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Biomedical subjects

N Barrett

Publications and source records attributed to N Barrett.

At least 19 recordsLinked to original sources
PubMed1992

High level expression of active human prothrombin in a vaccinia virus expression system.

We have worked out an efficient and time saving procedure for the expression of recombinant human prothrombin. The glycoprotein was expressed in the vaccinia virus expression system in several mammalian cell lines. The kidney cell lines Vero and BHK and the human cell line Hela were found to efficiently secrete prothrombin. Expression level of 3-4 micrograms of factor II per 10(6) cells per day corresponding to 18-23 mU per 10(6) cells per day were achieved. Since the expression levels obtained with the vaccinia virus/Vero cell system were comparable to those obtained in amplified transformed CHO cells it provides an alternative system for the efficient expression of human prothrombin and may allow to further elucidate structure-function relationships of (pro)thrombin and its various effectors.

Amino Acid Sequence↗
PubMed1992

Dental caries experience and prevalence of children afraid of dental treatment.

The aim of this study was to examine the clinical outcome with regard to dental caries of high self reported dental anxiety in a group of Scottish secondary schoolchildren. 1103 children participated in the study, mean age 14 yr (sd 0.35 yr), and the prevalence of high dental anxiety was 7.1% (95% CI = 5.6%, 8.6%). When these children were compared with their contemporaries their DMFT and all its components were higher but only the mean MT reached statistical significance after adjusting for gender and social class. Children with a high dental anxiety were 62% more likely to have at least 1 missing tooth due to caries. In addition this group when compared to the rest of the study population, had a significantly lower mean number of teeth fissure sealed and a lower proportion of children with sealants. No similar trend was obvious for children who had a high general fear. The dentally anxious more accurately perceived their treatment need and were more likely to defer, cancel or not turn up for dental appointments.

Adolescent↗
PubMed1991

Immunization of chimpanzees with the HIV-1 glycoprotein gp160 induces long-lasting T-cell memory.

The goal of the present study was to investigate the antigen-specific T-cell response to the recombinant HIV envelope glycoprotein (gp160) and to test the effect of various adjuvant formulations on the efficiency of T-cell priming as well as on magnitude and longevity of the gp160-specific T-cell response. Our studies revealed that, in combination with an appropriate adjuvant (lipid-based adjuvant or mineral carrier complex), immunization with recombinant gp160 led to the appearance of gp160-primed T cells. The T-cell response obtained was substantial (proliferative response of greater than 100,000 delta dpm after one primary and two booster immunizations), gp160-specific (proliferation only in response to gp160, no proliferation after addition of a mock gp160 preparation), and long-lasting (T cell responses of greater than 50,000 delta dpm were observed more than one year after the last booster). The results presented here differ from those of previous studies in that they show the presence of substantial and long-lasting T-cell memory toward the immunogen gp160. Therefore further investigations on the use of these preparations as HIV candidate vaccines appear to be justified.

Adjuvants, Immunologic↗
PubMed1991

Characterization of a vaccinia-derived recombinant HIV-1 gp160 candidate vaccine and its immunogenicity in chimpanzees.

The human immunodeficiency virus (HIV-1) envelope glycoprotein gp160 was produced in large-scale microcarrier cultures of Vero cells, using a system involving coinfection with two recombinant vaccinia viruses. The immunogenicity of this material was studied in conjunction with a number of different adjuvant formulations, and chimpanzees were then immunized with gp160 in conjunction with Al(OH)3, Al(OH)3 and sodium deoxycholate, and a lipid-based adjuvant. The Al(OH)3-gp160 vaccine formulation elicited very poor immune responses in two chimpanzees, and these animals were further immunized with gp160 in conjunction with a lipid-based adjuvant. Immunization with the latter formulation lead to induction of high-titer neutralizing antibodies, and, following challenge with HIV-1, one chimpanzee demonstrated no evidence of virus infection over a period of 3 years. The second chimpanzee, which had previously been infected with non-A, non-B hepatitis, and two animals immunized with gp160 with Al(OH)3 and deoxycholate were not protected against challenge.

AIDS Vaccines↗
PubMed1990

[AIDS vaccines: an enigma in vaccine development].

The principles of viral vaccine development and the immune responses to vaccination are described. An effective vaccine should stimulate both cellular and humoral immune responses to provide lasting protection against infection and disease. We describe specific problems associated with the development of an AIDS vaccine i.e. lack of experience with human retroviruses, the integration of the HIV genome in cellular DNA, HIV infection of critical cells in the immune system, persistence of HIV in the brain, large variations in the virus envelope gene, immune interactions with the CD-4 protein and the generation of infection enhancing antibodies. The strategies of AIDS vaccine development are discussed and the candidate vaccines are described with a report on the status of each vaccine trial in progress.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Clozapine: a new drug for schizophrenia.

Clozapine, a new drug for schizophrenia, was recently released for use. We have described the drug and nursing care involved for patients who are on acute inpatient unit for a trial of the drug. From our early observations, clozapine appears to be a promising drug for patients who have not responded to standard neuroleptics.

