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Biomedical subjects

H W Smith

Publications and source records attributed to H W Smith.

At least 19 recordsLinked to original sources
PubMed1991

Cleft lip and palate surgery in La Ceiba, Honduras.

The volume of experience in the surgical repair of cleft lip and palate deformities is limited in many areas of the United States. This deficit in experience exists not only for those in resident training programs but also for those who practice at universities or are in private practice. Physicians are performing too few operations to maintain their surgical skills in cleft lip and palate surgery. This deficit is also encountered by physicians in the major specialties of plastic surgery, oral surgery, and otolaryngology who perform cleft lip and palate surgery. Physicians from the United States can gain surgical experience in other countries through groups like the Medical Group Mission Christian Medical and Dental Society. Surgical experience is available in Central and South America, India, China, and Africa through similar organizations. The complexity of providing service to under-privileged people through organizations such as the Medical Group Mission Christian Medical and Dental Society is described.

Child↗
PubMed1991

Contribution of leukotriene B4 to airway inflammation and the effect of antagonists.

Inhalation of aerosols of ovalbumin in sensitized guinea pigs produced a marked, bronchoalveolar eosinophilia 24 hr after challenge. The lung eosinophilia was not prevented by the cyclooxygenase inhibitors, indomethacin or PAF antagonists (WEB-2086 and L-652731) but was inhibited by methylprednisolone, the 5-LO inhibitor, U-66858 and a series of structural analogs of LTB4, U-75302, U-77692, U-75485 and U-78489. The effectiveness of LTB4 antagonists but not PAF antagonists in vivo was consistent with in vitro studies in which LTB4 was shown to be far more chemotactic than PAF for guinea pig eosinophils. LTB4 elicited maximal directional migration of guinea pig eosinophils at concentrations from 10(-7) M to 10(-9) M while PAF showed no effect over the same concentration range. The structural analogs of LTB4 were shown to inhibit LTB4 induced chemotaxis of guinea pig eosinophils and produced a dose-related inhibition of binding of LTB4 to guinea pig eosinophil membranes. To add further proof to the hypothesis that LTB4 contributed to the antigen-induced lung eosinophilia we attempted to measure LTB4 release into BAL fluid immediately after and at various time points up to 24 hr after antigen inhalation. However, using a sensitive radioimmunoassay (detection limit 10 pg/ml) very low levels of LTB4 (24.9-67.9 pg/ml) or its metabolite, 20-OH LTB4 (24.9-98.2 pg/ml) were detected in BAL fluid and these levels did not increase significantly following antigen provocation. Inhalation of LTB4 aerosols in unsensitized Brown-Norway rats or inhalation of aerosols of ovalbumin in sensitized Brown-Norway rats also produced a marked "late-phase" eosinophil-rich influx of inflammatory cells into the lungs. The lung eosinophilia in the rat was prevented by two structurally unrelated leukotriene B4 (LTB4) antagonists, U-75302 and Ly255283. These data implicate LTB4 as a mediator of allergen-induced bronchopulmonary eosinophilia. Leukotriene B4 antagonists may provide leads for the development of compounds which inhibit the chronic airway inflammation associated with asthma in man.

Aerosols↗
PubMed1979

Site of Epstein-Barr virus replication in the oropharynx.

Cells and cell-free material in saliva, parotid secretions, and throat washings from patients with acute infectious mononucleosis and patients undergoing tonsillectomy were assayed for the presence of infectious Epstein-Barr (EBV) virus. The agent was invariably present in cell-free form in saliva; neither infectious virus nor viral antigens were found in the cells. Tonsillar lymphocytes from eight patients were also free of EBV. In 10 of 40 patients virus was recovered in secretions from parotid-gland orifices or ducts. These findings suggest that the salivary glands are the site of EBV production in the oropharynx.

Acute Disease↗
PubMed1979

Concanavalin A and wheat germ agglutinin receptors in the ascitic fluid of rat hepatomas.

The presence of glycopeptide lectin receptors in the ascitic fluid of rats bearing Novikoff or AS-30D hepatoma was investigated. Macrosialoglycopeptides, resistant to pronase digestion, were partially purified from the ascitic fluid of hepatoma-bearing rats by gel filtration on Sephadex G-50. A macrosialoglycopeptide fraction, isolated from the ascitic fluid of rats bearing the Novikoff hepatoma, possessed potent concanavalin A (Con A) receptor activity. This fraction possessed higher Con A receptor activity than did the comparable macrosialoglycopeptide fraction from the ascitic fluid of rats bearing the AS-30D hepatoma; this obeservation is in agreement with the Con A-induced agglutination properties of these 2 hepatoma cell lines and with the Con A receptor activities of the glycopeptides released from the surface of the hepatoma cells by papain digestion. Rat blood serum contained a comparable macrosialoglycopeptide fraction, which possessed weak Con A receptor activity. The macrosialoglycopeptide fractions from the ascitic fluid of hepatoma-bearing rats possessed wheat germ agglutinin receptor activity. However, this activity was also present in normal rat serum. These results suggest that glycopeptides present on the surface of Novikoff hepatoma cells are shed into the ascitic fluid and may be distinguished from components in normal serum by their Con A receptor activity.

