Choline acetyltransferase activity of spinal cord cell cultures increased by co-culture with muscle and by muscle-conditioned medium

Activity of the enzyme choline acetyltransferase (CAT), which mediates the synthesis of the neurotransmitter, acetylcholine, was increased up to 20- fold in spinal cord (SC) cells grown in culture with muscle cells for 2 wk. This increase was directly related to the duration of co-culture as well as to the cell density of both the SC and muscle involved and was not affected by the presence of the acetylcholine receptor blocking agent, α-bungarotoxin. Glutamic acid decarboxylase (GAD) activity was often markedly decreased in SC-muscle cultures while the activities of acetylcholinesterase and several other enzymes were little changed. Increased CAT activity was also observed when SC cultures were maintained in medium which had been conditioned by muscle cells or by undifferentiated cells from embryonic muscle. Muscle-conditioned medium (CM) did not affect the activities of SC cell GAD or acetylcholinesterase. Dilution or concentration of the CM directly affected its ability to increase SC CAT activity , as did the duration and timing of exposure of the SC cells to the CM. The medium could be conditioned by muscle cells in the presence or absence of serum, and remained effective after dialysis or heating to 58 degrees C. Membrane filtration data were consistent with the conclusion that the active material(s) in CM had a molecular weight in excess of 50,000 daltons. We conclude that large molecular weight material that is released by muscle cells is capable of producing a specific increase in CAT activity of SC cells.     

长春市儿童医院1998～2001年婴幼儿杯状病毒腹泻流行病学研究

人类杯状病毒(human calicivirus,HuCV)是引起儿童和成人非菌性胃肠炎的主要病原之一.为了掌握HuCV在我国的流行情况,1998年7月至2001年6月,从长春市儿童医院2343例5岁以下腹泻患儿中共收集粪便标本1264份,其中1056份来自2135例住院患儿.对轮状病毒检测为阴性的588份标本,经多价酶免疫试验(EIA)和两组引物反转录-聚合酶链反应(RT-PCR)检测HuCV,202份为阳性,其中住院患儿标本178份,HuCV检出率为16.9%.HuCV腹泻以2岁以下儿童为主(占96%),流行高峰季节为11月至次年3月.选择17株HuCV进行分子鉴定,15株属GⅡ-4群,1株属GⅡ-3群,另1株属GⅠ-2群,表明GⅡ-4群HuCV是我国流行的优势株.根据HuCV住院患儿的监测资料初步估计,HuCV腹泻住院率约为0.5‰～2.4‰.讨论了长春地区HuCV的流行趋势和疾病负担.以上结果为我国HuCV腹泻的预防和控制提供了科学依据.     

Nutrient-induced signal transduction through the protein kinase A pathway and its role in the control of metabolism, stress resistance, and growth in yeast

Yeast cells growing in the presence of glucose or a related rapidly-fermented sugar differ strongly in a variety of physiological properties compared to cells growing in the absence of glucose. Part of these differences appear to be caused by the protein kinase A (PKA) and related signal transduction pathways. Addition of glucose to cells previously deprived of glucose triggers cAMP accumulation, which is apparently mediated by the Gpr1-Gpa2 G-protein coupled receptor system. However, the resulting effect on PKA-controlled properties is only transient when there is no complete growth medium present. When an essential nutrient is lacking, the cells arrest in the stationary phase G0. At the same time they acquire all characteristics of cells with low PKA activity, even if there is ample glucose present. When the essential nutrient is added again, a similar PKA-dependent protein phosphorylation cascade is triggered as observed after addition of glucose to glucose-deprived cells, but which is not cAMP-mediated. Because the pathway involved requires a fermentable carbon source and a complete growth medium, at least for its sustained activation, it has been called “fermentable growth medium (FGM)-induced pathway.”     

