Unoperated Mice Research Articles

Surgical stress reduces mortality from endotoxin shock.

Surgical stress has been considered a preliminary to multiple organ failure through what has been termed a "two-hit" mechanism. Recent evidence, however, suggests that such stress has a beneficial influence in reducing endotoxin [lipopolysaccharide (LPS)]-mediated lethality. This study has been an effort to clarify whether and how LPS-mediated septic shock is prevented by a previous insult with mild (laparotomy) or severe (hepatectomy) surgical stress. LPS was injected intraperitoneally into mice after two-thirds hepatectomy or laparotomy only. Survival rates, and protein and messenger RNA (mRNA) levels for tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured. Most of the unoperated control mice died within 3 days after the LPS challenge. Mortality following LPS injection was reduced after laparotomy only or hepatectomy (P<0.05). A significant reduction in the mortality was observed from 2 days to 7 days after laparotomy only, and from 2 days to 4 weeks after hepatectomy. Correspondingly, the increase in the serum levels of TNF-alpha and IL-6 induced by the LPS injection was partially impaired by either laparotomy only or hepatectomy at an early (2 days) postoperative stage (P<0.05). At a later (7 days) stage, however, the serum level of IL-6 and its mRNA level in the spleen were elevated after the LPS challenge more quickly in the hepatectomy group than in the unoperated control group ( P<0.05). Surgical stress reduces LPS-induced lethality through biphasically regulating the levels of TNF-alpha and IL-6 production.

Upregulation of transcription factors in lung in the early phase of postpneumonectomy lung growth.

In the adult rodent, pneumonectomy results in compensatory lung growth characterized by cell proliferation. The molecular mechanisms governing this response remain unknown. We hypothesized that, in the early period postpneumonectomy, upregulated expression of transcription factors drives the growth process. We utilized a cDNA expression array to screen for upregulated transcription factors after left pneumonectomy in adult C57BL/6 mice, using unoperated mice as controls. Quantification of mRNA expression in the remaining lung at 2 h demonstrated a twofold or greater upregulation of six transcription factors: early growth response gene-1 (Egr-1), Nurr77, tristetraprolin, the primary inhibitor of nuclear factor-kappa B (I kappa B-alpha), gut-enriched Krüppel-like factor (GKLF), and LRG-21. Northern analysis was used to quantify the upregulation of expression of these genes relative to sham thoracotomy and unoperated controls. The largest increase was in Egr-1 (4.7-fold > naive). Time-course analysis over the first 24 h confirmed the transient nature of the early upregulation. In the context that postpneumonectomy lung growth is associated with cell proliferation and that genes such as Egr-1, Nurr77, LRG-21, and tristetraprolin have known roles in stress response, vascular biology, embryology, and cellular development, these data support the concept that transcription factors function early in the cascade of events leading to the compensatory response.

The effect of the serotonergic system on opioid withdrawal-like syndrome in a mouse model of cholestasis.

There is a marked elevation of endogenous opioid levels in plasma of human subjects with biliary cirrhosis as well as animal model of cholestasis. In addition, development of morphine tolerance and dependence has been shown to be inhibited by drugs which reduce brain serotonin levels. However, intracerebroventricular injection of serotonin increases the morphine analgesia. In the present study we have investigated the role of the serotonergic pathway in determining the withdrawal syndrome in a mouse model of cholestasis. There were three experimental groups: unoperated mice, sham operated mice and mice in which the main bile duct was ligated. Physical dependency was assessed by precipitating a withdrawal syndrome (writing, climbing, rearing, grooming and jumping) by naloxone (2 mg/kg) 5 days after induction of cholestasis. In separate experimental same groups, the antinociception was evaluated by the tail flick latency (TFL) test. Administration of serotonin receptors antagonists, cyproheptadine (10 mg/kg), methysergide (6 mg/kg) and ondansetron (10 mg/kg) attenuated withdrawal signs and decreased the antinociception. However, treatment by fluoxetine (15 mg/kg), an inhibitor of serotonin reuptake, increased the withdrawal signs and antinociception. These experiments lead us to conclude that the naloxone-precipitated withdrawal signs which occur in the mouse model of cholestasis are potentially dependent on the serotonergic pathway. Copyright 2000 John Wiley & Sons, Ltd.

