Robust induction of functional astrocytes using NGN2 expression in human pluripotent stem cells

Emerging evidence of species divergent features of astrocytes coupled with the relative inaccessibility of human brain tissue underscore the utility of human pluripotent stem cell (hPSC) technologies for the generation and study of human astrocytes. However, existing approaches for hPSC-astrocyte generation are typically lengthy or require intermediate purification steps. Here, we establish a rapid and highly scalable method for generating functional human induced astrocytes (hiAs). These hiAs express canonical astrocyte markers, respond to pro-inflammatory stimuli, exhibit ATP-induced calcium transients and support neuronal network development. Moreover, single-cell transcriptomic analyses reveal the generation of highly reproducible cell populations across individual donors, mostly resembling human fetal astrocytes. Finally, hiAs generated from a trisomy 21 disease model identify expected alterations in cell-cell adhesion and synaptic signaling, supporting their utility for disease modeling applications. Thus, hiAs provide a valuable and practical resource for the study of basic human astrocyte function and dysfunction in disease.

High-content synaptic phenotyping in human cellular models reveals a role for BET proteins in synapse assembly

Resolving fundamental molecular and functional processes underlying human synaptic development is crucial for understanding normal brain function as well as dysfunction in disease. Based upon increasing evidence of species-divergent features of brain cell types, coupled with emerging studies of complex human disease genetics, we developed the first automated and quantitative high-content synaptic phenotyping platform using human neurons and astrocytes. To establish the robustness of our platform, we screened the effects of 376 small molecules on presynaptic density, neurite outgrowth, and cell viability, validating six small molecules that specifically enhanced human presynaptic density in vitro. Astrocytes were essential for mediating the effects of all six small molecules, underscoring the relevance of non-cell-autonomous factors in synapse assembly and their importance in synaptic screening applications. Bromodomain and extraterminal (BET) inhibitors emerged as the most prominent hit class and global transcriptional analyses using multiple BET inhibitors confirmed upregulation of synaptic gene expression. Through these analyses, we demonstrate the robustness of our automated screening platform for identifying potent synaptic modulators, which can be further leveraged for scaled analyses of human synaptic mechanisms and drug discovery efforts.

Asynchronous excitatory neuron development in an isogenic cortical spheroid model of Down syndrome

The intellectual disability (ID) in Down syndrome (DS) is thought to result from a variety of developmental deficits such as alterations in neural progenitor division, neurogenesis, gliogenesis, cortical architecture, and reduced cortical volume. However, the molecular processes underlying these neurodevelopmental changes are still elusive, preventing an understanding of the mechanistic basis of ID in DS. In this study, we used a pair of isogenic (trisomic and euploid) induced pluripotent stem cell (iPSC) lines to generate cortical spheroids (CS) that model the impact of trisomy 21 on brain development. Cortical spheroids contain neurons, astrocytes, and oligodendrocytes and they are widely used to approximate early neurodevelopment. Using single cell RNA sequencing (scRNA-seq), we uncovered cell type-specific transcriptomic changes in the trisomic CS. In particular, we found that excitatory neuron populations were most affected and that a specific population of cells with a transcriptomic profile resembling layer IV cortical neurons displayed the most profound divergence in developmental trajectory between trisomic and euploid genotypes. We also identified candidate genes potentially driving the developmental asynchrony between trisomic and euploid excitatory neurons. Direct comparison between the current isogenic CS scRNA-seq data and previously published datasets revealed several recurring differentially expressed genes between DS and control samples. Altogether, our study highlights the power and importance of cell type-specific analyses within a defined genetic background, coupled with broader examination of mixed samples, to comprehensively evaluate cellular phenotypes in the context of DS.

Neurodevelopment in Down syndrome: Concordance in humans and models

Great strides have been made over the past 30 years in understanding the neurodevelopmental changes underlying the intellectual disability (ID) in Down syndrome (DS). Detailed studies of human tissue coupled with findings from rodent and induced pluripotent stem cells (iPSCs) model systems have uncovered the changes in neurogenesis, synaptic connectivity, and myelination that drive the anatomical and physiological changes resulting in the disability. However, there remain significant conflicting data between human studies and the models. To fully understand the development of ID in DS, these inconsistencies need to be reconciled. Here, we review the well documented neurodevelopmental phenotypes found in individuals with DS and examine the degree to which widely used models recapitulate these phenotypes. Resolving these areas of discord will further research on the molecular underpinnings and identify potential treatments to improve the independence and quality of life of people with DS.

