Metabolic Changes In Response Research Articles

Photoperiod-Induced Changes in Metabolic Response to Temperature in Drosophila melanogaster Meigen

Photoperiod-Induced Changes in Metabolic Response to Temperature in Drosophila melanogaster Meigen

Physiological and nutritional response of beef steers to combined infestations of horn fly and stable fly (Diptera: Muscidae).

Specific physiological and nutritional responses of beef steers to combined infestations of horn flies, Haematobia irritans (L.), and stable flies, Stomoxys calcitrans (L.), were measured in the laboratory. Measurements used as indicators of physiological stress were changes in heart rate, respiration rate, and rectal temperature. Various blood components were measured to assess metabolic changes in response to fly infestation. Dry matter and nitrogen digestibility and nitrogen retention were used as indices of feed utilization. Beef steers exposed to 100 horn flies plus 25 stable flies or 500 horn flies plus 50 stable flies per head had significantly increased heart rates, respiration rates, and rectal temperatures. Dry matter and nitrogen digestibility did not differ significantly among treatments, but nitrogen retention was significantly reduced in both fly-infested groups. Blood cortisol concentrations were significantly increased on day 12 in steers exposed to 100 horn flies plus 25 stable flies per head and on days 1, 8, and 10 in steers exposed to 500 horn flies plus 50 stable flies per head. Higher cortisol levels, vital signs, and steer activity contributed to reduced nitrogen retention in steers exposed to horn flies plus stable flies. No significant difference existed among treatments in levels of other blood components, and all values were within ranges considered normal.

Age-related changes in metabolic responses to chronic monoamine depletion in central dopaminergic and serotonergic systems of rats treated with reserpine

Groups of 5, 15, and 27-month-old rats were treated with reserpine (5 mg/kg IP) and killed after 1, 7, 14, and 21 days. Reserpine's effects on dopamine (DA) and serotonin (5HT) metabolism were studied in the striata and limbic areas, on the basis of changes in metabolite concentrations and a calculated index [Δ (C/M)] expressing changes in the molar ratio between metabolite and parent monoamine. Twenty-four hours after drug treatment, when the two monoamines reached a new steady-state, about 10% of the normal concentration, there was evident enhancement in the metabolism of striatal DA, indicated by HVA levels and Δ (C/M) changes. This increase was significantly lower in the senescent rats. In contrast with HVA, the levels of DOPAC were lowered in reserpinized rats. This effect, present in all three age groups, lasted up to 21 days in young and 14 days in adult and old rats. However, for this metabolite too, the Δ (C/M) indicated an increase in its formation which was lower in 27-month-old rats. Similar effects were observed in limbic areas, but here the age-related differences were less evident. Serotonin metabolism was also increased by reserpine as indicated by the Δ (C/M). This parameter was lower in young than in adult and old rats, at least in limbic area. Similarly, 5HIAA increased only in the senescent rats. These age-related differences were not evident in striata. In this rat population, aging apparently modified the compensatory metabolic responses of some dopaminergic and serotonergic systems. The direction of these changes, however, depends on the system and the brain region considered.

Nutritional status and energy metabolism of crayfish ( Procambarus clarkii, girard) muscle and hepatopancreas

1. 1. Food deprivation resulted in significant decreases in muscle carbohydrate, lipid and water content and increased ATP, ADP, AMP and total adenylate levels over the 21-day experimental period. 2. 2. In the hepatopancreas phosphoarginine was significantly higher on day 21 in the starved crayfish. 3. 3. Muscle energy charges remained within optimal (unstressed) ranges, while hepatopancreatic energy charges of food-deprived crayfish fell into suboptimal (stressed) ranges, indicating the necessity of examining organs separately to accurately ascertain metabolic changes in response to stressors.

Physiological and nutritional response of beef steers to infestations of the horn fly (Diptera: Muscidae).

Specific physiological and nutritional responses of beef steers to laboratory infestations of horn flies, Haematoma irritans (L.), were measured. Indicators of physiological stress were changes in heart rate, respiration rate, and rectal temperature. Blood cholinesterase, cortisol, creatine phosphokinase, glucose, hemoglobin, lactic dehydrogenase, packed cell volume, total protein, urea nitrogen, and white cell count were measured to assess metabolic changes in response to fly infestation. Dry matter and nitrogen digestibilities and nitrogen retention were used as indices of feed utilization. Beef steers exposed to 100 or 500 horn flies per head had significantly increased heart rates, respiration rates, and rectal temperatures. In addition, water consumption and urine production were significantly increased after exposure of steers to 500 horn flies per head. Urinary nitrogen excretion was significantly increased when steers were exposed to 500 horn flies per head and the value for steers exposed to 100 horn flies was intermediate between these and control steers. Dry matter digestibility and nitrogen digestibility did not differ significantly among treatments, but nitrogen retention was significantly reduced in both fly-infested groups. Blood cortisol concentrations were significantly increased on day 1 in steers exposed to 500 horn flies per head, and were numerically higher on most sampling days at both levels of fly infestation. Higher cortisol levels, combined with increased body temperatures and steer activity, contributed to reduced nitrogen retention in steers exposed to horn flies. No significant difference existed among treatments in levels of other blood components measured and all values were within ranges considered normal.

