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Biomedical subjects

J Cooper

Publications and source records attributed to J Cooper.

At least 469 records · Page 26Linked to original sources
PubMed1985

Invasion of erythrocytes in vitro by Plasmodium falciparum can be inhibited by monoclonal antibody directed against an S antigen.

A monoclonal antibody has been produced which binds to the heat stable S antigen present in the FCQ-27/PNG isolate of Plasmodium falciparum. This monoclonal antibody also inhibits the invasion in vitro of erythrocytes by malarial merozoites thus demonstrating that the S antigens of Plasmodium falciparum may be a target of protective immune responses.

Antibodies, Monoclonal↗
PubMed1985

New approaches to the study of cellulose biosynthesis.

Examples of a variety of approaches for studying the mechanism and regulation of cellulose biosynthesis are presented. Attempts to demonstrate conclusively a cellulose synthase activity using membrane preparations derived from higher plants have not been successful; the predominant UDP-glucose: beta-glucan-beta-glucosyltransferase detected in these preparations is a beta-(1----3)-glucan synthase that is dependent upon Ca2+ and a beta-glucobiose, such as laminaribiose or cellobiose, for activity. Xyloglucan glucosyltransferase activity is detected in all plant preparations examined and, in cotton fibres, the activity of this enzyme correlates well with the level of xyloglucan found in the fibre. Low activity for a Mg2+-dependent beta-(1----4)-glucan synthase is found in extracts from soybeans and mung beans, but not cotton fibres; this enzyme could represent either a dissociated form of xyloglucan glucosyltransferase or a partially latent form of cellulose synthase. In vitro translation of RNA from developing cotton fibres shows notable increases in the level of several relatively abundant translatable mRNAs associated with the time of onset of secondary-wall cellulose synthesis. In order to determine whether these apparent changes in gene expression represent enhanced expression of specific genes required for cellulose synthesis, several strategies are being developed for identification of specific polypeptides required for this process. One strategy involves the successful development of a technique for detection of glucan synthase activity in acrylamide gels, a technique that should prove useful for characterization of the polypeptide composition of such enzymes. We have also synthesized a photoaffinity analogue of 2,6-dichlorobenzonitrile (DCB), a potent and specific inhibitor of cellulose synthesis. The analogue is also an effective inhibitor in vivo, and upon ultraviolet irradiation of extracts in the presence of the radioactive analogue, we observe a relatively specific labelling of a polypeptide of 18 X 10(3)Mr. Finally, we have studied the spatial regulation and structural requirements for cellulose synthesis in internode cells of the alga Chara corallina. Cellulose deposition in vivo shows spatial localization, which correlates with acid and base bands along the cell. Using internodes perfused with solutions containing UDP-[14C]glucose and subsequently ligated, we were able to demonstrate synthesis of a highly insoluble cell-wall-localized glucan, thus offering hope that Chara can be developed as another useful system for studying the mechanism and regulation of cellulose synthesis.

Cell Membrane↗
PubMed1984

Binding and location of AMP deaminase in rabbit psoas muscle myofibrils.

It is shown that an interaction exists between AMP deaminase (EC 3.5.4.6) and myofibrils that is sufficiently strong (Kd congruent to 10(-10) M) for more than 99% of the binding sites for the enzyme to be filled in vivo. The binding is not strong enough, however, to stop removal of the enzyme during the extensive washing normally used in the preparation of myofibrils. Fluorescent antibodies to the enzyme label myofibrils close to the junction of the A- and I-bands. The invariance of the position of the antibody stripes at this site, over a range of sarcomere lengths, indicates that the enzyme is attached to the A-band. The intensity of the fluorescence declines in parallel with dissociation of the enzyme. In this muscle, the number of AMP deaminase binding sites per thick filament is approximately six, suggesting that the enzyme is located at a single axial position in each half A-band. Electron microscopy of negatively stained, antibody-labelled myofibrils reveals the distance between the AMP deaminase sites at opposite ends of an A-band to be 1.69(+/- 0.02 micron). Since the length of the A-band is 1.57 micron, the binding site for the enzyme must be significantly beyond where thick filaments have previously been thought to end.

