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Biomedical subjects

M Bergman

Publications and source records attributed to M Bergman.

At least 37 records · Page 2Linked to original sources
PubMed1992

The castability of unalloyed titanium in three different casting machines.

The general demand for a variety of fine detail work made of titanium has resulted in the development of equipment/systems for the casting of this metal. Dental casting machines suitable for the casting of titanium are now also available. The aim of the present study was therefore to evaluate the possibility of precision casting of dental crown restorations of unalloyed titanium. The three kinds of casting equipment currently used in Sweden were tested by evaluating the crown edge diameter of 10 titanium crowns processed by each one of the titanium casting machines. The results revealed that clinically acceptable margins can be obtained but also that further improvements in processing have to be achieved before titanium casting can be considered as uncomplicated as the casting of traditional dental gold alloys.

Crowns↗
PubMed1992

Base plate wax, dimensional stability and sorption of active components following treatment with disinfectant solutions.

The influence of seven disinfectants on the dimensional stability of a base plate wax, Tenax, was studied. Two methods for treatment were tested - immersion for one hour and spraying respectively. After spraying no significant influence on the wax could be established and after immersion four of the seven disinfectants, including Cidex and K-644, likewise had no significant influence on the dimensional stability. The wax specimens did not show any significant weight increase (less than one per cent) after immersion for four days but in four disinfectant solutions the surface properties of the wax specimens had changed showing that active components of the disinfectants were absorbed into or adsorbed on the wax surface.

Absorption↗
PubMed1992

Intraocular pressure level in glaucomatous and nonglaucomatous eyes after complicated cataract surgery and implantation of an AC-IOL.

The effects of a semiflexible, one-piece, open-loop anterior-chamber intraocular lens (AC-IOL) implanted after intracapsular or extracapsular cataract extraction complicated by posterior-capsular or zonular rupture on intraocular pressure (IOP) level and the control of previous glaucoma were studied in 48 eyes with primary implantation and in 10 eyes with secondary implantation. Fifty-four percent of the eyes with primary implantation had exfoliation syndrome; anterior vitrectomy was performed in 60.4%. An immediate pressure rise (IOP greater than or equal to 30 mm Hg) was observed in 29.3% of the eyes. The long-term IOP level (median follow up, 21.5 months) was less than or equal to 20 mm Hg in 83.7% and between 21 and 29 mm Hg in the remaining 16.3%. In three of the nine glaucomatous eyes, the medication had to be increased; in the remaining six, the IOP could be controlled with the previous or reduced medication or with none at all. In three out of the 49 (6.1%) nonglaucomatous eyes, glaucoma medication was started during the follow up. All of these eyes had exfoliation syndrome and two of the fellow eyes had similar IOPs and were receiving similar medication. The results indicate that the semiflexible, open-loop AC-IOL has little effect on IOP and seems to be a safe alternative, even in glaucomatous eyes, if a posterior chamber lens cannot be used.

Adult↗
PubMed1991

The effect of dietary vitamin E and beta-carotene on oxidation processes in the rat testis.

The effects of dietary vitamin E and beta-carotene were studied on enzymes involved in arachidonic acid metabolism and other related enzymes in the rat testis. Groups of rats were fed various soybean oil-based semi purified diets. Group 1 was fed a vitamin E-supplemented diet (+E - beta); Group 2 was fed a beta-carotene-supplemented diet (-E + beta); Group 3, the control group (-E - beta) was fed a vitamin E-deficient diet; and Group 4, the standard diet group (S), was fed vitamin E plus beta-carotene-standard diet. Soybean oxidized oil was added to the three diet groups - (+E - beta), (- E + beta) and (- E - beta), whereas the diet of S group contained non-oxidized oil. After 8 weeks rats were killed, blood and testis samples were collected for biochemical determinations. Vitamin E deficiency caused significant increase in testis thiobarbituric acid value and activities of testis NADPH oxidase, testis 15-lipoxygenase and in plasma pyruvate kinase. In contrast, significant decreases were observed in activity of testis prostaglandin synthetase, compared with antioxidant-supplemented diet groups. We also found a significant increase in 15-lipoxygenase activity in (- E + beta) diet group, compared with (- E - beta) diet group. Fatty acid analysis of testis parenchyma indicated decrease in palmitate (16:0) and arachidonate (20:4(n - 6)), and increase in oleate (18:1(n-6)) linoleate (18:2(n - 6)) and linolenate (18:3(n - 3)), when compared (-E - beta) diet group with vitamin E-supplemented diet groups. The results suggest that dietary vitamin E has a role in both enzymatic and non-enzymatic peroxidation of polyunsaturated fatty acids in the testis.

Animals↗
PubMed1991

Corrosion and strength of dental low-gold brazing materials.

