Search PubMed⌕ Search

Biomedical subjects

J F Head

Publications and source records attributed to J F Head.

At least 19 recordsLinked to original sources
PubMed2001

The crystal structure of nucleoplasmin-core: implications for histone binding and nucleosome assembly.

The efficient assembly of histone complexes and nucleosomes requires the participation of molecular chaperones. Currently, there is a paucity of data on their mechanism of action. We now present the structure of an N-terminal domain of nucleoplasmin (Np-core) at 2.3 A resolution. The Np-core monomer is an eight-stranded beta barrel that fits snugly within a stable pentamer. In the crystal, two pentamers associate to form a decamer. We show that both Np and Np-core are competent to assemble large complexes that contain the four core histones. Further experiments and modeling suggest that these complexes each contain five histone octamers which dock to a central Np decamer. This work has important ramifications for models of histone storage, sperm chromatin decondensation, and nucleosome assembly.

Amino Acid Sequence↗
PubMed2001

The crystal structure of MarR, a regulator of multiple antibiotic resistance, at 2.3 A resolution.

MarR is a regulator of multiple antibiotic resistance in Escherichia coli. It is the prototypical member of the MarR family of regulatory proteins found in bacteria and archaea that play important roles in the development of antibiotic resistance, a global health problem. Here we describe the crystal structure of the MarR protein, determined at a resolution of 2.3 A. This is the first reported crystal structure of a member of this newly-described protein family. The structure shows MarR as a dimer with each subunit containing a winged-helix DNA binding motif.

Amino Acid Motifs↗
PubMed2000

The crystal structure of the photoprotein aequorin at 2.3 A resolution.

Aequorin is a calcium-sensitive photoprotein originally obtained from the jellyfish Aequorea aequorea. Because it has a high sensitivity to calcium ions and is biologically harmless, aequorin is widely used as a probe to monitor intracellular levels of free calcium. The aequorin molecule contains four helix-loop-helix 'EF-hand' domains, of which three can bind calcium. The molecule also contains coelenterazine as its chromophoric ligand. When calcium is added, the protein complex decomposes into apoaequorin, coelenteramide and CO2, accompanied by the emission of light. Apoaequorin can be regenerated into active aequorin in the absence of calcium by incubation with coelenterazine, oxygen and a thiol agent. Cloning and expression of the complementary DNA for aequorin were first reported in 1985 (refs 2, 6), and growth of crystals of the recombinant protein has been described; however, techniques have only recently been developed to prepare recombinant aequorin of the highest purity, permitting a full crystallographic study. Here we report the structure of recombinant aequorin determined by X-ray crystallography. Aequorin is found to be a globular molecule containing a hydrophobic core cavity that accommodates the ligand coelenterazine-2-hydroperoxide. The structure shows protein components stabilizing the peroxide and suggests a mechanism by which calcium activation may occur.

Aequorin↗
PubMed2000

Reduction in serum IL-6 after vacination of breast cancer patients with tumour-associated antigens is related to estrogen receptor status.

Elevated serum IL-6 concentrations have been associated with poor prognosis in a variety of cancers, and decreases in serum IL-6 concentrations have been reported after chemotherapy. We have demonstrated that serum IL-6 concentrations are elevated in breast cancer patients [normal women 0.7 +/- 2.5 pg/ml (n=36), breast cancer patients 38.3 +/- 138.7 pg/ml (n = 111)]. After vaccination of breast cancer patients with a combination of tumour-associated antigens and biological adjuvants (IL-2 and GM-CSF), the concentration of IL-6 decreased significantly (P<0.05) to 8.1 +/- 14.6 pg/ml (n=85). Other studies have shown that oestrogen suppresses IL-6 production in oestrogen receptor positive breast cancer cells. We have demonstrated that the decrease in IL-6 associated with vaccination is related to the oestrogen receptor status of the tumours from breast cancer patients, as a decrease in IL-6 from 124.0 +/- 267.5 pg/ml (n=26) to 6.2 +/- 11.0 pg/ml (n=34) only occurs in patients with oestrogen receptor negative tumours. The IL-6 concentration in breast cancer patients with oestrogen receptor positive tumours remained unchanged (9.5 pg/ml before vaccination, and 9.3 pg/ml after vaccination). These results suggest that postmenopausal women with oestrogen receptor negative breast cancers, who do not respond well to either hormonal therapy with tamoxifen or adjuvant chemotherapy, may have a significant response to vaccination with autologous tumour-associated antigens.

