Proton nuclear magnetic resonance spectroscopy unambiguously identifies different neural cell types

Proton nuclear magnetic resonance (1H NMR) spectroscopy is a noninvasive technique that can provide information on a wide range of metabolites. Marked abnormalities of 1H NMR brain spectra have been reported in patients with neurological disorders, but their neurochemical implications may be difficult to appreciate because NMR data are obtained from heterogeneous tissue regions composed of several cell populations. The purpose of this study was to examine the 1H NMR profile of major neural cell types. This information may be helpful in understanding the metabolic abnormalities detected by 1H NMR spectroscopy. Extracts of cultured cerebellar granule neurons, cortical astrocytes, oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells, oligodendrocytes, and meningeal cells were analyzed. The purity of the cultured cells was > 95% with all the cell lineages, except for neurons (approximately 90%). Although several constituents (creatine, choline-containing compounds, lactate, acetate, succinate, alanine, glutamate) were ubiquitously detectable with 1H NMR, each cell type had distinctive qualitative and/or quantitative features. Our most unexpected finding was a large amount of N-acetyl-aspartate (NAA) in O-2A progenitors. This compound, consistently detected by 1H NMR in vivo, was previously thought to ne present only in neurons. The finding that meningeal cells have an alanine:creatine ratio three to four times higher than astrocytes, neurons, or oligodendrocytes is in agreement with observations that meningiomas express a higher alanine:creatine ratio than gliomas. The data suggest that each individual cell type has a characteristic metabolic pattern that can be discriminated by 1H NMR, even by looking at only a few metabolites (e.g., NAA, glycine, beta-hydroxybutyrate).(ABSTRACT TRUNCATED AT 250 WORDS)

Applications of magnetic resonance spectroscopy and diffusion-weighted imaging to the study of brain biochemistry and pathology

The first practical demonstration that nuclear magnetic resonance (NMR) spectroscopy could be applied to the study of brain biochemistry in vivo came in 1980, with the studies of the rat brain using a surface coil. Since then the technique has been rapidly and extensively developed into a versatile, non-invasive tool for the investigation of various aspects of brain biochemistry, physiology and disease. NMR is non-destructive and can be used to examine a wide variety of samples, ranging from localized regions within the whole brain in humans or animals, through tissue preparations (perfused organ, tissue slices and homogenates), to isolated cells and aqueous solutions, such as tissue extracts. 31P and 1H NMR spectra deriving from endogenous compounds of the brain in situ allow assessment of tissue metabolites and provide information about high-energy phosphates, lactate, certain amino acids, intracellular pH and ionic concentrations. Exogenous substrates or probes labelled with stable isotopes can also be introduced into the brain and used to monitor metabolism. Animal models of brain diseases have given some impetus to rapid progress in clinical NMR spectroscopy and also magnetic imaging techniques. The purpose of this article is to highlight the type of information available from these NMR techniques, and to present this in a neuroscience context, emphasizing the biochemical, physiological and pathological information that can be obtained using these methods.

NMR spectroscopy: current status and future possibilities

Nuclear magnetic resonance (NMR) spectroscopy is now established as a non-invasive method of studying metabolism in living systems, ranging from cellular suspensions to man. With respect to clinical applications, recent developments include the successful implementation of new techniques for spatial localisation, and in particular the acquisition of excellent 1H spectra from selected regions of the human brain. Localised 1H spectroscopy opens the way to monitoring a wide range of compounds that are inaccessible to 31P NMR, and should add considerably to the information that is available from 31P studies. NMR spectroscopy does, however, have its limitations, which arise primarily from the fact that it is an insensitive technique. This lack of sensitivity limits the spatial resolution for metabolic studies, and means that metabolites must be present at fairly high concentrations in order to produce detectable signals. In this article, we illustrate the scope and limitations of NMR spectroscopy by describing a few examples of studies undertaken on animals and humans.

Lugol's iodine dye-enhanced endoscopy in patients with cancer of the oesophagus and head and neck

Lugol's iodine dye indicates the presence of unsuspected early oesophageal cancers during endoscopy at which such cancers fail to show the characteristic black colour change. We evaluated Lugol's iodine dye-enhanced endoscopy in 17 patients with oesophageal cancer. In a further 37 patients with head and neck cancer we examined the use of Lugol's iodine since these patients have a 29% risk of synchronous oesophageal cancer. The oesophagus was sprayed with Lugol's iodine (1.5%) during endoscopy. Any areas not turning black were biopsied. In 13 patients with oesophageal cancer discrete areas beyond the macroscopically obvious primary tumour showed no change in colour. Biopsy revealed cancer in all cases. Six synchronous cancers were found in the head and neck group, one of which was identified only by the use of Lugol's iodine. Lugol's iodine augmented the information gained about the oesophageal mucosa during endoscopy. It revealed unsuspected cancer which altered the management of patients with primary oesophageal cancer as well as those with head and neck cancer. We recommend the routine use of Lugol's iodine-enhanced endoscopy for surveillance of all 'at risk' oesophageal cases.

Orbital infection secondary to sinusitis in children: diagnosis and management

A series of 18 children with orbital infection secondary to sinusitis is described. The presenting symptoms were headache and periorbital swelling but it was found to be impossible to determine the stage of the orbital infection on clinical grounds. CT scanning can accurately identify the presence of a sub-periosteal abscess but both axial and coronal sections may be needed to diagnose abscesses in the superomedial portion of the orbit. Cellulitis may be managed by antibiotic treatment alone, but if an abscess is present it should be drained immediately with a formal ethmoidectomy to decompress the orbit if there is any evidence of reduced visual acuity.

Diffusion-weighted imaging studies of cerebral ischemia in gerbils. Potential relevance to energy failure

BACKGROUND AND PURPOSE

Diffusion-weighted magnetic resonance imaging has been shown to be particularly suited to the study of the acute phase of cerebral ischemia in animal models. The studies reported in this paper were undertaken to determine whether this technique is sensitive to the known ischemic thresholds for cerebral tissue energy failure and disturbance of membrane ion gradients.

