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Biomedical subjects

F Nakamura

Publications and source records attributed to F Nakamura.

At least 235 records · Page 13Linked to original sources
PubMed1986

A quantitative immunohistochemical study on the pituitary LH gonadotrophs in the female Afghan pika after copulation.

The female Afghan pika is known as a species of copulatory ovulators exhibiting persistent estrus unless copulatory stimuli are employed. The plasma LH concentration rose quickly after copulation, peaked at 6 h and descended thereafter until 12 h. Before copulation (estrus), immunoreactive LH-containing cells of the pituitary in this species were filled with numerous large electron dense secretory granules, but the Golgi apparatus and the granulated endoplasmic reticulum were not well developed. One hour later the stainability of the cells was faint, their secretory granules were malls in size and in number, and were of low electron density. These alterations were the most predominant at 12 h after copulation. No exocytotic extrusion of secretory granules was observed throughout the experiment.

Animals↗
PubMed1986

Phasic contractions of canine and human coronary arteries induced by potassium channel blockers.

To gain insight into mechanisms underlying phasic coronary vasospasm in patients with variant angina pectoris, we studied whether phasic contractions could be induced in isolated canine and human coronary arteries by agents which block potassium channels. Phasic contractions of canine coronary arteries were always induced by 3,4-diaminopyridine (10(-2) M) and less frequently by 4-aminopyridine (10(-2) M). These agents also caused phasic contractions in human, swine and monkey coronary arteries and in canine basilar, carotid, renal and femoral arteries. The cycle length of phasic coronary contractions ranged from 30 sec to 1 hour, and the developed tension was 2.5 times greater than for potassium contractions. The contractions continued for more than 11 hours. Morphologically, perinuclear vacuolization, a characteristic change of vasospasm, appeared in the coronary smooth muscles. The phasic contractions were not eliminated by tetrodotoxin, atropine, phentolamine or yohimbine, but they were eliminated by nicorandil which activates potassium channels and nifedipine which blocks slow calcium channels. The results indicate that potassium channel blockers can induce phasic arterial contractions.

4-Aminopyridine↗
PubMed1986

[Auxiliary value of TPA in diagnosing neoplastic diseases].

The auxiliary value of TPA in diagnosing neoplastic diseases was compared to other tumor markers such as CEA, IAP and ferritin. The study population consisted of 59 patients with neoplastic diseases and 75 with benign diseases. The percentages of positive cases for TPA, CEA, IPA and ferritin were 58.9%, 39.0%, 66.7%, and 28.6% in neoplastic diseases and 4.5%, 1.4%, 47.1% and 19.7% in benign diseases, respectively. Both the specificity and sensitivity of TPA were as high as those of CEA. However, the positive rate of TPA was lower than that of CEA in lung cancer patients at stages I and II. TPA was indicated to be a suitable marker for combination assay with CEA in diagnosing neoplastic diseases.

Carcinoembryonic Antigen↗
PubMed1985

Development of a standard protocol for in vitro cytogenetic testing with Chinese hamster ovary cells: comparison of results for 22 compounds in two laboratories.

A major problem of cytogenetics testing in mammalian cells is lack of agreement of results among laboratories. Our objective was to develop a sensitive in vitro test protocol that was applicable to large-scale chemical screening and yielded comparable results in two laboratories. We used sister chromatid exchange (SCE) and chromosome aberration (CAb) tests in Chinese hamster ovary (CHO) cells. The initial protocol used standard cell densities, medium, batch of rat liver S9 for metabolic activation; positive, negative, and solvent controls; staining and scoring techniques; and fixation times. Treatment without S9 was for 8-12 hr (CAb) or 26 hr (SCE), and with S9 for 2 hr in serum-free medium. Bromodeoxyuridine (BrdUrd) (10 microM) was added to SCE cultures only, 2 hr after addition of the test chemical. Doses were based on the 50% toxicity level in a preliminary test of cell survival 24 hr after treatment. One hundred cells (CAb) or 50 cells (SCE) were scored from each control and from five dose levels. Five clastogens were tested in the first two-laboratory comparison: mitomycin-C, triethylenemelamine, N-methyl-N'-nitro-N-nitrosoguanidine, cyclophosphamide, and benzo(alpha)pyrene. There was quite good agreement between laboratories. Seventeen compounds were then tested "blind" in the two laboratories. As testing proceeded, some discrepancies occurred between the laboratories, and the protocol was modified in attempts to improve the resolution of marginal responses and make dose selection more consistent. The preliminary test for cell survival was omitted. A 10(5) dose range in a half-log series was tested, and cells were scored at the highest dose at which sufficient mitotic cells were obtained, and at the next two lower doses. By delaying fixation times, SCE and CAb were scored at doses that inhibited cell cycle progression. This protocol gave comparable results in the two laboratories in many cases and by testing up to a maximum dose, limited by solubility and/or toxicity, should detect a high proportion of clastogens and SCE inducers.

