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Biomedical subjects

M L King

Publications and source records attributed to M L King.

15 recordsLinked to original sources
PubMed1992

Determination of fenoverine, a modulator of smooth muscle motility, in capsules and in human plasma: application to dosage form stability and a pilot study in humans.

Fenoverine is a novel, potent, musculotropic, spasmolytic agent that affects primarily the gastrointestinal tract, bile duct, and female genital organs. A simple, specific, and accurate HPLC method was developed for the determination of fenoverine in capsules and plasma. This method has been successfully applied to stability studies of fenoverine capsules and to a pilot study in a normal, healthy volunteer following oral administration of fenoverine. For the determination of fenoverine in capsules, a Nucleosil 5-micron CN column, with acetonitrile:0.1 M ammonium acetate (60:40) as mobile phase and detection at 254 nm, was employed. The mean correlation coefficient of the calibration curve (n = 6) for the assay was 0.9999 over a concentration range of 24.6 to 147.6 micrograms/mL of fenoverine standard solutions. Fenoverine did not decompose significantly at 4, 45, 55, and 65 degrees C for 3 months. The mean correlation coefficients of within-day and between-day calibration curves were 0.9995 and 0.9999, respectively, over a range of 10 to 1000 ng/mL of fenoverine in plasma. The limit of detection was 10 ng in plasma.

Administration, Oral↗
PubMed1992

Exertional hypotension in thoracic spinal cord injury: case report.

Exertional hypotension is well described in quadraplegics, but there are few descriptions of this hemodynamic response in paraplegics or of treatment modalities to correct this condition. We describe a patient with a complete T3-4 spinal cord lesion who repeatedly demonstrated symptomatic hypotension with wheelchair sports and arm ergometry. We used gas exchange analysis and exercise echocardiography to delineate the mechanism for hypotension. These results enabled us to develop a simple treatment plan consisting of abdominal binding and elastic stockings to avoid recurrent symptoms.

Adult↗
PubMed1992

Case management.

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Humans↗
PubMed1990

Developmental expression of regionally specific cell surface antigens in the Xenopus gastrula.

Molecular markers for specific cell lineages would be useful in studies of cellular differentiation. To isolate such markers monoclonal antibodies (MoABs) were raised against plasma membranes isolated from gastrulating Xenopus embryos. Those antibodies that recognized subsets of cells within the embryo were selected by indirect immunofluorescence. The analysis of eight such MoAbs is presented. Western blot analysis showed that all but one MoAb recognized a complex pattern of glycoconjugates associated with glycoproteins. All the antigens recognized by the MoAbs were maternal in origin and displayed similar spatial patterns of pregastrular expression. This pattern of immunoreactivity at the apical surface was inherited passively during cleavage by the resulting superficial blastomeres suggesting that ectodermal specific markers of maternal origin are pre-localized to the cortical ooplasm in mature oocytes. We suggest that these maternal components may be specific glycosyl transferases. Three different patterns of expression were observed during gastrulation as exemplified by MoAbs 1F10C1, 3A4D1, and 6F10B6. MoAb 6F10B6 was specific for both neural and non-neural epithelium. MoAb 3A4D1 was specific for non-neural epidermis. MoAb 1F10C1 appeared to recognize a protein epitope on an extracellular component expressed by the superficial and involuting epithelial cells. The pattern of expression for the 1F10C1 antigen suggests that it may play a role in facilitating the movement of the involuting cells during gastrulation.

Animals↗
PubMed1989

The developmental expression of the heat-shock response in Xenopus laevis.

We have investigated the Xenopus heat-shock response of somatic cells, oocytes and embryos. Xenopus defolliculated oocytes displayed a highly variable response to heat shock depending on the culture medium. Intact follicles, however, respond to heat stress by synthesizing an invariant pattern of hsps. Although a subset of the hsp70/68 complex is expressed constitutively in the absence of heat shock in oocytes and embryos (hsc70), actual induction of hsps in response to stress does not occur until the blastula stage when transcription of the zygotic genome is first activated. By gastrulation, the hsps of somatic cells, including members of the hsp30/26 complex, were expressed coordinately in response to heat shock. We further show that Xenopus hsps have different solubilities perhaps reflecting their different subcellular locations. The 26,000-30,000 Mr complex (hsp30/26) was present almost exclusively in a detergent-insoluble fraction, as was 25-50% of the hsp70/68 complex and greater than 50% of hsp56, suggesting that these hsps may be associated with the cytoskeleton during a heat shock. In contrast, the other Xenopus hsps (hsp86, hsp75 and hsp61) were totally solubilized in a low-salt buffer.

Animals↗
PubMed1988

Localized maternal mRNA related to transforming growth factor beta mRNA is concentrated in a cytokeratin-enriched fraction from Xenopus oocytes.