Animals↗
PubMed1979

The effect on the virulence and infectivity of Salmonella typhimurium and Salmonella gallinarum of acquiring antibiotic resistance plasmids from organisms that had caused serious outbreaks of disease.

Antibiotic resistance plasmids from organisms that had caused serious epidemics, including those responsible for epidemics of chloramphenicol-resistant typhoid fever and dysentery in Central America, were transferred to a strain of Salmonella typhimurium and of Salmonella gallinarum. The virulence and infectivity of these R(+) forms were then compared with the R(-) parent forms in orally inoculated chickens.None of the R(+) forms were more virulent than their R(-) parent forms. The mortality rates they produced were either the same as or less than that of their R(-) parent forms. The mortality rates were not increased by feeding the chickens on diets containing antibiotics against which the plasmids provided resistance.The removal of the plasmids from some R(+) forms of decreased virulence was not accompanied by any alteration in virulence, indicating that they were less virulent mutants of the parent strain that had conjugated preferentially. In other cases their virulence was increased, indicating that the very possession of the plasmid was involved in their decreased virulence. Of four forms of the S. gallinarum strain harbouring the plasmid that had been incriminated in the Central American dysentery outbreak, one was as virulent as the parent R(-) form and the other three were less virulent. Preferential conjugation by an avirulent mutant was responsible for the lack of virulence of one of them but the very possession of the plasmid appeared responsible for the decreased virulence of the other two. The decreased virulence of de-repressed F(+) and I(+) forms of the S. typhimurium strain was increased to that of repressed F(+) form and of the parent form by plasmid removal.Organisms of the R(+) forms of the S. typhimurium strain were not excreted in larger amounts or for longer periods of time by infected chickens than organisms of the R(-) parent form were. Neither did organisms of the R(+) forms of this strain or the S. gallinarum strain spread more rapidly or more extensively from infected chickens to in-contact chickens than organisms of the R(-) parent forms did. When antibiotics against which the infecting R(+) organisms provided resistance were included in the diet of these chickens the R(+) organisms were usually excreted in greater amounts, for longer periods of time and spread more rapidly and more extensively from the infected chickens to the in-contact chickens.

Ampicillin↗
PubMed1979

Experimental infection of calves, piglets and lambs with mixtures of invasive and enteropathogenic strains of Escherichia coli.

Mixtures of mutant organisms of an invasive (IN) strain, a strain enteropathogenic (EP) for calves, lambs and piglets, and a non-pathogenic (NP) strain of Escherichia coli, that could be differentiated from each other by their antibiotic resistances, were given orally to an immunoglobulin-negative (IG-) and an immunoglobulin-positive (IG+) calf, lamb and piglet. By the use of appropriate antibiotic-containing culture media, the concentrations of organisms of each of the three strains in the contents of the alimentary tracts and tissues (liver, spleen, kidney, blood and mesenteric lymph glands) of the animals were estimated when they were killed. In the three IG- animals, the IN strain proliferated in the tissues and the EP strain proliferated in the small intestines; in general, the concentrations of the IN strain in the small intestines and the EP strain in the tissues, apart from the mesenteric lymph glands, were as low as those of the NP strain in these sites. The only strain that proliferated in the small intestine of the IG+ animals was the EP strain, which proliferated in the small intestine of the calf and piglet; no organisms of either strain were isolated from the tissues of these three animals, except from their mesenteric lymph glands.

Agammaglobulinemia↗
PubMed1979

Directional handle for Zeiss operating microscope.

A new directional handle for the Zeiss operating microscope is presented. This handle offers the advantage of single-handed (right or left) control by natural movement of the wrist. The handle may be used by grasping it through the see-through sterile drape or sterilized separately and placed outside the sterile microscope drape.

Humans↗
PubMed1979

Calibrated otoplasty.

The number of patients seeking correction of abnormally protruding ears has decreased in the past ten years because of changing hairstyles and concepts of body image. During the same time there has been an increase in the number of surgeon and surgical disciplines seeking to perform cosmetic otoplasty. To compensate for this deficit in total volume experience of the individual operator and to insure patients of a consistently acceptable cosmetic result, the concept of calibrated otoplasty is presented. A study was made of a large number of ears which appeared to be esthetically in harmony with each other and with the side of the head. The distance relationships obtained from this study were applied not only to the creation of a new antihelix in the first ear but the degree to which the ear projects from the side of the head. At the conclusion of the first ear operation, careful measurements were taken for use in the second ear operation to insure its being as near normal as the first in form and degree of projection of the ear from the head. This concept of calibrated otoplasty is explained in detail with illustrations of all required measurements plus a series of surgical illustrations showing application of the technique.

