Ghrelin receptor-knockout mice display alterations in circadian rhythms of activity and feeding under constant lighting conditions.

Ghrelin is an orexigenic hormone produced by the stomach. Ghrelin, however, may also be a modulator of the circadian system given that ghrelin receptors are expressed in the master clock, the suprachiasmatic nucleus (SCN) and several outputs of this region. To investigate this, we performed analyses of running wheel activity and neuronal activation in wild type (WT) and growth hormone secretagogue receptor-knockout (GHSR-KO) mice under various lighting conditions. GHSR-KO and WT mice were maintained under constant dark (DD) or constant light (LL) with ad libitum access to food before being placed on a schedule of temporally restricted access to food (4 h/day) for 2 weeks. There were no differences between KO and WT mice in free-running period under DD, but GHSR-KO mice required more days to develop a high level of food anticipatory activity, and this was lower than that observed in WT mice. Under LL, GHSR-KO mice showed greater activity overall, lengthening of their circadian period, and more resistance to the disorganisational effects of LL. Furthermore, GHSR-KO mice showed greater activity overall, and greater activity in anticipation of a scheduled meal under LL. These behavioral effects were not correlated with changes in the circadian expression of the Fos, Per1 or Per2 proteins under any lighting conditions. These results suggest that the ghrelin receptor plays a role in modulating the activity of the circadian system under normal conditions and under restricted feeding schedules, but does so through mechanisms that remain to be determined.

Circadian rhythm for tryptophan pyrrolase activity and its circulating substrate.

Hepatic tryptophan pyrrolase and its circulating substrate, whole blood tryptophan, have a circadian rhythmicity in mice. Intact adrenocortical function is required for the normal rhythmicity of both enzyme and substrate although an altered but less apparent rhythm persists in the adrenalectomized state.

Contraction and intracellular Ca(2+) handling in isolated skeletal muscle of rats with congestive heart failure.

A decreased exercise tolerance is a common symptom in patients with congestive heart failure (CHF). This decrease has been suggested to be partly due to altered skeletal muscle function. Therefore, we have studied contractile function and cytoplasmic free Ca(2+) concentration ([Ca(2+)](i), measured with the fluorescent dye indo 1) in isolated muscles from rats in which CHF was induced by ligation of the left coronary artery. The results show no major changes of the contractile function and [Ca(2+)](i) handling in unfatigued intact fast-twitch fibers isolated from flexor digitorum brevis muscles of CHF rats, but these fibers were markedly more susceptible to damage during microdissection. Furthermore, CHF fibers displayed a marked increase of baseline [Ca(2+)](i) during fatigue. Isolated slow-twitch soleus muscles of CHF rats displayed slower twitch contraction and tetanic relaxation than did muscles from sham-operated rats; the slowing of relaxation became more pronounced during fatigue in CHF muscles. Immunoblot analyses of sarcoplasmic reticulum proteins and sarcolemma Na(+),K(+)-ATPase showed no difference in flexor digitorum brevis muscles of sham-operated versus CHF rats. In conclusion, functional impairments can be observed in limb muscle isolated from rats with CHF. These impairments seem to mainly involve structures surrounding the muscle cells and sarcoplasmic reticulum Ca(2+) pumps, the dysfunction of which becomes obvious during fatigue.

Lipase inhibitors abolish contractions and cause depolarization in frog skeletal muscle fibres.

Single, intact frog muscle fibers were exposed to bromophenylacylbromide (BPB) or nordihydroguairetic acid (NDGA). Fibres first became unable to respond to electrical stimulation and then depolarized; this process was accelerated by repeated activation. In addition BPB, but not NDGA, eventually induced a contracture in the fibre. The contractile response to direct Ca-release from the sarcoplasmic reticulum by caffeine was unaffected by the drugs.

The antiandrogenic effects of delta 1-testolactone (Teslac) in vivo in rats and in vitro in human cultured fibroblasts, rat mammary carcinoma cells, and rat prostate cytosol.

