Fucosyltransferase expression in human platelets and leucocytes

The activities of -2-l-fucosyltransferase and -3-l-fucosyltransferase were measured in human platelets and leucocytes from normal donors, -2-l-Fucosyltransferase was found in platelets but not in leucocytes. In contrast -3-l-fucosyltransferase was not detected in platelets but was present in leucocytes where it was demonstrated in the neutrophil, monocyte and lymphocyte fractions.     

Electrically evoked contractions of the triceps surae during and following 21 days of voluntary leg immobilization

The effects of 21 days voluntary leg (plaster) immobilization on the mechanical properties of the triceps surae have been studied in 11 young female subjects, mean age 19.4 years. The results show that during the period of immobilization the mean time to peak tension (TPT) and half relaxation time (1/2RT) and tension (Pt) of the maximal twitch increased significantly (p less than 0.001) but the effects were short lived. Maximal tension and contraction times of the twitch recovered within 2-14 days following the removal of the plaster cast. The electrically evoked tetanic tensions at 10 Hz and 20 Hz did not change significantly (P greater than 0.1) during immobilization, but the 50 Hz tetanic tension (Po50) and maximal voluntary contraction (MVC) were reduced (p less than 0.05). The fall in Po50 and MVC was associated with 10% decrease in the estimated muscle (plus bone) cross-sectional area. The relative (%) change in Po50 and MVC following immobilization was related to the initial physiological status (as indicated by the response of the triceps surae to a standard fatigue test prior to immobilization) of the muscle. The rate of rise and recovery fall of the tetanus were slightly but significantly (p less than 0.01) reduced on day 7 of immobilization, but thereafter remained constant. The isokinetic properties of the triceps surae as reflected in the measured torque/velocity relation of the muscle in 4 subjects did not change significantly if account was taken of the slight degree of atrophy present following immobilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of pancreatic secretory process in the rat by low-molecular weight proteinase inhibitor

Oral application of a single dose of a new synthetic proteinase inhibitor Camostate (Foy-305) in male Wistar rats was carried out together with studies of in vitro amino acid incorporation followed by separation of proteins by two-dimensional gel electrophoresis. The aim of this experiment was to analyze changes produced by the inhibitor in total protein and individual enzyme biosynthesis. Administration of 100 mg/kg Foy-305 resulted in significant inhibition of total pancreatic protein synthesis, without changes in fractional rates for individual enzymes. 50 mg/kg Foy-305 induced a 10-fold elevation of cholecystokinin (CCK) levels in serum; this persisted for 3 h and led to a significant increase in the total rate of protein synthesis with peak values at 6 and 9 h (78% and 84% above control levels, respectively), returning to control by 15 h. Changes in fractional rates of synthesis occurred with a latency of 6 h and were restricted to amylase and the anionic form of trypsinogen and chymotrypsinogen. Amylase biosynthesis decreased by about 40% from control levels at 9 h to return to control levels by 15 h. Increased synthesis of trypsinogen and chymotrypsinogen was observed; this was also phasic. The results show similar enzyme-specific regulation as previously described for exogenous CCK stimulation and for the adaptation of the pancreas to diets enriched in protein. They demonstrate the effectiveness of pulsatory endogenous hormone release in the regulation of protein synthesis.     

Mapping of the gene for anti-müllerian hormone to the short arm of human chromosome 19

The gene coding for human anti-Müllerian hormone (AMH) was localized to subbands p13.2----p13.3 on chromosome 19, using in situ hybridization and Southern blot analysis of a panel of man-mouse and man-hamster somatic cell hybrids.     

