John W. Brown

Sea-to-air transfer of surface-active organic compounds by bursting bubbles

The bubble transport of natural surfactant materials from seawater to the air-water interface and to the air is investigated experimentally by a radiotracer test system. We have studied the rates at which four lipid materials of differing molecular structure are scavenged from artificial seawater and ejected into the atmosphere by air bubbles of various size distributions at differing airflow rates and bubbling times. We have found that the bubble transport to the air for all materials studied is linearly proportional to the quantity of material transported to the surface microlayer, and the constant of proportionality appears to be independent of the type of material but is a function of the airflow rate and bubble size. Small bubbles were found generally to be more effective in transporting surface-active organic compounds from seawater to the air.

A model for microbubble scavenging of surface‐active lipid molecules from seawater

We have examined microbubble scavenging of four different types of lipid materials (oleic acid, stearic acid, triolein, and cholesterol) from seawater. These experiments have covered a range of bubble diameters (approximately 200 to 750 μm), bubble Reynolds numbers (approximately 10 to 150), and bubble void fractions (approximately 0.08% to 1.3%). We present here a model which synthesizes the experimental results. The model is based on turbulent diffusion to a single bubble coupled with experimentally determined adsorption kinetics. We have also introduced into the model a factor to account for the dependency of the scavenging observations on bubble void fraction. The introduction of this factor can be anticipated, because the flow hydrodynamics of single bubbles and bubble plumes are quite different. However, these differences are not well enough understood at this time to permit a thorough theoretical explanation of the void fraction factor.

Effects of marine sponge extracts on mitogen-activated protein kinase (MAPK/ERK1,2) activity in SW-13 human adrenal carcinoma cells

Some species of marine sponge have been shown to produce metabolites with endocrine-altering and cell growth regulatory properties. Since cell division and differentiation are controlled, in part, by the mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK/ERK) cascade, we tested extracts (1.0mg/ml) from six shallow water marine species obtained in the Florida Keys for effects on MAPK/ERK(l,2) (sub-variant of EC 2.7.1.37) activity in incubations with SW-13 human adrenal carcinoma cells in culture. In these short-term incubations, extracts from two species, the purple bleeding sponge (Iotrochota birotulata) and the West Indian bath sponge (Spongia barbara), significantly inhibited MAPK/ERK(1,2) activity (to 51 and 44% of control levels, respectively) without altering cell survival. Western blots for phosphorylated and total ERK showed that ERK(2) predominated over ERK(1) by a factor of about 4:1 and that the phosphorylated forms of these isozymes were strongly suppressed by active extracts from both sponges. Another species, the green sponge (Haliclona veridis), whose extract has been shown previously to activate guanylate cyclase and to inhibit adenylate cyclase in a variety of mammalian tissues, was found not to affect MAPK/ERK(1,2) in human adrenal carcinoma cultures but did lyse and kill most of these cultured cells. Extracts from the sheepswool sponge (Hippospongia lachne) and the bleeding sponge (Oligoceras hemorrhages) did not significantly affect either MAPK/ERK(1,2) activity or the survival of attached cells. An extract from the fire sponge (Tedania ignis) did not alter MAPK/ERK(1,2) activity but did modestly decrease cell viability. These studies document for the first time species-specifc effects of marine sponge extracts on the MAPK/ERK(1,2) cascade and on the growth and survival of human adrenal carcinoma cells in culture.

Influence of Ethanol on Fetal Brain Cholinergic Enzyme Activities

Cultured brain cells from rat fetuses of ethanol-treated mothers demonstrated more than 2-fold elevations in choline acetyltransferase (ChAT) activity relative to those of control (saline-exposed) fetal brain cells. When cells from control animals were incubated in vitro for 5 days with 0.1% ethanol, ChAT activity was found to increase more than 4-fold. Brain cells from in utero ethanol-treated animals further exposed to ethanol in vitro for 5 days demonstrated significantly higher ChAT activity compared to cells exposed to ethanol only in vivo. These levels were more than 6 times greater than those of central nervous system cells never exposed to ethanol. Acetylcholinesterase (AChE) activity was significantly elevated (greater than 4-fold) in fetal brain cells when ethanol was present both in vivo and in vitro, but neither treatment alone resulted in any significant changes in AChE. These effects of ethanol on enzymes involved in acetylcholine metabolism may contribute to the different developmental neurologic abnormalities associated with fetal alcohol exposure.

