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Biomedical subjects

L Reid

Publications and source records attributed to L Reid.

At least 19 recordsLinked to original sources
PubMed1992

Pulmonary vascular lesions in the adult respiratory distress syndrome caused by inhalation of zinc chloride smoke: a morphometric study.

Two soldiers were fatally injured by accidental inhalation of zinc chloride (ZnCl2) from a smoke bomb. Although exposed to a relatively short but high smoke concentration, acute injury was minor and for 10 days the patients were clinically satisfactory. Unexpectedly, both then rapidly developed features typical of severe adult respiratory distress syndrome with pulmonary hypertension. Intubation and mechanical ventilation were instigated on day 15 (patient no. 1) and day 12 (patient no. 2) after the inhalation, but death followed at days 25 and 32, respectively. Lung vascular injury was assessed by angiography and morphometric techniques. The lungs showed extensive interstitial and intra-alveolar space fibrosis. Vessels showed a significant lumen reduction by contracture (that is, reduction in vessel external diameter) affecting preacinar and intraacinar arterial and venous segments, the extent of injury suggesting that hexite causes more severe venous injury than seen in other types of adult respiratory distress syndrome. In microvessels there was obliteration and widespread occlusion by endothelial cell proliferation and clot. No evidence of infection was identified during life or at autopsy. It is unclear whether the long lag time was due to the fact that the infection was not a complicating event or because steroids, administered prophylactically, had sufficed to delay, but not to prevent, the amplification of injury that seems responsible for the adult respiratory distress syndrome.

Adult↗
PubMed1991

The number of positively charged amino acids in the basic domain of Tat is critical for trans-activation and complex formation with TAR RNA.

The basic domain of Tat is required for trans-activation of viral gene expression. We have performed scanning peptide studies to demonstrate that only this domain is capable of binding to the TAR RNA stem-loop. Strikingly, the basic domain of the other human immunodeficiency virus trans-acting factor, Rev, but no other region, is also capable of binding to TAR. Peptide derivatives of Tat do not require the highly conserved glutamine residue at position 54 for TAR binding, since it may be substituted or deleted. In addition, the two lysine residues may be replaced by arginines. Analysis of binding and trans-activation demonstrated that homopolymers of arginine can completely substitute for the basic domain. Such homopolymers have high affinity for wild-type TAR RNA and lower affinity for mutant TAR. Homopolymers of six to nine arginines substituting for the basic domain of Tat enable full trans-activation in vivo. Homopolymers of at least seven arginines are required for detectable in vitro complex formation, although approximately 30% trans-activation is achieved with a mutant Tat containing only five arginines.

Amino Acid Sequence↗
PubMed1991

Pulmonary development in the fetal lamb: morphometric study of the alveolar phase.

The alveolar stage of intra-uterine lung development was analyzed morphometrically in 18 fetal lambs at 112, 124, 142, or 148 (term) days of gestation. The right lungs were fixed at uniform distending pressure and the tissue embedded in Epon for light microscopy. Over the whole period, right lung volume (VL) increased more rapidly than body weight to reach a mean value of 185 cm3 at term. The increase in VL was greatest between 112 and 124 days gestation. Throughout the period of study the distal lung consisted of alveolar-like air-spaces lined by walls with a single capillary system. Despite this mature morphology, further differentiation took place as established by two independent measurements. First, interalveolar wall thickness decreased from 4.12 +/- .03 microns at 112 days to 2.55 +/- .02 microns at term. Secondly, alveolar surface area increased at a greater rate than lung volume (as VL 1.06), suggesting a moderate increase in surface complexity, but not a subdivision of existing air-spaces. This latter finding was supported by numerical density values which remained fairly constant. We conclude that throughout this period active growth involves the addition of alveolar units of basically similar size. This is a similar process to the one noted previously in postpneumonectomy compensatory growth.

Animals↗
PubMed1991

Hypoxic remodeling of the rat pulmonary arterial microcirculation assessed by microdissection.

