In vitro activity of guinea pig transfer factor released into plasma.

Plasma fractions and plasma dialysate from 2,4-dinitrochlorobenzene- and tuberculin-sensitive guinea pigs that had been treated with either antilymphocytic serum or normal control serum were analyzed for their ability to transfer lymphocyte transformation, passive cutaneous anaphylaxis, and macrophage migration inhibition, as well as delayed hypersensitivity in vivo. Antilymphocytic serum caused rapid release of material, which has characteristics of transfer factor, into the plasma. It was dialyzable, migrated electrophoretically with the alpha globulins and albumin, possessed a 280/260 (nm) optical density ratio of 0.7, and caused in vitro lymphocyte transformation in the presence of the specific antigen. Passive cutaneous anaphylaxis antibodies were also present in the plasma of sensitive animals, but they were isolated in electrophoretic or dialysis fractions separate from those containing transfer activity.     

Contraction of guinea pig trachea with antibodies to guinea pig IgE. An in vitro model for asthma

Rabbit antiserum to guinea pig IgE was prepared. This antiserum absorbed IgE antibodies to dinitrophenyl determinants when examined by passive cutaneous anaphylaxis. This antiserum also provoked contraction of tracheal rings from normal guinea pigs in vitro. This system is a new model for asthma in which only IgE among immunoglobulins reacts.     

Biologic functions of the IFN-gamma receptors

Interferon-gamma (IFN-gamma) is a cytokine that plays an important role in inducing and modulating an array of immune responses. Cellular responses to IFN-gamma are mediated by its heterodimeric cell-surface receptor (IFN-gammaR), which activates downstream signal transduction cascades, ultimately leading to the regulation of gene expression. In order to study the role of IFN-gamma in a number of immune responses and pathways, researchers have generated mice with altered patterns of IFN-gammaR gene expression. These studies, together with analyses of naturally occurring mutations of the IFN-gammaR in man, have been instrumental in elucidating the diverse functions of IFN-gamma, and are the subject of this review.     

Synaptic responses of guinea pig cingulate cortical neurons in vitro.

1. Intracellular recordings were made from layer V/VI neurons of the guinea pig anterior cingulate cortex to investigate postsynaptic potentials (PSPs) evoked by electrical stimulation of the subcortical white matter (forceps minor). 2. Four distinct types of PSPs were recorded (at the resting potential) under normal physiological conditions; 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-sensitive excitatory postsynaptic potentials (EPSPs) were followed by bicuculline- or picrotoxin-sensitive depolarizing or hyperpolarizing inhibitory postsynaptic potentials (IPSPs), which were further followed by phaclofen-sensitive, long-lasting hyperpolarizing postsynaptic potentials (LPSPs). The average times-to-peak for the EPSP, depolarizing and hyperpolarizing IPSPs, and LPSP were 10, 22, 28, and 146 ms, respectively. 3. In the presence of CNQX and bicuculline, high-intensity electrical stimulation elicited a longer lasting EPSP with a time-to-peak of 21 ms. The amplitude and duration of the EPSP decreased with membrane hyperpolarization and increased with membrane depolarization. The EPSP was reversibly abolished by D,L-2-amino-5-phosphonovaleric acid (D,L-APV). 4. The bicuculline- or picrotoxin-sensitive depolarizing and hyperpolarizing IPSPs and the phaclofen-sensitive LPSP were markedly suppressed by CNQX, suggesting that glutamate (Glu) and/or aspartate nerve terminals project to GABAergic interneurons, and that the GABAergic interneurons are activated mainly by non-N-methyl-D-aspartate (non-NMDA) receptors. 5. In the presence of picrotoxin, the average reversal potential for the compound EPSP was 0 mV, which was similar to that (-6 mV) for the Glu-induced depolarization. In a solution containing D,L-APV at low concentrations, the average reversal potentials for the depolarizing and hyperpolarizing IPSPs and for the early and late components of the gamma-aminobutyric acid (GABA)-induced responses were -62, -72, -70, and -61 mV, respectively. Thus the value for the depolarizing IPSP was similar to that for the late response to GABA, whereas the value for the hyperpolarizing IPSP was almost the same as that for the early response to GABA. The average reversal potential of -90 mV for the LPSP was similar to -93 mV for the baclofen-induced hyperpolarization and to -94 mV for the spike afterhyperpolarization. 6. Application of phaclofen decreased the interspike interval of the spontaneous firing and reversed the increase in the interspike interval after subcortical stimulation. This result indicates that, even in a slice preparation, the anterior cingulate neurons are under tonic inhibitory control exerted by spontaneously active GABAergic interneurons.(ABSTRACT TRUNCATED AT 400 WORDS)     

