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Biomedical subjects

Y Hamada

Publications and source records attributed to Y Hamada.

At least 451 records · Page 25Linked to original sources
PubMed1987

Complete primary structure of vertebrate smooth muscle myosin heavy chain deduced from its complementary DNA sequence. Implications on topography and function of myosin.

The 1979 amino acid sequence of embryonic chicken gizzard smooth muscle myosin heavy chain (MHC) have been determined by cloning and sequencing its cDNA. Genomic Southern analysis and Northern analysis with the cDNA sequence show that gizzard MHC is encoded by a single-copy gene, and this gene is expressed in the gizzard and aorta. The encoded protein has a calculated Mr of 229 X 10(3), and can be divided into a long alpha-helical rod and a globular head. Only 32 to 33% of the amino acid residues in the rod and 48 to 49% in the head are conserved when compared with nematode or vertebrate sarcomeric MHC sequences. However, the seven residue hydrophobic periodicity, together with the 28 and 196 residue repeat of charge distribution previously described in nematode myosin rod, are all present in the gizzard myosin rod. Two of the trypsin-sensitive sites in gizzard light meromyosin have been mapped by partial peptide sequencing to 99 nm and 60 nm from the tip of the myosin tail, where these sites coincide with the two "hinges" for the 6 S/10 S transition. In the head sequence, several polypeptide segments, including the regions around the putative ATP-binding site and the reactive thiol groups, are highly conserved. These areas presumably reflect conserved structural elements important for the function of myosin. A multi-domain folding model of myosin head is proposed on the basis of the conserved sequences, information on the topography of myosin in the literature, and the predicted secondary structures. In this model, Mg2+ ATP is bound to a pocket between two opposing alpha/beta domains, while actin undergoes electrostatic interactions with lysine-rich surface loops on two other domains. The actin-myosin interactions are thought to be modulated through relative movements of the domains induced by the binding of ATP.

Amino Acid Sequence↗
PubMed1987

Increased neuropeptide Y-immunoreactive innervation of aganglionic bowel in Hirschsprung's disease.

The pathophysiology of Hirschsprung's disease has not been fully elucidated but is known to have a neurogenic basis. In recent years, new neural proteins and peptides have been discovered and our aim in this study was to use immunocytochemistry to investigate their involvement in the neuronal abnormalities associated with this condition. Large bowel samples from 9 children undergoing surgery for Hirschsprung's disease were compared with those taken from 8 children with other gastrointestinal diseases but no aganglionosis. Immunocytochemistry was carried out using antibodies to a wide range of neuron specific proteins and peptides. Examination of sections immunostained for the general neuronal markers, protein gene product 9.5, neuron specific enolase and neurofilament triplet proteins, allowed rapid identification of aganglionic segments. Nerves containing vasoactive intestinal polypeptide/peptide histidine methionine (VIP/PHM), galanin, substance P, somatostatin, met-enkephalin or calcitonin gene-related peptide (CGRP) showed a marked reduction in all layers of the aganglionic bowel. However, scattered VIP/PHM immunoreactive fibres were also found in the hypertrophied nerve bundles. In contrast with these reduced peptide-containing nerves, fibres displaying NPY immunoreactivity showed a marked increase in all aganglionic segments, particularly in the circular muscle where few are found normally. Our findings shed further light on the neurobiology of aganglionic bowel and suggest that immunostaining of neural proteins and the peptide NPY can aid rapid histopathological diagnosis of congenital aganglionosis.

Child, Preschool↗
PubMed1987

Haemolymph control of sericin gene expression studied by organ transplantation.

A factor that affects synthesis of sericin mRNAs of Bombyx mori was analyzed by organ transplantation and allatectomy. When silk glands of the third instar larvae were transplanted into the abdomen of fifth instar larvae, substantial amounts of sericin mRNAs were induced in the transplant. The induced sericin gene activity was suppressed upon re-transplantation into the abdomen of fourth instar larvae and induced again when the second hosts grew up to fifth instar larvae. An allatectomy performed on fourth instar larvae promoted production of these mRNAs, suggesting that the synthesis of sericin mRNA is regulated by the titer of juvenile hormone.

Animals↗
PubMed1987

Specificity change of antibody to (4-hydroxy-3-nitrophenyl)acetyl haptens by somatic hypermutation.