Artery segments were microdissected from distal acini of the rat lung and studied by light and electron microscopy. Morphometric methods were used to quantify the structure of the wall at defined levels within the normal axial pathway and to determine the changes after 5 and 7 days of whole-animal exposure to hypobaric hypoxia at an inspiratory O2 fraction of 0.1. In the normal lung, at the level of the terminal bronchiolus, the artery wall comprised up to six layers of smooth muscle cells (SMCs). At the respiratory bronchiolar level, however, the wall contained fewer than two layers of SMCs with a consistently circumferential orientation. By the second-generation alveolar ducts (AD2), the medial layer was lost, replaced by subendothelial precursor smooth muscle cells (PCs) resembling intermediate cells. At this and the next level (AD3), the PC layer was often circumferentially discontinuous. Regression analysis of the morphometric data suggested, however, that the smallest AD3 artery is likely to have a layer of PCs but with virtually no measurable separation between them and the endothelium. The mean maximum radial diameter of SMCs decreased along the axial pathway with a significant difference between diameters at terminal bronchiolus and AD2 levels; yet the diameter of endothelial cells remained the same. After 7 days of hypoxia, no change was noted in the number of smooth muscle layers, but at the AD2 level the relative area of media in the total wall increased. This was due in part to hypertrophy of PCs, as evidenced by an increase in their mean maximum radial diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Bronchial mucus hypersecretion in acute quadriplegia. Macromolecular yields and glycoconjugate composition.

In acute quadriplegia we have noted that about one in five patients develops unexplained production of markedly excessive and tenacious bronchial mucus. Spontaneous recovery from mucus hypersecretion usually occurs within weeks to months. Mucus samples collected from 12 patients have been found to be abnormal. Macromolecular contents of single aspirates yielded as much as 500 mg. Analytical ultracentrifuge analysis showed the mucus to contain considerable epithelial glycoprotein (GP) of typical buoyant density; its amino acid and carbohydrate compositions were characteristic of the GP from hypersecretory bronchial mucus such as in chronic bronchitis and cystic fibrosis. In five patients studied after recovery from hypersecretion, there tended to be relatively less GP. The mucus samples contained a high density glycoconjugate (GC): this had sugars of GP but also reacted positively with a monoclonal antibody to keratan sulfate. Its amino acid composition was different from that of GP: threonine was lower and glycine was higher than in GP. In mucus from one patient who died, chondroitin sulfate ABC and hyaluronic acid were identified as well. This suggests proteoglycans are involved in the pathophysiology of mucus hypersecretion. The sudden onset and spontaneous recovery of hypersecretion suggests that it is not due to gland hypertrophy. We speculate that in acute quadriplegia it is due to disturbed neuronal control of bronchial mucus gland secretion, perhaps related to initial disappearance and later reappearance of peripheral sympathetic nervous system tone.

Acute Disease↗
PubMed1990

Frontiers in mammalian cell culture.

For the past 60 years, fundamental discoveries in eukaryotic biology using mammalian cell cultures have been significant but modest relative to the enormous potential. Combined with advances in technologies of cell and molecular biology, mammalian cell culture technology is becoming a major, if not essential tool, for fundamental discovery in eukaryotic biology. Reconstruction of the milieu for cells has progressed from simple salt solutions supporting brief survival of tissues outside the body to synthesis of the complete set of structurally defined nutrients, hormones and elements of the extracellular matrix needed to reconstruct complex tissues from cells. The isolation of specific cell types in completely defined environments reveals the true complexity of the mammalian cell and its environment as a dynamic interactive physiological unit. Cell cultures provide the tool for detection and dissection of the mechanism of action of cellular regulators and the genes that determine individual aspects of cell behavior. The technology underpins advances in virology, somatic cell genetics, endocrinology, carcinogenesis, toxicology, pharmacology, hematopoiesis and immunology, and is becoming a major tool in developmental biology, complex tissue physiology and production of unique mammalian cell-derived biologicals in industry.

Allergy and Immunology↗
PubMed1989

Pulmonary hypoplasia and osteogenesis imperfecta type II with defective synthesis of alpha I(1) procollagen.

Perinatal lethal osteogenesis imperfecta (OI type II), a heritable disorder of connective tissue occurs approximately once in 60,000 live births. Phenotypic characteristics include defective cranial ossification and severe skeletal deformity due to intrauterine rib and long bone fractures. Lethal OI may be associated with intracranial hemorrhage or severe respiratory insufficiency. Pulmonary hypoplasia has been previously observed in OI type II, but has not been defined clinically. The infant described herein was born with OI type II and pulmonary hypoplasia. Pathological examination of airway branching patterns indicated that lung development had progressed to only the 10 week stage with immature acinar development. Investigation type I collagen synthesis by cultured dermal fibroblasts revealed the presence of electrophoretically abnormal alpha 1(I) polypeptides. These findings suggest that biochemically regulated processes, as well as mechanical factors, may impeded pulmonary development in similar cases of OI type II.

