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Biomedical subjects

F Bosman

Publications and source records attributed to F Bosman.

At least 127 records · Page 7Linked to original sources
PubMed1987

A mathematical description of the comminution of food during mastication in man.

Chewing performance was quantified by determining the particle-size distribution of comminuted food as a function of the number of chewing strokes. The rate of food breakdown was taken to be the result of a combined selection and breakage process; this was quantified in a mathematical model. A linear operation on the particle-size distribution described the changes in this distribution that resulted from an additional chewing stroke. Detailed information was obtained from eight subjects on the selection and breakdown of food particles of different sizes. There were considerable inter-individual differences in the selection chances for small particles. The mathematical method facilitates study of the influence of dental morphology and muscle-related factors on the comminution of food particles.

Adult↗
PubMed1987

Presence of cytomegalovirus in brown fat. Study in a rat model.

Cytomegalovirus infection of laboratory rats resulted in the appearance of virus and viral antigens in interscapular and periaortic brown fat. This appearance was limited to acute infection (first week post-infection) and was dependent on the route of inoculation. In our study virus could only be detected in subcutaneous brown fat in young rats (till 4 weeks of age), whereas in the deep brown fat (periaortic region) no age dependency was found.

Abdomen↗
PubMed1987

Verification of theoretical modeling of heat transmission in teeth by in vivo experiments.

A theoretical axisymmetric tooth model, simulating the conditions involved in the drinking of a liquid of a certain temperature, was compared with results of a similar in vivo experiment. The temperature changes as a result of one draught of a hot/cold liquid were recorded within the model as well as in the surrounding environment. The experimental data obtained were compared with the calculated results for the theoretical model as determined by the Finite Element Analysis. The temperatures recorded experimentally agreed reasonably with the calculated results. It can be concluded that the assumptions which have been made concerning the described thermal loading conditions lead to a good approximation of the physical reality.

Cold Temperature↗
PubMed1987

Measurement of selection changes and breakage functions during chewing in man.

Food comminution in man was studied in terms of intra-oral selection and breakage processes, with a silicone rubber used as test food, aided by a sieving procedure and simultaneous form- and color-labeling of particles. The subjects chewed on mixtures of particles with a specific form (either cubes or half-cubes). In addition, seven particle sizes, within a range of 1.2 to 8.0 mm, each had a specific color. Damaged cubes or half-cubes revealed their chance of being selected for breakage. The color of the fragments indicated their original size, and thus the breakage distribution of selected particles. The selection chance increased as a power function of particle size. The degree of fragmentation was, in general, maximal for a particle size of about 4 mm. Our double-labeling technique permits a detailed unraveling of anatomical and physiological variables in the chewing process.

Color↗
PubMed1986

Phorbol ester stimulates the synthesis and phosphorylation of a 48 kDa-intracellular protein in plasminogen activator secreting melanoma cells.

Phorbol ester (12-O-tetradecanoyl-phorbol 13-acetate) stimulates the secretion of tissue-type plasminogen activator by the melanoma cell line, Bowes. This effect is associated with increased levels of mRNAs for both tissue-type plasminogen activator and a 48 kDa-protein. Labelling of melanoma cells with L-[35S]methionine allowed to identify an intracellular protein which, by 3 criteria, was identical with the in vitro translation product of the 48kDa-protein mRNA: a Mr of 48,000 on electrophoresis in the presence of sodium dodecyl sulphate; inducibility by phorbol ester and failure of reducing agents to affect electrophoretic mobility. As detectable by L-[35S]methionine labelling, the protein was mainly localized in the cytosol. In vitro phosphorylation reactions, carried out on subcellular fractions revealed a membrane-associated protein which also had the three characteristics of the aforementioned 48 kDa-protein. Phosphorylation did not require Ca2+-ions. Addition of phorbol ester to the reaction mixtures increased the phosphorylation. Reconstitution experiments between membrane and cytosol fractions of phorbol ester-treated and untreated cells showed that the 48kDa protein occurs in a cytosolic, unphosphorylated and a membrane-bound, phosphorylated form and that the former is converted to the latter by a phorbol ester activated, membrane-associated protein kinase.

Cell Line↗
PubMed1986

Messenger RNA for a phorbol-ester induced 48,000 dalton protein from human melanoma cells.

Messenger RNA of the phorbol ester-induced 48kDa protein from human melanoma cells (Bowes) was isolated, characterized and used to study the protein processing. The 48kDa mRNA is induced simultaneously with that of tissue-type plasminogen activator. This induction is prominent as shown by sedimentation profiles on linear sucrose gradients. The mRNA can be isolated by classical phenol extractions, has a poly(A)-tail and sediments with a coefficient of 20 S. Translation in reticulocyte lysates yields a 48kDa protein whether the translation is modified with canine pancreas microsomal membranes or not. Analysis of 48kDa mRNA translation products by sodium dodecyl sulphate/polyacrylamide gel electrophoresis showed that the phorbol ester-induced 48kDa is a monomeric one-chain polypeptide. Glycosylation could not be detected, nor signal peptide cleaving, suggesting that it is a non-secreted intracellular protein.

