Ecotype-dependent control of growth,dormancy and freezing tolerance under seasonal changes in <Emphasis Type="Italic">Betula pendula</Emphasis> Roth

Woody plants in the temperate and boreal zone undergo annual cycle of growth and dormancy under seasonal changes. Growth cessation and dormancy induction in autumn are prerequisites for the development of substantial cold hardiness in winter. During evolution, woody plants have developed different ecotypes that are closely adapted to the local climatic conditions. In this study, we employed distinct photoperiodic ecotypes of silver birch (Betula pendula Roth) to elucidate differences in these adaptive responses under seasonal changes. In all ecotypes, short day photoperiod (SD) initiated growth cessation and dormancy development, and induced cold acclimation. Subsequent low temperature (LT) exposure significantly enhanced freezing tolerance but removed bud dormancy. Our results suggested that dormancy and freezing tolerance might partially overlap under SD, but these two processes were regulated by different mechanisms and pathways under LT. Endogenous abscisic acid (ABA) levels were also altered under seasonal changes; the ABA level was low during the growing season, then increased in autumn, and decreased in winter. Compared with the southern ecotype, the northern ecotype was more responsive to seasonal changes, resulting in earlier growth cessation, cold acclimation and dormancy development in autumn, higher freezing tolerance and faster dormancy release in winter, and earlier bud flush and growth initiation in spring. In addition, although there was no significant ecotypic difference in ABA level during growing season, the rates and degrees of ABA alterations were different between the ecotypes in autumn and winter, and could be related to ecotypic differences in dormancy and freezing tolerance.     

Adaptive and optimized COVID-19 vaccination strategies across geographical regions and age groups

We evaluate the efficiency of various heuristic strategies for allocating vaccines against COVID-19 and compare them to strategies found using optimal control theory. Our approach is based on a mathematical model which tracks the spread of disease among different age groups and across different geographical regions, and we introduce a method to combine age-specific contact data to geographical movement data. As a case study, we model the epidemic in the population of mainland Finland utilizing mobility data from a major telecom operator. Our approach allows to determine which geographical regions and age groups should be targeted first in order to minimize the number of deaths. In the scenarios that we test, we find that distributing vaccines demographically and in an age-descending order is not optimal for minimizing deaths and the burden of disease. Instead, more lives could be saved by using strategies which emphasize high-incidence regions and distribute vaccines in parallel to multiple age groups. The level of emphasis that high-incidence regions should be given depends on the overall transmission rate in the population. This observation highlights the importance of updating the vaccination strategy when the effective reproduction number changes due to the general contact patterns changing and new virus variants entering.     

Apolipoprotein E (apoE) polymorphism and its influence on ApoE concentrations in the cerebrospinal fluid in Finnish patients with Alzheimer's disease

The apoE phenotype of 83 patients with probable Alzheimer's disease (AD) and of 164 non-demented controls was determined by isoelectric focusing and Western blotting. The proportion of the e4 allele was 0.548 in AD and 0.202 in controls (P<0.0001). The effect was seen in both early-onset and late-onset AD patients. The risk of AD in 4 homozygotes was 18-fold greater than in individuals without the 4 allele. ApoE concentrations were measured in serum and cerebrospinal fluid (CSF) from a subgroup of patients with AD (n=72) and controls (n=84) by a sandwich enzyme-linked immunosorbent assay. Although serum apoE concentrations were lower in individuals with the 4 allele than in those without the e4 allele, CSF apoE concentrations did not vary in different phenotype groups. However, CSF apoE levels were lower in AD patients than in controls. We conclude that the inheritance of the 4 allele of apoE is a risk factor for AD in the Finnish population.     

Hematocrit reduction in bifurcations due to plasma skimming

Expressions and numerical values for hematocrit reduction are calculated as blood flows from a cylindrical feeding tube into a cylindrical capillary at a right-angle branch. Blood is considered to consist of two Newtonian fluids, plasma and red cell suspension, which have equal densities but different viscosities. The concentration profile of the red cells is concluded to depend on the size of the feeding tube. An estimate for the thickness of the plasma layer adjacent to the wall is obtained.     

