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Biomedical subjects

J N Scott

Publications and source records attributed to J N Scott.

16 recordsLinked to original sources
PubMed1991

Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney.

The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques 1) to identify possible sites of synthesis; 2) to compare the localization of ANP to known physiological effects; 3) to determine species differences, if any, in ANP localization; and 4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP, IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.

Amino Acid Sequence↗
PubMed1991

Localization of 125I-atrial natriuretic peptide (ANP) in the rat fetus.

In this in vitro autoradiographic study of ANP-binding sites in fetal rats, 125I-ANP bound to receptors in certain developing neural crest derivatives, including the boundary caps, dorsal root ganglia, and Schwann cells of peripheral nerves. Within the spinal cord, ANP receptors were localized in the roof plate and floor plate. The developing meningeal layer of the CNS, blood vessels, lung, liver, and wall of the herniated gut were also labeled. The topographical and temporal correlation of the appearance of ANP receptors with the developmental processes of the targets suggests that ANP in the fetus is multifunctional, and may be involved in diverse events such as gliogenesis, formation of axonal pathways or surfactant production.

Animals↗
PubMed1991

Beta-amyloid precursor protein gene is differentially expressed in axotomized sensory and motor systems.

The beta-amyloid precursor protein (APP) is involved in the degenerative and regenerative neural changes associated with aging and Alzheimer's disease. We studied the regulation of APP gene expression in a paradigm of degeneration and regeneration, the axotomized rat sciatic system. The sciatic nerves of rats were crushed and at intervals between 4 and 60 days, the affected dorsal root ganglia and spinal cord segments were processed for Northern analysis and in situ hybridization to evaluate various APP mRNA species. After nerve crush, dorsal root ganglia APP mRNA levels are increased for both APP695 (695 amino acids) and APPKPI (Kunitz protease inhibitor). Following reinnervation, APP695 returns to baseline but APPKPI remains elevated. In spinal cord there is a decrease of APP695, which returns to baseline following reinnervation. If regeneration is prevented, the initial phase of post-axotomy response for all APP forms persists for at least 60 days in both dorsal root ganglia and spinal cord. In situ hybridization confirms that the changes are referable to neurons. These findings indicate that neuron-target interactions are important in APP gene regulation; that the APP695 and APPKPI transcripts are differentially regulated following neuronal injury; and that different neuronal populations regulate APP expression in a cell-type specific manner.

Amyloid beta-Protein Precursor↗
PubMed1989

Ontogeny of atrial natriuretic peptide receptors in fetal rat kidney and adrenal gland.

With in vitro autoradiography, specific receptors for atrial natriuretic peptide (ANP) were localized in fetal rat kidney and adrenal glands. Receptors were present over renal vesicles, in the primitive renal medulla and throughout the adrenal gland as early as 16 days gestation. By 20 days gestation, several layers of developing renal corpuscles were present and ANP receptors were localized over developing glomeruli in each layer. Larger accumulations occurred over the juxtamedullary glomeruli. In the medulla, the receptors were localized in a reticular pattern near the pelvis. With emulsion coated sections, ANP receptors in developing renal corpuscles were seen primarily over the lower curve of S-shaped vesicles and around the periphery of the more mature corpuscles. In the renal medulla, receptors were localized over the interstitial cells. In the 16-day-old adrenal gland, ANP receptors were present throughout the cortical area but at 20 days gestation and 1 day postpartum receptors appeared more numerous in the peripheral region. These data suggest that ANP has important developmental effects in the kidney and adrenal gland and may be involved in regulation of body fluid homeostasis in the late gestation rat fetus.

Adrenal Glands↗
PubMed1988

Development of immunoreactive atrial natriuretic peptide in fetal hearts of spontaneously hypertensive and Wistar-Kyoto rats.

