Search PubMed⌕ Search

Biomedical subjects

J Wood

Publications and source records attributed to J Wood.

At least 127 records · Page 7Linked to original sources
PubMed1998

Effect of temperature on apical membrane remodeling in ADH-stimulated toad urinary bladders.

Pretreatment and removal of vasopressin (ADH) in toad urinary bladder renal model tissues induces endocytosis at 25 degrees C. The objective of the current study is to determine if apical membrane remodeling, as well as transepithelial water flow, can be affected by lowering the temperature to 15 degrees C. Control toad urinary bladders in the presence of an osmotic gradient at either 25 degrees C or 15 degrees C when visualized by scanning electron microscopy (SEM) show a typical apical membrane surface with no apparent surface differences. ADH-treated tissues following 15-min stimulation at 25 degrees C or 15 degrees C revealed a propagation of apical microvilli on their surface membranes. After 15 min following removal of ADH, bladder tissues at 25 degrees C or 15 degrees C showed surface invaginations involving over 44% and 80% of granular cells, respectively. The rate of water flow in tissues at 15 degrees C remained elevated compared to tissues held at 25 degrees C. This was consistent with the observation that ADH-stimulated tissues following washout at 15 degrees C still had marked apical membrane surface involvement. However, at 30 min and 60 min postwashout, ADH-stimulated tissues at 15 degrees C recovered considerably, with a reduction in the number of shallow apical membrane invaginations involving fewer than 33% and 20% of granular cells respectively. This may indicate that the membrane undergoes continuous remodeling even at cold temperature conditions but with a different half-time. Control bladder tissues subjected to transmission electron microscopy (TEM) reveal a dense cytoplasmic profile with a scattered distribution of secretory granules, rough ER cisternae, mitochondria, and little or no vacuolation. In contrast, ADH-stimulated bladder tissues displayed a vacuolated cytoplasm, expanded rough ER cisternae, and ruffled basolateral membranes. These observations suggest that the apical membrane undergoes considerable reorganization following cessation of hormone action and that lowering the temperature reduces the rate of membrane remodeling and thus may provide a means to monitor the processes of endocytosis and the mechanisms responsible for water channel retrieval.

Animals↗
PubMed1998

Passive transfer of growth-inhibitory antibodies raised against yeast-expressed recombinant Plasmodium falciparum merozoite surface protein-1(19).

Purified rabbit immunoglobulin raised against yeast-expressed recombinant FVO or 3D7 Plasmodium falciparum merozoite surface protein-1 (MSP-1) 19k-D C terminal fragment (MSP-1(19)) was transfused into malaria-naive Aotus nancymai monkeys that were immediately challenged with FVO asexual stage malaria parasites. Control monkeys received rabbit immunoglobulin raised against the sexual stage antigen Pfs25 or Aotus hyperimmune serum obtained from monkeys immunized by P. falciparum infection and drug cure. Passive transfer of rabbit anti-MSP-1(19) failed to protect against homologous or heterologous challenge and, when compared with negative controls, there were no differences in prepatent periods or time to treatment. Interestingly, rabbit anti-MSP-1(19), but not anti-Pfs25, immunoglobulin, and immune monkey serum prevented the development of antibodies directed against MSP-1(19) fragment by infected monkeys, indicating that the antibodies were reactive with native MSP-1(19) antigen in vivo. The prepatent period and time to treatment was greatly delayed in the two monkeys that received Aotus immune serum, both of which developed a chronic intermittent low level infection. In vitro parasite growth inhibition assays (GIAs) confirmed the presence of inhibitory activity (40% maximum inhibition) in concentrated anti-MSP-1(19) immunoglobulin (4.8 mg/ml), but the peak concentrations we achieved in vivo (1 mg/ml) were not inhibitory in vitro. Subinhibitory levels of anti-MSP-1(19) antibodies achieved by passive transfer were not protective against P. falciparum challenge.

Animals↗
PubMed1998

The effect of different forms of monocular occlusion on measures of central visual function.

