Search PubMed⌕ Search

Biomedical subjects

P P Weinstein

Publications and source records attributed to P P Weinstein.

At least 19 recordsLinked to original sources
PubMed1998

Morphology and differentiation of the coelomocytes of the free-living stages of Nippostrongylus brasiliensis.

With the use of observations on living and fixed and stained larvae of Nippostrongylus brasiliensis reared in charcoal-feces cultures, an integrated view is presented on the morphology and differentiation of the coelomocytes present in the body cavity of the 2 rhabditiform stages and the exsheathed third stage. Four coelomocytes are present in the newly hatched larva arranged linearly from the base of the esophagus to the genital primordium. They lie subventrally, the anterior 2 on the right side of the ventral nerve cord, the posterior 2 on the left side. Data on the growth of these cells and analysis of their fixed site location in the coelom are presented. The coelomocytes are firmly attached to the inner surface of the body wall by filopodia. However, aberrantly positioned coelomocytes suggest the possibility that detachment and migration may occur. A few minute cytoplasmic inclusions are present in the coelomocytes in living newly hatched larvae and may reach approximately 100 or more in each coelomocyte in the third stage. These inclusions exhibit 2 phases of a pigmentation process. They are colorless in the rhabditiform stages, but simultaneous with the initiation of the second molt to form the infective larva, the inclusions rapidly turn a pink to rose hue. A variety of previous experimental data strongly support the interpretation that the pigment represents an extraordinary concentration of vitamin B12 in the coelomocytes obtained by larval feeding on bacterial B12 synthesizers present in the charcoal-feces cultures.

Animals↗
PubMed1996

Vitamin B12 changes in Nippostrongylus brasiliensis in its free-living and parasitic habitats with biochemical implications.

Bacteria in rat feces cultures that had synthesized vitamin B12 were ingested by the free-living stages of Nippostrongylus brasiliensis and the vitamin was concentrated and stored in the third-stage infective filariform larvae. As assayed with Ochromonas malhamensis, the vitamin B12 content of a single filariform larva as well as the concentration expressed as microgram B12 per g filariform larvae reached extraordinarily high levels, the latter being the highest yet recorded for a metazoan organism. The stored B12 content of the filariforms surviving in fecal culture for as long as 104 days remained constant, whereas the B12 concentration rose due to gradual loss of larval body weight. This storage strategy ensured that a high level of the vitamin would be immediately available to the rapidly growing and differentiating worms following infection of the rat. The changing patterns of B12 content and concentration during the parasitic cycle were followed quantitatively and correlated with B12 turnover, increase in worm weight with growth, and incorporation of B12 into the eggs. The possible sources of B12 and its metabolic functions in nematodes are discussed.

Animals↗
PubMed1993

Developmental changes in the respiratory chain of Ascaris mitochondria.

The Ascaris larval respiratory chain, particularly complex II (succinate-ubiquinone oxidoreductase), was characterized in isolated mitochondria. Low-temperature difference spectra showed the presence of substrate-reducible cytochromes aa3 of complex IV, c+c1 and b of complex III (ubiquinol-cytochrome c oxidoreductase) in mitochondria from second-stage larvae (L2 mitochondria). Quinone analysis by high-performance liquid chromatography showed that, unlike adult mitochondria, which contain only rhodoquinone-9, L2 mitochondria contain ubiquinone-9 as a major component. Complex II in L2 mitochondria was kinetically different from that in adult mitochondria. The individual oxidoreductase activities comprising succinate oxidase, and fumarate reductase were determined in mitochondria from L2 larvae, from larvae cultured to later stages, and from adult nematodes. The L2 mitochondria exhibited the highest specific activity of cytochrome c oxidase, indicating that L2 larvae have the most aerobic respiratory chain among the stages studied. The Cybs subunit of complex II in L2 and cultured-larvae mitochondria exhibited different reactivities against anti-adult Cybs antibodies. Taken together, these results indicate that the complex II of larvae is different from its adult counterpart. In parallel with this change in mitochondrial biogenesis, biosynthetic conversion of quinones occurs during development in Ascaris nematodes.

Animals↗
PubMed1993

Growth and development of Brugia pahangi larvae under various in vitro conditions.

