Regulation of the preovulatory gonadotropin surge by endogenous steroids

Estradiol secreted by growing ovarian follicle(s) has been considered classically to be the neural trigger for the preovulatory surge of gonadotropins. The observation that the estradiol-induced gonadotropin surge in ovariectomized rats is of lesser magnitude and duration than that found in the cycling rat at proestrus has resulted in a search for other steroid regulators. Progesterone is a major regulator of the preovulatory gonadotropin surge. It can only act in the presence of an estrogen background, which is necessary for the synthesis of progesterone receptors. In the estrogen-primed ovariectomized rat, progesterone is able to initiate and enhance the gonadotropin surge to the magnitude observed on the day of proestrus and limit it to 1 day. The physiological role of progresterone in the induction of the preovulatory gonadotropin surge has been demonstrated by the attenuation of the progesterone-induced surge and the endogenous proestrus surge by progesterone receptor antagonist RU486 and the progesterone synthesis inhibitor trilostane. The promoter region of the follicle-stimulating hormone (FHS)-beta gene contains multiple progesterone response elements and progesterone brings about FSH release as well. The reduction of progesterone in the 5 alpha-position appears to be important for the regulation of progesterone secretion. Corticosteroids appear to play a significant role in the secondary FSH surge on late proestrus and early estrus.     

Historical stages in the development of maxillofacial surgery and stomatology at the N. N. Burdenko Main Military Clinical Hospital

Effect of level of dietary calcium on body adaptation to radionuclides and lead exposure was studied in experiments with rats. Effectivity of adaptation was evaluated by analysis of accumulation and elimination of xenobiotics and antioxidant activity of liver tissue and erythrocytes. Low and normal levels of calcium in diet of rats do not provide for long-term adaptation to exposure of Ce-137 and Pb. The diet enriched by calcium caused a significant protective-adaptation effect on stages of accumulation and biotransformation of xenobiotics.     

Historical development of whiteners: clinical safety and efficacy

Trimming composite restorations includes gross removal of excess material, contouring, and finishing. Many surfaces such as the lingual surface of anterior teeth or the occlusal surfaces of posterior teeth require the use of rigid rotating instruments. The purpose of our study was to assess the suitability of eight finishing diamonds, five tungsten carbide finishing burs, and one ceramically coated finishing instrument for trimming a small-particle hybrid composite material. A total of 70 specimens of Herculite XRV were treated with the different finishing instruments under simulated practice conditions, and surface roughness was recorded quantitatively using an optical laser pick-up. The resulting surfaces were examined qualitatively with the help of scanning electron microscopy (SEM). Cutting efficiency of the diamonds and burs was evaluated at a constant pressure of 2.5 N using 42 additional specimens of Herculite XRV. Significant differences were calculated using one-way ANOVA and pairwise contrasts by Tukey's multiple range test. The results showed that finishing diamonds were characterized by high cutting efficiency and relatively rough corresponding composite surfaces, whereas tungsten carbide finishing burs led to smooth composite surfaces but had little cutting efficiency. For gross removal and contouring of composite restorations, a 15-40 microns finishing diamond is recommended followed by a tungsten carbide bur for finishing the restoration.     

Growth and morphological transformations of Helicobacter pylori in broth media

Helicobacter pylori, a cause of peptic ulcer disease and certain types of gastric cancers, has usually been cultured on diverse agar-based media, resulting in a requirement for 2 to 4 days of growth at 37 degrees C. We have developed a novel broth medium consisting of a base medium supplemented with 2% newborn calf serum, Mg2+, Cu2+, Fe2+, Zn2+, Mn2+, and 1 mg of lysed human erythrocytes per ml. This medium supports rapid growth of H. pylori, with a doubling time of about 50 min. Optimal growth was obtained in a pH range higher than that supporting most other gram-negative bacteria (at pH 8.5). H. pylori cultured in this supplemented broth retains the spiral morphology seen in both histological sections and cultures from agar-based media and also retains a high urease activity. After 18 h in this broth, H. pylori transforms to a coccal form with a complete loss of urease activity. Previously these cocci have been reported to be senescent, since they could not be subcultured on agar medium. Our experiments suggest that some of the cocci can revert back to the spiral morphology with full recovery of urease activity when subcultured in fresh microaerobic broth medium.     

