Influence of block copolymer feature size on reactive ion etching pattern transfer into silicon.

A successful realisation of sub-20 nm features on silicon (Si) is becoming the focus of many technological studies, strongly influencing the future performance of modern integrated circuits. Although reactive ion etching (RIE), at both micrometric and nanometric scale has already been the target of many studies, a better understanding of the different mechanisms involved at sub-20 nm size etching is still required. In this work, we investigated the influence of the feature size on the etch rate of Si, performed by a cryogenic RIE process through cylinder-forming polystyrene-block-polymethylmethacrylate (PS-b-PMMA) diblock copolymer (DBC) masks with diameter ranging between 19-13 nm. A sensible decrease of the etch depth and etch rate was observed in the mask with the smallest feature size. For all the DBCs under investigation, we determined the process window useful for the correct transfer of the nanometric cylindrical pattern into a Si substrate. A structural and physicochemical investigation of the resulting nanostructured Si is reported in order to delineate the influence of various RIE pattern effects. Feature-size-dependent etch, or RIE-lag, is proved to significantly affect the obtained results.

Elemental distribution in fluorinated amorphous carbon thin films.

Focused ion beam-secondary ion mass spectrometry (FIB-SIMS) with 20 nm spatial resolution has been used to analyze amorphous fluorinated carbon thin films, deposited by plasma assisted chemical vapor deposition (PACVD), at micro- to nano-scale. Mass spectra and ion imaging of film surface were acquired and the presence and distribution of contaminants were investigated. Surface images show the secondary ion distribution for F(-), CH(-), CF(-). A change in size and topology of fluorine-rich areas is correlated with film hardness and with microstructure transition from diamond-like to polymer-like, as indicated by infrared and Raman spectroscopies. Based on the surface distributions of CF(-) and CH(-) and on the vibrational spectroscopy results, a mechanism of fluorine substitution for hydrogen and an attempt to explain the film structure and microstructure is proposed.

Tonicity of resuscitative fluids influences outcome after spinal cord injury.

OBJECTIVE: This investigation was designed to test the hypothesis that the tonicity of resuscitative fluids administered after spinal cord injury influences the magnitude of secondary injury and, therefore, outcome. METHODS: Rat spinal cords were compressed with 50 g of weight for 5 minutes to produce injury. After spinal cord injury, the animals were randomized into three experimental groups. Group 1 (n = 10) received no fluid resuscitation after spinal cord injury. Group 2 (n = 6) received 5 ml/kg of intravenously administered Ringer's lactate 1 minute after the removal of compression. Group 3 (n = 7) was treated with 5 ml/kg of intravenously administered 7.5% hypertonic saline 1 minute after the removal of compression. Neurological outcome was assessed daily for 10 days using the Basso, Beattie, and Bresnahan locomotor rating scale. Histological evaluations of the spinal cord were obtained on Day 10. RESULTS: The average number of recovery days before the rats were able to spontaneously void their bladders was significantly less (P < 0.05) in the hypertonic saline-treated group. Spontaneous hindlimb movement also occurred sooner in the hypertonic saline-treated animals. The average neurological score was significantly higher (P < 0.05) in the hypertonic saline-treated group during each of the 10 days of recovery. Histological evaluation supported the finding of attenuation of injury in the hypertonic saline-treated animals. CONCLUSION: The results of this investigation with a chronic model of spinal cord injury support the contention that hypertonic saline treatment may provide protection to the spinal cord after mechanical injury.

Computer-based neuroanatomy laboratory for medical students.

