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Biomedical subjects

L Barnett

Publications and source records attributed to L Barnett.

At least 19 recordsLinked to original sources
PubMed1992

Myeloid and lymphoid chimerism after T-cell-depleted bone marrow transplantation: evaluation of conditioning regimens using the polymerase chain reaction to amplify human minisatellite regions of genomic DNA.

Determining both myeloid and lymphoid chimerism after T-cell-depleted allogeneic bone marrow transplantation (BMT) could be helpful in the understanding of the biology of engraftment and could provide a rational method of assessing the ability of different conditioning regimens to promote engraftment. We prospectively investigated the role of different pretransplant conditioning regimens in 29 leukemic patients post-BMT by assessing myeloid and T-cell chimerism using a rapid and sensitive polymerase chain reaction (PCR) method. Minisatellites are hypervariable regions of DNA consisting of tandem repeats of a core nucleotide sequence, and allelic polymorphism results from differences in the number of the repeats. We used this variation to distinguish between donor and recipient cells post-BMT. Seventeen patients (9 sibling and 8 unrelated donors) received conditioning with hyperfractionated total body irradiation (TBI), thiotepa, and cyclophosphamide (Cy). Of the other 12 patients (all sibling donors), 11 received TBI plus Cy plus another agent: VP16, carboplatinum, or AZQ. One patient received TBI plus thiotepa plus VP16. All but one of the patients studied received marrow from HLA-identical donors. PCR analysis confirmed donor lymphoid engraftment within 8 days of transplant in six of six patients studied. All granulocyte DNA was of donor origin within the first 4 weeks of transplant, regardless of the conditioning regimen. The day +28 T cells were exclusively of donor origin in 14 of 17 patients who received TBI plus thiotepa plus Cy, but were mixed chimeric in 10 of 12 patients who received other conditioning regimens (P < .001). Early graft rejection was seen in one unrelated transplant recipient conditioned with TBI plus thiotepa plus Cy. Late graft failure was observed in 3 of 12 patients with mixed T-cell chimerism and in none of 16 patients with full donor chimerism at day +28. However, 5 of 16 patients who had complete T-cell chimerism at day +28 developed acute graft-versus-host disease (GVHD), whereas no patient with mixed chimerism had acute GVHD. Our results indicate that minisatellite PCR is a rapid and sensitive method for assessing chimerism post-BMT, that the donor T cells are important for consistent durable engraftment, and that TBI plus thiotepa plus Cy may be superior to the other regimens studied in inducing full donor chimerism. Larger numbers and longer follow-up are necessary to confirm these data and also to assess the relationship between complete donor T-cell chimerism and leukemia-free survival.

Adolescent↗
PubMed1992

Use of grafts smaller than the opening for keratoconic myopia and astigmatism. A prospective study.

A prospective study was conducted on 15 consecutive keratoconic eyes to evaluate the use of grafts smaller than the opening in keratoconic myopia and astigmatism. All surgeries were performed by the senior author. Average age of the patients was 41.1 years. Average follow-up was 1.6 years. After all sutures were removed, results showed an average decrease in myopia of 13.24 diopters (D) (range 1.75 to 23.25) principally from corneal flattening and a small reduction in axial length. Average postoperative spherical equivalent was -2.17 D (range +1.50 to -7.25). The average postoperative astigmatism was 3.78 D (range 1.75 to 6.00). This study and a previous retrospective study suggest that the use of grafts 0.25 mm smaller than the opening, i.e., 7.50/7.75 mm, for penetrating keratoplasty in keratoconus is justified.

Adult↗
PubMed1990

Anti-leukemia potential of interleukin-2 activated natural killer cells after bone marrow transplantation for chronic myelogenous leukemia.

