Vitrification of carnation in vitro: Changes in cell wall mechanical properties,cellulose and lignin content

Vitrification of internodes of carnation was brought about by culturing in liquid medium. Cell wall extensibility of these internodes was kinetically followed in comparison to that of normal plants using the constant stress method. Liquid culture induced increased immediate and total deformation capacities of the walls from the second day. Measurements indicated that these deformation capacities involved plastic properties rather than elastic ones. These changes were paralleled by decreased relative levels of cellulose and lignin.     

Conserved sequences flank variable tandem repeats in two alleles of the G surface protein of Paramecium primaurelia

We describe the cloning and the sequencing of a macronuclear DNA fragment of Paramecium primaurelia, strain 168, encompassing the entire coding region of the 168G surface protein gene. Comparison of its nucleotide and its deduced amino acid sequences to those of the allelic surface protein 156G, previously described, reveals the rigorous conservation of a highly periodic structure. This structure is based on the presence of 37 periods of about 75 residues, each period containing eight cysteine residues. The differences between the two proteins are clustered in the central part of the sequence, which is itself made of quasi-identical tandem repeats. We propose that these repeats constitute the domain exposed on the surface of the cells and present the characteristics of concerted evolution.     

Thyroid fine needle aspiration: the morphological features on ThinPrep® slide preparations. Eighty cases with histological control

This study had several purposes: to define cytomorphological features of thyroid cells that might be modified by alcohol fixation; to optimize May-Grünwald–Giemsa (MGG) staining on ThinPrep^® (TP; Cytyc Inc., Bexborough, MA, USA) slides and to compare the diagnostic accuracy of slides prepared by a liquid-based method with those obtained by conventional technique. This study included 120 cases of ultrasound-guided fine needle aspiration (FNA) of the thyroid and 55 FNAs performed on surgically resected thyroid specimens. Histological control was available in 80 cases. In the first group of 120 FNAs, a split-sample technique was used for the TP. Three screenings were performed: first, an individual screening of the conventional smears (CS) and of the TP, a second screening to compare cells observed on the TP with the histological control and a third screening to assess the previously defined diagnostic criteria. Twenty-seven TP cases (22%) were considered unsatisfactory for diagnosis compared with 10 in CS (8%). The high rate of unsatisfactory cases with TP is likely to be due to the use of the split-sample technique. The sensitivity was 94% for CS and 81% for TP. The specificity was 67% and 60% for CS and TP, respectively. Two occult papillary carcinomas were missed by both methods. As for the MGG staining, the modified technique used for TP resulted in the same quality as the standard procedure. Conversely, TP did however induce uncommon morphological features. In this study, sensitivity and specificity levels are higher for CS than for TP; the difference may be explained by the fact that the methanol fixative used for TP induces some cytological alterations, especially in oncocytic tumours and lymphocytic thyroïditis.     

Gradient of Growth, Spontaneous Changes in Growth Rate and Response to Auxin of Excised Hypocotyl Segments of Phaseolus aureus

Spontaneous growth was studied in excised mung bean (Phaseolus aureus Roxb.) hypocotyl segments. Measurements were made with a growth-recording apparatus using displacement transducers on single 5- to 6-millimeter samples excised from the growth zone immediately below the hook.     

Pattern of sea bass oocyte development after ovarian stimulation by LHRHa

The cyclic pattern of oocyte development in the sea bass, Dicentrarchus labrax L., was studied after induction of spawning by two injections, 24 h apart, of a luteinizing hormone releasing-hormone analog (LHRHa) administered at the end of vitellogenesis. The first difference in the developmental stage of the ovary and in the size-frequency distribution of oocytes between the LHRHa treated group and the control group, was detected 32 h after the first injection, the LHRHa group showing a higher proportion of the 900 μm diameter oocyte class (maturing oocytes) ( P <0.01). At 48 h LHRHa-treated females showed an increase in the 1000 and 1100 μm classes (maturing oocyte and ovulated eggs) ( P <0.01) and at 72 h these females exhibited a bimodal pattern, reaching the highest proportions in the 1100 (27.4%) and the 600 (14.7%) μm classes (ovulated eggs and advanced vitellogenic oocytes, respectively). Bimodal distributions were present in 80% of the LHRHa-treated females. Once oocyte final maturation was triggered by LHRHa the time needed for ovulation was about 48 h and the interval between consecutive ovulations and spawnings seemed to be 48–72 h.     

