Effects of ivermectin and albendazole against Anisakis simplex in vitro and in guinea pigs

The activity of ivermectin and albendazole against larval Anisakis simplex was tested in vitro and in experimentally infected guinea pigs. Before drug exposure the medium for half of the larvae was adjusted to pH 2.0 with 1 N HCl, whereas the other half was held at pH 7.0. To these solutions, ivermectin was added to full concentrations of 1, 2, 5, 10, 50, 100, or 200 microg/ml, and for albendazole, 300, 400, and 500 microg/ml. Animals from group I were given 0.1 ml of 1% (3.3 mg/kg) ivermectin, whereas guinea pigs from group II were each given 5-7 mg (16.6-23.3 mg/kg) of albendazole orally. The efficacy of both drugs against L, A. simplex was high in vitro and in vivo against the larvae in different organs of guinea pigs.     

Dendrobium huoshanense Polysaccharides Prevent Inflammatory Response of Ulcerative Colitis Rat through Inhibiting the NF-κB Signaling Pathway

The polysaccharides of the Chinese herbal medicine Dendrobium huoshanense exhibit anti-inflammatory effects in multiple organs through regulating the immune responses. In the present study, we constructed ulcerative colitis (UC) model rats using dextran sulfate sodium to investigate the anti-inflammatory effects of D. huoshanense polysaccharides (DHP). After oral administration of DHP for two weeks, the indices of UC symptoms, including the ratio of colon weight to length, Disease Activity Index (DAI), and Colon Mucosal Damage Index (CMDI), all decreased significantly compared with the UC model group. The histological sections also revealed better cell orders in DHP treatments than in the UC model rats. Moreover, in treatment with high dose of DHP (200 mg/kg), the treatment efficacy arrived the similar levels to those in the treatment with 300 mg/kg sulfasalazine, which is a typical medicine to treat UC. These results indicated that DHP has a high efficacy to treat UC in model rats. Furthermore, serum levels of interleukin-1β, tumor necrosis factor-α, interleukin-17, and transforming growth factor-β were assessed using the enzyme linked immunosorbent assay (ELISA) method, and the levels of nuclear factor-κB in colon tissue sections were determined using the immunohistochemical method. The results showed that all these indices decreased significantly after administration of DHP in UC model rats, which might be the mechanisms underlying the DHP-suppressed UC inflammation. Overall, this study indicated that DHP might be directly used to treat UC and is a promising source to develop novel drugs against UC.     

Augmentation of Host Resistance against Bacterial Infection by Treatment with Leustroducsin B,a New CSF Inducer

We tested the in vivo activity of leustroducsin B (LSN B), a new colony-stimulating factor (CSF) inducer isolated from the culture broth of Streptomyces platensis, with mice infected with Escherichia coli. Treatment with LSN B augmented the host resistance to lethal infection of E. coli at doses between 0.1 mg/kg and 1 mg/kg. Serum interleukin-6 (IL-6) levels were found to increase after this treatment, and superoxide anion generation of neutrophils was enhanced in vivo, suggesting that LSN B augmented the host resistance at least in part by inducing IL-6, which subsequently enhanced the bactericidal activity of the neutrophils.     

Comparative studies on multiple forms of serum cholinesterase in various species

Multiple forms of serum cholinesterase (ChE) were compared in 8 species by electrophoretic technique and the following characteristics were noted. The first moving fraction markedly hydrolyzed butyrylthiocholine and the activity was not inhibited by 10(-5)M eserine in the serum of some rabbits tested. Electrophoretic patterns of the ChE were obtained by use of two thiocholines as substrate, and the number of fractions against acetylthiocholine were more than against butyrylthiocholine in dogs, miniature pigs, rabbits, and hamsters. The activities of ChE fractions of dogs (C3), miniature pigs (C1, C2), rabbits (C1), and hamsters (C3) were inhibited by 6.1 X 10(-2)M caffein but not by 10(-4)M ethopropazine, which suggests that the fractions are all true-ChE.     