In vitro culture methods were utilized to investigate specific nutritional requirements of Brugia pahangi larvae. Infective third-stage larvae (L3) isolated from Aedes aegypti (Liverpool) mosquitoes were cultured in NCTC 135:IMDM (NI) medium plus various types of serum under 5% CO2/air and 5% CO2/N2 atmospheres. Larvae grew, developed, and molted to the fourth stage (L4); however, further growth and differentiation beyond the mid-L4 were minimal. Serum supplementation was necessary to induce molting of B. pahangi L3s. Iron-supplemented calf serum (FeCS) consistently promoted higher percentages of molting than the other 4 types of serum tested. Specific nutritional requirements for B. pahangi larvae were assessed through testing of supplements known to be important for growth of mammalian cells or other parasites in vitro. Addition of various concentrations and combinations of hemoglobin, insulin, transferrin, selenium, albumin, cholesterol, or a cell feeder layer did not improve larval growth, molting, or survival compared to that obtained with FeCS alone. The L4s derived from in vitro culture, when injected intraperitoneally into jirds, developed to sexually mature, microfilarial-producing adults in a normal in vivo time frame. Developing L4s isolated from jirds molted to young adults in vitro in NI medium plus serum.

Animals↗
PubMed1991

Transplantation into jirds as a method of assessing the viability and reproductive integrity of adult Acanthocheilonema viteae from culture.

The reproductive integrity and viability of adult female Acanthocheilonema viteae (syn. Dipetalonema viteae) maintained in culture for relatively long periods were assessed by transplantation into jirds. Worms cultured in chemically defined NI medium for approximately 3-4 wk remained active, but microfilarial release declined to barely detectable levels. Microfilarial production, however, was restored when the worms were transplanted subcutaneously into jirds. When cultured in NI medium beyond 4 wk no restoration of microfilarial production occurred on transplantation, presumably due to irreversible injury to the reproductive system. However, when NI medium was supplemented with fetal bovine serum resumption of microfilarial production occurred in transplanted females that had been in culture for as long as 2 1/2 mo. The addition of serum to NI medium played an important role in maintaining and protecting the functional integrity of the reproductive system.

Animals↗
PubMed1990

The effect of oxygen and carbon dioxide on the development of the free-living stages of Strongyloides ratti in axenic culture.

The effect of oxygen and carbon dioxide concentration on the development of the free-living stages of Strongyloides ratti in axenic culture was examined. Hatching of S. ratti eggs was inhibited at very low oxygen levels. Development of all organisms was inhibited in medium gassed with less than 4% O2 in 0.03% CO2 with the remainder N2. Between 8 and 21% O2 there was no significant difference in the percentage developing directly to filariform larvae, free-living females, or free-living males. Cultures gassed with CO2 concentrations greater than 1% in 21% O2 with the remainder N2 manifested inhibited development to filariform larvae, whereas concentrations between 5 and 7.5% enhanced development to free-living females. There was a positive effect on increasing the CO2 concentration from 0.03% to 5% on development to filariform larvae and male worms at levels of 1% and 2% oxygen in nitrogen, respectively. Direction of development, either directly to the filariform larva or to the free-living female, was influenced by CO2 and O2 concentrations encountered by the egg or the newly hatched larva of the parasitic female in axenic culture. The axenic culture system permits an important experimental approach to the study of factors modulating the differentiation of the free-living stages of Strongyloides.

Animals↗
PubMed1990

Biochemical analyses of secretory and excretory products of adult Dipetalonema viteae in culture.

Radioisotopically labeled glucose and pyruvate were employed to elucidate biochemical mechanisms utilized by the filariid Dipetalonema viteae during cultivation. Adults isolated from amicrofilaremic hamsters were incubated at 37 C in a mixture of NCTC135:IMDM (NI), with either D-[14C-(U)]glucose or [1-14C]pyruvate, under a gas phase of 5% CO2/N2 for 3 days. Labeled organic acids were separated and quantified by ion exchange chromatography. High performance liquid chromatography (HPLC) was used for separation and quantification of the 23 free amino acids in the NI medium. Ion exchange chromatography revealed that lactate was the major glycolytic end product, accounting for 90-97% of the original carbon utilized. Small amounts of radioactivity were recovered in succinate and variably in acetate fractions. HPLC analysis demonstrated that some amino acids increased, some decreased, and some remained at the initial concentration. Alanine exhibited the greatest change, consistently increasing from 2 to 4 times the original concentration. Analyses of purified amino acid peaks revealed radioactivity only in the alanine peak, accounting for 2-4% of the original carbon utilized.

