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S Lacks

Publications and source records attributed to S Lacks.

At least 19 recordsLinked to original sources
PubMed1995

Role of intravenous cyclophosphamide in the treatment of severe neuropsychiatric systemic lupus erythematosus.

PURPOSE: We assessed the outcome of 31 patients with severe neuropsychiatric (NP) systemic lupus erythematosus (NPSLE) treated with intravenous cyclophosphamide (IV-CYC), and identified clinical predictors of response to therapy. METHODS: The authors performed a retrospective chart review and classified patients by NP manifestation and response to therapy as measured by serial anatomic imaging and neurodiagnostic studies coupled with clinical assessment of improvement. RESULTS: Neuropsychiatric manifestations occurred with the following frequencies: organic brain syndromes (OBS) 55%, stroke syndromes 35%, peripheral or mononeuropathy 32%, seizures 29%, psychiatric symptoms 26%, transverse myelitis 16%, cranial neuropathies 13%, other 16%. Most patients had multiple NP manifestations, with a median of two. Ninety percent of patients had failed therapy with corticosteroids with or without cytotoxic drugs prior to treatment with IV-CYC. Eight patients received synchronous plasmapheresis along with IV-CYC. After treatment with IV-CYC, NP deficits substantially improved in 61% (group I), stabilized in 29% (group S), and progressively deteriorated in 10% (group P). Patients in group I had significantly fewer NP manifestations than combined group S+P, two versus four, and a lower frequency of OBS, 37% versus 83%. CONCLUSION: Intravenous cyclophosphamide appears to be an effective treatment for some patients with severe NPSLE refractory to other forms of therapy. Higher number of NP manifestations and presence of OBS may predict poor outcome and identify a group of patients for whom early aggressive therapy may be indicated.

Adult↗
PubMed1990

Morbidity associated with childhood systemic lupus erythematosus.

A complete analysis of the outcome of childhood onset systemic lupus erythematosus (SLE) requires determination of survival statistics and consideration of disease and treatment morbidity. The course of 32 patients with SLE diagnosed at or prior to age 16 and followed from 1979-1988 was analyzed with emphasis on the morbidity of pediatric SLE. Clinical characteristics were similar to those in previous studies. Five year survival, calculated by life-table analysis, was 85.3%, comparable to recent studies. Treatment consisted of corticosteroids (32 patients), antimalarials (14), cyclophosphamide (9) or azathioprine (2). Eighty-four percent of patients experienced a noninfectious drug related complication. A major infection contributed in all 5 patients who died. Higher total corticosteroid dose was associated with more severe infections. Eighty-eight percent of patients were left with chronic organ dysfunction. Survival in childhood onset SLE has improved, but morbidity remains a significant problem from organ dysfunction and complications of therapy. Our study is the first to address the issue of morbidity in childhood SLE.

Adolescent↗
PubMed1986

Acromegalic arthropathy: a reversible rheumatic disease.

Acromegalic arthropathy may be the initial manifestation of growth hormone over-production. The presence of an underlying endocrinopathy may go unrecognized for a long period of time because of the predominance of articular signs and symptoms. We describe 2 cases of acromegaly presenting with rheumatologic manifestations, the first resembling seronegative rheumatoid arthritis, the second, post traumatic low back syndrome. Unlike previous reports, both our cases showed resolution of musculoskeletal symptoms after pituitary surgery.

Acromegaly↗
PubMed1979

Uptake of circular deoxyribonucleic acid and mechanism of deoxyribonucleic acid transport in genetic transformation of Streptococcus pneumoniae.

