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Biomedical subjects

L Ratner

Publications and source records attributed to L Ratner.

At least 145 records · Page 8Linked to original sources
PubMed1989

Human immunodeficiency virus type 1 negative factor is a transcriptional silencer.

The negative factor (nef) of human immunodeficiency virus (HIV) type 1 acts to down-regulate virus replication. To decipher the step in the virus life cycle affected by nef, functional proviral clones with (pHIV F-) or without (pHIV F+) a deletion mutation in the nef gene were constructed. In CD4+ cells, 30- to 50-fold more virus was produced over the course of 18-20 days with cultures infected with F- compared to F+ virus. In CD4- cell lines, 2- to 10-fold greater virus production was found from cultures transfected with pHIV F- than those transfected with pHIV F+. The negative regulatory effects of nef on pHIV F- could be supplied in trans with a plasmid expressing only the nef gene product. Virus produced by COS-1 cells transfected with pHIV F- or pHIV F+ showed similar binding, uptake, uncoating, and reverse transcription. Analysis of HIV-1 RNA and structural protein levels and rates of viral RNA synthesis in CD4- cells also showed 2- to 10-fold higher levels in cells transfected with pHIV F- compared to pHIV F+. The activity of a HIV-1-chloramphenicol acetyltransferase (CAT) plasmid was also suppressed by nef, whereas other CAT plasmids were unaffected. These findings demonstrate that nef acts as a specific silencer of HIV-1 transcription. This activity may be critical for maintenance of HIV-1 latency in vivo.

Animals↗
PubMed1989

Role of the carboxy-terminal portion of the HIV-1 transmembrane protein in viral transmission and cytopathogenicity.

The transmembrane glycoprotein (gp41) of human immunodeficiency virus type-1 (HIV-1) has a long cytoplasmic domain of unknown functional significance. To investigate the role of the carboxy-terminal (C-terminal) portion of the HIV-1 envelope protein in viral replication, infectivity, and cytopathogenicity, we examined the properties of a panel of mutants with variable deletions in the 3'-env region. Deletion of the C-terminal 76 amino acids did not abolish production of reverse transcriptase upon transfection of COS-1 cells. Deletion of the C-terminal 6-14 amino acids appeared sufficient to alter the replication pattern, infectivity, and cytopathogenicity of some clones. The data suggest that conformational determinants or specific sequences are responsible for the observed changes, rather than simply the length of the gp41 cytoplasmic tail.

Cytopathogenic Effect, Viral↗
PubMed1989

Analogs of 3'-amino-3'-deoxyadenosine inhibit HIV-1 replication.

Several different nucleoside analogs have been demonstrated to inhibit retroviral RNA-dependent DNA polymerase activity in preference to cellular DNA-dependent DNA polymerases. 3'-Amino derivatives of 3-deoxyadenosine was analyzed for their antiviral activity toward HIV-1 and for their host cell toxicity. Puromycin aminonucleoside (PANS), PANS 5'-monophosphate, and 3'-amino-3'-deoxyadenosine triphosphate all inhibited HIV-1 replication in acutely infected cells. No significant antiviral effects of PANS were demonstrated in chronically infected cells. The effect of PANS was demonstrated at an early step in HIV-1 replication, most likely reverse transcription. 3'-Aminonucleoside analogs are a novel class of inhibitors of HIV-1 replication that require further analysis in cell culture and animal studies.

Antiviral Agents↗
PubMed1989

Specificity of polymerase chain amplification reactions for human immunodeficiency virus type 1 DNA sequences.

The polymerase chain amplification reaction (PCR) is a sensitive, specific, and quantitative assay of human immunodeficiency virus type 1 (HIV-1). The assay was performed with polymerases from Escherichia coli or Thermus aquaticus (Taq). A single pair of oligonucleotide primers within the long terminal repeat (LTR) sequences were used to detect HIV-1 sequences in infected cell cultures and fresh tissues of the large majority of infected individuals. The amplified product was a faithful copy of this LTR sequence. Utilization of a subsaturating number of cycles of amplification allowed quantitation of HIV-1 DNA sequences.

Base Sequence↗
PubMed1989

Viral protein R of human immunodeficiency virus types 1 and 2 is dispensable for replication and cytopathogenicity in lymphoid cells.

