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Biomedical subjects

J M Pollock

Publications and source records attributed to J M Pollock.

86 records · Page 5Linked to original sources
PubMed1986

Fetomaternal transplacental hemorrhage during pregnancy and after delivery.

One third of very weakly Rh-immunized women show no increase in their level of Rh immunization during pregnancy and after delivery. Administration of 300 micrograms of Rh immune globulin at 6-week intervals does not alter the incidence of lack of progression of Rh immunization in such women. Thirty-three Rh-positive women who ultimately delivered ABO-compatible babies, had Kleihauer fetal transplacental hemorrhage (TPH) screening tests carried out at 2-week intervals during pregnancy and shortly after delivery. One third of the 33 women had no detectable TPH or a TPH of 0.01 ml of fetal red cells. We conclude that one third of weakly Rh-immunized women failed to show any progression of their Rh immune response during pregnancy or after delivery because they were exposed to too few fetal red cells (0.01 ml or less) to produce such a response.

ABO Blood-Group System↗
PubMed1985

Transplacental fetal hemorrhage after amniocentesis.

A retrospective survey of Winnipeg Rh laboratory data from January 1, 1981 to December 31, 1984 determined that, despite placental localization, 2.6% of 974 women having amniocenteses performed at 16 to 18 weeks' gestation for genetic reasons and 2.3% of 1215 women having amniocenteses performed between 32 and 38 weeks' gestation had fetal-maternal transplacental hemorrhages greater than or equal to 0.1 mL of fetal red cells due to placental trauma. In 1.6 and 1.8%, respectively, the fetal transplacental hemorrhages were greater than or equal to 1 mL. Four of 99 alloimmunized women undergoing 257 amniocenteses for determination of severity of fetal erythroblastosis had fetal transplacental hemorrhages all greater than 5 mL of fetal red cells. The 1.9% incidence of fetal transplacental hemorrhages after amniocentesis in alloimmunized women is 83% less than the 11.2% incidence that occurred in the authors' institution from February 1963 to December 1966. However, in three of the four women, there was a very rapid rise in Rh antibody titer and increased severity of Rh fetal disease. Only the alloimmunized woman who meets strict criteria, indicating that her fetus is at risk of fetal death, should be subjected to amniocentesis, and then only after careful placental localization by ultrasound. Because fetal transplacental hemorrhages occur after amniocentesis despite ultrasound placental localization, 300 micrograms of Rh immune globulin should be administered to all unimmunized Rh negative women after amniocentesis.

Amniocentesis↗
PubMed1984

Reversal of Rh alloimmunization. Fact or fancy?

The Rh Laboratory could find no evidence that Rh immune globulin (RhIG) reduced the incidence of progression of Rh immunization in a clinical study of 36 weakly Rh-immunized women given 300 micrograms of RhIG at 6-week intervals during pregnancy and after delivery, and in a retrospective study of the natural course of weak Rh immunization in pregnant Rh-negative women not given RhIG and others given RhIG at 28 weeks' gestation and/or after delivery of an Rh-positive baby. Although the failure of about one-third of weakly immunized Rh pregnant women to show any progression of their Rh immunization may be due to relative immune unresponsiveness in some, we believe that most do not have any increase in their Rh immunization because they have no further exposure to Rh-positive fetal red cells. Serial Kleihauer testing of pregnant women at 2-week intervals is being carried out to test this hypothesis.

Blood Group Incompatibility↗
PubMed1983

Intrauterine transfusion: kinetics of absorption of donor cells in fetal lambs.

The absorption of red cells from the peritoneal cavity of fetal lambs was studied in 29 pregnant ewes at approximately 120 days' gestation. Onset of absorption was early, absorption was rapid, and virtually complete absorption was shown in 96% of the fetuses by 92 hours after intrauterine transfusion. The mean time to complete 99% absorption was 75.8 hours, about half the time supposed for human fetuses. The rate of absorption and the maximum level of donor cells in the fetal circulation are both directly related to the transfusion volume. The time required to complete absorption does not vary with the volume transfused: The more blood given at intrauterine transfusion, the faster the fetus absorbs it. This study suggests that absorption in the fetus following intrauterine transfusion is very efficient, and may be faster than previously thought.