DNA templates with blocked long 3' end single-stranded overhangs (BL3SSO) promote bona fide Cas9-stimulated homology-directed repair of long transgenes into endogenous gene loci

Knock-in of large transgenes by Cas9-mediated homology-directed repair (HDR) is an extremely inefficient process. Although the use of single-stranded oligonucleotides (ssODN) as an HDR donor has improved the integration of smaller transgenes, they do not support efficient insertion of large DNA sequences. In an effort to gain insights into the mechanism(s) governing the HDR-mediated integration of larger transgenes and to improve the technology, we conducted knock-in experiments targeting the human EMX1 locus and applied rigorous genomic PCR analyses in the human HEK293 cell line. This exercise revealed an unexpected molecular complication arising from the transgene HDR being initiated at the single homology arm and the subsequent genomic integration of plasmid backbone sequences. To pivot around this problem, we devised a novel PCR-constructed template containing blocked long 3' single-stranded overhangs (BL3SSO) that greatly improved the efficiency of bona fide Cas9-stimulated HDR at the EMX1 locus. We further refined BL3SSO technology and successfully used it to insert GFP transgenes into two important interferon-stimulated genes (ISGs) loci, Viperin/RSAD2, and ISG15. This study demonstrates the utility of the BL3SSO platform for inserting long DNA sequences into both constitutive and inducible endogenous loci to generate novel human cell lines for the study of important biological processes.

Sonic Hedgehog Pathway Modulation Normalizes Expression of Olig2 in Rostrally Patterned NPCs With Trisomy 21

The intellectual disability found in people with Down syndrome is associated with numerous changes in early brain development, including the proliferation and differentiation of neural progenitor cells (NPCs) and the formation and maintenance of myelin in the brain. To study how early neural precursors are affected by trisomy 21, we differentiated two isogenic lines of induced pluripotent stem cells derived from people with Down syndrome into brain-like and spinal cord-like NPCs and promoted a transition towards oligodendroglial fate by activating the Sonic hedgehog (SHH) pathway. In the spinal cord-like trisomic cells, we found no difference in expression of OLIG2 or NKX2.2, two transcription factors essential for commitment to the oligodendrocyte lineage. However, in the brain-like trisomic NPCs, OLIG2 is significantly upregulated and is associated with reduced expression of NKX2.2. We found that this gene dysregulation and block in NPC transition can be normalized by increasing the concentration of a SHH pathway agonist (SAG) during differentiation. These results underscore the importance of regional and cell type differences in gene expression in Down syndrome and demonstrate that modulation of SHH signaling in trisomic cells can rescue an early perturbed step in neural lineage specification.

Longitudinal neuroanatomical and behavioral analyses show phenotypic drift and variability in the Ts65Dn mouse model of Down syndrome

Mouse models of Down syndrome (DS) have been invaluable tools for advancing knowledge of the underlying mechanisms of intellectual disability in people with DS. The Ts(1716)65Dn (Ts65Dn) mouse is one of the most commonly used models as it recapitulates many of the phenotypes seen in individuals with DS, including neuroanatomical changes and impaired learning and memory. In this study, we use rigorous metrics to evaluate multiple cohorts of Ts65Dn ranging from 2014 to the present, including a stock of animals recovered from embryos frozen within ten generations after the colony was first created in 2010. Through quantification of prenatal and postnatal brain development and several behavioral tasks, our results provide a comprehensive comparison of Ts65Dn across time and show a significant amount of variability both across cohorts as well as within cohorts. The inconsistent phenotypes in Ts65Dn mice highlight specific cautions and caveats for use of this model. We outline important steps for ensuring responsible use of Ts65Dn in future research.This article has an associated First Person interview with the first author of the paper.

