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Biomedical subjects

C A Miller

Publications and source records attributed to C A Miller.

At least 109 records · Page 6Linked to original sources

Transgenic mouse model for neurocristopathy: Schwannomas and facial bone tumors.

We have characterized a strain of double transgenic mice with simian virus 40 large tumor antigen and prokaryotic lacZ under the control of the myelin basic protein promoter that develops spindle-cell sarcomas and osteogenic sarcomas at 5-7 months of age. Although poorly differentiated, the spindle-cell sarcomas were characterized as malignant Schwannomas based on their neural association, the presence of basal lamina, and expression of Schwann cell-specific genes. The osteogenic sarcomas were often multiple and appeared predominantly in the facial bones, less frequently in the ribs and vertebral column, and only rarely in the appendicular skeleton. Benign osteoblastic lesions were often observed adjacent to these sarcomas. Both the osteoblastic cells in the facial skeleton and Schwann cells are regarded as neural crest derivatives. The biological properties and anatomical location of these tumors suggest that they may share a common origin from the neural crest or its derivatives. R.P. Bolande [Hum. Pathol. (1974) 5, 409-429] introduced the term neurocristopathy as a unifying concept to describe such lesions arising from the neural crest or its derivatives. Cell lines established from both bone and Schwann cell tumors arising in these transgenic mice express simian virus 40 large tumor antigen mRNA as well as functional large tumor antigen. Such cell lines are potentially valuable in the search for markers that identify mammalian neural crest derivatives.

Animals↗

Calphotin: a Drosophila photoreceptor cell calcium-binding protein.

Monoclonal antibody 23E9 identifies a calcium-binding protein, calphotin, in photoreceptor cells of the Drosophila melanogaster compound eyes and ocelli. The antigen is restricted to a defined cytoplasmic region; it is not present in the rhabdomeres, nuclei, mitochondria, or rough endoplasmic reticulum. A corresponding cDNA recognizes a 3-kb mRNA with retinal specificity similar to the antigen and maps to band 86E/F-87A/B on chromosome 3. An open reading frame of 2595 bp encodes an estimated 85-kDa protein of unusual amino acid composition, with > 50% proline, alanine, and valine and very few basic residues. The C-terminal segment contains a leucine zipper motif uninterrupted by prolines. We found no significant similarities with the GenBank or National Biomedical Resource Foundation data bases. The location of the protein within a distinct cytoplasmic region suggests that it might function as a calcium-sequestering "sponge" to regulate the amount of free cytoplasmic calcium.

Amino Acid Sequence↗

The use of primidone in neonates with theophylline-resistant apnea.

OBJECTIVE: To determine whether primidone reduced the occurrence of apnea of prematurity in neonates with apnea resistant to theophylline. DESIGN: Retrospective review. SETTING: Neonatal intensive care unit. PARTICIPANTS: Sixteen premature infants (mean age, 27.8 weeks) in whom apnea and bradycardia recurred despite therapeutic levels of theophylline. Six of the patients were receiving assisted ventilation. INTERVENTION: Administration of primidone (10 to 15 mg/kg per day) orally or by nasogastric tube at a mean age of 35 days. RESULTS: Apnea and bradycardia decreased significantly 24 to 72 hours after initiation of primidone treatment (by 68% and 69%, respectively) compared with pretreatment events. We obtained similar results after a separate analysis of the 10 patients who had been weaned from assisted ventilation before treatment with primidone. No toxic reactions were observed. CONCLUSIONS: Primidone represents a possible adjuvant therapy in theophylline-resistant apnea of prematurity. Caution is advised, because of primidone's complex pharmacologic characteristics, until there are further controlled prospective studies.

Apnea↗

Improved recovery of immature myocardium with L-glutamate blood cardioplegia.

