Lamb ML et al. (1992) Worm Breeder's Gazette "The Pseudocleavage Furrow is Dispensible for Embryonic Development"

Rose LS, Kemphues KJ, Lamb ML

[Worm Breeder's Gazette, 1992]

In early one-cell embryos, prior to pronuclear migration, a series of anterior cortical contractions resolve into a single incomplete medial furrow called a psuedocleavage furrow. The pseudocleavage furrow disappears as the female pronucleus migrates through it to join the male pronucleus in the posterior. The role of the pseudocleavage is unclear, but because it occurs at a time when cytoplasmic rearrangements are taking place, and because mutations affecting cytoplasmic localization also lead to defects in pseudocleavage, we and others have wondered whether it plays an essential role in cytoplasmic localization. In the course of a mutant hunt we discovered that one maternal effect lethal line produced embryos that failed to undergo a pseudocleavage. The absence of pseudocleavage, however, segregated independently of the maternal effect lethal phenotype. We have now isolated a stable viable line that produces embryos with no pseudocleavage and no other obvious defects. Although we have examined only a few very early embryos from this line by time-lapse video microscopy, we find that in these embryos both the pseudocleavage furrow and the anterior contractions preceding it are absent. To convince ourselves that embryos lacking pseudocleavage were viable, we followed three such embryos from early pronuclear stage to hatching. We conclude, therefore, that the pseudocleavage furrow is dispensable. We are now studying the other events of the first cell cycle (asymmetric microfilament distribution, cytoplasmic streaming and P granule localization) in embryos from this line to determine if any of them are also absent. We will also study the genetic basis for the absence of pseudocleavage furrows in this strain.

Lamb ML et al. (1993) International C. elegans Meeting "The pseudocleavage furrow is dispensible."

Kemphues KJ, Simpson R, Lamb ML

[International C. elegans Meeting, 1993]

Lamb A L et al. (2010) Neuronal Development, Synaptic Function and Behavior, Madison, WI "A Role for daf-16 in the Response to Deprivation of Lethargus Quiescence"

Lamb A L, Raizen D M

[Neuronal Development, Synaptic Function and Behavior, Madison, WI, 2010]

Molting lethargus is a developmentally regulated period of quiescent behavior that has physiological and genetic similarities to sleep, including a homeostatic response to deprivation. We hypothesized that metabolic signaling by the insulin-like signaling pathway would be affected by deprivation of lethargus quiescence. A GFP::DAF-16 fusion protein was used to monitor the subcellular location of DAF-16 in response to forced swimming for 30 minutes. We found an increase in nuclear GFP::DAF-16 after deprivation compared to time-matched controls during L4 lethargus but not during the adult stage. To test in a different fashion whether deprivation causes reduced insulin signaling, we deprived daf-8 mutants of L1 lethargus quiescence. Daf-C mutants have a temperature sensitive period at the end of the L1 stage (Swanson and Riddle, 1981), suggesting that the dauer decision is made during L1 lethargus. Following quiescence deprivation during L1 lethargus but not earlier or later, there was an increase in dauer formation in comparison to control animals. Thus, insulin signaling is reduced by deprivation of lethargus quiescence. To test for a role for daf-16 in the behavioral response to deprivation of lethargus quiescence, we examined the behavior of daf-16 mutants following forced swimming during lethargus. Wild-type animals show elevated response latencies to octanol or to blue light stimulation following deprivation of lethargus quiescence. In contrast, four daf-16 alleles behaved the same after deprivation as they had in the absence of deprivation, indicating a defective homeostatic response to deprivation of lethargus quiescence. Introduction of daf-16 in several tissues rescues this defective homeostatic response, suggesting a non-cell autonomous role for daf-16 in this response. In contrast to daf-16 mutants, daf-2 mutants showed an exaggerated homeostatic response, which was partially daf-16 dependent, to deprivation of lethargus quiescence.

Lamb R et al. (2022) Front Mol Neurosci "PXF-1 promotes synapse development at the neuromuscular junction in Caenorhabditis elegans."

Dhar B, Cherra SJ, Lamb R

[Front Mol Neurosci, 2022]

Guanine nucleotide exchange factors (GEFs) are a family of proteins that modulate small G protein signaling. Mutations in a subfamily of GEFs that act on Rap, known as RapGEFs, have been associated with neurological disorders, and knockout mice display impairments in neuronal activity. However, the precise functions of RapGEFs in the nervous system remain unclear. Here, we have used the Caenorhabditis elegans neuromuscular junction, to investigate how the RapGEF homolog, PXF-1, regulates synaptic function. We found that loss of function mutations in pxf-1 reduced cholinergic activity at the neuromuscular junction. We observed that PXF-1 is expressed in the nervous system, and its expression in neurons is sufficient to promote synaptic activity. In pxf-1 mutant animals, there is a reduction in the levels of synaptic vesicles in cholinergic motor neurons but no change in the overall synapse numbers. In addition to synaptic vesicles proteins, we also found that filamentous actin, a scaffold for nascent synapses, was reduced at developing cholinergic synapses in pxf-1 mutant animals. Our studies indicate that PXF-1 regulates neuromuscular function by promoting the formation of actin filaments to support the development of motor neuron synapses.

