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Biomedical subjects

C L Jones

Publications and source records attributed to C L Jones.

At least 109 records · Page 6Linked to original sources

The crystal structure of beta-lactamase from Staphylococcus aureus at 0.5 nm resolution.

The preparation, crystallization and low-resolution structure determination of beta-lactamase (EC 3.5.2.6, 'penicillinase') from Staphylococcus aureus is described. The enzyme crystallizes in space group I222 with 1 molecule per asymmetric unit and cell dimensions a = 5.45(1), b = 9.39(1) and c = 13.87(2) nm. The structure was determined at 0.5 nm resolution by using phases calculated from (NH4)2Pt(CN)4 and KAu(CN)2 derivatives. The mean figure of merit mean value of m, for the 1106 reflexions used was 0.70. Difference Fourier syntheses for data collected from crystals soaked in platinum D-methionine and in 6-(4-hydroxy-3,5-di-iodobenzamido)penicilloic acid revealed the likely position of the active site of the enzyme.

Carbohydrates↗

Molecular cloning of staphylococcal enterotoxin B gene in Escherichia coli and Staphylococcus aureus.

We have cloned the Staphylococcus aureus entB gene in Escherichia coli, using pBR322 as the vector plasmid; however, no detectable staphylococcal enterotoxin B (SEB) was produced by the E. coli clones. When the entB gene was placed downstream from the strong lambda phage promoter, PR, SEB was synthesized at readily detectable levels in E. coli. Interestingly, mature SEB was almost exclusively present in the cytoplasmic fraction. The SEB precursor was found associated with the cell membrane. The entB gene was introduced back into S. aureus, and the clones were shown to produce SEB. The entB gene has been located to a 2.1-kilobase-pair region. Maxam-Gilbert sequencing of a part of the entB gene yielded a DNA sequence that corresponds to the known amino acid sequence of SEB. Southern hybridization experiments showed that the entB gene was present on identical restriction fragments in the chromosomes of SEB-producer strains. The entB gene is absent from SEB-nonproducer strains.

Chromosomes, Bacterial↗

Solubilization and partial purification of dihydroxyacetone-phosphate acyltransferase from guinea pig liver.

Dihydroxyacetone-phosphate:acyl coenzyme A acyltransferase (EC 2.3.1.42) was solubilized and partially purified from guinea pig liver crude peroxisomal fraction. The peroxisomal membrane was isolated after osmotic shock treatment and the bound dihydroxyacetone-phosphate acyltransferase was solubilized by treatment with a mixture of KCl-sodium cholate. The solubilized enzyme was partially purified by ammonium sulfate fractionation followed by Sepharose 6B gel filtration. The enzyme was purified 1200-fold relative to the guinea pig liver homogenate and 80- to 100-fold from the crude peroxisomal fraction, with an overall yield of 25-30% from peroxisomes. The partially purified enzyme was stimulated two- to fourfold by Asolectin (a soybean phospholipid preparation), and also by individual classes of phospholipid such as phosphatidylcholine and phosphatidylglycerol. The kinetic properties of the enzyme showed that in the absence of Asolectin there was a discontinuity in the reciprocal plot indicating two different apparent Km values (0.1 and 0.5 mM) for dihydroxyacetone phosphate. The Vmax was 333 nmol/min/mg protein. In the presence of Asolectin the reciprocal plot was linear, with a Km = 0.1 mM and no change in Vmax. The enzyme catalyzed both an exchange of acyl groups between dihydroxyacetone phosphate and palmitoyl dihydroxyacetone phosphate in the presence of CoA and the formation of palmitoyl [3H]coenzyme A from palmitoyl dihydroxyacetone phosphate and [3H]coenzyme A, indicating that the reaction is reversible. The partially purified enzyme preparation had negligible glycerol-3-phosphate acyltransferase (EC 2.3.1.15) activity.

Acyltransferases↗

The effect of poliovirus infection on the translation in vitro of VSV messenger ribonucleoprotein particles.

Messenger ribonucleoprotein (mRNP) particles were isolated and examined for the presence of factors involved in the inhibition of protein synthesis induced by poliovirus infection. Vesicular stomatitis virus (VSV) mRNPs were used as a model for cellular mRNPs. These mRNPs were translated in HeLa cell extracts with a similar efficiency and optimal conditions to that of purified mRNA, but they were not translated in extracts prepared from poliovirus-infected HeLa cells, which have been shown to be defective in cap-binding protein activity. We conclude that mRNP proteins do not include cap-binding protein activity, since the mRNPs were not able to bypass the restriction on translation of capped mRNAs in polio-infected cell extracts. In addition, VSV mRNPs were isolated from polio-superinfected cells, in which their translation was inhibited. These mRNPs were translated in vitro as well as normal VSV mRNPs. No evidence of a modification or a blocking factor on the mRNPs which prevented their translation following polio infection was observed. Thus, within the limits of the in vitro translation assays used, no factors involved in the discrimination between polioviral and cellular or VSV mRNA could be detected in the mRNP particle.

Carrier Proteins↗

Integrated systems: from library to campus and beyond.

Integrated library systems have not yet been created, although they have been emphasized for nearly two decades. Now and in the future, the task is even more complex because the principal issue is access to information itself, wherever it is located and in whatever form it may exist. The goal becomes more feasible because of changes in library practices achieved with technological innovation. Although individual elements of a campus-wide information system may already exist, the details for implementation are yet to be articulated.

Information Systems↗

Environmental analysis of neonatal intensive care.