Alterations of fetal brain biogenic amine metabolites by maternal ethanol exposure

1. Pregnant Sprague-Dawley rats treated chronically with ethanol (3 g/kg daily for the last third of pregnancy) had decreased placental weights at birth (ca 23%). 2. Whole fetal brain levels of HVA and 5-HIAA were similarly decreased 32 and 38%, respectively. 3. MHPG levels were also marginally reduced (i.e. 15% decline). 4. In the presence of a potent type A MAO inhibitor (harmaline, 10 mg/kg maternal weight 2 hr before fetal delivery) co-treatment with ethanol was found to result in a 60% elevation of whole fetal brain norepinephrine levels. 5. Other biogenic amines and metabolites were not altered by ethanol treatment.

Corticosteroid effects on cholinergic enzymes in ethanol-treated fetal brain cell cultures

In the presence of ethanol, corticosterone and dexamethasone inhibit choline acetyltransferase and acetylcholinesterase activities in cultured fetal brain cells of the rat. These results suggest that corticosteroids may have an important influence on the activity of cholinergic enzymes in the fetal brain and may antagonize the effects of ethanol in this setting.

Transport of surface-active organic materials from seawater to the air-water interface by an ascending current field

Surface slicks at sea are characterized by the occurence of capillary-wave damping materials at the air-water interface. Physical mechanisms causing such slicks are believed to include internal waves, Langmuir circulations, and other phenomena involving vertical or horizontal transport and compression of surfactants We report the rates of transport and deposition of four naturally occurring surface-active organic materials to the seawater-air interface by an ascending current field. Our results indicate that the susceptibility of these materials to transport by current follows the same relative order as their susceptibility by bubbles (although the latter rate is dramatically greater). The current transport results obtained can be explained by standard surface adsorption kinetics. Our data also indicate that subtle variations in the chemical structure and polarity of different materials may be major determining factors influencing their transport to the sea surface by currents.

Effects of salinity and surface tension on microbubble‐mediated sea‐to‐air transfer of surfactants

A series of experiments were conducted in artificial seawater to study the effects of salinity and surface tension on the bubble-mediated sea-to-air transfer of surfactant materials. The bubble transport of a surfactant tracer (14C-labeled oleic acid) from seawater to the air-water interface and, subsequently, to a 10-cm height above the water surface by bubble bursting was measured. The change in surface tension induced by bubbling was also determined. We have found that the amount of oleic acid transported to the water surface by bubble scavenging increases as the salinity increases. In consequence, so does the quantity of oleic acid ejected into the air. The ratio of the quantity of oleic acid ejected to a height of 10 cm above the water surface to the amount transported to the water surface was constructed. This ratio was found to increase with decreasing surface tension, indicating that the energetics of the bubble bursting process are strongly influenced by the surface tension encountered during bursting.

Biosynthesis of androgens by pheochromocytomas

Homogenates from four adrenal pheochromocytomas converted 4-14C-labeled pregnenolone, 17-hydroxyprogesterone, and dehydroepiandrosterone into androstenedione and testosterone. In addition to these androgens, labeled pregnane substrates were also transformed into corticosteroids, as previously reported, and this conversion occurred in even higher yield. The formation of labeled metabolites of either pathway was greater in homogenates from intraadrenal pheochromocytomas than in those derived from an extraadrenal tumor, but less than in preparations of hyperplastic adrenal cortex. Incubations of subcellular fractions isolated from an adrenal pheochromocytoma showed that the enzyme activities involved in androgen formation from the radioactive substrates studied were associated with the microsomes and required exogenous cofactors. In contrast to adrenocortical tissue, chromaffin cell preparations uniformly failed to convert substrate [4-14C] cholesterol into either androgens or corticosteroids. The data available demonstrate the presence in chromaffin tissue of all of the enzyme activities required for the biosynthesis of androgens and corticosteroids except for those involved in the side-chain scission of cholesterol.

Effects of ultraviolet radiation on the persistence of ocean surface slick microlayer pressure

Coastal seawater was collected on incoming high tides at the Rosenstiel School of Marine & Atmospheric Science. 3.51 of water was transferred to a plexiglass bubble-tank and aerated for 30 sec at a flow rate of 4.0 ml/min per cm2 of water surface area (158 cm2) using glass frits producing bubbles of 203 +/- 61 micrometers diameter. The surface pressure was then determined using calibrated spreading oils of known spreading pressure. After cleaning the seawater surface thoroughly, the water was re-aerated and allowed to stand for 1 to 3 hours in the absence and presence of longwave (365 nm) or shortwave (254 nm) ultraviolet (UV) light, both having an intensity of approximately 300 +/- 25 (mu) W/cm2. In the absence of UV radiation, the surface pressure fell to approximately 64% of its initial value after 1 hour of standing and to approximately 63% of its initial value after 3 hours. Comparable results were obtained in the presence of longwave UV exposure. Under shortwave UV radiation, the decline in surface pressure was substantially accelerated; becoming 55% of the initial value after 1 hour and 35% of the initial value after 3 hours.