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Biomedical subjects

C M Thomas

Publications and source records attributed to C M Thomas.

At least 253 records · Page 14Linked to original sources
PubMed1986

Effects of a single injection of a new depot formulation of an LH-releasing hormone agonist on spermatogenesis in adult rats.

Adult male Wistar rats were treated with a single injection (500 micrograms s.c.) of a new biodegradable depot formulation of the LH-releasing hormone (LHRH) analogue [D-Ser(But)6]AzGly10-LH-RH (Zoladex; ICI 118,630) to evaluate its potential for inhibiting spermatogenesis. The drug produced a marked (P less than or equal to 0.05) decrease in serum concentrations of FSH, LH and testosterone with a maximum effect 14 days after treatment. Since striking focal histological changes were seen in the testis after only 1 week, at a time when changes in serum gonadotrophins were minimal, there may be a direct effect of the LHRH analogue on spermatogenesis. Degenerative changes in germ cells as well as Sertoli cells could be observed. Flow-cytometric analysis of testicular cell suspensions showed a significant decline in the absolute numbers of haploid cells (spermatids), tetraploid cells (mainly pachytene spermatocytes) and of the numbers of cells in the S-phase of the cell cycle. This suggests that the drug also inhibits proliferation of spermatogonia and/or primary spermatocytes. Testis weight, serum hormone concentrations, and histological and cytological parameters returned to essentially normal values 52 days after the injection. It is concluded that this new method of administration may have practical and pharmacokinetic advantages for the purpose of reversible inhibition of spermatogenesis.

Animals↗
PubMed1986

Characterization of lectin-binding lymphocytes in goats with caseous lymphadenitis.

Numbers of lymphoid cells bearing markers for peanut agglutinin, wheat germ agglutinin, and anti-immunoglobulin G in healthy goats and in goats with caseous lymphadenitis were determined by use of immunofluorescent techniques. Results indicated that, when compared with healthy goats, diseased goats had normal numbers of anti-immunoglobulin G-positive cells (B cells), had significantly reduced numbers of peanut agglutinin-positive cells (T cells), and had fewer cells with receptor sites for Lens culinaris agglutinin and concanavalin A. Compared with healthy goats, numbers of peanut agglutinin-positive cells in goats with caseous lymphadenitis indicated that the goats may have had a compromised cell-mediated immunity.

Animals↗
PubMed1985

Regulation of the trfA and trfB promoters of broad host range plasmid RK2: identification of sequences essential for regulation by trfB/korA/korD.

Using a plasmid containing a transcriptional fusion in which the E.coli galK gene is expressed from the trfB promoter of broad host range plasmid RK2 we show that transcription from the trfB promoter is repressed by the products of both the trfB and korB genes as we have previously predicted from the sequence homology of the trfA and trfB promoters and the fact that the trfA promoter is regulated by trfB and korB. These loci, trfB and korB are normally transcribed from the trfB promoter. Thus the trfB incC korB operon of RK2 is doubly autogeneously regulated. In addition, we describe the isolation and characterization of a mutant trfA promoter which has become insensitive to repression by trfB as a result of a point mutation within the inverted repeat sequence previously predicted to be the trfB protein binding site. These results provide strong evidence for our previously proposed model for control of transcription from the trfA and trfB promoters.

Bacterial Proteins↗
PubMed1985

Evidence from cauliflower mosaic virus virion DNA for additional discontinuities in the plus strand.

Two-dimensional electrophoresis of cauliflower mosaic virus (CaMV) virion DNA and analysis of Southern blots using (+) strand-specific probes to the 5' termini of the beta (5.4 Kb) and alpha (2.6 Kb) strands, revealed the presence of molecules in addition to those predicted from the known structure of CaMV DNA. The presence of 8 Kb molecules of (+) sense after denaturation suggested that a small proportion of circular molecules have only a single discontinuity in the (+) strand. Other molecules, probably 5' coterminal with the beta strand but smaller than 5.4 Kb, indicated that a minority of the circular full length CaMV DNA contain additional gaps in the (+) strand. Consequently, molecules equivalent to the remainder of the beta strand could be identified using a single strand probe for a region towards the 3'-end of the beta strand. Computer analysis of the nucleotide sequence of CaMV DNA in the region of the proposed additional discontinuities revealed regions displaying some homology with the major (+) strand priming sites at the 5' ends of the beta and alpha strands. It is our contention that the additional (+) strand molecules of beta specificity are a consequence of minor (+) strand priming sites.