Proteolytic activity of guinea pig spermatozoa after induction of the acrosomal reaction in vitro

After inducing the acrosomal reaction in guinea pig spermatozoa in vitro, the sperm were tested for proteolytic activity by applying them to membranes of fixed gelatin. One to 5% of them showed slight evidence of proteolytic activity, while the rest were completely negative. Sperm that had retained their acrosomes throughout the incubation period displayed intense proteolytic activity. These results suggest that proteinases may be lost from spermatozoa as a result of the acrosomal reaction.     

In vitro guinea pig leukocyte reactions to Rickettsia rickettsii.

The presence of cell-mediated immunity in Rocky Mountain spotted fever-infected guinea pigs was determined by two in vitro assays: whole blood lymphocyte transformation (LT) and macrophage migration inhibition. Increased LT was detected as early as 1 week in guinea pigs infected with Rickettsia rickettsii and treated with oxytetracycline and was detected by two weeks in infected but untreated guinea pigs. Elevated LT was still detectable at 10 weeks postinfection. Guinea pigs vaccinated with killed rickettsiae failed to develop lymphocyte responsiveness; however, there was a rapid lymphocyte response after challenge with live organisms, suggesting potentiation by the vaccine. Vaccinated guinea pigs that were challenged and then treated with antibiotic failed to develop LT, suggesting that infection is necessary for the observed response. Macrophage migration inhibition was detected in both infected and vaccinated guinea pigs by 1 week after infection, but this response was no longer detected 4 to 5 weeks later. Antibody appeared at 2 to 3 weeks postinfection and was present at low levels through week 10. Antibody-treated rickettsiae were phagocytized and destroyed by guinea pig peritoneal macrophages, whereas normal serum-treated rickettsiae replicated and eventually destroyed the phagocytes.     

Ultrastructural development of guinea pig cytomegalovirus in cultured guinea pig embryo cells.

The ultrastructural development of guinea pig cytomegalovirus (GPCMV) in guinea pig embryo cells was studied using electron microscopy. Tubular structures were found in nuclei of virus infected cells, followed by the appearance of intranuclear inclusions containing virus nucleocapsids. While some nucleocapsids were enveloped at the inner nuclear membrane, others were released into the cytoplasm where they were associated with, or within, dense matrix which was subsequently enveloped by cytoplasmic membranes to form enveloped dense virions. Dense bodies without virus capsids were formed in the cytoplasm and enveloped in a similar manner. An involvement of the nuclear pores in the release of unenveloped virus capsids from the nucleus to the cytoplasm was postulated. Evidence that the enveloped dense virions and dense bodies shared common envelope antigen(s) was obtained by immunoelectron microscopy. The similarities and differences in the ultrastructural development of GPCMV and other cytomegaloviruses are discussed.     

Neuronal activity in the guinea pig medial vestibular nucleus in vitro following chronic unilateral labyrinthectomy

Unilateral labyrinthectomy (UL) causes ocular motor and postural disorders which disappear over time in a process of recovery known as vestibular compensation. Vestibular compensation is due to CNS plasticity which generates a partial recovery of resting activity in the vestibular nucleus ipsilateral to the UL, however the mechanism of this neural recovery is unknown. It has been suggested that other areas of the CNS may substitute non-vestibular sensory inputs for the missing labyrinthine input, thereby causing vestibular compensation. The present results show that resting activity can be recorded from medial vestibular nucleus (MVN) neurons in vitro, in brainstem slices from guinea pigs which have compensated for an ipsilateral UL. This result suggests that MVN neurons are capable of generating resting activity without inputs from many other CNS areas. Perfusion with high Mg2+ solution did not abolish resting activity in most cases, suggesting that part of the resting activity may be generated spontaneously by the neurons, possibly through changes in the electrical excitability of the cell membrane.     

