Evans Strain Research Articles

The rat Ruby ( R) locus is Rab38: identical mutations in Fawn-hooded and Tester-Moriyama rats derived from an ancestral Long Evans rat sub-strain.

Hermansky-Pudlak syndrome (HPS) is a group of rare, recessive disorders in which oculocutaneous albinism, progressive pulmonary fibrosis, bleeding diathesis, and other abnormalities result from defective biogenesis of multiple cytoplasmic organelles. Seven different HPS genes are known in humans; in mouse, at least 16 loci are associated with HPS-like mutant phenotypes. In the rat, only two HPS models are known, Fawn-hooded (FH) and Tester Moriyama (TM), non-complementing strains in which HPS-like hypopigmentation and platelet storage pool deficiency result from a mutation of the Ruby (red eyed dilution; R) locus on Chromosome (Chr) 1. We have identified the R locus as the Rab38 gene, establishing that rat R is homologous to mouse chocolate ( cht). Further, we show that FH and TM rats have identical Rab38 Met1Ile mutations, occurring on an identical Chr 1 marker allele haplotype, indicating that these two strains derive from a common ancestor. This ancestor appears to have been a sub-strain of the outbred Long Evans (LE) strain, and several modern LE sub-strains carry the Rab38 Met1Ile R mutation on the same Chr 1 marker haplotype. These findings have significant implications for the many past and ongoing studies that involve the FH and LE-derivative rat strains. Hermansky-Pudlak syndrome (HPS; MIM 203300) is a group of autosomal recessive diseases in which oculocutaneous albinism (OCA), progressive and fatal pulmonary fibrosis, and bleeding diathesis due to platelet storage pool deficiency result from defects in the biogenesis of specific cytoplasmic organelles and granules: melanosomes, lysosomes, and platelet dense granules. In humans, seven different HPS genes are known. In the mouse, at least 16 loci associated with HPS-like mutant phenotypes are known, seven of which are homologous to the human HPS loci.

Evaluation of the effects of chronic mild stressors on hedonic and physiological responses: sex and strain compared

The chronic mild stress (CMS) paradigm was developed in order to simulate in animals the symptom of anhedonia, a major feature of depression. Typically, changes in hedonic status are interpreted from a decrease in either intake or preference for a mild sucrose solution. Although the incidence of clinical depression is significantly higher in women than in men, the study of this disorder in most animal models of depression has been based on the responses of male rodents. The purpose of this study was to compare the effects of 6 weeks of CMS administration among male and female rats of two rat strains, Sprague–Dawley (SD) and Long Evans (LE), with respect to physiological (body, adrenal gland, and spleen weight) and biochemical (plasma corticosterone levels) indices of stress as well as evaluations of 1 and 24 h sucrose intake and preference. Estrous cycle was tracked throughout the study. Overall, our results indicate a slower rate of weight gain in animals, greater in males, exposed to the chronic stressor regime. Furthermore, CMS is shown to disrupt estrous cycling, predominantly in the Long Evans strain of rats. The main behavioral finding was a significant reduction in 24 h sucrose intake in female treated groups, which was not accompanied by alterations in preference. Corticosterone levels were elevated in CMS-treated animals relative to the singly housed control groups, but exposure to a subsequent stressor was not influenced by the stress history. Taken together, the effects of chronic stressor exposure are evident, based on physiological and biochemical indices, although none of the measures distinguished any striking gender specific reactions. The usefulness of sucrose intake or preference as behavioral indices of CMS-induced anhedonia in males and females is modest at best.

Long–Evans and Sprague–Dawley rats have similar skilled reaching success and limb representations in motor cortex but different movements: some cautionary insights into the selection of rat strains for neurobiological motor research

