Search PubMed⌕ Search

Biomedical subjects

D A Ross

Publications and source records attributed to D A Ross.

At least 55 records · Page 3Linked to original sources
PubMed2000

Effects of insulin and postruminal supply of protein on use of amino acids by the mammary gland for milk protein synthesis.

We examined the relationships between amino acid supply, net utilization of amino acid by the mammary gland, and milk protein yield, in investigations that utilized a hyperinsulinemic-euglycemic clamp. A two-way crossed factorial design was employed. There were two 12-d periods involving abomasal infusions of either water or a mixture of casein (500 g/d) plus branched-chain amino acids (88 g/d), with a hyperinsulinemic-euglycemic clamp during the last 4 d of each period. During the clamp, insulin was infused at 1.0 microg x kg BW(-1) x h(-1) to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. The insulin clamp treatments increased milk protein yield by 15 and 25% during abomasal infusion of water or casein plus branched-chain amino acids, respectively. Circulating concentrations of essential amino acids were reduced (33%) during insulin clamp treatments, especially branched-chain amino acids (41%). Arteriovenous difference of essential amino acids across the mammary gland was linearly related to their arterial concentrations. However, milk protein yield was not related to either arterial concentration or arteriovenous difference, for any of the essential amino acids. During insulin clamp treatments, the mammary gland was able to support the increased milk protein yields by increasing extraction efficiency of essential amino acids, mammary blood flow, and glucose uptake. Furthermore, a positive mammary balance of total amino nitrogen and carbon was maintained for all treatments. These adaptations demonstrate the unique ability of the mammary gland to adjust local conditions to allow for an adequate nutrient supply.

Abomasum↗
PubMed2000

Evaluation of whole blood and plasma in the interorgan supply of free amino acids for the mammary gland of lactating dairy cows.

We investigated the contribution of plasma and red blood cells to amino acid (AA) supply for milk protein synthesis during a combination of treatments that included abomasal infusion of casein and AA and utilization of a hyperinsulinemic-euglycemic clamp. Treatments resulted in substantial differences in circulating concentrations of AA, mammary uptake of AA, and rates of milk protein synthesis. Arterial concentrations of all AA in plasma were highly correlated with that of whole blood. Concentrations of AA in red blood cells were either higher (Asn+Asp, Gly, His, Leu, Met, Orn, Ser, Tau, Thr, and Tyr), lower (Ala, Arg, Cit, Cys, Ile, and Val), or similar (Gln+Glu, Phe, and Pro) to that of plasma. Arteriovenous difference measurements demonstrated that interorgan transfer of AA to the mammary gland was primarily by plasma. There was little involvement of red blood cells except for small quantities of Leu, Met, and Thr to the mammary gland; this contribution was greatest for Met and accounted for 14% of the total mammary uptake. Countercurrent transport of Gln + Glu, Asn + Asp, and Pro was also evident where these AA were extracted from plasma, but were released into red blood cells as blood passed through the mammary gland. This net influx of Gln+Glu, Asn+Asp, and Pro into red blood cells was equivalent to 26, 17, and 30% of their mammary uptake from plasma. Overall, the interorgan transport of free AA for the mammary gland was predominantly by plasma, and red blood cells were limited to minor contributions in mammary uptake for a few AA. Furthermore, arteriovenous differences of essential AA across the mammary gland were highly correlated between plasma and whole blood.

Amino Acids↗
PubMed1999

Catfish Oct2 binding affinity and functional preference for octamer motifs, and interaction with OBF-1.

The DNA-binding (POU) domain of the catfish Oct2 transcription factor was shown, by electromobility shift assays and surface plasmon resonance techniques, to have an affinity for the consensus octamer motif (ATGCAAAT) that was slightly higher than its affinity for a variant motif (ATGtAAAT). This observation is consistent with the transcriptional activation potentials of catfish Oct2 alpha and Oct2 beta, which were shown to activate transcription in catfish B and T cell lines to an equivalent extent from both the consensus and variant octamer motifs. When tested in a mouse plasmacytoma cell line, catfish Oct2 alpha and Oct2 beta, as well as mouse Oct2, showed higher transcriptional activation with the variant, as compared to the consensus, octamer motif. Catfish Oct2 was shown to function synergistically with the mammalian co-activator, OBF-1, activating octamer-dependent transcription in catfish T cells. The strong transcriptional activity of OBF-1 in catfish cells was dependent on the presence of octamer motif(s) at the proximal (promoter) rather than the distal (enhancer) position.

