ASO titer or not? When to use streptococcal serology: a guide for clinicians.

Clinicians frequently request serologic tests to provide evidence of prior infection by Streptococcus pyogenes, especially when suspecting a diagnosis of acute rheumatic fever or post-streptococcal glomerulonephritis. However, the interpretation of these tests is difficult and should take account of the clinical features, epidemiological setting, and pre-test probability, as well as the specific aspects of the assay. This review details the characteristics of streptococcal serologic assays and provides recommendations for their use and interpretation.

Noninvasive focal transgene delivery with viral neuronal tracers in the marmoset monkey.

We establish a reliable method for selectively delivering adeno-associated viral vectors (AAVs) across the blood-brain barrier (BBB) in the marmoset without the need for neurosurgical injection. We focally perturbed the BBB (∼1 × 2 mm) in area 8aD of the frontal cortex in four adult marmoset monkeys using low-intensity transcranial focused ultrasound aided by microbubbles. Within an hour of opening the BBB, either AAV2 or AAV9 was delivered systemically via tail-vein injection. In all four marmosets, fluorescence-encoded neurons were observed at the site of BBB perturbation, with AAV2 showing a sparse distribution of transduced neurons when compared to AAV9. The results are compared to direct intracortical injections of anterograde tracers into area 8aD and similar (albeit sparser) long-range connectivity was observed. With evidence of transduced neurons specific to the region of BBB opening as well as long-distance tracing, we establish a framework for focal noninvasive transgene delivery to the marmoset brain.

Safety, tolerability, and acceptability of Lactobacillus crispatus CTV-05 (LACTIN-V) in pregnant women at high-risk of preterm birth.

The vaginal microbiota is a determinant for the risk of preterm birth (PTB). Dominance of the vaginal niche by Lactobacillus crispatus associates with term delivery. This is the first observational clinical study of live vaginal biotherapeutics (Lactobacillus crispatus CTV-05 (LACTIN-V)) in pregnant women at high-risk of PTB. The primary aim was to explore safety, tolerability and acceptability of LACTIN-V in pregnancy. Women were offered a course of LACTIN-V at 14 weeks gestation for five consecutive days followed by weekly administration for six weeks. Participants were followed up at 15, 18-, 20-, 28- and 36-weeks' gestation and at delivery for assessment of adverse events, compliance and tolerability. Participants completed a questionnaire to gauge experience and acceptability. In total, 73 women were recruited, of whom eight withdrew, leaving a final cohort size of 61. Self-reported compliance to the course was high (56/60, 93%). Solicited adverse events were reported in 13 women (19%) including changes in vaginal discharge, odour, colour or consistency of urine, itching and vaginal bleeding. One unsolicited adverse event was reported as haematuria at 38 weeks gestation, but was judged to be unrelated to LACTIN-V. No serious adverse events occurred. One mild adverse event led to study withdrawal. Thirty-one women completed an experience and acceptability questionnaire. Women found LACTIN-V easy and comfortable to use and the majority (30/31, 97%) would use LACTIN-V in future pregnancies. Eight women (8/31, 26%) found the schedule of use difficult to remember. The rate of PTB <34 weeks in this cohort was 3.3% compared to 7% in a historical cohort of 2,190 women at similar background PTB risk. With satisfactory uptake and good compliance, we demonstrate that LACTIN-V is safe and accepted in pregnancy, with high tolerability. Further studies are needed to assess colonisation of Lactobacillus crispatus CTV-05 and clinical efficacy.

Noninvasive disruption of the blood-brain barrier in the marmoset monkey.

The common marmoset monkey (Callithrix jacchus) is a species of rising prominence in the neurosciences due to its small size, ease of handling, fast breeding, and its shared functional and structural brain characteristics with Old World primates. With increasing attention on modeling human brain diseases in marmosets, understanding how to deliver therapeutic or neurotropic agents to the marmoset brain noninvasively is of great preclinical importance. In other species, including humans, transcranial focused ultrasound (tFUS) aided by intravenously injected microbubbles has proven to be a transient, reliable, and safe method for disrupting the blood-brain barrier (BBB), allowing the focal passage of therapeutic agents that do not otherwise readily traverse the tight endothelial junctions of the BBB. The critical gap that we address here is to document parameters to disrupt the BBB reliably and safely in marmosets using tFUS. By integrating our marmoset brain atlases and the use of a marmoset-specific stereotactic targeting system, we conduct a series of systematic transcranial sonication experiments in nine marmosets. We demonstrate the effects of center frequency, acoustic pressure, burst period, and duration, establish a minimum microbubble dose, estimate microbubble clearance time, and estimate the duration that the BBB remains open to passage. Successful BBB disruption is reported in vivo with MRI-based contrast agents, as well as Evans blue staining assessed ex vivo. Histology (Hematoxylin and Eosin staining) and immunohistochemistry indicate that the BBB can be safely and reliably opened with the parameters derived from these experiments. The series of experiments presented here establish methods for safely, reproducibly, and focally perturbing the BBB using tFUS in the common marmoset monkey that can serve as a basis for noninvasive delivery of therapeutic or neurotropic agents.

