The role of carbon dioxide in the formation of end-products by Hymenolepis diminuta

The hypothesis that ambient CO₂ levels determine the end-products of energy metabolism excreted by Hymenolepis diminuta was tested by incubating the parasite in a range of CO₂ concentrations and measuring internal concentrations of adenine nucleotides and the excretion of organic acids. The strain of H. diminuta used was found to excrete mainly lactic acid and acetic acid. Succinic acid production was generally less than 5–10% of the total. At high CO₂ concentrations, the rate of excretion of lactic acid decreased while that of succinic acid increased, which conforms with the hypothesis. Acetic acid excretion did not vary significantly over the range of CO₂ concentrations used. Other results did not support the hypothesis. High CO₂ levels reduced the total amounts of acids excreted and the rate of succinic acid excretion was so small as to be ineffective in preventing the accumulation of H⁺ ions. When present in the incubation medium, succinic acid was taken up by H. diminuta. Lactic and acetic acid excretion was always sufficient to limit the accumulation of H⁺ ions. The conditions of incubation were shown not to be responsible for the low rates of succinic acid excreted. Incubation conditions and metabolic end-products were found to affect the rates of excretion of organic acids. There is thus a need, in work of this nature, to regulate and specify experimental conditions and to stipulate the strain of parasite used. The hypothesis was rejected and it was suggested that the energy metabolism of parasitic helminths is adapted to fluctuating O₂ and CO₂ tensions.     

Spontaneous feline sporotrichosis: A fine structural study

Fine structural details of the parasitic yeastlike phase of Sporothrix schenckii contained in biopsy tissue from a naturally-occurring case of disseminated feline sporotrichosis are described and illustrated by electron microscopy. Both free and phagocytosed fungal cells were observed. The fungal cells were contained within an extracellular, electron transparent vacuolar area which was bounded by a limiting membrane of probable host origin. The yeastlike cells were characterized by a conspicuous layer of osmiophilic microfilaments which occurred along the outermost surface of the cell wall. In many yeastlike cells, scattered, membranebound vacuoles containing electron opaque material were observed in the cytoplasm. Asteroid bodies were not observed.     

Preparation and testing of a polyvalent conjugate for direct fluorescent-antibody detection ofLegionella pneumophila

A polyvalent conjugate forLegionella pneumophila, the Legionnaires’ disease bacterium, was prepared by combining monospecific antibodies for the four recognized serogroups ofL. pneumophila. Pure cultures ofL. pneumophila and other bacteria representing 18 genera and 50 species of heterologous organisms were used in evaluating the reagent. A total of 358 specimens from patients suspected of having Legionnaires’ disease also were tested. The results show the practicality and advantages of using a polyvalentL. pneumophila conjugate for screening clinical specimens.     

Pollination ofOpunta basilaris andO. littoralis

The flowers ofOpuntia basilaris andO. littoralis in southern California are visited commonly by beetles(Carpophilus, Trichochrous) and bees (especially anthophorids, megachilids, and halictids), but are pollinated mainly by the bees. This agrees with observations presented in the previous papers in this series for other cactus species in Arizona and Texas. The available evidence indicates that the large, diurnal, cup-shaped flowers in cacti of the American Southwest are primarily bee-pollinated. Our earlier view that theseOpuntia flowers are also pollinated to a significant extent bynitidulid andmelyrid beetles must be modified now in the light of further evidence. Some pollination probably is carried out by small beetles, but it probably represents only a small proportion of the total pollination.Pollination of North American Cacti, III.—See alsoGrant & Grant (1979) andGrant & al. (1979).     

Peromyscus alcohol dehydrogenase: Lack of cross-reacting material in enzyme-negative animals

Two forms of alcohol dehydrogenase (ADH), coded by allelic genes, have been purified to homogeneity from Peromyscus. Monospecific antisera to the purified enzymes have been raised in rabbits. These antisera fail to detect cross-reacting material in the liver of ADH-negative animals on Ouchterlony plates. Immuno-titration of anti-ADH antiserum with ADH in liver extracts from AdhS/AdhS and AdhS/AdhN animals results in identical equivalence points, again suggesting the absence of cross-reacting material coded by the AdhN allele. Over a wide range of anti-ADH antiserum dilutions, radiolabeled protein was not immunoprecipitable from liver extracts of AdhN/AdhN animals. These immunochemical tests, in conjunction with previous studies, suggest that the AdhN allele in Peromyscus does not produce inactive polypeptide in normal levels that bears immunological determinants similar to those of the fast and slow ADH isozymes.     

The location of highly repetitious DNA in the somatic chromosomes of Drosophila melanogaster

In situ hybridization of Drosophila melanogaster somatic chromosomes has been used to demonstrate the near exact correspondence between the location of highly repetitious DNA and classically defined constitutive heterochromatin. The Y chromosome, in particular, is heavily labeled even by cRNA transcribed from female (XX) DNA templates (i.e., DNA from female Drosophila with 2 Xs and 2 sets of autosomes). This observation confirms earlier reports that the Y chromosome contains repeated DNA sequences that are shared by other chromosomes. In grain counting experiments the Y chromosome shows significantly heavier label than any other chromosome when hybridized with cRNA from XY DNA templates (i.e., DNA from male Drosophila with 1 X and 1 Y plus 2 sets of autosomes). However, the preferential labeling of the Y is abolished if the cRNA is derived from XX DNA. We interpret these results as indicating the presence of a class of Y chromosome specific repeated DNA in D. melanogaster. The relative inefficiency of the X chromosome in binding cRNA from XY and XYY DNA templates, coupled with its ability to bind XX derived cRNA, may also indicate the presence of an X chromosome specific repeated DNA.     

