The role of standard roentgenograms in the evaluation of instability of pelvic ring disruption

Anteroposterior pelvic roentgenograms of 154 patients with pelvic ring disruptions were evaluated to assess their value in the determination of pelvic instability. Three different categories of stability were roentgenographically recognizable: (1) stable, characterized by impacted vertical fracture of the sacrum, nondisplaced fracture of the posterior sacroiliac complex, and/or subtle fractures of the upper sacrum evidenced by asymmetry of the sacral arcuate lines; (2) unstable, characterized by hemipelvic cephalad displacement exceeding 0.5 cm, sacroiliac joint diastasis exceeding 1 cm and/or sacral or iliac diastatic fracture exceeding 0.5 cm; and (3) indeterminate (that is, suspicious but not diagnostic of pelvic instability), characterized by cephalad hemipelvic displacement of less than 0.5 cm, sacroiliac joint diastasis less than 1 cm, and/or diastatic fracture of the sacrum or ilium of less than 0.5 cm. Correlation of the standard roentgenographic, computed tomographic, and clinical orthopedic examinations revealed that pelvic stability was accurately evaluated on the standard pelvic roentgenograms in 88% of cases. Disruptions were stable in 70%, unstable in 18%, and suspect in 12% of patients, for whom adjunct roentgenographic and clinical examinations were required. Determination of pelvic stability in the manner described allows immediate identification of patients with a stable or unstable pelvic injury, as well as identification of those with indeterminate stability requiring further clinical or roentgenologic evaluation. Immediate recognition of pelvic instability on standard pelvic roentgenograms obviates the need for additional diagnostic studies that unnecessarily delay the institution of emergency therapeutic measures designed to control associated hemorrhage.

AIDS and the press: an analysis of the coverage of AIDS by Zimbabwe newspapers

An analysis of articles about HIV and AIDS in Zimbabwe newspapers for the period January 1987 to September 1988 reveals several areas of concern. An analysis of coverage before and after a Government campaign designed to increase awareness of issues related to AIDS indicated only a short term increase in press coverage of such issues. Articles were assigned to one of seven content categories: statistics, cure or vaccine, prevention, education and awareness, transmission and risk, counselling and care, and policy and economics. The relative lack of articles on counselling and care and on transmission and risk indicates possible gaps in public awareness of susceptibility to AIDS. There were few articles with a local basis, nor were there any personalized stories. This is likely to encourage feelings of distance and relatively low personal risk. In general, Zimbabwe newspapers show little of the sensationalist and prejudiced accounting of AIDS found in some British press coverage.

Diagnostic radiology. One week prelude to the clinical continuum

A one-week comprehensive program of diagnostic radiology was presented to 205 junior medical students just entering the clinical phase of their education. Course objectives were to familiarize the students with the various imaging modalities and their application to common clinical situations and to introduce an organized approach to interpretation of conventional radiographs. This course's one-week time frame was unique. Various educational activities were employed to allow the large number of students to participate actively in the educational process and to enable them to cope with the intensive presentation of unfamiliar vocabulary, materials, and modalities. Through this course, the students achieved an understanding of the impact of radiologic findings on clinical situations and of the necessity of designing an orderly radiologic workup tailored to patient needs and clinical presentation. Most importantly, they gained a functional knowledge of the decision-making process involved in radiology as well as in clinical medicine.

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.

Generalized eruptive pustular drug rash due to cephalexin

A 38-year-old woman developed a generalized pustular eruption 18 h after taking an oral cephalosporin (cephalexin). After having excluded other possible pustular dermatoses, we concluded that our patient's eruption was drug-induced.

Experience-independent development of dendritic organization in the avian nucleus laminaris

The third-order auditory neurons of the avian nucleus laminaris (NL) have distinct dorsal and ventral dendritic tufts that receive their predominant synaptic input from, respectively, the ipsilateral and contralateral cochlear nucleus. Beginning about embryonic day (E) 14 in the chick and continuing for some weeks after hatching, NL neurons undergo a complex series of morphological transformations that result in the formation of a steep anteromedial-to-posterolateral gradient of increasing total dendritic length across the nucleus. This gradient perfectly parallels the tonotopic axis of NL. It has been proposed that acoustically evoked activity in the auditory pathway contributes importantly to formation of the gradient of dendritic length in NL and to several other features of dendritic development. The present experiment tested this hypothesis by surgically removing both otocysts (embryonic precursors of the inner ear) and studying the developing NL in the absence of peripheral input. The results of a quantitative study of Golgi-impregnated material show that at E17 both the steepness and predictability of the spatial gradient of dendritic length in operated animals are indistinguishable from normal. Similarly, the correlation of dorsal and ventral dendritic lengths on individual cells in operated animals is not significantly different from normal. The absolute length of both dendritic fields is reduced below normal, although only dorsal dendrites show a statistically reliable (14%) decrease. This is a significantly smaller effect than the 44% length reduction seen previously in animals with unilateral otocyst removal (T.N. Parks: J. Comp. Neurol. 202:47-57, '81); symmetrical afferent input appears more important to the regulation of NL dendritic length than the absolute level of this input.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of Simonsiella sp. from a neonate