Autonomous activity in the isolated guinea pig bladder

Phasic changes in pressure have been reported to occur in the bladder which are not associated with micturition. Spontaneous intravesical pressure changes can be recorded from bladders in vitro or bladders in vivo isolated from the central nervous system suggesting that the bladder itself is capable of autonomous activity. Experiments using isolated cells and muscle strips indicate that the smooth muscle can generate spontaneous activity. Whether this is the origin of phasic changes in the intact organ remains unknown. The present study set out to establish the presence and characteristics of autonomous activity in the isolated guinea pig bladder. Multiple-point motion analysis and concurrent intravesical pressure recording were used to identify and quantify spontaneous and evoked activity. Highly complex autonomous activity was observed in unstimulated bladders. This activity comprised localised micro-contractions in single or multiple discrete regions, waves of activity and micro-stretches. Low-amplitude phasic 'micro-transients' were seen in the intravesical pressure trace in association with micro-contractions. Incremental increases in the intravesical volume recruited additional areas of activity. Atropine and tetrodotoxin had no effect on the micro-transients or micro-contractions. Exposure to the muscarinic agonist arecaidine (10-300 nM) initially increased the incidence of micro-contractions which subsequently became co-ordinated into phasic pressure rises and contraction waves, interspersed with periods of total quiescence. The findings describe the generation and co-ordination of autonomous activity in the bladder wall and also demonstrate complex phasic activity. This approach has shown the importance of assessing the integrative properties of the entire organ in studies of the physiology and patho-physiology of the bladder.     

Synaptic responses of guinea pig and rat central amygdala neurons in vitro.

1. To investigate postsynaptic potentials (PSPs), we made intracellular recordings from neurons of the amygdaloid central nucleus in slices from the guinea pig and rat brains maintained in vitro. The results from guinea pigs and rats were very similar. 2. In the presence of bicuculline (20 microM), focal electrical stimulation of the amygdaloid basal nucleus with low intensities elicited short-latency excitatory PSPs (EPSPs) followed by long-latency EPSPs. The short-latency EPSP was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX; 10-20 microM). The long-latency EPSP was preferentially abolished by D,L-2-amino-5-phosphonovaleric acid (D,L-APV; 40 microM) and was augmented by removal of extracellular Mg2+. The compound EPSP reversed at -4 mV, which was close to -1 mV, the reversal potential for pressure-ejected glutamate (Glu). 3. When the intensity of the focal stimulation was increased in the presence of bicuculline (20 microM), CNQX (20 microM), and D,L-APV (50 microM), a second EPSP with a short latency and a prolonged duration could be evoked in approximately 65% of the neurons. The EPSPs were reversibly blocked by d-tubocurarine (50 microM) or hexamethonium (200 microM) but were unaffected by atropine (1 microM) or a 5-hydroxytryptamine type 3 receptor antagonist, ICS-205930 (5-10 microM). In these neurons, acetylcholine (ACh; 1-3 mM) caused a depolarization, associated with a decreased input resistance. 4. In the presence of CNQX (20 microM) and D,L-APV (50 microM), single focal stimulation of the dorsolateral subdivision in the central nucleus with low intensities elicited a depolarizing inhibitory PSP (IPSP). The IPSP was reversibly abolished by bicuculline (20-40 microM). The reversal potential (-63 mV) for the IPSP was similar to the reversal potential (-61 mV) for the response to gamma-aminobutyric acid (GABA) applied by pressure ejection. 5. In the presence of bicuculline (20-40 microM) and CNQX (20 microM), a repetitive focal stimulus with high intensities delivered to the dorsolateral subdivision produced a hyperpolarizing PSP followed by a slow depolarization in most neurons. Of putative inhibitory amino acid transmitters, glycine (Gly; 3 mM) produced only a hyperpolarization, associated with a decrease in input resistance. Strychnine (1-2 microM) reversibly blocked both the Gly hyperpolarization and the synaptically evoked hyperpolarization. The reversal potential of -81 mV for the hyperpolarizing PSP was close to -82 mV for the Gly hyperpolarization. The reversal potential for the Gly response was shifted to less negative values by increasing the external K+ concentration or decreasing the extracellular Cl- concentration.(ABSTRACT TRUNCATED AT 400 WORDS)     

In vitro responses of guinea pig peritoneal macrophages to Legionella pneumophila.

Transmission and scanning electron microscopy were used to study the phagocytosis of virulent and avirulent strains of Legionella pneumophila. The interaction between L. pneumophila and peritoneal macrophages from normal guinea pigs or from animals that had survived infection was studied. The virulent strains survived and proliferated within the phagocyte after ingestion by either type of macrophage, whereas the avirulent strain of bacteria was killed by normal macrophages. Although the addition of immune serum enhanced phagocytosis, the outcome was the same as with normal serum.     

Antitumor activity of Listeria monocytogenes on a guinea pig fibrosarcoma.

