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Biomedical subjects

M Bergman

Publications and source records attributed to M Bergman.

At least 109 records · Page 6Linked to original sources
PubMed1990

Gene expression pattern of chicken erythrocyte nuclei in heterokaryons.

Expression of erythro-specific chick genes was studied in heterokaryons prepared by fusing chick erythrocytes (CE) with rat myoblasts. In this type of heterokaryon the inactive erythrocyte nucleus takes up nuclear proteins of myoblast origin and undergoes transcriptional reactivation. In order to study the stability of the genetic programming of the reactivated CE nucleus, chick gene expression was examined by analysis of RNA from the heterokaryons. Probes for several erythro- and chick-specific genes were used. The heterokaryons showed strong expression of the chick histone H5 and adult alpha-globin genes, while other genes, e.g. the transcription factor Eryf1 gene, normally expressed during erythroid differentiation, were not transcribed. Although the CE used were of the definitive lineage, the heterokaryons showed activation of the chick embryonic beta-globin gene, i.e. a gene normally expressed only in CE of the primitive lineage. We conclude that the reactivation of the mature CE nucleus in a rat cytoplasm resulted in a more immature erythroid gene expression pattern. The activation of the embryonic beta-globin gene indicated a switch of the lineage-specific gene expression pattern. This switch occurred in the absence of DNA replication. The strong expression of the globin and H5 genes in heterokaryons, in the absence of expression of the regulatory factor Eryf1, suggested the existence of Eryf1-independent regulatory mechanisms for erythroid gene expression in these cells.

Animals↗
PubMed1990

Side-effects of amalgam and its alternatives: local, systemic and environmental.

It is clearly established that dental restorative materials, like all other foreign materials introduced into the human body, may cause pathological changes both local and general in type. However, in a proper evaluation of the side-effects occurring, their type, severity and frequency have to be considered. Local side-effects of dental restorative materials on oral mucosa are of either irritative or allergic nature while systemic effects are mainly due to allergic and other kinds of hypersensitivity reactions. Most side-effects of dental restorative materials seem to be insignificant and of short duration, although systemic hypersensitivity reactions may be most harmful to those affected. Although the frequency of side-effects seems to be low in comparison with the vast number of restorations that are placed, it is reasonable to assume that the more complex and diverse application of an increasing number of dental materials will increase the frequency. Study of a group of patients, referred for investigation of possible side-effects of dental materials, revealed that several of these patients showed allergic reactions to constituents of their dental restorations. Environmental problems associated with the handling of waste amalgam are discussed.

Dental Amalgam↗
PubMed1989

Amino acid uptake and release in the guinea pig cochlear nucleus after inferior colliculus ablation.

This study attempts to determine if the neurons in the guinea pig inferior colliculus that project to the cochlear nucleus could use certain amino acid transmitters. The left inferior colliculus was ablated surgically to destroy projections descending to the cochlear nuclei. Nissl and silver stained sections of the brain stem indicated that this procedure destroyed most of the left inferior colliculus, but spared a small amount of collicular tissue ventrally and rostrally. Six to seven days after the ablation, degenerated fibers were present in the right inferior colliculus, in the left lateral lemniscus, and in the cochlear nucleus, bilaterally. Three to five days after the ablation, the uptake and electrically-evoked release of exogenous, radiolabeled D-aspartate, gamma-aminobutyrate, and glycine were measured in the three major subdivisions of the cochlear nucleus, the anteroventral, posteroventral, and dorsal divisions. These activities were compared to those in unlesioned controls. The ablation did not alter the uptake and release of the amino acids in the dorsal and posteroventral divisions of the cochlear nucleus. However, it lowered slightly (by 10-18%) the uptake and release of gamma-aminobutyrate and glycine in the anteroventral division, although the difference from the control group was not statistically significant. These findings suggest that most of the neurons in the inferior colliculus that project to the cochlear nucleus probably do not use glutamate, aspartate, gamma-aminobutyrate, or glycine as a transmitter. However, the possibility remains that a small proportion of the collicular projections to the anteroventral cochlear nucleus might use gamma-aminobutyrate or glycine as a transmitter.

Amino Acids↗
PubMed1989

Abnormal ambient glucose levels inhibit proteoglycan core protein gene expression and reduce proteoglycan accumulation during chondrogenesis: possible mechanism for teratogenic effects of maternal diabetes.

