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Biomedical subjects

A Chapman

Publications and source records attributed to A Chapman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Piriform cortex efferents to the entorhinal cortex in vivo: kindling-induced potentiation and the enhancement of long-term potentiation by low-frequency piriform cortex or medial septal stimulation.

The entorhinal cortex receives input from many cortical areas and mediates the flow of information between these sites and the hippocampal formation. Long-term synaptic plasticity in cortical efferents to the entorhinal cortex may contribute to the transmission of neural activity to the hippocampus, as well as the storage of information, but little is known about plasticity in these pathways. We describe here the use of evoked field potential recordings from chronically implanted electrodes in the rat entorhinal cortex to investigate synaptic plasticity in the large piriform (olfactory) cortex projection to the superficial layers of the entorhinal cortex. Both kindling-induced potentiation and long-term potentiation (LTP) were tested. In addition, we attempted to modulate LTP induction by the co-induction of frequency potentiation and by the co-activation of the medial septum. Epileptogenic kindling stimulations of the piriform cortex (1-s, 60-Hz trains 3 times/day for 5 days) were found to result in a reliable potentiation of field responses evoked by piriform cortex test pulses. Non-epileptogenic tetanization of the piriform cortex with 400-Hz 16-pulse trains reliably resulted in LTP effects. These effects could be augmented by embedding brief LTP induction stimuli within 11-pulse, 15-Hz trains that alone produce only frequency potentiation. Co-activating the medial septum with 10-Hz trains, just prior to tetanization of the piriform cortex, augmented LTP of piriform cortex inputs to the entorhinal cortex in an input-specific manner. All potentiation effects were found to last for periods of weeks. These findings demonstrate that both epileptogenic and non-epileptogenic piriform cortex stimulation induces lasting potentiation of population field responses in the entorhinal cortex of the awake rat. The LTP effects were inducible in a graded manner and were sensitive to the temporal context of stimulation. The finding that low-frequency activation of the septum can enhance plasticity in the entorhinal cortex adds to a body of data indicating a role for the medial septum in contributing to theta activity and plasticity in both the entorhinal cortex and hippocampal formation.

Animals↗
PubMed1997

Renal artery stenosis and unilateral focal and segmental glomerulosclerosis.

Focal and segmental sclerosed lesions in the glomeruli are found in several pathological entities and more often are found in the corticomedullary junction where renal blood flow and filtration pressure is maximal. Experimental data suggest that hyperfiltration injury results in focal and segmental glomerulosclerosis (FSGS). In keeping with this concept, malignant hypertension is a known cause of nephrotic-range proteinuria and nephrotic syndrome pathalobically represented by FSGS. We report a case of unilateral renal artery stenosis associated with nephrotic syndrome and FSGS in the contralateral kidney only. The kidney with the stenosed renal artery showed normal glomeruli with juxtaglomerular hyperplasia, suggesting that protection from hyperfiltration injury was provided by the presence of high-grade stenosis. Serum creatinine concentration, blood pressure, and proteinuria normalized after aorto-renal bypass surgery. This case shows the importance of hemodynamic factors on the pathogenesis of secondary FSGS and the progression of renal disease.

Adult↗
PubMed1996

CD11b+CD28-CD4+ human T cells: activation requirements and association with HLA-DR alleles.

Engagement of CD28 induces a major costimulatory pathway required by many CD4+ T cells in addition to activation via the TCR. In the absence of signals provided by CD28, ligation of the TCR alone can induce anergy or apoptosis in CD28+ cells. However, we report here characterization of a distinct subset of CD4+ T cells that are CD28-. Three autoreactive CD4+ human T cell clones that could be activated to produce IL-2 and proliferate by anti-CD3 alone were found to lack expression of CD28. CD28- clones that were activated with anti-CD3 alone were not anergic to restimulation via CD3. The presence of CD28-CD4+ T cells was verified in peripheral blood, and their frequency ranged from 0% to >22% of CD4+ T cells in different individuals. The percentage of CD28-CD4+ T cells in the peripheral blood of 57 individuals was significantly correlated with specific class II MHC alleles. Persons with HLA-DRB1*0401 and DR1 alleles had significantly higher numbers of CD28- T cells, while individuals with HLA-DR2(15) had significantly fewer CD28-CD4+ T cells than the mean. Like the CD28- clones, CD28-CD4+ T cells isolated from peripheral blood proliferated upon CD3 cross-linking in the absence of costimulation. The finding that CD28-CD4+ T cells resist induction of anergy following engagement of the TCR in the absence of conventional costimulation demonstrates one mechanism by which autoreactive T cells can escape processes that censor self-reactivity. The MHC associations observed suggest a relationship with autoimmunity and loss of self-tolerance.

