Revealing the single-channel characteristics of OprD (OccAB1) porins from hospital strains of Acinetobacter baumannii

Nowadays, reports of antimicrobial resistance (AMR) against many antibiotics are increasing because of their misapplication. With this rise, there is a serious decrease in the discovery and development of new types of antibiotics amid an increase in multi-drug resistance. Unfermented Acinetobacter baumannii from gram-negative bacteria, which is one of the main causes of nosocomial infections and multi-drug resistance, has 4 main kinds of antibiotic resistance mechanism: inactivating antibiotics by enzymes, reduced numbers of porins and changing of their target or cellular functions due to mutations, and efflux pumps. In this study, characterization of the possible mutations in OprD (OccAB1) porins from hospital strains of A. baumannii were investigated using single channel electrophysiology and compared with the standard OprD isolated from wild type ATCC 19,606. For this aim, 5 A. baumannii bacteria samples were obtained from patients infected with A. baumannii, after which OprD porins were isolated from these A. baumannii strains. OprD porins were then inserted in an artificial lipid bilayer and the current-voltage curves were obtained using electrical recordings through a pair of Ag/AgCl electrodes. We observed that each porin has a characteristic conductance and single channel recording, which then leads to differences in channel diameter. Finally, the single channel data have been compared with the gene sequences of each porin. It was interesting to find out that each porin isolated has a unique porin diameter and decreased anion selectivity compared to the wild type.

Acute mastoiditis in children: A tertiary care center experience in 2015-2021

Background

Acute mastoiditis is a suppurative infection of mastoid air cells and is the most common intratemporal complication of otitis media.

Aim

This study aimed to evaluate the demographic and clinical characteristics and treatment outcomes of children with acute mastoiditis (AM).

Patients and Methods

We retrospectively reviewed the medical records of hospitalized pediatric patients aged between 1 month and 18 years with a diagnosis of AM between May 2015 and December 2021.

Results

A total of 28 hospitalized children with AM were enrolled in this study, of whom 22 (78.6%) were males and 6 (21.4%) were females with a mean ± standard deviation age of 93.5 ± 53.2 months (range = 6 months-16.1 years). The most common clinical symptoms were postauricular erythema (n = 17, 60.7%), tenderness (n = 16, 57.1%), swelling (n = 14, 50%), fever (n = 14, 50%), and auricular protrusion (n = 7, 25%). Mastoiditis complications occurred in 10 (35.7%) children. The most common extracranial complication was subperiosteal abscess (n = 8, 28.6%). The erythrocyte sedimentation rate (ESR) and the rate of antibiotic use before hospitalization were higher in patients with complicated mastoiditis (P = 0.006 and P = 0.039, respectively). Surgery was performed in 12 (42.9%) patients. Statistically, more surgical interventions were performed in patients who developed complications (P = 0.003).

Conclusion

AM continues as an important disease of childhood. Successful results are obtained with systemic antibiotic therapy and additional surgical intervention as necessary. A careful evaluation of patients with a high ESR and those who received antibiotic therapy before hospitalization is appropriate due to the correlation between these factors and the risk of complication development.

Determination of therapeutic agents efficiencies of microsatellite instability high colon cancer cells in post-metastatic liver biochip modeling

Two distinct genetic mutational pathways characterized by either chromosomal instability or high-frequency microsatellite instability (MSI-H) are recognized in the pathogenesis of colorectal cancer (CRC). Recently, it has been shown that patients with primary CRC that displays MSI-H have a significant, stage-independent, multivariate survival advantage. Biological properties of CMS1 (MSI-H type) can affect therapeutic efficiencies of agents used in the treatment of CRC, and therefore become a new predictive factor of the treatment. But, the predictive impact of MSI-H status for adjuvant chemotherapy remains controversial. This study will assess whether there is any unnecessary or inappropriate use of treatment agents recommended for adjuvant therapy of stage 2 and 3 of disease and for palliative or curative treatment of liver metastatic disease in microsatellite instability high group, a molecular subtype of colon cancer. Within this scope, the efficiencies of fluorouracil- and oxaliplatin-based chemotherapeutic agents will be shown on stage 3 microsatellite instability high colon tumor cell lines first, and then a microfluidic model will be created, imitating the metastasis of colon cancer to the liver. In the microfluidic chip model, we will create in liver tissue, where the metastasis of microsatellite instability high colon cancer will be simulated; the effectiveness of chemotherapeutic agents, immunotherapy agents, and targeted agents on tumor cells as well as drug response will be assessed according to cell viability through released biomarkers from the cells. The proposed hypothesis study includes the modeling and treatment of patient-derived post-metastatic liver cancer in microfluidics which has priority at the global and our region and consequently develop personal medication.

