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Biomedical subjects

J Singer

Publications and source records attributed to J Singer.

At least 91 records · Page 5Linked to original sources
PubMed1985

The concentration of IgG in the serum is a major determinant of Fc-dependent reticuloendothelial function.

Defective Fc receptor-specific reticuloendothelial (RE) function has been reported in certain patients with a variety of immunologic and nonimmunologic diseases. The mechanism responsible for the impaired RE function is uncertain, but it could be caused by immune complexes that are present in many of these disorders. Alternatively, the impaired RE function could be a secondary effect of the high concentrations of monomeric IgG in the serum of these patients, since monomeric IgG can compete with complexed IgG for macrophage receptors in vitro. We studied the Fc-dependent RE function in 30 healthy control subjects and 27 patients using IgG-coated radiolabeled autologous red cells. There was a significant relationship between the concentration of IgG in the serum and the rate of clearance of antibody-sensitized cells (r = 0.51, P less than .01). Patients with hypergammaglobulinemia had the slowest Fc-dependent clearance, whereas those with hypogammaglobulinemia had the most rapid clearance. Immune complexes (Raji or polyethylene glycol) could not be shown to contribute to Fc-dependent RE clearance above the effect of the IgG in the serum. The unusually rapid clearance in a patient with hypogammaglobulinemia could be returned to normal by raising the concentration of IgG in the serum. This study supports the concept that serum (monomeric) IgG competes with immune complexed IgG for macrophage Fc receptors in vivo. The competition for Fc receptors determines the level of competence of Fc-dependent RE function. Based on the results of this study, one can predict that a number of disorders characterized by hypergammaglobulinemia also will have impaired Fc-dependent RE function.

Agammaglobulinemia↗
PubMed1984

Confirming evidence for the clonal development and stem cell origin of Philadelphia chromosome-negative chronic myelogenous leukemia.

A 74-year old woman with Ph1-negative chronic myelogenous leukemia (CML) and heterozygous for glucose-6-phosphate dehydrogenase (G6PD) was studied. Both A and B types of G6PD were found in skin. In contrast, white blood cells and platelets showed only a single G6PD type A. These results provide further evidence that Ph1-negative CML has a stem cell origin and develops clonally.

Aged↗
PubMed1984

Prevalence of nontraditional dental hygiene practice.

There is little knowledge of the number or the work characteristics of dental hygienists outside the private-practice setting. This survey was conducted to determine the percentage of hygienists practicing in nontraditional (nonprivate-practice) settings and the types of settings in which they are employed. Mail questionnaires were returned from a total of 21,847 (56.9%) of the hygienists in the survey sample. The percentage of active hygienists practicing in nontraditional settings was 11.8. Dental or dental hygiene schools, and government and nongovernment-supported clinics were the most frequent nontraditional practice settings. State supervision requirements were found to be associated significantly with the prevalence of nontraditional hygiene practice.

Dental Facilities↗
PubMed1984

Evidence for a multistep pathogenesis of a myelodysplastic syndrome.

Somatic cell genetic approaches utilizing the cellular mosaicism present in women heterozygous for glucose-6-phosphate dehydrogenase (G6PD) have provided information relevant to the pathogenesis of some neoplastic disorders. With these techniques, we studied a 61-year-old woman with a myelodysplastic syndrome. GdB/GdA heterozygosity was demonstrated in skin and cultured T lymphocytes, which exhibited both A and B type G6PD. In contrast, erythrocytes, platelets, granulocytes, and marrow nucleated cells displayed almost exclusively G6PD type B. In addition, 21 of 24 Epstein-Barr virus-transformed B lymphoblastoid lines that expressed a single immunoglobulin light chain showed only type B G6PD, suggesting that the stem cells involved by this disease were clonal and could differentiate to B lymphocytes as well as to mature granulocytes, erythrocytes , and platelets. Cultured skin fibroblasts and phytohemagglutinin-stimulated lymphocytes were karyotypically normal, but two independent abnormalities were found in marrow--47,XX, +8 and 46,XX,del(11)(q23). None of 14 type B G6PD lymphoblastoid lines analyzed in detail contained these karyotypic abnormalities, which strongly suggests that a visible chromosomal alteration is not the sole step in the development of this disease. We hypothesize that at least two events are involved in the pathogenesis of this patient's myelodysplasia: one causing proliferation of a clone of genetically unstable pluripotent stem cells and another inducing chromosomal abnormalities in its descendants.

Bone Marrow Cells↗
PubMed1984

Secondary malignancies after marrow transplantation.

Secondary malignancies after marrow transplantation have been observed in 20 patients: 19 patients underwent marrow transplantation for the treatment of a hemopoietic malignancy and one for aplastic anemia. All but three were given total body irradiation at doses of 8.0-15.75 Gy as part of the conditioning regimen. Secondary malignancies were composed of three groups: (a) Six patients had recurrence of leukemia (three acute lymphoblastic, two acute myeloblastic, and one chronic myelocytic) in cells of donor origin 62-1074 days after grafting. (b) Eight patients developed lymphoproliferative disorders (four of immunoblastic sarcoma type, one lymphoblastic, one follicular center cell, and one Hodgkin's lymphoma and one acute lymphoblastic leukemia) 54-730 days after grafting. In four of seven patients with appropriate studies these tumors were of donor-cell origin and in three of four tested the cells contained Epstein-Barr virus genome or expressed viral antigens. (c) Six patients developed solid tumors (two glioblastoma multiforme, two adenocarcinomas, one squamous cell carcinoma, and one sarcoma) 347-1875 days after grafting. All but two patients (one with glioblastoma and one with squamous cell carcinoma) have died. These data suggest that patients undergoing marrow transplantation for a hemopoietic malignancy may be at risk of developing secondary malignancies. The etiology appears to be multifactorial, including irradiation, immunosuppression, Epstein-Barr virus infections, and other factors.

