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Biomedical subjects

M Hunt

Publications and source records attributed to M Hunt.

At least 19 recordsLinked to original sources

Lith1, a major gene affecting cholesterol gallstone formation among inbred strains of mice.

The prevalence of cholesterol gallstones differs among inbred strains of mice fed a diet containing 15% (wt/wt) dairy fat, 1% (wt/wt) cholesterol, and 0.5% (wt/wt) cholic acid. Strains C57L, SWR, and A were notable for a high prevalence of cholelithiasis; strains C57BL/6, C3H, and SJL had an intermediate prevalence; and strains SM, AKR, and DBA/2 exhibited no cholelithiasis after consuming the diet for 18 weeks. Genetic analysis of the difference in gallstone prevalence rates between strains AKR and C57L was carried out by using the AKXL recombinant inbred strain set and (AKR x C57L)F1 x AKR backcross mice. Susceptibility to gallstone formation was found to be a dominant trait determined by at least two genes. A major gene, named Lith1, mapped to mouse chromosome 2. When examined after 6 weeks on the lithogenic diet, the activity of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.88) was downregulated as expected in the gallstone-resistant strains, AKR and SJL, but this enzyme failed to downregulate in C57L and SWR, the gallstone-susceptible strains. This suggests that regulation of the rate-limiting enzyme in cholesterol biosynthesis may be pivotal in determining the occurrence and severity of cholesterol hypersecretion and hence lithogenicity of gallbladder bile. These studies indicate that genetic factors are critical in determining gallstone formation and that the genetic resources of the mouse model may permit these factors to be identified.

Animals

Purification and characterization of phospho enol pyruvate carboxykinase from Trypanosoma brucei.

ATP-dependent phospho enol pyruvate carboxykinase (EC 4.1.1.49; PEPCK, ATP) was purified from glycosomes of cultured procyclic Trypanosoma brucei to electrophoretic homogeneity. The purified enzyme exhibited a mean specific activity of 83 units mg-1, as measured in the carboxylation direction at 30 degrees C. A similar activity was obtained for the decarboxylation reaction. The enzyme was shown to be a homodimer in solution with a subunit molecular mass of 59 kDa. Amino acid sequence analysis suggested that the PEPCK (ATP) is identical to the trypanosomal protein p60, the sequence of which was previously predicted from the corresponding nucleotide sequence by other investigators. The basic nature of the enzyme was indicated by a high isoelectric point (pH 8.9). The enzyme was found to be strictly dependent on adenosine nucleotides for activity, as well as on the presence of Mn2+. Mg2+ was found to be ineffective as activator of the trypanosomal enzyme, but a combination of subsaturating (< or = 300 microM) concentrations of Mn2+ and high concentrations of Mg2+ caused a synergistic effect on the carboxylation activity, indicating a dual cation requirement. Mn2+ is necessary to activate the enzyme and Mn2+ or Mg2+ most likely forms the cation-nucleotide complex as the active form of the substrate. Relatively high (5 mM) levels of ATP were required to produce a significant inhibition of the carboxylation reaction. Quinolinic acid, a structural analogue of oxaloacetate, completely inhibited the decarboxylation reaction at a 1 mM concentration. The apparent Michaelis constants of the enzyme were 490 microM for PEP, 37 microM for oxaloacetate, 40 microM for ADP, 10.3 microM for ATP, 970 microM for Mn2+ and 26 mM for HCO3-. Endogenous substrate concentrations were found to be 327 nmol PEP, 1486 nmol ADP, 4200 nmol ATP and 11.5 nmol Mn2+ (ml cell volume)-1. Our kinetic data suggest that under physiological conditions PEPCK (ATP) in T. brucei is bidirectional and that its activity is regulated primarily by mass action. The physiological relevance of the enzyme in procyclic T. brucei is discussed.

Amino Acid Sequence

Dopamine deficiency in a genetic mouse model of Lesch-Nyhan disease.

