General Practitioner referrals to Child and Adolescent Mental Health Services: Did they differ during Covid-19?

OBJECTIVES

The COVID pandemic has been associated with poorer mental health in youth. This study aimed to evaluate any change in General Practitioner (GP) referral pattern to Child and Adolescent Mental Health (CAMH) services during the first 10 months of Covid-19 and compare with a similar time frame in 2019.

METHODS

All accepted referrals to a CAMH Service in Dublin during the study time frame were reviewed. Referral letters were batch anonymised and clinical data extracted using a study specific proforma for analysis.

RESULTS

Referral numbers between the two time periods did not statistically differ. Proportionally more females were referred during the pandemic, increasing to 56.9%, n = 99, compared to 43.1%, n = 75 in 2019 (p = 0.01). Referrals were more often designated by the clinician as urgent during the pandemic (61.3%, n = 98) than before (39%, n = 62, p < 0.001). Referrals outlining self-harm or suicidal ideation increased significantly, from 42.1% (n = 67) to 55.9% (n = 90) (p = 0.014). Referrals for externalising problems fell from 2019 rates; ADHD (21.4%, n = 34 vs 11.1%, n = 18; p = 0.013), ASD (26.4%, n = 42 vs 16.1%, n = 26; p = 0.038) and conduct problems (23.3%, n = 37 vs 7.4%, n = 12; p < 0.001). Although numbers for psychosis in 2019 were low (10.7%, n = 17), these also fell significantly in 2020 (2.5%, n = 4; p < 0.001).

DISCUSSION

The finding of reduced referrals for ADHD and ASD has not previously been reported. With concerns regarding educational loss linked to online learning, it is crucial that these youth are not doubly disadvantaged by delayed referral and education decline.

A One Year Cost Analysis of Acute Paediatric Mental Health Presentations

Aim Examine costs associated with acute mental health presentations (AMHP) to a paediatric emergency department (ED) in 2016 and 2018. Methods Case identification and bed costs were calculated. Results In 2018, 163 youths attended the ED with AMHP, 122 (75%) were admitted (average 8 days), representing a yearly cost to the hospital of €1,028,020, average cost per patient €8,426. This marks an increase of €425,320 or €2,686 per patient compared to 2016. Arriving out of hours, presence of self-harm (SH) and discharge to an inpatient psychiatry bed were all associated with greater costs. Conclusion Despite increasing hospital costs associated with out of hours psychiatric emergencies, dedicated funding is not yet in place. All children should have access to urgent MH assessment. Work force planning and creation of pathways of care for young people with MH needs, including dedicated funding from HSE mental health division must be a priority.

Paediatric Consultation Liaison Psychiatry Services (PCLPS) -what are they actually doing?

Introduction Paediatric Consultation Liaison Psychiatry Services (PCLPS) are specialised services treating mental health difficulties co-morbid with medical problems. Methods Standardised clinical data was retrieved from all case notes (N=108) during the study timeframe (Jan-June 2016). Results The majority of children were female 59 (55%) with a mean age of 13. Presentation was typically via the Emergency Department (ED) (85, 79%), and of those, the majority (53, 62%) were 'out of hours' and for Deliberate Self-harm (44, 52%) Almost half of all cases seen (50, 46%) were previously known, and discharged back (84, 78%), to CAMHS. Discussion The majority of work conducted by the PCLPS involved children with acute or deteriorating psychiatry disorders, previously known to CAMHS, with a much smaller focus on typical liaison presentations. Adequate resourcing of hospital based PCLPS and 'out of hours' CAMHS are necessary to allow PCLPS provide a specialist service to children with combined medical and MH problems. Given the development of the National Children's Hospital, addressing these resourcing deficits is of vital importance.

Development of a Prototype Immunohistochemistry Assay to Measure Programmed Death Ligand-1 Expression in Tumor Tissue

CONTEXT

- With the abundance of therapeutics targeted against programmed death receptor-1 and its ligand (PD-L1) that are currently approved or in clinical development, there is interest in identifying those patients most likely to respond to these drugs. Expression of PD-L1 may be an indicator of an initial and robust inflammatory response to the presence of tumor cells. Therefore, tumors that express PD-L1 may be the most likely to respond to therapies that interrupt the negative feedback mechanism that leads to PD-L1 upregulation.

OBJECTIVE

- To develop a prototype immunohistochemistry assay using the anti-PD-L1 antibody clone 22C3.

DESIGN

- The assay was developed and optimized using commercially available reagents and archival tumor-bank tissue.

RESULTS

- The optimized immunohistochemistry method had high precision and reproducibility. Using the prototype assay in 142 non-small cell lung cancer and 79 melanoma archival tumor-bank tissue samples, PD-L1 staining was observed at the plasma membrane of nucleated tumor and nontumor cells and, in some cases, as a distinct lichenoid pattern at the tumor-stroma border. Using a preliminary scoring method, 56% (80 of 142) of non-small cell lung cancer and 53% (42 of 79) of melanoma samples were defined as PD-L1⁺ based on a modified H-score of 1 or more or the presence of a distinctive staining pattern at the tumor-stroma interface.

CONCLUSIONS

- The immunohistochemistry assay using the anti-PD-L1 antibody 22C3 merits further investigation in clinical trials and prevalence assessments to further understand the prognostic and predictive value of PD-L1 expression in cancer.

The effect of caffeine mouth rinse on self-paced cycling performance

The aim of the study was to determine whether caffeine mouth rinse would improve 30 min self-paced cycling trial. Twelve healthy active males (age 20.5±0.7 years, mass 87.4±18.3 kg) volunteered for the study. They attended the laboratory on 3 separate occasions performing a 30 min self-paced cycling trial. On one occasion water was given as a mouth rinse for 5 s (PLA), on another occasion a 6.4% maltodextrin (CHO) solution was given for 5 s and finally a caffeine solution (containing 32 mg of caffeine dissolved in 125 ml water; CAF) was given for 5 s. Distance cycled, heart rate, ratings of perceived exertion, cadence, speed and power output were recorded throughout all trials. Distance cycled during the CAF mouth rinse trial (16.2±2.8 km) was significantly greater compared to PLA trial (14.9±2.6 km). There was no difference between CHO and CAF trials (P=0.89). Cadence, power and velocity were significantly greater during the CAF trial compared to both PLA and CHO (P<0.05). There were no differences between trials for heart rate and perceived exertion (P>0.05). Caffeine mouth rinse improves 30 min cycling performance by allowing the participant to increase cadence, power and velocity without a concurrent increase in perceived exertion and heart rate.

