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Biomedical subjects

M M Mulder

Publications and source records attributed to M M Mulder.

10 recordsLinked to original sources
PubMed2001

Psychosocial impact of acne vulgaris. evaluation of the relation between a change in clinical acne severity and psychosocial state.

BACKGROUND: Although knowledge concerning the impact of acne vulgaris on quality of life has increased in recent years, relatively few studies have assessed the effect of a change in clinical severity on psychosocial state. OBJECTIVE: Assessment of the effect of a change in clinical acne severity on psychosocial state. METHODS: This was investigated by means of questionnaires and clinical assessments by acne patients and dermatologists. Fifty females with mild to moderate facial acne were seen before and after a 9-month treatment with oral contraceptives. RESULTS: The results showed a great variability in psychosocial impairment between individuals. After 9 months, a significant reduction in clinical severity was seen overall which did not relate to the significant improvements in self-esteem, stability of self-esteem and acceptance of appearance. CONCLUSION: Perceived psychosocial impairment is individually based, is greater in women who subjectively overrate their acne and does not relate to clinical improvement.

Acne Vulgaris↗
PubMed1998

Periurethral gland abscess: aetiology and treatment.

OBJECTIVES: To establish some characteristics of patients with periurethral gland abscess, its microbiological profile, and response to treatment. METHOD: The patients were seen at the Khami Road Clinic, Bulawayo, a municipal STD referral clinic, serving an urban population. Twenty consecutive men with periurethral abscesses were studied. Demographic data and a sexual history were obtained from each patient. Aspirates from the abscess cavities and urethral swabs were collected for microbiology, and blood samples taken for syphilis and HIV serology. The patients were treated by aspiration of the abscess cavities, followed by a single injection of kanamycin 2.0 g followed by a 1 week course of oral doxycycline 100 mg twice daily. RESULTS: Neisseria gonorrhoeae was cultured from three aspirates and five urethral specimens. Chlamydia trachomatis was found in two aspirates and three urethral specimens. Other organisms isolated included Gram negative and anaerobic bacilli. HIV antibody was detected in 13 of 18 patients tested. The response to initial treatment was good, but the abscesses ruptured in two patients, one of whom developed a urinary fistula. One patient required treatment with an alternative antimicrobial regimen. CONCLUSION: This study demonstrated a role for N gonorrhoeae and possibly for C trachomatis in the aetiology of periurethral abscess. The prevalence of HIV infection in these patients was high. The results of treatment of periurethral abscess by aspiration of pus and followed by antimicrobial therapy covering both N gonorrhoeae and C trachomatis were acceptable.

AIDS-Related Opportunistic Infections↗
PubMed1998

Skeletal myogenesis on elastomeric substrates: implications for tissue engineering.

Studies geared towards understanding the interaction between skeletal muscle and biomaterials may provide useful information for the development of various emerging technologies, ranging from novel delivery vehicles for genetically modified cells to fully functional skeletal muscle tissue. To determine the utility of elastomeric materials as substrates for such applications, we asked whether skeletal myogenesis would be supported on a commercially available polyurethane, Tecoflex SG-80A. G8 skeletal myoblasts were cultured on Tecoflex two-dimensional solid thin films fabricated by a spin-casting method. Myoblasts attached, proliferated, displayed migratory activity and differentiated into multinucleated myotubes which expressed myosin heavy chain on solid thin films indicating that Tecoflex SG-80A was permissive for skeletal myogenesis. Porous three-dimensional (3-D) cell scaffolds were fabricated in a variety of shapes, thicknesses, and porosities by an immersion precipitation method, and where subsequently characterized with microscopic and mechanical methods. Mechanical analysis revealed that the constructs were elastomeric, recovering their original length following 100% elongation. The 3-D substrates were seeded with muscle precursors to determine if muscle differentiation could be obtained within the porous network of the fabricated constructs. Following several weeks in culture, histological studies revealed the presence of multinucleated myotubes within the elastomeric material. In addition, immunohistochemical analysis indicated that the myotubes expressed the myosin heavy chain protein suggesting that the myotubes had reached a state of terminal differentiation. Together the results of the study suggest that it is indeed feasible to engineer bioartificial systems consisting of skeletal muscle cultivated on a 3-D elastomeric substrate.

