Transmission and Scanning Electron Microscopy of the Evaginative Budding Process in Heliophrya sp. (Ciliata,Suctoria)1

ABSTRACT. A sessile, tentacle-bearing protozoon, Heliophrya sp. (Suctoria, Ciliata), reproduces asexually by evaginative budding to form a ciliated swarmer, which begins metamorphosis to the adult form within 30 min of its release from the parent cell. Morphological features of embryogenesis were investigated using transmission and scanning electron microscopy and found to correspond, with certain exceptions, to the few previous reports concerning evaginative budding in suctorians. Following invagination of a portion of the pellicle to form an embryonic cavity within the parent cell, numerous kinetosomes, apparently formed de novo, organize into rows which surround the embryonic cavity and eventually develop cilia that project into the cavity. When the cavity is complete, its walls are extruded through an opening in the parent cell surface. Parent cell cytoplasm streams into the incipient swarmer, thus supplying it with at least the minimum requirement of all cytoplasmic organelles. The ciliated swarmer remains attached to its parent cell for several minutes before it detaches. A complete pellicle is formed in both parent and swarmer prior to detachment. The numerous mitochondria underlying the parent cell pellicle in the vicinity of the attachment area suggest that cross wall formation is an energy-dependent process.     

The Growth and Carbon Allocation Patterns of White Clover (Trifolium repens L.) Plants of Contrasting Branching Structure

The growth, morphology and carbon allocation patterns of F1progeny white clover (Trifolium repens L.) plants selected foreither low (‘LBF’) or high (‘HBF’) frequencyof stolon branching were compared in two controlled-environmentexperiments. Selections from within both a small-leaved (‘GrasslandsTahora’) and a large-leaved (‘Grasslands Kopu’)clover cultivar were compared, and plants were grown under arelatively lenient defoliation treatment (expt 1) or under threelevels of defoliation seventy (expt 2). Carbon allocation patternswere measured by ¹⁴CO₂ pulse-chase labelling using fully unfoldedleaves on the main (parent) stolon. LBF and HBF displayed consistent differences in the selectedcharacter though, within cultivars, the difference between selectionswas most pronounced for Kopu. The selections developed fundamentallydifferent branching structures resulting from differences inbranching frequency, with total branch weight per plant averaging122 mg for LBF and 399 mg for HBF (mean of both experiments).More C moved from parent stolon leaves to branches in HBF thanin LBF (mean 22.6% vs. 15.1% respectively of the ¹⁴C exportedfrom source leaves). More C also moved to stolon tissue in HBF,but, counterbalancing this and the difference in allocationto branches, less moved to developing leaves and roots on theparent stolon itself compared to LBF. However, the total weightof developing leaves and roots per parent stolon was generallygreater in HBF than in LBF, probably reflecting greater C importby these sinks from the higher number of branches present perplant in the former selection. HBF plants were consistentlylarger at harvest than LBF plants. There were no defoliationtreatment x selection interactions in C allocation patternsin expt 2. The implications of the results for plant performancein grazed pastures are discussed. Branching, carbon translocation, defoliation, growth, morphology, Trifolium repens, white clover     

New Fibrous Long Spacing Form of Collagen

PRECIPITATION of collagen from solution in the presence of chondroitin sulphates (or certain other glycosaminoglycans), followed by dialysis against water, leads to the formation of the fibrous long spacing (FLS) polymorphic form of collagen. Electron microscopy shows this to consist of banded fibrils with a periodicity in the range 1200–2400 Å and a symmetric intraperiod structure, in contrast to the 600–700 Å periodicity and polarized fine structure characteristic of native collagen fibrils. FLS was originally reported by Highberger et al.^1–3 and has been observed in three principal modifications, FLS I, FLS II and FLS III, differing in periodicity and arrangement of dense bands^4–6. This letter reports a new form of FLS, denoted FLS IV.     

Modeling Cretaceous-Tertiary boundary events with extant photosynthetic plankton: effects of impact-related acid rain

Griffis, K. & Chapman, D. J. 1990 10 15: Modeling Cretaceous-Tertiary boundary events with extant photosynthetic plankton: effects of impact-related acid rain. Lethaia , Vol. 23, pp. 379–383. OSIO. ISSN 0024–1164.
An acid rain phenomenon has previously been proposed as one of the consequences of a bolide impact contributing to the extinctions at the Cretaceous-Tertiary boundary. This hypothesis has been tested by observing the growth responses of four organisms under simulated acid rain conditions. Two of these phytoplankton, Ditylum (a diatom) and Thoracosphaera (a dinoflagellate). are genera that persisted through the boundary, while the other two, Coccolithus (a coccolithophorid) and Gonyaulax (a dinoflagellate), are post-boundary genera. Ditylum and Coccolithus survive the acid rain simulation. but with the loss of scales in Coccolithus . The two dinoflagellate are sensitive to acid rain simulations. with Gonyaulax unable to survive beyond seven days. The results indicate that acid rain may have contributed to the Cretaceous-Tertiary boundary extinctions. but that the changes resulting from the acid rain were not as severe as postulated or were short-lived and quickly dissipated. ▭ Acid rain, coccolithophorids. Cretaceous/Tertiary extinctions, diatons, dinoflagellates, phytoplankton .     