Gaseous transmitters and neuroendocrine regulation

Recent work has demonstrated that the brain has the capacity to synthesize impressive amounts of the gases nitric oxide (NO) and carbon monoxide (CO). There is growing evidence that these gaseous molecules function as novel neural messengers in the brain. This article reviews the pertinent literature concerning the putative role of NO and CO as critical neurotransmitters and biological mediators of the neuroendocrine axis. Abundant evidence is presented which suggests that NO has an important role in the control of reproduction due to its ability to control GnRH secretion from the hypothalamus. NO potently stimulates GnRH secretion and also appears to mediate the action of one of the major transmitters controlling GnRH secretion, glutamate. Evidence is presented which suggests that NO stimulates GnRH release due to its ability to modulate the heme-containing enzyme, guanylate cyclase, which leads to enhanced production of the second messenger molecule, cGMP. A physiological role for NO in the preovulatory LH surge was also evidenced by findings that inhibitors and antisense oligonucleotides to nitric oxide synthase (NOS) attenuate the steroid-induced and preovulatory LH surge. CO may also play a role in stimulating GnRH secretion as heme molecules stimulate GnRH release in vitro, an effect which requires heme oxygenase activity and is blocked by the gaseous scavenger molecule, hemoglobin. Evidence is also reviewed which suggests that NO acts to restrain the hypothalamic-pituitary-adrenal (HPA) axis, as it inhibits HPA stimulation by various stimulants such as interleukin-1 beta, vasopressin, and inflammation. This effect fits a proinflammatory role of NO as it leads to suppression of the release of the anti-inflammatory corticosteroids from the adrenal. Although not as intensely studied as NO, CO has been shown to suppress stimulated CRH release and may also function to restrain the HPA axis. Evidence implicating NO in the control of prolactin and growth hormone secretion is also reviewed and discussed, as is the possible role of NO acting directly at the anterior pituitary. Taken as a whole, the current data suggest that the diffusible gases, NO and CO, act as novel transmitters in the neuroendocrine axis and mediate a variety of important neuroendocrine functions.     

Recombinant vaccinia virus expressing Japanese encephalitis virus protein E

Contrasts are drawn between dental care based on fee-for-service and managed care financial arrangements. The advantages of fee-for-service include (for the profession) slow acceptance of managed care in dentistry compared to medicine; (for society and the patient) more community service, higher technical quality of work, and stimulation of innovations; and (for the individual dentist) the strong dentist-patient bond as well as professionalism.     

Production of tumor necrosis factor (TNF) by macrophages and T-lymphocytes of rodents as affected by acute gamma-irradiation

BACKGROUND: The current classification dividing patients with functional gastrointestinal symptoms into subgroups remains controversial. AIMS: To determine whether distinct symptom groupings exist in the community. METHODS: A random sample of Sydney residents in Penrith, Australia was mailed a validated self report questionnaire. Gastrointestinal symptoms including the Rome criteria for irritable bowel syndrome (IBS) and dyspepsia were measured. RESULTS: Among 730 respondents, the 12 month age and gender adjusted prevalence (adjusted to the Australian population) of IBS, dyspepsia, and gastro-oesophageal reflux were 11.8% (95% confidence interval (CI) 9.3 to 14.3%), 11.5% (95% CI 9.6 to 14.6%), and 17.5% (95% CI 14.2 to 19.9%), respectively. In total, 60% of the population reported four or more gastrointestinal symptoms. There was considerable overlap of IBS with dyspepsia and among the dyspepsia subgroups by application of the Rome criteria. Independently, 10 symptom groupings were identified by factor analysis. The underlying constructs measured by these factors were generally the major abdominal syndromes recognised by the Rome classification: dyspepsia, IBS, reflux, painless constipation, painless diarrhoea, and bloating, in addition to a number of more specific symptom groupings. CONCLUSION: Gastrointestinal symptoms are common and overlap in the community, but distinct upper and lower abdominal symptom groupings can be identified.     

Optimization of gadolinium-enhanced magnetic resonance angiography using an automated bolus-detection algorithm (MR SmartPrep). Original investigation

Gadolinium (Gd)-enhanced three-dimensional (3D) magnetic resonance angiography (MRA) is a quick method for performing noninvasive diagnostic angiography. A major technical obstacle to the successful implementation of this technique, however, is the proper coordination of the data acquisition with the contrast bolus. In this article, the use of an automated bolus-detection algorithm (MR SmartPrep), which triggers the initiation of data acquisition for Gd-enhanced 3D MRA is reviewed. Potential applications of this evolving technique are illustrated.     

Isolation of riboflavin-binding apoprotein from chicken egg protein and its use for determining riboflavin in biological samples

A riboflavine-binding protein has been isolated from egg white and its properties have been characterized. The apoprotein-employing techniques for riboflavine detection in foods, urine, and blood serum are highly competitive with conventional labor-consuming procedures and with the high expensive HPLC method in sensitivity and selectivity, and can be recommended for riboflavine detection in biological objects.