Engineered protease-resistant antibodies with selectable cell-killing functions

Molecularly engineered antibodies with fit-for-purpose properties will differentiate next generation antibody therapeutics from traditional IgG1 scaffolds. One requirement for engineering the most appropriate properties for a particular therapeutic area is an understanding of the intricacies of the target microenvironment in which the antibody is expected to function. Our group and others have demonstrated that proteases secreted by invasive tumors and pathological microorganisms are capable of cleaving human IgG1, the most commonly adopted isotype among monoclonal antibody therapeutics. Specific cleavage in the lower hinge of IgG1 results in a loss of Fc-mediated cell-killing functions without a concomitant loss of antigen binding capability or circulating antibody half-life. Proteolytic cleavage in the hinge region by tumor-associated or microbial proteases is postulated as a means of evading host immune responses, and antibodies engineered with potent cell-killing functions that are also resistant to hinge proteolysis are of interest. Mutation of the lower hinge region of an IgG1 resulted in protease resistance but also resulted in a profound loss of Fc-mediated cell-killing functions. In the present study, we demonstrate that specific mutations of the CH2 domain in conjunction with lower hinge mutations can restore and sometimes enhance cell-killing functions while still retaining protease resistance. By identifying mutations that can restore either complement- or Fcγ receptor-mediated functions on a protease-resistant scaffold, we were able to generate a novel protease-resistant platform with selective cell-killing functionality.

Cannabis use and childhood trauma interact additively to increase the risk of psychotic symptoms in adolescence

BACKGROUND

Adolescent cannabis use has been shown in many studies to increase the risk of later psychosis. Childhood trauma is associated with both substance misuse and risk for psychosis. In this study our aim was to investigate whether there is a significant interaction between cannabis use and childhood trauma in increasing the risk for experiencing psychotic symptoms during adolescence.

METHOD

Psychiatric interviews using the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) semi-structured instrument were carried out with 211 adolescents aged between 12 and 15 years and their parents as part of a population-based study. The interview enquired about early traumatic events, cannabis use and psychiatric symptoms in adolescence.

RESULTS

In separate analyses both cannabis use and childhood trauma were significantly associated with risk of experiencing psychotic symptoms. However, the presence of both childhood trauma and early cannabis use significantly increased the risk for psychotic symptoms beyond the risk posed by either risk factor alone, indicating that there was a greater than additive interaction between childhood trauma and cannabis use.

CONCLUSION

Our finding of a greater than additive interaction between childhood trauma and cannabis use may have implications for the identification of individuals at high risk of experiencing psychotic symptoms. For example, measures to actively discourage or intensively treat cannabis use in children and adolescents who have experienced abuse may help to prevent the development of psychosis in this vulnerable group. Our findings require replication in larger samples to confirm this interaction effect.

Thymidylate synthase polymorphisms and immunohistochemistry in non-small cell lung cancer

11101

Background: Recently, pemetrexed has been introduced into the treatment of non-small cell lung cancer (NSCLC). There's evidence that pemetrexed appears to be more efficient in non squamous NSCLC including adenocarcinoma (AC) and large cell carcinoma (LCC). TS represents a major target enzyme of pemetrexed. We evaluated the expression of TS among different histological types of NSCLC and its association with functional genetic polymorphisms of the TS gene. Methods: Archived tumor samples from 312 individuals with NSCLC were analyzed. Immunohistochemistry (IHC) was performed using a mouse monoclonal antibody to TS. TS stained sections were scored for cytoplasmic and nuclear localization. For each compartment, the tumor was evaluated for the estimated percentage of positive cells with the greatest intensity within the tumor. Intensity was scored on a scale of 0–4. A score of 3–4 was classified as high expression. Genotyping of TS-VNTR including the G/C SNP and TS1394del6 was performed by PCR based RFLP techniques. Genotypes supposed to be associated with low expression were grouped (group A: 2R/2R or 2R/3RC or 3RC/3RC + -6/-6) and compared to genotype groups associated with high expression (group B: 2R/3RG or 3RC/3RG or 3RG/3RG + -6/+6 or +6/+6). Results: IHC and polymorphisms could be performed successfully in 312 (100%) and 287 (92%), respectively. Distribution of histology was as follows: 50% AC, 42% squamous cell carcinoma (SCC), 3% LCC and 5% mixed or other histological subtypes. Group B genotypes were significantly more present in SCC than in AC (49% vs 23%, p=.002). Tumors with group B genotypes were more likely to display high nuclear staining intensity than group A tumors (30% vs. 17%, p=.077). A similar but not significant trend was seen for cytoplasmic staining intensity. There was no significant difference between histological subtypes of NSCLC with respect to TS protein expression. AC were more common than SCC to show a G1 differentiated tumors (8% vs 1%, p<.001). No difference between genotype groups were observed with respect to grading. Conclusions: TS polymorphisms are significantly associated with histology subtypes in NSCLC. These results represent a potential explanation for efficacy differences of pemetrexed in NSCLC and warrants further investigations.

[Table: see text]

Health services use in eating disorders

BACKGROUND

This study examined healthcare services used by adults diagnosed with an eating disorder (ED) in a large health maintenance organization in the Pacific Northwest.

METHOD

Electronic medical records were used to collect information on all out-patient and in-patient visits and medication dispenses, from 2002 to 2004, for adults aged 18-55 years who received an ED diagnosis during 2003. Healthcare services received the year prior to, and following, the receipt of an ED diagnosis were examined. Cases were matched to five comparison health plan members who had a health plan visit close to the date of the matched case's ED diagnosis.

RESULTS

Incidence of EDs (0.32% of the 104,130 females, and 0.02% of the 93,628 males) was consistent with prior research employing treatment-based databases, though less than community-based samples. Most cases (50%) were first identified during a primary-care visit and psychiatric co-morbidity was high. Health services use was significantly elevated in all service sectors among those with an ED when compared with matched controls both in the year preceding and that following the receipt of the incident ED diagnosis. Contrary to expectations, healthcare utilization was found to be similarly high across the spectrum of EDs (anorexia nervosa, bulimia nervosa, and eating disorders not otherwise specified).

CONCLUSIONS

The elevation in health service use among women both before and after diagnosis suggests that EDs merit identification and treatment efforts commensurate with other mental health disorders (e.g. depression) which have similar healthcare impact.

The use of an interactive computerized daily schedule in a busy interventional radiology practice increases efficiency

PURPOSE

The effect on efficiency of patient care in a busy academic interventional radiology practice was studied by the analysis of procedure times both before and after the implementation of a computerized interactive daily schedule. Procedure start and end times were retrospectively collected from the department's quality assurance database for two identical 6-month periods, representing the time before and after the deployment of the software. The delay in the start of the first case, the time between cases, and the time required to complete each day's work were compared for the two periods.