Spatiotemporal development of spinal neuronal and glial populations in the Ts65Dn mouse model of Down syndrome

BACKGROUND

Down syndrome (DS), caused by the triplication of chromosome 21, results in a constellation of clinical features including changes in intellectual and motor function. Although altered neural development and function have been well described in people with DS, few studies have investigated the etiology underlying the observed motor phenotypes. Here, we examine the development, patterning, and organization of the spinal cord throughout life in the Ts65Dn mouse, a model that recapitulates many of the motor changes observed in people with DS.

METHODS

Spinal cords from embryonic to adult animals were processed for gene and protein expression (immunofluorescence) to track the spatiotemporal development of excitatory and inhibitory neurons and oligodendroglia. Postnatal analyses were focused on the lumbar region due to the reflex and gait abnormalities found in Ts65Dn mice and locomotive alterations seen in people with DS.

RESULTS

Between embryonic days E10.5 and E14.5, we found a larger motor neuron progenitor domain in Ts65Dn animals containing more OLIG2-expressing progenitor cells. These disturbed progenitors are delayed in motor neuron production but eventually generate a large number of ISL1+ migrating motor neurons. We found that higher numbers of PAX6+ and NKX2.2+ interneurons (INs) are also produced during this time frame. In the adult lumbar spinal cord, we found an increased level of Hb9 and a decreased level of Irx3 gene expression in trisomic animals. This was accompanied by an increase in Calretinin+ INs, but no changes in other neuronal populations. In aged Ts65Dn animals, both Calbindin+ and ChAT+ neurons were decreased compared to euploid controls. Additionally, in the dorsal corticospinal white matter tract, there were significantly fewer CC1+ mature OLs in 30- and 60-day old trisomic animals and this normalized to euploid levels at 10-11 months. In contrast, the mature OL population was increased in the lateral funiculus, an ascending white matter tract carrying sensory information. In 30-day old animals, we also found a decrease in the number of nodes of Ranvier in both tracts. This decrease normalized both in 60-day old and aged animals.

CONCLUSIONS

We show marked changes in both spinal white matter and neuronal composition that change regionally over the life span. In the embryonic Ts65Dn spinal cord, we observe alterations in motor neuron production and migration. In the adult spinal cord, we observe changes in oligodendrocyte maturation and motor neuron loss, the latter of which has also been observed in human spinal cord tissue samples. This work uncovers multiple cellular perturbations during Ts65Dn development and aging, many of which may underlie the motor deficits found in DS.

Computer Graphics Illustration of the Operation of the Intervertebral Disc

The annulus fibrosus, the outer wall of the intervertebral disc, has a lamellar structure. Each lamella is reinforced by collagen fibres. A theory has been developed which allows the response of the fibre network to disc deformation to be calculated. The theory has been formulated in a form suitable for computer graphics display of its predictions. Results enable the effects of compression, torsion, flexion and shear of the disc to be readily appreciated.

Antibiotic failure in a renal transplant patient with Rhodococcus equi infection: an indication for surgical lobectomy

Rhodococcus equi is an animal pathogen that causes infrequent but challenging infections in immunocompromised individuals, few of which have been described in solid organ transplant recipients. Common clinical presentations include indolent cough, fever, and dyspnea, with necrotizing pneumonia and cavitation. We report a case of a dense right upper lung pneumonia with resultant R. equi bacteremia in a renal transplant recipient. Our patient initially responded to antibiotic treatment with resolution of bacteremia and clinical recovery, followed by interval progression in her right upper lobe consolidation on follow-up computed tomography scans. She underwent lobectomy for definitive therapy with resolution of symptoms. Lobectomy can be utilized in isolated infection after antibiotic failure with excellent clinical outcomes.

