Biomedical subjects

T Mera

Publications and source records attributed to T Mera.

15 recordsLinked to original sources

PubMed2006

Prolactin-releasing peptide is a potent mediator of stress responses in the brain through the hypothalamic paraventricular nucleus.

The effects of i.c.v. administration of prolactin-releasing peptide on neurons in the paraventricular nucleus of rats and plasma corticosterone levels were examined by measuring changes in Fos-like immunoreactivity, c-fos mRNA using in situ hybridization histochemistry, and plasma corticosterone using a specific radioimmunoassay. Approximately 80% of corticotropin-releasing hormone immunoreactive cells exhibited Fos-like immunoreactivity in the parvocellular division of the paraventricular nucleus 90 min after i.c.v. administration of prolactin-releasing peptide. The greatest induction of the c-fos mRNA expression in the paraventricular nucleus was observed 30 min after administration of prolactin-releasing peptide, and occurred in a dose-related manner. Plasma corticosterone levels were also significantly increased 30 min after administration of prolactin-releasing peptide. Next, the effects of restraint stress, nociceptive stimulus and acute inflammatory stress on the expression of the prolactin-releasing peptide mRNA in the dorsomedial hypothalamic nucleus, nucleus of the solitary tract and ventrolateral medulla were examined using in situ hybridization histochemistry for prolactin-releasing peptide mRNA. Restraint stress and acute inflammatory stress upregulated the prolactin-releasing peptide mRNA expression in the nucleus of the solitary tract and ventrolateral medulla. Nociceptive stimulus upregulated the prolactin-releasing peptide mRNA expression in the ventrolateral medulla. Finally, we observed that pretreatment (i.c.v. administration) with an anti-prolactin-releasing peptide antibody significantly attenuated nociceptive stimulus-induced c-fos mRNA expression in the paraventricular nucleus. These results suggest that prolactin-releasing peptide is a potent and important mediator of the stress response in the brain through the hypothalamic paraventricular nucleus.

Analysis of Variance↗

PubMed2005

Expression of immediate early genes and vasopressin heteronuclear RNA in the paraventricular and supraoptic nuclei of rats after acute osmotic stimulus.

Monitoring the expression of immediate early genes (IEGs) is useful for following stress-induced cellular responses in the neuroendocrine system. We have examined the transcriptional activities of four IEGs (c-fos, junB, NGFI-A and NGFI-B) and of the arginine vasopressin (AVP) gene in the hypothalamic paraventicular (PVN) and supraoptic nuclei (SON) of rats after acute osmotic stimuli, using in situ hybridization histochemistry. After intraperitoneal (i.p.) administration of hypertonic saline (2% body weight, 900 mOsm/kg), the expression levels of all IEG mRNAs were increased significantly both in the PVN and SON at as early as 10 min, peaked at 30 min and remained elevated until 60 min. The expression of AVP heteronuclear (hn)RNA also peaked at 30 min, and remained elevated until 180 min. Thirty min after i.p. administration of hypertonic saline (600 mOsm/kg), the expression levels of all IEG mRNAs in the PVN and SON were significantly increased in comparison with those after i.p. administration of isotonic saline (290 mOsm/kg). Regression analysis revealed that expression levels of the IEG mRNAs and AVP hnRNA were positively correlated with the plasma concentration of sodium, and the rates of increase of the expression levels of all IEG mRNAs were similar. The expression levels of all IEG mRNAs examined are useful markers for following the changes of the AVP gene transcription in the PVN and SON after acute osmotic stimuli in rats.

Animals↗

PubMed2000

[A case of portal-systemic encephalopathy associated with Sheehan's syndrome].

