Stereological and functional investigations on isolated adrenocortical cells: Zona fasciculata/reticularis cells of chronically ACTH-treated rats

Summary The morphology and function of isolated inner (zona fasciculata/reticularis) adrenocortical cells of rats pretreated with ACTH for 3, 6, 9 or 12 days were investigated. ACTH treatment induced a notable time-dependent enhancement in the steroidogenic capacity (corticosterone production) and growth of inner cells. The volumes of cells, mitochondrial compartment, membrane space [the cellular space occupied by smooth endoplasmic reticulum (SER) membranes] and lipid-droplet compartment, as well as the surface area of mitochondrial cristae and SER tubules, were increased in relation to the duration of ACTH pretreatment, and showed a highly significant positive linear correlation with both basal and stimulated corticosterone production. The acute exposure of isolated cells to ACTH provoked a striking lipid-droplet depletion, the extent of which was linearly and positively correlated with stimulated corticosterone secretion. The hypertrophy of the mitochondrial compartment and SER are interpreted as the morphological counterpart of the enhanced steroidogenic capacity of inner adrenocortical cells, inasmuch as the enzymes of steroid synthesis are located in these two organelles, and it is well known that chronic ACTH exposure stimulates the de novo synthesis of many of them in vivo. The rise in the number of lipid droplets, in which cholesterol is stored, is interpreted as being due to the fact that, under chronic ACTH treatment, the processes leading to cholesterol accumulation in adrenocortical cells (exogenous uptake and endogenous synthesis) exceed those of its utilization in basal steroid secretion. Cholesterol accumulated in lipid droplets as a reserve material may be rapidly utilized after acute ACTH exposure to meet the needs of the enhanced steroidogenic capacity of adrenocortical cells.     

The three-dimensional structure of the zona pellucida in growing and atretic ovarian follicles of the mouse

Summary The present study provides further details on the fine-structural three-dimensional architecture of the zona pellucida (ZP) in growing and atretic follicles of mice by use of ruthenium red in combination with the detergents Triton X100 and saponin. These detergents were used for extraction of the soluble fraction of the zonal proteins in an attempt to expose the structural zonal glycoproteins, which in turn can be viewed as minute three-dimensional networks upon transmission- and scanning electron-microscopic examination. By use of these methods, the ZP of growing follicles appeared to be formed by interconnected filaments which also bind to globular structures building up a three-dimensional lattice. In contrast, the ZP of stage I as well as other (II and III) stages of atretic follicles showed a structure characterized by the presence of closely packed granules connected with short filaments to form a close-mesh reticulum. This structural change of the ZP, which in the present study is also associated with the disappearance of gap junctions within the granulosa and cumulus cell population, might represent one of the early events involved in the onset of atresia. These changes, most probably depending on an altered secretory activity of both oocytes and follicle cells, might lead to a degradation of the ZP network structure and to its subsequent increased density (condensation). All these morphodynamic events eventually contribute to a sequestration of the oocyte in the early stage of atresia.     

Expression of HOX homeogenes in human neuroblastoma cell culture lines

Mammalian genes containing a class-I homeobox (HOX genes) are highly expressed in the embryonic nervous system. As a first step towards the molecular analysis of the role these genes play in neural cells, we studied the expression of four human HOX genes in five neuroblastoma (NB) cell lines - SK-N-BE, CHP-134, IMR-32, SK-N-SH and LAN-1 - during the process of differentiation induced by treatment with retinoic acid (RA). The four genes, HOX1D, 2F, 3E and 4B, located at corresponding positions in the four HOX loci, share a high degree of sequence similarity with the Drosophila Deformed homeotic gene and constitute a homology group, group 10. One of these genes, HOX1D, is not expressed in the cells used, whereas the other three are highly expressed in untreated and RA-induced NB cells, even though the expression pattern in the various lines is slightly different for the three genes. Our analysis reveals a complex and specific expression pattern in these lines, paving the way to an identification of different NB-cell populations by means of specific HOX gene expression schemes. On the other hand, in every line studied, morphological maturation toward a neuronal differentiated phenotype appears to be associated with increased HOX gene expression.     

Binding of flunitrazepam to differentiating neurons cultured in a chemically defined,hormone-supplemented medium

[³H]Flunitrazepam (FNZ) binding to cortical neurons from fetal rat brain was investigated in vitro. The use of a synthetic medium specific for neurons made it possible to plot a developmental curve of³H-FNZ binding in an almost pure neuronal culture. Detectable specific binding was present in vitro at time 0 (that is, the 16th gestational day). A progressive increase of binding, due to an increment in the number of recognition sites, was observed on the subsequent days. The affinity of the specific binding sites to³H-FNZ was enhanced by the addition of exogenous GABA, whereas the density was not affected.     

