Blockade of MUC1 expression by glycerol guaiacolate inhibits proliferation of human breast cancer cells

We sought to determine whether administration of glycerol guaiacolate at an optimal biological dose inhibits human breast cancer cell growth. Human breast cancer MCF-7 and ZR-75-1 cells were treated with glycerol guaiacolate and the therapeutic efficacy and biological activity of this drug was investigated on breast cancer cell growth. MCF-7 cells were injected into the mammary fat pad of overectamized female athymic nude mice. Ten days later, animals were treated with daily intraperitoneal injections of glycerol guaiacolate for six weeks. Tumor size and volume was monitored and immunohistochemistry analysis on MUC1, p21 and ki-67 was performed. Glycerol guaiacolate decreased breast cancer cell growth in a dose-dependent manner, decreased cell migration, and caused G1 cell cycle arrest. Our results demonstrate that glycerol guaiacolate inhibits MUC1 protein and mRNA expression levels and significantly increased p21 expression in human breast cancer cells as well as induced PARP cleavage. Similarly, glycerol guaiacolate inhibited breast tumor growth in vivo as well as enhanced p21 expression and decreased breast tumor cell proliferation (ki-67 expression). Collectively, our results demonstrate that glycerol guaiacolate decreased MUC1 expression and enhanced cell growth inhibition by inducing p21 expression in breast cancer cells. These findings suggest that glycerol guaiacolate may provide a novel and effective approach for the treatment of human breast cancer.

Probability of Signal Detection in a Vigilance Task

It is hypothesized that the probability of detecting a signal in a vigilance task depends upon its temporal location with respect to the preceding series of signals. Probability of detection should be at a maximum when the signal occurs after a temporal interval which is equivalent to the mean of the intervals between the preceding signals detected. The experimental results support this hypothesis.

Tissue factor-bearing microparticles derived from tumor cells: impact on coagulation activation

BACKGROUND

Tissue factor (TF)-bearing microparticles (MP) from different origins are thought to be involved in the pathogenesis of cancer-associated thrombosis. However, the role of circulating tumor cell-derived TF is not well understood.

METHODS

TF antigen and activity were measured in MP generated in vitro from human TF-expressing cancer cells by ELISA and clotting or thrombin generation assays, respectively. TF antigen and activity were also measured in vivo in cell-free plasmas from mice previously injected with in vitro-generated MP or in cell-free plasmas from nude mice bearing orthotopically injected human cancer cells.

RESULTS

Tumor cell-derived MP (TMP) exhibited strong TF-dependent procoagulant activity (PCA) in vitro and in vivo. Injection of TMP into mice was associated with acute thrombocytopenia and signs of shock, which were prevented by prior heparinization. Human TF antigen and activity could be detected in mouse cell-free plasmas up to 30 min after TMP injections. Human TF was detected in the spleen of injected mice and its clearance from circulation was delayed in splenectomized mice, suggesting the involvement of the spleen in the rapid clearance of circulating MP in vivo. Detectable levels of TF-dependent PCA and thrombin-antithrombin complex were found in cell-free plasmas from mice growing pancreatic human tumors, suggesting that circulating tumor-derived TF causes coagulation activation in vivo.

CONCLUSIONS

MP derived from certain cancer cells exhibit TF-dependent PCA both in vitro and in vivo. These results provide new information about the specific contribution of tumor-derived MP to the hypercoagulable state observed in cancer.

Radioiodine therapy of colon cancer following tissue-specific sodium iodide symporter gene transfer

We investigated the feasibility of using radioiodine therapy in colon carcinoma cells (HCT 116) following tumor-specific expression of the human sodium iodide symporter (hNIS) using the carcinoembryonic antigen (CEA) promoter. HCT 116 cells were stably transfected with an expression vector, in which hNIS cDNA has been coupled to a CEA promoter fragment. This promoter is responsible for tissue-specific expression of CEA in gastrointestinal tract epithelium, and has been shown to target therapeutic genes to colorectal cancer cells. Functional NIS expression was confirmed by iodide uptake assay, Western blot analysis, immunostaining and in vitro clonogenic assay. The stably transfected HCT 116 cells concentrated (125)I about 10-fold in vitro without evidence of iodide organification. In contrast, transfection of control cancer cells without CEA expression did not result in iodide accumulation. Western blot analysis using a hNIS-specific antibody revealed a band of approximately 90 kDa. In addition, immunostaining of stably transfected HCT 116 cells revealed hNIS-specific membrane-associated immunoreactivity. In an in vitro clonogenic assay approximately 95% of stably transfected HCT 116 cells were killed by exposure to (131)I, while only about 5% of NIS-negative control cells were killed. Further, using an adenovirus carrying the NIS gene linked to the CEA promoter, high levels of tumor-specific radioiodide accumulation were induced in HCT 116 cells. In conclusion, a therapeutic effect of (131)I has been demonstrated in colon carcinoma cells following induction of tumor-specific iodide uptake activity by CEA promoter-directed NIS expression in vitro. This study demonstrates the potential of NIS as a therapeutic gene allowing radioiodine therapy of colon cancer following tumor-specific NIS gene transfer.

The sodium-iodide symporter

The sodium-iodide symporter (NIS) is an intrinsic plasma membrane protein that mediates active transport of iodide in the thyroid gland and several other extra-thyroidal tissues. This activity has been utilized for many years for imaging the thyroid gland and for treatment of thyroid disease both benign and malignant. Cloning and characterization of NIS has more recently allowed research into its use in non-thyroidal cancers through gene transfer for both diagnosis and treatment.

Amino acid substitution at position 99 affects the rate of CRP subunit exchange

We investigated the characteristics of CRP having amino acid substitutions at position 99. Analysis of amino acid residue proximity to cAMP in molecular dynamics (MD) simulations of the CRP:(cAMP)(2) complex [García, A. E., and Harman, J. G. (1996) Protein Sci. 5, 62-71] showed repositioning of tyrosine 99 (Y99) to interact with the equatorial exocyclic oxygen atom of cAMP. To test the role of Y99 in cAMP-mediated CRP activation, Y99 was substituted with alanine (A) or phenylalanine (F). Cells that contained the WT or mutant forms of CRP induced beta-galactosidase in the presence of cAMP. Purified WT, Y99A, and Y99F CRP showed only a 3- to 4-fold difference in cAMP affinity. There were no apparent differences between the three forms of CRP in cAMP binding cooperativity, in CRP:(cAMP)(1) complex binding to lacP DNA, in the formation of CRP:cAMP:RNAP complexes at lacP, or in CRP efficacy in mediating lacP activity in vitro. The apo-form of Y99A CRP was more sensitive to protease than the apo-form of either WT CRP or Y99F CRP. Whereas the WT or Y99F CRP:(cAMP)(1) complexes were cleaved by protease at hinge-region peptide bonds, the Y99A CRP:(cAMP)(1) complex was cleaved at peptide bonds located at the subunit interface. The rates of subunit exchange for Y99A CRP, both in the apo-form and in a 1:1 complex with cAMP, were significantly greater than that measured for WT CRP. The results of this study show that tyrosine 99 contributes significant structural stability to the CRP dimer, specifically in stabilizing subunit association.

