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.

Transplantation of mouse mammary epithelial cells grown in primary collagen gel cultures

A technique for the transplantation of mouse mammary epithelial cells, grown in collagen gels, has been developed that demonstrates that the phenotype of the cells prior to culture was not altered by the culture conditions. Mammary epithelial cells from virgin and midpregnant C57BL/Crgl mice; virgin, midpregnant, and multiparous nonpregnant BALB/cfC3H/Crgl mice; a BALB/c hyperplastic alveolar nodule line, and mammary tumors from BALB/cfC3H/Crgl mice were embedded inside collagen gels and grown for 10 to 14 days in the presence of 25% swine serum plus cholera toxin (0.01 microgram/ml). The epithelial cells increased in number during the culture period. At the end of the culture period, the cells were removed from the collagen gels and transplanted to the gland-free mammary fat pads of 3-week-old syngeneic female mice. Culture in collagen gels increased the number of cells necessary to obtain a high percentage of mammary outgrowths as compared to cells not grown inside collagen gels. In general, mammary cells grown inside collagen gels gave rise to outgrowths, similar in phenotype to those from noncultured cells, and were representative of the tissue of origin. Mammary epithelial cells from C57BL/Crgl virgin donors grown in collagen gels for 10 to 14 days retained their ability to respond to the endogenous hormones of pregnancy and lactation of the host and formed lobuloalveolar structures full of secretion similar to the host's own mammary gland. The data indicate that the growth of mammary epithelial cells in collagen gels and subsequent transplantation into the gland-free fat pads of syngeneic hosts provides a simple system, wherein cells can be grown in vitro and their phenotypes determined in vivo.

Growth in primary culture of mouse submandibular epithelial cells embedded in collagen gels

Mouse submandibular glands were dissociated and the epithelial cells embedded in a collagen gel matrix. A characteristic and reproducible pattern of growth was seen resulting in three-dimensional outgrowths with ductlike structures projecting into the matrix. A sustained cell growth leading to a 5 to 10-fold increase in cell number was observed in less than 2 wk. The extent of this growth was found to be dependent on serum concentration. Of the three sera tested, swine serum was found to promote greater growth compared to fetal bovine serum or horse serum. Swine serum dose response studies have shown that a concentration of 2 to 5% in the medium elicited only a modest increase, if any, in cell number compared to the initial value within a period of 2 wk. Various hormones and growth factors were then added to this "maintenance" medium. Insulin was found to stimulate growth consistently and reproducibly in a dose-dependent manner. Ultrastructurally, the resulting outgrowths were comprised of polarized cells joined by apical tight junction and desmosomes. The outgrowths produced epidermal growth factor in response to dihydrotestosterone, triiodothyronine, and cortisol. The present system provides a method for sustaining growth and functional differentiation in primary culture of mouse submandibular gland epithelial cells.

Toxocara antibodies in veterinary personnel

The prevelance of antibodies to Toxocara canis was determined in 113 veterinary personnel from 22 animal clinics. One hundred and fourteen adult hospital in-patients served as controls. All participants completed a questionnaire supplying personal data and specifies regarding animal exposure and dog ownership. Antibodies to Toxocara were detected by enzyme linked immunosorbent assay (ELISA) employing as antigen, excretorysecretory products from second stage larvae of Toxocara canis.Toxocara antibodies were found in ten (8.8%) of 113 veterinary workers and in 11 (9.6%) of 114 controls. Antibody prevalence was no different between males and females. Toxocara infection was not associated with dog ownership in veterinary workers or in hospitalized controls. A breakdown of the specific occupations among veterinary personnel failed to show a difference in antibody prevalence, nor did years of service as a veterinary worker correlate with the presence of Toxocara antibody.Our results suggest that toxocariasis is not associated with direct humandog contact nor with occupational exposure to dogs.

The use of an excretory-secretory antigen for an ELISA specific sero-diagnosis of visceral larva migrans

In sera from patients with visceral larva migrans (VLM) syndrome, enzyme-linked immunospecific assay (ELISA) was used to detect IgG and IgE antibody anti-excretory-secretory antigen (ESA) from the second larval stage of Toxocara canis. The technical conditions of the assay were determined. The specificity of IgG ELISA-ESA (with OD values greater than 0.34) allowed the differentiation of VLM syndrome from ascaris or other human parasite infections.

