Uptake, release, and metabolism of alanine in neurons and astrocytes in primary cultures

The uptake, release, and metabolism of alanine were studied in primary cultures of cerebral cortical neurons or astrocytes and cerebellar granule neurons. All three cell types exhibited a saturable, sodium-dependent uptake of alanine with Km values (microM) of 256 +/- 30, 463 +/- 39, and 292 +/- 39, respectively, and Vmax values (nmol/min/mg) of 15.9 +/- 0.7, 7.9 +/- 0.01, and 17.4 +/- 0.8, respectively. The corresponding values (nmol/min/mg) for the specific activity of alanine aminotransferase were 4.7 +/- 0.4, 17.1 +/- 2.5, and 4.5 +/- 0.9 (all values represent the mean +/- SEM). Release of alanine from the cells was rectilinear with time over a 10 hr period in case of astrocytes (40 nmol/hr/mg) and cerebellar granule neurons (21 nmol/hr/mg). In cortical neurons the release rate declined from an initial value of 19 nmol/hr/mg during the first 3 hr to a value of less than 3 nmol/hr/mg during the subsequent 7 hr of incubation. Metabolism of [14C]alanine to 14CO2 was found to have a lag period of 15 min and subsequently the rate of CO2 production was constant over a 45 min period with a value of 0.5 nmol/min/mg in granule neurons and about 0.3 nmol/min/mg in the other two cell types. Altogether the results show that alanine is preferentially produced in and released from astrocytes and accumulated into both GABAergic cortical neurons and glutamatergic cerebellar granule neurons.

Glutamate effects on calcium homeostasis in cerebellar granule cells in primary cultures grown under depolarizing and nondepolarizing conditions

Cerebellar granule cell cultures are normally grown under partly depolarizing conditions (in a medium with approximately 25 mM K+), but these cultures can also be grown at a normal potassium concentration (5.4 mM K+), although some of their characteristics are altered. In this study, intracellular free calcium concentration and 45Ca uptake were measured in cerebellar granule cell cultures grown at either 25 or 5.4 mM extracellular potassium in the presence of glutamate, and/or some of its subtype-specific agonists and antagonists. Granule cells in cultures grown at 25 mM K+ responded to glutamate, but not to quisqualate, with an increase in free cytosolic calcium concentration and in 45Ca uptake. This increase in free cytosolic calcium concentration was dependent on extracellular calcium and it was antagonized by AP5 and ketamine, NMDA receptor antagonists. In contrast, granule cells in cultures grown at 5.4 mM K+ responded to both glutamate and quisqualate, and these responses were independent of extracellular calcium and not sensitive to AP5 and ketamine. In agreement with this, 45Ca uptake was not affected by glutamate. Neither of the two culture types responded to kainate with an increase in calcium concentration or uptake. These observations indicate that calcium uptake in granule cells in cultures grown at 25 mM K+ reflect NMDA activation of calcium influx, whereas the cells in cultures grown at 5 mM K+ increase cytosolic calcium concentration on account of intracellular release of bound calcium, caused by activation of the metabotropic receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte B and T cell subsets in peripheral blood from patients with asbestosis

Peripheral blood lymphocytes were analysed by indirect staphylococcus protein A (SPA) rosette assay using monoclonal antibodies that identify B cells, total T cells (OKT3+), helper-inducer T cells (OKT4+), and suppressor-cytotoxic T cells (OKT8+). The purpose of this investigation was to determine the characteristics of lymphocyte B and T subsets in peripheral blood, and the relation of the changes to radiographic abnormalities in workers exposed to asbestos.

Utilization of glutamine and of TCA cycle constituents as precursors for transmitter glutamate and GABA

In the present review evidence is presented that (1) glutamine synthesis in astrocytes is essential for synthesis of GABA in neurons; (2) alpha-ketoglutarate in the presence of alanine (as an amino group donor) can replace glutamine as a precursor for synthesis of transmitter glutamate, but maybe not as a precursor for transmitter GABA; (3) differences exist in the intraneuronal metabolic pathways for utilization of alpha-ketoglutarate plus alanine and of glutamine, and (4) alanine also functions as a substrate for oxidative metabolism in glutamatergic neurons. It should be emphasized that the supply of precursors for transmitter glutamate and GABA in glutamatergic and GABAergic neurons depends on metabolic processes in astrocytes regardless whether glutamine or alpha-ketoglutarate plus L-alanine function as the transmitter precursors. The key reason that an interaction with astrocytes is essential is that both pyruvate carboxylase, the major enzyme in the brain for net synthesis of tricarboxylic acid cycle intermediates, and glutamine synthetase, the enzyme forming glutamine from glutamate, are specifically located in astrocytes, but not in neurons.

