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Biomedical subjects

C Buck

Publications and source records attributed to C Buck.

At least 19 recordsLinked to original sources
PubMed1996

Class I-restricted presentation of an HIV-1 gp41 epitope containing an N-linked glycosylation site. Implications for the mechanism of processing of viral envelope proteins.

Uncertainty exists over the site of processing of viral envelope (env) proteins for recognition by CTL. The extracellular domains of env proteins are not present in the cytosol, the site where the class I Ag processing pathway begins. Rather, the ecto-domains of env proteins are cotranslationally translocated into the endoplasmic reticulum during biosynthesis. To clarify the site of processing of viral env proteins, we examined the processing of an HLA B*3501-restricted epitope in the extracellular domain of the HIV-1 env protein. Although this epitope contains an N-linked glycosylation signal sequence, CTL specific for this epitope recognize a nonameric peptide that has not been previously modified by attachment of oligosaccharide. This was demonstrated in two ways. First, an env-specific B*3501-restricted CTL clone recognized a nonglycosylated, synthetic nonamer representing the minimal B*3501-restricted epitope, but not the glycosylated or deglycosylated forms. Second, the naturally processed, B*3501-restricted, env peptide is identical with a nonglycosylated, synthetic nonamer. Thus, the naturally processed form of an env epitope containing an N-linked glycosylation site is derived from env protein that is not glycosylated at the relevant asparagine during biosynthesis. Since the addition of N-linked oligosaccharides occurs only after the glycosylation signal sequence (N-X-S/T) is translocated into the endoplasmic reticulum, the initial processing reaction for this epitope may take place in the cytosol. Low-frequency failure of signal sequence containing polypeptides to engage the translocation apparatus, resulting in synthesis and degradation in the cytosol, may represent an important mechanism for the generation of class I-restricted CTL responses.

Amino Acid Sequence↗
PubMed1995

Application of PCR for detection and identification of mycoplasma contamination in virus stocks.

A nested polymerase chain reaction (PCR) was used to detect and identify mycoplasma contaminants in viral stocks. The results of the PCR assay proved to be a sensitive and accurate indicator of the true status of the stock tested. Those samples positive by agar culture or Hoechst stain were also positive by PCR. Those samples that were inconclusive by Hoechst stain (10.05%) could be clearly determined to be mycoplasma positive or negative by PCR. The PCR assay also detected those fastidious species of mycoplasma that gave false negative results by the direct culture method. In many respects the PCR-based mycoplasma detection method described is superior to the agar culture and Hoechst staining detection methods. In this study, the PCR assay detected substantially more mycoplasma-positive viral stocks than did the agar culture assay. Due to its speed, sensitivity, and reliability, the PCR assay is of particular value in monitoring the process of removing mycoplasma from contaminated stocks. Furthermore, the PCR amplification products can be analyzed by restriction analysis to rapidly identify the species of the mycoplasma contaminating the stock tested.

Base Sequence↗
PubMed1995

Dialysis staff influence patients in formulating their advance directives.

Patients on chronic dialysis were surveyed to determine the degree to which completion of advance directives (ADs) was influenced by personal factors that patients bring to their dialysis situation (eg, demographic characteristics or personal preferences) and by environmental factors that are not under their control (eg, interaction with dialysis staff or hospital system). Of the 113 questionnaires distributed to the population of 40 hemodialysis and 73 peritoneal dialysis patients, 90 (80%) were completed. Although only 17% of the respondents had actually completed written ADs previously, respondents seemed to have a good general understanding of ADs, as evidenced by the 80% overall accuracy on a 19-question portion of the survey that tested knowledge regarding ADs. While a few personal factors, such as gender, dialysis, modality, perceived quality of life, and attitude toward death, were associated with completion of ADs, most other demographic variables, including age, marital status, religion, work status, number of years of education, disability status, locus of control, renal diagnosis, and number of years on dialysis, were not correlated. More prominently correlated with completion of ADs were environmental factors, such as having dialysis staff discuss ADs with patients, patients being asked to complete ADs at the time of hospitalization, and perception of staff as being comfortable discussing ADs with patients. The overall results of the survey suggest that discussing ADs as an ongoing activity may have been positively influenced by the Federal Patient Self-Determination Act of 1991.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Defective development of the embryonic and extraembryonic circulatory systems in vascular cell adhesion molecule (VCAM-1) deficient mice.