The antiandrogenic properties of delta 1-testolactone (17 alpha-oxa-D-homo-1,4-androstane-3,17-dione; Teslac) were investigated in vivo and in vitro. Teslac (75 mg/day for 7 days) inhibited the rise in ventral prostate weight induced by testosterone (T) (P less than 0.001), dihydrotestosterone (DHT) (P less than 0.05), and a combination of T plus 17 beta-estradiol (E2) (P less than 0.01) in immature castrate rats. Similar effects were seen on the seminal vesicles after T and T plus E2 (P less than 0.001). Teslac also decreased prostate and seminal vesicle weights in intact immature rats. The effects of Teslac were dose and time dependent. Teslac did not change the concentration of serum T or DHT. However, Teslac inhibited DHT binding to the androgen receptor (Ki = 2.5 +/- 0.8 X 10(-7) M) in cytosol of the rat prostate. Teslac also inhibited DHT binding to the androgen receptor in cultured human prepuce fibroblasts and cultured rat mammary tumor cells (Ki = 1.9 +/- 0.3 X 10(-5) M). The results indicate that Teslac, in addition to its antiaromatase activity, is an antiandrogen by virtue of its interaction with the androgen receptor.

A radioimmunoassay for 3,3',5'-L-triiodothyronine (reverse T3): assessment of thyroid gland content and serum measurements in conditions of normal and altered thyroidal economy and following administration of thyrotropin releasing hormone (TRH) and thyrotropin (TSH).

The present report describes the development of a radioimmunoassay for 3,3',5'-L-triiodothyronine (reverse T3) which is performed on unextracted serum. Utilizing this radioimmunoassay, 21 normal subjects had a mean (+/-SD) serum reverse T3 level of 60 +/- 12 ng/100 ml, 17 of 19 hyperthyroid patients had elevated serum reverse T3 levels, and 10 of 11 hypothyroid subjects had decreased serum reverse T3 concentrations. Thyroidal secretion of reverse T3 was assessed by measurements in samples obtained from the internal carotid artery and jugular vein of sheep following the administration of thyrotropin releasing hormone (TRH) or bovine thyrotropin (TSH). Reverse T3 levels were increased 45-60 min after TRH administration, but TSH administration produced inconsistent alterations in reverse T3, although 18 of 27 samples obtained after TSH injection were higher than their average respective baseline concentration and the mean peak reverse T3 level was 14% higher than baseline. Following TRH administration to 10 normal human subjects, mean serum reverse T3 levels significantly increased from 53.6 ng/100 ml to 56.3ng/100 ml (P less than .05). The thyroid gland content of reverse T3 in human autopsy material was 6.5 +/- 1.5 microng/g tissue. Both pregnancy and estrogen administration were associated with increases in serum reverse T3 concentrations presumably because of their ability to augment thyroxine binding globulin synthesis.

The effects of external potassium, multivalent cations and temperature on caffeine contractures in rat skeletal muscle.

The effects of multivalent cations, membrane potential and temperature on caffeine contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. The amplitude of the caffeine contracture was depressed by the removal of calcium and by the addition of a high concentration (1 mM) of lanthanum. Low concentrations of lanthanum (0.1-0.5 mM) augmented the caffeine contracture. Low levels of depolarization by potassium (10-40 mM) augmented the amplitude of the caffeine contracture, while higher concentrations of potassium depressed the contracture. Maximum augmentation of the caffeine contracture occurred with a higher concentration of potassium (20 mM vs 10 mM) in the e.d.l. than in the soleus muscle. The amplitude of contractures was directly related to temperature between 22 and 37 degrees C and inversely related to temperature below 22 degrees C. The effects of caffeine in rat skeletal muscle are suggested to be exerted on the sarcolemma and the mechanisms of action are by modification of the processes of activation and inactivation.

Potassium contractures and mechanical activation in rat skeletal muscle: effects of multivalent cations, temperature and tetracaine.

