On-line moisture determination of ore concentrates 'a review of traditional methods and introduction of a novel solution'.

The manual gravimetric drying moisture determination methods currently employed by most mineral processing plants fail to provide timely and accurate information required for automatic control. The costs associated with transporting and handling concentrates still represent a major portion of the overall treatment price. When considering the cash flow of a mining operation that is governed by both the smelter contract, with moisture penalties and the quantity and quality of the concentrates shipped, an efficient method of on-line moisture content would be a welcome tool. A novel on-line determination system for ore concentrate moisture content would replace the tedious manual procedure. Since the introduction of microelectronic-based control systems, operators have strived to reduce the treatment costs to the minimum. Therefore, a representative and timely determination of on-line moisture content becomes vital for control set points and timely feedback. Reliable sensors have long been on the 'wish list' of mineral processors since the problem has always been that you can only control what you can measure. Today, the task of moisture determination is still done by the classical technique of loss in weight utilizing uncontrolled procedures. These same methods were introduced in the earliest base metal concentrators. Generally, it is acceptable to have ore concentrate moisture content vary within a range of 7-9%, but controlling the moisture content below 8% is a difficult task with a manually controlled system. Many times, delays in manually achieving reliable feedback of the moisture content results in the moisture varying from 5-12% before corrective actions can be made. This paper first reviews the traditional and widely available methods for determining moisture content in granular materials by applying physical principles and properties to measure moisture content. All methods are in some form affected when employed on mineral ore concentrates. This paper introduces and describes a novel on-line moisture sensor employed for mineral processing de-watering applications, which not only automates the tedious tasks but also results in reliable moisture feedback that can be used in the optimization of the de-watering process equipment such as pressure or vacuum filters and fuel-fired driers. Finally, two measurement applications will be presented which indicate the usefulness and summarizes the measurement requirements for the proposed method of employing drag force and mechanical properties of the material itself to determine the moisture content.

Expression of mRNA for glial fibrillary acidic protein after experimental cerebral injury.

This study was undertaken to determine whether a mRNA for glial fibrillary acidic protein (GFAP) was present in increased amounts as a response to injury and, if so, how was its temporal expression related to the demonstration of GFAP by immunocytochemical techniques. A cerebral freeze-injury was produced in mice and at intervals thereafter the animals were anesthetized, perfused with formalin and histological sections of the brain through the injured area were prepared. A riboprobe for GFAP mRNA labeled with S35 and an immunocytochemical probe for GFAP were utilized to localize mRNA and GFAP immunoreactivity, respectively. For mRNA studies, the histological slide exposed to either sense or antisense probe was overlaid with x-ray film or dipped in photographic emulsion. The developed film was quantitated by digital image analysis. Emulsions were examined by dark-field microscopy. The results indicate that mRNA for GFAP is increased in the cortex in the environs of the injury by 6 hours, becomes maximal at 4-5 days, and is present in increased amounts up to 14 days. The message is enhanced in the adjacent cortex, the subpial region, the adjacent corpus callosum and in the ipsilateral and contralateral callosal radiations. This pattern of enhancement follows the distribution of post-injury edema. Glial fibrillary acidic protein is demonstrable at 24-48 hours after injury. Thus, there is a rapid response of the astrocyte to injury with increased mRNA expression that is followed by expression of GFAP immunoreactivity.

A 35-year experience with the post-sophomore fellowship in pathology: analysis of its effectiveness as a recruitment resource.

Recent reports have indicated a shortage of pathologists coming out of training programs over the next few years. This is due, in part, to a decrease in the number of medical students entering pathology and an overall decline in the popularity of the field as a specialty choice. Medical students electing to spend a year in a post-sophomore fellowship in pathology would be expected to enter the field at a higher than average rate. In this study, the specialty choices of 140 former student fellows were analyzed. The students included in the study were enrolled in a year-long University of California, Los Angeles post-sophomore fellowship in pathology between 1953 and 1988. Twenty-seven of the 140 students (19.3%) ultimately chose pathology as a career. This represents a 9- to 10-fold increase over the average percentage of medical students entering pathology through the match (less than 2%) for any given year. Of all students from the University of California, Los Angeles who entered pathology, 75% did not elect to spend a year in fellowship. Eighty percent of the former fellows chose some other field, medicine and surgery being the most popular choices.

