Piece Of Skull Research Articles

Say Cheese! Snapshots of the Living Mouse Brain

The human brain is a highly complex system comprised of billions of cells, called neurons, that are all interconnected. Normal brain function depends on effective communication between neurons, which requires signals to travel down a nerve cell and then over to the next cell it is connected to. Several diseases result from impairments in the communication between neurons, which is why it is important to study these signals in the living brain. Since the living human brain is difficult to study, scientists use simpler organisms like mice. To see mouse neurons, a piece of skull is replaced with a clear glass window. Powerful microscopes can then be used to capture snapshots of neurons deep inside live brains! Clever use of lasers to excite chemical “tags” inside the neurons makes them glow with fluorescent light. Join us as we explore the inner workings of neuron communication in the living brain.

Transcranial MRI-guided FUS-induced BBB opening in the rat brain

The blood-brain barrier (BBB) has been a major limitation in treating diseases of the brain because therapeutic agents are either unable to penetrate or have dose-limiting side effects in diffuse opening of the BBB. A previous study demonstrated that focused ultrasound (FUS) can locally open the BBB in a rabbit model when a piece of skull is removed and that magnetic resonance imaging (MRI) can be used to guide and monitor the procedure. This study examined whether the same desired effect of local BBB disruption can be achieved by applying FUS through an intact skull in a rat model. Twenty-eight Sprague-Dawley rats were anesthetized, shaved, and sonicated at four focal locations in the brain, using a 1.5-MHz focused transducer. Contrast-enhanced MR images were obtained before and after sonication. The images indicated contrast agent penetration at the focal coordinates following Optison-enhanced sonication. This study demonstrated that the distortion of the ultrasound beam by the rat skull was not significant enough to inhibit focal BBB opening. Subsequent experiments using MRI-guided FUS to aid in targeted drug delivery to brain tumors in a rodent model could thus be performed more efficiently without cranial surgery. [Research funded by NIH Grant No. CA76550.]

Trans-skull ultrasound therapy: the feasibility of using image-derived skull thickness information to correct the phase distortion

Recent papers have shown that focused ultrasound therapy may be feasible in the brain through an intact human skull by using phased arrays to correct the phase distortion induced by the skull bone. The hypothesis of this study is that the required phase shifts for the phased array can be calculated from the skull shape and thickness provided by modern imaging techniques. The shape and thickness of a piece of human skull was traced from the serial images and used in a theoretical model to calculate the phase distribution for a phased array. A 76-element phased array was manufactured and used in the tests. The piece of skull and the transducer array were positioned in a waterbath, and the ultrasound field distributions were mapped with and without the phase correction. The image-derived phase correction produced a sharp focus through the skull. These results showed that ultrasound brain therapy may be executed completely noninvasively through an intact skull by using a phased array and the skull thickness information derived from MRI scans.

Suoidea du Miocène inférieur de Laugnac (Lot-et-Garonne, France)

The fossil vertebrate locality of Laugnac is the type locality of the Neogene mammalian zone MN2b. It has yielded many remains of Suoidea belonging to two different genera.Xenohyus venitor is characterized by its large size and especially its large central upper incisors, I1/ and I2/. It is quite difficult to know its phyletic relationships because the material is not abundant.Hyotherium cf.meisneri is more abundant with a quite good skull, pieces of skull, jaws and isolated teeth. It belongs to a peculiar lineage different from that ofH. major from Saint Gerand-le-Puy, France. It has some similarities withAureliachoerus aurelianensis from later geological levels (MN3-MN5).

Application of a dipping procedure to construct a241Am skull phantom

The construction of reliable bone phantoms to calibrate whole body counting facilities for bone-seeking radionuclides has been a challenge for several research institutes. Different techniques have been applied to get uniform distribution of those nuclides in bone tissue. A241Am skull phantom was developed at the Institute of Radiation Protection and Dosimetry/Brazilian Nuclear Energy Commission's (IRD/CNEN) Whole Body Counting facility, using a dipping procedure. Preliminary tests were performed using non-radioactive ink solution. The first step was to choose the appropriate solvent to be used, since it was observed that acid solutions attack bone tissue. At the second step, pieces of skull were dipped into those solutions to check the extent and homogeneity of the penetration. The third step consisted of verifying the dipping time using a241Am standard solution. The homogeneity was checked with a high-purity germanium detector. Tissue-equivalent material was used to cover the skull surface and to simulate the low energy X and gamma radiation attenuation. The calibration factor and the detection limit were calculated for two phoswich detectors positioned at each side of the head, which is the standard geometry for this kind of measurement.

Wax-ester metabolism in the orange roughyHoplostethus atlanticus (Beryciformes: Trachichthyidae)

Freshly caught orange roughy (Hoplostethus atlanticus) obtained at the edge of the Chatham Rise, east of the South Island of New Zealand, in June 1988, were used to investigate tissue-specific lipid synthesis and to obtain blood for plasma lipoprotein analysis. Tissue slices prepared from an intraneurocranial fat deposit, pieces of skull (neurocranium), swimbladder and liver were incubated with radioactive acetate, palmitate and oleate, and the labelled lipids extracted and analysed. All four tissues could incorporate acetate label into fatty acids which were themselves incorporated into triacylglycerols and phospholipids although not into wax esters, the most abundant lipid class in these tissues. Exogenous palmitate and oleate were also incorporated into more complex lipids, with the label from oleate (but not palmitate) being found in wax esters as well as triacylglycerols and phospholipids. The distribution of the label in the wax esters showed that some reduction of the fatty acid to fatty alcohol had occurred. The only exception to this pattern was the swimbladder, which incorporated small amounts of palmitate-label into both the fatty acid and fatty alcohol portions of the wax esters. Lipoproteins were isolated from serum by centrifugation. All lipoprotein classes contained phospholipid, cholesterol, triacylglycerol, cholesteryl esters and wax esters. A very low-density lipoprotein class also contained large amounts of unesterified fatty acids, which are possibly artefacts resulting from storage of the samples. Significant quantities ofω-3 fatty acids were also found in the serum lipids.