AMP Deaminase↗
PubMed1984

Bacterial endotoxin isolated from a water spray air humidification system as a putative agent of occupation-related lung disease.

Outbreaks of hypersensitivity pneumonitis or humidifier fever were attributed to the inhalation of organic material aerosolized by a chilled-water spray humidification system. The purpose of this study was to isolate and characterize the serologically detectable antigen(s) present in extracts obtained from the humidification system. By using bicarbonate or phenol-water extractions or both, the antigen was isolated and characterized, using colorimetry, gas-liquid chromatography, reverse-phase high-performance liquid chromatography, and X-ray fluorescence. Carbohydrates, hexosamines, phosphorus, and even-numbered saturated and unsaturated fatty acids were constituents of the serologically detectable antigen. When tested in in vivo and in vitro assays, the antigen had demonstrable endotoxin activity. All subjects with biopsy-proven lung disease and a majority of subjects suspected of having lung disease had antibodies directed toward the purified endotoxin. The data strongly suggest that an aerosolized bacterial endotoxin is a putative agent inducing lung disease.

Alveolitis, Extrinsic Allergic↗
PubMed1984

Mutagenicity in gastric juice.

Mutagenicity has been measured in the gastric juice of 228 patients using the Ames bacteriological test system; while mutagenicity in control and duodenal ulcer patients did not differ from saline controls, mutagenicity was significantly increased compared with controls in patients suffering gastric ulcer (p less than 0.002), carcinoma (p less than 0.002), and in patients after gastric resection (p less than 0.01). A transient rise in mutagenicity was seen following H2 antagonist ingestion (p less than 0.002). Increased levels of mutagenicity were found to correlate closely with gastric juice pH and bacterial count. Histidine concentrations in gastric juice did not explain the mutagenicity results.

Duodenal Ulcer↗
PubMed1984

Accommodation dynamics in divergence excess exotropia.

Objective recording of accommodation dynamics was performed in four patients with divergence excess exotropia (two true and two simulated) and in three visually normal control subjects. The accommodative peak velocity/amplitude relationship was normal in the exotropic patients and in the control subjects. Latency for decreasing accommodation was increased significantly, and overshoot frequency was decreased, in the divergence excess exotropes of the true variety, thus demonstrating slightly slowed accommodation dynamics in this diagnostic group. These subtle deviations in response dynamics reflect central rather than peripheral mechanisms.

Accommodation, Ocular↗
PubMed1984

Cardioplegic protection of the child's heart.

The advantages and limitations of cardioplegia as a mode of myocardial preservation in the pediatric cardiac surgical context are investigated. Review of early mortality related to ischemic time demonstrated no difference in overall mortality in consecutive series each of 200 patients, the first protected by reperfusion between intermittent periods of aortic cross-clamping and the second protected by cardioplegia. There was a tendency to accept longer ischemic time with cardioplegia (p less than 0.01). Mortality with cardioplegia increased sharply beyond 85 minutes of ischemia. Cytochemical and biophysical assessment of 129 pairs of right ventricular biopsy specimens taken before and after ischemia usually demonstrated deterioration of myocardium despite cardioplegia, and poor scores were predictive of hospital death. Use of a logistic analysis suggested that about half the hospital deaths were attributable to inadequate myocardial preservation despite cardioplegia.

Age Factors↗
PubMed1983

Long-term prophylaxis of urinary infections in women: comparative trial of trimethoprim, methenamine hippurate and topical povidone-iodine.

We randomized 64 patients with a history of recurrent urinary tract infections among 3 regimens of long-term (1 year) prophylactic treatment: 20 were given 100 mg. trimethoprim at night, 25 received 1,000 mg. methenamine hippurate every 12 hours and 19 were asked to cleanse the perineum (especially the periurethral area) twice daily with povidone-iodine solution. The progress of patients in terms of urinary symptoms and/or bacteriuria, changes in periurethral flora, side effects, and hematological and biochemical profiles was followed at regular intervals. All treatments were effective in reducing the incidence of symptomatic attacks when compared to the 12 months immediately before therapy and there was little to choose between the individual regimens on this account. However, trimethoprim was tolerated better than were the other 2 treatment regimens. In the group given trimethoprim most of the breakthrough infections (71.4 per cent) that occurred were caused by trimethoprim-resistant organisms (usually Escherichia coli), while in the other 2 groups the incidence of trimethoprim-resistant organisms causing infection was low (2.7 per cent). Treatment with trimethoprim reduced significantly the periurethral colonization of Escherichia coli.

