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C H Jones

Publications and source records attributed to C H Jones.

At least 19 recordsLinked to original sources
PubMed1992

Genetic suppression analysis of sigma E interaction with three promoters in sporulating Bacillus subtilis.

Genetic evidence suggests that the sigma (sigma) subunit of RNA polymerase determines the specificity of promoter utilization, by making sequence-specific contacts with DNA. We examined the effects of two single amino acid(aa) substitutions in sigma E on the utilization of mutated derivatives of three different promoters in sporulating Bacillus subtilis. We found allele-specific suppression of mutations in all three promoters by each aa substitution in sigma E. These results provide strong evidence that sigma E interacts with each of these promoters in vivo. Moreover, the specificity of suppression of the mutations by the aa substitutions in sigma E lead us to speculate that the Met124 of sigma E closely contacts two adjacent bp in the -10 region of the promoters.

Amino Acids↗
PubMed1992

Mutant sigma factor blocks transition between promoter binding and initiation of transcription.

The sigma subunit of bacterial RNA polymerase is required for specific binding of the enzyme to promoters. This specificity is probably directed by two regions of most sigma factors that make sequence-specific contacts at two regions of promoters, the -10 and -35 regions. We found that a single amino acid substitution in the -10 recognition region of sigma E from Bacillus subtilis trapped RNA polymerase in a stable complex with promoter DNA in which it was unable to initiate transcription. Our results are consistent with the view that promoter utilization by RNA polymerase proceeds through several intermediate steps and suggest that the -10 recognition region of sigma factors may participate in a step that follows initial promoter binding.

Amino Acid Sequence↗
PubMed1992

Contingent tolerance to the anticonvulsant effects of carbamazepine, diazepam, and sodium valproate in kindled rats.

The effect of convulsive stimulation during periods of drug exposure on the development of tolerance to the anticonvulsant effects of carbamazepine (CBZ), diazepam (DZP), or sodium valproate (VPA) was studied in three similar experiments. In each experiment, amygdala-kindled rats were assigned to one of three groups: one group received a drug injection (CBZ, 70 mg/kg, IP; DZP, 2 mg/kg, IP; VPA, 250 mg/kg, gavage) 1 h before each of a series of 10 bidaily (one every 48 h) convulsive stimulations, a second group received the same dose of the drug 1 h after each of the 10 stimulations, and a third group served as a vehicle control. The drug tolerance test occurred in each experiment 48 h after the 10th tolerance-development trial; every rat received the appropriate dose of CBZ, DZP, or VPA 1 h before being stimulated. In each experiment, only the rats from the drug-before-stimulation group displayed a significant amount of tolerance to the drug's anticonvulsant effect. Thus the development of tolerance to the anticonvulsant effects of CBZ, DZP, and VPA was not an inevitable consequence of drug exposure; the development of tolerance was contingent upon the occurrence of convulsive stimulation during the periods of drug exposure. These results support the idea that functional drug tolerance is an adaptation to a drug's effects on ongoing patterns of neural activity, rather than to drug exposure per se.

Amygdala↗
PubMed1992

Effects of amino acid substitutions in the -10 binding region of sigma E from Bacillus subtilis.

The sigma subunit of bacterial RNA polymerase is required for specific binding to promoters. One region in most sigma factors makes sequence-specific contacts at the -10 region of its cognate promoters. To test the role of the amino acids in this -10 binding region, we examined the effects of 49 single-amino-acid substitutions in sigma E from Bacillus subtilis. We assayed the effect of each amino acid substitution on spore formation because sigma E is essential for endospore formation in B. subtilis. Our results showed that substitutions at several positions, including the highly conserved aromatic amino acid at position 102, had little or no detectable effect. Substitutions at another position, position 117, produced dominant negative mutations; we suggest that these mutations allow RNA polymerase containing the mutant sigma factor to bind specifically to promoters but prevent transcription initiation. Of the recessive defective alleles, those that produced substitutions at positions 113, 115, and 120 produced the most defective sigma factors. These results suggest that the residues at or near these positions in wild-type sigma E play important roles in sigma E function.

