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Biomedical subjects

C Buck

Publications and source records attributed to C Buck.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1989

Integrins isolated from Rous sarcoma virus-transformed chicken embryo fibroblasts.

Avian integrins are a complex of three integral membrane glycoproteins that are thought to have a role both in anchoring the cytoskeleton to the plasma membrane and establishing linkages to the extracellular matrix. We previously demonstrated that bands 2 and 3 of integrin are phosphorylated on both tyrosine and serine residues in chicken embryo fibroblasts (CEF) transformed with Rous Sarcoma virus (RSV) and other oncogenic retroviruses. The effects of RSV transformation on integrins from chick cells are now further characterized. The major site of tyrosine phosphorylation on band 3 in RSV transformed CEF has been identified as tyrosine 788. We also demonstrate that the product of the RSV oncogene, pp60v-src, can phosphorylate integrin in vitro, at the same residue. Tryptic peptide mapping and tunicamycin treatment indicates that a previously observed 4-8 k increase in the Mr of integrins from RSV-transformed cells can be attributed to an alteration in a post-translational modification such as glycosylation. Equilibrium gel filtration assays were used to test the ability of integrins from RSV-transformed CEF to interact with talin and fibronectin. Tyrosine phosphorylated integrins showed a decreased ability to interact with both these ligands in vitro. Conversely, integrins isolated from RSV-transformed CEF metabolically labeled in the absence of phosphatase inhibitor contained only low levels of phosphotyrosine and showed an almost normal ability to interact with ligands. Competition experiments indicated that the region of integrin containing tyrosine 788 is also important for talin binding to integrins.

Animals↗
PubMed1989

Tumor necrosis factor induces proliferation of neoplastic B cells from chronic lymphocytic leukemia.

The biologic effects of recombinant tumor necrosis factor-alpha (rTNF-alpha) and the expression of specific TNF membrane receptors on isolated neoplastic B cells from previously untreated patients with chronic lymphocytic leukemia (CLL) were investigated in vitro. Isolated B cells were incubated up to six days with various concentrations of rTNF-alpha (0.1 to 100 ng/mL). B cells from most patients proliferated ranged from two to 104 times that of unstimulated cells from the same patients. An optimal proliferative effect was achieved at 25 ng/mL rTNF-alpha and an incubation time between 96 and 120 hours, whereas a low concentration of rTNF-alpha (1 ng/mL) reduced [3H]TdR incorporation in four cases. Metaphase cells were detected in the rTNF-alpha-stimulated cultures that proliferated in response to rTNF-alpha. B cells from three of ten patients proliferated spontaneously and proliferation was further enhanced in two patients by rTNF-alpha. TNF binding assays gave a value of approximately 390 to 1,400 binding sites/cell for TNF and a dissociation constant (kd) of approximately 60 pmol/L. These data indicate that rTNF-alpha, in contrast to its cytotoxic/cytostatic effects, can also induce proliferation of tumor cells.

Adult↗
PubMed1988

A rapid method for the large scale preparation of bovine leukemia virus antigen.

Bovine leukemia virus (BLV) is the etiologic agent responsible for enzootic bovine leukosis. Detection of cattle seropositive for BLV and laboratory studies of BLV require the preparation of large quantities of BLV antigen. A convenient and economical method for concentrating virus from large volumes of cell culture medium involves the precipitation of the virus in the cold by polyethylene glycol (PEG). The present work demonstrates the feasibility of rapidly precipitating BLV with 10% PEG and subsequently separating the resuspended virus from the residual PEG on a disposable desalting column.

Antigens, Viral↗
PubMed1987

Cancer incidence in hypertensives.

Cancer incidence was measured over a 5-year period (1978 to 1982) in 4067 hypertensive patients, and 10,366 normotensive patients from general practices in southwestern Ontario. For cancer of all sites an elevated incidence was found among hypertensive patients. The elevation was most pronounced among newly diagnosed hypertensive patients, with hypertension of moderate or greater severity, and for sites that have been described in clinical reports as being capable of producing a rise in blood pressure. It is tentatively concluded that the causal direction is from cancer to hypertension, rather than the reverse. If this conclusion is correct, the associations that have been reported between cancer mortality and hypertension may be due to an effect of blood pressure upon survival from cancer.

Adult↗
PubMed1987

Early germ cell segregation and distribution in the quail blastodisc.