The effect of monensin on thyroglobulin secretion

The effect of monensin on the secretion of thyroglobulin was studied in open follicles isolated from pig thyroid tissue; in this system, thyroglobulin is secreted into the incubation medium. When monensin was present during a 4-h chase incubation after pulse-labelling with 3H-leucine, the secretion of labelled thyroglobulin was reduced by about 85%; in electron-microscopic autoradiographs of rat thyroid lobes labelled and chase-incubated under similar conditions the relative number of grains over follicle lumina was strongly reduced when monensin was present during the chase. These observations are in agreement with the consensus that monensin arrests transport of secretory proteins in the Golgi complex. In other experiments, pulse-labelled follicles were chase-incubated for 1.5 h whereby labelled thyroglobulin was transported from the RER to exocytic vesicles. Monensin present during a subsequent chase of 0.5 h caused only a moderate decrease of labelled thyroglobulin secretion. TSH present during the second chase-stimulated secretion in both control and monensin-exposed follicles. TSH also caused a drastic reduction of exocytic vesicles in rat thyroid lobes, and the number of vesicles remaining in the cells was the same in controls and lobes exposed to the ionophore. The observations are interpreted to show that monensin does not inhibit the basal or TSH-stimulated transport of thyroglobulin from the site of monensin-induced arrest in the Golgi complex to the apical cell surface or the exocytosis of thyroglobulin.     

Neuroanatomy of morphine-modulating peptides

Antisera against two mammalian peptides related to the molluscan cardioexcitatory peptide Phe-Met-Arg-Phe-NH2 were used to locate immunoreactive neurons in the rat brain, nerve fibres and terminals in the spinal cord, sympathetic ganglion cells and adrenal chromaffin cells. Immunoreactivity for the newly characterised octa- and octadecapeptide was detected in nerve cell bodies in the hypothalamic area, including parts of the dorsomedial, periventricular and paraventricular nuclei, and in the nucleus tractus solitarii. Nerve terminals in the superficial laminae of the spinal cord were also immunoreactive for these peptides, while the sensory ganglia were nonreactive. Some principal ganglion cells in the superior cervical ganglia exhibited bright immunofluorescence for the peptides, and a few adrenal medullary cells were immunoreactive. The presence of these peptides in the substantia gelatinosa of the spinal cord suggests that they may be involved in sensory neurotransmission, especially in the mechanisms mediating pain. In the hypothalamo-hypophysial system these peptides may be involved in the regulation of hormonal systems. They may also act as co-transmitters in the sympathetic nervous system.     

Surface charges of the membrane and cell adhesion substances determine the structural integrity of hair bundles from the inner ear of fish

Summary The hairs (stereocilia = stereovilli) of sensory cells from the inner ear of vertebrates are interconnected by several types of connectors, whose role is unknown. They appear to stabilize the hair bundle mechanically, and may be directly involved in mechano-electric transduction. Our transmission electron-microscopical investigation of sensory epithelia from two species of fish (Rutilus rutilus, Scardinius erythrophthalmus, both Leuciscidae) has shown that not only the connectors but also the surface charges of the membrane are important factors for determining the shape of the hair bundle and the spatial interrelation of the stereovilli. A reduction of the ionic strength in the medium leads to an increase in distance between the stereovilli. This may be the result of an extension of the spread of the surface potential of the membrane at low ionic strength. The connectors are not broken by the increase in distance between the stereovilli. They are EDTA (ethylene-diamine-tetra-acetic-acid) resistant as are some cell adhesion molecules such as N-CAM (nerve-cell adhesion molecule) and protein A from Dictyostelium discoideum. The connectors do not prevent polycation-induced fusion of adjacent stereovillar membranes.     

In vivo binding and uptake of low-density lipoprotein-gold- and albumin-gold conjugates by parenchymal and sinusoidal cells of the fetal rat liver

Summary To elucidate the participation of fetal rat liver cells in the receptor-mediated internalization of low-density lipoproteins (LDL), rat fetuses were injected with either LDL-gold or albumin-gold conjugates. The degree of binding and uptake of LDL-gold and albumin-gold by parenchymal and sinusoidal cells of the fetal rat liver differs markedly. Endothelial cells exhibit low LDL-gold uptake. In contrast, parenchymal cells internalize LDL-gold more actively (45 ± 8 LDL conjugates/100 m² cytoplasm within 60 min). Kupffer cells exceed this value by a factor of 20. The uptake of albumin-gold by endothelial and Kupffer cells is high, whereas it is extremely low in parenchymal cells. Estradiol pretreatment causes a significant doubling (p<0.05) of the LDL-gold particle density/100 m² cytoplasm both in parenchymal and Kupffer cells, whereas estradiol has no effect on the albumin uptake. The results strongly indicate that LDL uptake by parenchymal and Kupffer cells in the fetal rat liver is mediated by estrogen-inducible receptors, which may correspond to B, E receptors in the adult liver.     

A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.