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Biomedical subjects

R Carter

Publications and source records attributed to R Carter.

At least 199 records · Page 11Linked to original sources
PubMed1991

Genetic hybrids of Plasmodium falciparum identified by amplification of genomic DNA from single oocysts.

Individual oocysts from Plasmodium falciparum-infected Anopheles gambiae and Anopheles stephensi mosquitoes have been examined by the PCR technique, after their removal from the midgut. The DNA obtained from these oocysts has been amplified using oligonucleotide primers specific for part of the merozoite surface antigen MSA-1 gene. This technique distinguishes oocysts which are the products of self-fertilisation events from those which are the products of cross-fertilisation between different parasite clones.

Animals↗
PubMed1991

A stage specific gene expressed at the onset of gametocytogenesis in Plasmodium falciparum.

The gene encoding the gametocyte specific cytoplasmic protein Pfg27/25 of the human malaria parasite Plasmodium falciparum has been cloned. The gene encodes a highly hydrophilic non-repetitive protein which does not share obvious homologies with other polypeptides. The stage specificity of Pfg27/25 is controlled at the stage of the production of stable mRNA, which is detectable only in the sexual stages of the parasite, and contains long additional sequences outside the Pfg27/25 coding region. As the activation of Pfg27/25 gene expression occurs at an early stage of gametocytogenesis, the study of its regulation might provide information on the molecular events occurring after the parasite commitment to sexual differentiation and at the beginning of gametocyte formation.

Amino Acid Sequence↗
PubMed1991

A prospective comparison between magnetic resonance imaging, meta-iodobenzylguanidine scintigraphy and marrow histology/cytology in neuroblastoma.

A prospective comparison between magnetic resonance imaging (MRI), 123I meta-iodobenzylguanidine (mIBG) scintigraphy and posterior iliac crest marrow aspiration and trephine biopsy in 30 assessments (19 patients) showed concordance between the three techniques in 16 assessments (53.3%). In 10 (33.3%), MRI and mIBG revealed abnormalities not detected by marrow biopsy. MRI was the only technique to demonstrate marrow abnormality in four assessments (13.3%). In addition, MRI revealed more sites of abnormality in 16 parallel assessments. We conclude that MRI shows promise as a non-invasive means of detecting bone marrow infiltration by neuroblastoma, but that further evaluation of the specificity of MRI in this setting is indicated.

3-Iodobenzylguanidine↗
PubMed1991

Subclinical pulmonary function defects following autologous and allogeneic bone marrow transplantation: relationship to total body irradiation and graft-versus-host disease.

Pulmonary function results pre- and post-transplant, to a maximum of 4 years, were analyzed in 98 patients with haematological disorders undergoing allogeneic (N = 53) or autologous bone marrow transplantation (N = 45) between 1982 and 1988. All received similar total body irradiation based regimens ranging from 9.5 Gy as a single fraction to 14.4 Gy fractionated. FEV1/FVC as a measure of airway obstruction showed little deterioration except in patients experiencing graft-versus-host disease in whom statistically significant obstructive ventilatory defects were evident by 6 months post-transplant (p less than 0.01). These defects appeared to be permanent. Restrictive ventilatory defects, as measured by reduction in TLC, and defects in diffusing capacity (DLCO and KCO) were also maximal at 6 months post-transplant (p less than 0.01). Both were related, at least in part, to the presence of GVHD (p less than 0.01) or use of single fraction TBI with absorbed lung dose of 8.0 Gy (p less than 0.05). Fractionated TBI resulted in less marked restricted ventilation and impaired gas exchange, which reverted to normal by 2 years, even when the lung dose was increased from 11.0 Gy to between 12.0 and 13.5 Gy. After exclusion of patients with GVHD (30% allografts) there was no significant difference in pulmonary function abnormalities between autograft and allograft recipients.

