Biomedical subjects

Dusica Maysinger

Publications and source records attributed to Dusica Maysinger.

25 records · Page 2Linked to original sources

PubMed2003

Age-related neurodegenerative changes in the central nervous system of estrogen-deficient follitropin receptor knockout mice.

Age-related neurodegenerative conditions are characterized by neuronal death and degeneration that lead to a progressive functional decline. Among the factors influencing degenerative processes during aging are altered levels of neurotrophic ovarian steroid 17beta-estradiol (E2). The follitropin receptor knockout (FORKO) female mouse displays hormonal imbalance characterized by very low levels of circulating E2 and high levels of testosterone. FORKO mice (24 days and 20 months) were used to investigate structural and functional changes in the central nervous system. We now show that the lifelong depletion of the sex hormone E2 in female FORKO mice correlates with abnormal behavior associated with defined alterations in brain morphology early in life, especially in aged animals. Immunohistochemical studies showed significant increases in the size and number of immunoreactive glial fibrillary acidic protein glial cells found in several brain regions (cortex and hippocampus) and a dramatic decline in estrogen receptors alpha and beta in the amygdala of FORKO females. These changes were associated with increased signs of anxiety in these animals. In the present study, we provide evidence that the chronic depletion of sex hormone E2 from early development leads to neural impairments in adult and aged FORKO mice that are associated with hypertrophy of glial cells, cell loss in distinct brain regions, and abnormal behavior. We suggest that the hormonal imbalance found in the female FORKO mouse provides an experimental paradigm for the study of morphological correlates of the behavioral changes that often accompany menopause in women.

Age Factors↗

PubMed2003

Neotrofin, a novel purine that induces NGF-dependent nociceptive nerve sprouting but not hyperalgesia in adult rat skin.

We report peripheral actions in rats of Neotrofin, a purine derivative of therapeutic interest. Systemic injections mimicked NGF in eliciting sprouting of nociceptive nerves without affecting their regeneration. The sprouting was prevented by anti-NGF treatment, implicating endogenous NGF. We detected no Neotrofin-induced increases in cutaneous NGF levels or in retrograde NGF transport. In contrast, both NGF and phosphorylation of trkA increased significantly in DRGs, with a marginal appearance of phosphorylated trkA in axons. We conclude that the DRG effects of Neotrofin are responsible for its induction of sprouting. Neotrofin also induced a striking phosphorylation of axonal erk 1 and 2, which was, however, unaffected by anti-NGF treatment. We suggest that this NGF-independent MAP kinase activation is involved in nonsprouting functions of Neotrofin such as neuroprotection. Unlike injected NGF, Neotrofin did not induce hyperalgesia, supporting its candidacy as a treatment for peripheral neuropathies like those induced by diabetes and anticancer chemotherapy.

Aminobenzoates↗

PubMed2002

Islet-neogenesis-associated protein enhances neurite outgrowth from DRG neurons.

Islet-neogenesis-associated protein, INGAP, is a 175-amino-acid pancreatic acinar protein that stimulates pancreatic duct cell proliferation in vitro and islet neogenesis in vivo. To date, the mitogenic activity of INGAP has been identified only in nonneural tissues. The aim of this study was to examine the effects of a pentadecapeptide of INGAP (INGAP peptide), the biologically active portion of the native protein, in cultured dorsal root ganglia (DRG) explants from C57BL/6 mice. The present study provides evidence that INGAP peptide acts as a mitogen in the peripheral nervous system (PNS), and that it enhances neurite outgrowth from DRGs in vitro in a time- and dose-dependent manner. The neuritogenic action of INGAP peptide correlates with an increase in [(3)H]thymidine incorporation (P < 0.0001) and mitochondrial activity (P < 0.001). Results from these studies suggest that INGAP peptide promotes Schwann cell proliferation in the DRG which releases trophic factors that promote neurite outgrowth.

Animals↗

PubMed2002

The influence of MK-801 on the hippocampal free arachidonic acid level and Na+,K+-ATPase activity in global cerebral ischemia-exposed rats.

The influence of 20 min global cerebral ischemia on the free arachidonic acid (FAA) level and Na+,K+-ATPase activity in the rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20 min global cerebral ischemia and were sacrificed immediately, 0.5, 1, 2, 6, 24, 48, 72, and 168 h after ischemic procedure. The level of the FAA and the Na+,K+-ATPase activity was measured during all reperfusion periods examined. Various doses of MK-801 (0.3, 1.0, 3.0, and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. It was found that 20 min global cerebral ischemia induces a statistically significant increase of the FAA level immediately after ischemia and during the first 0.5 h of reperfusion. After a transient decrease, the level of FAA level increased again after 24 and 168 h of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 h after ischemic insult while application of 5.0 mg/kg of MK-801 exerted a protective effect during the first 24 h. Global cerebral ischemia induces the significant decline in the Na+,K+-ATPase activity in the hippocampus starting from 1 to 168 h of reperfusion. Maximal inhibition was obtained 24 h after the ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protection during the first 24 h while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined. Our results suggest that, in spite of different and complex pathophysiological mechanisms involved in the increase of FAA level and the decrease of the Na+,K+-ATPase activity, blockade of NMDA receptor subtype provides a very important strategy for the treatment of the postischemic excitotoxicity.

