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Biomedical subjects

I M Lang

Publications and source records attributed to I M Lang.

At least 37 records · Page 2Linked to original sources
PubMed1998

Characterization and mechanisms of the pharyngoesophageal inhibitory reflex.

The objectives of this study were to identify and to characterize the pharyngoesophageal inhibitory reflex (PEIR) in an animal model. Thirty-one cats (2.4-5.0 kg) were anesthetized using alpha-chloralose (45 mg/kg ip), and esophageal peristalsis was recorded manometrically. Secondary peristalsis was activated by rapid air injection (8-20 ml) at midesophagus or slow infusion of water through the manometric catheters. Neither stimulus activated primary peristalsis. The PEIR was activated by rapid water injection or focal mechanical stimulation of the pharynx. Rapid air injection activated secondary peristalsis in 92% of the trials, and slow water infusion activated 1 secondary peristalsis every 3.2 min. Pharyngeal stimulation by 0.3, 0.5, 0.8, or 1.0 ml of water inhibited or blocked ongoing secondary peristalsis in 67, 82, 97, or 93% of trials, respectively. Mechanical stimulation of the posterior wall of the pharynx with 11-20 g pressure attenuated secondary peristalsis in 96% of the trials or blocked secondary peristalsis in 41% of the trials. Centripetal electrical stimulation at 30 Hz, 0.2 ms, 2 V for 4 s of the superior laryngeal (SLN) or glossopharyngeal (GPN) nerves blocked or inhibited secondary peristalsis in 100% of the trials. Bilateral transection of the GPN (n = 8), but not the SLN (n = 6), blocked the PEIR. Anesthetization of the pharyngeal mucosa using lidocaine (2%) blocked the PEIR (n = 3). We concluded that 1) the PEIR exists in the cat, 2) mechanical stimulation of the pharynx more strongly activates the PEIR than water, 3) activation of either SLN or GPN afferents attenuates ongoing secondary peristalsis, 4) the receptors mediating the PEIR are located in the pharyngeal mucosa, and 5) both SLN and GPN contribute to the PEIR, but the GPN is the major afferent limb of this reflex.

Animals↗
PubMed1998

Elevated expression of urokinase-like plasminogen activator and plasminogen activator inhibitor type 1 during the vascular remodeling associated with pulmonary thromboembolism.

Information is lacking on the mechanisms involved in the organization, resolution, and repair of the vascular lumen after acute pulmonary thromboembolism. Because recent data suggest that the balance between plasminogen activators (PAs) and type 1 plasminogen activator inhibitor (PAI-1) plays a role in regulating cell migration within the extracellular matrix, we investigated the expression of these molecules by immunohistochemical and in situ hybridization analysis of pulmonary artery specimens from patients suffering fatal pulmonary embolism. The data were compared with the expression of these molecules in both patients' noninvolved pulmonary arteries and organ donor pulmonary arteries. Regions of initial organization and vascular remodeling were identified by a modified trichrome stain and by the presence of proliferating cell nuclear antigen (PCNA), a cell marker of proliferation. Staining for tissue-type PA antigen was low to undetectable in endothelial cells directly in contact with the fibrin-platelet thromboembolus and in areas in which the endothelial cell lining was replaced by cell growth into the thrombus. Urokinase-like PA (u-PA) expression was detected in mononuclear cells within the thrombus in the initial phase of thromboembolism and within cells migrating into the thrombus during the later stages of organization. PAI-1 expression was elevated in the monolayer of endothelial cells underlying the fresh platelet-fibrin thromboembolus and in a PCNA-positive cell population present between the pulmonary arterial intima and the thromboembolus that represents early organization. Increased expression of PAI-1 may play a role in inhibiting proteolysis and fostering the localization of the acute fibrin-platelet thrombus to the vascular wall, which is followed by the upregulation of u-PA in migrating cells during the reorganization process.

Adolescent↗
PubMed1998

Plasma Lp(a) levels are increased in patients with chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease resulting from the thromboembolic obstruction of the segmental and/or large size pulmonary arteries, subsequently leading to pulmonary arterial hypertension. Incomplete resolution of acute pulmonary emboli and thrombus organization are believed to be important for the development of the disease. Primary pulmonary hypertension (PPH) is a further disease that at present is poorly understood but shows a clinical picture similar to CTEPH. Since lipoprotein(a) [Lp(a)]. a genetically determined risk factor for atherosclerosis and thrombosis, has been found increased in plasma of patients with deep vein thrombosis and pulmonary embolism, we measured plasma Lp(a) levels in 40 patients with CTEPH and 50 patients with PPH and compared them to 50 matched controls. The median for Lp(a) plasma levels was significantly higher in CTEPH patients (26.6 mg/dl) than in PPH patients (9.6 mg/dl) and controls (7.2 mg/dl). Increased plasma Lp(a) could, therefore. play a significant role in the mechanisms of ongoing thrombosis and thrombus organization in CTEPH, while its possible role in PPH can be limited to a small number of patients.

