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S Wray

Publications and source records attributed to S Wray.

At least 127 records · Page 7Linked to original sources
PubMed1991

Spatially restricted expression of a member of a new family of murine Distal-less homeobox genes in the developing forebrain.

The homeobox genes of Drosophila perform key functions in embryonic pattern formation, and their vertebrate counterparts may play similar developmental roles. Using polymerase chain reaction technology, we have identified four murine homologs of the Drosophila Distal-less homeobox gene that are expressed in midgestation embryos. The homeodomains encoded by these genes vary considerably from other known homeodomain sequences and represent a new family of vertebrate homeobox genes. We isolated a cDNA for one of these genes (Dlx-2) and studied its expression by in situ hybridization from 8.5 days postcoitum (pc) until postnatal day 1. Dlx-2 shows a restricted pattern of expression in the ventral forebrain, extending from the olfactory bulb to the ventral diencephalon. This domain of expression may delineate an ontogenetically defined subdivision within the forebrain. The murine Distal-less genes are the first homeobox genes described whose expression in the central nervous system is exclusively restricted to the forebrain. Thus, the Distal-less genes may contribute missing positional cues not provided by the previously identified vertebrate homeobox genes.

Amino Acid Sequence↗
PubMed1990

The effects of metabolic inhibition on uterine metabolism and intracellular pH in the rat.

1. Uterine metabolism was studied in pregnant and non-pregnant rats by measuring high energy phosphates and intracellular pH (with 31-phosphorus nuclear magnetic resonance (31P NMR) spectroscopy) and lactic acid efflux. Isolated, superfused uteri were investigated during control conditions (30 degrees C) and in the presence of metabolic inhibitors and high [K+]. 2. In control conditions the ratio of phosphocreatine and ATP concentrations ([PCr]/[ATP]) was higher in the pregnant (0.88 +/- 0.09) than the non-pregnant uterus (0.52 +/- 0.04). When oxidative phosphorylation was inhibited by cyanide, there was a significant (P less than 0.01) decrease in [PCr] and [ATP] and an increase in the concentration of inorganic phosphate ([Pi]). These changes were greater in the non-pregnant than the pregnant uterus. 3. There was no difference in the mean value of resting pHi found in pregnant and non-pregnant uterus (7.19 +/- 0.04 and 7.17 +/- 0.03, external pH 7.4, n = 10 and 12 respectively). There was a significant intracellular acidification in both pregnant (0.31 +/- 0.04 pH unit) and non-pregnant (0.27 +/- 0.02 pH unit) uterine tissue in the presence of cyanide. These effects of cyanide on metabolites and pHi were fully reversed upon return to control solutions. 4. When both aerobic and anaerobic glycolysis were blocked by iodoacetate, there was a rapid disappearance of high energy phosphates from the 31P NMR spectrum and a large increase in the phosphomonoester spectral region, where sugar phosphate intermediates of glycolysis resonate. These changes were seen in both pregnant and non-pregnant uteri and were irreversible. 5. Lactate production was detected, in the presence of oxygen, in both pregnant and non-pregnant preparations (0.43 +/- 0.07 and 0.25 +/- 0.09 mumols g-1 min-1, respectively). In both preparations the rate of lactate production was markedly increased in the presence of cyanide. The increase was much more marked in non-pregnant (approximately 10-fold) than pregnant (approximately 5-fold) uteri, resulting in a very similar rate of lactate efflux in cyanide. 6. When lactate efflux in non-pregnant uteri was blocked by alpha-cyano-4-hydroxycinnamate, there was a significant acidification (0.21 +/- 0.04 pH unit, n = 6). The addition of cyanide produced a more pronounced acidification (0.34 +/- 0.04 pH unit) than that seen with either cyanide or alpha-cyano-4-hydroxycinnamate alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Quantitation of cerebral blood volume in human infants by near-infrared spectroscopy.