RESULTS

The average time of delay between cases was reduced after the implementation of the software (p < 0.025). More total cases were performed during the period of time after the implementation of the software, resulting in a greater work relative value unit production. Although the average number of cases performed per day was greater after the software was in use (p < 0.03), the average amount of time required to complete the day's work was not significantly changed (p = 0.08). There was no apparent effect on the average delay of the start of the day's first case (p = 0.34).

CONCLUSION

The use of a computerized interactive daily schedule has a positive effect on departmental efficiency by allowing more cases to be performed without lengthening the workday.

Identification and pharmacological characterization of native, functional human urotensin-II receptors in rhabdomyosarcoma cell lines

1 In an effort to identify endogenous, native mammalian urotensin-II (U-II) receptors (UT), a diverse range of human, primate and rodent cell lines (49 in total) were screened for the presence of detectable [125I]hU-II binding sites. 2 UT mRNA (Northern blot, PCR) and protein (immunocytochemistry) were evident in human skeletal muscle tissue and cells. 3 [(125)I]hU-II bound to a homogenous population of high-affinity, saturable (Kd 67.0+/-11.8 pm, Bmax 9687+/-843 sites cell(-1)) receptors in the skeletal muscle (rhabdomyosarcoma) cell line SJRH30. Radiolabel was characteristically slow to dissociate (< or =15% dissociation 90 min). A lower density of high-affinity U-II binding sites was also evident in the rhabdomyosarcoma cell line TE671 (1667+/-165 sites cell(-1), Kd 74+/-8 pm). 4 Consistent with the profile recorded in human recombinant UT-HEK293 cells, [125I]hU-II binding to SJRH30 cells was selectively displaced by both mammalian and fish U-II isopeptides (Kis 0.5+/-0.1-1.2+/-0.3 nm) and related analogues (hU-II[4-11]>[Cys(5,10)]Acm hU-II; Kis 0.4+/-0.1 and 864+/-193 nm, respectively). 5 U-II receptor activation was functionally coupled to phospholipase C-mediated [Ca2+]i mobilization (EC50 6.9+/-2.2 nm) in SJRH30 cells. 6 The present study is the first to identify the presence of 'endogenous' U-II receptors in SJRH30 and TE671 cells. SJRH30 cells, in particular, might prove to be of utility for (a) investigating the pharmacological properties of hU-II and related small molecule antagonists at native human UT and (b) delineating the role of this neuropeptide in the (patho)physiological regulation of mammalian neuromuscular function.

Interleukin-1 beta rapidly inhibits aortic endothelium-dependent relaxation by a DNA transcription-dependent mechanism

OBJECTIVES

This study examined the effects of interleukin-1 beta on isometric tension development and relaxation in isolated rat aortic rings in response to the alpha-1 adrenergic agonist phenylephrine, the endothelium-dependent vasodilator acetylcholine, and the endothelium-independent vasodilator sodium nitroprusside.

DESIGN

Randomized, controlled, paired design.

SETTING

Animal laboratory within a university department of physiology. SUBJECTS Paired aortic thoracic aortic rings from specific pathogen-free Sprague-Dawley rats.

INTERVENTIONS

Series I examined the potential for interleukin-1 beta to cause early arterial endothelial dysfunction. Paired aortic rings were incubated for 2 hrs with interleukin-1 beta or vehicle. Series II examined the potential for inhibition of DNA transcription to attenuate interleukin-1 beta-mediated endothelial dysfunction. Paired rings received either dactinomycin or vehicle before interleukin-1 beta incubation. Series III quantified the degree to which inhibition of DNA transcription inhibited early interleukin-1 beta-mediated endothelial dysfunction. Paired rings received either dactinomycin pretreatment followed by interleukin-1 beta incubation, or pretreatment and incubation with inert vehicles. Series IV assessed the effects of interleukin-1 beta on responsiveness to an exogenous nitric oxide donor, sodium nitroprusside, in the presence of the nitric oxide synthesis inhibitor N omega-nitro-L-arginine methyl ester.

MEASUREMENTS AND MAIN RESULTS

Incubation with interleukin-1 beta for 2 hrs had no effect on contractile response but attenuated endothelium-dependent relaxation significantly relative to control. Dactinomycin pretreatment inhibited early interleukin-1 beta-mediated endothelial dysfunction. The combination of interleukin-1 beta and dactinomycin produced effects on endothelium-dependent relaxation that were not different from that seen in rings not exposed to interleukin-1 beta. Interleukin-1 beta attenuated responsiveness to sodium nitroprusside relative to control.

CONCLUSIONS

Interleukin-1 beta causes an early impairment of endothelium-dependent vasorelaxation with an onset that precedes its effects on systemic contractility. This impairment occurs via a mechanism that is wholly or predominantly dependent on DNA transcription. The altered vasorelaxation induced by interleukin-1 beta is at least partly mediated by a reduction in nitric oxide responsiveness.

A randomized trial of a group cognitive intervention for preventing depression in adolescent offspring of depressed parents

BACKGROUND

Adolescent offspring of depressed parents are at high risk for development of depression. Cognitive restructuring therapy holds promise for preventing progression to depressive episodes.

METHODS

A randomized, controlled trial was conducted to prevent depressive episodes in at-risk offspring (aged 13-18 years) of adults treated for depression in a health maintenance organization (HMO). Potential adult cases were found by reviewing the HMO pharmacy records for dispensation of antidepressant medication and the mental health appointment system. Medical charts were reviewed for a depression diagnosis. Recruitment letters signed by treating physicians were mailed to adults. Eligible offspring had subdiagnostic depressive symptoms insufficient to meet full DSM-III-R criteria for affective disorder and/or a past mood disorder. These youth were randomized to usual HMO care (n = 49) or usual care plus a 15-session group cognitive therapy prevention program (n = 45).

RESULTS

We detected significant treatment-by-time (program) effects for the Center for Epidemiological Studies Depression Scale (P=.005) and the Global Assessment of Functioning scores (P =.04). Survival analysis of incident major depressive episodes during a median 15-month follow-up found a significant advantage (P =.003) for the experimental condition (9.3% cumulative major depression incidence) compared with the usual-care control condition (28.8%).

CONCLUSION

A brief, group cognitive therapy prevention program can reduce the risk for depression in the adolescent offspring of parents with a history of depression.

Drinking patterns, health care utilization, and costs among HMO primary care patients

A survey of 8,034 primary care patients in a health maintenance organization examined the relationship between alcohol consumption and health care costs and service use. Costs were estimated from service use data for 1 year before and 2 years after study enrollment. No strong, consistent relationships were identified between multiple indicators of drinking patterns and either health care costs or service use. Compared with total costs among very light drinkers, former drinkers were higher, lifetime abstainers were similar, and persons in the higher drinking levels tended to have lower but not significantly different costs. Drinking patterns did not appear to be an important predictor of short-term health care costs or service use in this setting. Further study of former drinkers is warranted to examine the role of alcohol-related illnesses in the decision to quit drinking.

