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Open access

Zdravko Šergo and Jasmina Gržinić

Open access

Lutz Volkmann

Abstract

Let G be a connected graph with minimum degree δ and edge-connectivity λ. A graph is maximally edge-connected if λ = δ, and it is super-edgeconnected if every minimum edge-cut is trivial; that is, if every minimum edge-cut consists of edges incident with a vertex of minimum degree. The clique number ω(G) of a graph G is the maximum cardinality of a complete subgraph of G. In this paper, we show that a connected graph G with clique number ω(G) ≤ r is maximally edge-connected or super-edge-connected if the number of edges is large enough. These are generalizations of corresponding results for triangle-free graphs by Volkmann and Hong in 2017.

Open access

Terry A. McKee

Abstract

Several recent papers have investigated unichord-free graphs—the graphs in which no cycle has a unique chord. This paper proposes a concept of strongly unichord-free graph, defined by being unichord-free with no cycle of length 5 or more having exactly two chords. In spite of its overly simplistic look, this can be regarded as a natural strengthening of unichordfree graphs—not just the next step in a sequence of strengthenings—and it has a variety of characterizations. For instance, a 2-connected graph is strongly unichord-free if and only if it is complete bipartite or complete or “minimally 2-connected” (defined as being 2-connected such that deleting arbitrary edges always leaves non-2-connected subgraphs).

Open access

Ruijuan Li and Bin Sheng

Abstract

Let T (XY, A) be a bipartite tournament with partite sets X, Y and arc set A. For any vertex xXY, the second out-neighbourhood N ++(x) of x is the set of all vertices with distance 2 from x. In this paper, we prove that T contains at least two vertices x such that |N ++(x)| ≥ |N +(x)| unless T is in a special class ℬ1 of bipartite tournaments; show that T contains at least a vertex x such that |N ++(x)| ≥ |N (x)| and characterize the class ℬ2 of bipartite tournaments in which there exists exactly one vertex x with this property; and prove that if |X| = |Y | or |X| ≥ 4|Y |, then the bipartite tournament T contains a vertex x such that |N ++(x)|+|N +(x)| ≥ 2|N (x)|.

Open access

Gunita Deksne, Vija Veisa, Dace Rezeberga, Ludmila Vīksna and Angelika Krūmiņa

Abstract

Toxoplasmosis is an important infection caused by the single-celled parasite Toxoplasma gondii, which is a zoonotic parasite causing widespread human and animal diseases, mostly involving the central nervous system. Humans can acquire toxoplasmosis by ingestion of raw or undercooked meat containing T. gondii tissue cysts, ingestion of oocysts shed by infected felids via contaminated food or water, and by vertical transmission to the fetus through the placenta from the mother during pregnancy. The aim of the present study was to determine the seroprevalence of specific anti-T. gondii IgG and IgM antibodies using a large set of clinical diagnostic laboratory data obtained over a 14-year period. In total, 25 069 unique patients were included in the present study. The overall specific anti-T. gondii IgG prevalence were 36.3%, which was significantly (p < 0.01) higher than IgM prevalence (2.4%). Mean age for IgG antibody-positive patients was 33.7 ± 12.2 years. A significant positive correlation (r = 0.99; p < 0.01) was observed between age group and anti-T. gondii IgG antibody prevalence, which ranged from 4.2% to 66.7%. The most prevalent (69.9%; 95% CI 69.2–70.7) comorbidities of patients tested for presence of anti-T. gondii IgG and IgM antibodies were classified as factors affecting health status which includes also monitoring of normal pregnancy.

Open access

Pēteris Tretjakovs, Juris Hofmanis, Dace Hofmane, Gita Krieviņa, Leons Blumfelds, Vitolds Mackēvičs, Aivars Lejnieks and Guntis Bahs

Abstract

The aim of the present study was to evaluate plasma levels of chemerin, myeloperoxidase (MPO), fibroblast growth factor-21 (FGF-21), thioredoxin reductase-1 (TrxR1), and matrix metallopeptidase-9 (MMP-9) in acquired aortic valve (AoV) stenosis patients to determine correlations between the studied cellular factors, and also clarify the predictive values of these factors as biomarkers in AoV stenosis. AoV stenosis patients were classified into three groups: 17 patients with mild AoV stenosis; 19 with moderate and 15 with severe AoV stenosis. Twenty-four subjects without AoV stenosis were selected as a control group. Our findings suggest that AoV stenosis might be associated with increased chemerin, TrxR1, MPO, and FGF-21 levels in plasma. Moreover, these factors and also MMP-9 already reached statistically significantly elevated levels in the early stages of AoV stenosis, but MPO levels were more pronounced in patients with moderate and severe AoV stenosis. Chemerin was correlated with all of the studied cytokines; TrxR1 and MMP-9 were correlated with several other cellular factors. Our findings (by ROC analysis) suggest that MPO and chemerin might serve as specific and sensitive biomarkers for AoV stenosis without grading the severity, but, in relation to mild AoV stenosis, TrxR1, FGF-21, and MMP-9 also reached good or moderate levels as biomarkers. The cellular factors might serve as novel diagnostic and prognostic biomarkers in AoV stenosis patients, while chemerin and MPO may be more powerful.

