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Biomedical subjects

J L Fox

Publications and source records attributed to J L Fox.

At least 199 records · Page 11Linked to original sources
PubMed1987

The multiple manifestations of the encephalocraniocutaneous lipomatosis syndrome.

A case is reported of a recently described neurocutaneous syndrome, manifested by a noncommunicating right lateral ventricular cyst, a left-sided lipoma of the scalp with alopecia, right-sided multiple truncal lipomas, right-sided ocular manifestations, left leg hypertrophy, and seizures. The findings in cases of encephalocraniocutaneous lipomatosis are described to demonstrate the spectrum of this syndrome.

Adolescent↗
PubMed1987

High-level C5a gene expression and recovery of recombinant human C5a from Escherichia coli.

Poor expression of a synthetic gene for the inflammatory mediator, C5a, was observed in E. coli grown in rich media. Varying the media composition markedly improved expression, although C5a levels still declined rapidly at the end of log phase. Using a protease-deficient strain, C5a was recovered at stationary phase in high yield (13 mg/liter of culture). Recovery was dependent on guanidinium hydrochloride extraction to solubilize the protein and glutathione treatment to promote correct folding. Two-thirds of the C5a retained an amino-terminal methionine. Both forms of recombinant C5a had activity similar to serum-derived C5a in binding to human neutrophil receptors and inducing chemotaxis. The 700-fold improvement in yield made it feasible to obtain gram amounts of C5a and provides an efficient system for site-directed mutagenesis.

Cloning, Molecular↗
PubMed1987

A combined infratemporal and posterior fossa approach for the removal of giant glomus tumors and chondrosarcomas.

Giant glomus jugulare tumors with a large posterior fossa extension are considered either inoperable or at least requiring of a two-stage operation. Likewise, the surgical approach and treatment for chondrosarcomas of the temporal bone are controversial. We describe a combined approach in which, with the aid of microsurgical and laser techniques, such tumors can be removed in one stage. The surgical approach involves a lateral infratemporal approach combined with a posterior fossa craniectomy. This technique was used in seven cases: five glomus jugulare tumors and two chondrosarcomas. There were no deaths, and surgical morbidity consisted of weakness in the facial nerve in four of these patients and gastrointestinal hemorrhage and respiratory distress syndrome in one patient.

Brain Neoplasms↗
PubMed1987

Syringomyelia after decompressive laminectomy for cervical spondylosis.

We describe a case of cervical spondylotic myelopathy in which deterioration occurred a month after decompressive laminectomy. Syringomyelia was then in evidence as seen by myelography and delayed metrizamide computed tomography scanning. The etiology of this finding and its possible relation to the course and treatment of cervical spondylotic myelopathy are discussed.

Adult↗
PubMed1987

cDNA and deduced amino acid sequence of human pulmonary surfactant-associated proteolipid SPL(Phe).

Hydrophobic surfactant-associated protein of Mr 6000-14,000 was isolated from ether/ethanol or chloroform/methanol extracts of mammalian pulmonary surfactant. Automated Edman degradation in a gas-phase sequencer showed the major N-terminus of the human low molecular weight protein to be Phe-Pro-Ile-Pro-Leu-Pro-Tyr-Cys-Trp-Leu-Cys-Arg-Ala-Leu-. Because of the N-terminal phenylalanine, the surfactant protein was designated SPL(Phe). Antiserum generated against hydrophobic surfactant protein(s) from bovine pulmonary surfactant recognized protein of Mr 6000-14,000 in immunoblot analysis and was used to screen a lambda gt11 expression library constructed from adult human lung poly(A)+ RNA. This resulted in identification of a 1.4-kilobase cDNA clone that was shown to encode the N-terminus of the surfactant polypeptide SPL(Phe) (Phe-Pro-Ile-Pro-Leu-Pro-) within an open reading frame for a larger protein. Expression of a fused beta-galactosidase-SPL(Phe) gene in Escherichia coli yielded an immunoreactive Mr 34,000 fusion peptide. Hybrid-arrested translation with this cDNA and immunoprecipitation of [35S]methionine-labeled in vitro translation products of human poly(A)+ RNA with a surfactant polyclonal antibody resulted in identification of a Mr 40,000 precursor protein. Blot hybridization analysis of electrophoretically fractionated RNA from human lung detected a 2.0-kilobase RNA that was more abundant in adult lung than in fetal lung. The larger RNA and translation product indicates that SPL(Phe) is derived by proteolysis of a large polypeptide precursor. The amino acid sequence of the predicted protein, beginning Phe-Pro-Ile-Pro-Leu-Pro-Try-, comprises a hydrophobic peptide that is a major protein component of surfactant lipid extracts used successfully to treat hyaline membrane disease in newborn infants. These proteins, and specifically SPL(Phe), may therefore be useful for synthesis of replacement surfactants for treatment of hyaline membrane disease in newborn infants or of other surfactant-deficient states.

