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Biomedical subjects

D Johnson

Publications and source records attributed to D Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2002

Toxic shock syndrome following cessation of prophylactic antibiotics in a child with a 2% scald.

Toxic shock syndrome (TSS) is a rare but serious complication of burns in children. Symptoms usually start within 3 days of the burn injury and even children with minor burns can be susceptible. Prompt diagnosis and rapid treatment is crucial in limiting the morbidity associated with this condition. We report here a 19-month-old child with a 2% scald who developed TSS following cessation of a 5-day course of flucloxacillin. This case highlights a number of issues regarding the use of prophylactic antibiotics and TSS as well as illustrating the continuing need to educate parents concerning the importance of seeking a prompt medical opinion if the child becomes ill following even a minor burn injury.

Bacterial Toxins↗
PubMed2002

Therapeutic management of HIV.

Highly active antiretroviral therapy (HAART) has been used to treat HIV for several years with a reduction in mortality and morbidity. However, some patients fail to achieve complete viral suppression. Durability of therapy cannot be guaranteed and cross-resistance may arise, making second-line therapy a complex issue. Toxicity and pharmacokinetic interactions with other drugs may complicate long-term efficacy of regimens. The reduction of viral burden can prevent progressive immunodeficiency and may decrease the risk of selecting resistant viruses. Triple therapy with a protease inhibitor showed a decrease in morbidity, mortality and durability, but protease-sparing therapies might yield fewer side-effects. Lipid-related toxicity of protease inhibitors has resulted in the use of nonnucleoside reverse transcriptase inhibitors (NNRTI) in HAART. However, a single mutation for an NNRTI can confer cross-class resistance that limits further options for second-line therapy. When choosing HAART it is crucial to achieve durability and to structure doses to suit the patient's lifestyle, and it is important for patients to initiate therapy when they are ready. The decision to change drug regimens following treatment failure or rebound will depend on the initial choice of HAART. Viral load reduction occurs rapidly in most patients on HAART but immune reconstitution is slow and occurs almost unaided. Therefore prophylaxis against opportunistic infections should not be stopped prematurely.

AIDS-Related Opportunistic Infections↗
PubMed2001

Elevated blood pressure in subjects with lipodystrophy.

OBJECTIVES: To assess the prevalence of elevated blood pressure in patients with lipodystrophy. DESIGN: Case-control study. PARTICIPANTS: Forty-two patients with abnormal body fat (100%) and serum lipids (86%) (HIV-positive cohort) were matched by age and sex to 42 HIV-positive controls without previously diagnosed lipodystrophy and to 13 HIV-negative controls. SETTING: Tertiary care, university-based, fully dedicated HIV clinic. MAIN OUTCOME MEASURES: Frequency and magnitude of elevated blood pressure during highly active antiretroviral therapy. RESULTS: There were 23 +/- 16 and 22 +/- 12 blood pressure measurements recorded per subject over 21 +/- 11 and 22 +/- 11 months for the HIV-positive cohort and HIV-positive controls, respectively. Three or more elevated readings occurred in 74% of the cohort and in 48% of the HIV-positive controls (P = 0.01) and accounted for 38 +/- 25% versus 22 +/- 26% (P = 0.01) of the total readings, respectively. The average of the three highest systolic readings (153 +/- 17 versus 144 +/- 15 mmHg; P = 0.01) and diastolic readings (92 +/- 10 versus 87 +/- 9 mmHg; P = 0.01) was greater for the cohort than for the HIV-positive controls. Family history of hypertension was more common in the cohort than in the controls but accounted for only 13% of the log odds ratio value for elevated blood pressure in the cohort. Systolic blood pressure was correlated with waist-to-hip ratios in the cohort (r = 0.45; P = 0.003) but not in the HIV controls (r = 0.06; P = 0.68) and tended to be related to fasting triglycerides (r = 0.34; P = 0.052) in subjects with HIV. CONCLUSIONS: Elevated blood pressure may be linked to the metabolic disorders occurring in patients with HIV, as in the dysmetabolic syndrome.

Adipose Tissue↗
PubMed2001

Observation of compressional Alfvén modes during neutral-beam heating on the national spherical torus experiment.

Neutral-beam-driven compressional Alfvén eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2omega(ci) to approximately 1.2omega(ci). The frequency has a scaling with toroidal field and plasma density consistent with Alfvén waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer.