Current Strategies for the Regeneration of Skeletal Muscle Tissue

Traumatic injuries, tumor resections, and degenerative diseases can damage skeletal muscle and lead to functional impairment and severe disability. Skeletal muscle regeneration is a complex process that depends on various cell types, signaling molecules, architectural cues, and physicochemical properties to be successful. To promote muscle repair and regeneration, various strategies for skeletal muscle tissue engineering have been developed in the last decades. However, there is still a high demand for the development of new methods and materials that promote skeletal muscle repair and functional regeneration to bring approaches closer to therapies in the clinic that structurally and functionally repair muscle. The combination of stem cells, biomaterials, and biomolecules is used to induce skeletal muscle regeneration. In this review, we provide an overview of different cell types used to treat skeletal muscle injury, highlight current strategies in biomaterial-based approaches, the importance of topography for the successful creation of functional striated muscle fibers, and discuss novel methods for muscle regeneration and challenges for their future clinical implementation.

Experimental Lactococcus garvieae infection in rainbow trout, Oncorhynchus mykiss, Walbaum 1792: a comparative histopathological and immunohistochemical study

The aim of this study was to induce Lactococcus garvieae infection in young and adult fish through different routes [intraperitoneal (IP) and immersion (IM)] and to investigate the pathogenesis and histopathological and immunohistochemical findings comparatively. For this purpose, a total of 180 rainbow trout (90 young, 20 ± 5 g and 90 adult, 80 ± 10 g) obtained from a commercial fish farm were used. The fish were divided into eight groups, four experimental groups (Young-Adult IP groups and Young-Adult IM groups, each contain 30 fish) and four control groups (Young-Adult IP Control groups and Young-Adult IM control groups, each contain 15 fishes). The experimental study was conducted using L. garvieae, and confirmatory identification was performed by PCR. The sequence result of the PCR amplicon of 16S rDNA from isolate L. garvieae LAC1 was determined and deposited in the GenBank database under accession number KC883976. Fish in the IP groups were intraperitoneally administered an inoculate containing 10(6) cfu mL(-1) bacteria 0.1 mL. In the IM groups, fish were kept in inoculated water containing 10(8) cfu mL(-1) bacteria for 20 min. Mortality as well as clinical and pathological findings was recorded daily, and significant differences in macroscopic and microscopic results were observed between the IP and IM administration groups. All tissue samples were immunohistochemically stained by the avidin-biotin-peroxidase complex and immunofluorescence (IF) methods using polyclonal antibody to detect L. garvieae antigens. In immunoperoxidase staining in the IP groups, positive reactions to bacterial antigens were most commonly seen in the spleen, kidney, heart, liver, peritoneum and swim bladder. In the IM groups, bacterial antigens were most commonly found in the eye, gill, spleen and kidney. In the IF method, the distribution of antigens in tissue and organs was similar to the reactions with immunoperoxidase staining. Finally, in this experimental study, an important correlation was seen between the distribution of L. garvieae antigens and lesions developing in many organ and tissues.