The development of immunoreactive atrial natriuretic peptide (ANP) was studied in fetal hearts of spontaneously hypertensive (SHR) and compared to normotensive Wistar-Kyoto (WKY) rats. While SHR fetal hearts were noticeably less developed than those of WKY at 10 and 11 days gestation, both strains showed ANP immunoreactive cells in some but not all primitive heart tubes. At 12 days additional ANP immunoreactive cells appeared in formative trabeculae of the ventricle and atrium. ANP cells were also observed in the myogenic layer of the truncus and bulbus arteriosus and their derivatives from 11 through 16 days, but not at 18 days. In both strains, there were more ANP cells in the left ventricle than in right beginning at day 13. There were no obvious strain differences in the developmental pattern and timing of ANP producing cells. However, on the day of birth, staining was reduced in hearts from some WKY newborn pups compared with hearts from SHR newborns and ventricular staining was reduced in both strains when compared to fetal hearts. These observations indicate that ANP is one of the earliest peptide hormones produced and that the predisposition to genetic hypertension does not appear to influence the development of ANP.

Animals↗
PubMed1988

Disability and dependency in elderly people in residential and hospital care.

Physical dependency and mental impairment were assessed in 143 residents of residential accommodation for the elderly and 125 patients in geriatric continuing-care wards in South Belfast. Although dependency, immobility and incontinence were more common in the hospital patients, there was considerable overlap in the disability levels in the two types of care. There was evidence of dementia in 51% of the residents and 71% of the patients, while 29% of residents and 70% of patients were incontinent. Overall, less than 1% of the elderly population was in each of residential or geriatric hospital care but the proportion rose with age and was greater in older women. About 17% of elderly people in South Belfast with dementia were in residential or geriatric hospital care. The projected increase in the number of oldest people, particularly women, and the increased risk of dementia in this age group, means that the need for residential and continuing hospital care for the elderly will continue to increase.

Age Factors↗
PubMed1988

Psychology of computer use: V. Computer use and the experience of time.

To determine whether estimates of duration are altered when people use computers, 60 undergraduates solved easy or difficult single-solution anagrams presented on paper and by computer. Subjects who solved easy anagrams presented on paper underestimated the duration of time allowed for the task, while subjects who completed the anagrams presented by computer overestimated that duration. Also, subjects who solved difficult anagrams presented on computers solved significantly fewer anagrams than did subjects who solved difficult anagrams presented on paper. Results are discussed in terms of contradictory results of past research regarding perceived complexity of events in intervals and the interaction of task type and time estimation.

Data Display↗
PubMed1987

Distribution of atrial natriuretic factor in fetal rat atria and ventricles.

An immunohistochemical study of rat fetal hearts at 20 days of gestation revealed the presence of immunoreactive atrial natriuretic factor (ANF) in cardiocytes of the left and right atria as well as in certain cells is the left and right ventricles. In the atria, cells of the adluminal pectinate muscles appear more densely labeled than the more peripheral mural cells. In the ventricles, immunoreactive cells were found only in adluminal cardiocytes of the presumptive trabeculae and papillary muscles. The results indicate that ANF is synthesized in the perinatal heart, and that the presence of this hormone in the ventricular cardiocytes may be of only temporary nature during certain stages of pre- and postnatal development.

Animals↗
PubMed1985

Effect of small doses of aspirin and acetaminophen on total menstrual loss and pain of cramps and headache.

90 women participated in a 4-month study. During the first 2 periods, they took no pain relievers whatsoever; during their last 2 periods they took 2 X 325 mg aspirin, acetaminophen or an identically packaged placebo every 4 h to total 8 tablets during the first 24 h of their periods beginning with spotting. For statistical analysis, periods 1 and 2 were combined and averaged, then compared with periods 3 and 4 combined and averaged. Total menstrual loss in grams, number of days of flow, and pain of cramps and headaches were analyzed by MANOVA for each of the three treatment groups. An ANOVA for each of these variables as well as for daily menstrual loss for the first 3 menstrual days was also performed. The MANOVA for all variables by the three treatment groups failed to show any significant differences. Similarly, ANOVAs for the individual variables failed to indicate significant differences except for the variable pain of cramps (p = 0.0072). The Duncan's Multiple Range Test for pain of cramps showed that the average pain for the placebo group was higher than for either the aspirin or the acetaminophen group, although the means for these two groups were not significantly different. These results indicate that neither aspirin nor acetaminophen in the doses given alter either total menstrual loss or the pattern of loss during the first 3 menstrual days. However, both preparations were found to be more effective than placebo in reducing pain of cramps.

Acetaminophen↗
PubMed1985

Placentas from spontaneously hypertensive rats and control strain Wistar-Kyoto rats.