Animals↗
PubMed1997

In vitro investigation of the St. Jude Medical Isoflow centrifugal pump: flow visualization and hemolysis studies.

Centrifugal blood pumps have become valuable therapeutic tools for cardiopulmonary bypass surgery. In addition, surgeons have used them as temporary ventricular assist devices, and this type of pump is also being developed for use as a permanent assist device and total artificial heart. However, centrifugal pumps create flow patterns that are significantly different from those the blood experiences physiologically. The St. Jude Medical Isoflow centrifugal pump has been used clinically during cardiopulmonary bypass surgery, yet no experimental results have been reported that describe the flow patterns within this pump or that quantify the hemolysis generated over a range of operating conditions. The purpose of this study was to investigate the flow patterns and hemolysis during 4 operating conditions. The experimental operating conditions included the design condition (6 L/min, 2,500 rpm, 350 mm Hg), a high flow condition (10 L/min, 2,500 rpm, 330 mm Hg), a low flow condition (2 L/min, 2,500 rpm, 370 mm Hg), and a near surge condition (2 L/min, 3,000 rpm, 550 mm Hg). The flow visualization results demonstrated that the flow within the impeller was well aligned with the impeller blades except near the inlet at the high flow condition. In contrast, the flow through the outlet was well aligned at the high flow condition while there was evidence of particle impact at the design condition, and the flow was disturbed at the low flow and near surge conditions. The indices of hemolysis (IH) for the 3 operating conditions at 2,500 rpm were 0.0082 +/- 0.0026 (mean +/- SD) for the design condition, 0.0035 +/- 0.0014 for the high flow condition, and 0.0326 +/- 0.0050 for the low flow condition. The indices for high and low flow were significantly different from that for the design condition (p < 0.05). The IH for the near surge condition (0.0748 +/- 0.0039) was significantly higher than that for all other conditions (p < 0.05). In addition to describing the flow patterns within the Isoflow, this study independently validated St. Jude Medical's reported IH at the design condition and showed how that IH significantly changed based on operating conditions.

Blood Flow Velocity↗
PubMed1988

Effect of macromolecular composition of microorganisms on the thermodynamic description of their growth.

Most models describing bacterial growth, including the original mosaic non-equilibrium thermodynamic (MNET) description, do not take into account that the macromolecular composition of the cells varies with growth rate. The MNET description of bacterial growth is extended to account for such a variation in macromolecular composition of the cells in order to make the MNET description more generally applicable. Klebsiella aerogenes NCTC 418 was cultured in a chemostat under glucose- or ammonia-limited conditions to determine the macromolecular composition at varying growth rate. The dilution rate has a strong influence on the macromolecular composition of the cells. Under glucose-limited conditions an increase of the RNA content of the cells was observed with increasing growth rate. The RNA content of the cells was much lower under ammonia-limited conditions of the cells than under glucose-limited conditions but also showed an increase with increasing growth rates. Under ammonia-limited conditions, the polysaccharide content strongly decreased with increasing growth rate. The other cellular components changed relatively less with changing growth rate. It is shown that the slope of the line relating catabolism to anabolism varies very little due to variation of the macromolecular cell composition with growth rate, at least under the tested conditions.

Ammonia↗
PubMed1988

Energetic consequences of two mutations in Escherichia coli K+ uptake systems for growth under potassium-limited conditions in the chemostat.

The energetics of growth of two Escherichia coli strains (TK 2240 and TK 2242) differing in Km of the high-affinity potassium uptake system and lacking the low-affinity system were studied in the chemostat under potassium-limited conditions. The results were compared with the results obtained previously (Mulder, M.M., Teixeira de Mattos, M.J., Postma, P.W. and Van Dam, K. (1986) Biochim. Biophys. Acta 851, 223-228) with the wild-type FRAG-1, having two potassium uptake systems, and FRAG-5, a mutant which lacks the high-affinity potassium uptake system. We postulated that the high-affinity potassium uptake system was able to generate such a steep gradient across the membrane that the low-affinity system would act in reverse, thus creating a futile cycle of potassium ions at the cost of energy. As a result, FRAG-1 would show a higher ATP turnover at all growth rates tested than the mutant FRAG-5, in which strain the proposed futile cycle is interrupted because of the lack of the high-affinity system. It is shown here that the results obtained with TK 2240 and TK 2242 are in line with our hypothesis of futile potassium cycling. Under our experimental conditions, the yield on potassium was not dependent on the kinetic parameters of the uptake systems. The (thermodynamic) energy demand of the uptake systems determined the carbon substrate conversion required to achieve this yield.

