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Biomedical subjects

H N Wood

Publications and source records attributed to H N Wood.

At least 19 recordsLinked to original sources
PubMed2001

Differing approaches to the identification of Munchausen by Proxy Syndrome (MBPS): a case of professional training or role of experiental exposure.

Much recent research recognises that a multidisciplinary team approach is best to manage Munchausen by Proxy Syndrome (MBPS), an extreme manifestation of factitious disorder by proxy (FDBP). Generally described as fabricating illness symptoms in a child to serve the adult caretaker's attention seeking needs, identification of the disorder remains problematic. Various relevant professionals differ in their emphasis and vary in their knowledge of the condition which in turn can inhibit collaborative investigation and intervention. Reasons for these difficulties are described together with a rationale for better interagency co-operation, not least because the outcome in some cases is the death of the child. The present paper discusses the implications of professional training in identification of MBPS and the value of previous exposure to cases in increasing likelihood of detection. An empirical study is described that presents working models used by different professionals to identify cases of MBPS (n=12). Analysis of qualitative interview material by means of a multidimensional scaling procedure revealed no clear grouping in terms of occupational specialism, rather commonalities of approach appeared related to previous experience with MBPS. The range of salient factors elicited was used to devise a parsimonious screening checklist intended for use by different professional groups. Finally, future research in terms of investigating psychometric profiles of MBPS child abusers and demonstrating the utility of the checklist for use by multidisciplinary teams in early detection and subsequent management of MBPS is discussed.

Journal Article↗
PubMed1987

The structural characterization of endogenous factors from Vinca rosea crown gall tumors that promote cell division of tobacco cells.

The ability of two compounds, a cytokinin and an auxin, to stimulate tobacco cell growth and differentiation has been known for greater than 30 years, but the molecular mechanism of this activation is still unknown. Previous reports of factors endogenous in crown gall tumors of Vinca rosea that could replace the cytokinin requirement in tobacco cell culture has motivated an investigation of these tissues. The optimization of a reverse-phase isolation scheme has led to the purification of sufficient material to allow for the identification of six different related compounds. The structures of two of these compounds have been assigned as a set of epimeric dehydrodiconiferyl alcohol beta-D-glycosides. The structure of these compounds suggests that they would most likely be derived from the plant cell wall.

Cell Division↗
PubMed1987

Cell division promoting activity of naturally occurring dehydrodiconiferyl glucosides: do cell wall components control cell division?

Naturally occurring isomers of the dehydrodiconiferyl glucosides have been isolated from Vinca rosea crown gall tumors and have been tested for cell division promoting activities in the tobacco pith and leaf assay systems. The enantiomeric isomers A and B are active, although they are required at concentrations up to 2 orders of magnitude higher than zeatin riboside to promote comparable growth. We estimate that the active dehydrodiconiferyl glucosides are present in rapidly growing tissues (tumor tissue, habituated tissue, cultured nontransformed tissue) in micromolar concentrations. In quiescent tobacco pith tissue, the levels of these compounds are reduced by a factor of 100. These results suggest that cytokinin may exert control of cell division through the accumulation of molecules (the dehydrodiconiferyl glucosides) that are apparent cell wall components.

Cell Division↗
PubMed1985

Modulation of oocyte maturation by cyclic adenosine 3', 5'-pyrophosphate.

The germinal vesicle (GV) of follicle-enclosed oocytes in mammals remains arrested at the dictyate state of meiosis. Upon releasing the oocytes from the follicles, the meiotic process resumes, leading to dissolution of the GV (GVBD), suggesting that factors in the follicular fluid sustain the meiotic arrest of oocytes. In the present study the spontaneous resumption of meiosis was blocked by the addition of cyclic adenosine 3', 5'-pyrophosphate (cAPP) plus dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP), at final concentrations of 25 and 50 microM, respectively. These compounds were ineffective when added separately at these concentrations. None of the other related compounds tested with dbcAMP blocked GVBD. Bovine follicular fluid (BFF) was analyzed for inhibitors of GVBD. BFF was extracted with 70% ethanol and the ethanolic extract chromatographed on Dowex 1-X8 column. The fraction eluted with 0.1 N HCl markedly inhibited GVBD of isolated mouse oocytes in combination with dbcAMP. The active BFF substance and cAPP block spontaneous GVBD of mouse oocytes and may be related substances. The present study supports the thesis that meiotic arrest at the dictyate stage in oocytes is sustained by factors present in follicular fluid and may act in association with cAMP.

Animals↗
PubMed1982

Variation in hormone autonomy and regenerative potential of cells transformed by strain A66 of Agrobacterium tumefaciens.