Animals↗
PubMed1985

Paratropomyosin: a new myofibrillar protein that modifies the actin-myosin interaction in postrigor skeletal muscle. I. Preparation and characterization.

A protein component which is released from skeletal-muscle myofibrils on the treatment with Ca2+ at concentrations above 10(-5) M and modifies the actin-myosin interaction was purified by a method involving column chromatography on Sephadex G-200 and DEAE-cellulose in succession. Although this protein resembles tropomyosin in some physicochemical properties, it has the same chain weight of 34,000 as the alpha-component of tropomyosin on SDS-polyacrylamide gel electrophoresis, and differed from tropomyosin not only in the amino acid composition but also in prolonging the clearing phase of superprecipitation of reconstituted actomyosin. We therefore concluded that this protein is a new myofibrillar one, and termed it "paratropomyosin." In postrigor muscle, it seems likely that paratropomyosin is released from its original locus with an increased concentration of Ca2+, and that it weakens rigor linkages formed between actin and myosin.

Actins↗
PubMed1985

Paratropomyosin: a new myofibrillar protein that modifies the actin-myosin interaction in postrigor skeletal muscle. II. Distinct function from tropomyosin.

The functional differences between paratropomyosin and tropomyosin were studied. The weight ratio of maximally bound paratropomyosin to F-actin was 1 : 7.6, whereas that of tropomyosin was 1 : 3.9. The actin-myosin interaction was markedly depressed by paratropomyosin under conditions where it was promoted by tropomyosin. Paratropomyosin had sensitized the actin-myosin-troponin system to Ca2+, but was much less effective than tropomyosin. Paratropomyosin showed an additive effect on the actomyosin systems containing tropomyosin, indicating that the binding site of paratropomyosin on F-actin is distinct from that of tropomyosin. Probably, due to greater affinity for myosin binding site on F-actin, paratropomyosin competes for the binding site and thus modifies the actin-myosin interaction. The role of paratropomyosin in tenderization of meat during postmortem ageing is also discussed.

Actins↗
PubMed1985

Relationship between characteristics of immunoreactive LH/FSH cells and the levels of gonadotropin in the female rat.

Morphological and functional changes of pituitary LH/FSH cells in the female rat were investigated using the parameters on the radioimmunoassay, immunohistochemistry and ultrastructure. Changes in immunostainability, populations of intensely immunostained LH and FSH cells and total volume of secretory granules were correlated with the changes in pituitary LH and FSH contents during the estrous cycle. The immunohistochemical feature of gonadotropin release is the transformation of intensely immunostained gonadotrophs into the weakly stained ones. Secretory granules of small diameter (less than 150 nm) were numerous just before LH and FSH surges then sharply declined along with LH and FSH surges. The number of secretory granules of large diameter (larger than 150 nm) also decreased when LH and FSH surges took place. Then the number increased progressively until 17.00 h on the day of diestrus, corresponding to the increase in pituitary LH and FSH contents. It is suggested that small secretory granules are a release pool while large ones are a reserve pool.

Animals↗
PubMed1984

Gene analysis in delta beta and delta (0) thalassemia.

