Design and interpretation of clinical research studies in oral medicine: a brief review

The objective of this short review is to help researchers improve the designs of their clinical studies. Also included is a discussion of the level of evidence provided by the various clinical research study designs.     

Serological investigation of pneumonia as it presents to the physician��s office

Purpose:

To define the etiology of pneumonia, using a battery of serological tests, among patients presenting to physicians’ offices in Cumberland County, Nova Scotia from July 2, 1989 to July 1, 1990.

Methods:

Patients presenting to their physician’s office with symptoms suggestive of pneumonia were invited to participate in the study by completing a questionnaire, having a chest radiograph and providing acute and convalescent phase serum samples. These serum samples were tested for antibodies to Mycoplasma pneumoniae, Coxiella burnetii, Legionella pneumophila, adenovirus, and influenza viruses A and B. Some of the samples were tested for antibodies to Chlamydia pneumoniae.

Results:

Seventy-five of the inception cohort of 203 patients had a chest radiograph compatible with pneumonia, a completed questionnaire and acute and convalescent phase serum samples. There were 39 females and 36 males with a mean age of 41.7 years. Twenty-six (35%) were admitted to hospital. The mortality rate was 3%. Forty-five per cent had a diagnosis made by serology: M pneumoniae, 22 (29%); influenza A virus, five (7%); C burnetii, L pneumophila, adenovirus, two (3%) each.

Conclusions:

While it is not possible to generalize about these findings because of ascertainment bias, the data suggest that M pneumoniae is a common cause of pneumonia presenting to a physician’s office and that mortality is low in this group of patients.     

High-frequency cell surface expression of a foreign protein in murine hematopoietic stem cells using a new retroviral vector

A retroviral vector (pSFF) derived from murine Friend spleen focus forming virus was used to transduce murine hematopoietic stem cells and express a cell surface marker protein, mutated murine prion protein, in vitro and in vivo after transplantation. To enhance retroviral vector integration in bone marrow cells, mice were treated with 5-fluorouracil (5-FU) to increase stem cell mitotic activity, which peaked on day 8 post-5-FU. The infectivity titer of the vector, pSFF-mPrP-3F4, was determined by a novel assay in which antigen-positive foci of infected cells were detected after replication and spread of the vector in cultures of mixed packaging cell lines. Infection of Sca-1+/Lineageneg- low cells with pSFF-mPrP-3F4 resulted in marker protein expression in 40% of the progeny cells after 7 days of culture. Transplantation of marrow cells or sorted Sca-1+/Lineageneg-low cells transduced with vector resulted in 3F4-positive mPrP expression in 11% to 37% of donor- derived peripheral blood leukocytes at 2 weeks. Though the percentage of 3F4-positive blood cells gradually declined, at 28 weeks 23% of recipient mice still maintained expression of the marker gene. Expression was observed in lymphoid, myeloid, and erythroid lineages and was detected in Sca-1+/Lineageneg-low marrow cells. The multilineage, high-frequency expression observed suggests that pSFF may be useful in gene therapy directed at hematopoietic stem cells and their differentiated progeny.     

Selective inhibition of the growth of human erythroid bursts by monoclonal antibodies against transferrin or the transferrin receptor

The relative requirements of colonies derived from erythroid (BFU-E) and myeloid (CFU-c) progenitors for transferrin were examined using monoclonal antibodies directed against the transferrin molecule (TF-6) or its cell surface receptor (TFR-A12, TFR1-2B). Growth of erythroid bursts was profoundly reduced at concentrations of all three antibodies that had no effect on CFU-c-derived colonies. When TFR1-2B was layered over cultures established one to seven days previously, further burst development was inhibited, and degeneration of early erythroid colonies was observed. Addition of erythropoietin augmented transferrin receptor expression on cells harvested after 1 to 2 weeks in culture and analyzed by flow cytometry. Recombinant human erythropoietin gave results comparable to those obtained in experiments using human urinary erythropoietin. Analysis of erythroblasts plucked directly from culture plates confirmed the presence of transferrin receptors on BFU-E-derived colonies. Thymidine incorporation was maximal early in the second week of culture and coincided with high transferrin receptor expression. These data demonstrate that transferrin must be available into the second week of culture to support the growth and differentiation of BFU- E-derived erythroid bursts, that the generation of erythroid colonies from BFU-E is more dependent on transferrin than myeloid colony formation from CFU-c, and that erythropoietin modulates the expression of transferrin receptors on growing bursts.     

