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Biomedical subjects

I Schwartz

Publications and source records attributed to I Schwartz.

At least 73 records · Page 4Linked to original sources
PubMed1994

Cloning and DNA sequence analysis of bmpC, a gene encoding a potential membrane lipoprotein of Borrelia burgdorferi.

Immunoscreening of a lambda gt11 genomic library of Borrelia burgdorferi expressed in Escherichia coli permitted detection of a clone containing a partial sequence of a B. burgdorferi gene encoding a protein with significant homology to TmpC of Treponema pallidum. Subsequent cloning and DNA sequence analysis revealed an open reading frame encoding a protein with 353 amino acid residues. The open reading frame is preceded by putative promoter sequences and a ribosome binding site, and is initiated with a TTG. The putative protein shares 26% identity with TmpC, contains a signal peptidase II sequence, and is also homologous to the gene products of the recently described bmpA and bmpB of B. burgdorferi. This gene has been designated bmpC. Additional sequencing and restriction analysis indicate that it is located at approximately 400 kbp on the chromosomal map of B. burgdorferi, immediately upstream of bmpA and bmpB.

Amino Acid Sequence↗
PubMed1994

Sequence analysis of the ribosomal RNA operon of the Lyme disease spirochete, Borrelia burgdorferi.

An 11,955-bp region of the Borrelia burgdorferi chromosome containing all the genes encoding ribosomal RNA (rRNA) has been sequenced. The region contains a single gene encoding 16S rRNA and two genes encoding the 23S and 5S rRNAs. The sizes of the 16S, 23S and 5S rRNAs encoded by these genes are 1537, 2926 and 112 nucleotides, respectively. In addition, the genes encoding tRNA(Ala) and tRNA(Ile) are located in the intergenic spacer between the 16S and 23S rDNAs. The tDNAs do not encode the common CCA 3' end which presumably must be added posttranscriptionally. All the genes are present in the same orientation, except for that encoding tRNA(Ile), which is transcribed from the opposite strand. The latter implies that the rDNAs are not transcribed as a single unit. The location of putative promoters and termination signals in the sequence suggest that the 16S rRNA and tRNA(Ala) are transcribed as a single unit, tRNA(Ile) is produced as an individual transcript and the 23S and 5S rDNAs are co-transcribed. Several of the features of this rDNA organization are unique, not having been described previously in any other eubacteria.

Base Sequence↗
PubMed1994

In vivo leukocyte tropism of bovine leukemia virus in sheep and cattle.

Bovine leukemia virus (BLV), an oncovirus related to human T-cell leukemia virus type I, causes a B-cell lymphoproliferative syndrome in cattle, leading to an inversion of the T-cell/B-cell ratio and, more rarely, to a B-cell lymphosarcoma. Sheep are highly sensitive to BLV experimental infection and develop B-cell pathologies similar to those in cattle in 90% of the cases. BLV tropism for B cells has been well documented, but the infection of other cell populations may also be involved in the BLV-induced lymphoproliferative syndrome. We thus looked for BLV provirus in other leukocyte populations in sheep and cattle by using PCR. We found that while B cells harbor the highest proviral load, CD8+ T cells, monocytes, and granulocytes, but not CD4+ T cells, also bear BLV provirus. As previously described, we found that persistent lymphocytosis in cows is characterized by an expansion of the CD5+ B-cell subpopulation but we did not confirm this observation in sheep in which the expanded B-cell population expressed the CD11b marker. Nevertheless, BLV could be detected both in bovine CD5+ and CD5- B cells and in sheep CD11b+ and CD11b- B cells, indicating that the restricted BLV tropism for a specific B-cell subpopulation cannot explain its expansion encountered in BLV infection. Altogether, this work shows that BLV tropism in leukocytes is wider than previously thought. These results lead the way to further studies of cellular interactions among B cells and other leukocytes that may intervene in the development of the lymphoproliferative syndrome induced by BLV infection.

Animals↗
PubMed1994

Pathobiology of bovine leukemia virus.