Viral protein R (VPR) is conserved in human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2). To assess its function, we have constructed mutations within the vpr coding regions of HIV-1 and HIV-2 predicted to express truncated VPR products. Infectious virus was produced by each proviral clone and showed similar replication kinetics and cytopathogenicity when compared with the corresponding parental proviral clone.

Animals↗
PubMed1988

A study of change in clinical service for general surgical patients.

The department of surgery at Long Island Jewish Medical Center in New York City conducted a study examining resource consumption and quality of care for patients referred to surgery from other hospital services, or "referred patients." Referred patients were compared with "nonreferred" surgery patients using several indicators of resource consumption. A quality assessment was also performed on a random sample from both groups using peer review organization guidelines. The study found that referred patients consumed more resources and may have received poorer quality care than nonreferred patients. Previous studies suggest that some resource utilization by referred patients may be avoidable. Thus, referral to the department of surgery may serve as an indicator for identifying patients in need of ongoing quality and/or utilization monitoring.

Health Resources↗
PubMed1988

Leukemias associated with human T-cell lymphotropic virus type I in a non-endemic region.

Human T lymphotropic virus type 1 (HTLV-I) is a retrovirus which is prevalent in southern Japan, the Caribbean Basin, and Africa. Recent seroprevalence studies in the United States suggest that there are about 50,000 infected individuals. The identification of 5 individuals with HTLV-I-associated leukemia/lymphoma referred to our center with relatively limited screening methods suggests that these disorders are more common than currently appreciated. Though 99% of infected individuals remain asymptomatic, this virus may cause immunosuppression, lymphomas, or myelopathy. The lymphomas have been classified as acute or chronic forms of adult T cell leukemia-lymphoma (ATLL). Acute ATLL is a T cell form of non-Hodgkin's lymphoma in an HTLV-I-infected individual with leukemia, skin infiltration, or hypercalcemia. This disorder is poorly responsive to chemotherapy and all patients should be referred for experimental protocols. Chronic ATLL is an insidious disease characterized by lymphadenopathy, skin infiltration of less than 10% of the body surface, and/or atypical lymphocytes with highly convoluted nuclei which include 1 to 10% of the nucleated cells in the peripheral blood, but no visceral involvement or hypercalcemia. The prognosis of these patients is not clearly defined. All individuals with mature T lymphocytic malignancies should be evaluated with HTLV-I-specific assays. The most sensitive and specific assays available include the enzyme linked immunoadsorbent antibody assay (ELISA) and the polymerase chain DNA amplification reaction assay. With improved laboratory techniques and greater awareness of the characteristics of this disease by clinicians, it is likely that the natural history of HTLV-I infection will be better defined, and improvements in therapeutic management will be developed.

Adult↗
PubMed1988

DRGs, orthopedic surgery, and age at an academic medical center.

The federal Medicare Diagnostic Related Group (DRG) hospital reimbursement system has been on line for 5 years. Hospitals contend that profit margins have dropped to dangerously low levels, due to the federal DRG Prospective Payment System. The authors analyzed all orthopedic surgical admissions to a large academic medical center under DRG reimbursement and characterized patients by age, resource utilization, and outcome. Total costs for the 1,040 orthopedic patients analyzed during a 15-month period added up to $9,718,800. Mean hospital cost per patient, mean hospital length of stay, percent outliers, and mortality generally increased with age. All age categories of patients 65 years of age and above generated financial losses under DRGs. Older orthopedic patients consumed a disproportionately larger share of resources than younger patients, and were more frequent users of the SICU and blood. The current DRG reimbursement scheme may be inequitable in relation to the older orthopedic surgery patient. If these findings are demonstrated at other medical centers, older orthopedic surgical patients could be limited in both their access and quality of care in the future.

Academic Medical Centers↗
PubMed1988

The identifier concept: variables to stratify patient costs within cardiothoracic surgical diagnostic related groups.

