A highly conserved α-tubulin sequence from Prunus amygdalus

The sequence of an -tubulin from Prunus amygdalus has been obtained by cDNA cloning. When this sequence is compared to that of the Tub1 gene from maize it shows a very high degree of similarity, much higher than any of the -tubulin sequences reported so far from plants. The expression of this gene is high in the stages of seed development where a high divisional activity is present. It is preferentially expressed in the radicular tissues as it is gene Tub1 in maize. Southern analysis indicates that this gene may from a subfamily of -tubulin genes having similar sequence and tissue specificity and existing at least in maize and in Prunus.     

Food Storage in Gray Jays: Source Type and Cache Dispersion

Animals that store food items in scattered sites must decide how to distribute their caches in space. Our theoretical approach is based on the assumption that such animals disperse their caches in a manner that maximizes the long-term rate of storage of recoverable (surviving) food items in the habitat. We investigate the cache-spacing behavior of theoretical scatter hoarders that encounter food sources differing in the energetic content of the items they contain. We then describe a field experiment in which gray jays (Perisoreus canadensis) were presented with both small- and large-item food sources. The jays compensated for source type by spacing larger-item caches more widely, a compensation that would tend to yield a high rate of storage of recoverable food energy over the long term and throughout the territory. Previous models do not adequately account for the observed patterns of cache dispersion.     

Determination of l-α-acetylmethadol, l-α-noracetylmethadol and l-α-dinoracetylmethadol in plasma by gas chromatography—mass spectrometry

A method is described for the simultaneous determination of l-α-acetylmethadol (LAAM) and its N-demethylated metabolites, l-α-noracetylmethadol (norLAAM) and l-α-dinoracetylmethadol (dinorLAAM), in plasma by gas chromatography—chemical ionization mass spectrometry. Deuterated internal standards for each analyte serve as carriers and control for recovery during sample purification on a solid-phase extraction column (C₁₈), and subsequent separation and analysis on a DB-17 capillary column. With this method, we have determined levels of LAAM, norLAAM, and dinorLAAM in small volumes of plasma (100 μl). The limit of quantitation for all analytes was approximately 1.0 ng/g plasma and the limit of detection was approximately 0.5 ng/g plasma. An experimental application is also described where these analytes are quantitated in plasma obtained from rats before, during, and after chronic administration of LAAM-HCl. Since this technique affords a selective and sensitive means of detection of LAAM and its active, N-demethylated metabolites in small samples of blood, it may enable patient compliance to be more easily assessed by allowing samples to be collected by a simple finger-prick technique.     

Continuous production of citric acid in the reciprocating-jet-bioreactor

In a comprehensive study batch and continuous production of citric acid has been investigated. Fermentations in the reciprocation-jet-bioreactor (RJBR) have been carried out with the fungi Aspergillus niger.In the present paper only the results of continuous fermentations are presented. The paper discusses the influence of medium composition in the influent, input of biomass and frequency of reciprocating motion on citric acid production.     

Confocal laser scanning microscopy reveals voltage-gated calcium signals within hippocampal dendritic spines

The induction of long-term potentiation (LTP) is generally assumed to be triggered by Ca²⁺ entry into dendritic spines via NMDA receptor-gated channels. A previous computational model proposed that spines serve several functions in this process. First, they compartmentalize and amplify increases in [Ca²⁺]_i. Second, they augment the nonlinear relationship between synaptic strength and the probability or magnitude of LTP induction. Third, they isolate the metabolic machinery responsible for LTP induction from increases in [Ca²⁺]_i produced by voltage-gated Ca²⁺ channels in the dendritic shaft. Here we examine this last prediction of the model using methods that combine confocal microscopy with simultaneous neurophysiological recordings in hippocampal brain slices. Either of two Ca²⁺-sensitive dyes were injected into CA1 pyramidal neurons. Direct depolarization of the neurons via the somatic electrode produced clear increases in Ca²⁺ signals within the dendritic spines, a result that was not predicted by the previous spine model. Our new spine model suggests that some of this signal could theoretically result from Ca²⁺-bound dye diffusing from the dendritic shaft into the spine. Dye diffusion alone cannot, however, explain the numerous cases in which the Ca²⁺ signal in the spine was considerably larger than that in the adjacent dendritic shaft. The latter observations raise the possiblity of voltage-gated Ca²⁺ entry directly into the spine or else perhaps via Ca²⁺-dependent Ca²⁺release. The new spine model accommodates these observations as well as several other recent experimental results. 1994 John Wiley & Sons, Inc.     

Rat epididymis-specific sperm maturation antigens. I. Evidence that the 26 kD 4E9 antigen found on rat caudal epididymal sperm tail is derived from a protein secreted by the epididymis

Monoclonal antibody 4E9, which was raised against a partially purified detergent extract of rat caudal epididymal sperm, recognizes the tail of sperm from the cauda, but not from caput epididymidis, as well as epithelial cells in a restricted region of the distal caput/corpus epididymidis and proteins in epididymal fluid from corpus and cauda epididymidis. The antigen is apparently a glycoprotein, since it is retained on a Ricinus communis agglutinin l lectin column. Epididymal fluid antigens have apparent M_rS of 38–26 kD, whereas the memrane-associated form of the molecule has an M_r of 26 kD. Immunocytochemical data and Western immunoblot data suggest that the membrane antigen is derived from the fluid antigen, which, in turn, is secrteted by the epididymal epithelium. Characterization of the membrane antigen indicates that it is tightly associated with the sperm surface, behaving as though it is an integral membrane protein. The antigen persists on ejaculated sperm. © 1994 Wiley-Liss, Inc.     

Characterization of a strain of cerebral endothelial cells derived from goat brain which retain their differentiated traits after long-term passage

Summary A strain of cerebral endothelial cells was established from isolated cortical microvessels of caprine brain. These cells, which are referred to as ECl cells, can be routinely subcultured to 32 passages without the loss of differentiated morphologic and immunologic traits. The ability to routinely subculture ECl cells is an important asset, given that isolated cerebral endothelial cells in mammals generally lose their differentiated traits after only 2 to 3 passages. ECl cells were shown to contain Factor VIII-related antigen, which is a specific marker for cells of endothelial origin. ECl cells morphologically demonstrated a scarcity of pinocytotic vesicles on their apical surfaces, a lack of trans-cytoplasmic vesicles, and the ability to form in culture confluent monolayers with tight junctional complexes. Therefore, ECl cells possess specific antigenic and ultrastructural features which classify them as being small vessel endothelial cells of the blood-brain barrier type. Cytogenetic evaluation of ECl cells demonstrated a normal female goat 60,XX karyotype and confirmed the apparent non-transformed nature of ECl cells due to the lack of chromosome abnormalities or rearrangements. Using scanning electron microscopy, ECl cells were also shown to form confluent monolayers on mixed nitrocellulose filters, a feature that will enable the development of an in vitro system to study trans-endothelial transport. Given that ECl cells are readily subcultured and grow well on nitrocellulose filters, and that they resemble cerebral endothelium in vivo, it seems evident that ECl cells can be used as a versatile model for the study of blood-brain barrier function, regulation, and pathology.