Down's syndrome in twins with discordant HL-A phenotypes

Summary A male twin pair discordant in morphological characteristics and HL-A phenotype but concordant in trisomy 21 and the blood group markers is reported.The coincidental occurrence of two rare conditions (nondisjunction and dizygotic twinning) and a high probability of monozygosity (inferred from the blood group findings) gave rise to the question of whether the boys might represent intermediates between dizygotic and monzygotic twins. Postcleavage fertilization can be excluded as a circumstance leading to intermediates since the twins have different maternal HL-A haplotypes.

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Zusammenfassung Ein männliches Zwillingspaar wird vorgestellt, das in einigen morphologischen Merkmalen und im HL-A-Phänotypus diskordant, hinsichtlich einer Trisomie 21 und der Blutgruppenmerkmale aber konkordant ist.Auf Grund des Zusammentreffens zweier seltener Ereignisse (nondisjunction und Zweieiigkeit), insbesondere aber auch wegen starker blutgruppenserologischer Hinweiswahrscheinlichkeiten für Eineiigkeit, wird die Frage gestellt, ob die Knaben möglicherweise eine intermediäre Position zwischen Eineiigkeit und Zweieiigkeit einnehmen. Von den Möglichkeiten, die zu einer solchen Zwischenstellung führen könnten, scheidet die einer Befruchtung des Eies erst nach der Furchung aus, da beide Zwillingspartner unterschiedliche mütterliche HI-A-Haplotypen aufweisen.

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Supported by the Deutsche Forschungsgemeinschaft.     

Familiäre 2/C-Translokation: 46,XY t (2p-; Cp+) und 46,XX Cp+

Zusammenfassung Bei einem Patienten mit multiplen Mißbildungen wurde eine Duplikation für die distale Hälfte vom kurzen Arm des Chromosoms 2 und eine Defizienz an einem C-Chromosom gefunden. In der Literatur sind vier Fälle mit ähnlicher Duplikation, jedoch jeweils einer klein n Defizienz am Chromosom 3 beschrieben worden. Ein Vergleich der klinischen Merkmale bei den fünf Patienten zeigt weitgehende Übereinstimmungen. Es wird gefolgert, daß die gleichartige Duplikation für das einheitliche klinische Bild der Patienten verantwortlich ist. Es wurden Chromosomenmessungen, Analysen der Replikationsmuster und Meioseuntersuchungen durchgeführt. Die Genloci für das Ss- und das Rh-System konnten von einer Lokalisierung auf dem duplizierten Segment ausgeschlossen werden.

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2/C translocation in father and daughter: 46,XY t (2p-;Cp+) and 46,XX Cp+

Summary In a patient with multiple anomalies, a duplication comprising the distal half of the short arm of chromosome 2 and a small deficiency of a C-chromosome was found. Four other cases from the literature exhibit a similar duplication combined with a small deficiency each of chromosome 3. Comparison of the clinical pictures of the five patients revealed a conformity in the major features. It is concluded that the duplication is responsible for the uniform appearance of these patients. The studies performed include chromosome measurements, examination of replication patterns and meiosis. The gene loci for the Ss and Rh systems could be excluded from localization on the duplicated segment.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

On the localization of genes on certain autosomes of man through chromosome aberrations

Summary Chromosome aberrations permit the assignment to and the exclusion of genes on certain chromosomes or definite segments. Only exclusion methods are discussed. All relevant data are compiled in a table from which it can be determined, which genetic systems are excluded from certain autosomal segments.

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Zusammenfassung Angeborene Chromosomenaberrationen ermöglichen die Zuordnung und den Ausschluß von Genen auf dem betroffenen Segment. Nur die für Lokalisierungsausschlüsse verwendbaren Methoden werden diskutiert. Aus einer Zusammenstellung der bisherigen Befunde wird ermittelt, welche genetischen Systeme von einer Lokalisierung auf bestimmten Autosomen(segmenten) des Menschen ausgeschlossen werden können.

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Direktor: Prof. Dr. Dr. H. Baitsch

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Supported by the Deutsche Forschungsgemeinschaft.     

