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Biomedical subjects

P C Doherty

Publications and source records attributed to P C Doherty.

At least 181 records · Page 10Linked to original sources

Differential effect of hybrid resistance on the localization of virus-immune effector T cells to spleen and brain.

The hybrid resistance (Hr) effect operates in the lymphocytic choriomeningitis (LCM) in vivo transfer model to inhibit both the level of cytotoxicity T lymphocyte (CTL) generation in spleen and the induction of inflammation in cerebrospinal fluid (CSF). The effect is seen when LCM virus-immune T cells that are homozygous for H-2Db are injected into virus-infected, immunosuppressed recipients that are heterozygous for this allele, or into radiation chimeras that express an appropriate F1 phenotype. Evidence that Hr to T-cell transfer is cell-dose-dependent and tends to diminish with age was found in both chimeric and normal F1 mice. Inhibition of the capacity of injected T cells to cause meningitis is a more sensitive measure of Hr than is the further stimulation of CTL effectors in recipient lymphoid tissue. The injection of large numbers of H-2b virus-immune T cells into (H-2k X H-2bF1----H-2k) virus-infected recipients did not induce any cellular extravasation into CSF, though potent H-2b-restricted CTL effectors were generated in recipient spleen. Evidence of minimal inflammatory process was found in one experiment where these chimeras were given a comparable dose of (H-2b X H-2d)F1 immune spleen cells. Development of this T-cell-mediated immunopathological process depends essentially on the expression of the appropriate H-2 restriction element on radiation-resistant host cells which, in this case, presumably constitute part of the physiological barrier between blood and CSF.

Animals↗

Acute experimental allergic encephalomyelitis in radiation bone marrow chimeras between high and low susceptible strains of mice.

Acute experimental allergic encephalomyelitis (EAE) is an autoimmune disease involving the central nervous system (CNS) that can be elicited in susceptible strains of mice by the subcutaneous inoculation of mouse spinal cord homogenate (MSCH) in conjunction with complete Freund's adjuvant. In order to localize the physiological compartment conveying susceptibility to mice for EAE induction, hematopoietic radiation chimeras were prepared between the highly responsive SJL and low responder B10.S strains. Upon challenge with SJL MSCH preparations, high incidence of clinical disease was exhibited by B10.S----SJL chimeras but not by SJL----B10.S mice, suggesting that non-bone-marrow-derived factors were influencing development of disease. The incidence of histological lesions in the CNS was high for virtually all experimental and control groups except normal B10.S and B10.S----B10.S reconstituted mice. In contrast, challenge with B10.S MSCH induced a high clinical incidence of EAE in both B10.S----SJL and SJL----B10.S chimeras, indicating a possible interstrain difference in the immunogenicity of relevant CNS antigens.

Animals↗

Stimulation of helper/delayed-type hypersensitivity T cells by flavivirus infection: determination by macrophage procoagulant assay.

West Nile virus (WNV)-immune spleen cells produced an inducer of macrophage procoagulant activity (MPCA) on restimulation with WNV in vitro. This response was specific for WNV and depended on the presence of Thy 1+, L3T4+ and also Ia+ cells but not Lyt 2+ cells. It could be induced by culture with large amounts of non-infectious, u.v.-irradiated virus or with high doses of infectious virus. Inoculation of mice with low titres of infectious, but not with u.v.-irradiated, virus primed for this in vitro response. The time of maximum production of procoagulant-inducing factor was also the period of greatest [3H]thymidine uptake and release of interleukin-2 (IL-2)-like activity. In bulk cultures, MPCA-inducing factor was more readily quantified than IL-2. T cells of the helper/delayed-type hypersensitivity class are thus stimulated by WNV and this aspect of cell-mediated immunity can be readily assayed in vitro.

Animals↗

Natural killer cells contribute to inflammation but do not appear to be essential for the induction of clinical lymphocytic choriomeningitis.