Inhibition of growth and metastasis of human pancreatic cancer growing in nude mice by PTK 787/ZK222584, an inhibitor of the vascular endothelial growth factor receptor tyrosine kinases

Since vascular endothelial growth factor (VEGF) plays a major role in tumor angiogenesis, we determined whether blockage of VEGF receptor signaling using a novel tyrosine kinase inhibitor (PTK 787) decreases the growth and metastasis of human pancreatic carcinoma growing orthotopically in nude mice. Human pancreatic L3.6pl cells were injected into the pancreas of nude mice. Seven days later, groups of mice were given daily oral administrations of PTK 787 alone, twice weekly i.p. injections of gemcitabine, or combination therapy. The mice were necropsied when control mice became moribund (day 35). Therapy with PTK 787 alone, gemcitabine alone, or the combination of both agents produced respectively 60%, 70%, and 81% inhibition in the volume of pancreatic cancers. The combination therapy significantly decreased the incidence of lymph node and liver metastasis, leading to a significant increase in survival. Microvessel density (MVD) was significantly decreased in tumors treated with either PTK 787 alone or PTK 787 plus gemcitabine. MVD directly correlated with tumor cell proliferation and inversely correlated with apoptosis of tumor cells and associated endothelial cells. Collectively, our results demonstrate that blockade of VEGF-R signaling may provide an additional approach to the therapy of pancreatic cancer.

Optimization for the blockade of epidermal growth factor receptor signaling for therapy of human pancreatic carcinoma

We determined the optimal administration schedule of a novel epidermal growth factor receptor (EGFR) protein tyrosine kinase inhibitor (PKI), PKI 166 (4-(R)-phenethylamino-6-(hydroxyl)phenyl-7H-pyrrolo[2.3-d]-pyrimidine), alone or in combination with gemcitabine (administered i.p.) for therapy of L3.6pl human pancreatic carcinoma growing in the pancreas of nude mice. Seven days after orthotopic implantation of L3.6pl cells, the mice received daily oral doses of PKI 166. PKI 166 therapy significantly inhibited phosphorylation of the EGFR without affecting EGFR expression. EGFR phosphorylation was restored 72 h after cessation of therapy. Seven days after orthotopic injection of L3.6pl cells, groups of mice received daily or thrice weekly oral doses of PKI 166 alone or in combination with gemcitabine. Treatment with PKI 166 (daily), PKI 166 (3 times/week), or gemcitabine alone produced a 72%, 69%, or 70% reduction in the volume of pancreatic tumors in mice, respectively. Daily oral PKI 166 or thrice weekly oral PKI 166 in combination with injected gemcitabine produced 97% and 95% decreases in volume of pancreatic cancers and significant inhibition of lymph node and liver metastasis. Daily oral PKI 166 produced a 20% decrease in body weight, whereas treatment 3 times/week did not. Decreased microvessel density, decreased proliferating cell nuclear antigen staining, and increased tumor cell and endothelial cell apoptosis correlated with therapeutic success. Collectively, our results demonstrate that three weekly oral administrations of an EGFR tyrosine kinase inhibitor in combination with gemcitabine are sufficient to significantly inhibit primary and metastatic human pancreatic carcinoma.

Position 127 amino acid substitutions affect the formation of CRP:cAMP:lacP complexes but not CRP:cAMP:RNA polymerase complexes at lacP

The lacP DNA binding and activation characteristics of CRP having amino acid substitutions at position 127 were investigated. Wild-type (WT) and T127C CRP footprinted lacP DNA in the presence of DNase I in a cAMP-dependent manner. The T127G, T127I, and T127S forms of CRP failed to footprint lacP both in the absence and in the presence of cAMP. Consistent with these data, WT and T127C CRP:cAMP complexes exhibited high affinity for the lacP CRP site whereas T127G, T127I, or T127S CRP:cAMP complexes exhibited low affinity for the lacP CRP site. CRP:cAMP:RNA polymerase (RNAP) complexes formed at lacP in reactions that contained WT, T127C, T127G, T127I, or T127S CRP. These results demonstrate that allosteric changes important for cAMP-mediated CRP activation are differentially affected by amino acid substitution at position 127. Proper cAMP-mediated reorientation of the DNA binding helices required either threonine or cysteine at position 127. However, cAMP-dependent interaction of CRP with RNAP was accomplished regardless of the amino acid at position 127. RNAP:lacP complexes that supported high-level lac RNA synthesis formed rapidly in reactions that contained WT or T127C CRP whereas RNAP:lacP complexes that supported only low-level lac RNA synthesis formed at slower rates in reactions that contained T127I or T127S CRP. The T127G CRP:cAMP:RNAP:lacP complex failed to activate lacP. The results of this study lead us to conclude that threonine 127 plays an important role in transduction of the signal from the CRP cyclic nucleotide binding pocket that promotes proper orientation of the DNA binding helices and only a minor, if any, role in the functional exposure of the CRP RNAP interaction domain.

Calcium-activated potassium channel-mediated arteriolar relaxation during endotoxic shock

The role of calcium-activated potassium (KCa) channels in the in vivo relaxation of arterioles was investigated before endotoxin shock (Pre-ENDT) and during endotoxin shock at 180 min (Post-ENDT). Diameters of 2nd and 3rd order (A2 and A3) arterioles in the left cremaster muscle of male Sprague-Dawley rats anesthetized with pentobarbital sodium were measured using videomicroscopy. Adenosine (ADO) at 534 micrograms intraarterially, topical ADO at 10(-3) M, and the endothelium-dependent agonist topical acetylcholine (ACH) at 10(-4) M significantly dilated both A2 and A3 arterioles Pre-ENDT and Post-ENDT. Topical tetraethylammonium chloride (TEA) at 1 mM blocked ADO (intraarterially and topical)-induced A2 and A3 arteriolar dilations Pre-ENDT and Post-ENDT. Arteriolar dilation to ACH was maintained Pre-ENDT, but was blocked by TEA in A2 and A3 arterioles Post-ENDT. The endothelium-independent agonist sodium nitroprusside (10(-5) M), when topically applied, caused maximal arteriolar dilation Pre-ENDT and Post-ENDT in the presence of TEA. The data show that vascular smooth muscle KCa channels are a significant factor in ADO-induced relaxation of cremaster microvessels and are not significantly affected by ENDT. The results also suggest that the mechanism for endothelium-dependent ACH vasodilation changes from a non-KCa channel-mediated mechanism Pre-ENDT to a KCa-mediated mechanism Post-ENDT.