The purpose of this study was to determine whether clinically used measures of central visual function were influenced by the method of monocular occlusion used. Twenty young visually normal subjects were tested both monocularly and binocularly using an Australian Vision Chart No. 5 (which includes high and low contrast letters) and the Pelli-Robson letter chart. During monocular assessments, the non-tested eye was occluded with either a translucent (frosted) diffuser, a +1.50 D (fogging) lens, or a white opaque occluder. A significant difference in monocular sensitivity between the three occluder types was found for Pelli-Robson contrast sensitivity, and the high and low contrast letter acuities, with poorest performance being recorded with the opaque occluder in all cases. The same trend was evident in the derived binocular summation ratios which were found to vary with the type of occluder used before the non-tested eye, as well as with the visual function measured. The data imply that binocular interactions occur during 'monocular' testing of central visual function and that these interactions vary with the method of occlusion used. The clinical ramifications of these results are discussed.

Adolescent↗
PubMed1997

The ATP-depleting reagent iodoacetamide induces the degradation of protein kinase C alpha (PKC alpha) in LLC-PK1 pig kidney cells.

The alkylating reagent iodoacetamide, a potent inhibitor of sulfhydryl proteases, was found to stimulate the selective degradation of protein kinase C alpha (PKC alpha) isoform (80 KDa). Treatment of LLC-PK1 cells with iodoacetamide (0.5-15 mM) for 30-90 minutes at room temperature allowed by western blotting on total cell homogenate, revealed the appearance of an 50 KDa band that was still recognized with the antibody. However, iodoacetamide (15 mM) resulted in the total disappearance of the 80 KDa protein. Serine protease inhibitors, metalloprotease inhibitors and leupeptin failed to prevent the degradation of PKC alpha. The degradation persisted at 4 degrees C and in the absence of Ca2+. Iodoacetamide had no direct effect on purified PKC alpha. PKC activities in iodoacetamide-treated cells were also inhibited. In conclusion, the degradation of PKC alpha is a novel phenomenon. The degradation process could not be prevented by known protease inhibitors or in the absence of Ca2+ or by incubation at 4 degrees C and appears to involve interactions with unknown cellular intermediates.

Adenosine Triphosphate↗
PubMed1997

Talking about feelings: young children's ability to express emotions.

OBJECTIVE: The aim is to establish which emotion-descriptive language is used by children at different ages. METHOD: Fifty-six children (aged 5 to 11 years) were presented with a set of plastic playpeople. Scenarios were enacted using the toys to elicit emotion descriptive vocabulary in response to the interviewer's question: How do you think s/he feels about that? Eight adult subjects participated as a control. RESULTS: Children under the age of 8 years have a limited repertoire of labels to describe emotions. Even 11-year-olds are unable to produce vocabulary which expresses emotion concepts described by adults. The implications of our findings for child-police interviews are discussed.

Adult↗
PubMed1997

Generation of an infectious cDNA of a highly cardiovirulent coxsackievirus B3(CVB3m) and comparison to other infectious CVB3 cDNAs.

An infectious cDNA of a highly myocarditic coxsackievirus B3 (CVB3m; Nancy strain) was cloned. Sequence data revealed 43 extra non-viral nucleotides upstream of the initial 5' sequence. However, the authentic 5' end sequence was maintained during replication of viral RNA transfected into HeLa cells, suggesting the RNA synthesizing complex edits the picornaviral 5' terminus sequence. Nucleotide sequences of the 5' nontranslated region and the capsid protein gene sequence of CVB3m were compared with the published sequences of five other CVB3 Nancy strains and two main lineages were found. In comparative assays for cardiovirulence, three of four CVB3 tested were cardiovirulent in adolescent male CD-1 mice. Only one of the three available CVB3 strains was neutralized with several anti-CVB3m monoclonal antibodies, suggesting that mutations in the surface epitopes of the capsid polypeptides contribute to antigenic drift within the serotype, perhaps in part through immunoselective pressures. Thus, phenotypic diversity of CVB3 within the prototype Nancy strain is an example of RNA viruses adapting to changing environments (cells, mice and humans) through mutations and selective pressure.

