Inhibition of microsporidian spore germination

Microsporidia are obligate intracellular parasites that are increasingly recognized as significant causes of disease in AIDS patients. Gordon Leitch, Govinda Visvesvara and Qing He here describe the deployment of the microsporidian spore infection apparatus, the polar filament, and show how this may be a useful site for chemotherapeutic interdiction of the infections caused by these parasites.     

RAPD fingerprints for identification and for taxonomic studies of elite poplar (Populus spp.) clones

RAPD (Random Amplified Polymorphic DNA) fingerprints have recently been used to estimate genetic and taxonomic relationships in plants. In this study RAPD analysis was performed on 32 clones belonging to different species of the genus Populus. Of these, 25 clones are registered in several countries for commercial use and, altogether, cover almost 50% of the worlds cultivated poplars. DNA was prepared from leaves and amplified by PCR using random oligonucleotide primers. Amplification products were separated by agarose-gel electrophoresis to reveal band polymorphisms. Four primers out of the 18 tested, were selected on the basis of the number and frequency of the polymorphisms produced. With these a total of 120 different DNA bands were reproducibly obtained, 92% of which were polymorphic. The polymorphisms were scored and used in band-sharing analyses to identify genetic relationships. With a few but interesting exceptions, these are consistent with the present taxonomy of the genus Populus and with the known predigrees of cultivated poplars. Moreover, the results show that RAPD analysis allows one to discriminate among all tested clones and can, therefore, be recommended as a convenient tool to defend plant breeders rights.     

The genetic characterisation of novel multi-addition doubled haploid lines derived from triticale x wheat hybrids

Two novel 46-chromosome doubled haploid lines, W66 and M17, derived from separate hexaploid triticale x bread wheat crosses, were characterised using cytological and biochemical markers. Both lines were shown to be relatively stable cytologically, over 11 and 8 generations of selfing, respectively. By examining mitotic and meiotic chromosomes, the stabilities of the two lines were shown to be similar with frequencies of 2n=46 in 74.2–85.5% of cells. However, over selfed generations, the rye chromosomes were shown to have lost some of their heterochromatin, which made it difficult to establish their continued presence using cytological techniques, such as C-banding alone. Cytological evidence from pairing studies, C-banding, and fluorescence in-situ hybridization, showed that both M17 and W66 are wheat/rye multi-addition lines with rye chromosome constitutions of 1R+6R, and 1R+4R, respectively. These conclusions were confirmed by isozyme and storage-protein analysis.     

Androgen deficiency and aging in men.

Androgen levels decrease with age in men. Androgen deficiency in men older than 65 years leads to asthenia, a decrease in muscle mass, osteoporosis, and a decrease in sexual activity. Androgen deficiency has been reported to cause changes in mood and cognitive function. The combination of these factors results in impaired quality of life in older men. Androgen replacement therapy in hypogonadal men increases bone and muscle mass, enhances muscle and cardiovascular function, and improves sexual function and general well-being; whether elderly men experience benefits of androgen replacement is not known. These benefits have to be weighed against the possible adverse effects of prostate and cardiovascular diseases. Careful long-term studies are needed to assess the risk-to-reward ratios of androgen or other hormone replacement therapy before treatment strategies similar to estrogen therapy for postmenopausal women are implemented.     

Characterization of Acetylcholine-induced Increases in Cytosolic Free Calcium Concentration in Individual Rat Pancreatic β-cells

