Rate of collagen deposition during healing and ventricular remodeling after myocardial infarction in rat and dog models

BACKGROUND

We hypothesized that the rate and amount of infarct collagen deposition during healing after myocardial infarction might influence ventricular remodeling in rat and dog models. The purpose of this study was to compare rates of infarct collagen deposition and ventricular remodeling in the two models.

METHODS AND RESULTS

Infarcted rat and dog hearts were removed at fixed time intervals between 1 and 50 days for measuring remodeling parameters and infarct and noninfarct collagen content (mg/g hydroxyproline). Collagen was less in sham rat (n=29) than dog (n=30) ventricles (3.32 versus 4.57 mg/g, P<.001) and markedly lower in the rat (n=48) than dog (n=59) infarcts throughout healing and by 50 days (9.98 versus 56.74 mg/g, P<.0001). Infarct collagen leveled off earlier and healing (histology) was completed sooner in the rat. Infarct scars were also thinner in the rat, with more (P<.0001) thinning and bulging (mm/g), and greater increase in ventricular volume. Although the mass to volume ratio decreased (P<.001) in both models, global remodeling was different, with greater transverse axis widening and globularity in the dog. Although infarct size, transmurality, heart rate, filling pressure, and blood pressure were greater in the rat, infarcts 10% to 30% in size in both models showed similar differences in infarct collagen and remodeling.

CONCLUSIONS

Compared with dog infarcts, rat infarcts exhibited faster healing and infarct collagen deposition and markedly lower infarct collagen. In addition to larger, more transmural, and thinner infarcts, and greater hemodynamic load, the lower infarct collagen in that model might be an important factor in the greater regional remodeling.

Effect of prolonged inotropic stimulation on ventricular remodeling during healing after myocardial infarction in the dog: mechanistic insights

OBJECTIVES

We hypothesized that positive inotropic stimulation during healing after myocardial infarction might increase contractile pull on the infarct segment, increase expansion and promote ventricular dilation.

BACKGROUND

The effect of prolonged inotropic stimulation on left ventricular remodeling during healing after myocardial infarction has not been studied.

METHODS

The effects of 6 weeks of inotropic stimulation on in vivo changes in left ventricular topography, function and mass (serial two-dimensional echocardiograms), hemodynamic variables, postmortem topography (planimetry) and collagen (hydroxyproline content) were studied in 36 chronically instrumented dogs randomized, 2 days after small anterior infarction, to digoxin (0.125 mg daily) and no digoxin (control group).

RESULTS

Heart rate and arterial and left atrial pressures were similar in the two groups, but the first derivative of left ventricular pressure (peak dP/dt), systolic thickening of the noninfarct wall and systolic thinning of the infarct wall were higher in the digoxin group during the 6 weeks. At 6 weeks, infarct scar size and collagen content were similar in both groups, but the digoxin group had more infarct expansion and thinning. Between 2 days and 6 weeks, the digoxin group showed more in vivo diastolic infarct expansion, thinning and bulging; more aneurysm but less global dilation and increase in mass; and no change in ejection fraction. The effects of inotropic stimulation on remodeling were more marked in infarcts with 100% than 85% transmurality.

CONCLUSIONS

Prolonged inotropic stimulation with digoxin during healing after small anterior infarction increases infarct bulging without decreasing infarct collagen content and preserves global ventricular size, mass and systolic function.

Cultural construction of health and institutional measures of change in rural Bangladesh: cases of BRAC's village organization and ICDDR,B's MCH-FP programmes

The study aims to examine the perceptions, causes, and treatment of diseases among the people of a few selected villages in Matlab and their relation to traditional culture and interventions made by BRAC and ICDDR,B in the form of rural development and MCH-FP programs. Four sets of villages were chosen purposively--two DSS and the other two non-DSS. In one of the DSS villages the MCH-FP program is underway, while the other does not have such programs. Likewise, one of the non-DSS villages has the rural development program of BRAC, while the other does not have any. From each village 10 respondents were selected purposively to gather information. The perception of disease is mostly defined in terms of the functions of the body. On very few occasions it is defined in terms of the action rendered by germs or the pathological condition of the body organs. The difference between the meaning and the actual diseases is often blurred. While identifying the causes, often the reference is made to invisible spirits, locally known as alga batash. The modes of treatment combine both modern and traditional elements. However, the health teaching educates them about the perception, causes, and treatment of certain diseases. In society, the elderly people, religious preachers, and traditional healers play important roles to influence the mind of the people. Sometimes gender relations and other structural features also bear on the minds of the illiterate poor. The difference between the intervention and non-intervention villages is expressed in the fact that the people of the intervention villages are constantly exposed to the agents making changes, while in the non-intervention villages it is intermittent. Traditional culture still plays an important role in the construction of disease perception and the choice of treatment, while modern approaches are combined with it. The intervention procedures widen modern approaches but could not eliminate the traditional notions altogether.

