Expression of fibrinogen receptors during activation and subsequent desensitization of human platelets by epinephrine

Epinephrine causes platelet aggregation and secretion by interacting with alpha 2-adrenergic receptors on the platelet surface. Platelet aggregation requires the binding of fibrinogen to a specific receptor on the membrane glycoprotein IIb-IIIa complex. Although the IIb-IIIa complex is identifiable on the surface of resting platelets, the fibrinogen receptor is expressed only after platelet activation. The current studies were designed to examine the effect of occupancy of platelet alpha 2-adrenergic receptors by epinephrine on the expression of fibrinogen receptors and on the aggregation of platelets. The ability of epinephrine to induce the expression of fibrinogen receptors was studied under two different conditions: acute stimulation (less than 1 min) and prolonged stimulation (50 to 90 min), the latter of which is associated with a reduction or "desensitization" of the platelet aggregation response. Expression of the fibrinogen receptor was monitored with 125I-fibrinogen as well as with 125I-PAC-1 (PAC-1), a monoclonal antibody that binds to the glycoprotein IIb-IIIa complex only after platelets are activated. Epinephrine caused an immediate increase in PAC-1 and fibrinogen binding that was dependent on occupancy of the alpha 2-receptor by epinephrine and on the presence of extracellular free Ca (KCa = 30 mumol/L). By itself, 1 mmol/L Mg was unable to support induction of the fibrinogen receptor by epinephrine. However, it did decrease the Ca requirement by about two orders of magnitude. Prolonged stimulation of unstirred platelets by epinephrine led to a 70% decrease in the aggregation response when the platelets were subsequently stirred. Despite their decreased aggregation response, desensitized platelets bound PAC-1 and fibrinogen normally, indicating that the loss of aggregation was not due simply to a decrease in fibrinogen receptor expression. Although desensitization was not affected by pretreatment of the platelets with aspirin, it was partially prevented when extracellular Ca was chelated by EDTA during the long incubation with epinephrine. These studies demonstrate that once platelet alpha 2-adrenergic receptors are occupied by epinephrine, extracellular Ca is involved in initiating the aggregation response by supporting the induction of the fibrinogen receptor and the binding of fibrinogen. Furthermore. Ca-dependent reactions subsequent to fibrinogen binding may be necessary for maximal platelet aggregation and are impaired when platelets become desensitized to epinephrine.     

Glycoprotein Ib and glycoprotein IX are fully complexed in the intact platelet membrane

Two new murine monoclonal antibodies, AK 1 and SZ 1, reactive with the human platelet glycoprotein (GP) Ib-IX complex have been produced by the hybridoma technique. Both AK 1 and SZ 1 immunoprecipitated the GP Ib-IX complex from Triton X-100-solubilized, periodate-labeled platelets. With trypsinized, labeled platelets, AK 1, SZ 1, and FMC 25 (epitope on GP IX) immunoprecipitated a membrane-bound proteolytic fragment of the GP Ib-IX complex consisting of GP IX and an congruent to 25,000 mol wt remnant of the alpha-chain of GP lb disulfide-linked to the beta-subunit. Unexpectedly, although AK 1 and SZ 1 immunoprecipitated purified GP Ib-IX complex, neither antibody immunoprecipitated the individual components of this complex, GP Ib or GP IX. When GP Ib and GP IX were recombined, however, AK 1 and SZ 1 again immunoprecipitated the reformed complex, strongly suggesting that both antibodies were recognizing an epitope present only on the intact complex. Cross-blocking studies indicated that AK 1 and SZ 1 recognized a very similar or identical epitope that was proximal to the epitope for FMC 25. Both AK 1 and SZ 1 bound to a similar number of binding sites (congruent to 25,000) on intact platelets as monoclonal antibodies directed against either GP lb or GP IX. The combined data suggests that GP lb and GP IX are fully complexed in the intact platelet membrane.     

Informant ratings of cognitive decline of elderly people: relationship to longitudinal change on cognitive tests

Formal assessment of cognitive decline with cognitive tests can be difficult, requiring either two measurement points or a comparison of 'hold' with 'don't hold' tests. Informant-based assessment provides an alternative approach because informants can adopt a longitudinal perspective and directly rate cognitive change. A study was carried out to assess the validity of informant ratings collected by means of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). A community sample of 500 subjects aged 74 or over underwent four cognitive tests on two occasions 3½ years apart. On the second occasion, informants filled out the IQCODE. Subjects rated as having moderate or severe decline were found to have greater change on the cognitive tests. These findings support the validity of informant ratings of cognitive decline.     

