Epithelial cell production and mucosal morphology in colonic obstruction

The purpose of this study was to determine the temporal course of changes in epithelial cell production and mucosal morphology following ligation of the rat's ascending colon. Control animals were sham ligated with a loose tie of suture, and ligated and control rats were pair red after surgery. Between the 12th and 24th postoperative h, crypt mitotic and [3H] thymidine labelling indices in the obstructed colon increased to a level of 75% greater than values obtained from unoperated rats. This response was accompanied by gains in the proportion of crypt cells engaged in the division cycle. By 72 h, the numbers of cells per total crypt length and crypt circumference were increased by 40 and 47%, respectively. In addition, morphometrical measurements revealed that crypt cell size in the obstructed colon was significantly greater than control value at 72 h. Colonic ligation had relatively minor effects on cell production and villus and crypt cell number in the terminal ileum. Contrasted with the obstructed bowel, proliferative indices distal to the ligature and in the ileum and colon of control rats diminished rapidly after surgery. Thus, limitation of the hyperproliferative response to the intestine immediately proximal to the ligature strongly suggests that the proliferative stimulus in colonic obstruction is local in action.     

ANABOLIC RESPONSES OF EMBRYONIC DORSAL ROOT GANGLIA TO NERVE GROWTH FACTOR, INSULIN, CONCANAVALIN A OR SERUM IN VITRO

—Intact and dissociated dorsal root ganglia from 8-day chick embryos were examined for their ability to incorporate radio-precursors into RNA and protein in unsupplemented medium or in medium supplemented with Nerve Growth Factor, insulin, Concanavalin A, fetal calf serum, or several combinations of such agents. In the absence of any agent, incorporation into RNA and protein declined with time. All four agents maintained or improved the initial incorporation rates, and optimal doses were determined in each case. Different combinations of two agents led to potentiated, full or partially additive, or inhibited effects; in particular, NGF promoted incorporation even in conjunction with insulin (additive) or serum (potentiating). Several differences were noted between the responses of intact and of dissociated ganglia.     

EXTRACELLULAR LYSIS OF THE BLUEGREEN ALGA PHORMIDIUM LURIDUM BY BDELLOVIBRIO BACTERIOVORUS1

When either cells of the bacterium, Bdellovibrio bacteriovorus (Stolp & Starr), strain 15143, or a heat-resistant lytic factor derived from these cells is added to viable cultures of Phormidium luridum var. olivacea Boresch all the algal cells underwent gradual lysis. This effect was obtained with a mean initial bdellovibrio:algal cell ratio of 7.5:1. When P. luridum was mixed with the bdellovibrio cultures the algal chlorophyll content showed an 8-fold decrease. Concomitantly, this interspecies interaction caused, a 75% inhibition of algal photosynthesis after-4 h. Heat, treatment of the B. bacteriovorus culture supernatant fluid increased its ability to inhibit photosynthesis approximately 14%. Light, microscopy showed pale granules and intracellular spaces to form in the P. luridum within 16 h after adding the bdellovibrio lytic factor. Subsequent morphological changes included the development of large intracellular spaces, intercellular spaces, spheroplast formation and finally Complete lysis of the algal cells.     

Limbs vs. Jaws: Can They Be Compared?

Current experimental research on mammalian limb muscle structureand function is compared to that on mammalian jaw muscles. Twomajor areas of comparison are stressed: structural and functional.Comparisons of limbs and jaws are made from the point of viewof the impact of recent studies on simple mechanical modelsof limb/jaw muscle function. Limb muscle structure is comparedto jaw muscles at the level of muscle architecture, muscle histochemicaland motor unit properties, and the organization of motor unitsinto neuromuscular compartments. Such comparisons reveal thatalthough limb muscles and jaw muscles might be organized insimilar ways, fundamental differences exist, both in terms ofmuscle structure and the functional conclusions which have beenbased on studies of muscle structure. The comparisons also demonstratethat much recent evidence from structural studies have had littledirect impact on simple models of muscle function but a muchlarger influence on the assumptions of the models. Comparisonsof limb/jaw muscle function from kinematic and EMG studies,indicate that many masticatory strategies are used by differentmammals but the basic problems of posture and locomotion havebeen met with essentially similar solutions, even among diversemammalian groups. The results of such comparisons demonstratethat both limb and jaw muscle function are sufficiently complexthat new or re-vitalized models are needed if the relationshipbetween structure and function are ever to be understood.     

Reversal or protection by light of the ethidium bromide induced petite mutation in yeast

Summary An intermediate in the ethidium bromide (EB) induced petite mutation pathway may be destabilized by daylight light to cause a reversion to the normal grande phenotype. Starved cells preincubated in the dark for up to 6 h with 100 g/ml EB could be reverted to grandes after one hour of light exposure, whereas similarly treated cells maintained in the dark expressed the petite mutation in more than 80 percent of the population. In addition, the production of petite mutants by EB in buffer could be prevented if cell suspensions were exposed to light immediately upon the addition of EB. Photoreversal of the EB-derived petite mutation in growing cells was less efficient presumably because the availability of an energy source caused a continuation of mutation events beyond the light revertible step to a non-reversible fixation of the mutation. Cells treated with EB in growth media at 4° C were more responsive to light protection and reversal of the mutation. This may be due to the cold inhibition of an enzyme which comes into play beyond the light sensitive step in the mutation pathway.     

ELECTRON MICROSCOPE OBSERVATIONS ON THE INTERACTION OF BDELLOVIBRIO BACTERIOVORUS WITH PHORMIDIUM LURIDUM AND SYNECHOCOCCUS SP. (CYANOPHYCEAE)1

The effects of Bdellovibrio bacteriovorus (Stolp & Starr) culture supernatants on Phormidium luridum var. olivacea Boresch and Synechococcus sp. were examined by transmission electron microscopy. Both normal (nonheat-treated) and heat-treated bdellovibrio supernatant caused the formation of intrathylakoidal vesicles in P. luridum in 24–48 h. This vesiculation increased until 96–129 h when the P. luridum showed loss of the mucopeptide layer in the cell envelope and subsequently lysed. Similar treatment of Synechococcus sp. with the bdellovibrio supernatants showed a different ultrastructural pattern with the apparent dissolution of many of the photosynthetic membranes in the bluegreen cells. Myelin-like membranous configurations were seen in some of these treated cells. The results suggest that an autolytic mechanism in P. luridum and Synechococcus sp. is stimulated by the bdellovibrio secretions.     

A Centrifugation Technique for Preparing Medium-Free Resinous Mounts of Feulgen-Stained Pollen Tubes

Air-dried pollen of Tradescantia paludosa and a colchicine doubled Allium ascalonium-fistulosum interspecific hybrid was sown in culture tubes on an inorganic salt-lactose liquid medium containing 0.02% colchicine. After a 16-20 hr incubation at 22 C, pollen tubes were harvested by centrifugation for 3-5 min at 1100-1400 rev/min and fixed with acetic-alcohol (1:3). Feulgen staining was carried out in the culture tubes with fluid changes made after the centrifugation following each step. Single drops of the final pollen-45% acetic acid suspension were flattened under silicone-treated coverglasses which were removed by the quick freeze technique prior to counterstaining with fast green, dehydration, and mounting in Diaphane or Canada balsam. Medium-free, Feulgen-stained, resin-mounted preparations of well-dispersed pollen tubes with arrested metaphases were obtained.