Mutations in the kissing-loop hairpin of human immunodeficiency virus type 1 reduce viral infectivity as well as genomic RNA packaging and dimerization

A stem-loop termed the kissing-loop hairpin is one of the most highly conserved structures within the leader of human immunodeficiency virus type 1 (HIV-1) and chimpanzee immunodeficiency virus genomic RNA. Because it plays a key role in the in vitro dimerization of short HIV-1 RNA transcripts (M. Laughrea and L. Jette, Biochemistry 35:1589-1598, 1996, and references therein; M. Laughrea and L. Jette, Biochemistry 35:9366-9374, 1996, and references therein) and because dimeric RNAs may be preferably encapsidated into the HIV-1 virus, alterations of the kissing-loop hairpin might affect the in vivo dimerization and encapsidation processes. Accordingly, substitution and deletion mutations were introduced into the kissing-loop hairpin of an infectious HIV-1 molecular clone in order to produce viruses by transfection methods. The infectivity of the resulting viruses was decreased by at least 99%, the amount of genomic RNA packaged per virus was decreased by 50 to 75%, and the proportion of dimeric genomic RNA was reduced from >80 to 40 to 50%, but the dissociation temperature of the genomic RNA was unchanged. There is evidence suggesting that the deletion mutations moderately inhibited CAp24 production but had no significant effect on RNA splicing. These results are consistent with the kissing-loop model of HIV-1 RNA dimerization. In fact, because intracellular viral RNAs are probably more concentrated in transfected cells than in cells infected by one virus and because the dimerization and encapsidation processes are concentration dependent, it is likely that much larger dimerization and encapsidation defects would have been manifested within cells infected by no more than one virus.

Far-field radiation of planar Gaussian sources and comparison with solutions based on the parabolic approximation

Previous research on the Gaussian beam was restricted in scope because of the paraxial assumption. Based on a rigorous solution of the Helmholtz equation, the radiation properties of a Gaussian source are reexamined. The results are different from what previous paraxial theory predicted. It is shown that the commonly used concept of the Gaussian beam and the separability of the field distribution along the two transverse axes may be misleading in certain conditions. Furthermore the theoretical upper limit on the beam divergence angle is shown to be 65.5 degrees .

[Qualitative grading of detrusor contractility in benign prostatic hyperplasia patients]

To grade qualitatively detrusor contractility in benign prostatic hyperplasia (BPH), we studied 120 BPH patients aged from 58 to 89 years. The pressure-flow studies were performed. The passive urethral resistance relation (PURR) and Schäfer diagram were used to analyse the results. The detrusor contractility was divided into 4 classes: very weak (VW), weak (W), normal (N), and strong (ST). The types of pressure-flow were high pressure--low flow (HP-LF), high pressure--high flow (HP-HF), low pressure--low flow (LP-LF) and low pressure--high flow (LP-HF) type. The results showed that the incidence of VW, W, N and ST class was 12.5%, 26.7%, 47.5% and 13.3% respectively; the incidence of HP-LF, HP-HF and LP-LF type was 55%, 1.7% and 43.3% respectively. The weak detrusor strength could become powerful by the surgery treatment of bladder outflow obstruction (BOO) and the function training of detrusor. The detrusor strength class of a BPH patient was improved from W before surgery to N after surgery in our studies. The principles of the fluid dynamics and urodynamic and the clinical application of the qualitative grading of detrusor contractility were discussed.

[Epidemiological study of external genital diseases in 5172 adolescents]

OBJECTIVE

To study the incidence of external genital diseases and the health status of external genitalia in male adolescents in china.

METHODS

5172 male adolescents aged 7-22 were sampled randomly to examine the diseases and health status of external genitalia. According to the diagnostic criteria in textbook Surgery (3rd edition), all examinations were carried out by urologists.

RESULTS

The total incidence of redundant prepuce was 67.79%, phimosis 10.09%, varicocele 19.82%, hydrocele 0.87%, concealed penis 0.68%, cryptorchidism 0.39%.

CONCLUSION

The health status of external genitalia in male adolescents is bad. Redundant prepuce and phimosis are common diseases. The examination of external genitalia should be carried out in the physical examination of admission. This study may provide the theoretical evidence for prevention and treatment of male external genital disease as well as the important data for study on andrology.

[Conventional and ambulatory urodynamic study on patients with chronic prostatitis syndrome]

To study the urodynamic findings of chronic prostatitis syndrome (CPS), 58 patients with chronic prostatitis and prostatodynia were subjected to the urodynamic investigation that included conventional medium filling urodynamic (CMG) tests (urethral pressure profile, filling cystometry, voiding pressure-flow study) and ambulatory urodynamic monitoring (AM) by using Dantec Menuet and Urodec 500 AM system. 55 BPH patients and 20 normal men were taken as control groups. CPS patients had function bladder outflow obstruction (FBOO). FBOO resulted in the detrusor instable (DIS, 12.1%), detrusor-sphincter dysnergia (DSD, 100%) and detrusor dysconstractility (DDC, 6.9%), and resulted in clinical symptoms. FBOO resulted from the urethal sphincter spasm and DSD.

