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Biomedical subjects

M Hill

Publications and source records attributed to M Hill.

At least 397 records · Page 22Linked to original sources
PubMed1980

Correlation between phagocytic and membrane surface properties reflected by partitioning of human peripheral blood monocytes in two-polymer aqueous phases.

Human peripheral blood monocyte-enriched fractions (identified by staining for peroxidase and by sizing) were obtained by velocity sedimentation at unit gravity of peripheral blood mononuclear cells. They were then fractionated by countercurrent distribution (a multiple-extraction procedure) in a charged Dextran/poly(ethylene glycol) aqueous phase system. The monocytes remained viable after the separation (order of 90%). Cells obtained from different cavities along the extraction train were tested for their ability to phagocytize latex particles. With increasing partition coefficient (presumably higher charge-associated membrane properties) the ratio of monocytes that phagocytized to monocytes that did not phagocytize increased appreciably. When, however, monocytes were permitted to phagocytize particles prior to countercurrent distribution, an increase in partition coefficient was associated with an appreciable decrease in the above-specified ratio. Control experiments indicate that the observed change in partitioning behavior cannot be ascribed to an alteration in size and/or density of the monocytes as a function of phagocytosis. It may be due to the internalization of charged surface groups during phagocytosis. We conclude that there is a correlation between the surface properties of monocytes (as reflected by partitiartitioning behavior cannot be ascribed to an alteration in size and/or density of the monocytes as a function of phagocytosis. It may be due to the internalization of charged surface groups during phagocytosis. We conclude that there is a correlation between the surface properties of monocytes (as reflected by partitioning) and their ability to ingest particles. Furthermore, an alteration in the surface charge-associated properties of monocytes as a consequence of phagocytosis is indicated by the cells' reduced partition coefficient.

Cell Membrane↗
PubMed1980

Recombinants between avian sarcoma virus genome and chicken helper factor gene of the host cell: cloning by transfection.

Chicken cells of chicken helper factor-positive (chf+) phenotype were infected with a cloned (envE-free) Rous sarcoma virus, subgroup D, and examined for the presence of parent and recombinant proviruses by transfection in chicken and turkey cells, respectively. It was found that most parent virus DNA is integrated into the host cell genome during the first 18 hr after infection, and no significant integration occurs between 18 and 72 hr after infection. On the other hand, no recombinant virus DNA was detected at 18 hr, although both unintegrated and integrated (provirus) forms of this DNA occurred 72 hr after infection. Recombination proviruses were also found in chronically virus-infected chf+ cells but not in chf- cells lacking virus-related RNA. Our results show that recombinants between the exogenous virus and endogenous chf gene can be cloned from the DNA of the host cell by transfection and suggest that a second replicative cycle of the virus is required to generate such recombinants.

Animals↗
PubMed1980

Tandem integration of avian retroviruses in double-infected cells.

Chicken embryo fibroblasts were chronically infected by both RAV-1 and SR-E, and established SR-E-transformed quail cells were superinfected with RAV-1. About 75 and 50% of double-infected and superinfected cells, respectively, produced both parental viruses. The DNA purified from these cells contained infectious provirus of both parents and no detectable recombinant provirus. In assays using agar overlay, about 5% of the transformed foci that were induced by the DNA of double-infected, but not superinfected, cells were found to contain the progeny of both parents. This observation suggests that in double infections with avian retroviruses, DNA of both parent viruses may integrate into the host genome either in tandem or in close proximity.

Animals↗
PubMed1980

Two-hit kinetics of focus formation in cells transfected with Rous sarcoma provirus.

DNA was purified from an established line of SR-E-transformed quail cells and was assayed for transfection in turkey cells. Transfection events were determined from foci of transformed cells growth under agar overlay which was used to prevent the spread of the progeny virus. It was found that transfection with Rous sarcoma proviruses follows two-hit kinetics, indicating that at least two (unlinked) provirus are required to give rise to a focus of transformed cells.

Animals↗
PubMed1980

Physical fitness and Embedded Figures Test performance of elementary school children.

The relationship between physical fitness and field independence was assessed by measuring embedded-figures test performance in the following four groups of children in Grades 4 through 6: (1) 93 boys high in physical fitness, (2) 92 girls high in physical fitness, (3) 67 boys low in physical fitness, and (4) 77 girls low in physical fitness. The group of girls low in physical fitness was significantly more field dependent than the other three groups. No significant differences were found among the other three groups. It appears that skill in physical activities may be related to the embedded-figures test performance of girls, but not boys. In fact, girls skilled in physical activities may be as field independent as boys.

Child↗
PubMed1979

Magnesium ion dependent adenosine triphosphatase activity of heavy meromyosin as a function of temperature between +20 and -15 degrees C.

