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Biomedical subjects

C M Lee

Publications and source records attributed to C M Lee.

At least 325 records · Page 18Linked to original sources
PubMed1983

Trichinella spiralis: changes in leucocytes during infection.

Rats infected with Trichinella spiralis were examined during the course of infection for various changes in the leucocytic population. In each experiment rats were divided into three groups: Group A, inoculated with Escherichia coli B-5-lipopolysaccharide (LPS) administered four days before each experiment; Group B, infected with Trichinella spiralis; and Group C, untreated controls.An extensive leucocytosis was observed in the peripheral blood and peritoneal cavity of infected rats. Regardless of the site (peripheral blood, bone marrow, peritoneal cavity), the most obvious change was an increase in eosinophils. Differential counts of peritoneal exudate cells also revealed a significant population of macrophages. Acid phosphatase activity, macrophage phagocytosis of polystyrene latex particles, and macrophage spreading revealed that peritoneal exudate cells from T spiralis-infected rats are activated from 6 to 48 days postinfection.This paper serves to reinforce existing information on the changes and state of the various leucocytic populations during infection with T spiralis and aids in assessing the activity change of macrophages.

Animals↗
PubMed1983

Interaction of nutrition and infection: effect of zinc deficiency on immunoglobulin levels in trypanosoma musculi infection.

Accumulative evidence in the scientific literature relating malnutrition and susceptibility to infection in human beings and animals has contributed significantly to the understanding of the maladies among the malnourished of the world. In the dispensation of health care systems around the world, little or no emphasis has been placed on trace-element nutrition. This paper adds to the available evidence by using a metabolic imbalance technique to investigate the effects zinc deficiency exert on the course of a parasitic infection. A model composed of zinc-deficient mice and Trypanosoma musculi was used to study changes in serum immunoglobulins.

Adult↗
PubMed1982

Dipeptidyl-aminopeptidase III of rat brain. Selective affinity for enkephalin and angiotensin.

The cytosolic dipeptidyl-aminopeptidase III (EC 3.4.14.4) from rat brain was partially purified using Arg-Arg-4-methoxy-beta-naphthylamide as a substrate. It was completely separated from aminopeptidase B on DEAE-Sephacel ion exchange chromatography. Similar to bovine pituitary dipeptidyl-aminopeptidase III, it has a pH optimum of 9, prefers Arg-Arg-4-methoxy-beta-naphthylamide as a substrate, and catalyzes the sequential release of dipeptides from the NH2 terminus of peptide substrates provided they are not smaller than a tetrapeptide. Among numerous biologically active peptides tested, angiotensins and enkephalins were the most preferred substrates with micromolar affinities, suggesting that dipeptidyl-aminopeptidase III may play a physiologic role in regulating enkephalin and/or angiotensin disposition.

Angiotensin II↗
PubMed1982

Endogenous GABA release from slices of rat cerebral cortex and hippocampus in vitro.

Using a rapid, simple and sensitive radioreceptor assay, a Ca2+-dependent K+-evoked release of endogenous GABA was demonstrated from rat cortical and hippocampal slices in vitro. This evoked-release of endogenous GABA was similar to that of [3H]GABA release (in its Ca2+ dependency) but differed from the latter in having a higher signal to noise level. Neither 5-HT nor a stable enkephalin analogue had any effect on endogenous GABA release from hippocampus slices.

Animals↗
PubMed1982

Enzymic inactivation of substance P in the central nervous system.

A membrane-bound 'substance P degrading enzyme' (EC 3.4.24.-) from human brain has been purified to apparent homogeneity. The enzyme was extracted from a membrane fraction of human diencephalon with a non-ionic detergent, Brij 35, and activity was monitored by measuring the rate of disappearance of added substance P using radioimmunoassay, bioassay or radiochemical assay. The enzyme is a thermolabile, neutral metallo-endopeptidase with a relative molecular mass of about 50000. It cleaves substance P between Gln6-Phe7, Phe7-Phe8 and Phe8-Gly9, with a ratio of 0.7:1:1. The breakdown products have been identified by a combination of reverse-phase high-performance liquid chromatography and amino acid analysis. A similar cleavage pattern of substance P has also been demonstrated in a synaptic membrane fraction prepared from rat brain, indicating that a 'substance P-degrading enzyme' is the major peptidase responsible for inactivating the peptide in rat brain membranes. The properties of this enzyme distinguished it from previously described peptidases for which substance P is a substrate. Its high selectivity and its affinity for substance P, among many other neuropeptides, suggest that it may be involved in the physiological inactivation of the peptide by neural tissues.

Animals↗
PubMed1982

Substance P receptors in the nervous system and possible receptor subtypes.