Blood-brain barrier and new approaches to brain drug delivery.

Morbidity caused by brain dysfunction affects more than 50 million persons in the United States. Although new neuropharmaceuticals have the potential for treating specific brain diseases, they may not effectively enter brain from blood. Safe strategies are needed for drug delivery through the brain capillary wall, which makes up the blood-brain barrier in vivo. Two of these strategies are reviewed, as are related new developments in the molecular and cell biology of the brain capillary endothelium. The production of chimeric peptides represents a physiologic-based strategy for drug delivery. It entails the covalent coupling of the neuropharmaceutical to a brain transport vector, allowing transportation through the blood-brain barrier. Another strategy is biochemical opening of the blood-brain barrier: intracarotid leukotriene infusion is a method for selectively increasing blood-brain barrier permeability in brain tumors without affecting barrier permeability in normal brain tissue.

In vitro interaction of astrocytes and pericytes with capillary-like structures of brain microvessel endothelium.

A new method to study the interaction of astrocytes and pericytes with cerebral capillary endothelial cells in vitro is described. Endothelial cells derived from bovine brain were cultured on gelatin coated slides and covered with type 1 collagen. Endothelial cells aggregated and formed capillary-like structures (CS) within 3 days. The lining cells of the CS stained immunohistochemically for factor VIII-related antigen. Astrocytes isolated from neonatal mice or pericytes from bovine brain were added to the preparations after the formation of CS. After various periods of co-culture, the slides were fixed with methanol and examined with the immunohistochemical stain for glial fibrillary acidic protein or smooth muscle actin to demonstrate astrocytes or pericytes respectively. Five hours after addition, only 10% of astrocytes were associated with CS. However, by 24 hours, 70% of the astrocytes had assumed a position adjacent to the CS. The astrocytes then developed processes which were intimately apposed to the CS by 3 days, at which time they resembled the in vivo structural relationship between astrocytes and microvessels that occur in areas of central nervous system injury. Progressive elongation of the astrocytes or their processes at the CS was evident at 6 and 9 days of co-culture. The cross-section of CS co-cultured with astrocytes showed continuous cells surrounding a lumen, and the endothelial cells appeared to be connected by tight junctions. When pericytes were added to CS cultures they also preferentially associated with CS, but the contact occurred more rapidly than with astrocytes, 50% being associated with CS by 5 hours. The CS were almost completely covered with elongated pericytes by 24 hours. A chemotactic assay was developed that showed that there was a chemotactic attraction of pericytes to the CS. Thus an in vitro system is now available to study the interrelationships of these cell types and their interaction in development, regeneration and differentiation of the blood-brain barrier.

Astrocyte growth stimulation by a soluble factor produced by cerebral endothelial cells in vitro.

Conditioned medium from isolated cerebral capillary endothelial cells (ECCM) was found to promote DNA synthesis in astrocytes and pericytes, but not in oligodendrocytes or endothelial cells (EC) in vitro. The astrocyte was the cell of primary interest and the cell tested in the following experiments. The effect of ECCM on astrocytes was concentration and time dependent. The growth factor was released by EC into the medium in a cumulative manner for up to 72 hours. This release was not the result of a nonspecific leakage of an internal store, since the DNA synthetic activity of cell lysates was negligible. The growth factor secretion per cell was higher in sparse than in confluent EC cultures and was partially inhibited by preincubation of EC with interleukin-1. The DNA synthetic activity was due to a peptide, different from basic fibroblast growth factor, transferrin, bovine fibronectin and platelet derived growth factor, with a molecular weight greater than 50,000. The peptide derived from the cerebral capillary EC could be involved in the local signaling between cell types that control new vessel formation in development, in regeneration after brain tissue injury, or in tumor formation.

