Zvezdana Kojic

Complexity reduction of chromatin architecture in macula densa cells during mouse postnatal development.

To determine whether complexity of chromatin structure in kidney macula densa cells (MDC) decreases during postnatal development in mice.

The opposite roles of glucocorticoid and α1-adrenergic receptors in stress triggered apoptosis of rat Leydig cells.

The stress-induced initiation of proapoptotic signaling in Leydig cells is relatively well defined, but the duration of this signaling and the mechanism(s) involved in opposing the stress responses have not been addressed. In this study, immobilization stress (IMO) was applied for 2 h daily, and animals were euthanized immediately after the first (IMO1), second (IMO2), and 10th (IMO10) sessions. In IMO1 and IMO2 rats, serum corticosterone and adrenaline were elevated, whereas serum androgens and mRNA transcription of insulin-like factor-3 in Leydig cells were inhibited. Reduced oxygen consumption and the mitochondrial membrane potential coupled with a leak of cytochrome c from mitochondria and increased caspase-9 expression, caspase-3 activity, and number of apoptotic Leydig cells was also observed. Corticosterone and adrenaline were also elevated in IMO10 rats but were accompanied with a partial recovery of androgen secretion and normalization of insulin-like factor-3 transcription coupled with increased cytochrome c expression, abolition of proapoptotic signaling, and normalization of the apoptotic events. Blockade of intratesticular glucocorticoid receptors diminished proapoptotic effects without affecting antiapoptotic effects, whereas blockade of intratesticular α(1)-adrenergic receptors diminished the antiapoptotic effects without affecting proapoptotic effects. These results confirmed a critical role of glucocorticoids in mitochondria-dependent apoptosis and showed for the first time the relevance of stress-induced upregulation of α(1)-adrenergic receptor expression in cell apoptotic resistance to repetitive IMOs. The opposite role of two hormones in control of the apoptotic rate in Leydig cells also provides a rationale for a partial recovery of androgen production in chronically stressed animals.

The effect of grain size on the biocompatibility, cell–materials interface, and mechanical properties of microwave‐sintered bioceramics

The effect of decreasing the grain size on the biocompatibility, cell-material interface, and mechanical properties of microwave-sintered monophase hydroxyapatite bioceramics was investigated in this study. A nanosized stoichiometric hydroxyapatite powder was isostatically pressed at high pressure and sintered in a microwave furnace in order to obtain fine grained dense bioceramics. The samples sintered at 1200°C, with a density near the theoretical one, were composed of micron-sized grains, while the grain size decreased to 130 nm on decreasing the sintering temperature to 900°C. This decrease in the grain size certainly led to increases in the fracture toughness by much as 54%. An in vitro investigation of biocompatibility with L929 and human MRC-5 fibroblast cells showed noncytotoxic effects for both types of bioceramics, while the relative cell proliferation rate, cell attachment and metabolic activity of the fibroblasts were improved with decreasing of grain size. An initial in vivo investigation of biocompatibility by the primary cutaneous irritation test showed that both materials exhibited no irritation properties.

Oxidized cotton as a substrate for the preparation of hormone-active fibers-characterization, efficiency and biocompatibility

Oxidized cellulose has a long history of safe and effective use in medical applications. In this paper, research has been directed towards obtaining hormone-active cellulose fibers in the form of an artificial insulin depot, and examination of its biocompatibility regarding cytotoxicity, sensitization, and irritation. The procedure of obtaining the fibrous insulin depot is based on the modification of cotton fibers with sodium periodate, followed by chemisorption of insulin from insulin aqueous solutions. In order to optimize the insulin chemisorption process, the influence of the fiber structure parameters, i.e. the aldehyde group content and iodine sorption value (ISV) on the chemisorption capacity was examined. The obtained artificial depot, containing ≈55 mg insulin/g of fibers, has been characterized in vitro by investigation of the desorption kinetics of the insulin from the fibrous depot. It has been shown that insulin is controllably released in quantities of 1.3-1.6 mg of insulin during 24 hours, in the course of 20 days. The results of biocompatibility tests have shown that the examined artificial depot neither shows irritating effects nor provokes sensitizing or cytotoxic effects. Therefore, these materials are acceptable for use in a direct contact with tissue of a living organism.

