Genduplikation durch polyploide Evolution: die Isoenzyme der Sorbitdehydrogenase bei herings- und lachsartigen Fischen (Isospondyli)

Zusammenfassung Die elektrophoretische Analyse der Isoenzyme der Sorbitdehydrogenase (SDH) bei verschiedenen Säugerspecies unter Einschluß des Menschen läßt darauf schließen, daß bei Säugern nur 1 Genlocus für dieses Enzym existiert. Auch bei Knochenfischen läßt sich in der Regel nur 1 SDH-Gen nachweisen. Eine Ausnahme bilden einige Species der Fischordnung Isospondyli. Innerhalb dieser Ordnung findet sich eine Diploid-tetraploid-Beziehung. Arten mit diploiden Charakteristika wie der Hering (Clupea harengus) besitzen 1 SDH-locus, an dem 3 Allele zu beobachten waren. Bei einigen phylogenetisch tetraploiden lachsartigen Fischen läßt sich eine Duplikation des SDH-Gens nachweisen. Während bei der Bachforelle (Salmo trutta) die nach der Tetraploidisierung zunächst identischen loci sich divergent entwickelt haben und jetzt diploidisiert sind, zeigen Regenbogenforelle (Salmo irideus) und Blaufelchen (Coregonus lavaretus) tetrasome Phänotypen der SDH. Beim Blaufelchen findet sich ein Überschuß an Heterozygoten, der auf eine meiotische Vorzugspaarung der Chromosomen mit identischen Allelen schließen läßt. Diese Befunde geben Einblick in den Mechanismus der Diploidisierung, der in der Evolution der höheren Wirbeltiere eine wesentliche Rolle gespielt haben dürfte.

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Sorbitol dehydrogenase isozymes in clupeoid fish: a further example of gene duplication through polyploid evolution

Summary Electrophoretic analysis of the sorbitol dehydrogenase isozymes (SDH) in various mammalian species including man revealed the existence of only 1 gene locus for this enzyme. As a rule, the same is true for Teleostean fishes. Some species of the fish order Isospondyli, however, represent an exception. Within this order, a diploid-tetraploid relationship exists. Species exhibiting diploid characteristics as the herring (Clupea harengus), are endowed with a single SDH gene locus at which 3 different alleles were observed. In some Salmonoid fish having passed through tetraploid evolution, a duplication of the SDH gene can be demonstrated. While in Salmo trutta the duplicated genes evolved divergently and became diploidized, in Salmo irideus and Coregonus lavaretus tetrasomic phenotypes occur. In Coregonus, the predominance of heterozygotes is to be interpreted as the consequence of preferential pairing of meiotic chromosomes endowed with identical alleles. These findings give some insight in the diploidization mechanism which may have played an important role during evolution of higher vertebrates.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Serology of Rubella—Comparison of Fluorescent Antibody,Complement Fixation and Neutralization Tests for Diagnosis of Current Infections and Determination of Sero-immunity

Neutralization, complement fixation (CF) and indirect fluorescent antibody (FA) assays for rubella virus were compared for sensitivity in the serologic diagnosis of infection, for demonstrating antibody in the sera of infants with suspected rubella syndrome, and in the detection of antibody elicited by past infection (determination of immunity status). The combination of CF and FA tests was shown to be the most useful for serologic diagnosis of infection, largely eliminating the need for the slower and more cumbersome interference neutralization test.Neutralizing antibodies were found to appear rapidly in the course of infection, antibodies demonstrable by immunofluorescent staining appeared slightly later, and CF antibodies were rarely demonstrable in sera collected earlier than 14 days after onset of illness. Antibodies detected by all three techniques showed good correlation in infants with clinical evidence of rubella syndrome and corresponding maternal sera. The indirect FA technique compared favorably with the neutralization test for the detection of antibody elicited by past infection (determination of immunity status) and offered distinct advantages in ease of technical performance and more rapid results. In both current and past infections, FA titers tended to be higher than neutralizing antibody titers.     

Behavioral treatment of isolated systolic hypertension in the elderly

Fifteen hypertensive patients were recruited from a geriatric medicine clinic for a research project designed to evaluate a Behavioral Stepped-Care treatment program of high blood pressure (HBP). All patients met the selection criteria of the Isolated Systolic Hypertension (ISH) in the Elderly (SHEP) clinical trial. During baseline, subjects recorded BP at home 9 times/day (3 times each, shortly after awakening, during the middle of the day, and within an hour of retiring) for 1 month and mailed that data to us daily. In addition, they came to the clinic weekly and had their BP recorded by a nurse. During treatment 1, systolic (SBP) feedback, they were trained to lower SBP at home using their sphygmomanometers. They also continued to monitor BP and to obtain weekly professional BP readings. During treatment 2 (relaxation), they were trained to relax; they followed the self-administration and data-collection protocol as in treatment 1. Each treatment phase lasted 3 months. Average monthly self-determined BP fell significantly from 166.4/85.8 (SBP/DBP) mm Hg during baseline to 153.3/81.2 by the end of the relaxation phase; average monthly professionally measured BP fell significantly, from 164.7/87.1 to 156.9/81.5. These findings show that a nurse-supervised, patient-administered behavioral treatment program of ISH can yield sustained, significant falls in BP.Ms. Pearce and Dr. Burton were supported in part by the Johns Hopkins Academic Nursing Home Award, PO, AG04402, from the National Institute on Aging. This material was presented in part at the annual meeting of the Gerontological Society of America, November 1988, San Francisco.     

