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.

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.

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.

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.

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.

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.

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.

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.

[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.

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.

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.

Morphological changes in the hypothalamic arcuate nucleus and median eminence in the golden hamster during the neonatal period.

The purpose of the present investigation was to study the ultrastructure of the arcuate nucleus (ARC) and median eminence of hamsters on days 1-15 of the neonatal period. From days 1-6, the neurons of the ARC had large nuclei and a small amount of cytoplasm which contained polysomes, mitochondria, RER, lysosomes and Golgi complexes. From days 7-15 there was an increase in the amount of cytoplasm as well as more extensive Golgi complexes and RER. Astrocytes were the predominant glial component in both the ARC and median eminence. Astrocytic processes were in juxtaposition to unmyelinated axons, dendrites, and synapses. Axodendritic and axosomatic synapses containing clear vesicles were observed in the neuropil on day 1. There was an increase in the number of dense-core vesicles in the axonal endings beginning on day 4. Concomitantly, there were increasing numbers of clear and dense-core vesicles (64-70 nm) in terminals of the external layer of the median eminence, whereas larger dense-core vesicles (105-140 nm) were distinguishable by day 10 immediately dorsal to the external layer. The capillaries of the median eminence were composed of nonfenestrated endothelium from days 1-9. Fenestrae began to appear about day 10. Ependymal cells lining the third ventricle had pinocytotic vesicles, microvilli, and bleb-like protrusions on their apical surfaces. Ependymal processes were adjacent to nerve processes in the neuropil of the ARC and in the external layer of the median eminence, where they contacted the perivascular space. Two types of supraependymal cells were seen in animals throughout the neonatal period. One resembled a neuron which sent processes along the ependymal surface and often between cells. The second type was similar to a macrophage. The results of this study demonstrate the maturation of the neural elements in the ARC/median eminence area of the neonatal hamster.

The numbers of neurons in the hypothalamic nuclei of young and reproductively senescent female golden hamsters.

The numbers of neurons in nine different hypothalamic nuclei were counted in every eighth section of serially-cut hypothalami in young (4 to 6 months) and reproductively senescent (15 to 18 months) female hamsters. There were no morphological differences discernible at the light microscopic level in the hypothalami of the aged hamster. There did not appear to be any significant differences in the lateral or rostral-caudal extent of these nuclei nor in neuron counts in old versus young animals. These results are discussed in light of species differences and possible functional alterations.

[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.

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.

[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.

The effects of mercury on the structure and function of the hypothalamo-pituitary axis in the hamster.

The neurons of the arcuate nucleus were studied ultrastructurally in female hamsters that were given saline or 1 mg mercuric chloride/day during one estrous cycle. Membranous whorls, composed of 4-26 concentric layers of smooth endoplasmic reticulum, were found in 7-8% of the neurons of control animals in diestrus (D3) and in proestrus (D3) and in proestrus (D4). Whorls were found in 5-16% of the neurons in mercury-treated animals on all days of the experimental period. The whorls appeared to be associated with RER and Golgi bodies. The levels of FSH and LH were measured in the plasma and pituitaries of both groups of animals. There was a significantly higher concentration of FSH in the pituitaries of experimental animals on D3 and of LH on D1C2 of the subsequent cycle; plasma levels of FSH and LH were similar in both groups throughout the experimental period. The relationship between the levels of gonadotropins and the presence of membranous whorls is discussed.