Object localization using a biosonar beam: how opening your mouth improves localization.

Determining the location of a sound source is crucial for survival. Both predators and prey usually produce sound while moving, revealing valuable information about their presence and location. Animals have thus evolved morphological and neural adaptations allowing precise sound localization. Mammals rely on the temporal and amplitude differences between the sound signals arriving at their two ears, as well as on the spectral cues available in the signal arriving at a single ear to localize a sound source. Most mammals rely on passive hearing and are thus limited by the acoustic characteristics of the emitted sound. Echolocating bats emit sound to perceive their environment. They can, therefore, affect the frequency spectrum of the echoes they must localize. The biosonar sound beam of a bat is directional, spreading different frequencies into different directions. Here, we analyse mathematically the spatial information that is provided by the beam and could be used to improve sound localization. We hypothesize how bats could improve sound localization by altering their echolocation signal design or by increasing their mouth gape (the size of the sound emitter) as they, indeed, do in nature. Finally, we also reveal a trade-off according to which increasing the echolocation signal's frequency improves the accuracy of sound localization but might result in undesired large localization errors under low signal-to-noise ratio conditions.

Bone SPECT in management of mandibular condyle hyperplasia. Report of a case and review of literature.

In the present paper we report the case of a 14-year-old girl suffering from condylar hyperplasia and enlargement of ipsilateral jaw body, stressing the importance of bone SPECT in the clinical management of this temporomandibular joint (TMJ) disorder. Condylar hyperplasia is an uncommon idiopathic monolateral disorder of jaw growth consistent with exuberant or persistent activity of the condyle nucleus finally involving sociopsychological aspects due to facial dysmorphism. Besides facial asymmetry our patient showed prognathism, malocclusion, worsening otalgia and headache. Conventional X-rays examinations and multislice spiral CT gave us important morphostructural information also thanks to 3D volume-rendered and virtual reconstructions, while bone SPECT by detecting an intense well focused (99m)Tc-MDP uptake allowed to achieve uninvasively the final diagnosis of primary condyle hyperplasia. In spite of the full imaging characterization of TMJ disorders, consensus on best timing and therapeutic approaches on condylar hyperplasia is yet to be reached. In the present case patient was first treated orthodontically, planning a "high" condylectomy intervention after at least 6 months.

Hospital-acquired infections in Italy: a region wide prevalence study.

Between October and December 2000, a region-wide prevalence study of hospital-acquired infections (HAI) was conducted in all public hospitals (59 facilities with ca. 16000 beds; 560000 admission yearly) in Piemonte Region, Italy, and in the one hospital of the neighbouring autonomous region of Valle d'Aosta. The study population comprised a total of 9467 patients hospitalized for at least 24 h. The prevalence of HAI was 7.84%, with marked differences in prevalence among the participating hospitals (range: 0-47.8%). The higher relative frequency of urinary tract infections (UTI; 52.7%) was due to the inclusion of urine cultures obtained on the day of the study from asymptomatic UTI in catheterized patients. A significant correlation was found with major risk factors related to medical procedures (urinary catheter, mechanical ventilation, surgical drainage, intravascular catheters). Patients with HAI were found to be older and to have a greater mean length of stay in hospital. Multiple logistic regression analyses showed that lack of independence, indwelling urinary catheter and mechanical ventilation were the risk factors more significantly associated with HAI. The use of antibiotics, in particular prophylactic agents used in surgery (cephalosporins, glycopeptides), provided an incentive for corrective intervention in antibiotic administration and in training of healthcare workers.

Interleukin-1, but not stress, stimulates glucocorticoid output during early postnatal life in mice.

The development of neuroendocrine functions depends not only on genetically determined mechanisms but also on phenotypic signals. Some of these signals may derive from the immune system. For example, interleukin-1 beta (IL-1 beta) stimulates glucocorticoid output during the early postnatal period, and administration of this cytokine at birth induces permanent alterations in the HPA axis in adulthood. We have extended these studies and found that the glucocorticoid response elicited in 5-day-old mice by a low dose of IL-1 beta is not desensitized by previous exposure to the cytokine. We have also compared the magnitude of the increase in corticosterone levels induced by IL-1 in 3-day-old and adult mice to that caused by acute stress. IL-1 beta and acute stress caused a comparable increase in corticosterone levels in adult mice. In newborn mice, however, IL-1 beta, but not restraint or cold stress, stimulated corticosterone output. Thus, IL-1 beta can elicit a corticosterone response during the postnatal stress-hyporesponsive period. Furthermore, when the corticosterone levels attained following IL-1 beta administration were compared to the basal levels of the hormone at a given age, the increase in plasma corticosterone levels was several fold higher in newborn than in adult animals. These data, together with the long-lasting endocrine effects of cytokine exposure at birth, suggest an important role of immune cytokines in the programming of neuroendocrine functions during ontogeny.

Central and peripheral mechanisms contribute to the hypoglycemia induced by interleukin-1.

The impact that neuroendocrine effects of cytokines have on general host homeostasis is reflected by the profound metabolic changes observed in parallel. The effect of interleukin-1 beta (IL-1 beta) on glucose blood levels serves as an example. Although IL-1 beta stimulates glucocorticoid output and decreases hepatic glycogen content, hypoglycemia is concomitantly detected in adult and newborn mice. This effect is observed even during fasting and is probably due to increased glucose transport into tissues. Even after a glucose load, IL-1-treated animals remain hypoglycemic, suggesting that central mechanisms that control the set point of glucose homeostasis are affected. Low doses of IL-1 beta injected i.c.v. can also induce hypoglycemia. Furthermore, central blockade of IL-1 receptors partially inhibits the hypoglycemia induced by peripheral administration of IL-1 beta. On the other hand, central depletion of catecholamines exacerbates IL-1-induced hypoglycemia. IL-1-mediated effects on glucose levels might be directed at providing more energy supply to tissues during processes with high metabolic demands.