Pathomorphological, immunohistochemical and bacteriological findings in budgerigars (Melopsittacus undulatus) naturally infected with S. Gallinarum

The present study describes the pathological and bacteriological findings and diagnosis by immunoperoxidase and immunofluorescence methods in budgerigars (Melopsittacus undulatus) naturally infected with Salmonella gallinarum obtained from three commercial budgerigar rearing farms. The course of the disease in young budgerigars was peracute or acute, whereas in adult budgerigars the disease was acute or chronic. Clinically, yellow-white diarrhoea was observed in the young budgerigars with the acute form. In the adult budgerigars with the acute and chronic forms, a decrease in feed and water consumption with loss in body condition together with greenish-yellow diarrhoea was generally noted. Peritonitis and pericarditis were the most common findings in young budgerigars at necropsy, while in adult budgerigars scattered grey-white necrotic foci were found in the livers. Histopathologically, the lesions in young budgerigars were characterized with fibrinonecrotic peritonitis and/or pericarditis and necrotic hepatitis. In adult budgerigars with acute infection, hepatic necrosis with focal heterophil infiltration was present; whilst lesions in the chronic cases were granulomatous in nature with the infiltration of macrophages, lymphocytes and histiocytes. For the detection of S. Gallinarum in formalin-fixed, paraffin-embedded tissues, the avidin-biotin peroxidase complex and immunofluorescence methods were used. Both methods showed bacteria to be localized in the liver, kidney, peritoneum, heart, spleen and intestines of both young and adult budgerigars. The results of the present study indicate that the avidin-biotin peroxidase complex method was more sensitive than the immunofluorescence method in the detection of the bacteria.

Tetrathyridiosis and tubulopapillary carcinoma occurring simultaneously in the mammary gland of a cat

This report describes a case of tubulopapillary carcinoma and concomitant tetrathyridiosis in a 5-year-old female cross-breed cat. A mass was located at right inguinal mammary gland and measured 5.5 × 5 × 3 cm in size with multilobulated to solid appearance. The cut surface of the mass had a centrally located large cyst (approximately 3 cm in diameter) surrounded by other smaller cysts. Histologically, the mass was diagnosed as tubulopapillary mammary carcinoma, intensely positive for AE1/AE3 cytokeratins. The cyst found at post-mortem examination was tetrathyridia of Mesocestoides species surrounded by inflammatory cells and a loose fibrous capsule. To the authors' best knowledge, this is the first description of a tubulopapillary carcinoma and tetrathyridiosis found simultaneously in the mammary gland of a cat.

Prediction of 10-year coronary heart disease risk in Caribbean type 2 diabetic patients using the UKPDS risk engine

OBJECTIVE

Primary prevention of Coronary Heart Disease (CHD) in diabetic patients should be based on absolute CHD risk calculation. This study was aimed to determine the levels of 10-year CHD risk in Caribbean type 2 diabetic patients using the diabetes specific United Kingdom Prospective Diabetes Study (UKPDS) risk engine calculator.

SUBJECTS AND METHODS

Three hundred and twenty-five (106 males, 219 females) type 2 diabetic patients resident in two Caribbean Islands of Tobago and Trinidad met the UKPDS risk engine inclusion criteria. Records of their sex, age, ethnicity, smoking habit, diabetes duration, systolic blood pressure, total cholesterol, HDL-cholesterol and glycated haemoglobin were entered into the UKPDS risk engine calculator programme and the absolute 10-year CHD and stroke risk levels were computed. The 10-year CHD and stroke risks were statistically stratified into <15%, 15-30% and >30% CHD risk levels and differences between patients of African and Asian-Indian origin were compared.

RESULTS

In comparison with patients in Tobago, type 2 diabetic patients in Trinidad, irrespective of gender, had higher proportion of 10-year CHD risk (10.4 vs. 23.6%, P<0.001) whereas the overall 10-year stroke risk prediction was higher in patients resident in Tobago (16.9 vs. 11.4%, P<0.001). Ethnicity-based analysis revealed that irrespective of gender, higher proportion of patients of Indian origin scored >30% of absolute 10-year CHD risk compared with patients of African descent (3.2 vs. 28.2%, P<0.001).

