Evidence for a major gene influencing 7-year increases in diastolic blood pressure with age.

The contribution of genetic factors to blood pressure levels is well established. The contribution of genes to the longitudinal change in blood pressure has been less well studied, because of the lack of longitudinal family data. The present study investigated a possible major-gene effect on the observed increase with age in diastolic blood pressure (DBP) levels. Subjects included 965 unmedicated adults (age > or = 18 years) in 73 pedigrees collected in Utah as part of a longitudinal cardiovascular family study. Segregation analysis of DBP change over 7.2 years of follow-up identified a recessive major-gene effect with a gene frequency of p = .23. There was also a significant age effect on the genotypic means, which decreased expression of the major gene at older ages. For those inferred to have the genotype responsible for large DBP increases, DBP increased 32.3%, compared with a 1.5% increase in the nonsusceptible group (P < .0001). The relative risk of developing hypertension between the susceptible and nonsusceptible groups after 7.2 years was 2.4 (P = .006). Baseline DBP reactivities to mental arithmetic (P < .0001), and isometric handgrip (P < .0001) stress tests were greatest in those assigned to the susceptible genotype. We conclude that age-related changes in DBP are influenced by a major gene. Characteristics of this major-gene effect for greater age-related blood pressure increases include greater reactivity to mental and physical stressors. The present study thus provides evidence for genetic control of changes in blood pressure, in addition to the previously suggested genetic control of absolute blood pressure level.     

锦橙汁囊的超微结构

用常规电镜方法观察了锦橙［Ｃｉｔｒｕｓｓｉｎｅｎｓｉｓ （Ｌ．） Ｏｓｂ．］汁囊从原始细胞到发育为一个具柄的成熟汁囊的过程中,汁囊构成细胞超微结构的变化。锦橙汁囊原始细胞及发育为球状体时的构成细胞以及柱状结构顶端的细胞都是一种典型的分生组织细胞。在细胞质中有包括线粒体、质体、内质网、核糖体等丰富的细胞器,但没有观察到高尔基体。这些分生细胞分裂一段时期后就停止活动,逐渐分化为适应贮藏功能的液泡化薄壁细胞。分生细胞开始分化时,在细胞中出现许多小液泡和高尔基体。这些小液泡逐渐地融合,同时细胞质变少,最后形成一个有中央大液泡的薄壁细胞,在紧贴细胞膜的薄薄的一层细胞质中有线粒体、质体、高尔基体以及含有许多脂滴的杂色体。但成熟果实中汁囊的薄壁细胞中几乎没有任何细胞器。     

Mitotic karyotypes of Brassica campestris and Brassica alboglabra and identification of the B. alboglabra chromosome in an addition line.

A Brassica campestris-alboglabra monosomic addition line (genome: AA + one chromosome from the C genome, 2n = 21) harbours the Brassica alboglabra (CC, 2n = 18) chromosome with the gene for erucic acid. In order to identify this chromosome, we have studied the mitotic prometaphase chromosomes of Brassica campestris (AA, 2n = 20), B. alboglabra, and the monosomic addition line. More pronounced differential staining and size differences of chromosomes were observed in B. campestris than in B. alboglabra. The karyotype of B. campestris was composed of four median (m), four submedian (sm), and two subterminal (st) chromosome pairs, while that of B. alboglabra was composed of three m, four sm, and two st chromosome pairs, provided that the length of the satellite was excluded when determining the arm ratio of the nucleolar chromosome. The alien chromosome from the C genome in the addition line was easily identified in the background B. campestris genome by its large size, its submedian centromere, and its differential staining pattern. When compared with the karyotype of B. alboglabra, the alien chromosome from the C genome in the monosomic addition line was revealed to be chromosome 4.     

Mutations of surface residues in Anabaena vegetative and heterocyst ferredoxin that affect thermodynamic stability as determined by guanidine hydrochloride denaturation.

The stability properties of oxidized wild-type (wt) and site-directed mutants in surface residues of vegetative (Vfd) and heterocyst (Hfd) ferredoxins from Anabaena 7120 have been characterized by guanidine hydrochloride (Gdn-HCl) denaturation. For Vfd it was found that mutants E95K, E94Q, F65Y, F65W, and T48A are quite similar to wt in stability. E94K is somewhat less stable, whereas E94D, F65A, F65I, R42A, and R42H are substantially less stable than wt. R42H is a substitution found in all Hfds, and NMR comparison of the Anabaena 7120 Vfd and Hfd showed the latter to be much less stable on the basis of hydrogen exchange rates (Chae YK, Abildgaard F, Mooberry ES, Markley JL, 1994, Biochemistry 33:3287-3295); we also find this to be true with respect to Gdn-HCl denaturation. Strikingly, the Hfd mutant H42R is more stable than the wt Hfd by precisely the amount of stability lost in Vfd upon mutating R42 to H (2.0 kcal/mol). On the basis of comparison of the X-ray crystal structures of wt Anabaena Vfd and Hfd, the decreased stabilities of F65A and F65I can be ascribed to increased solvent exposure of interior hydrophobic groups. In the case of Vfd mutants E94K and E94D, the decreased stabilities may result from disruption of a hydrogen bond between the E94 and S47 side chains. The instability of the R42 mutants is also most probably due to decreased hydrogen bonding capabilities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of 3α-hydroxysteroid dehydrogenase in rat brain and molecular cloning of multiple cDNAs encoding structurally related proteins in humans

