Human breast epithelial cells in serum-free collagen gel primary culture: growth, morphological, and immunocytochemical analysis

Human breast epithelial cells derived from various sources (fibroadenoma, reduction mammoplasty, and mastectomy tissues from premenopausal patients) have been cultured in collagen gel matrix using serum-free medium. Response to various additives has been analyzed for growth-promoting effect when added to a basal medium containing insulin, cholera toxin, and BSA. A consistent observation has been the effect of EGF and cortisol in growth stimulation of human breast epithelial cells, while separately, each additive elicited only a small response. Under this condition, employing EGF and cortisol combinations, these cells gave rise to organized colonies consisting of clusters of cells, usually spherical, without any duct-like extensions. Ultrastructural and immunocytochemical studies, using a panel of monoclonal and polyclonal antibodies, have shown that cell types and features that can be identified in the original breast tissue can also be delineated in the progeny populations. The topographical feature, consisting of lumina surrounded by a single inner layer of epithelial cells and an outer layer of basal/myoepithelial cells, can be re-created in the collagen gel system starting from small clumps of cells.

Amyloid angiopathy of Alzheimer's disease: amino acid composition and partial sequence of a 4,200-dalton peptide isolated from cortical microvessels

The cardinal lesions of Alzheimer's disease are neurofibrillary tangles, senile neuritic plaques, and vascular amyloid, the latter generally involving cortical arteries and small arterioles. All three lesions are composed of amyloid-like, beta-pleated sheet fibrils. Recently, a 4,200-dalton peptide has been isolated from extraparenchymal meningeal vessels, neuritic plaques, and neurofibrillary tangles. The assumption of N-terminal homogeneity in vascular amyloid has been used as an argument for a neuronal (versus blood) origin of the peptide. However, intracortical microvessels from Alzheimer's disease have not been previously isolated. The present studies describe the isolation of a microvessel fraction from Alzheimer's disease and control fresh autopsy human brain. Alzheimer's disease isolated brain microvessels that were extensively laden with amyloid and control microvessels were solubilized in 90% formic acid and analyzed by urea sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The arteriole fraction from the Alzheimer's subject with extensive amyloid angiopathy contained a unique 4,200-dalton peptide, whereas the arterioles or capillaries isolated from two controls and two Alzheimer's disease subjects without angiopathy did not. This peptide was purified by HPLC and amino acid composition analysis showed the peptide is nearly identical to the 4,200-dalton peptide recently isolated from neuritic plaques or from neurofibrillary tangles. Sequence analysis revealed N-terminal heterogeneity. The N-terminal sequence was: Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr, which is identical to the N-terminal sequence of the 4,200-dalton peptide isolated previously from extraparenchymal meningeal vessels and neuritic plaques.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular analysis of the regulatory region of the Escherichia coli K-12 tyrB gene

The tyrB gene from Escherichia coli K-12 was cloned and sequenced, and the transcriptional start point of tyrB was determined by primer extension. By using a fusion plasmid in which the lacZ structural gene is transcribed from the tyrB promoter, it was shown that the expression of tyrB is controlled at the transcriptional level by the TyrR protein, with tyrosine as corepressor. The fusion plasmid was used to isolate mutants in which the repression of tyrB had been abolished. The tyrB promoter-operator region of these mutants was sequenced, and the tyrB operator was identified. A comparison between the tyrB operator and those of the other genes belonging to the tyrR regulon is presented.

The electrophoretic isoenzyme patterns of strains of Entamoeba histolytica isolated in two major cities in Canada

The isoenzyme patterns of 92 isolates of Entamoeba histolytica from British Columbia and 28 from Ontario were determined. Seropositivity for E. histolytica was assessed by indirect hemagglutination and enzyme-linked immunosorbent assay in the one center and by ELISA and amebic gel diffusion in the other. In both British Columbia and Ontario nonpathogenic zymodemes I and III were most common. A newly described isoenzyme pattern was identified in Ontario. Only 9 of 120 zymodeme patterns identified were found to be pathogenic strains of E. histolytica. Pathogenic isolates were strongly correlated with clinical symptoms and seropositivity.

In situ patch-clamp recording of calcium-activated potassium channels from an identified leech neuron

The paired anterior lateral giant cells of the leech Haementeria have only two active voltage gated ionic currents. We took advantage of this simple complement of ionic currents to investigate the single channel properties of this cells' calcium-activated K+ current (I(K,Ca) in situ. Cell-attached patch recordings showed large, bursting events with a conductance of approximately 90-100 pS which had extrapolated reversal potential consistent with K+ events. The channel open time distribution was well described by a single exponential process while the channel closed times were bi-exponentially distributed. The results show that the single channel properties of I(K,Ca) in annelids closely resemble those of similar currents described in vertebrates.