Loss of Function ofTrp53,but NotApc,Leads to the Development of Esophageal Adenocarcinoma in Mice with Jejunoesophageal Reflux

Introduction. APCandTP53are tumor suppressor genes known to be altered frequently in human esophageal adenocarcinoma (EAC), which arises as a complication of reflux disease. To determine the functional role of these genes in the development of EAC, we have created reflux in mice gene-targeted for eitherTrp53orApc.Methods.Wild-type (WT), p53-knockout (Trp53−/−), orApc-mutated (ApcMin/+) mice were generated in our breeding colony. Total gastrectomy with esophagojejunostomy was performed at 6 weeks of age, creating jejunoesophageal reflux. Unoperated control mice were maintained under identical conditions. Mice were sacrificed at 30 weeks of age. Histology of the esophagus and jejunal anastamosis or gastroesophageal junction was reviewed by a single pathologist blinded to the genotype of the animal.Results.The esophagus was normal in all of the unoperated mice (6ApcMin/+, 6 WT, and 6Trp53−/−). All operated mice (6ApcMin/+, 12 WT, and 4Trp53−/−) had esophagitis, with squamous hyperplasia and early focal ulceration. Barrett's metaplasia was identified in 33% of the operatedApcMin/+(2/6) and 25% of theTrp53−/−(1/4) mice, but not in the WT mice. Of 4 operatedTrp53−/−mice, all developed severe dysplasia of the squamous epithelium and 2 (50%) had EAC on histology, although no gross tumors were seen. No severe dysplasia or carcinoma was identified in any of theApcMin/+or WT mice.Conclusions.Loss of eitherTrp53orApcleads to the development of columnar metaplasia, whereas loss ofTrp53,but notApc,leads to development of cancer in mice with jejunoesophageal reflux.

Plasticity of cerebral metabolic whisker maps in adult mice after whisker follicle removal—I. modifications in barrel cortex coincide with reorganization of follicular innervation

We investigated alterations of the metabolic whisker map of barrel cortex after the removal of the follicles of left whiskers Cl, C2 and C3 in adult albino mice. The quantitative autoradiographic [ 14C]deoxyglucose method was used to measure local cerebral metabolic rates for glucose in barrel cortex of mice two, four, eight, 64, 160 and 250 days after the lesion. Metabolic rates were measured in three groups of animals: (i) mice with lesions that had all whiskers clipped; (ii) mice with lesions that had left whiskers B1–3 and D1–3 stimulated; and (iii) unoperated mice that had left whiskers B1–3 and D1–3 stimulated. Compared with the metabolic rates in barrels Cl-3 of stimulated unoperated mice, barrels C1–3 of stimulated mice with lesions showed the first discernible increase in metabolic rate four days after the lesion. The increase became distinct at 64 days, but attained statistical significance only ∼ 160 days after the lesion. The lesion per se, i.e. without whisker stimulation, caused only a small increase in metabolic rate in barrels Cl-3 accounting for not more than one fourth of the increase in metabolic rate measured after whisker deflection. The removal of whisker follicles Cl-3 led, therefore, to an enlargement of the metabolic representations of the adjacent whiskers into the barrels deprived by the lesion. The gradual consolidation of the alterations of the metabolic whisker map coincided with the regeneration of follicular nerves in the whiskerpad. We detected anomalous deep nerves innervating follicles surrounding the lesion at ∼ 64 days, and the number of myelinated nerve fibres in the deep nerves of these follicles was increasing with increasing time after the lesion. The coincidence of peripheral and central change suggests that the reorganization of the innervation of the sensory periphery plays an important role in the persistent alterations of the cortical somatotopy in adults following a lesion in the sensory periphery.

