Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy.

The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.

Genetic authentication of ginseng and other traditional Chinese medicine.

The main objective of this paper is to review the chemical and genetic methods used in authentication of ginseng, especially the recent advances in microsatellite genotyping and its application to the authentication of other traditional Chinese medicines (TCM). The standardization and modernization of TCM hinge on the authentication of their botanical identities. Analysis of well-characterized marker compounds is now the most popular method for identifying the herbal materials and quality control of TCM, eg, ginsenoside profiling for authentication of Panax species. However, in many herbal species the chemical composition of the plant changes with the external environment and processing conditions, which lowers the reliability of these authentication methods. In the light of the advances in molecular biotechnology in the past few decades, genetic tools are now considered to provide more standardized and reliable methods for authentication of herbal materials at the DNA level. These genetic tools include random amplified polymorphic DNA (RAPD), DNA fingerprinting using multi-loci probes, restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), and microsatellite marker technology. The practicality of these methods varies in terms of their sensitivity, reliability, reproducibility, and running cost. Using ginseng as an example, we reviewed the advantages and limitations of these molecular techniques in TCM authentication. We have developed a set of microsatellite markers from American ginseng that are able to differentiate Panax ginseng and Panax quinquetolius with the resolution down to farm level, ie, confirmation of its botanical identity and origin. Compared with other molecular techniques, microsatellite marker technology is more robust, accurate, reproducible, reliable, and sensitive. This is essential for large-scale TCM authentication centers.

Correlation of chi orientation with transcription indicates a fundamental relationship between recombination and transcription.

Cross-over hot-spot instigator (Chi) sequences (5'-GCTGGTGG-3') are abundant, strand-specific, sequences, which locally increase recombination in Escherichia coli. Located within G-rich 'recombination islands', Chi orientations correlate with the orientations both of DNA replication and of transcription. Consistent with evidence from eukaryotic systems for a fundamental relationship between recombination and transcription, we find for E. coli Chi sequences, and for Haemophilus influenzae Chi-like sequences, that orientations correlate better with transcription than with replication. Complying with Szybalski's transcription direction rule, open reading frames in these prokaryotes have purine-rich mRNA-synonymous DNA strands. Hence, the G-richness of 'recombination islands' may reflect their correspondence with 'transcriptional islands' (genes). Comparison of a natural with the corresponding shuffled sequence, indicates a base order-dependent island unit of approx. 1kb. 1998 Elsevier Science B.V.

Cloning and differential expression during the sexual cycle of a meiotic endonuclease-encoding gene from the basidiomycete Coprinus cinereus.

The naturally synchronous meiosis of the fungus, Coprinus cinereus, provides an ideal system for the investigation of differential gene expression in relation to meiosis and fruiting body development. We have cloned a cDNA from the fruiting body of C. cinereus encoding the 12-kDa subunit of a meiotic endonuclease (mENase). The identification of the 12-kDa subunit cDNA clone was achieved by the mENase antiserum against a lambda gt11 cDNA expression library. It was confirmed by a direct match of the amino acid (aa) sequence obtained from purified 12-kDa polypeptide with the nucleotide sequence. Northern blot analysis using the cDNA clone as a probe showed that the mENase-encoding gene (MenA) for the 12-kDa subunit was expressed mainly in fruiting bodies and at a very low level in the asexual vegetative mycelium. In addition, it was differentially expressed in the early meiotic stages. The MenA transcript was most abundant in fruiting body primordia prior to the premeiotic S-phase; it remained high from karyogamy to early pachytene, declined drastically by late pachytene and diplotene, and was undetectable by sterigma stage. Western blot analysis showed that the mENase protein was produced at a very low level in mycelium; it was produced in great quantity during the early meiotic stages and decreased to a low level at the end of meiosis.

