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Biomedical subjects

D Walker

Publications and source records attributed to D Walker.

At least 145 records · Page 8Linked to original sources
PubMed1997

Protein characterization of Australian spotted fever group rickettsiae and monoclonal antibody typing of Rickettsia honei.

Rickettsial proteins rOmp A and rOmp B exist in both Rickettsia australis and Rickettsia honei but differ in molecular weight and antigenicity; in addition, they produce distinct immunogenic responses and appear to be to conformationally dependent antigens. Species-specific monoclonal antibodies for other spotted fever group rickettsial species did not react with R. honei. A PCR product of the repeat region of the rOmp A gene from R. honei was amplified and calculated to contain 11 repeat units.

Antibodies, Bacterial↗
PubMed1997

Hypoglossal neuropraxia following endotracheal intubation.

A case of hypoglossal nerve neuropraxia following elective drainage of bilateral chronic subdural haematomas is described. We postulate that the cause of neuropraxia was inadvertent extubation of the trachea with the cuff inflated, leading to compression and stretch of the nerve against the greater horn of the hyoid bone. The literature on cranial nerve palsies following endotracheal intubation is reviewed.

Aged↗
PubMed1997

Effect of alteration of maternal plasma progesterone concentrations on fetal behavioural state during late gestation.

Placental progesterone synthesis exposes the fetus to high levels of progesterone and progesterone metabolites during late gestation which may influence fetal behaviour. To determine the role of maternal progesterone synthesis in the control of fetal arousal state and fetal breathing movements (FBM), the effect of raising and lowering maternal progesterone concentrations was examined in chronically catheterised fetal sheep. Fetal and maternal vascular catheters, fetal tracheal and amniotic fluid catheters as well as electrodes for recording fetal electrocortical (ECoG), electro-ocular (EOG) and nuchal muscle electromyographic (EMG) activity were implanted between 118 and 122 days gestational age (GA). Progesterone, 100 mg, administered twice daily i.m. for 3 days (130-133 days GA) resulted in a marked elevation in maternal plasma progesterone concentrations (370 +/- 121%, n = 5, P < 0.05), but had no effect on fetal plasma concentrations. Fetal EOG episodes and the duration of fetal behavioural arousal were significantly suppressed throughout the progesterone treatment period (74.4-81.1% and 58-65% respectively, P < 0.05, n = 5). Four ewes received Trilostane (25 mg i.v.), a 3 beta-hydroxysteroid dehydrogenase inhibitor, between 136 and 140 days GA. Maternal and fetal progesterone concentrations were significantly lowered by 60 min after treatment (19.8 +/- 8.0% and 39.5 +/- 24.3% respectively, P < 0.05). The incidence of fetal EOG activity increased from a pretreatment level of 26.8 +/- 1.5 min/h to 30.3 +/- 2.8 min/h at 1-6 h and to 35.0 +/- 1.7 min/h (P < 0.05) during the 7-12 h after Trilostane treatment. The duration of FBM episodes was significantly higher at 1-6 h and 7-12 h after Trilostane treatment (19.5 +/- 3.0 and 23.6 +/- 5.5 min/h respectively, P < 0.05) compared with pretreatment levels (11.2 +/- 1.2 min/h). We conclude that increasing maternal progesterone levels suppresses fetal EOG activity and behavioural arousal, whereas reducing maternal progesterone synthesis leads to an elevation of EOG activity and FBM.

3-Hydroxysteroid Dehydrogenases↗
PubMed1997

Transferring electronic medical records.

This article outlines the variety of computing environments, application systems and data structures that are available to the general practitioner. The transfer of data from and to electronic medical records systems will become more important as their use increases. Transferability requires the ability to match the data elements between the conversing application systems, and carry out a series of communication steps. Ways to ensure data element matching are described. The communications steps are delineated, and methods of achieving these steps briefly explained. The transfer methods proposed by the medical software industry of Australia are dealt with in detail. They involve the creation of an industry standard 'meta-record' which acts as a standard interface or gateway to the real record. The communication steps are carried out by a medical record 'agent', which is created and maintained by an independent organisation.

Australia↗
PubMed1997

Evidence for fusion between multilamellar endosomes and autophagosomes in HeLa cells.

