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Biomedical subjects

Michael White

Publications and source records attributed to Michael White.

11 recordsLinked to original sources
PubMed2025

14 days of high-dose versus low-dose primaquine treatment in patients with Plasmodium vivax infection in Cambodia: a randomised, single-centre, open-label efficacy study.

BACKGROUND: Most malaria-endemic countries, including Cambodia, use a total dose of 3&#xb7;5 mg/kg of primaquine to eliminate Plasmodium vivax hypnozoites and prevent relapses. There are, however, indications that the lower dose of 3&#xb7;5 mg/kg is insufficient for tropical P vivax isolates, particularly in southeast Asia, and WHO now recommends a total dose of 7&#xb7;0 mg/kg in most countries. We aimed to determine the most effective regimen to eliminate P vivax hypnozoites to support elimination efforts of this malaria parasite. METHODS: We conducted an open-label, randomised controlled trial in Kampong Speu province, western Cambodia. Patients infected with P vivax aged at least 15 years were offered to participate. Exclusion criteria were severe malaria or other diseases requiring treatment, low haemoglobin (<8&#xb7;0 g/dL), pregnancy or breastfeeding, sensitivity to study drugs, and use of antimalarials in the preceding month. Enrolled patients were treated with an artesunate regimen of 2 mg/kg per day for 7 days. Patients with normal glucose-6-phosphate dehydrogenase (G6PD) levels were randomly assigned (2:2:1) to receive 3&#xb7;5 mg/kg (low dose [0&#xb7;25 mg/kg per day]), 7&#xb7;0 mg/kg (high dose [0&#xb7;5 mg/kg per day]), or no primaquine for 14 days. Patients with deficient G6PD levels were assigned to the no primaquine comparator arm. Patients were relocated to the study site in Aoral town where no malaria transmission occurs to ensure that they were not reinfected during their 90-day follow-up. After 90 days of relocation, G6PD-normal patients in the no primaquine arm were provided 3&#xb7;5 mg/kg of primaquine for 14 days to be taken unsupervised. At day 90, relocation was terminated, and patients were followed up monthly for 3 months until day 180. The primary outcome was P vivax recurrence within 90 days of relocated follow-up, assessed in all patients who completed treatment and complied with relocation without interruption. All patients enrolled and assigned to an intervention arm were included in the safety analysis. The study is registered on ClinicalTrials.gov and recruitment is completed (NCT04706130). FINDINGS: Between Nov 10, 2021, and Feb 10, 2024, 160 patients were enrolled and 147 were included in the primary analysis-59 were assigned to the no primaquine arm (37 assigned as G6PD deficient [median age 22 years, IQR 18-28]; 22 randomly assigned [18, 17-25]), 45 to the low-dose primaquine arm (23, 19-30), and 43 to the high-dose primaquine arm (22, 18-25). Participants were mostly male (135 [92%] of 147) and all Cambodian. 48 (81% [95% CI 69&#xb7;6-89&#xb7;2]) participants in the no primaquine arm had at least one P vivax recurrence within 90 days, as did 11 (24%, 14&#xb7;2-38&#xb7;7) in the low-dose group and two (5%, 0&#xb7;8-15&#xb7;5) in the high-dose group (p=0&#xb7;0141 for high vs low). After imputation for missing data, low-dose primaquine remained associated with more recurrences than high-dose primaquine (hazard ratio 0&#xb7;17 [95% CI 0&#xb7;04-0&#xb7;79], p=0&#xb7;0229). Both primaquine regimens were well tolerated with no serious adverse events reported. INTERPRETATION: Not providing primaquine to patients led to a considerable rate of P vivax recurrence. The risk of P vivax recurrence was substantially lower for 7&#xb7;0 mg/kg primaquine treatment compared with 3&#xb7;5 mg/kg. Tolerability and safety of both primaquine regimens in G6PD normal individuals was comparable. FUNDING: US National Institutes of Health (R01AI146590).

Humans↗
PubMed2003

The role of Ink4a/Arf in ErbB2 mammary gland tumorigenesis.