Choline uptake by cerebral capillary endothelial cells in culture.

A passage of choline from blood to brain and vice versa has been demonstrated in vivo. Because of the presence of the blood-brain barrier, such passage takes place necessarily through endothelial cells. To get a better understanding of this phenomenon, the choline transport properties of cerebral capillary endothelial cells have been studied in vitro. Bovine endothelial cells in culture were able to incorporate [3H]choline by a carrier-mediated mechanism. Nonlinear regression analysis of the uptake curves suggested the presence of two transport components in cells preincubated in the absence of choline. One component showed a Km of 7.59 +/- 0.8 microM and a maximum capacity of 142.7 +/- 9.4 pmol/2 min/mg of protein, and the other one was not saturable within the concentration range used (1-100 microM). When cells were preincubated in the presence of choline, a single saturable component was observed with a Km of 18.5 +/- 0.6 microM and a maximum capacity of 452.4 +/- 42 pmol/2 min/mg of protein. [3H]Choline uptake by endothelial cells was temperature dependent and was inhibited by the choline analogs hemicholinium-3, deanol, and AF64A. The presence of ouabain or 2,4-dinitrophenol did not affect the [3H]choline transport capacity of endothelial cells. Replacement of sodium by lithium and cell depolarization by potassium partially inhibited choline uptake. When cells had been preincubated without choline, recently transported [3H]choline was readily phosphorylated and incorporated into cytidine-5'-diphosphocholine and phospholipids; however, under steady-state conditions most (63%) accumulated [3H]choline was not metabolized within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of in vitro and in vivo models of drug transcytosis through the blood-brain barrier.

Drug and solute transport through in vitro and in vivo models of the blood-brain barrier (BBB) were compared to provide a measure of how well the in vitro model predicted BBB permeability found in vivo. The in vitro model employed bovine brain capillary endothelial cells in either primary tissue culture or as a continuous line grown on Transwells and placed in side-by-side diffusion chambers. The in vivo model of BBB transport utilized an internal carotid artery perfusion/capillary depletion method in anesthetized rats. BBB permeability in vivo and in vitro was measured for 15 radiolabeled drugs and for L-[3H]dopa, D-[14C]glucose and [3H]albumin. [3H]- or [14C]sucrose was used in vivo as a blood volume reference. Lipid solubility of each drug was measured based on the 1-octanol/Ringer's partition coefficient. The morphology of the endothelial cell in primary tissue culture was spindle-shaped and the morphology of the endothelial cell in continuous culture was cuboid-shaped. The cuboidal morphology demonstrated a 2-fold greater resistance to solute transport and was used for the majority of the in vitro studies. Drug and solute permeability coefficients (Pe) ranged from 3.9 X 10(-3) to 2.5 X 10(-1) cm/min in vitro and from 1.0 X 10(-5) to 2.1 X 10(-2) cm/min in vivo. The In of the permeability.surface area product in vitro correlated with the In partition coefficient (r = 0.62, P less than .0125) and the In permeability.surface area product in vivo correlated with the In partition coefficient (r = 0.84, P less than .0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Paragangliomas: assessment of prognosis by histologic, immunohistochemical, and ultrastructural techniques.