Lung volumes, chest wall configuration, and pattern of breathing in microgravity

We studied the changes in functional residual capacity (FRC), thoracoabdominal volume (Vw), and chest wall configuration in five normal subjects seated in an aircraft flying parabolic trajectories resulting in 20-s periods of microgravity. We measured vital capacity (VC), inspiratory capacity, and tidal volume by integrating airflow at the mouth and changes in rib cage and abdominal volume (delta Vrc and delta Vab, respectively, where delta Vrc + delta Vab = delta Vw) using induction plethysmography. During microgravity (0 Gz) FRC decreased by 413 +/- 70 (SE) ml and VC by 0.37 liter. The decrease in Vw did not differ from that in FRC and was entirely the result of reduction of Vab, the Vrc showing no significant change. During tidal breathing the abdominal contribution (delta Vab/delta Vw) increased from 0.39 +/- 0.08 at 1 Gz to 0.57 +/- 0.08 at 0 Gz. During brief periods of hypergravity (approximately 1.8 Gz) all changes were opposite in sign and relatively smaller. Limited data during "roller coaster" flight patterns suggested that, in contrast to configurational changes, the temporal pattern of breathing was uninfluenced by changes in Gz. We conclude that at the onset of weightlessness there are substantial changes in lung volume and thoracoabdominal configuration. Abdominal contribution to tidal excursions increases but the temporal pattern of breathing is unchanged.     

Pressure-diameter relationships of the upper airway in awake supine subjects

In awake supine normal subjects, dimensional changes of the oropharyngeal airway were measured during exposure to negative intraluminal pressures. The pressure was generated 1) "actively" by subjects inspiring against an externally occluded airway or 2) "passively" by external suction at the mouth during voluntary glottic closure with no inspiratory effort. Airway dimensions were imaged with X-ray fluoroscopy and anteroposterior diameters measured at levels corresponding to cervical vertebra 3 and 4 (C3 and C4). Cephalad axial displacement of the hyoid bone (CDHY) was also measured. During the "active" maneuver, airway diameters and position were maintained at resting levels despite airway pressure up to -15 cmH2O. In contrast, during the passive maneuver at -15 cmH2O, C3 was only 15 +/- 9% and C4 only 47 +/- 8% of control; CDHY was 5.6 +/- 1.8 mm. In three subjects airway wall apposition occurred and persisted until an active inspiratory effort. We conclude that, in the absence of inspiratory effort, negative oropharyngeal airway pressures result in marked narrowing and cephalad displacement of the upper airway, even during wakefulness. Therefore, our data suggest that the complex interaction of upper airway and thoracic muscle activity is critical in determining the effective compliance and patency of the upper airway, which is readily collapsible even in normal subjects.     

Subcellular distribution of carbonic anhydrase in Solanum tuberosum L. leaves

The intracellular compartmentation of carbonic anhydrase (CA; EC 4.2.1.1), an enzyme that catalyses the reversible hydration of CO₂ to bicarbonate, has been investigated in potato (Solanum tuberosum L.) leaves. Although enzyme activity was mainly located in chloroplasts (87% of total cellular activity), significant activity (13%) was also found in the cytosol. The corresponding CA isoforms were purified either from chloroplasts or crude leaf extracts, respectively. The cytosolic isoenzyme has a molecular mass of 255 000 and is composed of eight identical subunits with an estimated M _r of 30000. The chloroplastic isoenzyme (M _r 220000) is also an octamer composed of two different subunits with M _r estimated at 27 000 and 27 500, respectively. The N-terminal amino acid sequences of both chloroplastic CA subunits demonstrated that they were identical except that the M _r-27 000 subunit was three amino acids shorter than that of the M _r-27 500 subunit. Cytosolic and chloroplastic CA isoenzymes were found to be similarly inhibited by monovalent anions (Cl^–, I^–, N ₃ ^- and NO ₃ ^- ) and by sulfonamides (ethoxyzolamide and acetozolamide). Both CA isoforms were found to be dependent on a reducing agent such as cysteine or dithiothreitol in order to retain the catalytic activity, but 2-mercaptoethanol was found to be a potent inhibitor. A polyclonal antibody directed against a synthetic peptide corresponding to the N-terminal amino acid sequence of the chloroplastic CA monomers also recognized the cytosolic CA isoform. This antibody was used for immunocytolocalization experiments which confirmed the intracellular compartmentation of CA: within chloroplasts, CA is restricted to the stroma and appears randomly distributed in the cytosol.Abbreviations BSA bovine serum albumin - CA carbonic anhydrase - PMSF phenylmethylsulphonyl fluoride - BAM benzamidine - DTT dithiothreitol - 2-ME 2-mercaptoethanol - PVDF polyvinylidene difluoride The authors thanks P. Carrier and Dr. B. Dimon for technical assistance with the mass-spectrometry measurements.