Architecture and morphogenesis of grain sorghum, Sorghum bicolor (L.) Moench

Plant architecture has been neglected in most studies of biomass allocation in crops. To help redress this situation for grain sorghum (Sorghum bicolor (L.) Moench), we used a 3D digitiser to measure the dimensions and orientations of vegetative and reproductive structures and derived thermal time-based functions for architectural changes during morphogenesis. Our plants, which were grown in a greenhouse, controlled environment cabinets and the field, covered a large, three-fold, size range when mature. This allowed us to detect some general architectural relationships and to fit morphogenetic functions common across the size range we observed. For example, the relationship between the lengths of successive fully-expanded leaves within a plant was nearly constant for all plants. The lengths of existing leaf blades were accurate predictors of the lengths of up to six subsequently-formed blades in our plants. Similar constant relationships were detected for internode lengths in the panicle and for heights above ground of the collars of successive leaves, even though these traits varied a lot between growth conditions. We suggest that such architectural relationships may be used to link the effect of previous growth conditions to future growth potential, and in that way to predict future partitioning. Our results provide the basis for a preliminary model of sorghum morphogenesis which could eventually become useful in conjunction with crop models by allowing resource acquisition to be related to changes in plant architecture during development. (C) 1999 Elsevier Science B.V. All rights reserved.

Effects of medium thermoelasticity on high Rayleigh number steady-state heat transfer and mineralization in deformable fluid-saturated porous media heated from below

In this paper, a solution method is presented to deal with fully coupled problems between medium deformation, pore-fluid flow and heat transfer in fluid-saturated porous media having supercritical Rayleigh numbers. To validate the present solution method, analytical solutions to a benchmark problem are derived for some special cases. After the solution method is validated, a numerical study is carried out to investigate the effects of medium thermoelasticity on high Rayleigh number steady-state heat transfer and mineralization in fluid-saturated media when they are heated from below. The related numerical results have demonstrated that: (1) medium thermoelasticity has a little influence on the overall pattern of convective pore-fluid flow, but it has a considerable effect on the localization of medium deformation, pore-fluid flow, heat transfer and mineralization in a porous medium, especially when the porous medium is comprised of soft rock masses; (2) convective pore-fluid flow plays a very important role in the localization of medium deformation, heat transfer and mineralization in a porous medium. (C) 1999 Elsevier Science S.A. All rights reserved.

Low-molecular-weight peptidic and cyclic antagonists of the receptor for the complement factor C5a

Activation of the human complement system of plasma proteins during immunological host defense can result in overproduction of potent proinflammatory peptides such as the anaphylatoxin C5a. Excessive levels of C5a are associated with numerous immunoinflammatory diseases, but there is as yet no clinically available antagonist to regulate the effects of C5a. We now describe a series of small molecules derived from the C-terminus of C5a, some of which are the most potent low-molecular-weight C5a receptor antagonists reported to date for the human polymorphonuclear leukocyte (PMN) C5a receptor. H-1 NMR spectroscopy was used to determine solution structures for two cyclic antagonists and to indicate that antagonism is related to a turn conformation, which can be stabilized in cyclic molecules that are preorganized for receptor binding. While several cyclic derivatives were of similar antagonistic potency, the most potent antagonist was a hexapeptide-derived macrocycle AcF[OPdChaWR] with an IC50 = 20 nM against a maximal concentration of C5a (100 nM) on intact human PMNs. Such potent C5a antagonists may be useful probes to investigate the role of C5a in host defenses and to develop therapeutic agents for the treatment of many currently intractable inflammatory conditions.

An "openable," high-strength gradient set for orthopedic MRI

A novel three-axis gradient set and RF resonator for orthopedic MRT has been designed and constructed. The set is openable and may be wrapped around injured joints. The design methodology used was the minimization of magnetic field spherical harmonics by simulated annealing. Splitting of the longitudinal coil presents the major design challenge to a fully openable gradient set and in order to efficiently design such coils, we have developed a new fast algorithm for determining the magnetic field spherical harmonics generated by an are of multiturn wire. The algorithm allows a realistic impression of the effect of split longitudinal designs. A prototype set was constructed based on the new designs and tested in a 2-T clinical research system. The set generated 12 mT/m/A with a linear region of 12 cm and a switching time of 100 mu s, conforming closely with theoretical predictions. Preliminary images from the set are presented. (C) 1999 Academic Press.

