Mathematical model of oxygen transport in the cerebral cortex

To estimate the magnitude of hyperemia necessary to support oxidative metabolism in the cerebral cortex during functional activation, a mathematical model of O2 transport from capillary to tissue was developed. Radial and axial gradients of O2 pressure in tissue surrounding a single capillary were calculated at normal and increased cerebral metabolic rates for O2. Cone-shaped tissue geometry and nonlinear oxyhemoglobin dissociation were assumed. Local O2 consumption was assumed to be supported with local tissue pO2 greater than 1 mmHg. The distribution of tissue pO2 was also calculated during moderate hypoxemia (paO2=42 mmHg), using experimental values of red blood cell velocity measured in individual capillaries of the rat cerebral cortex using intravital video-microscopy. The model predicted that moderate increases (相似文献   

Mullite as an electrochemical probe for the determination of low oxygen activity in liquid iron

Oxygen activities in liquid iron deoxidized with aluminium were measured at 1873 K, using a mullite electrolyte having a Cr-Cr₂O₃ reference mixture. These results were compared with those obtained using commercial tube-type ZrO₂-8 mol% MgO and plug-type ZrO₂-9 mol% MgO probes, along with oxygen activities calculated from analysis. Oxygen activities from EMF measurements using mullite and plug-type probes were found to be in agreement with those calculated from the Al /AI₂O₃ equilibrium and those estimated from analyzed oxygen contents. Polarization effect due to electrochemical oxygen transport was observed in a commercial tube-type ZrO₂-based probe. Supersaturation in liquid iron deoxidized with aluminium was also measured at 1873 K.     

Restoration of oxygen uptake and blood flow in the rat cerebral cortex after halothane anaesthesia

The thoracic and lumbar curvatures of 105 Nigerian adults have been measured with a flexible rule (flexicurve). The lumbar curvature is relatively greater in women. Compared with a previous survey of Europeans, the curvatures in both men and women appear to be about 20 per cent greater in Nigerians. This is likely to be a genetic difference but the Nigerian practice of carrying heavy loads on the head may be a contributory factor.     

Slow oscillations as a probe of the dynamics of the locus coeruleus-frontal cortex interaction in anesthetized rats

Multiunit or single unit activity recorded simultaneously from frontal cortex (FC) and locus coeruleus (LC) under ketamine anesthesia revealed that both regions show slow oscillatory activity, together or separately. If, however, both regions are engaged in this oscillatory activity, there is a systematic relationship between their phases with peak LC firing always following FC firing by 200-400 ms. This was confirmed by cross-correlational analyses, which indicated that the two structures temporarily form a resonant system. The FC-LC resonant state is, however, loose enough to remain open to other intrinsic or extrinsic influences, keeping the measured frequencies of oscillations at each site slightly different, as demonstrated by a detailed analysis of the autocorrelograms. An injection of lidocaine at the frontal cortex site, while sharply reducing the prefrontal activity to essentially zero, leads to an increase of the LC activity and to a modification of the shape of the LC autocorrelogram, but does not change appreciably the phase relationship between the activity in the two structures during the diminishing activity in FC.     

Investigation of the kinetics of heterogeneous reactions with the aid of an oxygen probe

The feasibility of using a solid-electrolyte oxygen probe to monitor the kinetics of processes which are accompanied by the transfer of oxygen between a gas atmosphere and solid material in a laboratory reactor was shown. The equation describing such processes was derived. It was concluded that the solid-electrolyte probe can be used to control mass transport in commercial heat-treating furnaces.     

Neurotransmitter receptors in the developing cerebral cortex

This review deals with several aspects of neurotransmitter receptor development in the primate cerebral cortex. It describes the presence of multiple neurotransmitter receptors in the transient zones of the fetal cerebral wall. These zones are involved in the production and migration of cortical neurons and the establishment of appropriate innervation of the cortex. It also suggests functions that neurotransmitter receptors may perform in these embryonic zones. In addition, this review shows that a remarkable diversity of neurotransmitter receptors develops concurrently in disparate areas of the primate cerebral cortex and discusses the implications of this finding on our understanding of the general principles underlying development of the cerebral cortical circuitry. Finally, it speculates on factors that may be involved in regulation of neurotransmitter receptor development in the primate cerebral cortex.     

