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PubMed1978

Measurements of muscle stiffness and the mechanism of elastic storage of energy in hopping kangaroos.

1. A kangaroo hopping above a certain speed appears to consume less oxygen than a quadrupedal mammal, of similar weight, running at the same speed (Dawson & Taylor, 1973). This is thought to be achieved by storage of elastic energy in tendons and ligaments. 2. Energy can be stored in a tendon by stretching it, but only if the muscle fibres in series with it are stiff enough to resist most of the length change. We have measured length and tension changes in the contracting gastrocnemius muscle of the wallaby Thylogale during rapid, controlled stretches, and from this determined the amount of movement in muscle fibres and tendon (method of Morgan, 1977). 3. When the muscle was developing close to its maximum isometric tension, up to eight times as much movement occurred in the tendon as in the muscle fibres. This is made possible by the wallaby having a long and compliant tendon. 4. Measurement of work absorption by the muscle with a full length of free tendon and when the tendon had been shortened, showed that with the shortened tendon a larger proportion of movement occurred in the muscle fibres, producing a steep rise in work absorption by the muscle and a consequent increase in energy loss.

Animals↗

PubMed1991

Ribosome hopping and translational frameshifting are inadequate alternatives to translational attenuation in cat-86 regulation.

The induction of cat-86 by chloramphenicol has been proposed to follow the translational attenuation model. In the absence of inducer, the cat-86 gene is transcribed but remains phenotypically unexpressed because the transcripts sequester the ribosome binding site for the cat coding sequence in a stable stem-loop structure, preventing translation initiation. The translational attenuation model proposes that the natural inducer, chloramphenicol, stalls a ribosome in the leader region of cat transcripts, which causes localized melting of the downstream stem-loop structure, allowing initiation of translation of the cat-86 coding sequence. Although it is established that ribosome stalling in the cat-86 leader can induce translation of the coding sequence, several subsequent steps predicted by the model remain to be experimentally confirmed. As a consequence, the present evidence for cat-86 regulation can also be explained by two other potential control devices, ribosome hopping and translational frameshifting. Here we describe experiments designed to determine whether the alternatives to translational attenuation regulate cat-86. The results obtained are inconsistent with both competing models and are consistent with predictions made by the translational attenuation model.

Bacillus subtilis↗

PubMed1994

Expression of the Prevotella loescheii adhesin gene (plaA) is mediated by a programmed frameshifting hop.

The 2.4-kb plaA gene, which encodes a Prevotella loescheii galactoside-specific adhesin, contains a programmed frameshifting hop. The frameshift region consists of two UAA termination codons, two repeats of four identical bases between the terminators, and a stem-loop structure that has the potential to form a pseudoknot located downstream from the second UAA. The stem-loop and pseudoknot are features found in a number of retroviruses where frameshifting is a more common occurrence. The terminators, sequence repeats, and secondary structures were identified in both the P. loescheii plaA gene and the mRNA transcript. An in-frame fusion of the entire plaA frameshift region between codons 9 and 10 of the lacZ gene permitted relatively efficient expression (4 to 25% of that of the control) of beta-galactosidase in Escherichia coli.

Adhesins, Bacterial↗

PubMed2004

A long-distance translocatable phloem protein from cucumber forms a ribonucleoprotein complex in vivo with Hop stunt viroid RNA.

Viroids are highly structured plant pathogenic RNAs that do not code for any protein, and thus, their long-distance movement within the plant must be mediated by direct interaction with cellular factors, the nature of which is presently unknown. In addition to this type of RNAs, recent evidence indicates that endogenous RNAs move through the phloem acting as macromolecular signals involved in plant defense and development. The form in which these RNA molecules are transported to distal parts of the plant is unclear. Viroids can be a good model system to try to identify translocatable proteins that could assist the vascular movement of RNA molecules. Here, we demonstrate by use of immunoprecipitation experiments, that the phloem protein 2 from cucumber (CsPP2) is able to interact in vivo with a viroid RNA. Intergeneric graft assays revealed that both the CsPP2 and the Hop stunt viroid RNA were translocated to the scion. The translocated viroid is symptomatic in the nonhost scion, indicating that the translocated RNA is functional. The CsPP2 gene was cloned and sequenced. The analysis of its primary structure revealed the existence of a potential double-spaced-RNA-binding motif, previously identified in a set of proteins that bind to highly structured RNAs, which could explain its RNA-binding properties. The possible involvement of this phloem protein in assisting the long-distance movement of the viroid RNA within the plant is discussed.