Prospective payment systems using the diagnostic related group payment mechanism are changing the economic incentives offered to hospitals. This study of all cardiothoracic surgical patients (N = 1825) treated during a 2-year period at an academic medical center demonstrated that patients within cardiothoracic diagnostic related groups could be stratified as to resource consumption (i.e., hospital cost) by four clinical variables: intensive care unit or emergency admission and blood and plasma product utilization. Patients within each diagnostic related group with the variable had higher hospital costs as follows: intensive care unit (100% of patients had higher costs per diagnostic related group for intensive care unit versus non-intensive care unit admissions), blood (100% of patients), plasma product (100%), and emergency admission (92.2%). In addition, hospital costs increased as the factors accumulated. This study demonstrates that costs within cardiothoracic diagnostic related groups may be grouped by four clinical parameters that occur during the patient's hospital stay. One of these variables (i.e., emergency admission) may be suitable to modify diagnostic related group payment. The other variables could segment higher cost patients within a diagnostic related group; cost containment efforts directed at these patients might then provide savings for the hospital.

Blood Transfusion↗
PubMed1987

The sor gene of HIV-1 is required for efficient virus transmission in vitro.

The genome of the human immunodeficiency virus HIV-1 contains at least eight genes, of which three (sor, R, and 3' orf) have no known function. In this study, the role of the sor gene was examined by constructing a series of proviral genomes of HIV-1 that either lacked the coding sequences for sor or contained point mutations in sor. Analysis of four such mutants revealed that although each clone could generate morphologically normal virus particles upon transfection, the mutant viruses were limited in their capacity to establish stable infection. Virus derived from transfection of Cos-1 cells (OKT4-) with sor mutant proviral DNA's was resistant to transmission to OKT4+ "susceptible" cells under cell-free conditions, and was transmitted poorly by coculture. In contrast, virus derived from clones with an intact sor frame was readily propagated by either approach. Normal amounts of gag-, env-, and pol-derived proteins were produced by all four mutants and assays in both lymphoid and nonlymphoid cells indicated that their trans-activating capacity was intact and comparable with wild type. Thus the sor gene, although not absolutely required in HIV virion formation, influences virus transmission in vitro and is crucial in the efficient generation of infectious virus. The data also suggest that sor influences virus replication at a novel, post-translational stage and that its action is independent of the regulatory genes tat and trs.

Animals↗
PubMed1987

Sequences of the 5' portion of the human c-sis gene: characterization of the transcriptional promoter and regulation of expression of the protein product by 5' untranslated mRNA sequences.

The c-sis gene encodes the B polypeptide chain of platelet-derived growth factor (PDGF), and is expressed in a number of normal and pathological conditions. In order to study the control of synthesis of the human c-sis product, we have initiated a study of two regions of this genetic locus which regulate transcription and translation. A clone of the 5' portion of the gene was obtained which included 1361 nucleotides upstream of the RNA initiation site. Transcriptional promoter activity of this region was demonstrated in normal and transformed cells using a plasmid with the sequences upstream of the c-sis RNA initiation site fused to an indicator gene, chloramphenicol acetyl transferase. Experiments were also performed to identify other possible regulatory regions of the c-sis gene. These data demonstrated that a portion of the c-sis first exon encoding the 5' untranslated region of the c-sis mRNA inhibited synthesis of the PDGF B product in vitro. These results define regions of the c-sis gene whose activity may be important in the regulation of transcription and translation under normal conditions and in the pathogenesis several human diseases.

Base Sequence↗
PubMed1987

A lymphoproliferative disorder caused by human T-lymphotropic virus type I. Demonstration of a continuum between acute and chronic adult T-cell leukemia/lymphoma.

A 35-year-old black man is described who had a human T-lymphotropic virus type I (HTLV-I) infection while living in a non-endemic region. A lymphoproliferative disorder developed that might be considered as a transition stage between acute and chronic adult T-cell leukemia/lymphoma. This suggests that HTLV-I-induced neoplasias represent a continuous disease spectrum.

Adult↗
PubMed1987

Cytotoxic factors secreted by cells infected by human immunodeficiency virus type I.

Conditioned media from human immunodeficiency virus type I (HIV-1) infected cells were tested for cytotoxic cell-derived factors. The assay used a murine fibroblast cell line which is sensitive to the effects of tumor necrosis factors, but nonpermissive for HIV-1 replication. Cytotoxic activity was detected in cultures of peripheral blood mononuclear cells infected with HIV-1. However, no differences in activity were found in conditioned media from infected lymphoid or monocytoid cell lines compared to their uninfected counterparts. These data suggest that cytotoxic activities of this type are not mediators of cell killing resulting from HIV-1 infection. Thus, this cytotoxic activity is a direct or indirect result of virus replication or cytopathicity. One should consider a role for this cytotoxic factor, secreted by HIV-1 infected mononuclear cells, in various aspects of infection in vivo, such as AIDS encephalopathy or the systemic manifestations accompanying ARC.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Complete nucleotide sequences of functional clones of the AIDS virus.

