Fritz L. Lorscheider

Mercury exposure from "silver" tooth fillings: emerging evidence questions a traditional dental paradigm.

For more than 160 years dentistry has used silver amalgam, which contains approximately 50% Hg metal, as the preferred tooth filling material. During the past decade medical research has demonstrated that this Hg is continuously released as vapor into mouth air; then it is inhaled, absorbed into body tissues, oxidized to ionic Hg, and finally covalently bound to cell proteins. Animal and human experiments demonstrate that the uptake, tissue distribution, and excretion of amalgam Hg is significant, and that dental amalgam is the major contributing source to Hg body burden in humans. Current research on the pathophysiological effects of amalgam Hg has focused upon the immune system, renal system, oral and intestinal bacteria, reproductive system, and the central nervous system. Research evidence does not support the notion of amalgam safety.—Lorscheider, F. L., Vimy, M. J., Summers, A. O. Mercury exposure from “silver” tooth fillings: emerging evidence questions a traditional dental paradigm. FASEBJ. 9, 504–508 (1995)

MERCURY FROM MATERNAL SILVER TOOTH FILLINGS IN SHEEP AND HUMAN BREAST MILK A SOURCE OF NEONATAL EXPOSURE

Neonatal uptake of mercury (Hg) from milk was examined in a pregnant sheep model, where radioactive mercury (Hg203)/silver tooth fillings (amalgam), were newly placed. A crossover experimental design was used in which lactating ewes nursed foster lambs. In a parallel study, the relationship between dental history and, breast milk concentration of Hg was also examined in 33 lactating women. Results from the animal studies showed that, during pregnancy, a primary fetal site of amalgam Hg concentration is the liver, and, after delivery, the neonatal lamb kidney receives additional amalgam Hg from mothers milk. In lactating women with aged, amalgam fillings, increased Hg excretion in breast milk and urine correlated with the number of fillings or Hg vapor concentration levels in mouth air. It was concluded that Hg originating from maternal amalgam tooth fillings transfers across the placenta to the fetus, across the mammary gland into milk ingested by the newborn, and ultimately into neonatal body tissues. Comparisons are made to the U.S. minimal risk level recently established for adult Hg exposure. These findings suggest, that placement and removal of “silver” tooth fillings in pregnant and lactating humans will subject the fetus and neonate to unnecessary risk of Hg exposure.

The dental amalgam mercury controversy — inorganic mercury and the CNS; genetic linkage of mercury and antibiotic resistances in intestinal bacteria

Mercury (Hg) vapor exposure from dental amalgam has been demonstrated to exceed the sum of all other exposure sources. Therefore the effects of inorganic Hg exposure upon cell function in the brain and in the intestinal bacteria have recently been examined. In rats we demonstrate that ADP-ribosylation of tubulin and actin brain proteins is markedly inhibited, and that ionic Hg can thus alter a neurochemical reaction involved with maintaining neuron membrane structure. In monkeys we show that Hg, specifically from amalgam, will enrich the intestinal flora with Hg-resistant bacterial species which in turn also become resistant to antibiotics.

ADP-Ribosylation of Brain Neuronal Proteins Is Altered by In Vitro and In Vivo Exposure to Inorganic Mercury

Abstract: ADP‐ribosylation is an essential process in the metabolism of brain neuronal proteins, including the regulation of assembly and disassembly of biological polymers. Here, we examine the effect of HgCl2 exposure on the ADP‐ribosylation of tubulin and actin, both cytoskeletal proteins also found in neurons, and B‐50/43‐kDa growth‐associated protein (B‐50/GAP‐43), a neuronal tissue‐specific phosphoprotein. In rats we demonstrate, with both in vitro and in vivo experiments, that HgCl2 markedly inhibits the ADP‐ribosylation of tubulin and actin. This is direct quantitative evidence that HgCl2, a toxic xenobiotic, alters specific neurochemical reactions involved in maintaining brain neuron structure.

