Cuticular Membrane Fine Structure of Nicotiana tabacum L. Leaves

The cuticular membrane (CM) ofNicotiana tabacumL., includingthe cellin wall (CW), was examined to gain more informationabout the nature and chemical constitution of its fine structurefor possible inclusion in a model system, as recent literaturequestions its function as a major water permeability barrier.Different preparation techniques were used and the results evaluatedto select a method for future studies on tobacco leaf cuticles.Fixation with OsO₄included in the primary fixative, either asa vapour or in combination with other agents, followed by OsO₄aspost-fixative, gave good contrast of the CM. The lamellar structureof the tobacco cuticle proper (CP) was revealed by contrastingwith uranyl acetate and lead citrate. The fine lamellar structureof the CP was very clearly contrasted when KMnO₄was includedin the primary fixative. This was interpreted as indicatingthe tobacco CP to be polar. The reticulate fibrillar patternof the tobacco cuticular layer (CL) containing polysaccharideswas well contrasted when either OsO₄or paraformaldehyde wereincluded in the primary fixative. Cold fixation with glutaraldehydeand dimethyl sulphoxide and post-fixation with OsO₄revealedelectron-opaque material in the outer cutinized, irregularlyoutlined, region of the CW. These ultrahistochemical reactionsare discussed in relation to the known chemical compositionand possible water permeability of the CM. Cuticular fine structure; cuticular transpiration; Nicotiana tabacumL.     

Scanning electron microscopy of the labia of Baylisascaris procyonis (Nematoda)

The labial organization of adult Baylisascaris procyonis was studied by scanning electron microscopy, and found to be similar for males and females. The apical part of each lip was smooth, and the basal part reticulated. The dorsal lip possessed two dorsolateral double papillae and two internal labial papillae; the two subventral lips each had one ventrolateral double and one externolateral papilla, two internal labial papillae, and an amphid. The small papilla of each double set was dome-shaped and smooth, whereas the large papilla was broad and had a prominent central pore. The externolateral papillae had raised, highly sculptured surfaces with numerous slits and creases present. Amphids resembled those of previously studied nematodes. The internal labial papillae consisted of pits. Denticles arose as a single row from the apical edge of the inner labial surface, were usually evenly spaced, and pyramidal or conoidal in shape. They were typically unicuspid, but bicuspid denticles were occasionally seen. Denticle shape and size varied between specimens and on each specimen. A pit was seen in the cuticle in the central region of the denticular row of all lips. Several of these findings represent new information concerning ascaridoid nematodes.     

Molecular characterization of sylvatic isolates of Trichinella spiralis

Genetic relationships of 20 Trichinella isolates from Indiana wildlife were assessed and compared to Trichinella isolated from an infected swine herd. Trichinella larvae were isolated from coyotes, mink, raccoons, and red foxes. The larvae were maintained and amplified in white mice (ICR) and wild mice (Peromyscus leucopus). Differences in phenotypic characters of sylvatic isolates in the 2 laboratory hosts included an approximately 10-30-fold increase in parasite fecundity in wild mice. DNA for each isolate was extracted from Trichinella larvae and analyzed by dot-blot hybridization using a repetitive DNA probe pBP2 that recognizes DNA sequences specific for swine Trichinella. The probe hybridized only to Trichinella from swine and a single coyote isolate. Restriction endonucleases were used to digest DNA and the resulting fragments were separated by gel electrophoresis. Based on the presence of repetitive DNA sequences in the Trichinella genome, distinctive banding patterns were seen among the isolates. Trichinella isolated from swine had a pattern distinct from all sylvatic isolates except 1 from a coyote. Because this coyote was from the same general locality as the swine Trichinella outbreak, it was concluded that the isolate represents transmission of swine trichinellosis to the wildlife population. Further analysis using the enzyme Cla I identified unique banding patterns for wild isolates, suggesting that the sylvatic group is a genetically heterogeneous complex.     

Echinococcus multilocularis identified in Michigan with additional records from Ohio

Echinococcus multilocularis was identified in a coyote in Indiana in January 1990, prompting an investigation of the distribution and prevalence of the parasite in wild canids in Indiana and surrounding states. In 1990-1991, the parasite was found throughout northern and central Indiana, in northwestern Ohio, and in east-central Illinois. In 1993-1994, 162 wild canids (97 red foxes, 54 coyotes, 11 gray foxes) were collected from Michigan, and an additional 75 (55 red foxes, 7 coyotes, 13 gray foxes) from Ohio, and examined for this parasite. Of these, 15 wild canids (6.3%) were found to be infected with E. multilocularis , including 4 of 97 (4.1%) red foxes from Michigan and 9 of 55 (16.4%) red foxes and 2 of 7 (28.6%) coyotes from Ohio. In Michigan, all infected animals were from the central and southwestern parts of the state. No infected animals were found in northern Michigan, including the Upper Peninsula. In Ohio, infected animals were limited to the northwestern and west-central portions of the state. These findings constitute new state and distribution records for E. multilocularis in the midwestern United States and indicate that the parasite continues to spread eastward and into Michigan from the south.     