A tissue-implant reaction associated with subcutan implantation of alpha-tricalcium phosphate, dental ceramic and hydroxyapatite bioceramics in rats

Calcium phosphate ceramics are among the more commonly used and biocompatible ceramics. Recently, we have synthesized a new calcium phosphate ceramic, alpha tricalcium phosphate (aTCP). The aim of this study was to assess the biocompatibility of this original, in our laboratory modified, newly synthesized aTCP ceramic, by carefully evaluating the inflammatory reaction of soft tissue in response to its subcutaneous implantation, and by comparing this result with the results of already widely used virtually non-toxic, non-immunogenic, and almost chemically inert dental (DC) and hydroxy apatite (HAP) ceramics. Implants (diameter 5x2 mm) of aTCP, DC and HAP were implanted into 12 adult male rats subcutaneously. At 2 weeks and 12 weeks post-implantation, the animals were euthanized and the tissueimplant reactions were analyzed histologically. Evaluation of routine stained sections (5 _m, hematoxylin & eosin) of the cutis and subcutis surrounding the aTCP, DC and HAP ceramics revealed the following: 1) all the ceramic devices had fibrous connective tissue capsules; 2) there were significant differences in the tissue - implant reactions based on the estimated time, while there were no differences in the tissue-implant reaction based on the type of ceramic material; 3) two weeks after implantation hyperemia and cellular proliferation were the most expressive results, while twelve weeks after implantation extensive angiogenesis and collagen fibers production were the prominent findings for all types of implanted calcium phosphate ceramics.

Myocardial Na+ K+-ATPase and SERCA: Clinical and Pathological Significance From a Cytological Perspective

Structure and functions of Na+/K+-ATPase and SERCA are described with details on their subunits, isoforms, and intracellular localization. Main regulatory mechanisms are summarized. Molecular mechanisms of cell death and heart failure are explained with the analysis of the role of Na+/K+-ATPase and SERCA in these processes. Facts are considered from a cytological, pathological, and clinical perspective with an accent to new therapeutic strategies. The aim of this contribution is an overview of functional results in a structural context.

[Plasma levels of cortisol and opioid peptide beta-endorphin during spontaneous vaginal delivery].

INTRODUCTION Labor pain is very frequent in clinical practice, but the underlying mechanisms as well as numerous neuroendocrine responses activated by such pain have not been fully explained yet. OBJECTIVE The objective of the study was to determine the influence of labor pain on plasma levels of cortisol and opioid peptide beta-endorphin. METHOD Cortisol and beta-endorphin levels were measured in blood plasma of: health, non-pregnant women (group 1, n=8), health pregnant women (group 2, n=8) and in parturitions, through fourth ages (group 3, n=8). Plasma level ofcortisol was measured by radioimmunoassay, and beta-endorphin by enzyme immunoassay. Data were expressed as mean +/- standard error of mean and were analyzed by Students t test and Mann Whitney test. RESULTS Plasma level of cortisol in group 2 was significantly increased compared to the group 1. During labor progression, plasma level of cortisol was rising till the third labor age. Plasma level of cortisol in fourth labor age was not significantly different from the age one and group 1. Plasma level of beta-endorphin was (ng/L): in group 1: 64 +/- 20, group 2: 70 +/- 22, group 3: the first labor age: 75 +/- 15, the second labor age: 193 +/- 54, the third labor age: 346 +/- 97 and the fourth labor age: 114 +/- 31. CONCLUSION These results indicate that both beta-endorphin and cortisol are involved in regulation and modulation of labor pain and stress.