The interplay between single particle anisotropy and interparticle interactions in ensembles of magnetic nanoparticles.

This paper aims to analyze the competition of single particle anisotropy and interparticle interactions in nanoparticle ensembles using a random anisotropy model. The model is first applied to ideal systems of non-interacting and strongly dipolar interacting ensembles of maghemite nanoparticles. The investigation is then extended to more complex systems of pure cobalt ferrite CoFe2O4 (CFO) and mixed cobalt-nickel ferrite (Co,Ni)Fe2O4 (CNFO) nanoparticles. Both samples were synthetized by the polyol process and exhibit the same particle size (DTEM ≈ 5 nm), but with different interparticle interaction strengths and single particle anisotropy. The implementation of the random anisotropy model allows investigation of the influence of single particle anisotropy and interparticle interactions, and sheds light on their complex interplay as well as on their individual contribution. This analysis is of fundamental importance in order to understand the physics of these systems and to develop technological applications based on concentrated magnetic nanoparticles, where single and collective behaviors coexist.

Fatty acid supplements improve hair coat condition in rhesus macaques.

As captive rhesus macaques often exhibit hair loss, alopecia was quantified and behavior was recorded before, during, and after fatty acid supplementation in six macaques. Fatty acid treatment was associated with a decrease in alopecia and in self-grooming behavior. Therefore, fatty acids may be a viable treatment for alopecia in some captive primates.

Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears.

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Sensitivity to stress-induced reproductive dysfunction is associated with a selective but not a generalized increase in activity of the adrenal axis.

Stress-induced reproductive dysfunction is a relatively common cause of infertility in women. In response to everyday life stress, some individuals readily develop reproductive dysfunction (i.e., they are stress sensitive), whereas others are more stress resilient. Female cynomolgus monkeys, when exposed to mild combined psychosocial and metabolic stress (change in social environment + 20% reduced calorie diet), can be categorized as stress sensitive (SS; they rapidly become anovulatory in response to stress), medium stress resilient (MSR; they slowly become anovulatory in response to prolonged stress), or highly stress resilient (HSR; they maintain normal menstrual cycles in response to stress). In this study, we examined whether increased sensitivity to stress-induced reproductive dysfunction is associated with elevated adrenal axis activity by measuring 1) the diurnal release of ACTH and cortisol, 2) ACTH and cortisol in response to an acute psychological stress, 3) the percent suppression of cortisol in response to dexamethasone negative feedback, 4) the diurnal release of ACTH and cortisol following exposure to mild psychosocial and metabolic stress, 5) the concentration of cortisol in hair, and 6) adrenal weight. SS monkeys (n = 5) did not differ from MSR (n = 5) or HSR (n = 7) monkeys in any measurement of baseline HPA axis activity or the integrated measurements of chronic HPA axis activity. However, MSR + SS monkeys (n = 10) did secrete more cortisol than HSR monkeys during the daytime hours (1000-1800) following exposure to a novel social environment and reduced diet. We conclude that increased activity of the HPA axis is unlikely to be the primary mechanism causing increased sensitivity to stress-induced reproductive dysfunction.

Magnetic studies of CoFe2O4/SiO2 aerogel and xerogel nanocomposites.

The evolution of the structural and magnetic properties of nanocomposites formed by cobalt ferrite particles dispersed in xerogel and aerogel silica matrices (CoFe2O4/SiO2) have been studied as a function of the temperature of preparation and the amount of ferrite dispersed in the matrix. Wet samples with different amounts of CoFe2O4 in SiO2 matrix were prepared by sol-gel process in monolithic form. Xerogel and aerogel samples were prepared by controlled and hypercritical drying, respectively, and heated at various temperatures between 300 and 1100 degrees C. Superparamagnetic behavior has been observed by magnetization studies at room temperature for xerogels prepared at low temperature. Aerogel samples showed significant superparamagnetic fractions for all thermal treatment temperatures as determined by Mössbauer spectroscopy. Magnetization of the nanocomposites at 10 KOe applied field varied from 1 to 19 emu/g and the coercivity from 90 to 2320 Oe, respectively, for the different morphologies and textures of the analyzed material. The results show that besides the magnetization and coercivity depend on crystallite size, parameters such as ferrite content, porosity and drying conditions greatly influence the nanocomposite magnetic behavior.

Depressive disorders in childhood. I. A longitudinal prospective study of characteristics and recovery.

