1-week Conditions Research Articles

Evaluation of dried yeast and threonine fermentation biomass as partial fish meal replacements in the diet of red drum Sciaenops ocellatus

In response to the increasing demand and thus cost of fish meal (FM), alternatives to this ingredient have been extensively investigated in recent years. As such, research on various types of alternative protein feedstuffs, such as industrial microbial byproducts, is being pursued for FM replacement. To this end, the purpose of this study was to determine the efficiency of two single-cell protein sources, dried yeast (DY) and threonine fermentation biomass (TFB) as partial replacements for FM in the diet of red drum. A reference diet was formulated to contain 40% crude protein (CP) equally contributed from FM and soybean meal (SBM). In addition, four experimental diets were formulated with different inclusion levels of DY to supply 20, 30, 40 or 50% of dietary CP, and three additional diets had different inclusion levels of TFB to provide 10, 20 or 30% of dietary CP. Red drum juveniles were sorted by size (initially averaging 8.01±0.29g), and groups of 20 fish/aquarium were stocked into 30, 110-L aquaria. After feeding the reference diet for a 1-week conditioning period, triplicate aquaria were randomly assigned to each dietary treatment and fish were fed to apparent satiation for 8 weeks. In regard to weight gain, feed efficiency and survival, increasing inclusion levels of DY and TFB did not negatively affect these responses. Therefore, it can be concluded that, for the conditions in which this experiment was conducted, TFB and DY could replace up to 30 and 50% of the protein provided by FM/SBM (50/50%), respectively, without affecting red drum’s performance. In addition, distinctly different microbial communities in the gastrointestinal tract of fish fed the various diets was evident based on a denaturing gradient gel electrophoresis dendrogram analysis. In conclusion, DY and TFB are suitable alternatives for replacing FM in the diet of red drum, although more studies should be done to determine their maximum inclusion levels.

A Randomized, Double-blind Evaluation of Buprenorphine Taper Duration in Primary Prescription Opioid Abusers

Although abuse of prescription opioids (POs) is a significant public health problem, few experimental studies have investigated the treatment needs of this growing population. To evaluate, following brief stabilization with a combination of buprenorphine hydrochloride and naloxone hydrochloride dihydrate, the relative efficacy of 1-, 2-, and 4-week buprenorphine tapering regimens and subsequent naltrexone hydrochloride therapy in PO-dependent outpatients. A double-blind, 12-week randomized clinical trial was conducted in an outpatient research clinic. Following a brief period of buprenorphine stabilization, 70 PO-dependent adults were randomized to receive 1-, 2-, or 4-week tapers followed by naltrexone therapy. During phase 1 (weeks 1-5 after randomization), participants visited the clinic daily; during phase 2 (weeks 6-12), visits were reduced to thrice weekly. Participants received behavioral therapy and urine toxicology testing throughout the trial. The percentage of participants negative for illicit opioid use, retention, naltrexone ingestion, and favorable treatment response (ie, retained in treatment, opioid abstinent, and receiving naltrexone at the end of the study). Opioid abstinence at the end of phase 1 was greater in the 4-week compared with the 2- and 1-week taper conditions (P = .02), with 63% (n = 14), 29% (n = 7), and 29% (n = 7) of participants abstinent in the 4-, 2-, and 1-week conditions, respectively. Abstinence at the end of phase 2 was also greater in the 4-week compared with the 2- and 1-week conditions (P = .03), with 50% (n = 11), 16% (n = 4), and 20% (n = 5) of participants abstinent in the 4-, 2-, and 1-week conditions, respectively. There were more treatment responders in the 4-week condition (P = .03), with 50% (n = 11), 17% (n = 4), and 21% (n = 5) of participants in the 4-, 2-, and 1-week groups considered responders at the end of treatment, respectively. Retention and naltrexone ingestion also were superior in the 4-week vs briefer tapers (both P = .04). Experimental condition (ie, taper duration) was the strongest predictor of treatment response, followed by buprenorphine stabilization dose. This study represents a rigorous experimental evaluation of outpatient buprenorphine stabilization, brief taper, and naltrexone maintenance for treatment of PO dependence. Results suggest that a meaningful subset of PO-dependent outpatients may respond positively to a 4-week taper plus naltrexone maintenance intervention.