The organelles of the endocytic and autophagic pathways were studied in HeLa cells using immunoelectron microscopy and stereological techniques. In the absence of autophagic stimulation, characteristic particulate structures containing closely packed layers of membrane received the fluid-phase marker horseradish peroxidase after 25 min uptake. These multilamellar endosomes contained the majority of the cellular immunogold labeling obtained by using a monoclonal antibody (1B5) directed against a lysosomal glycoprotein. Lysosomes with homogeneous dense content were only poorly labeled. After stimulation of autophagy, two classes of autophagosome profile appeared. One had a double limiting membrane and content that resembled the surrounding cytoplasm. The other most abundant type possessed a single limiting membrane and contained multilamellar structures which were strikingly similar to multilamellar endosomes, not only in form, but also in volume and membrane packing density. Immunogold labeling showed that now the majority of 1B5 labeling was located in the class of autophagosomes which contained multilamellar structures. Stereological methods showed that, after autophagic stimulation, multilamellar endosomes had become depleted, while multilamellar structures had appeared within the autophagosomes. Taken together, these data provide evidence that autophagosomes of HeLa cells fuse with preexisting multilamellar endosomes.

Autophagy↗
PubMed1997

Case study. Outcomes management in orthopaedics.

Improving outcomes while maintaining quality and satisfaction in today's healthcare environment is a challenge. This article shares some of the foundation work and the results of an interdisciplinary team effort toward that goal. Changes in care practices and their impact on outcomes can promote the welfare of the patient, institution, and the nation's health.

Hospital Charges↗
PubMed1997

International collaborative study to evaluate a recombinant L ferritin preparation as an International Standard.

A recombinant L ferritin preparation, lyophilized in ampoules and designated 94/572, was evaluated by 18 laboratories in 9 countries for its suitability as an International Standard (IS). The preparation was assayed in a wide range of in-house and commercial immunoassays against the 2nd IS for ferritin (of spleen origin; 80/578). The immunological reactivity of the recombinant material was similar to that of the 2nd IS for ferritin in the majority of assays and demonstrated adequate stability in accelerated degradation studies. On the basis of the results presented here, the WHO Expert Committee on Biological Standardization established 94/572 as the 3rd IS for ferritin, recombinant.

Automation↗
PubMed1996

Endoscopic exploration and lymph node sampling of the axilla. Preliminary findings of a randomized pilot study comparing clinical and anatomo-pathologic results of endoscopic axillary lymph node sampling with traditional surgical treatment.

OBJECTIVE: To describe the technique of endoscopic exploration of the axilla. To compare this technique to open surgical treatment by comparing the following variables: operative time, peri-operative complications, duration of hospital stay, node's histology and morphologic aspects and esthetic results. MATERIALS: Standard instruments for traditional operative laparoscopy plus a lipo-aspirator (0.8 Bar). PATIENTS: Forty patients, 20 (group A) undergoing open surgery and 20 (group B) undergoing axilloscopy. All patients with early invasive breast cancer are eligible for conservative operative treatment. METHOD: Randomized study. The technique is described and preliminary results are presented. RESULTS: The operative time for axilloscopy is approximately double that for open surgery. A comparable number of lymph nodes is collected by axilloscopy and open surgery. The nodes collected by axilloscopy are more likely to be fractured. What is the clinical consequence? Two loco-regional relapses are observed in the endoscopic group. DISCUSSION: Axillary sampling by endoscopic procedure gives the same pathologic information than surgical axillary sampling. Anatomo-pathologic aspects of nodes and possibilities of relapses were two drawbacks of this procedure. CONCLUSION: Operative time is increased for axilloscopy compared with open surgery. The techniques yield comparable anatomo-pathologic results. It is still unknown whether this endoscopic technique is as effective as traditional surgery or if the frequency or severity of lymphedema is decreased by the endoscopic approach.

Adult↗
PubMed1996

Growth and differentiation of fast and slow muscles in fetal sheep, and the effects of hypophysectomy.