Enhancement of myocardial recovery with glutamate-enriched cold blood potassium cardioplegia (BPC) was evaluated using an isolated working heart model. Three groups of hearts from immature rabbits were subjected to 20 minutes of warm (37 degrees C) ischemia to allow energy depletion, followed by 90 minutes of hypothermic (10 degrees C) ischemia. Myocardial protection provided during hypothermia consisted of cardioplegia infusion, at 50 mm Hg every 30 minutes at 4 degrees C, of either St. Thomas' Hospital solution (group 1, n = 6), oxygenated BPC (group 2, n = 7), or oxygenated BPC enriched with 20 mmol/L L-glutamate (group 3, n = 7). Percent recovery of aortic flow was 87.6% +/- 6.3% (results expressed as mean +/- standard error of the mean) in group 3, which was significantly better than for either group 1 (63.4% +/- 4.0%) or group 2 (47.0% +/- 3.5%) (p < 0.05 by analysis of variance). Group 3 hearts had significantly better recovery of myocardial energy stores (mumol/g dry weight) compared with group 1 or 2 hearts: adenosine triphosphate, 17.8 +/- 1.1 versus 12.4 +/- 1.5 and 12.1 +/- 0.4; creatine phosphate, 25.9 +/- 1.8 versus 17.8 +/- 1.8 and 20.3 +/- 0.7; and glycogen, 140.7 +/- 12.6 versus 98.7 +/- 9.9 and 60.7 +/- 9.9 (p < 0.05). Glutamate-enriched BPC provided excellent myocardial protection after ischemia in this immature model, and this study quantitatively supports the use of glutamate-enriched BPC in neonatal clinical practice.

Animals↗

Characterization of wave I of the electrically evoked auditory brainstem response in the guinea pig.

This paper examines the first component of the electrically evoked auditory brainstem response (EABR) of the guinea pig. Short (20 microseconds/phase) and long (4000 microseconds/phase) duration rectangular current pulses were applied through a bipolar intracochlear electrode in acute preparations. Short-duration pulses evoked a synchronized response relatively free of stimulus artifact; long pulses facilitated examination of the integrative capacities of nerve fibers at relatively low current levels. In deafened control subjects, wave I of the EABR consistently demonstrated two positive peaks having different latency-level and adaptation recovery functions. The early component (wave Ia) showed less decrement in latency with increasing stimulus level and recovered faster in a forward-masking paradigm. Non-monotonicities in the adaptation recovery curves were also observed, more consistently in the wave Ib data. It is proposed that wave Ia arises from stimulation of the axons proximal to the spiral ganglion while wave Ib is initiated at the peripheral dendritic processes. Implications for human cochlear implant research are discussed.

Animals↗

Electrically evoked auditory brainstem response to stimulation of different sites in the cochlea.

It is often assumed that stimulation of the eighth nerve with brief current pulses results in a highly synchronous discharge of action potentials from the ensemble of excited nerve fibers. Latency data derived from the electrically evoked auditory brainstem response (EABR) of the guinea pig and human indicate that there is a baso-apical gradient of response latencies in both species. Place-specific stimulation of different regions of the guinea pig cochlea was achieved by positioning a narrowly spaced bipolar electrode into each of the four spiral turns. Peak latencies of EABR waves I and III both revealed longer latencies with increasing distance from the base. Different amplitude growth functions were obtained from each turn. Place-specific stimulation in humans implanted with the Nucleus 22-electrode device was achieved by presenting current pulses across electrodes spaced 1.5 mm apart. A gradient of wave V latencies was observed in all subjects studied. The presence of a latency gradient would influence results obtained in efforts to correlate evoked potential amplitude measures with nerve survival. It may also provide information useful in characterizing the surviving fiber population in human implant subjects.

Animals↗

Abnormal neuritic architecture identified by Di-I in Pick's disease.

The fluorescent stain Di-I combined with confocal microscopy identified an abnormal neuritic pattern in the cortices of frontal and anterior temporal lobes in postmortem tissues from patients with Pick's disease (PD). Focal, dense neuritic aggregates 50 to 200 microns in diameter were scattered throughout all cortical layers. The three-dimensional analysis provided by confocal microscopy revealed the neuritic clusters to consist of enlarged, randomly arrayed, dystrophic neurites that were not associated with amyloid deposits, astrocytic processes or capillaries. In the intervening neuropil, there were fewer neurites compared to controls. The occipital cortex, which is unaffected in PD, showed a neuritic architecture comparable to normal controls as did affected brain tissues from patients with Alzheimer's disease or remote, ischemic infarction. This neuritic pattern is, thus far, unique to PD and may reflect the loss of specific subpopulations of cortical neurons and proliferation of neurites of the remaining neurons.