Amino Acid Sequence↗
PubMed1987

Puberty due to a mixed germ cell tumour of the hypothalamus secreting BhCG and alpha-fetoprotein.

A 14 year-old boy presented with visual impairment due to a large suprasellar tumour secreting beta-human chorionic gonadotrophin (BhCG) and alpha-fetoprotein (alpha FP). He was sexually mature with an advanced bone age of 17 years, and suffering from partial hypopituitarism. Treatment with external radiotherapy resulted in a reduction of tumour size and fall of the serum testosterone BhCG and alpha FP levels. We conclude that pubertal development had been initiated and maintained by ectopic hCG production from his intracerebral mixed germ cell tumour. Patients with tumours in the pineal and suprasellar regions should be screened for elevated levels of BhCG and alpha FP. We suspect that many of these tumours cause precocious puberty by secreting BhCG.

Adolescent↗
PubMed1987

Physical model for non-steady-state dissolution of dental enamel.

The purpose of this study was to provide a rigorous theoretical understanding of the dissolution behavior of dental enamel over the entire time-course of demineralization and to simulate by computer an erosion-type caries lesion according to the physical "hydroxyapatite model". The appropriate diffusion equations which account for simultaneous diffusion and equilibrium of all species in enamel pores, boundary layer, and bulk solution, and which also take into consideration surface reaction kinetics, were employed to allow for calculation of the micro-environmental solution concentration and changes in the mineral density as a function of time and distance within the enamel. This comprehensive physical model for non-steady-state enamel dissolution also explicitly takes into account changes in the diffusivity and the dissolution rate constant as a function of mineral density. Demineralization experiments were conducted in 0.1 mol/L sink acetate buffer (pH = 4.50, mu = 0.50), with ground bovine dental enamel blocks of known surface area mounted (with beeswax) in a rotating disk apparatus. Mineral density profiles were quantified by means of contact x-ray microradiography. The physical model was used to predict mineral density profiles for given demineralization treatments. The experimental profiles agreed quite well with the predicted profiles, when the effective diffusivity of the enamel was assumed to be a function of porosity and when changes in surface area of the crystallites were taken into consideration.

Animals↗
PubMed1987

Effect of acid type on kinetics and mechanism of dental enamel demineralization.