Plasticity of cerebral metabolic whisker maps in adult mice after whisker follicle removal— II. Modifications in the subcortical somatosensory system

The follicles of whiskers C1–3 were removed from the left side of the snout of adult mice. Adjacent whiskers B1–3 and D1–3 were stimulated while local rates of glucose utilization were measured with the [ 14C]2-deoxyglucose method two, four, eight, 64, 160 and ∼250 days after follicle removal. Local metabolic activity in the trigeminal sensory brainstem and somatosensory thalamus was compared with that of unoperated mice with the same stimulation and of mice with the same lesion that had all whiskers clipped. Actual rates of glucose utilization were measured in brainstem subnuclei caudalis and interpolaris whereas metabolic activation was only assessable by colour-coded imaging in brainstem nucleus principalis and in the thalamic ventrobasal complex. Whisker stimulation activated the somatotopically appropriate loci in brainstem and thalamus. In addition, the territory deprived by follicle removal was metabolically activated in subnuclei caudalis and interpolaris at all time intervals examined. The activation was statistically significant in subnucleus interpolaris at two days, indicating that the metabolic representations of whiskers neighbouring the lesion rapidly expanded into the deprived territory. Nucleus principalis showed a broad metabolic activation at two and four days that was absent at the longer time intervals examined. Instead, at ∼250 days the metabolic representations of the whiskers adjacent to the lesion were enlarged into the deprived territory as in the subnuclei. Since metabolic whisker representation in the ventrobasal complex appeared to have changed in the same fashion, follicle removal apparently resulted in congruent modifications of the whisker map in the three nuclei of termination as well as in the thalamic relay at the longest time interval examined. Since metabolic responsiveness of the deprived barrels in barrel cortex of the same animals increased statistically significantly only several months after follicle removal, the novel neural responses in the brainstem were not effectively transmitted to barrel cortex immediately and the slowly evolving cortical modifications are more likely to be associated with regrowth of the connectivity of primary neuron. 28 By contrast, unmasking of hitherto suppressed inputs may underlie the early expansion of metabolic whisker representation in the brainstem.

Plasticity of metabolic whisker maps in somatosensory brainstem and thalamus of mice with neonatal lesions of whisker follicles.

We employed the autoradiographic deoxyglucose method to study metabolic whisker maps of the adult mouse somatosensory brainstem and thalamus after the neonatal removal of left whisker follicles C1, C2 and C3. Left whiskers B1-3 and D1-3 were deflected to metabolically activate the somatosensory pathway. Unoperated mice that were stimulated in the same fashion served as controls. Whisker stimulation resulted in an ipsilateral increase in metabolic activity in the three trigeminal brainstem structures in which the whiskers are represented topologically by segments of high cytochrome oxidase activity, i.e. subnucleus caudalis, subnucleus interpolaris and nucleus principalis. In the two subnuclei of mice with lesions and of controls, there was an increase in metabolic activity of the representations of the deflected whiskers, whereas the metabolic activity of representations A1-3 and E1-3 was low. Apart from these similarities, the metabolic activation of the representations originally representing whiskers C1-3 was remarkably greater in mice with lesions than in controls. This increase reached statistical significance in subnucleus caudalis and approached statistical significance in subnucleus interpolaris. In nucleus principalis the deprived territory was only partially activated and the degree of metabolic activation was less than in the subnuclei. In the thalamic ventrobasal complex of mice with lesions metabolic activity was unpatterned whereas two areas of metabolic activation were distinct in controls. Hence, the removal of whisker follicles in newborn mice resulted in the suppression of localized metabolic responses to whisker stimulation in the thalamus, whereas in the brainstem stimulus-related activity was prominent and the deprived territory became responsive to the stimulation of whisker follicles adjacent to the lesion. Apparently, the modification of the whisker representation at the first synapse of the pathway induces a diminution of localized responsivity in the thalamus.

Amygdala lesions block the effect of cocaine on memory in mice

Post-training cocaine intraperitoneal administration enhanced memory consolidation in unoperated and sham-lesioned mice tested in a one-trial inhibitory avoidance task. Bilateral electrolytical amygdala lesions blocked this effect. The results are interpreted in terms of involvement of neurotransmitter, and in particular dopaminergic, systems in the effects of cocaine on memory.