Laparoscopic appendectomy for simple and perforated appendicitis in children: the procedure of choice?

BACKGROUND/PURPOSE

Whether laparoscopic appendectomy (LA) is superior to open appendectomy (OA) for simple (SA) and perforated appendicitis (PA) in children is debatable. The operative experience of 4 senior pediatric surgeons at a single institution was studied over a 6-year period during a transition from OA in all cases to LA in all cases, to answer this question.

METHODS

All appendectomies from December 1993 to December 1999 were reviewed for operative technique (OA, LA), presence of perforation (SA, PA), operating time (OT), length of stay (LOS), morbidity, and mortality.

RESULTS

There were 1,128 appendectomies in children aged 14 months to 19 years, including 955 LA (653 in SA, 302 in PA) and 173 OA (86 in SA, 87 in PA). OT was equal for LA and OA in SA (52 minutes), but has dropped to less than 40 minutes for LA in the past year. OT in PA was slightly longer in LA versus OA (68 v. 58 minutes; P < .001) but recently has dropped in LA to less than 60 minutes. LOS in SA was 2 days for LA and 3 days for OA; in PA, LOS was 7 days in both LA and OA, but has dropped to 5 days for LA recently. Postoperative abscess rates and incidence of bowel obstruction did not differ between LA and OA in either group. There was no mortality.

CONCLUSIONS

LA is at least as safe and effective as, if not superior to, OA for both simple and perforated appendicitis. Postoperative pain is less, and recovery is faster, thereby reducing LOS and overall cost. The growing demand for this procedure can be satisfied without increase in cost, morbidity, or mortality. Laparoscopic appendectomy is our procedure of choice in children.

Working together to improve record keeping

Implementing changes in a hospital setting requires a structured approach to change management. This article describes the process of a project undertaken to improve record keeping in a children's hospital.

Hypercapnia-induced contraction in isolated pulmonary arteries is endothelium-dependent

It has been demonstrated previously that isohydric hypercapnia (IH) does not affect agonist-induced tension development in pulmonary arteries. The aim of the present study was to examine the effects of IH on depolarisation-induced, steady state tension in the isolated rat pulmonary artery. Rings were submaximally contracted with high KCl under control conditions (5% CO(2)-95% air). IH was achieved by switching to a modified PSS (isosmotic substitution of NaHCO(3) for NaCl), equilibrated with 10% CO(2) in air. On switching to IH, a significant increase in mean (+/-SEM) tension (25.3+/-6.3% Tmax) was observed in endothelium intact rings (n=6). Endothelial removal significantly reduced this response. Non-specific inhibition of nitric oxide synthase (NOS) isoenzymes (L-NAME, 10(-3) M) abolished the IH-induced increase in tension while inhibition of neuronal NOS (TRIM, 10(-5) M) was without effect. The relaxant response to the nitric oxide donor sodium nitroprusside was similar in IH and control conditions. These results suggest that IH caused an endothelium-dependent increase in depolarisation-induced tension by reducing NO production.

Trends in the prescribing of psychotropic medications to preschoolers

CONTEXT

Recent reports on the use of psychotropic medications for preschool-aged children with behavioral and emotional disorders warrant further examination of trends in the type and extent of drug therapy and sociodemographic correlates.

OBJECTIVES

To determine the prevalence of psychotropic medication use in preschool-aged youths and to show utilization trends across a 5-year span.

DESIGN

Ambulatory care prescription records from 2 state Medicaid programs and a salaried group-model health maintenance organization (HMO) were used to perform a population-based analysis of three 1-year cross-sectional data sets (for the years 1991, 1993, and 1995).

SETTING AND PARTICIPANTS

From 1991 to 1995, the number of enrollees aged 2 through 4 years in a Midwestern state Medicaid (MWM) program ranged from 146,369 to 158,060; in a mid-Atlantic state Medicaid (MAM) program, from 34,842 to 54,237; and in an HMO setting in the Northwest, from 19,107 to 19,322.

MAIN OUTCOME MEASURES

Total, age-specific, and gender-specific utilization prevalences per 1000 enrollees for 3 major psychotropic drug classes (stimulants, antidepressants, and neuroleptics) and 2 leading psychotherapeutic medications (methylphenidate and clonidine); rates of increased use of these drugs from 1991 to 1995, compared across the 3 sites.

RESULTS

The 1995 rank order of total prevalence in preschoolers (per 1000) in the MWM program was: stimulants (12.3), 90% of which represents methylphenidate (11.1); antidepressants (3.2); clonidine (2.3); and neuroleptics (0.9). A similar rank order was observed for the MAM program, while the HMO had nearly 3 times more clonidine than antidepressant use (1.9 vs 0.7). Sizable increases in prevalence were noted between 1991 and 1995 across the 3 sites for clonidine, stimulants, and antidepressants, while neuroleptic use increased only slightly. Methylphenidate prevalence in 2- through 4-year-olds increased at each site: MWM, 3-fold; MAM, 1.7-fold; and HMO, 3.1-fold. Decreases occurred in the relative proportions of previously dominant psychotherapeutic agents in the stimulant and antidepressant classes, while increases occurred for newer, less established agents.

CONCLUSIONS

In all 3 data sources, psychotropic medications prescribed for preschoolers increased dramatically between 1991 and 1995. The predominance of medications with off-label (unlabeled) indications calls for prospective community-based, multidimensional outcome studies.

Management of pediatric liver injuries: a 13-year experience at a pediatric trauma center

PURPOSE

This study of traumatic liver injuries (LI) in children reviews the authors' management and identifies the indications for surgical intervention.

METHODS

A total of 11,761 admissions over 13 years to a regional pediatric trauma center were surveyed.

RESULTS

LI were identified in 328 children. Mechanisms included 39% pedestrians struck by a vehicle, 34% motor vehicle occupants, 13% falls or discrete blows to the abdomen, 5% bicycle injuries, 5% child abuse, and 4% penetrating injuries. Eighty-seven of patients with LI were treated nonoperatively with a mortality rate of 17%. Six percent of deaths were attributed to the LI and massive hemorrhage, all of which presented with cardiopulmonary resuscitation (CPR) in progress, with the remainder of deaths attributed to massive head, neck, or chest injuries (HNCI, 90%) and sepsis (4%). Surgery was performed in 13% of all LI and included major hepatic vascular injury (MHVI) repairs (34%), hepatorrhaphies (34%), lobectomies (27%), and biliary repairs (4%). Excluding the nonoperative group deaths, the need for blood transfusion of more than 25 mL/kg in the first 2 hours as an indicator of surgical necessity or a MHVI had, respectively, a sensitivity of 34% and 67%, specificity of 98% and 97%, positive predictive value of 79% and 53%, negative predictive value of 89% and 98%, and prediction accuracy of 88% and 95%. In the surgical management group, the mortality rate was 23% with 40% of deaths attributed to MHVI, 30% a combination of MHVI and HNCI, 20% massive HNCI, and 10% sepsis.

