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Biomedical subjects

G Fox

Publications and source records attributed to G Fox.

At least 19 recordsLinked to original sources
PubMed1995

DNA polymerases alpha, delta, and epsilon of Novikoff hepatoma cells differ from those of normal rat liver in physicochemical and catalytic properties.

To investigate whether DNA replication in malignant cells deviates from that of normal cells we compared DNA polymerases alpha, delta, and epsilon from normal rat liver to the enzymes from fast-growing (malignant) Novikoff hepatoma cells. DNA polymerases were purified 300-fold by three chromatographic steps. Characterization included measurement of physicochemical constants (including sedimentation coefficients, diffusion coefficients, calculation of relative molecular masses), quantitation of catalytic activities using specific DNA primer templates (Km values) and inhibitors (Ki values), and identification of polypeptides which are strongly associated with DNA polymerases. Comparison of physicochemical and catalytic properties of DNA polymerases from both sources revealed similarities but also some important differences. DNA primase associated with DNA polymerase alpha, and 3'-5' exonuclease accompanying DNA polymerases delta and epsilon had similar activities. In contrast, the DNA-binding domain of DNA polymerases alpha and epsilon from hepatoma cells was altered since Km values, determined with the specific primer templates gapped calf thymus DNA and poly(dA.dT), were higher. Furthermore, sedimentation and diffusion coefficients, Stokes' radii, and frictional coefficient ratios of DNA polymerases alpha and epsilon from malignant cells significantly deviated. In addition, when the dNTP-binding sites were probed with specific inhibitors (aphidicolin, butylphenyl-dGTP, carbonyldiphosphonate, and dideoxy-TTP), significantly lower Ki values were obtained for the polymerases from Novikoff cells indicating lower affinity of the dNTP binding site to deoxyribonucleoside 5'-triphosphates. Altered catalytic and molecular properties are possibly a consequence of malignant transformation. It is to be expected that similar changes occur in DNA polymerases of other tumors. In particular, diminished affinity to primer templates and weakened nucleotide binding leads to lowered specificity of nucleotide selection in the base-pairing process and is therefore likely to cause an enhanced mutation rate during malignant progression.

Animals↗
PubMed1995

Insensitivity of the Hering-Breüer reflex to spontaneous changes in metabolic rate in the infant.

1. In infants, metabolic rate is highly variable. We investigated whether the strength of the vagal ventilatory inhibitory reflex was modified by the spontaneous changes in metabolic rate. 2. In 20 2-day-old infants, we measured the intensity of the Hering-Breüer expiratory-promoting reflex (inhibition of breathing during maintained lung inflation), the inspired and expired O2 and minute ventilation (VE), from which oxygen consumption (VO2) was calculated. The measurements were performed twice, a few hours apart [6 +/- 1 h SEM)]. 3. On average, VO2 differed by 39 +/- 7% between the two measurements, with no correlation with the time of the day (morning/afternoon) or the time interval from a meal. VE was also significantly higher (19 +/- 6%) when VO2 was higher, because of a larger tidal volume. The Hering-Breüer reflex (quantified as the apnoea time during lung inflation, either the absolute value or normalized by the airway pressure or lung volume) did not differ significantly between the two tests (< 5% difference, P > 0.05), and did not correlate with the changes in VO2 or VE. 4. We conclude that, in the infant, pulmonary vagal inhibition is not sensitive to changes in metabolic drive, presumably because of the low ventilatory chemosensitivity of the newborn.

Circadian Rhythm↗
PubMed1995

Tryptase and IgE concentrations in the respiratory tract of infants with acute bronchiolitis.

It has been proposed that a specific IgE response contributes to the immunopathology of acute respiratory syncytial virus (RSV) bronchiolitis but previous work has been difficult to replicate. Indirect evidence that might support this contention was sought by measuring total IgE concentrations in bronchoalveolar lavage (BAL) samples obtained from intubated infants and by attempting to detect mRNA for IgE in cells obtained from both the upper and lower respiratory tract. Evidence of significant mast cell activation was sought by measuring tryptase concentrations in BAL fluid and serum. Detectable concentrations of IgE were found in two of seven BAL samples obtained more than five days after intubation and mRNA for IgE was demonstrated in three of six BAL samples and three of six samples obtained from the upper respiratory tract. Tryptase was detectable in 11 of 12 BAL samples with the two highest values detected on day 1. These values were raised compared with control samples but were not such to suggest that mast cell degranulation is the major contributor to the inflammatory process. These results suggest that IgE may be produced in the airways of infants in response to RSV infection. The relationships between IgE production, RSV infection, and symptoms of acute bronchiolitis remain obscure.