Basal cells in the mouse olfactory epithelium after axotomy: immunohistochemical and electron-microscopic studies

The olfactory epithelium of mice after axotomy was investigated to clarify the stem cells of olfactory cells by double immunostaining using antikeratin (MA903) and anti-bromodeoxyuridine (BrdU) antibodies and by conventional electron microscopy. When a single dose of BrdU was given to mice 9 days after axotomy, immunostaining for BrdU was found in the globose basal cells which were negative for MA903, but not in the basal cells proper which were positive for MA903. The BrdU-immunoreactive cells increased 3- to 6-fold over the number of these cells in the controls, indicating active cell proliferation. At other postoperative days (4 and 14 days), fewer BrdU-immunoreactive cells were found. Furthermore, three pulses of BrdU resulted in numerous BrdU-immunolabelings in the globose basal cells and a few in the basal cells proper. There was no detectable difference in the number of labeled basal cells proper in operated and unoperated mice. In the electron micrographs 9 days after axotomy, the basal cells proper, flat-shaped in unoperated mice, appeared cylindrical or pyramidal in shape and the globose basal cells often lay between the basal cells proper. In unoperated controls, the globose basal cells were located above the flat-shaped basal cells proper. The results suggest that the stem cells of the olfactory cells are globose basal cells and not basal cells proper, and that the shape of basal cells proper changes in relation to the active proliferation of stem cells.

Relative efficacy of slow and fast alpha-motoneurons to reinnervate mouse soleus muscle

Contractile and histochemical properties of reinnervated motor units in soleus muscles of C57BL/6J mice were examined 1 mo after sectioning the soleus nerve. Fifty-one motor units were isolated by the technique of ventral root splitting. Their sizes ranged from 0.4 to 13.6% of whole muscle tetanic tension (Po) with a mean size of 5.3% Po corresponding to 19 motor units. In control unoperated mice, the range was 2.2-8.6% Po, with a mean size of 4.8% Po corresponding to 22 motor units. Although no clear relationship between unit time to peak tension and size was seen in control units, it appeared that in the reinnervated muscle the large units were also slow contracting, whereas the smaller units were predominantly fast contracting. Adenosinetriphosphatase (ATPase) staining revealed an increase in the proportion of muscle area occupied by type I fibers in reinnervated soleus compared with control soleus. Immunohistochemical staining of reinnervated soleus with monoclonal antibodies against type I and IIa myosin showed the presence of hybrid fibers containing both myosins. It is concluded that during reinnervation most motoneurons reinnervate the soleus muscle of the mouse. The hypothesis that slow motoneurons are more adept at expanding their innervating field than fast motoneurons is also supported by the data.

The amygdala mediates the impairing effect of the selective κ-opioid receptor agonist U-50,488 on memory in CD1 mice

The effect of the selective κ-opioid receptor agonist U-50,488 on passive avoidance behaviour was studied in CD1 mice bearing lesions of the amygdaloid complex. The results have shown that post-trial injections of U-50,488 in unoperated mice as well as lesions of the amygdaloid complex in untreated mice decreased retention performances. No further impairment was observed in lesioned mice treated with U-50,488, indicating that amygdala is involved in the mediation of the effects of κ-opioid receptor agonists on memory. The possibility that κ-opioid receptors could modulate the memory retention of CD1 mice by influencing their emotional state is discussed.

Thyrotropin releasing hormone-induced hyperthermia in mice: possible involvement of adrenal and pituitary glands.

To investigate the hyperthermic effect of thyrotropin releasing hormone (TRH) and its potentiation by exogenous catecholamines (CA), the role of the adrenal medulla and of the pituitary gland was studied in unoperated, adrenal-demedullated or hypophysectomized mice. In unoperated mice, TRH 40 mg kg-1 i.p. produced a hyperthermia which was accompanied by an increase in plasma noradrenaline (NA) and adrenaline (Ad). NA or Ad, both at a dose of 1 mg kg-1 i.p., enhanced the TRH-induced hyperthermia. Adrenal demedullation suppressed the hyperthermia and the increase of plasma CA produced by TRH but not the potentiation of this hyperthermia by exogenous CA. Hypophysectomy abolished the TRH-induced hyperthermia but not the increase of plasma CA or the potentiation of this hyperthermia by exogenous CA. These results suggest that, in mice, both the adrenal medulla and the pituitary gland play an essential role in TRH-induced hyperthermia but not in its potentiation.

