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Biomedical subjects

D Paul

Publications and source records attributed to D Paul.

At least 163 records · Page 9Linked to original sources
PubMed1987

Expression of functional cell-cell channels from cloned rat liver gap junction complementary DNA.

An oocyte expression system was used to test the relation between a complementary DNA (cDNA) clone encoding the liver gap junction protein and cell-cell channels. Total liver polyadenylated messenger RNA injected into oocytes induced cell-cell channels between paired oocytes. This induction was blocked by simultaneous injection of antisense RNA transcribed from the gap junction cDNA. Messenger RNA selected by hybridization to the cDNA clone and translated in oocyte pairs yielded a higher junctional conductance than unselected liver messenger RNA. Cell-cell channels between oocytes were also formed when the cloned cDNA was expressed under the control of a heat-shock promoter. A concentration-dependent induction of channels was observed in response to injection with in vitro transcribed gap junction messenger RNA. Thus, the liver gap junction cDNA encodes a protein that is essential for the formation of functional cell-cell channels.

Animals↗
PubMed1987

Human-immunodeficiency-virus infections in infants negative for anti-HIV by enzyme-linked immunoassay.

Of 85 children with human-immuno-deficiency-virus (HIV) infection based on clinical (opportunistic infection), epidemiological (mother a drug addict or known to be HIV infected), and immunological (helper-T-cell deficiency and impaired proliferative response to pokeweed mitogen) features, 9 were found to lack antibody to HIV as measured by a commercial enzyme-linked immunoassay (ELISA). All 9 children had detectable levels of HIV antigen in simultaneous plasma specimens, measured by a sensitive antigen-capture ELISA. The use of the western blot assay and an ELISA with recombinant HIV antigens was able to identify HIV infection in 4 of the 9 children.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Transformation of differentiated neonatal rat hepatocytes in primary culture by polyoma virus early region sequences.

Neonatal rat hepatocytes (NRH) in primary cultures were transformed upon transfection with plasmid pSV 5-neo containing polyoma virus (Py) early region sequences. Clones of cells (Py-NRH) resistant to the antibiotic G418 were obtained after selection in arginine-deficient medium with serum, epidermal growth factor (EGF), transferrin and insulin. They did not undergo senescence during serial subcultivation. One clone (Py-NRH Cl A) harbored a single integrated copy of Py early region sequences and expressed transforming Py genes, hepatocyte-specific transcripts, including albumin, alpha-fetoprotein (AFP) and tyrosine aminotransferase (TAT) mRNAs. Subclones isolated after about 45 cell doublings still contained albumin and AFP, but no TAT mRNAs, indicating that long-term stabilization of liver functions is not necessarily permanent unless selected for (e.g. arginine synthesis). Cells grew unrestricted in medium containing insulin and no longer required EGF. Cells grew in agar, secreted a beta-transforming growth factor-like activity into the medium and were tumorigenic in nude mice. Hybridization studies using v-erbB DNA as a probe showed that Py-NRH, unlike neonatal hepatocytes in primary culture, express the EGF receptor gene at low or undetectable levels. Py-NRH Cl A and a subclone (5A) derived from it, however, contained elevated levels of rat c-neu oncogene-related RNA, whereas levels in another subclone (3A) were low or undetectable. These findings demonstrate that a proto-oncogene was activated after transfection of hepatocytes with DNA tumor virus transforming genes. However, the expression of c-neu oncogene is not related to the maintenance of the transformed state.

Animals↗
PubMed1987

Doppler evaluation of umbilical venous and arterial blood flow in the second and third trimesters of normal pregnancy.

Duplex Doppler ultrasound was used to measure umbilical venous blood flow in 209 normal pregnant women between 20-40 weeks' gestation. The relationship between umbilical venous blood flow and gestational age increased with gestational age, and is described by the equation y = -187.02 + 12.7x. The relationship between flow per kilogram fetal weight and gestational age (y = 198.629 - 2.24x) yielded values of 153 mL/minute/kg at 20 weeks, 131 mL/minute/kg at 30 weeks, and 108 mL/minute/kg at 40 weeks. Doppler ultrasound was also used to evaluate umbilical arterial waveforms (systolic/diastolic ratio) in 171 normal pregnant women between 20-40 weeks. The relationship between systolic/diastolic ratios and gestational age (y = 6.46 - 0.12x) decreased with advancing gestational age, yielding mean systolic/diastolic ratios (+/- 2 SD) of 4.1 (5.6, 2.6) at 20 weeks, 3.6 (5.1, 2.1) at 24 weeks, 3.1 (4.6, 1.6) at 28 weeks, 2.6 (4.1, 1.1) at 32 weeks, 2.1 (3.6, 0.6) at 36 weeks, and 1.7 (3.1, 0.1) at 40 weeks.

Blood Flow Velocity↗
PubMed1987

Cyclic adenosine monophosphate stimulates biosynthesis and phosphorylation of the 26 kDa gap junction protein in cultured mouse hepatocytes.

