Peripheral vascular responses to hyperthermia in the rat

To investigate the sequence and nature of the peripheral vascular responses during the prodromal period of heat stroke, rats were implanted with Doppler flow probes on the superior mesenteric (SMA), left iliac (LIA) or left renal (LRA), and external caudal (ECA) arteries. Studies were performed in unanesthetized rats (n = 6) exposed to 46 degrees C and in chloralose-anesthetized animals (n = 11) at 40 degrees C. Core (Tc) and tail-skin temperatures, heart rate, and mean arterial blood pressure (MAP) were also monitored. In both groups, prolonged (70-150 min) exposure progressively elevated Tc from 37.0 to 44.0 degrees C. MAP rose to a plateau then fell precipitously as Tc exceeded 41.5 degrees C. SMA resistance increased throughout the early stages of heating, with a sharp decline from this elevated level 10-15 min before the precipitous fall in MAP. ECA resistance fell initially but increased in the terminal stage of heating. In unanesthetized animals, LIA resistance progressively declined. In chloralose-anesthetized animals LRA resistance rose progressively, then increased markedly as Tc exceeded 41.5 degrees C. These data support the hypothesis that a selective loss of compensatory splanchnic vasoconstriction may trigger the cascade of events that characterize heat stroke. This differential vascular response was similar in both unanesthetized and anesthetized animals.     

Close-range behaviour of male pea moths, Cydia nigricana, responding to sex pheromone re-released via the substrate

The close-range orientation behaviour of male pea moths, Cydia nigricana (F.) (Lepidoptera: Tortricidae), to a substrate contaminated with synthetic sex pheromone was studied in the field. The substrate was a sheet of polypropylene grass on a 1 m diam arena, on the upwind edge of which a pheromone trap had been placed previously for 1 h. After removal of the trap, moths continued to be attracted to the arena and to the vacated trap position. Video-recorded tracks showed that the moths behaved anemotactically whilst on the arena. When the arena was revolved so that the vacated trap position was on the downwind edge, moths continued to fly upwind on the arena, even though they were flying away from the original trap position and down a concentration gradient.     

Immunodeficiency in graft-versus-host disease. I. Mechanism of immune suppression

Irradiated CBA/J mice transplanted with H-2 compatible, minor histocompatibility disparate B10.BR bone marrow develop graft-versus-host disease (GVHD) if mature T lymphocytes are added to the marrow inoculum. In the setting of mild GVHD (receiving 10(4) or 10(5) T cells), by phenotypic analysis, lymphoid reconstitution occurs normally within 4 to 6 wk but there is a profound deficiency in the ability of splenic lymphocytes to respond to polyclonal activators such as LPS and Con A. This unresponsiveness is attributable to active suppression mediated by cells that express Thy-1 and can be removed with leucine methyl ester treatment. Thus, splenocytes from mice with GVHD suppress responses of normal T and B lymphocytes. Moreover, depletion of these suppressor cells restores normal function to splenocytes from mice with GVHD, and B cells isolated from these mice respond normally to T-dependent and -independent stimulation. Finally, IFN-gamma plays an important role in this suppression, because a neutralizing anti-IFN-gamma mAb significantly removes suppression of normal cells and restores functional responses of lymphocytes from mice with GVHD. These results provide insights into the mechanisms of immunodeficiency associated with GVHD, and suggest novel strategies for possible therapies for this disorder.     

Alcian blue staining of proteoglycans in polyacrylamide gels using the "critical electrolyte concentration" approach

A method is described here for Alcian blue staining of proteoglycans in polyacrylamide gels; this is illustrated using extracts obtained from bovine corneal stroma. Other available methods for visualization of proteoglycans can produce nonspecific staining and frequently a high background in the gel; with a "critical electrolyte concentration" approach, specific staining against a clear background can be obtained.     

Nigrostriatal Dopaminergic Neurons Remain Undamaged in Rats Given High Doses of l-DOPA and Carbidopa Chronically

Rats were fed maximally tolerated doses of L-3,4-Dihydroxyphenylalanine (L-DOPA) and carbidopa daily for 120 days in order to achieve a sustained elevation in brain dopamine levels. Some animals were also given buthionine sulfoximine, a gamma-glutamylcysteine synthetase inhibitor, in an unsuccessful effort to reduce brain glutathione contents. L-DOPA- and carbidopa-treated animals displayed no behavioral changes suggestive of nigrostriatal dopaminergic neuronal loss. When sacrificed 60 days after L-DOPA treatment ended, all rats had normal tyrosine hydroxylase activities and dopamine contents in their striata, and cell counts were normal in the substantia nigra. It therefore seems unlikely that a model of Parkinson's disease, suitable for exploring the etiological importance of glutathione deficiency, can be produced in rats merely by administering the largest tolerable doses of L-DOPA.     

Biopulping process design and kinetics

Biopulping is the solid-state fermentation of wood chips as a pretreatment for mechanical pulping processes. The two organisms that are currently of the greatest interest for biopulping are the white-rot fungi, Phanerochaete chrysosporium and Ceriporiopsis subvermispora. P. chrysosporium has been shown to successfully biopulp wood (33% energy savings; 39% improvement in tear index) without the need for sterilization of the wood or nutrient supplementation. Demonstrating the practical and economical feasibility of the biopulping process requires process modeling based on accurate kinetic data. Techniques to monitor dry weight loss and growth rate as functions of time using carbon dioxide production data have been developed. Growth was shown to be linear with time on unsupplemented chips and exponential with time on supplemented chips.     

