Acute Immobilization Stress and Intraventricular Injection of CRF Suppress Naloxone-Induced LH Release in Ovariectomized Estrogen-Primed Rats

The present study was undertaken to evaluate the role and possible interaction of the endogenous opioid peptide (EOP) and corticotropin-releasing factor (CRF) in the acute stress-induced suppression of gonadotropin secretion in ovariectomized estrogen-primed rats. An intravenous (i.v.) injection of naloxone (10 or 20  mg/kg), an EOP antagonist, significantly elevated serum luteinizing hormone (LH) levels within 10  min in non-stressed animals. The naloxone-induced LH release was completely eliminated when tested 30  min after the onset of acute immobilization. In a subsequent study, it was found that suppression of the naloxone-induced LH release occurred as early as 5  min after the stress onset, and was still evident 60  min after the end of a 30-min period of immobilization. The effect of naloxone was restored 3  h after liberation of the animal from the 30-min immobilization. An intraventricular (i.c.v.) injection of CRF (1 or 5  μg) also significantly suppressed, in a dose-related manner, the effect of a subsequent i.v. injection of naloxone. However, an i.c.v. injection of α -helical CRF(9-41) (25 or 50  μg), a CRF antagonist, prior to immobilization, could not interfere with the suppressive effect of stress on naloxone-induced LH release. These results suggest that both acute immobilization stress and CRF can inhibit the LH secretory activity without mediation by EOP neurons. However, the stress-related suppression may involve non-CRF mechanism(s).     

Titanium-porcelain system. Part III: effects of surface modification on bond strengths

During its development, titanium was found to be incompatible with conventional dental porcelains due to weak bond strength brought about by titanium's high yet oxidative nature. In spite of the development of new low-fusing porcelains designed for titanium application, previous studies have shown that sandblasting pre-treatment prior to porcelain application led to weakening of the metal-ceramic bonding. The aim of this study is to search for an effective alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. The research evaluated the bond strength of 165 samples of titanium-porcelain systems divided into 11 groups. A three-point flexural bend test was conducted to measure the force required to fracture the porcelain on the titanium substrate. A correlation between the type of surface treatment and the bond strengths of each group was evaluated if it resulted to significant differences. The study found significantly differences in the energy-to-break of titanium-porcelain systems treated with hydrochloric acid and sandblasting compared with the control group. The bonds strength achieved by the titanium-porcelain system when treated with hydrochloric acid is comparable to that of conventional metal-ceramic alloy system. Hydrochloric acid treatment of the titanium substrate is a promising alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system.     

Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations

The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations.The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.     

Synaptic mechanisms acting on lumbar motoneurons during postural augmentation induced by serotonin injection into the rostral pontine reticular formation in decerebrate cats

Intrapontine microinjections of serotonin in acutely decerebrated cats resulted in the bilateral augmentation of the postural muscle tone of the hindlimbs. Optimal injection sites were located in the dorsomedial part of the rostral pontine reticular formation corresponding to the nucleus reticularis ponds oralis (NRPo). In this study, attempts were made to elucidate the cellular basis for the serotoninergically induced augmentation of postural muscle tone by recording the electromyographic (EMG) activity of hindlimb extensor muscles, the monosynaptic reflex responses evoked by electrical stimulation of group Ia muscle afferent fibres and the membrane potentials of hindlimb alpha-motoneurons (MNs). Serotonin injections resulted not only in the augmentation of the EMG activity of gastrocnemius soleus muscles, but also in the restoration of EMG suppression, which was induced by previous injection of carbachol into the NRPo. Extensor and flexor monosynaptic reflex responses were facilitated by serotonin injections into the NRPo. Such reflex facilitation was not induced by serotonin injections into the mesencephalic or the medullary reticular formation. Intrapontine serotonin injections resulted in membrane depolarization of extensor and flexor MNs with decreases in input resistance and rheobase. Spontaneous depolarizing synaptic potentials (EPSPs) increased in both frequency and amplitude. Peak voltage of Ia monosynaptic EPSPs also increased. Serotonin injections which followed carbachol injections resulted in membrane depolarization of MNs along with an increase in the frequency of spontaneous EPSPs and a decrease in carbachol-induced inhibitory postsynaptic potentials. Following pontine carbachol injections, antidromic and orthodromic responses in MNs were suppressed. Discharges of MNs evoked by intracellular current injections were also suppressed, but were restored following serotonin injections. These results indicate that postsynaptic excitation, presynaptic facilitation and disinhibition (withdrawal of postsynaptic inhibition) simultaneously act on the hindlimb MNs during serotonin-induced postural augmentation and restoration.     

