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Biomedical subjects

B McLellan

Publications and source records attributed to B McLellan.

12 recordsLinked to original sources
PubMed2001

Association of mouse mammary tumor virus superantigen with MHC class II during biosynthesis.

Mouse mammary tumor viruses encode superantigens that interact with MHC class II proteins and stimulate T cells. We show here that presentation of mouse mammary tumor virus superantigen does not require DM. Furthermore, we have identified a strong class II peptide binding motif in the Mtv-7 superantigen, and we show that this motif is necessary for association with class II molecules in in vitro translation and in vivo functional assays. Our results suggest that endogenously synthesized viral superantigen can bind to MHC class II heterodimers during biosynthesis in the endoplasmic reticulum in a manner analogous to that used by the class II-associated invariant chain.

Amino Acid Motifs↗
PubMed1999

The efficacy of head immobilization techniques during simulated vehicle motion.

STUDY DESIGN: Laboratory experiment. OBJECTIVE: To compare the efficacy of different head immobilization techniques during motion simulating ambulance transport. BACKGROUND: A significant number of neurologic injuries associated with cervical spine fractures arise or are aggravated during emergency extrication or patient transport. Previous studies have not addressed the effect of head immobilization on the passive motion that could occur across the neck during transport. METHODS: Three different head-immobilization methods were compared in six healthy young adults by using a computer-controlled moving platform to simulate the swaying and jarring movements that can occur during ambulance transport. In all tests, the trunk was secured by means of a commonly used "criss-cross" strapping technique. Efficacy of head immobilization was evaluated using measures of head motion and neck rotation. RESULTS: None of the three immobilization techniques was successful in eliminating head motion or neck rotation. Movement of the trunk contributed substantially to the lateral bending that occurred across the neck. A new product involving the placement of wedges underneath the head provided some small, but statistically significant improvements in fixation of the head to the fracture board; however, there was no improvement in terms of the relative motion occurring across the neck. CONCLUSIONS: Somewhat improved fixation of the head to the fracture board can be achieved by placing wedges under the head; however, the benefits of any fixation method, in terms of cervical spine immobilization, are likely to be limited unless the motion of the trunk is also controlled effectively. Future research and development should address techniques to better control head and trunk motion.

Adult↗
PubMed1999

Early detection of arterial bleeding in acute pelvic trauma.

OBJECTIVE: To determine the accuracy of intravenous contrast-enhanced computerized tomography (CECT) in the detection of potentially life-threatening retroperitoneal hemorrhage in patients sustaining pelvic fractures, acetabular fractures or both. DESIGN: Retrospective review of sequential patients identified over a 1-year period by using a prospectively collected trauma database at two Level I trauma centers. MATERIALS AND METHODS: A group of patients admitted to one of two Level I trauma centers with pelvic or acetabular injuries between September 1, 1995, and September 30, 1996, was identified by using a prospectively collected trauma database. From this cohort, we selected those individuals who had undergone intravenous CECT scanning within 24 hours after admission and who had an Abbreviated Injury Score more than 3 because of their pelvic injury. Those individuals who required arterial embolization for uncontrolled hemodynamic shock were categorized as having "significant arterial bleeding" attributable to their pelvic injury. Individuals who regained hemodynamic ,stability without embolization were categorized as having "no significant arterial bleeding." Two observers who were blinded to clinical information and the results of angiography reviewed all injury radiographs and computed tomographic scans. The presence or absence of contrast extravasation on intravenous CECT was recorded. Each case was then categorized into a 2 x 2 table depending on the presence of contrast extravasation on CECT and the need for arterial embolization to determine the accuracy of the "contrast extravasation sign." RESULTS: Of the 192 eligible patients, 111 met the inclusion criteria. Eleven patients required an angiogram for ongoing hemodynamic instability. The sensitivity of extravasation on contrast enhanced computed tomography representing a significant arterial bleeding was 80%, and the specificity was 98%. The predictive value of a positive contrast "extravasation sign" was 80%, whereas the predictive value of a negative test was 98%. The likelihood ratio of a positive test was 40.4, and the likelihood ratio of a negative test was 0.204. CONCLUSION: The finding of contrast extravasation on CECT is highly suggestive of significant arterial bleeding that requires early angiographic embolization to restore hemodynamic stability.

Abbreviated Injury Scale↗
PubMed1996

Lack of MMTV superantigen presentation in MHC class II-deficient mice.

Mammary tumor viruses (MMTVs) as well as their endogenous counterparts encode superantigens which react with T cells expressing particular T cell receptor V beta chains. Several lines of evidence indicated that MHC class II is required for the functional presentation of these superantigens. Here we provide direct proof that the function of superantigens is abrogated in the absence of MHC class II expression. No deletion of Mls-1-reactive T cells was observed in MHC class II-deficient mice, and splenocytes from these animals did not stimulate Mls-1-reactive T cell hybrids in vitro. Furthermore, the viral spread in MHC class II-deficient mice, maternally infected with MMTV(C3H), was severely reduced. While initial infection in the gut-associated lymphocytes was comparable between MHC class II-deficient and normal mice, the level of infection in the spleen and the mammary tissue was much lower in the deficient animals. Quantitation of proviral DNA in spleen revealed a direct correlation between the magnitude of superantigen stimulation and degree of infection. These experiments document the direct effect of superantigen stimulation on viral amplification.

Animals↗
PubMed1996

Steroidal contraceptive use update, United States, 1989-1994.

