The role of gonadal steroids in feedback regulation of gonadotropin secretion at different stages of primate development

The serum gonadotropin response to castration was assessed in 8 foetal, 2 neonatal, 30 juvenile, and 2 adult rhesus monkeys (M. mulatta). In the 30 castrated juvenile monkeys and 8 sham-operated controls, concentrations of oestrone, oestradiol, androstenedione, dihydrotestosterone, testosterone and 17OH-progesterone were measured in 10 ml serum pools before, one month after, and one year after the surgical procedure. Castration during foetal life (83-137 days gestation) was followed within 48-72 h by a significant rise in serum FSH levels in males, but had no effect on the already high levels in females. Similarly, castration of males during the first post-natal month raised serum FSH and LH into the adult castrate range; however, after 3 months of age serum gonadotropin levels again declined to the normal juvenile range in spite of the open feedback loop. Orchiectomy of prepubertal juvenile monkeys (age 3 month-2 8/12 years) had no immediate effect on serum gonadotropins, but was followed by a delayed rise in FSH (at age 2 3/12-4 3/12 years) and LH (at age 2 7/12-4 4/12 years) to adult castrate levels. Orchiectomy of older prepubertal (by serum testosterone) or adult males resulted within a few days in a progressive and sustained rise in serum FSH and a more gradual rise in LH. Prepubertal gonadotropin regulation appeared to be sexually dimorphic, since ovariectomy in juvenile females (age 3 months-1 5/12 years) was followed by generally elevated, if somewhat erratic, serum FSH values, with a secondary rise in both FSH and LH levels at 2-2 1/12 years. In both sexes, prepubertal castration caused a significant and sustained decline in serum concentrations of oestradiol; castrated males also showed a decline in serum testosterone levels. Although prepubertal castration also caused in both sexes a slight decline in serum oestrone, and ovariectomy a decline in serum androstenedione and dihydrotestosterone, these effects were not sustained one year later, and values were not significantly different from sham-operated controls. Taken together, these data lend support to a model of primate sexual maturation in which the primary regulator of gonadotropin secretion in both sexes during the prolonged juvenile phase is central inhibition of the hypothalamic GnRH regulator. However, during foetal and neonatal life, and again following the onset of puberty, the major modulator of gonadotropin secretion becomes sex steroid-mediated feedback inhibition.     

Real-time imaging of human cortical activity evoked by painful esophageal stimulation

BACKGROUND & AIMS: Current models of visceral pain processing derived from metabolic brain imaging techniques fail to differentiate between exogenous (stimulus-dependent) and endogenous (non-stimulus-specific) neural activity. The aim of this study was to determine the spatiotemporal correlates of exogenous neural activity evoked by painful esophageal stimulation. METHODS: In 16 healthy subjects (8 men; mean age, 30.2 +/- 2.2 years), we recorded magnetoencephalographic responses to 2 runs of 50 painful esophageal electrical stimuli originating from 8 brain subregions. Subsequently, 11 subjects (6 men; mean age, 31.2 +/- 1.8 years) had esophageal cortical evoked potentials recorded on a separate occasion by using similar experimental parameters. RESULTS: Earliest cortical activity (P1) was recorded in parallel in the primary/secondary somatosensory cortex and posterior insula (approximately 85 ms). Significantly later activity was seen in the anterior insula (approximately 103 ms) and cingulate cortex (approximately 106 ms; P=.0001). There was no difference between the P1 latency for magnetoencephalography and cortical evoked potential (P=.16); however, neural activity recorded with cortical evoked potential was longer than with magnetoencephalography (P=.001). No sex differences were seen for psychophysical or neurophysiological measures. CONCLUSIONS: This study shows that exogenous cortical neural activity evoked by experimental esophageal pain is processed simultaneously in somatosensory and posterior insula regions. Activity in the anterior insula and cingulate-brain regions that process the affective aspects of esophageal pain-occurs significantly later than in the somatosensory regions, and no sex differences were observed with this experimental paradigm. Cortical evoked potential reflects the summation of cortical activity from these brain regions and has sufficient temporal resolution to separate exogenous and endogenous neural activity.     

