James V. O'Fallon

The Na+,K+-ATPase: a plausible trigger for voltage-independent release of cytoplasmic neurotransmitters.

Abstract: A comparison was made between the releasability of eight neurotransmitters from eight regions of mouse brain in response to either 60 μM‐K+ or 20 μM‐ouabain, a specific inhibitor of the Na+, K+‐ATPase. With few exceptions, all transmitters were released by either or both agents from each brain region examined. Potassium was superior in releasing the biogenic amines and acetylcholine, while the putative amino acid transmitters were generally releasable by both agents. Measurements of tissue depolarization using [3H]‐tetraphenylphosphonium uptake indicated that 60 μM‐K+ is capable of depolarizing brain tissue above the threshold necessary for initiating an action potential, but 20μM‐ouabain is not. The pattern of release by ouabain coupled with its failure to depolarize brain tissue at 20μM suggests that inhibition of the Na+,K+‐ATPase is capable of releasing cytoplasmic neurotransmitters in a voltage‐independent manner.

Effects of supplemental fat on growth performance and quality of beef from steers fed corn finishing diets

To measure the effects of dietary fat on feedlot performance and carcass characteristics, and on beef appearance, moisture binding, shelf life, palatability, and fatty acid content, 126 crossbred beef steers (321.1 +/- 0.57 kg of BW) were allotted to a randomized complete block (3) design with a 3 x 2 + 1 factorial arrangement of dietary treatments. The main effects were level of yellow grease (0, 3, or 6%) and alfalfa hay (3.5 or 7%) in corn-based diets containing 15% potato by-product (PB). The added treatment was 6% tallow and 7% alfalfa in a barley-based diet containing 15% PB. Dry matter intake and ADG were not affected by diet; however, G:F and diet NE content increased linearly (P < 0.10) with yellow grease. Kidney, pelvic, and heart fat (2.0 to 2.3 +/- 0.07) and yield grade (2.8 to 3.1 +/- 0.09) increased linearly (P < or = 0.05) with yellow grease. Steers fed corn plus 6% yellow grease had lower (P < 0.05) beef firmness and beef texture scores but greater (P < 0.01) fat color score than those fed barley plus 6% tallow. Moisture retention of beef was not affected by dietary treatment, except purge score during retail storage, which was decreased linearly (P < 0.01) from 2.1 to 1.6 +/- 0.06 by level of yellow grease. Steaks from steers fed barley plus 6% tallow had greater (P < 0.05) shear force than those from steers fed corn plus 6% yellow grease, and beef flavor increased linearly (P < 0.05) from 6.2 to 6.7 +/- 0.11 as the level of yellow grease increased. Level of yellow grease linearly increased (P < 0.01) transvaccenic acid (TVA) by 61% and CLA content of beef by 48%. Beef from steers fed corn plus yellow grease had lower (P < 0.05) palmitoleic and oleic acids and greater (P < 0.05) linoleic, TVA, and CLA than beef from steers fed the barley-tallow diet. Feeding yellow grease increased diet energy content, which increased carcass fatness, and altered beef fatty acid content, which increased beef flavor without affecting moisture retention, shelf life, or cooking properties of the beef. Additionally, beef from steers fed corn plus 6% yellow grease was more tender and had more polyunsaturated fatty acid content and CLA than beef from steers fed barley plus 6% tallow.

The Subcellular Distribution of β-Carotene in Bovine Corpus Luteum

Abstract The distribution of β-carotene was determined in various subcellular fractions of bovine corpus luteum. It was found in significant amounts in all subcellular fractions examined including nuclear, mitochondrial, microsomal, cytosolic, and floating lipid. Much of the β-carotene found in the crude nuclear and mitochondrial fractions was loosely bound and could be removed with repeated washings. In contrast, the microsomal β-carotene could only be removed by detergent extraction suggesting that it is an integral component of this membrane preparation. In the cytosol fraction β-carotene was bound to high-molecular-weight protein(s), quite possibly a plasma-derived lipoprotein. The subcellular distribution of β-carotene in corpus luteum is quite similar to the distribution of its metabolite, retinol, in liver. This finding coupled with other recently published data suggests that β-carotene could play a distinct role in corpora lutea function.