Adult↗
PubMed1997

Anatomy and physiology of the upper esophageal sphincter.

The upper esophageal sphincter (UES) is composed of the cricopharyngeus (CP), thyropharyngeus (TP; inferior pharyngeal constrictor [IPC] in humans), and cranial cervical esophagus. All 3 muscles may at times function to maintain tone in the UES, but only the CP contracts and relaxes in all physiologic states consistent with the UES. The CP is a striated muscle composed of variable-sized small (25-35 microm) muscle fibers that are primarily type I (slow twitch), highly oxidative, and contain abundant (40%) endomysial elastic connective tissue. The fibers may attach to the connective tissue framework, forming a muscular net. In humans and rats, but not other animals, the CP has no median raphe. The optimum length of the CP for development of active tension is about 1.7 times resting length; therefore, in some respects the CP acts more like cardiac than striated muscle. A passive tone in the CP is present and increases through all degrees of stretch. The high compliance of the CP allows it to be opened by distraction of other muscles (e.g., geniohyoideus) or increased intraluminal pressure. The CP is innervated by branches of the vagus nerves: pharyngoesophageal (PE), superior laryngeal (SLN), and recurrent laryngeal (RLN); glossopharyngeal (GPN); and cervical sympathetics. Only the PE and SLN provide motor fibers to the CP. The GLN may be sensory; the sympathetics may innervate the mucosa, blood vessels, and glands; but no functional innervation by the RLN has been identified. Parasympathetic ganglia and various peptides (galanin, cGRP, VIP, neuropeptide Y, substance P, tyrosine hydroxylase) have been found in the CP, but their role in control of the CP is unknown. The motoneurons of the CP are found in the nucleus ambiguus, and the innervation is ipsilateral for animal species in which the CP has a median raphe. These motoneurons are topographically organized with other pharyngeal and laryngeal muscles and the striated muscle esophagus. Pharyngeal motoneurons often have a respiratory rhythm, but not a spontaneous background discharge. Therefore, the CP motoneurons may not generate CP tone. Various reflexes control the tone of the CP. Distension of the esophagus causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. Pressure on the pharyngeal mucosa contracts the CP and UES and is mediated by a glossopharyngo-vagal reflex. Inflation of the lungs causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. The pharyngo-UES and pulmonary-UES reflexes may generate the respiratory rhythm often observed on UES pressure or electromyographic activity. The UES or CP also contracts with arousal or with changes in posture. All of these reflexes and responses and the passive elastic properties of the CP may contribute to the generation of tone in the CP and UES.

Animals↗
PubMed1997

MRI appearance of popliteal cysts in childhood.

Popliteal cysts are soft fluid-filled lesions of synovial origin which result from extrusion of joint fluid into the gastrocnemiosemimembranous bursa. They may occur in any age group, but 22-33 % occur in the first 15 years of life. In this age group they are rarely associated with intraarticular abnormalities and therefore rarely require treatment. This case report shows the magnetic resonance imaging (MRI) appearances of a popliteal cyst in two children.

Child↗
PubMed1997

MRI appearances of dysplasia epiphysealis hemimelica of the knee.

OBJECTIVE: The study was undertaken to describe the magnetic resonance imaging (MRI) appearances of dysplasia epiphysealis hemimelica (DEH) of the knee and to determine whether MRI provides additional information concerning the anomaly compared with more traditional methods of diagnosis. DESIGN AND PATIENTS: The subjects of the study were three children (one girl and two boys, aged 13 months, 3 years and 11 years) with DEH of the knee. All the patients had plain films of the knee and MRI scans. RESULTS AND CONCLUSION: Plain radiographs showed bone overgrowth and asymmetrical ossification centres with adjacent scattered calcifications which coalesced to form a lobulated irregular mass. MRI showed a definite cartilaginous or osteocartilaginous lesion. Its origin from the epiphysis was much more clearly defined. MRI showed the extent of the lesion non-invasively, as well as any potential cleavage plane between the epiphysis and the mass lesion. Abnormal surface nodularity and joint involvement could be determined. It is concluded that plain films supplemented with MRI provide the greatest amount of diagnostic information in cases of DEH. MRI is useful to show the exact location and extent of the lesion, any joint involvement and any potential cleavage between the epiphysis and the mass lesion.

