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Biomedical subjects

J R Sauer

Publications and source records attributed to J R Sauer.

At least 55 records · Page 3Linked to original sources
PubMed1991

Effect of ivermectin on the volume of blood ingested by two species of ticks (Acari: Ixodidae) feeding on cattle.

Females of the lone star tick, Amblyomma americanum (L.), and the American dog tick, Dermacentor variabilis (Say), were fed on ivermectin (Ivomec)-treated and untreated bovines to determine the effect of the acaricide on volume of blood ingested and to compare the weight differences between the treatment and control groups at various time intervals after attachment. Adult females from each genus were collected from Bos tarus hosts and subjected to hematin assays on three collection dates to estimate the volume of blood ingested. Before feeding, lone star ticks contained an average of 2.0 microliters of blood and had an average weight of 5.2 mg. Unengorged American dog tick females had an average blood volume of 3.3 microliters and a mean weight of 5.8 mg. Ticks of both species reacted to ivermectin by expressing lower mean weights, and they consumed smaller quantities of blood. Lone star tick females were significantly affected in terms of amount of blood consumed and body weight changes when compared with control ticks. After feeding on treated cattle, lone star tick females contained smaller quantities of blood than pretreatment females, but there were no significant differences observed until day 12 between the control and the treated groups. American dog tick females on treated hosts had measurable quantities of blood that were significantly different among the experimental groups.

Animals↗
PubMed1991

Putative new expression of genes in ixodid tick salivary gland development during feeding.

Poly(A+) mRNA-enriched fractions from salivary glands of partially fed Amblyomma americanum female ticks were translated in vitro with a rabbit reticulocyte translation system. Translated proteins were labeled with [35S]methionine, separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and identified by autoradiography. Thirty major identifiable polypeptides with molecular weights ranging from 14 to 136 kDa were synthesized from mRNA isolated from salivary glands of ticks weighing less than 100 mg. Polypeptides that comigrated at the same molecular weight were translated by mRNA from ticks at a more advanced stage of feeding (more than 300 mg) as were 8 others with molecular weights of 31, 71, 91, 106, 113, 118, and 128 kDa. Results demonstrated that differential gene expression may be stimulated in the developing salivary glands as the tick feeds.

Animals↗
PubMed1989

Protein phosphorylation and control of tick salivary gland function.

Tick salivary glands are controlled by nerves, dopamine being a neurotransmitter at the neuroeffector junction. Dopamine and cyclic AMP (cAMP) stimulate fluid secretion by isolated salivary glands. Dopamine activates an adenylate cyclase to increase intracellular cAMP within the female salivary glands. Phosphoproteins whose levels of phosphate are affected by cAMP-dependent protein kinase have been identified in subcellular fractions. Protein(s) phosphorylated by cAMP appears to activate protein phosphatase in the salivary glands. Another phosphorylation pathway appears to act through protein kinase C because of an ability of phorbol esters (known activators of protein kinase C) to stimulate the phosphorylation of proteins, and an ability of a peptide factor in tick brain to metabolize salivary-gland phosphoinositides, an event that often precedes activation of protein kinase C. Because cAMP modulates brain-factor-stimulated formation of inositol phosphates (products of phosphoinositide breakdown) an interrelationship between the two pathways seems likely. Evidence of regulatory processes, including protein phosphorylation/dephosphorylation reactions, will provide a basis for helping assess the physiological significance of secretory products and the role of the salivary glands in disease transmission.

Animals↗
PubMed1989

Population declines in North American birds that migrate to the neotropics.

Using data from the North American Breeding Bird Survey, we determined that most neotropical migrant bird species that breed in forests of the eastern United States and Canada have recently (1978-1987) declined in abundance after a period of stable or increasing populations. Most permanent residents and temperate-zone migrants did not show a general pattern of decrease during this period. Field data from Mexico were used to classify a subset of the neotropical migrants as using forest or scrub habitats during winter. Population declines during 1978-1987 were significantly greater among the forest-wintering species, while populations of scrub-wintering species increased. The same subset of neotropical migrants also showed overall declines in forest-breeding species, but no significant differences existed between species breeding in forest and scrub habitats. Neotropical migrant species that primarily use forested habitats in either wintering or breeding areas are declining, but a statistically significant association between habitat and population declines was detected only in the tropics.

Animals↗
PubMed1984

Adenosine-3',5'-monophosphate in salivary glands of unfed and feeding female lone star ticks, Amblyomma americanum (L.).

Basal levels of cAMP in salivary glands of female lone star ticks were found to be about 5 pmoles/mg protein during all stages of feeding. Glands stimulated with 10(-5)M dopamine and 10(-5)M dopamine plus theophylline exhibited significant increases in cAMP/mg protein. After stimulation by 10(-5)M dopamine was removed, cAMP decreased faster in glands from slowly feeding ticks (less than 200 mg) than in glands of rapidly feeding ticks (greater than 200 mg).

Adenylyl Cyclases↗
PubMed1983

Immunohistochemical localization of adenosine 3':5'-cyclic monophosphate in female ixodid tick Amblyomma americanum (L.) salivary glands.

Localization of adenosine 3':5'-cyclic monophosphate (cyclic AMP) in alveoli of salivary glands of female Amblyomma americanum (L.) was accomplished with an indirect immunofluorescent technique. Little cyclic AMP fluorescence was seen in Type I alveoli in glands of unfed females but considerable fluorescence was seen in Type I alveoli of glands obtained from females that had fed. The most intense cyclic AMP fluorescence was observed in complex granular cells of Type II and III alveoli in glands of unfed females and glands from females in early stages of tick feeding. In the latter stages of tick feeding an increase in fluorescence in Type III alveoli was observed in cells near the lumen, possibly adluminal interstitial or transformed granular cells.