Absorption↗
PubMed1982

Placental transfer of Rh antibody (anti-D IgG) during pregnancy.

Anti-D levels in blood taken immediately postpartum from Rh-negative women who have been given antenatal Rh immune globulin and the anti-D levels in the cord blood of their babies were measured semiquantitatively by a low ionic polybrene Auto Analyzer technique. When both mother and baby were Rh-negative a comparison of their anti-D levels was made against the interval between injection of the passive anti-D and delivery. Mothers' levels decreased as the interval increased, the regression coefficient for 73 maternal sera was -0.74. The drop in levels of cord blood was much less than that of the mothers' levels. The regression coefficient was -0.294 for 74 cord sera (one set of twins). The marked difference between cord blood and maternal blood levels of anti-D at delivery supports the hypothesis that the transfer of IgG across the placenta is predominantly from mother to fetus and not from fetus to mother.

Binding Sites, Antibody↗
PubMed1980

WinRho: Rh immune globulin prepared by ion exchange for intravenous use.

An Rh immune globulin [Rh IgG] for intravenous use, WinRho, has been prepared by the Winnipeg Rh Institute by a modification of the ion-exchange column method of Hoppe and colleagues. When administered to Rh-negative male and nonpregnant female volunteers WinRho was found to be nonpyrogenic, nontoxic, safe and protective against Rh alloimmunization. In a clinical trial with 240 microgram given at about 28 weeks' gestation and 120 microgram given after delivery to Rh-negative women at risk of Rh immunization WinRho was effective in preventing Rh immunization. Of the 870 women carrying Rh-positive fetuses who were treated with WinRho during pregnancy and were not tested several months after delivery 14 would have shown evidence of Rh immunization by the time of delivery if WinRho had been ineffective; none showed such evidence. Of the 1122 women carrying Rh-positive fetuses who were retested 4 to 6 months after delivery 83 would have shown evidence of Rh immunization at that time if WinRho had been ineffective; only 1 showed such evidence. The efficiency of yield of anti-D with the modified method of production, the fct that it can be given intravenously (a route that causes the patient less discomfort and immediately results in high anti-D levels) and the lower levels of contaminating IgA and IgM make WinRho the preparation of choice for preventing Rh immunization.

Chromatography, Ion Exchange↗
PubMed1979

Chromatin fractionation procedure that yields nucleosomes containing near-stoichiometric amounts of high mobility group nonhistone chromosomal proteins.

Initial results of an approach to the isolation of functionally active chromatin are described. Slight digestion of mouse myeloma nuclei at 0 degrees C with micrococcal nuclease, followed by dialysis against near-physiological saline solution containing 1 mM Mg2+, caused release of up to 17% of the nuclear DNA as soluble nucleoproteins. This soluble (S) fraction was relatively depleted in H1 histones and methylated DNA (5-methylcytosine) but highly enriched in RNA, single-stranded DNA, and nonhistone chromosomal proteins, particularly two species of the high mobility group identified as HMG 1 and HMG 2. The S fraction released most rapidly (6--8% of the total DNA) consisted mainly of mono- and small oligonucleosomes. The mononucleosomes appeared normal in terms of sedimentation behavior, DNA length, and content of histones H2A, H2B, H3, and H4, but lacked H1, and instead were associated with approximately stoichiometric amounts of HMG 1 and HMG 2. Studies using isolated, fluorescence-labeled, total mouse HMG proteins indicated that added HMG 1 and HMG 2 do not bind strongly to S-fraction nucleoproteins but that two smaller HMG species (probably HMG 14 and HMG 17) do bind preferentially to S-fraction mono- and dinucleosomes. These results argue against artifactual redistribution of HMG 1 and HMG 2 during this fractionation but suggest caution in interpreting the distribution of smaller HMG proteins after digestion of chromatin. The potential relationship of this soluble fraction to transcriptionally active chromatin is discussed.