磁共振形态学半定量评分对新生儿细菌性脑膜炎出院结局的评估价值

目的 分析MRI形态学半定量评分对新生儿细菌性脑膜炎出院结局的评估价值。方法 收集复旦大学附属儿科医院2011年7月至2013年12月NICU收治的出院诊断为新生儿细菌性脑膜炎的病例,采用基于大脑损伤MRI形态学分析的半定量评分,对头颅MRI图像进行回顾性分析。MRI形态学评价包括脑室扩大、脑室旁白质容积丢失、脑白质囊性病灶、内囊后肢髓鞘化异常、皮质信号异常、颅内脑外间隙异常、基底节信号异常、脑白质非囊性信号异常、脑室内出血、脑室积脓、脑膜异常强化、室管膜异常强化和脑脓肿。将上述13项评分归纳为脑白质异常（WMA）、脑灰质异常（GMA）和非脑实质异常（NPA）。同时采集患儿出生孕周、发病时间、MRI检查时间、发病至MRI检查间隔时间和出院结局。按照出生孕周分为早产儿组和足月儿组,再按照出院结局分为预后良好和预后不良亚组,在各组内比较亚组之间时间因素、MRI单项评分和综合评分的差异。结果 63例新生儿细菌性脑膜炎病例进入分析（早产儿组18例,足月儿组45例）。MRI单项评分构成预后良好和预后不良亚组间差异有统计学意义的指标：早产儿组中有脑室扩大(P=0.012)和脑室旁白质容积丢失(P=0.004);足月儿组有脑室扩大(P=0.002)、脑室旁容积丢失(P=0.040)、颅内脑外间隙异常(P=0.005)和脑室内出血(P=0.038)。MRI综合评分中,早产儿组WMA评分(P=0.001)和NPA评分（P=0.039）、足月儿组NPA评分(P=0.018)在预后不良和预后良好亚组之间分布差异有统计学意义。足月儿组和早产儿组内不同预后亚组的各时间因素差异未发现统计学意义或临床意义。结论 新生儿细菌性脑膜炎MRI脑室扩大和脑室旁白质容积丢失预示早产儿出院不良结局;脑室扩大、脑室旁白质容积丢失、颅内脑外间隙异常和脑室内出血预示足月儿出院不良结局。WMA评分高预示早产儿出院不良结局,NPA评分高预示早产儿和足月儿出院不良结局。     

Increased Ligament Thickness in Previously Sprained Ankles as Measured by Musculoskeletal Ultrasound

Context:Lateral ankle sprains are among the most common injuries in sport, with the anterior talofibular ligament (ATFL) most susceptible to damage. Although we understand that after a sprain, scar tissue forms within the ligament, little is known about the morphologic changes in a ligament after injury.Objective:To examine whether morphologic differences exist in the thickness of the ATFL in healthy, coper, and unstable-ankle groups.Design:Cross-sectional study.Setting:Laboratory.Results:A group-by-limb interaction was evident (P = .038). The ATFLs of the injured limb for the coper group (2.20 ± 0.47 mm) and the injured limb for the unstable group (2.28 ± 0.53 mm) were thicker than the ATFL of the “injured” limb of the healthy group (1.95 ± 0.29 mm) at P = .015 and P = .015, respectively. No differences were seen in the uninjured limbs among groups.Conclusions:Because ATFL thicknesses of the healthy group''s uninjured ankles were similar, we contend that lasting morphologic changes occurred in those with a previous injury to the ankle. Similar differences were seen between the injured limbs of the coper and unstable groups, so there must be another explanation for the sensations of instability and the reinjuries in the unstable group.Key Words: ankle instability, anterior talofibular ligament, morphology

Key Points

• The anterior talofibular ligament can be viewed using musculoskeletal ultrasound imaging.
• The anterior talofibular ligaments of previously sprained ankles were thicker than those of uninjured ankles.
• Although coper ankles were more functionally similar to healthy ankles than to unstable ankles, they were structurally different. Only further research can determine the relationship between ligament damage and functional stability of the ankle.