Administration, Topical↗
PubMed1983

Dissonance arousal: physiological evidence.

Two experiments were conducted to determine whether cognitive dissonance is accompanied by physiological arousal. In Experiment 1, a standard induced compliance paradigm was replicated and was found to produce the expected pattern of attitude change. In Experiment 2, physiological recordings were obtained within the same paradigm. Subjects who wrote counterattitudinal essays under high-choice conditions displayed significantly more nonspecific skin conductance responses than other subjects, but they did not change their attitudes. The results are interpreted as support for viewing dissonance as an arousal process. The results are also interpreted as indicating that the subjects misattributed their arousal to the physiological recording device. The significance of the findings for dissonance theory, misattribution phenomena, and social psychophysiological research methods is discussed.

Arousal↗
PubMed1983

The effect of stimulus variation on lexical learning.

At some early stage in a child's development of the comprehension and production of language, he/she must recognize that single words correspond to referents in the environment. How to best present the critical aspects of the environment to which a verbal label is attached is not entirely known. For language-impaired children it is important to know how to highlight this relationship between linguistic and nonlinguistic cues so that therapy will be most effective. To examine how language-impaired children best learn single word lexical items, nouns and verbs were taught expressively through two modes of stimulus presentation thought to highlight the nonlinguistic environment: object manipulation and picture identification. The efficacy of these two treatment conditions was assessed with four children functioning at Piaget's sensorimotor period of development by using a single subject, alternating treatments design. The results indicated individual variation in learning strategies. Two of the children learned more single words (nouns and verbs) in the object manipulation condition. One child learned equally well in both conditions and the fourth child learned best in the picture identification condition. Variables accounting for the individual variation are discussed.

Child, Preschool↗
PubMed1983

Reduction of asthenopia in patients with convergence insufficiency after fusional vergence training.

Seven patients with convergence insufficiency and related asthenopia underwent automated fusional convergence training. A matched-subjects control group crossover design was used to reduce placebo effects. All patients showed significant increases in vergence ranges with concurrent marked reduction of symptoms after training. All patients showed a flattening of and an increase in the base-out portion of their fixation disparity curve. Our results demonstrated the effectiveness of fusional vergence training in reducing asthenopia in these patients. Subsequent accommodation and vergence training using traditional orthoptic procedures yielded further reduction of asthenopia, as well as an increase in the base-out fusional range.

Adolescent↗
PubMed1983

Phosphotyrosine-containing proteins and expression of transformation parameters in cells infected with partial transformation mutants of Rous sarcoma virus.

We have examined the phosphorylation state of five proteins known to become phosphorylated on tyrosine during transformation by Rous sarcoma virus by using cells infected with a panel of partially transforming mutant viruses. Situations of viral mutant and growth temperature were found in which phosphorylation of some proteins occurred more extensively than that of others, indicating that mutations in the src gene had affected the specificity of pp60src for some of its substrates as well as affecting the activity of the enzyme. To obtain insight into the biological functions of these phosphorylations, comparisons were made between the degree of phosphorylation of these proteins and the expression of various indicators of the transformed phenotype. The data suggest that phosphorylation of proteins l, p, and q (Mr of 46,000, 39,000 and 28,000, respectively) is not sufficient to induce changes in adhesiveness, hexose transport or morphology. The phosphorylation of protein p or l or total phosphotyrosine content correlated well with the production of plasminogen activator, and the phosphorylation of proteins l and q correlated well with increased hexose transport. However, even when good correlations were observed, significant exceptions were sometimes noted. It thus remains possible that some phosphorylations on tyrosine observed in Rous sarcoma virus-transformed cells are not causally related to the expression of the measured parameters of transformation.

Animals↗
PubMed1983

Complications in cataract surgery.

Cataract surgery has a high rate of success. However, complications may affect any structure in the eye either during the immediate post op period or after. This paper will review the more common complications seen in aphakia.

Astigmatism↗