Most human tumors display inactivation of the p53 and the p16(INK4)/pRb pathway. The Ink4a/alternative reading frame (ARF) locus encodes the p16(INK4a) and p14(ARF) (murine p19(ARF)) proteins. p16(INK4a) is deleted in 40-60% of breast cancer cell lines, and p16(INK4a) inactivation by DNA methylation occurs in < or =30% of human breast cancers. In mice genetically heterozygous for p16(INK4a) or Ink4a/Arf, predisposition to specific tumor types is enhanced. Ink4a/Arf(+/-) mice have increased E micro -Myc-induced lymphomagenesis and epidermal growth factor receptor-induced gliomagenesis. ErbB2 (epidermal growth factor receptor-related protein B2) is frequently overexpressed in human breast cancer and is sufficient for mammary tumorigenesis in vivo. We determined the role of heterozygosity at the Ink4a/Arf locus in ErbB2-induced mammary tumorigenesis. Compared with mouse mammary tumor virus-ErbB2 Ink4a/Arf(+/-) mice, mouse mammary tumor virus-ErbB2 Ink4a/Arf(wt) mammary tumors showed increased p16(INK4a), reduced Ki-67 expression, and reduced cyclin D1 protein but increased mammary tumor apoptosis with no significant change in the risk of developing mammary tumors. These studies demonstrate the contribution of Ink4a/Arf heterozygosity to tumor progression is tissue specific in vivo. In view of the important role of Ink4a/Arf in response to chemotherapy, these transgenic mice may provide a useful model for testing breast tumor therapies.

Adenocarcinoma↗
PubMed2003

Serial analysis of gene expression in circulating gamma delta T cell subsets defines distinct immunoregulatory phenotypes and unexpected gene expression profiles.

Gene expression profiles were compared in circulating bovine GD3.5+ (CD8-) and GD3.5- (predominantly CD8+) gammadelta T cells using serial analysis of gene expression (SAGE). Approximately 20,000 SAGE tags were generated from each library. A comparison of the two libraries demonstrated 297 and 173 tags representing genes with 5-fold differential expression in GD3.5+ and GD3.5- gammadelta T cells, respectively. Consistent with their localization into sites of inflammation, GD3.5+ gammadelta T cells appeared transcriptionally and translationally more active than GD3.5- gammadelta cells. GD3.5- gammadelta T cells demonstrated higher expression of the cell proliferation inhibitor BAP 37, which was associated with their less activated gene expression phenotype. The immune regulatory and apoptosis-inducing molecule, galectin-1, was identified as a highly abundant molecule and was higher in GD3.5+gammadelta T cells. Surface molecules attributed to myeloid cells, such as CD14, CD68, and scavenger receptor-1, were identified in both populations. Furthermore, expression of B lymphocyte-induced maturation protein, a master regulator of B cell and myeloid cell differentiation, was identified by SAGE analysis and was confirmed at the RNA level to be selectively expressed in gammadelta T cells vs alphabeta T cells. These results provide new insights into the inherent differences between circulating gammadelta T cell subsets.

Animals↗
PubMed2003

Role for plastin in host defense distinguishes integrin signaling from cell adhesion and spreading.

Integrin ligation activates both cell adhesion and signal transduction, in part through reorganization of the actin cytoskeleton. Plastins (also known as fimbrins) are actin-crosslinking proteins of the cortical cytoskeleton present in all cells and conserved from yeast to mammals. Here we show that plastin-deficient polymorphonuclear neutrophils (PMN) are deficient in killing the bacterial pathogen Staphylococcus aureus in vivo and in vitro, despite normal phagocytosis. Like integrin beta2-deficient PMN, plastin-deficient PMN cannot generate an adhesion-dependent respiratory burst, because of markedly diminished integrin-dependent syk activation. Unlike beta2(-/-) PMN, plastin-deficient PMN adhere and spread normally. Deficiency of plastin thus separates the classical integrin receptor functions of adhesion and spreading from intracellular signal transduction.

Animals↗
PubMed2003

Gene discovery in the apicomplexa as revealed by EST sequencing and assembly of a comparative gene database.