Transgenes and gene suppression: telling us something new?

Transgenes provide unique opportunities to assess the relationship between genotype and phenotype in an organism. In most cases, introduction and subsequent expression of a transgene will increase (with a sense RNA) or decrease (with an antisense RNA) the steady-state level of a specific gene product. However, a number of surprising observations have been made in the course of many transgenic studies. We develop a hypothesis that suggests that many examples of endogenous gene suppression by either antisense or sense transcripts are mediated by the same cellular mechanism.

The immunosuppressive fungal metabolite gliotoxin specifically inhibits transcription factor NF-kappaB.

Opportunistic infections, such as aspergillosis, are among the most serious complications suffered by immunocompromised patients. Aspergillus fumigatus and other pathogenic fungi synthesize a toxic epipolythiodioxopiperazine metabolite called gliotoxin. Gliotoxin exhibits profound immunosuppressive activity in vivo. It induces apoptosis in thymocytes, splenocytes, and mesenteric lymph node cells and can selectively deplete bone marrow of mature lymphocytes. The molecular mechanism by which gliotoxin exerts these effects remains unknown. Here, we report that nanomolar concentrations of gliotoxin inhibited the activation of transcription factor NF-kappaB in response to a variety of stimuli in T and B cells. The effect of gliotoxin was specific because, at the same concentrations, the toxin did not affect activation of the transcription factor NF-AT or of interferon-responsive signal transducers and activators of transcription. Likewise, the activity of the constitutively DNA-binding transcription factors Oct-1 and cyclic AMP response element binding protein (CREB), as well as the activation of protein tyrosine kinases p56lck and p59fyn, was not altered by gliotoxin. Very high concentrations of gliotoxin prevented NF-kappaB DNA binding in vitro. However, in intact cells, inhibition of NF-kappaB did not occur at the level of DNA binding; rather, the toxin appeared to prevent degradation of IkappaB-alpha, NF-kappaB's inhibitory subunit. Our data raise the possibility that the immunosuppression observed during aspergillosis results in part from gliotoxin-mediated NF-kappaB inhibition.

A novel cohorting and isolation strategy for suspected COVID-19 cases during a pandemic.

BACKGROUND: The COVID-19 pandemic presents a significant infection prevention and control challenge. The admission of large numbers of patients with suspected COVID-19 disease risks overwhelming the capacity to protect other patients from exposure. The delay between clinical suspicion and confirmatory testing adds to the complexity of the problem. METHODS: We implemented a triage tool aimed at minimizing hospital-acquired COVID-19 particularly in patients at risk of severe disease. Patients were allocated to triage categories defined by likelihood of COVID-19 and risk of a poor outcome. Category A (low-likelihood; high-risk), B (high-likelihood; high-risk), C (high-likelihood; low-risk) and D (low-likelihood; low-risk). This determined the order of priority for isolation in single-occupancy rooms with Category A the highest. Patients in other groups were cohorted when isolation capacity was limited with additional interventions to reduce transmission. RESULTS: Ninety-three patients were evaluated with 79 (85%) receiving a COVID-19 diagnosis during their admission. Of those without a COVID-19 diagnosis: 10 were initially triaged to Category A; 0 to B; 1 to C and 4 to D. All high-risk patients requiring isolation were, therefore, admitted to single-occupancy rooms and protected from exposure. Twenty-eight (30%) suspected COVID-19 patients were evaluated to be low risk (groups C and D) and eligible for cohorting. No symptomatic hospital-acquired infections were detected in the cohorted patients. DISCUSSION: Application of a clinical triage tool to guide isolation and cohorting decisions may reduce the risk of hospital-acquired transmission of COVID-19 especially to individuals at the greatest of risk of severe disease.