Control of helicase loading in the coupled DNA replication and recombination systems of bacteriophage T4

The Gp59 protein of bacteriophage T4 promotes DNA replication by loading the replicative helicase, Gp41, onto replication forks and recombination intermediates. Gp59 also blocks DNA synthesis by Gp43 polymerase until Gp41 is loaded, ensuring that synthesis is tightly coupled to unwinding. The distinct polymerase blocking and helicase loading activities of Gp59 likely involve different binding interactions with DNA and protein partners. Here, we investigate how interactions of Gp59 with DNA and Gp32, the T4 single-stranded DNA (ssDNA)-binding protein, are related to these activities. A previously characterized mutant, Gp59-I87A, exhibits markedly reduced affinity for ssDNA and pseudo-fork DNA substrates. We demonstrate that on Gp32-covered ssDNA, the DNA binding defect of Gp59-I87A is not detrimental to helicase loading and translocation. In contrast, on pseudo-fork DNA the I87A mutation is detrimental to helicase loading and unwinding in the presence or absence of Gp32. Other results indicate that Gp32 binding to lagging strand ssDNA relieves the blockage of Gp43 polymerase activity by Gp59, whereas the inhibition of Gp43 exonuclease activity is maintained. Our findings suggest that Gp59-Gp32 and Gp59-DNA interactions perform separate but complementary roles in T4 DNA metabolism; Gp59-Gp32 interactions are needed to load Gp41 onto D-loops, and other nucleoprotein structures containing clusters of Gp32. Gp59-DNA interactions are needed to load Gp41 onto nascent or collapsed replication forks lacking clusters of Gp32 and to coordinate bidirectional replication from T4 origins. The dual functionalities of Gp59 allow it to promote the initiation or re-start of DNA replication from a wide variety of recombination and replication intermediates.

Phenological response of tundra plants to background climate variation tested using the International Tundra Experiment

The rapidly warming temperatures in high-latitude and alpine regions have the potential to alter the phenology of Arctic and alpine plants, affecting processes ranging from food webs to ecosystem trace gas fluxes. The International Tundra Experiment (ITEX) was initiated in 1990 to evaluate the effects of expected rapid changes in temperature on tundra plant phenology, growth and community changes using experimental warming. Here, we used the ITEX control data to test the phenological responses to background temperature variation across sites spanning latitudinal and moisture gradients. The dataset overall did not show an advance in phenology; instead, temperature variability during the years sampled and an absence of warming at some sites resulted in mixed responses. Phenological transitions of high Arctic plants clearly occurred at lower heat sum thresholds than those of low Arctic and alpine plants. However, sensitivity to temperature change was similar among plants from the different climate zones. Plants of different communities and growth forms differed for some phenological responses. Heat sums associated with flowering and greening appear to have increased over time. These results point to a complex suite of changes in plant communities and ecosystem function in high latitudes and elevations as the climate warms.

Elbow extension test to rule out elbow fracture: multicentre, prospective validation and observational study of diagnostic accuracy in adults and children

OBJECTIVE

To determine whether full elbow extension as assessed by the elbow extension test can be used in routine clinical practice to rule out bony injury in patients presenting with elbow injury.

DESIGN

Adults: multicentre prospective interventional validation study in secondary care. Children: multicentre prospective observational study in secondary care.

SETTING

Five emergency departments in southwest England.

PARTICIPANTS

2127 adults and children presenting to the emergency department with acute elbow injury.

INTERVENTION

Elbow extension test during routine care by clinical staff to determine the need for radiography in adults and to guide follow-up in children.

MAIN OUTCOME MEASURES

Presence of elbow fracture on radiograph, or recovery with no indication for further review at 7-10 days.

RESULTS

Of 1740 eligible participants, 602 patients were able to fully extend their elbow; 17 of these patients had a fracture. Two adult patients with olecranon fractures needed a change in treatment. In the 1138 patients without full elbow extension, 521 fractures were identified. Overall, the test had sensitivity and specificity (95% confidence interval) for detecting elbow fracture of 96.8% (95.0 to 98.2) and 48.5% (45.6 to 51.4). Full elbow extension had a negative predictive value for fracture of 98.4% (96.3 to 99.5) in adults and 95.8% (92.6 to 97.8) in children. Negative likelihood ratios were 0.03 (0.01 to 0.08) in adults and 0.11 (0.06 to 0.19) in children.