Conder GA et al. (1992) J Antibiot (Tokyo) "Anthelmintic activity of dioxapyrrolomycin."

Kuo MS, Nelson SJ, Johnson SS, DiRoma PJ, Marshall VP, Zielinski RJ, Conder GA, Haber CL, Cox DL

[J Antibiot (Tokyo), 1992]

Dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 produced by UC 11065 were evaluated as anthelmintics. Assays used to examine these compounds included effects on the free-living nematode Caenorhabditis elegans, ability to clear target nematodes (Haemonchus contortus and Trichostrongylus colubriformis) from jirds, and clearance of Haemonchus contortus from lambs. A crude extract of UC 11065 containing dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 was active against C. elegans and against H. contortus in the jird. Purified and/or synthetic samples of dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 were tested in the jird model; only dioxapyrrolomycin exhibited appreciable activity against H. contortus (greater than or equal to 90.9% clearance at 0.33 mg/jird), while none of the compounds showed appreciable activity against T. colubriformis. Dioxapyrrolomycin cleared 99.9% of H. contortus from lambs at 12.5 mg/kg. An in vitro migration study using susceptible and closantel-resistant H. contortus showed there is cross-resistance between dioxapyrrolomycin and closantel. Dioxapyrrolomycin appears to be a narrow-spectrum anthelmintic which works through a closantel-like mode-of-action.

Bartley, D. J. et al. (2005) Vet Parasitol "Further characterisation of a triple resistant field isolates of Teladorsagia from a Scottish lowland sheep farm"

Jackson, F., Sargison, N., Bartley, D. J., Jackson, E.

[Vet Parasitol, 2005]

Anthelmintic efficacies against juvenile developing populations of Teladorsagia species that were known to be resistant to anthelmintics from all three broad spectrum families were examined using a controlled efficacy test. Fenbendazole (FBZ), levamisole (LEV), ivermectin (IVM), combinations of these anthelmintics and moxidectin (MOX) were assessed in parasite nave lambs artificially infected with 8,000 third stage larvae (Tci5) and treated orally 8-day post-infection with the compounds at the manufacturers recommended dose rates, FBZ, 5 mg/kg body weight (BW); LEV, 7.5 mg/kg BW; IVM, 0.2 mg/kg BW; MOX (0.2 mg/kg BW). The lambs were slaughtered 14-day post-treatment. The arithmetic mean worm burden reductions resulting from oral treatments with FBZ; IVM; LEV; FBZ+IVM; FBZ+LEV; FBZ, LEV+IVM or MOX were 36%, 82%, 38%, 86%, 60%, 88% and 97%, respectively. The results illustrate that combination treatments showed improved efficacies against the juvenile population compared to individually administered treatments but that these improvements were not wholly effective. Moxidectin was the only treatment that was over 95% effective, though caution should be noted when advising the use of MOX prophylactically since 3% of the infection still survived this treatment. Treatments directed at juvenile stages of Tci5 were less effective, with the exception of IVM, compared to a similar trial using Tci5 where the same treatments were directed against a predominantly adult population. No interaction was detected comparing the timings of treatments and its effectiveness with the exception of IVM (two-way ANOVA, p < 0.05). These findings suggest that, on the whole, the selection processes for anthelmintic resistance (AR) may occur at an early stage of development within the parasites, having severe implications for the early detection of AR.

Chuang HS et al. (2011) Lab Chip "Dielectrophoresis of Caenorhabditis elegans."

Dabbish N, Bau HH, Raizen DM, Lamb A, Chuang HS

[Lab Chip, 2011]

We demonstrate for the first time the dielectrophoretic trapping and manipulation of a whole animal, the nematode Caenorhabditis elegans. We studied the effect of the electric field on the nematode as a function of field intensity and frequency. We identified a range of electric field intensities and frequencies that trap worms without apparent adverse effect on their viability. Worms tethered by dielectrophoresis (DEP) exhibit behavioral responses to blue light, indicating that at least some of the nervous system functions are unimpaired by the electrical field. DEP is useful to dynamically tether nematodes, sort nematodes according to size, and separate dead worms from live ones.

Jasmer DP et al. (1996) Proc Natl Acad Sci U S A "Haemonchus contortus GA1 antigens: related, phospholipase C-sensitive, apical gut membrane proteins encoded as a polyprotein and released from the nematode during infection."

