Search PubMed⌕ Search

Biomedical subjects

R A Cox

Publications and source records attributed to R A Cox.

At least 163 records · Page 9Linked to original sources
PubMed1979

A study of the organisation of the ribosomal ribonucleic acid gene cluster of Neurospora crassa by means of restriction endonuclease analysis and cloning in bacteriophage lambda.

1. Total Neurospora crassa DNA was restricted with endonucleases and fragments carrying rRNA coding sequences were identified by hybridization with Xenopus laevis ribosomal DNA probes. 2. The repeating unit of the rRNA gene cluster was found to be 8.6 kbp, arranged in a head-to-tail fashion. 3. Digestion with Hind III yielded fragments of 3.4 kbp and 5.2 kbp and both were cloned. 4. Digestion with Eco RI yielded fragments of 2.2 kbp, 3.0 kbp and 3.4 kbp; the 3.0 kbp fragment was cloned. 5. Sequences coding for RNA (S-rRNA)1 of the smaller subribosomal particle were found (at least 90%) in the 2.2 kbp EcoRI subfragment of the 5.2 kbp Hind III fragment. 6. The coding sequences for the major RNA species (L-rRNA) of the larger subribosomal particle were located mainly (at least 95%) in the 3.4 kbp Hind III fragment. 7. For comparison, a Hind III digest of total yeast DNA was cloned and recombinants containing a 6.4 kbp rDNA fragment were isolated.

Animals↗
PubMed1979

Cross-reactivity between antigens of Coccidioides immitis, Histoplasma capsulatum and Blastomyces dermatitidis in lymphocyte transformation assays.

The cross-reactivity of four Coccidioides antigens, three Histoplasma antigens, and two Blastomyces antigens were determined in lymphocyte transformation assays of 11 coccidioidin-reactive, histoplasmin-nonreactive subjects (group I), 13 coccidioidin-nonreactive, histoplasmin-reactive persons (group II), and 13 subjects who were skin test negative to both antigens (group III). Mycelial and yeast (or spherule)-phase antigens of the three fungi were included. Significant cross-reactivity was obtained with both coccidioidins, spherulin, and the alkali-soluble, water-soluble cell wall antigen of C. immitis, to the extent that the responses of histoplasmin-reactive persons were not statistically different (P > 0.05) from those of coccidioidin-reactive persons. In contrast, optimal dilutions of Histoplasma mycelial and yeast-phase lysates effectively distinguished (P < 0.01) responses of histoplasmin- and coccidioidin-reactive persons. The alkali-soluble cell wall antigen of H. capsulatum showed extensive cross-reactivity at most concentrations and was markedly stimulatory to lymphocytes of skin test-negative persons. Blastomycin elicited significant cross-reactions in histoplasmin-sensitive subjects and to a lesser extent in coccidioidin-sensitive subjects. The alkali-soluble cell wall antigen cross-reacted in cultures of histoplasmin-reactive persons but not in those of coccidioidin-reactive persons. All antigens effectively distinguished (P < 0.001) homologous responses of skin test-positive persons (groups I and II) from those of skin test-negative persons (group III). The extensive cross-reactivity in lymphocyte transformation assays in the absence of cross-reactivity in skin tests suggests that these two immune responses may be mediated by different T lymphocyte populations, may be elicited by different antigenic components, or both.

Antigens, Fungal↗
PubMed1979

Immunologic studies of patients with histoplasmosis.

Immunologic responses of patients with active histoplasmosis (Group I) were compared to the responses of healthy persons with positive histoplasmin skin-test reactions (Group II), and to those of healthy persons with negative histoplasmin skin-test reactions (Group III). Cellular immune responses were significantly depressed in patients. Seven (54 per cent) of 13 patients failed to respond to histoplasmin skin testing, and two (15 per cent) failed to respond to skin-test antigens unrelated to Histoplasma capsulatum. Lymphocyte transformation (LT) responses of patients were severely depressed in vitro (p less than 0.001) to Histoplasma antigens when compared to the responses of healthy, histoplasmin-reactive donors. Transformation responses to Candida antigen were not impaired in the patient population. Culturing lymphocytes of patients in serum obtained from healthy donors as opposed to autologous serum resulted in a significant (p less than 0.05) increase in LT responses to H. capsulatum. Responses to Candida antigen and to mitogens were not affected by the serum source. Serum-mediated suppression of LT responses correlated (p less than 0.01) with complement-fixing antibody titers to Histoplasma yeast-phase antigen and suggests that antibody, either alone or complexed with antigen, may suppress T-cell response in vitro in this disease.

Adolescent↗
PubMed1979

OER and RBE for negative pion beams of different peak widths.

Experimental data on survival curves for pion because of different peak widths under aerobic and hypoxic conditions are reported. Metabolic depletion of oxygen by the Chinese hamster cells (line V79) was used to obtain hypoxia. The results indicate that the RBE at the beam entrance (plateau) is approximately 1.0. When the Bragg peaks were broadened to widths of 1.3, 7.8, and 10.5 cm (at the 80% dose level), the RBE (50% cell survival) at the peak centres was 1.7, 1.6, and 1.2, respectively. The OER at the entrance was 2.4 compared with about 2.9 for X rays. The OER was independent of the survival level at which it was measured. The OER at the peak centres at widths of 1.3, 7.8, and 10.5 cm was 2.1, 2.4, and 2.2, respectively. These results indicate that, although the RBE at the centre of the 10.5 cm wide peak was significantly lower than at the centres of the 1.3 and 7.8 cm peaks, the OER values are similar for all peak widths used in this study.

Animals↗
PubMed1979

Ultrastructure of rat lungs following exposure to aerosols of dibenzoxazepine (CR).