METHODS

Diffusion-weighted images of the gerbil brain were acquired under two sets of experimental conditions: as a function of cerebral blood flow after controlled graded occlusion of the common carotid arteries (partial ischemia), as a function of time following complete bilateral carotid artery occlusion (severe global ischemia), and on deocclusion after 60 minutes of ischemia.

RESULTS

During partial cerebral ischemia, the diffusion-weighted images remained unchanged until the cerebral blood flow was reduced to 15-20 ml.100 g-1.min-1 and below, when image intensity increased as the cerebral blood flow was lowered further. This is similar to the critical flow threshold for maintenance of tissue high-energy metabolites and ion homeostasis. After the onset of severe global cerebral ischemia, diffusion-weighted image intensity increased gradually after a delay of approximately 2.5 minutes, consistent with complete loss of tissue adenosine triphosphate and with the time course of increase in extracellular potassium. This hyperintensity decreased on deocclusion following 60 minutes of ischemia.

CONCLUSIONS

The data suggest that diffusion-weighted imaging is sensitive to the disruption of tissue energy metabolism or a consequence of this disruption. This raises the possibility of imaging energy failure noninvasively. In humans, this could have potential in visualizing brain regions where energy metabolism is impaired, particularly during the acute phase following stroke.

Endoplasmic reticulum: the major contributor to the PDE peak in hepatic 31P-NMR spectra at low magnetic field strengths

31P-NMR spectra of liver in vivo, subcellular fractions and model systems were acquired in order to characterise further the hepatic phosphodiester peak seen at low magnetic field strengths previously shown to be predominantly due to phospholipid bilayers. The data obtained in this study in vitro suggested that the phospholipid membranes of the endoplasmic reticulum provide the dominant contribution to this phosphodiester peak. Support for this hypothesis was provided by experiments on rats. Phenobarbitone, which is known to induce proliferation of the endoplasmic reticulum produced a considerable increase in intensity of the phosphodiester peak in liver spectra in vivo.

Multiple primary cancers in Hong Kong Chinese patients with squamous cell cancer of the head or neck

BACKGROUND

The risk of multiple primary tumors in the head and neck area is higher than that in other areas of the body.

METHODS

A total of 573 patients with squamous cell carcinoma of the head or neck were studied prospectively during a 4.5-year period to determine the incidence of associated synchronous and metachronous second primary carcinoma.

RESULTS

Multiple primary carcinoma was found in 2.4% of these patients (69% with synchronous primary tumors). Sixty-three percent of all second primary tumors occurred in the esophagus.

CONCLUSIONS

This report emphasizes the importance of esophagoscopy in the initial assessment of patients with squamous cell carcinoma of the head or neck.

Necrotizing fasciitis of the face without significant trauma

Necrotizing fasciitis is a rare but well recognized clinical entity which most often occurs on the trunk, perineum or legs following surgery or trauma. The condition is much less common in the head and neck and it is particularly uncommon in the midface/periorbital region. In almost all the cases occurring in the neck the condition follows obvious dental or oropharyngeal sepsis and in all the cases of the scalp there is a history of previous surgery or trauma. However, necrotizing fasciitis of the midface/periorbital region may lack any obvious traumatic aetiology or may follow relatively minor trauma. The diagnosis in these cases may not be suspected and treatment may be delayed with fatal consequences. Treatment by wide excision of all affected skin can lead to disastrous cosmetic consequences in facial disease and it is suggested that disease control can be achieved by raising wide based skin flaps with excision of the underlying necrotic tissue. The flaps are then returned onto normal muscle with much improved cosmetic results. This paper discusses the diagnosis and treatment of patients with necrotizing fasciitis of the face which has arisen without significant trauma.

Regulated expression of monocyte chemoattractant protein-1 in normal human osteoblastic cells

An influx of monocytes is observed in many different physiological and pathophysiological states, including bone remodeling and injury. These cells appear at early stages of bone formation and repair and persist throughout the later stages. In experiments described here, unstimulated normal human osteoblastic cells did not produce detectable levels of monocyte chemotactic activity. However, interleukin-1 (IL-1)-stimulated normal human osteoblastic cells produced a chemoattractant that is similar to monocyte chemoattractant protein-1 (MCP-1) at the levels of mRNA expression, protein production, and chemotactic activity. Northern blot analysis indicates that IL-1 elicits a dose-dependent increase in MCP-1 mRNA in normal human osteoblastic cells. Two proteins of M(r) 9,000 and M(r) 13,000 were specifically immunoprecipitated with MCP-1 antiserum from IL-1-stimulated normal human osteoblastic cells. Monocyte chemotactic activity from IL-1-treated cells was blocked by MCP-1 antiserum. These studies establish that normal human osteoblastic cells can be induced to produce monocyte chemoattractants and that this is accounted for by the induced expression of MCP-1.

Specific expression of N-acetylaspartate in neurons, oligodendrocyte-type-2 astrocyte progenitors, and immature oligodendrocytes in vitro

To test the specificity of N-acetylaspartate (NAA) as a neuronal marker for proton nuclear magnetic resonance (1H NMR) spectroscopy, purified and characterized cultured cells were analyzed for their NAA content using both 1H NMR and HPLC. Cell types studied included cerebellar granule neurons, type-1 astrocytes, meningeal cells, oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, and oligodendrocytes. A high concentration of NAA was found in extracts of cerebellar granule neurons (approximately 12 nmol/mg of protein), whereas NAA remained undetectable in purified type-1 astrocytes, meningeal cells, and mature oligodendrocytes. However, twice the neuronal level of NAA was found in O-2A progenitors grown in vitro. In addition significant levels of NAA were also detected in cultures of immature oligodendrocytes. Our data partly support previous suggestions that NAA may be a useful neuronal marker for 1H NMR spectroscopic examination of the adult brain. However, they also raise the further possibility that alterations of NAA associated with some specific brain disorders, particularly disorders seen in newborn and young children, may reflect abnormalities in the development of oligodendroglia or their precursors.

