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Biomedical subjects

D C Johnson

Publications and source records attributed to D C Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1984

Binding to cells of virosomes containing herpes simplex virus type 1 glycoproteins and evidence for fusion.

Envelope proteins and lipids were extracted from purified herpes simplex virus type 1 virions with octyl glucoside and mixed with phosphatidylcholine for preparation of virosomes by removal of the detergent. Greater than 85% of the extracted envelope proteins, including all the glycoproteins and the nonglycosylated protein designated VP16, were associated with virosomes, which ranged in density from ca. 1.07 to 1.13 g/cm3. All the glycoproteins except gC were as susceptible to degradation by added protease in virosomes as in virions, indicating similar orientations in both. Approximately 30 to 40% of radiolabel incorporated into virosomes bound to HEp-2 cells within 1.5 h at either 4 or 37 degrees C. The cell-bound virosomes were enriched for gB and deficient in other glycoproteins, in comparison with unbound or total virosomes. Binding of virosomes to HEp-2 cells could be inhibited by purified virus, heparin, and monospecific antiviral antibodies. Polyclonal and monoclonal anti-gB antibodies were more effective at inhibiting virosome binding than were anti-gD or anti-gC antibodies. Virosomes depleted of gB or gD did not bind to cells as efficiently as did virosomes containing all the extracted enveloped components; this loss of binding activity was especially pronounced on depletion of gB. The binding of herpes simplex virus type 1 virosomes to cells is discussed in relation to possible heterogeneity of the virosomes and comparisons with binding of virions to cells. We also present electron microscopic evidence that bound virosomes can fuse with the cell surface.

Animals↗
PubMed1984

Correlation of LH, FSH and GnRH release during various brain-pituitary coincubations.

Hemipituitaries and various brain fragments from female albino rats were coincubated in the presence or absence of veratrine (a depolarizing agent). The release of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and gonadotropin-releasing hormone (GnRH) was measured by radioimmunoassay. In the absence of veratrine, none of the brain fragments affected LH and FSH release. In the presence of veratrine, large increases in LH and FSH release were caused by medial basal hypothalamic (MBH) fragments, slight increases were caused by suprachiasmatic:preoptic area fragments, and cerebral cortex fragments had no effect. LH and FSH release caused by brain fragments was significantly correlated with GnRH release and the GnRH concentrations attained during coincubations could account for all increases in LH and FSH release observed. Also, GnRH antiserum completely blocked increases in LH and FSH release during MBH-hemipituitary coincubations. The data indicate that the rat brain is unlikely to contain neurohormones other than GnRH capable of directly stimulating LH and FSH release in vivo.

Animals↗
PubMed1984

Baseline body temperatures, heart rates, and respiratory rates of moose in Alaska.

Baseline body temperatures (BT), heart rates (HR) and respiratory rates (RR) were obtained from Alaskan moose (Alces alces gigas Miller) at the Moose Research Center (MRC), Alaska. Excitability, seasons and drugs influenced the values to varying degrees. Excitability was the most influential factor. Safe expected ranges were: BT 38.4 to 38.9 C, HR 70 to 91 beats/min (b/min), and RR 13 to 40 respirations/min (r/min). These ranges incorporated all seasons, a central nervous system depressant drug and a paralyzing drug. Values which may be considered critical and an indication that corrective action should be taken include: BT 40.2 C, HR 102 b/min, and RR 40 r/min. It is recommended that persons trained in monitoring vital signs be on hand during moose capture and immobilization procedures.

Alaska↗
PubMed1983

The C17,20-lyase, 17 alpha-hydroxylase and aromatase activity in rat ovarian granulosa cells stimulated in vivo by gonadotropins.

Immature hypophysectomized rats were injected with PMS; some groups received hCG 48h later. The C17,20-lyase activity in the granulosa cells removed from the large preovulatory follicles was estimated by the amount of labelled acetic acid produced from 21 (14C) progesterone or 17-hydroxyprogesterone. 17 alpha-hydroxylase and aromatase activity were measured by the tritium exchange method. Although the granulosa cells contained lyase, it was considerably less than their hydroxylase activity. The remaining tissue, consisting of small follicles and hypertrophied thecal and interstitial tissue, had a great deal more lyase and hydroxylase activity than did the granulosa cells. The results are consistent with the view that granulosa cells can produce estrogen from progesterone and do not require androgen precursors from the theca and/or interstitium.

