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Biomedical subjects

J Humphreys

Publications and source records attributed to J Humphreys.

At least 73 records · Page 4Linked to original sources
PubMed1986

Development of a chemically defined serum- and protein-free medium for growth of human peripheral lymphocytes.

A chemically defined, protein-free medium (designated CFBI 1000, where CFBI = Clayton Foundation Biochemical Institute) that supports human peripheral lymphocyte proliferation has been developed. This medium allows exploration of individual metabolic differences by varying the medium composition as well as providing a base to explore further the mechanisms of lymphocyte activation in a system initially free of added macromolecular species other than mitogen. The peripheral blood lymphocyte is an ideal system for metabolic studies because it is easily obtained, is a primary resting cell that can be activated to proliferate, and presumably reflects both the genetic makeup and biochemical environmental history of the individual at the time the cells were formed. Examination of the role of various factors in lymphocyte activation and subsequent events may be simplified by the utilization of a medium that is protein-free and chemically defined. The CFBI 1000 medium supports the growth response of human peripheral lymphocytes to mitogen as measured by [3H]thymidine incorporation to an extent comparable to other media used widely in assessment of lymphocyte proliferation.

Aphidicolin↗
PubMed1984

Serology and genetics of an MNSs-associated antigen Dantu.

Dantu, a previously undescribed low-incidence red cell antigen, is inherited as a Mendelian dominant character. The Dantu antigen is associated with very weak s antigen, protease resistant N antigen and either very weak or no U antigen. Two of the propositi had previously been shown to have an unusual hybrid MNSs sialoglycoprotein, and it is probably this which carries these unusual N, s and U antigens as well as the Dantu antigen. A study of the family of one propositus suggests, by conventional genetics, that Dantu is not controlled by the MNSs locus; a possible explanation is given. Several examples of anti-Dantu are known, one was found to cause a positive direct antiglobulin reaction on neonatal red cells.

ABO Blood-Group System↗
PubMed1984

Maternal plasma inhibition of prostaglandin synthase during human pregnancy, parturition and the puerperium.

To study the possibility that circulating endogenous inhibitor(s) of prostaglandin synthesis (EIPS) represent a control mechanism for prostaglandin production during human pregnancy and parturition, we have measured maternal plasma EIPS levels serially during pregnancy, labour and the puerperium, and cross-sectionally during the course of labour. No significant trends were detected in relation to pregnancy or parturition. These results do not support a role for maternal plasma EIPS in the control of prostaglandin production during human pregnancy or labour.

Cyclooxygenase Inhibitors↗
PubMed1983

Sequence organisation in nuclear DNA from Physarum polycephalum. Arrangement of highly-repeated sequences.

Recombinant plasmids containing highly repetitive Physarum DNA segments were identified by colony hybridisation using a radioactively-labelled total Physarum DNA probe. A large number of these clones also hybridised to a foldback DNA probe purified from Physarum nuclear DNA. The foldback DNA probe was characterised by reassociation kinetic analysis. About one-half of this component was shown to consist of highly repeated sequences with a kinetic complexity of 1100 bp and an average repetition frequency of 5200. Direct screening of 67 recombinant plasmids for foldback sequences using the electron microscope revealed that about one-half were located in segments of DNA containing highly repetitive sequences; the remainder were present in clones containing low-copy number repeated elements. Analysis of two DNA clones showed that they contained repetitive elements located in over half of all DNA segments containing highly repetitive DNA and that the foci containing these highly repetitive sequences had different sequence arrangements. The results are consistent with the hypothesis that the most highly repeated DNA sequence families in the Physarum genome are few in number and are clustered together in different arrangements in about one-sixth of the genome. Over one-half of the foldback DNA complement in the Physarum genome is derived from these segments of DNA.

DNA, Fungal↗
PubMed1982

Effects of endocrine therapy on steroid-receptor content of breast cancer.