CONCLUSIONS

The majority of pediatric LI are not associated with hemodynamic instability and can be successfully managed nonoperatively (72%). Hemodynamic instability, as defined by the need for blood transfusion in excess of 25 mL/kg within the first 2 hours, was a strong indicator of a MHVI, which was often a lethal injury (70%).

Developing a culture of lifelong learning in a library environment

Between 1995 and 1996, the Annette and Irwin Eskind Biomedical Library (EBL) at Vanderbilt University Medical Center (VUMC) radically revised the model of service it provides to the VUMC community. An in-depth training program was developed for librarians, who began to migrate to clinical settings and establish clinical librarianship and information brokerage services beyond the library's walls. To ensure that excellent service would continue within the library, EBL's training program was adapted for library assistants, providing them with access to information about a wide variety of work roles and processes over a four to eight-month training period. Concurrently, customer service areas were reorganized so that any question--whether reference or circulation--could be answered at any of four service points, eliminating the practice of passing customers from person to person between the reference and circulation desks. To provide an incentive for highly trained library assistants to remain at EBL, management and library assistants worked together to redesign the career pathway based on defined stages of achievement, self-directed participation in library-wide projects, and demonstrated commitment to lifelong learning. Education and training were the fundamental principles at the center of all this activity.

Intramedullary pressure and pulmonary function during total knee arthroplasty

Twenty-eight patients who underwent unilateral total knee arthroplasty and 20 patients who underwent simultaneous bilateral total knee arthroplasties participated in this study and were randomized to have either a fluted or round 10-mm diameter femoral intramedullary alignment rod used during surgery. The intramedullary rods were cannulated and connected with pressure tubing to a monitor which provided measurements of pressure at the tip of each rod. Arterial blood gas measurements on room air were obtained before and on the morning after surgery. An arterial line was placed and an arterial blood gas measurement was obtained at the time of skin incision and again after tourniquet release. Pulmonary shunt was calculated from the arterial blood gas measurements. Intramedullary pressure during rod insertion was significantly higher for the groups of patients having the round compared with the fluted rod. The change in pulmonary shunt during surgery was lowest for the patients in the unilateral group having the fluted rod and highest for the patients in the bilateral group having the round rod. A fluted rather than a round intramedullary alignment rod should be used to minimize intramedullary pressure and pulmonary shunting during unilateral and bilateral total knee arthroplasties.

Separation of omphalopagus twins: unique reconstruction using syngeneic cryopreserved tissue

Omphalopagus twin girls were admitted for evaluation of possible separation and repair at age 7 days. Prenatal sonographic diagnosis occurred late in the third trimester and was followed by cesarean section delivery shortly thereafter. Results of extensive evaluation over the next 7 days including x-rays, computed tomography and ultrasound scan of the head and torso, and cardiac catheterization showed: the gastrointestinal tracts were separate and normal, the livers were joined but had separate biliary and vascular systems, and the hearts were separate with vastly different anatomy and function. One twin (twin A) had a normal heart with a small insignificant VSD. Twin B had a single ventricle, an incompetent A-V valve, stenotic pulmonic valve, ASD, PDA, and congenital heart block. Hemodynamic support of twin B was almost entirely from twin A. The vascular communications between the two consisted of a major connection between the internal mammary arteries and large arterial and venous connections traversing the joined livers. Because of continued deterioration of twin B, separation was undertaken at age 15 days. The separation included dividing the liver and the multiple large vascular connections. Two teams then reconstructed each twin separately. Twin B began showing signs of cardiac decompensation shortly after separation in spite of placement of a pacemaker, pulmonary artery banding, and ligation of the PDA. Cardiac function rapidly deteriorated and she died. Tissue from her chest wall was cryopreserved and placed in the tissue bank. Twin A underwent closure of her abdomen, and received a temporary bovine pericardial patch over the chest defect. She subsequently underwent placement of a graft of twin B's rib cage to bridge the bony chest defect and skin flap closure. She is presently taking a normal diet and thriving at home at age 18 months. The use of cryopreserved tissue from a syngeneic source provides a unique method of reconstruction in this situation.

Split tolerance to the MHC class I molecule H-2Dd in animals transgenic for its soluble analog

To determine whether the function of MHC molecules in tolerance and education is related to cell surface expression, we have produced two strains of transgenic mice in the C57Bl/6 background that express soluble analogs of the H-2D(d) class I protein. The transgenes were stably integrated and genetically transmitted in a Mendelian fashion. Messenger RNA for the hybrid genes was detected in all tissues analyzed in a class I-like pattern of expression, with the highest levels in lymphoid tissues. All mice bearing the transgenes expressed relatively high levels (0.1 mg/ml) of the encoded protein in their serum as assessed by Western blotting and enzyme-linked immunosorbent assay (ELISA). Gel filtration chromatography showed that the soluble H-2D(d) protein exists as a heterodimer with beta2-microglobulin and as higher order multimers in serum. Lymphoid cells from the transgenic mice showed no cell surface expression of the soluble class I protein in indirect immunofluorescence assays. Splenocytes from two independently derived transgenic lines generated primary cytotoxic and proliferative responses directed against membrane H-2D(d) antigens. Mice of both strains rejected tail skin from donors that differed from the B6 background at the H-2D(d) locus only, but with delayed kinetics compared to nontransgenic littermate controls. Mice expressing the transgenic protein on immunization did not produce antibodies that recognized soluble H-2D(d) in ELISA, whereas B6 mice generated strong antibody responses to challenge with splenocytes bearing cell surface H-2D(d). Thus, transgenic mice expressing soluble H-2D(d) were partially tolerant to stimulation by membrane-bound H-2D(d). As with the activation of T-cells, the induction and maintenance of immunologic tolerance apparently displayed different requirements depending upon the T-cell subpopulation involved.

Effect of total hip arthroplasty on cardiovascular fitness

Thirty patients who underwent total hip arthroplasty and 18 patients with medically treated arthritis participated in this study. Both groups of patients underwent a cardiovascular fitness exercise test on entering the study and 6 months, 1 year, and 2 years later. Fitness was assessed by patient performance on a graded maximal exercise test using a bicycle ergometer and metabolic cart. In the group of total hip arthroplasty patients, significant improvements in exercise duration (P = .011), maximum workload (P = .0013), peak oxygen consumption (P = .0036), and percentage of predicted maximum oxygen uptake achieved (P = .0002) were observed during the follow-up evaluation. In the group of control patients, decreases in exercise duration (P = .0001), maximum workload (P = .0001), and workload at anaerobic threshold (P = .0108) occurred without a significant change in the other measures of cardiovascular fitness. The results indicate that resumption of routine physical activities after total hip arthroplasty is associated with a corresponding improvement in cardiovascular fitness.