Impact of left ventricular unloading after late reperfusion of canine anterior myocardial infarction on remodeling and function using isosorbide-5-mononitrate

BACKGROUND

Late reperfusion during acute myocardial infarction results in delayed recovery of ventricular function and less remodeling, whereas ventricular unloading with nitrates improves function and attenuates remodeling. Whether late reperfusion combined with prolonged unloading with isosorbide-5-mononitrate (ISMN) might produce greater functional recovery and less remodeling than late reperfusion alone is not known.

METHODS AND RESULTS

In vivo left ventricular function and topography (echocardiograms), postmortem topography (planimetry), and collagen (hydroxyproline) were measured in dogs that were randomized to reperfusion 2 hours after left anterior descending coronary artery ligation, and ISMN (n = 12) or placebo (n = 12) was given as 25 mg IV over 4 hours followed by 50 mg PO QID for 6 weeks. Compared with placebo, the ISMN group had similar heart rate but lower left atrial pressure, mean arterial pressure, and rate-pressure products. Although in vivo baseline remodeling and functional parameters were similar in the two groups, by 6 weeks the ISMN group had smaller (P < or = .05) infarct and noninfarct segment lengths, ventricular volumes, and mass; less (P < .001) asynergy; and greater (P < .001) ejection fraction. More important, by 2 days, ejection fraction was 18% greater (P < .025) and asynergy 26% less (P < .05) with ISMN. At 6 weeks, ISMN showed less (P < or = .05) scar size, scar collagen, cavity dilation, noninfarct wall thickness, and apical bulging than placebo. In another 4 dogs, acute ISMN produced less improvement in function and remodeling than prolonged ISMN.

CONCLUSIONS

Late reperfusion of acute anterior myocardial infarction combined with prolonged ISMN unloading results in greater and earlier recovery of ventricular function and less remodeling than late reperfusion alone.

Purification and characterization of alpha-D-mannosidase from Aspergillus sp

alpha-D-Mannosidase from Aspergillus sp. was purified to homogeneity by preparative polyacrylamide gel electrophoresis (PAGE). The native enzyme of molecular mass 412 kDa (gel filtration) is made up of six identical subunits of molecular mass 69.2 kDa (SDS-PAGE) The enzyme is acidic (pI 4.5) and a glycoprotein with a carbohydrate content of 3.8%. The pH and temperature optima of the enzyme were in the range 6.0-6.5 and 50-55 degrees C, respectively. At pH 6.0 the enzyme was stable for 30 min at 50 degrees C. The Km and Vmax for p-nitrophenyl-alpha-D-mannopyranoside were 83 microM and 0.2 mumol/min per mg of the enzyme, respectively. The enzyme was strongly inhibited by 1 mM Hg2+ and Cu2+ and partially by 30 mM glucose and mannose. The enzyme hydrolysed Man-alpha-(1-3)Man at a very high rate followed by Man-alpha-(1-2)Man, while the rate of hydrolysis was low for Man-alpha-(1-6)Man. The rate of hydrolysis for high mannose oligosaccharide Man-6 was higher than for Man-9 and yeast mannan was not hydrolysed at all.

Analysis of Salmonella enteritidis isolates by arbitrarily primed PCR

An arbitrarily primed PCR (AP-PCR) was developed to analyze the genomic DNAs of Salmonella enteritidis isolates from human outbreaks and from avian sources. The AP-PCR generated seven distinct randomly amplified DNA patterns among the S. enteritidis isolates studied. Differences in the DNA patterns among isolates of S. enteritidis phage types 13a and 8 as well as among S. enteritidis phage type 14b were observed. The AP-PCR analysis can be used to determine the differences among isolates within the same phage types and may be useful for tracing back the source of S. enteritidis outbreaks in humans more precisely.