The effects of cations, temperature and tetracaine on potassium-induced contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. In the soleus, the threshold for the potassium contracture was lower (10-20 vs 20-40 mM), the peak amplitude was up to fourteen times larger, and the time course was about one half that in the e.d.l. muscle. The extent of inactivation of a test potassium contracture was directly related to the concentration of potassium in the conditioning solution and the period of exposure. Removal of calcium reduced the amplitude and time course of potassium contractures in both preparations. Addition of cobalt (10 mM) reduced the amplitude but prolonged the time course of contractures. Exposure of muscles to tetracaine (10(-5)-10(-6) M for 30 min) increased, but higher concentrations reduced, the amplitude of potassium contractures. When present for one minute, tetracaine (1 mM) moved the potassium activation curve to higher, and the potassium inactivation curve to lower, potassium concentrations.

Toxicity of single daily dose gentamicin in stem cell transplantation.

To determine the safety of single daily dose (SDD) gentamicin in recipients of stem cell transplantation (SCT), we evaluated all adult patients at MD Anderson Cancer Center who received SDD gentamicin for treatment of febrile neutropenia. Thirty-three patients received gentamicin 5 mg/kg i.v. every 24 h. Mean duration of therapy was 7 days (range 3-32 days). All patients received vancomycin and 17 received cisplatinum. All patients had normal renal function prior to therapy. Serum gentamicin levels were monitored only when renal function deteriorated. The incidence of nephrotoxicity and clinically significant ototoxicity was 3% and 12%, respectively. All four patients who developed ototoxicity had normal renal function before and during therapy. The mean duration of gentamicin therapy was significantly longer in patients who developed ototoxicity, 20 days vs 9 days (P = 0.001). Patients treated with SDD gentamicin for >10 days were more likely to develop ototoxicity (P = 0.045). Single daily dosing of gentamicin was associated with clinically significant ototoxicity in 12% of our patients. A larger randomized EORTC trial evaluating SDD vs MDD amikacin failed to detect a difference in ototoxicity. However, the median duration of therapy was only 8 days. The increased incidence of ototoxicity in our study may be due to prolonged therapy, type of aminoglycoside used, concomitant ototoxic agents, small sample size, or a combination of the above.

Granisetron (Kytril) plus dexamethasone for antiemetic control in bone marrow transplant patients receiving highly emetogenic chemotherapy with or without total body irradiation.

This prospective trial evaluated the efficacy and toxicity of granisetron for antiemetic control in patients receiving high-dose cyclophosphamide (CY)-containing regimens with/without TBI for bone marrow (BM) or peripheral blood stem cell (PBSC) transplantation or PBSC mobilization. Granisetron 1 mg i.v. plus dexamethasone 10 mg i. v. were administered daily 30 min before chemotherapy or radiation for a median of 5 days. Response was defined as the number of emetic episodes per 24 h: complete response, 0 and no emetic rescue; major response, 1-2; minor response, 3-5; failure, >5. One hundred patients were enrolled. Ninety-eight received CY-containing regimens and 26 of these additionally received TBI (12 Gy divided over 4 days). Response was complete on 216 (47%) of a total 456 patient days, major on 222 (49%), minor on 14 (3%), and failure on 4 (1%). Mean number of emetic episodes per patient per day and breakthrough medication required per patient per day was 0.24 (range 0-8) and 0. 40 (range 0-8), respectively. Adverse effects were minimal, with headache (20%) reported most frequently. Based on these results, granisetron plus dexamethasone is an effective and well-tolerated antiemetic regimen in BMT/PBSCT recipients conditioned with high-dose chemotherapy with/without TBI. Bone Marrow Transplantation (2000) 25, 1279-1283.

Antiemetic efficacy of granisetron plus dexamethasone in bone marrow transplant patients receiving chemotherapy and total body irradiation.