VCAM-1 is a cytokine-inducible cell surface protein capable of mediating adhesion to leukocytes expressing alpha 4 integrins. Mice deficient in VCAM-1 expression were produced by targeted homologous recombination in ES cells. VCAM-1-deficient embryos were not viable and exhibited either of two distinct phenotypes. Approximately half of the embryos died before embryonic day 11.5 and exhibited a severe defect in placental development in which the allantois failed to fuse with the chorion. The remaining VCAM-1-deficient embryos survived to embryonic day 11.5-12.5 and displayed several abnormalities in their developing hearts including a reduction of the compact layer of the ventricular myocardium and intraventricular septum. The hearts also contained significant amounts of blood in the pericardial space and lacked an epicardium. alpha 4 and VCAM-1 were found to be expressed in wild-type embryos in a reciprocal fashion in the chorion and allantois and in the epicardium and the underlying myocardium, although VCAM-1 was expressed in the intraventricular septum in the absence of adjacent alpha 4-expressing cells. These data suggest important roles for VCAM-1 and alpha 4 in the development of the placenta and the heart.

Allantois↗
PubMed1994

Interleukin-6: a sensitive parameter for the early diagnosis of neonatal bacterial infection.

OBJECTIVE: Early recognition is important for the successful treatment and outcome of neonatal infections. As interleukin-6 (Il-6) plays a critical role in the induction of C-reactive protein (CRP) synthesis in the liver, it was hypothesized that this cytokine could be detected earlier in blood than the CRP during the course of bacterial infection. DESIGN: In a prospective study of 298 newborns who were admitted to the nursery unit, CRP levels, blood cell count with differential, and Il-6 levels were determined at the time of admission and 24 hours after admission. Seventy-six newborns were excluded from the study because of incomplete or incorrect blood sampling. RESULTS: The remaining 222 newborns were assigned to one of five groups: 11 newborns with blood culture-positive sepsis (sensitivity of Il-6 on admission 73%), 15 newborns with clinical sepsis (sensitivity of Il-6 on admission 87%), 41 newborns with infection (sensitivity of Il-6 on admission 68%), and 54 newborns without clinical and laboratory evidence of infection (specificity 78%). The remaining 101 newborns were defined as a mixed group because the diagnosis of neonatal infection could not clearly be made. Seventy-five percent of infected newborns had negative Il-6 levels 24 hours after admission. Of the 18 infected newborns with negative Il-6 levels on admission, 10 newborns had elevated CRP levels, suggesting that Il-6 was already negative because of the short half-life of Il-6. Sensitivity of Il-6 in CRP-negative newborns on admission was 100% in newborns with blood culture-positive and clinical sepsis. Il-6 was more sensitive than CRP in infected newborns on admission (73% vs 58%). CONCLUSION: Il-6 is a sensitive parameter for diagnosing neonatal bacterial infection. The combination of CRP and Il-6 seems to be the ideal tool for the early diagnosis of neonatal infection.

Bacterial Infections↗
PubMed1993

The mouse t complex distorter-3 (Tcd-3) locus and transmission ratio distortion.

A novel central partial t haplotype was generated by screening for a recombination event between overlapping distal and proximal partial haplotypes. This haplotype contains just two elements--Tcrt and Tcd-3t--involved in the t-specific transmission ratio distortion phenotype. Breeding analysis of males that carry this chromosome provides evidence that Tcd-3 is, indeed, a distorter locus and not a second responder. Furthermore, the data indicate that a single well-defined distorter locus is insufficient to overcome completely the self-destructive, low transmission ratio distortion phenotype expressed by the t allele at the t complex responder locus, although a small, but highly significant, effect was observed.

Alleles↗
PubMed1992

Androgen concentrations in expressed prostatic secretions: no correlation with tissue levels.