CONCLUSION

The elbow extension test can be used in routine practice to inform clinical decision making. Patients who cannot fully extend their elbow after injury should be referred for radiography, as they have a nearly 50% chance of fracture. For those able to fully extend their elbow, radiography can be deferred if the practitioner is confident that an olecranon fracture is not present. Patients who do not undergo radiography should return if symptoms have not resolved within 7-10 days.

Anesthetic formulation of tumescent solutions

There is no standard or official recipe for the tumescent anesthetic solutions. The actual concentrations of lidocaine and epinephrine should depend on the areas to be treated and clinical situation. This article discusses the safe usage of tumescent solutions and the proper procedures and precautions to take when mixing these solutions.

Post-tumescent liposuction care. Open drainage and bimodal compression

The goals of post-liposuction care must be to minimize edema, bruising, and patient discomfort. The postoperative pain and edema resulting from sutured incisions and prolonged post-liposuction compression is an irrational remnant from the days before the tumescent technique. This article discusses various issues involving post-liposuction care.

A decision technology system for health care electronic commerce

Mounting costs have escalated the pressure on health care providers and payers to improve decision making and control expenses. Transactions to form the needed decision data will routinely flow, often electronically, between the affected parties. Conventional health care information systems facilitate flow, process transactions, and generate useful decision information. Typically, such support is offered through a series of stand-alone systems that lose much useful decision knowledge and wisdom during health care electronic commerce (e-commerce). Integrating the stand-alone functions can enhance the quality and efficiency of the segmented support, create synergistic effects, and augment decision-making performance and value for both providers and payers. This article presents an information system that can provide complete and integrated support for e-commerce-based health care decision making. The article describes health care e-commerce, presents the system, examines the system's potential use and benefits, and draws implications for health care management and practice.

Tumescent liposuction and improved postoperative care using Tumescent Liposuction Garments

The tumescent technique for liposuction, using large volumes of dilute lidocaine and epinephrine infiltrated into subcutaneous fat, has improved safety by eliminating the risks of general anesthesia and the massive blood loss associated with older techniques. This article describes the results of the author's search for ways to optimize patient care after tumescent liposuction. The tumescent technique has dramatically improved postoperative comfort and accelerated recovery time. Using microcannulas and multiple incisions for cannula access, leaving the incisions open without sutures, and wearing a specially designed Tumescent Liposuction (TLG) Garment for compression, patients return to work in 1 to 2 days, and the first postoperative follow-up office visit is 5 to 6 weeks after surgery.

Tumescent technique for local anesthesia improves safety in large-volume liposuction

The tumescent technique for local anesthesia improves the safety of large-volume liposuction ( > or = 1500 ml of fat) by virtually eliminating surgical blood loss and by completely eliminating the risks of general anesthesia. Results of two prospective studies of large-volume liposuction using the tumescent technique are reported. In 112 patients, the mean lidocaine dosage was 33.3 mg/kg, the mean volume of aspirated material was 2657 ml, and the mean volume of supernatant fat was 1945 ml. The mean volume of whole blood aspirated by liposuction was 18.5 ml. For each 1000 ml of fat removed, 9.7 ml of whole blood was suctioned. In 31 large-volume liposuction patients treated in 1991, the mean difference between preoperative and 1-week postoperative hematocrits was -1.9 percent. The last 87 patients received no parenteral sedation. In a second study, a 75-kg woman received 35 mg/kg of lidocaine on two separate occasions, first without liposuction and 25 days later with liposuction; peak plasma lidocaine concentrations occurred at 14 and 11 hours after beginning the infiltration and were 2.37 and 1.86 micrograms/ml, respectively.

Use of the tumescent technique for scalp surgery, dermabrasion, and soft tissue reconstruction

Application of the tumescent anesthetic technique in scalp surgery, dermabrasion, and soft tissue reconstruction is discussed. Vasoconstriction achieved by using tumescent anesthesia reduces bleeding even with dilute (1:320,000) epinephrine. Tumescent anesthesia also offers the advantages of decreased absorption at the site of infiltration, increased anesthetic infiltration, delayed absorption and lower peak blood plasma levels, and a longer lasting anesthetic effect.