Diseases of the heart in a working population; a study of morbidity and mortality in relation to cardiac status and nature of job

A sample consisting of 2,252 persons among 20,199 Los Angeles civil service employees was observed for the occurrence of heart disease. The first examination measured the prevalence. Based upon the diagnosis of 165 cases of heart disease, the prevalence was 73 per 1,000 persons examined. Two reexaminations, at intervals of 12 to 18 months, of persons with normal heart on the first examination were carried out and 52 additional cases were diagnosed. There were also 13 deaths of heart disease in persons first diagnosed as having normal heart, making a total of 65 "new" cases (36.6 per 1,000) during the 30-month period of observation. An annual estimated heart disease incidence of 15 per 1,000 appears reasonable. Based on 89 deaths, the cardiovascular disease death rate was 11 per 1,000 among persons entering the study with normal heart, and 133 per 1,000 persons diagnosed as having heart disease at entry. The ratio of newly diagnosed cases to deaths of heart disease was 4 to 1.Among men diagnosed as having normal heart there was little difference in death rates whether their jobs were physically strenuous or sedentary. Among the men with heart disease, however, the highest death rates are observed among those employed at sedentary jobs and at light exertion. This may, of course, be an indication of the employee's selection of the job rather than the effect of inactivity. The relative usefulness of minifilm x-ray, electrocardiograms and questioning as to history were considered.     

Inter-organ Synergism and the Control of Chlorophyll Accumulation in Sunflower (Helianthus annuus) Cotyledons

Prior to illumination, the embryonic axis of sunflower seedlingsmakes a contribution to the cotyledons which enables them togreen more rapidly when subsequently irradiated with white light.The contributions made to this stimulation by the hypocotylhook, hypocotyl, and roots have been investigated. Greeningin sunflower cotyledons reaches an optimum rate when they are6 d old. The developing embryonic axis not only promotes theattainment of this optimum rate but also aids in the maintenanceof this optimum rate as the cotyledons continue to age. Thisstimulatory effect appears to arise primarily from the rootsand can be duplicated by the exogenous application of benzyladenine. In contrast to previous reports we find that the hypocotyl hookplays no role in the control of greening when present duringillumination.     

Floristic composition and structure of a rainforest area 25yr after logging

In 1949 an area of undisturbed warm temperate rainforest (simple notophyll vine forest) in mid-north coastal New South Wales, Australia was studied in terms of both floristics and structure (Burges A. & Johnston R. D. J. Ecol. 41, 72-83, 1953). During 1955-56, the area in which the transect was located was logged. Over 90% of the upper closed canopy trees adjacent to the creek and on the lower slope and about 35% of canopy trees on the upper slope were removed. The area was reassessed in terms of floristics and structure in 1981. The greatest impact of logging in the study area was structural and largely confined to the flat adjacent to the creek and to the lower slope. With the exception of the remaining gaps covering 6% of the area, structural recovery time is estimated at 140-190 yr. In the gaps structural recovery may take up to 250 yr. All flowering plants, ferns and mosses previously recorded were present 25 yr after logging. The two alien plant species on the site are short lived intolerant species and gradually disappearing with canopy closure of the regenerating forest. The regeneration of the original tree species is healthy and vigorous with most regeneration resulting from the growth of advance regeneration present at the time of logging or the germination of new seedlings. Eleven per cent of the regeneration is attributable to coppicing. The importance of remnant canopy trees as a source of propagules for the trees and epiphytes is recognised. The larger openings are slower to recover as a result of lack of protection from frost. The stability of floristic composition of this area of warm temperate rainforest following heavy logging is demonstrated.     

Out-Patient Peritoneal Lavage Cytology In the Detection of Residual Epithelial Ovarian Cancer

Peritoneal lavage fluid cytology was performed in 87 out-patients with histologically proven epithelial ovarian cancer undergoing primary management. A total of 246 peritoneal lavages were attempted, usually with temporary cannulae (n = 229). From these, 184 samples were obtained, of which 156 (85%) were suitable for cytological analysis. The sensitivity of peritoneal lavage fluid cytology in 67 patients with known residual disease was 57% whereas serum CA 125 levels were elevated in 58 (87%). Pre- and post-treatment peritoneal lavage fluid cytology had prognostic value, but this was less than that of serum CA 125 measurements.