Molecular cloning of a Schizosaccharomyces pombe cDNA encoding lanosterol synthase and investigation of conserved tryptophan residues

A Schizosaccharomyces pombe cDNA encoding lanosterol synthase was cloned by complementing a Saccharomyces cerevisiae lanosterol synthase mutant. The predicted 83-kDa protein is 54-58% identical to other lanosterol synthases. The previously known lanosterol synthases contain 229 conserved residues, which should encompass the catalytically essential amino acids. This number is decreased dramatically by including the Sc. pombe lanosterol synthase in the analysis; 42 residues are no longer conserved and therefore are catalytically nonessential. We have begun mutagenic studies to identify catalytic residues from the remaining conserved residues. Mutant Sa. cerevisiae lanosterol synthase genes were generated in which phenylalanine was specifically substituted for conserved tryptophan residues. All of the resultant mutant enzymes retained the ability to complement the Sc. cerevisiae lanosterol synthase mutant, suggesting that these conserved tryptophan residues are not catalytically essential.

Arteriolar reactivity of endotoxin-tolerant rats after hemorrhage and reinfusion

Adrenergic and endothelium-dependent arteriolar reactivity are greatly reduced in hemorrhagic shock. However, development of tolerance to endotoxin may prevent the decrease. The reactivity of cremaster muscle arterioles was tested in pentobarbital-anesthetized endotoxin-tolerant (ENDT-T) and nontolerant control rats. Tolerance was developed by sublethal intraperitoneal injections of Escherichia coli endotoxin for 4 days (n = 9). Controls received saline (n = 9). Mean arterial pressure (MAP), arteriolar diameter-response curves to topical norepinephrine (NE) (10-9M to 10-3M) and responses to 10-3M acetylcholine (ACh) were obtained as follows 1) at control, 2) following hemorrhage to 40 mmHg. 3) after uptake of 25% of bled volume with the remainder infused, and 4) at 240 min post-hemorrhage. The A1, A2, and A3 arterioles were constricted following hemorrhage in the ENDT-T group and in the saline group. After reinfusion and in late shock, vessel diameters remained constricted. MAP increased to control levels (106 +/- 5 and 101 +/- 4 mmHg, respectively) following re-infusion in both groups but in late shock it decreased until death in the nontolerant group and decreased only minimally (96 +/- 4 mmHg) in the ENDT-T group. The nontolerant group NE ED50 increased from pre-hemorrhage to late shock (p < .05). The ENDT-T group ED50 was unchanged. The bleeding volumes of the two groups were not different. The survival time of the nontolerant group was 234 +/- 36 min, whereas the ENDT-T group all survived and were sacrificed at 427 +/- 30 min. The response to endothelium-dependent ACH vasodilation in late shock was significantly reduced in the saline group but was unchanged in the ENDT-T group. Alpha 1 receptor activity was maintained in both groups. Alpha 2 receptor activity was attenuated pre-hemorrhage and at 240 min post-hemorrhage in ENDT-T rats. In late shock, alpha 2 receptor activity was attenuated in nontolerant rats. The development of endotoxin tolerance prevents the loss of arteriolar responsiveness to NE and ACh. ENDT-T rats have attenuated alpha 2 receptor activity but not alpha 1 receptor activity.

Macro- and microcirculatory effects of IL-15

The recently isolated and cloned cytokine interleukin (IL)-15 was studied to ascertain its systemic and local cardiovascular effects. IL-15 was studied in rats anesthetized with 50 mg/kg sodium pentobarbital. In Group I, 10-50 micrograms of IL-15 were administered intravenously. Heart rate and arterial pressure decreased significantly for the duration of the study. In Group II, IL-15 was administered topically to the exposed cremaster muscle in four doses of 10 ng each. Heart rate and arterial pressure decreased significantly for the duration of the study. A1 and A2 arteriolar diameters decreased, but A3 diameters remained unchanged as determined by videomicroscopy. Vasodilation induced by either topical acetylcholine or nitroprusside was abolished by IL-15. Reduced heart rate and arterial pressure suggest reduced cardiac output. Arteriolar constriction due to abolished smooth muscle dilation was caused by IL-15.

Molecular cloning of the human gene encoding lanosterol synthase from a liver cDNA library

Lanosterol synthase [(S)-2,3-epoxysqualene mutase (cyclizing, lanosterol forming), EC 5.4.99.7] catalyzes the cyclization of (S)-2,3-oxidosqualene to lanosterol in the reaction that forms the sterol nucleus. We report herein the cloning and characterization of the human gene (OSC) encoding lanosterol synthase, a predicted 83 kDa protein of 732 amino acids. The deduced amino acid sequence is 36-40% identical to known yeast and plant homologues and 83% identical to Rattus norvegicus lanosterol synthase. The new gene was shown to encode lanosterol synthase. The yeast lanosterol synthase deficient mutant SMY8 was complemented by the human gene, and a cell-free homogenate of SMY8 expressing the human gene was shown to convert 2,3-oxidosqualene to lanosterol.

Maintenance of dynamic microvascular function and structure in a rat model of endotoxic shock by blockade of the interleukin-1 receptor

The microvascular and macrovascular effects of IL-1 receptor antagonist (IL-1ra) were examined in rat cremaster muscle A1, A2, and A3 arterioles by videomicroscopy to better define its protective effects during endotoxemia. Mean arterial pressure (MAP), arteriolar diameters, and responses to norepinephrine (NE) and acetylcholine (ACh) were examined hourly after the administration of Escherichia coli endotoxin (6 mg/kg intravenously). Animals received saline (Control) or IL-1ra (.2 mg/kg/min intravenously) beginning 1 h prior to endotoxin. Serum tumor necrosis factor-alpha (TNF-alpha) and nitrate/nitrite (NO) were determined terminally. Aortic endothelium was examined by electron microscopy (EM). All Control animals, but no IL-1ra animals, died within 6 h (p < .01).IL-1ra significantly attenuated endotoxin-induced vasoconstriction of A1 and A2 arterioles (p < .01), while MAP and NE threshold remained at baseline (p < .01 vs. Control). Serum TNF and NO were elevated following endotoxin (p < .001), but only TNF was decreased (p < .005) in animals receiving IL-1ra. Aortic endothelium was damaged in all Control animals but was spared with IL-1 antagonism. IL-1ra increases survival during endotoxic shock and attenuates production of TNF but not NO. IL-1ra maintains MAP, arteriolar diameters, reactivity of arterioles to NE and ACh, and the integrity of the aortic endothelium.

