On the design of a MEMS piezoelectric accelerometer coupled to the middle ear as an implantable sensor for hearing devices.

The presence of external elements is a major limitation of current hearing aids and cochlear implants, as they lead to discomfort and inconvenience. Totally implantable hearing devices have been proposed as a solution to mitigate these constraints, which has led to challenges in designing implantable sensors. This work presents a feasibility analysis of a MEMS piezoelectric accelerometer coupled to the ossicular chain as an alternative sensor. The main requirements of the sensor include small size, low internal noise, low power consumption, and large bandwidth. Different designs of MEMS piezoelectric accelerometers were modeled using Finite Element (FE) method, as well as optimized for high net charge sensitivity. The best design, a 2 × 2 mm2 annular configuration with a 500 nm thick Aluminum Nitride (AlN) layer was selected for fabrication. The prototype was characterized, and its charge sensitivity and spectral acceleration noise were found to be with good agreement to the FE model predictions. Weak coupling between a middle ear FE model and the prototype was considered, resulting in equivalent input noise (EIN) lower than 60 dB sound pressure level between 600 Hz and 10 kHz. These results are an encouraging proof of concept for the development of MEMS piezoelectric accelerometers as implantable sensors for hearing devices.

Mice overexpressing CRH show reduced responsiveness in plasma corticosterone after a5-HT1A receptor challenge.

Corticotropin-releasing hormone (CRH) overproduction and serotonergic dysfunction have both been implicated in a range of psychiatric disorders, such as anxiety and depression, and several studies have shown interactions between these two neurotransmitter systems. In this study, we investigated the effects of CRH challenge on hypothalamo-pituitary-adrenal (HPA) axis activity in female transgenic mice overproducing CRH. Furthermore, the effects of mild stress on HPA axis activity and body temperature were investigated in these mice. Pre- and post-synaptic 5-HT1A receptor function were studied by monitoring body temperature and plasma corticosterone levels after challenge with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propyl-amino)-tetralin (8-OH-DPAT). Hypothermia in response to 8-OH-DPAT treatment did not differ between transgenic and wild type mice, indicating unaltered somatodendritic 5-HT1A autoreceptor function in mice overproducing CRH. In wild type mice 8-OH-DPAT increased plasma corticosterone levels, but not in transgenic animals. CRH injection, however, increased corticosterone levels in both groups. These data suggest desensitization of post-synaptic, but not pre-synaptic, 5-HT1A receptors in mice overproducing CRH. These findings resemble those seen in depressed patients following 5-HT1A challenge, which is in accord with the hypothesized role of CRH in the pathogenesis of depression.

Regulation of the hypothalamic-pituitary-adrenocortical system in mice deficient for CRH receptors 1 and 2.

Recent investigations in mouse lines either deficient for the CRH receptor 1 (CRHR1) or 2 (CRHR2) suggest that the CRH neuronal system may comprise two separate pathways that can be coordinately and inversely activated in stress-induced hypothalamic-pituitary-adrenal (HPA) response and anxiety-like behavior. We generated mice deficient for both CRHR1 (Crhr1(-/-)) and CRHR2 (Crhr2(-/-)) to investigate the HPA system regulation in the absence of known functionally active CRH receptors under basal conditions and in response to different ethologically relevant stressors. To elucidate possible gene dose effects on the action of both CRH receptors, our analysis included heterozygous and homozygous CRHR1- or CRHR2-deficient mice, mutants lacking both CRH receptors, compound mutants with homozygous and heterozygous deficiency for either of the receptors, and their wild-type littermates. Both male and female Crhr1(-/-)Crhr2(-/-) mutants were viable, fertile, and indistinguishable in size from wild-type littermates. We show that the endocrine phenotype of mice lacking both CRHRs is dominated by the functional loss of CRHR1. CRHR2 does not compensate for CRHR1 deficiency, nor does the lack of CRHR2 exacerbate the CRHR1-dependent impairment of the HPA system function. Within the intraadrenal CRH/ACTH system, our data suggest different roles for CRHR1 and CRHR2 in fine-tuning of adrenocortical corticosterone release.

Psychological stress increases hippocampal mineralocorticoid receptor levels: involvement of corticotropin-releasing hormone.