Many rat strains are used for neurobiological studies of nervous system function and behavior. The most widely used strain for studies of the neural basis of movement is the out bred, pigmented Long–Evans strain, while the most widely used strains for the study of movement impairments in neurological disease are out bred albino rats, including Sprague–Dawley rats. Although previous research has indicated that there are strain differences in skilled movements displayed by different rat strains, there has been no explicit comparison of the Long–Evans and Sprague–Dawley strains. This was the purpose of the present study. The rats were video recorded as they learned to reach for single food pellets and the video records were subjected to frame-by-frame analysis. Component movements of reaching were scored using a system derived from Eshkol-Wachman Movement Notation (EWMN). The quality of movements was described using Laban Movement Analysis (LMA). Forelimb representations in motor cortex were defined electrophysiologically. Acquisition scores and success in reaching did not differ between the two strains, nor did the topographical representation of the forelimb in motor cortex. Long–Evans and Sprague–Dawley rats did differ in the movements used for reaching and on the quality of their movements. The movements of Sprague–Dawley rats resembled the movements of Long–Evans rats with motor system injury. That rat strains can show both quantitative and qualitative differences in movement is useful for the understanding of the genetic, neural, and behavioral organization of the motor system. The results are also relevant to the question of appropriateness of particular rat strains for studies of neurological diseases and the effects of albinism on motor behavior, and suggest that some of the most widely used rat strains for neurological investigations may be less than appropriate.

Genetic Vasopressin Deficiency Facilitates Performance of a Lateralized Reaction-Time Task: Altered Attention and Motor Processes

Brattleboro rats are a variety of the outbred Long-Evans strain that possess a single nucleotide deletion in the second exon of the arginine vasopressin gene, resulting in the synthesis of an altered protein that does not enter the normal secretory pathway. Rats heterozygous (di/+) for the deletion have a partial vasopressin deficiency and exhibit a variety of behavioral and neurochemical alterations compared with normal wild-type Long-Evans rats, which provide evidence for a CNS function for vasopressin. Here, we examined the acquisition and performance of a test of visuospatial attention by di/+ Brattleboro rats and their wild-type Long-Evans control counterparts. Surprisingly, di/+ rats exhibited superior performance of the task compared with wild-type controls; performance differences included greater accuracy of detection of visual target stimuli, faster overall reaction times, and fewer trial omissions. Di/+ rats also exhibited more approaches to the reinforcer receptacle at nonreinforcement times. These results indicate that alterations of vasopressin signaling result in a clear cognitive phenotype, including faster motor initiations and superior choice accuracy in a test of visual attention.

The effects of chronic mild stress on male Sprague–Dawley and Long Evans rats: I. Biochemical and physiological analyses

The chronic unpredictable mild stress (CMS) is a paradigm developed in animals to model the relatively minor and unanticipated irritants that lead to a state of anhedonia in some individuals. However, the effectiveness of CMS is sometimes difficult to establish, for which unique strain sensitivities has been attributed as one contributing factor. These considerations led us to design the present study, which was an investigation of the corticosterone response to CMS in two outbred rat strains—Sprague–Dawley and Long Evans. Animals were exposed to one of two conditions—control or CMS—for 3 weeks during which body weight and fecal count were regularly monitored. At the end of this period, blood was sampled at a variety of time intervals following induction of a brief restraint stressor. First, a significant effect of CMS on corticosterone levels was evident at time 0 (prior to the application of the acute restraint stressor) in both strains. Second, the typical quadratic pattern of stressor-elicited fluctuations in this measure was similar in both Sprague–Dawley and Long Evans rats, with consistently elevated levels for the first hour following exposure to the acute stressor; near baseline values were observed at 2 h. However, only in the Long Evans strain were CMS related values much less than that observed in the control group after restraint stress. Third, both strains showed a reduced weight gain in the CMS groups relative to control groups. Fourth, spleen and adrenal weights were similar across all groups. Fifth, fecal counts remained stable across weeks of treatment in all groups with the exception of the Long Evans rats exposed to CMS; in this group, average counts were systematically reduced over the treatment period. We conclude that a history of chronic stress significantly blunts corticosterone levels in Long Evans but not Sprague–Dawley rats following exposure to an acute stressor. Physiological indices however are less influenced by this experience, at least when the exposure is limited to 3 weeks.

Renal effects of recombinant prolactin in anaesthetized rats.