Effects of amlodipine, diltiazem, and verapamil on the anticonvulsant action of topiramate against maximal electroshock-induced seizures in mice

To assess the effect of 3 calcium channel antagonists (amlodipine, diltiazem, and verapamil) on the anticonvulsant action of topiramate (a new generation antiepileptic drug) in the mouse maximal electroshock seizure (MES) model. Amlodipine (20 mg/kg) significantly enhanced the anticonvulsant activity of topiramate in the MES test in mice, reducing its ED50 value from 54.83 to 33.10 mg/kg (p < 0.05). Similarly, diltiazem (5 and 10 mg/kg) markedly potentiated the antiseizure action of topiramate against MES, lowering its ED50 value from 54.83 to 32.48 mg/kg (p < 0.05) and 28.68 mg/kg (p < 0.01), respectively. In contrast, lower doses of amlodipine (5 and 10 mg/kg) and diltiazem (2.5 mg/kg) and all doses of verapamil (5, 10, and 20 mg/kg) had no significant impact on the antiseizure action of topiramate. Pharmacokinetic verification of the interaction of topiramate with amlodipine and diltiazem revealed that neither amlodipine nor diltiazem affected total brain topiramate concentration in experimental animals, and thus, the observed interactions were concluded to be pharmacodynamic in nature. The favorable combinations of topiramate with amlodipine or diltiazem deserve more attention from a clinical viewpoint because the enhanced antiseizure action of topiramate was not associated with any pharmacokinetic changes in total brain topiramate concentration.     

Effect of N- and M-cholinergic-potentiating and cholinergic-blocking agents on the epileptogenesis of a penicillin focus in the dorsal hippocampus

Chronic experiments on rabbits with penicillin epilepsy have shown that intravenous injections of the ACHE inhibitor galanthamine (1 mg/kg), and N-cholinergic-blockers, ganglerone (3 mg/kg) and eterofen (8 mg/kg), decreased or suppressed completely epileptogenesis manifestations. Combination of galanthamine with one of the N-cholinergic-blockers markedly increased their anticonvulsive actions. On the contrary, combination of galanthamine with the M-cholinergic-blocker metamizil (0.5 mg/kg) enhanced epileptogenesis activity. It is postulated that both M- and N-cholinergic mechanisms take part in the genesis of penicillin epilepsy. The use of N-cholinergic-blockers and their combinations with M-cholinomimetics as anticonvulsants seems expedient.     

Desmodium gangeticum: a potent anti-ulcer agent

The present study was designed to investigate anti-ulcerogenic property of ethanolic extract of Desmodium gangeticum (DG) against cold restraint (CRU, 2 hr cold restraint stress), aspirin (ASP, 150 mg/kg orally), alcohol (AL, absolute alcohol 1 ml/200gm) and pyloric ligation (PL, 4 hr pylorus ligation) induced gastric ulcer models in Sprague Dawley rats, and histamine (HST, 0.25 mg/kg) induced duodenal ulcer in guinea pigs. We found that DG at a dose of 200mg/kg, (orally), markedly decreased the incidence of ulcers in all the above models. DG showed significant protection against CRU (68.37%), AL (88.87%), ASP (38.2%), PL (40.63%) and HST (63.15%) induced ulcer models, whereas standard drug omeprazole (OMZ) showed protection index of 83.86, 56.35, 70.31 and 84.21%, respectively in CRU, ASP, PL and HST models. Sucralfate as standard drug showed 92.64% protection in AL model. DG significantly reduced acid secretion 41.61%, whereas OMZ produced 43.13% reduction. Treatment with DG showed increase in mucin secretion by 56.17%, whereas OMZ showed 12.45% increase. Anti-ulcer effect of DG may be due to its cytoprotective effect along with antisecretory activity and could act as a potent therapeutic agent against peptic ulcer disease.     