Freeform fabrication of functional aluminium prototypes using powder metallurgy

Freeform fabrication methods allow the direct formation of parts built layer by layer, under the control of a CAD drawing. Most of these methods form parts in thermoplastic or thermoset polymers, but there would be many applications for freeform fabrication of fully functional metal or ceramic parts. We describe here the freeforming of sinterable aluminium alloys. In addition, the building approach allows different materials to be positioned within a monolithic part for an optimal combination of properties. This is illustrated here with the formation of an aluminium gear with a metal-matrix composite wear surface. (C) 1999 Kluwer Academic Publishers.

Changing patterns of coronary heart disease in the hunter region of New South Wales, Australia

A population-based observational study of men acid women aged 35-69 years in the Hunter Region of New South Wales, Australia, was conducted to assess the impact. of risk-factor modification and increased drug therapy on the trends in major coronary events and case fatality. From 1985 to 1993, there were 3006 coronary deaths and 6450 nonfatal major coronary events. Rates of death and nonfatal myocardial infarction declined, but there was an increase in hospital admissions for prolonged chess pain. Reductions in cigarette smoking, diastolic blood pressure, total cholesterol, and increased use of aspirin can fully explain the 3.3% (95% confidence interval [CI] 2.4, 4.2) average annual reduction in rates of major coronary events for men and the 4.1% (95% CI 2.7, 5.5) reduction for women. In contrast, increased use of aspirin, beta-blockers, fibrinolytic therapy, and angiotensin-converting enzyme inhibitors explain less than hall of the 8.9% (95% CI 5.9, 11.8) and 6.9% (95% CI 2.7, 10.9) average annual reduction in case fatality in hospital for men and women, respectively. These trends suggest a decline in severity of coronary heart disease consistent with reductions in risk-factor levels and improved acute medical treatment. J CLIN EPIDEMIOL 52;8:761-771, 1999. (C) 1999 Elsevier Science Inc.

Quasispin graded-fermion formalism and gl(m vertical bar n)down arrow osp(m vertical bar n) branching rules

The graded-fermion algebra and quasispin formalism are introduced and applied to obtain the gl(m\n)down arrow osp(m\n) branching rules for the two- column tensor irreducible representations of gl(m\n), for the case m less than or equal to n(n > 2). In the case m < n, all such irreducible representations of gl(m\n) are shown to be completely reducible as representations of osp(m\n). This is also shown to be true for the case m=n, except for the spin-singlet representations, which contain an indecomposable representation of osp(m\n) with composition length 3. These branching rules are given in fully explicit form. (C) 1999 American Institute of Physics. [S0022-2488(99)04410-2].

GABA receptors inhibited by benzodiazepines mediate fast inhibitory transmission in the central amygdala

The amygdala is intimately involved in emotional behavior, and its role in the generation of anxiety and conditioned fear is well known. Benzodiazepines, which are commonly used for the relief of anxiety, are thought to act by enhancing the action of the inhibitory transmitter GABA. We have examined the properties of GABA-mediated inhibition in the amygdala. Whole-cell recordings were made from neurons in the lateral division of the central amygdala. Application of GABA evoked a current that reversed at the chloride equilibrium potential. Application of the GABA antagonists bicuculline or SR95531 inhibited the GABA-evoked current in a manner consistent with two binding sites. Stimulation of afferents to neurons in the central amygdala evoked an IPSC that was mediated by the release of GABA. The GABA(A) receptor antagonists bicuculline and picrotoxin failed to completely block the IPSC. The bicuculline-resistant IPSC was chloride-selective and was unaffected by GABA(B)-receptor antagonists. Furthermore, this current was insensitive to modulation by general anesthetics or barbiturates. In contrast to their actions at GABA(A) receptors, diazepam and flurazepam inhibited the bicuculline-resistant IPSC in a concentration-dependent manner. These effects were fully antagonized by the benzodiazepine site antagonist Ro15-1788. We conclude that a new type of ionotropic GABA receptor mediates fast inhibitory transmission in the central amygdala. This receptor may be a potential target for the development of new therapeutic strategies for anxiety disorders.