Ear, External↗
PubMed1978

Oral administration of neomycin to chickens experimentally infected with Salmonella typhimurium.

Groups of healthy chickens with a light experimental Salmonella typhimurium infection were fed on a diet containing 225 g per ton (1016 kg) of neomycin for two days. This brought about only a slight reduction in the incidence of chickens that were excreting S typhimurium in their faeces. Examination of caecal contents two days after the cessation of treatment revealed the neomycin had not had any effect in eliminating infection. In one experiment, the neomycin administration resulted in the emergence of enormous populations of Escherichia coli in the alimentary tract of treated chickens that possessed multiple antibiotic resistance of the transmissible type. For these reasons the practice of feeding broiler chickens on diets containing neomycin immediately before slaughter should be actively discouraged.

Administration, Oral↗
PubMed1978

The effect of antimicrobial feed additives on the colonization of the alimentary tract of chickens by Salmonella typhimurium.

Groups of 33 chickens were fed continuously on diets containing feed additives that are employed commercially for a variety of purposes, and were infected orally when 4 days old with a nalidixic acid-resistant mutant of Salmonella typhimurium. The amount of S. typhimurium organisms excreted in their faeces was estimated by culturing them at intervals and in a standard manner on brilliant green agar containing sodium nalidixate; when the chickens were killed their caecal contents were examined by the same technique.Avoparcin and lincomycin, like nitrovin and tylosin (Smith & Tucker, 1975b), favoured colonization of the alimentary tract by the S. typhimurium organisms as shown by the fact that the chickens to which they were fed excreted these organisms in their faeces in higher concentration and for longer periods of time than did chickens fed on non-medicated diets. Amprolium, monensin, dimetridazole, arsenilic acid and nitro-hydroxyphenylarsonate had no obvious effect on the salmonella excretion pattern.When only five chickens in each group were experimentally infected so that the effect of the feed additives on infections acquired by contact could be monitored, avoparcin, lincomycin, nitrovin and tylosin again favoured colonization of the alimentary tract with the S. typhimurium organisms and so did dimetridazole. Arsenilic acid, in contrast, hindered the development of infection. Amprolium, monensin and nitro-hydroxyphenylarsonate were without obvious effect.Many of the chickens that were fed on diets that favoured S. typhimurium colonization, but not those fed on non-medicated diets, were still excreting S. typhimurium organisms in their faeces when they were killed at 56 days of age, the age at which broiler chickens kept under commercial conditions are usually slaughtered.

Amprolium↗
PubMed1978

Molecular structure of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea.

The three-dimensional structure of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (MeCCNU, NSC-95441), an effective antitumor agent, has been determined by single-crystal x-ray diffraction. MeCCNU crystallizes in monoclinic space group P21/c, with cell dimensions a = 12.387, b = 10.810, and c = 10 .198 A , beta = 102.62 degrees , and Z = four molecules per unit cell. The structure was solved by direct phasing procedures and refinement by anisotropic least squares converged at a discrepancy index R = 0.065. The cyclohexyl ring is in the chair conformation with the plane of the nitrosourea moiety twisted approximately 90 degrees from the cyclohexyl ring. The carbon-nitrogen bonds of the urea group are significantly asymmetric.

Chemical Phenomena↗
PubMed1978

Thermosensitive antibiotic resistance plasmids in enterobacteria.

Of 775 conjugative plasmids found in enterobacteria mediating antibiotic resistance, 24 (3.1%) were thermosensitive (ts); they were most common in Klebsiella pneumoniae. Ts plasmids were also found in all the samples of sewage and river water examined. Over half of 73 ts plasmids from unrelated sources mediated resistance to chloramphenicol in addition to several other antibiotics. Many of them mediated resistance to mercury (53.4%), arsenite (38.4%) and tellurite (79.5%) but not to copper, cobalt and silver. Fifty-eight belonged to incompatibility group H2 and 12 belonged to the H1 group. Resistance to mercury, arsenite and tellurite was common in strains containing H2 plasmids but not in H1 plasmids. The 73 plasmids transferred at high rates at 22 and 28 degrees C and at lower rates at 15 degrees C; they transferred at very low rates or not at all at 37 degrees C. They could be divided into two sets according to whether they transferred at a high or at a low rate at 33 degrees C. Unlike the prototype plasmid, Rts 1, they were solely or mainly ts for transfer and not for replication and only one of them brought about a marked reduction in growth rate of its host organism at 42 degrees C. None of the 73 plasmids mediated colicin or haemolysin production. Three plasmids, all from K. pneumoniae, mediated utilization of lactose, two of sucrose and raffinose and three, all belonging to group H1, of citrate. None of the plasmids increased the pathogenicity of Salmonella typhimurium for chicks or Escherichia coli K12 for mice.

Animals↗