Biomedical subjects

T R Johnson

Publications and source records attributed to T R Johnson.

At least 145 records · Page 8Linked to original sources

PubMed1989

Multiple pregnancy with late death of one fetus.

Twenty cases of fetal death complicating a multiple pregnancy after 20 weeks' gestation are reviewed. We evaluated gestational age at diagnosis and delivery (29.3 +/- 0.7 and 31.8 +/- 0.9 weeks, respectively), interval from diagnosis to delivery (2.6 +/- 0.6 weeks), and cause of fetal death as a group and by type of placentation (76.5% monochorionic). Eighty-five percent of the surviving fetuses were delivered preterm, and the four neonatal deaths were all due to extreme prematurity, with a mean (+/- SEM) birth weight of 794 +/- 237 g. Perinatal mortality was 585 per 1000, 450 for twin A and 750 for twin B. The causes of fetal death varied. Maternal disseminated intravascular coagulation was not diagnosed in any pregnancy in the present series. The high risk of complications related to preterm birth, compared with the low risk of problems related to continuation of a multiple pregnancy after diagnosis of a fetal death, argues in favor of conservative management in this setting.

Female↗

PubMed1988

Auscultated fetal heart rate accelerations. III. Use of vibratory acoustic stimulation.

The auscultated acceleration test has been proposed as a simple, inexpensive screening test for fetal health; previous studies of the auscultated acceleration test used external stimulation to elicit fetal movement. This study was conducted to explore the ability of the auscultated acceleration test to predict nonstress test results when vibratory acoustic stimulation is used to elicit fetal reactivity. After antepartum nonstress testing on 100 gravid women between 28 and 43 weeks' gestation, a 6-minute auscultated acceleration test protocol was performed with two vibratory acoustic stimulations to the maternal abdomen if no spontaneous fetal heart rate acceleration occurred. The ability of the auscultated acceleration test to predict nonstress test results after selected variables were controlled for was as follows: sensitivity, 75%; specificity, 97.6%; false-positive results, 14.3%; and false-negative results, 4.7%. Logistic regression analysis indicated that, in addition to the auscultated acceleration test, gestational age and race contributed significantly to the prediction of nonstress test results. Although specificity and the false-positive rate were improved, the use of vibratory acoustic stimulations to elicit fetal movement did not improve the validity of the auscultated acceleration test in terms of sensitivity and false-negative results over previous studies. However, the auscultated acceleration test continues to show potential as an initial screening test for fetal assessment. In addition to recommendations for further research, methodologic issues related to sampling techniques are identified.

Acoustic Stimulation↗

PubMed1988

Regulation of nitrogenase gene expression in anaerobic cultures of Anabaena variabilis.

Derepression of nitrogenase gene expression was studied at the mRNA and enzyme activity levels in anaerobic cultures of Anabaena variabilis 29413. Cells, previously grown with ammonium chloride, were incubated in the absence of fixed nitrogen compounds under an Ar atmosphere with dichlorophenyldimethyl-urea present to inhibit oxygen evolution. The appearance of nitrogenase mRNA (measured by dot blot hybridization analysis) and nitrogenase activity (measured as acetylene-reducing activity) was followed, and the cells were also observed by phase-contrast microscopy. Nitrogenase mRNA could be detected after 1.5 to 2.0 h of nitrogen starvation; enzyme activity appeared about 1 h later. Although enzyme activity increased for many hours, mRNA levels reached a steady state rapidly. Neither heterocysts nor proheterocysts formed under these conditions; however, the cells were observed to shrink and become chlorotic. When anaerobic, derepressed cultures were exposed to oxygen, nitrogenase mRNA levels decreased very rapidly.

Anaerobiosis↗

PubMed1988

Effect of nitrogenous compounds on nitrogenase gene expression in anaerobic cultures of Anabaena variabilis.

The effects of several organic and inorganic nitrogen compounds on nitrogenase mRNA and enzyme activity levels were examined in anaerobic cultures of Anabaena variabilis 29413. Even low concentrations of exogenous ammonia (20 microM) prevented nitrogenase gene expression. Nitrate, in contrast, had little effect, even at very high concentrations. Neither compound had a significant direct effect on existing enzyme activity. The amino acids glutamine and glutamate did not repress nif gene expression. Methionine sulfoximine, but not 7-azatryptophan, was shown to eliminate the repressive effect of ammonia, and this action occurred at the mRNA level. Low concentrations of carbamyl phosphate caused a rapid decrease in nitrogenase mRNA levels. These results are consistent with the ideas that nif gene regulation in Anabaena spp. occurs primarily at the mRNA level and that ammonia, and possibly also glutamine and glutamate, is not the immediate effector of regulation.