In order to determine the mechanisms of relapse following response to endocrine therapy, we have measured the oestrogen receptor (RE) content of biopsies of breast cancer in patients receiving various types of endocrine treatment. RE content fell in responding (means of 260.2 to 12 fmol/mg protein) and in nonresponding (means of 155.1 to 31.8 fmol/mg protein) patients who had measurable receptor at the start of treatment. Some of these patients, and a further group of responders to endocrine therapy, were monitored until relapse. Tumour biopsies at the time of relapse showed that 10/14 tumour samples contained significant RE (mean of 86.7 fmol/mg protein; range less than 10-271 fmol/mg protein) after successful endocrine therapy. No relationship could be found between RE content and plasma gonadotrophin or steroid-hormone concentration, but the fall in RE content correlated with reduced numbers of tumour cells in the biopsy. These results indicate that relapse following successful endocrine therapy in breast cancer does not appear to be due to the emergence of RE-negative tumour cells. The fall in RE content during response to endocrine therapy may be due to reduced tumour-cell content of the biopsy.

Adult↗
PubMed1982

Regulation of pyruvate dehydrogenase kinase activity by protein thiol-disulfide exchange.

Endogenous kinase activity of highly purified pyruvate dehydrogenase complex from bovine kidney is markedly inhibited by N-ethylmaleimide and by certain disulfides. Inhibition by disulfides is highly specific and is reversed by thiols. 5,5'-Dithiobis(2-nitrobenzoate) is the most potent inhibitor, showing significant inhibition at a concentration as low as 1 microM. Cystamine, oxidized glutathione, pantethine, lipoic acid, lipoamide, ergothionine, insulin, oxytocin, and vasopressin were ineffective. Hydrogen peroxide and t-butyl hydroperoxide were inactive. The data indicate pyruvate dehydrogenase kinase (EC 2.7.1.99) contains a thiol group (or groups) that is involved in maintaining a conformation of the enzyme that facilitates phosphorylation and inactivation of its protein substrate, pyruvate dehydrogenase (EC 1.2.4.1). These findings suggest that modulation of pyruvate dehydrogenase kinase activity by thiol-disulfide exchange may be an important physiological mechanism for regulation of kinase activity and, hence, activity of the pyruvate dehydrogenase complex.

Animals↗
PubMed1982

Assay of plasma endogenous inhibitor(s) of prostaglandin synthase using an enzyme incubation - radioimmunoassay method.

A simple, reliable method with validations is described for the routine measurement of endogenous inhibitor(s) of prostaglandin synthase in blood plasma. Appropriate dilutions of plasma samples are incubated with bovine seminal vesicle prostaglandin synthase, sodium arachidonate and reduced glutathione. Prostaglandin E2 production is then quantitated by radioimmunoassay. The relative inhibitory potency of plasma samples is determined by comparison of prostaglandin E2 content in sample incubations with that of control incubations containing no plasma dilution. Possible applications and the suitability of this methodological approach are discussed.

Animals↗
PubMed1981

Iron-related modification of bacterial transfer RNA.

Transfer RNAs isolated from E. coli grown in media where ferric iron is not freely available show well characterized chromatographic changes due to the absence of the methylthio moiety of ms2i6A. The altered tRNA molecules include tRNA trp tRNA tyr, tRNA phe and two minor tRNA ser species. It has been suggested that methylthiolation of tRNA affects its function in regulation. We now show iron-related changes in tRNA trp from S. typhimurium, Ps. aeruginosa and K. pneumoniae. tRNA trp from S. typhimurium contains ms2i6A and it seems probable that the availability of iron affects the synthesis of ms2i6A-tRNA trp from i6A-tRNA trp in this organism. An iron-related methylthiolating system may also be operative in K. pneumoniae. S. marcescens tRNA trp, however was not affected by the availability of iron. Neither ms2i6A nor i6A was found in S. marcescens tRNA, although an, as yet unidentified, hydrophobic nucleoside was present.

Bacteria↗
PubMed1981

Comparative functional histopathology of human breast carcinoma xenografts.

A series of xenografts of human breast carcinomas has been established and serially transplanted in immune-suppressed mice. Certain structural and functional features of the original human tumours, including carcinoembryonic antigen and epithelial membrane antigen, continue to be expressed by the resulting xenografts. Stromal responses such as elastosis and oestrogen-receptor activity were lost by the xenografts. No metastases were detected in tumour-bearing mice. This study suggests that xenografts may have some value in experimental pathology as one type of model of human breast carcinoma.

