Warner-Bratzler and slice shear force measurements of 3 beef muscles in response to various aging periods after trenbolone acetate and estradiol implants and zilpaterol hydrochloride supplementation of finishing beef steers.

Our objectives were to determine the effects of zilpaterol hydrochloride (ZH) and the release rate of trenbolone acetate and estradiol-17ß on the Warner-Bratzler shear force (WBSF) and slice shear force (SSF) of longissimus lumborum (LL) and the WBSF of gluteus medius (GM) and psoas major (PM) in response to various aging periods. British × Continental steers (n = 168) were assigned to treatments in a 3 × 2 factorial. The main effects of treatment were implant (no implant, Revalor-S, Revalor-XS, Intervet/Schering Plough Animal Health, De Soto, KS) and ZH (0 or 8.3 mg/kg of DM for 20 d). Slaughter group was included as a random effect to account for the variation in days on feed (153 or 174 d). Loins (n = 96) were fabricated to obtain strip loin, top sirloin butt, and tenderloin subprimals. Five 2.54-cm steaks were cut from each subprimal and assigned to 1 of 5 aging periods (7, 14, 21, 28, or 35 d postmortem). Feeding ZH increased (P ≤ 0.01) LL WBSF and SSF values at each aging period compared with controls. Implanting increased (P < 0.05) LL WBSF values at 14 and 21 d, but did not affect LL SSF values (P > 0.05). Only Revalor-S increased (P ≤ 0.05) WBSF values at 28 and 35 d compared with no implant or Revalor-XS. The percentage of LL steaks with a WBSF value below 4.6 kg did not differ (P > 0.05) between ZH supplementation or implant strategy at any aging period, and by d 28, more than 99% of LL steaks registered WBSF values below 4.6 kg. Feeding ZH increased (P < 0.05) GM WBSF values only on d 21. Implant had no effect (P > 0.05) on GM WBSF values. The percentage of GM steaks with a WBSF value below 4.6 kg did not differ (P > 0.05) between ZH supplementation or implant strategy at any aging period. Neither ZH nor implant strategy affected PM WBSF values (P > 0.05). All PM WBSF values were below 4.6 kg on d 7. The results of this study indicated that feeding ZH increased WBSF and SSF of LL steaks, regardless of the aging period; however, the percentage of steaks with WBSF below 4.6 kg did not differ because of ZH or implant. Implanting increased LL WBSF values, but not SSF values. These results showed that although differences existed between implanting, as well as ZH supplementation of British × Continental steers, 99% of LL steaks were classified as tender based on WBSF values by extending aging to 28 d postmortem. It should be noted that 21.2% of 7-d, 13.8% of 14-d, and 17.3% of 21-d ZH steaks had WBSF values greater than 4.6 kg, but 0% of nonsupplemented steaks were greater than 4.6 kg at these aging periods. However, because ZH and implants can increase retail yield of valuable subprimals, such as the tenderloin, considerable value could be captured through ZH supplementation with anabolic implants because shear force was not affected in PM steaks.

Adenovirus-mediated knockout of a conditional glucokinase gene in isolated pancreatic islets reveals an essential role for proximal metabolic coupling events in glucose-stimulated insulin secretion.

The relationship between glucokinase (GK) and glucose-stimulated metabolism, and the potential for metabolic coupling between beta cells, was examined in isolated mouse islets by using a recombinant adenovirus that expresses Cre recombinase (AdenoCre) to inactivate a conditional GK gene allele (gklox). Analysis of AdenoCre-treated islets indicated that the gklox allele in approximately 30% of islet cells was converted to a nonexpressing variant (gkdel). This resulted in a heterogeneous population of beta cells where GK was absent in some cells. Quantitative two-photon excitation imaging of NAD(P)H autofluorescence was then used to measure glucose-stimulated metabolic responses of individual islet beta cells from gklox/lox mice. In AdenoCre-infected islets, approximately one-third of the beta cells showed markedly lower NAD(P)H responses. These cells also exhibited glucose dose responses consistent with the loss of GK. Glucose dose responses of the low-responding cells were not sigmoidal and reached a maximum at approximately 5 mM glucose. In contrast, the normal response cells showed a sigmoidal response with an KcatS0.5 of approximately 8 mM. These data provide direct evidence that GK is essential for glucose-stimulated metabolic responses in beta cells within intact islets and that intercellular coupling within the islet plays little or no role in glucose-stimulated metabolic responses.

Nontransferrin-bound iron in serum of patients receiving bone marrow transplants.