Information synthesis in key parts of the cerebral cortex as the basis of subjective experience

This paper discusses a number of principles of the organization of cerebral processes underlying subjective experiences. The concept developed here suggests that these experiences arise as a result of the synthesis of different types of information, this synthesis occurring in various parts of the cortex which have key roles in this mental function. The synthesis is made using information arriving from the external environment, information extracted from memory, and information arriving from motivational centers. The concept is based on studies of the cerebral mechanisms of perception and thought. Experiences are demonstrated to arise as a result of the synthesis, by neurons in the projectional cortex, of data describing the physical and informational properties of a stimulus; the mechanism of the synthesis is a circular movement of excitation from the projectional to the associative regions of the cortex, then to the hippocampus and motivational centers, with return of excitation to the projectional cortex. It is also demonstrated that the process of thought involves convergence of cortical connections on defined centers, which are called interaction foci. Different thought operations are associated with their own specific interaction focus topographies: in imaginative thinking, foci are located in the temporo-parietal cortex, while abstract thinking foci in the frontal cortex. It is suggested that information arriving by means of neural connections is compared and synthesized in interaction foci, and that this provides the basis for decision-making. The final part of this paper addresses the functional importance of mental phenomena and their possible effects on cerebral processes.     

Atomic contributions to the optical rotation angle as a quantitative probe of molecular chirality

Chiral molecules are characterized by a specific rotation angle, the angle through which plane-polarized light is rotated on passing through an enantiomerically enriched solution. Recent developments in methodology allow computation of both the sign and the magnitude of these rotation angles. However, a general strategy for assigning the individual contributions that atoms and functional groups make to the optical rotation angle and, more generally, to the molecular chirality has remained elusive. Here, a method to determine the atomic contributions to the optical rotation angle is reported. This approach links chemical structure with optical rotation angle and provides a quantitative measure of molecular asymmetry propagation from a center, axis, or plane of chirality.     

Assessment of intact Sarcocystis cystozoites as an ELISA antigen

Hereditary hemorrhagic telangiectasia (HHT), or Rendu-Osler-Weber disease, is an autosomal dominant disorder characterized by a triad of mucocutaneous and visceral telangiectasia, recurrent epistaxis and familial history. We reported a rare case of HHT associated with pulmonary and cerebral arteriovenous fistulae (AVF) and multiple cerebral arteriovenous malformations (AVM). The roles of multimodality therapies including artificial embolization, feeder clipping and stereotactic radiosurgery for these multiple cerebrovascular dysplasia in HHT were discussed. In particular the usefulness of radiosurgery to obliterate AVM was emphasized. It is especially useful for multiple AVM's associated with HHT. A 7-year-old boy had presented himself at another hospital 2 years previously with cyanosis of the lips and fingers on exertion. He was diagnosed as having pulmonary AVG and underwent surgery. His mother had suffered from epistaxis in her adolescence, and was then highly suspected as having HHT. She underwent surgical removal of a left fronto-parietal AVM at the age of 16 years. The family history then prompted the patient to have a brain CT done, which eventually demonstrated an abnormal enhancing mass at the left frontal region. He was transferred to our service for further evaluation. Left carotid angiograms demonstrated an AVF supplied by a dilated anterior internal frontal artery of the anterior cerebral artery (ACA), draining directly into the vein of the corpus callosum with a large aneurysmal dilatation, and then draining further into the straight sinus via the vein of Galen. In addition, right carotid angiograms revealed three small AVM's fed by the median artery of the corpus callosum, and the middle internal frontal and paracentral arteries of the right ACA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemisphere dominance of the cerebral cortex