Improvement in cardiovascular fitness after total knee arthroplasty

Patients who have osteoarthrosis involving weight-bearing joints typically have a gradual decline in physical activity, which is often associated with cardiovascular deconditioning. After joint replacement, many patients resume routine walking and recreational activities, which may improve aerobic capacity. The purpose of the present study was to determine the effect of total knee arthroplasty on cardiovascular fitness. Nineteen patients who had had total knee arthroplasty (the arthroplasty group) performed an exercise test for cardiovascular fitness preoperatively. Sixteen of these patients were tested again at one year postoperatively and thirteen, at two years postoperatively. Sixteen patients in whom osteoarthrosis of the knee was being treated medically (the control group) were tested at the time of enrollment in the study and one year later. Nine of these patients also were tested two years after enrollment. All of the patients completed the Arthritis Impact-Measurement Scales (AIMS) at each examination. Fitness was assessed by the performance of a progressive maximum exercise test with use of a bicycle ergometer and a metabolic cart. All patients achieved the anaerobic threshold. One year postoperatively, the patients in the arthroplasty group demonstrated an increase, which approached significance, in maximum oxygen consumption (measured in milliliters of oxygen per minute) (p = 0.07), maximum oxygen consumption corrected for body weight (p = 0.08), and percentage of predicted maximum uptake of oxygen (p = 0.06). Two years after the total knee arthroplasty, the patients had a significant improvement with regard to all three parameters (p = 0.008, 0.005, and 0.005, respectively). The patients in the control group demonstrated a significant decrease in duration of exercise and in maximum workload at one year (p = 0.003 and 0.005, respectively) and at two years (p = 0.008 for both parameters). Physical activity had increased in the arthroplasty group but not in the control group, as demonstrated by the results of the Arthritis Impact-Measurement Scales. These findings demonstrate a trend toward improvement in cardiovascular fitness one year after total knee arthroplasty and a significant improvement two years postoperatively for patients who had been able to resume routine functional activities because of the arthroplasty. These improvements compared favorably with the static pattern or the decline in the measures of fitness that were observed in the control group. Our results should be considered preliminary because of the relatively small number of patients who were studied.

Varus migration of PCA stems

Forty-seven patients with cementless, porous-coated anatomic hip replacements were evaluated after a minimum 2-year follow up with specific attention to varus migration of the stem. A cadaver study was done to define a relationship between projected size of the lesser trochanter seen radiographically, rotation of the femur, and stem position. Seven (15%) of the stems migrated into varus with the distal tip moving laterally. Thigh pain occurred in patients with varus migration and those with no change in stem position. A lower percent canal fill was seen on the lateral radiograph (P < .001) and larger average width of radiodense lines in zone 1 superolateral, and zone 6, midstem medial (P < .005) in the patients with varus migration. Poor distal stability associated with a lower percent canal fill at the stem tip seen on the lateral radiograph may result in varus migration.

Affinity purification and comparative analysis of two distinct human uracil-DNA glycosylases

Evidence is presented on two forms of uracil-DNA glycosylase (UDG1 and UDG2) that exist in human cells. We have developed an affinity technique to isolate uracil-DNA glycosylases from HeLa cells. This technique relies on the use of a uracil-DNA glycosylase inhibitor (Ugi) produced by the Bacillus subtilis bacteriophage, PBS2. Affinity-purified preparations of uracil-DNA glycosylase, derived from total HeLa cell extracts, reveal a group of bands in the 36,000 molecular weight range and a single 30,000 molecular weight band when analyzed by SDS-PAGE and silver staining. In contrast, only the 30,000 molecular weight band is seen in HeLa mitochondrial preparations. Separation of HeLa cell nuclei from the postnuclear supernatant reveals that uracil-DNA glycosylase activity is evenly distributed between the nuclear compartment and the postnuclear components of the cell. Immunostaining of a nuclear extract with antisera to UDG1 indicates that the nuclear associated uracil-DNA glycosylase activity is not associated with the highly conserved uracil-DNA glycosylase, UDG1. With the use of Ugi-Sepharose affinity chromatography, we show that a second and distinct uracil-DNA glycosylase is associated with the nuclear compartment. Immunoblot analysis, utilizing antisera generated against UDG1, reveals that the 30,000 molecular weight protein and a protein in the 36,000 range share common epitopes. Cycloheximide treatment of HeLa cells indicates that upon inhibition of protein synthesis, the higher molecular weight species disappears and is apparently post-translationally processed into a lower molecular weight form. This is substantiated by mitochondrial import studies which reveal that in vitro expressed UDG1 becomes resistant to trypsin treatment within 15 min of incubation with mitochondria. Within this time frame, a lower molecular weight form of uracil-DNA glycosylase appears and is associated with the mitochondria. Antibodies generated against peptides from specific regions of the cyclin-like uracil-DNA glycosylase (UDG2), demonstrate that this nuclear glycosylase is a phosphoprotein with a molecular weight in the range of 36,000. SDS-PAGE analysis of Ugi affinity-purified and immunoprecipitated UDG2 reveals two closely migrating phosphate-containing species, indicating that UDG2 either contains multiple phosphorylation sites (resulting in heterogeneous migration) or that two distinct forms of UDG2 exist in the cell. Cell staining of various cultured human cell lines corroborates the finding that UDG1 is largely excluded from the nucleus and that UDG2 resides mainly in the nucleus. Our results indicate that UDG1 is targeted to the mitochondria and undergoes proteolytic processing typical of resident mitochondrial proteins that are encoded by nuclear DNA. These results also indicate that the cyclin-like uracil-DNA glycosylase (UDG2) may be a likely candidate for the nuclear located base-excision repair enzyme.

Osteolysis associated with cemented total knee arthroplasty. A case report

Osteolysis induced by particulate debris occurs within 5 years after cementless total knee arthroplasty, but has not been reported to be a problem after cemented total knee arthroplasty. It has been suggested that the bone-cement interface may form a barrier to polyethylene-debris migration, thereby limiting bone loss. The authors have observed osteolysis in a 75-year-old woman 9 years after cemented total knee arthroplasty. An osteolytic area appeared to return to an area of normal bone architecture 3 years after the removal of synovium and particulate debris without implant revision.