Acute Disease↗
PubMed1995

Gastric flora in chronically mechanically ventilated patients. Relationship to upper and lower airway colonization.

The oropharynx, stomach, and trachea are all potential reservoirs for gram-negative organisms in mechanically ventilated patients. The pathogenic importance of each site in respiratory infection may differ between mechanically ventilated patients who are medically stable and the critically ill, and these differences may be important in understanding the pathogenesis of nosocomial infection. We prospectively studied seven patients requiring chronic ventilatory assistance who were otherwise medically stable to determine the pattern of gram-negative colonization of these three sites. Serial weekly oropharyngeal, gastric, and tracheal cultures were taken over a 6-mo period in our Respiratory Care Unit for chronically ventilator-dependent patients. Pseudomonas aeruginosa (PA) was present more frequently and persistently in the trachea than the oropharynx and stomach (p < 0.01) and members of the family Enterobacteriaceae (Ent. species) were also observed more commonly in the trachea than the oropharynx (p < 0.01). PA was seen in 6.7% of gastric specimens whereas Ent. species were found in 40% of gastric specimens. Six identical strains from a total of 53 gastric isolates and 128 oropharyngeal isolates were cultured coincidentally from these two sites. Coincidental isolation of 11 strains was observed in 177 tracheal isolates and 53 gastric samples. Documented transfers from stomach to oropharynx ascertained by sequential isolation occurred in one of 118 cultures and transfer from stomach to trachea occurred in three of 134 cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Ventilatory and metabolic responses to acute hyperoxia in newborns.

Hyperoxia has previously been found to increase metabolic rate (oxygen consumption [VO2] and CO2 production [VCO2]) in newborn mammals. We asked whether the same occurs in the newborn infant. Breathing pattern was measured in 25 full-term infants, 1 to 2 days of age, from the spirometric record obtained with a pneumotachograph attached to a face mask. Concentrations of O2 and CO2 were continuously measured at the mouth; VO2 and VCO2 were computed as the product of VE and the difference between inspired and expired concentration of the respective gases, 5 min of air (FIO2 = 0.21) and 5 min of O2 (FIO2 = 1). A bias flow through the mask and pneumotachograph delivered the inspired gas and eliminated the effects of the instrumental dead space. In neither case did measurements at 1 min significantly differ from those taken at 5 min. In hyperoxia VE increased in 22 of the 25 infants, in average +18% (p less than 0.001, paired two-tailed t test). Because of a rise in tidal volume (+35%, p less than 0.001) and a decrease in breathing rate (-11%, p less than 0.005) alveolar ventilation (VA) increased by about 58% (p less than 0.001). VO2 and VCO2 increased by 25% and 17%, respectively (p less than 0.001). The rise in VO2 was too large to be explained by the greater respiratory work of the hyperventilation, whereas that of VCO2 was not large enough to fully explain the increase in VA. We conclude that in newborn humans, as in other newborn species, the normoxic metabolic rate seems to be limited by the availability of O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide↗
PubMed1991

Great Lakes embryo mortality, edema, and deformities syndrome (GLEMEDS) in colonial fish-eating birds: similarity to chick-edema disease.

