Uptake of 3H-7-cholesterol along the arterial wall at an area of stenosis

Abnormal uptake of atherogenic substances and lipid infiltration have been believed to contribute to the localized genesis and development of atherosclerosis, as well as to late failures of synthetic arterial prostheses. To verify the theoretical prediction that accumulation of lipoproteins on the luminal surface of arterial walls occurs in the regions of disturbed flow, we have carried out an in vitro mass transfer experiment to test the effect of a pseudo steady recirculation flow on the uptake of 3H-7-cholesterol by the arterial wall at a surgically created stenosis. It was found that, as predicted by the theory, in the flow field of the stenosis the uptake of labeled cholesterol reached a maximum around the reattachment point of the vortex distal to the stenosis, where the wall shear stress was lowest (zero). This value of the highest uptake rate was almost twice the average, whereas the uptake level was at a minimum at the stenosis itself where the wall shear stress was highest. The lowest uptake was only 60% of the average. These results provide strong support to our hypothesis, based upon the theory that, in addition to the flow induced changes to the biologic function of endothelial cells, the disturbed flow with slow recirculation itself favors the accumulation of atherogenic lipoproteins at the blood-endothelium boundary, therefore playing an important role in the localized pathogenesis and development of atherosclerosis.

Why make monofilament sutures out of polyvinylidene fluoride?

In recent years some clinical reports have associated suture failures with polypropylene monofilaments. Therefore there is interest in developing an alternative suture material that is less thrombogenic than polyester and similar in handling characteristics but less prone to mechanical failure than polypropylene. To this end, Peters Laboratoire Pharmaceutique has developed a new monofilament suture material from polyvinylidene fluoride (PVDF), which has been subjected to a special treatment to modify its crystalline form and level of crystallinity. The purpose of this study was to evaluate its mechanical, chemical, and biologic properties and to compare its performance, in a peripheral vascular application, to that of a polypropylene control. A series of in vitro tests were performed to study the morphology, tensile properties, creep, surface chemistry, thermal characteristics, and resistance to iatrogenic trauma. In addition, an in vivo trial was undertaken in which vascular prostheses anastomosed with either PVDF or polypropylene sutures were implanted as a thoracoabdominal bypass for 6 months in the dog. Histologic and degradation analyses were performed on the explants. The results from the mechanical tests on 4-0, 5-0, and 6-0 PVDF and polypropylene sutures demonstrated that although both materials have similar breaking strengths, the PVDF has a higher extension at break, has less delayed extension when under tensile creep testing, and suffers less trauma than the polypropylene when compressed by a standard needle holder. While chemical analyses found evidence of surface oxidation on both types of sutures, thermal analysis confirmed that the level of crystallinity of the PVDF polymer is higher than that of the polypropylene control. During the pilot study in animals, PVDF sutures were found to have good handling and frictional characteristics that facilitated the tying of knots. Histologic analysis of the explants found no inflammatory cells in the tissue surrounding either the PVDF or polypropylene sutures, and scanning electron microscopic examination of the cleaned suture surfaces found no evidence of degradation during 6 months in vivo. Though preliminary in nature, these findings indicate that monofilament sutures made from PVDF provide an attractive alternative to those made from polypropylene for use in cardiovascular surgery. In addition to providing acceptable in vivo behavior and being easy to manipulate and more resistant to iatrogenic injury, PVDF materials can be sterilized by beta or gamma radiation and so can reduce dependence upon ethylene oxide and chlorofluorohydrocarbons.

Characterization and expression of the Xenopus c-Myb homolog

The c-Myb protein is a sequence specific DNA-binding transcriptional regulator that is critically involved in the regulation of hematopoietic differentiation. Its role in these processes suggests that the function of c-Myb may be important early in the establishment of the hematopoietic lineage. We have isolated cDNA and partial genomic clones representing the Xenopus c-Myb homolog (Xc-Myb) in order to examine the role this gene plays in early mesodermal patterning in the frog embryo. The establishment of these clones as c-Myb homologs, as opposed to Myb-related sequences, is based upon both predicted amino acid sequences and the location of the exon-intron boundaries within the Xc-Myb gene. Maternally derived Xc-Myb RNA is degraded following fertilization then, beginning at midblastula, re-accumulates throughout early development. Xc-Myb RNA is localized to the animal cap region of the early blastula. Following the onset of gastrulation expression predominates in the ventral half of the embryo. During neurulation expression of Xc-Myb is observed in both the anterior dorsal and ventral vegetal regions of the embryo. Expression of Xc-Myb occurs in several adult tissues, the highest levels of which are in the intestine, heart, liver, lung and ovary. Xc-Myb encodes a protein of 624 amino acids and exhibits a mobility in SDS-PAGE of approximately 75 kDa, identical with that of the murine c-Myb protein. Xc-Myb protein exhibits 70% identity with avian and 67% identity with mammalian c-Myb proteins.