A member of the genus Simonsiella, presumptively identified as S. muelleri, was isolated from a gastric aspirate taken from a neonate 15 min postpartum. The neonate showed a dental cyst and early eruption of teeth, confirmed by mandibular X ray. The morphological features, cultural characteristics, and antimicrobial susceptibility of the isolate are presented.

Location of T-cell leukaemia cells in a model rat system by means of a fluorescent probe

Fluorescence probes for the active centre of an enzyme associated with tumour cells have been used to locate leukaemia cells in a model rat system. These fluorescent techniques are inexpensive and rapid to carry out. The leukaemic cells can be located by fluorescence microscopy in frozen sections, wax embedded sections and resin embedded sections. The technique is illustrated with reference to sections of leukaemic rat kidney, epididymis and testis. These studies confirm earlier histological findings employing conventional staining techniques and have the advantage that individual leukaemia cells can be detected in leukaemic animals undergoing drug therapy. The evidence suggests that these techniques will be of value in further studies of the design of drugs directed to leukaemia cells.

Fluorescent inhibitors of a cell surface protease used to locate leukaemia cells in kidney sections

Guanidinobenzoatase is a trypsin-like protease on the surface of cells capable of migration, for example leukaemia cells. We have used a number of fluorescent probes that are competitive inhibitors of guanidinobenzoatase to locate leukaemia cells in resin sections of kidney tissue obtained from leukaemic rats. We have demonstrated how this competitive inhibition system can be used to direct desired molecules (such as cytotoxic drugs) to these cells and to monitor the arrival of such compounds at the active site of guanidinobenzoatase. The principles developed in this study could equally well be applied to other enzymes on other cells provided suitable competitive inhibitors were designed. The presence of an enzyme on the surface of a cell can be used to direct molecules to that cell provided that these molecules contain a functional group that acts as an inhibitor for the chosen enzyme.

Charge transfer-oxy radical mechanism for anti-cancer agents

The proposal is advanced that anti-cancer drugs generally function by charge transfer resulting in formation of toxic oxy radicals which destroy the neoplasm. Electrochemical studies were performed with some of the main types of agents: iminium ions (adenine iminium from alkylating species, iminium metabolite of 6-mercaptopurine, nitidine, other polynuclear iminiums) and metal complexes (Pt(II)diaquodiammine-guanosine, copper salicylaldoximes). Reduction potentials ranged from -0.4 to -1.2 V. Literature data for quinones are presented and radiation is discussed. Based on the theoretical framework, a rationale is offered for the carcinogen-anti-cancer paradox and the role of antioxidants.

Prepubertal growth and skeletal maturation in children with sickle cell disease

In a longitudinal study of 298 children with homozygous sickle cell (SS) disease and 157 children with hemoglobin SC disease, between birth and 9 years of age, observations of weight and height were made. These were compared with similar data derived from an age- and sex-matched group of 231 children with a normal hemoglobin (AA) genotype. Growth in children with SC disease was not significantly different from that in normal children, but children with SS disease had statistically significant, and progressive, deficits in both weight and height before 2 years of age. The average deficit approached 1 SD below the normal mean for age by 9 years. Observations of skeletal maturity, based on radiologic assessment of bone age at the wrist, were made on a proportion of these children at 5 and 8 years of age. Children with SS disease were significantly retarded at 8 years but not 5 years, which is consistent with increasing deficit in height. These observations confirm the early impact of SS disease on physical development and provide standards from which clinical expectations of growth may be derived. The relevance of these findings and their relationship to the characteristic delay in pubertal development is discussed together with a review of possible etiologic factors. The benign nature of SC disease is endorsed by the absence of an effect on growth in the prepubertal child.