[A survey on mother's nutritional knowledge-attitude on the feeding of young child in Guangdong province]

A survey on mother's nutrition knowledge-attitude on the feeding of young child was conducted in Guangdong province in 1995 among 414 mothers of 0 to 18 months old children. The results showed that the nutritional knowledge-attitude level of the mothers was low in both city and township. Only 51% of them had qualified level. The level of general nutritional concepts and the nutritional knowledge-attitude during weaning period were significantly lower than that of breastfeeding and follow-weaning. It suggests that the promotion of nutritional education in the feeding of young children is urgent in Guangdong province especially in township and rural area. It is necessary to focus on the improvement of nutritional knoweledge in weaning period and general nutrition concepts.

[Study of electrophysiological properties of large conductance K(+)-channels in outer hair cells from the guinea pig with patch-clamp technique]

The basic electrophysiological characteristics of large conductance K(+)-channels in the basolateral cell membrane of outer hair cells (OHC) from the guinea pig cochlea were studied with patch-clamp technique. Acutely isolated OHC preparations were obtained by enzymatic digestion and excised patches were made in cell-attached configuration to record single-channel currents led by patch-clamp micropipette and fed to patch-clamp amplifier. Data were sampled and analyzed on-line with a computer. The result showed that the typical properties of single channels of large conductance K(+)-channels were: 1. The channel was activated by depolarization of membrane and it showed a marked voltage-dependence. The channel had a unitary conductance of about 133 pS and the channel current reversed at about -30mV under asymmetrical K+ concentration gradient. 2. Tetraethylammonium (TEA, > 10 mmol/L), a potassium channel blocker, dose-dependently abolished the outward current. 3. The open probability (Po) and mean open time of this channel was markedly increased with elevation of cytoplasmic Ca2+ concentration. These results suggest that a population of voltage-dependent and Ca(2+)-activated K+ channel exists in the basolateral membrane of OHC of the guinea pig; it is characterized by a very high unitary conductance and high sensitivity to Ca2+ and is blocked by K+ channel blocker. This work provided valuable basic materials for further study on the regulation and drug influence of the type of single channels.

[The effect of anisodamine hydrochloride on globin chain synthesis in anemic mice]

We treated anemic mice with Anisodamine hydrochloride followed by Hb electrophoresis and detection of globin chain synthesis rate. We found that the synthesis of their globin chains remarkably increased and would last for approximately 10 days, While the results did not show any generation of fetal Hb, possible effect of the drug might come from the raising of alpha and beta globin chains of the adult mice.

[Construction of the wt-p53 gene recombinant retroviral vector. Inhibiting the growth of laryngocarcinoma cell line]

We have constructed wt-p53 gene recombinant retroviral vector. The p53 cDNA with positive regulative sequence was subcloned into the Xho I site between the two LTRs of the N2A retroviral vector which contained the cytomegalovirus promotor/enhancer for expression and a neomycin resistance gene allowing G418 selection in reverse orientation and established the PA317 packaging cell line producing virus. The recipient cell line of Hep2 (laryngocarcinoma) containing the abnormal p53 gene was transfected in vitro with fresh retroviral stock produced. The result showed that the constructed wt-p53 gene recombinant retroviral vector was able to suppress growth of laryngocarcinoma cell in vitro. These observations indicate that recombinant retrovirus expressing wild-type p53 may be the useful vectors for gene therapy of human laryngocarcinoma.

Maximum far-field divergence angle of a plane source

The far-field properties of a plane source with a constant phase distribution are presented. It is found, for the first time to our knowledge, that for any plane source the theoretical upper limit of the far-field divergence angle is shown to be 65.5°. This result is different from what previous propagation and diffraction theories predicted, and when the size of the source approaches zero, the far-field behavior of the plane source is also different from a spherical wave in half-space.