We have examined several aspects of neurotransmitter function in the brains of mice carrying a deletion mutation in the gene encoding the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). During the first 6 weeks of postnatal development, dopamine levels in whole-brain extracts from the mutant mice (HPRT-) failed to increase at rates comparable to normal animals, resulting in 40% lower dopamine levels throughout adulthood. Regional analysis in adult animals showed the caudoputamen to be the most severely affected region, with dopamine deficits of 48-64%. Dopamine levels in other regions were normal or less severely affected. The decrease in dopamine was accompanied by a decrease in tyrosine hydroxylase (TH) activity, the rate-limiting step in dopamine synthesis. Kinetic analysis of TH extracted from the caudoputamen of normal and HPRT- mice demonstrated a 45% decrease in Vmax with an increased affinity for the tetrahydropterin cofactor in the mutants. Labeling of midbrain dopamine neurons using TH immunohistochemistry revealed no obvious deficits in the number of midbrain dopamine neurons, but quantitative autoradiographic studies revealed significant reductions in the binding of 3H-N-[1-(2-benzo(beta)thiophenyl)cyclohexyl]piperidine (3H-BTCP) to dopamine uptake sites in the forebrain of the mutants. In contrast to these abnormalities of the dopamine systems in the mutant mice, other neurotransmitter systems appeared relatively unaffected. Norepinephrine, 5-HT, tryptophan hydroxylase, and glutamic acid decarboxylase were present at normal levels in the brains of the mutants. ChAT activity was slightly lower than normal in the caudoputamen of the mutant animals, but was normal in all other brain regions examined. These results indicate that HPRT deficiency is associated with a relatively specific deficit in basal ganglia dopamine systems that emerges during the first 2 months of postnatal development.

3,4-Dihydroxyphenylacetic Acid

Mobilization of peripheral blood progenitor cells by chemotherapy and granulocyte-macrophage colony-stimulating factor for hematologic support after high-dose intensification for breast cancer.

High-dose therapy with autologous marrow support results in durable complete remissions in selected patients with relapsed lymphoma and leukemia who cannot be cured with conventional dose therapy. However, substantial morbidity and mortality result from the 3- to 6-week period of marrow aplasia until the reinfused marrow recovers adequate hematopoietic function. Hematopoietic growth factors, particularly used after chemotherapy, can increase the number of peripheral blood progenitor cells (PBPCs) present in systemic circulation. The reinfusion of PBPCs with marrow has recently been reported to reduce the time to recovery of adequate marrow function. This study was designed to determine whether granulocyte-macrophage colony-stimulating factor (GM-CSF)-mobilized PBPCs alone (without marrow) would result in rapid and reliable hematopoietic reconstitution. Sixteen patients with metastatic breast cancer were treated with four cycles of doxorubicin, 5-fluorouracil, and methotrexate (AFM induction). Patients responding after the first two cycles were administered GM-CSF after the third and fourth cycles to recruit PBPCs for collection by two leukapheresis per cycle. These PBPCs were reinfused as the sole source of hematopoietic support after high doses of cyclophosphamide, thiotepa, and carboplatin. No marrow or hematopoietic cytokines were used after progenitor cell reinfusion. Granulocytes greater than or equal to 500/microL was observed on a median of day 14 (range, 8 to 57). Transfusion independence of platelets greater than or equal to 20,000/microL occurred on a median day of 12 (range, 8 to 134). However, three patients required the use of a reserve marrow for slow platelet engraftment. In retrospect, these patients were characterized by poor baseline bone marrow cellularity and poor platelet recovery after AFM induction therapy. When compared with 29 historical control patients who had received the same high-dose intensification chemotherapy using autologous marrow support, time to engraftment, antibiotic days, transfusion requirements, and lengths of hospital stay were all significantly improved for the patients receiving PBPCs. Thus, autologous PBPCs can be efficiently collected during mobilization by chemotherapy and GM-CSF and are an attractive alternative to marrow for hematopoietic support after high-dose therapy. The enhanced speed of recovery may reduce the morbidity, mortality, and cost of high-dose treatment. Furthermore, PBPC support may enhance the effectiveness of high-dose therapy by facilitating multiple courses of therapy.

Adolescent

Prenatal diagnosis of tetrasomy 12p by in situ hybridization: varying levels of mosaicism in different fetal tissues.

