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Biomedical subjects

M D Foster

Publications and source records attributed to M D Foster.

13 recordsLinked to original sources
PubMed2000

Performance of experimental sample injectors for high-performance liquid chromatography microcolumns.

An experimental injector for HPLC microcolumns and a 3-nl conductivity detector connected directly to the injector outlet with a 19-nl tube were used to study injector dispersion, guide the design of improved injectors, and suggest appropriate injection techniques. With regard to the small injection volumes required when no on-column concentration technique is used, we show that in some circumstances: (i) there are two volumes to be considered, the sample volume (that which is intended to be injected) and the effective injection volume (that which contains all the sample after it has completely emerged from the injector). Due to dispersion, the latter is often many times the former. An injector performance factor is defined as the ratio of the two volumes. (ii) A smaller sample chamber volume in an injector does not necessarily produce a proportionately smaller effective injection volume, in which case there is a reduction of peak height that degrades sensitivity without a commensurate reduction in peak width that would improve resolution. (iii) Adjusting the geometry of the sample chamber and stator passage can significantly improve injector performance, as illustrated for sample volumes from 2 nl to 1 microl. (iv) In some cases, reducing the diameter of an injector passageway in an attempt to reduce dispersion actually causes performance to worsen.

Chromatography, High Pressure Liquid↗
PubMed2000

Positive and negative responses to personal discrimination: does coping make a difference?

Although researches (e.g., K. L. Dion, K. K. Dion, & A. W.-p. Pak, 1992) have associated perceiving personal discrimination with negative psychological symptoms, group consciousness theorists (e.g., S. L. Bartky, 1977) have suggested that perceiving personal discrimination can be empowering. To attempt to reconcile these presumably opposing findings, the author suggested that the method of coping with perceiving personal discrimination would better predict whether the outcomes are negative or positive than would the perception of personal discrimination alone. Female university students (N = 262) in the United States completed questionnaires assessing perceptions of personal discrimination, psychological symptoms, and psychosocial behaviors. Coping mechanisms predicted psychosocial behaviors better than did personal discrimination: The more the participants used social support to cope, the more collective action and less helplessness behavior they reported. Also, the more the participants used avoidance to cope, the more helplessness behavior they reported.

Adaptation, Psychological↗
PubMed1998

Competitive adsorption of human serum albumin and gamma-globulin from a binary protein mixture onto hexadecyltrichlorosilane coated glass.

The kinetics of competitive adsorption of proteins onto hexadecyltrichlorosilane coated glass (HTS-glass) from model solutions containing fluorescein isothiocyanate (FITC)-labeled human serum albumin (HSA-FITC) and gamma-globulin (HGG-FITC) were studied by total internal reflection fluorescence (TIRF) spectroscopy. The processes of displacement of HSA-FITC by HGG are independent of the conformational state of HSA adsorbed onto glass. On HTS-glass, displacement of protein is hindered by the presence of large numbers of CH3-terminated alkyl tails which induce conformational (reorientational) changes in HSA-FITC and HGG-FITC adsorbed from simple solutions. In contrast to HSA, adsorption of HGG onto HTS-glass from a simple solution is characterized by the absence of irreversible adsorption in the initial portion of the kinetic curve. Competition between HSA and HGG-FITC induces replacement of end-on adsorbed HGG-FITC on HTS-glass surface with subsequent desorption of the HGG-FITC into solution. Upon further increase in the HSA concentration in solution the competition of HSA for adsorption sites prevails, which leads to a decrease in the amount of adsorbed HGG-FITC and, consequently, to a decrease in the rate of its displacement.

Adsorption↗
PubMed1994

Responding to sexual discrimination: the effects of societal versus self-blame.

Although self-blame has been considered to be a useful coping tool for victims, its benefits within the context of group discrimination are equivocal. The present research hypothesized that women encouraged to engage in self-blame for sex discrimination would be more likely to endorse accepting the situation or to endorse the use of individual, normative actions. In contrast, women encouraged to engage in societal blame for sex discrimination would be more likely to participate in nonnormative actions aimed at enhancing the status of women as a group. Female students in Canada were subjected to a situation of discrimination and were encouraged to blame either themselves or society. They were then given the opportunity to respond to the discrimination by endorsing various actions. A profile analysis of the endorsed actions indicated that the women encouraged to blame themselves were most likely to endorse accepting the situation, whereas the women encouraged to blame society endorsed nonnormative individual confrontation.

Adaptation, Psychological↗
PubMed1992

The influence of diabetes on free flap transfer: I. Flap survival and microvascular healing.

