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Biomedical subjects

D M Anderson

Publications and source records attributed to D M Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Composition of the gum from Combretum paniculatum and four other gums which are not permitted food additives.

Only three gum exudates are permitted for pharmaceutical and food use by international regulatory authorities, viz. gum tragacanth (Asiatic Astragalus spp.), gum karaya (Sterculia spp.) and gum arabic [Acacia senegal (L.) Willd.], but a wide range of other tree exudates is used for a variety of uses in their countries of origin. This paper presents analytical data for the gum exudates from Atalaya hemiglauca, Cassine aethiopica, Combretum paniculatum, Sclerocarya birrea, and Pseudocedrela kotschyi. These gums may have local technological applications, but are not recommended for addition to foodstuffs.

Amino Acids↗
PubMed1990

Toxin composition variations in one isolate of the dinoflagellate Alexandrium fundyense.

A commonly accepted paradigm in the study of saxitoxin-producing dinoflagellates is that the total concentration of all toxins (toxin content) in one isolate can vary with growth conditions, but that the relative abundance of each toxin (toxin composition) does not change. We demonstrate here that dramatic changes in toxin composition do occur in one isolate of Alexandrium fundyense. In nitrogen- and phosphorus-limited semi-continuous cultures, toxin composition varied systematically with growth rate. When cells grew slowly under severe nutrient limitation, toxin composition was dominated by one or at most two toxin epimer pairs; as nutrient stresses eased at higher growth rates, the toxin profiles became more heterogeneous. Steady-state, sustained nitrogen limitation favored the production of toxins C 1,2 and GTX I,IV, whereas phosphorus limitation produced cells with high relative abundance of GTX II,III. STX reached its highest relative abundance when growth was most rapid. The lack of observed compositional changes in most past studies is probably not due to inherent differences in toxin biosynthetic pathways between the strains of Alexandrium examined, but rather to differences in the physiology of cells grown under different culturing modes (batch vs semi-continuous), methods of toxin analysis, and dominant toxins in the particular isolates examined.

Animals↗
PubMed1990

Meeting information needs of significant others: use of the Cancer Information Service.

Although significant others (spouses, relatives and friends) of cancer patients play an important role in providing support and assistance to the patient, their need for information regarding the disease is frequently overlooked by the health care system. This analysis examines information needs of (1) diagnosed cancer patients, (2) significant others of diagnosed cancer patients and (3) the general public, as reflected in their calls to the Cancer Information Service (CIS), a national toll-free telephone inquiry service. Major focus is on the types of cancer-related subjects significant others inquire about, as well as how they first found out about the CIS. Results indicate that significant others are similar to diagnosed cancer patients in their need for additional information on specific cancer sites, treatment, and referrals for second opinions, but differ in their request for information on counseling services and clinical trials. Additionally, significant others and cancer patients are similar in how they find out about the CIS. In contrast, significant others differ from the general public in their information requirements, as well as in their source of referral to the CIS. While the CIS appears to be a channel of communication capable of addressing the dynamic information needs of significant others, further research concerning the effectiveness of the CIS and other channels of cancer information in satisfying the information requirements of significant others is recommended.

Adult↗
PubMed1989

Paralytic shellfish poisoning in northwest Spain: the toxicity of the dinoflagellate Gymnodinium catenatum.

The highly productive mussel fishery in the Rias Bajas region of northwest Spain has experienced several outbreaks of paralytic shellfish poisoning (PSP) beginning in 1976. In this study, similarities in the HPLC analyses of extracts from toxic shellfish, plankton tows and cultured dinoflagellates from the Rias Vigo and Pontevedra clearly indicate that Gymnodinium catenatum Graham is the organism responsible for recent PSP episodes. The toxin profile of the dinoflagellate contains an unusually high proportion of the low potency sulfocarbamoyl toxins (ca. 90-95 mole %), although a major portion of the overall toxicity is due to the more potent saxitoxin that is present at 5-10% of the total. Toxin profiles of shellfish showed approximately the same composition as that of the dinoflagellate, although the shellfish contained several carbamate toxins (GTX I, GTX II, GTX IV and NEO) that were not detected in G. catenatum culture extracts. The shellfish also contained decarbamoyl toxins (dc-GTX II and dc-GTX-III) at approximately 2% of the total profile. Since these were not detected in the dinoflagellate, their presence reflects either chemical or enzymatic conversion within the shellfish.

Animals↗
PubMed1989

The effect of indomethacin on experimental dental periapical lesions in rats.