Prenatal diagnosis of tetrasomy 12p is complicated by the discrimination of the 12p isochromosome from the duplication 21q as well as the level of mosaicism demonstrated in the particular tissue sampled. In this disease, a high percentage of chromosomally abnormal cells are generally found in fibroblastic cells, but lymphocyte karyotypes from the same individual may be normal. We report on the pregnancy of a 37-year-old female who presented to our centre at 16 weeks' gestation for genetic amniocentesis. Sonography of the fetus revealed dextrocardia and diaphragmatic hernia. Chromosome analysis of amniocytes demonstrated mosaicism of a 47,XY,+i(12p) line in 80 per cent of cells and a normal male line (20 per cent), consistent with the Pallister-Killian syndrome. Following termination, a 220 g male fetus of 18 weeks was examined. A flattened nose and low-set ears were noted. In situ hybridization with a chromosome 12 centromeric probe in lymphocytes and skin cells unequivocally confirmed the karyotype and showed the presence of a single centromere in the abnormal chromosome, suggesting a true isochromosome. Chromosome analysis of various fetal tissues was performed and the following percentages of abnormal cells were found: skin 100 per cent, chorion 50 per cent, placenta 30 per cent, and blood 80 per cent. The high frequency of tetrasomic cells in fetal blood at this early gestational age is noteworthy, since most reports of this syndrome show a very low percentage of abnormal cells postnatally.

Adult

An extended phase II trial of ifosfamide plus mesna in malignant mesothelioma.

Forty three patients with histologically confirmed malignant mesothelioma were entered onto an Eastern Cooperative Oncology Group phase II study of ifosfamide given with mesna. Eligibility criteria included adequate performance status, hemogram and renal functions. Ifosfamide was given at 1.5 g/m2 in 200 ml of normal saline over 30 minutes by intravenous infusion on days 1 to 5 of each 21 day cycle. Mesna was given at 300 mg/m2 on each day of ifosfamide at 0, 4 and 8 hours. Two patients were cancelled and one patient was ineligible. The most common toxicity was haematologic. More than 50% of the patients had at least one episode of severe or life threatening toxicity and 2 patients had lethal toxicity (1 renal and 1 pulmonary oedema attributed to treatment), and an additional 4 patients died while on study (2 of cardiac and 2 of cerebral vascular disease not considered directly related to treatment). Of the 40 eligible patients one was unevaluable for response, and one patient had a partial response lasting 6.3 months. Twenty four patients had a no change status with a median duration of 5 months. The median time to treatment failure for all eligible patients was 2.5 months. The median overall survival time (from registration) for all eligible patients was 6.9 months. In multi variable models, factors that predicted for a statistically significant poorer survival were age > or = 62, stage > or = 3, performance status poorer than 0 to 1 and prior surgery (i.e.: more than biopsy).(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Administration Schedule

CNS distribution of D1 receptors: use of a new specific D1 receptor antagonist, [3H]SCH39166.

D1 dopamine receptors have been localized using a radioactive form of a new specific antagonist, [3H]SCH39166. This compound has been shown, in in vitro binding studies, to be highly selective for the D1 receptor subtype; more so than its predecessor, [3H]SCH23390. These ligand binds saturably, reversibly and with high affinity. Use of appropriate conditions produces a high signal to noise binding ratio to D1 receptors in slide-mounted tissue sections. Autoradiographic localization of radiolabeled receptors shows high densities of the D1 receptor subtype in such brain structures as the caudate-putamen, nucleus accumbens, entopeduncular nucleus, and the substantia nigra pars reticulata. A lower density of receptors is found in a few other areas including lamina VI of the cerebral cortex. A distinct paucity of binding was apparent in lamina IV of the cerebral cortex and in the choroid plexus, two areas thought to have D1 receptors. SCH39166 thus represents a superior ligand for obtaining selective labeling of D1 receptors in autoradiographic and binding studies.

Animals

Nasopharyngeal brachytherapy with access via a transpalatal flap.

We used a posteriorly based transpalatal flap for interstitial nasopharyngeal brachytherapy in five patients with nasopharyngeal carcinoma. All of these implants were done with iodine 125 seeds. The disease in three of five patients has been controlled locally for 27, 30, and 40 months, respectively. Two patients experienced local failure and died. There have been no palatal healing problems despite high doses of previous radiation in all of our patients. No palatal incompetence has been seen. This technique appears safe and should be considered for discrete lesions of the high posterior or superior nasopharynx that cannot be approached by less invasive methods.

