Transient appearance of Ca-binding protein (spot 35-calbindin) in bronchial epithelial cells,thyroid parafollicular cells and thymic epithelial cells during the development of rats

Summary Tracheobronchial epithelium, thyroid organ, thymus, of the developing rats were examined by immunohistochemistry using anti-spot 35 calbindin-antiserum. At E 14, weak to moderate immunoreactivity for spot 35-calbindin was detected in the airway epithelia of the distal half of the trachea and the extrapulmonary bronchus. The immunoreactive cells increased in intensity at E 16–E 21, but decreased markedly after birth. These cells were non-ciliated cells and comprised a majority of the epithelial cells especially in the ventral/cartilaginous portion of the airway. They were characterized by microvilli, vacuoles, granular and agranular endoplasmic reticulum. Typical ciliated cells, which were much less numerous than the immunopositive non-ciliated cells, were immunonegative. In thyroid gland, calbindin-immunoreactive cells first appeared at E 18. They increased in number at E 20-P 1 and decreased gradually after P 7. These cells were the parafollicular cells characterized by numerous secretory granules and situated in close proximity to the basal surface of the follicular cells. In the thymus, immunoreactive cells appeared in the thymic medulla at E 20. They increased in number at P 1, but decreased gradually after P 7. They were stellate in shape and had vesicles, vacuoles, intermediate filaments and represented a subpopulation of thymic reticular epithelial cells. Such a transient appearance of spot 35-calbindin in these cells suggests that this protein may be involved in the regulation of differentiation or may be involved in the process of secretion during the limited developmental period.     

Changes in Targeting Efficiencies of Proteins to Plant Microbodies Caused by Amino Acid Substitutions in the Carboxy-terminal Tripeptide

It has been demonstrated that the carboxyl terminus of microbodyenzymes functions as a targeting signal to microbodies in higherplants. We have examined an ability of 24 carboxy-terminal aminoacid sequences to facilitate the transport of a cytosolic passengerprotein, ß-glucuroni-dase, into microbodies in greencotyledonary cells of trans-genic Arabidopsis. Immunoelectronmicroscopic analysis revealed that carboxy-terminal tripeptidesequences of the form [C/A/S/P]-[K/R]-[I/L/M] function as amicrobody-targeting signal, although tripeptides with prolineat the first amino acid position and isoleucine at the carboxylterminus show weak targeting efficiencies. All known micro-bodyenzymes that are synthesized in a form similar in size to themature molecule, except catalase, contain one of these tripeptidesequences at their carboxyl terminus. (Received April 14, 1997; Accepted April 8, 1997)     

P2-purinergic receptors are coupled to two signal transduction systems leading to inhibition of cAMP generation and to production of inositol trisphosphate in rat hepatocytes

Stimulation of P2-purinergic receptors by ATP resulted in activation of phosphorylase, which was associated with marked production of inositol trisphosphate (Ins-P3), in rat hepatocytes. ATP also inhibited forskolin-induced accumulation of cAMP in the presence of a phosphodiesterase inhibitor. On the contrary, adenosine or AMP never inhibited the cAMP accumulation, but increased hepatocyte cAMP; the stimulation was antagonized by a methylxanthine. Thus, P1-purinergic receptors are linked to adenylate cyclase in a stimulatory fashion in hepatocytes. Various kinds of purine nucleotides stimulating P2-receptors can be divided into two groups on the basis of their relative abilities to stimulate Ins-P3 production and to inhibit cAMP accumulation; the first group including adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), ADP, 5-adenylyl imidodiphosphate, GTP, and guanosine 5'-O-(3-thiotriphosphate) has an efficacy similar to that of ATP, and the second group of nucleotides including alpha, beta-methyleneadenosine 5'-triphosphate, beta, gamma-methyleneadenosine 5'-triphosphate (App(CH)2)p), and GDP exerts considerable inhibitory effects on cAMP accumulation, but only slight effects on inositol lipid metabolism. Treatment of hepatocytes with islet-activating protein, pertussis toxin, blocked the nucleotide-induced inhibition of cAMP accumulation, but exerted only a small effect on Ins-P3 production. In membranes prepared from hepatocytes, forskolin-stimulated adenylate cyclase was inhibited by GTP. This GTP-induced inhibition of the enzyme was susceptible to islet-activating protein and dependent on the concentration of ATP (or its derivatives, ATP gamma S or App(CH2)p). It is concluded that there are two types of P2-purinergic receptors: one is linked to adenylate cyclase via an inhibitory guanine nucleotide regulatory protein (Gi) and the other is linked to phospholipase C.     

Frequency of the fragile X syndrome in institutionalized mentally retarded females in Japan

Summary The fragile X [fra(X)] syndrome was screened on 190 Japanese institutionalized females with moderate to severe mental retardation. Two inmates with severe mental retardation (IQ 20) had the fra(X) chromosome in 26% and 15% of the cells examined, indicating that the prevalence of the fra(X) syndrome was about 1% in all female inmates and was about 3.27% in severely mentally retarded females with known causes. However, no female with fra(X) syndrome was found in 35 moderately retarded females. Both had brothers with the fra(X) syndrome and the prevalence was 10% in females with a family history of mental retardation. In addition, the replication study of the fra(X) chromosome in the patients supported the proposal that an excess of the early replicated fra(X) chromosome is related to the mental capacity in heterozygous females. Therefore, the fra(X) syndrome should not be ignored even in severely mentally retarded females with a family history, though the heterozygotes are commonly normal to subnormal in their mental development. in addition, the replication study of the fra(X) chromosome may help to estimate mental development in the carrier children.     