Open access

V.R. Kulli, B. Chaluvaraju and H.S. Boregowda

Abstract

Let G = (V, E) be a connected graph with vertex set V (G) and edge set E(G). The product connectivity Banhatti index of a graph G is defined as, PB(G)=ue1dG(u)dG(e) where ue means that the vertex u and edge e are incident in G. In this paper, we determine P B(G) of some standard classes of graphs. We also provide some relationship between P B(G) in terms of order, size, minimum / maximum degrees and minimal non-pendant vertex degree. In addition, we obtain some bounds on P B(G) in terms of Randić, Zagreb and other degree based topological indices of G.

Open access

Anda Vilmane, Inga Ziemele, Santa Rasa, Anna Terentjeva, Modra Murovska, Dace Gardovska, Yung-Cheng Lin and Zaiga Nora-Krūkle

Abstract

Lower respiratory tract infection (LRTI) is the major cause of morbidity and mortality of children in the world. In addition to respiratory syncytial virus, influenza virus types A and B, parainfluenza types 1, 2 and 3, and adenoviruses, several new respiratory viruses associated with LRTI were discovered in the 21st century. These are metapneumovirus, coronaviruses NL63 and HKU1, parainfluenza virus type four and human bocavirus one (HBoV1). HBoV1 was discovered in 2005 and is considered as the fourth most prevalent respiratory virus worldwide. However, the high frequency of co-infections detected together with HBoV1 raises doubt about whether HBoV1 is a true pathogen or just a bystander. This is the first study aimed to determine the presence of HBoV1 and 18 other respiratory viruses in nasopharyngeal aspirates (NPA) of children with LRTI in Latvia. Using multiplex real-time polymerase chain reaction method, the HBoV1 genomic sequence was detected in 60.0% of NPA samples, showing that HBoV1 prevalence is high among children with LRTI in Latvia. HBoV1 mono-infection was revealed in 6.67%. The most common co-infections associated with HBoV1 were rhinovirus, adenovirus, respiratory syncytial virus A and B, metapneumovirus, and enterovirus.

Open access

Alina Sultanova, Maksims Čistjakovs, Lība Sokolovska, Egils Cunskis and Modra Murovska

Abstract

Viral infections have been frequently cited as important environmental factors implicated in autoimmune thyroiditis (AIT) development, although no specific virus has yet been conclusively associated with the disease. Some evidence implicates human herpesvirus-6 (HHV-6) in this disease. The aim of this study was to investigate the role of the HHV-6 U83 gene expression in autoimmune thyroiditis development. Fifty-one patients with AIT following thyroidectomy and a control group of 30 autopsied subjects without thyroid pathologies for comparing virology results and 30 healthy blood donors for comparing serology results were enrolled in this study. HHV-6 U83 gene expression was determined using nested PCR with complementary DNA as the template acquired from thyroid gland extracted RNA. Plasma samples of AIT patients and blood donors were tested for IL-2, IL-4, IL-10, sTNF-RII and IL-1beta levels by ELISA. Virology results were compared with pro- and anti-inflammatory cytokine levels to determine possible interaction of HHV-6 with host immune response. HHV-6 U83 gene expression was found only in 24% (12/49) of AIT patient thyroid gland tissue samples and in none of the control group individuals, showing possible involvement of this gene in AIT development. However, no interaction between HHV-6 and changes in cytokine levels was found.

Open access

Ksenija Kramiča, Jeļena Eglīte, Aleksandrs Koļesovs, Tatjana Kramiča, Gaļina Titoviča, Diāna Džeriņa, Glafira Nikolajeva, Ludmila Vīksna and Oksana Koļesova

Abstract

Tuberculosis (TB) is still one of the top ten leading causes of death in the world. Compared to other Baltic and Eastern European countries, TB incidence (24.8 new cases per 100 000 people in 2017) in Latvia is relatively high. One of the regions with the highest TB incidence is Latgale (31.1 cases per 100 000 people). The aim of this pilot study was to identify markers of genetic predisposition to TB in Latgale. The study included 26 patients (16 males and 10 females) aged between 18 and 85 with bilateral TB pneumonia and without HIV infection. HLA typing was performed in HLA-DRB1, -DQA1, and -DQB1 loci by a polymerase chain reaction with low resolution sequence-specific primers. HLA-DRB1*07 and HLA-DRB1*11 alleles were identified as risk alleles for TB. HLA-DRB1*15 allele was a protective allele. Due to the limitations of this exploratory study, a broader study needs to be conducted to revealing specific risk and protective HLA Class II alleles for TB in the subpopulation of Latgale.