Human blood-brain barrier transferrin receptor

The kinetics of binding and endocytosis of 125I-human holotransferrin by isolated human brain capillaries was examined using this system as a model of the human blood-brain barrier (BBB). Both binding and endocytosis of the peptide by human brain capillaries was temperature-dependent and the binding was saturated by holotransferrin, but not by insulin, somatostatin, or vasopressin. Scatchard analysis of the binding reaction revealed a dissociation constant of 448 +/- 110 ng/mL (5.6 +/- 1.4 nmol/L) and a maximal binding constant (Ro) of 8.0 +/- 1.5 ng/mg protein. Thus, the affinity and capacity of the BBB transferrin receptor is within the same order of magnitude as the affinity and capacity of the BBB receptors for insulin, insulinlike growth factor-I, or insulinlike growth factor-II. The human brain capillary transferrin receptor was also detected with a mouse monoclonal antibody to the receptor using the avidin/biotin/peroxidase technique. In conclusion, these studies characterize the human BBB transferrin receptor and support the hypothesis that this receptor acts as a transport system which mediates the transcytosis of transferrin-bound iron through the brain capillary endothelial cell in man.

High molecular weight Alzheimer's disease amyloid peptide immunoreactivity in human serum and CSF is an immunoglobulin G

A radioimmunoassay (RIA) was developed to detect the 4200 Dalton amyloid (A4) peptide or it's precursor (A4P) in human serum or cerebrospinal fluid (CSF). A synthetic peptide containing the first 28 amino acids of the 43 amino acid A4 peptide was covalently coupled to bovine thyroglobulin and a polyclonal antiserum in rabbits was prepared. This antiserum was specific for vascular amyloid and neuritic plaques in Alzheimer's disease brain as detected by immunoperoxidase. The synthetic peptide, which has a tyrosine at residue 10, was iodinated with chloramine T and [125I]iodine and was purified to homogeneity by C4 reverse phase high performance liquid chromatography (HPLC). Extraction of human serum over a C18 Sep Pak cartridge indicated immunoreactive A4 peptide was not detectable in human serum. Conversely, high molecular weight A4 peptide immunoreactivity was detectable in human serum, at a concentration of 8.9 +/- 1.2 pmol-eq./ml, and in human CSF, at a concentration of 0.25 +/- 0.01 pmol-eq./ml, giving a CSF/serum ratio of 3.2%. The immunoreactivity in human serum was nearly completely removed by affinity deletion of serum immunoglobulin G (IgG), but not by affinity removal of IgA or IgM. Serum immunoreactivity was decreased 90% in hypogammaglobulinemia, and was increased 83% in human cord serum. There was no statistical difference in serum A4 immunoreactivity in Alzheimer's serum or CSF. Serum immunoreactivity in Down's syndrome was increased 50%. These studies indicate the high molecular weight A4P immunoreactivity in human serum or CSF is an IgG. Whether the A4 precursor in Alzheimer's disease is, in fact, an IgG, or whether there is an antibody in human serum and CSF that cross reacts with the A4 precursor cannot be determined until the serum immunoreactivity is purified and structurally characterized.

Estrogen receptor in dissociated and cultured human breast fibroadenoma epithelial cells

Estrogen binding was measured by a whole cell receptor assay in epithelial cells isolated from 20 premenopausal patients with breast fibroadenomas. A high affinity specific binding for estrogens was detected in the epithelial cells isolated from all 20 fibroadenomas. A relationship between estrogen binding and the phase in the menstrual cycle of the patient has been observed. Cell culture experiments using serum-free medium have also shown that estrogen binding can be augmented by cortisol.

Isolation of intact capillaries and capillary plasma membranes from frozen human brain

The development of methods for the isolation of brain capillaries and brain capillary plasma membranes makes possible biochemical studies of the blood-brain barrier (BBB), which is made up of brain capillaries. Studies aimed at assessing the role of the BBB in the pathogenesis of specific neurologic diseases, e.g., Alzheimer's disease or multiple sclerosis, will necessitate the isolation of capillaries from brain involved with specific pathology. Such tissue is most readily available from banks containing frozen human brain. The present studies show that intact capillaries and capillary plasma membranes can be isolated from frozen human brain, including as little as five g of multiple sclerosis plaque tissue. Capillaries from frozen human brain are enriched in gamma-glutamyl transpeptidase, factor VIII antigen, and a 46K protein which has recently been shown to be a BBB-specific protein. These studies provide the basis for future biochemical studies of human brain microvessels in neurologic disease.

Different mitogenic and phenotypic responses of human breast epithelial cells grown in two versus three dimensions

Human breast epithelial cells, derived from fibroadenomas, were cultured under conditions promoting growth in two-dimensions (2D) as monolayers using the collagen-coated dishes and in three-dimensions (3D) inside the collagen gel matrix. Both epidermal growth factor (EGF) and cortisol (F) were required for maximal stimulation in 3D growth, but only cortisol was required for 2D growth. The growth stimulation of exogenously added type IV collagen was no greater than that of type I as a substrate in both the 2D and 3D growth. Immunocytochemical staining, using a polyclonal actin antibody, showed homogeneous staining in all cells in 2D monolayers, whereas more restricted distribution was observed in 3D outgrowths in the collagen gel matrix. The same cells, when cultured in 2D vs 3D, elicit different responses and the original phenotypes may be better maintained in 3D.