A rapid and efficient, nonradioactive method for screening recombinant DNA libraries

In this report we present a rapid and inexpensive PCR-based method to screen recombinant DNA libraries. The efficiency of this method was demonstrated by the isolation of clones of interest from three different libraries using different vector systems. This method is nonradioactive and makes it easier to handle a large number of samples since there is no need for DNA extraction. The advantages and applications of the method are discussed.

Expression of two distinct homologues of Xenopus Max during early development

The Max protein belongs to the basic region-helix-loop-helix-leucine zipper family of transcriptional regulators. Max heterodimerizes with Myc family proteins to form sequence-specific DNA-binding complexes. In order to elucidate the potential role of Myc and Max during amphibian embryogenesis, we have isolated and analyzed the expression of two Xenopus Max complementary DNAs: XMax1 and XMax2. Comparison of XMax1 and XMax2 with their mammalian counterparts demonstrates a strikingly high degree of conservation at both the nucleotide and amino acid levels, with the exception of a 24-residue deletion in both XMax proteins within their COOH termini. In addition, the two Xenopus Max proteins differ in that XMax2 contains a unique 27-amino acid insertion that interrupts the COOH-terminal end of the zipper domain; XMax1 lacks this insertion. Despite these differences, both XMax1 and XMax2 can form complexes with either Xenopus or human c-Myc proteins. Analysis of XMax expression during embryogenesis reveals that both mRNA and protein are expressed throughout early development, including the egg, 32-cell stage, and midblastula transition. Although the expression of XMax1 RNA appears to predominate at all stages examined, the ratios of XMax1 to XMax2 protein vary during development as well as between different tissue culture cell lines, suggesting a potential for cell type-specific regulation. Our results demonstrate the presence of Xenopus Max throughout frog development, raising the possibility that Myc and Max could function as a complex even during early embryogenesis.

Histopathological and immunological investigations of synthetic fibres and structures used in three prosthetic anterior cruciate ligaments: in vivo study in the rat

Three types of prosthetic anterior cruciate ligaments were investigated by enzymatic and histological analysis of the tissue surrounding each implant and immunologically by a cytofluorometric analysis of T-cell populations in the peripheral blood of rats. Two of the prostheses had a braided construction, one made from polyester and the other from high performance polyethylene fibres. The third type also contained high performance polyethylene fibres, but had been manufactured in a knitted construction (Raschel high performance polyethylene). Five specimens from each prosthesis were implanted intraperitoneally in rats by a trocar for different periods of time up to 4 wk. A control group of rats underwent the surgery, but not the implant. No modification in peripheral T-cell populations was induced by the presence of any implant. Whilst the levels of acid phosphatase and esterase activity appeared to have increased slightly following implantation of any of the prostheses, such increases were not highly significant. Histologically, all three materials induced an intense acute inflammatory reaction at 3 d which gave way to a typical chronic response after 4 wk. The only major difference between the prostheses was that after 4 wk the polyester fibres exhibited less inflammation, and the surrounding tissue was more mature, more vascularized and more densely infiltrated with collagen than with the two high performance polyethylene implants. In conclusion, all three devices provided satisfactory biocompatibility in terms of cellular and healing response.

A new bioactive molecule for improving vascular graft patency: exploratory trials in dogs

Myxalin is a new bioactive molecule that we have isolated from the culture medium of Myxococcus xanthus, a non-pathogenic Gram negative bacterium. This glycopeptide possesses an antithrombotic effect in vivo and has been shown to promote human endothelial cell growth in vitro. With the object of exploring its ability to improve vascular graft healing and patency, myxalin was immobilized on 6 mm diameter knitted polyester prostheses using gelatin as a carrier, and the prosthesis was then implanted as an infrarenal abdominal arterial substitute in dogs for a period of 2 weeks. Two additional series of implantations were conducted for control purposes: one with gelatin-coated prostheses without myxalin, the other following normal preclotting of the polyester grafts. In order to select adequate sterilization conditions which can preserve the biological activity of myxalin, the prostheses were sterilized according to 3 different sterilization processes (gamma radiation and ethylene oxide either at 63 degrees C or 37 degrees C). At the sacrifice, all grafts were patent. The myxalin treated prostheses exhibited improved blood compatibility in terms of fewer thrombotic deposits and significant inhibition of platelet and fibrinogen uptake on their luminal surfaces. In addition, the development of a thin collagenous internal capsule with endothelial cells secreting high levels of prostacyclin was observed at both anastomoses of the myxalin-treated grafts sterilized by gamma radiation.