Culture Techniques↗
PubMed1989

Pulmonary development in the fetal lamb with severe bladder outlet obstruction and oligohydramnios: a morphometric study.

The lethal feature of male newborns with severe bladder outlet obstruction and oligohydramnios is pulmonary hypoplasia. We report a fetal lamb model of bladder outlet obstruction created in the early second trimester, and morphometric analysis of the profound pulmonary hypoplasia that resulted. At 55 to 65 days of gestation 8 consecutive male fetuses underwent surgical clipping of the urethra and urachus near the abdominal wall. A sham operation was performed in 1 female fetus. The lambs were delivered by cesarean section 10 weeks later. The right lungs were immediately fixed at a distending pressure of 25 cm. water. The results of the morphometric studies were compared to control animals from our earlier study of normal fetal lamb lung development; slides for both studies were scored in a blind, randomized fashion by 1 of us (S. G. D.). Although mean body weights for the groups were similar, mean right lung volume in the operated lambs was 63.8 cM.3 compared to 158 cM.3 in the control animals and 137 cM.3 in the sham operated fetus (p less than 0.0005). Relative volume of respiratory tissue was 87 per cent in the operated animals, and 92 per cent in the controls and the sham operated fetus (p less than 0.0005). Microscopic morphometry revealed an increased relative volume of inter-alveolar tissue in the experimental animals (35 compared to 23 per cent in the normal lambs, p less than 0.05), with a corresponding decrease in relative airspace volume. Alveolar numerical density and alveolar surface density were not statistically different between the groups, although total alveolar number and surface area were substantially decreased in the operated lambs due to the reduced mean lung volume. Mean alveolar wall thickness was increased at 3.6 microM. in the operated group versus 2.1 microM. in the normal group (p less than 0.0005) and 2.8 microM. in the sham operated fetus. Thus, the lung in the lamb with severe bladder outlet obstruction is hypoplastic and immature.

Amniotic Fluid↗
PubMed1989

Bladder irrigation or irritation?

Exfoliation rates of urothelial cells following bladder irrigation were studied in patients with long-term indwelling catheters and chronic urinary tract infections (UTI). The irrigations were associated with an increased shedding of urothelial cells. Ultrastructural studies of these cells demonstrated increased disruption when compared with those obtained from normal subjects without catheters or chronic infection. The findings suggest that bladder irrigation further damages the already disrupted urothelium, which may in turn increase the predisposition of the bladder to the recurrent infections, commonly associated with patients who have indwelling urinary catheters. Bladder irrigation methods and the indications for their use require reassessment.

Aged↗
PubMed1989

cAMP delays disappearance of gap junctions between pairs of rat hepatocytes in primary culture.

Freshly isolated adult rat hepatocytes were found to be coupled through gap junctions, but coupling decreased abruptly 5-8 h after plating the cells on plastic culture dishes in physiological saline containing insulin and fetal calf serum. Loss of intercellular coupling was associated with disappearance of 27-kDa gap junction protein and of gap junctions seen by electron microscopy or immunocytochemistry. This disappearance of coupling was delayed approximately 8 h by treatment of the cultures with membrane permeant adenosine 3',5'-cyclic monophosphate (cAMP) [but not guanosine 3',5'-cyclic monophosphate (cGMP)] derivatives. Levels of gap junction protein and anatomically identified junctions were also maintained by 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP). Level of mRNA encoding the gap junction protein was maintained longer in cells treated with 8-BrcAMP than in untreated cells, but 8-BrcAMP did not detectably increase the transcription rate. Thus prolongation of coupling must result at least partially from extension of the lifetime of gap junction mRNA, allowing translation of message and assembly of channels for a longer period after plating. Treatment of cells with mRNA or protein synthesis inhibitors (alpha-amanitin and cycloheximide) prolonged coupling to a similar extent as did treatment with 8-BrcAMP. alpha-Amanitin blocked transcription of gap junction mRNA, but levels of cytoplasmic mRNA encoding the 27-kDa gap junction protein were maintained, presumably by block of transcription of an mRNA degrading factor. The factor is probably a protein, since a similar effect on mRNA level was produced in cycloheximide-treated cells. Cells cultured in control medium were also observed to flatten as they became uncoupled, whereas cells cultured for as long as 16 h in elevated 8-BrcAMP remained round and well coupled. The correlation between shape and coupling strength was not obtained after treatment with the microtubule stabilizing agent, taxol, which maintained the spherical shape of the cells but did not delay the disappearance of dye coupling. Nocodazole, which blocks microtubule formation, also maintained the spherical shape of the cells but delayed the disappearance of dye coupling. In addition to gating by covalent modification or other mechanisms, hormones and drugs that alter the intracellular cAMP concentration may affect intercellular communication by changing the lifetime of the mRNA encoding the main gap junction protein, thereby decreasing or increasing its synthesis. In addition, cAMP may act by decreasing removal of junctions from appositional membranes.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Studies on the peptide core of human bronchial mucus glycoprotein.