Amino Acid Sequence↗

PubMed2006

Differential effect of bryostatin 1 and phorbol 12-myristate 13-acetate on HOP-92 cell proliferation is mediated by down-regulation of protein kinase Cdelta.

Bryostatin 1 is currently in clinical trials as a cancer chemotherapeutic agent. Although bryostatin 1, like phorbol 12-myristate 13-acetate (PMA), is a potent activator of protein kinase C (PKC), it induces only a subset of those responses induced by PMA and antagonizes others. We report that, in the HOP-92 non-small cell lung cancer line, bryostatin 1 induced a biphasic proliferative response, with maximal proliferation at 1 to 10 nmol/L. This biphasic response mirrored a biphasic suppression of the level of PKCdelta protein, with maximal suppression likewise at 1 to 10 nmol/L bryostatin 1. The typical phorbol ester PMA, in contrast to bryostatin 1, had no effect on the level of PKCdelta and modest suppression of cell proliferation, particularly evident at later treatment times. Flow cytometric analysis revealed changes in the fraction of cells in the G0-G1 and S phases corresponding to the effects on proliferation. Cells overexpressing PKCdelta exhibited a lower rate of cell proliferation compared with control untreated cells and showed neither a proliferative response nor a loss of PKCdelta in response to bryostatin 1. Conversely, treatment with PKCdelta small interfering RNA significantly increased the cellular growth compared with controls. We conclude that the differential effect on cellular proliferation induced by bryostatin 1 compared with PMA reflects the differential suppression of PKCdelta.

Bryostatins↗

PubMed1985

Ultrastructure of the epithelial cells of the ventral prostate from the hopping mouse Notomys alexis.

The large ventral prostate of the hopping mouse has abundant secretory units whose epithelial cells vary in height and which often have nuclei in the apical region of the cell. TEM observations indicated two epithelial cell types in which some unusual features occurred. Type A cells had granular endoplasmetic reticulum (GER) whose membranes often formed intracytoplasmic confronting cisternae. Type B cells had more fragmented and vesiculated GER with sparse ribosomes and less frequently also intracytoplasmic confronting confronting cisternae. In the latter cells, two types of granules were found, one of which was derived from the Golgi and the other possibly directly from the GER. Type A cells only had one type of granule present. A highly convoluted membrane was also found at the basal region in many of the cells. The significance of these unusual ultrastructural features has yet to be ascertained.

Animals↗

PubMedDate not supplied

Humulon, a bitter in the hop, inhibits tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin.

Humulon, one of the bitters in the hop, was isolated from the female flowers of Humulus lupulus. This component has inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation. At 1 mg/mouse, humulon inhibited markedly the tumor-promoting effect of TPA (1 microgram/mouse) on skin tumor formation following initiation with 7,12-dimethylbenz[a]anthracene (50 micrograms/mouse). Furthermore, humulon inhibited arachidonic acid-induced inflammatory ear edema in mice.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2003

HATs off to Hop: recruitment of a class I histone deacetylase incriminates a novel transcriptional pathway that opposes cardiac hypertrophy.

Histone acetylation, regulated by two antagonistic enzymes - histone acetyltransferases (HATs) and histone deacetylases (HDACs) - results in transcriptional changes and also plays a critical role in cardiac development and disease. A new study shows that overexpression of the atypical transcriptional corepressor homeodomain-only protein (Hop) causes cardiac hypertrophy via recruitment of a class I HDAC. In contrast to the body of work on transcriptional mechanisms that drive cardiac hypertrophy, including class II HDACs, this report elucidates a novel growth-suppressing transcriptional pathway in cardiac muscle that opposes hypertrophic growth.

