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PubMedDate not supplied

The 5 alpha-reductase activity of the subcortical white matter, the cerebral cortex, and the hypothalamus of the rat and of the mouse: possible sex differences and effect of castration.

Previous studies have shown that the central nervous system is able to convert testosterone into 17-beta-hydroxy-5-alpha-androstan-3-one (DHT), by the action of the enzyme 5-alpha-reductase. The data here presented show that, in the brain of the rat and the mouse of both sexes, the 5-alpha-reductase activity is more concentrated in the subcortical white matter than in the hypothalamus and in the cerebral cortex. The enzymatic activity is apparently higher in the rat than in the mouse brain. The formation of DHT in the subcortical white matter, in the hypothalamus and in the cerebral cortex of both rats and mice does not show any sexual difference. Moreover, in the rat no effect of short- or long-term castration or neonatal castration or testosterone replacement could be observed on the formation of DHT in the three brain structures considered (even in the subcortical white matter, the cerebral tissue more active in converting testosterone into DHT). The present data support the view that the 5-alpha-reductase present in the brain is not under androgenic control.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1993

Cognitive recovery correlates with white-matter restitution after head injury.

Longitudinal measurements of local cerebral perfusion (LCBF) and local partition coefficients (L lambda) using xenon-enhanced computed tomography were examined in six patients who had suffered from head injury at a mean age of 30 +/- 9.3 years. They were selected from a larger group with head injury because all were observed longitudinally to make excellent cognitive recovery some years after acute cerebral trauma. Results were compared with similar longitudinal measurements made in six age-matched neurologically normal volunteers. In the index group, cognitive test scores were reduced at the time of the first LCBP measurement but significantly improved to normal at the time of the second. The mean interval between measurements was 2.7 +/- 0.7 years. At the time of the first measurement, all six patients exhibited abnormal volumes of white matter with reduced Hounsfield numbers and LCBF and L lambda values. Abnormalities in volume of white matter and LCBF and L lambda values improved to normal at the time of the second measurement. Perfusion values for frontal cortex, putamen, and thalamus were still slightly reduced but also improved toward normal between measurements. Cognitive recovery correlated best with restoration of white matter integrity, suggesting that following head injury, cognitive impairments may be associated with temporary disconnections of corticothalamic projection systems.

Adult↗
PubMed1991

Studies on the environmental persistence of S-31183 (pyriproxyfen): adsorption onto organic matter and potential for leaching through soil.

Analytical methods were developed to allow the extraction and analysis of S-31183 (pyriproxyfen), 2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine, in organic matter from animal waste-water lagoons. Analysis of water and organic debris from a treated lagoon showed that the active ingredient readily adsorbed onto organic matter. S-31183 persisted on organic matter for over a 2-month period, during which time the concentration decayed at an exponential rate. In leaching trials with four different soil types, over 50% of the active ingredient applied remained in the upper 6 cm of a 30-cm soil column; there was no indication of a rapid potential for downward migration. The use of S-31183 for treating wastewater lagoons at doses which are effective for mosquito control did not result in any apparent problems of environmental incompatibility.

Adsorption↗
PubMed1983

Transitory macrophages in the white matter of the developing visual cortex. II. Development and relations with axonal pathways.

Clusters of 'gitter cells' develop in the white matter of the occipital cortex of the cat at the end of the first postnatal week. These clusters, and others already present at birth, disappear by the end of the first postnatal month. The life span of the clusters in the occipital white matter corresponds to the period when transitory callosal axons are eliminated. The clusters have close contact with callosal axons and can be labeled by HRP injected in the contralateral hemisphere and transported through the corpus callosum. One of the clusters clearly forms in a part of the white matter crossed by transitory callosal axons. The 'gitter cells' might be involved in the elimination of these axons. Consistent with this hypothesis, ultrastructural observations show groups of axons completely surrounded by 'gitter cell' cytoplasm as if they were being phagocytosed.

Aging↗
PubMed1991

Non-synaptic mechanisms of Ca(2+)-mediated injury in CNS white matter.

