Effect of sublethal ionizing radiation on rat Peyer's patch lymphocytes

After sublethal doses of ionizing radiation, rat Peyer's patch lymphocytes regenerated significantly more slowly than lymphocytes from spleen, thymus, and peripheral lymph nodes. Long Evans rats were exposed to 150 rad (40 rad/min) of whole-body irradiation from a 60Co, gamma-emitting source. On Days 1-20 postirradiation, single cell suspensions of lymphocytes from thymus, spleen, peripheral lymph nodes, and Peyer's patches were stained with mouse monoclonal antibody reagents specific for rat lymphocyte subpopulations (Ia+ cells, non-helper T-cell subsets, and helper T-cell subsets). Cells were then counterstained with Texas Red-conjugated, goat anti-mouse IgG and, at the same time, were also stained with fluorescein diacetate to determine viable lymphocytes. The stained lymphocytes were analyzed using a dual-laser, fluorescent-activated cell sorter (Becton-Dickinson FACS-II) from which the percentage of each lymphocyte subpopulation was determined. From our studies, we found that all subpopulations of lymphocytes were affected similarly by irradiation. In addition, we observed that viable lymphocyte subpopulation in thymus, spleen, and peripheral lymph nodes from irradiated animals returned to normal (nonirradiated control animals) levels 5-12 days postirradiation, while viable lymphocyte subpopulations in Peyer's patches from irradiated animals remained suppressed up to 20 days postirradiation. These results suggest that either the lymphocytes or, more likely, the microenvironment of Peyer's patches is more greatly damaged by ionizing radiation than that observed in other lymphoid tissue.     

Effector functions of CD8-positive guinea pig T lymphocytes

The response of guinea pig T lymphocytes to different stimuli was analysed with focus on the functions of CD8-positive T cells, which so far had been poorly defined in this animal model. For identification and purification of guinea pig cytotoxic T lymphocytes, three monoclonal antibodies, directed against the CD8 differentiation antigen were characterized and compared with respect to expression pattern and biochemical characteristics of the corresponding cell surface antigen. The antibodies were used for the identification of the cytotoxic T lymphocyte subpopulation within alloreactive T cell lines, and for the depletion of CD8-positive cells in in vitro assays. Purified CD4- and CD8-positive cells were tested for their ability to proliferate in response to antigen, mitogen or anti-guinea pig Thy-1 monoclonal antibodies. Both, CD4- and CD8-positive cells showed IL-2 release and subsequent proliferation after polyclonal stimulation. Cytotoxic activity in CD8-positive alloreactive T cells was expressed in vitro only after repeated stimulation.     

An ultrastructural study of the development of afferent and efferent synapses on outer hair cells of the guinea pig organ of Corti

The guinea pig organ of Corti was studied using transmission electron microscopy, the second turn of the cochlea being examined at various ages between 20 days before birth and 30 days postnatal. Outer hair cells were examined at each of these ages. At all ages studied, the efferent (presynaptic) terminals are large and are packed with synaptic vesicles, whereas the afferent (postsynaptic) terminals are generally smaller, with a relatively small number of vesicles. During development, the subsynaptic cistern changes from a fragmented, diffuse profile extending over 50-70% of the length of the efferent contact zones, to a continuous, compact structure spanning neighbouring synapses. Synaptic vesicles in the efferent terminals are predominantly rounded in early development, flattened vesicles appearing postnatally. The synaptic bodies at afferent synapses do not change noticeably during development. Quantitative analysis revealed that the area of efferent terminals and the length of their active zone increase with increasing age, the same parameters decreasing in afferent terminals. Synaptic vesicles in the efferent terminals decrease in diameter, but remain constant in afferent terminals, with increasing age. The number of hair cell membrane invaginations decreases as development proceeds.     

Immunohistochemical demonstration of estradiol in the guinea pig ovary

Histochemical study of estradiol in the guinea pig ovary using RIA antiserum revealed specific estradiol fluorescence in theca interna cells and in single cells of atretic follicles. The fluorescence intensity was highest in the estrus phase.     

A freeze-fracture study of afferent and efferent synapses of hair cells in the sensory epithelium of the organ of Corti in the guinea pig

Summary Afferent and efferent synapses of hair cells in the organ of Corti of the guinea pig have been examined in freeze-fracture replicas.Afferent synapse In the inner hair cells, intramembranous particles 10 nm in diameter are aggregated on the ridge on the P-face of the presynaptic membrane directly beneath the synaptic rod. In the outer hair cells, in which the synaptic rod is located in the presynaptic cytoplasm underneath the presynaptic membrane, small aggregations of intramembranous particles 10 nm in diameter can be found on the P-face of the presynaptic membrane corresponding to the site of the presynaptic dense projection. Intramembranous particles 10 nm in diameter are also densely aggregated on the P-face of the postsynaptic membrane of the outer hair cells.Efferent synapse of the outer hair cells Large intramembranous particles 13 nm in diameter are distributed in clusters composed of four to ten particles on the P-face of the presynaptic membrane. In the P-face of the postsynaptic membrane, disc-like aggregations of intramembranous particles 9 nm in diameter are found. The subsynaptic cistern covers the cytoplasmic surface of the postsynaptic membrane of the efferent synapse; it may cover more than one postsynaptic membrane when several efferent synapses are in close proximity to one another.     