Developmentally regulated alternative splicing in the Xenopus laevis c-Myc gene creates an intron-1 containing c-Myc RNA present only in post-midblastula embryos

Two distinct c-Myc RNA classes have been identified in Xenopus laevis, presumably expressed from the duplicated c-Myc locus (1, 6). The major Xenopus c-Myc transcripts arise from sites termed P1 and P2 similarly to those of the mammalian c-Myc genes. I have used a cloned Xenopus c-Myc gene to examine the regulated pattern of expression from this gene during early Xenopus embryogenesis. Analysis of the pattern of transcript processing indicates that not only are P1 and P2 differentially active during early development but alternatively spliced c-Myc RNAs are generated which contain sequences of the first intron. These intron-1 containing c-Myc RNAs are generated by alternative splicing of transcripts initiated from the major transcription start site, P2, and are observed only in RNA samples from post-midblastula embryos or Xenopus tissue culture cells. Xenopus tissue culture cells synthesize two major c-Myc proteins (p61 and p64). Xenopus RNAs that do not contain intron-1 sequences synthesize only the p61 species. Two closely spaced ATG codons at the 5' end of exon-2 are utilized equivalently to generate a p61 doublet. Intron-1 containing RNAs utilize an ATG codon in the intron sequences to synthesize the p64 species as well as the exon-2 ATG codons to synthesize the p61 doublet.

Influence of dietary fat on factors in serum that regulate thyroid cell metabolism

The type of dietary fat affected the production of cAMP by cultured thyroid cells incubated with mouse and rat sera. Greater amounts of cAMP were produced with serum from mice fed 30% rac-1(3)-palmitoyl glycerol and 4% safflower oil (PG + SO) than with serum from mice fed 30% rac-1(3)-palmitoyl glycerol (PG). The serum from mice fed PG + SO gave a response similar to that with calf serum. Sera were separated into lipoprotein and aqueous fractions by centrifugation. A combination of both the lipoprotein and aqueous fractions of serum from mice fed PG + SO was required for the increased response. Proteolysis of the aqueous fraction of the serum from either mice fed PG or rats fed 30% hydrogenated coconut oil (HCO) reduced the amount of cAMP produced by the thyroid cells. However, the same effect was not seen with aqueous fractions of calf serum or serum from mice fed PG + SO or rats fed HCO plus 5% corn oil. These findings suggest that there are at least three factors in serum capable of regulating thyroid cell metabolism that are controlled by the type of fat fed the animal.

A second tumor necrosis factor receptor gene product can shed a naturally occurring tumor necrosis factor inhibitor

An inhibitor of tumor necrosis factor (TNF) has been isolated from the human histiocytic lymphoma cell line U-937 that is capable of inhibiting both TNF-alpha and TNF-beta. Protein sequencing has verified that it is distinct from a previously described TNF inhibitor that is a soluble fragment of a TNF receptor molecule (TNFrI). The cDNA sequence of this second TNF inhibitor clone suggests that it is also a soluble fragment of a TNF receptor. Expression of this cDNA sequence in COS-7 cells verified that it encodes a receptor for TNF-alpha (TNFrII) that can give rise to a soluble inhibitor of TNF-alpha, presumably through proteolytic cleavage. The extracellular domain of TNFrII has significant homology with that of TNFrI and these two receptors share a striking conservation of cysteine residue alignment with the extracellular domain of the nerve growth factor receptor. These three receptor molecules are therefore members of a family of polypeptide hormone receptors.

The surface composition of commercial polyester arterial prostheses--an XPS study

The importance of identifying and quantifying the level of contaminants on the surface of biomaterials has long been recognized as a significant step towards predicting the biocompatibility and rate of healing of implantable devices. Yet suitable techniques for characterizing the surface chemistry of soft and flexible biomaterials with an uneven surface contour such as those used in vascular prostheses have only recently been made available. As a first step towards determining the effect of surface contaminants on the healing behaviour of vascular prostheses, this study used X-ray photoelectron spectroscopy (XPS) to characterize the surface chemistry of 14 virgin polyester arterial prostheses from a wide variety of sources. Generally speaking, all surfaces appeared relatively clean. However, the results indicate that certain prostheses were not manufactured with Dacron-like fibres, and that some exhibit significantly carbon-rich surfaces. This suggests that the surface of these devices has been modified either by a hydrocarbon lubricant or by vapour phase hydrocarbons during fabrication.

A non-AUG translational initiation in c-myc exon 1 generates an N-terminally distinct protein whose synthesis is disrupted in Burkitt's lymphomas

The c-myc gene comprises three exons with a single large AUG-initiated open reading frame extending from exon 2 through exon 3. Exon 1 lacks any AUG codons. Cells from a wide range of species produce two c-myc proteins that, while highly related, do not appear to arise from posttranslational interconversion. To understand the origin of the two proteins, we mapped them and analyzed the in vitro protein-coding capacity of c-myc cDNAs. Our findings show that the two proteins are derived from alternative translational initiations at the exon 2 AUG and at a non-AUG codon near the 3' end of exon 1, resulting in the production of proteins with distinct N termini. In Burkitt's lymphomas, the removal or specific mutation of exon 1 in c-myc translocations correlates with suppression of synthesis of the larger protein, and thus may contribute to the oncogenic activation of c-myc.