Aged↗

The partition (par) locus of pSC101 is an enhancer of plasmid incompatibility.

The incompatibility that pSC101-derived plasmids express toward each other is mediated by directly repeated sequences (iterons) located near the plasmid's replication origin. We report here that the pSC101 par locus, which stabilizes plasmid inheritance in dividing cell populations and alters DNA superhelicity, can function as a cis-acting enhancer of incompatibility, which we show is determined jointly by the copy number of the plasmid and the number of iterons per copy. A single synthetic 32 bp iteron sequence carried by the pUC19 plasmid confers strong pSC101-specific incompatibility in the absence of any other pSC101 sites but requires the par locus to express strong incompatibility when carried by a lower-copy-number plasmid. We propose a model by which the par locus can enhance the apparently antagonistic processes of incompatibility and pSC101 DNA replication while concurrently facilitating plasmid distribution during cell division.

Bacterial Proteins↗

cis-acting components in the replication origin from ribosomal DNA of Saccharomyces cerevisiae.

The ribosomal DNA (rDNA) repeats of Saccharomyces cerevisiae contain an autonomously replicating sequence (ARS) that colocalizes with a chromosomal origin of replication. We show that a minimal sequence necessary for full ARS function corresponds to a 107-bp rDNA fragment which contains three 10-of-11-bp matches to the ARS consensus sequence. Point mutations in only one of the 10-of-11-bp matches, GTTTAT GTTTT, inactivate the rDNA ARS, indicating that this consensus sequence is essential. A perfect match to a revised ARS consensus is present but not essential. Sequences up to 9 bp 5' from the essential consensus are dispensable. A broad DNA region directly 3' to the essential consensus is required and is easily unwound as indicated by: (i) hypersensitivity to nicking of an approximately 100-bp region by mung bean nuclease in a negatively supercoiled plasmid and (ii) helical instability determined by thermodynamic analysis of the nucleotide sequence. A correlation between DNA helical instability and replication efficiency of wild-type and mutated ribosomal ARS derivatives suggests that a broad region 3' to the essential ARS consensus functions as a DNA unwinding element. Certain point mutations that do not stabilize the DNA helix in the 3' region but reduce ARS efficiency reveal an element distinct from, but overlapping, the DNA unwinding element. The nucleotide sequence of the functionally important constituents in the ARS appears to be conserved among the rDNA repeats in the chromosome.

Base Sequence↗

Auditory system degeneration in Alzheimer's disease.

We observed a highly topographically specific and consistent pattern of degeneration in the auditory system of Alzheimer's disease (AD) patients. Senile plaques (SP) and neurofibrillary tangles (NFT) were distributed throughout the ventral nucleus of the medial geniculate body (MGB) and the central nucleus of the inferior colliculus (IC) in nine of nine AD patients. Adjacent nuclei within the MGB and IC were consistently spared. NFT and SP were also present in the primary auditory and the auditory association cortices. In all control tissues, there were neither SP nor NFT in any of the above sites. The cochlear nuclei were normal in tissues from both AD and control patients. The ventral nucleus of the MGB is the major thalamic relay station for auditory function and receives fibers from neurons of the central nucleus of the IC, with projections arranged tonotopically in a laminar pattern corresponding to a gradient of high-to-low frequency ranges. The degenerative changes distributed throughout these nuclei suggest that neuronal loss may include all frequency ranges in AD. In contrast, the clinical features of presbycusis in elderly patients include only high-frequency loss due to lesions peripherally in the cochlea or auditory nerves, rather than in the central auditory nuclei. These histologic changes in the brains of AD patients may provide an additional basis for altered cognitive function due to primary sensory deafferentation.

Aged↗

Maternal and infant care: comparisons between Western Europe and the United States.