To re-examine the controversial possibility that prolactin exerts renal effects, using recombinant mouse prolactin (rmP), in the presence and absence of circulating vasopressin. In experiment 1, the renal effects of rmP were examined in anaesthetized Brattleboro rats with hereditary hypothalamic diabetes insipidus (BDI) lacking circulating vasopressin and normal animals of the parent Long Evans (LE) strain. In experiment 2, salt and water excretion were studied in fluid-loaded normal Sprague-Dawley (SD) rats, some of which received rmP. In experiment 1, BDI and LE rats maintained in fluid balance were infused i.v. with each of three concentrations of rmP (10, 20 and 40 microg/ml per h) or maintained on 150 mmol/l NaCl vehicle (controls). In experiment 2, the SD rats were infused with 75 mmol/l NaCl in order to induce a state of diuresis comparable to that of BDI rats, some of them then receiving the rmP i.v. A profound rmP-induced dose-dependent decrease in urine excretion (P<0.005) and a lesser decrease in sodium excretion in the BDI rats was in marked contrast with the small but significant increase in urine excretion in the LE rats compared with controls (P<0.025). The rmP-infused fluid-loaded SD rats also demonstrated a significant (P<0.05) dose-related antidiuresis compared with the control animals, in addition to a decrease in sodium excretion. These results show that prolactin has a profound antidiuretic effect in the absence of circulating vasopressin. In contrast, when vasopressin is present in the circulation rmP has a small, but opposite, diuretic effect. Thus the use of a recombinant prolactin has provided evidence for renal effects of this hormone which are modified in the presence of the circulating neurohypophysial hormone vasopressin.

MURINE IL-2 SECRETING RECOMBINANT BACILLUS CALMETTE-GUÉRIN AUGMENTS MACROPHAGE-MEDIATED CYTOTOXICITY AGAINST MURINE BLADDER CANCER MBT-2

This study was to establish a more effective anti-cancer immunomodulating agent by constructing recombinant (r) Bacillus Calmette-Guérin (BCG) secreting alpha-antigen (alpha-Ag) fused murine (m) interleukin (IL)-2, and to study its biological activity on cell-mediated cytotoxicity against murine bladder cancer cell, MBT-2, in vitro. pSO246 plasmid vector ligated with mIL-2 gene was introduced into BCG by electroporation. Thioglycollate-elicited murine peritoneal exudate cells (PEC) were stimulated in vitro with parental BCG or rBCG and their cytotoxic activity and the cytokine production was studied. Cytokines were assayed by an enzyme-linked immunosorbent assay (ELISA) and L929 bioassay. Cytotoxicity was measured by 51Cr releasing assay. rBCG (alpha-Ag-IL-2) secreted functional IL-2 and augmented more efficient cytotoxicity to MBT-2 and cytokines such as IL-12, tumor necrosis factor and interferon (IFN)-gamma in PEC than parental BCG did. rBCG (alpha-Ag) had the same activity as BCG. Anti-IL-2 antibody reduced rBCG (alpha-Ag-IL-2)-mediated cytotoxicity and IFN-gamma production. Exogenous IL-2 also enhanced BCG-mediated cytotoxicity, but 100 times more IL-2 was required to express the same activity as rBCG (alpha-Ag-IL-2). Anti-IL-12 neutralizing antibody and the depletion of T cells and NK cells reduced IFN-gamma production by PEC stimulated with rBCG (alpha-Ag-IL-2), suggesting that T cells, NK cells and IL-12 participate in the enhancement of IFN-gamma production. rBCG secreting IL-2 showed significant antitumor activity and cytokine production and this will be a promising agent for bladder cancer patient to reduce both clinical dose and side effects of BCG for immunotherapy.

Interstrain differences in cognitive functions in rats in relation to status epilepticus