Current methods for measuring cerebral blood volume (CBV) in newborn infants are unsatisfactory. A new method is described in which the effect of a small change (5-10%) in arterial oxygen saturation (SaO2) on cerebral oxyhemoglobin [HbO2] and deoxyhemoglobin [Hb] concentration is observed by near-infrared (NIR) spectroscopy. Previous experiments in which the NIR absorption characteristics of HbO2 and Hb and the pathlength of NIR light through the brain were defined allowed changes in [HbO2] and [Hb] to be quantified from the Beer-Lambert law. It is shown here that CBV can then be derived from the expression CBV = (delta[HbO2] - delta[Hb])/(2. delta SaO2.H.R.), where H is the large vessel total hemoglobin concentration and R to the cerebral-to-large vessel hematocrit ratio. Observations on 12 newborn infants with normal brains, born at 25-40 wk of gestation and aged 10-240 h, gave a mean value for CBV of 2.22 +/- 0.40 (SD) ml/100 g, whereas mean CBV was significantly higher 3.00 +/- 1.04 ml/100 g in 10 infants with brain injury born at 24 to 42 wk of gestation and aged 4-168 h (P less than 0.05).

Blood Volume↗
PubMed1989

Spatiotemporal cell expression of luteinizing hormone-releasing hormone in the prenatal mouse: evidence for an embryonic origin in the olfactory placode.

The spatiotemporal cell expression of luteinizing hormone-releasing hormone (LHRH) was investigated in mice during prenatal development using light microscopic immunocytochemistry. LHRH immunoreactive cells were first detected in the epithelium of the olfactory pit on gestational day 11 1/2 (E11.5). Some LHRH cells were just outside the olfactory epithelium (OE), clustered on short 'tracks' which extended dorsocaudally. Immunopositive LHRH cells were not observed in any other regions. At E12.5, immunopositive cells were still detected in the OE, but now many LHRH cells were clustered on 'tracks' within olfactory areas. These 'tracks' started at the OE, bilaterally, and extended towards and abutted the basal telencephalic hemispheres. Some immunopositive cells were detected in the rostral telencephalon but not caudal to the telencephalon. The LHRH cells outside the OE were unipolar or bipolar, morphologically resembled mature LHRH neurons and appeared to contact neighboring LHRH cells. The distribution of LHRH cells at E13.5 was similar to E12.5, with the exception that immunopositive cells now extended from the telencephalon to the rostral diencephalon. From E14.5 to E17.5 the majority of LHRH cells were located within the forebrain; extending throughout the diencephalon. Immunopositive cells were not detected in the OE, but were scattered rostrocaudally in olfactory septal areas. By E16.5, LHRH cells within the brain were distributed in a pattern similar to that of the adult mouse. These findings illustrate that LHRH cells express their peptide phenotype early in ontogeny and before their distribution in the forebrain is detected. These data are consistent with the hypothesis that LHRH cells are derived from the olfactory placode and migrate into the forebrain during prenatal development.

Animals↗
PubMed1989

Prenatal ontogenesis of pro-opiomelanocortin in the mouse central nervous system and pituitary gland: an in situ hybridization and immunocytochemical study.

Pro-opiomelanocortin (POMC) mRNA detected by in situ hybridization and POMC/ACTH (adrenocorticotropin)-containing neurons detected by immunocytochemistry were first observed in the presumptive arcuate nucleus of embryonic mouse brain on gestational day 10.5 (E10.5). Immunostained fibers were also evident on E10.5 in the lateral and dorsal diencephalon. In these areas, a dense network of processes developed by E11.5 and extended into the mesencephalon. Fibers were detected in the myelencephalon at this stage and a day later (E12.5) in the spinal cord. Adult-like patterns of POMC/ACTH fibers were established in the diencephalon, mesencephalon, metencephalon and the myelencephalon between E13.5 and E15.5. POMC-expressing cells in the anterior and intermediate lobes of the pituitary gland appeared on E12.5 and E14.5, respectively. The early expression of POMC and the rapid establishment of dense fiber tracts in the brain is consistent with a role for POMC-derived peptides in the development of the central nervous system.

Animals↗
PubMed1989

Neurovisual outcome following proton radiation therapy.