PAM chlorophyll fluorometry: a new in situ technique for stress assessment in scleractinian corals, used to examine the effects of cyanide from cyanide fishing

Sodium cyanide is being used on reefs in the Asia-Pacific region to capture live fish for the aquarium industry, and to supply a rapidly growing, restaurant-based demand, The effects of cyanide on reef biota have not been fully explored. To investigate its effect on hard corals, we exposed small branch lips of Stylophora pistillata and Acropora aspera to cyanide concentrations estimated to occur during cyanide fishing. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques were used to examine photoinhibition and photosynthetic electron transport in the symbiotic algae (zooxanthellae) in the tissues of the corals, These measurements were made in situ and in real time using a recently developed submersible PAM fluorometer. In S. pistillata. exposure to cyanide resulted in an almost complete cessation in photosynthetic electron transport rate. Both species displayed marked decreases in the ratio of variable fluorescence (F-v) to maximal fluorescence (F-m) (dark-adapted F-v/F-m), following exposure to cyanide, signifying a decrease in photochemical efficiency. Dark-adapted F-v/F-m recovered to normal levels in similar to 6 d, although intense tissue discolouration, a phenomenon well-recognised as coral 'bleaching' was observed during this period, Bleaching was caused by loss of zooxanthellae from the coral tissues, a well-recognised sub-lethal stress response of corals. Using the technique of chlorophyll fluorescence quenching analysis, corals exposed to cyanide did not show light activation of Calvin cycle enzymes and developed high levels of non-photochemical quenching (q(N)), signifying the photoprotective dissipation of excess light as heat, These features are symptomatic of the known properties of cyanide as an inhibitor of enzymes of the Calvin cycle. The results of this in situ study show that an impairment of zooxanthellar photosynthesis is; the site of cyanide-mediated toxicity, and is the cue that causes corals to release their symbiotic zooxanthellac following cyanide exposure. This study demonstrates the efficacy of PBM fluorometry as a new tool for in situ stress assessment in zooxanthellate scleractinian corals. (C) 1999 Elsevier Science Ltd. All rights reserved.

Thermal and radiation curing of phenylethynyl terminated macromers

The thermal and gamma-irradiation induced curing of two phenylethynyl terminated composite resin systems, DFB/BPF and PETI5A, was investigated. Thermal curing of these matrix resin samples was performed at a temperature of 360 degrees C, gamma irradiation of the samples was conducted at 300 degrees C at a dose rate of 2.2 kGy h(-1). The reaction and subsequent loss of ethynyl groups in the resins for both cure methods was demonstrated by observing the decrease of the 2215 cm(-1) peak in the Raman spectra of the resins. Fully cured resin samples were found to have glass transition temperatures of 244-246 degrees C and 278-280 degrees C for DFB/BPF and PETI5A respectively. Similar relationships between T-g and fractional conversion were observed in both resins. The apparent polymerization rate, R-p, for thermal cure at 360 degrees C, was found to be 4.79 x 10(-2)% s(-1) in PETI5A and 3.22 x 10(-2)% s(-1) in DFB/BPF. Catastrophic degradation under nitrogen was observed to commence near 450 degrees C and 530 degrees C, with 5% weight losses occurring at 455 degrees C and 540 degrees C for DFB/BPF and PETI5A respectively. Gamma radiation induced cure at 300 degrees C was shown to be feasible, with full cure being reached with doses of 40 kGy for DFB/BPF and 100 kGy for PETI5A.

The influence of supra-optimal root-zone temperatures on growth and stomatal conductance in Capsicum annuum L.

Pepper (Capsicum annuum L.) plants were grown aeroponically in a Singapore greenhouse under natural diurnally fluctuating ambient shoot temperatures, but at two different root-zone temperatures (RZTs): a constant 20 +/- 2 degrees C RZT and a diurnally fluctuating ambient (A) (25-40 degrees C) RZT, Plants grown at 20-RZT had more leaves, greater leaf area and dry weight than A-RZT plants. Reciprocal transfer experiments were conducted between RZTs to investigate the effect on plant growth, stomatal conductance (g(s)) and water relations. Transfer of plants from A-RZT to 20-RZT increased plant dry weight, leaf area, number of leaves, shoot water potential (Psi(shoot)), and g(s); while transfer of plants from 20-RZT to A-RZT decreased these parameters. Root hydraulic conductivity was measured in the latter transfer and decreased by 80% after 23 d at A-RZT. Transfer of plants from 20-RZT to A-RZT had no effect on xylem ABA concentration or xylem nitrate concentration, but reduced xylem sap pH by 0.2 units. At both RZTs, g(s) measured in the youngest fully expanded leaves increased with plant development. In plants with the same number of leaves, A-RZT plants had a higher g(s) than 20-RZT plants, but only under high atmospheric vapour pressure deficit. The roles of chemical signals and hydraulic factors in controlling g(s) of aeroponically grown Capsicum plants at different RZTs are discussed.