Glutamate and glutamine metabolism and compartmentation in astrocytes

Metabolism of glutamate and glutamine in cultured mouse cerebral cortical astrocytes has been investigated using either radioactively labelled (14C) amino acids or 13C-labelled amino acids combined with NMR spectroscopy of cell extracts and lyophilyzed incubation media. Using [U-13C]glutamate it has been shown that in astrocytes exogenously supplied glutamate is primarily (70%) metabolized oxidatively through the tricarboxylic acid (TCA) cycle and to a lesser extent (30%) directly to glutamine. Glutamate metabolized in the TCA cycle is to a large extent recovered as lactate showing that the astrocyte-specific enzyme, malic enzyme is functionally active. Incubation with [U-14C]glutamine led to a higher specific radioactivity in glutamate than in glutamine. It could also be shown that glutamate and glutamine were metabolized differently to aspartate and alanine. These results taken together strongly suggest that glutamate/glutamine metabolism in astrocytes is compartmentalized and a model with multiple cytoplasmic and mitochondrial compartments of these amino acids is proposed.

Energy metabolism at the cellular level of the CNS

Evidence is accumulating that interactions between different cell types are of paramount importance for CNS function, for example, release of the excitatory transmitter glutamate from neurons and its preferential uptake into astrocytes. Some information is also available about energy metabolism in different cell types, or more often in models of different cell types (e.g., synaptosomes, cultured neurons, cultured astrocytes). In this review an attempt is made not only to correlate information obtained with different cell models but also to integrate this information with in vivo data, with histochemical observations, and with results obtained using brain slices. The emerging patterns indicate that neurons, synaptosomes, and astrocytes are all capable of complete glycolysis and oxidation of glucose. Elevated extracellular concentrations of potassium, known to occur in vivo, enhance energy metabolism by mechanisms that differ between neurons and astrocytes and to a large extent serve to reaccumulate extracellular potassium ions into adjacent cells. Monoaminergic agonists also stimulate energy metabolism, but mainly or exclusively in astrocytes. Profound differences are found between the effects of excess potassium and of aminergic transmitters, suggesting that high potassium concentrations enhance neuronal-astrocytic interactions, whereas the monoamines may tend to dissociate metabolic events in neurons and in astrocytes.

Long-lasting abolishment of noradrenaline induced stimulation of oxidative metabolism after chronic exposure of developing mouse astrocytes to cocaine

Rate of 14CO2 production from [l-14C]glutamate was determined as a measurement of oxidative metabolism in developing primary cultures of astrocytes, obtained from the neonatal mouse brain and grown in the absence (control) or presence of cocaine. From the age of 3 days, the drug-exposed cultures were grown in a tissue culture medium containing either 1 or 3 microM cocaine. After 2 months of chronic exposure to cocaine the metabolic rate showed an increase of approximately 50%, but there was a long lag period (several weeks) before this response occurred. In contrast to a marked stimulation of CO2 production when noradrenaline was added to untreated cultures of the same age, there was no similar effect of noradrenaline on cultures treated with cocaine. After exposure to cocaine for 21 days (24-day-old cultures), both the enhanced CO2 production and the abolishment of the normal response to noradrenaline persisted during 'withdrawal' (cessation of drug exposure) throughout the total period investigated, i.e. to an age of 60 days (corresponding to a withdrawal period of 36 days). The correlation of these findings with in vivo data is discussed.