Bilateral lesions of suprachiasmatic nuclei affect circadian rhythms in [3H]‐thymidine incorporation into deoxyribonucleic acid in mouse intestinal tract, mitotic index of corneal epithelium, and serum corticosterone

Investigations into the role of the suprachiasmatic nuclei (SCN) in the coordination of circadian rhythms have presented differing results. Several reports have shown that ablation of the suprachiasmatic nuclei (SCNA) alters the phase and amplitude of rhythms but does not abolish them. The present study investigates the effect of SCNA on the rhythms in cell proliferation in various regions of the intestinal tract as measured by the incorporation of [3H]-thymidine into deoxyribonucleic acid, in the mitotic activity of the corneal epithelium, and in serum corticosterone levels. The study involved mice with verified lesions of the SCN (six to 13 mice per time point) and control groups of both sham-operated and unoperated mice (seven of each per time point). The mice were killed in groups that represented seven time points over a single 24 hr span (3 hr intervals with the 0800 hr sampled both at start and end of the series). The tissues examined were the tongue, esophagus, gastric stomach, and colon for DNA synthesis, the corneal epithelium for mitotic index, and blood serum for corticosterone level. The most consistent result of SCNA was a phase advance in the rhythms in cell proliferation in the tongue, esophagus, gastric stomach, colon, and corneal epithelium. A reduction in rhythm amplitude occurred in the tongue, esophagus, and corneal epithelium; however, there was an amplitude increase for the stomach, colon, and serum corticosterone. The mesor (rhythm-adjusted mean) was increased by SCNA in all tissues except the corneal epithelium. These findings further support the role of the suprachiasmatic nuclear area in the control of rhythms in cell proliferation and corticosterone production, by acting as a "phase-resetter" and as a modulator of rhythm amplitude.

Depression of hepatic mixed-function oxidase activity by B. pertussis in splenectomized and athymic nude mice

Administration of Bordetella pertussis (B. pertussis), Corynebacterium parvum (C. parvum), and several other immunoactive substances is known to cause a marked decrease in the activity of the hepatic microsomal mixed-function oxidase system. The effect of C parvum has been reported to involve the reticuloendothelial system. In the present study, the effect of B. pertussis administration to decrease hepatic microsomal drug metabolism was studied in unoperated, sham-operated, and splenectomized mice as well as in athymic nude (nu/nu) mice and their phenotypically heterozygous (+/nu) littermates. Administration of B. pertussis to the splenectomized, sham-operated, and unoperated mice resulted in a decrease in the activity of the microsomal enzyme system that was approximately the same for each of the three groups of animals. Administration of B. pertussis to nu/nu mice and the +/nu mice also decreased the microsomal enzyme activity measured 24 hr after injection. However, at 7 days after B. pertussis administration, the hepatic drug-metabolizing activity of the nu/nu mice was not significantly different from control values, whereas the activity of the +/nu mice was still significantly depressed. The failure of splenectomy to prevent the decrease in microsomal mixed-function oxidase activity caused by B. pertussis indicated that the effect of this agent differs from that of C. parvum, whose effect was prevented by splenectomy. Indeed, the results obtained with the athymic nude mouse suggests that the depression of hepatic mixed-function oxidase activity by B. pertussis may involve T-cell dependent responses.

Olfactory bulb removal and taste aversion learning in mice

Bulbectomized and unoperated mice were given 1 h of exposure to a novel food (almond) before receiving an intraperitoneal injection of lithium chloride solution. Their consumption of almond was recorded for the subsequent 10 days. Mice of both groups acquired a marked aversion to almond, and the unoperated mice continued to eat little throughout the experiment. The bulbectomized mice resumed eating more rapidly and, by the third day after the induction of illness, their consumption of almond did not differ from that of a control group which had not been lithium treated. The integrity of the olfactory system appears necessary for the maintenance, though not the establishment, of a taste aversion.