Large-scale EST sequencing projects for several important parasites within the phylum Apicomplexa were undertaken for the purpose of gene discovery. Included were several parasites of medical importance (Plasmodium falciparum, Toxoplasma gondii) and others of veterinary importance (Eimeria tenella, Sarcocystis neurona, and Neospora caninum). A total of 55192 ESTs, deposited into dbEST/GenBank, were included in the analyses. The resulting sequences have been clustered into nonredundant gene assemblies and deposited into a relational database that supports a variety of sequence and text searches. This database has been used to compare the gene assemblies using BLAST similarity comparisons to the public protein databases to identify putative genes. Of these new entries, approximately 15%-20% represent putative homologs with a conservative cutoff of p < 10(-9), thus identifying many conserved genes that are likely to share common functions with other well-studied organisms. Gene assemblies were also used to identify strain polymorphisms, examine stage-specific expression, and identify gene families. An interesting class of genes that are confined to members of this phylum and not shared by plants, animals, or fungi, was identified. These genes likely mediate the novel biological features of members of the Apicomplexa and hence offer great potential for biological investigation and as possible therapeutic targets.

Animals↗
PubMed2003

Histopathologic evidence of tumor regression in the axillary lymph nodes of patients treated with preoperative chemotherapy correlates with breast cancer outcome.

BACKGROUND: The benefits of primary tumor downstaging and assessment of chemoresponsiveness have resulted in expanded applications for induction chemotherapy. However, the pathologic evaluation and prognostic significance of response in preoperatively treated lymph nodes have not been defined. METHODS: The axillary lymph nodes of 71 patients with locally advanced breast cancer treated with induction chemotherapy were evaluated for histological evidence of tumor regression as defined by the presence of nodal fibrosis, mucin pools, or aggregates of foamy histiocytes. RESULTS: Complete pathologic response in the breast and axilla occurred in 10 patients (14%); 19 (26.8%) had evidence of tumor regression in 1 or more lymph nodes. Patients without nodal metastases and no evidence of tumor regression had the best outcome (median disease-free survival, 31.5 months; relapse rate, 27%). Patients with residual nodal metastases and no evidence of treatment effect had the worst outcome (median disease-free survival, 19.8 months; relapse rate, 55%). The median disease-free survival was 22.1 months, and the relapse rate was 32% for patients with histopathologic evidence of tumor regression in the axillary lymph nodes. CONCLUSIONS: Detection of treatment effect in axillary lymph nodes after induction chemotherapy identifies a subset of patients with an outcome intermediate between that of completely node-negative and node-positive patients. The axillary lymph nodes of patients receiving preoperative chemotherapy should be routinely analyzed for the presence of these features.

Breast Neoplasms↗
PubMed2002

Ethnicity related differences in the survival of young breast carcinoma patients.

BACKGROUND: African-American women face an increased risk of early-onset breast carcinoma compared to white American women, and breast carcinoma has been reported to be particularly aggressive in premenopausal women. METHODS: Surveillance, Epidemiology, and End Results Program data were analyzed for 507 African-American and 1378 white patients from Detroit diagnosed with breast carcinoma under the age of 40 between 1990 and 1999. RESULTS: The proportion of in situ disease detected in African-American patients between 1995 and 1999 nearly doubled compared to the 1990-1994 interval (11.3% compared to 6.4%) but was consistently lower than the proportion of in situ disease seen in white patients for the same intervals (15.7% and 16.4% respectively). Evaluation of patients with invasive disease revealed that African-American patients had larger mean tumor size (3.4 cm versus 2.6 cm; P < 0.001), lower rates of localized disease (42.4% versus 52.1%; P < 0.001), higher rates of estrogen receptor negativity (61.9% versus 44.4%; P < 0.001), and higher proportions of medullary tumors (5.8% versus 3.3%; P = 0.021). Cox proportional hazards survival analysis adjusted for age, tumor size, nodal status, hormone receptor status, and histology showed higher mortality rates for African-American patients at all disease stages. Relative risk of death for African-American patients was 1.94 in patients with localized disease (95% confidence interval [CI], 1.23-3.05), 1.58 for regional disease (95% CI = 1.18-2.11), and 2.32 for distant disease (95% CI = 1.15-4.69). CONCLUSIONS: These findings show that young African-American breast carcinoma patients face an increased mortality risk. Additional studies evaluating risk and treatment response in this subset of patients are warranted.

