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Biomedical subjects

J Johnston

Publications and source records attributed to J Johnston.

At least 55 records · Page 3Linked to original sources
PubMed2000

Large-scale purification of recombinant human angiostatin.

A process for the purification of recombinant human angiostatin (rhAngiostatin), produced by Pichia pastoris fermentation operated at the 2000-L scale, is reported. rhAngiostatin was recovered and purified directly from crude fermentation broth by cation exchange expanded bed adsorption chromatography. Anion exchange chromatography, hydroxyapatite chromatography, and hydrophobic interaction chromatography were used for further purification. Full-length rhAngiostatin was separated from rhAngiostatin molecules fragmented by endoproteolysis. On average, 140 g of rhAngiostatin was produced per batch, with an overall yield of 59% (n = 9). The purification process was completed in approximately 48 h and used only inexpensive and nontoxic raw materials. Methods development, process synthesis, and process scale-up data are presented and discussed.

Ammonium Sulfate↗
PubMed2000

Changes in spiritual beliefs after traumatic disability.

OBJECTIVES: To discover the effect of sudden-onset disability on spirituality, specifically, to investigate changes following the onset of disability in spiritual concepts and to outline a theoretical framework consisting of relationships with the self, others, the world, and a supreme power. STUDY DESIGN: The study used a cross-sectional, qualitative approach to understand changes in spirituality from the perspective of the disabled person. Intensive semistructured interviews were conducted with 16 participants, each of whom had either a spinal cord injury or brain injury, within the 2-year period after discharge from rehabilitation. Changes in spiritual concepts were explored in relation to 3 types of relationships (intrapersonal, interpersonal, and transpersonal) and 5 themes (awareness, closeness, trust, purpose, and vulnerability). RESULTS: Specific changes in spirituality described by sample members were: greater awareness of the self; a change in their view of their own independence; a sense of purpose in life that was not present before the onset of the disability; greater awareness of their own mortality and vulnerability; a new understanding of trust, especially when depending on others; loss of some significant relationships; greater appreciation and closeness with others and the world; and greater understanding of other disadvantaged groups. CONCLUSIONS: The interviews portrayed a significant ability to conceptualize issues in a spiritual context in the 2-year period after discharge from rehabilitation. Further, the changes reported suggest a positive effect of spirituality in the adjustment period following onset.

Adult↗
PubMed2000

The medium-term findings in coronary arteries by intravascular ultrasound in infants and children after heart transplantation.

OBJECTIVES: The study purposes were to determine 1) whether intravascular ultrasound (IVUS) was more sensitive than angiography for the detection of post-transplant coronary artery disease (PTCAD) in pediatric patients; and 2) whether those transplanted as neonates reacted differently than older patients. BACKGROUND: Experience with IVUS for the diagnosis of PTCAD in children is limited. METHODS: Patients were divided into two groups: those transplanted as neonates (early group) and those transplanted in infancy or childhood (late group). Morphometric analysis was performed, including maximal intimal thickness (MIT) and intimal index (II). Stanford classification was used to grade lesion severity. Acute rejection and cytomegalovirus (CMV) status were correlated with MIT and II. RESULTS: Thirty children were studied (early group, n = 13; late group, n = 17). All segments studied were angiographically normal. Mean MIT and mean II were significantly greater in the late group (0.26 +/- 0.14 vs. 0.13 +/- 0.04 mm, p < 0.001 and 0.11 +/- 0.07 vs. 0.07 +/- 0.03 mm, p = 0.04, respectively). There was a significant correlation between MIT and II in those who had acute rejection in the late group. Patients in the late group who were CMV-positive had a significantly higher MIT compared with those in the late group with negative serology (p = 0.04). CONCLUSIONS: Intravascular ultrasound was more sensitive than angiography in detecting PTCAD after pediatric heart transplantation. There is a possible role for acute rejection and CMV in the development of PTCAD.

Adolescent↗
PubMed2000

Counselling: filling a gap in general practice.