An outbreak of erythema infectiosum (fifth disease) occurred in a North Carolina elementary school. Because rubella virus has been implicated as a possible cause of some cases of erythema infectiosum, we conducted an investigation to determine if the children were infected with rubella virus and to learn whether or not rubella virus vaccination prevents the disease. Throat swabs were obtained for viral isolation from 20 children with erythema infectiosum and from 25 healthy classmates; questionnaires were completed for 617 of the school's 817 students. One hundred fifty children (24%) reported having an acute exanthematous illness during the study period, and 45% of the ill children had one or more household contacts with a similar rash. No viruses were recovered from the children, and a history of rubella vaccination did not affect the risk of developing erythema infectiosum.     

Hypervascularization of the cerebral cortex in lead-induced encephalopathy

Pregnant rats were fed a diet containing 1.8% lead acetate for 8 days before delivery until the young were 3 month old. The density of the cerebral cortex capillaries of the infant rats and their convolution rate were studied morphometrically and noted to increase significantly according to the duration of lead treatment, as demonstrated by two-way analysis of variance. On the other hand, the thickness of the cortex reduced progressively. The increase of both capillary density and convolution rate is supposed to be related with this involution of cortex. This provides a quantitative insight of the previously described 'capillary activation' phenomenon, caused by lead encephalopathy and reveals it as a significant sequel of saturnine action.     

Dissolution of bornite in sulfuric acid using oxygen as oxidant

Leaching of natural bornite in a sulfuric acid solution with oxygen as oxidant was investigated using the parameters: temperature, particle size, initial concentration of ferrous, ferric and cupric ions, and using microscopic, X-ray and electronprobe microanalysis to characterize the reaction products. Additionally, stirring rate, pH and P_O2 were varied. Dissolution curves for percent copper extracted as a function of time were sigmoidal in shape with three distinct periods of reaction: induction, autocatalytic and post-autocatalytic which levelled off at 28% dissolution of copper. The length of the induction period was not reproducible, causing the dissolution curves to be shifted with respect to time. The dissolution curves in the autocatalytic and post-autocatalytic regions were reproducible, and this property was utilized to treat much of the kinetic data. The iron dissolution curves had four dissolution regions. An initial small but rapid release of iron to solution preceded the three periods just given for copper dissolution. Aside from this initial iron release, the iron and copper dissolution curves were almost identical.Stirring rate had no effect on dissolution of copper above 400 min^?1 nor did oxygen flow rate in the range 20–40 cm³/min. Dissolution rate was slightly dependent on oxygen partial pressure for P_O2 < 0.67. Hydrogen ion concentration had no effect except that sufficient acid was required to prevent hydrolysis and precipitation of iron salts.The dissolution rate was directly dependent on the reciprocal of particle diameter indicating possible surface chemical reaction control, but the activation energy of 35.9 kJ/mol (8.58 kcal/mol) for the autocatalytic region of copper dissolution is slightly too small for that, though not unreasonable. Initial addition of Fe²⁺ had a rather complex effect and markedly enhanced dissolution of copper, as also did initial addition of Fe³⁺. Microscopic analysis showed nuclei of two new phases, covellite and Cu₃FeS₄, in the induction region. The new phases grow rapidly in the autocatalytic stage, which is controlled by nuclei formation and chemical reaction. The post-autocatalytic region is characterized by complete transformation of bornite into covellite on the particle surfaces and Cu₃FeS₄ as an internal product with an X-ray spectrum very similar to that of chalcopyrite. The post-autocatalytic region is controlled by autocatalytic growth of newly formed phases. Further reaction beyond the autocatalytic region (percent copper dissolution > 28%) occurs so slowly with oxygen as oxidant that it was not studied.The rate of copper dissolution appears to be controlled by the rate of iron dissolution. Using that and the other experimental evidence a mechanism for reaction is proposed in which iron-deficient bornite, Cu₅Fe_?S₄, is formed on the surface by initial preferential iron dissolution. Labile Cu⁺ diffuses into this from Cu₅Fe_?SO₄ and unreacted bornite to produce CuS on the surface. Depletion of labile Cu⁺ ions from Cu₅FeS₄ produces Cu₃FeS₄ in the interior of the mineral particles.     