DNA, Circular↗
PubMed1985

Isolation of a fraction from cauliflower mosaic virus-infected protoplasts which is active in the synthesis of (+) and (-) strand viral DNA and reverse transcription of primed RNA templates.

Sub-cellular fractions, isolated from cauliflower mosaic virus (CaMV)-infected turnip protoplasts, are capable of synthesising CaMV DNA in vitro on an endogenous template and of reverse transcribing oligo dT-primed cowpea mosaic virus RNA. The activity was not detected in mock-inoculated protoplasts. In vitro-labelled DNA hybridized to single-stranded M13 clones complementary to the putative origins of (-) and (+) strand CaMV DNA synthesis and to restriction endonuclease fragments encompassing more than 90% of the CaMV genome. The synthesis of (-) and (+) strand DNA appeared asymmetric. The template(s) for in vitro CaMV DNA synthesis are in a partially nuclease-resistant form. Fractions capable of in vitro CaMV DNA synthesis contained CaMV RNA both heterogeneous and as discrete species; they also contained a range of different sizes of CaMV DNA. Several lines of evidence indicate that this range of in vitro-labelled CaMV DNA, extending from 0.6kb to 8.0kb in length, represents elongating (-) strand DNA. These are discussed in relation to their role as possible replicative intermediates.

Cloning, Molecular↗
PubMed1985

Comparison of the nucleotide sequences of the vegetative replication origins of broad host range IncP plasmids R751 and RK2 reveals conserved features of probable functional importance.

An 864 bp EcoRI fragment carrying oriVR751, the vegetative replication origin of broad host range IncP plasmid R751, was cloned and sequenced. Only the trfA gene of the IncP plasmid RK2 was required in trans for the function of oriVR751. The sequence of oriVR751 showed 65% overall homology to that of oriVRK2 determined previously. Highly conserved regions of probable functional importance were apparent, including two sets of direct repeats postulated to be interaction sites for the trfA protein(s), a putative dnaA protein binding site and a downstream inverted repeat of unknown function.

Base Sequence↗
PubMed1985

Regulation of replication and maintenance functions of broad host-range plasmid RK2.

Replication of broad host-range plasmid RK2 depends on a cisacting vegatative replication origin oriVRK2 and the polypeptide product(s) of the trans-acting gene trfA as well as on host-specified products. The trfA gene is the second cistron in a polycistronic unit whose first cistron may be kilD, one of 4 known RK2-specified kil loci (kilA, B, C, and D) which are inhibitory for bacterial host or plasmid vector in the absence of kor functions which suppress in trans the effect of their respective kil genes. Transcription of the operon containing trfA is negatively regulated by the products of both the trfB locus (alias korD and korA) and korB. The loci, trfB and korB, are expressed from a single transcriptional unit which we propose to be negatively autoregulated by the products of both loci, although an additional, weaker and unregulated transcript may also express korB. While deletions in the oriVRK2 region have indicated the presence of copy number control elements adjacent to and possibly overlapping with the minimal oriVRK2 segment, the overriding control of copy number seems to reside in the trfB and korB loci which in conjunction appear to reduce expression of the trfA gene to levels limiting for replication. Coregulation of trfA with kil genes may indicate that kil genes play a role in plasmid maintenance other than replication.

Bacterial Proteins↗
PubMed1985

Absorption of 17 beta-estradiol in a neovagina constructed from the peritoneum.

Estrogen absorption from the neovagina was studied by administering 2.0 mg of micronized 17 beta-estradiol (E2) neovaginally to 6 patients. The neovagina in each patient was constructed by using the peritoneum from the pouch of Douglas. A mean peak of circulating E2 concentrations more than 15-times the basal level was achieved 90 min after the application. Until 12.5 h after the application, the E2 levels were significantly (P less than 10(-6)) elevated. FSH levels were significantly (P = 0.003) changed in comparison to the basal serum concentration. There was no significant (P = 0.08) change in LH levels. The resorption of estradiol from the neovagina is similar to that seen in women with normal vaginas.

Administration, Topical↗
PubMed1985

Effect of aromatase inhibition by delta 1-testolactone on basal and luteinizing hormone-releasing hormone-stimulated pituitary and gonadal hormonal function in oligospermic men.