A counsellor worked for 1 year in three practices in a rural area where there was previously no practice-based counselling. The service was evaluated, using a range of methods, in order to inform general practitioners and policy-makers about the demand for counselling, where it fits with other services, its potential value and how to organise and audit the service efficiently. Five kinds of information were collected: administrative data; patients' views; well-being scores; GPs' perceptions of individual patients; and interviews with the counsellor, GPs and other primary care staff by an independent researcher. All the GPs used the service, referring 131 people. The most common reason for referral was 'relationship difficulties'. There were improvements in patients' well-being, self-awareness and coping skills, and high satisfaction among GPs and patients. Communication with other services was seen to improve. The counselling service was found to fill a gap by addressing the needs of a substantial group of patients for whom psychiatric care was inappropriate.

Attitude of Health Personnel↗
PubMed2000

Tris lipidation: a chemically flexible technology for modifying the delivery of drugs and genes.

1. One of the major challenges in the development of pharmaceuticals is their formulation with other materials to give them the desired bioavailability profile when administered into the body. 2. We have developed a flexible platform technology (Tris lipidation) to simply and effectively alter the lipophilicity of drugs. As implied by the name, the technology uses the common buffer Tris as a linker between the drugs of interest and a domain of variable hydrophobicity. 3. We demonstrate, using a mouse melanoma model, that Tris-lipidated conjugates of the widely used cytotoxic and anti-inflammatory drug methotrexate (MTX) display enhanced potency in the local treatment of tumours and reduced systemic toxicity when compared with the unconjugated drug. 4. With genes now being predicted to be the pharmaceuticals of the future, we show that Tris-lipidated cationic peptides can efficiently deliver DNA into (transfect) cells in culture. Furthermore, by comparing the abilities of variants of these Tris-based cationic lipids to transfect cultured cells, we demonstrate that modifications made to variable regions of Tris-lipidated compounds can dramatically alter their delivery profiles.

Animals↗
PubMed2000

Risk of HIV transmission from patients to surgeons in the era of post-exposure prophylaxis.

The HIV prevalence, among patients either undergoing, or with the potential to undergo, surgery were estimated using data from unlinked anonymous HIV surveys of patients in Glasgow hospitals during 1992-1997 in order to quantify the risk of surgeons acquiring HIV occupationally in the era of post-exposure prophylaxis (PEP) availability. A range of prevalence rates was applied to data on other factors influencing risk; these comprised, i) the probability of a percutaneous injury from a sharp instrument used on an HIV infected patient resulting in HIV transmission, ii) the number of injuries sustained and iii) whether or not PEP was administered. On the basis of, for example, a surgeon sustaining three percutaneous injuries over 12 months and not taking PEP after each, the annual risks ranged from 1 in 2,000,000 for urological/renal surgeons to 1 in 200,000 for those performing general surgery/ENT/gynaecological procedures. The administration of PEP after each injury would reduce these rates to 1 in 10,000,000 and 1 in 1,000,000 respectively. The risk of surgeons acquiring HIV occupationally in a city which has an HIV prevalence typical of most urban areas in the UK, is 'minimal' or 'negligible'. In the context of such low risk and our limited knowledge of the adverse effects of PEP, the risk assessment to decide whether or not to give PEP should be well informed and consistent. Current guidelines to help physicians and affected healthcare workers in their decision making need to be improved.

Adolescent↗
PubMed2000

Phenotypic markers as risk factors in schizophrenia: neurocognitive functions.

OBJECTIVE: To review the literature on neurocognitive measures as risk markers for schizophrenia and to present data from the Perth family study of schizophrenia. Of all the risk markers that have been identified, the most promising are deficits in sustained attention. METHOD: Inclusion in the review was determined by whether the research addressed a number of key questions: methods of assessing sustained attention; evidence of sustained attention deficits in patients and first-degree relatives including children; the importance of attentional dysfunction in the schizophrenic process and functional outcome; and the biological basis of sustained attention deficits. RESULTS: Sustained attention deficits are evident in both patients and a proportion of their first-degree relatives, a finding replicated in preliminary data from the Perth family study. The literature suggests that the attention deficit is a stable enduring trait that is independent of clinical state. The neural basis of the deficit may be a functional disconnection between prefrontal and parietal cortex. Attention impairment is an important predictor of functional outcome in patients and the development of social dysfunction in adulthood in the at-risk offspring of patients. However, sustained attention deficits that are measured in childhood results in an unacceptable high false-positive rate (21%) when predicting which at-risk offspring of parents with schizophrenia will develop a schizophrenia spectrum disorder, although the overall classification accuracy (78%) is impressive. CONCLUSIONS: The main findings are that sustained attention deficits are important risk markers for schizophrenia but need to be supplemented by other neurocognitive risk markers to improve predictive accuracy.