The anti-leukemia potential of natural killer (NK) cells has been evaluated in 40 patients transplanted for chronic myelogenous leukemia (CML) to determine whether differences in NK cell function were correlated with subsequent leukemic relapse. Cells from patients and their donors were tested in 51Cr release assays against fully allogeneic CML targets and against cultured K562 targets; cells from 26 patients were tested against host-derived CML targets that were cryopreserved before transplantation. Cultured CML targets (K562) were highly susceptible to lysis by freshly isolated peripheral blood lymphocytes (PBL) and to a greater degree by PBL cultured in medium containing interleukin-2 (IL-2) in all assays performed. In contrast, noncultured CML targets were lysed only by IL-2-activated cells from a subset of patients. When present, lytic activity to CML targets was detectable as early as 3 weeks after bone marrow transplantation, and remained positive throughout the posttransplant period. Optimal lytic activity developed within the first week of culture and required greater than or equal to 250 U/mL of IL-2 in the culture medium. Lytic activity to fully allogeneic and host-derived CML targets appeared to be mediated by CD16+ and CD56+ cells but not by CD3+ cells. Lysis of allogeneic CML targets was variable, but patients could be divided into two groups: those with and those without lytic activity to the majority of targets tested. The basis for the differences in lytic activity could not be ascribed to target susceptibility to lysis, the proportion of NK cells in the cultures, or to the phenotype of the NK cell subsets in the cultures. When tested in parallel, the lytic activity of donor and recipient cultures against host-derived CML targets was highly correlated, suggesting that there may be inherent differences in the ability of NK cells to recognize CML targets. The risk of relapse for patients who failed to generate lytic activity against host-derived CML targets was significantly increased over that for patients with lytic activity against host leukemia. These data indicate that posttransplant immunotherapy with IL-2 designed to activate NK cells will likely augment the graft-versus-leukemia potential of the graft.

Adolescent↗
PubMed1990

Characterisation of a short, highly repeated and centromerically localised DNA sequence in crested and marbled newts of the genus Triturus.

A 32-33 bp highly repeated DNA sequence, TkS1, has been isolated from genomic DNA of the newt Triturus karelini digested with the restriction endonucleases HaeIII or AluI. TkS1 is known to be localised in the centromeric heterochromatin of all the chromosomes in T. karelini and the related species T. cristatus. TkS1 has been shown to be present in varying amounts in the genomic DNA of a range of species of Triturus, including representatives of the two main subgenera Triturus and Palaeotriton. A programme of sequencing of monomers, dimers and trimers of TkS1 was carried out in order to determine the level of conservation of the sequence within and between species of Triturus. Altogether 204 monomer (32/33 bp) clones were made of TkS1 from three individuals of T. karelini, and one individual each of T. cristatus, T. carnifex, T. dobrogicus and T. marmoratus, all members of the subgenus Triturus and the cristatus species group. A number of dimer (64 bp) and trimer (96 bp) clones were also made from DNA of a single specimen of T. karelini digested with HaeIII or AluI. Three distinct types of TkS1 were identified in all species examined, except for T. marmoratus where only two of the types were found. The types were distinguished on the basis of certain recurring divergent patterns in monomers sequenced from T. karelini. Type 1 is mainly characterised by the presence of an AluI site at positions 24-27 and type 3 mainly by the presence of an additional base (C) at position 14. Type 2 normally lacks the AluI site and the C at position 14, as well as having a number of other distinguishing features. TkS1 and its three types have remained remarkably constant in sequence since before the divergence of T. marmoratus from other species in the cristatus species group, about 10 million years ago. Examination of all 204 monomer clones and comparison with consensus sequences for the three types shows less than 5% divergence at any one position in the sequence. There is good evidence from examination of dimer and trimer clones of TkS1 that the different types are intermingled with each other, and all three types are likely to be present on all chromosomes. Dimeric (64 bp) TkS1 clones constructed from AluI fragments of T. karelini DNA show evidence of a trimeric (96 bp) "supertype" with the pattern type 1-type 3-type 1 that is much more common than would be expected on a random basis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Effect of penetrating keratoplasty using grafts of various sizes on keratoconic myopia and astigmatism.