Upregulation of Bcl-x and Bfl-1 as a potential mechanism of chemoresistance, which can be overcome by NF-kappaB inhibition.

In A549 human lung adenocarcinoma cells, we found that TNF-alpha and several commonly used chemotherapeutic agents upregulated the expression of Bcl-x and/or Bfl-1/A1 through an NF-kappaB-dependent pathway. While parental A549 cells were resistant to the cytotoxic effects of both TNF-alpha and chemotherapy agents, NF-kappaB-blocked A549 cells were sensitized to both. Expression of either Bcl-x or Bfl-1/A1 in the NF-kappaB-deficient cells at physiological levels provided differential protection against TNF-alpha and chemotherapeutic treatment. These studies provide a potential mechanism for the phenomenon of chemotherapy-induced chemoresistance, and also reveal a potential strategy by which chemoresistance can be overcome.

Developmental changes in the subcellular localization of calretinin.

Brainstem auditory neurons in the chick nucleus magnocellularis (NM) express high levels of the neuron-specific calcium-binding protein calretinin (CR). CR has heretofore been considered a diffusible calcium buffer that is dispersed uniformly throughout the cytosol. Using high-resolution confocal microscopy and complementary biochemical analyses, we have found that during the development of NM neurons, CR changes from being expressed diffusely at low concentrations to being highly concentrated beneath the plasma membrane. This shift in CR localization occurs at the same time as the onset of spontaneous activity, synaptic transmission, and synapse refinement in NM. In the chick brainstem auditory pathway, this subcellular localization appears to occur only in NM neurons and only with respect to CR, because calmodulin remains diffusely expressed in NM. Biochemical analyses show the association of calretinin with the membrane is detergent-soluble and calcium-independent. Because these are highly active neurons with a large number of Ca2+-permeable synaptic AMPA receptors, we hypothesize that localization of CR beneath the plasma membrane is an adaptation to spatially restrict the calcium influxes.

Prostaglandin endoperoxide metabolism by bovine cerebral microvessels.

Isolated bovine cerebral microvessels were found to contain two prostaglandin endoperoxide-metabolizing activities: prostaglandin H2-E2 isomerase and prostacyclin synthetase. At low tissue protein concentrations (i.e., less than 1 mg/ml) and in the presence of reduced glutathione, formation of prostaglandin E2 was favored (about 80% of total prostaglandin products), whereas at higher protein concentrations, in the presence or absence of reduced glutathione, 6-keto-prostaglanding F1 alpha, the stable breakdown product of prostacyclin, was the major product (40-50% of total). Despite an increase in apparent prostacyclin formation, glutathione-enhanced prostaglandin E2 production was still evident at protein concentrations exceeding 1 mg/ml. No apparent enzymatic prostaglandin E2 forming activity was evident in whole cerebral cortex or pial artery homogenates although some GSH-enhanced prostaglandin E2 formation could be demonstrated in microsomes prepared from these tissues. These findings indicate that prostaglandin E2 formation is a dominant enzymatic endoperoxide-metabolizing activity in microvessels, and that this pathway may be primarily localized to the microvasculature. However, they also indicate that enzyme/substrate ratios and endogenous cofactor availability may affect the outcome of endoperoxide metabolism in the bovine cerebral microvasculature, Prostaglandin E2 and prostacyclin generated in the microvasculature could participate in the regulation of various functions, e.g., regional flow and capillary permeability.

RNA-mediated virus resistance in transgenic plants: exploitation of a cellular pathway possibly involved in RNA degradation.

Transgenic Nicotiana tabacum cv. Burley 49 plants were generated that express the 5' untranslated region of the tobacco etch potyvirus (TEV) genome ligated to a mutated version of the TEV coat protein gene sequence that rendered it untranslatable. Eight different transgenic plant lines were analyzed for transgene expression and for resistance to TEV. Three different responses were noted when the transgenic plant lines were inoculated with TEV: 1) some were highly resistant, and no virus replication occurred; 2) some were susceptible but able to recover from systemic TEV infection; and 3) some were susceptible to TEV infection. Plant tissue displaying the recovery phenotype was analyzed for virus replication and transgene expression. Recovered tissue could not be infected with TEV and had steady-state transgene RNA levels which were five- to eightfold lower than those of unchallenged transgenic plant tissue. Nuclear runoff assays suggested a post-transcriptional reduction in specific RNA levels. The highly resistant and recovery phenotypes associated with TEV challenge inoculation and the reduction of steady-state RNA levels in recovered transgenic leaf tissue may be manifestations of a common mechanism.

