Mallomonas nuussuaqensis nov. sp., a new species of silica-scaled chrysophytes from West Greenland

A new species of Mallomonas, M. nuussuaqensis was found to be common in samples collected from waterbodies on Nuussuaq/Nûgssuaq (70N-71N, West Greenland). The species has very compact silica scales with a thick broad marginal rim and a very thick and broad hood, which often occupies more than two thirds of the shield.     

A synopsis of medullosan pollen organs from the middle Pennsylvanian Mazon creek flora of northeastern Illinois, USA

Six kinds of medullosan pollen organs containing Monoletes-type pollen (prepollen) are described from the middle Pennsylvanian Mazon Creek flora of northeastern Illinois, USA. Codonotheca caduca Sellards and Schopfitheca boulayoides Delevoryas are redescribed and emended diagnoses and new reconstructions are provided. Three forms of Dolerotheca-type pollen organs are described for the first time, along with ultrastructural details of in situ pollen. A sixth kind of pollen organ, tentatively associated with the ovule Stephanospermum konopeonus (Langford) Drinnan, Schramke and Crane, is too poorly preserved for generic assignment but has pollen different from that of other Mazon Creek medullosan pollen organs. This new information on Mazon Creek plants provides important evidence on the diversity of medullosan “pteridosperms” in the flora. Characterization of in situ pollen provides a basis for continuing attempts to associate pollen organs with the variety of co-occuring dispersed ovules.     

Trophodynamics of the plankton community at Dogger Bank: predatory impact by larval fish

The trophodynamics of a coastal plankton community were studied,focusing on fish larvae and their copepod prey. The major objectiveswere to describe distributional overlap and evaluate the predatoryimpact by larval fish. The study was carried out across DoggerBank in the North Sea, August-September 1991. Sampling transectscrossed tidal fronts off the Bank and plankton at all trophiclevels showed peak abundance within frontal zones. Also Verticallythere was a significant overlap in distributional patterns ofthe plankton. Seven species of fish larvae were abundant, ofthese sprat (Sprattus sprattus) dominated. The abundance ofone group of fish larvae peaked in the shallow water close tothe Bank, whereas other species, including sprat, were foundin deeper water. Prey preference and predation pressure of fishlarvae were assessed using information on prey sizes and growthrates of larvae and the copepod prey. We estimated larval removalof preferred prey sizes to 3–4% day^–1, counterbalancedby a 3–7% day^–1' replenishment from copepod productionand growth. Additional predation pressure on copepods by aninvertebrate predator was estimated to 1–3%day^–1.In conclusion, the dynamics of fish larvae and other zooplankterswere closely linked. At peak abundances of fish larvae (>35mg dry weight m^–2), the accumulated predation on specificsize ranges of copepods, exerted by larvae and other predators,could exceed the ability of copepod replenishment and intra-/interspecificcompetition among predators might take place.     

A hydroxyproline-containing class IV chitinase of sugar beet is glycosylated with xylose

Two acidic chitinase isoforms, SP1 and SP2, have been purified to homogeneity from leaves of sugar beet (Beta vulgaris) infected with Cercospora beticola. SP1 and SP2 are extracellular proteins with an apparent molecular mass of 35 kDa and an approximate pI of 4.2. Since the only major difference was slightly diverging M _r's, only the SP2 chitinase was further characterized. Partial amino acid sequence data for SP2 was used to generate a polymerase chain reaction (PCR) clone employed for the isolation of a cDNA clone encoding SP2. SP2 exhibits significant structural identity with the class IV chitinases from sugar beet, rapeseed, bean and maize, but differs from the other members of this class in having a longer hinge region, comprising 22 amino acid residues, with a repeated TTP motif. Western blotting analyses, using antibody raised against SP2, demonstrated an induction of SP protein during infection with C. beticola. The induction was very local, with high protein accumulation found close to the infection site only. Amino acid compositional analysis of SP2 revealed that five out of fourteen prolines are hydroxylated. No glucosamine or galactosamine residues are present. Evidence was obtained that SP2 is glycosylated with a limited number (7) of xylose residues: (1) SP2 was stained with the periodic acid-Schiff (PAS) reagent, (2) electrospray mass spectrometry on SP2 gave a series of M _r's with a consistent increase between two molecular masses of 132 Da, (3) SP2 was recognized by an antibody specific for -1,4-D-xylopyranose. The vacuolar class I chitinases A and B in tobacco have recently been shown to comprise a new class of hydroxyproline-containing proteins (Sticher et al., Science 257 (1992) 655–657). The SP2 chitinase differs from these in being glycosylated and, thus, represents a novel type of hydroxyproline-containing glycoproteins in plants.     

Non-systemic expression of a stress-responsive maize polyubiquitin gene (Ubi-1) in transgenic rice plants

We have used the promoter, 1st exon and 1st intron of the maize polyubiquitin gene (Ubi-1) for rice transformation experiments and revealed the characteristic expression of Ubi-1 gene: (1) Ubi-1 gene is not regulated systemically but rather individual cells respond independently to the heat or physical stress; (2) Ubi-1 gene changes its tissue-specific expression in response to stress treatment; (3) the expression of Ubi-1 gene is dependent on cell cycle.     

Agonist Binding to α2-Adrenoceptors Is Elevated in the Locus Coeruleus from Victims of Suicide

Abstract: The binding of an agonist, p-[¹²⁵I]iodoclonidine, and an antagonist, [³H]yohimbine, to α₂-adrenoceptors was measured autoradiographically in the locus coeruleus from 10 pairs of antidepressant-free victims of suicide and age-matched controls. Agonist binding to α₂-adrenoceptors was significantly greater in the locus coeruleus from victims of suicide compared with control subjects. In contrast, antagonist binding to α₂-adrenoceptors in the locus coeruleus did not differ significantly between control and suicide subjects. HPLC analysis of norepinephrine in tissue sections of the locus coeruleus did not reveal any differences between control subjects and suicide victims, suggesting that differences in agonist binding are not a result of differences in retention of the endogenous agonist norepinephrine in tissue sections. The increase in agonist binding to α₂-adrenoceptors in the locus coeruleus of victims of suicide links an altered expression of the high-affinity state of autoinhibitory α₂-adrenoceptors with suicide.     

B1 and B2 Bradykinin Receptors Encoded by Distinct mRNAs

Abstract: Bradykinin receptors have been subdivided into at least two major pharmacological subtypes, B₁ and B₂. The cDNAs encoding functional B₂ receptors have recently been cloned, but no molecular information exists at present on the B₁ receptor. In this article, we describe experiments examining the possible relationship between the mRNAs encoding the B₁ and B₂ types of receptor. We showed previously that the Human fibroblast cell line W138 expresses both B₁ and B₂ receptors. In this report, we describe oocyte expression experiments showing that the B₁ receptor in W138 human fibroblast cells is encoded by a distinct mRNA ∼2 kb shorter than that encoding the B₂ receptor. We have used an antisense approach in conjunction with the oocyte expression system to demonstrate that the two messages differ in sequence at several locations throughout the length of the B₂ sequence. Taken together with the mixed pharmacology exhibited in some expression systems by the cloned mouse receptor, the data indicate that B₁-type pharmacology may arise from two independent molecular mechanisms.