The inflammatory exudate found in cerebrospinal fluid (CSF) of mice 6 days after intracerebral infection with lymphocytic choriomeningitis virus (LCMV) contains substantial populations of both cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Removal of NK cell activity by in vivo treatment with antibody to the asialo GM1 ganglioside and studies with NK-deficient bg/bg mice did not clearly determine whether NK cells contribute in any way to the development of clinical LCM. However, the LCM disease process induced in cyclophosphamide-suppressed, LCMV-infected recipients by the adoptive transfer of LCMV-immune spleen cells occurs in the absence of NK cell effector function in spleen, lymph nodes, or CSF of the recipients, though potent CTL populations are present in all of these sites. In this situation, NK cells are apparently not required for the induction of neurological symptoms that are indistinguishable from those of classical LCM.

Animals↗

Effects of chronic hyperprolactinemia on sexual arousal and erectile function in male rats.

Studies were conducted to determine if the inhibitory effects of chronic hyperprolactinemia on sexual behavior in male rats occur through reduced sexual arousal as opposed to reduced erectile function. Pituitary-grafted (hyperprolactinemic) and sham-operated, gonadally intact male rats were given standard tests of copulatory behavior, mounting behavior tests after genital anesthetization and penile reflex tests while restrained in a supine position. Beginning 7 days after pituitary transplantation, the number of erections displayed in penile reflex tests was significantly reduced in the pituitary-grafted animals. Increased intromission latencies and reduced intromission rates in tests of copulatory behavior were also observed at this time. Beginning 3-4 weeks after surgery, mounting rates were inhibited in hyperprolactinemic animals in both the copulatory behavior tests and tests of mounting behavior after genital anesthetization. Prolactin levels were significantly elevated in the pituitary-grafted animals, but serum testosterone levels were unaffected. To determine if the effects of hyperprolactinemia on erectile function occurred through changes in supraspinal input to neurons in the spinal cord controlling erectile function, pituitary-grafted and sham-operated male rats were subjected to spinal transection (between vertebral levels T6 and T9). Beginning 7 days later, penile reflex performance was re-examined. Hyperprolactinemic animals displayed significantly fewer erections during the initial test, but not in tests performed 10 and 13 days after spinal transection. The pituitary-grafted animals also showed a significant reduction in latency to the first erection with each successive test, suggesting a delayed recovery from increased supraspinal inhibitory input.(ABSTRACT TRUNCATED AT 250 WORDS)

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Hybrid resistance modulates the inflammatory process induced by lymphocytic choriomeningitis virus-immune T cells.

The magnitude of the meningitis occurring 72 hr after adoptive transfer of 8-day lymphocytic choriomeningitis (LCMV)-immune effector T cells from cyclophosphamide-treated or untreated donors into cyclophosphamide-suppressed, LCMV-infected recipients is modified by the hybrid histocompatibility (Hh) effect. Evidence of inhibition in (H-2Kd Dd X H-2Kb Db)F1, as compared with H-2Kb Db, recipient mice is found for H-2Kd Db, H-2Kd Db and (H-2Kk Db X H-2Kb Db)F1, but not for (H-2Kk Dk X H-2Kb Db)F1 or H-2Kb Dd, LCMV-immune donor populations. The effect is cell dose-dependent, and the inflammatory process is 2.5-10 times lower in F1 than in recipient mice of parental type. These data indicate that the Hh effect is not directed solely at precursor populations, or at T cells which bear idiotypes reactive to MHC glycoproteins expressed in the F1 recipients. The inflammatory process initiated by fully-functional, LCMV-immune T cells is inhibited in the same way. The fact that the levels of natural killer cell activity in the virus-infected, cyclophosphamide-treated recipients are not much higher than those in normal mice indicates that the operation of hybrid resistance in LCM is not likely to be a special case, and should be taken into account in all T cell transfer systems.

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Relapsing experimental allergic encephalomyelitis in radiation bone marrow chimeras between high and low susceptible strains of mice.