Animals↗

PubMed2002

Amylin-induced cytotoxicity is associated with activation of caspase-3 and MAP kinases.

Nanomolar concentrations of human amylin promote death of RINm5F cells in a time- and concentrationdependent manner. Morphological changes of chromatin integrity suggest that cells are predominantly undergoing apoptosis. Human amylin induces significant activation of caspase-3 and strong and sustained phosphorylation of stress-activated protein kinases, c-Jun N-terminal kinase (JNK) and p38, that precedes cell death. Extracellular signal-regulated kinase (ERK) activation was not concomitant with JNK and/or p38 activation. Activation of caspase-3 and mitogen-activated protein kinases (MAPKs) was detected by Western blot analysis. Addition of the MEK1 inhibitor PD 98059 had no effect on amylin-induced apoptosis, suggesting that ERK activation does not play a role in this apoptotic scenario. A correlative inhibition of JNK activation by the immunosuppressive drug FK506, as well as a selective inhibition of p38 MAPK activation by SB 203580, significantly suppressed procaspase-3 processing and the extent of amylin-induced cell death. Moreover, simultaneous pretreatment with both FK506 and SB 203580, or with the caspase-3 inhibitor Ac-DEVD-CHO alone, almost completely abolished procaspase-3 processing and cell death. Thus, our results suggest that amylin-induced apoptosis proceeds through sustained activation of JNK and p38 MAPK followed by caspase-3 activation.

Amyloid↗

PubMedDate not supplied

Cellular internalization of poly(ethylene oxide)-b-poly(epsilon-caprolactone) diblock copolymer micelles.

Poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) block copolymers self-assemble into micelles in aqueous solution. We have examined whether these micelles can internalize into P19 cells in vitro. Fluorescently labeled PEO(45)-b-PCL(23) block copolymer was prepared by conjugating a tetramethylrhodamine molecule to the end of the hydrophobic PCL block. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies yielded 24 +/- 2 and 25 +/- 2 nm, respectively, for the diameters of the micelles. The studies also showed that chemical labeling did not effect the morphology or size. When the rhodamine-labeled PEO(45)-b-PCL(23) block copolymer micelles were tested in vitro, time-, concentration-, and pH-dependence of the internalization process suggested that internalization proceeded by endocytosis. The results from these studies provide the first direct evidence for the internalization of PEO(45)-b-PCL(23) micelles. Future studies will utilize multiple labeling of these micelles, allowing questions to be addressed related to the fate of internalized micelles as drug carriers, the destination of the incorporated drugs or fluorescent probes released from micelles, and the identification of the subcellular localization of the whole drug-carrier system within cells, both in vitro and in vivo.

Animals↗

PubMedDate not supplied

Polycaprolactone-block-poly(ethylene oxide) micelles: a nanodelivery system for 17beta-estradiol.

Various hormone replacement regimens and delivery systems have been developed; however, there is still a need for additional, easily controllable and biocompatible systems. We have developed and characterized biocompatible polycaprolactone-block-poly(ethylene oxide) (PCL-b-PEO) micelles for the delivery of 17beta-estradiol (E2) and investigated their loading and release properties using fluorescence spectroscopy. The micelles are spherical aggregates that range in size from 20 to 40 nm, as determined by both transmission electron microscopy and dynamic light scattering. A high loading efficiency for E2 of up to 96%, as well as a high drug loading capacity of up to 4000 molecules of E2 per micelle (equivalent to 190% (w/w)), is obtainable. In addition, the E2 loading and release can be controlled by modifying the block length of the polycaprolactone core and the initial estradiol concentration. The release of E2 from the micelles showed a biphasic profile under perfect sink conditions: there is an initial burst release, followed by a slow and prolonged release for up to 5 days, until complete release is achieved. The release of E2 from the micelles was shown to be diffusional, as shown by the linearity of the release as a function of the square root of time. Approximate diffusion coefficients of the order of 10(-17) cm2/s were obtained. In vitro and in vivo experiments confirmed that the biological activity of E2 was retained after preparation of the micelles. This micelle carrier could serve as a versatile and efficient nanodelivery system for steroids and other poorly water soluble drugs that require solubilizing agents for delivery.

Animals↗