Afferent influences on the development of the brain stem auditory nuclei of the chicken: otocyst ablation.

The effects of embryonic deafferentation on the morphological development of the avian cochlear nuclei, n. angularis (NA) and n. magnocellularis (NM), were investigated. The right otocyst was surgically removed from chick embryos at 55 to 60 hours of incubation and the subsequent development of total volume, neuron number, and neuron cross-sectional area were studied with quantitative methods in animals sacrificed at 2-day intervals between embryonic days 9 and 19 and at 28 days posthatching. The development of NA and NM is severely affected by otocyst ablation. Between embryonic days 9 and 19, a large group of NA neurons in the medioventral portion of the nucleus on the operated side moves to an ectopic ventromedial position, while the remainder of this nucleus stays in its normal dorsolateral position. Beginning about day 13 of incubation, the normal increase in the volume of NA and the size of its neurons becomes progressively retarded and 40% of its neurons are lost. The growth of NM is also retarded after day 11 of incubation and the growth of mean neuron size is retarded after day 15. There is a 30% loss of neurons in NM which begins after embryonic day 11. The results indicate the primary cochlear fibers make a critical contribution to the growth and maintenance of their target neurons. The absence of this facilitative influence following otocyst ablation becomes apparent just at the time synapses would normally be formed between the the primary auditory afferents and the brain stem auditory neurons. The abnormal movement of neurons in nucleus angularis to an ectopic position after otocyst ablation suggests that primary auditory afferents may serve to stabilize the position of their target cells within the developing brain.

Morphology of axosomatic endings in an avian cochlear nucleus: nucleus magnocellularis of the chicken.

The axonal endings formed on the somata of neurons in the brainstem auditory nucleus magnocellularis (NM) were measured and classified in thin-sectioned material from adult chickens. Degeneration of primary endings after destruction of the basilar papilla and labeling of cochlear nerve fibers by injection of horseradish peroxidase (HRP) into the inner ear were used to determine which ending types arise from the cochlear ganglion. About 60% of the perikaryal surface is apposed by primary type terminals. These primary endbulbs are characterized by round clear synaptic vesicles distributed at an average density of 63 vesicles/micrometers 2 and a number of small, punctate, highly asymmetrical synaptic contacts. The primary type is the only class of endings which disappears after destruction of the basilar papilla and which is consistently labeled after HRP injections into the ear. These endings probably account for the "fast" EPSP seen in NM during stimulation of the cochlear nerve. NM neurons receive two types of nonprimary ending. About 13% of the perikaryal surface is apposed by a morphologically homogeneous class of small "symmetrical" endings; these are characterized by a flattened rhomboidal shape, numerous mitochondria, frequent coated vesicles, and small round or ovoid synaptic vesicles at an average density of 165 vesicles/micrometers 2. Most of the length of the apposition between ending and cell body is occupied by a synaptic complex with thin symmetrical presynaptic and postsynaptic densities. These endings were frequently found on short somatic processes. The second nonprimary axosomatic ending type in NM is most easily identified in experimental material; these endings occupy about 5% of the cell surface area and have a distinctly rounded profile in cross section. These endings typically exhibit clear round synaptic vesicles at a density of 111 vesicles/micrometers 2 arrayed before synaptic contacts which occupy a substantially larger fraction of the total apposition length than in the endbulbs. Many of these synaptic contacts show well-defined presynaptic grids and have postsynaptic densities intermediate in width between the endbulbs and the symmetrical endings. This second type of nonprimary ending may be responsible for the long-latency excitatory post-synaptic potentials seen in intracellular recordings from NM during electrical stimulation of the cochlear nerve. The morphology and distribution of the three ending types does not differ significantly along the posterior-to-anterior axis of NM.

Organization and development of the brain stem auditory nuclei of the chicken: primary afferent projections.