Adult↗
PubMed2000

Vaccination with a mixed vaccine of autogenous and allogeneic breast cancer cells and tumor associated antigens CA15-3, CEA and CA125--results in immune and clinical responses in breast cancer patients.

In breast cancer there is often overexpression of the breast cancer antigen CA15-3, the carcinoembryonic antigen (CEA) and the ovarian cancer antigen CA125, which makes them potential target antigens for immunotherapy. In this study, we used a multi-antigen vaccine, which included the following antigens: autologous breast cancer cells (AUTOC), allogeneic breast cancer MCF-7 cells (ALLOC), and the tumor associated antigens CA15-3, CEA and CA125, plus low doses of granulocyte/macrophage-colony-stimulating factor (GM-CSF) and interleukin 2 (IL-2). Forty-two breast cancer patients received weekly subcutaneous vaccination at the 1st, 2nd, 3rd, 7th, 11th and 15th weeks. Their lymphocyte proliferative responses to AUTOC, ALLOC, CA15-3, CEA and CA125 were tested in lymphocyte blastogenesis assays (LBA) before and after vaccination. The disease stage and serum CA15-3, CEA and CA125 concentrations were also determined pre- and post-vaccination. We found that the vaccine was safe, and the only major side effects were swelling at the site of injection, muscle pain, and weakness or fatigue. The vaccine induced a significant increase in post-vaccination lymphocyte proliferative responses to AUTOC, CA15-3, CEA and CA125 but not ALLOC, compared to pre-vaccination (p < 0.05, p < 0.01, p < 0.05, p < 0.01 and p > 0.05, respectively, a paired t Test). Computed tomography (CT), ultrasound or bone scan showed evidence of disease improvement in 2 (12%) patients after vaccination. Hepatic metastases were reduced in size and number and some actually disappeared one patient. Metastatic disease in the L5 vertebra and the skull decreased in size and some osteolytic sites completely healed in a second patient. In addition, 7 patients (44%) had stable disease and 7 patients (44%) had disease progression. We did not find vaccination significantly reduced serum tumor markers CA15-3, CEA and CA125 of these breast cancer patients. These results suggest that the vaccine mixture of autologous and allogeneic breast cancer cells and tumor associated antigens plus GM-CSF and IL-2 can be administered safely to breast cancer patients and there is evidence for improved immunity and clinical efficacy.

Adult↗
PubMed1998

Mutational and crystallographic analyses of interfacial residues in annexin V suggest direct interactions with phospholipid membrane components.

Annexin V belongs to a family of eukaryotic calcium-dependent membrane-binding proteins. The calcium-binding sites at the annexin-membrane interface have been investigated in some detail; however, little is known about the functional roles of highly conserved interfacial residues that do not coordinate calcium themselves. In the present study, the importance of tryptophan 185, and threonine or serine at positions 72, 144, 228, and 303, in rat annexin V is investigated by site-directed mutagenesis, X-ray crystallography, and functional assays. The high-resolution crystal structures of the mutants show that the mutations do not cause structural perturbations of the annexin molecule itself or disappearance of bound calcium ions from calcium-binding sites. The assays indicate that relative to wild-type annexin V, loss of the methyl substituent at position 72 (Thr72-->Ser) has no effect while loss of the hydroxyl group (Thr72-->Ala or Thr72-->Lys) causes reduction of membrane binding. Multiple lysine substitutions (e.g., Thr72,Ser144,Ser228,Ser303-->Lys) have a greater adverse effect than the single lysine mutation, suggesting that in annexin V the introduction of potentially favorable electrostatic interactions between the lysine side chains and the net negatively charged membrane surface is not sufficient to overcome the loss of the hydroxyl side chains. Replacement of the unique tryptophan, Trp185, by alanine similarly decreases membrane binding affinity. Taken together, the data suggest that the side chains mutated in this study contribute to phospholipid binding and participate directly in intermolecular contacts with phospholipid membrane components.

Alanine↗
PubMed1997

Antineoplastic drugs that interfere with iron metabolism in cancer cells.