The repair of congenital and acquired skull defects in childhood

Methylmethacrylate (sulfix-6 and palakos) are very useful materials for the closure of skull defects. The age of the patient and the time of operation are of secondary importance. These substances have the lowest complication rate, can be easily handled and produce a cosmetically satisfactory result. Rib transplants have in our hand not been associated with any complications, but they are cosmetically not always satisfactory as palpable spaces between the ribs remain and the postoperative wearing of a protective helmet is advisable. The use of the patient's own piece of skull or the external lamina are less satisfactory because there is always a tendency of absorption. Nevertheless, it should be used as a primary measure. In all the operations, meticulous sterility is mandatory and a sufficiently large and viable flap of scalp and galea must be used. In children with encephaloceles, cerebral spinal fluid fistulae have to be closed completely watertight. This can only be achieved by a multiple layer closure of the soft tissues; fibrin seal has been found to be especially useful in this operation.

A New Approach to Upper Cervical Injuries

Severe injuries to the upper cervical region can be the cause of death. Standard autopsy techniques are inadequate for examination of this area. Therefore a technique has been developed that gives excellent visualization and allows removal of the brain and spinal cord in one piece. With the body prone a midline incision is made from the top of the head to the sacrum. The skull is sawed in a circle from one side of the foramen magnum around the top of the skull to the other side of the foramen magnum. The lamina of the neural arches of the vertebral column are sawed. With the removal of the piece of skull and the posterior portions of the neural arches, the posterior half of the cerebral cortex, cerebellum, and entire spinal cord are exposed. The entire brain and spinal cord can be removed as a unit. Cases are selected by history, X-ray examination, or floppy head. Four cases in which this approach has been helpful are briefly mentioned.

Time course of biosynthetic cholesterol in the adult rat brain

In a first experiment, the time course of biosynthetic cholesterol was studied in the whole brain of adult rats, 1 h to 15 months after an intraventricular injection of 5-[ 14C]mevalonic acid. Radioactivities of nonsaponifiable compounds, sterols and cholesterol purified by gas-liquid chromatography were measured in the brain and those of precursor sterols and squalene fraction were calculated. In the other experiments, only cholesterol radioactivities were measured from 3 days to 1–3 months after injection (1) in the whole brain and in a piece of skull, (2) in the cerebellum and cerebral hemispheres and (3) in a fraction of whole brain homogenate and in cerebral myelin. The most striking results are the following: 1. Brain cholesterol specific radio-activity reaches two maxima, one at 3 days, and the other, slightly lower, at 1 month after injection. 2. After these two peaks, brain cholesterol specific radioactivity decreases as an exponential function of time, with a slope of 0.004 day −1. 3. Cholesterol specific radioactivity of myelin increases up to 40 days after injection whereas that of the other subcellular fractions decreases up to 6 days and increases from 6 to 40 days after injection. Two complementary explanations of these results are discussed. The first involves the existence of two groups of subcellular structures, those of group 1 exchanging their cholesterol with that of plasma, those of group 2 exchanging their cholesterol between themselves and with cholesterol of the first group. The second interpretation involves two chains of biosynthesis for brain cholesterol, working at different rates.

Elastomers for Implantation in the Human Body

Abstract In the continuing effort to heal the ills of their patients, the medical profession has endeavored to make use of many materials, not only as medicines, but also for mechanical devices which could be used to repair damage to the body. At first these devices were simple ones such as tree limbs for crutches, and for splints to hold broken bones in place. As technology developed, it became possible to make less utilitarian devices. Tycho Brahe, the famous astronomer, wore a gold nose to replace his own that was bitten off in a tavern brawl. As medicine became more sophisticated, attempts were made to replace subdermal tissues. These were mostly failures because of the lack of knowledge of sterility and because the body would reject most of the materials used. Some early successes were made, however, notably the use of silver plates to replace missing pieces of skull. It is only in the past 50 years that special alloys have been developed which allow the repair of many bone problems with a good degree of surety. Of recent date, tantalum, Vitalium, and 316L stainless steel have been used to make a wide variety of devices for permanent subdermal implants: hip joints, skull plates, wires, pegs, pins, screws, and plates. However, these are hard, and are, therefore, only useful for the repair of bones. Most of the body is made up of soft tissues, and soft materials must be used to replace or repair them. For instance, one cannot make a satisfactory esophagus from stainless steel, since any motion of the neck or even such small actions as pulsating blood vessels would cause cutting of the soft tissues next to the hard metal. Many soft materials were tried, but all, when placed in the tissues caused intense reactions, and they inevitably had to be removed. This paper will concern itself with the search for and the applications of elastomeric materials for permanent subdermal soft tissue replacement.