Oxygen transport during steady-state submaximal exercise in chronic hypoxia

Arterial O2 delivery during short-term submaximal exercise falls on arrival at high altitude but thereafter remains constant. As arterial O2 content increases with acclimatization, blood flow falls. We evaluated several factors that could influence O2 delivery during more prolonged submaximal exercise after acclimatization at 4,300 m. Seven men (23 +/- 2 yr) performed 45 min of steady-state submaximal exercise at sea level (barometric pressure 751 Torr), on acute ascent to 4,300 m (barometric pressure 463 Torr), and after 21 days of residence at altitude. The O2 uptake (VO2) was constant during exercise, 51 +/- 1% of maximal VO2 at sea level, and 65 +/- 2% VO2 at 4,300 m. After acclimatization, exercise cardiac output decreased 25 +/- 3% compared with arrival and leg blood flow decreased 18 +/- 3% (P less than 0.05), with no change in the percentage of cardiac output to the leg. Hemoglobin concentration and arterial O2 saturation increased, but total body and leg O2 delivery remained unchanged. After acclimatization, a reduction in plasma volume was offset by an increase in erythrocyte volume, and total blood volume did not change. Mean systemic arterial pressure, systemic vascular resistance, and leg vascular resistance were all greater after acclimatization (P less than 0.05). Mean plasma norepinephrine levels also increased during exercise in a parallel fashion with increased vascular resistance. Thus we conclude that both total body and leg O2 delivery decrease after arrival at 4,300 m and remain unchanged with acclimatization as a result of a parallel fall in both cardiac output and leg blood flow and an increase in arterial O2 content.(ABSTRACT TRUNCATED AT 250 WORDS)     

β-Dl-Methylene-aspartate,an inhibitor of aspartate aminotransferase,potently inhibitsl-glutamate uptake into astrocytes

[³H]Glutamate uptake into astrocytes in primary culture was potently inhibited by the aspartate analoguesl- andd-aspartic acid,Dl-threo--hydroxy-aspartic acid,l-aspartic acid--hydroxymate (IC50's: 136, 259, 168, and 560 M, respectively) and by -Dl-methylene-aspartate, a suicide inhibitor of asparate aminotransferase (IC50: 524 M), and by the endogenous sulphur-containing amino acidl-cysteinesulfinic acid (IC50: 114 M). [³H]Glutamate uptake was not significantly affected by either N-methyl-d-aspartate orDl-homocysteine thiolactone. These results demonstrate that other excitatory amino acids including aspartate andl-cysteinesulfinic acid (but excludingl-homocysteic acid) interact with the glutamate transport system of astrocytes. Inhibition of glutamate uptake may significantly increase the level of neuronal excitability.     

Role of the flagellum in cell-cycle-dependent expression of bacteriophage receptor activity in Caulobacter crescentus.

The rate of adsorption of Caulobacter bacteriophage phi CbK to Caulobacter crescentus is dependent on the structural integrity of the flagellum. Cells lacking part or all of the flagellum because of either mutation or mechanical shear were defective in adsorption, and the extent of the defect in adsorption reflected the amount of flagellar structure missing. Maximal adsorption rates were also dependent on cellular motility and energy metabolism, since adsorption to cells with paralyzed flagella was slower than adsorption to motile cells and inhibition of cellular energy metabolism with azide also reduced adsorption rates, even for nonmotile cells. Nevertheless, the flagellum is not the receptor for phage phi CbK, since flagellumless mutants adsorbed phi CbK at detectable rates. While some portion of the fluctuation in the phi CbK receptor activity during the C. crescentus cell cycle can be ascribed to the periodicity of flagellar loss and reappearance, the phage receptor activity remaining in flagellumless mutants was periodic in the cell cycle. Therefore, the periodic expression of phage receptor activity is an intrinsic property of the C. crescentus cell cycle, although the amplitude of the oscillation may be altered by the periodic expression of flagellar motility.     

Molecular cloning,nucleotide sequence and expression in Escherichia coli of the β-cyclodextrin glycosyltransferase gene from Bacillus circulans strain no. 8

Summary The -cyclodextrin glycosyltransferase (-CGTase) gene was isolated from a -library prepared from Bacillus circulans strain no. 8. It was subcloned into plasmid pTZ and expressed by its endogenous regulatory sequences in Escherichia coli JM 103. The structural gene was sequenced and showed an open reading frame for a polypeptide of 718 amino acid residues. The recombinant -CGTase had the same enzymatic properties as the extracellular CGTase (684 amino acid residues, corresponding to a mol. wt. of 74416) produced by B. circulans strain no. 8. The amino acid sequence showed the highest homology (74.6% identical amino acids) with the CGTase of B. circulans strain F-2, which had been erroneously described as an amylase. The homology with the enzyme from the alkalophilic Bacillus sp. strain no. 1011 was 71.4%. The amino acid sequence derived will be used for elucidating the three-dimensional structure of the enzyme. Offprint requests to: H. Bender