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Biomedical subjects

G R Newman

Publications and source records attributed to G R Newman.

51 records · Page 3Linked to original sources
PubMed1983

A simple post-embedding system for the rapid demonstration of tissue antigens under the electron microscope.

A simple and versatile technique for the preparation of ultra-thin sections, which can be stained immunohistochemically directly on electron microscope grids, is presented. An anti-hapten immunoperoxidase procedure has been adapted for use on tissue fixed in a purified monomeric glutaraldehyde--picric acid mixture, and embedded in 'L R White', a recently formulated plastic resin. This plastic tolerates the use of partial dehydration of tissue, resulting in higher antigenic yields. In addition, no etching of ultra-thin sections is necessary, and the whole immunostaining procedure can be completed in less than 2 h. A comparison of commonly used fixatives is discussed. High-resolution micrographs showing general staining (uranyl acetate--lead citrate) of rat pancreas, and immunostaining of insulin and TSH in storage granules in perfusion-fixed rat tissue and of lambda-chain immunoreactive cells in immersion-fixed human tonsil are included as examples.

Animals↗
PubMed1983

Receptor secretion hypothesis for regulation of hormone action.

It is well established that modulation of target cell responses to hormonal stimulation can occur through variation of the number of effective hormone receptors per cell. Recent experimental evidence suggests that an alternative or additional autoregulatory mechanism may operate via secretion by the cell of 'receptors' which can bind to, and thereby regulate, the concentration of free hormone in the extracellular space. We present here a brief general analysis of this 'receptor-secretion' model, together with an example which shows that it can readily account for the phenomenon of self-limiting growth seen in many tissues in response to sustained hormonal stimulation. The biological significance of the model is discussed, and the close analogy with B-lymphocyte regulation pointed out. Finally, two important implications are considered, for the pathogenesis of nodular hyperplasia and tumours in hormonally-controlled tissues.

Homeostasis↗
PubMed1983

Metal compound intensification of the electron-density of diaminobenzidine.

Diaminobenzidine (DAB), commonly used in immunocytochemistry as the substrate for peroxidase, has a low electron density. DAB has a known affinity for the salts of some metals and therefore an examination of the ability of six metal compounds (including osmium tetroxide) to increase the electron density associated with DAB deposits has been undertaken. Ultra-thin sections of unosmicated rat pituitary gland, embedded in L. R. White resin, were immunostained by a hapten sandwich immunoperoxidase method, using antibodies to ACTH and TSH. The unintensified electron density of the DAB polymer reaction product on the specific endocrine granules was compared with the electron density resulting from the use of each of the six metal compounds. Lead and silver nitrate gave unsatisfactory results, while phosphotungstic acid and uranyl acetate produced a limited increase in specific electron density under the conditions used. Gold chloride was found to give the highest electron density to the specific endocrine granules, followed closely by osmium tetroxide. Background staining was greater when osmium was used. We conclude that several metal compounds may be used to intensify the electron density of DAB, but of the ones tested, gold chloride, which is safer, more stable, and cheaper than osmium tetroxide, was clearly the best. This approach not only increases the electron density of the DAB reaction product, but allows of the possibility of quantitation using energy dispersive X-ray analysis.

3,3'-Diaminobenzidine↗
PubMed1981

A study of amyloid arthropathy in multiple myeloma.

Forty-three patients with classical multiple myeloma were studied to assess the prevalence and characteristics of amyloid arthropathy using clinical, radiological, and histological methods. Two patients were found to have amyloid arthropathy, and a third case is described in detail. Complement and cryoprecipitate analysis of the synovial fluid, and electronmicroscopy of the synovium, synovial debris and cartilage were undertaken in an attempt to shed further light onto the pathogenesis of what has hitherto been regarded as a rare complication of multiple myeloma. Complement components were not depressed and no evidence of specific light chain containing immune complexes was found in synovial fluid cryoprecipitates. Histochemical and electron microscopic localization of amyloid in perichondrocytic lacunae as well as in synovial fluid debris, synovium and the articular cartilage surface suggest the possibility that chondrocytes and synovial macrophages may share a role in processing immunoglobulin components as a prelude to the formation of amyloid fibrils. Amyloid arthropathy occurs in about 5 per cent of patients with multiple myeloma. The clinical picture can resemble rheumatoid arthritis with median nerve compression in the carpal tunnel and symmetrical arthritis of the wrists and small joints of the hands. Diagnosis can be established by examination of Congo red stained synovial fluid sediments under polarized light even in the absence of other clinical features of amyloidosis and when rectal biopsy is negative.

Aged↗
PubMed1978

Preparation and characterization of liposomes containing the Ca2+-activated photoprotein, obelin.