Hereditary proctalgia fugax and constipation: report of a second family

A second family with hereditary proctalgia fugax and internal anal sphincter hypertrophy associated with constipation is described. Anorectal ultrasonography, manometry, and sensory tests were conducted in two symptomatic and one asymptomatic subjects within the same family and further clinical information was obtained from other family members. The inheritance would correspond to an autosomal dominant condition with incomplete penetration, presenting after the second decade of life. Physiological studies showed deep, ultraslow waves and an absence of internal anal sphincter relaxation on rectal distension in the two most severely affected family members, suggesting the possibility of a neuropathic origin. Both of these patients had an abnormally high blood pressure. After treatment with a sustained release formulation of the calcium antagonist, nifedipine, their blood pressure returned to normal, anal tone was reduced, and the frequency and intensity of anal pain was suppressed. These together improved the quality of the patients' sleep, which had previously been very troubled because of night time attacks of anal pain.

A Salmonella-specific DNA probe and its use in southern hybridization for differentiation of Salmonella enteritidis

Chromosomal DNA from phage type 13a and Phage type 8 of Salmonella enteritidis (SE) was cloned in Escherichia coli using the plasmid pUC8. A 2.1-kilobase-pair (kbp) DNA fragment specific for Salmonella spp. was identified by colony, dot, and Southern hybridization analyses. When labeled and used as a probe (C7), this recombinant clone hybridized with the DNA of 18 Salmonella species but did not hybridize with the DNA of seven other enteric and non-enteric bacterial species. In Southern blot hybridization, this probe hybridized specifically to a 6.0 kbp BglI-digested DNA fragment of 17 SE isolates from human as well as avian sources, thus differentiating this fragment from DNA of 17 other Salmonella species. The C7 probe also hybridized to a 5-kbp fragment of one SE DNA derived from human and two SE DNA from poultry sources. This may indicate variation among SE isolates.

Combined captopril and isosorbide dinitrate during healing after myocardial infarction. Effect on ventricular remodeling, function, mass and collagen

OBJECTIVES

We sought to compare the effects of captopril plus isosorbide dinitrate versus monotherapy on infarct collagen content and left ventricular remodeling and function during healing after myocardial infarction.

BACKGROUND

Captopril or isosorbide dinitrate monotherapy can limit postinfarction dilation. Whether captopril inhibits infarct collagen content, or whether captopril plus isosorbide dinitrate might be more beneficial, is not known.

METHODS

In vivo remodeling variables and function (echocardiography), hemodynamic variables, postmortem topography (planimetry) and collagen content (hydroxyproline) were measured in 48 chronically instrumented dogs that were randomized 2 days after left anterior descending coronary artery ligation to 6 weeks of therapy with captopril, isosorbide dinitrate, captopril plus isosorbide dinitrate or placebo.

RESULTS

Compared with placebo, the three active therapies decreased blood pressure and left atrial pressure; limited infarct expansion, infarct thinning, noninfarct wall stretching and thickening; limited left ventricular dilation and increase in left ventricular mass; and decreased regional bulging, aneurysm frequency and left ventricular dysfunction. However, the decrease in asynergy and increase in volume ejection fraction were less with captopril or captopril plus isosorbide dinitrate than with isosorbide dinitrate. Infarct thinning and bulging at 6 weeks was also less with isosorbide dinitrate than with captopril. Although initial left ventricular asynergy, final scar sizes and noninfarct collagen content at 6 weeks were similar among the groups, collagen in the center of the infarct scar was less with captopril or captopril plus isosorbide dinitrate than with placebo or isosorbide dinitrate.

CONCLUSIONS

Monotherapy with captopril or isosorbide dinitrate, or their combination, improved all remodeling variables, but isosorbide dinitrate improved function more than captopril or captopril plus isosorbide dinitrate. Inhibition of infarct collagen content by captopril suggests that benefits with captopril represent a balance between positive and negative effects, and its combination with isosorbide dinitrate might be advantageous.

Effect of enalapril on ventricular remodeling and function during healing after anterior myocardial infarction in the dog

BACKGROUND

Ventricular remodeling after myocardial infarction involves changes in ventricular size, shape, structure, and matrix that impact on function. Prolonged angiotensin-converting enzyme inhibition after infarction with captopril reduces ventricular enlargement and improves clinical outcome, but whether enalapril produces similar benefits is controversial.