Adolescent↗
PubMed1983

Graft-versus-host disease and survival in patients with aplastic anemia treated by marrow grafts from HLA-identical siblings. Beneficial effect of a protective environment.

One hundred thirty patients with severe aplastic anemia were conditioned with cyclophosphamide for transplantation of marrow from HLA-identical siblings. The patients were selected for the present analysis according to the criterion of sustained marrow engraftment. Of the 130 patients, 97 are now alive between 1.4 and 11 years (median, 5) after transplantation. Twenty-nine of the thirty-three who died had either acute or chronic graft-versus-host disease (GVHD). Our analysis was directed at identifying factors predicting GVHD and survival after transplantation in patients. Our key findings were that moderately severe to severe acute GVHD had a strong adverse influence on survival; that a protective environment significantly reduced mortality, which corresponded in part to a reduction in and delayed onset of acute GVHD; that refractoriness to random-donor platelet infusions at transplantation adversely influenced survival, particularly among patients with acute GVHD; and that increasing age was associated with increased mortality.

Adult↗
PubMed1982

Treatment of chronic granulocytic leukaemia in chronic phase by allogeneic marrow transplantation.

Ten patients with chronic granulocytic leukaemia in the chronic phase have been treated with chemoradiotherapy followed by transplantation of bone marrow from HLA-identical siblings. Engraftment was achieved in all patients, and Philadelphia chromosome disappeared from the nine patients who had it before transplantation. Four patients have died, three with interstitial pneumonitis and one with severe graft-versus-host disease (GvHD). Six patients are alive and well in complete clinical, cytogenetic, and haematological remission, 1-3 years after transplantation, despite complications in three patients (one had interstitial pneumonitis, one had mild veno-occlusive disease of the liver, and one had severe GvHD).

Adult↗
PubMed1979

Methylation of DNA in mouse early embryos, teratocarcinoma cells and adult tissues of mouse and rabbit.

The distribution and amount of 5-methylcytosine (5-MeCyt) in DNA was measured for early embryos of mouse strain CF1 (2 to 4 cell stage to blastocyst) and mouse teratocarcinoma cells. In each case, the pattern of methylation was examined by use of the restriction enzymes Hha I and HPA II HPA II, which cut DNA at the sites 5'GCGC and 5'CCGG respectively, when the cytosines at these sites are not methylated. Mouse embryo DNA was found to have the same level of methylation as adult mouse tissues, and no changes in methylation were seen during differentiation of the teratocarcinoma cells. The ratio of 5-MeCyt/Cyt in DNA was measured by high performance liquid chromatography for the differentiating teratocarcinoma cells and for several adult mouse and rabbit tissues. The variation between tissues or between teratocarcinoma cells at different stages of differentiation was less than 10 percent. These results are discussed in view of proposals that 5-MeCyt plays a role in differentiation.

Animals↗
PubMed1979

Methylation of mouse liver DNA studied by means of the restriction enzymes msp I and hpa II.

The restriction enzymes Hpa II and Msp I both recognize the sequence 5'-CCGG (C, cytosine; G, guanine). However, Hpa II cuts mouse liver DNA to fragments four times larger than does Msp I. The size of DNA cut by Msp I is close to that predicted from base composition and nearest neighbor analysis. The most probable explanation of these results is that in mouse the site 5'-CCGG is highly methylated.

Animals↗
PubMed1979

Antepartum determination of pre-ejection period of fetal cardiac cycle: its relation to newborn body weight.

Simultaneous recordings of the fetal electrocardiogram and ultrasound Doppler-cardiogram were used for the determination of the pre-ejection period (PEP) of the fetal cardiac cycles. All 50 fetuses selected for the present study experienced uneventful perinatal lives despite maternal antepartum complications which required hospitalization. A significant positive correlation between the PEP and gestational age of the fetuses was again demonstrated. The PEP of the fetus measured within one week prior to delivery was also found to be significantly correlated with the newborn body weights at birth. Statistical analysis demonstrates that fetal body weight was more closely related to the physiologic lengthening of the PEP.

Birth Weight↗
PubMed1979

Avoiding patient relation stress in an orthodontic practice.

1. Consumer rights apply to the practice of orthodontics as well as other areas of health care. 2. To avoid consumer complaints, the orthodontist must be prepared to deal with personality problems as well as treatment complications in his practice. 3. Only by careful questioning of the patient before treatment will the orthodontist be able to detect possible future problems. 4. An explanation of informed consent by the orthodontist and an acknowledgement of it in writing, signed by the parent or responsible party, is now regarded as essential to avoid misunderstandings and complaints. 5. An informed patient leads to a better relationship with the orthodontist as well as a healthier atmosphere in which to practice.

Communication↗