Aldehyde-Lyases↗
PubMed1983

O-linked oligosaccharides are acquired by herpes simplex virus glycoproteins in the Golgi apparatus.

The O-linked oligosaccharides on mature forms of herpes simplex virus type 1 (HSV1) glycoproteins were characterized, and were found to account largely for the lower electrophoretic mobilities of these forms relative to the mobilities of immature forms. Other posttranslational modifications of HSV1 glycoproteins (designated gB, gC, gD and gE) were related temporally to the discrete shifts in electrophoretic mobilities that signal acquisition of the O-linked oligosaccharides. Fatty acid acylation (principally of gE) could be detected just prior to the shifts, whereas conversion of high-mannose-type N-linked oligosaccharides to the complex type occurred coincident with the shifts. The addition of O-linked oligosaccharides did not occur in cells treated with the ionophore monensin or in a ricin-resistant cell line defective in the processing of N-linked oligosaccharides. We conclude that extension of O-linked oligosaccharide chains on HSV1 glycoproteins, and probably also attachment of the first O-linked sugars, occurs as a late posttranslational modification in the Golgi apparatus.

Animals↗
PubMed1983

Movement of CO2 and HCO-3 from blood to brain in dogs.

The ratio of carbon dioxide (CO2) to bicarbonate (HCO-3) is important in acid-base homeostasis and to the central chemical drive to ventilation. The entry of HCO-3 from blood into the central nervous system (CNS) has been controversial, and the entry of CO2, assumed to be rapid, has not been separated from HCO-3 entry. Therefore the rates of movement of CO2 and of HCO-3 from blood to CNS were evaluated. The first-pass brain uptake of 11C-labeled CO2-HCO-3 was studied under conditions with and without carbonic anhydrase inhibition (CAI), with the isotope injected either as CO2 (acid injectate) or as HCO-3 (alkaline injectate) into the aortic arch of anesthetized dogs. The uptake of 11C under conditions without CAI was about 80% and remained the same whether the isotope was injected as CO2 or as HCO-3. The uptake of 11C under conditions of cerebroventricular administration of acetazolamide was 61.5 +/- 2.0% after injection as CO2 and 56.7 +/- 8.3% after injection as HCO-3. The uptake of 11C under conditions of systemic CAI was 50.3 +/- 3.0% after injection as CO2 and 19.3 +/- 1.1% after injection as HCO-3. The uptakes were comparable for the combination of cerebroventricular and intravenous acetazolamide. From the values for 11C uptake with systemic CAI and the uncatalyzed reaction rates for interconversion of CO2 and HCO-3, the first-pass brain uptake was calculated to be 87.7 +/- 7.8% for CO2 and 16.3 +/- 1.8% for HCO-3. Thus there is a very rapid diffusion of CO2 from blood to brain and a significant movement of HCO-3 from blood to brain.

Acetazolamide↗
PubMed1983

Oestradiol synthesis by granulosa cells from immature rats treated with pregnant mare's serum gonadotrophin.

Granulosa cells harvested from follicles in hypophysectomized or intact immature rats treated with 20 IU of pregnant mare's serum gonadotrophin (PMS) produced immunoreactive oestradiol (E2) when incubated in Krebs Ringer bicarbonate buffer containing an NADPH generating system; inclusion of steroid substrates in the medium increased the rate of synthesis. Further, tritiated E2 was synthesized when labelled progesterone was used as substrate. Granulosa cells removed from pre-ovulatory follicles on the morning of pro-oestrus in adult females also produced E2 in vitro. Although E2 synthesis was apparent by cells from immature hypophysectomized rats within 12 h of PMS treatment, it increased greatly with longer in vivo exposure to the gonadotrophin. Production was linear with the number of cells incubated and with time, at least through the first 30 min; the production rate decreased slightly with longer incubations. Exposure of the cells in vivo to hCG or ovine LH, before incubation, destroyed most of their ability to synthesize E2 even if progesterone or pregnenolone was added to the medium, but conversion of testosterone to E2 was reduced by only about 50%. Inhibitors of steroid synthesis, i.e. 4-OH-androstenedione, SU-10603, cyanoketone, or aminoglutethimide, greatly reduced the amount of E2 synthesized by the cells. The results indicate that granulosa cells exposed in vivo to gonadotrophins can synthesize E2 without the addition of androgenic substrate provided that cofactors are supplied. This finding has important implications for the current 'two cell' theory for oestrogen production by the ovary. A deficiency in steroidogenic enzymes within the granulosa cell appears to be an inadequate basis for the theory.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Catechol estradiol induced implantation in the mouse.