Kinetics of substrate reaction in the course of hydroperoxide-mediated inactivation of cytochrome P450 1A1

A schematic kinetic model is proposed for the hydroperoxide-mediated substrate reaction and cytochrome P450 inactivation. From the model, the relationships between the product concentration at infinite time (P infinity), the apparent rate constant of P450 inactivation (A), and the substrate concentrations are predicted, and the predictions were experimentally examined. The reciprocal of P infinity is proportional to the reciprocal of the substrate concentration in both CuOOH- and H2O2-supported substrate reactions. The reciprocal of P infinity is proportional to cumene hydroperoxide (CuOOH) concentration, but P infinity is independent of H2O2 concentration, indicating different effects of CuOOH and H2O2 in P450 inactivation. The apparent rate constant (A) is proportional to the reciprocal of the substrate concentrations, suggesting substrate protection of P450 from hydroperoxide inactivation. The model also suggests that a second CuOOH molecule may compete with substrate for binding to the P450 substrate binding site. Simulated kinetics of production formation vs time are quite consistent with the experimental kinetics.

Scalable and expressive medical terminologies

The K-Rep system, based on description logic, is used to represent and reason with large and expressive controlled medical terminologies. Expressive concept descriptions incorporate semantically precise definitions composed using logical operators, together with important non-semantic information such as synonyms and codes. Examples are drawn from our experience with K-Rep in modeling the InterMed laboratory terminology and also developing a large clinical terminology now in production use at Kaiser-Permanente. System-level scalability of performance is achieved through an object-oriented database system which efficiently maps persistent memory to virtual memory. Equally important is conceptual scalability-the ability to support collaborative development, organization, and visualization of a substantial terminology as it evolves over time. K-Rep addresses this need by logically completing concept definitions and automatically classifying concepts in a taxonomy via subsumption inferences. The K-Rep system includes a general-purpose GUI environment for terminology development and browsing, a custom interface for formulary term maintenance, a C+2 application program interface, and a distributed client-server mode which provides lightweight clients with efficient run-time access to K-Rep by means of a scripting language.

Ocular toxicity of intravitreous transforming growth factor-beta 1

PURPOSE

To evaluate the ocular toxicity of intravitreous transforming growth factor-beta 1 (TGF-beta(1)).

METHODS

Eyes of New Zealand white rabbits were injected intravitreally with TGF-beta(1) in doses of 20, 10, 5, 1 or 0.5 micrograms. Electroretinography and clinical examination were performed before and after the injection. At either 10 or 30 days after injection, the eyes were enucleated and examined histologically. The endothelium of fresh corneas, which had received 20 micrograms TGF-beta(1) or nothing, were checked 5 days after injection.

RESULTS

Corneal opacity was caused by doses > or = 10 micrograms in 7 of 7 eyes; by doses of 5 micrograms in 3 of 4 eyes; and by doses of 1 microgram in 1 of 4 eyes. Doses > or = 5 micrograms also caused pannus formation in 15 of 16 eyes. Ten days after injection there was some decrease in B-wave amplitude on electroretinography. Thirty days after injection the electroretinographic responses had recovered, except in the eyes injected with 20 micrograms TGF-beta(1), which still showed a decrease in step 1. Histological examination of paraffin sections did not demonstrate significant change. Corneal thickness of the eyes receiving 20 micrograms TGF-beta(1) was twice that of the normal cornea and some corneal endothelial cells lost their hexagonal shape.

CONCLUSION

TGF-beta(1) injected intravitreally at doses > or = 1 micrograms is toxic to the cornea. Retinal function is only slightly disturbed by 20 micrograms of TGF-beta(1).

Structure and properties of a herpesvirus of turkeys recombinant in which US1, US10 and SORF3 genes have been replaced by a lacZ expression cassette

In the process of generating an insertional mutant of herpesvirus of turkeys (HVT) expressing lacZ at the protein kinase (PK) locus, we isolated a recombinant which contained an intact PK gene but the short unique regions US1, US10 and SORF3 had been deleted and replaced by the lacZ cassette. Moreover, the virus contained duplicate copies of gD, gI and gE in an opposite orientation flanking lacZ, US2 and PK which were contiguous. These results are of interest in relation to the flexibility of the short unique segment (Us) and of the inverted repeats flanking Us of the alpha-herpesviruses. The recombinant expressed beta-galactosidase and was genetically stable in vitro and in vivo. Chickens inoculated with the virus developed antibodies to HVT antigens and to beta-galactosidase but the replication of the recombinant in vivo was impaired in comparison to parental HVT as shown by a reduction in the proportion of infected lymphocytes.

ORC and Cdc6p interact and determine the frequency of initiation of DNA replication in the genome

The origin recognition complex (ORC) binds replicators in the yeast S. cerevisiae in a manner consistent with it being an initiator protein for DNA replication. Two-dimensional (2D) gel techniques were used to examine directly initiation of chromosomal DNA replication in temperature-sensitive orc mutants. Unlike in wild-type cells, in orc2-1 and orc5-1 mutant cells, only a subset of replicators formed active origins of DNA replication at the permissive temperature. At the restrictive temperature, the number of active replicators was diminished further. Using a genetic screen, CDC6 was identified as a multicopy suppressor of orc5-1. 2D gel and biochemical analyses demonstrated that Cdc6p interacted functionally and physically with ORC. We suggest that ORC and Cdc6p form a prereplication complex at individual replicators and therefore cooperate to determine the frequency of initiation of DNA replication in the genome.