Vestibular efferent neurons forming projections to the saccule in the guinea pig

A comparative analysis was made of the distribution of vestibular efferent neurons projecting to the saccule and efferent cells sending out axons to the auditory nerve ("cochlear efferent neurons") in the guinea pig, using retrograde horseradish peroxidase axonal transport techniques. Saccular efferent neurons were discovered bilaterally in the subependymal granular layer at the base of the fourth cerebral ventricle and laterally to the facial nerve genu ispsilaterally in the parvocellular reticular nucleus, as well as nuclei of the superior olivary complex: the lateral olivary nucleus and lateral nucleus of the trapezoid body. Cochlear efferent neurons are located ipsilaterally in the pontine reticular caudal nucleus, in the anteroventral cochlear nucleus, and in the lateral and medial olivary nuclei. Neurons were found contralaterally in the medial nucleus of the trapezoid body. It thus emerged that location zones of vestibular saccular efferent neurons and those of cochlear efferent units partially overlapped. The possible involvement of saccular vestibular efferent neurons in the mechanisms of auditory perception is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 657–665, September–October, 1990.     

Influence of the efferent vestibular system on vestibulo-spinal reflexes in the guinea pig

The influence of the efferent vestibular system on vestibulo-spinal activity was investigated during experiments on guinea pigs decerebrated and following cerebellar extirpation at precollincular level. Efferent vestibular neurons forming compact groups ventromedially to the vestibular nuclei were excited by means of electrical stimulation. Electromyographic activity in the triceps brachii extensor muscles of the right and left forelimbs was adopted as a test reaction (crossed extensor reflex and locomotor activity produced by stimulating the mesencephalic locomotor region). Adequate stimulation of the vestibular apparatus was accomplished by static tilting and cyclic shifting of the animal around its longitudinal axis at angles of ±20°. The efferent vestibular system was found to exert a bilateral inhibitory action on vestibulo-spinal activity. Vestibular efferent stimulation produced a reduction in the intensity of vestibulo-fugal influences: it does not change the dynamics of vestibulo-spinal reflex effects, however. Mechanisms of vestibular efferent action on vestibular control of spinal motor activity are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 1, pp. 78–86, January–February, 1989.     

Lymphocyte traffic through granulomas: Differences in the recovery of indium-111-labeled lymphocytes in afferent and efferent lymph

Afferent lymphatics draining granulomas and efferent lymphatics from normal and stimulated lymph nodes were cannulated in sheep. There was a greatly increased output of cells in afferent lymph-draining chronic inflammatory sites or Freund's adjuvant-induced granulomas. Cells collected from these lymphatics were radiolabeled with ¹¹¹In and injected intravenously. The reappearance of these labeled cells in lymph at various sites was measured. Labeled afferent lymph cells migrated from blood through the granuloma back into afferent lymph in large numbers and with kinetics which were comparable to efferent lymphocytes recirculating through a lymph node. When labeled afferent lymph cells were injected the specific activity (cpm/10⁷ cells) in afferent lymph was five times higher than that in efferent lymph from a normal node. When efferent lymph cells were labeled the afferent lymph specific activity was one-half that in efferent lymph. It is suggested that the cells in afferent lymph migrate preferentially from blood through the granuloma and constitute a unique population of cells.     

Role of murine Peyer's patch lymphocytes against primary and challenge infections with Cryptosporidium parvum

In order to determine the role of Peyeros patch lymphocytes (PPL) in self-clearing of Cryptosporidium parvum infection in murine models, changes in PPL subsets, their cytokine expression, and in vitro IgG1 and IgA secretions by PPL were observed in primary- and challenge-infected C57BL/6 mice. In primary-infected mice, the percentages of CD4+ T cells, CD8+ T cells, sIgA+ B cells, IL-2+ T cells, and IFN-gamma+ T cells among the PPL, increased significantly (P < 0.05) on day 10 post-infection (PI). Secretion of IgG1 and IgA in vitro by PPL also increased on day 10 PI. However, all these responses, with the exception of IgG1 and IgA secretions, decreased in challenge-infected mice on day 7 post-challenge (= day 13 PI); their IgG1 and IgA levels were higher (P > 0.05) than those in primaryinfected mice. The results suggest that murine PPL play an important role in self-clearing of primary C. parvum infections through proliferation of CD4+, CD8+, IL-2+, and IFN-gamma+ T cells, and IgG1 and IgA-secreting B cells. In challenge infections, the role of T cells is reduced whereas that of B cells secreting IgA appeared to be continuously important.     