Teratogenicity of 3,3-dimethyl-1-phenyltriazene in the rat: histopathologic and ultrastructural alterations

3,3-Dimethyl-1-phenyltriazene (DMPT) is a methylating agent which is teratogenic, carcinogenic, and mutagenic. A single intraperitoneal injection of 30 mg DMPT/kg given to pregnant rats on day 12 of gestation produces malformations with minimal maternal toxicity. Malformations include skeletal deformities such as micrognathism, cleft palate, and digital malformations, as well as central nervous system hypoplasia. The purpose of the present study was to characterize the light and electron microscopic alterations produced by DMPT. Electron microscopy (EM) revealed that at 4 hr postinjection of DMPT, rare cells of the neural tube contained few membrane-bound aggregations of organelles and condensed chromatin; this change was consistent with apoptosis, a type of cell death characterized by morphologic and biochemical alterations distinct from necrosis. At 8 hr postinjection, apoptosis was more prominent in the neural tube and also observed in the mandibular process. At 16 hr postinjection, numerous apoptotic cells were interspersed with unaffected cells that contained phagocytized apoptotic bodies. Light microscopic examination of DMPT-exposed conceptuses showed apoptosis in the neural tube at 24 hr postinjection. Forty-eight hours postinjection, apoptosis, in decreasing order of severity, was observed in the neural tube, craniofacial processes, limb buds, and somites and liver. Apoptosis was absent in all tissues by 72 hr postinjection. Nervous tissues failed to achieve proper histologic organization, but all other tissues appeared microscopically normal from 72 hr postinjection until the end of gestation. There appeared to be some degree of tissue specificity to the effects of DMPT.     

Internal eliminated sequences interrupting the Oxytricha 81 locus: allelic divergence, conservation, conversions, and possible transposon origins

Internal eliminated sequences (IESs) often interrupt ciliate genes in the silent germline nucleus but are exactly excised and eliminated from the developing somatic nucleus from which genes are then expressed. Some long IESs are transposons, supporting the hypothesis that short IESs are ancient transposon relics. In light of that hypothesis and to explore the evolutionary history of a collection of IESs, we have compared various alleles of a particular locus (the 81 locus) of the ciliated protozoa Oxytricha trifallax and O. fallax. Three short IESs that interrupt two genes of the locus are found in alleles from both species, and thus must be relatively ancient, consistent with the hypothesis that short IESs are transposon relics. In contrast, TBE1 transposon interruptions of the locus are allele-specific and probably the results of recent transpositions. These IESs (and the TBE1s) are precisely excised from the DNA of the developing somatic macronucleus. Each IES interrupts a highly conserved sequence. A few nucleotides at the ends of each IES are also conserved, suggesting that they interact critically with IES excision machinery. However, most IES nucleotide positions have evolved at high rates, showing little or no selective constraint for function. Nonetheless, the length of each IES has been maintained (+/- 3 bp). While one IES is approximately 33 bp long, three other IESs have very similar sizes, approximately 70 bp long. Two IESs are surrounded by direct repeats of the sequence TTCTT. No other sequence similarities were found between any of the four IESs. However, the ends of one IES do match the inverted terminal repeat consensus sequence of the "TA" IESs of Paramecium. Three O. trifallax alleles appear to have been recipients in recent conversion events that could have been provoked by double-strand breaks associated with IES ends subsequent to IES transposition. Our findings support the hypothesis that short IESs evolved from ancient transposons that have lost most of their sequences, except those necessary for precise excision during macronuclear development.      

Biodiversity and ecology of epilithic diatoms in the Agnéby River,Ivory Coast

The ecology and taxonomy of the epilithic diatom flora of the Agnéby River, Ivory Coast were studied in 2012. Ten sites were investigated and diatoms were sampled on glass slides immersed for a period of 30 days during the wet and dry seasons. Physico-chemical parameters were measured at each site while sampling diatoms. Five taxa were largely dominant: Planothidium comperei CE Wetzel, N’Guessan and Tison-Rosebery, Eolimna minima (Grunow) Lange-Bertalot, Planothidium piaficum (JR Carter and Denny) CE Wetzel and Ector, Cocconeis schroederi Foged and Cocconeis scutellum var. parva (Grunow in Van Heurck) Cleve. Electrical conductivity, temperature, dissolved oxygen, nitrite and phosphorus were found to influence the distribution of taxa.