Animals↗
PubMed1981

A minimal-world-pair model for teaching the linguistic significance of distinctive feature properties.

A word level behavioral routine for the remediation of distinctive feature errors was developed for resolving some current theoretical criticisms of minimal-pair therapy. Seven children with moderate to severe non-organic phonological disabilities were taught to correctly discriminate and produce sounds in words by utilizing lexical contrasts. A one-group pretest-posttest design was utilized to establish that the number and severity of the sound substitutions decreased with training. Phonemic improvement was demonstrated with as few as three minimal-pair-words. A paradigm is proffered for future development and explanation.

Articulation Disorders↗
PubMed1981

N-methyl-N-nitrosourea-induced rat mammary tumors. Hormone responsiveness but lack of spontaneous metastasis.

N-Methyl-N-nitrosourea (MNU) given iv to rats 50-55 days old induced mammary tumors in 70% of F344/N and 91% W/ICRF inbred females with mean latency periods of 149 and 93 days, respectively. Reduction of the MNU dose did not affect tumor incidence in W/ICRF rats. Of the mammary tumors, 98% were classified histologically as adenocarcinomas, which grew progressively. Primary tumors of nonmammary origin were detected at low incidence. Upon histologic examination, no evidence was found for metastases of either the mammary or other primary tumors. No evidence for tumor-induced hypercalcemia was found. Oophorectomy at the time of MNU administration prevented tumor development; oophorectomy when at least 1 tumor/animal was palpable caused growth delay or regression. All MNU-induced and 7,12-dimethylbenz[a]anthracene-induced mammary tumors tested contained cytoplasmic estrogen receptor (ER) at similar concentrations and were indistinguishable histologically. MNU-induced tumors in F344 rats were transplantable and retained ER through three transplantations.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Alterations in tRNAs containing 2-methylthio-N6-(delta2-isopentenyl)-adenosine during growth of enteropathogenic Escherichia coli in the presence of iron-binding proteins.

Escherichia coli grown in chemically produced iron-deficient media have well characterized alterations in the chromatographic properties of tRNAs containing the modified nucleoside 2-methylthio-N6-(delta2-isopentenyl) adenosine. The present report shows that similar tRNA alterations occur in enteropathogenic E. coli inhibited by human milk and bovine colostrum, the inhibited bacteria containing 10% or less of the normal tRNA species. Adding sufficient iron to saturate the iron-binding capacity of the lactoferrin present in milk and colostrum reversed these changes which are probably due to a failure to methylthiolate the isopentenyladenosine. Although adding iron led to a rapid replacement of abnormal tRNA by the chromatographically normal species, and to a resumption of multiplication, the tRNA alterations are not directly related to the inhibition of growth. Strains of E. coli which grew normally in milk, colostrum and in defined media containing the iron-binding protein transferrin or ovotransferrin also contained about 90% of the abnormal species. Rapid conversion of abnormal tRNA to normal tRNA occurred on adding iron and in the absence of RNA synthesis. The tRNA changes are discussed in relation to their possible connection with both the adaptation of E. coli to growth under the iron-restricted conditions imposed by iron-binding proteins in tissue fluids and with bacterial pathogenicity.

Adenosine↗
PubMed1978

Alterations in the tRNA's of Escherichia coli recovered from lethally infected animals.

Escherichia coli grown in chemically defined iron-deficient media or in fluids containing the iron-binding proteins transferrin, lactoferrin, or ovotransferrin have well-characterized alterations in the chromatographic properties of tRNA's containing the modified nucleoside 2-methylthio-N6-(delta2-isopentenyl)-adenosine. The present work shows that similar tRNA alterations occur in E. coli O111 recovered from the peritoneal cavities of lethally infected guinea pigs and rabbits. Adding iron to these in vivo-grown bacteria resulted in the rapid conversion of chromatographically abnormal tRNA's to the normal species. The work strongly suggests that host iron-binding proteins, present in mucosal and other secretions, can affect the metabolism of invading organisms. The idea that the tRNA alterations are connected with the adaptation of E. coli to growth under the iron restricted conditions imposed by iron-binding proteins in tissue fluids, and thus with bacterial pathogenicity, is therefore made particularly attractive.

Animals↗