Tumor growth: suppression in mice by submanidibular gland extirpation.

Transplanted A-10 breast adenocarcinomas grew more slowly in young-adult male A/HeJ mice from which the submandibular glands had been extirpated than in sham-operated or unoperated control mice of the same strain. The mitotic index was lower in tumors from experimental animals than in those from controls. Vascularization about the tumor margins was also less prominent. The C1300 neuroblastoma grew more slowly in sialoadenectomized mice than in controls. Modulation of tumor growth by factors of salivary gland origin may have been responsible for these effects.

The Influence of Gonadectomy of Host on Parasitemia and Mortality of Mice Infected with Trypanosoma cruzi

Male CF1 mice were more susceptible to acute infections of Trypanosoma cruzi than female mice as evidenced by significantly greater maximum mean parasitemia of approximately 8.9 times 10-6 per ml in males as compared to 1.5 times 10-6 per ml in females. Mortality was also greater in males (80 to 90% as compared to 28% in females). Ovariectomy of female mice made them more susceptible than unoperated female of similar age and stock to the Brazil strain of T. cruzi as indicated by maximum mean parasitemia of 10.9 times 10-6 per ml in the former and 7.5 times 10-6 in the latter. Mortality of the ovariectomized mice was as great as 90% in some experiments while that of unoperated controls nerve exceeded 30%. Parasitemia and mortality is castrated male mice were not significantly different from unoperated male mice infected with T. cruzi.

Studies on the erythropoietic stimulating factor in the plasma of mice after receiving testosterone.

Abstract Plasma of mice injected with testosterone contained a detectable increase of an erythropoietic stimulating factor (ESF). ESF was no longer present if bilateral nephrectomy was performed 8 hours prior to collecting the plasma. On the other hand if both ureters were ligated 8 hours prior to sampling, the plasma levels were even higher than in unoperated mice. The plasma ESF activity following testosterone was neutralized by incubation with antierythopoietin, suggesting its identity with erythropoietin. We propose that testosterone stimulates erythropoiesis by altering the kidneys and thereby somehow increasing erythropoietin production.

Hormonal requirements for interpublic ligament formation in hypophysectomized mice.

We have studied the effects of hypophysectomy on hormonally induced “relaxation” of the pubic symphysis of mice. Hypophysectomy prevented interpubic ligament formation due to injection of estradiol cyclopentylpropionate (ECP). Combinations of ECP and relaxin were likewise less effective in hypophysectomized than in unoperated mice. Administration of thyroid did not improve the effectiveness of ECP, but enhanced the activity of a combination of ECP and relaxin, in hypophysectomized mice. STH preparations restored pubic ligament response both to ECP and to the combination of ECP and relaxin. Evidence is presented which suggests, but does not prove, that the action of STH extracts on the symphysis pubis may be due to STH activity proper, and not to contaminants.

MAMMARY GROWTH IN MALE MICE FED DESICCATED THYROID1

THE THYROID GLAND has been considered in relation to several aspects of repro I ductive function. Recently several investigations have been concerned with the effects of the removal of the thyroid or addition of thyroxin, thyroglobulin or desiccated thyroid upon lactation (1, 2). Feeding desiccated thyroid to male rats has been associated with changes in the histological structure of the mammary glands (3). During the course of experiments on the factors concerned in mammary growth in hypophysectomised male mice it became desirable to determine whether or not the concomitant general metabolic deficiency might alter the reactions of the animals. Experiments wereundertaken in which desiccated thyroid was added to the diet. The diet was first testedin unoperated male mice. Unexpectedly, the mammary glands of these unoperated mice showed a marked growth. The mice used in this investigation were hybrid males from 40 to 60 days of age and weighing from 16 to 21,5 gm. Before the mice were selected for this exper...