Restriction mapping of the globin genes from a homozygous delta beta thalassemia patient from Israel indicates that at least a 10-kilobase deletion is present extending 3' from within the large intervening sequence (IVS 2) of the delta globin gene and including the entire beta globin gene. Unique bands are seen when cellular DNA from this patient is digested with a variety of restriction endonucleases and hybridized with a probe specific for the delta IVS 2. Extensive analysis of the Israeli delta beta thalassemia DNA as well as material from an Italian delta beta thalassemia homozygote with enzymes which cleave more frequently in delta IVS 2 has localized the 5' end of the deletion to a 107-base pair region within delta IVS 2. This region contains a unique repetitive sequence (TG)4 which has been reported to be a specific recognition signal for recombination and may be involved in the formation of these mutant genes. Two homozygous delta(0) thalassemia DNA samples from Japan were also analyzed for gene rearrangements or other changes by restriction enzyme mapping. No changes from normal were seen using 14 different enzymes indicating the absence of large deletions in the region around the delta globin gene. More specifically, both the 5' and 3' splice junctions of the IVS 2 appear to be normal from hybridization of restriction fragments generated by HphI and AluI, respectively, with a delta IVS 2 specific probe. We have also shown that point mutations which could lead to termination codons are not present at codons 35, 37, 43, 61, and 121, since restriction enzymes which recognize these sites produce normal patterns. The delta(0) thalassemia phenotype in these two subjects is most likely due to a point mutation either at one of the other 24 potential termination codons not accessible to restriction analysis or to other single nucleotide changes which could either decrease delta globin gene transcription or lead to abnormal processing or transport of delta globin mRNA.

Base Sequence↗
PubMed1984

Hemoglobin Miyada: DNA analysis of the anti-Lepore beta delta fusion gene.

Hemoglobin Miyada, an anti-Lepore hemoglobin, represents the protein product of a nonhomologous crossover between beta and delta genes. The mutant globin is beta-like from the N terminus to amino acid 12, and delta-like from amino acid 22 through the C terminus, thus predicting a crossover site in the first coding region of the gene. DNA analysis, using multiple restriction endonucleases and hybridization to delta and beta globin gene-specific probes, confirms that the beta delta hybrid gene 1) is located on a single chromosomal fragment between normal delta and beta genes, and 2) has 5' beta promoter sequences, delta IVS 1 and 2, and 3' coding and flanking sequences.

Base Sequence↗
PubMed1983

Comparative study on the mechanical property of silk thread from cocoons of Bombyx mori L.

Specimens of bave (undegummed silk thread) were collected from cocoons of various origins of parent silkworm races, such as Japanese, Chinese, European, Korean and tropical origins, and from as many races as possible. An apparatus was set up to measure the dynamic elastic modulus of these specimens. In all the categories of the races tested, the elastic modulus was linearly related to the size of bave, regardless of the portion of cocoon layer from which the specimens were taken. This correlation was concluded to be universal to the silk thread of Bombyx mori L. species; however, values of the regression coefficient and of the elastic modulus were susceptible to the origin of silkworm races, depending on whether they were native or improved.

Animals↗
PubMed1982

A myofibrillar component that modifies the actin-myosin interaction in postrigor skeletal muscle.

A protein component that modified the interaction between actin and myosin was released from myofibrils on Ca2+-treatment, accompanying the weakening of Z disks. For its release 10(-4) M Ca2+ was required. The presence of the component facilitated the dissociation of thin and thick filaments from myofibrils and delayed superprecipitation of reconstituted actomyosin, independently of Ca2+ concentration. The component is probably a constituent of Z disks. In postmortem muscle, it is possible that the component is released from Z disks with an increased concentration of Ca2+, and that it weakens rigor linkages formed between actin and myosin, giving rise to lengthening of rigor-shortened sarcomeres.

Actins↗
PubMed1982

Age-related immunoglobulin levels in cynomolgus monkeys.

Serum immunoglobulin levels were measured with 144 domestically-bred cynomolgus monkeys, aged 0 day to 18 years. IgG level of the newborn just after birth was somewhat lower than that of their mother monkeys, continuing to decrease for 3 postnatal months. Thereafter, the level began to increase gradually till 4 to 5 years when an adult level was attained. IgA was detected on the day of birth in half of the animals and started to increase soon after birth, reaching an adult level in 5 to 6 years. A relatively low level of IgM was detected in all animals at birth. The increase of IgM level continued till 5 years of age. These patterns of immunoglobulin levels related to age are very similar to those of rhesus monkeys and human.

Age Factors↗