The pattern of primary auditory projections to the brain stem of young chickens was investigated using terminal degeneration methods and orthograde transport of horseradish peroxidase (HRP) or tritiated amino acid. Of particular interest was the question of whether nucleus laminaris (NL) receives primary afferents. A study of silver-stained degeneration pattersn in nucleus magnocellularis (NM) and NL at three intervals following unilateral interruption of the cochlear nerve revealed that by 48 hours after the lesion, degenerating terminals were found only in the ipsilateral nucleus angularis (NA), NM and lagenar projection areas but not in NL. Five- and eight-day survival times, however, also revealed degeneration bilaterally in NL. The appearance of terminal degeneration in NL at the longer survival times is attributed to the previously-reported severe and rapid transneuronal degeneration of neurons in NM following deafferentation and not to the presence of cochlear nerve terminals in NL. Injection of HRP or tritiated proline into the basilar papilla produced patterns of labeling similar to that seen in the 2-day degeneration material; HRP reaction product or autoradiographic label were seen only in the ipsilateral NA and NM and in the ipsilateral projection areas of the macula lagena but not in either NL. The patterns of primary auditory projections revealed by the three methods were quite similar to each other and to that previously reported for the pigeon and confirm the conslucion that the laminar nucleus of chickens does not receive primary afferents.

Induction of aberrant functional afferents to the chick cochlear nucleus.

Surgical extirpation of the otocyst on embryonic day (E) 3 in chick embryos prevents formation of the cochlear nerve and results in development of an aberrant axonal projection from the contralateral cochlear nucleus (nucleus magnocellularis, NM) to the deafferented NM. We have studied the morphology of this projection using horseradish peroxidase injections in NM axons and light and electron microscopy. The ability of the projection to activate its target neurons synaptically was assessed by means of extracellular microelectrode recording from in vitro preparations of the chick brainstem. The aberrant projection arises as a vertically directed branch from the contralaterally traveling NM axon at the medial border of nucleus laminaris (NL). This axonal branch forms boutonal endings that may terminate anywhere in NM but are most common in its ventral and medial regions. In our experiments, this projection is not seen on the unoperated side of experimental animals or in normal controls from E11 onward but is found on the operated sides of all experimental animals, including those with bilateral removal of the otocysts. The aberrant projection persists at least from E11 through hatching and has essentially identical features in unilaterally and bilaterally lesioned animals. The endings of the aberrant projection are boutonal in form and, in the electron microscope, exhibit all of the elements associated with normal synapses. Electrophysiological studies confirm that stimulation of the aberrant axons can elicit postsynaptic responses in NM and suggest that these synapses use an excitatory amino acid neurotransmitter.

Organization and development of brain stem auditory nuclei of the chicken: tonotopic organization of n. magnocellularis and n. laminaris.

Extracellular recordings of responses to tone-burst stimulation were used to determine the tonotopic organization of n. magnocellularis (NM) and n. laminaris (NL) in hatching chickens. NM cells show "primary-like" response patterns to ipsilateral stimulation, and are arranged in dorso-ventral isofrequency columns. Units responding to the highest frequency tones (about 4,100 Hz) are situated at the rostromedial pole of the medial division. Units with lower characteristic frequencies (CF's) are found at successively caudal and lateral sites, until extremely low CF's ( less than 500 Hz) are represented dorsoventrally in the daudolateral tail of the lateral division. No evidence was found of auditory input to the region which receives projections from the macula lagena. NL receives polarized, binaural, excitatory input. Units have similar CF's and thresholds to tones presented to either ear. The tonotopic organization in NL matches that found in NM--high CF's rostromedially and low CF's caudal and lateral. Quantitative procedures were developed for relating CF to the position of a unit within either nucleus. These analyses account for 79% and 89% of the frequency variance found within NM and NL, respectively, and predict the CF of a neuron by its position within each nucleus.

Organization and development of brain stem auditory nuclei of the chicken: organization of projections from n. magnocellularis to n. laminaris.