Cordyceps militaris Fruit Body Extract Decreases Testosterone Catabolism and Testosterone-Stimulated Prostate Hypertrophy

The androgens testosterone and dihydrotestosterone (DHT) are essential for a variety of systemic functions in mature males. Alteration of these hormones results in late-onset hypogonadism (LOH) and benign prostate hyperplasia (BPH). The fruit bodies of fungi of the genus Cordyceps have been regarded as folk medicine or health food with tonic and antifatigue effects. The extract from the fruit body of Cordyceps militaris parasitizing Samia cynthia ricini (CM) was evaluated as a novel-candidate natural product for ameliorating male andropause symptoms. To explore the effects of CM on LOH and BPH, CM was applied to rat models and cultured testicular cells and prostate cells. The concentrations of androgens in the serum and culture media were determined by ELISA. Expression of steroidogenic enzymes and androgen-related genes was evaluated by qPCR, and prostatic cell proliferation was assessed with the cell-viability assay. CM maintained the serum levels of testosterone and DHT, but inhibited testosterone-induced prostate hypertrophy. CM also increased the secretion of testosterone and DHT by primary testicular cells, with no changes in the mRNA expression of steroidogenic enzymes, but decreased the growth of prostatic cell lines. Our data suggest that CM could improve both LOH and BPH in males.     

A comparative study of measurement of arterial blood pressure using HEM-802F and arterial cannulation

Finger arterial blood pressures determined by a newly developed sphygmomanometer, HEM-802F, were compared with arterial pressure obtained from direct measurement of the radial artery. An excellent correlation was found between the two methods (systolic: r = 0.93, diastolic: r = 0.91), although there was a large variability among individual subjects. The range of differences between them are from +32 to –13mmHg for systolic and +15 to –25mmHg for diastolic blood pressure measurement. HEM-802F underestimated systolic pressure (–4.0mmHg) and overestimated diastolic pressure (+6.7mmHg), compared with intra-arterial readings.The HEM-802F was useful for the non-invasive arterial pressure monitoring during general anesthesia.(Shigemi K, Takahashi H, Hashimoto S et al.: A comparative study of measurement of arterial blood pressure using HEM-802F and arterial cannulation. J Anesth 4: 91–93, 1990)     

The role of perceived job stress in the relationship between smoking and the development of peptic ulcers

Although smoking has been considered a risk factor in causing pepticulcers, no study has examined the effects of job stress on the relationship between peptic ulcers and smoking. To establish a link between gastric or duodenal ulcers over two years and a state of perceived job stress, a questionnaire, including questions on demographics, smoking, history of peptic ulcer and perceived job stress was conducted. Follow-up surveys were carried out every six months to accumulate the data for this analysis and the time span of this follow up study was two years. To examine the role of perceived job stress on the relationship between smoking and peptic ulcers, stratified analyses were performed. Some specific causes of perceived job stress such as "Too much competition," "Schedule is too tight or pressed to work too hard" had high estimated relative risks: 2.13 with 95% confidence interval (CI) of 1.09-4.16 and 2.50 with 95% CI of 0.98-6.40, respectively. Stratified analyses suggested an effect-measure modification of perceived job stress in the relationship between peptic ulcers and smoking. Multiplicative and additive models suggest positive interaction between perceived job stress and smoking. These results suggest that specific perceived job stress is an effect modifier in the relationship between the history of the peptic ulcer and smoking.