The influence of acid type (pKa effects) of weak organic acid buffers on dissolution kinetics of dental enamel was critically examined for rigorous testing of the behavioral validity of the physical model of Patel et al. (1987). Quantitative evaluation of this model indicated that monitoring initial dissolution rates was a viable approach to critical testing of the model. Initial dissolution rates were determined in 0.1 mol/L acetate (pKa = 4.77), benzoate (pKa = 4.20), and salicylate (pKa = 2.98) buffers (pH = 4.50, mu = 0.50), with ground bovine enamel blocks of known surface area mounted in a rotating disk apparatus. The Levich theory was used to study dependence of dissolution rates on stirring rates in these buffers. The experimental data were analyzed by the physical model which includes pKa effects, complexation of the buffer anion with the other ions, surface kinetics, simultaneous diffusion and equilibrium of all species in enamel pores, diffusion layer thickness, and bulk solution composition. The KIAP (formula: see text) governing the dissolution reaction and the surface resistance factor were deduced from the model. Dissolution kinetics was also followed in these buffers in the presence of calcium or phosphate common ions. In effect, by conducting both the stirring rate studies and common ion experiments, we derived the driving force function independently by these two techniques. The results obtained in this study were consistent with the model, indicating that pKa effects on the dissolution of dental enamel can be accounted for quantitatively by the model, and it was found that weak acids do not influence either the apparent solubility or the surface reaction process of bovine dental enamel.

Acetates↗
PubMed1987

Factors affecting survival of children with malignant gliomas.

Fourty-four patients (23 male and 21 female, aged 2 to 20 years (mean, 9.6], harboring pathologically proven malignant glioma (Grades III and IV) were treated between 1976 and 1985. Tumor sites included the cerebral hemisphere (26 patients), thalamus (6 cases), brain stem (7 cases), and the cerebellum (5 cases). All patients underwent operation and initial treatment with steroids. Irradiation was given in 35 patients; 3 had adjuvant chemotherapy. At the time of study, 22 were deceased. The longest period of follow-up was 65 months. Survival curves were calculated from the date of the first visit to the date of the last evaluation or death. The mean survival times were 30 months for all patients, 14 months for cerebellar cases, 17 months for brain stem cases, 26 months for thalamic cases, and 33 months for cerebral hemisphere cases. However, the differences between mean survival times were not statistically significant. The patient's age was the single most significant factor, with those 5 to 10 years old having the worst survival curve (P = 0.0036). Irradiation was associated with an improved mean survival time (34 vs. 19 months); however, this was not statistically significant (P = 0.15). Girls had shorter mean survival times than boys (16.5 vs. 37 months, P = 0.0511). Otherwise, there was no clinical or radiological factor that indicated a better prognosis. This was also confirmed by chi 2 analyses comparing 72 factors between patients with more than 24 months of survival and those with less than 24 months of survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Primary structure of CTP:CMP-3-deoxy-D-manno-octulosonate cytidylyltransferase (CMP-KDO synthetase) from Escherichia coli.

The gene coding for CTP:CMP-3-deoxy-D-mannooctulosonate cytidylyltransferase (CMP-KDO synthetase), kds B, was previously cloned on a 9-kilobase Pst insert of Escherichia coli DNA into pBR 322 (Goldman, R. C., and Kohlbrenner, W. E. (1985) J. Bacteriol. 163, 256-261). Using a transposon mutagenesis approach we have now located kds B on this insert, which facilitated the isolation and sequencing of a 1.3-kilobase segment of DNA containing kds B and putative RNA polymerase and ribosome binding sites. The primary structure of CMP-KDO synthetase predicted by this nucleotide sequence was verified by amino acid composition and sequence analysis of purified CMP-KDO synthetase and cleavage fragments. Our results show that kds B consists of a 744-base open reading frame coding for a 248-amino acid peptide. The molecular weight of CMP-KDO synthetase calculated from the translated sequence is 27,486, taking into account the loss of the N-terminal methionine. These data define the transcriptional unit of kds B and its translation product in molecular terms, information prerequisite to our understanding of both the mechanism of CMP-KDO formation and the regulation of the KDO metabolic pathway in Gram-negative bacteria.

Amino Acid Sequence↗
PubMed1986

Evidence that the acetylcholine binding site is not formed by the sequence alpha 127-143 of the acetylcholine receptor.