Expanded PTFE prostheses as arterial substitutes in humans: late pathological findings in 73 excised grafts

Through collaboration of surgeons, pathologists and bioengineers at five centers in Canada and France, this study analyzed the late pathology and structural changes in 73 expanded PTFE arterial prostheses harvested from patients at autopsies and reoperations. The degree of tissue encapsulation increased with the duration of implantation but was reduced by the presence of infection. In several cases, the fibrous tissue penetrated the wall of the prosthesis and partitioned off the thin outer layer, thus disrupting the delicate microporous structure of the wall. The presence of aneurysms was observed in models that had no external reinforcing layer and among grafts that apparently suffered from surgical trauma. Wrinkling of grafts was noted at areas of flexion and was often associated with thickening of the external capsule and reduced luminal diameters. Endothelialization was found within only a few millimeters of the anastomoses. The luminal surfaces were generally not well healed. The PTFE structure was usually readily visible under a thin covering of loosely adhering thrombotic deposits. Bacteria were observed in 46% of the cases, even though only 29% were considered clinically infected. The incidence of lipid or cholesterol deposits was high. Avoiding iatrogenic trauma to the external wall of the prosthesis during implantation is important. Those features where design improvements are required to provide longer term structural integrity and dimensional stability in future models of expanded PTFE prostheses should be identified.

Characteristics of polyester arterial grafts coated with albumin: the role and importance of the cross-linking chemicals

Preclotting is mandatory prior to implanting a knitted polyester arterial graft, unless the structure is made impermeable to blood by coating with a bioerodible material. Before achieving wide-spread clinical acceptance, the technique of impregnating with cross-linked albumin must be optimized in order to develop a graft that is immediately implantable, easy to handle and suture and has improved healing characteristics. The choice of the chemical to cross-link the albumin is of paramount importance. In this study two alternative candidates have been evaluated by using a series of tests to measure the physical properties, the morphology and the cytocompatibility of albumin-coated grafts. A carbodiimide cross-linking agent appears more promising than glutaraldehyde, since it is equally effective in producing a blood impermeable prosthesis, yet presents improved biocompatibility and provokes a less intense inflammatory response from the host.

Polyester arterial grafts impregnated with cross-linked albumin: the rate of degradation of the coating in vivo

One of the techniques used to avoid preclotting a porous textile arterial prosthesis is to coat the graft with a layer of a bioerodible polymer. The efficacy of this treatment is dependent in part on the rate at which the polymer degrades after implantation. The focus of this study was therefore to investigate the rate of in vivo degradation of albumin-coated polyester (Dacron)-knitted vascular prostheses. Two types of cross-linked albumin were included: one using glutaraldehyde, the other using carbodiimide as the cross-linking agent. Radioactively labeled albumin-coated prostheses were implanted in the thoracic aorta and peritoneal cavity of dogs, and their rates of biodegradation in vivo were monitored over a 4-week period. The rate of biodegradation was found to depend upon the site of implantation. It occurred more rapidly in the peritoneal cavity where less than 20% of the albumin coating remained after 4 weeks in vivo in comparison to the approximately 30% in the thoracic aorta. The nature and intensity of the cellular response appeared to be related to the cytotoxic potential of the cross-linking agent. Glutaraldehyde induced an inflammatory response and a delay in healing, whereas carbodiimide caused only a mild tissue reaction.

In vivo evaluation of polyester arterial grafts coated with albumin: the role and importance of cross-linking agents

Previous in vitro studies have predicted that the type of chemical used to cross-link albumin-coated polyester arterial prostheses may influence the rate of bioerosion of the albumin layer in vivo. This study has confirmed that the healing process of this type of compound prosthesis does indeed depend on the nature and concentration of the cross-linking agent used. Four series of implantations in the thoracic aorta of dogs for scheduled periods for 4 h up to 6 months were conducted using 1.6% glutaraldehyde, 2.5% glutaraldehyde and 0.2 M carbodiimide as the alternative cross-linking agents plus a nonalbuminated preclotted polyester prosthesis which served as the control. The pathology of the explanted grafts revealed that in the short and medium term the rate of healing and the extent of tissue ingrowth was dependent initially on the presence of and later on the rate of bioerosion of the albumin layer. After 3 months in situ, the prostheses coated with albumin cross-linked with 1.6% glutaraldehyde and carbodiimide had healed more rapidly and were invaded by more extensive tissue ingrowth than the one cross-linked with 2.5% glutaraldehyde or the preclotted control. Moreover, the migration of cells over the carbodiimide-treated surface was the most fully developed and most regularly organized of all four series. Immunostaining revealed that the presence of glutaraldehyde induced an inflammatory response which failed to support the growth of normal luminal cells with the endothelial phenotype.