Signal requirements for lymphocyte activation: Role of a T-cell growth factor produced by guinea pig peritoneal exudate lymphocytes

Peritoneal exudate lymphocytes (PEL) from immunized guinea pigs, when pulsed with antigen, rapidly release a T-cell stimulatory factor (TSF). TSF nonspecifically enhances the proliferation of purified guinea pig T cells in the presence of another signal such as PMA, PHA, or Con A. On a per cell basis, antigen-pulsed PEL produce about 14 times more activity than similarly stimulated lymph node lymphocytes.Several lines of evidence support the view that TSF is the guinea pig equivalent of TCGF (IL-2). TSF containing supernatants have IL-2 activity when assayed on the IL-2-dependent CT6 cell line. When TSF containing supernatants were absorbed with CT6 cells, there was a significant decrease of both TSF activity as assessed on guinea pig T cells as well as IL-2 activity as assessed by the CT6 assay. Additionally, partially purified human and mouse IL-2 have TSF activity, while the macrophage product, IL-1, has no TSF activity. After chromatography on a S-200 column, TSF activity and IL-2 activity coelute at an apparent molecular weight of 19,000.     

Internalization of low-density-lipoprotein-specific receptors in leukemic guinea pig lymphocytes

Leukemic guinea pig lymphocytes (L2C) have ten times as many low-density lipoprotein (LDL) receptors as healthy lymphocytes, but LDL accounts for only 38% of the cholesterol in L2C cells, compared to more than 95% in normal cells. Our data show that LDL fails to regulate cholesterol biosynthesis and that there is a defect in LDL internalization and receptor turnover in L2C cells. We also demonstrate that the degradation of LDL is not a limiting process. By discriminating between binding and internalization, we show that internalization in L2C is much slower than in normal cells and that the decrease in metabolism is related to the slow turnover of the LDL receptors.     

The efferent connections of the lateral septal nucleus in the guinea pig: projections to the diencephalon and brainstem

Summary The anterograde Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique was used to determine the distribution of efferent fibers originating in the lateral septal nucleus of the guinea pig. For complementary detection of the chemical identity of the target neurons, double-labeling immunocytochemistry was performed with antibodies to PHA-L and to vasopressin, oxytocin, vasoactive intestinal polypeptide, serotonin or dopamine -hydroxylase, respectively. The hypothalamus received the majority of the PHA-L-stained septofugal fibers. Here, a specific topography was observed. (1) The medial and lateral preoptic area, (2) the anterior, lateral, dorsal, posterior hypothalamic and retrochiasmatic area, (3) the supraoptic, paraventricular, suprachiasmatic, dorsomedial, caudal ventromedial and arcuate nuclei, and (4) the tuberomammillary, medial and lateral supramammillary, dorsal and ventral premammillary nuclei always contained PHA-L-labeled fibers. The rostral portion of the ventromedial nucleus and the medial and lateral mammillary nucleus only occasionally showed weak terminal labeling. In other diencephalic areas, termination of PHA-L-labeled fibers was observed in the epithalamus and the nuclei of the midline region of the thalamus. In the mesencephalon, terminal varicosities occurred in the ventral tegmental area, interfascicular and interpeduncular nucleus, and periaqueductal gray. In addition, the dorsal and medial raphe nuclei of the metencephalon, together with the locus coeruleus and the dorsal tegmental nucleus, received lateral septal efferents.     

Membrane fluidity of guinea pig lymphocytes and the dysfunction of the respiratory airway and lymphocyte beta-adrenergic systems of the guinea pig

The beta-adrenergic receptor responsiveness of isolated guinea pig tracheal spirals can be negatively affected by intraperitoneal administration of the Gram-negative bacterium Haemophilus influenzae, four days prior to the experiment. The reduction in tracheal relaxation is accompanied by a decrease in beta-adrenergic receptor binding sites in splenic lymphocyte membranes and by a decrease in the fluidity of these membranes. The H. influenzae-induced dysfunction of both the respiratory airway and lymphocyte beta-adrenergic systems can be mimicked by modulating the amount of linoleic acid in the diet. This linoleic acid induced dysfunction of the beta-adrenergic system is also accompanied by a decrease in the plasma membrane fluidity of the splenic lymphocyte membranes of the guinea pigs. The role for plasma membrane fluidity in asthma is discussed in relation to current concepts for atopy.     

Intrinsic innervation of the uterus in guinea pig and rat

The pattern of distribution of cholinergic and adrenergic nerves in the uterus of albino rats and guinea pigs was examined histochemically. In the albino rat, the uterus was found well-innervated by both adrenergic and cholinergic nerves with a clear regional variation. Dense innervation was demonstrated at the tubal and cervical ends of the uterus and in the cervix. Cholinergic nerves supplying the glands were more numerous than the adrenergic nerves which were relatively few. In the guinea-pigs, the uterus was richly innervated by adrenergic nerves with a clear regional variation. No cholinesterase-positive nerves or nerve cells were demonstrated.