The ability of various related peptides and substance P analogues to compete for the binding of 3H-labelled substance P to rat brain membranes corresponds with their known biological activities, providing a simple model for studies of peptide receptors in the central nervous system. In salivary gland and brain slices substance P and related peptides stimulate the rate of incorporation of phosphatidylinositol, offering an alternative biochemical model for substance P receptor studies. Two types of receptor may be responsible for the actions of substance P on peripheral tissues: the SP-P type, where all tachykinins are approximately equally active, and the SP-E type, where eledoisin and kassinin are more potent than the other tachykinins. Alkyl esters of substance P appear to act as selective SP-P agonists.

Animals↗
PubMed1982

The possible existence of multiple receptors for substance P.

1. The possible existence of multiple receptors for substance P (SP) was investigated by examining the relative pharmacological potencies of SP and related peptides in contracting guinea pig ileum, in potentiating electrically evoked contractions of rat vas deferens preparations and in competing for 3H-SP receptor binding in rat brain membranes, and by comparing the extent of cross-tachyphylaxis of various analogues with SP in the guinea pig ileum. 2. Different rank orders of potencies were observed among SP, its C-terminal fragments, analogues and related tachykinins in the different test systems, and these could not be explained by differential access to the target organ receptors. 3. In contrast to SP and physalaemin, both eledoisin and a metabolically stable SP analogue, [pGlu5, MePhe8, Sar9]-SP5-11 exhibited differential recovery from SP tachyphylaxis in the guinea pig ileum, and part of their spasmogenic action in this preparation was atropine-sensitive. 4. The results suggest the possible existence of multiple SP receptors, and the specificity of those in the brain may be different from those in the gut. The structural and pharmacological basis for subdividing tachykinins into SP-physalaemin and eledoisin-kassinin families is also discussed.

Animals↗
PubMed1982

Immunoglobulin determinants on the surface of mouse splenic lymphocytes from Trypanosoma musculi-infected mice.

The splenic B-lymphocyte population of C57BL/6 mice was analyzed by flow microfluorometry to determine the relative density of surface immunoglobulin (sIg) during the course of infection with Trypanosoma musculi and after the injection of T. musculi derivatives. Cells were stained with fluorescent-conjugated antisera directed against 7S mouse immunoglobulins or the major sIg components, IgM and IgD. Evaluation of relative density of sIg was made through observation of histograms plotted by the Fluorescence Activated Cell Sorter (FACS). The FACS also provided the percentage of fluorescence-positive cells detected with each stain. The relative density of sIg was altered in all experimental groups as evidenced by abnormal histograms. These alterations in relative density of sIg persisted only on B cells of the trypanosome-infected and not the T. musculi-derivative-treated animals. The changes in sIg presumably resulted from sIgD modulation, because the histograms resulting from cells stained with anti-IgM remained unchanged. In the trypanosome-infected animals, there also was a reduction in the percentage of sIgD-positive cells near the end of the parasitemia. Observations of spleen sizes showed the same pattern of change with splenomegaly as with relative density of sIg. These data may be the result of the persistence of the parasite in host tissues after clearance of the blood infection.

Animals↗
PubMed1982

Characterization of [3H]desipramine binding associated with neuronal norepinephrine uptake sites in rat brain membranes.

A variety of evidence indicates that [3H]desipramine can label neuronal norepinephrine uptake sites in brain membranes. Pretreatment of rat cerebral cortical membranes with 0.3 M KCl increases the ratio of high affinity to low affinity saturable [3H]desipramine binding. With this improved tissue preparation, we have confirmed our earlier observation that the high affinity [3H]desipramine binding component (KD = 2 to 4 nM) is associated with norepinephrine neuronal uptake sites. The potencies of various antidepressant drugs in reducing [3H]desipramine binding correlate with their inhibition of neuronal [3H]norepinephrine accumulation. Like the norepinephrine uptake system, high affinity [3H]desipramine binding is dependent both on sodium and chloride, with half-maximal stimulation by 10 mM chloride. Although bromide can substitute for chloride to stimulate binding, other anions, including iodide, fluoride, acetate, citrate, and phosphate, are inactive. Comparable sodium and anion regulation of [3H]imipramine binding to serotonin uptake recognition sites also is observed. The association of [3H]desipramine binding sites with neuronal norepinephrine uptake sites is supported further by the selective abolition of high affinity [3H]desipramine binding following the destruction of central norepinephrine neurons by intraperitoneal administration of DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine). In vitro incubation of cerebral cortical membranes with DSP-4 also selectively abolishes the high affinity [3H]desipramine binding, an effect which cannot be reversed by repeated washing of the membranes, suggesting that DSP-4 alkylates neuronal norepinephrine uptake sites.

Animals↗
PubMed1981

Chromatographic behaviour and post-mortem stability of somatostatin in the rat and mouse brain.