Barbiturate and benzodiazepine modulation of GABA receptor binding and function

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) acts primarily on receptors that increase chloride permeability in postsynaptic neurons. These receptors are defined by sensitivity to the agonist muscimol and the antagonist bicuculline, and are also subject to indirect allosteric inhibition by picrotoxin-like convulsants and enhancement by the clinically important drugs, the benzodiazepines and the barbiturates. All of these drugs modulate GABA-receptor regulated chloride channels at the cellular level assayed by electrophysiological or radioactive ion tracer techniques. Specific receptor sites for GABA, benzodiazepines, picrotoxin/convulsants, and barbiturates can be assayed in vitro by radioactive ligand binding. Mutual chloride-dependent allosteric interactions between the four receptor sites indicate that they are all coupled in the same membrane macromolecular complex. Indirect effects of barbiturates on the other three binding sites define a pharmacologically specific, stereospecific receptor. All of the activities can be solubilized in the mild detergent 3-[(3-cholamidopropyl)-dimethylammonio]propane sulfonate (CHAPS) and co-purify as a single protein complex.

Cytolytic and biochemical properties of cytoplasmic granules of murine lymphokine-activated killer cells

The incubation of murine spleen cells in the lymphokine interleukin 2 (IL 2) gives rise to lymphokine-activated killer (LAK) cells capable of lysing fresh tumor cells in short-term lytic assays. During the course of cultures used to generate LAK cells, cytoplasmic granules were prepared and were analyzed for the presence of the cytolysin previously described in large granular lymphocytes (LGL) and cytotoxic T lymphocytes (CTL). Such cytolysin activity is initially undetectable, appears after 2 days of culture, and continues to increase until day 7. The LAK cytolysin has properties similar to those of previously described cytolysins with respect to nonspecific killing of various target cells, rapid kinetics, and absolute dependence on calcium. Antibodies raised against purified LGL tumor granules neutralized the activity of the LAK cytolysin. The precursors of both the LAK cells and the cells bearing the cytolysin are eliminated by treatment with anti-asialo-GM1 and complement, strongly suggesting that the actual LAK effector cells and the cytolysin-bearing cells are identical. Biochemical analysis of the LAK granules indicate that they contain the lysosomal enzyme arylsulfatase. The protein content of granules isolated from various days of culture with r-IL 2 undergoes a dramatic change, with major protein bands around 30,000 daltons becoming prominent, as well as the cytolysin protein band at 70,000 daltons. These data suggest that the mechanism of cell lysis by LAK cells is similar to that of CTL and natural killer-mediated lysis, and each of these forms of lymphocyte-mediated cytolysis is based on a granule exocytosis mechanism.

Cytolytic and biochemical properties of cytoplasmic granules of murine lymphokine-activated killer cells

The incubation of murine spleen cells in the lymphokine interleukin 2 (IL 2) gives rise to lymphokine-activated killer (LAK) cells capable of lysing fresh tumor cells in short-term lytic assays. During the course of cultures used to generate LAK cells, cytoplasmic granules were prepared and were analyzed for the presence of the cytolysin previously described in large granular lymphocytes (LGL) and cytotoxic T lymphocytes (CTL). Such cytolysin activity is initially undetectable, appears after 2 days of culture, and continues to increase until day 7. The LAK cytolysin has properties similar to those of previously described cytolysins with respect to nonspecific killing of various target cells, rapid kinetics, and absolute dependence on calcium. Antibodies raised against purified LGL tumor granules neutralized the activity of the LAK cytolysin. The precursors of both the LAK cells and the cells bearing the cytolysin are eliminated by treatment with anti-asialo-GM1 and complement, strongly suggesting that the actual LAK effector cells and the cytolysin-bearing cells are identical. Biochemical analysis of the LAK granules indicate that they contain the lysosomal enzyme arylsulfatase. The protein content of granules isolated from various days of culture with r-IL 2 undergoes a dramatic change, with major protein bands around 30,000 daltons becoming prominent, as well as the cytolysin protein band at 70,000 daltons. These data suggest that the mechanism of cell lysis by LAK cells is similar to that of CTL and natural killer-mediated lysis, and each of these forms of lymphocyte-mediated cytolysis is based on a granule exocytosis mechanism.

The anti-tumor efficacy of lymphokine-activated killer cells and recombinant interleukin 2 in vivo: direct correlation between reduction of established metastases and cytolytic activity of lymphokine-activated killer cells