Alleles↗
PubMed1991

Measurement of small-angle photon scattering for some breast tissues and tissue substitute materials.

For photon energies encountered in diagnostic radiology the shape of the scattering distributions for low-atomic-number media exhibits peaks in intensity close to the forward direction that are not predicted by conventional theoretical models. The positions and shapes of the peaks depend upon the interatomic and intermolecular configurations of the scatterers. The phenomenon is of particular interest because of its relevance to the understanding and modelling of x-ray imaging processes and the possibility that the peaking may be characteristic of tissue type. In the present study, peaks in the forward scattering distributions have been demonstrated for 19 samples of breast tissue and three tissue substitute materials using a position-sensitive photon detector and a 60 kVp x-ray source. Prominent features were observed for all samples investigated. Large differences were found in the shapes of the distributions between adipose and fibroglandular tissues and only small differences were found between carcinomas and fibroglandular tissues.

Adenofibroma↗
PubMed1991

Genetic evidence for interaction of sigma E with the spoIIID promoter in Bacillus subtilis.

During sporulation in Bacillus subtilis, new RNA polymerase sigma factors are produced. These sigma factors direct the transcription of genes that are required for this cellular differentiation. In order to determine the role of each sigma factor in this process, it is necessary to know which promoters are recognized by each sigma factor. The spoIIID gene product plays an important role in the establishment of mother cell-specific gene expression during sporulation. We found that substitution of an alanine at position 124 of the sporulation-specific sigma factor sigma E suppressed the effect of a single-base-pair transition at position -13 of the spoIIID promoter. This alanine substitution in sigma E did not suppress the effect of a transversion at position -12 of the spoIIID promoter. The allele specificity of the interaction between sigma E and the spoIIID promoter is strong evidence that sigma E directs transcription from the spoIIID promoter during sporulation. Position 124 in sigma E is located within a region that is highly conserved among the regions in other sigma factors that probably interact with the -10 regions of their cognate promoters.

Amino Acid Sequence↗
PubMed1990

Linguistic analogies and behavior: the finite-state behavioral grammar of food-hoarding in hamsters.

Rodger and Rosebrugh (1979) developed a method for identifying sets of rules by which discrete responses are combined to form functional sequences of behavior. In the present study, this so-called finite-state behavioral grammar method was used to analyze the food-hoarding behavior of Syrian golden hamsters (Mesocricetus auratus). Specifically, it was used to analyze 127 videotaped food-hoarding sequences that were observed in 14 male, adult hamsters in an apparatus that comprised a home compartment, a foraging area, and a connecting tunnel. An integral part of grammar derivation is the development of hypotheses about the function of the observed response patterns to guide the grammar derivation. Two such hypotheses guided the present analysis: first, we hypothesized that behaviors observed in the foraging area after the hamsters' cheek pouches were filled served an exploratory function; second, we hypothesized that behaviors observed in the home compartment prior to the hamsters emptying their cheeck pouches served to assess potential food deposition sites. In addition to generating these two hypotheses and the grammars for the hoarding sequences, this study demonstrates how the finite-state grammar method can be used as a productive means of gaining insights into the organization of consummatory response sequences.

Animals↗
PubMed1990

Defensive burying, nest relocation, and pup transport in lactating female rats.

A wire-wrapped wooden dowel was inserted through the wall of the nest compartment of a two-compartment box. There were four conditions. Some lactating female rats were shocked by the dowel when they first touched it, and some were not, after which the dowel was either immediately withdrawn from the chamber or left in place for the duration of the ensuing 30-min test period. Three defensive behaviours were observed during the tests: the mothers buried the shock source with bedding from the floor of the chamber, they transported their pups to the adjoining "safe" chamber, and they built a new nest in the safe chamber from material salvaged from their original nest. The shocked mothers that were confronted with the shock source throughout the test period displayed significantly more of each of these three defensive behaviours than did the mothers in the other three conditions. The methods used in this study provide a simple, reliable, safe paradigm for studying maternal defensive behaviour; the results indicate that the defensive capacities of the rat extend far beyond stereotypical flight, freeze, and fight responses, which have been the focus of most research on rodent defense.