Animals↗
PubMed1999

Critical pathways in anterior cranial base surgery.

New advances in anterior cranial base surgery have dictated the need for a comprehensive, multidisciplinary approach in the treatment of lesions of this area, necessitating multiple modes of diagnostic and surgical techniques. Traditional consideration of the complex problems presented by neoplastic involvement of the anterior cranial base predicated on isolated syndrome analysis is no longer sufficient to adequately assess tumor pathology. To address these complex problems, we discuss a method of localization of pathology based on anatomic structure and function as well as the corresponding surgical approach to the anterior cranial base.

Cavernous Sinus↗
PubMed1999

Subcranial approach to tumors of the anterior cranial base: analysis of current and traditional surgical techniques.

Tumors of the anterior cranial base have previously required a craniofacial resection to allow adequate tumor extirpation. An analysis of current and traditional techniques demonstrates a significant reduction in operative time, complication rate, and intensive care unit and total hospital length of stay with the use of the subcranial approach as compared with the traditional frontal craniotomy and lateral rhinotomy approach. The subcranial approach is both cost and time efficient and provides comparable morbidity and mortality rates.

Blood Loss, Surgical↗
PubMed1999

Knockout of cellular glutathione peroxidase gene renders mice susceptible to diquat-induced oxidative stress.

Two experiments were conducted to determine the protection and the underlying mechanisms of cellular glutathione peroxidase (GPX1) against lethal, acute oxidative stress induced by an intraperitoneal injection of 24 mg diquat/kg body weight. In experiment 1, mortality and survival times were compared among selenium (Se)-adequate or deficient GPX1 knockout mice [GPX1(-/-)] and wild-type mice (WT). In experiment 2, mice from these four groups were euthanized at 0, 1, 2, and 3 h after the injection of diquat to elucidate the time course of oxidative events. The stress produced 100% mortality in all of the groups except for the Se-adequate WT, which were euthanized on day 7 for analysis. The Se-deficient WT and the Se-adequate GPX1(-/-) had similar survival times (4.1 and 3.9 h), which were longer (p < .05) than that of the Se-deficient GPX1(-/-) (2.4 h). However, these three GPX1-deficient groups had higher levels (p < .05) of hepatic F2-isoprostanes and carbonyl contents and/or plasma alanine aminotransferase activities than those of the Se-adequate WT. The diquat-induced formations of hepatic F2-isoprostanes in these animals peaked at 1 h and preceded the rise of plasma alanine aminotransferase in the Se-adequate GPX1(-/-). Responses of hepatic superoxide dismutase activities to the diquat treatment were affected by the GPX1 level. In conclusion, GPX1 is the major selenoprotein to protect mice against the lethal oxidative stress induced by diquat.

Alanine Transaminase↗
PubMed1999

The treatment planning of segmental, conformal stereotactic radiosurgery utilizing a standard multileaf collimator.

Over a period of approximately 3 years, our institution has implemented and refined a system of Stereotactic Radiosurgery (SRS) which utilizes the standard multi leaf collimator (MLC) of the Scanditronix MM50 Racetrack Microtron and treats in an arrangement of segmental "pseudo-arcs." This system employs a commercial BRW based stereotactic frame which is mounted to the treatment table. With the exception of the table-mounted frame hardware there have been no modifications to the treatment machine to accommodate these treatments. By use of standard evaluation parameters (e.g., treatment time, planning time, dose conformance and dose heterogeneity ratios) this system compares quite favorably with reported data from institutions treating SRS with either a GammaKnife or a standard linear accelerator with tertiary collimators.

Brain↗
PubMed1999

Adenoid cystic carcinoma metastatic to the dura: report of two cases.