Cognitive functions of Long Evans ( N=30) and Wistar rats ( N=32) were compared using a Morris water maze. Under control conditions the Long Evans rats were more efficient in this test, their average escape latency after 5 days of training (6.4±0.1 s, mean±S.E.M.) was significantly shorter than that of the Wistar rats (11.0±0.1 s). When the training was completed seizures were induced by an intraperitoneal injection of pilocarpine (330 mg/kg in the Long Evans strain and 350 mg/kg in the Wistar rats) 30 min after pretreatment with N-methylscopolamine (1 mg/kg i.p.). Clonazepam (1 mg/kg i.p.) was used to interrupt clonic seizures after 2 hours of continuous activity. Approximately one quarter of rats in both strains did not develop seizures. Severe convulsive status epilepticus was common in Long Evans rats (23 out of 30). In contrast, only 12 Wistar rats generated convulsive status epilepticus and the same number of animals exhibited only bursts of motor seizures separated by periods without convulsions (temporary seizures). Mortality after pilocarpine-induced status epilepticus was considerably higher in the Long Evans rats than in the Wistar rats. After a latency of 2–3 weeks spontaneous recurrent seizures appeared in all animals surviving status. Cognitive memory was tested during the ‘silent period’ between status and recurrent seizures. The Long Evans rats were unable to find the platform at the 3rd and 6th day after status but then their performance rapidly improved. The performance of the Wistar rats undergoing status epilepticus was seriously deteriorated and it never normalized, whereas the animals with temporary seizures exhibited only a transitory marginal prolongation of latencies. The hippocampal formation was damaged by status epilepticus in rats of both strains — the Long Evans rats exhibited more extensive damage of subfields CA1 and CA3, whereas in the Wistar rats a complete destruction of hilar neurons was observed in addition to partial CA1 and CA3 damage.

EFFECTS OF ACETYLIC SALICYLIC ACID AND PENTOXIFYLLINE ON THE EFFICACY OF INTRAVESICAL BCG THERAPY IN ORTHOTOPIC MURINE BLADDER CANCER (MB49)

Intravesical immunotherapy with bacillus Calmette-Guerin (BCG), which has become the gold standard in the adjuvant treatment of superficial bladder cancer, is hampered by local side effects. Anti-inflammatory drugs may be helpful, but as an undesired side effect, therapeutic efficacy of BCG might be impaired. Therefore, we investigated the effects of anti-inflammatory drugs on the efficacy of intravesical BCG in an animal model. Syngenic tumor cells were implanted into the bladders of 75 mice according to our modification of the method. Mice were randomized to 5 groups with 15 animals each and treated with phosphate buffered saline (PBS), group 1; BCG, group 2; BCG + acetylic salicylic acid (ASA), group 3; BCG + pentoxifylline (POF), group 4; autoclaved BCG (aBCG), group 5. Intravesical instillation of 1.35 mg. BCG was initiated one day after tumor inoculation and repeated in weekly intervals for 4 instillations altogether. ASA and POF in doses of 200 mg./kg. and 150 mg./kg., respectively, were given continuously with the drinking water starting at the first instillation. Autoclaved BCG served as control for the importance of viability and was given at the same dose as viable BCG. Mice were monitored for survival, gross hematuria and body weight and after 28 days evaluated for bladder weight and tumor occurrence. Autoclaved BCG and PBS had no effect on tumor growth, whereas animals treated with viable BCG alone and in combination with POF and ASA, respectively, showed a significant reduction in bladder weight: PBS, 248 mg.; BCG, 140 mg. (p = 0.0009); BCG + ASA, 123 mg. (p = 0.0001); BCG + POF, 145 mg. (p = 0.0004); autoclaved BCG, 283 mg. (p = 0.21). Mice treated with BCG, BCG + ASA and BCG + POF showed a significantly higher proportion of survival until day 28 as compared to PBS alone. Autoclaved BCG had no therapeutic efficacy (Kaplan-Meier method/log rank test: BCG, p = 0.0053; BCG + ASA, p = 0.0044; BCG + POF, p = 0.0027; aBCG, p = 0.33). No significant differences among the 3 groups treated with viable BCG, with or without anti-inflammatory drugs, regarding bladder weight and survival were detectable. The efficacy of BCG therapy in murine orthotopic bladder cancer is dependent on BCG viability and is not compromised by ASA or POF. Clinical trials to evaluate the efficacy of routine ASA or POF to reduce BCG side effects in patients, using self-assessment criteria, should be initiated.

URINARY INTERLEUKIN-2 MONITORING DURING PROLONGED BACILLUS CALMETTE-GUERIN TREATMENT: CAN IT PREDICT THE OPTIMAL NUMBER OF INSTILLATIONS?

URINARY INTERLEUKIN-2 MONITORING DURING PROLONGED BACILLUS CALMETTE-GUERIN TREATMENT: CAN IT PREDICT THE OPTIMAL NUMBER OF INSTILLATIONS?

