Über das Wachstum der Pankreaszellen von Säugetieren als Monolayer Cultures

Zusammenfassung Glucose und Coffein erhöhen den Gehalt 4 und 7 Tage alter Zellen an immunologisch meßbarem Insulin (Ausgangsmaterial: Ratten- und Schweinepankreas). Morphologisch (Aldehydfuchsin, Pseudoisocyanin) sind bei coffeinbehandelten Zellen in der Intensität der Anfärbung und in der Granuladichte zeitabhängige Unterschiede zu beobachten, die an 4 Tage alten Zellen deutlicher als an 7 Tage alten zu erkennen sind. Coffein erhöht die Verfettung der Zellen. Weiter nimmt der Gehalt an sauren Mucopolysacchariden (Eisenbindungsreaktion) und an PAS-positivem Material zu. Diese Erhöhung läuft mit dem Anstieg des Insulingehaltes im Nährmedium parallel.

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Monolayer cultures of pancreatic tissueIII. Insulin release induced by coffein and glucose

Summary Glucose and caffeine increase the immunologically measurable insulin content of four and seven-day old cells (starting material: rats' or pigs' pancreas). In morphological examination (aldehyde fuchsin, pseudoisocyanin), time-dependent differences in the intensity of staining and granular density are observable in caffeine-treated cells; these phenomena are more distinct in four-day old cells than in seven-day old ones. Caffeine increases fatty degeneration of the cells. Furthermore, the content of acid mucopolysaccharides (iron-binding reaction) and of PAS positive material increases. This increase runs parallel with the rise in insulin content of the nutritive medium.

     

Transforming growth factor-β1 immobilises dendritic cells within skin tumours and facilitates tumour escape from the immune system

Human skin tumours often regress spontaneously due to immune rejection. Murine skin tumours model this behaviour; some regress and others progress in syngeneic immunocompetent hosts. Previous studies have shown that progressor but not regressor skin tumours inhibit dendritic cell (DC) migration from the tumour to draining lymph nodes, and transforming growth factor-₁ (TGF-₁) has been identified as a responsible factor. To determine whether increased production of TGF-₁ in the absence of other differences inhibits DC migration from the tumour and enables it to evade immune destruction, a murine regressor squamous cell carcinoma clone was transfected with the gene for TGF-₁. This enhanced growth in vitro and in vivo, causing it to become a progressor. TGF-₁ transfection reduced the number of infiltrating DCs by about 25%. Quantitation of CD11c⁺ E-cadherin⁺ (epidermally derived) DCs in lymph nodes determined that TGF-₁ reduced the number of DCs that migrated from the tumour to undetectable levels. This was supported by showing that TGF-₁ reduced DC migration from cultured tumour explants by greater than tenfold. TGF-₁ transfection also reduced the number of infiltrating CD4 and CD8 T cells. Thus, TGF-₁ production by skin tumours is sufficient to immobilise DCs within the tumour, preventing their migration to lymph nodes. This reduces the number of T cells that infiltrate the tumour, preventing regression. Thus, TGF-₁ is a key regulator of whether skin tumours regress or progress.     

Observations on the fine structure of the cercaria of Notocotylus attenuatus and formation of the cyst wall of the metacercaria

Summary The dorsal tegument of the mature cercaria of Notocotylus attenuatus is a syncytial, cytoplasmic layer, containing two types of secretory granule which are identifiable ultrastructurally. The type 1 secretory bodies are electron lucid, whereas most type 2 granules have a banded appearance. The ventral tegument contains granules which are secreted from the type 3 cells; the type 3 granules are membrane bound, electron dense, and consist of both an amorphous and a finely striated zone. The type 4 cells mainly contain cigar-shaped granules consisting of an amorphous core surrounded by concentric striations. The granules exhibit structural variability in shape and content. The type 4 cells undergo a cellular migration to the tegument during encystment. The structure of the posterior-lateral glands and mode of secretion of the granules are described. Possible functions of microtubules are discussed for each cell type. Details of some secretory processes involved in the formation of the hemispherical cyst wall are described. The layers of the cyst wall may be related to the granular contents of the various parenchymal cells of the cercaria. The tegument of the metacercaria originates primarily from the cytoplasm of the type 1, type 2, type 3 and type 4 cells.     

