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.     

PCNA-dependent DNA polymerase delta from rabbit bone marrow.

Proliferating cell nuclear antigen (PCNA) and PCNA-dependent DNA polymerase delta were partially purified and characterized from rabbit bone marrow. Rabbit DNA polymerase delta sediments at 8.2 S upon glycerol density gradient centrifugation. Similar to calf thymus PCNA-dependent DNA polymerase delta, a 125-123-kDa doublet and 48-kDa polypeptides correlate with DNA polymerase activity. Western blotting of rabbit DNA polymerase delta with polyclonal antibody to calf thymus PCNA-dependent DNA polymerase delta gives the same results as calf thymus delta; the 125-123-kDa doublet is recognized. PCNA-dependent DNA polymerase delta is resistant to inhibition by dideoxynucleotides and is relatively insensitive to inhibition by N2-[p-(n-butyl)phenyl]dGTP. A 3'-->5' exonuclease copurifies with the DNA polymerase. The processivity of DNA polymerase delta alone is very low but greatly increases with the addition of PCNA from rabbit bone marrow or calf thymus. Comparative studies of the original DNA polymerase delta from rabbit bone marrow demonstrate a lack of recognition by antibodies to calf thymus delta and a high degree of processivity in the absence of PCNA. Additionally, the originally described DNA polymerase delta is a single polypeptide of 122 kDa. These features would recategorize the original delta to the epsilon category by recently proposed convention. PCNA-dependent DNA polymerase delta is a relatively minor component of rabbit bone marrow compared to DNA polymerase alpha and PCNA-independent DNA polymerase delta (epsilon), the relative proportions being alpha, 60%; delta, 7%; and epsilon, 30%.     

Selective effect of zinc compared to other divalent metals on L-triiodothyronine binding to rat c-erbA alpha and beta proteins

The effects of zinc and other divalent metals on the [125I]T3 binding to rat c-erbA alpha and beta recombinant proteins were assessed. The addition of ZnCl2 caused a reversible and dose-dependent inhibition of [125I]T3 binding to rc-erbA beta proteins with half maximum inhibition occurring at 50-100 microM, but no significant effect on [125I]T3 binding to rc-erbA alpha under the same assay conditions. Scatchard analysis revealed a decrease in [125I]T3 binding capacity to beta protein without marked change in Kd values in presence of zinc. Moreover, significant inhibitions of [125I]T3 binding to both alpha and beta proteins were observed in the presence of 100 microM of either MnCl2, CdCl2 or CuCl2, but not MgCl2. Thus, the selective effect of zinc compared to other divalent metals to inhibit T3 binding to rc-erbA beta, but not alpha, proteins was documented and suggest a possible regulatory role for zinc in modulating the intracellular action of thyroid hormone.     

我国十省(市)十字花科蔬菜芜菁花叶病毒(TuMV)株系分化研究 Ⅰ.用Green氏方法划分株系

Provvidenti,R.(1980)和Green,S.K.(1985)先后用同一套鉴别寄主谱,研究了美国和我国台湾省的TuMV株系分化情况。本文用Green的方法,对由十省(市)7,982份病样中筛选出的19个TuMV主流分离物,在同一条件下进行了鉴定。结果表明,属于C_1株系的有黑_3分离物;属于C_4株系的有京_2、京_3、冀_2、宁_1(南京)、粤_1和川_1共6个分离物;属于C_5株系的有黑_1、辽_1、京_1、冀_1、沪_1、鲁_1、鲁_2共7个分离物。未检出C_2和C_3株系。黑_2、沪_2、宁_2和秦_1(陕西)共4个性状相近的分离物和冀_3分离物尚不能按Green的标准归类,暂分别定为C_(3-2)和C_6株系。此外,对Green氏方法应用于我国十字花科蔬菜TuMV株系分化研究中存在的问题作了讨论。