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Biomedical subjects

D C Ross

Publications and source records attributed to D C Ross.

At least 19 recordsLinked to original sources
PubMed2004

Resistance to disruption and gapping of peripheral nerve repairs: an in vitro biomechanical assessment of techniques.

One potential cause of suboptimal results after nerve repair is disruption or gapping of the neurorrhaphy in the postoperative period. This study assesses the biomechanical strength of five nerve repair techniques: fibrin glue, simple epineurial sutures, and three other novel neurorrhaphy methods. Fifty rabbit sciatic nerve segments were divided and repaired utilizing one of five different methods, producing five groups of ten specimens. Fibrin glue and four epineurial suture techniques (simple, horizontal mattress, "Tajima," "Bunnell") were employed. Repaired nerve segments were ramp-loaded to failure on an Instron 8300 materials-testing machine at a displacement rate of 5 mm/min. Gapping at the repair site was captured using high-resolution video. Differences among the five groups were assessed for significance using ANOVA and Fisher's protected least squares differences post-hoc testing. The mean force to produce disruption was higher for mattress suture repairs relative to simple repairs, but not significantly so (p = 0.31). Both were significantly stronger than fibrin glue repairs (p < 0.0001). "Tajima" and "Bunnell" repairs were both statistically stronger than glue (p < 0.0001), simple (p < 0.0001), or mattress (p = 0.0004) repairs, but not significantly different from one another (p = 0.48). Data for gapping at the repair site were similar with all suture techniques outperforming fibrin glue (p = 0.003). "Bunnell" repairs demonstrated the most resistance to gapping, compared to glue (p < 0.0001), simple (p = 0.0001), mattress (p = 0.007) and "Tajima" repairs (p = 0.01). These data demonstrate that repairs done utilizing fibrin glue are significantly weaker than all types of suture repairs. Two novel techniques for nerve repair (epineurial "Tajima" and "Bunnell") are significantly more resistant to disruption and gapping. Further evaluation to assess the effect of these repair techniques on function is required.

Animals↗
PubMed2003

Tensile strength of healing peripheral nerves.

Although the time required for a nerve to gain sufficient strength to withstand normal physiologic forces of joint motion is unknown, typically nerve repairs are protected up to 3 weeks postoperatively. The authors investigated the mechanical strength of a nerve repair as a function of time. Fifty adult Sprague-Dawley rats underwent sciatic nerve division and repair, and were sacrificed in groups of 10 at 0, 1, 2, 4, and 8 weeks. Repaired nerves were then mechanically loaded at 5 mm/min to failure. Gapping across the repair site was captured on high-resolution video. The contralateral sciatic nerve served as a control. A significant increase in tensile strength was gained between 0 and 1 week and between 2 and 4 weeks. Healing nerves achieved 63 percent of the strength of the control by 8 weeks. Controls showed no gain in strength over the testing period. Gapping occurred at lower forces at all time increments. From 0 to 1 week, a significant increase in load necessary to produce gapping was found, which did not increase significantly again until 8 weeks. These results may have implications for postoperative rehabilitation protocols in patients with nerve injuries.

Animals↗
PubMed2000

Dorsal perilunate dislocations and fracture-dislocations: questionnaire, clinical, and radiographic evaluation.

Twenty-two consecutive patients (23 wrists) underwent open reduction internal fixation of dorsal perilunate dislocations and fracture-dislocations through combined dorsal and volar approaches. One of 5 experienced wrist surgeons performed these procedures within an average of 3 days of injury (range, 0-26 days) and intercarpal fixation was kept within the proximal carpal row. Motion was instituted an average of 10 weeks (range, 5-16 weeks) after injury. All patients were males. The average age at the time of injury was 32 years (range, 16-60 years). The average follow-up period was 37 months (range, 13-65 months). Average flexion-extension motion arc and grip strength in the injured wrist were 57% and 73%, respectively, compared with the contralateral wrist. The scapholunate angle increased and the revised carpal height ratio decreased over time, which was statistically significant for both measurements. Three patients (3 wrists) required wrist arthrodesis and a fourth patient had an immediate scaphoid excision and 4-corner arthrodesis secondary to an irreparable scaphoid fracture. One patient required a proximal row carpectomy to treat septic arthritis. Nine of the remaining 18 wrists had radiographic evidence of arthritis, most often at the capitolunate or scaphocapitate articulations. Short form-36 mental summary scores were significantly greater than age- and gender-matched US population values; physical summary scores were significantly less. The disabilities of arm, shoulder, and hand evaluation, Mayo wrist score, and patient-rated wrist evaluation all reflected loss of function. Seventy-three percent of all patients had returned to full duties in their usual occupations and a total of 82% were employed.

