Blood oxygen transport in rats under hypothermia combined with modification of the L-Arginine-NO pathway.

Nitric oxide (NO) has high affinity to heme and by interaction with oxyhemoglobin (HbO2) is converted into nitrate to form methemoglobin (MetHb) as a side product. In combining with deoxy-Hb NO yields a stable molecule of nitrosyl-hemoglobin (HbFe(II)NO) that can further be converted into nitrate and hemoglobin (Hb). In addition, Hb was shown to transport NO in a form of S-nitrosohemoglobin (SNO-Hb). These features of the Hb and NO interaction are important for blood oxygen transport including hemoglobin-oxygen affinity (HOA). The present investigation was aimed to study the blood oxygen transport indices (pO2, pCO2, pH, HOA, etc.) in rats under hypothermia combined with a modification of L-arginine-NO pathway. To modify the L-arginine-NO pathway, rats were administered with N(G)-nitro-L-arginine methyl ester (L-NAME), L-arginine, or sodium nitroprusside (SNP) intravenously before cooling. A substantial impairment of oxygen delivery and development of hypoxia, with an important contribution of HOA into the latter accompanied the deep hypothermia in rats. All the experimental groups developed metabolic acidosis, less pronounced in rats treated with L-arginine only. In the experiments with a modification of the L-arginine-NO pathway, an enhanced cold resistance, attenuated oxygen deficiency, and a weaker oxyhemoglobin dissociation curve (ODC) shift leftwards were observed only after the administration of L-arginine. Neither SNP nor L-NAME had not any protective effects. L-Arginine lowered the value of standard P50 (pO2, corresponding to 50% Hb saturation with oxygen at 37 degrees C, pH 7.4, and pCO2 = 40 mmHg). The actual P50 (at actual pH, pCO2 and temperature) decreased by approximately 15 mmHg and was significantly higher than that under hypothermia without the drug treatment (21.03 +/- 0.35 vs 17.45 +/- 0.60 mmHg). NO also can contribute to this system through different mechanisms (HOA modification, vascular tone regulation, peroxynitrite formation, and effects).     

Proteinuria in long term streptozotocin diabetes in rats

The total protein excretion rate of Munich-Wistar rats studied 80–90 days after the induction of diabetes with streptozotocin was more than double that of age-matched controls. The urine proteins consisted of only albumin and pre-albumin fractions. Dextran/inulin clearance ratios were not higher in the diabetic rats, and it is concluded that the proteinuria is not due to an increased glomerular permeability to protein. Kidney size was increased 1.7 fold and body weight was 60% of control. Glomerular filtration rate uncorrected for kidney or body weight was also not different from controls.     

Cation transport in murine L fibroblasts cultured long term in a serum-free medium

Cation fluxes and intracellular content in mouse fibroblasts L, growing for more than three years in the Dulbecco modified Eagle's serum-free medium (clone L625sf) were measured as a function of culture density. The cells show no density-dependent inhibition of growth and in continuously growing cultures of L625sf cells internal potassium, and rubidium influx was found to remain high within a wide range of densities (5.10(4)-20.10(4) cells/cm2). A close correlation was revealed between the potassium transport and the proliferative state of L625sf cultures: the addition of 5% calf serum to logarithmically growing cultures leads to the increase in culture growth rate as well as to the increase in ouabain-inhibited rubidium influx and intracellular potassium content; a delay in culture growth rate due to medium depletion is accompanied by decreasing both the rubidium influx and the intracellular potassium content. It is concluded that L625sf cells being capable of multiplicating in serum-free medium remain sensitive to growth factors of serum and may be used for study of growth factor induction of cell proliferation and for identification of autocrine factors of cell growth.     