METHODS AND RESULTS

The effect of enalapril during healing between 1 day and 6 weeks after myocardial infarction on in vivo changes in ventricular size, shape, mass, and function (asynergy, or akinesis and dyskinesis, and ejection fraction), as determined by serial two-dimensional echocardiography, hemodynamics, postmortem topography (planimetered short- and long-axis ventricular contours), and collagen content (determined by levels of hydroxyproline, a marker for collagen), was measured in 25 instrumented dogs. The dogs were randomized 1 day after left anterior descending coronary artery ligation to a control group (no treatment) and a group receiving oral enalapril (2.5 mg BID). Compared with no treatment, enalapril produced a sustained lowering of left atrial pressure but no difference in heart rate and mean blood pressure over the 6 weeks. Also compared with no treatment, enalapril modified in vivo remodeling parameters between 1 day and 6 weeks, with less elongation of the asynergy-containing segment, a lower expansion index (ratio of endocardial lengths of infarct to non-infarct-containing segments demarcated by papillary muscle landmarks), less scar wall thinning, a lower thinning ratio (ratio of average thickness of infarcted wall to average thickness of the normal wall), smaller ventricular volume, less regional bulging and aneurysm frequency, prevention of the increase in ventricular mass, less total extent of asynergy, and higher volume ejection fraction. At postmortem examination, scar mass was similar in the two groups, but topographic maps with enalapril revealed less infarct bulging, flatter infarct scars, and less noninfarct wall thickness. In addition, postmortem collagen content was similar in noninfarct zones of the two groups but lower in infarct zones of the dogs given enalapril.

CONCLUSIONS

Prolonged enalapril therapy, in a dose that did not lower blood pressure, during healing after anterior infarction produced prolonged reduction of left ventricular preload in dogs. This diastolic unloading was associated with limitation of remodeling parameters (infarct expansion and thinning, progressive ventricular dilation and hypertrophy, and regional bulging), less total asynergy, and improved left ventricular ejection fraction. Although angiotensin-converting enzyme inhibition was associated with lower collagen content in the infarct area and altered scar topography, these effects did not impact negatively on overall remodeling and function.

Gastric emptying and the symptoms of vection-induced nausea

OBJECTIVES

To examine the hypothesis that nausea during vection arises directly from an underlying alteration in gastric motility.

DESIGN

The simultaneous application of vection and assessment of gastric emptying of a liquid, non-nutrient test meal allowed the examination of the interaction between changes in gastric motility and symptoms.

METHODS

Studies were conducted in 14 volunteers. Vection was induced by seating the subject inside a rotating circular drum, which was painted with vertical black and white stripes. In the control study (n = 8) the drum was not rotated. Gastric emptying was measured by gamma scintigraphy of a radiolabelled isosmotic saline test meal.

RESULTS

Vection induced upper abdominal sensations (epigastric awareness) in 10 subjects, eight of whom subsequently reported nausea; autonomic symptoms of sweating and pallor were experienced by 12 subjects. Two subjects remained completely asymptomatic during vection. None of the subjects experienced any sensations during the control study. Gastric emptying was significantly delayed during vection (P < 0.01). There was a highly significant correlation between gastric emptying and the intensity of nausea. However, examination of the gastric emptying profiles did not support any direct association between altered gastrointestinal motor activity and symptoms. Two subjects with slowing of gastric emptying exhibited no nausea or upper abdominal symptoms, while another two experienced nausea when the underlying rate of gastric emptying was similar to that of the control period.

CONCLUSIONS

The delay in gastric emptying of a liquid test meal induced by vection appears to be a variable epiphenomenon of nausea. A cause and effect relationship between gastric emptying and nausea therefore appears unlikely.

Experimental infection of northern bobwhite quail with Borrelia burgdorferi

Four-week-old northern bobwhite quail (Colinus virginianus) were inoculated subcutaneously with 10(6) organisms from a low passage culture of Borrelia burgdorferi. Blood was collected weekly for culture, antibody detection, and immunoblot analysis. Three weeks postinoculation, viable spirochetes were isolated from the blood of one bird, but not from kidney, spleen, liver, or heart; all infected birds from which preinfection antibody titer had been established, had antibodies by the enzyme-linked immunosorbent assay (ELISA). The inoculated birds did not show clinical signs of disease and there were no detectable gross or histopathologic lesions. Borrelia burgdorferi was detected in sections of kidneys on fluorescent antibody tests. Using a polymerase chain reaction (PCR) analysis to detect Borrelia burgdorferi DNA in tissue samples, the expected PCR product (DNA) of 246 base pairs was visible on agarose gel stained with ethidium bromide. The identity of the PCR product was confirmed by slot blot hybridization with Borrelia burgdorferi specific DNA probe. Thus, these birds sustained infections for at least 3 weeks without clinical signs and may play a role in the transmission of Borrelia burgdorferi.

