Evidence for hormonal control of diuresis after a blood meal in the mosquito Aedes aegypti

In previous studies we have presented evidence for the role of peptides, isolated from heads of the mosquito Aedes aegypti, in stimulating fluid secretion by isolated Malpighian tubules. In the present study we conducted experiments to investigate whether these peptides are involved in hormone-mediated diuresis after a blood meal. In vivo experiments showed that the head was required to maintain diuresis after the blood meal. Whereas feeding on blood triggered a prompt diuresis in the intact mosquito, subsequent decapitation caused a gradual, not an abrupt, decline in urine excretion rate. Hemolymph collected from mosquitoes fed blood significantly stimulated fluid secretion in vitro by isolated Malpighian tubules, whereas hemolymph from unfed or blood-fed decapitated mosquitoes did not. These results indicate that a diuretic factor was released into the hemolymph after a blood meal. This factor was not present in the hemolymph of decapitated females. We identified the head as a source of diuretic factors. Peptides isolated from a head extract by high-performance liquid chromatography, when injected into the hemocoel of blood-fed decapitated mosquitoes, triggered diuresis in vivo and also stimulated fluid secretion in isolated Malpighian tubules. These studies support the hypothesis that the head is a storage site for diuretic peptides that may be released after a blood meal to control diuresis.     

Interferon-gamma synergizes with tumor necrosis factor and with interleukin 1 and requires the presence of both monokines to induce antitumor cytotoxic activity in macrophages

Small concentrations of recombinant murine interferon-gamma (MuIFN-gamma), recombinant human interleukin 1 (HuIL-1), and recombinant murine tumor necrosis factor (MuTNF), added separately to cultures of thioglycolate-elicited peritoneal macrophages, produced no cytotoxic activity against L5178Y cells, a tumor cell line which is resistant to the direct toxic effects of these cytokines, either alone or in combination. However, small concentrations of MuIFN-gamma when combined with small concentrations of either HuIL-1 or MuTNF activated these macrophages to produce cytotoxic effects against L5178Y cells; small concentrations of HuIL-1 and MuTNF in combination had no macrophage activating activity. Specific antibody to MuTNF blocked the macrophage-activating synergistic effects of MuIFN-gamma + HuIL-1, and specific antibody to HuIL-1 blocked the macrophage-activating activity of MuIFN-gamma + MuTNF, indicating that MuTNF was induced in macrophage cultures treated with MuIFN-gamma + HuIL-1, and that murine IL-1 was induced in macrophage cultures treated with MuIFN-gamma + MuTNF. These results indicate that all three cytokines are required for induction of antitumor cytotoxic activation of macrophages. Experiments with a concentration of MuIFN-gamma which alone could activate macrophages revealed that both MuTNF and murine IL-1 were required for this activation. The demonstration that small concentrations of these three cytokines can act synergistically, but not separately, to activate macrophages indicates the importance of cytokine combinations in immunoregulation and in anti-tumor cell-mediated immune responses.     

Soluble 80-kd fragment of cell-CAM 120/80 disrupts cell-cell adhesion

Calcium-dependent cell adhesion molecules (CAMs) mediate intercellular adhesion in epithelial cells and in preimplantation mammalian embryos. One of these molecules, cell-CAM 120/80, is found on cells as a 120-kd membrane glycoprotein and as a soluble 80-kd species in conditioned culture medium [Damsky et al: Cell 34:455, 1983]. We have purified to homogeneity the soluble 80-kd fragment of cell-CAM 120/80 by using monoclonal antibody affinity chromatography. We have shown that the purified molecule can disrupt cell-cell adhesion in cultured epithelial cells, thus indicating that it is directly involved in the adhesive process. In addition, we have further characterized both the 120-kd cell-associated molecule and its 80-kd fragment, including N-terminal sequence analysis.     

Mosquito juvenile hormone: Identification and bioassay activity

Juvenile hormone III was identified in whole-body extracts of larval and adult Aedes aegypti. No juvenile hormone I or II was detected. The activity of juvenile hormones I, II and III, as well as two juvenile hormone analogues (methoprene, or ZR-515 and ZR-371) was examined in adults, whereas the activity of only the three naturally occurring hormones was studied in larvae. In the larval assay fourth-instar larvae were exposed to the juvenile hormones and their ability to eclose normally was measured. In the adult assay, abdomens were removed shortly after eclosion and the juvenile hormones or analogues were applied topically. Growth of the oöcytes to the resting stage was measured. In larval and adult bioassays juvenile hormone I was 10 × and 25 × more active, respectively, than juvenile hormone III. The bioassay and titre data taken together suggest that juvenile hormone III is the sole physiologically necessary juvenile hormone in Aedes.     