Journal Article↗
PubMed2001

A randomized study of the utility of human immunodeficiency virus RNA measurement for the management of antiretroviral therapy.

To compare frequent measurement with infrequent measurement of human immunodeficiency virus (HIV) RNA levels in the management of antiretroviral therapy, we conducted a clinical strategy study of 206 HIV-infected patients who had <500 CD4 cells/mm(3). Patients were randomized (1.5:1) to undergo frequent monitoring (at baseline and every 2 months) or infrequent monitoring (at baseline and twice yearly), with CD4 cell counts determined every 2 months. Patients received unrestricted antiretroviral therapy. In the primary analysis (at month 6), the frequent group had a mean HIV RNA reduction (+/- standard deviation) of 0.93+/-0.79 log(10) copies/mL, versus 0.48+/-0.83 log(10) copies/mL for the infrequent group (P=.0002). A trend (P=.1) toward improved survival was seen in the frequent group. Given this improved virological response, more frequent HIV RNA measurement than is recommended in published guidelines (every 3-4 months) may be appropriate.

Adult↗
PubMed2001

A novel phosphotyrosine mimetic 4'-carboxymethyloxy-3'-phosphonophenylalanine (Cpp): exploitation in the design of nonpeptide inhibitors of pp60(Src) SH2 domain.

The novel phosphotyrosine (pTyr) mimetic 4'-carboxymethyloxy-3'-phosphonophenylalanine (Cpp) has been designed and incorporated into a series of nonpeptide inhibitors of the SH2 domain of pp60(c-Src) (Src) tyrosine kinase. A 2.2 A X-ray crystal structure of 1a bound to a mutant form of Lck SH2 domain provides insight regarding the structure-activity relationships and supports the design concept of this new pTyr mimetic.

Animals↗
PubMed2001

The human mast cell: functions in physiology and disease.

Mast cells are multifunctional, tissue-dwelling cells capable of secreting a wide variety of mediators. They develop from bone marrow-derived progenitor cells, primed with stem cell factor (SCF), which mediates its actions by interacting with the SCF receptor or c-kit on the cell surface. Mast cells continue their maturation and differentiation in peripheral tissue, developing into two well described subsets of cells, MCT and MCTC cells, varying in content of tryptase and chymase as well as in immunobiology. Mast cells are activated by numerous stimuli, including antigen (acting via the high affinity IgE receptor, Fc?RI), superoxides, complement proteins, neuropeptides and lipoproteins resulting in activation and degranulation. Following activation, these cells express mediators such as histamine, leukotrienes and prostanoids, as well as proteases, and many cytokines and chemokines, pivotal to the genesis of an inflammatory response. Recent data suggests that mast cells may play an active role in such diverse diseases as atherosclerosis, malignancy, asthma, pulmonary fibrosis and arthritis. Mast cells directly interact with bacteria and appear to play a vital role in host defense against pathogens. Drugs, such as glucocorticoids, cyclosporine and cromolyn have been demonstrated to have inhibitory effects on mast cell degranulation or mediator release.

Arteriosclerosis↗
PubMed2001

Prospective evaluation of the effect of initiating indinavir-based therapy on insulin sensitivity and B-cell function in HIV-infected patients.

OBJECTIVE: To determine whether initiation of antiretroviral therapy that includes the protease inhibitor indinavir causes insulin resistance or abnormal B-cell function in study subjects with HIV infection. METHODS: Nonwasted, HIV-infected study subjects who did not have concurrent diabetes were prospectively evaluated by oral and intravenous glucose tolerance testing at baseline, at 2 weeks after starting indinavir monotherapy, and at another 6 weeks after initiating indinavir-based triple-therapy. RESULTS: Mean CD4 count at entry was 282 cells/microl and median HIV RNA was 33,000 copies/ml; all experienced a virologic response. Fasting glucose increased from 83.2 +/- 3.7 mg/dl at baseline to 86.8 +/- 3.2 at week 2 and 91.7 +/- 3.5 at week 8 (p =.003). Insulin sensitivity by minimal model analysis decreased by 30.5% over 8 weeks, from 3.83 +/- 0.63 min-1 per microU/ml x 10-4 to 3.09 +/- 0.53 at week 2 and 2.66 +/- 0.35 at week 8 (p =.01). Insulin secretion by the acute insulin response to intravenous glucose did not change (baseline 822 +/- 283 microU/ml x min, week 8 880 +/- 289; p = 0.4), and the insulin response to oral glucose (30 minute insulin:glucose ratio) fell from 1.69 +/- 0.54 microU/ml per mg/dl at baseline to 1.18 +/- 0.34 at week 8 (p =.05). CONCLUSION: During 8 weeks of indinavir-based therapy, fasting glucose increased and insulin sensitivity decreased, without a compensatory increase in insulin release. This combination of insulin resistance without augmented B-cell response may explain the hyperglycemia and other metabolic abnormalities seen in some protease inhibitor-treated patients.