Context rules of rightward overlapping reading

We have investigated the mechanism and sequence context rules governing ribosome frameshifting promoted by aminoacyl-tRNA limitation. In the case of one shifty sequence, frameshifting promoted by lysyl-tRNA limitation occurs at the sequence AAG C and is due to rightward movement of the ribosome so as to read the AGC triplet overlapping the hungry codon from the right. The frequency of this event is unaffected by sequence elements more than three bases to the left (upstream) or two bases to the right (downstream) of the hungry codon, and only slightly affected by the identity of the base two bases to the right. It is strongly affected by the base immediately to the right of the hungry codon, which becomes the wobble base of the shifted triplet; and by the third base of the hungry codon, even though the two synonyms (AAG and AAA) call for the same aminoacyl-tRNA; and by the identity of the base immediately to the left of the hungry codon. The latter result suggests that the aminoacyl-tRNA in the P site affects the maintenance of reading frame at the adjacent A site of the ribosome. However, the DNA sequence makes it seem unlikely that the P-site tRNA shifts to the right in concert with the A-site tRNA, a mechanism that can account for leftward frameshifting (in the opposite direction) in retroviral translation. The specificity of sequence determinants of leftwing versus rightwing frameshifting is discussed.

Effects of indomethacin on demineralized bone-induced heterotopic ossification in the rat

Indomethacin inhibits bone formation when treatment is initiated before the implantation of demineralized bone matrix (DBM). For the inhibition of bone induction to occur, indomethacin treatment had to be initiated 6 h or more before implantation of DBM. Initiating the drug treatment at or after the time of DBM implantation had no effects on the amounts of new bone formed. The inhibition by indomethacin is dose related over a range between 0.04 and 4 mg/kg body weight. Recovered day-1 DBM implants, transplanted into indomethacin pre- and posttreated syngeneic rats, formed bone at the same rate as controls did. However, recovered day-1 DBM implants lyophilized before transplantation showed decreased bone formation but significant dystrophic calcification as judged by a lower alkaline phosphatase activity and an elevated calcium content.

Alteration of collagen composition and cross-linking in keloid tissues

Collagen composition and cross-linking in human keloid and normal skin tissues were analyzed biochemically. CNBr peptides were separated by 2-dimensional (2-D) mapping and high performance liquid chromatography (HPLC). The amounts of type I and type III collagen was quantified by 2-D scanning densitometry of fluorographs of 2-D maps derived from samples radioactively labelled in vitro by [3H]-NaBH4 in dimethylformamide. Keloid tissues contained 31.6 +/- 2.2 percent type III collagen as compared to 21.4 +/- 2.7 percent type III present in normal human skin dermis. HPLC profiles of CNBr peptides showed that approximately 5 percent of the high molecular weight material in keloids is mercaptoethanol reducible, compared to insignificant amounts in normal skin. 2-D maps derived from CNBr peptides of keloid collagen demonstrated thiol reduction sensitive alpha 1(III)-CB9 dimer as well as 24,000- and 32,000-dalton CNBr peptides, which were not mercaptoethanol reduction sensitive in normal skin due to cross-linking via the lysyl oxidase pathway. Also, a group of 20,000- to 25,000-dalton CNBr peptides, in the alpha 1(I)-CB6 cross-linking region were prominent in keloid tissues.

Immobilization of enzymes with polyaziridines

A novel method of enzyme immobilization using a low molecular weight prepolymer of tri-functional aziridines which can immobilize enzymes both by covalent attachment and entrapment within a gel matrix is described. The enzymes are immobilized on a solid support and exhibit an excellent retention of enzymatic activity. The immobilization procedure is essentially a single step process which can be easily performed at room temperature or 4 degrees C in either aqueous solution or in an inert organic solvent. The polyaziridines used in the immobilization are nontoxic, available in bulk at low cost and completely miscible with water and many organic solvents, thus providing one of the most satisfactory methods of immobilization available.