A cell-based framework for modeling cardiac mechanics

Cardiomyocytes are the functional building blocks of the heart—yet most models developed to simulate cardiac mechanics do not represent the individual cells and their surrounding matrix. Instead, they work on a homogenized tissue level, assuming that cellular and subcellular structures and processes scale uniformly. Here we present a mathematical and numerical framework for exploring tissue-level cardiac mechanics on a microscale given an explicit three-dimensional geometrical representation of cells embedded in a matrix. We defined a mathematical model over such a geometry and parametrized our model using publicly available data from tissue stretching and shearing experiments. We then used the model to explore mechanical differences between the extracellular and the intracellular space. Through sensitivity analysis, we found the stiffness in the extracellular matrix to be most important for the intracellular stress values under contraction. Strain and stress values were observed to follow a normal-tangential pattern concentrated along the membrane, with substantial spatial variations both under contraction and stretching. We also examined how it scales to larger size simulations, considering multicellular domains. Our work extends existing continuum models, providing a new geometrical-based framework for exploring complex cell–cell and cell–matrix interactions.

     

Role of catalase in myocardial protection against ischemia in heat shocked rats

It was recently reported that in rats exposure to heat shock leads to appearance of a myocardial heat shock protein (HSP 70) and to an increase in myocardial catalase activity. This correlated with an improvement in post-ischemic function either in Langendorff-perfused hearts after low-flow ischemia or in working hearts after short-term, no-flow ischemia. We investigated the effect of the same hyperthermic treatment on functional recovery from no-flow ischemia of various durations in isolated working rat hearts performing at high or low external workloads. Rats were heated to core temperature of 42° C for 15 min. No significant protein oxidation (% oxidized methionine) was observed 2.5 hr after treatment. A protein with migration characteristics similar to HSP 70 was observed in hearts of heat shocked rats 24 hr after this treatment while their myocardial catalase activity was not increased. Hearts of similarly treated rats were excised 24 hr after hyperthermia and perfused in a working mode with Krebs-Henseleit buffer (1.25 mM Ca²⁺, 11 mM glucose). At 15 cm H₂O preload and 100 cm H₂O afterload after 30 min no-flow ischemia, control hearts recovered to 36.9%, 2%, 47.6%, and 21.5% of the preischemic values of heart rate-peak systolic pressure product (RPP), aortic output, coronary flow, and cardiac output, respectively. After only 25 min of ischemia the respective recovered values were 61.6%, 11.5%, 58.7%, and 33.5%. Throughout the recovery period these hemodynamic values were consistently higher in hearts of heat shocked animals than in those of control hearts but the differences were not statistically significant. After 25 min ischemia only 2 out of 7 control hearts recovered some aortic output, whereas in the heat shocked animals all 5 hearts recovered. After only 20 min of no-flow ischemia and at a lower workload (12.5 cm H₂O preload and 75 cm H₂O afterload), control hearts recovered to 85.1% of RPP, 54.1% of aortic output, and 68.3% of cardiac output. None of these variables was significantly improved by heat shock pretreatment. In summary, we were unable to demonstrate a similar degree of protective effect of heat shock pretreatment as compared to other reports where both HSP 70 and increased catalase activity were present. The reason(s) could be related to lack of induction of myocardial catalase activity in our study.     

Cholinergic Deafferentation of Dorsal Hippocampus by Fimbria-Fornix Lesioning Differentially Regulates Subtypes (m1-m5) of Muscarinic Receptors

Abstract: Unilateral aspiration lesions of the rostral supracallosal stria/cingulum bundle and fimbria-fornix were performed on adult female rats. Ten and 24 days post lesioning, an elevation (17%; p<0.01) of total muscarinic receptors was observed in lesioned versus control hippocampi. By using antisera selective for each of the five molecularly defined subtypes (m1-m5) of muscarinic receptors, significant changes were observed in the levels of expression for at least four receptor proteins. Three receptor subtypes increased in density: m1 by 14% (from 943 to 1,078 fmol/mg); m3 by 77% (from 150 to 268 fmol/ mg); and m4 by 29% (from 220 to 285 fmol/mg). In contrast, a 22% decrease in the density of m2 receptors was found (from 220 to 173 fmol/mg). Detectable levels of m5 receptors were low in the hippocampus (∼1% of total receptors), and reliable measurements were not obtained. The directions of these changes are likely to be related to the pre- or postsynaptic localization of these receptor subtypes.     

Expression and genomic organization of a dinoflagellate gene family

The luciferin-binding protein (LBP) of the dinoflagellate Gonyaulax polyedra is encoded by large gene family with at least two different members. To more fully understand the expression and genomic organization of this gene family, 40 full-length LBP cDNAs were isolated and mapped with the restriction enzymes Xho I, Eco RI, Pvu II and Hind III. All cDNAs isolated could be placed into one of two groups called LBP and LBP. Two LBP group cDNAs were completely sequenced and were found to share 99% identity at both the nucleotide and protein levels. One LBP cDNA was sequenced and was found to share only 86% sequence identity with the LBP group at both the nucleotide and protein levels. Both groups of message appear to be expressed at nearly equal levels since (1) two-dimensional gels of purified LBP show two protein isoforms present in roughly equal amounts and (2) northern blots using group-specific probes suggest that cellular levels of LBP and LBP mRNAs are identical. Genomic Southern blots using group-specific probes suggests that the copy number of both gene groups is very similar and that LBP gene loci are organized as tandem repeats of either LBP or LBP sequences.