CONCLUSIONS

The results of the study identified diabetic patients resident in Trinidad and patients of Indian origin as the most vulnerable groups for CHD. These groups of diabetic patients should have priority in primary or secondary prevention of coronary heart disease.

A comparative study of the prevalence of the metabolic syndrome and its components in type 2 diabetic patients in two Caribbean islands using the new International Diabetes Federation definition

BACKGROUND AND AIM

Tobago and Trinidad are two Caribbean islands with distinct genetic background and lifestyles; while Tobago is serene and a tourist centre, Trinidad is characterized by a hustling and bustling lifestyle. The study was aimed at determining and comparing the prevalence of the metabolic syndrome (MetS) and its critical components in type 2 diabetic patients using the new International Diabetes Federation (IDF) definition.

METHODS

Four hundred and thirteen (166 Tobago, 247 Trinidad) type 2 diabetic patients visiting 10 lifestyle disease clinics were studied. Blood pressure, anthropometric parameters (height, weight, body mass index and waist circumference) and overnight fasting blood samples were taken. Plasma glucose and serum triglycerides, total cholesterol, LDL- and HDL-cholesterol, insulin, and adiponectin were determined. Insulin resistance (IR) was determined using the HOMA method.

RESULTS

The patients in Tobago were significantly older than patients in Trinidad (p < 0.001) but the duration of diabetes (9.4 +/- 0.5 vs. 11.1 +/- 0.7 yr), medications, generalized (31.7 vs. 38.8%) and central (78.5 vs. 83.7%) obesity were similar (p > 0.05). In comparison with patients in Tobago, diabetic patients in Trinidad, irrespective of gender, had significantly higher prevalence of IDF critical components such as raised BP, raised triglycerides and reduced HDL-cholesterol (all, p < 0.001). Thus, while more patients in Trinidad were diagnosed with MetS based on three or four components, more patients in Tobago were diagnosed based on two components (p < 0.001).

CONCLUSIONS

There were high prevalence rates of the components of the MetS in both the islands of Tobago and Trinidad. Quantitatively, the aggregation of the components is higher in patients in Trinidad, which constitute greater risk for adverse cardiovascular outcome. Controlling central obesity should be the target in preventing MetS in the two islands.

Reduced phosphorylation of transcription factor Elk-1 in cultured fibroblasts of a patient with premature aging syndrome and insulin resistance

The effect of insulin and growth factor mediated signaling to gene regulation was investigated in cultured fibroblasts of a patient with a premature aging syndrome (metageria) and severe insulin resistance. Insulin receptor structure and function as well as major pathways activated by insulin, i.e. phosphatidyl inositol-3 kinase (PI-3 K) cascade or mitogen-activated protein kinase (MAPK) cascades, were functional. Inducibility of the proto-oncogene cfos, a representative endpoint of signaling pathways related to gene expression, by growth factors or insulin was reduced in patient cells. This reduced induction persisted in cfos promoter reporter gene studies indicating that the post receptor defect is localized proximal to the cfos promoter itself. Abundances of the transcription factors Elk-1 and SRF being major players in coupling of MAPKs to cfos promoter activation were not altered. However, basal and inducible phosphorylation of Elk-1 was impaired. In addition, basal and stimulated transcriptional activity mediated by Elk-1 was almost abolished in patient cells. Therefore these results identify a post receptor defect in cFos induction, which appears to be related to a functional alteration of Elk-1. A possible relation of this signal transduction defect to the specific premature aging syndrome remains to be elucidated.