Musculoskeletal ultrasound (MSUS) imaging is a new technique being used in the sports medicine setting. Compared with other imaging techniques, such as radiographic or magnetic resonance imaging (MRI), MSUS offers a safer, more time-efficient, and more cost-effective alternative. A real-time image can be captured via MSUS by using a transducer to send high-frequency sound waves into the body and recording the echo of the sound waves reflecting back, providing an image of the internal structure.^1,2 This method has been found to be effective in imaging upper extremity, lower extremity, and joint injuries.^1,3,4Oae et al³ reported greater than 90% accuracy for both MSUS and MRI in identifying injuries to the ankle. Lateral ankle sprains (LASs) are among the most common injuries in sport.⁵ An estimated 850 000 new ankle sprains occur each year in the United States,⁷ which does not include a 70% reinjury rate at the ankle.⁶ Ankle stability plays an important role in injury prevention. Passive stability of the ankle is predominantly the responsibility of ligaments supporting the bony structure of the talocrural joint because there are no musculotendinous insertions on the talus. Ligaments supporting the lateral complex of the ankle include the anterior talofibular ligament (ATFL), calcaneofibular ligament, and posterior talofibular ligament. The ATFL is a flat ligament that attaches from the anterior border of the lateral malleolus to the talus, just anterior to the lateral malleolus articular surface.⁸ The ATFL limits plantar flexion and inversion, motions that coincide with the most common mechanism of injury.⁸ As a result, the ATFL becomes vulnerable in a plantar-flexed and inverted position and is most susceptible to damage during an LAS.^5,6,9 An isolated tear of the ATFL occurs in about 80% of LASs.^10,11After an LAS, the fibrous structure of an ankle ligament is often disrupted by severe damage. Using MRI, Takao et al¹² reported visible scarring of the ATFL after injury. Using MSUS, McCarthy et al¹³ described a thickened ATFL, osseous spurs, and synovitic lesions after injury. Thickness values for the ATFL have been derived primarily from cadaveric studies^14,15; however, MRI-based in vivo studies demonstrated thickness of the ATFL to be in the range of 2 to 3 mm.^16,17 An abnormal ligament could affect the stabilizing properties of the ligament. In animal studies, although scar tissue formed within a ligament after injury, the newly scarred ligament allowed normal movement; however, the load capacity of that ligament was decreased by 60%.^18–20 Therefore, the strength of a ligament can be sufficient for active movement and injury rehabilitation soon after injury, but the decrease in load capacity of the scarred ligament may affect its stabilizing properties.Despite medical treatment and postinjury rehabilitation, more than 50% of individuals who sustain a moderate or severe ankle sprain experience some degree of residual disability and impairment due to symptoms such as pain, instability, loss of range of motion, and edema.^6,21 Those who do not fully recover from their ankle sprain often develop chronic ankle instability (CAI), which limits function not only in sport but also in activities of daily living. Patients with CAI typically complain of the ankle “giving way” or of repeated ankle sprains under seemingly low-risk conditions.²²Typically, CAI researchers have categorized participants into 2 groups: those with ankle instability (unstable) and those without ankle instability (healthy). The unstable group consists of individuals who experience recurrent sprains, sensations of instability, or both. Unfortunately, this method of grouping ignores those who sustained an ankle sprain but did not experience recurrent sprains or sensations of instability. In general, an ankle “coper” refers to an individual who has experienced an initial ankle sprain but not a subsequent sprain.²³ Only recently have copers been addressed in ankle-instability research.^24–29 Because copers are still a new cohort in this research, the classification of ankle copers differs somewhat among researchers.^25,28Although we understand that the fibrous nature of a ligament is disrupted after an LAS, little is known about the actual morphologic changes in a ligament. Therefore, the purpose of our study, using a mixed-model analysis, was to determine whether MSUS can be used to see differences in ligament thickness between the uninjured limb and the injured limb among the healthy, coper, and unstable groups. We hypothesized that the ligaments of the previously injured ankles would be thicker than the uninjured ankles.     

Key High‐efficiency Practices of Emergency Department Providers: A Mixed‐methods Study

Objective

The objective of this study was to determine specific provider practices associated with high provider efficiency in community emergency departments (EDs).

Methods

A mixed‐methods study design was utilized to identify key behaviors associated with efficiency. Stage 1 was a convenience sample of 16 participants (ED medical directors, nurses, advanced practice providers, and physicians) identified provider efficiency behaviors during semistructured interviews. Ninety‐nine behaviors were identified and distilled by a group of three ED clinicians into 18 themes. Stage 2 was an observational study of 35 providers was performed in four (30,000‐ to 55,000‐visit) community EDs during two 4‐hour periods and recorded in minute‐by‐minute observation logs. In Stage 3, each behavior or practice from Stage 1 was assigned a score within each observation period. Behaviors were tested for association with provider efficiency (relative value units/hour) using linear univariate generalized estimating equations with an identity link, clustered on ED site.

Results

Five ED provider practices were found to be positively associated with efficiency: average patient load, using name of team member, conversations with health care team, visits to patient rooms, and running the board. Two behaviors, “inefficiency practices,” demonstrated significant negative correlations: non–work‐related tasks and documentation on patients no longer in the ED.

Conclusions

Average patient load, running the board, conversations with team member, and using names of team members are associated with enhanced provider productivity. Identification of behaviors associated with efficiency can be utilized by medical directors, clinicians, and trainees to improve personal efficiency or counsel team members.