The relapsing form of experimental allergic encephalomyelitis (EAE) has been shown to be a useful model of the human disease, multiple sclerosis. This autoimmune disease is organ specific and appears to be primarily a cell-mediated disorder similar to the acute form of EAE. In order to understand better the regulatory mechanisms responsible for development of disease, radiation bone marrow chimeras were prepared between the highly susceptible SJL/J mouse and the resistant B10.S mouse. A high incidence of disease was seen in SJL----SJL and B10.S----SJL chimeras. A low incidence was seen in B10.S----B10.S and SJL----B10.S chimeras. The results were similar in mice immunized with CNS antigen of either BALB/c or B10.S origin. These results demonstrate that the immune system from the resistant B10.S mouse is capable of mediating relapsing EAE when present in a susceptible SJL host, while the SJL immune system was restricted in its ability to induce disease when present in a resistant B10.S host. This would indicate that restriction to the development of EAE may reside outside of the immune system, perhaps involving antigen recognition or presentation in the CNS itself.

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Prolactin stimulation of maternal behavior in female rats.

Inexperienced, hypophysectomized female rats treated with steroids were used in experiments to investigate the roles of the pituitary gland and prolactin in the expression of maternal behavior. Administration of ovine prolactin or treatment with ectopic pituitary grafts, which release prolactin into the circulation, stimulated maternal care in these females toward rat young. Steroid treatment alone, while stimulating maternal behavior in rats with intact pituitary glands, did not facilitate maternal responsiveness in hypophysectomized females. These findings indicate a stimulatory behavioral role for pituitary prolactin in the establishment of maternal care and suggest that exposure to prolactin during pregnancy helps to stimulate the immediate onset of maternal behavior at parturition.

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Consequences of a single Ir-gene defect for the pathogenesis of lymphocytic choriomeningitis.

The H-2Ld allele has been identified by others as the sole Ir gene in the H-2d haplotype for the cytotoxic T lymphocyte (CTL) response to mouse lymphocytic choriomeningitis virus (LCMV). The BALB/c-H-2dm2 (C-H-2dm2) mutant lacks H-2Ld, and thus should be ideal for assessing the contribution of virus-immune CTL to LCM immunopathology. Comparison of the C-H-2dm2 mice with congenic BALB/c mice revealed that there is a delay of about 24 h in the onset of severe inflammatory process and symptoms in the mutant strain, but the absence of H-2Ld did not prevent the later development of fatal disease in mice injected intracerebrally (i.c.) with neurotropic LCMV. This could indicate that virus-immune CTL are not the major mediators of clinical LCM. Spleen cells from LCMV-primed BALB/c mice did not show CTL activity for LCMV-infected C3H.OH, C-H-2dm2, or (CBA X C-H-2dm2)F1 target cells. However, immune lymphocytes from both the mutant and the F1 strains lyse virus-infected BALB/c cells. Furthermore, B10.HTG and, in some experiments, B10.A(5R) mice generated CTL lytic for LCMV-infected BALB/c, C-H-2dm2, and (CBA X C-H-2dm2)F1 macrophages. Apparently H-2Ld is immunodominant in the H-2d-restricted response to LCMV. However, in the absence of H-2Ld, it seems that H-2Kd and, to a lesser extent, H-2Dd also serve as Ir genes for the CTL response in this infection. Even so, the absence of the H-2Ld-restricting element results in a disease process which is either delayed in onset or less severe.

Alleles↗

Immune T cells can protect or induce fatal neurological disease in murine lymphocytic choriomeningitis.

Adoptively transferred immune spleen cells induce fatal neurological disease in cyclophosphamide-suppressed recipients injected intracerebrally (ic) with a large, but not small, dose of neurotropic lymphocytic choriomeningitis (LCM) virus. The elimination of virus from brain in the latter group, which survives without developing symptoms, depends upon the presence of Lyt 2+ lymphocytes. However removal of Lyt 2+ subset which is cytotoxic in vitro does not diminish the severity of the inflammatory process in vivo, though the onset of clinical disease is delayed in mice given Lyt 2-depleted populations and a larger ic dose of virus. The present findings are consistent with the idea that fatal LCM results from acute, synchronous damage to key functional cells in the central nervous system by virus-immune Lyt 2+, lymphocytes. Even so, if the number of virus-infected CNS cells is still relatively small at the time of T cell invasion, neurological symptoms are not recognized and the mice survive.

