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Biomedical subjects

M Silbert

Publications and source records attributed to M Silbert.

14 recordsLinked to original sources
PubMed2002

Simulation modelling of bacterial growth in yoghurt.

INDISIM, an individual-based simulator, was used to specifically study the influence of the shape and size of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in yoghurt processing. To this effect, two different sets of simulations were carried out. In the first set of simulations, it was assumed that the initial acidity of the medium has the same value as the acidity of the cytoplasm of the microorganisms. Hence, the differences in bacterial growth by the two species are only attributable to differences in their geometry. It was found that, in an optimum culture, the growth in biomass of S. salivarius subsp. thermophilus is larger than that of L. delbrueckii subsp. bulgaricus. An important factor for understanding this difference might be the larger mass-to-surface ratio of the former. In the second set of simulations, a simplified model of yoghurt, the parametrisation differs both in the geometry and the metabolism of the two species. The results of these simulations are in very good qualitative agreement with the experimental data of [Lait 69 (1989) 519]. Finally, by inhibiting the uptake of amino acids by S. salivarius subsp. thermophilus, the large relative importance of lactic acid in yoghurt processing was highlighted.

Biomass↗
PubMed2000

Persistent hyperplastic primary vitreous.

Persistent hyperplastic primary vitreous (PHPV) is a common congenital developmental anomaly of the eye that results following failure of the embryological, primary vitreous and hyaloid vasculature to regress. It typically presents unilaterally without associated systemic findings. Although the etiology is assumed to be identical in each of its three variants, PHPV is still subclassified into three presentations. The purely anterior presentation of PHPV is also known as persistent tunica vasculosa lentis and persistent posterior fetal fibrovascular sheath of the lens. It occurs in eyes with pathology of the anterior segment. This form typically involves cataract, glaucoma and a retrolenticular membrane. The purely posterior presentation of PHPV is termed falciform retinal septum and ablatio falcicormis congentia. It occurs in eyes with abnormalities confined to the posterior segment such as retinal folds, vitreal stalk, vitreal membranes, macular abnormalities and optic disc abnormalities. A combination of anterior and posterior presentations is the most commonly seen clinical presentation. Case report. We present a case in which an 11-year old male was referred to our office for reevaluation of a large angle esotropia, strabismic and deprivational amblyopia and previously diagnosed PHPV, OD. Conclusion. Without treatment, PHPV can produce recurrent intraocular hemorrhage, secondary glaucoma and eventually require enucleation. Early surgical intervention is necessary to prevent progressive pathologic changes and to obtain the best visual results. Finally, while PHPV is a documented source of leukocoria, clinicians should be aware of differential diagnoses which involve the white pupil (congenital cataract, retinoblastoma, Norrie's disease, retinopathy of prematurity, retinal detachment and Coat's disease).

Journal Article↗
PubMed1980

Hexamethonium modification of cardiovascular adjustments during combined static-dynamic arm exercise in monkeys.

In weight lifting and rowing, essentially the same groups of muscles contract in isometric (static) and isotonic (dynamic) fashion. To approximate the combined static-dynamic arm movements involved in rowing or lifting weights, four rhesus monkeys were trained to pull a T-bar and thereby avoid tail shock. Each animal received 8 daily test sessions in which loads (0.4, 0.8, 1.2, 1.6 kg), total pulls (3, 6, 9, 12 at a constant pull frequency, 0.5 Hz) and alternate sessions of pulling after injection of hexamethonium chloride (7 mg/kg) or saline were factorially combined. Our data indicate that heart rate in this model is primarily influenced by the duration of the dynamic exercise component (number of pulls) in this specific exercise task whereas both dynamic and static components affect systolic and diastolic blood pressure. After ganglionic blockade, heart rate and diastolic pressure do not change appreciably during T-bar pulling while the rise in systolic pressure is attenuated and varies primarily as a function of the static exercise component. The clinical implications of these experiments are discussed.

Animals↗