Nucleolar changes in human phytohaemagglutinin-stimulated lymphocytes

Summary The nucleoli of lymphocytes from circulating peripheral blood and from phytohaemagglutinin (PHA)-stimulated cultures (from 2 h–96 h) were studied using a silver method, RNA-specific fluorescent staining, and electron microscopy of ultrathin sections. In peripheral blood about 75% of the lymphocytes have one ring-shaped nucleolus composed of a distinct fibrillar centre surrounded by a dense pars fibrillaris and little granular material; the remaining lymphocytes showing two or more small ring-shaped nucleoli. With PHA stimulation, the number of cells with several nucleoli increases first (from 2 h–12 h). Next, cells containing one or, at most, two large nucleoli with nucleolonema devoid of fibrillar centers are seen (from 4 h on). 34 h after PHA, nucleoli of the compact type containing one or more fibrillar centres appear and comprise about 60% of the cells after 72 h. The appearance of more than one nucleolus per cell shortly after PHA administration suggests an activation of additional nucleolar organizer regions (NOR), which fuse to form one or two large nucleoli with nucleolonema. These are then transformed into compact nucleoli. The fibrillar centers stain preferentially with silver. They contain nonchromosomal proteins and may serve as stores for nucleolar proteins. The fusion of activated NORs during the first cell cycle explains the relatively high frequency of satellite associations in first mitoses compared to later mitoses after stimulation.     

Adaptive networks using learning matrices

Summary The performance of the Learning Matrix (LM) is suitable for the design of adaptive networks of higher complexity. It has been published, how to connect a LM with a generator of patterns (binary or nonbinary) and a ring-counter to result in an automatic classification of the presented patterns. This paper describes, how to connect two LM's to form an Autonomous Learning Matrix Dipole (ALD) and how to organize it, so that it adapts itself to an environment according to a given evaluation scale. For this purpose, a third type of input (beside e and b), namely h seems to be useful. This h-input controls the rate of adaptation of the LM.Using such ALD's, one may design adaptive structures of even higher complexity, for example with an adaptive internal model.The principle of Learning Matrices has been explained in detail (see e.g. IEEE Transactions on Electronic Computers, Vol. EC-12, No. 6, December, 1963, pp. 846–862). Using such learning matrices (LM), one may build up adaptive networks with rather interesting functions. Perhaps they are interesting for the physiologist and psychologist as well as for the engineer. Let us first recall the most essential details of the LM's.

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Zusammenfassung Die Funktion der Lernmatrix (LM) erlaubt den Entwurf adaptiver Netzwerke höherer Komplexität. Es wurde an anderer Stelle schon beschrieben, wie eine LM (binär oder nichtbinär) mit einem Generator für Eigenschaftssätze und einem Ringzähler zusammengeschaltet werden kann, um eine selbsttätige Klassifikation der angebotenen Eigenschaftssätze zu bewirken. Im vorliegenden Aufsatz wird erklärt, wie zwei LM so zusammengeschaltet werden können, dacß sich ein Autonomer Lernmatrix-Dipol (ALD) ergibt, und wie dieser zu organisieren ist, daß er sich einer gegebenen Außenwelt nach Maßgabe einer vorgegebenen Werteskala anpaßt. Zu diesem Zweck erweist sich außer den bisher beschriebenen beiden Zugangen zur LM (nämlich e und b) ein dritter sehr zweckmäßig, nämlich h. Dieser h-Eingang beeinflußt die Lerngeschwindigkeit der LM.Unter Verwendung solcher ALD's kann man adaptive Strukturen noch höherer Komplexität aufbauen, beispielsweise solche mit adaptivem innerem Modell.

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Visiting Professor of Electrical Engineering Stanford University.     

Silvering and gill “mitochondria-rich” cells in the eel,Anguilla anguilla

Gills of typical yellow and silver ells, Anguilla anguilla L., were examined by light and electron microscopy. In both eel types, mitochondria-rich cells were located in the epithelium covering the primary lamellae and consisted ofchloride cells and accessory cells. As compared to yellow eels, the primary gill epithelium of silver eels was thicker and contained larger and more numerous chloride cells with enlarged mitochondria. The accessory cells also increased in number but did not show significant modifications in their size or ultrastructural features. These observations indicate that, as far as mitochondria-rich cells are concerned, the silvering process in eels would be equivalent to smoltification in salmonids. It corresponds to a preparation for seawater life and is probably controlled by hormonal factors.     