Few trials exist regarding the antiemetic efficacy of granisetron in bone marrow transplant (BMT) recipients conditioned with high-dose chemotherapy and total body irradiation (TBI). In this single-center, open-label, prospective, trial, the antiemetic efficacy and safety of granisetron plus dexamethasone were evaluated in 26 patients conditioned with cyclophosphamide-containing regimens (the majority receiving 60 mg/kg per day on 2 consecutive days), and TBI (12 Gy divided over 4 days). Daily intravenous doses of granisetron 1 mg plus dexamethasone 10 mg were given 30 min prior to chemotherapy or radiation, and continued for 24 h after the last conditioning treatment for a median of 6 days (range 3-9). Emetic control was defined by the number of emetic episodes occurring within a 24 h period, or the requirement for rescue medication for nausea or vomiting. A total of 25 patients completed 186 evaluable treatment days. Response (emetic control by treatment days) was complete in 50% of patients, major in 48%, minor in 2%, and there were no failures. Adverse effects were minor, with diarrhea (15%), headache (14%), and constipation (11%) reported most often. Based on these results, the antiemetic regimen of granisetron plus dexamethasone appears effective and well tolerated during BMT conditioning with high-dose cyclophosphamide and TBI.

Headache, circumoral paresthesia, and facial flushing associated with high-dose carmustine infusion.

We describe seven patients who developed symptoms including severe headache, circumoral paresthesia, and facial flushing during high-dose carmustine (BCNU) infusion as part of the preparative regimen for autologous peripheral blood stem cell (PBSC) transplantation for metastatic breast cancer. Five patients responded to pain medications, including partial and complete opiate receptor agonists. Premedication of subsequent doses of BCNU with corticosteroids, pain medications, or benzodiazepines lessened, but did not prevent the same symptoms from recurring. The incidence and mechanism of this toxicity are unknown, but this adverse syndrome should be considered when administering high-dose BCNU infusions.

Failure of 3,3'-diiodothyronine administration to alter TSH and prolactin responses to TRH stimulation.

In order to determine whether elevations in serum 3,3'-diiodothyronine (3,3'T2) concentrations influence the hypothalamic-pituitary--thyroid axis, thyrotropin (TSH) and prolactin responses to thyrotropin-releasing hormone (TRH) were assessed in five patients both prior to and during 3,3'T2 administration. Mean (+/- SE) peak TSH responses to TRH were 168 +/- 64 microU/ml during 3,3'T2 administration and 168 +/- 65 muU/ml during 3,3'T2 administration. Mean basal and peak prolactin concentrations after TRH were 6 +/- 3 ng/ml and 54 +/- 26 ng/ml, whereas during 3,3'T2 administration the basal and peak prolactin levels were 6 +/- 2 ng/ml and 55 +/- 28 ng/ml, respectively. Hypothyroid rats administered triiodothyronine (10 migrogram b.i.d.) for 5 days had a mean TSH response to TRH stimulation of 0.051 +/- 0.003 mU/ml, whereas rats to whom saline or 3,3'T2 (50 microgram b.i.d.) had been given for the same time interval had mean TRH-induced TSH responses of 1.127 +/- 0.179 mU/ml and 1.324 +/- 0.286 mU/ml, respectively. None of the TSH or prolactin responses to TRH, in either human or rat studies, were apparently altered by 3,3'T2. These observations suggest that elevation of serum 3,3'T2 levels are not associated with alterations in the hypothalamic--pituitary--thyroid axis in the experimental systems employed.

Effects of CO2-induced acidification on the fatigue resistance of single mouse muscle fibers at 28 degrees C.

The role of reduced muscle pH in the development of skeletal muscle fatigue is unclear. This study investigated the effects of lowering skeletal muscle intracellular pH by exposure to 30% CO2 on the number of isometric tetani needed to induce significant fatigue. Isolated single mouse muscle fibers were stimulated repetitively at intervals of 4-2.5 s by using 80-Hz, 400-ms tetani at 28 degrees C in Tyrode solution bubbled with either 5 or 30% CO2. Stimulation continued until tetanic force had fallen to 40% of the initial value. Exposure to 30% CO2 caused a significant fall in intracellular pH of approximately 0.3 pH unit but did not cause any significant changes in initial peak tetanic force. During the course of repetitive stimulation, intracellular pH fell by approximately 0.3 pH unit in both normal and acidified fibers. The number of tetani needed to reduce force to 40% of the initial value was not significantly different in 5 and 30% CO2 Tyrode. The sole effect of acidosis was to reduce the rate of relaxation of force, especially in fatigued fibers. It is concluded that, at 28 degrees C, acidosis per se does not accelerate the development of fatigue during repeated tetanic stimulation of isolated mouse skeletal muscle fibers.