Induction of implantation is among the most sensitive responses to estrogens. The ability of catechol estradiols, 4-hydroxy-estradiol-17 beta (4-OH-E2) and 2-hydroxy-estradiol-17 beta (2-OH-E2), to induce implantation in ovariectomized pregnant mice was compared to that of estradiol-17 beta. Delayed implantation was maintained by the daily administration of 2 mg of progesterone. A single injection of 3 ng of estradiol-17 beta, 50 ng of 4-OH-E2, or 2,000 ng of 2-OH-32 consistently induce a full complement of implantation sites in all animals. Before the estrogenicity of the latter steroid can be established the lack of contaminating estrogens must be proved.

Animals↗
PubMed1982

Phospholipase A2 activity in the rat uterus: modulation by steroid hormones.

Phospholipase A2 (PLA2), an enzyme which provides free arachidonic acid for the synthesis of prostaglandins (PG), has been studied in the rat uterus under various experimental conditions. Uterine PLA2 activity increased 14 fold in hypophysectomized rats implanted with Silastic capsules containing estradiol-17 beta as compared to those treated with oil vehicle. Dexamethasone treatment reduced the PLA2 activity induced by estrogen by 78%. Hypophysectomized animals treated with progesterone (2mg/day) for 5 days had low levels of uterine PLA2 activity but a single injection of estradiol (10 micrograms/rat) given 24 h after the last injection of progesterone increased activity 5 fold within 12 h. Administration of the protein synthesis inhibitor cycloheximide in the rats treated with progesterone, before and after injection of estradiol, prevented the stimulating action of the estrogen on PLA2 activity. If the estrogen was given at the time of the last injection of progesterone, PLA2 activity did not increase until 22 h late and the level was much less than when progesterone was absent. The results are consistent with the view that estrogen stimulates uterine prostaglandin production because of its effect upon PLA2; this effect can be greatly reduced by a glucocorticoid. Progesterone may modulate the PLA2 stimulating effect of estrogen in order to direct the production of specific PGs by regulating the amount of arachidonic acid available for PG synthetase.

Animals↗
PubMed1982

Monensin inhibits the processing of herpes simplex virus glycoproteins, their transport to the cell surface, and the egress of virions from infected cells.

HEp-2 cells or Vero cells infected with herpes simplex virus type 1 were exposed to the ionophore monensin, which is thought to block the transit of membrane vesicles from the Golgi apparatus to the cell surface. We found that yields of extracellular virus were reduced to less than 0.5% of control values by 0.2 microM monensin under conditions that permitted accumulation of cell-associated infectious virus at about 20% of control values. Viral protein synthesis was not inhibited by monensin, whereas late stages in the post-translational processing of the viral glycoproteins were blocked. The transport of viral glycoproteins to the cell surface was also blocked by monensin. Although the assembly of nucleocapsids appeared to be somewhat inhibited in monensin-treated cells, electron microscopy revealed that nucleocapsids were enveloped to yield virions, and electrophoretic analyses showed that the isolated virions contained immature forms of the envelope glycoproteins. Most of the virions which were assembled in monensin-treated cells accumulated in large intracytoplasmic vacuoles, whereas most of the virions produced by and associated with untreated cells were found attached to the cell surface. Our results implicate the Golgi apparatus in the egress of herpes simplex virus from infected cells and also suggest that complete processing of the viral envelope glycoproteins is not essential for nucleocapsid envelopment or for virion infectivity.

Animals↗
PubMed1982

Aromatase activity in the rabbit blastocyst.