To predict clinical outcome, we studied 42 paragangliomas from 37 patients by routine histology, immunohistochemistry, and electron microscopy. A panel of antisera to neuron-specific enolase (NSE), chromogranin, and met-enkephalin was used to identify chief (type I) cells, and S-100 protein and glial fibrillary acid protein (GFAP) sustentacular (type II) cells. The intensity of staining of type I cells and the density of type II cells were assessed semiquantitatively (0 to 4+) in a total of 38 tumors. A total of 23 of 24 low-grade tumors (solitary, multiple, or associated with other neoplasms; 95.8%) contained type II cells immunoreactive with either S-100 protein or GFAP, and all were positive when S-100 protein and GFAP were used in combination. Five of the nine intermediate-grade (recurrent and/or locally aggressive) tumors were identified as glomus jugulare tumors (GJT). Three intermediate-grade GJTs were devoid of GFAP-reactive type II cells and four GJTs were negative for S-100 protein. Type II cells were identified in only one of five high-grade (malignant) paragangliomas and that tumor contained vanishingly rare cells that were weakly S-100 protein positive but GFAP negative. Sustentacular cell density and chief cell staining intensity were both inversely related to tumor grade. The most sensitive chief cell marker was NSE (92.1%), followed by chromogranin (84.2%). The least sensitive (73.0%) and specific marker was met-enkephalin. Combinations of NSE or chromogranin with met-enkephalin identified chief cells in all cases. Electron microscopy identified neurosecretory granule-containing chief cells, but was of less value in delineating sustentacular cells because of their scarcity and the absence of specific features. By comparison, immunohistochemistry was superior in identifying sustentacular cells. The use of an immunohistochemical panel, in addition to routine histology, can confirm the diagnosis of a paraganglioma and can give an indication of the likely prognosis for a patient.

Stimulation of glucose analogue uptake by cerebral microvessel endothelial cells by a product released by astrocytes.

Astroglial cells, both normal and neoplastic, secreted a product that stimulated glucose uptake by cerebral microvessel endothelial cells by 23% and 50%, respectively. Neither cerebral microvessel smooth muscle cells nor oligodendrocytes affected endothelial cell glucose uptake. The astrocytic product(s) did not affect glucose uptake by aortic endothelial cells. The effect on the cerebral microvessel endothelial cells increased with increasing time of exposure of the cells to the astroglial product(s), and required the constant presence of the astrocytic product to be maintained. The presence of a protein synthesis inhibitor during endothelial cell exposure to the astroglial conditioned medium blocked the stimulation of glucose uptake. Treatment of the astrocytic product with a protease destroyed its effectiveness. These results support the hypothesis that astrocytes induce the expression of at least one blood-brain barrier property by the cerebral microvasculature, and suggest that this induction may be produced by a protein released by the astrocytes.

The expression of S-100 protein and neuron-specific enolase in meningiomas.

The distribution of S-100 protein and neuron-specific enolase (NSE) was examined in 19 meningiomas using the peroxidase-antiperoxidase (PAP) immunohistochemical technique. Positive cytoplasmic staining for NSE was observed in 16 tumors, and comparable staining for S-100 protein was observed in eight tumors. The finding of S-100 protein and NSE immunoreactivity in fibroblastic, meningiotheliomatous, and transitional meningiomas raises the possibility that these morphologically distinct neoplasms derive from a common pluripotential cell capable of differentiation along diverse paths.

Induction of gamma-glutamyl transpeptidase in cultured cerebral endothelial cells by a product released by astrocytes.

gamma-Glutamyl transpeptidase (gamma GTP) is an enzyme found in cerebral capillary endothelial cells, the presumed site of the blood-brain barrier, but not in endothelial cells lining blood vessels in other parts of the body. Using a line of mouse cerebral microvessel endothelial cells (ME-ly cells) and a sensitive colorimetric assay to measure gamma GTP levels we demonstrated that primary cultures of mouse astrocytes and a line of rat C6 glioma cells released a soluble product(s) that induced the production of gamma GTP in cultured endothelial cells by 34% and 39%, respectively, over control levels. Cerebrovascular smooth muscle cells had no significant effect on gamma GTP levels in ME-ly cells, and the astrocyte product(s) had no effect on rabbit aortic endothelial cells. The induction of gamma GTP levels in ME-ly cells was apparent after one day of exposure to the astrocyte product(s) and increased in magnitude with increasing time of exposure of the ME-ly cells to the product(s). Removal of the product(s) from the ME-ly cells resulted in a return to control levels of gamma GTP in the ME-ly cells within 2 days. The presence of a protein synthesis inhibitor during incubation with the product(s) blocked the induction of gamma GTP in ME-ly cells, and treatment of the product(s) with 200 U/ml TPCK-trypsin destroyed its inductive properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential opening of the brain endothelial barrier following neutralization of the endothelial luminal anionic charge in vitro.