Epilepsy in Pakistan: a population-based epidemiologic study

A house-to-house, cross-sectional, population study of epilepsy on 24,130 individuals of all ages from southern Pakistan indicates an age-specific prevalence rate of 9.99 in 1,000 (14.8 in 1,000 in rural and 7.4 in 1,000 in urban areas) for recurrent, nonfebrile "active" epilepsy in Pakistan. Mean onset of epilepsy was 13.3 years, and 74.3% epileptic persons were aged < 19 years at onset of the disorder. The most common seizure type was tonicclonic in 77% [primary generalized tonic-clonic (GTC) in 59% and secondarily generalized in 18%], simple partial (SPS) in 5%, complex partial (CPS) in 6%, generalized absence in 1%, tonic in 3%, and myoclonic in 3% cases. Multiple seizures types in the same person were evident in 9.6% of only the generalized group. A putative cause could be suggested in 38.4% of cases: 32% had a positive family history of epilepsy, most common among siblings. Common perceived precipitants included fever in 29.2% and emotional disturbances in 16.6%. Only 3% of epileptic persons believed that their illness was due to super-natural causes. Treatment status was very poor, with only 2% rural and 27% urban epileptic persons receiving antiepileptic drugs (AEDs) at the time of the survey. We discuss the logistic and management problems of population-based epidemiologic studies in developing countries.

Effect of prolonged nitrate therapy on left ventricular remodeling after canine acute myocardial infarction

BACKGROUND

Prolonged nitrate therapy during healing between 2 days and 6 weeks after anterior myocardial infarction has the potential for limiting further left ventricular remodeling (or changes in topography) and preserving function. Longterm therapy throughout healing over 6 weeks might be more beneficial than short-term therapy over the first 2 weeks after infarction.

METHODS AND RESULTS

The effect of prolonged nitrate therapy between 2 days and 6 weeks during healing after infarction on serial parameters of ventricular remodeling (scar expansion, scar thinning, ventricular dilation, and hypertrophy) and function (asynergy or akinesis plus dyskinesis and ejection fraction) by serial two-dimensional echocardiography, hemodynamics, postmortem topography (computerized planimetry, geometric maps, and radiographs), and collagen content (hydroxyproline) was studied in 64 instrumented dogs randomized 2 days after left anterior descending coronary artery ligation to various nitrate regimens (n = 32) over the first 2 weeks (subgroup 1: 2% transdermal nitroglycerin at 8 AM and 4 PM, n = 6; subgroup 2: 2% transdermal nitroglycerin plus 2.6 mg of sustained-release oral nitroglycerin at 8 AM, 3 PM, and 10 PM, n = 5; subgroup 3: oral isosorbide dinitrate, 30 mg at 8 AM and 4 PM, n = 11) or 6 weeks (subgroup 4: isosorbide dinitrate, n = 10) and in matching controls (n = 32). Nitrate therapy reduced left atrial pressure, mean arterial pressure, and the rate-pressure product compared with controls over the 6 weeks. Postmortem scar mass and hydroxyproline were similar in control and nitrate groups. However, scar stretching and thinning, cavity dilation, noninfarct wall hypertrophy, and apical bulging were less with nitrates, especially in the long-term subgroup 4. In vivo remodeling parameters between 2 days and 6 weeks after ligation showed that, compared with controls, nitrate therapy prevented further stretching of the asynergic segment, decreased the expansion index, decreased further scar thinning, prevented the increase in ventricular volumes, reduced the frequency of ventricular aneurysm, prevented the increase in ventricular mass, reduced the extent of asynergy, and improved ejection fraction. Although the beneficial effect on topography and function was seen in all nitrate subgroups, the overall benefit was greater with long-term therapy over 6 weeks (subgroup 4) than short-term therapy confined to the first 2 weeks (subgroups 1, 2, and 3).