Studies on pH regulatory mechanisms in cultured astrocytes of DBA and C57 mice.

pH regulatory mechanisms in primary cultures of astrocytes from the cerebral cortex of neonatal audiogenic-seizure-susceptible DBA/2J (DBA) and genetically controlled C57BL/6J (C57) mice were studied with [14C]dimethyloxazolidine-2-4-dione (DMO) and [3H]-methyl-D-glucose (MDG). Effects of changing the concentration of Na+, K+, HCO3- or Cl- in medium, and/or of different transport blockers and metabolite inhibitor on intracellular pH (pHi) of cultured astrocytes were also studied. In nominal HCO3(-)-free HEPES-buffered Hanks' balanced salt solution (HEPES HBSS), when the pH of medium (pHo) was maintained at 7.4, the steady-state pHi of cultured astrocytes from DBA mice was 6.98 +/- 0.03, and that from C57 mice was 7.01 +/- 0.03. When the cells were incubated in HBSS containing 25 mM HCO3- and equilibrated with 5% CO2 (HCO3- HBSS, pHo = 7.4), pHi of both DBA and C57 astrocytes was approximately 0.1-0.15 pH units higher than that in HEPES HBSS. Reducing the pH or the Na+ concentration in media (pHo, [Na+]o) of either HEPES HBSS or HCO3- HBSS, pHi of both DBA and C57 astrocytes decreased markedly (0.25-0.45 pH units lower than the controls). The decrease in pHi was greater in HEPES HBSS than in HCO3- HBSS. Reducing the Cl- concentration ([Cl-]o) in either HEPES or HCO3- HBSS, pHi of astrocytes increased by 0.05-0.1 pH units. Increasing the K+ concentration ([K+]o) of or adding Ba2+ to the media increased the pHi of both DBA and C57 astrocytes accordingly. SITS, an anion transport inhibitor, decreased the pHi of both DBA and C57 astrocytes in HCO3- HBSS but not in HEPES HBSS. It enhanced the response of pHi to reduction in pHo. Amiloride, a Na(+)-H+ exchange inhibitor, decreased the pHi of both DBA and C57 astrocytes more in HEPES HBSS than in HCO3- HBSS. It enhanced the response of pHi to reduction in pHo and [Na+]o. Ouabain, an Na+,K(+)-ATPase inhibitor, decreased the pHi of cultured astrocytes in HEPES HBSS, but not in HCO3- HBSS. It also enhanced the response of pHi to changing pHo and [Na+]o in HEPES HBSS. Acetazolamide, a carbonic anhydrase inhibitor, decreased the pHi of astrocytes in both HEPES and HCO3- HBSS. Both bumetanide, an Na+,K+/Cl- cotransport blocker, and KCN, a metabolic inhibitor, produced no significant effect on the steady-state pHi or the response of pHi to changing ionic concentration in media in both DBA and C57 astrocytes.

Effect of elevated potassium on the ion content of mouse astrocytes and neurons.

Potassium is tightly regulated within the extracellular compartment of the brain. Nonetheless, it can increase 3- to 4-fold during periods of intense seizure activity and 10- to 20-fold under certain pathological conditions such as spreading depression. Within the central nervous system, neurons and astrocytes are both affected by shifts in the extracellular concentration of potassium. Elevated potassium can lead to a redistribution of other ions (e.g., calcium, sodium, chloride, hydrogen, etc.) within the cellular compartment of the brain. Small shifts in the extracellular potassium concentration can markedly affect acid-based homeostasis, energy metabolism, and volume regulation of these two brain cells. Since normal neuronal function is tightly coupled to the ability of the surrounding glial cells to regulate ionic shifts within the brain and since both cell types can be affected by shifts in the extracellular potassium, it is important to characterize their individual response to an elevation of this ion. This review describes the results of side-by-side studies conducted on cortical neurons and astrocytes, which assessed the effect of elevated potassium on their resting membrane potential, intracellular volume, and their intracellular concentration of potassium, sodium, and chloride. The results obtained from these studies suggest that there exists a marked cellular heterogeneity between neurons and astrocytes in their response to an elevation in the extracellular potassium concentration.

Effects of potassium on the anion and cation contents of primary cultures of mouse astrocytes and neurons.