BACKGROUND: To present the laboratory portion of our first-semester Human Neuroanatomy course at Temple University Medical School more effectively and efficiently and to replace the glass slide/microscope-based laboratory component of the course, we developed a computer-based substitute. METHODS: For this computer-based neuroanatomy laboratory program, we photographed the (a) gross brain sliced and dissected specimens and (b) all the glass slides, from the sacral cord through the head of the caudate nucleus. We digitized the photographed images and, using Multimedia ToolBook (Asymetrix), created a computerized atlas, laboratory guide, and a clinical problem-solving section. To assess the effectiveness of the computerized laboratory, we compared student performances between those classes that previously had the traditional laboratory with two succeeding classes that used the computer-based laboratory. RESULTS: Test score results of the laboratory portion of the course suggested that performance on laboratory material was virtually unchanged by the substitution of the computer program. By a survey taken at the end of the course, the students were very satisfied with the computerized program as a teaching method. CONCLUSIONS: The students and faculty enthusiastically agreed that the computer program was an effective substitute method for the traditional glass-slide laboratory and that it was a beneficial self-educational tool that fostered independent learning. The program encouraged student interaction and group learning and fostered independence. It was a more efficient method for faculty and students without sacrificing performance.

Transdermal absorption of radioprotectors in the rat using permeation-enhancing vehicles.

Topical radioprotection of rat skin with WR-2721 has not been effective presumably because the drug does not cross the stratum corneum to reach the epidermis and dermis. Earlier, we showed in the mouse that WR-2721 and cysteine dissolved in permeation-enhancing vehicles passed through the skin more readily than when in water. However, the most effective vehicles in the mouse were not necessarily as effective in the rat. Here we report that the most effective transport vehicles in the rat were (1) water with WR-2721, (2) water and dimethylformamide (DMF) with cysteine, and (3) water and DMF with prostaglandin E2 (PGE2). Pretreatment of the skin with dimethylsulfoxide (DMSO) further improved the transfer of the radioprotectors across the skin in most cases. After pretreatment with DMSO, the most effective vehicles were (1) water for WR-2721, (2) water and methyl-2-pyrrolidone (M-2-P) for cysteine, and (3) DMF for PGE2.

[The possible influence of bad habits on tooth morphogenesis. Clinical case]. / Possibile influenza di un'abitudine viziata sulla morfogenesi dentaria. Caso clinico.

Thumb sucking, if continued beyond the age of two, is commonly acknowledged to compromise correct craniofacial development, with consequent dental malposition. The observation of a deciduous central incisor morphology, lost traumatically by a thumb-sucking three years old boy with an apparent open-bite, makes us think this bad habit can influence teeth morphogenesis too.

[Germectomy of upper wisdom teeth. Clinical case]. / Germectomia dell'ottavo superiore. Caso clinico.

About complications during a third upper molar germectomy has been pointed out the possible slipping of the tooth below the masseter floor.

Transdermal absorption of radioprotectors using permeation-enhancing vehicles.

Radioprotectors are not currently used clinically due to concerns regarding toxicity and uncertainties regarding tumor protection. Topical radioprotection of skin might find clinical applications with protectors such as WR-2721, but laboratory studies in which protectors have been applied in water have not been promising. We have studied the absorption of 14C-WR-2721 and [14C]cysteine dissolved in skin permeation-enhancing vehicles through the skin of hairless mice and compared the absorption to that in water. Skin concentration of WR-2721 was increased most by dimethylformamide (DMF), but only propylene glycol increased absorption as far as the dermis, as measured by plasma concentration. Skin concentration of cysteine was improved by DMF, 2-pyrrolidone (2-P), and methyl-2-pyrrolidone (M-2-P); only dimethylsulfoxide (DMSO) resulted in increased plasma levels of the protector. Pretreating skin with DMSO before application of WR-2721, irrespective of the vehicle, improved its concentration within the skin. Plasma levels were improved (10 and 12 times) only with 2-P and DMF. Therefore, by choosing the appropriate vehicle, it is possible to breach the barrier of the stratum corneum and enhance the presence of the protector in all layers of the skin.

[A case of odontoma. Importance of an objective examination]. / Su un caso di odontoma. Importanza dell'esame obiettivo.

A case of odontoma which escaped attention at first objective examination and panoramic radiography makes it possible to stress the primary importance of inspection in dental practice.

Effects of hydrocephalus and surgical decompression on cortical norepinephrine levels in neonatal cats.