Prevention of organophosphate-induced toxicity in mice

bis-Quaternary amines, which are acetal analogues of hemicholinium-3, were synthesized and several compounds were potent chemicals to antagonize toxicity induced by the organophosphate, paraoxon. Structural requirements were specific and included two oxygen atoms (bis-acetal substitution) within 6 or 7 atom heterocyclic rings, oxygen atoms spaced 2-carbon atoms from the quaternary nitrogen, and carbonyl substitutions adjacent to the spacing moieties, either bicyclohexyl or biphenyl. Biological testing showed a positive potency correlation between the chemicals when data from the following tests were compared: antagonism in mice of paraoxon-induced motor impairment using the incline screen and toxicity, and ability to induce contractions of guinea-pig isolated ilea. The compounds were compared with the often used protective antagonist of organophosphate-induced toxicity, pyridostigmine. One compound, MFS-3, was seven times more efficacious and possessed a much higher therapeutic index. Possible mechanisms of action for these chemicals are discussed.

A unique insertion in the S gene of surface antigen--negative hepatitis B virus Chinese carriers

The presence of unique hepatitis B virus (HBV) variants has been investigated in two Chinese patients with chronic liver disease, whose sera were positive for HBV-DNA by dot blot hybridization or polymerase chain reaction (PCR) but hepatitis B surface antigen (HBsAg)-negative by conventional polyclonal antibody based immunoassays. PCR amplification of HBV-DNA followed by direct sequencing showed an insertion of six nucleotides, which introduced two additional amino acids between codons 122 and 123 in one patient (Isolate 1), whereas a nine nucleotide insertion in the other patient (Isolate 2) gave rise to three amino-acids between codons 123 and 124 immediately upstream from the 'a' determinant in the S gene. These insertions have not been described previously in any published sequences of the known subtypes and were absent from sequences of 30 HBsAg-positive Chinese patients from the same region. In the cases under study, the insertion is associated with four consecutive adenine molecules from nucleotides 516 to 519. It seems likely that this area is a hot spot for insertions in HBV. We found none of the previously described amino-acid deletions or substitutions in the pre-S1, pre-S2 and S genes, which are involved in unusual antigenic profiles. This finding suggests that genetic mutations in the S gene outside the 'a' determinant may be responsible for failure to detect HBsAg in some Chinese patients with chronic hepatitis caused by HBV infection.

Effect of antireflection coating on the performance of Faraday rotators

The transmission and reflection properties of Faraday rotators are investigated by use of the boundaryvalue approach. Transmission and reflection coefficient matrices are derived from boundary conditions and transmission and reflection functions. The performances of extinction ratio and insertion and return losses of Faraday rotators are calculated for yttrium iron garnet, bismuth-substituted iron garnet, and BiCaInVIG (a non-rare-earth iron garnet) Faraday rotators.

Analysis of an origin of DNA amplification in Sciara coprophila by a novel three-dimensional gel method

The replication origin region for DNA amplification in Sciara coprophila DNA puff II/9A was analyzed with a novel three-dimensional (3D) gel method. Our 3D gel method involves running a neutral/neutral 2D gel and then cutting out vertical gel slices from the area containing replication intermediates, rotating these slices 90 degrees to form the third dimension, and running an alkaline gel for each of the slices. Therefore, replication intermediates are separated into forks and bubbles and then are resolved into parental and nascent strands. We used this technique to determine the size of forks and bubbles and to confirm the location of the major initiation region previously mapped by 2D gels to a 1-kb region. Furthermore, our 3D gel analyses suggest that only one initiation event in the origin region occurs on a single DNA molecule and that the fork arc in the composite fork-plus-bubble pattern in neutral/neutral 2D gels does not result from broken bubbles.

Developmental progression of DNA puffs in Sciara coprophila: amplification and transcription

DNA amplification for two major DNA puffs (II/2B and II/9A) of the fungus fly Sciara coprophila increases steeply from 17 to 19 days after hatching (18 degrees C), resulting in almost 20-fold more DNA at these loci in mature larval salivary glands than in adult tissues. At 19 days after hatching when gene amplification reaches a plateau, there is a burst in the amount of mRNA encoded by these two DNA puffs. Expansion of the two puffs coincides with the increase in transcription rather than reinitiation of DNA replication. In contrast, an RNA puff (III/9B) undergoes no DNA amplification, and the burst in RNA produced by this locus occurs slightly later, at 20 days after hatching. The progression of cytological puffing and associated molecular events of DNA amplification and transcription correlate with features of the external phenotype of the larvae, especially the number of pigment granules in the eyespots that are the anlage to the adult eyes. The sequential and coordinated regulation of DNA puff replication and transcription is discussed.