Adenosine Triphosphate↗
PubMed1988

Continued growth of Escherichia coli after stopping medium addition to a K+-limited chemostat culture.

The steady-state bacterial dry wt of Escherichia coli, growing under K+-limited conditions in the chemostat, was inversely dependent on the growth rate. This phenomenon was more carefully investigated in medium-flow stop experiments. Growth did not stop immediately but continued for a time, initially at the same rate as before. The dry wt increased to a value corresponding to a steady-state growth rate near zero, independent of the initial specific growth rate. This was observed in both the wild-type strain and a mutant that lacked the high-affinity K+ uptake system. The wild-type strain maintained a low extracellular K+ concentration both in the chemostat under steady-state conditions and after stopping the medium flow. The mutant, on the other hand, maintained a much higher extracellular K+ concentration in the steady state, which decreased to much lower values after stopping the medium flow. From the increase in bacterial dry wt and the low external K+ concentration after stopping the medium flow it is concluded that the intracellular K+ is redistributed among the cells, including new cells. The growth yield on K+ was highest in the stationary growth phase of a batch culture and all steady-state cultures converged ultimately to this yield value after the medium flow had been stopped. It is proposed that the growth rate of E. coli under K+-limited conditions is determined by the intracellular K+ concentration.

Culture Media↗
PubMed1986

Energetic consequences of multiple K+ uptake systems in Escherichia coli.

The energetics of growth of Escherichia coli FRAG 1 under potassium-limited growth conditions and with glucose as sole carbon and energy source were studied in the chemostat and compared with those of a mutant, FRAG 5, defective in the high-affinity potassium uptake system. The steady-state concentration of biomass decreased with increasing growth rate and was the same in both parent and mutant. For each growth rate, the rate of production of ATP was higher in the parent than the mutant strain. Under potassium-limited conditions, FRAG 1 has at least two potassium uptake systems, an inducible high-affinity uptake system and a constitutive low-affinity uptake system (Rhoads, D.B., Waters, F.B. and Epstein, W. (1976) J. Gen. Physiol. 67, 325-341). Apparently, the presence of the high-affinity uptake system in the parent leads to an energy drain. We suggest that this energy drain is due to futile cycling of potassium ions. On the basis of a mosaic non-equilibrium thermodynamic description of bacterial growth, it is concluded that the growth behaviour under potassium limitation corresponds to that expected for a catabolite limitation.

Adenine Nucleotides↗
PubMed1985

Animal-vegetal polarity in the plasma membrane of a molluscan egg: a quantitative freeze-fracture study.

Using freeze-fracture electron microscopy, the numerical particle distribution in the fertilized Nassarius egg plasma membrane has been analyzed in four areas at different positions along the animal-vegetal axis of the egg. These areas can be distinguished by distinct microvilli patterns and differences in microvilli densities. In all areas, more IMPs (intramembrane particles) are present on the P face than on the corresponding E face. The ratio of the number of IMPs present on E and P face is similar in all areas (0.48-0.55) except for the most animal part of the vegetal hemisphere, where relatively more IMPs remain attached to the exterior half of the fractured membrane (E/P ratio = 0.88). The IMP density at the vegetal pole of the egg is considerably higher than in the animal hemisphere and in the animal part of the vegetal hemisphere. This difference is due to an increased number of IMPs in all size classes (4-18 nm). In the area adjacent to the vegetal pole the density of particles is also higher than in the two more animal areas, but here the difference is exclusively due to the smaller IMP size classes (4-8 nm). Statistical analysis of our data reveals that the area adjacent to the vegetal pole patch is significantly different from the other areas with respect to the distribution of the IMPs over the different IMP size classes. These results demonstrate the polar organization of the Nassarius egg plasma membrane. The possible role of this surface heterogeneity in the spatial organization of the egg cell and the later embryo is discussed.

Animals↗