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Biomedical subjects

A Nicholson

Publications and source records attributed to A Nicholson.

At least 91 records · Page 5Linked to original sources
PubMed1977

Isolation and characterization of Guinea pig properidin.

Guinea pig properdin was purified to homogeneity by employing as an assay during isolation its capacity to augment the hemolytic activity of a heterologous human C3b-dependent C3 convertase, C3B. The purified protein elicited a monospecific antibody response in a rabbit. The antiserum, by immunodiffusion, gave a reaction of identity between a protein in whole guinea pig serum and the immunogen. A solid phase immunoadsorbent prepared with the antiserum removed properdin function from the purified protein. The purified guinea pig protein exhibited the classical properdin function of reconstituting a human RP for zymosan-induced C3 inactivation. The guinea pig properdin also agglutinated red cell intermediates bearing either guinea pig or human C3b and retarded the decay of homologous C3 convertase, C3B. These activities are the same as those observed for purified human properdin and validate the amplification function of properdin on terminal component activation in a second species.

Animals↗
PubMed1976

Hydrolysis of peptides within lumen of small intestine.

The quantitative significance of intraluminal peptide hydrolases in the terminal stages of peptide digestion has been investigated, and the precise origins of these enzymes have been determined. Intestinal contents and mucosae were obtained from rats anethetized with ether. Experiments carried out on pancreaticobiliary secretions and germfree rats show that pancreatic and bacterial enzymes do not contribute significantly toward the luminal digestion of dipeptides. Chemical assay data, thermostability studies, and examination of electrophoretic mobilities of luminal peptide hydrolases indicate that jejunal enzymes originate predominantly from the cytoplasm of intestinal mucosal cells, whereas the brush border of muosal cells is a major source of the enzymes in the ileum. With glycl-L-phenylalanine and L-phenylalanyl-glycine as substrates, jejunal luminal activity was less than 2.6% of mucosal activity. Brush-border peptide hydrolase activity in ileal contents, however, was 11.9% and 40.7% of mucosal brush-border activity for the two substrates. Luminal enzymes thus play an insignifcant role in the terminal digestion of peptides in the jejunum, but have a much more important role in the ileal digestion of peptides.

Animals↗
PubMed1975

On the mechanism of cytolysis by complement: evidence on insertion of C5b and C7 subunits of the C5b,6,7 complex into phospholipid bilayers of erythrocyte membranes.

The doughnut hypothesis of cytolysis by complement [Mayer, M. M. (1972) Proc. Nat. Acad. Sci. USA 69, 2954-2958] describes an annular structure made up of C5b-9 (complement factors C5b, C6, C7, C8, and C9) which becomes inserted in the lipid bilayer of the cell membrane, thus creating a hole. We now present initial explorations of this hypothesis. EAC1-6 and EAC1-7 (sheep erythrocytes carrying rabbit antibody and complement factors C1 through C6 or C1 through C7, respectively), prepared with either 125I-C3 or 125I-C5 were incubated with trypsin and the release of bound 125I was measured. In the case of 125I-C3, all of the radioactivity was released by trypsin from both intermediates. With 125I-C5, trypsin released all of the 125I from EAC1-6, but only 40-55% from EAC1-7. Possible reasons for resistance of the C5b subunit in EAC1-7 to tryptic digestion are discussed; in terms of the doughnut hypothesis it would be due to shielding by lipid molecules as a consequence of insertion into the lipid bilayer. In accord with this interpretation we have also found that C5b in EAC1-7, but not in EAC1-6, resists elution by 0.3 M NaC1. Similarly, we have found that 125I-C7 in EAC1-7 resists stripping by trypsin. Hence, we now propose the hypothesis that hydrophobic polypeptide chains from the C5b and the C7 subunits of C5b,6,7 complex become inserted in the phospholipid bilayer and that subsequent reactions with C8 and C9 open a channel across the membrane.

Animals↗
PubMed1975

Suicidal attempts in an outer region of metropolitan Melbourne and in a provincial region of Victoria.

A two year study of attempted suicide was undertaken in two Victorian regions. Incidence rates of 16.7 and 22.1 per 10,000 population were found in the metropolitan and provincial regions respectively. A number of factors were considered and found relevant to the difference in incidence. In addition, other parameters including multiple attempts, seasonal distribution, method used, association with alcohol and referral to psychiatric care were considered. Our findings are compared with those of earlier studies reported in Australia.

Adolescent↗
PubMed1975

Heat labile opsonin system to pneumococcus.

