Distribution of FMRFamide-like immunoreactivity in the nervous system of the slug Limax maximus

Summary The distribution of FMRFamide-like immunoreactive neurons in the nervous system of the slug Limax maximus was studied using immunohistochemical methods. Approximately one thousand FMRFamide-like immunoreactive cell bodies were found in the central nervous system. Ranging between 15 m and 200 m in diameter, they were found in all 11 ganglia of the central nervous system. FMRFamide-like immunoreactive cell bodies were also found at peripheral locations on buccal nerve roots. FMRFamide-like immunoreactive nerve fibres were present in peripheral nerve roots and were distributed extensively throughout the neuropil and cell body regions of the central ganglia. They were also present in the connective tissue of the perineurium, forming an extensive network of varicose fibres. The large number, extensive distribution and great range in size of FMRFamide-like immunoreactive cell bodies and the wide distribution of immunoreactive fibres suggest that FMRFamide-like peptides might serve several different functions in the nervous system of the slug.     

Nicotinic Agonists Regulate α-Bungarotoxin Binding Sites of TE671 Human Medulloblastoma Cells

The TE671 human medulloblastoma cell line expresses a variety of characteristics of human neurons. Among these characteristics is the expression of membrane-bound high-affinity binding sites for alpha-bungarotoxin, which is a potent antagonist of functional nicotinic acetylcholine receptors on these cells. These toxin binding sites represent a class of nicotinic receptor isotypes present in mammalian brain. Treatment of TE671 cells during proliferative growth phase with nicotine or carbamylcholine, but not with muscarine or d-tubocurarine, induced up to a five-fold increase in the density of radiolabeled toxin binding sites in crude membrane fractions. This effect was blocked by co-incubation with the nicotinic antagonists d-tubocurarine and decamethonium, but not by mecamylamine or by muscarinic antagonists. Following a 10-13 h lag phase upon removal of agonist, recovery of the up-regulated sites to control values occurred within an additional 10-20 h. These studies indicate that the expression of functional nicotinic acetylcholine receptors on TE671 cells is subject to regulation by nicotinic agonists. Studies of the murine CNS have consistently indicated nicotine-induced up-regulation of nicotinic acetylcholine receptors, thereby supporting the identification of the toxin binding site on these cells as the functional nicotinic receptor. Although a mechanism for this effect is not apparent, nicotine-induced receptor blockade does not appear to be involved.     

Neutral Amino Acid Transport in Astrocytes: Characterization of Na+-Dependent and Na+-Independent Components of α-Aminoisobutyric Acid Uptake

Neutral amino acid transport is largely unexplored in astrocytes, although a role for these cells in blood-brain barrier function is suggested by their close apposition to cerebrovascular endothelium. This study examined the uptake into mouse astrocyte cultures of alpha-aminoisobutyric acid (AIB), a synthetic model substrate for Na+-dependent system A transport. Na+-dependent uptake of AIB was characteristic of system A in its pH sensitivity, kinetic properties, regulatory control, and pattern of analog inhibition. The rate of system A transport declined markedly with increasing age of the astrocyte cultures. There was an unexpectedly active Na+-independent component of AIB uptake that declined less markedly than system A transport as culture age increased. Although the saturability of the Na+-independent component and its pattern of analog inhibition were consistent with system L transport, the following properties deviated: (1) virtually complete inhibition of Na+-independent AIB uptake by characteristic L system substrates, suggesting unusually high affinity of the transporter; (2) apparent absence of trans-stimulation of AIB influx; (3) unusually concentrative uptake at steady state (the estimated distribution ratio for 0.2 mM AIB was 55); and (4) susceptibility to inhibition by N-ethylmaleimide. Direct study of the uptake of system L substrates in astrocytes is needed to confirm the present indications of high affinity and concentrative Na+-independent transport.     