Shoot and root organogenesis of Camellia sasanqua

In vitro-derived shoot tips, (10 mm) taken from primary cultures of Camellia sasanqua L., were evaluated for organogenesis when cultured on a half-strength MS medium supplemented with various concentrations of NAA, IBA, BA and GA₃. Maximum shoot proliferation and growth for juvenile and mature tissue was obtained when 0.54 M NAA, 8.8 M BA plus 14.4 to 28.9 M GA₃ was added to the culture media, with a pH between 4.5 and 5.0. In vitro-derived shoots (20 mm) from mature C. sasanqua Day Dream and juvenile C. sasanqua cultures initiated roots in vitro after immersion in 2.5 mM IBA for 30 min. Sixty percent of the mature shoots and 90% of the juvenile shoots initiated roots within 3 weeks of treatment with IBA.Abbreviations MS Murashige and Skoog (1962) - IBA lH-indole-3-butanoic acid - BA N-(phenyl-methyl)-lH-purine-6-amine - GA₃ gibberellic acid - kinetin N-(Z-furanyl-methyl)-lH-purine-6-amine - NAA l-naphthaleneacetic acid - L Linear - Q Quadratic     

The Catalytic Transition State in ATP Synthase

The catalytic transition state of ATP synthase has been characterized and modeled by combined use of (1) Mg-ADP–fluoroaluminate, Mg-ADP–fluoroscandium, and corresponding Mg-IDP–fluorometals as transition-state analogs; (2) fluorescence signals of -Trp331 and -Trp148 as optical probes to assess formation of the transition state; (3) mutations of critical catalytic residues to determine side-chain ligands required to stabilize the transition state. Rate acceleration by positive catalytic site cooperativity is explained as due to mobility of -Arg376, acting as an arginine finger residue, which interacts with nucleotide specifically at the transition state step of catalysis, not with Mg-ATP- or Mg-ADP-bound ground states. We speculate that formation and collapse of the transition state may engender catalytic site / subunit-interface conformational movement, which is linked to -subunit rotation.     

Cathodoluminescence Microscopy: A Useful Tool for Assessing Incremental Chemical Variation in Otoliths

Otoliths taken from fish from Eden Lake, Manitoba show yellow–green and red cathodoluminescence of varying intensity that corresponds to their annular structure. Proton-induced X-ray emission analysis shows manganese (Mn) concentrations of between 2 and 205ppm, zinc (Zn) concentrations between 2 and 290ppm and strontium (Sr) concentrations up to 1500ppm in the otoliths. The distribution of luminescence correlates with the distribution of Mn. The Mn, Zn and Sr are likely derived from the monzonitic rocks surrounding the lake. Variations in the distribution of cathodoluminescence may be a useful tool for evaluating changes in environmental chemistry and fish life histories.     

Amyloid-Beta Immunization in Alzheimer's Disease Transgenic Mouse Models and Wildtype Mice

Alzheimer's disease is the most prevalent form of dementia worldwide. Therapies are desperately needed to prevent and cure the disease. Mouse models of amyloid- deposition [APP and PSAPP transgenic (tg) mice] have been useful in determining the role of amyloid- (A) in both the pathogenesis and cognitive changes in AD. In addition, they have allowed scientists to investigate potential AD therapies in living animals. Active and passive A immunizations have been employed successfully in APP and PSAPP tg mice to lower cerebral A levels and improve cognition. Optimization of immunization protocols and characterization of immune responses in wildtype mice have been reported. Based on the promising results of A immunization studies in mice, a clinical trial was initiated for A vaccination in humans with AD. Although no adverse effects were reported in the Phase I safety trials, about 5% of AD patients in the phase II clinical trial developed meningoencephalitis, ending the trial prematurely in March 2002. Studies in AD mouse models and wildtype mice may help elucidate the mechanism for these unwanted side effects and will be useful for testing newer, safer vaccines for future use in human clinical trials.     