Adenoid cystic carcinoma (ACC) originating in the salivary and lacrimal glands usually spreads to the intracranial space by following cranial nerves into the cavernous sinus, temporal bone and cerebellopontine angle. We present two cases in which ACC metastasized extensively to the dura, suggesting that ACC has an affinity for the dura. Case 1, a 43-year-old man, was operated on 12 years earlier for invasive ACC of the right palate. He experienced recurrence of the tumor in the left cavernous sinus and sella, and extensive involvement of the dura of both right and left temporal fossae. Case 2, a 33-year-old woman, had spread of ACC to the right convexity dura and tentorium after undergoing a resection of a left-sided ACC tumor of the lacrimal gland two years earlier. Both patients underwent multiple resections and radiation treatment. Extensive, multifocal, bilateral spread of ACC to the dura in both cases indicates that ACC has an affinity for the dura.

Adult↗
PubMed1999

Cellular glutathione peroxidase protects mice against lethal oxidative stress induced by various doses of diquat.

This study was to determine if cellular glutathione peroxidase (GPX1) protects against acute oxidative stress induced by diquat. Lethality and hepatic biochemical indicators in GPX1 knockout mice [GPX1(-/-)] were compared with those of wild-type mice (WT) after an intraperitoneal injection of diquat at 6, 12, 24, or 48 mg/kg of body weight. Although the WT survived all the doses, the GPX1(-/-) survived only 6 mg diquat/kg and were killed by 12, 24, and 48 mg diquat/kg at 52, 4.4 and 3.9 hr, respectively. Compared with those of surviving mice that were sacrificed on Day 7, the dead GPX1(-/-) had diquat dose-dependent increases (P < 0.05) in plasma alanine aminotransferase (ALT) activities. The GPX1(-/-) also had higher (P < 0.05) liver carbonyl contents than those of the WT, but the differences were irrespective of diquat doses. Whereas hepatic total GPX and phospholipid hydroperoxide glutathione peroxidase activities or hepatic GPX1 protein was not significantly affected by the diquat treatment, liver thioredoxin reductase and catalase activities were lower (P < 0.05) in the GPX1(-/-) injected with 12 mg diquat/kg than those of other groups. In conclusion, normal GPX1 expression is necessary to protect mice against the lethality, hepatic protein oxidation, and elevation of plasma ALT activity induced by 12-48 mg diquat/kg.

Animals↗
PubMed1999

Craniofacial resection: decreased complication rate with a modified subcranial approach.

The authors have successfully utilized a modified subcranial approach to the anterior skull base, based upon the procedure first described by Joram Raveh, as an alternative to standard craniofacial resection. The complication rate of this procedure in 31 consecutive cases (28 tumors, 2 congenital malformations, and 1 mucocele) has been 19.4% with no permanent complications, no deaths, no new neurological deficits, no brain injuries, no infections, and no seizures. Minor complications without permanent sequelae included two cases of tension pnenmocephalus, a subdural hygroma, two transient cerebrospinal fluid leaks, and a case of bacterial meningitis secondary to fecal contamination of a lumbar drain in a child. Average length of hospitalization was 7.1 days (range 2 to 16 days). The overall complication rate is considerably below the complication rate for other reported craniofacial procedures. We describe the technique we have used and the results. The subcranial approach as described herein provides wide exposure of the anterior cranial base without brain retraction, does not require prolonged operating times or hospitalization, and has a potentially lower complication rate than reported for other transfrontal transbasal approaches.

Journal Article↗
PubMed1999

Preventing acute respiratory infections and diarrhoea in child care centres.

This study was designed to explore the physical characteristics and child care practices of child care centres as potential risk factors for respiratory infections and diarrhoea in children 3-35 mo of age. A dynamic cohort averaging 667 children from 40 child care centres in Campinas (Brazil) was followed up for 8 mo. Direct structured observations were made to collect information on the centres' physical structure, child activities and child care practices. Despite their good infrastructures, hand washing in the centres was infrequent, and nearly 30% of diaper changes were unhygienic. Risk factors for diarrhoea included the presence of flies during meals, infrequent child hand washing before meals, and infrequent child hand washing after defecation, with relative risks of 1.33, 1.73 and 1.63, respectively. There was 33% less diarrhoea in classes where soap was frequently used during diapering. Contrary to our hypotheses, ventilation, group size and child density were not associated with respiratory infections, as was the case for most other factors studied. Only mixing of groups and a larger classroom area were found to be negatively associated with lower and upper respiratory infections, respectively. The results indicate that improving hygiene practices is the only intervention in child care centre characteristics with good potential to reduce diarrhoea among attendees. For respiratory infections, no modifiable characteristic with intervention potential was identified.