Normal mammalian sera contain the heat labile opsonin system that promotes the phagocytosis of various microorganisms by polymorphonuclear leukocytes. Because the heat labile opsonin system is present in normal nonimmune sera and because it operates against various microorganisms in an apparently nonspecif manner, it is considered to play an important role during the early phase of an acute bacterial infection. The role of various factors participating in the heat labile opsonin system, and its in vivo significance are discussed.

Animals↗
PubMed1975

Interaction of C3b, B, and D in the alternative pathway of complement activation.

The interaction of ZXd2, an insoluble intermediate of the alternative pathway on zymosan (Z5), with factor B and the enzyme D proceeds in a two-step reaction: 1) B binds in the presence of Mg++ to ZXd2 to form the intermediate ZXd2B, 2) B bound to ZXd2 is subsequently activated enzymatically by D to yield the complex ZXd2B which cleaves C3. Evidence was obtained that C3b, which is present on ZXd2, is required for ZXd2B formation. Studies of the functional role of C3b for ZXd2B formation revealed that C3b is involved in the first reaction step i.e., binding of B to ZXd2 to yield ZXd2B. Formation of ZXd2B is inhibited by pretreatment of ZXd2 with either anti-C3 Fab or with C3b-INA. Low ionic strength of about 2 mS was found to favor the interaction of the C3b with B. Mg++ concentrations from 1 to 31 mM as well as variation of pH in the range from 6.2 to 8.5 did not greatly influence the reaction of B with ZXd2. For the enzymatic activation of B only C3b on ZXd2 and factor D are required. This is concluded from the finding that fluid phase C3b is sufficient for the activation of B in the presence of D. This does not exclude the fact that other proteins present on ZXd2 may help to stabilize the intermediate ZXd2B or the enzymatically active complex AXd2B, or both of them.

Animals↗
PubMedDate not supplied

Beliefs about dietary factors in breast cancer prevention among American women, 1991 to 1995.

OBJECTIVE: To estimate the percentage of American women in various demographic groups who believe or have heard that dietary factors have a role in breast cancer prevention and to assess changes between 1991 and 1995. METHODS: Telephone surveys were conducted of random samples of 509 women in 1991 and 510 women in 1995. Subjects were asked questions with increasing prompting to gauge their beliefs about the role of dietary factors in breast cancer prevention. RESULTS: The percentages of women citing dietary factors (reducing intake of fat or meat or increasing intake of vegetables, fruit, fiber, or vegetarian meals) as reducing the risk of developing breast cancer were 20% in 1991 and 23% in 1995. These numbers were lower among young, poor, and less educated women. When specifically prompted to consider dietary steps, the number citing such factors increased to 37% in 1991 and to 52% in 1995. CONCLUSION: The belief that there is a role for dietary factors in breast cancer is far from universal among American women, although some measures of the awareness of dietary factors increased significantly between 1991 and 1995. Women are more likely to cite mammography and breast self-examination as preventive steps, even though both are designed for detection rather than prevention. Additional efforts are needed to provide information on cancer prevention, particularly to young, poor, and less educated women, and to clarify the role of prevention as distinct from cancer detection.

Adult↗
PubMedDate not supplied

Giant colonic diverticulum.

BACKGROUND: Over 100 giant colonic diverticuli have been recorded in the literature to date. The magnetic resonance imaging (MRI) and pathophysiology of their aetiology have rarely been described. AIM: To report a giant colonic diverticulum along with the MRI of this clinical entity. RESULTS: An 87 year old female presented with symptoms of tenesmus, urgency and alteration in bowel habit. A type I giant colonic diverticulum was diagnosed and a segmental colonic surgical resection was performed. The plain abdominal radiograph, barium enema and MRI, along with classification and management options are presented. CONCLUSION: Giant colonic diverticuli are rare surgical curiosities that may be successfully treated with either primary segmental or extended colonic resection.

Aged↗
PubMedDate not supplied

Anastomoses of the ovarian and uterine arteries: a potential pitfall and cause of failure of uterine embolization.

Four women with symptomatic uterine fibroids were treated by uterine artery embolization (UAE). In all cases both uterine arteries were embolized via a single femoral puncture with polyvinyl alcohol using a selective catheter technique. In three cases, the ovarian artery was not visible on the initial angiogram before embolization, but appeared after the second uterine artery had been treated. In one case of clinical failure following UAE, a repeat angiogram demonstrated filling of the fibroids from the ovarian artery. Anastomoses between uterine and ovarian arteries may cause problems for radiologists performing UAE and are a potential cause of treatment failure.

Adult↗