Sealed primary molars are less likely to develop caries

BackgroundThe authors examined the association between light-polymerized resin-based fluoride-releasing sealants and the development of pit-and-fissure caries on primary molars.MethodsIn this 3-year retrospective study, the authors reviewed the dental records of 297 children (1,352 teeth) younger than 6 years who were at high caries risk. Sealant placement or nonplacement on primary molars in the outpatient clinic and operating room setting was recorded, and random-effects logistic regression analysis accounting for the effect of data clustering was performed to measure caries incidence over time.ResultsThe odds of developing pit-and-fissure carious lesions on sealed primary molars were 0.055 times (95% confidence interval [CI], 0.011 to 0.285; P = .001) and 0.013 times (95% CI, 0.001 to 0.159; P = .001) the odds of that on nonsealed primary molars in the outpatient clinic and in the operating room, respectively. In molars that became carious, those sealed were associated with longer time to caries development in both the outpatient clinic (2.69 years, 95% CI, 2.08 to 3.29) and operating room (1.97 years, 95% CI, 1.45 to 2.48).ConclusionsSealed primary molars were less likely to develop pit-and-fissure caries when placed in both the clinic and operating room settings.Practical ImplicationsDental sealants on primary molars should be considered for children at high caries risk.     

The Short-Term Follow-Up Effects of Hypnobehavioural and Cognitive Behavioural Treatment for Bulimia Nervosa

This study reports the short-term (nine months) follow-up effects of eight weeks of hypnobehavioural and cognitive behavioural treatment of bulimia nervosa. Of the 78 subjects who entered treatment, 48 completed a closed follow-up of nine months duration. The results based on this sample showed that there were no differences in abstinence from bingeing and purging between the treatments and that abstinence increased over time for both treatments. Also, there were no differences between treatments on eating pathology, bulimic behaviours or general psychopathology measures in the short term. Both treatment types were equally acceptable to patients. The results were compared with other studies. It was suggested that the model for HBT is comparable in validity with the model underlying CBT and that HBT could justifiably be recommended as an alternative to CBT.     

Microbiota links to neural dynamics supporting threat processing

There is growing recognition that the composition of the gut microbiota influences behaviour, including responses to threat. The cognitive‐interoceptive appraisal of threat‐related stimuli relies on dynamic neural computations between the anterior insular (AIC) and the dorsal anterior cingulate (dACC) cortices. If, to what extent, and how microbial consortia influence the activity of this cortical threat processing circuitry is unclear. We addressed this question by combining a threat processing task, neuroimaging, 16S rRNA profiling and computational modelling in healthy participants. Results showed interactions between high‐level ecological indices with threat‐related AIC‐dACC neural dynamics. At finer taxonomic resolutions, the abundance of Ruminococcus was differentially linked to connectivity between, and activity within the AIC and dACC during threat updating. Functional inference analysis provides a strong rationale to motivate future investigations of microbiota‐derived metabolites in the observed relationship with threat‐related brain processes.     

A neuroanatomical gradient in the pontine tegmentum for the cholinoceptive induction of desynchronized sleep signs