Alleles↗
PubMed1996

Current theory and practice: a study of pre-operative fasting.

This study examines the practice of pre-operative fasting in relation to fluids. Patients scheduled for elective surgery, and qualified nurses and anaesthetists were studied using a structured and semi-structured interview technique. Supporting the findings of previous studies, this study demonstrated that despite universal agreement between nurses and anaesthetists that patients routinely fast for longer than the recommended time for fluids, pre-operative fasting regimes are derived from routine practice. It was found that a single regime was used to encompass a range of operating times, leading to extended periods of fasting. These periods ranged from three and three quarter hours to 29 hours, with a mean and median fasting time of 11 hours. Fifty per cent of the anaesthetists in the study knew about recent research in this area of practice, but none of the nurses were aware of these recommendations. The absence of a hospital policy offering clear guidelines on the management of pre-operative fasting contributed to the prolonged periods for which patients were fasted. The study also highlighted the fact that patients receive insufficient information regarding the purpose and nature of their fast.

Anesthesiology↗
PubMed1996

Detection of the mec-A gene and phenotypic detection of resistance in Staphylococcus aureus isolates with borderline or low-level methicillinresistance.

Eighty-three isolates of Staphylococcus aureus for which MICs of methicillin of 4-16 mg/L had previously been recorded were tested for the presence of the mecA gene with a DNA probe and a PCR assay. There was complete agreement between the results obtained by these methods; 39 isolates were mecA-positive and 44 were mecA-negative. Using the presence of mecA as the defining standard, several phenotypic methods for determining resistance to methicillin were evaluated and a high-inoculum, agar-incorporation breakpoint test was found to offer the best combination of high sensitivity and high specificity. However twenty-seven of the 44 mecA-negative strains were methicillin-resistant according to agar dilution MICs (MIC > 4 mg/L on at least one of the four media used) but none had MICs exceeding 32 mg/L. One of the mecA-positive strains had a methicillin MIC of only 8 mg/L and did not appear to be heteroresistant. The clinical significance of these two groups of 'atypical' isolates may need further investigation. This study highlights the problems of detecting reliably S. aureus with low level methicillin resistance by phenotype methods and the usefulness of direct detection of the mecA gene.

Bacterial Proteins↗
PubMed1995

Isolation and characterization of species-specific DNA probes from Taenia solium and Taenia saginata and their use in an egg detection assay.

Cysticercosis results from ingestion of the eggs of the tapeworm Taenia solium. Reduction of the incidence of human and swine cysticercosis requires identification and treatment of individuals who carry the adult tapeworm. T. solium and Taenia saginata eggs cannot be differentiated on the basis of morphology; thus, in order to improve existing methods for the diagnosis of taeniasis, we have developed highly sensitive, species-specific DNA probes which differentiate T. solium and T. saginata. Recombinant clones containing repetitive DNA sequences which hybridize specifically with genomic DNAs from either species were isolated and characterized. T. solium-specific DNA sequences contained complete and truncated forms of a tandemly repeated 158-bp DNA sequence. An unrelated T. saginata DNA sequence was also characterized and shown to encode a portion of the mitochondrial cytochrome c oxidase I gene. T. solium- and T. saginata-specific DNA probes did not hybridize in dot blot assays either with genomic DNA from the platyhelminths Taenia hydatigena, Taenia pisiformis, Taenia taeniaeformis, Echinococcus granulosus, and Schistosoma mansoni or with genomic DNA from other eukaryotes, including Saccharomyces cerevisiae, Candida albicans, Cryptosporidium parvum, Entamoeba histolytica, Trypanosoma gambiense, Trypanosoma brucei, and Giardia lamblia, Caenorhabditis elegans, and human DNA. By using these T. solium and T. saginata DNA probes, a rapid, highly sensitive and specific dot blot assay for the detection of T. solium eggs was developed.

Animals↗
PubMed1995

Phase I study of paclitaxel and estramustine: preliminary activity in hormone-refractory prostate cancer.