Attenuation of arteriolar alpha 2-adrenoceptor sensitivity during endotoxemia

It is well documented that adrenergic responses after endotoxin (ENDT) administration are greatly reduced. The hypothesis of this study is that either alpha 1- or alpha 2-receptor activity is attenuated and the other receptor type is minimally affected during ENDT shock. Reactivity of the arterioles of left cremaster muscles of male Wistar rats anesthetized with pentobarbital sodium was studied using videomicroscopy. Femoral mean arterial pressure and first-, second-, third-, and fourth-order arteriolar diameters were measured. In group I, the decreases in arteriolar diameter and half-maximal effective dose (ED50) values with increasing phenylephrine concentration (alpha 1-adrenergic receptor agonist) were similar in all four branching orders before and after ENDT. In group II, the decreases in arteriolar diameter with increasing clonidine concentrations (alpha 2-adrenergic receptor agonist) were effectively attenuated by ENDT, and ED50 values were increased above control in all four branching orders. In group III, idazoxan (alpha 2-receptor antagonist) effectively blocked the vasoconstrictor effects of clonidine but did not affect the responses to phenylephrine before or after ENDT in all four arteriolar orders. In group IV, prazosin (alpha 1-adrenergic receptor antagonist) blocked the vasoconstrictor effects of phenylephrine before and after the administration of ENDT. However, vasoconstriction due to clonidine post-ENDT even at maximal dosage (10(-3) M), was greatly attenuated in all four branching orders as in group II. It is concluded that during endotoxemia the reduced adrenergic vasoconstrictor response of cremaster muscle arterioles is the result of attenuated activity of alpha 2-adrenergic receptors with minimal if any effects on alpha 1-adrenergic receptor activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of vasopressin microvascular responses by endotoxin, endothelin, and nitric oxide

The sensitivity of rat cremaster muscle arterioles to topically applied arginine vasopressin (AVP) is greatly increased by endotoxin (ENDT) [1]. The hypothesis is that the increase in vasoconstrictor sensitivity is in part due to modification of the AVP responses by endothelial compounds such as nitric oxide (NO) and endothelin. Reactivity of left cremaster muscle microvessels of pentobarbital anesthetized Sprague-Dawley rats was measured using videomicroscopy. Femoral arterial pressure as well as second and third order arteriolar (A2 and A3) vasoconstrictor threshold responses were determined for topical AVP (10(-15)-10(-6) M). These measurements were repeated in the presence of ENDT (6 mg/kg) alone and in the presence of the NO synthase inhibitor L-NAME (N omega-nitro-L-arginine methyl ester; 1 mg/kg) and ENDT (group 1). The control threshold (M)(-log) for arteriolar constriction by AVP was 9.4 +/- 0.7. After ENDT the threshold decreased significantly (P < 0.05) to 13.8 +/- 0.5, but returned to 9.0 +/- 0.5 after i.v. injected L-NAME. Acetylcholine (ACh) injected i.a. during AVP constriction significantly increased diameters at control and after ENDT, but not after L-NAME. In group 2 the AVP threshold was determined at control, after L-NAME plus hydroquinone (HQ), and at 30, 90, and 120 min post-ENDT in the presence of L-NAME + HQ. The AVP threshold at control was 9.0 +/- 0.3, after L-NAME 9.0 +/- 0.6, and after HQ 8.0 +/- 0.7. After L-NAME + HQ, the threshold was significantly increased to 7.3 +/- 0.2. After ENDT, in the presence of both antagonists, the threshold remained elevated at 7.4 +/- 0.2.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular endothelium in sepsis and endotoxemia

Since septic or endotoxin shock was high mortality and morbidity, mechanisms for cardiovascular collapse have been intensely investigated. The vascular response to catecholamines and other agonists is greatly attenuated. The mechanisms are considered to be related to changes in endothelium function. The endothelium releases vasoconstrictor and vasodilator compounds. These autocoids normally interact with systemic and other local vascular controls, but during endotoxemia this balance is severely altered. Large artery endothelia are destroyed whereas the microvessels remain intact and functional. The release of nitric oxide, prostacyclin and endothelin is greatly enhanced. The cytokines from endotoxin seem, however, to be the major causal agents of the syndrome and affect the endothelial or receptors on the endothelia differentially, dependent on tissue location.

In vitro femoral arterial responses to vasoconstrictor and vasodilator agents in endotoxin shock

The hypothesis for this study is that the decreased arterial response to catecholamines may be due to the effect of endotoxemia on vessel tone. One control ring was taken from one femoral artery of a Wistar rat and after endotoxin (ENDT) infusion (i.v. 6 mg/kg-1 hr.), one ring was removed from the contralateral artery. The post-ENDT rings were tested in four groups which were determined by the mean arterial pressure (MAP) levels at the time of dissection: 100 mmHg (120 min), 80 mmHg (270 min), 60 mmHg (300 min) or 40 mmHg (330 min). KCl, phenylephrine (PHE) and arginine-vasopressin (AVP) dose-response curves (DR) were obtained at a preload of 500 mg which allowed the maximum response in control rings. When compared at 500 mg preload the maximal active response to all agonists post-ENDT was decreased by about 50%. By increasing the preload on the ENDT rings to 800 mg, the active tension became 2.49 times the active tension of the control rings. Length-tension experiments also showed a greater response for post-ENDT rings and a greater preload at maximum response but the ring circumference was the same. In contrast the in vivo femoral artery diameters at 90 min post-ENDT (100 mmHg) were 82.6% of control. Endothelium-dependent relaxation by acetylcholine (ACh) was abolished by ENDT but endothelium-independent relaxation to nitroprusside (NP) was not affected. It is concluded that the resting tone and active tension of femoral artery smooth muscle is increased by ENDT and the decreased in vivo responsiveness to vasoconstrictor agonists may be the result of vessel constriction due to loss of endothelium. The results also suggest that in vitro comparison of vessels in studies of endotoxin shock be done at the same muscle length rather than at the same preload.

Effect of muscle length on the in vitro comparison of femoral arteries before and after endotoxin shock

Control and endotoxin-treated femoral arteries were compared in vitro for the effect of muscle length. Rats were anesthetized with pentobarbital, and endotoxin (6 mg/kg) was infused for 1 h. A control ring before endotoxin treatment and a ring after endotoxin treatment (blood pressure = 40 mmHg) were excised from the contralateral artery for length-tension and dose-response experiments with phenylephrine. The initial length for resting tension (Li) was shorter for endotoxic rings (1.23 +/- 0.01 vs. 1.41 +/- 0.02 mm in control), but the length of maximum active tension (Lmax) was the same. In length-tension experiments the values for active tension (6.36 +/- 0.61 vs. 4.06 +/- 0.60 x 10(3) dyn/cm), preload at Lmax (1,333 +/- 204 vs. 733 +/- 146 mg), and passive stiffness were increased after endotoxin. In dose-response experiments at the same preload, the endotoxic rings had a lower active tension (3.28 +/- 0.28 vs. 6.55 +/- 0.27 x 10(3) dyn/cm) but the same sensitivity. At Lmax, active tension (12.45 +/- 0.48 vs. 5.01 +/- 0.89 x 10(3) dyn/cm in control vessels) and sensitivity (half-maximum effective dose = 0.68 +/- 0.8 x 10(-6) vs. 1.39 +/- 0.29 x 10(-6) M in control vessels) were greater for endotoxic rings. These experiments show that phenylephrine sensitivity and active tension in the rat femoral artery are increased by endotoxin shock, and the importance of muscle length is implied.