From February 1981 to January 1984, 20 patients with a tumor of the upper clivus received proton irradiation at the Harvard Cyclotron Laboratory. For 15 patients with known neurovisual status (including visual acuity, color vision, visual field, and fundus examinations) we obtained a cumulative dose-volume histogram (DVH) of the optic nerves (ON) and the optic chiasm. The prescribed tumor doses ranged from 66.6 to 74.4 Cobalt Gray Equivalent (CGE) with a daily fraction size of 1.8 to 2.1 CGE. CGE is used because modulated protons have an RBE of 1.1 compared to 60Co. The follow-up ranged from 30 to 68 months (median 52). Two patients developed, 10 and 36 months post irradiation, a progressive visual deterioration affecting both eyes. This was attributed to an ON and a chiasm injury in one patient and to bilateral ON injury in the other patient. In the first patient, the dose-volume analysis indicated that approximately half of the ON and of the chiasm had received 65 CGE and 55 CGE, respectively. In the second patient, it indicated that a quarter of the left ON (LON) had received 55 CGE whereas the dose to the right ON (RON) was significantly less. This patient had diabetes mellitus which may be a predisposing factor. From this study, a complication rate of 20% (1/5) is observed when a substantial portion of the ON is taken to 65 CGE, while it doesn't exceed 12.5% (2/16) and 7.5% (1/13) at 55 CGE for the ON and for the chiasm, respectively. This suggests a tolerance dose implying a 10% rate of major complications close to 55 CGE. When a tumor requires a high radiation-dose, the exclusion of these structures at 55 to 60 Gy is recommended.

Adult↗
PubMed1989

Evidence that cells expressing luteinizing hormone-releasing hormone mRNA in the mouse are derived from progenitor cells in the olfactory placode.

In situ hybridization histochemistry and immunocytochemistry were used to study the prenatal expression of luteinizing hormone-releasing hormone (LHRH) cells in the mouse. Cells expressing LHRH mRNA and peptide product were first detected on embryonic day 11.5 (E11.5) in the olfactory pit. On E12.5, the majority of LHRH cells were located on "tracks" extending from the olfactory pit to the base of the telencephalon. From E12.5 to E15.5, LHRH cells were detected in a rostral-to-caudal gradient in forebrain areas. Prior to E12.5, cells expressing LHRH mRNA were not detected in forebrain areas known to contain LHRH cells in postnatal animals. Quantitation of cells expressing LHRH mRNA showed that the number of labeled cells on E12.5 (approximately 800) equaled the number of LHRH cells in postnatal animals, but more than 90% of these cells were located in nasal regions. Between E12.5 and E15.5, the location of LHRH cells shifted. The number of LHRH cells in the forebrain increased, while the number of LHRH cells in nasal regions decreased over this same period. These findings establish that cells first found in the olfactory pit and thereafter in forebrain areas express the LHRH gene and correspond to the position of LHRH immunopositive cells found at these developmental times. To further examine the ontogeny of the LHRH system, immunocytochemistry in combination with [3H]thymidine autoradiography was used to determine when LHRH cells left the mitotic cycle. We show that LHRH neurons exhibit a discrete time of birth, suggesting that they arise as a single neuronal population between E10.0 and E11.0. Postnatal LHRH neurons were "birth-dated" shortly after differentiation of the olfactory placode and before LHRH mRNA was expressed in cells in the olfactory pit. Taken together, these studies support the hypothesis that all LHRH cells in the central nervous system arise from a discrete group of progenitor cells in the olfactory placode and that a subpopulation of these cells migrate into forebrain areas where they subsequently establish an adult-like distribution.

Animals↗
PubMed1989

Differential effects of estrogen on luteinizing hormone-releasing hormone gene expression in slice explant cultures prepared from specific rat forebrain regions.

Five serially sectioned tissue slices (400 microns) from the preoptic area/hypothalamus of postnatal day 4 rats were cultured using a slice explant roller culture technique. After 18 days in culture, these slices thinned sufficiently to allow immunocytochemical and in situ hybridization histochemical assays for LHRH peptide and LHRH mRNA, respectively. Large numbers of neurons containing mRNA encoding LHRH were detected in these slices using in situ hybridization histochemistry (ISHH). These 35S-labeled cells were distributed in the cultured slices in a pattern similar to that found with LHRH immunocytochemistry and ISHH in vivo, indicating that LHRH neurons were maintained in these cultures in an organotypic manner. Densitometric single cell analyses after ISHH of the culture slices were performed using a Loats image analysis system, so as to provide a density value per cell (density/cell). Comparisons of these density values from the slice explants cultured in presence or absence of 10(-7) M estradiol found that: 1) under basal (control) culture conditions there were no consistent differences in the frequency distributions of the density/cell values between all the five slices derived from either male or female rats, 2) mean density/culture values under control conditions did not differ significantly between slices and sexes, 3) the presence of estradiol in the culture media resulted in an overall decrease in density/cell values, with the most significant decrease occurring in slice 3 which is comparable to the level of the organum vasculosum lamina terminalis/rostral preoptic area (OVLT/rPOA) in vivo, and 4) this decrease in density/cell values in slice 3 due to estradiol treatment, was greater in cultures derived from female vs. male tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Regulation of intracellular pH in rat uterine smooth muscle, studied by 31P NMR spectroscopy.