Adolescent↗
PubMed1991

Accuracy of CT in detecting squamous carcinoma metastases in cervical lymph nodes.

The accuracy of computed tomography (CT) in the assessment of nodal metastases was correlated retrospectively with the pathological examination in 28 patients with known head and neck squamous cell carcinoma, who underwent neck dissections. Three patients had bilateral neck dissections resulting in a total of 31 dissections. CT scanning correctly staged 28 of 31 neck dissections providing an accuracy of 90%, a sensitivity of 87.5% and a specificity of 100% in the detection of nodal metastases. Of the 21 true positives, underestimation of the extent of nodal disease occurred in seven cases. Regarding extracapsular nodal spread, CT resulted in an accuracy of 62%, a sensitivity of 62.5% and a specificity of 60%. All three false negatives for nodal metastases occurred in metastatic spread to the submandibular nodes. The existing criteria for assessment of nodal metastases with CT are sensitive and specific, but in the assessment of extranodal spread CT may not detect 37.5% of cases.

Carcinoma, Squamous Cell↗
PubMed1991

Antigenic polymorphism in malaria: is it an important mechanism for immune evasion?

Malarial infections do not readily evoke an effective protective immunity against re-infection. Possible reasons for this include the ability of the parasites to interfere with the host's immune response and to evade the response in an immune host, by, for example, exploiting antigenic polymorphism or variation. Antigenic polymorphism undoubtedly exists in malaria parasite populations but does this polymorphism actually contribute to immune evasion by the parasite? Here, Kamini Mendis and colleagues examine the evidence for this and its implications for future malaria vaccines.

Animals↗
PubMed1991

Larynx preservation using induction chemotherapy plus radiation therapy as an alternative to laryngectomy in advanced head and neck cancer. A long-term follow-up report.

Since 1977, we have used induction chemotherapy (CT) plus radiation therapy (RT) with curative intent in 35 advanced head and neck cancer (Ca) patients who otherwise would have required total laryngectomy. Fourteen patients had advanced Ca of the larynx or supraglottic larynx (SGL); 21 patients had Ca of the hypopharynx. In six patients the Ca was Stage III; in 26 patients it was Stage IV. Three patients had Stage II disease--2 with cancer of the pyriform sinus and one patient with Stage II SGL Ca who refused surgery. Chemotherapy consisted of platinum (P) + bleomycin in 18 patients until 1982, then P + fluorouracil in the next 17 patients. Total response rate was 77%--complete (CR) in 26% and partial (PR) in 51%. There were two toxic deaths. Surgery was limited to tracheostomy in 4 patients prior to CT and to radical neck dissection after CT in 4 others. Two patients required salvage laryngectomy at 11 and 31 months, respectively. One patient underwent partial laryngectomy with voice preservation. Thirty-two patients were evaluable for overall response after RT. Final disease-free status was achieved in 20/34. One long-term survivor was lost to follow-up (44 months) and 8 patients remained alive at 13+ to 109+ months. Median failure-free survival for all patients was no less than 24 months. Not counting 4 early deaths free of disease, 2-year local control using only chemotherapy plus radiation was 52% (16:31). Overall, 33 of 35 patients retained their voices. Sixteen patients (46%) have survived 2 years or longer. Survival of patients who achieved CR after induction chemotherapy was 48 months versus 14 months for those with less than a CR (p = 0.001). Patients with a hypopharyngeal primary had only a 33% 2-year local control rate with chemotherapy and radiation and a median survival of only 12 months versus 77% control and a minimum 39-month survival for those whose tumor arose in the larynx (p = 0.009). Induction chemotherapy plus radiation therapy is an effective strategy which can produce a high rate of larynx preservation, local control, and long-term survival in patients with advanced cancer of the larynx. Patients with hypopharyngeal primaries have a lesser rate of long-term survival and local control, despite similar overall response rates.