Fatal massive adrenal hemorrhage after bilateral total knee arthroplasty

Adrenal hemorrhage can occur in association with postoperative stress, trauma, myocardial infarction, infection, and chronic medical illness. Other risk factors for the development of spontaneous adrenal hemorrhage include a thromboembolic state and anticoagulation therapy, although it has rarely been observed following orthopedic surgery. The authors report the case of an otherwise healthy 61-year-old woman who died suddenly 9 days after bilateral total knee arthroplasty. The only abnormality found on postmortem examination was massive bilateral adrenal hemorrhage with destruction of nearly all adrenal tissue. Surgeons should be aware of this complication that, if recognized early, can be treated with steroid replacement.

Gamma delta T cells promote CD4 and CD8 expression by SCID thymocytes

Molecular studies of the gamma delta TCR, which is expressed by a minor subpopulation of T lymphocytes in all vertebrate species, have defined a subset which expresses a receptor with extreme junctional diversity and a second subset, most commonly found in epithelia, which expresses a receptor of very limited diversity. In the developing murine thymus, gamma delta T cells appear in an ordered sequence of specific V rearrangements, V gamma 3V delta 1 on day 14, V gamma 2V delta 1 on day 17, and subsequently V gamma 4V delta 5, V delta 6, or V delta 7. We demonstrate that the transfer of expanded populations of gamma delta cells from newborn thymus and cell lines expressing the invariant V gamma 3V delta 1 receptor into SCID mice, which lack T and B cells, results in the appearance of CD3-CD4+CD8+ thymocytes. Thus, one role of the early appearing V gamma 3V delta 1 T cells in thymic development in vivo is to promote CD4 and CD8 surface expression on precursor cells.

Pulmonary function during and after total hip replacement. Findings in patients who have insertion of a femoral component with and without cement

Eleven patients who had a femoral component inserted with cement and twenty-three who had a femoral component inserted without cement were studied prospectively for changes in the pulmonary shunt associated with total hip replacement. The levels of oxygen in the arterial blood and the platelet counts were measured preoperatively and each morning for three days after the arthroplasty. Levels of oxygen in the arterial blood were determined intraoperatively, once before and once after the femoral component was inserted. Intraoperative shunt values increased 28 per cent when a femoral component was inserted with cement (p < 0.05), but they did not change when cement was not used. The average postoperative shunt values were higher than the average preoperative shunt values for both groups of patients, but only the values on the second postoperative day after a procedure with cement were significantly higher (p < 0.05). The ability of the patient to tolerate an increase in pulmonary shunt should be assessed when the femoral component is to be cemented during total hip replacement.

Activation requirements of newborn thymic gamma delta T cells

We have analyzed the requirements for the induction of proliferative responses by thymic CD4-CD8- gamma delta T cells. Enriched populations of CD4-CD8- thymocytes from newborn mice, purified by negative selection with anti-CD4, anti-CD8, and anti-TCR alpha beta mAbs were found to contain approximately 20% gamma delta T cells that were p55IL-2R-. When these cells were cultured with a panel of lymphokines (IL-1, -2, -4, and -7), a small response was observed to some of the cytokines tested individually; however, combinations of certain lymphokines (IL-1 + 2, IL-1 + 7, and IL-2 + 7) were found to induce significant proliferation and the selective outgrowth (75-90%) of gamma delta T cells. These cells were IL-2R+, remained CD4-, yet expressed variable levels of CD8. A limited analysis with specific anti-V gamma and V delta mAb suggested that there had not been a selective expansion of preexisting V gamma 2, V gamma 3, or V delta 4 populations in response to the stimulatory lymphokine combinations. Thymic CD4-CD8- gamma delta T cells were unresponsive to stimulation with immobilized anti-pan gamma delta mAb alone. However, in the presence of immobilized anti-pan gamma delta mAb and IL-1, IL-2, or IL-7, but not IL-4, a vigorous proliferative response was observed. Phenotypic analysis showed that 80 to 95% of the proliferating cells were polyclonally expanded gamma delta T cells, expressed the p55IL-2R, and the majority remained CD4-CD8-. Blocking studies with anti-IL-2R mAb showed that stimulation with anti-pan gamma delta + IL-1, but not anti-pan gamma delta + IL-7 was dependent on endogenously produced IL-2. Collectively, these studies suggest that the activation requirements of newborn thymic gamma delta T cells differ markedly from alpha beta T cells in that gamma delta T cells 1) respond to combinations of cytokines in the absence of TCR cross-linking, 2) can respond to TCR cross-linking in the presence of exogenous cytokines, 3) but are unable to activate endogenous cytokine production solely in the presence of TCR cross-linking.

Activation requirements of newborn thymic gamma delta T cells

We have analyzed the requirements for the induction of proliferative responses by thymic CD4-CD8- gamma delta T cells. Enriched populations of CD4-CD8- thymocytes from newborn mice, purified by negative selection with anti-CD4, anti-CD8, and anti-TCR alpha beta mAbs were found to contain approximately 20% gamma delta T cells that were p55IL-2R-. When these cells were cultured with a panel of lymphokines (IL-1, -2, -4, and -7), a small response was observed to some of the cytokines tested individually; however, combinations of certain lymphokines (IL-1 + 2, IL-1 + 7, and IL-2 + 7) were found to induce significant proliferation and the selective outgrowth (75-90%) of gamma delta T cells. These cells were IL-2R+, remained CD4-, yet expressed variable levels of CD8. A limited analysis with specific anti-V gamma and V delta mAb suggested that there had not been a selective expansion of preexisting V gamma 2, V gamma 3, or V delta 4 populations in response to the stimulatory lymphokine combinations. Thymic CD4-CD8- gamma delta T cells were unresponsive to stimulation with immobilized anti-pan gamma delta mAb alone. However, in the presence of immobilized anti-pan gamma delta mAb and IL-1, IL-2, or IL-7, but not IL-4, a vigorous proliferative response was observed. Phenotypic analysis showed that 80 to 95% of the proliferating cells were polyclonally expanded gamma delta T cells, expressed the p55IL-2R, and the majority remained CD4-CD8-. Blocking studies with anti-IL-2R mAb showed that stimulation with anti-pan gamma delta + IL-1, but not anti-pan gamma delta + IL-7 was dependent on endogenously produced IL-2. Collectively, these studies suggest that the activation requirements of newborn thymic gamma delta T cells differ markedly from alpha beta T cells in that gamma delta T cells 1) respond to combinations of cytokines in the absence of TCR cross-linking, 2) can respond to TCR cross-linking in the presence of exogenous cytokines, 3) but are unable to activate endogenous cytokine production solely in the presence of TCR cross-linking.

Separation of the polyethylene liner from acetabular cup metal backing. A report of three cases

In three young patients with cementless Porous Coated Anatomic (PCA) total hip prostheses implanted two to four years previously, the polyethylene liner separated from metal backing. These cups were of the original PCA design, manufactured and packaged as single assembled components, rather than the more recent two-piece components packaged with interchangeable liners separate from the metal backing. Each case of separation was associated with the failure of the thin outer polyethylene rim and central polyethylene peg on the back of the liner that secures it to the metal backing. Cup liners should be securely attached to the metal backing. The possibility of polyethylene failure is considerable when cementless metal-backed acetabular cups are used in active young patients.