Nontransferrin-bound iron (NTBI) and other parameters of iron status were measured in 40 patients undergoing bone marrow transplantation (BMT) prior to conditioning therapy (between day -10 and -7), at the time of BMT (day 0), and 2 weeks later (day + 14). Serum iron and transferrin saturation values were normal before conditioning therapy. At day 0 serum iron values were high and median transferrin saturation was 98% (changes in the values of both serum iron and transferrin saturation, p < .0001). Transferrin saturation values were still elevated 2 weeks posttransplant (day +14 vs. baseline values, p = .0001). Starting at low NTBI levels pretransplant (median 0.4 micromol/l, range 0-4.2 micromol/l, controls: < or = 0.4 micromol/l), all patients revealed high levels on day 0 (median 4.0 micromol/l, range 1.9-6.9 micromol/l, p < .0001) and 2 weeks posttransplant (median 2.7 micromol/l, range 0-6.2 micromol/l, p < .0001). These observations indicate that the plasma iron pool in patients undergoing BMT increases to a level at which the normal ability to sequestrate iron becomes exhausted and considerable amounts of NTBI appear in serum. This "free" form of iron can mediate the production of reactive oxygen species and may cause organ toxicity in the early posttransplantation period.

Induction of aP2 gene expression by nonmetabolized long-chain fatty acids.

Long-chain fatty acids (FA) have been shown to regulate expression of the gene for the adipocyte FA-binding protein aP2. We examined whether this effect was exerted by FA themselves or by a FA metabolite. The alpha-bromo derivative of palmitate, an inhibitor of FA oxidation, was synthesized in the radioactive form, and its metabolism was investigated and correlated with its ability to induce aP2 in Ob1771 preadipocytes. alpha-Bromopalmitate was not utilized by preadipocytes. It was not cleared from the medium over a 24-hr period and was not incorporated into cellular lipids. Short incubations indicated that alpha-bromopalmitate exchanged across the preadipocyte membrane but remained in the free form inside the cell. In line with this, preadipocyte homogenates did not activate alpha-bromopalmitate to the acyl form. However, although it was not metabolized, bromopalmitate was much more potent than native FA in inducing aP2 gene expression. Induction exhibited the characteristics previously described for native FA, indicating that a similar if not identical mechanism was involved. The data indicated that induction of aP2 was exerted by unprocessed FA. Finally, in contrast to preadipocytes, adipocytes metabolized bromopalmitate. This reflected increased activity with cell differentiation of a palmitoyl-CoA synthase that could activate palmitate and bromopalmitate at about one-fifth the rate for palmitate. In preadipocytes, the predominant fatty-acyl-CoA synthase, arachidonyl-CoA synthase, had very low affinity for both FA. Increased activity of the palmitoyl-CoA synthase, which has a wider substrate range, is likely to be important for initiation of lipid deposition.

Circulating antibodies in rats bearing grafted colon carcinoma.

Sera from rats bearing primary or grafted colon carcinoma may contain antibodies that can react with antigenic determinants at the surface of cultivated colon cancer cells. Assays with various target cells and absorption experiments suggest that antigens recognized by circulating antibodies are common to independent lines of cultivated colon cancer cells. They are therefore cross-reacting, tumor-type-specific antigens. They could be embryonic or fetal antigens, because some sera from multiparous animals react with colon cancer cells. However, blocking experiments suggest that these antigens differ from the carcinofetal antigen previously demonstrated on the surface of intestinal cancer cells by xenoantiserum.

A carcinofetal antigen located on the membrane of cells from rat intestinal carcinoma in culture.

Heteroantisera were produced in rabbits by immunization with cultivated cells from rat intestinal carcinomas. The sera were made specific by in vivo absorption in syngeneic rats. On immunofluorescence, these sera recognized a membrane-associated antigen common to five different intestinal carcinomas and to fetal intestine. The antigen was not detected in noncancerous adult intestine, nonintestinal fetal tissues, or three nonintestinal tumor cell lines.

Antigens associated with chemically induced intestinal carcinomas of rats.

Rabbits were immunized with extracts of primary or grafted intestinal adeno-carcinomas induced by carcinogenic drugs in inbred rats. After absorption with normal tissue extracts, the antisera were able to recognize three tumor-associated antigens. Two of them were glycoproteins, present in cancer cells but also, in trace amounts, in mucous cells of the normal digestive tract. The third antigen is not detectable in the normal digestive system, but present in normal spleen; on im-unofluorescence, it is not located in the cancer cells, but in polymorphonuclear cells infiltrating the tumor. None of the three antigens cross-reacts with human carcinoembryonic antigen, or human or rat alphafetoprotein. On the other hand, one of the glycoprotein antigens is immunologically related to the human blood group A substance.