Aged↗
PubMed1991

Double blind crossover comparison of the effects of dual chamber pacing (DDD) and ventricular rate adaptive (VVIR) pacing on neuroendocrine variables, exercise performance, and symptoms in complete heart block.

OBJECTIVE: To compare the effects of dual chamber pacing (DDD) and ventricular rate adaptive pacing (activity sensing) (VVIR) in patients with complete heart block. DESIGN: Double blind crossover comparison with one month in each pacing mode. PATIENTS: 10 consecutive patients aged 23-74 presenting with complete anterograde atrioventricular block at rest and on exercise and with an intact atrial rate response received Synergyst I (Medtronic) pacemakers. MAIN OUTCOME MEASURES: Symptom scores, maximal exercise performance on a treadmill, and the plasma concentrations of atrial natriuretic peptide, adrenaline, and noradrenaline. RESULTS: No significant differences were identified between pacing modes in symptom scores for dyspnoea, fatigue, and mood disturbance; exercise time; and maximal oxygen consumption. One patient with intact ventriculoatrial conduction developed pacemaker syndrome during VVIR pacing. Resting plasma concentrations of atrial natriuretic peptide were raised in complete heart block and were restored to normal by DDD pacing but not by VVIR pacing. Resting plasma catecholamine concentrations were normal in complete heart block and in both pacing modes. During exercise the increase in the concentrations of all three hormones was similar in both pacing modes. CONCLUSIONS: In patients with complete anterograde and retrograde atrioventricular block, symptoms and maximal exercise performance were no better during DDD than during VVIR pacing.

Adult↗
PubMed1991

Conserved and variant epitopes of target antigens of transmission-blocking antibodies among isolates of Plasmodium falciparum from Malaysia.

Monoclonal antibodies (MAbs) directed against different epitope regions on three sexual stage-specific gamete surface proteins of Plasmodium falciparum, Pfs 25, Pfs 230, and Pfs 48/45, were used to study the genetic diversity of these epitopes among fresh isolates of P. falciparum from Malaysia, using immunofluorescence microscopy (IFA). Among 45 Malaysian isolates, one epitope of Pfs 25, designated region I, showed evidence of variable reactivity with MAbs among different isolates; the Pfs 25 epitope, region II, was universally recognized by MAbs in all isolates. Two apparently distinct epitope regions of Pfs 230 were defined by MAbs, one of which was universally recognized by MAbs among the 45 isolates; the other was conserved in all but three isolates. The epitope regions of gamete-surface protein Pfs 48/45, designated regions I, IIa, IIb, IIc, III, and IV, were examined for reactivity by IFA in 33 isolates. Epitope regions I, IIb, III, and IV were conserved in all isolates; regions IIa and IIc existed in variant forms.

Adolescent↗
PubMed1991

Infectious reservoir of Plasmodium vivax and Plasmodium falciparum malaria in an endemic region of Sri Lanka.

The infectious reservoir of Plasmodium vivax and P. falciparum in a malaria endemic region in Sri Lanka was defined in a population of 3,625 by directly feeding mosquitoes on a sample of infected individuals during a period of 17 months. The malaria case incidence in this population was concurrently monitored. P. vivax gametocyte densities were highest in the youngest age groups, and decreased steadily with increasing age. However, the infectivity per gametocyte appeared to be lower in the younger age groups than in the older ones. There was no significant correlation between the age of patients and their gametocyte densities for P. falciparum, to which this population was only recently exposed, nor was there a discernible trend in the infectivity per gametocyte in different age groups. The average infectivity of patients was lowest in the youngest (0-5 years) and the oldest (greater than 50) age groups. The contribution made by P. vivax patients in the different age groups to the reservoir of infection was estimated. Patients in the 6-25 year age groups made the largest contribution to the reservoir, followed by those in the 26-50 year age group. Patients in the youngest and the oldest age groups contributed least to the infectious reservoir. When population sizes in the different age groups were taken into consideration, the age groups between 6 and 50 years contributed almost equally to approximately 87% of the infectious reservoir. The reservoir of P. falciparum malaria was very small, being confined to 9% of the patients, and this appears to be a characteristic of epidemic malaria, as was the case with P. falciparum.