Our previous studies demonstrated that the incubation of human peripheral blood lymphocytes or murine splenocytes in recombinant interleukin 2 (RIL 2) resulted in the generation of lymphokine-activated killer (LAK) cells capable of lysing a broad spectrum of fresh tumors in short-term chromium-release assays. Moreover, injections of LAK cells plus RIL 2 were highly effective in eliminating established 3 day metastases in the lung and liver (1-3). We have examined several parameters to define whether or not the cytolytic activity of LAK cells as measured in vitro correlated directly with the in vivo anti-tumor efficacy of adoptively transferred LAK cells. LAK cells plus RIL 2 could mediate marked reductions of established pulmonary metastases in mice rendered T cell deficient by adult thymectomy and lethal, total body irradiation followed by reconstitution with T cell-depleted bone marrow and spleen cells. Thus there was no requirement for additional T lymphocytes of host origin for successful therapy with adoptively transferred LAK cells plus RIL 2. Fresh splenocytes depleted of T cells by anti-Thy-1.2 monoclonal antibody plus complement generated LAK cells that were as highly lytic to fresh tumor in vitro and were as effective in reducing established pulmonary metastases as those generated from untreated or complement-treated splenocytes. Thus the precursor to LAK cells with anti-tumor activity in vitro and in vivo did not express the Thy-1 antigenic marker. In contrast, treatment of LAK effector cells (those generated from a 3-day incubation of fresh, normal splenocytes in RIL 2) with anti-Thy-1.2 antibody plus complement reduced or abolished their in vitro cytolytic activity. However, when combined with the systemic administration of RIL 2, these T cell-depleted, non-lytic LAK cells remained as effective in reducing the number of established pulmonary metastases upon adoptive transfer as untreated or complement-treated lytic LAK cells.(ABSTRACT TRUNCATED AT 400 WORDS)

The anti-tumor efficacy of lymphokine-activated killer cells and recombinant interleukin 2 in vivo: direct correlation between reduction of established metastases and cytolytic activity of lymphokine-activated killer cells

Our previous studies demonstrated that the incubation of human peripheral blood lymphocytes or murine splenocytes in recombinant interleukin 2 (RIL 2) resulted in the generation of lymphokine-activated killer (LAK) cells capable of lysing a broad spectrum of fresh tumors in short-term chromium-release assays. Moreover, injections of LAK cells plus RIL 2 were highly effective in eliminating established 3 day metastases in the lung and liver (1-3). We have examined several parameters to define whether or not the cytolytic activity of LAK cells as measured in vitro correlated directly with the in vivo anti-tumor efficacy of adoptively transferred LAK cells. LAK cells plus RIL 2 could mediate marked reductions of established pulmonary metastases in mice rendered T cell deficient by adult thymectomy and lethal, total body irradiation followed by reconstitution with T cell-depleted bone marrow and spleen cells. Thus there was no requirement for additional T lymphocytes of host origin for successful therapy with adoptively transferred LAK cells plus RIL 2. Fresh splenocytes depleted of T cells by anti-Thy-1.2 monoclonal antibody plus complement generated LAK cells that were as highly lytic to fresh tumor in vitro and were as effective in reducing established pulmonary metastases as those generated from untreated or complement-treated splenocytes. Thus the precursor to LAK cells with anti-tumor activity in vitro and in vivo did not express the Thy-1 antigenic marker. In contrast, treatment of LAK effector cells (those generated from a 3-day incubation of fresh, normal splenocytes in RIL 2) with anti-Thy-1.2 antibody plus complement reduced or abolished their in vitro cytolytic activity. However, when combined with the systemic administration of RIL 2, these T cell-depleted, non-lytic LAK cells remained as effective in reducing the number of established pulmonary metastases upon adoptive transfer as untreated or complement-treated lytic LAK cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies to blood-brain barrier bind selectively to brain capillary endothelial lateral membranes and to a 46K protein

To begin elucidating the biochemical basis of the polarized membrane features of the blood-brain barrier (BBB), a series of immunochemical and immunoperoxidase studies were initiated with bovine brain microvessels that make up the BBB in vivo. A rabbit antiserum was prepared against isolated bovine brain BBB plasma membranes. The bovine microvessel plasma membranes were radioiodinated with chloramine-T, and the antiserum selectively immunoprecipitated a 46K protein. The antibodies directed against the 46K protein were quantitatively absorbed with bovine brain capillaries but not with rat kidney or liver powder. Only the capillaries of brain reacted with the rat kidney-absorbed antiserum in immunoperoxidase studies of ethanol-fixed, 8-micron sections of bovine brain cortex, whereas the capillaries in heart, liver, and kidney did not react. This antiserum also strongly illuminated the lateral membranes of isolated bovine brain capillary endothelial cells grown in primary tissue culture. These studies provide evidence for a polarized distribution of a surface antigen in bovine brain capillary endothelial cells that is not present in capillary endothelia of liver, heart, or kidney. The correlation of the immunoperoxidase and immunoprecipitation techniques suggests that a candidate for the asymmetrically distributed surface antigen in the BBB is the 46K protein. The relationship between the 46K protein and the composition of BBB tight junctions remains to be determined.

