黑卷尾繁殖期领域性的初步研究

鸟类的领域性是鸟类行为生态学研究的一个重要内容。在这方面国外进展很快,但国内工作较少,专文报道除三宝鸟之外,其它颇为罕见。1987年夏季,我们在太原市南郊对该地区的夏候鸟黑卷尾(Dicrurus macrocercus)的领域行为进行了观测。现将资料整理分析如下。一、工作区与工作方法太原盆地的自然环境和鸟类群落状况已有报道,在此不再赘述。工作区选在小马—加节两村之间约190ha的区域内(图1)。其     

烧伤后大鼠肠道菌群的改变及其易位

本文报告了25％烧伤后注射免疫抑制剂(地寨米松磷酸钠)大鼠7种肠道细菌的定量、内脏及血液的细菌培养和肠壁的病理形态学改变。单纯烧伤组(B组)和单纯注射免疫抑制剂组(Ⅰ组)动物肠壁的病理改变较轻,肠道菌群改变不明显,其肠道细菌易位率也很低。烧伤后注射免疫抑制剂的动物(BⅠ组)肠壁病变严重,肠道菌群改变明显。其中,肠杆菌在回肠、盲肠,结肠内容物中的菌量均明显升高;回肠内容物中拟杆菌的菌量明显减少;该组动物肠道细菌易位率也明显增高,达60％。此外,BⅠ组、Ⅰ组部分动物发生了由棒状杆菌及由棒状扦菌和肠杆菌混合引起的内源性感染。根据不同肠段肠壁病变严重程度、菌群变化的部位以及不同部位肠管生理功能的不同,我们推测,回肠以上肠段是肠道细菌易位的主要部位。     

Role of recurrent hydrophobic residues in catalysis of helix formation by T cell-presented peptides in the presence of lipid vesicles

We tested the hypothesis that the recurrence of hydrophobic amino acids in a polypeptide at positions falling in an axial, hydrophobic strip if the sequence were coiled as an alpha helix, can lead to helical nucleation on a hydrophobic surface. The hydrophobic surface could anchor such residues, whereas the peptide sequence grows in a helical configuration that is stabilized by hydrogen bonds among carbonyl and amido NH groups along the peptidyl backbone of the helix, and by other intercycle interactions among amino acid side chains. Such bound, helical structures might protect peptides from proteases and/or facilitate transport to a MHC-containing compartment and thus be reflected in the selection of T cell-presented segments. Helical structure in a series of HPLC-purified peptides was estimated from circular dichroism measurements in: 1) 0.01 M phosphate buffer, pH 7.0, 2) that buffer with 45% trifluoroethanol (TFE), and 3) that buffer with di-O-hexadecyl phosphatidylcholine vesicles. By decreasing the dielectric constant of the buffer, TFE enhances intrapeptide interactions generally, whereas the lipid vesicles only provide a surface for hydrophobic interactions. The peptides varied in their strip-of-helix hydrophobicity indices (SOHHI; the mean Kyte-Doolittle hydrophobicities of residues in an axial strip of an alpha helix) and in proline content. Structural order for peptides with helical circular dichroism spectra was estimated as percentage helicity from circular dichroism theta 222 nm values and peptide concentration. A prototypic alpha helical peptide with three cycles plus two amino acids and an axial hydrophobic strip of four leucyl residues (SOHHI = 3.8) was disordered in phosphate buffer, 58% helical in that buffer with 48% TFE, and 36% helical in that buffer with vesicles. Percentage helicity in the presence of vesicles of the subset of peptides without proline followed their SOHHI values. Peptides with multiple prolyl residues had circular dichroism spectra with strong signals, but since they did not have altered spectra in the presence of vesicles relative to phosphate buffer alone, the hydrophobic surface of the vesicle did not appear to stabilize those structures.     

Inositol 1,3,4,5-tetrakisphosphate is essential for sustained activation of the Ca2+-dependent K+ current in single internally perfused mouse lacrimal acinar cells