Acute Disease↗
PubMed1991

Clustering of malaria infections within an endemic population: risk of malaria associated with the type of housing construction.

The occurrence of malaria infections due to Plasmodium vivax and P. falciparum was monitored in a population of 3,023 people living in six contiguous villages in Kataragama, an area of endemic malaria in southern Sri Lanka, over a period of 17 months. The annual incidence of malaria in this population during the study period was 25.8%. Malaria attacks were clustered, occurring more frequently than expected in certain individuals and housing groups and less frequently than expected in others. In one of these villages, the distribution of cases was examined in relation to locality and to the type of house construction. There was a strong association between the malaria incidence and house construction, independent of location. The risk of getting malaria was greater for inhabitants of the poorest type of house construction (incomplete, mud, or cadjan (palm) walls, and cadjan thatched roofs) compared to houses with complete brick and plaster walls and tiled roofs. Houses that were better constructed had a significantly lower malaria incidence rate (10.5%) than those that were poorly constructed (21.2%; P less than 0.01, by Student's t-test). There was also a significantly higher number of indoor resting mosquitoes collected from the poorly constructed houses than from those better constructed; the average (geometric mean) of mosquito densities found in houses of better versus poor construction were 0.97 and 1.89 per collection in the dry season, and 1.95 and 3.42 per collection in the wet season, respectively (P less than 0.05 in both seasons). This indicated that the higher malaria risk associated with poorly constructed houses was at least partly due to higher human-mosquito contact among their inhabitants.

Animals↗
PubMed1991

Immune responses against sexual stages of Plasmodium vivax during human malarial infections in Sri Lanka.

During natural infections of P. vivax malaria a variety of immune responses to the infection affect infectivity of the parasites to mosquitoes. Sexual stage antigens present in the blood stage parasites induce antibodies which may either enhance or suppress the infectivity of the sexual parasites to mosquitoes. Subsequent infections of P. vivax do not, unless occurring within less than 4 months, boost this response indicating a very short immune memory for the relevant antigens. Blood infection also results in the release of cytokines and other non-antibody factors which together can mediate death of the blood stage sexual parasites. These factors are associated with paroxysm in non-immune individuals. In individuals from an endemic area with age-acquired anti-disease immunity clinical symptoms are mild and the parasite killing factors are not induced.

Animals↗
PubMed1991

Expression of p53 in premalignant and malignant squamous epithelium.

Using three antibodies (JG8, CM-1 and 1081) directed to the p53 protein, strong positivity was found in 16/47 (34.0%) of mucosal squamous cell carcinomas of the head and neck and in two squamous carcinoma cell lines (LICR-LON- HN5 and HN6Rr). The presence of the mutant p53 was confirmed in the cell lines as substitutions in exon 7 (codon 238, TGT greater than AGT) and exon 5 (codon 152, CCG greater than CTG) respectively. Positive staining was seen only in the undifferentiated cells and progressively lost as the cells keratinized, both in the tumour specimens and in the cell lines. Similar results were seen in areas of dysplasia, well removed from the site of the primary tumour. Staining of epidermal lesions showed positivity in 2/12 (16.6%) cases of Bowen's disease, 0/12 (0.0%) cases of solar keratosis, 0/10 (0.0%) basal cell carcinomas and in 3/20 (15.0%) squamous cell carcinomas. These results are discussed in relation to the multifocal origin of squamous cell carcinomas, the role of p53 mutations in squamous cell carcinomas from different sites and the significance of the 'basal' distribution of p53 as a normal growth regulator. The possible significance of the distribution of p53 in squamous epithelium as it relates to papilloma virus infection is also considered.

Amino Acid Sequence↗