Random PCR mutagenesis screening of secreted proteins by direct expression in mammalian cells

We have developed a general method for screening randomly mutagenized expression libraries in mammalian cells by using fluorescence-activated cell sorting (FACS). The cDNA sequence of a secreted protein is randomly mutagenized by PCR under conditions of reduced Taq polymerase fidelity. The mutated DNA is inserted into an expression vector encoding the membrane glycophospholipid anchor sequence of decay-accelerating factor (DAF) fused to the C terminus of the secreted protein. This results in expression of the protein on the cell surface in transiently transfected mammalian cells, which can then be screened by FACS. This method was used to isolate mutants in the kringle 1 (K1) domain of tissue plasminogen activator (t-PA) that would no longer be recognized by a specific monoclonal antibody (mAb387) that inhibits binding of t-PA to its clearance receptor. DNA sequence analysis of the mutants and localization of the mutated residues on a three-dimensional model of the K1 domain identified three key discontinuous amino acid residues that are essential for mAb387 binding. Mutants with changes in any of these three residues were found to have reduced binding to the t-PA receptor on human hepatoma HepG2 cells but to retain full clot lysis activity.

Detection of thymosin beta 4 in situ in a guinea pig cerebral cortex preparation using 1H NMR spectroscopy

In the present work we have investigated the macromolecules that contribute to the brain 1H NMR spectrum. The cerebral cortex showed distinct resonances at the uncrowded methyl- and methylene chemical shift scale of the spin-echo 1H NMR spectrum. The peaks at 1.22 and 1.40 ppm (relative to the methyl protons of N-acetyl aspartate at 2.02 ppm) arise from cerebral macromolecules without evidence for co-resonances from low molecular weight metabolites as shown by the spin-spin relaxation decays of these resonances. In addition to these NMR signals, peaks at 0.9 and 1.7 ppm from macromolecules were detected. These resonances are from proteins, and we have identified the polypeptides that contributed to the 1H NMR peaks. Two proteins that were present at concentrations of 250 and 350 micrograms/g of dryed tissue showed 1H NMR spectra that resembled the macromolecular pattern in the cerebral 1H NMR spectrum. They were identified as thymosin beta 4 and histone H1, respectively. Thymosin beta 4 was present in soluble high speed cytoplasmic fraction and in P2 pellet, whereas histone H1 was detected in nuclear enriched fraction. A chemical shift-correlated two-dimensional 1H NMR spectrum of thymosin beta 4 in vitro revealed a coupling pattern that matched the macromolecule in the cerebral cortex which we have previously noted (Kauppinen R. A., Kokko, H., and Williams, S. R. (1992) J. Neurochem. 58, 967-974). On the basis of both one- and two-dimensional NMR evidence, subcellular distribution and high concentration, we assign the 1H NMR signals at 0.9, 1.22, 1.40, and 1.7 ppm in the cerebral cortex to thymosin beta 4.

T2- and diffusion-weighted magnetic resonance imaging of a focal ischemic lesion in rat brain

We sought to evaluate the application of T2-weighted and diffusion-weighted magnetic resonance imaging techniques in the study of a focal ischemic lesion in the rat brain.

Unilateral cortical infarcts were induced using the photosensitive dye rose bengal and 560 nm light irradiation. Magnetic resonance images were recorded from a total of 11 rats at selected intervals from 1.5 hours to several days after induction of the lesion. Parallel experiments were performed in which Evans blue dye was injected into the lesioned animals either immediately after lesion induction (n = 11) or 1 hour before the animals were killed (n = 11). The second procedure was designed to show regions of blood-brain barrier permeability to plasma proteins at the time of sacrifice, whereas the first procedure showed the accumulation and subsequent dispersion of plasma protein following disruption of the blood-brain barrier.

Regions of the cortex highlighted by the T2-weighted images corresponded well to the pattern of dye staining seen from the first procedure while the diffusion-weighted images showed visual correspondence with the staining pattern obtained using the second procedure.

These results illustrate the complementary use of T2-weighted and diffusion-weighted magnetic resonance imaging in discerning the pathophysiology of developing lesions.

Perfusion and diffusion MR imaging

Diffusion-weighted images of the rat brain were obtained using the pulsed-gradient spin-echo method. An attempt was made to extract perfusion-related parameters from signal intensity data taken from the caudate-putamen region of the images, by using a nonlinear least-squares calculation to fit the Le Bihan biexponential expression (Le Bihan et al., Radiology, 168, 497 (1988)) to the data. The perfusion-related parameters could not be obtained with sufficient accuracy to be useful, although the perfusion-weighted images appear to contain meaningful qualitative information. An analysis of the perfusion model is presented and shows why the Le Bihan pseudo-diffusion coefficient is particularly difficult to measure with reasonable accuracy.

Detection of mobile proteins by proton nuclear magnetic resonance spectroscopy in the guinea pig brain ex vivo and their partial purification

Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to study metabolites of the brain cortex ex vivo. The superfused brain cortex preparation was judged to be metabolically viable on the basis of the 31P NMR spectrum (intracellular pH of 7.23 +/- 0.03 and phosphocreatine/ATP ratio of 1.21 +/- 0.09). Using 1H NMR a group of previously unidentified signals was detectable at 0.94, 1.22, and 1.40 ppm with a water-suppressed spin-echo sequence. These signals had shorter spin-spin relaxation times (51-54 ms) than N-acetylaspartate and lactate (84-93 ms) and also smaller saturation factors, an indication of shorter spin-lattice relaxation times than the latter two low-molecular-weight metabolites. The unidentified signals also displayed homonuclear coupling to other spins in the methine region of the spectrum. Acid extraction of the brain slices or cortex from animals that were killed yielded a mixture of proteins that exhibited NMR properties matching the 1H NMR signals in the brain cortex. The molecular mass of these thermoresistant, "mobile" proteins, which contained proline plus hydroxyproline (9-16% of all amino acids), ranged between 8 and 40 kDa. These "new" assignments of 1H NMR-detectable compounds may influence interpretation of NMR data of some metabolites, as their signals are in the vicinity of the -CH3 1H NMR peaks of lactate and alanine.