Dietary vitamin C requirement of red drum Sciaenops ocellatus

A feeding trial was conducted to determine the minimum dietary vitamin C requirement of juvenile red drum and characterize signs of vitamin C deficiency. Semipurified diets containing 400 g crude protein kg-1 from lyophilized red drum muscle and crystalline amino acids were used in the feeding trial. The basal diet without supplemental vitamin C contained approximately equal to 6 mg vitamin C kg-1 and was fed for a 1-week conditioning period. Red drum, initially averaging approximately equal to 3.6 g each, were fed diets supplemented with 0, 10, 20, 30, 45, 60, 75, or 150 mg vitamin C kg-1 as ascorbate polyphosphate for a period of 10 weeks. Fish fed the basal diet began to exhibit overt signs of vitamin C deficiency, including reduced weight gain, lordosis, scoliosis and loss of equilibrium after 8 weeks. Total ascorbate was undetectable in liver of fish fed the basal diet while liver ascorbate levels in fish fed the other diets generally reflected dietary supplementation. Regression analysis of weight gain data using the broken-line model resulted in a minimum vitamin C requirement (+/-SE) of 15 +/- 3 mg kg-1 diet.

A Technique for Conducting Noninvasive Cardiac Electrophysiology Studies in Conscious Swine

A noninvasive method was developed in swine for conducting cardiac electrophysiology (EP) studies without the potential confounding effects of sedatives or anesthetics. Following a 1-week conditioning regimen in the EP laboratory, 3-month-old Hanford miniature swine underwent transvenous pacemaker (PM) implantation under isoflurane anesthesia. Two bipolar screw-in pacing leads were inserted into the left external jugular vein, with one positioned in the right atrial appendage and one in the myocardium at the right ventricular apex. The leads were attached to a multiprogrammable pulse generator, and the pacing system was placed in a subcutaneous pocket. At weekly intervals following implantation, conscious, unsedated swine were restrained in a sling for noninvasive programmed stimulation (NIPS) using a programmable telemetry system. A NIPS protocol to induce arrhythmias was performed separately for the atrium and ventricle. Data for this model are reported. Complications occurred in 6 of 26 animals studied and included one infection of the PM pocket, three cases of dislodgement of the atrial lead, and rotation of the generator within the pocket in two animals, preventing communication with the PM. This technique has been used to perform EP studies successfully in swine and has been utilized in a variety of studies of the cardiac conduction system.

Effects of feeding and short-term fasting on water and electrolyte turnover in female mink (Mustela vison).

Daily (24 h) rates of water and electrolyte turnover were measured in a conventional balance study in ten adult female pastel mink (Mustela vison) given free access to a standard mink feed for a 1-week conditioning period, followed by a 4 d experimental period and a 2 d fasting period. Drinking water was available throughout. In addition, the completeness of urine collection and the fraction of urine collected with the faeces were determined using a new experimental technique based on 24 h recoveries of specific urinary markers such as tritiated p-aminohippuric acid ([3H]PAH) or 14C-labelled inulin ([14C]IN) continuously delivered by small Alzet osmotic pumps implanted intraperitoneally. During feeding the mean individual percentage recovery in urine of [3H]PAH released from the osmotic pumps ranged from 68 to 88% (median 78%). The mean percentage of urinary [3H]PAH recovered from faecal collections was 6% (range 3-12%). In response to fasting the mean individual percentage recovery of [3H]PAH in urine ranged from 62 to 78% (median 68%). For urinary [14C]IN the mean percentage recoveries in fed and fasted animals were 79 and 63% respectively. Furthermore, during fasting, withdrawal of the supplies of dietary water caused a slight but insignificant (P = 0.17) increase in the daily intake of drinking water and, hence, the animals maintained their normal water balance by a dramatic reduction in urine excretion (P < 0.001). At the same time urinary solute excretion declined significantly (P < 0.001), due in part to the cessation of dietary electrolyte intake and in part to reduced formation of urea, whereas urinary osmolality decreased only moderately. The mean 24 h balances of Na, K, Ca, Mg, Cl and P were close to zero and only minor differences between the feeding and fasting periods were observed. When corrected for the measured inaccuracies in urine collection the balance data obtained in the present study represent useful reference standards for normally fed and fasted non-growing mink and, to some extent, useful guidelines for future studies in experimental animals.