Several species of colonial fish-eating birds nesting in the Great Lakes basin, including herring gulls, common terns and double-crested cormorants, have exhibited chronic impairment of reproduction. In addition to eggshell thinning caused by high levels of DDT and metabolites, the reproductive impairment is characterized by high embryonic and chick mortality, edema, growth retardation, and deformities, hence the name Great Lakes embryo mortality, edema, and deformities syndrome (GLEMEDS). The hypothesis has been advanced that GLEMEDS in colonial fish-eating birds resembles chick-edema disease of poultry and has been caused by exposure to chick-edema active compounds that have a common mode of action through the cytochrome P-448 system. Detailed evidence has been collected from the following three groups of studies on herring gulls in the lower Great Lakes during the early 1970s; Forster's terns in Green Bay, Wisconsin in 1983; and double-crested cormorants and Caspian terns in various locations in the upper Great Lakes from 1986 onwards. It has proved difficult to establish not only the onset of the disease in the various species at various locations but also the period in which chick-edema active compounds were released. Anecdotal evidence suggested that serious egg mortality in Lake Ontario herring gulls first occurred in 1966, through the signs of chick-edema disease were not looked for until 1974. Only indirect evidence is available on the date of the release of one of the presumed causal agents, 2,3,7,8-tetrachlorodibenzo-p-dioxin, but highest levels may have occurred in the early to mid 1960s. More reliable data show that the onset of the improvement of reproduction of Lake Ontario herring gulls coincided with the declines in organochlorine compounds and particularly 2,3,7,8-TCDD and PCB. Similarly, information on the onset of the disease and exposures in the Forster's tern and double-crested cormorants in Green Bay is uncertain but bird banders did not observe deformities until the 1970s, which corresponds with the onset of high levels of PCB. If the disappearance of the Caspian tern from Saginaw Bay in the mid 1960s corresponds with the onset of GLEMEDS at that location, then there is a close temporal relationship to the onset of high PCB levels. Chick-edema disease is difficult to diagnose because there is no specific lesion, but rather there is a suite of lesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Drug-Induced↗
PubMed1990

Structural and serological evidence for a novel mechanism of antigenic variation in foot-and-mouth disease virus.

Changes resulting in altered antigenic properties of viruses nearly always occur on their surface and have been attributed to the substitution of residues directly involved in binding antibody. To investigate the mechanism of antigenic variation in foot-and-mouth disease virus (FMDV), variants that escape neutralization by a monoclonal antibody have been compared crystallographically and serologically with parental virus. FMDVs form one of the four genera of the Picornaviridae. The unenveloped icosahedral shell comprises 60 copies each of four structural proteins VP1-4. Representatives from each of the genera have similar overall structure, but differences in the external features. For example, human rhinovirus has a pronounced 'canyon' that is proposed to contain the cell attachment site, whereas elements of the attachment site for FMDV, which involves the G-H loop (residues 134-160) and C-terminus (200-213) of VP1, are exposed on the surface. Moreover, this G-H loop, which is a major antigenic site of FMDV, forms a prominent, highly accessible protrusion, a feature not seen in other picornaviruses. It is this loop that is perturbed in the variant viruses that we have studied. The amino acid mutations characterizing the variants are not at positions directly involved in antibody binding, but result in far-reaching perturbations of the surface structure of the virus. Thus, this virus seems to use a novel escape mechanism whereby an induced conformational change in a major antigenic loop destroys the integrity of the epitope.

Antibodies, Monoclonal↗
PubMed1990

The structure of foot-and-mouth disease virus: implications for its physical and biological properties.

The structure of foot-and-mouth disease virus has been solved at a resolution of 2.9 A by X-ray diffraction techniques. The overall structural organisation of the particle is similar to that seen in other picornaviruses but there are several unique features. Many of these help to explain its characteristic physical and biological properties. In particular the canyon or pit found at the surface of other picornaviruses is lacking, which has important implications for cell attachment and the process of infection. Also there are 60 large disordered protrusions at the surface corresponding to the major antigenic site. This disorder is of particular interest in relation to the striking ability of linear synthetic peptides to induce protective immunity against foot-and-mouth disease.

Animals↗
PubMed1989

The three-dimensional structure of foot-and-mouth disease virus at 2.9 A resolution.

The structure of foot-and-mouth disease virus has been determined at close to atomic resolution by X-ray diffraction without experimental phase information. The virus shows similarities with other picornaviruses but also several unique features. The canyon or pit found in other picornaviruses is absent; this has important implications for cell attachment. The most immunogenic portion of the capsid, which acts as a potent peptide vaccine, forms a disordered protrusion on the virus surface.

Algorithms↗
PubMed1989

The cell attachment site on foot-and-mouth disease virus includes the amino acid sequence RGD (arginine-glycine-aspartic acid).

