Cytophotometry of DNA in serial sections]

DNA of leprosy cells in serial paraffine sections stained after Felgen were studied photometrically in scanning microscope SPM with electron computer Wang 720C. Significant differences in extinction values (up to 30--35%) between individual sections within the same series were revealed. Cumulative results of different series were rather uniform. It was concluded that photometric studies of serial sections should be carried out for reliable determination of DNA.     

Interpretation of electron micrographs of single and serial sections

A method of securing serial sections for electron microscopy is described. Serial sections present certain anomalies of interpretation of a nature such that a complete and detailed three-dimensional reconstruction of the sectioned tissue cannot be made. These anomalies are discussed, as well as those which have been encountered in the interpretation of single sections. Observations of the following kinds have been made in an attempt to elucidate the interpretation of single and serial sections: differing methods of mounting adjacent sections, observation of the same section by high-angle stereoscopy, and examination of sections which have been shadowed prior to and subsequent to electron microscopy. It is found that the appearance of sections is independent of the choice of side to be placed against the formvar films. Stereoscopy shows that the appearance of fine structures is strongly dependent upon the direction of the penetrating electron beam with respect to the plane of the structures. Stereoscopy, combined with shadowing, shows quantitatively that extensive sublimation of polymer occurs upon normal exposure in the electron microscope. Observation of sections shadowed prior to electron microscopy indicates that varying amounts of material are removed between sections by the action of microtomy; i.e., it is probable that the sum of the thicknesses of several serial sections is considerably less than the total thickness of material removed from the block. It is believed that this effect, combined with the effect of sublimation, aids in explaining the failure of adjacent sections to exhibit continuity in their detailed structures.     

Chronobiologic organization of sleep

Interrelations between sleep and chronobiology as been studied in isolated experimental situations. A succession of hormonal regulations has been described to explain these mechanisms. Some disruptions of these regulations might be at the beginning of a lot of sleep pathologies (jet lag syndrome, burn out syndrome, insomnia...).     

Ultrastructural reconstruction of Taenia ovis oncospheres from serial sections

The cellular organisation of Taenia ovis oncospheres is interpreted from ultrathin serial sections and transmission electron microscopy following high pressure freezing and freeze-substitution. The surface of a hatched, non-activated T. ovis oncosphere is covered by an oncospheral membrane below which is the tegument bearing microvilli. The basal lamina of the tegument is underlain by broad bands of peripheral somatic musculature. Three pairs of hooks and associated muscles are present in the somatophoric third of the oncosphere. Approximately 19 cells of seven different types were identified which include: (i) a quadri-nucleated syncytium of penetration gland type 1 containing two lateral pairs of cell bodies interconnected by narrow cytoplasmic bridges (PG1); (ii) a quadri-nucleated syncytium of penetration gland type 2 (PG2); (iii) a single-nucleated median mesophoric gland cell; (iv) 10 somatic cells; (v) two germinative cells; (vi) two nerve cells; and (vii) a pair of median somatophoric cells. This study provides a clear understanding of the morphology of T. ovis oncospheres and forms the basis for further investigations into the biology of taeniid oncospheres.     

Chronobiologic Factors in Experimental Stress Ulcer

The available literature on chronobiologic factors in experimental stress ulcer is extremely small and thematically limited. It focuses almost exclusively on circadian rhythms and, within that, on rhythms related to light-dark cycles, activity and body temperature. Among these, only differences in ulcer induction related to circadian activity patterns have been adequately demonstrated. Other circadian patterns and other temporal phase relationships might be profitably explored, including those related to postnatal development. It is also likely that the important relationships between biorhythms and stress ulcer are not limited to ulcer induction. Future studies should address chronobiologic factors in predisposition, severity of illness, the probability of recovery and response to various therapeutic interventions.     

Three-dimensional architecture of the higher plant nucleolonema disclosed on serial ultrathin sections

Summary— The three-dimensional architecture of the nucleolonema of Vicia faba has been studied by applying a silver impregnation technique to serial ultrathin sections. This technique disclosed lateral and transverse segments of the nucleolonema which were heavily impregnated with silver. The lateral profiles of the nucleolonema segments were classified into three main categories; a segment made up of one to several rod-like filaments (type I); a ladder-like segment consisting of two parallel and of transverse filaments (type II); and a last type constructed from two parallel filaments (type III). Tracing of the lateral segments through serial sections has indicated that type I first appears, then either type II or III and finally type I reappears at the corresponding sites on sections. Types II and III remained constant in width, about 1.0 μm, along their longitudinal axes whereas the width of type I was significantly smaller than that of the two former. The lateral filaments of both types II and III showed heterogeneity in width on account of the presence of knobs intermittently distributed along them. The thickness of these knobs was about 0.35 μm. Combining the observations on serial ultrathin sections and the morphometrical data it is very probable that the elementary structure of the nucleolonema is a 0.35-μm thick filament that tightly coils up into a solenoid structure with a thickness of approximately 1.0 μm. This model can explain the appearance of open- and closed-argyrophilic rings in serial sections since transverse segments of the solenoid are expected to show the argyrophilic rings. The elementary filament of the nucleolonema solenoid was sometimes loosened. Judging from our cytochemical data at the electron microscope level, some argyrophilic proteins appear to reside in the axial space of the solenoid but both DNA and RNA were not detectable in this space.