Brazil↗
PubMed1999

Selenium-dependent cellular glutathione peroxidase protects mice against a pro-oxidant-induced oxidation of NADPH, NADH, lipids, and protein.

Since our prior work indicated that Se-dependent cellular glutathione peroxidase (GPX1) was necessary for protection against paraquat lethality, the present studies were to elucidate the biochemical mechanisms related to that protection. Four groups of mice [Se-deficient or -adequate GPX1 knockout and wild-type (WT)] were injected (i.p.) with 50 mg paraquat/kg body weight and tissues were collected 0, 0.5, 1, 2, 3, or 4 h after the injection. Whereas the ratios of NADPH/NADP and NADH/NAD in lung were reduced by 50-70% only 0.5 h after the injection in all groups, these two ratios in liver of the Se-adequate WT were significantly higher than those of the three GPX1 knockout or deficient groups 2-4 h after the injection. The paraquat-induced pulmonary lipid peroxidation and hepatic protein oxidation, measured as F(2)-isoprostanes and carbonyl contents, respectively, peaked at 1 h in these three groups. No such oxidative events were shown in any tissue of the Se-adequate WT throughout the time course. Whereas the F(2)-isoprostane formation was accelerated by both GPX1 knockout and Se deficiency in liver, it was not significantly elevated by the paraquat treatment in brain of any group. The paraquat injection also resulted in temporal changes in lung GPX activity and GPX1 protein in the Se-adequate WT, and significant reductions in lung total SOD activity in the GPX1 knockout or deficient groups. In conclusion, GPX1 plays a critical role in maintaining the redox status of mice under acute oxidative stress, and protects against paraquat-induced oxidative destruction of lipids and protein in vivo. These protections of GPX1 seem to be inducible and coordinated with those of other antioxidant enzymes.

Animals↗
PubMed1999

Indications and outcome of ictal recording with intracerebral and subdural electrodes in refractory complex partial seizures.

Intracranial electrophysiologic recording has often been used to localize ictal onset zones in presurgical evaluation of refractory complex partial seizures. Specific indications for intracranial ictal monitoring have not been analyzed in detail, however. The authors designed this study to test the utility of intracranial monitoring in specific indications and considered six specific indications for intracranial monitoring. They compared prospectively determined indications and outcomes of chronic intracerebral and subdural electrophysiologic recording in 50 consecutive patients whose ictal onset zones had been inadequately localized with interictal and ictal EEG using extracranial electrodes, magnetic resonance imaging, interictal[18F]fluorodeoxyglucose positron emission tomography, and neuropsychological testing. In 47 patients ictal onset zones were localized with intracranial recordings, leading to resections in 38 patients. Each indication for intracranial monitoring selected a group in which the majority went on to have efficacious epilepsy surgery (5-year follow-up). Definitive diagnosis of bilateral independent ictal onset zones in temporal lobe epilepsy required intracranial ictal EEG. Intracranial EEG localization supported efficacious resection in most patients, despite contradictory or nonlocalizing extracranial ictal EEG and neuroimaging abnormalities. Critical analysis of these specific indications for intracranial monitoring may be useful in multicenter evaluation of these techniques.

Brain↗
PubMed1999

Identification of electrocorticogram patterns as the basis for a direct brain interface.

