The Early Stages of Photosystem II Assembly Monitored by Measurements of Fluorescence Lifetime, Fluorescence Induction and Isoelectric Focusing of Chlorophyll-Proteins in Barley Etiochloroplasts

The relationship between functional and structural aspects ofPSII formation during greening of etiolated barley leaves hasbeen investigated using fluorescence lifetime measurements,fluorescence kinetics analysis and analysis of chlorophyll-proteincomplexes by IEF-PAGE. Two phases of different character couldbe distinguished in the course of the greening process in dark-grownplants. An early phase covering the first 3–4 h afterthe onset of illumination and a late phase covering the subsequentgreening. During the first phase the formation of PSII reactioncenters and their minor antenna components was observed as manifestedby the IEF-PAGE polypeptide pattern. This was accompanied byshortening of the slow and middle components of the fluorescencelifetime, as well as by the rapid drop in the amplitude of theslow component. A room temperature emission band at 676 nm wasassociated with uncoupled chlorophyll and with the slow fluorescencelifetime component during the first hours of greening. Duringthe late greening phase peripheral light-harvesting complexesof PSII were formed concomitantly to an increase in lifetimeand amplitude of the fast component and to a further decreasein the lifetime of the middle component. The gradual increasein PSII complexity during both phases of greening was also manifestedby changes in proportion and kinetic properties of PSII     

Haptoglobin glycoforms in a case of carbohydrate-deficient glycoprotein syndrome

Alterations in haptoglobin (Hp) glycosylation were examined in the plasma of the first patient with carbohydrate-deficient glycoprotein syndrome (CDGS) who was described in Poland. Hp concentration in the CDGS patient plasma was low (240mg/l) and the Hp phenotype was shown to be 2-2. Three glycoforms of the Hp subunit were observed in SDS-PAGE in CDGS. The densitometric analysis and molecular weight determinations suggested that 50% of glycoforms were fully glycosylated; 30% contained three out of four and 20% only two out of four glycan units compared to those that are present in Hp derived from healthy people. Results with lectins (concanavalin A and Sambucus nigra, Maackia amurensis and Alleuria aurantia agglutinins) indicate that all three glycoforms of subunit of CDGS-Hp contained biantennary complex glycans terminated with 2,6 bound sialic acid, but without fucose or 2,3 linked sialic acid. Hp glycosylation abnormalities described in this work suggest that this case was a type I carbohydrate-deficient glycoprotein syndrome.     

SARS-CoV-2 tropism,entry, replication,and propagation: Considerations for drug discovery and development

Since the initial report of the novel Coronavirus Disease 2019 (COVID-19) emanating from Wuhan, China, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has spread globally. While the effects of SARS-CoV-2 infection are not completely understood, there appears to be a wide spectrum of disease ranging from mild symptoms to severe respiratory distress, hospitalization, and mortality. There are no Food and Drug Administration (FDA)-approved treatments for COVID-19 aside from remdesivir; early efforts to identify efficacious therapeutics for COVID-19 have mainly focused on drug repurposing screens to identify compounds with antiviral activity against SARS-CoV-2 in cellular infection systems. These screens have yielded intriguing hits, but the use of nonhuman immortalized cell lines derived from non-pulmonary or gastrointestinal origins poses any number of questions in predicting the physiological and pathological relevance of these potential interventions. While our knowledge of this novel virus continues to evolve, our current understanding of the key molecular and cellular interactions involved in SARS-CoV-2 infection is discussed in order to provide a framework for developing the most appropriate in vitro toolbox to support current and future drug discovery efforts.     

Unstimulated primary CD4+ T cells from HIV-1-positive elite suppressors are fully susceptible to HIV-1 entry and productive infection

Elite controllers or suppressors (ES) are a group of HIV-1-infected individuals who maintain viral loads below the limit of detection of commercial assays for many years. The mechanisms responsible for this remarkable control are under intense study, with the hope of developing therapeutic vaccines effective against HIV-1. In this study, we addressed the question of the intrinsic susceptibility of ES CD4(+) T cells to infection. While we and others have previously shown that CD4(+) T cells from ES can be infected by HIV-1 isolates in vitro, these studies were confounded by exogenous activation and in vitro culture of CD4(+) T cells prior to infection. In order to avoid the changes in chemokine receptor expression that have been associated with such exogenous activation, we infected purified CD4(+) T cells directly after isolation from the peripheral blood of ES, viremic patients, and uninfected donors. We utilized a green fluorescent protein (GFP)-expressing proviral construct pseudotyped with CCR5-tropic or CXCR4-tropic envelope to compare viral entry using a fluorescence resonance energy transfer-based, single-round virus-cell fusion assay. The frequency of productive infection was also compared by assessing GFP expression. CD4(+) T cells from ES were as susceptible as or more susceptible than cells from viremic patients and uninfected donors to HIV-1 entry and productive infection. The results of this physiological study strongly suggest that differences in HIV-1 entry and infection of CD4(+) T cells alone cannot explain the elite control of viral replication.     

Sexual dimorphism in lizard body shape: the roles of sexual selection and fecundity selection

Sexual dimorphism is widespread in lizards, with the most consistently dimorphic traits being head size (males have larger heads) and trunk length (the distance between the front and hind legs is greater in females). These dimorphisms have generally been interpreted as follows: (1) large heads in males evolve through male-male rivalry (sexual selection); and (2) larger interlimb lengths in females provide space for more eggs (fecundity selection). In an Australian lizard (the snow skink, Niveoscincus microlepidotus), we found no evidence for ongoing selection on head size. Trunk length, however, was under positive fecundity selection in females and under negative sexual selection in males. Thus, fecundity selection and sexual selection work in concert to drive the evolution of sexual dimorphism in trunk length in snow skinks.     

Evaluation of detection of <Emphasis Type="Italic">Toxoplasma gondii</Emphasis> DNA in animal blood samples by quantitative PCR

Aim of the study: The purpose of this study was to find out the relationship between the phase of infection (acute or persistent) and the ability of quantitative PCR to detect DNA of Toxoplasma gondii in circulating leukocytes in blood. Methodology: Animal serum samples were examined (50 sheep, 47 dogs, 32 dairy cows, 91 wild boars and 36 rabbits) for the occurrence of IgM and IgG antibodies to T. gondii by ELISA. Uncoagulated blood samples from the same animals were examined for the detection of T. gondii DNA in circulating leukocytes by real-time PCR. Results: Only IgM antibodies, characteristic for acute infection, were detected in 45 of the 256 serum samples (17.6%). Only IgG antibodies, corresponding with chronic infection, were detected in 120 of the 256 samples (46.8%). In 91 of the 256 samples (35.5%) neither IgM or IgG were detected by ELISA. For real-time PCR, animals were divided into three groups based on the serological results: (group I — acute infection, group II — chronic infection, and group III — no infection). In group I, the presence of T. gondii DNA was detected in 9 out of 45 samples (20%), whereas in group II only 1 of 120 samples was positive for T. gondii DNA (0.8%). In group III, no DNA of T. gondii (0/91 samples) was detected by real-time PCR. Significance: The proof of DNA by real-time PCR in IgM positive samples was statistically significant in comparison to IgG positive samples (P<0.0001).