Differences in arterial and arteriolar endothelial structure during endotoxin shock

Previous studies of physiological and ultrastructural assessment changes in the walls of the femoral artery and A1, A2, and A3 arterioles in the rat cremaster muscle after infusion of Escherichia coli endotoxin (ENDT) (6 mg/kg-1 hr. period) indicate there may be a difference in the alteration of the endothelial structure of arteries and arterioles. Functionally, ENDT has been shown to abolish acetylcholine (ACh)-induced relaxation in the femoral artery [Zhou, PhD dissertation, University of South Florida, Tampa, 1992]. Dilations of A1 arterioles were shown to be reduced, but dilations of A2 and A3 arterioles were not significantly changed from control [Baker and Sutton, Am J Physiol, 264:H 1118-H 1123, 1993]. In the current study, ultrastructural evaluation of femoral arterial tissue post-ENDT at the mean arterial pressure (MAP) of 100 mm Hg revealed partially destroyed endothelial cells. The MAP decreased as the animal progressed into shock. At 80 mm Hg, 60 mm Hg and 40 mm Hg, essentially all endothelial cells were destroyed, with the internal elastic lamina denuded. In contrast, endotoxin damage in the A1, A2, and A3 arterioles was minimal even at a MAP of 40 mm Hg. Endothelial cells of A1 arterioles post-ENDT had more vacuoles than at control. Therefore, arteriolar endothelium was functionally and anatomically relatively undamaged, consequent to endotoxin administration, in contrast to femoral arteries where the endothelium was destroyed in a short time.

Secondary structure and backbone resonance assignments of the periplasmic cyclophilin type peptidyl-prolyl isomerase from Escherichia coli

Proton, carbon-13, and nitrogen-15 sequence-specific backbone assignments have been obtained for the periplasmic cyclophilin type cis-trans peptidyl-prolyl isomerase from Escherichia coli (167 residues, M(r) = 18,244). Assignments were obtained using both 1H, 13C, and 15N triple-resonance and 1H and 15N double-resonance three-dimensional (3D) NMR spectroscopy at pH 6.2, 25 degrees C. Complete or partial residue-specific assignments have been obtained for 165 of the 167 residues. The secondary structure has been characterized using long- and medium-range NOEs. The protein consists of an eight-stranded anti-parallel beta-sheet and two helices. The overall topology of E. coli cyclophilin is similar to that of human T-cell cyclophilin. Sequence alignment with human T-cell cyclophilin based on secondary structure homology implicates several residues in E. coli cyclophilin that may be crucial for binding the peptide substrate AC-A-A-P-A-AMC and the immunosuppressive drug cyclosporin A.

Relation of phenotype evolution of HIV-1 to envelope V2 configuration

Biological variability of human immunodeficiency virus type-1 (HIV-1) is involved in the pathogenesis of acquired immunodeficiency syndrome (AIDS). Syncytium-inducing (SI) HIV-1 variants emerge in 50 percent of infected individuals during infection, preceding accelerated CD4+ T cell loss and rapid progression to AIDS. The V1 to V2 and V3 region of the viral envelope glycoprotein gp120 contained the major determinants of SI capacity. The configuration of a hypervariable locus in the V2 domain appeared to be predictive for non-SI to SI phenotype conversion. Early prediction of HIV-1 phenotype evolution may be useful for clinical monitoring and treatment of asymptomatic infection.

Antagonism of acetylcholine and adenosine rat cremaster arteriolar vasodilation by combination of NO antagonists

It has become evident that complete elimination of the vasodilator response to agonists that require the release of nitric oxide (NO) is necessary for certain studies of the microcirculation. The A2 and A3 arterioles of the rat cremaster muscle microcirculation were studied by video-microscopy. At control, arterioles at rest or constricted by arginine vasopressin (AVP) were dilated by intra-arterially injected acetylcholine (ACh), intra-arterially injected adenosine (ADO) and topical adenosine. The NO antagonists, Nw-nitro-L-arginine methyl ester (L-NAME) and hydroquinone (HQ), which acts as an antagonist by generating free radicals, in maximal doses, individually partially blocked the vasodilator actions of intra-arterial ACh and intra-arterial ADO. Combining L-NAME and HQ eliminated the vasodilation by intra-arterial ACh and intra-arterial ADO. Sodium nitroprusside dilated the arterioles to the resting level or above at control and in the presence of the antagonists either individually or when combined. However, the NO antagonists did not block the arteriolar vasodilator responses to topical ADO. The reduction of the production of NO and enhancement of its destruction by superoxide radicals results in the total absence of the vasodilator response due to intra-arterially injected acetylcholine and adenosine. The data suggest that luminal ADO receptors cause arteriolar dilation by endothelial-dependent mechanisms and abluminal receptors cause dilation by another mechanism.

Arteriolar endothelium-dependent vasodilation occurs during endotoxin shock

Endotoxin shock has been reported to alter endothelial structure as well as function of large arteries from in vitro experiments. Cremaster muscle arteriolar dilator reactivity of pentobarbital-anesthetized rats was determined by videomicroscopy at control and 30, 90, 150, and 210 min after intravenous infusion of Escherichia coli endotoxin (6 mg/kg, 1-h period). The dilator response was tested by intra-arterial injections of 90 ng acetylcholine (ACh). At control A1, A2, and A3 arterioles dilated 45, 21, and 34%, respectively. Postendotoxin arterial pressure decreased progressively, the A1 arterioles constricted (P < 0.05), A2 diameters were unchanged and A3 diameters increased. Postendotoxin ACh dilations averaged 28, 23, and 25%. A1 dilation was significantly (P < 0.05) less than at control. Methylene blue (2.5 mg ia) attenuated the ACh response at control, but after endotoxin an intense downstream vasoconstriction resulted in stasis and reduced survival time occurred. Hydroquinone (HQ) partially blocked the responses to ACh postendotoxin. HQ significantly increased the survival time postendotoxin. It is evident postendotoxin that the endothelia of arterioles are functional and able to release nitric oxide (NO) throughout the entire survival period. The microvascular release of NO and the dilation response to ACh were substantially attenuated by methylene blue and HQ. The latter may block the more lethal effects of the inducible NO synthase.

Overexpression, purification, and characterization of yeast cyclophilins A and B

Two isoforms of yeast cyclophilins, yCyPA and yCyPB, have been subcloned, expressed in Escherichia coli, and purified to homogeneity. The full-length (163-amino acid) yeast CyPA was easily expressed and purified; however, only a genetically truncated, 186-residue form of yCyPB lacking a putative 20-amino acid signal sequence could be purified. Each yeast cyclophilin isoform is a peptidyl-prolyl isomerase, inhibitable by the immunosuppressive drug CsA (IC50's of 40 +/- 8 nM and 101 +/- 14 nM at 18 nM concentrations of yCyPA and yCyPB, respectively). Polyclonal antibodies raised against recombinant yCyPA detected native yCyPA in yeast cell extracts by both immunoprecipitation and Western blot analysis. However, polyclonal antibodies raised against recombinant yCyPB detected no native yCyPB in yeast cell extracts by Western blot analysis; small amounts of yCyPB were found in the culture broth, suggesting secretion extracellularly of this isoform. Northern analysis indicated that both yCyPA mRNA and yCYPB mRNA (at a much lower level) were detectable in cell-free extracts. Characterization of the yeast cyclophilin proteins demonstrated that their catalytic properties and sensitivity to CsA parallel those of the human cyclophilins.