Mutant Agrobacterium tumefaciens strain A66 is shown to differ from its wild-type progenitor (strain A6) by a spontaneous 2.7 kb DNA insert into the T-DNA region of its Ti plasmid. Tobacco stems transformed by A66 exhibit an attenuated response characterized by slow growth and shoot proliferation. Clonal analysis demonstrates that this response is due to an alteration in the growth and regenerative potential of transformed cells, rather than to variation in the frequency of fully autonomous cells within the primary tumor. Cloned A66 transformed tobacco cells exhibit an auxin requirement for growth that can be overcome by shoot proliferation. Other host species, however, may complement the A66 mutation yielding fully auxin-independent tumors when transformed by this bacterium.

Cell Transformation, Neoplastic↗
PubMed1978

Inhibition of mammalian protein kinase and phosphodiesterase activities by a cyclic AMP-like compound isolated from higher plants.

A cyclic AMP-like substance has been isolated from higher plant tissues which can be quantitated with the use of a radioimmunoassay similar to that described by A. L. Steiner, D. M. Kipnis, R. Utiger, and C. Parker [(1969) Proc. Natl. Acad. Sci. USA 64, 367-373]. This compound has been extensively purified and is chromatographically distinct from authentic cyclic AMP. This cyclic AMP-like compound inhibited beef heart 3':5'-cyclic-nucleotide phosphodietsterase (3':5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17), with half-maximal inhibition occurring at a concentration of 7.6 X 10(-10) M cyclic AMP equivalents. The compound also inhibited cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase; EC 2.7.1.37) from bovine heart, with half-maximal inhibition of mixed histone phosphorylation occurring at 8.0 X 10(-11) M cyclic AMP equivalents. Equipotent inhibition of phosphorylation and associated trace ATPase activity were observed with the purified catalytic subunit of cyclic AMP-dependent protein kinase from calf thymus with a synthetic heptapeptide as substrate. Moreover, steady-state kinetic analysis of this inhibition in the latter system showed it to be nonlinear and noncompetitive versus MgATP.

Adenosine Triphosphatases↗
PubMed1976

Studies on the recovery of crown gall tumor cells.

Our previous studies have shown that, while a persistent but potentially reversible suppression of the tumorous state appears to be a characteristic feature of the vegetative phase of teratoma shoot growth in the crown gall disease of plants, a recovery from that state occurs during the reproductive phase. An analysis has now been made of the reproductive process in an attempt to define the precise stage at which recovery occurs. The results of this analysis have shown that diploid somatic cells of teratoma-derived flower parts such as those found in petals and filaments are inherently neoplastic. On the other hand, haploid cells of plants grown from anthers of the same flowers and diploid cells of F(1) generation plants grown from teratoma-derived seed have, by generally accepted criteria, recovered from the tumorous state. These findings have been interpreted to mean that the loss of neoplastic properties occurs in crown gall teratoma cells during meiosis rather than during fertilization or later stages of the reproductive process.An analysis of more than 2000 teratoma-derived tumor shoots has shown, moreover, that a recovery from the tumorous state may also occur, although apparently as a very rare event, during the vegetative phase of teratoma shoot growth.

Journal Article↗
PubMed1976

Suppression of the neoplastic state with the acquisition of specialized functions in cells, tissues, and organs of crown gall teratomas of tobacco.

The neoplastic state in cells of tissues and organs that develop from cloned lines of crown gall teratomas of tobacco may be completely but reversibly suppressed. Stems and leaves found on teratoma shoots may appear morphologically normal and such organs contain all of the specialized cell types and are histologically and functionally indistinguishable from those found in normal tobacco shoots of comparable age. When however, specialized cells of several different kinds that are present in stems and leaves of the teratomas are excised from the plant and grown on a basic culture medium they again assume their neoplastic properties. The results of this study indicate that the morphogenetic factors and mechanisms that govern so precisely growth, cellular differentiation, and organogenesis during the normal course of development can completely suppress the tumorous state, leading to the formation of cells, tissues, and organs that appear normal in every respect but are, in fact, inherently neoplastic. Whether the normal or tumor phenotype is expressed appears to depend on the activation or repression of select biosynthetic systems, one of which, the auxin sytems, has been identified here.

Cell Differentiation↗
PubMed1974

A comparative study of cytokinesins I and II and zeatin riboside: a reply to Carlos Miller.