The intracellular free Ca²⁺ ion concentration ([Ca²⁺]i) was measured using fura-2 microspec-trofluorimetry in individual rat pancreatic β-cells prepared by enzymatic digestion and fluorescence-activated cell sorting. The mean basal concentration of [Ca²⁺]i in β-cells in the presence of 4.4 mM glucose and 1.8 mM Ca²⁺ was 112±1.6 nM (n=207). The action of acetylcholine (ACh) was concentration-dependent, and raising the concentration resulted in [Ca²⁺]i spikes of increasing amplitude and duration in some, but not all of the β-cells. In addition, the β-cells demonstrated variable sensitivity to ACh. The increases in [Ca²⁺]i were rapid, transient and were blocked by atropine at 10^-6M. A brief exposure to 50 mM K⁺ resulted in a transient increase in [Ca²⁺]i similar to that induced by ACh, but resistant to atropine. A high concentration of ACh (100μL 10^-4M or 10^-3M) induced [Ca²⁺]i oscillations in 11 out of 57 β-cells in the presence of 4.4 mM glucose. Using calcium channel blockers and Ca²⁺ free medium, the source of the increase in [Ca²⁺]i was deduced to be from extracellular spaces. Changing the temperature from 22 to 37°C did not affect the action of ACh on [Ca²⁺]i. These data strongly suggest that ACh exerted a direct action on [Ca²⁺]i in normal rat pancreatic β-cells and support a role for Ca²⁺ as a second messenger in the action of ACh.     

α-Domain of human metallothionein IA can bind to metals in transgenic tobacco plants

We have introduced a genetically marked Dissociation transposable element (Ds ^HPT ) into tomato (Lycopersicon esculentum) by Agrobacterium tumefaciens-mediated transformation. Probes for the flanking regions of the T-DNA and transposed Ds ^HPT elements were obtained with the inverse polymerase chain reaction (IPCR) technique and used in RFLP linkage analyses. The RFLP map location of 11 T-DNAs carrying Ds ^HPT was determined. The T-DNAs are distributed on 7 of the 12 tomato chromosomes. To explore the feasibility of gene tagging strategies in tomato using Ds ^HPT , we examined the genomic distribution of Ds ^HPT receptor sites relative to the location of two different, but very closely linked, T-DNA insertion sites. After crosses with plants expressing Ac transposase, the hygromycin phosphotransferase (HPT) marker on the Ds element and the excision markers β-glucuronidase (GUS) and Basta resistance (BAR) facilitated the identification of plants bearing germinally transposed Ds ^HPT elements. RFLP mapping of 21 transposed Ds ^HPT elements originating from the two different T-DNA insertions revealed distinct patterns of reintegration sites.     

榆耳有性结构及生活史的研究

本文通过电镜扫描、石腊切片及用苏木精染色法和DAPI荧光染色,对榆耳子实体有性结构进行观察,证实榆耳子实体菌盖结构分三层:上表层为毛层,表面着生有排列较密集顶端游离的菌丝,它们相互粘连呈菌丝束;中间层为髓部,由较疏松而相互交织在一起的薄壁菌丝组成,菌丝间充满胶质物质;下表层为子实层,表面起伏不平,呈不规则的疣状突起,上面着生担子和囊状体,担子无隔膜棍棒形,外表有不规则的网状纹饰,其顶部着生4个瓶梗状小梗,每个小梗上着生1个椭圆形或腊肠形担孢子,大小为2.5—3.0×6.0—6.5μm,担孢子表面有不规则的网状纹饰结构。在担子间的囊状体为长圆柱形或圆锥形,表面有较密的不规则的网状纹饰。 榆耳有性生殖为异宗配合。绝大多数担孢子含一个细胞核,很少数担孢子含两个细胞核。孢子萌发为一端萌发,也有少数为两端萌发。初生菌丝单核,不能形成子实体,当两种不同遗传性的交配型的初生菌丝结合后,形成具有锁状联合结构的双核菌丝,并可发育成子实体。榆耳具有典型减数分裂过程,不具有减数分裂后核分裂行为,四个子核分别进入四个担孢子内。 在初生菌丝或次生菌丝上,均可产生间生的或顶生的厚垣孢子。经过温度、光照和紫外线照射的诱发,均未发现有其它类型的无性孢子产生。因此,榆耳菌的生活史和大多数担子