Microinjection of cholinergic agonists into the pontine tegmentum was used to evoke a state which was polygraphically and behaviorally similar to desynchronized (D) sleep. This study was designed to test the hypothesis that the production of this pharmacologically induced D sleep-like state (D-ACh) was dependent upon the anatomical locus of drug administration within the pontine tegmentum. Four dependent variables of D sleep were measured: D latency, D percentage, D duration and D frequency. Multiple regression analysis and analysis of variance were performed to evaluate the relationship between the three-dimensional coordinates of the injection site (posterior, vertical and lateral) and these 4 dependent measures. The intrapontine site of drug administration accounted for a statistically significant amount of the variance in D latency, D percentage and D duration. There was no significant relationship between the anatomical site of saline injection and the dependent measures of D sleep. A significant increase in D frequency following microinjection of cholinergic agonists was found to be independent of injection site. Pontine injection sites which yielded the shortest D latencies were found to be the same sites from which the highest D percentages were evoked. Rostrodorsal pontine tegmental injection sites were most effective in producing the highest percentages of D-ACh with the shortest latencies to onset. Injections made more caudally and ventrally within the pontine tegmentum produced lower percentages of D-ACh with longer latencies to onset. These data suggest the existence of an anatomical gradient within the pontine tegmentum for the cholinoceptive evocation of a D sleep-like state, and further support the concept that D sleep is generated, in part, by pontine cholinergic mechanisms.     

The effect of smoking on immediate post-extraction socket filling with blood and on the incidence of painful socket

The effect of habitual smoking on post-extraction socket filling with blood and on the incidence of painful socket, was investigated. Data were collected from 2417 adult dental out-patients in whom 3541 extractions were performed under local anaesthesia. Post-operative socket filling with blood was significantly reduced in smokers, compared with non-smokers (p less than 0.01). There was a higher incidence of painful socket in heavy smokers (20 or more cigarettes per day), compared with nonsmokers (p less than 0.05). There was a significant relationship between immediate post-extraction socket blood level and the incidence of painful socket; sockets which showed poorer filling were more likely to develop painful socket (p less than 0.02). Smoking appeared to have an adverse effect upon the healing of extraction wounds.     

Quantitative histochemical evaluation of skeletal muscle ischemia and reperfusion injury

Acute arterial obstruction to the extremities is associated with significant morbidity and mortality. The evaluation of accompanying skeletal muscle injury has thus far been indirect and imprecise. Triphenyltetrazolium chloride (TTC) is an oxidation-reduction indicator which allows for the histochemical quantitation of skeletal muscle injury. In 21 anesthetized nonheparinized adult mongrel dogs, the isolated in vivo gracilis muscle underwent 4, 6, or 8 hr of ischemia with and without reperfusion. The muscles were excised and cut into 1-cm segments, representative muscle biopsies for electron microscopy were taken, each segment was stained in 1% TTC, and the total area of staining was measured with computerized planimetry. All control muscles stained completely with a dark red color. After 4, 6, or 8 hr of ischemia, quantitative measurements of muscle staining indicative of normal tissue were present in 98 +/- 1%, 59 +/- 5%, and 23 +/- 9% of the total muscle areas, respectively. Six hours of ischemia followed by reperfusion was associated with only 36 +/- 9% of the muscle being stained. Segmental TTC staining demonstrated that reperfusion was associated with greater injury, and less TTC staining, in the proximal portion of the gracilis muscle at the site of entry of the major arterial pedicle. The distal muscle did not demonstrate increased damage with reperfusion. It is hypothesized that protection of the distal muscle from reperfusion injury may be due to an absence of reflow farther away from the artery.     

Migratory double breeding in Neotropical migrant birds

Neotropical migratory songbirds typically breed in temperate regions and then travel long distances to spend the majority of the annual cycle in tropical wintering areas. Using stable-isotope methodology, we provide quantitative evidence of dual breeding ranges for 5 species of Neotropical migrants. Each is well known to have a Neotropical winter range and a breeding range in the United States and Canada. However, after their first bout of breeding in the north, many individuals migrate hundreds to thousands of kilometers south in midsummer to breed a second time during the same summer in coastal west Mexico or Baja California Sur. They then migrate further south to their final wintering areas in the Neotropics. Our discovery of dual breeding ranges in Neotropical migrants reveals a hitherto unrealized flexibility in life-history strategies for these species and underscores that demographic models and conservation plans must consider dual breeding for these migrants.