Expression of calbindin-D28K mRNA as a function of altered serum calcium and phosphorus levels in vitamin D-replete chick intestine

The availability of specific cDNA probes to the chick intestinal calbindin-D28K (CaBP) mRNA has allowed us to assess the regulation of this mRNA in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) administration. It has previously been demonstrated that dietary calcium and phosphorus can effect alterations in the steady-state intestinal levels of chick CaBP. We have examined whether or not perturbations in dietary calcium and phosphorus have an effect on the expression of the intestinal mRNA coding for CaBP in the vitamin D-replete chick. We found altered protein levels of CaBP as expected; however there was surprisingly no difference in steady-state CaBP mRNA levels between the different dietary groups. These data suggest that calcium and phosphorus regulation of CaBP occurs at a post-transcriptional level. In addition, we have examined what effect dietary manipulations of calcium and phosphorus levels have on the response of the vitamin D-replete intestine to 1,25(OH)2D3 administration as assessed by CaBP mRNA changes. Administration of 1,25(OH)2D3 to vitamin D-replete chicks maintained on normal calcium and phosphorus levels resulted in a less than 2-fold increase in CaBP mRNA levels. Previous studies have demonstrated that receptor occupancy goes up 6-fold under these conditions; therefore there is apparently a very tight regulation of CaBP gene activity. 1,25(OH)2D3 administration to chicks raised on either low calcium, high calcium, or low phosphorus vitamin D-replete diets similarly showed only small changes in the intestinal CaBP mRNA levels; however there seemed to be qualitative differences in response attributable to the dietary alterations.

Toxicity of palmitoyl glycerol to mice: hypothermia and reversal of the toxicity

Adult and weanling mice kept at low ambient temperatures show an increased sensitivity to the toxicity of dietary rac-1(3)-palmitoyl glycerol. When fed the palmitoyl glycerol, mice less than 6 wk old show a pronounced hypothermia that is prevented by adding safflower oil to the diet. A more moderate degree of hypothermia is seen with older animals. Once body temperature fell below 28 degrees C, replacing the toxic monoacylglycerol with safflower oil and/or raising the environmental temperature to 34 degrees C did not reverse the ultimate fatality caused by palmitoyl glycerol ingestion. If hypothermia was between 28 and 32 degrees C, high mortality was not reversed by feeding the unsaturated fat or raising the environmental temperature to 34 degrees C. However, a combination of both treatments reduced the mortality. Irrespective of body temperature, the hypothermia was eliminated by the warm ambient temperature, but mortality was high. Thus, although hypothermia is a sign of the toxicity of rac-1(3)-palmitoyl glycerol, it is not the immediate cause of death.

Toxicity of palmitoyl glycerol to mice: depression of thyroid function

Mice given propylthiouracil, a thyroid inhibitor, and fed a diet containing a nontoxic level of rac-1(3)-palmitoyl glycerol showed the hypothermia and mortality expected for a toxic dose, but did not show these signs when linoleate or oleate was added to the diet. Loss of radioiodine from the whole animal and thyroid gland was slower when mice were fed the toxic palmitoyl glycerol diet than when fed the same diet containing 4% safflower oil. However, mice fed the two diets did not differ in the extent of the incorporation of radioiodine, and essentially all was bound to protein in each case. Follicular thyroid cells from mice fed the potentially toxic diet that contained unsaturated fat were normal in appearance. Conversely, cells from mice fed the toxic diet were smaller and more densely stained, showing evidence of glycoprotein inside the cell. These findings show that the thyroid gland is affected by the palmitoyl glycerol diet. However, the thyroid is not the only organ affected, because giving either thyroxine or triiodothyronine had no effect on the toxicity of palmitoyl glycerol.

Expression of the c-myc proto-oncogene during development of Xenopus laevis

We isolated and characterized Xenopus laevis c-myc cDNAs from an oocyte-specific library. These cDNA clones encompass 2.35 kilobases of the X. laevis c-myc RNA and contain the entire coding domain of 1,257 nucleotides of the 419-amino acid-long X. laevis c-myc protein. The 2.7-kilobase X. laevis c-myc mRNA is expressed in the oocyte, maintained in the egg, and is present throughout the early cleavage stages of embryogenesis. At the time of transcriptional activation in the embryo the c-myc RNA levels show a significant decline and then reaccumulate continuously throughout the remainder of premorphogenic development. At the early neurula stage of embryogenesis the pattern of c-myc RNA expression is elevated in the mesoderm with respect to the endoderm and ectoderm. In the adult X. laevis the c-myc mRNA is expressed in some (e.g., skin, muscle) but not all differentiated tissues. The X. laevis c-myc protein migrates as a doublet of 61,000- and 64,000-dalton species. Both species are phosphorylated in oocytes and somatic cells, exhibit extremely short half-lives of less than 30 min, and are localized to the nuclear fraction of somatic cells. By contrast, the oocyte protein shows both cytoplasmic and germinal vesicle distribution and appears to be stable.