Automated sulfur hexafluoride washout functional residual capacity measurement system for any mode of mechanical ventilation as well as spontaneous respiration

A new sulfur hexafluoride (SF6) washout functional residual capacity (FRC) measurement system has been developed which will work with any mode of mechanical ventilation, as well as with spontaneous respiration. This system was evaluated in three different human studies. In the first two studies, the accuracy of the system was compared with He dilution and body plethysmography in 12 spontaneously breathing normal volunteers and in 12 spontaneously breathing chronic obstructive pulmonary disease (COPD) patients. In the third study, the reproducibility and efficacy of using the system in the ICU was tested in 12 adult respiratory distress syndrome (ARDS) patients who were mechanically ventilated with PEEP. In the normal volunteers, there was no significant difference between the three measurement techniques. In the COPD group, there was an overall significant difference between measurement techniques (F[2,28] = 17.18, p less than .0001) and the rank of the magnitude of the FRC measurements from lowest to highest was SF6 washout, He dilution, and body plethysmography. There was a significant difference in accuracy between the COPD and normal volunteer groups (F[2,28] = 12.24, p less than .0002). There were a total of 1,227 FRC measurements made on the 12 ARDS patients. The number of FRC measurements per patient was 102 +/- 13 (SEM). The "stable" periods were 14 +/- 2 h long and ranged from 60 min to 63.5 h. The reproducibility for all 12 patients was 188 +/- 17 ml or 11.7 +/- 0.7%. This automated SF6 washout system should make routine FRC measurements in patients who are being mechanically ventilated simple and easy to do.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of monoamine oxidase activity and monoamine effects on glutamate release in cerebellar neurons and astrocytes

Activities of monoamine oxidase (MAO) A and B were measured during the first month of postnatal development in mouse cerebellum and in primary cultures of either cerebellar granule cells or cerebellar astrocytes, derived from 7-day-old cerebella. In addition, effects of the two monoamines, serotonin (a MAO A substrate) and phenylethylamine (a MAO B substrate) on the release of glutamate under resting conditions and in a transmitter related fashion (i.e., potassium-induced, calcium-dependent glutamate release) were studied during the same period. Both MAO A and MAO B activities increased during in vivo development (beginning around postnatal day 14) and in cultured astrocytes (during a comparable time period and to a similar extent), but remained constant at a low level in granule cells. In 4-day-old cerebellar granule cell cultures there was no potassium-induced glutamate release but serotonin as well as phenylethylamine reduced the release in both the presence and absence of excess potassium. In 8- and 12-day-old granule cell cultures and in 8- and 18-day old astrocyte cultures there was a pronounced glutamate release during superfusion with 50 mM K+. In both neurons and astrocytes this response was inhibited by 1 nM of either serotonin or phenylethylamine. In the astrocytes the inhibition was followed by an increased release of glutamate in both the presence and absence of the high potassium concentration, whereas the 8-day-old neurons showed only a slight increase in glutamate release after the withdrawal of the monoamine and only in the absence of excess potassium. The response was almost identical in 8- and 18-day-old astrocytes in spite of the marked difference in MAO activities.

Ultrastructural study of neurons in metachromatic leukodystrophy

Neuronal inclusions were investigated with the electron microscope in several regions of the central nervous system (CNS) of a patient with late infantile metachromatic leukodystrophy (MLD). The neuronal perikarya of the spinal anterior horn cells and the neurons in the globus pallidus were distended with concentrically arranged lamellar inclusions which closely resembled membranous cytoplasmic bodies (MCB) of gangliosidoses. Large pyramidal neurons in the motor cortex also contained a few smaller MCB-like inclusions. These neuronal inclusions were relatively uniform in size and in morphology in contrast to pleomorphic inclusions in glial cells in MLD. Membrane-bound vacuoles containing moderately electron-dense granular materials or electron-dense aggregates were found in some pyramidal neurons in the Ammon's horn and cerebellar Purkinje cells. These changes were interpreted to represent the reaction of these neurons to subtle cellular injury which may or may not be related to metabolic derrangement in MLD.

Sister chromatid exchanges in lymphocytes of early cases of nasopharyngeal carcinoma and in 100 healthy subjects

Sister chromatid exchange rate was studied in 12 early diagnosed cases of nasopharyngeal carcinoma and in their paired controls. Exchange frequencies were also analyzed in 100 healthy subjects distributed in four regions of Hunan Province and correlated to nationality, age and sex. The incidence of sister chromatid exchange was significantly higher in the cancer patients than in the normal controls. No correlation was found between the frequency of sister chromatid exchange and region, nationality, age or sex.