Replication initiates at a confined region during DNA amplification in Sciara DNA puff II/9A

Two independent two-dimensional (2D) gel methods were used to map an origin of replication that is developmentally regulated by the steroid hormone ecdysone, namely an origin for DNA puff amplification in the fungus fly Sciara coprophila. Initiation of replication was found to occur within a small region of no larger than 6 kb by use of the neutral/neutral 2D gel method. Neutral/alkaline 2D gel analyses support the results of the neutral/neutral 2D gels and further define within the origin region an approximately 1-kb area where the majority of replication initiates. This is the first example of an origin of replication in multicellular eukaryotes that has been mapped by 2D gels to such a small defined region. Moreover, replication can be seen by the neutral/alkaline 2D gel method to proceed bidirectionally outward from this replication origin region. These data are consistent with an onion-skin mechanism whereby multiple rounds of DNA replication initiate at a specific origin of replication for Sciara DNA puff amplification.

The chirality of ground DNA knots and links

The chirality of ground DNA knots and links is described and characterized in terms of color symmetry groups (CSG), i.e. color symmetry groups I and II, which correspond to topochirality (topological chirality) and topoachirality (topological achirality) which bear an uncanny resemblance to point groups I (proper) and point groups II (improper) used for testing geochirality (geometrical chirality) and geoachirality (geometrical achirality), respectively. By regarding these two crossing modes in mirror images as white and black vertices, DNA knots and links with minimal crossings can be mapped to vertex-bicolored graphs under a working hypothesis that DNA knots and links exist in ground states with minimal energy m0. The color symmetry group of a vertex-bicolored graph G is defined as the set of all permutations and permutation asymmetrizations of the vertices of G that preserve its topology (connectivity), where asymmetrization, denoted as (a), is the operation of changing vertices' colors, and a permutation followed by an (a) is a permutation asymmetrization. The color symmetry groups I contains only permutations, whereas color symmetry groups II comprise permutation asymmetrizations as well as permutations. Four DNA knots and links in nature are analyzed and tabulated consisely. In addition, the well-known figure-of-eight knot and Borromean rings are discussed in much the same way.

Physical properties of the Escherichia coli transcription termination factor rho. 2. Quaternary structure of the rho hexamer

Under approximately physiological conditions, the transcription termination factor rho from Escherichia coli is a hexamer of planar hexagonal geometry [Geiselmann, J., Yager, T. D., Gill, S. C., Calmettes, P., & von Hippel, P. H. (1992) Biochemistry (preceding paper in this issue)]. Here we describe studies that further define the quaternary structure of this hexamer. We use a combination of chemical cross-linking and treatment with mild denaturants to show that the fundamental unit within the rho hexamer is a dimer stabilized by an isologous (or pseudoisologous) bonding interface. Three identical dimers of rho interact via a second type of isologous bonding interface to yield a hexamer with C3 or D3 symmetry. Cross-linking and denaturation experiments definitely rule out C6 and C2 symmetry for the rho hexamer. Data from fluorescence quenching, lifetime, and energy transfer experiments also argue against C2 symmetry. The simplest symmetry assignment that is not contradicted by any experimental data is D3; thus we conclude that the rho hexamer has D3 symmetry. We also consider the positioning of the binding sites for RNA and ATP relative to the coordinate reference frame of the D3 hexamer. Fluorescence energy transfer data are presented and integrated with data from the literature to arrive at a self-consistent model for the quaternary structure of the rho hexamer.

Inhibition of digestive proteinases of stored grain Coleoptera by oryzacystatin, a cysteine proteinase inhibitor from rice seed

Electrophoresis of midgut extracts from the rice weevil, Sitophilus oryzae, and the red flour beetle, Tribolium castaneum, in polyacrylamide gels containing sodium dodecyl sulfate and gelatin revealed there was one major proteinase (apparent molecular mass = 40,000) in the rice weevil and two major proteinases (apparent molecular masses = 20,000 and 17,000) in the red flour beetle. The pH optima using [3H]casein as substrate were about pH 6.8 for the rice weevil and pH 5.2 for the red flour beetle. Use of specific inhibitors, including L-trans-epoxysuccinyl-leucylamino-(4- guanidino)-butane (E-64), p-chloromercuriphenylsulfonic acid (PCMS), and oryzacystatin, indicated that nearly all of the proteinase activity against casein was contributed by cysteine proteinases. The estimated IC50 values for oryzacystatin were 2 x 10(-6) M and 4 x 10(-7) M when tested against midgut extracts from T. castaneum and S. oryzae, respectively.