Study using in-vivo binding of 125I-labelled hCG, light and electron microscopy of the repopulation of rat Leydig cells after destruction due to administration of ethylene-1,2-dimethanesulphonate

Gonadotrophin binding to rat Leydig cells after a single administration of ethylene dimethanesulphonate (EDS) (75 mg/kg i.p.) was followed by using intratesticular microdoses of 125I-labelled hCG, whilst corresponding morphological changes in the testicular interstitium were studied with light and electron microscopy. No discernible effect on 125I-labelled hCG binding compared with controls was observed until 24 h after treatment. Between 24 and 32 h a sharp decline in binding occurred which was correlated with extensive Leydig cell destruction. By 48 h the 125I-labelled hCG binding was negligible and no morphologically recognizable Leydig cells were found at this time. The specific binding remained low until 21 days after treatment and then a marked increase occurred to give nearly normal levels by 49 days. This was consistent with a generalized repopulation of the interstitium with Leydig cells, seemingly the result of differentiation of fibroblast-like precursor cells.

Evidence for the involvement of kainate receptors in synaptic transmission in the avian cochlear nucleus

Previous studies using various excitatory amino acid antagonists have shown that synaptic transmission between the auditory nerve and the cochlear nucleus of chickens (nuc. magnocellularis; NM) is mediated by non-N-methyl-D-aspartate (non-NMDA) receptors. In the present study we have attempted to define the subclass of non-NMDA receptor in the NM by examining the effects of various excitatory amino acid agonists on synaptically evoked field potentials in an in vitro preparation of the chicken brain stem. Both quisqualate and DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), whose actions operationally define the quisqualate receptor class, caused variable and weak depression of evoked responses in the NM, as did L-glutamate. Kainic acid, on the other hand, completely blocked postsynaptic responses at micromolar concentrations. We conclude that kainate-preferring non-NMDA receptors play a predominant role in mediating transmission in the NM.

Non-N-methyl-D-aspartate receptors mediating synaptic transmission in the avian cochlear nucleus: effects of kynurenic acid, dipicolinic acid and streptomycin

We have examined the effects of a number of excitatory amino acid antagonists on transmission at the cochlear nerve-nucleus magnocellularis synapse in the chicken. Using an in vitro preparation and bath application of drugs, we studied the effects of kynurenic acid and several related substances, streptomycin and a selective N-methyl-D-aspartate receptor antagonist, DL-alpha-aminosuberate. The last compound had no effect on evoked transmission. Of the various kynurenic acid-related compounds tested, only kynurenic and dipicolinic acid selectively altered responses in nucleus magnocellularis. Quinolinic acid, a kynurenic acid analogue that is structurally akin to dipicolinic acid but which acts selectively at N-methyl-D-aspartate receptors, was without effect. The effect of kynurenic acid was solely inhibitory, completely blocking postsynaptic responses with a potency dependent on the frequency of nerve stimulation. No such frequency dependence was seen with dipicolinic acid although this compound also completely suppressed evoked responses. In addition dipicolinic acid potentiated postsynaptic responses at concentrations only slightly lower than those causing inhibition. Streptomycin inhibited responses in nucleus magnocellularis but this effect seems to result partially from the ability of the drug to inhibit presynaptic calcium influx. Our finding that selective antagonists of N-methyl-D-aspartate receptors were ineffective while antagonists of both receptor types, such as kynurenic and dipicolinic acids, inhibited evoked responses reinforces the conclusion that postsynaptic receptors mediating transmission at this synapse are of the non-N-methyl-D-aspartate type [Nemeth et al. (1983) Neurosci. Lett. 40, 39-44].(ABSTRACT TRUNCATED AT 250 WORDS)

CT diagnosis of fluid in lesser sac mimicking thrombosis of inferior vena cava

A patient with ascites and fluid in the lesser sac mimicking the appearance of a clot in the inferior vena cava is described. A knowledge of liver anatomy, particularly the lesser sac in the region of porta hepatis, aids in avoiding this CT pitfall.

Tilted air-fluid interfaces on chest radiographs

Three patients had hydropneumothoraces in which the air-fluid interfaces were tilted from the horizontal. One was examined fluoroscopically, and the interface "seesawed" synchronously with the heartbeat. Displacement of the fluid by cardiac pulsation is the most likely usual cause of tilted air-fluid interfaces in the chest.

