Burton E. Vaughan

The movement of H+ and other ions at the onset of photosynthesis in ulva

Abstract A rapid extrusion of Na+ from Ulva, induced by light, also occurs with other cations, as evidenced by 86Rb+ and 85Sr2− tracer studies; anion movement (36Cl−, 35SO42− and [14C] acetate) is not affected by light. The Na− flux has a pH optimum of about pH 8, and has a time constant similar to that for the movement of H+ and HCO3− concerned in photosynthesis. Substitution experiments indicate that the only externally added ion necessary for the short-term light-induced ion movements is HCO3−.

SODIUM TRANSPORT IN ULVA

Abstract The transport of sodium through the marine algae Ulva lobata and Ulva expansa has been studied by a tracer analytical method. Sodium was transported across Ulva at a rate of 0.15% per min in the dark; this rate was slowed by ouabain and increased by formaldehyde. Dinitrophenol, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and ammonium ion had no effect on the dark rate. Light caused a transient, rapid light extrusion of sodium from the algae equal to approximately twice the amount of sodium expected during a two minute dark period. All the inhibitors adversely affected the efflux of sodium due to light. Comparison of the ability of choline and sucrose to elute sodium from Ulva showed that a high portion of the sodium can be released, but only by a process similar to ion exchange.

IRRADIATION EFFECT ON BIOELECTRIC ACTIVITY IN ISOLATED RAT STOMACH

Certain changes occurring in gastrointestinal tissue as a result of irradiation of the animal seem to involve the active transport mechanisms concerned with secretion or absorption of electrolytes (1), and at lower doses these changes occur in the absence of gross disturbances in diffusional transfer fluxes (2). The present study employing bioelectric parameters arose in the attempt to study irradiation effects on these active transport mechanisms by a more general approach than that employing singleand double-label tracers. Although this aim is achieved at the expense of information on the specific source of bioelectric activity, the approach seemed desirable for several reasons: Ion flux measurements can be obtained by in vivo tracer techniques of tested validity, but flux values show an inherently high biological variability (2, 3), unlike potential measurements. Also, similar measurements in isolated rat stomach have been hampered by necessary experimental com-promises related to tissue thickness, which may render a tracer analysis by itself equivocal (4). A more serious problem with flux measurements is that the ions metabolically transported may differ. In frog stomach active chloride secretion is believed to account primarily for the observed bioelectric potential (5), but in rat colon active sodium absorption is believed to account primarily for the observed potential (6), and in rat ileum both active sodium and active chloride movements are reported (7). The existence of a gastric sodium pump has been demonstrated in fetal and term rabbits (8), and in this connection we recently reported the specificity and quantitative dependence of all gastric bioelectric parameters on sodium ion in adult rat stomach maintained in vitro (9, 10). Despite these differences, bioelectric parameters should monitor the relative rate at which ions metabolically pumped precede counter ions moving by other means. The potential would measure the summated effects

FACTORS INFLUENCING THE DELAYED EFFECT OF IRRADIATION ON GASTRIC BIOELECTRIC ACTIVITY IN RAT.

In a previous report, an indirect effect of X-irradiation on gastric bioelectric activity was described in the rat (1). Normal gastric bioelectric activity in rat has been linked to sodium ion movement across the mucosa (2), and in the rabbit, at least, a similar sodium dependence of part of the gastric bioelectric current is known (3). However, little information is available on the factors influencing the irradiation effect on this ion transport system. That other factors may operate in conjunction with irradiation to inhibit electrical activity was suggested by a complex time course leading to the most severe depression in gastric bioelectric activity on the seventh to eighth postirradiation day. Little early effect was detectable, and the 7to 8-day minimum did not correlate well with the time course of other features of irradiation injury in the gastrointestinal tract of rats. Such injury, typical at higher X-ray doses, shows a 3-day critical time for biliary outpouring of sodium (4), and inhibition of normal ileal resorption of sodium is more marked at 67 hours than at earlier times (5). The time of bioelectric changes also seemed unrelated to the gastric epithelial surface renewal rate, which in nonirradiated rats has been estimated at 3 days (6). At similar and lower X-ray doses in the rat, several other kinds of change have been reported in the gastrointestinal tract, showing varying and in some cases overlapping time courses-for example, effects on motility (7, 8), on mucosal and intestinal weights and DNA (9, 10), on glucose oxidation (11), and on tissue cholinesterase (10). These findings suggest that certain of the irradiation effects might represent an end result of interactions at several tissue levels, as for example between extrinsic autonomic nerve tissue and the secretory epithelium, or between dietary factors and the epithelium. In the present report, dose sensitivity

ARTIFICIAL CULTURE OF MARINE SEA WEEDS IN RECIRCULATION AQUARIUM SYSTEMS

Abstract : Ulva as either sporeling or transplant could be cultured for periods of 3 months in closed recirculating aquarium systems. Early development of Ulva lobata sporelings proceeded normally and rapidly under conditions imposed and compared to closely related species, i.e., Ulva pertusa and Ulva lactuca. A modified Haxo-Sweeney enrichment was used, substituting B vitamins and organic phosphate for soil extract. Continuous flow ultra-violet sterilization and microfiltration were provided. pH was maintained automatically at 7.9 plus or minus 0.3, using tris buffer and gaseous CO2. Improved fluorescent illumination for 13-15 hours favored culture of sporelings and summer transplants. Irradiance was confined to the spectrum lying between approximately 380-725 millimicrons and amounted to 3.7 kilolux. From field observations, photoperiod appeared closely correlated to initiation of vegetative growth during early spring. Water temperature seemed to have a greater effect on the rapid maturation of gametes and zoospores. (Author)

X-ray inhibition of gastrin-stimulated acid secretion in relation to mucosal activity of (Na + , K + )-dependent ATPase.

Immediately after a dose of 240 R, whole-body x-irradiation, spontaneous (nonstimulated) acid secretion was inhibited. The inhibition was transient and acid secretion (pH 3.0) resumed promptly afte...

Electrical Conductivity and Cholinergic Activity of the Rat Gastric Mucosa, At 4 and 170 Hours after 600 R X-Irradiation

Gastric mucosas were prepared for incubation from excised whole stomachs of irradiated and nonirradiated rats. Measurements were made of transmucosal potential, direct current conductivity, and acetylcholine (ACh) response. When suitably prepared, the mucosa showed low conductivity values of

The effect of radiation on some functional and metabolic parameters of isolated rat stomach, in comparison to spleen changes.

12\ {\rm mmho}/{\rm cm}^{2}

A FAST‐FLOW SEALED DISK FILTER SYSTEM FOR MARINE AQUARIA

. Conductivity increased markedly after imposing brief electric shock

Biological implications of a marine release of 90Sr.

8\ {\rm mA}/{\rm cm}^{2}