The subcellular distribution of carnosine, carnosine synthetase, and carnosinase in mouse olfactory tissues

The dipeptide, carnosine, its synthetic enzyme, carnosine synthetase, and its degradative enzyme, carnosinase, appear to be localized in the cytosol of mouse olfactory bulb and epithelium. Mouse olfactory bulbs and epithelium were prelabeled in vivo with [3H]carnosine following intranasal irrigation with [3H]beta-alanine. [3H]carnosine co-distributed in olfactory bulb with lactate dehydrogenase with only 10% in the crude mitochondrial fraction. Similar results were also seen with endogenous carnosine distribution. Over 70% of the carnosine present in the crude mitochondrial fraction was localized in synaptosomes following sucrose gradient centrifugation. However, further fractionation of vesicle containing fractions from osmotically lysed crude mitochondrial fractions indicated that [3H]carnosine was not associated with vesicles. Nearly 70% of all the [3H]carnosine present in olfactory epithelium was soluble with most of the remainder in the crude nuclear fraction. The enzymes carnosine synthetase and carnosinase were clearly soluble in olfactory epithelium with 98% and 85% of the activity in the cytosol. Less than 2% was found in the crude mitochondrial fraction. In olfactory bulb both enzymes also appeared soluble.

Calculation of the pentose phosphate and Embden-Myerhoff pathways from a single incubation with [U-14C]- and [5-3H]glucose

A method that simultaneously determines Embden-Myerhoff pathway and pentose phosphate pathway (PPP) activities from an incubation with [U-14C]- and [5-3H]glucose is presented. The method relies on the use of unlabeled pyruvate and lactate to dilute out radiolabel entering the tricarboxylic acid cycle. Gluconeogenesis from pyruvate is prevented by the use of an incubation chamber that maintains a CO2 (and bicarbonate) free environment. The method, which includes the contribution by the recycling steps of the PPP, is especially useful when biological material is limited or developmental timing is critical.

Cellular localization of α-ketoglutarate: Glyoxylate carboligase in rat tissues

Abstract α-Ketoglutarate : glyoxylate carboligase activity has been reported by other laboratories to be present in mitochondria and in the cytosol of mammalian tissues; the mitochondrial activity is associated with the α-ketoglutarate decarboxylase moiety of the α-ketoglutarate dehydrogenase complex. The cellular distribution of the carboligase has been re-examined here using marker enzymes of known localization in order to monitor the composition of subcellular fractions prepared by differential centrifugation. Carboligase activity paralleled the activity of the mitochondrial matrix enzyme citrate synthase in subcellular fractions prepared from rat liver, heart and brain as well as from rabbit liver. Whole rat liver mitochondria upon lysis released both carboligase and citrate synthase. The activity patterns of several other extramitochondrial marker enzymes differed significantly from that of carboligase in rat liver. In addition, the distribution pattern of carboligase was similar to that of α-ketoglutarate decarboxylase and of α-ketoglutarate dehydrogenase complex. The data indicate that α-ketoglutarate : gloxylate carboligase activity is located exclusively within the mitochondria of the rat and rabbit tissues investigated. There is no evidence for a cytosolic form of the enzyme. Thus the report from another laboratory that the molecular etiology of the human genetic disorder hyperoxaluria type I is a deficiency of cytosolic carboligase must be questioned.