Tritaenia Maegdefrau et Rudolf, Mesozoic 'Sciadopitys-like' leaves in mass accumulations

The Late Jurassic to Early Cretaceous genus Tritaenia Maegdefrau et Rudolf 1969 is problematic because of: (1) missing authentic material of its type species, T. linkii (Roemer 1839) Maegdefrau et Rudolf; and (2) Watson and Harrison's (1998) synonymization of T. linkii with Pseudotorellia heterophylla Watson. This paper: (1) rectifies the status of T. linkii on the basis of newly recovered specimens carrying the original author's authentication; and (2) gives the basis for rejecting Watson and Harrison's claim that T. linkii and T. crassa (Seward) Bose et Manum 1991 represent linear leaves of the heterophyllous taxon Pseudotorellia heterophylla. The three species of Tritaenia known to date (T. crassa, T. linkii, T. scotica) are reviewed, and the genus is compared with other Mesozoic so-called 'Sciadopitys-like' hypostomatic leaves with a median stomatal zone, many of which occur in mass accumulations such as T. linkii. Deciduousness is indicated for T. linkii and T. crassa by their occurrence in mass accumulations and the possession of well-developed abscission scars. Known mass accumulations of fossil foliage are reviewed and their implications for palaeoenvironmental interpretations discussed.     

Effects of age,replicative lifespan and growth rate of human nucleus pulposus cells on selecting age range for cell-based biological therapies for degenerative disc diseases

Autologous disc cell implantation, growth factors and gene therapy appear to be promising therapies for disc regeneration. Unfortunately, the replicative lifespan and growth kinetics of human nucleus pulposus (NP) cells related to host age are unclear. We investigated the potential relations among age, replicative lifespan and growth rate of NP cells, and determined the age range that is suitable for cell-based biological therapies for degenerative disc diseases. We used NP tissues classified by decade into five age groups: 30s, 40s, 50s, 60s and 70s. The mean cumulative population doubling level (PDL) and population doubling rate (PDR) of NP cells were assessed by decade. We also investigated correlations between cumulative PDL and age, and between PDR and age. The mean cumulative PDL and PDR decreased significantly in patients in their 60s. The mean cumulative PDL and PDR in the younger groups (30s, 40s and 50s) were significantly higher than those in the older groups (60s and 70s). There also were significant negative correlations between cumulative PDL and age, and between PDR and age. We found that the replicative lifespan and growth rate of human NP cells decreased with age. The replicative potential of NP cells decreased significantly in patients 60 years old and older. Young individuals less than 60 years old may be suitable candidates for NP cell-based biological therapies for treating degenerative disc diseases.     

Mucin secretion by the human colon cell line LS174T is regulated by bile salts

We recently reported that bile salts play a role in the regulation of mucin secretion by cultured dog gallbladder epithelial cells. In this study we have examined whether bile salts also influence mucin secretion by the human epithelial colon cell line LS174T. Solutions of bile salts were applied to monolayers of LS174T cells. Mucin secretion was quantified by measuring the secretion of [3H]GlcNAc labeled glycoproteins. Both unconjugated bile salts as well as taurine conjugated bile salts stimulated mucin secretion by the colon cells in a dose-dependent fashion. Hydrophobic bile salts were more potent stimulators than hydrophilic bile salts. Free (unconjugated) bile salts were more stimulatory compared with their taurine conjugated counterparts. Stimulation of mucin secretion by LS174T cells was found to occur at much lower bile salt concentrations than in the experiments with the dog gallbladder epithelial cells. The protein kinase C activators PMA and PDB had no stimulatory effect on mucin secretion. We conclude that mucin secretion by the human colon epithelial cell line LS174T is regulated by bile salts. We suggest that regulation of mucin secretion by bile salts might be a common mechanism, by which different epithelia protect themselves against the detergent action of bile salts, to which they are exposed throughout the gastrointestinal tract.      