Adult

'Scripts' for dying at home--displayed in nurses', patients' and relatives' talk.

Perceptions and expectations reflecting what constitutes a 'good' death that seem to exist in Western societies are explored and compared with those presented by five symptom control team nurses at their home visits to 54 terminally ill cancer patients. These perceptions and expectations are termed 'scripts' for dying and are derived from the nurses', patients' and relatives' audio-recorded conversations over a 3-month period. The elements of the 'scripts' used were identified as: (a) control of physical symptoms, (b) acceptance of cancer and its prognosis, (c) preservation of hope and 'will to live', (d) mobility and 'fighting back', (e) enjoyment of life, (f) a peaceful death at home. How these components are determined from the conversations are presented and the responses of the patients to the nurses' 'scripts' are analysed. The dilemmas created by putting the 'scripts' into action for nurses, patients and relatives are discussed.

Attitude to Death

A changing pattern of epiglottitis.

A case review of epiglottitis at Geisinger Medical Center over the past 12 years demonstrates a decrease in the number of pediatric patients with epiglottitis and an increase in the number of adults with epiglottitis. In the last five years, the number of epiglottitis patients younger than 10 years has fallen (0 cases), while the number of patients over 10 years of age has increased (6 cases). The cause of epiglottitis, Hemophilus influenzae type b, remains constant in the pediatric as well as in the adult population. There appears to be an increasing frequency of epiglottitis in adults and a decreasing frequency of epiglottitis in children.

Adult

A phase II study of high-dose cyclophosphamide, thiotepa, and carboplatin with autologous marrow support in women with measurable advanced breast cancer responding to standard-dose therapy.

PURPOSE: The study was designed to determine the duration of complete response (CR) for patients with unresectable or metastatic breast cancer treated with high-dose cyclophosphamide, thiotepa, and carboplatin (CTCb) while responding to conventional-dose therapy. METHODS: Eligibility criteria included histologically documented metastatic or unresectable breast cancer, at least a partial response (PR) to conventional-dose therapy, no prior pelvic radiotherapy, cumulative doxorubicin of less than 500 mg/m3, and physiologic age between 18 and 55 years. Patients with inadequate renal, hepatic, pulmonary, and/or cardiac function or tumor involvement of marrow or CNS were excluded. Cyclophosphamide 6,000 mg/m2, thiotepa 500 mg/m2, and carboplatin 800 mg/m2 were given by continuous infusion over 4 days. After recovery, sites of prior bulk disease were to be radiated or resected if feasible. RESULTS: Of 29 registered patients, one died of toxicity (3%; hemorrhage). CRs and PRs continued a median of 16 and 5 months after transplant, respectively (26 and 9 months from initiation of chemotherapy for metastatic disease). Of 10 patients transplanted in CR, four have not progressed at 17 to 31 months after transplantation (25 to 43 months after beginning standard-dose therapy). One of four patients with uptake on bone scan as their only sites of residual disease before transplant and one of three who converted from PR to CR with transplant have not progressed at 27 and 29 months, respectively, after transplant. CONCLUSIONS: CTCb is an intensification regimen with a low mortality that delivers a significantly increased dose of agents with known activity at conventional doses in breast cancer. Although the duration of PR is short as expected, CRs appear to be durable.

Adult

Pulmonary toxicity associated with high dose chemotherapy in the treatment of solid tumors with autologous marrow transplant: an analysis of four chemotherapy regimens.

We retrospectively reviewed the pulmonary toxicity of six high dose chemotherapy protocols using four chemotherapy regimens in the treatment of solid tumors. All protocols used either high dose cyclophosphamide or ifosfamide in combination with one to three additional chemotherapeutic agents. In each protocol autologous bone marrow was reinfused post chemotherapy to shorten the period of severe myelosuppression. Of 178 patients there were 20 cases of fatal or life-threatening pulmonary toxicity including nine cases of pneumonia, nine cases of interstitial pneumonitis and two cases of pulmonary hemorrhage. Pulmonary function tests revealed modest changes in FEV1 and DLCO in the majority of patients, although 24 patients had more dramatic changes in DLCO suggesting interstitial damage. Significant decrements in FEV1 were seen in the BCNU containing regimen. Statistically significant or nearly significant decreases in DLCO were seen after all cyclophosphamide containing regimens. A regimen containing ifosfamide, carboplatin, and etoposide had minimal associated pulmonary toxicity.