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Increased serum prolactin levels mediate the suppressive effects of ectopic pituitary grafts on copulatory behavior in male rats.

To determine if deficits in sexual activity observed in pituitary-grafted male rats are due to elevated serum prolactin (PRL) levels found in these animals, the effects of whole pituitary grafts, pars distalis grafts, and ovine (o) PRL treatment on male copulatory behavior were compared. Adult sexually experienced CDF male rats were given four whole pituitary grafts, four pars distalis grafts, or were sham operated. Both groups of grafted animals exhibited suppressed copulatory behavior patterns when tested 18 days after pituitary transplantation. Animals given whole pituitary grafts had significantly longer latencies to mount (P less than 0.05) and to intromit (P less than 0.01) than did the sham-operated controls, while the animals given anterior pituitary grafts differed from the sham-operated controls in latencies to mount (P less than 0.05) and to intromit (P less than 0.01), as well as in the number of intromissions (P less than 0.05). Prolactin-injected animals had significantly reduced intromission rates (P less than 0.01) and significantly increased latencies to mount (P less than 0.05) and to intromit (P less than 0.01) when compared to vehicle-injected controls. Furthermore, the time course of behavioral suppression was similar in oPRL-treated animals to that observed in pars distalis-grafted males, with both groups showing the onset of deficits in sexual activity within 8 to 9 days from the induction of the hyperprolactinemic state. The similarity in pattern and time to onset of behavioral suppression in pituitary-grafted and oPRL-treated animals suggests that behavioral deficits observed in animals with pituitary grafts result from chronic elevation of serum PRL levels.

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Evidence of incomplete behavioral sexual differentiation in obese male Zucker rats.

Genetically obese male Zucker rats displayed lower rates of intromission behavior and ejaculated in significantly fewer tests than lean Zucker littermates. After castration and daily injections of a low dosage (5 micrograms/kg) or estradiol benzoate (EB) followed by progesterone (1 mg/kg), obese males displayed significantly higher lordosis quotients than lean controls. Continued daily administration of higher (10, 15 micrograms/kg) dosages of EB followed by progesterone caused significant reductions in lordotic responsiveness in obese males but not in lean controls. Thus, deficient masculine coital performance was correlated with altered receptive responsiveness to ovarian steroids in obese Zucker male rats. This suggests that the sexual differentiation of the developing brain may be deficient in obese Zucker males.

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Hyperprolactinemia and male sexual behavior: effects of steroid replacement with estrogen plus dihydrotestosterone.

To determine if alterations in the availability of the active metabolites of testosterone (T) are involved in the inhibition of sexual activity in hyperprolactinemic animals, the effects of four ectopic pituitary grafts on copulatory behavior were examined in castrated male rats given subcutaneous implants of T or estradiol-17 beta (E2) plus 5 alpha-dihydrotestosterone (DHT). Two weeks after implantation of the steroid-filled capsules, half the animals of each group were given pituitary grafts and the remainder were sham-operated. Tests of copulatory behavior were performed prior to, and one, two, and three months following pituitary transplantation. Pituitary grafting caused significant inhibition of copulatory behavior in both T and E2 + DHT treated animals. PRL levels were significantly higher in E2 + DHT treated grafted males than in T treated grafted animals (2000 +/- 140 vs. 395 +/- 26 ng/ml), but did not differ between the corresponding control groups (61 +/- 8 vs. 73 +/- 6 ng/ml). The results of these experiments preclude the possible involvement of alterations in steroid secretion by the testes or modifications of the conversion of T to its active metabolites in the effects of hyperprolactinemia on copulatory behavior.