Adult↗
PubMed2001

Effect of highly active antiretroviral therapy on the serological response to additional measles vaccinations in human immunodeficiency virus-infected children.

Children infected with human immunodeficiency virus (HIV) often lose their vaccine-induced antibody to measles virus. Before highly active antiretroviral therapy (HAART), an additional immunization against measles infrequently resulted in protective antibodies. The antibody response to an additional measles-mumps-rubella (MMR) vaccination was compared in 28 HIV-infected children who lacked protective antibody to measles virus and were undergoing HAART or non-HAART regimens. Serostatus was measured by automated enzyme-linked immunoassay. Nine (64.3%) of 14 children undergoing HAART, compared with 3 (21.4%) of 14 in the non-HAART group, had antibody to measles virus after the additional vaccination with MMR (P=.027). The groups showed no significant difference in CD4 cell values. Ten of 14 HAART patients had undetectable levels of HIV. The mean HIV load for the HAART group was 27,700 copies/mL (median, <400 copies/mL); for the non-HAART group, it was 86,000 copies/mL (median, 9000 copies/mL). Thus, HAART improves the response to an additional MMR vaccination, which is consistent with immune system reconstitution.

Antibodies, Viral↗
PubMed2001

Does renal failure cause an atherosclerotic milieu in patients with end-stage renal disease?

PURPOSE: Atherosclerotic vascular disease is the main cause of morbidity and mortality in patients with end-stage renal disease, but the independent contribution of renal failure rather than associated risk factors is unclear. We sought to examine the relative contribution of these factors to the severity of atherosclerosis by measuring intima-medial thickness and brachial artery reactivity in uremic patients and controls. SUBJECTS AND METHODS: Cardiovascular risk factors, including lipid and homocysteine levels, were evaluated in 213 patients (69 on hemodialysis, 60 on peritoneal dialysis, and 82 nonuremic controls). High-resolution B-mode ultrasonography with automated off-line analysis was used to measure the intima-medial thickness in the common carotid artery and to measure the lumen diameter of the brachial artery at rest, during reactive hyperemia, and after sublingual nitroglycerine. The correlations of risk factors with intima-medial thickness and brachial reactivity were examined using a general linear regression model. RESULTS: Patients with renal failure had a greater mean (+/- SEM) maximum intima-medial thickness than controls (0.83 +/- 0.02 mm versus 0.70 +/- 0.02 mm, P < 0.05), but the brachial artery response to reactive hyperemia was not significantly different between the renal failure patients and the control group (4.7% +/- 6.1% versus 6.1% +/- 8.6% dilatation, P > 0.05). The uremic state was an independent predictor of intima-medial thickness (r2 = 0.16, P < 0.001) but not of brachial artery reactivity (P = 0.99). CONCLUSION: The atherosclerotic burden in patients with renal failure, as indicated by an increased intima-medial thickness, may reflect effects of uremia that are independent of cardiovascular risk factors.

Adult↗
PubMed2001

A review of mechanisms controlling ovulation with implications for the anovulatory effects of polychlorinated dibenzo-p-dioxins in rodents.

Polychlorinated dibenzo-p-dioxins (PCDDs) can impinge on female fertility by preventing ovulation. In this review, the aspects of normal ovulatory physiology most relevant to our current understanding of PCDD action on the ovary are briefly reviewed. This is followed by a comprehensive assessment of data relevant to the effects of PCDDs during ovulation in the rat. PCDDs interrupt ovulation through direct effects on the ovary in combination with dysfunction of the hypothalamo-hypophyseal axis.

Animals↗
PubMed2001

Structured exercise improves physical functioning in women with stages I and II breast cancer: results of a randomized controlled trial.

