Expanding the clinical spectrum of biglycan-related Meester-Loeys syndrome

Pathogenic loss-of-function variants in BGN, an X-linked gene encoding biglycan, are associated with Meester-Loeys syndrome (MRLS), a thoracic aortic aneurysm/dissection syndrome. Since the initial publication of five probands in 2017, we have considerably expanded our MRLS cohort to a total of 18 probands (16 males and 2 females). Segregation analyses identified 36 additional BGN variant-harboring family members (9 males and 27 females). The identified BGN variants were shown to lead to loss-of-function by cDNA and Western Blot analyses of skin fibroblasts or were strongly predicted to lead to loss-of-function based on the nature of the variant. No (likely) pathogenic missense variants without additional (predicted) splice effects were identified. Interestingly, a male proband with a deletion spanning the coding sequence of BGN and the 5' untranslated region of the downstream gene (ATP2B3) presented with a more severe skeletal phenotype. This may possibly be explained by expressional activation of the downstream ATPase ATP2B3 (normally repressed in skin fibroblasts) driven by the remnant BGN promotor. This study highlights that aneurysms and dissections in MRLS extend beyond the thoracic aorta, affecting the entire arterial tree, and cardiovascular symptoms may coincide with non-specific connective tissue features. Furthermore, the clinical presentation is more severe and penetrant in males compared to females. Extensive analysis at RNA, cDNA, and/or protein level is recommended to prove a loss-of-function effect before determining the pathogenicity of identified BGN missense and non-canonical splice variants. In conclusion, distinct mechanisms may underlie the wide phenotypic spectrum of MRLS patients carrying loss-of-function variants in BGN.

The experience of one pediatric geneticist with telemedicine-based clinical diagnosis

Telemedicine has long been considered as an attractive alternative methodology in clinical genetics to improve patient access and convenience. Given the importance of the dysmorphology physical examination and anthropometric measurement in clinical genetics, many have wondered if lost information would hamper diagnosis. We previously addressed this question by analyzing thousands of diagnostic encounters in a single practice involving multiple practitioners and found no evidence for a difference in new molecular diagnosis rates. However, our previous study design resulted in variability in providers between in-person and telemedicine evaluation groups. To address this in our present study, we expanded our analysis to 1104 new patient evaluations seen by one highly experienced clinical geneticist across two 10-month periods before and after the start of the COVID-19 pandemic. Comparing patients seen in-person to those seen by telemedicine, we found significant differences in race and ethnicity, preferred language, and home zip code median income. The clinical geneticist intended to send more genetic testing for those patients seen by telemedicine, but due to issues with test authorization and sample collection, there was no difference in ultimate completion rate between groups. We found no significant difference in new molecular diagnosis rate. Overall, we find telemedicine to be an acceptable alternative to in-person evaluation for routine pediatric clinical genetics care.

A field release of genetically engineered gypsy moth (Lymantria dispar L.) nuclear polyhedrosis virus (LdNPV)

The gypsy moth (Lymantria dispar L.) nuclear polyhedrosis virus was genetically engineered for nonpersistence by removal of the gene coding for polyhedrin production and stabilized using a coocclusion process. A beta-galactosidase marker gene was inserted into the genetically engineered virus (LdGEV) so that infected larvae could be tested for its presence using a colorimetric assay. In 1993, LdGEV-infected gypsy moths were released in a forested plot in Massachusetts to test for spread and persistence. A similar forested plot 2 km away served as a control. For 3 years (1993-1995), gypsy moths were established in the two plots in Massachusetts to serve as test and control populations. Each week, larvae were collected from both plots. These field-collected larvae were reared individually, checked for mortality, and then tested for the presence of beta-galactosidase. Other gypsy moth larvae were confined on LdGEV-contaminated foliage for 1 week and then treated as the field-collected larvae. The LdGEV was sought in bark, litter, and soil samples collected from each plot. To verify the presence of the LdGEV, polymerase chain reaction, slot blot DNA hybridization, and restriction enzyme analysis were also used on larval samples. Field-collected larvae infected with the engineered virus were recovered in the release plot in 1993, but not in subsequent years; no field-collected larvae from the control plot contained the engineered virus. Larvae confined on LdGEV-contaminated foliage were killed by the virus. No LdGEV was recovered from bark, litter, or soil samples from either of the plots.