McGuire TC, Jasmer DP, Perryman LE

[Proc Natl Acad Sci U S A, 1996]

It was previously shown that the Haemonchus contortus apical gut surface proteins p46, p52, and p100 induced protective immunity to challenge infections in goats. Here, it is shown that the three proteins are all encoded by a single gene (GA1) and initially expressed in adult parasites as a polyprotein (p100GA1). p46GA1 and p52GA1 are related proteins with 47% sequence identity, including a cysteine-containing region, which appears to confer secondary structure to these proteins, and a region with sequence similarity to bacterial Tolb proteins. GA1 protein expression is regulated during the life cycle at the level of transcript abundance. Only p52GA1 has characteristics of a glycosylinositolphospholipid membrane-anchored protein. However, both p46GA1 and p52GA1 were released from the gut membrane by phosphatidylinositol specific-phospholipase C, suggesting that p46GA1 membrane association depends on interactions with a glycosylinositolphospholipid gut membrane protein. Finally, GA1 proteins occur in abomasal mucus of infected lambs, demonstrating possible presentation to the host immune system during H. contortus infection. The results identify multiple characteristics of the GA1 proteins that should be considered for design of recombinant antigens for vaccine trials and that implicate a series of cellular processes leading to modification and expression of GA1 proteins at the nematode apical gut surface.

Bartley DJ et al. (2004) Vet Parasitol "Characterisation of two triple resistant field isolates of Teladorsagia from Scottish lowland sheep farms."

Sargison N, Jackson F, Jackson E, Bartley DJ

[Vet Parasitol, 2004]

The anthelmintic resistance status of two field isolates derived from farms (farm A and B) located near Edinburgh were examined using both controlled efficacy tests (CET) and faecal egg count reduction tests (FECRT). Efficacies against fenbendazole (FBZ), levamisole (LEV) and ivermectin (IVM) and, for one isolate, against combinations of these anthelmintics and moxidectin were determined in naive lambs, artificially infected with the isolates and treated with the compounds at the manufacturers recommended dose rates. (FBZ, 5mg/kg bodyweight (BW); LEV, 7.5mg/kg BW; IVM, 0.2mg/kg BW; Moxidectin (MOX) 0.2mg/kg BW). In both field isolates, the predominant species found pre-treatment and the only species found post-treatment was Teladorsagia circumcincta. Resistance to FBZ, LEV and IVM was confirmed in CET and FECRT on farm A and to the latter two compounds on farm B, which had a history of benzimidazole resistance and where TBZ resistance was also demonstrated using an egg hatch assay (EHA). For the farm A isolate CET efficacies against FBZ; IVM; LEV; FBZ + IVM; FBZ + LEV; FBZ, LEV + IVM and MOX were 59, 60, 88, 94,93, 92 and 98%, respectively. The CET efficacies for the farm B isolate were 51% and 72% for LEV and IVM, respectively.

Quartey MO et al. (2021) Sci Rep "The A(1-38) peptide is a negative regulator of the A(1-42) peptide implicated in Alzheimer disease progression."

Pennington PR, Heistad RM, Nyarko JNK, Barnes JR, Bolanos MAC, Parsons MP, Knudsen KJ, De Carvalho CE, Leary SC, Mousseau DD, Buttigieg J, Maley JM, Quartey MO

[Sci Rep, 2021]

The pool of -Amyloid (A) length variants detected in preclinical and clinical Alzheimer disease (AD) samples suggests a diversity of roles for A peptides. We examined how a naturally occurring variant, e.g. A(1-38), interacts with the AD-related variant, A(1-42), and the predominant physiological variant, A(1-40). Atomic force microscopy, Thioflavin T fluorescence, circular dichroism, dynamic light scattering, and surface plasmon resonance reveal that A(1-38) interacts differently with A(1-40) and A(1-42) and, in general, A(1-38) interferes with the conversion of A(1-42) to a -sheet-rich aggregate. Functionally, A(1-38) reverses the negative impact of A(1-42) on long-term potentiation in acute hippocampal slices and on membrane conductance in primary neurons, and mitigates an A(1-42) phenotype in Caenorhabditis elegans. A(1-38) also reverses any loss of MTT conversion induced by A(1-40) and A(1-42) in HT-22 hippocampal neurons and APOE 4-positive human fibroblasts, although the combination of A(1-38) and A(1-42) inhibits MTT conversion in APOE 4-negative fibroblasts. A greater ratio of soluble A(1-42)/A(1-38) [and A(1-42)/A(1-40)] in autopsied brain extracts correlates with an earlier age-at-death in males (but not females) with a diagnosis of AD. These results suggest that A(1-38) is capable of physically counteracting, potentially in a sex-dependent manner, the neuropathological effects of the AD-relevant A(1-42).