Hepatocytes prepared from 18-day-old mouse embryos were grown in serum-free medium and reached confluence after two days in culture. The total amount of the 26 kDa gap junction protein decreased in these cells during the first 24 h in culture and increased again between day 1 and day 3 more than 10-fold. At day 3 a half-life time of 2.5 to 3 h was determined for the 26 kDa protein by [35S]methionine incorporation and immunoprecipitation using affinity-purified anti-26 kDa. Incorporation of [32P]orthophosphate into the 26 kDa protein of cultured hepatocytes was found at serine residues (98%) and tyrosine residues (about 2%). The addition of dibutyryl cyclic adenosine monophosphate (db cAMP) to the culture medium at day 2 had two effects: After 15 min the extent of phosphorylation of the 26 kDa protein increased 2.7-fold whereas the total amount of the 26 kDa protein increased only 1.2-fold. After 3 h of incubation with db cAMP, a 2.5-fold increase of the 26 kDa protein was noticed which was accompanied by a 3.2-fold increase in phosphorylation of serine residues. The effects of db cAMP on phosphorylation of the 26 kDa protein could be augmented or mimicked by the addition of isoproterenol, theophylline or forskolin to the culture medium of hepatocytes. In extracts of rat hepatocarcinoma MH1C1 cells and dog kidney MDCK cells, a phosphorylated 26 kDa protein can be immunoprecipitated using anti-liver 26 kDa. These results demonstrate that the gap junction 26 kDa protein can be posttranslationally modified by cAMP-dependent phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Fetal blood flow measurements in severe rhesus isoimmunization. A case report.

Maternal isoimmunization can result in fetal anemia. Current management of isoimmunized pregnancies involves amniocentesis and spectrophotometry. Pulsed Doppler ultrasound can provide fetal blood flow determinations from the fetal umbilical vein. A pregnancy complicated by severe rhesus isoimmunization was studied with Doppler ultrasound. Increased fetal umbilical blood flow was associated with increased fetal hemolysis. Umbilical vein blood flow decreased after intrauterine transfusion. Doppler ultrasound assessment of fetal blood flow is a useful noninvasive adjunct in isoimmunized pregnancies.

Adult↗
PubMed1987

Fetal heart rate measurement during maternal exercise--avoidance of artifact.

The purpose of this study was to investigate the possibility that motion artifact may override the recording of fetal heart rate (FHR) with Doppler ultrasound fetal monitors during maternal exercise on cycle ergometers and treadmills, and to test the efficacy of two-dimensional ultrasound directed M-mode echocardiographs for determining FHR during maternal treadmill exercise. Four pregnant women (26 to 30 yr, means = 28, gestational age = 28 to 34 wk) pedaled a cycle ergometer at 25 to 50 W, while a second group (N = 4) (24 to 36 yr, means = 29, gestational age = 30 to 37 wk) walked on a treadmill at either 1.5 or 2.0 mph. Fetal monitor recordings (Hewlett-Packard 8040A) were consistent with pedal rate in the range of 50 to 70 rpm and with stepping rate in the range of 70 to 76 steps per min at 1.5 mph and 100 to 106 steps per min at 2.0 mph on the treadmill. Actual mean FHRs (audible signal from fetal monitor) were in the normal range [150.5 +/- 10.25 bpm (cycle ergometer) and 148.8 +/- 2.3 bpm (treadmill)]. In a separate session, the cycle ergometer group walked on a treadmill at a maternal heart rate of 140 bpm while FHR was determined by two-dimensional ultrasound directed M-mode echocardiographs. Off-line analysis of fetal cardiac cycle time (clinical graphics analyzer) allowed accurate FHR measurements which were not confounded by motion artifact. Mean FHR during maternal treadmill exercise (158.0 +/- 12.0 bpm) was not different (P greater than 0.05) when compared to pre-exercise standing (140 +/- 3.6) and also during the post-exercise period (sitting) (151 +/- 6.5) compared to the sitting pre-exercise measurements (147 +/- 8.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[X-ray computed tomographic diagnosis of connective tissue tumors of the stomach of extrinsic development. Apropos of 6 cases].

Computed tomography findings appear to be very useful for the diagnosis of exogastric tumors on the basis of six cases: 4 leiomyosarcomas, 1 leiomyoblastoma and 1 schwannoma. The diagnosis of these usually large tumors arising within the gastric wall is often difficult through baryum opacification of the stomach (U.G.I.) owing to their exogastric growth. In the same way, endoscopy usually fails to evidence these tumors. Computed tomography permits to rule out an extrinsic tumor such as a hepatic or pancreatic one for instance and then to demonstrate the tumor originates within the gastric wall. The hypervascular pattern associated in most cases with central necrosis is demonstrated through contrast medium injection, what is a very typical and relatively constant-finding in these tumors.

Aged↗
PubMed1986

Selective effects of pirenperone on analgesia produced by morphine or electrical stimulation at sites in the nucleus raphe magnus and periaqueductal gray.