Placentas from spontaneously hypertensive rats (SHR) were compared to those of control strain Wistar-Kyoto rats (WKY) at 15, 18 and 20 days of gestation using light microscopic techniques. Placental lesions similar to those in pregnant hypertensive women were absent in both strains; however, other abnormalities were noted. Hemorrhage at the lateral edges of the decidua basalis appeared to be more extensive in the SHR than WKY at 15 days. At the same time, bloody vaginal discharges were noted in 18% of the SHR. Leukocytic encapsulation of 20-day placentas with viable fetuses was noted in two SHR dams but not in any WKY. It is thought that these differences may be related to the high maternal blood pressure in the SHR or to hormonal imbalance associated with the stress response in the SHR due to frequent monitoring of blood pressure.

Animals↗
PubMed1979

Response to cryptorchidism of the testis and epididymis of the opossum (Didelphis virginiana).

Adult male opossums, Didelphis virginiana, were rendered hemicryptorchid for 35 days. The cyrptorchid testis exhibited a significant reduction in weight, while the contralateral testis had a compensatory weight gain compared with testes of untreated animals. Histological changes in the cryptorchid testis included fibrosis of the tunica propria, involution of the seminiferous tubules and an apparent increase in the interstitial tissue. Many seminiferous tubules were empty and germinal cells were absent. Some Sertoli cells persisted, but the cytoplasm was vacuolated. Cryptorchid testes were characterized by mononuclear leucocytic invasion around the tubules, and some eosinophils were observed. Cryptorchidism in the opossum may induce a reaction similar to experimental orchitis.

Animals↗
PubMed1977

Microscopy of the junctional region between human coronal primary and secondary dentine.

The juction between human primary dentine and regular and irregular secondary dentine was examined with a number of different light and electron microscopic techniques. In decalcified material, a narrow band along the innermost surface of the primary dentine stained intensely. The walls of the tubules within the band stained intensely, whereas the tubular walls within the bulk of the primary dentine were not stained. Generally, the walls of the tubules in both types of secondary dentine were also preferentially stained. Although not readily apparent in ground sections, observations of thin sections revealed a dramatic reduction in the number of tubules in regular secondary dentine. Generally, the radiodensity of the intertubular matrix was the same in primary and secondary dentine and the intensely stained band was not seen radiographically. The pulpal ends of the tubules in primary dentine were often occluded with a material having the same radiodensity as peritubular matrix. Both patent and occluded tubules were seen in irregular secondary dentine. Scanning electron microscopy of acid-etched specimens of secondary dentine revealed that some tubules had irregular walls of highly mineralized matrix which was less acid-soluble then the peritubular matrix of primary dentine.

Cuspid↗
PubMed1977

Radioactivity in pituitaries and cerebrums of neonatal rats following [3H]-estradiol administration.

The uptake of radioactivity by the pituitary, cerebrum and muscle of female and male neonatal and prepuberal rats 1 hour after administration of [3H]-estradiol was measured by liquid scintillation. Tissues were homogenized and aqueous, lipid, and protein-nucleoprotein fractions were separated for quantification of radioactivity. No significant sex differences in the radioactivity associated with the pituitary fractions were noted at any of the ages studied.

Animals↗
PubMed1976

The interrelation of LH-RH, ovarian steroids and the adenohypophysis.

In this presentation experimental evidence is reviewed and new information is presented concerning the question of cyclic fluctuations in pituitary responsiveness to endogenous and exogenous hypothalamic-releasing hormones as well as the direct role of steroids in modulating pituitary sensitivity. Experiments are described which show that four-day and five-day cyclic rats respond differently to LH-RH, presumably because of differences in secretion patterns of ovarian steroids. The direct role of these steroids in this process was investigated both from the morphological (light and electron microscopy) and physiological (radioimmunoassay measurement of LH) viewpoint in hypophysectomized rats bearing pituitary homografts. It was found that steroids may directly alter both the morphology and the secretory function of pituitary gonadotrophs. Estradiol was found to depress the amount of LH that was secreted while progesterone was seen to influence primarily the time of LH release following LH-RH injection. Thus, it appears that direct feedback effects of ovarian steroids at the level of the pituitary are important regulators of the sensitivity of pituitary gonadotrophs to the LH- releaseing action of hypothalamic LH-RH.

Animals↗