Regeneration of Adult Rat Sensory Axons into Intraspinal Nerve Grafts: Promoting Effects of Conditioning Lesion and Graft Predegeneration

The effect of intraspinally implanted predegenerated peripheral nerve grafts and/or conditioning lesions on the regenerative capacity of central ascending sensory axons was investigated in the adult rat. Regenerating sensory fibers were analyzed after their transganglionic labeling with cholera toxin B subunit, usually 1 month after implantation. A conditioning lesion (transection of the tibial and peroneal nerve) caused a fivefold increase in the number of sensory fibers within the fresh graft when applied on the day of grafting and a sevenfold increase when applied 1 week before. In the latter case, a small portion of the fibers (10%) had reached the rostral end of the nerve graft. In the absence of a conditioning lesion, the number of fibers regenerating into a predegenerated nerve graft (collected from the distal part of the peroneal nerve that had been axotomized 1 week earlier) was similar to that found in a fresh graft. However, predegenerated grafts received three and five times more fibers than a fresh graft when conditioning lesions were applied on or 1 week before the day of grafting. With the combination of a predegenerated graft and a 1-week conditioning, most (>90%) of the regenerating fibers had reached the rostral graft-host border. In animals with a fresh graft, a portion of the axotomized fibers formed terminal club-like structures. Much fewer fibers displayed such clubs in animals with a predegenerated graft or a conditioning lesion, suggesting a preventive action of either treatment. A time-course study with the combined treatments showed that regenerating sensory fibers had already entered the graft after 3 days. Between 1 and 2 weeks, a maximum number of fibers had reached the rostral end of the nerve graft. However, after 2 months, the number of fibers was decreased, i.e., the initial advantage of predegeneration had diminished. The current results demonstrate the necessity of a conditioning lesion for successful regeneration of central sensory fibers, possibly resulting from an earlier induction of the neuronal growth response which allows the axon to enter the graft before the formation of a graft-host barrier. The predegeneration of the nerve graft augments the growth response of the axotomized central sensory fibers, probably by providing a more supportive terrain and/or enhancement of the neuronal response. The presence of a large number of fibers at the rostral graft-host border now provides the opportunity to investigate the effects of neurotrophic factors on the regenerative capacity of the ascending rat sensory fibers into the denervated spinal cord in vivo.

Effects of low-level x-irradiation on cat cerebella at different postnatal intervals. III. Changes in the morphology of interneurons in the molecular layer.

The whole head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of a newborn, 1-week, 2-week, 3-week, and a 4-week age condition while the age of sacrifice remained constant at 70 days. Going analysis revealed that the interneurons found in the molecular layer of the newborn, 1-week and 2-week condition were basket cells. Stellate cells were found in increasing numbers in the 3-week and 4-week conditions. Basket calls were found to occupy the entire molecular layer in the newborn and 1-week conditions resulting in an abnormal axonal plexus. The position of the basket cell soma was found to be in the same plane as its axonal projection. The branching point of the primary dendrite of Purkinje cells was found to correlate with the amount of molecular layer occupied by the abnormal basket cell plexus. Interneurons in the molecular layer were found to show different dendritic growth patterns dependent upon where their soma was located. Interneurons in the deep molecular layer showed only a decreased dendritic field, whereas interneurons in the middle and superficial moledular layer had an abnormal growth of dendrites into the deep molecular layer. A hypothesis is presented to account for the decreased dendritic arborization and the increased length of the primary dendrite before branching, the ectopic basket cell and their abnormally directed dendritic growth, and the difference in behavioral deficits between the newborn and the 1-week conditions.