Insulin-regulated transcription factors: molecular link between insulin resistance and cardiovascular risk factors

Patients with insulin resistance and/or type 2 diabetes have a 5-fold increase in cardiovascular mortality rate. Therefore, it is a current issue of discussion that arterial hypertension, lipid disorders as well as visceral obesity are coronary risk factors, which might belong to a syndrome that is caused by decreased insulin sensitivity. Concerning a possible molecular link between insulin resistance, atherosclerosis and obesity, we focus in our research on questions looking for a molecular link between lipid metabolism, insulin action, and obesity at a gene regulatory level. Alterations in the structure, function and regulation of transcription factors appear to be such signalling steps which might play an essential role in the pathogenesis and therapy of cardiovascular risk factors associated with insulin resistance, eg the so called metabolic syndrome. Recent examples are members of the nuclear hormone receptor superfamily, eg peroxisome proliferator-activated receptor (PPAR) isoforms and sterol regulatory element-binding proteins (SREBPs). Beside their regulation by different metabolites, these transcription factors are also targets of hormones, like insulin and leptin, growth factors, and inflammatory signals. Therefore, they appear to be a point of signalling convergence at a gene regulatory level. Major signalling pathways coupling receptors at the cell surface for hormones, growth factors as well as cytokines to gene regulatory events in the nucleus are the MAP-kinase cascades. We have recently defined different postreceptor defects in these pathways in patients with clinical phenotypes corresponding to congenital lipoatrophy. Therefore, these studies may identify novel pathways which play a role in the control of body weight, insulin sensitivity and cardiovascular risk.

Ribosomal subunit kinase-2 is required for growth factor-stimulated transcription of the c-Fos gene

Ribosomal subunit kinases (Rsk) have been implicated in the regulation of transcription by phosphorylating and thereby activating numerous transcription factors, such as c-Fos, cAMP responsive element binding protein (CREB), and nuclear receptors. Here we describe the generation and characterization of immortalized embryonic fibroblast cell lines from mice in which the Rsk-2 gene was disrupted by homologous recombinant gene targeting. Rsk-2-deficient (knockout or KO) cell lines have no detectable Rsk-2 protein, whereas Rsk-1 expression is unaltered as compared with cell lines derived from wild-type control mice. KO cells exhibit a major reduction in platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF)-1-stimulated expression of the immediate-early gene c-Fos. This results primarily from a reduced transcriptional activation of the ternary complex factor Elk-1 and reduced activation of the serum response factor. The reduced Elk-1 activation in KO cells occurs despite normal activation of the mitogen-activated protein kinase pathway and normal PDGF- and IGF-1-stimulated Elk-1 phosphorylation. By contrast, PDGF- and IGF-1-stimulated phosphorylation and transcriptional activation of CREB is unaltered in KO cells. Thus Rsk-2 is required for growth factor-stimulated expression of c-Fos and transcriptional activation of Elk-1 and the serum response factor, but not for activation of CREB or the mitogen-activated protein kinase pathway in response to PDGF and IGF-1 stimulation.

Characterization of a postreceptor signaling defect that impairs cfos expression in cultured fibroblasts of a patient with insulin resistance

Induction of cfos expression is a definite end point of signal transduction by receptor tyrosine kinases via MAPK cascades. We have examined signal transduction to transcription factor cFos in isolated fibroblasts of a patient with an inherited syndrome of insulin resistance. MAPK phosphorylation and activity were unaltered, but inducibility of cfos transcription was strongly impaired by insulin and reduced by PDGF. Induction of the cfos promoter via MAPK is mediated by activation of the ternary complex. Abundance of SRF or Elk-1 was unaltered, but Elk-1 phosphorylation following stimulation was reduced. Transient transfections with reporter genes under control of the Elk-1 binding ets/sre cis element or expression plasmids coding for the regulatory domain of Elk-1 fused to heterologous DNA binding domains revealed a defect of Elk-1 activation in the patient cells. These data identify a novel postreceptor defect of insulin and growth factors involving activation of transcription.