Animals↗
PubMed1989

Interaction of the lymphocyte-derived Epstein-Barr virus nuclear antigen EBNA-1 with its DNA-binding sites.

The Epstein-Barr virus (EBV) nuclear antigen EBNA-1 plays an integral role in the maintenance of latency in EBV-infected B lymphocytes. EBNA-1 binds to sequences within the plasmid origin of replication (oriP). It is essential for the replication of the latent episomal form of EBV DNA and may also regulate the expression of the EBNA group of latency gene products. We have used sequence-specific DNA-binding assays to purify EBNA-1 away from nonspecific DNA-binding proteins in a B-lymphocyte cell extract. The availability of this eucaryotic protein has allowed an examination of the interaction of EBNA-1 with its specific DNA-binding sites and an evaluation of possible roles for the different binding loci within the EBV genome. DNA filter binding assays and DNase I footprinting experiments showed that the intact Raji EBNA-1 protein recognized the two binding site loci in oriP and the BamHI-Q locus and no other sites in the EBV genome. Competition filter binding experiments with monomer and multimer region I consensus binding sites indicated that cooperative interactions between binding sites have relatively little impact on EBNA-1 binding to region I. An analysis of the binding parameters of the Raji EBNA-1 to the three naturally occurring binding loci revealed that the affinity of EBNA-1 for the three loci differed. The affinity for the sites in region I of oriP was greater than the affinity for the dyad symmetry sites (region II) of oriP, while the physically distant region III locus showed the lowest affinity. This arrangement may provide a mechanism whereby EBNA-1 can lowest affinity. This arrangement may provide a mechanism whereby EBNA-1 can mediate differing regulatory functions through differential binding to its recognition sequence.

Antigens, Viral↗
PubMed1989

Pes planus after tibial osteotomy.

When 100 patients who had had a high tibial osteotomy for monocompartmental arthritis were reviewed, 15 were found to have evidence of neurological impairment. A severe symptomatic pes planus deformity of the ipsilateral limb had developed in 4 patients within months of surgery. Electromyographic results showed evidence of dysfunction in the territory of the posterior tibial nerve in all 4 patients, and, in 3 there was evidence of deep peroneal nerve damage. All had surgery for varus malalignment.

Ankle Joint↗
PubMed1988

Daily hoarding opportunity entrains the pacemaker for hamster activity rhythms.

The effects on activity rhythms of a daily 30 min opportunity to leave the home cage and hoard seeds from an open field were assessed in Syrian hamsters housed in continuous dim illumination. Six of ten hamsters responded with clear entrainment of their activity rhythms to the hoarding opportunity, as demonstrated by responses to phase shifts and by the onset phase of subsequent freerunning rhythms. No entrainable component separate from the freerunning rhythm was ever observed. Two hamsters showed phase shifts in response to the hoarding opportunity, but they did not meet the criteria for stable entrainment, and two did not respond with noticeable changes in rhythmicity. Ablations of the suprachiasmatic nuclei (SCN) were attempted in three hamsters that had entrained stably to the hoarding time. The effects of partial lesions in two animals indicated that the entrained rhythm was controlled by the light-entrainable pacemaker represented by the SCN. The one animal with an apparently complete lesion, however, developed a clear, but irregular, increase in activity in anticipation of the daily hoarding time. SCN ablation apparently unmasked an oscillator system separate from the SCN and susceptible to entrainment by a nonphotic cue. The oscillator mechanism affected by daily hoarding opportunities in hamsters appears to be tightly coupled to the SCN pacemaker, in contrast to the system in rats that is synchronized by daily feeding schedules.