The localized maternal RNA Vg1 resides in the cortical region of the vegetal pole of fully grown Xenopus oocytes and is inherited by only a subset of blastomeres in the early embryo [Weeks, D. L. & Melton, D. A. (1987) Cell 51, 861-867]. Because RNA-cytoskeletal interactions may play a role in RNA localization, we have examined the association of Vg1 RNA with components of the oocyte's cytoskeleton. Gel and immunoblot analysis of a detergent-insoluble fraction revealed a greatly simplified protein pattern composed largely of cytokeratins and vimentin. In sharp contrast to the nonlocalized histone H3 mRNA, Vg1 RNA was concentrated some 35- to 50-fold in this insoluble fraction. Extractions at higher salt concentrations yielded preparations further enriched in cytokeratins and in the Vg1 RNA. Upon ovulation, VG1 RNA is released into the soluble fraction. This change in Vg1 RNA distribution coincides with the observed breakdown of cortical cytokeratin filaments [Klymkowsky, M. W., Maynell, L. A. & Polson, A. G. (1987) Development 100, 543-557] and the loss of Vg1 RNA from the cortical region. Our findings are consistent with the hypothesis that RNA-cytoskeletal interactions are involved in the localization and segregation of information during development.

Animals↗
PubMed1988

Expression and segregation of nucleoplasmin during development in Xenopus.

The spatial segregation of informational molecules in the unfertilized egg and embryo has been hypothesized to be a necessary phenomenon for the normal progression of development leading to the determination of cellular phenotypes. This study describes the selection of a monoclonal antibody (Mab: 2G6) that identifies an antigen (Ag: 2G6) which is localized in the germinal vesicle of oocytes and has a discrete pattern of inheritance during embryogenesis. The antigen displayed biochemical and physical characteristics very similar to nucleoplasmin, which is the histone-binding and nucleosome-assembly protein previously described. Immunoblot analysis with purified oocyte nucleoplasmin confirmed this relationship. Indirect immunofluorescence was used to study the temporal expression and spatial distribution of nucleoplasmin. From early cleavage stages through gastrulation, it is preferentially localized in nuclei of blastomeres at the animal pole. By tadpole stages, it was detected only in nuclei of postmitotic cells of the central nervous system and in nuclei of striated muscle. It was not detected in adult tissues. Western blot analysis during embryogenesis revealed at least five immunologically related polypeptides that displayed distinct patterns of expression during development. The different species observed most likely represent different levels of phosphorylation of nucleoplasmin. The more acidic forms, known to be more active in nucleosome assembly, were present during cleavage stages. Analysis of labelled oocyte proteins by two-dimensional immunoblots and autoradiography revealed that synthesis of nucleoplasmin was first detected in stage-2 oocytes, reached 60% maximum levels at stage 3, peaked at stage 4 and was undetectable in stage-6 oocytes. The amount of nucleoplasmin message present does not follow a similar pattern during oogenesis. These results suggest that the message undergoes pronounced changes in translational efficiency during oogenesis. A comparative immunoblot analysis using proteins from a variety of adult tissues revealed that, whereas the polyclonal antisera against amphibian vitellogenic oocyte nucleoplasmin recognized several different, tissue-specific polypeptides, two different monoclonal antibodies (Mab: b7-1D1, Mab: 2G6) failed to recognize any of the adult tissues tested. We conclude that nucleoplasmin is a family of closely related proteins with distinct embryonic and adult members.

Animals↗
PubMed1987

Do Xenopus oocytes have a heat shock response?

Xenopus oocytes have been reported to respond to heat shock in a unique fashion by inducing the translation of performed mRNA encoding the 70,000-Da heat shock protein (hsp70). We have reexamined Xenopus oocytes for this response by analyzing [35S]methionine-labeled oocyte proteins synthesized at ambient (22 degrees C) and at heat shock (35 degrees C) temperatures. Our objective was to use this response in studies directed at understanding how inactive messages are selected for translation. We found no evidence for the induction of hsp70 in completely defolliculated heat-shocked stage 6 oocytes, although they do appear to synthesize constitutively a 70-kDa protein which is a member of the hsp70 complex of proteins. Defolliculated oocytes were also found to be thermotolerant in vitro. Unfertilized eggs, naturally defolliculated at ovulation, also failed to induce detectable hsp70 synthesis after heat shock. In contrast, fibroblasts and the approximately 1000 follicle cells comprising the theca and follicular layers surrounding each oocyte have a classic heat shock response regulated at the transcriptional level. The hsp70 synthesized by stressed follicle cells was not transported into oocytes. We suggest that oocytes in general may represent an exception to the apparent universality of the heat shock response.

Animals↗
PubMedDate not supplied

Isolation and bioactivity of new tanshinones.

Two new diterpenoids, designated neocryptotanshinone and isotanshinone IIB, have been isolated from "Tan-Shen," the root of Salvia miltiorrhiza, together with a known compound, danshexinkun A. Their structures are established by spectral and physical data. Isotanshinone IIB exhibits significant inhibitory activity in vitro on ADP- and collagen-induced aggregation.

Abietanes↗
PubMedDate not supplied

Antitumor agents, 112. Emarginatine B, a novel potent cytotoxic sesquiterpene pyridine alkaloid from Maytenus emarginata.

A new sesquiterpene pyridine alkaloid, emarginatine B [2] has been isolated, along with maytansine [3], from Maytenus emarginata. Emarginatine B showed potent cytotoxicity against human KB cells (ED50 = 0.4 micrograms/ml). Spectral correlations established its structure as a 9-benzoate and C-8 epimer of emarginatine A [1]. The conformational aspect of the latter compound was elucidated by nmr studies, including the use of 2D-nmr techniques and difference nOe methods.

Antineoplastic Agents, Phytogenic↗