The role of prostaglandins in the pathogenesis of dental granulomas and associated bone loss was studied by testing the ability of indomethacin, a potent inhibitor of prostaglandin synthesis, to influence bone resorption in experimentally induced dental granulomas. The cusps of maxillary first molar teeth of Sprague-Dawley rats were ground away, exposing the dental pulps to the oral environment. Daily i.p. injections of 0.1 to 0.2 ml of indomethacin (10 mg per kg) dissolved in 95% ethyl alcohol were administered to one group of the rats while the other group received i.p. injections of 0.1 to 0.2 ml of 95% ethyl alcohol. The rats were killed after 6 wk and specimens of the molar teeth and surrounding jaw bone were taken for routine histopathological processing. The specimens from indomethacin-treated rats demonstrated milder inflammatory changes and a significantly lower degree of periapical alveolar bone resorption. These results support the suggestion that prostaglandins are involved in the events leading to bone resorption in dental periapical lesions.

Animals↗
PubMed1989

Characteristics of ankle-foot orthoses for management of the spastic lower limb.

A retrospective study was done on the effects of a change in the design of ankle-foot orthoses used in the treatment of 29 hemiplegic children. Nine of 13 children treated with plantarflexed ankle-foot orthoses required surgery, compared with only one of 16 with dorsiflexed ankle-foot orthoses. This difference is highly significant.

Ankle↗
PubMed1989

Diffusion of cancer education into schools.

Though implementing health education in schools has numerous advantages, many barriers impede adoption of effective curricula. Diffusion theory provides a framework for understanding why some school systems do not implement comprehensive, sequential, and behaviorally oriented curricula. Reasons for failure to provide optimal health education include competition for time, unawareness of resources and research results, political considerations, long-range planning difficulties, lack of teacher training, lack of testing, other academic priorities, uncertainty about responsibility for health education, and costs. Health educators can overcome such difficulties by working within existing curricular agendas, political interests, and budgets, and by organizing interventions through school health councils, while recognizing local programs, conditions, and resources.

Adolescent↗
PubMed1988

Geometrical aspects of the frustration in the cubic phases of lyotropic liquid crystals.

Bicontinuous cubic phases, composed of bilayers arranged in the geometries of periodic minimal surfaces, are found in a variety of different lipid/water systems. It has been suggested recently that these cubic structures arrive as the result of competition between two free-energy terms: the curvature energy of each monolayer and the stretching energy of the lipid chains. This scenario, closely analogous to the one that explains the origin of the hexagonal phases, is investigated here by means of simple geometrical calculations. It is first assumed that the lipid bilayer is of constant thickness and the distribution of the (local) mean curvature of the phospholipid-water interfaces is calculated. Then, assuming the mean curvature of these interfaces is constant, the distribution of the bilayer's thickness is calculated. Both calculations quantify the fact that the two energy terms are frustrated and cannot be satisfied simultaneously. However, the amount of the frustration can be smaller for the cubic phase than for the lamellar and hexagonal structures. Therefore, this phase can appear in the phase diagram between the other two, as observed in many recent experiments.

Crystallization↗
PubMed1988

Bioimmunoassay (BIA): a sandwich immunoassay scheme employing monoclonal antibodies and hormone receptors to quantify analytes.

When some antigens bind to receptors, a portion of the antigen remains exposed and can be recognized by labeled monoclonal antibodies. By measuring the amount of antibody bound to the antigen-receptor complex, one can quantify the amount of antigen that is present. Since this assay procedure depends on simultaneous receptor recognition of a biologically active site and antibody recognition of a distal epitope on the analyte, we call it a bioimmunoassay. Bioimmunoassays have many of the advantages of radioligand receptor assays (RRA) used to quantify biological activity and, depending on the choice of antibodies employed, may be more specific than RRA. In addition, since they are sandwich assays, they are usually more sensitive than RRA. Bioimmunoassays can be performed in several different modes and in the case described here we used a radiolabeled antibody to detect hormone-receptor complexes. Hence we term this example a bio-immunoradiometric assay or BIO-IRMA. We illustrate the properties of various assay procedures using a monoclonal antibody to the beta subunit of hCG which recognizes an epitope common to all other mammalian LH/hCG-like gonadotropins and which is capable of detecting 10 pg of hCG standard. In principle, this assay can be applied to any material capable of binding to a receptor, enzyme, etc. which can also be recognized by an antibody. Since it is a sandwich type of assay, it is subject to the same advantages and limitations of other sandwich assays except that it can be used to discriminate some biologically active and inactive analytes. Monoclonal antibodies which are prepared from spleen cells of animals immunized with antigen-receptor complexes and selected for their ability to bind antigen-receptor complexes should prove most useful for bioimmunoassay procedures.

Animals↗
PubMed1988

X-ray exposure.

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Humans↗
PubMed1988

Dietary assessment of maternal vitamin D intake and correlation with maternal and neonatal serum vitamin D concentrations at delivery.

