number and kind, which in turn would lead to an unusual evolutionary course, one unique in all respects. Mycoplasmas, then, are actually tachytelic bacteria. The unusual evolutionary characteristics of their ribosomal RNAs are the imprints of their rapid evolution.     

Changes in viscoelastic properties of rat lung parenchymal strips with maturation.

The lung extracellular matrix changes rapidly with maturation. To further our understanding of the mechanisms underlying lung tissue mechanics, we studied age-related changes in mechanical properties in lung parenchymal strips from baby (10-15 days old), young ( approximately 3 wk old), and adult ( approximately 8 wk old) rats. Subpleural strips were cut and suspended in a fluid-filled organ bath. One end of the strip was attached to a force transducer and the other to a servo-controlled lever arm. Measurements of force (F) and length (L) were recorded during sinusoidal oscillations of various amplitudes and frequencies. Resistance modulus (R) and elastance modulus (E) were estimated by fitting the equation of motion to changes in stress (T) and stretch ratio (lambda). Hysteresivity (eta) was calculated as follows: eta = (R/E)2pif, where f is frequency. Slow-cycling T-lambda curves were measured by applying a constant slow length change. Finally, quasi-static T-lambda curves were measured as stress was increased from 0 to 6 kPa and back to 0 kPa in stepwise increments. Our results showed that lung tissue from immature rats was stiffer and less hysteretic than tissue from more mature animals. In addition, tissue from baby animals behaved in a manner compatible with an increased vulnerability to plastic change.     

Activating and 'anxiogenic' effects of corticotropin releasing factor are not inhibited by blockade of the pituitary-adrenal system with dexamethasone

Central administration of corticotropin releasing factor (CRF) in rats produces pituitary-adrenal activation and a variety of "anxiogenic-like" effects. The present study was designed to explore the contribution of the peripheral pituitary-adrenocortical axis in mediating these CRF responses. Intraventricularly administered CRF produced suppression of responding in the conflict test and a marked locomotor activation. Neither behavioral effect was altered by the prior administration of dexamethasone in a dose that blocked pituitary-adrenal activation to CRF. These results support the hypothesis that behavioral effects of CRF are mediated by its action at central sites and not via an action on the pituitary-adrenocortical system.     

Rhizobium sp. strain ORS571 grows synergistically on N2 and nicotinate as N sources.

Rhizobium sp. strain ORS571 conducts synergistic, free-living N2 fixation and nicotinate oxidation. Explicitly, ORS571 is able to fix N2 aerobically because 6-OH-nicotinate acts as an intracellular O2 sink. Because 6-OH-nicotinate oxidation is mandatory for aerobic, free-living N2 fixation and because the synergistic processes yield ammonium from substrates (as the nitrogen source for growth), ORS571 is not a diazotroph.     

Partitioning of pulmonary resistance during constriction in the dog: effects of volume history

We assessed the relative changes in airways and lung tissue with bronchoconstriction, and the changes in each during and following a deep inhalation (DI). We partitioned pulmonary resistance (RL) into airway (Raw) and tissue (Vtis) components using alveolar capsules in 10 anesthetized, paralyzed, and open-chested dogs ventilated sinusoidally with 350-ml breaths at 1 Hz. We made measurements before and during bronchoconstriction induced by vagal stimulation or inhalation of histamine or prostaglandin F2 alpha (PGF2 alpha), each of which decreased dynamic compliance by approximately 40%. With histamine and PGF2 alpha the rise in RL was predominantly due to Vtis. With vagal stimulation there was a relatively greater increase in Raw than Vtis. At higher lung volumes, Vtis increases offset falls in Raw, producing higher RL at these volumes before and during constriction with PGF2 alpha and histamine. During constriction with vagal stimulation, the fall in Raw with inflation overrode the rise in Vtis, resulting in a lower RL at the higher compared with the lower lung volume. The changes seen after a DI in the control and constricted states were due to alterations in tissue properties, both viscous and elastic. However, the relative hysteresis of the airways and parenchyma were equal, since Raw, our index of airway size, was unchanged after a DI.     

Use of monoclonal antibodies as a diagnostic tool in human leukemia. I. Acute myeloid leukemia and acute phase of chronic myeloid leukemia

Various monoclonal antibodies (mAbs) detecting certain different epitopes on myeloid cells (VIMD5, D5 D6, OKM1, Leu-M3, VIEG4, OKIa 1) have been used in combination with conventional markers (antihuman myeloid hetero-antiserum, FcIgG-receptors, C3d-receptors) to further define the phenotypic heterogeneity of myeloid leukemia. Subsequent leukemic samples from previously untreated patients with acute myeloid leukemia (AML) (51 adults, 24 children) and from nine adult patients in the acute phase of chronic myeloid leukemia (CML-BC) were studied. It was possible to demonstrate quantitative differences in the expression of antigens on the various leukemia subtypes which could be exploited for diagnosis. Furthermore our results revealed that there is a very close correlation between the different surface phenotypes and the types morphologically assessed according to FAB-criteria.     

Relationship between soluble tumor necrosis factor (TNF) receptors and TNFα during immunotherapy with interleukin-2 and/or interferon α

Eleven metastatic cancer patients were studied during three different regimens of immunotherapy with interleukin-2 (IL-2) and/or interferon (IFN): group A received 4 days of IL-2 i.a. infusion (n=3), group B IFN s.c. during 5 days (n=4), followed on day 3 by 5 days of a continuous IL-2 i.v. infusion, and group C had 4 days of IL-2 i.v. infusion together with s.c. IFN on days 1 and 4 (n=4). Soluble tumor necrosis factor receptors (sTNFR) p55 and p75 and TNF concentrations in serum were analyzed before therapy and daily during 8 days of the first therapy cycle. sTNFR was measured by radioimmunoassay. sTNFR p55 increased in all patient groups from a baseline value of 5.2±0.9 ng/ml to a maximum of 13.6±1.2 ng/ml by days 3–4 (P=0.003). sTNFR p75 increased from 7.6±1.1 ng/ml to peak values of 30.1±2.6 ng/ml in groups A and B (P=0.02). In group C the sTNFR p75 response was weak (NS). In group B, the increase of both p55 and p75 occurred only after addition of IL-2 to IFN. TNF increased weakly during treatment with IFN alone (group B); it rose strongly during IL-2 and the combined treatment (groups A-C) from 8±2 pg/ml to 115±13 pg/ml (P=0.003). In group B, it reached the maximum 24 h after addition of IL-2 to IFN and decreased thereafter. there was a significant relationship between TNF and sTNFR p55 or sTNFR p75 in groups A and C, (P=0.001), but not in group B. Group C was also investigated during the third therapy cycle. The increase of sTNFR p75 was stronger (P=0.01) and that of TNF weaker than in the first cycle; the sTNFR p55 response was similar in both cycles. In conclusion sTNFR p55 and p75 are rapidly induced during IL-2 and IL-2+IFN treatment, the increase of sTNF receptors parallels or exceeds that of TNF and may influence the immunomodulatory effects of TNF during cytokine therapy.