Ammonia intoxication: effects on cerebral cortex and spinal cord.

The effect of an acute systemic ammonia intoxication on the metabolic states of the cerebral cortex and the spinal cord of the same animal was studied in the cat. The intravenous infusion of ammonium acetate (2 and 4 mmol/kg body weight/30 min) increased the gross levels of tissue NH4+, glutamine, glutamine/glutamate ratio, lactate, and the lactate/pyruvate ratio in the cerebral cortex and the spinal cord. Pyruvate increased, but significantly only in the spinal cord; aspartate decreased, but significantly only in the cerebral cortex. The infusion of ammonium acetate did not significantly change the levels of phosphocreatine, ATP, ADP, AMP, total adenine nucleotides, adenylate energy charge, glucose, glutamate, alpha-ketoglutarate, and malate in either tissue. The changes of NH4+, glutamine, and lactate levels as well as glutamine/glutamate and lactate/pyruvate ratios in the spinal cord correlated significantly with the corresponding changes of these metabolites in the cerebral cortex. Thus, cerebral cortex and spinal cord show certain specific and comparable metabolic changes in response to a systemic ammonia intoxication. The effect of ammonia intoxication on the increases of glutamine and lactate levels is discussed.

A rapid and reversible muscle fiber transformation in the rat

Muscle fibers (in untreated muscles) undergo physiologic and metabolic changes in response to nearby operative procedures. To elucidate this phenomenon the following experiments in rats were conducted: (a) excision of one sternohyoid superior muscle by a midline incision of the skin and the underlying superficial cervical fascia, (b) incision of skin and fascia [as in (a)], (c) incision of the skin [as in (a)] alone, and (d) application of a single anesthesia without surgical manipulations. At 3-day intervals the muscles were removed and serial sections were incubated for myosin ATPase and with antibodies recognizing fast (FM) or slow (SM) myosin, respectively. All these procedures induced a conspicuous muscle fiber transformation from fast to slow type within 6 to 9 days. The occurrence of transformed muscle fibers displayed an undulating time course attaining nearly control values within 3 days after the initial increase. These experiments demonstrated that a muscle fiber transformation can be brought about within a short time and by a variety of indirect stimuli.

Physiological and histochemical properties of the soleus muscle after denervation of its antagonists

Muscle fibers undergo physiological and metabolic changes in response to altered functional demands. For example, muscles exhibit prolonged contraction time and decreased ATPase activity when their synergists are removed. The present experiment was performed to determine whether inactivation of a muscle's antagonists produces physiologic and metabolic changes indicative of speeding. The common peroneal nerve was transected unilaterally in rats and the ipsilateral soleus muscle examined 7–8 months later. Evidence of physiological speeding was indicated by faster isotonic speed of shortening and isometric rate of tension development, decreased contraction time, and decreased tetanus; twitch tension ratio. Histological sections incubated for actomyosin ATPase activity revealed an increase in the proportion of dark, high-ATPase fibers. A quantitatively similar result was obtained when the central end of the transected nerve was implanted into the normally innervated soleus muscle. Under these conditions the implanted nerve did not form a transmissive neuromuscular connection. Thus, in contradistinction to previous assertions by Fex, we found no “trophic” effect specific to the implanted, nonfunctional nerve. Since the physiological and metabolic properties of muscle can be altered without nerve crossing, we suggest that these properties are regulated by an interaction between neural and muscular factors. A specific trophic function cannot be attributed to the nerve until the regulatory role of all factors is more fully evaluated.

SEASONAL CHANGES IN METABOLIC RESPONSE TO TEMPERATURE CHANGE.

SummaryThe metabolic response to a shift in temperature from 30°C to 25°C was measured on the same subjects over a one-year period. In winter metabolism reduced significantly when the change in temperature was made; in summer the change was reversed. Measurements made in the spring showed equivocal differences.