Using a tissue culture system based on a nearly pure population of avian precartilage mesenchymal cells, we have found that ambient glucose levels as little as 50% lower, or 100% higher, than normally present in embryonic sera are deleterious to cartilage development, as measured by the accumulation of highly sulfated proteoglycan and the corresponding cartilage-specific chondroitin sulfate core protein mRNA. Abnormal glucose concentrations in the ranges studied did not selectively influence cell replication, and the effects on chondrogenesis were not due to differences in overall protein synthesis or glucose utilization in the treatment groups. Core protein gene expression was more severely affected than accumulation of extracellular product, suggesting the existence of posttranscriptional compensatory mechanisms. The sensitivity to ambient glucose levels of both expression of the cartilage-specific chondroitin sulfate core protein gene and the accumulation of the corresponding extracellular matrix macromolecules during chondrogenesis suggest a molecular mechanism for the well-known adverse effect of maternal diabetes on embryonic skeletogenesis. The results further suggest that hypoglycemia resulting from stringent control of diabetes may also be deleterious to skeletal development.

Aggrecans↗
PubMed1989

Hypersensitivity reactions to dental materials in a referred group of patients.

151 patients referred to the Department of Oral Diagnosis, University of Umeå, for investigation regarding potential side-effects of dental materials were subjected to epicutaneous testing at a dermatology clinic. Twelve persons in this group had oral mucosal changes. Among the 151 patients 39 women and 7 men had positive skin reactions to one or more of the test substances used. The majority of the positive reactions were related to metals, particularly nickel, but a number of positive reactions to organic test substances were also noted. In many cases the substance which caused the positive skin reaction was also a known constituent of the restorative or prosthetic materials present in the oral cavity of the patient concerned. The clinical relevance of such findings should, however, be evaluated with great caution and this and connected problems are discussed.

Adult↗
PubMed1989

Model of mercury vapor transport from amalgam restorations in the oral cavity.

A model of the oral cavity was used as the basis for a discussion of the conditions prevalent during the transport of mercury vapor from amalgam restorations via the saliva to the gas phase of the oral cavity during respiration or during pumping of air through the mouth. It was found that the mercury diffusion rate through the saliva layer is independent of the air flow rate through the oral cavity. Mercury appears to be transported as atoms both in the aqueous phase of saliva and in the gas phase. The majority of the mercury atoms reaching the gas phase appears to originate directly from the surface of the amalgam restorations, passing through the saliva layer, while only a minority originates from mercury dissolved in the aqueous phase. The amount of mercury released per unit of time to the gas phase was shown to be independent of the air flow rate during respiration and pumping. Furthermore, the released mercury atoms are distributed partly to the gas phase, from which they are respired to the lungs and the environment, and partly to the saliva and the gastro-intestinal tract, by swallowing.

Dental Amalgam↗
PubMed1988

Eye-sighting preference of normal and hemiplegic children and adults.

Monocular eye-sighting preference was examined in 32 children with hemiplegia, 51 adult-onset hemiplegic patients and 57 normal children and adults. Eye preference was compared with ear preference on dichotic listening for 25 of the hemiplegic children. No independent association could be detected between eye preference and ear preference. In both the children and adults with hemiplegia the preferred eye tended to be on the same side as the damaged hemisphere. Among the adults, this tendency was more pronounced with more extensive lesions, as manifested by aphasia and/or hemianopia. These findings are interpreted as indicating that eye-sighting preference is unrelated to unitary hemispheric dominance, and that, unlike dominance for hearing and speech, it is not irreversible after a critical period of development. A simpler explanation than incomplete hemispheric dominance is offered for the weakly positive association between mixed laterality and cerebral dysfunction.

Adult↗
PubMed1988

Determination of the rate of release of intra-oral mercury vapor from amalgam.

The experimental and analytical difficulties associated with the measurement of mercury vapor in the oral cavity are considerable. In the present paper, the objective was to measure the amount of intra-oral mercury vapor in subjects with amalgams, by means of two sets of equipment based on different functional principles. In addition, it was found that the type of mercury source prevalent in the oral cavity had to be evaluated. The measuring technique used to obtain correct results is discussed, and an evaluation of the conditions for the application of the measuring equipment available was made. It was found that the amount of mercury released from the oral cavity was time-dependent. Furthermore, the amount of mercury released with the time kept constant was almost independent of the pumping flow rate up to 8 L/min. It was found that the tissue, saliva, and the amalgam restorations were not depleted of mercury during the measuring time. The results of the Mercollector-Mercometer measurements carried out on seven subjects with nine or more occlusal surfaces restored with dental amalgam and on three subjects without any amalgam restorations revealed that the rate of mercury release was in the range 0.03-0.34 ng/sec in the former group and less than 0.01 ng/sec in the latter. Based on the experimental results and on theoretical considerations, it was concluded that the amount of mercury released per time unit is the only quantity measurable.