The hydrolysis of Mg2+-adenosine 5'-triphosphate (ATP) by heavy meromyosin has been studied between +20 and -15 degrees C, especially in the low-temperature range, in a medium containing 30% (v/v) ethylene glycol by fluorometric, spectrophotometric, and potentiometric measurements. The time course of the fluorescence changes of the enzyme during the reaction depends markedly on the temperature in consequence of large differences between the activation energies of the various steps. The observed kinetics have been analyzed according to the simplified scheme of Bagshaw & Trentham [Bagshaw, C. R., & Trentham, D. R. (1974) Biochem. J. 141, 331-349]. The following results have been obtained. (1) The rate-limiting step of the reaction changes in this temperature range; at 20 degrees C M**.ADP.Pi is the predominant steady-state complex, and M*.ADP predominates at -15 degrees C, with a half-life of approximately 10 min. (2) As expected, on the basis that it is the dissociation of the M*.ADP complex which becomes rate limiting at low temperature, one observes, in the pre-steady-state below 0 degrees C, both a proton burst and a lag phase in ADP release. (3) At low temperature, the equilibrium M*.ATP in equilibrium M**.ADP.Pi is displaced to the left All the kinetic data obtained in this study are compatible with a simple pathway for the Mg2+-ATP hydrolysis by myosin and with sequential release of the reaction products.

Adenosine Triphosphatases↗
PubMed1979

The kinetics of synthesis of infectious unintegrated virus DNA in rous sarcoma virus infected chicken cells.

Infectious virus nucleic acids were extracted from the Hirt supernatant of chicken embryo fibroblasts infected for different times with the Schmidt-Ruppin strain of Rous sarcoma virus (RSV). Infectious DNA and DNA-RNA hybrid molecules could be recovered from 6 h after infection in experiments using 1.5 X 10(9) infected cells. Only small amounts of infectious virus DNA could be purified 6 h after infection whereas at 24 h approximately one infectious DNA molecule could be recovered for each input virus infectious unit. At 24 h, both infectious supercoiled and non-supercoiled molecules were found. The specific infectivity of the supercoiled fraction was less than that of the non-supercoiled fraction. Infectious supercoiled DNA could be recovered from 16 h after infection. Evidence is presented that both forms of unintegrated virus DNA may rest unintegrated for at least 8 days in the cell, though chronically infected cells were shown to contain less than one unintegrated molecule per 10(2) to 10(3) cells.

Avian Sarcoma Viruses↗
PubMed1979

Monomer and multimer covalently closed circular forms of Rous sarcoma virus DNA.

Covalently closed circular molecules of viral DNA synthesized in virus-infected cells are composed mainly of monomers sedimenting at 22 to 27S in neutral sucrose gradients. These monomers are detected by annealing with complementary DNA or transfection assay. However, 11% of the infectious circles sediment faster than monomers. There is a peak at 32S which may correspond to dimer molecules. Traces of infectivity (about 3%) found between 32S and 65S suggest the presence of higher oligomers. In alkaline sucrose gradients, covalently closed monomers are found at 64 to 71S. Infectivity of these monomers is reduced by alkali treatment to less than one-tenth, and, perhaps for this reason, no infectious dimers or higher oligomers are observed. It has been shown that upon resedimentation the dimers of 95 can be separated from monomers and detected by hybridization.

Animals↗
PubMed1979

In vitro synthesis of infectious DNA copies of the Rous sarcoma virus genome.

Detergent-disrupted virions of Rous sarcoma virus can synthesize in vitro an infectious viral DNA. Infectivity of the DNA was determined in transfection assays at the endpoint dilution. It was found that the specific infectivity of the crude endogenous reaction product was 34 infectious units/microgram. The endogenous reaction yielded up to 8.5 x 10(-7) infectious units per biologically active input virion, i.e., nearly 0.1 -1 infectious molecules. The possible structure of these molecules is discussed.

Avian Sarcoma Viruses↗
PubMed1979

Clinical assessment of patients undergoing CPR in the emergency department.

A problem frequently encountered in the emergency department is assessing the effectiveness of cardiopulmonary resuscitation (CPR), particularly when it is continued over a period of time. To evaluate the effectiveness of CPR in our emergency department we use a mechanical cardiopulmonary resuscitator (Michigan Instruments, Thumper) together with early invasive monitoring of pulse and blood pressure. This also allows for frequent monitoring of blood gases. Three patients are presented who underwent longterm CPR (ie, longer than one hour), and invasive monitoring. Results indicate that better management of the clinical status of patients undergoing prolonged resuscitation can be obtained by using continuous blood pressure and pulse monitoring, and frequent blood gas analysis. In addition, when frequent arrhythmias are taking place, this system allows for better determination of appropriate procedures and medications.

Aged↗
PubMed1978

Gray scale B scan characteristics of intra-abdominal cystic masses.

A comparison of the gray scale characteristics of 119 intra-abdominal cystic masses was performed. Each cystic mass was evaluated with regard to: 1) The presence or absence of internal echoes, septa, and fluid-fluid levels; 2) The appearance of the wall; 3) Conformity to adjacent organs and, 4) Changes in the surrounding soft tissues. Abscesses, hematomas, lymphoceles, urinomas, and necrotic tumors were evaluated. Necrotic tumors and some abscesses and hematomas have specific sonographic characteristics. In most cases, a definite diagnosis cannot be made from the sonographic appearance; however, in conjunction with the clinical history, the differential diagnosis can be narrowed to a couple of cystic lesions among the many that may be found in the abdomen. The diagnosis can be confirmed by aspiration under ultrasound. A comparison between these cystic masses and pancreatic pseudocysts, renal cysts, and ovarian cysts was made.

Abdomen↗