Animals↗
PubMed1997

Synergies and coincidence requirements between NO, cGMP, and Ca2+ in the induction of cerebellar long-term depression.

Parallel fiber synapses onto Purkinje neurons in acute cerebellar slices undergo long-term depression (LTD) when presynaptic activity coincides with postsynaptic depolarization. These electrical inputs can be respectively replaced by nitric oxide (NO) and Ca2+ photolytically released inside the Purkinje neuron, showing that these two messengers are sufficient for LTD induction. NO acts via cGMP production because inhibitors of guanylate cyclase prevent LTD but can be circumvented by photoreleased cGMP combined with Ca2+ elevation. Three inhibitors of cGMP-dependent protein kinase, Rp-8Br-PET-cGMPS, KT5823, and a novel pseudosubstrate peptide, all block LTD. LTD induction permits <10 ms gap between NO release and Ca2+ elevation, whereas 200-300 ms is allowed between uncaged cGMP and Ca2+ increase. This surprising difference in timing precision can be explained either by tighter localization and faster decay of cGMP when generated by NO rather than uncaging, or by two independent coincidence detectors in series.

Animals↗
PubMed1997

A simple program to create exact person-time data in cohort analyses.

BACKGROUND: Before disease rates can be calculated a tabulation of the length of follow-up for each person in the cohort has to be made. In complicated analyses such tabulations are often stratified by many characteristics, some which show no change with time, such as gender or year of birth, and some which do change with time, such as age or cumulative exposure. Available computer programs often restrict the way these tables can be made, particularly when handling time-dependent variables. METHODS: This paper presents a simple computer program which calculates the length of follow-up for each person in a study. RESULTS: Person-time data can be tabulated by a large number of variables using this method. This program is extremely flexible in the way that time-dependent variables can be created, can categorize observations by any unit of person-time, and will run on a range of platforms including a personal computer. CONCLUSIONS: This method should simplify the task of creating person-time data for analyses of disease rates in epidemiological studies.

Cohort Studies↗
PubMed1997

Light versus heavy sedation after cardiac surgery: myocardial ischemia and the stress response. Maritime Heart Centre and Dalhousie University.

UNLABELLED: The influence of light versus heavy sedation after coronary artery bypass graft (CABG) surgery on the development of postoperative myocardial ischemia has not been described. After uncomplicated CABG surgery, 50 patients were randomly assigned to receive LOW (n = 24; target Ramsay Sedation Score [RSS] = 2) or HIGH (n = 26; target RSS = 4) sedation with propofol. Analgesia was provided to maintain a visual analog scale (VAS) pain score <7. Myocardial ischemia was identified perioperatively using continuous 3-lead Holter monitoring. By measuring creatine kinase (CK) MB levels preoperatively, at entry to the intensive care unit (ICU), and every 12 h for 48 h; and by obtaining serial 12-lead electrocardiograms (ECG) (preoperatively; 2, 4, 12, 24, and 48 h after ICU admission, 8:00 AM the morning after surgery; and 5 min pre- and postextubation), myocardial infarction was identified. Endocrine stress response was assessed by measuring serum cortisol levels preoperatively, on admission to the ICU, and 24 h postoperatively. In a subset of patients (LOW n = 10, HIGH n = 11), plasma and urinary catecholamine levels were also measured. There were no between-group differences in demographics, operative course, hemodynamic variables, or cortisol levels while in the ICU. The VAS pain score and target RSS were achieved and sustained, and they differed between groups. There were three myocardial infarctions in each group by CKMB criteria alone. No ECG-identifiable myocardial infarction occurred. The ST segment versus time curve (LOW 187 +/- 295 versus HIGH 1071 +/- 2137 mm/min) differed between groups. Urinary and plasma catecholamine levels were similar between groups over the observation period. We conclude that the use of a reduced sedation regimen in combination with adequate analgesia did not result in an increased endocrine stress response or risk of myocardial ischemia. IMPLICATIONS: This randomized study of patients after coronary artery bypass surgery examined whether light (versus heavy) sedation with propofol in the intensive care unit was associated with an increased degree of myocardial ischemia. Using techniques to detect myocardial ischemia, including Holter monitoring, electrocardiogram, and myocardial enzyme measurements, no differences were found. We conclude that light sedation does not increase the endocrine stress response or the risk of myocardial infarction.