Rabbit blastocysts were homogenized by sonication, and centrifuged at 105 000 g for 60 min. The pellet was resuspended and incubated in phosphate buffer containing [1 beta-3H]testosterone and a NADPH generating system. The amount of 3H2O produced was determined by liquid scintillation counting. Enzyme activity was calculated, after subtracting blank values obtained with boiled embryos, and expressed as pig testosterone aromatized per embryo per hour. Aromatase activity was undetectable to low on Day 5 and increased on Day 6 of pregnancy. There was a 10-fold increase in activity in Day-6 embryos cultured for 24 h, with a further 6-fold increase in activity in Day-6 embryos cultured for 48 h. The enzyme had an apparent Km of 0.77 microM and was completely inhibited by an aromatase inhibitor. The results clearly indicate that the rabbit blastocyst has an increasing capacity for aromatization of testosterone at about the time of implantation.

Animals↗
PubMed1982

Profound hypothermia with circulatory arrest: nine years' clinical experience.

A total of 550 intracardiac operations were performed with the aid of profound hypothermia and circulatory arrest between March, 1971, and December, 1979. Both cooling and rewarming were effected by means of an extracorporeal heat exchanger. Overall mortality was 20%, falling to 10% in 1979. Highest risks were associated with operations in the neonatal period and for unusually complex defects. The technique has proved safe for straight forward corrections in young age groups and is especially valuable for selected complex lesions in older children and those requiring reoperation. Although circulatory arrest has greatly extended the range of corrective heart operation in infancy, we believe there is still a significant place for palliative procedures in appropriate circumstances. Neurologic complications attributed to the technique have been uncommon, and only 4.5% of the survivors have any recognizable residual neurologic lesion, whether coincidental or resulting from circulatory arrest. The technique is simple, reliable, and generally safe.

Child, Preschool↗
PubMed1982

Profession-specific training in health education.

In 1975, the African Regional Health Education Centre (ARHEC) inaugurated two training programmes in health programmes in health education: a two-year postgraduate course leading to a master's degree, and a one-year course preparing for a non-graduate diploma. The purpose of the latter was to give advanced training and updating to experienced health personnel who had either received a diploma in health education some years before or had been functioning as health educators. This was intended to be a temporary course, to phase out in three years. However, due to its popularity, it was extended in spite of certain negative aspects, mainly the fact that new graduates often return to their former positions with little opportunity to utilize fully their new skills. Those who succeeded best tried to merge health education with their basic professional practice (for example, nursing with patient education). ARHEC decided therefore to modify the programme of its advanced diploma course, which now provides for the teaching of a basic core of health education subjects to all students, and includes three modules to which students are assigned according to their previous training and their future professional activities: community health education and primary health care; hospital-based patient and family health education; and school health education. The practical field work, which is an essential aspect of the course, is tailored to the interests of students in each module. Preliminary evaluation indicates that this programme provides a better response to the needs of students and their employers and eliminates the problem of two categories of health educators (diploma and masters level). It is intended to create other modules dealing with the media, occupational health, and so on.

Clinical Competence↗
PubMed1981

Steroid 17 alpha-hydroxylase activity of ovarian granulosa cells from hypophysectomized immature rats treated with pregnant mare's serum gonadotropin (PMS).

Immature hypophysectomized rats were injected with 2mg of diethylstilbestrol to increase granulosa cell numbers and with 20 IU of PMS to stimulate ovarian growth. Steroid 17 alpha-hydroxylase activity of cultured granulosa cell, harvested from mature follicles 48 h after injection of PMS, was demonstrated using a tritium exchange assay with 17 alpha 3H-pregneneolone as substrate. For comparison, aromatase activity of the same cells was examined by a similar assay using 1 beta 3H-testosterone as the substrate. The activities of the two enzymes were similar when expressed in terms of the amount of substrate converted per unit time. While an NADPH generating system in the incubation medium was essential for demonstrating any hydroxylase activity, 10-15% of the total aromatase activity could be found without added cofactor. Attempts to alter hydroxylase activity of granulosa cells by inclusion of LH, FSH or prolactin in the incubation medium were unsuccessful. However, activity could be change by prostaglandins (PG) or agents which can alter PG synthesis. Activity was increased by low concentrations of phospholipase A2 (PLA2), histamine, and arachidonic acid (AA). Large doses of PLA2, or AA, were inhibitory. PGE2, but not PGF2 alpha, increased, while indomethacin decreased, hydroxylase activity. The results clearly indicate that granulosa cells in the rat have a potent 17-hydroxylase system and therefore do not support the widely held contention that lack of this enzyme is one of the bases for the need for two kinds of cells for ovarian estrogen production.

Animals↗