The distribution and number of primordial germ cells has been analyzed in quail blastodiscs from the incubated state to the 13-somite stage, treated in toto with monoclonal antibody QH1. Some cells were already positive in unincubated blastulas some 18 h earlier than described with other markers in previous studies of avian development. The number of PGCs increased from 2-3 in the unincubated state to more than 100 at the early primitive streak stage. During following stages their numbers did not increase significantly. At first these cells were isolated, thereafter they often assembled in small groups and progressively gathered into Swift's crescent. It is concluded that PGCs begin segregating in birds at the blastula stage and that they multiply until the primitive streak stage.

Animals↗
PubMed1987

The prognosis of hypertension according to age at onset.

Data from a program for hypertension screening and follow-up were used to study the relationship between age at onset of hypertension and the risk of cardiovascular complications. The risk for hypertensive subjects, compared with normotensive subjects of similar age, declined significantly as age of onset increased from 40 to 69 years. This pattern was not explained by differences in initial severity of hypertension, control of hypertension, obesity, smoking, or alcohol consumption. A sex-specific analysis showed that the pattern was confined to male subjects, but it is argued that it might be seen in female subjects if data for women of more advanced age were available. Further lines of investigation of this interesting phenomenon are proposed.

Adult↗
PubMed1987

The value of preoperative screening investigations in otherwise healthy individuals.

To assess the value of routine screening preoperative investigations in an otherwise healthy surgical population, the charts of 2570 patients undergoing cholecystectomy in two university teaching hospitals were reviewed. Of these, 1010 patients who were believed to be free of active disease other than cholelithiasis were selected for further study. Preoperative screening investigations were assessed in terms of frequency of use and abnormalities detected. The predictive values of these tests were analyzed and compared with information obtained from the history and physical examination. The frequency with which action was taken because of abnormal test results was also determined. Of the 5003 preoperative screening tests performed, abnormal results were obtained in 225. Of these, 104 were of potential importance. Action resulting from these abnormalities occurred in 17 cases. In only four patients could a conceivable benefit have arisen from a preoperative screening test. When compared with the results of the history and physical examination, routine preoperative investigations provided little further information that altered management in otherwise healthy surgical patients undergoing cholecystectomy.

Blood Cell Count↗
PubMed1986

Structure of integrin, a glycoprotein involved in the transmembrane linkage between fibronectin and actin.

We describe the isolation, characterization, and sequence of cDNA clones encoding one subunit of the complex of membrane glycoproteins that forms part of the transmembrane connection between the extracellular matrix and the cytoskeleton. The cDNA sequence encodes a polypeptide of 89 kd that has features strongly suggesting the presence of a large N-terminal extracellular domain, a single transmembrane segment, and a small C-terminal cytoplasmic domain. The extracellular domain contains a threefold repeat of a novel 40 residue cysteine-rich segment, and the cytoplasmic domain contains a tyrosine residue that is a potential site for phosphorylation by tyrosine kinases. We propose the name integrin for this protein complex to denote its role as an integral membrane complex involved in the transmembrane association between the extracellular matrix and the cytoskeleton.

Actins↗
PubMed1986

Phosphorylation of the fibronectin receptor complex in cells transformed by oncogenes that encode tyrosine kinases.

The fibronectin (FN) receptor in avian cells has been characterized previously as a complex of three membrane glycoproteins of about Mr 160,000, Mr 140,000, and Mr 120,000 (simply termed protein band 1, band 2, and band 3, respectively). Monoclonal antibodies to the band 3 protein of the complex prevent FN and laminin binding both in vivo and in vitro and enable the detection of the receptor proteins in the plasma membrane and in adhesion plaques. Association of the FN receptor proteins with the adhesion-plaque protein talin also has been reported. We now find that the band 2 and band 3 proteins in the complex are phosphorylated in Rous sarcoma virus-transformed chicken cells but not in normal chicken cells. Phosphorylation occurs predominantly on tyrosine and is accompanied by a reorganization of the receptor complex in the membrane of the transformed cells. Whereas normal cells contain the FN receptor in focal contacts and cellular processes between cells, v-src-transformed cells exhibit a more diffuse distribution of this receptor. In addition to the viral v-src oncogene, cells transformed by other avian oncogenes that also encode tyrosine kinases (v-fps, v-erbB, and v-yes) also express the receptor complex proteins in the phosphorylated state regardless of whether the transforming protein is detectable in adhesion plaques. These results suggest that the altered FN and laminin receptor proteins may contribute to the transformed phenotype, but their significance and role in the transformed state remain to be established.

Animals↗