The records of 72 consecutive keratoconic eyes undergoing penetrating keratoplasty were reviewed for changes in myopia and astigmatism. Ages of the patients averaged 32.7 years. All sutures were removed after three months. Follow-up average was 40.2 months. Results showed an average decrease in myopia of 6.63 diopters (D) in 60 eyes (82.86%) and an average increase in myopia of 1.88 D in 12 of 70 eyes (17.14%). The decrease/increase in myopia and postoperative astigmatism was compared for grafts equal to the opening, grafts smaller than the opening, and grafts larger than the opening. The largest average decrease in myopia was 13.86 D (range 6.63 to 20.00), which occurred when a graft smaller than the opening was used (P less than .01). This group also showed the least postoperative astigmatism (2.82 D) (P less than or equal to .01). From this study, it appears that the use of a graft 0.25 mm smaller than the trephine opening in the host (i.e., 7.50 mm graft/7.75 mm opening) for penetrating keratoplasty in keratoconus is justified. A prospective study is now in progress.

Adolescent↗
PubMed1987

Transformation of Arthrobacter and studies on the transcription of the Arthrobacter ermA gene in Streptomyces lividans and Escherichia coli.

We report the development of a plasmid-mediated transformation system for Arthrobacter sp. NRRLB3381, using the Streptomyces cloning vector pIJ702. Our procedure gives a transformation frequency of 10(3)/micrograms of plasmid DNA. In addition we have explored the expression of the Arthrobacter ermA gene in Streptomyces lividans and Escherichia coli, and shown that the ermA promoter is recognized in S. lividans not E. coli. The relationship between Arthrobacter, Streptomyces and E. coli promoters is discussed.

Arthrobacter↗
PubMed1986

Sexual activity after coronary bypass surgery.

Although successful rehabilitation of coronary artery bypass surgery (CABS) patients should include consideration of their sexuality, there is a paucity of data regarding their sexual activity (SA). One hundred thirty-four patients were interviewed in regard to the impact of surgery on their sexuality and the relation of SA to their work status. Eighty-four of the 92 previously sexually active patients and two of the inactive ones resumed SA. Sexual dissatisfaction prior to surgery was a negative factor (p less than .05), while return to work, in the group that was working before, was positive (p less than .05) for resumption of SA. The average time before resumption of SA after CABS was 7.8 weeks. Thirty-nine percent of patients decreased the frequency of SA. Seventeen percent of patients and 35 percent of their partners expressed fear of resumption of SA. Twenty-three percent of patients had symptoms during intercourse. The couples who resumed sexual activity had a closer emotional relationship (p less than .02). Two-thirds of the patients received sexual instructions, but in only 20 percent of the cases did the physician himself initiate discussion. Although after CABS patients fare much better in regard to SA when compared to myocardial infarction patients reported in other studies, CABS does not provide a net gain in SA and sexual functioning. Comprehensive sexual counseling is still not being adequately addressed.

Adult↗
PubMed1977

An investigation of some problems concerning nucleolus organizers in salamanders.

Observed differences in the sizes of lampbrush nucleolus organizers in Plethodon cinereus have been shown by in situ hybridization to reflect true molecular differences in the numbers of ribosomal cistrons located at these organizers. Likewise, from in situ hybridization experiments on lampbrush and spermatocyte chromosomes it has been shown that animals may be, and indeed usually are, heterozygous with respect to the numbers of ribosomal cistrons on each half of the nucleolus bivalent. Filter hybridizations carried out on 33 males from a New Jersey population and 20 males from a Connecticut population have shown a 7.5-fold range in the numbers of ribosomal cistrons per diploid cell in the New Jersey population, and a 2.5-fold range in the Connecticut population. In view of the general heterozygosity of nucleolus organizers in these animals, the actual range in nucleolus organizer sizes in the New Jersey population is estimated to be at least 15-fold.

Animals↗
PubMed1975

Keratoacanthoma centrifugum marginatum.

A keratoacanthoma centrifugum marginatum measured 20 X 14 cm at the time of surgical intervention. This lesion is characterized by continuing peripheral extention and central healing. Attention is drawn to the occurrence in the healing edge of a distinctive type of individual cell necrosis, which has been described by others in the more usual forms of keratoacanthoma. The findings are of interest, since this same mode of cellular death has recently been shown to be involved in the regression of various tissues, normal as well as abnormal.

Aged↗