Testicular invasion and relapse and meningeal involvement in a rat T-cell leukaemia

During the haematogenous dissemination of this acute rat T-cell (Roser) leukaemia, infiltration of both epididymal and testicular interstitial tissue has now been demonstrated, probably as an invariable occurrence. The gonadal duct system itself was not invaded. In contrast to an earlier histopathological study with this leukaemia, meningeal invasion has also been encountered during routine passage. Furthermore, subsequent to remissions induced by carmustine (BCNU), relapse could occur as long as 80 days after the 20 day end point in control animals. This was associated with extensive infiltration of the meninges as well as in the male gonadal interstitium, the proximal epididymis being particularly vulnerable. Two doses of carmustine at intervals of one week could eradicate the disease even during the phase of logarithmic growth of the leukaemic cells, this result depending upon the level of treatment and time of dosing post-inoculation with leukaemic cells. Females carrying the disease were shown to be more readily cured than males, probably related to entry of leukaemia cells into the gonadal interstitium. This T-cell leukaemia appears to be an excellent model for the study and prospective chemotherapy of testicular relapse in acute lymphoblastic leukaemia.

The role of erythropoietin, thrombopoietic stimulating factor, and myeloid colony-stimulating factors on murine megakaryocyte colony formation

Various growth factors including purified erythropoietin, colony-stimulating factor (CSF-1), and granulocyte-macrophage CSF (GM-CSF) were tested for their ability to stimulate megakaryocytopoiesis. Four separate preparations of erythropoietin were tested in highly defined cell culture medium. One unit of purified material stimulated small but significant numbers of megakaryocyte colonies, both in serum-containing and in serum-free cultures. All other erythropoietin preparations failed to induce megakaryocyte colony formation. Purified erythropoietin showed no synergistic activity with either WEHI-3 cell conditioned medium (WEHI-3CM, a source of both megakaryocyte CSF and megakaryocyte-potentiating activity) or P388D1 cell conditioned medium (P388D1CM, a preparation containing megakaryocyte potentiator). Partially purified thrombopoietic stimulatory factor did not stimulate directly megakaryocyte colony formation, but acted together with WEHI-3CM, augmenting the number of clonable progenitors detected. Optimal activity was observed at 12-25 micrograms protein per plate. Myeloid growth factors (CSF-1 and GM-CSF) were inactive in the murine megakaryocyte assay. The data show lineage specificity for the myeloid stimulators, but a purified erythropoietin preparation was found to stimulate a small level of megakaryocytopoiesis.

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)

Comparative protective actions of gonadotrophins and testosterone against the antispermatogenic action of ethane dimethanesulphonate

After a single dose of ethane dimethanesulphonate (EDS) (75 mg/kg) to rats the prolonged antispermatogenic action is due to a temporary elimination of the functional Leydig cell population. Replacement therapy with testosterone propionate (3 mg/day) maintains the spermatogenic epithelium but the EDS effect develops when hormone treatment is discontinued. In contrast, a short treatment with hCG (10-100 i.u./day) or LH (714 micrograms/day), starting before the EDS dose, permanently protects the spermatogenic epithelium. FSH treatment was completely ineffective. Although histological protection of spermatogenesis appeared complete with testosterone or hCG, effects on fertility remained but over different periods of time. Antispermatogenic and antifertility effects were produced in mice using much higher doses of EDS (5 X 250 mg/kg) but there was no protection from androgen or hCG. It is suggested that EDS binds to Leydig cells irreversibly, interfering with the action of gonadotrophin. At the dose level used the evidence suggests that the degree of reaction renders most of the Leydig cell population non-viable. A direct cytotoxic effect of the compound upon the spermatogenic epithelium might account for the inability of testosterone or hCG alone or in combination to maintain fertility at normal levels.

Prevention of pneumococcal infection in children with homozygous sickle cell disease

The efficacy of prophylactic penicillin and of 14 valent pneumococcal vaccine in preventing pneumococcal infection in homozygous sickle cell (SS) disease was investigated in 242 children aged 6 months to 3 years at entry. In the first five years of the trial there were 11 pneumococcal infections in the pneumococcal vaccine treated group, 10 by serotypes present in the vaccine. Type 23 accounted for five of these, and there was evidence of higher infection rates in those given the vaccine before age 1. No pneumococcal isolations occurred in the penicillin group while receiving penicillin, although four isolations occurred within one year of stopping penicillin. Probably the most effective prophylaxis against pneumococcal infection requires penicillin beyond the age of 3. The age at which pneumococcal vaccine should be given must await further data on antibody response and clinical efficacy in these patients.