The sequence alpha 127-143 of the alpha subunit of the acetylcholine receptor has been proposed to contain several important features: (1) the acetylcholine binding site, (2) the only N-glycosylation site of the alpha subunit, at asparagine-alpha 141, and (3) two cysteine residues, at alpha 128 and alpha 142, that may participate in a disulfide bond known to be near the binding site. We tested these hypotheses by using antisera to receptor and its subunits and monoclonal antibodies to the synthetic peptide alpha 127-143 cyclized by a disulfide bond between alpha 128 and alpha 142. Antisera to receptor and its alpha subunit were able to immunoprecipitate the iodinated peptide, and this reaction was inhibited by soluble receptor, but not by membrane-bound receptor. alpha-Bungarotoxin did not inhibit antiserum binding to solubilized receptor. Similarly, cholinergic ligands had little or no effect on binding to immobilized receptors of anti-peptide monoclonal antibodies. In addition, these monoclonal antibodies, when bound to the receptor, did not affect toxin binding kinetics. By contrast, preincubation with concanavalin A did inhibit monoclonal antibody binding. Reduction of the receptor significantly decreased the binding of three of the monoclonal antibodies, but subsequent alkylation with N-ethylmaleimide or the affinity labeling reagent bromoacetylcholine had no additional effect on binding. A dithiothreitol concentration about 100-fold higher that the one needed to reduce the disulfide near the acetylcholine binding site was necessary to inhibit monoclonal antibody binding. We conclude that the sequence alpha 127-143 is not fully exposed on the surface when the receptor is in the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1986

Location of antigenic determinants on primary sequences of subunits of nicotinic acetylcholine receptor by peptide mapping.

The binding domains of 28 monoclonal antibodies (mAbs) against the alpha, beta, and delta subunits of the Torpedo acetylcholine receptor were mapped on the primary sequences of these subunits. Small peptide fragments (2000-20,000 daltons) of the purified subunits were obtained by digestion with staphylococcal V8 protease and papain, separated on a discontinuous polyacrylamide gel electrophoretic system, and electroblotted onto diaminophenyl thioether paper. The blots were probed with the various monoclonal antibodies and also with antibodies against carboxy-terminal decapeptides of the alpha, beta, and delta subunits to identify the carboxy-terminal fragments. From inspection of the binding patterns of the various antibodies to the subunits fragments and the molecular weights of these fragments, and by using the carboxy termini of the subunits as reference points, it was possible to deduce the regions on the primary sequence of each subunit in which the antibodies bound and in some cases to order the binding sites within these sequences. mAb 148, which inhibits receptor function by cross-linking receptor molecules on the cytoplasmic side, was mapped to the sequence beta 368-406. The main immunogenic region of the native receptor, which is of pathological importance in the autoimmune disease myasthenia gravis, was mapped by using mAb 210 to within 80 amino acid residues (alpha 46-127). The overall antigenic structure of alpha subunits was examined. Synthetic peptides have been used to locate determinants responsible for 83% of the antibodies in antisera to denatured alpha subunits and 46% of the antibodies to denatured alpha subunits in antisera to intact receptor. Theoretical models of the transmembrane orientation of the subunit polypeptide chains were tested by determining whether mapped monoclonal antibodies bound to the extracellular or intracellular surface of receptor-rich membranes. Our results confirm previous reports that the carboxy termini of the subunits are exposed on the intracellular surface, as is part of the region between a putative channel-forming domain (M5) and a putative membrane-spanning region (M3). However, contrary to current theoretical models, the region between M5 and the putative membrane-spanning sequence M4 also appears to be on the intracellular surface, implying that M4 and M5 are not membrane-spanning domains.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1986

Separation of amino acid phenylthiohydantoin derivatives by high-pressure liquid chromatography.

Separation of the phenylthiohydantoin (PTH) derivatives of all 20 common amino acids is accomplished in approximately 11 min with excellent resolution by using high-pressure liquid chromatography. The chromatography is achieved at 50 degrees C on an Altex reversed-phase PTH-C18 column in an ammonium acetate-buffered acetonitrile, pH 4.5, mobile phase. Simple isocratic and linear gradient steps are used. Retention times for the various PTH-amino acids are very reproducible. Because the baseline is flat and free of background noise, PTH-amino acids can be detected in the low picomole range. The simplicity of this chromatographic system allows it to be easily automated.