CONCLUSIONS

Prolonged nitrate therapy, in various regimens during healing after infarction, effectively reduced left ventricular loading and prevented infarct thinning, further infarct expansion, progressive ventricular dilation, and the increase in mass. These effects were associated with decreased asynergy and improved ejection fraction. The beneficial effects were greater with long-term therapy over 6 weeks than short-term therapy over the first 2 weeks.

Amplification of Salmonella chromosomal DNA using the polymerase chain reaction

A Salmonella-specific polymerase chain reaction (PCR) was developed and standardized. The origin of the primers was a recombinant clone (C7) that contained Salmonella-specific HindIII fragment DNA of 2.1-kilobase pairs. Based on the sequence data of Salmonella enteritidis recombinant clone C7, two primers designated NK1 (21 nucleotides) and NK2 (24 nucleotides) were synthesized for use in the PCR. A Salmonella-specific 2.0-kilobase pair DNA product was amplified by the primers from 23 species of Salmonella, but not from 19 enteric and non-enteric bacteria. As little as 330 fg of Salmonella DNA was detected using either ethidium bromide/ultraviolet exposure of gels or Southern blot hybridization with a C7 clone.

Thermodynamic and kinetic studies on the mechanism of binding of methylumbelliferyl galactosides to the basic agglutinin from winged bean (Psophocarpus tetragonolobus)

The binding of winged bean basic agglutinin (WBA I) to 4-methylumbelliferyl (MeUmb) galactosides was examined by extrinsic fluorescence titration and stopped-flow spectrofluorimetry. Upon binding to WBA I, MeUmb alpha-galactosides show quenching in fluorescence intensity, decrease in UV absorbance with a concomitant blue shift, and decrease in fluorescence excited-state lifetimes. However, their beta-analogues show enhancement in fluorescence intensity, increase in UV absorbance with a red shift, and an increase in fluorescence excited-state lifetimes. This implies that the umbelliferyl groups of alpha- and beta-galactosides experience non-polar and polar microenvironments, respectively, upon binding to WBA I. Replacement of the anomeric hydroxyl group of galactose by 4-methylumbelliferyl moiety increases the affinity of resulting saccharides. Substitution of C-2 hydroxyl of galactose by an acetamido group leads to increased affinity due to a favorable entropy change. This suggests that acetamido group of MeUmb-alpha/beta-GalNAc binds to a relatively non-polar subsite of WBA I. Most interestingly, this substitution also reduces the association rate constants dramatically. Inspection of the activation parameters reveals that the enthalpy of activation is the limiting factor for the differences in the forward rate constants for these saccharides and the entropic contribution to the activation energy is small.

Detection of Mycoplasma gallisepticum infection in field samples using a species-specific DNA probe

Species-specific DNA probes for Mycoplasma gallisepticum (MG) were compared with serologic and isolation procedures as a routine diagnostic tool on field specimens acquired from chicken flocks experiencing egg-production losses and suspected of MG infection. The MG DNA probe clearly identified MG directly from tracheal specimens within 2 days, unlike the 7 to 10 days required for culture procedures. Cross-reaction of MG with M. synoviae continues to be a stumbling block in the serum plate agglutination test.

Effect of varying the rate and pattern of gastric distension on its sensory perception and motor activity

The aim of the present study was to see if varying the rate and pattern of gastric distension affected its motor and sensory responses to distension. A balloon was used to carry out distensions in male volunteers at constant rates of 20, 50, 100, and 200 ml/min. In addition rapid (75 ml/s) intermittent distensions (RID) were carried out with the use of a large hand-held syringe. Subjects were asked to indicate the first perception of the balloon, fullness, and discomfort. Increasing the rate of ramp distension caused all sensations to occur at higher volumes and higher pressures and reduced the frequency and amplitude of phasic oscillations in gastric pressure. During RID, the same sensations were experienced at much reduced volumes but were poorly sustained. These data suggest that ramp and RID are likely to induce gastric sensations by activating different populations of receptors. The responses to ramp distension are compatible with the activation of stretch receptors situated in parallel with the muscle elements, whereas RID appear to be activating a different population of rapidly adapting mechanoreceptors possibly situated in the mucosa.