Neutralized lidocaine with epinephrine for local anesthesia--II

The pain usually associated with intradermal injection of lidocaine and epinephrine is significantly attenuated by the addition of either sodium bicarbonate or sodium hydroxide to 1% lidocaine with epinephrine. This suggests that sodium bicarbonate attenuates pain by increasing the pH of the anesthetic solution. The clinical effects of a solution of lidocaine (1%) with epinephrine (1:100,000) and sodium bicarbonate (80 meq/L) were assessed after infiltration in skin. Anesthetic stored for 1 week caused nearly equal areas of anesthesia and vasoconstriction as an identical solution prepared on the day of use.

The tumescent technique. Anesthesia and modified liposuction technique

Using the tumescent technique, liposuction can remove large volumes of fat with minimal blood loss. A maximal safe dosage of dilute lidocaine using the tumescent technique is estimated to be 35 mg/kg. The slow infiltration of a local anesthetic solution of lidocaine and epinephrine minimizes the rate of systemic absorption and reduces the potential for toxicity. Dilution of lidocaine (0.05% of 0.1%) and epinephrine (1:1,000,000) further delays absorption and reduces the magnitude of peak plasma lidocaine concentrations. Using the tumescent technique for liposuction, peak plasma lidocaine levels occur 12 hours after the initial injection. Clinically significant local anesthesia persists for up to 18 hours. For liposuction, it is not necessary to use local anesthetics, which are longer acting and potentially more cardiotoxic than lidocaine.

Tumescent technique for regional anesthesia permits lidocaine doses of 35 mg/kg for liposuction

The tumescent technique for local anesthesia permits regional local anesthesia of the skin and subcutaneous tissues by direct infiltration. The tumescent technique uses large volumes of a dilute anesthetic solution to produce swelling and firmness of targeted areas. This investigation examines the absorption pharmacokinetics of dilute solutions of lidocaine (0.1% or 0.05%) and epinephrine (1:1,000,000) in physiologic saline following infiltration into subcutaneous fat of liposuction surgery patients. Plasma lidocaine concentrations were measured repeatedly over more than 24 hours following the infiltration. Peak plasma lidocaine levels occurred 12-14 hours after beginning the infiltration. Clinical local anesthesia is apparent for up to 18 hours, obviating the need for postoperative analgesia. Dilution of lidocaine diminishes and delays the peak plasma lidocaine concentrations, thereby reducing potential toxicity. Liposuction reduces the total amount of lidocaine absorbed systemically, but does not dramatically reduce peak plasma lidocaine levels. A safe upper limit for lidocaine dosage using the tumescent technique is estimated to be 35 mg/kg. Infiltrating a large volume of dilute epinephrine assures diffusion throughout the entire targeted area while avoiding tachycardia and hypertension. The associated vasoconstriction is so complete that there is virtually no blood loss with liposuction. The tumescent technique can be used with general anesthesia or IV sedation. However, with appropriate instrumentation and surgical method, the tumescent technique permits liposuction of large volumes of fat totally by local anesthesia, without IV sedation or narcotic analgesia.

Bannayan-Zonana syndrome associated with lymphangiomyomatous lesions

Bannayan-Zonana syndrome is an autosomal dominant condition that has not been well described in the dermatology literature. The typical case is characterized by macrocephaly, multiple angiomas, and multiple encapsulated or infiltrating lipomas. As in other autosomal dominant hamartoneoplastic syndromes, the degree of expression within one family frequently varies widely. Our patient had macrocephaly and angiomas, as well as lipomas with peculiar histologic features similar to lymphangiomyomas. Her father had a large nevus flameus on his leg, and lipomas with normal histologic appearance. The paternal grandfather had multiple encapsulated lipomas with normal histologic appearance. Neither father nor grandfather had macrocephaly.

Neutralized lidocaine with epinephrine for local anesthesia

The pain of infiltrating lidocaine with epinephrine into skin is reduced by the addition of sodium bicarbonate. The effect of varied concentrations of sodium bicarbonate on pain of infiltration of 1% lidocaine with epinephrine 1:100,000 was measured. Sodium bicarbonate at 40 and 100 meq/L of anesthetic solution caused significantly less pain than did 0 or 10 meq/L. The stability of epinephrine in a solution at pH 7.3 was also determined. Epinephrine concentration declined approximately 25% per week in anesthetic solution containing 100 meq/L sodium bicarbonate.