Acetyltransferases↗

PubMed1989

Adult acute lymphoblastic leukemia: results of the Iowa HOP-L protocol.

Fifty-nine consecutive previously untreated adult patients with acute lymphoblastic leukemia (ALL) were entered onto a prospective single-arm trial of doxorubicin, vincristine, prednisone, and asparaginase (HOP-L) induction therapy followed by CNS prophylaxis and 3 years of maintenance therapy. Consolidation therapy was not administered. The study population included a large number of older (greater than 50 years) patients. Seventy-five percent of patients achieved complete remission. With a median follow-up of 6 years, the median duration of complete remission is greater than 4 years, with 53% of patients expected to remain in remission at both 3 and 5 years. Overall, median survival duration is 27.9 months, with 45% and 35% of all patients expected to survive 3 and 5 years, respectively. Multivariate analysis identified patients with T-cell disease and mediastinal masses (P less than .001) and those with low values of lactic dehydrogenase (LDH) (P = .057) as being at greatest risk of relapse. Therapy was well tolerated by patients under age 35, but older patients suffered appreciable mortality. We conclude that this treatment program is effective therapy for adult ALL, yielding a large proportion of durable remissions despite the exclusion of consolidation therapy.

Adolescent↗

PubMed1995

Antioxidative activity of hop bitter acids and their analogues.

Hop bitter acids, humulones (1) and lupulones (2), were shown to have potent DPPH radical scavenging activity (RSA) and lipid peroxidation inhibitory activity (LIA). Furthermore, 5-acetyl lupulones (3) and 4-methyl lupulones (4) had more potent LIA than native lupulones but no RSA. This result indicates that the beta, beta'-triketone moiety of the lupulones has LIA.

Antioxidants↗

PubMed2006

Flavonoid glycosides extracted from hop (Humulus lupulus L.) as inhibitors of chemical mediator release from human basophilic KU812 cells.

The antiallergic properties of hop water extract (HWE) were studied by evaluating histamine release from human basophilic KU812 cells induced by calcium ionophore A23187. HWE significantly inhibited histamine release, but boiling water extract and chloroform-methanol extract did not show any inhibitory effect on it. A 50% methanol-eluted fraction separated from HWE by XAD-4 column chromatography (MFH) had a strong inhibitory effect as compared with HWE. Quercetin glycosides and kaempherol glycosides were identified in MFH, of which quercetin glycosides contributed to the inhibition of histamine release. Most quercetin in HWE existed in glycoside form and its quercetin content, obtained by acid hydrolysis, was about 200 mug/g. HWE and MFH significantly inhibited protein kinase C, which plays a pivotal role in the degranulation of chemical mediators. These results indicate that HWE can inhibit type-I allergic reactions.

Basophils↗

PubMed1997

Bone resorption inhibitors from hop extract.

We searched hop extract for active component(s) that inhibited bone resorption in the pit formation assay, and isolated xanthohumol and humulone as active ingredients. Especially humulone had extraordinarily strong inhibitory activity and the IC50 (concentration of 50% inhibition) value was 5.9 x 10(-9)M.

Bone Resorption↗

PubMed1997

Inhibition by hop bract polyphenols of cellular adherence and water-insoluble glucan synthesis of mutans streptococci.

The inhibitory effect of hop bract polyphenols (HBP) on cariogenic streptococci was investigated. It was found that the high molecular weight polyphenol (estimated about 36,000-40,000) inhibited the cellular adherence of Streptococcus mutans MT8148 (serotype C) and Streptococcus sobrinus ATCC 33478 (serotype g) at much small concentrations than the polyphenols extracted from oolong tea or green tea leaves. Furthermore, HBP also inhibited the action of glucosyltransferase, which was involved in the water-insoluble glucan synthesis, but did not suppress the growth and the acid production of the bacteria. These results suggest that HBP would be a candidate to act against dental caries caused by Mutans Streptococci.