A single nucleotide substitution in the promoter region of the apolipoprotein C-II gene identified in individuals with chylomicronemia

Apolipoprotein (apo) C-II plays a major role as a cofactor for lipoprotein lipase, the enzyme involved in the hydrolysis of triglyceride-rich particles. We identified in two relatives of a family (mother and son) massive hypertriglyceridemia with chylomicronemia. In these individuals apoC-II was not measurable in plasma by radial immunodiffusion. On isoelectric focusing of very low density apolipoproteins, trace amounts of apoC-II became obvious in the regular position. By sequencing, no abnormalities in the exons or neighboring intron sequences were detected. However, three alterations in the DNA sequence were found upstream from the transcription initiation site. Two variations could be explained by differences in previously published DNA sequences. The third variation (A-->G; position -86; Das et al. 1987. J. Biol. Chem. 262: 4787-4793) was present only in the homozygous form in the two hypertriglyceridemic probands. In 46 hypertriglyceridemic individuals outside the family, this mutation was not found. In electrophoretic mobility shift experiments with nuclear extracts from HepG2 cells, the 31 bp DNA fragment carrying the A-->G substitution resulted in a markedly diminished protein binding compared with the wildtype DNA fragment. In promoter reporter gene assays, the activity of the basal promoter was reduced in the case of the A-->G substitution and the deletion of the bases -91 to -58. The pedigree analysis and the experimental results are evidence that this is the first mutation in the apolipoprotein C-II gene where a single nucleotide substitution diminishes the binding of a transcription factor to a positive cis-acting clement in the promoter resulting in a depletion of apolipoprotein C-II in plasma.

Structure of the human apolipoprotein C-II gene promoter

To localize transcriptional active cis elements and to study the effect of a single base transition at -86 derived from a patient (PS) with an inherited severe form of hypertriglyceridemia a reporter gene transfection assay with apo C-II promoter fragments was performed. Sequences from -170 to -140, -140 to -59 and -59 to -39 were transcriptional active. The A to G transition at -86 reduced promoter activity to 25% (pC2PS-13). A nuclear protein bound sequence specific to a DNA fragment from -102 to -70, but disappeared when the point mutation at -86 was introduced. We found that one of these cis elements enhances promoter activity as a response of cAMP elevation. Apo CII mRNA level increases after incubation of HepG2 cells with 10 microM forskolin within 2 hours as measured by northern blot analyses. Incubation of transfected cells (pC2W) with forskolin [10 microM] or a cAMP analogue resulted in an 6-fold increase of luciferase activity within 6 hours and a subsequent decrease. The results suggest that several positive acting elements are located between -170 and -36 and that one of them may be responsible for promoter activation by cAMP. The reduction of promoter activity by the point mutation may be a consequence of impaired protein-DNA interaction.

SREBP-1 mediates activation of the low density lipoprotein receptor promoter by insulin and insulin-like growth factor-I

Transcription of the low density lipoprotein (LDL) receptor gene is regulated by intracellular cholesterol concentration, hormones, and growth factors. We studied the mechanisms by which insulin and estradiol stimulate promoter activity of the LDL receptor gene. Hormonal effects were analyzed in HepG2 cells after transient transfection with promotor reporter gene constructs. Successive 5' deletions of the LDL receptor promoter fragment from -537 to +88 revealed the sterol regulatory element 1 (SRE-1) between -65 and -56 as an insulin- and estradiol-sensitive cis-element. If the SRE-1 is point mutated at position -59 (C to G), which abolishes the binding of the SRE binding proteins (SREBP-1 and SREBP-2), no insulin or estradiol stimulatory effect on reporter gene expression was observed, indicating a role of SRE binding proteins in this regulatory mechanism. The concentration of the 125-kDa membrane-integrated SREBP-1 precursor protein in LDL repressed HepG2 cells is not altered by hormone treatment. Concentrations of SREBP-1 mRNA and precursor protein are reduced significantly by high and stable expression of an SREBP-1 antisense cDNA fragment in HepG2 cells (SREBP1(-) cells). Transfection of SREBP1(-) cells with promoter construct phLDL4 (-105 to +88) reduces induction of reporter gene activity by insulin and insulin-like growth factor-I to 35 and 17%, respectively, compared with HepG2 cells. The stimulatory effect of estradiol remains unchanged, and the inductions by pravastatin are enlarged. We conclude that different regulatory effects converge at SRE-1, but that SREBP-1 is selectively involved in the signal transduction pathway of insulin and insulin-like growth factor-I leading to LDL receptor gene activation.