SP., isolated from gypsy moths (Lymantria dispar L.) collected in portugal

A microsporidium Nosema portugal n. sp. was isolated from gypsy moths, Lymantria dispar L, collected near Lisbon, Portugal, in 1985. The life cycle includes two sequential developmental cycles, a primary and a secondary cycle. The primary cycle occurs in midgut epithelial cells, where primary spores are produced within 48 h. The primary spores immediately extrude their polar filaments, presumably to infect other cells. In the target tissues (salivary glands and fat body) the secondary development cycle is followed by the formation of environmental spores. Primary spores were also sometimes present in target tissues. Fresh unfixed and unstained primary spores have a large posterior vacuole and measured 4.8 x 2.7 &mgr;m. Ultrastructurally, they have 5-8 polar filament coils, a large posterior vacuole, abundant endoplasmic reticulum, and were binucleate. Mature unfixed and unstained environmental spores were highly refractive and the posterior vacuole and nuclei could not be seen through the spore coat. Fresh environmental spores measured 4.5 x 1.9 &mgr;m. Ultrastructurally, environmental spores were binucleate, with a typical polaroplast, 10-11 isofilar polar filament coils, and a series of 4-6 thin polar filament-like tubules situated at the posterior end of the row of typical polar filament coils. The ssu rRNA sequences strongly suggest that this species is more closely related to the Vairimorpha subgroup within the Nosema/Vairimorpha clade than to the Nosema subgroup. Copyright 1999 Academic Press.

Interactions between a Nosema sp. (Microspora: nosematidae) and nuclear polyhedrosis virus infecting the gypsy moth, Lymantria dispar (Lepidoptera: lymantriidae)

Simultaneous and sequential per os inoculations of gypsy moth larvae with the Lymantria dispar nuclear polyhedrosis virus (LdNPV) and a Nosema sp. from Portugal demonstrated that the interaction of two pathogens during coinfection was variable, ranging from synergistic to antagonistic. Susceptibility of gypsy moth larvae to viral infection was unaffected by simultaneous and subsequent microsporidian infection. This resulted from the comparatively slow pathogenesis of the microsporidium when compared to the virus. Viral infectivity, however, increased 10-fold when larvae were preinfected with Nosema sp. per os, or through transovarial infection. Time to death decreased for larvae infected with both pathogens compared to larvae infected with the virus alone. Polyhedron production was significantly reduced by microsporidian infection preceding viral infection. In this infection sequence, larvae died at an earlier stage and were less than half the mass of cadavers infected with virus alone. The biological significance of these results on gypsy moth population dynamics and the implication for use of this Nosema sp. from Portugal in gypsy moth biological control are discussed in the context of viral epizootiology.

Rebound swelling of astroglial cells exposed to hypertonic mannitol

BACKGROUND

Mannitol is widely used in anesthesia and critical care medicine. Although its clinical effects were originally attributed to osmotic dehydration of brain cells, other mechanisms have also been proposed. Osmotic dehydration of astroglial cells is opposed by powerful volume-regulating mechanisms that involve inward transport of electrolytes. These mechanisms have been studied previously by exposing cells to hypertonic saline gradients. Because of its potential clinical relevance, the volume response of astroglial cells exposed to hypertonic mannitol was investigated.

METHODS

Rat C6 glioma cells were cultured to confluence, and their volume behavior was observed by laser light scattering. After equilibration at physiologic temperature and pH, cells were abruptly exposed to hypertonic mannitol solutions. In separate experiments, C6 cells were exposed to hypertonic solutions containing radiolabeled mannitol, and its cellular uptake was determined.

