Growth and physiology of Azotobacter chroococcum in continuous culture.
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Adenosine Triphosphate↗
Biomedical subjects
H Dalton
Publications and source records attributed to H Dalton.
Effect of oxygen on growth of Azotobacter chroococcum in batch and continuous cultures.
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Ammonia↗
Heterologous expression of soluble methane monooxygenase genes in methanotrophs containing only particulate methane monooxygenase.
The methanotrophs Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b contain particulate methane monooxygenase (pMMO) and soluble methane monooxygenase (sMMO) genes. Other methanotrophs such as Methylomicrobium album BG8 and Methylocystis parvus OBBP contain only pMMO genes. Although molecular genetic techniques are poorly developed in methanotrophs, sMMO genes were expressed in methanotrophs normally containing only pMMO genes. This was achieved by conjugation using broad-host-range plasmids containing the native promoter and sMMO genes from Mc. capsulatus (Bath) and Ms. trichosporium OB3b. sMMO genes derived from Ms. trichosporium OB3b were expressed in an active form in Mcy. parvus OBBP and in Mm. album BG8. Therefore, all of the genes required for active sMMO synthesis were contained on the broad-host-range plasmids and were expressed in the heterologous hosts. Constitutive synthesis of pMMO was observed in Mm. album BG8 when grown at high and low copper-to-biomass ratios, while transcription of the recombinant sMMO genes was only observed under growth conditions of low copper-to-biomass ratios. Therefore, the regulatory protein(s) for sMMO synthesis was also present on the plasmid used, or the heterologous host contained a regulatory system for sMMO. Expression of sMMO genes in methanotrophs containing only pMMO will assist further investigations on the expression and regulation of MMO genes in methanotrophs.
Cloning, Molecular↗
Immune activation during cerebellar dysfunction following Plasmodium falciparum malaria.
Evidence for immune activation was investigated in 12 patients with a rare syndrome of self-limiting, delayed onset cerebellar dysfunction following an attack of falciparum malaria which occurred 18-26 d previously. Concentrations of tumour necrosis factor, interleukin 6 and interleukin 2 were all significantly higher in serum samples of patients during cerebellar ataxia than in recovery sera and in the sera of 8 patients who did not develop delayed cerebellar dysfunction following an attack of falciparum malaria. Cytokine concentrations in the cerebrospinal fluid were also significantly higher in ataxic patients than in controls. These findings suggest that immunological mechanisms may play a role in delayed cerebellar dysfunction following falciparum malaria.
Adolescent↗
Mechanical complications from insertion of subclavian venous feeding catheters: comparison of de novo percutaneous venipuncture to change of catheter over guidewire.
Since a percutaneous catheter insertion into the subclavian vein can be tedious, time consuming, and risky, we have compared the morbidity of 137 de novo subclavian catheter insertions to that of 93 reinsertions over guidewire. Mechanical complications were significantly higher (p less than 0.03) in those with catheter insertions (8.8%) than in those with the guidewire insertions (2.2%). These included pneumothorax (4), arterial puncture (4), catheter-size bleed (3), and hemothorax (1) in the catheter insertion group and local bleeding (1) and hydrothorax (1) in the guidewire insertion group. The difference in complications between methods is probably inherent in the techniques. Operator experience was not a factor: 55% of the physicians in each group had previously done less than 26 subclavian venous catheterizations. Preliminary analysis indicates that the infection rate, as determined by semiquantitative, cultures, is the same in each group. When considering the equal potential for infection, we conclude that change over a guidewire is an acceptable alternative to contralateral de novo percutaneous subclavian venipuncture for feeding catheter insertion. In view of fewer mechanical complications and greater ease of insertion, change of subclavian feeding catheters by guidewire is probably the method of choice.
Arteries↗
Transformation of follicular lymphoma. Expression of p53 and bcl-2 oncoprotein, apoptosis and cell proliferation.
Transformation in follicular lymphoma represents an abrupt transition in tumor biology. The protein product of the bcl-2 oncogene is overexpressed in most follicular lymphomas and inhibits apoptosis. The protein product of the p53 oncogene prevents cell proliferation and induces apoptosis and is overexpressed in the dysfunctional (mutated) form. We studied 15 transformed lymphomas (large cell type), 7 follicular lymphomas before transformation and 2 control groups of follicular center cell lymphomas with no evidence of transformation (9 small cleaved cell and 10 de novo large cell lymphomas). High p53 expression (> or = 45% cells) was detected by immunostaining in 9/15 transformed lymphomas as compared with 0/10 de novo large cell lymphomas and 1/7 follicular lymphomas. Overexpression of bcl-2 (> or = 50% cells) was similar in transformed (11/15) and de novo large cell lymphomas (6/10). The apoptotic index was high (> or = 2%) in all transformed and large cell lymphomas and low in all follicular lymphomas and in the control group of small cleaved cell lymphomas. The apoptotic index in the transformed lymphomas appeared to be independent of bcl-2 expression and was sometimes paradoxically high in the presence of both p53 and bcl-2 overexpression. The apoptotic index was weakly associated with bcl-2 expression in de novo large cell lymphomas. Expression of p53 did not correlate with proliferation index. Our results indicate that p53 overexpression is a specific step associated with transformation and may occur shortly before it. This is not seen in de novo large cell lymphoma. Furthermore, the high apoptotic index in transformed lymphomas often occurs despite overexpression of bcl-2 and p53, implying that other factors may induce apoptosis in these tumors.
Apoptosis↗
Perianal condylomata acuminata.
Anal and perianal condylomata acuminata are warts caused by infection with the human papillomavirus (HPV). The annual incidence of genital warts seems to have increased during the past few decades. Approximately 1.5 million consultations per year take place in the United States with this condition (1). Papillomavirus is a sexually transmitted disease, and is associated with several other venereal infections as well as with intraepithelial neoplasia and invasive squamous carcinoma. Only certain genotypes of HPV are carcinogenic, and can be precisely identified by in situ hybridisation techniques. There are many therapeutic alternatives, possibly reflecting the wide variability in treatment response.
Adult↗