Adult↗
PubMed1988

Laser welding of titanium in dentistry.

Unalloyed titanium of the quality used for osseointegrated implants by the method of Brånemark is also sometimes used for the metallic part of the prosthetic superstructure placed on the fixtures and for crowns and bridges of conventional type. Forty bars of titanium, 8 of ASTM B 348 grade-1 quality and 32 of ASTM B 348 grade-2 quality, were laser-welded, using dissimilar laser joint variables. Tensile strength, 0.2% proof stress, and percentage elongation of the welded bars were measured and compared with the corresponding values for the titanium bars as delivered and with those of brazed type-3 gold alloy bars of similar dimensions. The type of fracture was evaluated from fractographs. The results showed that the use of certain defined laser joint variables during welding produced values for the mechanical properties studied which were more favorable than those obtained from the brazed gold bars. The fracture of the titanium specimens was ductile, with dimples occurring at the fracture surfaces.

Dental Alloys↗
PubMed1988

A new instrument for mercury vapor evacuation during clinical work with dental amalgam.

Clinical work with dental amalgam, cutting as well as filling and polishing operations, results in an increased level of mercury vapor in the breathing zone of the patient and often also in that of the dentist. The mercury levels can be minimized by the use of a high volume evacuator which is handled by the nurse. Since many dentists cannot count upon continuous chairside assistance during work with dental amalgam a new instrument, combining the functions of a common dental mirror and an evacuator has been developed. The aim of the present work was to evaluate the mercury vapor evacuating capacity of the new instrument. The study was carried out in a model box especially designed for the in vitro tests performed. The amount of mercury in an area representing the patient's breathing zone was recorded directly and indirectly using an equipment based on atomic absorption spectrophotometry. The results revealed that the new instrument has the capacity for substantially reducing the mercury levels during filling, polishing and cutting amalgam. Thereby the short transitory exposure to mercury vapor during certain working moments can be reduced which should be beneficial both to the patient and to the dental staff.

Air Pollutants, Occupational↗
PubMed1988

Psychologic issues in diabetes care.

A clear perception of the psychologic factors affecting both the physician and the patient can greatly influence the course of therapy in diabetes. Genuine, realistic assessment and acceptance of the limitations inherent in physician-patient interactions will lead to considerably more satisfying personal and professional relationships.

Adaptation, Psychological↗
PubMed1987

The threshold-of-interference test: a new test of interhemispheric suppression in brain injury.

A new procedural version of the Willeford competing sentences test (Willeford. Audiol Hear Educ 1976;2:12-20) is introduced here for use with brain damaged patients. The threshold-of-interference test seeks the minimal level of the competing sentences at which the patient can no longer repeat the message at the test ear. Findings are reported for normal controls and for brain damaged adults, with clinical data and computerized axial tomography scan evidence. The threshold-of-interference test appears to be efficient, quick in administration, and particularly useful in exposing auditory processing anomalies, especially in right hemisphere damage.

Aged↗
PubMed1987

Plasma-selenium, glutathione peroxidase in erythrocytes and mercury in plasma in patients allegedly subject to oral galvanism.

Twelve patients with subjective symptoms, ascribed by the patients themselves to mercury released from dental restorations, were investigated. In addition to a general dental examination the following parameters were registered: the total number of amalgam surfaces in the mouth; potential and polarization of existing and accessible dental metallic restorations for calculation of intraoral currents. As regards the highest calculated intraoral current for each individual there was a statistically significant difference between the patient group and a control group consisting of 12 persons. An analysis of the amount of selenium, glutathione-peroxidase and mercury in the blood showed no differences between the patient and the control group. However, a statistically significant positive correlation could be seen between the total number of amalgam surfaces and the plasma-mercury level for patients and controls pooled together. The numerous other blood parameters analyzed did not reveal any differences between the groups.

Adult↗