Carcinogenic N-hydroxylaminopurine derivatives do not act as base analog mutagens in Salmonella typhimurium

N-Hydroxylaminopurines are highly mutagenic for growing as well as resting Salmonella typhimurium strain TA100 and to a lesser extent for strain TA98. Aminopurines, under similar conditions, are not mutagenic. N-Methylhydroxylaminopurine, under similar conditions, exhibits only minimal activity. The results are taken to indicate that unlike non-hydroxylated aminopurines, N-hydroxylaminopurines exert their mutagenicity not by acting as base analogs but by direct covalent binding with DNA-guanine.     

Conidiation of Hirsutella thompsonii var. synnematosa in submerged culture

Fourteen monosporal isolates of Hirsutella thompsonii grew vegetatively in various liquid media producing typical phialidic-like conidiophores. Hirsutella thompsonii var. synnematosa from Ivory Coast (HtIC) was the only pathotype which produced true conidia in submerged culture. HtIC began producing conidia after 3 days incubation reaching a peak ranging from 6.8 × 10⁵ to 9.7 × 10⁷ conidia/ml between 6 and 11 days. A concentration of 10 g/liter of corn steep liquor and 0.2% Tween 80 were essential for maximum conidiation. Submerged conidia had a smooth but somewhat rugose conidial walls, whereas aerially formed conidia were distinctly verrucose. Germination of submerged conidia ranged from 5.2 to 12.9% and were virulent causing 32.5% infection to adult citrus rust mites when sprayed on citrus foliage at 1.2 × 10⁹ conidia/ml.     

Correlation of hepatic cytosolic androgen binding proteins with androgen induction of hepatic microsomal ethylmorphine N-demethylase in the rat

Previous reports have demonstrated the presence of moderate to high affinity binding for androgens in the cytosol of livers from male rats. This binding was significantly lower in female rats or in immature rats of either sex. The hepatic androgen binding protein, which sedimented at approx. 4 S on sucrose density gradients, has been called a receptor which mediates the actions of androgens in the liver. The experiments in the present study were designed to evaluate the hepatic androgen binding protein for characteristics which have been attributed to receptors in other tissues and to correlate the presence of androgen binding with androgen induction of hepatic drug metabolism. In the current studies, we have shown that cytosol from the livers of male rats bound [3H]dihydrotestosterone [( 3H]DHT) and translocated this steroid ligand to the nucleus in a time and temperature dependent manner. Cytosol prelabeled with [3H]DHT, when passed over a column of denatured DNA cellulose, eluted in three radioactive peaks. Two of these peaks were absent when cytosol from livers of female or hypophysectomized males was used. In addition, the presence of high concentrations of hepatic androgen binding correlated well with the ability of androgen to induce ethylmorphine N-demethylase, a marker of microsomal cytochrome P-450-dependent drug metabolism. Values for both parameters were higher in males than in either females or hypophysectomized males. Testosterone treatment induced both parameters in ovariectomized females and 17 beta-estradiol repressed both in males. However, testosterone treatment failed to induce hepatic androgen binding in hypophysectomized males and immature males, both of which are also unresponsive to androgen induction of drug metabolism. The results suggest that one or more hepatic cytosolic androgen binding proteins possess several characteristics associated with steroid receptors in reproductive tract tissue. Furthermore, this binding may be implicated as a mediator for the androgen induction of at least one component of hepatic drug metabolism.     

Inhibition of aortic chemoreceptor discharge by pressor response to muscular contraction

We have examined the effect of static contraction of the hindlimb muscles on the discharge of aortic chemoreceptors in chloralose-anesthetized cats. The responses of the chemoreceptors to contraction were dependent on the arterial pressure response to this maneuver. When contraction reflexly evoked a pressor response of at least 20 mmHg, the discharge of 26 chemoreceptors was reduced from control levels by 53% (P less than 0.01). The contraction-induced inhibition of chemoreceptor discharge was prevented by phentolamine, an alpha-adrenergic antagonist that also attenuated the contraction-induced pressor response. In addition, the inhibition evoked by contraction was simulated by injection of phenylephrine and inflation of an aortic balloon, both of which evoked pressor responses. However, when contraction failed to significantly change arterial pressure, the discharge of 20 aortic chemoreceptors was not significantly changed from control levels. We conclude that the reflex pressor response to static contraction inhibits the discharge of aortic chemoreceptors. This inhibition of discharge needs to be considered when interpreting the effects of aortic barodenervation on the cardiovascular responses to exercise.     

Characterization of Certain Gram-Negative Bacteria from Surface Waters

Cultures of gram-negative bacteria with oxidative glucose metabolism were isolated from surface waters by a highly selective technique, and were classified into 11 types. The predominant type, making up about 50% of the isolated cultures, was cytochrome oxidase-positive, produced fluorescent pigment, and failed to grow at 37 C. A similar type, which differed in being cytochrome oxidase-negative, constituted about 10% of the isolates. Both types of bacteria probably were composed of more than one species. A third type, composed of purple-pigmented pseudomonads, made up approximately 30% of the isolated cultures, and probably represented the predominant species. Other bacterial types isolated constituted less than 10% of the cultures examined.     

Bombesin: potential integrative peptide for feeding and satiety

The neuropeptide bombesin (BBS) is examined with regard to possible designation as an integrative peptide. The term integrative peptide has been proposed to distinguish a subset of regulatory peptides. These peptides, distributed in the body and the brain, may function as hormones and neurotransmitters to integrate physiological and psychological functions. It is suggested that BBS may function as a peripheral and central satiety-inducing agent. The specific topics with regard to BBS include: feeding, satiety, and aversion; peripheral and central effects; learning, memory, and reward; route of injection; taste modulation; gastrointestinal activity; neurotransmitter status; mechanism and neuroanatomical site of action; and neural and humoral transmission.     

Spatial Patterns of Entomopathogenic Nematodes in Microcosms: Implications for Laboratory Experiments

Laboratory microcosms were used to: i) measure the effects of soil moisture on survival of Steinernema riobravis and ii) investigate the suitability of using microcosms to study motility and survival of these nematodes. Nematodes recovered from soil contained in petri dishes declined by more than 95% during 7 days, whereas nematodes recovered from the inner surfaces of dishes increased 35-fold. After 7 days in dishes, >20 times as many nematodes were recovered from dish surfaces than from soil. Nematodes exhibited a negative geotropism; greater numbers of nematodes were recovered from the lid surfaces than from the surfaces of dishes. Survivorship of nematodes in soil in plastic centrifuge tubes was somewhat greater than in petri dishes, and fewer nematodes ascended above the soil line in tubes than dishes. Downward migration of nematodes was inversely related to soil column diameter, possibly due to relatively unimpeded movement along container surfaces. An assay was developed by which nematodes were rinsed from the inner surfaces of centrifuge tubes into the soil. The resulting slurry was then processed on Baermann trays to recover motile nematodes. Nematode survival in soil in centrifuge tubes was higher at soil moistures between 2-4% than at lower (0.5-1.0%) and higher (4.0-12.0%) moisture levels. Survival of S. riobravis may be enhanced by quiescence induced by moisture deficits.