Adult↗
PubMed2002

Office-based ultrasound-guided cryoablation of breast fibroadenomas.

BACKGROUND: Fibroadenomas commonly found by palpation and routine mammography account for approximately 20% of open surgical breast biopsies. Alternatives to open surgery include tumor removal using an automated coring device and tumor ablation using heating or cooling elements. We report our initial experience with cryoablation of biopsy-proven benign fibroadenomas. METHODS: A table-top cryoablation system employing a 2.4-mm cryoprobe was used to treat biopsy-proven benign fibroadenomas up to 4 cm in maximum diameter in a prospective nonrandomized fashion. The cryoprobe was placed under ultrasound guidance. Using a treatment algorithm based on fibroadenoma size, all tumors were subjected to two freeze cycles with an interposing thaw. Skin appearance and temperature, probe temperature, iceball size, and patient comfort were closely monitored during the procedure. Follow-up examinations including ultrasonography and photographs were scheduled for up to 12 months postablation. RESULTS: Fifty patients with 57 core biopsy-proven benign fibroadenomas were treated. Seven early cases were treated in an ambulatory surgery center setting. The remaining procedures were completely office-based using only local anesthetic. Tumor diameter varied from 7 mm to 42 mm (mean 21 mm). The iceball engulfed the target lesion in each case. Transient postoperative side effects were local swelling and ecchymosis. Postoperative discomfort rarely required medication beyond acetaminophen or ibuprofen. Lesions showed progressive shrinkage and disappearance over 3 to 12 months. No skin injury was noted and appearance remained excellent. Patient satisfaction was excellent. CONCLUSIONS: With office-based use of ultrasound-guided cryoablation for fibroadenomas there was little or no pain, target lesions were reduced in size or eliminated, scarring was minimal, cosmesis outstanding, and patient satisfaction was excellent. Cryoablation offers a useful office-based alternative to surgical excision of benign fibroadenomas.

Adolescent↗
PubMed2002

Toxoplasma gondii-infected human myeloid dendritic cells induce T-lymphocyte dysfunction and contact-dependent apoptosis.

Dendritic cells ignite adaptive immunity by priming naïve T lymphocytes. Human monocyte-derived dendritic cells (MDDCs) infected with Toxoplasma gondii induce T-lymphocyte gamma interferon production and may thus activate T. gondii-specific immunity. However, we now demonstrate that T. gondii-infected MDDCs are poor at activating T lymphocytes and are unable to induce specific cytotoxic T lymphocytes. On the other hand, MDDCs acquiring nonviable T. gondii antigens directly, or indirectly through captured apoptotic or necrotic cell bodies, induce potent T-lymphocyte activation. T lymphocytes exposed to infected MDDCs are significantly impaired in upregulation of CD69 and CD28, are refractory to activation, and die through contact-dependent apoptosis mediated by an as-yet-unidentified mechanism not requiring Fas, tumor necrosis factor-related apoptosis-inducing ligand, leukocyte function antigen 1, intercellular adhesion molecule 1, tumor necrosis factor alpha, interleukin 10, alpha interferon, gamma interferon, prostaglandins, or reactive nitrogen intermediates. Bystander T lymphocytes that were neither infected nor apoptotic were refractory to activation, suggesting global dysfunction. Immunosuppression and T-lymphocyte unresponsiveness and apoptosis are typical of acute T. gondii infection. Our data suggest that infected dendritic cells contribute to these processes. On the other hand, host cells infected with T. gondii are resistant to multiple inducers of apoptosis. Thus, regulation of host cell and bystander cell apoptosis by viable T. gondii may be significant components of a strategy to evade immunity and enhance intracellular parasite survival.

Animals↗