Co-replication of satellite DNA of Chironomus melanotus with mainband DNA during polytenization

The DNAs of five Chironomus species, C. plumosus, C. nuditarsis, C. thummi thummi, C. melanotus, and Camptochironomus pallidivittatus, were investigated in analytical neutral isopycnic CsCl density gradients. DNA was isolated both from larval brains (diploid-DNA) and salivary glands (polytene-DNA). The buoyant densities of mainband DNAs were 1.692 g/cm³, with the exception of C. melanotus whose mainband had a density of 1.693 g/cm³. The densities correspond to a calculated GC content of 33% and 34% respectively. Only in C. melanotus was the DNA clearly resolved into mainband DNA and two distinct satellite shoulders: Satellite I, with a buoyant density of 1.684 g/cm³ (25% GC, calculated) and satellite II of 1.679 g/cm³ (19% GC, calculated). The two satellites comprise 15% of the total DNA in the diploid-DNA and they also occur in the polytene-DNA, where they make up 11%. The results are discussed in the general context of under- and overreplication in polyploid and polytene cells.     

Zur Histochemie von Hydrolasen im Hoden des Hundes und der Katze

Zusammenfassung Wir untersuchten das Verteilungsmuster von unspezifischer Esterase, alkalischer Phosphatase, Adenosintriphosphatase, 5-Nucleotidase und -D-Glucuronidase im Hoden von Hund und Katze. Besonders hervorzuheben sind eine starke Aktivität der unspezifischen Esterase in den Sertolizellen der Katze, der Reichtum der Membrana propria aller Hodentubuli an alkalischer Phosphatase und Adenosintriphosphatase sowie die kräftige Reaktion auf -D-Glucuronidase in den Leydigzellen beider Tierarten.Die Befunde werden diskutiert.

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Summary The localization of unspecific esterase, alkaline phosphatase, adenosine triphosphatase, 5-nucleotidase, and -D-glucuronidase in the testes of cat and dog was demonstrated by histochemical means. We observed a strong esterase activity in the Sertoli cells of the cat and high amounts of alkaline phosphatase and adenosine triphosphatase in the membrana propria of all seminiferous tubules. In both species the principal site of -D-glucuronidase was in the Leydig cells. Our findings obtained being discussed.

     

Mast cells in rat dermis and jejunal lamina propria show a five-fold difference in unit granule volume

Summary The cytoplasmic granules of mast cells have a periodic multimodal size distribution in which the volumes of individual granules are integral multiples of the intermodal distance, a volume defined as the unit granule or ₁. In this study, we used two 3-month-old male rats to analyze two classical mast cell subpopulations, dermal connective tissue-type mast cells and jejunal lamina propria mucosal mast cells, for the morphometric characteristics of their cytoplasmic granules. Both and the mean volume of individual cytoplasmic granules were much smaller in dermal than in jejunal mast cells (ratios of 1:5.5 and 1:4.2, respectively), but dermal mast cells contained 150% more granules per cell than did jejunal mast cells. The two types of mast cells did not differ significantly in total cell volume, nucleus volume, aggregate volume of cytoplasmic granules per cell or numbers of unit granules comprising a granule of mean volume. These findings add unit granule volume to the list of phenotypic characteristics which express significant variation in anatomically distinct populations of mast cells.     

Analysis of T cell receptor Vβ gene usage during the course of disease in patients with chronic hepatitis B

The T cell receptor (TCR) is a heterodimeric molecule expressed on the surface of T cells and recognizes foreign peptides presented by the major histocompatibility complex on the surface of antigen-presenting cells or virusinfected cells. Analysis of TCR usage by T cells which recognize hepatitis B virus (HBV) provides further insight into the participation of T cell populations during the course of disease. In this study, we examined the T-cell-proliferative response and the TCR V gene usage of peripheral blood mononuclear cells in 3 patients with clinical evidence typical of chronic hepatitis B. All 3 patients had significant T-cell proliferative responses against HBV core antigen (HBcAg) during the remission stage, while no responses were detected during the acute exacerbation stage. In addition, the TCR V₇ gene was utilized more frequently in T cells recognizing HBcAg during remission, while TCR V₁ and V₂ were utilized at a higher percentage during acute exacerbation. On the contrary, the T cell proliferative response against HBV surface antigen was undetectable and no specific V gene was utilized more frequently by all 3 patients, regardless of disease state. Our longitudinal studies, although based on a small sample of patients, demonstrate that the population of HBcAg-activated T cells alters during the course of disease in chronic hepatitis B patients.     