Endotoxin alteration of muscle microvascular renin-angiotensin responses

Endotoxin decreases arteriolar sensitivity to norepinephrine and sympathetic neural activity, but vasopressin sensitivity is increased. Vascular responses to the renin-angiotensin system may also be altered by endotoxin (ENDT). Reactivity of cremaster muscle microvessels of pentobarbital anesthetized Wistar rats was studied using videomicroscopy. Escherichia coli endotoxin (6 mg/kg) was infused i.v. over a 1 hr period. Femoral arterial pressure (Pm) and arteriolar diameter changes, to i.a. bolus injections (60 ng) of angiotensin II (AII) were obtained in Group A at control and at 30 and 90 min post-ENDT, and in Group B at control, 30 min after continuous infusion of saralasin (10 micrograms/min/kg) began, and at 30 and 90 min post-endotoxin. In Group A, the control Pm was 106 +/- 4 mm Hg, and at 30 and 90 min post-ENDT was 96 +/- 4 and 89 +/- 7 mm Hg. All increased Pm 29 +/- 4% before ENDT but the increase was significantly less (P less than .05) at 7 +/- 1% and 6 +/- 1% 30 and 90 min post-ENDT. In Group B, the control Pm was 116 +/- 6 mm Hg, 103 +/- 5 after saralasin, 85 +/- 2 after ENDT infusion, and 83 +/- 4 and 63 +/- 8 mm Hg at 30 and 90 min post-ENDT. All increased Pm 34 +/- 7% before saralasin but only 5 +/- 2% (P less than .05) during saralasin infusion. In Group A, the A1 and A2 arterioles were constricted significantly more post-endotoxin by AII than during control. A3 arterioles post-endotoxin were constricted similar to control amounts by AII.(ABSTRACT TRUNCATED AT 250 WORDS)

2'-Deoxy-2'-methylenecytidine and 2'-deoxy-2',2'-difluorocytidine 5'-diphosphates: potent mechanism-based inhibitors of ribonucleotide reductase

It has been found that 2'-deoxy-2'-methyleneuridine (MdUrd), 2'-deoxy-2'-methylenecytidine (MdCyd), and 2'-deoxy-2',2'-difluorocytidine (dFdCyd) 5'-diphosphates (MdUDP (1) MdCDP (2) and dFdCDP (3), respectively) function as irreversible inactivators of the Escherichia coli ribonucleoside diphosphate reductase (RDPR). 2 is a much more potent inhibitor than its uridine analogue 1. It is proposed that 2 undergoes abstraction of H3' to give an allylic radical that captures a hydrogen atom and decomposes to an active alkylating furanone species. RDPR also accepts 3 as an alternative substrate analogue and presumably executes an initial abstraction of H3' to initiate formation of a suicide species. Both 2 and 3 give inactivation results that differ from those of previously studied inhibitors. The potent anticancer activities of MdCyd and dFdCyd indicate a significant chemotherapeutic potential. The analogous RDPR of mammalian cells should be regarded as a likely target and/or activating enzyme for these novel mechanism-based inactivators.

Nutrient and nonnutrient renal blood flow

The role of prostaglandins in the distribution of total renal blood flow (TRBF) between nutrient and nonnutrient compartments was investigated in anesthetized mongrel dogs. Renal blood flow distribution was assessed by the xenon 133 freeze-dissection technique and by rubidium 86 extraction after ibuprofen treatment. Ibuprofen (13 mg/kg) significantly decreased TRBF by 16.3% +/- 1.2% (mean +/- SEM electromagnetic flow probe; p less than 0.005), but did not alter blood flows to the outer cortex (3.7 vs 4.3 ml/min per gram), the inner cortex (2.6 vs 2.7 ml/min per gram), and the other medulla (1.5 vs 1.5 ml/min per gram), which suggests a decrease in nonnutrient flow. In a separate group of animals the effect of reduced blood flow on the nutrient and nonnutrient components was determined by mechanically reducing renal arterial blood flow by 48%. Unlike the ibuprofen group, nutrient blood flows were proportionally reduced with the mechanical decrease in TRBF in the outer cortex (1.9 ml/min per gram, p less than 0.05), the inner cortex (1.4 ml/min per gram, p less than 0.05), and the outer medulla (0.8 ml/min per gram, p less than 0.01). These results indicate no shift between nutrient and nonnutrient compartments. Nutrient and nonnutrient renal blood flows of the left kidney were also determined by 86Rb extraction. After ibuprofen treatment, nonextracted 86Rb decreased to 12.1% from the control value of 15.6% (p less than 0.05). Mechanical reduction of TRBF did not significantly decrease the proportion of unextracted 86Rb (18.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Microvascular vasopressin effects during endotoxin shock in the rat

We have demonstrated decreased microvascular sensitivity to norepinephrine during endotoxin shock possibly related to reduced sympathetic receptor activity (Baker et al.: Circ Shock 12:165-176, 1984). The response to other vascular controls such as arginine vasopressin (AVP) may also be altered. Reactivity of the left cremaster muscle microvessels of pentobarbital anesthetized Wistar rats was studied using videomicroscopy and videodensitometry. Femoral arterial pressure (Pm), dose response curves of vessel diameters to topical arginine vasopressin (10(-15) to 10(-6) M), FITC-albumin mean transit times, and plasma velocities were obtained. Escherichia coli endotoxin (6 mg/kg i.v., LD100) was infused over a 1-hr period. Parameter measurements were repeated at 30 min and 90 min post-endotoxin. Both Pm and plasma velocities progressively decreased. Arteriolar constriction and the mean transit times of FITC-labeled albumin progressively increased. The threshold dose for AVP averaged 10(-9) M at control and decreased to 10(-14) M post-endotoxin. Venular diameters were not altered by AVP. The AVP antagonist did not alter the microvascular diameter response to endotoxin but did block the responses to topical and endogenous AVP since arterial pressure and flow velocity decreased at a significantly greater rate than in rats without antagonist. Plasma AVP levels were significantly increased by endotoxin. Reduced alpha adrenergic sensitivity may unmask the responsiveness to AVP or increase the sensitivity of AVP receptors. Increased endogenous AVP may require a smaller exogenous concentration of AVP for constriction.

Blood flow distribution with adrenergic and histaminergic antagonists

Superficial fibular nerve stimulation (SFNS) causes increased pre- and post-capillary resistances as well as increased capillary permeability in the dog hind paw. These responses indicate possible adrenergic and histaminergic interactions. The distribution of blood flow between capillaries and arteriovenous anastomoses (AVA) may depend on the relative effects of these neural inputs. Right hind paws of anesthetized heparinized dogs were vascularly and neurally isolated and perfused with controlled pressure. Blood flow distribution was calculated from the venous recovery of 85Sr-labeled microspheres (15 microns). The mean transit times of 131I-albumin and 85Sr-labeled microspheres were calculated. The effects of adrenergic and histaminergic antagonists with and without SFNS were determined. Phentolamine blocked the entire response to SFNS. Prazosin attenuated increases in total and AVA resistance. Yohimbine prevented increased total resistance, attenuated the AVA resistance increase, and revealed a decrease in capillary circuit resistance. Pyrilamine attenuated total resistance increase while SFNS increased capillary and AVA resistances. Metiamide had no effect on blood flow distribution with SFNS. The increase in AVA resistance with SFNS apparently resulted from a combination of alpha 1 and alpha 2 receptor stimulation but not histaminergic effects.

