Exclusion of linkage of loci on chromosome 19 with multiple endocrine neoplasia, type 2

Linkage between seven loci on chromosome 19 and multiple endocrine neoplasia type 2a (MEN2A) was examined in a single large Swedish pedigree. A total of 50 cM was excluded from the male genetic map by pairwise analysis and an estimated 63 cM by multipoint analysis. Using existing data on the likelihood of different marker-marker distances and taking into account current exclusions on other chromosomes, the probability that the gene for MEN2A segregating in this pedigree could still be located on chromosome 19 is approximately 0.28%.     

The seed dimorphism of Spergularia marina in relation to dispersal by wind and water

Summary The seeds of the halophyte Spergularia marina differ both within and between individuals in that they either possess or lack a membranaceous border. This paper presents a morphological study of the length, weight and area of the seed types, and their dispersal characteristics under experimental conditions of wind and water dispersal. The winged seeds are shown to be larger both by length and by weight. Their rate of descent increases with wing loading. If the wing is lacking, however, the rate of descent increases with weight only. The distance of dispersal is equal for both seed types except at low wind speeds, when the winged seeds disperse farther. If the seed wing is removed, the excised seeds have shorter dispersal distances. When dispersed by water, a difference in the distance seeds are dispersed can only be detected in the presence of vegetation. The winged seeds are more frequently trapped in the vegetation as compared to the unwinged seeds. The hypothesis that the seed dimorphism is an adaptation for differential dispersal distances is discussed.     

Column chromatography of human small-intestinal maltase, isomaltase and invertase activities

1. The maltase, isomaltase and invertase (sucrase) activities of solubilized mucosal preparations from human jejunum and ileum were studied with column chromatography on anion-exchange (diethylaminoethyl- and triethylaminoethyl-)cellulose and Sephadex G-200 gel. 2. On ion-exchange cellulose columns both kinds of enzyme preparations yielded two major disaccharidase peaks. The first peak contained maltase Ia (=isomaltase) and maltase Ib (=invertase). The second peak contained maltase II and maltase III. 3. On Sephadex G-200 gel columns jejunal preparations yielded the corresponding peaks as on ion-exchange columns, but the peaks appeared in the reverse order in the effluent. The ileal preparation studied yielded a single peak on gel columns, containing all the activities studied and eluted with the `void volume'. 4. Precipitation with ethanol did not affect the behaviour of the enzymes during ion-exchange chromatography. When gel filtration was performed after ethanol precipitation of the enzymes, however, two peaks were obtained also with the ileal preparation, and subfractionation of the invertase was obtained with both kinds of preparations. 5. The second peak from ion-exchange chromatograms, containing maltase II and maltase III, on concentration was found to have very weak isomaltase activity, probably exerted by these enzymes as such. This activity accounts for only about 1% of the total isomaltase activity of the mucosa. 6. The results support the concept of the specificity of the human small-intestinal disaccharidases previously described after heat-inactivation experiments. The subfractionation of the invertase that under certain conditions is seen on Sephadex G-200 columns appears most likely to be an artifact. Consequently the nomenclature for the human maltose-, isomaltose- and sucrose-splitting enzymes proposed by another research group after gel-filtration chromatography studies should be abandoned. It seems more logical to keep the nomenclature based on heat inactivation [maltase Ia (=isomaltase), maltase Ib (=invertase or sucrase), maltase II and maltase III] until increased knowledge about the specificity and structure of these enzymes makes possible a more rational nomenclature.     

Tetrasomy 15q: two marker chromosomes with no detectable alpha-satellite DNA.