Amino Acid Sequence↗
PubMed1986

Solid-phase sequencing on the gas-phase sequencer.

Automated Edman degradation has been successfully used for determining the primary structure of numerous peptides and proteins. Quantitative solid-phase Edman degradation has great potential use for amino acid sequence analysis of synthetic peptides assembled on resin support by the Merrifield procedure. We report here the combined use of a modified gas-phase sequencer program and our improved reversed-phase HPLC analysis for PTH-amino acids to carry out the sequence analysis on synthesized peptide resins. This approach is far more sensitive than using glass beads on the conventional solid-phase sequencer. The peptide was assembled on copoly (styrene-1% divinylbenzene) resin beads at an initial substitution of 0.54 mmol/g. On a routine basis, 10-15 resin beads are used, and a repetitive yield of 94% is obtained: as few as 4 beads can be successfully sequenced. The HPLC PTH-amino acid analysis is sensitive down to subpicomole quantities. This procedure offers a sensitive and rapid analytical tool for checking the purity of peptides as they are being assembled on solid support.

Amino Acid Sequence↗
PubMed1986

Al-Zahrawi and Arabian neurosurgery, 936-1013 AD.

The authors highlight the neurosurgical contributions of an Arabic surgeon by the name of Abul-Qasim Al-Zahrawi, known in Western literature as Abulcasis. This man lived during the Middle Ages from 936 to 1013 AD and wrote a 30-volume treatise on medicine. A significant part of his work on surgery consists of early descriptions of neurosurgical diagnosis and treatment, including the surgical treatment of head injuries and skull fractures, spinal injuries and dislocations, hydrocephalus and subdural effusions, headache, and many other medical afflictions. He described neurosurgical instruments such as cranial drills that avoided puncture of the dura mater. Abulcasis is known for his concepts of pain as a symptom and his emphasis on anatomy of the skull and brain in relation to the neurosurgical operations of that period. Because his works were translated from Arabic to Latin, Hebrew, and Turkish with only recent or limited translation into the modern occidental languages, the historic role played by this man has been largely unknown by neurosurgeons who are not fluent in these languages.

Brain Diseases↗
PubMed1986

High-level expression of a gene encoding the human complement factor C5a in Escherichia coli.

The synthetic C5a gene was initially found to be expressed poorly in Escherichia coli. We undertook studies to determine the reasons for poor expression and to increase expression. The work was focused on the role of the mRNA structure in C5a expression and stability of its product in E. coli. We present data on the effects of varying the sequence at the 5' end of mRNA as well as different ribosome-binding sites on expression. Evaluation of the stability of C5a showed rapid degradation of C5a in wild-type E. coli (half-life 3-5 min). Screening of several protease-deficient strains of E. coli showed that C5a was much more stable in an htpR strain carrying a mutation in the sigma subunit of RNA polymerase that is specific for heat shock promoters. The mutation is associated with a proteolytic deficiency. The half-life of C5a was increased to 20 min. By manipulating the expression vector, the regulatory region for the C5a gene, the host strain, growth conditions and methods for recovering the protein, C5a levels were increased 300-fold over previously reported amounts to about 3% of total cellular protein.

Base Sequence↗
PubMed1986

Persistence of primitive cerebral vasculature in a newborn. A case report of whole brain AVM.

A case of a two-day-old infant with a massive arteriovenous malformation involving the entire brain vasculature is reported. The appearance of the cerebral vasculature on computed tomography scans and angiographic studies in this newborn is similar to the primitive vasculature in an embryo. The findings in this case give strong support to ontogenesis maldevelopment as the etiology of cerebral arteriovenous malformations. The role of embryogenesis in the development of an arteriovenous malformation is discussed as it contrasts with other pathogenetic hypotheses.

Brain↗