Two cell-division-promoting factors, which have partition coefficients of 1.9 and 2.75 determined by 500-tube countercurrent distribution in a butanolwater system, have been repeatedly isolated in this laboratory from crown gall tumor tissues of Vinca rosea L. These substances have been given the trivial names cytokinesin I and cytokinesin II, respectively. Chemical and mass spectrometric analyses suggest that both cytokinesins are substituted hypoxanthines and are thus very different compounds from the 6-substituted adenyl cytokinins. Carlos Miller, using a very different and far more drastic isolation procedure, obtained one main cell-division-promoting factor from these same tumor tissues, which he identified as ribosyl-trans-zeatin. On the basis of this finding, and without an attempt to repeat our studies, questions have been raised by Miller concerning the existence of the cytokinesins as biologically active substances. We have, therefore, compared some pertinent physical, chemical, and biological properties of the cytokinesins with those of zeatin riboside, have demonstrated that these three substances can be cleanly separated from one another by a number of different methods and that each behaves as a pure substance in the several systems, and, finally, we have shown that the cytokinesins are not contaminated with ribosyl-trans-zeatin and thus do not owe their biological activity to such a contaminant.

Amino Alcohols↗
PubMed1973

Programming of cells for death under experimental conditions: relevance to the tumor problem.

An attempt was made in this study to determine more precisely the nature of the factors that are involved in the programming of cells for a form of terminal cellular differentiation that results in death. These studies demonstrated that both the cytokinesins, which are potent inhibitors of plant and animal adenosine 3':5'-cyclic monophosphate phosphodiesterases, and 8-bromoadenosine 3':5'-cyclic monophosphate, which is a stable, biologically active form of adenosine 3':5'-cyclic monophosphate, are highly effective in encouraging differentiation of parenchyma cells into tracheary elements with accompanying death. Since adenosine 3':5'-cyclic monophosphate and theophylline when used together were also effective, the results reported here suggest that adenosine 3':5'-cyclic monophosphate is somehow importantly involved in the conversion of parenchyma cells into tracheary elements in this system. The possible significance to the tumor problem generally of the programming of cells for terminal differentiation, with or without resulting death, is discussed.

Bromine↗
PubMed1973

8-bromoadenosine 3':5'-cyclic monophosphate as a promoter of cell division in excised tobacco pith parenchyma tissue.

8-Bromoadenosine 3':5'-cyclic monophosphate, when used in association with an auxin, can completely replace the cell-division-promoting activity of either a cytokinesin or a 6-substituted adenylyl cytokinin in excised tobacco pith parenchyma tissue. The 8-bromo derivative of adenosine 3':5'-cyclic monophosphate was found to be far more resistant to degradation by plant adenosine 3':5'-cyclic monophosphate phosphodiesterases than was adenosine 3':5'-cyclic monophosphate. These findings appear to provide further support for the suggestion made earlier that the cytokinesins, which are potent inhibitors of both plant and animal adenosine 3':5'-cyclic monophosphate phosphodiesterases, exert their cell-division-promoting effects as regulators of adenosine 3':5'-cyclic monophosphate.

Journal Article↗
PubMed1972

The inhibition of plant and animal adenosine 3':5'-cyclic monophosphate phosphodiesterases by a cell-division-promoting substance from tissues of higher plant species.

One member of a new class of cell-division-promoting factors, that has been given the trivial name of cytokinesin I, is a potent inhibitor of adenosine 3':5'-cyclic monophosphate phosphodiesterases of both plant and animal origin. Since an adenylate cyclase has been demonstrated in this study to be present in plant cells, the results suggest that cytokinesin I may be exerting its biological effects in promoting division in cells of higher plant species as a regulator of adenosine 3':5'-cyclic monophosphate.

Adenylyl Cyclases↗
PubMed1970

Revised identification of the chromophore of a cell division factor from crown gall tumor cells of Vinca rosea L.

Low-resolution mass spectrometry, UV spectra in acid, neutral, and alkaline solution, and nuclear magnetic resonance indicated that the chromophore of one member of a new class of cell division-promoting factors isolated from crown gall tumor tissues consisted of a 3,7-alkyl-2-alkylthio-6-purinone with one free proton in the ring. Glucose constitutes the sugar moiety.

Cell Division↗
PubMed1969

Studies on the distribution and properties of a new class of cell division--promoting substances from higher plant species.

One member of a new class of cell division-promoting substances, which are nicotinamide derivatives, has been found to be present in dividing cells of tobacco and cactus. These plants are taxonomically far removed from one another and from Vinca rosea L., the plant species from which the new substances were first isolated. Because of their apparent wide distribution among dicotyledonous plant species, the question is raised as to whether the nicotinamide derivatives rather than the purine cytokinins may not, in fact, be the naturally occurring cell division factors that are directly involved in promoting cytokinesis in higher plant species. Unequivocal evidence is presented to show that the nicotinamide derivatives do not owe their biological activity to contamination by 6-substituted purine cytokinins.

Cell Division↗