In an attempt to determine whether the androgen profiles of the prostate fluid (EPS) mirror the concentrations in the prostate tissue, we have measured testosterone and dihydrotestosterone (DHT) in EPS and correlated their levels to the concentrations found in hyperplastic prostate tissue (BPH) obtained from the same 19 patients. Although androgen concentrations in EPS were very high (testosterone = 106.7 +/- 81.9 ng/g dry weight; DHT = 54.2 +/- 11.2 ng/g dry weight), they did not reflect the concentrations measured in BPH tissue (testosterone = 7.56 +/- 1.54 ng/g dry weight; DHT = 10.54 +/- 0.63 ng/g dry weight). Additionally the accumulation of tissular DHT usually associated with BPH was not mirrored in the EPS specimens which demonstrated a relatively higher concentration of testosterone when compared to DHT. In EPS, there was also a very strong correlation between testosterone and DHT concentrations (r = 0.89; P less than 0.01). We have also measured zinc concentrations in EPS and BPH tissue but were unable to detect any relationship between the two parameters. Significantly, however, EPS zinc concentrations showed a close correlation with EPS testosterone (r = 0.73; P less than 0.01) and DHT (r = 0.69; P less than 0.01) concentrations.

Body Fluids↗
PubMed1992

Concerted evolution of the mouse Tcp-10 gene family: implications for the functional basis of t haplotype transmission ratio distortion.

The mouse Tcr locus is defined by its central role in the transmission ratio distortion phenotype characteristic of t haplotypes. A molecular candidate for Tcr has been identified in the form of a gene--Tcp-10b--expressed during spermatogenesis. Tcp-10b is one member of a multigene family present in two to four copies on different homologs of chromosome 17. The coding regions of the Tcp-10 genes present within two inbred strains were compared with those of the tw5 haplotype. The various gene family members are highly conserved relative to each other with a minimum nucleotide identity of 98.6% in all pairwise comparisons. Maximal parsimony analysis indicates that the Tcp-10 gene family has evolved in a concerted manner with the obliteration of nearly all individual gene-specific characteristics. As a consequence, the candidate for the full-length mutant Tcr gene product is distinguished by only a single, highly conservative, amino acid change. The data are consistent with the hypothesis that the effector of mutant Tcr activity is a second, alternatively spliced product that is expressed in a haploid- and allele-specific manner.

Alleles↗
PubMed1990

Immunohistochemical and molecular analysis of beta 1 and beta 3 integrins.

The expression and function of integrin subunits was examined by immunohistochemical staining of normal and malignant tissues and by producing specific changes in avian beta subunit cDNA that were subsequently expressed in mammalian cells. Most tissues express only a restricted number of integrins. These include primarily those thought to function as collagen/laminin receptors. With the exception of metastatic melanomas, tumors show a general down regulation of integrins. Structure/function studies of the beta subunit show that the cytoplasmic domain is required for inclusion in adhesion plaques and for promotion of adhesive functions; that the transmembrane domain is required for subunit association, but not proper alpha subunit selection; and that the amino terminal one third of the subunit must remain intact for subunit selection and ligand binding to occur.

Animals↗
PubMed1990

Receptors for tumor necrosis factor on neoplastic B cells from chronic lymphocytic leukemia are expressed in vitro but not in vivo.

Recombinant tumor necrosis factor-alpha (TNF-alpha) is a cytokine that induces proliferation of neoplastic B cells from patients with chronic lymphocytic leukemia (CLL). To gain insight into the mechanisms involved in regulating TNF responsiveness, we have examined TNF receptor expression on neoplastic B-CLL cells. We have demonstrated that freshly isolated neoplastic B cells from patients with CLL did not express TNF receptors. After 1 day of incubation in culture medium, TNF receptors were detectable in the range of 540 to 1,500/cell. Kinetic experiments revealed that receptor expression was half-maximal after 3 hours of culturing and required de novo protein synthesis. The Scatchard plots of TNF-alpha binding indicated a single set of high-affinity TNF receptors with a dissociation constant of 70 pmol/L. TNF receptor expression in vitro was found in all examined cases. All cytokines tested, with the exception of IL-2, did not influence the expression of TNF receptors. The TNF receptor expression is enhanced in B-CLL cells cultured in the presence of interleukin-2 when compared with the receptor expression of cells cultured in medium alone. Our data suggest that neoplastic B-CLL cells in patients with stable disease do not express TNF receptors in vivo and that an unknown mechanism suppressing TNF receptor expression in vivo may play a role in growth regulation of neoplastic B cells.

B-Lymphocytes↗
PubMed1990

The effect of appendage and scale loss on instar duration in adult firebrats, Thermobia domestica (Thysanura).