Anesthesia for liposuction in dermatologic surgery

Liposuction is now a well-established procedure in dermatologic surgery. The relative advantages and risks of the various forms of primary anesthesia and supplemental analgesia used for liposuction surgery in the office by dermatologic surgeons is described. Effective anesthetic techniques include infiltration of local anesthesia (LA) with or without intramuscular (IM), intravenous (IV), or nitrous oxide sedation, cryoanesthesia, and IV or inhalation general anesthesia (GA). Local anesthesia, using large volumes of dilute anesthetic solution containing lidocaine (0.05%), epinephrine (1:1,000,000), and sodium bicarbonate (12.5 meq/L), is a safe and effective modality for liposuction by dermatologists. In a study of 12 liposuction patients treated with this technique, the average lidocaine dose was 1181 mg (9.4 mg/kg/hr). The highest peak lidocaine blood level among all patients was 0.484 microgram/ml. Dermatologists should not assume the dual responsibility of surgeon and of monitoring patients given IV sedation. Any form of anesthesia has the potential for serious complications. The surgeon and office staff must be well trained and equipped to perform emergency resuscitation.

Diffuse lipomatosis and tuberous sclerosis

Diffuse lipomatosis, a classic example of an infiltrating fatty tumor, is a rare entity characterized by infiltration of adult-type adipose tissue into skin, subcutaneous tissue, and muscle. It usually involves a large portion of an extremity or the trunk. Some cases are associated with distant lipomas or angiomas, or hypertrophy of subjacent bone. The association of diffuse lipomatosis with tuberous sclerosis is reported.

Topical tritiated thymidine for epidermal growth fraction determination

Direct autoradiographic identification of the epidermal growth fraction (GF) requires the delivery of tritiated thymidine ([3H]dThd) to the skin during the time interval of an entire cell cycle. The GF in normal human epidermis has not been directly measured using this technique because the systemic infusion of radioactive [3H]dThd in benign skin conditions is precluded by ethical considerations. Studies were undertaken to assess the feasibility of measuring the epidermal GF in vivo by the topical delivery of [3H]dThd. The percutaneous penetration of [3H]dThd in various vehicles was evaluated to select an effective topical delivery system. A vehicle consisting of Azone, isopropanol, and water (2:49:49) was the best of 4 different vehicles tested. The optimal penetration of [3H]dThd, with respect to the concentration of Azone over a range of 0-4%, was achieved at 2%. During the initial 24 h following a single topical application of [3H]dThd to hairless mice the labeling increased linearly with time. In vivo studies in hairless mice produced a GF of 95% by both continuous systemic [3H]dThd infusion, and by twice daily topical [3H]dThd. Azone vehicles induced epidermal hyperplasia which was minimized by lowering the Azone concentration and by decreasing the frequency of applications from 24 to 48 h. These studies establish the rationale for using topical delivery of [3H]dThd for the in vivo measurement of epidermal GF.

Paraffinomas of the scalp

Four cases of scalp paraffinoma were seen in our clinics within the past year. This unusual condition results from intradermal injection of substances containing paraffin. The presence of paraffin in excised tissue was confirmed by thin-layer chromatography and infrared absorption spectrophotometry. Our patients received their treatments 35 to 42 years ago after responding to radio or newspaper advertisements that promised a cure for baldness. Two patients were initially observed with severe scalp inflammation and two were completely asymptomatic other than having lumpy scalps. Although these cases were readily diagnosed by history, eliminating other possibilities was greatly aided by use of xeroradiography, obviating the need for biopsy in asymptomatic cases.

Verrucous hemangioma

Two patients with verrucous hemangioma, a congenital vascular malformation, were seen. The typical lesion is a unilateral group of hyperkeratotic papules and nodules on a lower extremity. Unlike the more common capillary or cavernous hemangiomas, verrucous hemangiomas tend to enlarge and spread with time, and to recur after excision.