Ammonia↗

PubMed1988

Structure and regulation of genes encoding phycocyanin and allophycocyanin from Anabaena variabilis ATCC 29413.

Gene clones encoding phycocyanin and allophycocyanin were isolated from an Anabaena variabilis ATCC 29413-Charon 30 library by using the phycocyanin (cpc) genes of Agmenellum quadruplicatum and the allophycocyanin (apc) genes of Cyanophora paradoxa as heterologous probes. The A. variabilis cpcA and cpcB genes occur together in the genome, as do the apcA and apcB genes; the two sets of genes are not closely linked, however. The cpc and apc genes appear to be present in only one copy per genome. DNA-RNA hybridization analysis showed that expression of the cpc and apc genes is greatly decreased during nitrogen starvation; within 1 h no cpc or apc mRNA could be detected. The source of nitrogen for growth did not influence expression of the genes; vegetative cells from nitrogen-fixing and ammonia-grown cultures had approximately the same levels of cpc and apc mRNAs. Heterocysts had less than 5% as much cpc mRNA as vegetative cells from nitrogen-fixing cultures. Northern hybridization (RNA blot) analysis showed that the cpc genes are transcribed to give an abundant 1.4-kilobase (kb) RNA as well as two less prominent 3.8- and 2.6-kb species. The apc genes gave rise to two transcripts, a 1.4-kb predominant RNA and a minor 1.75-kb form.

Cyanobacteria↗

PubMed1987

Proliferation of group B streptococci in human amniotic fluid in vitro.

The group B Streptococcus is one of the most virulent organisms causing perinatal infection. Human amniotic fluid from the second and third trimesters was pooled and analyzed for electrolytes, protein, albumin, zinc, inorganic phosphorus, ferritin, lysozyme, and immunoglobulins. We inoculated replicates of specimens with known virulent strains of group B streptococci (893, 891, and 878) and Escherichia coli (C5) with Todd-Hewitt broth and normal saline solution used as controls. Group B streptococci strains 893 and 891 proliferated rapidly at rates similar to their rates in Todd-Hewitt Broth. Strain 878 grew at a rate slower than that of strains 893 and 891. The amniotic fluid specimens were similar with respect to factors reported as inhibitory to bacterial proliferation. Second- and third-trimester amniotic fluid supports the growth of group B streptococci as well as a culture medium optimized for bacterial growth. Strain-specific variance in group B streptococci growth rates in amniotic fluid may have clinical significance for those at risk for group B streptococci infection.

Amniotic Fluid↗

PubMed1987

Leukocyte esterase activity in human amniotic fluid for the rapid detection of chorioamnionitis.

Chorioamnionitis plays an important role in perinatal morbidity and mortality. Fast and accurate diagnosis poses a major problem. A prospective study was performed to assess the value of positive leukocyte esterase test (Chemstrip 9) for the diagnosis of chorioamnionitis during labor. We evaluated 21 patients with chorioamnionitis in labor at term and used 21 matched control subjects. The sensitivity and specificity of leukocyte esterase activity were compared with those of amniotic fluid cultures, Gram stains, maternal pyrexia and leukocytosis, and fetal tachycardia. The sensitivity in diagnosing chorioamnionitis was 91% and the specificity was 95%. The use of this test strip could provide a rapid, inexpensive screening test for chorioamnionitis.

Amniotic Fluid↗

PubMed1987

Effects of alterations of zinc-to-phosphorus ratios and meconium content on group B Streptococcus growth in human amniotic fluid in vitro.

Several authors have described the bacterial growth-altering properties of amniotic fluid. We examined Group B Streptococcus growth in aseptically obtained amniotic fluid in vitro after altering its zinc, phosphorus, and meconium contents. Zinc and phosphorus levels were calculated in amniotic fluid and in meconium. Separate solutions of zinc and phosphorus were added to yield concentrations of 0.7, 7.0, 70, and 700 mumol. The solutions were incubated with Group B Streptococcus III 893 and Escherichia coli C5 strains, and 24-hour growth curves were plotted. Meconium, 0.5 mg/ml, was added to each amniotic fluid + zinc and amniotic fluid + phosphorus solution, and growth curves were plotted. The rate of proliferation of Group B Streptococcus varied directly with the zinc concentration (700 = 70 greater than 7 greater than 0.7 mumol) and inversely with the phosphorus content (700 less than 70 less than 7 = 0.7 mumol). Meconium enhanced the proliferative effect of zinc and hindered the inhibitory effect of phosphorus. Thus one possible mechanism whereby meconium enhances bacterial growth in amniotic fluid may be by alteration of zinc-to-phosphorus ratios.