This study reports on the first step in the development of a direct brain interface based on the identification of event-related potentials (ERPs) from an electrocorticogram obtained from the surface of the cortex. Ten epilepsy surgery patients, undergoing monitoring with subdural electrode strips and grid arrays, participated in this study. Electrocorticograms were continuously recorded while subjects performed multiple repetitions for each of several motor actions. ERP templates were identified from action-triggered electrocorticogram averages using an amplitude criterion. At least one ERP template was identified for all 10 subjects and in 56% of all electrode-recording sets resulting from a subject performing an action. These results were obtained with electrodes placed solely for clinical purposes and not for research needs. Eighty-two percent of the identified ERPs began before the trigger, indicating the presence of premovement ERP components. The regions yielding the highest probability of valid ERP identification were the sensorimotor cortex (precentral and postcentral gyri) and anterior frontal lobe, although a number were recorded from other areas as well. The recording locations for multiple ERPs arising from the performance of a specific action were usually found on close-by electrodes. ERPs associated with different actions were occasionally identified from the same recording site but often had noticeably different characteristics. The results of this study support the use of ERPs recorded from the cortical surface as a basis for a direct brain interface.

Cerebral Cortex↗
PubMed1999

Detection of event-related potentials for development of a direct brain interface.

The study presented here is part of an ongoing effort to develop a direct brain interface based on detection of event-related potentials (ERPs). In a study presented in a companion article, averaged ERP templates were identified from electrocorticograms recorded during repetition of voluntary motor actions. Here the authors report on the detection of individual motor ERPs within the electrocorticogram using cross-correlation. An averaged ERP template was created from the first half of each electrocorticogram and then cross-correlated with the continuous electrocorticogram from the second half. Points where the cross-correlation value exceeded an experimentally determined detection threshold were considered to be detection points. A detection point was considered to be a valid "hit" if it occurred between 1 second before and 0.25 second after the recorded time of a voluntary action. The difference between the hit and false-positive percentages (HF-difference) was used as a metric of detection accuracy. HF-differences greater than 90 were found for 5 of 15 subjects, HF-differences greater than 75 were found for 8 of 15 subjects, and HF-differences greater than 50 were found for 12 of 15 subjects. The three other subjects with HF-differences less than 50 had electrode locations not well suited for recording movement-related ERPs. Recordings from sensorimotor and supplementary motor areas produced the highest yield of channels with HF-difference greater than 50; however, a number of channels with good performance were found in other areas as well. The results demonstrate the likely prospect of using ERP detection as the basis of a single-switch direct brain interface and that furthermore, there is a good possibility of obtaining multiple control channels using this approach.

Analysis of Variance↗
PubMed1999

Evolving experience with direct puncture therapeutic embolization for adjunctive and palliative management of head and neck hypervascular neoplasms.

OBJECTIVES: The use of percutaneous, direct puncture therapeutic embolization (DPTE) of hypervascular head and neck neoplasms is a relatively new modality that may be used to supplement or supplant conventional endovascular transarterial embolization. Although the preliminary clinical experience reported by a single group has been favorable, extensive case series experience is lacking. This prompted us to review our recent clinical experience with these techniques to determine safety, efficacy, and emerging role in the overall neurointerventional therapeutic armamentarium. STUDY DESIGN: A retrospective analysis of the previous 34 consecutive cases of hypervascular tumors undergoing DPTE referred to our service for therapeutic devascularization was performed. METHODS: Complete case record review was undertaken. Twenty-six of 34 cases involved DPTE of head and neck neoplasms. Conventional diagnostic angiography was performed for therapeutic planning and to assist in precise localization. When performed, standard microcatheter transarterial embolization techniques were used either before or after attempted DPTE. Cyanoacrylate embolic mixtures (n-butyl cyanoacrylate [NBCA], lipiodol, powdered tungsten) were used in 21 of 24 cases, and absolute ethanol in 3 of 24. Direct puncture angiography of the targeted tumor neovasculature was always performed before DPTE. RESULTS: Twenty-four of 26 cases had technically successful DPTE. Combined transarterial embolization with DPTE was used in 16 of 24 cases, although for the last 12 cases, 9 were treated predominantly or exclusively by DPTE. There were no major or minor clinical complications, and there was one asymptomatic technical complication. Total or near-total devascularization was achieved in all cases. All preoperative cases had excellent hemostasis within the resected tumor bed. CONCLUSIONS: Our results lend further support to the safety and efficacy of DPTE in the management of hypervascular neoplasms of the head and neck. With our increasing experience, this technique is evolving into a primary therapeutic modality for optimal tumor devascularization.

Adult↗