1. Liposomes bearing different net surface charges have been prepared and their ability to entrap the Ca2+-activated photoprotein, obelin, has been studied 2. Negatively-charged liposomes, composed of egg-yolk lecithin, cholesterol and phosphatidylserine, consistently produced the most homogeneous populations of liposomes after sonication, as shown by electron microscopy after negative staining. These consisted of a large proportion of uni- and bilamellar vesicles within the size range of 20--50 nm, external diameter. 3. Sonicated negatively-charged liposomes had a mean aqueous obelin space of 6.8 +/- 0.8 microliter/mumol of phospholipid compared to a mean space for inulin [14C]carboxylic acid of 5.1 +/- 0.8 microliter/mumol of phospholipid. 4. Sonication reduced the Ca2+ permeability of the negatively-charged liposomes, as measured by the utilization of entrapped obelin. 5. Preparations of uncharged (no phosphatidylserine) and positively-charged (stearylamine instead of phosphatidylserine), sonicated liposomes contained a greater proportion of larger vesicles, which were more permeable to Ca2+ than sonicated, negatively-charged liposomes. 6. Obelin, trapped within sonicated, negatively-charged liposomes, responded to increases in the free Ca2+ concentration within the liposomes caused by the bivalent-cation ionophore A23187 at concentrations as low as 19 nM. 7. The effect of A23187 was inhibited by Mg2+ at a low concentration of Ca2+ (10 muM), but not at 1 mM Ca2+. 8. It was concluded that obelin could be trapped in the aqueous compartment of sonicated liposomes which remained relatively impermeable to Ca2+. Furthermore, trapped obelin could respond to changes in the free Ca2+ concentration within these liposomes.

Calcimycin↗
PubMedDate not supplied

Tobacco and alcohol use in G-rated children's animated films.

CONTEXT: Tobacco and alcohol use among youth are major public health problems, but the extent to which children are routinely exposed to tobacco and alcohol products in children's films is unknown. OBJECTIVE: To identify the prevalence and characteristics associated with tobacco and alcohol use portrayed in G-rated, animated feature films. Design All G-rated, animated feature films released between 1937 and 1997 by 5 major production companies (Walt Disney Co, MGM/United Artists, Warner Brothers Studios, Universal Studios, and 20th Century Fox) that were available on videotape were reviewed for episodes of tobacco and alcohol use. MAIN OUTCOME MEASURES: Presence of tobacco and alcohol use in each film, type of tobacco or alcohol used, duration of use, type of character using substance (bad, neutral, or good), and any associated effects. RESULTS: Of 50 films reviewed, 34 (68%) displayed at least 1 episode of tobacco or alcohol use. Twenty-eight (56%) portrayed 1 or more incidences of tobacco use, including all 7 films released in 1996 and 1997. Twenty-five films (50%) included alcohol use. Smoking was portrayed on screen by 76 characters for more than 45 minutes in duration; alcohol use was portrayed by 63 characters for 27 minutes. Good characters use tobacco and alcohol as frequently as bad characters. Cigars and wine are shown in these films more often than other tobacco or alcohol substances. CONCLUSIONS: More than two thirds of animated children's films feature tobacco or alcohol use in story plots without clear verbal messages of any negative long-term health effects associated with use of either substance.

Alcohol Drinking↗
PubMedDate not supplied

Multiple hormone storage by 'polycrine' cells in the pancreas (from a case of nesidioblastosis).

Pancreatic tissue from a case of neonatal hypoglycaemia with nesidioblastosis has been studied by routine light and electron microscope techniques and by highly sensitive light and electron microscope immunolocalization methods. A hyperplastic nodule within the pancreas from this case contained enlarged distorted haemorrhagic islets, with a variable rim of exocrine tissue. Islet cells in these areas were shown to contain more than one hormone in separate granules. An immunoperoxidase system using hapten-labelled primary antibodies and photochemical amplification applied to serial semithin sections suggested a consistent overlap between insulin and glucagon immunoreactive cells. Serial ultrathin sections of tissue embedded in LR White showed that some heteromorphous cells with predominantly beta-granules also contained a minority population of granules which had either glucagon or glicentin immunoreactivity. In adjacent studies, the same techniques confirmed that the majority population of granules did indeed contain insulin, and immunocolloidal gold methods were used to show that glucagon and glicentin containing granules were present in the same cells. The significance of these findings is discussed, including the possibility that cells containing more than one granule type might represent a subpopulation of facultative cells in transit from producing one hormone to producing a second. The importance of sensitive immuno-electron microscopy in the investigation of endocrine lesions is stressed.

Cytoplasmic Granules↗
PubMedDate not supplied

[Psychological theories on delinquency].

The authors review the various psychological explanations of delinquency, based on a psycholgoical etiological approach, considered within three broad categories: 1) Unchanging intrapersonal factors; 2) Changeable intra-personal factors, and 3) Interpersonal factors. For each theory, three criteria of validity have been used, based on the theory explanatory power in relation to: 1) the differential rates of deliquency for various subgroups, and the peaking at age 16; 2) the various forms of delinquent behavior, and, 3) the individual motivations to delinquency. The implications for prevention, of the different theoretical approaches, are also briefly discussed. The interpersonal theories appear to offer the most fruitful research and action opportunities. The practical implications for primary prevention, particularly at the school level, are discussed.

Adolescent↗