Cuing Effect of "All of the above" on the Reliability and Validity of Multiple-Choice Test Items

It is generally acknowledged that alternatives such as none of the above and all of the above should be used sparingly in multiple-choice (MC) items. But the effect that all of the above has on the reliability and validity of an MC item is unclear This study compared the results of a single-response (SRa) item format that included all of the above as the correct response to a multiple-response (MR) item format that required examinees to select all of the available alternatives for a correct response. A crossover design was used to compare the effect of formats on student performance while item content, scoring method, and student ability levels remained constant. Results indicated that the SRa format greatly distorted examinee performance by elevating their scores because examinees who recognized two or more alternatives as being correct were cued to select all of the above. In addition, the SRafornat significantly reduced the reliability and concurrent validity of examinee scores. In summary, the MR format was found to be superior Based upon new empirical evidence, this study recommends that whenever an educator wishes to evaluate student understanding of an issue that has multiple facts, the SRa format should be avoided and the MR format should be used instead.

Initial experience with in vitro fertilization and embryo transfer at the University of Calgary/Foothills Hospital

SummaryThis report serves to describe the initial experience in a Canadian in vitro fertilization program. While our unit is still early on the learning curve, we are thus far gratified with a pregnancy rate of 17.3% per treatment cycle and 20% per laparoscopy.

Evaluation of Negation in Stems of Multiple-Choice Items

The opinion of some test experts is that negation (e.g., not, except) should be used sparingly or avoided in the stems of multiplechoice items. In these items, examinees are required to select the one alternative that is false from among those that are true. However, negation continues to be used and frequently accounts for 15-20% of the multiple-choice items within a given medical examination. A 90-item multiple-choice examination was administered in various formats to approximately 200 nursing students in each of two consecutive academic years. The findings of the present study provide evidence that the use of negation in stems should be limited and that the single-response, negatively worded (SRNW) item should often be converted to a multiple-response, positively worded (MRPW) item. This recommendation is based on the inherent cuing (ie., eliminating some alternatives by comparative deduction) within SRNW items and on an increase in the reliability and concurrent validity of MRPW test scores.

Development of a research elective program for first‐ and second‐year medical students

A Research Elective Program (REP) was designed to foster medical students’ investigative skills within the context of a research project. The REP enabled students to identify a research question, perform a literature review, design and implement a study, and draw conclusions based on their observations. The REP was divided into first‐ and second‐year courses and comprised 368 hr (17%) of the total curriculum time. Seventy‐two students submitted a written report on their project at the conclusion of each course. Advantages of the REP included opportunities for students to interact with a faculty member over an extended time period, to investigate an in‐depth question of their choosing, and to publish their findings in appropriate refereed journals. The objectives of the REP were fulfilled to the extent that new knowledge, understanding of the investigative process, and informatics skills were acquired by the students. The program was an effective and positive learning experience for the majority of students.

Negation in Stems of Single-Response Multiple-Choice Items: An Overestimation of Student Ability.

There is accumulating evidence that negation (e.g., not, except) should be used sparingly or avoided in the stems of multiple-choice items. In these items, examinees are required to select the one alternative that isfalse from among those that are true. The same items can also be given as positively worded multiple-response items in which the student is directed to identify those alternatives that are true. The present study compared the responses of examinees on single-response, negatively worded (SRNW) items and on multiple-response, positively worded (MRPW) items. The experimental design allowed students to respond to both SRNW and MRPW formats that employed identical item alternatives. The findings of this study provide further evidence that the use of negation in stems shouldbe limited and that the SRNW item should often be converted to an MRPW item. This recommendation is based on the inherent cuing (i.e., the artificial elevation of student scores) observed within SRNW items that significantly lowers item reliability and greatly distorts information about examinee performance.

Mercury and idiopathic dilated cardiomyopathy.

We read with interest the recent report on trace metals and idiopathic dilated cardiomyopathy by Frustaci et al. [(1)][1]. As far as we know, this is the first report to show that markedly increased concentrations of mercury (Hg) in cardiac tissue are associated with a specific cardiac pathology. A