Fibronectin: chains of domains with diversified functions

Fibronectin is now recognized to be a large, multifunctional, adhesive glycoprotein with a wide distribution in vivo. Other distinctive features of fibronectin include its domain structure and its various molecular and biological interactions thought to be involved in cell anchorage, elaboration of the extracellular matrix, hemostasis, chemotaxis and opsonization. Structural studies of the protein are indicating that the function correspond to specific interactive domains in the molecule and are revealing unique, internally homologous sequences in the primary structure. Many of the biological effects of fibronectin are shared by its proteolytic fragments which, interestingly, also seem to have effects of their own.     

The malZ gene of Escherichia coli, a member of the maltose regulon, encodes a maltodextrin glucosidase

We have characterized a maltodextrin glucosidase, previously described as a maltose-inducible, cytoplasmic enzyme that cleaves p-nitrophenyl-alpha-maltoside in Escherichia coli. The gene encoding the enzyme activity, referred to as malZ, is located at 9.3 min on the chromosomal map. We cloned the gene in a high copy number vector and purified the enzyme. It is a monomer, with an apparent molecular weight of 65,000. The enzyme degrades maltodextrins, ranging from maltotriose to maltoheptaose, to shorter oligosaccharides, the final hydrolysis products being maltose and glucose. We measured the kinetic parameters, Km and Vmax, for the hydrolysis to glucose of the five different substrates. The binding of the substrate is enhanced by increasing the number of glucosyl residues in the maltodextrin. In contrast, the maximum rate of hydrolysis (Vmax) is fastest for maltotriose. To study the mode of action of the enzyme, we quantitatively measured the amount of free glucose liberated from the different maltodextrin substrates after a long incubation. More glucose is liberated from the long dextrins, as compared to the shorter ones, showing that the primary hydrolysis product was glucose, not maltose. Furthermore, [14C]maltotriose, specifically labeled at the reducing end, was hydrolyzed to [14C]glucose and unlabeled maltose. These data demonstrate that the malZ gene product is a maltodextrin glucosidase, liberating glucose from the reducing end of malto-oligosaccharides. The nucleotide sequence of malZ and the deduced amino acid sequence showed that malZ encodes a protein with a molecular weight of 68,960. Homology to glucosidases, alpha-amylases, and pullulanases were observed. Conserved regions thought to represent active sites in dextrin hydrolases were found in the MalZ protein.     

The expression of a rab-related gene,rab18, is induced by abscisic acid during the cold acclimation process of Arabidopsis thaliana (L.) Heynh

We have isolated a rab-related (responsive to ABA) gene, rab18 from Arabidopsis thaliana. The gene encodes a hydrophilic, glycine-rich protein (18.5 kDa), which contains the conserved serine- and lysine-rich domains characteristic of similar RAB proteins in other plant species. The rab18 mRNA accumulates in plants exposed to low temperature, water stress or exogenous ABA but not in plants subjected to heat shock. This stress-related accumulation of the rab18 mRNA is markedly decreased in the ABA-synthesis mutant aba-1, the ABA-response mutant abi-1 or in wild-type plants treated with the carotenoid synthesis inhibitor, fluridone. Exogenous ABA treatment can induce the rab18 mRNA in the aba-1 mutant but not in the abi-1 mutant. These results provide direct genetic evidence for the ABA-dependent regulation of the rab18 gene in A. thaliana.     

Confined chorionic mosaicism in prenatal diagnosis

Summary Confined chorionic mosaicism, detected commonly on chorionic villus sampling (CVS) and occasionally in cultured amniotic fluid cells, is described in five pregnancies that showed confined chorionic mosaicism for trisomies 12, 13, 14, 17 and a marker chromosome. Cytogenetic findings in these pregnancies support the conclusion that within chorion some chromosomal mosaicism are confined to the trophectoderm derivatives while others to the extra-embryonic mesoderm. The etiology of confined chorionic mosaicism is discussed in relation to a significant role of multiple cell lineages contributing to the early development of placenta. The need is indicated for the use of both direct and long-term cultures in CVS prenatal diagnosis, and for the confirmatory testing of fetal blood or amniotic fluid in cases where mosaicism is detected in chorionic villi.