Adult↗
PubMed2000

Unlinked anonymous HIV study of hospital patients and general practice attenders in Glasgow, 1991-1997.

AIM: To determine whether HIV is spreading from injecting drug users and homosexual/bisexual males into lower risk heterosexual populations in Glasgow, Scotland, and to pilot a method of monitoring HIV prevalence which involves testing routine biochemistry specimens. METHODS: An unlinked anonymous HIV testing study of hospital patients and general practice attenders was conducted during January 1992 to December 1997. Testing was performed on routine biochemistry specimens from patients aged 16-49 years attending two hospitals with catchment areas covering the north and the east of the city. RESULTS: 78,260 specimens were tested in the study period and no patient objected to their samples being tested anonymously. HIV prevalence rates among male and female subjects were 0.63% and 0.01%, respectively; the large difference in prevalence resulted, in part, from the inclusion of HIV infected haemophiliac patients who attended one of the hospitals. Prevalence among male general practice patients ranged between 0.1% and 0.2%, while that for male patients attending surgical or surgically related specialties was 0.1%. CONCLUSIONS: The prevalence data indicate that HIV has not seeded from the high risk groups into the wider heterosexual population, and that the risk of a surgeon acquiring HIV occupationally is extremely low in a city which has an HIV prevalence similar to or greater than that seen in most other parts of the United Kingdom. Large numbers of residual specimens from busy biochemistry laboratories can be processed for unlinked anonymous testing without interfering with the laboratories' routine functions. This survey approach might be best suited to monitoring HIV trends in developing countries with relatively high prevalence rates and where transmission is principally heterosexual.

Adolescent↗
PubMed2000

Rate of force development and the lateralized readiness potential.

We examined the relationship between force and rate of force development aspects of movement dynamics and electroencephalogram motor components as reflected in the lateralized readiness potential (LRP). Using self-paced tasks, in Studies 1 and 3 we investigated whether differential speed and accuracy constraints in discrete and repetitive finger force production tasks influenced the LRP. These studies showed that speed tasks produced larger LRP than accuracy tasks regardless of whether the movement type was discrete or repetitive. In Studies 2 and 4 we studied four conditions with two levels of force and two levels of rate of force development. The largest LRPs were found with the greatest rate of force development. Overall, the four studies demonstrated that preparation for differential rates of force development is a major component reflected in the LRP.

Adult↗
PubMed1999

Posttransplant lymphoproliferative disorders in adult and pediatric renal transplant patients receiving tacrolimus-based immunosuppression.

Between March 27, 1989 and December 31, 1997, 1316 kidney transplantations alone were performed under tacrolimus-based immunosuppression at our center. Posttransplant lymphoproliferative disorders (PTLD) developed in 25 (1.9%) cases; the incidence in adults was 1.2% (15/1217), whereas in pediatric patients it was 10.1% (10/99; P<.0001). PTLD was diagnosed 21.0+/-22.5 months after transplantation, 25.0+/-24.7 months in adults and 14.4+/-18.2 months in pediatric patients. Of the 4 adult cases in whom both the donor and recipient Epstein Barr virus (EBV) serologies were known, 2 (50%) were seropositive donor --> seronegative recipient. Of 7 pediatric cases in whom both the donor and recipient EBV serologies were known, 6 (86%) were EBV seropositive donor --> seronegative recipient. Acute rejection was observed before the diagnosis of PTLD in 8 (53%) of 15 adults and 3 (30%) of 10 pediatric patients. Initial treatment of PTLD included a marked decrease or cessation of immunosuppression with concomitant ganciclovir therapy; two adults and two pediatric patients required chemotherapy. With a mean follow-up of 24.9+/-30.1 months after transplantation, the 1- and 5-year actuarial patient and graft survival rates in adults were 93% and 86%, and 80% and 60%, respectively. Two adults died, 3.7 and 46.2 months after transplantation, of complications related to PTLD, and 10 (including the 2 deaths) lost their allograft 3.7-84.7 months after transplantation. In children, the 1- and 5-year actuarial patient and graft survival rates were 100% and 100%, and 100% and 89%, respectively. No child died; one child lost his allograft 41.3 months after transplantation. One child had presumed recurrent PTLD that responded to discontinuation of tacrolimus and reinitiation of antiviral therapy. The mean serum creatinine level in adults was 2.5+/-1.2 mg/dl, and in children, it was 1.3+/-0.6 mg/ dl. Under tacrolimus-based immunosuppression, PTLD is less common after renal transplantation in adults than in children, but PTLD in children is associated with more favorable outcomes than in adults.