Bacterial Adhesion↗

PubMed2004

Enzymatic reactions by five chalcone synthase homologs from hop (Humulus lupulus L.).

The enzyme activities encoded in five cDNAs for chalcone synthase (CHS) homologs from hop were investigated. Only valerophenone synthase (VPS) and CHS_H1 showed both naringenin-chalcone and phlorisovalerophenone forming activity. Narigenin-chalcone production by VPS was much lower than by CHS_H1. Therefore, it is highly possible that flavonoid depends mainly on CHS_H1, while bitter acid biosynthesis depends mainly on VPS and CHS_H1.

Acyl Coenzyme A↗

PubMed2002

Frequency-hopping optical orthogonal codes with arbitrary time-blank patterns.

We investigate a general scheme of frequency-hopping optical orthogonal codes with a specified distance between adjacent frequency symbols and propose a novel code that allows time blanks between adjacent frequency symbols in code sequences. A time blank represents the absence of frequency symbols in code sequences and makes no interference with frequency components. The insertion of time-blank patterns can provide ample scope to generate much more code sequences than the conventional codes lacking in time-blank patterns, and we show this by constructing an algorithm to generate the proposed code. The performance analysis demonstrates that its performance is superior to that of the conventional codes in terms of the bit error rate. We also derive the upper bound on the proposed code set.

Journal Article↗

PubMed2004

Mode-hop-free fine tuning of an external-cavity diode laser with an intracavity liquid crystal cell.

A planar nematic liquid crystal (NLC) cell is incorporated into a Littman-type external cavity as the wavelength-tuning device for a semiconductor laser diode. By varying the driving voltage of the NLC cell and laser diode bias current simultaneously, we demonstrate single-mode oscillation and mode-hop-free tuning over 19.2 GHz at 775 nm. The result is in good agreement with the theoretical predictions.

Journal Article↗

PubMed2005

Rapid hop diffusion of a G-protein-coupled receptor in the plasma membrane as revealed by single-molecule techniques.

Diffusion of a G-protein coupled receptor, mu-opioid receptor (muOR), in the plasma membrane was tracked by single-fluorescent molecule video imaging and high-speed single-particle tracking. At variance with a previous publication, where gold-tagged muOR was found to be totally confined within a domain, which in turn underwent very slow diffusion itself, we found that muOR undergoes rapid hop diffusion over membrane compartments (210-nm and 730-nm nested double compartments in the case of normal rat kidney cell line), which are likely delimited by the actin-based membrane-skeleton "fence or corrals" and its associated transmembrane protein "pickets", at a rate comparable to that for transferrin receptor (every 45 and 760 ms on average, respectively), suggesting that the fence and picket models may also be applicable to G-protein coupled receptors. Further, we found that strong confinement of gold-labeled muOR could be induced by the prolonged on-ice preincubation of the gold probe with the cells, showing that this procedure should be avoided in future single-particle tracking experiments. Based on the dense, long trajectories of muOR obtained by high-speed single-particle tracking, the membrane compartments apposed and adjoined to each other could be defined that are delimited by rather straight boundaries, consistent with the involvement of actin filaments in membrane compartmentalization.

Actins↗

PubMed1992

Antigonadotropic activity of hop extract.

Biological activity of water soluble fractions F-1 and F-2, which were extracted from hop, was studied and its action mechanism was speculated using the immature female SD rats. Administration of the substance significantly inhibited the effects of pregnant mare serum gonadotropin (PMSG) on 22-day-old female rats. Thus, PMSG-induced increases in ovarian weight, estrogen secretion, number of ovulated egg, progesterone production, uterine thymidine kinase activity, and plasma LH level were suppressed significantly. Furthermore, addition of the substance to incubated ovarian cells of the second day after PMSG injection resulted in suppression of FSH-induced estradiol secretion in vitro, probably via cAMP-dependent mechanism. But addition of the substance to incubated pituitary cells from ovariectomized rats did not change in LH secretion.

Animals↗