Aged↗
PubMed1997

Midterm results with the Sorin Monostrut heart valve prosthesis.

OBJECTIVE: To monitor the hematological and clinical sequelae of a single tilting disc cardiac valve prosthesis. DESIGN: Prospective nonrandomized trial. SETTING: University teaching hospital. PARTICIPANTS: All patients receiving a single mechanical cardiac valve prosthesis were offered the Sorin Monostrut valve if they met the criteria for valve use. Seventy-five per cent of the patients entered were in New York Heart Association (NYHA) functional class III or IV. One hundred and forty-seven patients were subsequently followed at three months and then yearly after valve implantation for seven years. MAIN OUTCOME MEASURES: At one year, preoperative indexes of hemolysis were compared with three-month and one-year postoperative values. Actuarial curves for survival, freedom from cerebrovascular events and explantation were constructed for the seven-year follow-up period. RESULTS: Hemolysis, as measured by lactate dehydrogenase values, commonly occurs preoperatively, remaining significantly elevated three months and one year following valve implantation. Serum haptoglobin was normal preoperatively but was significantly low at one year. Anemia was uncommon and most patients had normal reticulocyte counts at one year. At three years, 81% of patients were in NYHA functional class I. CONCLUSIONS: Midterm results show that this valve is structurally reliable and meets all current requirements for a safe mechanical valve.

Adult↗
PubMed1996

Osteogenic protein-1 is required for mammalian eye development.

Osteogenic Protein-1 (OP-1/BMP-7) is a bone morphogenetic protein in the transforming growth factor-beta superfamily and has been shown to be expressed temporally and spatially during epithelial-mesenchymal interactions mediating tissue morphogenesis in early embryogenesis. In order to identify the primary role(s) for OP-1 in development, we carried out whole rat embryo cultures, over a 72-h period from primitive streak stages to early limb bud stages, in rat sera containing either OP-1 blocking antibodies (10 micrograms/ml) or nonreactive IgG. Rat embryos cultured with control antibodies developed normally, while those cultured with anti-OP-1 antibodies consistently exhibited over-all reduced size and absence of eyes. Histological sections revealed a greater reduction in neural retina development in the embryos treated with anti-OP-1 blocking antibodies. In situ hybridization and immunolocalization analyses indicate that OP-1 is expressed in the neuroepithelium of the optic vesicle at E11.5, is limited to the presumptive neural retina and developing lens placode, and is subsequently expressed in the neural retina, lens and developing cornea at E12.5-E13.5. Our results indicate that OP-1 mediates the inductive signals involved in mammalian eye development.

Animals↗
PubMed1996

Potential greater than additive vasorelaxant actions of milrinone and nitroglycerin on human conduit arteries.