The influence of forage diets and aging on beef palatability

To investigate the influence of diet and aging on beef palatability, lipid oxidative stability, and fatty acid composition, crossbred steers were assigned to Feedlot S (alfalfa and grain), Forage TR (triticale and annual ryegrass), Forage TK (triticale and kale), or Forage+Feedlot (grazing ryegrass, fescue and orchardgrass, finished on alfalfa and grain) dietary treatments. Heifers were finished on Feedlot H (alfalfa and grain). Longissimus and tricep muscles were sampled from these animals for steaks and ground beef, respectively. Steaks were either dry- or wet-aged for 14 d. Ground beef was dry-aged, wet-aged for 14 d, or not aged. Trained sensory panelists evaluated palatability attributes of steaks and ground beef. Diet did not influence sensory attributes of steaks or ground beef. Aging impacted (P<0.05) sensory attributes of ground beef. Diet and aging had no impact on lipid oxidative stability but affected fatty acid composition of raw ground beef.

Fatty acid composition of adipose tissue and muscle from Jersey steers was affected by finishing diet and tissue location

To determine the impacts of finishing diet and tissue type and location on fatty acid composition and palatability of Jersey beef, twenty steers were assigned to a factorial treatment design with initial weight (Light vs. Heavy) and finishing diet (70 vs. 85% concentrate) as treatments. Ribeye steaks were collected for sensory evaluation. Muscle, seam and subcutaneous (s.c.) fat from steaks, kidney fat (KF) and omental fat (OMF) were collected for fatty acid analysis. Initial weight and finishing diet had little impact on beef palatability. The 85% concentrate decreased polyunsaturated fatty acids (PUFA) in muscle and increased trans fatty acids in all tissues (P<0.05). The monounsaturated:saturated fatty acid ratio (MUFA:SFA) was highest in s.c. fat, intermediate in muscle and seam fat, and lowest in KF and OMF. The PUFA:SFA was highest in muscle, intermediate in s.c. and seam fat, and lowest in KF and OMF. Fatty acid composition differed greatly among tissues and the lower concentrate diet increased omega-3 and PUFA percentages in muscle.

Methyl viologen as a preferred electron acceptor in metabolic experiments

Widely used artificial electron acceptors, including dichlorophenol-indophenol, methylene blue, and phenazine ethosulfate, were shown to induce the nonenzymatic decarboxylation of pyruvate. This characteristic rendered these electron acceptors unsuitable for use in metabolic experiments. In contrast, methyl viologen stimulated the pentose phosphate pathway in mouse preimplantation embryos without decarboxylating pyruvate in the process. Furthermore, methyl viologen had no effect on the Embden-Myerhoff pathway and was not overtly toxic to mouse embryos. These features made methyl viologen a preferred artificial electron acceptor for metabolic studies.

Penetration of glyoxylate across die blood–brain barrier

GLYOXYLATE (0 = CH -COO-) is not only an intermediate in cellular metabolism but also an acute or subacute toxin in vcrtcbrates (ADINOLFI ef d., 1973; NABER er a/., 1956). Since blood and tissue levels of glyoxylate rise markedly in thiamine-dcficient rats (Lime. 1962: HAUSCHILDT & FELI~HEIM, 1971) and in some human disorders (BUCKLE, 1963: HOCKADAY rr [ I / . , 1964; CLAYTON er al., 1967). this compound may play a role in the pathogenesis of various disease conditions. Glyoxylate bas been implicated in the inhibition of several key metabolic reactions (RUFFO er a/., 1967; JOFIANSON & REEVES, 1977). Since in thiamine-deficient rats many of the major pathologic lesions occur in the brain stem, and elevated levels of glyoxylate (LIANG, 1962) and related compounds (GAITONDE, 1975) occur in the brain, it is ofinterest to determine whether serum glyoxylate can penetrate the bloodbrain barrier. OLDENDORF (1973) demonstrated carriermediated blood-brain barrier transport of several shortchain monocarboxylate anions, such as lactate. pyruvate. propionate and acetate; cross-inhibitory studies suggested that there is a single carrier system for the various monocarboxylate ions. One anion not included in the study by Oldendorf was glyoxylate; the present report shows that glyoxylate is also able to penetrate the blood-brain barrier. probably via the monocarboxylate carrier.