Cell and tissue responses of a murine tumour to phthalocyanine-mediated photodynamic therapy

Mice bearing a subcutaneously growing tumour (Colo 26) were injected intravenously with the photosensitiser chloroaluminum sulphonated phthalocyanine (5 mg/kg) 24 h prior to irradiating the tumour with laser light (675 nm; 50mW, 100 J/tumour). Energy status of the tumour, as assessed by the loss of high energy phosphates in the 31P-nuclear magnetic resonance spectra, was altered dramatically following treatment, such that the ATP fell to undetectable levels within 1 h of light irradiation. However, assessment of the clonogenic capacity of neoplastic cells isolated from dissociated tumours showed that these rapid changes in cellular metabolism were not reflected in similar rapid changes in cell viability. Reductions in clonogenic capacity, which fell to less than 0.1% of control values at 24h postirradiation, closely mirrored those resulting from the cessation of vascular perfusion. Evaluation of tumour blood flow, using the technique of hydrogen washout, showed that the treatment protocol evoked a gradual and selective reduction in flow within the tumour resulting in complete vascular stasis by approximately 5 h after treatment. The results indicate that while chloroaluminum sulphonated phthalocyanine-mediated photodynamic therapy caused early metabolic damage in neoplastic cells, loss of viability paralleled the induction of complete inhibition of vascular flow in the tumour.

The extracellular domain of the human interferon gamma receptor interacts with a species-specific signal transducer

At least two species-specific gene products are required for signal transduction by interferon gamma (IFN-gamma). The first is the IFN-gamma receptor, which binds ligand with high affinity in a species-specific manner. The second is an undetermined species-specific signal transducer(s). To determine whether the human IFN-gamma receptor (hIFN-gamma R) interacts directly with this signal transducer(s) and, if so, with what functional domain(s), we constructed expression vectors for the hIFN-gamma R and three hybrid human-murine IFN-gamma receptors. The hybrid receptors contained the extracellular, human IFN-gamma (hIFN-gamma) binding domain of the hIFN-gamma R, either the human or murine transmembrane domain, and either the human or murine intracellular domain. The vectors encoding these receptors were stably transfected into two mouse cell lines, one of which (SCC-16-5) contains a single copy of human chromosome 21. The resulting cell lines were treated with hIFN-gamma, and murine major histocompatibility complex class I antigen expression was analyzed by immunofluorescence flow cytometry. All transfected cell lines lacking human chromosome 21 remained insensitive to hIFN-gamma. However, all four of the IFN-gamma receptors were able to signal when expressed in the cell line containing human chromosome 21. We conclude that the extracellular domain of the IFN-gamma receptor is involved not only in the species specificity of IFN-gamma binding but also in signalling through interaction with an as yet unidentified species-specific factor(s) encoded by a gene(s) on human chromosome 21.

High-affinity binding of PDGF-AA and PDGF-BB to normal human osteoblastic cells and modulation by interleukin-1

Bone has the capacity for repair and regeneration. The repair process is thought to be locally regulated by growth factors. One of the growth factors that potentially plays a significant role in these processes is platelet-derived growth factor (PDGF). Two different PDGF genes have been identified, PDGF-A and PDGF-B, whose gene products give rise to biologically active dimers. We now report that PDGF-AA and PDGF-BB exhibit saturable binding to normal human osteoblastic cells. By Scatchard analysis we estimate that there are approximately 43,000 PDGF-AA binding sites per cell, with a dissociation constant (Kd) of 2.2 x 10(-10)M, and 55,000 high-affinity PDGF-BB binding sites per cell, with a Kd of 1.2 x 10(-10)M. The functional consequence of PDGF binding was also assessed. PDGF-AA and PDGF-BB both stimulated migration of normal human osteoblastic cells and stimulated thymidine incorporation. To gain insight into potential transmodulation of the PDGF response, we investigated the capacity of interleukin-1 beta (IL-1 beta), a cytokine that induces bone resorption, to modulate PDGF binding and PDGF-induced biological activity. IL-1 beta significantly reduced PDGF-AA binding and significantly decreased both PDGF-AA-mediated cell migration and thymidine incorporation. In contrast, IL-1 beta had only a small effect of PDGF-BB binding and PDGF-BB-induced biological activity in normal human osteoblastic cells.

Nondestructive detection of glutamate by 1H nuclear magnetic resonance spectroscopy in cortical brain slices from the guinea pig: evidence for changes in detectability during severe anoxic insults

31P and 1H nuclear magnetic resonance spectroscopy (NMR) was used to study the metabolism of intact superfused cortical brain slices during normoxia and anoxia. Attention was focused on quantification of 1H NMR-detected glutamate by a water-suppressed spin-echo method, using N-acetyl aspartate as an internal concentration reference. To quantify the 1H NMR signals, the spin-spin relaxation times and saturation effects were estimated for given metabolites. In addition, absolute concentrations of metabolites were determined by biochemical methods from acid extracts of the preparations after NMR experiments. Under aerobic conditions, 1H NMR detected 79% of the glutamate determined biochemically from the brain slice extracts. During anoxia in the absence of glucose when a severe energetic failure was evident, both 1H NMR and biochemical assays gave closely matching levels for glutamate. We conclude that in the brain cortex 21% of glutamate is located in an intracellular compartment in which this amino acid does not contribute to the 1H NMR signal. However, during severe anoxia an intracellular reorganisation occurs increasing the detectability of this amino acid neurotransmitter by NMR.

Sequence and functional characterization of the human purine nucleoside phosphorylase promoter

Purine nucleoside phosphorylase (PNP) is a ubiquitously expressed enzyme which contributes to the catabolism and recycling of nucleotides. To characterize the promoter region of the human PNP gene, the nucleotide sequence from a BamHI site located in the 5' untranslated region extending 2237 bp upstream to an XbaI site was determined. The transcriptional start site as determined by primer extension was 119 bp upstream of the coding sequence and consisted of a 5'-CA-3' dimer with A at +1. A TATA box was identified -24 to -29 bp upstream of the transcriptional start site. A CCAAT pentamer sequence in the inverted orientation was present at -51 to -55 bp and two GC rich regions were identified at -68 to -81 bp and -168 to -187 bp. Progressive 5' deletions of the 5' flanking region were fused to the chloramphenicol acetyltransferase (CAT) reporter gene and transient expression measured after transfection of murine NIH/3T3 fibroblasts. A 91 bp promoter (the shortest tested) provided CAT activity at 60% the level of a 216 bp promoter, possibly due to removal of the GC rich region between -168 and -187 bp. Longer promoters resulted in CAT expression at similar or lower levels than the 216 bp promoter indicating that this region contained all of the 5' flanking sequences affecting transcription from the PNP promoter.