OBJECTIVE: To update United States steroidal contraceptive use data for the period 1989 to 1994. STUDY DESIGN: Pharmaceutical marketing data were used to examine trends in the utilization and distribution of oral contraceptives, Norplant, and Depo-Provera. RESULTS: There were 56.8 million prescriptions for oral contraceptives dispensed through retail pharmacies in 1994. Estrogen and progestin doses remained fairly stable over time. The average ethinyl estradiol dose of formulations was approximately 34 microg per pill. Mentions for oral contraceptives among 35- to 44-year-old women increased. Approximately 169,000 Norplant systems were distributed from 1991 through 1994. More than 1.5 million milliliters of Depo-Provera were distributed from 1993 to 1994. CONCLUSIONS: Oral contraceptives remain a popular form of contraception. Parenteral formulations have been rapidly accepted.

Journal Article↗
PubMed1996

Psychosocial sequelae of motor vehicle collisions: a follow-up study.

One-hundred-and-forty-nine motor vehicle collision trauma victims were interviewed one year after discharge from a Regional Trauma Unit. Follow-up data indicated major post trauma problems such depression, anxiety, family stress, financial problems and driving fears. Almost 40% reported drinking driving after the crash with a greater proportion of alcohol (blood alcohol content) positive drivers engaging in drinking driving than blood alcohol content negative drivers. Notably, almost 16% of the blood alcohol content positive and 13% of the blood alcohol content negative reported involvement in another crash in the year since discharge.

Accidents, Traffic↗
PubMed1995

Significance of intra-abdominal extraluminal air detected by CT scan in blunt abdominal trauma.

The purpose of this study was to determine the frequency and significance of computed tomographic (CT) scan-detected pneumoperitoneum in blunt abdominal trauma. We retrospectively reviewed 118 consecutive CT scans of the abdomen in blunt abdominal trauma patients (mean Injury Severity Score 24), performed at our Regional Trauma Unit over a 12-month period. Seven (5.9%) patients had intra-abdominal extraluminal air. None of these seven patients had evidence of bowel perforation at laparotomy (two) or on clinical follow-up (five). All seven had chest tubes in place before the CT scan. None of the seven patients were on mechanical ventilation at the time of CT scan. In the setting of blunt abdominal trauma pneumoperitoneum does not necessarily indicate hollow viscus injury. It frequently is secondary to other etiologies, especially dissection of interstitial air from the chest, as suggested in this study. The decision for laparotomy should be based on a combination of the clinical findings, CT scan results, or other diagnostic tests such as peritoneal lavage.

Abdominal Injuries↗
PubMed1995

Implementing the Medicare electronic remittance advice.

Some hospitals have delayed converting to the electronic remittance advice recently implemented by the Health Care Financing Administration because the process is unfamiliar and because the electronic data interchange (EDI) translation software is expensive. However, the University of Pittsburgh Medical Center (UPMC) found that it could begin to reap the benefits of EDI technology by using existing software and hardware along with a common-sense approach to implementation. As a result, UPMC has begun an organizationwide EDI initiative designed to reduce costs and improve cash flow.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1993

Presentation of the Mls-1 superantigen by human HLA class II molecules to murine T cells.

Superantigens (SAG) presented in the context of MHC class II proteins stimulate a strong proliferative response in T cells expressing particular TCR V beta genes. Although this T-cell recognition is not MHC restricted, a strong hierarchy is observed in the ability of various MHC class II molecules to present SAG. Mls-1, encoded by the Murine Mammary Tumor Virus (MMTV) Mtv-7 sag gene, is the prototype of endogenous SAG. In the present study, we have analyzed whether this retroviral gene product can be presented in the context of human HLA class II proteins to murine T cells. Positive results were obtained with the DR isotype and in in vitro, as well as in vivo T-cell stimulation assays. However, the various DR beta alleles, expressed in combination with an identical DR alpha chain, differed in their Mls-1 presenting capacity, indicating that the MHC class II beta-chain contains the primary contact site for Mls-1. Interestingly, the same pattern of TCR V beta restriction was seen in response to Mls-1 presented in the context of human and mouse class II, suggesting that the TCR V beta specificity is uniquely determined by the retroviral SAG. Furthermore, Mls-1 presented in the context of the DQw1 and DPw2 isotypes did not elicit a T-cell response. The results from this study form the basis for further analysis of the exact region in the class II beta-chain that interacts with Mls-1.

Alleles↗
PubMedDate not supplied

A retrospective review of the relationship between facial fractures, head injuries, and cervical spine injuries.

Facial fractures are common in the multiply-traumatized patient, and the results of previous studies that have examined the relationship between facial fractures, cervical spine injuries, and head injuries have produced conflicting results. A retrospective review of 1,050 blunt-trauma patients during a 40-month period at a regional trauma unit revealed 168 patients with facial fractures. The average injury severity score (ISS) of these patients with facial fractures was 31 compared with an average ISS of 25.6 for the entire group. There were 266 facial fractures in these 168 patients: mandible (n = 72), maxilla (n = 74), zygoma (n = 52), orbital (n = 46), nasoethmoidal (n = 20), and frontal (n = 2). There were seven (4%) cervical spine injuries, three of which were atlanto-occipital subluxations in patients who ultimately died. Of the four surviving patients, one had a cord injury. In contrast, 145 (85%) showed evidence of head injuries; 64 (38%) of these head injuries were serious and 17 of these patients required craniotomy. The relationship of facial fractures and cervical spine injuries may be over emphasized; head injuries, although frequently minor, are much more commonly associated with facial fractures.

Adolescent↗