Effect of copper on inhibition by nitrapyrin of growth ofNitrosomonas europaea

Exponentially growing cultures ofNitrosomonas europaea were inhibited by addition of 0.5 g nitrapyrin ml^–1. This inhibition was increased by simultaneous addition of 0.046 g Cu²⁺ ml^–1 as copper sulfate. This contradicts a previous report that copper relieves inhibition of ammonia oxidation by nitrapyrin, which report has formed the basis for hypotheses regarding the mechanism of action of this inhibitor.     

The deposition of bacterial cells from laminar flows onto solid surfaces

In a previous article, the authors proposed a simple model for the rate of removal of bacterial cells from solid surfaces by fluid shear. This Model has been extended to include the deposition of cells from a flowing suspension. The theory is compared to experimentally obtained data for the deposition of Bacillus cereus cells onto the surface of glass capillaries. The effect of a hydrophobic surface, siliconized glass, and the addition of an antifoam agent to the suspension is also investigated.     

Confirmation of Occurrence of Hydroxamate Siderophores in Soil by a Novel Escherichia coli Bioassay

The occurrence of ferrichrome-type hydroxamate siderophores in soil was confirmed. In the presence of the iron-scavenging chelator ethylenediamine[di(o-hydroxyphenylacetic)acid], soil extract stimulated the growth of an Escherichia coli strain possessing the ferrichrome transport protein (TonA) but did not stimulate growth of a strain lacking this protein (TonA⁻). The siderophore concentration in a 1:1 (soil-water) extract was estimated to be approximately 78 nM. Specificity of the assay was supported by the absence of significant differential strain responses to ferric citrate, ferric 2,3-dihydroxybenzoate, enterochelin, ferrioxamine B, coprogen, and triacetylfusigen.     

The basal dendrites of Meynert cells in the striate cortex of the monkey

A study has been made of the basal dendrites of Meynert cells in the striate cortex of the macaque monkey in sections parallel to the pial surface impregnated by the Golgi technique. The longest basal dendrite observed extended up to 0.6 mm and the average length of the longest dendrite on each cell was about 0.28 mm. In general, the dendritic field was in the form of an ellipse with mean major and minor axes of 0.22 mm and 0.11 mm respectively, and encompassing an area of about 0.13 mm2. The directions of the major axes were perpendicular to the lunate sulcus in the sections adjacent to the lunate sulcus, and parallel to the horizontal meridian in sections taken from the region of the representation of the meridian, suggesting that the basal dendritic fields are orientated in parallel with the directions of the ocular dominance bands.     

Evidence for dysfunction in the regulation of cytosolic Ca2+ in excitation-contraction uncoupled dysgenic muscle

In noncontracting, dysgenic murine muscle, excitation is uncoupled from contraction. To test whether the gene lesion is expressed as a defect in the regulation of the intracellular free Ca2+ levels, cultured normal and dysgenic muscle at various stages of development (proliferative myoblasts, early, late, and mature myotubes) were exposed to increasing increments (0.5-mM steps) of extracellular Ca2+ in ionophore A23187-Ca2+-EGTA-buffered media. Normal and dysgenic muscle at all stages (except myoblast) displayed contractures at approximately 500 microM free Ca2+ and higher. Experiments using finer increments of Ca2+ and different ionophore concentrations indicated an external Ca2+ threshold for contracture at 265 microM Ca2+ for early and late myotubes and 47-78 microM for mature normal and dysgenic myotubes. Low extracellular concentrations of calcium (14 microM and 0.76 nM) caused elongation of both normal and dysgenic myotubes. Mature cells were depolarized by exposure to increasing extracellular K+ and monitored by intracellular recording; normal and dysgenic myotubes showed similar reductions in membrane potentials. Depolarization to -35 mV elicited contractures in normal myotubes, but even depolarization to -9 mV in dysgenic cells elicited no response. Thus steady-state depolarization of dysgenic muscle does not cause contractures, which can, however, be elicited by increasing the intracellular free Ca2+. These results offer new evidence for a possible defect in the regulation of Ca2+ levels in dysgenic muscle.     

CYTOLOGICAL AND CHEMICAL VARIATION IN PITYROGRAMMA TRIANGULARIS

The cytology and chemistry of three populations of the species complex Pityrogramma triangularis from Santa Barbara County, California, were studied. The basic chromosome number of these ferns is x = 30, and there are diploids, triploids, and tetraploids. Although gross morphology in the plants is similar, four chemical types are observed when extracts of the external frond pigments are analyzed. Ten of the twelve possible combinations of ploidy level and pigment types have been found. Correlations of spore condition, cytology, and chemistry which indicate either an autotetraploid or allotetraploid derivation of the complex are discussed.     

Australia Antigen and Liver Function Tests Following Infectious Hepatitis—A Study of 111 Patients in Quest of Aids in Blood Donor Screening

An epidemic of infectious hepatitis involving 99 patients and employees of a state mental hospital revealed Australia antigen Au(1) to be absent from the blood of all but one of the subjects when tested at six weeks, three months, nine months and 12 to 18 months after onset of jaundice. The single patient with Au(1) at 12 months had no enzyme abnormality to indicate residual liver disease.If Au(1) is the virus of hepatitis these data would support the concept that persistent or long standing viremia is not a feature of epidemic hepatitis. Moreover, results of this study suggest that the Au(1) test should not be used to establish the absence of a past history of hepatitis in blood donors. These data do not establish the value of the Au(1) test in blood donors with active viremia, but do suggest that of 111 patients with recent hepatitis 1 percent had persistent antigenemia and 4 percent probably had circulating antigen antibody complexes and constituted a potential risk to recipients of their blood. The degree of risk to recipients from transfused blood of post-hepatitis patients without demonstrable Au(1) cannot be assessed.     

The effects of potassium, 5-hydroxytryptamine, adrenocorticotrophin and angiotensin II on the concentration of adenosine 3′:5′-cyclic monophosphate in suspensions of dispersed rat adrenal zona glomerulosa and zona fasciculata cells

Dispersed rat adrenal cells prepared from both the capsule and the decapsulated gland were used to investigate the effects on cyclic AMP accumulation of known stimuli of steroidogenesis [ACTH (adrenocorticotrophin), angiotensin II, K(+) ions and 5-hydroxytryptamine]. Since glomerulosa-cell preparations from capsular strippings are normally contaminated with a proportion of fasciculata cells, cells purified by fractionation on a bovine serum albumin gradient were also used. The results showed that: (1) ACTH and angiotensin II stimulated cyclic AMP accumulation in both fractionated and unfractionated zona fasciculata cells; (2) 5-hydroxytryptamine and an increased extracellular K(+) concentration (from 3.6 to 8.4mm) had no effect on cyclic AMP concentrations in fasciculata cell preparations; (3) the addition of ACTH, angiotensin II, 5-hydroxytryptamine or K(+) to the incubation medium resulted in increased cyclic AMP concentrations in unpurified zona glomerulosa cell preparations; (4) fractionation and hence the virtual elimination of fasciculata contamination, did not affect the response to 5-hydroxytryptamine and increased K(+) concentration. However, the responses to ACTH and angiotensin II were markedly lowered but not abolished. These results strongly suggest a link between cyclic AMP production and steroidogenesis in the zone of the adrenal gland that specifically secretes aldosterone. All four agents used stimulated both steroid output and cyclic AMP accumulation. However, at certain doses of 5-hydroxytryptamine, K(+) and angiotensin II the significant increases in corticosterone output were not accompanied by measurable increases in cyclic AMP accumulation.