3H]5,7-dichlorokynurenic acid recognizes two binding sites in rat cerebral cortex membranes

Binding of [3H]5,7-dichlorokynurenic acid ([3H]DCKA), a competitive antagonist of the strychnine-insensitive glycine site of the N-methyl-D-aspartate (NMDA) receptor channel complex, was characterized in synaptic plasma membranes from rat cerebral cortex. Non linear curve fitting of [3H]DCKA saturation and homologous displacement isotherms indicated the existence of two binding sites: a specific, saturable, high affinity site, with a pKD value of 7.24 (KD = 57.5 nmol/l) and a maximum binding value (Bmax) of 6.9 pmol/mg of protein and a second site, with micromolar affinity. The pharmacological profile of both binding components was determined by studying the effect on [3H]DCKA and [3H]glycine binding of a series of compounds known to interact with different excitatory and inhibitory amino acid receptors. These studies confirmed the identity of the high affinity site of [3H]DCKA binding with the strychnine-insensitive glycine site of the NMDA receptor channel complex. 3-[2-(Phenylaminocarbonyl)ethenyl]-4,6-dichloroindole-2-carb oxylic acid sodium salt (GV 150526A), a new, high affinity, selective glycine site antagonist (1), was the most potent inhibitor of this component of binding (pKi = 8.24, Ki = 5.6 nmol/l). The low affinity component of [3H]DCKA binding was insensitive to the agonists glycine and D-serine and the partial agonist (+/-)-3-amino-1-hydroxy-2-pyrrolidone (HA 966), though recognised by glycine site antagonists. The precise nature of this second, low affinity [3H]DCKA binding site remains to be elucidated.     

Neuropsychology and pathology of the cerebral cortex

In all clinics we are faced with questions about certain aspects of cerebral dominance. We consider first the problem of recognition of faces where the right hemisphere plays a leading role. However, the disorders manifesting that function appear only bilateral lesions. This suggests that the left hemisphere participates in this process. The reception of language raises a problem which is analogous with the preceding: we propose the participation of both hemispheres in this activity: the left hemisphere is dominant in the analysis of phonemes and syntax, the right hemisphere seems implicated above all in the processing of prosodic aspects--in particular intonations and individual features of the voice.     

Measurement of uric acid as a marker of oxygen tension in the lung

Changes in O2 tension such as those associated with hypoxic ischemia or hyperoxia may potentially modulate purine nucleotide turnover and production of associated catabolites. We used an isolated perfused rat lung preparation to evaluate the effect of O2 tension on pulmonary uric acid production. Three O2 concentrations (21%, normoxia; 95%, hyperoxia; 0%, hypoxia) were utilized for both pulmonary ventilation and equilibration of recirculating perfusate. All gas mixtures contained 5% CO2 and were balanced with N2. We used Certified Virus Free Sprague-Dawley male rats weighting 250-300 g, four to five rats in each exposure regimen. After a 10-min equilibration period, we measured uric acid levels at 0 and 60 min in lung perfusate and at 60 min in lung tissue. After 60 min of ventilation/perfusion, we observed significant uric acid accumulation in both lung tissue (25-60%) and perfusate (8- to 10-fold) for all three O2 regimens. However, hypoxia produced substantially greater net uric acid concentrations (net = the difference between zero and 60 min) than either normoxia or hyperoxia (1.5-fold in lung tissue, and 2-fold in perfusate, respectively). The data suggest that pulmonary hypoxia results in greater purine catabolism leading to increased uric acid production. Vascular space uric acid, as measured in the recirculating perfusate, was proportional to lung weight changes (r = 0.99) with hypoxia exhibiting the greatest values, possibly reflecting a linkage between tissue perturbation and uric acid release. Thus, measurement of uric acid may serve as a useful marker of adenine nucleotide turnover and lung injury.