Role of serotonin2 receptors in regulating aggressive behavior

Quipazine and pirenperone , the drugs interacting with serotonin2 -receptors, more readily displaced 3H-spiroperidol from its binding sites in the frontal cortex than in the striatum. Pirenperone (0,07-0,3 mg/kg), antagonist of serotonin2 -receptors, selectively decreased the intensity of apomorphine aggressiveness. The antiaggressive action of haloperidol (0,01-0,2 mg/kg) was in correlation with its antistereotypic activity. Long-term administration of naloxone (0,5; 15,0 mg/kg), together with apomorphine (0,5 mg/kg) reduced the number of head-twitches caused by quipazine (2,5 mg/kg). The administration of quipazine 48 hours after the last injection of naloxone and apomorphine caused spontaneous aggressiveness that did not differ from apomorphine aggressiveness. Intracerebroventricular injection of cholecystokinin tetrapeptide (CCK-4) markedly enhanced the foot-shock aggression. The same dose of CCK-4 also decreased the intensity of quipazine (2,5 mg/kg) head-twitches. Compared to haloperidol, pirenperone was a more selective antagonist of CCK-4. After long-term apomorphine treatment (0,5 mg/kg during 10 days, twice daily), the effect of CCK-4 on aggressive behaviour was markedly enhanced. It is possible that two subtypes of serotonin2 -receptors exist in the brain and have opposite action on the aggressive behaviour. CCK-4 may play the role of an endogenous modulator of sensitivity of serotonin2 -receptors involved in the control of aggressiveness.     

Effects of Dietary Copper (II) Sulfate and Copper Proteinate on Performance and Blood Indexes of Copper Status in Growing Pigs

160 crossbred (Duroc × Landrace ×Yorkshire) gilts averaged 21.25 kg body weight were used to study the effects of dietary copper (II) sulfate (CuSO₄) and copper proteinate (Cu-Pr) on growth performance, plasma Cu concentration, ceruloplasmin activity, and erythrocyte Cu/Zn-superoxide dismutase (SOD) activity. All pigs were allotted to four treatments and fed with basal diets supplemented with 0 (control), 250 mg /kg Cu as CuSO₄, and 50 and 100 mg/kg Cu as Cu-Pr. Growth performance was determined based on two growth phase (phase 1: days 0 to 15, phase 2: days 15 to 30). After 30 days of the treatment, 16 pig blood samples (four per treatment) were collected for indexes of copper status determination. The experimental results showed that compared with control, pigs fed with 250 mg Cu/kg as CuSO₄ and 100 mg Cu/kg as Cu-Pr had higher average daily gain and average daily feed intake in the whole growth phase (d 0 to 30). In addition, 250 mg Cu/kg as CuSO₄ and 100 mg/kg Cu as Cu-Pr enhanced plasma ceruloplasmin activity (P < 0.05), and 100 mg/kg Cu as Cu-Pr increased erythrocyte Cu/Zn-SOD activity (P < 0.01) compared with the control. There was no obvious treatment response on plasma Cu concentration in the present study.     

大豆提取物（CKBN）对免疫低下小鼠免疫功能的影响

目的观察大豆提取物（CKBN）对免疫低下小鼠免疫功能的影响。方法腹腔注射环磷酰胺（cyclophosphamide,CTX）建立免疫功能低下小鼠模型,观察1、25、50、100 mg/kg剂量CKBN对免疫低下小鼠免疫功能的影响。结果25 mg/kg组的CKBN可显著增加免疫低下小鼠的脾指数;25、50、100 mg/kg组均能明显抑制环磷酰胺对小鼠外周血白细胞数量的影响,1 mg/kg组可显著提高单核细胞百分率,50 mg/kg组可显著提高中性粒细胞百分率;100 mg/kg组的IgG2a水平高于环磷酰胺组;1、25、50 mg/kg可显著提高腹腔巨噬细胞的吞噬功能;25 mg/kg组可显著提高NK细胞杀伤活性。结论CKBN能显著增强CTX造成的免疫低下小鼠的免疫功能。     

Production of Cloned Wuzhishan Miniature Pigs and Application for Alloxan Toxicity Test