Norepinephrine (NE) changes during hydrocephalus, and the effects of surgical decompression on these changes, were studied using a new model of neonatal hydrocephalus. Kittens 4 to 10 days old received intracisternal injections of a sterile solution of 25% kaolin. Control kittens were injected similarly with sterile injectable saline. Ultrasonography was used to follow the progression of ventriculomegaly and the initial effects of the shunts. A subgroup of hydrocephalic animals was shunted using a cerebrospinal fluid lumbar-peritoneal catheter. Hydrocephalic animals were killed at approximately 25 days of age (16-21 days after kaolin injection). Surgical decompression was performed at 12, 16, and 17 days after kaolin injection; these animals were killed 30 days after the shunts were inserted. Control animals were killed at 29 and 53 days of age, to correlate with the ages of the hydrocephalic and shunted animals, respectively. Cortical samples equivalent to Brodmann's areas 4, 22, and 17 were measured for NE using high-performance liquid chromatography. Hydrocephalus caused NE levels to decrease significantly in all cortical areas. These alterations followed a rostrocaudal gradient in severity, with mean reductions of 65.8, 83.9, and 95.8% in areas 4, 22, and 17, respectively. Partial recovery occurred in animals that received shunts 16 and 17 days after kaolin injection, such that NE reductions of 75.7, 56.2, and 81.6% were noted in areas 4, 22, and 17, respectively. Shunting at 12 days after kaolin injection produced complete recovery in areas 4 and 22, with only a 67.7% decrease in area 17. These results suggest that the projection fibers from the locus ceruleus are damaged by the direct effects of hydrocephalus. Axotomy or neuropraxia of these fibers could result in decreases in NE throughout the cerebral cortex. In addition, there appears to be a period of time during which surgical decompression will allow neuropraxic fibers to recover with partial restoration of NE levels. Earlier insertion of a shunt appears to allow for more recovery than later decompression.

WR-2721 entry into the brain across a modified blood-brain barrier.

Radioprotection of the CNS by WR-2721 has not been possible because of its inability to cross the blood-brain barrier (BBB) and so gain access to the neural tissue. Modification of the BBB using hypertonic arabinose (1.8 m), injected via the internal carotid artery (ica), permitted entry of ip-injected [14C]WR-2721 into the ipsilateral cerebral hemisphere. The BBB-modified hemisphere had a 5.34-fold increased uptake compared to nonmodified controls. Delivery as a bolus via the ica further enhanced uptake after BBB opening; WR-2721 was 3.73 times greater than by ip injection. A 20-fold increase of WR-2721 brain uptake has been calculated for ica administration with the BBB opened as compared to the ip route without BBB modification. Toxicity of ip-administered WR-2721 with the BBB open was only 1.4 times greater than non-modified controls and 1.96 times more toxic when delivered via the ica. These data demonstrate significant uptake of WR-2721 into the CNS, a previously unprotected organ, and provide a model for future radioprotective studies.

Evidence from Sertoli cell-depleted rats indicates that spermatid number in adults depends on numbers of Sertoli cells produced during perinatal development.