Amniotic Fluid↗

PubMed1987

Umbilical cord blood pH and Apgar scores as an index of neonatal health.

In an effort to determine the clinical usefulness of Apgar scoring and cord pH in neonatal management, specimens of umbilical cord blood were obtained after 257 of 329 consecutive deliveries at a community-based hospital. A notable number of babies who were born in a vigorous state were in fact acidotic (umbilical arterial pH greater than 1 SD below mean). Seventy-two percent of acidotic babies had an Apgar score greater than 7 at 1 minute, and 92% had an Apgar score greater than 7 at 5 minutes. Correlation coefficients of Apgar scores at 1 and 5 minutes and arterial pH with the health status of newborn infants were poor. A chi 2 analysis of arterial pH and Apgar scores at 1 and 5 minutes indicated that a larger number of sick babies had an Apgar score less than 7 and acidosis than expected by pure chance. However, the sensitivity values of the Apgar score at 1 minute (0.48) and 5 minutes (0.24) and the arterial pH (0.40) for predicting sick children limit the clinical usefulness of these tests. While technically feasible in a community hospital, routine cord pH measurements add little to neonatal evaluation and management.

Acid-Base Equilibrium↗

PubMed1987

Fetal heart rate patterns associated with amniotic fluid embolism.

Two cases with recorded fetal heart rate response during maternal amniotic fluid embolus are reported. Fetal heart rate abnormalities can be associated with the development of amniotic fluid embolus or occur during the acute events of amniotic fluid embolus. Attention to the management of amniotic fluid embolus in the mother must not neglect the fetus. Improvement of maternal oxygenation and perfusion can effect intrauterine resuscitation; however, when this is not successful early delivery of the fetus may be necessary for its survival.

Adult↗

PubMed1987

Prepartum diagnosis of limb-shortening defects with associated hydramnios.

Two cases of skeletal dysplasia with limb-shortening abnormalities are presented. In association with the skeletal abnormalities, gross hydramnios was noted. A review of the existing literature reveals that coexistent fetal skeletal dysplasia and hydramnios have an extremely poor prognosis, especially in the nonachondroplastic patient with singleton fetus. The two cases presented here and the accompanying review emphasize the importance of recognizing this association in providing appropriate counseling to parents.

Adult↗

PubMed1987

Cardiac hypertrophy in chick embryos induced by hypothermia.

A decrease in incubation temperature from 38 to 32 degrees C elicits a decrease in chicken embyro size and weight with concomitant heart enlargement if done after day 10 of incubation. When assayed at day 18 of incubation with the hypothermia started on day 11 or 14, evidence is presented that the heart enlargement is an hypertrophy with no detectable hyperplasia. Supporting data are presented for various physical parameters showing increases in heart wet and dry weight, volume, area, wall thickness, and cell size. There was little difference in DNA content and nuclear [3H]thymidine labeling index between hearts of control and hypothermic embryos. Hearts of hypothermic embryos showed a slight increase in water content and considerable increases in RNA, protein, and glycogen content per unit DNA. The average size of polysomes isolated from hypothermic hearts was larger than that of polysomes isolated from controls. Microscopic studies showed no obvious increase in amount of capillary beds, connective tissue, and myocardial cells. Annulate lamellae were found only in myocardial cells of hypothermic embryos in sparse amounts and low frequency but always associated with large deposits of glycogen.

Animals↗

PubMed1987

Fetal viral myocarditis and congenital complete heart block in a pregnancy complicated by systemic lupus erythematosus. A case report.

Congenital complete heart block has been associated with collagen vascular disorders. Many etiologies have been proposed for the myocarditis that develops and results in the complete heart block. Transplacental antibody transfer--specifically, antibodies to tissue-soluble ribonuclear protein antigen-A--has been implicated as the etiology of the myocarditis. This case supports the association of this antibody while suggesting that viral infection may serve as an initiator of the autoimmune destruction. Also, fetal viral infection alone must be considered a possible cause of congenital complete heart block.

Adult↗

PubMed1987

Frequency analysis of augmented CTL production associated with Corynebacterium parvum-induced tumour regression.