In the context of a prospective, longitudinal, and controlled nosologic study, the characteristics and diagnostic validity of major depressive disorder, dysthymic disorder, and adjustment disorder with depressed mood were examined in a school-aged cohort. The entities were distinguishable on several dimensions such as age at onset and pattern of recovery. Time to recovery from onset was most favorable for the adjustment disorders (90% remission rate during nine months) and least so for the dysthymias (89% remission rate during six years). Major depression and dysthymia were similar with respect to the prevalence of concurrent nonaffective disorders. For both, early age at onset predicted a more protracted illness. Treatment contacts, none of which were under the control of the investigators, had no clear impact on recovery from the depressions.

Physiological correlates of self-injurious behavior in captive, socially-reared rhesus monkeys.

This study examined the relationship between self-injurious behavior (SIB) in rhesus monkeys and several biological variables, including monoamine metabolites in cerebrospinal fluid (CSF) and circulating levels of ACTH, cortisol, and testosterone. Cisternal CSF and blood plasma samples were obtained from 23 individually housed male rhesus macaques, 14 of which had a veterinary record of self-inflicted wounding. CSF samples were analyzed for 5-hydroxyindole-3-acetic acid (5-HIAA), homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) using isocratic high-performance liquid chromatography with electrochemical detection (HPLC-EC). Plasma samples were analyzed for ACTH, cortisol, and testosterone using commercially available radioimmunoassays (RIAs). Rates of self-directed biting were determined by systematic observation of all monkeys. Monkeys with SIB did not differ from controls in their basal monoamine or gonadal activity. However, the SIB group showed consistently lower mean plasma cortisol levels than the control group. Plasma cortisol was negatively correlated with rates of self-directed biting. These results suggest a persistent dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis in monkeys with SIB. It is not yet clear whether this phenomenon of low cortisol represents chronically reduced adrenocortical secretion under basal conditions or a difference in response to the mild stress of capture and chemical restraint. The implications of these findings will be discussed with respect to SIB in humans as well as post-traumatic stress disorder (PTSD), a condition characterized by pituitary-adrenocortical hypoactivity.

Sex and species differences in the vasopressin innervation of sexually naive and parental prairie voles, Microtus ochrogaster and meadow voles, Microtus pennsylvanicus.

To study whether central systems that are implicated in functions associated with reproduction show different changes in males and females that become parental, the central vasopressin (AVP) innervation was compared in two species of voles: prairie voles, in which males and females provide parental care, and meadow voles, in which only females provide parental care. For both species, the densities of AVP-immunoreactive (AVP-ir) fibers in the lateral septum, lateral habenular nucleus, medial preoptic area and paraventricular nucleus of the thalamus were compared in males and females that were sexually inexperienced or had become parents 6 days before sacrifice. The lateral septum and lateral habenular nucleus presumably receive their projections from the bed nucleus of the stria terminalis and medial amygdaloid nucleus, while the other two areas presumably receive their projections from the suprachiasmatic nucleus. Differences between sexually naive and parental animals were found only in the presumed projections of the bed nucleus of the stria terminalis and medial amygdaloid nucleus. In both species, AVP-ir fiber densities in the lateral habenular nucleus and the lateral septum were much greater in males than in females regardless of parental state. In prairie voles, AVP-ir fiber density in the lateral septum and lateral habenular nucleus was reduced in parental males, while no differences were found in females. In parental meadow voles, the AVP-ir fiber density in the lateral septum did not show changes, while the fiber density in the lateral habenular nucleus was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial internal limiting membrane dystrophy. A new sheen retinal dystrophy.

OBJECTIVE: To describe the clinicopathologic features of a previously unreported retinal dystrophy. METHODS: Fourteen members of a single family were examined. The medical records of 2 additional family members were reviewed. Pathologic examination was performed on 2 eyes of 1 affected patient. RESULTS: Five individuals were identified with a retinal dystrophy characterized by a glistening inner retinal surface throughout the posterior pole. Visual loss occurred in 3 affected patients in later life owing to superficial polycystic retinal edema and retinal folds. Electroretinographic testing revealed a selective diminution of the b wave. Pathologic examination revealed an abnormal internal limiting membrane with schisis cavities in the inner retina. Endothelial cell swelling, pericyte degeneration, and basement membrane thickening were present in retinal capillaries. CONCLUSIONS: A previously unreported sheen retinal dystrophy is described. Pedigree analysis suggests an autosomal dominant mode of inheritance. A primary defect in Müller cells is the suspected, but unproved, cause. No effective treatment for the associated visual loss is known. The term familial internal limiting membrane dystrophy is proposed to describe this condition.

