催产时鳝卵磷酸酶活性的变化及其与排卵的关系

本实验采用Gomori组织化学法和磷酸苯二钠法,分别检测黄鳝卵ALP、ACP的细胞定位和活性变化。结果表明,催产后72h,ALP活性显著高于临近注射时(Oh),催产后48h和96h(p<0.05);临产前(催产后96h),ACP活性极显著高于试验组其它各时程(p<0.01)。提示ALP和ACP活性增强与卵母细胞成熟、排放有直接关系。本研究为探索排卵机制提供资料。     

Evaluation of Probiotic Properties of Novel Brazilian Lactiplantibacillus plantarum Strains

Probiotics and Antimicrobial Proteins - Beneficial effects of Lactiplantibacillus plantarum strains have been widely reported. Knowing that the effects of probiotic bacteria are strain-dependent,...     

PATTERNS OF PLANT ONTOGENY THAT MAY INFLUENCE GENOMIC STASIS

It is an axiom in biology that genes control the ontogeny and ultimately the final form of an organism. In plants a given morphological form can often arise through more than one ontogenetic pattern of cell divisions. Different ontogenetic patterns have different properties with regard to the final age in cell divisions of the initials in the meristems for a given morphological form. If mutation per genome per cell division is an important biological metric, then since the age of a cell in cell divisions is a function of ontogeny, the cellular ontogeny will influence the degree of mutation-loading in meristematic initials. Thus, ontogeny and form may affect the genes (by promoting or lessening genomic stasis) as well as, of course, being determined by the genes. This paper explores mathematically the relationship between different patterns of cell division and mutation-loading.     

A transposon insertion in the Arabidopsis SSR16 gene causes an embryo-defective lethal mutation

The SSR16 gene of Arabidopsis has been identified as a gene encoding a ribosomal protein S16 homolog through analysis of a transposon insertion mutation. The insertion mutation is lethal, arresting embryonic development at approximately the transition from the globular to the heart stage of embryonic development. Co-segregation of the mutant phenotype with the transposon-borne drug-resistance marker and loss of the inserted transposon concomitant with phenotypic reversion provided evidence that the transposon had caused the mutation. Sequences flanking the insertion site were amplified from DNA of viable heterozygotes by thermal asymmetric interlaced (TAIL) PCR. The amplified fragment flanking the 3' end of the inserted element was sequenced and found to be identical to an Arabidopsis expressed sequence tag (EST). The EST, in turn, contained a coding sequence homologous to the ribosomal protein S16 (RPS16) of bacteria such as Escherichia coli, Bacillus subtilis and Salmonella typhimurium , as well as Neurospora crassa mitochondria and higher plant plastids. Thus the gene identified by the embryo-defective lethal insertion mutation encodes an RPS16 homolog and has been designated the SSR16 gene.     

Transcapillary escape rate of albumin in humans during exercise-induced hypervolemia

Haskell, Andrew, Ethan R. Nadel, Nina S. Stachenfeld, KeiNagashima, and Gary W. Mack. Transcapillary escape rate of albuminin humans during exercise-induced hypervolemia. J. Appl. Physiol. 83(2): 407-413, 1997.To test thehypotheses that plasma volume (PV) expansion 24 h after intenseexercise is associated with reduced transcapillary escape rate ofalbumin (TER_alb) and that localchanges in transcapillary forces in the previously active tissues favorretention of protein in the vascular space, we measured PV,TER_alb, plasma colloid osmoticpressure (COP_p), interstitialfluid hydrostatic pressure (Pi), and colloid osmotic pressure in legmuscle and skin and capillary filtration coefficient (CFC) in the armand leg in seven men and women before and 24 h after intense uprightcycle ergometer exercise. Exercise expanded PV by 6.4% at 24 h (43.9 ± 0.8 to 46.8 ± 1.2 ml/kg, P < 0.05) and decreased total protein concentration (6.5 ± 0.1 to6.3 ± 0.1 g/dl, P < 0.05) andCOP_p (26.1 ± 0.8 to 24.3 ± 0.9 mmHg, P < 0.05), although plasmaalbumin concentration was unchanged. TER_alb tended to decline (8.4 ± 0.5 to 6.5 ± 0.7%/h, P = 0.11) and was correlated with the increase in PV(r = 0.69,P < 0.05). CFC increased in the leg(3.2 ± 0.2 to 4.3 ± 0.5 µl · 100 g¹ · min¹ · mmHg¹,P < 0.05), and Pi showed a trend toincrease in the leg muscle (2.8 ± 0.7 to 3.8 ± 0.3 mmHg, P = 0.08). These datademonstrate that TER_alb isassociated with PV regulation and that local transcapillary forcesin the leg muscle may favor retention of albumin in the vascular spaceafter exercise.