RESULTS

Hypertonic mannitol exposure produced initial cell shrinkage followed by rapid volume recovery and rebound swelling. The rebound swelling was similar in magnitude to the initial maximal shrinkage. For +40 mOsm and +70 mOsm mannitol challenges, mean volume recovery was 184+/-31% and 227+/-62%, respectively (where full recovery to baseline volume = 100%). Rebound swelling was substantially inhibited by furosemide. When exposed to mannitol in varying concentrations, uptake was linear, ranging from 82+/-7 nmol/mg to 406+/-26 nmol/mg protein. After 5 min, estimated intracellular concentrations of mannitol were similar to extracellular concentrations.

CONCLUSIONS

Unlike hypertonic saline, hypertonic mannitol exposure produces rebound cell swelling. Cellular penetration of mannitol appears to account for much of this phenomenon. The clinical implications of these observations remain to be determined.

Host Specificity of Microsporidia (Protista: Microspora) from European Populations of Lymantria dispar (Lepidoptera: Lymantriidae) to Indigenous North American Lepidoptera

Results of traditional laboratory bioassays may not accurately represent ecological (field) host specificity of entomopathogens but, if carefully interpreted, may be used to predict the ecological host specificity of pathogens being considered for release as classical biological control agents. We conducted laboratory studies designed to evaluate the physiological host specificity of microsporidia, which are common protozoan pathogens of insects. In these studies, 49 nontarget lepidopteran species indigenous to North America were fed five biotypes of microsporidia that occur in European populations of Lymantria dispar but are not found in North American populations of L. dispar. These microsporidia, Microsporidium sp. from Portugal, Microsporidium sp. from Romania, Microsporidium sp. from Slovakia, Nosema lymantriae, and Endoreticulatus sp. from Portugal, are candidates for release as classical biological control agents into L. dispar populations in the United States. The microsporidia produced a variety of responses in the nontarget hosts and, based on these responses, the nontarget hosts were placed in the following categories: (1) no infection (refractory), (2) atypical infections, and (3) heavy infections. Endoreticulatus sp. produced patent, host-like infections in nearly two-thirds of the nontarget hosts to which it was fed. Such generalist species should not be recommended for release. Infections comparable to those produced in L. dispar were produced in 2% of the nontarget hosts fed Microsporidium sp. from Portugal, 19% of nontarget hosts fed Microsporidium sp. from Romania, 13% fed spores of Microsporidium sp. from Slovakia, and 11% of nontarget species fed N. lymantriae. The remaining nontarget species developed infections that, despite production of mature spores, were not typical of infection in L. dispar. We believe it is very unlikely that these atypical infections would be horizontally transmitted within nontarget insect populations in the United States.

Cerebral blood flow velocity after mannitol infusion in children

PURPOSE

There is conflicting evidence as to whether the effect of mannitol on brain bulk arises from haemodynamic, rheologic, or osmotic mechanisms. If mannitol alters cerebral haemodynamics by inducing vasoconstriction, this change should be reflected in cerebral blood flow velocity (CBFV) in the middle cerebral artery (MCA). The purpose of this study was to evaluate the effect of mannitol on CBFV in children.

METHODS

Children scheduled for intracranial surgery were enrolled. After a loading dose of 10 micrograms.kg-1 of fentanyl, general anaesthesia was maintained with fentanyl (3 micrograms.kg-1.hr-1), 66% nitrous oxide, and isoflurane (0.2-0.5% inspired). Mean and systolic CBFV (Vm and Vs) and pulsatility index (PI) were recorded with a transcranial Doppler (TCD) directed at the M1 segment of the MCA. Mannitol was administered, 1 gm.kg-1 iv over 15 min. The osmolality (Osm), haematocrit (Hct), mean arterial pressure (MAP), heart rate (HR), and TCD variables were recorded before and 15, 30, 45, and 60 min after the mannitol infusion.

RESULTS

Mannitol infusion resulted in an increase in Osm and decrease in Hct (P < 0.05). Heart rate, MAP and arterial carbon dioxide tensions did not change (P > 0.05) during the measuring period. The Vm did not vary from baseline. The Vs and PI both increased briefly (P < 0.01 at 15 min and P < 0.05 at 30 min) after the mannitol, suggesting an increase in resistance distal to the MCA.