Lake Kinneret dissolved oxygen regime reflects long term changes in ecosystem functioning

Lake Kinneret (Israel) has undergone several prominent chemical and biological changes since 1970. Between 1970 and 1991 significant, long-term gradual increase were recorded in epilimnetic dissolved oxygen (DO) concentrations (about 20%), and in pH levels (0.2 units). Concomitantly there was a significant increase in hypolimnetic H₂S concentrations (about 75%) and a long-term gradual drop in zooplankton biomass (50%). Since 1994 these trends were reversed and the levels of the three chemical parameters have returned to those found in the 1970's and that of zooplankton to mid 1980's levels. The present study is an attempt to relate some of these long term changes by means of yearly oxygen budgets, based on fluxes of oxygen producing and consuming processes. This analysis raises the possibility that part of the long-term increase in epilimnetic DO and pH between 1970 to 1990 may be attributed to reduced inputs of organic matter from alochthonous sources and possibly to enhanced burial of organic matter in the bed sediments. However, the major cause for the observed increase in epilimnetic DO and pH is increased sedimentation of organic matter to the hypolimnion during stratification. As indicated by the amount of H₂S formed in the hypolimnion during stratification added to the amount of oxygen entrapped in this layer at the onset of thermal stratification, between 1970 to 1991 the sedimentation flux of organic matter increased by approximately 40%. It is estimated that during these two decades hypolimnetic respiration increased from ca. 8% of the annual amount of oxygen evolved due to photosynthesis during the early 1970's to ca. 12.5% during the 1980's. The shift in the layer of oxidative processes is suggested to be the result of a multi-annual decline in zooplankton grazing pressure, which led to increased sedimentation of organic matter. The reversed trends for DO, pH and H₂S since 1994 may have partially been due to the increase in zooplankton activity and partially due to changes in phytoplankton community structure.     

Angiogenic factors and the endometrium following long term progestin only contraception

Endometria from long term progestin only contraceptive-treated patients display abnormally enlarged blood vessels that are prone to bleeding as well as inflammation and possibly local diminution in blood flow. Such bleeding is also characterized by focal reductions in the expression of angiopoietin-1, a vessel stabilization and maturation agent, and excess production of the potent angiogenic agents, vascular endothelial growth factor and angiopoietin-2. In addition, tissue factor, the key initiator of hemostasis may play an angiogenic role either directly or via the activation of thrombin. This review article summarizes current findings related to the endometrial dysregulation of angiogenic/hemostatic agents following treatment with long term progestin only contraception. Studies in this area offer a promising avenue to alleviate abnormal uterine bleeding associated with this otherwise highly effective form of contraception     

Carotid baroreflex function during and following voluntary apnea in humans

Muscle sympathetic nerve activity (MSNA) and arterial pressure increase concomitantly during apnea, suggesting a possible overriding of arterial baroreflex inhibitory input to sympathoregulatory centers by apnea-induced excitatory mechanisms. Apnea termination is accompanied by strong sympathoinhibition while arterial pressure remains elevated. Therefore, we hypothesized that the sensitivity of carotid baroreflex control of MSNA would decrease during apnea and return upon apnea termination. MSNA and heart rate responses to -60-Torr neck suction (NS) were evaluated during baseline and throughout apnea. Responses to +30-Torr neck pressure (NP) were evaluated during baseline and throughout 1 min postapnea. Apnea did not affect the sympathoinhibitory or bradycardic response to NS (P > 0.05); however, whereas the cardiac response to NP was maintained postapnea, the sympathoexcitatory response was reduced for 50 s (P < 0.05). These data demonstrate that the sensitivity of carotid baroreflex control of MSNA is not attenuated during apnea. We propose a transient rightward and upward resetting of the carotid baroreflex-MSNA function curve during apnea and that return of the function curve to, or more likely beyond, baseline (i.e., a downward and leftward shift) upon apnea termination may importantly contribute to the reduced sympathoexcitatory response to NP.     

Blood oxygen transport in rats during lipopolysaccharide administration combined with modification of L-arginine-No system

Lipopolysacharide from Escherichia coli was intravenously administered to rats (5.0 mg/kg). L-arginine-No system was modified by intravenous injection of L-arginine, N(G)-nitro-L-arginine methyl ester or L-lysine-N(G)-acetamidine (nitric oxide synthase (NOS) substrate, nonselective NOS inhibitor, and selective inducible NOS inhibitor, respectively.) Lipopolysacharide-induced disorders of blood oxygen transport were the least during the selective inducible NOS inhibition. The protective effects of L-arginine and N(G)-nitro-L-arginine methyl ester were less prominent. Such features of NOS modification effect on the blood oxygen transport suggest that activation of inducible NOS may change the hemoglobin-oxygen affinity during the lipopolysacharide treatment.     