Change in the specificity of anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibodies (Abs) with time after immunization was studied. The early anti-NP Abs was specific to the ionized (phenolate) form of NP. The specificity changed with time and the late Abs became able to bind to the protonated (phenolic) form as well as the phenolate form of NP. The nucleotide sequences of mRNA coding for variable regions of heavy and light chains suggested that somatic hypermutation contributed to this change of the specificity.

Animals↗
PubMed1987

Increased lymphocyte transport by lipid absorption in rat mesenteric lymphatics.

The effect of olive oil administration on lymphocyte transport through mesenteric lymphatics was examined to see the possible involvement of nutritional absorption in lymphocyte traffic from the intestinal mucosa. After the olive oil administration to rats, remarkable increase in lymphocyte flux was observed within 2 h in lymph samples collected from rats with lymphatic fistula. The use of a high-speed microscopic video system made it possible to analyze accurately the lymphocyte transport in rapid movement that could not be detected by any of the ordinary video systems. The direct observation of mesenteric collecting lymphatics by this system showed an increment of lymphocyte transport from the intestinal mucosa by lipid absorption in 2 h. The contraction frequency of intestinal collecting lymphatics was also enhanced by olive oil administration. The densitometric analysis on video image was applied to estimate the extent of lipid absorption. The combination of a high-speed video system and the densitometric analysis revealed that the increase in lymphocyte flux occurred before lipid absorption reached its maximum and also demonstrated that the lymphocyte transport returned to control levels under the maximal absorptive condition. The results suggest that the fat absorption could be an important factor influencing the lymphocyte transport in the lymphatic system of intestine.

Absorption↗
PubMed1987

Inhibitory effect of somatostatin on cholera toxin-induced diarrhea and glycoenzyme secretion in rat intestine.

The effects of somatostatin on cholera toxin-induced secretory diarrhea and the appearance of glycoenzymes in the intestinal lumen and intestinal lymph were investigated in rat small intestine. After exposure to cholera toxin, marked fluid accumulation in the small intestinal tract and elevation of the jejunal mucosal cyclic AMP (cAMP) concentration were observed. The activity of alkaline phosphatase, aminopeptidase and sucrase increased in the intestinal lumen after toxin exposure. In intestinal lymph, alkaline phosphatase activity was increased after cholera toxin administration, while aminopeptidase activity remained unchanged. Somatostatin suppressed cholera toxin-induced secretory diarrhea, but it did not affect the elevated mucosal cAMP concentration. This peptide also inhibited the appearance of glycoenzymes in the intestinal lumen and lymph induced by cholera toxin administration. These results suggest that somatostatin exerts its inhibitory effects on cholera toxin-induced secretory diarrhea and on the appearance of glycoenzymes in the intestinal lumen and lymph by affecting processes beyond cAMP formation.

Alkaline Phosphatase↗
PubMed1987

Dual intrinsic and extrinsic origins of CGRP- and NPY-immunoreactive nerves of rat gut and pancreas.

The origins of nerves containing calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), and substance P were investigated in the rat stomach, pancreas, and colon, using immunocytochemistry combined with retrograde tracing and surgical and chemical denervation procedures. Compared with nerves containing vasoactive intestinal polypeptide (VIP) and galanin, which have primarily local origins in mammalian gut, CGRP-, NPY-, and substance P-immunoreactive nerves revealed dual extrinsic and intrinsic origins. Immunocytochemistry combined with retrograde tracing showed that the extrinsic CGRP- and substance P-immunoreactive nerves in the stomach and pancreas originate from bilateral dorsal root ganglia mainly at levels T8-T11, while those of the colon are derived from bilateral ganglia at S1 and, to a lesser extent, L1 and L6. Chemical denervations showed that neurons in these ganglia form a sensory input to the gut, and that those containing CGRP form the largest proportion. The results of combined retrograde tracing and immunocytochemistry indicated that extrinsic NPY-immunoreactive nerves originate from postganglionic sympathetic neurons lying in the coeliac and inferior mesenteric ganglia. These nerves were located mainly around blood vessels in gut and pancreas, showed sensitivity to 6-hydroxydopamine, and thus are likely to be noradrenergic. The present study provides a detailed mapping of the origins of some of the major peptide-containing nerves of the rat gastroenteropancreatic tract, thus providing further information on the anatomy of the enteric innervation.

Animals↗