Bovine leukemia virus (BLV) is a retrovirus similar to the human T-cell leukemia virus (HTLV). Most BLV infected animals (70%) develop a B-cell lymphoproliferative syndrome with altered productive traits and 1 to 5% die with B-cell lymphosarcomas. Although BLV infection is world-wide, western European countries have almost eradicated it by slaughtering the seropositive animals. BLV infection remains endemic in many countries including the United States and prophylactic strategies involving recombinant vaccine vectors, genetically modified BLV and transgenic animals resistant to the infection are under study.

Animals↗
PubMed1994

A distinctive property of Tth DNA polymerase: enzymatic amplification in the presence of phenol.

The ability of thermostable DNA polymerases to mediate template-dependent DNA synthesis in the presence of phenol has been examined as monitored by amplification of a specific Borrelia burgdorferi rRNA sequence. Tth DNA polymerase displayed the unique property of maintaining both DNA- and RNA-dependent DNA polymerase activities in the presence of 2%-5% (vol/vol) of phenol-saturated PBS buffer. Tth DNA polymerase mediated reverse transcriptase activity was unaffected by phenol-saturated phosphate-buffered saline concentrations as high as 15% (vol/vol). By contrast, Taq DNA Polymerase was inactive under these conditions. The ability to function in the presence of phenol can greatly simplify reverse transcriptase, PCR and reverse transcription-PCR protocols since the phenol-saturated aqueous phase of a phenol partition can be added directly to the reaction mixtures. The simplicity of the procedures described should have applicability to a broad range of basic research, clinical and forensic applications.

Borrelia burgdorferi Group↗
PubMed1993

Reconstruction of translation. Evidence for the involvement of the rescue protein in the association/dissociation of ribosomal subunits.

The in vitro reversal of conditionally lethal mutations has greatly aided the study of translation. N4316 is a mutant of Escherichia coli that has a temperature-sensitive defect in a protein called the rescue protein. Without the rescue protein, translation in vivo and in vitro is drastically reduced and frameshift errors, as well as increased read-through of nonsense codons, occurs. Using reversal of temperature-sensitivity as an assay, the rescue protein was purified from a ribosomal eluate of the parental (D10) strain. Composite polyacrylamide/agarose gel electrophoresis and sedimentation on sucrose density gradients were employed to examine the distribution of 70S ribosomes and ribosomal subunits in the mutant (N4316) and the parental (D10) extracts at restrictive (43 degrees C) and non-restrictive (35 degrees C) temperatures. Fewer polysomes and a larger proportion of 70S ribosomes relative to subunits were observed at 43 degrees C with N4316, but not with D10 extracts. Addition of the rescue protein had no effect at 35 degrees C with either strain, but restored the polysome pattern of N4316 at 43 degrees C. The purified rescue protein labelled by methylation retained activity and bound preferentially to 30S subunits. Rescue bound to 30S particles prevented the action of IF-3 fostering formation of 70S ribosomes. Thus the rescue protein enables formation of 70S ribosomes from 30S and 50S subunits. 70S ribosomes which contain the rescue protein are active in translation and resist dissociation induced by high centrifugal fields. We propose that the rescue protein alters the conformation of 70S ribosomes resulting in a tighter association of subunits which, in turn, fosters both higher rates and increased accuracy of translation.

Amino Acyl-tRNA Synthetases↗
PubMed1993

Molecular cloning and sequencing of infC, the gene encoding translation initiation factor IF3, from four enterobacterial species.

Translation initiation factor IF3 plays a crucial role in initiation of protein synthesis in bacteria. In order to elucidate the IF3 structural elements required for these functions, the evolutionary conservation of IF3 and its gene, infC, was investigated. Homologous infC sequences from Salmonella typhimurium, Klebsiella pneumoniae, Serratia marcescens and Proteus vulgaris were amplified by the polymerase chain reaction and sequenced. Analysis of these sequences, as well as that from Bacillus stearothermophilus, revealed several regions (e.g. residues 62-73 and 173-177) of absolute sequence conservation, suggesting an important role for these regions in IF3 function.