To examine the mechanism of lymphocytotoxicity induced by human T-lymphotropic virus type III/lymphadenopathy associated virus (HTLV-III/LAV), an in vitro model has been developed. Introduction of an HTLV-III/LAV proviral clone, HXB2, into normal lymphocytes results in the production of virions and cell death. The complete nucleotide sequence of the proviral form of HXB2 has now been determined. Its structure is quite similar to that previously determined for HTLV-III/LAV clones whose biological capacities had not previously been demonstrated. The biological function of two additional clones of HTLV-III/LAV, BH10 and HXB3, are reported. Clone BH10 which lacks the 5' long terminal repeat sequences (LTR) and a portion of the 3' LTR is reconstituted by substituting the corresponding sequences of HXB2 and is shown to be capable of generating infectious cytopathic virions. Clone HXB3, which has been partially sequenced, is also found to be capable of producing lymphocytopathic virus. Clone HXB3 differs from HXB2 in its lack of a termination codon in 3' orf, demonstrating that 3' orf plays no major role in virus replication or cytopathic activity. These data provide the necessary background to allow the identification of viral determinants of replication, cytopathic activity, and antigenicity using these functional proviral clones.

Base Sequence↗
PubMed1987

An outbreak of phototoxic dermatitis due to limes.

During the week beginning July 29, 1984, 12 children in a day camp in a suburb of Baltimore, Maryland, were noted to have skin eruptions consistent with phototoxic dermatitis. These eruptions were confined to the hands, wrists, and forearms, and appeared as discrete and confluent polymorphous patches and linear streaks. These eruptions were also macular, hyperpigmented, and nonpruritic. Clinical examination revealed that 97 (16%) of 622 children, seven (7%) of 104 counselors, and no adult staff members had a similar rash. Onsets of the rash ranged from July 19-August 11, with peak occurrence on July 25-27. All camp members were white. Sex did not vary significantly between those affected and not affected. The mean age (5.3 years) of affected children was significantly different from the mean age (6.9 years) of unaffected children (p less than 0.001). Attack rates for the eight camp units were highest in two units (57% and 74%, respectively) and ranged between 0-6% for the other six units. Activities involving work with hands by various camp units were investigated. Only exposure to making pomander balls (sachets) in arts and crafts class (when other activities were controlled for) was significantly associated with illness (p less than 0.03). In making pomander balls, children punctured the skin of limes (the principal component) with scissors, releasing oils known to contain photoreactive furocoumarin (psoralen) compounds. These compounds evidently coated the children's skin and, upon exposure to the sun, caused a phototoxic dermatitis. An environmental and botanical survey of the camp did not reveal other phototoxic agents with which campers may have had contact. This is one of the largest reported outbreaks of phototoxic dermatitis and the first in which a citrus fruit was implicated on a large scale.

Adolescent↗
PubMed1987

Trans-activation of long terminal repeat sequence-mediated gene expression is not a property of type D retrovirus replication.

Several retroviruses encode trans-acting factors which activate gene expression directed by long terminal repeat (LTR) sequences and play a role in the positive feedback regulation of virus replication. We have examined two Mason-Pfizer monkey virus (MPMV) strains for their ability to produce and respond to such factors. Plasmids with the LTR of either MPMV or type D retrovirus/New England (D/NE) were fused to the bacterial chloramphenicol acetyltransferase (CAT) gene. Introduction of these plasmids into several different human cell lines gave rise to significant CAT activity, demonstrating the strong transcriptional promoter activity of these LTRs. However, little or no increase in CAT activity was found upon transfection of these plasmids into MPMV- or D/NE-infected cell lines as compared with uninfected cell lines. Furthermore, CAT activity was not enhanced in uninfected cells by cotransfecting either a functional MPMV DNA clone, a plasmid expressing the human T-lymphotropic retrovirus trans-activator genes, tat-1 or tat-3. These data show that the property of trans-activation of LTR-mediated gene expression is a function in the replication of only certain retroviruses.

Cell Line↗