Clinical deficits after injury to the CNS are due, in large part, to dysfunction of white matter (myelinated fiber tracts), including descending and ascending tracts in the spinal cord. A crucial set of questions, in the search for strategies that will preserve or restore function after CNS injury, centers on the pathophysiology of, and mechanisms underlying recovery of conduction in, CNS white matter. These questions are relevant both to spinal cord injury, and to brain infarction, which frequently affects white matter.

Animals↗
PubMed1987

The total carbohydrate: organic carbon ratio as an indicator of sewage-derived organic matter in Burbo Bight sediments, Liverpool Bay, UK.

Sediments from the Burbo Bight, Liverpool Bay, were analysed for their total carbohydrate (TCH) and organic carbon (TOC) contents, and the TCH:TOC ratio (when the TCH is expressed as a percentage of the TOC) was used to give an indication of the amount of sewage-derived organic matter in the sediments. The %TCH values found ranged from 17-68 with an average of 40, indicating that sewage-derived organic matter constituted a significant fraction of the organic matter in the sediment. This appears likely to have been derived mainly from the Mersey Estuary outflow and the sewage sludge dumped in Liverpool Bay, but these two sources cannot be distinguished using this technique. It is suggested that further studies are required on the carbohydrates in sewage sludge and coastal sediments to satisfactorily establish this technique.

Journal Article↗
PubMed1988

Experimental measurements and computer predictions of copper complex formation by soluble soil organic matter.

Complexing of metals by organic matter can strongly influence their biological activity in the environment. The extent of copper complex formation by soluble organic matter extracted from an organic soil, a clay, and two sandy loams, was measured under identical conditions using two independent experimental methods. The results in every case fitted equations similar to Langmuir two-surface isotherms, but the values of complexing capacity and complexing strength were not the same for the organic matter from the four soils, and so were unsuitable for use in computer programs intended to predict concentrations of individual copper species in soil solutions. These concentrations can, however, be predicted by an empirical relationship between free and total copper at a constant pH and ionic strength.

Journal Article↗
PubMed1996

The impact of SO2 and SO2 + ascorbic acid treatments on growth and partitioning of dry matter in Trigonella foenum-graecum L.

To study the impact of SO(2) and SO(2) + ascorbic acid on growth and partitioning of dry matter in Trigonella foenum-graecum L., two-week-old plants were exposed to SO(2) for 2 h daily over a 42 day period. One of the exposed sets was treated with ascorbic acid. Plants were grown in a wire house and unexposed plants were used as controls for comparison. The parameters measured, such as dry weights of leaf, stem and root per plant, were found to be lower in the exposed sets than in the controls. The reductions were greater in dry weights of stem and root as compared with weights of leaves, indicating that the partitioning of the dry matter was altered. Greater amounts of soluble sugars and starch in the leaves of exposed plants, compared with the stem, also revealed that translocation was hampered. Reductions were greater in fruiting than in flowering, suggesting that fruit abortion was high. Although ascorbic acid treatment could mitigate the effect of SO(2), the differences were not found to be statistically significant. Significant changes were seen in fruit yield, suggesting that the effect of ascorbic acid is cumulative. The impact of SO(2) and SO(2) + ascorbic acid on partitioning of dry matter to different 'sinks' is discussed.

Journal Article↗
PubMed1987

Interrelationship between metabolism of tritiated water, 22sodium and dry matter intake by beef cattle consuming wheat straw and poultry litter in free choice.

1. Metabolism of tritiated water and 22sodium was studied in six beef cows under Mediterranean summer conditions in order to find whether the turnover of these tracers can be used to evaluate pasture intake. 2. The diet of the cows included ad libitum access to two components which were given separately in different troughs: one was poultry litter and the other was wheat straw, to simulate the dry pasture. 3. Voluntary daily dry matter intake (111 g/kg0.75) was unexpectedly high considering the low digestibility of the feed. 4. The assumptions of constant ratios of water intake to water turnover and of dry matter intake to water intake were confirmed. Consequently, dry matter intake was determined accurately from water turnover measurements. 5. Sodium intake was practically equal to sodium turnover and most of the sodium secreted in feces was of endogenous origin. 6. Pasture intake can be predicted from sodium turnover once the concentration in feed and water consumed is known.