Analysis of the mRNA coding for the chick vitamin D-induced calbindin and its regulation by 1,25-dihydroxyvitamin D3

We have used specific cloned cDNA probes generated from the mRNA coding for the vitamin D-induced 28,000-Da chick intestinal calcium binding protein (calbindin) to study the hormonal regulation of the expression of this mRNA by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. The calbindin-mRNA has been analyzed in chicken intestinal poly(A)+ mRNA samples as well as other chicken tissues by "Northern" blot analysis. There exists a predominant mRNA species of approximately 2000 nucleotides and two minor cross-hybridizing species that are nearly equivalent in proportion; their sizes are approximately 2600 and 3100 nucleotides. All three mRNA species are nonexistent in the chick intestine in the absence of vitamin D3 intake. However, all three mRNA species begin to accumulate at the same time in the chick intestine following the administration of the hormonally active metabolite of vitamin D3, 1,25-(OH)2D3. This response in the intestine is very similar to other steroid hormone-regulated gene products. All three mRNA species exist in the cell cytoplasm and are present on soluble polysome complexes, suggesting that all three are engaged in protein synthesis. Examination of other chick tissues (both vitamin D-deficient and -replete) reveals a close association between mRNA expression and previously observed calbindin expression. Each tissue is unique in the steady-state level of expression of the calbindin-mRNAs.

The cytocompatibility of compound polyester-protein surfaces using an in vitro technique

To avoid the need to preclot porous polyester (Dacron) vascular prostheses, we have proposed the use of a protein coating that will promote the growth and adhesion of endothelial cells. This study assessed the relative advantages of coating woven, knitted, and velour polyester fabrics with albumin, collagen, and a albumin-collagen mixture after preservation in saline or drying by a commercial dehydration process. Preclotted fabrics were used as controls. The cytocompatibility of these biopolymers was measured by an organotypic culture technique which relies on the migration of chick embryonic endothelial cells. After 7 d of culture the cytocompatibility was quantified by counting the cells in the area of migration and the morphology of the endothelial cells was observed by scanning electron microscopy. In general, the knitted and velour fabrics showed superior compatibility than the woven one. The results confirmed that collagen, either alone or combined with albumin, provides in most cases a more cytocompatible surface than albumin alone. A cell morphology most closely resembling that of natural arterial endothelial cells was observed on the albumin-collagen substrate.

Immunoglobulin interactions with surfaces of sheathed and unsheathed microfilariae

The sheath surface of Brugia pahangi microfilariae (mf) and the cuticle surface of Dirofilaria immitis mf were compared with regard to the ultrastructural arrangement of neutral and charged polysaccharides and binding of immunoglobulins from dog sera. Brugia pahangi: mf demonstrated large amounts of neutral sugar and negatively charged sugars just above the sheath surface, projecting some distance from the surface, in addition to a dense layer of sulphated material on the sheath surface. Microfilariae from high microfilaremic dogs showed no innately bound IgG or IgM when examined fresh from serum nor did they bind IgG or IgM from normal (NDS) or infected (IDS) dog sera after 48 h maintenance in RPMI 1640. Many of these mf did bind IgG and IgM from hyperimmune dog serum (ImDS) and these immunoglobulins were found binding at a distance from the sheath similar to that of the sugars. Dirofilaria immitis mf demonstrated much less neutral sugar at the cuticle surface, no negatively charged sugars and a diffuse, rather than dense, distribution of sulfated material extending from the cuticle. The majority of these mf showed innately bound IgG and IgM. After 48 h maintenance in RPMI 1640 D. immitis mf bound and shed IgG and IgM from NDS, high microfilaremia D. immitis IDS and D. immitis mf ImDS at distinctly different rates.

Fatal air embolism following penetrating lung trauma: an autopsy study

During a 3-month period an autopsy study was performed on cases of penetration lung trauma to assess the frequency and significance of air embolism. The technique of detecting air in the chambers of the heart and the coronary vessels was, in the early part of the study, to flood the pericardium with water and observe for air while stabbing the heart chambers. Later it was found preferable to manipulate the removed heart in a basin under water. Twelve cases demonstrated injury to the pulmonary parenchyma alone with no other injury, either intra- or extra-thoracic, to account for death. In nine of these cases significant amounts of air were demonstrated in the heart and coronary vessels using our autopsy techniques. Case reports are summarized to emphasize the clinical picture (unexplained hypovolemic shock, cerebral symptoms) and autopsy findings (evidence of air embolism). Successful management requires an awareness of the condition, correction of those factors exacerbating air embolism, and prompt thoracotomy in order to clamp the injured lung pedicle in patients failing to respond to therapy.