Marine protected areas for spatially structured exploited stocks

Many harvested marine and terrestrial populations have segments of their range protected in areas free from exploitation. Reasons for areas being protected from harvesting include conservation, tourism, research, protection of breeding grounds, stock recovery, harvest regulation, or habitat that is uneconomical to exploit. In this paper we consider the problem of optimally exploiting a single species local population that is connected by dispersing larvae to an unharvested local population. We define a spatially-explicit population dynamics model and apply dynamic optimization techniques to determine policies for harvesting the exploited patch. We then consider how reservation affects yield and spawning stock abundance when compared to policies that have not recognised the spatial structure of the metapopulation. Comparisons of harvest strategies between an exploited metapopulation with and without a harvest refuge are also made. Results show that in a 2 local population metapopulation with unidirectional larval transfer, the optimal exploitation of the harvested population should be conducted as if it were independent of the reserved population. Numerical examples suggest that relative source populations should be exploited if the objective is to maximise spawning stock abundance within a harvested metapopulation that includes a protected local population. However, this strategy can markedly reduce yield over a sink harvested reserve system and may require strict regulation for conservation goals to be realised. If exchange rates are high, results indicate that spawning stock abundance can be less in a reserve system than in a fully exploited metapopulation. In order to maximise economic gain in the reserve system, results indicate that relative sink populations should be harvested. Depending on transfer levels, loss in harvest through reservation can be minimal, and is likely to be compensated by the potential environmental and economic benefits of the reserve.

Effect of coinfection with STDs and of STD treatment on HIV shedding in genital-tract secretions - Systematic review and data synthesis

Objective: To determine whether coinfection with sexually transmitted diseases (STD) increases HIV shedding in genital-tract secretions, and whether STD treatment reduces this shedding. Design: Systematic review and data synthesis of cross-sectional and cohort studies meeting. predefined quality criteria. Main Outcome Measures: Proportion of patients with and without a STD who had detectable HIV in genital secretions, HIV toad in genital secretions, or change following STD treatment. Results: Of 48 identified studies, three cross-sectional and three cohort studies were included. HIV was detected significantly more frequently in participants infected with Neisseria gonorrhoeae (125 of 309 participants, 41%) than in those without N gonorrhoeae infection (311 of 988 participants, 32%; P = 0.004). HIV was not significantly more frequently detected in persons infected with Chlamydia trachomatis (28 of 67 participants, 42%) than in those without C trachomatis infection (375 of 1149 participants, 33%; P = 0.13). Median HIV load reported in only one study was greater in men with urethritis (12.4 x 10(4) versus 1.51 x 10(4) copies/ml; P = 0.04). In the only cohort study in which this could be fully assessed, treatment of women with any STD reduced the proportion of those with detectable HIV from 39% to 29% (P = 0.05), whereas this proportion remained stable among controls (15-17%), A second cohort study reported fully on HIV load; among men with urethritis, viral load fell from 12.4 to 4.12 x 10(4) copies/ml 2 weeks posttreatment, whereas viral load remained stable in those without urethritis. Conclusion: Few high-quality studies were found. HIV is detected moderately more frequently in genital secretions of men and women with a STD, and HIV load is substantially increased among men with urethritis, Successful STD treatment reduces both of these parameters, but not to control levels. More high-quality studies are needed to explore this important relationship further.

The binding of closantel to ovine serum albumin, and homogenate fractions of Haemonchus contortus

Closantel binds to the serum proteins of the host and affects blood sucking parasites when they ingest the brood of treated hosts. Closantel binds specifically to ovine serum albumin (K-a of 9.3 x 10(6)M(-1)) at site I, the warfarin/phenylbutazone binding site of albumin Closantel also binds to invertebrate haemocyanin and haemolymph. The strongest binding of closantel in homogenates of H. contortus is found in fractions containing soluble proteins. This binding is of low affinity and, because the site itself is not fully denaturable, it may not be proteinaceous. There is no detectable difference in binding affinity between homogenate fractions from closantel susceptible and resistant isolates of adult or larval worms suggesting that closantel resistance is not due to changes in the closantel receptor or carrier. (C) 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

Regarding "Edema and leg volume: Methods of assessment" (Letters to the Editor)

I noted with interest the article by Drs Perrin and Guex, entitled &dquo;Edema and leg volume: Methods of assessment,&dquo; published in Angiology 51:9-12, 2000. This was a timely and comprehensive review of the various methods in clinical use for the assessment of peripheral edema, notably in the leg. I would like to take this opportunity to alert readers to a further technique useful for this purpose, namely, bioelectrical impedance analysis. An early reportl described its use for the measurement of edema in the leg, but other than its successful use for the assessment of edema in the arm following masteCtoMy,2,1 the potential of the method remains to be fully realized. This is unfortunate since the method directly and quantifiably measures edema.