We investigated whether acute stressors regulate functional properties of the hippocampal mineralocorticoid receptor (MR), which acts inhibitory on hypothalamic-pituitary-adrenocortical activity. Exposure of rats to forced swimming or novelty evoked a significant rise in density of MR immunoreactivity in all hippocampal subfields after 24 hr, whereas exposure to a cold environment was ineffective. Time course analysis revealed that the effect of forced swimming on MR peaked at 24 hr and returned to control levels between 24 and 48 hr. In pyramidal neurons of CA2 and CA3, marked rises were already observed after 8 hr. Radioligand binding assays showed that corticotropin-releasing hormone (CRH) injected intracerebroventricularly into adrenalectomized rats also produced a rise in hippocampal MR levels; an effect for which the presence of corticosterone, but not dexamethasone, at the time of injection was a prerequisite. Moreover, pretreatment with the CRH receptor antagonist (d-Phe(12),Nle(21,38),alpha-Me-Leu(37))-CRH(12-41) blocked the effect of forced swimming on hippocampal MR levels. To investigate whether the rise in MR levels had any functional consequences for HPA regulation, 24 hr after forced swimming, a challenge test with the MR antagonist RU 28318 was conducted. The forced swimming exposed rats showed an enhanced MR-mediated inhibition of HPA activity. This study identifies CRH as an important regulator of MR, a pathway with marked consequence for HPA axis regulation. We conclude that the interaction between CRH and MR presents a novel mechanism involved in the adaptation of the brain to psychologically stressful events.

Influence of hemithyroidectomy on bromodeoxyuridine incorporation into DNA of rat thyroid follicular cells.

OBJECTIVE: To examine the bromodeoxyuridine (BrdU) incorporation into DNA of thyroid follicular cells (TFC) in the remaining thyroid lobe after hemithyroidectomy (hemiTx) in 1, 2, 3 and 4 weeks time after surgery. METHODS: The experiment was performed on male Wistar rats. The Cell Proliferation Kit (Amersham, UK) was used in order to detect the incorporated BrdU. The BrdU incorporation was expressed as a BrdU labeling index (BrdULI; a number of BrdU-immunopositive TFC per 1000 TFC). RESULTS: 1. No statistically significant changes of BrdULI were observed between the particular groups of sham-operated (shamTx)-rats in 1, 2, 3 and 4 weeks time after surgery, and in comparison of each of them to the controls (at time "0"); 2. In the first 2-week period after hemiTx, an increasing effect of that surgical procedure on BrdULI value was observed (the highest BrdULI value was detected 2 weeks after hemiTx); 3. In the third and fourth week after hemiTx, a decrease of BrdULI value was observed, as compared to BrdULI groups (in 1- and 2-week time after hemiTx), and to the controls (at time "0"); 4. An increase of weight of contralateral lobe was shown in 1, 2, 3 and 4 weeks after hemiTx in comparison to thyroid lobe weight in intact rats. CONCLUSIONS: During the first 2 weeks after hemiTx, the thyroid growth in the remaining thyroid lobe seems to ensue by hyperplasia mechanisms. The thyroid growth processes during subsequent 2 weeks (3rd and 4th) could result from other mechanisms - for example, from hypertrophy.

The brain mineralocorticoid receptor: greedy for ligand, mysterious in function.

Glucocorticoids exert their regulatory effects on the hypothalamic-pituitary-adrenocortical axis via two types of corticosteroid receptors: the glucocorticoid receptor and the mineralocorticoid receptor. Whereas the glucocorticoid receptor has a broad distribution in the brain, highest levels of mineralocorticoid receptor are found in the hippocampus. Based on the differential occupancy profile by endogenous glucocorticoids, glucocorticoid receptors are thought to mediate negative feedback signals of elevated glucocorticoid levels, whereas mineralocorticoid receptors control the inhibitory tone of the hippocampus on hypothalamic-pituitary-adrenocortical axis activity. Dysfunction of mineralocorticoid receptors and glucocorticoid receptors are thought to be implicated in stress-related psychiatric diseases such as major depression. Because of its intriguing features, we focus in this review on the mineralocorticoid receptor and provide data which reveal novel aspects of the pharmacology and physiology of mineralocorticoid receptors. Newly obtained results are presented, which help to solve the paradox of why dexamethasone binds with high affinity to mineralocorticoid receptors in vitro, yet binds poorly in vivo. Until recently, mineralocorticoid receptor protein and mRNA levels could only be routinely studied with in vitro cytosol binding assays, in vitro and in vivo receptor autoradiography, Northern blot analysis, and in situ hybridization. These methods are unfortunately hampered by several flaws, such as the necessity of adrenalectomy, no or poor neuroanatomical resolution, the fact that mRNA does not provide the same information as protein, or combinations of these factors. We present immunohistochemical data on mineralocorticoid receptors in the brain obtained by using commercially available antibodies, which alleviate many of these shortcomings. Furthermore, an in vivo microdialysis method is presented which allows the assessment of free corticosterone levels in the brain, which is critical for the study of the pharmacological basis of mineralocorticoid receptor (and glucocorticoid receptor) function. Finally, a novel aspect of the regulation of mineralocorticoid receptors is described which provides evidence that this receptor system is dynamically regulated. In conjunction with previously reported effects of antidepressants, these results have initiated a new concept on the cause of the hypothalamic-pituitary-adrenocortical axis disturbances often seen in stress-related psychiatric disorders such as major depression.