1. Isometric contractile characteristics of fast-twitch (flexor digitorum longus, FDL; medial gastrocnemius, MG) and slow-twitch (soleus) muscles were determined in pentobarbitone-anaesthetized fetal sheep between 90 and 140 days gestation. Five fetuses were hypophysectomized (HPX) at 90-95 days gestation and then studied at 138-140 days. 2. At 90-95 days gestation the time to peak of single twitch contractions for the soleus, MG and FDL were not significantly different from each other; the mean value (+/-S.E.M.) for all the muscles at this age was 77.6 +/- 9.0 ms. At 120-125 days gestation the MG and FDL contracted significantly faster (44.0 +/- 0.9 and 40.8 +/- 1.8 ms, respectively) than at 90-95 days, and did not change significantly thereafter. In contrast, the soleus muscle contracted more slowly (111.9 +/- 6.6 ms) at 138-140 days than at 90-95 days and 120-125 days gestation. 3. Soleus muscle consisted of type I fibres at all gestational ages. There was no significant change with gestational age in the relative numbers of type I and II fibres in the MG and FDL, but in the diaphragm the number of type I fibres increased and the number of type II fibres decreased between 125 and 138 days gestation. 4. HPX abolished the normal increase of soleus weight relative to body weight between 125 and 138 days but did not alter the change of twitch contraction time with age. HPX significantly prolonged twitch time to peak and time to half-relaxation of MG and time to half-relaxation of FDL at 138 days. 5. The maximum rate of rise of the isometric tetanic contraction was unchanged by HPX in all three hindlimb muscles, but fatigue of MG and FDL was increased. 6. The relative proportions of different fibre types in the hindlimb muscles and the diaphragm were unchanged by HPX, but there was a significant decrease in mean areas of type I and II fibres in the FDL and MG of the HPX fetuses.

Animals↗
PubMed1996

Ricin A chain fused to a chloroplast-targeting signal is unfolded on the chloroplast surface prior to import across the envelope membranes.

The initial stages of chloroplast protein import involve the binding of precursor proteins to surface-bound receptors prior to translocation across the envelope membranes in a partially folded conformation. We have analyzed the unfolding process by examining the conformation of a construct, comprising the presequence of a chloroplast protein linked to ricin A chain, before and after binding to the chloroplast surface. We show that the presequence is highly susceptible to proteolysis in solution, probably reflecting a lack of tertiary structure, whereas the A chain passenger protein is resistant to extremely high concentrations of protease, unless deliberately unfolded using denaturant. The A chain moiety is furthermore active, indicating that the presence of the presequence does not prevent formation of a tightly folded, native state. In contrast, receptor-bound p33KRA (fusion protein comprising the 33-kDa presequence plus 22 residues of mature protein, linked to the A chain of ricin) is quantitatively digested by protease concentrations that have little effect on the A chain in solution. We conclude that protein unfolding can take place on the chloroplast surface in the absence of translocation and without the aid of soluble factors.

Chloroplasts↗
PubMed1996

Hepatitis B virus mutations in the pre-S genome before and after liver transplantation.

Mutational changes in the pre-S region of hepatitis B virus (HBV) were analyzed in 20 patients who experienced HBV reinfection after orthotopic liver transplantation (OLT). HBV DNA was extracted from patient sera before and after OLT. The pre-S sequence was amplified via polymerase chain reaction, subcloned, sequenced, and analyzed. In 18 of 20 patients, mutational changes were found in the pre-S region pre- or post- OLT; 11 showed point mutations (1-10) and 7 cases major changes (insertions/deletions). For the point mutations, there was no trend in the selection of wild-type (wt) HBV before or after OLT in the pre-S region. Additional HBV reinfection during hepatitis B surface antigen antibody (anti-HBS) administration had no influence on selection pressure in the pre-S region. In contrast, insertions/deletions were more frequently found before OLT. In the 7 patients with deletions/insertions, changes in the hepatocyte attachment site were not seen after OLT. Interestingly, the only patient with changes in a major virus population after OLT had changes in the CCAAT-box of the S-promoter. As shown by gel shift analysis, this mutation was associated with loss of specific binding to this element and thus probably led to dysregulation of S-gene transcription. Major changes in the pre-S genome are mainly seen before OLT, and HBV reinfection does occur with the intact hepatocyte attachment sites after OLT. Anti-HBs (hepatitis B immune globulin [HBIg]) creates no selection pressure on the pre-S region. The mutation in the CCAAT-box of the S-promoter potentially leads to its dysregulation and may be associated with the occurrence of fibrosing cholestatic hepatitis after OLT.