Primary culture of human mammary epithelial cells embedded in collagen gels

Human mammary epithelial cells were dissociatd from mastectomy tissues. The contaminating fibroblasts were removed by the use of Percoll density-gradient centrifugation, which utilizes the difference in buoyant densities between epithelial cells and fibroblasts. A preparation highly enriched for mammary epithelial cells ws then embedded in collagen gel and cultured in Ham's F12 medium containing 12.5% horse serum, 2.5% fetal calf serum, 0.1 microgram cholera toxin/ml, an extract prepared from human male urine (L microgram protein/ml), and a hormone combination of 10 microgram insulin/ml, 10 microgram human placental lactogen/ml, 1 microgram aldosterone/ml, and 0.5 microgram hydrocortisone/ml. Sustained growth leading to an increase of tenfold to thirtyfold in cell number over the initial value was accomplished in primary culture, and this growth was maintained even after passage to secondary culture. Deletion of either the urine extract or the hormone combination resulted in less than optimal growth. Subsequent studies showed that hydrocortisone alone could replace the hormone combination. In addition, urine extract could be replaced by extracts prepared from human kidneys or brains. The collagen gel system provies a reproducible and consistent method for sustained three-dimensional growth of mammary epithelial cells from human breast tissue in primary as well as passaged cultures.

Growth factor- and cyclic nucleotide-induced proliferation of normal and malignant mammary epithelial cells in primary culture

Sustained growth of normal mouse mammary epithelial cells in primary culture, leading to an increase in cell number, in response to growth factors [epidermal growth factor (EGF) and fibroblast growth factor (FGF)] or cholera toxin has been achieved by embedding the cells inside collagen cells. Inclusion of agents known to increase the level of cellular cAMP have been found to be favorable for mammary epithelial cell proliferation. Cholera toxin is by far the best of all of the agents tested (prostaglandins E1 and E2, isoproterenol, theophylline, and dibutyryl cAMP). When growth factors (EGF or FGF) are added with cholera toxin, a synergistic effect resulting in a response much greater than with either of them alone is seen. This synergism was best seen in normal mammary epithelial cells from nonpregnant mice. The extent of this synergistic effect was found to be less in normal cells from pregnant mice, suggesting that these cells may be less responsive to EGF during pregnancy. Tumor cells were found to be rather inconsistent in their responses to EGF and cholera toxin, ranging from a minimal response, similar to that of normal cells from pregnant animals, to a maximal response, similar to that of normal cells from nonpregnant animals.

Primary culture of mouse mammary tumor epithelial cells embedded in collagen gels

Mammary tumor epithelial cells from BALB/cfC3H mice were dispersely embedded inside the collagen gels in Ham's F-12 medium containing horse serum. A sustained cell growth leading to a 5- to 10-fold increase in cell number over initial level was observed in less than 2 weeks. The extent of this growth was found to be dependent on serum concentration. However, addition of various protein and steroid hormones, both singly and in combination, to low-serum-containing medium failed to achieve a comparable level of growth to that promoted by higher serum concentration. Mammary tumor cells can now be consistently propagated in primary culture.

Sustained growth in primary culture of normal mammary epithelial cells embedded in collagen gels

Normal mammary epithelial cells from BALB/cfC3H midpregnant mice were freed from stromal cell types by Percoll density gradient centrifugation after collagenase digestion and were then embedded within collagen gels. Sustained growth leading to an increase in cell number was accomplished in response to cholera toxin and high concentrations of horse serum. The extent of growth was found to be dependent on the horse serum concentration, the maximum growth being attained at 50%. A serum concentration of 12.5% horse serum and 2.5% fetal calf serum, along with cholera toxin at 0.01 mug/ml, allowed maintenance but failed to cause any significant increase in cell number during the experimental period of 2 weeks. This same maintenance medium was used to determine the effects of various exogenously added steroids, protein hormones, and organ extracts on the proliferation of mammary epithelial cells in culture. Hormones failed to elicit any proliferative response, but extracts of kidney, brain, uterus, and spleen produced proliferative responses equal to or greater than the response obtained with 50% horse serum and cholera toxin. Kidney extracts prepared from midpregnant mice, virgin mice, and virgin mice given pituitary isografts all showed comparable activities, suggesting that the concentration of stimulatory factor(s) was not influenced by the hormonal status of the donor. Normal mammary epithelial cells that had undergone a 10- to 15-fold increase in cell number over initial values during 2-3 weeks in culture were passaged to secondary gel cultures. Outgrowth similar to those seen in primary culture were seen again in secondary culture. The present system provides a method for sustaining growth in culture of primary mammary epithelial cells from normal tissues.

Evaluation of enzyme-linked immunosorbent assay for the serodiagnosis of amebiasis

This report describes the development and evaluation of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to Entamoeba histolytica. Highly sensitive and reproducible results were obtained in antigen-coated plates prepared by air-drying at 37 degrees C. Comparison of the ELISA with indirect fluorescent antibody and indirect hemagglutination techniques showed that the former was slightly more sensitive than the two latter methods. The specificity was evaluated by testing specially chosen population groups. ELISA was negative in 96.4% of 693 normal adults and children and in 96.6% of 377 patients with various parasitic, bacterial, mycotic, and other clinical diseases. The assay was positive in 26% of 461 patients with suspected amebiasis and in all of 53 patients with amoebic liver abscess. The ELISA was found to be a specific, highly sensitive, and reliable procedure for detecting anti-E. histolytica antibodies in humans.