New mode of hypothalamic-pituitary-adrenocortical axis regulation: significance for stress-related disorders.

Two types of corticosteroid receptors have been identified in the brain and pituitary that play an important role in the regulation of the hypothalamic-pituitary-adrenocortical (HPA) axis. These glucocorticoid hormone binding receptors are the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). Evidently, a tight control of the concentration and function of these receptors is of prime importance for maintaining and regaining homeostasis after stressful challenges. Here, we describe a novel mechanism revealing a rapid upsurge in MR density in the hippocampus (a limbic structure highly involved in HPA axis regulation) after an acute psychologically stressful challenge. This rise in MR is accompanied by a stronger MR-mediated inhibitory control of the HPA axis. Thus, an acute stressful experience results in a reorganization of the HPA axis involving a principal role of the hippocampal MR. This novel mechanism may be of significance for increasing our understanding of the etiology of stress-related disorders.

Thymidine kinase activity in homogenates of rat thyroid lobes from euthyroid, hypothyroid and/or hyperthyroid rats incubated with EGF: studies ex vivo in vitro.

OBJECTIVE: To examine thymidine kinase (TK - ATP: thymidine 5'-phosphotransferase, EC 2.7.1.21) activity in homogenates of rat thyroid lobes incubated in vitro with epidermal growth factor (EGF). METHODS: The thyroid lobes were collected from euthyroid, hypothyroid and/or hyperthyroid animals. Hypothyroidism was developed in the experimental rats by an administration of 0.1 % solution of propylthiouracil (PTU) in drinking water for 2 weeks, while hyperthyroidism was obtained by daily i.p. injections of L-thyroxine (50 microg/kg, B.W.), also for 2 weeks. After collecting, the thyroids were incubated for 4 hours in RPMI 1640 medium with an addition of 20 mM of Hepes buffer, 15% FCS, penicillin (200 U/ml), streptomycin (10 ug/ml) and with EGF (Sigma) (0.1 ng/ml, 10 ng/ml, 1000 ng/ml). The control lobes were incubated without any addition of EGF to the medium. TK activity was expressed as the amount of reaction products, measured by ascending chromatography. RESULTS: 1. in the absence of EGF, TK activity in the homogenates of thyroid lobes from hypothyroid rats was lower, while it was higher in the lobes from hyperthyroid animals, when compared to these obtained from euthyroid controls; 2. EGF in the concentration of 0.1 ng/ml or 1000 ng/ml decreased, while that in the concentration of 10 ng/ml increased TK activity in lobes collected from euthyroid or hyperthyroid rats; 3. in the tissue collected from hypothyroid rats, the addition of EGF (0.1 ng/ml or 10 ng/ml) caused a slight increase in TK activity versus hypothyroid controls - a tendency towards diminishing TK activity could be observed as parallel to increasing EGF concentration. CONCLUSIONS: TK activity in the homogenates of rat thyroid lobes depends on the functional thyroid status and on applied EGF concentration in vitro.

Thymidine Kinase (EC 2.7.1.21) Activity in Homogenates of Human Thyroid Tissue, Following the Exposure to Epidermal Growth Factor (EGF) in vitro.

The activity of thymidine kinase (TK - EC 2.7.1.21) was measured in human thyroid tissue homogenates incubated in vitro. This enzyme functions as a part of the pyrimidine salvage pathway involved in DNA synthesis. The thyroid tissue was obtained from the thyroids of patients thyroidectomized at the Department of Endocrine Surgery, Medical University of lodz because of: 1. non-toxic nodular goiter (NTNG): tissue macroscopically unchanged, woman 46 yrs; 2. non-toxic adenoma (NTA), woman 37 yrs; 3. toxic adenoma (TA), woman 45 yrs. The tissue was incubated for 4 hours in RPMI 1640 medium (Gibco), containing Hepes buffer, 15 % FCS and the examined substance - epidermal growth factor (EGF) - used in five different concentrations (0.1 ng/ml, 1 ng/ml, 10 ng/ml, 100 ng/ml, 1000 ng/ml). The TK activity was measured according to Cheng and Prusoff (1974) as modified by Greger and Draminski (1989). The reaction products were separated by ascending chromatography. It was found that: 1. TK activity in thyroid tissue from NTNG and NTA did not significantly differ from control incubations without EGF, while it was significantly higher in the thyroid tissue from TA; 2. in the range of concentrations from 1 ng/ml to 1000 ng/ml, EGF increased TK activity in the macroscopically unchanged tissue from NTNG; 3. the incubation of the tissue from NTA with EGF resulted in the increase of TK activity in a concentration-dependent manner; 4. EGF stimulated TK activity in the tissue from TA, but the difference was significant only after the lowest EGF concentration. The obtained results suggest a possible role of EGF in the pathogenesis of NTNG, as well as of NTA and TA in humans.