Blood-brain barrier protein phosphorylation and dephosphorylation

Capillaries in vertebrate brain have unique permeability properties that make up the blood-brain barrier (BBB). Although it is known that capillaries are innervated by nerve endings of intracerebral origin and that brain capillary function is likely acutely regulated by neuronal inputs, the possible mechanisms of neuronal regulation of capillary function are at present unknown. One possible mode of regulation is via the phosphorylation of brain capillary proteins. The present studies characterize, for the first time, the major phosphoproteins in the bovine brain capillary using both intact bovine brain capillaries and plasma membrane fractions from bovine brain capillaries. The patterns of endogenous phosphorylation of capillary proteins are compared to similar patterns obtained with synaptosomal (P2) fractions from bovine brain. The major findings of this study are: (a) The activity of protein phosphorylation in brain capillaries is localized almost exclusively to the capillary plasma membrane, and is nearly comparable to the activity of protein phosphorylation in synaptosomal membranes. (b) A major phosphoprotein doublet in the capillary fraction comigrates on a sodium dodecyl sulfate gel with a major phosphoprotein doublet of approximate molecular weight of 80K in the synaptosomal fraction, and the latter is presumed to be synapsin I; in dephosphorylation assays the synaptosomal 80K phosphoprotein doublet is not subject to measurable dephosphorylation, whereas the capillary 80K doublet is subject to rapid dephosphorylation, and is essentially completely dephosphorylated within 5 s at 0 degrees C. (c) A prominent triplet of phosphoproteins with molecular weight of 50-55K is present in the capillary fraction, and is not present in the synaptosomal fraction; thus, this 50-55K triplet of phosphoproteins appears specific for brain capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration of functional low-density lipoprotein receptors by protein blotting in fibroblasts from a subject with homozygous receptor-negative familial hypercholesterolemia

We report the detection of low-density lipoprotein (LDL) receptors by the technique of receptor blotting in fibroblasts from a patient with homozygous familial hypercholesterolemia (FHC) previously classified as "receptor negative." Solubilized receptors were electrophoresed, transferred to nitrocellulose paper, treated with LDL followed by radiolabeled antibody to LDL, and visualized by autoradiography. GM 2000 FHC fibroblasts revealed LDL receptors with an apparent molecular weight of approximately 140,000, the same as in normal cells. LDL receptor activity by blotting in GM 2000 cells was greatly diminished in comparison with normal cells, but was calcium dependent. Receptor activity was also detectable by conventional monolayer binding and degradation assays. Thus, GM 2000 cells have profoundly diminished LDL receptor activity, but retain the genetic capacity to make LDL receptor material of normal molecular weight that is capable of binding LDL. Previous studies have demonstrated the presence of trace amounts of immunoreactive LDL receptor protein in fibroblasts from some receptor-negative FHC homozygotes. Our work extends these studies by demonstrating the ability of this material to bind LDL.

Human blood-brain barrier insulin receptor

A new model system for characterizing the human brain capillary, which makes up the blood-brain barrier (BBB) in vivo, is described in these studies and is applied initially to the investigation of the human BBB insulin receptor. Autopsy brains were obtained from the pathologist between 22-36 h postmortem and were used to isolate human brain microvessels which appeared intact on both light and phase microscopy. The microvessels were positive for human factor 8 and for a BBB-specific enzyme marker, gamma-glutamyl transpeptidase. The microvessels avidly bound insulin with a high-affinity dissociation constant, KD = 1.2 +/- 0.5 nM. The human brain microvessels internalized insulin based on acid-wash assay, and 75% of insulin was internalized at 37 degrees C. The microvessels transported insulin to the medium at 37 degrees C with a t1/2 = approximately 70 min. Little of the 125I-insulin was metabolized by the microvessels under these conditions based on the elution profile of the medium extract over a Sephadex G-50 column. Plasma membranes were obtained from the human brain microvessels and these membranes were enriched in membrane markers such as gamma-glutamyl transpeptidase or alkaline phosphatase. The plasma membranes bound 125I-insulin with and ED50 = 10 ng/ml, which was identical to the 50% binding point in intact microvessels. The human BBB plasma membranes were solubilized in Triton X-100 and were adsorbed to a wheat germ agglutinin Sepharose affinity column, indicating the BBB insulin receptor is a glycoprotein. Affinity cross-linking of insulin to the plasma membranes revealed a 127K protein that specifically binds insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of Ca2+ conductance in identified leech neurons by benzodiazepines

Benzodiazepines (BZs) in micromolar concentrations inhibit Mn2+- and Co2+-sensitive regenerative divalent cation potentials, which are revealed in the presence of tetraethylammonium ion, in leech nociceptive neurons (N cells). This BZ effect is reversible and dose-dependent. The BZs, like Mn2+ and Co2+, inhibit the maximum rate of depolarization (Vmax) and duration of divalent cation potentials at concentrations that do not significantly affect resting membrane potential or Vmax of the Na+-dependent action potential. Ultraviolet-induced BZ binding to micromolar-affinity sites in ganglia and isolated cells irreversibly blocks Ca2+ conductance in neurons without significantly affecting resting membrane potentials. BZ binding studies with leech neuronal membrane show saturable, specific binding in the micromolar concentration range that was similar to BZ binding to synaptosomal membrane fractions. The apparent Kd obtained from the micromolar-affinity BZ binding curve for leech ganglionic membrane preparations agrees well with the apparent Ki estimated from the dose-response curve measuring BZ inhibition of Vmax of the divalent cation potentials. These findings indicate that BZs act like Ca2+-channel antagonists in intact neuronal preparations and are consistent with the hypothesis that BZ binding to micromolar-affinity receptors modulates voltage-gated Ca2+ channels.