Adult↗
PubMed1996

Sacrospinous ligament fixation by palpation: variation of the Richter procedure.

OBJECTIVE: To present our method of sacro-spinous ligament fixation by palpation and compare it to the classical approach described by Richter. MATERIAL: In addition to the standard instruments needed for vaginal surgery, we use a Rasemond dissector, a small O'Shaugnessy dissector with smooth branches. We also use a Bengolea forceps and a monothread-nylon (Ethilon), decimal 4 suture loaded on a needle with a 30-mm curve. PATIENTS: Twenty patients underwent this procedure from 03/15/1978 to 05/19/1995. Their ages ranged from 46 to 86 years with a mean age of 64.7 years. METHOD: This was a retrospective study of the indications, results and complications associated with this technique. RESULTS: With an average follow-up of 7 years, we observed 90% success, 10% recurrences, and no complication directly attributable to this technique. This technique is valuable because of its effectiveness and simplicity. CONCLUSIONS: Sacrospinous fixation by palpation is more simple and provides the same results as the classic exposure technique. We describe the technique in this text. The efficacy of sacro-spinous ligament fixation by palpation would be improved by its systematic and bilateral use. Its value must be confirmed by a controlled prospective study to confirm our impression that our technique carries fewer risks.

Aged↗
PubMed1996

The development of diurnal rhythmicity in fetal suprachiasmatic neurons as demonstrated by fos immunohistochemistry.

Using Fos immunohistochemistry as a marker of cellular activity, we have shown that neurons in the suprachiasmatic nucleus of fetal sheep are active by 75 days gestation. From at least 90 days gestation (term is 146 days), these neurons are more active during the day (12.00) than at night (03.00) when pregnant ewes are exposed to a 12-h light-dark cycle with lights on at 07.00. The day-night difference in Fos immunoreactivity persisted when the lighting schedule was extended by 8 h to 03.00, although neurons were now more active at 03.00 than they were in fetuses maintained on the normal light-dark cycle. When ewes were maintained in constant light from 133 to 138 days, the day-night difference in Fos immunoreactivity in the fetal suprachiasmatic nucleus was abolished, suggesting that diurnal activity of the fetal suprachiasmatic nucleus is maintained by a signal related to the external lighting regime. In a twin pregnancy where one fetus was optically enucleated at 100 days gestation, the density of Fos-immunoreactive neurons in the suprachiasmatic nucleus during the day at 138 days was similar to the unoperated twin. This suggests that the effects of dim light in the uterus on the fetal retina do not account for the high level of Fos immunoreactivity in the suprachiasmatic nucleus in the daytime. We propose that a chemical messenger of maternal origin, possibly melatonin, suppresses the activity of fetal suprachiasmatic neurons during the night, and that fetal suprachiasmatic neurons have endogenous activity which is expressed fully during the daytime.

Animals↗
PubMed1996

Utility of clinical trial batteries in the measurement of Alzheimer's and Huntington's dementia.

Tests used as outcome measures in clinical trials of antidementia agents are not typically employed as part of diagnostic evaluations, and little information exists as to the sensitivity of these tests in terms of either differentiating demented patients from normal individuals or in distinguishing dementias of various types and etiologies. Sensitivity to mild dementia and sensitivity to impairment of various neuropsychological domains are, however, prerequisites for valid use of an instrument as an outcome measure in this context. The present study was undertaken to directly compare six different tests (three traditional psychometric tests and three clinical trial batteries) in terms of their sensitivity to detect and distinguish between mild dementia in patients with either Alzheimer's disease (n = 15) or Huntington's disease (n = 15), when compared to normal controls (n = 15). Tests included the Mattis Dementia Rating Scale, the Mini-Mental State Examination, the Wechsler Memory Scale-Revised, the Alzheimer's Disease Assessment Scale-Cognitive Subscale, the Computerized Drug Research (CDR) Cognitive Assessment System, and the Repeatable Battery for the Assessment of Dementia (RBAD). All of the tests were roughly equivalent in terms of their ability to discriminate normal subjects from mildly demented patients. Only the CDR and RBAD, however, were able to reliably discriminate between the two patient groups. The results are discussed in terms of the applicability of these tests as outcome measures for clinical trials in dementing disorders.

Adult↗