The sacral foramina

The sacral foramina, particularly the first three, are not simple fenestrations. Each foramen is a Y-shaped complex of canals, all with indefinite margins. The complexes lie obliquely at approximately 45 degrees to the coronal plane. An appreciation of these facts facilitates the recognition of the anatomy of plain films, tomographs, and computerized scans.

Testicular relapse in acute lymphoblastic leukaemia: studies with an experimental mouse model

Neither testis nor epididymis was found to be invaded by L1210 leukaemic cells in spite of widespread dissemination through other organs and tissues. The same applied to animals in relapse after protracted remissions induced by cyclophosphamide. Prior damage to the gonadal vascular endothelium by Cd++ did enable leukaemic cells to enter the testicular interstitium, but not the depleted seminiferous tubules. Injection of cells into the lymphatic sinus system of the testis led to rapid peritubular proliferation and systemic dissemination but the seminiferous tubules were not penetrated. The histological appearance resembled that of human ALL. The results suggest that the L1210 system, using the intratesticular route for inoculation can be used to examine the susceptibility to drugs of leukaemic cells in this environment. The potential of drugs to damage the vascular endothelium of the gonad and perhaps contribute to the development of testicular relapse could be assessed following intramuscular inoculation of cells.

Pharmacologic evidence for synaptic transmission mediated by non-N-methyl-D-aspartate receptors in the avian cochlear nucleus

The hypothesis that synaptic transmission between the auditory nerve and the cochlear nucleus is mediated by an excitatory amino acid acting through N-methyl-D-aspartate (NMDA) receptors was examined in an in vitro preparation of the chicken brainstem. The ability of various bath-applied excitatory amino acid receptor antagonists to inhibit synaptically-evoked responses was assessed by recording field potentials from nucleus magnocellularis (NM) following electrical stimulation of the cochlear nerve. Antagonists that selectively block responses mediated by NMDA receptors, such as D-alpha-aminoadipate and 2-amino-5-phosphonovalerate, were without effect on evoked transmission in NM. In contrast, antagonists that additionally act on non-NMDA receptors, such as cis-2,3-piperidine dicarboxylate and gamma-D-glutamylglycine, reversibly suppressed transmission. The results indicate that (1) transmission in the chicken auditory system is mediated by non-NMDA receptors, and (2) a substance(s) chemically akin to aspartate and glutamate may be the transmitter used by the auditory nerve in NM.

Stimulation of neuronal Na+, K+-ATPase by calcium

The effect of calcium on ATP-phosphohydrolase activity of rat brain homogenates has been investigated. In both the presence and absence of the chelating agent EDTA, free calcium within the concentration range 1.2 x 10(-7) to 5.0 x 10(-4) moles/l consistently affected only the activity of Na+, K+-ATpase; the activities of Mg2+-ATPase and Na+-ATPase were essentially unchanged by Ca2+; Ca2+-ATPase could not be demonstrated. In either the presence or absence of EDTA, concentrations of free-Ca2+ above 3 x 10(-6) moles/l caused an inhibition of Na+,K+-ATPase activity. In the presence of EDTA, concentrations of free-Ca2+ below 3 x 10(-6) moles/l were ineffective at altering Na+, K+-ATPase activity but, in the absence of EDTA, free-Ca2+ in this concentration range caused a marked stimulation of the enzyme. Evidence is presented to show that the stimulation of Na+, K+-ATPase by calcium is modulated by the regulatory protein calmodulin. Since the stimulation occurs over the range of concentrations at which calcium would be expected to be encountered within the cell, it is suggested that this is the major physiological effect of calcium on Na+, K+-ATPase.

Functional synapse elimination in the developing avian cochlear nucleus with simultaneous reduction in cochlear nerve axon branching

We studied the chick auditory system to determine whether there is a normal developmental reduction in the number of cochlear nerve axons innervating individual cochlear nucleus (nucleus magnocellularis, NM) neurons. We also examined the preterminal branching patterns of cochlear nerve axons during development. The number of cochlear nerve axons innervating individual NM neurons was estimated by counting the increments in the postsynaptic response as the intensity of cochlear nerve electrical stimulation was varied gradually; this number fell from a mean of 4.0 on embryonic day 13 (E13) to a mean of 2.2 on E17 and E18 and the 4th day after hatching. This highly reliable decline in functional convergence was accompanied by a decrease in the number of preterminal branches of cochlear nerve fibers innervating the NM. On E13 and E14, most axons stained by iontophoretic injections of horseradish peroxidase showed two distinct preterminal branches in the NM. By E17 and E18 and thereafter, cochlear nerve axons were unbranched and terminated with a characteristic single large calycine ending in the NM. There are about twice as many cochlear nerve axons as neurons in the NM and the number of fibers in the nerve appears to decline only slightly between E13 and E17. The 50% decline in the number of cochlear nerve axons making functional synapses on individual NM neurons therefore is associated principally with the concurrent elimination of cochlear nerve axon branching in the NM.