3α-Hydroxysteroid dehydrogenase in the brain is responsible for production of neuroactive tetrahydrosteroids that interact with the major inhibitory gamma-aminobutyric acid receptor complexes. Distribution of 3α-hydroxysteroid dehydrogenase in different regions of the brain in rats was evaluated by activity assay and by Western immunoblotting using a monoclonal antibody against liver 3α-hydroxysteroid dehydrogenase as the probe. The olfactory bulb was found to contain the highest level of 3α-hydroxysteroid dehydrogenase activity, while moderate levels of the enzyme activity were found in other regions such as cerebellum, cerebral cortex, hypothalamus and pituitary. Some activity was found in the rest of the brain such as amygdala, brain stem, caudate putamen, cingulate cortex, hippocampus, midbrain, and thalamus. The protein levels of 3α-hydroxysteroid dehydrogenase in different regions of the brain as detected by Western immunoblotting are comparable to those of the enzyme activity. We used the rat cDNA as the probe to screen a human liver λ gt11 cDNA library. A total of four different cDNAs were identified and sequenced. One of the cDNAs is identical to that of the human chlordecone reductase cDNA except that our clone contains a much longer 5′-coding sequence than previously reported. The other three cDNAs display high degrees of sequence homology to those of both rat 3α-hydroxysteroid dehydrogenase and human chlordecone reductase. We are currently investigating the functional relationship between the enzymes encoded by these human cDNAs and 3α-hydroxysteroid dehydrogenase.     

Simultaneous Determination of Fluzinamide and three of its active metabolites in plasma by high-performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic method has been developed for a new anticonvulsant, fluzinamide, and three of its active metabolites. This method requires only 0.5 ml of plasma, and it involves a single extraction with a mixture of hexane—dichloromethane—butanol (55:40:5). The plasma extract is chromatographed on a 10-μm, C₁₈ reversed-phase column and quantitated by ultraviolet absorbance at 220 nm. The concentration—response curve for all four compounds are linear from 0.05 μg/ml to at least 10 μg/ml. The extraction efficiency of this method is greater than 90%. The accuracy and precision of the method were tested by analyzing spiked unknown samples that had been randomly distributed across the concentration range. The mean concentrations found were within ± 9% of the various amounts added with a standard deviation of ± 3.5%. This method has been successfully applied to the analysis of samples obtained from fluzinamide-dosed dogs, healthy unmedicated volunteers, and patients who were at steady state with phenytoin, carbamazepine, and fluzinamide.     

Effect of parental feeding activity on squab-induced crop sac growth in ring doves (Streptopelia risoria)

Effects of parental regurgitation feeding activity on crop sac development were studied in mate-separated male and female ring doves given 2 hr of daily exposure to food-deprived or recently fed squabs, for 4 consecutive days during the early posthatching period of the breeding cycle. In both sexes, food-deprived squabs stimulated more squab-directed activity, more parental regurgitation feeding activity, and greater crop sac development than recently fed young. Crop sac weights of males in both groups tended to be positively correlated with one or more parental activities. Correlations obtained in males exposed to food-deprived young further suggested that tactile stimuli associated with regurgitation behavior may promote crop sac development. In contrast to males, crop sac weights of females in both groups were not highly correlated with any type of contact-related parental activity or group of activities. These results, together with previous findings, suggest that nontactile stimuli from young played some role in mediating female crop sac weight differences in the two exposure conditions.     

Ultrastructure of Butyrivibrio fibrisolvens: a gram-positive bacterium.

The cells of bacteria of the genus Butyrivibrio are universally described as being gram negative, and they produce an unequivocal gram-negative reaction in the standard staining procedure. However, their cell walls contain derivatives of teichoic acid, which are characteristic of gram-positive cells. In this study, the cell walls of two representative strains of Butyrivibrio were of the gram-positive morphological type, as seen by electron microscopy, but they were very thin (12 to 18 nm). The thinness of these cell walls may account for the tendency of these cells to stain gram negatively in the standard staining procedure. Ruthenium red staining revealed an extracellular structure surrounding cells of Butyrivibio sp. (strain C3). This structure was composed of individual "knobs" that sometimes mediated cell-to-cell adhesion in the culture.     

Partial amino acid sequence of human thyroxine-binding globulin. Further evidence for a single polypeptide chain.

The NH₂-terminal amino acid of highly purified thyroxine-binding globulin has been identified by dansyl chloride, cyanate and Edman degradation methods. All three gave alanine as the only amino terminal residue. Carbamylation and Edman degradation of the denatured protein yielded 0.86 and 0.98 – 1.05 mole of alanine per mole of protein, respectively. These data further indicate that thyroxine-binding globulin is composed of a single polypeptide chain. Automated Edman degradation gave the partial sequence as: Ala-Ser-Pro-Glu-Gly-Lys-Val-Thr-Ala-Asp-Ser-Ser-Ser-Gln-(Pro)-X-Ala-(Ser)-Leu-Tyr- A computer search revealed no homology of the NH₂-terminal segment of thyroxine-binding globulin with human prealbumin. The NH₂-terminal portion of prealbumin contains part of the thyroxine binding site.