To probe the relationship between the size of the Sertoli cell population, established during perinatal development, and production of germ cells in the adult testis, a Sertoli cell-depleted rat model was developed. This was accomplished by delivering an antimitotic drug, cytosine arabinoside (araC), directly to the testis of newborn pups. Initial studies of these araC-treated neonates indicated that 1) the drug is cleared rapidly from the testis; 2) it substantially reduces the level of Sertoli cell proliferation; 3) Sertoli cell division ceases at a normal time in spite of the previous drug treatment; and 4) araC itself has no residual effect on germ cell proliferation, which begins several days after the injection. Pups given araC were allowed to reach maturity, and their testes were perfuse-fixed for light microscopic morphometry. When the numbers of Sertoli cells in adult rats given araC as were compared with those in normal littermates, a 54% decrease in the size of the Sertoli cell population was detected in treated rats, now referred to as Sertoli cell-depleted. Moreover, when round spermatids were quantified and compared in normal and Sertoli cell-depleted adults, testes of the latter were found to contain 55% fewer round spermatids. Since, in the araC-treated group, the decrease in Sertoli cell population size was paralleled by a reduction in spermatid production of equal magnitude, the number of round spermatids per Sertoli cell was essentially identical in normal and Sertoli cell-depleted animals. Measurements of serum androgen-binding protein (ABP) and FSH in both groups indicated that the circulating level of ABP in Sertoli cell-depleted rats was approximately half, and the concentration of FSH approximately twice, that in normal animals. Thus, even though FSH is elevated in Sertoli cell-depleted rats, the production of ABP per Sertoli cell is unchanged. In addition, collective volume of Leydig cells and ventral prostate weights were normal in the Sertoli cell-depleted group, suggesting that Leydig cell function in these rats is normal. In summary, a Sertoli cell-depleted rat model has been produced by interfering specifically with Sertoli cell proliferation early in postnatal life, before onset of germ cell division. Moreover, our findings with this model indicate that production of normal numbers of germ cells in adults depends, at least in part, on the size of the Sertoli cell population. Thus, our observations identify the perinatal period, when the Sertoli cell population is established, as critical for development of quantitatively normal spermatogenesis in the adult.

Monoamine alterations during experimental hydrocephalus in neonatal rats.

The present study was designed to determine the selected monoamine changes that occur during infantile hydrocephalus. Obstructive hydrocephalus was induced in newborn rats by injection of a suspension of kaolin into the 4th ventricle and cisterna magna. Eleven days later, experimental animals and their sham-operated littermate controls were killed and pieces of frontoparietal cortex, neostriatum, cerebellar vermis, and brain stem were processed for high performance liquid chromatography. Grossly, the lateral ventricles were extremely enlarged, the cerebral cortex was thinned, the neostriatum was compressed, and portions of the tectum and cerebellum were vacuolated. Decreases in norepinephrine (71%), dopamine (73%), and serotonin (50%) were observed in the cerebral cortex, neostriatum, and cerebellum, respectively. Brain stem norepinephrine and serotonin were increased 70% and 50%, respectively. These increases may indicate impairment of axonal transport or damage to projections from the locus ceruleus and raphe region. These preliminary results suggest that infantile hydrocephalus causes perturbations in the levels of different monoamines in several brain regions. Such changes may critically influence neuronal function and development, as well as the therapeutic management of hydrocephalus.

The effects of anterior hypothalamic deafferentation on FSH-releasing activity in the intact female hamster.

To study the role of the anterior hypothalamic area (AHA) in the control of the estrous (E) rise of follicle stimulating hormone (FSH), female hamsters were subjected to anterior hypothalamic deafferentation (D) or sham deafferentation (S) on 1500 h of proestrus (P). Serum levels of FSH and luteinizing hormone (LH) were measured by radioimmunoassay and FSH and LH releasing activities measured by bioassay in the anterior (AH) and medial basal hypothalamus (MBH) at several time periods during P and E. D did not affect serum levels of LH, whereas there was an attenuation of FSH levels during P and E. D caused an increase in FSH releasing activity in the AH within 1 h, while LH releasing activity was elevated 8 h after D. In animals with D, LH releasing activity in the MBH was elevated during P and was similar to controls during E. FSH releasing activity in the MBH increased during early E and dropped precipitously by 1400 h of E. Collectively, these data demonstrate dichotomous changes in FSH and LH releasing activities and provide further evidence for dual control mechanisms for these two gonadotropins.

FSH- and LH-releasing activity in the hypothalamus of female hamsters during proestrus and estrus: effects of arcuate nucleus lesions.