Effects of tetraethylammonium-chloride and divalent cations on the afterhyperpolarization following repetitive firing in leech neurons

In leech Retzius cells, repetitive activity evoked a prolonged Ca2+-dependent after-hyperpolarization (PAH) (30-60 s) accompanied by an increase in input conductance. PAH persisted in Retzius cells, as well as in nociceptive (N) cells, when Sr2+ but not Mg2+ was substituted for Ca2+. In the presence of tetraethylammonium-chloride (TEA) or Ba2+, PAH was replaced by a Ca2+-dependent, Mg2+-blockable depolarization which was present in the order N greater than R. Careful study of the differences in such phenomena in identified cells may improve our understanding of the differential susceptibility of various neurons to hyperexcitability.

Intestinal parasites in metropolitan Toronto day-care centres

In 1981, 900 children (aged 3 months to 10 years) and 146 staff attending 22 day-care centres in metropolitan Toronto chosen at random provided a stool specimen in a survey for intestinal parasites. Of the children, 4% to 36% were infected in 20 of 22 centres. Overall, 19% of the children and 14% of the staff had intestinal parasites: 8.6% and 4.0% respectively had Dientamoeba fragilis, and 7.8% and 2.0% respectively had Giardia lamblia. The highest prevalence of dientamebiasis was in the 7- to 10-year-olds, whereas giardiasis was detected most frequently in the 6-year-olds. Infection with intestinal parasites was not correlated with age, sex, duration in the day-care centre, dog ownership, travel history, gastrointestinal symptoms or the proportion of children in the day-care centre who were born in less developed countries. Immigrant children and children of parents born in industrialized countries (including Canada) were more likely to be infected than were children born in Canada of parents from the developing world. Dientamebiasis was associated with cat ownership. Thus, intestinal protozoa--in particular, D. fragilis and G. lamblia--are endemic in Toronto day-care centres.

Procaine actions on tetrodotoxin sensitive and insensitive leech neurons

Procaine (0.1-10 mM) was applied to two kinds of identified neurons in segmental leech ganglia. Both Retzius (R) cells and nociceptive (N) cells responded by dose-dependent reduction of maximum rates of de- and repolarization during action potentials. However, the N cells, which are more sensitive to tetrodotoxin than R cells, were also 3 times more sensitive to procaine. The prolongation of action potentials produced by procaine in R cells was enhanced by low Ca but antagonized by high Ca. This implies that the drug interfered with repolarization by affecting a Ca-dependent mechanism. In alkaline solution (pH 8.5), sensitivity of the R cell to procaine approached that of the N cell at pH 7.4 suggesting that the drug acted at an intracellular site after passage through membrane lipids in its uncharged form. The combined effects of TTX and procaine, in concentrations which produced about 50% inhibition of dV/dTdep in N cells when given separately, were found to be intermediate between those predicted by two models which assume identical and independent sites of action, respectively. These data extend our earlier observations regarding the existence of two types of Na channels in mature leech neurons. They imply that the differential sensitivity to procaine among these cells may be a consequence of variable access to an otherwise identical 'receptor' and that TTX and procaine act on separate sites which may interact with each other.

Modulation of natural killer (NK) cells by autologous neutrophils and monocytes

Although natural killer (NK) cell activity is remarkably stable in healthy individuals, the number and cytotoxicity of the cells fluctuate in disease. In man, regulatory mechanisms are virtually unexplored but depressed NK cell function accompanies most chronic diseases. A suppressive role of monocytes/macrophages has been reported. Since neutrophils (PMN) and monocytes (M) often respond reciprocally to pathologic stimuli, experiments were designed to investigate whether increments in PMN and M per se could influence NK cell function. Peripheral blood NK cells obtained by Percoll gradient centrifugation were either cocultured with various concentrations of autologous PMN or M or they were exposed to diffusates of these granulocytes in Millipore chambers. The treated NK cells were washed and then mixed with melanoma target cells in various effector:target cell ratios. It was observed that PMN diffusates augmented cytotoxicity whereas monocyte diffusates decreased the killing function of NK cells markedly and in a dose dependent fashion (P less than 0.001). The stimulatory effect of PMN diffusates was heat labile and not attributable to interferon. The inhibitory effect of M diffusates was heat stable, not due to prostaglandins or lysozyme, and irreversible within 6 hr of observation. Binding of effector to target cells was enhanced by PMN-media, and significantly inhibited by monocyte diffusates . It is therefore possible that factors elaborated by neutrophils and monocytes in vivo could also influence NK cell function.