The tonotopic and topographic organization of the bilateral projection from second-order auditory neurons of nucleus magnocellularis (NM) to nucleus laminaris (NL) was examined in young chickens. In one group of birds, the NM axons which innvervate the contralateral NL were severed by cutting the crossed dorsal cochlear tract at the midline. Heavy terminal degeneration in NL was confined to the neuropil area immediately ventral to the perikaryl lamina. Very little degeneration was seen in the dorsal neuropil region. In a second series of animals, the charactertistic frequency (CF) of cells in an area of NM was first determined by microelectrode recording techniques and then a small electrolytic lesion was made through the recording electrode. Following survival periods of 24-48 hours, the distribution of projections from the lesioned area to the ipsilateral and contralateral NL was examined using the Fink-Heimer method. As previously described in the pigeon, projections from NM terminate densely in the neuropil region immediately dorsal to the ipsilateral NL cell bodies and ventral to the perikaryl layer on the contralateral side, providing each NL neuron with segregated binaural innervation. Lesions in any area of the NM produced degeneration confined to a limited caudo-rostral and medio-lateral portion of both laminar nuclei. To investigate this topographic relationship, the cuado-rostral extents of the lesion in NM and of the resulting degeneration in both NL were determined. Linear regression and correlation analyses then related these positional values to each other and to the CF found at the center of each lesion. All correlations were highly significant and ranged from 0.78 between the position of the lesion in NM and CF to 0.91 between the caudo-rostral position of degeneration in the NL ipsilateral and contralateral to the lesion. It is concluded that neurons in NM project in a very discrete topographic, tonotopic and symmetrical fashion to NL on both sides of the brain, contributing to the binaural response properties and tonotopic organization of neurons in NL. The results also suggest that the organization of projections from NM to NL could provide a mechanism for the differential transmission delay required by a "place" model of low-frequency sound localization.

Age- and position-dependent effects of monaural acoustic deprivation in nucleus magnocellularis of the chicken.

The effect of a moderately severe monaural conductive hearing loss on the development of neuronal size in the avian nucleus magnocellularis (NM) was investigated. NM is considered to be the homologue of the mammalian anteroventral cochlear nucleus and receives large calyceal synaptic endings from the cochlear nerve. Silicone plastic earplugs which produce a 40 dB broadband conductive hearing loss were placed in one external auditory canal of chick embryos on the 18th day of incubation. After hatching, all animals were housed in communal brooders and sacrificed at 4, 10, 25, and 60 days of age. Nissl-stained sections from paraffin- and plastic-embedded brains were used to sample neuronal cross-sectional areas in NM on the deprived and nondeprived sides of the brain. These samples were obtained separately in each brain from three posterior-to-anterior percentage quartiles within NM. Statistical analyses of these data showed that the severity of deprivation-induced cell size changes in NM varied as a function of both age and position. In the 4- and 10-day groups, no significant deprived-versus-nondeprived differences in neuronal size were seen in any area of the nucleus. At 25 days after hatching, only the third posterior-to-anterior quartile (i.e., 50-74%) showed a significant difference; this difference was also significantly greater than those in the second and fourth quartiles at this age. By 60 days, all three sampled areas in NM showed highly significant differences (averaging 12%) in mean neuronal cross-sectional area. Cell size values from the deprived and nondeprived sides of 60-day-old experimental animals were also compared with values from 60-day-old control subjects. Whereas the deprived NM cells were significantly smaller than controls, there was no evidence for a reliable hypertrophy in the nondeprived cells. Thus, the principal effect of the acoustic deprivation produced was to retard continued growth of the deprived neurons after 4 days of age.

A developmental gradient of dendritic loss in the avian cochlear nucleus occurring independently of primary afferents.

Cochlear nerve axons and their target neurons in nucleus magnocellularis (NM) of the chicken undergo extensive parallel structural transformations during development. Between embryonic days 12 and 17 (E12-E17), each immature highly branched axon condenses into a mature calyxlike ending applied to a single NM neuron. Simultaneously, NM neurons are transformed from multipolar cells with many long dendrites into spherical unipolar neurons with only an axon. We tested the hypothesis that cochlear nerve input is necessary for the transformation of NM cells by surgically destroying one otocyst on E3, thereby preventing formation of the nerve. Nucleus magnocellularis neurons from embryos at E11-E12, E13-14, and E17-18 were stained by horseradish peroxidase injected into their axons or by a Golgi-Hortega method. In camera lucida drawings, the number of dendrites on each cell was counted and the cell's position along the posterior-to-anterior and lateral-to-medial axes of the nucleus quantified. At E11-12, neurons throughout NM on both the deafferented and normally innervated sides of the brain have about ten dendrites. At E13-14, there is a steep spatial gradient in dendritic number bilaterally; cells at anteromedial positions have about two dendrites, while cells in posterolateral positions have an average of nine dendrites. By E17-18, only 14% of the neurons on either side have a dendrite, and these cells are evenly distributed throughout the nucleus. We conclude that cochlear nerve axons are not required for normal spatio-temporal gradients of dendritic loss, even though the absence of these axons causes severe atrophic changes in NM.(ABSTRACT TRUNCATED AT 250 WORDS)