Deoxyribonucleic acid (DNA) from the covalently closed circular DNA molecules of Pseudomonas phage PM2 was found to enter normally transformable cells of Streptococcus pneumoniae as readily as linear bacterial DNA. In a mutant of S. pneumoniae that lacks a membrane nuclease and is defective in DNA entry, as many molecules of PM2 DNA as of linear DNA were bound on the outside of cells at equivalent DNA concentrations. Bound DNA suffered single-strand breaks, but circular DNA with preexisting breaks was bound no better than closed circles. In the presence of divalent cations, DNA bound to cells of a leaky nuclease mutant showed double-strand breaks. At least the majority of PM2 DNA that entered normal cells was single stranded. These results are consistent with a mechanism for DNA entry in which DNA is first nicked on binding, then a double-strand break is formed by cleavage of the complementary strand, and continued processive action of the membrane nuclease facilitates entry of the originally nicked strand. Although the bulk of circular donor DNA appeared to enter in this way, the results do not exclude entry of a small amount of donor DNA in an intact form.

Bacteriophages↗
PubMed1975

A deoxyribonuclease of Diplococcus pneumoniae specific for methylated DNA.

A deoxyribonuclease specific for methylated DNA was isolated from Diplococcus pneumoniae. The enzyme, an endonuclease, degrades DNA for Escherichia coli to fragments of average molecular weight about half a million; it forms discrete fragments from phage lambda DNA. Methyl-deficient E. coli DNA is not attacked, neither is DNA from Micrococcus radiodurans, which contains no methylated adenine or cytosine. Nor is DNA from D. pneumoniae or phage T7 attacked. However, DNA from M. radiodurans, D. pneumoniae, and T7 is attacked after methylation with and E. coli extract. Methylated T7 DNA is degraded to discrete fragments. Although the genetic transforming activity of normal DNA from D. pneumoniae is not affected by the enzyme, transforming activity of methylated DNA is destroyed. The enzyme is designated endonuclease R Dpn I. Under certain conditions another enzyme of complementary specificity can be isolated. This enzyme, designated endonuclease R Dpn II, produces a similar pattern of fragments from the DNA of T7 without prior methylation of the DNA. It also degrades normal DNA for D. pneumoniae. It is suggested that this pair of enzymes plays a role in some unknown control process, which would involve a large fraction of the specific base sequences that are methylated in E. coli DNA and are present but not methylated in DNA from other sources.

Chromatography, Gel↗
PubMed1975

Identification of a deoxyribonuclease implicated in genetic transformation of Diplococcus pneumoniae.

A mutation of Diplococcus pneumoniae, end-1, reduces the major deoxyribonuclease activity of the cell, an endonuclease, to 10% of its normal value without impairing transformation. Further mutations, called noz, abolish the residual endonuclease activity and block transformation. The residual endonuclease is similar to the wild-type enzyme in size, charge, divalent cation dependence, inhibition by ribonucleic acid, and formation of oligonucleotide products. However, the mutant endonuclease is more temperature sensitive, which suggests that the end-1 mutation occurred in a structural gene for the enzyme. Genetic analysis showed that the noz mutations occur at the same genetic locus. A number of new end mutants were analyzed. Those that retained more than 1.4% of the normal endonuclease activity were essentially normal in transformation; those with less than 1% were defective. The transformation-defective end mutants appear to be blocked in the entry of deoxyribonucleic acid (DNA) since they carry out the prior step of binding DNA to the outside of the cell. The major endonuclease of the cell may act as a DNA translocase by attacking and degrading one strand of DNA, thereby facilitating entry of the complementary strand into the cell.

Cations, Divalent↗
PubMed1975

Membrane location of a deoxyribonuclease implicated in the genetic transformation of Diplococcus pneumoniae.

The cellular localization of enzymes in Diplococcus pneumoniae was examined by fractionation of spheroplasts. A deoxyribonuclease implicated in the entry of deoxyribonucleic acid (DNA) into the cell during genetic transformation was located in the cell membrane. This enzyme, the major endonuclease of the cell (endonuclease I), which is necessary for the conversion of donor DNA to single strands inside the cell and oligonucleotides outside, thus could act at the cell surface. Another enzyme, the cell wall lysin (autolysin), was also found in the membrane fraction. Other enzymes, including amylomaltase, two exonucleases, and adenosine triphosphate-dependent deoxyribonuclease, and a restriction type endonuclease, were located in the cytosol within the cell. None of the enzymes examined were predominantly periplasmic in location. Spheroplasts were obtained spontaneously on incubation of pneumococcal cells in concentrated sugar solutions. The autolytic enzyme appears to be involved in this process. Cells that were physiologically competent to take up DNA formed osmotically sensitive spheroplasts two to three times faster than cells that were not in the competent state. Although some genetically incompetent mutants also formed spheroplasts more slowly, other such mutants formed them at the faster rate.

