Adenovirus E1A makes two distinct contacts with the retinoblastoma protein.

Two regions near the amino terminus of the adenovirus E1A protein, which were first identified by sequence conservation among various adenovirus serotypes, have been shown by genetic studies to be essential for E1A-mediated transformation. These same regions are also required for interaction with a number of cellular proteins, including the retinoblastoma protein (pRB). Using synthetic peptides corresponding to portions of these conserved regions, we show that each region can bind independently to pRB. These interactions were observed in both competition and binding assays. In both types of assay, region 2 peptides (E1A amino acids 115 to 132) bound pRB with higher affinity than did region 1 peptides (E1A amino acids 37 to 54), while a peptide combining region 1 and 2 sequences consistently provided the highest-affinity interaction. Cross-blocking experiments using region 1 peptides and region 2 peptides suggested that these two regions of E1A make distinct contacts with pRB. These data support the notion that the pRB-binding domain of E1A contains at least two functional elements.     

Bovine pyruvate kinase isozymes and hybrid isozymes. Electrophoretic studies and tissue distribution.

Electrophoresis of various bovine tissue extracts revealed, in addition to the three major homotetrameric isozymes of pyruvate kinase (K₄, L₄, and M₄), numerous intermediate bands that behave electrophoretically as hybrid isozymes. Kidney, for example, contains both K-L and K-M hybrid sets. Representative hybrids from each set, tentatively identified as K₂L₂ and K₃M, were isolated from kidney by ionexchange chromatography and their subunit compositions were confirmed by dissociation and subsequent reassociation into new hybrid sets. All of the tissues examined that contain type K₄ also have substantial quantities of K-M hybrids, establishing the presence of the type M isozyme in a great many tissues other than striated muscle and brain, where it is most abundant. In addition, small quantities of K subunits apparently are produced even in striated muscle, which previously had been thought to contain only M₄. The pattern of hybrids and enzyme specific activities differ markedly within tissues from the same organ, as shown by dissection of the heart and great vessels. Aortic smooth muscle has a fairly uniform distribution of K-M hybrids, while cardiac muscle has mostly M₄ with a little KM₃. Connective tissue from heart valves, on the other hand, has a five-membered set dominated by K₃M, while Purkinje fibers have a five-membered set dominated by KM₃. The occurrence of K-M hybrids in these and many other tissues indicates that the distribution of mammalian pyruvate kinase isozymes is much more complex than previously reported.     

The reversibility of skeletal muscle pyruvate kinase and an assessment of its capacity to support glyconeogenesis.

The kinetics of pyruvate phosphorylation by rabbit skeletal muscle pyruvate kinase (EC 2.7.1.40) has been studied with a coupled assay using P-enolpyruvate carboxylase (EC 4.1.1.31) and malate dehydrogenase (EC 1.1.1.37). The reaction sequence is (See journal for formula). Although the equilibrium of the pyruvate kinase reaction by itself strongly favors pyruvate production, the over-all equilibrium of this coupled system favors the depletion of pyruvate, thus greatly reducing the problem of back reaction during the assay. In addition, the oxidation of NADH by malate dehydrogenase makes it possible to monitor the system with a spectrophotometer. The Michaelis constant of pyruvate kinase was found to be 0.9 mM for ATP and 7 mM for pyruvate, values that agree reasonably well with earlier studies using direct assays. However, the maximum velocity is about 6 mumol of pyruvate phosphorylated/min/mg of enzyme, which is very much faster than that indicated by earlier studies. These results suggest that the metabolic significance of the reverse reaction of muscle pyruvate kinase may have been underestimated. In particular, the data given here suggest that its rate in vivo is probably comparable to the observed rate of glycogen synthesis from lactate, making possible glyconeogenesis in muscle by pyruvate kinase reversal without the need for an enzymatic bypass of the kind employed by liver and kidney.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.     

PYRUVATE KINASE ISOZYMES IN NEURONS, GLIA, NEUROBLASTOMA, AND GLIOBLASTOMA

Abstract– The distribution of pyruvate kinase isozymes (EC 2.7.1.40) was examined in cells and tissues from the central and peripheral nervous system of the rat. Most tissues contain significant quantities of both the K₄ (fetal type) and M₄ (skeletal muscle type) isozymes plus tetrameric hybrids comprised of various combination of the type M and type K subunits. Retina, for example, contains a five-mem-bered hybrid set weighted toward K₄, while sciatic nerve and spinal cord have patterns very similar to that of adult brain, consisting predominantly of M₄ with small amounts of K₄ and K-M hybrids. This adult pattern is achieved by a gradual shift from a hybrid set dominated by K₄ in fetal life, to the pattern at birth at which time the two most prominent bands were M₄ and K₂M₂, and finally to the adult pattern by about 28 days after birth. Neurons and glial cells were isolated from rat and mouse brains at the various developmental levels. The pyruvate kinase isozyme patterns in the two cell types were similar to each other and to the patterns seen in whole brain homogenates at all ages, indicating similar rates of isozymic maturation in the two cell types. The correlation of maturation with pyruvate kinase isozyme patterns was further tested in cultures of malignant cell lines. A K-M hybrid set, weighted toward K₄, was seen in two clonal lines of mouse neuroblastoma under normal culture conditions. However, lowering the serum concentration in the culture medium or adding bromodeoxyuridine caused a shift in the patterns toward type M as the cells differentiated, mimicking in part the in vivo maturation of normal cells. On the other hand, a rapidly growing and poorly differentiated line of rat glioblastoma had only K₄ under all conditions examined.     