Assembly of storage protein oligomers in the endoplasmic reticulum and processing of the polypeptides in the protein bodies of developing pea cotyledons

Cotyledons of developing pea seeds (pisum sativum L.) were labeled with radioactive amino acids and glucosamine, and extracts were prepared and separated into fractions rich in endoplasmic reticulum (ER) or protein bodies, The time-course of synthesis of the polypeptides of legumin and vicilin and the site of their assembly into protein oligomers were studied using immunoaffinity gels and sucrose density gradients. When cotyledons were pulse-labeled (1-2 h), newly synthesized vicilin was present as a series of polypeptides with M(r) 60,000-65,000, and newly synthesized vicilin was present as series of polypeptides with M(r) 75,000, 70,000, 50,000, and 49,000. These radioactive polypeptides were found primarily in the ER (Chrispeels et al., 1982, J Cell Biol., 93:5- 14). During a subsequent chase period, newly synthesized reserve proteins were initially present in the protein bodies in the above-named polypeptides. Between 1 and 20 h later, radioactive legumin subunits (M(r) 40,000 and 19,000) and smaller vicilin polypeptides (M(r) 34,000, 30,000, 25,000, 18,000, 14,000, 13,000, and 12,000) appeared in the protein bodies. The appearance of these labeled polypeptides in the protein bodies was not the result of a slow transport from the ER (or cytoplasm). Newly synthesized legumin and vicilin polypeptides were assembled into oligomers of 8S and 7S, respectively, in the ER. They appeared in the protein bodies in these oligomeric forms before the appearance of the smaller polypeptides (M(r) less than 49,000). These results indicate that the smaller vicilin polypeptides (M(r) less than 49,000) arise delayed posttranslational processing of some or all of the larger vicilin polypeptides. The precursors of legumin are completely processed in the protein bodies 2-3 h after their synthesis. The processing of the vicilin precursors is much slower (6-20 h) and only a fraction of the precursor molecules are processed. As a result both large (M(r) more than 49,000) and small polypeptides of vicilin accumulate in the protein bodies, whereas legumin accumulates only as polypeptides of M(r) 40,000 and 19,000.     

Cytochemical demonstration of hydrogen peroxide in polymorphonuclear leukocyte phagosomes

Phagocytosis by polymorphonuclear leukocytes (PMN) is accompanied by specific morphological and metabolic events which may result in the killing of internalized micro-organism. Hydrogen peroxide is produced in increased amounts during phagocytosis (17) and in combination with myeloperoxidase and halide ions constitute a potent, microbicidal mechanism (8,9,11). There can be direct iodination of micro-organisms (10), or alternatively, other intermediate reaction products, i.e. chloramines and aldehydes (21), can exert a microbicidal effect. The H2O2-peroxidase-halide system is presumed to operate within the phagocytic vacuole (12,18). Myeloperoxidase, present in the primary granules of PMN, enters the phagocytic vacuole during degranulation (1,4,7), and halide ions are probably derived from the extracellular medium or are present in the PMN (see 11, 18). For the operation of this system in intact cells, the presence of H2O2 in the phagocytic vacuole is necessary, and indeed this has been suggested by the work of several investigators (12, 18, 21). In the present investigation, the diaminobenzidine reaction of Graham and Karnovsky (5), modified to utilize endogenous myeloperoxidase and hydrogen peroxide, has been applied to actively phagocytizing PMN to demonstrate cytochemically the presence of H2O2 in the phagocytic vacuole.     

Mitochondrial mismatch analysis is insensitive to the mutational process

Mismatch distributions are histograms showing the pattern of nucleotide (or restriction) site differences between pairs of individuals in a sample. They can be used to test hypotheses about the history of population size and subdivision (if selective neutrality is assumed) or about selection (if a constant population size is assumed). Previous work has assumed that mutations never strike the same site twice, an assumption that is called the model of infinite sites. Fortunately, the results are surprisingly robust even when this assumption is violated. We show here that (1) confidence regions inferred using the infinite- sites model differ little from those inferred using a model of finite sites with uniform site-specific mutation rates, and (2) even when site- specific mutation rates follow a gamma distribution, confidence regions are little changed until the gamma shape parameter falls well below its plausible range, to roughly 0.01. In addition, we evaluate and reject the proposition that mismatch waves are produced by pooling data from several subdivisions of a structured population.