Effect of ovariectomy and steroid hormone replacement on the recovery of arterial blood pressure following haemorrhage in anaesthetized Brattleboro rats.

There is increasing evidence that ovarian steroids inhibit vascular responsiveness to the neurohypophysial hormone vasopressin. The present study examined the recovery of the arterial blood pressure following a single (2 ml/100 g body weight) haemorrhage in ovariectomized (OVX) Brattleboro rats with hereditary hypothalamic diabetes insipidus (BDI) and rats of the parent Long Evans (LE) strain. Some groups of OVX rats received subcutaneous implants of either 17 beta-oestradiol (E2) or progesterone 7 days prior to haemorrhage. The arterial blood pressure recovery immediately following haemorrhage was significantly impaired in both groups of steroid-treated OVX LE rats compared with the OVX controls (both comparisons P < 0.05). The impairment in blood pressure recovery seen in the steroid-replaced OVX LE rats was similar to that seen in pro-oestrous rats (when ovarian steroid levels are raised) compared with male rats of this strain (P < 0.05). In contrast, ovariectomy with or without steroid replacement in BDI rats had no further effect on the already attenuated recovery of arterial blood pressure after haemorrhage in this strain. Heart rate responses to haemorrhage also showed strain differences, which were dependent on steroid treatment. Pro-oestrous female LE rats showed a small decrease in heart rate after haemorrhage, followed by a recovery process, and this initial bradycardia was markedly enhanced in the OVX steroid-treated animals. In contrast, untreated OVX LE rats showed an initial and sustained increase in heart rate which was significantly higher than in the steroid-treated OVX animals (P < 0.05). All BDI rats, irrespective of treatment, consistently showed an increased heart rate after haemorrhage. In conclusion, ovarian steroid replacement in OVX LE, but not vasopressin-deficient BDI, rats was associated with an attenuated pressor recovery after haemorrhage. This provides further evidence for the existence of an important inhibitory interaction between ovarian steroids and vasopressin. The initial decrease in heart rate observed in pro-oestrous and steroid-treated OVX LE rats after haemorrhage also appears to be related to an ovarian steroid-vasopressin interaction.

The short-term influence of b-FGF, NGF and Cerebrolysin on the memory impaired after fimbria-fornix lesion.

Neurotrophic factors were shown to prevent degeneration and to facilitate regeneration in damaged CNS. In an attempt to compare the effect of b-FGF, NGF and the nootropic drug Cerebrolysin® (Cer) (EBEWE Arzneimittel), naive 3-month-old rats (Long Evans strain) were trained to escape from water in the Morris pool to a hidden platform (3 consecutive days; D1, D2, D3; 8 trials/day). Next day, fimbria-fornix (FF) was unilaterally removed by suction. A needle connected to a micro-osmotic pump filled by b-FGF (0.2μg/ml) or NGF (11μg/m1 or 0.5μg/) was placed into the lateral ventricle ipsilateral to the lesion., Cer was applied via intraperitoneal injection (2.5m1/kg/day). One group was treated by Cer and NGF (11μg/m1)(group NGFCER). As control groups served intact (INT) and lesioned only rats (LES). After the 14-daytreatment (D19) rats were tested for their ability to remember the position of the platform. During the next 3 days (D20, D21, D22) rats were trained to find the platform placed in a opposite quadrant of the pool. The length of trajectory and escape latency were recorded and speed of swimming was calculated.

Pronounced juvenile circadian core temperature rhythms exist in several strains of rats but not in rabbits.

Torpor-like circadian variations of core temperature are well documented for suckling-age Zucker rat pups. To determine (1) whether this juvenile circadian rhythm is as strongly expressed in other rat strains, and (2) whether a similar rhythm is expressed in rabbit pups, we recorded core temperature and metabolic rate of artificially reared pups. Wistar, Brown Norway, and Long Evans pups were studied for 30 h under moderate cold loads (ambient temperature = 28 degrees C) when 9-11 days old, i.e. at the age and ambient temperature for which the rhythm has been most thoroughly characterized in Zucker rats. Chinchilla bastard rabbit pups were studied under similar conditions when they were 3-8 days old, the youngest age at which the rhythm can be easily detected in rats. Rat pups of each strain showed clear circadian rhythms with sharp decreases of core temperature and metabolic rate in subjective morning. Core temperature amplitudes were in the order Wistar < Brown Norway < Zucker < Long Evans strain. In contrast, the rabbit pups maintained stable high levels of core temperature and metabolic rate throughout the day. A torpor-like decrease of core temperature in the morning is thus not a peculiarity of the Zucker rat strain but also occurs in other pigmented rat strains, whereas rabbit pups at a similar developmental stage do not show a circadian core temperature rhythm.