Normal iron metabolism can be perturbed with iron chelators, toxic metals that bind to transferrin, toxic metals bound to transferrin or antineoplastic agents covalently linked to transferrin. These agents cause significant inhibition of tumor cell growth in cell culture and have been shown to have significant in vivo antineoplastic activity. Cell culture studies showed that deferoxamine mesylate inhibits cell growth and division in both the MCF-7 human breast and HeLa human cervical carcinoma cell lines. Animal studies demonstrated that when deferoxamine mesylate is injected intravenously into rats that are on a low iron diet, there is a significant reduction in the growth of 13762NF mammary adenocarcinomas. Gallium, indium and the antineoplastic agent cisplatin were bound to the iron binding site of transferrin and inhibit the growth of malignant carcinoma cell lines. Gallium-transferrin and indium-transferrin were at least 10 times more inhibitory to both MCF-7 and HeLa cell lines than their free salts. Further cell culture studies demonstrated that cisplatin-transferrin complexes act synergistically with doxorubicin to inhibit the growth of cultured MCF-7 cells. In a Phase I clinical trial of cisplatin-transferrin complex there was a 36% (four of 11 patients) response rate in breast cancer patients with advanced disease. In a second clinical study the sequential administration of deferoxamine mesylate (2 days at 6 g/day in 8 hrs), cisplatin-transferrin complex (7 days at 500 mg/day) and FAC (5-fluorouracil, doxorubicin and cyclophosphamide at 450, 45 and 450 mg/m2, respectively) to advanced breast cancer patients resulted in partial responses in seven of eight patients treated. Future work will concentrate on substituting transferrin based agents with daunorubicin or doxorubicin attached to the surface of the transferrin, and gallium or indium bound to the iron binding site, to increase efficacy of the second component of the sequential combination chemotherapy.

Animals↗
PubMed1996

Stereotaxic localization and core needle biopsy of nonpalpable breast lesions: two-year follow-up of a prospective study.

In August 1989, we began a prospective study of patients with abnormal mammograms to determine the clinical efficacy of stereotaxic localization and needle biopsy of nonpalpable breast lesions. By August 1990, 115 patients had undergone stereotaxic localization and needle biopsy of nonpalpable breast lesions using the Mammotest II (Fischer Imaging, Denver, CO) and an 18-gauge needle in a Bard Biopty gun (Bard Urological, Covington, GA). In 19 per cent (22 of 115) of the cases, the pathologist suggested open surgical biopsies of the lesions due to clinical judgment, or atypical or cancer cells in the core biopsy specimen. Of these 22 cases, 12 (54%) were found to be cancer on open surgical biopsy--10 per cent of all the patients. Of the remaining 93 patients with benign pathology, 9 were lost to follow-up by the end of the second year after closure of the study. The remaining 84 patients were followed by mammography and physical exam at 3 months, at 12 months, and yearly thereafter to determine whether cancer had been missed or developed at the biopsy site. The median follow-up was 24 months (mean, 23.3 months), and all 84 patients were found to have no evidence of malignant disease at follow-up. The small group (10 cases) of patients who were determined to have benign disease by open surgical biopsy were also found on follow-up to have no evidence of malignant disease (median follow-up, 20.5 months; and mean, 18.3 months). The accuracy of this stereotaxic procedure, combined with an approximately 80 per cent decrease in the more expensive and more invasive open surgical biopsy procedure, provides strong support for the use of this procedure on all nonpalpable breast lesions that would normally proceed to open surgical biopsy.

Adenocarcinoma, Mucinous↗
PubMed1994

Phototransduction. Shedding light on recoverin.

The crystal structure of recoverin reveals two functional Ca2+-binding sites and a surface hydrophobic feature that may be important for membrane-binding and recoverin's role in the rod cell's recovery from light.

Animals↗
PubMed1994

Comparison of estrogen and progesterone receptor status to lymphocyte immunity against tumor antigens in breast cancer patients.