Previous studies have shown the clinical feasibility of using three alternatives to dental casting gold alloys Type 3. In the present study brazed specimens of these alternatives were evaluated using a corrosion test and a tensile test according to a proposed ISO Standard (ISO/DIS 9333). Brazed specimens of a high-gold alloy were used as a reference. Furthermore, the microstructure of the brazed joints and the fracture surface characteristics were monitored. The present study revealed that none of the specimens exhibited any visual sign of chemical attack after suspension in the test solution for 7 days. The tensile strength testing resulted in stresses at fracture point that met the requirements of the proposed ISO Standard. All fractures were of the ductile type. Cohesive failures were seen in all specimens except in the reference alloy (JS C) specimens. No clear relationship between fracture surface appearance and tensile strength was found. Distinct demarcation lines between brazing and parent materials were seen. Based on the present results there seems to be no reason to reject the use of brazed constructions made of the alternative alloys Midas, Rajah, and Albacast.

Corrosion↗
PubMed1991

The effect of the three columns of the spine on the instantaneous axis of rotation in flexion and extension.

Instrumentation designed for stabilization and correction of spinal deformities must limit the amount of motion in flexion and extension. In flexion or extension, the vertebral bodies move about a specific point called the instantaneous axis of rotation. The ability of the implant to limit this motion is a function of its relation to the axis of rotation of the spine. The goal of this study was threefold: 1) to define the instantaneous axis of rotation of the spine in flexion and extension; 2) to study the effect of the loss of the three columns of the spine on the location of the instantaneous axis of rotation; and 3) to determine how the above parameters relate to the choice of anterior or posterior instrumentation. Ten human cadaver spines were subjected to compressive loads in flexion and extension. The columns of the spine were then destroyed in sequence at L3. The instantaneous axis of rotation for each vertebral body was found by the method of Reuleaux, and the effect of the compromise of the columns on the location of the instantaneous axis of rotation was noted. Understanding the exact location of the instantaneous axis of rotation after a specific injury would allow the clinician to objectively choose the best surgical approach and the appropriate instrumentation.

Humans↗
PubMed1991

cyl encodes a putative cytoplasmic tyrosine kinase lacking the conserved tyrosine autophosphorylation site (Y416src).

We have isolated a cDNA encoding a novel tyrosine kinase family member, named cyl (consensus tyrosine-lacking kinase), from the K562 human leukemia cell line. The deduced cyl protein lacks signal and transmembrane sequences but contains features of known cytoplasmic tyrosine kinases, including amino-terminal SH3 and SH2 domains. However, having very short amino and carboxy termini, cyl does not seem to belong to any of the previously characterized subfamilies of cytoplasmic tyrosine kinases. Furthermore, cyl lacks the highly conserved tyrosine autophosphorylation site (Y416src) in the tyrosine kinase catalytic domain. The cyl gene is located on human chromosome 15. It is expressed ubiquitously as two independently regulated mRNA species of 2.6 and 3.4 kb in human leukemia cell lines and fetal tissues.

Adrenal Glands↗
PubMed1990

Appearance and origin of snRNP antigens in chick erythrocyte nuclei reactivated in heterokaryons.

Fusion of terminally differentiated chick erythrocytes (CE) with transcriptionally active rat myoblasts results in heterokaryons in which the CE nuclei undergo reactivation of RNA synthesis and splicing. In order to analyze the transport and assembly of small nuclear ribonucleoprotein (snRNP) particles and larger molecular complexes engaged in RNA processing, we have examined CE nuclei in heterokaryons for the presence of four U snRNP-related nuclear antigens (Sm, 70,000 Mr, F78 and M3G-cap) and for one antigen (La), associated with RNA polymerase III transcripts. Inactive erythrocyte nuclei showed low levels of Sm and F78 antigens, but the other antigens were undetectable. Immediately after fusion, the fluorescence of the pre-existing chicken Sm antigen was detected in the CEn, and then the intensity of the signal increased rapidly during reactivation. The other antigens appeared more slowly, reaching full intensity at different time points after fusion. Blocking of chick transcription did not block the appearance of Sm, 70,000 Mr, cap and La antigens but did effectively inhibit the appearance of the F78 antigen. It has previously been demonstrated that the structure recognized by this monoclonal antibody is physically associated with functional splicing complexes. Blocking of translation in heterokaryons abolished uptake of snRNPs into the chicken nuclei. Taken together, the results indicate that rat snRNP complexes were imported into the chick nuclei after assembly in the cytoplasm. For all the studied antigens, except F78, this translocation was independent of chick RNA synthesis. The appearance of the F78 antigen was totally dependent on expression of chicken genes.

Animals↗
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↗