Pirenperone, a new serotonin antagonist with a selective affinity for the 5-HT2 receptor, was administered in conjunction with tests for the antinociceptive effects of morphine sulphate and electrical brain-stimulation at sites in the periaqueductal gray (PAG) and nucleus raphe magnus (NRM). Nociception was assessed by tail-flick latencies in a warm water bath and pirenperone (0.04-0.16 mg/kg) had no effect on baseline scores. When administered prior to morphine, pirenperone (0.16 mg/kg) caused significant attenuation of analgesia induced by morphine. Comparable effects of pirenperone were observed when analgesia was produced by electrical stimulation of the NRM. In contrast, pirenperone had no effect on the analgesic effects of PAG stimulation. This pattern of results suggests that a system involving supraspinal 5-HT2 receptors may modulate some of the antinociceptive effects of morphine and stimulation of the NRM. The differential effects of pirenperone on stimulation-produced analgesia at sites in the NRM and PAG is consistent with separate neural substrates for the analgesia observed from stimulation of these two brain regions.

Animals↗
PubMed1985

[Significance of fracture form and bone necrosis for the treatment of open tibial fracture].

In a retrospective analysis the author deals with 370 open fractures of the tibia which were administered from 1961 to 1980. Treatment by plate osteosynthesis proved to be superior to conservative management (13% wound infections, 11,3% aseptic complications). Special importance is attached to the degree of soft tissue damage as a cause of osteonecrosis in certain types of fractures. By presenting a new classification scheme of fractures of the tibia the author is able to derive that kind of treatment which is required.

Adult↗
PubMed1984

Rat platelets contain growth factor(s) distinct from PDGF which stimulate DNA synthesis in primary adult rat hepatocyte cultures.

Adult rat hepatocytes in primary cultures are stimulated to synthesize DNA in response to rat serum, whereas rat plasma is considerably less active. Biological activity is present in rat platelets and is secreted during aggregation in response to thrombin. The material secreted by rat platelets is heat labile and is sensitive to digestion with trypsin, suggesting that it is a protein. When assayed on 3T3 cells this material also stimulates DNA synthesis; however, the trypsin-sensitive activity is heat stable (100 degrees C, 10 min). These results indicate that rat platelets contain hepatotrophic activities which by virtue of their heat sensitivity are distinct from heat-stable platelet-derived growth factor (PDGF)-like mitogenic activities required by 3T3 cells for growth. It is possible that hepatotrophic platelet factors might be involved in mediating liver regeneration in the rat after partial hepatectomy.

Animals↗
PubMed1982

Human platelet basic protein. Its relation to low affinity platelet factor 4 and beta-thromboglobulin.

Human beta-thromboglobulin, low affinity platelet factor 4 and platelet basic protein have been purified to homogeneity from the material released by thrombin-stimulated platelets. Purification steps included isoelectric focusing and heparin-agarose chromatography. Antibodies against each of these proteins have been raised in rabbits. Antigenic identity of the proteins has been demonstrated in radioimmunoassay using 125I-labelled platelet basic protein or 125I-labelled low affinity platelet factor 4 and a variety of antibodies. The molecular weight of platelet basic protein estimated by gel filtration in 6 M guanidine hydrochloride using Sepharose 6B corresponded to approx. 10 000 daltons, slightly higher than that of beta-thromboglobulin (8851 daltons) and low affinity platelet factor 4 (9278 daltons). These findings raise the possibility that the formation of low affinity platelet factor 4 beta-thromboglobulin may be a consequence of the action of proteolytic enzymes on platelet basic protein.

Amino Acid Sequence↗
PubMed1982

The in vivo effects of a polyamine analogue on tissue stem cell proliferation.

We have studied by autoradiography the effects of 1,3-diaminopropane (DAP) upon cellular proliferation in a number of tissues in vivo in the rat. DAP is a structural analogue of the naturally occurring polyamine putrescine, and is believed to block cellular polyamine synthesis by supressing the induction of ornithine decarboxylase (the rate-limiting enzyme for polyamine biosynthesis). The continuous infusion of DAP into rats that had been partially hepatectomised prevented the subsequent waves of spermidine and DNA synthesis from taking place in the regenerating liver. The inhibition of DNA synthesis is accounted for primarily by a block in the entry of hepatocytes into S phase and not by a reduction in the rate of DNA synthesis itself. In contrast to the regenerating liver, DAP exerted minimal effects upon the proliferation of the gut epithelium and bone marrow elements. The proliferation of stem cells of these latter tissues, which are normally in a state of rapid and continuous proliferation unlike the liver, is thus much more resistant to perturbations in polyamine biosynthesis and function. DAP is consequently unable to arrest and so protect normal rapidly proliferating tissues from damage caused by anti-cancer drugs (e.g. hydroxyurea) that kill only proliferating cells. DAP cannot therefore be employed to selectively protect normal cells but not tumour cells from cytotoxic damage according to a principle we have previously established in tissue culture.

Animals↗