White matter

Alternatively, the first-order sensory neurons may initially enter the white matter of the spinal cord. In this case, the axons of these neurons may ascend the cord to the medulla or travel up or down the cord to a different spinal segment. Upon reaching its destination, the axon then enters the gray matter of the spinal cord and synapses with one or more of the neurons discussed previously. 

Ascending tracts. These tracts contain three successive neurons  

As discussed, the first-order neuron is the afferent neuron that transmits impulses from a peripheral receptor toward the CNS. Its cell body is located in the dorsal root ganglion. This neuron synapses with the second-order neuron whose cell body is located in the dorsal horn of the spinal cord or in the medulla of the brainstem. The second-order neuron travels upward and synapses with the third-order neuron, whose cell body is located in the thalamus. Limited processing of sensory information takes place in the thalamus. Finally, the third-order neuron travels upward and terminates in the somatosensory cortex where more complex, cortical processing begins. 

Fasciculus gracilis Fasciculus cuneatus Dorsal spinocerebellar Ventral spinocerebellar Lateral spinothalamic Ventral spinothalamic 

Lateral corticospinal Rubrospinal Ventral corticospinal rVestibulospinal 

---

S1P5 Brain, white matter tracts Gj/o. G12/13 Proliferation, cell rounding... 

Positron emission tomography studies using "C-toluene in nonhuman primates and mice showed a rapid uptake of radioactivity into striatal and frontal brain regions (Gerasimov et al. 2002). Maximal uptake of the radiotracer by these structures occurred 1 minutes after intravenous administration. Subsequently, clearance of the radiotracer from the striatal and frontal areas occurred rapidly, with a clearance half-life from peak uptake of 10—20 minutes. Radiotracer clearance from white matter appears to be slower... 

Filley CM, Heaton RK, Rosenberg NL White matter dementia in chronic toluene abuse. Neurology 40 332—334, 1990... 

In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels. 

Stys PK, Lipton SA (2007) White matter NMDA receptors an unexpected new therapeutic target Trends Pharmacol Sci 28 561-566... 

Small vessel/lacunar strokes have better short- and long-term (1-year) survival as compared to other stroke subtypes. In the NINDS trial of rt-PA within 3 hours of onset, patients classified as small vessel stroke on the basis of their clinical syndrome had a 50% chance of a normal NIHSS score at 3 months if they received placebo, increasing to 70% in the treatment group. In the Lausanne cohort, 95% were independent after their first event, as opposed to only 65% of the cardioembolic strokes and 49% with large vessel atherothrombotic infarctions. Eighty-two percent of patients with small vessel stroke were independent at 1 year. Even at the time of maximal deficit, between 38% and 64% of small vessel/lacunar patients were independent, with motor impairment and extent of white matter disease adversely affecting outcomes. " In TOAST, small vessel/lacunar stroke was the only subtype associated with a favorable outcome, independent of the NIHSS score. ... 

Nevertheless, useful information can be deduced from patterns of distribution. Glycine is concentrated more in the cord than cortex and in ventral rather than dorsal grey or white matter. This alone would be indicative of a NT role for glycine in the ventral horn, where it is now believed to be the inhibitory transmitter at motoneurons. GABA, on the other hand, is more concentrated in the brain than in the cord and in the latter it is predominantly in the dorsal grey so that although it is an inhibitory transmitter like glycine it must have a different pattern of activity. 

Figure 21.2 The anatomical organisation of the spinal cord, showing the grey and white matter with the laminae terminal zones of the different afferent fibre t5 pes...

Chloroform-methanol extracts of Borrelia burgdorferi were used for the identification of lipids and other related components that could help in the diagnosis of Lyme disease [58]. The provitamin D fraction of skin lipids of rats was purified by PTLC and further analyzed by UV, HPLC, GLC, and GC-MS. MS results indicated that this fraction contained a small amount of cholesterol, lathosterol, and two other unknown sterols in addition to 7-dehydrocholesterol [12]. Two fluorescent lipids extracted from bovine brain white matter were isolated by two-step PTLC using silica gel G plates [59]. PTLC has been used for the separation of sterols, free fatty acids, triacylglycerols, and sterol esters in lipids extracted from the pathogenic fungus Fusarium culmorum [60]. 

DTI has already been demonstrated to be effective in analyzing the internal micro structure of different tissues. For instance, orientation of nerve fiber bundles in the white matter of the brain or hollow fiber orientations in material science can be visualized using DTI [11],... 

Chicken (Leghorn) 5 d 1 x/d (GO) 240 F (axonal degeneration and demyelination in peripheral nerves and spinal cord white matter) Gaworski et al.. 1986 Durad MP280... 

The inhibition of two cholinesterase activities in blood can also be used to confirm exposure to certain organophosphate ester compounds. Red blood cell acetylcholinesterase is the same cholinesterase found in the gray matter of the central nervous system and motor endplates of sympathetic ganglia. Synonyms for this enzyme include specific cholinesterase, true cholinesterase, and E-type cholinesterase. Plasma cholinesterase is a distinct enzyme found in intestinal mucosa, liver, plasma, and white matter of the central nervous system. Synonyms for this enzyme include nonspecific cholinesterase, pseudocholinesterase, butyrylcholinesterase, and S-type cholinesterase (Evans 1986). Nonspecific cholinesterase is thought to be a very poor indicator of neurotoxic effects. 

The gray matter, which contains the cell bodies of neurons, is on the outer surface of the cerebrum and forms the cerebral cortex. The white matter, composed of the myelinated axons of neurons, is found underlying the cortex in the core of the cerebrum. These axons are bundled together according to function and organized into units referred to as tracts. The three types of tracts in the cerebrum are ... 

Figure 6.2 Frontal section of the brain. The cerebrum is composed of two types of tissue internal white matter and external gray matter which forms the cerebral cortex. Embedded within the cerebral hemispheres are other masses of gray matter, basal ganglia, and thalamus. The ventricles are filled with cerebrospinal fluid (CSF).

The cerebellum (Latin, little brain) is part of the hindbrain and is attached to the dorsal surface of the upper region of the brainstem. Although it constitutes only 10% of the total volume of the brain, it contains more than half of all its neurons. Its surface consists of a thin cortex of gray matter with extensive folding, a core of white matter, and three pairs of nuclei embedded within it. 

Explain the function of the white matter of the spinal cord... 

The gray matter is composed of nerve cell bodies and unmyelinated intemeuron fibers. The location of the gray matter in the spinal cord is opposite to that of the brain. In the brain, the gray matter of the cerebrum and the cerebellum is found externally forming a cortex, or covering, over the internally located white matter. In the spinal cord, the gray matter is found internally and is surrounded by the white matter. 

The white matter is composed of myelinated axons of neurons. These axons are grouped together according to function to form tracts. Neurons transmitting impulses toward the brain in the ascending tracts carry sensory information. Those transmitting impulses away from the brain in the descending tracts carry motor information. 

GRAY MATTER WHITE MATTER SPINAL NERVES... 

---