Amino Acid Sequence↗
PubMed1993

Polymerase chain reaction amplification of culture supernatants for rapid detection of Borrelia burgdorferi.

A combination of culture and polymerase chain reaction (PCR) amplification was employed to detect Borrelia burgdorferi in in vitro cultures of skin biopsy specimens. Spirochetes were observed by microscopic examination in 56% (20/36) of the cultures from patients with erythema migrans who had not received prior antibiotic treatment. No growth of Borrelia burgdorferi was detected in control cultures or those from patients who had received antibiotics. PCR analysis of culture supernatants agreed with microscopic evaluation in 50/51 evaluable cultures tested (both positive and negative). At two weeks of incubation Borrelia burgdorferi could be detected by PCR in 19/20 cultures (95%) compared to 14/20 (70%) by visual inspection. This study indicates that a combined culture-PCR test for detection of Borrelia burgdorferi is more rapid and specific than culture alone.

Borrelia burgdorferi Group↗
PubMed1993

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) and Lyme disease risk by deer exclusion.

The effect of deer exclosures upon the numbers of immature Ixodes scapularis Say, the vector of Lyme disease in the eastern United States, was examined at five sites in Westchester County, NY. Study areas ranged in size from 6 to 101 ha where deer had been excluded for a period of 25 yr by > 2.4-m-high fencing that surrounded each site. A total area of 40,506 m2 was drag-sampled during the study to measure tick abundance. Nymphal densities (ticks per 1,000 m2) averaged 4.6 (range, 1.3-9.6) inside exclosures and 27.7 (range, 7.3-79.4) outside. Larval densities averaged 36.7 (range, 1.2-132.1) inside exclosures and 354.4 (range, 7.5-914.5) outside. Comparisons between exclosure sites and outside areas immediately adjacent to the exclosure fence, where deer had unrestricted access, revealed that exclosures had 83% fewer host-seeking nymphs and 90% fewer host-seeking larvae. Tick numbers inside exclosures did not always decline with increasing distance from the fence. There was no significant difference in the rate of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner infection for host-seeking ticks collected inside (20%, n = 50) exclosures compared with ticks collected outside (26%, n = 50) exclosures. Deer fencing may provide a means of significantly reducing the abundance of I. scapularis and the risk of Lyme disease in relatively large areas without the need to reduce or eliminate the deer population.

Animals↗
PubMed1993

The influence of thyroid hormone replacement in a porcine brain death model.

This study was conducted to determine whether the administration of tri-iodothyronine (T3) to brain-dead donor pigs would improve hemodynamic instability, serum levels of thyroid hormones, or the outcome of transplantation of donor livers. Brain death was caused in young pigs (25-38 kg) by rapid inflation of an intracranially implanted balloon catheter. The animals were maintained on a ventilator and frequent measurements of acid/base balance, electrolytes, and glucose were made. At the end of 16 hr, livers were removed and implanted into prepared recipients. Serum-free tri-iodothyronine fell to zero at the end of 16 hr, and there was a 4-6-fold decline in free thyroxine (T4). The levels of serum reverse T3 (rT3) however, increased up to 6-fold. In animals treated with tri-iodothyronine 2 micrograms/hr, the serum levels of free T3 and T4 were not changed but the levels of serum reverse T3 (rT3) increased further. There were no apparent correlations between any hemodynamic parameter and serum thyroid hormone levels in the donors. After the liver transplants, recipients could be divided into those that survived longer than 6 days and those that did not. Although there were significant differences in the plasma levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, there was no correlation between survival and whether the donor had received tri-iodothyronine. Although other hormones, including insulin and cortisol, may also be necessary, there is no indication from these studies that the administration of tri-iodothyronine to brain-dead donors of liver grafts benefits the serum hormone levels in the donors or the subsequent survival of the recipients.

Animals↗
PubMed1992

Structure-function analysis of Escherichia coli translation initiation factor IF3: tyrosine 107 and lysine 110 are required for ribosome binding.