Preservation of functional integrity during long term storage of a biological membrane

Sarcoplasmic reticulum vesicles freeze-dried in the presence of trehalose retain most of their original biological activity for short periods. When the dry vesicles are stored for longer periods in air, Ca2+-transport becomes uncoupled from ATPase activity within a few days. However, when they are stored under vacuum, ATPase activity, Ca2+ transport, and coupling between Ca2+ transport and ATP utilization are maintained essentially intact for at least 110 days.     

Preservation of functional integrity during long term storage of a biological membrane

Sarcoplasmic reticulum vesicles freeze-dried in the presence of trehalose retain most of their original biological activity for short periods. When the dry vesicles are stored for longer periods in air, Ca²⁺-transport becomes uncoupled from ATPase activity within a few days. However, when they are stored under vacuum, ATPase activity, Ca²⁺ transport, and coupling between Ca²⁺ transport and ATP utilization are maintained essentially intact for at least 110 days.     

Monitoring the decline in AM fungus populations and efficacy during a long term bare fallow

Producing nonmycorrhizal plants in the field is a challenge due to the ubiquitous distribution of arbuscular mycorrhizal [AM] fungi and impacts of chemical treatments upon nontarget organisms. A field plot was covered with ground cover fabric to prohibit plant growth and take advantage of the obligate symbiotic nature of AM fungi to selectively starve and remove them from the soil microbiological community. The decline in the AM fungus population was monitored through spore counts and most probable number bioassays. Response to inoculation experiments were conducted to contrast the response of Allium porrum L. to inoculation with in vitro produced spores of Glomus intraradices Schenck and Smith when plants were grown in the AM fungus-depleted soil vs. soil from an adjacent, cropped plot. Data indicated a strongly diminished, yet still viable population of AM fungi after 39 months of bare fallow. Plants grown in cropped soil showed no growth response nor increase in percentage root length colonized as a result of inoculation, while the response to inoculation of plants grown in the covered soil increased as the population of AM fungi declined below 1 propagule cm^?3.     

Plasma catecholamines in rats during rewarming from induced hypothermia

The present study sought to quantitate the levels of plasma catecholamines [norepinephrine (NE), epinephrine (E), and dopamine (DA)] during induction and rewarming from hypothermia. Male rats (317 +/- 8 g) were made hypothermic by exposure to 0.9% halothane at -10 to -15 degrees C while blood pressure (carotid artery), heart rate, and colonic temperature (Tc) were monitored. Anesthesia was discontinued when Tc reached 28 degrees C. Tc continued to fall but was held at 20-20.5 degrees C for 30 min. Rewarming was then initiated by raising ambient temperature to 22 degrees C. Arterial blood samples were taken 1) before cooling, 2) just before rewarming, 3) when Tc reached 22 degrees C during rewarming, and 4) when Tc reached 27 degrees C during rewarming. Plasma was assayed radioenzymatically for catecholamines using both phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase procedures, and hypothermic induction resulted in significant increases in NE, E, and DA above control levels (P less than 0.01). With rewarming to Tc = 22 degrees C, all catecholamines increased above the level observed during hypothermia (P less than 0.01), and NE and DA increased still further (P less than 0.01) when Tc reached 27 degrees C. The levels of plasma catecholamines observed during hypothermia and during the rewarming phase indicate a role of the sympathoadrenal medullary system in the metabolic adjustments associated with hypothermia and recovery. During rewarming, the levels of E and NE attained exceed those at which both substances may be expected to act as circulating hormones.     

Gas transport during oscillatory flow in a network of branching tubes

A transport coefficient was measured for a range of oscillatory flow conditions in a branching network of tubes. Measurements were made both across the first generation of a three-generation network and the second generation of a four-generation network. The results for these two series of tests were similar, indicating that there was no significant effect due to the system boundaries. The results are cast in terms of an effective axial diffusion coefficient of the form (Formula: see text) where kappa is the molecular diffusivity, Vt is the local stroke volume (cc); and f is the oscillation frequency (Hz). These results are compared to those obtained by other investigators in branching systems of similar geometry. At low frequency, this result is found to be in approximate agreement with the steady flow result of Scherer, et al. [15]. This expression differs from the oscillatory flow results of Tarbell, et al. [19] for liquids, primarily in terms of the effects of oscillation frequency.