Adolescent↗
PubMed1999

Handedness in the NAS/NRC twin study.

In 1985, a hand preference survey was completed by 973 dizygotic and 1158 monozygotic male twin pairs, all veterans of World War II. This is the largest single twin study of handedness on record. As in state-of-the-art animal research, the laterality criterion was sensitive to both direction and consistency (degree, strong or weak) of handedness. Significant pairwise concordance was shown for the total group, and for consistency and directional factors separately. However, no zygosity differences were demonstrated.

Journal Article↗
PubMed1999

Epidemiology of Dupuytren's disease.

Studying the epidemiology of Dupuytren's disease allows the identification of populations at risk and may point to inferences regarding etiology. Data suggest the highest prevalence of the disease occurs in people of northern European stock. However, the disease does occur in nearly all populations examined. Dupuytren's disease occurs more frequently in men than women and becomes symptomatic approximately 10 years earlier in the lives of men than in women. Dupuytren's disease has been associated with a number of other diseases including seizure disorders, alcoholism, diabetes mellitus, and cigarette smoking. There is conflicting evidence as to whether manual labor or HIV seropositivity increases the prevalence of the disorder.

Dupuytren Contracture↗
PubMed1999

Specific phobia 10-16 years after treatment.

Twenty eight participants, initially treated for specific phobia as part of a comparative treatment study, were evaluated 10 to 16 years (X = 12 years) later. A comprehensive, in-person, semi-structured diagnostic interview was utilized, which also assessed comorbid disorders. Of 21 patients who had been rated as responders (much improved or very much improved) at treatment termination, 13 (62%) had clinically significant avoidance or endurance with dread subsequent to treatment. Among a subgroup of these responders who had been considered completely recovered (n = 11), 5 (45%) had clinically significant symptoms following treatment. None of the seven subjects who had been considered unimproved at treatment termination recovered from phobia symptoms in the intervening years. Positive response to treatment was associated with better long term outcome. Clinical characteristics, such as phobia subtype, age of onset, baseline severity, and lifetime comorbidity of other psychiatric disorders were not associated with long term outcome in this sample. Type of treatment was not associated with long term outcome. Results challenge the notion that recovery from specific phobia following treatment is characterized by complete and enduring cessation of symptoms.

Adult↗
PubMed1998

A controlled trial of timed bright light and negative air ionization for treatment of winter depression.

BACKGROUND: Artificial bright light presents a promising nonpharmacological treatment for seasonal affective disorder. Past studies, however, have lacked adequate placebo controls or sufficient power to detect group differences. The importance of time of day of treatment--specifically, morning light superiority--has remained controversial. METHODS: This study used a morning x evening light crossover design balanced by parallel-group controls, in addition to a nonphotic control, negative air ionization. Subjects with seasonal affective disorder (N = 158) were randomly assigned to 6 groups for 2 consecutive treatment periods, each 10 to 14 days. Light treatment sequences were morning-evening, evening-morning, morning-morning, and evening-evening (10,000 lux, 30 min/d). Ion density was 2.7 x 10(6) (high) or 1.0 x 10(4) (low) ions per cubic centimeter (high-high and low-low sequences, 30 min/d in the morning). RESULTS: Analysis of depression scale percentage change scores showed low-density ion response to be inferior to all other groups, with no other group differences. Response to evening light was reduced when preceded by treatment with morning light, the sole sequence effect. Stringent remission criteria, however, showed significantly higher response to morning than evening light, regardless of treatment sequence. CONCLUSIONS: Bright light and high-density negative air ionization both appear to act as specific antidepressants in patients with seasonal affective disorder. Whether clinical improvement would be further enhanced by their use in combination, or as adjuvants to medication, awaits investigation.