In astrocytes, as [K+]o was increased from 1.2 to 10 mM, [K+]i and [Cl-]i were increased, whereas [Na+]i was decreased. As [K+]o was increased from 10 to 60 mM, intracellular concentration of these three ions showed no significant change. When [K+]o was increased from 60 to 122 mM, an increase in [K+]i and [Cl-]i and a decrease in [Na+]i were observed. In neurons, as [K+]o was increased from 1.2 to 2.8 mM, [Na+]i and [Cl-]i were decreased, whereas [K+]i was increased. As [K+]o was increased from 2.8 to 30 mM, [K+]i, [Na+]i and [Cl-]i showed no significant change. When [K+]o was increased from 30 to 122 mM, [K+]i and [Cl-]i were increased, whereas [Na+]i was decreased. In astrocytes, pHi increased when [K+]o was increased. In neurons, there was a biphasic change in pHi. In lower [K+]o (1.2-2.8 mM) pHi decreased as [K+]o increased, whereas in higher [K+]o (2.8-122 mM) pHi was directly related to [K+]o. In both astrocytes and neurons, changes in [K+]o did not affect the extracellular water content, whereas the intracellular water content increased as the [K+]o increased. Transmembrane potential (Em) as measured with Tl-204 was inversely related to [K+]o between 1.2 and 90 mM, a ten-fold increase in [K+]o depolarized the astrocytes by about 56 mV and the neurons about 52 mV. The Em values measured with Tl-204 were close to the potassium equilibrium potential (Ek) except those in neurons at lower [K+]o. However, they were not equal to the chloride equilibrium potential (ECl) at [K+]o lower than 30 mM in both astrocytes and neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

pH regulation after acid load in primary cultures of mouse astrocytes.

Intracellular pH (pHi) recovery in primary cultures of mouse astrocytes after acid-loading was studied with the ion transport inhibitors (amiloride, SITS, acetazolamide, ouabain and bumetanide), and by reducing the concentration of Na+ or Cl- in HCO3- -free HEPES-buffered (HEPES) and in HCO3-/CO2 Hanks' balanced salt solution (HBSS). The pHi of astrocytes exposed to 15 mM NH4Cl decreased abruptly and began to recover slowly after 5 min. Exposure of the cells to NH4Cl for 2 min and reincubation in HEPES HBSS decreased pHi further within 1-2 min after removal of NH4Cl; pHi then recovered toward the control value. Cultures exposed to HCO3-/CO2 HBSS (10 mM/2%) showed changes in pHi in the opposite direction. These responses are unique to astrocytes and differ from those occurring in most other cells. Recovery of pHi after NH4Cl prepulse was markedly inhibited in low-Na+ and in amiloride-containing HEPES HBSS. Ouabain also reduced pHi recovery rate; however, SITS, acetazolamide and bumetanide did not. Therefore, Na(+)-H+ exchange is the major process for pHi recovery from acidification in HCO3- -free solution. In HCO3-/CO2 HBSS pHi recovery was markedly inhibited by SITS and acetazolamide, but not by amiloride, ouabain, or bumetanide. The inhibitory effect of SITS on pHi recovery was enhanced in low-Na+ HBSS. These results indicate that both Na+ and HCO3- are directly related to pHi recovery in HCO3-/CO2 solution after acid-load. Low-Cl HEPES HBSS and low-Cl HCO3-/CO2 HBSS media did not alter pH recovery rate. Thus, pHi recovery after acid-load is not Cl- -dependent, and therefore, does not involve a Na(+)-dependent Cl- -HCO3- exchange process. It appears that mouse astrocytes possess 3 acid-regulating systems: Na(+)-H+ exchange, Na(+)-HCO3- co-transport and Na(+)-independent Cl- -HCO3- exchange.

Preventing alcohol problems: survey of Canadian medical schools.

In preparation for a national conference on medical education in the prevention of alcohol problems, a survey of conference participants was conducted. Participants were undergraduate and postgraduate representatives from each Canadian medical school and representatives from 11 provincial and territorial alcohol and other drug agencies. There was agreement that physicians and medical schools have important roles in prevention and treatment of alcohol problems, with "traditional" medical roles seen as the most important. Current training is variable and was seen as inadequate, with more time devoted to treatment than prevention. To correct this situation, renewed priorities and faculty leadership are needed. Respondents felt that there should be uniform standards for assessing undergraduate students' skills in dealing with alcohol problems. Provincial alcohol and other drug agencies are underused in medical education in the prevention and treatment of alcohol problems.