Retinal venous sheathing in multiple sclerosis

Multiple sclerosis is among those disease entities in which sheathing of the retinal veins has been documented. A case with marked unilateral retinal vein sheathing in a patient with a diagnosis of multiple sclerosis is reported. Discussion with reference to epidemiology, etiology, histopathology, differential diagnosis, and management is presented.

Pathology of the skeleton and tendons of broiler chickens reared to roaster weights. II. Normal chickens

Broiler chickens were raised to 74 days of age under different feeding and housing regimens. Conformation, growth plates and tendon strength were studied in clinically normal chickens of various ages. A change with age from slight valgus deviation of the metatarsal bones to varus deviation was recorded. Separation of the proximal femoral epiphysis from the femur on disarticulation of the coxofemoral joint was a common post-mortem artifact. It was more common in chickens on full feed than in chickens fed a restricted amount of feed. Two distinct growth-plate abnormalities were recognized. Dyschondroplasia was most common in the proximal tibiotarsus and was almost completely absent in chickens fed a restricted amount of feed. Eosinophilic streaks were found in growth plates of the proximal femur and the thoracic vertebral bodies. The incidence of these streaks was not affected by feed restriction. It is suggested that these streaks represent microscopic tears in growth plates exposed to shear forces and that they may be similar to osteochondrosis in mammals. The tensile strength of the flexor digitus perforatus and perforans tendon to the third digit increased with age. It was not affected by housing or feeding regimen, but the ratio of tensile strength over body weight was less in chickens fed ad libitum than in those fed a restricted amount of feed.

Molecular cloning of a vitamin D-dependent calcium-binding protein mRNA sequence from chick intestine

We have constructed a recombinant cDNA library to facilitate study of the genomic actions of vitamin D3 and its hormonally active metabolite 1,25-dihydroxyvitamin D3 in initiation of the de novo biosynthesis of a 28,000-dalton vitamin D-dependent calcium binding protein (CaBP) present in chick intestine. The recombinant plasmids were prepared by the homopolymeric tailing and hybridization method using as a starting template poly(A)-enriched mRNA obtained from the intestinal mucosa of vitamin D3-replete (+D) chicks. Screening of 9,516 clones in this library was effected by using a comparative in situ colony hybridization technique with two [32P]cDNA probes; these probes were prepared from total poly(A)-RNA from chick intestinal mucosa of vitamin D-deficient (-D) chicks and a poly(A)-RNA specifically enriched for chick intestinal CaBP mRNA by immunoprecipitation of polysomes derived from vitamin D-replete (+D) chicks. We identified 26 clones that consistently displayed a significantly increased hybridization signal when comparing the -D vs. CaBP-enriched probe. Further evaluation of these clones by hybrid-selected translation showed the presence of CaBP-specific sequences. By "RNA gel" analysis of poly(A)-RNA, three independent mRNA species were found to hybridize to a CaBP clone; none of these RNA species were found in -D poly(A)-RNA. With this comparative colony hybridization procedure, we were able to identify CaBP-specific clones corresponding to a mRNA that is 0.1% of the total poly(A)-mRNA. The differential colony hybridization procedure using an enriched vs. a nonenriched probe should be of value in screening for other cDNA clones complementary to rare mRNA species.

Rotavirus and hemolytic enteropathogenic Escherichia coli in weanling diarrhea of pigs

Since the turn of the century, Escherichia coli has been implicated in the etiology of weanling diarrhea (colibacillosis). However, rotavirus--a virus that destroys enterocytes--has been shown recently to be causally associated with weanling diarrhea of pigs. The role of both rotavirus and hemolytic enteropathogenic E. coli in weanling diarrhea was assessed in this study. Pigs from a closed herd were farrowed and weaned by two markedly different systems: an "intensive care sanitary" system and a "conventional unsanitary" system. Pigs weaned at 3 weeks of age in the sanitary system usually experienced a rotaviral diarrhea about 16 days postweaning. No hemolytic E. coli were detected in feces from these pigs. Peers weaned at the same time by the unsanitary system commenced diarrhea 3 days postweaning. Rotavirus and nonhemolytic E. coli were detected in the feces at the onset of diarrhea and for a few days thereafter. Then, the aerobic fecal flora shifted to nearly pure hemolytic enteropathogenic E. coli. About 10 days later, the diarrhea waned, and the fecal flora shifted back to nonhemolytic E. coli. This hemolytic E. coli shedding pattern could not be duplicated in artificially inoculated sanitary pigs unless they were inoculated with the hemolytic E. coli during a rotaviral-associated diarrhea. Otherwise, the shedding of hemolytic E. coli was fleeting, and the diarrhea, if present, was mild. Pigs developed humoral antibodies to the rotavirus but not to the hemolytic E. coli. We conclude that rotavirus damages the epithelium of the small intestines, which changes the luminal environment to one that favors colonization by enteropathogenic E. coli.