Can memory requirements account for species' differences in invisible displacement tasks?

We tested the hypothesis that poor performance on the Piagetian invisible displacement task is related to increased memory requirements. Rhesus monkeys and orangutans received 3 types of problems (invisible, visible, and no transfer problems) each containing a number of steps equivalent to that of standard invisible displacements. If failure to solve invisible displacements was due to increased memory requirements, then the primates should perform at chance level on all 3 problems. However, rhesus monkeys solved visible and no transfer problems, but not invisible transfer problems. Half of the orangutans solved all 3 transfer problems, although their performance on invisible transfer problems was lower than that on the other problems. A subsequent cuing phase led to improved performance, and a few monkeys solved invisible transfer problems.

Successful treatment of postoperative Candida endophthalmitis in an eye with an intraocular lens implant.

Candida endophthalmitis developed in the left eye of a 71-year-old man two months after he underwent extracapsular cataract extraction and intraocular lens implantation. The symptoms included decreased vision and redness but no pain. The discovery of the cause of the endophthalmitis was delayed because it was initially treated as a sterile postoperative inflammation. Vitrectomy with intracameral amphotericin B and treatment with topical and systemic amphotericin B and flucytosine led to resolution of the infection and a final visual acuity of 20/80. It was not necessary to remove the intraocular lens.

Complications of acute symptomatic posterior vitreous detachment.

During a ten-year period, 172 eyes of 155 patients developed acute symptomatic posterior vitreous detachments. The study included only patients examined within three months of the onset of symptoms. The patients ranged in age from 22 to 82 years, with an average age of 60 years. Of the 172 eyes, 118 (69%) developed no retinal or vitreous complications. Retinal tears occurred in 14 eyes (8%) and vitreous or retinal hemorrhages occurred in 36 eyes (21%). Seventeen patients (11%) who had acute symptomatic posterior vitreous detachment in one eye later developed acute symptomatic posterior vitreous detachment in the fellow eye. The second posterior vitreous detachment developed within two years of the first one in 15 eyes (88%). In 13 patients (76%), the second eye responded in the same manner to the posterior vitreous detachment as had the first, that is, ten pairs of eyes had no further complications, two pairs had retinal or vitreous hemorrhages, and one pair had retinal breaks.

Vitrectomy in patients with decreased visual acuity secondary to asteroid hyalosis.

PURPOSE: To evaluate the role of vitrectomy in patients with decreased visual acuity solely attributable to asteroid hyalosis. METHOD: We retrospectively reviewed the records of patients with asteroid hyalosis and identified those who underwent vitrectomy for symptomatic asteroid hyalosis alone. RESULTS: After vitrectomy, nine of 10 eyes (10 patients) had at least 1 line of improvement in nonstandardized best-corrected visual acuity. In one eye, vision was unchanged postoperatively. The average gain was 3.44 lines. CONCLUSIONS: A small percentage of patients with asteroid hyalosis have decreased visual acuity caused solely or primarily by the asteroid hyalosis. Vitrectomy in these patients may alleviate symptoms and improve visual acuity.

Cohabitation alters vasopressin innervation and paternal behavior in prairie voles (Microtus ochrogaster).

The density of vasopressin-immunoreactive (AVP-ir) fibers in the lateral septum and lateral habenular nucleus is lower in prairie vole fathers--which display paternal behavior under natural conditions-than in sexually naive males. To see if these changes occur before or after the birth of pups, and whether they are related to changes in paternal behavior, we tested paternal responsiveness and measured AVP-ir fiber density in the lateral septum, lateral habenular nucleus, medial preoptic area, and paraventricular nucleus of the thalamus of sexually naive males and females (0P) and breeding pairs that were sacrificed shortly after mating (3P); during early (13P); or late gestation (21P); or after the birth of pups (6PP). Paternal responsiveness was increased in 3P males and reached a plateau in 13P males. AVP-ir fiber density did not change in the medial preoptic area and the paraventricular nucleus of the thalamus. The fiber density in the lateral septum and lateral habenular nucleus was affected differently in males and females. Among males, 3P animals had the lowest fiber density, while 13P and 6PP animals had an intermediate, and 0P and 21P animals the highest fiber density, whereas among females, no differences in fiber density were found. A second experiment showed that the decrease in fiber density in 3P males could be induced by cohabitation with an unfamiliar female but not by an unfamiliar male nor by relocation to a novel cage. The changes in AVP-ir fiber density shortly after mating suggest that these fibers may be involved in paternal responsiveness as well as in various other social behaviors that change after mating.