Untersuchungen zum Cytochrom-Oxydase-System aus anaerob im Licht und aerob im Dunkeln gewachsenen Zellen von Rhodopseudomonas capsulata

Zusammenfassung Das aerobe Oxydase-System aus aerob im Dunkeln und anaerob im Licht gewachsenen Zellen von Rps. capsulata wurde untersucht. Die aus Ultraschallextrakten durch 140 000 g-Zentrifugation gewonnen Partikelfraktion katalysiert die Oxydation von NADH, Succinat und reduziertem Cytochrom c (aus Pferdeherz). Die Oxydase-Aktivitäten der Partikel aus aerob im Dunkeln gewachsenen Zellen variieren von 0,10–0,38 mole O₂/min · mg Protein und sind im Durchschnitt 10mal höher als die Oxydase-Aktivitäten der Partikel aus anaerob im Licht gewachsenen Zellen. Die Partikel enthalten Cytochrom vom b-Typ und c-Typ. Cytochrom a konnte weder in den Partikeln aus anaerob im Licht noch in den Partikeln aus aerob im Dunkeln gewachsenen Zellen nachgewiesen werden. In den Partikeln aus aerob gewachsenen Zellen ist das Verhältnis Cytochrom b:Cytochrom c größer als in den Partikeln aus anaerob im Licht gewachsenen Zellen. Die Cytochromoxydase reagiert mit Cytochrom c (aus Pferdeherz), DCPIP und TMPD. Die entsprechenden k _m -Werte betragen 5 · 10^-5 m, 1,5 · 10^-4 m und 2 · 10^-4 m. Die Cytochromoxydase hat ein breites pH-Optimum zwischen pH 8,5 und 9,5. Sättigung der Oxydase mit O₂ tritt erst bei einem Partialdruck von 15 bis 20% O₂ ein. Die Oxydase wird durch KCN und NaN₃ (50% Hemmung bei 10^-5 m), nicht aber durch CO gehemmt. Die Partikel aus aerob im Dunkeln und anaerob im Licht gewachsenen Zellen katalysieren eine mit der Succinat-Oxydation einhergehende Phosphorylierung von ADP mit P/O-Werten von maximal 0,3.

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Studies on the cytochrome oxidase system of ligh-anaerobically and dark-aerobically grown cells of Rhodopseudomonas capsulata

Summary The aerobic oxidase-system from dark-aerobically and light-anaerobically grown Rps. capsulata was investigated. The particulate fraction sedimented from ultrasonic extracts by 140,000 g-centrifugation, catalyzed the oxidation of NADH, succinate and reduced cytochrome c (horse heart). The oxidase activities of the particles from dark-aerobically grown cells were in the range of 0.10–0.38 moles O₂/min x mg protein and were usually ten times as high as the oxidase activities from light-grown cells. The particles contain cytochromes of b-type and c-type. Cytochrome of a-type could be detected neither in the particles from light-grown nor in the particles from dark-grown cells. The highest values of the relation between cytochrome b and cytochrome c were found in the particles from darkaerobically grown cells. The cytochrome oxidase reacts with cytochrome c (horse heart), DCPIP and TMPD. The k _m -values are 5×10^-5 m, 1.5×10^-4 m, or 2×10^-4 m, respectively. The cytochrome oxidase exhibits a broad pH-optimum in the range of pH 8.5–9.5. Saturation of the oxidase with O₂ is observed at a partial pressure of 15–20% O₂. The oxidase is inhibited by KCN and NaN₃ (half inhibition at 10^-5 m), but not by CO. The particles from dark-aerobically and light-anaerobically grown cells catalyze phosphorylation of ADP in the dark coupled to the oxidation of succinate with maximum P/O-values of 0.3.

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Abkürzungen ADP Adenosindiphosphat - ATP Adenosintriphosphat - BChl Bacteriochlorophyll - CCCP Carbonylcyanid-m-chlorphenylhydrazon - DCPIP 2,6-Dichlorphenolindophenol - DNP 2,4-Dinitrophenol - NAD(P) Nicotinamid-Adenin-Dinucleotid(phosphat) - NAD(P)H reduziertes NAD(P) - R. Rhodospirillum - Rps. Rhodopseudomonas - TMPD N-Tetramethyl-p-phenylendiamin