Diffusion-weighted imaging of kainic acid lesions in the rat brain

We present T2-weighted and diffusion-weighted images of kainic acid lesions in the rat brain. Our observations show improved image contrast between edematous lesions and unaffected tissue using diffusion-weighted imaging. Furthermore, we show that the anisotropic intensity changes associated with this sequence can be used to highlight white matter tracts and to provide information concerning their orientation in the rat brain.

Measurement of transient cDNA expression in mammalian cells using flow cytometric cell analysis and sorting

Generalized methods for quantitative and sensitive measurement of transient cDNA expression in mammalian cells using flow cytometry (FCM) are described. The techniques are applicable to a wide variety of cDNAs encoding intracellular or cell surface protein products through the use of immunofluorescence- or nonimmunofluorescence-based detection methods. The methods illustrated have been optimized for sensitive detection of transfectants and efficient recovery of the encoding plasmids from the sorted cells. Expression levels and heterogeneities were compared using four methods of DNA transfer in addition to description of a novel method to optimize single copy transfer probabilities by multiparameter analysis. The overall sensitivities are compared by reconstruction and molecular cloning experiments to other methods of selection, such as immunoselection by panning. Through the measurement of multiple heterologous products per cell, or the measurement of multiple epitopes or binding sites per heterologous protein, expression levels on a single cell basis can be measured and correlated with other endpoints for various purposes. The ability to detect and recover rare clones based on a number of single and multiparameter selection criteria should significantly extend the use of transient mammalian cDNA expression methods for applications involving novel FCM-based reporter cDNA assays and for cloning certain rare surface-bound or secreted proteins using FCM.

Cerebral energy metabolism and intracellular pH during severe hypoxia and recovery: a study using 1H, 31P, and 1H [13C] nuclear magnetic resonance spectroscopy in the guinea pig cerebral cortex in vitro

1H and 31P nuclear magnetic resonance spectroscopy was used to study intracellular pH (pHi), high-energy phosphates, lactate, and amino acids in cortical brain slices superfused in Krebs-Henseleit bicarbonate buffer during and after severe hypoxia at 0, 10, and 50 mM glucose. An extensive drop in phosphocreatine (PCr) and a rapid build-up of intracellular lactate and H+ were the first signs of hypoxia. Adenosine triphosphate (ATP) was significantly more resistant to hypoxia provided that glucose was present. In the preparations that had been exposed to hypoxia in the presence of glucose, PCr became detectable within 2 min of reoxygenation, and both PCr and ATP concentrations were restored to 72-80% of normoxic levels within 30 min. Lactate was washed out, and pHi returned to normal within 4-8 min. Using 1-[13C]glucose as a tracer, we demonstrated that the rate of lactate production in the immediate posthypoxic period was at the prehypoxic level, indicating that the elevated lactate during this period was due solely to that produced during hypoxia. During reoxygenation of the preparations that were denied glucose during hypoxia, only 30% of total creatine + PCr and 18% of PCr were restored, and ATP was not detectable. The lactate concentration rose twofold in this period, and pHi became significantly more alkaline than before the hypoxic insult. Thus acute metabolic damage was considerably greater if glucose was absent during the insult, suggesting that either anaerobic ATP production or low pH may exert some protective effect against acute cell damage.

Identification of tumor hemorrhage in an animal model using spin echoes and gradient echoes

We report here how magnetic resonance imaging can be used to gain definitive information about tissue pathology by the combined use of spin-echo and gradient-echo sequences. We also show how artifacts arising from respiratory motion can be eliminated by using a simple respiratory gating technique.

Presence and transcription of intracisternal A-particle-related sequences in CHO cells

We have characterized sequences expressed in Chinese hamster ovary (CHO) cells which are related to the intracisternal A-particle (IAP) genes of mice and Syrian hamsters. Several cDNA clones homologous to Syrian hamster IAP probes have been isolated and used to evaluate the abundance and expression of these retroviruslike sequences. DNA blot analysis with homologous Chinese hamster IAP probes revealed that IAP-related sequences are present in CHO cell DNA at moderately repetitive levels (approximately 300 copies per haploid genome). Sequence analysis has revealed the existence of at least two distinct families of IAP-related sequences in CHO cell DNA. Family I sequences exhibit identical 4.5-kilobase-pair internal deletions relative to complete IAP genomes of mice or Syrian hamsters, but family II sequences showed no major sequence discontinuities relative to the IAP genes of other species. Both families are expressed as abundant cytoplasmic RNA in CHO cells, but only family II sequences produce abundant transcripts of a size consistent with that of a full-length IAP RNA. Intact gag, pol, or env open reading frames were not present in sequences of either family, although incomplete open reading frames spanning putative p27 and protease regions of IAP genes were observed.

A study of combined continuous ethinyl estradiol and norethindrone acetate for postmenopausal hormone replacement

In a blinded, prospective, dose-response pilot study of continuous estrogen-progestin replacement therapy, 77 thin, nonsmoking, white women, who were 12 to 60 months postmenopausal and had normal medical histories, were randomly assigned to receive one of five dose combinations of daily ethinyl estradiol and norethindrone acetate (20 micrograms and 1.0 mg, 10 micrograms and 1.0 mg, 10 micrograms and 0.5 mg, 5 micrograms and 1.0 mg, and 5 micrograms and 0.5 mg) or conjugated estrogens 0.625 mg on days 1 to 25 and medroxyprogesterone acetate 10 mg on days 16 to 25. An additional 10 women meeting the same criteria served as a comparison group by taking calcium only. During 12 months of therapy, continuous users had significantly less vaginal bleeding and spotting than did sequential users. As compared with baseline values, bone metabolism and computerized tomographic measurements of vertebral trabecular bone density at month 12 indicated reduced bone turnover and increased density in hormone users. Endometrial biopsy specimens were negative for hyperplasia and neoplasia. The continuous ethinyl estradiol-norethindrone acetate tablet, even at the lowest doses studied, provided the same salutary effects on bone, endometrium, and postmenopausal symptoms as sequential therapy while minimizing annoying vaginal bleeding and spotting.