Adolescent

Three-dimensional photon treatment planning in carcinoma of the larynx.

The role of three-dimensional (3-D) treatment planning in the definitive treatment of carcinoma of the larynx with radiation was evaluated at four institutions as part of an NCI contract. A total of 30 different treatment approaches were devised for two patients with larynx cancer. CT scans were obtained for both patients and various treatment planning tools were employed to optimize beam arrangements and to evaluate the resulting dose distribution. The effect on dose distribution of a number of factors was also examined: 1) the use of dose calculation algorithms which correct for tissue inhomogeneities, 2) the variation of the CT numbers used for inhomogeneity corrections to simulate inaccuracies in the knowledge of the CT numbers, and 3) the modification of beam energy. A multitude of data was used in plan evaluation and a numerical score was given to each plan to estimate the tumor control probability and the normal tissue complication probability. We found 3-D treatment planning to be of potential value in optimizing treatment plans in larynx cancer. Improved target coverage was achieved when complete information describing 3-D geometry of the anatomy was utilized. In some cases, the treatment planning tools employed, such as the beam's eye view, helped devise novel beam arrangements which were useful alternatives to standard techniques. We found little effect of change in CT number on dose distributions. A comparison between dose distributions calculated with tissue inhomogeneity corrections to those calculated without this correction showed little difference. We did find some improvement in the dose to the primary tumor volume at lower beam energies, but with an increased larynx volume potentially receiving doses above tolerance.

Adult

Three-dimensional photon treatment planning of the intact breast.

Three-dimensional treatment planning for the intact breast was performed on two patients who had undergone CT scanning. A total of 38 treatment plans were evaluated. Multiple plans were evaluated for each patient including plans with and without inhomogeneity corrections, plans using varying photon energies of 60Co, 4 MV, 6 MV, 10 MV, and 15 MV, and three-dimensionally unconstrained plans. Increased hot spots were appreciated in the central axis plane when lung inhomogeneity corrections were used. Additional hot spots were appreciated in off-axis planes towards the cephalad and caudad aspects of the target volume because of lung inhomogeneity corrections and changes in the breast contour. The use of 60Co was associated with an increase in the magnitude and volume of hot spots, whereas the use of higher energy photons such as 10 MV and 15 MV was associated with an unacceptable target coverage at shallow depths. Therefore, for the two patients studied, the use of a medium energy photon beam (such as from a 6 MV linear accelerator) appeared to be the energy of choice for treatment of the intact breast. The three-dimensionally unconstrained plans were able to improve slightly upon the standard plans, particularly with relationship of dose to normal tissue structures. Areas for future research were identified, including the use of tissue compensators.

Adult

Escalating doses of carboplatin with high-dose ifosfamide using autologous bone marrow as support: a phase I study.

In this phase I study, 16 adult cancer patients were treated with concurrent 4-day continuous infusions of ifosfamide at 12 g/m2 and escalating doses of carboplatin (400-1600 mg/m2) to determine the major non-haematological dose-limiting toxicity of the combination. Mesna was given by continuous infusion over 5 days for uroprotection (total dose per course = 15 g/m2). Autologous bone marrow support, which was mandated for subsequent dose levels once granulocytes remained below 500/microliters for more than 14 days in at least 2 patients entered at a given dose level, was used at dose levels above 400 mg/m2 carboplatin. Renal toxicity became dose-limiting at the maximum tolerated dose level of 1600 mg/m2 carboplatin. Temporary creatinine elevations above 2 mg/dl (median peak 2.6 mg/dl) were observed in 3 and irreversible renal toxicity occurred in 1 (peak creatinine 6.9 mg/dl, chronic creatinine 5-6 mg/dl) of the 5 patients entered at this dose level. Severe confusion and lethargy associated with rising creatinine developed in 2 patients. Two complete and four partial responses were documented in 14 heavily pretreated evaluable patients. The complete responses continue at 14+ and 20+ months in a patient with germ cell carcinoma and Ewing's sarcoma, respectively. Carboplatin appears to contribute to the renal toxicity of ifosfamide. Nevertheless, the combination of carboplatin and ifosfamide at 80% and 75% of the single-agent maximal tolerated doses respectively produced acceptable non-haematological toxicity. Further studies in the treatment of sarcoma, germ cell, ovarian and lung carcinomas with this combination are warranted.