Animal Feed↗
PubMed1991

Induction of corticospinal target finding by release of a diffusible, chemotropic factor in cervical spinal grey matter.

The outgrowth of corticospinal tract axons in rat spinal cord primarily occurs during the first postnatal week. Axons originating from a group of layer V pyramidal cell bodies situated in the anterior part of the cerebral sensorimotor cortex project mainly to the cervical gray matter (Joosten et al., Dev. Brain Res., 36 (1987) 121-130). By co-culturing explants of the anterior part of the sensorimotor cortex and of cervical spinal gray matter in 3-D collagen gels, a target-specific directional growth of cortical axons towards the cervical spinal gray explant could be demonstrated. After retrograde filling with the fluorescent tracer 1,1-dioctadecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI), in vivo as well as in vitro, most of the DiI-labelled cortical neurons were located in layer V of the cortical explant, and were characterized by a pyramidal shape. These data suggest that the cervical spinal gray matter target area becomes innervated by corticospinal axons through the release of a diffusible chemotropic factor.

Animals↗
PubMed1994

Secretory form of beta-amyloid precursor protein is much abundantly contained in the cerebral white matter in human brain.

To elucidate the metabolic process of beta-amyloid precursor proteins (APP) in cerebral gray and white matter of the human brain, we compared the content and characteristics of secretory APP between these two parts. The white matter contained much more secretory APP than the gray matter in both a control and a Down's syndrome brain, but no difference in the characteristics of the APP isoforms was detected. Our results suggest that, in the human brain, a considerable amount of APP is carried by axonal transport, during which some of the APP isoforms are processed to their secretory forms.

Aged↗
PubMed1995

Secretory cleavage of beta-amyloid precursor protein in the cerebral white matter produces amyloidogenic carboxyl-terminal fragments.

To elucidate the metabolic process generating amyloid-beta protein (A beta) from beta-amyloid precursor protein (APP) in human brain, we partially purified secretory forms and carboxyl-terminal fragments (CTFs) of APP from the white matter of a Down's syndrome brain. We obtained secretory forms of APP which lack the entire A beta sequence and CTFs which contain the full-length A beta from the cerebral white matter. Some A beta-lacking secretory APP isoforms in the white matter were derived from APP695. These results suggest that amyloidogenic CTFs can be produced by secretory cleavage of APP which is anterogradely transported through the axon in human brain.

Amyloid beta-Peptides↗
PubMed1983

Naloxone reversible inhibition of reticular neurones in the rat caudal medulla produced by electrical stimulation of the periaqueductal grey matter.

Chronic dorsal periaqueductal grey matter electrodes were implanted into adult rats under pentobarbitone anaesthesia. Stimulating these electrodes (25-300 microA) produced behavioural analgesia in 23 of 44 rats tested. In rats given the opiate antagonist naloxone attenuation of this analgesia was seen. In 14 rats displaying behavioural analgesia to periaqueductal grey matter stimulation acute electrophysiological experiments were performed under urethane anaesthesia. Microelectrode recordings were made from neurones, excited by noxious heat or pinch applied to the limbs and tail, and located in the reticular formation of the caudal medulla. Stimulation of the periaqueductal grey matter at an intensity sufficient to produce analgesia in the conscious animal produced direct inhibition of the firing of 62% of neurones tested, excited 23%, had no effect on 14% and attenuated the nociceptive responses of 66%. The inhibitions were characteristically long. Local application of naloxone by microiontophoresis attenuated these long inhibitions in 11 out of 16 neurons tested. Immunohistochemical localization of beta-endorphin containing structures in the vicinity of stimulating and recording sites suggested that the naloxone sensitive inhibition of nociceptive neuronal responses in caudal medulla reticular formation may be due to activation of beta-endorphin fibres descending through the periaqueductal area to the caudal medulla.

Action Potentials↗
PubMed1994

Cerebrovasodilatation of metabolic and non-metabolic origin elicited by chemical stimulation of the lateral periaqueductal gray matter in anaesthetized rats.