Do rhesus monkeys (Macaca mulatta) attribute knowledge and ignorance to others?

The ability of 4 rhesus monkeys (Macaca mulatta) to understand the causal connection between seeing and knowing was investigated. The subjects were tested to determine if they could discriminate between information provided by experimenters who randomly alternated between roles of guesser and knower. In a series of tests, the knower either hid food under 1 of 3 cups or watched as someone else hid the food. The guesser waited outside the room or covered her or his head until the food was hidden. The subjects watched this procedure occur but could not see which cup the food was hidden under. The knower pointed to the correct cup while the guesser pointed to an incorrect one. None of the macaques provided any evidence that they realized the different states of knowledge possessed by the guesser and knower. The results are consistent with the hypothesis that rhesus macaques are incapable of making inferences about the mental states of others.

Object permanence in orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus).

The authors tested orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus) on object permanence tasks. In Experiment 1, orangutans solved all visible displacements and most invisible displacements except those involving movements into 2 boxes successively. In Experiment 2, performance of orangutans on double invisible displacements and control displacements (assessing simple strategies) was compared. Orangutans did not use the simple strategy of selecting the box visited last by the experimenter. Instead, poorer performance on double invisible displacements may have been related to increased memory requirements. In Experiment 3, squirrel monkeys were tested using the procedure of Experiment 1. Squirrel monkeys solved visible but did not comprehend invisible displacements. Results suggest that orangutans but not squirrel monkeys possess Stage 6 object permanence capabilities.

Myogenic influences on the electrical auditory brainstem response (EABR) in humans.

Two cases demonstrating the effects of myogenic artifact on the electrical auditory brainstem response (EABR) when using a promontory stimulation site are presented. Intensity-response functions were obtained in the unparalyzed condition, then repeated after infusion of a neuromuscular paralyzing agent. In both cases, the myogenic response was observed at lower stimulus intensities than the EABR components. As intensity increased, the myogenic responses grew at extremely rapid rates and made any subsequent identification of auditory responses virtually impossible. To alleviate the adverse influence of myogenic components, general anesthesia and a paralyzing agent must be incorporated into the test protocol when acquiring the EABR using a promontory site of stimulation.

Transient hearing loss with metrizamide.

Two case studies are reported in which transient low frequency sensorineural hearing loss was experienced following myelography and CT scanning with metrizamide. Low frequency sensorineural hearing loss is considered to be the result of increased stiffness of one or both of the inner ear membranes. A review of the literature regarding an osmotic relationship between blood, cerebrospinal fluid, and the inner ear fluids attempts to explain how this phenomenon may have occurred with metrizamide. The transient sensorineural loss observed in the case studies presented is compared to the pathophysiology attributed to the formation of endolymphatic hydrops.

Auditory performance of children with cochlear ossification and partial implant insertion.

The management of the profoundly deaf child with a cochlear implant poses a special challenge, particularly when total ossification of the cochlea is present. In this setting, insertion of an electrode array into a child's cochlea is often difficult. Our experience supports the feasibility of partial insertion of a multichannel implant into the basal turn of an ossified cochlea. Five children with ossified cochleae who had undergone partial implantation of a multichannel electrode were compared with the performance of matched controls who had full insertion of multichannel implants. No dramatic differences were detected during a 6- to 18-month follow-up period on selected test measures. These preliminary results suggest that active electrode number may exert a limited effect on performance with a cochlear implant. Drilling out the basal turn of an ossified cochlea in conjunction with partial insertion of a multichannel implant appears to be an acceptable surgical and rehabilitational alternative for placement of a cochlear implant prosthesis in children with complete cochlear ossification.

Auditory brain-stem responses in children with previous otitis media.

The auditory brain-stem responses (ABRs) of 18 children who received tympanostomy tubes due to well-documented history of otitis media with effusion (OME) were compared with a matched control group with little or no history of effusion. The subjects in the OME group had significantly longer ABR latencies for waves III and V, with the most compelling delay for wave III and the III-I interwave interval. Although wave I prolongation in the OME group was not significant, the possible contribution of a peripheral effect on the latencies of waves III and V was investigated. The typical gender effect for the ABR latencies was unaltered in the OME group, and there was no group by gender interaction. We suggest that although the data support increased ABR latencies for children with a history of OME, they do not establish a causal relationship.