Maternal and cord blood 25-hydroxy vitamin D concentrations are positively and significantly correlated. If an easily obtainable maternal dietary history could be used to predict maternal and secondarily cord blood vitamin D status, it would be a useful means of assessing the vitamin D adequacy of the newborn. Therefore, a single assessment of maternal dietary vitamin D intake during the last trimester of pregnancy was correlated with maternal and newborn serum vitamin D concentration. Neither the correlation between maternal dietary history of vitamin D intake and maternal serum 25-hydroxy vitamin D level nor between maternal dietary history and cord blood 25-hydroxy vitamin D level was significant. These data indicate that a single maternal dietary history is an inadequate method of predicting neonatal vitamin status at delivery.

25-Hydroxyvitamin D 2↗
PubMed1987

Detection of conformational changes in human chorionic gonadotropin upon binding to rat gonadal receptors.

After binding to rat testicular or ovarian luteinizing hormone (LH) receptors, human chorionic gonadotropin (hCG) and mammalian LH can be detected with monoclonal antibodies directed against a conserved epitope on the beta subunit of the hormones. Two such anti-hCG/anti-LH monoclonal antibodies, known as B105 and B110, compete with one another for binding to this epitope region on free and receptor-bound hormone. By comparing the affinities of B105 and B110 for these two forms of hCG, we have detected apparent changes in the structure of the hormone which develop subsequent to receptor binding. Whereas the affinity of B105 for receptor-bound hCG is approximately 10-fold lower than that for free hCG, the affinity of B110 for receptor-bound hCG is nearly 20-fold greater than that for free hCG. Both B105.hCG and B110.hCG complexes bind to the receptor; however, they have approximately 25 and 50% lower affinity than hCG. Thus, although B110 binds better to the form of hCG which is bound to receptors, binding of B110 to hCG does not appear to induce a conformational change in the hormone which facilitates hormone-receptor binding. Consequently, both B105 and B110 partially inhibit binding of hCG to its receptors. Fab fragments of B105 and B110 are as effective as intact B105 and B110 in inhibiting the binding of labeled B105 and B110 to hCG-receptor complexes, suggesting that circular complexes which might be formed by the interaction of divalent antibody, two molecules of hCG, and two membrane-bound receptors or one divalent receptor are not contributing to the affinity of the antibodies for receptor-bound hCG. Alternatively, formation of circular complexes can explain an increase in apparent affinity of B105 for ovine or bovine LH-receptor complexes. Data obtained with B105 suggest either that the structure of the epitope is altered following binding or that a portion of the epitope is partially obscured when hCG binds to the receptor. In contrast, the data obtained using B110 are not explained by models in which steric factors reduce the affinity of the antibody for the hormone-receptor complex. Therefore, as a minimal explanation for these observations, we postulate that the conformation of the B105/B110 epitope region is altered following binding of the hormone to receptors. The nature of the conformational change and its relationship to LH/hCG action is unknown.

Animals↗
PubMed1987

Nonreceptor binding of human chorionic gonadotropin (hCG): detection of hCG or a related molecule bound to endometrial tissue during pregnancy using labeled monoclonal antibodies that bind to exposed epitopes on the hormone.

When hCG adsorbs to surfaces, including membranes from tissues that lack specific hCG receptors, it adsorbs with a particular orientation. Some sites on the alpha- and beta-subunits project away from the surface and can be detected with radiolabeled monoclonal antibodies. Other epitopes, which are located on a region on the hormone that presumably contacts the surface, lose their ability to bind antibody. Using antibodies specific for epitopes on hCG which remain exposed and can be detected when the hormone is adsorbed to rat brain homogenates, we found hCG or closely related substances bound to progestational decidual tissues. Immunologically reactive material adsorbed to the decidual tissue increased and decreased in parallel with the serum levels of hCG throughout pregnancy. Binding of labeled monoclonal antibody to substances similar or identical to hCG in other tissues, including placenta and fetal lung, but not red cells, also was identified. Unlike material adsorbed to decidual tissues, receptor-bound hCG was not recognized by any of our alpha-subunit-specific antibodies. This finding suggests either that the adsorbed hormone has a different orientation than receptor-bound hormone or that the adsorbed hormone has dissociated into subunits. These studies represent the first detection of nonreceptor binding of hCG or related molecules to tissues lacking receptors or presumed not to synthesize the hormone. The role of nonreceptor-bound hCG, if any, is unknown. Other than its effects on stimulation of luteal steroidogenesis during early pregnancy, the role of hCG during most of pregnancy has not been determined. Conceivably, the nonreceptor binding we identified is related to a role for hCG in pregnancy that is not associated with an action on the ovarian LH receptor.

Adsorption↗