Animals↗
PubMed1987

Genetic analysis of RNA polymerase-promoter interaction during sporulation in bacillus subtilis.

The discovery of secondary sigma factors in Bacillus subtilis that enable RNA polymerase to transcribe cloned sporulation genes in vitro has led to the proposal that the appearance of new sigma factors during sporulation directs RNA polymerase to the different temporal classes of sporulation genes. One sigma factor, which appears 2 h after the initiation of sporulation, is sigma E (formerly sigma 29). Mutations that inactivate the structural gene for sigma E prevent transcription from promoter G4. To determine whether sigma E-RNA polymerase interacts with the G4 promoter in vivo, we examined the effects of six single-base-pair substitutions in the G4 promoter on its utilization in vivo and in vitro by sigma E-RNA polymerase. The mutations in the G4 promoter affected utilization of the promoter in vivo in the same way that they affected its utilization in vitro by purified sigma E-RNA polymerase; therefore, we conclude that this polymerase interacts directly with the G4 promoter in vivo. The effects of these mutations also support the model in which sigma E-RNA polymerase utilizes promoters by interacting with two distinct sets of nucleotides located 10 and 35 base pairs upstream from the start point of transcription.

Bacillus subtilis↗
PubMed1979

Theoretical aspects and practical applications of moiré topography.

When a surface is observed at a distance through a parallel line grating which is illuminated by a source of light laterally displaced to the viewing axis, the grating is superimposed on its shadow and this gives rise to a moiré fringe pattern. The fringes represent cross-sections of the surface parallel to the grating plane. The principle of the formation of the contour map has been studied assuming a grating represented by a Fourier series, a source of light represented by a 3D intensity distribution and a viewing aperture of finite dimensions. The experimental system used for illumination and observation of the moiré fringes consists of an equispaced parallel-lined glass grating and two small light sources positioned symmetrically about the imaging device. The arrangement constitutes a 3D imaging system with an accuracy of the order of 1 mm. The technique has been applied in radiotherapy problems such as the design of contour compensators and the measurement of body contours. Moiré patterns have been analysed with the aid of a PDP-8 computer, and have been used to calculate surface areas and volumes such as in breast studies and superficial tumour measurements.

Humans↗
PubMed1979

Evaluation of a moiré imaging system.

Moiré fringe techniques can be used to measure surface topography. The factors that affect the formation of the fringes have been assessed theoretically by developing models of gratings and light sources of finite dimensions. In this way the effect of parameters such as the intensity distribution of the light source, the viewing aperture function, the lateral displacement of the source relative to the viewing axis, the viewing distance, the grating spacing and grating ratio have been evaluated. Other factors, related to the physical properties and geometry of the reflecting surface, are also investigated. Suggestions are made for the design of an optimum moiré imaging system.

Interferometry↗
PubMed1975

Thermography of the female breast: a five-year study in relation to the detection and prognosis of cancer.

More than 12,000 women have been examined thermographically in the Breast Unit of the Royal Marsden Hospital, London. Of these women 1,464 had biopsy and histology; 363(25 per cent) were found to have carcinoma and of these 68 per cent had abnormal thermograms, 13 per cent has some thermal asymmetry of doubtful significance and 19 per cent had normal thermal patterns. Fifty-seven per cent and 62 per cent of patients with Stage I and Stage II cancer, respectively, had abnormal thermograms whereas 83 per cent of patients with Stage III cancer had abnormal thermograms. Of 1,101 women who had benign lesions, 63 per cent had normal thermal patterns, 15 per cent had thermal asymmetry of doubtful significance and 22 per cent had abnormal thermograms. The subsequent histories of 172 cancer patients examined thermographically have been analysed and three-year survival rates have been correlated with thermography report, the clinical stage of the disease and the histotogical grade (Bloom, 1950) of the excised tumour. The mean three-year survival rates for patients with Stage II or Stage III cancer are 84 per cent for those with normal and 61 per cent for those with abnormal thermograms.

Adenofibroma↗