Growth and characterization of human skin epithelial cell cultures

Summary In 129 of 140 attempts, human skin cells were successfully cultured on the dermal collagen bed of sterile, dead pigskin. Diploid epithelial cells grew selectively on the collagen bed; fibroblasts grew on the glass surfaces of the culture dishes. The cultures could be subdivided physically up to six times at a 1:2 split ratio, but at least 24 to 48 cell generations were produced over the months the cells could be carried. Much of the cell multiplication resulted in maturation into distinct basal, squamous, granular, and keratinized cell layers. The cultured cells were considered epithelial because of their shape, possession of intercellular bridges, desmosomes and tonofibrils, and because they formed maturating epithelium in vitro and upon transplantation back to the original human donor. As the cells grew they digested the pigskin collagen, thus producing clear zones that could be used to monitor and quantitate cell growth. Multiplication of epithelial cells, rather than migration, was indicated by mitotic figures in colchicine-treated cultures and by DNA synthesis. Expert technical assistance was provided by Nancy Allen (cell culture); William Towler (electron microscopy); James Malone, Nona Scaife, and Joy M. Nicolet (cytogenetics); R. Thomas Campbell and Dorothy Sarver (photography); and V. L. Angerstein, Susan Ekker, and Arnater Yarbrough (histology). This work was supported by The United Fund Cancer Society of Summit County, the Greater Cleveland Associated Foundation (grant no. 3G3490X1), the National Institute of General Medical Services (grant no. 1 R01 GM 21929-01), and the Charles E. Merrill Trust.     

An evaluation of the micronuclei test using triethylenemelamine,trimethylphosphate, hycanthone and niridazole

To determine the feasibility of the micronuclie procedure for cytogenetic studies, a comparatively weak chromosome breaking agent, trimethylphosphate (TMP) and the potent alkylating agent, triethylenemelamine (TEM) were evaluated. The procedure followed was that of Matter and Schmid with the following modifications: (a) direct flushing of bone marrow with 0.2 ml calf fetal serum, (b) air drying slides for a period of only 1 h, and (c) the use of pH 6.0 phosphate buffer to dilute both the Wright and Giemsa stains.With this technique a dose-response curve was generated for both TMP and TEM, using mice as the experimental animal. With TMP, a doubling over background was found when a concentration of 0.5 g/kg per day for five days was administered. To establish a statistically significant doubling dose over the control, a minimum of five animals must be used woth 2000 polychromatic cells being analyzed per animal.Of the two antischistosomal agents tested, hycanthone yielded an increase of 20-fold in the number of mircronuclei over control at 40 mg/kg administered i.p. for five days, while with niridazole no increase in micronuclei at several concentrations tested both by single and multiple injection was found.The results obtained with these compounds compare favorably woth what has been reported for the standard in vivo metaphase analysis.     

Arabinogalactan proteins and arabinan pectins abound in the specialized matrices surrounding female gametes of the fern Ceratopteris richardii

Planta - Both male and female gametes of archegoniates are highly specialized cells surrounded by an extraprotoplasmic matrix rich in AGPs, which are speculated to facilitate development and gamete...     

The Excitotoxin Quinolinic Acid Induces Tau Phosphorylation in Human Neurons

Some of the tryptophan catabolites produced through the kynurenine pathway (KP), and more particularly the excitotoxin quinolinic acid (QA), are likely to play a role in the pathogenesis of Alzheimer''s disease (AD). We have previously shown that the KP is over activated in AD brain and that QA accumulates in amyloid plaques and within dystrophic neurons. We hypothesized that QA in pathophysiological concentrations affects tau phosphorylation. Using immunohistochemistry, we found that QA is co-localized with hyperphosphorylated tau (HPT) within cortical neurons in AD brain. We then investigated in vitro the effects of QA at various pathophysiological concentrations on tau phosphorylation in primary cultures of human neurons. Using western blot, we found that QA treatment increased the phosphorylation of tau at serine 199/202, threonine 231 and serine 396/404 in a dose dependent manner. Increased accumulation of phosphorylated tau was also confirmed by immunocytochemistry. This increase in tau phosphorylation was paralleled by a substantial decrease in the total protein phosphatase activity. A substantial decrease in PP2A expression and modest decrease in PP1 expression were observed in neuronal cultures treated with QA. These data clearly demonstrate that QA can induce tau phosphorylation at residues present in the PHF in the AD brain. To induce tau phosphorylation, QA appears to act through NMDA receptor activation similar to other agonists, glutamate and NMDA. The QA effect was abrogated by the NMDA receptor antagonist memantine. Using PCR arrays, we found that QA significantly induces 10 genes in human neurons all known to be associated with AD pathology. Of these 10 genes, 6 belong to pathways involved in tau phosphorylation and 4 of them in neuroprotection. Altogether these results indicate a likely role of QA in the AD pathology through promotion of tau phosphorylation. Understanding the mechanism of the neurotoxic effects of QA is essential in developing novel therapeutic strategies for AD.