Refractive errors in Singapore medical students.

The refraction of 128 third-year medical students aged 20-22 was studied using a Topcon autorefractometer. The population was predominantly Chinese and comprised 44% females and 56% males. The mean refractive error was -3.75 D for males and -4.76D for females. In all, 82% of the students were myopic, 72% were found to have astigmatism. This study confirms clinical impressions that Singapore students have one of the highest prevalence rates of myopia and astigmatism in the world.

Relation between pH regulation and iodide transport in turtle thyroid glands.

Mechanisms of pH recovery after alkalinization and acidification by exposing or prepulsing turtle thyroid slices with a Hanks' balanced salt solution (HBSS) containing NH4Cl or CO2 were studied by examining the effects of amiloride, 4-acetamido-4'-isocyanostilbene-2,2'-disulphonic acid (SITS), frusemide and acetazolamide, and of reducing the concentration of Na+ or Cl- in the incubation medium. When alkalinization was produced either during exposure to NH4Cl or after a CO2 pulse, the pH in thyroid slices rose rapidly and then recovered gradually. Addition of SITS (0.1 mmol/l) or reduction of the Cl- concentration markedly inhibited pH recovery. However, amiloride (0.1 mmol/l) and low Na+ in the medium had no significant effect on recovery from alkalinization induced by NH4Cl exposure or by a CO2 pulse. These data suggest that pH recovery from alkalinization in turtle thyroid gland is achieved by an exchange of internal HCO3- for external Cl-. When acidification was accomplished by either exposure to CO2 or removal of NH4Cl, the pH of thyroid slices fell rapidly and then recovered gradually. If amiloride was added or the Na+ concentration in the medium was reduced, the pH recovery was greatly attenuated. However, SITS and low Cl- in the medium did not affect the recovery from an acid load in turtle thyroid slices. These results suggest that pH recovery from acidification in turtle thyroid gland is achieved by an exchange of internal H+ for external Na+. Both frusemide and acetazolamide prevented the pH recovery in turtle thyroid slices during exposure to and withdrawal from NH4Cl. These results suggest that besides the Na(+)-H+ and Cl(-)-HCO3- exchange processes, other mechanisms may also be involved in pH regulation in turtle thyroid glands. Simultaneous uptakes into turtle thyroid slices of 125I- and 22Na+ and of 125I- and 36Cl- were studied during and following exposure to NH4Cl in the absence and presence of different transport inhibitors, such as frusemide, amiloride, SITS and acetazolamide. When the thyroid slices were exposed to HBSS containing 30 mmol/l NH4Cl (alkalinization phase), the tissue/medium (T/M) ratios of 125I- increased gradually, reached the highest point in 10 min, and were maintained at this level for the next 20 min. The T/M ratios of 22Na+ and 36Cl- of thyroid slices also slowly increased after exposure to NH4Cl.(ABSTRACT TRUNCATED AT 400 WORDS)

Uptakes of iodide and chloride by primary cultures of mouse astrocytes and neurons.

Primary cultures of both mouse astrocytes and neurons accumulate more 125I- than 36Cl- from the medium. The average cell/medium ratio of 125I- of astrocytes (1.01) is greater than that of neurons (0.74), whereas the ratio of 36Cl- of neurons (0.47) is greater than that of astrocytes (0.25). The equilibrium potentials of both 125I- and 36Cl- calculated from the cell/medium ratios in astrocytes and neurons are significantly lower than their corresponding resting transmembrane potentials which suggest that both iodide and chloride are actively transported into both cell types. With respect to different transport inhibitors, thiocyanate is more effective in inhibiting 125I- uptake whereas furosemide is more effective in inhibiting 36Cl- uptake. Radioiodide uptake by mouse astrocytes was directly proportional to the [Na+]o but was not significantly affected by changes of [Cl-]o or [HCO3-]o, except that it is low in bicarbonate-free medium. Radiochloride uptake by astrocytes was inversely related to [Cl-]o and [HCO3-]o and was not affected [Na+]o, except that it was low in sodium-free medium. Radioiodide uptake by neurons was directly related to [Na+]o between 60 and 140 mM and inversely related to [HCO3-]o between 10 and 40 mM, but it was not affected by [Cl-]o. Radiochloride uptake by neurons was directly related to [Cl-]o and to [Na+]o between 60 and 140 mM and was not affected by [HCO3-]o. However, in sodium-free medium both 125I- and 36Cl- uptakes into neurons were higher than those in [Na+]o between 5 and 60 mM. These results indicate that uptake of 125I- and 36Cl- into astrocytes and neurons are different in their ion dependence and that they are under separate regulation.