Cell Fractionation↗
PubMed1974

Role of a deoxyribonuclease in the genetic transformation of Diplococcus pneumoniae.

Two steps in the uptake of DNA by Diplococcus pneumoniae were characterized by analyzing mutants defective in transformation. A strain deficient in the two major deoxyribonucleases of D. pneumoniae takes up DNA normally and converts it to single strands within the cell and oligonucleotide fragments outside the cell. Extracts of this strain contain a residual deoxyribonuclease that produces similar oligonucleotide fragments in vitro. This enzyme is missing in transformation-defective mutants blocked in the second or entry step. Cells of this mutant class bind large amounts of DNA to their surface in a form accessible to external agents. Another class of nontransformable mutants fails to bind DNA at all. Their deoxyribonuclease content is unchanged, and they are apparently blocked in the first or binding step of DNA uptake. The binding step requires a source of energy and prior activation of the cells by competence factor. Entry may be independent of these requirements and may come about by action of the deoxyribonuclease on one strand of DNA with energy for the transport of the intact strand deriving from hydrolysis of the degraded strand. The enzyme may thus act as a DNA translocase.

Binding Sites↗
PubMed1973

Competence for deoxyribonucleic acid uptake and deoxyribonuclease action external to cells in the genetic transformation of Diplococcus pneumoniae.

A mutant of Diplococcus pneumoniae that apparently does not require activator can become competent for uptake of deoxyribonucleic acid (DNA) when grown in dilute cultures or in the presence of trypsin. Development of competence in both mutant and wild strains is temperature dependent, being 10-fold greater at 30 C than at 37 C. Induction of competence on a shift from 37 to 30 C requires protein synthesis and the presence of Mg(2+) and Ca(2+); uptake of DNA does not require protein synthesis. Competence decays exponentially at higher temperatures. As well as taking up DNA, competent cells release oligonucleotide fragments of donor DNA in the medium external to the cells. Normal strains release fragments comparable in amount to the DNA taken up; but, in a mutant selected for inability to degrade DNA in agar, the amount of fragments formed external to the cells is only 40% of DNA uptake. Requirements for external deoxyribonuclease action are identical to those for DNA uptake: prior development of competence and the presence during treatment with DNA of Mg(2+) ions and a source of energy.

Calcium↗
PubMed1970

Mutants of Diplococcus pneumoniae that lack deoxyribonucleases and other activities possibly pertinent to genetic transformation.

Mutants of Diplococcus pneumoniae that lacked the two major deoxyribonucleases of the cell-one an endonuclease, the other an exonuclease preferentially active on native deoxyribonucleic acid (DNA)-were obtained. The development of a method for detecting mutant colonies, based on the binding of methyl green to DNA, facilitated isolation of the mutants. Neither enzyme was essential for growth of the cells, for repair of ultraviolet damage, or for any phase of DNA-mediated transformation. Residual deoxyribonuclease activity in the double mutant corresponded to an exonuclease, approximately one-fifth as active as the major exonuclease, that attacked native and denatured DNA equally well. This activity appeared to be associated with the DNA-polymerase enzyme. A mutant that apparently lacked a cell wall lytic enzyme was also fully transformable. A mutant strain that was four times more sensitive to ultraviolet light than the wild type also transformed normally. Recipient cells of this strain were deficient in the repair of ultraviolet-irradiated transforming DNA. Mutants were found which, unlike the wild type, integrated donor markers only with high efficiency, thereby indicating that a particular cellular component that is susceptible to loss by mutation, such as an enzyme, is responsible for low integration efficiency.

Cell Wall↗