Animals↗
PubMed1986

Influence of carbohydrate side chains on activity of tissue-type plasminogen activator.

When messenger RNA (mRNA) from both untreated and phorbol ester-treated melanoma cells is translated in simple reticulocyte lysates, tissue-type plasminogen activator can be immunoprecipitated by an affinity-purified antibody as a approximately 52,000 mol wt protein, with no detectable biological (plasminogen activating) activity. When the reticulocyte lysate system is supplemented with a preparation of microsomal membranes, biological activity becomes detectable and a 63,000 mol wt protein can be immunoprecipitated with the same antibody. Furthermore, when natural tissue-type plasminogen activator (mol wt approximately equal to 70,000) is incubated with different glycosidases, distinct alterations in the electrophoretic mobility of the molecules are observed, together with alterations in the level of biological activity. While treatment with neuraminidase and beta-galactosidase caused decreases in activity, alpha-mannosidase caused an increase. These results suggest that the carbohydrate part of the molecule can influence its biological behavior.

Amides↗
PubMed1985

Influences of periodontal and mandibular-joint receptors on reflex sensitivity of human jaw-closing muscles.

Reflex sensitivity from stimulating the chin or the dental arch of the mandible and the influences of periodontal and mandibular joint receptors on jaw muscles were investigated by experiments with and without anaesthesia. The findings showed that periodontal receptors exert an inhibitory influence on motoneural excitability of jaw-closing muscles and facilitate alpha-motoneurones of the digastric muscle and that the silent period following a jaw jerk is partly caused by inhibition of alpha-motoneurones of jaw-closing muscles due to activity of periodontal receptors. The ratio of reflex activity in temporal and masseter muscles appeared to depend on the position of the applied stimulus. The mandibular joint receptors appear to play a major part in distributing active muscle-force over these muscles.

Adult↗
PubMed1985

Biology of rat cytomegalovirus infection.

Cytomegalovirus infection of Brown Norway rats was studied after intraperitoneal or subcutaneous inoculation of virus. No clinical illness was apparent during the 1st month postinfection (p.i.). Low titers of virus were detected in many organs at day 4 p.i. for the intraperitoneally inoculated animals and at day 11 p.i. for those inoculated subcutaneously. Thereafter, the virus disappeared from all tested organs except the salivary glands, where it appeared on day 11 p.i. and reached high levels by 4 weeks p.i. Histologically, no abnormalities were observed. The virus had an immunosuppressive effect during the 1st week p.i., as indicated by the immune response to sheep red blood cells.

Animals↗
PubMed1984

Distribution of particle sizes in food comminuted by human mastication.

The masticatory performance of an individual may be quantified by describing the size distribution of particles of a comminuted test food as a function of the number of chewing strokes. A standardized sieving method and a standardized artificial test food (Optosil) were used to obtain reproducible results. Some measurements were performed using peanuts. The distribution of particle sizes of the comminuted food was adequately described by a Rosin-Rammler distribution function for the seven participating individuals which characterizes the size distribution by the median particle size (x50) and the broadness of the distribution (b). The broadness variable b hardly depends on the number of chewing strokes, and the differences in b between the individuals are small. Considerable differences in the median particle sizes at a given number of chewing strokes were observed between the subjects, reflecting differences in efficiency of comminution of a test food. For all subjects, the median particle size decreased as a function of the number of chewing strokes N according to the relation, x50 = c X N-d. Variables c and d characterized the efficiency of comminution by the subjects.

Arachis↗
PubMed1983

Reflex sensitivity of human jaw-closing muscles during the silent period following a jaw jerk.

Two successive force impulses were exerted upon the mandible in the opening direction with intervals of 20 to 120 ms. Electromyographic responses were recorded from the right temporal and masseter muscles and from the anterior belly of the right digastric muscle. Mandibular movement was recorded in the sagittal plane. The first-force impulse evoked a jaw jerk followed by a silent period. The jaw jerk following the second-force impulse was depressed when the interval between the force impulses was shorter than a certain value. The depression was total for at least 20 ms after the first jaw jerk. It is suggested that the silent period is the result of more than one inhibitory mechanism. From comparison of the resulting mandibular movement with movements resulting from single-force impulses, it is concluded that the jaw jerk may contribute to a small but significant extent to the stiffness of jaw-closing muscles.

Adult↗