Microvascular responses of intact and adrenal medullectomized rats to hemorrhagic shock

Evidence indicates that during the later stages of hemorrhagic shock there appears to be a loss of response to the control systems that would normally maintain an adequate peripheral resistance. Therefore, the reactivity of the cremaster muscle microcirculation of pentobarbital-anesthetized Wistar rats, intact and adrenal medullectomized, was studied using videomicroscopy. The left cremaster muscle was spread over an optical port in a bath filled with modified Krebs solution (pH 7.4, 34 degrees C). The right femoral artery was cannulated for determination of mean arterial pressure (Pm) and for hemorrhage of the rat. Following control measurements of Pm and microvessel diameters, cumulative dose-response curves of arteriolar and venular diameters to topical norepinephrine (NE) (10(-9) - 10(-4) M) were obtained. The protocols for intact and medullectomized groups were: 1) hypovolemic shock (shed blood not reinfused)--hemorrhage of 3.2 ml/100 g, compensation allowed, and NE dose-response curves repeated and obtained again during late shock as determined by Pm declining below 60 mmHg; and 2) normovolemic shock (condition after reinfusion of shed blood)--hemorrhage into a reservoir to Pm of 40 mmHg, maintenance at this level until 25% of the bled volume had been taken back (irreversible shock), and then reinfusion of the remainder of the blood. After blood reinfusion, the NE dose-response curves were repeated and obtained again during late shock, as determined by Pm below 60 mmHg. In all of the bled animals, the A1 arterioles were constricted posthemorrhage. The A2 arterioles were constricted only in the hypovolemic intact group. The A3 arterioles of all groups were not significantly changed from control. The constricted arterioles remained so. However, the other arterioles in all groups were unchanged during the several hours until death. The threshold concentration of NE for constriction of arterioles (10% or greater) was significantly increased (decreased sensitivity) during shock in all four groups. The response of the medullectomized rats to normovolemic shock was similar to that of the intact group, indicating that the circulating catecholamines were not essential. The response of medullectomized rats to hypovolemic shock was more severe and indicated the need for circulating catecholamines to compensate for the blood volume loss.

Adrenergic and histaminergic neural interactions in dog paws

The mechanisms underlying the vascular responses of superficial fibular nerve stimulation (SFNS) have not been defined. Right hindpaws of anesthetized heparinized dogs were vascularly and neurally isolated, enclosed in a volume recorder, and perfused with controlled pressure. Vascular volume (VV) (131I-labeled albumin) and rate of tissue volume changes (VT) (plethysmography) were determined. SFNS increased blood flow resistance, reduced capillary filtration coefficient (CFC) and permeability-surface area product (PS) of 86Rb, increased VV, and reduced 131I-albumin recovery. VT increased at the rate of 3.35 +/- 0.45 ml/min. SFNS during terbutaline increased resistance, CFC, PS, and VV were unchanged, 131I-albumin recovery was complete, and VT increased at one-fourth the control rate. Phentolamine and yohimbine blocked all responses to SFNS. Prazosin with SFNS attenuated hemodynamic changes and VT increased to two-thirds of control, decreased VV, albumin, and Rb recovery but not PS and CFC. SFNS during pyrilamine maleate reduced VT increase to two-thirds of control rate and blocked decreases in PS and CFC. Metiamide did not change the SFNS responses, except to reduce vascular volume and VT. The combined histamine H1 and H2 blockers reduced VT increase to one-third of control and attenuated albumin loss, prevented histamine dilation, attenuated vasopressin and norepinephrine but not angiotensin constriction. SFNS stimulation increased precapillary resistance by alpha 1- and alpha 2-receptors and venous resistance by alpha 2-receptors and increased permeability by histamine release from endothelium.

Taking care of the doctors: the hospital's duty to evaluate, monitor, and discipline its medical staff

The heart of a hospital's credentialing responsibilities lies in its duties to evaluate, to monitor, and to discipline its medical staff. Some key elements of an effective credentialing system are the skills of the medical staff coordinator, the use of physician proctors to evaluate new applicants, careful investigation of applicants for initial appointment and for reappointment, and education for department chairmen. Inevitable problems include physicians who do not work harmoniously with others and allegations of incompetence and impairment.

Dependence of the length-tension relationship on agonist concentration in vascular smooth muscle

This study examines the dependence of the length-tension (L-T) relationship in vascular smooth muscle on its level of activation. A horizontal shift of the L-T relationship with a change in activation level has been shown in striated muscle when L-T curves could not be superimposed. Active force at each length was normalized to the maximum active force in each curve. Indices of a horizontal shift of a L-T curve include the initial length for an active response (Li) and the length for maximum active force (Lmax). In this study normalized L-T curves were obtained from rings of the dog anterior tibial artery at low (approximately ED50) and high (maximal activation) concentrations of potassium (K+), norepinephrine (NE), and calcium (Ca2+). The normalized curve with a low concentration of K+ or NE was shifted to the right of the curve obtained with a high concentration. Li and Lmax were significantly longer for a low concentration of K+ or NE than a high concentration. With the same concentration of NE (10(-5) M) no difference in the normalized L-T curves, in Li, or in Lmax were found when low (0.085 mM) Ca2+ experiments were compared to normal (1.7 mM) Ca2+ experiments. It may be concluded that the length-tension relationship in vascular smooth muscle is shifted to longer lengths with a decrease in the concentration of a chemical agonist but not by a decrease in external calcium. We suggest that a concentration dependent shift in the length-tension relationship may have a role in the regulation of blood flow.

Tibial nerve and deep fibular nerve effects on venous and extravascular volumes

The innervation of the vasculature of the dog hindpaw separately controls the series and parallel coupled vessels by means of the tibial, deep fibular, and superficial fibular nerves. The latter primarily affects veins. The venous effects of the tibial and deep fibular nerves have not been adequately defined. The right hindpaw of anesthetized dogs was vascularly and neurally isolated in a volume recorder. The animals were heparinized and the preparation autoperfused (constant pressure). Total tissue volume changes were determined by the volume recorder. Total vascular volume changes were calculated from changes in paw 51Cr-red blood cell radioactivity measured by a scintillation detector. Arterial pressure and paw blood flow were monitored. The tibial and deep fibular nerves were each separately stimulated at 1, 5, and 15 Hz. Deep fibular nerve stimulations resulted in progressively significant increases in precapillary flow resistance. Vascular and tissue volumes decreased with stimulation frequency but vascular volume decreased significantly less than tissue volume change. Tibial nerve stimulation resulted in significant precapillary resistance increases. Vascular and tissue volumes decreased by similar amounts. Thus, deep fibular nerve stimulation causes passive decrease in venous volume, reduced capillary pressure, and fluid absorption. Tibial nerve stimulation causes active arterial and venous constriction maintaining capillary pressure with minimal fluid transfer.