Adolescent↗
PubMed1999

Sustained activation of the raf-MEK-ERK pathway elicits cytokine unresponsiveness in T cells.

Activation of T cells via the TCR and other costimulatory receptors triggers a number of signaling cascades. Among them, the Ras-activated Raf-mitogen-activated protein/extracellular signal-related kinase (ERK) kinase (MEK)-ERK signaling cascade has been demonstrated to be crucial for both T cell development and activation. It has previously been demonstrated that high doses of Ag or anti-CD3 mAb are able to induce in T cells a nonresponsive state to subsequent treatment with cytokines such as IL-2. The precise biochemical mechanisms underlying this effect are not fully characterized. In this study, we demonstrate that cytokine nonresponsiveness is accompanied by the induction of the cyclin-dependent kinase inhibitor p21Cip1 that is mediated, at least in part, by the activation of the Raf-MEK-ERK pathway. Furthermore, we demonstrate that selective activation of the Raf-MEK-ERK signaling pathway in T cells is sufficient to induce cytokine nonresponsiveness in both a T cell clone and naive primary T cells. In this case, nonresponsiveness is accompanied by the induction of p21Cip1 and the prevention of p27Kip1 down-regulation, leading to inhibition of cyclin E/cyclin-dependent kinase 2 activity. These data suggest that anti-CD3 mAb-induced cytokine nonresponsiveness may be a consequence of hyperactivation of the Raf-MEK-ERK pathway, leading to alterations in the expression of key cell cycle regulators. These observations may provide a novel insight into the mechanisms of induction of peripheral tolerance.

Animals↗
PubMed1999

Anatomical evidence supporting the potential for modulation by multiple neurotrophins in the majority of adult lumbar sensory neurons.

Neurotrophins exert effects on sensory neurons through receptor tyrosine kinases (trks) and a common neurotrophin receptor (p75). Quantitative in situ hybridization studies were performed on serial sections to identify neurons expressing single or multiple neurotrophin trk receptor mRNA(s) in adult lumbar dorsal root ganglion (DRG) in order to examine the possibility of multi-neurotrophin modulation of phenotype via different trk receptors or various trk isoforms. Expression of mRNA encoding trkA, trkB, trkC, or p75 is restricted to select subpopulations representing approximately 41%, 33%, 43%, and 79% of DRG neurons, respectively. Colocalization studies reveal that approximately 10% of DRG neurons coexpress trkA and trkB mRNA; 19% coexpress trkA and trkC mRNA; and 18% coexpress trkB and trkC mRNA. Trilocalization of all three trk mRNAs is rare, with approximately 3-4% of neurons in this category. Overall incidence of expression of more than one full length trk mRNA occurs in approximately 40% of DRG neurons, whereas expression of individual trk mRNA is found in approximately 34%. Full length trk receptor mRNA is rarely detected without p75, implicating the latter in neuronal response to neurotrophins. Examination of two full-length isoforms of trkA reveal that they are coexpressed with relative levels of expression positively correlated. TrkC mRNAs corresponding to 14- or 39-amino acid insert isoforms colocalize with the non-insert trkC isoform, but the converse is not necessarily true. The data suggest that substantial subpopulations of adult sensory neurons may be modulated through interactions with multiple neurotrophins, the consequences of which are largely unknown.

Animals↗
PubMed1999

Results from the low level mercury sorbent test at the Oak Ridge Y-12 Plant in Tennessee.