Somatostatin-like immunoreactivity (SSLI) extracted from mouse and rat brains was found to be homogeneous and identical to authentic somatostatin (SS) in its chromatographic behaviour on reverse-phase high-performance liquid chromatography (HPLC). SSLI was found to be stable in mouse brain stored under post-mortem conditions simulating the handling of human autopsy material for up to 72 h. However, the amount of SSLI extractable by acetone-HCl was found to decrease over the first 10 h of post-mortem storage to about 25% of the control level, hence care must be exercised in choosing an appropriate extraction method for SSLI measurements in post-mortem brains.

Animals↗
PubMed1981

Release of somatostatin from extra-hypothalamic rat brain slices: inhibition by dopamine and morphine.

Calcium-dependent potassium-evoked release of somatostatin-like immuno-reactivity (SSLI) and preloaded [3H]noradrenaline ([3H]NA) could be demonstrated simultaneously from slices of rat cerebral cortex, globus pallidus and trigeminal nucleus. The release of [3H]NA from cortical slices differed from that of somatostatin (SS) in its K+-dependency, with the release of SS having a higher threshold. Both morphine (10 microM) and dopamine (50 microM) significantly inhibited the potassium-evoked release of SS from the cerebral cortex, without affecting its basal release. The effect of morphine was naloxone reversible.

Animals↗
PubMed1981

Norepinephrine neuronal uptake binding sites in rat brain membranes labeled with [3H]desipramine.

Neuronal uptake recognition sites in norepinephrine neurons have been labeled with the antidepressant [3H]desipramine. A high-affinity component of [3H]desipramine binding to rat cerebral cortex membranes is abolished selectively by 6-hydroxydopamine lesions, which destroy central catecholamine neurons. The high-affinity [3H]desipramine binding has a nanomolar affinity constant for desipramine and is inhibited by tricyclic antidepressants with potencies that correlate with their ability to inhibit the neuronal uptake of norepinephrine. [3H]Desipramine binding to the uptake sites is markedly stimulated by sodium, with potassium, lithium, and choline being much less effective. The ability to monitor norepinephrine neuronal uptake "receptors" in simple binding studies should permit a differential analysis of drug influences on the norepinephrine recognition site and the translocation mechanism. The regulation of [3H]desipramine binding by sodium may help clarify how sodium influences neurotransmitter uptake.

Adrenergic Fibers↗
PubMed1981

Temperature-sensitive mutant of Newcastle disease virus which has an altered nucleocapsid-associated protein.

Analysis of six temperature-sensitive (ts) mutants of Newcastle disease virus (NDV) representing each of six complementation groups by both SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis revealed that in only one mutant was there an alteration in the isoelectric point of a protein. This altered protein was the nucleocapsid-associated protein, NAP. In addition, the mobility of the haemagglutinin-neuraminidase protein, HN, was decreased on non-reduced SDS-PAGE in this mutant. All independent ts+ clones derived from this mutant had normal NAP but HN protein migrated at the decreased rate. Haemagglutinating activity of wide-type (ts+) and ts virions was equally thermostable. Wild-type and ts+ clones derived from this ts mutant were RNA(+) at both permissive and non-permissive temperatures, whereas the ts mutant was RNA(-) at the non-permissive temperature. This ts mutant appears to be a double mutant in both HN and NAP genes, the latter only being a temperature-sensitive lesion which affects virus-directed RNA synthesis.

Capsid↗
PubMed1981

Purification and characterisation of a membrane-bound substance-P-degrading enzyme from human brain.

A membrane-bound enzyme which degrades substance P (an undecapeptide) has been purified from human brain. The properties of this enzyme suggest that it may be involved in the physiological inactivation of the peptide by neural tissues. Enzyme activity was extracted from a membrane fraction of human diencephalon with a non-ionic detergent, Brij 35, and activity was monitored by measuring the disappearance of added substance P using radioimmunoassay, bioassay or radiochemical assay. The enzyme was purified about 1000-fold by chromatography on DEAE-cellulose, hydroxyapatite and Sephadex gel filtration columns. To identify the cleavage sites in substance P, the peptide was incubated with the purified enzyme and the breakdown products were separated by reverse-phase high-performance liquid chromatography and identified by amino acid analysis. The results suggested that the enzyme preparation was functionally homogeneous and it cleaved substance P between Gln6-Phe7, Phe7-Phe8 and Phe8-Gly9, with no exopeptidase action. The enzyme had a pH optimum in the range 7--9 and was strongly inhibited by metal-chelating agents, but not affected by most other peptidase inhibitors; it can thus be classified as a neutral metallo-endopeptidase. The enzyme was thermolabile and had a molecular weight of 40 000--50 000 as estimated by gel filtration, density-gradient ultracentrifugation and sodium dodecylsulphate gel electrophoresis. The highly purified substance-P-degrading enzyme could be distinguished from previously described peptidases for which substance P is a substrate. An important feature was that substance P was the preferred substrate among various other neuropeptides tested.

Amino Acids↗