[Diagnostic value of renal scintigraphy in the neonatal period: presentation of some clinical cases]. / Valore diagnostico della scintigrafia renale in epoca neonatale: presentazione di alcuni casi clinici.

The valuation of renal function using radiotracers represents an attractive methodology to value most renal and upper urinary tract diseases in newborns. Restrincting damage, lower irradiation and lack of dangerous side-effect are particularly desiderable in newborns. The radiotracers of choice in our studies were Tc-99m-labeled radiopharmaceutical (DTPA and DMSA), because of their favourable dosimetry. The given dose has been calculated according to the table set forth by the EAMN-Pediatric Task Group. We report some particular cases in which renal scintigraphy represented a good alternative in comparison with more injurious methods in diagnostic classification of newborns.

Alterations in the pituitary-adrenal axis of adult mice following neonatal exposure to interleukin-1.

Interleukin-1 (IL-1), a cytokine mainly derived from activated cells of the macrophage lineage, can stimulate the hypothalamus-pituitary-adrenal (HPA) axis. Acute and long-lasting effects on the HPA axis were induced by the administration of low doses of IL-1 to mice during the first 5 days of life. In 5-day-old mice, corticosterone blood levels were markedly elevated 2 h following the last injection of IL-1. IL-1-treated mice grew normally. When studied during adulthood, however, these animals showed a reduction in morning values of corticosterone and the ACTH/corticosterone ratio was increased. Furthermore, an inverse correlation between ACTH and corticosterone levels in blood and between ACTH content in the pituitary gland and corticosterone levels was observed in IL-1-treated mice. Lower blood levels of corticosterone were not due to a reduced sensitivity of the adrenal glands, because these animals responded normally to exogenous ACTH. Another alteration observed in IL-1-exposed adult mice was a reduction in ACTH-like immunoreactivity in the pituitary gland following acute cold and restraint stress. It is concluded that exposure of mice to IL-1 early in life causes long-lasting alterations in the HPA axis. Spleen cells from adult mice treated with IL-1 at birth also developed a stronger response to allogeneic antigens than did cells from control mice. This observation indicates the relevance of immune-neuroendocrine interactions during development.

Metabolic and endocrine effects of interleukin-1 in obese, diabetic Zucker fa/fa rats.

IL-1, a cytokine produced predominantly by cell from the macrophage lineage, can affect multiple neuroendocrine and metabolic functions. We report here effects of this cytokine in obese, diabetic Zucker fa/fa rats. These animals are modestly hyperglycemic, hyper-lipemic, and markedly hyperinsulinemic. Changes in the levels of glucose, lactate, triglycerides, free fatty acids, insulin, glucagon, and corticosterone were detected following a single intraperitoneal or intravenous injection of IL-1 into fa/fa rats. No comparable changes were observed following administration of insulin. In fa/fa rats, the diabetic status is particularly manifested by an abnormal glucose tolerance. Administration of a bolus injection of IL-1 normalized the response of diabetic fa/fa rats to a glucose load. These rats not only returned to their basal glucose levels quicker, but reached glucose concentrations in blood which were comparable to, or even lower than those of Fa/? rats. Although the mechanism underlying the effects of IL-1 in fa/fa rats are presently not clear, the results obtained suggest that this cytokine tends to normalize glucose homeostasis and stimulate fat mobilization in these animals.

Interleukin-1 stimulates aldosterone secretion: involvement of renin, ACTH, and prostaglandins.

Interleukin-1 (IL-1), a cytokine produced during infection and inflammation, mediates some of the endocrinological alterations that parallel these processes. The purpose of this study was to determine whether human recombinant IL-1 (hrIL-1) affects aldosterone output as well as renin and adrenocorticotropic hormone (ACTH) release, two key factors in the regulation of mineralocorticoid secretion. We observed that intravenous administration of hrIL-1 into conscious unrestrained rats elicited a marked and rapid rise in aldosterone plasma levels in a dose-dependent manner. The hrIL-1-induced increase in aldosterone levels was associated with enhanced renin activity and increased ACTH levels in plasma. Furthermore, aldosterone levels of IL-1-injected rats were positively correlated with plasma renin activity (PRA), suggesting that the renin-angiotensin system contributes to the changes observed in the levels of the mineralocorticoid hormone. ACTH seems also to be implicated in the aldosterone response to hrIL-1 because the profile of the kinetic curves of changes in the levels of the pituitary hormone and aldosterone was similar. Pretreatment with the cyclooxygenase inhibitor indomethacin markedly reduced the increase in aldosterone plasma levels and PRA induced by IL-1, indicating that prostaglandins are involved in these effects of the cytokine. These results suggest that IL-1 may play an important role in the control of homeostasis during infectious and inflammatory diseases.

Cytokines as modulators of the hypothalamus-pituitary-adrenal axis.

The hypothalamus-pituitary-adrenal (HPA) axis is stimulated during the course of certain immune, inflammatory and neoplastic processes. IL-1 is an important immunologically derived cytokine mediating the stimulation of this axis, although not the only one. We have compared the relative potencies of the cytokines IL-1, IL-6 and tumor necrosis factor (TNF), which share several biological actions, for stimulating ACTH and corticosterone output in freely-moving rats. Although all three cytokines can stimulate the HPA axis, IL-1 was the most potent. This effect of IL-1 was also present during the neonatal period, when the response of the HPA axis to acute stress is reduced in rodents. The results support the existence of an immune-HPA axis circuit. The biological and clinical relevance of this circuit is discussed.