Visualization of the uptake of high-density lipoprotein by rat aortic endothelial cells and smooth muscle cells in vitro

High-density lipoproteins (HDL) were conjugated to Fluorescein 1,1-dioctadecyl 3,3,3,3-tetramethylindocarbocyanine perchlorate (DiI) or colloidal gold for the investigation of ultrastructural aspects of binding and uptake of HDL by cholesterol-loaded cultured endothelial and smooth muscle cells from rat aorta. When cells were incubated for 2h at 4°C, HDL–DiI and HDL–gold conjugates were seen only on the cell surface. When cells were returned to incubation at 37°C for 5min, HDL–DiI appeared in the cytoplasm and colocalized with the fluorescent cholesteryl ester tag BODIPY-FL-C₁₂. HDL–gold conjugates appeared in the plasmalemmal invaginations and plasmalemmal vesicles. After incubation for 15min, most of the HDL–gold conjugates reappeared on the cell surface. After incubation for 30min, only a few conjugates were observed and they localized in lysosomal-like bodies. Quantitative data indicated that when the cholesterol-loaded cells were incubated at 4°C for 2h, the numbers of HDL–gold associated in clusters on the endothelial cell surface was 1.18 clusters/m. When cells were returned to incubation at 37°C for 5min, this value decreased to 0.7, increased again to 1.13 at 15min, and decreased to 0.29 at 30min. The numbers of clusters in the plasmalemmal invaginations were 0.06 clusters/m at 4°C for 2h, increased to 0.34 at 37°C for 5min and decreased gradually to 0.19 and 0.04 at 15 and 30min, respectively. The incidence of clusters in the plasmalemmal vesicles per non-nuclear cytoplasm was 0.01 clusters/m² at 4°C for 2h, increased significantly to 1.08 at 37°C for 5min, and decreased to 0.43 and 0.14 at 15 and 30min, respectively. This work supports that the plasmalemmal invaginations and plasmalemmal vesicles are linked to the HDL uptake in cholesterol-loaded aortic endothelial cells and smooth muscle cells.     

Abbau von 14C-, 3H- und 36Cl-markiertem γ-Hexachlorcyclohexan durch anaerobe Bodenmikroorganismen

Zusammenfassung Durch eine anaerobe Mischflora aus Ackerboden wurde -Hexachlorcyclohexan (-HCH) in 4–5 Tagen zu 90% abgebaut. Dabei erfolgte eine schnelle Abspaltung des Chlors in Form von Chloridionen und danach eine Freisetzung des C- und H-Anteiles in Form flüchtiger Verbindungen, in denen kein Chlor und auch kein CO₂ nachzuweisen war.Die Verwendung von ¹⁴C/³H- und ³⁶Cl/³H-doppelmarkiertem -HCH zeigte, daß die Cl- und H-Abspaltung nicht im Verhältnis von 1:1 erfolgte, sondern mehr Cl als H abgespalten wurde. Die flüchtigen Verbindungen enthielten andererseits höhere ¹⁴C- als ³H-Anteile. Gaschromatographische Untersuchungen zeigten ebenfalls eine rasche Verminderung des -HCH und die Bildung verschiedener Metabolite. Es wurde jedoch kein -Pentachlorcyclohexen nachgewiesen. Bei steigenden O₂-Gehalten in der Gasphase verminderte sich der -HCH-Abbau. Jedoch fanden auch noch bei 5% O₂ Chlorabspaltung und die Freisetzung flüchtiger Metabolite statt.-HCH wurde ebenfalls, jedoch langsamer, durch die anaerobe Mischflora abgebaut. Auch hier wurde Chlorid abgespalten, und es traten ebenfalls flüchtige Verbindungen auf, die kein Chlor enthielten.

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Degradation of ¹⁴C-, ³H- and ³⁶Cl-labelled -hexachlorocyclohexane by anaerobic soil microorganisms

Up to 90% of the -Hexachlorocyclohexane (-HCH) applied to an anaerobic mixed bacterial flora enriched from an arable soil were degraded within 4–5 days. Degradation resulted in a rapid release of chloride and in formation of chlorine-free volatile metabolites. CO₂ formation from the molecule was not detected.Investigations with ¹⁴C/³H- and ³⁶Cl/³H double-labelled -HCH indicated that the release of Cl and H did not occur in the ratio of 1:1. More Cl than H was split off. The volatile compounds contained more ¹⁴C than ³H. Gas chromatographic studies also showed the rapid decrease of -HCH and the formation of several metabolites. -Pentachlorocyclohexene was not detected. Increasing O₂-contents in the gas phase of cultures resulted in decreases of the compound's degradation. Release of chloride and of volatile metabolites were observed with O₂ contents in the gas phase up to 5%.-HCH was also, but more slowly as with -HCH, degraded by the anaerobic mixed flora. Chloride was released and volatile, chlorine-free metabolites were found.