Recombinant interleukin-2.

Recombinant interleukin (IL)-2 is a newly approved immunoregulatory protein produced by lymphocytes that exhibits a wide range of immunologic effects. It is a true biologic response modifier in that is has no known direct antitumor activity, but mediates its cytotoxicity through activation of effector cells including T cells, natural killer cells, and lymphokine-activated killer cells. Recombinant IL-2 has demonstrated activity in patients with renal cell carcinoma and melanoma, with objective response rates of approximately 15-20%. The median duration of response in renal cell carcinoma is 23 months. Toxicity experienced with high-dose IL-2 can be significant. The most common dose-limiting toxicities are hypertension, weight gain, oliguria, respiratory insufficiency, and neurotoxicity. These effects are generally manageable and reversible on discontinuation of therapy. Administration of low-dose IL-2 has emerged as a means of substantially reducing toxicity. At least in renal cell carcinoma, it appears that the response rate to low-dose IL-2 is comparable to that with higher dosages.

Contraction of rat soleus muscle and the effects of hypertonic treatments.

The effects of exposing rat soleus muscle to solutions made hypertonic by sucrose, mannitol, or urea for a period of 60 min and then to normal solutions for a further 30 min (hypertonic treatment) on twitch, tetanus, potassium, and caffeine contractures were examined. Following hypertonic treatments, twitch, tetanic, and potassium contracture tension were altered from control. The exact effects were dependent upon the concentration of solute used and the temperature. Electrically evoked contractions were abolished following hypertonic treatment with 400 mM sucrose or mannitol at 37 degrees C but 800 mM at 22 degrees C. Urea was less effective; only after hypertonic treatment with 800 mM were contractions of rat soleus muscle abolished at 37 degrees C, while at the lower temperature contractions could not be abolished. In general, caffeine contractures were reduced by hypertonic treatments at 37 degrees C but not at 22 degrees C. Hypertonic solutions themselves caused contractures of rat skeletal muscle, the amplitude of which directly depended on the concentration of solute used and the temperature. These contractures appeared to be due to the release of intracellular calcium from its stores. In hypertonic sucrose and mannitol but not urea solutions, the twitch was reduced and then abolished. Changes in contractile responses of rat soleus muscle during and after exposure to hypertonic solutions are suggested to be due to osmotically induced changes.

The effect of lithium and nitrate on potassium contractures in a glycerol-treated slow-twitch muscle of the rat.

Glycerol treatment (0.4 or 1.2 M) altered but did not abolish twitch, tetanus, potassium, or caffeine contractures in the rat soleus at 37 degrees C. The use of nitrate Krebs or lithium Krebs greatly reduced the effects of 1.2 M glycerol treatment on potassium contractures. The data indicate that the rat soleus is relatively resistant to the uncoupling effects of glycerol treatment and that both lithium and nitrate largely prevent these effects.

Contraction of rat skeletal muscle after glycerol treatments.

The effects of glycerol (400 to 1,200 mM) treatment on contractions of rat soleus muscles were investigated. Glycerol induced temperature- and concentration-dependent contractures which depended largely on extracellular calcium. Glycerol treatments reduced but did not abolish twitch, tetanus, and potassium contracture tension and these changes were far less at 22 than at 37 degrees C. Caffeine contractures were not altered following glycerol treatment at 22 degrees C, but were at 37 degrees C. It is suggested that the lesser effects of glycerol treatment on the soleus compared to other muscles may be due to its smaller transverse tubule system. Glycerol permeation and thus its osmotic action may be less in the soleus than in other muscles.