Translation initiation factor IF3 is required for peptide chain initiation in Escherichia coli. IF3 binds directly to 30S ribosomal subunits ensuring a constant supply of free 30S subunits for initiation complex formation, participates in the kinetic selection of the correct initiator region of mRNA, and destabilizes initiation complexes containing noninitiator tRNAs. The roles that tyrosine 107 and lysine 110 play in IF3 function were examined by site-directed mutagenesis. Tyrosine 107 was changed to either phenylalanine (Y107F) or leucine (Y107L), and lysine 110 was converted to either arginine (K110R) or leucine (K110L). These single amino acid changes resulted in a reduced affinity of IF3 for 30S subunits. Association equilibrium constants (M-1) for 30S subunit binding were as follows: wild-type, 7.8 x 10(7); Y107F, 4.1 x 10(7); Y107L, 1 x 10(7); K110R, 5.1 x 10(6); K110L, < 1 x 10(2). The mutant IF3s were similarly impaired in their abilities to specifically select initiation complexes containing tRNA(fMet). Toeprint analysis indicated that 5-fold more Y107L or K110R protein was required for proper initiator tRNA selection. K110L protein was unable to mediate this selection even at concentrations up to 10-fold higher than wild type. The results indicate that tyrosine 107 and lysine 110 are critical components of the ribosome binding domain of IF3 and, furthermore, that dissociation of complexes containing noninitiator tRNAs requires prior binding of IF3 to the ribosomes.

Amino Acid Sequence↗
PubMed1992

Use of a novel technique of cutaneous lavage for diagnosis of Lyme disease associated with erythema migrans.

OBJECTIVE: Determining the microbial cause of cellulitis is often difficult. In this study, a novel two-needle lavage technique was used to culture Borrelia burgdorferi from the skin of suspected erythema migrans lesions. DESIGN: The yield of lavage cultures for B burgdorferi was compared with that of a 2-mm skin biopsy sample. SETTING: A Lyme disease diagnostic center located in an area in which Lyme disease is epidemic. PATIENTS: Forty-five patients with suspected erythema migrans who had not been treated with antimicrobial agents. INTERVENTION: Cutaneous lavage of the advancing edge of a suspected primary erythema migrans lesion was done for all 45 participants, 33 of whom also had a skin biopsy of the same lesion at an identical (14) or an adjacent (19) site. MAIN OUTCOME MEASURES: Growth of B burgdorferi in in vitro culture. RESULTS: Lavage fluid cultures grew B burgdorferi in 13 (29%) of the 45 cases (95% confidence interval [CI], 16% to 44%). Among the 33 cases in which both lavage and skin biopsy cultures were done, the yield of lavage culture was less than that of biopsy culture (P less than .09, 12/33 vs 20/33). If contaminated cultures are excluded, this difference is significant (P less than .05, 12/30 vs 20/27). CONCLUSION: Cutaneous lavage is a new diagnostic technique for recovery of B burgdorferi from erythema migrans lesions that has potential applicability to other types of cutaneous infections.

Biopsy↗
PubMed1992

Doctor-patient communication in a cancer ward.

This study explored doctor-patient interaction by focusing on a specific type of encounter in an oncology ward, designed to enable discussion of the case by the doctors and informing the patient. In line with the cognitive orientation theory of Kreitler and Kreitler, the encounter's effects were examined in regard to three aspects--disease, treatment, and general state--on four levels: the information the patients have, their feelings, the information they desire, and the information they consider desirable. The patients were 52 men and women with different cancer diagnoses. Comparable questionnaires were administered to the patients before and after the meeting, and to the doctors only after it. The patients responded before and after also to Spielberger's scales of state anxiety and state anger. The results showed that patients claimed they had gained hardly any new information concerning the disease and their overall state. There were no decreases in the desired and desirable information. Their feelings were affected negatively to a slight extent, especially concerning treatment. In a quarter of the subjects, anxiety decreased and was replaced by anger. In regard to all levels and aspects there was a large gap between the evaluations of doctors and patients. The major conclusions were that patients and doctors differ in the meaning they assign to information, and that patients are conflicted in regard to asking for the personally relevant information they want.