Air Ionization↗
PubMed1997

Thermodynamic factors controlling the interaction of quinoline antimalarial drugs with ferriprotoporphyrin IX.

The interaction of a variety of quinoline antimalarial drugs as well as other quinoline derivatives with strictly monomeric ferriprotoporphyrin IX [Fe(III)PPIX] has been investigated in 40% aqueous DMSO solution. At an apparent pH of 7.5 and 25 degrees C, log K values for bonding are 5.52 +/- 0.03 (chloroquine), 5.39 +/- 0.04 (amodiaquine), 4.10 +/- 0.02 (quinine), 4.04 +/- 0.03 (9-epiquinine), and 3.90 +/- 0.08 (mefloquine). Primaquine, 8-hydroxyquinoline, 5-aminoquinoline, 6-aminoquinoline, 8-aminoquinoline, and quinoline exhibit no evidence of interaction with Fe(III)PPIX. The enthalpy and entropy changes for the interaction of quinolines with Fe(III)PPIX, as determined from the temperature dependence of the log K values, exhibit a compensation phenomenon that is suggestive of hydrophobic interaction. This is supported by the finding that the interactions of chloroquine and quinine with Fe(III)PPIX are weakened by increasing concentrations of acetonitrile. Interactions of chloroquine, quinine, and 9-epiquinine with Fe(III)PPIX are shown to remain strong at pH 5.6, the approximate pH of the food vacuole of the malaria parasite which is believed to be the locus of drug activity. Implications for the design of antimalarial drugs are briefly discussed.

Antimalarials↗
PubMed1997

Upper limb Escherichia coli cellulitis in the immunocompromised.

The neutropenic state characteristic of acute lymphoblastic leukaemia (ALL) predisposes to infections involving Gram-negative bacilli. An Escherichia coli cellulitis originating in the first web space of the hand is described in a patient undergoing reinduction chemotherapy for ALL. Proximal extension of the infection progressed at a very rapid rate and required a forequarter amputation as a life saving measure. Due to the blunted inflammatory response in neutropenic patients, the need for close monitoring and quick intervention is stressed.

Adult↗
PubMed1997

Are patients satisfied with results from residents performing aesthetic surgery?

An 8-year survey of patient satisfaction in an academic aesthetic surgery clinic at the University of Toronto was carried out by means of a mailed questionnaire. A total of 265 questionnaires were mailed; 131 completed questionnaires (49.4 percent) were returned. Of these, 93.1 percent would recommend this clinic (88.1 percent in the first year of operation and 95.4 percent in the subsequent 7 years), and 92.9 percent would undergo the same procedure again, if required (88.3 percent in the first year and 95.0 percent in the next 7 years). The highest patient satisfaction (10 of 10) was seen in augmentation mammoplasty (average, 9.1); blepharoplasty (average, 9.0); rhytidectomy (average, 7.8), and rhinoplasty (average, 6.9). The results obtained compared favorably with recently published data of more experienced surgeons.

Adolescent↗
PubMed1996

The chemical mechanism of beta-haematin formation studied by Mössbauer spectroscopy.

Spontaneous formation of beta-haematin (malaria pigment) from haematin in acetate solution follows pseudo-zero-order and not autocatalytic kinetics. Acetate appears to facilitate the reaction by solubilizing the haematin and acting as a phase-transfer catalyst, a role which, in vivo, could be fulfilled by carboxylic acids or amino acids.

Acetates↗
PubMed1996

Predictors of response and nonresponse to light treatment for winter depression.