We have employed thiol-Sepharose chromatography following deglycosylation to analyze the protein core of bronchial epithelial mucus glycoprotein (MGP), isolated by a two stage density gradient ultracentrifugation. Deglycosylation using triflouromethanesulfonic acid resulted in loss of greater than 90% of carbohydrate. The deglycosylated core protein was reduced and the sulfhydryl residues activated with 2-2'dipyridyl disulfide. This preparation was then bound covalently to thiol-Sepharose, and eluted specifically with reducing agents. Our results demonstrate that bronchial MGP contains cysteine residues potentially capable of forming disulfide bonds. Pepsin digestion studies suggest that cysteine residues are present near both the heavily glycosylated region and the naked peptide region. Thiol-Sepharose chromatography resolved several mucin-associated proteins (MAPS) that did not bind to the column. Amino acid analysis showed that the largest of these (200 kDa) is enriched in serine/threonine, like MGP that absorbed to the column: the two smallest (20 kDa and 60 kDa) are similar to the proline rich proteins reported in salivary mucin. These associated proteins, although not linked by disulfide bonds to the MGP, are, nevertheless, tightly bound to it, since they were only recovered after deglycosylation and thiol chromatography.

Animals↗
PubMed1989

The effect of heparin on the haemodynamic and structural response in the rat to acute and chronic hypoxia.

In the mouse, heparin administered intermittently, has been shown to reduce the right ventricular hypertrophy (RVH) caused by hypoxia. We have investigated in the rat the effect of heparin on the haemodynamic and pulmonary vascular structural remodelling produced by hypoxia, with special reference to the new muscularization of peripheral arteries. Heparin at one of two doses (30 and 50 u/kg/h) was administered by continuous intravenous infusion from a miniosmotic pump to rats during 10 days exposure to hypobaric hypoxia and its effect examined on mean pulmonary artery pressure (PPa), RVH and, using morphometric techniques, vascular structural remodelling. Hypoxia produced the haemodynamic and structural changes previously described in this model. Heparin had no significant effect on PPa; a slight reduction in RVH was seen in the high-dose heparin group. After heparin, the narrowing of the axial pulmonary artery lumen caused by hypoxia was less: heparin reduced the proportion of arteries that became muscularized, particularly at alveolar duct level where the pericyte is the precursor smooth muscle cell. Heparin did not diminish the increase in medial thickness or reduction in external diameter of muscular arteries. Some rats, after chronic hypoxia, did not respond to an acute hypoxic challenge yet were no different from 'responders' in other haemodynamic and structural features. Including all rats, the mean acute pressor response to hypoxia was unaffected by heparin: taking only responder rats, a trend was apparent that heparin reduced the rise in PPa on acute hypoxic challenge.

Animals↗
PubMed1988

Postnatal growth of the sheep lung: a morphometric study.

Stereologic methods were used to study lung development in sheep from 2 to 171 days of age. Most growth occurs within the first 2 months when there is a threefold increase in lung volume, but allometric relationships show that this increase does not keep pace with body weight. Alveolar and capillary surface areas increase as lung volume to a power only slightly larger than 1, suggesting a modest increase in complexity; this is confirmed by only a two- to threefold increase in total alveolar number. Allometric power functions are essentially unchanged even during the first 30 days so that throughout development, the surface for gas exchange is added at a fairly constant rate. A slight increase in septal volume during the first 30 days is probably due to relative increase in capillary luminal volume through a progressive distension of capillaries. The results suggest that the active newborn lamb requires an alveolar lung, but in the postnatal period functional needs increase only moderately. In contrast, other mammals, such as the rat, are helpless as newborns and have a primitive saccular lung that must undergo considerable morphogenesis to meet the demands of the active adult.