Actions of procaine on specific nociceptive cells in leech central nervous system

The effects of the local anesthetic, procaine, on the electrophysiological properties of the leech neurons responding to nociceptive stimuli (N cells) were examined in isolated segmental ganglia in Macrobdella . In the N cell situated laterally in ganglia 7 to 19, procaine produced a depolarization; whereas in the N cell situated medially, it caused a hyperpolarization. These changes in membrane potential were accompanied by a decrease in input resistance, persisted in solutions containing 20 mM MgCl2, and were reversible after drug washout. The depolarization induced by procaine in the lateral N cell was abolished in Na-free solutions. The hyperpolarization produced by procaine in the medial N cell persisted in low chloride solutions and was enhanced by about 30% when the K concentration was reduced to one-tenth of its control value. Therefore, it seems likely that an increase in the resting K conductance was a contributing factor to this hyperpolarization. Procaine greatly prolonged the action potential of the lateral but not the medial N cell. This effect was not solely a consequence of the membrane potential change produced by the drug. Ganglia 5, 6, 20, and 21 contained two rather than four cells with N-like properties. These neurons were N-like by virtue of the shape of their action potential and their morphological similarities to the N cells found in ganglia 7 to 19, as well as by their selective sensitivities to nociceptive mechanical stimulation of the skin. The cells in ganglia 5 and 6 responded to gut stimulation, as did the medial N cells in ganglia 7 to 19.(ABSTRACT TRUNCATED AT 250 WORDS)

Different enzyme classes associated with human natural killer cells may mediate disparate functions

Previous studies have shown that degradation of the acute phase reactant serum amyloid A (SAA) is mediated by enzymes on the plasma membrane of lymphocytes and monocytes. The responsible enzymes had properties of neutral elastases. The present investigations were conducted to explore whether human NK cells enriched by Percoll gradient centrifugation have similar activity and if so, whether the same or different enzyme classes are responsible for proteolysis as well as for tumor cell lysis. Accordingly, human NK cells were enriched on discontinuous Percoll gradients after which the cells were incubated either with SAA or with [3H] proline-labeled melanoma cells at various effector to target cell ratios. When SAA degradation was followed by SDS-polyacrylamide gel electrophoresis, NK fractions proved to be as effective in digesting the protein as unfractionated mononuclear leukocytes. To characterize the enzymes that may be involved in cytotoxicity on the one hand, and SAA degradation on the other, the NK fractions were treated with the following inhibitors: diisopropylfluorophosphate (DFP), soybean trypsin inhibitor, N-p-tosyl-L-lysine chloromethylketone (TLCK), the elastase inhibitors elastatinal, Ac-Ala-Ala-Pro-Val-CH2Cl, Meo-Suc-Ala-Ala-Pro-Val-CH2Cl, and an inhibitor of aryl sulfatase, Na2SO4. Preincubation of the cells with DFP or elastase inhibitors abolished their ability to hydrolyze SAA but did not affect their ability to kill tumor cells. On the other hand TLCK, a potent inhibitor of cytotoxicity, did not bring about any reduction in the proteolysis of SAA. DFP and Na2SO4 diminished cytotoxicity partially. Elimination of NK cells by sorting after incubation of lymphocytes with the monoclonal antisera Leu-7 and Leu-11 abolished cytotoxicity as well as proteolysis. The observations are compatible with the concept that NK cells carry several enzymes with different substrate specificities that may be involved in disparate cellular functions.

Different enzyme classes associated with human natural killer cells may mediate disparate functions

Previous studies have shown that degradation of the acute phase reactant serum amyloid A (SAA) is mediated by enzymes on the plasma membrane of lymphocytes and monocytes. The responsible enzymes had properties of neutral elastases. The present investigations were conducted to explore whether human NK cells enriched by Percoll gradient centrifugation have similar activity and if so, whether the same or different enzyme classes are responsible for proteolysis as well as for tumor cell lysis. Accordingly, human NK cells were enriched on discontinuous Percoll gradients after which the cells were incubated either with SAA or with [3H] proline-labeled melanoma cells at various effector to target cell ratios. When SAA degradation was followed by SDS-polyacrylamide gel electrophoresis, NK fractions proved to be as effective in digesting the protein as unfractionated mononuclear leukocytes. To characterize the enzymes that may be involved in cytotoxicity on the one hand, and SAA degradation on the other, the NK fractions were treated with the following inhibitors: diisopropylfluorophosphate (DFP), soybean trypsin inhibitor, N-p-tosyl-L-lysine chloromethylketone (TLCK), the elastase inhibitors elastatinal, Ac-Ala-Ala-Pro-Val-CH2Cl, Meo-Suc-Ala-Ala-Pro-Val-CH2Cl, and an inhibitor of aryl sulfatase, Na2SO4. Preincubation of the cells with DFP or elastase inhibitors abolished their ability to hydrolyze SAA but did not affect their ability to kill tumor cells. On the other hand TLCK, a potent inhibitor of cytotoxicity, did not bring about any reduction in the proteolysis of SAA. DFP and Na2SO4 diminished cytotoxicity partially. Elimination of NK cells by sorting after incubation of lymphocytes with the monoclonal antisera Leu-7 and Leu-11 abolished cytotoxicity as well as proteolysis. The observations are compatible with the concept that NK cells carry several enzymes with different substrate specificities that may be involved in disparate cellular functions.