Summary We have examined the effects of various inositol polyphosphates, alone and in combination, on the Ca²⁺-activated K⁺ current in internally perfused, single mouse lacrimal acinar cells. We used the patch-clamp technique for whole-cell current recording with a set-up allowing exchange of the pipette solution during individual experiments so that control and test periods could be directly compared in individual cells. Inositol 1,4,5-trisphosphate (Ins 1,4,5 P₃) (10–100 m) evoked a transient increase in the Ca²⁺-sensitive K⁺ current that was independent of the presence of Ca²⁺ in the external solution. The transient nature of the Ins 1,4,5 P₃ effect was not due to rapid metabolic breakdown, as similar responses were obtained in the presence of 5mm 2,3-diphosphoglyceric acid, that blocks the hydrolysis of Ins 1,4,5 P₃, as well as with the stable analoguedl-inositol 1,4,5-trisphosphorothioate (Ins 1,4,5 P(S)₃) (100 m). Ins 1,3,4 P₃ (50 m) had no effect, whereas 50 m Ins 2,4,5 P₃ evoked responses similar to those obtained by 10 m Ins 1,4,5 P₃. A sustained increase in Ca²⁺-dependent K⁺ current was only observed when inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5 P₄) (10 m) was added to the Ins 1,4,5 P₃ (10 m)-containing solution and this effect could be terminated by removal of external Ca²⁺. The effect of Ins 1,3,4,5 P₄ was specifically dependent on the presence of Ins 1,4,5 P₃ as it was not found when 10 m concentrations of Ins 1,3,4 P₃ or Ins 2,4,5 P₃ were used. Ins 2,4,5 P₃ (but not Ins 1,3,4 P₃) at the higher concentration of 50 m did, however, support the Ins 1,3,4,5 P₄-evoked sustained current activation. Ins 1,3,4 P₃ could not evoke sustained responses in combination with Ins 1,4,5 P₃ excluding the possibility that the action of Ins 1,3,4,5 P₄ could be mediated by its breakdown product Ins 1,3,4 P₃. Ins 1,3,4,5 P₄ also evoked a sustained response when added to an Ins 1,4,5 P(S)₃-containing solution. Ins 1,3,4,5,6 P₅ (50 m) did not evoke any effect when administered on top of Ins 1,4,5 P₃. In the absence of external Ca²⁺, addition of Ins 1,3,4,5 P₄ to an Ins 1,4,5 P₃-containing internal solution evoked a second transient K⁺ current activation. Readmitting external Ca²⁺ in the continued presence internally of Ins 1,4,5 P₃ and Ins 1,3,4,5 P₄ made the response reappear. We conclude that both Ins 1,4,5 P₃ and Ins 1,3,4,5 P₄ play crucial and specific roles in controlling intracellular Ca²⁺ homeostasis.     

Retrovirus-mediated transgenic keratin expression in cultured fibroblasts: specific domain functions in keratin stabilization and filament formation.

With retrovirus-mediated gene transfer, we used intact and deleted keratin proteins to investigate the molecular basis of intermediate filament function. Three levels of assembly show a different stringency for the involvement of individual keratin domains: protein accumulation requires the alpha helix domains; stable filament formation additionally requires both N- and C-terminal domains of either one of the two interacting keratins, suggesting that head to tail homotypic interaction is important for effective elongation; and higher order organization of the cytoplasmic network depends on correct type I-type II pairing of keratins. The presence of two distinct interaction sites along potentially different axes may explain the characteristic morphology of keratin intermediate filament networks.     

Response of exocrine pancreas to corticosterone and aldosterone after adrenalectomy

The long-term effect of adrenalectomy (Adx) on the exocrine pancreas was examined in female adult rats. Pancreatic amylase concentration decrease to 50% of the control level starting 10 days after Adx, whereas the levels of trypsinogen and lipase remained unchanged. Replacement studies beginning 24 h after surgery with corticosterone (B, 1 mg/100 g body wt) or aldosterone (ALDO, 8 micrograms/100 g body wt) alone did not prevent the decline in amylase after Adx. However, when both hormones were administered together, pancreatic amylase concentration was maintained at a level similar to that of the control group. Serum corticosterone levels in the rats receiving B alone or B + ALDO were not different, and were comparable to levels found in normal rats. Both ALDO and B, given for 5 days starting 10 days after Adx, were required to restore amylase concentrations toward control values. When spironolactone (SPIRO, 3 mg/100 g body wt), a specific mineralocorticoid receptor blocker was administered bid together with ALDO + B, it blocked the increase in pancreatic amylase seen in ALDO + B treated rats but did not affect the serum corticosterone levels. These results suggest that mineralocorticoids are also involved in modulating the level of amylase in the rat exocrine pancreas.     

Infertility induced in rats by immunization with synthetic peptide segments of a sperm protein.

Three peptide segments (YAL-198, YAL-201 and YAL-212) corresponding to the extracellular domain of a human sperm protein designated as YWK-II antigen were synthesized as multiple antigen peptide (MAP). Male and female rats were immunized with the YWK-II-MAPs and fertility determined. In a group of 12 female rats immunized with YAL-198, seven animals were infertile and two animals were subfertile. When immunized with YAL-201 and YAL-212, 4 and 2 animals were infertile, respectively. In a group of 15 males immunized with YAL-198, 2 animals were infertile and 6 were subfertile. Two animals immunized with YAL-201 were subfertile. All control male and female rats immunized with bovine serum albumin and adjuvant were fertile. Sera obtained from infertile rats immunized with YAL-198 contained higher titers of antibodies compared to those obtained from fertile animals. The present study shows that immunization with synthetic peptide segments of a sperm protein can effectively reduce fertility.