Wuzhishan miniature pig is one of the four most important pig breeds in China and has many major economic characteristics. Herein, we successfully used SCNT to clone Wuzhishan miniature pig. First, ear fibroblasts were isolated from a 2-year-old female Wuzhishan miniature piglet to be used as the donor cell. Second, good-quality COCs were selected from ovaries obtained from pigs at a local slaughterhouse and cultured. Mature eggs with the first polar body and ear fibroblasts were applied SCNT. Lastly, we in total produced 12 piglets with 7 piglets surviving to adults. Next, we used these pigs to test alloxan toxicity and to build T I D diabetes type. We know that diabetes mellitus is a chronic heterogeneous metabolic disease characterized by a high blood glucose level and abnormal insulin secretion. In this study, T I D (type I diabetes) was experimentally induced in cloned Wuzhishan miniature pigs with alloxan. In brief, an intravenous injection of alloxan (group B: 170 mg/kg, n = 3) was administered to pigs weighing between 27 and 39 kg. Sterile saline was administered to control pigs (n = 3). We determined the glycometabolism related index, performed an intravenous glucose tolerance test, and carried out immunohistochemistry experiments. There were no significant differences in body weight, blood glucose, and serum insulin in all groups, before treatment. The level of blood glucose was significantly higher (P < 0.05) in group B (12.18 ± 0.70 mmol/L) than in the control (2.93 ± 0.39 mmol/L). By contrast, the level of serum insulin was lower in group B (5.641 ± 0.573 μIU/mL) than in the control (7.578 ± 0.539 μIU/mL). Histological studies by hematoxylin and eosin (H&E) revealed a loss of β-cells in the pancreas from pigs treated with 170 mg/kg alloxan. Immunolocalization studies showed a decrease in insulin reactivity in this treatment group as well. To conclude, our model holds promise in future studies of diabetes drug testing and islet xenotransplantation.     

Characterization of a hypertriglyceridemic transgenic miniature pig model expressing human apolipoprotein CIII

Hypertriglyceridemia has recently been considered to be an independent risk factor for coronary heart disease, in which apolipoprotein (Apo)CIII is one of the major contributory factors, as it is strongly correlated with plasma triglyceride levels. Although ApoCIII transgenic mice have been generated as an animal model for the study of hypertriglyceridemia, the features of lipoprotein metabolism in mice differ greatly from those in humans. Because of the great similarity between pigs and humans with respect to lipid metabolism and cardiovascular physiology, we generated transgenic miniature pigs expressing human ApoCIII by the transfection of somatic cells combined with nuclear transfer. The expression of human ApoCIII was detected in the liver and intestine of the transgenic pigs. As compared with nontransgenic controls, transgenic pigs showed significantly increased plasma triglyceride levels (83 ± 36 versus 38 ± 4 mg·dL(-1), P < 0.01) when fed a chow diet. Plasma lipoprotein profiling by FPLC in transgenic animals showed a higher peak in large-particle fractions corresponding to very low-density lipoprotein/chylomicrons when triglyceride content in the fractions was assayed. There was not much difference in cholesterol content in FPLC fractions, although a large low-density lipoprotein peak was identified in both nontransgenic and transgenic animals, resembling that found in humans. Further analysis revealed markedly delayed clearance of plasma triglyceride, accompanied by significantly reduced lipoprotein lipase activity in post-heparin plasma, in transgenic pigs as compared with nontransgenic controls. In summary, we have successfully generated a novel hypertriglyceridemic ApoCIII transgenic miniature pig model that could be of great value for studies on hyperlipidemia in relation to atherosclerotic disorders.     

Cytochemical and ultracytochemical studies of peroxidase activity in rabbit blood granulocytes under hydrocortisone effect

Cytochemically peroxidase activity has been examined on the light optical and ultrastructural levels in blood granulocytes of the rabbits after a single (5 mg/kg) and multiple (1 and 5 mg/kg every 24 hrs during 4 weeks) administrations of hydrocortisone. Under electron microscope peroxidase activity was detected in the blood of intact rabbits into typical primary granules (TPG) and small polymorphic granules (SPG) of neutrophils as well as into specific granules of basophils sometimes in perinuclear space and GER channels. 6 h after hydrocortisone injection peroxidase activity in neutrophils increased, the reaction product in both kinds of cytoplasmic granules was electron denser than in the controls. After multiple hydrocortisone (1 mg/kg) administrations peroxidase general activity in granulocytes has not considerably changed, but the number of TPGs and SPGs was decreased in neutrophils. Multiple administrations of a higher dose of hydrocortisone (5 mg/kg) have induced peroxidase activity decreasing in neutrophils and a decrease in the number and electron density of TPGs and SPGs in them. In basophils there was a significant accumulation of the reaction product of high electron density in perinuclear space, in specific granules and GER channels. The conclusions has been drawn that a short-term raising of hydrocortisone level stimulates and prolonged hypercorticism inhibits peroxidase activity in neutrophils and, consequently, their function.     