[Diagnosis value of lateral pharyngeal roentgenography in snoring disease]

In this paper, X-ray findings of the lateral pharynx before uvulopalatopharyngoplasty in 14 cases of snoring disease were studied. The results are as follows. There is less than 5 mm in anterior-posterior airway of pharyngeal cavity (13 cases), and 8 mm (1 case), in diameter. Minimum 2 mm, average 4.4 mm. There is less than 25 mm length of uvula (7 cases), 28-35 mm (7 cases). Minimum 22 mm, average length is 27.9 mm. Shape of uvula is thick and long (12 cases), thick and short 1 case, thin and long 1 case. The etiology, abnormal X-ray finding and X-ray examination of the lateral pharynx, etc. in snoring disease have been discussed.

Performance of Some Heat-Sensitive Differential Agars Prepared and Melted by Microwave Energy 1

The viable cell count performance of some heat-sensitive differential agars prepared and remelted by microwave energy was evaluated for Salmonella choleraesui , Streptococcus faecalis and Escherichia coli . The conventional boiling method was used for comparison. No significant difference was found between the microwave oven processed agar and the conventional-boiling processed agar in viable cell counts of the target bacteria. Heating and reheating of violet red bile agar, bismuth sulfite agar, and KF Streptococcus agar by both methods did not change agar performance. However, remelting of desoxycholate citrate agar by both methods resulted in a substantial lowering of viable cell counts.

Insulin infusion in conscious dogs. Effects on systemic and coronary hemodynamics, regional blood flows, and plasma catecholamines

Cardiovascular actions of insulin were studied by intravenous infusions of insulin (4 and 8 mU/kg per min) in normal conscious dogs. This resulted in increases in cardiac output, heart rate, and left ventricular derivative of pressure with respect to time (dP/dt) and dP/dt/P, as blood glucose was reduced. The inotropic and chronotropic effects of insulin were not related to hypoglycemia, as they persisted even when blood glucose was restored to control values or when it was prevented from falling by a simultaneous infusion of glucose. These cardiac effects were accompanied by increases in plasma catecholamines, and were abolished by propranolol pretreatment. Both plasma epinephrine and norepinephrine increased during insulin hypoglycemia, but only norepinephrine increased during insulin infusion when euglycemia was maintained. Mean arterial blood pressure did not change significantly during insulin hypoglycemia, but rose if euglycemia was maintained, probably due to the selective increase in norepinephrine in the latter condition. A pressor response also occurred in propranolol-pretreated dogs during insulin hypoglycemia, but was abolished when the animals also had been pretreated with phentolamine, indicating that the vasoconstrictor action of insulin was mediated via alpha adrenergic receptors. Insulin infusion increased left ventricular work and myocardial blood flow in dogs with and without hypoglycemia. Myocardial blood flow, however, did not change significantly during insulin infusion in dogs pretreated with propranolol. As propranolol also diminished the inotropic response, it appears that the increase in myocardial blood flow caused by insulin in the normal dog is causally related to the increased myocardial metabolic demand. Insulin also produced vasomotor effects on other vascular beds. In skeletal muscle, blood flow was increased under all study conditions, except during insulin hypoglycemia after propranolol-pretreatment when unopposed alpha-mediated vasoconstriction was present. The persistent increase in flow during both alpha and beta adrenergic blockade suggests that insulin has a direct dilator effect on skeletal muscle vasculature. In the adrenal gland, flow was increased except during euglycemia, when no rise in plasma epinephrine was observed, suggesting coupling between adrenal flow and catecholamine release. In the splanchnic bed, flow was decreased during euglycemia, when plasma norepinephrine rose, and during beta adrenergic blockade with propranolol, when unopposed alpha-mediated vasoconstriction also predominated. A similar pattern was found in the kidney, except that renal blood flow also fell after combined alpha and beta adrenergic blockade. The results show that the vasomotor effects on regional flows are mediated both via adrenergic mechanisms, and in the case of skeletal muscle and kidney, via mechanisms unrelated to sympathetic stimulation.