Restoration of energy metabolism and resolution of oedema following profound ischaemia

Cerebral ischaemia was produced in 2 groups of gerbils by occlusion of the common carotid arteries for 30 minutes, resulting in cerebral oedema. In group 1 cerebral oedema was measured by specific gravity microgravimetry, and in group 2 brain metabolism and blood flow were measured by 31P and 1H NMR spectroscopy and hydrogen clearance respectively. In group 1 the brain water content did not return to control levels by 180 minutes of reperfusion. Energy metabolism, determined by 31P NMR spectroscopy returned to control by 12 minutes, intracellular pH (pHi) by 20 minutes, and lactate, determined by 1H NMR spectroscopy, by 50 minutes. There was a lag of about 10 minutes before lactate began to be cleared from the brain. We suggest that while pHi is low, Na+/H+ exchange will negate the Na+ extrusion driven by the Na+/K+ ATPase. When pHi approaches normal there will be a net extrusion of Na+, taking osmotic water with it, and presumably with passive washout of lactate. This may be the cause of the initial delay in lactate clearance.

Management of the inflammatory aural polyp

Investigation into the underlying disease causing an aural polyp is often hampered when the polyp itself obscures the tympanic membrane. This retrospective analysis of 65 patients undergoing aural polypectomy was carried out to identify any predictive factors for underlying cholesteatoma and to determine a correct management strategy for aural polyps. The duration of symptoms, size of polyp, size of conductive component of hearing loss and bacteriology of otorrhoea were unhelpful as predictors of the underlying disease. Radiological evidence of bony erosion of the mastoid is a useful sign of cholesteatoma when present. Aural polypectomy resulted in 58.3 per cent of ears becoming inactive. It is proposed that aural polypectomy and histological assessment should be employed as initial treatment with mastoid exploration reserved for those ears thus identified as high risk for cholesteatoma.

Gluconeogenesis and the protection of hepatic intracellular pH during diabetic ketoacidosis in rats

Studies were made of the mechanism whereby hepatic gluconeogenesis is increased in diabetic ketoacidosis (DKA) despite evidence in vitro of inhibition of gluconeogenesis by systemic acidosis. In perfused livers taken from normal rats, marked inhibition of lactate uptake and glucose output was achieved by simulation of metabolic acidosis in the perfusate. In perfused livers obtained from animals with DKA, lactate uptake and glucose output were greater than in normal perfused liver at all values of perfusate pH, and it was not possible to demonstrate significant inhibition of gluconeogenesis from lactate by perfusate acidosis. Varying severity of acidosis was induced in rats by (a) HCl infusion, (b) NH4Cl ingestion or (c) experimental DKA. Hepatic intracellular pH (pHi) was measured in vivo by 31P-n.m.r. spectroscopy. Whereas at the severer degrees of systemic acidosis marked falls in hepatic pHi were seen in the HCl- and NH4Cl-treated animals, little fall was seen in rats with DKA. The protection of hepatic pHi in rats with DKA was not due to differences in respiratory compensation compared with the other groups. It is suggested that this protection of hepatic pHi in DKA may be responsible for the failure of acidotic inhibition of gluconeogenesis from lactate. Possible reasons for pHi protection in DKA are considered. There is no difference in hepatic energy status as assessed in vivo by ATP/Pi ratios between control, DKA and NH4Cl-treated rats. DKA rats show a striking decrease in hepatic glycerophosphoethanolamine content.

Photodynamic therapy in the treatment of malignant tumours of the skin and head and neck

Photodynamic therapy utilizes a tumour-localizing photosensitive substance which, when activated by light of an appropriate wavelength, releases cytotoxic substances causing destruction of the malignant tumour with preservation of surrounding normal tissues. In this technique the only drug/light combination which has been regularly used to date is that of haematoporphyrin derivative and red light at a wavelength of 630 nm usually produced by a dye or gold vapour laser. A pilot/feasibility study was set up in Southampton in 1983, with ethical permission, to treat tumours of the skin and head and neck which had failed all other treatment modalities or for which there was no practical alternative therapy. Thirty-eight patients were treated in this study and all tumours showed a response; significant palliation was achieved in a number of patients. Basal cell carcinomas and the multiple lesions of Bowen's disease were found to be particularly suitable for this form of therapy and prolonged local control was achieved in a number of patients.

Phosphodiesters in the liver: the effect of field strength on the 31P signal

31P NMR spectra of the rat liver were recorded in vivo at 2.35 and 8.5 T. There was a large peak in the phosphodiester region of spectra obtained at 2.35 T which was much reduced at 8.5 T. The peak at 2.35 T is unlikely to be primarily from free cytosolic phosphodiesters, which would not be expected to display such a marked field dependence.

Observation of cerebral metabolites in an animal model of acute liver failure in vivo: a 1H and 31P nuclear magnetic resonance study

Acute liver failure was induced in rats by a single intragastric dose of carbon tetrachloride. This causes hepatic centrilobular necrosis, as indicated by histological examinations, and produces a large increase in the activity of serum alanine aminotransferase. The plasma NH4+ level (mean +/- SEM) was 123 +/- 10 microM in the control group and 564 +/- 41 microM in animals with acute liver failure (each n = 5). 31P nuclear magnetic resonance (NMR) was used to monitor brain cortical high-energy phosphate compounds, Pi, and intracellular pH. 1H NMR spectroscopy was utilised to detect additional metabolites, including glutamate, glutamine, and lactate. The results show that the forebrain is capable of maintaining normal phosphorus energy metabolite ratios and intracellular pH despite the metabolic challenge by an elevated blood NH4+ level. There was a significant increase in the brain glutamine level and a concomitant decrease in the glutamate level during hyperammonaemia. The brain lactate level increased twofold in rats with acute liver failure. The results indicate that 1H NMR can be used to detect cerebral metabolic changes in this model of hyperammonaemia, and our observations are discussed in relation to compartmentation of NH4+ metabolism.