Action potential prolongation: an effect of physostigmine (eserine) upon Retzius cells in the leech C.N.S

Physostigmine (PHY; eserine) prolongs the action potentials in the Retzius cells within leech ganglia to about 800 ms. The effect was reversible and occurred at concentrations of 1-10 mM which are several orders of magnitude greater than those required to inhibit cholinesterase. The prolonged action potentials showed an early, spike-like depolarization followed by a plateau. The initial depolarization exhibited a strong dependence on external Na+ while the amplitude of the plateau had somewhat less Na+ dependence: 52 and 24 mV/decade, respectively. The duration of the plateau was increased by elevating Na+ and decreased by elevating Ca2+. Increasing the action potential frequency, by intracellular stimulation, decreased both the duration and amplitude of the plateau. Neostigmine, di-isopropylphosphofluoridate, and acetylcholine did not prolong RZ action potentials. Thus, the membrane effects of physostigmine appear to be independent of any inhibition of cholinesterase or accumulation of acetylcholine.

Frequency domain analysis of electrotonic coupling between leech Retzius cells

Transfer functions of the input impedance Z(f) and coupling ratio H(f) were measured from the paired Retzius cells of leech segmental ganglia, using sinusoidal and pseudorandom test test currents. The data were compared with two classes of linear electric circuit models of electrotonic coupling, one with a purely resistive junction, and the other with a finite equivalent cable coupling the two somata. Model simulations suggested the phase behavior of the coupling ratio as a sensitive discriminator between these two cases. For resistive coupling, the phase of the coupling ratio asymptotically approaches -90 degrees at high frequencies, while for a cable segment, at least 0.5 length constants in length, it crosses -90 degrees with a definite negative slope and continues to more negative values. Measured phase lags of the coupling ratio in Retzius cell preparations consistently exceeded -90 degrees at frequencies above 50 Hz, and phase plots crossed -90 degrees with significantly negative slopes. We conclude therefore that a significant cable segment contributes to the coupling between Retzius cell somata.

Comparison of the growth of normal and neoplastic mouse mammary cells on plastic, on collagen gels and in collagen gels

The growth of normal and neoplastic mouse mammary cells was compared in primary cultures on plastic, on rat tail collagen gels and in rat tail collagen gels. Cells on plastic grew for the first few days, then stopped with only a 1- to 3-fold increase in cell number after 2 weeks in culture. Cells grown on or in collagen gels grew continuously over the 2-week culture period with up to 10-fold increase in cell number for cultures on collagen gels and a 20-fold increase for cells embedded in collagen gels. The difference in growth rates between cells grown in collagen gel and those grown on collagen gels was due, in part, to the three-dimensional growth of the colonies in collagen gel their two-dimensional growth on collagen gel. Cells grown on and in collagen gel can produce an electron-dense basal lamina-like structure which is associated with collagen IV and laminin as judged by immunofluorescence. Cells grown on plastic do not form this structure. Cis-OH-proline blocks the production of collagen and inhibits the growth of the cultured cells indicating collagen production to be involved in growth. Rat tail collagen gels are a superior substratum for the growth of mouse mammary cells and this may be related to the cells' ability to form a collagen IV-containing basal lamina-like structure.

The effect of dichloroacetate on the phosphorylation of mitochondria proteins

Succinyl-CoA synthetase and the alpha-subunit of pyruvate dehydrogenase are phosphorylated after incubation of mitochondria from brain, heart, and liver with [gamma-32P]ATP. Dichloroacetate, a known specific inhibitor for pyruvate dehydrogenase kinase, inhibits not only the phosphate incorporation into the alpha-subunit of pyruvate dehydrogenase but also the autophosphorylation of succinyl-CoA synthetase. AMP also inhibits the phosphorylation of both proteins. Phosphorylation of the alpha-subunit of pyruvate dehydrogenase in liver mitochondria is significantly lower than in mitochondria from other tissues.

Synthetic peptide analogs of skeletal troponin C: fluorescence studies of analogs of the low-affinity calcium-binding site II

Two 12-residue peptides were synthesized by the solid-phase method as structural analogs of a Ca2+-binding loop of rabbit skeletal troponin C. The sequence of the analogs corresponds to the binding loop of the Ca2+-specific low affinity binding site II (residues 63-74) but with two amino acid substitutions. In one analog, Phe-72 was replaced by tyrosine. In the other Gly-66 was substituted by serine and Phe-72 by tyrosine. The intrinsic fluorescence of the peptides was enhanced upon addition of Tb3+ or large excess of Ca2+. From the enhancement of Tb3+ emission association constants in the range (2-3) X 10(5) M-1 and a binding stoichiometry of 1 were determined for Tb3+ binding to the peptides. Large excess of Ca2+ displaced Tb3+ from the Tb3+-peptide complexes and from these results apparent stability constants of 500-700 M-1 were deduced for Ca2+ binding. Preliminary proton nuclear magnetic resonance results on one of the peptides indicated that La3+ induced considerable perturbation of the amide proton resonances of several residues, including the aspartate at position 3, the tyrosine at position 10, and the two glutamates at the C-terminus. The results suggest involvement of these residues in cation coordination.