The effect of verapamil on mechanical performance of acutely ischemic and reperfused myocardium in the conscious dog

The effect of verapamil, an inhibitor of transmembrane calcium flux, was studied in intact conscious dogs with myocardial ischemia produced by inflating a balloon cuff implanted on the left anterior descending coronary artery. Six dogs received a continuous infusion of verapamil (10 microgram/kg per min) beginning prior to coronary occlusion, and six received normal saline infusions. Systolic ejection shortening (SES) was measured from subendocardial ultrasonic crystals implanted in the central ischemic zone (IZ) and border zone (BZ), and in a nonischemic control zone (CZ). Hearts were paced at a constant heart rate with periodic introduction of closely coupled extrasystoles. SES was measured both for normally paced beats and during postextrasystolic potentiation (PESP). Regional myocardial blood flow was measured by injecting radioactive microspheres before, during, and after coronary occlusion. There were no significant differences between verapamil-treated dogs and saline control dogs in mean aortic pressure, heart rate, left ventricular end-diastolic pressure or dP/dt, cardiac output, or regional myocardial blood flow in IZ, BZ, or CZ. Differences in mechanical performance between two groups were noted, however. In the IZ, SES was abolished completely for normally paced beats in both groups but was significantly preserved for PESP beats in the verapamil-treated animals. In the BZ, SES was significantly reduced for normally paced beats only in the saline controls, and PESP responses were preserved to a significantly greater degree in the verapamil-treated animals. These results indicate that verapamil pretreatment exerts beneficial effects upon mechanical performance of ischemic myocardium. Since no changes in systemic hemodynamics or regional myocardial blood flow were observed, the effect may be due to the calcium-antagonistic properties of the agent.

Acute renovascular hypertension in conscious dogs. Interaction of the renin-angiotensin system and sympathetic nervous system in systemic hemodynamics and regional blood flow responses

The effects of acute renovascular hypertension on the sympathetic nervous system, regional blood flow and cardiac function were studied in conscious dogs submitted to renal artery occlusion by inflation of a cuff implanted previously around one renal artery. We then compared the alterations in plasma renin and catecholamine levels and in the various hemodynamic parameters induced by those maneuvers in intact dogs, to those in dogs pretreated with alpha- and beta-adrenergic receptor blockers. Subsequently, the converting enzyme inhibitor teprotide was administered to inhibit angiotensin formation in both experiments. Our results suggest that both the renin-angiotensin system and the sympathetic system contribute to the rise in blood pressure. The hemodynamic changes and alterations in regional blood flows accompanying this acute hypertension appear to be due mostly to the increase in plasma angiotensin, since prior adrenoceptor blockade only attenuated their magnitude but did not alter their direction. However, angiotensin-induced coronary vasoconstriction was observed only in adrenergically blocked but not intact animals, probably because of the protective effect of baroreceptor-mediated reflex sympathetic coronary vasodilation.

Conditioning effects of chronic infusions of dobutamine. Comparison with exercise training

We studied the conditioning effects of chronic infusion of dobutamine and exercise training in three groups of chronically instrumented dogs. One group was infused with normal saline, a second group was infused with dobutamine (40 mug/kg per min), and the third group was exercised on a treadmill at 4 mph, up a 10 degrees incline. Each group was either infused or exercised for 2 h a day, 5 d a week for 5 consecutive wk. Resting heart rate and arterial blood lactate concentration, measured at weekly intervals, decreased progressively in the dobutamine and exercise groups, but not in the group that received normal saline infusion. Cardiovascular responses to submaximal treadmill exercise were not changed by 5 wk of normal saline infusion. However, the increases in heart rate, cardiac output, mean aortic blood pressure, arterial blood lactate, plasma renin activity, and norepinephrine concentration during exercise were significantly smaller after 5 wk of conditioning with either dobutamine or exercise training. After conditioning, the increases in arteriovenous oxygen difference during exercise were larger in the latter two groups, but the increases in total body oxygen consumption did not differ before and after conditioning. To assess ventricular function, we intravenously infused methoxamine both before and after conditioning. The slope of the line that related systolic aortic blood pressure and mean left atrial pressure increased in the animals conditioned with either dobutamine or exercise, indicating enhanced myocardial contractility. Left ventricular blood flow was lower in these two groups of animals than it was in the normal saline group. Left ventricular weight did not differ among the three groups. Our results show that chronic infusion of dobutamine produced cardiovascular and metabolic conditioning effects like those produced by exercise training, and further suggest that sympathetic stimulation during exercise plays a role in physical conditioning.

Regulation of cardiac output during 2,4-dinitrophenol-induced tissue hypermetabolism in the dog