Precise Control of Phase Separation Enables 12% Efficiency in All Small Molecule Solar Cells

Compared to conjugated polymers, small‐molecule organic semiconductors present negligible batch‐to‐batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small‐molecular organic solar cells (SM‐OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small‐molecular donors H13 and H14 , created by fluorine and chlorine substitution of the original donor molecule H11 , are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open‐circuit voltage with IDIC‐4F as acceptor. Due to kinetic and thermodynamic reasons, H13 ‐based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14 ‐based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14 ‐based SM‐OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM‐OSCs using IDIC‐4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine‐tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.     

Modelling optimal vaccination strategy for SARS-CoV-2 in the UK

The COVID-19 outbreak has highlighted our vulnerability to novel infections.Faced with this threat and no effective treatment, in line with many other countries, the UK adopted enforced social distancing (lockdown) to reduce transmission—successfully reducing the reproductive number R below one. However, given the large pool of susceptible individuals that remain, complete relaxation of controls is likely to generate a substantial further outbreak. Vaccination remains the only foreseeable means of both containing the infection and returning to normal interactions and behaviour. Here, we consider the optimal targeting of vaccination within the UK, with the aim of minimising future deaths or quality adjusted life year (QALY) losses. We show that, for a range of assumptions on the action and efficacy of the vaccine, targeting older age groups first is optimal and may be sufficient to stem the epidemic if the vaccine prevents transmission as well as disease.     

Temperature and precipitation drive temporal variability in aquatic carbon and GHG concentrations and fluxes in a peatland catchment

The aquatic pathway is increasingly being recognized as an important component of catchment carbon and greenhouse gas (GHG) budgets, particularly in peatland systems due to their large carbon store and strong hydrological connectivity. In this study, we present a complete 5‐year data set of all aquatic carbon and GHG species from an ombrotrophic Scottish peatland. Measured species include particulate and dissolved forms of organic carbon (POC, DOC), dissolved inorganic carbon (DIC), CO₂, CH₄ and N₂O. We show that short‐term variability in concentrations exists across all species and this is strongly linked to discharge. Seasonal cyclicity was only evident in DOC, CO₂ and CH₄ concentration; however, temperature correlated with monthly means in all species except DIC. Although the temperature correlation with monthly DOC and POC concentrations appeared to be related to biological productivity in the terrestrial system, we suggest the temperature correlation with CO₂ and CH₄ was primarily due to in‐stream temperature‐dependent solubility. Interannual variability in total aquatic carbon concentration was strongly correlated with catchment gross primary productivity (GPP) indicating a strong potential terrestrial aquatic linkage. DOC represented the largest aquatic carbon flux term (19.3 ± 4.59 g C m^?2 yr^?1), followed by CO₂ evasion (10.0 g C m^?2 yr^?1). Despite an estimated contribution to the total aquatic carbon flux of between 8 and 48%, evasion estimates had the greatest uncertainty. Interannual variability in total aquatic carbon export was low in comparison with variability in terrestrial biosphere–atmosphere exchange, and could be explained primarily by temperature and precipitation. Our results therefore suggest that climatic change is likely to have a significant impact on annual carbon losses through the aquatic pathway, and as such, aquatic exports are fundamental to the understanding of whole catchment responses to climate change.     

Classification and nomenclature of all human homeobox genes

Background

The homeobox genes are a large and diverse group of genes, many of which play important roles in the embryonic development of animals. Increasingly, homeobox genes are being compared between genomes in an attempt to understand the evolution of animal development. Despite their importance, the full diversity of human homeobox genes has not previously been described.

Results

We have identified all homeobox genes and pseudogenes in the euchromatic regions of the human genome, finding many unannotated, incorrectly annotated, unnamed, misnamed or misclassified genes and pseudogenes. We describe 300 human homeobox loci, which we divide into 235 probable functional genes and 65 probable pseudogenes. These totals include 3 genes with partial homeoboxes and 13 pseudogenes that lack homeoboxes but are clearly derived from homeobox genes. These figures exclude the repetitive DUX1 to DUX5 homeobox sequences of which we identified 35 probable pseudogenes, with many more expected in heterochromatic regions. Nomenclature is established for approximately 40 formerly unnamed loci, reflecting their evolutionary relationships to other loci in human and other species, and nomenclature revisions are proposed for around 30 other loci. We use a classification that recognizes 11 homeobox gene 'classes' subdivided into 102 homeobox gene 'families'.

Conclusion

We have conducted a comprehensive survey of homeobox genes and pseudogenes in the human genome, described many new loci, and revised the classification and nomenclature of homeobox genes. The classification scheme may be widely applicable to homeobox genes in other animal genomes and will facilitate comparative genomics of this important gene superclass.