Dissection of an inflammatory process induced by CD8+ T cells

A massive delayed type hypersensitivity (DTH) reaction occurs in the cerebrospinal fluid (CSF) of mice with lymphocytic choriomeningitis (LCM). In this article, Peter Doherty and colleagues analyze this reaction together with the population dynamics of the regional lymph node to give a comprehensive picture of the events underlying this CD8+ T-cell-mediated immunopathological disease. Their findings are of general relevance to the understanding of inflammation.

Phenotypic and functional analysis of the cellular response in regional lymphoid tissue during an acute virus infection

A phenotypic and functional analysis has been made of the cellular response in regional lymphoid tissue of C57BL/6J mice infected with lymphocytic choriomeningitis virus. Massive recruitment of nondividing cells occurred from 3 days after infection, with total numbers of CD8+ T lymphocytes, B220+ B cells, and Thy-1- B220- null cells being high from day 4 to day 6. In contrast, the peak counts for CD4+ T cells were recorded on day 4 and declined dramatically thereafter. Enhanced expression of IL-2R and Ly-24, both of which can be regarded as T cell activation markers, was found for both the CD4+ and the CD8+ subsets, being most prominent for the CD8+ T cells on day 6. Evidence of T cell proliferation was not recognized until days 5 and 6, coincident with enhanced responsiveness of the lymphocytes to rIL-2 and the development of virus-specific cytotoxic activity. Elimination of the CD4+ T cells by treatment of mice with mAb did not modify either the pathogenesis of lymphocytic choriomeningitis, or the expression of activation markers on the CD8+ T cells which are known to be the key effectors in this disease. Thus, the pattern of responsiveness for the CD8+ population is of recruitment to the lymph node, progressive increase in the expression of activation markers and enhanced sensitivity to rIL-2, with late proliferation and generation of cytotoxic activity. This model provides a system for the rigorous in vivo analysis of parameters influencing lymphocyte differentiation and activation in a virus infection.

Phenotypic and functional analysis of the cellular response in regional lymphoid tissue during an acute virus infection

A phenotypic and functional analysis has been made of the cellular response in regional lymphoid tissue of C57BL/6J mice infected with lymphocytic choriomeningitis virus. Massive recruitment of nondividing cells occurred from 3 days after infection, with total numbers of CD8+ T lymphocytes, B220+ B cells, and Thy-1- B220- null cells being high from day 4 to day 6. In contrast, the peak counts for CD4+ T cells were recorded on day 4 and declined dramatically thereafter. Enhanced expression of IL-2R and Ly-24, both of which can be regarded as T cell activation markers, was found for both the CD4+ and the CD8+ subsets, being most prominent for the CD8+ T cells on day 6. Evidence of T cell proliferation was not recognized until days 5 and 6, coincident with enhanced responsiveness of the lymphocytes to rIL-2 and the development of virus-specific cytotoxic activity. Elimination of the CD4+ T cells by treatment of mice with mAb did not modify either the pathogenesis of lymphocytic choriomeningitis, or the expression of activation markers on the CD8+ T cells which are known to be the key effectors in this disease. Thus, the pattern of responsiveness for the CD8+ population is of recruitment to the lymph node, progressive increase in the expression of activation markers and enhanced sensitivity to rIL-2, with late proliferation and generation of cytotoxic activity. This model provides a system for the rigorous in vivo analysis of parameters influencing lymphocyte differentiation and activation in a virus infection.

Persistence of the irradiated host component in thymocyte populations from bone marrow radiation chimeras infected with lymphocytic choriomeningitis virus

The thymus of chimeras made using T cell-depleted donor bone marrow from Thy1.1+ mice and 950 rad Thy 1.2+ recipients is dominated initially by cells expressing the Thy 1.2+ phenotype of the irradiated host. The thymocyte population recovered at 2 weeks after reconstitution comprises 80% Thy 1.2+ cells (host), the remainder being Thy 1.1+ (donor). This situation is normally reversed within a further week, with the host Ty 1.2+ (donor). This situation is normally reversed within a further week, with the host Thy 1.2+ thymocytes being present at a frequency of less than 5% from Week 4. Infection with lymphocytic choriomeningitis virus (LCMV) at 1 week after reconstitution with bone marrow causes a profound and persistent drop in the total number of thymocytes. The decline is equivalent for all categories of donor-derived thymocytes defined by two-color flow microfluorometric analysis for CD4 and CD8. However, there is a partial compensation by the retention of cells originating from the Thy 1.2+ host, which constitute 30-40% of the total thymocyte pool as late as 8 weeks after administration of bone marrow in the LCMV-infected chimeras. These radiation-resistant precursors give rise to CD4-8-, CD4-8+, CD4+8-, and CD4+8+ thymocytes, with the latter category being present at increased frequency. The potential skewing of the mature T cell repertoire as a consequence of persistent virus infection is discussed.

Mouse strain variation in Ly-24 (Pgp-1) expression by peripheral T cells and thymocytes: implications for T cell differentiation

The cell surface glycoprotein Ly-24 has been proposed as a useful marker for the identification of in vivo-primed T cells. Analysis of Ly-24 surface expression by T cells from different mouse strains has shown variation in Ly-24 expression that is not H-2 linked; however, mice of the Ly-24.1 allele (e.g. BALB/c) express relatively high amounts, whereas Ly-24.2 strains (e.g. C57BL/6) are low expressors. In BALB/c (Ly-24 high) and C57BL/6 (Ly-24 low) mice, Ly-24 was expressed by both CD4- CD8+ and CD4+ CD8- subpopulations of single-positive T cells and thymocytes Among CD4- CD8- thymocytes, the overall expression of Ly-24 was similar in both mouse strains. Analysis of CD4+ and CD8+ single-positive thymocytes from newborn and adult BALB/c mice showed that the neonatal population contained fewer Ly-24+ cells. However, using the cell surface markers J11d and CD3, neonatal single-positive thymocytes were found to contain larger numbers of cells with the Ly-24-J11d+CD3 low to negative phenotype. Taken together, these results show that in BALB/c (Ly-24 high) mice, as soon as functional mature phenotype (CD3+) CD4+ and CD8+ single-positive thymocytes are generated, they already express Ly-24. These data cast doubt on the usefulness of Ly-24 expression as a universal marker of in vivo-primed T cells and suggest that in BALB/c mice thymus migrants may well be Ly-24+. Expression of Ly-24 by thymocytes is discussed in the context of current models of intrathymic T cell differentiation.