This study was undertaken to determine the effect of neutralization of brain endothelial cell luminal membrane anionic charge on endothelial permeability properties. Mouse brain microvessel endothelial cells were grown to confluence on a nitrocellulose filter. The permeability of the endothelium to Evan's blue dye (EBD) (molecular weight 960) and fluoresceinated dextran (FITC-D) (molecular weight 20,000), both polar molecules, was assessed before and after the exposure of the endothelium to cationic ferritin (CF) or native ferritin (NF). The use of CF resulted in a significant increase in permeability of the endothelium to EBD compared to NF. This result indicates that ablation of endothelial surface anionic charge enhances endothelial transport of a small, polar-charged molecule. Cationic ferritin did not increase the permeability of FITC-D compared to NF. This negative result is not surprising because FITC-D differs from EBD in terms of charge and solubility as well as in size. The electrical resistance of the endothelial cell layer after the application of CF was unchanged from baseline values suggesting a transcellular rather than a paracellular route of the EBD leakage.

Diagnostic immunopathology.

The application of immunologic techniques to tissue sections has added a new dimension to the investigation and classification of various processes. Virtually every section of diagnostic pathology has been enhanced by using specific monoclonal antibodies or polyclonal antiserum. Neoplasms formerly diagnosed as poorly differentiated or anaplastic may be precisely identified as to their origin through the use of specific membrane or cytoplasmic markers. Other cellular products, including viruses, hormones, enzymes or highly specific proteins, are also available to study neoplastic and nonneoplastic processes. New and more specific reagents are regularly becoming available for the diagnostic repertoire of pathologists. We present some of the principles of diagnostic immunopathology to show the scope and importance of the techniques.

Blood-brain barrier: interface between internal medicine and the brain.

The blood-brain barrier separates brain interstitial space from blood and is formed by brain capillary endothelial cells that are fused together by epithelial-like tight junctions. Study of the blood-brain barrier traditionally has been a relatively arcane field, even for neurobiologists. However, advances over the last 10 years in understanding the transport physiology and cell biology of the brain capillary endothelial cell now provide insights into the pathogenesis of such problems as brain glucopenia, hepatic encephalopathy, therapeutic efficacy of alpha-methyldopa, brain edema in diabetic ketoacidosis, Alzheimer's disease, brain tumors, and lupus cerebritis.

Effect of inorganic lead on some functions of the cerebral microvessel endothelium.

The effect of inorganic lead on two functions of cerebral microvessel endothelium, cell division and glucose analog uptake, was investigated. Lead concentrations considered to be toxic in humans inhibited both functions in cultured endothelial cells. Both effects were dependent on the length of lead exposure and dose over the range of 10(-4) to 10(-6) M lead acetate. After 4 days of exposure there were 76% fewer cells in 10(-4) M lead-exposed cultures relative to control cultures. After 4 days of exposure to 10(-5) M lead there were 55% fewer cells, and after 10(-6) M lead exposure there were 15% fewer cells. Two days after 10(-4) M lead exposure [methyl-3H]thymidine incorporation into endothelial cells was inhibited by 71%. Incorporation was inhibited 47% by 10(-5) M lead but 10(-6) M lead did not inhibit incorporation after 2 days of exposure. Glucose analog uptake was inhibited in both contact-inhibited and log-phase cells; however, the latter were more sensitive to lead and this increased sensitivity correlated with a higher lead content in this cell population. Both the specific carrier-mediated and the nonspecific components of glucose analog uptake were inhibited by exposure of the endothelial cells to lead. A lead exposure of 40 min produced a significant effect on the uptake mechanism. In order to manifest its effects the lead had to be present in serum-containing medium, suggesting that some serum component was necessary to present the lead to the endothelial cells. These findings imply that the initial target of inorganic lead in the CNS may be the plasma membrane of the capillary endothelial cells, and that lead may act by altering the physiological function of these membranes.