The abnormal quinine drinking aversion in the Brattleboro rat with diabetes insipidus is reversed by the vasopressin agonist DDAVP: A possible role for vasopressin in the motivation to drink

The Brattleboro rat with hypothalamic diabetes insipidus (BDI) has an abnormal aversion to drinking quinine-adulterated water compared with normal rats of the parent Long Evans (LE) strain. This BDI animal tolerates marked hypovolemia and decreased body weight in preference to drinking the quinine-adulterated fluid, indicative of a reduced motivation to drink. Acute or chronic treatment of BDI rats with desamino-8D arginine vasopressin (DDAVP) restored to normal their drinking response to quinine solution. Partial restoration of fluid turnover in BDI rats with hydrochlorothiazide, which has an antidiuretic effect in diabetes insipidus (when vasopressin is absent), failed to abolish the abnormal drinking response to quinine-adulterated solution in 8 out of 12 animals. In contrast, induction of diabetes mellitus in LE rats, which resulted in a marked polydipsia and polyuria even though vasopressin was still present, did not impair the drinking response to quinine solutions. These results suggest that the abnormal drinking response to quinine-adulterated fluid in BDI rats is reversed by treatment with the vasopressin V2-receptor agonist DDAVP but is unlikely to be a consequence of the restoration of fluid turnover to normal levels by a renal action. A possible central action involving vasopressin and the motivation to drink is discussed.

Outcome in Carcinomain situof Bladder Treated with Intravesical Bacille Calmette-Guérin

Summary— Fifty-three patients with carcinoma in situ of the bladder were treated with Evans strain BCG given intravesically. Complete remission was achieved after either one or two 6-weekly courses in 53% of patients. The median duration of remission was 32 months. Treatment-related bladder symptoms were minor during the first course, more severe during the second. There was no relation between severity of symptoms and likelihood of response. With a median follow-up of 32 months, disease progression has occurred in 10% of complete responders, whereas failure to respond on either cystoscopic, histological or cytological grounds was associated with a 48% progression rate. Although intravesical BCG produces impressive responses in carcinoma in situ of the bladder, managed conservatively the condition remains a dangerous one.

Outcome in carcinoma in situ of bladder treated with intravesical bacille Calmette-Guérin.

Fifty-three patients with carcinoma in situ of the bladder were treated with Evans strain BCG given intravesically. Complete remission was achieved after either one or two 6-weekly courses in 53% of patients. The median duration of remission was 32 months. Treatment-related bladder symptoms were minor during the first course, more severe during the second. There was no relation between severity of symptoms and likelihood of response. With a median follow-up of 32 months, disease progression has occurred in 10% of complete responders, whereas failure to respond on either cystoscopic, histological or cytological grounds was associated with a 48% progression rate. Although intravesical BCG produces impressive responses in carcinoma in situ of the bladder, managed conservatively the condition remains a dangerous one.

Vasopressin administration via microdialysis into the septum interferes with the acquisition of spatial memory in rats

The role of vasopressin (AVP) in the septohippocampal system in spatial memory was studied in 27 male hooded rats of the Long Evans strain. The rats were implanted with a septal microdialysis probe and assigned to 3 groups. Two days later, they were trained on 3 consecutive days (12 daily trials) to locate the hidden underwater platform in the Morris water maze (MWM) while the probes were perfused with either artificial cerebrospinal fluid (aCSF) or aCSF containing vasopressin or the V 1 antagonist d(CH 2) 5Tyr(Me)AVP (AAVP). Another group of rats ( n = 8) remained untreated. Groups receiving microdialysis of aCSF or AAVP acquired the MWM task at the same rate as untreated animals. On the other hand, place navigation learning was significantly impaired by microdialysis of AVP during all sessions. The results indicate that endogenous AVP (at least that affecting the V 1 receptor subtype) is not indispensable for the acquisition of spatial memories in the MWM, whereas excessive presence of synthetic AVP interferes with spatial learning.

