Merri Creek: Managing an urban waterway for people and nature

The restoration of Melbourne's Merri Creek demonstrates the potential for achieving environmental improvements through a process that integrates the technical, ecological and social aspects.     

Leukocyte adhesion molecule expression during intense resistance exercise

We hypothesized that expression of L-selectinand very late antigen-4 (VLA-4) integrin adhesionmolecules would influence cell type-specific redistribution duringexercise. Women subjects performed six sets of 10-repetition maximumsquats. L-selectin and VLA-4 integrin were measured by using flowcytometry pre- and postexercise on peripheral blood neutrophils andlymphocytes (n = 29 subjects) andlymphocyte subsets (n = 70 subjects),respectively. Neutrophil concentration increased 41.8%(P < 0.001), whereas the percentexpressing L-selectin was unchanged (79%). Lymphocyte concentrationincreased 61.8% (P < 0.001). Thepercent of T cells expressing L-selectin decreased from 73.5 ± 8.9 to 68.2 ± 11.4% (P < 0.001); the combined population of natural killer and B cells expressing L-selectin decreased from 80.4 ± 22.5 to 62.7 ± 25.8% (P < 0.001).VLA-4 integrin was expressed by nearly all lymphocytes both pre- andpostexercise. The proportional decrease in L-selectin positive cellscould have resulted from 1) sheddingof L-selectin, 2) selective entry ofL-selectin-negative subsets, or 3)selective removal of L-selectin-positive subsets.

     

Biphasic effect of cryosurgery of the prostate on lymphocyte proliferation

In a preliminary study, cryosurgery of the prostate in patients with prostatic cancer has been observed to possess a biphasic effect on the proliferative responsiveness of peripheral blood lymphocytes (PBL) to the plant mitogen, phytohaemagglutinin. Phytohaemagglutinin-stimulated PBL cultured in autologous serum obtained up to 1 week postoperatively showed reduction from their preoperative levels. In contrast, cultures in homologous serum showed increased responsiveness following cryosurgery. Although depression of lymphocyte proliferation in autologous serum was transitory, gradually returning to approximate or exceeding levels of lymphocytic reactivity observed preoperatively, such depression may facilitate reduced host surveillance to potential infectious agents and to metastatic tumour cells, leading to an alteration of tumour-host homeostasis. Further studies will be required to delineate the possible clinical significance of the present observations.     

Time dependent model for hemoglobin and allosteric enzymes. II

The time-dependent theory developed in Part I is specialized to treat tetrameric hemoglobin, and the results of the theory for dimeric-and tetrameric hemoglobin are compared with data on the kinetics of the reactions of hemoglobin with carbon monoxide and oxygen at various salt concentrations for the case of large concentration of ligand relative to that of hemoglobin. The fit of the theoretical results to the data suggests that hemoglobin at a 2 M salt concentration is predominantly dimeric and that the tetramer should be taken as the functional unit to explain the kinetics of the reactions of normal hemoglobin. A relationship is established between the time-dependent theory arid Adair's Intermediate Compound Hypothesis (I.C.H.) for hemoglobin, as brought to its present state by Gibson and Roughton. A generalization (G.I.C.H.) of the I.C.H. is presented and is shown to be equivalent to the time-dependent theory in the limit of infinite ligand concentration. The I.C.H. is shown to be an excellent approximation to the centralized theory (G.I.C.H.) in this limit.     

The response by microorganisms to steady state growth in controlled concentrations of oxygen and glucose. I. Candida utilis

Dissolved oxygen and glucose concentrations have been independently maintained at various concentrations for extended periods during growth of Candida utilis in continuous culture. Simultaneous observations of cytochrome concentration, growth rate, rates of uptake of oxygen and glucose and rates of production of CO₂, ethanol and acid have been made during steady states at various levels of oxygen and glucose. There is an inverse relationship between dissolved oxygen and cytochrome and between glucose cocentration and cytochrome. Studies of the transient state following a step change from high to low dissolved oxygen show that there is a lag of about 10 hr during which there is no change in the above parameters. This is followed by rapid oscillatory changes in cytochrome content and a change to a more fermentative metabolism.     

Circular dichroism of beta turns in peptides and proteins.

Circular dichroism (CD) spectra are reported for two groups of cyclic hexapeptides having beta turns whose geometry can be firmly established by X-ray crystallography and by NMR spectroscopy. One series contains the sequence L-Pro-D-Phe in the geometry of the classical type II beta turn, while the second group has the sequence D-Phe-L-Pro in the closely related geometry of the gramicidin S turn. CD data on the hydrogenated peptides show that in neither series do Cotton effects due to the aromatic phenylalanyl chromophore make a significant contribution to the spectra in the 195--240-nm region. In spite of the close geometric similarity of the beta turns of these two groups of peptides, their CD spectra are quite distinct. Furthermore, comparison of our data with the CD spectra of published models for beta-turn structures suggests that it may not be possible to characterize the contribution of all beta turns to the CD spectra of proteins by a single model curve. the CD spectra of model beta turns will be more useful in characterizing the folding of oligopeptides and sequence polypeptides, where a single type of turn is present.