Life cycle and production ofCladopelma virescens (Mg.) (Diptera: Chironomidae) in Lake Banyoles (NE Spain)

Life cycles and annual production of the chironomidCladopelma virescens are studied at two different depths in the sublittoral (5m) and the profundal (12m) zones of the karstic Lake Banyoles (NE Spain). Two generations were completed by this chironomid in the two sampling stations studied. Production was estimated with two different methods: increment-summation (IS) and size-frequency (SF). In the IS method the smoothed survivorship curves were estimated because of the absence of the smaller instars in the samples. The mean annual production varied from 44 to 70 mg m^–2y^–1 in the deeper station and from 215 to 270 mg m^–2y^–1 in the shallower, depending on whether the size-frequency or increment summation method was used. Annual P/B varied between 5.07 and 5.67, and 6.14 and 4.11 respectively. Due to the many assumptions to be made with the IS method, we suggest the SF method in this case, because the values given by the two methods are of the same order of magnitude.     

Gene expression during tuber development in potato plants

Potato tubers are modified stems that have differentiated into storage organs. Factors such as day-length, nitrogen supply, and levels of the phytohormones cytokinin and gibberellic acid, are known to control tuberization. Morphological changes during tuber initiation are accompanied by the accumulation of a characteristic set of proteins, thought to be involved in N-storage (i.e. patatin) or defense against microbial or insect attack (i.e. proteinase inhibitor II). Additionally, deposition of large amounts of starch occurs during tuber formation, which is paralleled by an increase in sucrose synthase and other enzymes involved in starch biosynthesis (i.e. ADP-glucose pyrophosphorylase, starch synthases, and branching enzyme). Potential controlling mechanisms for genes expressed during tuberization are discussed.     

Cell surface molecules and fibronectin-mediated cell adhesion: effect of proteolytic digestion of membrane proteins

Proteases have been used as a tool to investigate the role of surface molecules in fibronectin-mediated cell adhesion. Proteolytic digestion of membrane-proteins by pronase (1 mg/ml for 20 min at 37 degrees C) completely inhibited adhesion of baby hamster kidney (BHK) fibroblasts on fibronectin-coated plastic dishes. Various degrees of inhibition were also obtained after treatment with proteinase K, chymotrypsin, papain, subtilopeptidase A, and thermolysin. Protein synthesis was required to restore the adhesive properties of pronase-treated cells, showing the protein nature of the molecules involved in adhesion to fibronectin. A peculiar feature of these proteins was their resistance to cleavage by trypsin. After prolonged trypsin treatment (1 mg/ml for 20 min at 37 degrees C), cells adhered and spread on fibronectin-coated dishes, even when protein synthesis was inhibited by 4 microM cycloheximide. Under these conditions only three glycoproteins (gp) of molecular weight 130,000, 120,000, and 80,000 were left on the cell surface. These were precipitated by a rabbit antiserum against BHK cells that also inhibited adhesion of trypsin-treated cells. gp120 and gp80 were left at the cell surface after mild pronase digestion (0.2 mg/ml for 20 min at 37 degrees C), under conditions not affecting adhesion. These data suggest that these glycoproteins may be involved in fibronectin-mediated cell adhesion in some yet unknown way.     

Studies on the outer surface of normal and RSV-transformed BHK fibroblast plasma membrane

The probe trinitrobenzene sulphonate (TNBS) was used to selectively label the cell surface of normal and Rous sarcoma virus-transformed BHK fibroblasts. A five-fold increase in the number of TNBS-binding groups exposed on the outer membrane surface after neoplastic transformation was measured. The extra trinitrophenyl (TNP) groups bound by transformed cells were mostly removable by mild trypsinization and no differences were found between the amount of TNP bound by phospholipids in both normal and transformed cells. SDS-acrylamide patterns of TNP-labelled membrane proteins purified from normal and transformed cells showed only minor differences. This led to the conclusion that the increased exposure of TNBS-binding groups was due mainly to different binding properties of membrane proteins towards the probe rather than the appearance of new surface components in transformed cells.