Premature infants, visiting parents, and staff in two intensive care units (ICUs) were observed around the clock for 3 weeks to study the early experiences of these infants: types of medical and general care, adult to infant personal attentions, interactions, infant activities (by sensory mode), and factors affecting these patterns of care. Infants case histories included family, medical, and environmental data such as number of days on oxygen or in an incubator. In-depth interviews and epidemiological assessment of psychiatric symptomatology of persons identified in the observations as primary care providers were used to study the psychodynamics of the ICU environment. Data were analyzed longitudinally for each infant and cross-sectionally to identify trends along environmental, sensory mode, and interaction variables. For example, despite increases in respiratory capacity, infant vocalization continued to decrease significantly as the number of days increased with mechanical ventilation, in oxyhoods, incubators, and even in an ICU environment. In effect, initial suppression of vocalization for medical reasons was subsequently reinforced by the ICU environment. The amount of time parents spent with their infants significantly correlated inversely to the number of miles between home and hospital (range of 5 to 180 miles) and dropped to zero for infants transported more than 50 miles (three of 10 such infants became wards of the State during hospitalization). Staff-infant contact for medical card was 10.6% of observation time (12 30-minute observations pre infant per day), 10.9% for general care, 15.4% personal attention simultaneous with care tasks, plus 3.8% additional personal attention. These extrapolate to 6.1 hours of infant contact per day. Personal attention correlated significantly with medical care, and at even a higher level with general care, personal attention independent of tasks, and staff rank order of preference for individual infants, thus differentiating between the nurturing care of preferred infants and the more impersonal care provided to infants lower in staff preference. Factors affecting preference were long term prognosis, family-infant lower in staff preference. Factors affecting preference were long term prognosis, family-infant and staff-family relations, staff sense of success or failure from working with an infant, familiarity, ethical issues, and the physical and perceptual accessibility of the infant. Persons identified in the observations as primary care providers exhibited a significantly higher degree of psychiatric symptomatology (psychosocial dysfunction, depression, general psychopathology, and psychosomatic symptomatology) than a representative sample of the general population. This symptomatology had links to their attachment to the high risk infants, to the care provider's life history, and to reasons for liking their work. Such findings indicate a need to expand the environmental model used to study the early experiences of high risk premature infants.

Adult↗

Patent ductus arteriosus: anatomy and surgery in a cat.

A 5-month-old cat with patent ductus arteriosus (PDA) and probable small ventricular septal defect had severe cardiomegaly and congestive heart failure. The cat improved slightly with medical therapy and markedly after surgical closure of the ductus. A 4th left intercostal space thoracotomy gave good exposure. The external anatomy of the PDA was similar to that of a short, wide PDA in dogs; however, the internal aortic orifice was situated more cranial than in dogs, as evidenced by preoperative cardiac catheterization. Examination 1 year later showed marked reductions in heart size and electrocardiographic amplitude. The cat was 1 of 3 with clinically diagnosed PDA at the University of Pennsylvania from 1968 to 1980. The prevalence of PDA in 14,224 cats (0.2/1,000) was significantly less than in 68,049 dogs (4.7/1,000).

Animals↗

Requirements for DI particle prophylaxis against vesicular stomatitis virus infection in vivo.

In contrast to biologically active DI particles, neither u.v.-inactivated standard virus nor either of two different homologous u.v.-inactivated DI particles showed any prophylactic effect when injected intracerebrally into mice concomitantly challenged with VSV. Although u.v.-inactivated DI particles did not prevent death when given with the challenge virus, they did significantly lengthen the time until death occurred. Also, both u.v.-inactivated standard virus and DI particles protected mice against late challenge (at 3 or 10 days after treatment). Dosage titrations of preparations of two different active DI particles showed significant prophylaxis against simultaneous challenge with numbers of DI particles 10- to 100-fold lower than those which gave no prophylaxis when u.v.-inactivated. Thus, prophylaxis in this system in this system required biologically active DI particles.

Animals↗

Bacterial contamination of expressed breast milk.

In a study of breast milk collected into sterile bottles rinsed in 1% hypochlorite solution the hypochlorite solution adherent to the sides of the bottles apparently caused a large reduction in bacterial contamination of the milk after storage at 4 degrees C for up to four hours. Heating expressed breast milk at 62.5 degrees C for five minutes destroyed over 90% of the Escherichia coli, Staphylococcus aureus, and group B beta-haemolytic streptococci inoculated into the milk samples. Rinsing collecting bottles with hypochlorite solution may be valuable in collecting milk with a low bacterial content for human-milk banks. Furthermore, the currently accepted pasteurisation time of 30 minutes may be excessive.

Escherichia coli↗

Subcellular localization of acyl coenzyme A: dihydroxyacetone phosphate acyltransferase in rat liver peroxisomes (microbodies).

Upon differential centrifugation of rat liver homogenate, the enzyme acyl-CoA:dihydroxyacetone-phosphate acyltransferase (EC 2.3.1.42) was found to be localized in the light mitochondrial (L) fraction which is enriched with lysosomes and peroxisomes. Peroxisomes were separated from lysosomes in a density gradient centrifugation using rats which were injected with Triton WR 1339. By comparing the enzyme distribution with the distribution of different marker enzymes, it was concluded that dihydroxyacetone phosphate acyltransferase is primarily localized in rat liver peroxisomes (microbodies). Similarly, the enzyme acyl dihydroxyacetone-phosphate:NADPH oxidoreductase (EC 1.1.1.101) was shown to be enriched in the peroxisomal fraction, although a portion of this reductase is also present in the microsomal fraction.

Acyltransferases↗