     

The molecular defect in propionic acidemia: Exon skipping caused by an 8-bp deletion from an intron in the PCCB allele

Propionic acidemia is an autosomal recessive metabolic disease resulting from a deficiency of propionyl CoA carboxylase (PCC) activity. To investigate the genetic basis of propionic acidemia, we isolated a cDNA encoding the precursor of the subunit of human PCC ( PCC). The cloned cDNA sequence was 1,832 bp long and the open reading frame of 1,617 nucleotides encoded a polypeptide of 539 amino acids with a molecular mass of 58,202 Da. The human PCC sequence shared a high degree of homology (91%) with the full-length cDNA of rat PCC at the amino acid level; there were only 47 differences among 539 amino acid residues compared. Polymerase chain reaction amplification and sequencing of cDNA from a subunit-deficient Japanese patient revealed a deletion of 101 nucleotides consisting of one exon from mature mRNA. This deletion resulted in a frameshift and a stop codon in the new frame. Analysis of the genomic DNA revealed a homozygous 8-bp deletion from bp3 to bp10 of the intron just downstream of the deleted exon. This deletion disrupted the consensus 5 splice signal and led to exon skipping.     

“Primäre” und “Sekundäre” Differenzierung im Zusammenhang mit der Photomorphogenese von Keimpflanzen (Sinapis alba L.)

Zusammenfassung Die Anthocynsyanthese des Senfkeimlings ist phytochromabhängig. Lediglich zwei Gewebe, die Epidermis der Cotyledonen und die Subepidermis des Hypocotyls sind zu dieser Anthocyansynthese fähig. Erst 24 Std nach Aussaat ist Anthocyansynthese möglich und bereits etwa 60 Std nach Aussaat (25° C; Standardbedingungen vgl. Methoden) erlischt dei Fähigkeit zur Anthocyansynthese weitgehend und zwar unabhängig von der Menge des synthetisierten Anthocyans. Die höchste Empfindlichkeit für Licht besitzt das Anthocyan bildende System etwa 36 Std nach Aussaat. — Teilt man den Keimling unmittelbar vor der Anthocyanmessung in 4 Segmente auf (Abb. 9) und mißt den Anthocyangehalt der Segmente getrennt, so stellt sich heraus, daß die Fähigkeit zur Anthocyansynthese im mittleren und basalen Bereich des Hypocotyls rapide verloren geht. Im oberen Hypocotylabschnitt hingegen und in den Cotyledonen nimmt diese Fähigkeit erst zu, und die Abnahme ist langsamer. —Es werden Argumente für die Auffassung entwickelt, daß das spezifische und dynamische Zellmuster, das man hinsichtlich der P₇₃₀-abhängigen Anthocyansynthese vorfindet, ein Ausdruck der primären Differenzeierung sei (vgl. Abb. 4). P₇₃₀ hingegen, so stellen wir uns vor, wirkt unspezifisch im Rahmen einer sekundären Differenzierung, indem es potentiell aktive Gene (P₇₃₀) in Funktion setzt. Welche Gene in den einzelnen Zellen des Dunkelkeimlings potentiell aktiv sind, legt die primäre Differenzierung fest. — Diese Vorstellungen werden durch den Befund gestützt, daß eine Applikation von Actinomycin D zu einer zeitlich sehr viel ausgedehnteren Anthocyansynthese führt; offenbar deshalb, weil die genetisch kontrollierte Entwicklung des primären Differenzie-rungsmusters gebremst wird. Eine Folge wäre, daß die Inaktivierung der zur Anthocyansynthese benötigten Gene, die normalerweise etwa 60 Std nach Aussaat erfolgt, weit hinausgezögert wird.

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Primary and secondary differentiation in connection with photomorphogenesis of seedlings (Sinapis alba L.)