Amino Acids↗
PubMed1978

Rh isoimmunization during pregnancy: antenatal prophylaxis.

Of 3533 Rh-negative women who began a pregnancy without detectable Rh antibodies, 62 (1.8%) demonstrated evidence of Rh isoimmunization during pregnancy or within 3 days after delivery. All denied transfusions as well as abortions or previous pregnancies not followed by the administration of Rh immune globulin. Rh isoimmunization during pregnancy or within 3 days after delivery, which will not be prevented by the administration of Rh immune globulin after delivery, is the most important cause of residual Rh isoimmunization. A clinical trial of antenatal administration of Rh immune globulin, initially at 34 weeks's and subsequently at 28 and 34 weeks' gestation, in 1357 Rh-negative pregnant women who were delivered of Rh-positive babies, was effective in preventing the development of Rh isoimmunization during pregnancy or within 3 days after delivery. Antenatal prophylaxis with Rh immune globulin will be necessary if the incidence of Rh isoimmunization is to be reduced to its lowest possible level. Antenatal prophylaxis at 28 weeks' gestation is now an insured service in Manitoba.

Antibody Formation↗
PubMed1978

Antenatal prophylaxis of Rh isoimmunization: 28-weeks'-gestation service program.

Two (0.18%) of 1086 Rh-negative primigravidas or multigravidas treated similarly in all previous pregnancies, who were given a single injection of Rh immune globulin (300 mug) at 28 weeks' gestation and subsequently were delivered of Rh-positive babies, had demonstrable Rh isoimmunization at the time of that injection and must be considered "logistic" failures of antenatal prophylaxis. The remaining 1084 (who were treated again after delivery) had no evidence of Rh isoimmunization at delivery and none of the 512 screened at 6 months after delivery appeared to be immunized. If the 28th-week injection had not been protective, one would have expected 14 of the 1084 to have been demonstrably Rh isoimmunized and evidence of Rh isoimmunization to have persisted in 6 of the 512 observed 6 months after delivery.Six of 719 Rh-negative multigravidas who had not received Rh immune globulin after previous pregnancies or had been treated only after delivery showed evidence of Rh isoimmunization despite a single injection of Rh immune globulin at 28 weeks in a subsequent pregnancy. In three of the six the cause was most likely "sensibilization" due to previous exposure to Rh-positive blood or an untreated Rh-positive pregnancy. in 3 of the remaining 716 (0.42%) there may have been true failure of antenatal Rh prophylaxis administered at the 28th week. One would have expected this figure to be 12 of 716 if antenatal Rh prophylaxis at 28 weeks' gestation were totally unsuccessful.It is concluded that a single intramuscular injection of Rh immune globulin, 300 mug, is 88% effective in preventing Rh isoimmunization during pregnancy in Rh-negative primigravidas and in multigravidas treated antenatally in all previous pregnancies, and is 75% effective in preventing Rh isoimmunization in Rh-negative multigravidas untreated during previous pregnancies. The majority of failures are due to Rh isoimmunization during pregnancy prior to antenatal prophylaxis at 28 weeks.

Antibody Formation↗
PubMed1978

Methylation of DNA in early development: 5-methyl cytosine content of DNA in sea urchin sperm and embryos.

By separating formic acid hydrolysates with high pressure chromatography on an Aminex-10 column, we determined the ratio of 5-methyl cytosine to cytosine and other bases of DNA from sea urchin sperm and nuclei of embryos from early cleavage through pluteus stages. Contrary to several previous reports, we could not find any measurable changes in the methylation levels of embryonic nuclear DNAs at different stages of development. We also found no consistent differences between the methylation levels of sea urchin sperm and embryonic nuclei or the 5-methyl cytosine content of fish (Mugil cephalus) sperm and liver nuclei. While these measurements would not have detected subtle variations associated with differentiation, they would have indicated the gross changes previously reported for embryos or between sperm and somatic nuclei had those changes been present.

Animals↗