[The role of genetic factors in the pathogenesis of thyroid neoplasms]. / Rola czynników genetycznych w powstawaniu nowotworów tarczycy.

This paper summarizes the current knowledge on the role of genetic factors in the development of thyroid neoplasms. The introduction of the methods and concepts of molecular genetics (as, e.g. recombinant DNA technology) have elucidated etiopathogenesis of the majority of thyroid tumours and, in the future, can make the diagnosis easier. Mutations of genes involved in the control of cellular growth and/or differentiation (ras, c-myc, RET, met) affect the development of thyroid neoplasms. Loss of heterozygosity (LOH) may suggest the presence of tumor suppressor genes and has been reported in thyroid follicular carcinomas. Activation of tyrosine kinase, whether by specific oncogene amplification or by rearrangement, appears to be highly specific for the transformation of thyroid follicular cells into papillary tumours. Cytogenetic studies have shown frequent clonal abnormalities in thyroid follicular adenomas and carcinomas.

INFLUENCE OF EGF ON THE RELATIVE VOLUMES OF COLLOID, EPITHELIUM AND STROMA AND ON THYROCYTE NUCLEI SIZE IN RAT THYROID LOBES IN VITRO.

The epidermal growth factor (EGF) is believed to be a potent growth factor for the thyroid gland. In the present study, we have examined the relative volumes of the main histological compartments (colloid, epithelium and stroma) and the size of thyrocyte nuclei (the mean volume, the mean intersection area and the mean perimeter) in the rat thyroid lobes incubated in vitro for 18 hrs with EGF, applied in 5 different concentrations: 0.1, 1.0, 10, 100 and 1000 ng/ml. Morphometric evaluation was performed, using a computer image analysis system, developed by us. We found that EGF - in concentration of 100 ng/ml - increased the relative volume of stroma when compared to controls, as well as to all the other groups incubated in exposure to that growth factor (used in different concentrations); at the same time, EGF decreased the relative volume of epithelium in the thyroid gland (statistical significance has been recorded only vs. EGF concentrations of 10 ng/ml and 1000 ng/ml). On the other hand, we observed that EGF - in concentration of 100 ng/ml - significantly increased the mean nuclear volume and the mean intersection area of thyrocyte nuclei when compared to the controls, as well as to EGF in concentrations of 1 ng/ml and 1000 ng/ml. With regards to the mean perimeter, a significant increase of its length was noted in the EGF(100 ng/ml)-exposed group vs. the group incubated with an addition of EGF (1 ng/ml).

[Comparative analysis of fine needle aspiration biopsy results performed in the laboratory of thyroid diseases, University School of Medicine in Lodz in 1985-91 with results of postoperative histopathologic examinations]. / Analiza porównawcza wyników biopsji aspiracyjnych cienkoiglowych tarczycy wykonanych w Samodzielnej Pracownii Tyreologii Instytutu Endokrynologii Akademii Medycznej w Lodzi w latach 1985-1991 z rezultatami pooperacyjnych badan histopatologicznych.

From 1985 to 1991 there were 5889 fine-needle aspiration biopsies of thyroid performed in our laboratory. 703 cytological diagnoses based on biopsy specimens taken from 679 patients, were compared with the results of postoperative histopathological examinations. There were 14% non-diagnostic biopsies. The statistical analysis was performed considering difficulties in differentiation between follicular adenomas and follicular carcinomas. Difficulties in evaluation of biopsies of cystic lesions were also considered. The results of cytological and histopathological examinations were agreeing with one another in 88% cases. In regard to diagnosis of malignant neoplasms, the sensitivity of the cytological investigation was equal to 63% and the specificity equaled to 90%. While considering detection of papillary carcinomas, the sensitivity was equal to 67%. Our results are in a compliance with the view, that the fine-needle aspiration biopsy is a useful method in a preoperative diagnosis of thyroid lesions.