A 66-year-old woman had had recurrent episodes of disturbed consciousness whenever she had been constipated or dehydrated. She had been inactive and afflicted with obstinate constipation since she had menopause at age of 32. She underwent gastrectomy for gastric ulcer at age of 37. Laboratory examination showed marked hyperammonemia, reduction in Fisher ratio, and poor excretion of ICG. Furthermore, hypopituitarism and secondary hypothyroidism were found. She was diagnosed as Sheehan's syndrome. A T1-weighted MRI demonstrated symmetrical high intensity in the bilateral globus pallidus and empty sella. The histological examination of the liver revealed a mild lymphocytic infiltration without liver cirrhosis. Abdominal angiography showed a large shunt vessel between the splenic vein and the left renal vein. After embolization of the shunt vessel, hyperammonemia and neurological impairment improved. Additionally multiple hormones replacement has been useful to reduce the drugs of standard therapy for hepatic coma. In this case, we speculated that Sheehan's syndrome accelerated the constipation and worsened the shunt encephalopathy.

Aged↗

PubMed1998

Spatial distribution of myosin heavy chain isoforms and lactate dehydrogenase M4 in the limb musculature of two crossbred lambs.

Sixteen different skeletal muscle samples were distributed in the cross-section of eight hip and thigh muscles. Contractile characteristics were assessed by measuring myosin heavy chain (MHCI, MHCIIa, MHCIIb) composition by electrophoresis. Glycolytic capacity was estimated by immunochemical quantitation of the LDH-M4. Histochemistry was used as a reference. The MHC isoform composition of most of the muscles in this study was heterogeneous. When an intramuscular transversal regionality was observed (semitendinosus, vastus lateralis, vastus medialis and rectus femoris muscles), MHCI percentage increased toward deeper layers, while MHCIIb and LDH-M4 decreased. The pattern of MHCIIa isoform distribution was less evident. Within semimembranosus and gluteus medius muscles, proportions of MHC isoforms were constant. Gradients of variation of MHCI and MHCIIb isoforms across rectus femoris and vastus medialis muscles were sharper than those of semitendinosus and vastus lateralis muscles. For the vastus lateralis muscle, these gradients may also be modified according to the breed. Breed effect was mainly shown by MHCIIb and MHCI isoforms and was not observed at all the sampling points of the muscles. These observations show that breed effect on muscle contractile and metabolic characteristics is not uniformly expressed throughout the muscle. Results of a comparison may differ according to the muscle and sampling location.

Animals↗

PubMed1992

Descending pain inhibitory system involved in acupuncture analgesia.

The descending pain inhibitory system (DPIS) associated with acupuncture analgesia (AA), caused by low frequency stimulation of an acupuncture point, was identified by the results of lesion and stimulation procedures previously determined to differentiate the afferent and efferent paths in rats. The DPIS starts in the posterior arcuate nucleus and descends to the hypothalamic ventromedian nucleus (HVM) from whence it divides into two pathways: one path, the serotonin mediated path, descends through the ventral periaqueductal central gray (V-PAG) and then to the raphe magnus (RM). The other, the noradrenaline mediated path, descends through the reticuloparagigantocellular nucleus (NRPG) and part of the reticulogigantocellular nucleus (NRGC). The afferent and efferent paths are both present in the RM and NRGC, and were separately identified by means of the analgesia (SPA) produced by stimulation of the separate regions in AA responders and nonresponders, because SPA of these regions in nonresponders produced only efferent pathway mediated analgesia.

Acupuncture Analgesia↗

PubMed1991

Longitudinal observation of cementum regeneration through multiple fluorescent labeling.

The assessment of new attachment after periodontal treatment has been the focus of continuous research. An approach to longitudinally examine the deposition of cementum was devised by using fluorescence microscopy (FL), contact microradiography (CMR), and toluidine blue staining (TBS) after the injection of three labeling agents known to be incorporated within newly mineralized tissues with different tones: tetracycline, calcein, and alizarin complexion. Three adult Japanese monkeys (male, 6.0 to 8.3 Kg weight) were used for this experiment. Bone defects were surgically created in 24 mandibular sites and a copper plate was inserted for a period of 4 weeks to promote microbial colonization to form periodontal pockets. Scaling and root planing (baseline) were then performed, and the fluorescent agents were administered twice weekly leaving a 1 week interval between the different agents. The mandibular specimens were fixed in neutralized formalin and embedded in polyester resin. Undecalcified sections were prepared 3, 6, and 9 weeks after baseline. Cementum regeneration was confirmed in 18 out of 24 sites; in 6 samples only epithelial proliferation was observed. Regeneration could be seen as early as 2 weeks after debridement. Cementum was identified by observation under FL of a labeled structure, discrimination in the degree of mineralization of dentin by CMR, and by the presence of functional collagen fibers and location of the epithelial border by TBS. In this study the use of three different labeling agents using the three observation techniques was shown to be effective for the longitudinal assessment of cementum regeneration.