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Hyperprolactinemia inhibits development of Leydig cell tumors in aging Fischer rats.

In inbred CDF (Fischer 344) male rats autopsied at the age of 18-24 months, testicular tumors were present in 24 of 36 control animals but in none of 28 males rendered hyperprolactinemic by transplantation of anterior pituitaries from adult females under the renal capsules. In another experiment, microscopically detectable Leydig cell adenomas were present in each of 11 control animals at the age of 14.5 months but in none of 11 males in which hyperprolactinemia was induced by treatment with diethylstilbestrol. Development of testicular tumors had initially little effect on basal and hCG-stimulated plasma testosterone and androstenedione levels but eventually led to atrophy of the seminal vesicles. Incubated tumor tissue produced large quantities of progesterone and responded to hCG in vitro by an increase in progesterone but not testosterone secretion. Daily sperm production and epididymal sperm reserves were significantly reduced already during early stages of Leydig cell tumor development. We propose that hyperprolactin prevents development of Leydig cell tumors by suppression of plasma LH levels and suggest that age-related reductions in gametogenic and steroidogenic functions of the testes in Fischer rats are due to development of Leydig cell tumors rather than to aging per se.

Age Factors↗

Coital stimuli controlling luteinizing hormone secretion and ovulation in the female ferret.

A series of experiments focused on the masculine coital behaviors controlling pituitary luteinizing hormone (LH) secretion and reflex ovulation in the estrous female ferret. An initial experiment investigated which coital stimuli from the male are required to induce ovulation. It was found that corpus luteum formation, which served as an index of ovulation, occurred in estrous female ferrets only if the male achieved a penile intromission. Neck gripping, mounting, and pelvic thrusting behavior without intromission by the male failed to induce ovulation. A second experiment investigated the timing and magnitude of the coitus-induced LH surge associated with ovulation. Blood was obtained via jugular catheters from estrous females in various mating situations. Plasma LH concentrations were measured by a heterologous radioimmunoassay that was validated for use in the ferret. A significant surge in plasma LH occurred only when an intromission was achieved by the stud male. Plasma LH was significantly elevated 2.0 h after the introduction of the male, peak values were reached 6.0 h later, and this elevation lasted on average 5.7 hours (5/5 females). No LH rise occurred in 2/2 female ferrets in which only neck gripping, mounting, and pelvic thrusting, but no intromission, were allowed to occur. The ferret mating pattern and the resultant LH response differ from those seen in three other induced ovulators (cat, vole, and rabbit) in which the male's intromission latency and duration are much shorter than in the ferret, and in which a distinctive peak in plasma LH often occurs within 1 h after mating.

Animals↗

Participation of cyclophosphamide-resistant T cells in murine lymphocytic choriomeningitis.

A severe inflammatory process can be induced by transferring lymphocytic choriomeningitis virus (LCMV)-immune spleen cell populations into cyclophosphamide (Cy)-suppressed, LCMV-infected recipients. The extent of cellular invasion can be quantified accurately by counting cells obtained from the cisterna magna. The underlying lymphocyte-target cell interactions are apparently very specific, with massive cellular invasion being dependent on the donor and recipient sharing class I major histocompatibility complex glycoproteins. Unlike the situation found by others for delayed-type hypersensitivity in the mouse footpad, the inflammatory process in the cisterna magna was induced to a similar extent by unmanipulated LCMV-immune spleen cells and by lymphocyte populations from mice that were pretreated with 150-200 mg/kg of Cy. This dose of Cy did not eliminate cytotoxic T lymphocytes (CTL) in the mouse strains used. However, immune spleen cells from Cy-pretreated mice showed a reduced capacity to clear virus from the brain. Virus persisted even though the inflammatory process resolved. These results support earlier conclusions that immune CTL are directly responsible for the induction of severe meningitis in LCM, although CTL obviously do not constitute the sole effectors involved in eliminating virus from the central nervous system.

Animals↗