Mycoplasma gallisepticum F-vaccine strain-specific polymerase chain reaction

A Mycoplasma gallisepticum (MG) F-vaccine strain polymerase chain reaction (PCR) (MGF-PCR) was developed and standardized. The origin of the primers was a clone (p08-M6#17) that contained an MG F-strain-specific DNA fragment of 6.0 kilobase pairs designated fMGF-1. Both ends of fMGF-1 (BamHI and EcoRI) were sequenced, and regions adequate for the primers were chosen. Seven 25-base primers were synthesized, and two near the EcoRI end (MGF-P1 left [L] and right [R]) were selected for MGF-PCR, MGF-P1 L and R amplified a DNA product of 524 base pairs (bp) that was directed at F-strain-related MG only. None of 16 other species of avian mycoplasmas that were tested yielded MGF-PCR product. MGF-PCR was able to consistently detect F-strain samples containing 54 cells or more and inconsistently (at least one positive out of five replicates) in samples with fewer organisms. The MGF-PCR products were visualized either by gel electrophoresis or Southern blot hybridization with a probe containing an identical base sequence as the 524-bp product amplified by MGF-PCR. The MGF-PCR was 1000 to 10,000 times more sensitive than dot-blot assays using two MG F-strain-specific probes.

Risk factors associated with hydropericardium syndrome in broiler flocks

A prospective study was undertaken to identify the epidemiological factors associated with the development and spread of the hydropericardium syndrome in broiler flocks. Data were collected between July 1989 and April 1990 from 131 flocks in 105 broiler production units pertaining to their demography, management practices, prophylactic procedures and concurrent diseases. The incidence rate of the syndrome in the whole population was 46.6 per cent. There were significant associations between the incidence in a flock and visits by a poultry vaccination crew (P = 0.014), the number of flocks raised (P = 0.004) and the source of light and heat (P = 0.007). Flocks that had one or more visits by a poultry crew were 15 times more likely to be affected by the syndrome than flocks that had no such visits. Premises where one flock was raised were nearly three times more likely to be affected than premises where two flocks were raised, and the use of electricity as a source of light and heat entailed a much lower risk of hydropericardium syndrome than kerosene oil.

Functional impact of remodeling during healing after non-Q wave versus Q wave anterior myocardial infarction in the dog

OBJECTIVES

This study was undertaken to compare changes in left ventricular remodeling and function during healing after a first anterior non-Q wave versus a Q wave myocardial infarction in the dog.

BACKGROUND

Whether ventricular remodeling is more severe after anterior Q wave than after anterior non-Q wave infarction has not been studied systematically.

METHODS

Serial remodeling and functional variables (two-dimensional echocardiography), electrocardiography and hemodynamic data were recorded over 6 weeks in 58 instrumented dogs subjected to left anterior descending coronary artery ligation or ligation plus collateral obliteration. Postmortem topography and transmurality (by planimetry) and infarct collagen (hydroxyproline) were measured at 6 weeks.

RESULTS

At 6 weeks, infarct collagen was similarly increased in both groups, but the Q wave group had greater infarct size (7.2% vs. 4.5%, p less than 0.025) and greater transmurality (88% vs. 58%, p less than 0.001), higher left atrial pressures, more infarct expansion (expansion index 2.62 vs. 2.31, p less than 0.001), more thinning (thinning ratio 0.62 vs. 0.72, p less than 0.001), greater cavity dilation (diastolic volume 88 vs. 72 ml, p less than 0.001), more regional bulging in the short-axis view (depth 4.9 vs. 1.9 mm, p less than 0.001), more regional asynergy (18% vs. 7%, p less than 0.001), lower global ejection fraction (40% vs. 48%, p less than 0.001), more endocardial and epicardial bulging in the long-axis view and greater incidence of aneurysm (82% vs. 36%, p less than 0.005), left ventricular thrombus (64% vs. 0%, p less than 0.0005) and ventricular arrhythmias. Echocardiograms obtained during a 6-week period indicated that left ventricular topographic deterioration and dysfunction were present in the earliest postinfarction study at 2 days in both groups but were more frequent in the Q wave group. Regional myocardial blood flow (24 dogs) was lower in the Q wave than in the non-Q wave group. Scanning electron microscopy (10 dogs) revealed preservation of the epicardial collagen matrix in the non-Q wave but not the Q wave group.

CONCLUSIONS

Anterior Q wave infarction is associated with greater transmurality and more postinfarction left ventricular remodeling and dysfunction than is non-Q wave infarction.