Patterns of prey utilization in a web of orb-weaving spiderAraneus pinguis (Karsch)

The pattern of prey utilization of the orb-weaving spider Araneus pinguis was studies by comparing between arthropods restrained in the empty webs (spiders were removed) and those unattacked in the intact webs (spiders were not removed). The number of arthropods was larger in the empty webs than in the intact webs. In the empty webs, web area, mesh width, number of radii, and signal thread length were presumed to affect the number of arthropods left in a single web. As for the intact webs, web area, mesh width, and web-exposure time were important factors. In the empty webs, the density of arthropods decreased away from the hub. On the other hand, the density of unattacked arthropods in the intact webs was the same throughout the web. Arthropods in the empty webs were larger than those in the intact webs. The upper limit in size of unattacked arthropods increased along with the distance from the hub in the intact webs, but not in the empty webs. These results indicate increase in the minimum size of eaten arthropods increased in the former. This positive sizedistance relation may have resulted from the adaptive switching of spiders’ alternative foraging methods (i.e., the rapid attack at encounter and the later eating during web deconstruction) on the basis of the prey profitability.     

Distribution of intraventricularly injected horseradish peroxidase in cerebrospinal fluid compartments of the rat spinal cord

Summary The circulation of the cerebrospinal fluid along the central canal and its access to the parenchyma of the spinal cord of the rat have been analyzed by injection of horseradish peroxidase (HRP) into the lateral ventricle. Peroxidase was found throughout the central canal 13 min after injection, suggesting a rapid circulation of cerebrospinal fluid along the central canal of the rat spinal cord. It was cleared from the central canal within 2 h, in contrast with the situation in the brain tissue, where it remained in the periventricular areas for 4 h. In the central canal, HRP bound to Reissner's fiber and the luminal surface of the ependymal cells; it penetrated through the intercellular space of the ependymal lining, reached the subependymal neuropil, the basement membrane of local capillaries, and appeared in the lumen of endothelial pinocytotic vesicles. Furthermore, it accumulated in the labyrinths of the basement membrane contacting the basolateral aspect of the ependymal cells. In ependymocytes, HRP was found in single pinocytotic vesicles. The blood vessels supplying the spinal cord were classified into two types. Type-A vessels penetrated the spinal cord laterally and dorsally and displayed the tracer along their external wall as far as the gray matter. Type-B vessels intruded into the spinal cord from the medial ventral sulcus and occupied the anterior commissure of the gray matter, approaching the central canal. They represented the only vessels marked by HRP along their course through the gray matter. HRP spread from the wall of type-B vessels, labeling the labyrinths, the intercellular space of the ependymal lining, and the lumen of the central canal. This suggests a communication between the central canal and the outer cerebrospinal fluid space, at the level of the medial ventral sulcus, via the intercellular spaces, the perivascular basement membrane and its labyrinthine extensions.     

Early human disturbance of the natural environment recorded in annually laminated sediments of Lake Gosciaz,central Poland

Palynological records from the annually laminated sediments of Lake Gosciaz are presented for the period ca. 7600–3900 conventional B.P. Indications in percentage and influx diagrams of Mesolithic and Early Neolithic human impact on the natural environment around the lake are discussed and compared with the archaeological evidence. The first indications of human disturbance start at ca. 6700 B.P. and in the following period four disturbance phases with interruptions are distinguished. A relationship between the Elm Decline and an increasing thickness of annual sediment layers as a consequence of increased soil erosion is suggested. Some hitherto unrecognized or incompletely known microfossils are identified and figured, and their palaeoecological significance is discussed. The records of akinetes of Aphanizomenon probably indicate increasing eutrophication of the lake. Charred fragments of grass epidermis are possibly indicative of openings in the forest.     

山西永济白草坪组具刺疑源类的发现及其地质意义

该文着重报道了山西永济白草坪组(一般认为系中元古界上部相当于蓟县系的层位),以具刺疑源类为主的微化石群,计有4类6属15种,其中包括1新属,4新种,1新组合,1亲近种,2未定种,新属是具细网状纹饰的复杂具刺疑源类Shuiyousphaeridium Yan gen.nov.,4新种是Shuiyousphaeridium membraniferum Yan sp.nov.,Dictyosphaera incrassate Yan sp.nov.,Foliomorpha stipuliferaYan sp.nov.,Manicosiphoninema shuiyouense Yan sp.nov.。本微化石群以球形疑源类为主体,以具刺疑源类的大量发育为特征,并伴生有推测是绿藻和褐藻的化石,其组合面貌与蓟县上前寒武系各组皆有明显区别,具有更高的进化程度,从生物地层标志推测白草坪组所在的汝阳群应归入震旦系。白草坪组具刺疑源类可能是横裂甲藻的原始分子,它在地层对比和藻类进化方面皆具有重要意义。     