A limiting-dilution frequency assay was employed to estimate the increased production of cytolytic T lymphocytes (CTL) associated with Corynebacterium parvum-induced regression of the P815 mastocytoma growing subcutaneously in semisyngeneic mice. It was found that intratumour C. parvum functioned to augment greatly the underlying concomitant production of CTL that occurs normally in response to a progressively growing untreated immunogenic tumour. The lymph node draining a C. parvum-treated tumour contained about eight times more CTL than the lymph node draining a control tumour. Intratumour C. parvum also caused a large increase in CTL production in the spleen and an increase in the number of CTL that could accumulate in a peritoneal exudate. At the peak of the anti-tumour response, the largest number of CTL was found in the draining lymph node (1.66 X 10(5], followed by the spleen (3.47 X 10(4) and by a 24-hr casein-induced peritoneal exudate (6.01 X 10(3]. Presumably, this greatly augmented production of CTL explains why C. parvum given intralesionally early enough during tumour growth can cause the regression of the weakly immunogenic P815 mastocytoma.

Animals↗

PubMed1986

Surgical emergencies of the uterine adnexae during pregnancy.

During the 5-year period 1976-1980, seven cases of emergent surgical disease of the adnexae during pregnancy were encountered. The incidence of 1:1832 deliveries approximated that of appendicitis (1:1603 deliveries) during the same period. There were three cases of adnexal torsion, two ruptured ovarian cysts with hemorrhage, one heterotopic pregnancy, and one ruptured endometrioma. The right side was more commonly the site of the pathology, and abdominal pain the only consistent presenting symptom. Fever, tachycardia, and leukocytosis were inconsistent findings. Culdocentesis was positive in two cases. Four desired pregnancies were carried successfully to term postoperatively. Surgical emergencies of the adnexae will be encountered during pregnancy more commonly than is generally recognized. Aspects of obstetric management are described. If prompt surgical intervention is undertaken in pregnancy when the clinical picture suggests an acute abdomen, a satisfactory outcome can be expected.

Adnexal Diseases↗

PubMed1986

Assessing gestational age.

Decision making in obstetrics is based on accurate knowledge of fetal gestational age. Menstrual dating based on the last menstrual period is an accurate method for estimating gestational age. Other reliable indicators are fundal height, quickening, the date that the fundus reaches the umbilicus and the date that fetal heart tones are first auscultated. Combinations of these data approach the reliability of menstrual dating. Biochemical assays are useful in early pregnancy. Ultrasound is indispensable when the clinical situation is questionable.

Chorionic Gonadotropin↗

PubMed1985

Leukocyte esterase activity in the rapid detection of urinary tract and lower genital tract infections in obstetric patients.

Infections of the vagina and urinary tract are important problems for the obstetrician. Examination of the vaginal discharge and urine for the presence of leukocytes is an important part of the evaluation for vaginitis and urinary tract infections. Neutrophils contain several esterases that are not present in serum, urine, or vaginal secretions. These esterases are not influenced by bacteria, commonly used drugs, or variable compositions of urine or vaginal secretions. A prospective study was performed to assess the sensitivity and specificity of leukocyte esterase activity as measured by dipstick (Chemstrip 9, Biodynamics) for the prediction of vaginitis and urinary tract infections during pregnancy. Results were compared with those obtained from potassium hydroxide smears, wet preps, and urine cultures. The vaginal discharge and urine of 65 patients was tested for leukocyte esterase activity on their initial OB visit. Leukocyte esterase was 100% sensitive and 100% specific for detecting urinary tract infections. It was 100% sensitive and 90% specific for predicting vaginal infections. Trichomonas infections accounted for the positive leukocyte esterase results when the urine culture was negative. On the basis of this study we believe that leukocyte esterase activity is sufficiently sensitive and specific to permit use of this test as a rapid and inexpensive screening procedure for vaginitis and urinary tract infections.

Chlamydia Infections↗

PubMed1985

Hybrid selection of messenger ribonucleoprotein for serum albumin: analysis of specific message-bound proteins.

The messenger RNA for chicken serum albumin together with its specific binding proteins was purified by hybrid selection using filter-bound cloned albumin cDNA. Under conditions where hybridization of the protein-mRNA complex was specific for the immobilized cDNA sequence, no dissociation of the complex into its protein and RNA components was apparent. Electrophoretic analysis of albumin mRNA-specific binding proteins showed three major bands. Two of these were prominent in total poly(A) messenger ribonucleoprotein. The third band was of much greater relative intensity in the albumin mRNA-specific proteins than in total poly(A) messenger ribonucleoprotein. The results suggest that the proteins bound to albumin mRNA represent only a subset of the total population of poly(A) mRNA-associated protein.

Animals↗