Alanine↗
PubMed1989

Significance of the distribution of 57Co-vitamin B12 in Spirometra mansonoides (Cestoidea) during growth and differentiation in mammalian intermediate and definitive hosts.

The distribution of labeled cyanocobalamin (CN-[57Co]Cbl = [57Co]-vitamin B12) in pleurocercoids and adult tapeworms of Spirometra mansonoides was studied during development in mice 22 days days PI, respectively. Plerocercoid scolices, obtained by cutting away their bodies or by in vitro enzymatic dissolution of the bodies, were pulsed with CN- magnitude of 57Co Cbl for 1h at 37 degrees C and reimplanted subcutaneously into mice or given per os to cats. In regenerated plerocercoids, the highest concentration of magnitude of 57Co Cbl occurred in the scolex and then decreased posteriorly in the newly-formed tissues of the body. Approximately 60% of the total magnitude of 57Co Cbl present remained concentrated in the scolex following body regeneration plerocercoids and adult tapeworms of Spirometra mansonoides was studied during development in mice 22 days post-infection (PI) and in cats 16 days PI, respectively. Plerocercoid scolices, obtained by cutting away their bodies or by in vitro enzymatic dissolution of the bodies, were pulsed with CN-[57Co]Cbl for 1 h at 37 degrees C and reimplanted subcutaneously into mice or given per os to cats. In regenerated plerocercoids, the highest concentration of [57Co]Cbl occurred in the scolex and then decreased posteriorly in the newly-formed tissues of the body. Approximately 60% of the total [57Co]Cbl present remained concentrated in the scolex following body regeneration for up to 109 days PI. This high [57Co]Cbl concentration in the plerocercoid scolex was bound to protein and appears to be maintained by a complex homeostatic mechanism in association with directional transport of [57Co]Cbl to the scolex with ultimate depletion along the length of the body.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Dipetalonema vitae: survival of adult females and microfilarial release in both a chemically defined and serum-supplemented medium.

Studies were conducted on survival and microfilarial release of afult Dipetalonema viteae in culture, using worms of various ages derived from jirds. In chemically defined NI medium (a 1:1 mixture of NCTC 135 and Iscove's modified Dulbecco's medium) under a gas phase of 5% CO2 in nitrogen (pO2 of medium approximately 40 mm Hg), the peak of microfilarial release of several thougsand microfilariae per female per 24 hr occurred at approximately day 10. Thereafter, microfilarial release declined and generally ended about 1 mo after the start of culture. The adult females moved actively for about 50 days or more and survived up to 82 days in NI medium alone. The females in NI medium supplemented with fetal bovine serum showed serpentine movement for approximately 2 mo. Some of the worms survived more than 83 days. The total number of microfilariae deposited in culture by D. viteae increased as adult females grew in size (volume) over time. Microfilarial deposition continued to increase after worms reached maximum size, deposition reaching a plateau between approximately 300 and 400 days of age. Thereafter, microfilarial deposition decreased as females continued to age. Addition of fetal bovine serum to the NI medium increased the number of microfilariae released and extended the period of release.

Animals↗
PubMed1987

Cobalamin and folate metabolism in helminths.

