Soybean root nodule ultrastructure during dark-induced stress and recovery

Summary Root-nodules of soybean plants dark-stressed for 8 days and then allowed to recover for up to 17 days were examined by transmission electron microscopy. Control nodules possessed all the ultrastructural features characteristic of infected and uninfected nodule cells. Minimal changes in the appearance of host cells and bacteroids occurred during the first four days of dark stress. After 8 days of dark stress, damage was observed in the cellular and organelle membranes; however, very few changes were observed in the bacteroids. Nodule structure continued to degrade during the first two days of recovery after which time nodules either recovered or completely degraded. In the former case, structural integrity returned to all nodule cells. In the latter case all structural integrity of the host cell disappeared; however, bacteroids appeared intact suggesting that they remained viable.Published as Paper no. 7974, Journal Series, Nebraska Agriculture Research Division.     

A scenario-based approach to modeling development: a prototype model of C. elegans vulval fate specification

Studies of developmental biology are often facilitated by diagram “models” that summarize the current understanding of underlying mechanisms. The increasing complexity of our understanding of development necessitates computational models that can extend these representations to include their dynamic behavior. Here we present a prototype model of Caenorhabditis elegans vulval precursor cell fate specification that represents many processes crucial for this developmental event but that are hard to integrate using other modeling methodologies. We demonstrate the integrative capabilities of our methodology by comprehensively incorporating the contents of three seminal papers, showing that this methodology can lead to comprehensive models of developmental biology. The prototype computational model was built and is run using a language (Live Sequence Charts) and tool (the Play-Engine) that facilitate the same conceptual processes biologists use to construct and probe diagram-type models. We demonstrate that this modeling approach permits rigorous tests of mutual consistency between experimental data and mechanistic hypotheses and can identify specific conflicting results, providing a useful approach to probe developmental systems.     

Contribution of intrinsic reactivity of the HIV-1 envelope glycoproteins to CD4-independent infection and global inhibitor sensitivity

Human immunodeficiency virus (HIV-1) enters cells following sequential activation of the high-potential-energy viral envelope glycoprotein trimer by target cell CD4 and coreceptor. HIV-1 variants differ in their requirements for CD4; viruses that can infect coreceptor-expressing cells that lack CD4 have been generated in the laboratory. These CD4-independent HIV-1 variants are sensitive to neutralization by multiple antibodies that recognize different envelope glycoprotein epitopes. The mechanisms underlying CD4 independence, global sensitivity to neutralization and the association between them are still unclear. By studying HIV-1 variants that differ in requirements for CD4, we investigated the contribution of CD4 binding to virus entry. CD4 engagement exposes the coreceptor-binding site and increases the "intrinsic reactivity" of the envelope glycoproteins; intrinsic reactivity describes the propensity of the envelope glycoproteins to negotiate transitions to lower-energy states upon stimulation. Coreceptor-binding site exposure and increased intrinsic reactivity promote formation/exposure of the HR1 coiled coil on the gp41 transmembrane glycoprotein and allow virus entry upon coreceptor binding. Intrinsic reactivity also dictates the global sensitivity of HIV-1 to perturbations such as exposure to cold and the binding of antibodies and small molecules. Accordingly, CD4 independence of HIV-1 was accompanied by increased susceptibility to inactivation by these factors. We investigated the role of intrinsic reactivity in determining the sensitivity of primary HIV-1 isolates to inhibition. Relative to the more common neutralization-resistant ("Tier 2-like") viruses, globally sensitive ("Tier 1") viruses exhibited increased intrinsic reactivity, i.e., were inactivated more efficiently by cold exposure or by a given level of antibody binding to the envelope glycoprotein trimer. Virus sensitivity to neutralization was dictated both by the efficiency of inhibitor/antibody binding to the envelope glycoprotein trimer and by envelope glycoprotein reactivity to the inhibitor/antibody binding event. Quantitative differences in intrinsic reactivity contribute to HIV-1 strain variability in global susceptibility to neutralization and explain the long-observed relationship between increased inhibitor sensitivity and decreased entry requirements for target cell CD4.     

The surgical treatment of Dupuytren's contracture: a synthesis of techniques

Dupuytren's disease is an affliction of the palmar fascia. Selective fasciectomy is recommended once contracture has occurred. Alternatives for wound closure include tissue rearrangement, the open palm technique, and full-thickness skin grafting. In this prospective study, a new "synthesis" technique was used to treat a cohort of patients with advanced Dupuytren's disease. The results were then compared with those of a second cohort of patients who underwent the open palm technique. Thirty consecutive patients were selected. Ten patients (nine men and one woman; average age, 67 years) underwent the open palm technique, and 20 patients (18 men and two women; average age, 70 years) underwent the synthesis method. Follow-up was 3.5 years for the open palm group and 2.7 years for the synthesis group. All patients in both groups improved with respect to motion, function, appearance, and satisfaction. Objectively, for the open palm technique, metacarpophalangeal joint contracture decreased from 50 degrees to 0 degrees, and proximal interphalangeal joint contracture decreased from 40 degrees to 6 degrees. Using the synthesis method, metacarpophalangeal joint contracture decreased from 57 degrees to 0 degrees, and proximal interphalangeal joint contracture decreased from 58 degrees to 10 degrees. The Disabilities of the Arm, Shoulder, and Hand Test scores decreased from 37 to 30 in both groups. There were no significant differences between groups in these parameters. The two significant intergroup differences were healing time (40 days for the open palm technique versus 28 days for the synthesis method) and recurrence rate (50 percent for open palm versus 0 percent for synthesis). The synthesis technique combines with success the best features of current methods for the surgical treatment of advanced Dupuytren's disease.     