Effects of 4,4'-di-isothiocyano-2,2'-stilbene disulphonate on iodide uptake by primary cultures of turtle thyroid follicular cells.

Iodide uptake by primary cultures of turtle thyroid follicular cells is directly proportional to the Na+ concentration and is inversely proportional to the HCO3- concentration in culture medium, but is not affected by the Cl- concentration. Addition of 4,4'-di-isothiocyano-2,2'-stilbene disulphonate (DIDS; 10 mumol/l and higher doses) to medium containing different concentrations of Na+ (5-140 mmol/l), HCO3- (0-40 mmol/l) and Cl- (120 mmol/l) generally enhanced iodide uptake by the cultured cells; however, there was no significant effect in Na+-free and in low Cl- (90 mmol/l and less) medium. The inhibitory effects on iodide uptake of ouabain, frusemide and perchlorate were attenuated by DIDS which also antagonized the stimulatory effects on iodide uptake of TSH, although both DIDS and TSH increased the 125I- cell/medium ratio when they were given alone. At doses of 100 mumol/l and higher, DIDS lowered the intracellular pH of cultured cells when the pH of the medium was maintained at a constant level. It also increased the intracellular Cl- concentration, but had no effect on intracellular Na+ or K+. The input and specific resistances of cell membranes in cultured thyroid cells and in isolated thyroid slices increased (decreased conductance) after adding DIDS to the perfusion fluids. Both Na+/K+- and HCO3(-)-ATPase activities in homogenates of turtle thyroid tissue were inhibited by DIDS. Results from this investigation demonstrate (1) that in addition to preventing the leak of iodide from thyroid cells, DIDS may act to increase the sensitivity of the Na+-anion carrier to I- and thereby increases iodide uptake, and (2) that a HCO3(-)-Cl- exchange system is present in the thyroid cell membrane and appears to be linked to the transport of iodide into thyroid cells.

Effect of incomplete obstruction on feline esophageal function with a clinical correlation.

This study was performed because of the observation of unexplained esophageal dysfunction in patients with incomplete esophageal obstruction. A Gore-Tex band, measuring 110% of resting esophageal circumference, was placed about the esophagus at the gastroesophageal junction of 17 cats to produce incomplete obstruction by limiting the normal distention that occurs with swallowing. Esophageal manometry was performed before surgery and at 1 and 4 weeks after surgery. Lower esophageal high-pressure zone pressure was not influenced, but sphincter relaxation was impaired. Evaluation of esophageal body contractions showed that simultaneous contractions increased from 0% before surgery to 68% at 1 week and 85% at 4 weeks after surgery (p less than 0.001 versus preoperative for both comparisons). The incidence of repetitive contractions increased from 3.1% before surgery to 10.5% at 1 week and 10.9% at 4 weeks after surgery (p = NS). The average contraction pressure decreased from 22.5 mm Hg before surgery to 13.9 mm Hg at 4 weeks after surgery (p less than 0.05). Barium swallows showed esophageal dilatation, that was confirmed on gross examination. Histologic examination was remarkable only for retention esophagitis. Sham surgery in three cats with identical mobilization of the gastroesophageal junction did not affect motility. Motility returned to normal after the band was removed in three cats. Manometric evaluation of 15 patients with distal esophageal peptic strictures and 17 patients with excessively tight antireflux repairs showed a significantly increased (p less than 0.001) frequency of simultaneous contractions, 35% and 34%, compared with the 2.1% of 25 normal subjects. The following conclusions can be drawn: Partial obstruction alters feline esophageal body function and these achalasia-like changes are reversible on relief of the obstruction and similar motility aberrations occur in patients because of mechanical or functional distal obstruction; this suggests that dysmotility can synergistically contribute to dysphagia.