Attenuated development of ischemic brain edema in vasopressin-deficient rats.

Brain edema formation was investigated in the vasopressin-deficient Brattleboro rat using a middle cerebral artery occlusion model of early ischemic injury. Water and sodium accumulation after 4 h of ischemia were attenuated 36 and 20%, respectively, in the Brattleboro strain as compared to the control Long-Evans strain. This effect was independent of differences in animal size and state of hydration. In addition, measurements of cerebral blood flow indicated that Brattleboro and Long-Evans rats had equal levels of ischemia following middle cerebral artery occlusion. Systemic treatment of Brattleboro rats with vasopressin normalized their serum electrolyte concentrations and osmolarity but did not alter sodium or water accumulation in the ischemic brain. In contrast, intraventricular administration of vasopressin in Brattleboro rats increased edema formation to that seen in control rats. The reduced water and sodium accumulation in Brattleboro rats subjected to middle cerebral artery occlusion may be related to alterations in blood-brain barrier permeability since the blood-to-brain sodium flux was 36% less in the ischemic tissue of the Brattleboro as compared to the Long-Evans strain. These results support the hypothesis that central vasopressin is a regulator of brain volume and electrolyte homeostasis. Furthermore, our findings suggest a role for central vasopressin in the development of ischemic brain edema.

Intravesical Evans Strain BCG Therapy: Quantitative Immunohistochemical Analysis of the Immune Response within the Bladder Wall

Previous studies have demonstrated that it is the local immune response which is of importance for the anti-tumour activity of BCG therapy. We have investigated this by quantitative immunohistochemical analysis of serial bladder mucosal biopsies taken before, during and after an eight week course of intravesical Evans strain BCG therapy and three monthly thereafter in 16 patients (15 extensive CIS and one extensive G2pTa papillary tumour). This particular group of patients had a 67% complete response rate at six months post-treatment. The main findings on immunohistochemical analysis were the universal induction of MHC Class II antigens by urothelial cells which was statistically significant up to 6 months after completion of therapy, coupled with a T cell dominated cystitis. Increases in CD3+ T cell infiltration of the lamina propria and that of the CD4+ “Helper” subset which predominated were significant up to 3 months post-therapy and these cells showed evidence of increased immunological activation as shown by increased interleukin-2 receptor and MHC Class II antigen expression. There were also significant increases in CD68+ macrophage and the incidence of CD22+ B cell aggregates but CD57+ NK cells were sparse both before and after therapy. The degree of mononuclear cell infiltration for all markers examined (except CD57) was significantly greater in those biopsies in which the urothelial cells expressed MHC Class II antigens than in those that did not. Also the degree of T cell infiltration (CD3, CD4 and CD8) was significantly greater in the eight patients deemed to have had a complete response compared to those seven with a partial response or treatment failure. These results are discussed in terms of possible mechanisms of action for BCG therapy and in particular the role of enhanced antigen presentation by tumour cells.

Evidence against melanin as the mediator of retinal phototoxicity by short-wavelength light

Albino and pigmented (black-hooded) rats of the Sprague-Dawley and Long Evans strains, respectively, were compared in terms of their susceptibility to retinal damage by ultraviolet-A light. Anesthetized animals were exposed to ultraviolet-A light ( λ max = 360 nm) for 4 hr and retinal damage was assessed 1 week later by electroretinographic analysis and measurement of outer nuclear layer thickness. Albino and pigmented animals showed approximately the same severity of ultraviolet-A retinal damage as a function of exposure irradiance. Furthermore, both pigmentation strains showed swelling and vesiculation of rod inner segment mitochondria as an early manifestation of damage. An abbreviated study on a congenic rat strain (F344- c/+) of albino and pigmented littermates again demonstrated an equal susceptibility to ultraviolet-A phototoxicity for both pigmentation phenotypes. These findings provide evidence that melanin is not the mediator of short-wavelength phototoxicity to the retina, since damage readily occurred in albino animals completely lacking this chromophore.