Estramustine phosphate is a unique antimitotic agent that binds to tubulin and microtubule-associated proteins. Preclinically, estramustine combined with other microtubule inhibitors, like vinblastine or paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), produced additive or greater antimitotic and cytotoxic effects. Clinically, the estramustine/vinblastine combination has significant activity in hormone-refractory prostate cancer. We have begun a phase I study of paclitaxel by 96-hour continuous infusion every 3 weeks combined with daily oral estramustine (600 mg/m2). Eighteen patients with refractory solid tumors have received paclitaxel doses ranging from 80 to 140 mg/m2. Grade 3 or 4 granulocytopenia occurred in one of seven and two of four patients treated at the 120- and 140-mg/m2 dose levels, respectively. The latter two patients experienced grade 3 mucositis and had mean plasma paclitaxel levels exceeding 0.1 mumol/L. Other toxicities, principally nausea and hepatic function abnormalities, have been mild. The apparent steady-state concentrations of paclitaxel 100 and 120 mg/m2 administered with estramustine are similar to those reported for single-agent paclitaxel administered as a 96-hour infusion at doses of 100 and 120 mg/m2. In contrast, at the 140 mg/m2 dose level, paclitaxel concentrations increased throughout the infusion, and steady state was not reached in three of the four patients treated. Objective responses have been observed in two of three patients with adenocarcinoma of the esophagus and in two patients with hormone-resistant prostate cancer and measurable soft tissue metastases. Two additional patients with prostate cancer have been treated with the estramustine/paclitaxel combination, one achieving a major response and the other stable disease. The recommended phase II dose for 96-hour infusional paclitaxel with daily oral estramustine is at least 120 mg/m2. Studies to determine the effect of estramustine on paclitaxel pharmacokinetics are continuing. The antitumor activity observed merits phase II studies of this combination in hormone-resistant prostate cancer and other malignancies.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Seconds count: the Kenny and Jeremy stories.

In this era of health care reform and restraint, there is a resurgence of interest in health promotion and injury prevention. This renewal has added another dimension to the practice of nursing--the expectation that health teaching is included in our interactions with families. This paper will explore submersion injuries in children which, according to Brill, (1987) are uniquely preventable. The ultimate aim of discussing this topic is an increased commitment by nurses to the prevention of submersion injuries.

Child, Preschool↗
PubMed1994

[A new cause of prolonged fever of unknown origin: progesterone substitution therapy].

OBJECTIVES: Over the last 3 years, we examined 15 patients on progesterone substitution therapy who presented prolonged fever. Many explanations had been put forward before the diagnosis was suggested. We recall the thermogenic effect of progesterone. METHODS: Based on a retrospective analysis, we reported the clinical and biological features of 15 patients with prolonged fever due to progesterone substitution therapy and prospectively followed the temperature curves of 9 menopaused women who received substitution therapy for the first time. RESULTS: The 15 case reports were quite typical. Often onset occurred with an acute infectious episode. Following this episode, the patients continued to take their temperature and discovered persistent fever. The context was often one of anxiety-depression rich in functional symptomatology. Laboratory findings included a normal sedimentation rate in all patients. Several days after treatment withdrawal temperature returned to normal. The prospective study confirmed the thermogenetic effect of almost all progesterone substitution drugs. CONCLUSION: The thermogenic effect of natural progesterone is well known but it must be recalled that all progesterone agents with 5-beta metabolites have the same effect. Since metabolic clearance is long, the thermogenic effect may persist for several days after withdrawal.

Adult↗
PubMed1994

[Antiphospholipid syndrome. 20 cases].

OBJECTIVES: We analyzed the clinical and biological characteristics as well as the clinical course and outcome observed in 20 patients with antiphospholipid antibodies and clinical signs including thrombosis or repeated spontaneous abortion to better identify the recently described antiphospholipid syndrome. METHODS: We retrospectively studied all patients observed in our unit from 1981 to 1992 who fulfilled the following inclusion criteria: a) at least one episode of arterial or venous thrombosis and/or repeated spontaneous abortions, b) positive for antiphospholipid antibodies. RESULTS: Twenty patients were included, 3 with systemic lupus erythematosus (according to the American Rheumatism Association criteria). Arterial or venous thrombosis occurred in 9 and 16 respectively, including exceptional cases of cerebral phlebitis and thrombosis of dermal capillaries. High blood pressure was recorded in 8. Only 1 or 2 types of antiphospholipid antibodies were found in most patients. Anticardiolipin, a circulating anticoagulant and a false-positive Bordet-Wassermann reaction were found together in only 3 out of 16. In addition, the antibody level varied independently from the thrombotic events. There was no case with a clinical course from primary antiphospholipid syndrome to systemic erythromatosus lupus. The effect to treatment on occurrence of new thrombotic events was studied. Three patients suffered one or more haemorrhagic events during antivitamin K treatment. CONCLUSION: It is difficult to establish a differentiation between primary antiphospholipid syndrome, systemic lupus erythematosus and lupus-like syndromes, and precise methods of identifying antiphospholipid antibodies should be further developed.

4-Hydroxycoumarins↗
PubMed1994

[Pachydermodactyly: report of a case].

This 20 year old white patient complained of progressive thickening of his fingers over a period of four years. The second, third and fifth fingers of each hand indeed appeared podgy. The soft tissue on each side of the first phalanx was swollen, firm without adherence to the bone. The skin of the interdigital space was hyperpigmented and lichenified. This case illustrates the clinical and histologic features of digital fibromatosis which are discussed.

Adult↗