The loss of appendages immediately following a moult shortens the subsequent intermoult interval in adult Thermobia domestica. The loss of increasing numbers of appendages accelerates the ensuing moult incrementally. Leg amputation at sites distal to the trochanter-femoral autotomy plane has comparable effects in accelerating the moult. Functional legs regenerated at the first moult following amputation are at least 80% of normal length, while abdominal cerci are regenerated at a slower pace, attaining about 20% of normal length at the first post-operative moult. Scale loss also causes an acceleration of the following moult. It is proposed that changes in diffuse sensory input, rather than specific proprioceptive feedback, mediate the acceleration of the moult cycle.

Animals↗
PubMed1990

Tumor necrosis factor-alpha, but not lymphotoxin, stimulates growth of tumor cells in hairy cell leukemia.

We investigated the effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) and recombinant lymphotoxin (rLT) in the growth modulation of purified hairy cell leukemia (HCL) cells. In response to rTNF-alpha, HCL cells from five of eight patients showed a 3 to 23-fold thymidine incorporation above their unstimulated controls. The effect was time and dose dependent with a maximum between 10 and 25 ng/ml rTNF-alpha after 120-hr incubation. rLT (1-50 ng/ml), however, could not enhance DNA synthesis in six of six cases. Cell number of rTNF-alpha stimulated cells ranged from 2-3 x 10(6)/ml from days 0-50 whereas cell number of unstimulated controls decreased from 3 x 10(6)/ml at day 0 to 0.01-0.02 x 10(6)/ml after 50 days in culture. rTNF-alpha induced proliferation could be suppressed in all HCL cell populations by 0.3 ng/ml recombinant interferon alpha (100 U/ml rIFN-alpha). TNF binding studies in two patients revealed that both TNF-sensitive HCL cells (1,990 +/- 148 receptors/cell) as well as TNF-insensitive HCL cells (1,261 +/- 101 receptors/cell) express specific receptors for TNF-alpha. These data show that rTNF-alpha and rLT have different effects on the growth of HCL cells. In addition there is a subgroup of patients who show no response to rLT or rTNF-alpha.

Adult↗
PubMed1990

[Thrombocyte growth factor].

PDGF is one of the principal mitogens for cultured cells of mesenchymal origin. Apart from aggregated platelets PDGF can be secreted by a number of cells. There is a striking homology between the amino-acid sequence of PDGF and that of a transforming protein of simian-sarcoma virus. PDGF is an important chemotactic protein for cells implicated in wound healing. Furthermore, recent publications suggest a possible role in the pathogenesis of several diseases. This article summarizes studies and recent findings on the structure, biology, and functional role of PDGF.

Animals↗
PubMed1989

[Major gynecologic surgery in the geriatric patient].

A retrospective analysis of 256 important interventions in geriatric gynecologic patients (over 70 years of age) was carried out. There were 77 vaginal, 86 abdominal, 9 combined abdomino-vaginal and 82 breast operations. Minor (131) and major (31) complications are described in detail. Two postoperative deaths accounted for a mortality rate of 0.8% in these patients. It is emphasized, that on the premises of a thorough evaluation of the possible treatments, a modern anesthesiologic technique, a well devised operative strategy and the modern postoperative care we can nowadays justify extensive surgery even in the very old gynecologic patient.

Aged↗
PubMed1989

Rationale for combining tamoxifen and interferon in the treatment of advanced breast cancer.

Several investigators have discussed the possible combination of tamoxifen and interferon (IFN) in the treatment of breast cancer patients. The rationale in combining these drugs is that IFN induces the expression of estrogen receptors and therefore increases the sensitivity of breast cancer cells toward the growth-inhibitory activity of tamoxifen. In this paper we review the literature on the IFN-mediated expression of estrogen receptors and the postulated synergism of tamoxifen and IFN in the growth inhibition of breast cancer cell lines. Our results indicate that neither type I nor type II IFN increases the expression of estrogen receptors in MCF-7 cells. Together with tamoxifen both type I and type II IFN mediate additive but not synergistic growth inhibition of MCF-7 cells. On the basis of these results it is feasible to test tamoxifen and IFN as combined therapy in breast cancer patients. Preliminary clinical data show that the combination of 30 mg tamoxifen and 2 x 10(6) IU IFN-alpha as daily doses may induce WHO grade 3 leukopenia and thrombopenia in patients who are pretreated with polychemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