31P nuclear magnetic resonance of rat pancreatic grafts

This study investigates whether phosphate metabolite concentrations and intracellular pH alter in early acute rejection of rat pancreatic allografts. In vitro biochemical assays, in vitro 31P nuclear magnetic resonance spectroscopy, and in vivo 31P NMR spectroscopy of the grafts were compared. Duct-ligated, vascularized rat pancreatic isografts and allografts were transplanted onto the infrarenal aorta of the recipients with inferior vena cava venous drainage. In order to obtain reproducible acute rejection, allografting was performed across a major histocompatibility barrier. For the in vitro experiments freeze-clamped graft extracts were prepared and analyzed for adenosine triphosphate concentration by fluorimetry, then placed in an 8.5 Tesla vertical bore magnet. 31P NMR spectra were recorded using a Bruker AM 360 spectrometer operating at 145.7 MHz for 31P. Spectra were acquired from nontransplanted controls; 3-day, 5-day, and 1-month posttransplant isografts, and 3-day and 5-day posttransplant allografts. All grafts examined were functioning satisfactorily. The ATP content of the extracts was significantly lower in the 3- and 5-day allografts than the respective isografts. Invasive in vivo 31P NMR spectra were recorded using surface coils adjacent to the grafts from functioning 5-day posttransplant isografts and allografts (i.e., 3 days prior to an expected elevation in blood sugar from acute rejection in the allografts). The ATP/inorganic phosphate ratios and pH from the in vivo spectra were significantly lower in the allografts than in the isografts. It is concluded that changes in intracellular metabolism occur early in the process of acute rejection and that 31P NMR spectroscopy may provide a means of diagnosing this before current methods.

Analysis of the signal for attachment of a glycophospholipid membrane anchor

The COOH terminus of decay accelerating factor (DAF) contains a signal that directs attachment of a glycophospholipid (GPI) membrane anchor. To define this signal we deleted portions of the DAF COOH terminus and expressed the mutant cDNAs it CV1 origin-deficient SV-40 cells. Our results show that the COOH-terminal hydrophobic domain (17 residues) is absolutely required for GPI anchor attachment. However, when fused to the COOH terminus of a secreted protein this hydrophobic domain is insufficient to direct attachment of a GPI anchor. Additional specific information located within the adjacent 20 residues appears to be necessary. We speculate that by analogy with signal sequences for membrane translocation, GPI anchor attachment requires both a COOH-terminal hydrophobic domain (the GPI signal) as well as a suitable cleavage/attachment site located NH2 terminal to the signal.

Ammonia causes a drop in intracellular pH in metabolizing cortical brain slices. A [31P]- and [1H]nuclear magnetic resonance study

[31P]- and [1H]Nuclear magnetic resonance spectroscopy were used to study metabolism in cortical brain slices in the guinea-pig during acute exposure to pathophysiological concentrations of ammonia. Intracellular acidification, measured from the chemical shift of endogenous inorganic phosphate, was observed without any change in cellular energy status or concentrations of lactate, glutamate and glutamine. The initial acidification, which developed over a period of 9 min appeared to be heterogeneous, on the basis of a splitting of the inorganic phosphate resonance in a number of experiments, corresponding to pH changes of 0.07 and 0.27 pH units. Subsequently a homogeneous acidification, of 0.15 pH units, developed by 23 min following exposure to ammonia. Intracellular pH recovered within 6 min after discontinuation of the ammonia load. In the absence of external bicarbonate, intracellular pH was 0.12 units more acidic than in the bicarbonate buffer and ammonia caused a further acidification by 0.16 units. When glutamine synthase inhibitor, methionine sulphoximine, was added, there was a slow fall in intracellular pH. Under these conditions, subsequent addition of ammonia failed to cause acidification directly. Thus acute elevation of ammonia does not lead to a change in cerebral high-energy phosphate or lactate metabolism, but may be associated with a fall in cortical intracellular pH.

Acute cerebral ischaemia: concurrent changes in cerebral blood flow, energy metabolites, pH, and lactate measured with hydrogen clearance and 31P and 1H nuclear magnetic resonance spectroscopy. III. Changes following ischaemia

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anaesthesia. At the same time, intracellular pH and the concentrations of lactate and high-energy phosphates were measured in the brain using 1H and 31P nuclear magnetic resonance spectroscopy. Flow and metabolism have been followed during either a 15- or a 30-min ischaemic period (induced by bilateral carotid occlusion) and for up to 1 h of recovery. There was no significant difference between the flow characteristics of the two experimental groups. High-energy phosphate levels and pH returned to control within approximately 20 min of the end of the ischaemic period. Lactate clearance, following a 30-min occlusion, was slower than the recovery of pH. The concentration of free ADP, calculated from the creatine kinase equilibrium, was lower during the recovery phase than under control conditions.

The role of the carbon dioxide laser in treatment of carcinoma of the tongue

This paper presents 35 patients with carcinoma of the tongue who have been treated in Southampton using the Carbon Dioxide laser. The treatment programme for each individual patient was determined by radiotherapists and surgeons in a combined head and neck/oncology clinic. T1 carcinomas were treated by primary laser excision biopsy whereas larger tumours were treated first by conventional radiotherapy unless there was a significant contraindication to this treatment modality. Of 10 patients with T1 lesions nine are alive and well and disease free, but one patient died of other causes with no sign of recurrence. The minimum follow-up period has been two years. Of 25 patients with T2 and T3 lesions treated either before or after radiotherapy, nine are alive and disease-free, eleven died of disease and five patients died of other causes with no evidence of recurrence.

Quantitative estimation of lactate in the brain by 1H NMR

1H NMR was used to detect lactate accumulation in the intact gerbil brain postmortem. The lactate concentration was estimated from the spectra by comparison to signals from N-acetylaspartate, creatine + phosphocreatine, and water. The effects of T2, phase modulation, and solvent suppression were taken into account. The estimated concentrations were compared to determinations performed on the same brains after extraction. The lactate concentration estimated from the intact brain spectra was between 70 and 90% of the values determined in vitro, on the extracts, depending on the concentration standard used. If N-acetylaspartate was used as the standard then the proportion of detected lactate (92%) was not significantly different from 100%.