Knowledge about the source, metabolism and functions of cobalamins and folates in helminths remains fragmentary. It is likely that all helminths, whether free-living or parasitic, cannot synthesize cobalamins and folates de novo. Folates, but not cobalamins, appear to be ubiquitous in helminths. Of the parasitic helminths that take up free cobalamins in vitro, all but one species showed no uptake of cobalamin bound to transport proteins, although the latter type of cobalamin by far predominates in vivo. Certain free-living and parasitic helminths in vitro and in vivo took up a variety of folyl and antifolyl monoglutamates, but it is not known whether helminths can take up any folyl polyglutamates. Helminths that have any folate-dependent metabolism appear able to produce polyglutamylated forms of the required tetrahydrofolate coenzymes. Helminths that possess a functional cobalamin-dependent pathway from succinyl CoA to propionyl CoA appear able to form the required adenosylcobalamin coenzyme. Only free-living helminths may possess a cobalamin (and 5-methyltetrahydrofolate)-dependent pathway from homocysteine to methionine. It is likely that all helminths possess the 5,10-methylenetetrahydrofolate-dependent pathway from deoxyuridylate to thymidylate. All helminths appear able to salvage purine bases and nucleosides, but 10-formyltetrahydrofolate-dependent de novo purine ribonucleotide synthesis has been demonstrated unequivocally only in nematodes. The primitive parasitic groups of helminths exhibit cobalamin metabolism, whereas the more highly evolved ones seem to have lost the mechanisms for uptake and the associated biochemical pathways utilizing cobalamins.

Animals↗
PubMed1985

Effects of an azasteroid on growth, development and reproduction of the free-living nematodes Caenorhabditis briggsae and Panagrellus redivivus.

The azasteroid, 25-azacoprostane (ASA-6), was evaluated for its effects on the growth, development and reproduction of the free-living nematodes, Caenorhabditis briggsae and Panagrellus redivivus. The axenic culture medium for either species of nematode consisted of Caenorhabditis briggsae Maintenance Medium (CbMM): formalin-killed Escherichia coli (1:1) with or without the addition of 5 micrograms cholesterol per ml and/or 25 micrograms ASA-6 per ml medium. All cultures also contained 50 micrograms Tween 80 per ml medium. After two generations of growth in sterol-deficient media, both species displayed a decrease in mean length, a decrease in the percent development to the adult stage and an inhibition of reproductive capability. These effects were more apparent in the sterol-deficient medium containing ASA-6. In the presence of cholesterol and ASA-6, growth and reproduction of C. briggsae, but not of P. redivivus, was inhibited after five generations. Morphologic abnormalities of azasteroid-inhibited worms were similar to those shown by worms cultured in sterol-deficient medium. These results suggest that different species of nematodes may exhibit different responses to azasteroid and that sterol utilization and metabolism may vary between nematode species. In addition, the similarities between the known effects of azasteroid inhibition in insects and those presented in this study on nematodes suggest a similar mechanism of action by the inhibitor in both groups of organisms.

Animals↗
PubMed1984

Effects of azasteroids on growth and development of the free-living stages of Nippostrongylus brasiliensis and Nematospiroides dubius.

25-Azasteroids were evaluated for their effects on the growth and development of the free-living stages of Nippostrongylus brasiliensis and Nematospiroides dubius. Increasing the concentration of 25-azasteroids in axenic cultures of either species resulted in a decrease in the percentage and mean length of larvae that developed to the third stage. Morphologic abnormalities of inhibited larvae were similar to those shown by larvae cultured in sterol-deficient medium. Addition of cholesterol to the culture medium reversed the inhibitive effects of azasteroid. Azasteroid completely inhibited growth and development of N. brasiliensis when the only sterol present in the culture medium was sitosterol. These results suggest similar pathways of sterol metabolism and similar mechanisms of action by azasteroids in the nematodes and insects that have been studied.

Animals↗
PubMed1984

In vitro cultivation of Dipetalonema viteae third-stage larvae: effect of the gas phase.

The effect of the gas phase on the in vitro growth and development of Dipetalonema viteae (Nematoda: Filarioidea) third-stage larvae obtained from the tick vector and 3 day infections of jirds was examined. Measurements of the oxygen (pO2) and carbon dioxide (pCO2) tensions and the pH in the medium were made for each gas phase. In cultures gassed with 5% carbon dioxide in nitrogen the pO2 was between 32 and 50 mm Hg, the pCO2 ranged from 25 to 40 mm Hg and the pH was between 7.2 and 7.4. This gas phase resulted in the best growth and development of third-stage larvae to the fourth-stage. Survival and development of larvae were decreased in cultures with oxygen tensions less than 20 mm Hg and greater than 50 mm Hg.

Animals↗