OBJECTIVE: The authors' goal was to determine whether the pattern and severity of depressive symptoms predict response to light treatment for seasonal affective disorder. METHOD: Subjects with winter depression (N = 103) were given bright light treatment. Seventy-one were classified as responders, 15 as nonresponders, and 17 as partial responders. Using depression rating scale data and correlational and multivariate analysis, the authors sought predictors of response in baseline symptom and scale scores. RESULTS: Responders were characterized by atypical symptoms, especially hypersomnia, afternoon or evening slump, reverse diurnal variation (evenings worse), and carbohydrate craving. By contrast, nonresponders were characterized mainly by melancholic symptoms, retardation, suicidality, depersonalization, typical diurnal variation (mornings worse), anxiety, early and late insomnia, appetite loss, and guilt. The ratio of atypical to classical symptoms of depression, rather than severity per se, best predicted treatment outcome for the group as a whole. Pretreatment expectations were positively correlated with improvement on the Hamilton Depression Rating Scale but not on a supplementary scale of atypical symptoms. CONCLUSIONS: Light-responsive seasonal affective disorder is distinguished by a dominant atypical symptom profile closely associated with depressed mood. Nonresponders from a clinically distinct group with melancholic features. The patient's symptom profile, therefore, should be considered when diagnosing seasonal affective disorder and selecting treatment.

Adolescent↗
PubMed1995

Periodate modification of human serum transferrin Fe(III)-binding sites. Inhibition of carbonate insertion into Fe(III)- and Cu(II)-chelator-transferrin ternary complexes.

Periodate modification of human serum transferrin produces a species that binds Fe(III) weakly at pH 7.4 contrary to previous reports that Fe(III)-binding activity is completely lost. Ternary complexes of periodate-modified transferrin and either Fe(III) with nitrilotriacetate (NTA), oxalate, citrate, or EDTA, or of Cu(II) with oxalate could be formed. Peak wavelength maxima of these spectral bands are identical to those reported for native transferrin in the absence of bicarbonate. No carbonate ternary complexes of periodate-modified transferrin with Fe(III), Al(III), Cu(II), or Zn(II) could be formed. Conditional (Fe(NTA)) binding constants (log K) for C- and N-terminal modified sites are 7.33 and 7.54, respectively. The respective extinction coefficients at 470 nm are decreased 45% compared with the native protein. The electron paramagnetic resonance spectrum of the complex closely resembles that of the Fe(III)-NTA ternary complex formed with native transferrin in the absence of bicarbonate. Anions, including bicarbonate, at high concentrations destabilize formation of this Fe(III)-NTA ternary complex, while Fe(III) chelators readily remove the bound Fe(III). Bicarbonate, sulfate, and pyrophosphate still bind to the modified binding sites in the absence of metal although with slightly lower affinity and with lower molar difference absorptivities. Results are interpreted as an inhibition of a crucial protein conformational change by an intramolecular cross-link, preventing formation of the particularly stable metal-carbonate ternary complex from the less stable metal-chelate ternary complex. The method can be used to produce monosited transferrins.

Anions↗
PubMed1994

Quinoline anti-malarial drugs inhibit spontaneous formation of beta-haematin (malaria pigment).

Polymerisation of haematin to beta-haematin (haemozoin or malaria pigment) in acidic acetate solutions was studied using infrared spectroscopy. The reaction was found to occur spontaneously between 6 and 65 degrees C, in 0.1-4.5 M acetate and pH 4.2-5.0. The anti-malarial drugs quinine, chloroquine and amodiaquin were found to block spontaneous beta-haematin formation, while the anti-malarially inactive 9-epiquinine and 8-hydroxyquinoline had no effect on the reaction, as did primaquine, a drug which is active only against exo-erythrocytic stages of infection. It is argued that the intra-erythrocytically active anti-malarial agents act by binding to haematin, blocking beta-haematin formation and leaving toxic haematin in the parasite food vacuoles.

Antimalarials↗
PubMed1994

Ganglioside GM1 reduces fetal alcohol effects in rat pups exposed to ethanol in utero.

We have investigated the effect of in utero ethanol exposure and ganglioside GM1 pretreatment on the endogenous ganglioside profile of the rat fetal brain. Prenatal ethanol exposure on gestation day (GD) 7 and GD8 and/or GD13 and GD14 leads to a very significant increase in the ganglioside GM1 content in at least 50% of the pup brains when assayed on GD20. This treatment protocol also results in significant decrease in the content of polysialogangliosides GD1a, GT1b, and GQ1b. GM1 treatment of pregnant dams before ethanol administration prevented this alteration in pup brain ganglioside profile. Ganglioside GM1 pretreatment appears to block the cellular membrane changes associated with fetal alcohol effects and thereby minimizes alterations in brain maturation and associated behavioral dysfunction.

Animals↗