Calcinosis↗
PubMed1997

Central inhibition of nitric oxide synthase modulates upper gastrointestinal motor activity.

We investigated the role of central nitric oxide (NO) synthase inhibition in the modulation of fasting gastrointestinal motor activity and gastric emptying rate of solid nutrient meals in conscious dogs. N(omega)-nitro-L-arginine methyl ester and N(omega)-nitro-L-arginine were infused intracerebroventricularly. Circular muscle contractions were recorded with surgically implanted strain gauge transducers. Gastric emptying was measured by a radiolabeled meal. The inhibition of NO synthase in the brain suppressed phase III activity in the stomach and the duodenum but not in the jejunum or the ileum. However, the central inhibition of NO synthase had no significant effect on the rate of gastric emptying of solid nutrient meals or the duration of postprandial disruption of migrating motor complex cycling. The central actions of NO synthase inhibition were blocked by bilateral truncal vagotomy but not by intravenous administration of propranolol or phentolamine. We conclude that the inhibition of NO synthase in the brain generates a stimulus that selectively inhibits gastric and duodenal phase III activities. This stimulus, however, may not affect the postprandial gastroduodenal motor activity or the rate of gastric emptying of solid nutrient meals.

Animals↗
PubMed1997

Correlation of electrical and contractile activities of the cricopharyngeus muscle in the cat.

We correlated the electrical and contractile activities of the cricopharyngeus (CP) to better understand the function of the CP and the upper esophageal sphincter (UES). In 40 decerebrate cats, we recorded resting and active tension of the CP and CP force and electromyographic (EMG) activity simultaneously during electrical stimulation of the pharyngoesophageal (PE) nerve, esophageal distension, or swallowing. In six intact cats, the change in diameter of the UES during food swallows was determined in two planes using videofluoroscopy. We found that resting tension of the CP developed quickly with stretch, and the strain-energy function, y = 6.5e3.4(z-1), fit (r = 0.94 +/- 0.06) this relationship. Active tension peaked at 1.68 +/- 0.03 times resting length, which is greater than the maximum distension during swallowing. Activation and relaxation of the CP occurred in approximately 50 and 120 ms, respectively. PE nerve stimulation bilaterally caused a force equal to approximately 90% of the summed force generated by separate stimulation of each PE nerve. The magnitude of the EMG response of the contralateral CP was approximately 18% of the ipsilateral response to unilateral PE nerve stimulation. We conclude that the CP exhibits tension throughout its physiological range of stretch. The CP functions more like a bilateral than a single contiguous muscle, and more like cardiac than striated muscle with regard to its passive elastic properties.

Animals↗
PubMed1997

Characterization of the pharyngo-UES contractile reflex in humans.

Preliminary human studies suggest the presence of an upper esophageal sphincter (UES) contractile reflex triggered by pharyngeal water stimulation. The purposes of this study were to further characterize this reflex and determine the threshold volume for its activation. We studied 10 healthy young volunteers by manometric technique before and after topical pharyngeal anesthesia. UES pressure responses to various volumes and temperatures of water injected into the pharynx were elucidated. At a threshold volume, rapid-pulse and slow continuous pharyngeal water injection resulted in significant augmentation of UES pressure in all volunteers. Threshold volume for inducing UES contraction averaged 0.1 +/- 0.01 ml for rapid-pulse injection and was significantly smaller than that for slow continuous injection (1.0 +/- 0.2 ml). UES pressure increase duration averaged 16 +/- 4 s. Augmentation of UES resting tone by injection of water with three different temperatures was similar. This augmentation was abolished after topical anesthesia. Conclusions were that stimulation of the human pharynx by injection of minute amounts of water results in a significant increase in resting UES pressure: the pharyngo-UES contractile reflex. The magnitude of pressure increase due to activation of this reflex is not volume or temperature dependent. Loss of pharyngeal sensation abolishes this reflex.

Adult↗
PubMed1996

Expression of Kunitz protease inhibitor--containing forms of amyloid beta-protein precursor within vascular thrombi.