1. The mechanism of vasorelaxation for phosphodiesterase III inhibitors is mediated by increase of cAMP whereas for nitrovasodilators, cGMP. The purpose of this study was to test the hypothesis that the phosphodiesterase III inhibitor milrinone and nitroglycerin (NTG) may have greater than additive effects in human arteries. 2. Internal mammary artery segments (IMA, n = 90) taken from 23 patients were studied in organ chambers. The effect of milrinone (3 microM), NTG (10 nM), or the combination was tested in IMA rings precontracted with potassium (K+, 25 mM) or U46619 (10 nM). Concentration-contraction curves for K+ or U46619 were established in other rings treated with milrinone (70 microM), NTG (0.1 microM), or the combination for 10 min. 3. In K(+)-induced contraction, the combination produced more relaxation (45.4%) than did either milrinone (7.9%, P < 0.05) or NTG (3.8%, P < 0.05) alone. This relaxation was significantly more than the theoretical overadditive effect (P < 0.05). Similar results were seen in U46619-induced contraction (94.1% by the combination vs 70.7% by milrinone, P < 0.05, or 36.1% by NTG, P < 0.05). Pretreatment with the combination depressed contraction to a higher extend compared with milrinone alone (P < 0.05) for the K(+)-induced contraction and to NTG alone (P < 0.05) in U46619-induced contraction. Treatment with the combination also shifted EC50 rightward and this shift was significantly more than that caused by treatment with NTG alone (P < 0.05). 4. We conclude that there is a greater than additive vasorelaxant effect of PDE III inhibitors and nitrovasodilators in human conduit arteries. This effect may be beneficial to patients undergoing coronary artery bypass grafting and to other patients requiring these vasodilators. Reduced doses of the vasodilators in concentration may be sufficient to produce vasodilatation similar to that produced by either of them alone at higher concentrations.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1996

Audio-teleconferencing as a medium for distance learning: its application for continuing education in optometry.

This paper describes a highly successful pilot program of four audio-teleconferences that was offered in 1993 to optometrists based in rural and regional areas of Queensland. The program represents the first application of such technology for this purpose, either within Australia or overseas. It accessed the facilities of eight of a network of 38 open learning centres across Queensland and comprised an integrated package of three workshops, each of 3 hours duration, covering issues relating to the eye disease, glaucoma, and a stand-alone workshop covering general practice/legal issues. A 'complex directed conference model' of audio-teleconferencing was used, with each workshop incorporating a slide presentation and companion workbook that described individual pre-workshop preparatory activities and was structured to provide a focus for group discussions during the workshop. The program demonstrated audio-teleconferencing to be both a cost- and educationally-effective medium for the delivery of continuing education to a widely distributed audience.

Australia↗
PubMed1996

Comparative effects on bone mineral density of tibolone, transdermal estrogen and oral estrogen/progestogen therapy in postmenopausal women.

The aim of the study was to assess the comparative effects on bone mineral density (BMD) in routine clinical practice of tibolone and estrogen (given either unopposed or combined with cyclical progestogen) in postmenopausal women who had not previously received estrogen or other menopausal therapy. BMD was measured in the spine and hip by dual energy X-ray absorptiometry (DEXA) at 12-month intervals over 3 years in 82 consecutive postmenopausal women referred for climacteric therapy. Of these, 35 women received tibolone, 24 transdermal estradiol alone and 12 conjugated equine estrogens together with cyclical progestogen; 11 received no therapy other than calcium. BMD increased significantly in the spine in those taking tibolone over 3 years (p < 0.0001 at 1 year; p < 0.0001 at 2 years; and p = 0.03 at 3 years). In those treated with conjugated equine estrogens and cyclical progestogen, BMD in the spine also increased significantly over the first 2 years (p = 0.03 at 1 year; p = 0.004 at 2 years), but not at 3 years. However, although BMD in the spine also rose over 3 years in the women treated with transdermal estradiol alone, the increase was not statistically significant. No significant change in the BMD of either the spine or the hip was observed in the control group. A significant difference in the increase of BMD in the spine between the different treatment groups was observed at 2 years (p = 0.004) in favor of those taking tibolone or conjugated equine estrogens, compared to women who received transdermal estradiol. The highest proportion of individual responders to therapy after 2 years' treatment was observed in those receiving tibolone or conjugated equine estrogens. There was no significant change in the BMD of the hip over 3 years, irrespective of the therapy taken, although there was a tendency towards a progressive increase in the women on tibolone. Neither the age of the women, their body mass index or pretreatment BMD had a significant effect on changes in bone density. Since tibolone effected a greater increase in spine BMD than did either conjugated equine estrogen with progestogen or transdermal estradiol alone, it is particularly suitable for older women who often have more advanced osteoporosis and who would not accept a return of cyclical bleeding.

Administration, Cutaneous↗