Two patients with specific and similar phenotypes were both found to have an unusual marker chromosome present in 70%-80% of their lymphocytes at routine cytogenetic examination. The marker chromosomes were isolated by flow sorting and were amplified by degenerate oligonucleotide-primed PCR. These libraries and a cosmid probe located at 15q26 were used to characterize the marker chromosomes by FISH. Both marker chromosomes were found to consist of duplicated chromosome material from the distal part of chromosome 15q and were identified as inv dup(15) (qter-->q23::q23-->qter) and inv dup(15) (qter-->q24::q24-->qter), respectively. Hence, the markers did not include any known centromere region, and no alpha-satellite DNA could be detected at the site of the primary constriction. Tetrasomy 15q may be a new syndrome, associated with a specific type of marker chromosome. In addition, further analyses of this type of marker chromosome might give new insight into the structure and function of the mammalian centromere.     

Concentrations of Amino Acids in Extracellular Fluid After Opening of the Blood-Brain Barrier by Intracarotid Infusion of Protamine Sulfate

Abstract: This article evaluates the influence of an opening of the blood-brain barrier (BBB) on compounds in brain extracellular fluid. The concentrations of amino acids and some other primary amines were determined in dialysates sampled from the right parietal cortex of rats before and after an intracarotid infusion of protamine sulfate. Extravasated plasma proteins were visualized by Evans blue/albumin and immunohistochemistry. CSF albumin— an indicator of blood-CSF barrier opening—was quantified with immunoelectrophoresis. The brains were macroscopically edematous after 10 mg but not after 5 mg of protamine sulfate. The higher dose led to a 50% death rate. The concentrations of amino acids did not change 10 min after the BBB opening. No significant alterations in the amino acid concentrations were observed after the lower dose. The concentrations of glutamate, aspartate, GABA, glycine, taurine, and phosphoethanolamine increased significantly within 50–80 min after the infusion of 10 mg of protamine sulfate. CSF albumin levels were significantly increased 1 h after infusion. We conclude that a dysfunction of the BBB, of a degree known to induce brain edema (10 mg of protamine sulfate), significantly increases the extracellular concentration of excitatory amino acids, GABA, taurine, and phosphoethanolamine in the extracellular space.     

Gravitropically-stimulated seedlings show autotropism in weightlessness

In a spaceflight experiment, autotropism by oat ( Avena sativa L.) coleoptiles following gravitropic responses was prominent in weightlessness: counter-reactions led to the straightening of the curved coleoptiles. This was not the case during clinorotation on earth. The autotropic reactions appeared to be related to the stimulus received during the stimulus period, i.e. the greater the response the greater the autotropic counter-reaction. Previous models of the gravitropic system which predicted that coleoptiles would not straighten in weightlessness are disproved. A modification to one of the models is proposed which includes the autotropic response observed in spaceflight. The nature of the counter-reactions in the absence of gravitropic stimulation is discussed.     

Short period leaf movements in Oxalis regnellii

Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm⁻², the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed.     

Structural basis for differential receptor binding of cholera and Escherichia coli heat-labile toxins: influence of heterologous amino acid substitutions in the cholera B-subunit

The closely related B-subunits of cholera toxin (CTB) and Escherichia coli heat-labile enterotoxin (LTB) both bind strongly to GM1 ganglioside receptors but LTB can also bind to additional glycolipids and glycoproteins. A number of mutant CT B-subunits were generated by substituting CTB amino acids with those at the corresponding positions in LTB. These were used to investigate the influence of specific residues on receptor-binding specificity. A mutated CTB protein containing the first 25 residues of LTB in combination with LTB residues at positions 94 and 95, bound to the same extent as native LTB to both delipidized rabbit intestinal cell membranes, complex glycosphingolipids (polyglycosylceramides) and neolactotetraosylceramide, but not to non-GM1 intestinal glycosphingolipids. In contrast, when LTB amino acid substitutions in the 1–25 region were combined with those in the 75–83 region, a binding as strong as that of LTB to intestinal glycosphingolipids was observed. In addition, a mutant LTB with a single Gly-33→Asp substitution that completely lacked affinity for both GM1 and non-GM1 glycosphingolipids could still bind to receptors in the intestinal cell membranes and to polyglycosylceramides. We conclude that the extra, non-GM1 receptors for LTB consist of both sialylated and non-sialylated glycoconjugates, and that the binding to either class of receptors is influenced by different amino acid residues within the protein.