Although recent clinical case presentations suggest that diabetes does not predispose free tissue transfers to increased risk of failure, this remains an open question. The present study used a syngeneic rat strain (Lewis) for free groin flap transplantations between normal rats and streptozotocin-induced diabetic rats (2 months' duration of symptoms), to investigate the influence of diabetes on flap transfer. Flap survival at 1 week, vascular patency, flap histology and ultrastructure, and scanning electron microscopy of anastomotic sites and of corrosion casts of flap vasculature were used as bases for comparison. No differences were found in comparisons of flap survival between any groups of transfer combinations (normal flap onto normal recipient, diabetic flap onto normal recipient, normal flap onto diabetic recipient, and diabetic flap onto diabetic recipient); 100% success was achieved in each group. No differences were found in histology or corrosion casts. Transmission electron microscopy revealed a thickening of the capillary basement membrane in rat diabetic skin after only 8 weeks of symptoms. This ultrastructural finding is consistent with similar capillary basement membrane thickening seen in many other tissues of short- and long-term diabetic animals and humans. Re-endothelialization across the arterial anastomosis at 2 weeks postoperatively was significantly faster in normal versus diabetic animals (p less than 0.05). The predominantly negative findings of this study support the application of free flap transfers in diabetic patients. It is concluded that reconstructive efforts involving free tissue transfer may not be contraindicated in diabetic patients.

Animals↗
PubMed1991

Audit of ranitidine administration in parenteral nutrient solutions.

An audit of the use of ranitidine administered in parenteral nutrient (PN) solutions is reported. Pharmacists at a 747-bed teaching institution developed criteria addressing justification of the use of ranitidine in PN solutions, process indicators for monitoring, and outcome measures. All patients who received ranitidine in their PN solutions between October 29 and November 22, 1989, were included in the study. Data were collected on a standardized form. A total of 23 evaluable patients received ranitidine in PN solutions during the study period. No inappropriate uses of ranitidine were identified. Patients with renal impairment tended to be underdosed. There were no duplicate administrations of ranitidine by the i.v. minibag and PN solution routes. However, on four occasions the PN solution was interrupted for more than six hours; additional ranitidine by i.v. minibag was ordered for only one of these patients. Testing of nasogastric aspirates for pH was not performed in 17 of the 22 patients who needed this test. Gastrointestinal bleeding was observed in two patients, both of whom were not monitored for gastric pH and were underdosed. A program is being developed to promote the safe and effective use of ranitidine administered in PN solutions. An audit of the administration of ranitidine in PN solutions showed that the drug is usually used appropriately at the institution and that most of the patients had positive clinical outcomes.

Evaluation Studies as Topic↗
PubMed1990

Free tissue transfer and calcanectomy as treatment of chronic osteomyelitis of the os calcis: a case report.

Chronic osteomyelitis of the os calcis presents a formidable management dilemma. Successful treatment requires aggressive surgical debridement of devitalized bone and soft tissue and appropriate antibiotic therapy. Difficulties arise, however, when radical debridement results in significant loss of weight-bearing bone. Recalcitrant osteomyelitis of the os calcis or major loss of bone secondary to debridement has been treated by amputation. Advances in microsurgical reconstruction now provide the opportunity for limb salvage in this situation.

Adult↗
PubMedDate not supplied

Neutron and X-ray reflectivity studies of human serum albumin adsorption onto functionalized surfaces of self-assembled monolayers.

Neutron and X-ray reflectivity (NR and XR) have been widely used for the investigation of the structure of thin organic films. Here we demonstrate how these sensitive techniques may be applied to the study of protein adsorption to well-characterized self-assembled monolayers (SAMs) with different chemical functionalities. NR can be used for in situ study, while XR provides complementary information on the initial surfaces and dried layers measured in air after protein has been adsorbed. In situ measurements of adsorption of human serum albumin onto a hydrophilic NH2-terminated monolayer clearly show the presence of a thin layer of adsorbed protein next to the SAM. Adsorption of albumin onto a hydrophobic, deuterated, CD3-terminated SAM causes even bigger changes in the NR. Upon replacing the protein solution with protein-free buffer solution, the reflectivities from both kinds of monolayers do not change, demonstrating that the albumin adsorption is irreversible after several hours of contact with the protein solution. X-ray reflectivity measurements of dried substrates performed ex situ in air provide a lower bound estimate of the amount of protein which must be at the interface in situ. This combination of techniques provides a uniquely sensitive approach for studying changes that occur upon protein adsorption at an interface.

Adsorption↗
PubMedDate not supplied

Hip fractures: condylocephalic rod versus compression screw.

In a series of 70 consecutive patients with nonpathologic intertrochanteric or subtrochanteric hip fractures, the first 35 were treated by a single semi-flexible condylocephalic nail. The second 35 patients were treated by a sliding compression screw and side-plate. The groups were comparable regarding age and intercurrent medical illness. The average anesthesia time and blood loss were nearly the same in each group. The incidence of failure of fracture fixation was high in the group treated by the condylocephalic nail, statistically significant at p less than .001. None of the patients treated by the sliding compression screw and side-plate lost fracture fixation. In this series, condylocephalic nails did not provide good fixation of this type of fracture and did not lessen surgical morbidity.

Aged↗