A series of studies between 1986 and 1990 gathered data on maternal and infant care in ten Western European countries with lower infant mortality rates than the United States and compared the findings both within the European countries and in aggregate with the United States. Results from these studies reveal great variation among the study countries in how perinatal care is financed, staffed by professional and nonprofessional health workers, and provided by public clinics or private offices, and in the number of and locale of the recommended number of prenatal visits. Invariably consistent among the study countries is the nearly complete enrollment of childbearing women in early and continuous prenatal care, and the strong linkage of that care to a generous spectrum of social supports and financial benefits. None of the benefits generally pertains in the United States. The relevance of these observations for the United States suggests that current policies intended to lower economic barriers to a highly medicalized version of maternity care may yield disappointing results unless the perinatal sequence is linked to a more generous set of maternity-related social supports and financial benefits than is now contemplated.

Adolescent↗

Longitudinal observations on a selected group of local health departments: a preliminary report.

A study is in progress to document changes in selected public health departments over the past decade and to use those observations for proposing an assessment protocol that may be helpful in measuring progress toward achieving one of the Health Objectives for the Nation for the Year 2000. Objective no. 8.14 reads: "Increase to at least 90 percent the proportion of people served by a local health department that is effectively carrying out the core functions of public health." The study re-surveys a group of 14 departments that were the subjects of intensive case studies between 1979 and 1981. Some preliminary observations from follow-up study of these departments in 1992 include: growth in budget and staff and even larger growth in pressure for services, especially for personal health care; reorganization that splits away some programs of comprehensive ambulatory care and responsibility for public hospitals, while increasing the aggregation of human service agencies, including public health, under locally organized umbrella agencies; increase in preventive, screening, and categorical programs under public health sponsorship; drastic change in patterns of financing, featuring nearly total loss of direct federal grants, and increase in fee income; increase in the number of community and migrant health centers in the public health jurisdictions under study; diminished collaborative interaction with private practitioners; and continued close collaboration between health departments and community health centers in several communities. The implications of these changes are discussed. Subsequent reports will be based on efforts to measure the impact of specific events of the 1980s on public health performance, and will describe experience with a community-based surveillance approach for assessing public health performance.

Humans↗

Platelet and fibrinogen survival in calves implanted with artificial heart and ventricular assist device--correlation with autopsy findings.

The two main ingredients of blood clots formed on artificial surface are platelets and fibrinogen. In this study, we measured platelet and fibrinogen survival in calves implanted with total artificial heart (TAH) and left ventricular assist device (LVAD), and correlate these data with autopsy findings. Platelet survival with autologous 111In-labeled platelets was performed on nine calves implanted with TAH and five with LVAD. Fibrinogen survival with 131I-labeled homologous fibrinogen was performed on six calves with TAH and three with LVAD. Platelet survival was significantly shortened in both groups of animals: 5.89 +/- 0.52 days, control 6.46 +/- 0.31 days, p = 0.0013; fibrinogen survival was normal: 8.79 +/- 1.20 days, control 8.64 +/- 1.16 days. At autopsy two calves with TAH had multiorgan thromboembolism. Two other animals with TAH and four with LVAD had focal renal infarcts. Most animals had minor clot formation within the prosthetic device. Major septic complications occurred in four calves with TAH and one with LVAD. Continuous platelet activation by artificial surface probably explains the shortened platelet survival and thromboembolic complications.

Animals↗

Surgical treatment of the spontaneous spinal epidural abscess.

Seven cases of spontaneous epidural abscess are reviewed. Three patients had posterior abscesses and no evidence of vertebral body osteomyelitis. These patients had excellent outcomes with laminectomies and antibiotics. Because of significant vertebral destruction, two patients with vertebral osteomyelitis required posterior fixation after laminectomy. Two other patients with vertebral osteomyelitis had complete destruction of the vertebral body and required anterior decompression and fusion in addition to posterior fixation. In the four patients with vertebral osteomyelitis, morbidity was high, reflecting their age and significant medical problems. This review supports the contention that medically stable patients with posterior epidural abscesses can be treated with laminectomy and antibiotics with little risk of progressive instability. The proper surgical treatment of anterior epidural abscesses secondary to osteomyelitis requires knowledge about the amount of destruction of the supporting columns, the amount of neural compression secondary to the purulence, and the patient's general medical condition.