Effect of borohydride reduction on antibodies

The effect of borohydride reducing reagents on monoclonal and polyclonal antibodies was examined by enzyme-linked immunosorbent assay (ELISA). Each antibody showed different stability characteristics to the reducing reagents. Sodium cyanoborohydride was at least five times milder toward immunological activity than sodium borohydride, however, sodium cyanoborohydride with a catalytic amount of metal ion (Zn2+ or Al3+) can be as harsh as sodium borohydride. Activated hydrophobic borohydrides, 9BBN-pyridine, did not have any advantages in respect to the stabilities of antibodies. Antibodies to be used for immunosorbent purification must be evaluated individually to determine whether their structure is stable to immobilization reagents and conditions prior to their linkage to the column support.

[Experience in the surgical treatment of 748 patients with lung cancer]

A series of 748 patients with lung cancer as treated by surgery from 1961 to 1984 is reported. Regular lobectomy was done in 445 (74%) patients, bronchoplastic lobectomy in 67 (11.2%), segmental or wedge excision in 15 (2.5%) and pneumonectomy in 74 (12.3%) in which the ratio of left to right pneumonectomy was 2.9:1. Overall resection rate was 80.4% (601/748) and resection mortality was 1.2% (7/601) (death within 30 days of operation). Overall 5 year survival rate was 42% (169/402). The 5 year survival rate was 35.3% for pneumonectomy, 54.1% for bronchoplastic lobectomy, 42.3% for regular lobectomy and 16.7% for segmental or wedge excision. In this analysis, emphasis is laid to the therapeutic validity of the different modes of surgery. Statistical data show that only when the indication of different surgical interventions are strictly adhered to and the reasonable procedures are carried out, could better results be obtained. In surgical treatment of lung cancer, it is an important principle to eradicate the tumor and its metastatic foci as thorough as possible and to conserve the respiratory function as much as possible. Regular lobectomy has now become the "standard" and first choice operation. Pneumonectomy should be reserved for the patients with absolute necessity due to the extent of the lesion, adequate cardiopulmonary function and possibility of a permanent cure. Pneumonectomy is substituted by bronchoplastic lobectomy to a certain degree, preserving more of the lung function and improving the living quality after operation and long term results. Extensive practice of this surgical modality is advised.

[Comparative ultrastructure of the normal mucosa and the adenocarcinoma cells of the human large intestine]

This paper presents the comparative observation by transmission electron microscopy (TEM) of ten cases of adenocarcinoma of the large intestine and the normal colon mucosa. The ultrastructural features of the carcinoma cells were as follows: The basement membrane was perforated by cytoplasmic projections of the carcinoma cells, extending into the lamina propria. The membrane of the neighbouring cells was quite smooth, the interdigitation appeared sparse and the intercellular space was often dilated. The phenomenon of desmosome separation was found. Therefore, careful observation of the changes in the cell membrane is helpful in the diagnosis of colonic adenocarcinoma.

A study of dynamic development in radiolesion and cell death of eukaryotes after exposure to ionizing radiation--the visualization of the dynamic reaction by means of cytochemical method with lactate dehydrogenase (LDH) as a nuclear marker and radiation-induced nuclear anomalization by an ultramicrostructural manifestation: a dynamic explanation

The present work deals with the radiation effect on adult rats suffering from acute, whole-body irradiation with cobalt-60 gamma rays of dosages 100R and 300R respectively. The morphological alteration of the lymphocytic nucleus and exhibition of cytochemical reaction of LDH in intra- or extra-nuclear region has been observed at the end of predetermined time intervals after irradiation. A close relationship between the percentage of damage of the lymphocytic nucleus and that of positivity of LDH reaction is seen from their variations with time parallel. From technical color microphotographs which exhibit cytochemical reactions, the existence of enzyme LDH in the nucleus so far obscure has been visually recognized. The events happening in enzymic reaction and the leakage of enzyme across the nuclear envelope reflect the dynamic nature. The ultrastructural alteration of nuclear anomalization confirms the dynamic development of inducing radiolesion. The experimental facts inspire us to attempt an explanation of cellular radiolesion and cell death owing to ionization radiation in light of the dynamic concept.