Anger↗
PubMed1992

rRNA gene organization in the Lyme disease spirochete, Borrelia burgdorferi.

Lyme disease is the most common vector-borne disease in the United States. The causative agent is the spirochete Borrelia burgdorferi. The copy number and organization of the genes encoding the rRNAs of this organism were determined. There is a single gene for 16S rRNA and two copies each of the 23S rRNA and 5S rRNA genes. All of the genes are located within a chromosomal fragment of approximately 9.5 to 10.0 kb. The 23S and 5S rRNA genes are tandemly duplicated in the order 23S-5S-23S-5S and are apparently not linked to the 16S rRNA gene, which is situated over 2 kb upstream from the 23S-5S duplication. The individual copies of the 23S-5S duplication are separated by a 182-bp spacer. Within each 23S-5S unit, an identical 22-bp spacer separates the 23S and 5S rRNA sequences from each other. The genome organization of the 23S-5S gene cluster in a number of different B. burgdorferi isolates obtained at a number of different geographical locations, as well as in several other species of Borrelia, was investigated. All isolates of B. burgdorferi tested displayed the tandem duplication, whereas the closely related species B. hermsii, B. anserina, and B. turicatae all contained a single copy of each of the genes. In addition, different geographical isolates of B. burgdorferi can be differentiated on the basis of a restriction fragment length polymorphism associated with the 23S-5S gene cluster. This polymorphism can be a useful tool for the determination of genetic relatedness between different isolates of B. burgdorferi.

Base Sequence↗
PubMed1992

Diagnosis of early Lyme disease by polymerase chain reaction amplification and culture of skin biopsies from erythema migrans lesions.

Current laboratory diagnosis of Lyme disease relies on tests for the detection of antibodies to Borrelia burgdorferi, the etiologic agent of the disease. These tests are often unreliable because of a lack of sensitivity and specificity and test-to-test variability. The purpose of this study was to evaluate the sensitivity and specificity of polymerase chain reaction (PCR) amplification for detection of B. burgdorferi in skin biopsy specimens. Forty-six 2-mm skin biopsy samples were obtained from 44 patients with a clinical diagnosis of erythema migrans, 9 of whom were receiving antibiotic therapy at the time of biopsy. Specimens were ground in BSK medium with separate aliquots taken for culture and PCR. Of the specimens from the untreated group, 57% (21 of 37) were positive by culture and 22% (8 of 37) were culture negative; 22% (8 of 37) of the cultures were uninformative because of contamination. By comparison, 22 (59%) of 37 specimens were positive by PCR amplification. Of 21 culture-positive samples, 13 (62%) were also positive by PCR analysis. Thus, the sensitivity of the PCR was 59 to 62%, based on either a clinical or cultural diagnosis of untreated Lyme disease. None of the nine specimens from antibiotic-treated patients grew in culture, whereas two of the nine were positive by PCR analysis. Given the complexity and time required for culture, PCR is a promising technique for the diagnosis of early Lyme disease.

Base Sequence↗
PubMed1992

Vesicular erythema migrans.

BACKGROUND: Lyme disease is the most common vector-borne disease in the United States. The characteristic rash, erythema migrans, is an early sign of the disease. Clinical criteria remain the "gold standard" for diagnosis at this stage of illness. OBSERVATIONS: Five (8%) of 65 patients with erythema migrans seen in a Lyme disease diagnostic center in Westchester County, New York, had a lesion with vesicles. Borrelia burgdorferi was cultured from two of five. In one case the positive culture came from a swab of the blister fluid. CONCLUSIONS: Recognition of erythema migrans and its variants is important, since early treatment of Lyme disease may prevent late complications. Vesicular erythema migrans should be added to the differential diagnosis of inflammatory vesicular rashes in the appropriate clinical setting.

Adolescent↗