Rotaviral antibodies in cow's milk

In the past, it has been reported that neonatal diets made from unheated cow's milk were superior to those made from heated cow's milk. It was observed that piglets were equally protected from rotaviral diarrhea when they were fed diets made from either unheated milk that came from a cow immunized against porcine rotavirus or from a cow that was not immunized. Because of this observation, we examined four pools of "normal" cows' colostrum and 58 samples of "normal" cow's milk for the presence of antibody to rotavirus. All pools of colostrum, collected in four different years, had immunofluorescent antibody titers of 1:100 to rotavirus. Seventy-two percent of the samples of milk were also positive--titer no higher than 1:10. Antibodies to rotavirus were found in cow's milk at a creamery prior to but not after pasteurization. Rotaviral antibodies were detected in one out of eight brands of milk bought at the market--perhaps indicating inadequate pasteurization for this brand. These results support the proposition that, at least in part, unheated milk is superior to heated milk because unheated milk contains antibody to an ubiquitous enteropathogen like rotavirus.

The calf reo-like virus (rotavirus) vaccine: an ineffective immunization agent for rotaviral diarrhea of piglets

Rotavirus, in a commercially available calf vaccine, did not replicate in newborn colostrum-free piglets inoculated orally with one half of a calf dose. Gross and microscopic examination of these vaccinated piglets revealed no lesions consistent with rotaviral infection and vaccinated piglets were susceptible to challenge by porcine rotavirus. Challenged piglets vomited, had diarrhea and became severely dehydrated. Rotavirus was visualized in their gut fluid. Villi in the small intestines were shortened, blunted and fused. Rotaviral antigens were seen in enterocytes.

Role of rotavirus (reo-like) in weanling diarrhea of pigs

Piglets weaned abruptly and precociously at 3 weeks of age and placed in a crowded nursery commenced diarrhea 3 to 5 days later. Death losses were low (approximately 6%), but weight gain ceased for 2 weeks. Large numbers of rotavirus (reo-like) particles were seen by electron microscopy in diarrhetic fluids. Sections of intestines showed a loss of adsorptive surface in that villi were shortened and fused with adjacent villi. Immunofluorescence revealed rotaviral antigens within damaged enterocytes. Rotavirus-containing gut fluid was harvested from sick, weaned piglets. This fluid, filtered free of bacteria, was used to inoculate per os colostrum-deprived piglets. These infected piglets developed diarrhea and dehydration, and large numbers of rotaviral particles were seen in their diarrhetic fluid. Also, rotaviral antigens were present in aberrant enterocytes, and the intestinal villi were shortened. Since the weaned piglets (3 weeks old) came from sows that were providing their piglet's intestine with passive antibody protection via milk, we concluded that the abrupt removal of the piglet from the gut-bathing antibody combined with the stress of weaning produced a neonate vulnerable to the ubiquitous rotavirus. Similar circumstances may prevail and operate in exacerbating rotaviral diarrhea in neonates of other species of mammals.

Rearing regimen producing piglet diarrhea (rotavirus) and its relevance to acute infantile diarrhea

Piglets were weaned when 1 day old and thus were denied further access to the antibodies supplied by their dam's milk. They were placed in a nursery in which contamination by the ubiquitous rotavirus steadily increased with continuous use causing a progressive increase in the incidence of vomiting, diarrhea, and death among the piglets. A similar syndrome involving an antigenically related rotavirus and analogous management practices occurs in human infants.

Reovirus-like agent associated with fatal diarrhea in neonatal pigs

Large numbers of a reovirus-like agent were visualized with electron microscopy in bacteria-free gut homogenates obtained from piglets with a fatal diarrhea resembling transmissible gastroenteritis. The syndrome, of vomiting, diarrhea, dehydration, and death, was reproduced in piglets artificially infected with these bacteria-free gut homogenates. Reovirus-like particles persisted in serial piglet passage and none was seen in uninfected, asymptomatic controls. Hyperimmune sera (made in recovered piglets) aggregated the reovirus-like particles, as judged by immunoelectron microscopy, and neutralized the infectious agent. The cytoplasm in enterocytes on infected intestinal epithelium fluoresced when this hyperimmune sera was used in an indirect fluorescent antibody test. Feeding cow colostrum or diets containing porcine gamma globulin protected infected piglets. No cytopathogenic effect was noted in infected tissue cultures, nor did this agent affect neonatal guinea pigs, hamsters, mice, and rats. The agent did not agglutinate human O or A erythrocytes.