Adult

GM-CSF potentiated peripheral blood progenitor cell (PBPC) collection with or without bone marrow as hematologic support of high-dose chemotherapy: two protocols.

High-dose chemotherapy with autologous bone marrow support (ABMS) achieves prolonged relapse-free survival in relapsed lymphomas and leukemias and has provided durable complete responses in certain solid tumors. The principal morbidity and mortality result from the infectious and bleeding complications during the 3-4 week aplasia until the bone marrow autograft can recover. Hematopoietic growth factors, alone or used after chemotherapy, increase the number of circulating progenitor cells in the peripheral blood compartment. In one trial, 12 patients with solid tumors were treated with high-dose chemotherapy and supported with both bone marrow and peripheral blood progenitor cells (PBPC) collected after GM-CSF administration. Reconstitution of bone marrow function occurred quickly (ANC greater than 500/microliters by day 17; platelet-transfusion independence by day 16), resulting in short hospital stays (median, 28 days). In a second study, 12 patients with metastatic breast cancer responding to induction chemotherapy (doxorubicin, 5-fluorouracil, and methotrexate) were given GM-CSF during induction to collect PBPCs during leukocyte recovery. These PBPCs were used as the sole hematopoietic support during high-dose chemotherapy with cyclophosphamide, thiotepa, and carboplatin. Granulocyte and platelet reconstitution were extremely rapid (median, 14 and 12 days, respectively). When compared with 29 patients undergoing the same intensification therapy using ABMT as sole support, time to hematopoietic recovery, transfusion requirements, and duration of hospital stay were all significantly improved for the patients receiving PBPC. PBPC with or without marrow may enhance the safety, tolerance, and cost of high-dose therapy. Moreover, PBPC may render multiple course combination, high-dose therapy feasible.

Antineoplastic Combined Chemotherapy Protocols

Being friendly and informal: reflected in nurses', terminally ill patients' and relatives' conversations at home.

The aspect of the study discussed is part of the analysis of audio-recorded, naturally occurring conversations between symptom control team (SCT) nurses, terminally ill cancer patients and their relatives in their own homes over a 3-month period. Using an ethnographic, extended case-study approach, four 'role formats' were identified as consistently used by the SCT nurses to carry out their work through conversation, one of them being 'friendly and informal'. The SCT nurses explicitly made it known to patients and their relatives that they intended to be 'friendly and informal'. How such a claim was translated into practice, both non-conversationally and through conversation, is the focus of this paper. Being 'friends' and being 'friendly and informal' with patients and clients is frequently advocated in medical and nursing literature, but how this is achieved in practice and the responses of patients seems unstudied. Therefore, the analysis discussed in this paper opens up for critical reflection an unquestioned, taken-for-granted aspect of practice where it is demonstrated how 'friendliness and informality' are conveyed through chatting and how it differs from 'formal' conversations.

Communication

Use of leucocyte alkaline phosphatase (LAP) score in differentiating malignant from benign paraproteinaemias.

The leucocyte alkaline phosphatase (LAP) score of peripheral blood neutrophils was examined in 20 patients with multiple myeloma and compared with the score in 18 patients with monoclonal gammopathy of undetermined significance (MGUS). The mean (95% confidence limit) LAP score in those with multiple myeloma was 186 (169-218) compared with 92 (64-120) in the MGUS group. In the multiple myeloma group all but one patient had a high LAP score, irrespective of disease. No cause for raised LAP, such as infection, was present in any of the patients with multiple myeloma. In the MGUS group six patients had a raised LAP score; in two of them another cause for such a rise was present (autoimmune haemolytic anaemia and primary thrombocythaemia). In neither group did the LAP score correlate with duration of the disease, bone marrow plasma cell count, paraprotein concentration, haemoglobin, total white cell or neutrophil count. It is concluded that a normal LAP count in patients with paraproteinaemia suggests a benign condition, but a raised count does not indicate a malignant condition.

Aged