     

Mutations in the SLC3A1 Transporter Gene in Cystinuria

Cystinuria is an autosomal recessive disease characterized by the development of kidney stones. Guided by the identification of the SLC3A1 amino acid–transport gene on chromosome 2, we recently established genetic linkage of cystinuria to chromosome 2p in 17 families, without evidence for locus heterogeneity. Other authors have independently identified missense mutations in SLC3A1 in cystinuria patients. In this report we describe four additional cystinuria-associated mutations in this gene: a frameshift, a deletion, a transversion inducing a critical amino acid change, and a nonsense mutation. The latter stop codon was found in all of eight Ashkenazi Jewish carrier chromosomes examined. This report brings the number of disease-associated mutations in this gene to 10. We also assess the frequency of these mutations in our 17 cystinuria families.     

Increased α1 receptor density in brown adipose tissue of cafeteria-fed rats

A possible general corollary between ₁-receptor density in brown adipose tissue and the degree of activation of the tissue was investigated. For this purpose, the effect of cafeteria feeding on ₁-adrenergic receptors in brown adipose tissue of seven-week-old female rats was studied by the use of the ₁-antagonist (³H)prazosin. In cafeteria-fed rats, the K_D of the ₁-receptor for (³H)prazosin was unchanged (about 0.35 nM), but the receptor density was doubled (up to 40 fmol per mg of membrane protein). This was also observed when the results were expressed per unit of a plasma-membrane marker (5-nucleotidase). It was concluded that an increased ₁-receptor density is seen not only in cold-acclimated rats, but also in other conditions where brown fat is activated, and a possible general physiological significance of ₁-adrenergic pathways in brown adipose tissue is discussed.     

The biology ofChlamydomyxa montana: Ultrastructure of the cyst

Summary Cells ofChlamydomyxa montana Lankester photosynthesize within a cyst under bright light and ingest diatoms in an excysted amoeboid form during periods of low light intensity. Cyst cell walls are partially comprised of cellulose and vary in thickness. The cells are multinucleate and intracellular bacteria are closely associated with the nuclei. A pair of centrioles is also present adjacent to individual nuclei. Chloroplasts are numerous and thylakoids are generally organized into bands of three. No endoplasmic reticulum was found surrounding the plastids, nor was a complete girdling lamella ever observed within.C. montana chloroplasts appear to be its own but this protist does not precisely fit into an algal class.     

Effect of Carbon Source and the Role of Cyclic Adenosine 3′,5′-Monophosphate on the Caulobacter Cell Cycle

The expression of cell cycle events in Caulobacter crescentus CB13 has been shown to be associated with regulation of carbohydrate utilization. Growth on lactose and galactose depends on induction of specific enzymes. Prior growth on glucose results in a delay in enzyme expression and cell cycle arrest at the nonmotile, predivisional stage. Dibutyryl cyclic adenosine 3',5'-monophosphate (AMP) was shown to stimulate expression of the inducible enzymes and, thus, the initiation of the cell cycle. beta-Galactosidase-constitutive mutants did not exhibit a cell cycle arrest upon transfer of cultures from glucose to lactose. Furthermore, carbon source starvation results in accumulation of the cells at the predivisional stage. The cell cycle arrest therefore results from nutritional deprivation and is analogous to the general control system exhibited by yeast (Hartwell, Bacteriol. Rev. 38:164-198, 1974; Wolfner et al., J. Mol. Biol. 96:273-290, 1975), which coordinates cell cycle initiation with metabolic state. Transfer of C. crescentus CB13 from glucose to mannose did not result in a cell cycle arrest, and it was demonstrated that this carbon source is metabolized by constitutive enzymes. Growth on mannose, however, is stimulated by exogenous dibutyryl cyclic AMP without a concomitant increase in the specific activity of the mannose catabolic enzymes. The effect of cyclic AMP on growth on sugars metabolized by inducible enzymes, as well as on sugars metabolized by constitutive enzymes, may represent a regulatory system common to both types of sugar utilization, since they share features that differ from glucose utilization, namely, temperature-sensitive growth and low intracellular concentrations of cyclic guanosine 3',5'-monophosphate.     

Cloning of bacteriophage T5 promoters

Summary Bacteriophage T5 was subjected to combined hydrolysis with the restriction endonuclease PstI and HindIII and the resulting fragments were inserted into the plasmid pBR322. Selection of transformants for Ap^s-Tc^r-phenotype made it possible to screen the hybrid plasmids that contained promoter sequences in the cloned fragments.Two PstI/HindIII fragment, 720 bp (51% of the T5 DNA length) and 1,200 bp (70%) were cloned in this study. Tc^r levels for these plasmids were as high as 18 g/ml and 75 g/ml, respectively. The presence of Escherichia coli RNA polymerase binding sites on both fragments was shown using the nitrocellulose filter assay. These binding sites are situated between 35 bp and 95 bp from the HindIII cleavage site on the 1,200 bp fragment; and within 420 bp from the HindIII site on the 720 bp fragment.Abbreviations Ap ampicillin - Tc tetracycline - bp base pairs - NTPs nucleoside triphosphates - PBB polymerase binding buffer