The sacral arcuate lines in upper sacral fractures

The anteroposterior radiographs of 50 patients with multiple fractures of the pelvic ring were analyzed and the findings compared with the interpretation made at the time of admission. Thirty-six of the 50 patients (72%) had associated sacral fractures. Sixty-one percent of the sacral fractures had been missed on the initial examination. Disruption, displacement, deformity, and density changes of the sacral arcuate lines are described as signs of sacral fracture.

Organization and development of brain stem auditory nuclei in the chick: ontogeny of postsynaptic responses

The onset of responsiveness to eighth nerve stimulation was examined in n. magnocellularis and n. laminaris, (second- and third-order neurons) of the chick brainstem auditory system. Extracellular microelectrode mapping techniques were used to examine postsynaptic responses in in vitro brainstem preparations. Two specific questions were addressed. First, what is the earliest time at which postsynaptic action potentials can be evoked in n. magnocellularis and n. laminaris by eighth nerve stimulation? Second, does responsiveness to eighth nerve stimulation develop along a spatial gradient in n. magnocellularis and, if so, how does this gradient compare with other developmental events observed in the chick auditory system? Postsynaptic responses in n. magnocellularis were first recorded at 11 days of incubation. Nucleus laminaris responses to direct stimulation of n. magnocellularis were also first recorded at 11 days, although n. laminaris responses to eight nerve stimulation were not seen until 12 days of incubation. A gradient of response development within n. magnocellularis was indicated by mapping of responsive sites on days 11-13. At 11 days, responses to eighth nerve stimulation were restricted to the most anteromedial portion of n. magnocellularis. Between 11 and 13 days, cells in increasingly more posterolateral portions of n. magnocellularis became responsive. This anteromedial-to-posterolateral gradient in n. magnocellularis is correlated with the basal-to-apical gradient of morphogenesis observed in the basilar papilla and morphogenetic gradients previously observed in n. magnocellularis and n. laminaris.

Synaptic excitation of the second and third order auditory neurons in the avian brain stem

Synaptic potentials were examined in the second- and third-order auditory neurons of nucleus magnocellularis and nucleus laminaris in the chick. Brain stems of mature chick embryos were explanted and maintained in vitro for 4 to 8 h. Field potentials, extracellular spike potentials and intracellular potentials evoked by 8th-nerve stimulation were examined. Eighth-nerve stimulation reliability elicited four identifiable field potentials which could be attributed to: (i) the afferent volley of the 8th-nerve axons, (ii) postsynaptic responses of n. magnocellularis neurons, and (iii) ipsilaterally and, (iv) contralaterally-evoked n. laminaris postsynaptic responses. Intracellular-recorded postsynaptic potentials were characterized by a rapid rise time and short duration. They were apparently monosynaptic with a synaptic delay of 0.4 ms. In each n. magnocellularis neuron the 'fast' excitatory postsynaptic potentials were composed of 1 to 3 all-or-none components. 'Slow' excitatory postsynaptic potentials were characterized by a longer latency, a longer duration and graded amplitude variation in proportion to the intensity of 8th-nerve stimulation. Both 'fast' and 'slow' excitatory postsynaptic potentials had similar reversal potentials. Since the 8th nerve makes monosynaptic connection with n. magnocellularis neurons, it is likely that at this synapse the 'fast' excitatory postsynaptic potentials were produced, while the 'slow' potential may be attributable to the convergence of many boutonal synapses of unknown origin. Intracellular injections of horseradish peroxidase into n. magnocellularis revealed that its efferents bifurcate below the nucleus and send one axon to the contralateral n. laminaris while the other axon forms a highly divergent projection to the ipsilateral laminar nucleus. The intracellular records obtained from n. laminaris are consistent with this anatomical finding in that graded excitatory postsynaptic potentials were elicited by 8th-nerve stimulation.