Aromatase inhibition by delta 1-testolactone (TL), 500 mg twice daily for 4 weeks, in nine patients with idiopathic oligospermia lowered circulating estradiol (E2) levels by about 30%, enhanced the secretion of follicle-stimulating hormone (+ 30%), 17-hydroxyprogesterone (17-OHP) (+ 40%), and testosterone (T) (+ 30%), but did not affect serum luteinizing hormone levels. Despite E2 lowering, there was an accumulation of 17-OHP over T, suggesting 17, 20-lyase inhibition. Unexpectedly, administration of TL almost completely deleted the T response to continuous luteinizing hormone-releasing hormone infusion present before TL therapy, despite similar gonadotropin release. Because the 17-OHP response to the luteinizing hormone-releasing hormone infusion was even higher during therapy, the 17,20-lyase lesion seemed aggravated despite substantial reduction of E2 levels. Although the present data suggest that estrogens play a less dominant role in the origin of the late steroidogenetic lesion than previously assumed, the suggestion also arises that TL per se, in addition to its antiestrogenic action, exerts an inhibiting effect on the 17,20-lyase locus, which may obscure the beneficial effect of reducing E2.

Adult↗
PubMed1985

Serum luteinizing hormone-releasing hormone (LH-RH) and gonadotropic hormones in men after a bolus dose of LH-RH: comparison of different doses and routes of administration.

Serum levels of luteinizing hormone-releasing hormone (LH-RH), LH, and follicle-stimulating hormone (FSH) were measured for 60 minutes after 5- and 20-micrograms bolus doses of LH-RH given either intravenously or subcutaneously to 20 healthy men, for the study of LH-RH pharmacokinetics and the corresponding pituitary gonadotropin release. Intravenous (5- and 20-micrograms) LH-RH administration revealed much sharper LH-RH pulses, with significantly higher levels between 1 and 5 minutes (P less than 0.001) but lower levels between 30 and 60 minutes (P less than 0.05), compared with the subcutaneous route. No statistically significant differences were observed in the magnitude and time occurrence of maximum LH release or in the area under the LH response curves between intravenous and subcutaneous LH-RH administration, either in the 5-micrograms or in the 20-micrograms group. FSH responses were small and insignificant in all the performed tests. The intravenous route of administration seems preferential in therapeutic regimens that use pulsatile exogenous LH-RH, because the conditions of intermittent pituitary stimulation are more adequately fulfilled and the risk of dose accumulation is reduced. Furthermore, LH-RH doses of 5 micrograms are capable of producing adequate pituitary LH release, whereas increases in the pulse dose up to 20 micrograms seem to have no additional effects.

Adult↗
PubMed1985

A priority dispatch system for emergency medical services.

A decision tree priority dispatch system for emergency medical services (EMS) was developed and implemented in Atlanta and Fulton County, Georgia. The dispatch system shortened the average response time from 14.2 minutes to 10.4 minutes for the 30% of patients deemed most urgent (P less than or equal to .05); resulted in a significant increase in the use of advanced life support units for this group (P less than or equal to .02); decreased the number of calls that required a backup ambulance service; and significantly increased conformity to national EMS response time standards for critically ill and injured patients (P less than or equal to .0009). Due to dispatch error, 0.3% of calls were dispatched as least severe but subsequently were found to be most urgent.

Emergency Medical Service Communication Systems↗
PubMed1985

Cloning and deletion analysis of a genomic segment of Bacillus subtilis coding for the sdhA, B, C (succinate dehydrogenase) and gerE (spore germination) loci.

From a Bacillus subtilis gene bank constructed in Escherichia coli and based on a low copy number cloning vector we have isolated a hybrid plasmid, pSH1047, containing an 8.0 kb segment of B. subtilis DNA coding for the sdhA, B and C genes, which code for the component polypeptides of succinate dehydrogenase, and the gerE gene, which may code for or regulate a protease involved in producing spores which germinate normally. We report the restriction map of this segment and the analysis of deletion derivatives which allow us to correlate the physical and genetic maps of these chromosomal segments.

Bacillus subtilis↗
PubMed1985

Comparison of the analytical characteristics and clinical usefulness in tumour monitoring of fifteen hCG(-beta) immunoassay kits.