We attempted to elucidate the mechanisms operating in the mediation of the cerebrovasodilator action of the defence area within the periaqueductal gray matter, employing radiolabelled microsphere flowmetry in 50 anaesthetized rats. The caudal two-thirds of this brain region were chemically stimulated with N-methyl-D-aspartate (1 nmol as 100 nl in a 10-mM solution). Besides eliciting a distinctive pattern of haemodynamic defence responses, the stimulation consistently provoked a cerebrovasodilator action, preferentially in the supratentorial brain regions. In particular, 56% of the overall flow increase in the parasagittal cerebral cortex was solely attributable to the unique cerebrocortical vasodilator action of the periaqueductal gray matter, independent of unspecific effects of concomitantly occurring hypertension itself. This flow change was not associated with a specific change in the metabolic rate for O2 of this cortical region. We conclude that the major part of the unique cerebrocortical vasodilator action provoked from the defence area within the periaqueductal gray matter was mediated by non-metabolic mechanisms. The involvement of the metabolic mechanism could be of only minor importance, if any. Cerebral vasodilatation may be involved in the natural defence reactions for coping with the emergency that threatens the animal.

Anesthesia↗
PubMedDate not supplied

Magnetic resonance signal intensity ratio of gray/white matter in children. Quantitative assessment in developing brain.

Magnetic resonance imaging (MRI) findings in 87 children with various clinical entities were used to determine the signal intensity ratio of gray/white matter in T1- and T2-weighted images using a 1.5 T MR Scanner. Signal intensity ratio changes in both T1- and T2-weighted images correlated well with advancing age (y = 0.9349-0.001575, r = -0.584, P < 0.0001 in T1-weighted images; y = 0.9798 + 0.002854, r = 0.723, P < 0.0001 in T2-weighted images), but the correlation was more linear when we included only normally developed (34) children (y = 0.9689-0.001967, r = -0.654, P < 0.0001 in T1-weighted images; y = 0.9882 + 0.002965, r = 0.747, P < 0.0001 in T2-weighted images). Abnormal ratios were observed in patients with congenital hydrocephalus, inherited metabolic diseases and cerebral palsy. Although the gray/white matter differentiation would not delineate the myelination itself, measurement of the signal intensity ratio of gray/white matter is a practical way to evaluate delayed myelination in a busy MR center.

Adolescent↗
PubMed1991

Sources of T1 variance in normal human white matter.

The major factors contributing to T1 variance at 0.5 T in white matter were studied in healthy people. Anatomical location of the white matter sampled and differences between individuals contributed 74% of the total variance in serial measurements of the same subjects. There was also significant change over time within an individual subject that could not be attributed to machine drift. This information permitted estimates to be made concerning adequate sample size in future studies that examine for pathological white matter T1 change.

Adolescent↗
PubMed1992

Visual rating of magnetic resonance images of human cerebrospinal fluid spaces and white brain matter: relation to sex and age in healthy volunteers.

The size of the cerebrospinal fluid spaces and the occurrence of white matter lesions were estimated from the intracranial volumes of 76 apparently healthy adult volunteers of different ages using 0.02-T/0.8-MHz magnetic resonance imaging. A relation between the occurrence of white matter lesions and the size of cerebrospinal fluid spaces independent of age could not be demonstrated. In men, white matter changes were more numerous and lateral ventricular size was larger, but sex differences were not statistically significant except for lateral ventricular size. The results confirm that age is the most significant parameter correlated with alterations in brain anatomy over time. Body mass and other clinical parameters were not influential factors in the present material.

Age Factors↗
PubMed1992

The extracellular matrix of cerebral gray matter: Golgi's pericellular net and Nissl's nervösen grau revisited.

Glial hyaluronate-binding protein (GHAP) and a large aggregating chondroitin sulfate proteoglycan (Ag-Pg) similar to a fibroblast proteoglycan (versican) were localized in bovine, dog and cat central nervous system (CNS) gray matter by indirect immunofluorescence. The distribution of the two hyaluronate-binding proteins was identical with that of hyaluronate, an extracellular glycosaminoglycan. All substances formed a finely reticulated mesh in the neuropil with a condensation of the stain around large neurons. It is concluded that in gray matter, as in white matter, the extracellular matrix (ECM) contains hyaluronate-protein aggregates. We suggest that the hyaluronate-protein aggregates correspond to the pericellular network first described by Golgi.

Animals↗