Effects of Oxyamylose and Polyacrylic Acid on Foot-and-Mouth Disease and Hog Cholera Virus Infections

Two interferon-inducing polycarboxylates were tested for antiviral activity on foot-and-mouth disease (FMD) virus infections in mice, guinea pigs, and swine. Polyacrylic acid, given intraperitoneally, had a protective effect on infection by FMD virus administered in the peritoneal cavity of mice and in the foot pad of guinea pigs. Chlorite-oxidized oxyamylose (COAM) was effective in mice at a dosage of 2 mg/kg. Swine were not protected against naturally transmitted FMD by 120 mg/kg of COAM nor by polyacrylic acid. Swine were not totally unresponsive to COAM since it delayed symptoms of hog cholera. Interferon was not detected in the serum of COAM-treated swine. With FMD virus, an example was found of activity of interferon inducers in experimental hosts and lack of activity in a natural host.     

Effect of excessive dietary fluoride on nutrient digestibility and retention of iron, copper, zinc, and manganese in growing pigs

Ninety-six crossbred growing pigs were used to evaluate the effects of fluoride levels on growth performance, nutrient digestibility, and the retention of minerals in tissues. Four dietary treatments were formulated by supplementing fluorine (as NaF) to a corn-soybean basal diet (39.75 mg/kg F) to provide the following added fluorine levels: 0, 50 100, and 150 mg/kg fluorine. The results showed pigs of the 100 and 150 mg/kg fluorine-added groups had decreased average daily gain (ADG) and increased feed gain ratio (F/G) compared to the control (p<0.05). Apparent digestibility of protein and calcium in 100 and 150 mg/kg fluorinetreated groups was significantly lower than that of the control (p<0.05). On the other hand, iron, copper, zinc, and manganese levels in most tissues of the 100 and 150 mg/kg fluorine groups were markedly changed compared to the control (p<0.05). However, growth performance, nutrient digestibility, and mineral concentrations in all tissues of pigs were not significantly affected by the addition of 50 mg/kg fluorine (p>0.05). Thus, this study suggested that excess fluoride levels could decrease growth performance and change the retention of iron, copper, zinc, and manganese in pigs.     

Immunostimulatory effect of Tinospora cordifolia Miers leaf extract in Oreochromis mossambicus

Immunostimulatory effect of leaf extract of T. cordifolia on (i) specific immunity (antibody response), (ii) non-specific immunity (neutrophil activity) and (iii) disease resistance against Aeromonas hydrophila was investigated in O. mossambicus. Ethanol and petroleum ether extracts of the leaves were used. Both ethanol and petroleum ether extracts administered at doses of 0.8, 8 or 80 mg/kg body weight, prolonged the peak primary antibody titres upto one to three weeks. Ethanol extract at the dose of 8 mg/kg and petroleum ether extract at the doses of 0.8 or 8 mg/kg enhanced the secondary antibody response. All the doses of ethanol extract significantly enhanced neutrophil activity. Fish injected with petroleum ether or ethanol extract at a dose of 8 mg/kg were protected against experimental infection with virulent A. hydrophila. The results indicates the potential of T. cordifolia leaf extracts for use as an immunoprophylactic to prevent diseases in finfish aquaculture.     

Role of N-methyl-D-aspartate (NMDA) receptors in experimental catalepsy in rats

N-methyl-D-aspartic acid (NMDA; 40 mg/kg, i.p.) did not elicit catalepsy, but it potentiated the cataleptic effect of haloperidol and GABAB receptor agonist, baclofen. MK-801 (0.2 mg/kg, i.p.), NMDA-receptor antagonist, reversed haloperidol- but not baclofen-induced catalepsy. MK-801 also potentiated the anticataleptic effect of scopolamine and bromocriptine against haloperidol-induced catalepsy. Dihydropyridine (DHP) calcium-channel antagonists such as nimodipine and nitrendipine (10 mg/kg, i.p.), reversed the anticataleptic effect of MK-801, and potentiated the cataleptic effect of haloperidol, as well as baclofen. These observations indicate the involvement of NMDA receptors in catalepsy, and suggest a potential clinical implication of NMDA-receptor antagonists in Parkinson's disease.     