Abscess↗

Magnetic resonance imaging of trauma to the thoracic and lumbar spine. The importance of the posterior longitudinal ligament.

Magnetic resonance imaging was used to evaluate 24 patients with injuries to the thoracic, thoracolumbar (T12-L1), or lumbar spine. Correlation of the magnetic resonance imaging findings to surgical therapy and outcome was evaluated, with particular attention to the longitudinal ligaments. The ability of the magnetic resonance imaging to detect the extent of trauma to the spinal cord parenchyma and to the anterior and posterior longitudinal ligaments was found to be important in guiding the surgical approach to these spine fractures.

Adolescent↗

Characterization of neutral proteinases from Alzheimer-affected and control brain specimens: identification of calcium-dependent metalloproteinases from the hippocampus.

Three neutral proteinases from human hippocampal tissue have been identified and partially characterized using substrate gel electrophoresis. The proteinases showed activity when gelatin was used as the substrate, but had no detectable activity against casein. Based on the results of inhibition studies and the calcium requirements, it was concluded that the activities were due to calcium-dependent metalloproteinases. The apparent molecular weights were 130,000 (MP-130), 100,000 (MP-100), and 70,000 (MP-70). Half-maximal activities were observed with 20 microM Ca2+ for MP-130, 40 microM Ca2+ for MP-100, and 800 microM Ca2+ for MP-70. In the presence of Ca2+, Zn2+ reestablished the activities of the three metalloproteinases at a lower concentration than did either Co2+ or Mn2+. One millimolar Al3+ inhibited 67% of the MP-70 activity, but did not affect the MP-100 and MP-130 activities. An analysis of Alzheimer-affected hippocampal and control samples showed that the specific activity (in units per milligram of sodium dodecyl sulfate-soluble protein) of MP-70 varied less than the activities of MP-100 and MP-130 between the two groups. Although p-amino-phenylmercuric acetate (p-APMA) increased the activities of MP-70 by 70% in both groups of specimens, the resulting activities from Alzheimer samples were greater than those from control samples (p less than 0.01). A wide range of MP-100 specific activity was observed in both groups, and its mean activity was higher in Alzheimer-affected samples (p less than 0.05). Treatment with p-APMA increased the activity of MP-100 only 25% in both groups of tissue samples. MP-130 activity was detected predominantly in Alzheimer-affected hippocampal specimens, and treatment with p-APMA failed to increase its activity in both the control and the Alzheimer-affected specimens. The results demonstrate an elevated level of metalloproteinase activities, capable of degrading tissue matrix components, in the hippocampus from postmortem Alzheimer patients.

Aged↗

Glucocorticoids exacerbate kainic acid-induced extracellular accumulation of excitatory amino acids in the rat hippocampus.

Glucocorticoids (GCs) compromise the ability of hippocampal neurons to survive various insults, and do so, at least in part, by exacerbating steps in the glutamate/N-methyl-D-aspartate (NMDA)/calcium cascade of damage. As evidence, GCs impair uptake of glutamate by hippocampal astrocytes, the GC endangerment of the hippocampus is NMDA receptor dependent, and GCs exacerbate kainic acid (KA)-induced calcium mobilization. These observations predict that GCs should also exacerbate KA-induced accumulation of extracellular glutamate and aspartate. To test this, adrenalectomized rats were given replacement GCs in either the low or high physiological range. Three days later, rats were anesthetized and 1 mM KA was infused through a dialysis probe placed in the dorsal hippocampus. Extracellular amino acid concentrations in the dialysate were then assessed by HPLC. After KA infusion, high-GC rats (30 +/- 3 micrograms/dl) had significantly elevated concentrations of glutamate and aspartate compared with low-GC rats (all less than 0.95 micrograms/dl). The glutamate accumulation was due to GCs raising pre-KA concentrations, whereas the aspartate accumulation was due to GCs exacerbating the KA-induced rise. Glutamine concentrations were unaffected by KA, whereas the high-GC regimen elevated glutamine concentrations both before and after KA. Taurine concentrations rose after infusion of KA, but were unaffected by GC regime, whereas alanine concentrations were unaffected by either manipulation. Serine concentrations were unaffected by KA, but were depressed both before and after KA in high-GC rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