CONCLUSION

The time course of CBFV changes produced by mannitol corresponds with previous animal data concerning cerebrovascular tone. Our results suggest that mannitol briefly increases cerebrovascular resistance and thereby diminishes cerebral blood volume.

Coagulation factor deficiencies during initiation of extracorporeal membrane oxygenation

OBJECTIVE

We examined the hypothesis that critically ill patients receiving extracorporeal membrane oxygenation (ECMO) have reduced clotting factor levels, which may contribute to the risk of hemorrhagic complications.

METHODS

Blood samples were collected from 19 patients before and 1 hour after initiation of ECMO. Heparin present in samples was removed by ECTEOLA (epichlorohydrin triethanolamine) cellulose resin adsorption, and coagulation factors were assayed by automated techniques. Factor deficiency was defined as levels at least 2 SD less than published age-adjusted reference values.

RESULTS

Thirteen patients (68%) had deficiencies of two or more factors before ECMO. Despite inclusion of factor-containing blood products in the ECMO priming solution, 10 patients (53%) had deficiencies of two or more factors after initiation of ECMO. Four patients had intracranial hemorrhages and were found to be deficient in five or more factors at the time of cannulation.

CONCLUSIONS

Severe coagulation factor deficiencies are often present in patients requiring ECMO, and coagulation factors provided through the circuit prime are insufficient to ensure correction of these deficiencies. Deficiency of multiple coagulation factors may contribute to the risk of intracranial hemorrhage during ECMO; the practice of excluding factor-containing solutions from the circuit prime should be examined prospectively.

Intensive blood and plasma exchange for treatment of coagulopathy in meningococcemia

Eight pediatric patients with fulminant meningococcemia, purpura, and disseminated intravascular cogulation who by multiple prognostic scoring systems were anticipated to have a poor outcome underwent intensive plasma exchange (IPE) or whole blood exchange (WBE) in addition to standard medical therapy. IPE/WBE was initiated shortly after admission with a mixture of both fresh frozen plasma and cryoprecipitate as the replacement solution. All IPE procedures were performed using a continuous flow system and a red cell prime. The mean fibrinogen level increased from 62 to 192 mg/dl, the prothrombin time (PT) decreased from a mean of 32.4 seconds to 15.1 seconds, and the mean activated partial thromboplastin time (APTT) decreased from 89.5 seconds to 40.1 seconds following completion of the initial IPE/WBE. There was a corresponding improvement in all coagulation factor levels but only slight improvement in antithrombin III (ATIII) and protein C levels. Seven of eight patients survived (87.5%) their initial presentation with the sole early death attributed to meningitis with cerebral edema. Mean fluid balance after the procedure was +10.8 +/- 5.87 cc/kg. There were no significant bleeding or cardiovascular complications during the procedure. There was no clinical or radiographic evidence of fluid overload after the procedure. This experience demonstrates that IPE/WBE may be conducted safely in critically ill, unstable pediatric patients and is effective in rapidly improving coagulopathy without fluid overload.

Doppler sensor placement during neurosurgical procedures for children in the prone position

Precordial ultrasonic Doppler devices are effective monitors for detecting venous air emboli (VAE). However, placing an ultrasonic probe on the anterior part of the chest of a prone patient can lead to dislodgment or pressure sores and makes the probe inaccessible to the anesthesiologist. The purpose of this study was to compare placement of a Doppler probe on the patient's back with the traditional precordial site for the ability to detect VAE. We enrolled infants and children undergoing neurosurgical procedures in the prone position in the study. After establishment of general anesthesia and endotracheal intubation, we applied an ultrasonic Doppler probe to the right sternal border of the patient's chest. Anterior insonation was performed with the patient in the supine position. Saline was rapidly injected to verify the efficacy of the monitor (injection test). The patient was turned to the prone position and we placed the Doppler probe between the right scapula and spine. Posterior insonation with saline injection was performed with the patient in the prone position. We obtained positive tests in all patients from the anterior site. Positive tests were obtained from the posterior site in 23 of 24 (96%) children < 10 kilograms (group I), 28 of 39 (72%) children between 10 and 20 kg (group II), and 6 of 22 (27%) children > 20 kilograms (group III). This study demonstrates that a posterior Doppler probe can be effective for monitoring infants at risk of VAE. However, this method is not reliable in children weighting > 10 kg.