Role of endogenous nitric oxide on PAF-induced vascular and respiratory effects

The role of endogenous nitric oxide (NO) on vascular and respiratory smooth muscle basal tone was evaluated in six anaesthetized, paralysed, mechanically ventilated pigs. The involvement of endogenous NO in PAF-induced shock and airway hyperresponsiveness was also studied. PAF (50 ng/kg, i.v.) was administered before and after pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg, i.v.), an NO synthesis inhibitor. PAF was also administered to three of these pigs after indomethacin infusion (3 mg/kg, i.v.). In normal pigs, L-NAME increased systemic and pulmonary vascular resistances, caused pulmonary hypertension and reduced cardiac output and stroke volume. The pulmonary vascular responses were correlated with the increase in static and dynamic lung elastances, without changing lung resistance. Inhibition of NO synthesis enhanced the PAF-dependent increase in total, intrinsic and viscoelastic lung resistances, without affecting lung elastances or cardiac activity. The systemic hypotensive effect of PAF was not abolished by pretreatment with L-NAME or indomethacin. This indicates that systemic hypotension is not correlated with the release of endogenous NO or prostacyclines. Indomethacin completely abolished the PAF-dependent respiratory effects.     

Glutathione Peroxidase Activity and Erythrocyte Lipid Peroxidation as Indices of Selenium and Vitamin E Status in Young Pigs

A randomized, blocked 23 factorial experiment was conducted with 48 pigs from sows fed a diet low in selenium and vitamin E. From 3 to 12 weeks of age the piglets were kept in single pens and fed a basic diet consisting mostly of barley, dried skim milk, soybean meal and dried yeast, and containing 55 µg selenium and 3 mg vitamin E per kg. The treatment factors — i.e. feed supplements — were 2 levels of Se (nil, 60 µg/kg), 2 levels of vitamin E (nil, 50 mg/kg), and 2 levels of the feed antioxidant ethoxyquin (nil, 150 mg/kg). Blood samples, collected at termination of the experiment, were examined for glutathione peroxidase activity (GSH-Px) and resistance against erythrocyte lipid peroxidation (ELP) to evaluate Se and vitamin E status, respectively. Analysis of variance showed the GSH-Px activity to be litter-dependent (P < 0.001) and influenced by selenium supplementation (P < 0.001) but not by the other supplements or by interactions between supplements. Resistance against ELP was influenced only by vitamin E supplementation (P < 0.001). GSH-Px and ELP thus seem to be valuable and simple methods for evaluating, respectively, Se status and vitamin E status in growing pigs.     

Myelosuppression in the Pig (Sus scrofa): Uteroferrin Reduces the Myelosuppressive Effects of 5-Fluorouracil in Young Pigs

The present study investigated the ability of uteroferrin to modulate the myelosuppressive effects of 5-fluorouracil (5-FU) in young pigs (Sus scrofa). Pigs (28–35 days of age; n = 6 per treatment) were infused with equal amounts of 5-FU on days 0 and 1 of the experimental period (37.5 mg/kg cumulative dose). Uteroferrin (100 μg/kg in 0.9% NaCl) or control (equivalent volume of 0.9% NaCl) was administered to pigs as intramuscular injections twice daily (08:00 and 20:00 hr) on days 1 through 21. Peripheral blood cell number, composition and progenitor cells were determined over 28 days. Treatment of pigs with 5-FU resulted in a rapid dose-dependent (P < 0.05) leukocytopenia. Concurrent treatment of pigs with uteroferrin reduced (P < 0.05) the rate of 5-FU-induced leukocytopenia (44 vs 77 ± 7% decline from baseline on day 3) and enhanced (P < 0.05) the recovery from 5-FU on days 10 and 12 postinfusion. The positive effect of uteroferrin on leukocytes resulted primarily from a protection and/or enhanced recovery of neutrophils and monocytes. In addition, uteroferrin attenuated (P < 0.05) the suppression of red blood cell numbers after 5-FU administration (6.9 vs 6.1 ± 0.2 × 10⁶ cells/μl on day 3), an affect reflected in increased hematocrit and hemoglobin concentrations. The effects of uteroferrin appeared to result from enhancement of the proliferation and/or differentiation of primitive pluripotent stem cells resistant to 5-FU, as concurrent treatment of pigs with uteroferrin resulted in a protection and/or enhanced recovery (P < 0.05) of CFU-GEMM, CFU-GM and BFU-E progenitor cells in the peripheral blood. These results are the first to demonstrate that uteroferrin can reduce the myelosuppressive effects of 5-FU in the pig and suggest that uteroferrin has hematopoietic growth factor activity in vivo.