Estimation of transport distance of fine particulate organic matter in relation to channel morphology in tailwaters of the Lake Biwa and reservoir dams

Knowledge on transport and deposition of fine particulate organic matter (FPOM) from reservoir dams is increasingly required for habitat management and restoration of dam tailwater ecosystems. Variations in the transport distance of FPOM, however, have never been studied well, particularly in relation to channel morphology, due to channel size restrictions of artificial tracers such as corn pollen when applied to larger river channels. This study aims to show the relations between FPOM retention efficiency and channel morphology in dam tailwaters using lentic plankters as tracers. We estimated the mean transport distance, S _p, by calculating downstream reduction ratios of lentic tracer plankters and calculated the deposition velocity, v _dep. Suspended FPOM samples were collected in tailwaters of two river channels below reservoir dams and two artificial canals below Lake Biwa in the Yodo River system. The longest S _p (19.2 km) and the shortest one (2.2 km) were recorded in the deep canal and shallow canal, respectively, showing a positive correlation with channel hydraulic radius. The values of v _dep were 4.7–6.4 times higher in river channels than in artificial canals. These results indicate that increasing complexity of bed morphology can minimize S _p, whereas bed degradation and armored bed materials may lead to increased S _p. Advantages of lentic plankters as tracers for estimating distance ranges of reservoir dam impact on river ecosystems are also discussed.     

Effect of a high-protein diet on the gene expression of a trypsin-sensitive, cholecystokinin-releasing peptide (monitor peptide) in the pancreas

The adaptation to a high protein diet of the concentration and mRNA level of a trypsin-sensitive, cholecystokinin-releasing peptide (monitor peptide), which was proposed to be the mediator of the cholecystokinin release in response to protein intake, was investigated in the rat pancreas. Adult rats were placed on one of two isocaloric diets. One group was fed a 22% casein diet (control diet) and the other a 64% casein diet (high-protein diet) for 14 days. In order to quantify the monitor peptide separately from pancreatic secretory trypsin inhibitor (PSTI-II), which is highly similar in its amino acid and mRNA nucleotide sequences to the monitor peptide but has less cholecystokinin-releasing activity, we used specific assay methods: HPLC was used for determining the monitor peptide concentration in zymogen granules and a synthetic oligonucleotide probe for determining the mRNA of the monitor peptide in the pancreas. The concentrations in the zymogen granules and the mRNA levels in the pancreas of the two peptides increased in parallel during the adaptation to the high protein diet, indicating that these two peptides were under the same control during the adaptation. The concentration and mRNA level of the monitor peptide, which were measured after 0, 3, and 14 days, increased throughout the experiment period, as did the concentration of trypsin. This suggested that the monitor peptide and trypsin may respond to similar signals during the adaptation to a high protein diet and that this apparent coordination may facilitate the adaptation of the pancreas to the diet.     

Prophages integrating into prophages: A mechanism to accumulate type III secretion effector genes and duplicate Shiga toxin-encoding prophages in Escherichia coli

Bacteriophages (or phages) play major roles in the evolution of bacterial pathogens via horizontal gene transfer. Multiple phages are often integrated in a host chromosome as prophages, not only carrying various novel virulence-related genetic determinants into host bacteria but also providing various possibilities for prophage-prophage interactions in bacterial cells. In particular, Escherichia coli strains such as Shiga toxin (Stx)-producing E. coli (STEC) and enteropathogenic E. coli (EPEC) strains have acquired more than 10 prophages (up to 21 prophages), many of which encode type III secretion system (T3SS) effector gene clusters. In these strains, some prophages are present at a single locus in tandem, which is usually interpreted as the integration of phages that use the same attachment (att) sequence. Here, we present phages integrating into T3SS effector gene cluster-associated loci in prophages, which are widely distributed in STEC and EPEC. Some of the phages integrated into prophages are Stx-encoding phages (Stx phages) and have induced the duplication of Stx phages in a single cell. The identified attB sequences in prophage genomes are apparently derived from host chromosomes. In addition, two or three different attB sequences are present in some prophages, which results in the generation of prophage clusters in various complex configurations. These phages integrating into prophages represent a medically and biologically important type of inter-phage interaction that promotes the accumulation of T3SS effector genes in STEC and EPEC, the duplication of Stx phages in STEC, and the conversion of EPEC to STEC and that may be distributed in other types of E. coli strains as well as other prophage-rich bacterial species.     

New Plasmid-Mediated Phosphorylation of Gentamicin C in Staphylococcus aureus

A clinical isolate of Staphylococcus aureus resistant to gentamicin, kanamycin and 3′,4′-dideoxykanamycin B contained two enzymes capable of inactivating gentamicin, i.e., an aminoglycoside 2″-phosphotransferase and aminoglycoside acetyltransferase.