1. Cardiac output increased in proportion to oxygen consumption in intact chloralose-anaesthetized dogs after four successive intravenous infusions of 2,4-dinitrophenol (11 mumol/kg; 2 mg/kg). 2. Splenectomy abolished the increase in cardiac output after the first three doses of 2,4-dinitrophenol. beta-Adrenoreceptor blockade by practolol, on the other hand, did not prevent the cardiac output rise after the first 2,4-dinitrophenol infusion, but further increases by 2,4-dinitrophenol infusion were abolished. When splenectomy and beta-adrenoreceptor blockade were combined, cardiac output did not increase significantly after all four doses of 2,4-dinitrophenol. 3. Cardiac output and mean systemic arterial blood pressure increased when the splenic venous blood collected after 2,4-dinitrophenol infusion was infused intraportally. 4. In a vascularly isolated, but normally innervated, lower half-body cross-perfusion preparation, cardiac output and mean systemic arterial blood pressure increased in the upper half-body when tissue hypermetabolism was produced in the cross-perfused area by 2,4-dinitrophenol. Neith pulmonary artery wedge pressure nor heart rate changed significantly. 5. This circulatory stimulation, after regional 2,4-dinitrophenol infusion, was abolished or was prevented from occurring by splenectomy. 6. It appears that the normal cardiac output response to tissue hypermetabolism requires both an intact spleen and normally functioning beta-adrenoreceptors.

Effects of arterial hypoxemia and splenic nerve stimulation on myocardial adenosine 3',5'-Monophosphate in dogs

Epinephrine infusion, 5-percent oxygen breathing, and splenic nerve stimulation were employed to increase cardiac output by 50-100% in anesthetized dogs. Epinephrine infusion as expected, increased plasma and myocardial cyclic AMP concentrations. Arterial hypoxemia increased cyclic AMP concentration in plasma but not in the heart. Practolol pretreatment abolished the increase in plasma cyclic AMP concentration and reduced the rise in cardiac output during hypoxemia. Splenic nerve stimulation was not associated with increases in either plasma or myocardial cyclic AMP. Adenylate cyclase activity was increased by addition of plasma into the incubation medium. However, splenic venous plasma obtained during splenic nerve stimulation did not increase adenylate cyclase activity more than control plasma obtained before stimulation. We conclude that the positive inotropic action of arterial hypoxemia and splenic nerve stimulation does not depend on the adenylate cyclase-cyclic AMP system.

Effects of splenectomy and beta-adrenoceptor blockade on cardiac output response to acute hypoxemia

Acute hypoxemia produced by the inhalation of 8% and 5% oxygen increased cardiac output in intact anesthetized dogs by 38% and 62%, respectively. Although practolol, a cardioselective beta-adrenergic blocking agent, reduced the increase in cardiac output in dogs subjected to severe hypoxemia (5% O(2) breathing) from 62% to 43%, it only slightly reduced the cardiac output rise in dogs subjected to moderate hypoxemia (8% O(2) breathing). Splenectomy, on the other hand, abolished the increase in cardiac output produced by moderate hypoxemia except for a small initial rise, but it reduced the increase in cardiac output during severe hypoxemia only to 37%. The entire increase, except for a small initial rise, disappeared only when splenectomized dogs were pretreated with practolol. Sham operation did not affect the cardiac output response to hypoxemia. It is concluded that an intact spleen is required for a significant portion of the increased cardiac output that occurs during both moderate and severe hypoxemia and that catecholamines do not participate in the regulation of cardiac output unless severe hypoxemia occurs.

Mechanisms regulating the cardiac output response to cyanide infusion, a model of hypoxia

When tissue metabolic changes like those of hypoxia were induced by intra-aortic infusion of cyanide in dogs, cardiac output began to increase after 3 to 5 min, reached a peak (220% of the control value) at 15 min, and returned to control in 40 min. This pattern of cardiac output rise was not altered by vagotomy with or without atropine pretreatment. However, this cardiac output response could be differentiated into three phases by pretreating the animals with agents that block specific activities of the sympatho-adrenal system. First, ganglionic blockade produced by mecamylamine or sympathetic nerve blockade by bretylium abolished the middle phase of the cardiac output seen in the untreated animal, but early and late phases still could be discerned. Second, beta-adrenergic receptor blockade produced by propranolol shortened the total duration of the cardiac output rise by abolishing the late phase. Third, when given together, propranolol and mecamylamine (or bretylium) prevented most of the cardiac output rise that follows the early phase. When cyanide was given to splenectomized dogs, the duration of the cardiac output response was not shortened, but the response became biphasic, resembling that seen after chemical sympathectomy. A similar biphasic response of the cardiac output also resulted from splenic denervation; sham operation or nephrectomy had no effect on the monophasic pattern of the normal response. Splenic venous blood obtained from cyanide-treated dogs, when infused intraportally, caused an increase in cardiac output in recipient dogs; similar infusion of arterial blood had no effects. THESE RESULTS SUGGEST THAT THE CARDIAC OUTPUT RESPONSE TO CYANIDE INFUSION CONSISTS OF THREE COMPONENTS: an early phase, related neither to the autonomic nervous system nor to circulating catecholamines; a middle phase, caused by a nonadrenergic humoral substance released from the spleen by sympathetic stimulation; and a late phase, dependent upon adrenergic receptors but not upon sympathetic transmission.