PURPOSE: Self-directed and supervised exercise were compared with usual care in a clinical trial designed to evaluate the effect of structured exercise on physical functioning and other dimensions of health-related quality of life in women with stages I and II breast cancer. PATIENTS AND METHODS: One hundred twenty-three women with stages I and II breast cancer completed baseline evaluations of generic and disease- and site-specific health-related quality of life, aerobic capacity, and body weight. Participants were randomly allocated to one of three intervention groups: usual care (control group), self-directed exercise, or supervised exercise. Quality of life, aerobic capacity, and body weight measures were repeated at 26 weeks. The primary outcome was the change in the Short Form-36 physical functioning scale between baseline and 26 weeks. RESULTS: Physical functioning in the control group decreased by 4.1 points, whereas it increased by 5.7 points and 2.2 points in the self-directed and supervised exercise groups, respectively (P =.04). Post hoc analysis showed a moderately large (and clinically important) difference between the self-directed and control groups (9.8 points; P =.01) and a more modest difference between the supervised and control groups (6.3 points; P =.09). No significant differences between groups were observed for changes in quality of life scores. In a secondary analysis of participants stratified by type of adjuvant therapy, supervised exercise improved aerobic capacity (+3.5 mL/kg/min; P =.01) and reduced body weight (-4.8 kg; P <.05) compared with usual care only in participants not receiving chemotherapy. CONCLUSION: Physical exercise can blunt some of the negative side effects of breast cancer treatment, including reduced physical functioning. Self-directed exercise is an effective way to improve physical functioning compared with usual care. In participants not receiving chemotherapy, supervised exercise may increase aerobic capacity and reduce body weight compared with usual care.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Genetic control of the cell proliferation-differentiation balance in the developing skull vault: roles of fibroblast growth factor receptor signalling pathways.

Activating mutations of genes encoding the transmembrane tyrosine kinase receptors fibroblast growth factor receptors (FGFRs)1-3, and haploinsufficiency of the transcription factor TWIST, cause human craniosynostosis syndromes that typically involve the coronal suture. We have investigated the functional roles of these genes in development of the coronal suture in mouse fetuses, and tested the effects of increasing FGFR signalling by applying exogenous FGF2 to the suture. The results indicate that the proliferation-differentiation balance in normal sutural development involves a gradient of extracellular FGF from the region of differentiation, in which Fgfr1 is expressed, to the sutural mesenchyme, in which low levels of FGF are associated with Fgfr2 expression in osteogenic stem cells. Experimental increase of sutural FGF levels leads to down-regulation of Fgfr2, up-regulation of Fgfr1, up-regulation of the osteogenic differentiation gene Osteopontin, and cessation of proliferation. Twist is expressed in the midsutural mesenchyme and is partially co-expressed with Fgfr2, consistent with the possibility that it is involved in maintaining proliferation through regulating transcription of Fgfr2.

Animals↗
PubMed2001

Enhanced apoptotic activity of a p53 variant in tumors resistant to wild-type p53 treatment.

TP53 is the most commonly altered tumor-suppressor gene in cancer and is currently being tested in Phase II/III gene replacement trials. Many tumors contain wild-type TP53 sequence with elevated MDM2 protein levels, targeting p53 for degradation. These tumors are more refractory to treatment with exogenous wild-type p53. Here we generate a recombinant adenovirus expressing a p53 variant, rAd-p53 (d 13-19), that is deleted for the amino acid sequence necessary for MDM2 binding (amino acids 13-19). We compared the apoptotic activity of rAd-p53 (d 13-19) with that of a recombinant adenovirus expressing wild-type p53 (rAd-p53) in cell lines that differ in endogenous p53 status. rAd-p53 (d 13-19) caused higher levels of apoptosis in p53 wild-type tumor lines compared with wild-type p53 treatment, as measured by annexin V-FITC staining. In p53-altered tumor lines, rAd-p53 (d 13-19) showed apoptotic activity similar to that seen with wild-type p53 treatment. In normal cells, no increase in cytopathicity was detected with rAd-p53 (d 13-19) compared with wild-type p53 treatment. This variant protein displayed synergy with chemotherapeutic agents to inhibit proliferation of ovarian and breast cell lines. The p53 variant showed greater antitumor activity in an established p53 wild-type tumor compared with treatment with wild-type p53. The p53 variant represents a means of expanding TP53 gene therapy to tumors that are resistant to p53 treatment due to the cellular responses to wild-type p53.

Adenoviridae↗