An in vitro bioassay was used to characterize the pattern of follicle-stimulating hormone (FSH)- and luteinizing hormone (LH)-releasing activities in the anterior (AH) and medial basal hypothalamus (MBH) during proestrus (P) and estrus (E) in the hamster. Regularly cycling hamsters were decapitated at 12.00, 16.00, 20.00 and 23.00 h of P and 02.00, 05.00, 08.00, 11.00, 14.00 and 17.00 h of E and sera assayed for FSH and LH. Neutralized extracts of the AH and MBH were incubated with a hemipituitary (HP), which was obtained from estrogen- and progesterone-primed ovariectomized rats. The incubation media were assayed for FSH and LH and the results expressed as nanograms of gonadotropin released per milligram HP. There was a surge of serum FSH and LH at 16.00 h of P and a surge of serum FSH only on E. LH-releasing activity in the AH and MBH declined late on P. This activity in the MBH increased by 08.00 h of E. FSH-releasing activity declined markedly in the MBH early on E when serum levels of FSH, but not LH, were rising. Conversely, low serum levels of FSH and high FSH releasing activity were found in the AH and MBH of animals with a chemically induced lesion of the arcuate nucleus. These data suggest that an FSH-releasing hormone may play an important role in the neuroendocrine control of FSH release.

Alterations in insulin and glucagon secretion by monosodium glutamate lesions of the hypothalamic arcuate nucleus.

This study was performed to determine the effects of monosodium glutamate (MSG) induced lesions of the hypothalamic arcuate nucleus (ARC) on glucose tolerance and insulin and glucagon secretion in male golden hamsters. Eight day old hamsters were given a single s.c. injection of 5.8 mg/g BW MSG or hypertonic saline (controls). Studies were initiated when the hamsters were 3 months of age. At this age there were no body weight differences. Glucose (180 mg/100 g BW) was administered via stomach tube to 18 control and 18 MSG-treated hamsters. Animals were anesthetized with ether and a single blood sample from the portal vein was taken either before or at 30 or 60 min after glucose administration (n = 6/group). Glucose concentrations were similar in both groups at all time periods. Insulin concentrations in the MSG group were significantly (P less than 0.05) elevated in MSG-treated hamsters compared to controls at the 60 min time point. Glucose suppressed glucagon (P less than 0.05) in control but not in MSG-treated hamsters. The MSG group had significantly more glucagon (P less than 0.05) in portal vein blood at 30 min after glucose administration than did the control hamsters. Molar insulin/glucagon ratios did not differ between the 2 groups which likely accounts for the lack of differences in blood glucose levels. These results suggest a role for the ARC in regulating pancreatic function.

Neuron numbers in hypothalamic nuclei of young, middle-aged and aged male rats.

Morphologic analysis of nine hypothalamic areas revealed significant decreases in the number of neurons per unit area in the ventral medial and arcuate nuclei. These data suggest that altered neuron numbers in the VMW and perhaps the ARC may participate in the well documented reductions in endocrine and neuroendocrine function observed in aging rats.

Immunohistochemical localization of luteinizing hormone-releasing hormone (LHRH) in the hypothalamus of adult female hamsters treated neonatally with monosodium glutamate or hypertonic saline.

The immunohistochemical localization of luteinizing hormone-releasing hormone (LHRH) was studied in paraffin and vibratome-sectioned tissue from adult female hamsters that were treated neonatally with monosodium glutamate (MSG) or hypertonic saline. There appeared to be a reduction in LHRH-positive fibers in the median eminence of animals with an MSG-induced lesion of the arcuate nucleus in paraffin-embedded tissue. However, when unembedded tissue was cut on a vibratome, the distribution of LHRH-positive fibers and perikarya was similar in both groups of animals. Fibers were seen coursing through the periventricular area and lateral hypothalamus to the median eminence. In addition, LHRH-positive fibers were seen in the organum vasculosum of the lamina terminalis, subfornical organ, septal and preoptic areas, fasciculus retroflexus, habenular complex, and several regions in the basal forebrain. Animals that were pretreated with colchicine had LHRH-positive perikarya in the medial habenular nucleus, diagonal band of Broca, and the medial olfactory tract.