城镇污水诱发青蛙蝌蚪红细胞微核及其在环境监测中的应用

本文利用青蛙(Rana nigromaculata Hallowell)蝌蚪红细胞微核试验,作为检测城镇污水诱变活性的一种新的监测技术。在16d生活污水处理的实验中,青蛙蝌蚪红细胞微核细胞率2d后就呈现统计上的显著增加,并随处理时间的延长而增高,第12d达到最大值。在不同浓度混合污水处理实验中,蝌蚪红细胞微核细胞率呈现明显的剂量依赖性增加。上述实验证明城镇生活污水和混合污水都具有较强的诱变活性。作者从遗传毒理学的角度评价了湖北黄州综合生物塘系统对污水诱变活性的净化效能。城镇混合污水经综合生物塘各级塘处理,蝌蚪微核细胞率逐级下降,由进水的7.54‰下降到最后出水的1.52‰,接近对照(1.07‰)水平。其中综合生物塘的藻菌单元比水生植物单元对污水诱变活性具有更强的净化效力。本文提出污水“诱变指数”可作为综合生物塘一项功能评价指标。     

Dopamine Metabolites in Rat Cisternal Cerebrospinal Fluid: Major Contribution from Extrastriatal Dopamine Neurones

The interpretation of central 3,4-dihydroxyphenylethylamine (dopamine, DA) metabolism, as indicated by determinations in rat cisternal CSF, was investigated using intrastriatal injection of the DA neurotoxin 6-hydroxydopamine (6-OHDA) and intraperitoneal injection of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). DA turnover was subsequently determined by measurement of the rate of accumulation of total 3,4-dihydroxyphenylacetic acid and homovanillic acid (DOPAC + HVA) in the CSF after probenecid was given. Two days later the rats were killed, and metabolism of DA and 5-hydroxytryptamine (5-HT) was investigated by determining levels of the amines and their metabolites in brain regions. Although 6-OHDA greatly decreased striatal DA metabolism, this was not paralleled by DA turnover as indicated by CSF, as this fell only moderately and approximately in parallel with results for the brain as a whole. 5-HT metabolism was essentially unaltered. DSP4 considerably depleted noradrenaline and caused smaller decreases of 5-HT metabolism in some regions. However, DA metabolism was not significantly affected, either in brain or CSF, which suggests that noradrenaline neurones make only a small contribution to central DA metabolism. Results as a whole suggest that DOPAC and HVA concentrations in rat cisternal CSF reflect whole brain DA metabolism and derive predominantly from DA neurones in extrastriatal regions of the brain.     

Bony Fish Myelin: Evidence for Common Major Structural Glycoproteins in Central and Peripheral Myelin of Trout

Peripheral nervous system (PNS) myelin from the rainbow trout (Salmo gairdneri) banded at a density of 0.38 M sucrose. The main myelin proteins consisted of (1) two basic proteins, BPa and BPb (11,500 and 13,000 MW, similar to those of trout central nervous system (CNS) myelin proteins BP1 and BP2), and (2) two glycosylated components, IPb (24,400 MW) and IPc (26,200 MW). IPc comigrated with trout CNS myelin protein IP2 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas trout CNS myelin protein IP1 had a lower molecular weight (23,000). Following two-dimensional separation, however, both IPb and IPc from PNS showed two components; the more acidic component of IPc comigrated with IP2 from CNS. PNS tissue autolysis led to the formation of IPa (20,000 MW), consisting of two components in isoelectric focusing of which again the more acidic one comigrated with the CNS autolysis product IP0. Limited enzymatic digestion of isolated IP proteins from PNS and CNS led to closely similar degradation patterns, being most pronounced in the case of IP2 and IPc. Immunoblotting revealed that all IP components from trout PNS and CNS myelins reacted with antibodies to trout IP1 (CNS) and bovine P0 protein (PNS) whereas antibodies to rat PLP (CNS) were entirely unreactive. All BP components from trout PNS and CNS myelins bound to antibodies against human myelin basic protein. On the basis of these studies trout PNS and CNS myelins contain at least one common IP glycoprotein, whereas other members of the IP myelin protein family appear closely related. In the CNS myelin of trout the IP components appear to replace PLP.(ABSTRACT TRUNCATED AT 250 WORDS)