Animals↗
PubMed1982

A dopamine sensitive adenylate cyclase in the salivary glands of Amblyomma americanum (L.).

1. Enzyme activity, basal or dopamine-stimulated (10 microM), was linear with time to 25 min and with protein concentration to 0.8 mg protein/ml of final assay volume. Activity was maximal between pH 7.0 and 7.5. 2. Mg2+ maximally stimulated basal or dopamine-sensitive adenylate cyclase activity at about 4 mM. 3. Adenylate cyclase had a Km of 0.042 mM for ATP and maximum velocities for basal and dopamine-stimulated activity of 107 and 179 pmol cyclic AMP formed/mg protein per min, respectively. 4. Half-maximal stimulation of the enzyme occurred at about 4.2 x 10(-7) M dopamine with the threshold being less than 10(-9) M. Dopamine increased the Vmax but had no effect on the Km of ATP. 5. Eighty-five to 90% of the adenylate cyclase activity was found in the particulate fraction. 6. Calcium ion produced a marked inhibition of adenylate cyclase activity above 0.04 mM and half-maximal inhibition occurred near 0.1-0.2 mM.

Adenosine Triphosphate↗
PubMed1982

Alveolar structure of salivary glands of the lone star tick, Amblyomma americanum (L.): unfed females.

Alveoli in the salivary glands of unfed Amblyomma americanum (L.) females (postnymphal ticks that had not yet taken a bloodmeal as an adult) were studied. As in other species of female ixodid ticks, the salivary glands consisted of three alveoli, one agranular and two granular. The agranular alveoli were directly attached to the anterior portion of the main salivary duct, consisted of approximately 13 to 14 cells, and were without valves. Six peripheral cells had tortuous, plasma membrane infoldings with closely associated mitochondria, an abundance of lipidlike droplets and relatively flat apical surfaces. A relatively large, clear, "central" cell occupied most of the alveolar midsection. The "central" cell made contact with the alveolar tubular lumen through an opening of a previously undescribed, concentric, myoepithelial-like cell that we call a "constrictor" cell. Granular alveoli consisted of approximately 14 to 16 cells. Type II granular alveoli have two complex granular cells in close proximity to the cuticular alveolar valve, whereas Type III alveoli have only one. Thin epithelial cells separate adjacent granular cells in both alveolar types and only one "cap" cell with myoepithelial-like features lining the alveolar lumen in weblike fashion was present. We hypothesize that the cap cell may play a significant role in helping propel secretions from alveoli to associated ducts.

Animals↗
PubMed1981

Evidence for a D1 dopamine receptor in the salivary glands of Amblyomma americanum (L.).

Adenylate cyclase from the salivary gland of the lone star tick, Amblyomma americanum, is stimulated by several derivatives of phenylethylamine; dopamine, noradrenaline, adrenaline and isoproterenol. Octopamine and iota-DOPA had no effect on basal adenylate cyclase activity. Dopamine had the highest potency and the lowest Ka, 0.4 micron; followed by adrenaline and noradrenaline, 23 micron; and isoproterenol, 0.15mM. When either noradrenaline or adrenaline was added to dopamine, each at its maximally effective concentration, no additional stimulation of gland cyclase activity was noted. Furthermore, adrenaline and noradrenaline together did not equal the potency of dopamine alone. The most potent inhibitors of gland cyclase activity were the dopamine receptor antagonists. The phenothiazine drugs (thioridazine, chlorpromazine, and fluphenazine) were more effective inhibitors of cyclase activity than the butyrophenone drug (haloperidol). The inhibition constants (Ki) for the phenothiazine drugs were: 60nM for thioridazine, 1.9 micron for chlorpromazine and 2.3 micron for fluphenazine. The inhibition of adenylate cyclase activity was found to be specific for the (+) enantiomer of butaclamol, a stereospecific dopamine receptor antagonist. Our findings suggest that the lone star tick salivary gland adenylate cyclase has a D1 type dopamine receptor.

Adenylyl Cyclases↗
PubMed1979

Involvement of calcium and cyclic AMP in controlling ixodid tick salivary fluid secretion.

Catecholamine-stimulated salivary fluid secretion (in vitro) by ixodid ticks is reduced by deletion or lowering the concentration of exogenous bathing medium Ca++. The Ca++ antagonist, verapamil, reversibly inhibits dopamine-stimulated secretion. Ionophore A-23187 is unable to induce glands to secrete. Studies in which labeled and unlabeled Ca++ flux were measured indicate that catecholamines induce release of calcium from intracellular stores during secretion. Cyclic AMP/theophylline-stimulated secretion is inhibited by verapamil, and the exclusion of calcium from the support medium. It is concluded that the primary catecholamine stimulus induces cyclic AMP formation and mobilization of Ca++ (intra- and extracellular). Cyclic AMP and calcium are thought to interact to control secretion within the fluid transporting cells of types II and III alveoli.

Animals↗
PubMed1978

The relationship of phosphodiesterase and cyclic AMP to the process of fluid secretion in the salivary glands of the ixodid tick Amblyomma americanum.

Phosphodiesterase (PDE) activity in the salivary glands of the female. Amblyomma americanum decreased as the tick progressed from a slow to a rapid phase of feeding, while the rate of fluid secretion increased when glands were stimulated with cyclic AMP and theophylline. Dopamine stimulated PDE activity and an 'inhibitory' factor was found in glands obtained from rapidly engorging ticks which decreased PDE activity. These findings are discussed as they relate to the process of fluid secretion by salivary glands of feeding ixodid ticks.

Animals↗