Importance of some factors on the dimorphism of Candida albicans

The passage between the yeast and mycelial forms of Candida albicans B 311-10 was studied by using the minimal syntehtic medium of Shepherd et al. [19] modified without biotin and with low glucose concentrations. It was observed that biotin, aminoacids and particularly pH are not important factors in the dimorphism of C. albicans. The only factor of notable importance in the passage of yeast form to mycelial form in C. albicans was glucose concentration.     

Deletion 2q31.3→2q33.3: gene dosage effect of ribulose 5-phosphate 3-epimerase

In a new case of interstitial del(2q), measurements of ribulose 5-phosphate 3-epimerase activity suggested that the locus for this enzyme might be localized to the subregion 2q32q33.3.     

Pericentric inversion of chromosome 19 in three families

Summary Pericentric inversion of chromosome 19 has been found in several members of three unrelated families from a restricted geographical region. In one of the families, an additional pericentric inversion of chromosome 9 was observed. Reproductive problems, multiple abortions in two families and a neonatal death in the third, were present. A review of previously described cases is included, and the genetic risk connected with this type of rearrangement is also discussed.     

Effects of membrane potential on Na cotransports in eel intestinal brush-border membrane vesicles: Studies with a fluorescent dye

Summary The Na-dependent transport of a number of organic molecules (d-glucose,l-proline,l-alanine,l-phenylalanine) in brush-border membrane vesicles isolated from the intestine of the eel (Anguilla anguilla) was monitored by recording the fluorescence quenching of the voltage-sensitive cyanine dye 3,3-diethylthiacarbocyanine iodide (DiS-C₂(5)). The experimental approach consisted of: a) generating an inside-negative membrane potential mimicking in vivo conditions: b) measuring the rate of membrane potential decay (i.e., the rate of fluorescence quenching decay) due to Na-neutral substrate cotransport. Rates of membrane potential decay showed saturation on substrate concentration andK _app values (the substrate concentration giving 50% of the maximal rate) were estimated for Na-dependent transport ofd-glucose (0,099mm),l-alanine (0.516mm),l-proline (0.118mm) andl-phenylalanine (2.04mm). The influence of an inside-negative membrane potential on the affinity of the transporter for glucose and for sodium is discussed.     

Successional pathways of Mediterranean evergreen vegetation on Sicily

The Mediterranean evergreen vegetation of Sicily, comprised in the belt of the Quercetea ilicis, occupies a large part of the island. Human intervention (cutting, fire, pasture) has brought about a degradation of the natural vegetation. This study is based on our phytosociological research of the Quercetea ilicis belt on Sicily.

With the ‘habitat comparison’ method, the dynamical relations between the different vegetation units have been defined.

We distinguish the following stages, with reference to their vegetation structure:

• a herbaceous stage formed by steppic vegetation, preceded by various types of nitrophilous-ruderal vegetation on abandoned fields;

• a garrigue stage dominated by half-shrubs;

• a macquis stage with various distinct plant communities, four communities being important in regressive successions, and three in progressive ones;

• a woodland and shrub-woodland stage with three different substages: pre-existent forests, present woodlands, and woodlands which tend towards the final, stable stage of vegetation (potential natural vegetation).

The dynamic relationships both in progressive and regressive successions have been synthesized in a scheme. In this scheme we have shown the main stages of the vegetation in their dynamics and we have constructed different series of vegetation types in two altitudinal belts, which are determined by varying environmental conditions of today.

The results also show that in some cases the progressive series follow different pathways than the regressive series, and the final stage of the progressive series is different from the original vegetation.

     

Phospholipid base exchange enzyme activity in sarcolemmal membranes from the heart of cardiomyopathic hamsters

The activity of phospholipid base exchange enzymes has been evaluated in cardiac sarcolemmal membranes from Syrian Golden hamsters and from a hamster strain (UM-X7.1) characterized by a genetic form of hypertrophic cardiomyopathy. No choline base exchange activity and only a little serine base exchange activity were detected, whereas the ethanolamine base exchange enzyme was found highly active in membranes from both strains. For this reason, the present study is focussed on the ethanolamine base exchange enzyme. The apparent Km for ethanolamine of ethanolamine base exchange enzyme from Syrian Golden membranes and from UM-X7.1 strain membranes are 18 and 32 μM, respectively. The specific activity of the sarcolemmal ethanolamine base exchange enzyme is lower in the UM-X7.1 strain than in Syrian Golden hamsters. The calcium-dependence of the enzyme appears different when the membranes from the two strains are compared. Indeed, after removal of the membrane-bound divalent cations, comparable activities are found in both membrane preparations, whereas, upon addition of Ca²⁺ to the incubation mixtures, the activity of the enzyme is enhanced in the membranes from Syrian Golden strain more than in those from UM-X7.1 strain. The cholesterol content of sarcolemmal membranes is higher in the cardiomyopathic strain than in the Syrian Golden hamsters. A possible relation between changes of the membrane lipid composition and of the ethanolamine base exchange activity is discussed.