Intracellular pH (pHi) affects smooth muscle function, yet little is known concerning its regulation. I have therefore investigated pH regulation in rat uterus, using 31P-NMR spectroscopy. A change in extracellular pH(pHe) of 1 pH unit (7.4 to 6.4) elicited a 0.29 change in pHi; smaller changes in pHe were accompanied by proportionately smaller changes in pHi. The pH changes were reversible. There was no fall of uterine ATP or phosphocreatine during the pH changes.

Adenosine Triphosphate↗
PubMed1988

Characterization of the near infrared absorption spectra of cytochrome aa3 and haemoglobin for the non-invasive monitoring of cerebral oxygenation.

Near infrared (IR) spectroscopy can give continuous, direct information about cerebral oxygenation in vivo by providing signals from oxygenated and deoxygenated haemoglobin and cytochrome aa3. Due to a lack of precise spectral information and uncertainties about optical path length it has previously been impossible to quantify the data. We have therefore obtained the cytochrome aa3 spectrum in vivo from the brains of rats after replacing the blood with a fluorocarbon substitute. Near infrared haemoglobin spectra were also obtained, at various oxygenation levels, from cuvette studies of lysed human red blood cells. Estimates of optical path length have been obtained. The data were used to construct an algorithm for calculating the changes in oxygenated and deoxygenated haemoglobin and oxygenated cytochrome aa3 in tissue from changes in near IR absorption.

Animals↗
PubMed1988

A critical assessment of methods of measuring metabolite concentrations by NMR spectroscopy.

Many NMR studies are made by scientists and clinicians in order to measure metabolite levels. There is a growing need to obtain absolute quantification of these metabolites. We have therefore reviewed the methods that are available and those which are being developed, for studies in vivo and on isolated tissues. We describe the following methods and assess their advantages and limitations: (1) Conventional spectroscopy and area ratios, (2) Tissue extracts, (3) External capillary, (4) Internal endogenous marker, (5) Internal exogenous marker, (6) External marker in bath, (7) Reference to internal 1H water concentration, (8) Gradient-localized spectroscopy and (9) Fourier series analysis localization. The relevant biological and technical aspects associated with quantification of metabolite concentrations are also discussed. This includes NMR visibility, origin of the NMR signals, definitions of concentration, influence of the RF coil, data collection and data analysis.

Humans↗
PubMed1988

Grafts containing fetal hippocampal tissue reduce activity and improve passive avoidance in hippocampectomized or trimethyltin-exposed rats.

Embryonic Day 16 or 17 rat tissue containing either hippocampus with some medial pallial anlage or cerebellar/alar plate anlage was transplanted to the site of the ablated hippocampus of otherwise normal adult rats or adult rats previously exposed to the neurotoxin trimethyltin. Ninety to one hundred five days later these rats were compared to control rats in acquisition of passive avoidance and in open field activity. Transplantation of both types of tissue produced behavioral recovery on both tasks in rats with hippocampal lesions that had not been exposed to trimethyltin. Only hippocampal transplants produced recovery of function in rats given trimethyltin. Although transplants of hippocampal tissue had an organotypic structure that was easily differentiated with cell and fiber stains from that of the cerebellar transplants, neither of these routine histological procedures nor immunocytochemical analysis revealed differences between transplants made into normal rats or toxicant-exposed rats. Either of two mechanisms may account for the ability of the transplants to produce behavioral recovery. These are reconstruction of damaged circuitry by the transplant and neurotrophic action of the developing transplant on the host brain. The second mechanism alone may be sufficient to restore function in brain-lesioned but otherwise normal rats. Therefore, either type of transplant is effective. Both mechanisms may be necessary for recovery in brain-lesioned, toxicant-exposed rats. Therefore, only transplants of tissue homotypic to the tissue removed from the brain are effective.

Animals↗
PubMed1988

Estimation of optical pathlength through tissue from direct time of flight measurement.

Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3 +/- 0.3 times the head diameter.

Animals↗