A mercury sorbent test was performed near the headwaters of the Upper East Fork Poplar Creek at the Oak Ridge Y-12 Plant in Tennessee. The sorbents SIR-200 (ResinTech), Keyle:X (SolmeteX), and GT-73 (Rohm and Haas) were the best materials tested for low level mercury removal. Each of these sorbents has a thiol-based active site. None of the tested sorbents reduced the mercury concentration to less than the existing 12 ng/l NPDES limit. For this small scale test, SIR-200, Keyle:X, and GT-73 reduced the mercury concentration to less than 51 ng/l, which is a regulatory treatment goal. The other sorbents tested, including granular activated carbon (Filtrasorb 300), did not reduce the mercury concentration below 51 ng/l at any tested flow up to 5 bed volumes per minute. Because of the cost and large volume of sorbent, a wastewater treatment plant for this stream would be prohibitively expensive to construct and maintain.

Absorption↗
PubMed1999

A prospective, randomized trial of tacrolimus/prednisone versus tacrolimus/prednisone/mycophenolate mofetil in renal transplant recipients.

BACKGROUND: Between September 20, 1995 and September 20, 1997, 208 adult patients undergoing renal transplantation were randomized to receive tacrolimus/prednisone (n=106) or tacrolimus/prednisone/mycophenolate mofetil (n=102), with the goal of reducing the incidence of rejection. METHODS: The mean recipient age was 50.7+/-13.7 years. Sixty-three (30.3%) patients were 60 years of age or older at the time of transplantation. The mean donor age was 34.5+/-21.7 years. The mean cold ischemia time was 30.5+/-9.2 hr. The mean follow-up is 15+/-7 months. RESULTS: The overall 1-year actuarial patient survival was 94%; the overall 1-year actuarial graft survival was 87%. When the patient and graft survival data were stratified to recipients under the age of 60 who did not have delayed graft function, the overall 1-year actuarial patient survival was 97%, and the corresponding 1-year actuarial graft survival was 93%. There were no differences between the two groups. The overall incidence of rejection was 36%; in the double-therapy group, it was 44%, whereas in the triple therapy group, it was 27% (P=0.014). The mean serum creatinine was 1.6+/-0.8 mg/dl. A total of 36% of the successfully transplanted patients were taken off prednisone; 32% of the patients were taken off antihypertensive medications. The incidence of delayed graft function was 21%, the incidence of cytomegalovirus was 12.5%, and the initial and final incidences of posttransplant insulin-dependent diabetes mellitus were 7.0% and 2.9%; again, there was no difference between the two groups. CONCLUSIONS: This trial suggests that the combination of tacrolimus, steroids, and mycophenolate mofetil is associated with excellent patient and graft survival and a lower incidence of rejection than the combination of tacrolimus and steroids.

Adolescent↗
PubMed1999

Molecular analysis of the combining site of a monoclonal antibody against spermine.

The structural basis of the binding of the polyamine spermine to the monoclonal antibody SPM8-2 was studied using computer modelling, ELISA methods and chemical modifications of the binding site residues. Paratope modelling showed that the antibody combining site forms a highly negatively charged cavity mainly shaped by aspartic acid and tyrosine residues which contact the tetra-positively charged spermine molecule by electrostatic interactions and hydrogen bondings. The importance of the electrostatic environment for spermine binding to SPM8-2 is emphasised by the strong dependency on pH and ionic strength. Specific chemical modifications of carboxylate groups and tyrosine residues of the antibody adsorbed to microtiter plates resulted in decreased binding of the N1-biotin-spermine conjugate used to monitor the activity of the antibody. These observations are consistent with a key role of aspartate and tyrosine residues in complex formation with spermine. These studies, important to our understanding of antibody-hapten specificity, may also shed light on important motifs responsible for protein-polyamine interactions.

Amino Acid Sequence↗
PubMed1999

Cognitive scripts in autistic children and adolescents.

People normally rely on cognitive scripts to structure social interaction. As the dysfunctional social behavior of people with autism extends to situations that are commonly scripted, one wonders whether a partial explanation might be either absent or deficient scriptal representations. Twenty-four relatively high-functioning subjects with autism were compared to typically developing children who had been selected to be similar to the autistic subjects in terms of nonverbal mental age and language level. All subjects were presented with a series of three tasks designed to assess the presence of cognitive social scripts. Results indicated that basic scriptal knowledge was intact but that reliable differences in expressive language persisted.

Adolescent↗