Estrogen (ER) and progesterone receptor (PgR) content of tumors were determined by both the dextran-coated charcoal (DCC) cytosol and immunocytochemical assays (ICA), and these hormone receptor results were compared to lymphocyte immunity against tumor antigen(s) for 52 breast carcinoma patients. Hormone receptor analysis by both methods demonstrated that 60% of the patients' tumors had ERs, while 44% were positive for PgRs. The ICA procedure was more sensitive than the cytosol technique for determining PgR content of the tumors. This increased sensitivity was not observed for ER by ICA. Patient age, tumor size, and nodal status were not related to the ER and PgR receptor status. A total of 21/52 (40%) of the patients had positive lymphocyte immunity against tumor antigen. This immunity was independent of patient age, tumor size, and nodal status. There was no significant relationship between lymphocytic immunity against tumor antigen and ER or PgR content of tumors, suggesting that patient lymphocyte immunity against tumor is independent of hormone receptor status. This is further evidence that lymphocyte immunity against tumor antigen status is an independent prognostic indicator that may be useful in the selection of a subset of node negative patients for adjuvant chemotherapy.

Age Factors↗
PubMed1994

Relationship of serum and tumor levels of iron and iron-binding proteins to lymphocyte immunity against tumor antigen in breast cancer patients.

Fifty-two breast cancer patients were evaluated for levels of several molecules related to iron metabolism including determining their tumor tissue and serum ferritin levels, serum transferrin levels, and serum iron levels. In addition the patients' lymphocyte immunity against autologous tumor antigen was investigated. Forty percent (21 of 52) of the patients had lymphocyte immunity against tumor antigen. Iron metabolism molecules were expressed in abnormal quantities in some breast cancer patients: 27% (13 of 49) had elevated tumor tissue ferritin levels, 4% (2 of 49) had abnormally high serum ferritin, 10% (5 of 49) had abnormally low serum transferrin levels, and 43% (21 of 49) had depressed serum iron levels. None of these abnormalities in iron metabolism are associated with tumor immunity. These iron metabolism molecules may be indicative of rates of cell proliferation or may influence growth of breast cancer cells, but do not appear to influence host lymphocyte immunity against tumor associated antigens.

Antigens, Neoplasm↗
PubMed1993

A novel cell culture technique for electron microscopy.

A simplified technique for the monolayer growth of cultured cells and their in situ embedment on the inner surface of the pyramidal portion of the Beem capsule for electron microscopy has been developed. The results demonstrated that the cell monolayers grew well on the surface of the Beem capsule and could be embedded in situ. Electron micrographs showed cells in their natural state of contact with one another. The plasma membrane and intracellular organelles were well preserved. This method minimizes many difficult steps and eliminates the disruption of cells by scraping, pelleting, or enzymatic reaction to remove them.

Humans↗
PubMed1993

Breast thermography is a noninvasive prognostic procedure that predicts tumor growth rate in breast cancer patients.

Our recent retrospective analysis of the clinical records of patients who had breast thermography demonstrated that an abnormal thermogram was associated with an increased risk of breast cancer and a poorer prognosis for the breast cancer patient. This study included 100 normal patients, 100 living cancer patients, and 126 deceased cancer patients. Abnormal thermograms included asymmetric focal hot spots, areolar and periareolar heat, diffuse global heat, vessel discrepancy, or thermographic edge sign. Incidence and prognosis were directly related to thermographic results: only 28% of the noncancer patients had an abnormal thermogram, compared to 65% of living cancer patients and 88% of deceased cancer patients. Further studies were undertaken to determine if thermography is an independent prognostic indicator. Comparison to the components of the TNM classification system showed that only clinical size was significantly larger (p = 0.006) in patients with abnormal thermograms. Age, menopausal status, and location of tumor (left or right breast) were not related to thermographic results. Progesterone and estrogen receptor status was determined by both the cytosol-DCC and immunocytochemical methods, and neither receptor status showed any clear relationship to the thermographic results. Prognostic indicators that are known to be related to tumor growth rate were then compared to thermographic results. The concentration of ferritin in the tumor was significantly higher (p = 0.021) in tumors from patients with abnormal thermograms (1512 +/- 2027, n = 50) compared to tumors from patients with normal thermograms (762 +/- 620, n = 21). Both the proportion of cells in DNA synthesis (S-phase) and proliferating (S-phase plus G2M-phase, proliferative index) were significantly higher in patients with abnormal thermograms. The expression of the proliferation-associated tumor antigen Ki-67 was also associated with an abnormal thermogram. The strong relationships of thermographic results with these three growth rate-related prognostic indicators suggest that breast cancer patients with abnormal thermograms have faster-growing tumors that are more likely to have metastasized and to recur with a shorter disease-free interval.

Age Factors↗