Spontaneous iron overload in alpha-thalassemic mice

Because clinical disorders of spontaneous iron overload have no experimental counterpart, we studied iron distribution (atomic absorption analysis) and intestinal absorption (59Fe) in mice with hereditary alpha-thalassemia. Mice heterozygous for a radiation-induced alpha-Hb gene deletion exhibit a mild hemolytic anemia, like the human condition, with microcytosis, reticulocytosis, splenomegaly, and chemical evidence of defective alpha-chain synthesis. Quantitative iron determination showed that total iron content in spleen, liver, and kidney, but not heart or lung, of adult alpha-thalassemic mice was greater (P less than .05) than that in unaffected littermates. Iron concentration was also increased in liver (P less than .001), spleen (P = .025), kidney (P = .058), and heart (P = .010); in general, the greater the iron concentration in liver, the greater that in spleen (r = .39, P = .009), kidney (r = .70, P less than .001), and heart (r = .46, P less than .001). In mice examined 8 months postoperatively, splenectomy, as compared to sham operation, significantly raised iron content in extrasplenic tissues, but did not affect total body iron. At 10-11 weeks of age, but no longer at 12-14 weeks, thalassemic mice showed higher rates of iron absorption than age-matched controls. Thus, alpha-thalassemic mice display an early occurring iron absorption defect, leading to a modest, sustained, nonprogressive iron overload, and thereby represent a valuable model for exploring disorders of iron homeostasis.     

Recombinant Human Deoxyribonuclease Improves Atelectasis in Mechanically Ventilated Children with Cardiac Disease

Objective. To investigate whether a mucolytic agent, recombinant human deoxyribonuclease (rhDNase), improves atelectasis in children with cardiac illness requiring mechanical ventilation. Design. A retrospective cohort study on consecutive patients receiving short‐term (≤14 days) rhDNase therapy for atelectasis in the cardiac intensive care unit from January 2005 through February 2007 was carried out. Data relating to patient characteristics, gas exchange, ventilatory parameters, and chest radiographs were collected and analyzed. The effectiveness of rhDNase therapy in the presence of neutrophils and/or bacteria in the pre‐rhDNase therapy tracheal aspirates was also investigated. Results. rhDNase was effective in significantly improving established atelectasis without any major changes in gas exchange and ventilatory parameters. Therapeutic effect of rhDNase is most effective in ameliorating atelectasis in the lungs within 10 doses. rhDNase was more effective in improving chest radiographic atelectasis score in patients who had > moderate amounts of polymophonuclear neutrophils (P value = 0.0008), or bacteria (P value = 0.007) or both (P value = 0.004) present in their pre‐rhDNase therapy trachea aspirate. No adverse effects were seen with rhDNase administration in the study cohort. Conclusions. rhDNase can be safely and effectively used to improve atelectasis in mechanically ventilated children with cardiac disease especially in the presence of bacteria and/or moderate amounts of polymophonuclear neutrophils in the pre‐rhDNase therapy tracheal aspirate.     

“类代谢物”作为药物库设计和选择的标准

目前药物筛选库受限于预测“类药物”或“类先导物”理想药动学和结构标码的生物物理性质。然而,近来调查表明,为了进入细胞,多数药物需要溶质载体以正常转运自然产生的中间代谢物,很多药物还可能发生相似的相互作用。人代谢物组日益全面的概述使人们可以对“类代谢物”概念进行评价。我们利用有关的化学信息学分子标码空间比较了已知药物和库化合物与天然代谢物（内源分子）的相似性,其中,已知药物比多数库化合物与这些内源分子更类似。     

A novel protein tyrosine phosphatase gene is mutated in progressive myoclonus epilepsy of the Lafora type (EPM2)

Progressive myoclonus epilepsy of the Lafora type or Lafora disease (EPM2; McKusick no. 254780) is an autosomal recessive disorder characterized by epilepsy, myoclonus, progressive neurological deterioration and glycogen-like intracellular inclusion bodies (Lafora bodies). A gene for EPM2 previously has been mapped to chromosome 6q23- q25 using linkage analysis and homozygosity mapping. Here we report the positional cloning of the 6q EPM2 gene. A microdeletion within the EPM2 critical region, present inhomozygosis in an affected individual, was found to disrupt a novel gene encoding a putative protein tyrosine phosphatase (PTPase). The gene, denoted EPM2, presents alternative splicing in the 5' and 3' end regions. Mutational analysis revealed that EPM2 patients are homozygous for loss-of-function mutations in EPM2. These findings suggest that Lafora disease results from the mutational inactivation of a PTPase activity that may be important in the control of glycogen metabolism.      

Impaired growth in children with asthma during treatment with conventional doses of inhaled corticosteroids

We describe 6 (4F, 2M) prepubertal children with moderate asthma diagnosed at a mean age of 2.8 years. All patients were treated with inhaled corticosteroids in a dose of between 300 and 800 mcg of beclomethasone diproprionate (becotide) daily, given either as an aerosol or rotahaler. Mean height velocity SDS decreased from −0.8(range +0.5 to −2.0)to −3.2(range −1.3 to −4.8) when the dose was increased. Alternatively, when the dose was reduced or stopped, mean height velocity SDS increased from −3.2 (range −2.0 to −4.8) to +0.8 (range −1.2 to +2.7). Careful assessment of height velocity is indicated in all children receiving treatment with inhaled corticosteroids.