Acute volume regulation of brain cells in response to hypertonic challenge

BACKGROUND

Hypertonic dehydration of the brain through administration of osmotic agents, either alone or in combination with "loop" diuretics, has been a mainstay in the treatment of increased intracranial pressure for decades. Controversy exists, however, as to the mechanism and long-term value of such therapy. Although many cell types possess volume regulatory mechanisms capable of opposing hypertonic dehydration, such behavior in the brain is poorly understood.

METHODS

As a model for the mammalian central nervous system, the real-time volume behavior of rat C6 glioma cells was observed by laser light scattering during hypertonic challenge. Cells were allowed to equilibrate in isotonic balanced salt solutions at physiologic pH and temperature, and then rapidly exposed to hypertonic solutions. Experiments were conducted in the presence and absence of sodium, chloride, and the loop diuretic bumetanide to assess their roles in volume regulation.

RESULTS

In response to acute, large (70 mOsm) hypertonic exposures, cells immediately shrank and then rapidly regulated their volume completely back to control within minutes. In the presence of the loop diuretic bumetanide, the volume regulatory process was significantly inhibited with only 54% recovery observed at concentrations of 10(-4) M. Volume regulation was also significantly inhibited by removal of extracellular sodium and chloride.

CONCLUSIONS

Brain cells possess powerful, electrolyte-dependent and bumetanide-sensitive volume-regulatory mechanisms that directly oppose attempted osmotic shrinkage. These observations suggest a possible new mechanism for the clinically observed synergistic effects of loop and osmotic diuretics in reduction of brain volume.

Coagulopathy as a predictor of outcome in meningococcal sepsis and the systemic inflammatory response syndrome with purpura

OBJECTIVE

To identify simple, contemporary predictors of both morbidity and mortality in pediatric patients with purpuric sepsis syndrome in order to provide a basis for future study of innovative interventions.

DESIGN

Retrospective study.

SETTING

An 18-bed multidisciplinary intensive care unit (ICU) in a large pediatric hospital.

PATIENTS

A total of 53 patients, ranging in age from 18 days to 17 yrs (mean 4.9 yrs) with either culture-proven meningococcal sepsis or the systemic inflammatory response syndrome with purpura, who were admitted to the ICU during the period from January 1, 1982 through March 15, 1992.

METHODS

A computerized database was constructed containing the characteristics of these patients at presentation, during the first 24 hrs of hospitalization, and on discharge. Single variables were screened for significance between "good" (intact survival) and "poor" (mortality or survival with significant morbidity) outcome groups. Those variables found to be most significant were then tested for sensitivity, specificity, and predictive value. The best predictors identified in this manner were then compared with the two most-cited prognosticating strategies as applied to these patients.

MEASUREMENTS AND MAIN RESULTS

Coagulopathy (defined as a partial thromboplastin time > 50 secs or serum fibrinogen concentration < 150 mg/dL [4.4 mumol/L]) at the referral site or on ICU admission was identified as an excellent predictor of poor outcome: sensitivity, specificity, positive and negative predictive values of a low serum fibrinogen value, being 81%, 95%, 93%, and 88%, and of prolonged partial thromboplastin time, being 95%, 90%, 86%, and 97%, respectively. Classical prognosticating strategies were found to be inadequately associated with mortality, yet comparable with coagulopathy in identifying patients destined for clinically important morbidity.

CONCLUSIONS

We conclude that: a) outcome of pediatric patients with meningococcal sepsis or the systemic inflammatory response syndrome with purpura can be predicted rapidly, more easily, and with overall accuracy superior to classical prognostication strategies by the simple presence or absence of coagulopathy; b) when applied to a contemporary population, classical prognostication strategies lack value for prediction of mortality, yet remain valid for prediction of "poor outcome" (significant morbidity + mortality); c) when evaluating treatment strategies for such patients, the presence of serious coagulopathy may potentially be useful as an index of illness severity.