Effects of vasodilation on plasma distribution in SHR cremaster muscle microvessels

Alterations in the structure, number, reactivity, contractility and sensitivity of resistance vessels of hypertensive animals have been reported. If the etiology of hypertension is due to one or a combination of these factors, it could logically be expected that the distribution of blood flow from the arterial to venous circulation through parallel microcirculatory circuits could be affected. The right cremaster muscles of pentabarbital anesthetized Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) (6-8 weeks old) were exposed and prepared for fluorescent videomicroscopy. The right iliac artery was cannulated with PE-10 tubing, the tip of which was placed at the aortic bifurcation for bolus injections of FITC-dextran (70,000 molecular weight) and arterial pressure measurement. Passage of the indicator through the microcirculation was recorded on videotape during control and during vasodilation by topical application of adenosine (0.2 M). Time-concentration curves were recorded by means of dual window videodensitometry upon replay of the tape. Arterial pressure averaged 85 +/ 3 mm Hg in WKY rats and 110 +/- 5 mm Hg in SHR. Arteriolar flow velocity varied directly with small arteriolar diameter. Dilation significantly reduced the venular appearance (ta), mean transit time (t), and curve width time (tE) in WKY and SHR. The ta was significantly more reduced in SHR than WKY. This would suggest that, in WKY, dilation may have opened some new parallel circuits but principally increased flow velocity through existing circuits. In SHR, new shorter and/or higher velocity circuits were opened as evidenced by the reduced ta with the longer and/or lower velocity circuits largely unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature effects on dog hindpaw series and parallel vascular circuits

The effect of environmental temperature (skin surface) on distribution of blood flow between the parallel vascular circuits has been assessed in vascularly and neurally isolated hindpaws perfused at constant pressure. The paw was sealed in a chamber filled with water at 10, 20, 30, or 40 degrees C. Peripheral resistance increased as the temperature decreased in both innervated and denervated paws. Resistance in the denervated paws was less than in the innervated paws at all temperatures. Recovery of 85Sr microspheres was less at 40 degrees C than at 10, 20, or 30 degrees C in the denervated paws but did not change in innervated paws. Capillary availability (diffusion capacity and filtration coefficient) increased with each elevation in temperature in both groups. At 10 degrees C both arteriovenous (AV) shunt and capillary flows were low in innervated paws with low capillary and high shunt flow in denervated paws. At 20 and 30 degrees C capillary flow increased with temperature and arteriovenous anastomosis (AVA) flow was unchanged in denervated paws. In innervated paws AV shunt flow fraction slightly increased, with capillary perfusion markedly increased as temperature was elevated. The increased capillary flow in both groups passed through an enlarged capillary bed, whereas the number and/or diameter of AVAs remained essentially unchanged.

Innervation sites of dog hindpaw series and parallel vascular circuits

The neural control of the distribution of blood flow between the parallel nutritional and nonnutritional vascular circuits in the dog hindpaw has been assessed. The right hindpaw of anesthetized dogs was vascularly and neurally isolated and placed in a volume recorder sealed by the skin flap. The animals were heparinized. The autoperfused preparation was isovolumetric during the control period. The inflow tubing had side arms for measurement of perfusion pressure and for injections of indicators (131I-albumin, 86Rb and 85Sr-microspheres). Vascular volume changes were determined from venous time-concentration curves and by plethysmography. The peripheral cut ends of the superficial and deep fibular nerves and the tibial nerve were individually stimulated at 5 and 11 Hz. The permeability surface area product of 86Rb and the capillary filtration coefficient were determined and A-V shunt patency was assessed by the venous recovery of 85Sr 15 microns microspheres. Each nerve stimulation increased blood flow resistance. Superficial fibular nerve innervation included essentially uniform effects on the arterioles and A-V shunts, the upstream arteries and also the veins. Deep fibular nerve stimulation indicated that its innervation included the arteries and the A-V shunt nonexchange vessels. Tibial nerve stimulations indicated that its innervation included the A-V shunt vessels and veins with minimal influences on the arteries and arterioles.

Red blood cell and plasma distribution in SHR cremaster muscle microvessels

Distribution of blood in the cremaster muscle microvasculature of spontaneously hypertensive (SHR) and Wistar-Kyoto normotensive (WKY) rats was determined by fluorescence videomicroscopy and densitometry. Bolus intra-arterial injections of fluorescein isothiocyanate (FITC)-dextran or dichlorotriazenylaminofluorescein-treated red blood cells (DTAF-RBC) produced time-concentration curves in the series-coupled segments. WKY and SHR mean arterial pressure averaged 89 +/- 6 and 125 +/- 5 mmHg, respectively. Arteriolar diameters were not different between the two groups. The smallest SHR venules (V4) and larger diameters than those of WKY (P less than 0.05), whereas V3 and V2 were not different. WKY diameters for V1 were significantly greater than those of SHR. The mean transit (t) and appearance times (ta) of both indicators were equal at the largest arteriole (A1) in both groups. In A2, A3, and A4 the t for both indicators were generally lower in SHR than in WKY rats but not significantly. The venular t were significantly greater in SHR than in WKY rats with DTAF-RBC consistently less than FITC-dextran values. The greater cross-sectional area of V4 in SHR than WKY rats would reduce flow velocity and elevate t. Dispersion (ta/t = 1.0 indicates no dispersion) of both indicators was less in WKY than in SHR. The ratios for both groups increased at V4 because ta increased more than t. Shorter circuits for red blood cells than for plasma and less plasma skimming exists in WKY than in SHR.

Microvessel mean transit time and blood flow velocity of sulfhemoglobin-RBC

An indicator dilution technique is described for obtaining time-concentration curves subsequent to bolus injections of sulfhemoglobin red blood cells (SH-RBC), which have a deep greenish-brown color (absorption peak 620 nm vs. 542 and 564 nm for normal red cells). The series- and parallel-coupled microvessels of cat mesentery were studied. This is accomplished by means of video microscopy with a two-window intensity-sensitive video sampler system. The relationship between SH-RBC concentration in blood and optical measurement is linear. Blood flow velocities were calculated from the difference in mean transit times between two points along a vessel. When this technique is used in association with the previously reported method for determining time-concentration curves for the plasma indicator FITC-dextran the mean transit time (t) for red blood cells was less than for plasma in arterioles. The reproducibility of t and flow velocity for both SH-RBC and FITC-dextran from successive injections were reported. The mean transit time ratio of arteriolar SH-RBC to FITC-dextran averages 0.89. Blood flow velocity calculated from SH-RBC is greater than that calculated from FITC-dextran in these same arterioles. The ratio of the velocities averages 1.29.