Alveolar Bone Loss↗

PubMed1990

Digital subtraction of radiograph in evaluating alveolar bone changes after initial periodontal therapy.

The purpose of this study was to determine the effect of initial periodontal therapy on crestal bone remineralization with the use of a digital subtraction method for quantitative analysis. Fifteen crestal sites randomly selected from five patients were examined at the initial visit, after completion of oral hygiene instruction, and 1, 3, and 6 months after scaling and root planing with standardized radiographs. The radiographs were digitized by means of a drum-scanning microdensitometer with a sampling aperture of 50 microns producing 256 gray levels and corrected for difference of contrast between image pairs. Results were as follows: (1) statistically significant changes were observed even 1 month after the therapy and (2) the extent of changes was quantitatively expressed and monotonically increased with time. These results indicate that subtraction radiography may be a reproducible and quantitative method for the evaluation of periodontal therapy.

Alveolar Process↗

PubMed1989

[Digital subtraction radiography for the detection of periodontal bone changes].

This study was performed to evaluate the efficacy of digital subtraction radiography in detecting alveolar bone changes. In order to test the sensitivity of quantitative evaluation by subtraction radiography, a copper equivalent thickness obtained from digitized radiographs was compared with the actual mineral content of bone phantoms with 15 different minerals and 25 bone specimens. Results demonstrated that the copper equivalent thickness correlated well with the actual mineral content (bone phantoms: gamma s = 1.0, bone specimens: gamma s = 0.985). In order to test the ability of digitized subtraction radiography in assessing alveolar bone changes in vivo, subtraction images were compared with histological features. The experimental angular bony defects were treated with conservative periodontal therapy in 3 monkeys. The standardized radiographs were taken longitudinally after therapy, and subtraction images were made from the sequentially obtained radiographs. In addition, for fluorescent histomorphometrical evaluations of new bone formations, the animals were dosed with oxytetracycline, calsein solution and arizarin complex solution. Radiographic and histological evaluations were scheduled to provide healing periods of 2, 3, 4, 5, 6 and 9 weeks after periodontal therapy. Subtraction radiography offered an objective method to follow histological changes of alveolar bone, and the copper equivalent thickness obtained from subtraction radiographs correlated with the histometric bone volume (gamma s = 0.9023, p less than 0.01). The results of these studies indicated that subtraction radiography was useful in monitoring alveolar bone changes associated with periodontal disease and treatment and that the quanitative measurement of periodontal bone changes by subtraction radiography was feasible.

Alveolar Process↗

PubMed1989

[Process of regeneration of cementum observed by various fluorescent-labeling methods].

The purpose of this study was to evaluate the effect of various fluorescent-labeling methods on longitudinal information associated with the process of regeneration of cementum after periodontal therapy. Mandibular bilateral premolars and molars in three monkeys were used. Prior to the labeling, experimental periodontitis was surgically produced at the mesial site of each tooth. In four weeks, scaling and root planing were carried out, and time marking was performed by injection of 3 kinds of fluorescent-labeling materials, tetracycline hydrochloride (30 mg/kg), calcein (8 mg/kg), and alizarin complexon (20 mg/kg), intramuscularly. The animals were sacrificed 4 days after the last injection and serial sections without decalcification were prepared. They were examined under a fluorescence microscope and further observed by contact microradiography (CMR) and staining with toluidine blue. According to the observations made by fluorescence microscopy, marked regeneration of the cementum was revealed by each of the 3 labeling agents. Also, the presence of regenerated cementum was supported by the observations by CMR and after toluidine blue staining. In addition, the regeneration of new cementum was shown to start in about 2 weeks after scaling and root planing. Judging from the results of this experiment, the various fluorescent-labeling methods seem to be effective for observing the process of regeneration of cementum.

Animals↗

PubMed1988