BACKGROUND: The presence of patent neovessels within vascular occlusions in chronic thromboembolic pulmonary hypertension suggests that local mechanisms exist to regulate the coagulation system. This study investigated the expression of a potent inhibitor of Factor IXa and Factor XIa (ie, protease nexin-2/ amyloid beta-protein precursor, A beta PP) in the organized vascular occlusions harvested from patients with this disease. METHODS AND RESULTS: Immunohistochemical analysis revealed intense immunoreactivity for A beta PP in the single layer of cells that line the neovessels. A positive signal was also detected by in situ hybridization analysis with the use of a 35S-UTP-labeled antisense riboprobe that recognizes the various alternatively spliced mRNA forms of this molecule. To identify the forms of A beta PP produced within the thrombi, total RNA was extracted from the thrombi, reverse transcribed, and subjected to amplification with the use of the polymerase chain reaction (PCR) and primers that flank the region encoding the alternatively spliced 56-amino acid Kunitz-type protease inhibitor (KPI) domain. The major PCR products consisted of 255 bp and 312 bp and corresponded to transcripts encoding this domain (ie, A beta PP751 and A beta PP770). In situ hybridization analysis with the use of a 35S-UTP-labeled antisense riboprobe complementary to the region encoding the KPI domain confirmed the presence of these mRNA species in nucleated cells lining the neovessels. CONCLUSIONS: The expression of KPI-containing isoforms of A beta PP in thrombus endothelial cells may represent one mechanism utilized in this disease to shift the local hemostatic balance and preserve regional vessel patency.

Adult↗
PubMed1996

Purification of storage granule protein-23. A novel protein identified by phage display technology and interaction with type I plasminogen activator inhibitor.

Type 1 plasminogen activator inhibitor (PAI-1) is a key regulator of the fibrinolytic cascade that is stored in a rapidly releasable form within platelet alpha-granules. To identify proteins that may participate in the targeting or storage of this potent inhibitor, this report investigates the applicability of utilizing filamentous bacteriophages to display proteins expressed by cells containing a regulated secretory pathway and their enrichment based upon an interaction with PAI-1. For this purpose, RNA was extracted from AtT-20 cells (i.e. a classical model cell system for intracellular protein sorting), reverse transcribed, amplified using polymerase chain reaction primers containing internal restriction sites, and cloned into the phagemid pCOMB3H for expression as fusion constructs with the bacteriophage gene III protein. Escherichia coli was transformed with the phagemids and infected with VCSM13 helper phage, and the resulting AtT-20 cDNA-bacteriophage library was enriched by panning against solid- and solution-phase PAI-1. The enriched cDNA library was subcloned into a prokaryotic expression vector system that replaces the gene III protein with a decapeptide tag for immunologic quantitation. One novel cDNA clone (i.e. A-61), which preferentially recognized solution-phase PAI-1 and reacted positively with antibodies derived from a rabbit immunized with alpha-granules, was subcloned into the prokaryotic expression vector pTrcHis to create a construct containing an N-terminal six-histidine purification tag. This construct was expressed in E. coli, purified by nickel-chelate chromatography followed by preparative SDS-polyacrylamide gel electrophoresis, and utilized for the generation of polyclonal antibodies. Immunoblotting analysis employing antibodies against the purified A-61 construct revealed a 23-kDa protein present in the regulated secretory pathway of AtT-20 cells. The 23-kDa molecule was purified from media conditioned by AtT-20 cells by ion exchange chromatography on DEAE-Sephacel, molecular sieve chromatography on Sephacryl S-100, chromatofocusing on Polybuffer exchanger 94, and affinity chromatography on PAI-1-Sepharose. N-terminal amino acid sequencing of a 16-kDa Lys-C proteolytic fragment of the 23-kDa storage granule protein was employed to confirm its identity with the cDNA sequence of clone A-61. These data indicate that phage display of cDNA libraries fused to the C-terminal region of the gene III protein and their enrichment via an interaction with a target molecule can be utilized to define other proteins present within a particular cellular pathway.

Amino Acid Sequence↗
PubMed1996

Recombinant rabbit Fab with binding activity to type-1 plasminogen activator inhibitor derived from a phage-display library against human alpha-granules.

The display of panels of antibody (Ab) fragments on the surface of filamentous bacteriophage offers a way of making Ab with defined binding specificities. Because rabbit Ab are routinely utilized as immunologic probes in a variety of biological techniques, the aim of this study was to design and utilize primers for the amplification of mRNAs encoding rabbit kappa light and gamma heavy chains for the construction of an Ab library from this species. Using the polymerase chain reaction, a diverse Ab library with a repertoire of 2 x 10(7) clones was derived from the spleen and bone marrow of a rabbit that had been immunized with purified human platelet alpha-granules. From this library, specific clones were isolated after three rounds of affinity selection with binding activity to type-1 plasminogen activator inhibitor, a trace protein contained in platelet alpha-granules. These data indicate that recombinant phage-displayed Ab libraries obtained after immunization with complex biological antigens can be employed for the isolation of rabbit monoclonal Fab against specific antigens contained in the biological sample.