Animals↗
PubMed1987

Characteristics of lung pericytes in culture including their growth inhibition by endothelial substrate.

Pericytes and endothelial cells from the same sample of adult rat lung have been separately established in culture by use of selective growth media. The endothelial cells are positive and the pericytes negative for angiotensin-converting enzyme activity and tissue plasminogen activator. Morphologically in culture, the pericytes are similar to pericytes from bovine retina and other sites and show positive immunofluorescence to both human platelet (non-muscle) myosin and smooth muscle myosin. In this respect they resemble smooth muscle cells grown from the rat main pulmonary artery, but lack the myofilaments and dense bodies characteristic of muscle cells. Lung endothelial cells and fibroblasts are positive only for platelet myosin. Pericytes in culture demonstrate an unusual growth response to endothelial substrate, obtained by removing confluent endothelial monolayers with nonionic detergent or alkali. When plated onto this material at low density, pericyte growth is inhibited. By contrast, the substrate stimulates the growth of endothelial cells and has no effect on smooth muscle cells. Initial attachment of endothelial cells and pericytes to the substrate is similar.

Animals↗
PubMed1987

Correlation of pulmonary ACE activity and capillary surface area during postnatal development.

Although a considerable amount of information is available regarding the remodeling and growth of the pulmonary arterial circulation, relatively little is known regarding postnatal development of the pulmonary microcirculation. We hypothesized that the maximal velocity (Vmax) of pulmonary angiotensin-converting enzyme (ACE) activity, measured from indicator-dilution outflow curves using a synthetic substrate, 3H-labeled benzoyl-phenylalanyl-alanyl-proline (BPAP), is directly related to the capillary endothelial cell surface area in the lungs of developing lambs. Accordingly we measured apparent kinetics of pulmonary ACE activity in 22 anesthetized ventilated lambs (2-171 days old) and compared our functional assessment to simultaneous in vivo determinations of CO diffusing capacity (DLCO) and postmortem structural assessment of alveolar septal dimensions using stereology and electron microscopy. There was a progressive increase in Vmax of ACE in this age group, with little change in apparent affinity for BPAP. Similar functional manifestation of growth was noted by an age-dependent increase in DLCO. Neither Vmax nor DLCO was significantly affected by an increase in left atrial pressure to 19 Torr (via inflation of a balloon in the left atrium), suggesting little recruitment of vessels under conditions of the present protocol. A close correlation was observed when either Vmax for ACE activity or DLCO was plotted vs. capillary endothelial cell surface area. Double logarithmic transformation of capillary endothelial cell surface area, Vmax-ACE and DLCO vs. lung volume revealed power functions with slopes all greater than that predicted from isotropic growth, suggesting selective differential postnatal development of the endothelium of the alveolar septum in lambs from 2-171 days of age.

Animals↗
PubMed1987

Chronic exposure to sulfur dioxide. Physiologic and histologic evaluation of dogs exposed to 50 or 15 ppm.

Seven adult mongrel dogs were exposed to SO2 gas at 2 different concentrations (15 and 50 ppm) on a daily basis for 5 to 11 months. Mucous hypersecretion and airway obstruction (a sustained increase in pulmonary resistance) developed in 4 dogs exposed to 50 ppm SO2. Histologic examination of the dogs' airways demonstrated epithelial thickening and an increase in size of the mucous glands. No inflammatory cell infiltration of the airways was noted and, in addition, responsiveness to inhaled histamine and methacholine did not change. The increase in lung resistance correlated with increase in mucous gland volume and airway wall thickening, but not with any change in airway responsiveness. Dogs exposed to 15 ppm SO2 showed minimal histologic and physiologic changes compared with control dogs. Previous work with a similar model of chronic bronchitis, using higher level SO2 exposure, has demonstrated an association of airway inflammation with decreased responsiveness to inhaled bronchoconstrictors. In the present study, with a lower exposure level to SO2 (50 versus 200 ppm), we found similar histologic findings associated with airway obstruction, but in the absence of airway inflammation, responsiveness to inhaled bronchoconstrictors was unchanged. This supports the theory that chronic airway inflammation may be associated with decreased responsiveness to inhaled bronchoconstrictors. This contrasts with the hyperresponsiveness induced by acute exposure to irritant gases noted by others.

Airway Resistance↗