Three solutions for preservation of the rabbit heart at 0 degree C. A comparison with phosphorus-31 nuclear magnetic resonance spectroscopy

Phosphorus-31 nuclear magnetic resonance has been used to measure changes in tissue adenosine triphosphate and pH that occur during hypothermic preservation of rabbit hearts. Three potential preservation solutions were studied: the St. Thomas' Hospital no. 1 cardioplegic solution, Bretschneider's HTP solution, and a solution originated in our laboratory, CP5, which we have previously studied in the rabbit heart with functional assessment by Langendorff perfusion. After being flushed with one of these solutions, each heart was stored at 0 degrees C for 12 hours, during which time it was subjected to repeated phosphorus-31 nuclear magnetic resonance scans. It was shown that adenosine triphosphate levels decayed more slowly with CP5 than with either of the other solutions or in the control experiments. Adenosine triphosphate decay was also slower with Bretschneider's HTP than with St. Thomas' Hospital solution, but pH was somewhat better maintained with Bretschneider's HTP than with either other solution or in the control hearts, although the pH did not decrease drastically in any group. CP5 was designed to prevent cell swelling and to reduce the uptake of calcium during storage, for which reasons it contains 30 mmol/L glucose and 0.1 mmol/L calcium. The potassium content is somewhat higher and the sodium and magnesium content somewhat lower than in St. Thomas' Hospital solution, with the objective of stabilizing intracellular concentrations of these ions during storage.

Does exposure of preovulatory oocytes to ultrasonic radiation affect reproductive performance?

Ultrasonography of preovulatory oocytes has been reported to lead to reduced litter size in rats. Because of the growing popularity of ultrasound-guided follicular aspiration in human in vitro fertilization programs, further study of ultrasonic radiation's effect on the preovulatory oocyte is warranted. We used 106 virgin Sprague-Dawley rats which, on the evening of proestrus, received ultrasonic radiation of sham treatment after the onset of the luteinizing hormone (LH) surge. No differences were found between control (C) and experimental (US) animals in pregnancy rate, number of corpora lutea, implantations, pups, and mean pup and placental weights at autopsy on day 22 of pregnancy. Ultrasonic radiation applied to meiotically active, preovulatory oocytes did not affect the reproductive performance of these rats.

Dose-dependent effects of postmenopausal estrogen and progestin on antithrombin III and factor XII

The frequent use of estrogen and progestin replacement for treatment in postmenopausal women makes assessment of its effect on the coagulation system of interest. Although the amount of estrogen used to achieve the desired therapeutic effect is lower than the lowest doses in oral contraception, the age and medical condition of this population may amplify any hormone-induced risk. The common impression is that postmenopausal replacement therapy does not increase risk for thromboembolic disease, but no large epidemiologic studies of estrogen replacement have addressed that question. In this randomized prospective study, we examined the effects of varying low doses of an estrogen-progestin preparation on the titers of clotting factors in postmenopausal women. The coagulation factors selected for investigation were among those that have been reported to be significantly altered in the plasma samples of high-dose estrogen users. There were no changes in prothrombin time, factor X, fibrinogen, factor VII, or fibrinopeptide A in any of the hormone-treated groups. Mild but significant shortening of the partial thromboplastin time and elevation of factor XII titer were noted in all treatment groups. The titer of antithrombin III was reduced in the group given 20 micrograms ethinyl estradiol, but not in the groups given 5 or 10 micrograms. The clinical significance of these changes is difficult to determine in postmenopausal women receiving sex hormone replacement. However, we have not noted any thromboembolic episodes in our volunteers after a 1-year follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Biotransformation of aromatic compounds. Monitoring fluorinated analogues by NMR

The results presented here illustrate the power of NMR in the non-invasive analysis of microbial transformations. Whilst the definitive identification of products requires purification and full structural elucidation. NMR can provide rapid insights into the nature of these reactions and their regulation in vivo. In addition, once the products have been identified NMR methods allow rapid assessment of the effects of genetic and physiological manipulation, and on competing metabolic fluxes with mixed substrates and branched pathways.

Acute cerebral ischaemia: concurrent changes in cerebral blood flow, energy metabolites, pH, and lactate measured with hydrogen clearance and 31P and 1H nuclear magnetic resonance spectroscopy. II. Changes during ischaemia

CBF has been measured with the hydrogen clearance technique in the two cerebral hemispheres of the gerbil under halothane anesthesia. This has been correlated with changes in local pH, tissue lactate, and phosphorus energy metabolites measured in the same animals with 1H and 31P nuclear magnetic resonance spectroscopy. We demonstrate a threshold flow value for the metabolic changes associated with energy failure at a level similar to the values previously reported for electrical failure and tissue water accumulation, but higher than that associated with breakdown of extracellular potassium homeostasis.

Intracellular metabolites in rat muscle following trauma: a 31P and 1H nuclear magnetic resonance study

Hind limb skeletal muscle was studied in vivo in a rat trauma model using nuclear magnetic resonance (NMR) spectroscopy. The model used was a 25% body surface area, full-thickness burn administered under anaesthesia. Two groups of six rats were studied. Weight loss was observed in the experimental group whilst the control group continued to gain weight. Concentration ratios involving intramyocellular phosphocreatine (PCr), creatine (Cr), adenosine triphosphate (ATP), inorganic phosphate (Pi), anserine (Ans) and taurine (Tau) were measured. No change in the ratios of PCr/Pi, PCr/ATP, Ans/PCr + Cr and Tau/PCr + Cr were seen between the two groups. Intracellular pH was the same in the two groups. NMR spectroscopy in vivo gives values of Pi and PCr that differ from those obtained by conventional techniques. NMR values are probably more accurate as no degradation occurs during measurement, the measurements being repeatable and noninvasive.

Spectral resolution in clinical magnetic resonance spectroscopy

We observe linewidths of 0.1-0.4 ppm in 31P spectra of human muscle, liver, and brain. T2 measurements of muscle phosphocreatine, together with previous brain studies, indicate that further improvements in linewidth to 0.02-0.05 ppm might often be achieved, but in some lesions magnetic susceptibility variations may limit spectral resolution.