Fifteen immunoassay kits for serum hCG(-beta) measurements have been compared for their analytical characteristics and clinical usefulness in tumour monitoring. Three out of 13 radioimmunoassays and two sandwich hCG immunoassays represent the 'one-component' techniques for intact hCG detection since they are based on antiserum raised against intact hCG. Within this group, method-comparison slopes ranged between 0 X 149 and 0 X 374. The remaining 10 radioimmunoassays all apply antiserum against hCG-beta and are designated 'two (or more)-component' assays since they detect both intact hCG and the free beta-subunit ('total hCG'). For this reason these assays are of potential value for tumour monitoring. Additional criteria for this are: (1) the expression of assay results in terms of 1st IRP-hCG instead of the unstructured use of the 2nd IS or the 1st IRP-hCG-beta; (2) documentation of cross-reactivities especially for the free beta-subunits of hCG and hLH which are almost completely lacking; (3) establishment of the minimum detectable dose in the presence of normo-to-hypergonadotrophic hLH levels in serum (the 'clinical sensitivity') to allow the follow-up of tumour regression especially in the low-dose region. Method-comparison analysis for these assays revealed regression slopes between 0 X 001 and 0 X 873.

Antibody Specificity↗
PubMed1984

Analysis of the trfA region of broad host-range plasmid RK2 by transposon mutagenesis and identification of polypeptide products.

Broad host-range plasmid RK2 is a member of the Escherichia coli incompatibility group P. Unlike most other groups of plasmids, members of the P group are capable of efficient transfer between and maintenance in most gram-negative bacterial species. It is of interest whether this broad host-range results from differences between the mechanism of replication of broad and narrow host-range plasmids. The regions of RK2 required for replication in E. coli have previously been defined as an origin of vegetative replication, oriVRK2 , and a gene, trfA , specifying a positively required trans-acting product. In this study Tn1723 transposon insertions have been used to map the trfA gene and determine its functional gene product. The Tn1723 insertions define the outer limits of the gene, a promoter region, a "leader" region not essential for trfA activity and a coding region. Three polypeptides of 13 X 10(3), 43 X 10(3) and 32 X 10(3) molecular weight are produced from this region and the production of a 32 X 10(3) Mr polypeptide is shown to be correlated with trfA activity in E. coli. Analysis of polypeptides produced from transposon insertion derivatives in which all but 35 base-pairs of inserted DNA is deleted, along with the effect of these insertions on trfA activity, suggest that the 43 X 10(3) and 32 X 10(3) Mr polypeptide coding sequences overlap in the same reading frame and that all three polypeptides (13 X 10(3), 32 X 10(3) and 43 X 10(3) Mr) may be translated from the same initial transcript.

Chromosome Mapping↗
PubMed1984

Nucleotide sequence of the trfA gene of broad host-range plasmid RK2.

The nucleotide sequence of a 1622 base-pair segment of the broad host-range IncP plasmid RK2 (identical to RP1, RP4, R18 and R68) was determined. This region includes the trfA gene, encoding a trans-acting product essential for vegetative plasmid replication. The nucleotide sequence, together with the results described in the accompanying paper by Shingler & Thomas, indicates that the trfA gene encodes two polypeptide products (of 382 and 285 amino acids) by utilizing different translational start points within a single open reading frame. The region common to both trfA polypeptides includes a sequence with homology to a number of proteins that bind to double-stranded DNA. The trfA gene is preceded by another open reading frame, encoding a polypeptide of 116 amino acids of unknown function. Both cistrons are transcribed from a promoter outside the region of sequence reported here; however, much higher levels of the short polypeptide than of either of the trfA gene products are observed. Possible mechanisms for the control of the relative levels of the products of this operon are discussed, together with features of the trfA gene that may be important for its function in the diverse gram-negative bacterial species in which RK2 can be maintained.

Amino Acid Sequence↗
PubMed1984

The trfA and trfB promoter regions of broad host range plasmid RK2 share common potential regulatory sequences.

The positions of the trfA and trfB promoters of broad host range IncP plasmid RK2 (identical to RP1, RP4, R68 and R18 ) were identified by RNA polymerase protection studies, and the nucleotide sequences of the promoter regions determined. A mutation within the trfA promoter sequence is associated with loss of kilD activity. In addition a probable promoter region for the kilB locus was identified. The three promoter regions share common palindromic sequences which may serve as sites for the coordinate regulation of replication and kil functions.

Base Sequence↗