Three groups of 18 animals were exposed respectively to the following large doses of dibenz (b.f)-1:4 oxazepine (CR) aerosols, 78,200,140,900 and 161,300 mg/min/m3. Animals were killed at intervals from 15 min to 2 days, and the lungs examined macroscopically, by electron microscopy and conventional histology. There were no deaths during or after exposure. Macroscopically the lungs from all rats appeared normal. Microscopically there were a few areas of mild congestion, haemorrhage and emphysema, but there was little variation between the different groups. Electron micrographs revealed some morphological alteration of the epithelium and endothelium but only occasional changes in the interstitium. The alterations took the form of "ballooning" of the endothelium with isolated foci of swelling and thickening of the epithelium. Interstitial oedema was observed in one animal only which was exposed to the highest concentration. The effects appeared similar in all groups, and are thought to be transient. The results of this investigation suggest that even high doses of CR aerosols cause minimal damage to the lung, and the structural alterations which do occur are believed to be due to the stress to which the animals were subjected during the exposure period.

Aerosols↗
PubMed1978

A heavy particle comparative study. Part II: cell survival versus depth.

Cell-survival measurements with depth of penetration were made for a series of incident doses of proton, helium, carbon, neon, argon, negative pion, neutron, and 60Co photon beams. Cultured human cells (T1) suspended in a gel-containing medium were used, and the measurements were found to be very useful in facilitating the design of ridge filters to produce iso-effects in the region of interest. Heavy charged particle beams (proton, helium, carbon, neon, and negative pion) were found to produce similar cell killing with depth of penetration. Because of saturation effects at higher LET, argon ions were less effective in killing aerated cells at depth, compared with other heavy charged-particle beams. Cell killing at depth in the region of interest, compared with that at the entrance, was not significantly different for single-field exposures when the Bragg peaks were broadened to cover a width of 10 cm. However, when two opposed fields with overlapping peaks were used, a large enhancement in killing was obtained in the peak region.

Argon↗
PubMed1978

A heavy particle comparative study. Part III: OER and RBE.

The results of a comparative study of heavy particles of interest in radiotherapy are reported in four parts. In this Part III, cell-survival measurements under aerobic and hypoxic conditions were made for various heavy particle beams. For heavy charged-particle beams, the measurements were made at the beam entrance (plateau), peak centre (10 cm wide peaks), and distal peak (1 cm from dose fall-off). Chinese hamster cells (V79) were used. Metabolic depletion was used to obtain hypoxia. The results indicate that the differences in RBE between the entrance region and peak are not very large when the Bragg peaks are broadened to 10 cm. The RBE for argon ions remains the same at the entrance and peak centre, and the RBE at the distal side of the Bragg peak is significantly reduced compared to the peak centre and entrance region because of saturation effects at high LET. The OER for protons is not significantly different from that for X rays. The OER for helium ions, carbon ions, and negative pions is larger, for neon ions is similar, and for argon ions is smaller when compared with fast neutrons. The OER values for heavy ions are higher than expected and could be due to a large delta-ray penumbra associated with the energy deposited by energetic heavy ions. The oxygen effect may depend upon energy deposition over distances of the order of nanometers.

Argon↗
PubMed1978

Bronchogenic cyst mimicking a pulmonary varix.

A 14-year-old boy initially had severe hemoptysis and a coin lesion in the left lower lobe on the chest x-ray film. Pulmonary arteriographic studies suggested the presence of a pulmonary varix. Pathologic examination of the specimen obtained at surgery revealed a bronchogenic cyst. Pulmonary varices are extremely rare. Bronchogenic cysts must be included in the differential diagnosis of these lesions.

Adolescent↗
PubMed1977

An improved filter-disc assay for 3H-DNA and serum deoxyribonucleases.

1. The filter-paper disc assay for tritium-labeled nucleic acids was modified to reduce washing and manipulation. Evaluation of the procedure indicated greatly enhanced counting efficiency for tritium, complete removal of nuclease digestion products and retention of even nanogram levels of radioactive DNA on the discs in the presence of protein. The modified assay was quite sensitive and had a coefficient of variation of 5.2%. Quite low concentrations of DNase I and endogenous human serum nuclease activity were readily measured by the improved technique, 22 sera yielding a mean value equivalent to about 0.5 ng DNase I/ml serum. We are now using the disc assay to follow serum DNA and DNase levels in patients with autoimmune disorders and various types of cancers.

DNA↗
PubMed1977

In vivo and in vitro cell-mediated immune responses to a cell wall antigen of Blastomyces dermatitidis.

An alkali-soluble, water-soluble cell wall fraction of Blastomyces dermatitidis, designated B-ASWS, was evaluated as an antigen for detecting in vivo (skin tests) and in vitro migration inhibition factor (MIF) production and lymphocyte transformation (LT) responses in Blastomyces-infected guinea pigs. The biological activity of B-ASWS was compared with that of blastomycin KCB-26. The superiority of B-ASWS, in terms of its sensitivity and specificity, was evident in in vivo and in vitro assays. Skin tests responses were obtained in 21 of the 24 Blastomyces-infected guinea pigs, whereas only one of the 14 Histoplasma-infected guinea pigs were significantly greater than those obtained using cell populations from Histoplasma-infected or noninfected guinea pigs. The con-MIF and LT in peritoneal exudate cells and lymph node cells of homologuosly infected animals. In each biological system, the response of the Blastomyces-infected guinea pigs were significantly greater than those obtained using cell populations from Histoplasma-infected or non-infected guinea pigs. The contrasting efficacy of B-ASWS as compared with blastomycin KCB-26, suggests that the cell wall antigen will be a useful tool for detecting cell-mediated immune responses in blastomycosis.

Animals↗