Listeria monocytogenes-mediated tumor inhibition was studied in strain 13 guinea pigs by using a methylcholanthrene-induced fibrosarcoma (MCA-1). Mixtures of Listeria and tumor cells in ratios of 1:100, 1:200, or 1:400 (Listeria:MCA-1 cells) led to significant suppression of tumor growth. Intralesional injection of tumors on day 6 posttransplantation led to the regression of a highly significant number of tumors. Animals receiving injections of Listeria, either in a mixture with tumor cells or intralesionally, displayed enhanced skin test reactivity to a tumor extract. Tumor regressors were resistant for at least 2 to 3 months after the initial transplant to rechallenge with MCA-1 cells. Thus, with this particular tumor-host system, Listeria was successfully employed as an antitumor agent with no visibly detrimental side effects to the host.     

Choline acetyltransferase activity in rat and guinea pig heart following vagotomy.

Choline acetyltransferase (CAT), which serves as a marker for the preganglionic and postganglionic parasympathetic cholinergic neurons in heart, was measured in heart regions in rats and guinea pigs after either a right or a left unilateral cervical vagotomy or a sham operation. One day after a left vagotomy in rat, CAT activity was decreased in the region of the SA and AV nodes. In rats killed on the 2nd, 4th, and 8th day after left vagotomy, the activity of CAT in these regions increased to the control level. CAT activity in the remainder of the heart did not decrease. In guinea pig 1 wk after a left vagotomy, CAT activity was decreased in the anterior interventricular septum but not in other regions. Selective increases in enzyme activity were noted in the right atrial appendage following left vagotomy and in the superior interventricular septum following right vagotomy. These results suggest that compensatory increases in CAT activity occur that may be related to collateral sprouting similar to that observed in the frog heart.     

The in vitro morphogenesis of the guinea pig egg cylinder

Summary The guinea pig embryo has been grown from the blastocyst to the egg cylinder stage in vitro. Moreover, histological, cytological and cytophotometrical studies have shown that the in vitro-derived egg cylinders closely resemble age-matched, in vivo embryos. In addition, constituent tissue layers were also isolated from the in vivo and the in vitro-derived egg cylinders. These were subsequently grown in culture and found to be, upon cytophotometrical study, similar in nuclear DNA content. Results thus obtained further support the idea that morphogenesis in culture paralleled normal development.     

Membrane properties of guinea pig cingulate cortical neurons in vitro

1. The passive and active membrane properties of guinea pig cingulate cortical neurons were studied in vitro using the slice preparation. Results were reported for intracellular recordings made from neurons that were penetrated in layers V/VI of the anterior cingulate cortex areas 1 and 3. 2. The neurons had an average resting potential of -71 mV, an input resistance of 71 M omega, a spike amplitude of 93 mV, and a spike duration of 1.6 ms. The firing occurred regularly at an average rate of 13 spikes/s at the membrane potential of -55 mV, suggesting that they are probably regular spiking pyramidal cells. 3. The voltage decay following a hyperpolarizing current pulse could always be fitted by two exponentials in most cells. The slope of the charging function was analyzed to estimate the two cable theory parameters of the neurons, based on a simple Rall model: the electrotonic length (LN) of the equivalent dendritic cylinder and the conductance ratio (rho) of the dendrites to that of the soma. There were no significant differences in the LN (0.9-1.1) and the rho (2.8-3.0) of neurons in normal media and solutions containing tetrodotoxin (TTX), Cs+ and low Ca2+, indicating that the neurons may be electrically compact. 4. In most cells the steady-state current-voltage (I-V) relationship revealed three distinct types of rectification: an anomalous inward rectification in the hyperpolarizing direction, a subthreshold inward rectification, and a delayed outward rectification in the depolarizing direction. 5. The anomalous rectification was increased in high K+ solutions and was decreased in low K+ solutions. Analysis of the Ba2+ and Cs+ sensitivity confirmed that the anterior cingulate neurons had two distinct types of anomalous rectification, one that was time dependent and Ba2+ insensitive and the other that was fast and Ba2+ sensitive. Ionic analyses indicated that the time-dependent anomalous rectification was due to an increased permeability to both Na+ and K+, whereas the fast, Ba(2+)-sensitive rectification was probably only K+ dependent. 6. The subthreshold inward rectification was depressed by TTX, lidocaine, or Co2+, as well as the reduction of extracellular Na+, whereas it was augmented by extracellular Ba2+. This persistent Na(+)-Ca2+ conductance triggered the generation of Na(+)-dependent action potentials. 7. The delayed outward rectification was recorded in the potential range between -65 and -20 mV.(ABSTRACT TRUNCATED AT 400 WORDS)