The amino acid sequence RGD (arginine-glycine-aspartic acid) is highly conserved in the VP1 protein of foot-and-mouth disease virus (FMDV), despite being situated in the immunodominant hypervariable region between amino acids 135 and 160. RGD-containing proteins are known to be important in promoting cell attachment in several different systems, and we report here that synthetic peptides containing this sequence are able to inhibit attachment of the virus to baby hamster kidney (BHK) cells. Inhibition was dose-dependent and could be reversed on removal of the peptide. A synthetic peptide corresponding to a portion of the same hypervariable region but not containing the RGD sequence did not inhibit virus attachment under the same conditions. Antibody against the RGD region of VP1 blocked attachment of the virus to BHK cells, and neutralizing monoclonal antibodies, which neutralize virus by preventing cell attachment, were blocked by RGD-containing peptides from binding virus in an ELISA test. Cleavage of the C-terminal region of virus VP1 in situ with proteolytic enzymes reduced cell attachment, and antiserum against a peptide corresponding to this region was also able to inhibit attachment of virus to BHK cells. These results indicate that the amino acid sequence RGD at positions 145 to 147 and amino acids from the C-terminal region of VP1 (positions 203 to 213) contribute to the cell attachment site on FMDV for BHK cells.

Amino Acid Sequence↗
PubMed1989

Cost of neonatal intensive and special care.

A detailed costing of neonatal intensive and special care was made for the year 1986 at the Rotunda Hospital. Cost was expressed at 1986 prices in punts. There was 1,364 admissions including external transfers giving a total of 10,086 bed days, divided into 1,044 intensive care and 9,042 special care bed days. The total cost of intensive and special care was 1,342,500 pounds. Costs per inpatient day were 288 pounds for intensive and 115 pounds for special care. Sixty percent of the intensive care bed days were used by infants weighting less than 1,500 g birth weight and 93% by infants less than 2,500 g birth weight; this emphasizes the effect of population mix on resource use. The average cost of intensive care survivors by birth weight were: less than 1,000 g - 16,226 pounds (8,052 pounds-23,535 pounds); 1,000 g-1,499 g - 13,412 pounds (1,898 pounds-22,456 pounds); 1,500 g-2,499 g - 8,864 pounds (633 pounds-17,666 pounds); 2,500 g + - 5,123 pounds (384 pounds-12,636 pounds). The average cost of all admissions to special or intensive care was 984.24 pounds. Using this figure (984.24 pounds) and assuming that 13% of all births in 1986 required special or intensive care the total health care expenditure on neonatal special or intensive care in 1986 amounts to 8.03 million pounds of a total Department of Health budget of 1,269 million pounds. By allocating infants to the currently used neonatal diagnostic related groupings (DRGs) and assigning costs at 1987 US reimbursement levels, the total cost to the Rotunda would be 1,878,750 pounds punts. The current level of DRGs derived from the reimbursement rates in the United States which is insufficient to meet the actual cost incurred there, is 40% greater than current total funding of neonatal intensive and special care in the Rotunda. Current funding levels in the United Kingdom are 13% to 80% greater than in the Rotunda.

Costs and Cost Analysis↗
PubMed1987

Crystallization and preliminary X-ray diffraction analysis of foot-and-mouth disease virus.

Foot-and-mouth disease virus has been crystallized with the objectives of (1) determining the composition and conformation of the major immunogenic site(s) and (2) comparing its structure with those of the related polio, rhino and Mengo viruses, representing the other three genera of the picornaviruses. Most of the work has been done with virus strain O1BFS 1860, which crystallized as small rhombic dodecahedra of maximum dimension 0.3 mm. Virus recovered from crystals was infectious, and was indistinguishable from native virus both in protein composition and buoyant density. The stability of the crystals in the X-ray beam was comparable with that of other picornavirus crystals and they diffracted to a resolution of better than 2.3 A. Initial analysis of the X-ray diffraction data shows the virus to be positioned on a point of 23 symmetry in a close-packed array so that examples of all the icosahedral symmetry elements, except the 5-fold axes, are expressed crystallographically. The cell dimensions are a = b = c = 345 A, alpha = beta = gamma = 90 degrees, with a space group of I23. The diameter of the virus particle is 300 A. Despite the small size of the crystals, diffraction data have been collected to a reasonable resolution using a synchrotron source. Phasing of the diffraction data will be attempted using the methods of molecular replacement.

Aphthovirus↗