Amino Acid Sequence↗
PubMed1996

Calcium-dependent stabilization of type I plasminogen activator inhibitor within platelet alpha-granules.

Type 1 plasminogen activator inhibitor (PAI-1) is known to be synthesized in an active conformation but it is rapidly converted into an inactive conformation (t1/2 1 h) upon incubation at 37 degrees C. This study was initiated to investigate the mechanism that account for the presence of active PAI-1 in anucleated platelets that have a mean life span of 9-12 days in the circulation. Stabilization experiments with a functional immunoassay indicated that the activity of PAI-1 in both platelets and in isolated alpha-granules was prolonged in comparison to the rapid inactivation of this molecule in their lysates (t1/2 1 h). Although combined ligand blot/immunoblot analysis revealed that vitronectin was the major PAI-1 binding protein in platelets, vitronectin/PAI-1 complexes were not detected in alpha-granules using a two-site immunoassay. Co-incubation of alpha-granules with a number of agents that disrupt pH gradients (e.g. ionophores) had no effect on the stability of PAI-1 activity, whereas incubation of alpha-granules with the calcium ionophore A23187 reduced the half-life of PAI-1 to the levels observed for PAI-1 in solution. Addition of calcium ions to intact alpha-granules was an effective means of neutralizing the ionophore's effect on PAI-1 activity. Fractionation of alpha-granule proteins on molecular sieving columns using conditions known to be present within storage granules (e.g. a high calcium concentration) revealed the presence of PAI-1 in fractions with a molecular mass of > 10(6) daltons. Immunoabsorption of PAI-1 from these column fractions followed by negative staining revealed 25-nm diameter complexes of alpha-granule proteins under the electron microscope. PAI-1 activity associated with these complexes was prolonged in the presence of calcium ions and these high Mr complexes were shown to be composed of a defined set of proteins that can be dissociated from PAI-1 by chelation of calcium ions. These data indicate that PAI-1 is stabilized by its packaging with other alpha-granule proteins in a calcium-dependent manner.

Blood Platelets↗
PubMed1996

Prothrombotic activation of pulmonary arterial endothelial cells in a patient with tuberculosis.

Activation of endothelial cells occurs in response to numerous physiological stimuli and results in the concerted expression of endothelial cell proteins that change the nonthrombogenic intimal surface of a vessel into a thrombogenic surface, with the subsequent development of local thrombosis. For example, both type 1 plasminogen activator inhibitor and tissue factor expression are mediated by endothelial cell stimulation in vitro; however, in contrast to type 1 plasminogen activator inhibitor, it has been difficult to detect tissue factor associated with endothelial cells in vivo. This case study describes the presence of both type 1 plasminogen activator inhibitor and tissue factor antigen associated with pulmonary arterial endothelial cells of a patient exhibiting a mycobacterial infection. The disease was associated with chronic hemoptysis and characterized by extensive tissue destruction and local thrombosis within the pulmonary artery. The data show that conditions occur in vivo in which local thrombosis is associated with increased levels of type 1 plasminogen activator inhibitor and tissue factor.

Arteries↗
PubMed1996

Inhibition of nitric oxide synthase in the brain suppresses colonic motor activity.

The effects of inhibition of nitric oxide (NO) synthase in the brain on colonic motor activity were investigated in conscious dogs. Intracerebroventricular (ICV) infusion of N omega-nitro-L-arginine methyl ester (L-NAME) and N omega-nitro-L-arginine (L-NNA) significantly suppressed colonic motor activity. The inhibitory effects occurred 1 h after the end of the infusion and lasted for at least 4 h. This suppression was blocked by a concurrent infusion of L-arginine but not D-arginine. The suppression of colonic motor activity was not blocked by bilateral truncal vagotomy or intravenous administration of phentolamine, an alpha-receptor antagonist, and propranolol, a beta-receptor antagonist. ICV infusion of L-NAME had no significant effect on the occurrence of giant migrating contractions in the colon. By contrast, intravenous administration of L-NAME at higher doses significantly enhanced colonic motor activity. We conclude that the inhibition of NO synthesis in the brain suppresses, whereas the inhibition of NO synthesis in peripheral neurons stimulates, colonic motor activity. The central effect may be mediated by a decrease in cerebral blood flow due to the inhibition of NO synthesis in cerebral arteries.

Animals↗