Effects of sodium on iodide transport in primary cultures of turtle thyroid cells.

Iodide uptake by primary cultures of turtle thyroid cells decreased linearly with reduction of Na+ concentration in the medium, but changes in medium Cl- concentration did not affect iodide uptake. Ouabain, furosemide, monensin, and perchlorate all decreased 125I-uptake by cultured thyroid cells, whereas amiloride and triamterene did not. Ouabain, monensin, perchlorate, and amiloride depolarized the membrane of cultured cells, whereas furosemide and triamterene had no effect. Ouabain and perchlorate increased intracellular Na+ and Cl- and decreased K+ activities; furosemide and monensin reduced all three ions, but triamterene had no effect. Amiloride decreased intracellular Na+ and increased intracellular Cl- activities, however, its effect on K+ activity could not be determined because of interference by this compound of the K+ ion exchanger. All the agents, except furosemide, inhibited Na+-K+-ATPase activity. These experiments demonstrate that 1) Na+-I- cotransport is responsible for most iodide accumulation in thyroid cells; 2) Na+-I- cotransport system is linked to the Na+-K+ pump; 3) active iodide transport does not always correlate with Na+-K+-ATPase activity; 4) a perchlorate-sensitive iodide transport system is present in thyroid cells; 5) transport processes, not involved in active iodide transport (Na+-Cl- cotransport and Na+-H+ counter transport), are also present in cultured thyroid cells.

Role of glial cation and anion transport mechanisms in etiology and arrest of seizures.

The intrinsic processes involved in the initiation and arrest of seizures are not completely understood. Cortical and cerebellar inhibitory mechanisms, accumulation of metabolic products, and glial uptake of extracellular potassium (K+o), anions, and released neurotransmitters are all important processes that limit focal firing and terminate a seizure once it has been initiated. Of these, the intrinsic cortical inhibitory mechanisms--i.e., recurrent and surround inhibition--appear to be the most important. Active cation and anion transport processes are two metabolic events that have yet to be elucidated but clearly could be involved in terminating a seizure discharge. For example, without an active mechanism to transport chloride, opening of the chloride channel by the inhibitory transmitter GABA would not result in increased chloride permeability. The transient hypoxia and hypercapnia and lactic acidosis that follows a severe tonic-clonic seizure produces a mixed systemic metabolic and respiratory acidosis. In experimental animals, the hypercapnia that results is sufficient to block seizure discharges. Increasing the CO2 concentration significantly reduces the extension to flexion (E/F) ratio of mice given maximal electroshock seizures (MES) and increases the time required for 50% of the animals to recover sufficiently from a first MES to be able to have another MES. The decreased E/F ratio and the increased recovery time (RT50) are both indicative of a decrease in seizure activity. Since the extent to which CO2 is allowed to accumulate in the brain is regulated by the glial specific enzyme carbonic anhydrase (CA), it follows that the glial cell has an integral role in the mechanisms involved in arresting seizure activity. In contrast, hypoxia increased the E/F ratio and decreased the RT50, evidence that seizure activity was enhanced. Another metabolic factor affecting duration of seizure activity, susceptibility to seizures, and recovery from seizures is glucose. Recovery from seizures depends in part on an adequate supply of this energy source. An inverse correlation (R = 0.95) between RT50 and blood sugar was found when the blood sugar was altered experimentally by treatments that altered the endocrine status (pancreatectomy, treatment with alloxan, cortisol, insulin, glucagon, and dextrose). Since glial cells contain (as glycogen) the small amount of glucose present in the brain, they probably hasten the ability of the brain to recover normal function following a seizure.(ABSTRACT TRUNCATED AT 400 WORDS)