Apical membrane turnover is accelerated near cell-cell contacts in an embryonic epithelium.

During embryogenesis, the killifish Fundulus heteroclitus forms a monolayered tight epithelium called the enveloping layer (EVL). These epithelial cells have been shown to rearrange during epiboly, as they spread to cover the large yolk cell. Membrane remodeling by exocytosis and endocytosis is important in establishing and maintaining the apical-basolateral polarity of many epithelial cells and is a necessary component of epithelial rearrangements, as cells constantly break contacts and reform tight junctions. To study these phenomena in Fundulus heteroclitus embryos, we labeled the apical membranes of EVL cells with fluorescent lectins and lipids and followed membrane dynamics. Apical membrane components were found to be highly immobilized, allowing us to observe localized sites of apical membrane turnover in situ, over the period of several days. We found that apical membrane turnover in the EVL cells of post-epiboly killifish embryos is accelerated at cell-cell contacts, in a peripheral band of apical membrane which closely borders circumferential tight junctions. Moreover, this turnover rate is increased during epiboly, when the cells are actively rearranging. To investigate whether this increased membrane turnover may be related to the mechanical forces experienced by the rearranging EVL cells, post- epiboly embryos, whose EVL cells no longer rearrange, were subjected to mechanical deformation. In these manipulated embryos, apical membrane turnover was accelerated at cell-cell contacts in EVL cells which experienced externally applied mechanical tension. These results suggest that local mechanical tension may modulate regional apical membrane turnover within EVL cells during the process of epiboly.

On the convergent cell movements of gastrulation in Fundulus.

Mainly because of its transparency, the Fundulus gastrula constitutes ideal material for direct study of morphogenetic cell movements in vivo. Marking studies show that deep cells of the germ ring converge toward and enter the embryonic shield, where they undergo extension. Those close to the shield move faster. Analysis of videotapes reveals that all deep cells of the dorsal germ ring move toward the shield. But none moves in a direct line. All meander considerably. Germ ring cells nearer the shield move toward it at a higher net rate than those farther away because they meander less. This suggests that exogenous factors promote their directionality. Cells in the prospective yolk sac adjacent to the germ ring also show net convergence, but they meander more. Directional forces are apparently stronger in the germ ring. Converging deep cells move both by filolamellipodia and, less frequently, by blebs. However, there is very little individual cell movement; all cells are almost always in adhesive contact with other cells in moving cell clusters. Clusters vary constantly in size, continually aggregating with other cells and other clusters and splitting. Filolamellipodial cells show contact inhibition of cell movement. Nevertheless, they move and do so directionally, presumably in part because, as members of cell clusters, much of their movement is passive. They also show intercalation or invasive activity, but, consistent with their contact-inhibiting properties, only when neighboring cells separate and provide free space. Cells moving by blebbing locomotion are non-contact inhibiting and intercalate readily. Cell division continues during convergence. Although this temporarily arrests their movement, the daughter cells soon join in the mass convergent movement.

Fundulus deep cells: directional migration in response to epithelial wounding.

During the normal embryogenesis of the killifish Fundulus heteroclitus deep cells migrate in an apparently random fashion throughout the subepithelial space of the yolk sac. These cells migrate by blebbing locomotion, and individual cells show tendencies for persistence in the directionality of their movement. Immediately after the wounding of the yolk sac epithelium (the enveloping layer), these deep cells reorient and migrate directionally toward the site of wound closure. This directional migration results in the aggregation of a large number of cells at the wound site. The response is both rapid and widespread; cells as far away as 800 micron respond as quickly as those nearby, and by 100 min after wounding up to 90% of the blebbing deep cells within this radius have clustered about the wound site. Then, cells begin to disperse, and by 150 min after wounding, it is almost impossible to tell where the wound had been made. Because of the transparency of the Fundulus yolk sac, this phenomenon can be utilized as a model system for observing details of in vivo directional cell movements. Time-lapse video micrography has revealed that the modes, rates, and overall cell morphologies during locomotion are identical for cells migrating in both unwounded and wounded embryos. What is different in the wounded embryos is that a single directionality is imposed upon a large population of cells, resulting in aggregation. Several aspects of the aggregation phenomenon suggest that a possible attractant originating at the wound site may travel through the subepithelial space by diffusion.

Three cell recognition changes accompany the ingression of sea urchin primary mesenchyme cells.

At gastrulation the primary mesenchyme cells of sea urchin embryos lose contact with the extracellular hyaline layer and with neighboring blastomeres as they pass through the basal lamina and enter the blastocoel. This delamination process was examined using a cell-binding assay to follow changes in affinities between mesenchyme cells and their three substrates: hyalin, early gastrula cells, and basal lamina. Sixteen-cell-stage micromeres (the precursors of primary mesenchyme cells), and mesenchyme cells obtained from mesenchyme-blastula-stage embryos were used in conjunction with micromeres raised in culture to intermediate ages. The micromeres exhibited an affinity for hyalin, but the affinity was lost at the time of mesenchyme ingression in vivo. Similarly, micromeres had an affinity for monolayers of gastrula cells but the older mesenchyme cells lost much of their cell-to-cell affinity. Presumptive ectoderm and endoderm cells tested against the gastrula monolayers showed no decrease in binding over the same time interval. When micromeres and primary mesenchyme cells were tested against basal lamina preparations, there was an increase in affinity that was associated with developmental time. Presumptive ectoderm and endoderm cells showed no change in affinity over the same interval. Binding measurements using isolated basal laminar components identified fibronectin as one molecule for which the wandering primary mesenchyme cells acquired a specific affinity. The data indicate that as the presumptive mesenchyme cells leave the vegetal plate of the embryo they lose affinities for hyalin and for neighboring cells, and gain an affinity for fibronectin associated with the basal lamina and extracellular matrix that lines the blastocoel.

Decision for alcohol detoxication: a method to standardize patient evaluation.

We have presented a tested method of evaluation of the patient with acute alcohol intoxication and/or abstinence syndromes, which we recognize needs further modification and refinement. However, we wish to encourage continued development and standardization of an evaluation instrument that ultimately can become widely accepted. This should reduce the current confusion concerning the diagnosis, extent, and severity of the acute phase of alcohol dependence. If this can be accomplished, the questions (and the controversy) of drug vs non-drug and medical vs nonmedical treatment become moot; rather, a continuum of care will exist which is based on meaningful use and interdisciplinary communication of symptom severity as a foundation for rational treatment approaches.

The subacute phase of alcoholism.

Aggressive intervention in the medical and psychosocial problems of the subacute phase of alcoholism allows the physician to assume a holistic approach to the alcohol-addicted individual and provides a basis for eventual arrest of the chronic disease. A variety of metabolic abnormalities and physiologic disorders require attention. Management of psychologic problems requires the use of rational authority, early psychotherapy, judicious short-term psychopharmacology and use of available community resources.

Diuretic-antidepressant combination in alcoholic depressives--preliminary findings.

Six patients suffering from primary affective illness and habitual excessive drinking, who had not responded to tricyclic antidepressant and/or electroconvulsive therapy, were treated with a combined diuretic-tricyclic (furosemide-amitriptyline) regimen. The patients acted as their own control. Four patients, two unipolars and two bipolars, had complete remissions, while the other two patients with chronic depression showed symptomatic improvement. The implications of sodium retention for the pathogenesis of depression and alcoholism are discussed and a hypothetical positive feedback system which maintains depression and alcoholism in alcoholic depressives is proposed.