Isolation of a fast decay in submillisecond Chlorella luminescence

Using a simple He-Ne (632.8-nm) laser phosphoroscope steady-state luminescence from Chlorella pyrenoidosa was studied from 50 μs to 1.1 ms between 1 ms long exciting flashes. The following results were obtained: (1) prior freezing or ultraviolet irradiation changed the time course of the luminescence to a rapid decay with a half-time of about 110 μs; (2) 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) suppressed the 110-μs luminescence; (3) spectrally, all observed luminescence was, within possible error, identical to fluorescence; (4) no effect on the luminescence intensity from pulsed magnetic fields up to 30 kgauss was observed; (5) the relative fluorescence yield, measured simultaneously with luminescence, was found to be constant.Our principal conclusions, supported mainly by experiments with DCMU, are: (1) the 110-μs decay is a distinct component of the total steady-state luminescence; (2) prior freezing or ultraviolet irradiation isolates this component of the luminescence by suppressing all other components; (3) the half-time and intensity of this component are temperature independent in the interval 0–22 °C.     

Real-time change detection of steady-state evoked potentials

Steady-state evoked potentials (SSEP) are the electrical activity recorded from the scalp in response to high-rate sensory stimulation. SSEP consist of a constituent frequency component matching the stimulation rate, whose amplitude and phase remain constant with time and are sensitive to functional changes in the stimulated sensory system. Monitoring SSEP during neurosurgical procedures allows identification of an emerging impairment early enough before the damage becomes permanent. In routine practice, SSEP are extracted by averaging of the EEG recordings, allowing detection of neurological changes within approximately a minute. As an alternative to the relatively slow-responding empirical averaging, we present an algorithm that detects changes in the SSEP within seconds. Our system alerts when changes in the SSEP are detected by applying a two-step Generalized Likelihood Ratio Test (GLRT) on the unaveraged EEG recordings. This approach outperforms conventional detection and provides the monitor with a statistical measure of the likelihood that a change occurred, thus enhancing its sensitivity and reliability. The system’s performance is analyzed using Monte Carlo simulations and tested on real EEG data recorded under coma.     

Exogenous IL-10 overexpression reduces perforin production by activated allogenic CD8+ cells and prolongs cardiac allograft survival

Perforin is a cytolytic mediator produced by cytotoxic T cells (CD8(+) cells) and natural killer cells. We previously reported that ex vivo IL-10 gene therapy induced apoptosis of allogenic infiltrative CD8(+) cells and significantly prolonged cardiac allograft survival. To further test the hypothesis that localized IL-10 overexpression in cardiac allografts may also effect the alloreactive CD8(+) T cell function by downregulating its perforin production, we used a rabbit functional heterotopic allograft heart transplant model. Human recombinant IL-10 gene complexed with liposome was intracoronary delivered into the cardiac allografts ex vivo. The percentage of apoptotic infiltrative CD8(+) cells in cardiac allografts was increased 6-fold in the gene therapy group vs. the control group, whereas the percentage of perforin-positive CD8(+) cells was decreased 2.9-fold (P < 0.01). Perforin expression level in the allograft myocardium of the gene therapy group was deceased 3.2-fold (P < 0.01). The amount of infiltrative perforin-positive CD8(+) cells and perforin expression level were inversely correlated with IL-10 transgene and protein expression level in the myocardium of cardiac allografts (P < 0.01), the percentage of apoptotic cardiac myocytes (P < 0.01), and the peak left ventricular systolic pressure of cardiac allografts (P < 0.01) but significantly correlated with the infiltrative T cell cytotoxicity (P < 0.01) and allograft rejection score (P < 0.01). These results suggest that localized IL-10 gene therapy prolongs cardiac allograft survival, at least in part, through downregulation of perforin production by activated allogenic CD8(+) T cells. Reduction of cytolytic function of cytotoxic effector cells prevents the apoptosis of cardiac myocytes.     

Highway or byway: the metabolic role of the GABA shunt in plants

Much of the recent work on the gamma-aminobutyrate (GABA) shunt in plants has concentrated on stress/pest-associated and signalling roles. However, fifty years after the structural elucidation of the pathway, aspects of its regulation and even of its biological significance remain largely obscure. Here, we assess the importance of GABA metabolism in plants, reviewing relevant biological circumstances and taking advantage of high-throughput data accessibility and computational approaches. We discuss the premise that GABA metabolism plays a major role in carbon and nitrogen primary metabolism. We further evaluate technological developments that will likely allow us to address the quantitative importance of this shunt within the biological processes to which it contributes.