Summary Anthocyanin synthesis of the mustard seedling (Sinapis alba L.), a typical phytochrome-dependent photoresponse has been further investigated. — It has been found that only two types of tissue can synthesize anthocyanin under the influence of active phytochrome (=P₇₃₀), namely, the epidermis of the votyledons and the subepidermal layer in the hypocotyl (Fig. 2, 3). — Under our standard conditions (25° C; cf. methods) phytochrome-potentiated anthocyanin synthesis is only possible 24 hours after sowing and it ceases about 60 hours after sowing, independent of the amount of anthocyanin which has been accumulated (Fig. 5, 6). On the basis of the whole seedling the highest sensitivity of the anthocyanin producing system to light is around 36 hours after sowing (Fig. 8). Within the tissues which are capable of forming anthocyanin there is a characteristic shift of the ability to respond to P₇₃₀ as the seedling ages. If we devide the seedling into 4 segments (Fig. 9) it turns out that in the basal and middle part of the hypocotyl the ability to form anthocyanin is rapidly lost whereas in the upper part of the hypocotyl and in the cotyledons this ability even increases at first. The following decrease is slower than in the basal parts (Fig. 10, 11).It is argued that this specific and dynamic cellular pattern of responsiveness to P₇₃₀ can be regarded as a manifestation of a primary differentiation in the course of which the genotype of each individual cell in the dark-grownt seedling is devided into 3 functional types of genes: active, inactive, and potentially active genes (P₇₃₀) (Fig. 4). — In connection with anthocyanin synthesis P₇₃₀ is thought to act exclusively at the level of secondary differentiation, i.e., it is thought to initiate the action of potentially active genes via a signal-chain. The action of P₇₃₀ is non-specific. The specificity of the photoresponse of an individual cell is determined by the status of its primary differentiation (Fig. 4).If the process of differentiation is slowed down (e.g. by the application of low doses of Actiomycin D) anthocaynin synthesis can continue much longer than under our standard conditions where it ceases around 60 hours after sowing (Fig. 12). This fact seems to indicate that the loss of the ability to form anthocyanin is due to an inactivation of pertinent genes by the process of primary differentiation, which is itself, as one would expect, under the control of genes.

     

Mapping oligogenic resistance to powdery mildew in mungbean with RFLPs

We have used restriction fragment length polymorphisms (RFLPs) to map genes in mungbean (Vigna radiata) that confer partial resistance to the powdery mildew fungus, Erysiphe polygoni. DNA genotypes for 145 RFLP loci spanning 1570 centimorgans of the mungbean genome were assayed in a population of 58 F₂ plants. This population was derived from a cross between a moderately powdery mildew resistant (VC3980A) and a susceptible (TC1966) mungbean parent. F₃ lines derived from the F₂ plants were assayed in the field for powdery mildew response and the results were compared to the RFLP genotype data, thereby identifying loci associated with powdery mildew response. A total of three genomic regions were found to have an effect on powdery mildew response, together explaining 58% of the total variation. At 65 days after planting, two genomic regions were significantly associated with powdery mildew resistance. For both loci, the allele from VC3890A was associated with increased resistance. At 85 days, a third genomic region was also associated with powdery mildew response. For this locus, the allele from the susceptible parent (TC1966) was the one associated with higher levels of powdery mildew resistance. These results indicate that putative partial resistance loci for powdery mildew in mungbean can be identified with DNA markers, even in a population of modest size analyzed at a single location in a single year.     

Endocrine cells in the human fetal small intestine

Summary In this report we describe the time of appearance and ultrastructural features of enteroendocrine cells (EECs) in the human fetal small intestine (SB) between 9 and 22 weeks gestation. Thirteen distinctive EECs were identified in fetal SB. Two of these, not found in normal adult SB, appeared within the stratified epithelium of the proximal SB at 9–10 weeks. They were arbitrarily termed primitive and precursor cells. As in all fetal EECs, the pale cytoplasm of the primitive cell contains a distinctive population of secretory granules (SGs). Primitive cell SGs average 200–330 nm; some have dense cores with lucent halos while others are filled with a homogeneous dense or flocculent material. The SGs of the precursor cells are larger, averaging up to 1 m in diameter and their contents vary in electron density. A third group of cells not described in normal adult SB was arbitrarily termed transitional cells. These have two populations of SGs; one resembles the SGs of the precursor cells, and the other resembles the SGs of some of the specific adult type EECs. Transitional EC, S, I and G cells are seen. In addition, mature appearing EC, S, G, I, L, D, and D₁ cells were identified by 12 weeks of gestation. The primitive, precursor, and transitional cells may represent sequential developmental precursors of adult type EECs.Supported by Research Grant AM-17537 from the National Institutes of Health, Besthesda, MarylandThe authors would like to thank Ms. Linda Barstein for her excellent technical assistance