Adolescent↗
PubMed1989

Efficiency of the polymerase chain reaction for the detection of human immunodeficiency virus type (HIV-1) DNA in the lymphocytes of infected persons: comparison to antigen-enzyme-linked immunosorbent assay and virus isolation.

Seventy-one human immunodeficiency virus type (HIV-1)-positive patients were investigated by polymerase chain reaction (PCR), virus isolation, and antigen detection for the existence of HIV in blood. The identification of HIV DNA by PCR, using three different pairs of primers, yielded a clearly higher detection rate (86%) than with two primer pairs (75%) and was far more sensitive than virus isolation (45%) and antigen ELISA (14%). The PCR-negative results were clearly correlated to asymptomatic clinical stages. However, there was a limited correlation between the clinical stage of disease and the amount of HIV DNA that could be detected in equal numbers of CD4+ cells from different patients, which might be due to their treatment with azido-thymidine (AZT).

Acquired Immunodeficiency Syndrome↗
PubMed1989

Large-scale production and purification of a vaccinia recombinant-derived HIV-1 gp160 and analysis of its immunogenicity.

The human immunodeficiency virus (HIV-1) envelope gene was expressed in large-scale microcarrier cultures of Vero cells using a system involving coinfection with two recombinant vaccinia viruses. One recombinant contained the bacteriophage T7 RNA polymerase gene under control of a vaccinia virus promoter. The second contained the HIV-1 gp160 gene flanked by T7 promoter and termination sequences. The protein was expressed on the surface of infected cells, and it was shown to have a molecular weight of 160 kD and to react with gp41 and gp120 specific monoclonal antibodies. After purification by successive affinity and ion-exchange chromatography, the protein was demonstrated to be present in a particulate form with a diameter in the range of 15-30 nm. When injected into goats a high-titer gp160 specific antibody response was elicited and group-specific neutralizing activity could be demonstrated in vitro. The immunogenicity of the protein was also studied in conjunction with a number of adjuvant formulations, and the highest potency in mice was obtained using a preparation with 0.2% Al(OH)3 and 0.25% deoxycholate.

Adjuvants, Immunologic↗
PubMed1988

Subclavian stenosis: a major complication of subclavian dialysis catheters.

Subclavian catheterisation is frequently used for acute vascular access for haemodialysis and is thought to rarely result in long-term clinical problems. Venography in 36 cases, however, revealed subclavian stenosis in 18 (50%), of whom five developed clinical problems. The incidence of subclavian-vein stenosis was related to the duration of catheterisation (P less than 0.05). It may also be more common in black patients. Subclavian catheterisation is therefore not necessarily an ideal form of acute vascular access.

Catheterization, Central Venous↗
PubMed1987

[Comparison of two ELISA kits for the demonstration of antibodies against LAV/HTLV-III].

Eight hundred sera from a non-risk group and thousand sera from people at risk for acquiring AIDS were tested for the presence of LAV/HTLV-III specific antibodies by ELISA test kits manufactured by Du Pont and Organon. Western Blot analysis was used as a confirmatory test. All Western Blot positive sera were also positive in the Du Pont ELISA which in addition revealed a very low rate of false positive results (0.44%). In the Organon ELISA negative results were obtained with one positive and one questionable positive serum, as determined by Western Blot. The possible problem of test sensitivity being too low has been taken into account by the manufacturer by changing the calculation of cut-off values.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Composition and supramolecular organization of the tectorial membrane.

We have shown that collagen accounts for approximately 40% of the total protein of the tectorial membrane (TM) of the guinea pig and have estimated several essential parameters of TM composition including dry weight, wet weight, and water content. The major collagenous protein was definitively identified as type II collagen by SDS-PAGE, CNBr peptide mapping, and immunoblot assays. Quick-freeze, deep-etch electron microscopy of the guinea pig TM demonstrated a dense meshwork of fibers embedded in a complex microfibrillar matrix which may consist of proteoglycans; the larger fibers were similar in size and appearance to type II collagen fibers of elastic cartilage. Finally, the comparative free amino acid profiles of TM strongly suggest that the TM is chemically transparent with respect to endolymph. Thus, the TM appears to consist of a highly hydrated matrix mechanically stabilized by type II collagen fibers.

Amino Acids↗
PubMed1978

Excitation-contraction coupling in skeletal muscle: blockade by high extracellular concentrations of calcium buffers.

High concentrations (80 to 90 millimolar) of the calcium buffers EGTA and citrate (less than 10(-7) molar free calcium ion) reversibly block excitation-contraction coupling in intact frog skeletal fibers, but do not block caffeine-induced contractures. Solutions containing the same free calcium concentration but lower concentrations of calcium buffer (1 millimolar) do not block excitation-contraction coupling. These results suggest that excitation-contraction coupling requires the presence of calcium in a "protected" extracellular compartment, probably the transverse tubular network, and that calcium is actively transported into this compartment from the muscle cell cytoplasm.

Action Potentials↗